Journal of Inorganic Materials ›› 2017, Vol. 32 ›› Issue (5): 495-501.

• Orginal Article •

### Effects and Oxidation Kinetics of Holding Time on the β-Sialon Bonded MgAl2O4-C Composites

Yun-Fei SONG, Shao-Hua WANG(), Cheng-Ji DENG(), Hong-Xi ZHU, Jian-Peng LIU, Jun DING, Chao YU

1. The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China
• Received:2016-07-18 Revised:2016-09-09 Online:2017-05-20 Published:2017-05-02
• About author:SONG Yun-Fei. E-mail: 1054827854@qq.com

Abstract:

A β-Sialon bonded MgAl2O4-C refractory was prepared in-situ by fused spinel, silicon powder, flake graphite as raw materials, and calcium lignosulfonate with the concentration of 1.25 g/mL as the binder. The samples were sintered under N2 atmosphere at 1450℃ for 1, 2 3 and 4 h, respectively. The effects of holding time on the conventional physical properties, phase compositions and microstructure of MgAl2O4-C refractory were investigated. The phase composition and microstructure of the sintered samples were investigated by X-ray diffraction (XRD) and Scanning Electron Microscope (SEM), respectively. XRD patterns showed that there were no evident differences on the phase compositions and the silicon phase had completely disappeared to form SiC, Si3N4 or β-Sialon (Si3Al3O3N5). The β-Sialon crystals had columned microstructure stagger on each other when holding time was 3 h. With the holding time increasing from 1 h to 4 h, the increased SiO gas lead to an increase of apparent porosity and a decrease of bulk density. In addition, the cold crushing strength and flexural strength of the samples sintered at 1450℃ for 3 h reach the highest. Research on oxidation kinetics of composite material indicates that oxidation process can be divided into three stages: chemical reaction rate controlling stage, diffusion rate controlling stage, and co-effect controlling of chemical reaction and diffusion rate stage.