2008 Vol. 23, No. 02

自由态二维碳原子晶体—单层石墨烯
YANG Quan-hong, LU Wei, YANG Yong-gang, WANG Mao-zhang
2008, 23(02): 97-103.
Abstract(3977) PDF(1016)
Abstract:
Graphene is a kind of ideal twodimensional atomic crystal, which was successfully prepared and identified in recent years. Due to many special properties, graphene has attracted more and more attention from scientists in diverse areas and nowadays has become one of the hottest topics in the area of materials science and condensedmatter physics. Graphene is the building unit for all sp2 carbon materials, such as zerodimensional fullerenes, onedimensional carbon nanotubes and threedimensional bulk graphite, and has many unique electronic properties . This paper introduces the discovery history and molecular structure of graphene and reviews latest advances on unique electronic properties and potential applications.
铬酸溶液后处理增强碳纳米管的场发射特性
Shih-Fong Lee, Yung-Ping Chang, Li-Ying Lee
2008, 23(02): 104-110.
Abstract(2971) PDF(646)
Abstract:
A simple method is described to functionalize the surface and to modify the structures of multiwalled carbon nanotubes (MWCNTs) grown on silicon substrates using chromium trioxide (CrO3) solution. Unlike nitric acid (HNO3) used in the conventional posttreatment for MWCNTs, the chemical reaction with CrO3 involves amorphous carbon and the carbon nanotubes themselves. It is expected that the surface morphology, chemical composition, and field emission of MWCNTs should be significantly changed after CrO3 solution treatment. The results showed that after 20min of CrO3 solution treatment, the emission currents were enhanced compared with the asgrown MWCNTs. However, extended treatment over 20min was found to degrade the field emission properties of the film. The enhancement in field emission after 20min of CrO3 solution treatment can be ascribed to the modification of surface morphology, the increase in surface density of MWCNTs, and the lowering of the work function. Prolonged CrO3 treatment dissolves MWCNTs and thus results in a decrease in field emission.
EDLC电容和电极活性炭孔型及其表面积之间的关系
WANG Li-hong, Masahiro TOYODA, Michio INAGAKI
2008, 23(02): 111-115.
Abstract(3655) PDF(829)
Abstract:
The dependence of electric double layer capacitance on the pore structure of commercially available activated carbons in both nonaqueous and aqueous electrolytes was studied. Capacitance in the nonaqueous electrolyte (propylene carbonate solution of 1mol/L triethylmethylammonium tetrafluoroborate) was linearly related to that in the aqueous electrolyte (1mol/L H2SO4 solution). The contributions of the microporous surface area, Cmicro., and the surface formed on account of other large pores, Cext., were separately evaluated, the former being small and depending strongly on current density and the latter being almost constant.
喷雾热解法制备高产率石墨/炭纳米纤维及其特征研究
Bipin Kumar Gupta, O.N.Srivastava
2008, 23(02): 116-120.
Abstract(2776) PDF(1064)
Abstract:
Gramscale (>1g) synthesis and characterization of graphitic/carbon nanofibers (GNFs) is described. The GNFs were grown by the spray pyrolysis of benzene and characterized by Xray diffraction and transmission/scanning electron microscopy. The optimum growth conditions for a high yield of GNFs were found to be a spray nozzle diameter (inner diameter) of ~0.52mm, a flow rate of benzene solution of ~5mL/min, a reaction temperature of ~750℃, and a flow rate of hydrogen, as carrier gas, of ~1500mL/min. The typical length and diameter were ~60μm and ~250nm, respectively. Most of the GNFs exhibited coiled/helicallike fibers. The yield of GNFs in the spray pyrolysis growth mode was found to be of the order of 1.45g per run.
PAN预氧化纤维的炭化过程
WEN Yue-fang, CAO Xia, YANG Yong-gang, LI Hui, GUO Jian-qiang, LIU Lang
2008, 23(02): 121-126.
Abstract(3804) PDF(699)
Abstract:
The microstructural evolution, elemental composition and gas releasing character of preoxided polyacrylonitrile (PAN) fibers during continuous carbonization were investigated by Raman spectroscopy, XRD, XPS and TGMS. Results indicate that the sp2 C—C bond length, crystal size and graphitization degree increase. The increase of orientation degree and the decrease of micropore volume are the fundamental reasons for the improvement of density and tensile strength of carbon fibers. Surface and global carbon contents of preoxidized PAN fibers, and both low temperature and high temperature carbonized fibers indicate that the loss of noncarbon atoms during carbonization propagates from the exterior to the interior of the fibers. TGMS indicates that gases are released mainly at low temperature in carbonization. The crosslinking of trapezoid giant molecular chains to release nitrogen takes place at a high temperature during carbonization.
不同刹车压力下炭/炭复合材料的摩擦磨损性能
YU Shu, HUANG Bai-yun, XIONG Xiang, ZHANG Chuan-fu
2008, 23(02): 127-132.
Abstract(2873) PDF(637)
Abstract:
The effect of braking pressure on the tribological properties of carbon/carbon composites manufactured by isothermal and thermalgradient chemical vapor depositions was investigated by optical microscopy, scanning electron microscopy and a laboratory dynamometer. Results indicate that the coefficient of friction decreases and weight loss increases with braking pressure from 0.35MPa to 1.82MPa. The oxidation erosion of rough laminar is lower than that of smooth laminar because of its better microstructure. The wear debris of rough laminar can be easily deformed plastically, leading to a thin and uniform film on the friction surface that reduces the oxidation erosion.
辅助活化法制备超级活性炭的机理
LIU Xin-mei, DAI Xiao-dong, ZHANG Jian, SONG hui, YAN Zi-feng
2008, 23(02): 133-138.
Abstract(4178) PDF(720)
Abstract:
The role of different alkali and alkaliearth metal halides in the preparation of high surface area activated carbons by KOH activation was investigated. The samples were quickly quenched after activation temperature and time was reached. Results indicated that pore size distribution of the high surface area activated carbons was strongly affected by the diameter of the metal cation and reduction activity of the metal. The anion acted as electron donor to increase the activity of active sites. Surface etching to expand micropore openings occurred at low activation temperature and indepth etching was preferred at high activation temperature.
磷酸钙涂覆炭织物体外细胞毒性的评价
HAN Hong-mei, Gary J. Phillips, Sergey V. Mikhalovsky, Andrew W. Lloyd
2008, 23(02): 139-143.
Abstract(2641) PDF(764)
Abstract:
The success or failure of medical implants often depends on the cellsurface behavior after implantation of the device. This study investigated the use of woven carbon fabric, which had been sonoelectrochemically coated with calcium phosphate, to enhance bone cell attachment and proliferation in vitro. Human osteoblastlike cells, MG63, were used to study the interactions between cells and the material and assess the cytotoxicity of the substrates. The cytotoxicity of the materials was assessed using an MTS ((3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2Htetrazolium, inner salt)) assay to determine the viability of the osteoblastlike MG63 cells in direct contact with the carbon fabric or calcium phosphate coated carbon fabrics, and to assess the cytotoxicity of extracts from these materials. The morphology of the surface adherent cells was assessed by scanning electron microscopy (SEM). Results showed that neither carbon fabrics nor calcium phosphate coated materials were cytotoxic. Furthermore, cell attachment and proliferation were enhanced by coating carbon fabrics with calcium phosphate. SEM showed that the cells had a normal morphology and were well spread similar to those seen in the tissue culture plate control. These flexible calcium phosphate coated fabrics could, therefore, have uses in the reconstruction of bone in orthopaedic and dental surgery.
炭/炭复合材料表面等离子体喷涂羟基磷灰石涂层的生物学性能
CAO Ning, BAI Yun-qiang, MA Quan-sheng, SUI Jin-ling, LI Mu-sen
2008, 23(02): 144-148.
Abstract(3074) PDF(499)
Abstract:
Hydroxyapatite (HA) coatings were prepared on carbon/carbon (C/C) composites by plasma spraying and tested by in vitro and in vivo methods. The Xray diffraction results indicated that the coatings consisted of HA, αtricalcium phosphate, and tetracalcium phosphate. The in vitro biological behavior of the HA coatings was studied in a Ringer solution. With increasing immersion time, new particles appeared on the surface of the coatings and these particles became bigger through agglomeration. In the days after the implantation, the experimental animals had no inflammation and rejection, and the coatings were firmly attached to the substrate. Histological observation showed that there was obvious bone tissue reconstruction on the surface of the coatings. In this light, the HA coatings plasmasprayed on C/C composites have excellent biological behavior and show promise as a bone repairing material.
碳纳米管和炭黑在橡胶体系增强的协同效应
FAN Zhuang-jun, WANG Yao, LUO Guo-hua, LI Zhi-fei, WEI Fei
2008, 23(02): 149-153.
Abstract(3434) PDF(832)
Abstract:
Rubber/carbon composites were prepared by mixing multiwalled carbon nanotubes (MWCNTs), carbon black or a mixture of carbon black and MWCNTs with rubber by a laboratory tworoll mill. Results showed that MWCNTs could effectively improve elastic modulus, stress at a defined enlongation, abrasion resistance and electrical properties compared to the carbon black additive. However, the tensile strength, tear strength, strain to failure, viscosity and processing properties of the MWCNT based composites were rather poor. The properties of the composites with both MWCNTs and carbon black added were improved effectively by the formation a grapeclusterlike reinforcing structure. When the weight ratio of MWCNTs to carbon black was 1∶4, the tear strength (78.4kN/m), hardness (68) and abrasion loss (0.112cm3/km) of the rubber/MWCNTcarbon black composite were better than those of the rubber/carbon black composite and the strain to failure (470%) and viscosity (65Pa · s) were better than those of the rubber/MWCNT composite. The rubber/MWCNT composites had excellent dynamic mechanical properties and could be used in tyres with low roll hysteresis and fatigue loss resistance.
石油油浆常压研制泡沫炭
YANG Xiao-jun, ZHA Qing-fang, LI Hong-nan, LI Xue-jun, CHENG Xiang-ling
2008, 23(02): 154-158.
Abstract(2912) PDF(764)
Abstract:
Pitchbased carbon foam containing pores of diameter 150400μm was produced from an intermediate pitch obtained from aromatic rich oil extracted from heavy oil FCC (fluid catalytic cracking) slurry by heating at atmospheric pressure. The effect of molecular weight distribution of the pitch on the formation of the foam was studied qualitatively. The variation of microscopic morphology, crystallite size, the interlayer spacing of microcrystal, and the density of the carbon foam carbonized from 800 to 1400℃ were also investigated. It was found that the wider the molecular weight distribution of the intermediate material, the worse the foam. Optical microscopy and scanning electron microscopy revealed that with increasing carbonization temperature, closed pores were opened and more pores were in twisted form. Xray diffraction patterns indicated that the graphite microcrystal size decreased from 2.3 to 1.5nm and their interlayer spacing increased from 0.3459 to 0.3477nm below 800℃. From 800 to 1400℃, the graphite microcrystal size increased from 1.5 to 4.2nm and the interlayer spacing decreased from 0.3477 to 0.3454nm. The density of the carbon foams decreased form 0.52 to 0.16g/cm3 during the carbonization.
用Weibull统计方法评价Ni-P镀层对炭纤维抗拉强度的影响
JI Ying-lu, LU Chun-xiang, ZHOU Pu-cha, YANG Yu, LU Xiao-xuan, LI Yong-hong, YUAN Shu-xia, HE Fu
2008, 23(02): 159-164.
Abstract(3453) PDF(789)
Abstract:
Ni-P coated carbon fibers were prepared by a chemical plating method. The microstructures of uncoated and coated carbon fibers were investigated by SEM and XRD, and the surface atom compositions were studied by EDS. The tensile strength of the carbon fibers was analyzed by a Weibull statistical method. Results show that the number of defects on the carbon fiber surfaces decreases after Ni-P coating. When the thickness of the NiP coating reaches 0.149μm, the tensile strength of carbon fibers exhibits a maximum value of 3.10GPa, a 8.77% increase compared to the uncoated carbon fibers, which might be ascribed to the elimination of a number of surface defects by the NiP coating.
苯酚-间甲酚-糠醛基炭气凝胶的制备及微结构控制
LONG Dong-hui, ZHANG Jie, YANG Jun-he, HU Zi-jun, LI Tong-qi, CHENG Guo, ZHANG Rui, LING Li-cheng
2008, 23(02): 165-170.
Abstract(3942) PDF(1323)
Abstract:
Carbon aerogels rich in mesopores were prepared by the solgel polycondensation of phenol, mcresol, and furfural by an acid catalyst in a 1propanol solution, followed by supercritical 1propanol drying and pyrolysis. The effect of the ratios of mcresol to phenol (mC/P) on the properties of aerogels was investigated. The aerogels were characterized by infrared spectroscopy, N2 adsorption, scanning and transmission electron microscopy. It was found that the microstructure of carbon aerogels could be adjusted by the mC/P ratio. The average mesopore size of carbon aerogels decreased from 47 to 13nm with increasing mC/P ratio. The surface area calculated using the BrunauerEmmettTeller method, external surface area, and mesopore volume of carbon aerogels, all exhibited maxima at the mC/P ratio of 0.33.
静电纺丝法制备聚丙烯腈基纳米炭纤维及其表面结构表征
GU Shu-ying, WU Qi-lin, REN Jie
2008, 23(02): 171-176.
Abstract(3783) PDF(880)
Abstract:
Carbon nanofibers with diameters in the range of 100nm to 300nm were obtained by stabilizing and carbonizing electrospun polyacrylonitrile (PAN) precursors. The morphologies and structures of the nanofibers and PAN precursors were investigated by scanning electron microscopy, scanning tunneling microscopy, and differential scanning calorimetry. The diameters of the PAN precursors and carbon nanofibers showed a log normal distribution. The cyclization exothermic peak shifted to a lower temperature for electrospun fibers, which suggested that cyclization could be more easily initiated. Pits 10nm in length and 5nm in width formed on the surface of the carbon nanofibers, caused by the rough surface of the electrospun precursors and their shrinkage during heat treatment.
预氧化过程中PAN纤维皮芯结构的变化
LIU Jie, LI Jia, WANG Lei, MA Zhao-kun, LIANG Jie-ying
2008, 23(02): 177-184.
Abstract(3247) PDF(839)
Abstract:
The core/shell structure of polyacrylonitrile (PAN) fibers formed during preoxidation was investigated by DSC, FTIR, SEM, optical microscopy and density measurement. Five precursors were used to correlate the core/shell structure with their thermochemical reactivity. It was found that the morphologies of the core/shell structures are highly relevant to the reactivity, microstructure and density of PAN fibers, and the quality of the resultant carbon fibers depends strongly on the degree of preoxidation.
溴插层热解炭的制备
LU Jin-hua, LI He-jun, LI Ke-zhi
2008, 23(02): 185-188.
Abstract(3147) PDF(527)
Abstract:
Pyrolytic carbon prepared by chemical vapor deposition was intercalated by bromine in the liquid phase at 20℃ for 48h with a weight ratio of bromine to carbon of 6. XRD, SEM and XPS were used to characterize the product. Results show that a new XRD diffraction peak appears after intercalation. XPS further shows that the bromine and carbon are chemically bonded.
炭毡传感特性研究
SONG Xian-hui, LU Yong, ZHANG Xiao-yu, LI Zhuo-qiu
2008, 23(02): 189-192.
Abstract(2337) PDF(489)
Abstract:
The change in the electrical resistance of a carbon fiber felt upon loading and unloading was investigated. The resistance is highly sensitive to deformation, which increases or decreases reversibly under loading or unloading within the elastic deformation regime. The resistance versus load has satisfactory linearity and repeatability, which can be used to measure the load on the carbon fiber felt with a high accuracy. The carbon fiber felt pretreated by electric baking has a better repeatability than does the untreated sample. Carbon fiber felt can be used as a new sensor element to provide online reliable information about the deformation of a concrete structure.