Superior thermal conductivity of carbon nanoscroll based thermal interface materials

As the electronic industry moves toward higher power consumption, integrated functions and minimized geometry, one of the important challenges is the dramatically increasing power density. Thus, efficient thermal management has become a critical requirement for the design of modern electronic packages. A promising approach for this challenge is to find a high performance thermal interface materials (TIMs) made of a material with extremely high thermal conductivity. In this work, an innovative carbon-based nanomaterial, carbon nanoscroll (CNS) will be presented to yield extremely high thermal conductivity and have great potential as the component of TIMs in electronic packages. A CNS can be regarded as a monolayer graphene rolling up in a spiral form with a structure similar to a multi-walled carbon nanotube (CNT). Unlike the closed CNTs, CNS is topologically open-ended, like a Swiss roll. Using molecular dynamics (MD) simulations, the thermal conductivity of CNSs is investigated to be comparable to graphene, i.e. 3000- 5000 Wm^-1K^-1. Various factors that impact the thermal transport behavior of CNSs are investigated extensively. The MD simulation results show that the thermal conductivity of CNS is sensitive to the number of CNS walls, temperature, defects and functionalization. When the number of walls increases from 1 to 3, the thermal conductivity of CNSs is reduced by ~8.9%. With environmental temperature rising from 300 K to 400K, the thermal conductivity of CNSs decreases by ~16.5%. When the CNSs have single vacancy defects or functionalized hydrogen, their thermal conductivity decreases gradually with the higher densities of defects or functionalization. The results reveal that the vertical aligned CNSs can be superior to vertical aligned CNTs in serving as the thermal interface materials in electronic packages, due to their higher thermal conductivity. CNSs can also be used as superior thermally conductive fillers in polymeric TIMs. Usi- g effective medium theory, the thermal conductivity of polymeric TIMs composited of epoxy resin matrix and CNS fillers is calculated. It is found that polymeric TIMs with epoxy resin matrix and 10% volume fraction of CNS fillers yield an effective thermal conductivity of ~79 Wm^-1K^-1, which is one magnitude higher than the commonly used TIMs in current electronic packaging industry. The present work reveals new insights about the extremely high thermal conductivity of CNS and its great potential in improving the thermal management of electronic packages.