2020 Vol. 35, No. 5

Graphical Contents
2020, 35(5): .
Abstract(79) PDF(98)
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A review of nanocarbon-based molecularly imprinted polymer adsorbents and their adsorption mechanisms
QIN Lei, LIU Wei-feng, LIU Xu-guang, YANG Yong-zhen, ZHANG Li-an
2020, 35(5): 459-485. doi: 10.1016/S1872-5805(20)60503-0
Abstract(1427) PDF(514)
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Nanocarbon materials have become a class of ideal supports for surface molecularly imprinted materials because of their low density, high strength, environment-friendliness, controllable structure and modifiable surface. Thus, nanocarbon-based surface molecularly imprinted polymer adsorbents (C-SMIPs) have achieved satisfactory performance for the removal and enrichment of organic compound pollutants in liquids. This review summarizes C-SMIPs based on various nanocarbon materials for the treatment of ecological environmental pollutants in water during the last five years. The structural characteristics and adsorption features of these C-SMIPs have been comprehensively and systematically analyzed and compared. It is found that the low limit of adsorption capacity is usually decided by the carbon support while the upper limit depends more on the imprinted layer. Specifically, C-SMIPs based on porous carbon nanospheres or graphene oxide usually have large adsorption capacities. It can also be inferred that the essence of C-SMIP adsorption towards target molecules is physical adsorption at the solid-liquid interfaces, the chemical-like adsorption found in the literature is caused by an extremely strong interaction between active sites and the adsorbate by multiple non-covalent bonds like ionic bonds, hydrogen bonds, electrostatic interactions, and van der Waals forces, which settles the long-standing controversy on the nature of adsorption for C-SMIPs. Moreover, analysis and discussion of the literature provide some theoretical and practical evidence for support optimization, imprinting method amelioration, and adsorption parameter selection, which may promote the development and applications of C-SMIPs.
A review on recent advances in carbon aerogels: their preparation and use in alkali-metal ion batteries
GAO Xin-ran, XING Zheng, LI Zi-jian, DONG Xiao-yu, JU Zhi-cheng, GUO Chun-li
2020, 35(5): 486-507. doi: 10.1016/S1872-5805(20)60504-2
Abstract(988) PDF(411)
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Carbon aerogels with a three-dimensional (3D) hierarchical porous network could be promising carbon-based materials for electrochemical energy storage systems because of their rapid electron/ion transport, remarkable physicochemical stability and excellent cycling performance. They have also been used to host electrochemical active materials (transition metal oxides/sulfides/phosphides) in pores to improve the electron conductivity and to buffer large volume changes. In this review, recent advances in their synthesis, functionalization/modification and use in alkali-metal ion batteries, either alone or as composites, are summarized. The challenges for future research on carbon aerogels are discussed and development opportunities are proposed.
A review of graphene-based catalysts for oxygen reduction reaction
YAN Rui, WANG Kai, WANG Cong-wei, GUO Quan-gui, WANG Jun-zhong
2020, 35(5): 508-521. doi: 10.19869/j.ncm.1007-8827.20170141
Abstract(476) PDF(206)
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The oxygen reduction catalyst is one of the core materials of fuel cells. Research progress on graphene-based catalysts for the oxygen reduction reaction in fuel cells is summarized with a focus on their electrochemical activity, stability and CO tolerance. These catalysts include Pt/graphene, non-precious metal/graphene such as Pd or its alloy/graphene, non-metallic/graphene such as Fe, Co or Ni species/graphene, graphene quantum dots, porous graphene, and graphene doped or co-doped with N, B, P, S and I.
A wearable strain sensor based on carbon derived from linen fabrics
LIANG Jing-jing, ZHAO Zong-bin, TANG Yong-chao, LIANG Zhi-hui, SUN Lu-lu, PAN Xin, WANG Xu-zhen, QIU Jie-shan
2020, 35(5): 522-530. doi: 10.1016/S1872-5805(20)60505-4
Abstract(597) PDF(203)
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A stretchable, skin-mountable and wearable strain sensor is important because of its possible applications in monitoring our daily life and work, such as robotic intelligent equipment, health-monitoring, human motion detection and remote precise diagnosis. A linen fabric-derived carbon (LDC) has been rationally integrated with 2D graphene and 1D silver nanowires by impregnation of the linen fabric with a graphene oxide suspension followed by carbonization and final impregnation with a suspension of silver nanowires. The Ag nanowires/graphene/linen-derived carbon (Ag-GLDC) composite sensor exhibits excellent stretchability (>60%), good cycling stability, and high sensitivity with gauge factors of 11.2, 36.8 and 74.5 for strains of 0-20%, 20%-40%, 40%-60%, respectively. The composite sensor has been successfully used to monitor the vigorous motion of human body joints (wrist, knee and elbow), suggesting its potential use in human motion detection. This work provides a new method for the preparation of flexible and wearable composite strain sensors with high performance.
Improved oxygen reduction performance of a N, S co-doped graphene-like carbon prepared by a simple carbon bath method
YE Xiao-wen, HU Li-bing, LIU Min-cong, WANG Gang, YU Feng
2020, 35(5): 531-539. doi: 10.1016/S1872-5805(20)60506-6
Abstract(504) PDF(132)
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Rationally designing and optimizing metal-free electrocatalysts for the oxygen reduction reaction (ORR) is of great importance for fuel cells and metal-air batteries, but remains a great challenge. A N,S-codoped graphene-like carbon (GLC) was synthesized by a simple carbon-bath pyrolysis method, in which urea and thiourea (1:1 w/w) were used as both the sacrificial template and source of nitrogen and sulfur, and glucose as the carbon precursor. A mixture of these materials was placed in a crucible that was contained in a larger crucible full of carbon powder. Compared with N-doped or S-doped GLCs synthesized using only urea or thiourea, respectively, the N,S-codoped GLC had a pore volume of 0.63 cm3/g and a larger specific surface area of 583.68 m2/g, the highest micropore to total surface area of 29.39% and micropore to total pore volume of 12.70%, and the highest pyridinic-N and graphitic-N content of up to 92.2%. The N,S-codoped GLC showed a high electrocatalytic activity for ORR with a mid-wave potential (E1/2) of 0.82 VRHE, which was more positive than that of Pt/C (E1/2=0.80 VRHE) in an alkaline electrolyte. The N,S-codoped GLC catalyst had better stability and superior methanol tolerance compared with commercial Pt/C (20 wt%), a benchmark catalyst.
MoS2/graphene/carbonized melamine foam composite catalysts for the hydrogen evolution reaction
LI Wen, CHEN Jun-wei, XIAO Zong-liang, XING Jing-bo, YANG Chen, QI Xiao-peng
2020, 35(5): 540-546. doi: 10.1016/S1872-5805(20)60507-8
Abstract(535) PDF(126)
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A melamine-based carbon foam was obtained from a melamine foam (2 cm×2 cm×2 cm), which was then coated with graphene by immersing it in 400 mL of a suspension of reduced graphene oxide in water with concentrations of 25 to 100 mg/L. MoS2/graphene/carbonized melamine foam composites for use as catalysts for the hydrogen evolution reaction were synthesized by the hydrothermal growth of MoS2 nanosheets on the graphene-coated carbon foams in a mixed solution of molybdic acid disodium salt and thiourea. Results indicate that MoS2 nanosheets with a thickness of 15-20 nm were uniformly distributed on the three-dimensional carbon foam substrates coated with different amounts of graphene. The amount of graphene coating has a great influence on the hydrogen evolution performance. The composite prepared with a graphene concentration of 25 mg/L has the best electrochemical performance, its initial overpotential at a 10 mA cm-2 current density is 163 mV, and the corresponding Tafel slope is 76 mV dec-1. It has also the lowest impedance, which shows that coating the carbon foam with an appropriate amount of reduced graphene oxide accelerates electron migration and improves the hydrogen evolution performance.
Impact of the microstructure of polycarboxylate superplasticizers on the dispersion of graphene
WANG Qin, ZHAN Da-fu, QI Guo-dong, WANG Yue, ZHENG Hai-yu
2020, 35(5): 547-558. doi: 10.1016/S1872-5805(20)60508-X
Abstract(528) PDF(115)
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Graphene can not only toughen cement-based materials, but also give them sensing ability. However, the uniform dispersion of graphene in a cement matrix is the major problem in the fabrication process. Four polycarboxylate superplasticizers (PCEs) with different charge densities and side-chain lengths were synthesized and the effects of their microstructures on the dispersibility of graphene in deionized water and in solution in cement pores were examined by UV-Vis spectroscopy, dynamic light scattering and optical microscopy with a large depth of field. A mechanism for the dispersion of graphene in the two media was also proposed. In deionized water, PCEs with a higher charge density showed more electrostatic repulsion, which improved the graphene dispersion efficiency. Conversely, PCEs with a lower charge density and longer side-chains gave a lower graphene dispersion. In solution in the cement pores, however, a PCE with a high charge-density produced a low graphene dispersibility, due to a cross-linking Ca2+-bridging effect. This effect was insignificant in cement pores for a solution containing low charge-density PCEs. Moreover, it was found that PCEs with the longer side-chains produced the worst graphene dispersion efficiency in both media. Overall, PCEs with a low charge density and relatively short side chains are more suitable for the preparation of graphene-composited cement pastes.
The effect of adding Cu on the nitrogen removal efficiency of Ti for the synthesis of a large type IIa diamond under high temperature and high pressure
GUO Ming-ming, LI Shang-sheng, FENG Lu, HU Mei-hua, SU Tai-chao, GAO Guang-jin, WANG Jun-zhuo, YOU Yue, NIE Yuan
2020, 35(5): 559-566. doi: 10.1016/S1872-5805(20)60509-1
Abstract(356) PDF(106)
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Large single crystal diamonds were synthesized using Ti/TiC and Cu as additives in the Fe64Ni36-C system under 5.6 GPa and at 1 543 K. The synthesized crystals were characterized by optical microscopy and infrared spectroscopy. Results show that both Ti and TiC react with N to form TiN and Ti (C1-x,Nx), respectively, which leads to a poor nitrogen removal efficiency and a large number of inclusions and pits in the crystals. Co-doping Ti or TiC with Cu promotes the decomposition of TiC to release Ti, which improves the nitrogen removal efficiency, and thereby reduces the number of defects and inclusions in the diamond crystals. A high-quality type Ⅱa diamond crystal was optimally synthesized when the Ti/Cu contents were 1.70 wt.%/1.06 wt.% (Ti:Cu=4:2.5).
Preparation, microstructure and properties of three-dimensional carbon/carbon composites with high thermal conductivity
LI Bao-liu, GUO Jian-guang, XU Bing, XU Hui-tao, DONG Zhi-jun, LI Xuan-ke
2020, 35(5): 567-575. doi: 10.1016/S1872-5805(20)60510-8
Abstract(555) PDF(298)
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Three-dimensional (3D) carbon/carbon (C/C) composites with high thermal conductivity were prepared from a preform prepared by orthogonally weaving continuous mesophase pitch-based fibers in the x and y directions and commercial PAN-based carbon fibers in the z-direction, which were densified by three cycles of chemical vapor infiltration (CVI) and graphitization to a density of 1.58 g/cm3 (3CVI), followed by four cycles of liquid pressure impregnation (LPI), carbonization and graphitization to give a density of 1.84 g/cm3 (3CVI+4LPI). The effects of the microstructure and the relative contributions of the fibers and matrix carbon to the thermal conductivity and mechanical properties of the C/C composites were investigated. Results indicate that the CVI pyrolytic carbon (PyC) is highly crystalline and oriented along the fiber axis. The thermal conductivities of the 3CVI and 3CVI+4LPI C/C composites in the x-y plane are respectively 115.9 and 234.7 W/m·K, while those in the z-direction are only 18.6 and 41.5 W/m·K. The thermal diffusivity and thermal conductivity mainly depend on the fiber type, the volume fractions of the fibers and the type of pyrolytic carbon. The thermal conductivity of the composites is improved by increasing the volume fraction of pitch-based carbon fibers and using matrix carbon that is easily graphitized. The mechanical properties of the two C/C composites are greatly improved compared with those of 1D-C/C and 2D-C/C composites.
Mechanical and thermal conduction properties of carbon/carbon composites with different carbon matrix microstructures
LIU Xia, DENG Hai-liang, ZHENG Jin-huang, SUN Ming, CUI Hong, ZHANG Xiao-hu, SONG Guang-sheng
2020, 35(5): 576-584. doi: 10.1016/S1872-5805(20)60511-X
Abstract(431) PDF(205)
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Four carbon/carbon composites with densities of 1.75-1.81 g/cm3 were produced with matrix carbons derived from (a) coal tar pitch and furfural acetone resin by impregnation-carbonization, (b) natural gas by isothermal chemical vapor infiltration and (c) xylene by film-boiling chemical vapor infiltration. Their mechanical properties and thermal conductivities (TC) were compared and correlated to the matrix carbon microstructures. Results showed that the strength of the composites decreased as the carbon matrix changed from natural gas pyrocarbon (PyCN), to resin-derived carbon, to xylene PyC (PyCX), and to pitch-derived carbon. The highest flexural and interlaminar shear strengths of 208.7 and 26.4 MPa, respectively, were obtained for the PyCN matrix. The large amount of fiber pull-out and step-like matrix fracture contributed to a high toughness of composites with PyCN and PyCX matrices. Relatively low strength and toughness were obtained for the pitch-derived carbon. The change of TC with the matrix type was consistent with the graphitization degree and apparent crystallite height. The highest in-plane and out-of-plane TC reached 148.2 and 75.4 W/(m·K), respectively, for the PyCX matrix, which was due to its carbon layers having the highest preferred orientation. The chaotic structure and large number of defects of the resin-derived carbon produced a relatively low TC. PyCN was the most suitable matrix for composites with excellent mechanical properties. PyCX should be used to improve the TC and toughness of the low-cost composites.
Synthesis of a hydroxylamino-modified silicone oil for use in a polyacrylonitrile oil emulsion in carbon fiber production
LI Jian-hua, JIANG Yan-bo, WANG Zhen-yu, GUO Jia-dong, JIA Hong-fei, GAO Ai-jun, LI Zhi-yao, TANG Jun, YANG Chun-cai
2020, 35(5): 585-590. doi: 10.19869/j.ncm.1007-8827.20190135
Abstract(736) PDF(180)
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In order to prepare a stable oil emulsion suitable for polyacrylonitrile (PAN) in carbon fiber production, a hydroxylamino-modified silicone oil (HA-PDMS) was synthesized by a three-step procedure and mixed with a commercial epoxy-modified silicone oil in water to prepare an oil emulsion of PAN (P-OE) in carbon fiber preparation. The structure of the intermediate products and P-OE were analyzed by FT-IR and 1H-NMR. The major properties of P-OE were investigated by a laser particle size analyzer, thermogravimetric analyzer and surface tension instrument and compared with those of the commercial one used in Japan (J-OE). The polyacrylonitrile solution in dimethyl acetamide was drawn by wet spinning and impregnated in P-OE and J-OE to obtain P-PAN and J-PAN, respectively, which were carbonized to obtain carbon fibers P-CF and J-CF. The Roder friction coefficient, hairiness and tensile strength of P-PAN, J-PAN, P-CF and J-CF were tested to compare the performance of the two kinds of oil emulsions for use in PAN-based carbon fiber production. Results show that the tensile strength of P-PAN is higher than that of J-PAN. Compared with J-CF, the tensile strength and tensile modulus of P-CF are higher and the hairiness is greatly reduced. P-OE is superior to J-OE for the use as an oil emulsion of PAN in production of PAN-based carbon fibers.
Polymerization kinetics and control of the components of a mesophase pitch
LIANG Zheng-wu, LU Yong-gen, SUN Zhu-lin, LUO Han
2020, 35(5): 591-598. doi: 10.1016/S1872-5805(20)60512-1
Abstract(516) PDF(164)
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It is important to increase the content of pyridine soluble in mesophase pitch to improve its spinnability. A naphthalene isotropic pitch was used as the raw material to prepare mesophase pitch by polymerization. The components of the polymerized products were analyzed by solvent extraction with benzene and pyridine, and classified as benzene soluble (BS), pyridine insoluble (PI) and benzene insoluble but pyridine soluble (BI-PS). The effects of polymerization temperature, time and the components of the raw material on the distribution of the components and optical texture of the mesophase pitch were investigated. The reaction kinetic constants were calculated assuming a consecutive reaction from BS to BI-PS, then to PI. Results show that a mesophase pitch with a relatively uniform distribution of components is obtained after reaction at 430 oC for 20 h from an isotropic pitch pre-polymerized at 400 oC for 10 h. The mesophase pitch synthesis reaction has a significant auto-acceleration effect in that the reaction rate constant of a heavy component is larger than a light one. The reaction rate becomes faster and faster as the molecular weight of the pitch increases in the latter stage of the synthesis reaction. Therefore, the initial component of raw pitch, reaction temperature and time have a decisive influence on the distribution of components in the mesophase pitch.
Formation of mesophase from the components of high temperature coal tar pitch
XU Lei, WANG Xiang-jun, YANG Tao, CHI Yong-qing, SONG Yan, SONG Huai-he, LIU Zhan-jun
2020, 35(5): 599-608. doi: 10.19869/j.ncm.1007-8827.20190161
Abstract(961) PDF(229)
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High temperature coal tar pitch was extracted with n-hexane, toluene and pyridine to produce a N-heptane-soluble component (HS), a N-heptane insoluble-toluene soluble component (HI-TS), a toluene insoluble-pyridine soluble component (TI-PS) and a pyridine insoluble component (PI). Mesophase pitch was prepared by direct thermal polycondensation using HS, HI-TS, TI-PS as the raw materials. Polarizing microscopy was used to observe the microstructure of the three mesophases, and their contents were measured by extracting thermal polycondensation products with tetrahydrofuran. Results showed that with increasing reaction temperature from 400℃ to 460℃, the HS tends to form mesophase pitch with larger anisotropic domains while the HI-TS and TI-PS produce flow-textured and mosaic structures with mesophase contents above 90%.
Preparation of visible-light photocatalysts of Bi2O3/Bi embedded in porous carbon from Bi-based metal organic frameworks for highly efficient Rhodamine B removal from water
SONG Chi, WANG Lin-jie, SUN Si-miao, WU Ying, XU Li-jie, GAN Lu
2020, 35(5): 609-618. doi: 10.1016/S1872-5805(20)60513-3
Abstract(784) PDF(156)
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A series of ternary composite photocatalysts of Bi2O3/Bi embedded in porous carbon (Bi2O3/Bi/PC) was prepared by the high-temperature pyrolysis of a bismuth-based metal organic framework (CAU-17(Bi)). They were used as photocatalysts for the degradation of organic Rhodamine B dye (RhB) in water under visible light. Results showed that the Bi2O3/Bi/PC composites with different Bi2O3/Bi ratios could be obtained through changing the extent of the carbothermal reduction of Bi2O3 during pyrolysis. The photocatalyst pyrolyzed at 800 oC showed the highest photocatalytic performance and had a wide applicable pH value range and excellent recyclability and stability. The components in the ternary composites exhibited a synergetic effect in the remova l of RhB, where Bi2O3 acted as a low-band gap semiconductor, metallic Bi transferred electrons generated by visible light excitation to the graphitic structure in porous carbon to inhibit the recombination of electrons with holes. The holes and peroxide radicals were the main active species. This study provides a new way for the design and preparation of visible-light active and high-performance photocatalysts for organic contaminant degradation in aqueous media by using metal organic frameworks as a multicomponent precursor.