Single-walled Carbon Nanotubes Loading Research Articles

High microwave absorption performances for single-walled carbon nanotube—epoxy composites with ultra-low loadings

Microwave-absorbing polymeric composites based on single-walled carbon nanotubes (SWNTs) are fabricated via a simple yet versatile method, and these SWNT—epoxy composites exhibit very impressive microwave absorption performances in a range of 2 GHz–18 GHz. For instance, a maximum absorbing value as high as 28 dB can be achieved for each of these SWNT—epoxy composites (1.3-mm thickness) with only 1 wt% loading of SWNTs, and about 4.8 GHz bandwidth, corresponding to a microwave absorption performance higher than 10 dB, is obtained. Furthermore, such low and appropriate loadings of SWNTs also enhance the mechanical strength of the composite. It is suggested that these remarkable results are mainly attributable to the excellent intrinsic properties of SWNTs and their homogeneous dispersion state in the polymer matrix.

Dynamic interactions between poly(3-hexylthiophene) and single-walled carbon nanotubes in marginal solvent.

Interfacial interactions between conjugated polymers and carbon nanotubes are pivotal in determining the device performance of nanotube-based polymer electronic devices. Here, we report on interfacial structures and crystallization kinetics of poly(3-hexylthiophene) (P3HT) in the presence of single-walled carbon nanotubes (SWNTs) in anisole by means of transmission electron microscope (TEM) and ultraviolet-visible (UV-vis) absorption spectroscopy. Confined on SWNT surfaces, the P3HT forms nanofibril crystals perpendicular to the long axis of SWNTs. The equilibrium dissolution temperature of the P3HT crystals in anisole is determined to be 381 ± 10 K according to the Hoffman-Weeks extrapolation approach. Upon cooling, the polymer solution spontaneously undergoes a time-dependent chromism. Various kinetics factors such as crystallization temperature, concentration, and SWNT loading have been investigated. It is found that the growth rate (G) of the crystals scales with concentration (C) as G ∝ C(1.70±0.16). The Avrami model is utilized to analyze the nucleation mechanism and the Avrami exponents vary between 1.0 and 1.3. The Lauritzen-Hoffman theory is applied to study the chain-folding process. The fold surface free energy is calculated to be (5.28-11.9) × 10(-2) J m(-2). It is evident that the addition of 0.30 wt % SWNTs reduces the fold surface free energy by 55.6%.

Electronic Properties of Conjugated Polyelectrolyte/Single‐Walled Carbon Nanotube Composites

Two narrow-bandgap conjugated polyelectrolytes (CPEs) of identical backbone structure but different pendant charges are used to disperse single-walled carbon nanotubes (SWNTs) in MeOH. Films of the resulting CPE:SWNT composites have electrical conductivity dependent on the SWNT loading, which can be increased with acid vapor treatment. The anionic CPE gives higher electrical conductivity for the composite immediately after deposition, whereas a more-significant increase is observed for the cationic counterpart after acid treatment.

Characterization of optical, thermal and electrical properties of SWCNTs/PMMA nanocomposite films

The optical, thermal and electrical behavior of single-wall carbon nanotubes (SWCNTs)/poly(methyl methacrylate) (PMMA) composite are studied as a function of SWCNTs concentration. The nanocomposites were prepared in the form of films by solution casting technique. The concentrations of SWCNTs in SWCNTs/PMMA films were 0, 0.5, 1, 1.5, 2, 3.5, 5, 7.5, and 10 wt%. High-resolution transmission electron microscopy showed that SWCNTs doped in PMMA is less fragmented as compared to the powder SWCNTs. This is due to the interactions with polymers as well as the fabrication method. X-ray diffraction patterns of SWCNTs/PMMA composite films indicated that there is no covalent interaction between SWCNTs and PMMA. In addition, it demonstrates a homogeneous dispersion of SWCNTs in PMMA matrix. The optical properties of SWCNTs/PMMA films of SWCNTs concentration from 0 to 2.0 wt% have shown that the absorption intensity of the composite was enhanced ≈8.5 times as compared to the plain PMMA. Photoacoustic spectroscopy technique was used as a powerful and non-destructive tool to determine the thermal diffusivity (α), thermal effusivity (e) and thermal conductivity (k). The composites exhibited ≈160 % improvement in k at 2.0 wt%. Furthermore, the DC electrical conductivity measurements of SWCNTs/PMMA showed that the percolation threshold value was about 2.0 wt% of SWCNTs loading.

Effect of carbon nanotube incorporation into polythiophene-fullerene-based organic solar cells

The effect of single-walled carbon nanotube (SWNT) incorporation within bulk heterojunction photovoltaic devices based on poly(3-hexylthiophene) − [6,6]-phenyl-C61-butyric acid methyl ester (P3HT−PCBM) (1:1 w/w) active layers was investigated. Both full-length and shortened SWNTs were introduced within the P3HT−PCBM layer at loadings in the range of 0−2 wt%. For full-length SWNTs, it was found that device efficiency decreased at all SWNT loading levels and annealing temperatures, which ranged from 80 to 225 °C. The highest average external efficiencies in the absence of SWNTs reached approximately 2%, while the best efficiencies in devices incorporating the full-length SWNTs only reached 1.3%. When shortened SWNTs were incorporated, device efficiency was unchanged upon annealing at 160 °C (average values of approximately 2%), but the efficiency improved by nearly 50%, relative to controls when devices were annealed at 70 °C. Active layer analysis by grazing incidence X-ray diffraction indicated that nanotubes did not increase polymer crystallinity. Knowing that shortened SWNTs are good hole conductors, it is postulated that the improved device efficiency is due to improved hole transport through the SWNTs in devices where the hole-transporting polymer has not been allowed to adopt its optimal morphology due to underannealing.

静电诱导自组装碳纳米管薄膜的结构表征与电学性能

To provide building blocks for high-performance Micro-electro-mechanical System(MEMS)devices,Layer-by-layer(LbL)self-assembly of Single-walled Carbon Nanotube(SWNT)/polymer films was proposed and their properties were characterized and tested.The surface morphologies of the SWNT/polymer films observed under a Scanning Electron Microscope(SEM)show high strength,dense and random network structures.Raman spectra of all characteristic peaks for the SWNT in radial breathing mode,disorder mode and tangential mode demonstrate the presence of the SWNT in overall good quality and a loading state.Real time Quarts Crystal Microbalance(QCM)online monitoring illustrates that the deposition thickness and the SWNT loading fraction in the nanocomposite can be controlled in a large range based on LbL sequential deposition process.When the cycle number of polymers increase from 0to 5,the average film thickness increases from 6.31to 111.59nm,and theSWNT volume fraction decreases from 72.35%to 14.78%.In addition,the electric properties of the SWNT/polymer films under the influence of SWNT loading fraction and film thickness were investigated through current-voltage characterization.These results provide experimental and theoretical bases for potential applications of SWNT films in MEMS devices.

Roll to Plate Printed Stretchable Silver Electrode Using Single Walled Carbon Nanotube on Elastomeric Substrate

Stretchable electronics may open new applications in display, sensors and actuators. To attain the stretchable electronics, the ink formulation should be compatible with elastomeric substrates. Here, we present the formulation of silver nanoparticles and single walled carbon nanotubes (SWNTs) for printing stretchable silver electrodes on the elastomeric substrates. Highly conductive stretchable electrodes can be printed directly on the poly(styrene-b-butadiene-b-styrene) (PSBS) substrates by roll to plate (R2P) gravure printer. During the stretching test, R2P printed silver based stretchable electrodes show the high conductivity of 1000 S cm(-1) at 0.27 wt% of SWNT loading. Furthermore, the resistance of the printed silver electrode was not changed up to 15% of tensile strain.

Anomalous Thermal Conduction Characteristics of Phase Change Composites with Single-Walled Carbon Nanotube Inclusions

We report strikingly large contrasts in the thermal conductivity enhancement of phase change alkane in liquid and solid state with single-walled carbon nanotube (SWCNT) inclusions. With a small SWCNT loading of 0.25 wt % a strikingly high, 250% enhancement is achieved in the solid state and a nominal enhancement of 10% is achieved in the liquid state. The thermal conductivity contrast between solid and liquid state was found to increase with increasing SWCNT loading. The thermal conductivity contrast was more pronounced in the presence of SWCNTs compared to the presence of exfoliated graphite nanoplatelets reported in the literature.

Influence of the reaction stoichiometry on the mechanical and thermal properties of SWCNT-modified epoxy composites

Previous studies suggest that carbon nanotubes (CNTs) have a considerable influence on the curing behavior and crosslink density of epoxy resins. This invariably has an important effect on different thermal and mechanical properties of the epoxy network. This work focuses on the important role of the epoxy/hardener mixing ratio on the mechanical and thermal properties of a high temperature aerospace-grade epoxy (MY0510 Araldite as an epoxy and 4,4′-diaminodiphenylsulfone as an aromatic hardener) modified with single-walled carbon nanotubes (SWCNTs). The effects of three different stoichiometries (stoichiometric and off-stoichiometric) on various mechanical and thermal properties (fracture toughness, tensile properties, glass transition temperature) of the epoxy resin and its SWCNT-modified composites were obtained. The results were also supported by Raman spectroscopy and scanning electron microscopy (SEM). For the neat resin, it was found that an epoxy/hardener molar ratio of 1:0.8 provides the best overall properties. In contrast, the pattern in property changes with the reaction stoichiometry was considerably different for composites reinforced with unfunctionalized SWCNTs and reduced SWCNTs. A comparison among composites suggests that a 1:1 molar ratio considerably outperforms the other two ratios examined in this work (1:0.8 and 1:1.1). This composition at 0.2 wt% SWCNT loading provides the highest overall mechanical properties by improving fracture toughness, ultimate tensile strength and ultimate tensile strain of the epoxy resin by 40%, 34%, 54%, respectively.

Characterization of zinc oxide dye-sensitized solar cell incorporation with single-walled carbon nanotubes

Abstract

Antimicrobial PVK:SWNT nanocomposite coated membrane for water purification: Performance and toxicity testing

This study demonstrated that coated nitrocellulose membranes with a nanocomposite containing 97% (wt%) of polyvinyl-N-carbazole (PVK) and 3% (wt%) of single-walled carbon nanotubes (SWNTs) (97:3 wt% ratio PVK:SWNT) achieve similar or improved removal of bacteria when compared with 100% SWNTs coated membranes. Membranes coated with the nanocomposite exhibited significant antimicrobial activity toward Gram-positive and Gram-negative bacteria (∼80–90%); and presented a virus removal efficiency of ∼2.5 logs. Bacterial cell membrane damage was considered a possible mechanism of cellular inactivation since higher efflux of intracellular material (Deoxyribonucleic acid, DNA) was quantified in the filtrate of PVK-SWNT and SWNT membranes than in the filtrate of control membranes. To evaluate possible application of these membrane filters for drinking water treatment, toxicity of PVK-SWNT was tested against fibroblast cells. The results demonstrated that PVK-SWNT was non toxic to fibroblast cells as opposed to pure SWNT (100%). These results suggest that it is possible to synthesize antimicrobial nitrocellulose membranes coated with SWNT based nanocomposites for drinking water treatment. Furthermore, membrane filters coated with the nanocomposite PVK-SWNT (97:3 wt% ratio PVK:SWNT) will produce more suitable coated membranes for drinking water than pure SWNTs coated membranes (100%), since the reduced load of SWNT in the nanocomposite will reduce the use of costly and toxic SWNT nanomaterial on the membranes.

Impact of Polymer Matrix on the Electromagnetic Interference Shielding Performance for Single-Walled Carbon Nanotubes-Based Composites

Composites of acrylonitrile butadiene styrene (ABS), epoxy and soluble cross-linked polyurethane (SCPU) with various loadings of single-walled carbon nanotubes (SWCNTs) were prepared. Their electromagnetic interference (EMI) shielding effectiveness (SE) in the frequency range of 8.2-12.4 GHz (X band) was studied. Well-dispersed SWCNT composites were created in these three representative polymer matrixes. The choice of polymer matrix greatly affects the conductivity, percolation threshold, and EMI shielding properties of the SWCNT/polymer composites. Enhanced EMI SE performances were observed for the composites with better dispersed SWCNTs. Moreover, the EMI SE performances strongly correlated with SWCNT loading in the polymer matrix. The best SWCNT dispersion was achieved in the epoxy matrix: 20-30 dB EMI SE was obtained with 15 wt% SWCNTs.

Fabrication of all-in-one multifunctional phage liquid crystalline fibers

Novel hybrid materials with multifunctionality are attractive systems because of their efficiency and versatility for carrying out tasks in parallel. In the present work, controllable formation of multifunctional and micrometer-sized composite fibers is gained via incorporating single-walled carbon nanotubes (SWCNTs) and magnetic iron oxide nanoparticles into a biotemplate, M13 phage in liquid-crystalline phase. It is found that these phage composite fibers possess high and durable natural fluorescence except those with SWCNT loadings higher than 10%. SWCNTs, imparting improved mechanical properties and electrical conductivity, align themselves parallel to the long axis of the fibers in the phage matrix. No SWCNTs or magnetic nanoparticles were observed on the external surface of phage composite fibers, so that the superficial phages are still able to provide binding sites for further surface modification. The composite fibers were also demonstrated to be non-cytotoxic platforms to support cell adhesion and growth. The virus-based multifunctional composite fibers, integrating fluorescence, electrical conductivity, magnetism, improved mechanical properties, and biocompatibility, offer a new prospect of an all-in-one tool, as well as potential applications ranging from tissue engineering to biomedical devices.

Mechanical properties of perfect and defective zigzag single-walled carbon nanotubes under axial compression

Axial buckling behavior of perfect and defective zigzag single-walled carbon nanotubes (SWCNTs) is studied by molecular dynamics (MD) simulations. Different effects of three typical categories of defect on the axial buckling properties of SWCNTs are investigated. MD simulation results show that the buckling behavior of defective tubes is quite different from the perfect tube. The critical buckling load of zigzag SWCNTs is significantly reduced with different defect appeared in the tube wall, and the effective elastic modulus are also slightly but distinguishingly influenced by individual defect. It is revealed that an Stone-Thrower-Wales defect could induce greater decrease of the rigidity a single vacancy defect or a double vacancies one. The harmful effects of defects do not depend simply on the size of the defective area, but related strongly to the buckling modes of the defective SWCNTs which specifically differ from each other due to the different defect structures.

Single‐wall carbon nanotubes dispersion behavior and its effects on the morphological and mechanical properties of the electrospun nanofibers

AbstractThe dispersion behavior of single‐walled carbon nanotube (SWCNT) has important effects on morphological and mechanical properties of SWCNT composite nanofibers. The relationship of the dispersion conditions with morphological and mechanical characteristics for SWCNT / polyacrylonitrile (PAN) / polyvinylpyrrolidone (PVP) composite nanofibers have been examined. The SEM and TEM analyses of the nanofibers revealed that the deformation in the nanofiber structures increases with increasing concentration of SWCNTs. Tensile results showed that only 2 wt% SWCNT loading to the electrospun composite nanofibers gave rise to 10‐fold and 3‐fold increase in the tensile modulus and tenacity of nanofiber layers, respectively. Essentially, high mechanical properties and uniform morphology of the composite nanofibers were found at SWCNT concentration of ∼2 wt% due to their stable and individual dispersion. POLYM. COMPOS., 33:1951–1959, 2012. © 2012 Society of Plastics Engineers

Temperature Dependent Thermal Conductivity Increase of Aqueous Nanofluid with Single Walled Carbon Nanotube Inclusion

We investigated the thermal and electrical conductivity of water seeded with single-walled carbon nanotubes (SWCNT) synthesized using the alcohol catalytic chemical vapour deposition method. Sodium deoxycholate was used as the surfactant to prepare stable nanofluids, which we then thoroughly characterized by microscopic and spectroscopic methods. Electrical conductivity measurements showed power law dependence with respect to SWCNT loading, while the thermal conductivity increase showed a linear dependence on loading. The effective thermal conductivity of the nanofluid was also found to increase with increasing temperature. Viscosity of the nanofluids showed a threefold increase compared to the thermal conductivity increase, which may play a crucial role in utilizing this fluid for practical applications. We compare experimental results with existing analytical models and discuss the critical role of thermal boundary resistance, which limits the improvement in thermal conductivity. Influence of SWCNT aggregation in the increase of effective thermal conductivity is also discussed. *Corresponding author. Tel: +81-3-5841-6421. Fax: +81-3-5800-6983. E-mail address: maruyama@photon.t.u-tokyo.ac.jp (S. Maruyama) 2

Tunable mechanical properties of layer-by-layer self-assembled carbon nanotube/polymer nanocomposite membranes for M/NEMS

This paper presents layer-by-layer (LbL) self-assembly of single-walled carbon nanotube (SWNT)/polymer membranes with a well-dispersed wide-range tunable volume fraction of functionalized SWNTs. The surface morphology of the SWNT/polymer membranes shows a high strength, dense and random network structures. The quartz crystal microbalance (QCM) characterization illustrates that the deposition thickness and the SWNT loading fraction in SWNT nanocomposites can be controlled in a large range based on LbL sequential deposition process. The Young's modulus of the self-assembled SWNT/polymer composite membranes is characterized by a combinative approach of piezoelectric excitation and laser vibrometer measurement. The Young's modulus of SWNT/polymer nanocomposites is tunable from hundreds to tens of GPa, as a function of the SWNT volume fraction. Such significant enhancement of LbL self-assembled SWNTs offers a way in which the embedded SWNTs can realize the true potential to strengthen SWNT/polymer nanocomposites. Conventional mixture models such as rule-of-mixture model and Halpin–Tsai model fail to explain the structure–property regime in nanoscale at a high SWNT fraction ratio. This observed tunability can serve as a benchmark to tailor the design of nanocomposite thin films for potential applications to MEMS and NEMS devices.

Rheological and Tribological Properties of Carbon Nanotube/Thermoplastic Nanocomposites Incorporating Inorganic Fullerene-Like WS2 Nanoparticles

The rheological and tribological properties of single-walled carbon nanotube (SWCNT)-reinforced poly(phenylene sulphide) (PPS) and poly(ether ether ketone) (PEEK) nanocomposites prepared via melt-extrusion were investigated. The effectiveness of employing a dual-nanofiller strategy combining polyetherimide (PEI)-wrapped SWCNTs with inorganic fullerene-like tungsten disulfide (IF-WS2) nanoparticles for property enhancement of the resulting hybrid composites was evaluated. Viscoelastic measurements revealed that the complex viscosity η, storage modulus G', and loss modulus G″ increased with SWCNT content. In the low-frequency region, G' and G″ became almost independent of frequency at higher SWCNT loadings, suggesting a transition from liquid-like to solid-like behavior. The incorporation of increasing IF-WS2 contents led to a progressive drop in η and G' due to a lubricant effect. PEEK nanocomposites showed lower percolation threshold than those based on PPS, ascribed to an improved SWCNT dispersion due to the higher affinity between PEI and PEEK. The SWCNTs significantly lowered the wear rate but only slightly reduced the coefficient of friction. Composites with both nanofillers exhibited improved wear behavior, attributed to the outstanding tribological properties of these nanoparticles and a synergistic reinforcement effect. The combination of SWCNTs with IF-WS2 is a promising route for improving the tribological and rheological performance of thermoplastic nanocomposites.

Reactive fillers based on SWCNTs functionalized with matrix-based moieties for the production of epoxy composites with superior and tunable properties

Composite materials based on epoxy matrix and single-walled carbon nanotubes (SWCNTs) are able to exhibit outstanding improvements in physical properties when using a tailored covalent functionalization with matrix-based moieties containing terminal amines or epoxide rings. The proper choice of grafted moiety and integration protocol makes it feasible to tune the composite physical properties. At 0.5 wt% SWCNT loading, these composites exhibit up to 65% improvement in storage modulus, 91% improvement in tensile strength, and 65% improvement in toughness. A 15 °C increase in the glass transition temperature relative to the parent matrix was also achieved. This suggests that a highly improved interfacial bonding between matrix and filler, coupled to improved dispersion, are achieved. The degradation temperatures show an upshift in the range of 40–60 °C, which indicates superior thermal performance. Electrical conductivity ranges from ∼10−13 to ∼10−3 S cm−1, which also shows the possibility of tuning the insulating or conductive behaviour of the composites. The chemical affinity of the functionalization moieties with the matrix and the unchanged molecular structure at the SWCNT/matrix interface are responsible for such improvements.

Poly(trimethylene terephthalate‐block‐tetramethylene oxide) elastomer/single‐walled carbon nanotubes nanocomposites: Synthesis, structure, and properties

AbstractNanocomposites based on poly(trimethylene terephthalate)‐block‐poly(tetramethylene oxide) (PTT‐PTMO)‐segmented copolymer and COOH‐functionalized single‐walled carbon nanotubes (SWCNTs) were prepared by in situ polymerization method. The obtained nanocomposites were characterized by thermogravimetric analysis, scanning electron microscopy, differential scanning calorimetry (DSC), DMTA, wide‐angle x‐ray scattering (WAXS), small‐angle X‐ray scattering, and tensile testing. The nanocomposites with low SWCNTs loading (<0.5 wt %) shows uniform dispersion of CNT in polymer matrix. As the SWCNTs loading in the nanocomposites increase, the significant improvement of thermo‐oxidative stability was observed. It was found that the nanocomposites have slightly higher degree of crystallinity (determined by DSC and WAXS) of poly(trimethylene terephthalate) (PTT) hard phase than neat PTT‐PTMO copolymer. The melting point of PTT hard phase and glass transition temperature of poly(tetramethylene oxide)‐rich phase were not affected by the presence of CNTs in polymer matrix. The SWCNTs played a role as nucleating agent in PTT‐PTMO matrix, which led to increase in the crystallization rate. Tensile tests showed that the tensile strength of the nanocomposites with 0.05–0.3 wt % loading of SWCNTs have improved tensile strength in comparison to the neat PTT‐PTMO copolymer without reduction elongation at break. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012