化学气相沉积法制备平直多壁碳纳米管的研究

本文研究了用焦炭还原二氧化碳后的一氧化碳作碳源,化学气相沉积法合成平直的多壁碳纳米管的工艺.研究表明在化学气相沉积条件下,用焦炭还原二氧化碳得到的一氧化碳在适当的铁基催化剂作用下,采用催化剂/碳原子共沉积的工艺可以生产出平直、并且内径很大的多壁碳纳米管.碳源中催化剂的浓度影响着纳米管的形成,而沉积温度对其没有影响.     

沉积温度对PECVD制备碳纳米管形貌的影响

采用等离子体增强化学气相沉积技术,以C2H2、H2和N2为反应气体,在镀Ni催化剂的Si基底上成功制备出多壁碳纳米管薄膜.采用扫描电镜研究了沉积温度对碳管形貌的影响,进一步通过扩散机制分析了多种形貌CNTs的生长机制.结果表明:沉积温度对催化剂的刻蚀和碳纳米管薄膜的形成起着决定作用,获得定向性良好、分布均匀、密度适中的碳纳米管的最佳温度是700℃.     

阵列式碳纳米管雷达波吸收性能研究

研究了阵列式碳纳米管的雷达波吸收性能.采用化学气相沉积(CVD)工艺制备阵列式碳纳米管薄膜,并采用SEM 和TEM 对其进行观测.观测显示:阵列式碳纳米管薄膜中碳纳米管排列规则,有很好的定向性,直径30～50 nm.阵列式碳纳米管薄膜平铺在铝板上并用环氧树脂固定制成试样,采用反射率扫频测量系统HP8757E矢量网络分析仪检测阵列式碳纳米管吸波性能.结果表明:阵列式碳纳米管在2～18 GHz频段的较高频段表现出良好的吸波性能.吸波性能随薄膜厚度不同而改变.阵列式碳纳米管薄膜厚度为0.2 mm 时,雷达波吸收性能最佳,峰值R为-15.87 dB,波峰出现在17.83 GHz,带宽分别为4.25 GHz(R<-10 dB)和6.40 GHz(R<-5 dB).     

晶须状多壁碳纳米管导电液及透明导电薄膜的研究

以碳纳米管醇分散剂TNADIS(粉末状聚合物分散剂)作为分散剂,同时应用超声振荡和高速剪切相互配合的工艺制成多壁碳纳米管(MWCNT)乙醇导电液.通过拉曼光谱,TEM和SEM表征MWCNTs的微观形态,通过离心,静置以及丁达尔效应的检测分析MWCNTs导电液的分散情况和稳定性.结果显示,添加0.05wt;分散剂时碳纳米管分散效果最佳,未石墨化MWCNTs的分散效果优于石墨化后的MWCNTs,且静置五个月后导电液依然保持良好的稳定性.应用此导电液通过旋涂工艺制得的涂覆均匀的MWCNTs透明导电薄膜,旋涂3min的透明导电薄膜方块电阻为0.34 kΩ/sq.     

催化剂膜厚对碳纳米管薄膜生长的影响

采用射频等离子体增强化学气相沉积技术,以Ni为催化剂,在Si基底上沉积出定向性良好的碳纳米管.用扫描电镜表征了催化剂颗粒大小和相应的碳纳米管形貌.深入研究了催化剂膜厚对碳纳米管牛长的影响.结果表明:不同度的催化剂薄膜经刻蚀形成的颗粒密度、尺寸、分布等对碳纳米管的合成质量起主要作用.催化剂厚度≤5 nm时,形成的颗粒密度较小而且分布不均,制备的碳纳米管产量低、定向性差.催化剂厚度≥15 nm时,形成的颗粒较大,粘连在一起,生长时大部分被非晶碳包覆,几乎没有碳纳米管的生长.催化剂厚度为10 nm时,形成的颗粒密度大、分布较均,制备的碳纳米管纯度高、定向性好.     

火焰热解法生长定向碳纳米管

本文研究了火焰热解法的碳纳米管制备实验(催化剂为Fe/Mo/Al2O3),发现在火焰热解法条件下碳纳米管阵列可在火焰热解腔中定向生长,产物较为整齐,碳管形态较好.本课题组之前在电场作用下采用Fe(CO)5为催化剂,在V型体火焰中亦可制得碳纳米管阵列,对比两者发现热解腔内制得阵列碳纳米管长度较长,定向性更优;而电场作用下的V型体火焰中制得阵列中的碳纳米管较直.进而,在火焰热解法制备中施加电场,发现随电压增加,碳纳米管阵列更直,碳管长度和产量明显增长.     

热解火焰法合成碳纳米管:催化剂与合成环境的影响

以CO为碳源,通过氧炔焰形成热解火焰合成了碳纳米管.为了详细研究催化剂与合成环境对合成产物的影响,实验分别应用不同催化剂在不同合成环境中进行取样分析.结果表明:催化剂颗粒尺寸直接决定合成产物的种类,不同产物对合成温度也有不同要求,过高温火焰环境会遏制碳纳米管的合成.最终得出,Fe/Mo/Al2O3载体催化剂适合在热解腔内部830℃无氧的环境下催化合成小直径的单壁、双壁和三壁碳纳米管,而由Fe(CO)5热解-附着-聚合产生的Fe催化剂颗粒适合在600℃的V型体火焰中催化合成大直径多壁碳纳米管.     

气体流量对热解火焰法合成碳纳米管的影响

采用热解火焰法制备了碳纳米管,研究了不同气体流量对碳纳米管制备的影响.结果表明:He流量变化会对碳纳米管形态产生影响,CH4、H2流量变化对碳纳米管形态影响不大;He、H2、CH4流量变化会影响碳纳米管的产量,当He、H2、CH4流量比2∶3∶6时,碳纳米管产量最高且产物主要是单壁、双壁、三壁碳纳米管.     

单壁碳纳米管储氢过程的GULP模拟

利用GULP软件的蒙特卡罗模块对常温(T=300 K)下单壁碳纳米管(SWNT)管内物理吸附储氢进行了模拟.研究和讨论了5种半径的扶手椅管在T=300 K时的吸附等温线,给出了同一管径在不同压强下氢气分子在碳纳米管中分布变化的对比图,并对T=300 K,P=10 MPa时不同管径的碳纳米管储氢能力进行了对比.结果显示,常温下压强不大于10 MPa时单壁碳纳米管吸附氢气的质量储氢容量不超过1.8;,体积吸附量不超过22 kg·m-3,表明纯单壁碳纳米管具有一定的吸附氢气的能力,但其存储能力与美国能源部提出的研究目标尚有一定差距,还需通过改变碳纳米管的结构、特性等方法来改善其储氢特性.     

Fe/Mo/Al2O3催化剂热解火焰法合成单壁、双壁和三壁碳纳米管:合成温度、取样时间与CO流量的影响

本文重点描述了应用Fe/Mo/Al2O3载体载入式催化剂,以CO为碳源,通过氧炔焰形成热解火焰合成单壁、双壁和三壁碳纳米管的实验过程.研究了合成温度,取样时间以及碳源气体CO流最对最终产物的影响.结果表明,830℃的合成温度可以满足合成单壁、双壁和三壁碳纳米管所需要的高温环境,消除载体催化剂聚合物对碳纳米管的包裹,大幅提高合成产物的产量;10 min的取样时间以及0.4 L/min的CO流量可以良好分散载体催化剂聚合物团簇,进而优化产物形态和进一步提高产量.     

Influence of MWCNT on the properties of hydrogen bonded liquid crystals

A hydrogen bonded complex molded between p-n-octylbenzoicacid (8BA) and m-fluorobenzoic acid (FBA) is isolated and doped with predetermined quantity of Multi Walled Carbon Nano Tube (MWCNT) in order to achieve better thermal and electrical performance. The obtained series of liquid crystal nano systems comprising of three mesogens, varying in the weight percentage of MWCNT are analyzed by Polarizing Optical Microscope (POM), Differential Scanning Calorimetry (DSC) and Fourier Transform Infra-Red (FTIR) spectroscopy. Different aspects of the MWCNT – liquid crystal combination, evaluation of MWCNT's effect on selected properties of liquid crystals which are relevant to display related applications are discussed. In addition, Frederik's transitions of MWCNT dispersed liquid crystals reveal the direct effect of bundles of MWCNT on liquid crystal reorientation.     

离子轰击对准直碳纳米管生长的影响

利用负偏压增强热丝化学气相沉积系统,在辉光放电的情况下制备出准直碳纳米管,并用扫描电子显微镜研究了不同负偏压对准直碳纳米管生长的影响.结果表明随着负偏压的增大,准直碳纳米管的平均直径减小,平均长度增大.由于辉光放电的产生,在衬底表面附近形成阴极鞘层,以及在阴极鞘层内形成大量的离子和在衬底表面附近形成很强的电场导致了离子对衬底表面的强烈轰击.最后,分析和讨论了离子的轰击对准直碳纳米管生长的影响.     

阵列式碳纳米管微波受激发射光子

采用化学气相沉积工艺(CVD)制备阵列式碳纳米管(ACNT)薄膜并检测薄膜的微波性能.当ACNT薄膜受到微波照射时,强烈地发射光子,产生耀眼的的白光,红外测温仪显示温度高达1200℃,但ACNT并不氧化燃烧.ACNT薄膜经球磨成粉状后,光子发射性能消失,在微波照射下 ACNT粉末和普通碳纳米管(MWCNT)表现相近,吸收微波能量后开始燃烧并发出红色的火焰,实测温度为720℃.研究显示ACNT具有优异的场发射性能.     

Engineering ZnO nanowire surfaces via a chemical method

Quasi‐aligned porous ZnO nanowire arrays are promising architectures for potential applications in catalysts, gas sensors and solar cells. However, processes for conversion of ZnO nanowire arrays into porous ones have rarely been reported. Here, we report a facile chemical method for the synthesis of ZnO nanowire array with porous surface. The morphology and structure of the obtained products have been investigated with field‐emission scanning electron microscopy and high‐resolution transmission electron microscopy. Time‐dependent experiments have also been carried out to better understand the formation process of porous structures on the nanowire surfaces. The obtained porous ZnO nanowire arrays may find potential applications in catalysts, solar cells and gas sensors due to the large surface area of the yielded products.     

Self-organized nanocomb of ZnO fabricated by Au-catalyzed vapor-phase transport

Based on a vapor-phase transport process, self-organized nanocomb structures of ZnO were fabricated on Au-coated Si substrate by employing a mixture of ZnO and graphite powders as source materials. The morphology of the product showed a ribbon-like stem and nanorod array aligned evenly along one side of the nanoribbon. It was found that the nanoribbon grew mainly along direction and the self-assembled branching nanorods grew epitaxially along [0 0 0 1] orientation from the (0 0 0 2) plane of the stem. The growth process was analyzed in detail.     

新型碳纳米管材料吸附剂性能研究

本文研究了碳纳米晶体材料-多壁碳纳米管作为新型挥发性有机化合物采样吸附剂的性能和效果.实验结果表明,碳纳米管比表面积较大,对VOCs回收率高,有更强的吸附能力;本底低,干扰少,再生性能良好,可重复使用,不易老化;机械强度好,化学惰性,更能耐高温且有较长的寿命;采样管采集VOCs时对低碳数的化合物,采样稳定性好;具有较大的穿透容量,用于富集不同浓度不同体积的大气样品,能够有效防止采样过程中发生穿透现象,所以碳纳米管作为大气中挥发性有机化合物采样吸附剂具有巨大潜力.     

Influence of Additives and Surface Topography on the Alignment of Nematic Liquid Crystals

Observations of the influence of a simultaneous action of different surface topographies and polar or nonpolar additives in small concentration on the alignment properties of liquid crystal molecules are reported. The additive dependence of the threshold behaviour of planar aligned liquid crystal cells is also studied.     

A Variable Tilt Smectic A Electro-Optic Effect Giving Stored Colours

A smectic A phase was aligned with a uniformly high tilt such that it appeared coloured between crossed polarisers. By applying an electric field the tilt angle of the structure increased progressively giving a Newton Spectrum series of colours. The colours remain on removal of the drive voltage.     

Effect of Temperature,Time, Concentration,Annealing, and Substrates on ZnO Nanorod Arrays Growth by Hydrothermal Process on Hot Plate

Crystallography Reports - Well aligned 1D ZnO nanostructures are important for optoelectronic and nanoscale electronic devices. In this report, 1D ZnO nanorods were synthesized by very simple, low...