Subjects -> MANUFACTURING AND TECHNOLOGY (Total: 363 journals)
    - CERAMICS, GLASS AND POTTERY (31 journals)
    - MACHINERY (34 journals)
    - MANUFACTURING AND TECHNOLOGY (223 journals)
    - METROLOGY AND STANDARDIZATION (6 journals)
    - PACKAGING (19 journals)
    - PAINTS AND PROTECTIVE COATINGS (4 journals)
    - PLASTICS (42 journals)
    - RUBBER (4 journals)

MACHINERY (34 journals)

Showing 1 - 27 of 27 Journals sorted alphabetically
Acta Mechanica Solida Sinica     Hybrid Journal   (Followers: 8)
Advanced Energy Materials     Hybrid Journal   (Followers: 31)
Applied Mechanics Reviews     Full-text available via subscription   (Followers: 27)
CORROSION     Full-text available via subscription   (Followers: 20)
Electric Power Components and Systems     Hybrid Journal   (Followers: 7)
Foundations and TrendsĀ® in Electronic Design Automation     Full-text available via subscription   (Followers: 1)
International Journal of Machine Tools and Manufacture     Hybrid Journal   (Followers: 8)
International Journal of Machining and Machinability of Materials     Hybrid Journal   (Followers: 4)
International Journal of Manufacturing Technology and Management     Hybrid Journal   (Followers: 8)
International Journal of Precision Technology     Hybrid Journal   (Followers: 1)
International Journal of Rapid Manufacturing     Hybrid Journal   (Followers: 3)
International Journal of Rotating Machinery     Open Access   (Followers: 2)
Journal of Machinery Manufacture and Reliability     Hybrid Journal   (Followers: 2)
Journal of Manufacturing and Materials Processing     Open Access  
Journal of Mechanics     Hybrid Journal   (Followers: 9)
Journal of Strain Analysis for Engineering Design     Hybrid Journal   (Followers: 5)
Journal of Terramechanics     Hybrid Journal   (Followers: 4)
Machine Design     Partially Free   (Followers: 183)
Machine Learning and Knowledge Extraction     Open Access   (Followers: 12)
Machines     Open Access   (Followers: 4)
Materials     Open Access   (Followers: 4)
Mechanics Based Design of Structures and Machines: An International Journal     Hybrid Journal   (Followers: 8)
Micromachines     Open Access   (Followers: 2)
Pump Industry Analyst     Full-text available via subscription   (Followers: 1)
Russian Engineering Research     Hybrid Journal  
Sensor Review     Hybrid Journal   (Followers: 2)
Surface Engineering and Applied Electrochemistry     Hybrid Journal   (Followers: 6)
Similar Journals
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Materials
Number of Followers: 4  

  This is an Open Access Journal Open Access journal
ISSN (Print) 1996-1944
Published by MDPI Homepage  [84 journals]
  • Materials, Vol. 15, Pages 3429: Investigation on Strain Hardening and
           Failure in Notched Tension Specimens of Cold Rolled Ti6Al4V Titanium Alloy
           

    • Authors: Hao Zhang, Tao Gao, Jian Chen, Xunpeng Li, Haipeng Song, Ganyun Huang
      First page: 3429
      Abstract: Uniaxial and notched tension samples are utilized to investigate the damage and failure of titanium alloy Ti6Al4V. The strain fields on the samples are obtained by the digital image correlation (DIC) method. Strain localization occurs before fracturing in all samples, and the width and size of the localized zone are characterized. Slant fractures are observed in uniaxial and notched tension specimen, which indicate that the initiation and propagation of cracks in thin sheet specimens are highly affected by the shear stress. Numerical simulations were performed for identification of hybrid hardening laws, and the results were compared with the experiments. The influence of the stress triaxiality on damage mechanism of Ti6Al4V was analyzed by observation of the specimen fracture surfaces using SEM. The results show that a higher stress triaxiality facilitates the formation and growth of micro-voids, which leads to a decrement of strain at failure.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103429
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3439: Europium Clustering and Glassy Magnetic
           Behavior in Inorganic Clathrate-VIII Eu8Ga16Ge30

    • Authors: Nicolás Pérez, Manaswini Sahoo, Gabi Schierning, Kornelius Nielsch, George S. Nolas
      First page: 3439
      Abstract: The temperature- and field-dependent, electrical and thermal properties of inorganic clathrate-VIII Eu8Ga16Ge30 were investigated. The type VIII clathrates were obtained from the melt of elements as reported previously. Specifically, the electrical resistivity data show hysteretic magnetoresistance at low temperatures, and the Seebeck coefficient and Hall data indicate magnetic interactions that affect the electronic structure in this material. Heat capacity and thermal conductivity data corroborate these findings and reveal the complex behavior due to Eu2+ magnetic ordering and clustering from approximately 13 to 4 K. Moreover, the low-frequency dynamic response indicates Eu8Ga16Ge30 to be a glassy magnetic system. In addition to advancing our fundamental understanding of the physical properties of this material, our results can be used to further the research for potential applications of interest in the fields of magnetocalorics or thermoelectrics.
      Citation: Materials
      PubDate: 2022-05-10
      DOI: 10.3390/ma15103439
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3440: The Relationship between Osteoinduction
           and Vascularization: Comparing the Ectopic Bone Formation of Five
           Different Calcium Phosphate Biomaterials

    • Authors: Yun He, Yu Peng, Lishuang Liu, Sha Hou, Junyu Mu, Liang Lan, Lijia Cheng, Zheng Shi
      First page: 3440
      Abstract: The following five kinds of Ca-P biomaterials including hydroxyapatite (HA) and/or tricalcium phosphate (TCP) were implanted in the muscle of 30 BALB/c mice (n = 6): 20 nm HA (20HA), 60 nm HA (60HA), 12 µm HA (12HA), 100 nm TCP (100TCP) and 12 µm HA + 100 nm TCP (HATCP). Then, all animals were put on a treadmill to run 30 min at a 6 m/h speed each day. Five and ten weeks later, three mice of each group were killed, and the samples were harvested to assess the osteoinductive effects by hematoxylin eosin (HE), Masson’s trichrome and safranine–fast green stainings, and the immunohistochemistry of the angiogenesis and osteogenesis markers CD31 and type I collagen (ColI). Results: The numbers of blood vessels were 139 ± 29, ± 118 ± 25, 78 ± 15, 65 ± 14 in groups HATCP, 100TCP, 60HA and 20HA, respectively, which were significantly higher than that of group 12HA (12 ± 5) in week 5 (p < 0.05). The area percentages of new bone tissue were (7.33 ± 1.26)% and (8.49 ± 1.38)% in groups 100TCP and HATCP, respectively, which were significantly higher than those in groups 20HA (3.27 ± 0.38)% and 60HA (3.43 ± 0.27)% (p < 0.05); however, no bone tissue was found in group 12HA 10 weeks after transplantation. The expression of CD31 was positive in new blood vessels, and the expression of ColI was positive in new bone tissue. Conclusions: Nanoscale Ca-P biomaterials could induce osteogenesis in mice muscle, and the osteoinductive effects of TCP were about 124% higher than those of 20HA and 114% higher than those of 60HA. The particle size of the biomaterials affected angiogenesis and osteogenesis. There was a positive correlation between the number of blood vessels and the area percentage of new bone tissue; therefore, osteoinduction is closely related to vascularization. Our results provide an experimental basis for the synthesis of calcium–phosphorus matrix composites and for further exploration of the osteoinductive mechanism.
      Citation: Materials
      PubDate: 2022-05-10
      DOI: 10.3390/ma15103440
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3441: AFM Characterization of Halloysite Clay
           Nanocomposites’ Superficial Properties: Current State-of-the-Art and
           Perspectives

    • Authors: Mariafrancesca Cascione, Valeria De Matteis, Francesca Persano, Stefano Leporatti
      First page: 3441
      Abstract: Natural halloysite clay nanotubes (HNTs) are versatile inorganic reinforcing materials for creating hybrid composites. Upon doping HNTs with polymers, coating, or loading them with bioactive molecules, the production of novel nanocomposites is possible, having specific features for several applications. To investigate HNTs composites nanostructures, AFM is a very powerful tool since it allows for performing nano-topographic and morpho-mechanical measurements in any environment (air or liquid) without treatment of samples, like electron microscopes require. In this review, we aimed to provide an overview of recent AFM investigations of HNTs and HNT nanocomposites for unveiling hidden characteristics inside them envisaging future perspectives for AFM as a smart device in nanomaterials characterization.
      Citation: Materials
      PubDate: 2022-05-10
      DOI: 10.3390/ma15103441
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3442: Simulation-Based Process Design for
           Asymmetric Single-Point Incremental Forming of Individual Titanium Alloy
           Hip Cup Prosthesis

    • Authors: Sirine Frikha, Laurence Giraud-Moreau, Anas Bouguecha, Mohamed Haddar
      First page: 3442
      Abstract: Advanced manufacturing techniques aimed at implants with high dependability, flexibility, and low manufacturing costs are crucial in meeting the growing demand for high-quality products such as biomedical implants. Incremental sheet forming is a promising flexible manufacturing approach for rapidly prototyping sheet metal components using low-cost tools. Titanium and its alloys are used to shape most biomedical implants because of their superior mechanical qualities, biocompatibility, low weight, and great structural strength. The poor formability of titanium sheets at room temperature, however, limits their widespread use. The goal of this research is to show that the gradual sheet formation of a titanium biomedical implant is possible. The possibility of creative and cost-effective concepts for the manufacture of such complicated shapes with significant wall angles is explored. A numerical simulation based on finite element modeling and a design process tailored for metal forming are used to complete the development. The mean of uniaxial tensile tests with a constant strain rate was used to study the flow behavior of the studied material. To forecast cracks, the obtained flow behavior was modeled using the behavior and failure models.
      Citation: Materials
      PubDate: 2022-05-10
      DOI: 10.3390/ma15103442
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3443: Artificial Neural Network with a
           Cross-Validation Technique to Predict the Material Design of Eco-Friendly
           Engineered Geopolymer Composites

    • Authors: Yaswanth Kuppusamy, Revathy Jayaseelan, Gajalakshmi Pandulu, Veerappan Sathish Kumar, Gunasekaran Murali, Saurav Dixit, Nikolai Ivanovich Vatin
      First page: 3443
      Abstract: A material-tailored special concrete composite that uses a synthetic fiber to make the concrete ductile and imposes strain-hardening characteristics with eco-friendly ingredients is known as an “engineered geopolymer composite (EGC)”. Mix design of special concrete is always tedious, particularly without standards. Researchers used several artificial intelligence tools to analyze and design the special concrete. This paper attempts to design the material EGC through an artificial neural network with a cross-validation technique to achieve the desired compressive and tensile strength. A database was formulated with seven mix-design influencing factors collected from the literature. The five best artificial neural network (ANN) models were trained and analyzed. A gradient descent momentum and adaptive learning rate backpropagation (GDX)–based ANN was developed to cross-validate those five best models. Upon regression analysis, ANN [2:16:16:7] model performed best, with 74% accuracy, whereas ANN [2:16:25:7] performed best in cross-validation, with 80% accuracy. The best individual outputs were “tacked-together” from the best five ANN models and were also analyzed, achieving accuracy up to 88%. It is suggested that when these seven mix-design influencing factors are involved, then ANN [2:16:25:7] can be used to predict the mix which can be cross-verified with GDX-ANN [7:14:2] to ensure accuracy and, due to the few mix trials required, help design the SHGC with lower costs, less time, and fewer materials.
      Citation: Materials
      PubDate: 2022-05-10
      DOI: 10.3390/ma15103443
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3444: New Functional Organic Materials and Their
           Photoelectric Applications: A New Open Special Issue of Materials

    • Authors: Ruonan Yin, Jing-Jing Lv
      First page: 3444
      Abstract: New Functional Organic Materials and Their Photoelectric Applications is a new open Special Issue of Materials, which focuses on designing and fabricating advanced functional organic optoelectronic materials and makes great contributions to investigating their properties, related applications, and underlying mechanisms [...]
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103444
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3445: The Effect of Residual Solvent in
           Carbon−Based Filler Reinforced Polymer Coating on the Curing
           Properties, Mechanical and Corrosive Behaviour

    • Authors: Nurul Husna Othman, Mazli Mustapha, Nabihah Sallih, Azlan Ahmad, Faizal Mustapha, Mokhtar Che Ismail
      First page: 3445
      Abstract: Solution mixing, which is one of the standard methods of producing Graphene−based Nanocomposites (GPC) may not be as efficient as it is expected due to the presence of residual solvent in the cured product. Therefore, the influence of including acetone in the preparation of Graphene Oxide−based epoxy coating (GO−EP) on the curing behaviour, mechanical and corrosive behaviour was studied. FTIR and TGA analysis confirmed that the GO−EP prepared by ultrasonication (GO−EP U) indicated the presence of more low−molecular−weight/low crosslinked (LMW/LC) sites than GO−EP prepared by stirring (GO−EP MS). Meanwhile, the tensile strength and hardness of GO−EP MS was 20% and 10% better than GO−EP U which confirmed that the presence of a lower number of LMW/LC could prevail over the agglomeration of GO sheets in the GO−EP MS. Pull−off adhesion tests also confirms that the presence of remaining acetone would cause the poor bonding between metal and coating in GO−EP U. This is reflected on the electrochemical impedance spectroscopy (EIS) results, where the GO−EP U failed to provide substantial barrier protection for carbon steel after 140 days of immersion in 3.5 wt% NaCl. Therefore, it is essential to consider the solvent effect when solvent is used in the preparation of a coating to prevent the premature failure of high−performance polymer coatings.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103445
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3446: Life Cycle Assessment-Based Comparative
           Study between High-Yield and “Standard” Bottom-Up Procedures
           for the Fabrication of Carbon Dots

    • Authors: Sónia Fernandes, Joaquim C. G. Esteves da Silva, Luís Pinto da Silva
      First page: 3446
      Abstract: Carbon dots (CDs) are carbon-based nanomaterials with remarkable properties that can be produced from a wide variety of synthesis routes. Given that “standard” bottom-up procedures are typically associated with low synthesis yields, different authors have been trying to devise alternative high-yield fabrication strategies. However, there is a doubt if sustainability-wise, the latter should be really preferred to the former. Herein, we employed a Life Cycle Assessment (LCA) approach to compare and understand the environmental impacts of high-yield and “standard” bottom-up strategies, by applying different life cycle impact assessment (LCIA) methods. These routes were: (1) production of hydrochar, via the hydrothermal treatment of carbon precursors, and its alkaline peroxide treatment into high-yield CDs; (2) microwave treatment of carbon precursors doped with ethylenediamine; (3) and (6) thermal treatment of carbon precursor and urea; (4) hydrothermal treatment of carbon precursor and urea; (5) microwave treatment of carbon precursor and urea. For this LCA, four LCIA methods were used: ReCiPe, Greenhouse Gas Protocol, AWARE, and USEtox. Results identified CD-5 as the most sustainable synthesis in ReCiPe, Greenhouse Gas Protocol, and USEtox. On the other hand, in AWARE, the most sustainable synthesis was CD-1. It was possible to conclude that, in general, high-yield synthesis (CD-1) was not more sustainable than “standard” bottom-up synthesis, such as CD-5 and CD-6 (also with relatively high-yield). More importantly, high-yield synthesis (CD-1) did not generate much lower environmental impacts than “standard” approaches with low yields, which indicates that higher yields come with relevant environmental costs.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103446
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3447: Experimental Validation and Evaluation of
           the Bending Properties of Additively Manufactured Metallic Cellular
           Scaffold Structures for Bone Tissue Engineering

    • Authors: Mohammad O. Al-Barqawi, Benjamin Church, Mythili Thevamaran, Dan J. Thoma, Adeeb Rahman
      First page: 3447
      Abstract: The availability of additive manufacturing enables the fabrication of cellular bone tissue engineering scaffolds with a wide range of structural and architectural possibilities. The purpose of bone tissue engineering scaffolds is to repair critical size bone defects due to extreme traumas, tumors, or infections. This research study presented the experimental validation and evaluation of the bending properties of optimized bone scaffolds with an elastic modulus that is equivalent to the young’s modulus of the cortical bone. The specimens were manufactured using laser powder bed fusion technology. The morphological properties of the manufactured specimens were evaluated using both dry weighing and Archimedes techniques, and minor variations in the relative densities were observed in comparison with the computer-aided design files. The bending modulus of the cubic and diagonal scaffolds were experimentally investigated using a three-point bending test, and the results were found to agree with the numerical findings. A higher bending modulus was observed in the diagonal scaffold design. The diagonal scaffold was substantially tougher, with considerably higher energy absorption before fracture. The shear modulus of the diagonal scaffold was observed to be significantly higher than the cubic scaffold. Due to bending, the pores at the top side of the diagonal scaffold were heavily compressed compared to the cubic scaffold due to the extensive plastic deformation occurring in diagonal scaffolds and the rapid fracture of struts in the tension side of the cubic scaffold. The failure in struts in tension showed signs of ductility as necking was observed in fractured struts. Moreover, the fractured surface was observed to be rough and dull as opposed to being smooth and bright like in brittle fractures. Dimple fracture was observed using scanning electron microscopy as a result of microvoids emerging in places of high localized plastic deformation. Finally, a comparison of the mechanical properties of the studied BTE scaffolds with the cortical bone properties under longitudinal and transverse loading was investigated. In conclusion, we showed the capabilities of finite element analysis and additive manufacturing in designing and manufacturing promising scaffold designs that can replace bone segments in the human body.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103447
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3448: Water Corrosion of Tungsten Target for
           Accelerator-Driven Neutron Source

    • Authors: Yupeng Xie, Qiuyu Sun, Yaocheng Hu, Xiaobo Li, Zhaopeng Qiao, Jie Wang, Sheng Wang
      First page: 3448
      Abstract: The water corrosion of tungsten as a target material can affect the safe operation of accelerator-driven neutron source. This paper reported the corrosion behaviors of tungsten in ultrapure water and tap water for 7, 14, 21, 30 and 60 days. Moreover, ICP-MS, XRD, XPS, SEM-EDS and LSCM were used to analyze the components in solutions, crystalline structures, chemical compositions and surface morphologies. It was found that the dissolution of tungsten, due to corrosion, reached its maximum between 30 days and 60 days in both solutions. The cube-shape substance, CaWO4, was the main corrosion product after tungsten in tap water. The tungsten oxide was changed from WO3 to WO2 during the corrosion of tungsten in ultrapure water. Compared with tungsten in ultrapure water, tungsten in tap water had its surface completely destroyed, with a dense diamond shape. Therefore, based on the analysis from this study, the corrosion mechanisms of tungsten in ultrapure and tap water were revealed.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103448
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3449: The Effect of Magnesium Hydroxide Addition
           on the Extinguishing Efficiency of Sodium Bicarbonate Powders

    • Authors: Piotr Izak, Mateusz Biel, Joanna Mastalska-Popławska, Paweł Janik, Piotr Mortka, Piotr Lesiak
      First page: 3449
      Abstract: This article analyzes the possibility of the modification of BC powder (a mixture of sodium bicarbonate and calcium carbonate) with magnesium hydroxide (Mg(OH)2). Extinguishing efficiency as well as the influence of this additive on other physicochemical properties were determined by performing a 13B fire test, rheological measurements of the powders, thermal tests (thermogravimetry (TG) and differential scanning calorimetry (DSC) in combination with quadrupole mass spectrometry (QMS)) and microscopic observations of the powders’ surface (scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDS)). It was found that the increase of the Mg(OH)2 content causes deterioration of the rheological properties by increasing the slope angle of the flow curve in relation to the normal stress (the tangent of the flow curve slope varying from 0.258 for 5% of Mg(OH)2 up to 0.330 for 20% of Mg(OH)2). However, at the same time, the increased content of Mg(OH)2 increases the total energy of the chemical decomposition reaction (from −47.27 J/g for 5% of Mg(OH)2 up to −213.6 J/g for 20% of Mg(OH)2) resulting in the desirable higher level of heat removal from the fire. The initial extinguishing effect of the fire becomes more effective as the hydroxide content increases (within the first 2 s), but at a later stage (from t = 63 s), the temperature is no longer sufficient (it is below 350 °C) for thermal decomposition of Mg(OH)2. As such, the optimal content of Mg(OH)2 is 10–15%. The obtained results allowed for the assessment of the impact of individual powder components on its extinguishing effect and will contribute to the development of science in the field of developing new types of extinguishing powders.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103449
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3450: Ultrasound Study of Magnetic and
           Non-Magnetic Nanoparticle Agglomeration in High Viscous Media

    • Authors: Bassam Jameel, Tomasz Hornowski, Rafał Bielas, Arkadiusz Józefczak
      First page: 3450
      Abstract: Ultrasound attenuation spectroscopy has found wide application in the study of colloidal dispersions such as emulsions or suspensions. The main advantage of this technique is that it can be applied to relatively high concentration systems without sample preparation. In particular, the use of Epstein-Carhart-Allegra-Hawley’s (ECAH) ultrasound scattering theory, along with experimental data of ultrasound velocity or attenuation, provide the method of estimation for the particle or droplet size from nanometers to millimeters. In this study, suspensions of magnetite and silica nanoparticles in high viscous media (i.e., castor oil) were characterized by ultrasound spectroscopy. Both theoretical and experimental results showed a significant difference in ultrasound attenuation coefficients between the suspensions of magnetite and silica nanoparticles. The fitting of theoretical model to experimental ultrasound spectra was used to determine the real size of objects suspended in a high viscous medium that differed from the size distributions provided by electron microscopy imaging. The ultrasound spectroscopy technique demonstrated a greater tendency of magnetic particles toward agglomeration when compared with silica particles whose sizes were obtained from the combination of experimental and theoretical ultrasonic data and were more consistent with the electron microscopy images.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103450
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3451: Novel Multifunctional Spherosilicate-Based
           Coupling Agents for Improved Bond Strength and Quality in Restorative
           Dentistry

    • Authors: Zbigniew Raszewski, Dariusz Brząkalski, Marek Jałbrzykowski, Daria Pakuła, Miłosz Frydrych, Robert E. Przekop
      First page: 3451
      Abstract: The aim of this study was to investigate the restorative connections of composite materials after fracture, under controlled conditions of treating the materials with novel, spherosilicate-based (SS) primers bearing both methacryl (MA) and trimethoxysilyl (TMOS) groups. The chemistry of methacrylate group insertion and reactive groups hydrolysis has been studied with the aid of 1H NMR (Nuclear Magnetic Resonance) spectroscopy. The light-cured resin composites were repaired by activating the connection site with the obtained primers and, for comparison, a silane (methacryloxypropyltrimethoxysilane, MATMOS) as a conventional coupling agent bearing the same reactive groups. The resistance of such a joint was tested in a three-point bending test after 24 h and 28 days period of sample conditioning. The effect of bond application was also studied, showing that spherosilicate-based primers may be used more effectively than MATMOS for two-step (primer-composite) restorative process, while for silane, the three-step process with bond application is crucial for satisfactory joint quality. The joint failure mode was determined by microscopic analysis and it was found that SS-4MA-4TMOS and SS-2MA-6TMOS application resulted in mostly composite, and not joint, failure. After 28 days of conditioning, the flexural strength of the joint repaired with SS-4MA-4TMOS was at 94% of the neat, solid material under the same procedure. However, the strength of the neat composite was observed to decline during the conditioning process by ~30%. The joint behavior was explained on the basis of the gradual hydrolysis effect (the greatest decrease being observed for silane).
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103451
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3452: Investigation of Strength Properties for
           Concrete Containing Fine-Rubber Particles Using UPV

    • Authors: Yeol Choi, Il-Hyun Kim, Hyeon-Jin Lim, Chang-Geun Cho
      First page: 3452
      Abstract: Since the early 1990s, many studies were conducted to utilize waste tires as a replacement for natural coarse and fine aggregates in concrete, known as rubberized concrete or rubber-concrete. In this paper, an experimental study was performed on the strength properties of concrete containing fine-rubber particles as a replacement of fine aggregate, using destructive and non-destructive tests. Ultrasonic pulse velocity (UPV) tests were used to evaluate the strength property of rubber-concrete as a non-destructive test. Compressive and splitting tensile strengths were determined for four different volume contents of fine-rubber particles and exponential equations were proposed for the relationship between compressive, splitting tensile strength and the UPV of rubber-concrete, respectively. With the limited conditions in this paper, it found that UPV tests could also be used to estimate the compressive and tensile strengths of rubber-concrete, that are used in other types of concrete.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103452
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3453: A Resistivity Plate Loading Device for
           Assessing the Factors Affecting the Stiffness of a Cement-Stabilized
           Subgrade

    • Authors: Huaiping Feng, Ackah Frank Siaw, Hailiang Wang
      First page: 3453
      Abstract: The extent of mixing in the stabilization process and the control of the cement content (C) and water content (w) in the mixture are key to the outcome of the engineering performance of a cement-stabilized subgrade. Intelligent Compaction (IC) quality control has improved quality control and management practices during construction. Intelligent Compaction Measurement Values (ICMVs) selected to evaluate the stiffness properties of cement-stabilized soils do not directly relate to the stiffness properties of the cement-stabilized subgrade and do not consider w and C. Additional tests need to be conducted for calibration of ICMVs. In this study, our solution is the development of a resistivity plate loading test. The resistivity plate loading test features the flexibility in determining the soil stiffness, w, C, and other important factors, such as the time of test effect (hydration) (T) and dry density (ρd). To verify the accuracy of the testing method, laboratory experimental studies were conducted on cemented soils considering ρd, w, C, and T at different factor levels. Multiple response studies based on grey rational analysis (GRA) were conducted. Analysis of the input factors was performed, and their effects on the measured responses were quantified. According to the study, the ρ measured by the device was a powerful indicator of stiffness, ρd, w, C, and T, which showed that the device can be useful equipment for quality control and an advancement in the in situ testing technologies and test equipment. A statistical regression model based on the linear and linear plus interaction terms among the factors is proposed to predict the average responses.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103453
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3454: Detection of Chlorpyrifos Using
           Bio-Inspired Silver Nanograss

    • Authors: Hyunjun Park, Joohyung Park, Gyudo Lee, Woong Kim, Jinsung Park
      First page: 3454
      Abstract: Chlorpyrifos (CPF) is widely used as an organophosphorus insecticide; however, owing to developmental neurotoxicity, genotoxicity, and other adverse effects, it is harmful not only to livestock but also to humans. Therefore, the use of CPF was recently regulated, and its sensitive detection is crucial, as it causes serious toxicity, even in the case of residual pesticides. Because it is hard to detect the chlorpyrifos directly using spectroscopy (especially in SERS) without chemical reagents, we aimed to develop a SERS platform that could detect the chlorpyrifos directly in the water. In this study, we utilized the intrinsic properties of natural lawns that grow randomly and intertwine with each other to have a large surface area to promote photosynthesis. To detect CPF sensitively, we facilitated the rapid fabrication of biomimetic Ag nanograss (Ag-NG) as a surface-enhanced Raman spectroscopy (SERS) substrate using the electrochemical over-deposition method. The efficiency of the SERS method was confirmed through experiments and finite element method (FEM)-based electromagnetic simulations. In addition, the sensitive detection of CPF was enhanced by pretreatment optimization of the application of the SERS technique (limit of detection: 500 nM). The Ag-NG has potential as a SERS platform that could precisely detect organic compounds, as well as various toxic substances.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103454
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3455: Influence of Industrial Metakaolin Waste
           on Autoclaved Fiber Cement Properties Changes in Standard Fire Environment
           

    • Authors: Tomas Veliseicik, Ramune Zurauskiene, Modestas Kligys, Mark Dauksevic
      First page: 3455
      Abstract: An investigation was conducted on the influence that industrial metakaolin waste (IMW) has on the properties of autoclaved fiber cement composition (FCC) samples. FCC samples were made from fiber cement plate’s typical components using the same proportions. In samples, IMW was used instead of cement in 10%, 20%, 30% proportions and in 50%, 100% proportions instead of ground quartz. Differential thermal analysis (DTG), thermogravimetric analysis (TGA), ultrasound pulse velocity (UPV), density, porosity and optical microscope (OM) research methods were used to identify the micro and macrostructure of samples. Mechanical properties were evaluated using flexural and compressive strength research methods. It was established that IMW was used instead of cement in fiber cement composition samples up to 10% and in fiber cement composition samples instead of ground quartz forms density microstructure structure because of Al-rich tobermorite. As a result, the flexural and compressive strength increased. Samples with higher content of IMW instead of cement had unreacted IMW and a less dense microstructure. In this case, flexural and compressive strength decreased. All FCC samples were fired in a standard fire curve (ISO 842) for 30 min. Samples of mechanical properties were established by doing flexural and compressive strength tests, and which results showed the same trends.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103455
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3456: Flake Graphene-Based Nanomaterial Approach
           for Triggering a Ferroptosis as an Attractive Theranostic Outlook for
           Tackling Non-Small Lung Cancer: A Mini Review

    • Authors: Joanna Pancewicz, Wiesława Ewa Niklińska, Adrian Chlanda
      First page: 3456
      Abstract: Lung cancer is a highly aggressive neoplasm that is now a leading cause of cancer death worldwide. One of the major approaches for killing cancer cells is related with activation of apoptotic cell death with anti-cancer drugs. However, the efficiency of apoptosis induction in tumors is limited. Consequently, the development of other forms of non-apoptotic cell death is up to date challenge for scientists worldwide. This situation motivated us to define the aim of this mini-review: gathering knowledge regarding ferroptosis—newly defined programmed cell death process characterized by the excessive accumulation of iron—and combining it with yet another interesting nanomaterial-based graphene approach. In this manuscript, we presented brief information about non-small lung cancer and ferroptosis, followed by a section depicting the key-features of graphene-based nanomaterials influencing their biologically relevant properties.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103456
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3457: Biomimetic Organic-Inorganic Hybrid
           Membranes for Removal of Fluoride Ions

    • Authors: Yun Chen, Hao Kong, Lei Guo, Gang Wei
      First page: 3457
      Abstract: Carbon nanofibers (CaNFs) exhibit promising applications in the fields of environmental science and nanotechnology, and self-assembled peptide nanofibers (PNFs) are useful for the biomimetic synthesis of organic-inorganic hybrid nanomaterials and the fabrication of functional hybrid membranes for the removal of various pollutants from water. In this work, we report the biomimetic synthesis of hybrid nanomaterials by the interweaving of CaNFs and PNFs. Using the biomimetic mineralization properties of PNFs, ZrO2 nanoparticles were synthesized along the nanofiber surface, and then functional nanohybrid porous membranes were prepared by the vacuum filtration technology. For the fabrication of membranes, the amount of PNFs and ZrO2 precursors in the hybrid membrane were optimized. The designed organic-inorganic hybrid membranes exhibited high removal performance for fluorine ion (F−) from water, and the removal efficiency of the fabricated membranes towards F− ion-containing aqueous solution with a concentration of 50–100 mg/L reached more than 80%. In addition, the nanofiltration membranes revealed good adsorption capacity for F− ions. It is expected that the strategies shown in this study will be beneficial for the design, biomimetic synthesis, and fabrication of nanoporous membranes for economic, rapid, and efficient water purification.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103457
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3458: Mechanical and Durability Analysis of Fly
           Ash Based Geopolymer with Various Compositions for Rigid Pavement
           Applications

    • Authors: Muhammad Faheem Mohd Tahir, Mohd Mustafa Al Bakri Abdullah, Shayfull Zamree Abd Rahim, Mohd Rosli Mohd Hasan, Andrei Victor Sandu, Petrica Vizureanu, Che Mohd Ruzaidi Ghazali, Aeslina Abdul Kadir
      First page: 3458
      Abstract: Ordinary Portland cement (OPC) is a conventional material used to construct rigid pavement that emits large amounts of carbon dioxide (CO2) during its manufacturing process, which is bad for the environment. It is also claimed that OPC is susceptible to acid attack, which increases the maintenance cost of rigid pavement. Therefore, a fly ash based geopolymer is proposed as a material for rigid pavement application as it releases lesser amounts of CO2 during the synthesis process and has higher acid resistance compared to OPC. This current study optimizes the formulation to produce fly ash based geopolymer with the highest compressive strength. In addition, the durability of fly ash based geopolymer concrete and OPC concrete in an acidic environment is also determined and compared. The results show that the optimum value of sodium hydroxide concentration, the ratio of sodium silicate to sodium hydroxide, and the ratio of solid-to-liquid for fly ash based geopolymer are 10 M, 2.0, and 2.5, respectively, with a maximum compressive strength of 47 MPa. The results also highlight that the durability of fly ash based geopolymer is higher than that of OPC concrete, indicating that fly ash based geopolymer is a better material for rigid pavement applications, with a percentage of compressive strength loss of 7.38% to 21.94% for OPC concrete. This current study contributes to the field of knowledge by providing a reference for future development of fly ash based geopolymer for rigid pavement applications.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103458
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3459: Effect of 3-Mercaptopropyltriethoxysilane
           Modified Illite on the Reinforcement of SBR

    • Authors: Zhepeng Wang, Hao Zhang, Qiang Liu, Shaojuan Wang, Shouke Yan
      First page: 3459
      Abstract: To achieve the sustainable development of the rubber industry, the substitute of carbon black, the most widely used but non-renewable filler produced from petroleum, has been considered one of the most effective ways. The naturally occurring illite with higher aspect ratio can be easily obtained in large amounts at lower cost and with lower energy consumption. Therefore, the expansion of its application in advanced materials is of great significance. To explore their potential use as an additive for reinforcing rubber, styrene butadiene rubber (SBR) composites with illites of different size with and without 3-mercaptopropyltriethoxysilane (KH580) modification were studied. It was found that the modification of illite by KH580 increases the K-illite/SBR interaction, and thus improves the dispersion of K-illite in the SBR matrix. The better dispersion of smaller size K-illite with stronger interfacial interaction improves the mechanical properties of SBR remarkably, by an increment of about nine times the tensile strength and more than ten times the modulus. These results demonstrate, except for the evident effect of particle size, the great importance of filler–rubber interaction on the performance of SBR composites. This may be of great significance for the potential wide use of the abundant naturally occurring illite as substitute filler for the rubber industry.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103459
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3460: Study on Hot Deformation Behavior of an
           Antibacterial 50Cr15MoVCu Tool Steel

    • Authors: Ziyuan Liu, Zhao Yang
      First page: 3460
      Abstract: Hot deformation behaviors of an antibacterial 50Cr15MoVCu tool steel were studied. The flow stress curves presented three typical characteristics: (i) a single peak dynamic recrystallization curve, (ii) a monotone incremental work-hardening curve, and (iii) the equilibrium dynamic recovery curve. The flow stress increased with the increase of the deformation rate at each deformation temperature and decreased with the increase of the deformation temperature at the same deformation rate. The thermal activation energy and material constants were Q of 461.6574 kJ/mol, A of 3.42 × 1017, and α of 0.00681 MPa−1, respectively. The high temperature constitutive equation was: Z= ε˙exp(Q/RT)=3.42 × 1017[sinh(0.0068 × σ)]5.6807. Based on the processing maps and microstructure evolution, the best hot working process was a deformation temperature of 1050 °C and deformation rate of 0.001 s−1.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103460
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3461: Management of Solid Waste Containing
           Fluoride—A Review

    • Authors: Małgorzata Olejarczyk, Iwona Rykowska, Włodzimierz Urbaniak
      First page: 3461
      Abstract: Technological and economic development have influenced the amount of post-production waste. Post-industrial waste, generated in the most considerable amount, includes, among others, waste related to the mining, metallurgical, and energy industries. Various non-hazardous or hazardous wastes can be used to produce new construction materials after the “solidification/stabilization” processes. They can be used as admixtures or raw materials. However, the production of construction materials from various non-hazardous or hazardous waste materials is still very limited. In our opinion, special attention should be paid to waste containing fluoride, and the reuse of solid waste containing fluoride is a high priority today. Fluoride is one of the few trace elements that has received much attention due to its harmful effects on the environment and human and animal health. In addition to natural sources, industry, which discharges wastewater containing F‒ ions into surface waters, also increases fluoride concentration in waters and pollutes the environment. Therefore, developing effective and robust technologies to remove fluoride excess from the aquatic environment is becoming extremely important. This review aims to cover a wide variety of procedures that have been used to remove fluoride from drinking water and industrial wastewater. In addition, the ability to absorb fluoride, among others, by industrial by-products, agricultural waste, and biomass materials were reviewed.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103461
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3462: Revealing Localised Mechanochemistry of
           Biomaterials Using In Situ Multiscale Chemical Analysis

    • Authors: Nicholas T.H. Farr
      First page: 3462
      Abstract: The study of mechanical and chemical phenomena arising within a material that is being subjected to external stress is termed mechanochemistry (MC). Recent advances in MC have revealed the prospect not only to enable a greener route to chemical transformations but also to offer previously unobtainable opportunities in the production and screening of biomaterials. To date, the field of MC has been constrained by the inability of current characterisation techniques to provide essential localised multiscale chemically mapping information. A potential method to overcome this is secondary electron hyperspectral imaging (SEHI). SEHI is a multiscale material characterisation technique applied within a scanning electron microscope (SEM). Based on the collection of secondary electron (SE) emission spectra at low primary beam energies, SEHI is applicable to the chemical assessment of uncoated polymer surfaces. Here, we demonstrate that SEHI can provide in situ MC information using poly(glycerol sebacate)-methacrylate (PGS-M) as an example biomaterial of interest. This study brings the use of a bespoke in situ SEM holder together with the application of SEHI to provide, for the first time, enhanced biomaterial mechanochemical characterisation.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103462
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3463: Changes in the Structural Composition and
           Moisture-Adsorption Properties of Mechanically Rolled Bamboo Fibers

    • Authors: Wenjuan Zhao, Jian Zhang, Wenfu Zhang, Jin Wang, Ge Wang
      First page: 3463
      Abstract: The chemical content, mechanical capability, and dimensional stability of bamboo fibers (BFs) are all directly related to the hygroscopic behavior, which is crucial for industrial applications. To support the utilization of BFs, the structural and chemical composition of BFs with different opening times after mechanical rolling were investigated in this study, and the Guggenheim–Anderson–de Boer (GAB) model was selected to predict their moisture-adsorption properties. The results showed that the length and diameter of the fibers gradually decreased with the increase in the number of openings, and the fibers gradually separated from bundles into single fibers. It was also observed that the treated BFs exhibited different equilibrium moisture contents (EMCs). BFs with a smaller number of openings had a higher hemicellulose content and more exposed parenchyma cells on the fibers, which increased the number of water adsorption sites. As the number of openings increased, the parenchyma cells on the fibers decreased, and the lignin content increased, which reduced the number of fiber moisture-adsorption sites and decreased the EMC of the fibers.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103463
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3464: Numerical Analysis of Mechanical
           Characteristics of Constant-Resistance, Energy-Absorbing and Anti-Scour
           Bolts

    • Authors: Zhi Tang, Hao Wu, Ying Liu, Yishan Pan, Jinguo Lv, Dezhi Chang
      First page: 3464
      Abstract: In order to improve the impact resistance mechanical properties of bolt, the requirements of rock burst roadway support must be met. Based on the requirements that the anchor should have a reasonable deformation load threshold, high stroke efficiency, constant reaction force and stable repeatable deformation damage mode. A constant resistance anti-impact device was designed, and a new constant resistance energy-absorbing impact anchor rod was designed in combination with a conventional anchor rod, and the working principle of a constant resistance energy-absorbing impact anchor rod was given. ABAQUS finite element software was used to analyze the mechanical properties of bolt and the results showed that the constant resistance energy-absorbing anti-shock anchor has a stable and repeatable deformation damage mode under both static and impact loads, and the three indexes of the constant resistance energy-absorbing anti-shock anchor, such as yield distance, impact resistance time and energy absorption, are significantly better than those of the conventional anchor. The impact energy and impact velocity have less influence on the load-bearing capacity and stroke efficiency of the impact device. The impact velocity has less influence on the indices of the rod yield load, breaking load, absorbed energy and the yield distance of a conventional anchor and constant resistance energy-absorbing anti-stroke anchor, and the impact resistance time decreases non-linearly with the increase in the impact velocity.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103464
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3465: Burst Pressure Prediction of Subsea
           Supercritical CO2 Pipelines

    • Authors: Yan Li, Wen Wang, Zhanfeng Chen, Weipeng Chu, Huijie Wang, He Yang, Chuanyong Wang, Yuxing Li
      First page: 3465
      Abstract: To improve transportation efficiency, a supercritical CO2 pipeline is the best choice for large-scale and long-distance transportation inshore and offshore. However, corrosion of the pipe wall will occur as a result of the presence of free water and other impurities present during CO2 capture. Defects caused by corrosion can reduce pipe strength and result in pipe failure. In this paper, the burst pressure of subsea supercritical CO2 pipelines under high pressure is investigated. First, a mechanical model of corroded CO2 pipelines is established. Then, using the unified strength theory (UST), a new burst pressure equation for subsea supercritical CO2 pipelines is derived. Next, analysis of the material’s intermediate principal stress parameters is conducted. Lastly, the accuracy of the burst pressure equation of subsea supercritical CO2 pipelines is proven to meet the engineering requirement by experimental data. The results indicate that the parameter b of UST plays a significant role in determining burst pressure of pipelines. The study can provide a theoretical basis and reference for the design of subsea supercritical CO2 pipelines.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103465
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3466: Numerical Analysis of Guided Waves to
           Improve Damage Detection and Localization in Multilayered CFRP Panel

    • Authors: Mastan Raja Papanaboina, Elena Jasiuniene, Egidijus Žukauskas, Liudas Mažeika
      First page: 3466
      Abstract: Multilayered carbon fiber-reinforced polymers (CFRP) are increasingly used in aircraft components because of their superior mechanical properties. However, composite materials are vulnerable to impact loads, resulting in delamination-type damage which, if unnoticed, could lead to catastrophic structural failure. The objective of this research was to investigate possibilities to improve damage detection and the localization using signal processing methods. Numerical modeling using the semi-analytical finite element (SAFE) method was performed to obtain guided wave dispersion curves and to perform modal analysis. From the modal analysis, mode for inspection of the composite with delamination type defects was selected. From the numerical simulation, mode interaction with delamination along the longitudinal direction was analyzed and the location of the defect was estimated by measuring the time of flight (ToF) of the signal using Hilbert transform (HT) and continuous wavelet transform (CWT). The CWT has shown better results in estimating the delamination location compared with HT. The depth of delamination was characterized in the frequency domain by comparing the amplitude of the mode. Inverse fast Fourier transform (IFFT) is recommended to reconstruct the reflected and transmitted modes for better damage detection and to reduce the complexity of signal interpretation.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103466
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3467: The Effect of Irrigation with Citric Acid
           on Biodentine Tricalcium Silicate-Based Cement: SEM-EDS In Vitro Study

    • Authors: Katarzyna Dąbrowska, Aleksandra Palatyńska-Ulatowska, Leszek Klimek
      First page: 3467
      Abstract: There are various factors that may interfere with the activity of biomaterials during endodontic therapy. One of them is the canal system irrigation procedure with different rinsing solutions performed after the placement of bioactive cements. The authors investigate the influence of citric acid, a chelating agent, on the surface and the chemical composition of Biodentine tricalcium silicate-based cement using a multimethod approach. Twenty samples were divided into two groups based on the material setting time. They were subjected to citric acid irrigation with or without ultrasonic activation for 5 and 20 min. The chemical analysis was made with energy dispersive spectroscopy (EDS). The visual assessment of Biodentine surface was carried out in scanning electron microscope (SEM). The volume of material loss during the procedure was measured with Keyence optic microscope and dedicated digital software. Statistical analysis was performed. The results of the study show that the irrigation with citric acid influenced the surface appearance of the material and changed its chemical composition in both investigated groups. The ultrasonic activation (US) of the liquid has also aggravated its impact. Further research is needed to assess if that fact may change the sealing properties of the material influencing the long-term clinical outcome.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103467
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3468: Additive Digital Casting: From Lab to
           Industry

    • Authors: Ena Lloret-Fritschi, Elia Quadranti, Fabio Scotto, Lukas Fuhrimann, Thibault Demoulin, Sara Mantellato, Lukas Unteregger, Joris Burger, Rafael G. Pileggi, Fabio Gramazio, Matthias Kohler, Robert J. Flatt
      First page: 3468
      Abstract: Concrete construction harms our environment, making it urgent to develop new methods for building with less materials. Structurally efficient shapes are, however, often expensive to produce, because they require non-standard formworks, thus, standard structures, which use more material than is often needed, remain cheaper. Digital fabrication has the potential to change this paradigm. One method is Digital Casting Systems (DCS), where the hydration of self-compacting concrete is controlled on the fly during production, shortening the required setting time and reducing hydrostatic pressure on the formwork to a minimum. This enables a productivity increase for standard concrete production. More importantly, though, it enables a rethinking of formworks, as the process requires only cheap thin formworks, thus, unlocking the possibility to produce optimised structural members with less bulk material and lower environmental cost. While DCS has already proven effective in building structural members, this process faces the challenge of moving into industry. This paper covers the next steps in doing so. First, we present the benchmark and expectations set by the industry. Second, we consider how we comply with these requirements and convert our fast-setting self-compacting mortar mix into a coarser one. Third, we present the next generation of our digital processing system, which moves closer to the industrial requirements in terms of size and the control system. Finally, two prototypes demonstrate how DSC: (a) increases standard bulk production by 50% and (b) can be cast into ultra-thin formworks. We discuss the results and the short-term industrial concerns for efficiency and robustness, which must be addressed for such a system to be fully implemented in industry.
      Citation: Materials
      PubDate: 2022-05-11
      DOI: 10.3390/ma15103468
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3469: Scale-Up and Testing of Polyurethane
           Bio-Foams as Potential Cryogenic Insulation Materials

    • Authors: Maria Kurańska, Ugis Cabulis, Aleksander Prociak, Krzysztof Polaczek, Katarzyna Uram, Mikelis Kirpluks
      First page: 3469
      Abstract: This article compares the properties of closed-cell PUR bio-foams produced on a laboratory scale and on an industrial scale. In the formulation used, the polyol premix contained 40 wt.% of a bio-polyol based on rapeseed oil. Selected useful properties of the foams obtained on the two scales and the use of one-step and spraying methods were compared. In the case of the spraying method, the experimental system was compared to a commercial one. Given the possibility of applying the bio-foams in insulation systems for cryogenic and liquefied natural gas (LNG) applications, a compressive strength analysis of the foams was carried out at room temperature as well as at −196 °C. It was found that the foams modified with the bio-polyol were characterized by a higher compressive strength at low temperatures than commercial foams based on a petrochemical polyol.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103469
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3470: Rubus ellipticus Sm. Fruit Extract
           Mediated Zinc Oxide Nanoparticles: A Green Approach for Dye Degradation
           and Biomedical Applications

    • Authors: Jyoti Dhatwalia, Amita Kumari, Ankush Chauhan, Kumari Mansi, Shabnam Thakur, Reena V. Saini, Ishita Guleria, Sohan Lal, Ashwani Kumar, Khalid Mujasam Batoo, Byung Hyune Choi, Amanda-Lee E. Manicum, Rajesh Kumar
      First page: 3470
      Abstract: Rubus ellipticus fruits aqueous extract derived ZnO-nanoparticles (NPs) were synthesized through a green synthesis method. The structural, optical, and morphological properties of ZnO-NPs were investigated using XRD, FTIR, UV-vis spectrophotometer, XPS, FESEM, and TEM. The Rietveld refinement confirmed the phase purity of ZnO-NPs with hexagonal wurtzite crystalline structure and p-63-mc space group with an average crystallite size of 20 nm. XPS revealed the presence of an oxygen chemisorbed species on the surface of ZnO-NPs. In addition, the nanoparticles exhibited significant in vitro antioxidant activity due to the attachment of the hydroxyl group of the phenols on the surface of the nanoparticles. Among all microbial strains, nanoparticles’ maximum antibacterial and antifungal activity in terms of MIC was observed against Bacillus subtilis (31.2 µg/mL) and Rosellinia necatrix (15.62 µg/mL), respectively. The anticancer activity revealed 52.41% of A549 cells death (IC50: 158.1 ± 1.14 µg/mL) at 200 μg/mL concentration of nanoparticles, whereas photocatalytic activity showed about 17.5% degradation of the methylene blue within 60 min, with a final dye degradation efficiency of 72.7%. All these results suggest the medicinal potential of the synthesized ZnO-NPs and therefore can be recommended for use in wastewater treatment and medicinal purposes by pharmacological industries.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103470
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3471: Effect of Sintering Temperature on
           Adhesion Property and Electrochemical Activity of Pt/YSZ Electrode

    • Authors: Jixin Wang, Jiandong Cui, Xiao Zhang, Wentao Tang, Changhui Mao
      First page: 3471
      Abstract: The (Pt/YSZ)/YSZ sensor unit is the basic component of the NOx sensor, which can detect the emission of nitrogen oxides in exhaust fumes and optimize the fuel combustion process. In this work, the effect of sintering temperature on adhesion property and electrochemical activity of Pt/YSZ electrode was investigated. Pt/YSZ electrodes were prepared at different sintering temperatures. The microstructure of the Pt/YSZ electrodes, as well as the interface between Pt/YSZ electrode and YSZ electrolyte, were observed by SEM. Chronoamperometry, linear scan voltammetry, and AC impedance were tested by the electrochemical workstation. The results show that increasing the sintering temperature (≤1500 °C) helped to improve adhesion property and electrochemical activity of the Pt/YSZ electrode, which benefited from the formation of the porous structure of the Pt/YSZ electrode. For the (Pt/YSZ) electrode/YSZ electrolyte system, O2− in YSZ is converted into chemisorbed O2 on Pt/YSZ, which is desorbed into the gas phase in the form of molecular oxygen; this process could be the rate-controlling step of the anodic reaction. Increasing the sintering temperature (≤1500 °C) could reduce the reaction activation energy of the Pt/YSZ electrode. The activation energy reaches the minimum value (1.02 eV) when the sintering temperature is 1500 °C.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103471
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3472: Finger Bending Sensing Based on
           Series-Connected Fiber Bragg Gratings

    • Authors: Qijing Lin, Kun Yao, Na Zhao, Yunjing Jiao, Zelin Wang, Bian Tian, Libo Zhao, Gangding Peng, Zhuangde Jiang
      First page: 3472
      Abstract: Smart wearable devices are occupying an increasingly important position in scientific research and people’s life fields. As an indispensable component of smart wearable devices, sensors play a crucial role in their sensing and feedback capabilities. In this paper, we investigate the bending gesture sensing for the most dexterous part of human anatomy, the finger. Based on series-connected fiber Bragg gratings (FBGs), recognition of finger bending posture is achieved by MATLAB modeling and the cubic spline interpolation.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103472
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3473: Future Trends in Endodontics: How Could
           Materials Increase the Long-Term Outcome of Root Canal Therapies'

    • Authors: Alessio Zanza, Rodolfo Reda, Francesco Pagnoni, Shankargouda Patil
      First page: 3473
      Abstract: The goals of endodontic therapies are the prevention or the elimination of apical periodontitis of endodontic origin, ensuring the stability of results over time in order to avoid the recurrence of the disease and preventing teeth from requiring extraction [...]
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103473
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3474: Synthesis of High Crystallinity 1.13 nm
           Tobermorite and Xonotlite from Natural Rocks, Their Properties and
           Application for Heat-Resistant Products

    • Authors: R. Siauciunas, G. Smalakys, A. Eisinas, E. Prichockiene
      First page: 3474
      Abstract: The main measure to reduce energy losses is the usage of insulating materials. When the temperature exceeds 500 °C, silicate and ceramic products are most commonly used. In this work, high-crystallinity 1.13 nm tobermorite and xonotlite were hydrothermally synthesized from lime and Ca–Si sedimentary rock, opoka. By XRD, DSC, TG and dilatometry methods, it has been shown that 1.13 nm tobermorite becomes the predominant compound in stirred suspensions at 200 °C after 4 h of synthesis in the mixture with a molar ratio CaO/SiO2 = 0.83. It is suitable for the production of insulating products with good physical–mechanical properties (average density < 200 kg·m−1, compressive strength ~0.9 MPa) but has a limited operating temperature (up to 700 °C). Sufficiently pure xonotlite should be used to obtain materials with a higher operating temperature. Even small amounts of semi-amorphous C–S–H(I) significantly increase its linear shrinkage during firing. It has also been observed that an increase in the strength values of the samples correlated well with the increase in the size of xonotlite crystallites. The optimal technological parameters are as follows: molar ratio of mixture CaO/SiO2 = 1.2; water/solid ratio W/S = 20.0; duration of hydrothermal synthesis at 220 °C—8 h, duration of autoclaving at 220 °C—4 h. The average density of the samples was ~180 kg·m−1, the operating temperature was at least 1000 °C, and the compressive strengths exceeded 1.5 MPa.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103474
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3475: Manufacturing of Complex
           Silicon–Carbon Structures: Exploring SixCy Materials

    • Authors: Skyler Oglesby, Sergei A. Ivanov, Alejandra Londonõ-Calderon, Douglas Pete, Michael Thompson Pettes, Andrew Crandall Jones, Sakineh Chabi
      First page: 3475
      Abstract: This paper reports on the manufacturing of complex three-dimensional Si/C structures via a chemical vapor deposition method. The structure and properties of the grown materials were characterized using various techniques including scanning electron microscopy, aberration-corrected transmission electron microscopy, confocal Raman spectroscopy, and X-ray photoelectron spectroscopy. The spectroscopy results revealed that the grown materials were composed of micro/nanostructures with various compositions and dimensions. These included two-dimensional silicon carbide (SiC), cubic silicon, and various SiC polytypes. The coexistence of these phases at the nano-level and their interfaces can benefit several Si/C-based applications ranging from ceramics and structural applications to power electronics, aerospace, and high-temperature applications. With an average density of 7 mg/cm3, the grown materials can be considered ultralightweight, as they are three orders of magnitude lighter than bulk Si/C materials. This study aims to impact how ceramic materials are manufactured, which may lead to the design of new carbide materials or Si/C-based lightweight structures with additional functionalities and desired properties.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103475
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3476: Effects of Fused Silica Addition on
           Thermal Expansion, Density, and Hardness of Alumix-231 Based Composites

    • Authors: Luciano M. Rodrigues, Bojan A. Marinkovic
      First page: 3476
      Abstract: Fused silica is a ceramic with promising applications as a filler in composites due to its near-zero thermal expansion. Substitution of heavy cast iron with Al-based light alloys is of utmost importance for the automotive industry. However, the high thermal expansion of Al alloys is an obstacle to their use in some applications. As such, ceramic fillers are natural candidates for tuning thermal expansion of Al-based matrices, due to their inherently moderate or low thermal expansion. Alumix-231 is a new promising alloy, and fused silica has never been used before to lower its thermal expansion. Composites with the addition of 5 to 20 vol.% of fused silica were developed through powder metallurgy, and the best results in terms of reduction of thermal expansion were reached after liquid phase sintering at 565 °C. Coefficients of thermal expansion as low as 13.70 and 12.73 × 10−6 °C−1 (between 25 and 400 °C) were reached for the addition of 15 and 20 vol.% of fused silica, a reduction of 29.9% and 34.8%, respectively, in comparison to neat Alumix-231. In addition, the density and hardness of these composites were not significantly affected, since they suffered only a small decrease, no higher than 6% and 5%, respectively. As such, the obtained results showed that Alumix-231/fused silica composites are promising materials for automotive applications.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103476
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3477: Hydration and Mechanical Properties of
           

    • Authors: Daolin Wang, Qinli Zhang, Yan Feng, Qiusong Chen, Chongchun Xiao, Hongpeng Li, Yujing Xiang, Chongchong Qi
      First page: 3477
      Abstract: The application of granulated copper slag (GCS) to partially replace cement is limited due to its low pozzolanic activity. In this paper, reconstituted granulated copper slag (RGCS) was obtained by adding alumina oxide (Al2O3) to liquid copper slag. Blended cement pastes were formulated by a partial substitute for ordinary Portland cement (OPC) with the RGCS (30 wt%). The pozzolanic activity, mechanical development, and the microstructure were characterized. The results show that 5–10 wt% Al2O3 contributes to the increase in magnetite precipitation in RGCS. The addition of Al2O3 alleviates the inhibition of C3S by RGCS and accelerates the dissociation of RGCS active molecules, thus increasing the exothermic rate and cumulative heat release of the blended cement pastes, which are the highest in the CSA10 paste with the highest Al2O3 content (10 wt%) in RGCS. The unconfined compressive strength (UCS) values of blended cement mortar with 10 wt% Al2O3 added to RGCS reach 27.3, 47.4, and 51.3 MPa after curing for 7, 28 and 90 d, respectively, which are the highest than other blended cement mortars, and even exceed that of OPC mortar at 90 d of curing. The pozzolanic activity of RGCS is enhanced with the increase in Al2O3 addition, as evidenced by more portlandite being consumed in the CSA10 paste, forming more C-S-H (II) gel with a higher Ca/Si ratio, and a more compact microstructure with fewer pores than other pastes. This work provided a novel, feasible, and clean way to enhance the pozzolanic activity of GCS when it was used as a supplementary cementitious material.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103477
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3478: Prediction of Mechanical Properties of
           Fly-Ash/Slag-Based Geopolymer Concrete Using Ensemble and Non-Ensemble
           Machine-Learning Techniques

    • Authors: Muhammad Nasir Amin, Kaffayatullah Khan, Muhammad Faisal Javed, Fahid Aslam, Muhammad Ghulam Qadir, Muhammad Iftikhar Faraz
      First page: 3478
      Abstract: The emission of greenhouse gases and natural-resource depletion caused by the production of ordinary Portland cement (OPC) have a detrimental effect on the environment. Thus, an alternative means is required to produce eco-friendly concrete such as geopolymer concrete (GPC). However, GPC has a complex cementitious matrix and an ambiguous mix design. Aside from that, the composition and proportions of materials utilized may have an impact on the compressive strength. Similarly, the use of robust and efficient machine-learning (ML) approaches is now required to forecast the strength of such a composite cementitious matrix. As a result, this study anticipated the compressive strength of GPC with waste resources using ensemble and non-ensemble ML algorithms. This was accomplished through the use of Anaconda (Python). To build a strong ensemble learner by integrating weak learners, adaptive boosting, random forest (RF), and ensemble learner bagging were employed. Furthermore, ensemble learners were utilized on non-ensemble or weak learners, such as decision trees (DT) and support vector machines (SVM) via regression. The data encompassed 156 statistical samples in which nine variables, namely superplasticizer (kg/m3), fly ash (kg/m3), ground granulated blast-furnace slag (GGBS), temperature (°C), coarse and fine aggregate (kg/m3), sodium silicate (Na2SiO3), and sodium hydroxide (NaOH), were chosen to anticipate the results. Exploring it in depth, twenty sub-models with ensemble boosting and bagging approaches were trained, and tuning was performed to achieve the highest possible coefficient of determination (R2). Moreover, cross K-Fold validation analysis and statistical checks were performed via indicators for the evaluation of the models. The result revealed that ensemble approaches yielded robust performance compared to non-ensemble algorithms. Generally, an ensemble learner with the RF and bagging approach on a DT yielded robust performance by achieving a better R2 as 0.93, and with the lowest statistical errors. The communal model in artificial-intelligence analysis, on average, improved the accuracy of the model.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103478
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3479: Composite Materials Based on Gelatin and
           Iron Oxide Nanoparticles for MRI Accuracy

    • Authors: Mioara Drobota, Stelian Vlad, Luiza Madalina Gradinaru, Alexandra Bargan, Iulian Radu, Maria Butnaru, Cristina Mihaela Rîmbu, Romeo Cristian Ciobanu, Magdalena Aflori
      First page: 3479
      Abstract: The majority of recent studies have focused on obtaining MRI materials for internal use. However, this study focuses on a straightforward method for preparing gelatin-based materials with iron oxide nanoparticles (G–Fe2O3 and G–Fe3O4) for external use. The newly obtained materials must be precisely tuned to match the requirements and usage situation because they will be in close touch with human/animal skin. The biocompatible structures formed by gelatin, tannic acid, and iron oxide nanoparticles were investigated by using FTIR spectroscopy, SEM-EDAX analysis, and contact angle methods. The physico-chemical properties were obtained by using mechanical investigations, dynamic vapor sorption analysis, and bulk magnetic determination. The size and shape of iron oxide nanoparticles dictates the magnetic behavior of the gelatin-based samples. The magnetization curves revealed a typical S-shaped superparamagnetic behavior which is evidence of improved MRI image accuracy. In addition, the MTT assay was used to demonstrate the non-toxicity of the samples, and the antibacterial test confirmed satisfactory findings for all G-based materials.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103479
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3480: Advances in Permanent Deformation Modeling
           of Asphalt Concrete—A Review

    • Authors: Mequanent Mulugeta Alamnie, Ephrem Taddesse, Inge Hoff
      First page: 3480
      Abstract: Permanent deformation is one of the dominant asphalt concrete damages. Significant progress has been made to realistically predict the damage. In the last decade, the mechanistic approach has been the focus of research, and the fundamental theories of viscoelasticity, viscoplasticity, continuum mechanics, and micromechanics are applied to develop the material laws (constitutive equations). This paper reviews the advancement of permanent deformation models including analogical, microstructural, and continuum-based methods. Pavement analysis using the nonlinear damage approach (PANDA) is the most comprehensive and theoretically sound approach that is available in the literature. The model coupled different damages and other phenomena (such as cracking, moisture, and phenomena such as healing, aging, etc.). The anisotropic microstructure approach can be incorporated into the PANDA approach for a more realistic prediction. Moreover, the interaction of fatigue and permanent deformation is the gap that is lacking in the literature. The mechanistic approaches have the capacity to couple these damages for unified asphalt concrete damage prediction.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103480
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3481: Using the Smith-Watson-Topper Parameter
           and Its Modifications to Calculate the Fatigue Life of Metals: The
           State-of-the-Art

    • Authors: Tadeusz Łagoda, Sabrina Vantadori, Karolina Głowacka, Marta Kurek, Krzysztof Kluger
      First page: 3481
      Abstract: The Smith-Watson-Topper parameter (SWT) in its original form was designed to estimate the fatigue life of metal materials in a uniaxial load state (tension–compression) in the range up to fatigue crack initiation, with non-zero mean values. This parameter is based on the analysis of both stress and strain. Therefore, the stress–strain criterion is the focus, rather than the energy criterion. This paper presents the original SWT model and its numerous modifications. The first part presents different versions of this parameter defined by the normal parameters. Then, it presents versions defined through the tangent parameter and the most promising parameter defined through the tangent and normal parameters. It was noted that the final form of the equivalent value is defined either by stress or by an energy parameter. Therefore, the possible characteristics from which the fatigue life can be determined are also presented.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103481
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3482: Spatial Dispersion in Hypercrystal
           Distributed Feedback Lasing

    • Authors: Bartosz Janaszek, Paweł Szczepański
      First page: 3482
      Abstract: This work is a first approach to investigate the role of spatial dispersion in photonic hypercrystals (PHCs). The scope of the presented analysis is focused on exploiting nonlocality, which can be controlled by appropriate design of the structure, to obtain new light generation effects in a distributed feedback (DFB) laser based on PHC, which are not observable under weak spatial dispersion. Here, we use effective medium approximation and our original model of threshold laser generation based on anisotropic transfer matrix method. To unequivocally identify nonlocal generation phenomena, the scope of our analysis includes comparison between local and nonlocal threshold generation spectra, which may be obtained for different geometries of PHC structure. In particular, we have presented that, in the presence of strong spatial dispersion, it is possible to obtain spectrally shifted Bragg wavelengths of TE- and TM-polarization spectra, lowered generation threshold levels for both light polarizations, generation of light of selected light polarization (TE or TM), or simultaneous generation of TE- and TM-polarized waves at different frequencies with controllable spectral separation, instead of single mode operation anticipated with local approach.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103482
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3483: Spin Polarization of Mn Could Enhance
           Grain Boundary Sliding in Mg

    • Authors: Vei Wang, Jun-Ping Du, Hidetoshi Somekawa, Shigenobu Ogata, Wen Tong Geng
      First page: 3483
      Abstract: Segregation of rare earth alloying elements are known to segregate to grain boundaries in Mg and suppress grain boundary sliding via strong chemical bonds. Segregation of Mn, however, has recently been found to enhance grain boundary sliding in Mg, thereby boosting its ductility. Taking the Mg (2¯114) twin boundary as an example, we performed a first-principles comparative study on the segregation and chemical bonding of Y, Zn, and Mn at this boundary. We found that both Y-4d and Mn-3d states hybridized with the Mg-3sp states, while Zn–Mg bonding was characterized by charge transfer only. Strong spin-polarization of Mn pushed the up-spin 3d states down, leading to less anisotropic Mn–Mg bonds with more delocalized charge distribution at the twin boundary, and thus promotes grain boundary plasticity, e.g., grain boundary sliding.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103483
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3484: Response Surface of Speed-Loading Path to
           Grain Refinement during Current-Heating Compression at SAE 5137H Steel

    • Authors: Guo-Zheng Quan, Kun Yang, Yan-Ze Yu, Xue Sheng, Zhi-Hang Wen, Chao-Long Lu
      First page: 3484
      Abstract: In thermal deformation of materials, grain refinement induced by dynamic recrystallization (DRX) is often pursued to obtain excellent mechanical properties. Here, the thermal deformation behaviors of SAE 5137H steel were investigated and characterized at temperature and strain rate range of 1123–1483 K and 0.01–10 s−1. Meanwhile, a design approach in speed-loading paths for grain refinement during current-heating compression was proposed, and these paths are linked to a typical three-dimensional (3D) response surface. Depending on the acquired stress–strain curves, the flow behaviors of this steel were analyzed and the typical 3D processing map was constructed to clarify the stable processing parameter domains during the continuous deformation process. Then, by the typical 3D processing map and microstructure observation, the 3D deformation mechanism map was constructed to connect the processing parameters and microstructural mechanisms. Subsequently, the 3D activation energy map was constructed to evaluate these deformation mechanisms, and the enhanced deformation mechanism map was constructed. Eventually, based on the enhanced deformation mechanism map, the speed-loading paths for SAE 5137H steel during current-heating compression were designed and they are mapped in a 3D response surface.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103484
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3485: Numerical Study of the Optimum Fiber
           Content of Sealing Grease Using Discrete Element Method

    • Authors: Xiong Zhou, Yingjie Wei, Yuyou Yang, Pengfei Xu
      First page: 3485
      Abstract: A sealing grease plays a crucial role in the sealing of shield tails. Its pumpability and pressure sealing resistant sealing performance are greatly affected by the fiber content. In this study, discrete element method models were used to simulate the pressure-resistant tests of sealing grease in order to investigate the influence of viscosity grade and fiber’s aspect ratio on the optimum fiber content of sealing grease. Meanwhile, the rationality of the optimum fiber number determined based on the sealing performance was verified with the unbalanced force and fiber area proportion obtained in the simulation, of which the variation curves with the increasing fiber number were practically identical. The simulation results elucidated that the viscosity of grease had little effect on the optimum fiber content for sealing grease. However, the increase in viscosity can improve the sealing effect, and increasing the fiber’s aspect ratio can reduce the fiber number to reach a specific seal state. Based on the analysis of the total number of fiber spheres for the models with different fiber’s respect ratios, it can be concluded that the sealing grease sample made of the same fiber material and quality can reach the same seal state and seal effect, independent on fiber’s aspect ratio.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103485
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3486: Acoustic Emission Monitoring of
           Progressive Damage of Reinforced Concrete T-Beams under Four-Point Bending
           

    • Authors: Deba Datta Mandal, Mourad Bentahar, Abderrahim El Mahi, Alexandre Brouste, Rachid El Guerjouma, Silvio Montresor, François-Baptiste Cartiaux
      First page: 3486
      Abstract: Acoustic Emission (AE) is revealed to be highly adapted to monitor materials and structures in materials research and for site monitoring. AE-features can be either analyzed by means of physical considerations (geophysics/seismology) or through their time/frequency waveform characteristics. However, the multitude of definitions related to the different parameters as well as the processing methods makes it necessary to develop a comparative analysis in the case of a heterogeneous material such as civil engineering concrete. This paper aimed to study the micro-cracking behavior of steel fiber-reinforced reinforced concrete T-beams subjected to mechanical tests. For this purpose, four-points bending tests, carried out at different displacement velocities, were performed in the presence of an acoustic emission sensors network. Besides, a comparison between the sensitivity to damage of three definitions corresponding to the b-value parameter was performed and completed by the evolution of the RA-value and average frequency (AF) as a function of loading time. This work also discussed the use of the support-vector machine (SVM) approach to define different damage zones in the load-displacement curve. This work shows the limits of this approach and proposes the use of an unsupervised learning approach to cluster AE data according to physical and time/frequency parameters. The paper ends with a conclusion on the advantages and limitations of the different methods and parameters used in connection with the micro/macro tensile and shear mechanisms involved in concrete cracking for the purpose of in situ monitoring of concrete structures.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103486
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3487: Green Deal and Circular Economy of Bottom
           Ash Waste Management in Building Industry—Alkali (NaOH)
           Pre-Treatment

    • Authors: Nikolina Poranek, Beata Łaźniewska-Piekarczyk, Lidia Lombardi, Adrian Czajkowski, Magdalena Bogacka, Krzysztof Pikoń
      First page: 3487
      Abstract: This study aims to investigate the possibilities of municipal waste incineration bottom ash (MSWIBA) utilization in the construction sector. MSWIBA development fits into the European Green Deal, Sustainable Development Goals (SDGs), and the Circular Economy (CE). This manuscript describes current MSWIBA treatment such as solidification, ceramization, vitrification, chemical activation (NaOH, CaOH2, NA2SiO3 + NaOH, Na2CO3 + NaOH, NH4OH), acid treatment with diluted solutions (HCl, H2SO4), chemical stabilization (FeSO4, PO43−), chelation, etc. For the purpose of comparative research, MSWIBA before valorization, after valorization, and after NaOH pre-treatment was investigated. In terms of their physico-chemical properties, the tested samples were examined. Three kinds of MSWIBA were used as a substitute for 30% of cement in mortars. The mortars were tested for 28-day strength. Leachability tests were performed in acid, aggressive, alkali, and neutral water environments. Life Cycle Assessment (LCA) analysis was carried out, which presented the environmental benefits of MSWIBA management in construction.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103487
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3488: Layered Perovskites BaM2In2O7 (M = La,
           Nd): From the Structure to the Ionic (O2−, H+) Conductivity

    • Authors: Nataliia Tarasova, Anzhelika Galisheva, Irina Animitsa, Ksenia Belova, Anastasia Egorova, Ekaterina Abakumova, Dmitry Medvedev
      First page: 3488
      Abstract: The design of new oxide compounds that can be used as oxygen- or proton-conducting electrolytes for solid oxide fuel cells is actively in progress. Despite the intensive research activities regarding electrolytes with perovskite/fluorite structures, the search for other structural alternatives is of paramount importance. In this study we focus on a novel material with significantly improved properties for the electrochemical purposes. The two-layered BaNd2In2O7 perovskite with a Ruddlesden–Popper structure was investigated as a protonic conductor for the first time. In detail, its local structure, water uptake, and the ionic (O2−, H+) conductivity were comprehensively studied. The nature of rare-earth elements (M = La, Nd) in the structure of BaM2In2O7 on the structural and transport properties was revealed. The presented analysis showed that the composition of BaNd2In2O7 is nearly pure proton conductor below 350 °C. This work opens up a new way in the design of protonic conductors with double-layered perovskite structure.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103488
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3489: Effect of Annealing Process on the
           Microstructure and Texture of Cold-Rolled High-Purity Al-0.5%Cu Plates

    • Authors: Kuiwen Yuan, Jiaxin Chen, Dan Yang, Zhiqing Zhang
      First page: 3489
      Abstract: As a kind of typical high stacking fault energy materials, recrystallization behavior of high purity Al-0.5%Cu alloy is significantly influenced by the annealing process. In this study, different heating rate, target temperature, and holding time were discovered to have profound impact on the microstructures and textures of Al-0.5%Cu plates. Electron backscatter diffraction (EBSD), scanning electron microscope (SEM), and X-ray diffraction (XRD) were utilized for analyzing the evolution of the microstructure and texture in the subsequent microstructural characterization. Vickers hardness tests were employed for measuring hardness of specimens. The results showed that no obvious recrystallization was observed at lower temperature and the composition of texture influenced by rising temperature, heating rate affected initial recrystallization temperature, grain size, and strength of textures. After recrystallizing completely, the size of microstructures and the distribution of textures had little change with the extension of holding time.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103489
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3490: Plutonic Rocks as Protection Layers to
           Concrete Exposed to Ultra-High Temperature

    • Authors: Fernando França de Mendonça Filho, Cláudia Romero Rodriguez, Erik Schlangen, Oğuzhan Çopuroğlu
      First page: 3490
      Abstract: Concrete structures perform poorly when withstanding thermal shock events, usually requiring repair or replacement after one single instance. In certain industries (such as petrol, metallurgic and ceramics), these events are not only likely but frequent, which represents a considerable financial burden. One option to solve this issue would be to decrease the heating rate imposed onto the concrete material through the use of a protective surface layer. In this work, the suitability of dunite and microgabbro as protective materials is explored through X-ray diffraction, thermal dilation, optical microscopy, X-ray microtomography, thermo-gravimetric analysis and a compressive test. Further, the thermal dilation was used as an input to simulate a composite concrete-rock wall and the respective stresses caused by a thermal shock event. The dehydration of chrysotile in dunite and the decomposition of analcime, chamosite and pumpellyite in microgabbro were both favourable for the performance of the stones in the desired application. The thermal stability and deformation were found in the range of what can be applied directly on concrete; however, it was clear that pre-heating treatment results in a far more durable system in a cyclic thermal load situation.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103490
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3491: Comparative Analysis of Strength and
           Deformation Behavior of Cemented Tailings Backfill under Curing
           Temperature Effect

    • Authors: Zheng Pan, Keping Zhou, Yunmin Wang, Yun Lin, Fahad Saleem
      First page: 3491
      Abstract: Mineral resources are increasingly being developed in cold and permafrost regions. However, the mechanical and physical properties of cemented tailings backfill (CTB) cured at normal temperature are no longer applicable. To clarify the reasons for this variability, a series of tests were performed. The mechanical properties of CTB with different cement–tailings ratios (CTR, 1:4, 1:8, 1:12, 1:16, and 1:20) were tested at different curing ages (3, 7 and 28 days) and curing temperatures (20 °C, 5 °C, −5 °C, and −20 °C). The differences of CTB in mechanical and physical properties under positive- and negative-temperature curing conditions were analyzed, and the microscopic failure process of CTB under negative-temperature curing conditions was discussed. The results revealed that the mechanical properties and deformation behavior of CTB under positive- and negative-temperature curing conditions were different. The frozen CTB had higher early strength than the standard-temperature curing condition (20 °C), and the lower the temperature, the higher the early strength. The low-temperature curing condition, on the other hand, was not beneficial to CTB’s long-term strength. The low-temperature curing condition was not conducive to the long-term strength of CTB. After yielding, strain hardening and strain softening appeared in the deformation behavior of frozen backfill, indicating ductility. In contrast to the typical-temperature curing condition, the frozen CTB showed a new failure pattern that has little relation to curing time or CTR. Furthermore, the failure process of frozen backfill was reviewed and studied, which was separated into four stages, and altered as the curing time increased. The results of this study can act as a guide for filling mines in permafrost and cold climates.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103491
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3492: Special Issue: Materials, Design and
           Process Development for Additive Manufacturing

    • Authors: Vadim Sufiiarov
      First page: 3492
      Abstract: Additive manufacturing is a dynamically developed direction of modern digital manufacturing processes, which in some cases is already being used to create high-tech products, and in others there are active investigation on new materials and the design and development of technological processes [...]
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103492
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3493: Wave Dissipation and
           Energy−Absorption Characteristics of Wave−Absorbing Metal
           Plates with Different Aperture Sizes and Thicknesses under
           True−Triaxial Static−Dynamic−Coupling Loading

    • Authors: Linqi Huang, Xin Wu, Sijian Zeng, Xibing Li
      First page: 3493
      Abstract: Deep rock masses exist in a complex environment with multi−field coupling; therefore, it is necessary to develop a true−triaxial static−dynamic−coupling loading test machine to explore their characteristics and mechanical response mechanism. To meet the test requirements of true−triaxial loading and strong disturbance, a wave−absorbing metal plate was selected as the boundary material between the granite and transmission end, and the modified SHPB was used to perform static−dynamic−coupling loading tests. In this study, two series of experiments on wave− absorbing metal plates were conducted, which were fixed aperture sizes with different thicknesses and fixed thicknesses with different aperture sizes. The static−dynamic−coupling loading tests on each aperture size and plate thickness were carried out under the condition of equal energy impact. The effects of the aperture size and plate thickness on the incident− and reflection−stress curves, reflectivity, energy consumption law, energy evolution, and other mechanical properties of the wave−absorbing metal plate materials were studied. The results show that the peak stress and reflectivity decrease with increasing aperture size and plate thickness, and the influence of the thickness is greater than that of the aperture size. The energy−absorption rate of the wave−absorbing metal plate increased with increasing thickness and aperture size and was maximized when the aperture size and thickness were 6–7 mm and 3–4 mm, respectively. The variation trend of the energy reflectance is opposite to that of the energy absorption and reaches a minimum when the aperture size is 6–7 mm and plate thickness is 3–4 mm. The energy transmittance of the wave−absorbing metal plate fluctuated in a stable range, but the variation range was less obvious compared to that of the energy−absorption rate.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103493
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3494: Peridynamic Simulation of Dynamic Fracture
           Process of Engineered Cementitious Composites (ECC) with Different Curing
           Ages

    • Authors: Weiye Hou, Yuyang Hu, Chengfang Yuan, Hu Feng, Zhanqi Cheng
      First page: 3494
      Abstract: The mechanical properties of engineered cementitious composites (ECC) are time-dependent due to the cement hydration process. The mechanical behavior of ECC is not only related to the matrix material properties, but also to the fiber/matrix interface properties. In this study, the modeling of fiber and fiber/matrix interactions is accomplished by using a semi-discrete model in the framework of peridynamics (PD), and the time-varying laws of cement matrix and fiber/matrix interface bonding properties with curing age are also considered. The strain-softening behavior of the cement matrix is represented by introducing a correction factor to modify the pairwise force function in PD theory. The fracture damage of ECC plate from 3 to 28 days was numerically simulated by using the improved PD model to visualize the process of damage fracture under dynamic loading. The shorter the hydration time, the lower the corresponding elastic modulus, and the smaller the number of cracks generated. The dynamic fracture process of early-age ECC is analyzed to understand the crack development pattern, which provides reference for guiding structural design and engineering practice.
      Citation: Materials
      PubDate: 2022-05-12
      DOI: 10.3390/ma15103494
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3495: Prediction of Deformation-Induced
           Martensite Start Temperature by Convolutional Neural Network with Dual
           Mode Features

    • Authors: Chenchong Wang, Da Ren, Yong Li, Xu Wang, Wei Xu
      First page: 3495
      Abstract: Various models were established for deformation-induced martensite start temperature prediction over decades. However, most of them are empirical or considering limited factors. In this research, a dual mode database for medium Mn steels was established and a convolutional neural network model, which considered all composition, critical processing information and microstructure images as inputs, was built for Msσ prediction. By comprehensively considering composition, processing and microstructure factors, this model was more rational and much more accurate than traditional thermodynamic models. Also, by the full use of images information, this model has stronger ability to overcome overfitting compared with various traditional machine learning models. This framework provides inspiration for the similar data analysis issues with small sample datasets but different data modes in the field of materials science.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103495
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3496: Innovation Process for Optical Face
           Scanner Used to Customize 3D Printed Spectacles

    • Authors: Cristian Gabriel Alionte, Liviu Marian Ungureanu, Tudor Mihai Alexandru
      First page: 3496
      Abstract: Many people for different reasons end up wearing glasses to correct their vision. From time immemorial, there has been an unquestionable ability to associate people with glasses. Designing the glasses according to the physiognomy of each person opens a new path for a completely new optical experience. The frames are designed to fit perfectly on the face, are comfortable on the nose, and are positioned at an optimal distance from the cheeks and eyelashes. Three-dimensional printing technology offers the possibility to customize any form of glasses at a low cost with average quality. In this type of technology, the printer receives a digitized model of the spectacle frame (usually in STL file format) that must meet the parameters related to the wearer’s anatomy. Therefore, this paper presents an innovative process, an optical method used to scan the wearer’s face to design a parameterized design of the spectacle frames. The procedure has a measurement phase for quantifying the anatomical features of the wearer’s face, a para-metric design phase of the glasses for adjusting the design parameters according to the anatomical characteristics, and a manufacturing phase in which the custom eyeglass frame will be manufactured using 3D printing technology. The aim of this study was to create an innovative process that could be tested as an educational 3D printing system that could be used by undergraduate students (studying under an optometry program), a process that would begin at optometric prescription stage and can be used in the educational laboratory of the Department of Mechatronics and Precision Mechanics from the Politehnica University of Bucharest. Using this method we obtained a custom spectacle frame that can be prototyped using 3D printing. The 3D-printed polylactic acid (PLA) frames are lightweight, flexible, durable, and the innovative photogrammetry process gives designers the ability to create custom designs that cannot be created with traditional manufacturing techniques.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103496
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3497: Strength Tests of Alloys for Fixed
           Structures in Dental Prosthetics

    • Authors: Łukasz Bojko, Anna M. Ryniewicz, Wojciech Ryniewicz
      First page: 3497
      Abstract: The production of fixed prosthetic restorations requires strength identification in terms of cognition and the targeted clinical applications. The aim of the study is to evaluate the static strength in axial tensile and compression tests of titanium and cobalt alloys for the supporting foundations of crowns and bridges produced using Computer Aided Design and Manufacturing (CAD/CAM) technologies: Direct Metal Laser Sintering (DMLS) and milling. The test materials are samples of Ti6Al4V and CoCrMo alloys obtained using digital technologies and, for comparison purposes, CoCrMo samples from traditional casting. For the studied biomedical alloys, R0.05, Rp0.2, Rm and Ru were determined in the tensile tests, and in the compression tests R0.01, Rp0.2 and the stress σ at the adopted deformation threshold. Tensile and compression tests of titanium and cobalt alloys indicate differences in strength parameters resulting from the technology applied. The manufacturing of the structures by DMLS provides the highest stress values that condition elastic deformations for cobalt biomaterials: R0.05 = 1180 MPa, R0.01 = 1124 MPa and for titanium biomaterials: R0.05 = 984 MPa, R0.01 = 958 MPa. The high resistance to deformation of CoCrMo and Ti6Al4V from DMLS may be beneficial for fixed prosthetic structures subjected to biomechanical stresses in the stomatognathic system and the impact of these structures on the dento-alveolar complex.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103497
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3498: Multi-Layer Simulation of the Powder Bed
           Selective Laser Processing of Alumina for Residual Stress and Distortion
           Evaluation

    • Authors: Mohamed Abdelmoula, Gökhan Küçüktürk
      First page: 3498
      Abstract: A numerical model was developed to simulate the real process of alumina powder bed selective laser processing (PBSLP) to thoroughly investigate the residual stress and distortion experienced in printed parts when multi-layer scanning with a CO2 laser source is considered. The model contains a user-defined function (UDF) for the laser source, temperature-dependent material properties, scanning strategies, and build orientations, and it is solved using ANSYS 2020R2. In addition, the model’s validation was confirmed with experimental results. The results revealed that a high scanning speed (up to 1200 mm/s) and low laser power are effective for the PBSLP of alumina, owing to alumina’s high absorptivity for CO2 lasers, and a high manufacturing rate can be achieved. During the multi-layer printing simulation, the accumulated heat inside the part increased gradually with an increased number of printed layers. Additionally, the calculated residual stress exceeded the yield limit for all the studied build orientations due to the printed part’s high-temperature difference. When preheating was applied, the residual stress decreased by 23% and the distortion decreased by 54%. For the successful PBSLP of ceramics, commercial printers cannot be used effectively. A particular printer equipped with a temperature controller and a preheating system is required for ceramics.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103498
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3499: Artificial Anisotropy in Ge2Sb2Te5 Thin
           Films after Femtosecond Laser Irradiation

    • Authors: Aleksandr Kolchin, Dmitrii Shuleiko, Mikhail Martyshov, Aleksandra Efimova, Leonid Golovan, Denis Presnov, Tatiana Kunkel, Victoriia Glukhenkaya, Petr Lazarenko, Pavel Kashkarov, Stanislav Zabotnov, Sergey Kozyukhin
      First page: 3499
      Abstract: Ge2Sb2Te5 (GST225) looks to be a promising material for rewritable memory devices due to its relatively easy processing and high optical and electrophysical contrast for the crystalline and amorphous phases. In the present work, we combined the possibilities of crystallization and anisotropic structures fabrication using femtosecond laser treatment at the 1250 nm wavelength of 200 nm thin amorphous GST225 films on silicon oxide/silicon substrates. A raster treatment mode and photoexcited surface plasmon polariton generation allowed us to produce mutually orthogonal periodic structures, such as scanline tracks (the period is 120 ± 10 μm) and laser-induced gratings (the period is 1100 ± 50 nm), respectively. Alternating crystalline and amorphous phases at the irradiated surfaces were revealed according to Raman spectroscopy and optical microscopy studies for both types of structures. Such periodic modulation leads to artificial optical and electrophysical anisotropy. Reflectance spectra in the near infrared range differ for various polarizations of probing light, and this mainly results from the presence of laser-induced periodic surface structures. On the other hand, the scanline tracks cause strong conductivity anisotropy for dc measurements in the temperature range of 200–400 K. The obtained results are promising for designing new GST225-based memory devices in which anisotropy may promote increasing the information recording density.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103499
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3500: Prediction of the Compressive Strength for
           Cement-Based Materials with Metakaolin Based on the Hybrid Machine
           Learning Method

    • Authors: Jiandong Huang, Mengmeng Zhou, Hongwei Yuan, Mohanad Muayad Sabri Sabri, Xiang Li
      First page: 3500
      Abstract: Cement-based materials are widely used in construction engineering because of their excellent properties. With the continuous improvement of the functional requirements of building infrastructure, the performance requirements of cement-based materials are becoming higher and higher. As an important property of cement-based materials, compressive strength is of great significance to its research. In this study, a Random Forests (RF) and Firefly Algorithm (FA) hybrid machine learning model was proposed to predict the compressive strength of metakaolin cement-based materials. The database containing five input parameters (cement grade, water to binder ratio, cement-sand ratio, metakaolin to binder ratio, and superplasticizer) based on 361 samples was employed for the prediction. In this model, FA was used to optimize the hyperparameters, and RF was used to predict the compressive strength of metakaolin cement-based materials. The reliability of the hybrid model was verified by comparing the predicted and actual values of the dataset. The importance of five variables was also evaluated, and the results showed the cement grade has the greatest influence on the compressive strength of metakaolin cement-based materials, followed by the water-binder ratio.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103500
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3501: Medium- and Long-Term Re-Treatment of Root
           Canals Filled with a Calcium Silicate-Based Sealer: An Experimental Ex
           Vivo Study

    • Authors: Giulia Bardini, Elisabetta Cotti, Terenzio Congiu, Claudia Caria, Davide Aru, Montse Mercadè
      First page: 3501
      Abstract: This study investigated the possibility of re-treating a calcium silicate-based sealer (CSBS), compared to an epoxy-resin sealer (RBS), using rotary instrumentation at different times from obturation (1 month/1 year). Thirty-six human mandibular premolars, extracted as a result of orthodontic or periodontal problems, were instrumented and randomly divided into three groups of 12: BR and BR*, which were filled with CSBS and re-treated after one month and one year of storage, respectively, and AH, which was filled with RBS and re-treated after one month. The same re-treatment protocol was used for all teeth, and the times required for the procedure was recorded. The re-treated specimens were longitudinally sectioned and examined at the stereomicroscope (SM) at 20× magnification. Image J Software was used to process the microphotographs. The percentage of residual filling materials in the root canal and the apical third, the ability to reach working length WL and patency, and the time taken to complete the re-treatment were recorded and analyzed by ANOVA and post hoc Bonferroni test (p = 0.05). Scanning electron microscopy (SEM) and coupled energy-dispersive spectroscopy (EDS) were applied to representative samples to evaluate canal cleanliness and chemical elements. Patency and WL were re-established in all of the teeth. Residual filling materials were retained in all specimens of the three groups. The mean percentage of residual materials was significantly different between BR and BR* (p-value = 0.048), with BR* showing the highest values. The mean time to complete re-treatment was significantly lower for AH, followed by BR (p = 0.0001) and BR* (p = 0.0078). Conclusions: After both medium and long storage periods, the CSBS can be concluded to have been successfully removed from canals with simple anatomy.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103501
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3502: Investigating the Impact of Cu2+ Doping on
           the Morphological, Structural, Optical, and Electrical Properties of
           CoFe2O4 Nanoparticles for Use in Electrical Devices

    • Authors: Shahroz Saleem, Muhammad Irfan, Muhammad Yasin Naz, Shazia Shukrullah, Muhammad Adnan Munir, Muhammad Ayyaz, Abdullah Saeed Alwadie, Stanislaw Legutko, Jana Petrů, Saifur Rahman
      First page: 3502
      Abstract: This study investigated the production of Cu2+-doped CoFe2O4 nanoparticles (CFO NPs) using a facile sol−gel technique. The impact of Cu2+ doping on the lattice parameters, morphology, optical properties, and electrical properties of CFO NPs was investigated for applications in electrical devices. The XRD analysis revealed the formation of spinel-phased crystalline structures of the specimens with no impurity phases. The average grain size, lattice constant, cell volume, and porosity were measured in the range of 4.55–7.07 nm, 8.1770–8.1097 Å, 546.7414–533.3525 Å3, and 8.77–6.93%, respectively. The SEM analysis revealed a change in morphology of the specimens with a rise in Cu2+ content. The particles started gaining a defined shape and size with a rise in Cu2+ doping. The Cu0.12Co0.88Fe2O4 NPs revealed clear grain boundaries with the least agglomeration. The energy band gap declined from 3.98 eV to 3.21 eV with a shift in Cu2+ concentration from 0.4 to 0.12. The electrical studies showed that doping a trace amount of Cu2+ improved the electrical properties of the CFO NPs without producing any structural distortions. The conductivity of the Cu2+-doped CFO NPs increased from 6.66 × 10−10 to 5.26 × 10−6 ℧ cm−1 with a rise in Cu2+ concentration. The improved structural and electrical characteristics of the prepared Cu2+-doped CFO NPs made them a suitable candidate for electrical devices, diodes, and sensor technology applications.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103502
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3503: Improved Ion/Ioff Current Ratio and
           Dynamic Resistance of a p-GaN High-Electron-Mobility Transistor Using an
           Al0.5GaN Etch-Stop Layer

    • Authors: Hsiang-Chun Wang, Chia-Hao Liu, Chong-Rong Huang, Min-Hung Shih, Hsien-Chin Chiu, Hsuan-Ling Kao, Xinke Liu
      First page: 3503
      Abstract: In this study, we investigated enhance mode (E-mode) p-GaN/AlGaN/GaN high-electron-mobility transistors (HEMTs) with an Al0.5GaN etch-stop layer. Compared with an AlN etch-stop layer, the Al0.5GaN etch-stop layer not only reduced lattice defects but engendered improved DC performance in the device; this can be attributed to the lattice match between the layer and substrate. The results revealed that the Al0.5GaN etch-stop layer could reduce dislocation by 37.5% and improve device characteristics. Compared with the device with the AlN etch-stop layer, the p-GaN HEMT with the Al0.5GaN etch-stop layer achieved a higher drain current on/off ratio (2.47 × 107), a lower gate leakage current (1.55 × 10−5 A/mm), and a lower on-state resistance (21.65 Ω·mm); moreover, its dynamic RON value was reduced to 1.69 (from 2.26).
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103503
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3504: Preparation of Nano-Apatite Grafted
           Glass-Fiber-Reinforced Composites for Orthodontic Application: Mechanical
           and In Vitro Biofilm Analysis

    • Authors: Abdul Samad Khan, Alaa Alshaia, AlAnood AlDubayan, Sundus Alarifi, Abdulaziz Alamri, Hanan Aldossary, Syed Zubairuddin Ahmed, Ijlal Shahrukh Ateeq, Abbas Saeed Hakeem, Suriya Rehman
      First page: 3504
      Abstract: This study aimed to fabricate nano-hydroxyapatite (nHA) grafted/non-grafted E-glass-fiber-based (nHA/EG) and E-glass fiber (EG) orthodontic retainers and to compare their properties with commercially available retainers. Stainless-steel (SS) retainers and everStick Ortho (EST) were used as control groups. The retainers were evaluated with Raman spectroscopy and bonded to bovine teeth. The samples were fatigued under cyclic loading (120,000 cycles) followed by static load testing. The failure behavior was evaluated under an optical microscope and scanning electron microscope. The strain growth on the orthodontic retainers was assessed (48h and 168h) by an adhesion test using Staphylococcus aureus and Candida albicans. The characteristic peaks of resin and glass fibers were observed, and the debonding force results showed a significant difference among all of the groups. SS retainers showed the highest bonding force, whereas nHA/EG retainers showed a non-significant difference from EG and EST retainers. SS retainers’ failure mode occurred mainly at the retainer–composite interface, while breakage occurred in glass-fiber-based retainers. The strains’ adhesion to EST and EG was reduced with time. However, it was increased with nHA/EG. Fabrication of nHA/EG retainers was successfully achieved and showed better debonding force compared to other glass-fiber-based groups, whereas non-linear behavior was observed for the strains’ adhesion.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103504
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3505: Experimental Study on the Flexural
           

    • Authors: Wenhu Gu, Hengrui Liu, Yun Dong
      First page: 3505
      Abstract: Reinforcement corrosion poses a great threat to the safety of reinforced concrete structures, and the fiber-reinforced polymer is the ideal material to partially replace steel bars due to the high strength, light weight and good durability. However, the selection of appropriate fiber materials and a reasonable ratio of fiber bar to steel bar is not clear. Here, we measured the mechanical properties of fiber bars containing aramid fiber and carbon fiber. The deflection deformation, crack distribution and maximum crack width of the concrete upon various loads were experimentally and theoretically investigated. The predictions of the maximum crack width and deflection of reinforced concrete beams under various loads were proposed in ACI standard, which may provide guidance for further applications of fiber-belt-bar-containing concrete beams.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103505
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3506: Correction: Borinelli et al. VOC Emission
           Analysis of Bitumen Using Proton-Transfer Reaction Time-Of-Flight Mass
           Spectrometry. Materials 2020, 13, 3659

    • Authors: Jaffer Bressan Borinelli, Johan Blom, Miguel Portillo-Estrada, Patricia Kara De Maeijer, Wim Van den bergh, Cedric Vuye
      First page: 3506
      Abstract: The authors wish to make the following corrections to this paper [...]
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103506
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3507: Marine and Agro-Industrial By-Products
           Valorization Intended for Topical Formulations in Wound Healing
           Applications

    • Authors: Ana-Maria Prelipcean, Andreea Iosageanu, Alexandra Gaspar-Pintiliescu, Lucia Moldovan, Oana Craciunescu, Ticuta Negreanu-Pirjol, Bogdan Negreanu-Pirjol, Raul-Augustin Mitran, Mariana Marin, Ugo D’Amora
      First page: 3507
      Abstract: Over the past years, research attention has been focusing more on waste-derived, naturally derived, and renewable materials, in the view of a more sustainable economy. In this work, different topical formulations were obtained from the valorization of marine and agro-industrial by-products and the use of Carbopol 940 as gelling agent. In particular, the combination of extracts obtained from the marine snail, Rapanosa venosa, with Cladophora vagabunda and grape pomace extracts, was investigated for wound healing purposes. Rapana venosa has demonstrated wound healing properties and antioxidant activity. Similarly, grape pomace extracts have been shown to accelerate the healing process. However, their synergic use has not been explored yet. To this aim, four different formulations were produced. Three formulations differed for the presence of a different extract of Rapana venosa: marine collagen, marine gelatin, and collagen hydrolysate, while another formulation used mammalian gelatin as further control. Physico-chemical properties of the extracts as well as of the formulations were analyzed. Furthermore, thermal stability was evaluated by thermogravimetric analysis. Antioxidant capacity and biological behavior, in terms of cytocompatibility, wound healing, and antimicrobial potential, were assessed. The results highlighted for all the formulations (i) a good conservation and thermal stability in time, (ii) a neutralizing activity against free radicals, (iii) and high degree of cytocompatibility and tissue regeneration potential. In particular, collagen, gelatin, and collagen hydrolysate obtained from the Rapana venosa marine snail represent an important, valuable alternative to mammalian products.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103507
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3508: A Comparative Study on p- and n-Type
           Silicon Heterojunction Solar Cells by AFORS-HET

    • Authors: Wabel Mohammed Alkharasani, Nowshad Amin, Seyed Ahmad Shahahmadi, Ammar Ahmed Alkahtani, Ili Salwani Binti Mohamad, Puvaneswaran Chelvanathan, Tiong Sieh Kiong
      First page: 3508
      Abstract: Despite the increasing trend of n-type silicon wafer utilization in the manufacturing of high-efficiency heterojunction solar cells due to the superior advantages over p-type counterparts, its high manufacturing cost remains to be one of the most crucial factors, which impedes its market share growth with state-of-the-art silicon heterojunction (SHJ) solar cells demonstrating high conversion efficiencies from various configurations, the prospect of using an n-type wafer is debatable from a cost-efficiency point of view. Hence, a systematic comparison between p- and n-type SHJ solar cells was executed in this work using AFORS-HET numerical software. Front and rear-emitter architectures were selected for each type of wafer with ideal (without defects) and non-ideal (with defects) conditions. For ideal conditions, solar cells with p-type wafers and a front-emitter structure resulted in a maximum conversion efficiency of 28%, while n-type wafers demonstrated a maximum efficiency of 26% from the rear-emitter structure. These high-performance devices were possible due to the optimization of the bandgap and electron-affinity for all passivating and doping layers with values ranging from 1.3 to 1.7 eV and 3.9 to 4 eV, respectively. The correlation between the device structure and the type of wafers as demonstrated here will be helpful for the development of both types of solar cells with comparable performance.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103508
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3509: Stress Relaxation Behavior of Additively
           Manufactured Polylactic Acid (PLA)

    • Authors: Alcide Bertocco, Matteo Bruno, Enrico Armentani, Luca Esposito, Michele Perrella
      First page: 3509
      Abstract: In this work, the stress relaxation behavior of 3D printed PLA was experimentally investigated and analytically modeled. First, a quasi-static tensile characterization of additively manufactured samples was conducted by considering the effect of printing parameters like the material infill orientation and the outer wall presence. The effect of two thermal conditioning treatments on the material tensile properties was also investigated. Successively, stress relaxation tests were conducted, on both treated and unconditioned specimens, undergoing three different strains levels. Analytical predictive models of the viscous behavior of additive manufactured material were compared, highlighting and discussing the effects of considered printing parameters.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103509
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3510: Ecotoxicity of Recycled Aggregates:
           Application of a Prediction Methodology

    • Authors: Margarida B. Maia, Jorge de Brito, Isabel M. Martins, José D. Silvestre
      First page: 3510
      Abstract: Due to environmental concerns, the search for sustainable construction solutions has been increasing over the years. This global concern is creating a trend in the use of recycled aggregates resulting from construction and demolition wastes from different sources. In addition to their physical and mechanical properties, it is important to analyse their ecotoxicological risk to determine whether their leachates might be an issue. To assess ecotoxicity, biological tests should be performed for different trophic levels. This type of test is expensive and needs a high level of expertise, which leads to a lack of studies on recycled aggregates including ecotoxicity analysis. This paper presents a set of predictive ecotoxicity results based on the published studies on recycled aggregates. These results are the outcome of applying an innovative methodology previously developed and validated by the authors aiming to foresee the ecotoxicological fate of building materials’ constituents and products. The application of this methodology enables the classification of a recycled aggregate product as safe or unsafe in terms of ecotoxicity risk, while keeping biological testing to a minimum.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103510
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3511: The Effect of Cylindrical Liner Material
           on the Jet Formation and Penetration Capability of Cylinder-Cone-Shaped
           Charge

    • Authors: Yifan Wang, Zhijun Wang, Yongjie Xu, Zhen Jin
      First page: 3511
      Abstract: The jet formation and penetration capacity of cylinder-cone-shaped charges against steel targets were studied using the method of numerical simulation. Cylinder-cone-shaped charge models with five cylindrical liner materials, including nickel, tungsten, tantalum, steel 4340 and copper, were established to investigate the penetration capability and were compared with the classical conical-shaped charge. Moreover, the influence of the connection method of the cylindrical liner and the truncated liner on the jet performance was examined. The results show that the head velocity of the projectile formed by the cylinder-cone-shaped charge with a cylindrical nickel liner was larger than that with other cylindrical liner materials; in addition, it was larger by 50.2% compared with that formed by the classical conical-shaped charge. The penetration depth of the steel target by the cylinder-cone-shaped charge with a cylindrical copper liner was the largest, which could be 51.7% higher than that of a classical conical-shaped charge at a standoff of 2.5 D. For 2.0 D and 2.5 D standoff distances, the penetration depths were increased by 18.4% and 29.5%, respectively, by using the connection method of putting the cylindrical nickel liner on the neck of the truncated liner compared with that of the previous cylinder-cone-shaped charge with a cylindrical nickel liner.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103511
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3512: Concurrent Topology Optimization for
           Maximizing the Modal Loss Factor of Plates with Constrained Layer Damping
           Treatment

    • Authors: Zhanpeng Fang, Lei Yao, Junjian Hou, Yanqiu Xiao
      First page: 3512
      Abstract: Damping performance of the plates with constrained layer damping (CLD) treatment mainly depends on the layout of CLD material and the material physical properties of the viscoelastic damping layer. This paper develops a concurrent topology optimization methodology for maximizing the modal loss factor (MLF) of plates with CLD treatment. At the macro scale, the damping layer is composed of 3D periodic unit cells (PUC) of cellular viscoelastic damping materials. At the micro scale, due to the deformation of viscoelastic damping material affected by the base and constrained layers, the representative volume element (RVE) considering a rigid skin effect is used to improve the accuracy of the effective constitutive matrix of the viscoelastic damping material. Maximizing the MLFs of CLD plates is employed as the design objectives in optimization procedure. The sensitivities with respect to macrodesign variables are formulated using the adjoint vector method while considering the contribution of eigenvectors, while the influence of macroeigenvectors is ignored to improve the computational efficiency in the mesosensitivity analysis. The macro and meso scales design variables are simultaneously updated using the Method of Moving Asymptotes (MMA) to find concurrently optimal configurations of constrained and viscoelastic damping layers at the macro scale and viscoelastic damping materials at the micro scale. Two rectangular plates with different boundary conditions are presented to validate the optimization procedure and demonstrate the effectiveness of the proposed concurrent topology optimization approach. The effects of optimization objectives and volume fractions on the design results are investigated. The results indicate that the optimized layouts of the macrostructure are dependent on the objective mode and the volume fraction on the meso scale. The optimized designs on the meso scale are mainly related to the objective mode. By varying the volume fraction on the macro scale, the optimized designs on the meso scale are different only in their detailed size, which is reflected in the values of the equivalent constitutive matrices.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103512
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3513: Hot Ductility Prediction Model of Cast
           Steel with Low-Temperature Transformed Structure during Continuous Casting
           

    • Authors: Dae-Geun Hong, Sang-Hum Kwon, Chang-Hee Yim
      First page: 3513
      Abstract: When various alloying elements are added or the cooling rate is increased, steel grades with U- or V-typed ductility behavior show N-shaped ductility behavior in which the ductility decreases in the low-temperature region. This study proposes a method that uses N-shaped data fitting and random forest to predict ductility behavior of steel grades that have bainite microstructure. To include the phenomenon in which that ductility decreases below the intermediate temperature, the data range was extended to temperature T < 700 °C. To identify the T range in which the ductility decreases at T < 700 °C, an N-shaped data fitting method using six parameters was proposed. Comparison with the experimental values confirmed the effectiveness of the proposed model. Also, the model has better ability than models to predict bainite start temperature TBS. In a case study, the change of ductility behavior according to the cooling rate was observed for Nb-added steel. As the cooling rate increased from 1 °C/s to 10 °C/s, the formation of hard phase was relatively promoted, and different transformation behaviors appeared. This ability to predict the ductility behavior of alloy steels with a bainite microstructure, and to predict TBS below the intermediate temperature enables effective control of the secondary cooling conditions during continuous casting process, minimizing the formation of cracks on the slab surface.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103513
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3514: Experimental Study on Recentering Behavior
           of Precompressed Polyurethane Springs

    • Authors: Young-Hun Ju, Iman Mansouri, Jong-Wan Hu
      First page: 3514
      Abstract: Traditional seismic design has a limitation in that its performance is reduced by significant permanent deformation after plastic behavior under an external load. The recentering characteristics of smart materials are considered to be a means to supplement the limitations of conventional seismic design. In general, the recentering characteristics of smart materials are determined by their physical properties, whereas polyurethane springs can regulate the recentering characteristics by controlling the precompression strain. Therefore, in this study, 160 polyurethane spring specimens were fabricated with compressive stiffness, specimen size, and precompression strain as design variables. The compression behavior and precompression behavior were studied by performing cyclic loading tests on a polyurethane spring. The maximum stress and maximum strain of the polyurethane spring showed a linear relationship. Precompression and recentering forces have an almost perfect linear relationship, and the optimal level of precompression at which residual strain does not occur was derived through regression analysis. Additionally, a prediction model for predicting recentering force based on the linear relationship between precompression and recentering force was presented.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103514
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3515: Research Progress of Alumina-Forming
           Austenitic Stainless Steels: A Review

    • Authors: Ling Liu, Cuilin Fan, Hongying Sun, Fuxiao Chen, Junqing Guo, Tao Huang
      First page: 3515
      Abstract: The development of Alumina-Forming Austenitic (AFA) stainless steel is reviewed in this paper. As a new type of heat-resistant steel, AFA steel forms an alumina protective scale instead of chromia in a corrosive environment. This work summarizes the types of developed AFA steels and introduces the methods of composition design. Various precipitates appear in the microstructure that directly determine the performance at high temperatures. It was found that alloy elements and the heat treatment process have an important influence on precipitates. In addition, the corrosion resistance of AFA steel in different corrosive environments is systematically analyzed, and the beneficial or harmful effects of different elements on the formation of alumina protective scale are discussed. In this paper, the short-term mechanical properties, creep properties and influencing factors of AFA steel are also analyzed. This work aims to summarize the research status on this subject, analyze the current research results, and explore future research directions.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103515
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3516: Orthogonal Experimental Study on Concrete
           Properties of Machine-Made Tuff Sand

    • Authors: Dunwen Liu, Wanmao Zhang, Yu Tang, Yinghua Jian, Yongchao Lai
      First page: 3516
      Abstract: Machine-made sand instead of natural sand has become an inevitable choice for the sustainable development of the concrete industry. Orthogonal experiment and grey correlation analysis were used to investigate the performance of machine-made tuff sand concrete. The optimal concrete mix ratio of machine-made sand was obtained by orthogonal test and its working performance was verified. Grey correlation analysis was applied to compare the factors affecting the mechanical properties of the machine-made sand concrete. The test results show that the sand rate has the greatest degree of influence on slump and slump expansion. The mineral admixture has the greatest effect on the 7-day compressive strength of the concrete. Additionally, the water–cement ratio has the greatest influence on the 28-day compressive strength. The mechanical and working properties of the machine-made sand concrete reach the optimum condition when the mineral admixture is 20%, the sand rate is 46%, the stone powder content is 10% and the water–cement ratio is 0.30. Comparing different fine aggregate concretes of similar quality, we conclude that the mechanical and working properties of tuff sand concrete and limestone sand concrete and river sand concrete are similar. The compressive strengths of the mechanism concrete show the greatest correlation with roughness and the least correlation with stone powder content. The stone powder content has almost no effect on the compressive strength of concrete when the stone powder content does not exceed a certain range. The results of the study point out the direction for the quality control of concrete with machine-made sand.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103516
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3517: The Effect of Severe Shot Peening on
           

    • Authors: Timo Rautio, Matias Jaskari, Tejas Gundgire, Terho Iso-Junno, Minnamari Vippola, Antti Järvenpää
      First page: 3517
      Abstract: Severe shot peening (SSP) was used on additive manufactured 316L by laser powder bed fusion. The effect of the post processing on the surface features of the material was analyzed through residual stress measurements, tensile testing, hardness-depth profiles, and fatigue testing by flexural bending. The results showed that SSP can be utilized to form residual stresses up to −400 MPa 200 μm below the surface. At the same time, a clear improvement on the surface hardness was achieved from 275 HV to near 650 HV. These together resulted in a clear improvement on material strength which was recorded at 10% improvement in ultimate tensile strength. Most significantly, the fatigue limit of the material was tripled from 200 MPa to over 600 MPa and the overall fatigue strength raised similarly from a low to high cycle regime.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103517
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3518: 100th Anniversary of Brillouin Scattering:
           Impact on Materials Science

    • Authors: Seiji Kojima
      First page: 3518
      Abstract: L. Brillouin predicted inelastic light scattering by thermally excited sound waves in 1922. Brillouin scattering is a non-contact and non-destructive method to measure sound velocity and attenuation. It is possible to investigate the elastic properties of gases, liquids, glasses, and crystals. Various kinds of phase transitions, i.e., liquid–glass transitions, crystallization, polymorphism, and denaturation have been studied by changing the temperature, pressure, time, and external fields such as the electric, magnetic, and stress fields. Nowadays, Brillouin scattering is extensively used to measure various elementary excitations and quasi-elastic scattering in the gigahertz range between 0.1 and 1000 GHz. A brief history, spectroscopic methods, and Brillouin scattering studies in materials science on ferroelectric materials, glasses, and proteins are reviewed.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103518
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3519: Influence of Beam Figure on Porosity of
           Electron Beam Welded Thin-Walled Aluminum Plates

    • Authors: Matthias Moschinger, Florian Mittermayr, Norbert Enzinger
      First page: 3519
      Abstract: Welded aluminum components in the aerospace industry are subject to more stringent safety regulations than in other industries. Electron beam welding as a highly precise process fulfills this requirement. The welding of aluminum poses a challenge due to its high tendency to pore formation. To gain a better understanding of pore formation during the process, 1.5 mm thick aluminum AW6082 plates were welded using specially devised beam figures in different configurations. The obtained welds were examined with radiographic testing to evaluate the size, distribution, and the number of pores. Cross-sections of the welds were investigated with light microscopy and an electron probe microanalyzer to decipher the potential mechanisms that led to porosity. The examined welds showed that the porosity is influenced in various ways by the used figures, but it cannot be completely avoided. Chemical and microstructural analyzes have revealed that the main mechanism for pore formation was the evaporation of the alloying elements Mg and Zn. This study demonstrates that the number of pores can be reduced and their size can be minimized using a proper beam figure and energy distribution.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103519
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3520: A Method for Determining Ultimate Grouting
           Pressure for Reinforcement of Masonry Arch Dam with Mortar Deterioration:
           A Case Study

    • Authors: Jia’ao Yu, Zhenzhong Shen, Liqun Xu, Chuankai He
      First page: 3520
      Abstract: The deterioration of mortar has an adverse impact on the deformation and stress state of the masonry arch dam, after freeze-thaw cycles, in long-term operation. The purpose of this paper is to investigate the effect of reinforcement grouting on the stress of a thin masonry arch dam and propose a reasonable grouting method in the case of mortar deterioration. The determination of the ultimate grouting pressure is another main focus. The masonry material was generalized by combining a linear elastic model and the proportional weighted average under the condition of deterioration caused by freeze-thaw cycles. A series of analytical methods were proposed for the research of grouting effect on dam stress, based on which the ultimate grouting pressure is calculated in various cases. Results demonstrate that the dam tensile stress may exceed the allowable value in the following operation. Then, some recommended methods for the grouting layout and the estimation of grouting pressure were put forward by integrating the grouting field test with numerical analysis for reinforcement. The research conclusions might have a guiding significance for the reinforcement of similar projects.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103520
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3521: A First-Principles Study on the Hydration
           Behavior of (MgO)n Clusters and the Effect Mechanism of Anti-Hydration
           Agents

    • Authors: Yu Gao, Long Dong, Liang Huang, Zhong Huang, Faliang Li, Haijun Zhang, Shaowei Zhang
      First page: 3521
      Abstract: Magnesia-based refractory is widely used in high-temperature industries; its easy hydration is, however, a key concern in refractory processing. Understanding the hydration mechanism of MgO will help in solving its hydration problem. Herein, the hydration behavior of (MgO)n (n = 1–6) at the molecular level and the effect mechanisms of several anti-hydration agents on the hydration of (MgO)4 were investigated with first-principles calculations. The results indicated that the following: (1) The smaller the (MgO)n cluster size, the more favorable the hydration of MgO and the tendency to convert into Mg(OH)2 crystal; (2) Anti-hydration agents can coordinate with the unsaturated Mg atom of (MgO)4 to form a bond, increasing the coordination number of Mg, thus reducing its activity when reacting with H2O; (3) The greater the number of −COOH groups and the longer the chain length in the anti-hydration agents, the better its effect of inhibiting the hydration of MgO. These findings could enhance the understanding of the mechanism of hydration of MgO and provide theoretical guidance for the design of novel anti-hydration agents.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103521
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3522: Thermal Radiation Shielding and Mechanical
           Strengthening of Mullite Fiber/SiC Nanowire Aerogels Using In Situ
           Synthesized SiC Nanowires

    • Authors: Hui Xu, Xiaolei Li, Zongwei Tong, Baojie Zhang, Huiming Ji
      First page: 3522
      Abstract: Traditional solid nanoparticle aerogels have been unable to meet the requirements of practical application due to their inherent brittleness and poor infrared shielding performance. Herein, combining vacuum impregnation and high-temperature pyrolysis, a novel micro/nano-composite fibrous aerogel was prepared via in situ synthesis of silicon carbide nanowires (SiC NWS) in mullite fiber (MF) preform. During this process, uniformly distributed SiC NWS in the MF preform serve as an enhancement phase and also act as an infrared shielding agent to reduce radiation heat transfer, which can significantly improve the mechanical properties of the mullite fiber/silicon carbide nanowire composite aerogels (MF/SiC NWS). The fabricated MF/SiC NWS exhibited excellent thermal stability (1400 °C), high compressive strength (~0.47 MPa), and outstanding infrared shielding performance (infrared transmittance reduced by ~70%). These superior properties make them appealing for their potential in practical application as high-temperature thermal insulators.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103522
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3523: Compressive Strength Evaluation of
           Ultra-High-Strength Concrete by Machine Learning

    • Authors: Zhongjie Shen, Ahmed Farouk Deifalla, Paweł Kamiński, Artur Dyczko
      First page: 3523
      Abstract: In civil engineering, ultra-high-strength concrete (UHSC) is a useful and efficient building material. To save money and time in the construction sector, soft computing approaches have been used to estimate concrete properties. As a result, the current work used sophisticated soft computing techniques to estimate the compressive strength of UHSC. In this study, XGBoost, AdaBoost, and Bagging were the employed soft computing techniques. The variables taken into account included cement content, fly ash, silica fume and silicate content, sand and water content, superplasticizer content, steel fiber, steel fiber aspect ratio, and curing time. The algorithm performance was evaluated using statistical metrics, such as the mean absolute error (MAE), root mean square error (RMSE), and coefficient of determination (R2). The model’s performance was then evaluated statistically. The XGBoost soft computing technique, with a higher R2 (0.90) and low errors, was more accurate than the other algorithms, which had a lower R2. The compressive strength of UHSC can be predicted using the XGBoost soft computing technique. The SHapley Additive exPlanations (SHAP) analysis showed that curing time had the highest positive influence on UHSC compressive strength. Thus, scholars will be able to quickly and effectively determine the compressive strength of UHSC using this study’s findings.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103523
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3524: Influence of Work Hardening on the Surface
           of Backup Rolls for a 4-High Rolling Mill Fractured during Rolling
           Campaign

    • Authors: Rumualdo Servin-Castañeda, Sixtos Antonio Arreola-Villa, Alejandro Perez-Alvarado, Ismael Calderón-Ramos, Ruben Torres-Gonzalez, Alonso Martinez-Hurtado
      First page: 3524
      Abstract: Backup rolls are the main tool in a four-high rolling mill; the rolling forces applied in load cells promote the fatigue of the material due to mechanical contact between backup rolls and work rolls. This work investigated the causes of recurrent failures in backup rolls, with cracking always initiated on the surface of the roll body and finishing in the main radius between neck and roll body. Aiming to find the causes of failure, visual inspection and morphology of the fracture were performed, complemented with mechanical tests of hardness on the stress concentration area, in addition to validating the results by applying the finite element method, using ANSYS Mechanical Static Structural Software. It was concluded that the fatigue crack initiated on the surface of BUR due to work hardening continued growing up over the fatigued material, creating beach marks, and finally, a fracture occurred in the main radius of BUR due to stress concentration. The work hardening is the main cause of spalling on BURs and other mechanical components exposed to mechanical contact.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103524
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3525: Jerky Motion of the Reaction Front during
           Discontinuous Dissolution in a Fe-13.5 at.% Zn Alloy

    • Authors: Mateusz Chronowski, Jarosław Opara, Boris Straumal, Brigitte Baretzky, Pawel Zięba
      First page: 3525
      Abstract: This paper studies the go- and -stop movement of a receding reaction front (RF) during a discontinuous dissolution (DD) process. A special simulation procedure was applied for the DD reaction to predict a jerky motion of the RF. The Fe-13.5 at.% Zn alloy was selected in which go- and -stop behaviour was revealed in the form of characteristic lines (called “ghost lines”) showing successive positions of receding RF. The results presented for the DD process are quite different from those relevant for the DP reaction at the same Fe-13.5 at.% Zn alloy in terms of go- and -stop motion and movement distance. For the presented case, the go- and -stop periods are relatively long and obtain an order of several dozen seconds, while for the DP reaction, it was only a few seconds. A similar conclusion was formulated after a comparison of the movement distance which, for the DD reaction, is usually longer by 1–2 orders of magnitude. The simulation results of the DD reaction indicate a good agreement with the experimental data presented in the literature for the same dissolution rate. It is necessary to emphasize that the simulation is the only source of data for z parameter changes during the -stop period of the DD reaction.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103525
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3526: Analysis of the Effect of Catalytic
           Additives in the Agricultural Waste Combustion Process

    • Authors: Tomáš Najser, Błażej Gaze, Bernard Knutel, Adam Verner, Jan Najser, Marcel Mikeska, Jerzy Chojnacki, Ondřej Němček
      First page: 3526
      Abstract: This paper presents the research results of the effect of using calcium oxide and potassium permanganate on the combustion of pellets from wheat bran and beet pulp. The measurements were performed in the technical laboratory of the Centre of Energy Utilization of Non-Traditional Energy Sources in Ostrava. The research examined the effect of the use of chemical substances on the amount of air pollutants from biomass thermal conversion in a low-power boiler and the process temperature. First, we performed technical and elementary analyses of agricultural waste. The raw material was then comminuted, mixed with a selected additive, pelletized, and finally burned in a low-power boiler. The additive was added in three proportions: 1:20, 1:10, and 1:6.67 (i.e., 15%) relative to the fuel weight. The combustion process efficiency was measured using a flue gas analyzer and three thermocouples attached to the data recorder. From the measurement results, we were able to determine the percentage reduction of pollutant emissions into the atmosphere (CO, NOx, and SO2) due to the use of additives. Because emission standards are becoming increasingly stringent and fuel and energy prices are rising, the results presented in this article may be useful to agri-food processing plants that want to manage these materials thermally.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103526
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3527: Influence of Pulse–Pause Sequences
           on the Self-Heating Behavior in Continuous Carbon Fiber-Reinforced
           Composites under Ultrasonic Cyclic Three-Point Bending Loads

    • Authors: Aravind Premanand, Frank Balle
      First page: 3527
      Abstract: Several studies have been conducted in the Very High Cycle Fatigue (VHCF) regime on Carbon Fiber Reinforced Polymers (CFRP) in search of their fatigue limit beyond their typical service life, which is itself in the order of 108 loading cycles. The ultrasonic fatigue test (UFT) method has been recently gaining attention for conducting fatigue experiments up to 109 loading cycles. This can be attributed to the reduction of testing time, as the testing facility operates at a cyclic frequency of 20 kHz. The fatigue loading in UFT is usually performed in a pulse–pause sequence to avoid specimen heating and undesirable thermal effects. For this study, the pulse–pause combination of the UFT methodology was explored and its influence on the self-heating behavior of the CFRP material was analyzed. This was realized by monitoring the temperature evolution in the CFRP specimens at different pulse–pause combinations and correlating it with their final damage morphologies. From the obtained results, it is concluded that the specimen heating phenomenon depends on several variables such as cyclic loading amplitude, the pulse–pause combination, and the damage state of the material. Finally, it is proposed that the test procedure, as well as the testing time, can be further optimized by designing the experiments based on the self-heating characteristic of the composite and the glass transition temperature (Tg) of the polymer matrix.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103527
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3528: Investigations on the Performance of
           Shotcrete Using Artificial Lightweight Shale Ceramsite as Coarse Aggregate
           

    • Authors: Shengjun Hou, Fuhai Li, Huiqi Tang, Tao Wen, Zhao Chen, Hao Gao
      First page: 3528
      Abstract: In this study, a type of artificial lightweight shale ceramsite (ALSC) was used as the coarse lightweight aggregate for shotcrete (LAS), of which the mechanical properties, chloride penetration ion resistance, and rebound behavior were investigated. Based on the experimental results on compressive, tensile, and bond strength, LAS meet the strength requirements, and the replacement rate of fly ash (FA) and silica fume (SF) are suggested to be kept at ~15% and 10%, respectively, to result in the best mechanical properties of LAS. Adding FA and SF to the mixture significantly improved the chloride ion penetration resistance (CPR) of LAS because of morphology effects and secondary hydration of FA and SF that lead to a denser microstructure of the mixture. The electric flux and chloride ion migration coefficient (DRCM) of LAS decreased by 56% and 67%, respectively, with FA increasing from 0 to 10%. The electric flux and DRCM further decreased by 71% (153C) and 66% (3.24 m2/s), respectively, with FA increasing from 10 to 20%. As 5–10% SF was further added, the electric flux and DRCM of LAS decreased to extremely low levels; for instance, with FA = 10% and SF = 10%, DRCM = 1.61 m2/s, and the electric flux was too small and could be ignored. The contact stresses between aggregate and shotcrete mixtures were measured to investigate the rebound trend of ALSC in shotcrete. According to the analyses of the theoretical model of the rebound behavior of aggregate in shotcrete proposed by Armelin and Banthia, because of the reduced contact stresses between ALSC and mortar and the smaller density of LAS compared with normal-weight aggregate, the rebound rate of ALSC was about half of that of normal-weight aggregate in the shooting process of the shotcrete.
      Citation: Materials
      PubDate: 2022-05-13
      DOI: 10.3390/ma15103528
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3529: Spectral and Angular Characteristics of
           the High-Contrast Dielectric Grating under the Resonant Interaction of a
           Plane Wave and a Gaussian Beam

    • Authors: Stefano Bellucci, Volodymyr Fitio, Tatiana Smirnova, Iryna Yaremchuk, Oleksandr Vernyhor, Yaroslav Bobitski
      First page: 3529
      Abstract: The resonant interaction of a plane wave and a one-dimensional Gaussian beam with a high-contrast dielectric grating was analyzed. Rigorous coupled wave analysis (RCWA) was used to numerically model the diffraction of a plane wave by the grating. RCWA, a discrete Fourier transform at the fulfillment (of the conditions) of the sampling theorem, was used to study diffraction of the Gaussian beam. The grating can be considered as a one-dimensional photonic crystal along which the waveguide mode propagates under resonance. The corresponding photonic crystal has both allowed and forbidden photonic bands for the propagating waveguide mode under resonance due to the high-contrast dielectric permittivity. There is no significant difference between the spectral and angular characteristics under the interaction of the plane wave or the Gaussian beam with grating, if the waveguide mode is in the forbidden photonic bandgap. The reflection coefficient from the grating is practically equal to unity for both cases. Resonant spectral and angular characteristics become wider at the Gaussian beam diffraction compared to the resonance curves for the plane wave in the case when the waveguide mode is in the allowed photon bandgap. The reflection coefficient from the grating becomes less than unity and its value tends to unity when the Gaussian beam width increases.
      Citation: Materials
      PubDate: 2022-05-14
      DOI: 10.3390/ma15103529
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3530: Filament Transport Control for Enhancing
           Mechanical Properties of Parts Realised by Fused Filament Fabrication

    • Authors: Arianna Rossi, Giulia Morettini, Michele Moretti, Lorenzo Capponi
      First page: 3530
      Abstract: The fused filament fabrication (FFF) process is widely used for producing prototypes and functional parts for diverse applications. While FFF is particularly attractive due to its cost-effectiveness, on the other hand, the fabricated parts have limitations in terms of large manufacturing time and reduced mechanical properties. The latter is strongly influenced by the fabrication process parameters, which affect the interlayer bonding and the adhesion between consecutive layers. Several works presented in the literature analysed the correlation between mechanical properties and process parameters. It was demonstrated that an increase in the fabrication feed rate causes slippage between filament and the feeding system, which leads to a decrease in the extruded material flow, and thus in part density. This work aims to investigate how the limitation of the slippage phenomenon affects the mechanical properties of parts fabricated using the FFF process. A prototype machine, equipped with a closed-loop control system on filament transport, was used to fabricate samples for tensile tests and dynamical mechanical analysis. Samples fabricated enabling the filament transport control showed an increase both in ultimate tensile strength and elongation at break for those fabricated with disabled control, whilst a decrease in stiffness was observed. In addition, the results showed that the use of a filament transport control system on a FFF machine increases the possibility of fabricating high value-added parts.
      Citation: Materials
      PubDate: 2022-05-14
      DOI: 10.3390/ma15103530
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3531: Morphological Transformation in Polymer
           Composite Materials Filled with Carbon Nanoparticles: Part 1.—SEM
           and XRD Investigations

    • Authors: Elena Ivan’kova, Igor Kasatkin, Gleb Vaganov, Vladimir Elokhovskiy, Alexander Bugrov, Vladimir Yudin, Ewa Pavlova, Miroslav Slouf
      First page: 3531
      Abstract: HDPE-based nanocomposite fibers have been extruded from a melt and drawn up to draw ratio DR = 8. Two kinds of carbon nanodiscs (original ones and those exposed to additional annealing) have been used as fillers. Obtained nanocomposite fibers have been investigated with the help of different experimental methods: rheology, SEM and WAXS. It has been demonstrated that the annealed carbon nanodiscs possess a nucleation ability that finally leads to strong transformation of the material morphology.
      Citation: Materials
      PubDate: 2022-05-14
      DOI: 10.3390/ma15103531
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3532: Analysis of Material-Characterization
           Properties of Post-Production Waste—The Case of Apple Pomace

    • Authors: Weronika Tulej, Szymon Głowacki
      First page: 3532
      Abstract: The paper presents the material-characterization properties of apple pomace—the post-production waste of juice pressing. Tests were carried out on the basic physical properties of apple pomace: color, specific-density, and energy properties. Extensive material-composition analyses based on DSC (differential scanning calorimetry) and TGA (thermogravimetry) methods were also performed. It has been shown that pomace, due to its energy value, can be a good fuel. The obtained thermal data confirm the presence of cellulose, hemicelluloses, lignins and pectins in the analyzed pomace. The results confirm that dried apple pomace is microbiologically stable with good health-promoting properties.
      Citation: Materials
      PubDate: 2022-05-14
      DOI: 10.3390/ma15103532
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3533: Dry Sliding Wear and Corrosion Performance
           of Mg-Sn-Ti Alloys Produced by Casting and Extrusion

    • Authors: Davoud Bovand, Hassan Abdollah-Pour, Omid Mirzaee, Sara Bagherifard
      First page: 3533
      Abstract: The aim of the present study is to investigate the role of Ti on corrosion and the wear properties of Mg-5Sn-xTi (x = 0, 0.15, 0.75, 1.5 wt.%) alloys. The samples were fabricated by conventional casting followed by hot extrusion, and the studies were examined by means of a pin-on-disc tribometer at various loads of 6, 10, and 20 N with constant sliding velocities of 0.04 m/s at ambient temperature. The corrosion performance, using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), was studied in a basic solution containing 3.5 wt.% NaCl. The observation indicated a drop in the wear rate with an increase in Ti, while the average coefficient of friction was raised in higher Ti contents compared to the base material. The sample with 0.15 wt.% Ti exhibited superior wear properties at 6 and 10 N of normal force, while the sample with 0.75 wt.% Ti presented better wear resistance for 20 N. Electrochemical test observations demonstrated that the Ti deteriorated the corrosion features of the Mg-5Sn alloy, owing to the galvanic effects of Ti. The Mg-5Sn alloy exhibited excellent corrosion behavior (corrosion potential (Ecorr) = −1.45V and current density (Icorr) = 43.92 A/cm2). The results indicated the significant role of Ti content in modulating wear and corrosion resistance of the Mg-5Sn alloy.
      Citation: Materials
      PubDate: 2022-05-14
      DOI: 10.3390/ma15103533
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3534: Synthesise and Characterization of
           Cordierite and Wollastonite Glass—Ceramics Derived from Industrial
           Wastes and Natural Raw Materials

    • Authors: Gamal A. Khater, Amany A. El-Kheshen, Mohammad M. Farag
      First page: 3534
      Abstract: Industrial waste is one of the primary sources that harm the environment, and this topic has occupied many scientists on how to take advantage of these wastes or dispose of them and create a clean environment. By-pass cement dust is considered one of the most dangerous industrial wastes due to its fine granular size and its volatilization in the air, which causes severe environmental damage to human and animal health, and this is the reason for choosing the current research point. In this article, eight samples of glass–ceramics were prepared using by-pass cement dust and natural raw materials known as silica sand, magnesite, and kaolin. Then melted by using an electric furnace which was adjusted at a range of temperatures from 1550 to 1600 ∘C for 2 to 3 h; the samples were cast and were subjected to heat treatment at 1000 ∘C for 2 h based on the DTA results in order to produce crystalline materials. Various techniques were used to study the synthesized glass–ceramic samples, including differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscope (SEM), and thermal expansion coefficient (CTE). X-ray analysis showed that the phases formed through investigated glass–ceramic samples consisted mainly of β- wollastonite, parawollastonite, diopside, anorthite, and cordierite. It was noticed that β- the wollastonite phase was formed first and then turned into parawollastonite, and also, the anorthite mineral was formed at low temperatures before the formation of the diopside mineral. SEM showed that the formed microstructure turned from a coarse grain texture to a fine-grained texture, by increasing the percentage of cordierite. It also showed that the increase in time at the endothermic temperature significantly affected the crystalline texture by giving a fine-grained crystalline texture. The linear thermal expansion measurements technique used for the studied glass–ceramic samples gives thermal expansion coefficients ranging from 6.2161 × 10−6 to 2.6181 × 10−6 C−1 (in the range of 20–700 ∘C), and it decreased by increasing cordierite percent.
      Citation: Materials
      PubDate: 2022-05-14
      DOI: 10.3390/ma15103534
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3535: Scalable MXene and PEDOT-CNT Nanocoatings
           for Fibre-Reinforced Composite De-Icing

    • Authors: Gediminas Monastyreckis, Juan Tortosa Siles, Petr Knotek, Maria Omastova, Andrey Aniskevich, Daiva Zeleniakiene
      First page: 3535
      Abstract: In this study, the de-icing performance is investigated between traditional carbon fibre-based coatings and novel MXene and poly(3,4-ethylenedioxythiophene)-coated single-walled carbon nanotube (PEDOT-CNT) nanocoatings, based on simple and scalable coating application. The thickness and morphology of the coatings are investigated using atomic force microscopy and scanning electron microscopy. Adhesion strength, as well as electrical properties, are evaluated on rough and glossy surfaces of the composite. The flexibility and electrical sensitivity of the coatings are studied under three-point bending. Additionally, the influence of ambient temperature on coating’s electrical resistance is investigated. Finally, thermal imaging and Joule heating are analysed with high-accuracy infrared cameras. Under the same power density, the increase in average temperature is 84% higher for MXenes and 117% for PEDOT-CNT, when compared with fibre-based coatings. Furthermore, both nanocoatings result in up to three times faster de-icing. These easily processable nanocoatings offer fast and efficient de-icing for large composite structures such as wind turbine blades without adding any significant weight.
      Citation: Materials
      PubDate: 2022-05-14
      DOI: 10.3390/ma15103535
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3536: Nearly Lattice-Matched GaN Distributed
           Bragg Reflectors with Enhanced Performance

    • Authors: Ye Tian, Peng Feng, Chenqi Zhu, Xinchi Chen, Ce Xu, Volkan Esendag, Guillem Martinez de Arriba, Tao Wang
      First page: 3536
      Abstract: Heavy silicon-doping in GaN generally causes a rough surface and saturated conductivity, while heavily silicon-doped n++-AlGaN with ≤5% aluminum can maintain an atomically flat surface and exhibit enhanced conductivity. Given this major advantage, we propose using multiple pairs of heavily silicon-doped n++-Al0.01Ga0.99N and undoped GaN instead of widely used multiple pairs of heavily silicon-doped n++-GaN and undoped GaN for the fabrication of a lattice-matched distributed Bragg reflector (DBR) by using an electrochemical (EC) etching technique, where the lattice mismatch between Al0.01Ga0.99N and GaN can be safely ignored. By means of using the EC etching technique, the n++-layers can be converted into nanoporous (NP) layers whilst the undoped GaN remains intact, leading to a significantly high contrast in refractive index between NP-layer and undoped GaN and thus forming a DBR. Our work demonstrates that the NP-Al0.01Ga0.99N/undoped GaN-based DBR exhibits a much smoother surface, enhanced reflectivity and a wider stopband than the NP-GaN/undoped GaN-based DBR. Furthermore, the NP-Al0.01Ga0.99N/undoped GaN-based DBR sample with a large size (up to 1 mm in width) can be obtained, while a standard NP-GaN/undoped GaN-based DBR sample obtained is typically on a scale of a few 100 μm in width. Finally, a series of DBR structures with high performance, ranging from blue to dark yellow, was demonstrated by using multiple pairs of n++-Al0.01Ga0.99N and undoped GaN.
      Citation: Materials
      PubDate: 2022-05-14
      DOI: 10.3390/ma15103536
      Issue No: Vol. 15, No. 10 (2022)
       
  • Materials, Vol. 15, Pages 3537: A Low-Cost Porous Polymer Membrane for Gas
           Permeation

    • Authors: Selim Haouari, Denis Rodrigue
      First page: 3537
      Abstract: In this work, an efficient technique was used to produce porous membranes for different applications. Polyethylene (PE) was selected for the matrix, while corn starch (CS) was used to create the porous structure via leaching. The membranes were produced by continuous extrusion (blending)–calendering (forming) followed by CS leaching in a 20% aqueous acetic acid solution at 80 °C. A complete characterization of the resulting membranes was performed including morphological and mechanical properties. After process optimization, the gas transport properties through the membranes were determined on the basis of pure gas permeation including CH4, CO2, O2, and N2 for two specific applications: biogas sweetening (CH4/CO2) and oxygen-enriched air (O2/N2). The gas separation results for ideal permeability and selectivity at 25 °C and 1.17 bar (17 psi) show that these membranes are a good starting point for industrial applications since they are low-cost, easy to produce, and can be further optimized.
      Citation: Materials
      PubDate: 2022-05-14
      DOI: 10.3390/ma15103537
      Issue No: Vol. 15, No. 10 (2022)
       
 
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