Abstract
The thermal properties of polycrystalline Ti3SiC2 in the 25 °C-1000 °C temperature range determined by Rietveld refinement of high temperature neutron diffraction data, show that at all temperatures, the amplitudes of vibration of the Si atoms are higher than those of the Ti and C atoms. Up to 700 °C, the vibrations of the Si atoms are quite isotropic but the vibrations of the other atoms are greater along the c-than along the a-axis. The amplitudes of vibration of the Ti atoms adjacent to the Si atoms are higher and more anisotropic than for the other Ti atom sandwiched between the C-layers. Good agreement is obtained between the bulk thermal expansion coefficients measured by dilatometry, 9.1(±0.2)×10-6 °C-1, and the values from the neutron diffraction results, 8.9(±0.1)×10-6 °C-1. The thermal expansion coefficients along the a-and c-axes are, respectively, 8.6(±0.1)×10-6 °C-1 and 9.7(±0.1)×10-6 °C-1. The heat capacity is 110 J/mol K at ambient temperatures and extrapolates to ≈155 J/mol K at 1200 °C. The room temperature thermal conductivity is 37 W/m K and decreases linearly to 32 W/m K at 1200 °C. The thermal conductivity is dominated by delocalized electrons.
| Original language | English |
|---|---|
| Pages (from-to) | 429-439 |
| Number of pages | 11 |
| Journal | Journal of Physics and Chemistry of Solids |
| Volume | 60 |
| Issue number | 4 |
| DOIs | |
| State | Published - Apr 1999 |
Funding
This research was sponsored by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Transportation Technologies, as part of the High Temperature Materials Laboratory User Program, Oak Ridge National Laboratory, ORNL, managed by Lockheed Martin Energy Corp. for the US Department of Energy under contract DE-AC05-96-OR22464. This work was also partially funded by the Division of Materials Research of the National Science Foundation (DMR 9705237). CRJ was supported in part by an appointment to the ORNL Postdoctoral Research Associates program jointly administered by Oak Ridge Associated Universities and Oak Ridge Institute for Science and Education. The authors would also like to thank Dr. Bryan Chakoumakos for assistance with the neutron powder diffraction data collection and processing.