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
• ISSN: 2187-0764; 2187-0764
• DOI: 10.1080/21870764.2021.1917113

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.