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Processing of stepped-density alumina via gelcasting and reaction bonding techniques

Montgomery, J. K. and Faber, K. T. (2000) Processing of stepped-density alumina via gelcasting and reaction bonding techniques. Scripta Materialia, 42 (3). pp. 283-287. ISSN 1359-6462. doi:10.1016/S1359-6462(99)00342-5.

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Ceramics that combine property gradients or steps in monolithic bodies are increasingly being sought as alternatives to ceramic composites made of multiple dissimilar materials. Furthermore, more sophisticated applications specify single components to serve many functions that often require disparate properties. For example, oxygen impermeability and high compliance may need to be coupled with low thermal conductivity in thermal barrier coatings or a thin, oxygen permeable membrane may need to be coupled to a rigid porous support for electrochemical gas extraction. Density graded materials are also of interest for structural applications, as one may couple a thin, dense wear resistant layer with a lightweight support structure or a porous, flaw tolerant surface with a dense, stiff support structure. However, graded density ceramics are difficult to process due to the need to accommodate differential volume changes upon firing. For example, a green body containing a particle size gradient would result in graded density due to higher densification of the small particle portion upon firing. However, due to the non-uniform volume changes throughout the specimen, sintering stresses occur which cause macroscopic cracking. This paper presents a novel method to produce stepped-density alumina bodies which maintain mechanical integrity by eliminating non-uniform volume changes. The processing instead relies on a reaction bonding technique.

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Faber, K. T.0000-0001-6585-2536
Additional Information:Copyright © 2000 Acta Metallurgica Inc. Published by Elsevier. (Received August 12, 1999) (Accepted September 19, 1999). Thanks to Dr. Mark Janney of Oak Ridge National Laboratory for providing information on alternate gelcasting systems and to Tom Easley and Dr. Rodney Trice for publication suggestions. These studies were supported by the NSF through DMR-9800257.
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Subject Keywords:Functionally graded materials; Structural ceramics; Casting; Reaction bonded
Issue or Number:3
Record Number:CaltechAUTHORS:20140908-181324208
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Official Citation:J.K Montgomery, K.T Faber, Processing of stepped-density alumina via gelcasting and reaction bonding techniques, Scripta Materialia, Volume 42, Issue 3, 17 January 2000, Pages 283-287, ISSN 1359-6462, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49400
Deposited By: George Porter
Deposited On:09 Sep 2014 20:17
Last Modified:10 Nov 2021 18:43

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