Preparation of multi-walled carbon nanotube–Fe composites and their application as light weight and broadband electromagnetic wave absorbers

Multi-walled carbon nanotube （MWCNT）-Fe composites were prepared via the metal organic chemical vapor deposi- tion by depositing iron pentacarbonyl on the surface of MWCNTs. The structural and morphological analyses demonstrated that Fe nanoparticles were deposited on the surface of the MWCNTs. The electromagnetic properties of the MWCNTs were significantly changed, and the absorbing capacity evidently improved after the Fe deposition on the MWCNT surface. A minimum reflection loss of -29.4 dB was observed at 8.39 GHz, and the less than -10 dB bandwidth was about 10.6 GHz, which covered the whole X band （8.2-12.4 GHz） and the whole Ku band （12.4-18 GHz）, indicating that the MWCNT-Fe composites could be used as an effective microwave absorption material.

Ultrasensitive electrochemical determination of metronidazole based on polydopamine/carboxylic multi-walled carbon nanotubes nanocomposites modified GCE

An ultrasensitive electrochemical sensor based on polydopamine/carboxylic multi-walled carbon nanotubes(MWCNTs à COOH) nanocomposites modified glassy carbon electrode(GCE) was presented in this work, which has been developed for highly selective and highly sensitive determination of an antimicrobial drug, metronidazole. The preparation of polydopamine/MWCNTs–COOH nanocomposites/GCE sensor is simple and possesses high reproducible, where polydopamine can be coated on the surface of MWCNTs–COOH via a simple electropolymerization process. Under optimized conditions, the proposed sensor showed ultrasensitive determination for metronidazole with a wide linear detection range from5 to 5000 mmol/dm^3 and a low detection limit of 0.25 mmol/dm^3(S/N=3). Moreover, the proposed sensor has been successfully applied for the quantitative determination of metronidazole in real drug samples. This work may provide a novel and effective analytical platform for determination of metronidazole in application of real pharmaceutical and biological samples analysis.

Crystallization Behavior and Mechanical Properties of Poly(vinylidene fluoride)/multi-walled Carbon Nanotube Nanocomposites

Poly（vinylidene fluoride）（PVDF）/multi-walled carbon nanotube（MWCNT） nanocomposites were prepared by means of ultrasonic dispersion method. X-ray diffraction（XRD） results indicate that incorporating MWCNTs into PVDF caused the formation of β phase. A thermal annealing at 130 ℃ confirmed that the β phase was stable in the nanocomposites. Differential scanning calorimetry（DSC） results indicate that the melting temperature slightly increased while the heat of fusion markedly decreased with increasing MWCNT content. The tensile strength and modulus of PVDF were improved by loading the MWCNTs. The scanning electron microscopy（SEM） observations showed that MWCNTs were uniformly dispersed in the PVDF matrix and an interfacial adhesion between MWCNT and PVDF was achieved, which was responsible for the enhancement in the tensile strength and modulus of PVDE.

Composition Dependent Magnetic Properties of Ni-Co-P Coated Carbon Nanotubes

Carbon nanotubes were coated with a layer of nickel-cobalt-phosphorus （Ni-Co-P） alloy with different compositions of Ni/Co through electroless plating. The effects of the concentration ratio of Co^2＋ to Ni^2＋, bath temperature, and pH on deposition rate are discussed. The prepared carbon nanotubes covered with Ni-Co-P were characterized and analyzed by fieldemission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, energy dispersive spectroscopy, and a vibrating sample magnetometer. The results show that the deposition rate reached the maximum when the concentration ratio of Co^2＋ to Ni^2＋ is 1 and the pH is 9; the deposition rate increases with the increase of bath temperature. The measurements of the magnetic properties of the obtained carbon nanotubes covered with Ni-Co-P indicate that the magnetic properties greatly depend on the concentration ratio of Co^2＋ to Ni^2＋, and the magnetic saturation reaches the maximum value when the Co^2＋ to Ni^2＋ ratio is 1. In addition, there are two peaks in the coercivity curve at Co^2＋ to Ni^2＋ ratios of 1/2 and 4/1, while the two peaks in the magnetic conductivity curve are located at Co^2＋ to Ni^2＋ ratios of 1/4 and 4/1.

Structure and Properties of Self-assembled Narural Rubber/Multi-walled Carbon Nanotube Composites

Natural rubber （NR）/multi-walled carbon nanotube （MWCNTs） composites were prepared by combining self-assembly and latex compounding techniques.The acid-treated MWCNTs （H2SO4：HNO3=3：1,volume ratio） were self-assembled with poly （diallyldimethylammonium chloride） （PDDA） through electrostatic adhesion.In the second assembling,NR/MWCNTs composites were developed by mixing MWCNTs/PDDA solution with NR latex.The results show that MWCNTs are homogenously distributed throughout the NR matrix as single tube and present a great interfacial adhesion with NR phase when MWCNTs contents are less than 3 wt%.Moreover,the addition of the MWCNTs brings about the remarkable enhancement in tensile strength and crosslink density compared with the NR host,and the data peak at 2 wt% MWCNTs loadings.When more MWCNTs are loaded,aggregations of MWCNTs are gradually generated,and the tensile strength and crosslink both decrease to a certain extent.

Adsorption of Cr(Ⅵ) in wastewater using magnetic multi-wall carbon nanotubes

Magnetic multi-wall carbon nanotubes were prepared with wet chemical treatments and characterized by a transmission electron microscope （TEM） and X-ray diffraction （XRD）. They were used as adsorbents for the removal of Cr（VI） in aqueous solutions. The effects of adsorbent dosage, the concentration of Cr（VI） in aqueous solution, temperature, and pH value on the removal efficiency were studied. Results showed that the adsorption capacity of the magnetic multi-wall carbon nanotubes increased with the initial Cr（VI） concentration, but decreased with the increase of adsorbent dosage. The adsorption amount increased with contact time. The adsorption kinetics were best represented by the pseudo second-order kinetic model, and the adsorption isotherms indicated that the Langmuir model better reflected the adsorption process. The ob- tained calculation results for the Gibbs free energy revealed that the adsorption was a spontaneous and endothermic process. The enthalpy deviation was 3.835 kJ.mol 1. The magnetic multi-wall carbon nanotubes showed significant potential for application in adsorption of heavy metal ions.

Pyrolyzed Iron Phthalocyanine-Modified Multi-Walled Carbon Nanotubes as Composite Anode in Marine Sediment Microbial Fuel Cells and Its Electrochemical Performance

Improving the performance of anode is a crucial step for increasing output power of marine sediment microbial fuel cells(MSMFCs)to drive marine monitor to work for a long term on the ocean floor.A pyrolyzed iron phthalocyanine modified multi-walled carbon nanotubes composite(FePc/MWCNTs)has been utilized as a novel nodified anode in the MSMFC.Its structure of the composite modified anode and electrochemical performance have been investigated respectively in the paper.There is a substantial improvement in electron-transfer efficiency from the bacteria biofilm to the modified anode via the pyrolyzed FePc/MWCNTs composite based on their cyclic voltammetry(CV)and Tafel curves.The electron transfer kinetic activity of the FePc/MWCNTs-modified anode is 1.86 times higher than of the unmodified anode.The maximum power density of the modified MSMFC was 572.3±14 m W m^-2,which is 2.6 times larger than the unmodified one(218.3±11 m W m^-2).The anodic structure and cell scale would be greatly minimized to obtain the same output power by the modified MSMFC,so that it will make the MSMFC to be easily deployed on the remote ocean floor.Therefore,it would have a great significance for us to design a novel and renewable long term power source.Finally,a novel molecular synergetic mechanism is proposed to elucidate its excellent electrochemical performance.

Microwave Absorption Properties of Carbon Nanotubes-Epoxy Composites in a Frequency Range of 2 - 20 GHz

In this work, multi-walled carbon nanotubes (MWCNTs)-epoxy composites with MWCNTs (outer diameter less 8 nm) loadings from 1 to 10 wt% were fabricated. The microstructures, dielectric constant, and microwave absorption properties of the MWCNTs-epoxy composite samples were investigated. The measurement results showed that the microwave absorption ratio of the MWCNTs-epoxy composite strongly depend on the MWCNT loading in the composites. The microwave absorption ratio up to 20%-26% around 18-20 GHz was reached for the samples with 8-10 wt% MWCNT loadings. The high absorption performance is mainly attributed to the microwave absorption of MWCNTs and the dielectric loss of MWCNTs-epoxy composites.

Improvement of Interlaminar Fracture Properties of Out of Autoclave Manufactured Carbon Fiber Reinforced Polymers Using Multi-Walled Carbon Nanotubes

The present study aims to the development of Out of Autoclave (OoA) Carbon Fiber Reinforced Polymers (CFRPs) with increased interlaminar fracture toughness by using MWCNTs. The introduction of MWCNTs into the structure of CFRPs has been succeeded by using carbon nanotube-enriched sizing agent for the pretreatment of the fiber preform using an in-house developed methodology that can be easily scaled up. The positive effect of the proposed methodology on the interlaminar fracture toughness of the CFRP laminate was assessed by the increase of Mode I and Mode II interlaminar fracture toughness of the composites. Different wt% MWCNTs concentrations were used (namely 0.5%, 1%, 1.5% and 2.5%). It was found that the nanomodified composites exhibit a significant increase of the interlaminar critical strain energy release rate GIC and GIIC of the order of 103% and 62% respectively, in the case of 1.5 wt% MWCNTs weight content. Scanning Electron Microscopy (SEM) of the fracture surfaces of CFRP samples revealed the contribution and the associated synergistic mechanisms of MWCNTs to the increase of the crack propagation resistance in the case of nano-modified CFRPs compared to the reference material.

Molecularly imprinted sensor based on carboxylated carbon nanotubes/Keggin-type polyoxometalates nanocomposite for the detection of furazolidone

Due to its properties of mutagenic,teratogenic,and carcinogenic,the detection of furazolidone(FZD)in aquaculture is of great importance for food safety and human health.In this study,molecularly imprinted fi lms modifi ed with carboxylated multi-walled carbon nanotube-phosphomolybdic acid composite were used to fabricate an electrochemical sensor for the determination of FZD.The nanocomposites were characterized using infrared spectroscopy,scanning electron microscopy,energy-dispersive X-ray spectroscopy,and X-ray diff raction.The electrochemical characteristics of the modifi ed electrodes were examined using electrochemical impedance spectroscopy,cyclic voltammetry,and diff erential pulse voltammetry.The sensor exhibited exceptional catalytic performance.The calibration curves were acquired in the concentration range of 6 nmol·L^(−1)to 0.6μmol·L^(−1),with a limit of detection of 3.38 nmol·L^(−1).Additionally,the sensor proved successful in recognizing FZD in shrimp samples with satisfactory recoveries and precision.The method provides a strategy to construct a molecularly imprinted electrochemical sensing platform using nanomaterials,which has great promise in the field of food safety.

Study on the Mechanical Properties of Carbon Nanotube/Polyacrylonitrile Composite Fibers

The method of preparing the multi-walled carbon nanotubes (MWNTs)-polyacrylonitriIe (PAN) composite fibers is described and the effects of draw ratio on the mechanical properties of CNT/PAN fibers have also been discussed. The results show that the degrees of MWNTs dispersion in the polymer matrix have much effect on the mechanical properties.

Fabrication and mechanical properties of MWCNTs-reinforced aluminum composites by hot extrusion

Over the past decade,the interest in aluminum composites reinforced with carbon nanotubes has grown significantly.Studies have been carried out to overcome problems with uniform dispersion,interfacial bonding,void formation and carbide formation of the composites.In the present work,multi-wall carbon nanotubes(MWCNTs) aluminum composites were produced.High-energy ball milling with the aim at developing well-dispersed MWCNTs Al composites was followed by cold compaction,sintering,and hot extrusion at 500 ℃.Different amounts of stearic acid as processing control agent(PCA) is used in order to minimize cold welding of the Al particles,and to produce finer particles.Differential scanning calorimetry(DSC),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and X-ray diffraction(XRD) were employed to analyze the MWCNTs,the aluminum powder,and the composites’ microstructural behavior.The hardness and tensile properties of the composites are also evaluated.The results showed 500% increase in yield stress after the addition of 1 wt% MWCNTs in Al-MWCNTs based composite.The ball-milling time of 4 h is found to be sufficient as excessive milling time destroys a vast number of MWCNTs.

Electrochemical detection and degradation of ibuprofen from water on multi-walled carbon nanotubes-epoxy composite electrode

This work describes the electrochemical behaviour of ibuprofen on two types of multi-walled carbon nanotubes based composite electrodes, i.e., multi-walled carbon nanotubes-epoxy （MWCNT） and silver-modified zeolite-multi-wailed carbon nanotubes-epoxy （AgZMWCNT） composites electrodes. The composite electrodes were obtained using two-roll mill procedure. SEM images of surfaces of the composites revealed a homogeneous distribution of the composite components within the epoxy matrix. AgZMWCNT composite electrode exhibited the better electrical conductivity and larger electroactive surface area. The electrochemical determination of ibuprofen （IBP） was achieved using AgZMWCNT by cyclic voltammetry, differential-pulsed voltammetry, square-wave voltammetry and chronoamperometry. The IBP degradation occurred on both composite electrodes under controlled electrolysis at 1.2 and 1.75 V vs. Ag/AgCl, and IBP concentration was determined comparatively by differential-pulsed voltammetry, under optimized conditions using AgZMWCNT electrode and UV-Vis spectrophotometry methods to determine the IBP degradation performance for each electrode. AgZMWCNT electrode exhibited a dual character allowing a double application in IBP degradation process and its control.

Effects of temperature on MWCNTs/PDMS composites based flexible strain sensors

Conductive polymer composites(CPCs)are widely used in the flexible strain sensors due to their simple fabrication process and controllable sensing properties.However,temperature has a significance impact on the strain sensing performance of CPCs.In this paper,the strain sensing characteristics of MWCNTs/PDMS composites under temperature loading were systematically studied.It was found that the sensitivity decreased with the increase of temperature and the phenomenon of shoulder peak also decreased.Based on the theory of polymer mechanics,it was found that temperature could affect the conductive network by changing the motion degree of PDMS molecular chain,resulting in the change of sensing characteristics.Finally,a mathematical model of the resistance against loading condition(strain and temperature),associated with the force−electrical equivalent relationship of composites,was established to discuss the experimental results as well as the sensing mechanism.The results presented in this paper was believed helpful for the further application of strain sensors in different temperature conditions.

Solar photocatalytic decomposition of two azo dyes on multiwalled carbon nanotubes(MWCNTs)/TiO_(2)composites

Multi-walled carbon nanotubes(MWCNTs)/TiO_(2)composite photocatalysts with high photoactivity were prepared by sol-gel process and further characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),Fourier transform infrared(FT-IR),and UV-vis absorption spectra.Compared to pure TiO_(2),the combination of MWCNTs with titania could cause a significant absorption shift toward the visible region.The photocatalytic performances of the MWCNTs/TiO_(2)composite catalysts were evaluated for the decomposition of Reactive light yellow K-6G(K-6G)and Mordant black 7(MB 7)azo dyes solution under solar light irradiation.The results showed that the addition of MWCNTs enhanced the adsorption and photocatalytic activity of TiO_(2)for the degradation of azo dyes K-6G and MB 7.The effect of MWCNTs content,catalyst dosage,pH,and initial dye concentration were examined as operational parameters.The kinetics of photocatalytic degradation of two dyes was found to follow a pseudo-first-order rate law.The photocatalyst was used for seven cycles with photocatalytic degradation efficiency still higher than 98%.A plausible mechanism is also proposed and discussed on the basis of experimental results.

Covalent and Non-covalent Chemical Modification of Multi-walled Carbon Nanotubes with Tetra-（4-hydroxylphenyl）porphyrin and Its Complexes

Multi-walled carbon nanotubes （MWNTs） were covalently and non-covalently functionalized with tetra- （4-hydroxylphenyl） porphyrin （THPPH2） and its complexes （ZnTHPP） forming dispersible nanohybrids in organic solution. The morphology of the nanohybrids was observed with transmission electron microscopy. The structure of the product was characterized by FT-IR, UV-Vis spectrophotometer, fluorescence spectroscopy and thermogravim- etric analysis. The photo-induced electron-transfer process of the nanohybrids in organic solution was also revealed.

基于CMWCNT/Nafion的增强型离子聚合物金属复合材料的制备及致动性能

离子聚合物金属复合材料(IPMC)是一种新型的电活性材料,具有体积小、质量轻、驱动电压低等优点,但驱动力小、稳定工作时间短等问题限制着其柔性致动性能。提出了一种基于银基IPMC的增强型致动器,通过在IPMC的基底聚合物中掺杂羧基化多壁碳纳米管(CMWCNT),来提高IPMC的整体机械性能和致动性能。其中,掺杂质量分数0.5%CMWCNT的IPMC的最大尖端位移和驱动力分别增加至未优化银基IPMC的1.60倍与2.32倍,该性能的提升归因于CMWCNT良好的导电性和羧基对水合阳离子迁移的加速作用。与未优化的银基IPMC相比,掺杂质量分数0.5%CMWCNT时IPMC驱动速率可提升至3.57倍。研究结果可为IPMC在各领域的应用发展提供参考。

Photocatalytic Degradation of Phenol over MWCNTs-TiO2 Composite Catalysts with Different Diameters

Titania-based composite catalysts were prepared through a sol-gel route employing multi-walled carbon nanotubes with different diameters. The materials were characterized using thermogravimetric analysis, nitrogen adsorption-desorption isotherm, powder X-ray diffraction, scanning electron microscopy, and diffuse reflectance UV-Vis absorption spectra. The application of the catalysts to photocatalytic degradation of phenol was tested under UV-Vis irradiation. A synergetic effect on phenol removal was observed in case of composite catalysts, which was evaluated in terms of apparent rate constant, total organic carbon removal and photonic efficiency.

Three Phase Composite Cylinder Assemblage Model for Analyzing the Elastic Behavior of MWCNT-Reinforced Polymers

Evolution of computational modeling and simulation has given more emphasis on the research activities related to carbon nanotube(CNT)reinforced polymer composites recently.This paper presents the composite cylinder assemblage(CCA)approach based on continuum mechanics for investigating the elastic properties of a polymer resin reinforced by multi-walled carbon nanotubes(MWCNTs).A three-phase cylindrical representative volume element(RVE)model is employed based on CCA technique to elucidate the effects of inter layers,chirality,interspacing,volume fraction of MWCNT,interphase properties and temperature conditions on the elastic modulus of the composite.The interface region between CNT and polymer matrix is modeled as the third phase with varying material properties.The constitutive relations for each material system have been derived based on solid mechanics and proper interfacial traction continuity conditions are imposed.The predicted results from the CCA approach are in well agreement with RVE-based finite element model.The outcomes reveal that temperature softening effect becomes more pronounced at higher volume fractions of CNTs.

Influence of tool rotation speeds on mechanical and morphological properties of friction stir processed nano hybrid composite of MWCNT-Graphene-AZ31 magnesium

The ever-increasing demand for light weighted hard materials for transportation industries encouraged researchers to develop composites with excellent mechanical properties which can transform it into more economical and eco-friendly.Reinforcing the metals with carbonaceous nanomaterials are progressively in focus due to their excellent capability to inculcate and tailor the properties of MMCs.In the present research,a hybrid nanocomposite of MWCNT-Graphene-AZ31 Mg alloy has been developed by using variable tool rotation speeds with friction stir processing(FSP).Optimized reinforcement ratio of 1.6%vol.MWCNT and 0.3%vol.of graphene have been used with variable tool rotation speeds,whereas other processing parameters are kept constant.The developed specimens were investigated using standard testing equipment for evaluating and comparing the mechanical properties on the basis of the microstructure of the processing regions and their morphological analysis,according to the ASTM standards.The obtained results revealed an improvement of 19.72%in microhardness and 77.5% of compressive strength in comparison with the base metal AZ 31 Magnesium alloy,with a tool rotational speed of 1400rpm.The values of tensile stress and percentage area reduction were recorded as less than that of the base metal matrix,but an increasing trend has been observed in the values of both with the improvement on rotational speeds of the tool.The effectual strengthening mechanisms are analyzed on the bases of SEM images and observed that discussed and found that grain refinement strengthening is the major contributor to the strength of the nanocomposite.