丝网印刷制备碳纳米管场发射阴极的研究

碳纳米管(CNT)是理想的场发射阴极材料.本文分析了CNT的长度、直径以及排列密度与CNT阴极场增强因子的关系,研究了大面积CNT场发射阴极的丝网制备技术,包括CNT浆料配制、阴极电极的制作、阴极烧制方法和表面处理方法.文中实际制备了CNT阴极,利用二极管结构测试了对其表面处理前后的场发射性能.实验结果证明,采用本文所研究的制备技术能够印制高性能的场发射CNT阴极,该研究为制备大面积CNT阴极阵列提供了技术基础.     

环己烷浮游催化法制备超长碳纳米管阵列

采用非芳香烃类环己烷作为碳源,通过浮游法实现了超长垂直碳纳米管(Carbon nanotube,CNT)阵列的生长。研究表明:浮游催化过程中反应温度、催化剂前体补给速度、进料速度、生长气氛等因素对CNT阵列的生长影响显著。在直径为25mm的石英反应器中,反应温度、催化剂前体二茂铁的补给速度、碳源环己烷的补给速度、反应气氛分别控制在820℃、0.24mg/min、0.12mL/min、640mL/min(H2/Ar=1∶15)的生长窗口内,实现了CNT阵列的快速协同生长。在单因素考察的基础上,通过对宏观参数的调变,可以制备出长度达5.0mm的CNT阵列。所获得的CNT取向一致,长径比大于105,纯度达到96.7%。     

金属基底上定向碳纳米管阵列的生长及其场发射性质

在金属基底上,以铁为催化剂,硅做过镀层,乙烯为源气体,通过普通的化学气相沉积方法生长出垂直基底排列的碳纳米管(CNT)阵列.扫描电子显微镜和透射电镜观察表明,生长的CNT具有阵列形貌和多缺陷的结构.对CNT阵列的场发射性质进行了测量,在10 μA/cm2时不锈钢和镍基底上的开启电场分别为1.25 V/μm 和1.57 V/μm.     

有机质掺杂碳纳米管阵列场发射性质的研究

碳纳米管(CNT)作为理想的场发射阴极材料,在场发射阴极阵列中的密度与阴极的场发射性能有着非常密切的关系。通过解拉普拉斯方程,得到碳管阵列密度对场增强因子的影响,同时通过对不同阵列密度的碳纳米管阵列进行有机质的填充解决了碳纳米管阵列在制备过程中的定向排列问题,并对所需碳管与有机质的质量比进行了理论计算,结果表明,阵列密度和管间距对碳管与有机质的质量比有很大影响。     

取向碳纳米管膜/氰基树脂复合材料的制备与性能强化机制

以浮动催化化学气相沉积法(FCCVD)碳纳米管(CNT)膜为原料,通过氰基树脂溶液浸渍法制备CNT预浸膜,然后采用热辅助牵伸和热压固化的方法制备高取向CNT膜复合材料。详细分析了热处理的温度和树脂溶液浓度对CNT预浸膜拉伸性能的影响,从而得到合适的热辅助牵伸工艺,并考察固化工艺对复合材料性能的影响。在此基础上,从浸润特性、CNT取向程度和层间剪切性能方面揭示CNT膜复合材料力学性能的强化机制。结果表明与传统CNT膜牵伸工艺相比,CNT预浸膜热牵伸工艺更有利于制备高取向CNT膜复合材料。热牵伸的温度和树脂溶液的浓度是制备高取向、低孔隙CNT预浸膜的关键因素。通过固化工艺的改变可有效调控氰基树脂的反应程度碳纳米管薄膜/氰基树脂复合材料的拉伸性能。经高温后固化处理后,CNT膜/氰基树脂复合材料的拉伸强度和模量分别高达2 748 MPa和302GPa。优异的树脂浸润特性、层间剪切强度以及高的CNT取向度使CNT膜复合材料中CNT更有利于协同承载,从而提高其力学性能。     

电泳和电镀法增强碳纳米管场发射特性的研究

碳纳米管(CNT)和衬底的电学接触问题是获得高性能CNT电子器件的一个关键性的问题。本文采用电泳电镀方法制备CNT冷阴极,有效改善了CNT与衬底间接触电阻,增强了碳纳米管场发射性能。电泳电镀法制备的碳纳米管冷阴极场发射的开启电场(电流密度为10μA.cm-2时的电场)由2.95 V.μm-1降低到1.0V.μm-1,在电场为8V.μm-1时电流密度由0.224增加到0.8112mA.cm-2。在电流密度为800μA.cm-2时进行1h的场发射稳定性测试,结果表明,电泳电镀法所得CNT场发射电子源电流密度几乎不变,而且电流密度比较稳定;而只有电泳的方法获得的CNT场发射电子源电流密度波动较大,电流不稳定且呈较快的衰减趋势,1h后减少到原来的75%。采用电泳电镀方法制备CNT阴极,CNT的根部被纳米银颗粒覆盖和包裹,使CNT与衬底接触更加牢固而紧密,又由于银具有很好的导电性,从而大大减小了接触电阻,因此电泳电镀法能大大改善CNT与衬底的电学接触性能。     

ZnO纳米棒/CNTs复合阴极的制备及其场发射性能的研究

采用水热法和喷涂法制备ZnO纳米棒/CNTs复合材料,并测试其场发射性能。首先采用水热法在ITO电极基面生长ZnO纳米棒阵列,随后通过喷涂技术在ZnO纳米棒阵列表面沉积碳纳米管(CNTs)。使用扫描电子显微镜和X-射线衍射分别表征样品的结构和形貌特征。结果表明,经喷涂沉积的CNT薄膜均匀地包裹在ZnO纳米棒尖端。对该复合材料采用二极结构测试其场发射性能,通过测试结果发现,ZnO纳米棒/CNTs复合材料可明显改善ZnO纳米棒阵列及CNT薄膜的场发射性能,该复合材料具有低开启电场强度(约0.96V/μm),高场增强因子(9881)。因此,ZnO纳米棒/CNTs复合材料是最有前景的场发射阴极材料之一。     

一种应用于PDP显示单元的CNT辅助电极制备方法及其性能评价

建立了一种应用于等离子显示器(PDP)显示单元的碳纳米管(CNT)辅助电极制备工艺方法,创新性提出了场发射作为PDP平板显示的辅助性应用,并对制备的CNT辅助电极样片进行了性能评价。文章通过三维轮廓和SEM微观形貌测试手段,表征工艺过程中CNT辅助电极的宏观尺度和微观形貌。通过拉曼光谱、傅里叶红外光谱、粒径分布和ZETA电位表征与其性能直接相关的体系分散性。通过对荷电盐浓度、电泳电压、电泳时间和阴阳极板间距的系统分析和优化,获得优化电泳参数。通过关键参数对比确定了前后处理工艺及其效果。对CNT辅助电极的场发射性能进行测试,初步评价其辅助性能并考察其与PDP单元制备流程的兼容性。优化工艺制备的CNT辅助电极场发射开启电压在10μA/cm2的电流密度时低至1.2 V/μm。虽然在MgO保护层制备后增大至1.6 V/μm,但仍可保证其作为PDP辅助电极的典型功能。所建立的CNT辅助电极制备方法具备与PDP显示单元制备工艺有良好兼容性。     

碳纳米管/聚苯胺空心球复合材料的制备与电化学性能

以无机材料Fe3O4为模板,将在碳纳米管(CNT)功能化后,包裹在模板表面,然后再将苯胺单体接枝在CNT表面,之后采用化学氧化法,将接枝于CNT表面的苯胺单体聚合成聚苯胺(PANI),从而制备CNT/PANI空心球复合材料。用傅立叶变换红外光谱、扫描电子显微镜对复合材料进行成分和形貌的表征。用循环伏安法、恒流充放电和循环寿命等电化学测试手段来表征复合材料的电化学性能。研究结果表明所制备的复合材料比容量可达到185F/g(有机电解液),高于同样条件下所制备的纯PANI和采用一般方法所制备的CNT/PANI复合材料的电化学容量(65F/g,152F/g),显示出良好的应用前景。     

取向碳纳米管/环氧树脂复合薄膜制备及结构与性能表征

碳纳米管(Carbon nanotube, CNT)/环氧树脂(Epoxy resin, EP)纳米复合材料中树脂含量、分布、CNT取向及其与树脂间界面结合是制备高性能纳米复合材料的关键因素。为了探究树脂分布和CNT/EP复合材料性能之间的关系,采用浮动催化化学气相沉积法制备的CNT薄膜和EP为原料,通过浸渍、牵伸、清洗和热压固化工艺制备CNT/EP复合薄膜。利用聚焦离子束结合扫描电子显微镜定性表征树脂在复合膜中的分布状态。结果表明,随着树脂含量增加,树脂在复合薄膜表面富集程度增加。在最优工艺条件下制备的纳米复合材料中CNT含量为66.14wt%, 拉伸强度和拉伸模量达到1405 MPa和46.7 GPa。      

纳米碳管阵列

在概括纳米碳管阵列特异的场发射效应及在场发射器方面应用前景的基础上，介绍了合成纳米碳管阵列的研究历程以及化学气相沉积法在纳米碳管阵列合成方面的重要意义，就当前纳米碳管阵列的快速合成与低温合成两个发展方向进行了概述，并指出等离子体化学气相沉积法能有效地用于纳米碳管阵列的低温合成。     

Influence of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> buffer layer on catalyst morphology and spinnability of carbon nanotube arrays

Carbon nanotube (CNT) fibers spun from vertically aligned CNT arrays hold great promise in promoting CNT’s practical applications. Their production and properties strongly depend on the spinnability of the arrays. Herein, we study the influence of Al₂O₃ buffer layer on catalyst morphology and the spinnability of CNT arrays. Long and vertically aligned CNT arrays have been obtained from a wide range of Al₂O₃ buffer layer thickness, but the spinnable ones have only derived from a narrow range of the thickness. It is further found that the Al₂O₃ buffer layer can regulate the size and size distribution of the catalyst particles through balancing surface diffusion and inter-layer diffusion. Small, dense, and uniform-distributed nanoparticles are fingerprinted as the optimal catalyst for growing long and spinnable CNT arrays and can be obtained at a proper thickness of buffer layer. By using a tailored tri-layered Fe/Al₂O₃/SiO₂ catalyst, the obtained CNT arrays could reach a height of 500–800 µm and are highly spinnable.     

Super-long aligned TiO2/carbon nanotube arrays

5?mm long aligned titanium oxide/carbon nanotube (TiO(2)/CNT) coaxial nanowire arrays have been prepared by electrochemically coating the constituent CNTs with a uniform layer of highly crystalline anatase TiO(2) nanoparticles. While the presence of the TiO(2) coating was confirmed by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and x-ray diffraction, the resultant TiO(2)/CNT coaxial arrays were demonstrated to exhibit minimized recombination of photoinduced electron-hole pairs and fast electron transfer from the long TiO(2)/CNT arrays to external circuits. This, in conjunction with the aligned macrostructure, facilitates the fabrication of TiO(2)/CNT arrays for various device applications, ranging from photodetectors to photocatalytic systems. Thus, the millimeter long TiO(2)/CNT arrays represent a significant advance in the development of new macroscopic photoelectronic nanomaterials attractive for a variety of device applications beyond those demonstrated in this study.     

Macroscopic carbon nanotube assemblies: preparation, properties, and potential applications

As classical 1D nanoscale structures, carbon nanotubes (CNTs) possess remarkable mechanical, electrical, thermal, and optical properties. In the past several years, considerable attention has been paid to the use of CNTs as building blocks for novel high-performance materials. In this way, the production of macroscopic architectures based on assembled CNTs with controlled orientation and configurations is an important step towards their application. So far, various forms of macroscale CNT assemblies have been produced, such as 1D CNT fibers, 2D CNT films/sheets, and 3D aligned CNT arrays or foams. These macroarchitectures, depending on the manner in which they are assembled, display a variety of fascinating features that cannot be achieved using conventional materials. This review provides an overview of various macroscopic CNT assemblies, with a focus on their preparation and mechanical properties as well as their potential applications in practical fields.     

Ultrahigh Frequency Carbon Nanotube Transistor Based on a Single Nanotube

Single-walled carbon nanotube field-effect transistors (CNT FETs) are predicted to have intrinsic cutoff frequencies approaching the THz range. Here ldquointrinsicrdquo means that the parasitic capacitance due to fringing fields is negligible compared to the gate-source capacitance required to modulate the conductance. In practice, although there are strategies proposed to mitigate this based on parallel arrays of CNT FETs, this parasitic capacitance dominates most geometries (even aligned arrays to date). In this work we show nanotube transistor performance with maximum stable gain above 1 GHz (even including the parasitics) by combining ldquoon-chiprdquo the electrical properties of 100 CNT FETs fabricated on one long nanotube. This also solves the problem of impedance matching by boosting the on current to a large (mA) value, and at the same time allows one to extract properties of each individual CNT FET, since they are identical in electrical characteristics as they are made out of the same CNT. This strategy opens the door to applications of carbon nanotube devices in the RF and microwave frequency range, a technologically relevant portion of the spectrum for both wired and wireless electronics, that has been (until now) incompatible with nanotube device technology.     

定向碳纳米管阵列在石英玻璃基底上的模板化生长研究

分别以带有刻痕的石英玻璃和溅射过Au膜的石英玻璃为生长基底，通过催化裂解二茂铁和二甲苯混合物的方法，在基底上制备出了模板化的定向碳纳米管(CNT)阵列．扫描电镜(SEM)和透射电镜(TEM)观察表明：在这两种基底上生长的定向碳纳米管阵列的模板化程度都很高，其中的碳纳米管多为直径在20-50nm的多壁管(MWNT)，且具有很好的定向性．本文还分析、对比了基底材料对定向碳纳米管生长的影响，初步探讨了定向碳纳米管模板化生长的形成机制．     

Carbon nanotube thermal interface material for high-brightness light-emitting-diode cooling

Aligned carbon nanotube (CNT) arrays were fabricated from a multilayer catalyst configuration by microwave plasma-enhanced chemical vapor deposition (PECVD). The effects of the thickness and annealing of the aluminum layer on the CNT synthesis and thermal performance were investigated. An experimental study of thermal resistance across the CNT array interface using the modified ASTM D5470 standard was conducted. It was demonstrated that the CNT-thermal interface material (CNT-TIM) reduced the thermal interfacial resistance significantly compared with the state-of-art commercial TIM. The optimized thermal resistance of the CNT arrays is as low as 7?mm(2)?K?W(-1). The light performance of high-brightness light-emitting diode (HB-LED) packages using the aligned CNT-TIM was tested. The results indicated that the light output power was greatly improved with the use of the CNT-TIM. The usage of the CNT-TIM can be also extended to other microelectronics thermal management applications.     

Effect of density variation and non-covalent functionalization on the compressive behavior of carbon nanotube arrays

Arrays of aligned carbon nanotubes (CNTs) have been proposed for different applications, including electrochemical energy storage and shock-absorbing materials. Understanding their mechanical response, in relation to their structural characteristics, is important for tailoring the synthesis method to the different operational conditions of the material. In this paper, we grow vertically aligned CNT arrays using a thermal chemical vapor deposition system, and we study the effects of precursor flow on the structural and mechanical properties of the CNT arrays. We show that the CNT growth process is inhomogeneous along the direction of the precursor flow, resulting in varying bulk density at different points on the growth substrate. We also study the effects of non-covalent functionalization of the CNTs after growth, using surfactant and nanoparticles, to vary the effective bulk density and structural arrangement of the arrays. We find that the stiffness and peak stress of the materials increase approximately linearly with increasing bulk density.     

A combination of capillary and dielectrophoresis-driven assembly methods for wafer scale integration of carbon-nanotube-based nanocarpets

The wafer scale integration of carbon nanotubes (CNT) remains a challenge for electronic and electromechanical applications. We propose a novel CNT integration process relying on the combination of controlled capillary assembly and buried electrode dielectrophoresis (DEP). This process enables us to monitor the precise spatial localization of a high density of CNTs and their alignment in a pre-defined direction. Large arrays of independent and low resistivity (4.4 × 10(-5) Ω m) interconnections were achieved using this hybrid assembly with double-walled carbon nanotubes (DWNT). Finally, arrays of suspended individual CNT carpets are realized and we demonstrate their potential use as functional devices by monitoring their resonance frequencies (ranging between 1.7 and 10.5 MHz) using a Fabry-Perot interferometer.     

Dielectrophoresis‐Assisted Integration of 1024 Carbon Nanotube Sensors into a CMOS Microsystem

Carbon‐nanotube (CNT)‐based sensors offer the potential to detect single‐molecule events and picomolar analyte concentrations. An important step toward applications of such nanosensors is their integration in large arrays. The availability of large arrays would enable multiplexed and parallel sensing, and the simultaneously obtained sensor signals would facilitate statistical analysis. A reliable method to fabricate an array of 1024 CNT‐based sensors on a fully processed complementary‐metal‐oxide‐semiconductor microsystem is presented. A high‐yield process for the deposition of CNTs from a suspension by means of liquid‐coupled floating‐electrode dielectrophoresis (DEP), which yielded 80% of the sensor devices featuring between one and five CNTs, is developed. The mechanism of floating‐electrode DEP on full arrays and individual devices to understand its self‐limiting behavior is studied. The resistance distributions across the array of CNT devices with respect to different DEP parameters are characterized. The CNT devices are then operated as liquid‐gated CNT field‐effect‐transistors (LG‐CNTFET) in liquid environment. Current dependency to the gate voltage of up to two orders of magnitude is recorded. Finally, the sensors are validated by studying the pH dependency of the LG‐CNTFET conductance and it is demonstrated that 73% of the CNT sensors of a given microsystem show a resistance decrease upon increasing the pH value.