Subjects -> METALLURGY (Total: 59 journals)
Showing 1 - 10 of 10 Journals sorted alphabetically
Acta Metallurgica Slovaca     Open Access   (Followers: 2)
Advanced Device Materials     Open Access   (Followers: 6)
American Journal of Fluid Dynamics     Open Access   (Followers: 44)
Archives of Metallurgy and Materials     Open Access   (Followers: 9)
Asian Journal of Materials Science     Open Access   (Followers: 4)
Canadian Metallurgical Quarterly     Hybrid Journal   (Followers: 21)
Complex Metals     Open Access   (Followers: 2)
Energy Materials : Materials Science and Engineering for Energy Systems     Hybrid Journal   (Followers: 24)
Graphene and 2D Materials     Open Access   (Followers: 6)
Handbook of Ferromagnetic Materials     Full-text available via subscription   (Followers: 1)
Handbook of Magnetic Materials     Full-text available via subscription   (Followers: 2)
High Temperature Materials and Processes     Open Access   (Followers: 6)
Indian Journal of Engineering and Materials Sciences (IJEMS)     Open Access   (Followers: 11)
International Journal of Metallurgy and Alloys     Full-text available via subscription   (Followers: 2)
International Journal of Metals     Open Access   (Followers: 7)
International Journal of Minerals, Metallurgy, and Materials     Hybrid Journal   (Followers: 12)
International Journal of Mining and Geo-Engineering     Open Access   (Followers: 4)
Ironmaking & Steelmaking     Hybrid Journal   (Followers: 5)
ISIJ International - Iron and Steel Institute of Japan     Full-text available via subscription   (Followers: 26)
Izvestiya Vuzov. Poroshkovaya Metallurgiya i Funktsional’nye Pokrytiya (Proceedings of Higher Schools. Powder Metallurgy аnd Functional Coatings)     Full-text available via subscription   (Followers: 2)
JOM Journal of the Minerals, Metals and Materials Society     Hybrid Journal   (Followers: 35)
Journal of Advanced Joining Processes     Open Access  
Journal of Central South University     Hybrid Journal   (Followers: 1)
Journal of Cluster Science     Hybrid Journal  
Journal of Heavy Metal Toxicity and Diseases     Open Access  
Journal of Iron and Steel Research International     Hybrid Journal   (Followers: 11)
Journal of Materials & Metallurgical Engineering     Full-text available via subscription   (Followers: 2)
Journal of Materials Processing Technology     Hybrid Journal   (Followers: 21)
Journal of Metallurgical Engineering     Open Access   (Followers: 4)
Journal of Sustainable Metallurgy     Hybrid Journal   (Followers: 3)
Materials Science and Metallurgy Engineering     Open Access   (Followers: 7)
Metal Finishing     Full-text available via subscription   (Followers: 20)
Metallurgical and Materials Engineering     Open Access   (Followers: 7)
Metallurgical and Materials Transactions A     Hybrid Journal   (Followers: 42)
Metallurgical and Materials Transactions B     Hybrid Journal   (Followers: 32)
Metallurgical and Materials Transactions E     Full-text available via subscription   (Followers: 2)
Metallurgical Research & Technology     Full-text available via subscription  
Metallurgical Research and Technology     Full-text available via subscription   (Followers: 8)
Metallurgy and Foundry Engineering     Open Access   (Followers: 3)
Mining, Metallurgy & Exploration     Hybrid Journal  
Powder Diffraction     Full-text available via subscription   (Followers: 1)
Powder Metallurgy     Hybrid Journal   (Followers: 35)
Powder Metallurgy and Metal Ceramics     Hybrid Journal   (Followers: 7)
Powder Metallurgy Progress     Open Access   (Followers: 5)
Practical Metallography     Full-text available via subscription   (Followers: 6)
Rare Metals     Hybrid Journal   (Followers: 3)
Revista de Metalurgia     Open Access  
Revista del Instituto de Investigación de la Facultad de Ingeniería Geológica, Minera, Metalurgica y Geográfica     Open Access  
Revista Remetallica     Open Access   (Followers: 1)
Russian Metallurgy (Metally)     Full-text available via subscription   (Followers: 4)
Science and Technology of Welding and Joining     Hybrid Journal   (Followers: 8)
Soldering & Surface Mount Technology     Hybrid Journal   (Followers: 2)
Steel Times lnternational     Partially Free   (Followers: 19)
Transactions of the IMF     Hybrid Journal   (Followers: 14)
Transactions of the Indian Institute of Metals     Hybrid Journal   (Followers: 5)
Tungsten     Hybrid Journal  
Universal Journal of Materials Science     Open Access   (Followers: 3)
Welding in the World     Hybrid Journal   (Followers: 8)
Welding International     Hybrid Journal   (Followers: 11)
Вісник Приазовського Державного Технічного Університету. Серія: Технічні науки     Open Access  
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Powder Metallurgy and Metal Ceramics
Journal Prestige (SJR): 0.221
Number of Followers: 7  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1573-9066 - ISSN (Online) 1068-1302
Published by Springer-Verlag Homepage  [2655 journals]
  • Effect of TiB 2 on the Phase Composition, Microstructure, and Tribological
           Properties of AlCoCrFeNi/TiB 2 Composites
    • Abstract: High entropy alloys (HEAs) attract more and more attention due to their simple structure, high strength and hardness, good ductility, and excellent softening, oxidation, corrosion, and wear resistance properties. Among the known HEA systems, the AlCoCrFeNi alloy exhibits complicated microstructure and excellent mechanical properties. In this study, the AlCoCrFeNi/TiB2 composites were prepared via power metallurgy route in combination with spark plasma sintering (SPS) technology. At first, the AlCoCrFeNi HEA powders were prepared by gas-atomization technology under Ar atmosphere with the high purity of raw elemental materials. The commercial TiB2 powders with average particle size of about 2 μm were used as the reinforcing agent to prepare the AlCoCrFeNi/TiB2 composites. The effect of TiB2 content on the phase, microstructure, and tribological properties of the synthesized AlCoCrFeNi/TiB2 composites were investigated by XRD, SEM, and EPMA, whereas also through friction and wear tests. The results show that phase transformation occurs with σ phase formation after sintering. The TiB2 particles tend to agglomerate and grow up with increased TiB2 content. The effect of TiB2 on the tribological behavior of the composites was studied through measuring the coefficient of friction (COF) and wear rate (W). The resulting values of COF and W show that the wear resistance of AlCoCrFeNi/TiB2 composites is improved with increasing the TiB2 content.
      PubDate: 2021-03-11
       
  • Modeling of Multimodulus Elastic Behavior of Damaged Powder Materials
           Using Computational Micromechanics
    • Abstract: The work aimed to improve the fundamental acoustic defectoscopy principles of green compacts and weakly sintered materials. A theoretical method for determining the elastic properties of powder porous materials with distributed microdefects has been proposed. The nonlinear elastic multimodulus (different stiffness in tension and compression) behavior of this material has been described by micromechanical averaging on a representative cell. According to the mechanics of composites, the cell geometry represents the structure of a heterogeneous material, and the boundary conditions on a representative cell enable relating the stress–strain state at the macro- and meso-level. The averaging was carried out by computer simulation using the finite element method with an adaptive mesh, which automatically condensed in the places of the large gradient stress–strain. The structure of the representative cell corresponds to a powder material with ‘imperfect’, i.e., partially stratified, interparticle contacts. In the proposed model, the rheological response of a porous, damaged material is specified by three elastic moduli. The structure of such a material is described by two internal state parameters, namely, the porosity and the degree of interparticle contacts delamination. That is, the elastic moduli are functions of porosity and damage. Accordingly, several values of elastic moduli were calculated for a discrete density and damage range. The advantage of this approach is focused precisely on the powder materials rather than on any damaged material, in general, which allows considering the real structure of the damaged material using the mechanics of microheterogeneous materials. The developed structure-sensitive elasticity model enabled establishing the relationship between the defectiveness of a porous sample and the resonant frequency of its free vibrations.
      PubDate: 2021-03-02
       
  • The Co–Ni–Zr Phase Diagram in the Zr–ZrCo–ZrNi Region I. Phase
           Equilibria in the Zr–ZrCo–ZrNi System at Subsolidus Temperature,
           900°C, and 800°C
    • Abstract: The phase equilibria in the Zr–ZrCo–ZrNi system at subsolidus temperature and at 900 and 800°C were first studied using physicochemical analysis methods, and solidus surfaces and isothermal sections at 900 and 800°C were constructed. Isomorphic Zr2Co and Zr2Ni compounds with a tetragonal crystal structure of AlCu2 (θ) type form a continuous series of solid solutions dividing the Zr–ZrCo–ZrNi system into two subsystems: Zr–Zr2Co–Zr2Ni and ZrCo–ZrNi–Zr2Ni–Zr2Co. The equilibria on the solidus surface of the Zr–Zr2Co–ZrCo–Zr2Ni system and at 900°C differ significantly. This is associated with the Zr3Co-based η phase formed by peritectoid reaction 〈β − Zr〉 + 〈Zr2Co〉 → η at 980°C, being close to theL ↔ θ + β eutectic crystallization temperature (986°C), in the binary Zr–Co system. At 900 and 800°C, the 𝜂 phase dissolves up to 14.5% Ni. The solidus surface of the ternary Zr2Co–Zr2Ni–ZrCo–ZrNi system shows a three-phase equilibrium of the θ phase with the ZrCo (δ) and ZrNi (δ2) phases of the ZrCo–ZrNi quasibinary section: δ + δ2 + θ. The plane of this tie-line triangle extends significantly at 900 and 800°C as the solubility of nickel in the cubic ZrCo-based phase of CsCl type changes. At room temperature, all alloys of the ZrCo–ZrNi–Zr2Ni–Zr2Co subsystem should contain three phases: δ + δ2 + θ. The solidus surface of the Zr–ZrCo ZrNi system is thus completed by surfaces corresponding to the homogeneity regions of the δ, δ2, δ, and β phases, θ + δ + δ2 tie-line triangle plane, and ruled surfaces representing the upper boundary of the two-phase θ + δ2, θ + δ, and θ + δ volumes. At 900 and 800°C, two three-phase equilibria, η + θ + β and δ + δ2 + θ, are observed in the system.
      PubDate: 2021-03-02
       
  • High-Entropy Ceramics for Thermal Barrier Coatings Produced from ZrO 2
           Doped with Rare-Earth Metal Oxides
    • Abstract: Current studies of ceramic topcoat materials for thermal barrier coatings (TBCs) of next generation focus mainly on ternary, quaternary, and more complex oxide systems. The use of high-entropy ZrO2-based ceramics doped with a mixture of rare-earth metal (REM) oxides for TBCs was studied, and the properties of thermal barrier ceramic layers deposited by EB-PVD in one process cycle were examined. For research, a CeO2-based REM concentrate (light concentrate (LC)) with the following composition (wt.%) was chosen: 62.4 CeO2, 13.5 La2O3, 10.9 Nd2O3, 3.9 Pr6O11, 0.92 Sm2O3, 1.2 Gd2O3, 0.24 Eu2O3, 2.66 ZrO2, 1.2 Al2O3, and 1.7SiO2; the total content of other oxides was 1.38. Targets for depositing the thermal barrier ceramic layer were produced by the ceramic synthesis method from the 85 wt.% M-ZrO2–15 wt.% LC mixture. Two-layer metal/ceramic TBCs were deposited employing the UE-174 industrial electron-beam installation operated at ELTECHMACH (Vinnytsia) onto model blades manufactured by directional crystallization from the ZhS-26VI alloy. A rough dense glossy coating was produced. The coating on the blade suction side and leading edge was 85 μm thick and on the blade pressure side was 70 μm thick. The coating phase composition represented a mixture of F-ZrO2 and M-ZrO2. Dense columnar crystallites collected into feather-like structures were observed in the ceramic layer. Vertical pores that formed between the crystallites were located perpendicularly or at an angle to the surface. A complex Al2O3-based spinel layer 2–2.5 μm thick grew between the ceramic topcoat and metallic bond coat layers. The ceramic layer acquired a laminar structure under the synergistic effect of components in the ZrO2–REM concentrate mixture in the vapor deposition process. The microstructural features of the coating determined the microhardness gradient in height. Thermal cycling experiments showed that this coating withstood 161 thermal cycles, which was higher than the standard YSZ coating did (138 thermal cycles). Previous studies showed that ZrO2 stabilization with REM oxide concentrates was promising for the microstructural design of the thermal barrier ceramic layer.
      PubDate: 2021-03-02
       
  • Information on the Annual Report of the Ukrainian Commission on Phase
           Diagrams and Thermodynamics
    • Abstract: The Alloy Phase Diagram International Commission (APDIC) promotes the effective dissemination of data on phase diagrams and thermodynamics of phases in accordance with the required quality standards and furthers the application of phase diagrams in research and industry. The annual report of the Ukrainian Commission on Phase Diagrams and Thermodynamics, which is a member of APDIC as one of the national participants, presents information on the findings of Ukrainian scientists in this field in 2017–2019. Information on the research findings is presented in a table, collecting data on the systems studied and results obtained and listing references to the published papers.
      PubDate: 2021-03-01
       
  • Thermodynamic Properties of Tungsten Disulfide from First Principles in
           Quasi-Harmonic Approximation
    • Abstract: The standard values (T = 298.15 K) of thermodynamic properties of hexagonal tungsten disulfide 2H-WS2 were calculated from first principles using density functional theory and quasi-harmonic approximation with finite displacements in supercells. Local density approximation was chosen as the exchange-correlation functional and the calculation was performed without Van der Waals corrections. The calculated data are in good agreement, except for the enthalpy of formation, with reliable experimental results, eliminating the discrepancies between the experimental results from different sources and increasing the overall reliability of thermodynamic data for tungsten disulfide. Additionally, the data agreement suggests that greater attention should be paid to experimental studies of the phonon spectrum of 2H-WS2, particularly in the Γ → K region of the low-energy dispersion, where the deviations between the calculation and inelastic neutron scattering are significant. The values of the heat capacity, entropy, and enthalpy of tungsten disulfide are recommended for incorporation into thermodynamic databases and practical application, and the parameters used to calculate these quantities are recommended as initial parameters in firstprinciples studies of the 2H-WS2 properties related to the vibrational spectrum. The calculated value of ∆fH°(2H-WS2, 298.15 K) = –275 ± 0.5 kJ ∙ mole–1 is about 10% below the median of the existing literature data and about 15% below the experimental result accepted as the most reliable. To improve the result, the calculation requires additional attention, for example, by the application of Van der Waals corrections or hybrid approximations to the exchange-correlation functional.
      PubDate: 2021-03-01
       
  • Titanium-Doped Powder Coatings with a TiN Layer on 9KhS Steel and VK8
           Hardmetal Substrates
    • Abstract: The phase and chemical compositions, structure, and properties of titanium/aluminum-doped coatings with a TiN layer on 9KhS steel and VK8 hardmetal substrates were studied. A TiN layer 5.0–5.5 μm thick was applied by the physical vapor deposition method. The alloys were doped with titanium and aluminum in fusible containers in a mixture of powders consisting (wt.%) of 40.0 Ti, 5.0 Al, 5.0 Al2O3, and 5 NH4Cl at 1050°C for 4 h. Multilayer coatings including Al2O3, Fe2Ti4O, TiC, and TiN formed on the 9KhS substrate and Al2O3, TiAlCO2, TiC, and TiN coatings on the hardmetal substrate. The TiN layer completely inhibited the penetration of aluminum into the 9KhS substrate and of aluminum and oxygen into the VK8 hardmetal substrate. The coating on 9KhS steel had no Feα(Al) layer, and the coating on VK8 hardmetal had no area containing aluminum and oxygen. Individual layers in the coatings exhibited high microhardness: 35.6 GPa for the TiC layer on 9KhS steel, 29.0 GPa for the TiC layer on VK8 hardmetal, and 23.4–23.6 GPa for the TiN layer on both substrates. The cross-sectional structure of the coatings was virtually porousless, showing good adhesion between the individual layers and the substrate, being characteristic of diffusionhardened coatings. The wear resistance of the coated 9KhS steel was 6.9 times higher than that of the uncoated steel in dry sliding friction conditions. The coated 9KhS steel showed an extreme dependence of the wear on the sliding velocity. Mechanically fastened indexable hardmetal cutting tools with coatings demonstrated 8.3 times higher resistance than uncoated tools tested by 40Kh13 steel cutting. The coatings developed can substantially increase the performance of 9KhS steel and VK8 hardmetal tools.
      PubDate: 2021-03-01
       
  • Effect of Selective Laser Melting Parameters on the Melt Pool Formed by
           Single Tracks of the Heat-Resistant Inconel 718 Nickel Alloy
    • Abstract: The characteristics of single-track melt pools, such as size, shape, and stability, formed by the heatresistant Inconel 718 nickel alloy powder subjected to selective laser melting (SLM) were studied. The objective was to determine the range of optimal SLM parameters to provide a stable track with a depth of two to three layers. Single tracks were built using various combinations of process parameters: laser power from 50 to 400 W with a step of 30 W and scanning speed from 450 to 1000 mm/sec with a step of 50 mm/sec (144 modes in total). An Axiovert 200M MAT light microscope (Carl Zeiss) was employed to examine the cross sections of single tracks and evaluate the geometrical parameters of the melt pools. Features pertaining to the effect of the scanning speed and laser power on single-track depth and width and their ratio were experimentally studied. An unstable track formed at low power (P = 50 W) and low scanning speed (V = 450–500 mm/sec), while no track appeared at all at higher speeds. A stable track formed at power P = 80–200 W at low speeds (V = 500–900 mm/sec) and became unstable and intermittent when speed increased to V = 1000 mm/sec. With higher laser power (P = 230–400 W) and low process speeds, a continuous track formed but had an increased variable width, being indicative of a deviation from the stable track formation conditions. It was first established that the intensity of the scanning speed effect (450–1000 mm/sec) on the single track depth varies by more than 2.5 times depending on the laser power (50–400 W). The process parameters that would ensure the formation of an optimal single track in terms of geometric parameters were determined.
      PubDate: 2021-03-01
       
  • Structural and Electrical Properties of Magnesium-Doped CoFe 2 O 4
    • Abstract: In this paper, magnesium-doped CoFe2O4 (Co0.5Mg0.5Fe2O4) compound was synthesized by a solidstate reaction route. The impact of Mg inclusion on the structural parameters of the obtained compound and the subsequent development of thermally-assisted electro-active areas has been systematically examined, as this compound has a fit composition for doping at the site of Co due to its relevantly equal atomic radius. Also, Mg was established as highly ferroelectric and low-weight material. The compound structure and microstructure have been analyzed using the method of scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The dielectric properties were studied over a broad spectrum of frequency and temperature, and quite low dielectric loss was recorded. In the context of impedance and conductivity formalism, frequency-dependent electrical information has been evaluated at varying temperatures. The Nyquist plot represents the effect of grain and grain boundary. Thermally activated non-Debye type relaxation processes were observed in the composites. Jonscher universal power law follows the frequency-dependent AC conductivity at different temperatures. Temperature dependence of AC conductivity at various frequencies indicates a negative temperature coefficient of resistance (NTCR) behavior. Estimating the magnitudes of activation energies in different temperature ranges enables defining the nature of the species involved in the conduction system.
      PubDate: 2021-03-01
       
  • Effect of Various Additives on the Hydrolysis Performance of
           Nanostructured MgH 2 Synthesized by High-Energy Ball Milling in Hydrogen
    • Abstract: Magnesium hydride is a promising material for hydrogen generation via hydrolysis owing to high hydrogen storage capacity, mild reaction conditions, and low cost of magnesium metal. Unfortunately, the hydrolysis reaction of MgH2 is rapidly hindered due to the formation of a passive Mg(OH)2 layer. Various additives can be used to improve the efficiency of the reaction. The present study examines the influence of 5 wt.% EDTA and TiC–2TiB2 additives on the hydrolysis of the nanostructured MgH2 and compares it with the hydrolysis performance of pure MgH2 and MgH2 + 5 wt.% AlCl3 for the first time. MgH2 was synthesized by high-energy ball milling of Mg powder in hydrogen gas, while MgH2-based nanocomposites were prepared either by mixing the obtained MgH2 with 5 wt.% of additives or by milling Mg with 5 wt.% of additive in hydrogen. The synthesized MgH2 is nanosized, containing a mixture of β-MgH2 and high-pressure γ-modification of MgH2. The hydrogen generation performance in terms of MgH2 conversion rate and hydrogen yield was determined volumetrically. It was found that the MgH2 + 5 wt.% EDTA composite displays the lowest reactivity among the tested materials, probably due to the interaction of MgH2 with EDTA during the ball milling. Pure MgH2 and MgH2 + 5 wt.% (TiC–2TiB2) composite demonstrate almost twice as better hydrolysis performance, which is, however, still quite far from application requirements. The maximum hydrogen yield of 557 mL/g MgH2 and conversion rate of 30.3% was observed for MgH2 + 5 wt.% AlCl3 composition after 10 min of hydrolysis, which can be attributed to the destabilization of the Mg(OH)2 layer by chlorine ions.
      PubDate: 2021-03-01
       
  • Polymer Materials Reinforced with Silicon Nitride Particles for 3D
           Printing
    • Abstract: Comprehensive research into the production of a ceramic-reinforced polymer material from highdensity polyethylene or polypropylene and β-Si3N4 powder was conducted. The incorporation of silicon nitride ceramic particles (5 and 10 vol.%) into the polymers to make polymer–ceramic filaments was studied step by step. High-quality polypropylene–ceramic filaments could be obtained at an extrusion temperature of 150°C with an extrusion speed of 20 cm/min and polyethylene–ceramic filaments at 160°C and 30 cm/min. Data on the shape and size distribution of Si3N4 particles were used to simulate the elementary volume of the filaments to determine the mechanical properties of the composites applying a 2D finite-element model. The reinforcement of the polypropylene/polyethylene-matrix material by 10 vol.% Si3N4 particles was not sufficient because the composite elastic modulus increased insignificantly and the critical strain decreased substantially to incorporate a greater volume of hard particles to improve the elastic modulus. To assess the quality of the polymer–ceramic filaments, parts of different shape (washer and auger) from reinforced and unreinforced filaments were designed and printed. The printed polymer–ceramic parts demonstrated a smooth surface and had no ledges or discontinuous areas. The mechanical (Vickers and Brinell hardness) and tribological (volume wear) properties of the materials were examined. Wear tests of the polyethylene–Si3N4 composite showed that its wear resistance tended to improve with increasing ceramic content of the filament. The low abrasive wear of the Si3N4-reinforced polypropylene/polyethylene material and the behavior of ceramic particles in contact with the indenter indicate that the composite has high fracture resistance in 3D printing.
      PubDate: 2021-03-01
       
  • The Structure and Properties of 65 wt.% Fe–35 wt.% FKh800 Chromium
           Carbide Steel Doped with Titanium Boride Additions
    • Abstract: The effect of TiB2 additions on the structure, phase composition, and mechanical and tribological properties of materials in the Fe–FKh800 system was studied. The introduction of titanium boride additions activated compaction of the iron-based composites through sintering with participation of the liquid phase that emerged with the formation of low-melting Fe–C–B (Tm ~ 1050°C) and γ-Fe–Fe2B–TiB2 (Tm ~ 1162) eutectics and led to a 50–70°C decrease in the sintering temperature of the compacts. Titanium boride additions between 0.38 to 0.74 wt.% provided 20–25% higher bending strength of the 65 wt.% Fe–35 wt.% FKh800 composite with a slight increase in hardness. Metallographic studies, X-ray diffraction, and electron microprobe analysis of the Fe–35 wt.% FKh800–TiB2 materials showed that titanium boride additions promoted a multiphase, microheterogeneous matrix-reinforced composite, consisting of Kh17 chromium steel, double M7C3 and M3C iron–chromium carbides, and complex Me3(CB) carboborides. The influence of TiB2 additions on the wear resistance of the composites subjected to dry friction against fixed diamond wheel particles and ShKh15 steel was studied. The study showed that the abrasive mass wear (Im) of carbide steels decreased from 36.94 to 14.8 mg/km and their linear wear (Il) decreased from 0.197 to 0.079 mm/km with TiB2 additions increasing from 0.38 to 1.48 wt.%. Titanium boride additions ranging from 0.38 to 2.2 wt.% reduced the mass wear rate from 4.9 to 1.9 mg/km in dry friction of the composite against a ShKh15 steel counterface with 50–55 HRC hardness and decreased the friction coefficient from 0.49 to 0.38.
      PubDate: 2021-03-01
       
  • Nanostructured Carbon Fiber Modified by Silver Nanoparticles for the
           Medical Application
    • Abstract: In this work, the feasibility of synthesizing new composite system for the medical application using an activated carbon fiber nanostructured materials with silver nanoparticles through immobilization by adsorption from solutions (ACFNM/AgNP) has been studied. The stability of the obtained composite system in physiological solutions as a modern sorption application form has been examined. Optimal modes of carbonized fabric activation are proposed for synthesis of nanostructured carbon fiber with high sorption capacity. The size distribution of silver nanoparticles after the ultrasonic treatment of the original silver solution in glycerol was proved to significantly decrease in the size of the agglomerates formed in the solution. It has been shown that after ultrasonic treatment, the silver nanoparticles were actively adsorbed by the porous structure of the carbon matrix. Treatment of carbon fiber with silver nanoparticles showed their uniform adsorption on the surface of the carbon matrix to form silver agglomerates with sizes of ~90–120 nm and 250– 300 nm. When studying the physicochemical stability of the obtained composite systems in biological solutions it was revealed that the intensity of silver release from the surface of the ACFNM/AgNP composite depends on the volumetric capacity of the carbon matrix, the initial concentration of silver in the solution, and the chemical composition of biological media. At that, the amount of silver in the water filtrate was established to be greater than in physiological solutions after the interaction. It was shown that the initial silver concentration of 25 mg/L in a suspension of glycerol is most optimal for creating of stable ACFNM/AgNP composite systems. Besides, the slower release of silver from the surface of carbon matrices into physiological solutions of different salt composition ensures a prolonged effect of silver in modern sorption application forms for medical purposes. The ACFNM/AgNP composite system with a capacity of carbon matrix of 1.0 cm3/g and an initial concentration of silver in a solution of 25 mg/L was recommended for the future development of modern application materials.
      PubDate: 2021-03-01
       
  • Electrochemical Corrosion of Composite Ceramics and Thermal Spray Coatings
           in the ZrB 2 –SiC–AlN System
    • Abstract: Polarization studies of the ZrB2–SiC–AlN compact ceramic material and thermal spray coatings of the same composition were conducted in a 3% NaCl solid solution to analyze their cathodic and anodic behavior. The compact ceramic material was produced by hot pressing, the plasma-sprayed coating 240 μm thick was deposited onto a C/C–SiC graphite substrate, and the detonation-sprayed coating 340 μm thick was applied to 12Kh18N9T stainless steel. The microstructure and phase composition of the compact sample and thermal spray coatings were examined. The microstructure was heterophase in all cases. The compact sample and plasma-sprayed coating contained SiC, AlN, and ZrB2 as the main phases, and the detonation-sprayed coating additionally had a small amount of nickel and zirconium oxide. Electron microprobe analysis showed that the plasma-sprayed coating had 20 wt.% oxygen; i.e., the coating contained oxide phases in the amount not revealed by X-rays. The compact ceramic sample showed exceptionally high resistance to electrochemical oxidation: electrochemical potential, Ecorr, at which corrosion current occurs is very high and constitutes +1.51 eV. For the detonation- and plasma-sprayed coatings, Ecorr = –0.25 and –0.05 eV, respectively. The great resistance of the compact ceramic material to electrochemical oxidation correlates with its resistance to high-temperature oxidation above 1700°C. This is due to the formation of an Al2O3–SiO2 mullite film on the surface. The lower resistance of the coatings to electrochemical oxidation compared to the compact material is associated with their increased porosity.
      PubDate: 2020-11-28
      DOI: 10.1007/s11106-020-00173-2
       
  • Detonation-Sprayed Coatings of (Ti, Cr)B 2 –NiAlCr Composite Materials
           II. Mechanical and Tribotechnical Properties
    • Abstract: The mechanical and tribotechnical properties of detonation-sprayed coatings produced from (Ti, Cr)B2–NiAlCr composites were studied. The influence of various preliminary substrate treatment methods and refractory-to-metal ratio in the spray material on the coating–substrate adhesion strength, σad, was analyzed. Spraying a sublayer had no significant effect on the coating adhesion strength. The adhesion strength σad increased by 25–30% with the metal content changing from 25 to 75%, while σad = 120–145 MPa even at 25% NiAlCr. The hardness of the coatings changed within rather narrow limits (HV0.2 = 7–12 GPa), but the refractory-to-metal ratio varied over a wide range. The coatings containing a minimum amount of the metal component (25%) were predicted to have higher hardness, HV0.2 = 10–12 GPa, though it was almost half the hardness of the sintered compact material. At equal contents of the refractory and metal components, HV0.2 = 9–10 GPa; for the material containing 75% of the metal component, HV0.2 = 7–8 GPa. The tribotechnical properties of the coatings were studied in dry sliding friction conditions with ball-ondisk tests. At the initial friction stage, high pressures appeared in the contact zone (P ≥ 500 MPa). Therefore, in addition to high hardness, the coatings should have high strength. At 50–75% (Ti, Cr)B2, besides abrasion processes, brittle fracture and spalling of the coatings occurred. The best characteristics were shown by the coating produced from the material containing 25% (Ti, Cr)B2. Since the (Ti, Cr)B2 particles are fine, wetted well by the NiAlCr alloy, and uniformly distributed over the starting material and associated coating, even their relatively low content (25%) promotes high abrasion resistance and adhesion.
      PubDate: 2020-11-28
      DOI: 10.1007/s11106-020-00175-0
       
  • Thermodynamic Properties and Phase Equilibria in Ba–Sn Alloys
    • Abstract: The mixing enthalpies for liquid Ba–Sn alloys were determined by isoperibolic calorimetry at 1300 K over the entire composition range. Large exothermic mixing effects ( ∆Hmin = –54.8 ±± 1.8 kJ/mole at xBa = 0.56) were found. They are indicative of strong interaction between different components and of short ordering in the liquid alloys. The thermochemical properties of the melts and barium stannides and the phase equilibria in the Ba–Sn system were used to calculate the activities of components, molar fractions of associates, and formation enthalpies and entropies for liquid BaxSn1–x alloys with the ideal associated solution (IAS) model. Two associates, BaSn and Ba2Sn, were selected for the calculation. The calculated activities of components in the Ba–Sn melts show very large negative deviations from the ideal solution, which is consistent with their thermochemical properties. The maximum concentration of each associate is approximately 0.65 for respective compositions. The calculated formation enthalpies for BamSnn intermetallics are quite high exothermic values that agree well with the published data for BaSn3 and only qualitatively for Ba2Sn. The formation enthalpy for the associate agrees with that for the respective BaSn intermetallic and is slightly less exothermic for Ba2Sn. This all indicates that the bonding energies between different atoms in the respective intermetallics and melts are close to each other and quite high. The formation entropy for the Ba2Sn associate is lower and that for BaSn is higher in magnitude. This demonstrates different degrees of ordering in BaSn and Ba2Sn associates and intermetallics. This may be due to different changes in the oscillation frequencies of atoms and other factors. The calculated liquidus curve of the Ba–Sn phase diagram agrees with data for the Sn–Sr system.
      PubDate: 2020-11-28
      DOI: 10.1007/s11106-020-00178-x
       
  • Structural State of High-Entropy Fe 40–x NiCoCrAl x Alloys in
           High-Temperature Oxidation
    • Abstract: The evolution of phase composition and mechanical properties and the formation of oxide layers on Fe40–xNiCoCrAlx (x = 5 and 10 at.%) alloys in long-term oxidation at 900 and 1000°C were studied. In the initial cast state, depending on the aluminum content and valence electron concentration, the alloys contain only an fcc solid solution (VEC = 8 e/a) or a mixture of fcc and bcc phases (VEC = = 7.75 e/a). Thin continuous oxide scales containing Cr2O3 and NiCr2O4 spinel formed on the surface of both alloys oxidized at 900°C for 50 h. A further increase in the annealing time to 100 h leads to the formation of aluminum oxide Al2O3 in the scale on the Fe30Ni25Co15Cr20Al10 alloy, having high protective properties. An increase in the oxidation temperature to 1000°C results in partial failure of the protective layer on the alloy with 10 at.% Al. Long-term holding at 900°C (100 h) + 1000°C (50 h) does not change the phase composition of the Fe35Ni25Co15Cr20Al5 alloy matrix, being indicative of its high thermal stability. In the two-phase Fe30Ni25Co15Cr20Al10 alloy, the quantitative ratio of solid solutions sharply changes: the amount of the bcc phase increases from 4 to 54 wt.% and its B2-type ordering is observed. The mechanical characteristics of the starting alloys and those after long-term high-temperature annealing were determined by automated indentation. The hardness (HIT) and elastic modulus (E) of the cast Fe35Ni25Co15Cr20Al5 alloy are equal to 2 and 147 GPa, respectively, and decrease to 1.8 and 106 GPa after a series of long-term annealing operations. The Fe30Ni25Co15Cr20Al10 alloy shows the opposite dependence: HIT increases from 2.5 in the initial state to 3.1 GPa after annealing and E decreases from 152 to 134 GPa. This indicates that the Fe30Ni25Co15Cr20Al10 alloy is promising as a high-temperature oxidation-resistant and creep-resistant material.
      PubDate: 2020-11-28
      DOI: 10.1007/s11106-020-00180-3
       
  • Effect of Heat Treatment on the Physicochemical Properties of Ultrafine
           ZrO 2 –Y 2 O 3 –CeO 2 –Al 2 O 3 –CoO Powders
    • Abstract: Variations in the phase composition, specific surface area, and morphology of structural components in the ultrafine powder of composition (wt.%) 70 (90 ZrO2 (3 Y2O3, 2 CeO2)–10 Al2O3)–30 CoAl2O4 (70ZA30CoA), produced by hydrothermal synthesis combined with mechanical mixing, were studied in the heat treatment process up to 1300°C. The study employed Xray diffraction, scanning and transmission electron microscopy, petrography, and BET. The formation of CoAl2O4 in the 70ZA30CoA powder in the heat treatment process was accompanied by reversible phase transformations: T-ZrO2 → M-ZrO2 → T-ZrO2. The M-ZrO2 content increased from 15% to 46% in the temperature range 850–1000°C and decreased to 13% after heat treatment to 1150°C. The process involved slight coarsening of the primary T-ZrO2 particles, while the size of the primary M-ZrO2 particles remained practically unchanged. The phase transformation was due to a decrease in the free energy of the ultrafine 70ZA30CoA powder, representing a thermodynamically nonequilibrium system. The phase composition changed color of the 70ZA30CoA powder in the following sequence: gray → gray blue → dark cyan → bright blue. Morphological analysis of the structural components showed that the CoAl2O4 formation and reversible T-ZrO2 → M-ZrO2 phase transformation were accompanied by shape change, loosening, and subsequent sintering of the agglomerates. The chain-like agglomerates of various shapes and sizes indicate that the 70ZA30CoA powder sinters actively at 1300°C. The decrease in the specific surface area from 46 to 1 m2/g depending on the heat treatment temperature was determined by the development of three structural transformation processes: formation of CoAl2O4, phase transition of the ZrO2 solid solution, and sintering of the 70ZA30CoA powder. The established regularities are of fundamental importance for the microstructural design of ZrO2 composites such as ZrO2–Y2O3–CeO2–Al2O3–CoO materials of blue and other colors for various applied purposes.
      PubDate: 2020-11-28
      DOI: 10.1007/s11106-020-00169-y
       
  • Effect of Processing Parameters on the Structure and Properties of Powder
           Fe–Al Intermetallic Compounds Obtained by Sintering and Impulse Hot
           Pressing
    • Abstract: The paper examines the effect of high-energy grinding and post-treatment conditions on the structure and physical and mechanical properties of iron aluminide Fe–15 wt.% Al obtained by sintering and impulse hot pressing. It was shown that the grinding of a mixture of iron and aluminum powders in a planetary mill results in the formation of lamellar particles whose morphology is preserved in the alloy structure after sintering and impulse hot pressing. After grinding, sintered intermetallic compounds obtained from powder mixtures demonstrate low physical and mechanical properties due to the low quality of grain boundaries. The use of impulse hot pressing for compaction of samples from milled powders at temperatures of 850–1150°C significantly increases the density of intermetallic compounds compared to sintered materials of a similar composition—from 5 to 6.5 g/cm3. The increase in the temperature of impulse hot pressing contributes to an increase in mechanical characteristics, where the maximum values of bending strength and fracture toughness are 880 MPa and 21 MPa · m0.5, respectively. Subsequent hightemperature annealing (1350–1450°C) leads to an improvement of the quality of grain boundaries with the formation of a predominantly discontinuous grid, coagulation of impurity segregation, and, as a result, to a sharp increase in bending strength and fracture toughness, which are 1400 MPa and 27 MPa · m0.5, respectively. It was shown that the interparticle rupture observed in the samples after impulse hot pressing at relatively low temperatures changes to transcrystalline after hightemperature annealing.
      PubDate: 2020-11-28
      DOI: 10.1007/s11106-020-00171-4
       
  • High-Density Mo–W–Cu Pseudoalloys Based on Homogenous Mo–25% W
           Powder Alloy Produced by Reducing Oxide Powders in Moving Layers
    • Abstract: The article aimed to obtain a structural material with increased plasticity and density of 98.5–99.5% based on (Mo–25% W)–20 vol.% Cu pseudoalloys with a homogeneous refractory skeleton obtained by a single-time pressing and sintering of the dispersed mixture at temperatures 1400–1500°C. The production of a dispersed granulated Mo–25% W alloy with a powder particle size of 0.1–0.3 μm through the decomposition of complex ammonium paramolybdate and paratungstate salts into oxide compounds xWO3 · yMoO3 with their subsequent reduction by hydrogen in a rotary chamber was studied. Considering the temperature and decomposition time of complex salts in the moving layers, the physical and technological properties (such as phase composition, oxygen content, specific surface, bulk density, and tap density) of complex oxide powders xWO3 · yMoO3 and metal Mo– 25% W powders after reduction by hydrogen were compared with the corresponding properties of powders obtained in a stationary tube furnace in fixed layers. Temperature dependencies of porosity in (Mo–25% W)–20 vol.% Cu pseudoalloys after sintering at the temperature between 900 and 1500°C has been examined. It has been established that compaction of dispersed powder mixtures of (Mo–25% W)–20 vol.% Cu and homogenization of Mo–25% W alloy after sintering begin at the temperature 300°C lower than when sintering mechanical mixtures of commercial metal powders. It has been shown that (Mo–25% W)–20 vol.% Cu pseudoalloys obtained by liquid-phase sintering at 1500°C for 1 hour have the following characteristics: at 20°C, the ultimate tensile strength σt == 490 MPa, relative elongation δ = 1.1, Brinell hardness HB = 3.3 GPa, and at 500°C— σt == 370 MPa, δ = 4.4, and HB = 2.7 GPa.
      PubDate: 2020-11-27
      DOI: 10.1007/s11106-020-00170-5
       
 
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