Amorphous highly conductive coatings Ti-Al-C, (Ti,Mo)-Al-C and (Ti,Cr)-Al-C were deposited on titanium alloy substrates by hybrid magnetron using T2AlC and Ti3AlC2 MAX-phases-based targets and in parallel cathode-arc evaporation of Mo or Cr targets. The (Ti,Cr)-Al-C coating showed the highest electrochemical corrosion resistance among all deposited coatings in 3.5 wt% NaCl aqueous solution at 25 degrees C: corrosion potential Ecorr = 0.044 V vs. saturated calomel electrode, corrosion current density icorr = 2.48 x 10-9 A/cm2. The (Ti,Cr)-Al-C coating also demonstrated the highest long-term oxidation resistance, and after heating in air at 600 degrees C for 1000 h, its surface electrical conductivity became even slightly higher after long-term heating: increased from sigma = 9.84 x 106 S/m to sigma = 4.35 x 105 S/m, which is explained by the crystallization of the amorphous coating during heating process. The nanohardness and Young's modulus of the coating after deposition were within 15 GPa and 240 GPa, respectively. The hybrid magnetron deposited (Ti,Cr)-Al-C coatings can be used to protect interconnects in lightweight molten carbonate fuel cells elements.

The molybdenum nitride coating deposited by the vacuum arc method was one of the first coatings to be used for the protection of machine tools and machine parts. The vacuum arc method allows the deposition of molybdenum nitride with different stoichiometry and crystalline phases of cubic γ-Mo₂N and hexagonal δ-MoN. The binary system of Mo–N offer a high potential to enhance the tribological properties of common hard coatings, owing to their ability to form lubricious oxides (Magnéli phases) at elevated temperatures. However, the application of Mo-N coatings at high temperatures is limited to 500°C [1]. The work aim is to investigate the effect of deposition process parameters (bias voltage), tribopair Al₂O₃, ShKh15 steel, ShKh15 steel with CrN, TiN and MoN coatings and test temperature on the tribological properties of MoN coatings deposited by cathodic arc evaporation method on 15Х12ВНМФ steel. In all coatings deposited on steel at a nitrogen pressure of 0.3 Pa and bias potentials (-30, -50 and -70 V), hexagonal molybdenum nitride δ-MoN was found. The nanohardness of the deposited coatings is at the level of 34.1...34.7 GPa, and the Young's modulus is 437...471 GPa. The MoN coating on the steel substrate is characterized by low wear at the level of 1.57-2.43·10⁻⁵ mm³/Nm at room temperature tests. An increase in the test temperature to 500 °С leads to a significant (by an order of magnitude) increase in the wear coefficient of 1.83-2.17·10⁻⁴ mm³/Nm. This is due to the low resistance of molybdenum nitride to oxidation at this temperature. Molybdenum nitride oxidizes to molybdenum oxide, which can lead to rapid degradation of the coating under load. The lowest coefficient of friction for the MoN coating was recorded in a pair with a TiN-coated steel ball (0.37), and the lowest wear (10⁻⁷ mm³/N·m) for the MoN – steel and MoN – TiN pairs.

Structure, physicomechanical characteristics, and fracture micromechanisms under static and cyclic loading of samples cut from clad 2 mm thick sheet made of 1161AT alloy of the Al–Cu–Mg–Mn–Zr system with a reduced content of Si and Fe (up to 0.1 wt

The composition, structure, and tribological characteristics at 20 °C and 500 °C of coatings obtained by the vacuum arc deposition method using a MAX phase Ti2AlC based cathode were investigated. These characteristics were compared to those of titanium nitride coating. It was shown that at a potential of -50 V, a composite coating of TiC and Ti3AlC phases forms. Meanwhile, at a potential of -100 V, a composite consisting of TiC and α-Ti is formed. At 20 °C, the friction coefficient and specific wear rate of these coatings in contact with a ball made of ShKh15 steel under a load of 2 N are comparable to those of TiN coating. At 500 °C, the wear resistance of the composite (TiC+α-Ti) coating is twice as high as that of TiN coatings. There was no clear correlation between microhardness and the tribological characteristics of the coatings.

The paper studies oxidation resistance and electrical conductivity of dense coatings produced by vacuum-arc deposition technique on α-titanium thin (0.1 mm) substrate using a hot pressed Ti2AlC–TiC target. The coatings were deposited at low (7 mA/cm2) and high (15 mA/cm2) current densities on the substrate and marked LCD and HCD, respectively. This provided different local chemical and phase compositions of the coatings. It was found that phase compositions of the coatings differ from that of the target. The HCD coating has high oxidation resistance evaluated in terms of the specific weight gain (Δm/S = 0.06 mg/cm2) as well as high surface electrical conductivity (σ = 1.23·106 S/m) after long-term (1000 h) holding at 600 °C in the air due to the formation of an over thin (450 nm) Ti–Al-(C, O, N) near-surface layer. The thin titanium substrate with such Ti–Al–C coating is recommended as a lightweight interconnect of an intermediate-temperature solid oxide fuel cell.

Tribological properties of TiN and CrN coatings deposited by cathodic arc method at three different bias potentials -50, -150 and -300V on Ti-6Al-4V alloy in pair with alumina have been investigated. X-ray diffraction analysis showed that single-phase textured cubic nitrides of TiN and CrN were formed in these coatings. It is shown that the friction coefficient of the coatings is practically equal to that established for the Ti6Al4V alloy, but the wear rate is more than an order of magnitude lower than for the titanium alloy substrate. Coatings deposited at a potential of -50 V show optimal tribological properties at temperatures 20 and 500°C. Friction coefficients for TiN coatings are 0.4-0.8 at 20°C and 0,75 at 500°C; for CrN coatings they are 0.5 at 20°C and 0,7 at 500°C. Wear rates for TiN coatings are 0.86·10-5 мм3/Нм at 20°C and 3.56·10-5 мм3/Нм at 500°C; for CrN coatings they are 1.43·10-5 мм3/Нм at 20°C and 7.13·10-5 мм3/Нм at 500°C.

Physicomechanical characteristics of 15Kh16k5N2MVFAB-Sh steel (0.15C–16Cr–5Co–2Ni–0.7V–0.6Mo–0.3Nb–0.4N): wear resistance at 20°C and 500°C and resistance to fretting fatigue at 20°C without and with coatings obtained by the method of vacuum-arc deposition using targets based on the MAX phases of Ti_2AlC and (Ti_1-xNb_x)_2AlC , where x = 0.1 and 0.2, are investigated. At 20°C the friction coefficient and the wear specific rate of all coatings are greater than that of the studied steel in contact with a ShKh15 steel (1.0C–1.5Cr–0.3Ni–0.3Mn–0.3Si–0.25Cu) ball under a load of 2 N. Unambiguous relationship between microhardness and tribological characteristics of materials has not been recorded. The resistance to fretting fatigue of the samples with Ti_2AlC -based coating in contact with the Ni-alloy (17Cr–12W–11Fe–6Co–3Ti–1.5Nb–1.6Al) in high-cycle region (N > 10^5 cycles) is significantly higher than that of uncoated samples. The tribological characteristics of all materials decrease at 500°C but the least for samples with Ti_2AlC based coating. We have not found positive influence of niobium doping on the wear and fretting fatigue resistance of these coatings.

Nanopowder of iron oxide (mainly Fe3O4) has been obtained by electroerosion dispersion method and was used for manufacturing of gradient polymer-based microwave absorbing materials which absorb (1) on 36.6 GHz with a level of absorption of 99% (with a maximum penetration -40 dB and reflection -23 dB) and (2) on 10 GHz and 36.6 GHz with an absorption of 90% and 98.4%, correspondently (with a maximum reflection -18 dB and -10 dB and penetration -40 dB and -60 dB, respectively). It was demonstrated, that change of magnetic properties of the absorbing material under mechanical load can be used for non-destructive control. Sintered under high pressure-high temperature conditions (2 GPa, at 900, 1000, 1100, 1200 and 1300 & DEG;C for 4 min) iron oxide nanopowder in presence of hexagonal boron nitride (hBN) demonstrated soft magnetic behavior. Electron Backscatter Diffraction (EBSD) study has showed that during sintering the grains have grown beyond the superparamagnetic size limit inspire short annealing time. The structure of sintered materials was investigated using X-ray diffraction with a full-profile fitting procedure. The materials sintered at 2 GPa at 900 and 1000 & DEG;C contained 75-80 wt% of FeO and 25-20 wt% Fe. Materials sintered at 1100 oC, along with 32 wt% FeO and 2 wt % Fe, contained a significant amount of Fe3N: 66 wt%. However, materials sintered at 1200-1300 & DEG;C contain almost pure Fe3N phase. Thus, under conditions of high pressures and temperatures with increasing sintering temperature, reduction of iron oxide was observed, followed by its nitriding with nitrogen released from the boron nitride, which led to a reduction of coercive force and thus improving soft magnetic characteristics of the sintered materials. The scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) study of the sample, sintered at 1300 oC showed approximate composition of Fe3N0.8C0.3-0.6O0.06-0.3.

The results of modeling and experimental study of the hot isothermal pressing process of various thicknesses strips from cast cylindrical workpieces of 1570 and 1545 alloys of Al-Mg-Sc system are presented. The temperature-force parameters of the process and the pressed strip geometry to obtain its minimum damage are established. It is shown that during pressing of a ∅ 30 mm workpiece at 360°C the calculated damage ω = 0.35-0.45 for a strip with a cross-section of 30×12 mm without visually observable surface cracking. In the strip with a cross-section of 30×6 mm at ω = 0.50-0.55, macrocracks are recorded.

STRUCTURAL MATERIALS: MANUFACTURE, PROPERTIES, CONDITIONS OF USE The effect of reducing the magnesium content and doping with scandium, zirconium, manganese, chromium, and rare-earth metals on the structure, phase composition, strength, plasticity, and crack resistance, as well as the potential and corrosion current of alloys of the Al-Mg and Al-Mg-Sc systems obtained using magnetohydrodynamic foundry was investigated. Installation a positive effect of reducing the magnesium content, replacing manganese with chromium, and alloying with lanthanum in alloys of the Al-Mg-Sc system in the cast state and after deformation processing (extrusion, pressing, and rolling) was established. It is shown that due to dispersion strengthening by secondary intermetallics of chromium and lanthanum, this alloy in the cast state after homogenization is superior in strength to the well-known alloys of grades 1570 and 1545. After hot and cold rolling, it is not inferior to these alloys in terms of strength and plasticity, but has higher corrosion resistance characteristics. It was found that in terms of structural strength, which is comprehensively determined by the characteristics of strength and cyclic crack resistance, such alloys are superior to the well-known Al-Mg-Sc, Al-Mg and Al-Cu-Mg systems. The results of modeling the stress-strain state and damage of strips of different thicknesses during hot isothermal pressing are presented. The temperature-force parameters of the process and the geometry of the pressed strip are set to obtain its minimal damage.

We study the microstructure, strength, and micromechanisms of fracture of 50

Physical and mechanical properties of thin sheets (0.5 mm) of titanium grades VT1-0 and OT4-1 in the operating conditions of intermedium-temperature fuel cell were compared. It is established that the heat and oxidation resistance of the OT4-1 alloy was dominated by titanium VT1-0, which allows it to be considered as a promising substrate material for the manufacture of thin interconnects of solid oxide fuel cell. The oxidation resistance of Ti–Al-C coatings obtained by magnetron deposition under different modes has been studied. The 2.5 μm thick coating obtained by the method of magnetron deposition having the Young’s modulus close to the OT4-1 alloy substrate can be considered promising for this purpose.

We study the heat resistance and electric conductivity of the specimens of Crofer 22 APU steel, which is traditionally used for the production of interconnects of solid-oxide fuel cells, a bulk composite based on the Ti2AlC MAX phase, and a vacuum-arc coating of the Ti–Al–C system on a thin (0.5 mm) VT1-0 titanium sheet in the intact state and after long-term holding (1000 h) in air at 600°. We study the evolution of the phase compositions of the composite and the coating in the course of long-term holding in oxidizing media and the changes in the oxidation resistance and electric conductivity observed in the course of this evolution. It is shown that thin (0.5 mm) titanium interconnects with the indicated coating may serve as an efficient alternative to the interconnects made of the Crofer-type steel, which enables us to avoid the negative influence of chromium on the serviceability of solid-oxide fuel cells and significantly (by ~ 50%) decrease the weight of batteries of these cells.

We study the structure and properties of an alloy of the Al–Mg–Sc system, which has a lowered magnesium content (4.55–4.65 wt.

We study the microstructure, phase composition, strength and plasticity characteristics, and crack-growth resistance under cyclic loading of thermally deformed (by extrusion, pressing, and rolling) castings of Al-Mg-Sc alloys (of the 1570 and 1545 types) with different magnesium contents obtained as a result of magnetohydrodynamic stirring of melt. It is shown that the grain size of the alloy after rolling and the amount of grain-boundary precipitates of intermetallic compounds decrease as the magnesium content of the alloy becomes lower. The mechanical characteristics of both alloys ambiguously depend on the procedure and temperature of thermomechanical treatment. It is shown that the parameter of structural strength of the investigated alloys (complexly determined by the characteristics of strength and fatigue crack-growth resistance) is higher than for the available Al-Mg-Sc, Al-Mg, and Al-Cu-Mg alloys. At the same time, its lowest value was recorded for the alloy with fine grains.

We study micro- and nanostructures and the physicomechanical characteristics of D16chT, V95pchT1 and V95pchT2 aluminum alloys (analogs of 2524-T3, 7475-T6, and 7475-T761 foreign alloys, respectively) in the as-received state and after simulated degradation, which imitates the influence of long-term operation of these alloys. By using the obtained characteristics of strength sigma(YS) and sigma(UTS), plasticity delta(5), fatigue threshold delta K-th, cyclic fracture toughness delta K-fc and specific electric conductivity sigma, it is shown that, if the contents of impurities decrease (silicon down to 0.08-0.18 wt.% and iron down to 0.2-0.23 wt.%), then we do observe the degradation of these alloys under the long-term action of temperature and force factors simulating the actual operating conditions.

This work is devoted to the demonstration of a real multifunctional material -zirconia based nanopowders, which can be used in the manufacture of various types of devices that convert natural energy sources into electricity (electrolyte and anode for SOFC, moisture-to-electricity converter). It was shown that such characteristics of nanopowders as parti-cle size, specific surface area, and type of surface centers, which depend on the temper-ature of nanopowder synthesis, could play both a positive and a negative role in the formation of the functional properties of a device. It was found that the synthesis of 8YSZ nanopowders at 700 degrees C is optimal for the manufacture of a dense electrolyte material and a porous SOFC anode material during sintering at 1400-1450 degrees C. The addition of a small amount of Al2O3 at the synthesis stage accelerates the sintering of the SOFC electrolyte material by 120 degrees C and leads to increasing the density to 97% of the theoretical value. The strength of the sintered anode material practically does not change after reduction in an atmosphere of N2-10% H2-5% CO2 and the value is 100 MPa. The synthesis temperature of 8YSZ nanopowder at 700 degrees C is also optimal for the manufacture of porous converters of ambient humidity into electricity. The formation of particles with a given size and type of surface centers allows generating an electric po- tential (100-200 mV) for hundreds of hours, which is 2-3 times higher than that of larger and smaller powders. The result of the work show that there are optimal conditions for the synthesis of powders (synthesis method, additives, synthesis temperature), as a result of which nanopowders are formed with characteristics (particle size, specific surface area, morphology) necessary and sufficient for the manufacture of several types of materials for devices of alternative energy. (c) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

We study the influence of one-time reduction and redox cycling at 600°С in different hydrogencontaining media in the absence and in the presence of carbon dioxide on the strength and electric conductivity of ceramics of the ZrO 2 –Y 2 O 3 –CeO 2 –Al 2 O 3 –NiO–CuO system with lowered Y 2 O 3 content and various ratios of the amounts of the ceramic and metallic phases. It is shown that cermets with different mass fractions of the nickel phase after reduction in pure hydrogen have high electric conductivity, which meets the requirements imposed on the anode materials. However, even in the absence of bulk microcracking, their strength after reduction becomes twice lower. The investigated ceramics in the initial state and cermets subjected to reduction at 600°С in different working media are characterized by the quasibrittle micromechanism of fracture. The redox treatment of cermets causes an insignificant increase in their electric conductivity but guarantees the level of strength close to the strength of the original ceramics, i.e., proves to be an efficient technology for improving the physicomechanical properties of Ni-containing anodes of solid-oxide fuel cells, including the case where CO 2 impurities are present in the working medium.

We study the regularities of changes in the microstructure, strength, electric conductivity, and micromechanism of fracture of 50% (ZrO2–8 mole% Y2O3–2 wt.% Al2O3) + 50% (NiO–5 wt.% CuO) ceramics and the corresponding cermet [intended for manufacturing of the anodes (substrates) in solid-oxide fuel cells] caused by reduction in high-temperature (600°С) Ar–5% H2 and N2–10% H2–5% CO2 gas mixtures. It is shown that the investigated cermet has a higher strength and electric conductivity if the calcination temperature of the initial powders is lowered from 900°С to 700°С and their sintering temperature is lowered from 1450°С to 1400°С. The signs of pollution of this material with carbon compounds were not detected. We also did not reveal any decrease in its strength and electric conductivity after reduction carried out at 600°С in a N2–10% H2–5% CO2 gas mixture as compared to the characteristics of the same material reduced in an Ar–5% H2 mixture.