Multi-walled Carbon Nanotube Coatings Research Articles

Enhancing supercapacitor performance through design optimization of laser-induced graphene and MWCNT coatings for flexible and portable energy storage

The field of supercapacitors consistently focuses on research and challenges to improve energy efficiency, capacitance, flexibility, and stability. Low-cost laser-induced graphene (LIG) offers a promising alternative to commercially available graphene for next-generation wearable and portable devices, thanks to its remarkable specific surface area, excellent mechanical flexibility, and exceptional electrical properties. We report on the development of LIG-based flexible supercapacitors with optimized geometries, which demonstrate high capacitance and energy density while maintaining flexibility and stability. Three-dimensional porous graphene films were synthesized, and devices with optimized parameters were fabricated and tested. One type of device utilized LIG, while two other types were fabricated on LIG by coating multi-walled carbon nanotubes (MWCNT) at varying concentrations. Characterization techniques, including scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy, and voltammetry, were employed to analyze the fabricated devices. AFM analysis revealed a surface roughness of 2.03 µm for LIG due to laser treatment. SEM images displayed compact, dense, and porous surface morphology. XRD analysis confirmed the presence of graphene and graphene oxide, which was further supported by energy-dispersive X-ray spectroscopy (EDX) data. Raman spectroscopy indicated that the fabricated samples exhibited distinct D and G bands at 1362 cm–1 and 1579 cm–1, respectively. Cyclic voltammetry (CV) results showed that LIG's capacitance, power density, and energy density were 6.09 mF cm–2, 0.199 mW cm–2, and 3.38 µWh cm–2, respectively, at a current density of 0.2 mA cm–2. The LIG-MWCNT coated electrode exhibited a higher energy density of 6.05 µWh cm–2 and an areal-specific capacitance of 51.975 mF cm–2 compared to the LIG-based devices. The fabricated device has potential applications in smart electronics, nanorobotics, microelectromechanical systems (MEMS), and wearable and portable electronics.

Electrophoretic Deposition of Multi-Walled Carbon Nanotube Coatings on CoCrMo Alloy for Biomedical Applications.

Carbon nanotubes are a promising material for use in innovative biomedical solutions due to their unique chemical, mechanical, electrical, and magnetic properties. This work provides a method for the development of ultrasonically assisted electrophoretic deposition of multi-walled carbon nanotubes on a CoCrMo dental alloy. Functionalization of multi-walled carbon nanotubes was carried out by chemical oxidation in a mixture of nitric and sulfuric acids. The modified and unmodified multi-walled carbon nanotubes were anaphoretically deposited on the CoCrMo alloy in an aqueous solution. Chemical composition was studied by Fourier transform infrared spectroscopy. Surface morphology was examined by scanning electron microscopy. The mechanism and kinetics of the electrochemical corrosion of the obtained coatings in artificial saliva at 37 °C were determined using the open-circuit potential method, electrochemical impedance spectroscopy, and anodic polarization curves. The capacitive behavior and high corrosion resistance of the tested electrodes were revealed. It was found that the kinetics of electrochemical corrosion of the CoCrMo electrode significantly decreased in the presence of the functionalized multi-walled carbon nanotube coating. Electrophoretic deposition was shown to be an effective, low-cost, and fast method of producing nanotubes with controlled thickness, homogeneity, and packing density.

Electrochemical deposition multi-walled carbon nanotube coatings on the surface of Ti6Al4V alloy for enhancing its biotribological properties

Ti6Al4V alloys have potential applications as bone implants. However, their poor biotribological performances affected the service life. In this work, carboxylic multi-walled carbon nanotubes (CMWNT) coatings were grafted on the surface of Ti6Al4V alloys by electrochemical deposition for enhancing the biotribological properties. The CMWNT coatings showed lower coefficient of friction and wear rates, with the reduction of wear rates of 6% in dry condition and 90% under simulated body fluid (SBF) lubrication. This result might be ascribed to the transfer of friction behavior from sliding friction to rolling friction. In addition, the tribological regularity of CMWNT coating with the frequency and load were discussed. Under dry friction, with the increase of frequency and the decrease of normal load, the COF of the CMWNT coating decreased. In SBF lubrication, the COF decreased and the wear rate increased with the increase of frequency. Moreover, the excellent anti-wear properties were observed at the below of 10 N. These findings indicate that the CMWNT coating has an excellent protective effect on titanium alloy, and has a certain application potential in the biomedical field.

An experimental study of spectral radiative properties of multi-walled carbon nanotube coating for heat dissipation

Thermal management serves a crucial role in the stable operation of electronic equipment due to its miniaturization and functionality. Enhancing radiation heat transfer through heat dissipation coating is an effective method to improve the heat dissipation performance of electronic devices in thermal management of narrow space. In this paper, we employed the high emissivity property of multi-walled carbon nanotubes to improve the radiative heat dissipation performance of the coating. The effect of the distribution of multi-walled carbon nanotubes on the emissivity of the coating was studied with the finite-difference time-domain method. The emissivity of the coating with random distribution of multi-walled carbon nanotubes was found to be greater than that of the coating with vertical distribution of multi-walled carbon nanotubes. In order to further investigate the radiative properties of randomly distributed multi-walled carbon nanotube coatings, we experimentally investigated the effect of coating thickness and multi-walled carbon nanotube mass fraction on the spectral radiative properties of the coatings. We obtained the relationships between coating thickness, carbon nanotube mass fraction and coating radiation power. The data can provide some guidance for the regulation of radiation power of heat dissipation coatings and the selection of common coating processes. The maximum average emissivity and radiation power of the multi-walled carbon nanotube coating is 0.97, and 491.6 W m−2, respectively.

Biomass-Derived Carbon/Sulfur Composite Cathodes with Multiwalled Carbon Nanotube Coatings for Li-S Batteries

Lithium sulfur (Li-S) batteries stand out among many new batteries for their high energy density. However, the intermediate charge–discharge product dissolves easily into the electrolyte to produce a shuttle effect, which is a key factor limiting the rapid development of Li-S batteries. Among the various materials used to solve the challenges related to pure sulfur cathodes, biomass derived carbon materials are getting wider research attention. In this work, we report on the fabrication of cathode materials for Li-S batteries based on composites of sulfur and biomass-derived porous ramie carbon (RC), which are coated with multiwalled carbon nanotubes (MWCNTs). RC can not only adsorb polysulfide in its pores, but also provide conductive channels. At the same time, the MWCNTs coating further reduces the dissolution of polysulfides into the electrolyte and weakens the shuttle effect. The sulfur loading rate of RC is 66.3 wt.%. As a result, the initial discharge capacity of the battery is 1325.6 mAh·g−1 at 0.1 C long cycle, and it can still maintain 812.5 mAh·g−1 after 500 cycles. This work proposes an effective double protection strategy for the development of advanced Li-S batteries.

Influence of Far Infrared TiO2 and Multi-Walled Carbon Nanotubes Coatings on the Performance of a Hot Water Heater

This study selects titanium dioxide (TiO2) and multi-walled carbon nanotubes (MWCNTs) as far-infrared materials (FIRMs), and further adds water-based acrylic coatings to prepare far-infrared coatings (FIRCs). FIRCs are uniformly coated on #304 stainless steel sheets to make the test samples, which are then installed between the shell and insulation material of the hot water heater to measure the influences of various FIRCs on the performance of the hot water heater. The research results show no significant difference in the heating rate or heat insulation performance of the hot water heater with or without FIRCs coating. However, the uniformity of the water temperatures of the test samples is significantly improved with FIRCs. Considering that the uniformity of water temperature will inhibit the heating rate and heat insulation performance of the hot water heater, TiO2-FIRC should provide better performance improvement when applied to the hot water heater in this study. The application of TiO2-FIRC to large-scale hot water heaters with a high aspect ratio will effectively improve the quality of hot water supply in the future.

Biotribological properties of Ti-6Al-4V alloy treated with self-assembly multi-walled carbon nanotube coating

Ti-6Al-4V alloy has been widely applied in biomedical field due to its good biocompatibility, non-toxicity and excellent anti-corrosion. However, the poor tribological performance limits its application. In this paper, in order to enhance the biotribological properties of Ti-6Al-4V alloy, carboxylic multi-walled carbon nanotubes (CMWNT) coatings were grafted on the surface by chemical self-assembly technology. Raman spectroscopy and scanning electron microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDX) were utilized to characterize the microstructures of the coatings. The CMWNT coatings showed lower coefficient of friction and wear rates under dry sliding and simulated body fluid (SBF) lubrication. Furthermore, the biotribological mechanisms of CMWNT coatings under both conditions were discussed. Analyses of worn surfaces indicated that the rolling friction between the microtubes due to the spalling and fracture of CMWNT during the friction process was a major factor for improving biotribological behavior.

Carbon nanomaterials coatings – Properties and influence on nerve cells response

The goal of this study was to investigate the influence of multi-walled carbon nanotubes (MWCNTs) before and after chemical functionalisation, graphene oxide (GO), and hybrid coating deposited on a titanium (Ti) surface on the nerve cell response in vitro. The physicochemical properties of the surface of the carbon nanomaterial coatings deposited on the Ti substrate using electrophoretic deposition were investigated, followed by biological tests. Scanning and transmission electron microscopy and X-ray photoelectron spectroscopy were used to evaluate the microstructure and chemistry of the carbon nanomaterial coatings. Electrochemical characterisation of the carbon nanomaterial coatings on metal substrates was investigated using cyclic voltammetry and cathodic charge storage capacity. During in vitro analysis, all samples were placed in direct contact with human neuroblastoma SH-SY5Y cells. The viability were analysed after 48 and 72 h of culture. Moreover, the cell morphology in contact with the carbon nanomaterial coatings was observed using fluorescence microscopy. Additionally, the neurite outgrowth and number of pyknotic nuclei were examined using cell microphotographs.GO exhibited the best biological results among all analysed samples, with a positive effect on cell viability, neural cell morphology, and especially neurite outgrowth, and significantly improved the biological properties of the other hybrid (nanocomposite) coatings. GO coating is not an electrochemically active material, thus its applicability for the production of electrodes for nerve stimulation is limited. However, it may be useful as a scaffold for nerve cell stimulation and regeneration. The advantageous electrochemical activity of MWCNT coatings and a satisfactory cell response greater than the Ti surface alone will pave the way for further research on electrodes for nerve cell stimulation.

Formation of homogenous copper film on MWCNTs by an efficient electroless deposition process

Abstract In this study, copper-coated multi-walled carbon nanotubes (MWCNTs) were prepared using electroless deposition process with an efficient bath composition. As-received MWCNTs underwent acid treatment and subsequent sensitization with tin and activation with palladium before the copper coating process. The electroless deposition process was performed in a bath, which contained copper sulphate pentahydrate as a copper precursor, potassium sodium tartrate as a complexing agent, and formaldehyde as a reducing agent. Surface modifications of MWCNTs were studied by Fourier transform infrared spectroscopy, imaging techniques (scanning electron microscopy, transmission electron microscopy), and X-ray diffraction. On the basis of the results, it was observed that the coating layer covers most surfaces of the nanotubes. Furthermore, copper oxide is also deposited on the surfaces of MWCNTs. The total amount of metals after each sensitization, activation, and metallization step was determined by thermo gravimetric method and induced coupled plasma atomic emission spectroscopy. Coating of MWCNTs was accomplished successfully through adjusting proper chemical ratios and concentrations. The calculated bath efficiency was about 99%.

Super-hydrophobic multi-walled carbon nanotube coatings for stainless steel

We have taken advantage of the native surface roughness and the iron content of AISI 316 stainless steel to directly grow multi-walled carbon nanotube (MWCNT) random networks by chemical vapor deposition (CVD) at low-temperature () without the addition of any external catalysts or time-consuming pre-treatments. In this way, super-hydrophobic MWCNT films on stainless steel sheets were obtained, exhibiting high contact angle values () and high adhesion force (high contact angle hysteresis). Furthermore, the investigation of MWCNT films with scanning electron microscopy (SEM) reveals a two-fold hierarchical morphology of the MWCNT random networks made of hydrophilic carbonaceous nanostructures on the tip of hydrophobic MWCNTs. Owing to the Salvinia effect, the hydrophobic and hydrophilic composite surface of the MWCNT films supplies a stationary super-hydrophobic coating for conductive stainless steel. This biomimetical inspired surface not only may prevent corrosion and fouling, but also could provide low friction and drag reduction.

Recent Advances in Biofuel Cells: From Enzyme Immobilization to Implanted Devices

The ever-increasing depletion of fossil fuels and the need for clean methods of producing electricity have stimulated the emergence of abiotic and enzyme-based fuel cells that convert chemical energy into electrical energy at room temperature [1]. Taking into account that the interface activity was related to the immobilized amount of catalysts and the specific surface of the conductive substrate, 3D structures were designed via the use of carbon nanotubes as building block [2]. Carbon nanotubes exhibit nanowire morphology, biocompatibility and excellent conductivity. Furthermore, nanotube modified electrodes offer a large electroactive surface together with a highly porous three-dimensional structure. The recent advances in term of enzyme immobilization via functionalized films electropolymerized onto nanotube coatings will be described. For instance, the combination of carbon nanotube coating and electropolymerized photoreactive films constitutes an original strategy for the covalent immobilization of proteins by irradiation. We describe, here, the successful electrogeneration of a photoactivatable polypyrrole-diazirine film onto multi-walled carbon nanotube coatings and its use for the covalent binding of proteins [3].Moreover, the oriented immobilization of laccase on carbon nanotube was carried out to enhance the direct electron transfer. The possibility to functionalize carbon nanotubes by attaching specific docking sites for enzymes via electrogenerated polymer or pyrene derivatives exhibiting p-stacking interactions will be reported [4,5].We report also the first example of a glucose/H2O2 biofuel cell operating at 5 mM glucose under air (Figure 1). At a bienzymatic cathode, the direct wiring of horseradish peroxidase achieves the electrocatalytic reduction of H2O2 produced during the oxidation of glucose [6]. This represents a novel alternative to the use of laccases or bilirubin oxidases in conventional glucose/O2biofuel cells for implantable applications.Taking into account that conductive nanostructured materials such as carbon nanotubes became highly appropriate candidates for the elaboration of biofuel cells and electrochemical supercapacitors, we report here for the first time, the original combination of these two devices. The possibility to recharge supercapacitors with an internal energy source could thus represent a significant improvement for the performance of biofuel cells. In this context, we propose an original hybrid battery-capacitor system using a compression of enzymes-carbon nanotubes as supercapacitors and electrodes for a biofuel cell setup (Figure 1). This hybrid supercapacitor/biofuel cell enables high power discharge cycles, the carbon nanotube disks being continuously recharged through the biocatalytic energy conversion under physiological conditions [7].Figure 1: Schematic presentation of the functioning principle of a glucose-H2O2biofuel cell and scheme of the electrochemical double layer supercapacitor – biofuel cell hybrid system.

Biofunctionalization of Multiwalled Carbon Nanotubes by Irradiation of Electropolymerized Poly(pyrrole-diazirine) Films

A photoactivatable poly(pyrrole-diazirine) film was synthesized and electropolymerized as a versatile tool for covalent binding of laccase and glucose oxidase on multiwalled carbon nanotube coatings and Pt, respectively. Irradiation of the functionalized nanotubes allowed photochemical grafting of laccase and its subsequent direct electrical wiring, as illustrated by the electrocatalytic reduction of oxygen. Moreover, covalent binding of glucose oxidase as model enzyme, achieved by UV activation of electropolymerized pyrrole-diazirine, allowed a glucose biosensor to be realized. This original method to graft biomolecules combines electrochemical and photochemical techniques. The simplicity of this new method allows it to be extended easily to other biological systems.

The evaluation of the performance of two pyroelectric detectors with vertically aligned multi-walled carbon nanotube coatings

Two LiTaO3 pyroelectric detectors coated with vertically aligned multi walled carbon nanotube (MWCNT) black coatings were assembled and evaluated using NPL’s detector characterisation facilities. The vertically-aligned nanotube array (VANTA) black coatings were grown on a silicon substrate and subsequently lifted off the silicon and bonded on the pyroelectric crystal substrates. Despite some drawbacks, this method was shown to provide a reliable way of coating delicate substrates such as pyroelectric crystals with VANTA coatings. The performance of the coated and uncoated detectors was evaluated and compared by coating only half of the active area of the test detectors, leaving the other half uncoated. The relative spectral responsivity of the VANTA-coated pyroelectric detectors was shown to be spectrally flat in the 0.8–14μm wavelength range within the uncertainty of the measurements. The spatial uniformity of response of both detectors exhibited fine structure which was assigned either to the thickness of the VANTA coatings or to their bonding to the pyroelectric crystal. Both coated and uncoated detectors exhibited a super-linear response. This observation was expected in the case of the uncoated detectors, but was surprising in the case of the coated detectors and indicates that the thermal conductivity of vertically aligned multi-walled carbon nanotubes is high along their long axis. The spatial variations of the phase delay experienced by the signal propagating through the VANTA coatings indicate that the thermal diffusivity of the coatings is not spatially uniform.

Magnetron sputtering Si interlayer: A protocol to prepare solid phase microextraction coatings on metal-based fiber

Use of metal fibers in solid phase microextraction (SPME) can overcome the fragility drawback of conventional fused-silica ones. However, the surface modification of metal substrates is rather difficult, which largely prevents many mature traditional techniques, such as sol–gel and chemical bonding, being used in fabrication of SPME coating on metal-based fibers. This study demonstrates a protocol to resolve this problem by magnetron sputtering a firm Si interlayer on stainless steel fiber. The Si interlayer was easily modified active group, and attached with a multiwalled carbon nanotubes (MWCNTs) coating using the reported approach. The as-prepared MWCNTs/Si/stainless steel wire fiber not only preserved the excellent SPME behaviors of MWCNTs coatings, but also exhibited a number of advantages including high rigidity, long service life, and good stability at high temperature, in acid and alkali solutions. This new surface modification technique might provide a versatile approach to prepare sorbent coatings on unconfined substrates using traditional methods.

The effect of multi-walled carbon nanotube pretreatments on the electrodeposition of Ni–MWCNTs coatings

Two different chemical treatments were performed on multi-walled carbon nanotubes (MWCNTs), namely functionalization, and shortening-functionalization processes. Then, nickel–MWCNTs coatings were co-electrodeposited. The results showed that the chemically shortened nanotubes were behaved as inert particles, and embedded into the nickel matrix, whilst the long functionalized nanotubes showed metallic behavior and during electrodeposition, they were incorporated into the nickel matrix. In similar plating condition, the amount of co-deposited shortened nanotubes was more than elongated ones. Furthermore, it was revealed that the pretreatment of nanotubes significantly affected the microstructure, surface morphology, hardness and corrosion resistance of deposited coatings.

Multiwalled carbon nanotubes/ZnO nanowires composite structure with enhanced ultraviolet emission and faster ultraviolet response

We report on the fabrication of multiwalled carbon nanotubes (MWCNTs)/ZnO nanowires (NWs) composite structures obtained by coating the vertically grown ZnO NWs with a solution of MWCNTs, dispersed in 2-propanol. By increasing the number of coatings, a network of MWCNTs layer is formed. The composite structure shows enhanced ultraviolet emission and faster ultraviolet photoresponse time constants for multiple MWCNTs coatings ( n = 5 and 2) compared to the bare ZnO NWs. The enhanced emission and faster photoresponse are correlated with the MWCNTs mediated surface plasmon resonance effect and faster electron transfer between the ZnO and the MWCNTs, respectively.

Coating of multiwalled carbon nanotubes with polymer nanospheres through microemulsion polymerization

We report a simple and noncovalent method for coating multiwalled carbon nanotubes (MWCNTs) with polyaniline (PANI) nanospheres using a microemulsion polymerization method. In this method, aniline polymerization is performed with MWCNTs in the presence of sodium dodecyl sulfate (SDS), which serves as both a surfactant and a dopant. Morphological, structural, thermal, and electrical properties of MWCNT–PANI nanocomposites were analyzed. The TEM results of the nanocomposites prepared with surfactant reveal that 30–50-nm-diameter PANI nanospheres were coated on the surface of the MWCNTs. Composites prepared without surfactant were found to be in core–sheath-type cable structures. The conductivities of the nanocomposites synthesized through microemulsion polymerization were found to be one order of magnitude higher than both the conductivities of pure PANI and the composites prepared via in situ chemical polymerization without an assisting SDS surfactant. The mechanism for the formation of nanostructured composites is presented.

Electrochemical characterization of multi-walled carbon nanotube coated electrodes for biological applications

Carbon nanotubes, if used as a coating film on a conductive substrate, can substantially raise the charge storage capacity and lower the impedance of electrodes without significant increases to the geometric area. This is especially interesting in the case of stimulation of nervous tissue. We design implantable electrodes targeted at wide frequency stimulation of deep brain structures. Here we report on results in vitro with multi-walled carbon nanotubes coatings applied onto stainless steel substrates using direct current electrophoresis. We experimentally demonstrate, through electrochemical techniques such as cyclic voltammetry and impedance spectroscopy, the enhanced performance of multi-walled carbon nanotube (MWCNT) coatings for implantable electrodes by contrasting our experimental results against the more traditional stainless steel substrate characteristics. We also investigate surface morphology of aged electrodes. The interest in aged electrodes is dual fold: implantable electrodes have to be mechanically stable and present high shelf life. On the other hand, chemical modifications of the surface should be characterized. The effect of superficial oxygen adsorption on the aged MWCNT electrodes is observed through a modified cyclic voltammetric spectrum, but not through any changes in impedance spectroscopy.

Hydrophobic Coating of Multi-Walled Carbon Nanotubes by Using a HMDSO Glow Plasma under Low Pressure

Hydrophobic Coating of Multi-Walled Carbon Nanotubes by Using a HMDSO Glow Plasma under Low Pressure

Tandem Action of Early−Late Transition Metal Catalysts for the Surface Coating of Multiwalled Carbon Nanotubes with Linear Low-Density Polyethylene

The homogeneous surface coating of multiwalled carbon nanotubes with linear low-density polyethylenes, containing from 3 to 34 branches per 1000 carbon atoms, has been achieved for the first time by combining the polymerization-filling technique (PFT) with tandem copolymerization catalysis. This method, which takes advantage of the use of ethylene as single monomer feed, allows for the breakup of the native nanotube bundles and provides an effective way to control the branching in the PEs produced at the nanotube surface. TEM micrographs of the composite materials have shown an interesting dependence of the PE-coating morphology on the experimental parameters of the tandem system.