Chemical and Thermal Shock Resistance Properties of Porous Silicon Carbide Ceramics

Abstract

Porous silicon carbide (SiC) ceramics have been considered as promising candidates as the catalytic support, mechanical seals, hot-gas and molten-metal filters, gas turbine system, heat exchanger tubes, etc. due to their excellent properties. In such applications under corrosive atmosphere, the SiC ceramic materials experienced different type of corrosions such as; deposit-induced corrosion, passive oxidation, active oxidation, scale volatility, scale interactions, etc., depending on their composition. SiC ceramic filters can withstand aggressive chemical and thermal shock conditions during their use, being more advantageous than polymeric or metallic materials. Thermal and chemical resistance properties ultimately determine the suitability and service life of ceramics for applications in corrosive atmosphere. Detailed study on the effect of thermal shock and corrosion in strong acidic/alkaline conditions at elevated temperature on porous SiC ceramics and the microstructure and mechanical property evolutions of the corroded SiC ceramics are still very few. It is always a preferable choice to have prior information on thermal shock and corrosion resistance properties of any new material before selecting the material for applications in one or more corrosion environments. Therefore in this chapter it is aimed to review and quantitatively assess different types of thermal and chemical corrosion at various temperatures on the microstructure, materials properties and flexural strength of porous SiC ceramics prepared by various methods. A brief summary is given on the current state of knowledge on the effect of chemical and thermal corrosion, influence of the chemical corrosion conditions (type of salt, acid/alkali, temperature, pressure, etc) and thermal shock resistance (cooling/heating as a function of quenching temperatures and quenching cycles, etc) on the material and mechanical properties.