Zhang Xu-Dong, Zhang Zi-Tong, Wang Hong-Zhang, Cao Bing-Yang
Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Engineering Mechanics, Tsinghua University, Beijing100084, China.
Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing100084, China.
ACS Appl Mater Interfaces. 2023 Jan 18;15(2):3534-3542. doi: 10.1021/acsami.2c20713. Epub 2023 Jan 5.
Thermal interface materials (TIMs), as typical thermal functional materials, are highly required to possess both high thermal conductivity and low Young's modulus. However, the naturally synchronized change in the thermal and mechanical properties seriously hinders the development of high-performance TIMs. To tackle such a dilemma, a strategy of codoping solid fillers and liquid metal fillers into polymer substrates is proposed in this study. This strategy includes a large amount of liquid metals that play the role of thermal paths and a small amount of uniformly dispersed solid fillers that further enhance heat conduction. Through the synergistic effect of the liquid metal and solid fillers, the thermal conductivity can be improved, and Young's modulus can be kept small simultaneously. A typical TIM with a volume of 55% gallium-based liquid metal and 15% copper particles as fillers has a thermal conductivity of 3.94 W/(m·K) and a Young's modulus of 699 kPa, which had the maximum thermomechanical performance coefficient compared with liquid metal TIMs and solid filler-doped TIMs. In addition, the thermal conductivity of the solid-liquid metal codoped TIM increased sharply with an increase of liquid metal content, and Young's modulus increased rapidly with an increase of the volume ratio of copper and polymer. The high-low-temperature cycling test and large-size light-emitting diode (LED) application demonstrated that this TIM had stable physical performance. The synergistic effect of the solid fillers and liquid metal fillers provides a broad space to solve the classic tradeoff issue of the mechanical and thermal properties of composites.
热界面材料（TIMs）作为典型的热功能材料，对其同时具备高导热率和低杨氏模量有着很高的要求。然而，热性能和机械性能的自然同步变化严重阻碍了高性能TIMs的发展。为了解决这一困境，本研究提出了一种将固体填料和液态金属填料共掺杂到聚合物基体中的策略。该策略包含大量充当热通道的液态金属以及少量均匀分散的固体填料，后者进一步增强热传导。通过液态金属和固体填料的协同作用，可以提高热导率，同时保持较小的杨氏模量。一种典型的TIM，以55%的镓基液态金属和15%的铜颗粒作为填料，其热导率为3.94W/(m·K)，杨氏模量为699kPa，与液态金属TIMs和固体填料掺杂的TIMs相比，具有最大的热机械性能系数。此外，固液金属共掺杂TIM的热导率随着液态金属含量的增加而急剧上升，杨氏模量随着铜与聚合物体积比的增加而迅速增大。高低温循环测试和大尺寸发光二极管（LED）应用表明，这种TIM具有稳定的物理性能。固体填料和液态金属填料的协同作用为解决复合材料机械性能和热性能之间的经典权衡问题提供了广阔空间。
