Abstract
Composite ceramics containing ∼25 vol% of the Mo-Si-C ternary compound and SiC (referred to as MS) were reaction hot pressed up to 96% relative density. The electrical resistivity of the composite processed at 2150 °C decreased from ∼4.60 Ω cm at room temperature to 4.15 Ω cm at 700 °C. Thermal conductivity of the MS ceramics processed at 2150 °C was above 100 W/m K at room temperature, decreasing to between 62 and 68 W/m K at 500 °C. Using the Eucken model for thermal conductivity, the interconnected SiC phase in the MS materials was calculated to have a room temperature thermal conductivity between 160 and 170 W/m K. As compared to a baseline SiC composition, the continuous SiC in the MS materials had an average increase in thermal conductivity of ∼50% over the temperature range of room temperature to 500 °C. This increase in thermal conductivity was attributed to the accommodation of impurities that would typically be present in SiC grains and grain boundaries (e.g., N and O) into the ternary phase.
| Original language | English |
|---|---|
| Pages (from-to) | 854-859 |
| Number of pages | 6 |
| Journal | Intermetallics |
| Volume | 16 |
| Issue number | 7 |
| DOIs | |
| State | Published - Jul 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. The authors would also like to thank Ms. Jennifer Gilmore for technical assistance.
Keywords
- A. Molybdenum silicides
- B. Thermal properties
- C. Reaction synthesis
- F. Diffraction
- F. Electron microscopy, scanning