微孔对单壁纳米碳管储氢性能的影响

用巨正则蒙特卡罗分子模拟方法研究了单壁纳米碳管中的微孔即单壁纳米碳管基本孔-内管腔和管间孔对单壁纳米碳管储氢性能的影响.与低温下氮气吸附实验结果的比较发现单壁纳米碳管的内管腔是吸附的主要位置.分析单壁纳米碳管内管腔中吸附势的叠加和利用效率，发现管径为2nm左右时单壁纳米碳管内管腔的储氢容量最高.当单壁纳米碳管阵列的管间距增加时，单壁纳米碳管的管间孔也会成为有效的氢吸附位. 关键词： Monte Carlo方法 单壁纳米碳管 储氢 微孔     

纳米碳管阵列场增强因子的计算

采用悬浮球模型，结合对称的镜像电荷层方法，对静电场中纳米碳管阵列的场增强因子进行了计算，并在考虑极板间距的情况下，对其计算结果做了修正.结果表明：纳米碳管阵列的间距对纳米碳管阵列的场发射性能影响很大.当纳米碳管阵列中碳管间距小于碳管高度时，场增强因子随间距的减小而急剧减小；而当碳管间距显著大于碳管高度时，场增强因子几乎不变.但当考虑阴阳极之间单位面积通过的场发射电流时，可论证当管间距与管高度相若时，能使场发射电流密度最佳(最大).另外，极板间距对场增强因子的影响很小，但是可以通过减小极板间距，来降低纳米碳管作为场发射体的场发射的开启电压，优化纳米碳管的场发射性能. 关键词： 纳米碳管阵列 场增强因子 开启电压     

双壁纳米碳管的制备及其结构研究

用含有铁族金属硫化物的复合石墨棒作阳极，在氢气氛围下实施电弧放电，制备出了双壁纳米碳管.经透射电子显微镜观察与分析，发现在蒸发室内壁及阴极周围的附着物中，都含有双壁纳米碳管. 关键词： 双壁纳米碳管 透射电子显微镜     

碳纳米管增强铝基复合材料电子理论研究

采用自行开发计算机软件，建立了铝晶粒大角度重位点阵晶界模型及碳纳米管与铝金属的界面结构，利用递归法计算了纳米碳管增强铝基复合材料的电子结构参数(铝晶界、铝与纳米管界面及纳米管的结构能，体系费米能级等). 计算结果表明：Σ为5的晶界结构能最低，比较稳定；纳米碳管在铝晶粒的晶界处与铝形成的界面结构能较低，复合材料中纳米碳管主要分布在铝晶粒的晶界处；铝提高纳米碳管的结构能，降低纳米碳管的稳定性，增强碳管的物理化学活性，且管口处的碳原子稳定性较差，易与周围环境中的原子结合生成稳定结构. 关键词： 电子结构 晶界 铝复合材料 纳米管     

纳米碳管阵列场发射电流密度的理论数值优化

以纳米碳管阵列为研究对象,利用镜像悬浮球模型及Fowler-Nordheim电流密度公式,对纳米碳管阵列的场发射电流密度进行计算,进而综合考虑场发射增强因子及场发射电流密度对纳米碳管阵列场发射性能进行定量优化.参考碳管阵列场发射电流密度最大值及场发射增强因子,表明当纳米碳管阵列间距为碳管高度十分之一时,纳米碳管阵列的场发射性能得到优化.与以前的理论估算结果相比,优化的阵列间距进一步减小.当纳米碳管间距过大,场发射增强因子增加,而场发射电流密度会在更大程度上减小;当纳米碳管密度较大时,场发射增强因子受到静电 关键词： 纳米碳管 场发射 增强因子 电流密度     

高纯单壁纳米碳管大量制备的新方法和工艺条件

在单壁纳米碳管大量制备方面提出了新方法和工艺条件.反复实验及电子显微镜分析表明,利用该方法和工艺条件,可以获得高产量、高纯度单壁纳米碳管.单根给定长度的含有金属的复合石墨阳极与阴极成一定角度在高温氦电弧中放电数分钟,即可获得1.0g以上含有60%左右的单壁纳米碳管的生成物.这为高纯单壁纳米碳管的规模化生产奠定了基础 关键词： 单壁纳米碳管 电弧放电 透射电子显微镜分析     

甘氨酸在纳米碳管中的吸附及性质的分子模拟

采用分子力学、分子动力学方法模拟研究了甘氨酸分子在单壁纳米碳管中的吸附和扩散行为 ,并对甘氨酸分子在纳米碳管中的构象和能量进行了优化 .模拟计算结果表明 ,甘氨酸在纳米碳管中的构象发生了伸缩和扭转 ,这种构象的改变将会导致氨基酸生物性能的改变 ;纳米碳管对氨基酸分子具有较强的吸附作用 ,其中纳米碳管和甘氨酸分子之间的π -π相互作用增加了纳米碳管对氨基酸的吸附能 .模拟过程中氨基酸分子和纳米碳管之间的运动会保持很强的协同效应 ,使模拟体系构型在能量上处于最稳定的状态     

超细0.4nm直径单壁碳管的光学特性

由于纳米碳管的优异机械特性及其丰富多采的光学和电学特性，它自1991年被发现以来一直受到科学家的青睐，纳米碳管研究已成为当今世界上发展最迅速，竞争最激烈的科学前沿领域之一。怎样才能把纳米碳管做得更细小，尺寸更均匀以及如何使众多的纳米碳管排列规整，一直是纳米碳管研究中的难题。我们利用多孔的沸石晶体作为载体，首次成功地研制出了尺寸均一，排列规整的超细单壁纳米碳管，这些超细纳米碳管具有独特的性能，低温下（＜20K）甚至呈现出前所未有的一维超导现象。详细介绍了这些超细单壁纳米碳管的制备过程，并着重介绍其在可见光区的光吸收，光发射以及二次谱波的倍频特性。     

高效循环电弧放电法制备大量单壁纳米碳管的研究

介绍一种利用电弧放电法高效率制备大量单壁纳米碳管的新方法.以钨代替传统的石墨棒作为放电阴极，采取循环式往返放电法.同时利用高分辨透射电子显微镜及拉曼光谱对制备的单壁纳米碳管进行了观察、表征.实验证明：以钨为阴极的循环电弧放电法可以初步实现单壁纳米碳管的高效率、大批量生产. 关键词： 单壁纳米碳管 钨电极 拉曼光谱     

微波等离子体技术在ICF制靶中的应用

 为了提高ICF精密制靶的质量，提出用微波等离子体（MP）技术，包括等离子体薄膜制备、等离子体反应性离子束刻蚀、聚焦离子束刻蚀、掺杂纳米金属粉末制备和掺杂纳米金属粉末的表面包覆改性等技术，去加以改进和解决。此方法与其它成膜技术相结合，在ICF精密制靶中得到广泛应用。     

Absolute negative conductivity in zig-zag carbon nanotubes in the presence of a magnetic field

The volt-ampere and gauss-ampere characteristics of zig-zag carbon nanotubes are calculated at low temperatures based on the average electron method. The characteristics obtained are analyzed as functions of the magnetic field strength. It is revealed that a constant electric field can arise spontaneously in carbon nanotubes upon application of an alternating high-frequency electric field. This effect can be due to the nonequilibrium electron subsystem of the carbon nanotubes.     

Effect of carbon nanotubes on the anode performance of natural graphite for lithium ion batteries

A comparative investigation was carried out on carbon black and multiwalled carbon nanotubes as conductive additives in spherical natural graphite for lithium ion batteries. Scanning electron microscopy images showed that carbon nanotubes interlaced graphite particles in series to form a three-dimensional network. The constant current charge-discharge experiments showed that carbon nanotubes were more effective in improving reversible capacity and cycle stability. The reversible capacity was improved to 366 mAh/g and the cycle stability was improved effectively when carbon nanotubes were used. The research is of potential interest to the application of carbon nanotubes as conductive additives in anode materials for high-power lithium ion batteries.     

聚甲基丙烯酸甲酯-功能化多壁碳纳米管的制备及性能

"以羧基多壁碳纳米管、甲基丙烯酸甲酯作为原料,过氧化苯甲酰作为引发剂,采用原位聚合法制备聚甲基丙烯酸甲酯-功能化多壁碳纳米管．利用投射电子显微镜、扫描电子显微镜、核磁共振、傅立叶转换红外光谱,热重分析和拉曼光谱对合成产物进行分析表征．结果表明,聚甲基丙烯酸甲酯共价接枝到羧基碳纳米管表面,羧基碳纳米管的含量影响合成产物的表观形态．核磁共振研究表明聚甲基丙烯酸甲酯-功能化多壁碳纳米管在氘代氯仿中有一定的溶解性．"     

Defect electron states in carbon nanotubes and graphite from the NEXAFS spectroscopy data

Experimental results of studying the electronic structure of single-walled and multi-walled carbon nanotubes as well as graphite by X-ray absorption spectroscopy (or NEXAFS spectroscopy) are presented. The C1s absorption spectra are measured with high energy resolution using the equipment of the Russian-German beamline of the BESSY electron storage ring. Features found in absorption spectra of carbon nanotubes and graphite for the first time are interpreted in the case of carbon nanotubes as the contribution of electron states appearing due to the imperfection of their structure both under the nonequilibrium synthesis conditions and during the subsequent producing manipulations.     

Study on structure change of carbon nanotubes depending on different reaction gases

Aligned carbon nanotubes were grown by plasma-enhanced hot filament chemical vapor deposition using different reaction gases and they were investigated by scanning electron microscopy and transmission electron microscopy. It is found that the hollow carbon nanotubes were formed using methane and hydrogen as the reaction gases, but the bamboo-structured carbon nanotubes were grown when ammonia was added into the reaction gases, indicating that the structure of the aligned carbon nanotubes was changed depending on different reaction gases. On setting of diffusion of carbon, the effects of the nitrogenous gas on the structure change of carbon nanotubes are studied.     

New aspects on pulsed laser deposition of aligned carbon nanotubes

We have grown carbon nanotubes (CNT) by pulsed laser deposition (PLD) at 1000 °C in Ar atmosphere. A Nd/YAG laser was used for irradiation of a graphite target containing Ni and Co rods. High-resolution scanning electron microscopy (HRSEM) and transmission electron microscopy (TEM) images showed that “closed” carbon nanotubes were grown between clusters of metallic particles, so that the individual nanotubes were arranged in parallel to each other forming a shape of “Rope-Bridge”. The nanotubes structure was analyzed by high-resolution transmission electron microscopy (HRTEM) and their type was found to be of MWNT, containing about five SWNT. Total diameter was 5-20 nm and their length was about 1 μm. High homogeneous distribution carbon nanotubes were grown and different structures were observed such as well-aligned carbon nanotubes, bamboo-like and Y-junction carbon nanotubes.     

Specific features of the electronic structure of fluorinated multiwalled carbon nanotubes in the near-surface region

The C 1s and F 1s X-ray photoelectron spectra of fluorinated multiwalled carbon nanotubes with different fluorine contents have been measured using the equipment of the Russian-German beamline at the BESSY storage ring by varying the energy of exciting photons. It has been established that two fluorocarbon phases in which the chemical bonding is characterized by a different electron transfer from carbon atoms to fluorine atoms are formed in the near-surface region of nanotubes with fluorine concentrations of 10–39 wt %. The content of the dominant first phase with a large electron transfer in nanotubes remains unchanged with an increase in the probing depth. This phase is identified as a bulk phase formed as a result of the covalent attachment of fluorine atoms to graphene layers of the graphite skeleton without its destruction. The second phase with a small electron transfer is a near-surface phase, because it is predominantly located within two or three upper graphene monolayers and its contribution considerably decreases with an increase in the probing depth of fluorinated multiwalled carbon nanotubes.     

Hydrogen-free spray pyrolysis chemical vapor deposition method for the carbon nanotube growth: Parametric studies

Spray pyrolysis chemical vapor deposition (CVD) in the absence of hydrogen at low carrier gas flow rates has been used for the growth of carbon nanotubes (CNTs). A parametric study of the carbon nanotube growth has been conducted by optimizing various parameters such as temperature, injection speed, precursor volume, and catalyst concentration. Experimental observations and characterizations reveal that the growth rate, size and quality of the carbon nanotubes are significantly dependent on the reaction parameters. Scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy techniques were employed to characterize the morphology, structure and crystallinity of the carbon nanotubes. The synthesis process can be applied to both semiconducting silicon wafer and conducting substrates such as carbon microfibers and stainless steel plates. This approach promises great potential in building various nanodevices with different electron conducting requirements. In addition, the absence of hydrogen as a carrier gas and the relatively low synthesis temperature (typically 750 °C) qualify the spray pyrolysis CVD method as a safe and easy way to scale up the CNT growth, which is applicable in industrial production.     

Effect of thermal motion of residual gas molecules on the degradation of the field emission cathode based on carbon nanotubes

The rate of degradation of carbon nanotubes in an electron field emission cathode is calculated taking into account thermal motion of the residual gas atoms. As the degradation mechanism, we consider the sputtering of the surface of carbon nanotubes by ions formed as a result of ionization of residual gas molecules by electron impacts. It is shown that the allowance for the initial thermal motion of atoms, the ionization of which is a source of ions, considerably reduces the degradation rate as compared to the results of approximate calculations based on the assumption of motionless atoms.     

Study of multilayer carbon nanotubes subjected to the impact of a nanosecond high-energy ion beam

The impact of a nanosecond high-energy ion beam on the structure and morphology of multilayer carbon nanotubes and their ensembles is studied using transmission electron microscopy and scanning electron microscopy. It is shown that ion-beam irradiation leads to a decrease in the outer diameters of carbon nanotubes, which is related to the destruction of their outer layers. In addition, the secondary growth of carbon nanotubes with smaller diameters and the growth of bulblike formations, inside which structures with interplanar distances that are close to those of nanodiamond are fixed, are observed.