Percentage Of Multi-walled Carbon Nanotubes Research Articles

Electro-elastic and piezoresistive behavior of flexible MWCNT/PMMA nanocomposite films prepared by solvent casting method for structural health monitoring applications

Abstract Electrical, mechanical and piezoresistive behavior of flexible thin films of multi-walled carbon nanotubes (MWCNT) embedded in poly(methyl methacrylate) (PMMA) matrix are investigated for structural health monitoring applications. Three sets of MWCNT/PMMA nanocomposite thin films at various weight percentage of MWCNT are fabricated using solvent casting method. Dichloromethane (DCM) is used as a solvent. The percolation threshold for electrical conductivity is found to be 3 weight percentage of MWCNT. The mechanical properties of thin films are evaluated via monotonic uniaxial tensile test. The rate of loading is 1 mm/min and applied load and crosshead displacement are sampled at 10 Hz frequency. Experimental results showed that addition of 10 weight percentage of MWCNT leads to a significant improvement in the tensile strength of PMMA by 291% and tensile strain by 122%. The piezoresistive behavior at different weight percentage of MWCNT is evaluated and highest gage factor of 4.37 is achieved at the percolation threshold.

Effect of type, percentage and dispersion method of multi-walled carbon nanotubes on tribological properties of epoxy composites

In this work the wear behaviour of epoxy matrix composites with different types and percentages of multiwalled carbon nanotubes (MWCNTs) has been studied. Three different types (NC3100, NC3150 and NC3152) and percentages (0.1 and 0.5wt%) of MWCNTs were dispersed into an epoxy resin by a calendering process. The tribological properties of epoxy-MWCNTs nanocomposites were investigated using “pin-on disc” wear testing machine under different conditions (counterpart material, distances and sliding speeds test). Scanning electron microscopy and 3D optical profilometer were used to observe the worn surfaces of the samples. Compared with neat epoxy, the composites with MWCNTs showed a lower mass loss, friction coefficient and wear rate, and these parameters decreased with the increase of MWCNT percentage. Also, the results demonstrated that the epoxy composites with 0.5wt% of amino-MWCNT (NC3152) have the best tribological properties.

Investigation on wear properties of AZ31-MWCNT nanocomposites fabricated through mechanical alloying and powder metallurgy

Abstract The wear properties of Mg alloy AZ31 (Al 3%, Zn 1%, rest Mg) nanocomposites reinforced with multi-wall carbon nanotubes (MWCNTs) were studied by conducting experiments on pin-on-disc wear test apparatus. The composites were fabricated by powder metallurgy technique by homogeneously reinforcing variable percentages of MWCNTs (0.33 wt%, 0.66 wt%, and 1.0 wt%) into Mg alloy AZ31 matrix through mechanical alloying. The effect of varying percentages of MWCNTs on the wear properties of AZ31-MWCNT nanocomposites and the mechanism behind that were investigated through scanning electron microscope and energy dispersive spectroscope analysis. The microstructure investigation revealed that an increase in reinforcement of MWCNTs in AZ31 alloy increased the hardness and reduced the wear rate of the composites with 0.33 wt% and 0.66 wt% due to homogeneous distribution and high interfacial strength between AZ31 and MWCNTs. However, with the addition of 1.0 wt% MWCNTs to AZ31 alloy led to high agglomeration of MWCNTs, resulting in poor interfacial strength and weak bonding between AZ31 and conglomerated MWCNTs, subsequently increasing the wear rate.

Experimental Investigation on the Effect of Multiwalled Carbon Nanotubes and Nano-SiO2 Addition on Mechanical Properties of Hardened Cement Paste

This paper investigates the behaviour of hardened cement paste reinforced with multi-walled carbon nano-tubes (MWCNTs) and Nano-SiO2 (NS). In these composites, the percentage of MWCNTs was fixed at 0.75% by weight of cement, while the percentage of NS was fixed at 0.5% by weight of cement. Dispersion of both MWCNTs and NS was carried out using ultrasonic energy method. The novel nano-composite specimens developed were tested for compression and flexure in order to evaluate their mechanical properties such as compressive strength, flexural strength, toughness and ductility. These results were then compared with the results of plain cement control beams. Scanning electron microscopy was conducted to examine the bond between the MWCNTs and the cement matrix.

Single-Step Synthesis of LaMnO3/MWCNT Nanocomposites and Their Photocatalytic Activities

Composites of the nano-sized perovskite-type oxide of LaMnO3 and multi-walled carbon nanotubes (MWCNTs) were synthesized in a single step using the sol-gel method. Their photocatalytic activities for the degradation of various water-soluble dyes under visible light were evaluated. The prepared samples were characterized by thermogravimetry analysis, scanning electron microscopy transmission electron microscopy, X-ray diffraction, photoluminescence spectroscopy and UV-vis diffused spectroscopy. Results showed that LaMnO3 nanoparticles grew on the surface of MWCNTs with a grain size of around 20 nm. Photocatalysis measurements revealed that the LaMnO3/MWCNT nanocomposites had greater photocatalytic activities than pure LaMnO3 nanoparticles, and the mass percentage of MWCNTs showed that 9.4% possessed the highest photocatalytic activity. These results indicate that LaMnO3/MWCNT nanocomposites are promising candidates as highly effective photocatalysts.

Facile conductive bridges formed between silicon nanoparticles inside hollow carbon nanofibers

This paper reports on a simple and effective method for improving the electrochemical performance of silicon nanoparticle-core/carbon-shell (Si-core/C-shell) nanofibers. Instead of increasing the encapsulation amount of Si nanoparticles, additional conductive paths between the Si nanoparticles were formed by incorporating a small percentage of multi-walled carbon nanotubes (MWNTs) (e.g., 5 wt% with respect to Si) into the Si nanoparticle core. The electrical conductivity of a single Si-core/C-shell nanofiber was measured by a four-point probe using four nano-manipulators, which showed a more than five times increase according to MWNT addition. A galvanostatic charge-discharge test demonstrated that a small amount of MWNTs greatly improved the electrochemical performance of the Si-core/C-shell nanofibers (e.g., a 25.1% increase in the Li-ion storage capability) due to the enhanced participation of Si through the additional conductive paths formed between the Si nanoparticles.

Structural, Microwave, and Magnetic Properties of Self-Assembled Substituted Strontium Ferrite Dot Array on Multiwalled Carbon Nanotubes

Self-assembled Ni-Co-Sn substituted strontium ferrite dot array was formed on the outer surface of functionalized multiwalled carbon nanotubes (MWCNTs) by means of hetero-coagulation. The structural properties were evaluated by X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy, and field emission scanning electron microscopy. The obtained results indicate that the single phase strontium ferrite dot array was deposited with almost constant dot spacing on MWCNTs. It was found that the substitution cations preferentially occupy the 12 k sites. Vibrating sample magnetometer (VSM) graphs confirmed that the values of saturation magnetization and coercivity have strong correlation with the volume percentage of MWCNTs. Reflection loss and permittivity values of nanocomposite were also enhanced by increasing the volume percentage of carbon nanotubes in the absorbing media.

Unusual Thermal Properties of Polylactides and Polylactide Stereocomplexes Containing Polylactide-Functionalized Multi-Walled Carbon Nanotubes

A novel and simple method for the preparation of linear, high-molar-mass, thermally stable polylactide stereocomplexes (sc-PLA) with multiwalled carbon nanotubes (MWCNTs) covalently attached to enantiomeric PLA chains is presented. The MWCNTs modified with organic spacers terminated with −OH groups were used as initiators for the ring-opening polymerization (ROP) of enantiomeric l- and d-lactides. The weight percentage of MWCNTs in the final stereocomplexes was approximately 1 wt %. The nascent (as-polymerized) polymer samples obtained by the ROP in bulk at 130 °C exhibited unusually high melting temperatures (≥190 °C) as well as enthalpies of fusion close to that estimated for polylactides with 100% crystallinity. PLA stereocomplexes were prepared from equimolar mixtures of l-PLA and d-PLA that also contained MWCNT-g-PLA, either by precipitation from solution or, for the first time, as a thin film via the slow evaporation of solvent. Crystallization in the form of stereocomplexes after melting was, unusu...

Nanotube-reinforced tannin/furanic rigid foams

Tannin/furanic foams compressive strength and impact resistance are improved by addition of small percentages of multiwall carbon nanotubes after sonication of the mixture of components before blowing of the foam. These improvements although clear are limited by the limited proportion of nanotubes that can be added to the foam, higher proportions causing unhandable increases in viscosity of the blowing mixture. Scanning electron microscopy examination at high magnification of the nanotube filled foams showed an even distribution of the nanotubes imbedded in the foam cell walls in certain zones but an apparent lack of nanotubes in other cell wall zones.

Effect of MWCNTs Doping on the Morphology, Structure and Properties of Chitosan Beads

A series of chitosan (CS)/multi-walled carbon nanotubes (MWCNTs) composite hydrogel beads with different MWCNTs contents are prepared via a solution blending method. The effects of MWCNTs on the morphology, structure and properties of chitosan beads have been investigated. Digital pictures show that the composite beads obtained are of good morphological characteristics, and the SEM micrographs indicate that the addition of MWCNTs into CS beads made the surface of the CS/MWCNTs hydrogel beads contain much larger wrinkles. Fourier transform infrared spectra (FTIR) show that the main chain of CS bead is not changed, but there are some electrostatic interactions between CS and MWCNTs, which lead to very significant changes in the crystallization behavior of CS and MWCNTs. The thermal stability of CS/MWCNTs composites at high temperatures is increased with the existence of MWCNTs, indicating a possible electrostatic interaction between MWCNTs and CS lattices to limit the motivation of CS. The adsorption capacity of CS beads doped with a lower percentage of MWCNTs (0.02 wt%) for acid fuchsin is 112.76 mg/g, higher than that of pure CS beads (35.62 mg/g).

Experimental investigation on the study of mechanical and microstructural properties of hybrid composite cement beams reinforced with multi-walled carbon nanotubes and carbon fibres

This paper investigates the behavior of reinforced cement composite beams with multi-walled carbon nanotubes and carbon fibers. The percentage of carbon fibers was fixed at 0.25 wt% of cement, while the percentage of multi-walled carbon nanotubes was fixed at 0.75 wt% of cement. Dispersion of both multi-walled carbon nanotubes and carbon fibers was carried out using the ultrasonic energy method. Composite beams were tested under flexure in order to evaluate their mechanical properties such as flexural strength, toughness and ductility. These results were then compared with the results of plain cement control beams. Microstructural tests like scanning electron microscopy, thermo gravimetric analysis and energy dispersive X-ray analysis were conducted on hybrid nanocomposite material, to study the dispersion of carbon nanotubes and carbon fibers, bonding of carbon nanotubes in C-S-H, temperature effects and the elemental composition. From the study it is concluded that the load-carrying capacity of composite beams under three-point loading is substantially higher than for plain controlled beams.

New sensitive layers for surface acoustic wave gas sensors based on polymer and carbon nanotube composites

Abstract Surface acoustic wave (SAW) gas sensors based on polymers and carbon nanotube composites as sensitive layers were investigated for the detection of low concentrations of volatile organic compounds as octane and toluene. Several nanocomposites based on polyepichlorohydrin (PECH) and polyetherurethane (PEUT) with different percentage of multiwalled carbon nanotubes (MWCNT) were tested to study the effect of MWCNTs in the response of sensors. The sensors exhibited at room temperature high response to volatile gases (toluene and octane) but did not detect other gases tested as H2, NH3, NO2 and CO.

A comparison between magnetic and reflection loss characteristics of substituted strontium ferrite and nanocomposites of ferrite/carbon nanotubes

Large-scale carbon nanotubes (CNTs)/substituted strontium ferrite nanocomposites have been fabricated by hetero-coagulation. The structure and morphology of nanoparticles and nanocomposites were evaluated by high-resolution transmission electron microscopy (HRTEM). HRTEM confirmed that strontium ferrite was successfully attached to carbon nanotubes. The vibrating sample magnetometer (VSM) confirmed the relatively strong dependence of saturation magnetization with the volume percentage of multi-walled carbon nanotubes (MWCNTs). Reflection loss of nanocomposites at 12–18 GHz was evidently enhanced, as compared to that of strontium ferrite nanoparticles. The maximum reflection loss increased significantly with an increase in volume percentage of MWCNTs. It was proved that the microwave absorbing bandwidth was modulated simply by manipulating the thickness of nanocomposites. Reflection loss evaluations indicate that the nanocomposites display a great potential application as wide-band electromagnetic wave absorbers.

Optimization of Multilayer Shields Made of Composite Nanostructured Materials

In this paper, we propose a multilayer nanostructured composite for broadband shielding applications. Layers disposal, electrical parameters, and thicknesses are optimized through a winning particle optimization algorithm to achieve the minimization of the transmitted waves. The structures are simulated by including the forward/backward scattering matrix formalism in the optimization code. The adopted algorithm is the recently introduced winning particle optimization. Manufacturing of the composites is grounded on the optimization procedure. Thanks to the macroscopic absorption features of such nanostructured layers, very thin and lightweight composites can be produced. Several weight percentages of multiwall carbon nanotubes are considered in composite base material manufacturing, also including 6wt% and 15wt% in order to enhance the electromagnetic shielding performance. Prototypes are tested in the microwave region, showing the reliability of the optimization procedure.

First Study on the Formation of Strontium Ferrite Thin Films on Functionalized Multi-Walled Carbon Nanotube

Substituted strontium ferrite (SrFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12-x</sub> (Cr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sub> ) thin films were formed along the surface of multiwalled carbon nanotubes (MWCNTs). Mössbauer spectroscopy indicates that the substituted cations preferentially occupy the 12 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> sites. X-ray diffraction (XRD), transmission electron microscope (TEM), field emission scanning electron microscope (FE-SEM), vibrating sample magnetometer (VSM), and vector network analyzer were used to analyze the structure, static, and high-frequency magnetic properties of the prepared samples. It was found that with an increase in substitution content, the saturation of magnetization decreases while the coercivity increases. The CNTs could enhance the real and imaginary parts of permittivity of ferrites. With an increase in volume percentage of MWCNTs, the reflection loss values were increased.

Experimental Investigation on Effect of Carbon Nanotubes and Carbon Fibres on the Behavior of Plain Cement Mortar Composite Round Bars under Direct Tension

This paper investigates the behavior of reinforced cement mortar composite round bars with multiwalled carbon nanotubes (MWCNTs) and carbon fibers (CFs). The percentage of CFs was fixed at 2.25 wt% of cement, while the percentage of MWCNTs was fixed at 0.5, by wt% of cement. Dispersion of both MWCNTs and CFs was carried out using ultrasonic energy method. Composite round bars were tested under direct tension in order to evaluate their mechanical properties such as ultimate load, deflection criteria, and stress-strain behavior. These results were then compared with the results of plain cement control round bars. From the study, it is shown that the load carrying capacity of composite bars under direct tension is substantially higher than the plain controlled bar.

Experimental investigations to study the effect of carbon nanotubes reinforced in cement-based matrix composite beams

The present paper investigates the behaviour of cement beams reinforced with multi-walled carbon nanotubes (MWCNTs). The addition of MWCNTs was varied at 0.25, 0.5, 0.65, 0.75, 0.85, and 1 per cent by weight of cement. Dispersion of MWCNTs was carried out using ultrasonic energy. Composite beams were tested under flexure in order to evaluate their mechanical properties such as flexural strength and load–deflection criteria. These results were then compared with those from plain cement control beams. The present work also investigated the optimum percentage of MWCNTs that gives the best results in terms of both enhanced properties and economy. Scanning electron microscopy was conducted to examine the bond between the MWCNTs and the cement matrix.

Experimental investigation of the effect of carbon nanotubes and carbon fibres on the behaviour of plain cement composite beams

In this article, the behaviour of reinforced cement composite beams with multi-walled carbon nanotubes (MWCNTs) and carbon fibres (CFs) is investigated. The percentage of CFs was fixed at 0.25 wt% of cement, while the percentage of MWCNTs was varied from 0.25, 0.5, 0.75, 1 wt% of cement. Dispersion of both MWCNTs and CFs was carried out using ultrasonic energy. Composite beams were tested under flexure in order to evaluate their mechanical properties such as flexural strength, toughness and ductility. These results were then compared with the results of plain cement control beams. The present work also investigates the optimum percentage of fibres that gives the best results both in terms of enhanced properties and economy.

Mechanical properties of thermoplastic natural rubber reinforced with multi-walled carbon nanotubes

This study investigated the mechanical properties of thermoplastic natural rubber (TPNR) nanocomposites reinforced by multi-walled carbon nanotubes (MWNTs). The TPNR nanocomposites were prepared using melt blending method from polypropylene, natural rubber, and liquid natural rubber as a compatibilizer, respectively, with 1—7 wt% of MWNTs. The tensile strength and Young’s modulus increased by almost 39% and 30%, respectively, at 3 wt% of MWNTs. The elongation at break decreased with increase in the percentage of MWNTs. The maximum impact strength was recorded at 5 wt% of MWNTs which was increased by 74% as compared with a pristine TPNR sample. The effect of MWNTs was also confirmed by DMA; it showed that the storage modulus E′, loss modulus E′′, and glass transition temperature (Tg) also increased for all MWNT reinforced samples. SEM micrographs confirm the effect of good dispersion of MWNTs and their interfacial bonding in TPNR.

New sensitive layers for surface acoustic wave gas sensors based on polymer and carbon nanotube composites

Surface acoustic wave (SAW) gas sensors based on carbon nanotube polymer composites as sensitive layers were investigated for the detection of low concentrations of volatile organic compounds as octane and toluene. Several nanocomposites based on polyepichlorohydrin (PECH) and polyetherurethane (PEUT) with different percentage of multiwalled carbon nanotubes (MWCNT) were tested to study the effect of MWCNTs in the response of sensors.