Effect of Adding Nanocrystalline γ－Al_2O_3 on Sintering Behavior of Alumina Fibers

The effect of adding nanocrystalline γ-Al2O3 powders on the sintering behavior of alumina fibers was investigated. The nanocrystalline powders will be stuffed into the pores formed from the packing of micron-sized alumina powders when the fiber is extruded. In the case of 40% nanocrystalline γ-Al2O3 in the mixed powders, the relative green density increases from 65% to 80%. The fiber can be sintered to near theoretical density at relatively low temperature because it is of higher density, narrower pore size distribution and smaller mean pore size. The diametric shrinkage of the fibers extruded from the nanocrystellineγ--Al2O3 is higher than that made from micron-sized powders. γ-Al2O3 phase is transformed to α-Al2O3 during sintering process.