Porous mullite ceramics with a fully closed-cell structure fabricated by direct coagulation casting using fly ash hollow spheres/kaolin suspension. Issue 11 (1st August 2020)

• Record Type: Journal Article
• Authors: Chen, Shuang; Cai, Wei-Hao; Wu, Jia-Min; Ma, Yi-Xin; Li, Chen-Hui; Shi, Yu-Sheng; Yan, Chun-Ze; Wang, Yong-Jun; Zhang, Hong-Xing
• Is Part Of: Ceramics international. Volume 46:Issue 11(2020)Part A
• Page Start: 17508
• Page End: 17513
• Publication Date: 2020-08-01
• Subjects: Porous mullite ceramics -- Fly ash hollow spheres -- Direct coagulation casting -- Rheology -- Closed-cell structure; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2020.04.046
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: Porous mullite ceramics with a fully closed-cell structure were fabricated by direct coagulation casting (DCC) using fly ash hollow spheres (FAHSs) as the non-sacrificial pore-forming agent. Kaolin powder was used as the filler and the suspension stabilizer, and bentonite was used as the rheological additive, respectively. The effects of bentonite on the stabilization mechanism of suspension and properties of the porous ceramics were investigated. It is found that 1 wt% additional bentonite is efficient in improving the suspension stability from 2 h to at least 24 h, due to increased suspension viscosity, thixotropy and yield stress. Densification of the kaolin powder during sintering eliminates the open pores, and the closed pores from FAHSs remain to yield a fully closed-cell structure. The porous mullite ceramics have a total porosity ranging from 44.73% to 46.12%, in which 99% of the pores are closed. Bentonite also increases the compressive strength of porous mullite ceramics by 14.4%, and compressive strength of 58.07 ± 5.44 MPa can be achieved.