S. A. Suvorov

Vermiculite — a Promising Material for High-Temperature Heat Insulators

Vermiculite, a mineral of natural occurrence of the group of hydromicas, when heated to above 300°C, expands to become a highly efficient heat-insulating material. The expanded vermiculite, owing to its unique properties – low bulk density, low heat conductivity, relatively high melting point, chemical inertness, endurance, and environmental safety – can be used as a filler for heat-insulating materials. Heat insulators based on expanded vermiculite can be used in thermal power units with the hot-wall temperature not exceeding 1150°C as replacement for lightweight chamotte components and fibrous heat insulators.

High-Temperature Heat-Insulating Materials Based on Vermiculite

The production technology and composition of high-temperature heat-insulating materials based on vermiculite have been developed, as applied to the conditions of the Borovichi Refractory Works. Using these materials makes it possible to lower material consumption in thermal machinery, reduce inefficient heat losses, and decrease by 10 – 15 times the total fuel consumption in continuous furnaces and by more than 45% in batch furnaces.

Chemical Equilibria Involving Lanthanum Chromite

The equilibrium vapor composition over lanthanum chromite in reducing, oxidizing, and neutral gas media has been analyzed. A thermodynamic assessment of the LaCrO3 thermal dissociation reaction is given. A characterization of electric properties of LaCrO3 in gas media of variable composition is given based on the calculated proportion of oxidized and reduced chromium forms in the vapor phase over LaCrO3.

Microwave Synthesis of Materials from Aluminum Oxide Powders

High-temperature synthesis with the use of microwave energy is used to fabricate corundum materials with a relative density of 95 – 99% of the theoretical value from aluminum oxide powders with different grain sizes and prehistory. The microstructure of the materials is composed of grains with a size close to the initial one and closed spherical pores.

Rapid Synthesis of Finely Dispersed Sialon Powder by Carbothermal Nitridation of Kaolin

A powder based on β-sialon is prepared by carbothermal nitridation. A scheme for rapid synthesis of β-sialon with controlled dispersity at high temperature is developed. The critical size range of β-sialon particles is determined. Experimental data on phase composition and particle size of the synthetic sialon powders are in agreement with theory.

ELASTIC REFRACTORY MATERIALS

The author presents regression dependences and functional properties of composite organomineral elastic refractory materials (ERM) in the form of products, their application, and efficiency of their use.

Optimizing the Plastic Properties of Binding Clays with Use of a Simplex-Lattice Method of Experimental Design

The effect of plasticizers on the plastic properties of refractory clay mixtures is studied. Optimal concentrations for additions are specified. Applications to the serial production of aluminosilicate materials at the Borovichskii Refractory Kombinat Joint-Stock Co. are reported.

Microwave Synthesis of Corundum Materials with Various Densities

Materials with various densities obtained by high-temperature microwave synthesis from aluminum oxide powders with various grain sizes and prehistories, which are modified by additives of radio-transparent and radio-absorbing substances, are described. The process of high-temperature consolidation of the initial particles by a welding mechanism provides a high level of strength in the materials.

A Physicochemical Study of Properties of Integrated High-Temperature Heat-Insulating Materials

Results of a study of properties of integrated high-temperature heat-insulating materials based on expanded vermiculite are reported. These materials combining low heat conductivity and high strength, have a potential for use as lining refractories in thermal power units with operating temperatures not exceeding 1100°C.

Microwave synthesis of corundum-zirconia materials

High-strength corundum-zirconia composites are synthesized from commercial fused corundum powders using a microwave heating technique. The high strength of synthesized materials is due to the cementing effect of an eutectic phase crystallized at the corundum grain boundary. The level of strength is determined by the rate of heat exchange between the generating and absorbing phases of the material.