Sinterable powders from laser driven reactions : annual report

Abstract

Extremely fine, uniform ceramic powders were synthesized from laser heated gas phase reactions. Resulting Si, Si N4 and SiC powders have been characterized in terms of parameters wich are important for densification processes. They are virtually ideal. The spherical particles typically have mean diameters from 120 to 1000 A. The standard deviation is typicaliy 25-45% and the diameter of the largest observed particle is typically less than twice that of the smallest particle. Purities are extremely high. The laser heated process has been modeled in terms of fluid flow and heat transfer criteria. Many fundamental property measurements were made to provide data for these calculations. The process is extremely efficient; X 95% of the SiH4 is reacted in a single pass through the laser beam and approximately 2 kwhr. of energy are required per kilo of Si3N4.