Investigation of the CNTD Mechanism and Its Effect on Microstructural Properties of SiC and AlN

摘要

The report describes the development of a CNTD process for silicon carbide. Following earlier work on resistance-heated substrate, attempts were made to develop a furnace process for CNTD SiC. High temperature flexure testing of SiC-coated graphite bend bars showed that the CNTD SiC was superior to other conventional SiC materials over the whole range of temperatures tested. Problems were encountered in attaining uniformity and repeatability of the material. All deposits tested showed a two-phase structure of Si and SiC. Highly variable compressive surface stresses were observed by XRD techniques. Attempts to develop a CNTD process for AlN were not successful. However, grain refinement and improvement in physical properties were achieved when AlN deposits were 'doped' with Si. The electrical and thermal properties of CVD AlN were comparable to other AlN materials. The IR transmittance characteristics were found to be inferior, possibly due to impurities in the deposit. (Author)