The aluminum matrix composites (AMCs) reinforced with silicon carbide have attracted significant interest in several high-tech industries. Typically, aluminum matrix composites (AMCs) reinforced with nanophase ceramics like silicon carbide whisker (SiCw) combined high strength with ductility and low thermal expansion with high thermal conductivity.
We adopted the superlattice (SL) models to investigate the mechanical and thermal properties of Al/SiCw nanocomposites.
For calculations, we applied DFT method combined with classical molecular mechanics (CMM) using ab initio MD-derived machine-learning interatomic potential (MLIP).
Using the harmonic IFCs, the phonon dispersion curves and phonon density of states (DOS) were obtained using the ALAMODE code.
As shown in the figure, harmonic phonon modes with imaginary energies do not exist in the curve, indicating that the Al-SiC crystal is thermodynamically stable under ambient conditions as confirmed in the previous experiments.
The Al-atomic rattling vibrations inside the over-sized Al-SiC system can lead to intense scattering of the heat-carrying acoustic and low-energy optical phonons, consequently lowering the lattice thermal conductivity.
The κl values were found to reach the saturated values at the MFP of about 300 and 350 nm, respectively, and the main heat-carrying phonons were confirmed to have the MFP values in the range of 1~200 nm.
Therefore, it is suggested that the thermal conductivity is below 1.0W m-1K-1 for nano-structured Al-SiC with dimensions smaller than 30nm.
The research results have been published in the "PHYSICAL REVIEW B 109"under the title of "Harmonizing mechanical and thermal properties in Al/SiC superlattices: Ab initio machine-learning-potential study"(https://doi.org/10.1103/PhysRevB.109.075426).
