THERMAL DIFFUSIVITY OF CARBONS AND GRAPHITES IN THE TEMPERATURE RANGE FROM 1800 TO 3300K
AEROSPACE CORP EL SEGUNDO CA LABS DIV
Pagination or Media Count:
Improved and new steady periodic heat flow methods for the direct measurement of the thermal diffusivity of carbons and graphites at very high temperatures were developed. Their main features are techniques that overcome the difficulties arising from the radiative environment with thermal conductance much greater than that of the material under investigation. The thermal diffusivities of various carbons and graphites were determined with these techniques and were found to be essentially independent of temperature throughout the entire range investigated. It is argued that the observed c- direction conduction in pyrolytic graphite is probably not of intrinsic nature, but is at best a small component of the a-direction conduction caused by tilt angle variations of the microcrystallites. It is further suggested that the heat conduction in graphites at high temperatures is substantially of electronic nature, a point supported by Lorenz numbers based on more recent data. The essentially temperature-independent diffusivity of graphite reflects, then, the behavior of ordinary metals above the Debye temperatures.
- Ceramics, Refractories and Glass
- Solid State Physics