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.

A comparative study of polymer nanocomposites containing multi-walled carbon nanotubes and graphene nanoplatelets

Featuring exceptional mechanical and functional performance, MWCNTs and graphene(nano)platelets(GNPs or Gn Ps;each platelet below 10 nm in thickness) have been increasingly used for the development of polymer nanocomposites. Since MWCNTs are now cost-effective at US$30 per kg for industrial applications, this work starts by briefly reviewing the disentanglement and surface modification of MWCNTs as well as the properties of the resulting polymer nanocomposites. GNPs can be made through the thermal treatment of graphite intercalation compounds followed by ultrasonication;GNPs would have lower cost yet higher electrical conductivity over 1,400 S cmthan MWCNTs. Through proper surface modification and compounding techniques, both types of fillers can reinforce or toughen polymers and simultaneously add anti-static performance. A high ratio of MWCNTs to GNPs would increase the synergy for polymers. Green, solvent-free systhesis methods are desired for polymer nanocomposites. Perspectives on the limitations, current challenges and future prospects are provided.

Synthesis and Application of Nanocomposite Reinforced with Decorated Multi Walled Carbon Nanotube with Luminescence Quantum Dots

Amidst the COVID-19 pandemic, environmental problems such as energy crisis, global warming, and contamination from pathogenic micro-organisms are still prevailed and strongly demanded progress in high-performance energy storing and anti-microbial materials. The nanocomposites are materials that have earned large interest owing to their promising applications for countering global issues related to sustainable energy and a flourishing environment. Here, polypyrrole coated hybrid nanocomposites of multi-walled carbon nanotube and cadmium sulfide quantum dots named MCP were synthesized using facile and low-cost in-situ oxidative polymerization method. Characterization techniques confirmed the synthesis. Electrochemical studies showed that the nanocomposite 1-MCP showed an impressively higher super capacitance behavior in comparison to f-MWCNT, 7-MCP and 5-MCP. The improved performance of the nanocomposites was attributed mainly to the good conductivity of carbon nanotubes and polypyrrole, high surface area, and stability of the carbon nanotubes and the high electrocatalytic activity of the cadmium sulfide quantum dots. Owing to the synergistic effect of MWCNT, CdS, and PPy the synthesized ternary nanocomposite also inhibited the growth and multiplication of tested bacteria such as S. aureus, and E. coli completely within 24 h. On the whole, the assimilated nanocomposite MCP opens promising aspects for the development of upcoming energy storage devices and as an antibacterial agent.

The Packaging Materials with Carbon Nanotube/Polymer Composites

A polymer-based carbon nano-tubes (CNTs) composite with high electromagnetic (EM) wave shielding effectiveness (SE) and with high mechanical property is developed for packaging of electronic modulus or devices.The liquid crystal polymers (LCP) and melamine formaldehydes (MF) polymer are used to study the orientation effect of CNTs in various polymeric matrix.The influences of orientation,aspect ratio,and mass fraction of CNTs upon the shielding effectiveness (SE) of CNTs-composites are investigated.The higher the orientation,aspect ratio,and weight percentages of nano-materials are, the higher the SE of the carbon composites.The highest SE for the CNTs/LCP nano composite obtained is more than 62 dB. This results may lead to the developing for CPU IC chip packaging.

Experimental Evaluation of Thermal Conductivity and Other Thermophysical Properties of Nanofluids Based on Functionalized (-OH) Mwcnt Nanoparticles Dispersed in Distilled Water

A possible way to increase thermal conductivity of working fluids, while keeping pressure drop at acceptable levels, is through nanofluids. Nanofluids are nano-sized particles dispersed in conventional working fluids. A great number of materials have potential to be used in nanoparticles production and then in nanofluids;one of them is Multi-Walled Carbon Nano Tubes (MWCNT). They have thermal conductivity around 3000 W/mK while other materials used as nanoparticles like CuO have thermal conductivity of 76.5 W/mK. Due to this fact, MWCNT nanoparticles have potential to be used in nanofluids production, aiming to increase heat transfer rate in energy systems. In this context, the main goal of this paper is to evaluate from the synthesis to the experimental measurement of thermal conductivity of nanofluid samples based on functionalized (-OH) MWCNT nanoparticles. They will be analyzed nanoparticles with different functionalization degrees (4% wt, 6% wt, and 9% wt). In addition, it will be quantified other thermophysical properties (dynamic viscosity, specific heat and specific mass) of the synthetized nanofluids. So, the present work can contribute with experimental data that will help researches in the study and development of MWCNT nanofluids. According to the results, the maximum increment obtained in thermal conductivity was 10.65% in relation to the base fluid (water).

Natural Convection Melting in a Rectangular Heat Storage Tank of Carbon Nanotube Dispersed Latent Heat Storage Material

A dispersion system fluid can convect even if the dispersoid is a solid phase.Therefore,heat exchange performance can be improved while maintaining fluidity using a material with high thermal conductivity as the dispersoid.This study presents the melting performance evaluation results of a latent heat storage material with a carbon nanotube(CNT)dispersion system with high thermal conductivity,which enhances the thermal conductivity of the latent heat storage material and does not limit free convection.Increasing the thermal conductivity and enhancing the melting convection of the heat storage material result in increased latent heat storage speed.In this study,the thermal conductivity of the latent heat storage material was successfully increased by dispersing CNTs in the material.When 0.1%(in mass)of multi-wall CNT(MWCNT)was dispersed in a paraffin-based latent heat storage material,the shear stress increased by 1.5 times at a shear rate of 500 s^(-1),while taking into account the potential effects of convective inhibition.Therefore,a latent heat storage experiment was conducted in a rectangular heat storage tank using the CNT dispersion composition ratio as a parameter.A rectangular vessel with a heated vertical surface was used for the latent heat storage experiment.The melting speed was determined by comparing the amount of latent heat stored in a CNT-dispersed latent heat storage material and a single-phase latent heat storage material sample.The experimental results show that the time required for the latent heat storage material to completely melt in the heat storage tank was the shortest for the single-phase latent heat storage material sample.However,the fastest melting progress was observed for the sample with 0.02%(in mass)MWCNT content in the melting rate range of up to approximately 40%in the tank.The results indicate that this phenomenon is caused by the difference in the melting rates in the upper part of the tank.The generated data are useful for determining the shape and heat transfer surface arrangement of the latent heat storage tank.

Carbon Nano Material Synthesis from Polyethylene by Chemical Vapour Deposition

Three different types of Polyethylene family, High Density Polyethylene, (HDPE), Low Density polyethylene (LDPE) and Linear Low Density polyethylene (LLDPE) polymers having different molecular weight and density;were pyrolyzed in the temperature range of 550°C - 1050°C under H2, N2 and Ar gases. Taguchi Optimization technique was applied to find out the best operating conditions to get maximum yield of carbon nano material (CNM). For Taguchi op- timization, experimental set up was done in two different temperature ranges i.e. 550°C - 750°C and 850°C - 1050°C. CNMs synthesized were characterized by SEM, TEM, Micro Raman and XRD analysis. HDPE was found to yield maximum CNM. Its pyrolysis at 750°C under hydrogen atmosphere for 2h gave carbon nano beads and some carbon nano tubes. Whereas under same conditions at 1050°C more multi wall carbon nano tubes (MWCNT) were produced, with some carbon nano beads. XRD data confirmed the graphitic nature of carbon-nanotube. The intensities of G-band and D-band of Raman spectra suggested that CNM has more defect sites and spectra were similar for CNM obtained in both the temperature ranges. The TGA analysis of CNM obtained at 550°C - 750°C, indicated that they are not amor- phous carbon and CNM obtained at 850°C - 1050°C decomposed at 624°C - 668°C;suggesting that CNT synthesized at this temperature range were more crystalline than what was obtained at the 550°C - 750°C.

Improving the electroconductivity and mechanical properties of cellulosic paper with multi-walled carbon nanotube/polyaniline nanocomposites

Cellulose is the most abundant renewable polymer in the nature,and cellulosic paper is widely used in our daily life.Conferring electroconductivity to cellulosic paper would allow this conventional material to hold great promise for a wide range of energy-related applications.In the present work,multi-walled carbon nanotube(MWCNT)/polyaniline(PANI)nanocomposites were synthesized via in situ oxidation polymerization process and characterized by FT-IR and TEM.Subsequently,the application of the synthesized MWCNT/PANI nanocomposites as a wet-end filler for the production of electro-conductive paper was demonstrated/developed.Results showed that the cellulosic paper was imparted with an electro-conductivity of up to 0.14 S·m^(-1) while exhibiting a pronounced improvement in mechanical properties as a function of the added MWCNT/PANI nanocomposites.

碳纤维增强树脂基复合材料的层间颗粒增韧技术研究进展

碳纤维增强树脂基复合材料(CFRP)具有高强高模的优点,被广泛应用于汽车、体育、船舶、航空航天等领域,达到了材料轻量化的要求。目前使用较多的树脂基体以环氧树脂(EP)等热固性树脂为代表,普遍存在脆性大、韧性差的问题,导致复合材料层合板容易在层间发生开裂。层间增韧是一种有效的增韧方式,它可以在不改变基体树脂粘度的情况下对特定区域进行增韧,提高材料的断裂韧性。本文介绍了层间断裂模式并总结了层间断裂韧性(ILFT)测试的数据处理方法,总结了聚合物颗粒与无机纳米颗粒(主要是碳纳米管)的颗粒种类、增韧机制、引入方式,并主要通过层间断裂韧性评价了各种颗粒的增韧效果。

A strategy resisting wrinkling of sandwich structures reinforced using functionally-graded carbon nanotubes

Sandwich structures have been widely applied in the wing and the horizontal tail of the aircraft,so face sheets of such structure might occur wrinkling deformation in the process of service,which will largely decrease capability of sustaining loads.As a result,this paper aims at proposing a reasonable strategy resisting wrinkling deformation of sandwich structures.To this end,an enhanced higher-order model has been proposed for wrinkling analysis of sandwich structures.Buckling behaviors of a five-layer sandwich plate are firstly analyzed,which is utilized to assess performance of the proposed model.Subsequently,wrinkling behaviors of four sandwich plates are further investigated by utilizing present model,which have been evaluated by using quasi threedimensional(3D)elasticity solutions,3D Finite Element Method(3D-FEM)results and experimental datum.Finally,the present model is utilized to study the buckling and the wrinkling behaviors of sandwich plates reinforced by Carbon Nano Tubes(CNTs).In addition,influence of distribution profile of CNTs on wrinkling behaviors has been analyzed,and a typical distribution profile of CNTs has been chosen to resist wrinkling deformation.Without increase of additional weight,the present strategy can effectively resist wrinkling deformation of sandwich plates,which is rarely reported in published literature.

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.

静电纺丝制备MWCNT_(s)/PVA定向导热复合纤维膜

将浓HNO_(3)和浓H_(2)SO_(4)酸化处理后的多壁碳纳米管(MWCNT_(s))加入聚乙烯醇(PVA)纺丝液中,通过静电纺丝法制备了不同MWCNT_(s)含量的MWCNT_(s)/PVA复合纤维膜。FT-IR分析表明,酸化后的MWCNT_(s)表面含有大量羟基和羧基。TEM分析表明,MWCNT_(s)在PVA内部呈定向线性排列。有效导热通道的形成,使得MWCNT_(s)/PVA复合纤维膜的水平导热系数显著增大,5%MWCNT_(s)/PVA的水平导热系数为1.32W/(m·K),为纯PVA纤维膜导热系数的6.6倍。同时,MWCNT_(s)的添加提高了复合纤维膜的热稳定性,5%MWCNT_(s)/PVA的热分解温度达到295.7℃,比纯PVA纤维膜提高了14.4℃。利用红外热像仪探测了MWCNT_(s)/PVA复合纤维膜应用于LED灯的散热效果,5%MWCNT_(s)/PVA纤维膜能有效降低LED灯珠的附近温度约11℃。

缠绕型碳纳米管增强陶瓷基复合材料的有效刚度和应力分析

以直线型、余弦波型和缠绕型空心碳纳米管增强陶瓷基复合材料的三维特征体积单元模型为研究对象,利用满足精确周期性边界条件的均质化法计算该模型的有效弹性模量和局部应力,分析碳纳米管的几何形状、尺寸和力学特性对碳纳米管复合材料力学性能的影响,并与经典混合法则、Halpin-Tsai法及其他数值模拟的结果进行对比.结果表明:碳纳米管的几何缠绕特性对横向变形有较好的限制作用;缠绕型复合材料的力学性能呈曲线变化,比直线型和余弦波型碳纳米管复合材料更容易受几何特性的影响:缠绕型碳纳米管的最大轴向应力和最大等效应力随碳纳米管外径的增大而增大,但碳纳米管的各向异性会降低碳纳米管的最大应力,导致缠绕型碳纳米管复合材料传递应力的能力减弱;双尺度均质化法和有限元法结合能有效反映力学性能的变化特征,是分析具有复杂微观结构力学性能的有效方法.

Supramolecular precursor strategy for the synthesis of holey graphitic carbon nitride nanotubes with enhanced photocatalytic hydrogen evolution performance

A simple one-step thermal polymerization method was developed for synthesis of holey graphitic carbon nitride nanotubes,involving direci eating of mixtures of melamine and urea or melamine and cyanuric acid in specific mass ratios.Supramolecular structures formed betweer the precursor molecules guided nanotube formation.The porous and nanotubular structure of the nanotubes facilitated efficient charge carrier nigration and separation,thereby enhancing photocatalytic Hz production in 20 vol.%lactic acid under visible light irradiation.Nanotubes synthesized using melamine and urea in a 1:10 mass ratio(denoted herein as CN-MU nanotubes)exhibited a photocatalytic hydroger production rate of 1,073.6μmol·h^-1·^-g with Pt as the cocatalyst,a rate of 4.7 and 3.1 times higher than traditional Pt/g-CN4 photocatalysts prepared from graphitic carbon nitride(g-CN4)obtained by direct thermal polymerization of melamine or urea,respectively.On the basis of their outstanding performance for photocatalytic H2 production,it is envisaged that the holey g-C3N4 nanotubes will find widespread uptake in other areas,including photocatalytic CO2 reduction,dye-sensitized solar cells and photoelectrochemical sensors.

碳纳米管对RGO/CNT-CNP涂层吸光性能的影响

为获得对可见光到近红外光具有优异吸收性能的吸光涂层,以还原氧化石墨烯(reduced graphene oxide,RGO)作框架、碳纳米颗粒(carbon nano particles,CNP)和碳纳米管(carbon nano tubes,CNT)作附着物,采用高压静电喷涂技术制备了RGO/CNT_(x)-CNP吸光涂层(x为CNT的直径),研究了CNT的直径对RGO/CNT_(x)-CNP涂层形貌和吸光性能的影响。结果表明:RGO/CNP涂层对波长为400~1400 nm的光的平均吸收率为90.5%;加入CNT使RGO以一定角度倾斜堆叠,从而形成具有不同尺寸光学腔的复合结构,RGO/CNT_(x)-CNP涂层的光吸收性能显著改善;随着CNT直径的增大,CNT覆盖RGO框架的面积增加,RGO/CNT_(x)-CNP涂层的表面粗糙度增大,微米级和纳米级光学腔的数量增加,从而涂层的吸光率提高;采用直径为20 nm的CNT制备的RGO/CNT20-CNP涂层具有最佳的吸光性能,对可见光到近红外光的平均吸收率达94.1%。

Nano-sized graphitic carbon in authigenic tube pyrites from offshore southwest Taiwan, South China Sea, and its implication for tracing gas hydrate

Gas hydrates are a significant energy resource and are usually detected by bottom simulating reflection and submarine geochemical anomalies. Authigenic minerals are related to gas hydrates, with carbonates, sulfates and sulfides being important tracing minerals. Authigenic tubular pyrites were collected from offshore southwest Taiwan in the South China Sea, and were investigated by scanning electron microscopy(SEM) and high-resolution transmission electron microscopy (HRTEM). Authigenic tubular pyrite was composed of framboidal pyrite, within which nanosized graphitic carbon of low crystallinity was discovered. The graphitic carbon coexisted with pyrite and had a texture similar to carbon nanotubes and nanocones, indicating that they likely precipitated from carbon supersaturated C-H-O fluid. Pyrite may act as a catalyst for the conversion of CH 4 to C. The discovery of nanosized graphitic carbon in pyrite indicated it was deposited in sediments that were supersaturated with methane fluid. Thus, nanosized graphitic carbon may be another tracing species for submarine gas hydrates. The discovery of nanosized graphitic carbon deposited in a low temperature environment will enlighten our understanding of the laboratory synthesis and industrial production of graphitic carbon.

Experimental and DFT insights into nitrogen and sulfur co-doped carbon nanotubes for effective desulfurization of liquid phases:Equilibrium&kinetic study

Herein,nitrogen and sulfur co-doped carbon nanotubes(NS-CNT)adsorbents were synthesized via the chemical vapor deposition technique at 1000°C by employing the camphor,urea and sulfur trioxide pyridine.In this study,desulfurization of two types of mercaptans(dibenzothiophene(DBT)and tertiary butyl mercaptan(TBM)as nonlinear and linear forms of mercaptan)was studied.In this regard,a maximum capacity of NS-CNT was obtained as 106.9 and 79.4 mg/g and also the removal efficiencies of 98.6%and 88.3%were achieved after 4 h at 298K and 0.9 g of NS-CNT for DBT and TBM,respectively.Characterization of the NS-CNTs was carried out through exploiting scanning electron microscopy(SEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),and elemental analysis(CHN).The isotherm equilibrium data could be ascribed to the Freundlich nonlinear regression form and the kinetic data was fitted by nonlinear form of the pseudo second order model.The negative values of ΔS^(0),ΔH^(0) and ΔG^(0) specify that the adsorption of both types of mercaptans was a natural exothermic process with a reduced entropy.Maintenance of more than 96%of the adsorption capacity even after nine cycles suggest the NS-CNT as a superior adsorbent for mercaptans removal in the industry.Density functional theory(DFT)calculations were also performed to peruse the effects of S/N co-doping and carbon monovacancy defects in CNTs toward the adsorption of DBT and TBM.

电去离子系统复合型电极材料研究进展

电去离子技术(CDI)是基于双电层理论发展起来的一种低能耗、低成本、绿色高效的脱盐技术,其吸附电极是电去离子装置的最核心部件,决定了装置的吸附能力。电去离子装置的电极材料需要有较高的比表面积、合理的孔径分布和良好的导电性,国内外学者对其进行了广泛的研究。研究发现,活性炭、碳纳米管、石墨烯、金属-有机框架材料等均具有优异的物理化学特性、较高的比表面积、良好的吸附性能,在电去离子系统中表现出较好的吸附能力,但是以上4种材料也存在着循环寿命短、化学稳定性差、能量回收率低等不足,在今后的研究中需要不断进行研究优化。

富含介孔结构的氮化碳/碳纳米管复合催化剂高效电催化还原CO_(2)为CO

氮掺杂材料中的吡啶氮被认为是电还原CO_(2)为CO的最活跃的氮催化位点.以双氰胺(dicyandiamide,DCDA)为氮源,氧化碳纳米管(carbon oxide nanotubes,CNTs-O)为分散剂,通过静电吸附-煅烧法制备了富含吡啶氮的氮化碳/碳纳米管(CN_(x)/CNTs)介孔复合催化剂.通过改变DCDA与CNTs-O的质量比,合成了具有不同石墨化氮化碳(g-C_(3)N_(4))含量的复合催化剂.通过一系列表征及电化学测试得出,当DCDA/CNTs-O质量比为0.5时,得到的CN_(0.5)/CNTs具有最优的还原CO_(2)为CO的电催化性能.在-1.0 V vs.RHE下CN_(0.5)/CNTs的CO法拉第效率(Faradaic efficiency,FE)高达94.1%,生成CO的电流密度为-13.27 mA/cm^(2),通过24 h长时间电解后依然保持着较高的法拉第效率(FECO>85%).