Deposition Of Carbon Nanotubes Research Articles

Deposition of carbon nanotubes onto glass fibers using ultrasound standing waves

Deposition of carbon nanotubes onto glass fibers using ultrasound standing waves

Electrochemiluminescent immunoassay for the determination of CA15-3 and CA72-4 using graphene oxide nanocomposite modified with CdSe quantum dots and Ru(bpy)3 complex.

Anovel immunoassay is introducedbased on co-reactant enhancing strategy for the electrochemiluminescent (ECL) determination of CA15-3 and CA72-4 tumor markers in real samples. For the preparation of the signaling probe, CA15-3 and CA72-4 antibodies first were labeled using Ru(bpy)32+-N-hydroxysuccinimide ester (Ru(bpy)32+-NHS) and conjugated with L-cysteine capped cadmium selenide (CdSe) quantum dots. Finally, it was cross-linked with chitosan-grafted graphene oxide (GO@CS) nanocomposite. The capture probe was constructed by deposition of multi-walled carbon nanotubes (MWCNT) at the surface of dual-working gold screen-printed electrodes (MWCNT-dwSPE) and covalent attachment of capture CA15-3 and CA72-4 antibodies to MWCNT-dwSPE. ECL signals were recorded by applying cyclic potential ranging from 0.3 to 1.1 V (vs. pseudo-reference Ag/AgCl) at the scan rate of 100 mV.s-1. This immunoassay was used for determination of CA15-3 and CA72-4 in real samples the detection limits of 9.2 μU.ml-1 and 89 μU.ml-1 within linear ranges of 10 μU.ml-1-500 U.ml-1 and 100 μU.ml-1-150 U.ml-1, respectively. This immunoassay also showed acceptable accuracy with recoveries in the range 96.5-108 % and high reproducibility with RSD of 3.1 and 4.9.

Anisotropic Carbon Nanotube Structures with High Aspect Ratio Nanopores for Li-Ion Battery Anodes

Technological advances in membrane technology, catalysis, and electrochemical energy storage require the fabrication of controlled pore structures at ever smaller length scales. It is therefore important to develop processes allowing for the fabrication of materials with controlled submicron porous structures. We propose a combination of colloidal lithography and chemical vapor deposition of carbon nanotubes to create continuous straight pores with diameters down to 100 nm in structures with thicknesses of more than 300 μm. These structures offer unique features, including continuous and parallel pores with aspect ratios in excess of 3000, a low pore tortuosity, good electrical conductivity, and electrochemical stability. We demonstrate that these structures can be used in Li-ion batteries by coating the carbon nanotubes with Si as an active anode material.

Comparison of carbon nanotube deposition on HfB2, ZrB2, and TiB2 by chemical vapor decomposition

CNTs were successfully synthesized on refractory metal diborides (HfB2, ZrB2, and TiB2) via CVD, with Ni as the catalyst at about 850–1200 °C. The obtained powders were densified via SPS at 1400–1700 °C to obtain a composite. The microstructures of the grown CNTs were characterized. The mechanical performances of the as-received materials were tested to evaluate the enhancing impact of CNTs grown in situ. Phase analysis of the final materials was conducted by XRD to eliminate the effects of impurities. The optimal strength and toughness, respectively, were 1013 ± 48 MPa and 10.7 ± 0.5 MPa·m1/2 for TiB2-Ni-CNT composites; 988 ± 47 MPa and 9.4 ± 0.4 MPa·m1/2 for ZrB2-Ni-CNT composites; and 912 ± 43 MPa and 8.5 ± 0.3 MPa·m1/2 for HfB2-Ni-CNT composites. The CNTs grown in the boride matrix exhibited uniform dispersion, resulting in further enhancement.

Catalytic activity of K10 montmorillonite in the chemical vapor deposition of multi-wall carbon nanotubes from methane

The catalytic activity of K10 montmorillonite (K10Mt) as a substrate during the chemical vapor deposition (CVD) of carbon nanotubes (CNT) was investigated. The influence of free iron present in the structure of K10Mt during CNT synthesis was investigated. The synthesis was carried out both on samples containing free iron and after its chemical extraction. The structural and microstructural parameters of the samples were characterized by scanning electron microscopy with X-ray dispersion spectroscopy (SEM/EDS), energy dispersive transmission electron microscopy (TEM/EDS), X-ray fluorescence spectroscopy, X-ray diffraction (XRD), infrared spectroscopy (FTIR), and Raman spectroscopy, and X-ray photoelectron spectroscopy. It was found that K10Mt, before Fe removal, was covered with coarser forms of carbon with rounded shapes characteristic for pyrolytic carbon deposits, while after chemical purification the K10Mt particles were covered with regular forms of CNT. During the CVD process at 850 °C, multi-walled carbon nanotubes about 1 μm in length were formed on the surface of pure K10Mt. Under the conditions of synthesis, the K10-Mt/CNT nanocomposites were formed. After extraction of free iron from K10Mt, the most likely nucleation sites for CNT growth were Mg- and Fe-containing compounds structurally integrated with the K10Mt substrate, such as iron phosphides, magnesia, and magnesium aluminate.

Constant Phase Element Analysis of Ordered Carbon Electrodes Via Electrochemical Impedance Spectroscopy and Cyclic Voltammetry

Electrochemical double layer capacitors exhibit constant phase element (CPE) behavior in both their cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) response. Recently, Allagui et. al [Sci. Rep., vol. 7, September, p. 46828, 2017.] presented equations for finding CPE parameters from CV measurements. EIS data for porous electrodes exhibiting CPE behavior can be fit using the de Levie model. In this work, several ordered carbon electrodes of varying pore length were prepared by chemical vapor deposition (CVD) of carbon nanotubes (CNTs) within anodized aluminum oxide (AAO) templates. These electrodes were used to create supercapacitors with neat EMIM-BF4 ionic liquid electrolyte. CPE parameters Q and α were found for each device from both CV and EIS, and they are in good agreement between the two methods. However, the values of resistance, another fitting parameter in both models, vary drastically. The physical origin of these resistances is discussed. Additionally, the capacitance of the devices was calculated from both methods, using the Brug formula in the case of EIS. These capacitances disagree greatly, except for the thickest AAO templates (the longest pores). The devices in agreement also showed the lowest resistance values from CV. It is not apparent whether the agreement in capacitance is related to the pore dimensions or the extracted resistance values. {DISTRIBUTION STATEMENT A. Approved for public release; Distribution is unlimited 412TW-PA-20496]

Characterization and selective deposition of carbon nanotubes from carbon nanoparticles mixture using mild acid treatment and electrokinetic manipulation

Particle manipulation is often required in the fabrication of microelectronic devices such as transistors and sensors. In this work, we succeeded in depositing aligned carbon nanotubes (CNTs) from an oxidized conglomerates carbon mixture using a simple low power procedure consisting of mild acid treatment and frequency-dependent dielectrophoretic (DEP) force. The treatment improved the dispersity and solubility of CNTs due to the functional groups introduced on their surface. The DEP force was generated with an AC signal of 1 MHz and 7.07 Vrms to attract the CNTs to a transparent electrode gap of 50 μm. Treatment quality was confirmed and characterized by Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), energy dispersive x-ray analysis (EDX) and high-resolution transmission electron microscopy (HRTEM). Ultraviolet-visible spectroscopy (UV-vis) and dynamic light scattering (DLS) were used to analyze the dispersity and solubility of carbon particles and their size distribution in different solvents. The morphology of the deposited CNTs and amorphous carbon were observed by optical microscope and field-emission scanning electron microscope (FESEM). The procedure used in this work is cost-effective, scalable and essential for future assembly. Furthermore, the transparency of the system makes it suitable for real-time observation, transparent sensors, and the ability to integrate it into microfluidic channels.

Experimental evaluation of machinability performance of CNT coated HSS tool during turning of titanium alloy

The present research deals with the deposition of carbon nanotubes (CNT) over the HSS tool, and to evaluate the machining performance of the coated tool with respect to the important machinability aspects like cutting tip temperature, cutting forces, surface roughness and tool wear and life. The plasma enhanced chemical vapour deposition (PECVD) technique was employed to deposit CNTs over the substrate. Microstructural investigations through SEM and Raman spectroscopy were carried out to acknowledge the dense deposition of CNTs. Scratch test was also performed to validate the bonding strength of the coated layer with the substrate. Machining experimental results under three different cutting conditions, concluded that the CNT coated tool is the right potential candidate for turning tougher materials. Drastic depletion in cutting tip temperature and cutting forces to the extent of 70 to 80 % was observed for coated tool due to the excellent mechanical and thermal properties of CNTs. However, there was no significant effect of coating to influence the surface roughness at a lower level of cutting conditions, but considerable improvement has been observed at elevated cutting condition. The tool wear and life analysis explored the steady improvement to a remarkable extent. Very specifically, under elevated machining conditions, tool life investigations concluded the fact that the CNT coated tool has a tool life of more than 60 minutes with negligible failure.

Guided Healing of Damaged Microelectrodes via Electrokinetic Assembly of Conductive Carbon Nanotube Bridges.

The subject of healing and repair of damaged microelectrodes has become of particular interest as the use of integrated circuits, energy storage technologies, and sensors within modern devices has increased. As the dimensions of the electrodes shrink together with miniaturization of all the elements in modern electronic devices, there is a greater risk of mechanical-, thermal-, or chemical-induced fracture of the electrodes. In this research, a novel method of electrode healing using electrokinetically assembled carbon nanotube (CNT) bridges is presented. Utilizing the previously described step-wise CNT deposition process, conductive bridges were assembled across ever-larger electrode gaps, with the width of electrode gaps ranging from 20 microns to well over 170 microns. This work represents a significant milestone since the longest electrically conductive CNT bridge previously reported had a length of 75 microns. To secure the created conductive CNT bridges, they are fixed with a layer of electrodeposited polypyrrole (a conductive polymer). The resistance of the resulting CNT bridges, and its dependence on the size of the electrode gap, is evaluated and explained. Connecting electrodes via conductive CNT bridges can find many applications from nanoelectronics to neuroscience and tissue engineering.

Significant role of molybdenum promoted TiO2 catalysts for carbon nanotubes production and their polymer nanocomposites

Role of specific catalysts system is still a thrust area for the synthesis of carbon nanotubes. Titania-supported Fe and Co catalysts were prepared using the sol-gel and wet-impregnation method. These catalysts were used for the deposition of multiwalled carbon nanotubes (MWNTs) from xylene by the catalytic chemical vapour deposition (CCVD) technique at 800 °C. In the present work, the effect of the addition of molybdenum with monometallic catalyst had been investigated from the viewpoint of the growth of the carbon nanotubes (CNTs). The results showed that the presence of molybdenum in minor amount with Fe/Co-based catalysts can increase the amount of deposition of CNTs. CNTs-Epoxy resin composites were fabricated using prepared carbon nanotubes with a CNTs loading of 0.2 wt% and performed flexural testing measurement. These multi-components systems of titania and carbon nanotubes have a capacity to enhance many properties significantly for specific applications.

Ion-to-electron capacitance of single-walled carbon nanotube layers before and after ion-selective membrane deposition

The capacitance of the ion-to-electron transducer layer helps to maintain a high potential stability of solid-contact ion-selective electrodes (SC-ISEs), and its estimation is therefore an essential step of SC-ISE characterization. The established chronopotentiometric protocol used to evaluate the capacitance of the single-walled carbon nanotube transducer layer was revised in order to obtain more reliable and better reproducible values and also to allow capacitance to be measured before membrane deposition for electrode manufacturing quality control purposes. The capacitance values measured with the revised method increased linearly with the number of deposited carbon nanotube–based transducer layers and were also found to correlate linearly before and after ion-selective membrane deposition, with correlation slopes close to 1 for nitrate-selective electrodes, to 0.7 and to 0.5 for potassium- and calcium-selective electrodes.Graphical abstract

Resistivity of mesopore-confined ionic liquid determined by electrochemical impedance spectroscopy

Ordered carbon nanotube (CNT) arrays with pore diameter 24.4 ± 4.6 nm formed within anodized aluminum oxide (AAO) bonded to Si were used as electrodes for supercapacitors with neat EMIM-BF4 ionic liquid as the electrolyte. A series of devices with increasing AAO thickness (equal to CNT length) were tested using electrochemical impedance spectroscopy (EIS). Data were fit using the de Levie model of porous electrodes to determine the electrochemically active surface area and the in-pore electrolyte resistivity. The results indicate that uncatalyzed chemical vapor deposition (CVD) of CNTs in AAO can lead to blocked CNTs and reduced active area. The average resistivity of the electrolyte within the pores across the four devices tested was determined to be approximately 383 Ω cm, more than five times higher than the reported bulk resistivity of 70.9 Ω cm. It is possible that the enhanced resistivity is due to hydrophilic surface functionalities on the surface of the CNTs.

Reducing Variability in Chemical Vapor Deposition of Carbon Nanotubes Based on Gas Purification and Sample Support Redesign

Abstract The synthesis of vertically aligned carbon nanotubes (CNTs), also referred to as CNT forest, by chemical vapor deposition (CVD) is an intricate process that is sensitive to multiple factors other than control of temperature, pressure, and gas flows. In particular, growth is highly sensitive to factors like ambient humidity, as well as small quantities of oxygen-containing species and carbon deposits inside the reactor. These typically uncontrolled factors significantly affect growth reproducibility and hinders the fundamental study of process–structure–property relationship for these emerging materials. Accordingly, universally applicable design modifications and process steps toward improving growth consistency are sought after. In this study, we introduce two new modifications to our custom-designed multizone rapid thermal CVD reactor and demonstrate their impact on growth: (1) reconfiguring the inlet gas plumbing to add a gas purifier to the helium (He) line, and (2) designing a new support wafer for consistent loading of substrates. We use statistical analysis to test the effectiveness of these modifications in improving growth and reducing variability of both CNT forest height and density. Analysis of our experimental results and hypothesis testing show that combining the implementation of He purifier with the redesigned support wafer increases forest height and reduces the variability in height (17-folds), both at statistically significant and practically significant levels.

Initial competing chemical pathways during floating catalyst chemical vapor deposition carbon nanotube growth

Ferrocene (Fc) is an effective precursor for the direct synthesis of high quality single-walled carbon nanotubes (SWCNTs) via floating catalyst chemical vapor deposition (FCCVD). However, the formation mechanism of the Fe floating catalyst and the SWNCT growth precursors, such as carbon chains, during Fc decomposition are not well understood. Here, we report first principles nonequilibrium quantum chemical molecular dynamics simulations that investigate the decomposition of Fc during FCCVD. We examine the influence of additional growth precursors including ethylene, methane, CO, and CO2 on the Fc decomposition mechanism and show that the dissociation of these species into C2Hx radicals and C atoms provides the key growth agents for the nucleation of carbon chains from Fc-derived species such as cyclopentadienyl rings. Without an additional growth precursor, Fc decomposes via the spontaneous cleavage of Fe–C and C–H bonds, thereby enabling Fe atoms to cluster and form the floating catalyst. On the basis of these simulations, we detail the two competing chemical pathways present during the initial stages of FCCVD: Fe catalyst nanoparticle growth and carbon chain growth. The latter is accelerated in the presence of the additional growth precursors, with the identity of the precursor determining the nature of the balance between these competing pathways.

Multicomponent architectured battery-type flexible yarns for high-performance wearable supercapatteries

Rational design of light weight, flexible and wearable yarn-type electrodes with selectively designed battery-type materials has attracted a promising research interest for the development of high-performance miniatured energy storage devices. However, the relatively lower energy storage performance caused by poor mass loading of existing fiber/yarn-based devices limits their practical applicability in a wide range. Herein, an unique plaiting approach is demonstrated to design flexible and wearable yarn-type supercapatteries (YSCs) with high electrochemical performance. With ubiquitous polyester fabric fibers (PFs) in a plaiting form, PFs are converted into highly conductive plaited PFs via dual layered metallization with superior surface roughness. Upon deposition of carbon nanotubes and nickel cobalt double hydroxides on metallized PFs, an efficient battery-type electrode is designed, which exhibits a high specific capacity of 162.8 mAh g−1 with an excellent cycling stability of 93.3% in alkaline electrolyte. The two-electrode system-based solid-state YSCs are further assembled using multicomponent architectured battery-type and capacitive-type activated carbon electrodes, which enables a high potential of 1.55 V with superior energy and power densities (30.49 Wh kg−1 and 1137.26 W kg−1), respectively. By capitalizing high energy storage, the solar charging-based YSC is practically examined to be able to energize various wearable electronics.

Highly stretchable durable electro-thermal conductive yarns made by deposition of carbon nanotubes

The polymer yarns are originally electrical insulators. Their structure does not provide valence electrons to conduct electrical current. The coating of carbon nanotubes (CNT) over the nylon yarn enables it to become a good conductor of heat and electricity. The objective of present study is to impart the electrical conductivity to the Nylon 6/Spandex yarn by coating the CNT. The physical properties of CNTs were studied by SEM analysis. The electrical properties of CNT coated yarns were investigated in relaxed and stretched state. The conductive yarns showed low resistance under high stretch load. Furthermore, the heating performance of the CNT coated yarns was analyzed by applying the different range of voltages at the surface of the yarns. The maximum temperature of about 280 °C was recorded when the applied voltages were 5 V for 60 min. Moreover, the durability of CNT coated yarns was observed against severe washing. The yarns showed good retention of the CNT even after severe washing, as proved by a very small loss in the electrical conductivity of the yarns.

A Functionalized Paper Strip‐Based Platform for Rapid Detection of Anticancer Drug Concentrations

This article presents a compact, low‐cost, robust, and flexible test platform for determining the concentration of drugs in fluids. This device is based on a PVC foil card containing copper conductive foils in which disposable paper test strips are inserted. The paper test strips are overlaid with deposition of multiwalled carbon nanotubes (MWCNTs) acting as a sensing layer. When a paper test strip is inserted into the test card, the conductive path between two copper lines is established. A drop of test fluid on the sensing MWCNT layer changes the conductivity in a concentration‐dependent manner, enabling calculation of the drug concentration after measurement of the electrical resistance at the copper terminals. An equivalent electrical circuit was also proposed to model the response of the fabricated sensor. It was shown that model parameters are dependent on the concentration of the cytostatic drug methotrexate. Additionally, the fabricated sensor demonstrated the ability to differentiate the same concentration of methotrexate and cyclophosphamide. The complete readout electronics and polynomial transfer function for calculating drug concentrations were also developed and are presented.

Facile deposition of multiwalled carbon nanotubes via electrophoretic deposition in an environmentally friendly suspension

The present work focuses on the application of electrophoretic deposition (EPD) as a facile process to generate homogeneous layers of multi walled carbon nanotubes (MWCNTs) using water as an environmentally friendly solvent. The EPD process requires a pretreatment of the commercially available MWCNT powder to create a surface charge on the surfaces of the MWCNTs as well as to realize stable suspensions. After pre-treatment, the electrophoretic mobility of the MWCNTs was approximately μ ≈ − 4.3 · 10−4cm2V−1s−1 and the resulting ζ-potential is in the range of ζ ≈ −55 mV. The suspension showed no sedimentation over 50 days. The EPD was carried out at an applied voltage of 50 V. The MWCNTs were successfully deposited as open porous layers on gold as well as on aluminum. The specific double layer capacitance of the MWCNT-layers on gold amounts to C ≈ 11.9 Fg−1.However, on aluminum as substrate, the EPD of the MWCNTs is associated with the formation of a thin barrier like oxide film. In this case a major part of the applied voltage drops down across the oxide film and only a minor part across the suspension. Consequently, the field strength in the suspension decreases. Moreover, the capacitance of the oxide film dominates the whole capacitance of the electrode. The specific capacitance amounts to C = 0.3 mFg−1 related to the deposited mass of MWCNTs.

Improving flexural and dielectric properties of carbon fiber epoxy composite laminates reinforced with carbon nanotubes interlayer using electrospray deposition

Abstract The electrospray deposition method was used to deposit carbon nanotubes (CNT) onto the surfaces of woven carbon fiber (CF) to produce woven hybrid carbon fiber–carbon nanotubes (CF–CNT). Extreme high-resolution field emission scanning electron microscopy (XHR-FESEM), X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR) were used to analyze the woven hybrid CF–CNT. The results demonstrated that CNT was successfully and homogenously distributed on the woven CF surface. Woven hybrid CF–CNT epoxy composite laminates were then prepared and compared with woven CF epoxy composite laminates in terms of their flexural and dielectric properties. The results indicated that the flexural strength, flexural modulus and dielectric constant of the woven hybrid CF–CNT epoxy composite laminates were improved up to 19, 27 and 25%, respectively, compared with the woven CF epoxy composite laminates.

Dye-sensitized solar cells based on MK2 dye, PMMA-based quasi-solid electrolyte, and flexible CNT counter electrode

In this paper, a dye-sensitized solar cell based on organic MK2 dye, a quasi-solid electrolyte, and a flexible counter electrode was investigated. Two types of TiO2 nanoparticles with different sizes were used to make the photoanode with a bi-layer structure. The quasi-solid electrolyte was made based on polymethylmethacrylate (PMMA) and iodide/triiodide couple. The counter electrode was fabricated by electrophoresis deposition of carbon nanotube (CNT) mixed with diallyl dimethylammonium chloride (PDDA) on a flexible stainless-steel mesh. A cellulose separator was used to improve the stability of the solar cell. A simple and low-cost sealing method using polypropylene-based tape has been proposed and used for conducting the stability test. The maximum conversion efficiency of 2.5% (under simulated AM 1.5) was obtained with the fabricated quasi-solid dye-sensitized solar cells.