电弧法制备单壁碳纳米管的机理及进展

本文介绍了单壁碳纳米管的结构和性质,叙述了电弧法制备碳纳米管的方法与原理,及制备技术的发展和改进。     

化学气相沉积法制备单壁碳纳米管研究进展

单壁碳纳米管的独特性能使其成为一种有着极大应用前景的新兴纳米材料,本文主要介绍了催化剂、裂解温度、载气等因素对化学气相沉积法（CVD）制备单壁碳纳米管的影响和采用化学气相沉积制备定向单壁碳纳米管方面的研究进展情况。     

活化稀土金属以宏量制备单壁碳纳米管

过去的三十几年见证了制备单壁碳纳米管(SWNTs)的催化剂由传统金属到氧化物与碳化物的演变过程。由于传统催化剂所制备SWNTs的产量低且表征手段受限,因此难以建立催化剂组成与SWNTs手性分布之间的关系。基于此,利用稀土金属钕(Nd)作为催化剂,通过“碱性载体”策略,实现了SWNTs的宏量制备。SWNTs纯化后,通过多种电子显微技术以及光学表征手段对其进行了系统表征。700℃下,利用Nd催化剂实现了(6,5)型SWNTs的高选择性制备,与铁族金属催化剂所制备的SWNTs类似。基于Nd纳米粒子的低熔点特点,提出了Nd催化剂生长SWNTs的气-液-固成核机制,并利用生长动力学对SWNTs的手性分布进行了解释。     

非金属纳米粒子诱导生长单壁碳纳米管

采用四乙氧基硅烷(Tetraethylorthosilicate,TEOS),在chemical vapor deposition(CVD)体系中制备二氧化硅薄膜,退火形成Si O2纳米粒子生长SWNTs。通过改变各种实验条件,如温度、催化剂纳米粒子、碳源及载气流量等,对非金属纳米粒子诱导生长SWNTs阵列进行系统研究。     

以无毒液体石蜡为碳源制备多壁碳纳米管

以无毒的液体石蜡为碳源、二茂铁为催化剂前驱体、含硫化合物二甲基亚砜为生长促进剂,采用浮动催化热分解法制备多壁碳纳米管,通过TEM、SEM、XRD、Ram an、TG等对产物形貌和结构进行了表征。结果表明,在1 100~1 280℃条件下,能够制备出晶化程度较高的多壁碳纳米管,并且随着温度的升高,多壁碳纳米管由弯曲型向直形转变。     

煤基碳纳米管的制备

碳纳米管是一类新型纳米炭，具有很多潜在的应用价值，用煤为碳源制备碳纳米管可以降低其成本，本文介绍了电弧放电法和等离子体法制备煤基碳纳米管研究情况，以及相应的煤基碳纳米管生长机制。     

硝酸法纯化碳纳米管的研究

本文采用YNi2合金为催化剂使用电弧放电的方法制备单壁碳纳米管.采用硝酸回流法进行处理,分别经过超声、回流、水洗、研磨、培烧,得到较纯净的碳纳米管.分别用近红外光谱、拉曼光谱、热重分析进行表征.纯化后的碳纳米管可以进一步用来化学修饰、金属和半导体性的分离等.     

煤基电弧法制备碳纳米管的影响因素

以煤为原料,通过一定的处理,代替石墨作为碳纳米管的制备原材料,介绍了电弧放电制备煤基碳纳米管的方法,分析了操作参数、催化剂、煤种对煤基碳纳米管生成的影响,研究了各个因素在制备过程中的相互作用,从而降低了生产成本。     

Sigma-Aldrich公司同意与Southwest NanoTechnologies公司签署协议共同经销SWeNT单壁碳纳米管

Sigma-Aldrich公司和单壁碳纳米管领先生产商SouthWest NanoTechnologies公司宣布签署协议,Sigma-Aldrich公司将给各大科研机构销售SouthWest NanoTechnologies公司生产的单壁碳纳米管。     

己二胺接枝单壁碳纳米管用于环氧复合材料

利用碳二亚胺活化碳纳米管上羧基的方法将1,6-己二胺接枝到单壁碳纳米管上。通过酸碱滴定确定了碳纳米管壁上羧基的含量,并对产物进行了红外和热重分析。将改性后的碳纳米管用于环氧复合材料,测试了材料的力学性能和电性能,并通过扫描电镜观察了断裂面的形貌。结果表明,羧基化碳纳米管上35%左右的羧基发生了酰胺化反应,碳纳米管上平均每100个碳原子接枝上2个己二胺分子链。经己二胺接枝改性后的碳纳米管在环氧树脂中的分散质量和界面粘合均得以明显改善。SWNT质量分数为1%时,复合材料的拉伸强度、弹性模量和断裂伸长率分别为(89.13±3.97)MPa,(2.03±0.18)GPa,(2.95±0.29)%,较纯环氧树脂分别提升了108%,28%和8%;电导率由纯环氧树脂的1.45×10-15 S/cm提高到7.36×10-4 S/cm。复合材料的性能有了很大的提高。     

Improved field emission stability from single-walled carbon nanotubes chemically attached to silicon

ABSTRACT: Here we demonstrate the simple fabrication of a single walled carbon nanotube (SWCNT) field emission electrode which shows excellent field emission characteristics and remarkable field emission stability without requiring post treatment. Chemically functionalized SWCNTs were chemically attached to a silicon substrate. The chemical attachment led to vertical-alignment of SWCNTs on the surface. Field emission sweeps and Fowler-Nordheim plots showed that the Si-SWCNT electrodes field emit with a low turn-on electric field of 1.5 V mu m-1 and high electric field enhancement factor of 3965. The Si-SWCNT electrodes were shown to maintain a current density of > 740 mu A cm -1 for 15 hr with negligible change in applied voltage. The results indicate that adhesion strength between SWCNTs and substrate is a much greater factor in field emission stability than previously reported.     

Ferrocene-filled single-walled carbon nanotubes

Ferrocene molecules are successfully introduced into the inner hollow space of Single-walled carbon nanotubes (SWNTs) to get ferrocene-filled SWNTs (Fc@SWNTs). This nanohybrid material was carefully characterized by high resolution microscopy, FTIR spectrum, and Cyclic voltammetry (CV). This new material may not only act as air stable n-type field-effect transistors based on nanotubes, but it may also be employed as building blocks for various devices based on the redox activity of ferrocene. What’s more, upon high temperature annealing, the encapsulated ferrocene molecules will decompose and change into interior tubes, forming double-walled carbon nanotubes (DWNTs). This provides convincing evidence that ferrocene molecules are inserted into the hollow cavities SWNTs. This result also presented a controllable way to synthesize DWNTs.     

Synthesis and Raman characterization of boron-doped single-walled carbon nanotubes

A systematic study was carried out to dope single-walled carbon nanotube (SWNT) bundles with varying amounts of boron using the pulsed laser vaporization technique. Targets containing boron concentrations ranging from 0.5 to 10 at.% boron were prepared by mixing elemental boron with carbon paste and the Co/Ni catalysts. The laser-generated products that were obtained from these targets were characterized by high resolution transmission electron microscopy, electron energy loss spectroscopy (EELS), thermoelectric power (TEP) measurements, and Raman scattering experiments. Electron microscopy and Raman studies revealed that the presence of various levels of boron concentration in the target strongly affected the products that were prepared. SWNTs were found in the products prepared from targets containing up through 3 at.% boron, and high resolution EELS estimated that less than 0.05-0.1 at.% boron is present in the SWNT lattice. The absence of SWNT bundles in the products derived from targets containing more than 3 at.% boron implies that the presence of excess boron in the carbon plume severely inhibits the carbon nanotube growth. The overall effect of the boron incorporation primarily leads to: (i) a systematic increase in intensity of the disorder-induced band (D-band) upon boron doping, with increasing D-band intensity observed for higher doping levels, (ii) a systematic downshift in the G′-band frequency due the relatively weaker C-B bond, and (iii) a non-linear variation in the RBM and G′-band intensities which is attributed to shifts in resonance conditions in the doped tubes. Resonant Raman spectroscopy thus provides large changes in the intensity of prominent features even when the dopant concentration is below the detectable limit of EELS (0.05-0.1 at.%). Thermoelectric power data also provide complementary evidence for the presence of a small boron concentration in the SWNT lattice which transforms the SWNTs into a permanently p-type material.     

Preparation and characterisation of single-walled carbon nanotubes functionalised with amines

The amines octadecylamine, 2-aminoanthracene, 1-H,1-H-pentadecafluorooctylamine, 4-perfluorooctylaniline and 2,4-bis(perfluorooctyl)aniline, have been reacted with chemically modified single-walled carbon nanotubes (SWCNTs). The chemical modification consisted on a thermal treatment in air of arc discharge-grown SWCNTs with an optional purification with HNO₃. The selected amines have been allowed to interact with the obtained materials and with those resulting from an additional treatment with thionyl chloride. The resulting materials were characterised with different spectroscopic techniques such as X-ray photoelectron spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy, Raman spectroscopy, electron energy loss spectroscopy and fluorescence spectroscopy complemented with the thermogravimetric analysis and transmission electron microscopy. The chemically modified SWCNTs exhibit different solubility properties depending on the amines and the solvents used.     

Nonlocal material properties of single-walled carbon nanotubes

Natural frequencies of single-walled carbon nanotubes (SWCNTs) obtained using a model based on Eringen's nonlocal continuum mechanics and the Timoshenko beam theory are compared with those obtained by molecular dynamics simulations. The goal was to determine the values of the material constant, considered here as a nonlocal property, as a function of the length and the diameter of SWCNTs. The present approach has the advantage of eliminating the SWCNT thickness from the computations. A sensitivity analysis of natural frequencies to changes in the nonlocal material constant is also carried out and it shows that the influence of the nonlocal effects decreases with an increase in the SWCNT dimensions. The matching of natural frequencies shows that the nonlocal material constant varies with the natural frequency and the SWCNT length and diameter.     

Improvement in growth yield of single-walled carbon nanotubes with narrow chirality distribution by pulse plasma CVD

A pulse plasma chemical vapor deposition (CVD) technique was developed for improving the growth yield of single-walled carbon nanotubes (SWNTs) with a narrow chirality distribution. The growth yield of the SWNTs could be improved by repetitive short duration pulse plasma CVD, while maintaining the initial narrow chirality distribution. Detailed growth dynamics is discussed based on a systematic investigation by changing the pulse parameters. The growth of SWNTs with a narrow chirality distribution could be controlled by the difference in the nucleation time required using catalysts comprising relatively small or large particles as the key factor. The nucleation can be controlled by adjusting the pulse on/ofF time ratio and the total processing time.     

受限在单壁碳纳米管中水分子的扩散

将碳纳米管引入到与生命息息相关的离子通道膜的研究逐渐成为热点,其中的关键是要了解受限在膜孔道(碳纳米管)中的水分子行为.采用分子动力学模拟的方法研究分析了水分子在(6,6)、(7,7)、(8,8)等不同孔径的单壁碳纳米管内的扩散,模拟表明常温下水分子在(6,6)型管内形成水分子单链,在(7,7)型管内形成相互交错的水分子双链,在(8,8)型管内形成四边形堆叠结构.模拟比较了(8,8)管中水与体相下水的扩散系数,结果显示,水在(8,8)管中的扩散系数比体相下水的扩散系数要高出两个数量级.