Growth of carbon nanotubes on diatomite

We report the formation of vertical carbon nanotubes utilizing diatomite as a substrate. This new material combines the advantages of carbon nanotubes and diatomite in one material. The SEM investigations showed that the average diameter of the carbon nanotubes was 60 nm and the growth was through the tip growth mechanism. Raman spectroscopy was also used for the carbon nanotubes characterization and showed two intensive peaks around 1350 cm⁻¹ and 1580 cm⁻¹ and several peaks at low frequency range from 100 cm⁻¹ to 500 cm⁻¹ which are assigned to the radial breathing mode (RBM) and used as a characteristic of single wall carbon nanotubes. The photoluminescence measurements at the room temperature showed two very narrow intensive overlapping peaks near the ultraviolet range at energy of about 3 eV. And there are two peaks with lower intensity in the infrared region at 830 nm and at 940 nm (or 1.49 eV, 1.3 eV respectively).     

Effect of hydrogen plasma pretreatment on growth of carbon nanotubes by MPECVD

We have grown carbon nanotubes (CNTs) with a microwave (μW) plasma enhanced chemical vapor deposition (MPECVD) method, which has been regarded as one of the most promising candidates for the synthesis of CNTs due to the vertical alignment, the low temperature and the large area growth. We use methane (CH₄) and hydrogen (H₂) gas for the growth of CNTs. Ni catalytic layer (10 nm thick) were deposited on the Ti-coated Si substrate by RF magnetron sputtering method. In this work, we report the effects of pretreatment μW power on the growth of CNTs. We have pretreated the Ni catalytic layer in different μW power (600, 700, and 800 W) and grown same μW power (800 W). Scanning electron microscopy (SEM) images show Ni catalytic layer diameter and density are varied dependent with their pretreatment conditions. Raman spectroscopy of CNTs shows that I_D/I_G ratios and G-peak positions vary with pretreatment conditions.     

Growth of carbon nanotubes on glass substrate by MPECVD

We have grown carbon nanotubes (CNTs) with a microwave plasma-enhanced chemical vapor deposition (MPECVD) method, which has been regarded as one of the most promising candidates for the synthesis of CNTs due to the vertical alignment, the low temperature and the large area growth. We had used methane (CH₄) and hydrogen (H₂) gas for the growth of CNTs. 10-nm-thick Ni catalytic layer were deposited on the Ti-coated glass substrate by RF magnetron sputtering method. In this work, we report the low-temperature growing properties of the CNTs on glass substrate with a MPECVD. We have pretreated the Ni/Ti/glass catalytic layer in different microwave power (600, 700, 800, and 900 W) and grown the CNTs in the same microwave power (800 W). SEM (Scanning electron microscopy) images of the Ni catalytic layer shows the diameter and density variation to be dependent with the pretreatment conditions. Raman spectroscopy of CNTs shows that the synthesized CNTs were multi-wall CNTs.     

Preparation of CVD diamond coatings on gamma titanium aluminide using MPECVD with various interlayers

CVD diamond coatings were deposited on to γ-TiAl surfaces using a microwave plasma enhanced CVD to improve wear properties and the performance of γ-TiAl. Diamond coatings were directly deposited on to γ-TiAl substrates and deposited on to TiC, Ti₅Si₃, Al₂O₃ + TiO₂, and Si interlayers prepared on γ-TiAl substrates. The diamond coatings deposited directly on γ-TiAl suffered severe delamination and cracked. Those deposited on TiC and Ti₅Si₃ interlayers partially delaminated, whereas those deposited on Al₂O₃ + TiO₂ and Si interlayers adhered well to the underlying surfaces. The diamond films obtained were characterized using scanning electron microscopy, Raman spectroscopy, and X-ray diffraction. Raman spectra showed that polycrystalline and nanocrystalline diamond films grew on γ-TiAl. Residual internal stresses of the diamond coatings deposited on interlayered-γ-TiAl were estimated experimentally from Raman spectra. The coatings prepared on Al₂O₃ + TiO₂/γ-TiAl and Si/γ-TiAl showed lower residual stresses.     

Direct growth of aligned carbon nanotubes on bulk metals

There are several advantages of growing carbon nanotubes (CNTs) directly on bulk metals, for example in the formation of robust CNT-metal contacts during growth. Usually, aligned CNTs are grown either by using thin catalyst layers predeposited on substrates or through vapour-phase catalyst delivery. The latter method, although flexible, is unsuitable for growing CNTs directly on metallic substrates. Here we report on the growth of aligned multiwalled CNTs on a metallic alloy, Inconel 600 (Inconel), using vapour-phase catalyst delivery. The CNTs are well anchored to the substrate and show excellent electrical contact with it. These CNT-metal structures were then used to fabricate double-layer capacitors and field-emitter devices, which demonstrated improved performance over previously designed CNT structures. Inconel coatings can also be used to grow CNTs on other metallic substrates. This finding overcomes the substrate limitation for nanotube growth which should assist the development of future CNT-related technologies.     

碳纳米管的改性与应用

本文主要介绍对碳纳米管不同位置的修饰以及其应用等方面的研究进展,并对今后的研究方向进行展望.     

直接在金属基片上生长超长宏观定向碳纳米管

在水辅助氧化作用下，直接在金属镍片上生长出宏观上定向生长的螺旋状碳纳米管，其长度达到7mm，直径在100-200nm，测试其场发射特性，开启场强为1．6V／μm，最大发射电流密度可达6mA／cm^2。     

碳纳米管在催化反应中的应用

综述了近年来碳纳米管用作催化剂或者载体的研究进展,与传统的催化剂相比,碳纳米管作催化剂或载体都表现出更好的活性、选择性和稳定性.     

Curved carbon nanotubes: From unique geometries to novel properties and peculiar applications

Incorporating pentagons and heptagons into the hexagonal networks of pristine carbon nanotubes （CNTs） can form various CNT-based nanostructures, as pentagons and heptagons will bend or twist the CNTs by introducing positive and negative curvature, respectively. Some typical so-made CNT-based nanostructures are reviewed in this article, including zero-dimensional toroidal CNTs, and one-dimensional kinked and coiled CNTs. Due to the presence of non-hexagonal rings and curved geometries, such nanostructures possess rather different structural, physical and chemical properties from their pristine CNT counterparts, which are reviewed comprehensively in this article. Additionally, their synthesis, modelling studies, and potential applications are discussed.     

碳纳米管的等离子体功能化及其聚苯胺复合材料的制备

采用等离子体技术对碳纳米管(CNTs)功能化,而后与苯胺原位聚合制备CNTs/聚苯胺(PANI)复合材料。电导测试结果表明:相对于CNTs的强酸氧化法(0.936S/cm),等离子体处理更易获得高电导率的复合材料(2.86S/cm)。相应的最佳等离子体工艺参数为:处理功率50W、时间5min、压力0.08Torr、温度110℃、磁场线圈电流0.08A及电极距离5cm。SEM观察发现:聚合后,CNTs的光滑表面转变成粗糙结构,同时管径增加了80nm。XRD、FTIR及Raman结果均证实:PANI被均匀包覆于CNTs的表面。     

在金属薄膜衬底上定向生长碳纳米管

研究和探讨了预处理和温度影响对碳纳米管定向生长机制的作用。利用等离子体增强化学气相沉积(PECVD)的方法,以金属Fe薄膜为催化剂,在单晶硅衬底上定向生长碳纳米管(CNT)。通过给予不同的预处理时间和温度条件,在Fe/Si衬底上沉积出碳纳米管,通过扫描电子显微镜(SEM)进行表征,将不同的条件下生长的碳纳米管进行对比。结果表明,在适当的工艺条件下,可以生长出方向性好,纯度高的碳纳米管。     

碳纳米管/高分子阻燃复合材料研究进展

综述了近年来各种类型的碳纳米管(CNTs)/高分子阻燃复合材料的研究进展,重点对其制备方法、阻燃性能进行了分析总结,并阐释了CNTs与传统阻燃剂复配时对复合物的协同阻燃作用,最后探讨了以CNTs作为阻燃添加剂的阻燃机理,展望了CNTs作为阻燃添加剂的应用前景。     

Effects of boron-doping on the morphology and magnetic property of carbon nanotubes

Boron carbide nanotubes (nano-fibers) was prepared by B powder and carbon nanotubes (CNTs) at high temperature in a vacuumed quartz tube. The morphology, microstructure, component and magnetic property of samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and magnetic property measurement system (MPMS) controller. The results showed that B-doping CNTs have great difference in the morphology and magnetic property from those of pristine CNTs. __________ Translated from Journal of Functional Materials, 2006, 37(9): 1398–1400 (in Chinese)     

Electrodes based on nano-tree-like vanadium nitride and carbon nanotubes for micro-supercapacitors

Vanadium nitride(VN) was deposited by DC-sputtering on a vertically aligned carbon nanotube(CNTs)template for the purpose of nano-structuration. This led to the fabrication of hierarchically composite electrodes consisting of porous and nanostructured VN grown on vertically aligned CNTs in a nano-treelike configuration for micro-supercapacitor application. The electrodes show excellent performance with an areal capacitance as high as 37.5 m F cm~(-2) at a scan rate of 2 mV s~(-1) in a 0.5 MK_2SO_4 mild electrolyte solution. Furthermore, the capacitance decay was only 15% after 20,000 consecutive cycles. Moreover,the capacitance was found to increase with VN deposit thickness. The X-ray photoelectron spectroscopy analyses of the electrodes before and after cycling suggest that the oxide layers that form at the VN surface is the responsible for the redox energy storage in this material. Such electrodes can compete with other transition metal nitride based electrodes for micro-supercapacitors.     

Direct electrical measurements on single-molecule genomic DNA using single-walled carbon nanotubes

A unique nanoelectronic platform, based on single-walled carbon nanotubes (SWNTs), has been fabricated for measuring electrical transport in single-molecule DNA. We have tested 80 base pairs of single- and double-stranded DNA (ssDNA and dsDNA, respectively) of complex base sequences. About a 25-40 pA current (at 1 V) was measured for the dsDNA molecule covalently attached to the SWNT electrode at its termini. In the absence of base pair stacking, a ssDNA carries a feeble current of approximately 1 pA or less. Gate-voltage-dependent I-V characteristics revealed that the bridging dsDNA molecule acts as a p-type channel between SWNT source and drain electrodes.     

炭/炭复合材料表面等离子体喷涂羟基磷灰石涂层的生物学性能

采用等离子体喷涂法在炭/炭复合材料基体上制备了羟基磷灰石涂层,并对所制材料开展体外模拟和试验.结果表明:在体外模拟生理环境的Ringer溶液中,涂层组成相随浸泡时间发生变化.涂层表面有新生羟基磷灰石结晶析出并聚集长大.骨内种植试验期间,动物末出现排异和炎症反应,涂层与基体结合良好.组织学观察发现,涂层与骨界面处有明显的组织改建和新骨形成形态.炭/炭复合材料表面等离子体喷涂羟基磷灰石涂层作为一种潜在的骨组织修复材料具有良好的应用前景.     

Fibrous growth of strontium substituted hydroxyapatite and its drug release

The effect of strontium on the crystallization of helical ribbon of hydroxyapatite (HAp) was investigated by single diffusion technique in silica gel matrix at 27 °C and physiological pH. Fibers of HAp were obtained on addition of strontium. The length of the HAp fibers, were found to decrease as the strontium substitution increases. The presence of strontium ion increased the crystallinity as well as crystallite size of HAp. The strontium substituted HAp (Sr-HAp) has similar stoichiometry to that of biological apatite. Sr-HAp was found to have increased surface area (35%) compared to control. Further, strontium substitution leads to an enhancement of in vitro bioactivity. The cumulative in-vitro amoxicillin drug release in phosphate buffer solution (PBS, pH 7.2) showed a prolonged release profile for Sr-HAp.     

Selectivity in the hydroxyapatite synthesis from eggshell using different thermal treatments

Hydroxyapatite can be obtained, selectively, from eggshells using different thermal treatments. The thermal treatment controls, to a large extent, the efficiency of the chemical reaction to produce this particular inorganic phase. Different calcium phosphate phases can be obtained just by changing the thermal treatment. Particularly, it is possible to synthesize Hidroxyapatite and Whitlockita in different proportions by adjusting the heating rate of the reacting compounds. Electronic Publication     

The effect of multi-walled carbon nanotubes/hydroxyapatite nanocomposites on biocompatibility

In the present study, multi-walled carbon nanotubes/hydroxyapatite (MWCNTs/HA) nanocomposites with various MWCNT contents were manufactured by sol-gel processing. The MWCNTs/HA powder was characterized using field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman analysis. The results show that the MWCNTs were fully covered with HA nanoparticles and help forming the crystallized hydroxyapatite. In addition, in vitro tests highlighted the excellent biocompatibility of the MWCNTs/HA composite.     

Controlled growth of carbon nanotubes

Carbon nanotubes have extraordinary mechanical and electronic properties and hold great promise for future applications. The most important aspects of this structure are its low density, high aspect ratio, one dimensionality, high mechanical strength and high electrical and thermal conductivity. We present a short, state-of-the-art account of tailored nanotube growth. To provide these properties in real devices there exists a need for producing nanotubes on substrates. The challenge in the creation of mesoscale nanotube-based architectures and tailored nanotube networks consisting of thousands of tubes in a predefined order is obviously great. Currently, chemical vapour deposition (CVD) appears to be the most powerful method for achieving such required structures. We describe our work on a new synthesis method, based on catalytic CVD using mainly gas-phase catalyst delivery. Gas-phase catalyst delivery allows us to assemble single-walled and multi-walled carbon nanotubes in predetermined multiple orientations on substrates to build one- to three-dimensional architectures. We are able to control, to a large extent, the types of nanotubes produced, their lengths, locations and their orientations. The ability to make mesoscale architectures with nanotubes should lead us to develop applications in areas such as nano-electromechanical systems.