Mullite formation in kaolinite-{alpha}-alumina

Journal Article · Tue Feb 01 04:00:00 EST 1994 · Acta Metallurgica et Materialia

DOI:https://doi.org/10.1016/0956-7151(94)90503-7· OSTI ID:143149

Liu, Kuochung; Thomas, G ^[1]; Caballero, A; Moya, J S; De Aza, S ^[2]

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1. Univ. of California, Berkeley (United States). Dept. of Materials Science and Mineral Engineering
2. Inst. de Ceramica y Vidrio, Madrid (Spain). Dept. of Ceramics

The primary and secondary mullite formation in high purity kaolinite-{alpha}-alumina have been studied by conventional processing, XRD, TEM, AEM, and optical microscopy. After a 4h firing at 1,300 C or below, only monosized primary mullite was formed in platy kaolinite, leaving {alpha}-alumina largely inert. Bimodal mullite crystals demonstrating secondary mullite nucleation and primary mullite growth were observed after 4h firing at 1,400 C. At 1,400 C and above, the rapid kinetics of secondary mullite formation, the characteristics of the co-existing glassy phase and the microstructure, as well as the evidence of liquid phase sintering strongly support that solution-precipitation via a transitory liquid phase was the major mechanism for secondary mullite formation. Secondary mullite formation via inter-diffusion, though also observable, was considered as a minor route in the kaolinite-{alpha}-alumina reaction.

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 143149
• Journal Information: Acta Metallurgica et Materialia, Journal Name: Acta Metallurgica et Materialia Journal Issue: 2 Vol. 42; ISSN 0956-7151; ISSN AMATEB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
CHEMICAL COMPOSITION
CRYSTAL GROWTH
KAOLINITE
MULLITE
PHASE STUDIES
SINTERING