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  • Reduced graphene oxide hydrogels prepared in the presence of phenol for high-performance electrochemical capacitors
    New Carbon Mater. (IF 1.387) Pub Date : 2019-11-20
    Xiang-li Gao, Cui-xian Liu, Gao-yi Han, Hua Song, Yao-ming Xiao, Hai-han Zhou

    Reduced graphene oxide (GO) hydrogels were synthesized by the hydrothermal treatment of GO in the presence of phenol to obtain rGOHPhs, where phenol acted as both a reducing agent and a structure regulator for the hydrogels. The influence of the mass ratio of GO to phenol and the hydrothermal temperature on the capacitive behavior of the rGOHPhs were investigated. Results indicate that the rGOHPhs have a more developed three-dimensional pore network than the rGOH samples without phenol under the same hydrothermal conditions. The optimum rGOHPh was prepared at 160 °C for 12 h with a GO/phenol mass ratio of 1/1.25 and had a larger micropore and total pore volume than rGOH prepared under the same hydrothermal conditions. The optimum rGOHPh had a specific capacitance of about 260.0 F g−1 at a scan rate of 1 mV s−1, which is much higher than that of the rGOH (182.5 F g−1). Furthermore, the optimum rGOHPh has an excellent rate capability (138.1 F g−1 at 500 mV s−1) and a good cycling stability (98.3% capacitance retention after 12 000 cycles). A capacitor assembled using the optimum rGOHPh had energy densities of about 8.9 and 2.0 Wh Kg−1 at power densities of 0.125 and 16 kW kg−1, respectively, which are higher than most of the GO-based capacitors reported in the literature. The well-developed pore network is ascribed to the phenol and its oxidation product quinone that were adsorbed on the rGO surface as spacers and redox pairs to provide pseudo capacitance.

    更新日期:2019-12-11
  • A flexible carbon nanotube-pyrolytic carbon sandwich paper with a stable structure and high heat-dissipation capacity
    New Carbon Mater. (IF 1.387) Pub Date : 2019-11-20
    Xue-song Liu, Qian-gang Fu, Hui Wang, Ya-long Wei, Qiang Song

    A thin layer of pyrolytic carbon (PyC) was deposited on a carbon nanotube paper (CNP) by chemical vapor deposition from methane to improve its structural stability while maintaining its excellent mechanical and thermal conductivity performance. The resulting material consisted of layers of PyC carbon on the outer surfaces, a layer of bare CNTs in the center, and layers of CNTs infiltrated with PyC between the outer and inner layers. The resulting sandwich material could be cut into any size without breaking the surrounding material. The CNTs in the center layer were stretched after the CNP was bent 500 times around a cylindrical die, leading to an increase of tensile strength from 8.58 to 11.41 MPa. The outer PyC layers and the PyC-infiltrated layers retained their integrity. The thermal diffusivity and heat-dissipation capacity of the sandwich paper remain almost the same before and after bending, which is attributed to the undamaged CNTs and PyC layers. This paper has potential applications as a lightweight and flexible heat-dissipation material at high temperatures.

    更新日期:2019-12-11
  • Nanohybrids of silver nanoparticles grown in-situ on a graphene oxide silver ion salt: simple synthesis and their enhanced antibacterial activity
    New Carbon Mater. (IF 1.387) Pub Date : 2019-11-20
    Kai-rong Xiong, Ye-ru Liang, Yi Ou-yang, Ding-cai Wu, Ruo-wen Fu

    Advanced antimicrobial agents that treat infectious diseases are greatly needed. Various silver-based nanomaterials have been developed and are considered potential candidates for many commercial products, but they lack durability and adequate antibacterial activity. A new class of nanohybrids of silver nanoparticles (AgNPs) grown in-situ on graphene oxide (GO) using a silver ion salt was synthesized by a simple ultrasonic mixing method. The structure and composition of the nanohybrids were investigated by SEM, TEM, FTIR, TGA, XRD and XPS. Results indicated that GO acts not only as a negatively charged macromolecule for capturing Ag+ ions, but also a reducing agent to reduce the Ag+ ions to AgNPs. The heterogeneous structure leads to abundant well-dispersed AgNPs and Ag+ ions on the GO support. The as-prepared nanohybrids make full use of the advantages of both AgNPs and GO-Ag+ salts, leading to improved and long-term antibacterial activity against both S.aureus and E. coli.

    更新日期:2019-12-11
  • Effects of the high-temperature treatment of C/C composites on their tribological properties
    New Carbon Mater. (IF 1.387) Pub Date : 2019-11-20
    Xi Ou-yang, Zhuan Li, Peng Xiao, Guan-yi Chen, jin-wei Li, Peng-fei Liu

    C/C composites prepared by chemical vapor infiltration (CVI) were subjected to high temperature treatment (HTT) at 2300 °C under an Ar atmosphere. C/C-SiC composites were prepared by liquid silicon infiltration (LSI) of the C/C composites before HTT. The C/C composites before (A) and after (B) HTT were mated with the C/C-SiC to form friction pairs to investigate their tribological properties. Results indicated that the average coefficient of friction (COF) and stable COF of the C/C-B are 0.280 and 0.65 while that of the C/C-B are 0.451 and 0.55, respectively. The average linear wear rate of the C/C-A and the C/C-B are 3.7 and 8.9 μm/(slide cycle), respectively. SEM reveals that the wear debris of the C/C-A is particulate while that of the C/C-B are the sheets, and the friction surface is more flat for C/C-B than C/C-A. HTT leads to a softening of the carbon, increases the wear rate, but improves the stable COF of the C/C composites. The wear mechanisms of the composites are mainly grain-abrasion, oxidation loss and fatigue wear.

    更新日期:2019-12-11
  • Effects of the oxygen content of reduced graphene oxide on the mechanical and electromagnetic interference shielding properties of carbon fiber/reduced graphene oxide-epoxy composites
    New Carbon Mater. (IF 1.387) Pub Date : 2019-11-20
    Ye Li, Shi-tai Liu, Jian-ming Sun, Shuang Li, Jun-lin Chen, Yan Zhao

    Unidirectional carbon fiber/reduced graphene oxide nanosheet-epoxy laminate composites (CF/RGONs-epoxy) were produced by impregnating the CFs with epoxy acetone solutions containing RGONs, followed by solvent evaporation and curing at 180 °C under 0.6 MPa. The RGONs were prepared by the Hummers method and reduced to different oxygen contents using hydrazine monohydrate by adjusting the reduction temperature. The effect of the content of RGONs on the mechanical properties and electromagnetic interference (EMI) shielding effectiveness of the composites was investigated. Results indicate that in contrast to the detrimental effect of GO on the flexural and thermal properties, the addition of RGONs improves the mechanical property and EMI shielding effectiveness of the composites without sacrificing their thermal properties. RGONs with a relatively lower oxygen content show more apparent mechanical reinforcement while RGONs with a relatively higher oxygen content show a more obvious improvement on EMI shielding effectiveness. The improved interfacial properties are mainly ascribed to the toughening effects of the RGONs.

    更新日期:2019-12-11
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