Mullite phase development in pure and mullite matrix composites
- Univ. of Illinois, Urbana, IL (United States)
The mullite phase development has been studied extensively for a long time using many different starting materials. Recently, the mullite formation kinetics and mechanisms were re-investigated using chemically prepared gels or powders because chemical compositions and mixing ratios of such starting materials were easy to control. However, numerous conflicting investigations have been reported about the mullite formation mechanisms. The mullite formation mechanisms in chemically derived starting materials can be classified into three general categories related to the {open_quotes}mixing scale{close_quotes} of starting materials: (1) direct mullite formation from a single-phase gel or powder at around 980{degrees}C without intermediate phase; (2) the mullite formation through reaction between {gamma}-Al{sub 2}O{sub 3} (or {theta}-Al{sub 2}O{sub 3}) and amorphous silica at above 1250{degrees}C in a colloidal gel or powder; (3) the mullite transformation through an intermediate Al-Si spinel phase. The main objective of the current study was to determine the microstructural/microchemical characteristics of mullite formation in mullite and mullite/zirconia composites with or without MgO, through direct microstructural observations especially for: (1) the relationship of mullite formation to the pre-mullite spinel phase, and (2) the effect of zirconia and MgO on the mullite matrix phase development.
- DOE Contract Number:
- FG02-91ER45439
- OSTI ID:
- 96552
- Report Number(s):
- CONF-940416--
- Country of Publication:
- United States
- Language:
- English
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