氮化铝纳米锥的低温生长与场发射性能(英文)

考察了在600℃以下通过反应AlCl3+NH3→AlN+3HCl制备AlN纳米锥的规律,结果表明在500℃时仍可获得AlN纳米锥,当温度为480℃时则无氮化物生成。场发射测试显示在500~600℃温区内制得的AlN纳米锥的开启电场处于14.2~20 V·μm-1范围,且随制备温度升高而减小。结果表明AlN纳米锥可在低温条件下获得,且具有较好的场发射性能。     

MWPCVD低温合成纳米碳管的生长机理

The synthesis of carbon nanotubes (CNTs) at low temperature has received a great deal of attention and be-comes a challenging issue. But few model which accounts for the growth of CNTs is suited for the synthesis of CNTs by microwave plasma chemical vapor deposition (MWPCVD) at low temperature because most researchers conclude that the growth mechanism is determined by the catalyst-supporter interaction while ignored the diffusion of carbon in the catalyst. In this paper, under the catalytic effect of cobalt supported by SiO₂ and Al₂O₃, CNTs are synthe-sized by MWPCVD at about 500℃, and tip-growth, the model which accounts for the catalytic growth of CNTs is outlined. It is the temperature difference between the upper and bottom of the catalytic particle that results in the diffusion of carbon atoms from upper to the bottom, and precipitation of saturated carbon on the bottom surface to form CNTs.     

电沉积纳米锥镍的生长机理及其性能的研究

本文通过恒电流沉积法在柔性覆铜基板上制备了具有纳米锥阵列结构的黑色镍层,制备的纳米锥镍的底部约为200 nm, 高度约为1 μm,且大小均一,分布致密。本文探讨了镍电沉积中电流密度和主盐浓度对纳米锥镍结构形貌的影响,结果表明低电流密度和高主盐浓度有利于纳米锥镍的形成。电沉积过程中保持镍离子的供应充足是锥镍结构产生的关键因素之一, 而高电流密度会影响镍离子浓度的浓差极化,从而影响锥镍的成核过程。温度、主盐浓度以及结晶调整剂的变化会导致镍颗粒的形貌发生圆包状和针锥状结构的相互转化。温度升高具有一定的细化晶粒作用,锥镍结构需要在大于50 ^oC的条件下生成。结晶调整剂能够改变沉积过程中的晶面择优生长,且可以调控镍晶粒的形貌,使得生成的锥结构分布均匀, 颗粒细致。结果表明,在4.0 mol·L^-1 NH₄Cl和1.68 mol·L^-1 NiCl₂·6H₂O体系中沉积出分布均匀的纳米锥镍阵列结构。本文利用氯化铵作为纳米锥镍的晶体改性剂,通过分子动力学模拟理论上分析了NH₄⁺在镍表面的吸附过程。计算结果表明镍不同晶面上NH₄⁺吸附能的差异引起各晶面镍沉积速率的差异, 从而导致纳米锥镍阵列的形成。本文呢进一步结合形貌表征,提出了纳米锥镍阵列的电沉积生长的两步生长机理,包括前期的成核生长和后期的核生长过程,前期成核过程为优势生长,生成大量的晶核, 为锥镍的生长提供了生长位点,而后期的核生长过程表现为锥状镍核的择优生长, 最终形成完整均匀的锥镍阵列结构。本文制备的纳米锥镍结构还具有优异的亲水性和良好的吸光效果, 对于近紫外和可见光的吸收率大于95%, 具有较好的应用前景。     

镍基板上低温合成定向纳米碳管

纳米碳管具有非常优异的场发射效应 ,亮度高、均匀且稳定的纳米碳管场效应发射器 ,例如平板显示器、阴极射线管以及信号灯等有着非常广阔的应用前景 [1] .由于纳米碳管的场发射效应与纳米碳管的方向性有关[2 ] ,因此定向纳米碳管的制备及其场发射性能研究是当前的一个研究热点     

微波等离子体化学气相沉积法低温制备直纳米碳管膜

Among the three main methods for the synthesis of carbon nanotubes (CNTs)， chemical vapor deposition (CVD) has received a great deal of attention since CNTs can be synthesized at significantly low temperature. Plasma chemical vapor deposition methods can synthesize CNTs at lower temperature than thermal CVD. But in the usual catalytic growth of CNTs by CVD， CNTs are often tangled together and have some defects. These will limit the property research and potential applications. How to synthesize the straight CNTs at low temperature becomes a challenging issue. In this letter， straight carbon nanotube (CNT) films were achieved by microwave plasma chemical vapor deposition (MWPCVD) catalyzed by round Fe-Co-Ni alloy particles on Ni substrate at 610℃. It was found that， in our experimental condition， the uniform growth rate along the circumference of round alloy particles plays a very important role in the growth of straight CNT films. And because the substrate is conducting， the straight CNT films grown at low temperature may have the benefit for property research and offer the possibility to use them in the future applications.     

纳米空腔堆积的一维碳纳米结构的合成与表征

Quasi-periodically intermittent hollow-cavity-stacked one-dimensional carbon nanostructures were obtained by microwave plasma chemical vapor deposition from the mixture of CH₄ and N₂ on Fe/γ-Al₂O₃ catalyst. This structure was characterized by transmission electron microscope (TEM), high-resolution TEM and X-ray energy dispersive spectral analysis. The results indicate that the trace impurity of nitrogen might account mainly for the formation of these novel nanostructures. The structural units in these one-dimensional carbon nanostructures are full of nanocavities, which may be of potential importance in hydrogen storage.     

六硼化铕亚微米管的电子场发射性能(英文)

以铕(Eu)粉末和三氯化硼(BCl3)作为前驱体,用简单的化学气相沉积方法制备了六硼化铕(EuB6)亚微米管。用XRD,SEM拉曼光谱,和TEM来表征EuB6微米管的形貌和晶体结构。场发射测试结果表明:根据F-N公式,场发射电流和电场之间在不同的阶段分别满足直线关系。     

分叉碳纳米管的催化生长

Branching carbon nanotubes were synthesized by pyrolysis of acetylene at 700℃ over oxygen-free copper and γ-Al₂O₃-supported Cu unitary or Cu/Fe binary catalysts. The morphologies of the as-grown products were charac-terized by transmission electron microscopy. The results indicated that the branching structures were closely related to the Cu component of the catalysts. We proposed that the special electronic structure (3d¹⁰4s¹) of Cu play the crucial role in the formation of the heptagon defects related to the branching structures.     

纳米碳管电极的制备与电化学检测性能研究

纳米碳管由于其独特的物理和化学性能及广阔的应用前景而备受关注,其相关研究涉及到众多领域[1￣3]。在电化学分析领域,与其它碳电极材料相比,纳米碳管电极具有较大的电极表面积和较高的电子传递速率,其使用能增大响应电流、降低检出限,是目前电化学分析电极中一个十分引人注目     

碳纳米管的最新制备技术及生长机理

结合笔者的工作综述了碳纳米管的制备技术及生长机理的最新研究进展，重点介绍了近两年来碳纳米管制备的进展情况，包括传统制备方法的改进（电弧放电法、化学气相沉积法和激光蒸发法）、新型制备技术、特殊结构的碳纳米管制备；同时探讨了碳纳米管的各种生长机理；最后提出了碳纳米管制备技术和生长机理的发展方向。     

Field Emission Properties of Multi-walled Carbon Nanotubes Grown on Silicon Nanoporous Pillar Array

"Multi-walled carbon nanotubes (CNTs) were grown on a silicon nanoporous pillar array (Si-NPA) by thermal chemical vapor deposition. Surface morphologies and microstructure of the resultant were studied by a field emission scanning electron microscope, Raman spectrum, transmission electron microscope, and highresolution transmission electron microscopy. The composition of samples was determined by energy dispersive X-ray spectroscopy (EDS). The results showed that a great deal of CNTs, with diameter in the range of 20-70 nm, incorporated with Si-NPA and a large scale nest array of CNTs/Si-NPA (NACNT/Si-NPA) was formed. EDS analysis showed that the composition of carbon nanotubes was carbon. Field emission measurements showed that a current density of 5 mA/cm2 was obtained at an electric field of 4.26 V/1m, with a turn-on field of 1.3 V/1m. The enhancement factor calculated according to the Fowler-Nordheim theory was ?11,000. This excellent field emission performance is attributed to the unique structure and morphology of NACNT/Si-NPA, especially the formation of a nest-shaped carbon nanotube array. A schematic drawing that illustrates the experimental configuration is given. These results indicate that NACNT/Si-NPA might be an ideal candidate cathode for potential applications in flat panel displays."     

分子基材料聚集态结构的场发射性质研究

场发射在扫描电子显微镜、平面显示器、压力传感器、加速度传感器以及电子束可寻址记忆器件等许多领域中得到了广泛的应用,分子基材料由于其结构和能带可设计,性质可调和柔性易加工等显著特点,被认为是新一代的场发射材料。本文综述了近年来分子基材料聚集态结构的场发射性质研究的新进展,特别是分子基材料的结构和聚集态形貌和尺寸对场发射性质的影响以及通过对分子基材料的杂化优化其场发射的性质,展望了分子基材料聚集态结构场发射的应用前景和发展趋势。     

Synthesis and Characterization of Multi-Branched Carbon Fibers and Their Proposed Growth Mechanism

In this study, carbon fibers with different morphologies in their initial growth period have been obtained by the chemical vapor deposition using nano-copper particles as a catalyst at 250°C and then we have investigated the formation mechanism of the carbon fibers. Otherwise, we have noted that multi-branched carbon fibers with different morphologies were synthesized, and proposed the growth models for carbon fibers. X-ray diffraction, field emission scanning electron microscopy, transmission electron microscope, energy-dispersive x-ray were used to characterize the products.     

自偏压作用下纳米碳管的定向生长

以玻璃为基板材料, 在550 ℃的低温条件下利用微波等离子体化学气相沉积法合成了定向纳米碳管.结果表明, 在利用微波等离子体化学气相沉积法合成纳米碳管时, 因等离子体作用存在于基板表面的自偏压对纳米碳管的定向生长起着非常重要的作用.自偏压的作用总是使纳米碳管的生长垂直于基板表面.     

Shape‐Controlled Growth of Carbon Nanostructures: Yield and Mechanism

Carbon nanostructures with precisely controlled shapes are difficult materials to synthesize. A facet‐selective‐catalytic process was thus proposed to synthesize polymer‐linked carbon nanostructures with different shapes, covering straight carbon nanofiber, carbon nano Y‐junction, carbon nano‐hexapus, and carbon nano‐octopus. A thermal chemical vapor deposition process was applied to grow these multi‐branched carbon nanostructures at temperatures lower than 350 °C. Cu nanoparticles were utilized as the catalyst and acetylene as the reaction gas. The growth of those multi‐branched nanostructures was realized through the selective growth of polymer‐like sheets on certain indexed facets of Cu catalyst. The vapor–facet–solid (VFS) mechanism, a new growth mode, has been proposed to interpret such a growth in the steps of formation, diffusion, and coupling of carbon‐containing oligomers, as well as their final precipitation to form nanostructures on the selective Cu facets.     

Solid–Vapor Reaction Growth of Transition‐Metal Dichalcogenide Monolayers

Two‐dimensional (2D) layered semiconducting transition‐metal dichalcogenides (TMDCs) are promising candidates for next‐generation ultrathin, flexible, and transparent electronics. Chemical vapor deposition (CVD) is a promising method for their controllable, scalable synthesis but the growth mechanism is poorly understood. Herein, we present systematic studies to understand the CVD growth mechanism of monolayer MoSe₂, showing reaction pathways for growth from solid and vapor precursors. Examination of metastable nanoparticles deposited on the substrate during growth shows intermediate growth stages and conversion of non‐stoichiometric nanoparticles into stoichiometric 2D MoSe₂ monolayers. The growth steps involve the evaporation and reduction of MoO₃ solid precursors to sub‐oxides and stepwise reactions with Se vapor to finally form MoSe₂. The experimental results and proposed model were corroborated by ab initio Car–Parrinello molecular dynamics studies.