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Field emission patterns with atomic resolution of single-walled carbon nanotubes by field emission microscopy

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Science China(Physics,Mechanics & Astronomy) 2003年第1期46卷 33-40页

作者：侯士敏张兆祥刘惟敏罗骥张耿民顾镇南赵兴钰彭练矛吴锦雷薛增泉 Department of Electronics Peking UniversityBeijing 100871China College of Chemistry and Molecular Engineering Peking UniversityBeijing 100871China

Electron emission properties of single-walled carbon nanotubes (SWCNTs) assembled on a tungsten tip were investigated using field emission microscopy (FEM). The transmission electron microscopy (TEM) micrograph confirmed the existence of an SWCNT bundle on the W tip. Under appropriate experimental conditions,a series of FEM patterns with atomic resolution were obtained. These patterns arose possibly from the field emission of the open end of an individual (16,0) SWCNT protruding from the SWCNT bundle. The magnification factor and the resolution under our experimental conditions were calculated theoretically. If the value of the compression factor β was set at β= 1.76, the calculated value of the magnification factor was in agreement with the measured value. The resolving powerof FEM was determined by the resolution equation given by Gomer. The resolutionof 0.277 nm could be achieved under the typical electric field of 5.0×107 V/cm, which was close to the interatomic separation 0.246 nm between carbon atoms along the zigzag edge at the open end for the (16, 0) SWCNT. Consequently, our experimental results were further supported by our theoretical calculation.

关键词： field emission microscope, single-walled carbon nanotubes, resolving power, atomic resolution.

Chemical modification and the photoluminescence stabilization of titanic acid nanotubes

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Science China Chemistry 2006年第2期49卷 155-161页

作者： ZHANG Xingtang WANG Yumei ZHANG Chunmei JIANG Xiaohong TIAN Baoli LI Yuncai HUANG Yabin DU Zuliang Key Laboratory for Special Functional Materials Henan University Kaifeng 457001 China Key Laboratory for Special Functional Materials Henan University Kaifeng 457001 China Key Laboratory for Special Functional Materials Henan University Kaifeng 457001 China Key Laboratory for Special Functional Materials Henan University Kaifeng 457001 China Key Laboratory for Special Functional Materials Henan University Kaifeng 457001 China Key Laboratory for Special Functional Materials Henan University Kaifeng 457001 China Key Laboratory for Special Functional Materials Henan University Kaifeng 457001 China Key Laboratory for Special Functional Materials Henan University Kaifeng 457001 China

Titanic acid nanotubes (H2Ti2O4(OH)2) were surface-modified with cetyl alcohol through dehydration reaction because of existence of Ti–OH. The modified nanotubes were characterized by transmission electron microscopy (TEM), Fourier Transform Infrared (FT-IR) spectrometry and pho-toluminescence (PL) spectra. The results indicate that the modified nanotubes can be easily dis-persed into organic solvent such as chloroform and toluene in contrast with the unmodified nanotubes, which makes it easier to be assembled by LB technique. Moreover, the Ti-O-CH2(CH2)14CH3 on the surface of the nanotubes can hinder the adsorption of water and consequently the photoluminescence property of the nanotubes can be stabilized. Even though kept in humid condition or in air for a long time, the modified nanotubes also maintain the special photoluminescence property in the visible re-gion.

关键词： titanic acid nanotubes, surface-modification, photoluminescence.

Synthesis of carbon nanotubes with Ni/CNTs catalyst

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Science China(Technological Sciences) 2003年第3期46卷 303-308页

作者：李春华姚可夫阮殿波梁吉徐才录吴德海 Department of Mechanical Engineering Tsinghua Univeristy

Carbon nanotubes (CNTs), owing to their large specific area, good chemical stability and modifiable surface properties after acidic or basic treatment, can be used as catalytic support materials. In this paper, the activities and selectivities of two catalysts, i. e. Ni catalyst supported by carbon nanotubes (Ni/CNTs) and that supported by diatomite (Ni/SiO2), are compared. It is found that the quality of the carbon nanotubes synthesized by the two catalysts is similar, but the yield of the former is 1.5 times higher than that of the latter. The excellent performance of the Ni/CNTs catalyst should be ascribed to the larger specific surface area and proper pore distribution and the structure of the carbon nanotube support.

关键词： carbon nanotubes, catalytic support, synthesis.

Low-temperature catalytic preparation of multi-wall MoS_(2)nanotubes

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Science China Chemistry 2003年第2期46卷 191-195页

作者：陈军李锁龙高峰徐强 Koji Tanaka Institute of New Energy Material Chemistry Nankai University Tianjin 300071 China

In the catalytic reduction atmosphere of H2+CH4+C4H4S, the ball-milled precursor (NH4)2MoS4 is heated to 300(C for decomposition. The as-synthesized product is characterized by XRD, SEM, TEM, HRTEM, EDX, and BET. The results show that multi-wall MoS2 nanotubes are obtained. The length of the nanotubes is around 3-5 (m. The diameters of the nanotubes are homogeneous, with an inner diameter of (15 nm, an outer diameter of (30 nm, and an interlayer (002) d-spacing of 0.63 nm. This catalytic thermal reaction occurring at low temperatures is important for the large-scale preparation of similar transition-metal disulfide nanotubes.

关键词： MoS2, nanotubes, catalytic thermal decomposition, specific surface area.

Carbon nanotubes Act as Conductive Additives in the cathode of Lithium Ion Batteries

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合成化学 2004年第Z1期12卷 132-132页

作者： Wang Guoping Zhou Gumin Qu MeiZhen Wang Guixing Wang Yunshi Zhong Hong Yu Zuolong Chengdu Institute of Organic Chemistry Chinese Academy of Sciences Chengdu610041 China Chengdu Institute of Organic Chemistry Chinese Academy of Sciences Chengdu610041 China Chengdu Institute of Organic Chemistry Chinese Academy of Sciences Chengdu610041 China Chengdu Institute of Organic Chemistry Chinese Academy of Sciences Chengdu610041 China Shenzhen Nanotech Port Co. Ltd. Shenzhen518057 China Department of Chemical Engineering Central South University Changsha410083 China Chengdu Institute of Organic Chemistry Chinese Academy of Sciences Chengdu610041 China Shenzhen Nanotech Port Co. Ltd. Shenzhen518057 China

The layered compounds LiCoO2, LiNiO2 and spinel compound LiMn2O4 have served as very effective cathode active materials in lithium ion rechargeable batteries. Generally, their high conductive resistance easily results in a serious polarization and poor utilization of active *** order to make full use of the active materials and increase the capacity, the charge-discharge rate and the cycle life of lithium ion batteries, conductive additives are often added into the above cathode materials to form a conductive network. Carbon materials, such as carbon black, graphite powders and chemical vapor deposit carbon fibers have been widely used as conductive additives owing to their high electrical conductivity and chemical inertness. To effectively utilize the active materials, the contents of these carbon additives in the cathode often reach up to 10～20wt%. This leads to a great need for binder, for example, 10wt% or more. It follows therefore a considerable increase in volume of the lithium batteries and lower energy density because of the large amount of carbon additives and binder in the *** substituting carbon nanotubes (CNTs) for carbon black, graphite powders or chemical vapor deposit carbon fibers, much conductive additives and binder are saved, and the cathode with only 3～5wt% of conductive additives CNTs shows excellent rate capacity. At the discharge rate 0.5C,2.0C and 3.0C, the LiCoO2 cathode with CNTs exhibits discharge capacity up to 134mAh/g, 126 and 120mAh/g, respectively. The explanation is given as follows. Firstly, their microstructure and graphitic crystallinity are very important for electron transport. CNTs employed in the experiments comprise an array of complete graphite sheets seamlessly wrapped into cylindrical tubes which are concentrically nested like the rings of a tree trunk. Thus, the process of -electrons transport occurs in graphite sheet in super-conjugative manner when they move from one end to the other end in CNTs. Appare

关键词： carbon nanotubes, lithium ion battery, cathode, rate capacity, conductive additive

Catalysis by Using TiO_2 Nanoparticles and nanotubes

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合成化学 2004年第Z1期12卷 121-121页

作者： Chien Shu-Hua Kuo Ming-Chih Liou Yuh-Cherng Institute of Chemistry Academia Sinica Taipei 11529 China Taiwan And Department of Chemistry National Taiwan University Taipei 10764 TaiwanInstitute of Chemistry Academia Sinica Taipei 11529 China Taiwan And Department of Chemistry National Taiwan University Taipei 10764 TaiwanInstitute of Chemistry Academia Sinica Taipei 11529 China Taiwan And Department of Chemistry National Taiwan University Taipei 10764 Taiwan

TiO2 has attracted considerable attention due to its stability, non-toxicity, low cost, and great potential for use as a photocatalyst in environmental applications. Since strong metal-support interaction (SMSI) of titania-supported noble metals was first reported in 1978, titania supported catalyst has been intensively studied in heterogeneous catalysis. However, the effective catalytic activity was restricted due to the low surface area of TiO2. Recently, TiO2-based nanotubes were extensively investigated because of their potentials in many areas such as highly efficient photocatalysis and hydrogen *** the present study, formation of titanium oxide (TiO2) nanotubes was carried out by hydrothermal method, with TiO2 nanoparticle-powders immersed in concentrated NaOH solution in an autoclave at 110 ℃. Preparation of nano-size Pt on TiO2-nanoparticles or TiO2-nanotubes was performed by photochemical deposition method with UV irradiation on an aqueous solution containing TiO2 and hexachloroplatinic acid or tetrachloroauric acid. The TEM micrographs show that TiO2-nanotubes exhibit ～300 nm in length with an inner diameter of ～ 6 nm and the wall thickness of ～ 2 nm, and homogeneous nanosize Pt particles (～ 2 nm) were well-dispersed on both nanoparticle- and nanotube- titania supports. It also shows the nanotube morphology was retained up2o n Pt-immobilization. Nitrogen adsorption isotherm at 77K resulted a high surface area (～ 200m/g) of TiO2-nanotubes, which is about 40 times greater than that of 'mother' TiO2 nanoparticles (～5 m/g). All the spectroscopic results exhibited that the nanotube structure was not significantly affected by the immobilized Pt particles. Ti K-edge XANES spectra of TiO2 nanotube and Pt/TiO2-nanotube represent that most titanium are in a tetrahedral coordination with few retained in the octahedral *** the in-situ FT-IR experiments, an IR cell was evacuated to a pressure of 10-5 torr at room temperature as soon as the catalyst-pelle

关键词： TiO2, nanoparticles, nanotubes, catalysis

Fluoride and lead adsorption on carbon nanotubes

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合成化学 2004年第Z1期12卷 54-54页

作者： WANG Shuguang1, LI Yanhui2 1.School of Environmental Science and Engineering, Shandong University, Jinan 250100, China 2. Department of Mechanical Engineering, State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Beijing 100084, China School of Environmental Science and Engineering Shandong University Jinan 250100 China Department of Mechanical Engineering State Key Laboratory of Automotive Safety and Energy Tsinghua University Beijing 100084 China

The properties and applications of CNT have been studied extensively since Iijima discovered them in 1991[1,2]. They have exceptional mechanical properties and unique electrical property, highly chemical stability and large specific surface area. Thus far, they have widely potential applications in many fields. They can be used as reinforcing materials in composites[3], field emissions[4], hydrogen storage[5], nanoelectronic components[6], catalyst supports[7], adsorption material and so on. However, the study on the potential application of CNT, environmental protection field in particular, was hardly ***[8] et al. reported that CNT had a significantly higher dioxin removal efficiency than that of activated carbon. The Langmuir adsorption constant is 2.7 × 1052, 1.3 × 1018 respectively. The results indicated that CNT is potential candidate for the removal of micro-organic pollutants. However, the reports on the CNT used as fluoride and heavy metal adsorbent are *** this paper, A novel material, alumina supported on carbon nanotubes (Al2O3/CNT), was prepared from carbon nanotubes and Al(NO3)3. X-ray diffraction (XRD) spectra demonstrate that alumina is amorphous, and scanning electron microscope (SEM) images show that CNT and alumina are homogeneously mixed. Furthermore, the fluoride adsorption behavior on the surface of Al2O3/CNT has been investigated and compared with other adsorbents. The results indicate that Al2O3/CNT has a high adsorption capacity, with a saturation adsorption capacity of 39.4 mg/g. It is also found that the adsorption capacity of Al2O3/CNT is 3.0～4.5 times that of γ-Al2O3while almost equal to that of IRA-410 polymeric resin at 25 ℃. The adsorption isotherms of fluoride on Al2O3/CNT is fit the Freundlich equation well, optimal pH ranging from 5.0 to *** in this paper, a novel material, modified carbon nanotubes (CNT), was prepared from carbon nanotubes and HNO3 under boiling condition. Infrared spectroscopy (IR) demonstrates

关键词： carbon nanotubes, modification, fluoride removal, lead removal.

Oxidation behavior of CNTs and the electric double layer capacitor made of the CNT electrodes

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Science China(Technological Sciences) 2003年第4期46卷 349-354页

作者：李辰砂王大志梁彤祥李贵涛王晓峰曹茂盛梁吉 Department of Mechanical Engineering Tsinghua University School of Material Science and Engineering Tsinghu University

The effect of CO2 oxidized carbon nanotubes (CNTs) on the performance of electric double layer capacitors (EDLCs) was studied. CO2 oxidation increased the specific area and improved the dispersity of CNTs. Specific capacitance of the polarizable electrodes in EDLCs based on the oxidized CNTs were obviously improved and the maximum specific capacitance of 47 F/g was obtained. CO2 oxidizing CNTs is hence an effective way to improve the performances of EDLCs based on the CNT electrodes.

关键词： carbon nanotubes, electric double layer capacitor, oxidation

Effect of acid oxidization of carbon nanotube electrode on the capacitances of double layer capacitors

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Science China(Technological Sciences) 2004年第3期47卷 257-264页

作者： Li Chensha1,WANG Dazhi1,LIANG Tongxiang2,WANG Xiaofeng1 & LIANG Ji1 1. Department of Mechanical Engineering, Tsinghua University,Beijing 100084, China 2. Institute of Nuclear Energy Technology, Tsinghua University,Beijng 102201,China Department of Mechanical Engineering Tsinghua University Beijing 100084 China Institute of Nuclear Energy Technology Tsinghua University Beijing 102201 China

Polarizable electrode of electric double layer capacitor was made from carbon nanotubes. The effect of acid oxidation of electrode on the specific capacitance was studied. Oxidation removed the redundant carbon, expanded the pore size and introducedf some kinds of functional groups on the surface of CNTs. The specific capacitance of the electrodes winth organic electrolyte was increased from 21.4 to 49.6 F/g after being oxidized at a volume ratio H2SO4 to HNO3 of 3:1.

关键词： carbon nanotubes, electric double layer capacitor, specific capacitance.