Achieving ultrahigh thermal conductivity in Ag/MXene/epoxy nanocomposites via filler-filler interface engineering

Polymer composites with super-high thermal conductivity have attracted many interests in aerospace and electrical fields. However, traditional polymer composites usually suffer from low thermal conductivity because of the high interfacial thermal resistance. Herein, by adopting a multi-dimensional filler composed of micro-silver (AgMP) and nano-silver (AgNP) particles, we prepare an epoxy/Ag composite with the maximum thermal conductivity of 58.3 W/m·K. Based on this, by introducing trace amount (0.12 vol%) of MXene, the thermal conductivity of the epoxy/Ag/MXene composite further increases to 72.7 W/m·K, which is 24.7% higher than that of Ag/Epoxy composites. Both of the super-high thermal conductivity enhancement in epoxy/Ag and epoxy/Ag/MXene composites should be attributed to the unique bridging effect of AgNP particles or MXene flakes. AgNP bridges AgMP via sintering while the MXene flakes bridge AgNP and/or AgMP by the strong interaction between MXene flakes and the Ag particles. The significant effect of the bridging between filler particles on the thermal conductivity of composites is elucidated and verified by FEM simulations. These findings provide new insights into the thermal transport in polymer-based composites and also suggest an approach to prepare polymer composites with super-high thermal conductivity.