Final technical rept. 1 Apr 1974-30 Jun 1975
GENERAL ELECTRIC CORPORATE RESEARCH AND DEVELOPMENT SCHENECTADY NY
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Measurement of the rate of oxidation and creep rate in air of chemically vapor deposited Si3N4 at around 1500C are reported. Attempts to prepare pure, dense Si3N4 bodies by hot pressing powder at ultra-high pressures were partially successful. Resistance heaters made of dense, sintered SiC were tested and found to have in-use lifetimes at least 10 times longer than those of commercially available heaters tested in the same way. It was found that the resistivity of B containing dense, sintered beta-SiC could be changed through compensation of the B acceptors by N donors introduced from the sintering furnace atmosphere during firing. The thermal EMF of a junction made of p- and n-types of dense sintered beta-SiC was measured over the temperature range from 100C to 1500C and found to be 0.95 volt at 1500C. A way was found to densify B4C without hot pressing. Bodies of B4C having about 94 of theoretical density were made by using conventional sintering processes and doping the powder with either SiC or B4C. Extensive work presented herein on the sintering of covalently bonded solids beta-SiC, Si, alpha-Si3N4, AlN.
- Ceramics, Refractories and Glass
- Solid State Physics