新型炭材料

Graphene-based macroform: preparation, properties and applications

ZHANG Li-fang1, 　WEI Wei1

2013, 28(3): 161-171.

Abstract(1572)

PDF(3080)

Abstract:
The graphene-based macroform (GM) is a new category of macroscopic carbon materials assembled from graphene nanosheets. It possesses superior physical and chemical properties inherited from individual graphene nanosheets, and moreover, has a tunable micro-texture and controlled macro-morphology, which is useful in various areas. In this paper, different macroscopic forms and preparation methods of GM are reviewed, where the self-assembly method is highlighted. The physical and chemical properties of GM are briefly introduced, and the potential applications including energy storage and conversion, catalysis, bio-medicine and other aspects are discussed in detail. Finally, the opportunities and challenges of research and applications of GM are commented on, and it is concluded that the assembly of graphenes into fibers, films and blocks is an effective strategy towards their practical applications.

Preparation and electrochemical performance of a CuO/graphene composite

DING Xiang

2013, 28(3): 172-177.

Abstract(1319)

PDF(2504)

Abstract:
Graphene oxide was synthesized from expanded graphite powder by a simple one-step oxidation method. A CuO/graphene composite was then obtained using a hydrothermal method. The samples were characterized using AFM, XRD, SEM, TEM and electrochemical measurements. Results show that CuO acts as a spacer to prevent the agglomeration of graphene sheets. The graphene formed a 3D conducting network for fast electron transfer, as well as space to accommodate the volume expansion/contraction of CuO during the discharge/charge process. The CuO/graphene composite exhibits enhanced electrochemical performance compared with pure CuO and graphene, such as improved initial coulombic efficiency (69.9%) and a reversible capacity of 748.3 mAh/g with 81.3% retention after 50 cycles.

Preparation of corn starch-based monolithic porous carbons

YU Chang

2013, 28(3): 178-183.

Abstract(1270)

PDF(1187)

Abstract:
Corn starch-based monolithic porous carbons were prepared by gelatinization of corn starch with or without nickel acetate as a structure modifier, followed by freeze drying and carbonization. The effect of gelatinization parameters such as the concentrations of the starch and addition of nickel acetate on the pore structures of the monoliths was investigated. It was found that the crystallinity of the gelled starch was lower than that of the pristine starch. The concentrations of the starch and nickel acetate simultaneously had an important influence on the pore structure of the gelled starch and the porous carbon monoliths produced. The gelled starch or Ni-doped gelled starch can be obtained using a 10 mass% starch concentration without or with the addition of 0.1 mol/L nickel acetate. The carbon monoliths derived from the Ni-doped or undoped gelled starch had a semi-closed or open pore structure. The semi-closed pores resulted from a severe volume contraction of nearly 80% with the addition of nickel acetate.

Electromagnetic wave absorbing properties of multi-wall carbon nanotube/Fe₃O₄ hybrid materials

HOU Cui-ling

2013, 28(3): 184-190. doi: 10.1016/S1872-5805(13)60075-X

Abstract(1566)

PDF(1442)

Abstract:
Multi-wall carbon nanotube/Fe₃O₄ hybrids were prepared by a chemical synthesis-hydrothermal treatment method and their electromagnetic wave absorbing properties were investigated in the frequency range of 8.2-12.4 GHz (X band). As-prepared hybrids were characterized by transmission electron microscopy, X-ray diffraction and vibrating sample magnetometer. Results indicated that the surface of multi-wall carbon nanotubes was attached to magnetic Fe₃O₄ nanoparticles. The Fe₃O₄ content increased and the magnetism of the hybrids was enhanced by increasing the concentrations of Fe²⁺ and Fe³⁺ in solution. The minimum reflection loss (-18.22 dB, 12.05 GHz) was the lowest and the absorbing bandwidth was the widest when the concentrations of Fe²+ and Fe³⁺ were 0.02 and 0.04 mol/L, respectively.

Formation of carbon nanotubes catalyzed by rare earth oxides

SONG Jin-ling1, 2, 　ZHAO Jiang-hong2

2013, 28(3): 191-198. doi: 10.1016/S1872-5805(13)60076-1

Abstract(1277)

PDF(997)

Abstract:
Multi-wall carbon nanotubes (MWCNTs) were synthesized by detonation-assisted chemical vapor deposition using a series of rare earth (RE) oxides as catalysts. Energy dispersive X-ray spectroscopy, selected area electron diffraction and powder X-ray diffraction show that the catalysts, usually located outside the MWCNTs, have not been reduced, in sharp contrast to conventional catalysts in the form of metals or carbides. With the help of intermediate objects found in TEM images, it is proposed that the formation of MWCNTs follows a particle-wire-tube step-wise evolution mechanism. The RE oxides may play a major role in promoting the self-assembly of anisotropic carbon nanoparticles into a 1-D structure, and the cavities in the tubes evolve through structure self-reorganization and crystallization of the particles.

Functionalization of carboxylated multi-wall carbon nanotubes with 3,5-diphenyl pyrazole and an investigation of their toxicity

Hasan Tahermansouri1|　Esmail Biazar2

2013, 28(3): 199-207. doi: 10.1016/S1872-5805(13)60077-3

Abstract(1413)

PDF(998)

Abstract:
Carboxylated multi-wall carbon nanotubes (MWCNT-COOH) were first modified by 1,3-diphenylpropane-1,3-dione to form a MWCNT-ketone and then by hydrazine to produce MWCNT-pyrazole. All modified samples were characterized by FT-IR, Raman spectroscopy, SEM, elemental analysis, TGA, DTG. Their interactions with living cells were investigated. The toxicity of the samples was evaluated with unrestricted somatic stem cells and viable cell numbers were measured by reduction of living cells with 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. Results indicated that there is one diketone group in MWCNT-ketone and one 3,5-diphenyl pyrazole group in MWCNT-pyrazole per 28 and 72 carbon atoms of MWCNTs, respectively. MWCNT-ketone had the lowest toxicity in all samples investigated.

Preparation of an anti-oxidative SiC/SiO₂ coating on carbon fibers by a sol-gel method

XIA Ke-dong1, 2

2013, 28(3): 208-214.

Abstract(1313)

PDF(1072)

Abstract:
A SiC/SiO₂ ceramic coating on carbon fibers was prepared by a sol-gel method followed by heat treatment at high temperature. The structure and the morphology of the SiC/SiO₂ coating were characterized by X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. The oxidation resistant properties of the carbon fibers with and without the coating were compared by thermogravimetric analysis. Results indicate that a uniform and continuous coating can improve the oxidation resistance of carbon fibers. The oxidation resistance of the coated carbon fibers increased with increases in the sol concentration and heat treatment temperature. A coating of thickness 300 nm increased the onset oxidation temperature by about 200℃ and the single fiber tensile strength was decreased by 37.7% compared with the pristine carbon fibers. After isothermal oxidation at 700℃ for 90 min, the single fiber tensile strength of the coated carbon fibers was decreased to 1.37 GPa. The oxidation resistance of the fibers was decreased when the coating thickness exceeded 400 nm due to the spallation of the coating.

Properties of plasma-spray coated hydroxyapatite on carbon/carbon composites pretreated by an argon plasma

NI Xin-ye1

2013, 28(3): 215-221.

Abstract(1193)

PDF(1100)

Abstract:
Carbon/carbon composites pretreated by an argon plasma were coated by hydroxyapatite (HA) using a plasma spraying method. The morphology, the compositions of the coating and bond strength between HA and substrate were investigated by scanning electron microscopy, X-ray diffraction, infrared spectrometry and a scratching test. Results indicate that although the morphology and phase compositions of the HA coating are similar, the substrate critical load, above which apparent spallation of the coating occurs, was 14.0 and 8.9 N with or without the pretreatment respectively, indicating that the argon plasma pretreatment improves the bond strength between the coating and the substrate.

Effect of Al content in an Al/Si layer on the oxidation behavior of the Mo/Si-Al/Si double-layer coated C/C composites at 1370℃

LAI Zhong-hong1, 2

2013, 28(3): 222-227.

Abstract(1186)

PDF(862)

Abstract:
A Mo/Si slurry was coated onto the surface of Al/Si-coated carbon fiber reinforced carbon (C/C) composites and vacuum-sintered to form a fused double-layered coating. The effect of the Al content (6 and 10 mass%) in the Al/Si layer on the oxidation resistance of the composites was investigated. Results indicate that the presence of Al effectively prevents liquid Si infiltration into the composites. The composite with the 10 mass% Al has a much lower oxidation resistance than that with the 6 mass% Al. It is revealed that when the Al content is 10 mass% an Al phase dispersed around MoSi₂ grains is found in the Mo/Si layer, which decreases the oxidation resistance of the composite at 1370℃. This can be ascribed to voids generated within the Mo/Si layer due to the outward diffusion of Al and pores in Al₂O₃ formed during oxidation, which provide paths for oxygen diffusion.

Characterization and dispersion of carbon spheres modified by HNO₃/H₂O₂ oxidization in water

GUO Xing-mei1, 　LIU Hai-xing1, 　YANG Yong-zhen2

2013, 28(3): 228-234.

Abstract(1250)

PDF(1084)

Abstract:
Carbon spheres (CSs) were modified by a mixture of HNO₃ and H₂O₂ with different volume ratios and concentrations to improve their dispersability in a liquid. The morphologies and microstructures of the modified CSs were characterized by field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectrometry and acid-base titration. Results show that the amount and types of oxygen-containing groups can be tuned by the concentration and ratio of HNO₃/H₂O₂. HNO₃ favors the formation of carboxyl and carbonyl groups while H₂O₂ introduces mainly hydroxyl. The amount of oxygen-containing functional groups increases with the concentration of the oxidants when the volume ratio of HNO₃/H₂O₂ is 1, which is as high as 2.164 mmol/g when the concentrations of HNO₃ and H₂O₂ are 16 and 8.8 mol/L, respectively. The resulting CSs have a remarkable dispersability and stability in water.

The production of high surface area porous carbonaceous materials from polysiloxane

DUAN Li-qun, 　MA Qing-song, 　CHEN Zhao-hui

2013, 28(3): 235-240. doi: 10.1016/S1872-5805(13)60078-5

Abstract(1265)

PDF(1164)

Abstract:
Nanoporous carbonaceous materials with high surface area were prepared by the pyrolysis of polymethyl(phenyl)siloxane resin (SR249) under vacuum at a controlled temperature (1250-1350℃) followed by leaching in hydrofluoric acid (HF). Their compositions and structures at different pyrolysis temperatures were investigated by X-ray diffraction, Raman spectroscopy, elemental analysis, transmission electron microscopy and N₂ adsorption. The SiO₂ phase in the pyrolysis products was regarded as a natural template and could be leached away by HF. The pyrolysis temperature and leaching had important effects on the compositions and structures of the carbonaceous materials. Their specific surface areas were very low (<55m²/g) before leaching, but the specific surface area and total pore volume increased significantly after leaching, and could be as high as 1148m²/g and 0.608cm³/g, respectively when pyrolysis was carried out at 1300℃. The pore size of all the samples after leaching was in the narrow range of 1-4nm. TEM showed that the free carbon phase, SiC nanocrystallines and silicon oxycarbide ceramics wrapped each other.

2013 Vol. 28, No. 3

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