文献类型：期刊文献

英文题名：Microwave selective heating-enhanced reaction rates for mullite preparation from kaolinite

作者：Zhang, Ziyuan[1];Qiao, Xiuchen[1];Yu, Jianguo[1,2]

机构：[1]E China Univ Sci & Technol, Sch Resource & Environm Engn, Shanghai 200237, Peoples R China;[2]E China Univ Sci & Technol, State Key Lab Chem Engn, Shanghai 200237, Peoples R China

年份：2014

卷号：4

期号：6

起止页码：2640

外文期刊名：RSC ADVANCES

收录：;EI(收录号：20135217140318);WOS:【SCI-EXPANDED(收录号:WOS:000329037100013)】；

基金：The work described in this paper was funded by the Shanghai Pujiang Program (PJ200700339), the Science and Technology Commission of Shanghai Municipality (10dz12004901), the Shanghai Leading Academic Discipline Project (B506) and the Innovation Program of Shanghai Municipal Education Commission (11CXY25), the National Natural Science Foundation of China (21176082), the Specialized Research Fund for the Doctoral Program of Higher Education (2011007 4110002) and the Fundamental Research Funds for the Central Universities (ECUST).

语种：英文

外文关键词：Alumina - Aluminum oxide - Silica - Dielectric devices - Kaolinite - Dielectric losses - Reaction rates - Microwaves - Microwave heating

摘要：Mullite is becoming increasingly important for use in refractory lining, structural ceramic and catalyst products. The kaolinite-mullite process is a simple method to prepare mullite. Under conventional heating kaolinite has to be heated at 1400 degrees C for 1 h to form well-ordered orthorhombic mullite (3Al(2)O(3)center dot 2SiO(2)) that is accompanied by the formation of cristobalite. However, under microwave heating at 900 degrees C for 5 min and 1200 degrees C for 1 min, respectively, kaolinite transformed to well-ordered orthorhombic mullite without the formation of cristobalite. The ultra-fast heating rate of microwaves, due to selective heating, accelerated the nucleation and growth of mullite grains and changed the mullitization route of kaolinite. Before mullitization, the capacity for microwave absorption of decomposed kaolinite is dependent on the amount of structural OH up to a temperature of 522 degrees C and is then dependent on the amount of metakaolinite, gamma alumina and amorphous silica that are present in the sample. The dielectric loss of pseudo-tetragonal mullite has the highest value of the dielectric losses for all of the phases that result from the kaolinite-mullite process.