The effect of citric acid on the kaolin activation and mullite formation
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- 作者：Chenyang Zhang ; Zhijie Zhang ; imzhang@scut.edu.cn" class="auth_mail" title="E-mail the corresponding author ; Yue Tan ; Mingfeng Zhong
- 关键词：Kaolin ; Activation ; Citric acid ; Mullite ; Formation temperature
- 刊名：Ceramics International
- 出版年：2017
- 出版时间：January 2017
- 年：2017
- 卷：43
- 期：1
- 页码：1466-1471
- 全文大小：1617 K
文摘
The mullite phase in porcelain is important to the porcelain strength; however, its formation from clay minerals usually requires high temperature. Here we found that the activation of kaolin by citric acid would lower the formation temperature of mullite phase to 935.1 °C, which is 67.5 °C lower than that for the raw kaolin. Needle-like mullite crystal, a desired crystal shape in kaolin, could be observed in activated kaolin at 1050 °C. The reduction of mullite formation temperature is due mainly to the surface change in kaolin. Upon citric acid activation, the pseudohexagonal platelets of kaolinite crystal are disintegrated to non-uniform flakes, and the specific surface area increases from 8.18 m2/g to 31.21 m2/g, both leading to improved activity of kaolin and increased sintering driving force. The results are of interest in producing high-strength porcelain at reduced sintering temperatures and consequent energy saving for sintering process.