C/SnO2纳米管芯复合结构的原位生长及生长机理

采用化学气相沉积(CVD)方法在经表面活性剂处理过的Si(100)衬底上原位合成了C/SnO2纳米复合结构。利用扫描电子显微镜(SEM)、X射线能量色散谱(EDS)、透射电子显微镜(TEM)等分析仪器分别对所制备样品的形貌、成分及微结构进行表征。研究发现:制备产物为非晶态碳纳米管复合物。该碳纳米管复合物呈现出管芯复合结构,成分为碳纳米管包覆的结晶良好的SnO2纳米线,且其生长方向沿(200)晶面。并在此基础上分析讨论了其生长机理,推测这种C/SnO2纳米管芯复合结构的生长是同步进行的,同时表面活性剂的碳化对形成碳纳米管有着重要作用。     

爆炸辅助气相沉积法制备炭纳米线的研究

根据爆炸辅助气相沉积法生长碳纳米管的机理,设计了两种制备炭纳米线的方案:(1)使用低活性铁-镍二元金属催化剂;(2)对钴催化剂作用下碳纳米管的生长实施冷冻。透射电子显微镜显示这两种方法制备的炭纳米线均为纳米颗粒组装而成,具有非常粗糙的表面。其中,使用铁-镍二元催化剂所制炭纳米线直径分布不均匀,黏结情况严重;而在冷冻钴催化剂作用下炭纳米管生长过程所得的炭纳米线直径分布比较均匀,黏结情况也大为减少。这两种纳米线的差别与金属催化剂的活性有关。光催化降解亚甲基蓝实验表明:冷冻碳纳米管生长所得炭纳米线具有良好的催化辅助功能,可以提高ZnS纳米晶的光催化活性。     

生长温度对InAs/GaAs横向异质结构纳米线形貌及晶体结构的影响

低维半导体材料因其超常的物理性能而受到了广泛关注和研究。本文采用金属有机物化学气相沉积（MOCVD）技术,利用金作催化剂制备了InAs/GaAs横向异质结构纳米线,并讨论了不同生长温度情况下InAs横向异质材料对纳米线形貌及晶体结构的影响。提高InAs材料的生长温度,可以有效地抑制纳米线的纵向生长,使其实现横向异质结构的生长。在异质结构纳米线横向生长时发生了侧面晶面旋转的现象,这是纳米线表面重构后侧面趋向能量更低的晶面的结果。本文的研究工作为推动微纳技术的发展提供了相应的理论基础和科学依据。      

碳纳米管填充金属Ag纳米线及其机理研究

通过湿化学法将金属Ag成功填入碳纳米管,填充物的形态为纳米线状.用浓硝酸通过沸点回流法对碳纳米管进行处理,处理后不但除掉了其表面的杂质,而且碳纳米管端帽打开并明显被切短.AgNO3溶液通过毛细作用进入开口后的碳纳米管中,在450℃用H2进行还原,还原后碳纳米管被Ag纳米线填充,Ag纳米线直径为20～40nm,长度100nm～10μm.通过透射电镜(TEM)和X射线衍射(XRD)分析研究了Ag纳米线的微观形态和结构.在实验基础上探讨了金属Ag纳米线的形成机理.     

定向生长的多壁碳纳米管2～18GHz复介电常数与复磁导率谱

研究了定向生长的多壁碳纳米管2～18GHz的复介电常数与复磁导率谱.定向生长的碳纳米管的介电常数要小于采用普通化学气相沉积法制备的碳纳米管,而磁导率大于采用普通化学气相沉积法制备的碳纳米管.透射电镜观察发现定向生长的碳纳米管中腔内规则分布着纳米Fe颗粒,同时也有部分Fe颗粒被碳层片所包覆,沉积在碳纳米管的外表面上. Fe颗粒的存在可以解释定向生长的碳纳米管所具有的较高的磁导率.在定向生长的碳纳米管制备过程中,通过调节催化剂进给数量和速度可以调节Fe颗粒在碳纳米管中的分布,这为碳纳米管的电磁性能的调控提供了一种新的途径.     

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.     

碳化硅纳米线的制备及表征

以化学气相沉积法制备的纳米碳管粗产物和各向同性煤沥青为原料,采用热压成型工艺制备了纳米碳管/沥青复合材料,复合材料经1600℃高温热处理产物中生成了纤维状碳化硅(SiC)纳米线。扫描和透射电子显微分析表明所制备的SiC纳米线表面较为光洁,长度约为几个微米,直径约为30~80nm。二次电子像及其能谱分析表明原料中的金属镍颗粒和纳米碳管对SiC纳米线的生长具有重要作用。     

化学气相沉积反应中金属-碳协同催化碳纳米管生长的理论和实验证据

从理论和实验角度研究了金属-碳协同催化的化学气相沉积反应中碳纳米管的成核和生长过程.结果表明:多壁碳纳米管的成核和生长不仅受金属的催化作用,碳核一旦形成也会促进碳纳米管向轴向和径向的生长.金属催化剂颗粒仅仅在促进最内层碳核的形成及生长,碳原子向有序的石墨结构转化有催化作用.多壁碳纳米管和单壁碳纳米管形成的本质区别在于是否存在碳的自催化作用.     

工艺条件对氧化硅纳米结构的影响

通过金属催化化学气相沉积法,采用四氯化硅作为硅源合成了棒状氧化硅纳米结构.对产物进行了场发射扫描电镜、透射电镜及附带X射线能谱仪的表征测试.生长工艺条件包括沉积位置、反应时间、氩气冲洗次数和基板对产物纳米结构的影响进行了探讨,其中前三者分别影响气相硅源的浓度、获取硅源的量和残余氧的浓度,而基板的成分和表面粗糙度对纳米结构的生长影响显著.     

大面积取向生长碳纳米管的ECR-CVD方法制备与表征

本文采用电子回旋共振微波等离子体化学气相沉积方法(ECR-CVD),以CH4和H2为气源、Fe3O4 纳米粒子为催化剂,未加电场,在多孔硅基底上制备出大面积取向生长碳纳米管.使用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)、X射线能量色散分析(EDX)对样品形貌和结构进行表征.结果显示:合成的碳纳米管为多壁碳管;碳纳米管直径60 nm～90 nm,长度约8 μm;碳纳米管展现出中空管状和链状两种结构;碳纳米管的生长采取催化剂底端生长模式.     

Single crystal GaN nanowires

Single crystal gallium nitride nanowires have been obtained by heating gallium acetylacetonate in the presence of carbon nanotubes or activated carbon in NH3 vapor at 910 degrees C. GaN nanowires also were obtained when the reaction of gallium acetylacetonate with NH3 was carried out over catalytic Fe/Ni particles dispersed over silica. The former procedure with carbon nanotubes is preferable because it avoids the presence of metal particles in the nanowire bundles.     

Crystallographic alignment of high-density gallium nitride nanowire arrays

Single-crystalline, one-dimensional semiconductor nanostructures are considered to be one of the critical building blocks for nanoscale optoelectronics. Elucidation of the vapour-liquid-solid growth mechanism has already enabled precise control over nanowire position and size, yet to date, no reports have demonstrated the ability to choose from different crystallographic growth directions of a nanowire array. Control over the nanowire growth direction is extremely desirable, in that anisotropic parameters such as thermal and electrical conductivity, index of refraction, piezoelectric polarization, and bandgap may be used to tune the physical properties of nanowires made from a given material. Here we demonstrate the use of metal-organic chemical vapour deposition (MOCVD) and appropriate substrate selection to control the crystallographic growth directions of high-density arrays of gallium nitride nanowires with distinct geometric and physical properties. Epitaxial growth of wurtzite gallium nitride on (100) gamma-LiAlO(2) and (111) MgO single-crystal substrates resulted in the selective growth of nanowires in the orthogonal [1\[Evec]0] and [001] directions, exhibiting triangular and hexagonal cross-sections and drastically different optical emission. The MOCVD process is entirely compatible with the current GaN thin-film technology, which would lead to easy scale-up and device integration.     

Nanotubes in a gradient electric field as revealed by STM TEM technique

We have investigated the behavior of two nanotube systems, carbon and boron nitride, under controlled applied voltages in a high-resolution transmission electron microscope (TEM) equipped with a scanning tunneling microscope (STM) unit. Individual nanotubes (or thin bundles) were positioned between a piezomovable gold electrode and a biased (up to ±140 V) STM tip inside the pole-piece of the microscope. The structures studied include double-and multi-walled carbon nanotubes (the latter having diverse morphologies due to the various synthetic procedures utilized), few-layered boron nitride nanotube bundles and multi-walled boron nitride nanotubes (with or without functionalized surfaces). The electrical breakdown, physical failure, and electrostatic interactions are documented for each system. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users.     

Carbon nanotube nanoelectronic devices compatible with transmission electron microscopy

We report on a novel method to fabricate carbon nanotube (CNT) nanoelectronic devices on silicon nitride membrane grids that are compatible with high resolution transmission electron microscopy (HRTEM). Resist-based electron beam lithography is used to fabricate electrodes on 50 nm thin silicon nitride membranes and focused-ion-beam milling is used to cut out a 200 nm gap across a gold electrode to produce the viewing window for HRTEM. Spin-coating and AC electrophoresis are used as methods to deposit small bundles of carbon nanotubes across the electrodes. We demonstrate the viability of this approach by performing both electrical measurements and HRTEM imaging of solution-processed CNTs in a device.     

气相沉积生长单壁纳米碳管束

采用流动催化热解碳氢化合物方法制备出具有一定取向的单壁纳米碳管束。研究了单壁纳米碳管束的生长过程,发现单壁纳米碳管的生长过程是在气流飘浮单个催化剂颗粒中完成。这与热解碳氢化合物制备定向的多壁纳米碳管在基体催化上生长过程有所不同。根据单壁纳米碳管生长过程,推测出单壁纳米碳管束生长速度的数量级为10^-5m/s。     

Novel vapor phase reactions for the synthesis and modification of carbon nanotubes and inorganic nanowires

Several vapor phase methods have been developed for the preparation and modification of carbon nanotubes and inorganic nanowires. Thus, nebulized spray pyrolysis has been employed for the synthesis of carbon nanotubes and metal nanowires. Multi-walled carbon nanotubes (MWNTs) with fairly uniform diameters and aligned nanotube bundles have been obtained by nebulized spray pyrolysis using solutions of organometallics such as ferrocene in hydrocarbon solvents. Single-crystalline nanowires of zinc, cadmium, cobalt, and lead are obtained by the decomposition of metal acetates. By reacting acid-treated carbon nanotubes with vapors of metal halides, followed by reaction with water and calcination chemically-bonded oxide layers can be obtained on the nanotubes. A similar procedure has been employed to prepare chemically-bonded oxide layers on Al2O3, ZnO, and silicon nanowires by the reaction of the metal halides with the surface hydroxyl groups present on these nanowire surfaces.     

MoS_2与TiO_2一维纳米复合材料的制备与表征

本文采用气相还原法制备了MoS2包覆TiO2的一维纳米复合材料,首先用水热法制备TiO2纳米管,并制备前驱体(NH42)MoS4;用浸渍法将(NH4)2MoS4附着于TiO2纳米管表面;然后利用氢气还原前驱体得到MoS2包覆层。用X射线衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)表征所得产物的结构及微观形貌。结果表明当还原反应温度较高(≥600℃)时,产物呈烧结状态,而当反应温度为500℃时,可以得到表面均匀包覆MoS2的TiO2纳米管复合材料,其中包覆层MoS2的结晶程度较低。在此基础上,本文提出了该产物的生长模型,并对包覆前后的样品做荧光性能分析。     

硼碳氮纳米管制备方法的研究进展

三元化合物硼碳氮纳米管作为碳纳米管和氮化硼纳米管的衍生物,其禁带宽度主要取决于纳米管的成分,与手性和直径无关,且在0~5.5 eV范围内可调;另外,硼碳氮纳米管具有优良的电学性能、高硬度、高耐磨性及高温抗氧化等性质,使其在电子、光电子和纳米器件等领域具有广阔的应用前景。综述了硼碳氮纳米管制备方法的研究现状,并介绍了材料的生长机理、结构、性质和应用前景,简述了工艺条件对纳米管形成的影响,并对今后硼碳氮纳米管的研究方向提出了设想与展望。     

Interfacial heat flow in carbon nanotube suspensions

The enormous amount of basic research into carbon nanotubes has sparked interest in the potential applications of these novel materials. One promising use of carbon nanotubes is as fillers in a composite material to improve mechanical behaviour, electrical transport and thermal transport. For composite materials with high thermal conductivity, the thermal conductance across the nanotube-matrix interface is of particular interest. Here we use picosecond transient absorption to measure the interface thermal conductance (G) of carbon nanotubes suspended in surfactant micelles in water. Classical molecular dynamics simulations of heat transfer from a carbon nanotube to a model hydrocarbon liquid are in agreement with experiment. Our findings indicate that heat transport in a nanotube composite material will be limited by the exceptionally small interface thermal conductance (G approximately 12 MW m(-2) K(-1)) and that the thermal conductivity of the composite will be much lower than the value estimated from the intrinsic thermal conductivity of the nanotubes and their volume fraction.     

Nanococoon seeds for BN nanotube growth

A modification in the conventional arc-discharge method for synthesis of nanotubes is presented. By injecting pure nitrogen gas directly into the plasma we have greatly increased the amount of boron nitride nanotubes produced. Isolated nanotubes and bundles were characterized by TEM. The vast majority of the nanotubes were double-walled with outer diameter around 3 nm. The predominance of double-walled BN nanotubes is seen as a direct result of the distribution of the number of graphitic BN layers for the nanococoons, second major product of the synthesis. Detailed HRTEM examination of the ends of BN nanotubes indicates continuity between the graphitic BN layers that coat boron nanoparticles, that is nanococoon, and the nanotube. At the other end of the nanotubes a flat angular cap was observed. HRTEM images of nanotube ends give support to a root-based growth mechanism.