Deposition Of Nanotubes Research Articles

Influence of carbon nanotubes coatings onto carbon fiber by oxidative treatments combined with electrophoretic deposition on interfacial properties of carbon fiber composite

To improve the interfacial performance of carbon fiber (CF) and epoxy resin, carbon nanotubes (CNTs) coatings were utilized to achieve this purpose through coating onto CF by the treatment with hydrogen peroxide and concentrated nitric acid combined with electrophoretic deposition (EPD) process. The influence of electrophoretically deposited CNTs coatings on the surface properties of CFs were investigated by Fourier transform infrared spectrometer, atomic force microscopy, scanning electron microscopy and dynamic contact angle analysis. The results indicated that the deposition of carbon nanotubes introduced some polar groups to carbon fiber surfaces, enhanced surface roughness and changed surface morphologies of carbon fibers. Surface wettability of carbon fibers may be significantly improved by increasing surface free energy of the fibers due to the deposition of CNTs. The thickness and density of the coatings increases with the introduction of pretreatment of the CF during the EPD process. Short beam shear test was performed to examine the effect of carbon fiber functionalization on mechanical properties of the carbon fiber/epoxy resin composites. The interfacial adhesion of CNTs/CF reinforced epoxy composites showed obvious enhancement of interlaminar shear strength by 60.2% and scanning electron microscope photographs showed that the failure mode of composites was changed after the carbon fibers were coated with CNTs.

On the Motion of Carbon Nanotube Clusters near Optical Fiber Tips: Thermophoresis, Radiative Pressure, and Convection Effects.

We analyze the motion of multiwalled carbon nanotubes clusters in water or ethanol upon irradiation with a 975 and 1550 nm laser beam guided by an optical fiber. Upon measuring the velocities of the nanotube clusters in and out of the laser beam cone, we were able to identify thermophoresis, convection and radiation pressure as the main driving forces that determine the equilibrium position of the dispersion at low optical powers: while thermophoresis and convection pull the clusters toward the laser beam axis (negative Soret coefficient), radiation pressure pushes the clusters away from the fiber tip. A theoretical solution for the thermophoretic velocity, which considers interfacial motion and a repulsive potential interaction between the nanotubes and the solvent (hydrophobic interaction), shows that the main mechanism implicated in this type of thermophoresis is the thermal expansion of the fluid, and that the clusters migrate to hotter regions with a characteristic thermal diffusion coefficient D(T) of 9 × 10(-7) cm(2) K(-1) s(-1). We further show that the characteristic length associated with thermophoresis is not that of the nanotube clusters size, O(1) μm, but that corresponding to the microstructure of the clusters, O(1) nm. We finally discuss the role of the formation of gas-liquid interfaces (microbubbles) at high optical powers on the deposition of carbon nanotubes on the optical fiber end faces.

The deposition of globular polypyrrole and polypyrrole nanotubes on cotton textile

Cotton textile was coated with polypyrrole in situ during the oxidation of pyrrole with iron(III) chloride in aqueous medium. Such polymerization results in the globular polypyrrole coating of fibres. In the presence of methyl orange, the coating with polypyrrole nanotubes was obtained. Nanotubular polypyrrole is more conducting and more stable towards the loss of conductivity after deprotonation than globular form. On the contrary, when deposited on cotton, the surface conductivity with the globular form was higher and stability with respect to washing better. This is due to the fact, that the coating with globular form is considerably thicker compared with the deposited nanotubes. This is visible by the difference in colour, black and brown for the globular and nanotubular forms, respectively, and also confirmed by infrared and Raman spectroscopies. The reduction in conductivity after repeated washing is large and the textile becomes practically non-conducting for both polypyrrole forms. The repeated chemical cleaning of the textile with globular polypyrrole coating, however, is associated only with the marginal decrease in conductivity.

Electrochemical determination of Cu(II) ions using glassy carbon electrode modified by some nanomaterials and 3-nitroaniline

Abstract The aim of this research was to investigate the effect of the several nanomaterials in electrochemical determination of Cu(II) ions. For this aim, firstly the deposition of graphene oxide (GO), graphene, magnetite (Fe3O4), gold-chitosan (AuChts) or multilayer carbon nanotubes (MWCNTs) on the glassy carbon (GC) electrode surface was performed. Then the electrochemical modification of electrode by poly-3-nitroaniline (poly-3NA) was performed by 100 potential cycles in the range between +0.9 V and +1.4 V vs. Ag/AgNO3 at the sweep rate of 100 mV/s. For electrochemical reduction of nitro groups present on modified GC electrode surface, potential cycling was performed in 100 mM HCl between −0.1 V and −0.8 V vs. Ag/AgCl/(KClsat.) at the sweep rate of 100 mV/s. Nanomaterial and poly-3NA modified electrodes were applied in the determination of Cu(II) ions by differential pulse voltammetry. It was determined that GC electrodes consecutively modified with MWCNTs, poly-3NA and then by electrochemical reduction of nitro groups were the most sensitive towards Cu(II) ions with detection limit of 0.5 × 10−9 M.

High Surface Area Multi-Wall Carbon Nanotube Electrodes for H2-Br2 fuel Cells

The regenerative H2-Br2 fuel cell has been a subject of great interest and is considered as one of the great candidates for large scale electrical energy storage [1, 2]. Since the bromine reactions in this fuel cell system do not need any precious metal catalysts, plain porous carbon paper can be used as an electrode material. However, these porous carbon electrodes have low surface area and hence multiple electrode layers are employed to improve the active surface area [2]. In our previous study, we used a two-step synthesis process that involves electrodeposition of catalyst nanoparticles followed by chemical vapor deposition (CVD) of carbon nanotubes [3]. Scanning electron micrographs of the materials obtained by this process are shown in Figure 1. As a way to simplify the process and reduce the cost of the produced material, a single step process is explored. In this process the catalyst nanoparticles are deposited on the carbon electrode via thermal reduction in a hydrogen environment and subsequently carbon nanotubes are grown. The whole process is accomplished in a single step. This new process, its effectiveness, and the performance of the materials created by this new process will be discussed in this presentation. References Haley Kreutzer, Venkata Yarlagadda, and Trung Van Nguyen, J. Electrochem Soc., 159(7), F331 (2012).Kyu Taek Cho, Paul Ridgeway, Adam Z. Weber, Sophia Haussener, Vincent Battagalia, and Venkat Srinivasan, J. Electrochem. Soc., 159(11), A1806 (2012).Venkata Yarlagadda and Trung Nguyen, ECS Transactions, 58(36), 25 (2014). Acknowledgements This work was funded by NSF through grant number EFRI-1038234 and DOE/ARPA-E under award number DE-AR000026. Figure 1

Deposition of carbon nanotubes in commonly used sample filter media

ABS TRACT: There is no single standard technique or methodology to characterize the size, structure, number, and chemical composition of airborne carbon nanotubes. Existing analytical instruments and analytical techniques for evaluating nanoparticle concentrations cannot simultaneously provide morphology, state of agglomeration, surface area, mass, size distribution and chemical composition data critical to making occupational health assessments. This research utilized scanning electron microscopy and thermogravimetric analysis to assess the morphology and mass of carbon nanotubes collected using various commercial sample filters. It illustrated carbon nanotube agglomeration, deposition and distribution in commonly used sample filter media. It also illustrated that a sufficient mass for carbon nanotube analysis by thermogravimetric analysis is uncommon under most current research and production uses of carbon nanotubes. Individual carbon nanotubes were found to readily agglomerate with diameters ranging from 1 – 63 µm. They were collected at the face of or within the filter. They were not evenly distributed across the face of the filters.

Study of the Electrophoretic Deposition of Chitosan/Halloysite Nanotubes/Titanium Dioxide Composite Coatings Using Taguchi Experimental Design Approach

This study presents experimental results on the electrophoretic deposition (EPD) of chitosan/halloysite nanotube/titanium dioxide composite coatings based on the Taguchi design of experiments (DOE) approach. Taguchi array of L18type with mixed levels of the control factor was used to study the influence of EPD parameters, including halloysite nanotubes concentration, electric voltage and deposition time, on deposition yield. For identifying the significant factors that affected the deposition yield, multivariate analysis of variance (MANOVA) and regression analysis based on partial least-square method were used. The coatings were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy analyses, respectively. It was found that the deposition time has significantly influenced the deposition rate but the halloysite nanotube concentration and the applied voltage have the smallest effect on the deposition. The optimum condition for high yield of deposition with low standard deviation is achieved when the concentration of halloysite nanotubes is 0.3 g/L and the applied voltage is 40 volt with 300 sec. as a deposition time. The predicted EPD conditions were verified by experiments and qualitative agreement was obtained.

Nanotube-based source of charges for experiments with solid helium at low temperatures

Methods of preparation of the field-emission sources of charges from carbon nanotubes suitable for study of injected charges in solid helium at low temperatures T < 1 K are presented. The sources have been prepared by arc discharge deposition of nanotubes onto a flat copper substrate or by mechanical rubbing of nanotubes into porous metal surface. The test study of the voltage-current characteristics of a diode cell with the nanotube source in superfluid He II have shown that at voltages above 120 V one can observe a relatively large current I ≥ 10–13 A of negative charges in liquid helium. The field and temperature dependences of positive and negative currents in solid 4He were studied in samples grown by the blocked capillary technique. Usage of the nanotube based source of injected charges had permitted us for the first time to observe motion of the positive charges in solid helium at temperatures below 0.1 K. The current-voltage dependence could be described by a power law I∼Uα, with the value of the ...

Fabrication of multi-walled carbon nanotube thin films via electrophoretic deposition process: effect of water magnetization on deposition efficiency

In this study, the effect of water magnetization was investigated on the performance of electrophoretic deposition (EPD) of multi-walled carbon nanotubes (MWCNTs). Magnetization of water was carried out via two different methods including static and dynamic magnetization processes. It has been found that magnetization of water, as the EPD medium, could enhance several characteristics of MWCNT thin films (MWCNT-TFs). Application of magnetized water as solvent in EPD process resulted in higher electrical conductivity of EPD suspension; consequently, required deposition time was reduced and the electrolysis of water, which is known as one of the main disadvantages of water-based EPDs, was controlled to some extent. Surface morphology of MWCNT-TFs was studied via scanning electron microscopy, and notable enhancement was detected in uniformity and density of MWCNT-TF network. Significant improvement was achieved in electrical conductivity (up to 54 % increase in current) of MWCNT-TF by measuring the current versus voltage characteristics of MWCNT-TFs.

Natural Ceramic Nanotube Substrates for Surface-Enhanced Raman Spectroscopy

Natural halloysite clay nanotubes are cheap and available in large quantities, thus seem superior to the other nanotube-based materials. Halloysite nanotubes are used to form structured substrates for surface-enhanced Raman scattering (SERS). Specifically, layered aluminum-halloysite- (noble) metal substrates were prepared by deposition of halloysite nanotubes on aluminum foil, followed by thin metal film coatings via vacuum evaporation. The composite substrates required no capping agent on the metal surface and thus avoided background peaks in the Raman spectra, making them well suited for SERS studies. Gold-, silver-, and copper-coated substrates exhibited SERS for p-mercaptobenzoic acid, whereas uncoated and platinum-coated substrates did not. The SERS enhancement factors for the gold-, silver-, and copper-coated substrates were, by a conservative estimate, 1.4 × 105, 3.5 × 104, and 3.5 × 103, respectively. Interestingly enough, the SERS enhancement factors of substrates decrease in a row: Au > Ag > Cu, which differ from those for the corresponding metal nanoparticles.

The role of ions in plasma catalytic carbon nanotube growth: A review

While it is well-known that the plasmaenhanced catalytic chemical vapor deposition (PECVD) of carbon nanotubes (CNTs) offers a number of advantages over thermal CVD, the influence of the various individual contributing factors is not well understood. Especially the role of ions is unclear, since ions in plasmas are generally associated with sputtering rather than with growing a material. Even so, various studies have demonstrated the beneficial effects of ion bombardment during the growth of CNTs. This review looks at the role of the ions in plasmaenhanced CNT growth as deduced from both experimental and simulation studies. Specific attention is paid to the beneficial effects of ion bombardment. Based on the available literature, it can be concluded that ions can be either beneficial or detrimental for carbon nanotube growth, depending on the exact conditions and the control over the growth process.

Influence of deposited CNTs on the surface of carbon fiber by ultrasonically assisted electrophoretic deposition

The surface property of carbon fiber directly affects the interface performance between carbon fiber and matrix. To improve the surface property of carbon fiber, we proposed a simple method to prepare carbon nanotubes /carbon fiber hybrid fiber via ultrasonically assisted electrophoretic deposition (EPD). Surface morphologies and surface functional group of carbon fibers were examined by atomic force microscopy (AFM), scanning electron microscopy (SEM) and fourier transform infrared spectrometer (FTIR), respectively. The results show that the deposition of carbon nanotubes changed the surface morphologies of carbon fibers and introduced polar groups (C=O and C-O) to carbon fiber surface. Comparing the results with EPD-only, ultrasonically assisted EPD increased the uniformity of carbon nanotubes coatings whereas only sparse and not uniformly deposition formed without ultrasonic.

Inter-fiber stresses in composites with carbon nanotube grafted and coated fibers

Abstract Deposition of carbon nanotubes (CNT) on fiber surfaces is a promising technique to add functionalities to polymer composites. Upon deformation, these CNTs generate local stress heterogeneities which may affect properties of the interphase and the composite. The stress disturbance depends on the morphology of deposited CNT assemblies also linked to a deposition technique. In the present work, two types of morphologies are investigated: (1) CNTs grown on fibers; and (2) CNTs deposited in fiber coatings. The difference in the two cases is the orientation of CNTs near the fiber interface: radial for grown CNTs and tangent for CNTs in the coatings. Different parameters including CNT length, morphology of the grafting and density of the coating are evaluated. The analysis is performed using a recently developed two-scale model. Results show that CNT grafted and coated fibers produce distinctly different interface stresses.

Electrochemical Deposition of ZnO Nanotubes with Small Dimples on the External Surface

To improve the photoelectric conversion efficiency of dye-sensitized solar cells, various semiconductor oxides, including zinc oxide (ZnO) and titanium oxide (TiO2), have been studied as photo electrodes. ZnO generally possesses better electron conductivity than TiO2, although TiO2 is one of the best substrate for the stable loading of dye molecules due to the strength of the dye-TiO2 chemical interaction. Therefore, it is important to improve the ZnO loading performance without diminishing its electron conductivity. ZnO nanotubes are known to exhibit high surface area and high conductivity. Recently, we focused our research on the high density ZnO nanotubes prepared by one-step electrodeposition at moderate temperature (<100 °C). Since the surface of the oxide semiconductor plays a significant role for loading the dye molecules, we report how the deposition conditions influence the surface morphology of the one-step electrodeposited ZnO.

Atmospheric pressure barrier discharge at high temperature: Diagnostics and carbon nanotubes deposition

Atmospheric pressure dielectric barrier discharge (DBD) in Ar/H2 gas feed with C2H2 or CH4 admixture was studied at room and high temperature of 680 °C by plasma diagnostics (electrical measurements, fast camera imaging, and optical emission spectroscopy). It was shown that filamentary DBD in pure Ar or Ar/H2 can be converted into homogeneous discharge by an acetylene admixture. Fast intensified charge-coupled device (ICCD) camera proved that this homogeneous discharge is an atmospheric pressure glow discharge (APGD) at room temperature whereas at high temperature the discharge mode switches at every half-period between APGD and atmospheric pressure Townsend discharge. The high temperature discharges (610–710 °C) in Ar/H2/C2H2 and Ar/H2/CH4 were also investigated with respect to a surface bound deposition of carbon nanotubes using 5 nm thick iron layer as a catalyst. CNTs were deposited without any dedicated catalyst pretreatment phase. The quality of CNTs, namely, their density, vertical alignment, and width of the diameter distribution, was better for the C2H2 gas feed and higher temperatures.

Electrophoretic deposition of multi-walled carbon nanotubes on porous anodic aluminum oxide using ionic liquid as a dispersing agent

Multi-wall carbon nanotubes (MW-CNTs) have been arranged in nanochannels of anodic aluminum oxide template (AAO) by electrophoretic deposition (EPD) to make a vertically-aligned carbon nanotube (VA-CNT) based electrode. Well ordered AAO templates were prepared by a two-step anodizing process by applying a constant voltage of 45V in oxalic acid solution. The stabilized CNTs in a water-soluble room temperature ionic liquid (1-methyl-3-octadecylimidazolium bromide), were deposited in the pores of AAO templates which were conductive by deposition of Ni nanoparticles in the bottom of pores. In order to obtain ideal results, different EPD parameters, such as concentration of MWCNTs and ionic liquid on stability of MWCNT suspensions, deposition time and voltage which are applied in EPD process and also optimal conditions for anodizing of template were investigated. The capacitive performance of prepared electrodes was analyzed by measuring the specific capacitance from cyclic voltammograms and the charge–discharge curves. A maximum value of 50Fg−1 at the scan rate of 20mVs−1was achieved for the specific capacitance.

Controlled modification of carbon nanotubes and polyaniline on macroporous graphite felt for high-performance microbial fuel cell anode

Polyaniline (PANI) was electropolymerized on the surface of macroporous graphite felt (GF) followed by the electrophoretic deposition of carbon nanotubes (CNTs). The as-prepared macroporous material was characterized by scanning electron microscopy, water contact angle goniometry and electrochemical techniques. Upon the modification of PANI, a rough and nano-cilia containing film is coated on the surface of the graphite fibers, transforming the surface from hydrophobic to hydrophilic. The subsequent modification by CNTs increases the effective surface area and electrical conductivity of the resulting material. The power output of a mediator-free dual-chamber microbial fuel cell (MFC) constructed from the GF anode and an exoelectrogen Shewanella putrefaciens increases drastically with the CNT modification. The CNT/PANI/GF MFC attains an output voltage of 342 mV across an external resistor of 1.96 kΩ constant load, and a maximum power density of 257 mW m−2, increased by 343% and 186%, compared to that of the pristine GF MFC and the PANI/GF MFC, respectively. More bacteria are attached on the CNT/PANI/GF anode than on the PANI/GF anode during the working of the MFC. This strategy provides an easy scale-up, simple and controllable method for the preparation of high-performance and low-cost MFC anodes.

Subchronic toxicity and cardiovascular responses in spontaneously hypertensive rats after exposure to multiwalled carbon nanotubes by intratracheal instillation.

The tremendous demand of the market for carbon nanotubes has led to their massive production that presents an increasing risk through occupational exposure. Lung deposition of carbon nanotubes is known to cause acute localized pulmonary adverse effects. However, systemic cardiovascular damages associated with acute pulmonary lesion have not been thoroughly addressed. Four kinds of multiwalled carbon nanotubes (MWCNTs) with different lengths and/or iron contents were used to explore the potential subchronic toxicological effects in spontaneously hypertensive (SH) rats and normotensive control Wistar-Kyoto (WKY) rats after intratracheal instillation. MWCNTs penetrated the lung blood-gas barrier and accumulated in the liver, kidneys, and spleen but not in the heart and aorta of SH rats. The pulmonary toxicity and cardiovascular effects were assessed at 7 and 30 days postexposure. Compared to the WKY rats, transient influences on blood pressure and up to 30 days persistent decrease in the heart rate of SH rats were found by electrocardiogram monitoring. The subchronic toxicity, especially the sustained inflammation of the pulmonary and cardiovascular system, was revealed at days 7 and 30 in both SH and WKY rat models. Histopathological results showed obvious morphological lesions in abdominal arteries of SH rats 30 days after exposure. Our results suggest that more attention should be paid to the long-term toxic effects of MWCNTs, and particularly, occupationally exposed workers with preexisting cardiovascular diseases should be monitored more thoroughly.

Surface modification of plastic substrates via corona-pretreatment and its effects on the properties of carbon nanotubes for use of flexible transparent electrodes

In this study, the surface of polyethylene terephthalate (PET) substrates was modified via corona treatment before the deposition of carbon nanotubes (CNTs), and the effects of such surface modification on the properties of the CNTs for flexible transparent electrodes were investigated. The changes in the surface roughness, contact angle, and surface energy of the PET substrates due to the corona treatment were characterized in terms of the applied corona energies, PET feeding directions, and treatment times. The higher corona energies, the more frequent treatment times, and the bi-directional treatment produced the larger surface roughness of the PET substrates. The results of the contact angles and the surface energies indicated that the surfaces of the PET substrates became hydrophilic from hydrophobic after the corona treatment. The analysis using X-ray photoelectron spectroscopy confirmed that oxygen polar groups appeared when the PET substrates were corona-treated. In addition, the increase in the CNTs' sheet resistance values due to their repeated outer and inner bending (up to 16,000 times) was found to have been significantly alleviated when the CNTs were deposited on the corona-treated PET substrates. This confirmed that the adhesion of the CNTs was improved after the corona pretreatment of the PET substrates.

MOCVD of a Nanocomposite Film of Fe, Fe3O4 and Carbon Nanotubes from Ferric Acetylacetonate: Novel Thermodynamic Modeling to Reconcile with Experiment

ABSTRACTThermodynamic modeling of the MOCVD process, using the standard free energy minimization algorithm, cannot always explain the deposition of hybrid films that occurs. The present investigation explores a modification of the procedure to account for the observed simultaneous deposition of metallic iron, Fe3O4, and carbon nanotubes from a single precursor. Such composite films have potential application in various device architectures and sensors, and are being studied as electrode material in energy storage devices such as lithium ion batteries and supercapacitors.With ferric acetylacetonate [Fe(acac)3] as the precursor, MOCVD in argon ambient results in a nanocomposite of CNT, Fe, and Fe3O4 (characterized by XRD and Raman spectroscopy) when growth temperature T and total reactor pressure P are in the range from 600°C-800°C and 5-30 torr, respectively. No previous report could be found on the single-step formation of a CNT-metal-metal oxide composite. Equilibrium thermodynamic modeling using available software predicts the deposition of only Fe3C and carbon, without any co-deposition of Fe and Fe3O4, in contrast with experimental observations. To reconcile this contradiction, the modeling of the process was approached by taking the molecular structure of the precursor into account, whereas “standard” thermodynamic simulations are restricted to the total number of atoms of each element in the reactant(s) as the input. When Ocon (statistical average of the oxygen atom(s) taken up by each metal atom during CVD) is restricted to lie between 0 and 1, thermodynamic computations predict simultaneous deposition of FeO1-x, Fe3C, Fe3O4 and C in the inert ambient. At high temperature and in a carbon-rich atmosphere, iron carbide decomposes to iron and carbon. Furthermore, FeO1-x yields Fe and Fe3O4 when cooled below 567°C. Therefore, the resulting film would be composed of Fe3O4, Fe and C, in agreement with experiment. The weight percentage of carbon (∼40%) calculated from thermodynamic analysis matches well with experimental data from TG-DTA.