多壁碳纳米管在红外波段的散射特性研究

采用Bessel和Hankel函数级数模技术,对不同多壁碳纳米管在红外波段的电磁散射特性进行了研究.结果表明,不同半径、不同纳米管数目对入射的横磁波与横电波的散射现象产生不同的影响.在横磁波垂直入射时,不同结构多壁碳纳米管对其频率的选择性不明显,相同半径纳米管对横磁波的散射强度随纳米管数目的增加而增强,但其峰值不变;而在横电波入射时,不同结构多壁碳纳米管表现出强烈的频率选择性,其散射强度随半径、管数目的增加而明显增强.研究结果对利用碳纳米管进行红外波段的探测具有一定意义.     

单根多壁碳纳米管的电学测试

提出了一种制备多壁碳纳米管的简单方法.以乙醇为碳源,利用催化化学气相沉积工艺制备了碳纳米管.用较为简单的设备在较低的反应温度下,在基底上生长了取向多壁碳纳米管阵列.利用扫描电子显微镜内部的纳米操纵仪对单根碳纳米管进行操纵,并测试了单根多壁碳纳米管的电学特性.     

单根多壁碳纳米管的电学测试

提出了一种制备多壁碳纳米管的简单方法。以乙醇为碳源,利用催化化学气相沉积工艺制备了碳纳米管。用较为简单的设备在较低的反应温度下,在基底上生长了取向多壁碳纳米管阵列。利用扫描电子显微镜内部的纳米操纵仪对单根碳纳米管进行操纵,并测试了单根多壁碳纳米管的电学特性。     

多壁碳纳米管薄膜在THz波段的传输与偏振特性

利用化学气相沉积法制备了三种类型多个超有序排列的多壁碳纳米管薄膜样品,通过太赫兹时域光谱技术,获取相位和振幅信息,详细研究了薄膜在太赫兹波段的传输特性。结果表明:超有序多壁碳纳米管薄膜在纳米管轴向方向与垂直于轴向方向表现出明显的光、电各向异性特性;测试的介电常数实部为负,虚部为正,证实了制备的薄膜具有金属性;薄膜具有的各向异性为研究其偏振特性提供了直接证据,随着薄膜厚度的增加,偏振度和消光比增加,其9 m厚的自由薄膜度可以获得99%的偏振度。研究结果对开展超有序多壁碳纳米管薄膜在太赫兹偏振器、调制器与光开关等领域的研究有重要指导意义。     

电子束非热辐照诱导多壁碳纳米管的结构转变

借助高分辨透射电子显微镜(TEM)原位观察了室温时在相同电子束辐照条件下不同形态多壁碳纳米管(MWCNT)的结构不稳定性转变。实验发现:两端固定、轴向平直的MWCNT直径均匀收缩,且收缩速率先增大后减小;而一端固定、另一端自由的MWCNT径向收缩不明显,但是会进行较快的轴向收缩。基于表面纳米曲率效应和非热激活效应,提出碳原子的融蒸和扩散机制,突破了传统的碰撞(knock-on)机制的局限。对上述实验现象进行了全面深入的分析与讨论,研究为新一代MWCNT为基的纳米结构或纳米器件设计及加工提供了可靠工艺参数。     

多壁碳纳米管/棉织物复合柔性电极的制备

近年来柔性超级电容器在柔性电子设备领域起到越来越重要的作用,其中电活性材料与织物的结合是制备柔性电极的关键。本文针对棉织物进行多壁碳纳米管的高密度堆积性研究,并进行循环伏安曲线测试、充放电测试和交流阻抗测试。研究表明,该复合材料具备电极的应用性质,以及良好的循环稳定性和弯曲性,为进一步制备高电容量的柔性超级电容器打下了基础。     

用电镜照片定量描述多壁碳纳米管的曲折状态

碳纳米管的形貌受制备方法以及各种后处理过程的影响.为了清楚地描述碳纳米管的形貌特征,本文建立了一种用电镜照片对碳纳米管曲折状态进行定量表征的方法.将一定数量多壁碳纳米管的高分辨透射电镜或扫描电镜照片进行观察和统计分析后,通过引入曲折因子（tortuosity factor TF）和计算标尺（calculating scale CS）两个参数,可以定量表征多壁碳纳米管的曲折程度.本文用该方法对三种不同的多壁碳纳米管进行了表征：纳米聚团流化床反应器制备的多壁碳纳米管、浮游法制备的超长阵列多壁碳纳米管以及静电纺聚环氧乙烷纳米纤维中的多壁碳纳米管.结果显示在所统计的计算标尺范围内,不同多壁碳纳米管的曲折因子有着显著的差异,进而根据多壁碳纳米管曲折因子的差异深入分析了制备方法以及处理过程对其形貌的影响.     

聚苯胺-多壁碳纳米管掺杂聚乙烯醇的z扫描研究

为了提高聚苯胺的非线性光学性能以及实际应用价值,使用原位聚合法制备了聚苯胺-碳纳米管复合体掺杂聚乙烯醇薄膜,并利用单光束z扫描技术,在波长532nm、脉宽8ns的条件下研究了这种材料的3阶非线性光学性质,计算其3阶非线性光学系数。结果表明,与聚苯胺本体相比,薄膜样品的非线性光学性能得到明显的提高,将其制备成薄膜为今后的实际应用打下基础。     

多壁碳纳米管的极限强度测量及其辐射诱导交联改进

由于碳纳米管优异的力学性质,人们对其应用的研究越来越多,从弹道盔甲到纳米电子器件等。然而,由于在样品制备过程中引入的杂质以及不适当的测量手段,这些性质的测量还不能达到理论预测值。本文报道了平均断裂强度〉100GPa的多壁碳纳米管,超过以前观察的3倍．这些结果也与量子力学估算的仅包括偶然空位缺陷的碳纳米管结果非常吻合,吻合率是自由缺陷管期望值的80％。这可能是由于在样品制备过程中不进行化学处理,避免了缺陷的形成。利用高分辨图像可以直接确定断裂层的数量和外层的手性。与相似直径的无辐射样品相比,在200keV下,电子辐射10、100、1800s可以导致最大承载提高2．4、7．9、11．6倍,该效应被归因于层间的交联。计算模拟结果也表明了不同辐射诱导交联缺陷对层间负载分配的影响。     

一种高精度的TOA估计方法

提出了一种 CDMA系统的高精度的信号到达时延(TOA)的估计方法。在不提高采样频率的情况下,使用积分-清除电路对接收信号进行采样,将离散信号用离散傅里叶变换(DFT)转换到频率域中,然后根据 CDMA信号模型和多径信道模型以及已知的扩频码的离散频谱,估计出信号相对于一个码片周期的整数部分 TOA;再在离散频率域中用最小二乘法估计出信号到达的小数部分 TOA,该方法即使在采样频率不高的情况下,也有很高的精度,而且运算量小,因此是一种有效的高精度 TOA估计方法。     

大面积多壁碳纳米管薄膜光电响应实验

为了研究大面积多壁碳纳米管(MWNTs)的光电响应特性,利用剥离技术和旋涂法制备了大 面积MWNTs薄膜器件;采用532nm激光作为激励光源,当激光照射薄 膜器件不同位置时,测试其光电流和光电 压。实验结果表明,激光诱导产生的光电流/电压与光照位置有关,当光照位置在器件两端 时,光电流、光电压 最大,两端的光电流分别为0.04μA、－0.06μA和光电压分别为0.04mV、－0.06mV; 当激光照射在器件几 何中心时,光电流、光电压趋于0。分析表明,光热电效应是光电流、电压产生和变化的主 要原因。     

Photovoltaic properties of multi-walled carbon nanotubes deposited on n-doped silicon

Multi-wall carbon nanotubes (MWCNTs), grown by catalytic chemical vapor deposition (CCVD) over Fe supported on alumina catalyst, using isobutane as feedstock, are dispersed in aqueous solutions of sodium dodecyl sulfate. Stable and highly photosensitive heterojunctions are developed by liquid-phase deposition of MWCNTs/surfactant mixtures on the top of n-doped monocrystalline silicon wafers. Electrical measurements performed in the dark and under broad-band visible light, show that the hybrid solar cells, despite their non-optimized design, have conversion energy efficiency of the order of 3%.     

Negative permittivity and negative permeability of multi-walled carbon nanotubes/polypyrrole nanocomposites

Multi-walled carbon nanotubes(MWCNTs)/polypyrrole(PPy) nanocomposite particles were synthesized by in-situ polymerization. Negative permittivity and negative permeability appeared simultaneously in MWCNTs/PPy nanocomposites with different content of MWCNTs. It was found from SEM analysis that MWCNTs/PPy nanocomposite particles were randomly packed with a large number of micropores, and formed a lot of conductive loops around the micropores, some MWCNTs could be cross the micropores and increase the number of conductive loops. In the meantime, MWCNTs themselves in MWCNTs/PPy composite also formed many conductive networks. The negative permittivity behavior stem from the plasma oscillation of delocalized electrons in the conductive networks, and the negative permeability was attributed to the diamagnetic response of ring currents in the plentiful conductive loops. This study should initially find a double negative metamaterial in polymer composites.     

Structural and optical properties of functionalized multi-walled carbon nanotubes

Herein, we report the functionalization of multiwalled carbon nanotubes (MWCNTs) using meta-Chloroperoxybenzoic acid (mCPBA) as an oxidizing agent. Epoxy groups are incorporated into the sidewall of MWCNTs and the prepared functionalized multiwalled carbon nanotubes (F-MWCNTs) were characterized using FT-IR spectroscopy, X-ray diffraction, Raman spectroscopy and UV–visible spectroscopy. Morphology of MWCNTs and F-MWCNTs was determined using Scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM results clearly indicated that the diameter of F-MWCNTs is increased by 120% as compared to neat MWCNTs. From UV–visible spectroscopy data, band gap of F-MWCNTs was calculated using Tauc equation and it was found to be 3.9 eV. Photo emission property of F-MWCNTs was analyzed using photoluminescence spectroscopy. F-MWCNTs showed nice emission in the visible region and it depended upon the excited wavelength. These functionalized carbon nanotubes could find use as tunable optoelectronic devices in future nanotechnology.     

Preparation of molecularly imprinted polymer coated magnetic multi-walled carbon nanotubes for selective removal of dibenzothiophene

Novel molecularly imprinted polymers (MIPs) on the surface of magnetic multi-walled carbon nanotubes (MMWCNTs) were prepared using dibenzothiophene (DBT) as template, methacrylic acid (MAA) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linking agent and ammonium persulfate (APS) as initiator. The synthetic product was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and Fourier transform infrared spectroscopy (FTIR). Batch mode adsorption studies were performed to evaluate the adsorption kinetics, adsorption isotherms, and selective recognition of MMWCNTs-MIP. The kinetic data were analyzed using pseudo-first-order and pseudo-second-order equation. The pseudo-second-order exhibited the best fit for the kinetic studies (R²= 0.9985), which indicates that chemisorption process limits adsorption of DBT. The adsorption equilibrium of DBT using MMWCNTs-MIP could be well-defined with the Langmuir isotherm model instead of the Freundlich isotherm model, and the maximum adsorption capacity was calculated as 47.8 mg g^–1. Compared with magnetic non-imprinted polymer (MNIP), magnetic MIP (MMIP) possessed a better adsorption property toward DBT, showing its potential for deep desulfurization.     

High-Tc superconductivity in entirely end-bonded multi-walled carbon nanotubes

We report that entirely end-bonded multi-walled carbon nanotubes (MWNTs) can exhibit superconductivity with a transition temperature (T_c) as high as 12 K, which is approximately 30 times greater than T_c reported for ropes of single-walled nanotubes. We find that the emergence of this superconductivity is highly sensitive to the junction structures of the Au electrode/MWNTs. This reveals that only MWNTs with optimal numbers of electrically activated shells, which are realized by end bonding, can allow superconductivity due to intershell effects.     

阵列式碳纳米管制备研究

CVD工艺制备碳纳米管阵列,二甲苯(C6H4(CH3)2)作为碳源气体,二茂铁(C10H10Fe)作为催化剂前驱体,反应温度为700～800℃,碳纳米管直径30～60nm,长度50～60μm。     

碳纳米管中纳米空间的物质结构

填充碳纳米菅不但能改变碳纳米管本身的电学和力学性质,而且能改变被填充物质的性质.本文就有关多层、双层、单层碳纳米管的管内填充,主要以TEM为表征技术,对碳纳米管内纳米限域空间中物质的结构、性质等的研究作了简要的总结.     

碳纳米管团聚结构的电镜研究

纳米聚团床催化裂解法制得的碳纳米管均以团聚体形式存在，本文利用电子显微镜观察了两种碳纳米管团聚体的团聚结构，分散形态及微观结构，研究表明，纳米聚团床催化裂解法制备的碳纳米管具有多级团聚结构，范德华力及缠绕作用共同造成了多级团聚体的形成，细长的碳纳米管分散困难，易絮凝；短小弯曲的碳纳米管易于分散。     

Comparative study of the influence of the solvent on the catalytic growth of carbon nanotubes

The catalytic growth by chemical vapor deposition is a well-established route to single-wall carbon nanotubes (SWNTs). In this process, the choice and preparation of the metal catalyst determines the nanotube growth. The system Fe/Mo is known to yield a large percentage of SWNTs. In order to make use of SWNTs in electronic or electromechanical devices, the patterned growth relies on lithography techniques like photolithography or electron beam lithography. Many standard lithographic processes, i.e. the combination of photoresist and lift-off procedure, are not compatible with Fe/Mo catalyst solutions, resulting in low SWNT yield. We present a systematic study of the influence of the catalyst solvent on the patterned SWNT growth. Most remarkably, the use of water as a solvent is the basis for integrating SWNT with the established processing techniques due to its compatibility with any lithographic process and the simultaneous high SWNT yield.