Morphology Of Multiwalled Carbon Nanotubes Research Articles

Catalytic particles formation from thin nickel films for the synthesis of multi-walled carbon nanotubes

We have investigated the formation of a catalyst for the synthesis of multi-walled carbon nanotubes (MWCNT) using nickel-on-titanium thin films. Nickel decomposes into nanoparticles in the synthesis setup prior to MWCNT growing through the plasma enhanced chemical vapor deposition method. Oxidation and reduction of the catalyst are conducted to control the morphology of the formed nanoparticles array. In this case, the redox treatments required preventing the formation of silicides and Ti–Ni alloys are combined with the well-known effect of low-temperature disintegration (dewetting) of thin films. Detailed studies using a combination of Auger, atomic force, scanning (SEM), and transmission electron microscopy (TEM) show the interaction of metals on a silicon substrate, the influence of treatments parameters on the catalyst's state. The features and morphology of MWCNT synthesized on the obtained catalysts were studied via Raman spectroscopy, SEM and TEM. Overall, showing a link between the catalyst formation process and MWCNT growth, we demonstrate a technological and versatile method for controlling of nanotube growth for various applications.

Effect of functionalization and Li-doping methods to hydrogen storage capacities of MWCNTs

One of the most important problems of today has been found alternative and renewable energy sources to fossil fuels. Hydrogen comes to the fore because it is abundant, does not cause environmental problems, and can be stored when not in use. Furthermore, compared to fossil fuels, hydrogen has the highest energy density. However, the most important obstacle to the use of hydrogen energy is its transportation and storage. In this study, the functionalized multi-walled carbon nanotubes were first produced from multi-walled carbon nanotube (MWCNT) by different chemical reactions and, then Li-doped MWCNTs and Li-doped functionalized MWCNTs by solvent and hydrothermal methods. Samples were characterized using Brunner–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FTIR), differential thermal analysis/thermogravimetry (DTA/TG), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Finally, the hydrogen storage capacities of all samples were measured using IMI PSI gas storage instrument. New bands belonging to functional groups were observed in the FTIR-ATR spectrum of MWCNT. Functionalized MWCNTs degraded at different temperatures and steps. SEM images showed that the changes in the morphology of MWCNT with functionalization and Li-doping occured. The linear behavior observed in the Nyquist plots showed that the electrochemical process was controlled by ion diffusion. Raman analysis showed that while there was no significant change in the position of the Raman bands. While the BET surface area of MWCNT decreased with functionalization, an increase in its hydrogen storage capacity was observed in general. The hydrothermal method was more effective than the solvent method and functionalization in increasing the hydrogen storage capacity of MWCNT. All samples had higher hydrogen storage capacity at cryogenic temperatures. Li-doped MWCNT by hydrothermal method had the highest hydrogen storage capacity at 80 bar and 77 K, and its storage capacity value was 2.85 wt%. While the isotherm curves obeyed Henry’s law at room temperature, they exhibited multilayer adsorption behavior at cryogenic temperatures. The adsorption process was physical and isotherm type was Type IV.

Ultrasmall platinum nanoparticles synthesized in reline deep eutectic solvent explored towards the voltammetric sensing of riboflavin in beverages and biological fluids

We report a solvothermal synthesis of ultrasmall platinum nanoparticles (USPtNPs) with an average size of 0.204 ( ± 0.008) nm using reline deep eutectic solvent (DES) as a stabilizing medium at a temperature of 80 ºC. SEM and EDS were used to morphologically characterize the USPtNPs. These revealed approximately spherical shapes with emission lines characteristic of platinum. DES was characterized by FT-IR and NMR, which indicated its formation through hydrogen bonds between the precursors. DSC was also used to characterize the precursors and the formed DES. Furthermore, an electrochemical sensor for determining riboflavin (RB) in commercial energy drinks and biological fluids was developed using the USPtNPs together with multiwalled carbon nanotubes (MWCNT). The USPtNPs-DES/MWCNT/GCE film was characterized by SEM, which demonstrated the characteristic tubular morphology of MWCNT. The RB voltammetric response was studied, and a significant enhanced on the current response was observed, especially due to the USPtNPs. This sensor displayed a linear response for RB in the range of 0.02–1.2µmol L−1, with a limit of detection of 1.8 nmol L−1. Besides detectability at nanomolar range, excellent performance was verified for repeatability and anti-interference features. The sensor based on extraordinary USPtNPs synthesized in DES in a simpler and environmentally friendly way was successfully applied to determine RB in different matrices.

MWCNTs polymer nanocomposite with enhanced thermomechanical properties and electrical insulation for effective encapsulation

This study presents the effect of the variation in weight fraction of multiwall carbon nanotubes (MWCNTs) in polymer with the objective of enhancing the thermo-mechanical properties along with the electrical insulating properties. Polymer multi-walled nanocomposites (PMWCNC) and MWCNTs/Al2O3 bi-layer nanocomposites were prepared by solution mixing method with ultrasonication and magnetic stirring, then molded in vertical sandwich molds, made of acrylic and aluminum sheet as per ASTM standards. The tensile strength of PMWCNC was enhanced by 32%, 23%, 15%, and 5% compared to unmodified epoxy with the incorporation of 1 wt%, 0.75 wt%, 0.5 wt%, and 0.25 wt% of MWCNTs. The dispersion morphology of MWCNTs in epoxy was observed with field emission-scanning electron microscope (FE-SEM). The thermogravimetric analyzer (TGA) investigation found that increasing the weight percentage of MWCNTs resulted in improved thermal stability. The enhanced electrical conductivity of PMWCNC caused by the addition of MWCNTs was countered through the deposition of a thin film layer of alumina-filled polymer nanocomposite on the top surface of PMWCNC to retain the electrical insulation properties. The representative volume element (RVE) technique was employed to predict the effective modulus of nanocomposite based on the various constituent properties, weight fractions and interfacial behavior between MWCNTs and epoxy with the help of finite element analysis. Additionally, Modified Mori-Tanaka (MMT) micromechanics scheme was used to find the effective elastic modulus of the nanocomposite with the help of the MATLAB code. The elastoplastic behavior of polymer nanocomposites was also simulated in ANSYS APDL through the Voce model. The enhanced thermomechanical properties while retaining the electrical insulation properties suggest that the MWCNTs-based polymer would make the electronic chip more reliable.

Diamine Oxidase-Conjugated Multiwalled Carbon Nanotubes to Facilitate Electrode Surface Homogeneity.

Carbon nanomaterials have gained significant interest over recent years in the field of electrochemistry, and they may be limited in their use due to issues with their difficulty in dispersion. Enzymes are prime components for detecting biological molecules and enabling electrochemical interactions, but they may also enhance multiwalled carbon nanotube (MWCNT) dispersion. This study evaluated a MWCNT and diamine oxidase enzyme (DAO)-functionalised screen-printed electrode (SPE) to demonstrate improved methods of MWCNT functionalisation and dispersion. MWCNT morphology and dispersion was determined using UV-Vis spectroscopy (UV-Vis) and scanning electron microscopy (SEM). Carboxyl groups were introduced onto the MWCNT surfaces using acid etching. MWCNT functionalisation was carried out using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-Hydroxysuccinimide (NHS), followed by DAO conjugation and glutaraldehyde (GA) crosslinking. Modified C-MWNCT/EDC-NHS/DAO/GA was drop cast onto SPEs. Modified and unmodified electrodes after MWCNT functionalisation were characterised using optical profilometry (roughness), water contact angle measurements (wettability), Raman spectroscopy and energy dispersive X-ray spectroscopy (EDX) (vibrational modes and elemental composition, respectively). The results demonstrated that the addition of the DAO improved MWCNT homogenous dispersion and the solution demonstrated enhanced stability which remained over two days. Drop casting of C-MWCNT/EDC-NHS/DAO/GA onto carbon screen-printed electrodes increased the surface roughness and wettability. UV-Vis, SEM, Raman and EDX analysis determined the presence of carboxylated MWCNT variants from their non-carboxylated counterparts. Electrochemical analysis demonstrated an efficient electron transfer rate process and a diffusion-controlled redox process. The modification of such electrodes may be utilised for the development of biosensors which could be utilised to support a range of healthcare related fields.

Optimization of thin polystyrene waste embedded multiwall carbon nanotubes (MWCNT) film for solid electrolyte of flexible dye-sensitized solar cell (DSSC)

The consumption of organic solvent in a conventional liquid-based electrolyte give rise to the solvent’s evaporation, hermetic sealing of the cell as well as lack of cell durability. In order to avoid fluidity and potential leakage, the composite polymer-based electrolyte has been investigated. Thus, the main objective of this study is to develop thin polystyrene waste embedded multiwall carbon nanotube (MWCNT) film with improving electrochemical properties as electrolyte host for flexible DSSC application. In this study, the MWCNT will be functionalized with carboxyl group using sulfonitric solution. Transmission electron microscope (TEM) were used to evaluate the morphology of MWCNT. Different weight percentage of the functionalized MWCNT were embedded into the polystyrene and their effect on the morphology, and uniformity of the thin polymer films were analysed using field emission electron microscope (FESEM). The electrochemical properties of the prepared polystyrene embedded MWCNT based polymer electrolyte were studied using electrochemical impedance spectroscopy (EIS). The finding shows that the optimum loading of MWCNTs in the thin polystyrene waste embedded MWCNTs film is 0.003 g. These composition exhibits the highest ionic conductivity and the lowest resistance. Further increase in the amount of MWCNTs results in reducing the ionic conductivity due to the percolation network of the MWCNT with the polystyrene.

Investigation of high temperature vulcanized and room temperature vulcanized silicone rubber based on flexible piezo‐electric energy harvesting applications with multi‐walled carbon nanotube reinforced composites

AbstractFlexible energy harvester can be able to produce continuous voltage output under the mechanical deformations. High temperature vulcanized (HTV) and room temperature vulcanized (RTV) silicone rubbers are used for making the flexible piezo‐electric energy harvester. A total of 1 and 2 phr of multi‐walled carbon nanotube (MWCNT) are used as the electrode material mixed with the rubber solution for the preparation of flexible electrode. Cyclic loading machine is used for the application of 2 Hz of bi‐axial load and uniaxial compression load in the specimen. One centimeter depth of displacement is applied during the bi‐axial cyclic loading and 4 mm amplitude of displacement is applied during the compression loading. Tensile and compression tests are performed to determine the engineering properties of the material. Tensile load withstanding value of the silicone rubber is increasing as increasing the MWCNT filler in the rubber. Tensile value of the pure HTV silicone rubber is 10.020 N and for 2 phr MWCNT reinforced rubber is 22.106 N. Compressive withstanding load of pure HTV rubber is 189.565 N and for 2 phr MWCNT reinforced rubber is 287.066 N. HTV silicone rubber is the highly stiffness material on compares with RTV rubber based on the tensile and the compressive value. Transmission electron microscopy, optical micrographs, and scanning electron microscope show the morphology of MWCNT and surface image of specimen. A total of 2 mm substrate based 2 phr MWCNT reinforced HTV flexible energy harvester undergo decrease in voltage during the cyclic loading due to breakage of electrode. A total of 2 phr MWCNT electrode‐based sample can be able to produce more output voltage than 1 phr MWCNT electrode‐based sample during bi‐axial and compression loading. More voltage is produced in the compression specimen than bi‐axial one.

Synthesis and characterization of catalytic CVD growth pristine and functionalized MWCNT

The catalyzed CVD method is considered significant for the production of low cost and high yield carbon nanostructures. In this study, multiwall carbon nanotubes (MWCNTs) were synthesized using a facile and efficient way with the modified CVD method, using Co nanoparticles as the metallic catalysis for MWCNT growth, in a distinct temperature range of 650–750 °C. The structural and magnetic properties of pristine and functionalized MWCNT (p-MWCNT and f-MWCNT) are investigated in the temperature range of 10–300 K. The phase structure of all MWCNT samples was analyzed using various characterization techniques, namely, x-ray diffraction, Raman, and x-ray photoelectron spectroscopy. Scanning electron microscopy and particle size analysis suggested that the diameter of MWCNTs increases with a rise in the growth temperature, but the nanotube density decreases at 750 °C. Temperature-dependent magnetization studies of the p-MWCNT and f-MWCNT samples were investigated using a quantum design physical property measurement system-vibrating sample magnetometer mode. The magnetic properties and the effect of the growth temperature and acid functionalization on the morphology of MWCNT were also investigated. The results revealed that the diamagnetism effect of the graphitic nanotubes is dominating for p-MWCNT, and it reduces for f-MWCNT. A possible explanation for this feature is discussed in detail in the later part of this article. It may be considered that this study, which emerged with different growth temperatures of MWCNTs using a facile method for gaining control over magnetic properties, can be fundamental for further consideration of magnetic MWCNTs for various potential applications.

Influence of dispersion technique/time on dispersion stability, aspect ratio and morphology of multi-walled carbon nanotubes

Current interest in nanoscience and nanotechnology has motivated a remarkable research effort in carbon nanotubes (CNTs), which has addressed a variety of issues and produced several new findings. The uniform and stable dispersion of CNTs in solvents/nanocomposites is often a necessity for their effective use in advanced materials. In this study, the dispersion states of multiwalled carbon nanotubes (MWCNTs) in numerous solvents were analysed by UV-vis spectroscopy and visual observations (photographic images). Furthermore, the influence of sonication and ball milling time on the MWCNT morphology and dispersion was analysed through scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that the MWCNT was highly dispersible in DMF, isopropanol, chloroform and acetone, and the dispersion state of MWCNT in these solvents can be classified as dispersed. The obtained results indicate that the oxidation incorporates oxygen-containing groups on the surface of MWCNTs, which establish the electrostatic stability needed for long-period stable dispersion in solvents. Morphological investigation of MWCNTs shows less than 20 min of dispersion is insufficient to achieve untangled CNTs with good dispersion, while 20-60 min of dispersion demonstrates CNTs bonding, intersections, junctions and number of defects on MWCNTs due to high energy involved. Apart from this, significant MWCNT shortening has been observed for the dispersion period of 90 min-6 h. The investigation of the dispersibility of MWCNTs in different solvents and the effect of sonication and ball milling time on the MWCNT morphology and dispersion are important for enhancing the comprehensive understanding of its applications.

Electrically Conductive Composite based on Functionalized Carbon Nanotubes/Epoxy Resin

This work is devoted to the study of the effect of carbon nanotubes functionalization on the electrical conductivity of composite materials based on them. Carbon nanotubes were functionalized by treatment in nitric acid and isopropyl alcohol. Changes in the morphology of multi-walled carbon nanotubes during liquid-phase functionalization were investigated using Auger-electron microscopy. Samples of composite material on the basis of initial and functionalized carbon nanotubes and epoxy resin were prepared and the concentration dependence of electrical conductivity using the four-probe method was studied. The study reveals the effect of functionalization in various solutions on the electrophysical properties of the obtained carbon nanotubes/epoxy composites.

Green synthesis of ZnO nanoparticles decorated on polyindole functionalized-MCNTs and used as anode material for enzymatic biofuel cell applications

Presently, one of the most important aspects for the development of enzymatic biofuel cells (EBFCs) is to synthesize the novel electrode materials that possess high current density, low open-circuit voltage (OCV) and long-term stability. To achieve the above attributes, lots of new strategies are being used by the researchers for the development of advanced materials. Nowadays, nanomaterials and nanocomposites are the promising material that has been utilized as effective electrode material in solar cells, supercapacitors and biofuel cells application. Herein, we account for a novel electrocatalyst as electrode material that comprised ZnO nanoparticles decorated on the surface of polyindole (PIn)-multi-walled carbon nanotube (MWCNT), for the immobilization of glucose oxidase (GOx) enzyme and mediator (Ferritin). The PIn-MWCNT scaffold is prepared via in situ chemical oxidative polymerization of indole on the surface of MWCNT and assessed by myriad techniques. The micrograph of scanning electron microscopy (SEM) designated the interconnected morphology of MWCNTs in the polymer matrix. X-ray diffraction spectroscopy (XRD) and Fourier transform infrared spectroscopy (FTIR), confirm the crystallinity and different functional groups available in the synthesized material, respectively. The electrochemical assessment demonstrates that the ZnO/PIn-MWCNT/Frt/GOx nanobiocatalyst exhibits much higher electrocatalytic activity towards the oxidation of glucose with a maximum current density of 4.9 mA cm−2 by consuming 50 mM glucose concentration in phosphate buffer saline (PBS) (pH 7.4) as the testing solution by applying 100 mVs−1 scan rates. The outcomes reflect that the as-prepared ZnO/PIn-MWCNTs/Frt/GOx biocomposite is a promising bioanode for the development of EBFCs.

Preparation and characterization of carbon nanotubes by pulsed laser ablation in water for optoelectronic application

Abstract In the present work, preparation of multi-walled carbon nanotubes (MWCNTs) and carbon nanoparticles (CNPs) by using pulsed laser ablation of a graphite target in water without using catalyst was demonstrated. The effect of laser wavelength on the optical absorption and structural properties has been studied. X-ray diffraction (XRD) data shows the synthesized CNTs were polycrystalline and a peak related to the diamond structure was observed. Scanning electron microscope (SEM) investigation displays that the average diameter of CNTs synthesized with 532 nm was 20 nm and few micrometers in length, while the CNTs synthesized with 1064 nm have an average diameter of 75 nm and lengths of few sub-micrometers. Some of CNPs were noticed to deposit on the CNTs. Transmission electron microscope (TEM) was used to study the morphology of MWCNTs. Raman spectra confirm formation of MWCNTs during the presence of three peaks belonged to D-band, G-band and 2D-band. The intensity ratio of IG/ID is larger than unity for MWCTs prepared by two laser wavelengths. The colloidal MWCNTs prepared by 532 nm laser pulses showed higher absorption than that of MWCNTs prepared with 1064 nm. The current-voltage characteristics and responsivity of hybrid In/p-MWCNTs/n-Si heterojunction photodetectors prepared at different CNTs film thicknesses were investigated at room temperature. The responsivity of hybrid MWCNTs/n-Si photodetector has two peaks of response, the first peak was found at 650 nm and the second peak located at 850 nm. The maximum responsivity was 0.53 A/W at 532 nm was found for the photodetector fabricated with 532 nm laser. The energy band diagram of MWCNTs/Si heterojunction was constructed under illumination condition.

A realistic study of 3D composition of carbon nanotubes and carbonaceous nanocompounds from different soils around coal power plant

Information on the effects of multi-walled carbon nanotubes (MWCNTs) on topsoil around coal power plants (CPPs) is still very limited. In the present work, the influences of MWCNTs on potential hazardous elements (PHEs) and environmental carbonaceous compounds in agrarian topsoil around CPPs of Latin America were investigated. The environmentally elevated proportions of MWCNTs and PHEs can cause damage to developing a fetus. The ecological impacts of industrial energy byproducts generated by MWCNTs were also studied. The surface morphologies of MWCNTs and PHEs detected in topsoil samples were analyzed by advanced electron microscopy in a combination of energy dispersive X-ray spectroscopy (EDS). The alterations could be originated due to the different geophysical constituents and superficial structure, which in turn disturbed their geoavailability in studied topsoil. It was found that a large amount of MWCNTs and amorphous carbonaceous matters, which are responsible for adsorbing PHEs, existed in soils around CPPs. Hence, these findings could be used to better understand the geochemical properties of PHEs near CPPs.

Comprehensive study of effects of filler length on mechanical, electrical, and thermal properties of multi-walled carbon nanotube/polyamide 6 composites

In spite of active studies on multi-walled carbon nanotube (MWCNT)-incorporated polymer, MWCNTs of different thickness and lengths have been employed. Here, the effects of MWCNT morphology, specifically its length, on the mechanical, thermal, and electrical properties of MWCNT/polymer composites were examined in comparison with theoretical modeling. Field-emission scanning electron microscopy and micro-computed tomography observations revealed that short MWCNTs were dispersed more uniformly than long MWCNTs in a polyamide 6 (PA6) polymer. Correlation of this result with the tensile performance revealed that at low MWCNT concentrations the long-MWCNT/PA6 composite showed superior tensile properties since the effect of length was dominant. However, at high MWCNT concentrations, the short-MWCNT/PA6 showed superior tensile properties to the long-MWCNT/PA6 due to the better dispersion of the former. The thermal conductivity gradually improved with increasing MWCNT concentration, showing larger improvement for the long-MWCNT/PA6, while the electrical conductivity reached percolation threshold at 1 wt% for both MWCNTs.

Influence of the nanostructure of silica supports on the growth and morphology of MWCNTs synthesized by CCVD method

Abstract Due to the influence of its superficial physical parameters on the interaction with catalyst, mesoporous silica is commonly referred as suitable support to grow carbon nanotubes (CNTs) by catalytic chemical vapor deposition (CCVD) method. Faced with the various possibilities of applying nanostructured SiO2/CNTs composites, this work aims to evaluate and clarify the influence of the silica mesoporosity and morphology on the quality and amount of CNTs produced by CCVD process. Five different nanostructured silicas (n-SiO2) were produced by sol-gel method. Basically, four silica samples were synthesized with the addition of an acidic catalyst and one with a basic catalyst. Thermogravimetric analysis, Raman spectroscopy, transmission electron microscopy and scanning electron microscopy were used to characterize the silica supports and the as-grown CNTs produced in this work. The obtained results show differences in the morphology of the synthesized CNTs according to the physical properties of each n-SiO2. The mesoporous silica structure, due to different pore size distribution and volume, affected the interaction between the support and the catalyst, and, consequently, the quality and amount of the synthesized multi-walled carbon nanotubes (MWCNTs). Silica supports with either high mesopore volume, or high mesopore size, provide the highest quantities of as-grown CNTs materials. However, in terms of quality of as-grown CNTs, the supports with lower mesopores volume were more adequate to the MWCNTs synthesis. Nevertheless, the presence of pores with compatible size may have allowed an improved anchorage of catalyst particles inside these pores favoring the growth of CNTs with good quality.

Polyurethane hybrid membranes with confined mass transfer channels: The effect of functionalized multi-walled carbon nanotubes on permeation properties

Aiming to prepare pervaporation membranes with confined mass transfer channels, multi-walled carbon nanotubes (MWCNTs) with and without functionalization were incorporated into polyurethane (PU) polymer matrices. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and Raman spectroscopy were employed to explore the effect of functionalization on the morphologies of MWCNTs. The changes in the morphologies of the resulting PU hybrid membrane were then characterized by SEM, TEM, and XRD. Swelling-sorption and pervaporation experiments of benzene and cyclohexane were employed to evaluate the separation performances of various hybrid membranes. The results showed that the introduction of many oxygenated functional groups onto the MWCNT surfaces through functionalization not only efficiently inhibited the MWCNT aggregation but also improved the distributions of the MWCNTs in solvents and polymer materials. Due to the 1D tube structures of the MWCNTs with conjugated π bonds, the addition of well-distributed MWCNTs into the hybrid membranes not only increased the benzene sorption abilities of the membranes but also enhanced the benzene diffusion selectivities due to the strong driving force for the molecules in the confined mass transfer channels. A higher content of well-distributed MWCNTs in the membrane yielded a higher separation performance for benzene. Additionally, increasing the operating temperature in the pervaporation experiments accelerated the molecular motion and weakened the affinity between the benzene molecules and the walls of the MWCNTs, increasing the permeation fluxes of the membranes while decreasing the benzene separation factors.

PHBV/MWCNT Films: Hydrophobicity, Thermal and Mechanical Properties as a Function of MWCNT Concentration

The introduction of multi-walled carbon nanotubes (MWCNTs) into polymer matrixes has been an important tool to alter and improve some properties in polymer nanocomposites, including biodegradable polymers such as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). In this work, PHBV nanocomposites with 0.05, 0.50, 1.00, 1.50 and 2.00 wt % of MWCNTs were produced by solvent casting. MWCNT morphology and structure were characterized by Raman spectroscopy, and transmission electron microscopy (TEM). It was observed that MWCNTs have a considerable amount of amorphous carbon (AC) onto their surface and a wide distribution of the tube diameter. MWCNTs act as the nucleating agent in the PHBV matrix, as verified by differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) showed that thermal stability was not significantly affected. The nanofiller dispersion into the PHBV matrix was not effective for concentrations from 1 wt % according to the micrographs obtained in scanning electron microscopy (SEM). The contact angle was changed with the introduction of MWCNTs, turning the nanocomposites hydrophobic and improving the mechanical tensile properties of the PHBV matrix.

Direct growth of MWCNTs on modified stainless steel surface for flexible lithium ion batteries

Abstract Multi-walled carbon nanotubes (MWCNTs) were grown directly on a modified surface of stainless steel foil (304 SS) using thermal chemical vapor deposition (CVD). Before the MWCNT growth, the polishing procedure followed by the oxidation treatment on 304 SS was considered as a modified process. To understand the effects of this modification on the growth of MWCNTs, the as-received 304 SS and the polished 304 SS without oxidation treatment were further investigated for comparisons. Scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and X-ray diffraction were used to study the morphology of MWCNTs and their substrates. It was found that the good quality and the dense growth of MWCNTs were grown on the modified 304 SS. Furthermore, the electrochemical measurements were performed within 1M LiCl electrolyte to assess the possibility to use the MWCNTs coupled to 304 SS as electrode material. The optimum oxidation period for the representative capacitive behavior of MWCNTs grown on polished 304 SS is 45 seconds. This finding may lead to a pre-process for improving the MWCNTs grown on metal alloy substrates used for flexible electrode in lithium ion batteries (LIBs) and other flexible electrode works.

Continuous synthesis of aligned carbon nanotube arrays on copper substrates using laser-activated gas jet

A method has been developed for continuous synthesis of carbon nanotube (CNT) arrays on large-area metal substrates using a reactor that moves above the substrate surface with a given scan rate. The reagent vapors pass through the region of plasma laser discharge towards the substrate surface screened by an argon flow from the external atmosphere. Vertically aligned multi-walled CNTs (MWCNTs) are formed on copper as a result of decomposition of ethylene and the vapor of iron pentacarbonyl. The main parameters of laser plasma discharge, gas jets, and concentrations of feed compounds have been estimated in terms of their effect on the growth rate and MWCNT morphology. The measurements of MWCNTs/Cu field emission characteristics have been used to determine optimal synthesis parameters for the fabrication of effective field emission cathodes.

Salt and pH effect on thermoresponsive behavior of multiwalled carbon nanotube (MWCNT)/poly(N-vinylcaprolactam) dispersion

The influence of different salts and pH on the stability of the aqueous dispersion of multiwalled carbon nanotubes (MWCNTs) non-covalently modified by thermosensitive poly(N-vinylcaprolactam) (PVCL) was studied. The PVCL/MWCNT dispersion was prepared by adding MWCNTs into aqueous PVCL solution with the subsequent ultrasonication and centrifugation. The morphology of MWCNTs and MWCNT/PVCL composites was characterized by TEM. The aggregation temperatures of the MWCNT/PVCL dispersion and the lower critical solution temperature (LCST) of PVCL aqueous solution were determined for different salt types and concentrations as well as pH in the temperature range between 20 and 60 °C. Specific ion effect on LCST of PVCL was analyzed in terms of the Hofmeister series. In the presence of kosmotropes, both the MWCNT/PVCL dispersion aggregation temperature and the LCST of PVCL are well consistent with the Hofmeister series of ions. However, opposite trends were observed for LCST of PVCL and the MWCNT/PVCL dispersion aggregation temperature when adding chaotropic anions. The dynamic light scattering (DLS) technique was used to study the PVCL aggregation kinetics at a temperature above the LCST at different pH values. These results demonstrate that specific thermoresponsive properties of the MWCNT/PVCL dispersion at pH < 3 correlate with the behavior of the individual PVCL macromolecules in acid media above the LCST.