Thermal conductivity of pure silicon oxycarbide glass predicted from Wigner transport theory

XK Gu and S Hu and F Xie and L Cao and X Zhang, MOLECULAR SIMULATION, 51, 493-503 (2025).

DOI: 10.1080/08927022.2025.2503326

Polymer-derived silicon oxycarbide (SiOC), known for their exceptional thermal stability, corrosion resistance, and adaptability to additive manufacturing, are highly promising for thermal protection applications. The thermal properties of SiOC materials are significantly influenced by their microstructures, which can be manipulated through controlled pyrolysis conditions. To explore this relationship, understanding the thermal conductivity of pure SiOC glass is crucial. In this work, we employ a recently developed machine-learning interatomic potential coupled with Wigner transport theory to investigate the thermal properties of fused silica and SiOC glass. We discover that SiOC glass exhibits lower thermal conductivity than fused silica, with a weak temperature dependence above 600 K. Detailed analyses of the spectral distribution function and participation ratio reveal that carbon atoms enhance the localisation of vibrational modes by altering the silicon- oxygen tetrahedron networks. Furthermore, the introduction of sub- nanometre pores substantially reduces thermal conductivity, primarily due to density changes that affect specific heat. This research offers valuable insights into the thermal transport properties of SiOC glass and lays the groundwork for developing analytical models to predict the thermal conductivity of SiOC glass ceramics with dispersed nanodomains.

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