Compatibility of CoO, Co0.5Mg0.5O, and CoAl2O4 with containment metals

• Published in: Journal of nuclear materials Vol. 79; no. 1; pp. 95 - 109
• Main Authors: Kanne, W.R., Smith, P.K.
• Format: Journal Article
• Language: English
• Published: 01.01.1979
• ISSN: 0022-3115
• DOI: 10.1016/0022-3115(79)90436-7

Long-term interactions of refractory metals and noble metals with CoO, Co0.5Mg0.5O, and CoAl2O4 were investigated 1000 deg C and 1850 deg C to select encapsulation materials for radioisotopic power applications of 60Co. Rhenium was the only refractory metal that exhibited no solid-state reactions with the oxides of cobalt. However, vapour transport of rhenium probably by ReO3(g) was found to be extensive at temperatures above 1500 deg C because of intrinsic high oxygen pressures over the cobalt oxides and small ( < 1 deg C) temperature gradients. Transport kinetics analyses suggest rhenium, then, may not be a suitable container for cobalt oxides for thousands of hours at temperatures over 1200 deg C. Short-term exposures (1000 h at 1500 deg C) and analyses indicate that iridium will be compatible with cobalt oxides and that vapour transport will be negligible. Superalloys were shown to react with cobalt oxides at 1000 deg C, primarily by reduction of cobalt oxides by chromium. 18 ref.--AA