Fracture strength and microstructures of Si{sub 3}N{sub 4}/SiC nanocomposites
- Hanyang Univ., Seoul (Korea, Republic of)
- Korea Institute of Science and Technology, Seoul (Korea, Republic of)
Nano-size SiC particles (20 vol%) with different particle sizes were dispersed in Si{sub 3}N{sub 4} matrix, and Si{sub 3}N{sub 4}/SiC nanocomposites with various sintering additives were hot pressed at 1800{degrees}C. Fracture strength of the nanocomposites used Al{sub 2}O{sub 3} and Y{sub 2}O{sub 3} as sintering additives was 1680 MPa at room temperature, but strength degradation was shown due to low softening temperature of grain boundary phase above 1200{degrees}C. Fracture strength above 1200{degrees}C was improved by dispersing SiC particles with an average particle size of 30 nm and reducing content of sintering additive. Si{sub 3}N{sub 4}/30 nm SiC nanocomposite with 4 wt% Y{sub 2}O{sub 3} exhibited strength of 1050 MPa at room temperature, and strength was retained up to 1400{degrees}C showing slight strength degradation. This sample deformed elastically just before rupture at 1400{degrees}C, and fracture surface of specimen tested at 1400{degrees}C were very similar to that tested at room temperature. XRD results showed that grain boundary phase of the nanocomposites was crystallized without post-heat treatment. HREM study indicated that intergranular SiC particles were directly bonded to Si{sub 3}N{sub 4} grains without amorphous phase. Therefore retention of fracture strength from room temperature to 1400{degrees}C was attributed to the suppression of grain boundary sliding by intergranular SiC particles and secondary crystalline phase.
- OSTI ID:
- 530687
- Report Number(s):
- CONF-9604124-; TRN: 97:003389-0023
- Resource Relation:
- Conference: 98. annual meeting of the American Ceramic Society, Indianapolis, IN (United States), 14-17 Apr 1996; Other Information: PBD: 1996; Related Information: Is Part Of Ceramic transactions: Advances in ceramic-matrix composites III. Volume 74; Bansal, N.P.; Singh, J.P. [eds.]; PB: 667 p.
- Country of Publication:
- United States
- Language:
- English
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