Microstructure of Hydrated Magnesia and MgAl₂O₄ Spinel Layer between Magnesia and Alumina

Abstract:

Tests were performed to investigate the microstructure of MgAl₂O₄ spinel layer between magnesia and alumina after high temperature thermal treatment (1500 °C and 1600°C). The first test involved fused magnesia and alumina sol. Hydration of magnesia powders was studied in a controlled condition that soaked in aqueous solution at 80 °C for up to 1h and 2h. Microstructures of the samples were investigated by SEM, EDS, which showed that the formation of Mg (OH)₂ made magnesia particles cracking, separated many punier particles. The punier particles combined with alumina sol, generated spinel at high temperature. A microstructurally distinct layer with granulate grains of up to 50μm width was observed after 3 h at 1600 °C. Spinel layer bordered alumina layer, and separated from magnesia layer. However, it was not found distinct spinel layer after 3 h at 1500 °C. The formation of small amount of spinel embedded in the layer of alumina, and penetrated the alumina layer. In the spinel layer , Spinel phase close to alumina layer contained 8.79% Mg by atomic, while spinel phase away from alumina layer contained 13.07% Mg by atomic.

• Periodical: Key Engineering Materials (Volumes 602-603)
• Pages: 363-366
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.602-603.363
• Online since: March 2014
• Authors: Cheng Long Lu, Wei Ke Peng, Hong Xi Zhu*, Cheng Ji Deng, Wen Jie Yuan, Jun Li
• Keywords: Hydration, Microstructure, Sintering, Spinel

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