Hydrothermal synthesis of aluminum oxide

• Main Authors: Cheng-he Liu, 劉政和
• Other Authors: Ming-tsai Liang
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/09979425292670906801

碩士 === 義守大學 === 生物技術與化學工程研究所碩士班 === 97 === This study utilized continuous hydrothermal synthesis to produce flake boehmite with various morphology and size and spherical aluminum oxide.Based on the difference of heating,this study concluded that: (1) Produced by direct heating: 1.By up-flowing reactor,hexagonal flake of boehmite was obtained,and its mean size was 0.7 ~1.0 um.; 2.By down-flowing reactor,long hexagonal flake of boehmite was obtained, and its mean size was 1.43~2.69 um; 3.Morphology and size of the boehmite was mainly affected by the residence time in hydrothermal condition; 4.Flake boehmite without agglomeration can be obtained in the range of 220~290 C with 0.01 M of aluminum nitrate solution as the nutrition. (2) Produced in Supercritical Water Flame 1.Morphology of the produced boehmite was mainly determined by temperature.Aluminum oxide was obtained as temperature higher than 420 C,and only boehmite was found as lower than 420 C. 2.Nucleation occurred right after hydrolysis.Particles grow as temperature increases because of decrease of solubility of boehmite in acidic environment.While the growing particles were cooled after temperature passed over the critical temperature,the dramatic decrease of solubility could lead to another additional nucleation.Therefore,the obtained particles could show bimodal distribution.This was observed,if temperature of the supercritical water flame was ranged from 400 to 420 C. 3.While temperature of the supercritical water flame was below 400 C,the solubility of boehmite in acidic was higher than that in alkaline environment.Therefore the particle was remained its size as grown at high temperature.A little larger and much narrower particle of boehmite could be obtained.