Zirconia refractories

Results on the thermal conductivity of powders of monoclinic zirconia as a function of the grain size are presented. It is established that of all the investigated sintered powders of monoclinic ZrO₂ the 1 – 0.5-mm and 2 – 1-mm fractions have the lowest thermal conductivity and the least apparent density (2.190 and 2.262 g/cm³). Fused powders of monoclinic and stabilized ZrO₂ have a higher thermal conductivity than their sintered counterparts. Powders prepared from monoclinic ZrO₂ with a burning-off addition of polystyrene have larger pores in the grains, which increases the share of the radiation component in the heat transfer, and hence their thermal conductivity is higher than in powders obtained by sintering pure monoclinic ZrO₂. For the same reason, powders from void granules of the 3 – 0.5-mm fraction have a higher thermal conductivity than sintered monoclinic powders of ZrO₂.Translated from Ogneupory, No. 1, pp. 26 – 29, January, 1995.