GRAIN SIZE EFFECTS ON THE THERMAL CONDUCTIVITY OF CERAMIC OXIDES

摘要

Dense, fine grained alumina samples were employed in a study of the effect of grain size on thermal conductivity in polycrystalline alumina. The thermal conductivity in the temperature range from 100°C to 1000°C decreased slightly but significantly as the average grain size was varied from 10u to 4u to 2u. The decrease in thermal conductivity with decreasing grain size was found to follow closely an additive reciprocal volume relationship, which has been discussed by several investigators. The role of impurities in masking this effect in dense alumina samples of purity exceeding 99% was shown by measuring the thermal conductivity of specimens with small variations in impurity content.nThe strength and modulus of elasticity of these fine grained alumina s were also measured. Several questions were raised concerning the data obtained which have not been resolved. Dense samples of MgO have also been produced using hot pressing techniques and strength and elasticity properties measured. These results are incomplete and not well understood.