Probing Interfacial Thermal Conductance Under Extremely Large Temperature Differences via Ultrafast X-Ray Diffraction

Probing the interfacial thermal transport under extremely large temperature difference (ELTD) is critical for thermal protection and heat dissipation in extreme environments yet challenging. However, conventional optical thermoreflectance methods work only over narrow temperature ranges and thus fail for ELTD conditions characterized by a broad temperature evolution range. Here, we circumvent this limitation by employing a table-top ultrafast X-ray diffraction (UXRD) system, which exploits the nearly linear lattice thermal expansion over a wide temperature range. We investigate interfacial thermal transport in a W thin film on a MgO substrate under ELTD conditions and determine that the interfacial thermal conductance (ITC) value increases from 6.43 × 108 W m−2 K−1 to 8.71 × 108 W m−2 K−1 as the maximum temperature of W rises from 670 K to 2334 K, accompanied by an increase in the maximum interface temperature difference from 302 K to 1451 K based on the finite volume method (FVM). The results reside at a relatively high level among reported ITC values for conventional metal-oxide interfaces, which may originate from the simultaneous increase in interface temperature difference and mean interface temperature. This work demonstrates UXRD as an effective tool for ELTD thermal measurements and fills a critical knowledge gap regarding interfacial thermal transport under extreme conditions.