Ceramic-metal composite formation by reactive metal penetration [electronic resource].

Published:: Washington, D.C. : United States. Dept. of Energy, 1996.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Physical Description:: 10 pages : digital, PDF file
Additional Creators:: Sandia National Laboratories
United States. Department of Energy
United States. Department of Energy. Office of Scientific and Technical Information
Access Online:: www.osti.gov

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Summary:

Ceramic-metal composites can be made to near-net-shape by reactive penetration of dense ceramic preforms by molten metals. Reactive metal penetration is driven by a strongly negative Gibbs energy for reaction. For Al, the general form of the reaction is (x+2) Al + (3/y) MO[sub y] yields Al[sub 2]O[sub 3] + M[sub 3/y]Al[sub x], where MO[sub y] is an oxide that is wet by molten Al. In low PO[sub 2] atmospheres and at temperatures above about 900 degrees C, molten Al reduces mullite to produce Al[sub 2]O[sub 3] and Si. The Al/mullite reaction has a delta G[sub r] degree(927 degrees C) of -338 per mole of mullite and, for fully dense mullite, the theoretical volume change on reaction is less than 1%. Experiments with commercial mullite containing a silicate grain boundary phase average less than 2% volume change on reaction. In the Al/mullite system, reactive metal penetration produces a fine-grained alumina skeleton with an interspersed metal phase. With > or =15 vol.% excess aluminum, mutually interpenetrating ceramic-metal composites are produced. Properties measurements show that ceramic-metal composites produced by reactive metal penetration of mullite by Al have a Young`s modulus and hardness similar to that of Al[sub 2]O[sub 3], with improved fracture toughness. Other compositions also are candidates for in- situ reaction synthesis, but they exhibit differences in reaction kinetics, most probably due to different wetting behavior.

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Note:

Published through SciTech Connect.
11/01/1996.
"sand--96-0818c"
" conf-9609265--2"
"DE96015316"
1. international conference on ceramic and metal matrix composites (CMMC-1), San Sebastian (Spain), 9 Sep 1996.
Ewsuk, K.G.; Loehman, R.E.; Fahrenholtz, W.G.; Lakshman, B.B.

Funding Information:

AC04-76DP00789
AC04-94AL85000

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