氧化镍/碳@碳纳米管负极材料的制备及储锂性能(英文)

将核壳的聚吡咯基的碳@碳纳米管(C@CNT)与纳米片组装的氧化镍(Ni O)微球结合,制备了一种多孔的锂离子电池负极材料(Ni O/C@CNT),该材料(Ni O/C@CNT)与纯的Ni O和Ni O/CNT相比,其容量值和循环稳定性能明显提高。在50 m A·g-1的电流密度下,经过20次循环后,其可逆容量达到573 m A·g-1,容量保持率为68.6%。这些性能的提高是由于核壳结构的C@CNT的导电缓冲性引起的。C@CNT具有诸如多孔结构、大比表面积、高电化学活性、高电子导电性和良好的浸润性等许多优点,这些优点有利于避免电极材料显著的体积变化,因此在锂嵌入和脱出过程中可减少电极容量衰减并提高传质速率。

碳纳米管@球形氮化碳核壳结构光催化剂的构筑及其性能

以二氰二胺、三聚氯氰和碳纳米管(CNT)为原料,采用溶剂热法制备了一系列以CNT为核、不同CNT添加量的碳纳米管@球形氮化碳(CNT@CNMS)核壳结构可见光响应的催化剂。采用XRD、FT-IR、TEM、XPS、紫外可见光谱(UV-vis)、电化学阻抗(EIS)和光致发光光谱(PL)等分析方法对催化剂的结构、性能进行了表征。通过电化学表征计算出CNMS的价带与导带位置。结果表明,CNMS均匀的生长到管状CNT表面,形成CNT@CNMS核壳结构;制备的CNT@CNMS核壳催化剂比表面积增大,且可见光吸收性能明显增强。光催化性能实验表明,当CNT质量为20 mg时,制备的催化剂光催化活性最高,反应120 min,4-硝基苯酚的降解率高达54.44%,其降解效果明显高于CNMS。

Field Emission from a Mixture of Amorphous Carbon and Carbon Nanotubes Films

A mixture of amorphous carbon and carbon nanotubes films was synthesized on stainless steel plates by a micro- wave plasma enhanced chemical vapor deposition system. The source gases were hydrogen and methane with flow rates of 100 and 16sccm,respectively,with a total pressure of 5.0kPa. The surface morphology and the structure of the films were characterized by field emission scanning electron microscopy （SEM） and Raman scattering spectroscopy. Field emission properties of as-deposited film were measured in a vacuum room below 5 ×10^ 5 Pa. The experimental results show that the initial turn-on field is 0. 9V/μm; The current density is 4.0mA/cm2 and the emission sites are dense and uniform at an electric field of 3.7V/μm. These results indicate that such a mixture of amorphous carbon and carbon nanotubes films is a promising material for field emission applications.

Vapor-grown carbon fibers enhanced sulfur-multi walled carbon nanotubes composite cathode for lithium/sulfur batteries

Vapor-grown carbon fibers （VGCFs） were introduced as conductive additives for sulfur-multiwalled carbon nanotubes （S-MWCNTs） composite cathode of lithium-sulfur batteries. The performance of S-MWCNTs composite cathodes with carbon black and VGCFs as sole conductive additives was investigated using scanning electron microscopy （SEM）, galvanostatic charge-discharge tests and electrochemical impedance spectroscopy （EIS）. The results show that the S-MWCNTs composite cathode with VGCFs displays a network-like morphology and exhibits higher activity and better cycle durability compared with the composite cathode with carbon black, delivering an initial discharge capacity of 1254 mA＆#183;h/g and a capacity of 716 mA＆#183;h/g after 40 cycles at 335 mA/g. The interconnected VGCFs can provide a stable conductive network, suppress the aggregation of cathode materials and residual lithium sulfide and maintain the porosity of cathode, and therefore the electrochemical performance of S-MWCNTs composite cathode is enhanced.

Entropy analysis of SWCNT & MWCNT flow induced by collecting beating of cilia with porous medium

In this article, we considers the thermodynamics analysis of creeping viscous nanofluid flow in a horizontal ciliated tube under the effects of a uniform magnetic field and porous medium. Moreover, energy analysis is performed in the presence of an internal heat source and thermal radiation phenomena. The thermal conductivity of base fluid water is strengthened by considering the carbon nanotubes (CNTs). Mathematical formulation operated, results in a set of non-linear coupled partial differential equations. The governed differential system is transformed into an ordinary differential system by considering suitable similarity variables. Exact solutions in the closed form are computed for the temperature, momentum and pressure gradient profiles. In this study, special attention is devoted to the electrical conductivity of the CNTs. Streamlines patterns are also discussed to witness the flow lines for different parameters. Thermodynamics analysis shows that entropy of the current flow system is an increasing function of Brinkmann number, magnetic parameter, nanoparticle concentration parameter and Darcy number.

Synthesis of Higher Alcohols from Syngas over Alkali Promoted K-Co-Mo Catalysts Supported on Multi-walled Carbon Nanotubes

A series of carbon nanotubes-supported K-Co-Mo catalysts were prepared by a sol-gel method combined with incipient wetness impregnation. The catalyst structures were characterized by X-ray diffraction, N2 adsorption-desorption, transmission electron microscopy and H2-TPD, and its catalytic performance toward the synthesis of higher alcohols from syngas was investigated. The as-prepared catalyst particles had a low crystallization degree and high dispersion on the outer and inner surface of CNTs. The uniform mesoporous structure of CNTs increased the diffusion rate of reactants and products, thus promoting the reaction conversion. Furthermore, the incorporation of CNTs support led to a high capability of hydrogen absorption and spillover and promoted the formation of alkyl group, which served as the key intermediate for the alcohol formation and carbon chain growth. Benefiting from these characteristics, the CNTs supported Mo-based catalyst showed the excellent catalytic performance for the higher alcohols synthesis as compared to the unsupported catalyst and activated carbon supported catalyst.

Synthesis and evaluation of carbon nanotubes composite adsorbent for CO2 capture： a comparative study of CO2 adsorption capacity of single-walled and multi-walled carbon nanotubes

As a preliminary investigation towards obtaining carbon nanotube composite adsorbent for CO2 capture, in this study CO2 adsorption performance of three commercial carbon nanotubes （CNTs） one single-walled carbon nanotubes （SWCNTs）, and two （2） different multi-walled carbon nanotubes （referred to as A-MWCNTs and B-MWCNTs） were evaluated and compared. The purpose of this study was to compare the different types of CNTs and select the best to serve as the solid anchor in the development of a hydrophobic composite adsorbent material for CO2 capture. The N2 physi- sorption of the CNTs was conducted to determine their surface area, pore volume and pore size. In addition, morphology and purity of the CNTs were checked with Transmission Electron Microscopy and Raman Spectroscopy, respectively. The CO2 adsorption capacity of the CNTs was evaluated using Thermo-gravimetric analysis （TGA） at 1.1 bar, at operating temperature ranged from 25 to 55 ~C and at different CO2 feed flow rates, in order to evaluate the effects of these variables on the CO2 adsorption capacity. The results of CO2 adsorption with the TGA show that CO2 adsorption capacity for both SWCNTs and MWCNTs was the highest at 25 ~C. Changing the CO2 flowrates had no significant effect on the adsorption capacity of MWCNTs, but decreasing the CO2 flow rate resulted in the enhancement of the CO2 adsorption capacity of SWCNTs. Overall, it was found that the SWCNTs displayed the highest CO2 adsorption capacity （29.97 gCO2/kg ad- sorbent） when compared to the MWCNTs （12.09 gCO2/kg adsorbent）, indicating a 150% increase in adsorption capacity over MWCNTs.

Dielectrophoretic assembly of semiconducting single-walled carbon nanotube transistor

A novel burning technique for making a semiconducting single-walled carbon nanotubes （SWNTs） transistor assembled by the dielectrophoretic force was suggested. The fabrication process consisted of two steps. First, to align and attach a bundle of SWNTs between the source and drain, the alternating （AC） voltage was applied to the electrodes. When a bundle of SWNTs was connected between two electrodes, some of metallic nanotubes and semi-conducing nanotubes existed together. The second step is to burn the metallic SWNTS by applying the voltage between two electrodes. With increasing the voltage, more current flowed through the metallic SWNTs, thus, the metallic SWNTs burnt earlier than the semiconducting one. This technique enables to obtain only semi-conducting SWNTs connection in the transistor. Through the 1--V characteristic graph, the moment of metallic SWNTs burning and the characteristic of semi-conducing nanotubes were verified.

Effect of carbon nanotube and silicon carbide on microstructure and dry sliding wear behavior of copper hybrid nanocomposites

Microstructure and tribological properties of copper-based hybrid nanocomposites reinforced with copper coatedmultiwalled carbon nanotubes (MWCNTs) and silicon carbide (SiC) were studied. Carbon nanotube was varied from 1% to 4% withsilicon carbide content being fixed at 4%. The synthesis of copper hybrid nanocomposites involves ball milling, cold pressing andsintering followed by hot pressing. The developed hybrid nanocomposites were subjected to density, grain size, and hardness tests.The tribological performances of the nanocomposites were assessed by carrying out dry sliding wear tests using pin-on-steel disctribometer at different loads. A significant decrease in grain size was observed for the developed hybrid composites when comparedwith pure copper. An improvement of 80% in the micro-hardness of the hybrid nanocomposite has been recorded for 4% carbonnanotubes reinforced hybrid composites when compared with pure copper. An increase in content of CNTs in the hybridnanocomposites results in lowering of the friction coefficient and wear rates of hybrid nanocomposites.

Optimizing electrophoretic deposition conditions for enhancement in electrical conductivity of carbon fiber/carbon nanotube/epoxy hybrid composites

The effectiveness of optimizing electrical conductivity of carbon fiber/carbon nanotube （CNT）/epoxy hybrid composites via Taguchi method was demonstrated. CNTs were induced on carbon fabric by electrophoretic deposition （EPD） technique. The essential deposition parameters were identified as l） the deposition time, 2） the deposition voltage, 3） the mass fraction of CNTs in suspension, and 4） the distance between the electrodes. An experimental design was then performed to establish the appropriate levels for each factor. An orthogonal array of L9 （34） was designed to conduct the experiments. Electrical conductivity results were collected as the response. The relative influences of design parameters on the response were discussed. Using the model, signal to noise （S/N） ratio and response characteristics for the optimized deposition parameter combination were predicted. The results show clearly that the optimum condition of electrophoretic deposition （EPD） process improves the electrical conductivity of carbon/epoxy hybrid composites.

Laccase biosensor using magnetic multiwalled carbon nanotubes and chitosan/silica hybrid membrane modified magnetic carbon paste electrode

A simple and rapid strategy to construct laccase biosensor for determination of catechol was investigated. Magnetic multiwalled carbon nanotubes (MMCNT) which possess excellent capability of electron transfer were prepared by chemical coprecipitation method. Scanning electron microscope (SEM) and vibrating sample magnetometer (VSM) were used to identify its surfacetopography and magnetization, respectively. Laccase was immobilized on the MMCNT modified magnetic carbon paste electrode by the aid of chitosan/silica (CS) hybrid membrane. Using current-time detection method, the biosensor shows a linear response related to the concentration of catechol in the range from 10-7 to 0.165×10-3 mol/L. The corresponding detection limit is 3.34×10-8 mol/L based on signal-to-noise ratios (S/N) ≥3 under the optimized conditions. In addition, its response current retains 90% of the original after being stored for 45 d. The results indicate that this proposed strategy can be expected to develop other enzyme-based biosensors.

Biomedical X-ray Imaging Enabled by Carbon Nanotube X-ray Sources

Although discovered more than 100 years ago, X-ray source technology has evolved rather slowly. The recent invention of the carbon nanotube （CNT） X-ray source technology holds great promise to revolutionize the field of biomedical X-ray imaging. CNT X-ray sources have been successfully adapted to several biomedical imaging applications including dynamic rnicro-CT of small animals and stationary breast tomosynthesis of breast cancers. Yet their more irnportant biomedical imaging applications still lie ahead in the future, with the devel- oprnent of stationary rnulti-source CT as a noteworthy exarnple.

Large-area growth of ultra-high-density single-walled carbon nanotube arrays on sapphire surface

A scalable approach to obtaining high-density, large-area single-walled carbon nanotube （SWNT） arrays is essential for realizing the full potential of SWNTs in practical electronic devices; this is still a great challenge. Here, we report an improved synthetic method for large-area growth of ultra-high-density SWNT arrays on sapphire surfaces by combining Trojan catalysts （released from the substrate, to assure ultra-high density） with Mo nanoparticles （loaded on the surface, to stabilize the released Trojan catalysts） as cooperating catalysts. Dense and perfectly aligned SWNTs covered the entire substrate and the local density was as high as 160 tubes/pro. Field-effect transistors （FETs） built on such arrays gave an output current density of -488 μA/μm at the drain-source voltage （Vds） = the gate-source voltage （Vgs） = -2 V, corresponding to an on-conductance per width of 244 μS/μm. These results confirm the wide range of potential applications of Trojan-Mo catalysts in the structure-controlled growth of SWNTs.

Novel Photodetectors Based on Double-Walled Carbon Nanotube Film/TiO2 Nanotube Array Heterodimensional Contacts

A new kind of photodetector based on a double-walled carbon nanotube （DWCNT） film and a TiO2 nanotube array with hetrodimensional non-ohmic contacts has been fabricated. Due to the dimensionality difference effect, the DWCNT film/TiO2 nanotube array photodetector exhibits a much higher photocurrent-to-dark current ratio and photoresponse relative to an Au film/TiO2 nanotube array device, even at small bias voltage. The photocurrent-to-dark current ratio reached four orders of magnitude and a high photoresponse of 2467 A/W was found upon irradiation at 340 nm. Furthermore, the photosensitive regions could be extended into the visible range. The photocurrent-to-dark current ratio reached approximately three orders of magnitude upon irradiation at 532 nm, where the photon energy is much lower than the band gap of TiO2.

Italicized carbon nanotube facilitating water transport:a molecular dynamics simulation

While the preferential movement of water inside carbon nanotube is appealing for water purification,our understanding of the water transport mechanism through carbon nanotube(CNT)-based membrane is far from adequate. Here we conducted molecular dynamics simulations to study how the alignment of the CNTs in the membrane affects the water transport through the CNT membrane. It was shown that compared to the conventional CNT membrane where the alignment of CNTs was vertical to membrane surface, the ‘‘italicized CNT membrane'' in which the contact angel between membrane surface and the CNT alignment is not 90° offered a higher transmembrane flux of water. The expanded exposure of more carbon atoms to water molecules reduced the energy barrier near the entrance of this italicized CNT membrane, compared to the vertical one. For water flows through the italicized CNT membrane, the Lennard-Jones interaction between water and nanotube as function of central path of the CNT changes from ‘‘U'' to ‘‘V'' pattern, which significantly lowers energy barrier for filling water into the CNT,favoring the water transport inside carbon nanotube. Above simulation indicates new opportunities for applying CNT in water purification or related fields in which water transport matters.

Ultrahigh Density Modulation of Aligned Single-Walled Carbon Nanotube Arrays

Controlling the densities of aligned single-walled carbon nanotube arrays （SWNTs） on ST-cut quartz is a critical step in various applications of these materials. However the growth mechanism for tuning SWNT density using the chemical vapor deposition （CVD） method is still not well understood, preventing the development of efficient ways to obtain the desired results. Here we report a general ＂periodic＂ approach that achieves ultrahigh density modulation of SWNT arrays on ST-cut quartz substrates--with densities increased by up to -60 times compared with conventional methods using the same catalyst densities--by varying the CH4 gas ＂off＂ time. This approach is applicable to a wide range of initial catalyst densities, substrates, catalyst types and growth conditions. We propose a general mechanism for the catalyst size-dependent nucleation of SWNTs associated with different free carbon concentrations, which explains all the observations. Moreover, the validity of the model is supported by systematic experiments involving the variation of key parameters in the ＂periodic＂ CVD approach.

Carbon-based spintronics

Carbon-based spintronics refers mainly to the spin injection and transport in carbon materials including carbon nanotubes,graphene,fullerene,and organic materials.In the last decade,extraordinary development has been achieved for carbon-based spintronics,and the spin transport has been studied in both local and nonlocal spin valve devices.A series of theoretical and experimental studies have been done to reveal the spin relaxation mechanisms and spin transport properties in carbon materials,mostly for graphene and carbon nanotubes.In this article,we provide a brief review on spin injection and transport in graphene,carbon nanotubes,fullerene and organic thin films.

Nano-structured red phosphorus/porous carbon as a superior anode for lithium and sodium-ion batteries

To enhance electrochemical performance of li- thium or sodium-ion batteries （LIBs or NIBs）, active materials are usually filled in porous conductive particles to produce anode composites. However, it is still challenging to achieve high performance anode composites with high specific capa- city, excellent rate performance, high initial Coulombic effi- ciency （ICE） and long cycle life. Based on these requirements, we design and fabricate activated carbon-coated carbon na- notubes （AC@CNT） with hierarchical structures containing micro- and meso-pores. A new structure of phosphorus/car- bon composite （P@AC@CNT） is prepared by confining red P in porous carbon through a vaporization-condensation-con- version method. The micro-pores are filled with P, while the meso-pores remain unoccupied, and the pore openings on the particle surface are sealed by P. Due to the unique structure of P@AC@CNT, it displays a high specific capacity of 1674 mA h g-i at 0.2 C, ultrahigh ICE of 92.2%, excellent rate per- formance of 1116 mA h g-i at 6 C, and significantly enhanced cycle stability for LIBs. The application of P@AC@CNT in NIBs is further explored. This method for the fabrication of the special composites with improved electrochemical per- formance can be extended to other energy storage applica- tions.

An integrated nanocarbon–cellulose membrane for solid-state supercapacitors

In this work, we demonstrate the assembly of oxidised carbon nanohybrids(o CNHs) with a commercial cellulose membrane for solid-state supercapacitors. The o CNHs–cellulose membranes were prepared by filtering a water dispersion of o CNHs through the cellulose membrane. The o CNHs were derived from carbon nanotubes via a modified Hummer's method and contained both closed tubes and unzipped tubes, which indicated a hybrid geometrical structure. The solid-state supercapacitor based on the o CNHs–cellulose membranes showed a high areal capacitance of *75 m F/cm^2 at a low scan rate(5 m V/s)and excellent stability for 1,000 cycles.

Equilibrium Configurations of Lipid Bilayer Membranes and Carbon Nanostructures

The present article concerns the continuum modelling of the mechanical behaviour and equilibrium shapes of two types of nano-scale objects： fluid lipid bilayer membranes and carbon nanostructures. A unified continuum model is used to handle four different ease studies. Two of them consist in representing in analytic form cylindrical and axisymmetric equilibrium configurations of single-wall carbon nanotubes and fluid lipid bilayer membranes subjected to uniform hydrostatic pressure. The third one is concerned with determination of possible shapes of junctions between a single-wall carbon nanotube and a fiat graphene sheet or another single-wall carbon nanotube. The last one deals with the mechanical behaviour of closed fluid lipid bilayer membranes （vesicles） adhering onto a fiat homogeneous rigid substrate subjected to micro-injection and uniform hydrostatic pressure.