Search

For the first time, a new ceramic "Ideal," a diamond-silicon carbide composite obtained in the reaction-diffusion Turing process, which makes it possible to obtain materials with the optimal set of physical and mechanical properties, is studied. An elastic-brittle fracture related to the propagation of a shock wave in a two-component system is noted. The dynamic elastic limit, determined by the properties of silicon carbide, is found to be 13.4 GPa. Its dynamic elastic limit and spall strength in the region of the elastic deformation are measured. The impact compressibility of ceramics up to a pressure of 625 GPa is determined. [ABSTRACT FROM AUTHOR]

Ceramic materials based on B4C–SiC are obtained by using the method of hot slip casting followed by reaction sintering (impregnation with liquid silicon). Composite ceramic samples are characterized by low density and porosity, and have strong mechanical characteristics. The microstructure of the obtained material is studied, and the uniformity of the distribution of boron carbide and silicon carbide particles in the structure of ceramic materials is demonstrated. [ABSTRACT FROM AUTHOR]

Si3N4-based ceramics have been produced by hot pressing in the temperature range 1550–1650°C using α-Si3N4 starting powder and CaO–Al2O3 (48 : 52 wt %) sintering aids. The powders and the ceramics have been characterized by dilatometry, scanning electron microscopy, and X-ray diffraction, and we have measured the microhardness and density of the ceramic samples. The results demonstrate that the sintering aid reacted with Si3N4 to form Ca-α-SiAlON. At 40 wt % sintering aids, all of the silicon nitride was converted into Ca-α-SiAlON. We have clarified general trends in the effect of the amount of sintering aids on the properties of the ceramic samples. [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]

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]