2012 Vol. 27, No. 04

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Preparation of oriented graphite/polymer composite sheets with high thermal conductivities by tape casting
ZHOU Shao-xin1, 2, 　ZHU Yuan1, 　DU Hong-da2, 　LI Bao-hua2, 　KANG Fei-yu1
2012, 27(04): 241-249. doi: DOI: 10.1016/S1872-5805(12)600
Abstract(1889) PDF(1265)
Abstract:
Oriented graphite/polymer composite sheets were prepared using natural, crystalline flake graphites as raw materials, polyvinyl butyral as binders, polyethylene glycol and dibutyl phthalate as plasticizers by a tape-casting method at room temperature. The dependences of the binder contents and the blade heights on the orientation of the composite sheets were studied, and the effect of the orientation on the thermal conductivity was investigated. X-ray diffraction patterns and scanning electron microscope images showed that as-prepared samples showed different degrees of orientation. The thermal conductivity increased with the degree of orientation. The highest thermal conductivity of 490 W/(m · K) could be achieved by optimizing the binder contents and the blade heights.
Preparation of graphene-supported Pt-Co nanoparticles and their use in oxygen reduction reactions
MA Yan-wen1, 2
2012, 27(04): 250-257. doi: 10.1016/S1872-5805(12)60016-X
Abstract(2164) PDF(1007)
Abstract:
Electrocatalysts of graphene-supported Pt-Co alloy nanoparticles (Pt-Co/G) were prepared by a simultaneous reduction of mixtures of graphene oxide and Pt(IV), Co(II) ions with ethylene glycol assisted by a microwave and further H2 treatment at 300 ℃. As-prepared Pt-Co/G catalysts were characterized by transmission electron microscopy, energy-dispersive X-ray spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy. The Pt-Co binary alloy nanoparticles with a size of 3-8 nm were homogeneously dispersed on the graphene. Compared with the monometallic Pt/G and commercial Pt/C catalysts, the Pt-Co/G catalysts have a high stability and increased electrocatalytic activity that is conducive for the oxygen reduction reaction, suggesting their potential application in fuel cells.
Synthesis of nitrogen-doped graphene and its catalytic activity for the oxygen reduction reaction in fuel cells
MA Gui-xiang1, 2, 　ZHAO Jiang-hong1, 　ZHENG Jian-feng1, 　ZHU Zhen-ping1
2012, 27(04): 258-265.
Abstract(2306) PDF(4526)
Abstract:
Graphene was synthesized by the detonation-assisted reduction of graphite oxide (GO) prepared by the modified Hummers method. Nitrogen-doped reduced GO（N-RGO）was obtained through an in-situ nitrogen-doping during detonation. The morphology, elemental composition and structure of the N-RGO were characterized by TEM, SEM, IR, XPS, XRD and Raman spectroscopy. The catalytic activity of the N-RGO as a fuel cell electrode for the oxygen reduction reaction (ORR) was investigated by a rotating ring disk electrode technique. Results showed that the GO was exfoliated and reduced to few layer graphene by the detonation. The oxygen-containing species of GO were reduced and the C/O molar ratio was increased to 26.2, which is much higher than for RGO. Nitrogen, as high as 2.11 at%, was incorporated into the graphene structure. The diffusion-limited current for ORR increased from 0.24 mA for RGO to 0.49 mA for N-RGO, indicating a higher catalytic activity of N-RGO for ORR than that of RGO.
The effect of heat treatment on the electrical conductivity of highly conducting graphene films
WANG Yong-zhen, 　WANG Yan, 　HAN Fei, 　CAI Xiao-lan
2012, 27(04): 266-270.
Abstract(2108) PDF(1345)
Abstract:
Graphene oxide films were prepared by the modified Hummers method, which includes sonication, aggregation and self-assembly. The graphene films were obtained by vacuum heat treatment of the graphene oxide films. XRD, SEM, FTIR and Raman spectroscopy were used to investigate the microstructure evolution of the films during preparation. It is found that self-assembly is a simple method to produce graphene oxide films with controllable size and perfect stacks of graphene oxide layers. Heat treatment gives the graphene films high electrical conductivities. The electrical conductivity of the films increases up to 536S/cm with increasing heat treatment temperature under vacuum.
Dispersion of expanded graphite as nanoplatelets in a copolymer matrix and its effect on thermal stability, electrical conductivity and permeability
Gyanaranjan Prusty1, 　Sarat K Swain1, 2
2012, 27(04): 271-277. doi: 10.1016/S1872-5805(12)60017-1
Abstract(2882) PDF(1164)
Abstract:
Expanded graphite/polyacrylonitrile-co-poly (methyl methacrylate) (EG/PAN-co-PMMA) composites were prepared by the incorporation of EG at various concentrations (1, 2, 3, and 4%, w/w) into PAN-co-PMMA by an in situ emulsifier-free emulsion polymerization method. As-synthesized composites were characterized by UV/VIS and FT-IR, XRD, SEM, TEM and TGA. The thermal stability of the copolymer was significantly improved by the addition of EG. The oxygen permeabilities of the composites were substantially reduced and the electrical conductivities of the composites were significantly increased by increasing the EG content.
The performance of dye-sensitized solar cells using different carbon materials as counter electrodes
FENG Jun
2012, 27(04): 278-282.
Abstract(1861) PDF(1126)
Abstract:
Counter electrode films for dye-sensitized solar cells (DSSCs) were prepared by screen printing using graphite, activated carbon, carbon black and carbon nanotubes (CNTs) as raw materials. The effects of pore structure, BET surface area and the sheet resistance of the as-prepared counter electrode films on the performance of DSSCs were investigated. Results show that the conductivity of the raw materials is not the crucial factor for the performance of the DSSCs. The performance of the DSSC is not directly improved by increasing the BET surface area of the raw materials. It is also related to the pore size distribution of carbon materials, the particle shape and their alignment. The DSSCs assembled using CNT film counter electrodes with a BET surface area of 31.163 m2 · g-1 show the largest photoelectric conversion efficiency of 5.87%.
Effect of the addition of carbon black and carbon nanotubes on the structure and oxidation resistance of pyrolysed phenolic carbons
LIANG Feng
2012, 27(04): 283-287. doi: 10.1016/S1872-5805(12)60018-3
Abstract(2583) PDF(975)
Abstract:
Carbon black (CB) and carbon nanotubes (CNTs) were used as additives in phenolic resin. The effects of the additives and heat treatment temperature on the oxidation resistance and structure of carbon from the pyrolysed phenolic resin were investigated by differential scanning calorimetric analysis, X-ray diffraction, scanning electron microscopy, and mercury intrusion porosimetry. It was observed that both CNTs and CB improved the graphitization degree and oxidation resistance of the pyrolytic carbons. The graphitization degree of carbons containing CNTs was higher than that of those with CB, but the oxidation resistance of the former was lower due to the higher porosity in the microstructure. An increase in the heat treatment temperature also resulted in an improvement in the graphitization degree and oxidation resistance of the carbons.
Evolution of the skin-core structure of PAN-based carbon fibers with high temperature treatment
SU Can-jun
2012, 27(04): 288-293.
Abstract(1981) PDF(982)
Abstract:
PAN-based carbon fibers were subjected to high temperature heat treatment (HTT) at 1500-2500℃ and the evolution of the skin-core structure of the carbon fibers was investigated by elemental analysis, XRD, TEM and Raman spectroscopy. Results showed that nitrogen content and d002 decreased, and carbon content and La increased with HTT temperature. La increased sharply with temperature above 1900℃. The Raman spectra taken at four points in radial directions indicated that the intensity of the G band at the skin was stronger than at the core with no change in peak position at 1700℃. However, the G peak position decreased from 1588.2 to 1582.2cm-1, the width of the G band at half maximum intensity decreased from 46.3 to 28.9 and that of D band from 46.9 to 36.7cm-1 from core to skin after HTT at 2500℃. The differences of microstructure in the core and skin at different temperatures are related closely to the differences in nitrogen removal efficiency and temperature. At temperatures below 1900℃, nitrogen near the skin is more easily removed due to a shorter diffusion path and a higher temperature on the skin, leading to a slower increase of La with temperature on the skin than in the core. At temperatures above 1900℃, nitrogen is removed completely and graphitization on the skin is more rapid than in the core, leading to a large skin-core difference with the skin portion having a high modulus and the core portion a high strength.
Preparation of activated carbons by ZnCl2 activation from herb residues under vacuum
YANG Juan
2012, 27(04): 294-300.
Abstract(1990) PDF(1008)
Abstract:
Activated carbons were prepared by ZnCl2 activation from herb residues under an absolute pressure of 30kPa and the Doehlert matrix was used to optimize activation temperature and impregnation ratio based on adsorption capacities of methylene blue and iodine by the activated carbons. Results showed that activation temperature and impregnation ratio had little effect on the total yield of the activated carbons. The activation temperature had a greater influence than the impregnation ratio in methylene blue and iodine adsorption. The optimized activated carbon was obtained under an activation temperature of 474℃ and an impregnation ratio of 1.225, and had a methylene blue value and an iodine value of 316 and 994mg · g-1, respectively. The experimental values agree well with those calculated from the Doehlert model. The activated carbon optimized in this study had a higher adsorption capacity compared with commercial ones.
Synthesis of ordered mesoporous carbon with dual templates as structure directing agents
ZHANG Yu, 　WANG Tong-hua
2012, 27(04): 301-306.
Abstract(1907) PDF(925)
Abstract:
Ordered mesoporous carbons were prepared by pyrolysis of polymer blends, which were formed by the organic-organic self-assembly of resorcinol-formaldehyde pre-polymers and tri-block copolymers under acidic conditions. The tri-block copolymer mixtures of F127 and P123 were used as structure-directing agents. The samples were characterized by X-ray diffraction, transmission electron microscopy and nitrogen adsorption. Results show that the degree of order of mesoporous carbons exhibits a maximum with increasing holding time from 24 to 72h. When the molar ratio of the F127 to P123 is 1, the mesoporous carbon obtained has the most ordered hexagonal mesostructure (P6mm), with a typical BET surface area of 640.34m2/g, pore size of 3.68nm and pore volume of 0.59cm3/g.
Intermittent growth of a diamond film by direct current hot cathode plasma chemical vapor deposition
JIANG Hong-wei, 　HUANG Hai-liang, 　JIA Xiang-hua, 　YIN Long-cheng
2012, 27(04): 307-310.
Abstract(1709) PDF(749)
Abstract:
A diamond film was intermittently prepared by direct-current (DC) hot-cathode plasma chemical vapor deposition (PCVD). The intermittent growth was carried out by alternating deposition under methane flow for 20 min and etching for 10 min without methane flow. For comparison, a diamond film was continuously prepared under the same growth conditions without etching. Scanning electron microscopy, Raman spectroscopy and XRD were used to characterize surface morphology, texture and purity of the two diamond films. Results indicated that the diamond film produced by the intermittent growth had smaller amounts of non-diamond phase and its grains were more uniform than that produced by the continuous growth without etching. Amorphous carbon and graphite formed during deposition on the surface of the diamond film can be reduced by etching.
Effect of hafnium carbide content on the ablative performance of carbon/carbon composites as rocket throats
LI Shu-ping1
2012, 27(04): 311-314.
Abstract(2222) PDF(982)
Abstract:
Hafnium carbide (HfC) modified carbon/carbon (HfC-C/C) composites were prepared by impregnating carbon felts with a saturated HfOCl2 · 8H2O ethanol solution and heat treating at 600℃ to form HfO2/C composites that were then densified with pyrocarbon by chemical vapor infiltration and graphitized at 2 100℃ to convert HfO2 into HfC. The HfC-C/C composites as rocket throats were ablated at 7 MPa and around 3 200℃ for 3 s by an experimental solid rocket motor. Results showed that the HfC-C/C composites with HfC contents more than 5.7 mass% had a stable period with a constant ablation rate and the duration of this period increased with HfC content. The overall ablation rate was decreased by 25.2 and 49.6% for the composites having 5.7 and 8.7 mass% HfC respectively as compared with the composite with 2.5 mass% HfC.
How will carbon material lead to a low carbon society ----A review of Carbon 2012
LIU Xu-guang1, 2
2012, 27(04): 315-318.
Abstract(1726) PDF(1460)
Abstract:
A review is given of the Annual World Conference on Carbon, which was held on June 17-22, 2012 in Krakow, Poland and organized by the Polish Carbon Society. In this conference, 5 plenary lectures, 30 keynote lectures, 220 oral presentations and 465 posters were divided into 10 topics, i.e., carbons for energy storage; carbons for health and environmental protection; precursors, processing and technology; carbon nanomaterials; porous carbons; carbon-based composites; graphene; new methods for carbon characterization; computation and modeling; and industrial news. Besides traditional modification on surface area and porosity, doping with hetero atoms such as N, B and P or compositing with metals or metal oxides have been developed into effective means for modifying carbon materials for improved adsorption, catalysis and energy-storage performance. The applications of novel carbon structures like nanotubes are still limited by the controllable and scalable preparation, processability and reactivity. Research on the structure and properties of graphene is moving from curiosity-oriented to application-oriented. Mathematical formulation or modeling of pore structures has been promoted by the progress in characterization methods. The modification of the surface/interface in carbon materials, which plays important roles in determining their physical, chemical or mechanical properties is still a focus of research activity in carbon materials.
A brief overview of the Tenth Cross-Strait Symposium on Carbon Materials
LI Jia
2012, 27(04): 319-320.
Abstract(1522) PDF(1279)
Abstract:
The Tenth Cross-Strait Symposium on Carbon Materials was held in Baotou City, Inner Mongolia, P. R. China from Aug. 1 to 4, 2012. It was hosted by Tsinghua University and Inner Mongolia University of Science & Technology. More than 60 cross-strait carbon scientists participated in the conference, and 31 presentations were given, including 15 keynote talks and 16 oral presentations. The presentations were classified into the following eight topics: highly efficient conversion and applications of coal, carbon fibers and carbon-based composites, special carbon-graphite materials, nano-structured carbons and their applications, carbon materials for energy storage, preparation and applications of graphene, evaluation and performance of new carbon materials, and other new carbon materials. The four-day symposium has increased cross-strait academic exchange and has advocated close academic cooperation in the field of carbon materials.

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