Dissemination of IT for the Promotion of Materials Science (DoITPoMS)

DoITPoMS Micrograph Library Full Record for Micrograph 549

Full Record for Micrograph 549

Link to full size image of micrograph 549
[179 KB]

View micrograph
.. in new window

View micrograph and record
.. in new window

You can also view and download the micrographs on Flickr
Micrograph no
Brief description
Misoriented interphase boundary between h-BN (precipitate) and SiC grains (within a silicon nitride particulate-reinforced silicon carbide composite)
boron nitride, ceramic Link to MATTER Glossary entry for ceramic, composite material Link to MATTER Glossary entry for composite material, silicon carbide, silicon nitride
Ceramic, Composite
Si3N4-SiC composite
Not specified
Standard codes
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).
Sample preparation
High resolution electron microscopy (HREM)
Length bar
1.2 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.
Dr K M Knowles
Department of Materials Science and Metallurgy, University of Cambridge
Licence for re-use
Attribution-NonCommercial-ShareAlike 4.0 International
Related micrographs