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。     

Potential and challenges of metal-matrix-composites reinforced with carbon nanofibers and carbon nanotubes

With a continuous improvement of the production techniques for carbon nanofibers and carbon nanotubes along with an improvement of the available qualities of the materials, these reinforcements have been introduced into polymers, ceramics and metals. While in the field of polymers first success stories have been published on carbon nanofiller reinforcements, up to now metals containing these types of nanofillers are still a topic of intensive research. Basically a similar situation were found in those days, when micron sized carbon fibers came on the market. Today many applications of carbon fiber reinforced composites are existing, while metals reinforced with conventional carbon fibers are still only found in niche applications.     

Synthesis of individual ultra-long carbon nanotubes and transfer to other substrates

In this article, we report the synthesis of ultra-long carbon nanotubes (CNTs) by thermal chemical vapour deposition method. Ultra-long, individual and aligned CNTs were directly grown on a flat silicon substrate. The orientation of the nanotubes was found parallel to the gas flow direction. The ultra-long CNTs were grown with different transition metallic salts, such as nickel chloride, iron (III) chloride, cobalt acetate and ruthenium acetate, as the catalysts. The influence of the growth conditions, such as growth temperature, reactive gas flow on the length and alignment of the CNTs was studied in detail. By using different catalysts, ultra-long single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs) were successfully grown. These ultra-long CNTs were transferred to other substrates by two methods. (1) The first method is to use polydimethylsiloxane as a stamp. (2) The second method is to use KOH as an etching agent. The diameter and length of the CNTs were characterised by transmission electron microscope, scanning electron microscope, atomic force microscope and Raman spectroscopy. The results indicate that the length of the CNTs can reach up to 4?mm. The diameter of the SWCNTs is in the range of 0.7–2.1?nm and the diameter of the MWCNTs is approximately 150?nm.     

Development of composites incorporating carbon nanofibers and nanotubes

Nanocomposites provide significantly increased modulus, thermal, and electrical properties when compared to traditional reinforced composites. Present work was undertaken to study the microstructure, thermal, and electrical properties of carbon nanostructured reinforced polymer matrix composites. Composites were made with carbon nanofibers and nanotubes (produced by CVD method) as reinforcement with thermoplastic polymers as matrices. The amount of nanoreinforcements was varied between 1 to 5 wt% in different matrices. The problems associated with dispersion of reinforcing materials have been studied. Dispersion of nanofillers in thermoplastics, microstructures, and thermal stability of the reinforced thermoplastics have been studied using SEM, DSC, and TGA. Experimental results show that small amount of carbon nanofillers present in thermoplastic matrix systems enhance the thermal, mechanical, and electrical properties of the composites.     

Ion-exchange iron sorption by carbon nanotubes and nanofibers

We have studied room-temperature equilibrium in systems containing an aqueous Fe(II) or Fe(III) salt solution and carbon nanofibers or carbon nanotubes with various contents of functional groups. The sorption capacity of the sorbents has been determined as a function of contact time, sorbent weight to solution volume ratio, salt concentrations in solution, solution pH, and sorbent “solubility” (degree of functionalization). Equilibrium data have been described by the Langmuir and Freundlich equations, and the sorption kinetics have been represented by a first-order or pseudo-second-order equation. We have demonstrated that the sorption process can be accelerated by physical activation of the system.     

Electrical conductivity of polyvinylidene fluoride nanocomposites with carbon nanotubes and nanofibers

Polyvinylidene fluoride nanocomposites with low loading levels of pristine multiwalled carbon nanotubes, carboxyl functionalized multiwalled carbon nanotubes and vapor grown carbon nanofibers were prepared by a versatile coagulation method. The alternating current electrical conductivity of these composites in the frequency range of 40-12 MHz was investigated. The alternating current conductivity of percolating nanocomposites followed a universal dynamic response. Therefore, both the direct current plateau and frequency dependent regime were observed. The percolation threshold of three composite systems was determined to be 1.0, 0.98, and 1.46 vol.%, respectively. Moreover, the percolative nanocomposites exhibited nonlinear current-voltage responses, demonstrating the presence of tunneling conduction.     

One-step fabrication of carbon nanotubes decorated with graphitic nanoflakes for energy storage systems

We have used a bias-assisted microwave plasma chemical vapor deposition system to synthesize carbon nanotubes presenting graphitic nanoflakes, named coral-like carbon nanotubes, and well-aligned carbon nanotubes on carbon cloth substrates. Applying an external bias of -100 V led to the growth of well-aligned carbon nanotubes. In the absence of an external bias, the coral-like nanotubes presenting graphite nanoflakes were formed. The specific surface areas of the well-aligned and coral-like carbon nanotubes electrodes were 90.31 and 143.69 m2/g, respectively. In terms of energy storage, we estimated the capacitance of the coral-like carbon nanotube electrode to be ca. 194 F/g in an electrolyte of 1 M H2SO4. This value is almost double that of the well-aligned carbon nanotubes electrode (104 F/g), presumably because the presence of the carbon nanoflakes had a positive influence on the migration and adsorption of ions within the electrode. The fitting results indicated that the coral-like carbon nanotubes electrode behaved as a traditional electrochemical capacitor. Durability tests revealed that the coral-like carbon nanotube electrode was reliable, with a decay of 9% in capacitance over 1000 cycles.     

Vapor sensing performances of PVDF nanocomposites containing titanium dioxide nanotubes decorated multi-walled carbon nanotubes

Inorganic nanocarbon hybrid materials are good alternatives for superior electrochemical performance and specific capacitance to their traditional counterparts. Nanocarbons act as a good template for the growth of metal nanoparticles on it and their hybrid combinations enhance the charge transport and rate capability of electrochemical materials without sacrificing the specific capacity. In this study, titanium dioxide nanotubes (TNT) are synthesized hydrothermally in the presence of multi-walled carbon nanotubes (MWCNT) where the latter acts as base template material for the metal oxide nanotube growth. The MWCNT–TNT hybrid material possesses very high dielectric strength and this is used to enhance the dielectric property of the polymer polyvinyledene fluoride (PVDF). Solution mixing was used to prepare the PVDF/MWCNT–TNT nanocomposites by varying the filler concentrations from 0.5 to 2.5 wt%. Excellent vapor sensing was noticed for the PVDF nanocomposites with different rate of response towards commonly used laboratory solvents. The composites and the fillers were characterized for its morphology and structural properties using scanning and transmission electron microscopy, X-ray diffraction studies and infrared spectroscopy. Vapor sensing was measured as relative resistance variations against the solvent vapors, and the dielectric properties of the composites were measured at room temperature during the frequency 10²–10⁷ Hz. Experimental results revealed the influence of filler synergy on the properties of PVDF and the enhancement in the solvent vapor detectability and dielectric properties reflects the ability of these composite films in flexible vapor sensors and in energy storage.     

Hierarchical agglomerates of carbon nanotubes as high-pressure cushions

We report the cushioning behavior of highly agglomerated carbon nanotubes. The nanotube agglomerates can be repeatedly compacted to achieve large volume reduction (>50%) and expanded to nearly original volume without structural failure, like a robust porous cushion. At a higher pressure range (10-125 MPa), the energy absorbed per unit volume is 1 order of magnitude higher than conventional cushion materials such as foamy polystyrene. The structure of hierarchical agglomerates can be controlled for tailoring the cushioning properties and obtaining a lower cushioning coefficient (higher energy absorption) over a wide range of pressures (1-100 MPa). The mechanism was studied in terms of morphology evolution of the nanotube aggregates and pore size distribution during compression.     

Graphite nanoplatelets/multiwalled carbon nanotubes hybrid nanostructure for electrochemical capacitor

Recently, the focus on carbon based nanostructures for various applications has been due to their novel properties such as high electrical conductivity, high mechanical strength and high surface area. In the present work, we have investigated the charge storage capacity of modified graphite nanoplatelets and hybrid structure of graphite nanoplatelets-multiwalled carbon nanotubes (MWNTs). These MWNTs can be used as spacers to reduce the possibility of restacking of graphite nanoplatelets and hence increases the surface area of the hybrid carbon nanostructure thereby high degree of metal oxide decoration is achieved over the hybrid structure. MWNTs were prepared by catalytic chemical vapor deposition technique and further purified with air oxidation and acid treatment. Graphite was treated with conc. nitric acid and sulphuric acid in the volumetric ratio of 1:3 for 3 days and these modified graphite nanoplatelets were further stirred with MWNTs in equal weight ratio to form hybrid nanostructure. Further, ruthenium oxide (RuO2) nanoparticles were decorated on this hybrid structure using chemical route followed by calcination. RuO2 decorated hybrid carbon nanostructure was characterized by using X-ray diffraction, Electron microscopy and Raman spectroscopy. The performance of the hybrid structure based nanocomposite as electrochemical capacitor electrodes was analyzed by studing its capacitive and charge-discharge behaviours using cyclic voltammetry and chronopotentiometry techniques and the results have been discussed.     

Improvement of thermal contact resistance by carbon nanotubes and nanofibers

Interfacial thermal resistance results of various nanotube and nanofiber coatings, prepared by chemical vapor deposition (CVD) methods, are reported at relatively low clamping pressures. The five types of samples examined include multi-walled and single-walled nanotubes growth by CVD, multi-walled nanotubes grown by plasma enhanced CVD (PECVD) and carbon nanofibers of differing aspect ratio grown by PECVD. Of the samples examined, only high aspect ratio nanofibers and thermally grown multi-walled nanotubes show an improvement in thermal contact resistance. The improvement is approximately a 60% lower thermal resistance than a bare Si-Cu interface and is comparable to that attained by commercially available thermal interface materials.     

通过碳纳米管与硫化锌纳米晶体复合提高硫化锌的光催化活性

在碳纳米管悬浮夜中,通过Zn(NO3)2与Na2S反应制备了硫化锌/碳纳米管复合物.研究发现:回流后处理以及合适的加料顺序,对强化硫化锌纳米晶体和碳纳米管的结合非常重要.亚甲基蓝水溶液的光降解试验显示:碳纳米管可有效提高硫化锌纳米晶体的光催化活性.原因是碳纳米管与硫化锌纳米晶体的紧密结合改善了电子迁移的界面,促使硫化锌激发电子快速向碳纳米管迁移,从而抑制了激发电子与空穴的复合.     

Application of laser-induced incandescence to the detection of carbon nanotubes and carbon nanofibers

Laser-induced incandescence applied to a heterogeneous, multielement reacting flow is characterized by temporally resolved emission spectra, time-resolved emission at selected detection wavelengths, and fluence dependence. Two-pulse laser measurements are used to further probe the effects of laser-induced changes on the optical signal. Laser fluences above 0.6 J/cm2 at 1064 nm initiate laser-induced vaporization, yielding a lower incandescence intensity, as found through fluence-dependence measurements. Spectrally derived temperatures show that values of excitation laser fluence greater than this value lead to superheated plasmas with temperatures well above the vaporization point of carbon. The temporal evolution of the emission signal at these fluences is consistent with plasma dissipation processes, not incandescence from solidlike structures. Two-pulse laser experiments reveal that other material changes are produced at fluences below the apparent vaporization threshold, leading to nanostructures with different optical and thermal properties.     

In situ synthesis of ceria decorated carbon nanotubes by chemical vapor deposition

Ceria decorated carbon nanotubes (CNTs) were in-situ synthesized by chemical vapor deposition using a Ni/Ce/Cu catalyst. Ceria nanoparticles, with a diameter of about 3-8 nm, were highly dispersed on the CNTs, and it is believed that they are formed at the same time as the CNTs.     

Nitrogen-doped multiwalled carbon nanotubes decorated with copper(I) oxide nanoparticles with enhanced capacitive properties

We report on the enhanced capacitive properties of a copper(I) oxide nanoparticle (Cu₂O NP)-decorated multiwalled carbon nanotube (MWCNT) forest with nitrogen (N) doping. A careful in situ solid-state dewetting and plasma doping method was developed that ensured homogeneous decoration and contamination-free Cu₂O NPs with N doping on the nanotube sidewalls. The morphology and structure of the hybrid materials were characterised by scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, Raman spectroscopy and X-ray photoemission spectroscopy. The electrochemical performance of the hybrid materials was investigated by cyclic voltammetry and galvanostatic charge/discharge tests in a 0.1 M Na₂SO₄ electrolyte. The electrochemical tests demonstrated that the Cu₂O NP/N-MWCNT electrode exhibits a specific capacitance up to 132.2 F g^?1 at a current density of 2.5 A g^?1, which is 30% higher than that of the pure MWCNT electrode. Furthermore, the electrode could retain the specific capacitance at 85% stability over 1000 cycles. These observations along with the simple assembly method for the hybrid materials suggest that the Cu₂O NP/N-MWCNT could be a promising electrode for supercapacitor applications.     

Fabrication and characterisation of multiwalled carbon nanotubes decorated by magnetic Ni nanoparticles

Abstract

Magnetic carbon nanotube (CNT) composites have been successfully fabricated by employing a microwave assisted method after sensitisation and activation. The phase structures and morphologies of the composites were characterised in detail by transmission electron microscope and X-ray powder diffraction. The results show that sensitisation and activation are absolutely necessary for a dense layer of magnetic nanoparticles obtained on the surface of CNTs. Magnetic measurements using a vibrating sample magnetometer demonstrate that the prepared composites are ferromagnetic.     

Effect of matrix glass transition on reinforcement efficiency of epoxy-matrix composites with single walled carbon nanotubes,multi-walled carbon nanotubes,carbon nanofibers and graphite

This study compares the mechanical and thermal properties of glassy and rubbery epoxy–matrix composites reinforced with 1 and 4 wt.% single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), graphite, and carbon nanofibers (CNFs). The tensile modulus of most glassy composites was higher than that of the epoxy and increased with higher filler concentration and 4% graphite/epoxy and 4% SWCNT/epoxy exhibited approximately the same highest tensile modulus. The elongation of glassy composites was significantly lower than that of the epoxy and decreased with increasing filler loading. Most rubbery composites showed a higher tensile modulus and elongation than the epoxy and the modulus increased with rising filler content and 4% SWCNT/epoxy showed the highest tensile modulus and tensile strength. In the rubbery regime, glassy and rubbery composites displayed a higher storage modulus than the corresponding epoxy and 4 wt.% SWCNT/epoxy composites showed a 300% improvement in storage modulus compared to the epoxy.