Author/Authors :
Shayesteh، M نويسنده Deparetment of Chemical Engineering, University of Sistan and Bluchestan, Zahedan, Iran , , Shafiee Afarani، M نويسنده Department of Materials Engineering, University of Sistan and Bluchestan, Zahedan, Iran , , Samimi، A نويسنده Deparetment of Chemical Engineering, University of Sistan and Bluchestan, Zahedan, Iran , , khorram، M نويسنده Deparetment of Chemical Engineering, University of Sistan and Bluchestan, Zahedan, Iran ,
Abstract :
In this work, boehmite sol was prepared by a previously applied and validated method; hydrolysis of aluminum
chloride hexa-hydrate. In order to obtain precise results, the effect of pH after adding precipitating agent, aging
time, peptizing temperature and ultrasonic vibration time on the crystallite size of final precipitate were
investigated in a narrow range. The preparation conditions applied in the production step of nanocrystalline
boehmite affected on the desired alumina phase. Experiments were set based on the statistical design of
experiments (Taguchi method). Furthermore the influence of calcination on crystallization and phase
transformation of the precipitate was investigated using X-ray diffractometry (XRD) and simultaneous thermal
analysis (STA) techniques. To evaluate the results, the obtained data were statistically analyzed. Considering
the statistical analysis of experiments, the pH after adding precipitating agent is the major parameter affecting
crystallite size. In contrast, aging time has the smallest effect on the crystallite size. In addition, Transmission
electron microscopy (TEM) of the samples revealed that the particle size of the powders was well distributed in
the nano-size range. Taguchi prediction on the crystallite size was 2.096±0.139 nm (with confidence interval of
95%) which confirmed by a verification experiment (2.064 nm).
