Reaction sintering and microstructures of zirconia/metal mixed powders
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Reaction-sintered zirconia ceramics with a low firing shrinkage were prepared from ZrO2/Al/MgAl powder mixtures by reaction sintering and the effect of the milling characteristics of the raw powders was investigated. The powder mixtures of flaky Al with Ca-PSZ were not effectively comminuted by attrition milling compared with the alumina mixtures. However by using alumina balls rather than zirconia balls the grinding efficiency of attrition milling could be greatly increased. By contrast to fused Ca-PSZ powders natural baddeleyite was much more easily pulverized with MgAl powders. During heating, Mg and Al firstly became to oxide and subsequently converted to spinel (MgAl2O4) and finally the unreacted MgO seemed to stabilize the zirconia. The oxides which formed in the oxidation process had a very fine grain size so that the reaction sintering was more effective in densification and producing a homogeneous microstructure. The mechanical properties of the reactionsintered stabilized zirconia/spinel composite were better than those of the zirconia composite only stabilized by MgO.
Abstract
Reaction-sintered zirconia ceramics with a low firing shrinkage were prepared from ZrO2/Al/MgAl powder mixtures by reaction sintering and the effect of the milling characteristics of the raw powders was investigated. The powder mixtures of flaky Al with Ca-PSZ were not effectively comminuted by attrition milling compared with the alumina mixtures. However by using alumina balls rather than zirconia balls the grinding efficiency of attrition milling could be greatly increased. By contrast to fused Ca-PSZ powders natural baddeleyite was much more easily pulverized with MgAl powders. During heating, Mg and Al firstly became to oxide and subsequently converted to spinel (MgAl2O4) and finally the unreacted MgO seemed to stabilize the zirconia. The oxides which formed in the oxidation process had a very fine grain size so that the reaction sintering was more effective in densification and producing a homogeneous microstructure. The mechanical properties of the reactionsintered stabilized zirconia/spinel composite were better than those of the zirconia composite only stabilized by MgO.