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We have studied the spontaneous comminution of cast materials consisting of a Mn-doped Cr2AlC MAX phase and chromium, manganese, and aluminum carbides and aluminides. The materials were prepared in the form of ingots by self-propagating high-temperature synthesis (SHS) in a 3-L reactor at an argon pressure p = 5 MPa. The starting mixtures consisted of manganese(IV) oxide, chromium(III) oxide, aluminum (ASD-1), and carbon. The presence of aluminum carbide (Al4C3) in a cast material has been shown to lead to spontaneous comminution of the cast material (without mechanical or chemical influences) into powders with a crystalline particle size under 100 μm. The particle size reduction has been shown to result from reaction between aluminum carbide and atmospheric moisture. The synthesized materials have been characterized by X-ray diffraction and X-ray microanalysis, and we have studied structural and phase states of particles of the desired products obtained as a result of self-comminution of a cast SHS material.

Experimental data are presented on the high-temperature synthesis of cast composite materials in the Cr–Al–C system with different relative amounts of the MAX phase Cr2AlC and chromium carbides and aluminides. The experiments were carried out in multipurpose self-propagating high-temperature synthesis (SHS) reactors at an argon pressure p = 5 MPa. The starting mixtures consisted of calcium chromate (CaCrO4), aluminum (ASD-1), and carbon powders. It has been shown that varying the percentage of carbon in the starting mixture may have a significant effect on the synthesis process and the phase composition and microstructure of the final products. It has been found that, in the case of the stoichiometric starting mixture composition, the synthesis yields cast composite materials consisting predominantly of the MAX phase Cr2AlC and containing the lower chromium carbide Cr7C3 and the chromium aluminide Cr5Al8. The addition of excess (superstoichiometric) carbon to the starting mixture leads to an increase in the percentage of the MAX phase Cr2AlC in the synthesis product, disappearance of the chromium aluminide Cr5Al8, and the formation of the higher chromium carbide Cr3C2 instead of the lower carbide. The final synthesis products have been characterized by X-ray diffraction and local microstructural analysis. The structure and composition of the synthesis products obtained under various conditions have been determined.

This paper reports the preparation of cast dimolybdenum pentaboride by a self-propagating high-temperature synthesis (SHS) metallurgy method. Experiments were carried out in SHS reactors at an initial excess gas (Ar) pressure p0 = 5 MPa. In the experiments, we used thermite-type starting mixtures consisting of molybdenum oxide, aluminum, boron oxide, and elemental boron powders. The combustion of such mixtures yields two types of final product: Mo2B5 and Al2O3. The combustion temperatures of the starting mixtures used in our experiments have been shown to exceed the melting points of the final products, which are thus formed in a liquid (cast) state. Under the effect of gravity, the heavier phase Mo2B5 settles down to form a lower ingot, whereas the lighter phase Al2O3 forms an upper ingot. The synthesis products have been characterized by X-ray diffraction and local microstructural analysis. The results demonstrate that the composition and amount of the starting mixture have a significant effect on the synthesis parameters and the composition and microstructure of the Mo2B5. We have optimized conditions for the preparation of single-phase cast dimolybdenum pentaboride.

Experimental data are presented on the high-temperature synthesis of cast inorganic materials in the MgO–Al2O3 system. Experiments were carried out in multipurpose self-propagating high-temperature synthesis (SHS) reactors at an argon pressure p = 5 MPa. The starting mixtures used in the experiments consisted of molybdenum(VI) and magnesium(II) oxides and aluminum. It has been shown that, varying synthesis parameters, one can control the phase composition and microstructure of the final oxide products. We have optimized synthesis conditions for the preparation of single-phase magnesium aluminate spinel, MgAl2O4. The SHS products have been characterized by X-ray diffraction and local microstructural analysis.

This paper reports the high-temperature synthesis of cast Cr2AlC from mixtures of chromium(III) oxide, chromium(VI) oxide, aluminum, and carbon at an increased inert gas (Ar or N) pressure in a 3-L self-propagating high-temperature synthesis reactor at an initial argon pressure pi = 5 MPa. The reaction products were characterized by X-ray diffraction and X-ray microanalysis. The results indicate that the ingots obtained under optimized conditions consisted of Cr2AlC and Cr3C2 with a ratio of about 85 : 15.

This work examines general trends in the autowave synthesis of cast Mo-W-Si ceramics in a reactor at an elevated gas pressure using highly exothermic mixtures of molybdenum oxide, tungsten oxide, aluminum, and silicon. The results indicate that the gas (N2, Ar) pressure in the reactor and reactant ratio have a strong effect on the combustion process. We have obtained cast solid solutions with a controlled MoSi2: WSi2 ratio.

Regularities of synthesis and sintering of molybdenum disilicide are studied. The synthesis is carried out in the combustion mode (self-propagating high-temperature synthesis) with the use of high-caloric mixtures of molybdenum oxide with aluminum and silicon. The cast synthesis product (MoSi2) is subjected to grinding and subsequent sintering. The studies show that the basic parameters that influence the process of synthesis and its regularities are gas pressure in the reaction vessel and sizes of silicon particles. The sintering process, microstructure, and characteristics of sintered samples may be controlled through varying the sintering temperature and ratios of the ZrO2 and Y2O3 additives.

The combustion synthesis, microstructure, chemical composition, and phase composition of cast Al2O3-Cr2O3 materials are described. The synthesized solid solutions are based on corundum or chromia, depending on the Al2O3 and Cr2O3 contents. Using self-propagating high-temperature synthesis, a cast aluminum oxynitride is obtained for the first time.