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Ti3SiC2 was synthesized by hot pressing at 1400°С for 15 and 30 min at a pressure of 30 MPa from powder mixtures, mainly from Ti/Si/TiC and Ti/TiSi2/TiC. The amount of the Ti3SiC2 phase synthesized from these mixtures was 94.0 and 95.9 vol %, respectively (1400°С, 30 min). The Ti3SiC2 phase crystallized as elongated grains. The effect of the hot pressing time on the formation of the Ti3SiC2 phase from the starting Ti/Si/TiC powders was determined. The final products contained titanium carbide and a small amount of silicon carbide as intermediate phases (for composites containing the starting silicon carbide powders). An excess of silicon leads to the formation of the largest amount of the Ti3SiC2 phase. [ABSTRACT FROM AUTHOR]

AlMgB14-based materials have been synthesized by spark plasma sintering of an Al12Mg17–B powder mixture at 1300 and 1400°C. The phase composition, structure, and properties of these materials have been studied. According to X-ray powder diffraction evidence, spark plasma sintering leads to the formation of the AlMgB14 phase and the MgAl2O4 spinel. The content of the AlMgB14 phase in the materials is ~95 wt %. At a sintering temperature of 1400°C, the resulting material has a hardness and relative density of 30.1 GPa and 99.3%, respectively. It has been demonstrated that a major source of oxygen in the powder mixture is a B2O3 oxide film on the boron powder surface. Thus, when the Al12Mg17 intermetallic powder is used as a precursor, the reaction of AlxMgy intermetallic compounds with B2O3 leads to the formation of the MgAl2O4 spinel. [ABSTRACT FROM AUTHOR]

The system xBa(PO3)2·(99 – x)(AlF3–BaF2–CaF2–MgF2–SrF2)–1NdF3, where x = 2, 5, 10, 15, 20, 30, and 40 mol %, is considered. The dependences of the thermal coefficient of linear expansion, Tg, Tx. Tx–Tg, HV, and K1C on the concentration of Ba(PO3)2 are determined. It is found that an increase in the concentration of Ba(PO3)2 with the uniform replacement of the fluoride component leads to a decrease in the thermal coefficient of linear expansion, an increase in the glass transition temperature and crystallization, and a broadening of the interval Tx–Tg. It is shown that an increase in Ba(PO3)2 in the glass leads to an increase in microhardness HV and fracture toughness K1C of the glasses. The main thermomechanical characteristics of the studied glasses are compared with those of their commercial analogs. [ABSTRACT FROM AUTHOR]

Various mixtures of initial Ti/Si/C, Ti/Si/TiC, Ti/SiC/C, Ti/SiC/TiC, Ti/TiSi2/TiC, and TiH2/SiC/C powders were used to synthesize Ti3SiC2 by sintering at 1300 and 1400°C for 1 – 5 h. Ti/Si/TiC and Ti/TiSi2/TiC powders were best for synthesizing Ti3SiC2. The amount of synthesized Ti3SiC2 reached 98.3 and 90.3 vol% at a sintering temperature of 1400°C for 1 h. Ti3SiC2 was synthesized and grew in the form of elongated grains. The influence of the sintering time and temperature on formation of the MAX-phase Ti3SiC2 from the initial Ti/Si/C powders was determined. TiC and a small amount of SiC were always present as intermediate phases in the final products. An excess of Si contributed to the highest formation of Ti3SiC2. [ABSTRACT FROM AUTHOR]

The influence of the synthesis temperature on the phase composition, size distribution, and morphology of AlMgB14 particles, obtained by direct interaction of powders of elementary Al, Mg, and B with the addition of free carbon in vacuum 10 – 2 Pa at 1200 – 1400°C, was studied. The synthesized powders were analyzed by means of x-ray diffraction, SEM, EDX, and laser diffraction. The highest mass content of the main phase AlMgB14 (94%) was obtained at synthesis temperature 1200 – 1300°C with 1 h soaking. Impurity MgAl2O4 as well as magnesium-depleted spinel and AlB12 were recorded at soaking temperature above 1300°C. [ABSTRACT FROM AUTHOR]

The melting (decomposition) point for AlMgB14 aluminum magnesium boride containing alumomagnesium spinel as an impurity (5.5 wt %) is experimentally evaluated. The melting is accompanied by the release to the gas phase. The decomposition process covers the temperature range of (2400–2573) ± 30 K. A partial loss of Mg is observed at 2073 K. The structure and element composition of crystallized objects are also studied. [ABSTRACT FROM AUTHOR]

The melting (decomposition) point for AlMgB14 aluminum magnesium boride containing alumomagnesium spinel as an impurity (5.5 wt %) is experimentally evaluated. The melting is accompanied by the release to the gas phase. The decomposition process covers the temperature range of (2400–2573) ± 30 K. A partial loss of Mg is observed at 2073 K. The structure and element composition of crystallized objects are also studied. [ABSTRACT FROM AUTHOR]

The system xBa(PO3)2·(99 – x)(AlF3–BaF2–CaF2–MgF2–SrF2)–1NdF3, where x = 2, 5, 10, 15, 20, 30, and 40 mol %, is considered. The dependences of the thermal coefficient of linear expansion, Tg, Tx. Tx–Tg, HV, and K1C on the concentration of Ba(PO3)2 are determined. It is found that an increase in the concentration of Ba(PO3)2 with the uniform replacement of the fluoride component leads to a decrease in the thermal coefficient of linear expansion, an increase in the glass transition temperature and crystallization, and a broadening of the interval Tx–Tg. It is shown that an increase in Ba(PO3)2 in the glass leads to an increase in microhardness HV and fracture toughness K1C of the glasses. The main thermomechanical characteristics of the studied glasses are compared with those of their commercial analogs. [ABSTRACT FROM AUTHOR]

Various mixtures of initial Ti/Si/C, Ti/Si/TiC, Ti/SiC/C, Ti/SiC/TiC, Ti/TiSi2/TiC, and TiH2/SiC/C powders were used to synthesize Ti3SiC2 by sintering at 1300 and 1400°C for 1 – 5 h. Ti/Si/TiC and Ti/TiSi2/TiC powders were best for synthesizing Ti3SiC2. The amount of synthesized Ti3SiC2 reached 98.3 and 90.3 vol% at a sintering temperature of 1400°C for 1 h. Ti3SiC2 was synthesized and grew in the form of elongated grains. The influence of the sintering time and temperature on formation of the MAX-phase Ti3SiC2 from the initial Ti/Si/C powders was determined. TiC and a small amount of SiC were always present as intermediate phases in the final products. An excess of Si contributed to the highest formation of Ti3SiC2. [ABSTRACT FROM AUTHOR]

The use of high-modulus ceramic materials under conditions simulating the screen protection of space objects from damage by fragments of space man-made debris is considered. The introduction of an aluminum jet at a speed of ~ 10 km/s into an aluminum barrier located behind brittle material screens was experimentally studied. A comparative analysis of the parameters of the residual cavity in the barrier made it possible to reveal the effect of the structural rearrangement of the ceramic material on the effectiveness of screen protection. [ABSTRACT FROM AUTHOR]

In this paper, a new diamond–silicon carbide ceramic composite material—Ideal—is studied and its mechanical characteristics are determined. For the first time, a comprehensive determination of Poisson's ratio, shear modulus, bulk modulus, and transverse sound velocity is carried out. Poisson's ratio is in the region of 0.008 to 0.01, which, in turn, indicates the absolutely brittle nature of the failure of the Ideal ceramic under loading. The criteria that allow evaluating different materials used for body armor are calculated. [ABSTRACT FROM AUTHOR]

The possibility of producing geometrically complex mechanical-engineering products based on reaction-sintered silicon carbide using two methods was investigated — mechanical processing of polymerized workpieces before sintering and molding by hot slip casting under pressure. The resulting silicon carbide ceramic materials are characterized by low density of the order of 3.04 – 3.07 g/cm3, porosity ≤ 1%, and bending strength 320 – 360 MPa. Materials based on silicon carbide modified with boron carbide have density 2.72 g/cm3, porosity about 1%, and bending strength of 280 MPa. [ABSTRACT FROM AUTHOR]

The high-temperature strength properties of silicon carbide-based ceramic materials reaction-sintered in air and vacuum are proved by experimental data. The ultimate bending strength of pressed and cast ceramic material samples at temperatures up to 1400°C was measured as a criterion. High-temperature tests demonstrate the guaranteed strength of ceramics above 100 MPa. An example of the manufacture of a complex shaped ceramic product using the hot slip casting processing under pressure into additive water-soluble forms is given. An approval of the combined technology makes it possible to manufacture bladed ceramic elements with a thickness of about 1 mm. [ABSTRACT FROM AUTHOR]

This paper studies the resistance to oxidation of various grades of commercial diamond powders. The kinetics of diamond oxidation in air is studied by optical and electron microscopy, as well as X-ray microscopic and thermal analysis. The relationship between the size of diamond grains, their morphology, and their impurity composition with temperature, heat release, and the rate of the process is studied. It is established that the main factor affecting the behavior of diamond during its combustion is the type of impurities present in the powders, followed by the grain size and its morphology. A complex multistage nature of the oxidation process is discovered. [ABSTRACT FROM AUTHOR]

The results of studying the structure of additively manufactured permanent magnets based on AlNiCo35 alloy are presented. Structural features are identified with optical and electron microscopy, and the phase composition is determined with X-ray diffractometry. The possibility of manufacturing magnets by selective laser melting of metal powder is shown. [ABSTRACT FROM AUTHOR]