Deposition Of Carbon Nanotubes Research Articles

Co-laminar Microfluidic Microbial Fuel Cell Integrated with Electrophoretically Deposited Carbon Nanotube Flow-Over Electrode

Co-laminar Microfluidic Microbial Fuel Cell Integrated with Electrophoretically Deposited Carbon Nanotube Flow-Over Electrode

Electrophoretic deposition of carbon nanotubes on aluminium for capacitor application

ABSTRACT Multiwalled carbon nanotubes (MWCNT) were electrophoretically deposited from an environmentally friendly aqueous solution on aluminium current collectors which were carbon coated by physical vapour deposition. The carbon coating proved to be stable under electrophoretic deposition (EPD) conditions up to EPD voltage of U = 50 V and avoided any undesirable oxidation of the aluminium during the deposition process. The kinetics of the deposition was described and could be easily controlled by the suspension concentration and the deposition time. The deposition rate at U = 50 V is about 0.03 mg cm−2 min−1. As anodic oxide formation could be prevented the electrical contact to the current collector was improved allowing the surface area to be increased by MWCNT to be used as a double-layer capacitor. The gravimetric capacitance obtained was about 8 F g−1.

The control of ITO conductive coating relief via laser-oriented deposited carbon nanotubes

The paper presents the analysis of the surface relief of ITO conductive layers structured with single-walled carbon nanotubes. The deposition of ITO films and carbon nanotubes was carried out by laser-oriented method using a CO2 laser. The optical scheme was matched to the control electric grid; the strength of the electric field was varied in the range of 100–600 Vcm–1. To analyze the surface, atomic force microscopy in the contact mode and measurement of the wetting angle by sessile drop method was used. Roughness of pure ITO was about 1.8 nm, while in laser-vacuum deposition of carbon nanotubes, roughness varied from 6.4 nm to 22.1 nm with an increase in the electric field during deposition. The relationship between roughness and surface area of coatings and the wetting angle was considered. An increase in the wetting angle from 101.8 degrees, in the case of pure ITO, to 115.0-128.6 degrees, with the deposition of carbon nanotubes, was shown. The results obtained indicate an improvement in the resistance of ITO coatings to moisture during the deposition of carbon nanotubes, which makes it possible to expand their operating conditions and scope in optical electronics, laser and display technology.

A simple simulation-derived descriptor for the deposition of polymer-wrapped carbon nanotubes on functionalized substrates.

Controlling the deposition of polymer-wrapped single-walled carbon nanotubes (s-CNTs) onto functionalized substrates can enable the fabrication of s-CNT arrays for semiconductor devices. In this work, we utilize classical atomistic molecular dynamics (MD) simulations to show that a simple descriptor of solvent structure near silica substrates functionalized by a wide variety of self-assembled monolayers (SAMs) can predict trends in the deposition of s-CNTs from toluene. Free energy calculations and experiments indicate that those SAMs that lead to maximum disruption of solvent structure promote deposition to the greatest extent. These findings are consistent with deposition being driven by solvent-mediated interactions that arise from SAM-solvent interactions, rather than direct s-CNT-SAM interactions, and will permit the rapid computational exploration of potential substrate designs for controlling s-CNT deposition and alignment.

Machinability Performance Investigation of TiAlN‐, DLC‐, and CNT‐Coated Tools during Turning of Difficult‐to‐Cut Materials

Titanium alloy‐based components are now attracted by the industries with their distinguished properties even though they are difficult to machine. The tooling industries encounter numerous problems in machining these metals like higher tool wear, huge volumes of cutting fluid consumption, and shorter tool life. The objective of this research is to enhance the surface of the cutting tool with carbon nanotube (CNT) deposition to solve the aforementioned difficulties. This research used the plasma‐enhanced chemical vapor deposition method to coat CNT on high‐speed steel tools. Microstructural investigations were performed using a scanning electron microscope and a Raman spectroscopic technique to ensure the homogenous deposition of CNT. Additionally, scratch testing was also conducted to assess the adhesive strength of the deposited layer to the substrate. Finally, the machining performance of the CNT‐coated tool was compared with commercially available diamond‐like carbon (DLC) and titanium aluminum nitride (TiAlN)‐coated tools. Machining experiments conducted under three distinct cutting levels revealed that the CNT‐deposited tool is appropriate for turning more challenging materials. CNT‐coated tools showed substantial decreases in cutting tooltip temperature, turning forces, and tool wear compared to DLC and TiAlN‐coated tools. In particular, tool life studies conducted under elevated machining circumstances recorded the enhancement in tool life as 96.3% and 26.8% in comparison with TiAlN and DLC, respectively.

Effect of surfactant concentration on the evaporation-driven deposition of carbon nanotubes: from coffee-ring effect to strain sensing.

Carbon nanotubes (CNTs) as electrically conductive materials are of great importance in the fabrication of flexible electronic devices and wearable sensors. In this regard, the evaporation-driven self-assembly of CNTs has attracted increasing attention. CNT-based applications are mostly concerned with the alignment of CNTs and the density of CNT films. In the present work, we focus on the latter by trying to achieve an optimal evaporation-driven deposition with the densest CNT ring. Although surfactants are used for effective dispersion and colloidal stabilization of CNTs in the aqueous phase, their excessive usage induces Marangoni eddies in the evaporating sessile droplets, leading to poor ring depositions. Thus, there is an optimum surfactant concentration that contributes to CNTs deagglomeration and results in the densest ring-like deposition with relatively high thickness. We report that this optimum concentration for sodium dodecyl sulfate (SDS) as a surfactant can be approximately considered as much as the concentration of multi-walled carbon nanotubes (MWCNTs) as the colloidal nanoparticles. Optimal depositions show the lowest electrical resistances for each CNT concentration, making them suitable for electronic applications. We also propose the multiple depositions method in which a new droplet is printed after the complete evaporation of the previous droplet. This method can lead to denser rings with a higher conductivity using lower concentrations of CNTs. Lastly, we fabricate strain sensors based on the optimal evaporation-driven deposition of CNTs which show higher gauge factors than the commercial strain gauges, corroborating the applicability of our method.

Charge Manipulation Based Selective Functionalization of 3D Printed Structures for Functional Devices

AbstractAs a rapid prototyping technology, digital light processing (DLP)‐based 3D printing has prospect in electronics for its excellent molding speed and accuracy. Although complex and precise models can be obtained by the DLP‐based 3D printing, the functionalization of the printed models is still a challenge. Herein, a cost‐effective, efficient, and scalable approach based on the electrostatic interaction for the selective deposition of multiwalled carbon nanotubes (MWCNTs) on structures printed by DLP technique is reported. The structures are fabricated by alternatively DLP 3D printing of neutrally and positively charged resins, with positively charged resin for attracting MWCNTs with negative charges. The positive and negative charges come from the cationic groups incorporated into the polymer matrix and the anionic dispersant on the MWCNTs, respectively. By controlling the pH and concentration of the functional material dispersion, as well as the deposition time, the characteristics of the deposited functional materials, including thickness and conductivity, can be modulated. In addition, an all‐solid‐state supercapacitor is developed by this method, delivering a capacitance of 30 µF cm−2 and a good electrochemical stability.

Binder-free CoMn2O4/carbon nanotubes composite electrodes for high-performance asymmetric supercapacitor

This study presents the fabrication of supercapacitor electrodes composed of CoMn2O4 (CMO) nanosheets coated onto carbon nanotubes which are grown on a stainless-steel mesh (SSM). The synthesis includes chemical vapor deposition of carbon nanotubes (CNTs) on the SSM followed by annealing at 450 °C in air for 2 h in order to generate defects for further electrodeposition of CMO nanosheets. The electrodeposited CMO exhibits excellent pseudocapacitive performance owing to high oxidation potential of cobalt as well as the fast electron transportation ability of manganese. By controlling the deposition time of CMO, favorable morphology and excellent capacitance can be achieved. Furthermore, the direct growth of CMO on CNTs/SSM prevents the use of binders or additives and avoids undesired resistances. The binder-free CMO/CNT electrode exhibits a superior specific capacitance of 732 F/g at a scan rate of 2 mV/s. Furthermore, an asymmetric supercapacitor was fabricated by paring the CMO/CNT electrode with activated carbon as an anode. The asymmetric supercapacitor exhibits an energy density of 47.39 W/kg with a power density of 400 Wh/kg together with good stability of 77% capacitance retention after 5000 cycles, which suggest that the composite electrode is of great significance for practical energy storage devices.

Electrochemical Improvement of the MWCNT/Al Electrodes for Supercapacitors.

An original technique of chemical deposition (CVD) by catalytic pyrolysis of ethanol vapor was used to directly grow multiwall carbon nanotubes (MWCNTs) layers on aluminum foil. The grown nanotubes had excellent adhesion and direct electrical contact to the aluminum substrate. This material was perfect for use in electrochemical supercapacitors. In this work, the possibility of a significant increase in the specific capacity of MWCNTs by simple electrochemical oxidation was investigated. The optimal conditions for improving the characteristics of the MWCNT/Al electrodes were found. Electrochemical treatment of MWCNT/Al electrodes in a 0.005 M Na2SO4 solution at a potential of 4–5 V for 20–30 min increased the specific capacity of MWCNTs from 30 F/g to 140 F/g. The properties of modified nanotubes were investigated by X-ray photoelectron spectroscopy, cyclic voltammetry (CV), and impedance spectroscopy. A significant increase in the concentration of oxygen-containing functional groups on the surface of MWCNTs was found as a result of electrochemical oxidation. The modified MWCNT/Al electrodes maintained excellent stability to multiple charge–discharge cycles. After 20,000 CVs, the capacity loss was less than 5%. Thus, the results obtained significantly expanded the possibilities of using MWCNT/Al composite materials obtained by the method of direct deposition of carbon nanotubes on aluminum foil as electrodes for supercapacitors.

High-yield microplasma synthesis of monodisperse sub-3 nm diameter metal nanoparticles explained by a charge-mediated formation mechanism

The size and composition of nanoparticles are instrumental to many catalytic processes; for example, their controlled synthesis is key to achieving high yield and quality in aerosol chemical vapor deposition (CVD) of carbon nanotubes (CNTs). Using a custom-built atmospheric pressure DC microplasma reactor, we synthesize sub-3 nm iron nanoparticle aerosols at high number concentration (>109 #/cm3) with narrow size distribution (σg<1.3) from a ferrocene vapor precursor. We demonstrate precise diameter control down to 1.1 nm and maximum yield near unity. We invoke a charge-mediated formation mechanism to show that the ∼ 10 μs plasma residence time is sufficient to dissociate the precursor and partially ionize the resulting iron vapor, yet too short for the aggregation of clusters beyond 10 atoms. Thus, particle growth occurs primarily downstream of the plasma domain through aggregation of neutral and ionized vapor and clusters. This model closely reproduces the observed particle size distributions with the selection of an appropriate fractional ionization, yet is insufficient to entirely explain the rapid growth rate observed experimentally. This mechanism is different from that of existing microplasma processes, which have a longer residence time allowing particle formation to occur within the plasma, and may explain the demonstrated capability to co-optimize nanoparticle yield, throughput, and diameter control at a level exceeding the performance of previously published thermal and microplasma methods.

Enhanced microwave regeneration of a polymeric adsorbent through carbon nanotubes deposition

Microwave (MW) regeneration can be an effective alternative to conventional adsorbent regeneration methods; however, regeneration of MW-transparent adsorbents can be challenging. In this study, multiwall carbon nanotube (CNT) was used to enhance the MW absorption and regeneration of Dowex Optipore V503, a commercial hypercrosslinked polymeric adsorbent with low dielectric loss factor. CNTs were dispersed in sodium dodecyl sulfate solution and physically deposited on the surface of the adsorbent at different weight percent (wt %). On average, coating the adsorbent with 0.1 to 0.3 wt% of CNT resulted in a 3 to 24% decrease in its surface area. Dielectric properties measurement revealed a sharp increase in the loss factor from 0.05 to 1.30 after coating the adsorbent with 0.3 wt% of CNT. MW energy needed to heat the adsorbent by 1 °C decreased from 722 to 13 J/g at 0.3 wt% of CNT owing to improved MW absorption by CNT-coated adsorbent. Finally, 5 cycles of n-heptane adsorption and MW-assisted regeneration were completed for CNT-coated and as-received adsorbent samples. The deposition of a very small amount of CNTs (0.1 to 0.3 wt%) on the adsorbent increased the MW-assisted desorption efficiency by 103% to 284% compared to the as-received adsorbent. These results are encouraging because they show that addition of small amounts of CNT can be effective in enhancing the MW regeneration of MW-transparent adsorbents.

Spray deposited thin uniform NiO/Spiro-OMeTAD composite hole transport layer with top carbon nanotube electrode

Thin Spiro-OMeTAD and NiO nanoparticles layers, as well as their composite layer was formed by layer-by-layer spray deposition as hole-transport layer (HTL), with followed carbon nanotubes (CNT) deposition to form Ti/TiO2/HTL/CNT structures. Layers’ uniformity was estimated by Raman intensity maps, AFM and current-voltage characteristics of the CNT layer and between CNT and Ti contacts. The possibility of formation of thin, less than 100 nm, pinhole-free uniform composite NiO/Spiro-OMeTAD layer by spray-deposition was shown, which manifests itself as continuous HTL even after top CNT layer deposition.

Microstructure and Mechanical Properties of Laser Surface-Treated Ti13Nb13Zr Alloy with MWCNTs Coatings

Abstract Laser surface modification of titanium alloys is one of the main methods of improving the properties of titanium alloys used in implantology. This study investigates the microstructural morphology of a laser-modified surface layer on a Ti13Nb13Zr alloy with and without a carbon nanotube coating deposited by electrophoretic deposition. Laser modification was performed for samples with and without carbon nanotube coating for two different laser powers of 800 W and 900 W and for different scan rates: 3 mm/s or 6 mm/s at 25 Hz, and the pulse duration was 2.25 ms or 3.25 ms. A scanning electron microscope SEM was used to evaluate the surface structure of the modified samples. To observe the heat-affected zones of the individual samples, metallographic samples were taken and observed under an optical microscope. Surface wettability tests were performed using a goniometer. A surface roughness test using a profilograph and a nanoindentation test by NanoTest™ Vantage was also performed. Observations of the microstructure allowed to state that for higher laser powers the surfaces of the samples are more homogeneous without defects, while for lower laser powers the path of the laser beam is clearer and more regular. Examination of the microstructure of the cross-sections indicated that the samples on which the carbon nanotube coating was deposited are characterized by a wider heat affected zone, and for the samples modified at 800 W and a feed rate of 3 mm/s the widest heat affected zone is observed. The wettability tests revealed that all the samples exhibit hydrophilic surfaces and the samples with deposited carbon nanotube coating increase it further. Surface roughness testing showed a significant increase in Ra for the laser-modified samples, and the presence of carbon nanotubes further increased this value. Nanoindentation studies showed that the laser modification and the presence of carbon coating improved the mechanical properties of the samples due to their strength.

Assembly of long carbon nanotube bridges across transparent electrodes using novel thickness-controlled dielectrophoresis.

The assembly of carbon nanotubes (CNTs) across planner electrodes using dielectrophoresis (DEP) is one of the standard methods used to fabricate CNT-based devices such as sensors. The medium drag velocity caused by electrokinetic phenomena such as electrothermal and electroosmotic might drive CNTs away from the deposition area. This problem becomes critical at large-scale electrode structures due to the high attenuation of the DEP force. Herein, we simulated and experimentally validated a novel DEP setup that uses a top glass cover to minimize the medium drag velocity. The simulation results showed that the drag velocity can be reduced by 2-3 orders of magnitude compared with the basic DEP setup. The simulation also showed that the optimum channel height to result in a significant drag velocity reduction was between 100μm and 240μm. We experimentally report, for the first time, the assembly and alignment of CNT bridges across indium tin oxide (ITO) electrodes with spacing up to 125μm. We also derived an equation to optimize the CNT's concentration in suspensions based on the electrode gap width and channel height. The deposition of long CNTs across ITO electrodes has potential use in transparent electronics and microfluidic systems.

Electrophoretic deposition of carbon nanotubes: recent progress and remaining challenges

ABSTRACT Electrophoretic deposition (EPD) is a powerful technique to assemble carbon nanotube (CNT) coatings and composite films with controlled architectures. This comprehensive review of the EPD of CNTs and CNT-containing composites focuses on achievements within the last 15 years and ongoing challenges. Stable CNT suspensions are a pre-requisite for successful EPD and have been prepared by a variety of strategies, discussed here. The resulting film microstructure is determined by the initial feedstock, the suspension, and the EPD approach applied, as well as a variety of EPD processing parameters. Nanocomposites can be prepared via co-deposition, sequential deposition, or post-deposition treatments, to introduce metallic, ceramic or polymeric phases. There are numerous potential applications for both homogeneous and patterned CNT films, including as structural reinforcements for composites, as field emission, energy storage and conversion devices, as well as in biomedical applications. The advantages and disadvantages of EPD processing in these contexts are discussed.

Interlaminar fracture toughness properties of hybrid glass fiber-reinforced composite interlayered with carbon nanotube using electrospray deposition

Abstract The electrospray deposition (ESD) method was used to deposit carbon nanotubes (CNTs) onto the surface of glass fiber (GF). The morphology of the hybrid CNTs-GF was analyzed using a field emission scanning electron microscope, and the images indicated that the CNTs were uniformly and homogenously deposited onto the GF’s surface. Laminated composite based on GF and hybrid CNTs-GF were then fabricated via vacuum-assisted resin transfer molding. The mode I interlaminar fracture toughness was measured using the double cantilever beam test method. The hybrid CNTs-GF showed a 34% increase in fracture toughness relative to the control sample. The mechanism of interlaminar fracture toughness enhancement was elucidated via fractography, where fiber bridging, adhesive and cohesive failures, hackles, and coarse matrix surface were observed along the crack pathways.

Enhancement of electrode performance through surface modification using carbon nanotubes and porous gold nanostructures

Recently, the demand for the sensitive detection of nanomaterials and biomolecules has been increasing for evaluating the toxicity of nanomaterials and early diagnosis of diseases. Although many studies have developed new detection assays, these are heavily influenced by the capabilities of the detection equipment. Therefore, the aim of the present study was to improve electrode performance by modifying the surface of the detection electrode using a simple method. Electrode surface modification was performed using carbon nanotubes (CNT) and porous gold nanostructures (NS) with excellent electrical and chemical properties. Through the simple physical deposition of CNT and electrochemical reduction of NS, the increasement of the electrode surface area was achieved. Because of the CNTs attached to the electrodes at the first step, the metal ions constituting the NS can adhere well to the electrodes. Nanoparticles with a porous structure can be generated through electrochemical reduction (cyclic voltammetry) of metal ions attached to electrodes. Consequently, the surface area of the electrode increased and electrochemical performance was improved (confirmed by atomic force microscopy, Nyquist plot and Bode plot). To quantitatively confirm the improvement of electrode performance according to the surface change through the proposed treatment technique, DNA was detected. Unlike previous surface modification studies, the developed surface treatment technique can be applied to a variety of detection equipment. To confirm this, the detection was performed using two detection devices with different operating principles. DNA detection using the two types of equipment confirmed that the detection limit was increased by approximately 1000-fold through applying a simple surface treatment. In addition, this method is applicable to detect various sizes of nanomaterials. The method proposed in this study is simple and has the advantage that it can be applied to various devices and various materials.

Study on Bimetallic Catalysts for Carbon Nanotube Growth on the Surface of Continuous Carbon Fibres

We investigated the influence of bimetallic catalysts with various compositions on the growth of carbon nanotubes (CNTs) on the surface of continuous carbon fibers (CFs). The samples were analyzed and characterized by scanning electron microscopy, transmission electron microscopy, and Raman spectrometry. The catalyst plays an essential role in the catalytic chemical vapor deposition of CNT. The performance of these catalysts was estimated referenced to both catalyst and CNT morphologies, while the influences of each catalytic components were summarized according to the results. This work prepared and studied six different bimetallic catalysts composed by Cu, Fe, and Ni, and pure Fe catalyst was employed as a control group. Fe and Ni have been widely studied, while the reports of catalysts containing Cu are rare. We found that pure Fe catalyst leads to banded and clustered CNT distribution, and the addition of Cu can provide uniform and slender CNTs. The efficiency of catalyst can be significantly increased by adding Ni, producing CNTs as well as superfluous amorphous carbon. We determined that bimetallic catalyst can utilize multiple catalytic abilities of various metals by adjusting its composition, which can contribute to obtaining high-quality CNTs on CF surface.

Experimental assessment on machinability performance of CNT and DLC coated HSS tools for hard turning

The present work investigates the deposition of carbon nanotubes (CNT) over the HSS tool. Also, it assesses the machining capacity of the coated tool with respect to some of most important aspects of the machinability, such as surface roughness, cutting tool-tip temperature, cutting forces, tool wear, and service life. The Plasma Enhanced Chemical Vapour Deposition (PECVD) technique was used to deposit CNTs over the substrate. To recognize the dense deposition of CNTs, microstructural analysis was carried out through Scanning Electron Microscopy (SEM) and Raman spectroscopy. Further, a scratch test was embedded to validate the bonding strength of the covered layer substrate. Machining experiments were performed using CNT and Diamond-Like Carbon (DLC) coated tools. The analysis of experimental outcomes for three different cutting environments shows that the CNT coated tool represent a viable candidate for machining of harder materials. We have observed a dramatic reduction of the cutting tool tip temperature and cutting forces due to the excellent mechanical and thermal properties of CNTs. Indeed, the CNT coated tools prove their suitability when compared with the DLC coated tools. The analysis of tool wear demonstrated a much lower wear condition for CNTs tools when comparing to DLC coating one. This was translated in longer tool life for the CNT coated tool, which was about 28 min longer with only marginal failure under high cutting conditions when comparing to DLC one.

Boosting Catalytic Lifetime in Chemical Vapor Deposition of Carbon Nanotubes by Rapid Thermal Pretreatment of Alumina-Supported Metal Nanocatalysts

Boosting Catalytic Lifetime in Chemical Vapor Deposition of Carbon Nanotubes by Rapid Thermal Pretreatment of Alumina-Supported Metal Nanocatalysts