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1.
In this study, electrical conductivity of a vinyl ester based composite containing low content (0.05, 0.1 and 0.3 wt.%) of double and multi-walled carbon nanotubes with and without amine functional groups (DWCNTs, MWCNTs, DWCNT-NH2 and MWCNT-NH2) was investigated. The composite with pristine MWCNTs was found to exhibit the highest electrical conductivity. Experiments aimed to induce an aligned conductive network with application of an alternating current (AC) electric field during cure were carried out on the resin suspensions with MWCNTs. Formation of electric anisotropy within the composite was verified. Light microscopy (LM), scanning electron (SEM) and transmission electron microscopy (TEM) were conducted to visualize dispersion state and the extent of alignment of MWCNTs within the polymer cured with and without application of the electric field. To gain a better understanding of electric field induced effects, glass transition temperature (Tg) of the composites was measured via Differential Scanning Calorimetry (DSC). It was determined that at 0.05 wt.% loading rate of MWCNTs, the composites, cured with application of the AC electric field, possessed a higher Tg than the composites cured without application of the AC electric field.  相似文献   

2.
Study was made of the effect of multiwall carbon nanotubes (MWCNTs) and polymeric compatibilizer on thermal, mechanical, and tribological properties of high density polyethylene (HDPE). The composites were prepared by melt mixing in two steps. Carbon nanotubes (CNTs) were melt mixed with maleic anhydride grafted polyethylene (PEgMA) as polymeric compatibilizer to produce a PEgMA-CNT masterbatch containing 20 wt% of CNTs. The masterbatch was then added to HDPE to prepare HDPE nanocomposites with CNT content of 2 or 6 wt%. The unmodified and modified (hydroxyl or amine groups) CNTs had similar effects on the properties of HDPE-PEgMA indicating that only non-covalent interactions were achieved between CNTs and matrix. According to SEM studies, single nanotubes and CNT agglomerates (size up to 1 μm) were present in all nanocomposites regardless of content or modification of CNTs. Addition of CNTs to HDPE-PEgMA increased decomposition temperature, but only slight changes were observed in crystallization temperature, crystallinity, melting temperature, and coefficient of linear thermal expansion (CLTE). Young’s modulus and tensile strength of matrix clearly increased, while elongation at break decreased. Measured values of Young’s moduli of HDPE-PEgMA-CNT composites were between the values of Young’s moduli for longitudinal (E11) and transverse (E22) direction predicted by Mori-Tanaka and Halpin-Tsai composite theories. Addition of CNTs to HDPE-PEgMA did not change the tribological properties of the matrix. Because of its higher crystallinity, PEgMA possessed significantly different properties from HDPE matrix: better mechanical properties, lower friction and wear, and lower CLTE in normal direction. Interestingly, the mechanical and tribological properties and CLTEs of HDPE-PEgMA-CNT composites lie between those of PEgMA and HDPE.  相似文献   

3.
The aim of this study is to investigate temperature dependence of electrical conductivity of carbon nanotube (CNT)/polyester nanocomposites from room temperature to 77 K using four-point probe test method. To produce nanocomposites, various types and amounts of CNTs (0.1, 0.3 and 0.5 wt.%) were dispersed via 3-roll mill technique within a specially formulized resin blend of thermoset polyesters. CNTs used in the study include multi walled carbon nanotubes (MWCNT) and double-walled carbon nanotubes (DWCNT) with and without amine functional groups (–NH2). It was observed that the incorporation of carbon nanotubes into resin blend yields electrically percolating networks and electrical conductivity of the resulting nanocomposites increases with increasing amount of nanotubes. However, nanocomposites containing amino functionalized carbon nanotubes exhibit relatively lower electrical conductivity compared to those with non-functionalized carbon nanotubes. To get better interpretation of the mechanism leading to conductive network via CNTs with and without amine functional groups, the experimental results were fitted to fluctuation-induced tunneling through the barriers between the metallic regions model. It was found that the results are in good agreement with prediction of proposed model.  相似文献   

4.
Bud-branched nanotubes, fabricated by growing metal particles on the surface of multi-wall carbon nanotubes (MWCNTs), were used to prepare poly(vinylidene fluoride) (PVDF) based nanocomposites. The results of differential scanning calorimetry (DSC) showed that the introduction of the MWCNTs and bud-branched nanotubes both increased the crystallization temperature, while no significant variation of Tm (melting temperature), ΔHc (melting enthalpy) and ΔHm (crystallization enthalpy) occurred. The results of wide angle X-ray diffraction (WAXD) tests showed that α-phase was the dominated phase for both pure PVDF and its nanocomposites, indicating the addition of the MWCNTs and bud-branched nanotubes did not alter the crystal structures. Dynamic mechanical analysis (DMA) tests showed that bud-branched nanotubes were much more efficient in increasing storage modulus than the smooth MWCNTs. In addition, no significant variation of the Tg (glass transition temperature) was observed with the addition of MWCNTs and bud-branched nanotubes. Tensile tests showed that the introduction of MWCNTs and bud-branched nanotubes increased the modulus. However, a dramatic decrease in the fracture toughness was observed for PVDF/MWCNTs nanocomposites. For PVDF/bud-branched nanotubes nanocomposites, a significant improvement in the fracture toughness was observed compared with PVDF/MWCNTs nanocomposites.  相似文献   

5.
Multi-walled carbon nanotube (MWCNT)/polyetherimide (PEI) nanocomposite films have been prepared by casting and imidization. A homogeneous dispersion of MWCNTs throughout the PEI matrix is observed by scanning electron microscopy of fracture surfaces, which shows not only a fine dispersion of MWCNTs but also strong interfacial adhesion with the matrix, as evidenced by the presence of many broken but strongly embedded carbon nanotubes (CNTs) in the matrix and by the absence of debonding of CNTs from the matrix. Differential scanning calorimetry and dynamic mechanical analysis show that the glass transition temperature of PEI increases by about 10 °C by the addition of 1 wt% MWCNTs. Mechanical testing shows that for the addition of 1 wt% MWCNTs, the elastic moduli of the nanocomposites are significantly improved by about 250% while the tensile strength is comparable to that of the matrix. This improvement is due to the strong interfacial interaction between the MWCNTs and the PEI matrix which favors stress transfer from the polymer to the CNTs.  相似文献   

6.
The mechanical and thermo-mechanical properties of polybenzoxazine nanocomposites containing multi-walled carbon nanotubes (MWCNTs) functionalized with surfactant are studied. The results are specifically compared with the corresponding properties of epoxy-based nanocomposites. The CNTs bring about significant improvements in flexural strength, flexural modulus, storage modulus and glass transition temperature, Tg, of CNT/polybenzoxazine nanocomposites at the expense of impact fracture toughness. The surfactant treatment has a beneficial effect on the improvement of these properties, except the impact toughness, through enhanced CNT dispersion and interfacial interaction. The former four properties are in general higher for the CNT/polybenzoxazine nanocomposites than the epoxy counterparts, and vice versa for the impact toughness. The addition of CNTs has an ameliorating effect of lowering the coefficient of thermal expansion (CTE) of polybenzoxazine nanocomposites in both the regions below and above Tg, whereas the reverse is true for the epoxy nanocomposites. This observation has a particular implication of exploiting the CNT/polybenzoxazine nanocomposites in applications requiring low shrinkage and accurate dimensional control.  相似文献   

7.
孙晓刚 《材料导报》2003,17(12):70-72
单壁碳纳米管和多壁碳纳米管的合成和应用研究得到广泛的关注和重视,并已取得了许多令人鼓舞的成果。双壁碳纳米管(DWCNTs)作为介于单壁碳纳米管和多壁碳纳米管之间的一种特殊结构碳纳米管,由于潜在的应用价值及作为研究碳纳米管层间作用最简单和理想的模型开始得到高度重视。介绍了双壁碳纳米管合成方法及理论和应用研究取得的进展。  相似文献   

8.
The prime objective of this work is to optimize the mechanical and thermo-mechanical properties of e-glass/epoxy composites by utilizing amino-functionalized multi-walled carbon nanotubes (MWCNTs–NH2) through a combination of dispersion method. At first, 0.1–0.4 wt.% of MWCNT–NH2 was integrated into SC-15 epoxy suspension using a combination of ultra-sonication and calendaring techniques. E-glass/epoxy nanocomposites were than fabricated at elevated temperature with the modified resin using hand layup and compression hot press. 3-Point flexural and dynamic mechanical analysis (DMA) results demonstrated a linearly increasing trend in properties from 0 to 0.3 wt.% loading. Micrographs of MWCNTs incorporated epoxy and e-glass/epoxy samples revealed uniform dispersion of MWCNTs in epoxy, good interfacial adhesion between CNTs and polymer, and improved interfacial bonding between fiber/matrix at 0.3 wt.% loading. An improved dispersion and hence an improved crosslink interaction between MWCNT–NH2 and epoxy lead to the stronger shift of the mechanical and thermo-mechanical properties of the composites.  相似文献   

9.
《Composites Part B》2013,45(1):394-402
Load transfer efficiency from matrix to carbon nanotubes (CNTs) plays an important role in the mechanical response of CNTs nanocomposites as it may affect the effectiveness of the nano-reinforcements. For double-walled carbon nanotubes (DWCNTs), the outer graphene layer as well as the inner layer may be responsible for the load bearing capacity. In this study, the load transfer efficiency within DWCNTs was investigated using a multiscale simulation scheme. The multiscale simulation consists of two steps. First, the atomistic behaviors between the adjacent graphite layers in DWCNTs were characterized using molecular dynamic (MD) simulation, from which a cylindrical equivalent continuum solid of DWCNTs with embedded spring elements was proposed to describe the interactions of neighboring graphene layers. Two kinds of interatomistic properties in DWCNTs, i.e., van der Walls (vdW) interactions and artificial build-up covalent bonds, were considered in the equivalent solid. Subsequently, the equivalent solid was implemented as reinforcement in the micromechanical model of CNTs nanocomposites for evaluating the load transfer efficiency. Results indicated that the DWCNTs with covalent bonds exhibit superior load transfer efficiency than those with only vdW interactions. In addition, when the DWCNTs get long, the load transfer efficiency of DWCNTs increases accordingly.  相似文献   

10.
利用化学气相沉积法,以Fe-Mo/Al_2O_3为催化剂,催化分解甲烷气体制备碳纳米管(CNTs).研究了温度,反应时间和气体流速对碳纳米管结构的影响.结果显示:温度是影响碳纳米管壁厚的关键参数.低温导致壁厚为2 nm~7 nm的多壁碳纳米管(MWCNTs)的生成.相对地,高温有利于双壁碳纳米管(DWCNTs)的生长,而更高的温度促使单壁碳纳米管(SWCNTs)的产生.进一步升高温度,得到了壁厚为3 nm~15 nm的MWCNTs和大的炭颗粒.  相似文献   

11.
Due to their exceptional mechanical properties, carbon nanotubes (CNTs) are considered to be one of the most promising reinforcing materials for the next generation of high-performance nanocomposites. In this study, the reinforcing effect of highly dispersed multiwall carbon nanotubes (MWCNTs) in cement paste matrix has been investigated. The MWCNTs were effectively dispersed in the mixing water by using a simple, one step method utilizing ultrasonic energy and a commercially available surfactant. A detailed study on the effects of MWCNTs concentration and aspect ratio was conducted. The excellent reinforcing capabilities of the MWCNTs are demonstrated by the enhanced fracture resistance properties of the cementitious matrix. Additionally, nanoindentation results suggest that the use of MWCNTs can increase the amount of high stiffness C–S–H and decrease the porosity. Besides the benefits of the reinforcing effect, autogenous shrinkage test results indicate that MWCNTs can also have a beneficial effect on the early strain capacity of the cementitious matrix, improving this way the early age and long term durability of the cementitious nanocomposites.  相似文献   

12.
Well-dispersed multi-walled carbon nanotubes (CNTs) reinforced Al2O3 nanocomposites were successfully fabricated by hot-pressing. The resulting promising improvements in fracture toughness, by 94% and 65% with 2 and 5 wt.% CNTs addition respectively, compared with monolithic Al2O3, were attributed to the good dispersion of CNTs within the matrix, crack-bridging by CNTs and strong interfacial connections between the CNTs and the matrix. The interfacial phase characteristics between CNTs and Al2O3 were investigated via combined techniques. It is believed that a possible aluminium oxy-carbide as the primary interfacial phase was produced via a localized carbothermal reduction process. This interface phase presumably has good chemical compatibility and strong connections with both CNTs and the matrix and led nanocomposites to higher fracture toughness.  相似文献   

13.
为了改善Ti/反应型聚酰亚胺(PMR)树脂界面的黏结强度,从而提高Ti-碳纤维(CF)/PMR超混杂层板的力学性能,本文探究了添加多壁碳纳米管(MWCNTs)对Ti-CF/PMR超混杂层板力学性能的影响。将不同质量分数(0wt%、2.5wt%、5.0wt%和7.5wt%)的MWCNTs利用超声分散法均匀分散于PMR树脂中,随后进行Ⅰ型断裂韧性试验,探究添加MWCNTs对Ti-CF/PMR超混杂层板界面性能的影响,最后选取最优含量的MWCNTs同时添加到PMR胶层和CF/PMR树脂中,并进行弯曲试验,探究添加MWCNTs对Ti-CF/PMR超混杂层板力学性能的影响。通过SEM观察和分析了相应的失效模式和增强机制。结果表明:当MWCNTs含量为5.0wt%时,Ⅰ型层间断裂韧性提高了74%;同时添加5.0wt% MWCNTs于PMR胶层和CF/PMR复合材料树脂中,Ti-CF/PMR超混杂层板的弯曲性能较未添加MWCNTs提高了42%。这是由于MWCNTs在PMR胶层和CF/PMR树脂中的分布均匀性较高,且能分散并承受界面层转移到纤维层的载荷,并利用自身拔出、断裂、桥接、脱黏来吸收并消耗断裂能量,进一步提升Ti-CF/PMR超混杂层板的弯曲性能。   相似文献   

14.
A facile synthetic scheme of amine-grafted multi-walled carbon nanotubes (MWCNTs) using silane coupling agent has been illustrated, which has not been reported in literature. The fabricated MWCNTs were characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD) and field emission scanning electron micrograph (FESEM). The results indicate that the amine groups have been grafted onto the surface of MWCNTs and symmetry of MWCNTs was not destroyed, simultaneously, they generated such large polar forces among nanotubes that they formed close-packed structure. Also, they were well dispersed in resin matrix and their distribution was relatively homogenous because there was less nanotubes pulled out on the fracture surface. The thermal analysis was taken for investigation of the thermal stability and thermal decomposition behavior. The comparative analysis proved the existence of amine groups and its total weight of 11 wt.%. The efficient interaction between amine grafted MWCNTs enhanced the crosslink density and the values of glass transition temperature which confirmed the efficient compatibility with resin matrix.  相似文献   

15.
Plasma-enhanced chemical vapor deposition was used to modify the multiwall carbon nanotubes (MWCNTs) using ammonia (NH3) plasma. For various durations of NH3 plasma treatment, a scanning electron microscope, X-ray, Raman spectroscopy and contact angle measurement were used to ascertain several characteristics of the MWCNTs. The experimental results show that: (1) the length of the MWCNTs is reduced, if the duration of the plasma treatment is increased; (2) the NH3 plasma treatment can incorporate amine (NH2 ) or amino (NH) functional groups onto the MWCNT surface; (3) the plasma treated carbon nanotubes become more hydrophilic.  相似文献   

16.
In this investigation, specimens of MWCNT-epoxy nanocomposites were prepared by two different dispersion methods including the use of ultrasonication, and high speed shear mixing. The dispersion degree between MWCNT and polymer resin was analyzed after completing the curing reaction, by scanning electron microscopy. The effect of the nanotubes dispersion achieved on the properties of the manufactured nanocomposite was analyzed through static three point bending tests and dynamic mechanical thermal analysis. Interesting results concerning the dispersion effect of MWCNTs added to the polymer matrix on the storage and loss moduli as well as on tanδ and T g values of the specimens manufactured by the sonication and high speed shear mixing methods were derived.  相似文献   

17.
ABSTRACT

Metal matrix nanocomposites (MMNCs) consist of a metal matrix reinforced with nanoparticles, featuring physical and mechanical properties very different from those of the matrix. Especially carbon nanotubes (CNTs) can improve the matrix material in terms of wear resistance, damping properties, and mechanical strength. The present investigation deals with the synthesis and characterization of aluminum matrix reinforced with micro-B4C particles, and multiwall carbon nanotubes (MWCNTs) which have been prepared by powder metallurgy route. Powder mixture containing fixed weight (%) of B4C and different wt% of MWCNT as reinforcement constituents that are uniaxial cold pressed and later green compacts are sintered in continues electric furnace. Microstructure and Mechanical properties such as microhardness and density are examined. Microstructure of samples has been investigated using scanning electron microscope (SEM). X-ray diffraction(XRD), energy dispersive x-ray (EDAX), atomic force microscope (AFM), and transmission electron microscope (TEM). TEM microstructure of the nanocomposite shows the homogeneous dispersion of MWCNT in the aluminum matrix. The results indicated that the increase in wt % of MWCNT improves the bonding and mechanical properties.  相似文献   

18.
A floating catalyst chemical vapor deposition (FC-CVD) method was designed and fabricated to produce high-quality and -quantity carbon nanotubes. The design parameters like the hydrogen flow rate; reaction time and reaction temperature were optimized to produce high yield and purity of Multi-Wall Carbon Nanotubes (MWCNTs). Multi-Walled Carbon Nanotubes (MWNTs) were used to prepare natural rubber (NR) nanocomposites. Our first efforts to achieve nanostructures in MWNTs/styrene butadiene rubber (SBR) nanocomposites were formed by incorporating carbon nanotubes in a polymer solution and subsequently evaporating the solvent. Using this technique, nanotubes can be dispersed homogeneously in the NR matrix in an attempt to increase the mechanical properties of these nanocomposites. The properties of the nanocomposites such as tensile strength, tensile modulus, elongation at break and hardness were studied. Using different percentages of carbon nanotubes from 1 wt% to 10 wt%, several nanocomposites samples were fabricated. Significant improvements in the mechanical properties of the resulting nanocomposites showed almost 10% increase in the Young's modulus for 1 wt% of CNTs and up to around 200% increase for 10 wt% of CNTs.  相似文献   

19.
This paper reports the alignment of multi-walled carbon nanotubes (MWCNTs) in an epoxy matrix as a result of DC electric fields applied during composite curing. Optical microscopy and polarized Raman spectroscopy are used to confirm the CNT alignment. The alignment of CNTs gives rise to much improved electrical conductivity, elastic modulus and quasi-static fracture toughness compared to those with CNTs of random orientation. An extraordinarily low electrical percolation threshold of about 0.0031 vol% is achieved when measured along the alignment, which is more than one order of magnitude lower than 0.034 vol% with random orientation or that measured perpendicular to the aligned CNTs. The examination of the fracture surfaces identifies pertinent toughening mechanisms in aligned CNT composites, namely crack tip deflection and CNT pullout. The significance of this paper is that the technique employed here can tailor the physical, mechanical and fracture properties of bulk nanocomposites even at a very low CNT concentration.  相似文献   

20.
A novel class of epoxy matrix hybrid nanocomposites has been developed containing multiwalled carbon nanotubes (MWCNTs) and nanodiamonds (NDs) to explore the combined effect of nanoreinforcements on the mechanical performance of nanocomposites. Both the nanofillers were functionalized before incorporating into epoxy matrix to promote interfacial interactions. The concentrations of both MWCNTs and NDs in the nanocomposites were increased systematically, i.e. 0.05 wt.%, 0.1 wt.% and 0.2 wt.% while composites containing individual nanoreinforcements were also manufactured for comparison. The developed nanocomposites were characterized microstructurally by scanning electron microscopy (SEM) and mechanically by tensile, flexural, impact and hardness tests. Homogeneous dispersion of MWCNTs and NDs was observed under SEM, which resulted in the enhancement of mechanical properties of nanocomposites. The composites containing 0.2 wt.% MWCNTs and 0.2 wt.% NDs showed 50% increase in hardness while tensile strength and modulus enhanced to 70% and 84%, respectively. Flexural strength and modulus also showed a rise of 104% and 56%, respectively. Interestingly, fracture strain also increased in both the tensile and flexural testing. The impact resistance increased to 161% showing a significant improvement in the toughness of hybrid nanocomposites.  相似文献   

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