Specimen size affects the first few hours of primary outgassing and thus the fraction of total amount of volatile species being driven off at the end of primary outgassing. Primary outgassing (1350/sup 0/C at 0.1 mPa (10/sup -6/ torr) for 70 h) causes no increases in the thermal conductivity of CBCF3 insulation.
The dominating gaseous species of secondary outgassing are CO and CO/sub 2/. The total outgassing of CBCF3 insulation during generator start-up and operation is equivalent to the weight loss during secondary outgassing, (i.e., 0.08 mg per gram of CBCF3 insulation). Primary outgassing at 1350/sup 0/C and 0.1 mPa (10/sup -6/ torr) for 70 h seems satisfactory because reabsorption during exposure to argon or air is minimal and the total weight loss during secondary outgassing is also very small. A carbon-bonded carbon-fiber (CBCF3) thermal insulation has been developed and has demonstrated acceptable strength, thermal conductivity, and outgassing properties for the Selenide Isotope Generator.
