2020 Vol. 35, No. 1

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2020, 35(1): .
Abstract(94) PDF(87)
Abstract:
Recent advances in graphene materials used in Li-S batteries
LIU Yong-zhi, WANG Yong, WANG Cong-wei, WANG Jun-ying, WANG Jun-zhong
2020, 35(1): 1-11.
Abstract(861) PDF(260)
Abstract:
The lithium-sulfur battery is considered one of the most promising next-generation secondary batteries owing to its high theoretical specific capacity (1 675 mAh/g) and high energy density (2 600 Wh/kg). Graphene has excellent electrical conductivity, a high surface area and open space as well as an excellent electrochemical performance, and is considered the ideal platform for loading low-conductivity sulfur and lithium sulfide for the use as the cathodes of lithium-sulfur batteries. This article summarizes recent developments on graphene and graphene-based materials for lithium-sulfur batteries, including nanocomposites of sulfur with (reduced) graphene oxide, heteroatom-doped graphene, three-dimensional graphene foams and graphene-porous carbon. The impact of these graphene-based nanocomposites with various compositions and microstructures on improvements in the performance and mechanism of lithium-sulfur batteries are discussed. Prospects for lithium-sulfur battery development are outlined.
Preparation and properties of a glucose biosensor electrode based on an ionic liquid-functionalized graphene/carbon nanotube composite
ZOU Lei, WANG Shan-shan, QIU Jun
2020, 35(1): 12-19. doi: 10.1016/S1872-5805(20)60472-3
Abstract(354) PDF(113)
Abstract:
A novel glucose biosensor electrode was fabricated by loading a glassy carbon electrode with a 1-methyl imidazole-based ionic liquid-functionalized graphene/carbon nanotube (CNTs) composite, which was used to immobilize horseradish peroxidase (HRP) and glucose oxidase (GOD) for glucose detection. SEM, AFM and FTIR were used to investigate the microstructures and morphology of the electrode. The electrochemical performance of the electrode was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Results indicate that the electrode has an excellent electrocatalytic activity towards glucose. A biosensor prepared at the optimal loading amount of the composite and HRP/GOD ratio has a linear range of 0.004-5 mM, a detection limit of 3.99×10-7 M and a sensitivity of 53.89 μA mM-1 cm-2 for glucose detection with an excellent stability and reproducibility. The excellent performance of the biosensor is ascribed to the stable three-dimensional structure of the composite, where graphene sheets provide a large surface area for immobilizing the two enzymes and CNTs inserted between the graphene sheets to decrease electron transfer resistance.
Purification of coal tar pitch by a combined thermal condensation and filtration method
MENG Yu-chen, MA Zhao-kun, CAO Rui-xiong, SONG Huai-he
2020, 35(1): 20-25.
Abstract(807) PDF(146)
Abstract:
Raw coal tar pitch with an ash content of 1100 ppm and a quinolone insoluble (QI) fraction of 8 wt% was first thermally condensed at 420℃ for different times, then dissolved in pyridine at 100℃ for 1 h under stirring and finally filtered under a pressure of 0.1-0.3 MPa with meshes of different sizes to lower the ash and QI contents. The effects of the thermal condensation time and aperture size of the mesh on the purification efficiency were investigated. Results indicated that the ash content of the refined pitch first decreased and then increased slightly, but the pitch yield decreased with condensation time. The ash content and yield of refined pitch decreased with decreasing the aperture size. The purification efficiency was improved greatly by thermal condensation. SEM observation of the surface morphology of the residue revealed that mesophase spheres formed by heterogeneous nucleation during the thermal condensation had the ability to adsorb ash components and primary QI to decrease their contents in the refined pitch. The slight increase of the ash content with a condensation time greater than 5 h was caused by coalescence of mesophase spheres to form large spheres and domains, which decreased their adsorbing ability. A refined pitch with an ash content of 90 ppm and a QI content of 0.6 wt% was obtained using a condensation time of 5 h and a mesh aperture size of 13 μm, which meets the requirement for preparing most advanced carbon materials.
Mechanical and friction-wear properties of two C/C composites using pre-oxidized polyacrylonitrile fibers and carbon fibers as the reinforcements
WANG Lian-yi, LUO Rui-ying, SHAGN Hai-dong, CUI Guang-yuan
2020, 35(1): 26-33.
Abstract(438) PDF(115)
Abstract:
Two preforms based on pre-oxidized polyacrylonitrile fibers (OPFs) and a Chinese version of T-300 carbon fibers (CFs) were densified to 1.7 g/cm3 by chemical vapor infiltration. The microstructures and mechanical and friction-wear properties of the two C/C composites were investigated. Results indicate that both composites exhibit a pseudo-plastic fracture mode with similar bending strengths of 127 MPa for the CF C/C composite and 113 MPa for the OPF C/C composite. The interlaminar shear strength of the OPF C/C composite is 13.4 MPa, which is 30.26% higher than that (10.01 MPa) of the CF C/C composite. It is easier to obtain pyrocarbon with a rough lamellar structure for the OPF reinforcement than with the CF one. The OPF C/C composite always gives a more stable COF and lower wear rate than the CF-based one, regardless of the braking conditions used. When the brake pressure is 0.65 MPa and the braking speed is 20-25 m/s, the OPF C/C composite has excellent abrasive wear resistance with a coefficient of friction near 0.35 and a linear wear rate of 1.3-1.5 μm per braking procedure.
An electrochemical sensor for dopamine detection using poly-tryptophan composited graphene on glassy carbon as the electrode
GONG Qiao-juan, HAN Hai-xia, WANG Yong-dong, YAO Chen-zhong, YANG Hai-ying, QIAO Jin-li
2020, 35(1): 34-41. doi: 10.1016/S1872-5805(20)60473-5
Abstract(512) PDF(129)
Abstract:
A sensitive electrochemical sensor for dopamine (DA) determination was developed using electrochemically polymerized L-tryptophan on graphene-coated glassy carbon (GC) as the electrode. The composite electrode showed an excellent electrochemical catalytic activity towards DA oxidation. The peak oxidation current, recorded by differential pulse voltammetry, is logarithmically proportional to the DA concentration from 0.2 to 100 μM. The electrode has a high detection selectivity in the presence of a high concentration of ascorbic acid and a low detection limit of 0.06 μM, which has been used for DA detection in real samples. The success of the sensor in DA detection is ascribed to a combined effect of the high surface area and high conductivity of graphene and π-π stacking interaction between graphene and p-L-Trp.
The relationship between the mechanical properties and microstructures of carbon fibers
WANG Mei-ling, BIAN Wen-feng
2020, 35(1): 42-49. doi: 10.1016/S1872-5805(20)60474-7
Abstract(357) PDF(99)
Abstract:
Differences in the microstructure of carbon fibers are subtle for carbon fibers with similar mechanical properties. The mechanical properties and microstructures of six carbon fibers were investigated by a universal material testing machine, X-ray diffraction, small angle X-ray scattering and Raman spectroscopy to reveal the relationship between the tensile strengths of carbon fibers and their microstructures. Results indicate that the tensile strength increases with decreasing d002 or ID/IG values, and increases with increasing Lc for five of the six carbon fibers examined. Differences in the tensile strength were characterized by a Weibull modulus increase with increasing micropore radius. The Griffith theory over-estimates the tensile strength of the six carbon fibers. A more accurate formula is proposed to correlate the tensile strength with the microstructures of carbon fibers based on both the Griffith and Weibull theories, which takes into account the tensile strength loss due to the three-layer structure of carbon fibers (an inner-surface layer, an outer-surface layer and a core), defects and the tensile strength of carbon fibers, and is validated by the experimental data on T300 carbon fibers from other researchers.
Preparation and electrochemical performance of the N-doped hollow pitch-based activated carbon fibers as supercapacitor electrodes
YUE Dan, YANG Jian-xiao, SUN Bing, SHI Kui, ZHU Hui, LI Xuan-ke
2020, 35(1): 50-57.
Abstract(539) PDF(102)
Abstract:
Mixtures of polyethyleneimine (PEI) and ethylene tar pitch (0, 15, 20, 30 wt% of PEI) were melt-spun, stabilized, carbonized and activated to prepare nitrogen-doped (N-doped) activated carbon fibers (ACFs). The morphology, porous structure and surface chemistry of the N-doped ACFs were characterized by N2 adsorption, XPS and SEM. Their electrochemical performance as supercapacitor electrode materials was investigated. Results indicate that the specific surface area, pore volume and number of nitrogen-containing functional groups of the N-doped ACFs are much increased compared to undoped ACFs. PEI pyrolysis during the carbonization of the fibers leads to the formation of hollow N-doped ACFs that increases the utilization% of the surface area, resulting in a significant increase of the specific capacitance. When 20 wt% PEI was added, the specific surface area of the N-doped ACF reached 2 756 m2/g, its pore sizes ranged from 0.7 to 2 nm, and its specific capacitance reached 314 F/g at 0.5 A/g, which is much higher than that (194 F/g) of the undoped ACF.
The microstructures and properties of graphite flake/copper composites with high volume fractions of graphite flake
LIU Ben, ZHANG Dong-qing, LI Xiang-fen, GUO Xiao-hui, SHI Jing, LIU Zhan-jun, GUO Quan-gui
2020, 35(1): 58-65. doi: 10.1016/S1872-5805(20)60475-9
Abstract(506) PDF(140)
Abstract:
Graphite flake (average lateral size of 292 μm and average thickness of 13 μm)/copper composites with high volume fractions (72.08%-93.34%) of graphite flake were produced by a vacuum hot pressing method. Results show that the composites are anisotropic due to the alignment of the surface planes of the graphite flakes perpendicular to the pressing direction. With increasing volume fraction of graphite flakes, the density of the composites decreased from 4.07 to 2.63 g cm-3, with the relative density apparently decreasing when the volume fraction of the flakes is more than 82.6%. In addition, the in-plane electrical conductivity decreased from 14.71% to 2.45% of the international annealed copper standard, the in-plane coefficient of thermal expansion decreased from 6.6 to 2.2×10-6/K, the in-plane bend strength decreased from 42.48 to 14.63 MPa, and the in-plane compressive strength decreased from 45.75 to 20.46 MPa while the in-plane thermal conductivity showed a maximum of 663.73 W m-1 K-1 at a volume fraction of GF 82.6%. The maximum in-plane thermal conductivity is caused by inter-flake pores that are not fully infiltrated by Cu. The in-plane and out-of-plane thermal conductivity agree well with a modified layers-in-parallel model and a modified layers-in-series model, respectively.
Improving the thermal and mechanical properties of an alumina-filled silicone rubber composite by incorporating carbon nanotubes
LIN Jia-long, SU Shi-ming, HE Yan-bing, KANG Fei-yu
2020, 35(1): 66-72. doi: 10.1016/S1872-5805(20)60476-0
Abstract(607) PDF(114)
Abstract:
Carbon nanotubes (CNTs) can be used to improve the thermal and mechanical properties of composites because of their excellent characteristics. Methyl vinyl silicone rubber matrix composites filled with alumina (Al2O3) powder and CNTs were fabricated by a conventional mechanical blending method. The effects of the mass fraction of Al2O3 powder, surface modification of Al2O3 powder by silanization with dodecyltrimethoxysilane and the addition of CNTs on the thermal conductivity, Young's modulus and hardness of the composites were investigated. Results showed that a higher mass fraction of Al2O3 powder results in a higher thermal conductivity of the composites. When the mass fraction of Al2O3 powder was fixed, the thermal conductivity, Young's modulus and hardness of the composites were obviously improved by surface modification of the powder and adding a small amount of CNTs. A combination of the modified Al2O3 filler and CNT filler improves the interfacial interaction between the fillers and rubber matrix by the formation of better heat conduction channels and network structures in the rubber matrix, thereby improving the thermal conductivity and mechanical properties of the composites.
Properties of carbon nanotube/ethylene-propylene rubber composites prepared by an in-situ gas phase polymerization method
SHEN Kai-quan, LI Hua-yi, WANG Yao
2020, 35(1): 73-79.
Abstract(387) PDF(71)
Abstract:
Carbon nanotube/ethylene-propylene rubber composites were prepared by gas-phase polymerization of the monomers in an autoclave loaded with carbon nanotubes under agitation. The aggregation of rubber particles during polymerization was effectively prevented by adding more than 6.76 wt% carbon nanotubes that were well dispersed in the composites. The addition of carbon nanotubes had no effect on the melting and thermal decomposition temperatures of the rubber. The composites with carbon nanotubes had a significantly better conductivity and tensile strength than those with conductive carbon black or those obtained with the same formulations using a mechanical blending method.
Thermal conduction and tribological properties of carbon/carbon composites densified by xylene pyrolysis using La as a catalyst
DENG Hai-liang, ZHENG Jin-huang, YIN Zhong-yi, YAO Dong-mei, SU Hong, ZHANG Xiao-hu, SI Song-hua
2020, 35(1): 80-86.
Abstract(440) PDF(75)
Abstract:
Carbon/carbon composites with densities of 1.72-1.73 g/cm3 were fabricated by film boiling chemical vapor infiltration of a needle-pierced preform using xylene as a carbon precursor and LaCl3 as a catalyst, followed by resin impregnation and graphitization. The effects of the catalyst content on the thermal conduction and tribological properties of the composites were investigated by SEM, thermal tests with a laser flash instrument, and friction tests. Results showed that the thermal conductivities in the through thickness and in-plane directions, the friction coefficient, and the wear rate all had maxima at 6 wt% for LaCl3 contents from 0 to 15 wt%. The maximum thermal conductivities were about 58.5 and 75.6% higher than those of the composites without a catalyst in the through thickness and in-plane directions, respectively. A smooth friction film was most easily formed on the friction surface of the composite fabricated with a 6 wt% catalyst content, resulting in the lowest coefficient of friction and wear rate as well as the highest braking stability.
Preparation of CoNiP nanoparticles supported on nitrogen-doped carbon nanotubes as high performance electrocatalysts for the hydrogen evolution reaction
XIA Ji, LI Shao-min, GAO Sen, XIE Song, LIU Hao
2020, 35(1): 87-96. doi: 10.1016/S1872-5805(20)60477-2
Abstract(609) PDF(131)
Abstract:
CoNiP nanoparticles dispersed on nitrogen-doped carbon nanotubes (NCNTs) as electrocatalysts for the hydrogen evolution reaction were prepared by impregnating the NCNTs with a solution containing Ni(NO3)2·6H2O and Co(NO3)2·6H2O, followed by calcination at 500℃ for 2 h and phosphorization at 350℃ for 2 h in a furnace with a crucible of sodium hypophosphite upstream of the CoNiO2/NCNT that served as the phosphorization agent. Results indicated that the CoNiP/NCNT catalysts had the advantages of low overpotential and high durability. The sodium hypophosphite content was a crucial factor affecting the performance of the catalysts. The optimized CoNiP/NCNT catalyst with an appropriate content of the phosphorization agent (0.2 g sodium hypophosphite/0.02 g CoNiO2/NCNT) exhibited the best performance with an onset-overpotential of 44 mV and an overpotential of 75 mV at a current density of 10 mA cm-2 in 0.5 M H2SO4. After the chronopotentiometry measurement for 24 h, the overpotential showed a decrease of only 6 mV, indicating its excellent durability.

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