Synthesis of carbon nanotube array using corona discharge plasma-enhanced chemical vapor deposition

A corona discharge phasma-enhanced chemical vapor deposition with the features of atmospheric pressure and low temperature has been developed to synthesize the carbon nanotube array ,The array was synthesized from methane and hydrogen mixture in anodic aluminum oxide template channels in that cobalt was electrodeposited at the bottom.The characterization results by the scanning electron microscopy,transmission electron microscopy,energy dispersive X-ray spectroscopy and Raman spectroscopy indicate that the array consists of carbon nanotubes with the diameter of about 40 nm and the length of more than 4 μm, and the carbon anotubes are mainly restrained within the channels of templates.     

Decoration of activated carbon nanotubes by assembling nano-silver

A facile solution processed strategy of synthesizing nano silver assembled on carbon nanotubes (CNTs) at room temperature was put forward. Activated carbon nanotubes were used as precursors for preparing silver-decorated nanotubes. The nature of the decorated nanotubes was studied using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The inert surfaces of carbon nanotubes were activated by introducing catalytic nuclei via an oxidation-sensitization-activation approach. Activated carbon nanotubes catalyzed the metal deposition specifically onto their surfaces upon immersion in electroless plating baths. The method produced nanotubes decorated with silver. The extent of silver decoration was found to be dependent on fabrication conditions. Dense nano silver assembled on nanotube surfaces could be obtained by keeping a low reaction rate in the solution phase. The results here show that this method is an efficient and simple means of achieving carbon nanotubes being assembled by nano metal.     

电弧法合成填充金属纳米粒子的碳纳米管

用阳极弧法合成了碳纳米管内包覆铁和钴等金属纳米粒子.对合成物用透射电子显微镜(TEM)、X射线衍射(XRD)、电子能谱(EDS)和Raman光谱等方法进行了鉴定和表征.发现包覆粒子的多壁碳纳米管的平均直径约为35nm,其端部和内部包覆的粒子不连续分布、粒径基本均匀,约为20nm.分析了阳极弧等离子体法合成碳纳米管内包覆金属纳米粒子的形成机理.     

多壁碳纳米管氨基化修饰

将多壁碳纳米管高温处理除去无定形碳、然后用混酸（硫酸／硝酸）对碳纳米管进行表面羧基化．将羧基化碳纳米管与二氯亚砜反应得到酰氯化碳纳米管,然后将其分别与4,4＇-二氨基二苯砜（DDS）、1,3-二（3-氨丙基）-1,1,3,3-四甲基二甲硅醚（＆DA）、4＂,4＂＇-六氟异亚丙基-二（4-苯氧基苯胺）（FA）等二胺反应得到不同氨基化碳纳米管,FTIR,Raman,EDX,XRD,SEM,TGA分别对氨基化碳纳米管的结构与性能进行表征．通过对其在不同溶剂中的分散性的测试,氨基化碳纳米管在乙醇中的分散性明显优于未经修饰过的碳纳米管．     

氨基化的水溶性多壁碳纳米管的合成及表征

通过聚醚酰亚胺修饰得到了氨基化的多壁碳纳米管,并采用傅里叶变换红外光谱、透射电镜、拉曼光谱和热重分析对产物进行表征。通过估算,平均每根383 nm长的多壁碳纳米管接枝上了1 200个聚醚酰亚胺分子,约含一级胺的数目为28万个,即平均每100个碳原子接上了1.8个一级胺,大大增加了多壁碳纳米管表面的氨基数量。此外,修饰后的碳纳米管的溶解度显著提高,约2 mg/mL,利于进一步开发其在生物传感器、药物载带、组织工程、生物显像等生物医药领域的应用。     

Nanoscale hydrodynamics: enhanced flow in carbon nanotubes

Nanoscale structures that could mimic the selective transport and extraordinarily fast flow possible in biological cellular channels would have a wide range of potential applications. Here we show that liquid flow through a membrane composed of an array of aligned carbon nanotubes is four to five orders of magnitude faster than would be predicted from conventional fluid-flow theory. This high fluid velocity results from an almost frictionless interface at the carbon-nanotube wall.     

六角排列碳纳米管阵列的场增强因子的计算

通过求解Laplace方程得到六角排列的碳纳米管(CNTs)阵列的管尖端电场强度和场增强因子,具体研究CNTs的自身线度、阵列密度及阵列形状对CNTs的场增强因子的影响.研究结果表明,场增强因子随CNTs长径比的增加而增加,对于长径比一定的CNTs阵列,对应着一个最佳阵列密度,如管长为 6 μm、管径分别为5 nm、13 nm、20 nm的CNTs阵列对应的最佳阵列密度为3.05×1011 cm-2、4.83×1010 cm-2、2.12×1010 cm-2.在相同的阵列密度下,六角排列CNTs阵列的场发射性能要优于四方排列的CNTs阵列.计算得到六角排列CNTs阵列上端面的电势分布曲线.     

Effects of Temperature and Catalyst Concentration on the Growth of Aligned Carbon Nanotubes

The effects of preheating and pyrolysis temperatures and catalyst concentration on the synthesis of aligned carbon nanotubes （CNTs） using ferrocene as the catalyst and xylene as the carbon source in chemical vapor deposition were experimentally studied. The as-grown aligned CNTs were characterized by field emission scanning electron microscopy, transmission electronic microscopy, high-resolution transmission electronic microscopy, and Raman spectroscopy. The growth rate, the diameters, and the degree of crystal structure of the aligned CNTs were all found to depend on the preheating and pyrolysis temperatures and the catalyst concentration. The optimized conditions for the growth of aligned CNTs resulted in a rapid growth rate of 20.4 um/min, with the CNTs having a good, uniform crystal structure, and clean surfaces with little amorphous carbon. The results also show that higher preheating temperatures and lower ferrocene concentrations favor the growth of single-walled CNTs.     

催化剂厚度对碳纳米管直径的影响

由于碳纳米管具有独特的结构和性能，因而自从被发现以来一直受到人们的关注。近年来，已利用各种方法成功地合成出碳纳米管，特别是利用化学气相沉积方法制备高度准直的碳纳米管。分析了该方法中催化剂厚度对碳纳米管直径的影响，利用负衬底偏压热灯丝CVD系统和不同厚度的NiFe催化剂在Si衬底上直接生长，并用扫描电子显微镜来研究碳纳米管的生长过程。结果表明催化剂颗粒封闭了碳纳米管的顶端，催化剂厚度对碳纳米管的直径有较大的影响，碳纳米管的平均直径随催化剂厚度的增大而增大。     

功能化多壁碳纳米管增强涂层用于金属保护

通过多巴胺自发氧化聚合形成包裹的多壁碳纳米管（PDA@FMWCNT）.利用聚多巴胺（PDA）的易附着能力,在铜（Cu）表面构造了基于PDA@FMWCNT的复合材料薄膜.利用拉曼（Raman）光谱、傅里叶变换红外光谱（FT-IR）、X射线光电子光谱（XPS）和扫描电子显微镜（SEM）对复合材料的结构进行了表征.利用电动位极化和电化学阻抗谱（EIS）法评价了PDA@FMWCNT在盐溶液中对金属的腐蚀保护性能.结果表明,PDA@FMWCNT复合涂层具有良好的防腐蚀性,并详细描述了其保护机理.     

基板焙烧温度与合成时间对V型火焰法于不锈钢基板直接生长碳纳米管的影响

为了实现于锅炉中直接制备附着碳纳米管的各类构件,采用自主研发的V型火焰法,在不锈钢基板上直接快速生长碳纳米管。通过SEM、XRD谱和Raman光谱分析了基板预处理温度和合成时间对碳纳米管生长过程,并对不同条件下产物的形态、结晶度进行了分析;通过EDS分析了附着碳纳米管的基板元素含量变化。结果表明：通过调整基板的焙烧温度,能够控制基板上碳管的密度和质量,焙烧温度为500~600oC时产物的产量和质量最优;本实验条件下,铁是促进碳纳米管生长的活性位点;碳纳米管的生长经过碳的溶解、扩散和析出的过程,本实验条件下,2min后碳管开始生长,7min得到的碳管均匀覆盖于基板表面,管壁笔直,杂质少。可见,V型火焰法能够直接在经过焙烧的不锈钢板上生长碳管,且合成时间短,预处理过程简单,为批量生产附着碳纳米管构件提供了简单有效的途径。     

以AAO模板为基底可控合成一维碳纳米材料

将不负载任何活性组分的阳极氧化铝模板分别放入两段炉中,700℃下催化裂解乙炔可控合成一维碳纳米材料,反应气氛分别为氩气和氢气;产物通过扫描电子显微镜和高分辨透射电子显微镜进行了表征.结果表明:当反应气氛为氩气时,第一段炉中模板表面为相互缠绕的蠕虫状的碳纳米管,其直径在100nm左右,模板孔内为开口的碳纳米管,其直径约为50nm左右;第二段炉中模板表面沉积了密集的碳纳米棒,其形貌规整,棒体很直,散落在模板表面,粗的直径约200nm,细的约100nm,长度短的不到1μm,长的约2.5μm;当反应气氛为氢气时,模板表面沉积了规整的直立碳纳米棒,其长度长的约1μm,短的约为100nm,粒径约为50nm.所合成的碳纳米棒为实心的断断续续的石墨片层组成的波纹状结构.     

低温碳纳米管的XPS光谱特征研究

采用X射线光电子能谱对后处理前后的低温碳管(LT-CNTs)进行表面特征分析.发现纯化后碳管的O/C原子比升高,经过Ar气保护下的高温煅烧的后处理后,其O/C原子比降低,比表面积增大.对C1 s峰的拟合分析表明,碳管表面的含氧基团发生改变,深度纯化碳管时,大量活性碳原子变为羟基(C-O),大量的羰基(C=O)变为羧基(O-C=O).同时,大部分化学吸附的氧气将解吸,氧气的解吸将使C-O键或O-C=O转变为C=O双键等形式,且伴随碳管电学性质的改变,由明显的金属性转变为半导体性.     

压强对PECVD制备碳纳米管的影响

采用等离子体增强化学气相沉积技术(PECVD),以C2H2、H2和N2为反应气体,在镀Ni催化剂的Si基底上成功制备出多壁碳纳米管薄膜.并通过扫描电镜拍摄其表征,系统、深入地研究了沉积压强对碳管形貌的影响.结果表明:沉积压强对催化剂的刻蚀和碳纳米管薄膜的形成起着重要作用,获得定向性良好、分布均匀、密度适中的碳纳米管的最佳沉积压强是300 Pa.     

热处理对多壁碳纳米管储氢性能的影响

文章采用容量法测量在常温下压力升高到10 MPa时,多壁碳纳米管的吸附储氢性能,分析了热处理对碳纳米管的结构和吸附储氢量的影响。采用透射电镜(TEM)、激光拉曼光谱(Raman)和低温N2吸附(BET)对碳纳米管的微观结构进行表征。结果发现,热处理能明显地提高碳纳米管的石墨化程度,热处理后碳纳米管的质量储氢容量从原来的1.90%升高到2.17%。     

微波法制备碳纳米管负载ZnCdS纳米粒子及其光催化性能

用微波法制备了碳纳米管负载ZnCdS纳米复合材料(ZnCdS/CNTs).通过扫描电子显微镜(SEM),透射电镜(TEM)和X-射线粉末衍射(XRD)测试表明:平均粒径为25 nm六方纤锌矿结构的ZnCdS纳米粒子均匀分散在碳纳米管表面.ZnCdS/CNTs纳米复合材料在可见光下光催化降解甲基橙和罗丹明溶液.结果表明:催化剂用量为0.02g/L条件下,对初始浓度均为100mg/L的甲基橙和罗丹明溶液进行可见光光照50min后,降解率分别达到97%和96.7%;催化剂重复使用3次后,光照50min后甲基橙和罗丹明的降解率仍可达到92%和91%.     

不同过渡层和电场方向对碳纳米管或纤维生长的影响

利用等离子体增强化学气相沉积系统沉积了碳纳米管或纤维，并用扫描电子显微镜研究了它们的生长和结构．为避免碳纳米管或纤维在生长过程中从衬底Si表面上脱落，先在Si表面上溅射沉积了金属过渡层Ti或Ta，然后再沉积催化剂NiFe．结果发现Ti和Ta过渡层对碳纳米管或纤维的结构有很大的影响．另外，还发现衬底Si放在支架的不同位置，碳纳米管或纤维的生长方向不同，这可能是由于辉光放电产生的非均匀电场所致．对不同过渡层和电场方向对碳纳米管或纤维生长的影响进行了分析和讨论．     

催化裂解法制备大孔径碳纳米管

Ni-Cu-Al催化剂中加入少量碳酸钠,催化裂解甲烷制备了大孔径碳纳米管,碳纳米管的产量为2.4g/g.cat。用这种方法制备的碳纳米管的内径约为20 nm~60 nm,外径约为40 nm~80nm。用扫描电镜(TEM)和X射线衍射(XRD)研究了碳纳米管的形貌和微结构。分析结果表明:用这种方法制备的碳纳米管不仅内径较大而且石墨化程度较高。碳酸钠的加入引起了甲烷转化率和碳产率的轻微下降。实验结果表明:碳酸钠是一种温和的毒物,它能影响Ni-Cu-Al催化剂的催化活性,导致大孔径碳纳米管的生成。文中还讨论了大孔径碳纳米管的生长机理。     

氧化热处理对不锈钢基碳纳米管结构及其电化学检测性能的影响

采用化学气相沉积法,以不锈钢基体中的Fe、Ni等成分为催化剂,直接在其表面生长碳纳米管并进行氧化热处理。采用场发射扫描电镜观察制备的碳纳米管形貌及尺寸,并采用接触角测量方法检测试样亲水性质,结合透射电镜、拉曼光谱和XPS检测分析氧化热处理引起的碳管形貌和特征差异,最后考察尿酸在碳纳米管电极上的电化学响应。结果表明,氧化热处理使碳纳米管平滑的表面变得粗糙,暴露出了更多的边平面结构,并且碳纳米管从疏水变为超亲水状态,使其在电化学反应过程中电极表面能够更好地与溶液中的物质接触,有利于材料电化学性能的提高;以经过氧化热处理的碳纳米管为电极,能够在大量抗坏血酸存在的条件下选择性地测定尿酸。     

Different effects of substrates on the morphologies of single-walled carbon nanotubes

In this work, different effects of substrates on the morphologies of single-walled carbon nanotubes （SWNTs） are studied. SWNTs were produced by floating catalytic chemical vapor deposition using CH4 as carbon source gas and Ar as carrier gas. Then the SWNTs were deposited on lithography-patterned different substrates. The as-grown SWNTs at the boundaries between SiO2 and metal were characterized by scanning electron microscopy, atomic force spectroscopy and Raman spectroscopy. It is found that SWNTs deposited on low-conductivity substrates trend to have curved morphologies and some of them form rings, while SWNTs deposited on metal sub- strates remain straight and orientated. The mechanism of these effects was also discussed, which is closely related to the thermal conductivities and the principle of energy dissipation.