Study of the Diffusion Behavior of Seawater Absorption in Multi-Walled Carbon Nanotubes/Halloysite Nanotubes Hybrid Nanofillers Modified Epoxy-Based Glass/Carbon Fiber Composites

In the maritime industry, cost-effective and lightweight Fiber Reinforced Polymer (FRP) composites offer excellent mechanical properties, design flexibility, and corrosion resistance. However, their reliability in harsh seawater conditions is a concern. Researchers address this by exploring three approaches: coating fiber surfaces, hybridizing fibers and matrices with or without nanofillers, and interply rearrangement. This study focuses on evaluating the synergistic effects of interply rearrangement of glass/carbon fibers and hybrid nanofillers, specifically Multi-walled carbon nanotubes (MWCNT) and Halloysite nanotubes (HNT). The aim is to enhance impact properties by minimizing moisture absorption. Hybrid nanocomposites with equal-weight proportions of two nanofillers: 0 wt.%, 1 wt.%, and 2 wt.% were exposed to seawater for 90 days. Experimental data was subjected to modelling through the application of Predictive Fick’s Law. The study found that the hybrid composite containing 2 wt.% hybrid nanofillers exhibited a 22.10% increase in impact performance compared to non-modified counterparts. After 90 days of seawater aging, the material exhibited enhanced resistance to moisture absorption (15.74%) and minimal reduction in impact strength (8.52%) compared to its dry strength, with lower diffusion coefficients.

Temperature Dependent Surface Resistivity Measures of Commercial, Multiwall Carbon Nanotubes (MWCNT), and Silver Nano-Particle Doped Polyvinyl Alcohol (PVA) Films

Pure and doped Polyvinylidene difluoride (PVDF) films, for the detection of infrared radiation, have been well documented using the mechanism of pyroelectricity. Alternatively, the electrical properties of films made from Polyvinyl Alcohol (PVA) have received considerable attention in recent years. The investigation of surface resistivities of both such films, to this point, has received far less consideration in comparison to pyroelectric effects. In this research, we report temperature dependent surface resistivity measurements of commercial, and of multiwall carbon nanotubes (MWCNT), or Ag-nanoparticle doped PVA films. Without any variation in the temperature range from 22°C to 40°C with controlled humidity, we found that the surface resistivity decreases initially, reaches a minimum, but rises steadily as the temperature continues to increase. This research was conducted with the combined instrumentation of the Keithley Model 6517 Electrometer and Keithley Model 8009 resistivity test fixture using both commercial and in-house produced organic thin films. With the objective to quantify the suitability of PVDF and PVA films as IR detector materials, when using the surface resistivity phenomenon, instead of or in addition to the pyroelectricity, surface resistivity measurements are reported when considering bolometry. We found that the surface resistivity measurements on PVA films were readily implemented.

NMP/PVP-MWCNTs湿度传感器制备与测试

碳纳米管制备敏感薄膜时往往会因其分散性差,无法保证纳米薄膜的均匀性,从而影响传感器的性能。使用N-甲基吡咯烷酮(NMP)与聚乙烯吡咯烷酮(PVP)作为分散剂对多壁碳纳米管进行表面活性处理,制备以多壁碳纳米管为湿敏材料的电阻型湿度传感器。传感器用微机电系统(MEMS)工艺制备叉指电极作为湿敏电阻,在100℃下将多壁碳纳米水溶液组装在电极上,使用原子力显微镜(AFM)、扫描电子显微镜(SEM)对湿敏薄膜进行形貌表征。经测试,传感器线性度为0.99806,灵敏度为42.99923Ω/%,相对湿度20%~70%循环测试时响应时间为5 s,恢复时间为6 s,且传感器具有良好的重复性和稳定性。

具有宽带微波吸收性能的MWCNTs/SiC纳米复合材料的点击化学法制备及性能研究

多壁碳纳米管/碳化硅(MWCNTs/SiC)纳米复合材料,以电阻型微波吸收剂MWCNTs为基体材料,电介质型微波吸收剂碳化硅作为损耗介质通过点击反应制备。采用XRD,IR,XPS,TG,SEM,矢量网络分析仪进行该复合材料的结构表征和微波吸收性能测试。此外还探讨了不同投料比,对复合材料的微波吸收性能的影响。实验结果表明:MWCNTs/SiC二元纳米复合材料由点击法成功制备;当投料的质量比MWCNTs:SiC=1∶1时,MWCNTs/SiC二元纳米复合材料在2.0 mm的厚度下,其最小反射损耗(RLmin)达到了-44.96 dB,在1.5 mm的超薄厚度下有效吸收的最宽带宽(RL<-10 dB)达到5.04 GHz(从12.66~17.93 GHz,覆盖了Ku波段的87.8%);此外,MWCNTs/SiC二元纳米复合材料可以在整个X波段有效吸收电磁波,厚度范围为2.0~2.5 mm。并且,通过调整吸收层的厚度,几乎可以有效覆盖所有的C、X和Ku波段。MWCNTs和SiC之间通过点击反应以共价键连接,分子内部形成导电通道,产生足够的载流子,在外加电场的作用下产生感应电流,也可以衰减电磁波,从而增强对电磁波能量的消耗。

基于PDMS/MWCNTs的柔性温度传感器

柔性可穿戴设备在人体运动检测、实时健康监测、医学保健方面显现出广阔的应用前景。本文制备了一种具有负电阻温度系数(NTC)的聚二甲基硅氧烷(PDMS)/多壁碳纳米管(MWCNTs)复合材料,并利用此复合材料制备了一种柔性温度传感器。此传感器温度传感机制是,MWCNTs的载流子浓度随着温度升高而增加,PDMS/MWCNTs的电阻率减小。当MWCNTs质量分数为PDMS的10%时,在30~41℃范围内,传感器温度灵敏度为-0.183%/℃,相对电阻变化线性度为99.94%,并具有良好的重现性与稳定性。可以预见,基于PDMS/MWCNTs的柔性温度传感器,不仅可以用于监测人体与物体的温度变化,而且在可穿戴医疗设备中也有巨大的潜力。

Towards the low temperature growth of uniform diameter multi walled carbon nanotubes by catalytic chemical vapour deposition technique

Mesoporous MCM-41 molecular sieves containing f-block transition elements（gadolinium） with various Si/Gd ratios（50,75 and 100） were synthesised by a hydrothermal method.Their mesoporous structure was confirmed by X-ray diffraction,nitrogen sorption studies,thermogravimetric analysis,scanning and transmission electron microscopy.The local environment of Gd in the material was studied by electron paramagnetic resonance.The compatibility of the catalyst for the synthesis of uniform diameter CNTs by varying the temperature from 400 to 650°C with fixed flow rates of N2 and C2H2（140 ml/min and 40 ml/min,respectively）.The product is mostly metal containing thin MWCNTs with diameter of 1020 nm.Characterisation shows that a combination of Gd-MCM-41（100） catalyst gives a high yield of high quality MWCNTs under optimum growth conditions.

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.

Carbon nanotubes as conducting support for potential Mn-oxide electrocatalysts： Influences of pre-treatment procedures

Different oxygen and nitrogen containing functional groups were created on the surface of the multiwalled carbon nanotubes. The multi-walled carbon nanotubes were treated in ultrasonic bath with sulfuric or nitric acid. Furthermore the surface texture was modified by increase of the roughness. In particular after treatment with the oxidizing nitric acid, in comparison to the H2SO4 or ultra-sonic treated samples,craters and edges are dominating the surface structures. Manganese oxide was deposited on the multiwalled carbon nanotubes by precipitation mechanism. Various manganese oxides are formed during the deposition process. The samples were characterized by elemental analysis, microscopy, thermal analysis,Raman spectroscopy, and by the zeta potential as well as X-ray diffraction measurements. It was shown that the deposited manganese oxides are stabilized rather by surface texture of the multi-walled carbon nanotubes than by created functional groups.

Glassy carbon electrode modified with multi-walled carbon nanotubes sensor for the quantihication of antihistamine drug pheniramine in solubilized systems

A sensitive electroanalytical method for quantification of pheniramine in pharmaceutical formulation has been investigated on the basis of the enhanced electrochemical response at glassy carbon electrode modified with multi-walled carbon nanotubes in the presence of sodium lauryl sulfate.The experimental results suggest that the phcniramine in anionic surfactant solution exhibits electrocatalytic effect resulting in a marked enhancement of the peak current response.Peak current response is linearly dependent on the concentration of pheniramine in the range 200-1500 μg/mL with correlation coefficient 0.9987.The limit of detection is 58.31 μg/m L.The modified electrode shows good sensitivity and repeatability.

Mechanical Properties and Microstructure of Sulfur Aluminate Cement Composites Reinforced by Multi-walled Carbon Nanotubes

The effect of multi-walled carbon nanotubes（MWCNTs） on the mechanical properties and microstructure of sulfur aluminate cement（SAC） composites was investigated. The dispersed MWCNTs were added into SAC in various weight contents.The results of mechanical properties of the MWCNTs/SAC composites indicated that the addition of 0.08 wt% MWCNTs can improve the SAC compressive strength, flexural strength, and bend-press ratio by 15.54%, 52.38%, and 31.30% at maximum, respectively. The degree of SAC hydration and porosity and pore size distribution of the matrix were measured by X-ray diffraction（XRD）, thermal analysis（TG/DTG）, and mercury intrusion porosimetry（MIP）. Results show that the addition of MWCNTs in SAC composites can promote the hydration of SAC and the formation of C-S-H gel, reduce the porosity and refine the pore size distribution of the matrix. The microstructure was characterized by scanning electron microscopy（SEM） and energy dispersive spectroscopy（EDS）. It is found that the MWCNTs have been dispersed homogeneously between the hydration products of SAC paste and act as bridges and networks between cracks and voids, which prevents the development of the cracks and transfers the load.

Effects of layer number and initial pressure on continuum-based buckling analysis of multi-walled carbon nanotubes accounting for van der Waals interaction

The structural instability of multi-walled carbon nanotubes(MWCNTs) has captured extensive attention due to the unique characteristic of extremely thin hollow cylinder structure. The previous studies usually focus on the buckling behavior without considering the effects of the wall number and initial pressure. In this paper, the axial buckling behavior of MWCNTs with the length-to-outermost radius ratio less than 20 is investigated within the framework of the Donnell shell theory. The governing equations for the infinitesimal buckling of MWCNTs are established, accounting for the van der Waals(vd W) interaction between layers. The effects of the wall number, initial pressure prior to buckling, and aspect ratio on the critical buckling mode, buckling load, and buckling strain are discussed, respectively. Specially, the four-walled and twenty-walled CNTs are studied in detail, indicating the fact that the buckling instability may occur in other layers besides the outermost layer. The obtained results extend the buckling analysis of the continuum-based model, and provide theoretical support for the application of CNTs.

Effects of temperature change on the rheological property of modified multiwall carbon nanotubes

Solvent-free nanofluids hold promise for many technologically significant applications.The liquid-like behavior,a typical rheological property of solvent-free nanofluids,has aroused considerable interests.However,there has been still lack of efficient methods to predict and control the liquid-like behavior of solvent-free nanofluids.In this paper,we propose a semi-discrete dynamic system with stochastic excitation describing the temperature change effects on the rheological property of multiwall carbon nanotubes(MWCNTs)modified by grafting sulfonic acid terminated organosilanes as corona and tertiary amine as canopy,which is a typical covalent-type solvent-free nanofluid system.The vibration of the grafting branches is simulated by employing a structure-preserving approach,and the shear force of grafting branches at the fixed end is computed subsequently.By taking the shear forces as an excitation acting on the MWCNTs,the axial motion of the MWCNTs is solved with the 7-point Gauss-Kronrod quadrature rule.The critical temperature associated with the appearance of the liquid-like behavior as well as the upper bound of the moving speed of the modified MWCNTs is determined,which can be used to predict and control the liquid-like behavior of the modified MWCNTs in engineering applications.

Carbon Black and Multi Wall Carbon Nanotubes Loaded Polyurethane Foam Composite Flexible Thermal Radiator

Carbon black (CB) or multi walled carbon nanotubes (MWCNT) loaded polyurethane conductive foams are used as heaters, electrodes, radar absorbers and shielding. This paper discusses the performance of an innovative flexible thermal radiator (FTR) constructed with CB filled or MWCNT filled conductive foam and powering electrode structure constructed with textiles manufacturing process (knitting, weaving or nonwoven). Silver (Ag) yarns are used for the powering electrodes construction. This paper discusses the construction, electro-thermal analysis, performance and applications of FTR. Also this paper compare the thermal and electrical characteristics of CB filled and MWCNT filled FTRs. The electro-thermal model is simulated by using finite element methods.

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.

New Strategy for Chemically Attachment of Imine Group on Multi-Walled Carbon Nanotubes Surfaces: Synthesis, Characterization and Study of DC Electrical Conductivity

This paper used a new approach of preparing poly-composites by covalent linkage between the MWCNT’s by imine group. The Poly (Imine)/MWCNT Composite was synthesized by the solution blending method from reacted amino multi-walled carbon nanotubes (MWCNT-NH2) with Terephthalaldehyde (TPAL). The obtained poly-composite was characterized by FT-IR, UV-Vis, XRD, TEM, SEM, TGA, DSC and DC electrical conductivity. The formation of Poly (Imine)/MWCNT composite was confirmed. The DC electrical conductivity of poly-composites was within the range 2.3 × 10–4 - 5.3 × 10–4 S/cm due to the interaction between the nanotubes.

搅拌摩擦加工制备的MWCNTs／Mg复合材料的阻尼性能

采用搅拌摩擦加工法制备不同含量多壁碳纳米管镁基复合材料(MWCNTs/Mg),并对该复合材料的显微结构和阻尼性能进行分析。结果表明:MWCNTs/Mg复合材料的高温阻尼性能较基体的高温阻尼性能有一定程度的提高;MWCNTs的添加量越大,MWCNTs/Mg复合材料的阻尼性能增加越大;MWCNTs/Mg复合材料的阻尼—温度曲线出现了两个内耗峰。MWCNTs/Mg复合材料阻尼性能受频率影响随温度区间的变化而不同。

MWCNTs/E51复合涂层的耐磨性能研究

向耐腐蚀材料环氧树脂中添加适量的碳纳米管粉末(MWCNTs),可以改善环氧树脂涂层的耐磨损性能。使用原位复合法生成新的复合材料,并用SEM、表面形貌仪和MM200摩擦磨损实验机进行观察和测试。结果表明,向环氧树脂基体中添加MWCNTs可以增强材料的摩擦磨损性能。当添加10%的MWCNTs粉末时,改性环氧树脂涂层的耐磨性能提高到226%。对复合材料制作工艺和实验结果进行了分析,初步解释了MWCNTs对环氧树脂增强作用的机理。

不同pH合成的MWCNTs-WO3复合材料的室温气敏性能

为提高WO3的气敏性能，采用水热合成法，以钨酸钠（Na2WO4．2H2O）和多壁碳纳米管（MWCNTs）为原料，合成多壁碳纳米管与三氧化钨（MWCNTs—W03）复合材料。通过调节溶液的pH，对合成复合材料的形貌、尺寸进行控制合成，并在常温下对NO的气敏性能进行检测。研究结果表明：所得样品均为六方相W03和MWCNTs，复合材料的尺寸随着pH（pH=2～5）的增大而增加，形貌也由棒状转化为立方体状。当pH=3时，W03与MWCNTs相互结合形成网状复合材料，对NO表现出良好的气敏性能，室温条件下对体积分数为9．7×10^-5的NO灵敏度可达16．8％，具有响应时间快，选择性好的优点。

一种新型MWCNTs/氟碳漆防腐蚀导电涂层

为了解决现有石油化工企业防腐蚀导电涂料存在的防腐蚀性能低、耐磨性差、涂层易溶胀溶解的问题,选取耐蚀性好、耐磨性优良的氟碳涂料为基料,添加碳纳米管为填料制备了新型防腐蚀导电材料。通过表面粗糙度测试、力学性能测试、电化学阻抗谱(EIS)和傅里叶变换红外光谱(FTIR)技术,研究了多壁碳纳米管(MWCNTs)的加入对氟碳漆涂层表面粗糙度、力学性能、紫外老化以及化学结构的影响。结果表明:MWCNTs/氟碳漆防腐蚀导电涂层跟纯氟碳漆涂层相比表面粗糙度变化不大,拉伸强度和弹性模量分别增大了150%和133%,紫外加速老化24,72,144,216h后的耐蚀性也有所增强,MWCNTs不影响氟碳漆的化学结构。

复合电沉积Ni-MWCNTs及镍电结晶的研究

研究了水平阴极方式复合电沉积Ni-MWCNTs(Ni-多壁碳纳米管)。采用硫酸镍基础电解液,添加适当表面活性剂和光亮剂,MWCNTs为2～2.5g/L,电流密度为2.5A/dm2时,获得的Ni-MWCNTs沉积层结构致密,复合沉积层中MWCNTs含量达22.45%。复合电沉积层表面微观形貌照片显示,MWCNTs在复合电沉积层中占主要体积,镍的电结晶形态呈球形,结晶点位置位于MWCNTs管壁缺陷处及部分管端处,MWCNTs的管端和管壁缺陷处的Ni晶粒相互连接,形成牢固的复合沉积层。复合电沉积层中MWCNTs含量受电解液中MWCNTs浓度、电流密度以及光亮剂影响,在MWCNTs上的Ni沉积层连续性直接受MWCNTs管壁上缺陷的数量和连续性影响,形成晶核的缺陷尺度至少在1nm以上。