Enhanced field emission from nano-graphite coated carbon nanotubes

An effective method by low energy carbonhydrogen ion treatment to enhance field emission of the carbon nanotubes (CNTs) is demonstrated. Comparing with control, field emission (FE) currents of the CNTs by carbonhydrogen ion irradiation increased, and the turn-on field and the threshold field decreased significantly. The structure characteristic revealed by transmission electron microscopy demonstrates that CNTs are coated by nano-graphite particles after being treated with low energy carbonhydrogen ion and that there are large quantities of defects and grain boundaries in the coated layer. It is considered that the coating layer can decrease the effective surface work function of CNTs and correspondingly increase field emission. In addition, the defects, the grain boundaries and the C-H dipoles forming in the process of the low energy ions irradiation can effectively enhance the field emission.

The Electrocatalytic Activity of Bare Pyrolytic Graphite and Single Wall Carbon Nanotube Modified Glassy Carbon Sensors Is Same for the Quantification of Bisoprolol Fumarate

A comparison of voltammetric behavior of bisoprolol fumarate (BF) at edge and basal plane pyrolytic graphite electrodes (EPPGE/BPPGE) has been made with single wall carbon nanotube modified glassy carbon. The electrochemical properties are investigated exercising the cyclic voltammetry and square wave voltammetry (SWV). Enhanced peak current associated with bisoprolol fumarate oxidation at EPPGE is due to its better electron transfer property. Quantification of bisoprolol fumarate was carried out at pH 7.2 at both the pyrolytic graphite electrodes. Well-defined peak has been observed at ~ 792 and 954 mV at EPPGE and BPPGE respectively for bisoprolol fumarate oxidation. The detection limit is found to be 2.8 × 10–7 M and 7.3 × 10–7 M for EPPGE and BPPGE respectively. A comparison of common quantification parameters for bisoprolol at carbon nanotube modified glassy carbon electrode and bare BPPGE and EPPGE has been made and it is observed that carbon naotube modified glassy carbon exhibits sensitivity and detection limit close to that observed at bare basal plane pyrolytic graphite electrode. The method developed is applicable for determination of bisoprolol fumarate in pharmaceutical preparations and real samples.

Ultra Sensitive Determination and Preconcentration of Cd²⁺, Cu²⁺and Pb²⁺after Multi-Walled Carbon Nanotubes Adsorption

Multi-Walled carbon nanotubes are used as preconcentrating probes for the quantitative determination of trace cadmium, copper and lead in environmental and biological sample using graphite Furnace Atomic Absorption Spectrometry and inductively coupled Plasma Optical Emission spectrometry. The method is based on the electrostatic interactions of positively charged Cd+, Cu+ and Pb+ with the negatively charged multi-walled carbon nanotubes (MWCNTs) for the preconcentration and isolation of analytes from sample solutions. Effective preconcentration of trace cadmium, copper and lead was achieved in a pH range of 5 - 7, 5 - 7 and 4 - 7, respectively. The retained cadmium, copper and lead were efficiently eluted with 0.3 mol·L-1 HCl for graphite Furnace Atomic Absorption Spectrometry determination. The multi-walled carbon nanotubes packed micro-column exhibited fairly fast kinetics for the adsorption of cadmium, copper and lead, permitting the use of high sample flow rates up to at least 3 mL·min-1 for the flow injection on micro-column preconcentration without the loss of the retention efficiency. The detection limits (3σ) were 0.03, 0.01 and 0.5 ng·mL-1 for Cd, Cu and Pb, respectively. The relative standard deviation under optimum condition is less than 2.9% (n = 10). The developed method was successfully applied to the determination of trace Cd, Cu and Pb in a variety of environmental and biological samples.

Single-Wall Carbon Nanotube Growth from Graphite Layers-a Tight Binding Molecular Dynamics Simulation

The growth of single-wall carbon nanotube from graphite layers is studied by tight binding molecular dynamics simulation. Given temperature of 2500 K or 3500 K and an interval of 0.25 nm for the two layers of graphite, a single-wall carbon nanotube with a zigzag shell will be produced. On the other conditions the carbon nanotube cannot grow or grows with too many defects. All carbon nanotube ends have pentagons which play an important role during the tube ends closing.

Self-assembled synthesis of oxygen-doped g-C3N4 nanotubes in enhancement of visible-light photocatalytic hydrogen

Currently,photocatalytic water splitting is regarded as promising technology in renewable energy generation.However,the conversion efficiency suffers great restriction due to the rapid recombination of charge carriers.Rational designed the structure and doping elements become important alternative routes to improve the performance of photocatalyst.In this work,we rational designed oxygen-doped graphitic carbon nitride(OCN)nanotubes derived from supermolecular intermediates for photocata lytic water splitting.The as prepared OCN nanotubes exhibit an outstanding hydrogen evolution rate of 73.84μmol h^(-1),outperforming the most of reported one dimensional(1D)g-C_(3)N_(4) previously.Due to the rational oxygen doping,the band structure of g-C_(3)N_(4) is meliorated,which can narrow the band gap and reduce the recombination rate of photogene rated carriers.Furthermore,the hollow nanotube structure of OCN also provide multiple diffuse reflection during photocata lytic reaction,which can significantly promote the utilization capacity of visible light and enhance the photocatalytic water splitting performance.It is believed that our work not only rationally controls the nanostructure,but also introduces useful heteroatom into the matrix of photocatalyst,which provides an effective way to design high-efficiency g-C_(3)N_(4) photocatalyst.

基于响应面法的地热钻采碳纳米管复合水泥基材料的研究

针对现有导热固井水泥存在的性能不足问题,本文研制了一种新型地热钻采碳纳米管复合水泥基材料(CNTs-CC)。首先,选用石墨、氮化硅作为主要导热填料,硅微粉作为热稳定材料,碳纳米管作为协同增强填料,初步研制出纳米复合水泥材料基础液;其次,基于响应曲面法Box-Behnken试验设计,开展17组配比优化试验,构建了以2 d抗压强度和导热系数为响应指标的二次多项式预测模型,结合方差分析和响应曲面考察了各因素对响应指标的影响,并得到胶凝材料最优配比;最后,对复合水泥基材料的工程性能进行评估,并结合XRD与SEM研究了材料的水化机理。结果表明:复合水泥基材料的导热性能与抗压强度受多因素交互作用影响,其中早强剂与减水剂交互影响显著;CNTs-CC水泥石28 d抗压强度达8.15 MPa,导热系数为2.236 W/(m·K);导热填料不参与水化过程,碳纳米管粉可发挥“填充”及“桥连”效应,外加剂调控水化进程。

碳基材料应用的研究进展

碳基材料因结构多样、表面化学性质丰富、可调控性强、比表面积大、孔结构丰富、热稳定性好、机械强度高及吸附容量高等优点被广泛应用于催化及储能领域。分析了石墨烯、碳纳米管、碳纳米线及碳化硅等碳基材料的制备方法、改性方法及应用领域,综述了碳基材料的研究进展,对其未来发展方向进行了展望。

碳材料活化过硫酸盐降解有机污染物的研究进展

基于过硫酸盐的高级氧化技术具有操作简单、高效环保等优点,碳材料活化过硫酸盐被广泛应用于有机污染物的降解过程中。碳材料表面富含多孔结构、各种活性官能团且其本身具有优异的导电性和化学稳定性,能够有效地活化过硫酸盐通过自由基或非自由基途径降解有机污染物,在催化领域发挥出较大的应用潜力,有望成为新一代的绿色催化剂。本文综述了石墨烯、碳纳米管、活性炭、生物炭以及石墨相氮化碳在过硫酸盐高级氧化中的实际应用。

锂碳复合材料研究进展

金属锂具有较高的理论比容量和较低的密度,将其作为负极材料,电池将获得较高的能量密度。然而,在实际应用中受不可控的锂枝晶、非活性锂的形成和积累、锂的体积膨胀及不稳定的固体电解质膜等因素的影响,限制了金属锂的商业化应用。将金属锂与碳材料复合制备锂碳材料可有效缓解上述问题。锂碳复合材料包括锂-石墨烯复合材料、锂-石墨复合材料、锂-碳纤维复合材料和锂-碳纳米管复合材料等。分类介绍了锂碳复合材料及其制备方法和电化学性能,并指出每类锂碳复合材料的优势和存在的问题,最后展望了未来锂碳材料的发展方向。

球磨法制备硅基负极材料及其增强的储锂性能研究

以微米硅为原料,采用高能球磨法制备碳纳米管/还原氧化石墨烯/硅负极材料。采用扫描电子显微镜、X-射线衍射、傅里叶红外光谱和电化学测试技术对材料的晶型结构、形貌及电化学性能等进行研究。结果表明,球磨在保持硅的晶体结构不发生变化的前提下,既可降低硅颗粒的尺寸,又能促进氧化石墨的部分还原和剥离,使其转为石墨烯。当碳纳米管添加量为1%、氧化石墨添加量为5%时,所制备的负极材料具有较好的电化学性能,在0.4 A/g的电流密度下循环200次,放电比容量为1779.7 mAh/g。这主要是因为碳纳米管和还原的氧化石墨烯能够在硅负极建立高效的导电网络,增加电子的传递速率,同时降低硅负极脱嵌锂过程时锂离子的电荷转移电阻和提高锂离子扩散速率。

Influence of adding carbon nanotubes and graphite to Ag-MoS_2 composites on the electrical sliding wear properties

Silver matrix composite brushes were fabricated by means of powder metallurgy, which included pressing at 300 MPa and then sintering for 1 h in pure H2 protective atmosphere at 700 ℃ and repressing at 500 MPa. Four kinds composites with different compositions were produced, and the mechanical properties and electrical wear performance were investigated. The results showed that the composite added with carbon nanotubes had a higher hardness and strength, a lower contact voltage drop and an excellent anti-wear property in electrical sliding wear, because of the reinforcement ability of carbon nanotubes. Adding graphite to the composite also decreased the wear loss and contact voltage drop, because graphite had an electrical current conducting ability which not only made the current pass the lubricating films easily but also eliminated and reduced the arc and spark effectively.

Efficient Photoelectrochemical Water Splitting by g-C_3N_4/TiO_2 Nanotube Array Heterostructures

Well-ordered TiO_2 nanotube arrays(TNTAs)decorated with graphitic carbon nitride(g-C_3N_4) were fabricated by anodic oxidization and calcination process.First, TNTAs were prepared via the anodic oxidation of Ti foil in glycerol solution containing fluorinion and 20%deionized water. Subsequently, g-C_3N_4 film was hydrothermally grown on TNTAs via the hydrogen-bonded cyanuric acid melamine supramolecular complex. The results showed that g-C_3N_4 was successfully decorated on the TNTAs and the g-C_3N_4/TNTAs served as an efficient and stable photoanode for photoelectrochemical water splitting. The facile deposition method enables the fabrication of efficient and low-cost photoanodes for renewable energy applications.

Effect of Carbon Source on Crystal Morphology of SiC in-situ Formed in AI_2O_3-Si-C Matrix

Three kinds of Al2O3- Si- C matrix specimens were prepared using tabular corundum powder and Si powder as starting materials,ultrafine flake graphite,nano carbon black,and carbon nanotubes as carbon sources,respectively,to research the effect of micro or nano carbon materials on structure and morphology of formed Si C crystals. The specimens were fired at 1 000,1 200 and 1 400℃ for 3 h in carbon-embedded condition,respectively.The phase composition was studied by XRD and the crystal morphology of Si C was investigated by FESEM. The results show that：（ 1） the amount of Si C increases with the firing temperature rising;（ 2） the in-situ reaction mechanism and the formed Si C crystal morphology vary with carbon source： carbon nanotubes are generally converted into Si C whiskers by carbon nanotubes-confined reaction; Si and nano carbon black react to nucleate quickly,and the nucleated Si C crystals grow evenly in all directions forming Si C particles; Si C whiskers are produced from edge to internal of ultrafine flake graphite.

Carbon nanotubes/graphitic carbon nitride nanocomposites for all-solid-state supercapacitors

All-solid-state supercapacitors with high power density and working stability are high-efficiency energy storage devices for smart electronic equipment. Developing electrode materials with fast ions and electrons transport is critical to improving the energy storage capability. Here, we report carbon nanotubes/graphitic carbon nitride nanocomposites with large specific surface area, porous structure and high electrical conductivity toward high-performance supercapacitors. The large surface area with porosity provides reservoir for ion accommodation during charge-discharge processes, and the high conductivity facilitates electrons and ions transport. Furthermore, nitrogen sites in electrodes contribute significant pseudocapacitance for supercapacitors. The nanocomposites based device gives a high specific capacity of 148 F g^(–1) at current density of 1 A g^(–1) with good rate capability from 1 to 10 A g^(–1). Additionally, the device displays excellent working stability with capacitance retention of 93%even after 10000 cycles at 1 A g^(–1) under 0.8 V in air. This study sheds light on design of nanocomposites with highly efficient charge transfer and will accelerate development of next-generation solid state energy devices.

Plasma-enhanced Deposition of Nano-Structured Carbon Films

By pre-treating substrate with different methods and patterning the catalyst, selective and patterned growth of diamond and graphitic nano-structured carbon films have been realized through DC Plasma-Enhanced Hot Filament Chemical Vapor Deposition (PE-HFCVD). Through two-step processing in an HFCVD reactor, novel nano-structured composite diamond films containing a nanocrystalline diamond layer on the top of a nanocone diamond layer have been synthesized. Well-aligned carbon nanotubes, diamond and graphitic carbon nanocones with controllable alignment orientations have been synthesized by using PE-HFCVD. The orientation of the nanostructures can be controlled by adjusting the working pressure. In a Microwave Plasma Enhanced Chemical Vapor Deposition (MW-PECVD) reactor, high-quality diamond films have been synthesized at low temperatures (310℃-550℃) without adding oxygen or halogen gas in a newly developed processing technique. In this process, carbon source originates from graphite etching, instead of hydrocarbon. The lowest growth temperature for the growth of nanocrystalline diamond films with a reasonable growth rate without addition of oxygen or halogen is 260℃.

Evaluation and Characterization of Mechanical,Electrical,and Thermal Properties of Polymer Nanocomposites Reinforced with Different Allotropes of Carbon

The present work aims to present the results based on the processing of nanocomposites,which consist of matrix materials like epoxy and filler materials such as conjugated nanomaterials/allotropes of carbon,namely,carbon black,graphite,and multiwalled carbon nanotube(MWCNT)used for targeted applications.To improve the physical and chemical properties and to facilitate a better interfacial interface between the polymer and nanotube,functional MWCNT is used during the preparation of the composite.The prime objective of the study is to establish the thermal,mechanical,and electrical properties of nanocomposites using experimental methods.It has been observed from the experimental results that carbon nanotube(CNT)based composite exhibits higher mechanical(tensile and hardness)and thermal properties as compared with the others.The electrical properties are found to be better in a graphite-based composite.Although CNT has superior mechanical and thermal properties,the exorbitant price limits its use.Hence,the allotropes of carbon may be used judiciously considering both the cost and property requirements of the targeted application.The work also studies the dispersion state of nanofibers through scanning electron microscopy(SEM).

Fundamental Open Questions on Engineering of “Super” Hydrogen Sorption in Graphite Nanofibers: Relevance for Clean Energy Applications

Herein, some fundamental open questions on engineering of “super” hydrogen sorption (storage) in carbonaceous nanomaterials are considered, namely: 1) on thermodynamic stability and related characteristics of some hydrogenated graphene layers nanostructures: relevance to the hydrogen storage problem;2) determination of thermodynamic characteristics of graphene hydrides;3) a treatment and interpretation of some recent STM, STS, HREELS/LEED, PES, ARPS and Raman spectroscopy data on hydrogensorbtion with epitaxial graphenes;4) on the physics of intercalation of hydrogen into surface graphene-like nanoblisters in pyrolytic graphite and epitaxial graphenes;5) on the physics of the elastic and plastic deformation of graphene walls in hydrogenated graphite nanofibers;6) on the physics of engineering of “super” hydrogen sorption (storage) in carbonaceous nanomaterials, in the light of analysis of the Rodriguez-Baker extraordinary data and some others. These fundamental open questions may be solved within several years.

碳纳米管及其改性复合材料的研究进展与展望

本文重点介绍了近几年碳纳米管及其复合材料的研究进展,对碳纳米管的特性,以及功能填料与高分子材料制备成高性能复合材料的合成工艺、材料性能和具体应用进行了分类介绍,最后对碳纳米管及其改性复合材料今后的发展方向进行了展望。

碳填充电纺PET薄膜的介电特性研究

为获得高介电常数、低介质损耗的新型聚合物薄膜材料,本文以石墨和碳纳米管填充PET,利用静电纺丝法制备PET复合材料,研究碳纳米管和石墨不同填充量对于复合材料的电阻率、工频介电常数、介质损耗及击穿场强等特征参数的影响。结果表明,PET复合材料的工频介电常数和介质损耗均随着填料的增加先增加后略有减小。在填充碳纳米管后工频介电常数最大值达到401.73,介质损耗最大值仅为2.421%。在填充石墨后工频介电常数最大值达到327.29,介质损耗最大值为1.857%,击穿场强最小值仍达到8.03 kV/mm。石墨和碳纳米管的添加使材料的介电常数得到了显著提升。

金属-石墨相氮化碳纳米管异质结的光催化研究进展

异质结构是一系列含有不同组分材料形成的单一结构的纳米复合材料。金属-石墨相氮化碳纳米管异质结材料由于具有金属和氮化碳纳米管组合的独特结构、良好的抗光腐蚀性能、较高的可见光利用率、更多的活性位点和较低的还原反应电位等特点被广泛关注。此外,异质结本身特有的结构和光学性能极大提高和拓展了其在光催化领域的潜在应用。该文介绍了金属材料的性质、金属-氮化碳纳米管异质结的制备方法和结构调控以及该复合材料近期在光催化应用中的进展。阐述了金属-石墨相氮化碳纳米管异质结材料的性质、制备方法以及该材料在光催化领域中的应用,提出了金属-石墨相氮化碳纳米管异质结材料目前的局限性和未来的发展趋势。