Evidence of ZrO2 sol–gel transition by gelation time and viscosity
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Sol–gel transition is a stage of the sol that evolves towards the formation of a gel-like network and that exhibits gradually a mobility loss. Hence, the measurement of both viscosity and gelation time is expected to evidence the sol–gel transition occurrence. ZrO2 sols were prepared using zirconium oxychloride octahydrated as precursor material. The structures of the sols before and after gelation were characterized by TEM. Gelation time depends on the concentrations of the reactants and the aging temperature. Viscosity increases linearly with the gelation time firstly, and then increases exponentially nearby the sol–gel transition point. TEM results show the gel is granular before the sol–gel transition point, and appears as brain-like structure after this point. The determination of the sol–gel transition point is to enable the optimum aging time of a sol and to perform the next operations which determine the desired shape of gel (bulk, film, powder, etc.).
KeywordsSol–gel Zirconia Gelation time Viscosity Transition process
The authors gratefully acknowledge the financial support provided by Sino-French International Science and Technology Cooperation Program (No. 2011DFA52000), National Natural Science Foundation of China (Nos. 51262013 and 51362015), the projects of Jiangxi Provincial department of Science and Technology (No. 20132BBE50019), and the projects of Jiangxi Provincial department of Education (No. KJLD13077).
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