2010 Vol. 25, No. 05

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Preparation of zeolite/carbon foam monolithic composites with a hierarchical structure
XIAO Nan, LING Zheng, WANG Liu-ping, ZHOU Ying, QIU Jie-shan
2010, 25(05): 321-324.
Abstract(2589) PDF(1483)
Abstract:
T-type zeolite/carbon foam composites with a hierarchical structure were prepared by carbonizing polyurethane foam impregnated with a mixture of polyamic acid and T-type zeolite. The carbonization was conducted at 900℃ in flowing nitrogen. The as-prepared composites were examined using SEM, XRD and N2 adsorption techniques. It has been found that the foam-like monolith consists of open cells with an average size of ca. 500μm, and T-type zeolites are anchored on the cell walls of the foam with their structure remaining unchanged even after heat treatment at 900℃. The zeolite/CF composites with a BET surface area of 328m2/g are microporous, and have a narrow pore size distribution centered at 0.45 nm.
Carbon microtubes produced from coconut oil
S. Paul, S. K. Samdarshi
2010, 25(05): 325-328. doi: 10.1016/S1872-5805(09)60036-6
Abstract(1732) PDF(1456)
Abstract:
The synthesis of a new class of carbon with tubular morphologies is reported. Carbon microtubes (CMTs), having a high aspect ratio were prepared from a natural renewable precursor (coconut oil) by chemical vapor deposition. The CMTs were synthesized in a nitrogen atmosphere at a temperature of 1 175 ℃ and at a flow rate of 100 mL/min using ferrocene as catalyst. The synthesized CMTs were characterized by SEM, EDX, TEM, and Raman spectroscopy. The internal diameters of the tubes are around one micron and the external diameters were in the range of 1. 7 μm to 2. 1 μm.
Preparation and characterization of carbon/carbon aircraft brake materials with long service life and good frictional properties
SU Jun-ming, XIAO Zhi-chao, LIU Yong-qiong, MENG Fan-cai, PENG Zhi-gang
2010, 25(05): 329-334. doi: 10.1016/S1872-5805(09)60037-8
Abstract(2187) PDF(2415)
Abstract:
A320 series aircraft carbon/carbon brake materials were prepared by processing a needle-punched carbon fiber preform with quasi-three-dimensional integrity. The preform was first impregnated with a resin and heated to 800℃ to convert the resin to carbon. This was followed by chemical vapor infiltration (CVD) using propylene as the source gas and a radial thermal gradient ("external heating, internal cooling" or "internal heating, external cooling"). For the CVD process the performs were separated by graphite pads to allow free flow of propylene along the channels thus formed. The final brake discs were obtained by a further hightemperature treatment from 1600-2400℃. These carbon brake discs were compared with the advanced discs made abroad in terms of ground test and service performance. The two kinds of carbon brakes have the same friction coefficients under the designed landing energy and overload energy braking condition for A320 airplanes. Especially, under the aborted take-off condition, the friction coefficient of the domestically developed carbon brake disc was 21-48% higher and the static friction coefficient was 28% higher than that of the ones provided by the aircraft manufacturer. The average brake service life exceeds 2700 landings, 24% times larger than the original ones.
Microstructure of the pyrocarbon in aligned carbon nanotube/carbon composites
LI Zhi, GONG Qian-ming, WANG Ye, WU Jian-jun, LIANG Ji
2010, 25(05): 335-342.
Abstract(2963) PDF(1446)
Abstract:
Aligned carbon nanotube reinforced carbon matrix (ACNT/C) composites were fabricated by densifying an ACNT preform with chemical vapor infiltration (CVI) and their microstructure was investigated by XRD, SEM, HRTEM, polarized light microscopy and Raman spectroscopy. Results show that the pyrocarbon in ACNT/C composites was of mainly rough lamella type, while that in traditional carbon/carbon composites obtained using the same process was of typically smooth lamella type with a larger interlayer spacing and a smaller layer stack height. Pyrocarbon around CNTs shows a clear annular graphiticlayered microstructure with good interfacial bonding between CNTs and pyrocarbon. This might be ascribed to the intermolecular interaction between CNTs and aromatic molecules, i.e., CNTs have abundant radial delocalized conjugated π-π electrons, which can attract polynuclear aromatic molecules with a similar structure through van der Waals forces. These polynuclear aromatic molecules are therefore oriented around the CNT outer surface under a "soft epitaxy" mechanism. In contrast, carbon fibers composed of turbostratic carbon have no such effect during CVI.
High temperature thermophysical properties of carbon/carbon composites prepared by chemical liquid-vapor deposition
LIU Xiao-rong, JIN Ming-lin, ZHANG Zhuo, YANG Jun-he, OU YANG Chun-fa
2010, 25(05): 343-347.
Abstract(1789) PDF(1230)
Abstract:
To reduce the cost and shorten the production time of carbon/carbon (C/C) composites for high speed train brakes, C/C composites were prepared from preforms made of polyacrylonitrile-based preoxidized fibers. They were densified by rapid chemical liquidvapor infiltration followed by cycles of impregnation-carbonization and graphitization at 2300℃. Thermophysical properties of the composites at temperatures from 30 to 800℃ were investigated. Results showed that the thermal diffusivities of the C/C composites decreased nonlinearly with temperature both in parallel (X-Y) and perpendicular (Z) directions to the side of the preforms, while the specific heat increased nonlinearly with temperature. The thermal conductivity was anisotropic. In the X-Y direction it exhibited a maximum value of 186. 7W · m-1 · K-1 at 200℃, but in the Z direction it remained almost unchanged with temperature. The maximum thermal conductivity in the X-Y direction was 5. 8 times higher than in the Z direction. It was found by analyzing the Wiedemann-Franz ratio that thermal conduction in the C/C composites might be dominated by phonons at low temperature and by electrons at high temperature.
Photoelectrocatalytic properties of Ag-CNT/TiO2 composite electrodes for methylene blue degradation
ZHANG Feng-jun, CHEN Ming-liang, OH Won-chun
2010, 25(05): 348-356. doi: 10.1016/S1872-5805(09)60038-X
Abstract(1811) PDF(2035)
Abstract:
Carbon nanotubes modified with silver (Ag-CNTs) were used for the fabrication of Ag-CNT/TiO2 composite electrodes. The electrodes were characterized by X-ray diffraction, transmission and scanning electron microscopy, and energy dispersive Xray analysis. It was found that TiO2 particles were distributed uniformly in the CNT networks, and silver particles were fixed on the surface of the CNTs. . The composite electrodes exhibited a high photoelectrocatalytic (PEC) activity. The PEC degradation efficiency for methylene blue (MB) was a synergistic effect of photodegradation of TiO2, increased electrical conductivity by the CNT networks, an effect of the silver and a function of the applied potential. Especially, the composites treated with silver revealed an enhanced photo-degradation ability for MB and the PEC activity increased with increasing silver content.
The influence of gas pressure and bias current on the crystallinity of highly boron-doped diamond films
JIA Fu-chao, BAI Yi-zhen, QU Fang, SUN Jian, ZHAO Ji-jun
2010, 25(05): 357-362. doi: 10.1016/S1872-5805(09)60039-1
Abstract(2031) PDF(1462)
Abstract:
Highly boron-doped diamond (BDD) films were deposited by hot filament chemical vapor deposition on a silicon substrate with different gas pressures and bias currents. The surface morphology and the structure of the diamond films were analyzed by scanning electron microscopy, Raman spectroscopy, and X-ray diffraction. Results indicated that the quality of the highly BDD films tended to be improved when the gas pressure decreased from 3 to 1. 5kPa, whereas they showed an opposite trend with a further decrease of the gas pressure from 1. 5 to 0. 5 kPa. An appropriate bias current (3A) was favorable in improving the qualities of the diamond films and a higher bias current led to an increase of the non-diamond phase in the films.
Gold nanocluster-enhanced electrochemical activity of a phosphorus-doped tetrahedral amorphous carbon film
LIU Ai-ping, ZHU Jia-qi, HAN Jie-cai
2010, 25(05): 363-369.
Abstract(2111) PDF(1436)
Abstract:
An electrochemical electrode of a phosphorus-doped tetrahedral amorphous carbon film modified with gold nanoclusters (Au/ta-C∶P) was prepared by electrodepositing gold nanoclusters on the surface of ta-C∶P film synthesized by filtered cathodic vacuum arc technology. The microstructure, surface morphology and electrochemical behavior of ta-C∶P and Au/ta-C∶P films were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy and electrochemical voltammetry. Results indicated that a pulse bias of -80V was favorable for doping phosphorus into the carbon network to improve the electrical conduction and electrochemical activity of the film. Furthermore, gold nanoclusters increased the effective surface area of the ta-C∶P electrode, enhanced the activity and reversibility towards the ferricyanide oxidation reaction and improved the activity for the catalytic oxidation of dopamine. All of these revealed the potential applications of ta-C∶P and Au/ta-C∶P films in electroanalysis and biosensors.
Mesoporous carbons derived from citrates for use in electrochemical capacitors
ZHOU Jin, YUAN Xun, XING Wei, SI Wei-jiang, ZHUO Shu-ping
2010, 25(05) doi: 10.1016/S1872-5805(09)60040-8
Abstract(2039) PDF(1425)
Abstract:
Two mesoporous carbons were prepared by simple pyrolysis of commercial magnesium or barium citrate and tested as electrode materials for electrochemical double-layer capacitors (EDLCs), denoted MgC and BaC, respectively. The as-prepared carbon materials were characterized by N2 adsorption, scanning electron microscopy and Fourier transform infrared spectrometry. Nitrogen adsorption measurements demonstrated that the porosity of the prepared carbons was related to the type of metal cation. BaC possesses a typical bimodal pore size distribution (PSD) at 3. 8 and about 15nm, while MgC was between smallsize mesoporous and microporous. The carbons were tested as electrode materials using different electrochemical means such as cyclic voltammetry and constant current charge-discharge. Very high specific capacitance (180F · g-1 for MgC and 171F · g-1 for BaC) was achieved in an ionic liquid electrolyte. BaC proved to be an excellent electrode material with a high rate performance for EDLC application and exhibited an energy density up to 53. 3Wh · kg-1 and a high maximum specific power density of 20kW · kg-1 in IL electrolyte. The good capacitive performance of BaC is attributed to its bimodal PSD and hydrophilic surface properties.
Templated mesoporous carbons and their performance for electric double layer capacitors
WANG Yan-su, WANG Cheng-yang
2010, 25(05): 376-381. doi: 10.1016/S1872-5805(09)60041-X
Abstract(2131) PDF(1459)
Abstract:
Templated mesoporous carbons with high surface area were successfully prepared by the carbonization of a mixture of thermoplastic precursor pitch with MgO precursors (magnesium acetate and citrate) at 950℃ in a N2 atmosphere. The BET surface area of the carbons obtained reached a very high value without any activation process. The carbons were rich in mesopores. The electrochemical performance of mesoporous carbons prepared as electrode materials for electric double layer capacitors were also investigated. Measurement of capacitance was carried out in a mass fraction 30% KOH electrolyte. Results showed that the mesoporous carbons had a high specific capacitance and perfect rate performance. In particular, the sample prepared with a mass ratio of MgO to pitch of 4 for the magnesium citrate template showed a fairly high capacitance, about 284F · g-1 at a current density of 20mA · g-1 and 236F · g-1 at 1000mA · g-1. The impedance of all the capacitors was smaller than 3. 5Ω.
Fluidity of onion-like fullerenes in mice aftera functionalization modification
ZHANG Hong-wei, WANG Yan, WANG Chong-yu, ZHANG Xue-ying, GUO Jun-jie
2010, 25(05): 382-388.
Abstract(1945) PDF(1325)
Abstract:
Water-soluble onion-like fullerene (OLF) derivatives were prepared by chemical bonding of L-cysteine, an important amino acid in organisms, to OLFs. The L-cysteine OLFs were characterized by SEM, XRD, IR, TGA and XPS. Results showed that hydrophilic groups added to the surface of OLFs such as -OH and -NH3 made L-cysteine OLFs good water-soluble derivatives. Experiments in mice demonstrated that the water-soluble fullerene derivatives were well distributed in the histolytic organism because of their excellent solubility and fluidity in humoral liquid.
Properties and preparation of an HClO4-CrO3-Graphite intercalation compound
ZHOU Ming-shan, LIU Li-mei, LI Cheng-jun, TAO Yong
2010, 25(05): 389-394.
Abstract(1815) PDF(1322)
Abstract:
A graphite intercalation compound (GIC) was prepared by the chemical oxidation method using natural graphite flakes, CrO3 and HClO4 as raw materials. The composition and structure of the GIC were characterized and analyzed by FTIR, XRD, TG and the effects of amount of the reactants, reaction temperature and time on the expansion volume of the GIC were investigated. Results showed that the intercalates were ClO4-、Cr2O72- and the biggest expansion volume of 555mL · g-1 was achieved with a weight ratio of natural graphite flakes∶CrO3∶HClO4 being 1∶0. 3∶5, a reaction temperature of 30℃ and reaction time of 60min. The GIC had an excellent vacuum stability and 8mm wave attenuation ability.
The development and prospects of carbon science
—A report on the annual world conference on carbon, Carbon’ 10
ZHANG Qiang
2010, 25(05): 395-399.
Abstract(1845) PDF(1654)
Abstract:
  The annual world conference on carbon, Carbon 2010, was held in Clemson, USA, July 11-16, 2010, and was hosted by the American Carbon Society, Clemson University, and Center for Advanced Engineering Fibers and Films. About 410 attendees from 35 countries participated in the conference, and 510 papers were accepted for presentation, including 4 plenary lectures, 5 award lectures, 32 keynote lectures, 214 oral presentations, and 255 posters, involving 12 topics, namely, graphenes, nanotubes and fullerenes, precursor synthesis and characterization, conversion processes, microstructure and properties, molecular modeling, novel experimental measurements, electronics and sensors, fibers and composites, biology and medicine, environment and safety, energy storage and generation, and other novel uses. Graphenebased materials, molecular simulation of porous carbon, carbon science at the interface with biological systems, and neutron irradiation damage in graphite were the subjects of the plenary lectures. Studies on nanocarbons are quite active, in particular, in the field of carbon nanotubes and graphene, and rapid progress has been made in the electrochemical properties, energy conversion and energy storage applications of these carbon materials.

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