碳纳米管/纳米铁颗粒杂化结构的制备及形成机理

采用催化化学气相沉积法将由C包覆的纳米铁颗粒(FeNP)原位沉积于碳纳米管(CNTs)表面并形成不同形貌的碳纳米管/纳米铁颗粒(CNTs/FeNP)杂化结构。使用扫描电子显微镜、透射电子显微镜对制备的杂化结构进行微观形貌分析和结构表征。结果显示,纳米铁颗粒通过石墨片层结构与碳纳米管相连,具有良好的界面结合。当噻吩的添加量较低时,产物中碳纳米管的直径减小,产量增多。当噻吩的添加量超过0.5%时,可以得到CNTs/FeNP杂化结构。使用X射线能谱仪、X射线衍射仪分析了杂化结构的成分及其相对含量,结果显示体系中的Fe主要以α-Fe、γ-Fe和Fe3C的形式存在,并且Fe的含量随噻吩含量的增加不断增加。通过研究纳米铁颗粒的形成及其在碳纳米管表面的沉积,揭示了CNTs/FeNP杂化结构的形成机理。     

磷对浮动催化裂解法制备单壁碳纳米管产率和直径的影响

采用浮动催化裂解法研究了磷作为促进剂对SWNTs制备的影响.实验表明,在SWNTs的制备过程中添加适量的磷促进剂可以大幅度提高SWNTs的产率;采用扫描电子显微镜(SEM),透射电子显微镜(TEM)和拉曼光谱(Raman spectroscopy)对产物进行微观结构分析,发现磷有利于较小管径SWNTs的合成.根据表征结果推测SWNTs以Yarmulke帽模型生长.适量的添加磷的能有效的提高纳米铁颗粒的催化活性,促进Yarmulke帽的形成.     

电晕放电法合成载铁碳纳米管

利用电晕放电增强化学气相沉积技术制备了载铁碳纳米管阵列,采用TEM、SEM和XRD等对载铁碳纳米管进行表征,发现了两种类型的碳纳米管,且含铁纳米颗粒无论大小均被包裹在碳纳米管的管壁中.IR热成像仪分析发现碳纳米管合成温度不高于250℃.     

一维纳米材料光学可视化研究获进展

清华大学化工系魏飞教授带领的团队在一维纳米材料的光学可视化方面取得了重要进展。该研究团队以单根超长碳纳米管为研究材料，通过气相自组装的方式在单根碳纳米管上负载二氧化钛纳米颗粒．实现了单根碳纳米管在光学环境下的可视化。所负载的二氧化钛颗粒分布在数十至数百纳米，由于这种粒径大小的纳米颗粒对可见光有很强的散射能力（遵循米氏散射），使得它们在低倍的光学显微镜甚至普通的放大镜下就可以用肉眼看到。正是有了这些纳米颗粒的标记作用，负载有单个或多个这种纳米颗粒的单根碳纳米管就可以在光学显微镜下被清晰地观察并准确定位。实现这种一维纳米材料光学可视化的方法过程简单．不需要复杂的设备．其过程只需要几秒钟的时间，非常简单高效。     

油基纳米流体的电导率

以1种典型成品油和2种典型原油为基液,采用两步法制备油基纳米流体,研究含不同质量分数的球形氧化铁纳米颗粒与大长径比碳纳米管对油样电导率的影响,分析油基纳米流体电导率变化的主要机理。结果表明:氧化铁油基纳米流体电导率没有明显增大,碳纳米管油基纳米流体电导率均显著增大;碳纳米管成品油基纳米流体的渗流阈值(质量分数,以下同)为0.27%,添加质量分数为2%的碳纳米管分散液的成品油基纳米流体电导率增大5.83×1010倍;2种添加碳纳米管的原油基纳米流体与成品油基纳米流体的电导率变化规律类似,渗流阈值为0.1%~0.3%,添加质量分数为0.5%的碳纳米管分散液的原油基纳米颗粒电导率增大近1 000倍;大长径比碳纳米管通过在原油中建立电桥,有效增大了原油电导率。     

聚癸二酸甘油酯/碳纳米管纳米复合材料的制备与性能

通过一步法得到了力学性能优异的碳纳米管(CNT)改性的聚癸二酸甘油酯纳米复合材料。将CNT分散在甘油中后与癸二酸进行缩聚反应,通过改变碳纳米管的添加量、癸二酸与甘油之间的配比以及固化时间得到了一系列的聚酯纳米复合材料。结果表明:CNT能明显的提高弹性体的强度和硬度,该纳米复合材料具有优异的力学性能,同时研究了CNT对玻璃化转变温度和凝胶含量等影响,并通过扫描电镜观察材料断面形貌,可以发现一定量的碳纳米管可以较均匀地分散在聚合物中。     

空气氧化法提纯碳纳米管的研究

以乙炔为原料气，采用铁-镍复合催化剂，在700℃下，由化学气相沉积法(CVD)制得了直径为10nm～30nm的多壁碳纳米管(MWNT)。然后通过空气氧化法对所获碳纳米管进行提纯，去除了碳纳米管中的无定形炭、炭纳米颗粒及炭纤维等非晶碳成分，提高了碳纳米管的纯度；并研究了提纯温度和时间的关系。结果表明：碳纳米管在空气中440℃加热3h后，烧损率趋于平稳，基本上稳定在2％左右。使用透射电镜(TEM)考察提纯前后碳纳米管的形貌，发现碳纳米管在空气中440℃加热3h后，非晶碳成分基本去除，纯度得到提高。     

碳纳米管/导电聚苯胺纳米复合纤维的合成与表征

为实现碳纳米管在树脂内形成一体化导电网络，从而制备出透明导电性能最优的有机透明导电涂层，必须把导电性的碳纳米管纤维在树脂内有效地组装成一体化导电结构网络。本文报道运用在树脂内可以自组装的导电苯胺来实现碳纳米管纤维自组装的方法．合成出了导电聚苯胺纳米薄膜均匀包覆的碳纳米管/导电聚苯胺纳米复合纤维．并运用透射电镜、傅立叶红外光谱以及四探针法表面电阻测试仪对合成出的具有精细微观结构的纳米复合纤维进行了表征．发现合成出了理想的碳纳米管/导电聚苯胺纳米复合纤维，并且其导电性较碳纳米管和导电聚苯胺自身都有大幅度的提高。这种特殊结构的纳米复合纤维的制备为组装高性能的聚合物基透明导电涂层奠定了坚实基础，而且这种自组装方法为各种纳米纤维的组装提供了可能。     

在碳纳米管上负载硫化镉的研究

研究了在碳纳米管表面负载硫化镉纳米颗粒的工艺及其影响因素.研究结果表明:使用经过酸氧化处理的碳纳米管在硫化镉溶液中与硫代乙酰胺进行反应可以在碳管表面沉积尺寸较小,分布较致密而且均匀的硫化镉纳米颗粒.     

NiZnCo铁氧体包覆铁填充碳纳米管的吸波性能

利用溶胶凝胶法制备了Ni0.5 Zn0.45 Co0.05 FezO4/铁填充碳纳米管复合粉末,实现了Ni0.5Zn0.45 Co0.05Fe2O4纳米颗粒对碳管的包覆.并用同轴法测量了纳米复合粉末与石蜡混合物的电磁参数,其中纳米复合粉末的添加量分别为30%和60%,根据电磁参数计算了材料的反射率.结果表明纳米复合粉末的主要吸波频段在2～6GHz,当纳米复合粉末添加量为60%(质量分数),厚度为2mm时,微波吸收峰值出现在大约4GHz处,达到5.8dB.与纯Ni0.5Zn0.45 Co0.05Fe2O4纳米粉末相比有了比较明显的提高.     

辅助气体对RF-PECVD制备碳纳米管薄膜形貌的影响

采用射频等离子体增强化学气相沉积(RF-PECVD)技术,以Ni为催化剂,经600℃裂解C2H2在Si基底上制备出定向碳纳米管薄膜。采用扫描电子显微镜(SEM)表征了刻蚀后Ni颗粒与沉积的碳纳米管薄膜的形貌。研究了辅助气体对等离子体预处理催化剂与碳纳米管生长的影响。结果表明:辅助气体(H2与N2)流量比对催化剂颗粒尺寸、分布以及碳纳米管生长有显著影响;合适的气体流量比有利于减少碳纳米管薄膜的杂质颗粒,促进其定向生长。预处理过程中气体流量比H2:N2=20:5时,预处理后催化剂Ni颗粒分布密度大、粒径小且分布范围窄,适合碳纳米管均匀着床;沉积生长碳纳米管薄膜时,H2:N2=20:15可得到纯度高、定向性好的碳纳米管。     

Systematic study on synthesis and purification of double-walled carbon nanotubes synthesized via CVD

Carbon nanotubes have unique properties, such as thermal and electrical conductance, which could be useful in the fields of aerospace, microelectronics and biotechnology. However, these properties may vary widely depending on the dimensions, uniformity and purity of the nanotube. Nanotube samples typically contain a significant percentage of more allotropes forms of carbon as well as metal particles left over from catalysts used in manufacturing. Purity characterization of double-walled carbon nanotubes (DWCNTs) is an increasingly popular topic in the field of carbon nanotechnology. In this study, DWCNTs were synthesized in a catalytic reaction, using Fe:MgO as catalyst and methane or methane/ethanol as carbon feedstock for chemical vapor deposition (CVD). The addition of ethanol as carbon feedstock allowed to investigate the influence of oxygen on the sample quality. The purification of the as-produced material from the metallic particles and the catalyst support was performed by sonication in an acid solution. The influence of the duration of the acid treatment using ultrasound on the sample purity was investigated, and the optimal value of this parameter was found. Transmission electron microscopy (TEM) images confirmed the removal of impurities and served to elucidate the morphology of the samples. The purity of carbon nanotubes was analyzed using thermal gravimetric analysis (TGA). The Raman spectra of the samples, as a measure of the concentration of defects, were also reported.     

Few-layer nano-graphene structures with large surface areas synthesized on a multifunctional Fe:Mo:MgO catalyst system

We present the synthesis of nano-graphene structures with large surface areas and high purity over a high-yield Fe:Mo:MgO catalytic system. Two different hydrocarbon sources, acetylene and methane, were used, and their role in determining the size and morphology of the few-layer graphene sheets was studied. In addition, varying the active metal loading of the catalyst system influenced the formation and type of the resulting carbon nano-structures, e.g., carbon nanotubes or few-layer graphene. Growth of nano-graphene sheets was detected after only 5-min reaction time over this multifunctional catalytic system. High purity and crystalline graphene structures were synthesized indicating another advantage of using this particular catalyst system. This catalytic chemical vapor deposition can be scaled up for large-scale few-layer graphene production.     

Studies of the CO oxidation kinetic regularities on Cu–Co–Fe oxide catalysts,bulk and deposited on the carbon nanotubes

The effect of catalysts of the carbon nanotubes synthesis and of the technology of a Cu–Co–Fe active oxide mass deposition on the kinetic regularities of the CO oxidation reaction has been studied. It has been shown that the experimental data on both catalysts, bulk Cu–Co–Fe and deposited onto carbon nanotubes, agree with the Eley–Readil kinetic scheme. Based on the suggested mechanism, the effective reaction rate constants have been calculated by various methods. It has been shown that the use of Cu–Co–Fe catalysts deposited on carbon nanotubes offers considerable promise.     

Effects of amino group on the properties of carbon nanotubes

The surfaces of multi-walled carbon nanotubes were grafted with amino functional groups by reacting acyl-chloride-functionalized carbon nanotubes (CNTs) with hexamethylene diamine, which improves the surfactivity of CNTs. The dispersity, surface morphology, and thermogravimetry of acid-treated and amino-functionalized CNTs were investigated. Amino-functionalized CNTs were added into epoxy resin to analyze the effects of amino functional groups on the properties of resin composites. It was found that the properties of CNTs, such as morphology and scale, were not affected by amino functional groups, but the dispersity in water was highly improved. Amino-functionalized CNTs are better dispersed in resin matrix, and the mechanical properties of composites are improved significantly, whereas the conductivity of composites is not enhanced as expected.     

洁净单壁碳纳米管在Fe2O3／Al2O3二元气凝胶催化剂上的水辅助合成

分别以甲烷-氧气和甲烷-氢气-水的混合气作为反应气源,利用Fe2O3/Al2O3二元气凝胶作为催化剂于900℃反应30min合成了单壁碳纳米管.并采用SEM、XRD、TEM,高分辨透射电子显微镜(HRTEM)以及Raman光谱等分析技术对所制得的碳产物的结构和形貌进行了表征,以研究反应气氛中水蒸气的引入对单壁碳纳米管生长的影响.结果表明:反应气氛的组成对最终所形成的碳产物的产率和结构有着密切的关联.通过控制氢气载入甲烷-氢气-水的混合气氛中水蒸气的量可以合成低无定形碳的沽净单壁碳纳米管.     

碳纳米管增强PA6复合材料的机理

在探讨碳纳米管的加入对PA6复合材料力学性能影响的基础上，用扫描电镜(SEM)、拉曼光谱和特性粘数法对碳纳米管增强PA6复合材料的机理进行了初步探讨。结果表明，碳纳米管的加入提高了PA6的强度，此时碳纳米管能以纳米状态均匀地分布在基体中，且碳纳米管与PA6之间在界面存在一定的相互作用，同时碳纳米管在原位复合过程中未对高分子链段的增长带来负面影响，反而使PA6的聚合程度略有增大。     

功能化多壁碳纳米管负载铁离子改性双极膜的制备与表征

分别用未功能化的多壁碳纳米管(MWCNTs)、羟基化多壁碳纳米管(MWCNTs-OH)、羧基化多壁碳纳米管(MWCNTs-COOH)、磺酸基化多壁碳纳米管(MWCNTs-SO3H)改性羧甲基纤维素钠(CMC)-聚乙烯醇(PVA)/壳聚糖(CS)-聚乙烯醇双极膜(BPM)的阳离子交换膜层。采用力学性能分析、接触角测定、电流密度-槽电压曲线等对改性前后双极膜的性能进行表征,并测定了改性前后双极膜中Fe~(3+)的流失量。结果表明,经功能化多壁碳纳米管改性后,双极膜的亲水性和力学性能得到了显著提高。功能化多壁碳纳米管和Fe~(3+)对催化中间界面层水解离有协同作用,大大提高了中间界面层水解离效率,降低了双极膜的膜阻抗和槽电压。此外,改性后双极膜中Fe~(3+)的流失量有了明显的下降,从而保持了双极膜结构和催化水解离性能的稳定性。     

Preparation of carbon nanostructures from medium and high ash Indian coals via microwave-assisted pyrolysis

This study is focused on valorizing low value and low quality Indian coals via microwave pyrolysis to produce good quality carbon nanostructures in the heat-treated coal char. The effects of operating conditions such as coal type, coal:susceptor (Fe) mass ratio, and microwave power on product yield and quality are evaluated. The quality of the heat-treated coal char was assessed using different characterization techniques such as electron microscopy, porosimetry, X-ray diffraction, and Raman spectroscopy. The addition of Fe enhanced the heating rates, and led to the formation of carbon nanotubes and nanoparticles. Increasing the proportion of Fe resulted in increase in size of nanotubes and nanoparticles, which is attributed to the fusion of small tubes and particles caused by enhanced localized heating. The yield of carbon nanostructures was more from medium ash (~45%) than from high ash coal (~37%) due to the high fixed carbon and low ash content in the former. In addition to char, coal tar and non-condensable gases were characterized. The major compounds in the coal tar were aromatic hydrocarbons, simple phenols and aliphatic hydrocarbons. Hydrogen and methane were the major gases from medium ash coal, while hydrogen, methane and CO were produced in significant quantities from high ash coal. Microwave-assisted pyrolysis is shown to be a promising process to produce carbon nanostructures in a short time period as compared to conventional thermal processes.