由煤或焦炭制备纳米碳质材料的新进展

评述了以煤为碳源制备富勒烯、纳米碳管、竹节形碳管、铁嵌入的纳米碳棒和由碳包覆的金属纳米粒子等各种纳米材料。认为：等离子体电孤放电法是由煤制备各种纳米碳质材料最常用的方法，随电弧条件及电极性质的不同，所制备的纳米碳质材料可有各种不同形态及结构、由于煤是分子固体而石墨是晶格固体，两种碳源的反应机理有明显不同。在等离子体电弧加热时，煤分解并产生许多具有简单芳烃结构的分子，在纳米碳质材料的形成过程中，这些分子可能作为纳米碳质材料的结构单元，同时原煤中的矿物质在合成过程中也起着重要作用，因此煤本身的性质对纳米材料的制备极为重要。煤是成本低廉且储量最丰富的碳源，将是大规模工业化生产纳米碳质材料最好的碳源之一。     

一种基于CVD法的纳米碳管微观分析及场致发射特性的研究

将化学气相沉积法（CVD）制备的纳米碳管提纯后，用透射电镜（TEM）观测了它的微观结构，通过实验对纳米碳管在不同温度下生长的结构特性进行了分析比较，得出了纳米碳管生长的最佳温度为750℃；并对纳米碳管粉体的拉曼（Raman）光谱进行了分析，得到了与透射电镜观测相一致的结论；最后测试了纳米碳管的场致发射特性．     

载气在CVD法制备纳米碳管工艺中的作用

纳米碳管是性能优异的具有准一维特征的纳米材料,CVD法是制备纳米碳管的典型工艺之一。本文以乙炔气体为原料气体、循环失效后的贮氢电极舍金材料作为反应催化剂,研究了在相同反应条件下,CVD法制备纳米碳管过程中载气对纳米碳管形貌和产率的影响。通过对产物TEM观察和TG分析发现,虽然载气不直接参与合成反应但对产物产率和形貌有很大的影响,氢气作为载气可以获得形貌和热稳定性更好的纳米碳管。     

纳米碳管/环氧树脂复合材料的制备及力学性能

报道了利用催化裂解法制备的纳米碳管合成环氧树脂复合材料的技术及工艺条件。利用透射电子显微镜(TEM)对制备的复合材料进行观察表征;通过拉伸及压缩实验对纳米碳管/环氧树脂复合材料的力学性能进行了测试。实验结果表明:纳米碳管的加入可以明显地改变环氧树脂基体材料的力学性能。     

镁钼氧化物催化剂制备多壁纳米碳管的初步研究

采用溶胶-凝胶法合成了可用来催化裂解甲烷大量制备高质量和较高纯度的多壁纳米碳管的镁钼氧化物催化剂．实验表明该催化剂具有较高的活性和催化效率，反应2h后，制备的多壁纳米碳管的量接近原始催化剂量的30倍．并用透射电镜、高分辨透射电镜、激光拉曼和热重分析对制得的粗产品进行了表征，结果表明：碳管的直径在10～22nm之间，且随着反应时间的延长，制备的纳米碳管石墨化程度增加，反应1h后，粗产品中碳管含量达95％，同时，对催化剂的特殊催化生长机理作了讨论，生长过程中多层Mo颗粒析出在MgO载体表面是碳管成柬的主要原因．     

溶胶玻璃原位合成碳纳米管的研究

目前，碳纳米管的各种制备方法如电弧法、激光消融法、催化热解法及化学气相沉积法等，都是在500～3500℃温度范围内经由气固相接触表面合成的，从而使反应的深度和广度都受到了限制．利用固相热解法尝试在溶胶玻璃中原位合成碳纳米管，该方法可以使反应在整个固相范围内同时发生，而不只是在气固相的表面合成．在制备样品的过程中采用了溶胶-凝胶法，成功地将碳源(乙酰丙酮)和催化剂(硝酸钴)均匀地分散在SiO，溶胶玻璃中，制备了纳米级的复合材料．另外，选择了乙酰丙酮作碳源，将碳纳米管的合成温度降到了400℃，实现了在低温固相条件下原位合成碳纳米管．最后通过TEM对生成的纳米碳管进行表征．     

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。     

纳米碳管内包覆外来物质的研究进展

纳米碳管具有纳米尺度的准一维中空结构,这使得在其中空管腔内填充外来物质成为可能。填充纳米碳管的理化性能与填充物的种类、结构、组分密切相关,因而人们可以根据需要自主设计和组装各种类型的填充纳米碳管。通过综述目前在纳米碳管内填充外来物质领域的研究动态,介绍填充预先制备的纳米碳管和在制备纳米碳管的过程中同时包覆外来物质的各种物理和化学制备方法及其可能的微观机制,阐述了这类被填充的纳米碳管在电子工业、信息技术、生物化学以及医学等领域的应用前景,并对今后尚待开展的纳米碳管与填充物质的相互作用规律、这种量子线的物理性能及其阵列的制备技术等研究工作进行了探讨和展望。     

选择冲洗法在碳纳米管内部填充金属粒子

报道一种直接合成纳米碳管衍生材料的方法.利用纳米碳管的表面张力和毛细管作用,经过注入和选择冲洗法的两步法,制备填充铁、钴和镍的纳米碳管.通过选择合适的注入和洗脱溶液,金属粒子只会填充在纳米管内部.使用扫描电镜和扫描透射电镜研究证实金属粒子仅存在于纳米碳管内部.     

用单壁纳米碳管制备葡萄糖生物传感器的研究

以单壁纳米碳管为代表材料,对利用纳米碳管制备葡萄糖生物传感器中纳米碳管的作用和纳米碳管修饰电极的方法、酶的固定化方法及电极种类等因素对传感器性能的影响进行了研究.研究结果表明,纳米碳管的加入能有效地改善传感器的电化学性能,利用二茂铁和单壁纳米碳管共同修饰电极所制得的传感器的性能要好于仅用单壁纳米碳管修饰电极制得的传感器.在酶的固定化方法中,戊二醛交联法要略好于明胶包埋法;而利用铂电极制备出的生物传感器对葡萄糖的响应电流要明显高于利用金电极和玻碳电极制备出的生物传感器.这些结论对于开发纳米碳管在生物传感领域及生命科学相关领域的应用有参考价值.     

Studying the growth of carbon nanotubes on carbon fibers surface under different catalysts and electrochemical treatment conditions

A special electrochemical anodic oxidation (EAO) method was applied to modify the surface of carbon fibers (CFs) with fatty alcohol polyoxyethylene ether phosphate (O₃P), triethanolamine (TEA), fatty alcohol polyoxyethylene ether ammonium phosphate (O₃PNH₄), and ammonium bicarbonate (NH₄HCO₃) used as the electrolyte respectively. Then different catalysts, including Ni, Co, and Cu, were used to catalyze the growth of carbon nanotubes (CNTs) on the surface of CFs. The variation regulation of structure and property of CNTs on CFs surface was investigated by different methods. The results showed that the optimal effect of surface modification of CFs was achieved when O₃PNH₄ served as an electrolyte and the optimal electrochemical treatment intensity (ETI) was 100C/g. Also, with temperature variety, there are different microstructure changes for CNTs that adopt different catalysts. Through the experiment, a uniform catalyst coating was obtained on the surface of CFs after reduction process, which laid the foundation for the growth of uniform and regular CNTs.     

Hybrid carbon nanotube–carbon fiber composites with improved in-plane mechanical properties

In this study carbon nanotubes (CNTs) were grown on carbon fibers to enhance the in-plane and out-of-plane properties of fiber reinforced polymer composites (FRPs). A relatively low temperature synthesis technique was utilized to directly grow CNTs over the carbon fibers. Several composites based on carbon fibers with different surface treatments (e.g. growing CNTs with different lengths and distribution patterns and coating the fibers with a thermal barrier coating (TBC) layer) were fabricated and characterized via on- and off-axis tensile tests. The on-axis tensile strength and ductility of the hybrid FRPs were improved by 11% and 35%, respectively, due to the presence of the TBC and the surface grown CNTs. This configuration also exhibited 16% improvement on the off-axis stiffness. Results suggest that certain CNT growth patterns and lengths are more pertinent than the other surface treatments to achieve superior mechanical properties.     

Grafting carbon nanotubes onto carbon fiber by use of dendrimers

A novel method is developed for grafting carbon nanotubes (CNTs) onto the carbon fiber (CF) surface by use of dendrimers. CF surface is functionalized by an adsorbed dendrimers layer. After an oxidation treatment, CNTs with carboxyl, carbonyl or hydroxyl groups are grafted onto the amino-functionalized CFs via chemical interactions. Homogeneous multi-scale structures with different CNT densities and lengths are gained successfully. Functional groups and morphology of the resulting materials are examined by X-ray photoelectronspectroscopy (XPS), Fourier transform-infrared spectrometer (FTIR), and scanning electron microscopy (SEM).     

On the role of activation mode in the plasma- and hot filaments-enhanced catalytic chemical vapour deposition of vertically aligned carbon nanotubes

Catalytic chemical vapor deposition (CCVD) with different activation modes (thermal; hot filaments-enhanced; direct current plasma-enhanced and both hot filament and direct current plasma-enhanced) are achieved in order to grow vertically aligned carbon nanotubes (VA CNTs). By widely varying the power of the different activation sources of the gas (plasma, hot filaments, substrate heating) while keeping identical the substrate temperature (973 K) and the catalyst preparation, the results point out the important role of ions in the nucleation of carbon nanotubes (CNTs), as well as the etching behaviour of highly activated radicals such as H˙ in the selective growth of vertically aligned films of CNTs. Moreover, it is demonstrated that, within the deposition conditions (temperature, pressure, flow rate) used in this study, oriented carbon nanotubes can be grown only when both ions, mainly generated by the gas discharge plasma, and highly reactive radicals, mainly formed by the hot filaments, are produced in the gas phase. We propose that highly energetic ions are needed to nucleate the carbon nanotubes by increasing the carbon concentration gradient whereas the highly reactive radicals allow the selective growth of vertically aligned CNTs by preventing carbon deposition on the whole surface through chemical etching of edge carbons in graphene sheets.     

A chemical method to graft carbon nanotubes onto a carbon fiber

A simple method is developed for grafting carbon nanotubes (CNTs) onto a carbon fiber surface. CNT and carbon fiber undergo an oxidation treatment. Oxidation generates oxygen, like carboxyl, carbonyl or hydroxyl groups, or amine groups on nanotubes and carbon fiber surface. Functionalized CNTs are dispersed in a solvent and deposited on carbon fibers. The bonds between CNT and carbon fiber are operated by esterification, anhydridation or amidization of the chemical surface groups. The resulting materials are characterized by scanning electron microscopy (SEM). CNTs form a 3D network around the carbon fibers. Likewise, CNT bonding between two fibers is observed.     

Integrating carbon nanotube into activated carbon matrix for improving the performance of supercapacitor

A method of in situ integrating carbon nanotubes (CNTs) into activated carbon (AC) matrix was developed to improve the performance of AC as a supercapacitor electrode. Glucose solution containing pre-dispersed CNTs was hydrothermally carbonized to be a char-like intermediate product, and finally converted into a “tube-in-AC” structure by the chemical activation using KOH. The “tube-in-AC” composite had oxygen content of 12.98 wt%, specific surface area of 1626 m²/g and 90% of 1–2 nm micropores. It exhibited capacitance of 378 F/g in the aqueous KOH electrolyte and excellent cyclibility under high current, that is, the capacitance only decreased 4.6% after 2000 cycles at scanning rate of 100 mV/s. These performances of “tube-in-AC” electrode are better than those of commercial AC electrodes, post-mixed with CNTs or carbon black.     

Purification of single-walled carbon nanotubes

The discovery of carbon nanotubes (CNTs) created much excitement and stimulated extensive research into the properties of nanometer-scale cylindrical networks. From then on, various methods for the synthesis and characterization of aligned CNTs-both single-walled (SWCNTs) and multi-walled (MWCNTs) by different methods have been hotly pursued. Unfortunately, most methods currently in use produce raw multi component solid products, only a small fraction of which contains carbon nanotubes. The balance of the material is composed of residual catalyst particles (some of which are encased in concentric graphitic shells), fullerenes, other graphitic materials and amorphous carbon. These impurities cause a serious impediment for their detailed characterization and applications. If the carbon nanotube is ever to fulfill its promise as an engineering material, large, high quality aliquots will be required. A number of purification methods involving elimination processes such as physical separation, gas phase and liquid phase oxidation in combination with chemical treatments have been developed for nanotube materials. Though the quantitative determination of purity remains controversial, reported yields are best regarded with an appropriate level of skepticism on the method of assay. In this article, a review is given on the past and recent advances in purification of SWCNTs.     

Purification and separation of single-walled carbon nanotubes (SWCNTs)

Purification or separation of single-walled carbon nanotubes (SWCNTs) is one of the most fundamental steps before they are used for research and technological applications. Based on the difference of their physical and chemical properties, separation of carbon nanotubes (CNTs) can be categorized into three groups: length separation, metallic and semiconducting tubes separation and chirality separation. In this review, we first briefly review the purification of CNTs and then focus on the different methods for the separation of CNTs.     

Substrate engineering for Ni-assisted growth of carbon nano-tubes

The growth of carbon multi-walled nano-tubes (MWCNTs) using metal catalyst (e.g. Ni, Co, and Fe) has been extensively investigated during the last decade. In general, the physical properties of CNTs depend on the type, quality and diameter of the tubes. One of the parameters which affects the diameter of a MWCNT is the size of the catalyst metal islands. Considering Ni as the metal catalyst, the formed silicide layer agglomerates (island formation) after a thermal treatment. One way to decrease the size of Ni islands is to apply SiGe as the base for the growth. In this study, different methods based on substrate engineering are proposed to change/control the MWCNT diameters. These include (i) well-controlled oxide openings containing Ni to miniaturize the metal island size, and (ii) growth on strained or partially relaxed SiGe layers for smaller Ni silicide islands.     

Laser-induced graphene and carbon nanotubes as conductive carbon-based materials in environmental technology

Nanotechnology and nanomaterials have attracted interest due to their potential in mitigating contemporary environmental challenges, such as the stressors imposed by increased industrial and agricultural activities, and the deterioration of air, soil and water quality. In particular, advanced technologies that harness carbon-based nanomaterials are poised to emerge as tools that provide new solutions for the global water crises. These tools include, electrically conductive membrane processes, which uniquely combine a separation process with a functional surface. In this respect, laser-induced graphene (LIG) and carbon nanotubes (CNTs) are electrically conductive carbon nanomaterials that hold great utility in a multitude of environmental applications, including the development of fouling-resistant systems for desalination and water treatment, enhanced separation methods, and innovative pollutant sensing and electrocatalytic platforms. Consequently, this review article describes and compares some important recent advances in LIG- and CNT-based electroactive surfaces. The discussion of LIG as an emerging carbon material set in context with CNTs is intended to shed light on future directions and development possibilities to meet the growing global challenges in terms of water treatment applications of both materials as well as other electrically conductive carbon-based nanomaterials exhibiting exceptional performance and versatility.