电场诱导碳纳米管阵列准直生长的研究

在传统的热化学气相沉积(CVD)的基础上,引入针尖电场,开展了电场对碳纳米管阵列准直性改善的研究。利用扫描电子显微镜(SEM)和Raman光谱两种表征手段,研究了加电场与不加电场两种情况下得到的碳纳米管(CNT)阵列的准直性,证明了电场对碳纳米管阵列准直生长的有效性。文章还对电场诱导碳纳米管阵列准直生长的机理进行了初步的探讨,认为电场使碳纳米管极化是CNT阵列准直生长的主要原因。     

基于单准直透镜的阵列准直器研究

提出了一种基于单准直透镜和光纤阵列的阵列准直器, 深入研究了此种方案的光路无胶和光路有胶的两种实现方式; 并基于高斯光束传输矩阵和q参数相关理论, 从理论上详细地计算、推导了各变量之间的关系, 并进行了模拟仿真及实验验证, 得到了理论和实验一致的结果. 对两种实现方式的结构及封装设计也进行了初步的摸索和实验, 并制作出了性能良好的阵列准直器. 理论和实验表明, 该方案具有易加工、低成本、易封装、性能优等特点, 也易于扩展成多维阵列准直器, 可为可重构光分插复用器系统和光交叉连接系统的发展提供强有力的器件支撑.     

离子轰击入射角对溅射参数的影响

本文用基于两体碰撞近似的蒙特-卡罗模拟方法研究离子轰击入射角对溅射参数的影响,讨论了入射角与溅射产额、溅射粒子能谱、角分布和阈能的关系,并把计算结果与某些半经验公式和实验数据进行了比较。 关键词：     

Ar+轰击石墨表面生成碳纳米管和碳纳米多面体

报道了一种用60keV Ar⁺轰击石墨生成碳纳米管和纳米碳壳层多面体颗粒的方法.高分辨透射电子显微镜研究指出，这些纳米多层结构物的尺寸约在20nm到0.4μm之间，碳原子层之间的距离为0.34nm.基于高分辨透射电子显微镜图像，建议了一个关于“组合碳多面体”的生长模型. 关键词：     

离子轰击产生湍层氮化硼

用高分辨率透射电子显微镜检查了N+2离子轰击后的氮化硼样品.发现在片状六方形氮化硼sp2层的弯折区,有0.35mm晶面间距的湍层氮化硼形成.虽然其形成机制尚不清楚,但是基于束流–固体相互作用观点的讨论可能是了解湍层氮化硼结构生长过程的关键所在.     

碳纳米管的生长机理、可控生长及应用探索

碳纳米管的可控制生长,及其宏观尺度结构的制备,对于碳纳米管的应用具有重要的意义,为了实现准确的生长控制,对碳纳米管生长机理的深入了解是不可缺少的前提条件.文章介绍了我们近年来在碳纳米管生长机理、可控生长及其应用方面的一些进展.通过引入^13C标记法,我们证实了化学气相沉积法中碳纳米管以析出模式生长;实时改变生长的气相成份和流量,可以在碳纳米管阵列上留下标记序列,并据此测量出其生长速率及活化能.将超顺排碳纳米管阵列的合成扩展到4英寸规模,并发展了用挥发性有机溶剂处理碳纳米管线的方法,大大提高了其强度和可操作性.处理后的碳纳米管线可以方便地用于热电子源、高电流密度冷阴极以及荧光灯等.热界面材料在IT产业中具有重要的应用背景,我们用碳纳米管阵列制备的复合材料具有极高的热导率和极低的界面热阻,同时发展了化学修饰、端部剪裁、金属集热层等新技术以制备高性能的碳纳米管热界面材料.     

硅锥场发射阵列中离子轰击现象的分析

离子轰击影响尖端场致发射器件的稳定性和工作寿命.阐述了数值模拟硅锥阴极离子轰击现象的基本理论,并以硅锥场发射阵列的一个单元结构为例模拟了气体-电子碰撞电离产生的正离子回轰尖端的全过程,对模型中的硅锥受损的位置和程度进行了分析,得出了一些结论.     

碳纳米管的生长机理、可控生长及应用探索

碳纳米管的可控制生长,及其宏观尺度结构的制备,对于碳纳米管的应用具有重要的意义,为了实现准确的生长控制,对碳纳米管生长机理的深入了解是不可缺少的前提条件.文章介绍了我们近年来在碳纳米管生长机理、可控生长及其应用方面的一些进展.通过引入13C标记法,我们证实了化学气相沉积法中碳纳米管以析出模式生长;实时改变生长的气相成份和流量,可以在碳纳米管阵列上留下标记序列,并据此测量出其生长速率及活化能.将超顺排碳纳米管阵列的合成扩展到4英寸规模,并发展了用挥发性有机溶剂处理碳纳米管线的方法,大大提高了其强度和可操作性.处理后的碳纳米管线可以方便地用于热电子源、高电流密度冷阴极以及荧光灯等.热界面材料在IT产业中具有重要的应用背景,我们用碳纳米管阵列制备的复合材料具有极高的热导率和极低的界面热阻,同时发展了化学修饰、端部剪裁、金属集热层等新技术以制备高性能的碳纳米管热界面材料.     

基于双目标识别和准直数学模型改进的光路自动准直方法

针对原有大型激光装置在双光学目标条件下无法实现光路对接准直的缺点,本文提出了一种基于双目标识别和准直数学模型改进的光路自动准直方法,主要从双目标识别算法实现和多光路、双目标准直数字模型的构建两个方面进行优化。首先,提出基于圆拟合的双光学目标识别图像处理算法,实现了双光学目标的识别,为光路对接准直的成功提供保障;其次,构建新的多光路、双目标自动准直数学模型,为光路准直中各个准直参数的标定和计算提供指导;最后,优化准直流程的调度,对多个光路进行并行准直,提高光路对接准直流程的效率。实验结果表明：本文提出的基于圆拟合的双光学目标识别算法实现了光路对接准直流程中的模拟光目标和主激光目标的识别,识别误差精度小于3个像素,处理时间小于1 s,满足了大型激光装置光路对接准直过程对于精度和效率的要求。本文构建的基于多光路、双目标自动准直数学模型对于光路对接准直流程的成功具有指导意义。     

化学气相沉积法制备定向碳纳米管阵列

以二茂铁和二甲苯分别作为催化剂和碳源，采用一种无模板的化学气相沉积法，使用单温炉设备，成功地制备了高度定向的碳纳米管阵列.分别用扫描电子显微镜、透射电子显微镜和电子能量散射谱、拉曼光谱对碳纳米管阵列进行形貌观察和表征, 并研究了不同工艺参数对碳纳米管阵列形貌的影响.结果表明：在生长温度为800℃，催化剂浓度为0.02g/mL，抛光硅片上容易获得高质量的定向碳纳米管阵列，在此优化条件下生长的定向碳纳米管的平均生长速率可达25μm/min.     

利用微波等离子体增强化学气相沉积法定向生长纳米碳管的研究

利用微波等离子体增强化学气相沉积法在氢气和甲烷的混合气体中定向生长纳米碳管.经扫描电子显微镜观察与分析，发现纳米碳管在与基板垂直的方向上整齐排列，管径较均匀且长度基本相同. 关键词： 微波等离子体 纳米碳管     

Functionalization of vertically aligned carbon nanotubes with polystyrene via surface initiated reversible addition fragmentation chain transfer polymerization

Here we demonstrate the covalent attachment of vertically aligned (VA) acid treated single-walled carbon nanotubes (SWCNTs) onto a silicon substrate via dicyclohexylcarbodiimide (DCC) coupling chemistry. Subsequently, the pendant carboxyl moieties on the sidewalls of the VA-SWCNTs were derivatized to acyl chlorides, and then finally to bis(dithioester) moieties using a magnesium chloride dithiobenzoate salt. The bis(dithioester) moieties were then successfully shown to act as a chain transfer agent (CTA) in the reversible addition fragmentation chain transfer (RAFT) polymerization of styrene in a surface initiated “grafting-from” process from the VA-SWCNT surface. Atomic force microscopy (AFM) verified vertical alignment of the SWCNTs and the maintenance thereof throughout the synthesis process. Finally, Raman scattering spectroscopy and AFM confirmed polystyrene functionalization.     

超长定向含铁多壁碳纳米管阵列的制备

采用无模板化学气相沉积法,以二茂铁为催化剂,二甲苯为碳源,利用单温炉加热装置制备了定向碳纳米管阵列。运用扫描电子显微镜、透射电子显微镜、拉曼光谱和X射线衍射仪等对定向碳纳米管阵列的形貌、成分和物相进行细致的分析和表征。结果表明：制得的碳纳米管阵列具有良好的定向性和多壁管状结构,并且石墨化程度高;碳纳米管中除碳元素外,管中包含有少量以纳米颗粒和纳米线形式存在的铁及其化合物,主要成分是铁和碳化铁。结合碳纳米管的制备和透射电子显微镜分析表征结果,认为超长碳纳米管阵列的生长模式为底部生长方式,即经历催化剂分解、催化、成核、长大、中毒、凝聚成粒和连接成线的循环过程,正是由于碳源和催化剂的连续供应促成了碳纳米管阵列的快速定向生长。     

Improving the field-emission properties of carbon nanotubes by magnetically controlled nickel-electroplating treatment

A novel magnetically controlled Ni-plating method has been developed to improve the field-emission properties of carbon nanotubes (CNTs). The effect of the magnetic field and Ni-electroplating on CNT field-emission properties was investigated, and the results are demonstrated using scanning electron microscopy, J-E and the duration test. After treatment, the turn-on electric field declines from 1.55 to 0.91 V/μm at an emission current density of 100 μA/cm², and the emission current density increases from 0.011 to 0.34 mA/cm² at an electric field of 1.0 V/μm. Both the brightness and uniformity of the CNT emission performance are improved after treatment.     

碳纳米管的稳定性研究

石墨晶体结构遭到破坏时,总是碎化为微小尺寸的片状粉末.孤立的石墨烯片在其边缘存在大量的悬挂键,使得石墨烯片的能量较高,状态也不稳定.石墨烯片卷曲形成碳纳米管后,悬挂键减少,系统能量相应降低.另一方面,石墨烯片卷曲形成碳纳米管将产生相应的形变势能,形变势能的产生将抵消由于减少石墨烯片边缘上的悬挂键所带来的能量降低,使碳纳米管的能量可能高于石墨烯片的能量,导致碳纳米管结构的不稳定.在建立碳纳米管生成的力学模型并进行深入理论分析的基础上得出了碳纳米管可以稳定存在的最小直径约为0.32nm的结论. 关键词： 碳纳米管 稳定性 形变势能 键能     

Stimulation of the local growth of aligned carbon nanotubes by pulse laser exposure of the substrate

The local stimulation of carbon nanotubes (CNT) growth at the laser-modified sites that have been obtained by excimer laser irradiation at 248 nm causing a local surface modification has been investigated by two different processing methods. The influence of the laser processing parameters on the CNT growth is compared for the irradiation of thin spin-coated iron nitrate films on silicon substrates and the backside irradiation of a fused silica substrate being in contact with an iron nitrate solution. Both techniques cause the formation of catalytic surface sites either by decomposition of the film or by deposition from the solution. For both laser modification approaches the local growth of vertical aligned nanotubes has been observed. In the case of spin-coated film the laser irradiation conditions have only a small influence on the CNT growth whereas at backside modification by means of a solution a strong dependence on the laser processing parameters has been found.     

Physics and applications of aligned carbon nanotubes

Ever since the discovery of carbon nanotubes (CNTs) by Iijima in 1991, there have been extensive research efforts on their synthesis, physics, electronics, chemistry, and applications due to the fact that CNTs were predicted to have extraordinary physical, mechanical, chemical, optical, and electronic properties. Among the various forms of CNTs, single-walled and multi-walled, random and aligned, semiconducting and metallic, aligned CNTs are especially important since fundamental physics studies and many important applications will not be possible without alignment. Even though there have been significant endeavors on growing CNTs in an aligned configuration since their discovery, little success had been realized before our first report on growing individually aligned CNTs on various substrates by plasma-enhanced chemical vapor deposition (PECVD) [Science 282 (1998) 1105–1108]. Our report spearheaded a new field on growth, characterization, physics, and applications of aligned CNTs. Up to now, there have been thousands of scientific publications on synthesizing, studying, and utilizing aligned CNTs in various aspects. In this communication, we review the current status of aligned CNTs, the physics for their alignment, their applications in field emission, optical antennas, subwavelength light transmission in CNT-based nanocoax structures, nanocoax arrays for novel solar cell structures, etc.

The focus of this review is to examine various aligned CNT systems, either as an individual or as an array, either the orientation is vertical, parallel, or at other angles to the substrate horizon, either the CNT core structures are mostly hollow channels or are composed of complex compartments. Major fabrication methods are illustrated in detail, particularly the most widely used PECVD growth technique on which various device integration schemes are based, followed by applications whereas current limitations and challenges will also be discussed to lay down the foundation for future developments.     

Hydrophobic vertically aligned carbon nanotubes on Corning glass for self cleaning applications

Vertically aligned carbon nanotubes were prepared by Plasma enhanced chemical vapor deposition (PECVD) on inexpensive Corning glass substrates using different under layers. The samples were functionalised by a simple 1H,1H-2H,2H perfluorodecyl-trichlorosilane (FDTS) and hexane mixture. The surface roughness of the CNTs and protective FDTS coating provides an ideal hydrophobic surface of around 141°. Auger spectroscopy analysis was performed to confirm fluorination of the sample. It was also found titanium provides a suitable under layer support for Ni catalyst due to the wetability of the two elements.     

Potential energy,force distribution and oscillatory motion of chloride ion inside electrically charged carbon nanotubes

In this research, a continuum-based model is presented to explore potential energy, force distribution and oscillatory motion of ions, and in particular chloride ion, inside carbon nanotubes (CNTs) decorated by functional groups at two ends. To perform this, van der Waals (vdW) interactions between ion and nanotube are modeled by the 6-12 Lennard-Jones (LJ) potential, whereas the electrostatic interactions between ion and functional groups are modeled by the Coulomb potential and the total interactions are analytically derived by summing the vdW and electrostatic interactions. Making the assumption that carbon atoms and charge of functional groups are all uniformly distributed over the nanotube surface and the two ends of nanotube, respectively, a continuum approach is utilized to evaluate the related interactions. Based on the actual force distribution, the equation of motion is also solved numerically to arrive at the time history of displacement and velocity of inner core. With respect to the proposed formulations, comprehensive studies on the variations of potential energy and force distribution are carried out by varying functional group charge and nanotube length. Moreover, the effects of these parameters together with initial conditions on the oscillatory behavior of system are studied and discussed in detail. It is found out that chloride ion escapes more easily from negatively charged CNTs which is followed by uncharged and positively charged ones. It is further shown that the presence of functional groups leads to enhancing the operating frequency of such oscillatory systems especially when the electric charges of ion and functional groups have different signs.