ZrO_2強化MgOの耐熱衝撃性

概要

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The effect of a second phase ( ZrO_2 particles) on the thermal shock resistance of MgO was thvestigated. MgO doped with 1 mol% LiF and MgO dispersed with 10 mol% ZrO_2 (t-ZrO_2 or c-ZrO_2) were fabricated by sintering. Sintered specimens were heated to various temperatures, quenched into water or lubricating oil, and then examined by the 4-point bending test to investigate the severity of the thermal shock. The critical temperature difference ΔT_c at which the fracture stress of specimens considerably decreased was higher in MgO dispersed with c- ZrO_2 (200 K in water and 650 K in lubricating oil) or t-ZrO_2 (250 K and 620 K) than that in MgO doped with LiF (115 K and 300 K). These results have been attributed partially to the increase in fracture stress of MgO due to the existence of dispersed ZrO_2. The strength of MgO dispersed with t-Zr02 did not instantaneously decrease at the temperature difference in excess of ΔT_c. This behavior was not observed in other specimens. It was thought to be caused by the microcracks created by m- ZrO_2 which was also present in the specimen. The critical temperature difference ΔT_c of specimens quenched in lubricating oil was higher than ΔT_c quenched in water. It was qualitatively in accordance with the prediction of the calculation of heat transfer coefficient.
1989-08-01