不同结构碳纳米管的电磁波吸收性能研究

研究了单壁、多壁碳纳米管(聚团状、阵列状)以及未纯化与纯化后碳纳米管在2～18 GHz范围内的电磁波吸收性能. 通过测定不同结构碳纳米管粉体的介电常数以及磁导率, 得到损耗因子及衰减常数大小顺序为: 阵列状多壁碳纳米管>原生聚团状多壁碳纳米管>纯化聚团状多壁碳纳米管>原生单壁碳纳米管>纯化后单壁碳纳米管. 相比多壁碳纳米管, 单壁碳纳米管衰减常数随频率变化较小, 且具有较宽的吸收峰. 模拟计算和实验测试结果都表明, 碳纳米管/聚合物复合材料具有优良的电磁吸波性能.     

述评碳纳米管储氢研究*

碳纳米管因被认为可能是氢能的主要载体而备受关注,但几年来的文献报道不尽一致.本文评述了关于单壁和多壁碳纳米管对氢气的吸附实验和模拟计算研究结果,探讨了碳纳米管作为储氢材料的可行性.     

碳纳米管的还原反应

用硝酸和硫酸的混合物对单壁碳纳米管进行切割,然后用SOCl2将切割后碳纳米管上的羧基转变为酰氯,以LiAIH4作为还原剂,对单壁碳纳米管进行了还原,并用FT-IR,Raman,XPS对还原后的单壁碳纳米管进行了结构表征.     

碳纳米管基气体传感器研究进展

碳纳米管具有灵敏度高、响应快和工作温度低等优异的气敏特性,近年来碳纳米管基气体传感器的研究成为研究热点.概述了碳纳米管基气体传感器的种类、结构特点、气敏性能和未来的发展方向,着重介绍了纯的碳纳米管包括单壁碳纳米管、多壁碳纳米管和碳纳米管阵列的气敏特性,以及碳纳米管的修饰或碳纳米管与高分子材料、氧化物等复合对其气敏性能的影响.     

在不同激发波长下的单壁碳纳米管的拉曼光谱研究

采用直流电弧法制备单壁碳纳米管样品,用457.5和632.8nm两种不同的激发光分别测得单壁碳纳米管的正常拉曼光谱和共振拉曼光谱.通过理论分析得到了单壁碳纳米管的直径分布,进一步推测了其类型及结构参数;对单壁碳纳米管的正切拉伸模的成分进行了归属.在632.8nm激发波长下得到了IG/ID值随激光功率变化的曲线,认为在2.5mW时,单壁碳纳米管缺陷的结构可能发生了改变.在用457.5nm波长激发的单壁碳纳米管的拉曼光谱中,首次发现了1421cm-1的拉曼谱峰.     

单壁碳纳米管的结构控制生长方法

单壁碳纳米管在原子尺度的结构变化即可导致其电学、光学方面等性质的多样性和非连续的变化——如电学性质上可呈现半导体性或金属性。然而,在单壁碳纳米管表现出诸多优异性能的同时,如何实现碳纳米管的结构控制制备仍面临严峻的挑战。本文以单壁碳纳米管的管径、导电属性和手性控制为目标,介绍单壁碳纳米管的结构控制生长方法,主要包括温度扰动法、金属催化剂结构设计法、生长气氛调控法、外场辅助法、基底诱导法、非金属粒子催化法和sp2碳结构模板法等。并在此基础上总结了单壁碳纳米管结构控制生长的基本思路及实现途径,以期为后续单壁碳纳米管的规模化应用奠定基础。     

单壁碳纳米管的手性测量

单壁碳纳米管的制备方法主要包括物理法和化学法两种,不同制备方法的产物中包含很多种不同手性指数的单壁碳纳米管及杂质,而不同手性的单壁碳纳米管其作用完全不同,从而有不同的应用。采用化学方法——钴钼催化剂气相沉积法和物理方法——激光烧蚀气相沉积法制备单壁碳纳米管,用紫外–可见–近红外吸收光谱、荧光光谱及拉曼光谱法分别对其进行手性测量。结果表明,钴钼催化剂气相沉积法制得样品富含半导体型单壁碳纳米管,而激光烧蚀气相沉积法制得样品中主要为金属型单壁碳纳米管。分别得到了两种制备方法样品的手性分布。     

非离子型表面活性剂Tween 60用于碳纳米管的双水相分离

单壁碳纳米管以其优异的电学和光学性能受到了广泛的关注,高性能器件等应用要求使用性质均一的单壁碳纳米管.因此,不同结构的单壁碳纳米管的分离具有重要意义.双水相萃取是一种能够对单壁碳纳米管进行结构分离的新方法,分离结果稳定可靠,且不需要复杂的设备,具有简捷、高效、易扩大规模等特点.本文通过调节脱氧胆酸钠(DOC)和非离子型...     

碳纳米管结构对碳纳米管载Pt催化剂电催化性能的影响

在制备单、双壁及不同管径的多壁碳纳米管(CNTs)的基础上, 用液相还原法把Pt沉积到单、双壁和管径不同的多壁CNTs上. 发现制得的CNTs载Pt(Pt/CNTs)催化剂对甲醇氧化的电催化活性随CNTs管径减小而增加. 这归结于管径小的CNTs的比表面积较大, 含氧基团多, 有利于提高Pt粒子分散度, 加上管径小的单壁CNTs具有更高的导电性, 这些因素都有利于提高Pt/CNTs催化剂对甲醇氧化的电催化活性.     

溴吸附对碳纳米管导电性能的提高

通过溴蒸气的吸附, 提高多壁碳纳米管(MWNT)的本征导电性能,加溴多壁碳纳米管的电导率提高3倍. 通过拉曼光谱, 紫外可见光谱, 红外吸收光谱, 近红外吸收光谱和X光电子能谱等方法研究, 结果表明: 溴与多壁碳纳米管之间存在共轭作用, 使多壁碳纳米管表面的电子云分布发生了变化, 导致空穴载流子的产生, 增加了载流子浓度, 提高了多壁碳纳米管的导电性能.     

中分子毒素在碳纳米管上的吸附

研究了两种不同形态的碳纳米管(随机生长多壁碳纳米管(MWCNTs)及定向生长多壁碳纳米管(ACNTs))对典型中分子毒素的吸附性能. 并与两种现有商用血液灌流吸附材料(活性炭(AC)及大孔吸附树脂(MR))进行了对比. 结果显示, 碳纳米管(CNTs)具有优异的中分子吸附能力, 其中MWCNTs对典型中分子毒素的吸附量可达47.18 mg·g-1, 为活性炭的10.8倍, 为大孔吸附树脂的5.5倍. 此外, 碳纳米管的吸附非常迅速, 中分子毒素在MWCNTs及ACNTs达到吸附平衡的时间仅为10 min和15 min, 而活性炭及大孔吸附树脂则分别需要60 min及120 min. 碳纳米管优异的吸附性能得益于其独特的微观结构所形成的发达的中孔. 因此, 碳纳米管可望成为高效的吸附材料, 应用于血液灌流中.     

Field-effect characteristics and screening in double-walled carbon nanotube field-effect transistors

Field-effect transistors (FETs) have been fabricated using double-walled carbon nanotubes (DWCNTs), and electrical transport measurements have been carried out on 125 DWCNT FETs. Among these devices, 52 were found to show basically semiconducting field-effect characteristics, 44 show metallic characteristics, and 29 show neither pure semiconducting nor metallic characteristics. These 3 distinct types of field-effect characteristics were identified as resulting from the semiconducting (S)-S, metallic (M)-M or M-S, and S-M combinations of the two shells of the DWCNT. While the S-S and M-M or M-S DWCNT devices exhibit similar field-effect characteristics to those by single-walled carbon nanotube (SWCNT) devices, the S-M device responds uniquely to the external gate voltage. In particular, it was found that free charges in the inner metallic shell may screen the outer semiconducting shell from the gate effect and that the screening is directly related to the intershell interaction, which increases with increasing temperature and tube diameter. The screening is disadvantageous to the performance of DWCNT FETs, and a similar effect is expected to occur in MWCNTs.     

Preparation of micelle-encapsulated single-wall and multi-wall carbon nanotubes with amphiphilic hyperbranched polymer

The hyperbranched polyester (Boltorn^TM H20) was modified by maleic anhydride and then polystyrene (H20-MAh-PSt) to form amphiphilic micelles in water. The single-wall and multi-wall carbon nanotubes (SWCNTs and MWCNTs, respectively) were encapsulated in the formed micelles through non-covalent interactions. The formed structures were confirmed by FTIR, NMR, GPC, and XPS analysis. The dispersion and aggregation behaviors were observed by TEM and UV-vis and Raman spectroscopic analysis. The results showed that the dispersion performance of the obtained micelle-encapsulated carbon nanotubes in water was greatly improved compared to the pure carbon nanotubes. From the TEM observation, the individual SWCNT structure and the uniform polymer coating around the surface of SWCNT were seen after crosslinking. The Raman spectroscopic measurements also demonstrated that for the crosslinked samples, no effect occurred associated with concentration-dependent carbon nanotube aggregation.     

碳纳米管改性聚苯硫醚熔纺纤维的结构与性能研究

将多壁碳纳米管(MWCNTs)和聚苯硫醚(PPS)经过熔融挤出后制备成复合材料切片,并采用熔融纺丝法制得碳纳米管改性聚苯硫醚复合纤维.采用扫描电镜(SEM)、拉曼光谱、示差扫描量热分析(DSC)、动态机械分析(DMA)以及力学性能测试等表征手段研究了复合纤维中碳管的分散状态,与基体的界面作用,复合纤维的结晶性能以及力学性能,从而探讨了聚苯硫醚/碳纳米管复合纤维体系的微观结构与宏观性能之间的关系.研究表明,聚苯硫醚分子结构与碳纳米管之间具有的π-π共轭作用使碳管较为均匀的分散在基体中,界面结合较为紧密.同时熔融纺丝过程中的拉伸作用使碳管进一步解缠并使碳管沿纤维拉伸方向取向.另一方面,拉曼光谱显示拉伸作用有效地增强了界面作用,有利于外界应力的传递.碳管的良好分散以及强的界面作用使复合纤维力学性能得到大幅度的提高,当碳管含量达到5 wt%时,复合纤维的模量有了明显的提高,拉伸强度较纯PPS纤维提高了近220%.     

Direct electrolytic exfoliation of graphite with hemin and single-walled carbon nanotube: Creating functional hybrid nanomaterial for hydrogen peroxide detection

We present a new, facile and efficient method to prepare functional graphene (GN) hybrid nanomaterials using direct electrolytic exfoliation of graphite robs in hemin (HN) and single-walled carbon nanotube (SWCNT) solution. During the exfoliation process, HN and SWCNT were simultaneously adsorbed on the surface of GN nanosheets through noncovalent π–π interaction, and then 3D GN–HN–SWCNT hybrid nanomaterials were formed. Due to the synergic effect among GN, HN, and SWCNT, these hybrid nanomaterials possessed excellent electrocatalysis properties and were used to construct novel electrochemical biosensor for H₂O₂ determination. The results displayed a wide linear range of 0.2 μM–0.4 mM and a low detection limit of 0.05 μM. Moreover, the developed sensor was successfully applied for real samples, such as beverages, and showed great promise in routine sensing applications.     

磺化聚苯乙炔/多壁碳纳米管复合材料导电特性和机理的研究

将磺化聚苯乙炔(SPPA)与多壁碳纳米管(MWCNTs)超声共混制备得到SPPA/MWCNTs复合材料. 用X光电子能谱仪、固体紫外-可见分光光度计、X射线衍射仪、四探针、场发射扫描电镜等对复合材料导电特性及机理进行研究. 结果表明: SPPA/MWCNTs 复合材料中SPPA与MWCNTs发生电荷转移而被掺杂, 并且由于SPPA与MWCNTs间的电荷转移, 彼此间存在一定的相互作用力; 复合材料电阻呈负温度系数效应; SPPA/MWCNTs复合材料电导率发生两次突跃. 可能的导电机理为, 复合材料中SPPA不仅被MWCNTs物理填充, 同时还被MWCNTs掺杂, 复合材料中存在两种导电通路, 一是SPPA与MWCNTs的碳原子发生电荷转移而被掺杂, 彼此之间存在一定的相互作用力, 导致SPPA包裹MWCNTs形成独立导体单元, 这种独立单元相互接触形成导电通路; 二是MWCNTs彼此之间相互接触形成导电通路, 并建立了该导电机理的理论模型.     

All-organic actuator fabricated with single wall carbon nanotube electrodes

Compliant electrodes to replace conventional metal electrodes have been required for many actuators to relieve the constraint on the electroactive layer. Many conducting polymers have been proposed for the alternative electrodes, but they still have a problem of poor thermal stability. This article reports a novel all- organic actuator with single wall carbon nanotube (SWCNT) films as an alternative electrode. The SWCNT film was obtained by filtering a SWCNT solution through an anodized alumina membrane. The conductivity of the SWCNT film was about 280 S/cm. The performance of the SWCNT film electrode was characterized by measuring the dielectric properties of NASA Langley Research Center – Electroactive Polymer (LaRC-EAP) sandwiched by the SWCNT electrodes over a broad range of temperature (from 25 to 280 °C) and frequency (from 1 kHz to 1 MHz). The all-organic actuator with the SWCNT electrodes showed a larger electric field-induced strain than that with metal electrodes, under identical measurement conditions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2532–2538, 2008     

Shape memory properties of polyethylene/ethylene vinyl acetate /carbon nanotube composites

The safe operation of electrical equipment relies on advanced polymer insulation to contain electrical pathways. Polymer sheath materials should be mechanically robust and chemically stable in order to protect the internal metal wiring from environmental attack. Polyethylene (PE) and ethylene vinyl acetate (EVA) have often been used as electrical cable jacket materials for electrical power industry. Partially crosslinked PE is able to shrink and wrap tightly around the metal wires upon stimulated by external heat, exhibiting shape memory behaviour. In this work, multiwalled carbon nanotubes (MWCNTs) were introduced to partially crosslinked linear medium density polyethylene (LMDPE) and EVA blend in order to enhance the shape memory performance at lower temperature by promoting the thermal transfer and antistatic properties of the polymer nanocomposite. The morphologies of the partially crosslinked and non-crosslinked composites are analysed. The MWCNTs preferentially resided in the EVA phase while the peroxide crosslinking process drastically altered the morphology and electrical properties. The addition of 3 wt% of MWCNTs resulted in a percolation transition and enhanced the alternating current (AC) conductivity by 10 orders of magnitude for non-crosslinked LMDPE/EVA and by 3 orders of magnitude for crosslinked LMDPE/EVA composites. LMDPE/EVA (80/20) containing 3 wt% MWCNTs possessed excellent shape recovery of 100% and shape fixing of 82%. The addition of MWCNTs can not only promote the shape memory efficiency of the polymer sheath material, but also introduce antistatic properties to avoid electrical shocking or sparking.     

碳纳米管的羟甲基化及其马来酸酐接枝研究

利用甲醛的亲电性能, 对化学气相沉积法(CVD)制备的多壁碳纳米管(MWCNTs)进行羟甲基化, 并在此基础上酯化接枝马来酸酐, 运用透射电子显微镜(TEM)、红外光谱和Zeta电位仪表征了改性后的MWCNTs的表面结构. TEM结果显示, 酯化后的MWCNTs明显增粗, 说明表面已附有物质. 红外结果表明, 羟甲基后的MWCNTs的表面有了羟基和亚甲基, 而马来酸酐酯化接枝后的MWCNTs有亚甲基和酯基官能团. 光学图像分析表明, 经甲醛处理后的MWCNTs在水溶液中的分散性明显提高, 而马来酸酐酯化接枝后的MWCNTs在二甲苯中的分散性明显增强. Zeta电位的测试结果表明, 甲醛处理过的MWCNTs颗粒在水中, 负电荷增多, 增强了其在悬浮液在溶液中的稳定性.     

血红蛋白在壳聚糖修饰碳纳米管上的电化学特性及对过氧化氢的电催化分析

用壳聚糖对多壁碳纳米管进行修饰,构建了一种用于固定血红蛋白的新型复合材料,并研究了血红蛋白在该碳纳米管上的电化学性质及其对过氧化氢的电催化活性.扫描电镜结果表明,壳聚糖修饰的多壁碳纳米管呈单一的纳米管状,并能均匀分散在玻碳电极表面.紫外光谱分析表明血红蛋白在该复合膜内能很好地保持其原有的二级结构.将该材料固定在玻碳电极上后,血红蛋白能成功地实现其直接电化学.根据峰电位差随着扫描的变化,计算得到血红蛋白在壳聚糖修饰的碳纳米管膜上的电荷转移系数为0.57,表观电子转移速率常数为7.02 s-1.同时,该电极对过氧化氢显示出良好的催化性能,电流响应信号与H2O2浓度在1.0×10-6 ～1.5×10-3 mol/L间呈线性关系,检出限为5.0×10-7 mol/L.修饰电极显示了良好的稳定性.