Nanoscale Si-C and Al-O-(N,C) ceramic powders by laser synthesis from gaseous precursors

Laser induced photosynthesis has been employed to produce nanosized aluminium oxide powders. The dependence of reaction outcomes on the process parameters in particular on reactant gases (trimethylaluminium TMA and nitrous oxide) relative concentration, has been investigated in several different conditions. The experimental results indicate two main reaction paths. Low TMA relative concentration leads to the formation of nanocrystalline gamma-Al2O3 with traces of Al3O3N compounds. Increasing the TMA concentration the synthesis of aluminium oxicarbide (Al2OC) is observed. Only the first reaction path is able to produce, after calcining at 1400 degrees C, nanosized alpha-Al2O3 powder. Preliminary attempts in sintering laser produced silicon carbide have shown, that, due to the nanometric dimension of the powder particles, it is possible to retain the beta-SiC low temperature phase even for sintering temperature up to 2150 degrees C.