2006 Vol. 21, No. 04

通过与热塑性树脂共热处理来改造活性炭的孔结构研究
Rie Nonaka, Yoko Nishi, Naoto Ohta, Michio Inagaki
2006, 21(04): 289-296.
Abstract(2620) PDF(1313)
Abstract:
Three activated carbons having different surface areas, coconut-shell based (AC-C), pelletized (AC-P) and bamboo-derived (AC-B), were modified by mixing them with four thermoplastic precursors, poly(vinyl alcohol) (PVA), hydroxy propyl cellulose (HPC), citric acid (CiA), and fluorine-containing polyimide (FPI) followed by heat treatment at 900℃ for 1h. The porous structures of the modified activated carbons were characterized by nitrogen adsorption and SEM. It was found that the thermoplastic precursors modified the porous structure of AC-B more significantly compared with the other two, AC-P and AC-C. PVA, HPC, and CiA modification resulted in the reduction of surface area of AC-B, which is attributed to a different modification of the micropore structure; PVA eliminated all micropores, HPC eliminated ultra-micropores preferentially, and CiA decreased the volume of ultra-micropores, whereas it increased that of super-micropores. On one hand, the addition of 30 mass% CiA to AC-B resulted in an increase in external surface area by 170%. On the other hand, the modifier FPI increased the surface area by increasing ultra-micropores to approximately twice that of the original activated carbons. By the selection of modifier, the distribution of micropore size in the substrate-activated carbons can be modified, either by decreasing or by increasing ultra-micropores.
乙炔热裂解沉积对PAN基炭纤维性能的影响
Ko Tse-Hao, Lin Jui-Shiang
2006, 21(04): 297-301.
Abstract(2453) PDF(1377)
Abstract:
Polyacrylonitrile(PAN)-based carbon fibers (CFs) were coated with a carbon film by chemical vapor deposition using acetylene as precursor. The morphologies of the as-received and modified CFs were observed using SEM and AFM, and their mechanical properties, crystalline parameters, and electrical conductivity were measured after graphitization. It was found that the graphitized CFs that were prepared showed excellent mechanical properties (2GPa for strength and 270GPa for modulus) and good electrical conductivity, (5×10−4Ω cm) compared with the unmodified ones.
利用“二次焦”制备高强炭/石墨材料
LIU Zhan-jun, GUO Quan-gui, CAO Ya-xiu, LIU Chang-an, SONG Jin-ren, LIU Lang
2006, 21(04): 302-306.
Abstract(2269) PDF(1388)
Abstract:
The “second coke” was prepared by mixing binder pitch with pitch coke followed by carbonization at elevated pressure. The carbon/graphite composites were prepared by using this powdered “second coke” as filler and coal-tar pitch as binder. The effect of the average particle size of the “second coke” on the mechanical strength, shrinkage behavior and open porosity of the composites was studied. Results showed that the composites had high mechanical strength. The compressive and flexural strengths after heat-treatment at 1300℃ were 310.0 and 113.7MPa respectively. The influence of the average particle size on the mechanical strength was remarkable when the heat-treatment temperature was under 1300℃. The volumetric shrinkage of the composites was decreased by decreasing the average particle size of the filler. The open porosity of the composites exhibited a maximum at 850℃.
纳米碳管结构差异对树脂炭包覆硅/纳米碳管复合材料电化学性能的影响
ZHANG Yong, LIU Chang, LI Feng, CHENG Hui-ming
2006, 21(04): 307-314.
Abstract(2482) PDF(1305)
Abstract:
Silicon/carbon nanotube/polyvinyl alcohol (PVA)-derived carbon composites were prepared by carbonization of PVA, and the differences of single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs) and multi-walled carbon nanotubes (MWCNTs) as resilient conductive networks to buffer the volume change of the silicon were investigated. Due to the much higher aspect ratio, SWCNTs and DWCNTs provide a better wrapping effect than do MWCNTs to buffer the volume change of silicon. SWCNTs and DWCNTs have similar diameter, aspect ratio and aggregation form. However, DWCNTs exhibit better structure stability than SWCNTs during electrochemical cycling, and consequently contribute a higher degree of resiliency to buffer the volume change of the silicon.
插层化合物在膨化过程中的热分解动力学
REN Hui, KANG Fei-yu, JIAO Qing-jie, CUI Qing-zhong
2006, 21(04): 315-320.
Abstract(4060) PDF(1803)
Abstract:
The phase transformations and thermal decomposition of the following graphite intercalation compounds (GICs), HNO3-CH3COOH-GIC, H2SO4-GIC and H2SO4-CH3COOH-GIC, were measured by an FTIR-associated TG apparatus. Using Kissinger and Ozawa principles, the kinetic parameters of some typical exfoliation reactions were evaluated and the thermal decomposition mechanism of the exfoliation process was determined. When the heating rate was in the range of 20–80℃/min, the activation energies of the exfoliation reactions were all less than 120 kJ/mol.
分形维数和弹性模量衰减表征2D-C/SiC的拉伸蠕变损伤
WU Xiao-jun, QIAO Sheng-ru, HOU Jun-tao, HAN Dong, LI Mei
2006, 21(04): 321-325.
Abstract(2218) PDF(1268)
Abstract:
Tensile creep tests of 2D-C/SiC composites were carried out at 1300℃ or 1500℃ under vacuum. When the creep time reached 0h, 0.5h, 2h, 10h, 25h, 50h, the testing was stopped and the specimen was removed from the furnace to examine the surface morphology by SEM, and the elastic modulus by a vibration device. The fractal dimension of the surface micro-cracks was evaluated from SEM micrographs. It was found that during creep many micro-cracks are produced on the sample surface and the fractal dimension of the cracks increased from 0 to 1. Both the fractal dimension and elastic modulus changes can be used to evaluate the creep damage of the composites, and they give similar damage curves. Both the damage parameter D vs. creep time and the fractal dimension vs. creep time curves include two stages: a fast developing stage of creep damage followed by a slower changing stage. In the slow stage, the damage curves evaluated from elastic modulus show an initial decline and then rise again. However, those evaluated from the fractal dimension monotonically increase with creep time. Considering matrix cracks as the main form of creep damage, the variation of fractal dimension mainly reflects the local damage of crept specimens while the variation of elastic modulus reflects the damage in the whole specimen.
沥青基球状活性炭对几种生理分子的吸附性能
TENG Na, LIANG Xiao-yi, LIU Chao-jun, LIU Xiao-jun, ZHANG Rui, QIAO Wen-ming, LING Li-cheng
2006, 21(04): 326-330.
Abstract(2357) PDF(1363)
Abstract:
The adsorption behavior of uremically-toxic creatinine, physiologically-beneficial α-amylase and lipase from aqueous solutions into pitch-based spherical activated carbons (PSACs) with different BET surface areas and pore structures was studied by UV spectrophotometry. The adsorption isotherms and dynamic adsorption curves of creatinine were investigated. The adsorption isotherms of creatinine were fitted by the Freundlich equation, from which the parameters of the equation were determined. Results showed that PSACs had better adsorptive selectivity for creatinine than for α-amylase and lipase. The equilibrium adsorption capacity of PSACs for creatinine was influenced by the solution concentration, pore structure and BET surface area of the PSACs. The larger the mesopore volume, the higher the creatinine adsorption rate. Mesopores and macropores played an important role in the adsorptive selectivity for α-amylase and lipase. The larger the pore sizes of the PSACs, the higher the adsorptive selectivity for α-amylase and lipase.
纳米炭纤维的表面润湿行为
ZHOU Jing-hong, SUI Zhi-jun, LI Ping, DAI Ying-chun, YUAN Wei-kang
2006, 21(04): 331-336.
Abstract(2553) PDF(1212)
Abstract:
The surface chemical properties and wettability of carbon nanofibers(CNFs)synthesized by CVD were studied by wicking kinetic measurements. The influence of the microstructure, preparation conditions and the surface modification of the CNFs on their wettability in different solvents were investigated. Results indicated that the preparation conditions such as catalyst composition, and especially the carbon source, have an obvious effect on the surface properties and wettability of CNFs. CNFs from Fe/γ- Al2O3 and C2H4 has the worst wettability in water, while CNFs from Ni/γ- Al2O3 and CO has the best wettability in cyclohexane. Measurement of contact angle in cyclohexane, acetone, ethanol and water showed that interaction between the CNF surface and the solvent changed significantly with the solvent used. The contact angles of CNFs from Fe/γ- Al2O3 and CO in water, acetone and ethanol relative to that in cyclohexane (in which the contact angle is arbitrarily set to 0°), are 81.6°,45.2°,24.8° respectively. It is believed that a small polarity of the CNF surface leads to its higher wettability in a non-polar solvent such as cyclohexane than in polar solvent such as water. The nature of the CNF surface groups and the wettability of CNFs in different solvents could be tailored by different surface modifications. Treatment in concentrated nitric acid increased the CNF wettability both in water and in cyclohexane, while treatment in hydrogen peroxide decreased the CNF wettability in both solvents. Interestingly, thermal treatment in argon increased the CNF wettability in water, but decreased it in cyclohexane.
耐温型炭纤维乳液上浆剂
CAO Xia, WEN Yue-fang, ZHANG Shou-chun, YANG Yong-gang
2006, 21(04): 337-342.
Abstract(2650) PDF(1806)
Abstract:
The performance of a heat-resistant sizing agent, composed of thermoplastic polyimide GCPITM and thermosetting epoxy 618, for carbon fibers was investigated by thermal analysis, granularity analysis, acid-alkali-titration, contact angle, and interfacial shear strength tests. It was shown that the composite emulsion has an excellent stability, is acid and alkali resistant and has a small particle size with a narrow distribution. The wettability of the emulsion to the surface of the carbon fibers can be improved by using a poly(ethylene oxide) alkyl ether surfactant. The sized carbon fibers have an improved wear resistance. The interfacial shear strength of sized carbon fibers with bismaleimide resin QY8911 shows an increase of 97% compared with that of unsized fibers. In addition, the interfacial shear strength of sized carbon fibers at 350℃ is 75.62% of the value at room temperature.
炭纤维阳极氧化法表面改性
GUO Yun-xia, LIU Jie, LIANG Jie-ying
2006, 21(04): 343-348.
Abstract(2742) PDF(1459)
Abstract:
The surface of polyacrylonitrile (PAN)-based carbon fibers (CFs) was modified by anodic oxidation and characterized by atomic force microscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and dynamic mechanical thermal analysis. It was found that the roughness and specific surface area of the carbon fibers were increased after oxidation treatment. The contents of hydroxyl and carbonyl groups of the treated PAN-CFs were higher than those of the untreated ones. The loss tangent peak value (tanδmax) of the treated carbon fiber reinforced epoxy resin composites (CFRP) declined compared with the untreated ones, and the glass transition temperature of the epoxy resin was increased. The interlaminar shear strength (ILSS) of the CFRP can be increased by 25% under an appropriate oxidative treatment, and the loss of tensile strength was only 5%. The interfacial adhesion parameters A and α were quantitatively evaluated, and their values were consistent with the results of ILSS of CFRP.
流化床CVD法制备单壁碳纳米管:反应温度与时间的影响
ZHANG Qun-feng, YU Hao, LUO Guo-hua, QIAN Wei-zhong, WEI Fei
2006, 21(04): 349-354.
Abstract(2859) PDF(1613)
Abstract:
The effect of temperature and reaction time on the growth of SWCNTs was investigated in a lab-scale fluidized bed reactor using Fe/MgO as catalyst for the easy purification of the as-grown product. Methane was used as the carbon source and online gas chromatography was used to obtain the real-time conversion of methane. The products were characterized by TEM, TGA and Raman spectroscopy. It is found that a low reaction temperature leads to a low activity of the catalyst, while a high temperature increases the deactivation of the catalyst. The optimum temperature was found to be 900℃. High quality SWCNTs were formed within ten minutes and amorphous carbon was found for a longer reaction time.
C/C复合材料磷酸盐防氧化涂层
HOU Liang-liang, LUO Rui-ying, BI Yan-hong, LI Jun, LUO Jing-hua, JIN Zhi-hao
2006, 21(04): 355-359.
Abstract(2516) PDF(1363)
Abstract:
Four phosphate antioxidative coatings with different compositions were prepared using a slurry brushing method, and were characterized by weight loss kinetics, thermal cyclic performance and seawater immersion tests. Changes in the microstructure of the coating before and after oxidation were also characterized using SEM and XRD. Results show that the antioxidative properties of a coating are determined by the self-healing, compactness, adherence, and chemical inertness of the coating, which are all determined by the composition. The weight loss kinetics study under oxidative conditions show that between 600 and 700℃, the oxidation is controlled by kinetics with an activation energy of 139kJ/mol. Between 700 and 800℃, the oxidation is controlled by diffusion with an activation energy of 93kJ/mol.
水溶液中组装碳纳米管/硫化锌纳米晶复合膜
FAN Dong-mei, FENG Shou-ai, ZHU Zhen-ping
2006, 21(04): 360-364.
Abstract(2235) PDF(1417)
Abstract:
ZnS nanocrystal/CNT composite films were synthesized by the reaction of Na2S with Zn(NO3)2 in an aqueous solution containing CNTs purified by 65% HNO3. The composite films were characterized by transmission electron microscopy, X-ray diffraction, selected area electron diffraction and energy dispersive X-ray spectroscopy. Results show that the CNTs act as the framework of the composite films and the ZnS nanoparticles are either anchored on the surface of the CNTs or filled apertures in the CNT network. The ZnS nanoparticles have a well-crystallized wurtzite structure and a uniform diameter of around 5nm. The ZnS/CNT composite is expected to improve the photocatalytic ability of ZnS due to the unique conductive and wave absorptive properties of the CNTs.
等离子体射流法制备高纯竹节状碳纳米管
ZHOU Ying, Xiao Nan, SUN Yu-feng, SUN Tian-jun, ZHAO Zong-bin, QIU Jie-shan
2006, 21(04): 365-368.
Abstract(2757) PDF(1372)
Abstract:
Bamboo-shaped carbon nanotubes (BCNTs) were synthesized continuously in high yields from ethanol in an arc plasma jet under atmospheric pressure with ferrocene as catalyst. The products obtained were characterized by TEM and HRTEM. The typical arc plasma conditions for the mass production of BCNTs at atmospheric pressure that can be achieved in about 120s are direct current, 220-240A; voltage, 140–150V; the injecting rate of ethanol and ferrocene mixture (100∶1 by weight), 50mL/min. It was found that the as-prepared BCNTs with a fishbone-type wall exist in an entangled state and have a uniform outer diameter of ca. 20nm and a length of several microns. The purity of BCNTs in the final product is estimated to be over 90%. BCNTs with branched morphologies are also observed occasionally. It is believed that several steps are involved in the growth of BCNTs. Once the mixture of ethanol and ferrocene is injected into the arc plasma reactor, ethanol undergoes decomposition reactions, releasing a large amount of active carbon species that work as the building blocks of BCNTs. At the same time, ferrocene is decomposed, yielding aggregated Fe particles that function as a catalyst for the growth of BCNTs. Active carbon species are immediately adsorbed by or dissolved inside the catalyst particles formed in situ, and graphene layers nucleate on the surfaces of the catalyst particle and finally grow into bamboo-shaped tubular structures because of the diffusion of carbon species inside the catalyst particles, and more importantly because of the difference in the mobilities of the catalyst particles and the graphitic shell.
沥青活性炭的制备方法
WANG Yun-long, ZHANG Sheng-wan, DU Wen, WANG Wei
2006, 21(04): 369-373.
Abstract(1818) PDF(1326)
Abstract:
Medium coal tar pitch was loaded onto porous corn stalks by solution soaking, and the resulting composite was oxidatively stabilized at 400℃ for 2h in air or heat-treated under nitrogen in the same conditions to make an infusible pitch. The infusible pitch was shattered, mixed with KOH and activated at 800℃ for 0.5 to 2h to prepare activated carbons, which were characterized by iodine adsorption. It was found that the time for the oxidative stabilization was significantly shortened by loading pitch onto the corn stalks. When the oxidative stabilization was performed at 400℃ for 2h in air, the particle size was above 100 mesh, the ratio of alkali to the infusible pitch was 5∶1. After activation at 800℃ for 1h, the activated carbon obtained had the highest iodine adsorption value.
有序介孔炭的模板合成进展
SONG Huai-he, LI Li-xia, CHEN Xiao-hong
2006, 21(04): 374-383.
Abstract(2675) PDF(2518)
Abstract:
Ordered mesoporous carbons (OMCs) made from templates, such as MCM-41 or other molecular sieves possess a regular channel structure, narrow pore size distribution and high specific surface area, which have potential applications in catalysis, separation, adsorption. Based on the classification and synthesis mechanism of silica-based mesoporous molecular sieves, current research advances on OMCs have been introduced with emphasis on important factors in synthesis including type of templates and precursors for carbons, as well as their applications in electric double layer capacitor and catalysis. It is pointed out that the research trend on OMCs should emphasize reducing the cost of silica templates, simplifying process steps and improving their controllability.