One Step Synthesis and Growth Mechanism of Carbon Nanotubes

A simple one step,reproducible,synthesis route for carbon nanotubes was proposed.No external catalyst was used for the synthesis.These nanotubes were obtained after decomposition of acetone at 650 ℃ in a specially designed autoclave.The pressure generated due to decomposition of acetone played a vital role in the synthesis.The X-ray diffraction pattern and transmission electron microscopy of the sample showed that the diameter of nanotubes is in the range of 3—14 nm.The thermo gravimetric analysis showed 3%weight loss below500 ℃;the content of amorphous carbon is very less.The growth mechanism of CNTs was also proposed in the present paper.     

Single Wall Carbon Nanotubes—Health,Safety and Environmental Status

SWCNTs(single wall carbon nanotubes)are a universal additive that improves the properties of numerous base materials.Their exceptional physical and chemical cha...     

Single-walled Carbon Nanotubes Regularly Aligned in Channels of Zeolite Single Crystal

We report the synthesis of single-wall carbon nanotubes (SWCNs) formed in 1-nm-sized channels of zeolite crystal by pyrolysis of tripropylamine molecules. The SWCNs are mono-sized and parallelly aligned along the crystal direction. In the present paper, we report the polarized Raman spectra measured for the wellaligned SWCNs, which gives us information about structural symmetry. Electrical transport properties of the SWNTs are measured in the temperature range of 0.3 K ～ 300 K. The conductivity of the SWCNs is monotonically decreased with decreasing temperature. The observed temperature dependence of zero-field conductance, In(σ) ～ 1/√T, could be explained well in terms of electron localization caused by imperfections and impurities in the nanotubes.     

Dispersion of the Nonlinear Optical Susceptibility in Single‐Wall Carbon Nanotubes

Abstract

We have calculated the dispersive behavior of the third‐order nonlinear susceptibility χ⁽³⁾ (?ω₃; ω₁, ω₁, ?ω₂) in single‐wall carbon nanotubes (SWCNTs) responsible for optical frequency mixing of the form ω₃ = 2ω₁ ? ω₂. The dispersive resonance of χ⁽³⁾ (?ω₃; ω₁, ω₁, ?ω₂) is shown to occur when the frequency ω₃ = 2ω₁ ? ω₂ is generated near the band gap of SWCNTs due to three‐wave mixing. A very sharp peak of χ⁽³⁾ (?ω₃; ω₁, ω₁, ?ω₂) reaching extremely high values ～10^?4 esu at the newly generated frequency ω₃ can be observed when not only ω₃ is close to the band gap of the system, but also when the frequencies of incident fields are near such a resonance.     

Research on the Relationship between Density of States and Conducting Properties of Single-walled Carbon Nanotubes

The analytical expression of the electronic density of states (DOS) for single-walled carbon nanotubes (SWNTs) has been derived on the basis of graphene approximation of the energy E(k) near the Fermi level EF. The distinctive properties of the DOS, the normalized differential conductivity and the current vs bias for SWNTs are deduced and analyzed theoretically. The singularities in the DOS (or in the normalized differential conductivity) predict that the jump structure of current (or conductance)--bias of SWNTs exists. All conclusions from the theoretical analysis are in well agreement with the experimental results of SWNT‘s electronic structure and electronic transport. In other words, the simple theoretical model in this paper can be applied to understand a range of spectroscopic and other measurement data related to the DOS of SWNTs.     

碳纳米管技术研究进展

作为重要的纳米功能纤维,碳纳米管有着令人振奋的广阔的应用前景,引起了世界范围内研究人员的广泛关注.综述了国内外碳纳米管技术的最新研究进展,比较了电弧放电、激光烧蚀以及化学气相沉积等3种主要的碳纳米管合成技术,并着重讨论了当前流行的化学气相沉积法,探讨了拉曼散射、激光诱导荧光、瑞利散射等分子光谱技术在碳纳米管表征中的应用,介绍了碳纳米管出色的力学、机电、场发射、电化学等特性以及基于碳纳米管的电子器件如场效应管、单电子管等.     

Synthesis of Carbon Fibers in the Decomposition of Acetylene and Propane–Butane Mixture in a Plasma Jet

Carbon fibers are prepared during the conversion of acetylene and propane–butane mixture in a jet of the helium and argon plasma without using catalysts. The synthesis is carried out in a plasma jet reactor. The synthesis products are studied by electron microscopy, synchronous thermal analysis and energy dispersive X-ray spectroscopy. The effect of the synthesis parameters on the structure and properties of the carbon fibers prepared in the volume is established. When the propane–butane mixture is decomposed in an inert medium, conditions are found for the synthesis of cylindrical carbon nanofibers of a tortuous shape with a diameter of up to 20 nm and a length-to-diameter ratio of up to 1000. The decomposition of acetylene at 350 Torr produces nanofibers formed by a chain of straight cylinders with a diameter of up to 20 nm, and cylindrical fibers are synthesized in the form of spirals of up to 200 nm in diameter at 150 Torr.     

Flower-shaped CuO Nanostructures： Synthesis, Characterization and Antimicrobial Activity

In the present work, flower-like CuO nanostructures were synthesized by reflux condensation method without using any surfactants or templates. Structural analysis by X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR） and Raman studies revealed the formation of highly crystalline single phase CuO, exhibiting monoclinic structure. Morphological analysis by field emission scanning electron microscopy （FESEM） showed flower-shaped CuO hierarchical architecture made up of interpenetrating self-assembled nanosheets. Optical analysis by UV-Vis diffused reflectance spectra （DRS） exhibited considerable blue-shift in the optical band gap due to quantum confinement effect. Photoluminescence （PL） spectrum showed both UV as well as visible emissions. The antibacterial activity of flower-shaped CuO nanostructures were tested against gram-positive （Bacillus subtilis, Bacillus thuringiensis） and gram-negative （Salmonella paratyphi, Salmonella paratyphi-a, Salmonella paratyphi-b, Escherichia coil and Pseudomonas aeruginosa） bacteria. Also, the antifungal activity of CuO was investigated against Aspergillus niger, Rhizopus oryzae, Aspergi/lus flavus, Cladosporium carrionii, Mucor, Penicilliurn notatum and Alternaria alternata. Results demonstrate that the flower-shaped CuO nanostructures act as an effective antimicrobial agent against pathogenic bacteria and fungi.     

Carbon nanotube dispersion in aluminum matrix composites—Quantification and influence on strength

Carbon nanotube (CNT) incorporation in metal matrix composites is hampered by the development of attractive van der Waals forces, which lead to the formation of CNT agglomerates. Therefore, a detailed quantification and characterization of CNT agglomerates and consequently CNT dispersion can enlighten their influence in composites strength. This work presents a comprehensive study, quantifying agglomerates by size, for three different composites (2, 4, and 6 CNT vol%), made with an aluminum-silicon matrix by a powder metallurgy route. From the obtained experimental data, an empirical model that attempts to predict the tensile strength of these composites from CNT agglomerates analysis is presented.     

碳纳米管储氢

近年来,碳纳米管由于其独特的力学、电学等性能以及在众多方面的潜在应用,越来越受到世界各国科学家的关注.最近,碳纳米管由于其大表面积和中空的结构,被应用于氢气储存.本文介绍了该领域最新的一些研究结果     

Molecular Simulation of Hydrogen Adsorption Density in Single-Walled Carbon Nanotubes and Multilayer Adsorption Mechanism

The adsorption of hydrogen onto single-walled carbon nanotubes (SWCNTs) was studied by molecular dynamics (MD) sim'lation. It was found that the hydrogen molecules distribute regularly inside and outside of the tube. Density distribution was computed for H2 molecule. Theoretical analysis of the result showed the multilayer adsorption mechanism of SWCNTs. The storage of H2 in SWCNTs is computed, which provides essential theoretical reference for further study of hydrogen adsorption in SWCNTs.     

利用场发射显微镜研究单壁碳纳米管的场发射特性

利用场发射显微镜研究了单壁碳纳米管(SWCNTs)的场发射特性.由于实验中所用的SWCNTs的长度基本一致,因此能同时观察到多根SWCNTs的场发射像.SWCNTs的场发射像随着热处理温度的升高而变化,直至热处理温度过高而塌缩.在一定的实验条件下,观察到了具有精细结构的单根碳纳米管顶端"帽子"的场发射像.电流-电压(I-U)曲线分析表明,SWCNTs的电流来源于场发射.     

碳纳米管储氢的研究与进展

本文概述了碳纳米管的结构性能及制备技术 ,并介绍了目前有关碳纳米材料特别是碳纳米管储氢的理论与实验上的研究进展     

纳米碳管储氢实验和机理研究

本文简要回顾了储氢材料研究的发展情况 ,主要介绍了纳米碳管储氢的实验进展。作者对纳米碳管储氢的机理方面进行了初步探讨 ,针对单壁纳米碳管 ,提出了一种解离凝聚机制     

失效AB5型贮氢合金电极材料在制备纳米碳管中的应用

纳米碳管是一种性能优异的新型功能材料.利用循环失效后的AB5型贮氢合金电极材料作为反应催化剂、乙炔气体作为原料气体通过CVD法制备出多壁纳米碳管,研究了经过破碎、清洗、氧化处理后的失效AB5型贮氢合金电极材料在合成纳米碳管中的催化性能,讨论了不同氧化温度处理催化剂对纳米碳管产率、形貌和结构稳定性的影响.结果表明,氧化处理温度对催化剂的催化效能有明显的影响,600℃为最佳氧化处理温度.以氧化处理后的失效AB5型贮氢合金电极材料作为催化剂制备碳纳米管,方法简单易行,为废旧镍氢电池负极材料的回收再利用提供了一种新的思路.     

Hydrogen Storage Alloy and Carbon Nanotubes Mixed Catalyst in a Direct Borohydride Fuel Cell

In this study, carbon nanotubes (CNTs) were mixed with AB5-type hydrogen storage alloy (HSA), as catalyst for an anode in a direct borohydride fuel cell (DBFC). As comparision, a series of traditional carbon materials, such as acetylene black, Vulcan XC-72R, and super activated carbon (SAC) were also employed. Electrochemical measurements showed that the electrocatalytic activity of HSA was improved greatly by CNTs. The current density of the DBFC employing the HSA/CNTs catalytic anode could reach 1550 mA·cm-2 (at -0.6 V vs the Hg/HgO electrode) and the maximum power density of 65 mW·cm-2 for this cell could be achieved at room temperature. Furthermore, the life time test lasting for 60 h showed that the cell displayed a good stability.     

Hydrogen storage capacity of single-walled carbon nanotube prepared by a modified arc discharge

Single-walled carbon nanotubes (SWCNTs, the mean diameter of 1.35 nm) were produced by a modified arc discharging furnace using a mixture powder of KCl and Co-Ni alloy as catalyst at 600°C. The hydrogen storage capacity of SWCNTs was enhanced by the mechanism of atom hydrogen spillover from the supported catalyst. The temperature effect on the hydrogen storage capacity of as-grown SWCNTs was investigated. The relative experiments of SWCNT hydrogen uptake and release were carried out by a high-pressure volumetric gas-adsorption measurement system. The experimental results indicated that the hydrogen storage capacity of SWCNTs increased with the environmental temperatures decreasing. The hydrogen storage capacity of SWCNTs was up to 1.73 wt% at 77 K for 2 hours under the pressure of 10 MPa, and the corresponding releasing hydrogen capacity is about 1.23 wt% under ambient pressure.