Zirconia-based ceramics find wide application in engineering due to their very high hardness, resistance to elevated temperatures, and high fracture toughness. Among stabilizers of the advantageous tetragonal zirconia phase, yttria allows for better grain size refinement than ceria does; thus, Y2O3 is the most widely used. In the present study, comparative analysis was performed for yttria-stabilized zirconia (YSZ) and ceria-stabilized zirconia (CSZ) in terms of sinterability, densification, and mechanical properties, including hardness and resistance to plastic deformation. The results proved that CSZ sintered in similar conditions as YSZ exhibits similar properties, including an elastic modulus of 200-220 GPa and H/E of 0.070-0.076. In particular, the hardness of the ZrO2-5 wt% CeO2 ceramic appeared to be 14.6 ± 0.5 GPa, close to that of ZrO2-3 wt% Y2O3, which was 14.20 ± 0.74 GPa. However, SiC addition to ZrO2-5 wt% CeO2 composites increased hardness substantially up to 16.8 ± 0.8 GPa. Moreover, the fracture toughness of CSZ was 2.5 times higher than that of YSZ sintered under identical conditions. Thus, CeO2 can be a good, cheaper alternative to the traditionally used Y2O3 stabilizer for submicron-grained tetragonal zirconia ceramics.

Abstract Signs of overdoping were observed on the superconducting GdBa 2 Cu 3 O 7-δ (GdBCO) layers of commercially produced coated conductors (CC) after a re-oxygenation through the thin (2 μm) silver layer at oxygen pressures of 100-160 bar, and 600-800 °C. An increase in the charge carrier density n H (100 K) up to 7.86×10 21 cm −3 , a decrease in the c -lattice parameters of GdBCO down to 1.1715(5) nm, a peak in the normalized resistivity close to the transition temperature are compatible with an increase of oxygen doping level up to p = 0.1740. Consequently, the self-field critical current density ( J c ) at 77 K increased by 21.5% to J c = 2.7 MA/cm 2 after reoxygenation at 160 bar oxygen at 800 °C for 3 h. At 5 K in the self-field, J c of this sample reached 30.2 MA/cm 2 . Its superconducting GdBCO layer was characterized by the parameter c =1.1727(1) nm, the superconducting transition temperature T c =92.63 K, the charge carrier density n H (100 K)=7.3×10 21 cm −3 , and the oxygen doping of its CuO planes was p =0.1727.

The effect of SiC content and powder characteristics on HfB₂–SiC composites was studied. The best composite (HfB₂ + 30 wt.% SiC, 5-10 μm) showed high density (6.54 g/cm3), hardness (Hv = 38.6 GPa), fracture toughness (K1с = 7.7 MPa·m⁰·⁵), and Young’s modulus (510 GPa). Ablation tests revealed superior thermal stability compared to pure HfB₂ and composites with finer or differently shaped SiC powders. Enhanced performance is due to optimal SiC morphology, solid solution formation, and uniform phase distribution.

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 electromagnetic characteristics, particularly the real εr′ and imaginary εr″ parts of the dielectric constant, of new AlN-based composites with additions of powdered diamond, soot, and diamond with 3–5 wt.

Treatment of GdBCO_CC under 100 bar of O 2 at 600 °C for 3 h led to an increase in J c (77K, 0 T) by 6% up to 2.67 MA/cm 2 and a decrease in the c-parameter of Gd123 to 1.17310 nm, which may be associated with its overdoping with oxygen (the charge carrier density in superconducting Gd123 layer was 6.91×10 21 cm 3 ). No strong correlation was observed between J c , T c , c-parameter of RE123 (RE=Eu, Gd) and carrier density n H of EuBCO_CC and GdBCO_CC treated at 300-800 °C, 1-160 bar O 2 for 3-12 h.

To study the possibility of overdoping with oxygen and, thus, an increase in the charge carrier density, n(H)(100 K), in RE123 layers (RE = Eu, Gd) with the aim of increasing the critical current density, Jc, oxygenation was carried out in the pressure range of p(O2) = 1-160 bar and temperatures of T-S = 300-800 degrees C during tau = 3-12 h of commercial EuBCO and GdBCO coated conductors (CC), from which the protective Cu layer and, in half of the cases, the Ag layer were chemically removed before oxygenation. The evidences of overdoping were observed about what were witnessed an increase of n(H)(100 K), reduction of c-lattice parameters of RE123 (RE = Eu, Gd) of superconducting layers, behavior of normalized resistivity before superconducting transition, and J(c) variation, however, the conditions to achieve optimal doping were not found yet. Treatment under 100 bar of O-2 for 3 h of GdBCO_CC (with Ag layer) at 600 degrees C led to an increase in J(c) (77 K, 0 T) from 2.57 to 2.67 MA/cm(2), n(H)(100 K) increased from 6.55 x 10(21) to 6.91 x 10(21) cm(-3), and J(c)(5 K, 0 T) = 28.94 MA/cm(2) was observed after the treatment. The increase in J(c) (77 K, 0 T) from 2.10 to 2.28 MA/cm(2) for GdBCO_CC (without Ag layer) was observed after treatment at 300 degrees C under 100 bar of O-2 for 3 h. In the both cases c-parameter of Gd123 decreased from 1.1735(1) to 1.1731(0) nm. For EuBCO_& Scy;& Scy; after treatment a decrease in c-parameters of Eu123 was observed: from 1.1738(8) to 1.1734(5) nm (for the Ag-coated sample under 100 bar O-2 at 300 degrees C) and from 1.1740(2) to 1.1736(3) nm (for the sample without Ag under 160 bar O-2 at 800 degrees C), but we failed to increase n(H)(100 K) and J(c) of the studied samples. However, the studies are still ongoing.

Abstract—For structurally homotypical specimens different in the ZrO2 content from the (94WC–6Co) + ZrO2 matrix material used in diamond-containing Сdiamond–(WC–Co) composites formed by spark plasma sintering, the dependences of the relative density ρrel, the ultimate strength under compression Rcm and bending Rbm, the microhardness НV, and the fracture toughness KIс on the zirconia content have been established. The addition of 6 wt

The study is devoted to the electrodynamic properties of composite materials based on AlN–5 wt

Materials containing transition metals such as Zr, Hf, Ta, Mo, W, or Nb in conjunction with B, C or N are deemed ultrahigh temperature materials. Our research UHTCs centers on composites founded on ZrB2, ZrC, HfB2, HfC and their solid solutions, with an expanded array of properties compared to existing materials. An elevated level of mechanical and damping characteristics is achieved through strong interconnectivity between grain phases due to use starting nanopowders and high and moderate pressures. These ceramic composites show promise for use as construction and wear-resistant materials in high-temperature environments. In order to reduce cracking and fragility of the obtained composites, our work also considered the use carbon- and silicon-containing additives that initiate the formation of laminar structures in the materials. It is known that the interfaces between the layers and the different nature of the 1st and subsequent layers give the structure of the material the ability to quench cracks [1]. Since it is known that the addition of silicon can be used to reduce the consolidation temperature of UHTM, as well as to increase the mechanical stability [2] of such materials by dissolving silicon in the matrix structure [3], we employed silicon-containing additives (MoSi2, Si3N4, ZrSi2 and SiC) in study. We used hot pressing (30 MPa) and high pressure/temperature techniques – recessed-anvil HPA (4.1 GPa, due 1800 oC) when compacting samples. For example, HP samples HfC – 10, 20 and 30 wt.% MoSi2 were characterized by microhardness (HV49) up to 18.7, 19.5 and 22.1 GPa respectively, and density 10.82, 11.03 and 11.46 g/cm3 respectively. Thus, when we used 20 wt.% MoSi2 to ZrB2, it was possible to reduse the sintering temperature at HP to 1700 oC (more than 200 degrees), and the material showed a microhardness of about 23.7 GPa at density 5.86 g/cm3. At both, composites significantly exceeded pure materials results, at the same conditions synthesizing.

The results of studying the thermal conductivity of hot-pressed AlB12–AlN ceramic composites with different AlN concentrations were presented. The thermal conductivity coefficient was measured for composite specimens at room temperature and approximated for AlB12.

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 intensive development of hydrogen technologies has made very promising applications of one of the cheapest and easily produced bulk MgB2-based superconductors. These materials are capable of operating effectively at liquid hydrogen temperatures (around 20 K) and are used as elements in various devices, such as magnets, magnetic bearings, fault current limiters, electrical motors, and generators. These applications require mechanically and chemically stable materials with high superconducting characteristics. This review considers the results of superconducting and structural property studies of MgB2-based bulk materials prepared under different pressure–temperature conditions using different promising methods: hot pressing (30 MPa), spark plasma sintering (16–96 MPa), and high quasi-hydrostatic pressures (2 GPa). Much attention has been paid to the study of the correlation between the manufacturing pressure–temperature conditions and superconducting characteristics. The influence of the amount and distribution of oxygen impurity and an excess of boron on superconducting characteristics is analyzed. The dependence of superconducting characteristics on the various additions and changes in material structure caused by these additions are discussed. It is shown that different production conditions and additions improve the superconducting MgB2 bulk properties for various ranges of temperature and magnetic fields, and the optimal technology may be selected according to the application requirements. We briefly discuss the possible applications of MgB2 superconductors in devices, such as fault current limiters and electric machines.

In recent decades, MAX phases have attracted considerable attention from the scientific community due to their unique combination of metallic and ceramic properties, which provide exceptional mechanical, thermal, electrical and chemical characteristics. The synthesis of MAX phases in the form of coatings is of increasing interest for many applications. The aim of this review is to summarize the progress made in the synthesis of coatings based on MAX phases using different methods. The advantages and characteristics of the implementation of ion-plasma physical vapor deposition methods are discussed. The use of ion-plasma methods allows to significantly reduce the synthesis temperature of MAX phases due to the high energy of the particles forming the coating. The effect of deposition parameters on the composition, structure and properties of the coatings is analyzed. Coatings with high protective properties and prospects for their application in industry are considered. This part of the review focuses on methods for depositing MAX phase based coatings.

Superconductivity in a nitride of the MAX-phase family was reported by A.D. Bortolozo et al. in Ti 2 InN ( a = 0.3074 nm, c = 1.3975 nm) with a transition temperature of 7.3 K. In this study, we report on Ti 2 InN MAX phase-based samples (with up to 94 wt.% of Ti 2 InN) synthesized by several methods, which, unfortunately, did not comply with bulk superconductivity of this compound. The Ti 2 InN materials were synthesized from Ti 2 InN precursor powder of 93-95 wt.% purity (obtained by the method proposed by A.D. Bortolozo et al. [1]) according to the following routes: (1) at 130 bar of N 2 , leading to 54 wt.% of Ti 2 InN ( a = 0.3076(1), c = 1.4012(5) nm); (2) in a sealed quartz ampoule in Ar, (88.5 wt.% Ti 2 InN, a = 0.3076(1), c = 1.4012(4) nm); (3) by spark plasma sintering (SPS) in contact with hBN at 45 MPa (94 wt.% Ti 2 InN, a = 0.3077(7), c = 1.4021(5) nm), and (4) by high quasihydrostatic pressure - high temperature sintering (HP-HT) in contact with hBN at 4 GPa (83.5 wt.% Ti 2 InN, a = 0.3075(3), c = 1.4017(5) nm). Despite all the manufactured samples demonstrated superconducting behaviour with T c (onset) near 5 K and the samples prepared by SPS and HP-HT methods were highly dense, a very broad magnetic transition (ac susceptibility) not saturating down to 2 K has been observed. No macroscopic Meissner phase was established and the magnetization was far too weak to evidence bulk superconductivity of the entire sample and hence of Ti 2 InN. However, a superconducting gap of about 1.2 - 2.1 mV was derived from point-contact spectroscopy at some areas of HP-HT sintered samples. The dispersed crystalline admixture grains of TiN phase in Ti 2 InN matrices of our samples or a metallic In-alloy are most probable candidates for the superconducting phase in our materials.

Magnesium doping can effectively reduce zinc vacancy point defects in ZnGeP 2 crystals, thereby improving optical transmittance at 2 μm.

In the last few decades, aluminum nitride (AlN) and boron nitride (BN) have become a point of interest to many researchers and scholars from different disciplines around the world. Due to its attractive properties, AlN has been successfully used in various applications, starting from advanced ceramics materials, additive for grain size control in micro-alloyed steels, through optoelectronics and microelectronics, and finally to semiconductors. On the other hand, BN has broad applications in various fields, such as 2D material, lubricant material, superhard and semiconductor material as well as many others. This study focuses on the mixed AlN/BN compounds, in particular, boron-rich AlN and aluminum-rich BN systems, thus having the entire range of AlN/BN compositions. The special focus was on structural properties investigated using the hybrid B3LYP method. Important structural properties were investigated to offer novel technological and industrial applications of mixed AlN/BN materials.

The new composite materials with a high level of dielectric constant were created on the AlN-based. These materials were obtained by the hot pressing method at temperatures of 1800-1820 °C and a pressure of 15 MPa from powders mixtures AlN-Y₂O₃-5%C(soot), AlN-Y₂O₃-3%C(diamond powder - DP), AlN-Y₂O₃-5%C(DP)-5%Mo. The structural and phase composition of the composites was investigated by X-ray phase analysis using the Rietveld method and using a Zeiss Evoma15 SEM. The measurements of the complex dielectric constant in the frequency range of 12.4-18 GHz were carried out by the waveguide method using the Keysight P9375A vector microwave circuit analyzer. The main AlN phase and the presence of new phases: С(graphite), Al₃(O,N)₄, and Al in the materials structures were revealed by the X-ray phase method. The graphitization process of DP is characteristic for these compositions and at free sintering [1]. In addition, the formation of Mo₂C is observed in the system AlN-Y₂O₃-C(DP)-Mo. Also, thanks to X-ray studies and SEM with analysis of the quantitative elemental composition in the main phases by the EDS method, was established the presence of a low concentration of O in the AlN lattice and was revealed the location of conductive phases (C, Mo₂C) in the structure of materials. The results of measurements of electrodynamic characteristics showed that the developed new composite materials with graphite phase inclusions have constant dielectric characteristics in the entire frequency range and are at the level of ɛr = 12.38-33.03 and tgδ=0.06-0.51. Composites with soot had the highest values of dielectric constant (33) and losses (0.51). Preservation of high dielectric characteristics of composites, and at the same time increasing the level of dielectric permeability, is achieved due to the features of structure formation, in particular, arrangement of conductive phases grains (C, Mo₂C) in the structure of composites and minimization of contacts between them.

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.

The work describes the creation hard AlB12C2-based ceramic materials under by hot pressing and by high pressure-high temperature conditions. The high mechanical performance of the materials we obtained are similar to those of boron carbide, which can be explained by the structural features of B4C and AlB12/ AlB12C2 [1], namely the presence of almost identical structural elements - regular icosahedrons of boron atoms. The possibility of modifying the structure and properties by introducing additives became the reason for conducting research. To obtain the material, sintering of a powder mixture of of αAlB12 and SiC was used. Relatively cheap nanopowders (50-150 nm, with a specific surface area of 21-15 m2/g) α-AlB12 synthesized by PhD. V.B. Muratov (IPM NASU) were used in work [2]. The hot pressing at 30 MPa 1800-1970 оC of two compounds from α-AlB12 nanopowder with 15 (I) and 20 (II) wt.% SiC addition can result in formation of ceramic elements having according x-ray an-is 88 wt.% AlB12C2-12 wt.% Al2O3-SiC(additives) and 85.5 wt.% AlB12C2-14.5 wt.% Al2O3-SiC(additives) phases compositions respectively. Both materials turned out to be light (density rI=2.6 and rII=2.36 g/cm3) and quite dense (porosity PI=5 %; PII=8 %). Samples of the first (I) material were demonstrated HV - 23.3 GPa hardness, fracture toughness K1c - 5.0 MPa•m0.5 and samples of the second (II) material showed HV - 25.6 GPa, K1c - 5.7 MPa•m0.5 accordingly. The sintering under high-pressure apparatus at 4,1 GPa generally allows to reduce sintering temperatures. At a reduced temperature to 1700 oC at 4.1 GPa and holding for 8 min, the samples were perfect on the outside, but with a large amount of internal stress. This material had hardness HV - 25.2 GPa and fracture toughness K1c - 4.2 MPa•m0.5 at density rIIІ=2.75 g/cm3 and porosity PIII=5 %. High performance characteristics of the obtained composites can be explained by the formation of solid solutions in the structure.