Controlled preparation of vanadium pentoxide films and their multicolor electrochromic properties

This chapter contains sections titled: Abstract Introduction Experimental Procedure Results Conclusions Acknowledgments References

C/C composite surface modified by electrophoretic depositing SiC nanowires and its brazing to Nb

Micro arc oxidation (MAO) and electrophoretic deposition (EPD) process are employed to fabricate a dense coating on magnesium alloy to protect it from corrosion in engineering application. The EPD film changes the damping characteristic of magnesium alloy, and both the MAO and EPD process change the bending stiffness of samples being treated. Damping loss factor (DLF) test and sound transmission experiments were carried out for AZ31B magnesium alloy with coating fabricated by MAO and EPD processes. The results indicate that DLF is improved in frequency range from 0–850 Hz. Bending stiffness of the samples is improved with MAO and EPD treatment. As a result, the sound transmission loss (LST) is improved in the stiffness control stage of the sound transmission verse frequency curve. To the samples by electrophoresis process, the LST is improved in frequency range from 2500–3200 Hz, because the damping loss factor is improved with EPD process. The results are useful for the surface treatment to enhance the damping loss factor, LST and widespread application of magnesium alloy while improving the corrosion resistance.

Electrophoresis deposition of Ag nanoparticles on TiO2 nanotube arrays electrode for hydrogen peroxide sensing

The electrophoretic deposition (EPD) process enables more uniform coating layers and saves time over the traditional laminating (LN) process. LiNi0.8Co0.1Mn0.1O2 (NCM811) is prepared by EPD and LN processes in this study. The electrode materials, which are composed of active materials, conductive agents, and binders, are more uniformly dispersed on the substrate by the EPD process when compared with the LN process. Since the weight ratio of NCM811 can be changed through the EPD process, the specific capacity is calculated by weighing the deposited active materials after the process. The crystal structure and particle morphology of the prepared cathode electrode are investigated by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. The electrode prepared by EPD delivers a specific discharge capacity of 189.3 mAh g-1 at a current rate of 0.2 C at the first cycle and exhibits capacity retention of 88.6% after the 40th cycle. Compared with LN, EPD shows a good rate capability at various current rates from 0.2 to 2.5 C. These results provide the evidence of the superior electrochemical properties and process efficiency of the electrodes prepared by EPD.

Electrophoretic deposition of aluminum particles from pure propan-2-ol suspensions

Study on the friction reducing effect of graphene coating prepared by electrophoretic deposition

Electrophoretic deposition (EPD) process has certain advantages such as it can be applied for a mass production and also can be combined with magnetic crystal alignment technique. In this work, we prepared lead-free 85(Bi0.5Na0.5)TiO3–15BaTiO3 (85BNT–15BT) piezoelectric ceramics by conventional uniaxial pressing and EPD process. Various conditions were optimized such as suspension media, applied electrical field, and deposition time in order to yield dense green ceramics of 85BNT–15BT composition using EPD process. 85BNT–15BT ceramics prepared using EPD process revealed the Curie temperature of about 250 °C, coercive field of about 30 kV/cm, and piezoelectric constant (d 33) of 75 pC/N. The EPD-processed samples exhibited structural and electrical properties similar to that of the conventionally processed one suggesting the successful fabrication of 85BNT–15BT piezoelectric ceramics by EPD method without composition deviation. This study lays a foundation on the fabrication of Bi-based lead-free piezoelectric ceramics by an alternative route other than the conventionally practiced solid-state reaction method maintaining the similar chemical composition, moreover, leaving a large space to explore more in the future.

Eggshell waste is rich source of calcium carbonate and can be applied to protect steel pipe from corrosion. Calcium carbonate precipitation can be naturally formed as a coating to protect steel pipe from oxygen diffusion. However, with calcium carbonate formed due to natural process, it is difficult to achieve the adequate thickness and capable of protecting the steel pipe. By adapting his corrosion protection mechanism, application of eggshell is of mild steel to eliminate the lengthy and complicated corrosion control system has been practiced. In this research, the eggshell powder was applied to coat the mild steel substrate using the electrophoretic deposition (EPD) process. The EPD process is simple and cheap. The eggshell was successfully coated on mild steel substrates at deposition voltage ranged between 20 to 100 volts and sintering temperatures at 400, 500 and 600°C. The best coating morphology and adhesion strength were determined at deposition voltage of 100 volts for 1 minute and sintering temperature at 600°C. These conditions are based on the morphology of the eggshell surface and the highest adhesion strength of the coated samples. The finding demonstrates the ability of the eggshell to be coated on steel substrate using the EPD process with good adhesion strength.

Nanosized platinum particles supported on carbon black carriers (Pt∕C) are popular for use in fabrication of proton exchange membrane fuel cells (PEMFCs). Here, an electrophoretic deposition (EPD) process is proposed to investigate the power performance of Pt∕C nanopowders onto various carbon-based electrodes for the PEMFC applications in a better controlled and cost-effective manner. Novel deposition of Pt∕C nanocatalysts and Nafion® solution via electrophoretic process give rise to higher deposition efficiency and a uniform distribution of catalyst and Nafion ionomer on the electrodes of PEMFCs. Preparation of an EPD suspension with good dispersivity is much desirable for an agreeable overall performance of catalyst coating in terms of types of organic solvents, milling processes, and use of pH adjusting agents and surfactants in the EPD suspension. The EPD suspension was prepared by sonication of mixture of Pt∕C nanopowders, Nafion solution and isopropyl alcohol, the optimal pH value of which was reached by using acetic acid or ammonium hydroxide. The colloidal stability of EPD suspension was achieved at pH ∼10 for an EPD suspension of either Pt∕C catalysts or mixture of Pt∕C catalysts and Nafion ionomer. A nicely distributed deposition of Pt∕C nanocatalysts and Nafion ionomer on both hydrophilic or hydrophobic carbon-based electrodes was successfully obtained by using Pt∕C concentration of 1.0g∕l, electrical field of 300V∕cm, and deposition time of 5min. Microstructural analysis results indicate that Pt∕C nanopowders not only embrace the entire surface of carbon fibers but also infiltrate into the gaps and voids in fiber bundles such that a higher contact area of the same loading of Pt∕C nanocatalysts through the EPD process is thus expected. At present, the EPD process can effectively save more of Pt catalyst loading on electrodes in PEMFC, as compared to conventional methods, such as screen printing, brushing, or spraying through the similar level of power performance for PEMFCs.

The electrophoretic deposition process of Ni nano-particles in organic suspension was employed for self-repairing of heat exchanger tubes. For this purpose, Ni nano-particles prepared by levitation-gas condensation were dispersed into the solution of ethanol with the addition of dispersant. The pitted Ni alloy specimen was prepared by applying a potential of 0.9 V (vs. Ag/AgCl) in aqueous 0.1 M NaCl solution. For electrophoretic deposition of Ni nano-particles on the specimen, a constant electric field of 100 V cm-1 was applied to the specimen for 180 s in Nidispersed solution. It was found that as the electrophoretic deposition time increased, the size of the pit remarkably decreased due to the agglomeration of Ni nano-particles at the pit with a higher current value rather than the outer surfaces of the specimen with a lower current value. Moreover, the current density increased with electrophoretic deposition time and reached a constant value. From the above, it is concluded that as the electrophoretic deposition proceeds, the pit becomes smaller in size, and hence the nano-particles more extensively aggregate at the pit by lyosphere distortion.

Introduction Interest in controlling the assembly of the nanostructured materials has recently increased due to their great potential for a wide range of applications [1]. The processes of nanostructured materials require more complex methods. The electrophoretic deposition (EPD) of ceramic materials has become attractive not only because of its high versatility but also because of low cost equipment [2]. EPD process can be applied to various types of substrates such as fibers, cloths and complex shaped metals [3]. Development of composites with multi-scale reinforcements consisting of multi-walled carbon nanotubes or carbon nanofibers has also been explored [4]. Although coating metal oxide on various types of substrates by EPD has been well studied, few studies have been performed regarding the deposition on conductive fabrics such as metal plated fabrics or carbon fabrics. Such a flexible, soft and nonfragile substrate is being explored for flexible and wearable functional device, but the deposition behaviors and the properties of the deposits have not been thoroughly investigated.In this study, ZnO nanoparticles and other nanostructures were coated by EPD on flexible fabrics and solid plate substrates. The effects of particle size, pH of suspension, applied voltage and substrate type on the EPD kinetics and morphological properties were investigated. The structural and optical properties of deposit ZnO layers by EPD were also examined by SEM, XRD and UV–Vis DRS.Experimental Four different sizes (50, 100, 200, and 400 nm) of commercial ZnO powders were used. ZnO particles were mixed with ethanol. PEI was added as a dispersant and the pH levels of the suspensions were adjusted with NH4OH. Other shapes of nanostructures were also synthesized for EPD. The deposition process was performed using two electrodes, fixed with distance of 10 mm, vertically immersed in prepared suspensions. Stainless steel plates, copper plates, copper coated fabrics, carbon fabrics were used as the working electrode and stainless steel plates were used as the counter electrode. The deposited area on the each substrate was 1 cm2. The experiments were performed within 1-5 min under a constant voltage of 10-100 V. The structural and optical properties of deposit ZnO layers by EPD were analyzed by using SEM, XRD and UV–Vis DRS.Results To study the effect of particle size and pH in suspension, EPD performed with 4 different sizes of ZnO nanoparticles. The suspension was prepared at different pH ranging from 8 to11, and a constant voltage of 50 V was applied for 5 min. For all suspension, deposition weights showed sharp decrease over pH 10 and increased with the decrease of the particle size, which may result from the change of zeta potential in the solution.The effect of applied voltage was verified by EPD with 4 different size of ZnO powders at pH 9 for 1 min with the applied voltage of 10-100 V. The experimental results were compared with Zhang’s equation [5]. The deposition weight increase with the voltage increase, as expected.ZnO nanoparticles were deposited on flexible fabrics and solid plates for comparison. The weight gain of the deposit on both substrates was measured as a function of applied voltage. The weight gain of ZnO deposits on both Cu coated fabric and Cu plate increased linearly with the applied voltage, but larger deposition weight on Cu coated fabric was observed. Larger surface area of woven fabric due to non-flat surface can be attributed to more deposition of ZnO nanoparticles.XRD patterns show only peaks of ZnO and substrates. No preferred orientation of ZnO layers was observed. Morphologies of deposited layers show smaller particle size shows denser layer. In addition, higher electric field in EPD process promotes particles to be coated more quickly, but uniform and dense coating may be limited. The optical properties of dried ZnO layer prepared EPD show comparable results to reported bulk ZnO ceramic.Conclusions Nanostructured ZnO was deposited on fabric substrates by EPD on fabric. Dominant parameters to determine EPD process on the fabric were investigated by comparing reported EPD empirical equations. Among the investigated parameters, particle size in suspension appears to play an important role in EPD kinetics. The characterization results of the nanostructured ZnO on fabrics could provide a path to promote the development of flexible or wearable devices.AcknowledgementsThis research was supported by Agency for Defense Development (ADD) as global corporative research for direct urine fuel cell.

Electrochemical properties of protoporphyrin IX zinc(II) films

The long term fixation of biomedical implants constitutes an issue in the clinical praxis. Implant fixation can be improved by functionalizing its surface. In fact, the tissue response around an implant is conditioned by its surface morphological and chemical properties. Coatings for implants (orthopedic and dental) function at the bone-implant fixation interface. As proved by research activities in the biomedical field, coatings with topographic features in the nano- and micro-range are promising in terms of enhanced osteointegration, thus improved implant fixation. As for surface chemistry, titanium dioxide (TiO2) is an estabilished material for biomedical implants thanks to its outstanding physical and chemical properties such as high corrosion resistance and good biocompatibility. Electrophoretic deposition (EPD) is a simple and versatile coating technique. According to literature, EPD is an emerging potential coating technique for biomedical implants. In this work, the use of EPD in the preparation of TiO2 coatings characterized by a controlled multi-scale structured surface was addressed. For this aim, EPD was combined with a new procedure of particle functionalization and with the use of a fugitive spacer (polystyrene, PS) for the sintering treatment. A control and better understanding of the EPD process were achieved through a preliminary parametric study on EPD of TiO2 nanoparticles and PS microbeads. Particle concentration was found to play a key role in the EPD deposit formation of TiO2 nanoparticles (cathodic) and PS microbeads (anodic). A threshold value of particle concentration was identified, below which no deposit growth occurred. An interpretation of this finding was provided on the base of a new formulation of the EPD deposition mechanism. The results of the particle concentration study contributed to the preparation of suspensions with TiO2-PS composite particles, which could be used for cathodic EPD. Composite TiO2-PS particles with TiO2 nanoparticles covering PS microbeads were obtained in a newly developed wet colloidal process based on heterocoagulation and the use of polyelectrolytes. The resulting TiO2-PS particles were cathodically deposited on Ti6Al4V substrates. A sintering post-treatment caused the burning out of the PS beads and the densification of the TiO2 nanoparticles. The desired coatings with controlled micro- and nano-topography were achieved. The investigation on the role of particle concentration in EPD and the new interpretation of the deposition mechanism bring a deeper understanding of the EPD process. The achievement of TiO2 coatings with controlled morphology in the micro- and nano-range prepared by cathodic EPD on Ti6Al4V substrates is a contribution to the ongoing research on biomedical implants. Mechanical tests and surface analysis evaluating wettability and in vitro cell behavior with the achieved coatings are relevant topics for further research.

Electrophoretic deposition of reduced graphene oxide nanosheets on TiO2 nanotube arrays for dye-sensitized solar cells