Toughening of Si{sub 3}N{sub 4} ceramics by nano SiC particles in grain boundary phase
- Nagaoka Univ. of Technology, Niigata (Japan)
The purpose of the present work is to toughen the weak grain boundary phase in Si{sub 3}N{sub 4} ceramics by forming a nanocomposite grain boundary phase of SiC nano particles. The SiC nano particles are formed by a reaction between coated carbon and an oxide phase on the surface of Si{sub 3}N{sub 4} powder. The carbon is coated by thermal decomposition of CH{sub 4} gas. The surface oxygen content is controlled by an oxidation surface treatment. The sintered bodies are obtained by hot pressing at 1800{degrees}C for 1 h. With an increase in the carbon content, the fracture toughness and bending strength first increase, then reach maximum values at the same amount of carbon addition, and decrease. The carbon contents at which the fracture toughness and bending strength exhibit maximum values decrease with an increase in the surface oxygen content. The generated SiC particles are found not only in the grain boundary phase but also in the Si{sub 3}N{sub 4} grains by TEM observation. The fracture mode changes from inter to transgranular fracture with an increase in the number of SiC particles.
- OSTI ID:
- 62844
- Report Number(s):
- CONF-940315--
- Country of Publication:
- United States
- Language:
- English
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