Mechanochemical activation of aluminum powder and synthesis of alumina based ceramic composites

The microstructure and chemical reactivity of aluminum powder ball milled in ethanol medium have been investigated in this study. It has been shown that the milling environment plays an important role on the chemical behavior of the milled aluminum powder. Aluminum particles ball milled in ethanol could physically bond a significant amount of hydroxyl (OH) and alkyl (CH) functional groups, the presence of which drastically changes the oxidation behavior of the milled powder. Such mechanochemically activated (MA) aluminum powder obtained by ball milling in ethanol was found to oxidize at temperatures less than half of that for oxidation of original powder. This is thought to be because of refinement and modification of particle surface of MA aluminum powder. Moreover, even at the reduced temperature of oxidation, the MA aluminum powder oxidizes mainly in the form of high temperature phases such as γ-Al2O3 and α-Al2O3 (corundum). Utilizing the specific chemical behavior of MA aluminum powder, we demonstrated that it is possible to prepare alumina–SiC ceramic composites directly from the mixture of MA aluminum and SiC compounds at significantly lower temperature. Some important parameters of the synthesized ceramics have been investigated.