EFFECTIVE THERMAL-CONDUCTIVITY OF A PACKED-BED OF HOLLOW ZIRCONIA MICROSPHERES, UNDER VACUUM AND UNDER 100 KPA OF ARGON

Measurements have been made of the effective thermal conductivity of a packed bed of hollow, yttria-stabilized zirconia microspheres, under vacuum and under 100 kPa of argon gas. Above 1400 K the spheres begin to sinter together. Before this occurs, the conductivity is given under vacuum by A1T3 + A2 with A1 = 2 x 10(-11) W.m-1.K-4 and A2 = 0.01 W.m-1.K-1. The thermal conductivity increases strongly with both the gas pressure and the degree of sintering of the spheres. The measured values can be fitted reasonably well by a model developed by Takegoshi et al. These results may have some applicability to the development of high-temperature thermal insulation.