A review of carbon nanotubes in modern electrochemical energy storage

The quest for sustainable energy storage solutions is more critical than ever,with the rise in global energy demand and the urgency of transition from fossil fuels to renewable sources.Carbon nanotubes(CNTs),with their exceptional electrical conduct-ivity and structural integrity,are at the forefront of this endeavor,offering promising ways for the advance of electrochemical energy storage(EES)devices.This review provides an analysis of the synthesis,properties,and applications of CNTs in the context of EES.We explore the evolution of CNT synthesis methods,including arc discharge,laser ablation,and chemical vapor deposition,and highlight the recent developments in metal-organic framework-derived CNTs and a novel CNT aggregate with a three-dimensional ordered macroporous structure.We also examine the role of CNTs in improving the performance of various EES devices such as lith-ium-ion,lithium-metal,lithium-sulfur,sodium,and flexible batteries as well as supercapacitors.We underscore the challenges that remain,including the scalability of CNT synthesis and the integration of CNTs in electrode materials,and propose potential solu-tions and future research directions.The review presents a forward-looking perspective on the pivotal role of CNTs in shaping the fu-ture of sustainable EES technologies.

Dispersion and Performance Properties of Carbon Nanotubes (CNTs) Based Polymer Composites: A Review

Carbon nanotubes (CNTs) based polymer composites have variety of engineering applications (electromagnetic shielding, antistatic coatings, high-strength low-density corrosion-resistant components, lightweight energy storage and many more);due to their excellent mechanical, electrical, chemical, magnetic, etc. properties. In the polymer nanocomposites CNTs are dispersed in the polymeric matrix. However the dispersion may be uniform or may not be uniform. The biggest challenge is the effective dispersion of individual CNTs in the polymer matrices, as CNTs tends to form clusters and bundles due to strong van der Waals’ forces of attraction. The aggregated structure continue until physical (Mechanical) or chemical modification (Encapsulation/surface modification) of CNTs. Few modification methods such as vigorous mixing of the polymers damages CNTs structure, and may hinder their properties. But these problems can be overcome by mechanical or chemical modification of CNTs surfaces. In the chemical modification, the modifier or the long tail surfactant may encapsulate and/or partially wrap the CNTs surfaces. In this review, recent work on CNTs based polymer nanocomposite is carried out with few modifiers/encapsulating agents. Incorporation of CNTs in polymer matrix changes the performance properties such as tensile strength, tensile modulus, elongation at break, toughness, Dynamic mechanical thermal analysis (DMTA), etc. The phase morphology of the composite materials throws light on the properties of CNTs based polymer nanocomposite. Moreover phase morphology may be directly correlated with the behavior of the material, hence reviewed here through transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Furthermore review is also carried out on the non-isothermal crystallization (DSC) and rheology of CNTs polymer nanocomposite.

Temperature-Responsive Tensile Actuator Based on Multi-walled Carbon Nanotube Yarn

Many temperature indicators or sensors show color changes for materials used in food and medical fields.However, they are not helpful for a color-blind person or children who lack judgment. In this paper, we introduce simply fabricated and more useful low-temperature indicator(~30 °C) for devices that actuates using paraffin-infiltrated multiwalled carbon nanotube(MWCNT) coiled yarn. The density difference of MWCNT yarn provides large strain(~330 %)when heat causes the melted polymer to move. Furthermore, the MWCNT yarn decreases the melting point of paraffin.These properties allow control of the actuating temperature. In addition, mechanical strength was enhanced by MWCNT than previously reported temperature-responsive actuators based on shape memory polymers. This simply fabricated temperature indicator can be applied in latching devices for medical and biological fields.

Tensile and Electro-Mechanical Properties of Carbon Nanotube Film Twisted Yarn with Adjustable Diameter

Carbon nanotube(CNT)yarns with adjustable diameters were manufactured by twisting CNT films with varied twists.Different from traditional CNT fibers,CNT yarns exhibited a larger diameter(423μm)and a higher tensile force(1988 cN).The results showed that CNT yarns with the twist angle of 35°exhibited the highest conductivity(886 S/cm)and the highest tensile strain(35%).

Effects of Orientation of Carbon Nanotubes on CNT Bundle Based Silk Composite Using Finite Element Method

Carbon Nanotubes (CNTs) have exceptional mechanical properties. They are the stiffest and strongest material, yet discovered, because of their high length to diameter ratio. In this paper a Representative Volume Element (RVE) model of CNT-silk composite is made. Then the orientations of the CNTs in the composite are varied and the effects of this variation are observed. The change is mainly observed between the interfaces of CNT and silk. Also there is a change in Young’s Modulus. COMSOL Multiphysics 4.2a is used for building model and performing simulations.

Study on Low-Temperature Properties of the Asphalt Modified by Carbon Nanotubes(CNTs)and Crumb Rubber(CR)

The effect of adding crumb rubber(CR)and carbon nanotubes(CNTs)on the low-temperature properties of virgin asphalt was studied.Using the force-ductility test and the bending beam rheometer(BBR)test,the deformation resistance and rheological properties of asphalt samples at low temperatures were evaluated,respectively.Based on the result of BBR test,the creep functions of the Burgers model and the Zener model were used to fit the low-temperature creep characteristics of the asphalt samples.Furthermore,the differential scanning calorimetry(DSC)test and the attenuated total reflection-Fourier transform infrared spectroscopy(ATR-FTIR)test were utilized to appraise the low-temperature stability and chemical properties of asphalt samples,respectively.The results showed that CR significantly improved the low-temperature properties of virgin asphalt,while CNTs had little effect.Moreover,during the degradation of CR,aromatic and aliphatic components were released.In particular,the aliphatic components of CR-modified asphalt were much higher than those of virgin asphalt,which had a significant effect on improving the low-temperature properties of the asphalt.The DSC test results showed that CR enhanced the low-temperature stability of the asphalt,while the addition of CNTs presented a slightly negative effect.

Sensing Property of Carbon Nanotube Yarn Embedded in Ethylene Vinyl Acetate (EVA) Elastomer

Carbon nanotube (CNT) has remarkable piezoresistive properties,which makes its extremely sensitive to the mechanical force. In this study,the CNT yarn with the strength of 90 MPa and the strain sensing gage factor of 1.75 was selected and embedded into the ethylene vinyl acetate (EVA) elastomer as a sensing material.By measuring the electric resistance changing under the stretching,bending,longitudinally and transversely compressing of the CNT embedded EVA, the resistance changing curves and their linear correlations were obtained and analyzed. The result shows that the gage factor under the tensile test is the highest( 2.51),which is higher than the original value of CNT yarn (1.75). The gage factors of the CNT yarn embedded into EVA elastomer under bending and longitudinal and transverse compression are 2.29,1.55 and 0.79,respectively.

Impacts of Parameter Scaling for Low-Power Applications Using CNTFET （Carbon Nanotube Field Effect Transistor） Models： A Comparative Assessment

This paper provides an extension to the earlier work wherein a comparison between different models that had studied the effects of several parameters scaling on the performance of carbon nano tube field-effect transistors was presented. The evaluation for the studied models, with regard to the scaling effects, was to determine those which best reflect the very essence of carbon nano-tube technologies. Whereas the models subject this comparison （Fettoy, Roy, Stanford, and Southampton） were affected to varying degrees due to such parametric variations, the Stanford model was shown as still being valid for a wide range of chiralities and diameter sizes; a model that is also applicable for circuit simulations. In this paper, we present a comparative assessment of the various models subject to the study with regard to the effect of incorporating multiple carbon nanotubes in the channel region. We also assess the effect of oxide thickness on transistor performance in terms of the supply voltage threshold effects. Results leveraging our findings in this ongoing research endeavor reveal that many research efforts were not efficient to high degree due to high delay and not valid for circuit simulations.

Carbon nanotubes:Evaluation of toxicity at biointerfaces

Carbon nanotubes (CNTs) are a class of carbon allotropes with interesting properties that make them productive materials for usage in various disciplines of nanotechnology such as in electronics equipments, optics and therapeutics. They exhibit distinguished properties viz., strength, and high electrical and heat conductivity. Their uniqueness can be attributed due to the bonding pattern present between the atoms which are very strong and also exhibit high extreme aspect ratios. CNTs are classified as singlewalled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) on the basis of number of sidewalls present and the way they are arranged spatially. Application of CNTs to improve the performance of many products, especially in healthcare, has led to an occupational and public exposure to these nanomaterials. Hence, it becomes a major concern to analyze the issues pertaining to the toxicity of CNTs and find the best suitable ways to counter those challenges. This review summarizes the toxicity issues of CNTs in vitro and in vivo in different organ systems (bio interphases) of the body that result in cellular toxicity.

An Overview of Carbon Nanotubes and Graphene for Biosensing Applications

With the development of carbon nanomaterials in recent years, there has been an explosion of interests in using carbon nanotubes(CNTs) and graphene for developing new biosensors. It is believed that employing CNTs and graphene as sensor components can make sensors more reliable, accurate, and fast due to their remarkable properties. Depending on the types of target molecular, different strategies can be applied to design sensor device. This review article summarized the important progress in developing CNT-and graphene-based electrochemical biosensors, field-effect transistor biosensors, and optical biosensors. Although CNTs and graphene have led to some groundbreaking discoveries, challenges are still remained and the state-of-the-art sensors are far from a practical application. As a conclusion, future effort has to be made through an interdisciplinary platform, including materials science, biology, and electric engineering.

Dispersion of multiwalled carbon nanotubes in aluminum powders

Multiwalled carbon nanotubes (MWNTs) were treated with the reflux within the concentrated nitric acid for 0-25 h to purify and disperse the tangled MWNTs. The effect of reflux time on the morphology and the weight loss of MWNTs were investigated. Meanwhile,the dispersion of MWNTs with 0-2.0 wt.% in 2024Al powders using mechanical stirring with an assisting ultrasonic shaker in ethanol was also studied. The results show that the reflux time markedly affects the morphology of MWNTs. The weight loss of MWNTs i...

Simple method to rapidly fabricate chain-like carbon nanotube films and its field emission properties

A simple process to fabricate chain-like carbon nanotube （CNT） films by microwave plasma-enhanced chemical vapor deposition （MPCVD） was developed successfully. Prior to deposition, the Ti/Al2O3 substrates were ground with Fe-doped SiO2 powder. The nano-structure of the deposited films was analyzed by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and Raman spectroscopy. The field electron emission characteristics of the chain-like carbon nanotube films were measured under the vacuum of 10-5 Pa. The low turn-on field of 0.80 V/μm and the emission current density of 8.5 mA/cm2 at the electric field of 3.0 V/μm are obtained. Based on the above results, chain-like carbon nanotube films probably have important applications in cold cathode materials and electrode materials.

Carbon nanotube and graphene reinforced magnesium matrix composites:A state-of-the-art review

Magnesium(Mg)composites reinforced with carbon-based nanomaterial(CBN)often exhibit low density,enhanced strength,good conductivity,improved wear resistance,and excellent biocompatibility when compared to current industry Mg alloys.This review aims to critically evaluate recent developments in Mg-CBN composites and is divided into five sections:First,a brief introduction to Mg-CBN composites is provided,followed by a discussion of different fabrication techniques for these composites,including powder metallurgy,casting,friction stir processing,and selective laser melting.A particular focus is on the current processing challenges,including dispersion strategies to create homogeneous Mg-CBN composites.The effect of processing on the quantifying disorder in CBNs and distinguishing different sp2carbon materials is also highlighted.Then,the effect of CBN on various properties of Mg-CBN composites is thoroughly analyzed,and the strengthening efficiency of CNTs and graphene in the Mg matrix is examined.Finally,the potential applications of Mg-CBN composites in various industries are proposed,followed by a summary and suggestions for future research directions in the field of Mg-CBN composites.

Nonlinear in-plane thermal buckling of rotationally restrained functionally graded carbon nanotube reinforced composite shallow arches under uniform radial loading

The nonlinear in-plane instability of functionally graded carbon nanotube reinforced composite(FG-CNTRC)shallow circular arches with rotational constraints subject to a uniform radial load in a thermal environment is investigated.Assuming arches with thickness-graded material properties,four different distribution patterns of carbon nanotubes(CNTs)are considered.The classical arch theory and Donnell’s shallow shell theory assumptions are used to evaluate the arch displacement field,and the analytical solutions of buckling equilibrium equations and buckling loads are obtained by using the principle of virtual work.The critical geometric parameters are introduced to determine the criteria for buckling mode switching.Parametric studies are carried out to demonstrate the effects of temperature variations,material parameters,geometric parameters,and elastic constraints on the stability of the arch.It is found that increasing the volume fraction of CNTs and distributing CNTs away from the neutral axis significantly enhance the bending stiffness of the arch.In addition,the pretension and initial displacement caused by the temperature field have significant effects on the buckling behavior.

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.

Electroless plating Ni-P matrix composite coating reinforced by carbon nanotubes

Ni-P matrix composite coating reinforced by carbon nanotubes (CNTs) was deposit ed by electroless plating. The most important factors that influence the content of carbon nanotubes in deposits,such as agitation,surfactant and carbon nanot ubes concentration in the plating bath were investigated. The surface morphology,structure and properties of the Ni-P-CNTs coating were examined. It is found that the maximum content of carbon nanotubes in the deposits is independent of carbon nanotubes concentration in the plating bath when it is up to 5 mg/L. The test results show that the carbon nanotubes co-deposited do not change the str ucture of the Ni-P matrix of the composite coating,but greatly increase the ha rdness and wear resistance and decrease the friction coefficient of the Ni-P-C NTs composite coating with increasing content of carbon nanotubes in deposits.

Fluidization dynamic characteristics of carbon nanotube particles in a tapered fluidized bed

In this work,a tapered fluidized bed(TFB)without a distributor for fluidizing carbon nanotube(CNT)was applied for improving the dead zone,blockage,and fracture of distributor,which occurred in actual production.Experiments were performed under different superficial gas velocities,static bed heights,CNT agglomerate size,and positions of pressure probe.To obtain multi-perspective and multi-scale understanding of fluidization dynamics of gas–CNT flow in the TFB without a distributor,the standard deviation,skewness,kurtosis,wavelet decompositions and homogeneous index analysis methods were adopted.Some noticeable phenomena were observed.Particle movements including inter-particle,gas–particle and particle–wall dominate dynamic characteristics.The amplitudes of pressure fluctuations of coarse agglomerated multi-walled CNT were more sensitive to the gas velocity than that of fine agglomerated multi-walled CNT.The sensitively of energy contribution of the meso-and macrostructures was that the sensitivity of the measured position was less than the sensitivity of the energy contribution by the changes of particle size,and the sensitivity of the energy contribution by the changes of particle size was less than the energy contribution by the changes of gas velocity.The fluidization quality of coarse agglomerated multi-walled CNT was better than that of fine agglomerated multi-walled CNT,which was verified by the skewness and wavelet analysis.

Carbon Nanotube Based Chemical Sensors

Carbon nanotubes CNTs)have been receiving enormous attention in the last decade due to their extraordinary mechanical properties and unique elec- tronic properties.This combination has produced an unprecedented range of applications for CNTs:elec- tronic,logic and memory chips,chemical and biosen- sots,composites,lithium batteries,gas storage,filters and membranes,etc.This presentation will focus on carbon nanotube based sensors and discuss fabrication, testing and performance.

Distribution of electric field for carbon nanotube assembly: Simulation (I)

The distribution of electric field for the alignment and attachment of carbon nanotubes (CNTs) was simulated. To be attached at the desired place, the aligned and attracted CNTs should be stayed in the desired area called the stable region or the quasi-stable region for an instant where the change of electric field is minimized. Since the conical electrode has the very narrow sized quasi-stable region, few CNTs can be attached. The rectangular electrodes have a wide stable region, so lots of CNTs can be attached. The results indicate that the round electrode which has a proper sized quasi-stable region is more effective for aligning and attaching a single CNT than the conical or rectangular shaped electrodes.

IR study on surface chemical properties of catalytic grown carbon nanotubes and nanofibers

In this study, the surface chemical properties of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) grown by catalytic decomposition of methane on nickel and cobalt based catalysts were studied by DRIFT (Diffuse Reflectance Infrared Fourier Transform) and transmission Infrared (IR) spectroscopy. The results show that the surface exists not only carbon-hydrogen groups, but also carboxyl, ketene or quinone (carbonyl) oxygen-containing groups. These functional groups were formed in the process of the material growth, which result in large amount of chemical defect sites on the walls.