Yajuan Zhong

Low-Temperature Aluminum Reduction of Graphene Oxide, Electrical Properties, Surface Wettability, and Energy Storage Applications

Low-temperature aluminum (Al) reduction is first introduced to reduce graphene oxide (GO) at 100-200 °C in a two-zone furnace. The melted Al metal exhibits an excellent deoxygen ability to produce well-crystallized reduced graphene oxide (RGO) papers with a low O/C ratio of 0.058 (Al-RGO), compared with 0.201 in the thermally reduced one (T-RGO). The Al-RGO papers possess outstanding mechanical flexibility and extremely high electrical conductivities (sheet resistance R(s) ~ 1.75 Ω/sq), compared with 20.12 Ω/sq of T-RGO. More interestingly, very nice hydrophobic nature (90.5°) was observed, significantly superior to the reported chemically or thermally reduced papers. These enhanced properties are attributed to the low oxygen content in the RGO papers. During the aluminum reduction, highly active H atoms from H(2)O reacted with melted Al promise an efficient oxygen removal. This method was also applicable to reduce graphene oxide foams, which were used in the GO/SA (stearic acid) composite as a highly thermally conductive reservoir to hold the phase change material for thermal energy storage. The Al-reduced RGO/SnS(2) composites were further used in an anode material of lithium ion batteries possessing a higher specific capacity. Overall, low-temperature Al reduction is an effective method to prepare highly conductive RGO papers and related composites for flexible energy conversion and storage device applications.

Thermophysical properties of high-density graphite foams and their paraffin composites

Abstract High-density graphite foams (GFs) were prepared from mesophase pitch with or without mesocarbon microbeads at different foaming temperatures and pressures, followed by carbonization and graphitization at 1 273 and 2 973 K, respectively. In one case, pitch was repeatedly infiltrated into the graphitized foam at 573 K followed by carbonization to increase its density. Paraffin was infiltrated into the GFs to form GF/paraffin composites. Factors determining the thermophysical properties of the GFs and thermal behavior of the GF/paraffin composites were investigated. The microstructure and thermophysical properties of the foams were found to be greatly influenced by the pitch fraction, foaming temperature and foaming pressure. The thermal conductivity of the foams determines the thermal behavior of the GF/paraffin composites. The thermal diffusivity of the GF/paraffin composites investigated can be increased 768 to 1588-fold compared with that of paraffin. The latent heat of the composites has an almost linear relationship with the mass fraction of paraffin in the composites. The composites are suitable candidates for passive cooling of electronics.

Rapid microwave synthesis of graphene directly on h-BN with excellent heat dissipation performance.

We report a new rapid household microwave method to successfully grow graphene on h-BN flakes without using any catalysts. We obtained a novel uniform multilevel matrix of vertical graphene sheets on h-BN flakes. The unique structure possessed outstanding electron conductivity and thermal properties (29.1 W m(-1) K(-1)).