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Materials Today Advances
Number of Followers: 0  

  This is an Open Access Journal Open Access journal
ISSN (Online) 2590-0498
Published by Elsevier Homepage  [3200 journals]
  • Synthesis of two-dimensional porous aromatic frameworks via triple
           condensation reaction

    • Abstract: Publication date: June 2019Source: Materials Today Advances, Volume 2Author(s): Zhen Shu, Yulan Tian, Huaqiang CaoPorous aromatic frameworks (PAFs) are composed of aromatic rings which are connected by C–C bonds. A general synthesis method to prepare PAFs is to build new C–C bond among aromatic rings through various cross-coupling reactions by using metal complex catalysts. However, the construction of PAFs through formation of new aromatic rings is rarely mentioned in the literature. In this work, two kinds of two-dimensional (2D) PAFs are obtained by the triple condensation reaction of acetyl aryl compounds. Compared with the general method, this synthetic method has the advantages that the reaction does not require any metal catalysts and can be carried out in the air with high yield. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images display the large-scale 2D structure of the product. 13C solid-state nuclear magnetic resonance (13C ss-NMR) and Fourier-transform infrared (FT-IR) spectra are used to prove the decreasing number of acetyl groups and the formation of aromatic rings after the condensation reaction completed. Thermal gravimetric analysis (TGA) and contact angle (CA) test measurements demonstrate good thermal stability and hydrophobicity of materials. The new types of PAFs are promising candidates for potential applications such as water-oil separation, antibacterial properties, etc.Graphical abstractImage 1
  • Beyond conventional secondary electron imaging using spectromicroscopy and
           its applications in dopant profiling

    • Abstract: Publication date: June 2019Source: Materials Today Advances, Volume 2Author(s): W. Han, A. Srinivasan, A. Banerjee, M. Chew, A. KhursheedDespite decades of research, the technique of measuring dopant concentration by the scanning electron microscope (SEM) has so far been limited to probing idealized test pn junction specimens, where only step dopant concentrations have been quantified. This article presents experimental results to demonstrate that the key to making this method reliable is to use a high signal-to-noise secondary electron (SE) energy spectrometer attachment and how quantifying small changes in spectral signal shape overcomes longstanding problems, such as making dependable measurements in the presence of a silicon native oxide layer. Dopant profiling of a solar cell precursor device were also found to be in good agreement with other conventional dopant profiling methods. In addition, new possibilities have been discovered, such as in situ measurement of native oxide thickness and the mapping of space-charge density. These results point towards SE energy spectroscopy having the potential to become a new analytical technique for SEMs.Graphical abstractImage 1
  • Four-dimensional imaging and quantification of viscous flow sintering
           within a 3D printed bioactive glass scaffold using synchrotron
           X-ray tomography

    • Abstract: Publication date: June 2019Source: Materials Today Advances, Volume 2Author(s): A. Nommeots-Nomm, C. Ligorio, A.J. Bodey, B. Cai, J.R. Jones, P.D. Lee, G. PoologasundarampillaiBioglass® was the first material to form a stable chemical bond with human tissue. Since its discovery, a key goal was to produce three-dimensional (3D) porous scaffolds which can host and guide tissue repair, in particular, regeneration of long bone defects resulting from trauma or disease. Producing 3D scaffolds from bioactive glasses is challenging because of crystallization events that occur while the glass particles densify at high temperatures. Bioactive glasses such as the 13–93 composition can be sintered by viscous flow sintering at temperatures above the glass transition onset (Tg) and below the crystallization temperature (Tc). There is, however, very little literature on viscous flow sintering of bioactive glasses, and none of which focuses on the viscous flow sintering of glass scaffolds in four dimensions (4D) (3D + time). Here, high-resolution synchrotron-sourced X-ray computed tomography (sCT) was used to capture and quantify viscous flow sintering of an additively manufactured bioactive glass scaffold in 4D. In situ sCT allowed the simultaneous quantification of individual particle (local) structural changes and the scaffold's (global) dimensional changes during the sintering cycle. Densification, calculated as change in surface area, occurred in three distinct stages, confirming classical sintering theory. Importantly, our observations show for the first time that the local and global contributions to densification are significantly different at each of these stages: local sintering dominates stages 1 and 2, while global sintering is more prevalent in stage 3. During stage 1, small particles coalesced to larger particles because of their higher driving force for viscous flow at lower temperatures, while large angular particles became less faceted (angular regions had a local small radius of curvature). A transition in the rate of sintering was then observed in which significant viscous flow occurred, resulting in large reduction of surface area, total strut volume, and interparticle porosity because the majority of the printed particles coalesced to become continuous struts (stage 2). Transition from stage 2 to stage 3 was distinctly obvious when interparticle pores became isolated and closed, while the sintering rate significantly reduced. During stage 3, at the local scale, isolated pores either became more spherical or reduced in size and disappeared depending on their initial morphology. During stage 3, sintering of the scaffolds continued at the strut level, with interstrut porosity reducing, while globally the strut diameter increased in size, suggesting overall shrinkage of the scaffold with the flow of material via the strut contacts.This study provides novel insights into viscous flow in a complex non-idealized construct, where, locally, particles are not spherical and are of a range of sizes, leading to a random distribution of interparticle porosity, while globally, predesigned porosity between the struts exists to allow the construct to support tissue growth. This is the first time that the three stages of densification have been captured at the local and global scales simultaneously. The insights provided here should accelerate the development of 3D bioactive glass scaffolds.Graphical abstractImage 1
  • Polymer nanocomposites functionalised with nanocrystals of zeolitic
           imidazolate frameworks as ethylene control agents

    • Abstract: Publication date: June 2019Source: Materials Today Advances, Volume 2Author(s): E.M. Mahdi, C. Cuadrado-Collados, J. Silvestre-Albero, Jin-Chong TanAbstractEthylene (C2H4) management involves the usage of materials such as KMnO4 or processes such as ozone oxidation or combined photocatalysis/photochemistry. The ubiquity of C2H4, especially in an industrial context, necessitates a simpler and much more effective approach, and herein we propose the usage of tuneable polymer nanocomposites for the adsorption of C2H4 through the modification of the polymer matrices via the incorporation of nanocrystals of zeolitic imidazolate frameworks (nano-ZIFs). We demonstrate that the inclusion of ZIF-8 and ZIF-7 nanocrystals into polymeric matrices (Matrimid and polyurethane [PU]) yields robust nanocomposites that preserve the C2H4 adsorption/desorption capacity of nanocrystals while shielding it from degrading factors. We report new insights into the adsorption/desorption kinetics of the polymer and its corresponding nanocomposites, which can be tailored by exploiting the underlying polymeric molecular interactions. Importantly, we also elucidated the retention of the intrinsic structural framework dynamics of the nano-ZIFs even when embedded within the polymeric matrix, as evidenced from the breathing and gate-opening phenomena. Our findings pave the way for bespoke designs of novel polymer nanocomposites, which will subsequently impact the deployment of tailored nanomaterials for effective industrial applications.
  • Porous carbon fibers made from collagen derived from an animal by-product

    • Abstract: Publication date: March 2019Source: Materials Today Advances, Volume 1Author(s): N.V. Salim, X. Jin, S. Mateti, H. Lin, V. Glattauer, B. Fox, J.A.M. RamshawUtilization of reproducible and degradable biomass, particularly that from inexpensive, abundant, and sustainable resources opens an effective way to create high-value carbon materials. Here, we explore for the first time, the direct synthesis of porous carbon fibers from collagen derived from chicken feet in a sustainable method. Chicken feet can provide an abundant supply of young (normally 
  • Solid-state nuclear magnetic resonance spectroscopy of cements

    • Abstract: Publication date: March 2019Source: Materials Today Advances, Volume 1Author(s): B. Walkley, J.L. ProvisAbstractCement is the ubiquitous material upon which modern civilisation is built, providing long-term strength, impermeability and durability for housing and infrastructure. The fundamental chemical interactions which control the structure and performance of cements have been the subject of intense research for decades, but the complex, crystallographically disordered nature of the key phases which form in hardened cements has raised difficulty in obtaining detailed information about local structure, reaction mechanisms and kinetics. Solid-state nuclear magnetic resonance (SS NMR) spectroscopy can resolve key atomic structural details within these materials and has emerged as a crucial tool in characterising cement structure and properties. This review provides a comprehensive overview of the application of multinuclear SS NMR spectroscopy to understand composition–structure–property relationships in cements. This includes anhydrous and hydrated phases in Portland cement, calcium aluminate cements, calcium sulfoaluminate cements, magnesia-based cements, alkali-activated and geopolymer cements and synthetic model systems. Advanced and multidimensional experiments probe 1H, 13C, 17O, 19F, 23Na, 25Mg, 27Al, 29Si, 31P, 33S, 35Cl, 39K and 43Ca nuclei, to study atomic structure, phase evolution, nanostructural development, reaction mechanisms and kinetics. Thus, the mechanisms controlling the physical properties of cements can now be resolved and understood at an unprecedented and essential level of detail.
  • Controlled synthesis of g-C3N4@BiPO4 core–shell nanorods via low
           temperature reassembled strategy

    • Abstract: Publication date: March 2019Source: Materials Today Advances, Volume 1Author(s): Y. Wang, W. Luo, W. Jiang, Z. Wei, Y. ZhuThe g-C3N4@BiPO4 nanorod core–shell structure photocatalysts were prepared by a new neutral hydrothermal reaction system combined with low temperature reassembled strategy. The CN precursors were successfully reassembled on the surface of BiPO4 nanorod to form ultrathin g-C3N4 layer (about 1 nm) under low temperature. Due to the formation of the core–shell structure, it can effectively promote the separation of photogenerated charge, thereby greatly improving the photocatalytic activity under UV light irradiation. The photodegradation activity of the phenol by the g-C3N4@BiPO4 nanorod core–shell structure photocatalyst annealing at the optimized conditions exhibits 1.6 times that of pure BiPO4 nanorod. The relationship between core–shell structure and photocatalytic activity under UV light irradiation was profoundly revealed through a comprehensive contrast experiment, and the mechanism of the enhancement activity of core–shell structure photocatalyst was also explored. It was found and detailedly demonstrated that the CN precursors prepared by neutral hydrothermal reaction can be polymerized into graphite-like phase C3N4 on the surface of Bi-based photocatalytic materials via low temperature thermal catalytic reassembled method. The novel method was proved to be a universal method for construction of core–shell structures. The establishment of g-C3N4@BiPO4 core–shell structure can provide blueprints for the construction of other organic–inorganic interface electric field catalytic system and can greatly improve the attractive prospect in practical applications owing to the perfect photocatalytic performance.Graphical abstractImage 1
  • High-resolution transmission electron microscopy investigation of
           diffusion in metallic glass multilayer films

    • Abstract: Publication date: March 2019Source: Materials Today Advances, Volume 1Author(s): S.V. Ketov, Yu P. Ivanov, D. Şopu, D.V. Louzguine-Luzgin, C. Suryanarayana, A.O. Rodin, T. Schöberl, A.L. Greer, J. EckertAbstractLack of plasticity is one of the main disadvantages of metallic glasses. One of the solutions to this problem can be composite materials. Diffusion bonding is promising for composite fabrication. In the present work the diffusion process in glassy multilayer films was investigated. A combination of advanced transmission electron microscopy (TEM) methods and precision sputtering techniques allows visualization and study of diffusion in amorphous metallic layers with high resolution. Multilayered films were obtained by radio frequency sputter deposition of Zr-Cu and Zr-Pd. The multilayers were annealed under a high vacuum (10−5 Pa) for 1 and 5 h at 400 °C, that is, well below the crystallization temperatures but very close to the glass-transition temperatures of both types of the glassy layer. The structural evolution in the deposited films was investigated by high-resolution transmission electron microscopy. It was observed that, despite the big differences in the atomic mass and size, Pd and Cu have similar diffusion coefficients. Surprisingly, 1 h of annealing results in formation of metastable copper nanocrystals in the Zr-Cu layers which, however, disappear after 5 h of annealing. This effect may be connected with nanovoid formation under a complex stress state evolving upon annealing, and is related to the exceptionally slow relaxation of the glassy layers sealed with a Ta overlayer.
  • Synthesis and superior cathode performance of sandwiched LiMn2O4@rGO
           nanocomposites for lithium-ion batteries

    • Abstract: Publication date: March 2019Source: Materials Today Advances, Volume 1Author(s): Yinghao Chen, Yulan Tian, Yunzhong Qiu, Zhifang Liu, Huanhuan He, Baojun Li, Huaqiang CaoAbstractSpinel LiMn2O4 nanoparticles (NPs) loaded on reduced graphene oxide are prepared via a facile one-pot solvothermal method. The samples are characterized by transmission electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and thermogravimetry analysis. The resultant LiMn2O4-reduced graphene oxide nanocomposites material shows better performances as cathode for lithium-ion batteries than pure LiMn2O4 or physical mixing of LiMn2O4 and reduced graphene oxide. The LiMn2O4-reduced graphene oxide retains about 110 mAh g−1 at 0.5 C after 150 cycles, indicating a better cycling stability than pure LiMn2O4 electrode. The resistance of the LiMn2O4-reduced graphene oxide nanocomposite cell presents great reduction due to the existence of reduced graphene oxide. The wrapping of reduced graphene oxide on LiMn2O4 NPs provides a few-layer conduct fishnet structure, which can greatly shorten the electron transfer path. This work shows the potential applications of the LiMn2O4-reduced graphene oxide as cathode material for high-power lithium-ion batteries.
  • Ultrafast dynamics of laser-metal interactions in additive manufacturing
           alloys captured by in situ X-ray imaging

    • Abstract: Publication date: March 2019Source: Materials Today Advances, Volume 1Author(s): Aiden A. Martin, Nicholas P. Calta, Joshua A. Hammons, Saad A. Khairallah, Michael H. Nielsen, Richard M. Shuttlesworth, Nicholas Sinclair, Manyalibo J. Matthews, Jason R. Jeffries, Trevor M. Willey, Jonathan R.I. LeeAdvanced in situ characterization is essential for determining the underlying dynamics of laser-material interactions central to both laser welding and the rapidly expanding field of additive manufacturing. Traditional characterization techniques leave a critical experimental gap in understanding the complex subsurface fluid flow and metal evaporation dynamics inherent in laser-induced heating of the metal. Herein, in situ ultra-high-speed transmission X-ray imaging is revealed to be essential for bridging this information gap, particularly via comparison with and validation of advanced multiphysics simulations. Imaging on submicrosecond timescales enables correlation between dynamics of the laser-generated vapor–liquid interface and melt pool surface instabilities in industrially relevant alloys. X-ray imaging and complimentary simulations reveal vapor depression oscillations and rapid expansion due to reflection of the processing laser from the front surface of the vapor depression. Pore formation studies at steady state and during prompt removal of laser heating at the end of track reveal that the rapidly solidifying melt pool traps pores near the base of the vapor-filled depression. Moreover, pores within the melt pool are entrained by Marangoni convection which overcomes the force of buoyancy and forces the pores downward from the surface immediately before solidification. Observed solidification kinetics, consistent with previous results, give insight into surface morphology and porosity in the processed material. The information presented here is key for defining the physical models that describe laser-material interaction and ultimately increases our understanding of the emerging field of laser-based metal additive manufacturing.Graphical abstractImage 1
  • Materials Today Advances—a new open access journal for the
           materials community

    • Abstract: Publication date: March 2019Source: Materials Today Advances, Volume 1Author(s): Jamie Warner, Stewart Bland
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
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