碳纳米管的制备

综述了碳纳米管的几种制备工艺和相关的生长机制,还介绍了近两年来碳纳米管制备的进展情况,包括新型制备技术、特殊结构的碳纳米管制备。     

Boron and Nitrogen Doped Single walled Carbon Nanotubes as Possible Dilute Magnetic Semiconductors

The structure of single walled armchair and zig-zag carbon nanotubes having 70 atoms and two carbons replaced by boron or nitrogen is obtained at minium energy using HF/6-31G* molecular orbital theory. The calculations show that the ground state of the zig-zag tubes is a triplet state while for the armchair tubes it is a singlet. In the zig-zag tubes the density of states at the Fermi level is greater for the spin down states compared to the spin up state indicating that the doped tubes could be ferromagnetic.     

碳纳米管的纯化进展

碳纳米管具有独特的结构和性能,目前生产的碳纳米管均存在有一定的杂质,对其发展应用有很大阻碍,除杂十分必要。本文综述了目前碳纳米管纯化所采用方法及相关机理,分析了各自的利弊,认为简单易行而又有较高收率且成本低廉的碳纳米管纯化方法仍是重要的研究方向。     

Adsorption of Pyridine from Aqueous Solution by Surface Treated Carbon Nanotubes

Abstract

The surface treatment of multi‐walled carbon nanotubes (MWCNTs) with acid, heat, ultrasonic, and polyvinyl alcohol has been examined. The original CNTs and four treated CNTs were first used as adsorbents to remove pyridine from water and the adsorption isotherms of pyridine on CNTs were studied. At the same time, the effect of pH, temperature, and the adsorption kinetics on the adsorption of pyridine were also evaluated. The experiments show that the adsorption of pyridine on different CNTs is mainly a physical process and the data fit the Freundlich adsorption isotherm well. The short time needed to reach equilibrium as well as the high adsorption capacity of pyridine suggests that CNTs possess highly potential applications for pyridine removal from water.     

碳纳米管的改性及其应用

碳纳米管因其具有独特的物理化学性质在许多领域具有潜在的应用价值。碳纳米管表面改性是实现其应用价值的主要手段之一。介绍了碳纳米管表面改性方法的研究进展,以及改性碳纳米管在复合材料、医学、环保、储能等领域的一些应用。     

碳纳米管的制备研究

本文介绍了国内外碳纳米管(CNTS)最新研究进展,分析了制备碳纳米管所必需的3个关键条件：碳源、催化剂、能源;并分别研究了它们对碳纳米管生长的影响。通过碳纳米管的生长机理探讨了大规模制备碳纳米管的可行性。     

碳纳米管增强聚合物复合材料研究进展

综述了碳纳米管增强聚合物复合材料研究进展,介绍了碳纳米管的力学性能、碳纳米管增强聚合物的制备方法,阐述了近年来原位聚合、电纺丝、层层自组装等方法在这类复合材料制备中的应用。     

化学气相沉积法合成纳米碳管阵列研究

研究以环己烷为前驱体采用化学气相沉积法制备纳米碳管阵列。将催化剂二茂铁定量溶解在环己烷中,通过载气夹带进入反应器中,采用化学气相沉积方法定向生长出炭纳米管阵列,此法有效地控制反应体系中的催化剂含量,使生产稳定性及重现性较好。并通过透射电子显微镜、扫描电子显微镜、拉曼光谱及X射线衍射对产品形态和结构进行分析和表征,所制备出的纳米碳管阵列形态比较规整,纯度较高,具有较好的石墨微晶结构;并对纳米碳管的生长机理进行了详细讨论。     

碳纳米管制备方法的研究进展

碳纳米管具有独特的一维纳米结构,具有极大的比表而积及其优异的物理化学性能,在纳米电子器件、储氢材料、传感器等领域有着巨大的应用前景。文章综述了碳纳米管几种主要的制备方法,如电弧放电法、化学气相沉积法、激光蒸发法、模版法等,通过介绍最新的制备方法和进展,为研究人员提供进一步的参考价值。     

Carbon Nanotubes for Supercapacitor

As an electrical energy storage device, supercapacitor finds attractive applications in consumer electronic products and alternative power source due to its higher energy density, fast discharge/charge time, low level of heating, safety, long-term operation stability, and no disposable parts. This work reviews the recent development of supercapacitor based on carbon nanotubes (CNTs) and their composites. The purpose is to give a comprehensive understanding of the advantages and disadvantages of carbon nanotubes-related supercapacitor materials and to find ways for the improvement in the performance of supercapacitor. We first discussed the effects of physical and chemical properties of pure carbon nanotubes, including size, purity, defect, shape, functionalization, and annealing, on the supercapacitance. The composites, including CNTs/oxide and CNTs/polymer, were further discussed to enhance the supercapacitance and keep the stability of the supercapacitor by optimally engineering the composition, particle size, and coverage.     

碳纳米管非共价包裹鲁米诺的化学发光研究

浓HNO_3通过沸点回流法对碳纳米管(Carbon Nanotubes,CNTs)进行处理,去除表面杂质并对CNTs切断开管,在开口处被修饰上羧基、羟基等基团。增加了碳纳米管(CNTs)在水及有机溶剂中的溶解性,另外通过湿化学法,在均相溶液中对碳纳米管(CNTs)包裹鲁米诺(Luminol)的实验条件也进行了优化,选择直径大的碳纳米管(CNTs)且溶解性较好的溶剂二甲亚砜(DMSO)。在检测方面采用Luminol-Co~(2+)-H_2O_2化学发光体系,对包裹鲁米诺(Luminol)的碳纳米管(CNTs)进行化学发光测试,该方法简单,灵敏。     

On the Growth and Microstructure of Carbon Nanotubes Grown by Thermal Chemical Vapor Deposition

Carbon nanotubes (CNTs) were deposited on various substrates namely untreated silicon and quartz, Fe-deposited silicon and quartz, HF-treated silicon, silicon nitride-deposited silicon, copper foil, and stainless steel mesh using thermal chemical vapor deposition technique. The optimum parameters for the growth and the microstructure of the synthesized CNTs on these substrates are described. The results show that the growth of CNTs is strongly influenced by the substrate used. Vertically aligned multi-walled CNTs were found on quartz, Fe-deposited silicon and quartz, untreated silicon, and on silicon nitride-deposited silicon substrates. On the other hand, spaghetti-type growth was observed on stainless steel mesh, and no CNT growth was observed on HF-treated silicon and copper. Silicon nitride-deposited silicon substrate proved to be a promising substrate for long vertically aligned CNTs of length 110–130 μm. We present a possible growth mechanism for vertically aligned and spaghetti-type growth of CNTs based on these results.     

Radial Corrugations of Multi-Walled Carbon Nanotubes Driven by Inter-Wall Nonbonding Interactions

We perform large-scale quasi-continuum simulations to determine the stable cross-sectional configurations of free-standing multi-walled carbon nanotubes (MWCNTs). We show that at an inter-wall spacing larger than the equilibrium distance set by the inter-wall van der Waals (vdW) interactions, the initial circular cross-sections of the MWCNTs are transformed into symmetric polygonal shapes or asymmetric water-drop-like shapes. Our simulations also show that removing several innermost walls causes even more drastic cross-sectional polygonization of the MWCNTs. The predicted cross-sectional configurations agree with prior experimental observations. We attribute the radial corrugations to the compressive stresses induced by the excessive inter-wall vdW energy release of the MWCNTs. The stable cross-sectional configurations provide fundamental guidance to the design of single MWCNT-based devices and shed lights on the mechanical control of electrical properties.     

磁性多壁碳纳米管吸附处理甲基橙模拟废水的研究

对多壁碳纳米管进行纯化处理后采用化学共沉淀法制成磁性多壁碳纳米管(mMWNT),研究了其对甲基橙废水的处理效果,考察了投加量、吸附时间、pH值、温度等因子的影响。结果表明,mMWNT成功负载了Fe3O4和γ-Fe2O3;mMWNTs投加量为6 g/L时甲基橙的去除率可达99.2%;甲基橙去除率随时间呈逐渐增大趋势直至吸附平衡;实验的最佳pH为1时,去除率最高;温度为30℃时,去除率达到80%。mMWNT吸附处理甲基橙模拟废水过程符合准二级吸附动力学方程。     

Structural Modification in Carbon Nanotubes by Boron Incorporation

We have synthesized boron-incorporated carbon nanotubes (CNTs) by decomposition of ferrocene and xylene in a thermal chemical vapor deposition set up using boric acid as the boron source. Scanning and transmission electron microscopy studies of the synthesized CNT samples showed that there was deterioration in crystallinity and improvement in alignment of the CNTs as the boron content in precursor solution increased from 0% to 15%. Raman analysis of these samples showed a shift of ~7 cm⁻¹ in wave number to higher side and broadening of the G band with increasing boron concentration along with an increase in intensity of the G band. Furthermore, there was an increase in the intensity of the D band along with a decrease in its wave number position with increase in boron content. We speculate that these structural modifications in the morphology and microstructure of CNTs might be due to the charge transfer from boron to the graphite matrix, resulting in shortening of the carbon–carbon bonds.     

Synthesis and Enhanced Field-Emission of Thin-Walled,Open-Ended,and Well-Aligned N-Doped Carbon Nanotubes

Thin-walled, open-ended, and well-aligned N-doped carbon nanotubes (CNTs) on the quartz slides were synthesized by using acetonitrile as carbon sources. As-obtained products possess large thin-walled index (TWI, defined as the ratio of inner diameter and wall thickness of a CNT). The effect of temperature on the growth of CNTs using acetonitrile as the carbon source was also investigated. It is found that the diameter, the TWI of CNTs increase and the Fe encapsulation in CNTs decreases as the growth temperature rises in the range of 780–860°C. When the growth temperature is kept at 860°C, CNTs with TWI = 6.2 can be obtained. It was found that the filed-emission properties became better as CNT growth temperatures increased from 780 to 860°C. The lowest turn-on and threshold field was 0.27 and 0.49 V/μm, respectively. And the best field-enhancement factors reached 1.09 × 10⁵, which is significantly improved about an order of magnitude compared with previous reports. In this study, about 30 × 50 mm² free-standing film of thin-walled open-ended well-aligned N-doped carbon nanotubes was also prepared. The free-standing film can be transferred easily to other substrates, which would promote their applications in different fields.     

超电容器碳纳米管与钼复合电极材料的研究

以碳纳米管（CNTs）为基体材料，用浓硝酸回流处理碳纳米管，TEM（透射电子显微镜）研究表明碳纳米管的端帽被部分打开，通过液相反应对碳纳米管进行表面改性，制备CNTs／Mo复合电极材料，复合电极使电解液和导电材料的接触面积增大，使电极反应的有效表面积增大，反应场所有所增加，从而提高电极电化学反应的活性。基于此复合材料的超电容器具有高比电容、高稳定性、良好的可逆性和长寿命等特点。循环伏安结果表明：CNTs/Mo复合电极的比电容比纯CNTs电极要高出20％。     

Catalytic Routes Towards Single Wall Carbon Nanotubes

Single wall carbon nanotubes (SWCNT) have become a strategic material in the area of nanotechnologies nowadays, and catalytic chemical vapor deposition seems to be the most promising technique in view of an industrial‐scale production. However, the selective catalytic production of single wall carbon nanotubes is still a challenge, since catalytic systems performances both in terms of selectivity and activity are still relatively low. One of the main challenges for the catalytic growth of SWCNT is the control of the catalyst nanoparticles size distribution along the high temperatures required by the process. This article provides a comprehensive overview of the state of the art of the strategies that have been followed to selectively grow single wall carbon nanotubes. It focuses on catalysts preparation and activity/selectivity and on the growth mechanism of these nanostructures. Particular attention is given to the identification of the parameters that control the selectivity of the reaction, such as the choice of the metal/support couple, the particle’s sizes, and the chemical vapor deposition conditions.     

Catalytic Routes Towards Single Wall Carbon Nanotubes

Single wall carbon nanotubes (SWCNT) have become a strategic material in the area of nanotechnologies nowadays, and catalytic chemical vapor deposition seems to be the most promising technique in view of an industrial-scale production. However, the selective catalytic production of single wall carbon nanotubes is still a challenge, since catalytic systems performances both in terms of selectivity and activity are still relatively low. One of the main challenges for the catalytic growth of SWCNT is the control of the catalyst nanoparticles size distribution along the high temperatures required by the process. This article provides a comprehensive overview of the state of the art of the strategies that have been followed to selectively grow single wall carbon nanotubes. It focuses on catalysts preparation and activity/selectivity and on the growth mechanism of these nanostructures. Particular attention is given to the identification of the parameters that control the selectivity of the reaction, such as the choice of the metal/support couple, the particle's sizes, and the chemical vapor deposition conditions.     

Study on the Reusability of Multiwalled Carbon Nanotubes in Biodegradable Chitosan Nanocomposites

The mechanical properties, water absorption, biodegradation, multiwalled carbon nanotubes (MWCNTs) recovery and reusability of chitosan/oxidized MWCNTs nanocomposites were investigated. The highest Young's modulus (E) was obtained by the nanocomposites with 0.1 wt.% MWCNTs, while further increase of MWCNTs loading decreases the tensile strength (TS) and E. The water absorption and degradation rate of the nanocomposites were decreased by the loading of MWCNTs; 89.7% of MWCNTs were recovered by physical base separation. Thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and tensile test results showed that the recovered MWCNTs displayed properties similar to the oxidized MWCNTs, suggesting the possibility of reuse and recycle.