基于HRTEM和Raman分析定向多壁碳纳米管阵列的生长机理

以二茂铁、二甲苯为前驱体,石英为衬底,在850 oC的管式炉内采用化学气相沉积法制备出了定向碳纳米管阵列. 高分辨透射电子显微镜和拉曼光谱的结果表明：碳纳米管阵列具有良好的定向性和多壁管状结构,石墨化程度高,并且只在表面存在少量单壁碳纳米管.定向多壁碳纳米管阵列的生长模式为“底部”生长模式,即在生长的初期,当催化剂颗粒较小时,析出的碳原子生成了单壁碳纳米管或与其性质类似的多壁碳纳米管(一般层数小于5层);催化剂颗粒逐渐长大后,大量的碳原子析出后生成了普通的多壁碳纳米管,从而形成了单壁碳纳米管只存在于碳纳米管阵列膜表面和多层碳纳米管膜表面与界面的现象.     

单壁碳纳米管在场发射显示器中的应用研究

采用丝网印刷法将利用电弧放电法制备的单壁碳纳米管印刷在玻璃板上作为场发射显示器阴极材料，利用荧光粉阳极测试了其发光亮度，并研究其场发射性能.实验结果表明，单壁碳纳米管作为场发射显示器阴极材料具有较低的开启电场和较大的场发射电流密度，显示出良好的场发射特性.     

单壁碳纳米管太赫兹超表面窄带吸收及其传感特性

由于碳纳米管具有优异的电学和光学特性,因此在光电子学领域具有广泛的应用前景.本文使用真空抽滤法,将单壁碳纳米管粉末分散液通过真空过滤的方式,制备了一种各向同性的单壁碳纳米管薄膜;进而提取了薄膜在0.4—2.0 THz范围内介电参数,并设计了一种基于单壁碳纳米管薄膜的新型太赫兹超表面窄带吸收器,这种超表面吸收器是由方形与工字形狭缝谐振器构成.实验和仿真结果表明,提出的太赫兹超表面吸收器在0.65,0.85,1.16和1.31 THz处存在4个明显的共振吸收峰,实现了最高可达90%的完美吸收.利用多重反射干涉理论阐明了这种多频带新型太赫兹超表面的吸收机制.通过在超表面器件表面覆盖具有不同折射率的介质层,深入研究了超表面作为折射率传感器的传感性能.研究结果表明,这种新型超表面吸收器用于折射率传感具有较高的灵敏度,为进一步开发新型碳基太赫兹超表面吸收器提供了新的思路和方案.     

CO2连续激光蒸发制备单壁碳纳米管及其Raman光谱的研究

讨论了在室温下用波长10.6μm的CO2连续激光制备单壁碳纳米管的工艺条件和生长机理.用大功率CO2连续激光蒸发制备单壁碳纳米管,所用激光功率400—900W,高分辨透射电镜观察表明单壁碳纳米管直径1.1—16nm,随着激光功率的增加稍微增加.本文还分别用波长为514.5nm和632.8nm激发光测量了CO2红外激光制备的单壁碳纳米管的一级和二级Raman光谱,发现在Raman特征峰的位置、强度上都存在差异.还将用CO2红外激光制备的单壁碳纳米管的Raman光谱与用YAG激光制备的单壁碳纳米管的Raman光谱进行了比较. 关键词： 单壁碳纳米管 CO2连续激光 Raman光谱     

碳纳米管薄膜层间改性复合材料 在不同应变率下的力学性能

将浮动催化化学气相沉积法制备的碳纳米管膜作为碳纤维层间改性材料,采用热压成型工艺制备了碳纳米管膜/碳纤维/环氧树脂混杂复合材料,并对其进行准静态II型断裂韧性实验以及准静态和动态压缩实验。碳纳米管膜层间改性后,复合材料的II型断裂韧性比未改性材料提高约60%,扫描电镜图像显示增韧机理主要是碳纳米管对基体的桥联。压缩实验结果表明,准静态压缩下碳纳米管膜改性材料在面内和面外两个方向的压缩强度都得到一定提高,动态面外压缩时改性后材料的压缩强度提高约9%,但是动态面内压缩时压缩强度没有提高,断口形貌显示这主要是碳纳米管膜内的分层所致。     

单壁碳纳米管非线性力学行为的数值模拟

单壁碳纳米管的力学行为是纳米复合材料和纳米器械的基本问题之一.使用有限元方法系统地研究了单壁碳纳米管的轴压和纯弯变形，并将有限元模拟结果和分子动力学模拟结果进行了比较.研究结果表明单壁碳纳米管的轴压屈曲载荷受直径变化的影响；单壁碳纳米管在弯曲载荷作用下的屈曲和后屈曲行为强烈地依赖于管长和管径的变化，合理地选择碳纳米管的弹性模量和壁厚，有限元方法能够很好地解释碳纳米管的屈曲机理.研究大尺度的纳米力学问题时，有限元方法将会成为更加准确、快捷的数值模拟方法.     

单壁碳纳米管非线性力学行为的数值模拟

单壁碳纳米管的力学行为是纳米复合材料和纳米器械的基本问题之一.使用有限元方法系统地研究了单壁碳纳米管的轴压和纯弯变形,并将有限元模拟结果和分子动力学模拟结果进行了比较.研究结果表明单壁碳纳米管的轴压屈曲载荷受直径变化的影响;单壁碳纳米管在弯曲载荷作用下的屈曲和后屈曲行为强烈地依赖于管长和管径的变化,合理地选择碳纳米管的弹性模量和壁厚,有限元方法能够很好地解释碳纳米管的屈曲机理.研究大尺度的纳米力学问题时,有限元方法将会成为更加准确、快捷的数值模拟方法. 关键词： 单壁碳纳米管 非线性力学行为 有限元     

直立在金膜表面的单壁碳纳米管的研究

用水溶胶体将单壁碳纳米管（ＳＷＣＮＴｓ）组装在晶态金膜表面,用扫描隧道显微镜（ＳＴＭ）研究了表面单壁碳纳米管直立于金膜表面,单根碳管的长度约在１０－１５ｎｍ之间。     

一种高效的用含水乙醇制备单壁碳纳米管的方法

本文采用流化床反应器,利用MgO作为催化剂载体,以Mo和Fe为催化剂。让Ar气流携带含水的乙醇蒸汽进入反应器,通过化学气相沉积(CCVD)法合成了单壁碳纳米管(SWCNTs)。利用拉曼光谱和透射电镜(TEM)对所合成的单壁碳纳米管质量进行检测。实验结果表明无水乙醇中加入7%的水反应温度在950℃时,制备的单壁碳纳米管的质量最好而且管径分布非常均匀。     

纳米CdS/碳纳米管复合材料的光电特性

基于CdS良好的光学性质和单壁碳纳米管(SWCNT)优异的电子学性质, 制备了纳米CdS/SWCNT复合材料和纳米CdS/聚乙烯亚胺(PEI)功能化SWCNT复合材料, 并利用日光灯光源模拟太阳光研究了它们的光电性质. 结果表明, 纳米CdS/SWCNT复合材料呈现显著的负光电导现象, 而纳米CdS/PEI-SWCNT复合材料呈现强烈的正光电导现象. 用电子转移理论对这一结果进行了解释. 两样品在大角度弯折的情况下, 光电性质均基本没有变化. 因此, 纳米CdS/碳纳米管复合材料在光电领域, 尤其是新兴的柔性光电子学领域有着良好的应用前景. 关键词： 碳纳米管 CdS 光电材料 复合材料     

Thermal properties of single-walled carbon nanotube crystal

In this work, the thermal properties of a single-walled carbon nanotube (SWCNT) crystal are studied. The thermal conductivity of the SWCNT crystal is found to have a linear dependence on temperature in the temperature range from 1.9 K to 100.0 K. In addition, a peak (658 W/mK) is found at a temperature of about 100.0 K. The thermal conductivity decreases gradually to a value of 480 W/mK and keeps almost a constant in the temperature range from 100.0 K to 300.0 K. Meanwhile, the specific heat shows an obvious linear relationship with temperature in the temperature range from 1.9 K to 300.0 K. We discuss the possible mechanisms for these unique thermal properties of the single-walled carbon nanotube crystal.     

Carbon Nanotube/P(VDF-TrFE) Nano-Composite Characterization by Total Reflection X-Ray Fluorescence

In continuation of our research on carbon nanotube/P(VDF-TrFE) nano-composites [1], total x-ray fluorescence (TXRF) is engaged in a novel characterization of these materials regarding their compositions, purities, and structural analysis. Samples such as single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), P(VDF-TrFE) copolymer, SWCNT/P(VDF-TrFE), and MWCNT/P(VDF-TrFE) were analyzed by TXRF. The synthetic quartz used as a substrate was analyzed as reference material for the TXRF measurements. The ethanol and the dimethylformamide (DMF) used as solvents for carbon nanotubes and copolymers respectively were also analyzed by TXRF to determine whether they have an influence or not on the TXRF of the previous material. The preliminary results showed that single-walled and multi-walled carbon nanotubes prepared by the arc-discharge method contain catalytic particles such as Fe, Co, and Ni used to obtain SWCNT while there were no metal or impurities in MWCNT. The TXRF spectrum of CNT/P(VDFTrFE) showed the same results as we found previously with background due to the P(VDF-TrFE) copolymer scattered signal. __________ Published in Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 5, pp. 700–702, September–October, 2005.     

A nonlocal Levinson beam model for free vibration analysis of zigzag single-walled carbon nanotubes including thermal effects

A nonlocal Levinson beam model is developed to study the free vibrations of a zigzag single-walled carbon nanotube (SWCNT) in thermal environments. The equivalent Young’s modulus and shear modulus for a zigzag SWCNT are derived using an energy-equivalent model. The present study illustrates that the vibration characteristics of an SWCNT are strongly dependent on the temperature change and on the chirality of a zigzag carbon nanotube. The investigation of the chirality and temperature effects on free vibration of carbon nanotubes may be used as a useful reference for the application and the design of nanoelectronic and nanodrive devices, nano-oscillators, and nanosensors, in which carbon nanotubes act as basic elements.     

Bundling influence on ultrafast optical nonlinearities of single-walled carbon nanotubes in suspension and composite film

Nonlinear optical characteristics of single-walled carbon nanotubes (SWCNTs) dispersed in dichlorobenzene and imbedded in polymer were investigated at 800 nm using the time-resolved optical Kerr gate technique. For systematic study of the influence of SWCNT bundling on optical nonlinearities, SWCNT solutions with different concentrations and a series of SWCNT/polymer composites deposited on glass substrates with different concentrations and thicknesses were prepared. The nonlinear response was comparable to the pulse duration of the laser used (～90 fs) both in SWCNT solutions and SWCNT/polymer composites. Over three orders of magnitude enhancement was observed in the third-order nonlinear susceptibility of SWCNT/polymer composite film compared with that of SWCNT solution. An appreciable reduction of microscopic and macroscopic nonlinearities was observed with increasing SWCNT concentrations due to stronger bundling of SWCNTs.     

Mechanical properties of nickel-coated single-walled carbon nanotubes and their embedded gold matrix composites

The effects of nickel coating on the mechanical behaviors of armchair single-walled carbon nanotubes (SWCNTs) and their embedded gold matrix composites under axial tension are investigated using molecular dynamics (MD) simulation method. The results show that the Young's moduli and tensile strength of SWCNTs obviously decrease after nickel coating. For armchair SWCNTs, the decreased ratio of the Young's moduli of SWCNTs with smaller radius is larger than that of SWCNTs with larger radius. A comparison is made between the response to Young's modulus of a composite with parallel embedded nanotube and the response of a composite with vertically embedded nanotube. The results show that the uncoated SWCNT can enhance the Young's modulus of composite under the condition of parallel embedment, but such improvement disappears under the condition of vertical embedment because the interaction between SWCNT and gold matrix is too weak for effective load transfer. However, the nickel-coated SWCNT can indeed significantly improve the composite behavior.     

Development of hydrogel microstructures on single-walled carbon nanotube films

In this study, the development of polyethylene glycol (PEG) hydrogel microstructures led to the micropatterning of single-walled carbon nanotube (SWCNT) films. Polyethylene glycol was patterned in a process analogous to photolithography in order to manufacture high-density arrays of micrometer-scale hydrogel wells on SWCNT film surfaces. These microwells were composed of hydrophobic SWCNT films surrounded by hydrophilic PEG hydrogel walls. Effects of PEG hydrogel microstructures on the micropatterning of SWCNT films were systematically investigated under different substrates prepared with 3-(trichlorosilyl)propyl methacrylate or octadecyltrichlorosilane solution. A characterization of protein adsorption and an electrochemiluminescence (ECL) reaction were performed to evaluate the biocompatible and electrical efficiency of the patterned SWCNT films in various applications. The proteins selectively adhered to the SWCNT surface inside the microwells, while adherent proteins were absent from the hydrogel walls. In the ECL reaction, the SWCNT films patterned with PEG hydrogel exhibited good, stable ECL behavior, a sign that patterned SWCNT films can be used as flexible and transparent electrodes.     

First-principles study of the switching characteristics of the 15,16-dinitrile DDP/CPD-based optical molecular switch with carbon nanotube electrodes

We have studied the switching characteristics of an optical molecular switch based on the 15,16-dinitrile dihydropyrene/cyclophanediene (DDP/CPD) molecule with two single-walled carbon nanotube (SWCNT) electrodes using first-principles transport calculations. It is shown that the DDP shows an overall higher conductance than the CPD at low bias which is independently of the SWCNT chirality. Meantime, the conductance of the molecular switch can be tuned by the chirality of the SWCNT.     

Fabrication and electrochemical properties of free-standing single-walled carbon nanotube film electrodes

An easily manipulative approach was presented to fabricate electrodes using free-standing single-walled carbon nanotube (SWCNT) films grown directly by chemical vapor deposition.Electrochemical properties of the electrodes were investigated.In comparison with the post-deposited SWCNT papers,the directly grown SWCNT film electrodes manifested enhanced electrochemical properties and sensitivity of sensors as well as excellent electrocatalytic activities.A transition from macroelectrode to nanoelectrode behaviours was observed with the increase of scan rate.The heat treatment of the SWCNT film electrodes increased the current signals of electrochemical analyser and background current,because the heat-treatment of the SWCNTs in air could create more oxide defects on the walls of the SWCNTs and make the surfaces of SWCNTs more hydrophilic.The excellent electrochemical properties of the directly grown and heat-treated free-standing SWCNT film electrodes show the potentials in biological and electrocatalytic applications.     

147 fs碳纳米管倏逝场锁模全光纤掺铒光纤激光器

利用化学腐蚀法在光纤包层表面成功制备了调制深度为3.9%的单壁碳纳米管饱和吸收体.组建了环形腔结构的全光纤掺铒光纤激光器,以制备的单壁碳纳米管薄膜为锁模元件,利用倏逝场锁模实现了锁模输出.锁模脉冲的中心波长为1556 nm,3 dB光谱带宽为24 nm,脉冲宽度为147 fs,重复频率为150 MHz.在520mW抽运功率下,平均输出功率为21 mW,相应的单脉冲能量为0.14 nJ.