Preparation And Thermal Conductivity Of Graphite Nanoplate Composite Films

Recently, with the development of smart electronics and wearable electronics, electronic components tend to be intergrated, miniaturized and mulitifunctional, which leads to the significant increasing on heat dissipation and power density. This increasing then has strict requirement on thermal management technology, especially on materials with high thermal conductivity. Graphite nanoplates with low cost are similar to graphene, and has high thermal conductivity. It is attractive and interesting to prepare graphite films with high thermal conductivity by graphite nanoplates, and apply them to the thermal management of electronics. In this paper, GNP/CMC(Graphite Nanoplates/ Carboxymethylcellulose) and GNP/r GO(Graphite Nanoplates/Reduced Graphene Oxide) films were fabricated by evaporation deposition and cast-coating using graphite nanoplates, and the related processing parameters were systhematically explored. Moreover, the tensile strength, thermal/electric conductivity of as-prepared samples was measured, and the relavent cooling effects were also investigated.Graphite nanoplates by ultrasonic exfoliation were used as raw materials, and they were mixed with CMC and then deposited on substrates in order to parepare GNP/CMC films. In addtion, the effect of rolling/heat treatment and CMC contents on their tensile strength and thermal/electronic conductivity of as-prepared films were investigated. The results showed that graphite nanoplates with their thickness of ~50nm and size of 2~10μm have layer-by-layer structure and smooth surface. And their edges were slightly curved and no obvious agglomeration were found. GNP/CMC film with the ratio of GNP:CMC=30:7 has the excellent comprehensive properties: the density is 1.11g/cm3, the tensile strength is 14.2MPa, the electric resistivity is 3.89mΩ·cm, square resistance is 0.87Ω/□, the thermal diffusion coefficient is 115.7mm2/s, and the thermal conductivity is 72.1W/(m·K). The experiemental cooling results of as-prepared films showd that GNP/CMC film with the ratio of GNP:CMC=30:3 can drop the chip temperature to 43.7oC with the power density of 2W/cm2.The graphene oxide(GO) by modified Hummers method and GNP were used as raw materials to prepare GNP/r GO(Reduced Graphene Oxide) films. The effect of heat treatment and GO contents on their tensile strength and thermal/electric conductivity of as-prepared GNP/r GO films were investigated. The results showed that r GO with their thickness of ~25nm and size of 2~5μm have layer-by-layer structure, and was seriously curved. After 950 oC heat treatment, GNP/r GO film with the ratio of GNP:r GO=1:3 has the excellent comprehensive performance: the tensile strength is 16.9MPa, the electric resistivity is 4.14mΩ·cm, the square resistance is 1.48Ω/□, the thermal diffusion coefficient is 1080.6mm2/s, and the thermal conductivity is 323.8W/(m·K). The experiemental cooling results of as-prepared GNP/r GO films showd that GNP/r GO film with the ratio of GNP:r GO=1:3 can drop the chip temperature to 75 oC with the power density of 2W/cm2, meaning that as-prepared GNP/r GO films have remarkable cooling effect. Moreover, the cooling effect of GNP/r GO film with the ratio of GNP:r GO=1:3(the decreased temperature of 75oC) is better than that of EGP(the decreased temperature of 73oC), but lower than that of PGS(the decreased temperature of 82oC). Expanded graphite paper(EGP) and pyrolytic graphite film(PGS) are two common used graphite films in electronic cooling. The results showed that GNP/r GO films have potential application in future.