Advanced nanostructures for thermal management and heat regulation

 The pursuit of high electronics performance in a variety of applications has led to a dramatic increase in processor power density, and this trend is expected to continue. Despite the recent advancements in thermal management technologies, the stringent environment poses new challenges to heat regulation. For heat rejection, interfaces between materials have become crucial barriers to thermal transport. Therefore, it is imperative to develop high-performance thermal interface materials (TIM) that can thermally bridge the interface to meet the more severe needs. In terms of thermal infrared emission, the capability of artificially overcoming its intrinsic incoherence and realizing its manipulation in a controllable manner is also in demand.     

In this dissertation, we developed a nanostructured 3D “sandwich” TIM composed of graphene-coated copper nanowires (g-CuNWs) sandwiched between two thin copper films. From the thermal (frequency domain thermoreflectance) and mechanical (nanoindentation) characterizations, this “sandwich” TIM reveals ultralow thermal resistance which is 1 order of magnitude lower than solder, while at the same time, ultrahigh mechanical compliance and high flexibility. In order to eliminate the reliance on the soldering process, a double-sided CuNWs-in-glue composite film is achieved. The long-term reliability of both the 3D “sandwich” and the composite film is demonstrated by the temperature cycling test. As for thermal infrared emission, to enable radiative heat flux manipulation in a controllable manner, a near-field thermal rectifier is first studied. It is based on nanowire and nanocross pairs while one terminal being phase change material, vanadium dioxide (VO2). Consequently, a tunable bidirectional thermal rectification effect is manifested. Finally, an electrically-driven metastructure based on Yagi-Uda nanoantenna is designed and analyzed for artificially surmounting the incoherence of thermal emission.