Micrograph 546 and full record
- Micrograph no
- 546
- Brief description
- Delamination cracks seen in h-BN particles subjected to compressive stress in the (0001) planes (within a silicon nitride particulate-reinforced silicon carbide composite)
- Keywords
- boron nitride, ceramic , composite material , silicon carbide, silicon nitride
- Categories
- Ceramic, Composite
- System
- Si3N4-SiC composite
- Composition
- Not specified
- Standard codes
- Reaction
- Processing
- To form the composite, hot isostatic pressing in tantalum cans is used, with a boron nitride layer sprayed onto the internal surface of the can (to prevent the tantalum reacting with the SiC).
- Applications
- Sample preparation
- Technique
- High resolution electron microscopy (HREM)
- Length bar
- 10 nm
- Further information
- The occurrence of BN inclusions results from the introduction of colloidal BN into the hot isostatic pressing process. They are formed from B2O3 present as a thin surface film on the BN particles in the barrier layer. B2O3 will be molten during the pressing process and will diffuse rapidly into the powder compact and react with Si3N4 to form BN. Such inclusions can be related to failure under thermal cycling or creep test conditions (due to cavities and microcracks associated with them), may be grain growth controllers, and may influence crack deflection and slow crack growth at high temperatures. Delamination cracks probably originate during crystal growth or under the subsequent compression or shear stresses.
- Contributor
- Dr K M Knowles
- Organisation
- Department of Materials Science and Metallurgy, University of Cambridge
- Date
- 01/10/02
- Licence for re-use
- Attribution-NonCommercial-ShareAlike 4.0 International
- Related micrographs
- Micrograph 547: h-BN inclusion (precipitate) in a b-Si3N4 grain (within a silicon nitride particulate-reinforced silicon carbide composite) (20 nm)
- Micrograph 549: Misoriented interphase boundary between h-BN (precipitate) and SiC grains (within a silicon nitride particulate-reinforced silicon carbide composite) (1.2 nm)
- Micrograph 551: A regularly stepped interface boundary between h-BN (precipitate) and Si3N4 grains (within a silicon nitride particulate-reinforced silicon carbide composite) (10 nm)
- Micrograph 552: An amorphous phase trapped at a triple junction between Si3N4 grains (within a silicon nitride particulate-reinforced silicon carbide composite). (20 nm)
- Micrograph 553: Image of part of a crystalline triple junction between SiC grains (within a silicon nitride particulate-reinforced silicon carbide composite) (6 nm)
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