The phase composition and microstructural evolution of a novel MgO-C-Al-Si refractory used in bottom-blowing elements at high temperatures in flowing nitrogen

• Published in: Journal of Asian Ceramic Societies Vol. 9; no. 3; pp. 794 - 805
• Main Authors: Yan, Mingwei, Zhang, Jiayu, Yang, Yumin, Liu, Kaiqi, Sun, Guangchao
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 03.07.2021; Taylor & Francis Group
• Subjects: bottom-blowing element; MgO-C-Al-Si; microstructure; nitrogen; phase composition
• DOI: 10.1080/21870764.2021.1917113
• ISSN: 2187-0764

A novel MgO-C-Al-Si refractory with low carbon content used in bottom-blowing elements was prepared, and its phase composition and microstructural evolution were investigated by XRD, SEM and EDS after being treated at 1200-1600°C in flowing nitrogen. Results show that the samples are composed of MgO, Al 4 C 3 , SiC, Al 4 SiC 4 , MgAl 2 O 4 , Mg 3 Al 2 N 4 and Al 2 O 3 at 1200-1400°C, while the samples are composed of MgO, Al 4 C 3 , SiC, Al 4 SiC 4 , Al 4 Si 2 C 5 , MgAl 2 O 4 , Mg 3 Al 2 N 4 and Al 2 O 3 at 1500-1600°C. Al and Si present gradient reactivity at high temperatures and Al has priority over Si to react with MgO, forming MgAl 2 O 4 . Based on the microstructure analysis, we find that the higher the temperatures are, the more abundant the products. Al(g), Al 2 O(g), SiO(g), Mg(g) and CO(g), as the gas-gas reaction substances, react to form many of Al 4 SiC 4 flakes containing Mg, O and N within pores or gaps of the refractory, along with trace amounts of SiC whiskers and MgAl 2 O 4 spinel whiskers. In addition, the surface morphology of the magnesia aggregates is modified by the MgAl 2 O 4 spinels and Al 4 SiC 4 flakes, owing to the synergistic effect of Al and Si. Further, some physical properties are also characterized.