CVD法制备微旋管状炭纤维的微观形貌

采用化学气相沉积（ＣＶＤ）法,使溶有少量杂质的乙炔在自制的过渡金属催化剂和Ｓ／Ｐ助剂的作用下热分解,合成了结构类似于ＤＮＡ的微旋管状炭纤维,且具有很好的再现性。微旋管状炭纤维是由两根炭纤维规则地二重旋郑匹合而成旋管,其直径约５ｕｍ。乙炔和氢气的比例及温度对产量及微观形貌有很大的影响。     

甲烷催化裂解制备毛线状炭纤维及其微观结构

以甲烷为碳源，硫酸亚铁为催化剂前驱体，通过化学气相沉积在石墨基板上制得毛线状炭纤维。扫描电子显微镜观察得知所制炭纤维具有毛线状结构，由许多直径更小的子纤维交叉合并而成。单束毛线状炭纤维的直径为4μm-8μm。高分辨透射电子显微镜显示构成纤维的碳层排列不平直，存在偏转角，有序排列的碳层被分割成许多有序微晶区域。进一步采用X射线衍射和激光拉曼光谱等分析手段对其微观结构进行表征，表明毛线状炭纤维中碳层排列有序度较高，石墨微晶尺寸较大（La≈5nm），层间距较小（d002=0．340nm）。推测毛线状炭纤维生长机理符合“吸附-扩散-析出”过程，形成毛线状结构主要由催化剂颗粒直径决定。     

气相生长纳米炭纤维的研究进展

综述了当前气相生长纳米炭纤维的研究现状,对纳米炭纤维的制备方法、结构特征、性能和应用前景进行了概述,并简述了本研究小组采用改进流动催化剂法制备的纳米炭纤维。     

乙炔热裂解沉积对PAN基炭纤维性能的影响

利用有机溶剂去除PAN基炭纤维表面的集束剂与染剂.然后通过乙炔热裂解沉积对其进行表面改性,以期获得兼具高机械强度和优良导电性的高性能PAN基炭纤维.采用SEM、AFM、XRD、Raman等方法对PAN基炭纤维在改性前后的微观结构、结晶性、抗拉强度、弹性模量、导电性等进行了分析.研究结果表明采用化学气相沉积法可以提高或者明显改善石墨化处理后的PAN基炭纤维的力学性能(抗拉强度为2GPa,弹性模量为270GPa)和导电性(5×10-4Ω·cm).     

碳化硅纳米纤维/炭纤维共增强毡体的制备

以电镀Ni颗粒为催化剂,采用化学气相沉积(CVD)法,在炭纤维表面原位生长SiC纳米纤维(SiC-NF),制备出SiC纳米纤维/炭纤维共增强毡体.XRD和SEM分析表明生成的SiC纳米纤维物相为β-SiC,平均长度可达几十微米,直径在几十到几百个纳米之间.通过改变电镀镍的时间,研究了催化剂Ni颗粒的大小、形态及分布对SiC-NF生长情况的影响,研究结果表明,催化剂Ni颗粒分布越细小、均匀,催化活性越大,所生长的纳米SiC纤维也越细长,分布越均匀.     

NaCl担载Fe催化CVD法合成纳米洋葱状富勒烯

以简单的浸渍法制备的NaCl担载Fe作催化剂,化学气相沉积法在400℃下裂解乙炔,并直接将产物于650℃氩气气氛中保温2h,以提高产物的石墨化程度.通过扫描电子显微镜对催化剂进行了表征,结果显示,大多数Fe粒子已被载体氯化钠分散为粒径在10～40nm之间的纳米颗粒;通过高分辨透射电子显微镜和X射线衍射仪对样品进行了表征,结果显示,本实验合成了粒径在20～50nm之间的石墨化程度稍高的内包Fe3C的纳米洋葱状富勒烯.     

Fe催化PAN炭纤维原位生长纳米炭纤维

为了研究气相生长纳米炭纤维在炭／炭复合材料制备中的应用，采用均热式化学气相沉积技术，以针刺PAN炭纤维薄毡为基体，二茂铁为催化剂前驱体，丙烯为炭源，氮气为载气，在炉压1．0kPa-1.3kPa，沉积温度880℃、920℃下进行了Fe催化PAN炭纤维原位生长纳米炭纤维的实验。经不同时间沉积后的样品在扫描电镜（SEM）下进行观察，发现880℃时沉积4h后在PAN炭纤维周围生成大量的原位生长纳米炭纤维，而在920℃时因催化剂失效导致热解炭对Fe催化剂颗粒包覆，形成颗粒状热解炭。     

利用CVD法由松节油催化分解合成微米炭纤维

以石墨为基体,硫酸镍为催化剂,利用化学气相沉积通过松节油的催化分解合成了微米炭纤维.利用酸处理和水洗的方法将纤维从石墨和金属杂质中分离出来.利用光学显微镜和扫描电镜发现得到的纤维直径在3 μm～5μm.同时,由于自组装的作用也生成了一些海绵状的微米纤维.     

乙炔催化裂解制备碳纳米带及其结构表征

以乙炔（C2H2）为碳源,铁为催化剂,通过化学气相沉积技术在单晶硅衬底上制备了碳纳米带.采用场发射SEM、TEM、激光Raman光谱等先进分析手段对其形态和结构进行了表征.研究发现：碳纳米带是一种准二维材料,厚度约30nm,宽度在几百纳米,长度在100μm量级.碳纳米带的碳层沿着与其生长轴方向一致的（002）晶向排列,碳层的边缘都弯曲折叠成封闭结构.碳纳米带中碳层的排列不很平直,其中存在大量的层错.由此认为碳纳米带可用于能源等领域.     

FeCl3催化生长脱油沥青基气相生长炭纤维

以脱油沥青（DOA）为碳源,氯化铁为催化剂,在氩气和氢气的混合气氛下利用化学气相沉积法（CVD）制备了不同形貌的气相生长炭纤维（VGCFs）。讨论了在温度为1100℃时,不同的反应时间（分别为10min,20min,25min,30min和40min）对产物形貌和结构的影响。利用场发射扫描电镜（FE-SEM）、高分辨透射电镜（HRTEM）、X-射线衍射（XRD）和拉曼（Raman）光谱,对不同工艺参数下合成的产物进行了结构表征。结果表明：随着反应时间的增加,气相生长炭纤维的形貌由弯曲变得相对平直,进而相互贯穿;当反应时间为10min和20min时,气相生长炭纤维的直径分布在1.0μm～1.2μm之间;当反应时间为25min,30min和40min时,气相生长炭纤维的直径分布范围分别为250nm～300nm,350nm～400nm,700nm～800nm。另外,还观察到了V型的气相生长炭纤维。     

用作气相催化反应体系CNF/泡沫炭催化剂载体的合成

以中间相沥青为碳质前躯体,采用自发泡法制得泡沫炭.为了提高比表面积,泡沫炭经质量分数65％的HNO3氧化后,采用化学气相沉积法在其表面生长一层纳米炭纤维(CNFs).泡沫炭表面生长一层CNFs后,其比表面积和导热系数分别由40m2/g、107W/mK相应提高到198 m2/g、125W/mK.这种结构的CNFs/泡沫炭复合材料可以用作气相催化反应体系的催化剂载体.     

Synthesis of carbon nanofibers/mica hybrids for antistatic coatings

The use of carbon nanofibers (CNFs) as polymer additive has been impeded due to the problem associated with the dispersion of CNFs. In this study, CNFs/mica hybrids were synthesized by catalytic decomposition of CO over mica supported iron catalysts to increase their dispersity in polymer matrix. Antistatic coatings were prepared by dispersing the as-synthesized hybrids into epoxy with low shearing agitation and then casting the mixture by a coater. With the help of mica, the CNFs could be easily dispersed into the resin uniformly. The morphology of the CNFs, their distributions on mica surface and the size of mica, are discriminated to have great effect on surface resistivity of the coating.     

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.     

Direct synthesis of Y-junction carbon nanotubes by microwave-assisted pyrolysis of methane

Both Y-junction carbon nanotubes and individual carbon nanotubes were synthesized without any additive catalyst by microwave decomposition of methane. Detailed microstructures of as-synthesized products have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The results show that these Y-junction CNTs possess an internal bamboo-shaped structure, and some three dimensional multi-terminal junctions are also observed on CNTs. As gas flow rate decreased to 15 sccm, only individual nanotubes could be obtained. A possible mechanism is proposed for the synthesis of the Y-junction carbon nanotubes on these observations. This technique may also have great potential in making other nano-structured carbon materials on a large scale and at low cost.     

Catalyst-free growth of oriented single-walled carbon nanotubes on mica by ethanol chemical vapor deposition

In this letter, it is reported for the first time that single-walled carbon nanotubes (SWNTs) can grow on mica substrate without additional catalyst by chemical vapor deposition (CVD) using ethanol as carbon source. The single-wall structure was characterized by Raman spectra and AFM (Atomic Force Microscopy) measurements. The growth of carbon nanotubes on mica surface contributes to the small amount of iron oxide in bare mica. The uniform dispersion and nanosized Fe particles formed from the reduction of iron oxide favor for the growth of SWNTs. Horizontally aligned superlong SWNTs arrays can be successfully generated on the mica surface, which is proved to be guided by the gas flow and under “kite growth mechanism”. The mica is a machinable material which can be easily cut and made a narrow slit on, thus the nanotubes can traverse the slit which can be in millimeter scale and long suspended SWNTs can be generated. This will provide an opportunity to manipulate individual SWNT for various purposes.     

Horizontally oriented carbon nanotubes coated with nanocrystalline carbon

Single-walled carbon nanotubes (CNTs) and multi-walled CNTs of length 2-5 mm were grown from Fe/Mo nanoparticles and Fe thin film catalyst, respectively, by thermal chemical vapor deposition. Following CNT growth, the CNTs were in-situ coated with nanocrystalline carbon shells of thickness 100-1500 nm. Horizontally oriented CNTs with carbon shells in the direction of the feeding gas were visible under a regular optical microscope. They were easily manipulated by optical manipulators, and CNT probes can thus be fabricated.     

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.     

Synthesis of carbon nanofiber films and nanofiber composite coatings by laser-assisted catalytic chemical vapor deposition

Uniform carbon nanofiber films and nanofiber composite coatings were synthesized from ethylene on nickel coated alumina substrates by laser-assisted catalytic chemical vapor deposition. Laser annealing of a 50 nm thick nickel film produced the catalytic nanoparticles. Thermal decomposition of ethylene over nickel nanoparticles was initiated and maintained by an argon ion laser operated at 488 nm. The films were examined by scanning electron microscopy and by transmission electron microscopy. Overall film uniformity and structure were assessed using micro-Raman spectroscopy. Film quality was related to the experimental parameters such as incident laser power density and irradiation time. For long irradiation times, carbon can be deposited by a thermal process rather than by a catalytic reaction directly over the nanofiber films to form carbon nanocomposite coatings. The process parameters leading to high quality nanofiber films free of amorphous carbon by-products as well as those leading to nanofiber composite coatings are presented.