碳纳米管的可控长度拾取及导电性分析

拾取指定长度的半导体性碳纳米管对大规模制造碳纳米管场效应管具有重要意义.本文提出了一种利用原子力显微镜探针和钨针对碳纳米管进行可控长度拾取的方法并进行了碳纳米管导电性分析.在扫描电子显微镜下搭建微纳操作系统,针对切割操作过程中原子力显微镜探针、钨针和碳纳米管的接触情况进行了力学建模和拾取长度误差分析.建立了单根金属性碳纳米管、单根半导体性碳纳米管及碳纳米管束与钨针接触的电路模型,推导了接入不同性质碳纳米管后电路的电流电压特性方程.使用原子力显微镜探针对碳纳米管的空间位姿进行调整,控制钨针对碳纳米管上目标位置进行通电切割,同时获取切割电路中的电流电压数据.实验结果表明,本文提出的方法能够有效控制所拾取碳纳米管的长度,增加碳纳米管与原子力显微镜探针的水平接触长度能够减小碳纳米管形变导致的拾取长度误差,建立的电流电压特性方程能够用于分析碳纳米管的导电性.     

可溶性碳纳米管Z扫描实验研究

以可溶性碳纳米管为研究对象,进行了Z扫描实验.实验中通过改变样品的参量,研究了材料在不同浓度和不同厚度下的Z扫描曲线特性;实验分别在532nm和1064nm的激光下进行,并分别进行了开孔和闭孔实验.材料的闭孔 Z扫描曲线没有明显的峰谷对称结构,而开孔Z扫描曲线呈现关于原点对称的单一谷形状,表明样品存在较强的非线性吸收效应,非线性吸收可能是其主要的光限幅机理.     

基于碳纳米管的湿度检测仪的研究与实践

通过对湿度检测的重大意义进行分析,得出了本湿度检测仪的价值和意义,介绍了仪器的设计思路和应用前景,同时介绍了一种特殊的信号采集方法,从而将电阻的变化直接转化为信号的频率变化,再将此高频信号传入单片机,从而实现对信号的数字处理。文章中还涉及了软件程序设计,主要包括频率信号的频率读取和LED数码管显示的Keil C语言程序...     

基于单目视觉的航天器位姿测量

鉴于实时高精度航天器位姿测量不仅是航天器实时监控和跟踪的重要技术保证,同时也是实时调整和补偿航天器姿态的主要依据,提出一种基于单目视觉的航天器实时位姿测量方法,利用高精度旋转平台几何摄像机的方式对被测目标进行位姿解算。该方法不需要对被测目标进行几何约束,同时也不用进行转站测量,因而可以进行动态实时的在线位姿检测。航天器位姿实验结果表明:该单目视觉测量方法姿态测量误差小于0.05°,位置测量误差小于0.02 m,满足实际工程0.1°和0.05 m的精度需求。     

可溶性碳纳米管Z扫描实验研究

以可溶性碳纳米管为研究对象，进行了Z扫描实验.实验中通过改变样品的参量，研究了材料在不同浓度和不同厚度下的Z扫描曲线特性；实验分别在532nm和1064nm的激光下进行，并分别进行了开孔和闭孔实验.材料的闭孔Z扫描曲线没有明显的峰谷对称结构，而开孔Z扫描曲线呈现关于原点对称的单一谷形状，表明样品存在较强的非线性吸收效应，非线性吸收可能是其主要的光限幅机理.     

碳纳米管的热解法制备、电子显微镜观察及拉曼光谱研究

以二茂铁和二甲苯为原料在Ar和H2 气氛中不同温度下热解制备出了不同直径分布的碳纳米管。在 740℃、780℃、82 0℃和 880℃下制备出的碳纳米管的外径分布分别为 1 7-80nm、2 0 - 73nm、40 - 70nm、1 7- 2 7nm。拉曼光谱和透射电子显微镜 (TEM )观察表明 ,在82 0℃下制备的碳纳米管晶形最完整     

基于单目相机的三点式激光器测距及位姿估计方法研究

针对现有基于单目相机的三点式激光器视觉测量系统易受激光特征点的2D图像检测误差、相机畸变误差、图像中心点坐标误差以及焦距等影响,提出一种新的测距及位姿估计方法,使姿态角的求解仅与距离值、相机固定参数和激光器安装位置相关.首先,控制三个激光器在平行射出光的情况下,对单目相机进行内参标定,初步解算相机中心点的位姿坐标;然后...     

基于碳纳米管分子封装的一维电子波函数扫描

利用第一性原理,设计并研究了一类基于单臂碳纳米管的分子封装的分子体系．计算表明,半环葫芦脲类化合物可有效封装碳纳米管,引入微弱的分子间相互作用,对碳纳米管的电子态能级结构分布 仅带来微弱影响．半环葫芦脲分子与碳纳米管在管径方向的一维电子态波函数充分耦合,进而有效改变了一些前沿分子轨道的波函数在管径两头的分布以及相应的电子布居浓度．基于电子输运的模拟,发现半环葫芦脲分子在碳纳米管一维方向滑动时的某个电压下的电导变化可准确反映电子态波函数在相应分子导电通道上的一维分布信息．     

接触电阻对碳纳米管场发射的影响

基于改进的悬浮球模型,计算了碳纳米管和衬底间的接触电阻存在时碳纳米管顶端的局域电场, 并结合Fowler-Nordheim (F-N)场发射规律研究了接触电阻对碳纳米管场发射的影响.研究表明,接触电阻的存在,在高电场区域接触电阻抑制了碳纳米管的电子场发射,导致在高电场区域出现电流饱和及FN直线偏折现象.其原因可归结为接触电阻使得在碳纳米管顶端的局域电场相对于没有接触电阻时相对地减少. 关键词： 碳纳米管 场发射 接触电阻 电流饱和     

Nanomanipulator-assisted fabrication and characterization of carbon nanotubes inside scanning electron microscope

We have installed two nanomanipulators, which can travel about 20mm with a minimum increment of 1 nm, for manipulation of nanostructured materials inside field-emission scanning electron microscope (FE-SEM). Both manipulators render motions in x, y, and z directions, providing various manipulation freedoms such as moving, bending, cutting, and biasing. In addition, we have conducted in situ characterization of the electrical breakdown of multi-walled carbon nanotubes (MWCNTs). Our results demonstrate the possibility that MWCNTs can be used as a gas sensor.     

Field emission of individual carbon nanotubes in the scanning electron microscope

The field emission of individual multiwall carbon nanotubes grown by chemical vapor deposition was measured in a scanning electron microscope. By using a sharp anode, we were able to select one nanotube for measurements in carefully controlled conditions. Single nanotubes follow the Fowler-Nordheim law, and the dependence of the field enhancement with interelectrode distance and nanotube radius is in good agreement with the recent model of Edgcombe and Valdré. Our results suggest that only nanotubes with the highest field enhancement factors, i.e., at least 8x higher than those of the average nanotube population, contribute to the emitted current in usual large area measurements.     

Molecular dynamics simulation of an argon cluster filled inside carbon nanotubes

The effects of the diameters of single-walled carbon nanotubes （SWCNTs） （7.83A to 27.40A） and temperature （20 K-45 K） on the equilibrium structure of an argon cluster are systematically studied by molecular dynamics simulation with consideration of the SWCNTs to be fixed. Since the diameters of SWCNTs with different chiralities increase when temperature is fixed at 20 K, the equilibrium structures of the argon cluster transform from monoatomic chains to helical and then to multishell coaxial cylinders. Chirality has almost no noticeable influence on these cylindrosymmetric structures. The effects of temperature and a non-equilibrium sudden heating process on the structures of argon clusters in SWCNTs are also studied by molecular dynamics simulation.     

多壁碳纳米管中的多通道弹道输运特性

借助于扫描电子显微镜中可移动金属探针的测量系统,实现了探针电极与W衬底上生长的单根多壁碳纳米管一端的完美接触.研究了单根多壁碳纳米管室温下的电输运特性,发现多壁碳纳米管具有非常高的电流承载能力.对于直径100nm的碳纳米管,其电阻为34.4Ω,流经碳纳米管的最大电流可达7.27 mA,对应的电导为 460—490G0 .这一实验结果表明,大直径的多壁碳纳米管在室温下可以实现多通道弹道输运,是未来纳电子器件与电路的理想互联导线.     

卷曲方式对Rh原子在单壁碳纳米管内外吸附的影响

碳纳米管曲率与卷曲方式是同时存在并影响金属原子在碳纳米管内外吸附行为的重要因素, 单独研究卷曲方式对金属吸附行为的影响较困难. 选取曲率相近、卷曲方式不同的扶手椅型(6, 6)、锯齿型(10, 0)与手性(8, 4)单壁碳纳米管(SWCNT), 利用密度泛函理论研究了Rh原子在SWCNT内外的吸附行为. 构型优化表明:由于SWCNT卷曲方式不同, 导致Rh原子在(6, 6),(10, 0)与(8, 4)SWCNT内外吸附的稳定构型不同; 不同卷曲方式亦使SWCNT与Rh原子相互作用的C原子不同, 导致Rh 关键词： 密度泛函理论 单壁碳纳米管 Rh原子 卷曲方式     

Carbon linear chains inside multiwalled nanotubes

Multiwalled carbon nanotubes have been deposited on graphite cathodes by using an arc discharge technique in He atmosphere, with the insertion of a catalytic Ni-Cr mixture as well as without catalysers. The topography of such deposition has been investigated by SEM, while a parallel micro-Raman study has revealed, in particular regions of the deposited cathodes, strong bands in the range 1780-1860 cm⁻¹, assignable to linear carbon chains inside the nanotubes. The variation of intensity, frequency and bandwidth of such bands has been investigated, in relation with the spectral characters of the host multiwalled carbon nanotube. In the cathode deposited without catalyst a quite ordered configuration of multiwalled carbon nanotubes is obtained in the central zone, while the maximum concentration of linear carbon chains is found in a ring shaped zone just inside the border. In sample obtained with catalyst the deposited multiwalled carbon nanotubes appear always more disordered, and a remarkable concentration of carbon chains appears in some zones, with a more casual distribution.     

Design of soliton electron lattices in carbon nanotubes by a magnetic field

Electron states in the conduction band of carbon nanotubes are studied in the presence of a constant magnetic field perpendicular to the tube axis within the framework of Hubbard's model. Numerical solutions describing electron density waves corresponding to soliton lattices are obtained. The possibility of control over the electron lattice parameters with the help of a constant magnetic field is established. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 17–23, December, 2008.