共查询到20条相似文献，搜索用时 15 毫秒
1.
S. Bellayer J.&#x;W. Gilman N. Eidelman S. Bourbigot X. Flambard D.&#x;M. Fox H.&#x;C. De&#x;Long P.&#x;C. Trulove 《Advanced functional materials》2005,15(6):910-916
Well‐dispersed multiwalled carbon nanotube (MWNT)/polystyrene nanocomposites have been prepared via melt extrusion, using trialkylimidazolium tetrafluoroborate‐compatibilized MWNTs. Quantification of the improvement is realized via transmission electron microscopy and laser scanning confocal microscopy image analysis. Differential scanning calorimetry and Fourier‐transform infrared and X‐ray diffraction analysis show evidence for a π‐cation, nanotube–imidazolium interaction and the conversion from an interdigitated bilayer, for the imidazolium salt, to an ordered lamellar structure, for the imidazolium on the surface of the MWNTs. 相似文献
2.
J. Zhu H. Peng F. Rodriguez‐Macias J.&#x;L. Margrave V.&#x;N. Khabashesku A.&#x;M. Imam K. Lozano E.&#x;V. Barrera 《Advanced functional materials》2004,14(7):643-648
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 nanotube‐reinforced epoxy composites also exhibited an increased strain to failure, which suggests higher toughness. 相似文献
3.
A new approach is developed for cutting conventional micrometer‐long entangled carbon nanotubes (CNTs) to short ca. 200 nm long segments with excellent dispersion. CNTs with different lengths are used as anode materials in Li‐ion batteries. The reversible capacity of the Li‐ion batteries is increased and the irreversible capacity is decreased upon shortening the length of the CNTs. The reason for this is that the insertion/extraction of Li ions is easier into/from short CNTs as compared to long CNTs because of the shortened length and the presence of lateral defects. Moreover, short CNTs have a lower electrical resistance and Warburg prefactor, resulting in better rate performance at high current densities. The present study suggests that short segments of CNTs obtained by cutting long CNTs may possess novel properties that may be useful for a wide variety of applications. 相似文献
4.
X.&#x;L. Li Y.&#x;Q. Liu L. Fu L.&#x;C. Cao D.&#x;C. Wei Y. Wang 《Advanced functional materials》2006,16(18):2431-2437
A simple and versatile approach has been developed to synthesize different carbon nanotube (CNT)–nanoparticle hybrid materials. The strategy is based on the nondestructive (noncovalent) functionalization of pristine CNTs and the subsequent in situ synthesis of a variety of different nanoparticles, including metal, semiconductor, and insulator particles, on the modified CNTs. This strategy has been demonstrated here with Pt, CdS, and silica nanoparticles. It is believe that this technique will provide a simple and convenient route to efficiently assemble a wide variety of nanoscale particles/clusters on the surfaces of CNTs, and will enable the construction of nanoscale heterostructures with novel functionalities in nanotechnology. 相似文献
5.
Biodegradable poly(?‐caprolactone) (PCL) has been covalently grafted onto the surfaces of multiwalled carbon nanotubes (MWNTs) by the “grafting from” approach based on in‐situ ring‐opening polymerization of ?‐caprolactone. The grafted PCL content can be controlled easily by adjusting the feed ratio of monomer to MWNT‐supported macroinitiators (MWNT‐OH). The resulting products have been characterized with Fourier‐transform IR (FTIR), NMR, and Raman spectroscopies, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). After PCL was coated onto MWNT surfaces, core/shell structures with nanotubes as the “hard” core and the hairy polymer layer as the “soft” shell are formed, especially for MWNTs coated with a high density of polymer chains. Such a polymer shell promises good solubility/dispersibility of the MWNT–PCL nanohybrids in low‐boiling‐point organic solvents such as chloroform and tetrahydrofuran. Biodegradation experiments have shown that the PCL grafted onto MWNTs can be completely enzymatically degraded within 4 days in a phosphate buffer solution in the presence of pseudomonas (PS) lipase, and the carbon nanotubes retain their tubelike morphologies, as observed by SEM and TEM. The results present possible applications for these biocompatible PCL‐functionalized CNTs in bionanomaterials, biomedicine, and artificial bones. 相似文献
6.
C. Y. Wang T. H. Chen S. C. Chang S. Y. Cheng T. S. Chin 《Advanced functional materials》2007,17(12):1979-1983
The vigorous response of multiwalled carbon nanotubes (MWNTs) to microwave irradiation, leading to the release of a large amount of heat, is used to locally melt a plastic matrix adjacent to the nanotubes within a period of seconds. This results in the intercalation of the MWNTs into the polymer matrix at room temperature without any physical damage to the polymer. The so‐called “microwave welding” approach creates a new paradigm for the formation of very strong MWNT–polymer bonds without the use of any adhesive, and represents a significant step forward for the fabrication of functional nanotube composites. Here, we demonstrate the implications of the anisotropic alignment of MWNTs in polymers, patterned conductors/resistors for soft electronics, and high‐strength composites, where the MWNTs are ‘soldered' to flexible polymer substrates. 相似文献
7.
S. Wang Z. Liang P. Gonnet Y.‐H. Liao B. Wang C. Zhang 《Advanced functional materials》2007,17(1):87-92
Single‐walled carbon nanotubes (SWNTs) are functionalized through both covalent and noncovalent bonding approaches to enhance dispersion and interfacial bonding. The coefficient of thermal expansion (CTE) of the functionalized‐SWNT‐reinforced epoxy composites are measured with a thermal mechanical analyzer (TMA). Experimental results indicate that changes of the glass‐transition temperature (Tg) in functionalized SWNT–polymer composites are dependent upon the functionalization methods. The CTE below the glass‐transition temperature of nanocomposites with a 1 wt % loading of nanotubes is substantially diminished compared to a neat polymer. A reduction in the CTE of up to 52 % is observed for nanocomposites using functionalized nanotubes. However, the CTE above the Tg significantly increases because of the contribution from phonon mode and Brownian motions of a large number of SWNTs in resin‐crosslinked networks, but the increments are compromised by possible interfacial confinement. A tunable CTE induced through nanotube functionalization has application potentials for high‐performance composites, intelligent materials, and circuit protections. 相似文献
8.
Single‐walled carbon nanotubes (SWNTs) are recognized as the ultimate carbon fibers for high‐performance, multifunctional composites. The remarkable multifunctional properties of pristine SWNTs have proven, however, difficult to harness simultaneously in polymer composites, a problem that arises largely because of the smooth surface of the carbon nanotubes (i.e., sidewalls), which is incompatible with most solvents and polymers, and leads to a poor dispersion of SWNTs in polymer matrices, and weak SWNT–polymer adhesion. Although covalently functionalized carbon nanotubes are excellent reinforcements for mechanically strong composites, they are usually less attractive fillers for multifunctional composites, because the covalent functionalization of nanotube sidewalls can considerably alter, or even destroy, the nanotubes' desirable intrinsic properties. We report for the first time that the molecular engineering of the interface between non‐covalently functionalized SWNTs and the surrounding polymer matrix is crucial for achieving the dramatic and simultaneous enhancement in mechanical and electrical properties of SWNT–polymer composites. We demonstrate that the molecularly designed interface of SWNT–matrix polymer leads to multifunctional SWNT–polymer composite films stronger than pure aluminum, but with only half the density of aluminum, while concurrently providing electroconductivity and room‐temperature solution processability. 相似文献
9.
B. Chen M. Cinke J. Li M. Meyyappan Z. Chi J.&#x;P. Harmon P.&#x;A. O'Rourke&#x;Muisener L. Clayton J. D'Angelo 《Advanced functional materials》2005,15(7):1183-1187
Using Raman spectroscopy, we demonstrate that the anisotropic interaction between single‐walled carbon nanotubes (SWNTs) and poly(methyl methacrylate) (PMMA) causes significant changes in the electronic properties of their composites. Two different procedures were used to prepare the composites: melt blending and in‐situ UV polymerization. Resonant Raman studies relate the electronic density of states (DOS) of the SWNTs to the corresponding vibration symmetry changes of both the PMMA and the SWNTs. Our results show that, in the melt‐blended sample, the SWNTs—originally semiconducting—became predominantly metallic. The changes in the electronic properties were also confirmed by dielectric constant measurements. We propose that the anisotropic interaction between PMMA and SWNTs in the melt‐blended composite is the dominant reason for the observed electronic character change. 相似文献
10.
We report a new approach of reactive spinning to fabricate thermosetting cyanate ester micro‐scale diameter fibers with aligned single walled carbon nanotubes (SWNTs). The composite fibers were produced by first dispersing the SWNTs (1 wt %) in cyanate ester (CE) via solvent blending, followed by pre‐polymerization, spinning and then multiple‐stage curing. The pre‐polymerization, spinning and post‐spinning cure temperatures were carefully controlled to achieve good spun crosslinked fibers. Both pristine and amino‐functionalized SWNTs were used for the reinforced fiber spinning. Amino‐functionalized SWNTs (f‐SWNTs) were prepared by reacting acid‐treated SWNTs with toluene 2,4‐diisocyanate and then ethylenediamine (EDA). FTIR, optical microscopy and scanning electron microscopy (SEM) showed that the amino‐functionalized SWNTs were covalently and uniformly dispersed into the cyanate ester matrix and aligned along the fiber axis. The alignment was further confirmed using polarized Raman spectroscopy. The composite fibers with aligned amino‐functionalized SWNTs possess improved tensile properties with respect to neat CE fibers, showing 85, 140, and 420% increase in tensile strength, elongation and stress‐strain curve area (i.e., toughness), respectively. NH2‐functionalization of SWNTs improves their dispersibility, alignment and interfacial strength and hence tensile properties of composite spun fibers. Fiber spinning to align SWNTs using thermosetting resin is novel. Others have reported fiber spinning to align SWNTs in thermoplastics. However, thermosetting CE resins offer the advantages of low and controllable viscosity during spinning and reactivity with amino functional groups to enable f‐SWNT/CE covalent bonding. 相似文献
11.
K. K. Kim S.‐M. Yoon J.‐Y. Choi J. Lee B.‐K. Kim J. M. Kim J.‐H. Lee U. Paik M. H. Park C. W. Yang K. H. An Y. Chung Y. H. Lee 《Advanced functional materials》2007,17(11):1775-1783
The effect of dispersant structures for dispersing single‐walled carbon nanotubes (SWCNTs) is investigated. The monomer 3‐hexylthiophene is used as the starting material for the development of a series of oligomers that are used to disperse SWCNTs in an organic solvent. The series is obtained by varying the number of head groups, the regioregularity of head groups, and the head‐to‐tail ratios of the hexyl group in the oligomers. The SWCNT solutions are characterized with UV‐vis–near‐IR spectroscopy and transmission electron microscopy. An increase in the number of head groups improves the dispersity of SWCNTs, and a regioregular oligomer plays an important role in dispersing SWCNTs. Furthermore, Raman spectroscopy and X‐ray photoelectron spectroscopy shows that the sulfur atom head groups enhance interactions between the thiophenes and the SWCNT walls. The analysis demonstrated that a well‐designed thiophene oligomer could afford well‐dispersed SWCNT solutions with long‐term dispersion stability, even with an extremely low dispersant concentration (weight ratio of CNTs/dispersant is one and the dispersant concentration is 0.1 g L–1). 相似文献
12.
Limin Gao Erik T. Thostenson Zuoguang Zhang Tsu‐Wei Chou 《Advanced functional materials》2009,19(1):123-130
The expanded use of advanced fiber‐reinforced composites in structural applications has brought attention to the need to monitor the health of these structures. It has been established that adding carbon nanotubes to fiber‐reinforced composites is a promising way to detect the formation of microscale damage. Because carbon nanotubes are three orders of magnitude smaller than traditional advanced fibers, it is possible for nanotubes to form an electrically conductive network in the polymer matrix surrounding the fibers. In this work, multi‐walled carbon nanotubes are dispersed into epoxy and infused into a glass‐fiber preform to form a network of in situ sensors. The resistance of the cross‐ply composite is measured in real‐time during incremental cyclic tensile loading tests to evaluate the damage evolution and failure mechanisms in the composite. Edge replication is conducted to evaluate the crack density after each cycle, and optical microscopy is utilized to study the crack mode and growth. The evolution of damage can be clearly identified through the damaged resistance parameter. Through analyzing the damaged resistance response curves with measurements of transverse crack density and strain, the transition between different failure modes can be identified. It is demonstrated that the integration of an electrically conducting network of carbon nanotubes in a glass fiber composite adds unique damage‐sensing functionality that can be utilized to track the nature and extent of microstructural damage in fiber composites. 相似文献
13.
T. Chatterjee K. Yurekli V.&#x;G. Hadjiev R. Krishnamoorti 《Advanced functional materials》2005,15(11):1832-1838
Dispersions of single‐walled carbon nanotubes (SWNTs) in poly(ethylene oxide) (PEO) assisted by a lithium‐based anionic surfactant demonstrate an electrical percolation of 0.03 wt.‐% and a geometrical percolation, inferred from melt rheometry, of 0.09 wt.‐%. Both the melting temperature and the extent of crystallinity of the PEO crystals decrease with increasing SWNT loading. Raman spectroscopy of the nanocomposites indicates a down‐shift of the SWNT G‐modes and suggests that the nanotubes are subjected to tensile stress transfer from the polymer at room temperature. 相似文献
14.
S. Peeterbroeck F. Laoutid J.‐M. Taulemesse F. Monteverde J.‐M. Lopez‐Cuesta J. B. Nagy M. Alexandre P. Dubois 《Advanced functional materials》2007,17(15):2787-2791
High‐density polyethylene coated multiwalled carbon nanotubes (c‐MWNTs) and multiwalled carbon nanotubes (MWNTs) have been dispersed into an ethylene vinyl acetate (EVA) copolymer by mechanical kneading. The effect of c‐MWNTs on tensile properties, thermo‐oxidative degradation, and fire behavior has been studied in comparison with virgin EVA and EVA/MWNTs nanocomposites. Due to the better dispersion of the coated nanotubes, the incorporation of 3 wt % of c‐MWNTs leads to an increase of the Young's modulus, the cohesion of the combustion residues, and a decrease of the peak heat‐release rate. 相似文献
15.
J. Li P. C. Ma W. S. Chow C. K. To B. Z. Tang J.‐K. Kim 《Advanced functional materials》2007,17(16):3207-3215
Critical factors that determine the percolation threshold of carbon nanotube (CNT)‐reinforced polymer nanocomposites are studied. An improved analytical model is developed based on an interparticle distance concept. Two dispersion parameters are introduced in the model to correctly reflect the different dispersion states of CNTs in the matrix—entangled bundles and well‐dispersed individual CNTs. CNT–epoxy nanocomposites with different dispersion states are fabricated from the same constituent materials by employing different processing conditions. The corresponding percolation thresholds of the nanocomposites vary over a wide range, from 0.1 to greater than 1.0 wt %, and these variations are explained in terms of dispersion parameters and aspect ratios of CNTs. Important factors that control the percolation threshold of nanocomposites are identified based on the comparison between modeling data and experimental results. 相似文献
16.
Mohammad Naraghi Graham H. Bratzel Tobin Filleter Zhi An Xiaoding Wei SonBinh T. Nguyen Markus J. Buehler Horacio D. Espinosa 《Advanced functional materials》2013,23(15):1883-1892
The production of carbon nanotube (CNT) yarns possessing high strength and toughness remains a major challenge due to the intrinsically weak interactions between “bare” CNTs. To this end, nanomechanical shear experiments between functionalized bundles of CNTs are combined with multiscale simulations to reveal the mechanistic and quantitative role of nanotube surface functionalization on CNT‐CNT interactions. Notably, the in situ chemical vapor deposition (CVD) functionalization of CNT bundles by poly(methyl methacrylate) (PMMA)‐like oligomers is found to enhance the shear strength of bundle junctions by about an order of magnitude compared with “bare” van der Waals interactions between pristine CNTs. Through multiscale simulations, the enhancement of the shear strength can be attributed to an interlocking mechanism of polymer chains in the bundles, dominated by van der Waals interactions, and stretching and alignment of chains during shearing. Unlike covalent bonds, such synergistic weak interactions can re‐form upon failure, resulting in strong, yet robust fibers. This work establishes the significance of engineered weak interactions with appropriate structural distribution to design CNT yarns with high strength and toughness, similar to the design paradigm found in many biological materials. 相似文献
17.
18.
Clay was introduced into single‐walled carbon nanotube (SWNT)/epoxy composites to improve nanotube dispersion without harming electrical conductivity or mechanical performance. Unlike surfactant or polymer dispersants, clay is mechanically rigid and known to enhance the properties (e.g., modulus, gas barrier, and flame retardation) of polymer composites. Combining nanotubes and clay allows both electrical and mechanical behavior to be simultaneously enhanced. With just 0.05 wt % SWNT, electrical conductivity is increased by more than four orders of magnitude (from 10–9 to 10–5 S cm–1) with the addition of 0.2 wt % clay. Furthermore, the percolation threshold of these nanocomposites is reduced from 0.05 wt % SWNT to 0.01 wt % with the addition of clay. SWNTs appear to have an affinity for clay that causes them to become more exfoliated and better networked in these composites. This clay‐nanotube synergy may make these composites better suited for a variety of packaging, sensing, and shielding applications. 相似文献
19.
J.&#x;N. Coleman M. Cadek R. Blake V. Nicolosi K.&#x;P. Ryan C. Belton A. Fonseca J.&#x;B. Nagy Y.&#x;K. Gun'ko W.&#x;J. Blau 《Advanced functional materials》2004,14(8):791-798
Polymer–multiwalled carbon nanotube composite films were fabricated using two types of polymer matrices, namely poly(vinyl alcohol), (PVA) and chlorinated polypropylene. In the first case, the PVA was observed to form a crystalline coating around the nanotubes, maximising interfacial stress transfer. In the second case the interface was engineered by covalently attaching chlorinated polypropylene chains to the nanotubes, again resulting in large stress transfer. Increases in Young's modulus, tensile strength, and toughness of × 3.7, × 4.3, and × 1.7, respectively were observed for the PVA‐based materials at less than 1 wt.‐% nanotubes. Similarily for the polypropylene‐based composites, increases in Young's modulus, tensile strength and toughness of × 3.1, × 3.9, and × 4.4, respectively, were observed at equivalent nanotube loading levels. In addition, a model to describe composite strength was derived. This model shows that the tensile strength increases in proportion to the thickness of the interface region. This suggests that composite strength can be optimized by maximising the thickness of the crystalline coating or the thickness of the interfacial volume partially occupied by functional groups. 相似文献
20.
A method is presented for dispersing ropes or bundles of single‐walled carbon nanotubes (RCNTs) in a polycarbonate (PC) matrix. Films of PC/RCNT composites are produced, with thicknesses ranging from 10 to 60 μm, and containing small concentrations (0.06–0.25 wt.‐%) of RCNT. Our process is based on a unique method of hot casting, annealing, and drying from dichlorobenzene solution. A wet annealing prior to complete drying yields a uniform and transparent film. Despite the low RCNT loading, scanning electron microscopy (SEM) analysis of the films after fracture reveals that the RCNTs form an entangled network throughout the film, which is a key requirement for enhanced properties. An increase of up to 30 % in the Young's modulus, as compared to PC, results with this method of composite fabrication. 相似文献