No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Reinforcing Epoxy Polymer Composites Through Covalent Integration of Functionalized Nanotubes
Advanced Functional Materials
Abstract
Strong interfacial bonding and homogenous dispersion have been found to be necessary conditions to take full advantage of the extraordinary properties of nanotubes for reinforcement of composites. We have developed a fully integrated nanotube composite material through the use of functionalized single-walled carbon nanotubes (SWNTs). The functionalization was performed via the reaction of terminal diamines with alkylcarboxyl groups attached to the SWNTs in the course of a dicarboxylic acid acyl peroxide treatment. Nanotube-reinforced epoxy polymer composites were prepared by dissolving the functionalized SWNTs in organic solvent followed by mixing with epoxy resin and curing agent. In this hybrid material system, nanotubes are covalently integrated into the epoxy matrix and become part of the crosslinked structure rather than just a separate component. Results demonstrated dramatic enhancement in the mechanical properties of an epoxy polymer material, for example, 30-70% increase in ultimate strength and modulus with the addition of only small quantities (1-4 wt.-%) of functionalized SWNTs. The nano tube-reinforced epoxy composites also exhibited an increased strain to failure, which suggests higher toughness.
... The properties of nanocomposites reinforced with CNTs are highly affected by the interphase. Barber et al. [24], McCarthy et al. [25], Lourie et al. [26], Jin et al. [27] and Zhu et al. [28] using different approaches observed a strong bond between CNTs and the resin. There are few evidences on confirming the weak bond between CNTs and polymers. ...
... Considering Eqs. (28) and (29), radial part of the stress concentration tensor can be rewritten as a function of mechanical properties and the radii of all phases as: ...
... Inserting Eqs. (28), (29) and (34)(35)(36) into the last relation gives: ...
This article deals with the effect of CNTs debonding from the surrounding matrix on the fracture toughness of carbon nanotubes/epoxy nanocomposites. Hence, a multiscale modeling of fracture toughness improvement of nanocomposites due to CNTs debonding was developed. This energy dissipation mechanism takes place at a zone around the crack tip. A representative volume element containing a carbon nanotube, its surrounding resin and the interphase was chosen in order to develop the multiscale model. Using experimental data available in the literature, the influence of several parameters such as weight fraction of the CNT, the interphase thickness and Young's modulus were studied by the present model. It was concluded that the interphase characteristics as well as the CNT weight fraction strictly affect the fracture toughness enhancement caused by the debonding mechanism and the debonding stress around the CNT. In addition, the influence of CNTs debonding on the fracture toughness of nanocomposites was investigated.
... SWCNTs. Several studies [6,47,48,53,113,118] have concluded that adding SWCNTs to epoxies could significantly enhance their mechanical properties. For instance, Ashrafi et al. [6] found that incorporation of 0.1 wt % of SWCNT increased mode I and mode II interlaminar fracture toughness by 13% and 28%, respectively, compression-after-impact (CAI) strength by 3.5%. ...
... Moreover, the addition of functionalised SWCNTs to an epoxy matrix, as in [47,48,113], could enhance the mechanical characteristics of the SWCNTs/epoxy nanocomposites. For instance, Zhao et al. [113] used asymmetric diamine molecules, N-BOC-1,6-diaminohexane functionalised-SWCNTs. ...
... The chemical methods include creating surface functionalities on CNTs, thus enhancing their chemical interactions/compatibility with a matrix, resulting in improved dispersion [83][84][85]120]. Although several functionalisation processes have been developed, such as amine [48,53,100,106], silane [62,102], or fluorine treatments [49], the limited active sites on CNTs surface may lower efficiency of functionalisation, thereby reduce the dispersibility of CNTs in adhesives [83]. The non-covalent physical treatments, such as application of surfactants [121,123,124] and polymer coating followed by surfactant treatment [79,83], are particularly attractive due to the physical adsorption and rarely damage the structure of CNTs [124]. ...
Retrofitting, strengthening, and repairing of deteriorated concrete structures have adopted epoxy adhesives for decades to bond fibre reinforced polymer (FRP) materials to the substrate of the deteriorated concrete elements. Despite being the most commercially used solutions, epoxy adhesives show several disadvantages, in terms of the performance of the strengthened elements and the toxicity of the material. Cement-based adhesives (CBAs) have been also considered for retrofitting concrete elements, but their use is very limited due to their poor performance, for instance, their low mechanical properties (i.e. compressive and tensile strength) compared to epoxy adhesives. The nanomaterial-modified epoxy adhesives and nanomaterial-modified CBAs (i.e. innovative high-strength self-compacting cement adhesives (IHSSC-CA)) have been effective substitutes with their extraordinary mechanical and thermal properties. This paper overviews the development of adhesives for FRP-strengthened concrete elements, in particular of epoxy and CBAs with the addition of nanoparticles. Both the mechanical and thermal properties of strengthening FRP and bonding interfaces with various adhesives are firstly investigated and compiled, and then the performance of retrofitted/strengthened-concrete elements with the FRP composites using neat and nanoparticles-modified adhesives is studied to examine the effectiveness of the modified adhesives over neat adhesives for retrofitting. Based on the compiled developments, further developments are identified, and recommendations are made for future research and innovations in this subject area.
... 51 However, during the fabrication process, the incorporation of a polymer using procedures such as ultrasonication and surfactant and chemical modication improve the synergistic homogeneity of the constituent composite, thereby wrapping the semiconductors used around the polymer chain, leading to the formation of nanocomposite photocatalysts with less possibility of agglomeration. 50,52 The impact of reduced agglomeration by the polymer equally improves the overall conductivity and imparts appreciative mechanical features in the composite. 52,53 Additionally, it should be noted that another cause of agglomeration of catalysts in photocatalysis can arise from the use of excess catalyst during in the photocatalytic process of dye-laden effluent. ...
... 50,52 The impact of reduced agglomeration by the polymer equally improves the overall conductivity and imparts appreciative mechanical features in the composite. 52,53 Additionally, it should be noted that another cause of agglomeration of catalysts in photocatalysis can arise from the use of excess catalyst during in the photocatalytic process of dye-laden effluent. 36,54 Furthermore, the other impacts of PANI in the composite blend include improved optoelectronic features of the photocatalyst blend. ...
The challenges associated with photocatalysts including their agglomeration, electron-hole recombination and limited optoelectronic reactivity to visible light during the photocatalysis of dye-laden effluent make it necessary to fabricate versatile polymeric composite photocatalysts, and in this case the incredibly reactive conducting polyaniline can be employed. The selection of polyaniline among the conducting polymers is based on its proficient functional impacts in composite blends and proficient synergism with other nanomaterials, especially semiconductor catalysts, resulting in a high photocatalytic performance for the degradation of dyes. However, the impacts of PANI in the composite matrix, which result in the desired photocatalytic activities, can only be assessed using multiple characterization techniques, involving both microscopic and spectroscopic assessment. The characterization results play a significant role in the detection of possible points of agglomeration, surface tunability and improved reactivity during the fabrication of composites, which are necessary to improve their performance in the photocatalysis of dyes. Accordingly, studies revealed the functional impacts of polyaniline in composites including morphological transformation, improved surface functionality, reduction in agglomeration and lowered bandgap potential employing different characterization techniques. In this review, we present the most proficient fabrication techniques based on the in situ approach to achieve improved functional and reactive features and efficiencies of 93, 95, 96, 98.6 and 99% for composites in dye photocatalysis.
... The addition of the epoxy functionalized ANFs into the epoxy resin mixture resulted in a significant increase in viscosity, which causes micro void defects in the crosslinked nanocomposites. [115,116] However, despite the increased number of defects, the Young's modulus of 1.5 and 2.0 wt % nanocomposites were 14.7 and 13.0% higher than that of the neat resin, respectively, and the tensile strength of those nanocomposites were 12.4 and 12.9% higher compared to the neat resin, respectively. ...
... The surface modification using GPTMS increased the viscosity of the epoxy resin mixture significantly during the mixing process. [116] The average Young's modulus and tensile strength of ANF, CNC, AC, and fAC reinforced epoxy nanocomposites are displayed in Figure 6.5, and Figure 6.6 shows representative stress-strain curves of epoxy samples reinforced with 1.5 wt % nanofillers. As shown from our previous studies, ANFs and CNCs were found to be beneficial for reinforcing epoxy nanocomposites due to their high aspect ratio and ...
Polymer nanocomposites have received attention for a wide range of applications over the past few decades due to their high mechanical properties. With the introduction of a relatively low weight fraction of nanofillers, polymer nanocomposites have shown superior properties to composites reinforced with macro- or micro-sized fillers. The properties and performance of polymer nanocomposites are affected by the morphology and dimensions of the nanofillers and the interfacial interactions between polymer matrices and nanofillers. Recently, aramid nanofibers (ANFs) have been obtained through the dissolution and deprotonation process of macroscale aramid fibers in a solution with dimethyl sulfoxide and potassium hydroxide. ANFs have shown great potential as a reinforcing filler for polymer nanocomposites due to their excellent mechanical properties, high aspect ratio, and large surface area. In addition to these unique characteristics, there are rich functionalities on the surface of ANFs that can be used to introduce surface modification agents or multifunctional nanomaterials on the ANFs. Therefore, the properties of polymer nanocomposites can be further increased through the introduction of functionalized ANFs that enhance their chemical and mechanical interaction. In this work, ANFs are modified using various silane coupling agents to reinforce rubber nanocomposites for tire tread and epoxy nanocomposites. The silane coupling agent treatment improves the dispersion of ANFs in polymer matrices and chemical interfacial interaction between the matrices and ANFs through covalent linkages between them. The functionalization of ANFs is investigated using characterization techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Rubber nanocomposites reinforced with functionalized ANFs exhibit improved mechanical properties and tire performance metrics, including an 11.3% increase in abrasion resistance and 14.7% improvement in fuel efficiency, without decreasing wet grip performance. As shown from the results of rubber nanocomposites, functionalized ANF reinforced epoxy nanocomposites also show enhanced tensile strength, elastic modulus, fracture toughness, and dynamic mechanical properties due to the improved interfacial interaction. In addition, this work also considers the hybridization of ANFs using other strong nanomaterials such as graphene oxides (GOs) and cellulose nanocrystals (CNCs) for the reinforcement of tire tread rubber nanocomposites and epoxy nanocomposites. The novel hybrid materials based on ANFs are expected to contribute to improved chemical and mechanical interaction within nanocomposites through the extensive branching and network structure of the hybrid fillers and covalent bonding between the polymer matrix and fillers. The hybrid filler reinforced rubber nanocomposites and epoxy nanocomposites exhibit a synergetic effect of nanofillers on increasing mechanical properties and performance compared to the nanocomposites reinforced with ANFs or GOs or CNCs alone. Especially, the ANF/GO hybrid filler reinforced rubber compounds show an 18.2% improvement in abrasion resistance and 21.8% improvement in rolling resistance. Thus, the research presented in this dissertation provides novel reinforcement methods to improve the overall performance of tire tread rubber nanocomposites, including abrasion resistance and fuel efficiency, which can help overcome energy and environmental challenges. In addition, thermosetting polymers using functionalized ANFs are expected to have an impact in the field of structural polymer composites with improved properties.
... Two-component cured EP resins have excellent postcure adhesion, mechanical strength, corrosion resistance, insulation and adhesiveness [1][2][3]. Therefore, they are widely used in various industrial areas, such as high-performance coatings, adhesives, electronics, architecture, composites, automobile, aviation, aerospace and other fields [4][5][6]. However, there still exist some problems in the practical application [7,8]. ...
... In formula (2), Ea was the activation energy, R was the gas constant and k 0 was the rate constant. Here a represents the degree of cure or extent of cure and was proportional to the reaction enthalpy. ...
An efficient and economical strategy for rapid microencapsulation of 1-butylimidazole (1-BMI) was developed. The strategy is based on the thiol-yne click reaction of trimethylolpropane tris(3-mercaptopropionate) and 1,7-octadiyne in oil-in-water emulsion. The thiol-yne click reaction is not only green and efficient, but also improves the cross-linking density of shell. Thus, the obtained shell prevents the leakage of curing agent and prolongs the storage period of EP/MCs system. The whole process of preparing 1BMI-MCs only took 40 min. Moreover, the effects of stirring speed and the ratio of 1BMI on the size and core content of microcapsules (MCs) were investigated. Results demonstrated that the optimal particle size was about 10.8 μm, and the maximum content of 1BMI in MCs was 33% corresponding to 60% 1BMI in oil phase. Afterward, the 1BMI MCs were used as latent curing agent (LCA) for epoxy resin (EP). In the curing reaction of the epoxy resin, the 1BMI-MCs exhibited a delayed kinetic behavior compared to pure 1BMI. Furthermore, the E-51/MCs system had a storage term of 16 weeks. The shell material not only had no effect on curing effect of E-51, but also toughen the cured EP systems. This paper provided a promising method for long-term storage of LCA.
... Fibres are known to have a relatively high aspect ratio (20-500) and are flexible. The impact of fibre/nano-fibres [79,82,84], nanotubes [85,86] and whiskers [87,88] on the efficiency of dental composites has been widely studied in literature and known to have enhanced mechanical properties. Nanotubes are slightly different from fibres as they too have a high aspect ratio but possess hollow centres giving them a tubular shape. ...
... The most used glass fibres in dentistry are E-glass and S-glass such in Vectris Pontic and FiberKor [79] (Fig. 4). S-glass is more expensive and has a shorter lifespan than E-glass, and it also has higher tensile strength (4700-4800 MPa) and elastic modulus (86-93 GPa) compared to E-glass of tensile strength (1950-2050 MPa) and elastic modulus (72)(73)(74)(75)(76)(77)(78)(79)(80)(81)(82)(83)(84)(85) [79,90,95]. ...
In restorative dentistry, dental composites have become a popular material of choice due to the increasing aesthetic demands and address challenges like recurrent cavities and restorative bulk fracture, which are the most common causes of dental composite failure. To address these issues, various types and shapes of reinforcement fillers were researched to enhance the mechanical properties of composite formulations over conventional composites. Furthermore, antibacterial agents and ion-releasing fillers are used to prevent secondary caries and promote the remineralisation of dental tissue. This review article aims to review the literature of dental resin composites, focusing on various filler categories and their impact on the materials' performance, to aid future development of dental resin composites for clinical applications with optimal properties that can overcome current limitations.
... 76,77 Such a distribution potentially prevents cracks and damage to the composites when subjected to external force, consequently enhancing the mechanical properties of the composites. 78 Based on the SEM analyses, it was determined that the HT synthesis method provided the most morphologically suitable grain structure and distribution for the target structure, when compared to the methods of CP, MW, and SS. Additionally, EDX results were showed that HA synthesis was achieved with a Ca/P ratio of approximately 1.67 in all experimental groups as it was stated in Table 1. ...
To investigate the reinforcing effect of nanoflower‐like hydroxyapatite (NFHA) in resin‐based dental composites, we synthesized a novel NFHA using microwave irradiation (MW), hydrothermal treatment (HT), and sonochemical synthesis (SS). Silanized NFHA was then used as the reinforcing filler in dental resin composites. We characterized the structure and morphology of various HA nanostructures using x‐ray diffraction, scanning electron microscope, and TEM. The mechanical performance of dental resin composites reinforced with silanized NFHA was measured using a universal testing machine. Spherical HA, synthesized through chemical precipitation (CP), served as the control group. One‐way analysis of variance was employed for the statistical analysis of the acquired data. The results demonstrate that the nanoflower morphology significantly was improved mechanical and physical properties. After conducting trials, the NFHA synthesized using MW and HT showed a substantial enhancement in mechanical and physical properties compared to the other structures. Therefore, it can be concluded that NFHA can serve as a novel reinforcing HA filler, providing regenerative properties to resin composites with sufficient mechanical strength.
... for TCP2, and 81% for TCP3, respectively. As illustrated in Fig. 3d, the load transfer efficiency of TiO 2 @CNTs is higher than most of other fibres [42][43][44][45][46][47][48]. Typically, the tensile strength of the TCP3 film reached up to 80 MPa, nearly 1.45 times that of PEF film. ...
Carbon nanotubes (CNTs) have been regarded as ideal functional fillers for enhancing superior mechanical properties of polymer composites. However, the performances of CNTs-based composites are well below the theoretical values, due to the poor dispersion of inert CNTs and weak interfacial interaction with the polymer matrix. Herein, “hydrothermal and in-situ growth” approach is induced to synthesize multiscale TiO2@CNTs functional fillers. Such the TiO2@CNTs show excellent dispersibility and strong interfacial bonding with matrix. The biobased TiO2@CNTs/poly(ethylene furandicarboxylate) (TCP) composite films are prepared via loading a small amount (0.05–0.2 wt%) of TiO2@CNTs. When the mass content of fillers is 0.2 wt%, TCP composite film exhibits the optimal of strength (80 MPa), Young's modulus (4.12 GPa), and toughness (1.2 MJ/m3). Moreover, the presence of TiO2 nanoparticles endow the films with excellent oxygen barrier and UV-shielding properties. We believe these composite films promise a spread application potential in high-performance food packing materials.
... Qian et al. [14] found that that by adding only 1 wt.% nanotubes to polyester resin resulted in increasing its elastic modulus from 35 to 42 %, while its polymer strength was increased by 25%. Zhu et al. [15] studied the stress-strain response of CNTs in epoxy resins and observed that addition of merely 1-4 wt.% CNTs yielded an increase of 30-70% in elastic properties. There are different classes of fillers that have been used for reinforcement purposes, namely nanofibers such as CNTs, layered silicates e.g. ...
Developing and designing engineering materials with desirable properties, such as high strength to weight ratio, formability, corrosion resistance and biocompatibility, among many other properties, is crucial, especially in modern engineering and material science industries. This is influenced by the demand for high-performing and more efficient materials in biomedical, aerospace, and automotive engineering, as well as in other engineering sectors where such materials are required. However, it is challenging to attain such materials, and this has raised the attention of numerous research studies in composite and nanocomposite materials. Composite materials are formed as the result of combining two or more distinct materials to yield advanced materials with properties that are entirely different from the original materials. This paper investigates the effects of reinforcing High-Density polyethylene (HDPE) with Multi-Walled Carbon Nanotubes (MWCNT) nanoparticles at weight fractions of 0, 0.5, 1, and 1.5 wt.%. In this paper, only the elastic properties of the HDPE were evaluated at these different weight fractions. The results show that a weight fraction of 1 wt.% of MWCNTs nanoparticles offered the best reinforcement for HDPE/MWCNT nanocomposites among the investigated weight fractions.
... The concentration of nanofillers in the samples was limited to 1.5 wt% due to the formation of micro voids in samples with a higher concentration of nanofillers even after the degassing procedure. The surface modification using GPTMS increased the viscosity of the epoxy mixture significantly during the mixing process [62]. The average Young's modulus and tensile strength of ANF, CNC, AC, and fAC reinforced epoxy nanocomposites are displayed in figures 5 and 6 shows stress versus strain curves of epoxy samples reinforced with 1.5 wt% nanofillers. ...
The mechanical properties of polymer nanocomposites can be improved by incorporating various types of nanofillers. The hybridization of nanofillers through covalent linkages between nanofillers with different dimensions and morphology can further increase the properties of nanocomposites. In this work, aramid nanofibers (ANFs) are modified using chlorinated cellulose nanocrystals (CNCs) and functionalized with 3-glycidoxypropyltrimethoxysilane to improve the chemical and mechanical interaction in an epoxy matrix. The integration of CNC functionalized ANFs (fACs) in the epoxy matrix simultaneously improves Young's modulus, tensile strength, fracture properties, and viscoelastic properties. The test results show that 1.5 wt % fAC reinforced epoxy nanocomposites improve Young's modulus and tensile strength by 15.1% and 10.1%, respectively, and also exhibit 2.5 times higher fracture toughness compared to the reference epoxy resin. Moreover, the glass transition temperature and storage modulus are found to increase when fACs are incorporated. Thus, this study demonstrates that the enhanced chemical and mechanical interaction by the CNC functionalization on the ANFs can further improve the static and dynamic mechanical properties of polymer nanocomposites.
... The non-covalent functionalization is just to put chemical molecules on CNT surface without forming covalent bonds. [38,39] For example, Zhu et al. [40] amino-functionalized CNT surfaces and increased the tensile strength of 1.0 wt% SWCNTs/epoxy composite by 25.3%. They further functionalized SWCNTs by carboxyl groups using H 2 SO 4 /HNO 3 acids and found that the tensile strength of 1.0 wt% SWCNTs/ epoxy composite increases by 14.2%. ...
Short single‐wall carbon nanotubes (SWCNTs)/epoxy composites were fabricated by a procedure of cutting and functionalizing SWCNTs, dispersion and curing, with a very low weight ratio of SWCNTs from 0.03% to 0.5%. It was found that the tensile fracture strength of composites increases with increasing SWCNT content initially, then reaches a maximum at 0.05 wt% and finally decreases with further increasing the SWCNT content. The fracture strength of the composite with 0.05 wt% SWCNTs (78.46 MPa) is ~160% of that of pure epoxy sample (48.64 MPa). A model analysis based on the competition of local matrix fracture and the debonding of short SWCNT was proposed. It revealed that there is a transition from local matrix fracture to the debonding of SWCNT when the SWCNT content increases, this transition leads to the decrease in the tensile strength. Further analyses indicated that the content of carbon nanotubes (CNTs) at the transition depends on their radius and length. Considering the effect of surface cracks on the fracture strength of pure epoxy sample, the theoretical analyses are qualitatively in agreement with the experimental results. The present study partly explains why the fracture strength of CNT reinforced composites has various results for a similar CNT loading in previous works. A schematic representation of the model cell of single‐wall carbon nanotubes (SWCNT) reinforced epoxy composites (A) and the forces suffered by SWCNT and matrix (B). A prediction dependence of fracture stress on the SWCNT content in the composites is given in (C).
... In light of this, it has been observed that some polymer/CNT nanocomposites have tensile strengths between 0.1 and 5 GPa and Young's moduli between 5 and 200 GPa [76]. Using CNTs as reinforcement generally improved the mechanical properties of some polymers, including epoxy [77][78][79][80], polystyrene (PS) [81], polyethylene [82,83], PMMA [84,85], poly (pphenylene benzobisoxazole) (PBO) [86], polyvinyl alcohol (PVA) [87], polyester elastomers (PEE) [88], polycarbonate (PC) [89], polyamide-6 [90], To prevent agglomerations or bundles that adversely influence the mechanical properties of PMNCs, typically when CNTs content exceeds 2-3%, the optimal CNT loading must be carefully examined [92]. The detrimental impact on the tensile strength of nanocomposite is specifically caused by the inadequate interfacial interaction between CNT and polyester [93,94,95,96,97]. ...
Due to the anisotropic, heterogeneous structure, and advanced mechanical properties of these materials combined with the size effects in micromachining, micromachining of nanocomposites is thought to be a challenging operation. In terms of high cutting force, poor surface quality, and rapid tool wear, it results in worse machinability. The first of these two parts of this review paper will provide a thorough overview of the mechanical characteristics of diverse nanocomposites, while the second part will concentrate on the micro-machinability of these nanocomposite materials.
... 50 We next compared the mechanical properties of CNTs@ANFs films with those of other CNTs/polymer composites consisting of randomly oriented CNTs. The present polymer matrices for CNT bulk composites include mostly thermoplastic (such as chlorinated polypropylene (CPP)) 51 and thermosetting (such as epoxy) 52 polymers. Remarkably, the reported mechanical properties for SWCNTs/epoxy and SWCNTs/CPP composites are far worse than those of CNTs@ANFs films, mostly because of the poor performance of polymer substrates. ...
Porous carbon nanotubes (CNTs) framework has long been considered as one promising candidate for supercapacitors, but its flexible applications have been restricted by the extremely low mechanical performance. More importantly, efficiently integrating the stack capacitance and mechanical stability has not yet been fully realized for CNTs-based supercapacitors. Herein, practically feasible CNTs-based electrode is designed by introducing aramid nanofibers (ANFs) film. A pre-constructed double-layer CNTs@ANFs architecture, the first example of loading intact CNTs porous coating on synthetic polymer substrate at mg cm-2 level, realizes impressive strengthening and toughing of CNTs framework (11.5- and 78.6-times improvement in strength and toughness, respectively). Benefiting from robust mechanical properties, double-layer film achieves compact capacitance delivery (118.6 F cm-3) by in situ tailoring surface chemistry of CNTs and subsequently coupling high-loading polyaniline (PANI) through electrochemical means. Furthermore, a flexible solid-state supercapacitor based on PANI@CNTs@ANFs film electrode delivers an ultrahigh volumetric capacitance of 9.4 F cm-3 with a stack energy density of 0.78 mWh cm-3. The prominent structure-function relationship validated in this work represents a substantial breakthrough for optimizing porous CNTs framework towards flexible and compact capacitive energy storage, which is of both fundamental and technical importance for the advanced structural energy and power systems.
... It owns good impact resistance, excellent heat and chemical resistance, high hardness and strength, high adhesive strength, and high electrical insulation. [4][5][6][7] Nanocomposites with platelet structure nanofillers such as graphene nanoplatelets (GNPs) and montmorillonite (MMT) nanoclay present a good modulus, strength, and barrier properties. Also, the graphene reinforced nanocomposites show excellent electrical and thermal properties. ...
The mechanical properties of nanocomposites are significantly affected by the dispersion of nanofillers. In this study, the synergetic effect of hybrid fillers, including surfacemodified montmorillonite (MMT) nanoclay and graphene nanoplatelets (GNPs) on the dispersion quality and mechanical characteristics of epoxy‐based nanocomposites was investigated. It was manifested that the incorporation of GNPs‐MMT hybrid into pure epoxy improves the dispersion of nanoplatelets and consequently, the tensile and flexural properties. The maximum tensile and flexural strength was obtained for the sample containing 0.15 wt% GNPs and 1 wt% MMT that was 19% and 17.4% higher than the neat epoxy, respectively. The experimental analyses were followed by Mori–Tanaka, Halpin–Tsai, and two‐parameter Weibull distribution methods to model the mechanical behavior of nanocomposites. The modeling and experimental results as well as the microscopic analysis revealed the variation of toughening mechanisms from micro to nano scale. Improved dispersion of graphene nanoplatelets/montmorillonite in epoxy and its effect on the mechanical properties of the nanocomposite.
... On the contrary, the reduction/modification of GO by TA and Ce 3+ increased the tensile properties of the epoxy composites, which might be ascribed to the better dispersion of the modified nanosheets. Grafting TA with highly concentrated hydroxyl groups on the GO sheets led to the physical/chemical interfacial interactions with the polymeric matrix, providing higher tensile properties and hence higher plasticity [72][73][74]. Moreover, the deposition of the Ce 3+ resulted in lower Young's modulus, tensile strength, and work of fraction compared to the TA-rGO-EP coating. ...
There has been an explosion of interest toward incorporating graphene-based nanomaterials for corrosion protective coatings. In this study, tannic acid (TA) was employed as a green reducing agent of graphene oxide (TA-rGO) to provide promising nanoplatforms with good dispersion in an epoxy matrix for enhanced mechanical and anti-corrosion properties. In addition, these nanoplatforms were doped with cerium cations ([email protected]) to improve active corrosion protection. The designed nanosheets were characterized by several techniques, including FT-IR, XRD, UV–visible, FE-SEM/EDS, TEM, TGA, and XPS. TA improved the thermal properties of graphene oxide significantly with only 40% weight loss up to 800 °C. Furthermore, EIS studies revealed that introducing [email protected] nanoplatforms into epoxy coating led to ∼71.5% improvement in active corrosion protection in a saline solution due to the smart release of Ce³⁺. In addition, [email protected] nanoplatforms presented excellent barrier properties without electrolyte diffusion after 10 weeks of immersion. In terms of mechanical properties, [email protected] and TA-rGO-EP nanocomposites showed higher cross-linking densities and tensile strengths than unfilled epoxy, originating from improvement in the level of dispersion and interaction of nanoplatforms with the polymer.
... Epoxy resin is the most popular and highly demanding commercial thermosetting polymer, which has been extensively used in various fields such as coatings, [134][135][136][137][138] adhesives, [139][140][141][142] and advanced composites [143][144][145][146][147][148] due to its unique chemical resistance, excellent adhesion, and mechanical properties. 149,150 However, petrochemical based epoxy resins are not environmentally benign. ...
Considering the limits of petrochemical availability and their toxicity, there has been rapid development and innovation in the field of alternatives for petrochemical adhesives. The carcinogenicity of formaldehyde has reduced the demand for formaldehyde-based wood adhesives, which has resulted in the development of adhesives based on renewable resources. This review article summarizes various works published on bio-derived adhesives focusing on tannin. Increasingly acknowledged renewability, sustainability, lower cost, and chemical modification opportunities make tannin a credible precursor for developing competent bio-based adhesives. Henceforth, the chemistry of tannin, its usefulness, possible chemical modification, and compatibility in an attempt to synthesize bio-based adhesives is also being highlighted and compared with its hydrocarbon-derived counterparts. In addition to this, categories of tannin, and techniques available for their extraction along with their pluses and misuses, have also been explained. Moreover, this review includes a detailed discussion on tannin as a raw material for preparing epoxy, polyurethane, polyethylenimine, and furfuryl-based adhesives. It is expected that by exploring further possibilities of chemical modification, tannin can be a potential candidate that can compete with the petrochemical-based adhesives, thereby paving the way for the advancement of bio-adhesives.
... Epoxy is readily available and inexpensive to create polymer composites. In addition, the thermal, electrical, and mechanical properties of an epoxy composite can be easily controlled by varying the mixing ratio or changing the materials [15][16][17]. Thus, we chose an epoxy of low mass density: Stycast 1266 A/B (Loctite) prepared by mixing a curing agent and resin at a volume ratio of 1:3. ...
A parametric array (PA) loudspeaker generates highly directional sound beams by exploiting the PA phenomenon. Before such loudspeakers were fabricated from stepped plate transducers, arrays of small ultrasonic radiators were employed. A stepped plate transducer generates broadband PA sound by exploiting the multi-resonance characteristics of its structure, even though it has only a single radiator. However, the design process is difficult because the plate must be thicker than the steps. In this study, we present a new method for fabrication of stepped plate PA loudspeakers (SPPALs); we employ a Langevin transducer, a circular aluminum plate, and composite polymer steps. The new stepped plate is fabricated by molding the composite steps on a flat plate. This is unlike the conventional stepped plate, in which both the plate and steps are made of the same metal. Using this method, although the radiation plate is thinner than the steps, such stepping is associated with minimal changes in the natural frequency and mode shape. Therefore, the SPPAL design process is simplified. We experimentally confirmed that the new stepped plate exhibited the desired bending mode. The SPPALs exhibited a maximum sound pressure of 61 dB at 2 m and a half-power beam width of < 5°; the sound was highly directional.
... Epoxy resin also has good water resistance and chemical resistance as well as the advantages of high elastic modulus, lightweight, high adhesion, and high strength. It can be prepared into composite materials with different functional properties by adding various filling materials [3,[6][7][8][9]. Therefore, epoxy resin is one of the best packaging materials for embedded ultrasonic transducers as "smart aggregates" in concrete structures [10][11][12][13][14]. ...
Aiming to improve the thermal properties of ultrasonic transducers used in concrete structure, a novel amino-functionalized multi-walled carbon nanotubes (MWCNTs) reinforced epoxy/cement composite was designed to prepare the packaging layer of ultrasonic transducers. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), thermal conductivity test, and thermal expansion test were conducted to investigate the effects of different amounts of amino-functionalized MWCNTs (amino-MWCNTs) on the thermal properties of the transducer packaging materials. The results showed that, the optimal thermal properties of the ternary composite are achieved when the amino-MWCNT content of epoxy matrix is 1.25 wt.%. Compared with the epoxy/cement binary composite, the thermal conductivity of the ternary composite with the optimal content of amino-MWCNTs at 25 °C increased by 116.3%, and the expansion ratio at 60 °C reduced by 51.6%. The improvement of thermal properties of the ternary composite is benefit from the homogeneous dispersion of amino-MWCNTs in the matrix. The addition of amino-MWCNTs in the transducer is proved to improve the thermal properties of the embedded transducer packaging layer in concrete structure under the action of alternate wetting and drying thermal cycles.
... They have the same strengthening and toughening mechanisms as fibrous fillers. Nanotubes vary in chemical composition, with the most widely studied being carbon nanotubes [79]. According to Zhang et al., silanized methacrylic groups on the surface of carbon nanotubes improved the flexural strength of the resin composite by 23%, from 115 to 142 MPa, albeit its appearance was un-aesthetically dark [80]. ...
Dental resin composites (DRCs) with diverse fillers added are widely-used restorative materials to repair tooth defects. The addition of fillers brings an improvement in the mechanical properties of DRCs. In the past decade, diverse fillers have emerged. However, the change of emerging fillers mainly focuses on the chemical composition, while the morphologic characteristics changes are often ignored. The fillers with new morphologies not only have the advantages of traditional fillers (particles, fibrous filler, etc.), but also endow some additional functional characteristics (stronger bonding ability to resin matrix, polymerization resistance, and wear resistance, drug release control ability, etc.). Moreover, some new morphologies are closely related to the improvement of traditional fillers, porous filler vs. glass particles, core-sheath fibrous vs. fibrous, etc. Some other new morphology fillers are combinations of traditional fillers, UHA vs. HA particles and fibrous, tetrapod-like whisker vs. whisker and fibrous filler, mesoporous silica vs. porous and silica particles. In this review, we give an overall description and a preliminary summary of the fillers, as well as our perspectives on the future direction of the development of novel fillers for next-generation DRCs.
... [4] The existence of this phenomenon may lead to premature failure of the interface so that it is difficult to achieve the desired enhancement effect. [5][6][7] To overcome this problem, many methods have been put forward to optimize the surface of carbon fiber with greater roughness or better surface activity, [8] such as sizing, [9,10] oxidation modification, [11][12][13] plasma treatment, [14] surface grafting, [15] and so on. Among these modification methods, electrodeposition is a simple, efficient, and easily controlled method. ...
Composites with high strength and toughness are the goals that people pursue. However, the strength and toughness of composites are generally contradictory, and the performances of carbon fibers (CFs) reinforced composites mainly depend on the interfacial bonding strength between fibers and matrix. By observing the skein, we designed a coating similar to the skein on the CF surface, so that the matrix could penetrate into the cavities of the “skein” to improve the interface bonding strength of the composites. In this work, the skein‐like silver coating was obtained on the CF surface by electrodeposition method, and the rigid polyurethane (RPU) matrix composites were prepared to evaluate the properties of materials. Compared with pure RPU, the strength and toughness of skein‐like Ag‐CFs/RPU composites were significantly improved by 87.1 % and 70.2 %, respectively. The satisfactory results were due to the skein‐like silver coating on the fiber surface. The skein structure made the interface between the matrix and the fibers stronger through penetration, and it could also play a pinning role and increase the crack propagation path. The silver coating also gave the composites better electromagnetic properties, which reflected the conductivity and electromagnetic interference shielding performances were 2.4×10⁻⁵ S/M and 59.83 dB, respectively.
A novel generation of composite sandwich beams with laminated carbon fiber-reinforced polymer skins and pultruded glass fiber-reinforced polymer core materials was examined for their flexural behavior. The strength and failure mechanisms of the composite sandwich beams in flatwise and edgewise configurations were investigated using three-point static bending tests. These sophisticated composite structures must be designed and used in a variety of sectors, and our research provides vital insights into their performance and failure patterns. In comparison to the reference specimens (FGM-1), the carbon nanotube-reinforced specimens' bending capacity was affected and ranged from −2.5% to 7.75%. The amount of the carbon nanotube addition had a substantial impact on the beams' application level and load-carrying capacity. Particularly, the application of 0.5 wt% additive in the outermost fiber region of the beams, such as in FGM-4, led to an increase in the bending capacity. However, the stiffness values at the maximum load were decreased by 0.3%-18.6% compared to FGM-1, with the minimum level of the decrease in FGM-4. The experimental results were compared with the theoretical calculations based on the high-order shear deformation theory, which yielded an approximation between 11.99% and 12.98% by applying the Navier's solution. KEYWORDS composite sandwich beam, carbon nanotube, glass fiber-reinforced polymer, carbon fiber-reinforced polymer, flexural behavior, strength, bending capacity, stiffness
In this work, this study aimed to overcome the inherent disadvantage of low thermal stability and brittleness of epoxy resins. A novel modifiers containing alkynyl‐ and allyla‐ groups, (E)‐1‐(4‐(allyloxy)‐3‐methoxyphenyl)‐N‐(3‐ethynylphenyl)methanimine (MNEM) was prepared and confirmed by Fourier transform infrared spectroscopy (FTIR) and ¹ H‐nuclear magnetic resonance ( ¹ H NMR), and selected to improve the thermal stability and toughness of bisphenol A‐type epoxy resin (E51). The blend resins were produced by blending with different contents of MNEM into E51 resin, named E‐MNEM resins. Meanwhile, the thermal stability, mechanical properties, and micromorphology of E‐MNEM blends were analyzed in details. It was found that the thermal stability of E‐MNEM resins was improved by increasing the proportion of MNEM. Compared with E‐0MNEM resin, when the MNEM concentration reached 40 wt%, the char yield ( Y c ) increased from 14.95 to 29.62%, reflecting a 98.1% improvement. In addition, an appropriate concentration of MNEM could be conductive to improving the mechanical properties. An improvement of 25.5 and 7.1% in elongation and tensile strength along with the maximum value of 17.6 kJ/m ² for the impact strength was achieved by the cured E‐MNEM resins containing 20 wt% of MNEM. Finally, the fracture surface morphology of the E‐MNEM resins was analyzed by the scanning electron microscope (SEM).
In the development of National Aeronautics and Space Administration (NASA)'s Unmanned Aerial Vehicles (UAVs), lightweight and durable materials play a crucial role for extended high‐altitude flights. Nanoparticle‐reinforced polymer composites meet these requirements, exhibiting resistance to environmental degradation. Despite their potential, the outstanding specific strength, corrosion resistance, and dimensional stability at elevated temperatures of graphene–epoxy nanocomposites have not been fully realized due to inadequate dispersion and spatial orientation within epoxy matrices. Our recent research has introduced a mathematical framework aimed at optimizing alignment parameters for graphene nanoplatelets (GNPs) and Fe 3 O 4 ‐attached GNP under a weak DC magnetic field. Subsequently, nanocomposites reinforced with GNP and aligned Fe 3 O 4 –GNP nanoparticles were fabricated using optimized parameters, and their alignment was characterized using various techniques. The current study examines the influence and comparative impact of alignment and weight percentage (wt%) loading of both nanoparticles on various mechanical properties, including tensile and compressive strength, along with failure mechanisms. It was observed that both GNP and aligned Fe 3 O 4 –GNP enhance the mechanical properties of nanocomposites, particularly notable improvements from aligned Fe 3 O 4 –GNP. The Young's modulus of GNP nanocomposites increased by 17%, while aligned Fe 3 O 4 –GNP contributed significantly to a 31% enhancement in the Young modulus.
Highlights
Epoxy nanocomposites featuring well‐dispersed GNP and Fe 3 O 4 –GNP nanoparticles.
Proper alignment of Fe 3 O 4 –GNP within the epoxy nanocomposite was achieved.
Mechanical properties improved with GNP and aligned Fe 3 O 4 –GNP incorporation.
The aligned Fe 3 O 4 –GNP exhibits advanced potential for engineering applications.
The chemically functionalized carbon nanotubes (f-CNTs) and hydrogen bonding modified polymer composites (CPCs) exhibit unique chemical, mechanical, electrical, and thermal properties and are emerging as promising materials to achieve extraordinarily high electrical and thermal conductivity, lightweight and anticorrosion, superior strength and stiffness for potential applications in the aerospace and automotive industries, energy conversion, and optical and electronic devices, therefore, attracting considerable research efforts over the past decade. In this review, the fundamentals of the topics on f-CNTs, hydrogen bonding, and CNT directional alignment have been briefly introduced. The research on the electrical, thermal, and mechanical properties have been reviewed. The effects of the CNT morphology, hydrogen bonding, CNT alignment and aspect ratio, and the interactions between the constitutes on the CPC performance is critical to understand the fundamentals and challenges of designing such materials with desired properties and their potential applications. However, to gain a comprehensive and quantitative understanding of the effects of these factors on the performance of CPCs, further studies by computer modeling, especially MD simulations, will be highly needed for effective new/novel material design and development.
</strong
Covalent modification of multiwalled carbon nanotubes (MWCNTs) is an efficient way to improve the interfacial interaction and compatibility between MWCNTs and the matrix. In this article, MWNCTs were covalently modified by 4,4′‐difluorobenzophenone (DB) to allow temperature‐tolerant functional groups on the walls. These surface‐functionalized MWCNTs (MWCNTs‐DB) were then attached to poly(ether ether ketone) (PEEK) resins by in situ grafting polymerization, to prepare high‐strength PEEK nanocomposites. The addition of 1 wt% MWCNTs‐DB improved the tensile and flexural strength of the PEEK nanocomposite by 28% and 22%, respectively, compared with pristine PEEK. In particular, the optimal break at strain of the PEEK nanocomposites reaches 39%. The glass transition temperature of the PEEK nanocomposites increased from 148 to 153°C, indicating strong interfacial interactions between MWNCTs and PEEK. Furthermore, scanning electron microscopy images confirmed the amelioration of MWNCTs dispersion in PEEK resins achieved by in situ grafting polymerization. Our results demonstrate the potential of surface‐functionalized carbon nanotubes for use in high‐temperature applications and offer innovative protocols for designing and preparing high‐performance nanocomposites with enhanced mechanical properties, which could have applications in various fields such as aerospace, automotive, and biomedical engineering.
A carbon nanotube (CNT)/epoxy nanocomposite was prepared using a photochemical surface modification process of CNTs. The vacuum ultraviolet (VUV)-excimer lamp treatment created reactive sites on the CNT surface. Increasing the irradiation time increased the oxygen functional groups and changed the oxygen bonding state such as C=O, C-O, and -COOH. By the VUV-excimer irradiation on CNTs, the epoxy infiltrated well between the CNT bundles and formed a strong chemical bond between CNT and epoxy. The tensile strength and elastic modulus of the nanocomposites with VUV-excimer irradiated sample during 30 min (R30) were found to increase by 30 and 68% compared to using pristine CNT, respectively. R30 was not pulled out and remained embedded in the matrix until the fracture occurred. The VUV-excimer irradiation is an effective surface modification and functionalization method for improving the mechanical properties of CNT nanocomposite materials.
Epoxy resins were the most widely used adhesives. Nevertheless, the high dielectric constant (Dk) and dielectric loss (Df) dramatically limited their application in the fifth-generation (5G) technologies. Herein, eugenol epoxy...
Delamination still remains one of the common concerns in continuous fibers reinforced polymer composites. In the literature, the incorporation of nanoconstituents into constitutive composites plies has been suggested with the aim of improving interface toughness. In this study, vertically aligned carbon nanotubes forests (VACNTs) are transferred at composites interfaces, and mode I (DCB tests) and mode II (ENF tests) fracture tests carried out on composite samples. Microscopic analysis of reference and nano-engineered composites help to understand fracture behavior and toughness. While the crack path in ENF samples is observed at interlaminar VACNTs-resin interfaces, the crack path in DCB samples is intralaminar, located within the unidirectional carbon fiber plies. These microscopic observations give explanation for unstable crack propagation in nano-engineered ENF samples and the unchanged toughness from the nano-engineered to the reference zone in DCB samples.
The incorporation of vertically aligned carbon nanotubes (VACNTs) between composites plies has been said to enhance the through-thickness strength, and it can also decrease the risk of interply delamination and reduce crack initiation. Thanks to these high mechanical performances, nano-engineered hybrid composites are seen as promising for highly demanding structural reinforcement applications. This paper is part of a study that focuses specifically on the methodology for transferring VACNTs onto a prepreg surface while maintaining their initial vertically aligned morphology. The chosen method involved bonding the VACNTs’ forest through capillary impregnation of the forest by the prepreg’s resin. Key parameters for an effective transfer and to achieve a partial capillary rise of the resin into the VACNTs will be discussed here.
The aim of this article was to investigate the effect of carbon nanotubes (CNTs) on the buckling behavior of fiber-reinforced polymer (FRP) composites. The materials used included three layers: carbon-fiber-reinforced polymer (CFRP), epoxy and CNTs. A set of mechanical tests, such as compression and buckling tests, was performed, and also analytical solutions were developed. Damage analysis was also carried out by controlling the damage initiation and crack progression on the composite samples. Experimental results revealed that using 0.3% with CNT additives enhanced the buckling performance of the composite. Finally, the average load-carrying capacity for the clamped–clamped boundary condition was 268% higher in the CNT samples and 282% higher in the NEAT samples compared to the simple–simple condition.
The characteristics of the debonding process zone involving macroscale, microscale, and nanoscale mechanisms along CNT interface influence the fracture behavior of nanocomposites and their structural integrity. In current article, a multi‐scale and multi‐mechanism modeling approach with a cylindrical RVE comprising CNT, interphase, and matrix is developed to assess such damage progression and energy dissipation occurring at the nanoscale. The model considers the dominant damaging phenomena emerging in CNT/epoxy nanocomposites, that is, CNT debonding with an interphase zone around nanoparticles, cavitation, and plastic deformation of nanovoids. Enhancement of fracture toughness with the weight fraction of CNT is investigated with a qualitative variation of geometric and mechanical properties of the interphase, cavitation, and plastic yielding adopting strain energy release rate procedures. The fracture energy is shown to be critically influenced by the stiffness ratio of interphase to the matrix, interphase thickness, and hardening exponent. The model is validated using experimental and analytical data. The model has harmonized the relevance of the macro‐, micro‐, and nanoscale. The multi‐scale and multi‐mechanism models have evaluated the zone shielding fracture. Dominant mechanisms, that is, CNT debonding, cavitation, and plastic yielding are studied. The interphase modulus, thickness, and hardening exponent, all impact fracture toughening.
In this work, a fluorine-containing diene compound (TFBAM) derived from vanillin was synthesized for modifying epoxy resin (E51). The chemical structure of TFBAM was confirmed by Fourier transform infrared (FTIR) and Nuclear magnetic resonance ( ¹ HNMR) spectroscopies. The modified resins (E-TFBAM) were successfully prepared through the introduction of TFBAM into E51, and the consequences of TFBAM dosages on the curing behavior, thermal, mechanical and dielectric properties of E-TFBAM resins were dissected in details. The results revealed that an appropriate concentration of TFBAM could be conductive to improving the thermal stability and dielectric properties of E-TFBAM thermosets without damaging the mechanical properties. The dielectric permittivity and loss of 2.82-2.71 and 0.024-0.015 were obtained when the addition of TFBAM was 30 wt%, with 10–10.2% and 36.8–44.4% of reduction. Additionally, the impact strengths and elongation at break of E-30 TFBAM resin increase to 18.0 kJ/m ² and 4.7%, respectively. Overall, this research can be seen as essential for expanding the application of the epoxy resins in high-end fields.
This chapter sheds light on the pros and cons of the implication of carbonaceous
nanofillers in the context of aerospace. Carbonaceous nanoparticles such as carbon
nanotube, graphene, nanodiamond, fullerene, carbon black, etc. have opened new
stimulating research capacities in space nanoscience and nanotechnology.
Carbonaceous nanofillers possess unique intrinsic structural, mechanical, thermal,
electrical, optical, and other meritorious properties, useful for multifunctional space
architectures. Even very low nanofiller contents have been found effective in
improving the matrix characteristics using various processing strategies. Although
these nanoparticles have been found extremely promising in aerospace arenas, the
application of the nanofillers have been limited because of dispersion and compatibility concerns. In this regard, the functionalization of carbonaceous nanofiller has been considered important to improve the dispersion and compatibility with the polymers. Consequently, this chapter focuses on the vital facets of the important types of nanocarbons, nanofiller modification, and the distribution tendencies in the matrices.
Epoxy resins are well-known adhesive materials, however, the high dielectric constant (Dk) limited their application in microelectronic devices. Additionally, non-degradability is a bottleneck for all thermosetting resins, and the discarded resins posed the great threat to environment. Herein, a bio-based eugenol epoxy was grafted onto the polymethylhydrosiloxane (PMHS-x) main chain via a hydrosilylation reaction to simultaneously lower the Dk and enable degradability. The curing kinetics of bio-based silicone/epoxy hybrid resins with methyl hexahydrophthalic anhydride (MHHPA) or 4,4′-diaminodiphenylmethane (DDM) were studied. The cured resins exhibited low Dk and hydrophobicity by taking advantage of the low polarity, large molecular volume and high dissociation energy of the siloxane segments. The polysiloxane degradation process took place under alkaline conditions, allowing the retrieval of reinforced fibers from the composites. To better illustrate the superiority of the bio-based silicone/epoxy hybrid resins, quartz fiber reinforced composites were prepared. Compared to the commercial epoxy based composite, the impact strength of the PMHS-x with a silicon hydrogen content of 0.8 × 10⁻² mol·g⁻¹ was increased by 26.5 %, meanwhile, the Dk was decreased by 16.7 %. The bio-based silicone/epoxy hybrid resins not only alleviated the environmental pollution but also provided a reliable approach for fiber recycling from epoxy composites. The low polarity and degradability were integrated into bio-based silicone/epoxy hybrid resins, which provided a novel way to prepare environment-friendly materials suitable for microelectronic devices.
A simple and effective method based on in situ infrared spectroscopy and two-dimensional (2D) correlation analysis was applied to research the chemical changes and curing reaction mechanism of epoxy resin and amine curing agents. It is generally agreed that the epoxy groups in epoxy resin react with amino groups to form new C–N and hydroxyl groups during the curing reaction process. However, detailed information about the curing reaction mechanism of epoxy resin and amine curing agents has rarely been reported. In this work, the curing reaction mechanism can be deeply understood from the results of 2D correlation analysis. Due to the nucleophilic addition reaction of amino and epoxy groups, the nitrogen atoms of primary amines easily combine with the carbon atoms in epoxy groups, which forms new C–N groups. Then, the C–O bonds in epoxy groups break; finally, as the N–H bonds in primary amines break, the hydrogen atoms combine with the oxygen atoms to form new hydroxyl groups. In situ infrared spectroscopy and two-dimensional (2D) correlation analysis was applied to research the chemical changes and curing reaction mechanism of epoxy resin and amine curing agents. The curing reaction mechanism can be deeply understood from the results. Due to the nucleophilic addition reaction of amino and epoxy groups, the nitrogen atoms easily combine with the carbon atoms, which forms new C-N groups. Then, the C-O bonds break; finally, as the N-H bonds in primary amines break, the hydrogen atoms combine with the oxygen atoms to form new hydroxyl groups.
Polyhedral oligomeric silsesquioxane (POSS) is an ideal nano particle for epoxy polymer to reduce dielectric constant and enhance mechanical properties due to its hollow cage type organic silicon. However, the poor compatibility between POSS and epoxy resin has always been the key factor limiting the amount of addition and the improvement of performance. Herein, a modified epoxy (EGP) with POSS dangling chain is designed, that is, mercaptopropyl isobutyl POSS (POSS-SH) is grafted to diglycidyl ether of 4,4’-diallyl bisphenol-A (DADGEBA) backbone via ‘thiol-ene’ click reaction. Compared with the reported researches, thiol-ene click chemistry shows efficient and controllable, which makes the grafting efficiency of POSS-SH close to 100%. Covalent bond linking between POSS and DADGEBA constrains the aggregation and phase separation of POSS, and the content of used POSS is up to 50%. As expected, the obtained polymer (EGP-x-DDM) cured by 4,4’-diaminodiphenylmethane (DDM) presents low dielectric constant and dielectric loss, as well as tensile strength and tensile modulus are enhanced by 22.9% and 31.6%, respectively. The novel epoxy resin EGP has potential application in the electronic and electrical field.
Recent studies have extensively studied the use of composites of carbon nanotubes (CNTs) dispersed in epoxy resin to mechanically reinforce hydrogen storage and lightweight vehicle applications. The mechanical properties of the composite are strengthened due to load transfer from the epoxy matrix to the CNTs when an external force is generated. However, there is a limit to the level of reinforcement that can be achieved by simply dispersing CNTs in the epoxy polymer. In this study, a composite was prepared by dispersing functionalized CNTs with carboxyl groups, which formed covalent bonds with the epoxy resin (EPON 862). The covalent bonding improved the load transfer from the epoxy resin to the CNTs, which increased the Young’s modulus and ultimate tensile strength of the composite. In addition, the interfacial interaction and adhesion between the matrix and the filler were improved by the covalent bonding, thereby improving the degree of dispersion. The changes in elastic modulus and ultimate tensile strength according to the nanofiller content and the presence of the functional groups in the MWCNT were observed, and exhibited consistent values.
This chapter deals with nanoreinforced thermoset resins. Use of various types of nanofillers namely layered silicate, carbon nanotube, graphene, polyhedral oligomeric silsesquioxanes, silver nanoparticle, block copolymers for preparing thermoset nanocomposite are presented. The concept of simultaneous toughening and reinforcement is also covered. The mechanism of toughening of thermoset matrix using nanomaterials is elaborated. A brief review of recent advances in the field of polymer nanocomposite is presented. The research activities on addressing the issues of dispersion of nanoparticles and interfacial bonding are reviewed critically.
Polymer nanocomposites based on high melting tem.perature semi-crystalline polymers are difficult to prepare because of the limited means available to achieve good nanoparticle dispersion for greatly improved properties. In this study, we demonstrate an alternative strategy for preparation of high-performance PEEK/MWCNT nanocomposites via an interfacial crystallization approach. The utilization of polyetheretherketimine (PEEKt) to prepare PEEK nanocomposites eliminates the difficult solvent issues and enables solution mixing and subsequent crystallization of PEEK on MWCNTs. This strategy facilitates a homogeneous dispersion of pristine MWCNTs into the PEEK matrix without any need of surfactant or compatibilizer. Upon drying, the PEEK/MWCNT powder were then molded into various dimensions for mechanical property measurements. As expected, significant improvements are realized. The PEEK/MWCNT nanocomposites that exhibit good dispersion of MWCNT in PEEK are ideal for applications in energy production field, electrochemical devices, and coatings under harsh conditions.
With contemporary advances in nanotechnology, thermoset nanocomposites present numerous advantages compared to conventional macrocomposite materials. Moreover, with the commercialization of nanomaterials such as nanoclays (NCs), carbon nanotubes (CNTs), nanosilica (NS), polyhedral-oligomeric-sil-sesquioxanes (POSS), tungsten-disulfide (WS2) fullerenes and tubes, and graphene (Gr), new potential routes have been opened to tailor thermosetting polymers in the nanoscale range. Due to the large surface area of the nanosize particles only small amounts are needed to cause significant changes in the mechanical, physical and thermal properties of polymer nanocomposites. When the surface area of the nanoparticles is modified, additional dimension for formulation of structural adhesives, composite matrices and other thermosetting polymers arise, for a variety of applications. The formulation sequence and conditions in addition to its composition were found to govern the structure and properties of the resulting nanocomposites.
This chapter will review and analyze the various thermoset nanocomposites containing: NCs, CNTs, NS, POSS, WS2, and Gr.
Manganese dioxide nanoflowers (MnO2-F) and nanowires (MnO2-W) are synthesized and MnO2 nanostructures reinforced (0.1 wt.%) epoxy composites are fabricated. The reinforcing effects are studied through tensile, flexural, and impact tests. SEM, TEM, EDAX, XRD, and FTIR characterization techniques are used to understand the interaction between epoxy and the MnO2 nanofiller. It is observed that MnO2 nanostructures have greatly enhanced the mechanical properties of epoxy composites. The tensile strength of EP/MnO2-F composites has improved by 73%, percentage elongation increased for EP/MnO2-F composites by 173%, and flexural strength of EP/MnO2-W has improved by 15%, respectively. Impact strength increased by 35% for EP/MnO2-F nanocomposites.
Well-aligned bundles of single-wall carbon nanotubes under tensile stresses were observed to fracture in real-time by transmission electron microscopy. The expansion of elliptical holes in the polymer matrix results in a tensile force in bridging nanotubes. The polymer matrix at both ends of the bundles deforms extensively under the tension force, and fracture of the nanotubes occurs in tension within the polymer hole region rather than in shear within the gripping polymer region at the ends of the bundles. This provides evidence of significant polymer-nanotube wetting and interfacial adhesion.
Single-wall fullerene nanotubes were converted from nearly endless, highly tangled ropes into short, open-ended pipes that
behave as individual macromolecules. Raw nanotube material was purified in large batches, and the ropes were cut into 100-
to 300-nanometer lengths. The resulting pieces formed a stable colloidal suspension in water with the help of surfactants.
These suspensions permit a variety of manipulations, such as sorting by length, derivatization, and tethering to gold surfaces.
Multiwall carbon nanotubes have been dispersed homogeneously throughout polystyrene matrices by a simple solution-evaporation method without destroying the integrity of the nanotubes. Tensile tests on composite films show that 1 wt % nanotube additions result in 36%-42% and ~25% increases in elastic modulus and break stress, respectively, indicating significant load transfer across the nanotube-matrix interface. In situ transmission electron microscopy studies provided information regarding composite deformation mechanisms and interfacial bonding between the multiwall nanotubes and polymer matrix.
Single-wall fullerene nanotubes have been made soluble in various organic solvents, including chloroform, methylene chloride, and tetrahydrofuran by covalently attaching alkanes to their sidewalls. Sidewall-alkylated nanotubes are obtained by reacting sidewall-fluorinated nanotubes with alkyl magnesium bromides in a Grignard synthesis or by reaction with alkyllithium precursors. Covalent attachment to the sidewalls was confirmed by UV–visible spectroscopy, which is also used to show that the alkane sidewall groups can be removed by oxidizing them in air to recover pristine nanotubes.
We show that composites with improved uniformity and dispersion can be formed using chemically functionalized carbon nanotubes. A significant enhancement of the mechanical properties was obtained at low nanotube loading. In contrary to previous results from pristine nanotubes, the composites show efficient load transfer between the fillers and matrix.
The mechanical behavior of multiwalled carbon nanotube/epoxy composites was studied in both tension and compression. It was found that the compression modulus is higher than the tensile modulus, indicating that load transfer to the nanotubes in the composite is much higher in compression. In addition, it was found that the Raman peak position, indicating the strain in the carbon bonds under loading, shifts significantly under compression but not in tension. It is proposed that during load transfer to multiwalled nanotubes, only the outer layers are stressed in tension whereas all the layers respond in compression. © 1998 American Institute of Physics.
20 mm long ropes consisting of soundly aligned single-walled carbon nanotube (SWNT) ropes, synthesized by the catalytic decomposition of hydrocarbons, were employed for direct tensile strength measurements. The average tensile strength of SWNT rope composites is as high as 3.6±0.4 GPa, similar to that of carbon fibers. The tensile strength of SWNT bundles was extrapolated from the strength of the composites to be 2.3±0.2 to 14.2±1.4 GPa after simply taking into account the volume fraction of SWNT bundles in the minicomposite, and the tensile strength of single SWNTs was estimated to be as high as 22.2±2.2 GPa. The excellent mechanical properties of SWNTs will make them an ideal reinforcement agent for high performance composite materials. © 2000 American Institute of Physics.
Considerable improvement in the dispersion of purified single-walled carbon nanotubes (SWNTs) in an epoxy composite was obtained through functionalization of the SWNTs by using an optimized H2SO4/70% HNO3 acid treatment and subsequent fluorination. Epoxy composites containing 1 wt % nanotubes were processed by dissolving the functionalized SWNTs in dimethylformamide and mixing with the epoxy resin thereafter. The functionalized nanotubes were observed to be highly dispersed and well integrated in the epoxy composites. The enhancement of mechanical properties of the latter was indicated by a 30% increase in modulus and 18% increase in tensile strength. This work demonstrates the practical use of combining acid treatment and fluorination to achieve functionalization and unroping of SWNTs. The functionalized SWNTs can be integrated into epoxy composites through the formation of strong covalent bonds in the course of epoxy ring-opening esterification and curing chemical reactions.
The influence of chemical cross-links between a single-walled fullerene nanotube and a polymer matrix on the matrix−nanotube shear strength has been studied using molecular dynamics simulations. A (10,10) nanotube embedded in either a crystalline or amorphous polyethylene matrix is used as a model for a nonbonded interface (in the absence of cross-links). The simulations predict that shear strengths and critical lengths required for load transfer can be enhanced and decreased, respectively, by over an order of magnitude with the formation of cross-links involving less than 1% of the nanotube carbon atoms. At this level of chemical functionalization, calculations also predict that there is a negligible change in tensile modulus for a (10,10) nanotube.
Multiple-walled carbon nanotubes (MWNTs) produced using the chemical vapor deposition method were functionalized via attaching aminopolymer poly(propionylethylenimine-co-ethylenimine) to the nanotubes. Two different reaction conditions based on acylating the nanotube-bound carboxylic acids and on directly heating nanotubes in the polymer melt were used and compared. Both methods were effective in the nanotube functionalization, and the polymer-attached MWNTs were found to be soluble in many common organic solvents and in water. Results from the characterization of the functionalized nanotube samples using electron microscopy, optical spectroscopy, NMR, and thermal analysis techniques are presented and discussed.
Interfacial interaction is one of the most critical issues in carbon nanotube/polymer composites. In this paper the role of nonionic surfactant is investigated. With the surfactant as the processing aid, the addition of only 1 wt % carbon nanotubes in the composite increases the glass transition temperature from 63 °C to 88 °C. The elastic modulus is also increased by more than 30%. In contrast, the addition of carbon nanotubes without the surfactant only has moderate effects on the glass transition temperature and on the mechanical properties. This work points to the pathways to improve dispersion and to modify interfacial bonding in carbon nanotube/polymer composites.
The ability to modify the surface of carbon nanotubes is of crucial importance for their utilization in different applications. In the present paper we report on the chemical modification of multiwalled carbon nanotubes (MWNT) by means of epoxide-based functional groups. MWNT were first carboxylated along their walls. This was followed by further reactions to attach di-glycidyl ether of bisphenol-A-based epoxide resin. The behavior of the modified nanotubes in various solvents was altered due to the chemical changes, and analytical techniques were utilized to detect the chemical attachments. The implications of the surface modification achieved are discussed primarily in terms of nanotube−polymer composite applications.
The local elasticity of individual single-walled carbon nanotube (SWNT) bundles and the load transfer in epoxy composites containing SWNTs and carbonaceous soot material formed during nanotube synthesis were studied. The composites were loaded to failure, axially in tension and compression, after which the fracture surface was examined. Micro-Raman spectra and scanning electron micrographs revealed that it is the low-modulus features of the bundles, and not the axial modulus of individual tubes, that control the mechanical stability and strength of the composite. Nanotube reinforcement increases the toughness of the composite by absorbing energy because of their highly flexible elastic behavior during loading.
Highly purified single-wall carbon nanotubes (SWNTs) were fluorinated to form "fluorotubes", which were then solvated as individual tubes in various alcohol solvents via ultrasonication. The solvation of individual fluorotubes was verified by dispersing the tubes on a mica substrate and examining them with atomic force microscopy (AFM). Elemental analysis of the tubes reveals that light sonication in alcohol solvents does not remove significant amounts of the fluorine. While these solutions are metastable, they will persist long enough (over a week) to permit solution-phase chemistry to be carried out on the fluorotubes. For example, the solvated fluorotubes can be precipitated out of solution with hydrazine to yield normal, unfluorinated SWNTs, or they can be reacted with sodium methoxide to yield what are apparently methoxylated SWNTs. These reaction products have been examined with elemental analysis and a variety of spectroscopies and microscopies.
Single wall carbon nanotubes (SWNTs) and vapor grown carbon fibers (VGCFs) were compounded with poly(acrylonitrile-co-butadiene-co-styrene) (ABS) to create composite materials for use with Extrusion Freeform Fabrication (EFF). The composite materials possessed homogeneously dispersed fibers that were oriented with EFF processing. The VGCF and SWNT reinforced materials processed by EFF displayed improved tensile modulus compared to similarly processed ABS and composite material with isotropic fiber orientation, and the SWNT reinforced material displayed the highest properties, strength and modulus, of the materials studied. The materials containing oriented VGCFs and SWNTs showed modulus improvements of 44 and 93%, respectively.
Multi-walled carbon nanotube/epoxy resin composites have been fabricated. By choosing an over-aged hardener, relatively soft and ductile matrix, a rubbery epoxy resin, has been obtained. This made possible to evaluate the effect of nanotube addition on the whole stress-strain curve up to high strain level. The mechanical and electrical properties of the composite with different weight percentages of nanotubes have been investigated. The Young's modulus and the yield strength have been doubled and quadrupled for composites with respectively 1 and 4 wt.% nanotubes, compared to the pure resin matrix samples. Conductivity measurements on the composite samples showed that the insulator-to-conductor transition took place for nanotube concentration between 0.5% and 1 wt.%.
Since their first observation nearly a decade ago by Iijima (Iijima S. Helical microtubules of graphitic carbon Nature. 1991; 354:56–8), carbon nanotubes have been the focus of considerable research. Numerous investigators have since reported remarkable physical and mechanical properties for this new form of carbon. From unique electronic properties and a thermal conductivity higher than diamond to mechanical properties where the stiffness, strength and resilience exceeds any current material, carbon nanotubes offer tremendous opportunities for the development of fundamentally new material systems. In particular, the exceptional mechanical properties of carbon nanotubes, combined with their low density, offer scope for the development of nanotube-reinforced composite materials. The potential for nanocomposites reinforced with carbon tubes having extraordinary specific stiffness and strength represent tremendous opportunity for application in the 21st century. This paper provides a concise review of recent advances in carbon nanotubes and their composites. We examine the research work reported in the literature on the structure and processing of carbon nanotubes, as well as characterization and property modeling of carbon nanotubes and their composites.
Carbon nanotubes (CNTs) can be used to compound poly (methyl methacrylate)/carbon nanotube (PMMA/CNT) composites by an in situ process. The experimental results show that CNTs can be initiated by AIBN to open their π-bonds, which imply that CNTs may participate in PMMA polymerization and form a strong combining interface between the CNTs and the PMMA matrix. Through the use of an improved in situ process, the mechanical properties and the heat deflection temperatures of composites rise with the increase of CNTs. The dispersion ratio of CNTs in the PMMA matrix is proportional to the reaction time of polymerizing MMA before CNTs are added into the PMMA mixture.
Nanophase materials — metals or ceramics with very small grain sizes — have been fairly disappointing. It was thought that small grains should result in much harder metals. It turns out that they are harder but also more brittle. We also hoped that ceramics with very small grains would be much stronger but that hasn't really been demonstrated yet. Yet there is still reason to expect that nanometre-scale composite materials might turn out to be better than conventional composites, such as the carbon fibre-epoxy composites used in high-performance aircraft. For example, we could use nanometre-sized fibres to strengthen a polymer matrix, and carbon nanotubes are now available in sufficient quantities to test this idea. When researchers met at a conference in Alaska, to discuss the challenge of making nanocomposites, it became clear that inputs from several fields will be needed to make it work.
Naked metallic and semiconducting single-walled carbon nanotubes (SWNTs) were dissolved in organic solutions by derivatization
with thionychloride and octadecylamine. Both ionic (charge transfer) and covalent solution-phase chemistry with concomitant
modulation of the SWNT band structure were demonstrated. Solution-phase near-infrared spectroscopy was used to study the effects
of chemical modifications on the band gaps of the SWNTs. Reaction of soluble SWNTs with dichlorocarbene led to functionalization
of the nanotube walls.
Small-diameter (ca. 0.7 nm) single-wall carbon nanotubes are predicted to display enhanced reactivity relative to larger-diameter nanotubes due to increased curvature strain. The derivatization of these small-diameter nanotubes via electrochemical reduction of a variety of aryl diazonium salts is described. The estimated degree of functionalization is as high as one out of every 20 carbons in the nanotubes bearing a functionalized moiety. The functionalizing moieties can be removed by heating in an argon atmosphere. Nanotubes derivatized with a 4-tert-butylbenzene moiety were found to possess significantly improved solubility in organic solvents. Functionalization of the nanotubes with a molecular system that has exhibited switching and memory behavior is shown. This represents the marriage of wire-like nanotubes with molecular electronic devices.
The reactions of single-walled carbon nanotubes (SWNTs) with succinic or glutaric acid acyl peroxides in o-dichlorobenzene at 80-90 degrees C resulted in the addition of 2-carboxyethyl or 3-carboxypropyl groups, respectively, to the sidewalls of the SWNT. These acid-functionalized SWNTs were converted to acid chlorides by derivatization with SOCl(2) and then to amides with terminal diamines such as ethylenediamine, 4,4'-methylenebis(cyclohexylamine), and diethyltoluenediamine. The acid-functionalized SWNTs and the amide derivatives were characterized by a set of materials characterization methods including attenuated total reflectance (ATR) FTIR, Raman and solid state (13)C NMR spectroscopy, transmission electron microscopy (TEM), and thermal gravimetry-mass spectrometry (TG-MS). The degree of SWNT sidewall functionalization with the acid-terminated groups was estimated as 1 in 24 carbons on the basis of TG-MS data. In comparison with the pristine SWNTs, the acid-functionalized SWNTs show an improved solubility in polar solvents, for example, alcohols and water, which enables their processing for incorporation into polymer composite structures as well as for a variety of biomedical applications.
- J L Bahr
- R E Smalley
- J M Tour
J. L. Bahr, R. E. Smalley, J. M. Tour, J. Am. Chem. Soc. 2001, 123,
6536.
Margrave, ªChemistry of Carbon Nanotubesº
- V N Khabashesku
V. N. Khabashesku, J. L. Margrave, ªChemistry of Carbon Nanotubesº, in Encyclopedia of Nanoscience and Nanotechnology, American Scientific Publishers, Stevenson Ranch, CA 2004, Vol. 1, p. 849.
- Z Jia
- Z Z Wang
- C Xu
- J Liang
- B Wei
- D Wu
Z. Jia, Z. Z. Wang, C. Xu, J. Liang, B. Wei, D. Wu, Mater. Sci. Eng. A
1999, 271, 395.
- H Peng
- L B Alemany
- J L Margrave
- V N Khabashesku
- F Li
- H M Cheng
- S Bai
- G Su
H. Peng, L. B. Alemany, J. L. Margrave, V. N. Khabashesku, J. Am.
Chem. Soc. 2003, 125, 15 174.
[31] http://www.cnanotech.com
[32] F. Li, H. M. Cheng, S. Bai, G. Su, Appl. Phys. Lett. 2000, 77, 3161.
______________________
648 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
http://www.afm-journal.de
- S Allaoui
- H Bai
- H M Cheng
- J B Bai
S. Allaoui, H. Bai, H. M. Cheng, J. B. Bai, Compos. Sci. Technol.
2002, 62, 1993.
- M L Shofner
- F J Rodriguez-Macias
- R Vaidyanathan
- E V Barrera
M. L. Shofner, F. J. Rodriguez-Macias, R. Vaidyanathan, E. V. Barrera, Composites, Part A 2003, 34, 1207.
- H Geng
- R Rosen
- B Zheng
- H Shimoda
- L Fleming
- J Liu
- O Zhou
H. Geng, R. Rosen, B. Zheng, H. Shimoda, L. Fleming, J. Liu,
O. Zhou, Adv. Mater. 2002, 14, 1387.
- J E Riggs
- Z Guo
- D L Carroll
- Y P Sun
J. E. Riggs, Z. Guo, D. L. Carroll, Y. P. Sun, J. Am. Chem. Soc. 2000,
122, 5879.
- J Chen
- M A Hamon
- R C Haddon
J. Chen, M. A. Hamon, R. C. Haddon, Science 1998, 282, 95.
- Y Lin
- M Apparao
- B Rao
- E Sadanadan
- Y Kenik
- Sun
Y. Lin, M. Apparao, B. Rao, E. Sadanadan, A Kenik, Y. Sun, J. Phys.
Chem. B 2002, 106, 1294.
- X Gong
- J Liu
- S Baskaran
- R D Voise
- J S Young
X. Gong, J. Liu, S. Baskaran, R. D. Voise, J. S. Young, Chem. Mater.
2000, 12, 1049.
- J Liu
- A G Rinzler
- H Dai
- J H Hafner
- R K Bradley
- P J Boul
- A Lu
- T Iverson
- K Shelimov
- C B Huffman
J. Liu, A. G. Rinzler, H. Dai, J. H. Hafner, R. K. Bradley, P. J. Boul,
A. Lu, T. Iverson, K. Shelimov, C. B. Huffman, F. Rodriguez-Macias,
Y. Shon, T. R. Lee, D. T. Colbert, R. E. Smalley, Science 1998, 280,
1253.
- S J V Frankland
- A Caglar
- D W Brenner
S. J. V. Frankland, A. Caglar, D. W. Brenner, M. Griebel, J. Phys.
Chem. B 2002, 106, 3046.
- A Eitan
- K Jiang
- D Dukes
- R Andrews
- L S Schadler
A. Eitan, K. Jiang, D. Dukes, R. Andrews, L. S. Schadler, Chem. Mater. 2003, 15, 3198.
Toughened Composites, ASTM special technical publication
- N J Johnston
N. J. Johnston, Toughened Composites, ASTM special technical publication, ASTM, Philadelphia, PA 1985, p. 937.
- K T Lau
- S Q Shi
K. T. Lau, S. Q. Shi, Carbon 2002, 40, 2961.
[13] P. M. Ajayan, L. S. Schadler, C. Ciannaris, A. Rubio, Adv. Mater.
2000, 12, 750.
- D Qian
- E C Dickey
- R Andrews
D. Qian, E. C. Dickey, R. Andrews, T. Rantell, Appl. Phys. Lett. 2000,
76, 2868.
- S S Wong
- A T Woolley
- E Joselevich
- C T Cheung
- C M Lieber
S. S. Wong, A. T. Woolley, E. Joselevich, C. T. Cheung, C. M. Lieber,
J. Am. Chem. Soc. 1998, 120, 8857.
- E T Thostenson
- Z F Ren
- T W Chou
E. T. Thostenson, Z. F. Ren, T. W. Chou, Compos. Sci. Technol. 2001,
61, 1899.
- E V Barrera
E. V. Barrera, JOM 2000, 52, 38.
- K T Lau
- S Q Shi
K. T. Lau, S. Q. Shi, Carbon 2002, 40, 2961.
- P M Ajayan
- L S Schadler
- C Ciannaris
- A Rubio
P. M. Ajayan, L. S. Schadler, C. Ciannaris, A. Rubio, Adv. Mater.
2000, 12, 750.
- K T Lau
K. T. Lau, Carbon 2002, 40, 1605.
- J Liu
- A G Rinzler
- H Dai
- J H Hafner
- R K Bradley
- P J Boul
- A Lu
- T Iverson
- K Shelimov
- C B Huffman
- F Rodriguez-Macias
- Y Shon
- T R Lee
- D T Colbert
- R E Smalley
J. Liu, A. G. Rinzler, H. Dai, J. H. Hafner, R. K. Bradley, P. J. Boul,
A. Lu, T. Iverson, K. Shelimov, C. B. Huffman, F. Rodriguez-Macias,
Y. Shon, T. R. Lee, D. T. Colbert, R. E. Smalley, Science 1998, 280,
1253.