2019 Vol. 34, No. 5

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2019, 34(5): .
Abstract(103) PDF(112)
Abstract:
Reduced graphene oxide hydrogels prepared in the presence of phenol for high-performance electrochemical capacitors
GAO Xiang-li, LIU Cui-xian, HAN Gao-yi, SONG Hua, XIAO Yao-ming, ZHOU Hai-han
2019, 34(5): 403-416. doi: 10.1016/S1872-5805(19)60022-3
Abstract(424) PDF(252)
Abstract:
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℃ 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.
A flexible carbon nanotube-pyrolytic carbon sandwich paper with a stable structure and high heat-dissipation capacity
LIU Xue-song, FU Qian-gang, WANG Hui, WEI Ya-long, SONG Qiang
2019, 34(5): 417-425. doi: 10.1016/S1872-5805(19)60023-5
Abstract(451) PDF(213)
Abstract:
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.
Nanohybrids of silver nanoparticles grown in-situ on a graphene oxide silver ion salt: simple synthesis and their enhanced antibacterial activity
XIONG Kai-rong, LIANG Ye-ru, OU-YANG Yi, WU Ding-cai, FU Ruo-wen
2019, 34(5): 426-433. doi: 10.1016/S1872-5805(19)60024-7
Abstract(345) PDF(203)
Abstract:
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.
The preparation of activated carbon from walnut shell bio-oil distillation residues
TANG Guo-xu, ZHANG Li-qiang, ZHU Xie-fei, ZHU Xi-feng
2019, 34(5): 434-440.
Abstract(589) PDF(242)
Abstract:
Activated carbons were prepared from walnut shell bio-oil distillation residues using the KOH activation method. Two factors which have an impact on the pore structure of the activated carbon were investigated, (i) carbonization temperature and (ii) heating rate. The carbon precursors and activated carbons were characterized by FTIR, XRD and SEM. Results showed that carbonization temperature and heating rate both affect the micro-crystalline size and surface functional groups which play a decisive role in the activation process. The activated carbon prepared from walnut shell bio-oil distillation residues treated with a 10℃/min heating rate to 400℃, where they were held for 2 h and then activated with KOH (3:1), has the highest specific surface area (2 056 m2/g)。Its iodine adsorption capacity is 1891 mg/g and its adsorption capacity of methylene blue is 407 mg/g. This study confirmed that the walnut shell bio-oil distillation residue can be used as a raw material for the preparation of activated carbon and provides a new way of using bio-oil distillation residues.
Preparation and adsorption performance of a graphene oxide- manganese oxide hybrid for uranium removal
YANG Ai-li, ZHU Yu-kuan, LI Ping, YANG Peng
2019, 34(5): 441-446.
Abstract(506) PDF(118)
Abstract:
In order to increase the adsorption capacity and improve the solid-liquid separation in the post-treatment processes a hybrid graphene oxide-manganese oxide (GOMO) material was fabricated under ultrasonic radiation. The structures and micro-morphology of as-prepared adsorbents were characterized by FT-IR, Raman spectroscopy, SEM and XPS. The effect of solution pH, ionic strength, contact time and initial uranium concentration on uranium removal efficiency was investigated. The adsorption mechanism was investigated by adsorption isotherms, FT-IR and XPS. The solution pH had a significant influence on the removal of uranium. Results showed that GOMO had a favorable adsorption performance. For a uranium solution with an initial concentration of 10 mg/L, the removal rate rapidly reached nearly 100%. The maximum adsorption capacities of GO and GOMO were 75.46 mg/g and 143.34 mg/g, respectively. The adsorption progress of GOMO fitted the Langmuir isotherm model and the pseudo-second-order model well. In the practical applications, the removal efficiency of GOMO for uranium from nuclear industry waste liquid is significantly higher than that of GO.
Effect of graphene on the growth and development of Raspberry tissue culture seedlings
HU Xiao-fei, ZHAO Jian-guo, GAO Li-yan, WANG Hai-yan, XING Bao-yan, YAO Jian-zhong, ZHOU Yu-quan, XUE Bin-long, XUE wei
2019, 34(5): 447-454.
Abstract(546) PDF(168)
Abstract:
Raspberry subcultured tissue seedlings were used as test materials for the effect of different concentrations of graphene on the growth of raspberry seedlings and the development of adventitious roots. The graphene was characterized by a laser particle size analyzer, STEM, TEM, XPS and Raman spectroscopy. A root analysis system and SEM were used to systematically characterize the seedling height, root length, root specific surface area, number of branches, number of root tips and root micromorphology, thus determining the optimum concentration of graphene for the growth of raspberry tissue culture seedlings. The results showed that with increasing graphene concentration, the seedling height, root length, root tip number and root specific surface area of the seedlings all showed a trend of first increasing and then decreasing. The optimum concentration of graphene was 2 mg·L-1, the seedling height of tissue culture seedlings was 1.46 times that of the control group, and the root length, specific surface area, number of root tips and their bifurcation number were about twice that of the control group.
Preparation and microwave absorption properties of magnetic functional porous biomass carbon composites
YANG Qi-xin, YU Lu-jun, DONG Yu-bing, FU Ya-qin, ZHU Yao-feng
2019, 34(5): 455-463.
Abstract(530) PDF(153)
Abstract:
Magnetic functional biomass carbon (Fe3O4/porous biomass carbon) microwave absorbing materials with both dielectric loss and magnetic loss were prepared by carbonization and a hydrothermal method. With increasing FeCl3 concentration, aggregated Fe3O4 nano-crystallites on the surface of the carbon increased under a hydrothermal temperature of 200℃, with a uniform particle size with an average of about 200 nm. The effects of the morphology, structure and Fe3O4 content on the microwave absorbing properties of the composites were investigated, and the mechanism of multi-loss microwave absorption was also analyzed. The results show that when the concentration of FeCl3 is 4 mmol, the magnetically functionalized biomass-carbon composite has an excellent microwave absorbing performance in the range 2-18 GHz, and the thickness is 2 mm. The maximum reflectance loss at 11.42 GHz is up to -42.2 dB, and the effective bandwidth is 3.14 GHz (reflection loss is less than -10 dB).
Microstructure characteristics and ablation behavior of an Al1.92Cr0.08O3-SiC-ZrC anti-ablation coating
PENG Zheng, SUN Wei, XIONG Xiang, CHEN Zhao-ke, WANG Ya-lei, XU Yong-long
2019, 34(5): 464-471.
Abstract(676) PDF(155)
Abstract:
A novel oxide-carbide coating system was achieved on a C/C-ZrC-SiC composite surface by low-pressure plasma spraying and a slurry method, with Cr doping to improve the thermal stability of the coating. The phase compositions and microstructure characteristics of composites were characterized by XRD, SEM and EDS. The ablation properties were tested in an oxy-acetylene environment at temperatures up to 2500℃ for 120 s. The results show that the C/C-ZrC-SiC substrate coated with the Al1.92Cr0.08O3-SiC-ZrC coating exhibits a significant improvement in ablation resistance, with the mass and linear ablation rates decreased by 66% and 76% respectively. This is caused by the highly dense and stable protective structure formed during ablation. The pinning effect of the ZrO2 phase and the thermal-stability efficiency of Cr2O3 provide and explanation for the reduction of the volatilization of SiO2 and Al2O3 at high temperature. Continuous and robust multi-oxide scales on the surface comprised of ZrO2 grain skeletons and molten Al1.96Cr0.04O3-SiO2 cause the superior anti-ablation property.
Effects of the high-temperature treatment of C/C composites on their tribological properties
OU-YANG Xi, LI Zhuan, XIAO Peng, CHEN Guan-yi, LI jin-wei, LIU Peng-fei
2019, 34(5): 472-481. doi: 10.1016/S1872-5805(19)60025-9
Abstract(335) PDF(199)
Abstract:
C/C composites prepared by chemical vapor infiltration (CVI) were subjected to high temperature treatment (HTT) at 2 300℃ 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.
Effect of sizing agent on carbon fiber density measurements using a floatation method
PAN Yue-xiu, FANG Yuan, HAN Da-wei, SONG Yi-jun, LI Long, GAO Jian-li, ZHU Shi-peng, YANG Yun-hua
2019, 34(5): 482-488.
Abstract(356) PDF(139)
Abstract:
The density of T300 carbon fiber, as well as the amount of sizing and micro-structure were measured, before and after removing the sizing. The results showed that there was apparent stratification when measuring the density of the carbon fiber by the sink/float method, without removing the sizing. The upper sample layer was seriously flocculated with an excessive sizing amount of 2.17%, while the bottom-layer also flocculated. Two methods including acetone extraction and pyrolysis, were conducted to removing the sizing. It was shown that the measured amounts of sizing for the two methods were 1.20% and 1.53%, respectively. For the sample after immersion in acetone, there was still stratification in the sink/float test, with the upper sample layer flocculated because of the remaining sizing; while samples at the bottom dispersed relatively well. However, for the thermally treated samples the sizing was adequately removed, which resulted in the uniform density and dispersion during the test. This indicates that the non-uniform distribution of sizing agent on the surface of the CFs is the main reason for stratification during the density measurement. Therefore, the sizing must be fully removed in order to obtain an accurate density for the carbon fibers. Moreover, it can be seen that pyrolysis is an effective way to remove the CF sizing agent.
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
LI Ye, LIU Shi-tai, SUN Jian-ming, LI Shuang, CHEN Jun-lin, ZHAO Yan
2019, 34(5): 489-498. doi: 10.1016/S1872-5805(19)60026-0
Abstract(592) PDF(168)
Abstract:
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℃ 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.

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