Synthesis and processing of Al{sub 2}O{sub 3}/Al composites by in situ reaction of aluminum and mullite
- Univ. of New Mexico, Albuquerque, NM (United States)
- Sandia National Lab., Albuquerque, NM (United States)
- Pask Research and Engineering, Berkeley, CA (United States)
Al{sub 2}O{sub 3}/Al composites were formed by reacting molten aluminum metal with dense mullite ceramic preforms. The composites produced by this reactive metal penetration process (RMP) have a two phase, interpenetrating microstructure in which both the ceramic and the metal are continuous in three dimensions. Scanning electron microscopy (SEM) micrographs of composites produced by RMP show a fine microstructure comprised of interlocked metal and ceramic phases, with a feature size of approximately 2 {mu}m. RMP is a relatively rapid process with metal penetration rates of nearly 5 mm/hour at 1,100 C after a short incubation period. An activation energy of 92 kJ/mole was calculated from reaction rate data. Transmission electron microscopy (TEM) micrographs reveal that aluminum metal penetrates along the mullite grain boundaries before reaction with the mullite grains, indicating that diffusion along grain boundaries may be the rate limiting step for the reaction. Thermodynamic information, results of microstructure analyses, and kinetic data indicate that RMP proceeds in 4 stages: (1) Al melting and the formation of a thermodynamically stable metal/ceramic interface; (2) depletion of oxygen from the grain boundaries intersecting the ceramic/metal interface; (3) Al metal penetration into the ceramic preform along grain boundaries; and (4) Al reaction with and conversion of individual mullite grains.
- Research Organization:
- Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 77961
- Report Number(s):
- CONF-950201-; ISBN 0-87339-283-3; TRN: IM9531%%11
- Resource Relation:
- Conference: Annual meeting and exhibition of the Minerals, Metals and Materials Society (TMS), Las Vegas, NV (United States), 12-16 Feb 1995; Other Information: PBD: 1995; Related Information: Is Part Of In situ reactions for synthesis of composites, ceramics, and intermetallics; Barrera, E.V.; Marquis, F.D.S.; Frazier, W.E.; Fishman, S.G.; Thadhani, N.N.; Munir, Z.A.; PB: 226 p.
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COMPOSITE MATERIALS
SYNTHESIS
MICROSTRUCTURE
ALUMINIUM OXIDES
ALUMINIUM
MAGNESIUM
MANGANESE ADDITIONS
SILICON ADDITIONS
CHROMIUM ADDITIONS
MULLITE
CHEMICAL REACTION KINETICS
LIQUID METALS
OPTICAL MICROSCOPY
SCANNING ELECTRON MICROSCOPY
TRANSMISSION ELECTRON MICROSCOPY
GRAIN BOUNDARIES
DIFFUSION
ACTIVATION ENERGY