UC Riverside

As transistors continue to decrease in size and packing densities increase, thermal management becomes a critical bottleneck for development of the next generation of compact and flexible electronics. The increase in computer usage and ever-growing dependence on cloud systems require better methods for dissipating heat away from electronic components. The important ingredients of thermal management are the thermal interface materials. The discovery of excellent heat conduction properties of graphene and few-layer graphene stimulated research on practical applications of graphene fillers in thermal interface materials. The initial studies of graphene fillers in thermal interface materials were focused almost exclusively on curing epoxy-based composites. However, many thermal management applications require specifically noncuring thermal paste type materials. This dissertation reports on the synthesis and thermal conductivity measurements of noncuring thermal paste based on mineral oil with the mixture of graphene and few-layer graphene flakes as the fillers. The relatively simple composition has been selected in order to systematically compare the performance and understand the mechanisms governing heat conduction. It was found that graphene thermal paste exhibits a distinctive thermal percolation threshold with the thermal conductivity revealing a sublinear dependence on the filler loading. This behavior contrasts with the thermal conductivity of curing graphene thermal interface materials, based on epoxy, where super-linear dependence on the filler loading is observed. The performance of graphene thermal paste was benchmarked against top-of-the-line commercial thermal pastes. The obtained results show that noncuring graphene thermal interface materials outperforms the best commercial pastes in terms of thermal conductivity, at substantially lower filler concentration. The results of this dissertation research shed light on the thermal percolation mechanism in noncuring polymeric matrices laden with quasi-two-dimensional fillers. Considering recent progress in graphene production via liquid phase exfoliation and oxide reduction, it is possible that the undertaken approach will open a pathway for large-scale industrial application of graphene in thermal management of electronics.