Effects of reducing environment and fusible components on carbothermal reduction–nitridation reaction of coal gangue at high temperature under N2 atmosphere. Issue 17 (1st December 2019)

• Record Type: Journal Article
• Authors: Ma, Zhibin; Wen, Chaolu; Yan, Kezhou; Guo, Yanxia; Cheng, Fangqin
• Is Part Of: Ceramics international. Volume 45:Issue 17(2019)Part B
• Page Start: 22829
• Page End: 22840
• Publication Date: 2019-12-01
• Subjects: Coal gangue -- Coal-coke powder -- CRN reaction -- Fusible components -- β-SiAlON; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2019.07.325
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: The synthesis of SiAlON materials by the carbothermal reduction–nitridation (CRN) method paves the way for utilization of coal gangue with significant economic benefits. Excessive carbon (C), which provides a high residual C content in the product, is added to the raw materials to ensure a high yield of SiAlON. The industrial solid waste of coal-coke powder is used as a reductant. In this study, the effects of the reducing environment and C content on the CRN reaction of coal gangue using corundum and graphite crucibles are investigated and a method to reduce the amount of C added to the raw materials is proposed. The process is carried out under a N2 flow in the range of 1300–1500 °C with a holding time of 3 h. The effects of fusible components including CaO, Fe2 O3, and MgO on the CRN reaction and micromorphology are discussed. The graphite crucible considerably promotes the conversion of mullite to β-SiAlON and is effective for the reduction in residual C content in the product. When the graphite crucible is used, the mullite wholly transforms to β-SiAlON and corundum, and β-SiAlON and AlN at 1400 °C when the C contents in the raw materials are 11% and 18%, respectively. The content of residual C in the product is approximately 1% (or lower). The β-SiAlON content decreases with the additions of CaO and MgO in the raw materials owing to sintering and melting. The addition of Fe2 O3 promotes the formation of β-SiAlON whiskers according to the vapor–liquid–solid mechanism. These results would be useful in parameter optimization for a cleaner production of β-SiAlON powder using the CRN method.