Showing papers by "Huaqing Xie published in 2015"

Thermal conductivity enhancement in thermal grease containing different CuO structures

Abstract: Different cupric oxide (CuO) structures have attracted intensive interest because of their promising applications in various fields. In this study, three kinds of CuO structures, namely, CuO microdisks, CuO nanoblocks, and CuO microspheres, are synthesized by solution-based synthetic methods. The morphologies and crystal structures of these CuO structures are characterized by field-emission scanning electron microscope and X-ray diffractometer, respectively. They are used as thermal conductive fillers to prepare silicone-based thermal greases, giving rise to great enhancement in thermal conductivity. Compared with pure silicone base, the thermal conductivities of thermal greases with CuO microdisks, CuO nanoblocks, and CuO microspheres are 0.283, 0256, and 0.239 W/mK, respectively, at filler loading of 9 vol.%, which increases 139%, 116%, and 99%, respectively. These thermal greases present a slight descendent tendency in thermal conductivity at elevated temperatures. These experimental data are compared with Nan's model prediction, indicating that the shape factor has a great influence on thermal conductivity improvement of thermal greases with different CuO structures. Meanwhile, due to large aspect ratio of CuO microdisks, they can form thermal networks more effectively than the other two structures, resulting in higher thermal conductivity enhancement.

Liquid Cooling of Tractive Lithium Ion Batteries Pack with Nanofluids Coolant.

Abstract: The heat generated from tractive lithium ion batteries during discharge-charge process has great impacts on the performances of tractive lithium ion batteries pack. How to solve the thermal abuse in tractive lithium ion batteries pack becomes more and more urgent and important for future development of electrical vehicles. In this work, TiO2, ZnO and diamond nanofluids are prepared and utilized as coolants in indirect liquid cooling of tractive lithium ion batteries pack. The results show that nanofluids present superior cooling performance to that of pure fluids and the diamond nanofluid presents relatively excellent cooling abilities than that of TiO2 and ZnO nanofluids. During discharge process, the temperature distribution of batteries in batteries pack is uniform and stable, due to steady heat dissipation by indirect liquid cooling. It is expected that nanofluids could be considered as a potential alternative for indirect liquid cooling in electrical vehicles.

Electrochemical Performance of Graphene Oxide/Polyaniline Composite for Supercapacitor Electrode.

Abstract: Composite film of graphene oxide (GO) and polyaniline (PANI) nanofibers is synthesized by in situ polymerization of aniline monomer in the GO suspension (GO/PANI composite). The morphology of the composite is examined by scanning electron microscopy (SEM) and transition electron microscopy (TEM). GO nanosheets are homogeneously coated by PANI nanofibers with diameter of 45 nm. Electrochemical performances are characterized by cyclic voltammetry (CV) and galvanostatic charge/discharge techniques. Supercapacitors based on the GO/PANI conductive composite exhibit high specific capacitance (676 F/g) at a discharge current density of 1.0 A/g in 1 M H2SO4 solution, which is much higher than PANI electrode (230 F/g). The excellent performance is attributed to the synergetic effect of GO and PANI nanofibers, which can shorten ion diffusion length and make higher materials utilization. Moreover, the composite electrode presents excellent long cycle life during charge/discharge processes. After 1000 cycles, the specific capacitance decreases 9% of initial capacitance compared to 32% for PANI nanofibers. This technique provides a feasible solution for developing high performance electrical energy storage devices.

Thermal Properties of Polymethyl Methacrylate Composite Containing Copper Nanoparticles.

Abstract: Thermal functional Materials have wide applications in thermal management fields, and inserting highly thermal conductive materials is effective in enhancing thermal conductivity of matrix. In this paper, copper nanoparticles were selected as the additive to prepare polymethyl methacrylate (PMMA) based nanocomposite with enhanced thermal properties. Uniform copper nanoparticles with pure face-centered lattice were prepared by liquid phase reduction method. Then, they were added into PMMA/N, N-Dimethylmethanamide (DMF) solution according to the different mass fraction for uniform dispersion. After DMF was evaporated, Cu-PMMA nanocomposites were gained. The thermal analysis measurement results showed that the decomposition temperature of nanocomposites decreased gradually with the increasing particle loadings. The thermal conductivity of the Cu-PMMA nanocomposites rose with the increasing contents of copper nanoparticles. With a 20 vol.% addition, the thermal conductivity was up to 1.2 W/m · K, a 380.5% increase compared to the pure PMMA. The results demonstrate that copper nanoparticles have great potential in enhancing thermal transport properties of polymer.

Thermal Properties of Phase Change Composites Containing Ferric Oxide Nanoparticles.

Abstract: We prepared a series of homogeneous nanocomposites by suspending Fe2O3 nanoparticles into paraffin wax (PW) matrix. Fe2O3/PW nanocomposites have reduced both solid-solid phase change latent heat capacity (Ls-s) and solid-liquid phase change latent heat capacity (Ls-l) with an increase in the mass fraction of Fe2O3 nanoparticles. There is almost equable solid-solid phase change temperature (Ts-s) between PW and Fe2O3/PW composites, as well as melting temperature (Ts-l). Fe2O3 nanoparticle addition leads to substantial enhancement in the thermal conductivity of Fe2O3/PW and the enhancement ratio increases with the nanoparticle loading. Thermal conductivity of Fe2O3/PW composite with 3.0 wt% nanoparticles is about 0.27 W/(m · K) at 15 °C, which close to that of γ-Al2O3/PW with 5.0 wt% nanoparticles but higher than that of ZnO/PW containing 5.0 wt% nanoparticles. At 60 °C, Fe2O3/PW has higher thermal conductivity than γ-A12O3/PW and ZnO/PW contained with same fraction of nanoparticles.