Synthesis of Al2O3/SiC powders using microwave-induced combustion reaction

Nanocomposites Al2O3/SiC powders have been synthesized by a microwave-induced combustion process using aluminium nitrate, beta -SiC (powders) and urea, The effect of preheating the solution before the combustion reaction and the effect of the characteristic of the SiC powders, in the crystallization of the alumina, by combustion reaction were evaluated. The preheating of the liquid solution at about 150 degreesC before heating in the microwave oven guaranteed the homogeneity of the solution and modified the characteristics of the products. The mechanism of heating in the microwave oven was favorable to the uniform emission of gases and fast dissipation of heat, promoting formation of different foam and nanocomposites Al2O3/SiC powders with characteristics that were different from those produced conventionally. The direct conversion of liquid solution to the final solid product was assured, and the segregation commonly found in conventional mixing of powders (alumina-SiC) was avoided. The different characteristics of the SiC powders have strong influence in the flame time of the combustion reaction and consequently in the crystallization of the alumina and characteristics of the Al2O3/SiC nanocomposites powders. The SiC particles were not oxidized during the reaction and partial reaction with alumina did not occur; SiC particles remained as a distinct and separate phase.