Nanocomposites Al2O3/SiC powders have been synthesized by a microwave-induc
ed 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 t
he liquid solution at about 150 degreesC before heating in the microwave ov
en guaranteed the homogeneity of the solution and modified the characterist
ics of the products. The mechanism of heating in the microwave oven was fav
orable to the uniform emission of gases and fast dissipation of heat, promo
ting 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 assure
d, and the segregation commonly found in conventional mixing of powders (al
umina-SiC) was avoided. The different characteristics of the SiC powders ha
ve strong influence in the flame time of the combustion reaction and conseq
uently in the crystallization of the alumina and characteristics of the Al2
O3/SiC nanocomposites powders. The SiC particles were not oxidized during t
he reaction and partial reaction with alumina did not occur; SiC particles
remained as a distinct and separate phase.