2008 Vol. 23, No. 04

纳米洋葱状富勒烯的研究现状及前景
XU Bing-she
2008, 23(04): 289-301.
Abstract(2399) PDF(1792)
Abstract:
As an important member of the fullerene family, nano onionlike fullerenes (NOLFs) have a unique hollow cage and concentric shell structure, which endow them with some special properties. Based on these properties, many potential applications, such as energy storage materials, highperformance and hightemperature wearresistance materials, superconductive materials and biomaterials, have been widely proposed. This review summarizes some of the major achievements in the field of NOLFs, including structure, preparation, growth mechanism, purification, functionalization, and properties. Possible applications are also suggested.
Ni催化剂在N2 O/N2/NH3中退火对碳纳米管表面结构及场发射特性的影响
Shih-Fong Lee| Yung-Ping Chang| Li-Ying Lee
2008, 23(04): 302-308.
Abstract(2534) PDF(1313)
Abstract:
Ni catalyst was annealed in N2 O/N2/NH3 in order to study the effects of the annealing on the surface morphology and fieldemission characteristics of synthesized carbon nanotubes (CNTs). The morphology and composition of the CNTs show that the grain size and composition of the Ni catalyst can be modified by N2 O, N2, and NH3 pretreatments. Scanning electron microscopy images of evaporated Ni after N2 O pretreatment show that the Ni particles are more uniformly distributed, and their sizes are relatively small. It is found that the CNTs grown on Ni pretreated with N2 O have the highest surface density and the highest emission current. This improvement is accomplished through the more uniformly distributed and smaller Ni particles obtained by N2 O pretreatment. The growth of amorphous carbon is also suppressed. The reasons for this improvement are that nitrogen and oxygen atoms dissociated from N2 O in the pretreatment can oxidize the catalyst particles and inhibit their growth so that the resulting Ni metal nuclei become smaller and more uniformly distributed, which is beneficial to CNT growth.
氧化前处理对炭气凝胶孔结构的影响
ZHANG Rui, LI Wen, HU Zi-jun, LONG Dong-hui, XIE Ying-bo, CHENG Guo, LING Li-cheng, YANG Jun-he
2008, 23(04): 309-313.
Abstract(4168) PDF(976)
Abstract:
Organic aerogels, prepared by solgel polymerization of phenolic and furfural, were oxidized at 110 to 170℃ for 1 to 7h in air. The effect of oxidation temperature and time on the pore structure of the carbon aerogels was investigated. It is found that oxidation under appropriate conditions can stabilize a nanonetwork of organic aerogels during pyrolysis by preventing plasticity. However, the oxidative effect on micro, meso and macropores is quite different. A mild condition is appropriate for macropores while a severe condition is needed for meso and micropores due to a faster diffusion of air into macropores than into meso and micropores. The appropriate oxidation parameters for an improved mesopore volume and surface area are 130℃ for 7h or 150℃ for 3h in air.
乙醇热解制备C/C复合材料探索研究
YAN Xia-feng, ZHANG Shou-yang, LI He-jun, LI Wei, ZHANG Xiao-ming
2008, 23(04): 314-318.
Abstract(2677) PDF(837)
Abstract:
Ethanol, which is a renewable resource, was used as a precursor to prepare carbon/carbon (C/C) composites by chemical vapor infiltration (CVI), and the relationship between density and infiltration time was investigated. The flexural strength was determined by a threepoint bend test. The microstructure and fracturesurface morphology of the composites were observed by polarized light microscopy and scanning electron microscopy respectively. Results show that the bulk density reaches 1.47g/cm3 for a 96h densification, a significant improvement in densification efficiency compared with other precursors. A hightextured carbon matrix, consisting of rough laminar pyrocarbon, can be easily obtained. The C/C composites exhibit a pseudoplastic failure behavior. Ethanol is a new promising precursor for the densification of C/C composites.
调变Ni/Mo/MgO催化剂中Ni/Mo比例可控合成薄壁碳纳米管
ZHANG Qiang, LIU Yi, HU Ling, QIAN Wei-zhong, LUO Guo-hua, WEI Fei
2008, 23(04): 319-325.
Abstract(2482) PDF(795)
Abstract:
Thinwalled carbon nanotubes (CNTs) were prepared from methane decomposition using Ni/Mo/MgO as catalysts loaded with 1% mole fraction of Ni and smaller proportion of Mo. The relationship between CNT diameter and Ni/Mo ratio was studied by SEM, TEM, XRD and Raman spectroscopy. The particle size and the active phase of the catalyst could be modulated by the Ni/Mo ratio. With decreasing Ni/Mo ratio, a NiMo alloy was first formed, and then an isolated Mo phase was formed on the catalyst, as characterized by TEM and XRD. The NiMo alloy, with very small size, was responsible for the growth of thinwalled CNTs , whereas, the Mo phase was related to the formation of largediameter thickwalled CNTs. The thinwalled CNTs with outer diameter of 3.0nm and inner diameter of 1.3nm could be obtained with high selectivity, a narrow diameter distribution, and high purity by controlling the Ni/Mo ratio at 6. Raman spectra confirmed the formation of thinwalled CNTs with few defects. The formation of thinwalled CNTs was mainly attributed to a rapid surface diffusion and precipitation of carbon on the small metal alloy crystallites.
活性竹炭对苯酚的吸附动力学
ZHU Jiang-tao, HUANG Zheng-hong, KANG Fei-yu, FU Jin-he, YUE Yong-de
2008, 23(04): 326-330.
Abstract(2655) PDF(868)
Abstract:
Dynamic adsorption of phenol at 30℃ on activated bamboo charcoal was investigated. Effects of phenol initial concentration and adsorbent size on kinetics were discussed. Three models were used to study the adsorption kinetics. It was found that a pseudosecondorder equation provided the best correlation to the data. The initial adsorption rates derived from the model increased with concentration and decreased with size. An intraparticle diffusion was the ratecontrolling step for the adsorption of phenol on activated bamboo charcoal.
化学气相沉积反应中金属-碳协同催化碳纳米管生长的理论和实验证据
DU Gui-xiang, KANG Zhi-rong, SONG Jin-ling, ZHAO Jiang-hong, SONG Chang, ZHU Zhen-ping
2008, 23(04): 331-338.
Abstract(2604) PDF(747)
Abstract:
The nucleation and growth of carbon nanotubes (CNTs) using chemical vapor deposition with a metalcarbon catalyst have been studied experimentally and theoretically. Results suggest that the nucleation and growth of multiwalled CNTs are not due to the metal alone, but that carbon nuclei (once formed) also contribute to radial and axial growth. Metal particles mainly promote the nucleation and growth of the innermost carbon shell(s), and catalyze the ordering of the carbon atoms to form graphene structures. The intrinsic difference between multiwalled CNT formation and singlewalled CNT formation seems to be associated with a selfcatalytic function of carbon nuclei.
温度、炭纤维和硅土粉对轻量混凝土力学性能的影响
Harun TANYILDIZI
2008, 23(04): 339-344.
Abstract(2545) PDF(924)
Abstract:
The effect of temperature, and carbon fiber and silica fume contents on the mechanical properties (compressive and flexural strength) of lightweight concretes was investigated. Samples containing silica fume (mass fractions of 0 and 10%) and carbon fibers (mass fractions of 0, 0.5, 1, and 2%) were prepared. The compressive and flexural strengths of the samples were determined after they had been exposed to high temperatures (400, 600, and 800℃). The Taguchi method was used to determine the optimum conditions and to reduce the number of experiments. The significance of the three factors affecting the mechanical properties of lightweight concretes was determined using the Anova analysis and the Ftest. Results showed that the most important factor for mechanical properties was temperature, followed by carbon fiber and silica fume contents. The optimum parameters for compressive strength were different from those for flexural strength.
有序石墨烯导电炭薄膜的制备
CHEN Cheng-meng, YANG Yong-gang, WEN Yue-fang, YANG Quan-hong, WANG Mao-zhang
2008, 23(04): 345-350.
Abstract(4175) PDF(1100)
Abstract:
Graphite oxide was synthesized by the Hummer method, followed by ultrasonic delamination in water to produce a stable hydrosol of graphene oxide sheets. Then, a flowdirected assembly of this graphene oxide was produced in a celluloseacetatebased microfilter to form an ordered nanostructured membrane. The membrane was treated by chemical reduction and carbonization for deoxidation and regraphitization, which increased its electrical conductivity while retaining its shape. The graphenebased conductive membrane had a conductivity of 184.8S/cm. A reductive treatment before the carbonization increased the mass of residual carbon in the resulting membranes.
洁净单壁碳纳米管在Fe2 O3/Al2 O3二元气凝胶催化剂上的水辅助合成
LI Xuan-ke, Aidan Westwood, Andy Brown, Rik Brydson, Brian Rand
2008, 23(04): 351-355.
Abstract(2429) PDF(659)
Abstract:
A Fe2O3/Al2O3 binary aerogel was used as a catalyst for the synthesis of singlewalled carbon nanotubes (SWCNTs) by the catalytic decomposition of CH4H2 and a CH4H2water mixture at 900℃ for 3min. The influence of water vapor on the growth of SWCNTs was investigated by characterizing the morphology and structure of the carbon products using scanning electron microscopy, Xray diffraction, transmission electron microscopy, and Raman spectroscopy. Results show that SWCNTs with a high purity were synthesized under the mixed atmosphere of CH4H2water when the amount of water vapor present was controlled by bubbling H2 through water. The yield and microstructure of the asformed carbon products can be correlated with the composition of the reaction mixture.
固体渗硼增强多孔炭的抗氧化性
ZHA Qing-fang, HU Xing-hua, GUO Yan-sheng, WU Ming-bo, Li Zhao-feng, ZHANG Yu-zhen
2008, 23(04): 356-360.
Abstract(2449) PDF(625)
Abstract:
Porous carbon prepared by KOH chemical activation was doped with boron using B4C as an additive (mass fraction of 10%) by heat treatment at 850℃ for 5 h to increase its antioxidative ability. This effect is a result of a decrease in the number of active sites on the surface of the carbon after heat treatment, which inhibits its reaction with the oxidizing gas. The volume of micro and mesopores and BET surface area decreased after the doping. Although the activity of the doped porous carbon in catalytic cracking evaluated in a microreactor decreased after the doping, it still reached a higher value (70%) than that of porous carbon.
RF炭气凝胶孔结构的控制及其电化学性能研究
ZHAO Hai-xia, ZHU Yu-dong, LI Wen-cui, HU Hao-quan
2008, 23(04): 361-366.
Abstract(2957) PDF(910)
Abstract:
Carbon aerogels were prepared using a solgel process with resorcinol and formaldehyde as raw materials and sodium carbonate as catalyst, followed by ambient drying and carbonization. They were then activated by carbon dioxide. The activated materials were used as electrode materials of electric doublelayer capacitors and their electrochemical behavior was characterized by constant current chargedischarge experiments and cyclic voltammetry in an electrolyte of 6mol/L KOH aqueous solution. Results showed that the BET surface area and total pore volume of the aerogels were increased greatly by CO2 activation. When the carbon aerogel was activated by CO2 at 900℃ for 3h, its BET surface area increased from 633m2/g to 1271m2/g, and the corresponding specific capacitance increased from 81F/g to 172F/g at a current density of 1mA/cm2. When the current density was increased from 1 to 30mA/cm2, the specific capacitance of the activated sample decreased from 172 to 131F/g, indicating that the sample possessed an excellent power capability.
三元FeCl3-NiCl2-GICs的表征及微波吸收性能
YANG Li, LIU Hong-bo, LI Fu-jin, ZOU Yan-hong, HE Huan
2008, 23(04): 367-373.
Abstract(2248) PDF(727)
Abstract:
Ternary FeCl3NiCl2GICs were synthesized by the molten salt method. Natural graphite powder was used as host material and a mixture of FeCl3 and NiCl2 as intercalant. The stage structure,surface topography and components of the GICs were studied by XRD, SEM and EDS. The electrical conductivity and electromagnetic parameters were determined by a transmission reflection network analyzer. Results show that the host graphite is expanded and its edges are eroded badly during intercalation. The degree of erosion levels off with an increase of stage number. For the FeCl3NiCl2GICs with different stages, the distribution of Cl is uniform in the graphite layers, while Fe and Ni is nonuniformly distributed in every flake. The percentage of Fe increases from the edge to the center of the FeCl3NiCl2GICs flake while Ni shows the opposite behavior. The resistivity of the FeCl3NiCl2GICs decreases first, then increases with an increase in stage number. The GICs have relatively good microwave absorption properties and their maximum theoretical reflection loss first decreases, then increases with increasing stage number. Stageone FeCl3NiCl2GICs has the highest reflection loss, which is -10.3dB when the thickness is 2mm.
活性中间相炭微球的制备及机理研究
LI Tie-hu, CHANG Tian-jie, JI Yong-bin, WANG Da-wei
2008, 23(04): 374-377.
Abstract(2314) PDF(976)
Abstract:
Mesocarbon microbeads (MCMBss) were activated by KOH and K2CO3 and were analyzed by Xray diffraction, nitrogen adsorption and scanning electron microscopy. Results showed that the KOH activated MCMBss had a BET surface area of 2775m2/g. They had an amorphous structure and graphite crystallites were destroyed by activation. The activation mechanism involves a series of chemical reactions and potassium intercalation.
螺旋行波管衰减器炭涂层的特性表征
Vikas Kumar, Anil Vohra, Vishnu Srivastava
2008, 23(04): 378-381.
Abstract(1957) PDF(548)
Abstract:
Attenuator coatings of carbon were deposited on alumina support rods by pyrolytic deposition, aquadag coating and arc discharge to absorb the reflections and to improve the stability of a helical traveling wave tube. An experimental set up involving a narrowheight waveguide with a hole was used to measure the attenuation of the coated rods at 6.0GHz frequency by carrying out reflection and transmission measurements using a scalar network analyzer. The same structure was also simulated by using a high frequency structure simulator (HFSS). Results indicate that the aquadagcoated films provide a maximum loss or absorbance and are suitable as the attenuator coating. The simulated results by HFSS agree well with the experimental observations.
炭纤维水泥基材料的湿敏性研究
HAN Bao-guo, OU Jin-ping
2008, 23(04): 382-384.
Abstract(3103) PDF(890)
Abstract:
The electrical resistivity of cements with additions of carbon fibers or carbon black (CACs) at different drying times and soaking times was measured by a directcurrent fourpole method. The influence of water content in the CACs on their electrical resistivity was studied. It was found that the electrical resistivity of the CACs decreases with drying time and increases with soaking time. The electrical resistivity of CACs is sensitive to the change of their inner water content and they have a good humidity sensing property.