Thermal Conductivity Reduction in Heterostructure Multilayer Composites by Phonon Density of State Mismatch

The interfacial phonon transport tuning, depending on the phonon density of states (PDOS) of mating materials, has received considerable attention. However, it has been mainly implemented in nanoscale superlattice structures. Here, we report successful thermal conductivity (κ) modulation in bulk-scale multilayer composites. Single-layer silicone rubber composites, embedded with PDOS-mismatched AlN, BN, or SiC particles, are alternately stacked to construct heterostructure multilayer composites. The molecular dynamics simulation reveals that the SiC-BN combination has the highest PDOS mismatch and interfacial thermal resistance. The experimental analysis also agrees that the SiC-BN combination has the smallest acoustic impedance transmittance and the highest κ reduction ratio of 14.9% (8 layers), demonstrating the reliability of two independent analyses. The κ reduction ratio is as high as 37.3% when PDOS-mismatched vermiculite and silica aerogel particles are alternately impregnated into glass wool, resulting in 2.87 mW m^-1 K^-1 in vacuum (24 layers). The PDOS mismatch is a key phonon design factor even for bulk-scale multilayer composites. It might find applications in refrigerators, household appliances, and building insulation panels.