Nonlinear stability of advanced sandwich cylindrical shells comprising porous functionally graded material and carbon nanotube reinforced composite layers under elevated temperature

The nonlinear stability of sandwich cylindrical shells comprising porous functionally graded material(FGM) and carbon nanotube reinforced composite(CNTRC)layers subjected to uniform temperature rise is investigated. Two sandwich models corresponding to CNTRC and FGM face sheets are proposed. Carbon nanotubes(CNTs) in the CNTRC layer are embedded into a matrix according to functionally graded distributions. The effects of porosity in the FGM and the temperature dependence of properties of all constituent materials are considered. The effective properties of the porous FGM and CNTRC are determined by using the modified and extended versions of a linear mixture rule, respectively. The basic equations governing the stability problem of thin sandwich cylindrical shells are established within the framework of the Donnell shell theory including the von K’arm’an-Donnell nonlinearity. These equations are solved by using the multi-term analytical solutions and the Galerkin method for simply supported shells.The critical buckling temperatures and postbuckling paths are determined through an iteration procedure. The study reveals that the sandwich shell model with a CNTRC core layer and relatively thin porous FGM face sheets can have the best capacity of thermal load carrying. In addition, unlike the cases of mechanical loads, porosities have beneficial effects on the nonlinear stability of sandwich shells under the thermal load. It is suggested that an appropriate combination of advantages of FGM and CNTRC can result in optimal efficiency for advanced sandwich structures.

Preparation of multi-walled carbon nanotube-reinforced TiNi matrix composites from elemental powders by spark plasma sintering

Carbon nanotube (CNT)-reinforced TiNi matrix composites were synthesized by spark plasma sintering (SPS) employing elemental powders.The phase structure,morphology and transformation behaviors were studied.It was found that thermoelastic martensitic transformation be-haviors could be observed from the samples sintered above 800 ℃ even with a short sintering time (5min),and the transformation tempera-tures gradually increased with increasing sintering temperature because of more Ti-rich TiNi phase formation.Although decreasing the sin-tering temperature and time to 700 ℃ and 5min could not protect defective MWCNTs from reacting with Ti,still-perfect MWCNTs re-mained in the specimens sintered at 900 ℃.This method is expected to supply a basis for preparing CNT-reinforced TiNi composites.

Effects of carbon nanotubes on hydrogen storage property of Mg-based nanocomposites

Mg-based hydrogen storage nanocomposites added with carbon nanotubes(CNTs) were prepared by mechanical milling under the atmosphere of hydrogen. The results show that because of their own excellent heat conductivity and good hydrogen storage ability, the carbon nanotubes improve the mass transfer and heat transfer properties of the Mg-based nanocomponents, thus enhancing the kinetic property of hydrogen absorption and desorption of the hydrogen storage nanocomposites, and raising the hydrogen storage capacity. Due to the addition of the carbon nanotubes, the milling stress in the process of preparing the Mg-based nanocomposites is reduced, the components can be closely bonded easily, and the additives can play better catalytic roles.

Covalent organic frameworks/carbon nanotubes composite with cobalt(II)pyrimidine sites for bifunctional oxygen electrocatalysis

With characteristics and advantages of functional composite materials,they are commendably adopted in numerous fields especially in oxygen electrocatalysis,which is due to the significant synergies between various components.Herein,a novel bifunctional oxygen electrocatalyst(Co-CNT@COF-Pyr)has been synthesized through in-situ growth of covalent organic frameworks(COFs)layers on the outer surface of highly conductive carbon nanotubes(CNTs)followed by coordination with Co(Ⅱ).For electrocatalytic OER,Co-CNT@COF-Pyr reveals a low overpotential(438 mV)in alkaline electrolyte(1.0 M aqueous solution of KOH)with a current density of 10 mA cm^(-2),which is comparable to most discovered COF-based catalysts.For electrocatalytic ORR,CoCNT@COF-Pyr exhibits a low H_(2)O_(2) yield range(9.0%-10.1%)and a reaction pathway close to 4e^(-)(n=3.82-3.80)in alkaline electrolyte(0.1 M aqueous solution of KOH)within the test potential range of 0.1-0.6 V vs.RHE,which is superior to most reported COF-based catalysts.Hence,this research could not only offer an innovative insight into the construction of composites,but also facilitate the practical application of renewable fuel cells,closed water cycle,and rechargeable metal-air batteries.

Electroless deposition of Cu on multiwalled carbon nanotubes

Copper has been deposited on the surface of multiwailed carbon nanombes （MWNTs） and inside MWNTs by electroless deposition. The as-prepared Cu-MWNT composite materials have been characterized by X-ray diffractometer （XRD）, transmission electron microscopy （TEM）, and electrochemical measurement. XRD analyses showed that Cu was a face-centered cubic （fcc） structure. The average size of Cu was calculated by Scherrer＇s formula from XRD data, and it was 11 nm. TEM revealed that Cu grains on the surface of MWNTs were uniform with the sizes of about 30-60 nm. The electrochemical measurement indicated that Cu-MWNT composite materials possessed fine electron conductivity.

Effect of Surfactant Stabilizers on the Distribution of Carbon Nanotubes in Aqueous Media

The results of a study on the homogeneity of suspensions are described considering the effect of different types of surfactant stabilizers and their concentrations on the uniform distribution of a carbon nanotubes（CNTs）-based modifying additive to construction materials in an aqueous medium. This problem was solved herein by using surfactants and ultrasound. The sonication treatment of CNTs particle agglomerates allowed for dispersing their globules and achieving a 15-20-fold decrease in their average size, for which it became possible to make better use of the CNTs as cement modifier. As a result of the experimental studies carried out, the effect of the surfactant type and concentration promoting uniform distribution of the CNTs in the bulk of the suspension and, correspondingly, in the structural composite matrix was revealed. The CNTs-based additive improved the physical-mechanical and operational characteristics of the material.

Glass-Reinforced Plastic Filled by Multiwall Carbon Nanotubes and Their Modified Forms

The effect of modifying the surface of multiwall carbon nanotubes (CNT’s) by oxygen and nitrogen on the strength characteristics of the fiberglass filled with them was investigated by testing for tension and bending. The method of obtaining nitrogen-containing nanostructures is developed. It was shown that in the epoxide system LR285-LH286 hydrophobic CNT’s (outgoing) at introducing into the catalyst polymerization of LH286, increase the strength with respect to unreinforced CNT’s by 48% - 54%. Oxidized CNT’s (200 A?h/kg) introduced into the resin LR285 increase the strength by 59%. The distribution of the filler particles in size, both in the epoxy resin and in the catalyst, depends on their concentration nonlinear, and correlates with the strength characteristics of the composite.

Forced vibration analysis of nano-composite rotating pressurized microbeam reinforced by CNTs based on MCST with temperature-variable material properties

In this study, free and forced vibration analysis of nano-composite rotating pressurized microbeam reinforced by carbon nanotubes （CNTs） under magnetic field based on modify couple stress theory （MCST） with temperature-variable material propertiesis presented. Also, the boundary conditions at two ends of nano-composite rotating pressurized microbeam reinforced by CNTs are considered as simply supported. The governing equations are obtained based on the Hamilton＇s principle and then computed these equations by using Navier＇s solution. The magnetic field is inserted in the thickness direction of the nano-composite microbeam. The effects of various parameters such as angular velocity, temperature changes, and pressure between of the inside and outside, the magnetic field, material length scale parameter, and volume fraction of nanocomposite microbeam on the natural frequency and response systemare studied. The results show that with increasing volume fraction of nano-composite microbeam, thickness, material length scale parameter, and magnetic fields, the natural frequency increases. The results of this research can be used for optimization of micro-structures and manufacturing sensors, displacement fluid, and drug delivery.

Advanced hemocompatible polyethersulfone composite artificial lung membrane with efficient CO_(2)/O_(2)exchange channel constructed by modified carbon nanotubes network

Artificial lung membranes as the core module of the extracorporeal membrane oxygenation technology(ECMO)execute the function of extracorporeal blood-gas barrier accomplishing CO_(2)/O_(2)exchange with blood.However,the unsatisfactory hemocompatibility and difficulty in functionalization are the promi-nent challenges faced by current artificial lung membrane materials.In this study,polyethersulfone(PES)composite membranes with self-anticoagulant property and high gas exchange efficient are fabricated by blending PES matrix with poly(vinylamine)(PVAm)modified carboxylic carbon nanotubes(mCNTs)and citrate-based poly(octamethylene-citrate)(POC)pre-polymers.The mCNTs construct specific gas transfer channels within the composite membranes to enhance the gas permeability,while the POC pre-polymers provide anticoagulant property based on the chelation to blood Ca^(2+)and the inactivation effect to in-trinsic coagulation factors.Importantly,directed by the actual ECMO gas exchange mode,we design a gas-liquid convectional circulation device that could evaluate gas exchange efficiency for the composite membranes under mimetic ECMO state.Therefore,this strategy not only proposes a new design method of advanced artificial lung membranes to solve the practical challenges in the current ECMO technology,but also establishes a scientific testing method to evaluate the gas exchange performance for new-type artificial lung membrane materials in the future.

Evaluation for cell affinity of the composite material containing carbon nanotubes

The composite material of poly-(L-lactide) (PLLA) and carbon nanotubes (CNTs) were prepared. Itssurface morphologies and property were worked out by us-ing atomic force microscopy (AFM) and contact angle meas-urement. Moreover, the prime cytocompatibility was used to investigate the biocompatibility of the composite materialcontaining CNTs and the effects of CNTs on one aspect of cell function, cell affinity. The results obtained indicate that thecomposite material of PLLA and CNTs possesses good bio-compatibility for both the 3T3 fibroblasts and Oct-1 os-teoblast-like cells. The addition of CNTs will greatly affectcell affinity of the material, which may be disadvantage for the cell adhesion.

CIPs@Mn_(0.8)Zn_(0.2)Fe_(2)O_(4)-CNTs复合材料低频吸波性能研究

随着5G无线通信与低频雷达侦察技术的飞速发展,低频电磁波辐射已成为当代的严重问题。目前,中高频段吸波材料的研究已趋于成熟,而设计低频段吸波材料仍面临巨大的挑战,亟待研究者们解决。基于四分之一波长相消机制,本研究设计了0.5~3 GHz低频段复合吸波材料。采用简单的一步水热法,诱导铁氧体在羰基铁粉与碳纳米管表面生长,制备出CIPs@Mn_(0.8)Zn_(0.2)Fe_(2)O_(4)-CNTs三元复合材料,对比研究了碳纳米管含量对材料吸收峰频率的影响。实验结果表明,引入碳纳米管,一方面为材料带来了界面极化、偶极极化等额外的损耗机制,增加了材料的衰减系数;另一方面基于四分之一波长相消机制,高介电与高磁导率的耦合,使材料在低频段获得良好的阻抗匹配。最终,在4 mm厚度下,样品分别在2.11与1.75 GHz处,获得了–40.8与–32.1 dB的反射损耗,–10 dB带宽分别为1.70~2.70 GHz和1.40~2.20 GHz。该复合材料制备工艺简单,低频吸收性能良好,具有很大的应用潜力,为开发更有效的低频吸波材料提供了新的思路和方法。

Effects of Multi-walled Carbon Nanotubes on the Electromagnetic Absorbing Characteristics of Composites Filled with Carbonyl Iron Particles

The electromagnetic （EM） wave absorbing property of silicone rubber filled with carbonyl iron particles （CIPs） and multi-walled carbon nanotubes （MWCNTs） was examined. Absorbents including MWCNTs and spherical/ flaky CIPs were added to silicone rubber using a two-roll mixer. The complex permittivity and complex permeability were measured over the frequency range of 1-18 GHz. The two EM parameters were verified and the uniform dispersion of MWCNTs and ClPs was confirmed by comparing the measured reflection loss （RL） with the calculated one. As the MWCNT weight percent increased, the RL of the spherical CIPs/silicone rubber composites changed insignificantly. It was attributed to the random distribution of spherical ClPs and less content of MWCNTs. On the contrary, for composites filled with flaky ClPs the absorption bandwidth increased at thickness 0.5 mm （RL value lower than -5 dB in 8-18 GHz） and the absorption ratio increased at lower frequency （minimum -35 dB at 3.5 GHz）. This effect was attributed to the oriented distribution of flaky CIPs caused by interactions between the two absorbents. Therefore, mixing MWCNTs and flaky CIPs could achieve wider-band and higher-absorption ratio absorbing materials.

Improving interface adhesion in TiNi wire/shape memory epoxy composites using carbon nanotubes

In order to increase both the interfacial strength and interphase region strength between TiNi wires and shape memory epoxy,a novel interface structure including aminated CNTs was designed.The morphology shows that after electroplating and etching,continuous and homogeneous concave-convex layers form on the surface of astreated TiNi wires,meanwhile aminated CNTs were planted on the surface which could react with shape memory epoxy at the interface region.The interfacial shear strength increases first with the CNT content rising but then a dramatic drop happens,and the maximum is obtained at CNT content of 0.6 g·L^(-1),which is about twice the result of acid etching TiNi wires.

Enhancement in ballistic performance of composite hard armor through carbon nanotubes

The use of carbon nanotubes in composite hard armor is discussed in this study.The processing techniques to make various armor composite panels consisting of Kevlar■29 woven fabric in an epoxy matrix and the subsequent V50 test results for both 44 caliber soft-point rounds and 30 caliber FSP(fragment simulated projectile)threats are presented.A 6.5%improvement in the V50 test results was found for a combination of 1.65 wt%loading of carbon nanotubes and 1.65 wt%loading of milled fibers.The failure mechanism of carbon nanotubes during the ballistic event is discussed through scanning electron microscope images of the panels after the failure.Raman Spectroscopy was also utilized to evaluate the residual strain in the Kevlar■29 fibers post shoot.The Raman Spectroscopy shows a Raman shift of 25 cm^(−1) for the Kevlar■29 fiber utilized in the composite panel that had an enhancement in the V50 performance by using milled fiber and multi-walled carbon nanotubes.Evaluating both scenarios where an improvement was made and other panels without any improvement allows for understanding of how loading levels and synergistic effects between carbon nanotubes and milled fibers can further enhance ballistic performance.

碳纳米吸附材料在水处理中的应用进展

随着工业的发展,各种工业废水的处理问题引起了广泛的关注。碳纳米材料特殊的结构决定了其具有超强的吸附能力,在水处理工艺中体现出巨大的应用潜力。综述了三种碳纳米吸附材料即碳纳米管复合材料、石墨烯复合材料及碳包磁性纳米材料近年在水处理方面的研究现状,并对研究现状进行了总结,对未来发展方向进行了展望。

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。

多壁碳纳米管对无石棉垫片力学性能和耐老化性能的影响

为了研究热氧老化条件下多壁碳纳米管(MWCNTs)对无石棉垫片性能的影响,以加入不同种类和不同添加量MWCNTs制备的无石棉垫片为研究对象,测试了老化前后无石棉垫片的压缩率、拉伸强度和老化系数。结果表明:老化试验后,无石棉垫片压缩率降低、拉伸强度提高;未添加MWCNTs的原始垫片压缩率和拉伸强度变化最大,压缩率下降6.06%,拉伸强度提高5.02MPa;添加MWCNTs的垫片压缩率和拉伸强度相对差均小于原始垫片的相对差;不同种类MWCNTs对垫片老化后的性能影响不同;添加羟基化多壁碳纳米管(MWCNTs-OH)的垫片老化前后性能变化最小;添加质量分数1.2%MWCNTs-OH的垫片老化前后性能变化最小,垫片的耐老化性提升最明显。

CNT@Ni-MOFs的制备及其在超级电容器中的应用

金属有机骨架(MOFs)材料因其具有较高的比表面积和结构功能多样性而在超级电容器中具有广阔的应用前景。通过溶剂热法制备电化学性能优异的碳纳米管@镍基金属有机骨架(CNT@Ni-MOFs)复合材料。使用X射线衍射、扫描电子显微镜及X射线光电子能谱对其成分和结构进行表征,研究结果表明:CNT@Ni-MOFs结构是由柔性CNT连接着棒状结构的Ni-MOFs形成的导电网络结构,其棒状结构的Ni-MOFs直径约0.5μm,长度为4~5μm。研究了反应时间对CNT@Ni-MOFs结构和电化学性能的影响,结果表明:当反应时间为12 h时,Ni-MOFs生长完整且均匀,Ni-MOFs颗粒数量适中且均匀负载于CNT上,同时还减少了团聚发生。CNT@Ni-MOFs复合电极具有比单独Ni-MOFs更好的比电容性能,其中CNT@Ni-MOFs12在电流密度1 A/g下的比电容达到719.8 F/g,而Ni-MOFs的比电容仅为87.1 F/g,且CNT的比电容也仅仅为43.5 F/g。此外,扫描速率为200 mV/s下,CNT@Ni-MOFs12电极材料经1 000次的线性伏安循环测试后其比电容保持率为96.8%。

多壁碳纳米管/聚苯胺纳米纤维复合材料的制备及其吸附性能研究

为了探究掺杂后聚苯胺(PANI)吸附染料的性能,以有机酸、多壁碳纳米管(MWCNTs)为掺杂剂,过硫酸铵为氧化剂,通过原位氧化聚合法合成了多壁碳纳米管/聚苯胺(MWCNTs/PANI)纳米纤维复合材料,利用紫外-可见光分光光度计、傅里叶变换红外光谱仪、X射线衍射仪、扫描电子显微镜对其结构、组成及微观形貌进行表征。使用MWCNTs/PANI纳米纤维复合材料和PANI对刚果红溶液进行吸附实验,发现复合材料吸附效果更优异,吸附率达到95%左右。通过吸附动力学研究复合材料的吸附机理,结果表明MWCNTs/PANI纳米纤维复合材料吸附刚果红的过程符合准二级动力学模型。