纳米ZrO_2－Al_2O_3复合粉末注浆成型与烧结行为研究

Slip Casting and Sintering Behavior of Nanometer Sized Zirconia-Alumina Powders

平均粒径为２０ｎｍ的ＺｒＯ_２添加５～１５ｖｏｌ％的粒径为２００ｎｍ的Ａｌ_２Ｏ_３粉末注浆成型与烧结特性表现出与普通微米及亚微米级粉末不同的特性：浆料具有较低的含固量，粘度为５厘泊时为５５ｗｔ％；浆料呈微弱触变性：生坯具有较低相对密度，仅为理论值的３５．５％；少量Ａｌ_２Ｏ_３（５～１０ｖｏｌ％）促进复合材料的烧结，但也伴随着Ａｌ_２Ｏ_３晶粒异常长大。上述现象归因于纳米粉末具有非常高的比表面，粉末表面吸附大量紧吸附水不能被石膏模所排除，而粉末巨大的表面能促进了烧结过程中的质点扩散。

The suspension,rheology and sintering behavior of the aqueous slurry of nanometer size Al_2O_3 and ZrO_2 powders were studied. The both powders had zeta potentials over-40mV at pH 10 when 0.8～1. 2wt% poly(acrylic acid, PAA) was used as a dispersant with an average molecular weight of 2000～3000. The slurry exhibited thixotropic behavior and had maximum solid content 55 wt% for slip casting corresponding to the viscosity of 5×10￣(-2) Pa s. The relative densities of the green bodies increased slowly with an increase of solid content in slurry but never more than 35%.These were attributed to the nanometer size powders with very high specific surface, on which a large amount of tightly absorbed water in the cakes can not be taken in by the Paris plaster mold.The influences of Al_2O_3 content on sintering and microstructure evaluation were alse investigated.5￣10 vol% Al_2O_3 promoted the composites sintering ability but the 15vol% Al_2O_3 particulate hindered its densification. The average grain sizes were 0.6～1.4μm for zirconia and 3～8μm for alumina(exaggerated Al_2O_3 grain grain growth)for the composites at 1530￣1580℃ pressureless sintering for 4h.