Effects of alumina particle size and zirconia powder extra-addition on sintering property of alumina granula-ted powder
This work aims at improving the sintering property of zirconia toughened alumina(ZTA)granula-ted powder.ZTA slurries were prepared through ball milling using alumina powder with different particle si-zes(d50:1.72 μm,3.48 μm and 13 nm)and yttria stabilized zirconia(YSZ)as the main starting materials,adding binders and dispersants.The effect of the YSZ extra-addition(0,5％,10％,15％and 20％,by mass)on the rheological property of the slurries was investigated.ZTA granulated powders were prepared using the spray drying method,and then the powders were pressed into shapes and fired at different tem-peratures(1 520,1 600,and 1 680 ℃).The linear shrinkage and relative density of the fired samples were determined.The results show that:(1)the ZTA slurries exhibit shear thinning behavior and possess a yield stress;the rheological properties of the slurries are well-described by the Herschel-Bulkley model,with a high correlation coefficient(＞0.98);(2)the particle size of the prepared ZTA granulated powders is main-ly within the range of 125 to 45 μm,demonstrating a wide distribution;(3)the optimal formulation is 99 mass％activated alumina powder(d50=1.72 μm),1 mass％nano-alumina(d50=13 nm),and 15 mass％YSZ(extra-adding);this formulation results in a Carr coefficient of 8.62％,a water content of 0.22％,and an angle of repose of 25.2°;after firing at 1 600 ℃ for 2 h,the sample exhibits a relative density of 94.8％and a linear shrinkage rate of 18.2％.
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