Effect of sub-minute high temperature heat treatments on the thermal conductivity of carbon-bonded carbon fiber (CBCF) insulation

摘要

The thermal conductivity of carbon-bonded carbon fiber insulation in vacuum was determined before and after short duration heat treatments to model the effect of varying degrees of graphitization. Specimens of the insulation were heat-treated for 10, 15 and 20 seconds at 2673, 2873, 3073, and 3273 K. The dimensions and mass of each specimen was recorded before and after heat treatments. The thermal conductivity of the heat treated specimens was measured as a function of temperature up to 2273 K. These data are compared with previously measured specimens heat treated at the same temperatures for 1 minute and one sample heat-treated at 3273 K for 1 h. The thermal conductivity increases with both the heat treatment temperature and time at temperature. The thermal conductivity data has been modeled to obtain equations that predict the thermal conductivity of the insulation as a function of temperature (673 K (le) T (le) 3773 K) and heat treatment conditions of time (0 (le) t (le) 20 s) and temperature (2673 K to 3773 K).