The influence of silica nano-inclusions on the structure of methane crystal observed in thermal conductivity experiment

[Display omitted] •The nanocomposites from crystalline methane and SiO2 nanopowders were obtained.•The thermal conductivity of the nanocomposites was determined at low temperatures.•A simple time relaxation model was applied to analyze the experimental data. The preliminary results of experimental investigations of the thermal conductivity of nanocomposites built of amorphous silica nanoparticles embedded in the structure of crystalline methane are presented. The investigations were carried out on the samples containing the particles of linear dimensions of 5, 10–20 and 42nm. The measurements were performed with steady-state heat flow method in the temperature interval 2–35K. A very simple thermal conductivity model shows that the dependence of the thermal conductivity coefficient of the investigated nanocomposites on temperature can be successfully described by taking into account only two mechanisms of the heat carrier dissipation: scattering of phonons by methane crystal grain boundaries and phonon-phonon interaction in U-processes. It was found that the low-temperature phonon mean free path is inversely proportional to the linear dimension of the nanopowder particles embedded in the methane crystal structure.