Abstract
Mechanical and thermal properties were characterized for two AlN:BN:SiC composite ceramics produced from BN with different particle sizes. The ceramics were hot pressed at temperatures from 1950 to 2100 °C to ∼97% relative density. For both materials, the matrix (90:10 vol% SiC:AlN) had a grain size of ∼0.4 μm, and the BN grains (10 vol%) were crystallographically aligned. Microhardness values were between 20 and 22 GPa, while fracture toughness values were between 2.5 and 3.1 MPa m1/2. Other properties were found to be dependent on testing direction. Elastic moduli were between 260 and 300 GPa and strengths were ∼630 MPa for small particle BN additions. Thermal conductivity was calculated to be between 25 and 37 W/m K at room temperature and 17 and 25 W/m K at 900 °C. The low values compared to traditional SiC ceramics were attributed to AlN-SiC solid solution formation and sub-micron matrix grain sizes.
| Original language | English |
|---|---|
| Pages (from-to) | 239-246 |
| Number of pages | 8 |
| Journal | Materials Science and Engineering: A |
| Volume | 494 |
| Issue number | 1-2 |
| DOIs | |
| State | Published - Oct 25 2008 |
Funding
This work was supported by the Army Space and Missile Defense Command under grant number BAA DASG60-00-0005 and in part by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Transportation Technologies as part of the High Temperature Materials Laboratory User Program at Oak Ridge National Laboratory managed by the UT-Battelle LLC, for the Department of Energy under contract DE-AC05000OR22725. Financial support for A. Buchheit was provided by the Department of Education under the Graduate Assistance in Areas of National Need (GAANN) Fellowship.
Keywords
- Aluminum nitride
- Boron nitride
- Hot pressing
- Mechanical properties
- Silicon carbide
- Thermal properties