湿式ボールミル粉砕したα-Fe₂O₃粉の焼結特性に及ぼすボールミルからの不純物の影響

抄録

Alpha-Fe₂O₃ powder was ground by ball-mill with alumina and zirconia balls. Densification behavior with respect to both specific surface area and the amount of impurities from the balls was investigated. The onset temperature of shrinkage for the powders milled with alumina balls decreased with increasing specific surface area and decreasing impurity contents. On the other hand, the onset temperatures for the powder milled with zirconia balls increased, although the specific surface area of the powder was increased by milling. Density and microstructure of the samples sintered at 1100°C for 10h were evaluated. Relative densities of sintered samples by the powders with 3.5mol% and 1.1mol% Al₂O₃ were 99.4% and 99.3%, respectively. Average grain sizes of these samples were 5.4μm and 10.1μm, respectively. The relative density of sintered sample by the powder with 0.7mol% ZrO₂ was 97.8%. This value was lower than those by the powders milled with alumina balls, although there was no difference in specific surface area in these powders. This result indicates that Al₂O₃ does not influence the densification of α-Fe₂O₃, however ZrO₂ inhibits densification. The cause of densification inhibition by ZrO₂ was considered that the diffusion rate of oxigen ion is decreased by the decrease of oxigen ion vacancies, which is caused by the dissolution of ZrO₂ in α-Fe₂O₃.