Condensation of Ultrafine Silica from a Laser-Induced Plume

Abstract

ABSTRACTThe different silica-phase morphologies formed in synthesizing silica-metal matrix composites layers have been studied, using a new evaporation technique, involving rapid condensation of silica from a laser beam induced-ceramic plume. This process occurs within a reactive gas environment (98.5% hydrogen, 1.5% methane), with a heated tungsten filament in proximity to the laser beam-material interaction zone. The silica phase in the composite layers deposited on a nickel substrate exhibited different metastable morphologies, namely, nanometer-size amorphous fibers or linear-chain shape aggregates. There appeared to be a correlation between the morphology of the deposits and the position of the heated tungsten filament. When the tungsten filament was absent, silica was deposited in the form of clusters. In this case, depending on the beam-ceramic target interaction times, there was a shift in the Si-O stretching vibration characteristics. The laser beam-ceramic target interaction and the formation of the laser-induced ceramic plume are briefly discussed. Characterization techniques involved FTTR, X-ray diffraction, Auger and microprobe analysis, EDX and WDX analysis, SEM and TEM.