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Title: Ceramic composites reinforced with modified silicon carbide whiskers and method for modifying the whiskers

Abstract

Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

Inventors:
;
Issue Date:
OSTI Identifier:
7028459
Patent Number(s):
4994416 A
Application Number:
PPN: US 7-444479
Assignee:
Martin Marietta Energy Systems, Inc., Oak Ridge, TN (United States)
DOE Contract Number:  
AC05-84OR21400
Resource Type:
Patent
Resource Relation:
Patent File Date: 1 Dec 1989
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; COMPOSITE MATERIALS; FABRICATION; SILICON CARBIDES; SURFACE TREATMENTS; WHISKERS; BONDING; CRACK PROPAGATION; HEAT TREATMENTS; CARBIDES; CARBON COMPOUNDS; CRYSTALS; JOINING; MATERIALS; MONOCRYSTALS; SILICON COMPOUNDS; 360601* - Other Materials- Preparation & Manufacture; 360201 - Ceramics, Cermets, & Refractories- Preparation & Fabrication

Citation Formats

Tiegs, T N, and Lindemer, T B. Ceramic composites reinforced with modified silicon carbide whiskers and method for modifying the whiskers. United States: N. p., 1991. Web.
Tiegs, T N, & Lindemer, T B. Ceramic composites reinforced with modified silicon carbide whiskers and method for modifying the whiskers. United States.
Tiegs, T N, and Lindemer, T B. Tue . "Ceramic composites reinforced with modified silicon carbide whiskers and method for modifying the whiskers". United States.
@article{osti_7028459,
title = {Ceramic composites reinforced with modified silicon carbide whiskers and method for modifying the whiskers},
author = {Tiegs, T N and Lindemer, T B},
abstractNote = {Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1991},
month = {2}
}