Spectroscopic Studies on Pure and Histidine-Functionalized Multiwalled Carbon Nanotubes

Electron paramagnetic resonance, Fourier transform infrared, and ultraviolet-visible studies were carried out for pure and histidine-functionalized multiwalled carbon nanotubes. Electron paramagnetic resonance absorption spectral data were found to be the best fit for the Gaussian lineshape. The g-values indicate the presence of magnetic impurities in the samples and the interaction between the localized electrons and delocalized electrons in the nanotubes trapped at defects or magnetic ion sites. The electron spin concentration decreases with increasing concentration of histidine, which implies that the unpaired electrons undergo a reduction process in the histidine-functionalized multiwalled carbon nanotubes. Fourier transform infrared study confirms the presence of functional groups in pure and histidine-functionalized multiwalled carbon nanotubes. Ultraviolet-visible study reveals the formation of a charge transfer complex in histidine-functionalized multiwalled carbon nanotubes.     

New Hybrid Material Based on Multiwalled Carbon Nanotubes Decorated by Rhenium-Tungsten Nanodendrites

Re–W nanoparticles are deposited onto multiwalled carbon nanotubes by the metal organic chemical vapor deposition technique. A mixture of dirhenium decacarbonyl and tungsten hexacarbonyl is used as a precursor. Nanoparticles of hybrid materials are studied by scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray phase analysis. It is found that in a wide range of ratios of the precursors (dirhenium decacarbonyl and tungsten hexacarbonyl), the crystalline component is a Re–W phase, and the morphology of the nanoparticles is the same as that of the nanodendrites.     

Studies on the Nonisothermal Crystallization Behavior of Polypropylene/Multiwalled Carbon Nanotubes Nanocomposites

Polypropylene/multiwalled carbon nanotubes (PP/MWNTs) nanocomposites were prepared by a melt compounding process. The morphology and nonisothermal crystallization of these nanocomposites were investigated by means of optical microscopy, scanning electron microscopy, and differential scanning calorimetry. Scanning electron microscope micrographs of PP/MWNTs composite showed that the MWNTs were well dispersed in the PP matrix and displayed a clear nucleating effect on PP crystallization. Avrami theory, modified by Jeziorny and Mo's method, was used to analyze the kinetics of the nonisothermal crystallization process. It was found that the addition of MWNTs improved the crystallization rate and increased the peak crystallization temperature of the PP/MWNTs nanocomposites as compared with PP. The results show that the Jeziorny theory and Mo's method successfully describe the nonisothermal crystallization process of PP and PP/MWNTs nanocomposites.     

Preparation and Characterization of Chitosan-Blended Multiwalled Carbon Nanotubes

Composites comprised of chitosan (CS) and multiwalled carbon nanotubes (MWCNTs) were fabricated by milling and ultrasonication dispersion methods. Scanning electron microscopy images showed homogeneous dispersion of MWCNTs throughout the CS matrix for samples prepared by either ultrasonication or milling methods. Further, the crystallinity of the CS component was found to decrease with the addition of MWCNTs, although the decomposition temperature and the storage modulus (E′) of the samples were improved. The decomposition temperature for the composite prepared by milling was 7°C higher than that by the ultrasonication. Meanwhile, the E′ decreased relatively slowly with temperature in the dynamic mechanical analysis measurements. In addition, IR analysis implied an interaction between CS and MWCNTs, which likely originated from hydrogen bonds between the amino, hydroxyl, and carboxyl groups of the two components. Compared with the ultrasonication, milling was more effective to promote the formation of the hydrogen bonds between CS and the MWCNTs and thus enhance the thermal stability of CS.     

Bistability of Multiwalled Carbon Nanotubes Arranged on Plane Substrates

Physics of the Solid State - Stationary states of multi-walled carbon nanotubes have been studied. The numerical simulation showed that nanotubes become bistable systems at rather large diameters....     

碳纳米管的纯化及其在聚乙烯醇中的分散

采用硫酸和硝酸混合酸对多壁碳纳米管(MWNTs)进行纯化,利用红外光谱(IR)、X射线衍射(XRD)对MWNTs进行了表征;聚乙烯醇/乙醇(V/V=1:1)溶液分散MWNTs,循环伏安法(CV)测试了碳纳米管/聚乙烯醇膜修饰电极的电化学性能.实验结果表明,混酸处理可以提高碳纳米管的纯度及石墨化程度,并可以在碳纳米管上引入羧基功能团;碳纳米管可以均匀地分散在聚乙烯醇/乙醇溶液中并形成稳定的悬浮液,同时碳纳米管/聚乙烯醇膜修饰电极对苯二酚具有明显电化学催化活性.     

可溶性多壁碳纳米管光限幅机理研究

根据光限幅与Z扫描实验研究了可溶性多壁碳纳米管的光限幅机理.通过现象分析、数据处理以及类比研究,证实材料的光限幅特征符合非线性吸收效应.对厚样品的独特现象进行了解释,讨论了其他机理的影响.根据Z扫描公式,计算了实验材料的三阶非线性系数.通过分析证实了非线性吸收在可溶性多壁碳纳米管的光限幅中发挥着主要作用.对厚介质的特殊现象进行的分析和计算表明,对于较厚介质和激光连续加热的情况下,其他机理的影响并不能完全否定,其特殊现象可能与微气泡的气穴作用有关.     

以碳纳米管阵列为场致发射阴极的X射线源研究

碳纳米管具有优异的场发射性能 ,是一种很有前景的电子发射源。实验使用印刷方法将碳纳米管制备于玻璃基底 ,并作为X射线源的阴极。阳极材料为铜 ,其顶端为半球形 (半径为 2mm)。高压电源输出在 0～ 19kV之间可调。射线源工作真空度为 1× 10 -4Pa ,利用流气式正比计数器测到了铜kα 谱线 ,并且进行了连续 4h的运行。实验结果表明X射线源发光稳定 ,碳纳米管可以作X射线源的阴极。最后提出了改进的X射线源结构。     

Structural Analysis of Collapsed, and Twisted and Collapsed, Multiwalled Carbon Nanotubes by Atomic Force Microscopy

A fully collapsed multiwalled carbon nanotube (MWCNT1) section and a different twisted and fully collapsed MWCNT were observed with tapping-mode atomic force microscopy. The collapsed section of MWCNT1 was significantly more flexible than the uncollapsed sections, and advanced 120 nm within 1 month. The collapse of MWCNT1 was most likely initiated by its interaction with the surface, and possibly a water meniscus. The ability of carbon nanotubes to radially deform under the influence of surface interactions is in striking contrast with their extremely high axial rigidity.     

Thermal and Tensile Properties of Epoxy Nanocomposites Reinforced by Silane-functionalized Multiwalled Carbon Nanotubes

Epoxy nanocomposites with unmodified multiwalled carbon nanotubes (u-MWCNTs) and silanized multiwalled carbon nanotubes (si-MWCNTs) were prepared by a cast molding method. The effects of 3-aminopropyltriethoxysilane functionalization of MWCNTs on thermal, tensile, and morphological properties of the nanocomposites were examined. The nanocomposites were characterized by thermogravimetric analysis, dynamic mechanical thermal analysis, and tensile testing. The results showed that epoxy composites based on si-MWCNTs showed better thermal stability, glass transition temperature, and tensile properties than the composites based on u-MWCNTs. These results prove the effect of silane functionalization on the interfacial adhesion between epoxy and MWCNTs. This was further confirmed by morphology study of fractured surfaces of nanocomposites by field emission scanning electron microscopy.     

多壁碳纳米管/铋膜修饰电极示差脉冲溶出伏安法测定水中镉和铅

制备多壁碳纳米管/壳聚糖纳米复合物修饰玻碳电极,用于同位镀铋膜法连续测定水中镉和铅离子的含量.将多壁碳纳米管分散在壳聚糖溶液中,滴涂在玻碳电极表面制得修饰电极;在含铋的溶液中,采用示差脉冲溶出伏安法测定了镉、铅离子的浓度;考察了沉积电位、富集时间对溶出电流的影响.在优化的实验条件下,对浓度在0-0.2μmol/L范围内...     

多壁碳纳米管/壳聚糖多层膜修饰电极的电化学行为研究

采用新型分散方法制备了多壁碳纳米管/壳聚糖多层膜修饰玻碳电极,研究了在修饰剂总量相同的情况下,不同修饰层数膜电极的循环伏安、计时库仑曲线及电化学阻抗行为,并采用交流阻抗等效电路分析方法,对拟合的阻抗数据进行了解析。结果表明,电极的膜修饰层数的增加,不仅使膜层的缺陷增多,而且使电极的界面阻抗、溶液阻抗和电子转移阻抗明显减小,电极反应逐渐呈Warburg扩散阻抗特征,从而使电极的灵敏度和可逆性得到改善。     

Critical Exponents of Gelation and Conductivity in Polyacrylamide Gels Doped by Multiwalled Carbon Nanotubes

Polyacrylamide (PAM) doped by multiwalled carbon nanotube (MWNT) gels were prepared with different amounts of MWNTs varying in the range between 0.1 and 15 wt%. The PAM–MWNT composite gels were characterized by the steady state fluorescence technique (SSF). The alternative electrical conductivity (AC) of PAM–MWNT composite gels was measured by the dielectric spectroscopy technique. Observations around the gel point, t _gel for PAM–MWNTs composite gels showed that the gel fraction exponent β obeyed the percolation result. The critical exponent r of AC electrical conductivity for the composite PAM–MWNT gel was also measured and found to be about 2.0, which agrees with a random resistor network.     

基于碳纳米管场致发射的电子枪的初步研究

给出了基于碳纳米管场致发射电子枪的初步研究结果. 碳纳米管场致发射试验证明碳纳米管是一种很好的场致发射材料. 试验中, 在极间场强2.7MV/m的情况下得到的电流发射密度为0.5mA/cm².     

X射线吸收谱研究碳与硅的纳米线/管

由于X射线吸收谱中的总电子产额(TEY)和荧光产额(FLY)具有不同的取样探测深度,分别对样品的表面和体内敏感,因而两者的综合应用为纳米材料的整体分析提供了有力的依据,是透射电子显微镜(TEM)、X射线衍射(XRD)等传统方法分析纳米材料时的补充。同时,通过对TEY和FLY记录的X射线吸收谱的评述,作者认为X射线吸收谱可以准确、可靠地用来进行纳米线和纳米管的生长及其机理、取向、化学键合、缺陷与螺旋性等方面的研究。因此X射线吸收谱具有传统方法无法比拟的优势,是纳米材料研究领域强有力的表征工具。     

Microscopic and Macroscopic Structures of Carbon Nanotubes Produced by Pyrolysis of Iron Phthalocyanine

By pyrolysis of iron phthalocyanine (FePc), either in a patterned or non-patterned fashion, under an Ar/H₂ atmosphere, we have demonstrated the large-scale production of aligned carbon nanotubes perpendicular to the substrate surface useful for building devices with three-dimensional structures. Depending on the particular pyrolytic conditions used, carbon nanotubes with a wide range of microscopic structures having curved, helical, coiled, branched, and tube-within-tube shapes have also been prepared by the pyrolysis of FePc. This, coupled with several microfabrication methods (photolithography, soft-lithography, self-assembling, micro-contact transfer, etc.), has enabled us to produce carbon nanotube arrays of various macroscopic architectures including polyhedral, flower-like, dendritic, circular, multilayered, and micropatterned geometries. In this article, we summarize our work on the preparation of FePc-generated carbon nanotubes with the large variety of microscopic and macroscopic structures and give a brief overview on the perspectives of making carbon nanotubes with tailor-made microscopic/macroscopic structures, and hence well-defined physicochemical properties, for specific applications.     

MCNTs及KOH活化MCNTs对曙红Y的吸附性能

以有机染料曙红Y为去除目标,利用紫外光谱法以MCNTs及KOH活化MCNTs为吸附剂研究了其对曙红Y的吸附特性,利用扫描隧道电镜(SEM),X射线粉末衍射(XRD)和BET法对KOH活化MCNTs进行了表征;实验结果表明,在相同的条件下,KOH活化MCNTs较未经处理的MCNTs对曙红Y有更好的吸附性能,另外研究了pH值和温度对吸附量的影响,结果表明溶液pH值和温度对吸附量影响较大,并利用吸附动力学和等温吸附曲线探究了其吸附过程的动力学和热力学特点.     

Modifying the Structure of Multiwalled Carbon Nanotubes with Continuous and Pulsed Ion Beams

Physics of the Solid State - Changes in the local atomic and electronic structure and the chemical state of the surface of multiwalled carbon nanotubes (MWCNTs) irradiated with continuous and...     

Electrical Properties of Isotactic Polypropylene/Multiwalled Carbon Nanotubes Composites Prepared by Vibration Injection Molding

To study the effect of vibration field on the electrical conductivity properties of nanocomposites, isotactic polypropylene (iPP)/multiwalled carbon nanotubes (MWCNT) composites were prepared by conventional injection molding and vibration injection molding. Results showed that the electrical conductivity of iPP/MWCNT composites was significantly promoted by vibration injection molding. Vibration injection molded samples had a percolation threshold of about 2.7 wt% compared with the threshold of about 4.5 wt% for conventional injection molded samples. The effects of test locations and vibration frequency on the electrical conductivity of composites were investigated. The samples exhibited an inhomogeneity along the injection direction. The electrical conductivity of the samples was different at different test locations and increased with increasing vibration frequency. Polarized light microscopy (PLM) results indicated that vibration injection molding can induce MWCNT aggregates to be stretched and oriented along the flow direction, which could form conductive networks and greatly enhance the electrical conductivity of iPP/MWCNT composites.     

金/多壁碳纳米管复合材料的合成及其三阶非线性光学性质

通过化学吸附法制备了金/多壁碳纳米管复合材料.采用X射线衍射仪、透射电子显微镜和紫外可见光谱仪对复合材料进行表征,制备的金纳米颗粒平均粒径为6nm,且均匀分散在碳纳米管表面.在脉冲宽度为30ps、波长为532nm的激光光源激发下,运用Z扫描技术分别研究金/多壁碳纳米管复合材料和多壁碳纳米管的三阶非线性光学性质.实验结果表明:金/多壁碳纳米管复合材料呈现正的非线性折射效应和饱和吸收性质,其三阶非线性极化率χ(3)为1.89×10-12 esu,比多壁碳纳米管高2.6倍.