Synergistic effects in network formation and electrical properties of hybrid epoxy nanocomposites containing multi-wall carbon nanotubes and carbon black

Epoxy nanocomposites including multi-wall carbon nanotubes (MWCNT) and carbon black (CB) were produced and investigated by means of electrical conductivity measurements and microscopical analysis. Varying the weight fraction of the nanoparticles, electrical percolation behaviour was studied. Due to synergistic effects in network formation and in charge transport the inclusion of both MWCNT and CB in the epoxy matrix leads to an identical electrical behaviour of this ternary nanocomposite system compared to the binary MWCNT-epoxy system. For both types of nanocomposites an electrical percolation threshold of around 0.025 wt% and 0.03 wt% was observed. Conversely, the binary CB nanocomposites exhibit a three-times higher percolation threshold of about 0.085 wt%. The difference between the binary MWCNT-epoxy and the ternary CB/MWCNT-epoxy in electrical conductivity at high filler concentrations (e.g. 0.5 wt%) turns out to be less than expected. Thus, a considerable amount of MWCNTs can be replaced by CB without changing the electrical properties.     

Mechanical and thermal properties of epoxy nanocomposites reinforced with amino-functionalized multi-walled carbon nanotubes

The functionalized multi-walled carbon nanotubes (MWNTs) with amino groups were prepared after such steps as oxidation, the addition of carboxyalkyl radicals, acylation and amidation. Besides oxidated-MWNTs/epoxy nanocomposites, amino-functionalized MWNTs/epoxy nanocomposites, in which MWNTs with amino groups acted as a curing agent and covalently attached into the epoxy matrix, were fabricated. Subsequently, the effects of MWNT content on the mechanical and thermal properties for the two systems were investigated. It is found that both the tensile strength and impact strength enhance with the increase of MWNT addition, and the most significant improvement of the tensile strength (+51%) and especially impact strength (+93%) is obtained with amine-treated MWNTs at an 1.5 wt.% content. Moreover, the thermal stability of the nanocomposites also distinctly improves. The improvement of the properties of the amine-treated MWNTs system is more remarkable than those of o-MWNTs system. The reasons for these changes were discussed.     

Influence of electrolessly silver-plated multi-walled carbon nanotubes on thermal conductivity of epoxy matrix nanocomposites

In this work, multi-walled carbon nanotubes (MWCNTs) were electrolessly Ag-plated in order to investigate the effect of plating time on the thermal conductivity of Ag-plated MWCNTs-reinforced epoxy matrix composites. MWCNT surfaces were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS). The thermal conductivity of Ag-plated MWCNT-reinforced epoxy nanocomposites was measured using the thermal equilibrium method with ASTM D5470. From the results, it was found that the thermal conductivity of the composites enhanced with increasing plating time. In particular the Ag-10/EP sample showed more than 150% enhancement of the thermal conductivity compared to the as-received CNTs/EP sample. These results were attributed to the high contents of Ag particles and the increase of the interfacial adhesion between the Ag-CNTs and EP matrix in the composites.     

Impact behavior and fractographic study of carbon nanotubes grafted carbon fiber-reinforced epoxy matrix multi-scale hybrid composites

Carbon nanotubes are the most promising reinforcement for high performance composites. Multiwall carbon nanotubes were directly grown onto the carbon fiber surface by catalytic thermal chemical vapor deposition technique. Multi-scale hybrid composites were fabricated using the carbon nanotubes grown fibers with epoxy matrix. Morphology of the grown carbon nanotubes was investigated using field emission scanning electron microscopy and transmission electron microscopy. The fabricated composites were subjected to impact tests which showed 48.7% and 42.2% higher energy absorption in Charpy and Izod impact tests respectively. Fractographic analysis of the impact tested specimens revealed the presence of carbon nanotubes both at the fiber surface and within the matrix which explained the reason for improved energy absorption capability of these composites. Carbon nanotubes presence at various cracks formed during loading provided a direct evidence of micro crack bridging. Thus the enhanced fracture strength of these composites is attributed to stronger fiber–matrix interfacial bonding and simultaneous matrix strengthening due to the grown carbon nanotubes.     

Dispersion and reinforcing mechanism of carbon nanotubes in epoxy nanocomposites

Carbon nanotube based epoxy composites have been fabricated at room temperature and refrigeration process using sonication principle. Flexural moduli, electrical conductivity, glass transition temperature of epoxy resin as well as nanocomposite samples have been determined. Distribution behaviour of carbon nanotubes in the epoxy matrix was examined through scanning electron microscopy. Composite samples showed better properties than resin samples due to strengthening effect of the filled nanotubes. Refrigerated nanocomposites obtained increasing mechanical property because of better dispersion due to low temperature settlement of polymers. Improvement of electrical conductivity was due to the fact that aggregated phases form a conductive three-dimensional network throughout the whole sample. The increasing glass transition temperature was indicative of restricting movement of polymer chains that ascribe strong interaction presented between carbon nanotubes and epoxy chains that was again supplemented by Raman study and SEM.     

Mechanical properties of epoxy nanocomposites reinforced with very low content of amino-functionalized single-walled carbon nanotubes

Functionalized single-walled carbon nanotubes (SWNTs) with amino groups were prepared by oxidation, acylation, and amidation of SWNT surfaces. Epoxy/SWNT composite membranes were fabricated using a very low content of amino-grafted SWNTs (< or = 0.08 wt%) as fillers. SWNTs with amino groups acted as a curing agent, covalently bonding to the epoxy matrix. The influence of SWNT content on the mechanical properties of epoxy/amino-functionalized SWNT composite membrane was investigated. It is found that the tensile strength of composites is enhanced with the increase of SWNTs. Only 0.01 wt% of SWNT-R-NH, leads to improvement of the epoxy tensile strength by 9.5%, and 0.08 wt% of SWNT-R-NH2 increased tensile strength by 13.6%. For comparison purposes, epoxy/pristine-SWNT films were also prepared. The improvement of the tensile strength of the amino-functionalized SWNTs system is more remarkable than that of pristine SWNT system at very low weight-percentage loading. The amino groups on the surface of SWNTs can be covalently attached to the epoxy matrix, which effectively improves the dispersion and adhesion of SWNTs in epoxy. This leads to the enhancement in mechanical properties of the epoxy composite. Mechanical results between functionalized and pristine nanotubes are discussed in detail.     

Mechanical behaviour of graphene and carbon fibre reinforced epoxy based hybrid nanocomposites for orthotic callipers

ABSTRACT

The current analysis examines the efficiency of a composite with polymer matrix reinforced with carbon fibre and graphene at the micro and nano level respectively as an alternative material for aluminium components of Orthotic callipers. An attempt has been made to use both the carbon fibre and graphene as hybrid reinforcement with the matrix as epoxy resin. The addition of graphene and carbon fibre was 2% and 10% respectively by weight of epoxy. Dispersion of graphene was carried out using an ultrasonic sonicator and carbon fibres were a reinforced using hand lay-up technique. The total fabrication was carried out under vacuum to ensure void-free test samples. The samples were tested under tension and 3 Point Bending condition to estimate the Tensile and Flexural properties, under permissible load and deflection criteria. The results found were then compared with presently used material for orthotic callipers extensively used by amputees suffering from the locomotive, gait issues, and polio-affected survivors. The proposed composite showed higher strength, lower deformation and higher stiffness with a lower weight-to-volume ratio as compared to presently used material, i.e. aluminium.     

Ceramic matrix composites containing carbon nanotubes

Due to the remarkable physical and mechanical properties of individual, perfect carbon nanotubes (CNTs), they are considered to be one of the most promising new reinforcements for structural composites. Their impressive electrical and thermal properties also suggest opportunities for multifunctional applications. In the context of inorganic matrix composites, researchers have particularly focussed on CNTs as toughening elements to overcome the intrinsic brittleness of the ceramic or glass material. Although there are now a number of studies published in the literature, these inorganic systems have received much less attention than CNT/polymer matrix composites. This paper reviews the current status of the research and development of CNT-loaded ceramic matrix composite (CMC) materials. It includes a summary of the key issues related to the optimisation of CNT-based composites, with particular reference to brittle matrices and provides an overview of the processing techniques developed to optimise dispersion quality, interfaces, and density. The properties of the various composite systems are discussed, with an emphasis on toughness; a comprehensive comparative summary is provided, together with a discussion of the possible toughening mechanism that may operate. Last, a range of potential applications are discussed, concluding with a discussion of the scope for future developments in the field.     

Mechanical properties of carbon nanotubes and their polymer nanocomposites

More than 10 years have passed since carbon nanotubes (CNT) have been found during observations by transmission electron microscopy (TEM). Since then, one of the major applications of the CNT is the reinforcements of plastics in processing composite materials, because it was found by experiments that CNT possessed splendid mechanical properties. Various experimental methods are conducted in order to understand the mechanical properties of varieties of CNT and CNT-based composite materials. The systematized data of the past research results of CNT and their nanocomposites are extremely useful to improve processing and design criteria for new nanocomposites in further studies. Before the CNT observations, vapor grown carbon fibers (VGCF) were already utilized for composite applications, although there have been only few experimental data about the mechanical properties of VGCF. The structure of VGCF is similar to that of multi-wall carbon nanotubes (MWCNT), and the major benefit of VGCF is less commercial price. Therefore, this review article overviews the experimental results regarding the various mechanical properties of CNT, VGCF, and their polymer nanocomposites. The experimental methods and results to measure the elastic modulus and strength of CNT and VGCF are first discussed in this article. Secondly, the different surface chemical modifications for CNT and VGCF are reviewed, because the surface chemical modifications play an important role for polymer nanocomposite processing and properties. Thirdly, fracture and fatigue properties of CNT/polymer nanocomposites are reviewed, since these properties are important, especially when these new nanocomposite materials are applied for structural applications.     

Mechanical and electrical properties of hot-pressed borosilicate glass matrix composites containing multi-wall carbon nanotubes

Borosilicate glass matrix composites reinforced with 10 wt% multiwall carbon nanotubes (CNTs) were fabricated using a conventional powder processing route and uniaxial hot pressing. The microstructure of the composites contained aggregates of CNTs which had not been infiltrated by the viscous glass during hot-pressing leaving a ∼9% residual porosity. As a result, the mechanical properties (hardness, elastic modulus, fracture toughness and fracture strength) were not improved in comparison to those of the monolithic glass matrix. However the brittleness index (B), which is the ratio of hardness to fracture toughness, decreased with addition of CNTs, which indicates that the composites should exhibit improved contact damage and wear resistance. Electrical resistivity measurements revealed that the addition of 10 wt% CNTs to the normally insulating borosilicate glass decreased its resistivity to 13 Ω cm in comparison to the high value (10¹⁵ Ω cm) of the monolithic glass.     

Mechanical and electrical properties of nanocomposites containing hybrid fillers of disk-like copper and conductive carbon black

Electrically conductive rubber (ECR) was prepared through conventional rubber mixing techniques on a two-roll mill, which the conductive filler was polymer-coated Cu nano-disk and conductive carbon black (CCB). The effect of Cu nanoparticles content on the mechanical and electrical resistivity properties of ECR was further investigated. The obtained results of six different compositions for ECR with 0, 5, 10, 15, 20 and 25 per hundred of rubber (phr) of Cu nanoparticles loading were compared. It was found that ECR has lower volume resistivity and high tensile strength, compared with rubber containing commercial Cu particles. These results suggest that when the Cu particles are nano-disk and surface modified, the mechanical and stability properties of the rubber can be synchronously improved.     

Thermo-physical properties of epoxy nanocomposites reinforced with amino-functionalized multi-walled carbon nanotubes

The modification of multi-walled carbon nanotubes (MWNTs) with amine groups was investigated by FTIR, Raman spectroscopy and XPS after such steps as carboxylation, acylation and amidation. Nanotube-reinforced epoxy polymer composites were prepared by mixing amino-functionalized MWNTs with epoxy resin and curing agent. DSC, TGA, SEM and flexural test were used to investigate the thermal and mechanical properties of the composites. The results showed that amino-functionalized MWNTs could enhance the interfacial adhesion between the nanotubes and the matrix, thus greatly improve the thermal and mechanical properties of the resin epoxy bulk material.     

The reinforcement role of different amino-functionalized multi-walled carbon nanotubes in epoxy nanocomposites

Functionalization with different amino groups of multi-walled carbon nanotubes was achieved and nanotube-reinforced epoxy nanocomposites were prepared by mixing amino-functionalized multi-walled carbon nanotubes with epoxy resin. Differential scanning calorimetry, thermogravimetric analysis and bending tests were used to investigate the thermal and mechanical properties of the nanocomposites. The results showed that different kinds of amino-functionalized multi-walled carbon nanotubes would have different effects on the thermal and mechanical properties of the nanocomposites. The reinforcement mechanism of amino-functionalized multi-walled carbon nanotubes in epoxy resin was discussed.     

Vapor sensing performances of PVDF nanocomposites containing titanium dioxide nanotubes decorated multi-walled carbon nanotubes

Inorganic nanocarbon hybrid materials are good alternatives for superior electrochemical performance and specific capacitance to their traditional counterparts. Nanocarbons act as a good template for the growth of metal nanoparticles on it and their hybrid combinations enhance the charge transport and rate capability of electrochemical materials without sacrificing the specific capacity. In this study, titanium dioxide nanotubes (TNT) are synthesized hydrothermally in the presence of multi-walled carbon nanotubes (MWCNT) where the latter acts as base template material for the metal oxide nanotube growth. The MWCNT–TNT hybrid material possesses very high dielectric strength and this is used to enhance the dielectric property of the polymer polyvinyledene fluoride (PVDF). Solution mixing was used to prepare the PVDF/MWCNT–TNT nanocomposites by varying the filler concentrations from 0.5 to 2.5 wt%. Excellent vapor sensing was noticed for the PVDF nanocomposites with different rate of response towards commonly used laboratory solvents. The composites and the fillers were characterized for its morphology and structural properties using scanning and transmission electron microscopy, X-ray diffraction studies and infrared spectroscopy. Vapor sensing was measured as relative resistance variations against the solvent vapors, and the dielectric properties of the composites were measured at room temperature during the frequency 10²–10⁷ Hz. Experimental results revealed the influence of filler synergy on the properties of PVDF and the enhancement in the solvent vapor detectability and dielectric properties reflects the ability of these composite films in flexible vapor sensors and in energy storage.     

聚酰亚胺/多壁碳纳米管杂化薄膜力学性能研究

采用不同长径比的多壁碳纳米管通过原位聚合法制备一系列多壁碳纳米管改性的聚酰胺酸胶液,并经热亚胺化途径制备聚酰亚胺杂化薄膜。利用扫描电子显微镜(SEM)观察薄膜的断面形貌,采用红外光谱仪(FT-IR)分析酸化前后多壁碳纳米管表面官能团的变化,并采用电子万能试验机对薄膜的力学性能进行测试,分析了多壁碳纳米管的含量和长径比对杂化薄膜力学性能的影响。结果表明,小掺杂量下,长径比大的多壁碳纳米管更有利于增强PI杂化薄膜的拉伸强度;而长径比小的多壁碳纳米管使杂化薄膜拉伸强度提高的碳纳米管掺杂量范围更宽。     

A review on the effect of oxide nanoparticles,carbon nanotubes,and their hybrid structure on the toughening of epoxy nanocomposites

Journal of Materials Science - Epoxy-based polymer nanocomposite is an advanced and high-performance material with numerous applications in automobiles, railways, aerospace, and construction...     

Effect of amino-functionalization on the interfacial adhesion of multi-walled carbon nanotubes/epoxy nanocomposites

Two types of multi-walled carbon nanotubes (MWCNTs) functionalized with different amino-organics, dicyanodiamide and phenylbiguanide, respectively, were achieved in this paper. The physico-chemical properties of MWCNTs before and after amino group modification were characterized by thermogravimetric analysis (TGA), Raman spectroscopy and inverse gas chromatography (IGC). The results showed that amino-functionalization changed evidently the surface properties of MWCNTs, such as the dispersive surface energy (decreased from 122.95 mJ/m² to 18.65 mJ/m² and 25.69 mJ/m², respectively) and specific surface energy (decreased from 8.84 mJ/m² to 0.56 mJ/m² and 4.60 mJ/m², respectively) for two functionalized MWCNTs. And then, the interfacial adhesion states of the functionalized MWCNTs/epoxy nanocomposites were investigated using scanning electron microscope (SEM) and dynamic mechanical analysis (DMA). The results also indicated that the dispersion of MWCNTs in epoxy resin and the interfacial adhesion of MWCNTs/epoxy nanocomposites were both strongly dependent on the surface physico-chemical properties of functionalized MWCNTs, and the effect of MWCNTs functionalized by phenylbiguanide with slightly higher polarity was better.     

Studies on preparation and properties of the multi-walled carbon nanotubes (MWNTs)/epoxy nanocomposites

The MWNTs were coated with polyaniline (PANI) by in situ chemical oxidation polymerization method. FTIR spectroscopy, scanning electron microscope (SEM) and X-ray diffraction (XRD) indicated that the MWNTs were coated with PANI. The MWNTs/epoxy nanocomposites were fabricated by using the solution blending method. Differential scanning calorimetry (DSC), tensile testing, HP 4294A impedance analyzer and SEM were used to investigate the properties of the nanocomposites. The results showed that the modified carbon nanotubes were well dispersed in the polymer matrix. The nanocomposites have enhancements in mechanical, thermal and dielectric properties compare with the neat epoxy resin. The nanocomposites were proven to be a good polymer dielectric material.     

Mechanical characterization of copper coated carbon nanotubes reinforced aluminum matrix composites

In this investigation, carbon nanotube (CNT) reinforced aluminum composites were prepared by the molecular-level mixing process using copper coated CNTs. The mixing of CNTs was accomplished by ultrasonic mixing and ball milling. Electroless Cu-coated CNTs were used to enhance the interfacial bonding between CNTs and aluminum. Scanning electron microscope analysis revealed the homogenous dispersion of Cu-coated CNTs in the composite samples compared with the uncoated CNTs. The samples were pressureless sintered under vacuum followed by hot rolling to promote the uniform microstructure and dispersion of CNTs. In 1.0 wt.% uncoated and Cu-coated CNT/Al composites, compared to pure Al, the microhardness increased by 44% and 103%, respectively. As compared to the pure Al, for 1.0 wt.% uncoated CNT/Al composite, increase in yield strength and ultimate tensile strength was estimated about 58% and 62%, respectively. However, in case of 1.0 wt.% Cu-coated CNT/Al composite, yield strength and ultimate tensile strength were increased significantly about 121% and 107%, respectively.