Characteristics and Preparation of multi-walled carbon nanotubes-polyvinyl alcohol nanocomposites via ionic mechanism

2H-MoS ₂ Modified Nitrogen-Doped Hollow Mesoporous Carbon Spheres as the Efficient Catalytic Cathode Catalyst for Aprotic Lithium-Oxygen Batteries

The present work reports a novel synthesis procedure to decorate multiwall carbon nanotubes (MWCNTs) by silver (Ag) nanoparticles (NPs) via silver nitrate (AgNO3) followed by incorporation of these decorated MWCNTs into polymers to form the nanocomposite. The samples of functionalized MWCNTs (FMWCNTs), Ag-decorated MWCNTs (Ag-MWCNTs) and polymer/Ag-MWNCT composites were investigated using various characterization techniques. The field-emission scanning electron microscope (FESEM) image of Ag-MWCTs reveals the uniform distribution of Ag nanoparticles over the surface of MWCNTs. Energy-dispersive X-ray spectroscopy (EDX), elemental mapping, X-ray diffraction (XRD) and Raman spectroscopy confirmed the successful formation of Ag-decorated MWCNTs. FESEM images and UV–Vis absorption spectra of polymer/Ag-MWNCTs composites clearly validates the development of polymer/Ag-MWCNT composites. Finally, the polymer/Ag-MWCNT-based devices were fabricated to compare the electrical performance with those comprising the pristine polymers. The 3D conducting pathways formed by MWCNT and extremely high conductivity of Ag contribute to the improved current levels and reduced cut-in voltage in the Ag-MWCNTs compared to the pristine devices. The electrical transport study also shows a significant modification in the dominant transport mechanism by addition of Ag-MWCNT in the polymer matrix. The present study could pave the path for the development of various cost-effective high-performance electronic devices based on Ag-MWCNT/polymer composites.

An aromatic azo-polymer, poly(thiourea-azo-naphthyl), has been synthesized using 1-(5-thiocarbamoylaminonaphthyl)thiourea and diazonium salt solution of 2,6-diaminopyridine. Poly(thiourea-azo-naphthyl) was easily processable using polar solvents and had high molar mass, 57 × 103 g/mol. Electrically conducting and mechanically and thermally stable polymer/multi-walled carbon nanotube nanocomposites were obtained via melt processing technique. Fine distribution of multi-walled carbon nanotubes in a polymer matrix played an essential role in the preparation of polymer/multi-walled carbon nanotube nanocomposites based on interfacial interaction between multi-walled carbon nanotubes and polymer matrix. Field emission-scanning electron microscopy images revealed good dispersion of filler and adhesion of matrix on the surface of multi-walled carbon nanotubes. Accordingly, increasing the amount of multi-walled carbon nanotubes from 1 to 5 wt% increased the electrical conductivity from 2.42 to 4.11 S cm−1. Percolation behavior of the composite was also studied. Tensile modulus for 1 wt% nanocomposite was 4.2 GPa, which increased up to 6.8 GPa on 5 wt% filler addition. A relationship between nanotube loading and thermal stability of the materials was also observed. Ten percent gravimetric loss increased from 502℃ to 538℃ in the presence of 1 wt% multi-walled carbon nanotube. Similarly, glass transition increased from 227℃ to 245℃ in the presence of 5 wt% multi-walled carbon nanotube. Enhancement of the physical properties of multi-walled carbon nanotube-reinforced polymer nanocomposites was accredited to the non-covalent interactions (π–π interactions and secondary bond forces).

The nanocomposites of polythiophene and carboxylated multiwalled carbon nanotubes (MWCNTs) were synthesized by in-situ chemical oxidative polymerization method using anhydrous ferric chloride (FeCl3) as an oxidant. The MWCNTs functionalized and ultrasonicated to obtain uniform dispersion within the polythiophene matrix. Field emission scanning electron microscopy was used to characterize the morphology of the nanocomposite. X-Ray diffraction, Fourier Transform Infrared Spectroscopy, Raman spectroscopy, and thermogravimetric analysis were used to characterize the synthesized MWCNT-polythiophene nanocomposites. It was found that in-situ polymerized polythiophene layer matrix was formed on carboxylated MWCNT and there was uniform dispersion of MWCNTs within the polythiophene matrix with significant interaction between polythiophene and MWCNTs. The sensitivity response of the prepared MWCNT-polythiophene nanocomposite sensors was studied in using Ammonia gas. The synergistic effects of the polythiophene-coated MWCNTs improve the gas sensing properties. Results showed that the sensitivity increased with ammonia concentration and it is also affected by the MWCNT content in polythiophene matrix. Furthermore, the sensor in pellet form reported here is robust, cost effective, and relatively stable at room temperature.

The effect of different types of multiwall carbon nanotubes (MWCNTs) on the morphological, magnetic and viscoelastic properties of magnetorheological elastomers (MREs) are studied in this work. A series of natural rubber MRE are prepared by adding MWCNTs as a new additive in MRE. Effects of functionalized MWCNT namely carboxylated MWCNT (COOH-MWCNT) and hydroxylated MWCNT (OH-MWCNT) on the rheological properties of MREs are investigated and the pristine MWCNTs is referred as a control. Epoxidised palm oil (EPO) is used as a medium to disperse carbonyl iron particle (CIP) and sonicate the MWCNTs. Morphological and magnetic properties of MREs are characterized by field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM), respectively. Rheological properties under different magnetic field are evaluated by using parallel plate rheometer. From the results obtained, FESEM images indicate that COOH-MWCNT and CIP have better compatibility which leads to the formation of interconnected network in the matrix. In addition, by adding functionalized COOH-MWCNT, it is shown that the saturation magnetization is 5% higher than the pristine MWCNTs. It is also found that with the addition of COOH-MWCNT, the magnetic properties are improved parallel with enhancement of MR effect particularly at low strain amplitude. It is finally shown that the use of EPO also can contribute to the enhancement of MR performance.

Due to the strong hydrophobic and van der Waals interactions between individual carbon nanotubes (CNTs), these particles easily aggregate with themselves. When CNTs were introduced into a polymer matrix as a filler, aggregations formed that can adversely affect the mechanical and thermal properties of polymer/CNTs composites. To prevent aggregation, covalent functionalizations via chemical treatments using H₂SO₄/HNO₃, H₂O₂/H₂O and a silane coupling agent(STX)-glycidoxypropyltrimethoxysilane, GPTMS) on the CNTs were chosen in this study. Moreover, the effect of the functional groups on the solubility of CNTs in tetrahydrofuran (THF) was investigated. The surface-modified multi-walled carbon nanotubes (MWCNTs) were also characterized and compared with pristine MWCNTs using several techniques. Morphology changes in surfacemodified MWCNTs were observed by Raman spectroscopy and Field-Emission Scanning Electron Microscopy (FE-SEM) images. Qualitative analyses of the functional groups on the surface-modified MWCNTs were performed by Fourier Transform Infrared Spectroscopy (FT-IR). Additionally, quantitative analyses were performed by X-Ray Photoelectron Spectroscopy (XPS), Energy Dispersive Spectroscopy (EDS), a titration method and Thermogravimetric analysis (TGA).

Polyvinyl alcohol wrapped multiwall carbon nanotube (MWCNTs) network on fabrics for wearable room temperature ethanol sensor

Investigation on production and characterization of bionanocomposites based on surface functionalized multi-walled carbon nanotubes and optically active poly(ester-imide) having L-isoleucine units

Electrically conducting nanofibers based on cellulosic materials offer cheap and safe class of materials that can be used for water desalination. In the present work, high conducting cellulose triacetate (CTA) nanofibers containing multiwall carbon nanotubes (MWCNTs) with very low percolation threshold concentration (0.014 wt%) were produced by electrospinning. Unprecedentedly, a hydrophilic ionic liquid consists of 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) was used to dissolve CTA producing a solution of 10 wt%. This CTA solution was used to engineer both bare CTA nanofibers and CTA nanofibers impregnated with MWCNT. The fabricated nanofibers were characterized by the field emission-scanning electron microscopy (FE-SEM) and the high-resolution transmission electron microscopy (HR-TEM). Both FE-SEM and HR-TEM images showed that the MWCNTs were inserted and uniformly distributed inside electrospun nanofibers. Furthermore, mechanical properties such as tensile strength of MWCNTs loaded-CTA electrospun nanofibers was significantly improved by up to 280 % and 270 % for the Young modulus, when compared with the bare CTA fibers. In addition, the surface properties as the hydrophilicity of electrospun nanofibers membrane was enhanced due to the presence of MWCNTs. Moreover, the electrical conductivity of MWCNT loaded-CTA electrospun nanofibers was greatly enhanced after the implementation of the MWCNTs inside the CTA fiber. The performance of composite nanofiber for water desalination was examined in a lab-scale classic capacitive deionization (CDI) unit, at different concentrations of salt. The obtained data revealed that the electro-adsorption of anions and cations on the surface of MWCNTs loaded-CTA electrospun nanofibers electrodes were monitored with time and their concentration were decreased progressively with time and reaches equilibrium.

Improved mechanical properties of NbC-M2 high speed steel-based cemented carbide by addition of multi-walled carbon nanotubes

The oxygenation of multi-wall carbon nanotubes (MWCNTs) was performed via a radio frequency dielectric barrier discharge (RF-DBD) in an Ar/ plasma mixture. The relative intensity of the Ar/ plasma species was characterized by optical emission spectroscopy (OES). The effects of treatment time, RF power and oxygen gas percentage on the chemical composition and surface morphology of MWCNTs were investigated by means of x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and field emission scanning electron microscopy (FE-SEM). The results of FTIR and XPS revealed the presence of oxygen-containing functional groups on the MWCNTs treated in an Ar/ plasma at an RF power of 50 W and pressure of 400 Pa. The amount of oxygen functional groups (C=O, C–O, and O–COO) also increased by increasing treatment time up to 6 min, but slightly decreased when treatment time was increased by 10 min. The increase of oxygen gas percentage in the plasma mixture does not affect the oxygen content in the treated MWCNTs. Meanwhile, MWCNTs treated at high power (80 W) showed a reduction in oxygen functional groups in comparison with low RF power conditions. The Raman analysis was consistent with the XPS and FTIR results. The integrity of the nanotube patterns also remained damaged as observed by FE-SEM images. The MWCNTs treated in RF-DBD using the Ar/ plasma mixture showed improved dispersibility in deionized water. A correlation between the OES data and the observed surface characterization for an improved understanding of the functionalization of MWCNTs in Ar/ plasma was presented.

Electrically conductive nanocomposites polymer of poly(vinyl alcohol)/PVA, glutaraldehyde (GA) and multiwalled carbon nanotubes (MWCNT) has been successfully synthesized. The polymer nanocomposites were prepared by mixing PVA, GA (crosslinker), and MWCNT dispersion with an aid of ultrasonic homogenizer at 50 °C. The content of MWCNT, in particular, was varied in order to determine the effect of MWCNT on electrical conductivity of polymer composites. The polymer mixture was casted into a disc to obtain thin film. The electrical conductivity, surface morphology, and mechanical properties of the composites film were investigated by means of four probes method, FTIR spectroscopy, X-ray diffraction, SEM, AFM, and tensile strength measurement, respectively. It was found that the optimum composition of PVA (10%): GA (1%): MWCNT (1%) was 20:20:3 in volume ratio. The addition of MWCNT induced the electrically conductive network on polymer matrix where the electrical conductivity of nanocomposites film significantly increased up to 8.28 x 10-2 S/sq due to reduction of the contact resistance between conductive filler. Additionally, the mechanical strength of nanocomposites polymer were significantly increased as a result of MWCNT addition. Modification of morphological structure of composite film as indicated by FTIR spectra, X-ray diffraction patterns, SEM, and AFM images verified the effective MWCNT filler network in the polymer matrix.

This study focuses on the electrical properties of polycarbonate (PC)/poly(ε-caprolactone) (PCL)-multiwall carbon nanotube (MWCNT) nanocomposites. MWCNTs were incorporated into thermoplastic PC matrix by simple melt blending using biodegradable PCL based concentrates with MWCNT loadings (3.5 wt%). Because of the lower interfacial energy between MWCNT and PCL, the nanotubes remain in their excellent dispersion state into matrix polymer. Thus, electrical percolation in PC/PCL-MWCNT nanocomposites was obtained at lower MWCNT loading rather than direct incorporation of MWCNT into PC matrix. AC and DC electrical conductivity of miscible PC/PCL-MWCNT nanocomposites were studied in a broad frequency range, 101−106 Hz and resulted in low percolation threshold (pc) of 0.14 wt%, and the critical exponent (t) of 2.09 from the scaling law equation. The plot of logσDC versus p−1/3 showed linear variation and indicated the existence of tunneling conduction among MWCNTs. At low MWCNT loading, the influence of large polymeric gaps between conducting clusters is the reason for the frequency dependent electrical conductivity. Transmission electron microscopy and field emission scanning electron microscopy showed that MWCNTs were homogeneously dispersed and developed a continuous interconnected network path throughout the matrix phase and miscibility behavior of the polymer blend. POLYM. ENG. SCI., 54:646–659, 2014. © 2013 Society of Plastics Engineers

In this article, we present the morphology and properties of core-shell nanocomposites of poly(N-vinyl carbazole) (PNVC) with multi-walled carbon nanotubes (MWCNTs). Nanocomposites were synthesized by the in situ solid-state polymerization of N-vinylcarbazole (NVC) at an elevated temperature in the presence of MWCNTs. Fourier transform infrared (FTIR) studies confirmed the ability of MWCNTs to initiate the in situ polymerization of NVC monomers and the presence of PNVC polymer in the nanocomposites. X-ray photoelectron spectroscopy (XPS) studies supported the FTIR results. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images showed the homogeneous covering of MWCNTs outer surfaces by PNVC matrix. The Raman spectroscopy studies also revealed the homogeneous wrapping of MWCNTs outer surfaces without disturbing the inherent electronic structure of MWCNTs. Thermogravimetric analyses revealed a significant improvement of thermal stability of the nanocomposites in the higher temperature region. The core-shell nanocomposites showed interesting fluorescence properties. The dc (direct current) electrical conductivity of pure PNVC dramatically improved after nanocomposites formation with MWCNTs and degree of improvement was dependent on the loading of MWCNTs in the nanocomposites. For example, dc electrical conductivity increased from 10(-16)-10(-12) S x cm(-1) for pure PNVC to approximately 12 S x cm(-1) for nanocomposite containing 50 wt% MWCNTs.

A series of polycarbonate (PC)/acrilonitrile butadiene rubber (NBR)/multi-wall carbon nanotube (MWCNT) nanocomposites were prepared via melt compounding in an internal mixer. The effect of the MWCNT content on the morphology and the thermal and mechanical properties of the prepared nanocomposites were studied. The morphologies of the samples were investigated by field-emission scanning electron microscopy (FESEM) and the thermal properties by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The tensile mechanical results of the nanocomposites showed a decrease in elongation at break with an increase of only 2 wt% of MWCNT content in the PC/NBR blends, and an increasing value in elastic modulus and tensile strength of the nanocomposites. The FESEM images showed that the MWCNTs had good affinity with the polymers and no compatibilizer was needed for making the nanocomposites. The DSC and TGA results showed an increase in thermal stability with addition of MWCNTs because of the more thermally stable carbon nanotubes particles which was uniformly dispersed within the nanocomposites.