Electrophoretic Deposition: Fundamentals and Applications III

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Authors: Shigeo Hayashi, Junpei Onoe, Kazuyoshi Ebina, Nobuhiro Kodama
Abstract: Electrophoretic deposition (EPD) and infiltration (EPI) behavior of a natural zeolite (clinoptilolite, produced in Akita prefecture, Japan) particles on/into a steel and a porous glass substrates were investigated for the purpose of the environmental purification. The obtained deposit of the zeolite prepared by the EPD was less durable against peeling off compared with the EPI process, but it was improved by use of silica sol particles as a binder. Ion uptake efficiency of the EPD sample was superior to that of the EPI sample, that will be caused by the shape factor of the zeolite particle deposit.
Authors: Christos Argirusis, Jana Grosse-Brauckmann, Georgia Sourkouni, Gilles Taillades, Jaques Roziere
Abstract: The present study uses electrophoretic deposition of yttrium doped barium cerate to prepare SOFC half cells on nickel/barium cerate (Ni/BaCe) and nickel / yttria stabilized zirconia (Ni/YSZ) substrates. Therefore we investigated charging and agglomeration behaviour of nanosized barium cerate powder in different solvents by means of a micro electrophoresis experiment and dynamic light scattering. Stable suspensions of barium cerate were prepared and deposition kinetics was examined prior to the preparation of thin membranes on the two cermets. Tests with different solvents and additive combinations showed that methyl-ethyl-keton (MEK) with addition of polyacrylic acid (PAA) is the best combination for the use of the suspension for electrophoretic deposition. Electrophoretic deposition in this case is a simple and low cost method to produce homogenous and dense layers in the scale of microns.
Authors: Ai Miyamoto, Hideyuki Negishi, Akira Endo, Bao Wang Lu, Keiji Sakaki, Takao Ohmori, Hiroshi Yanagishita, Kunihiro Watanabe
Abstract: The preparation of a thick coating of mesoporous silica (MPS) on metal substrates by electrophoretic deposition (EPD) has been studied for application to an advanced desiccant cooling system. In this study, we investigated the EPD mechanism of MPS in acetone under a constant applied voltage for the fabrication of a thick MPS coating. We consider that the main contributors to the resistance between the deposition electrode and the counter electrode are the deposited MPS layer and the EPD bath. The current density was measured during EPD under a constant applied DC voltage. The current density decreased as the EPD progressed, and the resistance increased between the electrodes. The AC impedance between the deposition substrate and the counter electrode was measured in the range of 10 Hz-80 kHz. We observed a single semicircle in the impedance plots.  We investigated the influence of the MPS powder concentration of the EPD bath and the amount of deposition layer on the total resistance. We found that the resistance caused by forming the MPS layer increased as EPD progressed whereas the resistance of EPD bath was almost constant through the EPD process. Moreover, we determined the EPD mechanism of MPS powder in acetone.
Authors: Sayaka Yanagida, Akira Nakajima, Yoshikazu Kameshima, Kiyoshi Okada
Abstract: This study investigated the effect of surface roughness on a coating of TiO2 submicron powders that had been applied on a stainless steel mesh using electrophoretic deposition (EPD). Roughness was provided to the surface of EPD coating using UV pre-illumination to the suspension prepared by isopropyl alcohol and commercial TiO2 powder. The Ra value was increased around 20% by this treatment. The rough coating provided a higher photocatalytic decomposition rate of 1,4-dioxane in water than a smooth coating obtained from the suspension without UV pre-illumination. That increase is attributable to the increase of the reaction field on the coating surface.
Authors: Mamiko Kawakita, Tetsuo Uchikoshi, Laxmidhar Besra, Tohru Suzuki, Jin Kawakita, Yoshio Sakka
Abstract: Crystal-oriented and crack-free thin TiO2 films with a good interfacial adhesion on indium-tin oxide (ITO) glass substrates for photoelectrodes were fabricated by the electrophoretic deposition (EPD) method in a 12 T strong magnetic field. A binder-free suspension for the EPD was prepared by dispersing TiO2 in the mixture of 2-propanol and 2,4-pentanedione. The electrophoretic mobility and the sedimentation rate were measured at various ratios of the mixed solution. The optimized state of the suspension exhibiting the highest surface charge potential and producing deposits with the highest green density was obtained at the 50:50 mixing ratio. The TiO2 films were characterized by XRD and SEM analyses. The photo-current measurement was also conducted to investigate the relation between the photo-anode characteristics of a dye-sensitized solar cell and the plane orientation of the TiO2 films
Authors: John Blackburn
Abstract: The potential for the commercial use of EPD as a manufacturing technique has been established. Rigs and equipment have been designed and constructed for the EPD of ceramic components to a range of geometries including tubes and plates. Components have been produced with uniform thickness up to 3mm, or with varying thickness. Systems have also been operated to produce ceramic coatings on metal substrates including flat foils, tubes, rods and complex shapes. Coatings of ZrO2, cerium gadolinium oxide (CGO), cermet mixtures, (La0.8Sr0.2)0.98Mn oxide (LSM), TiO2 and Al2O3 have all been successfully produced and such layers can be achieved with a deposition time of <2 minutes. Multiplying the number of EPD cells which can be operated simultaneously enables the average deposit time to be reduced to a level where commercial production becomes feasible. Thicker crack-free layers of the above materials up to 150micron have been produced for applications where a robust porous structure is required. XRD, SEM and EDX results have shown that the EPD methods developed for use in these systems are capable of producing layers from binary or ternary mixtures of suspension without segregation within the formed layers.
Authors: Peter Hope
Abstract: Semi-automatic handguns characterised by the classic Colt 1911 model rely on a reciprocating slide mechanism for loading and ejecting. The moving surfaces require a tight fit to maintain firing accuracy while having ease of movement to avoid misloading or jamming. The electrophoretic painting method is ideal for coating complex geometries where engineering tolerances need to be maintained. The anodically depositable paint system developed for this application incorporates nanosilica for reinforcement of the resin binder and a blend of polytetrafluoroethylene, boron nitride and molybdenum disulphide to provide a self-lubricating anti-corrosive coating. Colourants have been added to provide various appearance attributes. The formulating procedures for producing this type of complex electrophoretic paint are described. This includes considerations of manufacture, shelf life, shipping, application by the customer, and compliance with health and environmental regulations as well as meeting the extreme performance requirements of the end use.
Authors: Hui Xu, Ian P. Shapiro, Ping Xiao
Abstract: Yttria stabilized zirconia (YSZ) particle suspension in acetylacetone (ACAC) was deposited onto Fecralloy substrates by using EPD and then constrained sintered at 1200°C. Before EPD, the operational pH value of the suspension was adjusted with addition of acetic acid or base triethanolamine (TEA). The effect of suspension pH on the deposition of EPD coatings was studied with respect to the suspension stability, coating density and microstructure. Results showed that the zeta potential decreased to close to zero with the increase of pH value from 4.4 to 7.4, then increased with further increase of the pH. This ‘U’ shape zeta potential-pH relationship was probably resulted from the adsorption of TEA. This reduced the degree of particle coagulation and increased the packing density of the EPD coatings; therefore, promoted the sequent sintering of coatings which was evaluated by micro-hardness.
Authors: Hideyuki Negishi, Akira Endo, Ai Miyamoto, Keiji Sakaki, Takao Ohmori
Abstract: Ordered mesoporous silica (MPS) is expected to be used as an adsorbent for energy-efficient desiccant cooling systems. For practical use, it is important to be able to fabricate thick MPS coatings on metal supports. As we reported previously, MPS coatings on metal substrates can be formed using the electrophoretic deposition (EPD) method. Since MPS adsorbs a certain amount of water depending on the relative humidity, the amount of water adsorbed in MPS influences electrification, dispersion stability, and EPD behavior. In this study, we investigated the influence of water on the formation of thick MPS coatings by using an acetone bath. MPS powder was placed in a humidity-controlled vessel prior to EPD to adsorb water. The deposited amount tended to increase when dry MPS powder was used and when the water content of the acetone was reduced. In addition, the deposited amount was constant for 24 hours or more when the MPS powder was immersed in acetone containing 0.15 vol% of water. We found that dried MPS powder and acetone containing less than 0.45 vol% water were suitable for the stable preparation of thick MPS coatings. Consequently, 100 m-thick MPS coatings were successfully fabricated with the EPD method using dried MPS powder and an acetone bath containing 0.15 vol% water
Authors: Ian P. Shapiro, Xiao Feng Zhao, Hui Xu, Ping Xiao
Abstract: The constrained sintering behavior of yttria stabilized zirconia coatings containing 1 wt. % alumina produced using electrophoretic deposition has been studied. Coatings have been characterized by scanning electron microscopy, micro-hardness and fluorescence spectroscopy after sintering in air at 1100°C and 1200°C. These coatings were compared with those that additionally contained 1 wt. % soda-lime glass. Micro-hardness and fluorescence spectroscopy are shown to accurately monitor the density of the coatings. Fluorescence spectroscopy showed that the density across the coating is even, as expected from modelling literature. The addition of 1 wt. % of soda-lime glass is shown to improve the sintered density of coatings.

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