Microstructures of electron beam welding joint of CNTs/Al composites

Carbon nauotube（ CNT） reinforced aluminum metal matrix composites were welded by electron beam welding and the microstructures of welded joints were investigated. The result showed that the interracial reaction happened between the CNTs and Al matrix, which resulted in producing brittle Al4 C3 compounds in electron beam welds. The extent of interfacial reaction varies gradually in the depth and width direction. The length of the reactants Al4C3 became short duo to the temperature gradient in the molten pool. The quantity and size of Al4 C3 compounds increased with the increase of beam current and the decrease of welding speed in the middle zone of weld. However, no needle-like phase Al4C3 was observed in HAZ.

Properties of CNTs/MoSi2 composites prepared by spark plasma sintering

Molybdenum disilicide(MoSi_2) based composites with various contents of carbon nanotubes(CNTs) were fabricated by spark plasma sintering(SPS) in vacuum under a pressure of 25 MPa.The composites obtained under a sintering temperature of 1500 °C and time of 10 min exhibited optimum mechanical properties at room temperature in terms of fracture toughness and transverse rupture strength.MoSi_2 based composite with 6.0% CNTs(volume fraction) had the highest fracture toughness,transverse rupture strength and hardness,which were improved by about 25.7%,51.5% and 24.4% respectively,as compared with pure MoSi_2.A Mo_(4.8)Si_3C_(0.6) phase was detected in CNTs/MoSi_2 composites by both X-ray diffraction(XRD) method and microstructure analysis with scanning electron microscopy(SEM).It is believed that the fine grains and well dispersed small Mo_(4.8)Si_3C_(0.6) particles had led to a higher hardness and strength of CNTs/MoSi_2 composites because of their particle pullout,crack deflection and micro-bridging effects.

Deformation behaviors and processing maps of CNTs/Al alloy composite fabricated by flake powder metallurgy

Deformation behaviors of CNTs/Al alloy composite fabricated by the method of flake powder metallurgy were investigated by hot compression tests, which were performed in the temperature range of 300?550 °C and strain rate range of 0.001? 10 s?1 with Gleeble?3500 thermal simulator system. Processing maps of the CNTs/Al alloy at different strains were calculated to study the optimum processing domain. Microstructures before and after hot compressions were characterized by electron backscattered diffraction (EBSD) method. Stress?strain curves indicate that the flow stress increases with the increase of strain rate and the decrease of temperature. The processing maps of the CNTs/Al alloy at different strains show that the optimum processing domain is 500?550 °C, 10 s?1 for hot working. EBSD analysis demonstrates that fully dynamic recrystallization occurs in the optimum processing domain (high strainrate 10 s?1), whereas the main soften mechanism is dynamic recovery at low strain rate (0.001 s?1).

Hot deformation and processing maps of as-sintered CNT/Al-Cu composites fabricated by flake powder metallurgy

The deformation behaviors of as-sintered CNT/Al-Cu composites were investigated by isothermal compression tests performed in the temperature range of 300-550°C and strain rate range of 0.001-10 s-1 with Gleeble 3500 thermal simulator system.Processing maps based on dynamic material model(DMM)were established at strains of 0.1-0.6,and microstructures before and after hot deformation were characterized by scanning electron microscopy(SEM),electron backscatter diffraction(EBSD)and high-resolution transmission electron microscopy(HRTEM).The results show that the strain has a significant influence on the processing maps,and the optimum processing domains are at temperatures of 375-425°C with strain rates of 0.4-10 s-1 and at 525-550°C with 0.02-10 s-1 when the strain is 0.6.An inhomogeneous distribution of large particles,as well as a high density of tangled dislocations,dislocation walls,and some sub-grains appears at low deformation temperatures and strain rates,which correspond to the instability domain.A homogeneous distribution of fine particles and dynamic recrystallization generates when the composites are deformed at 400 and 550°C under a strain rate of 10 s-1,which correspond to the stability domains.

Effect of pyrolysis temperature on properties of ACF/CNT composites

Activated carbon fiber/carbon nanotube(ACF/CNT) composites were fabricated by chemical vapor deposition(CVD) process.The effects of pyrolysis temperature on properties of ACF/CNT composites,including BET specific surface area,mass increment rate and adsorption efficiency for rhodamine B in solution,were investigated by scanning electron microscopy.The results show that the pyrolysis temperature is a key factor affecting the qualities of ACF/CNT composites.The mass increment rate and BET specific surface area sharply decrease with the increase of pyrolysis temperatures from 550 ℃ to 850 ℃ and the minimum diameter of CNTs appears at 750 ℃.The maximum adsorption efficiency of ACF/CNT composites for rhodamine B is obtained at 650 ℃.ACF/CNT composites are expected to be useful in adsorption field.

A machine-learning-enabled approach for bridging multiscale simulations of CNTs/PDMS composites

Benefitting from the interlaced networking structure of carbon nanotubes(CNTs),the composites of CNTs/polydimethylsiloxane(PDMS)have found extensive applications in wearable electronics.While hierarchical multiscale simulation frameworks exist to optimize the structure parameters,their wide applications were hindered by the high computational cost.In this study,a machine learning model based on the artificial neural networks(ANN)embedded graph attention network,termed as AGAT,was proposed.The datasets collected from the micro-scale and the macro-scale simulations are utilized to train the model.The ANN layer within the model framework is trained to pass the information from micro-scale to macro-scale,while the whole model is aimed to predict the electro-mechanical behavior of the CNTs/PDMS composites.By comparing the AGAT model with the original multiscale simulation results,the data-driven strategy is shown to be promising with high accuracy,demonstrating the potential of the machine-learning-enabled approach for the structure optimization of CNT-based composites.

Effect of electrical current on tribological property of Cu matrix composite reinforced by carbon nanotubes

Cu matrix composite reinforced with 10%（volume fraction） carbon nanotubes（CNTs/Cu） and pure Cu bulk were prepared by powder metallurgy techniques under the same consolidation processing condition.The effect of electrical current on tribological property of the materials was investigated by using a pin-on-disk friction and wear tester.The results show that the friction coefficient and wear rate of CNTs/Cu composite as well as those of pure Cu bulk increase with increasing the electrical current without exception,and the effect of electrical current is more obvious on tribological property of pure Cu bulk than on that of CNTs/Cu composite;the dominant wear mechanisms are arc erosion wear and plastic flow deformation,respectively;CNTs can improve tribological property of Cu matrix composites with electrical current.

Cerium vanadate/carbon nanotube hybrid composite nanostructures as a high-performance anode material for lithium-ion batteries

The pristine CeVO_(4) and CeVO_(4)/CNT hybrid composite nanostructured samples were facilely synthesized using a simple silicone oil-bath method.From the X-ray diffraction results,the formation of tetragonal CeVO_(4) with an additional minor phase of V_(2)O_(5) was identified.When investigated as an anode material for lithium(Li)-ion batteries,the CeVO_(4)/CNT hybrid composite nanostructure(HCNS) electrode demonstrated improved Li storage performance over the pristine CeVO_(4).The Li insertion/de-insertion electrochemical reaction with the CeVO_(4) was analyzed on the basis of cyclic voltammetry study.The cyclic voltammetry analysis revealed that the three-step reduction of V^(5+) to V^(3+), V^(3+) to V^(2+), and V^(2+) to V+ processes is involved and among them,only V^(5+) to V^(3+) is reversible during the Li-ion insertion into CeVO_(4).The CeVO_(4)/CNT HCNS electrode exhibited a discharge capacity as high as 443 mA h g^(-1)(capacity retention of 96.3%) over 200 cycles at 100 mA g^(-1), whereas the pristine CeVO_(4) is limited to 138 mA h g^(-1)(capacity retention of 48%).Even at a high current density of 500 mA g^(-1), the CeVO_(4)/CNT HCNS electrode delivered an excellent reversible capacity of 586.82 mA h g^(-1) after 1200 cycles.

Fracture model for the prediction of the electrical percolation threshold in CNTs/Polymer composites

In this paper, we propose a 3D stochastic model to predict the percolation threshold and the effective electric conductivity of CNTs/Polymer composites. We consider the tunneling effect in our model so that the unrealistic interpenetration can be avoided in the identification of the conductive paths between the CNTs inside the polymer. The results are shown to be in good agreement with reported experimental data.

Evolution,Control,and Effects of Interface in CNT/Al Composites:a Review

This review summarizes the work carried out in the field of interface study in carbon nanotube reinforced aluminum （CNT/A1） composites. Much research work has been conducted to reveal the evolution of CNT/A1 interface in producing the composite with the purpose of achieving uniform distribution of CNTs and tight interfacial bonding. The effect and principles of coating were reviewed along with the illustration of ＂intermetallic interphases＂ design. Different roles of CNT/Al interface in structural and functional application were elucidated, and the future work that needs attention was addressed.

Structure-dependent electromagnetic wave absorbing properties of bowl-like and honeycomb TiO_(2)/CNT composites

Materials that can efficiently absorb electromagnetic waves(EMWs)are required to deal with electromagnetic pollution.Structure design appears to be an efficient way to improve the EMW-absorption performance of such materials,particularly when adjustment of the constitution or mixing ratio is limited.In this study,bowl-like and honeycomb titanium dioxide/carbon nanotube(TiO_(2)/CNT)composites with different CNT contents were fabricated using the methods of hierarchical and mixing vacuum-assisted filtration,respectively.Compared to the honeycomb structure,the bowl-like structure simultaneously facilitated greater interfacial polarization and conduction loss in favor of dielectric polarization,and augmented multiple reflections.The high porosity of the honeycomb structure was conducive to optimizing the impedance matching characteristics.The bowl-like TiO_(2)/CNT composite exhibited a minimum reflection loss(RL_(min))of-38.6 dB(1.5 mm)with a wide effective absorption band(EAB;<-10 dB)of4.2 GHz,while the honeycomb TiO_(2)/CNT composite showed an RLminof-34.8 dB(2.1 mm)with an EAB of 4.3 GHz.The required mixing ratio in the matrix was only 15 wt%,outperforming that of the most closely related composites.Thus,both the bowl-like and honeycomb TiO_(2)/CNT composites are ideal candidates for light-weight and highly efficient EMW-absorbing materials.

Effect of Carboxymethyl Cellulose(CMC) Functionalization on Dispersion, Mechanical, and Corrosion Properties of CNT/Epoxy Nanocomposites

Carbon nanotube(CNT)/epoxy nanocomposites have a great potential of possessing many advanced properties.However,the homogenization of CNT dispersion is still a great challenge in the research field of nanocomposites.This study applied a novel dispersion agent,carboxymethyl cellulose(CMC),to functionalize CNTs and improve CNT dispersion in epoxy.The effectiveness of the CMC functionalization was compared with mechanical mixing and a commonly used surfactant,sodium dodecylbenzene sulfonate(Na DDBS),regarding dispersion,mechanical and corrosion properties of CNT/epoxy nanocomposites with three different CNT concentrations(0.1%,0.3%and 0.5%).The experimental results of Raman spectroscopy,particle size analysis and transmission electron microscopy showed that CMC functionalized CNTs reduced CNT cluster sizes more efficiently than Na DDBS functionalized and mechanically mixed CNTs,indicating a better CNT dispersion.The peak particle size of CMC functionalized CNTs reduced as much as 54%(0.1%CNT concentration)and 16%(0.3%CNT concentration),compared to mechanical mixed and Na DDBS functionalized CNTs.Because of the better dispersion,it was found by compressive tests that CNT/epoxy nanocomposites with CMC functionalization resulted in 189%and 66%higher compressive strength,224%and 50%higher modulus of elasticity than those with mechanical mixing and Na DDBS functionalization respectively(0.1%CNT cencentration).In addition,electrochemical corrosion tests also showed that CNT/epoxy nanocomposites with CMC functionalization achieved lowest corrosion rate(0.214 mpy),the highest corrosion resistance(201.031Ω·cm^(2)),and the lowest porosity density(0.011%).

Bending,buckling and vibration analyses of MSGT microcomposite circular-annular sandwich plate under hydro-thermo-magneto-mechanical loadings using DQM

The purpose of this paper is to investigate the bending,buckling,vibration analyses of microcomposite circular-annular sandwich plate with CNT reinforced composite facesheets under hydro-thermo-magneto-mechanical loadings are presented using first order shear deformation theory(FSDT)and modified strain gradient theory(MSGT)that includes three material length scale parameters.Also,an isotropic homogeneous core is considered for microcomposite circular-annular sandwich plate.The generalized rule of mixture is employed to predict mechanical,moisture and thermal properties ofmicrocomposite sandwich plate.By using Hamilton’s principle,governing equations are solved by differential quadrature method(DQM)for a circular annular sandwich plate.The predicted results are validated by carrying out the comparison studies for the FGM plates by modified couple stress theory(MCST).The obtained results are given to indicate the influence of the material length scale parameter,core-to-facesheet thickness ratios,magnetic effect,thermal andmoisture effects on the dimensionless deflection,critical buckling load,and natural frequency of microcomposite circular sandwich plate.The results can be employed in solid-state physics,materials science,nano-electronics,and nano electro-mechanical devices such as microactuators,and microsensor.

Synthesis of Fe-doped carbon hybrid composed of CNT/flake-like carbon for catalyzing oxygen reduction

Carbon-based materials with tunable properties have emerged as promising candidates to replace Pt-based catalysts for accelerating oxygen reduction reaction(ORR)in fuel cells or metal-air batteries.In this work,we constructed a carbon hybrid which consists of one-dimensional(1D)carbon nanotubes and flake-like carbons by pyrolysis of leaf-like metal-organic frameworks.The optimal hybrid electrocatalyst of Fe_(7%)-L-CNT-900 possesses the desired features for ORR,including active Fe species,high degree of graphitization,large specific surface area,and hierarchical porous structures.Consequently,Fe_(7%)-L-CNT900 performs a high electrocatalytic activity for ORR with a half-wave potential of 0.88 V,which is comparable to that of Pt/C(20 wt.%).This strategy provides an insight into the investigation of highly efficient and low-cost composite electrocatalyst for oxygen reduction reaction.

Molecular and crystal assembly inside the carbon nanotube:encapsulation and manufacturing approaches

Encapsulation of different guestspecies such as molecules and ions inside carbon nanotubes （CNTs） has been reported in the literatures during the last 15 years and repre sents an exciting development of nanoengineering of novel materials and composites. The reported nanocomposite mate rials show the semiconducting properties with potential applications in nanosensors, nanounits and nanocircuits as well as advanced energy transfer and storage properties, and encompass manufacturing for novel nanowires, nanoelectronic devices with properties designed with optoelectronic, spin tronic and nanomagnetic qualities. This review reports on a wide range of encapsulation references with particular focus on single molecules, atomic chains, metal halides and polymers encapsulated inside CNTs. The encapsulation methods and the chemical and physical qualities of these novel materials are crucial for the future manufacturing of novel innovations in nanotechnology, and represent therefore the current stateof theart of encapsulation methods in advanced manufacturing.

Greatly increased visible-light photocatalytic activity of SnS_(2)/carbon nanotube composite for Cr(VI)reduction:Insights into effects of solid acid structure

A composite of SnS_(2)and carbon nanotube(CNT)was successfully synthesized as a visible-light-driven photocatalyst with a mechanochemical method.In comparing with SnS_(2),the SnS_(2)/CNT composite im-proved much the photocatalytic removal of Cr(VI)in acidic condition,which was confirmed to its special solid acid structure.During the synthesis of the SnS_(2)/CNT composite by ball milling,S-C p-πbonding was formed between sulfur atoms in SnS_(2)and carbon atoms in CNT.The generated S-C p-πbonding enhanced the transfer of photo-induced electrons in the bulk phase of the composite photocatalyst un-der visible light irradiation.Moreover,the persistent radical sites on CNT were able to trap photo-induced electrons and served as conjugated acid sites in the photocatalysis,which increased surface concentration of protons through their association with H+.These made the catalyst have a solid acid structure with plentiful surface protons,promoting the interfacial electron transfer between the catalysts and Cr(VI)and increasing the source of H+for the reduction of Cr(VI).As a result,the photocatalytic reduction rate of Cr(VI)on the SnS_(2)/CNT composite were dramatically enhanced,being about 800%that on SnS_(2).On the basis of various characterizations and probe experiments,we confirmed the significance of the solid acid structure of the photocatalyst and clarified the catalytic mechanism of the new photocatalyst.Our finding may provide a new strategy to prepare highly active photocatalysts for proton-involved reactions.

An eco-friendly and highly sensitive loofah@CF/CNT 3D piezoresistive sensor for human activity monitoring and mechanical cotrol

Three-dimensional(3D)porous piezoresistive sensors are widely used because of their simple fabrication and convenient signal acquisition.However,because of the dependence on organic skeleton materials and the complexity of conductive coating preparation,the electrical and mechanical properties of 3D wearable piezoresistive sensors have gradually failed to accommodate many emerging fields.Here,a new flexible 3D piezoresistive sensor(NF3PS)with high sensitivity and a wide measurement range is proposed,which comprises a natural porous loofah as a flexible framework and carbon fiber/carbon nanotube(CF/CNT)multiscale composite as a conductive coating.Composed of cellulose and lignin,the irregular,porous loofah has excellent mechanical strength,elasticity,and toughness,ensuring a repeated compression/recovery behavior of the NF3PS.In addition,compared with the single-size carbon coating,the coupling of multiscale CF/CNT composite coating improves sensitivities over a range of pressures.The NF3PS demonstrates a sensitivity of 6.94 kPa^(-1) with good linearity in the pressure range of 0–11.2 kPa and maintains a sensitivity of 0.28 kPa^(-1) in an ultrawide measurement range of 11.2–84.6 kPa.Considering flexibility,robustness,and wide-ranging linear resistance variation,the feasibility of the NF3PS in human activity monitoring,mechanical control,and smart homes is verified.This work provides a novel strategy for a new generation of 3D flexible pressure sensors for improving sensitivity and measurement range and demonstrates attractive applications in wearable sensors.

Preparation and electrocatalytic properties of gold nanoparticles loaded carbon nanotubes

Nano gold （Au） particles loaded carbon nanotubes （Nano-Au/CNTs） were prepared by a new method. Polar groups and defects were introduced on the surface of the prepared Nano-Au/CNTs by a mixed acids treatment process, and their electrocatalytic properties were investigated in this study. Comparing with the traditional preparation method, the particle nano size of Au can be controlled and it is easier to wash the sodium citrate by this method. Comparing t performance.

Gradient CNT/PVDF piezoelectric composite with enhanced force-electric coupling for soccer training

Real-time monitoring of ball–shoe interactions can provide essential information for high-quality instruction in personalized soccer training,yet existing monitoring systems struggle to reflect specific forces,loci,and durations of action.Here,we design a self-powered piezoelectric sensor constructed by the gradient carbon nanotube/polyvinylidene fluoride(CNT/PVDF)composite to monitor the interactions between the ball and the shoe.Two-dimensional Raman mapping demonstrates the gradient structure of CNT/PVDF prepared by programmable electrospinning combined with a hot pressing.Benefitting from the synergistic effect of local polarization caused by the enrichment of CNT and the reduced diffusion of silver patterns in gradient structure,the as-prepared composite exhibits enhanced force-electric coupling with an excellent sensitivity of 80 mV/N and durability over 15,000 cycles.On this basis,we conformally attach a 3×3 sensor array to a soccer shoe,enabling real-time acquisition of kick position and contact force,which could provide quantitative assessment and personalize guidance for the training of soccer players.This self-powered piezoelectric sensor network system offers a promising paradigm for wearable monitoring under strong impact forces.