Thermally induced crystallization of mechanosynthesized chlorapatite-titania composite nanopowders

详细信息    查看全文

• 作者：Bahman Nasiri-Tabrizi ; Abbas Fahami ; ^{ab.fahami@gmail.com" class="auth_mail}
• 关键词：Crystallization ; Chlorapatite&ndash ; titania ; Composite nanopowder ; Subsequent annealing ; Reaction mechanism
• 刊名：Ceramics International
• 出版年：July, 2014
• 年：2014
• 卷：40
• 期：6
• 页码：8201-8210
• 全文大小：6595 K

文摘

The thermally induced crystallization of mechanosynthesized chlorapatite-titania composite nanopowder was investigated. Firstly, the composite nanopowder was produced after 5 h of milling. The mechanosynthesized powder was annealed in the range 900-1300 掳C for 1 h. The 5 h milled sample showed the crystallite size and lattice strain of about 23卤1 nm and 0.0107卤0.00054, respectively. During the subsequent annealing, crystallization of the milled sample at 900 掳C and severe decomposition of nanocomposite at 1300 掳C were detected. Accordingly, the fraction of crystalline phase reached a maximum around 96卤4% at 900 掳C and then declined to 80卤4% at 1300 掳C. The lattice strain decreased drastically to about 0.0002卤0.00001 at 1300 掳C, while the crystallite size increased significantly to around 277卤14 nm. Based on the obtained data, the unit cell volume of CAp went down during the thermal treatment due to the ion exchange reaction between chlorapatite and titania. According to the electron microscopic observations, the morphological features of composite nanopowders were influenced strongly by the annealing temperature. The 5 h milled sample was composed of spheroidal particles with an average size of about 35 and 190 nm before and after annealing at 900 掳C, respectively. At 1100 掳C, the coalescence of nanospheres was dominant. Finally, a porous composite structure comprised of coarse grains with an average size of about 1 渭m along with finer grains with a mean size of around 100 nm was formed at 1300 掳C.