化学气相沉积工艺制备绳状纳米碳管的研究

用硝酸铁作催化剂,乙炔作碳源气体,高纯氮气作稀释气体,在750℃下化学气相沉积生长了绳状纳米碳管,用高分辨扫描电镜观察了所得绳状纳米碳管的形貌.纳米碳管的直径为100～200nm,长度为10～20 μm.文中还提出了绳状纳米碳管的生长机理.     

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。     

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。     

碳氢化合物气相催化热分解制备纳米碳管的研究

主要研究了碳氢化合物气相催化热分解制备纳米碳管的方法：浮游催化法，并对其结果作了深入讨论。使用浮游催化法可以制得大量、高质、等径、笔直的纳米碳管，也可以用这种方法来制备单壁纳米管。通过场发射透射电子显微镜（TEM）对产物形貌进行观察分析，在实验中考察了对纳米碳管生长具有显著影响的几个工艺参数，诸如含硫添加剂、反应温度以及氢气流速等，讨论了它们对产物形貌的影响，并对它们的作用机理进行了初步探讨。采用正交实验的方法找到了浮游催化法制备纳米碳管的最优工艺参数。     

化学气相沉积法合成碳纳米管研究进展

碳纳米管由于其独特的结构和优异的电学、光学、力学、热学等物理化学性能,在材料、电子器件、传感器、催化剂和能源等领域具有广泛的应用前景,但是如何低成本批量制备高品质的碳纳米管是实现碳纳米管大规模应用的关键。本文综述了近年来化学气相沉积法合成碳纳米管的研究进展,表明化学气相沉积法是大规模可控制备碳纳米管最有效的方法,并对其未来的发展方向进行了分析和展望。     

纳米碳管的研究进展

本文对纳米碳管的结构、种类作了概括介绍；对纳米碳管的制备方法、纯化方法及主要应用作了详细的综述；并对纳米碳管研究中存在的问题及今后发展趋势作了简单介绍。     

化学气相沉积法修饰丝光沸石催化α—蒎烯异构化反应

本文用化学气相沉积法修饰人工合成丝光沸石，用程序升温脱附法研究了其酸性质，以经ＣＶＤ修饰的氢型丝光沸石为催化剂催化α－蒎烯的异构化反应，发现产物中单环化合物以异松油类为主。     

等离子体改性对纳米碳管电化学检测性能的影响

利用微波等离子体化学气相沉积法制备了与电极基底结合良好的纳米碳管电极,用空气等离子体将该纳米碳管电极功能化,并以功能化的电极为工作电极,利用循环伏安法对毒性很强的酚的混合物进行检测。根据氧化还原峰电位的不同可以区分出邻苯二酚和对苯二酚,与石墨电极相比,功能化的纳米碳管电极具有更好的电催化性能。利用该电极测定酚的混合物是一种准确、快速、有效的测定方法。合成纳米碳管电极的最佳工艺条件为:功率为400 W,压强为3.0 kPa,甲烷流速为2 mL/m in,氢气流速为50 mL/m in;功能化纳米碳管的最佳工艺条件为:功率为150 W,压强为1.0 kPa,空气的流速为50 mL/m in。     

Co／Mo催化剂制备碳纳米管的研究

以氧化铝凝胶负载Co／Mo合金为催化剂，C2H2为碳源，用CVD法合成了纯度较商的多壁碳纳米管（MWCNT）。通过甩TEM和XRD等方法，对碳纳米管（CNTs）进行了表征，表明制备的碳纳米管具有较高的石墨化程度。研究得出当催化剂的沉淀pH=7．5，H2为还原气和载气，升温速率为50℃／min时，碳纳米管的纯化后的产率高达85％，为下一步的大规模化生产打下了良好构基础。     

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.     

(Mg,Co)O Solid-Solution Precursors for the Large-Scale Synthesis of Carbon Nanotubes by Catalytic Chemical Vapor Deposition

Single- and double-walled carbon nanotubes were produced in high yield using the selective reduction of solid solutions of Mg_{1– x} Co _x O in a methane and hydrogen atmosphere at 1000°C. The solid solutions were prepared using combustion synthesis with urea as the fuel. The BET surface areas ranged from 10 to 65 m²/g depending on the fuel content. A single crystalline phase was obtained only for fuel-rich compositions. Increased fuel content increased the surface area by a factor of 6. However, very high fuel contents (>4 times the stoichiometric amount) caused a demixed solid solution. Surface-area measurements and Raman spectra showed that the quantity of nanotubes formed depended on the surface area and composition of the precursor oxide.     

Preparation of Carbon Nanotubes (CNTs)-Cordierite Monoliths by Catalytic Chemical Vapor Deposition as Catalyst Supports for Ammonia Synthesis

Tunable carbon nanotubles (CNTs)-coated monoliths as catalyst supports were prepared by catalytic chemical vapor deposition (CCVD) over deposited cobalt on cordierite. The influence of the preparation conditions such as the cobalt nitrate loading on the cordierite monoliths, the flow rate of reaction gases, reaction time and temperature on CNTs yield, thermal properties and structural features of the resulting materials were studied. The CNTs-cordierite was characterized by TEM/HREM, SEM, N₂ physisorption and TGA. The SEM showed that a relatively homogeneous mesoporous layer of CNTs covered on the surface of the cordierite monoliths. Comparing with the bare cordierite, the BET surface area and pore volume of CNTs-cordierite increased significantly. CNTs have penetrated into the cordierite substrate and led to a remarkable mechanical stability of the CNTs-cordierite monoliths against ultrasound maltreatment. The CNTs content, BET surface area, pore volume and thermal properties of CNTs-cordierite monoliths all could be changed by the variation of the synthesis conditions. Barium promoted ruthenium catalysts supported on the as-synthesized materials showed much higher activity for ammonia synthesis than their counterparts deposited on bare cordierite monoliths. Furthermore, the catalytic activity linearly increased with the BET surface area of CNTs-cordierite monoliths. The CNTs-cordierite monoliths were proved to be promising candidates as catalyst supports and the performance of catalysts supported on as-prepared materials would be easily modified by changing the growth conditions of CNTs.     

气体流量对化学气相沉积法制备碳纳米管的影响

用化学气相沉积法裂解乙炔制备无序多壁碳纳米管,以Fe/S iO2粉状物作为催化剂,考察了气体流量等环境因素对碳纳米管生长的影响。通过TEM和SEM分析得出,当N2流量分别为200、500和800 mL/m in时,碳纳米管的平均直径分别为20、36和82 nm,即碳纳米管的直径随着N2流量的升高而增大。当N2流量增加到800mL/m in时,还生成了大量的直径约为20~30 nm的碳纳米球。不通H2制备不出碳纳米管。     

The Influences of H2 Plasma Pretreatment on the Growth of Vertically Aligned Carbon Nanotubes by Microwave Plasma Chemical Vapor Deposition

The effects of H₂ flow rate during plasma pretreatment on synthesizing the multiwalled carbon nanotubes (MWCNTs) by using the microwave plasma chemical vapor deposition are investigated in this study. A H₂ and CH₄ gas mixture with a 9:1 ratio was used as a precursor for the synthesis of MWCNT on Ni-coated TaN/Si(100) substrates. The structure and composition of Ni catalyst nanoparticles were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The present findings showed that denser Ni catalyst nanoparticles and more vertically aligned MWCNTs could be effectively achieved at higher flow rates. From Raman results, we found that the intensity ratio of G and D bands (I _D/I _G) decreases with an increasing flow rate. In addition, TEM results suggest that H₂ plasma pretreatment can effectively reduce the amorphous carbon and carbonaceous particles. As a result, the pretreatment plays a crucial role in modifying the obtained MWCNTs structures.     

Development of Tantalum Pentoxide Coatings by Chemical Vapor Deposition

Thermochemical considerations clearly indicate a need for the protection of SiC and Si₃N₄ materials from HC1- and Na₂SO₄-induced corrosion. Ta₂O₅ has been identified as a material which may be suitable for such a protective coating. Thermodynamic calculations have indicated a range of temperatures, pressures, and reactant concentrations under which Ta₂O₅ coatings may be formed as a single phase by chemical vapor deposition. Ta₂O₅ coatings exhibiting a range of microstructures were obtained experimentally.