化学气相沉积法制备碳纳米管

碳纳米管（CNTs）是一种具有独特理化性能和结构的一维纳米材料,也是当今纳米材料研究的焦点之一．在化学、生物、医药、能源、电子元件等诸多领域具有极高的应用价值．本文以有机溶剂环己烷为碳源．利用化学气相沉积法（CⅥ））在管式电阻炉内,以氩气为栽气,二茂铁为催化剂,一定温度条件下,制备了直径约为50nm,长度达几十微米以上的多壁碳纳米管（MWNTs）．采用拉曼光谱、扫描电镜、透射电镜、X-射线粉末衍射等测试手段,表征了碳纳米管的微观形貌和结构特征．通过对实验结果的分析和讨论,对CVD制备法中碳纳米管的生长机理进行了尝试性探讨。     

预置镍化学气相沉积法制备定向碳纳米管(英文)

采用化学气相沉积法(CVD),在溅射了镍薄膜的硅基底上制备了定向碳纳米管薄膜。对镍薄膜的氨气预处理过程及其机理进行了研究。结果发现预处理后的岛状区域随着薄膜厚度的增加而增加,纳米粒子区域的变化则与之相反。对5nm的镍薄膜进行预处理能获得细化和均匀分布的纳米粒子,有利于定向碳纳米管的生长。碳纳米管的生长过程及其细微结构与温度有很大关系。碳源的分解、碳原子在催化剂内部的扩散以及催化剂粒子的团聚三者之间的竞争决定了碳纳米管的生长情况。本文分析了碳纳米管的顶部生长模式及该模式下催化剂粒子的形态变化。     

催化化学气相沉积法制备螺旋形多壁碳纳米管(英文)

以乙炔为碳源、FeMo/MgO催化剂为模板,采用催化化学沉积法制备了螺旋状多壁碳纳米管(hs-MWC-NTs)。其中FeMo/MgO模板,由作为发泡和助燃剂的柠檬酸燃烧而制成。FeMo/MgO催化剂的XRD谱图揭示其具有微晶的通性。应用SEM、TEM和Raman光谱剖析了合成的炭材料。SEM和TEM观察表明获得了hs-MWC-NTs;Raman光谱的D峰和G峰确认了所获碳纳米管(CNTs)的结晶状态。结果表明:此法乃是合成直径10nm～20nm螺旋形多壁碳纳米管的最容易和简便方法。     

化学气相沉积法合成碳纳米管的研究进展

本文主要评述了化学气相沉积法合成碳纳米管的最新研究进展，结合我们在这方面的工作，重点讨论了催化剂、碳源、反应温度对合成碳纳米管质量和产率的影响，并对这一领域的发展趋势作了展望。     

化学气相沉积法制备多壁碳纳米管

以带程序升温装置的管式电阻炉为实验装置,采用化学气相沉积法,在一定的工艺条件下裂解二茂铁与双鸭山精煤的混合物制备出多壁碳纳米管.采用透射电镜、Raman光谱以及X射线衍射技术对碳纳米管产物进行表征,同时研究了碳纳米管的生长机理.     

化学气相沉积法低温合成螺旋碳纳米管

以水溶性氯化钠负载Fe做催化剂,直接通过化学气相沉积法在没有掺杂任何含硫气体噻吩的条件下催化裂解乙炔在450℃下进行反应制备纳米碳材料。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:在该条件下制备了选择性较高的螺旋碳纳米管,其直径在25~200nm之间,绝大部分碳纳米管都有着非常规整的螺旋性并且其螺距很短。所制备螺旋碳纳米管晶格没有好的连续性,中间有断痕出现,并且排列也很不规则,为一种有缺陷的石墨结构。     

化学气相沉积法制备大面积定向碳纳米管

以二茂铁、二甲苯、氩气分别为催化剂先驱体、碳源、载气,直径100mm的刚玉管为反应室,石英玻璃为基底,催化热解制备定向碳纳米管.在50 min内,获得长600μm的定向碳纳米管阵列.SEM和TEM研究表明:二茂铁的二甲苯溶液导入反应室的入口温度控制在大约300℃时,能得到定向碳纳米管阵列;当载气流量从500ml/min增加到2000ml/min时,CNTs生长速度加快,长度增加;间歇地滴入二茂铁和二甲苯混合物,可能得到多层碳纳米管薄膜.     

无氢化学气相沉积法制备碳纳米管

采用无氢的化学气相沉积法（CVD）进行碳纳米管的制备技术研究,并成功地制备了由20—φ80nm左右,长度为50-100μm左右的碳纳米管。通过改变气体的流量等影响因素实现了定向碳纳米管薄膜和多层碳纳米管薄膜以及其它各种形态的碳纳米管的制备。采用微区Raman光谱、扫描电子显微镜（SEM）和透射电子显微镜（TEM）等方法对产物的形貌和结构进行了表征,结果表明采用无氢CVD法可以制备出多种形态的碳纳米管。     

炭纤维表面生长碳纳米管

采用化学气相沉积工艺在炭纤维表面生长了碳纳米管,并观察了它的微观形貌,且对其影响因素进行了初步研究.结果表明:纤维表面的纵向沟槽可以负载催化剂粒子,是生长碳纳米管的物理基础;催化剂的浓度太高,金属粒子容易团聚长大,所得碳纳米管的管径较大;而催化剂浓度太低,则不能在炭纤维整个表面均匀生长碳纳米管;最佳的催化剂溶液的浓度是0.05mol/L的硝酸钴.比较了铁、钴、镍三种过渡金属催化剂,从形成的碳纳米管的质量来看,钴催化剂最佳.     

甲烷化学气相沉积法合成小直径双壁碳纳米管

采用化学气相沉积法（CVD）以甲烷与氢气为原料,在900℃合成了大量的小直径双壁碳纳米管。我们用硝酸铁和氧化镁粉末的混合物作催化剂,三氧化二铝和钼酸铵作条件催化剂,研究表明条件催化剂的使用有利于双壁碳纳米管的选择性生长,可提高双壁碳纳米管的质量及其在产品中的比例,用扫描电子显微镜（SEM）、高分辨透射电镜（HRTEM）、热失重分析（TGA）和拉曼光谱（Raman）等分析纳米管的形貌和结构,结果发现其内径范围在0．62～0．88nm,外径范围在1．21～1．33nm之间。     

Synthesis and characterization of Y-shaped carbon fibers by chemical vapor deposition

In this work, Y-shaped carbon fibers with high purity were successfully synthesized by CVD using copper tartrate as a catalyst precursor at low reaction temperature, 279 °C. A model has been proposed for interpreting the mechanism of the Y-shaped carbon fibers growth. It is suggested that the introduction of hydrogen is the key factor to the formation of three carbon fibers growth faces on every the agglomeration of copper monocrystalline catalyst particles and lead to the formation of Y-shaped carbon fibers subsequently. The Y-shaped carbon fibers were characterized by field emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction.     

定向碳纳米管的化学气相沉积制备法

报道了一种简便有效的合成定向碳纳米管 (CNTs)的化学气相沉积 (CVD)制备方法。以铁为催化剂 ,乙炔为碳源 ,采用单一反应炉 ,直接在石英基底上沉积催化剂颗粒薄膜 ,成功合成了定向性好、管径均匀的高质量大密度的碳纳米管     

Hot-wire chemical vapor deposition of carbon nanotubes

Hot-wire chemical vapor deposition (HWCVD) has been employed for the continuous gas-phase generation of both carbon multi-wall and single-wall nanotube (MWNT and SWNT) materials. Graphitic MWNTs were produced at a very high density at a synthesis temperature of 600 °C. SWNTs were deposited at a much lower density on a glass substrate held at 450 °C. SWNTs are typically observed in large bundles that are stabilized by tube–tube van der Waals’ interactions. However, transmission electron microscopy analyses revealed only the presence of isolated SWNTs in these HWCVD-generated materials.     

热化学气相沉积法在硅纳米丝上合成碳纳米管

利用热化学气相沉积法在负载不同厚度催化剂的硅纳米丝(SiNW)表面生长碳纳米管(CNTs),探讨了生长条件对所合成SiNW-CNT的结构和场发射特性的影响.这种类似树状的三维结构具有较高碳纳米管表面密度及降低的电场筛除效应等潜在优势.使用拉曼光谱( Raman)、电子显微镜(SEM)、透射电子显微镜(TEM)、能量扩散分光仪(EDS)分析了碳纳米管的结构性质,并在高真空下施加电场测得碳纳米管的场发射特性.结果表明:随硅纳米丝上负载催化剂镍膜厚度的变化,所合成碳纳米管的表面特性、结晶结构及功函数改变,导致电子发射难易程度的改变,进一步影响碳纳米管的场发射特性.     

Quantitative elucidation of the rapid growth and growth saturation of millimeter-scale vertically aligned carbon nanotubes by hot-filament chemical vapor deposition

We report the rapid synthesis of millimeter-long vertically-aligned carbon-nanotubes (VACNTs) by hot-filament chemical-vapor-deposition without the use of water vapor. The growth rate increased initially up to ~ 190 μm/min but decreased thereafter resulting in the growth of up to 2.2 ± 0.2 mm in 23 ± 2 min. A thermodynamic model driven by a carbon-concentration gradient can account for very rapid initial growth with Arrhenius-type exponential temperature dependence. Another model devised for the quantitative elucidation of the monotonic decrease in growth-rate and quasi saturation of VACNT growth confirmed that the growth kinetics of VACNTs are controlled by the concomitant contribution of a diffusion-limited precursor supply and reaction-driven catalyst deactivation.     

Synthesis of carbon nanowalls by hot-wire chemical vapor deposition

Carbon nanowall (CNW) is a carbon nano-material which has a wall structure that stood on substrates. CNWs can be synthesized by hot-wire chemical vapor deposition (HWCVD) using methane without hydrogen dilution. The synthesis of CNWs by HWCVD is discussed along with reviewing the experimental results. The growth of CNWs is affected by hydrogen dilution ratio and substrate surface temperature. Based on these results, it is suggested that hydrogen radical density and substrate surface temperature are the important parameters for the synthesis of CNWs. The growth process of CNWs is also discussed.     

化学气相沉积法快速生长定向纳米碳管

利用化学气相沉积法，采用二甲苯为碳源，二茂铁为催化剂，氮气作保护气，在石英基底上催化裂解生长定向纳米碳管，试验结果表明：在775℃，120min的条件下，可生长出长达200μm厚的定向纳米碳管薄膜；在775℃，反应时间为60min～120min时，纳米碳管的长度为100μm～200μm，而纳米碳管的直径变化不明显。而无氢气，较高的反应温度和连续的催化剂供给对快速生长定向纳米碳管有重要的影响。     

Carbon dioxide as a carbon source for synthesis of carbon nanotubes by chemical vapor deposition

Carbon dioxide was successfully used as carbon source in the synthesis of carbon nanotubes (CNTs) by chemical vapor deposition (CVD) over Fe/CaO catalyst. The product was evaluated using both transmission electron microscopy (TEM) and Raman spectroscopy. Crooked and branching structures of multi-walled carbon nanotubes (MCNTs) with diameters of around 50 nm were observed on the TEM micrographs. Raman spectrum results show that the nanotubes have small defects, which is in agreement with the results of TEM. The influence of reaction variable such as furnace temperature and types of support media was also studied and the reaction mechanism was then discussed in this paper.     

Growth control of carbon nanotubes by plasma enhanced chemical vapor deposition

Plasma enhanced chemical vapor deposition (PECVD), which enables growth of vertically aligned carbon nanotubes (CNTs) directly onto a solid substrate, is considered to be a suitable method for preparing CNTs for nanoelectronics applications such as electron sources for field emission displays (FEDs). For these purposes, establishment of an efficient CNT growth process has been required. We have examined growth characteristics of CNTs using a radio frequency PECVD (RF-PECVD) method with the intention to develop a high efficiency process for CNT growth at a low enough temperature suitable for nanoelectronics applications. Here we report an effect of pretreatment of the catalyst thin film that plays an important role in CNT growth using RF-PECVD. Results of this study show that uniform formation of fine catalyst nanoparticles on the substrate is important for the efficient CNT growth.     

Optimization of synthesis condition for carbon nanotubes by chemical vapor deposition on Fe-Ni-Mo/MgO catalyst

Catalyst and reaction conditions are the main affecting factors for the yield and quality of carbon nanotubes (CNTs) produced by the chemical vapor deposition (CVD) method. In this paper a ternary component catalyst based on Fe-Ni-Mo/MgO was explored using methane as precursor. The influences of temperature and methane concentration were investigated, and the as-produced CNTs were characterized by SEM, HRTEM, XRD and TGA. The diameter of the CNTs is in the range of 20-30 nm and the maximum carbon yield can reach up to 80 times of the catalyst under the selected condition. The purity of the as-prepared CNTs is over 93%. Our results indicated that this novel tercomponent catalyst presented a good catalytic activity for manufacturing high quality and quantity of CNTs.