NANOSCALE SI-C AND AL-O-(N,C) CERAMIC POWDERS BY LASER SYNTHESIS FROMGASEOUS PRECURSORS

Laser induced photosynthesis has been employed to produce nanosized al uminium oxide powders. The dependence of reaction outcomes on the proc ess parameters in particular on reactant gases (trimethylaluminium TMA and nitrous oxide) relative concentration, has been investigated in s everal different conditions. The experimental results indicate two mai n reaction paths. Low TMA relative concentration leads to the formatio n of nanocrystalline gamma-Al2O3 with traces of Al3O3N compounds. Incr easing the TMA concentration the synthesis of aluminium oxicarbide (Al 2OC) is observed. Only the first reaction path is able to produce, aft er calcining at 1400 degrees C, nanosized alpha-Al2O3 powder. Prelimin ary attempts in sintering laser produced silicon carbide have shown, t hat, due to the nanometric dimension of the powder particles, it is po ssible to retain the beta-SiC low temperature phase even for sintering temperature up to 2150 degrees C.