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Vibration characteristics of double-walled carbon nanotubes (DWCNTs) with conveying fluid are analyzed based on the Euler–Bernoulli beam theory and using the wave propagation approach. The DWCNTs are considered as two nanotube shells coupled through the van der Waals interaction between them. The influences of internal moving fluids, such as flow velocity and mass density of fluids, on the vibration frequency of DWCNTs and the DWCNTs embedded in an elastic matrix are investigated in detail. The effect of matrix surrounding carbon nanotubes is considered as a spring element defined by the Winkler model. In this paper, we consider the double-walled nanotubes with an inner diameter of 2.2 nm and an outer diameter of 3.0 nm. According to this analysis, the numerical results indicate that the vibration frequency for the first mode (mode 1) reduces to zero at a critical flow velocity in the case of higher flow velocity, which coincides with the previous study based on a single beam model. The critical flow velocity is largely affected by the fluid properties and the vibration modes. [ABSTRACT FROM AUTHOR]

Carbon nanotubes may hold scientific promise in nanotechnology as nanopipes conveying fluid. In this paper, the wave propagation in double-walled carbon nanotubes (DWCNTs) conveying fluid is studied based on the Euler–Bernoulli beam theory. The influences of internal moving fluids, such as flow velocity and mass density of fluids, on the sound wave propagation of DWCNTs or the DWCNTs embedded in an elastic matrix are investigated in detail. The DWCNTs are considered as a two-shell model coupled together through the van der Waals interaction between two adjacent nanotubes. According to the proposed theoretical approach, the results indicate that fluid flow through carbon nanotubes affects the wave speed and the critical frequency in the carbon nanotubes. The amplitude ratios of the inner to outer nanotubes are largely affected by the fluid velocity and density when the vibrational frequency in nanotubes is larger than 1.5 Hz. The theoretical investigation may give a useful reference for potential application and design of nanoelectronics and nanodevices. [ABSTRACT FROM AUTHOR]

Wave propagation approach of single- and double-walled carbon nanotubes conveying fluid is presented through the use of the continuum mechanics. A simplified Flügge shell equations are proposed as the governing equations of motion for carbon nanotubes studied here. For the double-walled nanotubes, the deflection of nested tubes is considered to be coupled through the van der Waals interaction between two adjacent nanotubes. Effects of filled fluid property and nanotube diameter on the wave propagation are investigated and analyzed based on the proposed elastic continuum model. The theoretical investigation may give a useful reference for potential design and application of nanoelectronics and nanodevices. [ABSTRACT FROM AUTHOR]

Barium titanate (BT) nanoparticles were fabricated using sol-gel method, and then immobilized onto the surface of carbon nanotubes (CNTs) to fabricate heterogeneous barium titanate@carbon nanotube (BT@CNT) nanocomposites. The electromagnetic (EM) wave absorption ability increased as the weight fraction of BT@CNT increased. The BT@CNT 30 wt.% nanocomposites with thickness of 1.1 mm showed a minimum reflection loss (R.L.) of ∼ − 37.2 dB (> 99.98% absorption) at 13.9 GHz with a response bandwidth of 1.6 GHz (12.3 ∼ 13.9 GHz), and were the best absorber when compared to similar nanocomposites with different thicknesses. The relationship between conductivity and EM wave absorption properties was also discussed. Appropriate conductivity also plays an important role to obtain optimum absorption performance. BT@CNT nanocomposites exhibited significant absorption ability, and this indicates that they can be utilized as an effective EM wave absorber material. Left: absorption performance and response bandwidth of BT@CNT 30 wt.% nanocomposites with various thicknesses. Right: TEM image of BT@CNT. [ABSTRACT FROM AUTHOR]

The electromagnetic wave absorption properties of single- and double-layer silver nanoparticle/carbon nanotube (Ag/CNT) nanocomposites were evaluated. The reflection loss (R.L.) of the samples was calculated based on the measured complex permittivity and permeability. The double-layer composites constructed from CNT 30 wt.% and Ag/CNT 30 wt.% with total thickness of 3.3 mm showed a minimum R.L. of ∼−52.9 dB (over 99.999% absorption) at 6.3 GHz. The bandwidth of reflection loss less than −10 dB was observed at 3 regions, with wideness of 3.5, 0.8, and 1.5 GHz. Thin absorber with large R.L. and wide response bandwidth at low and high frequency regions can be obtained with double-layer composites. The capability to modulate the absorption and bandwidth of these samples to suit various applications in different frequency bands indicates that these nanocomposites could be an excellent electromagnetic wave absorber. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) are nanomaterials with extremely favorable mass sensor properties. In this paper, we propose that CNTs under clamped boundary condition and an axial tensile load are considered as CNT-based resonators. Moreover, the resonant frequencies and frequency shifts of the CNTs with attached nanomass are investigated based on vibration analysis, which used the nonlocal Euler-Bernoulli beam model. Using the present methods, we analyze and discuss the effects of the aspect ratio, the concentrated mass and the axial force on the resonant frequency of the CNTs. The results indicate that the CNT beam under the axial tensile loads could provide higher sensitivity as nanomechanical mass sensor. [ABSTRACT FROM AUTHOR]

The electromagnetic wave absorption properties of double-layer barium titanate/carbon nanotube (BTO/CNT) nanocomposites were evaluated. The BTO/CNT nanomaterials were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy. The reflection loss ( R.L. ) of the samples was calculated based on the measured complex permittivity and permeability. The minimum R.L. of single-layer BTO/CNT 30 wt% nanocomposites sample with a thickness of 1.1 mm reached ~−30.3 dB (over 99.9% absorption) at 13.8 GHz, and the bandwidth of the reflection loss less than −10 dB (over 90% absorption) was 1.5 GHz. The double-layer composites consist of BTO/CNT 30 wt% (absorption layer) with thickness of 1.0 mm and BTO 30 wt% (matching layer) with thickness of 0.3 mm showed a minimum R.L. of ~−63.7 dB (over 99.9999% absorption) at 13.7 GHz, and the bandwidth of the reflection loss less than −10 dB was 1.7 GHz. Wider response bandwidth, >1.7 GHz also can be achieved with different designs of double-layer absorbers. The R.L. significantly improved and wider response bandwidth can be obtained with double-layer composites. The capability to modulate the absorption and bandwidth of these samples to suit various applications in different frequency bands indicates that these nanocomposites could be an excellent electromagnetic wave absorber. [ABSTRACT FROM AUTHOR]

Barium titanate/carbon nanotube (BTO/CNT) hybrid nanocomposites were fabricated by sol–gel method. The BTO/CNT hybrid nanomaterials were characterized using X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, Raman and X-ray photoelectron spectroscopy. The BTO/CNT hybrid nanomaterials were then loaded in paraffin wax with different weight percentage, and pressed into toroidal shape with thickness of 1.0 mm to evaluate their complex permittivity and complex permeability using vector network analyzer. The reflection loss of the samples was calculated according to their measured complex permittivity and permeability. The minimum reflection loss of the BTO/CNT 60 wt.% hybrid nanocomposites sample with a thickness of 1.0 mm reached 29.6 dB (over 99.9% absorption) at 13.6 GHz, and also exhibited a wide response bandwidth where the frequency bandwidth of the reflection loss of less than −10 dB (over 90% absorption) was from 12.1 to 13.8 GHz. The BTO/CNT 60 wt.% hybrid nanocomposites with thickness of 1.1 mm showed a minimum reflection loss of ∼−56.5 dB (over 99.999% absorption) at 13.2 GHz and was the best absorber when compared with the other samples of different thickness. The reflection loss peak shifted to lower frequency and wider response bandwidth can be obtained as the thickness of the samples increased. The capability to modulate the absorption band of these samples to suit various applications in different frequency bands simply by manipulating their weight percentage and thickness indicates that these hybrid nanocomposites could be a promising electromagnetic wave absorber. [ABSTRACT FROM AUTHOR]

We fabricated an actuator that was made from polyurethane (PU) with carbon nanotubes (CNTs) as the filler. To improve the dispersion of the CNTs, a mild hydrothermal treatment was carried out. Carboxyl and hydroxyl groups were introduced to the surface of the CNTs, and they were found to be highly dispersed in polar solvents such as dimethylformamide. To evaluate these films, we mainly focused on electrical properties, such as dielectric spectroscopy, space charge measurements, and actuator behavior. We found that the PU/CNTs film bents toward the cathode when an electric field was applied, and it reverted to its original position when the electric field was removed. Upon the inclusion of the CNTs as the filler for the polymer, the electrical properties of the films improved significantly. The highly polarized films had a high relative permittivity, and this produced a higher Maxwell pressure, which assisted the actuation. A high accumulated charge density was observed from space charge measurements in some of the films, and this explains the bending direction and the actuation mechanism. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) are nanomaterials with many potential applications due to their excellent mechanical and physical properties. In this paper, we proposed that CNTs with clamped boundary condition under axial tensile loads were considered as CNT-based resonators. Moreover, the resonant frequencies and frequency shifts of the CNTs with attached mass were investigated based on two theoretical methods, which are Euler-Bernoulli beam theory and Rayleigh's energy method. Using the present methods, we analyzed and discussed the effects of the aspect ratio, the concentrated mass and the axial force on the resonant frequency of the CNTs. The results indicate that the length of CNTs could be easily changed and could provide higher sensitivity as nanomechanical mass sensor. Moreover, the resonant frequency shifts of the CNT resonator increase significantly with increasing tensile load acting on the CNTs. [ABSTRACT FROM AUTHOR]

A nanocomposite actuator film incorporated with carbon nanotubes (CNTs) was fabricated and evaluated. The materials are polyurethane and modified CNTs as the filler. The CNTs were modified using microwave-induced polymerization modification route to improve the dispersion. The actuator performance test revealed that the films bent to the cathode side when voltage was succeeded and reverted to their original position when the voltage was removed. Moreover, the electrical properties were evaluated and the charge accumulation was observed near the anode side when voltage is applied to the films. Based on this asymmetric charge density inside the films, a model which predicts the bending direction and actuation mechanism was suggested. [ABSTRACT FROM AUTHOR]

Multi-walled carbon nanotubes (MWCNTs) and shape memory polyurethane (SMP) were used to prepare MWCNT/SMP composites for electromagnetic interference (EMI) shielding. The uniform distribution of MWCNTs was confirmed by field emission scanning electron microscopy (SEM). The electrical conductivity of the composites was tested by the four-probe method, and the results suggested that the conductivity of the samples was significantly increased by the presence of MWCNTs. The conductivity reached 35 S/m when the MWCNT loading was 9 wt%. Dynamic mechanical analysis (DMA) revealed that the composites exhibited higher storage moduli than pure SMP. In addition, the shielding effectiveness (SE) of composites with various MWCNT loading and thickness were measured over 4–7 and 13–16 GHz. The highest SE achieved was close to 35 dB for MWCNT/SMP composites with the thickness of 2 mm and MWCNT loading of 9 wt%. The SE increased as the thickness and conductivity of the composites increased. Moreover, the SE was enhanced as the frequency increased. [ABSTRACT FROM AUTHOR]

The article discusses the synthesis of functionalized multi-walled carbon nanotubes (MWCNT) via microwave-induced polymerization modification route and polybenzimidazole (PBI) nanocomposite films containing a percentage of functionalized MWCNT. The polymer's successful grafting to the MWCNT with a polymer layer that was several nanometers thick is addressed. Tensile test and dynamic mechanical analysis (DMA) were used to measure the mechanical properties of the nanocomposite films.

Abstract: The instability of single-walled carbon nanotubes (SWCNTs) under compressive loading has been observed experimentally by TEM and may limit their performance and structural integrity as atomic force microscopy (AFM) tips. Double-walled carbon nanotubes (DWCNTs) with inner and outer nanotubes of different lengths are proposed as AFM probes, and a theoretical approach based on a nanobeam model is developed for investigating the critical buckling stress of the DWCNTs under an axial compressive load. The influence of structural parameters on the buckling stress of DWCNT AFM probes are analyzed using this approach. The results show that the influence of the length mismatch between inner and outer nanotubes, as well as buckling modes on the buckling stress of DWCNTs was significant. [Copyright &y& Elsevier]

Abstract: The induced electric-field has been applied to measure the elastic modulus of carbon nanotubes. However, the vibrational modes of the multi-walled carbon nanotubes are quite different from those of the single-walled carbon nanotubes. Analysis of the vibration characteristics of double-walled carbon nanotubes (DWCNTs) with simply supported boundary condition are carried out based on Euler–Bernoulli beam theory. The DWCNTs are considered as two nanotube shells coupled through the van der Waals interaction between them. It is found that the vibrational modes of DWCNTs are noncoaxial intertube vibrations, and the deflections of the inner and outer nanotubes can occur in the same or in opposite deflections. In the same vibrational mode, the resonant frequencies of DWCNTs with deflections between the inner and outer nanotubes in the same direction are smaller than those of DWCNTs with the opposite deflections. [Copyright &y& Elsevier]

Abstract: The nanocomposites with carbon nanotubes (CNTs) and shape memory polymer (SMP) were developed for electrical applications. The specimens with different CNTs weight fractions were prepared. Their electrical resistivities and electromagnetic interference (EMI) shielding effectiveness (SE) were investigated. The electrical resistivity was examined by four-probe method at different testing temperatures of 25,35,45,55 and 65°C around glass transfer temperature (T g). As a result, for the developed nanocomposites, even lower weight fraction of CNTs could achieve a high level of conductivity and a low percolation threshold for CNTs content was confirmed. The electrical resistivity for the developed nanocomposites is dependant obviously on temperature with a linear relation like metals. The interconnected conducting network was formed more easily than other fillers. For the EMI SE measurements, a near-field antenna measurement system was used. The experiments to evaluate EMI SE were carried out in three different frequency bands, 8–26.5GHz (K band), 33–50GHz (Q band) and 50–75GHz (V band). The EMI SE of CNT/SMP nanocomposites have a strong dependence of carbon nanotube content and the specimen thickness at all of three frequency bands. The higher frequency, the larger EMI SE. For the materials with 5.5wt% VGCFs both experiment and analysis will agree well, and theoretical prediction proposed for EMI SE may be useful. [Copyright &y& Elsevier]

Moisture from the breath is a ubiquitous water energy source. The inability to continuously provide water molecules limits its application in moisture-induced electricity generation. This study first develops an electricity-sustainable breath-moisture-induced electricity generator (BMIEG) during intermittent exhalations. The generator is fabricated by the end-to-end connection of two equal asymmetric regional sandwich structural graphene oxide/carbon nanotube based composite films, making it continuously expandable without limit. The BMIEG presents a slow discharging behavior when exhalation is stopped, and it continually lights up a light-emitting diode in the intermittent exhalation process with a simple size expansion of a series of array arrangements. Additionally, the BMIEG is freely assembled using a capacitor to achieve variable voltage and/or stabilized voltage electricity supply. The flexibility and reusability of the generator show its considerable application prospects in wearable electronic products. [Display omitted] • A regionally sandwich structural GO/CNT based composite film for use. • A dual-drive generator mechanism based on the regional hydrophilicity differences. • A wearable electricity generator can continuously supply power under exhalations. [ABSTRACT FROM AUTHOR]

Abstract: We synthesized zinc ferrite nanochains, assembled from nanoparticles, using a carbon nanotubes (CNTs) template method. The resulting nanochains were systematically characterized with respect to crystal structure, morphology, elemental composition, magnetic properties and specific surface area by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), superconducting quantum interference device (SQUID) magnetometry, and the N2 adsorption method. The morphology results showed that the zinc ferrite particles with diameters of 10–20nm were structurally linked to form nanochains. The magnetic property investigation indicated that the zinc ferrite nanochains exhibited ferromagnetic behavior and possessed a saturation magnetization of 45.4emug−1 at 300K. We addressed the growth mechanism by analyzing the experimental conditions and characterization results. This method may be applicable to synthesizing other metal oxide nanochains as well. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a theoretical analysis of the torsional buckling instability of double-walled carbon nanotubes (DWCNTs) and the DWCNTs embedded in an elastic medium is presented based on the continuum elastic shell model and Winkler spring model. Using the proposed theoretical approach, the influences of the aspect ratio, the buckling modes and the surrounding medium on the torsional stability are examined in detail. The simulation results show that the torsional instability of DWCNTs can occur in different buckling modes according to the aspect ratio. The van der Waals (vdW) interaction force between nanotubes reinforces the stiffness of nanoshells. Thus, the DWCNTs possess higher buckling stability than the SWCNTs without considering vdW interaction force. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the Euler–Bernoulli beam model is used to analyze the resonant vibration of double-walled carbon nanotubes (DWCNTs) with inner and outer nanotubes of different lengths. The resonant properties of DWCNTs with different inner and outer nanotube lengths are investigated in detail using this theoretical approach. The resonant vibration is significantly affected by the vibrational modes of the DWCNTs, and by the lengths of the inner and outer nanotubes. For an inner or outer nanotube of constant length, the vibrational frequencies of the DWCNTs increase initially and then decrease as the length of another nanotube increases. A design for nanoelectromechanical devices that operate at various frequencies can be realized by controlling the length of the inner and outer nanotubes of DWCNTs. This investigation may be helpful in applications of carbon nanotubes such as high frequency oscillators, dynamic mechanical analysis and mechanical sensors. [ABSTRACT FROM AUTHOR]

Abstract: In this Letter, a theoretical analysis of the resonant vibration of double-walled carbon nanotubes (DWCNTs) and the DWCNTs embedded in an elastic medium is presented based on Euler–Bernoulli beam model and Winkler spring model. The vibration modes of DWCNTs are quite different from those of single-walled carbon nanotubes (SWCNTs). The resonant vibrations of DWCNTs are found to have in-phase and anti-phase modes, in which the deflections of the inner and outer nanotubes occur in the same and opposite directions, respectively. For the vibration of DWCNTs with the same harmonic numbers, the resonant frequencies of anti-phase mode are larger than the ones of in-phase mode. Moreover, influence of the surrounding medium on the resonant vibrations is investigated using the Winkler spring model. The results show that surrounding medium makes a strong impact on the vibration frequencies of in-phase mode, but little on those of anti-phase mode. [Copyright &y& Elsevier]

Abstract: Epoxy resins are widely applied in cryogenic engineering and their cryogenic mechanical properties as important parameters have to be improved to meet the high requirements by cryogenic engineering applications. Carbon nanotubes (CNTs) are regarded as exceptional reinforcements for polymers. However, poor carbon nanotube (CNT)–polymer interfacial bonding leads to the unexpected low reinforcing efficiency. This paper presents a study on the cryogenic mechanical properties of multi-walled carbon nanotube reinforced epoxy nanocomposites, which are prepared by adding multi-walled carbon nanotubes (MWCNTs) to diglycidyl ether of bisphenol-F epoxy via the ultrasonic technique. When the temperature decreases from room temperature to liquid nitrogen temperature (77K), a strong CNT–epoxy interfacial bonding is observed due to the thermal contraction of epoxy matrix because of the big differences in thermal expansion coefficients of epoxy and MWCNTs, resulting in a higher reinforcing efficiency. Moreover, synthetic sequence leads to selective dispersion of MWCNTs in the brittle primary phase but not in the soft second phase in the two phase epoxy matrix. Consequently, the cryogenic tensile strength, Young''s modulus, failure strain and impact strength at 77K are all enhanced by the addition of MWCNTs at appropriate contents. The results suggest that CNTs are promising reinforcements for enhancing the cryogenic mechanical properties of epoxy resins that have potential applications in cryogenic engineering areas. [Copyright &y& Elsevier]

Piezoelectric composite hydrogels have been developed as interfaces connecting biological organs and electronic devices owing to their flexibility, biocompatibility, and electromechanical behavior, which enable the conversion of environmental stimuli into electronic signals. This study presents a multifunctional hydrogel that is soft, deformable, conductive, and piezoelectric. Using water as solvent and ZnO carbon nanotube (CNT) modified polyvinyl alcohol/agar/tannin as active ingredient, a one-pot green solution mixing method was used to prepare piezoelectric hydrogel with multi-network structure. The T5C5Z4 composite hydrogel designed in this paper has excellent performance in the sensing test, and can also clearly and accurately generate signals for slight movements of body parts. The T5C5Z4 composite hydrogel also has stable piezoelectric performance. In this paper designs a 100 g ball with a radius of 10 mm that falls freely from different heights and contacts with composite water (6 cm*3 cm*4 mm) to output different electrical signals, and the output voltage also increases with the height with increasing. The composite hydrogel has also been demonstrated as a sensing-detectable, piezoelectrically stimulated flexible bioelectronic materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights • Novel three phase composite nanofibers were synthesized for sustained antibacterial properties. • The nanocomposite was prepared from PVA, carbon nanotubes and silver nanoparticles. • The PVA/carbon nanotubes-AgNP nanofibers ensures safer and long-term antibacterial activities. • The nanocomposite confirmed durable antibacterial activities for the tested time (72 h). Abstract Herein we present our research on a novel three phase antibacterial wound dressing prepared from carbon nanotubes, silver nanoparticles (AgNPs) and polyvinyl alcohol nanofibers. The AgNPs were generated on carbon nanotubes surfaces to synthesize carbon nanotubes-AgNP nanoparticles which were added into the polyvinyl alcohol nanofibers prior to electrospinning to prepare PVA/carbon nanotubes-AgNP composite nanofibers. All characterizations confirmed the three phase nanofiber architecture. Owing to growth of AgNPs on carbon nanotubes surfaces and embedding into PVA nanofibers the wound dressings are proposed for sustained and safer wound healing applications. The antibacterial test results confirmed excellent bactericidal and prolonged bacterial growth inhibition properties of the nanocomposites which suggest their suitability as sustained antibacterial wound dressing biomaterial. [ABSTRACT FROM AUTHOR]

Shape memory polymers (SMPs) have received great attention and scientific interest in widespread technological development during last few decades. Besides the development of novel SMPs, various techniques have been practiced for characterization of shape memory effect (SME) of SMPs. In this study, the shape memory effect and recovery stress property of the carbon nanotube (CNT)/waterborne epoxy (WEP) nanocomposites below and above the glass transition temperature ( T g ) of the nanocomposites and under isostrain and isostress were systematically investigated via thermal mechanical analysis (TMA), respectively. The experimental results showed that the nanocomposites exhibit excellent shape memory effect. The shape memory fixity and recovery ratios were approximately 100% even below glass transition temperature ( T g ). A remarkable point is that the strain of the nanocomposites suddenly increased with the temperature decreasing in a certain period of the heating-cooling cycles under isostress condition and the strain increment increased with temperature in general. Especially at low temperature, the recovery stress was very sensitive to temperature under isostrain condition of ±0.25 °C temperature with differential of 25.5 °C developed pressure difference of 0.20 MPa. Moreover, TMA is a practical method for quantifying the SME and recovery stress properties of SMPs and their composites. [ABSTRACT FROM AUTHOR]

In the present study, the effect of epoxy-graft-polyoxyethylene octyl phenyl ether (EP-g-TX100) on the processing and properties of the novel carbon nanotube (CNT)/water-borne epoxy (WEP) triple-shape memory nanocomposites was investigated. Generally, common epoxy or CNT/epoxy nanocomposites only possess dual-shape memory effect (DSME) that can remember only one temporary shape. In addition, CNTs aggregation and chemically inactive surface have remained a vexing problem that limits CNTs in composite application. In order to obtain excellent CNT/epoxy triple-shape memory effect (TSME) nanocomposites prepared via environmental friendly approach, EP-g-TX100 was synthesized and introduced to the CNT-epoxy system as a reactive emulsifier for epoxy emulsion, a non-covalent dispersant for CNTs, and a new reversible phase for TSME epoxy system. The multifunction self-made TX100-dangled epoxy surfactant for preparing CNT/epoxy TSME nanocomposites was first reported. The experimental results show that EP-g-TX100 had a good emulsifying ability to emulsify epoxy in water. CNTs were homogenously dispersed and well incorporated into WEP matrix and significantly improved the mechanical properties of the CNT/WEP nanocomposites. The final nanocomposites exhibited excellent TSME as we expected. [ABSTRACT FROM AUTHOR]

Abstract: Double-walled carbon nanotubes (DWCNTs) are being investigated for use as latent materials for drug carriers. However, the surface effects cannot be ignored when drugs or other functional materials, such as nickel or silver, adhere to the surface of the outer tube of a DWCNT. In this paper, the vibrational frequency of DWCNTs, while accounting for surface effects, is studied using the nonlocal Timoshenko beam model. The influence of the surface elasticity modulus, residual surface stress, nonlocal parameter, axial half-wave number and aspect ratio are investigated in detail. The results show that the vibrational frequency is significantly affected by the surface material, nonlocal parameter, vibration mode and aspect ratio. In short DWCNTs on condition of higher vibrational modes, the influences of the surface and nonlocal effects on vibration are more pronounced. [Copyright &y& Elsevier]

Abstract: Cryogenic mechanical properties are important parameters for epoxy resins used in cryogenic engineering areas. In this study, multi-walled carbon nanotubes (MWCNTs) were employed to reinforce diglycidyl ether of bisphenol F (DGBEF)/diethyl toluene diamine (DETD) epoxy system modified by poly(ethersulfone) (PES) for enhancing the cryogenic mechanical properties. The epoxy system was properly modified by PES in our previous work and the optimized formulation of the epoxy system was reinforced by MWCNTs in the present work. The results show that the tensile strength and Young’s modulus at 77K were enhanced by 57.9% and 10.1%, respectively. The reported decrease in the previous work of the Young’s modulus of the modified epoxy system due to the introduction of flexible PES is offset by the increase of the modulus due to the introduction of MWCNTs. Meanwhile, the fracture toughness (K IC) at 77K was improved by about 13.5% compared to that of the PES modified epoxy matrix when the 0.5wt.% MWCNT content was introduced. These interesting results imply that the simultaneous usage of PES and MWCNTs in a brittle epoxy resin is a promising approach for efficiently modifying and reinforcing epoxy resins for cryogenic engineering applications. [Copyright &y& Elsevier]

Abstract: A theoretical vibrational analysis of the radial breathing mode (RBM) of double-walled carbon nanotubes (DWCNTs) subjected to pressure is presented based on an elastic continuum model. The results agree with reported experimental results obtained under different conditions. Frequencies of the RBM in DWCNTs subjected to increasing pressure depend strongly on circumferential wave numbers, but weakly on the aspect ratio and axial half-wave numbers. For the inner and outer tubes of DWCNTs, the frequency of the RBM increases obviously as the pressure increases under different conditions. The range of variation is smaller for the inner tube than the outer tube. [Copyright &y& Elsevier]

Abstract: Multi-walled carbon nanotubes (MWCNTs) with improved dispersion property have been prepared by a mild and fast hydrothermal treatment. The hydrothermal process avoids using harsh oxidants and organic solvents, which is environmental friendly and greatly decreases the damage to intrinsic structure of MWCNTs. The modified MWCNTs were highly soluble in polar solvents such as water, ethanol and dimethylformamide. Morphological observation by TEM indicated that the diameter and inherent structure were well reserved in modified MWCNTs. X-ray photoelectron spectroscopy and Raman spectroscopy were used to quantify functional groups created on the MWCNT surface, and to determine rational parameters of hydrothermal process. [Copyright &y& Elsevier]

In this work, we successfully synthesized a new functional nano-additive called potassium carboxylate functionalized multi-wall carbon nanotubes (MWCNTs-COOK) and introduced it into the interfacial polymerization system to fine-tune the structure and properties of the nanofiltration (NF) membrane. The embedded MWCNTs-COOK (150 ppm) tightened the network-crosslink structure of the selective layer and contributed to a dense hydrophilic membrane surface with high positive chargeability. In addition, MWCNTs-COOK nano-additives in membrane created some intrinsic fast transport channels for water molecules. The MWCNTs-COOK(150 ppm)-assisted NF membrane exhibited a remarkable high flux of 12.23 L/m2hbar, a high separation factor S Li,Mg of 58, and a high difference in Li+ and Mg2+ rejections around 77%, indicating an excellent Li+ enrichment and Mg2+ removal capabilities, and breaking through the trad-off limit of permeate flux. Simultaneously, the comprehensive performance of the NF membrane can be maintained stably even in long-term utilization. This work opens a simple and effective pathway for accelerating Li+ enrichment and Mg2+ removal, which has great potential for lithium extraction application. [ABSTRACT FROM AUTHOR]

Herein we propose cellulose acetate/carbon nanotube/silver nanoparticles (CA/CNT/Ag) nanofiber composite for antibacterial applications. The nanofiber composite are expected to avoid harmful effects of silver (i.e. argyria and argyrosis) owing to anchoring of silver nanoparticles on carbon nanotubes (CNTs) and embedding of the composite inside cellulose acetate (CA) matrix. The carbon nanotubes/silver nanoparticles (CNT/Ag) nanocomposite localized inside the CA polymer matrix allow minimal/no direct contact of silver nanoparticles with human cells and are expected to show reduced silver leaching. The cellulose acetate (CA) nanofibers loaded with silver nanoparticles anchored multiwall carbon nanotubes (CNT/Ag) were fabricated by electrospinning. The samples were studied with scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), Fourier transform infra-red spectroscopy (FTIR), tensile strength tests and antibacterial assays. Synthesis of the CNT/Ag nanocomposite was confirmed with XPS, XRD, EDS and TEM analysis. SEM images showed regular morphology of the CA/CNT/Ag nanofiber composites. TEM images depicted anchoring of silver nanoparticles on CNTs and embedding of CNT/Ag in the CA nanofiber matrix. The antibacterial test results demonstrated excellent antibacterial performance of the CA/CNT/Ag. The CA/CNT/Ag samples ensured effective bacterial growth inhibition on agar plates, in liquid medium (optical density, OD 590nm) (for 48 h) and in bactericidal assay (relative cell viability, %). Our results suggested CA/CNT/Ag composite nanofibers as potential candidate for safer antibacterial applications. Unlabelled Image • A novel CA/CNT/Ag nanofiber composite was prepared for antibacterial properties. • The CA/CNT/Ag nanocomposite produced bactericidal performance for 48 h. • Anchored Ag0 and embedded in CA matrix, helps to avoid harmful silver side-effects. • The CA/CNT/Ag nanocomposite demonstrated long-time antibacterial performance. [ABSTRACT FROM AUTHOR]