Phase- and structure-formation processes during self-propagating high-temperature synthesis in the system Al – MgCO3 – SiO2 – C

Abstract

Phase and structure formation processes occurring in the system Al – MgCO3 – SiO2 in the course of selfpropagating high-temperature synthesis are examined. The dependences of the structure and the phase composition of the composite materials formed on the ratio of the initial components are determined. It is shown that self-propagating high-temperature synthesis can be used to produce ceramic composite materials based on the spinel and silicon carbide phases. An effective method of obtaining composite materials is self-propagating high-temperature synthesis (SHS). SHS technology is a powder technology but it differs fundamentally from other powder technologies used in metallurgy by the fact that to realize synthesis powders are combusted and not heated in high-temperature facilities. The synthesis process proceeds by means of its own release of heat as a result of the interaction between the components of the initial mixture with valuable condensed products being formed, which makes it possible to decrease costs and reduce the energy consumption for production and, therefore, decrease prime costs [1]. Phase formation in the process of combustion of powdered mixtures occurs directly in the reaction volume, and the crystalline compounds formed grow into particles of other compounds. In the process it becomes possible to obtain composite crystalline phases, which is difficult to do under ordinary conditions. An example is a composition consisting of spinel and silicon carbide. Aluminomagnesia spinel MgO Al 2 O 3 is a ceramic material with adequate mechanical strength and good corrosion and radiation resistance; it is widely used in metallurgy, machine building, instrument building, the chemical industry as linings for inductors and electric resistance furnaces, filters for melts, high-temperature electric insulators, and articles for other purposes. Spinel ceramic finds wide applications in the manufacture of protective cases for thermocouples and crucibles for melting metals. Aluminomagnesia spinel is also a promising refractory material, used in heating equipment in its own form and with the addition of magnesia refractories during fabrication [2, 3]. The kinetic difficulties in the synthesis of spinel via the reaction