B. A. Goldin

Preparation of Ti3SiC2

Phase relations in the Ti-C-SiC system are studied with the aim of optimizing Ti3SiC2 synthesis. The optimal starting-mixture compositions for the synthesis of phase-pure Ti3SiC2 powder can be represented by the formula 3Ti + (1 − z)C + (1 + z)SiC, where z = 0.2–0.6. In the temperature range 1630–1670 K under dynamic vacuum, the excess silicon vaporizes from the sample. The processes leading to the formation of impurity phases are discussed.

Vacuum carbothermal processing of low-iron bauxites

The sequence of the phase formation processes in carbothermal processing of low-iron bauxites in a vacuum is investigated. A new technology for dry firing treatment of natural aluminosilicate material is offered. The possibility of production of a wide range of products is suggested.

Nonlinear effects in corundum and ilmenite in high frequency electromagnetic fields

This paper details the results of a comparative study of two materials having the same structure, but drastically different radiophysical characteristics. Corundum ceramic samples were synthesized from pure substances by firing a charge in air at 1450°C for 1 h. The second material was prepared from natural ilmenite without heat treatment using an epoxy polymer binder. Measurements of the transmission and reflection factors within the frequency range of 8–26 GHz indicate that corundum ceramic samples scatter electromagnetic radiation (EMR) exhibiting a pronounced dispersion of the reflection and transmission factors. On the contrary, ilmenite samples absorb EMR showing no dispersion at all. The differences in the radiophysical characteristics are due to the presence of magnetic impurities in the crystal lattices of corundum and ilmenite and the specific features of the spin-phonon interaction in dielectric and ferrite materials.

Crack-resistant ceramics based on bauxites

Low-iron Timan bauxites (the Komi Republic, Russia) can be used for the production of a ceramic material with high mechanical properties suitable for engineering structural purposes. Specific natural and some synthetic oxide and fluorine additives promote the sintering and increase the strength and the crack resistance of alumina ceramics, which is also attributed to the special features of the microstructure. 1 Komi Institute of Chemistry of the Scientific Center of the Ural Branch of the Russian Academy of Sciences, Russia.

High-temperature carbidization of carboniferous rocks

Processes of thermal metamorphism of carboniferous rocks have been studied experimentally. The conditions of high-temperature interaction of shungite carbon with components of the contained rocks, leading to formation of carbide compounds, have been determined. The results of this investigation contribute to the works on searching for new raw material for prospective material production.

Mechanical Properties of Bauxite Ceramics

This paper reports a study of mechanical properties of bauxite ceramics. The influence of the form of corundum grains, composition of the glass phase and solid solutions of mullite and aluminum titanate in the corundum matrix on mechanical properties of bauxite ceramics are also discussed.

The Effect of Sesquioxides of 3d-Transition Elements on the Strength of Synthetic Mullite and Mullite-Based Materials

Mullite synthesized from alumina and silica with the sesquioxide of a 3d-transition metal added (Me = Sc, Ti, V, Cr, Mn, and Fe) is capable of forming solid solutions of composition Al6–xMexSi2O13. It is shown, using data obtained by methods of x-ray phase analysis, electron paramagnetic resonance, infrared spectroscopy and magnetic susceptibility, that the aluminum atoms located at octahedral positions of the mullite lattice can be isomorphously replaced by Me metals. The effect of this replacement on the strength of mullite and mullite-based ceramics is considered.

North ural apovulcanites as raw material for porcelain production

The apovulcanites from the Republic of Komi which are analogues of porcelain rocks are studied as a material of the quartz-feldspar type for electrotechnical, household, and sanitary ware ceramics. The effect of kaolinite clay and low-iron Timanskii bauxite on the production conditions, the structure, and the properties of apovulcanite-based ceramics is investigated. It is shown that apovulcanite can be used in production of porcelain articles.