Yuming Wu

Enhanced thermal conductivity for poly(vinylidene fluoride) composites with nano-carbon fillers

Polymer composites with high thermal conductivity have recently attracted much attention, along with the rapid development of electronic devices toward higher speeds and performance. Here, we reported a facile method to prepare poly(vinylidene fluoride) (PVDF) composites with nano-carbon fillers including zero-dimensional superfullerene (SF), one-dimensional carbon nanotubes (CNT) and two-dimensional graphene sheets (GS) by simple solution blending and compression molding. The effects of these nano-carbon fillers on the thermal conductivity of PVDF composites were systematically investigated. It was found that PVDF composites exhibit a higher thermal conductivity than that of neat PVDF. Among them, the thermal conductivity of PVDF composites with 20 wt% two-dimensional GS reaches a maximum (2.06 W m−1 K−1), which is approximately 10-fold enhancement in comparison to that of the neat PVDF. Such highly thermal conductive PVDF composites may enable some prospective applications in advanced thermal management.

High quality graphene films with a clean surface prepared by an UV/ozone assisted transfer process

Graphene shows great promise as a transparent conductive electrode for optoelectronic applications. However, residues generated during the graphene transfer process lead to the degradation of device performance. Here, we show that a combination of UV/ozone pretreatment with the conventional process of graphene transfer can help in obtaining a large area graphene film with a clean surface on arbitrary substrates. In general, after CVD growth, a graphene film would be formed on both bottom and upper surfaces of a Cu foil. With UV/ozone pretreatment, a graphene layer with an undamaged and clean surface can be obtained, which is free of the residues. In addition, the quality of the obtained graphene can also be improved, which is revealed by the increase of the I2D/IG ratio from 2.0 to 3.6 for graphene films prepared without and with UV/ozone pretreatment, respectively. The transferred graphene films show higher transparency (97.5% at 550 nm), and the electron mobility (1178 cm2 V−1 s−1) can be improved by a factor of two compared to that prepared by the conventional transfer process (685 cm2 V−1 s−1). Considering its high efficiency, low cost, and easy scalability, the UV/ozone-assisted transfer method can be beneficial to the performance of graphene-based device applications such as transparent conducting electrodes.

Enhanced Thermal Conductivity of Polyimide Composites with Boron Nitride Nanosheets

A strategy was reported to prepare boron nitride nanosheets (BNNSs) by a molten hydroxide assisted liquid exfoliation from hexagonal boron nitride (h-BN) powder. BNNSs with an average thickness of 3 nm were obtained by a facile, low-cost, and scalable exfoliation method. Highly thermally conductive polyimide (PI) composite films with BNNSs filler were prepared by solution-casting process. The in-plane thermal conductivity of PI composite films with 7 wt% BNNSs is up to 2.95 W/mK, which increased by 1,080% compared to the neat PI. In contrast, the out-of plane thermal conductivity of the composites is 0.44 W/mK, with an increase by only 76%. The high anisotropy of thermal conductivity was verified to be due to the high alignment of the BNNSs. The PI/BNNSs composite films are attractive for the thermal management applications in the field of next-generation electronic devices.

Enhanced thermal transport performance for poly(vinylidene fluoride) composites with superfullerene

High thermal conductive polymer composites have recently attracted much attention, along with the quick development to the electronic devices toward higher speed. The addition of high thermal conductive fillers is an efficient method to solve this problem. Here, we introduced superfullerene (SF), a novel zero-dimensional carbon-based filler, and incorporated into PVDF by a solution method. The effects of SF filler on the thermal conductivity of PVDF composites were systematically investigated. It was found that PVDF composites exhibited an improvement in thermal conductivity at a low SF loading. PVDF composites with only 5 wt% SF filler present the thermal conductivity value of 0.365 Wm-1K-1, which is as much as 121 % enhancement in comparison with that of neat PVDF. In view of the excellent thermal transport performance, the composites may enable some applications in thermal management in the future.

Anisotropic thermal conductive properties of cigarette filter-templated graphene/epoxy composites

Herein, a cigarette filter-templated graphene/epoxy composite was prepared with enhanced thermal conductive properties. The through-plane thermal conductivity of the epoxy composite was up to 1.2 W mK−1, which was 4 times that of it in the in-plane (0.298 W mK−1) after only 5 filtration cycles. The thermal conductive anisotropy and improvement in the through-plane thermal conductivity of the epoxy composite were attributed to the particular structure of cigarette filter-templated graphene in the epoxy matrix. The unique structure formed effective conductive pathways in the composite to improve the thermal transportation properties. The excellent thermal transportation properties allow the epoxy composite to be used as an efficient heat dissipation material for thermal management applications.

Effective thermal transport highway construction within dielectric polymer composites via a vacuum-assisted infiltration method

Materials with superior thermal conduction, stable electrical insulation, and excellent mechanical strength that can be obtained at low cost are desirable for electronic packaging and thermal management in electrical engineering systems. There is therefore relentless interest in developing highly robust thermally conductive and electrically insulating polymer-based composites. Herein, a facile and environmentally friendly method to construct three-dimensional thermal transport channels in a poly(vinyl alcohol) (PVA) matrix composite is reported. The formation of thermal transport highways improves the thermal conductivity up to 4.79 W m−1 K−1 for alumina (Al2O3) loading of 45.4 vol% in the composites. The thermal conductivity achieved is the highest value for this Al2O3 content range compared with reported work, and is 1700% compared with that of pure PVA. In the meantime, the composites still retain outstanding electrical insulation properties and excellent mechanical strength. The heat-conducting and electrically insulating composites not only have promising applications in electronic packaging and electrical engineering systems, but the technically facile vacuum-assisted infiltration method is a new avenue for the mass production of spherical filler/polymer composites.

Correction: High quality graphene films with a clean surface prepared by an UV/ozone assisted transfer process

Correction for ‘High quality graphene films with a clean surface prepared by an UV/ozone assisted transfer process’ by Hongyan Sun et al., J. Mater. Chem. C, 2017, 5, 1880–1884.