碳纳米管/环氧树脂复合材料的静电自组装制备及性能

采用静电自组装法制备了均匀分散的碳纳米管环氧树脂复合材料,并对比分析了普通碳纳米管和功能化碳纳米管对环氧树脂热学和电学性能的影响。采用透射电镜(TEM)观察到碳管和树脂乳液自组装形成"葡萄藤"状结构,扫描电镜(SEM)观察发现,碳管可在环氧树脂中均匀分散并形成网络。电、热性能研究发现,添加3%普通碳纳米管可降低环氧树脂表面电阻率7个数量级,导热系数较纯树脂提高112%,而羧基化碳纳米管表面电阻率仅降低4个数量级,导热系数仅提高86%。     

硅基底上图形化自组装膜的构筑

为在硅基底上得到不同化学基团修饰的图形,采用传统的光刻技术与自组装相结合的方法,成功地制备了由甲基与氨基末端官能团组成的图形化自组装膜。将图形化自组装膜泡入碳纳米管DMF(N,N-二甲基甲酰胺)分散液中,图形化自组装膜的氨基区域能均匀吸附一层分散液中碳纳米管,而甲基没有,表明图形化自组装膜的不同自组装膜区域的不同表面性质,证实了该方法的可行性。     

在聚四氟乙烯基底上层层自组装功能化多壁碳纳米管薄膜的研究

将多壁碳纳米管(MWNTs)通过羧酸化以及氨基化处理,分别得到功能化的MWNT-COOH和MWNT-NH2,然后在聚四氟乙烯(PTFE)基底上层层自组装功能化MWNT薄膜。研究了邻苯二甲酸二乙二醇二丙烯酸酯(PDDA)预处理和MWNTs不同层数对薄膜质量以及导电性能的影响。结果表明,PDDA预处理能够改善PTFE基底的组装效果。随着组装层数的增加,层层自组装MWNT薄膜表面更均一,而且表面的MWNTs也更密集,从而使经MWNTs修饰过的PTFE基底的导电性能得到改善。     

碳纳米管的自组装研究进展

用自组装技术组装的碳纳米管具有新奇的光、电、催化等功能和特性，因此具有良好的发展前景。近年来，许多方法已经用于碳纳米管的组装；综述了化学吸附自组装、静电自组装、模板辅助自组装及DNA操纵下的自组装等几种主要的碳纳米管的组装方法，并对各种方法的特点及研究现状进行了评述。     

羟丙基纤维素修饰碳纳米管及其在水中的自组装

羟丙基纤维素(HPC)通过物理吸附包覆到多壁碳纳米管(MWCNTs)的表面,得到HPCMWCNTs。HPC是一种水溶性纤维素,可显著地提高MWCNTs与水的相亲性。通过比较修饰前后碳纳米管的水接触角及其在水中的分散性,证明HPC已成功地吸附到MWCNTs的表面。动态稳定性测试表明分散体系并非真正稳定,随着时间变化,HPCMWCNTs自组装成束状并沉降到容器底部。透射电子显微镜和扫描电子显微镜显示MWCNTs在自组装体内取向、平行排列。自组装体有整齐的头部和相对松散的尾部,这些圆柱状聚集体的径向尺寸为4~8μm,轴向尺寸为25~35μm。修饰过的MWCNTs由亲水的HPC和憎水的MWCNTs组成,在亲水/疏水的相互作用下,两亲性的HPCMWCNTs在水中形成了"相互垂直的微相分离",从而导致改性MWCNTs有规则的自组装。     

碳纳米管/壳聚糖载体的静电自组装及其表征

采用混酸氧化法制备表面带负电的羧基化碳纳米管分散体系,以叶酸靶向受体改性壳聚糖,通过羧基化碳纳米管与叶酸改性壳聚糖进行静电自组装,制备了生物相容性好、肿瘤靶向性高的碳纳米管/壳聚糖药物复合载体材料(FA/CS-SWCNTs).利用FTIR、XPS、SEM和TG等分析方法对相应产物的形貌和结构进行了研究.实验结果表明叶酸改性壳聚糖成功组装到羧基化碳纳米管上,热重分析显示该复合材料中壳聚糖的质量分数达到35％,其中叶酸在壳聚糖上的偶联率为8.1％,该载体材料具有良好的亲水性、安全性和靶向性等优点,有望成为新型的肿瘤靶向功能载体材料.     

单壁碳纳米管/聚苯胺自组装薄膜的制备及性能研究

依靠化学键组装法在导电玻璃ITO表面制备了单壁碳纳米管/聚苯胺薄膜.通过VV-vis光谱证实了导电聚苯胺和单壁碳纳米管之间存在着电子相互作用,循环伏安测试表明,经过聚苯胺的化学共价修饰后,单壁碳纳米管薄膜的电化学稳定性得到了显著提升.     

具有不同黏附力Al-Mg-Si合金超疏水表面的制备与表征

基于位错刻蚀理论利用溶液浸泡处理A1-Mg-Si合金在其表面形成微观粗糙表面结构,采用自组装技术在此表面制备FDTS自组装分子膜.采用X射线衍射仪、扫描电子显微镜和表面粗糙度仪对试样表面形貌进行了表征;采用接触角测量仪对试样表面接触角进行了测量.结果表明,试样经溶液浸泡处理和沉积自组装分子膜后,其表面润湿性实现了由亲水到超亲水再到超疏水的转变;改变溶液浸泡时间得到具有不同微观结构的表面,沉积自组装分子膜后得到的超疏水表面具有不同的滚动接触角,其表面黏附力具有明显差异.分析认为,超疏水表面的获得是溶液浸泡处理得到的粗糙表面结构和低表面能物质FDTS自组装分子膜共同作用的结果;表面黏附力的差异是试样表面微观形貌的不同造成水滴在其表面所处状态的差异引发的.     

基于层层自组装纳米碳管薄膜的应变传感器

以层层自组装单壁碳纳米管网状薄膜为敏感材料,在柔性基底上制作了应变传感器,并对薄膜和器件性能进行了测试。测试结果表明:薄膜组装均匀,电导性良好,电阻随组装层数增加呈指数态下降;器件对应变呈现较好的敏感特性、线性响应和可恢复性,灵敏度为4.25;通过添加防护层屏蔽外界湿度及光照影响,传感器稳定性显著提高。该传感器可用于弯曲表面的应力应变检测。     

碳纳米管/导电聚苯胺纳米复合纤维的合成与表征

为实现碳纳米管在树脂内形成一体化导电网络，从而制备出透明导电性能最优的有机透明导电涂层，必须把导电性的碳纳米管纤维在树脂内有效地组装成一体化导电结构网络。本文报道运用在树脂内可以自组装的导电苯胺来实现碳纳米管纤维自组装的方法．合成出了导电聚苯胺纳米薄膜均匀包覆的碳纳米管/导电聚苯胺纳米复合纤维．并运用透射电镜、傅立叶红外光谱以及四探针法表面电阻测试仪对合成出的具有精细微观结构的纳米复合纤维进行了表征．发现合成出了理想的碳纳米管/导电聚苯胺纳米复合纤维，并且其导电性较碳纳米管和导电聚苯胺自身都有大幅度的提高。这种特殊结构的纳米复合纤维的制备为组装高性能的聚合物基透明导电涂层奠定了坚实基础，而且这种自组装方法为各种纳米纤维的组装提供了可能。     

Application of cryomilling to enhance material properties of carbon nanotube reinforced chitosan nanocomposites

Cryomilled multiwall carbon nanotube (MWCNT) reinforced chitosan nanocomposites having improved conductivity have been prepared by solution casting method. The MWCNTs were crushed to smaller particles via cryomilling, which was effective in cleaving the nanotubes regularly as well as in reducing the entanglements and agglomeration. The cryomilled CNTs were chemically oxidized by acid and base methods, where basic oxidation generated high graphitic structure. The cryomilled and oxidized CNTs were characterized by XRD, Raman spectroscopy, FTIR and SEM. The conductivity of the nanocomposites was improved by cryomilling and it was further improved by chemical oxidation. Base oxidized cryomilled CNT/chitosan nanocomposites showed large improvement in conductivity compared to all other nanocomposites having 1 wt.% CNT content. Thermal stability and tensile properties of the CNT/chitosan nanocomposites also have been improved significantly by the incorporation of acid and base oxidized cryomilled CNTs. SEM picture of the fractured surface and FTIR showed nano-level dispersion of the functionalized CNTs and good chemical interaction between chitosan and CNTs respectively.     

An effective and green H_2O_2/H_2O/O_3 oxidation method for carbon nanotube to reinforce epoxy resin

Facile green oxidation methods are always desired to functionalize carbon nanotubes(CNTs) in the production of advanced CNT/epoxy composites. In the present work, an optimized H_2O_2/H_2O/O_3 oxidation method was developed, and performances of the H_2O_2/H_2O/O_3 oxidized CNT in epoxy matrix were tested and compared with that of the H_2O/O_3 oxidized CNT and the most commonly used concentrated HNO_3 oxidized CNT. The physical and chemical characteristics of the obtained oxidized CNTs were systematically characterized via transmission electron microscopy(TEM), X-ray photoelectron spectroscopy(XPS) and Raman. Mechanical performances of the obtained composites were explored by tensile tests,impact tests, dynamic mechanical analysis(DMA) and fracture toughness tests. It was found that the H_2O_2/H_2O/O_3 oxidized CNT exhibited all-around overwhelming advantages over the concentrated HNO_3 oxidized CNT on reinforcing the epoxy matrix, while the H_2O/O_3 oxidized CNT only improved the material strength. Reinforcing mechanisms for the different methods oxidized CNTs were studied and compared.The optimized H_2O_2/H_2O/O_3 oxidation method makes scaled production possible, avoids environment pollutions, and holds great potentials to replace the most commonly used concentrated HNO3 oxidation method to oxidize CNT during the preparation of the advanced CNT/epoxy composite.     

Microstructure and mechanical properties of CNT/Ag nanocomposites fabricated by spark plasma sintering

Carbon nanotube/silver (CNT/Ag) nanocomposites include CNT volume fraction up to 10?vol.% were prepared by chemical reduction in solution followed by spark plasma sintering. Multiwalled CNTs underwent surface modifications by acid treatments, the Fourier transform infrared spectroscopy data indicated several functional groups loaded on the CNT surface by acid functionalisation. The acid-treated CNTs were sensitised and activated. Silver was deposited on the surface of the activated CNTs by chemical reduction of alkaline silver nitrate solution at room temperature. The microstructures of the prepared CNT/Ag nanocomposite powders were investigated by high-resolution scanning electron microscopy (HRSEM), transmission electron microscopy and X-ray powder diffraction analysis. The results indicated that the produced CNT/Ag nanocomposite powders have coated type morphology. The produced CNT/Ag nanocomposite powders were sintered by spark plasma sintering. It was observed from the microstructure investigations of the sintered materials by HRSEM that the CNTs were distributed in the silver matrix with good homogeneity. The hardness and the tensile properties of the produced CNT/Ag nanocomposites were measured. By increasing the volume fraction of CNTs in the silver matrix, the hardness values increased but the elongation values of the prepared CNT/Ag nanocomposites decreased. In addition, the tensile strength was increased by increasing the CNTs volume fraction up to 7.5?vol.%, but the sample composed of 10?vol.% CNT/Ag was fractured before yielding.     

Fabrication of nanocomposites based on carbon nanotubes containing Pt nanoparticles and TiO<Subscript>2</Subscript>

Using conical multiwalled carbon nanotubes (CNTs), we have prepared Pt/CNT and Pt/TiO₂/CNT nanocomposites with an average platinum particle size of 3–5 nm, Pt/Ti molar ratio on the surface in the range 3.5–4, and C/Pt = 21–22. Titania was deposited onto the CNTs through titanium tetrachloride (TiCl₄) hydrolysis. Platinum particles were produced by reducing chloroplatinic acid (H₂PtCl₆) with sodium borohydride (NaBH₄) in the presence of CNTs. The composition and structure of the composites have been studied using X-ray photoelectron spectroscopy, electron microscopy, X-ray diffraction, and thermogravimetry. The materials have been tested as catalysts for hydrogen oxidation and oxygen reduction. The results demonstrate that the modification of Pt/CNT with titania enhances the catalytic activity of the material.     

Influence of various plasma treatment on the properties of carbon nanotubes for composite applications

In present work, the effects of hydrogen and oxygen plasma treatments on the structural properties of carbon nanotubes (CNTs) synthesized by catalytic CVD (Chemical Vapor Deposition) have been systematically investigated. Field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy were used to characterize the microstructural changes of the CNTs. The oxygen plasma treatment resulted in that the nanoparticles were appeared at the surface of CNTs. At high r.f. power (300 Watt), the microstructure of CNT was changed from nanotube type to nano particles. Long plasma treatment time changed the CNT morphology dramatically. For hydrogen plasma, however, there was no change in microstructure of CNT From the Raman analysis, the crystallinity of CNT was deteriorated by the plasma treatment, regardless of plasma power, treatment time, and gas types. The CNTs treated in oxygen plasma for 90 min showed excellent dispersion properties in aqueous solution.     

Electrochemical properties and myocyte interaction of carbon nanotube microelectrodes

Arrays of carbon nanotube (CNT) microelectrodes (nominal geometric surface areas 20-200 μm(2)) were fabricated by photolithography with chemical vapor deposition of randomly oriented CNTs. Raman spectroscopy showed strong peak intensities in both G and D bands (G/D = 0.86), indicative of significant disorder in the graphitic layers of the randomly oriented CNTs. The impedance spectra of gold and CNT microelectrodes were compared using equivalent circuit models. Compared to planar gold surfaces, pristine nanotubes lowered the overall electrode impedance at 1 kHz by 75%, while nanotubes treated in O(2) plasma reduced the impedance by 95%. Cyclic voltammetry in potassium ferricyanide showed potential peak separations of 133 and 198 mV for gold and carbon nanotube electrodes, respectively. The interaction of cultured cardiac myocytes with randomly oriented and vertically aligned CNTs was investigated by the sectioning of myocytes using focused-ion-beam milling. Vertically aligned nanotubes deposited by plasma-enhanced chemical vapor deposition (PECVD) were observed to penetrate the membrane of neonatal-rat ventricular myocytes, while randomly oriented CNTs remained external to the cells. These results demonstrated that CNT electrodes can be leveraged to reduce impedance and enhance biological interfaces for microelectrodes of subcellular size.     

Strong Electrochemiluminescence Emission from Oxidized Multiwalled Carbon Nanotubes

Carbon nanotubes (CNTs) as well‐known nanomaterials are extensively studied and widely applied in various fields. Nitric acid (HNO₃) is often used to treat CNTs for purification purposes and preparing oxidized CNTs for various applications. However, too little attention is paid to investigating the effect of HNO₃ treatment on the optical properties of CNTs. In this work, it is observed for the first time that HNO₃‐oxidized multiwalled carbon nanotubes (ox‐MWCNTs) have strong electrochemiluminescence (ECL) activity, which enables ox‐MWCNTs to become new and good ECL carbon nanomaterials after carbon quantum dots (CQDs) and graphene quantum dots (GQDs). Various characterization technologies, such as transmission electron microscope (TEM), X‐ray photoelectron spectroscopy (XPS), and Raman spectroscopy, are used to reveal the relationship between ECL activity and surface states. The ECL behaviors of ox‐MWCNTs are investigated in detail and a possible ECL mechanism is proposed. Finally, the new ECL nanomaterials of ox‐MWCNTs are envisioned to have promising applications in sensitive ECL sensing and in the study of CNT‐based catalysts.     

Synthesis and purification of bimetallic catalysed carbon nanotubes in a horizontal CVD reactor

Carbon nanotubes (CNTs) were synthesised by a conventional chemical vapour deposition (CVD) method using acetylene as carbon source and a bimetallic catalyst of Fe–Co supported on a CaCO₃ support. The CNTs were characterised by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy (RS), energy dispersive X-ray spectroscopy (EDS) and thermogravimetric analysis (TGA). The TEM images show clustered CNTs and reveal the outer and inner diameters of these nanomaterials. The XRD analysis shows the characteristic broad peak of graphitised carbon; the RS indicates that these materials have a high degree of crystallinity while the TGA shows the high thermal stability of the materials. EDS analysis also indicates that the purification method employed was able to remove the impurities in the CNT samples.     

Mechanical strength improvement of polypropylene threads modified by PVA/CNT composite coatings

Poly (vinyl alcohol)/carbon nanotube (PVA/CNT) composite was coated on the surface of polypropylene thread for toughness enhancement. Multiwall carbon nanotubes (MWNTs) were treated in acid and alkali to get water-soluble nanotubes, and then embedded into poly (vinyl alcohol) (PVA) matrix, resulting in polymer-carbon composite with homogeneous nanotube dispersion. The stress-strain measurements show that the tensile strength and toughness of the PVA/CNT coated thread increased by 117% and 560%, respectively. These results are supportive of good interfacial bonding between the carbon nanotubes (CNTs) and polymer matrix.     

Structure and electrochemical performance of ZnO/CNT composite as anode material for lithium-ion batteries

Metal oxides are well-known potential alternatives to graphite as anode materials of lithium-ion batteries, and they can deliver much higher reversible capacities than graphite even at high current densities. In this study, hexagonal disk-shaped ZnO are synthesized by a facile solution reaction of ZnCl₂ and its composite is prepared in the presence of carbon nanotubes (CNTs). The as prepared ZnO/CNT composite has been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, fourier transform-infrared spectroscopy and Rutherford backscattering spectroscopy. Electrochemical characterization by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic discharge/charge tests demonstrate that the conversion reactions in ZnO and ZnO/CNT electrodes enable reversible capacity of 478 and 602 mAh g^?1, respectively for up to 50 cycles. Our investigation highlights the importance of anchoring of small ZnO particles on CNTs for maximum utilization of electrochemically active ZnO and CNTs for energy storage application in lithium-ion batteries.