Sinterable Powders from Laser Driven Reactions
Abstract
Novel methods for producing ideal powders for fabricating Si3N4 ceramic parts have been investigated. The characteristics sought were principally uniformly small diameter, equiaxed, high purity particles which are free of agglomerates. Two laser processes were studied. In the first, a CO2 laser source was used to heat the reactant gases by coupling directly to them. Silicon (Si) and Si3N4 powders have been synthesized directly from SiH4 and NH3/ SiH4 mixtures respectively. The spatially well-defined reaction zone and the combination of the rapid heating rates with the short times at reaction temperatures yielded very uniform and small diameter particles. Si3N4 powders were produced with particle diameters entirely within the range of 100-200 A. The particles are equiaxed and nearly spherical. The Si powders had the same general characteristics, but exhibited a slightly larger range of diameters. The second process uses selective heating to reduce the size of oversized particles or agglomerates as well as modifying the shape of high aspect ratio particles. This process is based on the decreasing absorption efficiency of a particle to light when its diameter is less than the wavelength of the incident light. Light induced comminution was demonstrated. We have successfully demonstrated both processes for producing superior Si and Si3N4 powders.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1978
- Accession Number
- ADA063064
Entities
People
- John S. Haggerty
- W. R. Cannon
Organizations
- Massachusetts Institute of Technology