Relation of the number of cross-links and mechanical properties of multi-walled carbon nanotube films formed by a dehydration condensation reaction

Multi-walled carbon nanotube (MWCNT) films were prepared by employing a condensation reaction utilizing 1,3-dicyclohexylcarbodiimide (DCC) to cross-link each MWCNT with carboxylic acid and hydroxyl groups. Morphological changes in the resultant MWCNT films were monitored using scanning electron microscopy and showed that the MWCNTs were randomly intertwined in the films. The prepared MWCNT films were 17 mm in diameter and 20 microm in thickness, and the apparent density was 0.59 g/cm(3). Fourier transform-infrared spectroscopy confirmed that each MWCNT modified with carboxylic acid and hydroxyl groups was cross-linked through the ester bond. It was found that the ratio of the number of ester cross-links and carbon atoms of the nanotubes per unit apparent volume (cm(3)) of condensed-MWCNT films was 5.27 x 10(-3) using thermogravimetric analysis (TGA). The tensile strength and Vickers hardness of condensed-MWCNT films achieved an average of 15 and 9.2 MPa, respectively, and were greater than those of free-standing MWCNT films without ester bond.     

多壁碳纳米管/玻璃纤维/含邻苯二甲腈的苯并噁嗪树脂复合材料的电学与力学性质(英文)

采用溶液共混法及层压成型的方法制备了多壁碳纳米管/玻璃纤维/含双邻苯二甲腈的苯并噁嗪树脂复合材料,并考察了该纳米复合材料的力学及电学性质。材料的渗滤阀值为碳纳米管含量为0.7%,此时,材料也表现出最好的机械性能。通过扫描电镜对材料的断面进行了考察,发现在碳纳米管含量为0.7%时形成了网状结构,因此此时复合材料表现出最好的电学及力学性质。复合材料在碳纳米管含量低于7%时具有很低的吸水性。     

Synergy effects of multi-walled carbon nanotube and graphene nanoplate filled epoxy adhesive on the shear properties of unidirectional composite bonded joints

In this paper, multi-walled carbon nanotubes (MWCNTs) and graphene nanoplates (GNPs) were dispersed into epoxy adhesive by sonication method to investigate their synergy effects on the shear properties of unidirectional composite bonded single lap joints (SLJs). The effect of the viscosity of epoxy resin and hardener on the dispersion process was studied. Testing results showed that the incorporation of MWCNTs and GNPs significantly improved the shear strength and elongation of SLJs at failure. 0.75 wt% MWCNTs/GNPs hybrids reached the highest enhancement of shear strength and elongation by 36.6% and 33.2%, respectively. In addition, the thermal stability of epoxy adhesive was improved by nanofillers in some extent. Finally, the failure mode of SLJs and fracture surfaces of the bonding area as well as the damage mechanism of nanofillers were analyzed.     

Synergetic effects of carbon nanotube and graphene addition on thermo-mechanical properties and vibrational behavior of twill carbon fiber reinforced polymer composites

The effect of carbon based nanoparticles addition, such as Multi Wall Carbon Nanotube (MWCNTs) and Graphene Nano Platelets (GNPs), on mechanical and thermal properties of Carbon Fiber Reinforced Polymer Composites (CFRPs) was experimentally investigated. 2/2 twill woven carbon textile was used to fabricate the CFRP samples. The main aim of this study was to improve the weak interface behavior of carbon fibers with polymers by using its own nanoparticles in the structure of CFRPs. The obtained results from thermal tests, such as storage modulus, loss factors, glass transition temperature and loss weight percentage, were compared to reveal the influence of nanoparticles in the structure of CFRPs. The effects of MWCNTs and GNPs addition on natural frequency and damping ratio of multi scale composites were studied by using vibrational tests. The effect of nanoparticles addition on water uptake nature of CFRPs was investigated by hydrophobicity test. The results showed that MWCNT and GNP nanoparticles improved the mechanical and dynamic behavior of CFRP composite materials by improving the modulus of elasticity, tensile strength, flexural modulus, strength, ILSS, critical buckling load, and natural frequency. Furthermore, the thermal characteristics of CFRPs, such as storage modulus, thermal stability and thermal conductivity, were improved by the addition of carbon based nanoparticles. It was observed that the MWCNT multi scale composites had better performance than the GNP. According to the results of hydrophobicity test, the addition of MWCNTs enhanced the hydrophobic nature while the GNPs increased the hydrophilic nature of CFRPs.     

Mechanical properties of polyimide/multi-walled carbon nanotube composite fibers

A series of polyimide (PI)/multi-walled carbon nanotube (MWCNT) composite fibers were prepared by copolymerizing a mixture of monomers and carboxylic-functionalized MWCNTs, followed by dry-jet wet spinning, thermal imidization, and hot-drawing process. The content of the carboxylic groups of MWCNTs significantly increased when treated with mixed acid, whereas their length decreased with treatment time. Both the carboxylic content and length of MWCNTs influenced the mechanical properties of the composite fibers. Fiber added with 0.1 wt% MWCNTs treated for 4 h exhibited the best mechanical properties, i.e., 1.4 GPa tensile strength and 14.30% elongation at break, which were 51% and 32% higher than those of pure PI fibers, respectively. These results indicated that a suitable MWCNT content strengthened and toughened the resultant PI composite fibers, simultaneously. Moreover, raising draw ratio resulted in the increase of tensile strength and tensile modulus of the composite fibers.     

Electrochemical properties of myoglobin deposited on multi-walled carbon nanotube/ciprofloxacin film

We report the direct electrochemical and electrocatalytic properties of myoglobin (MB) on a multi-walled carbon nanotube/ciprofloxacin (MWCNT/CF) film-modified electrode. A highly homogeneous MWCNT thin-film was prepared on an electrode surface using ciprofloxacin (CF) as a dispersing agent. MB was then electrochemically deposited onto the MWCNT/CF-modified electrode. The MB/MWCNT/CF film was characterized by scanning electron microscopy and UV-visible spectroscopy (UV-vis). UV-vis spectra confirmed that MB retained its original state on the MWCNT/CF film. Direct electrochemical properties of MB on the MWCNT/CF film were investigated by cyclic voltammetry. The formal potential and electron transfer rate constant were evaluated in pH 7.2 buffer solution as -0.327V and 300s(-1), respectively. In addition, the MB/MWCNT/CF-modified electrode showed excellent electrocatalytic properties for the reduction of hydrogen peroxide (H(2)O(2)). The MB/MWCNT/CF-modified electrode was used for the detection of H(2)O(2) at concentrations from 1×10(-6)M to 7×10(-4)M in pH 7.2 buffer solution. Overall, the MB/MWCNT/CF-modified electrode was very stable and has potential for development as a H(2)O(2) sensor.     

Effects of graphene and carbon nanotube fillers on the shear properties of epoxy

The effects of quantity of graphene and carbon nanotube‐based fillers and their pendant functional groups on the shear properties of a thermoset epoxy were investigated. Two novel functionalized graphenes, one with epoxy functionality and the other with an amine, are synthesized for this purpose. Nanocomposites are prepared at concentrations of 0.5, 1, 2, 3, 5, and 10 wt % and the effects of functionalization on the homogeneity of dispersion and the shear mechanical properties are investigated. The properties of the epoxy nanocomposites containing epoxy‐ and amine‐functionalized graphene are compared with those containing graphene oxide, Claisen‐functionalized graphene, neat multiwalled carbon nanotubes (MWNTs), three types of epoxy‐functionalized MWNT (EpCNT), and the unfilled epoxy. One of the EpCNT ( EpCNT3 ) was found to increase the plateau shear storage modulus by 136% (1.67–3.94 MPa) and the corresponding loss modulus by almost 400% at a concentration of 10 wt %. Several other fillers were also found to increase shear properties at certain concentrations. A hybrid system of EpCNT3 and graphite was also studied, which improved the storage modulus by up to 51%. SEM images reveal a correlation between thorough dispersion of the additive and enhancement of shear modulus. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 997–1006     

High performance lithium-sulfur batteries by facilely coating a conductive carbon nanotube or graphene layer

A dual-layer cathode electrode is constituted by facilely coating a conductive carbon nanotube or graphene layer on the pristine sulfur cathode electrode. The conductive layer can effectively improve the conductivity and suppress the polysulfide diffusion, giving rise to an enhanced electrochemical performance for Li-S batteries.     

银/碳纳米管纳米复合物制备及性质研究

基于苯环与碳纳米管之间较强的π-π共轭效应和醛基对银氨溶液的还原作用,利用吸附在碳纳米管上的香草醛分子原位还原[Ag(NH3)2]+,成功获得了纳米银/碳纳米管(Ag-NPs/CNTs)复合纳米材料。紫外-可见吸收光谱和荧光光谱结果表明,碳纳米管对香草醛分子有较强的吸附作用及银纳米粒子的形成。透射电镜结果表明,碳纳米管表面形成了大小约5.0 nm银纳米颗粒。所制备的纳米复合材料表现出较明显的荧光特性,且对浓度为1.0×10-7～6.0×10-7 mol/L的H2O2表现出较好的电催化还原能力。     

A review on the mechanical,electrical and EMI shielding properties of carbon nanotubes and graphene reinforced polycarbonate nanocomposites

Recently, it has been found that carbon nanotubes (CNTs) and graphene could prove to be the most promising carbonaceous fillers in polymers nanocomposites field because of their better structural and functional properties. Their uniform dispersion in polymer matrix leads to significant improvements in their several properties. This paper reviews the effect of nanofillers, ie, CNTs, derivatized CNTs, and graphene on the polycarbonate nanocomposite and its application in aerospace, automobile, sports, electronic sectors, and various industries. The comparative analysis of carbon‐based fillers on the different properties of polycarbonate nanocomposites is also included.     

Synergistic effects of functionalized graphene and functionalized multi-walled carbon nanotubes on the electrical and mechanical properties of poly(ether sulfone) composites

Mixed fillers composed of functionalized graphene (f-G) and functionalized multi-walled carbon nanotubes (f-CNTs) (f-G-f-CNTs) were prepared and their synergistic effects in terms of enhancing the electrical conductivity and tensile modulus of poly(ether sulfone) (PES) composites were investigated. The results indicate that the electrical conductivity of the 5 wt% f-G-f-CNTs(W_f-G/W_f-CNTs = 1:1)/PES composite was 2.2 times higher than that of the 5 wt% f-G/PES composite and 8.9 times higher than that of the 5 wt% f-CNTs/PES composite. Moreover, the tensile modulus of the 5 wt% f-G-f-CNTs(W_f-G/W_f-CNTs = 1:1)/PES composite relative to that of the 5 wt% f-G/PES composite and 5 wt% f-CNTs/PES composite increased by 16.5% and 50.6%, respectively. Additionally, enhancements in the electrical conductivity and tensile modulus of the PES composite depended on the weight ratio of f-G and f-CNTs in the mixed fillers. The electrical conductivity and tensile modulus exhibited maximum values when the weight ratios of f-G and f-CNTs were 1:3 and 1:1, respectively. When the weight ratio of f-G and f-CNTs was fixed at 1:1, the f-G-f-CNTs(W_f-G/W_f-CNTs = 1:1)/PES composite showed a percolation threshold of 0.22 vol%, much lower than that of the f-G/PES composite.     

Study on mechanical properties of elastomers reinforced by zinc dimethacrylate

In this work, mechanical properties of various elastomers with the representative structural features reinforced by zinc dimethacrylate (ZDMA) were studied. The results showed that there is great difference in reinforcing effects of ZDMA for different elastomers. Strain-stress curves revealed that the tensile-induced crystallization of chains might be the main reason for high strength of ZDMA/rubber composites at room temperature. The saturation and regularity of rubber chains are two essential features to determine the mechanical properties of the composites at room temperature. The kind of ZDMA makes considerable impact on performances of ZDMA/rubber composites, except for ZDMA/hydrogenated nitrile-butadiene rubber (HNBR) composite. The high temperature strengths of ZDMA/rubber composites are not high and are dominated by the polarity and saturation of matrix. Basing on the previous researching, a possible model for microstructure of ZDMA/rubber composites was put forward, which could well interpret the observed phenomenon.     

纳米碳纤维涂层固相微萃取探头的制备及性能分析

采用纳米碳纤维(CNF)作为固相涂层制备了固相微萃取探头(SPME)并进行了评价.该涂层对苯系物(BTX)富集能力强,最高使用温度可达260℃,250℃解析条件下使用50次以上涂层无脱落现象.与活性碳涂层相比,尽管萃取量略小,但其解析时间仅为活性炭的60%,具有更高的精密度和准确度.对BrIX固相微萃取.气相色谱分析结果表明,样品质量浓度在0.1～38.7μg/L范围内与色谱峰面积呈良好线性关系(r=0.9891～0.9940),相对标准偏差为3.9%～5.3%,方法的检出限为2.5×10~(-3)μg/L.     

聚吡咯／多壁碳纳米管修饰电极对多巴胺的测定

制备了聚吡咯/多壁碳纳米管(PPy/MWNT)复合膜修饰电极。研究了神经递质多巴胺(DA)在该修饰电极上的电化学行为。实验表明,PPy/MWNT复合膜修饰电极对DA的电催化作用优于PPy修饰电极。在pH=4.10的0.2mol/L醋酸-醋酸钠缓冲溶液中,DA在该修饰电极上的CV曲线于0.31V和0.28V处出现一对灵敏的氧化还原峰,峰电位差△Ep比裸玻碳电极降低58mV,比PPy修饰电极降低28mV,峰电流显著增加。氧化峰电流ipa与DA浓度在1.0×10-4~7.8×10-8mol/L范围内呈良好的线性关系,线性回归方程为ip(μA)=0.2512 1.2300C(×10-5mol/L),相关系数r=0.9992,检出限为3.9×10-8mol/L。常见物质对DA的检测无干扰,DA注射液样品检测回收率为94%~104%。     

Reversible electrochemistry of DNA on multi-walled carbon nanotube modified electrode

Calf thymus DNA was electrochemically oxidized at a multi-walled carbon nanotube modified electrode. The potentials for DNA oxidation at pH 7.0 were 0.71 and 0.81 V versus SCE, corresponding to the oxidation of guanine and adenine residues, respectively. The initial 6e-oxidation of adenine, observed in the first scan, resulted a quasi-reversible 2e-redox process of the oxidation product in the following scans.     

Enhanced electrical and mechanical properties of multiwall carbon nanotube rubber composites

Multiwall carbon nanotube‐filled elastomers are prepared by solution blending using a sonication process. It is shown that the processing conditions have a strong effect on the composite properties especially on electrical properties, which are very sensitive to nanotube dispersion within the elastomeric matrix. The percolation threshold is seen to be shifted to a lower nanotube content than that previously reported. With regard to the unfilled elastomer, large increases in the elastic and tensile moduli are obtained with the nanotube loading, thus highlighting the potential of this type of particles as reinforcing fillers for elastomeric matrices. Raman spectroscopy under strain has been used to evaluate the strength of the polymer–filler interface. Weak interfacial interactions are deduced, but the debundling of the nanotubes and the orientational effects of the polymeric chains are observed when the composite is submitted to a uniaxial deformation. Copyright © 2012 John Wiley & Sons, Ltd.     

Preparation of polymer nanocomposites with enhanced mechanical properties using hybrid of graphene and partially wrapped multi-wall carbon nanotube as nanofiller

Triblock copolymer of poly(p-dioxanone) and polyethylene glycol end-capped with pyrene moieties ((Py-PPDO)₂-b-PEG) was synthesized and used as modifier for multi-wall carbon nanotubes (MWCNTs). Nano-aggregates ((Py-PPDO)₂-b-PEG@MWCNTs) with shish-kebab like partially wrapped morphology and very good stability were obtained by incorporating the copolymer with MWCNTs. The bare MWCNT sections of (Py-PPDO)₂-b-PEG@MWCNTs were able to induce π-π interactions with graphene (GE) and resulted in a novel GE/(Py-PPDO)₂-b-PEG@MWCNTs hybrid. The dispersity of GE in solution or polymer matrix was therefore greatly improved. The PCL nanocomposite films using GE/(Py-PPDO)₂-bPEG@MWCNTs as hybrid nanofiller exhibited obviously improved mechanical properties especially at very low hybrid nanofiller content. The influence of the nanofiller content and feed ratio of GE/MWCNTs on the mechanical properties of composites films was evaluated. When the feed ratio of GE to MWCNTs is 2:8 and the total loading of nanofiller is only 0.01 wt%, the tensile strength of the composite film increased by 163% and the elongation at break increased by 17% compared to those of neat PCL. These results can be attributed to fine dispersion of the nanofillers in PCL matrix and the hybrid interactions between GE and MWCNTs. Therefore, this work provides a novel method for preparing polymer nanocomposites with high mechanical performance and low nanofiller loading.     

Influence of carbon shell structure on electrochemical performance of multi-walled carbon nanotube electrodes

Core/shell nanostructures have received considerable attention due to the synergistic effect of their combination of materials. In this work, core/shell carbon/multi walled carbon nanotubes (MWNTs) (C-MWNTs) composed of core MWNTs and carbon shells were prepared to obtain a new type of carbon electrode materials. Carbon shells containing nitrogen groups were prepared by coating polyaniline (PANI) onto the MWNTs by in situ polymerization and subsequent carbonization at 850 °C. After carbonization, the C-MWNTs contained 5.84% nitrogen and showed a hollow structure and crystallinity like that of pristine MWNTs. In addition, the C-MWNTs exhibited electrochemical performance superior to that of pristine MWNTs, and the highest specific capacitance (231 F g⁻¹) of the C-MWNTs was obtained at a scan rate of 0.1 A g⁻¹, as compared to 152 F g⁻¹ for pristine MWNTs. This superior performance is attributed to the maintenance of high electrical conductivity by the π–π interaction between the carbon layer and the MWNTs, increased specific surface area of C-MWNTs, and the presence of nitrogen groups formed on the carbon electrode after the carbonization of the shell PANI.     

TiO2陶瓷膜的制备及性能研究

本文以钛酸丁酯为起始原料，采用聚合凝胶法，制备了有支撑的TiO2多孔陶瓷分离膜。研究了载体孔径，TiO2溶胶条件，制膜工艺过程(浸涂、干燥等)条件对TiO2膜成膜性质的影响，并通过对TiO2陶瓷膜耐酸、碱性的实验，证明了其纯水通量、孔径大小基本不变，再生恢复性良好。     

Enhanced thermal and mechanical properties of poly (vinylidene fluoride) nanocomposites reinforced by liquid-exfoliated graphene

We report the preparation and enhanced thermal and mechanical properties of poly (vinylidine diflouride) (PVDF) nanocomposites reinforced by few-layer graphene flakes which are produced by the direct liquid-phase exfoliation of pristine graphite. Graphene flakes are found to homogeneously disperse in PVDF, reduce the bubble defects and thus the porosity of PVDF, and change PVDF’s crystallinity. Thermogravimetric analysis indicates that graphene can accelerate the fracture of hydrogen bond connecting PVDF and N-Methyl pyrrolidone molecules. 1.5?wt% graphene loading leads to around 20?°C enhancement in the melting temperature of PVDF. The mechanical properties like Young’s modulus (EIT), yield stress (σy), and hardness (H) of the nanocomposites are investigated by nanoindentation technique. A 1.0?wt% loading of graphene is found to increase EIT, σy, and H of PVDF by ～337%, ～102%, and ～228%, respectively.

• Highlights

• Few-layer graphene was produced by liquid-phase exfoliation.

• Graphene were added to PVDF to enhance thermal and mechanical properties of polymer.

• Mechanical properties of PVDF/graphene composite films were investigated by nanoindentation.