Infrared temperature gradient microstructure mapping for optimizing filler dispersion in oriented h-BN/Al2O3/PDMS thermal interface materials

High-performance thermal interface materials require continuous heat-conduction networks, whereas filler agglomeration can disrupt heat transport and cause nonuniform heat dissipation. For h-BN/polymer composites, direct visualization of filler dispersion is challenging because of the low x-ray attenuation and weak contrast of h-BN. Here, we establish an infrared thermal microscopy workflow to map two-dimensional temperature fields and quantify contiguous high-gradient regions after Gaussian denoising. Using this thermal-field-based analysis, we identify the emergence of enhanced thermal heterogeneity as the h-BN loading exceeds 44 wt. %, which is consistent with the deterioration of the effective heat-conduction network and the observed reduction in through-plane thermal conductivity. At higher loadings, enlarged thermally resistive regions and stronger local temperature gradients indicate deteriorated heat-transfer pathways. This framework converts microscopic thermal fields into quantitative descriptors of heat-flow heterogeneity and network degradation when direct visualization is not feasible.