以高纯氢氧化铝为主要原料,利用扫描电子显微镜、X射线衍射、X射线荧光光谱及X射线光电子能谱等技术,研究了引入 NH4F 或 AlF3对 α-Al2O3转变特征、氧化铝粉体及陶瓷显微结构的影响.结果表明:引入NH4F或AlF3促进α-Al2O3晶体形貌由颗粒状向片状转变.但是经高温煅烧,形成的片状α-Al2O3晶体又转变为颗粒状晶粒.粉体经不同压力成型后的块状样品,在1300℃煅烧后,α-Al2O3晶体仍保留片状形态.但是进一步升温到1600℃烧结的氧化铝陶瓷,晶体形貌由片状逐渐转变为多面体.热压条件下,氧化铝陶瓷晶体仍能够保持片状,没有出现多面体形态.随着烧结温度的提高,样品烧结致密化程度不断增大,相对密度从77.6% 增加到92.2%.相比以片状粉体为原料烧结的α-Al2O3陶瓷,以颗粒状粉体为原料烧结的陶瓷相对密度要大,在1600℃烧结的α-Al2O3陶瓷密度从92.2%提高到93.0%.%α-Al2O3powders and alumina ceramic were prepared by high pure AlOOH as the precursor material. Effects of NH4F or AlF3on the transformation and microstructure of the α-Al2O3powders and ceramic were investigated by scanning electron microscopy,X-ray diffraction,X-ray fluorescence and X-ray photoelectron. The results show that the introduction of NH4F or AlF3promotes the morphology of α-Al2O3to change from particle-like to plate-like shape. However,the α-Al2O3platelets will revert to grains again after calcinated at high temperature. The plate-like α-Al2O3can maintain the disk shape after calcinated at 1300℃,when the α-Al2O3powders are pressed into disk under different pressure. The morphology of α-Al2O3crystals changes from platelet to polygonal when they are further sintered up to 1600℃. However,under hot pressing condition,the platelet α-Al2O3crystals don't show the polygonal morphology. The densification of α-Al2O3ceramic is strengthened and the relative density of the ceramics increases from 77.6% to 92.2% with the rise of the sintering temperature. The density of α-Al2O3ceramic prepared with particle-shaped powders is larger,compared to that prepared with plate-like powders,which increases from 92.2% to 93.0% after sintered at 1600℃.
展开▼
