I. Zhitomirsky

Application of electrophoretic and electrolytic deposition techniques in ceramics processing

Electrodeposition is gaining increasing interest as a ceramic processing technique for a variety of technical applications. Major advances in the areas of electrophoretic deposition (EPD) and electrolytic deposition (ELD) achieved in the last 24 months include the fabrication of: electrodes and films for solid oxide fuel cells, fibre-reinforced and graded ceramic composites, nanostructured materials as well as a variety of advanced films and coatings for electronic, biomedical, optical, catalytic and electrochemical applications.

ELECTROPHORETIC DEPOSITION OF HYDROXYAPATITE

Hydroxyapatite powders were prepared by a chemical precipitation method and electrophoretically deposited on Ti6Al4V surgical alloy substrates. The powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), particle size distribution and zeta potential measurements. Prior to electrophoretic deposition, anodic films were obtained on Ti6Al4V and studied by the Auger method. It was established that experimental conditions of powder preparation, electric field and stirring have a significant influence on suspension stability and deposit morphology. The deposition yield was studied at various deposition durations and applied voltages. Sintered coatings were studied by SEM and XRD.

Electrophoretic hydroxyapatite coatings and fibers

Submicron hydroxyapatite (HA) powders were prepared by a chemical precipitation method and electrophoretically deposited on individual carbon fibers, carbon fiber bundles and felts. After burning out of the fibrous carbon substrates the corresponding ceramic replicas were sintered. Experimental conditions were found for the formation of uniform HA coatings and hollow HA fibers of various diameters. The inner diameter of the hollow HA fibers can be controlled by variation of the number of carbon fibers in the bundle. The influence of the applied voltage on coating uniformity and deposition rate is discussed. Obtained coatings and fibers were characterized by SEM.

Electrophoretic deposition of ceramic materials for fuel cell applications

La0.8Sr0.2Ga0.875Mg0.125O3-x (LSGM), La0.8Sr0.2Co0.2Fe0.8O3-d (LSCF), yttria stabilized zirconia (YSZ) and (Ce0.8Gd0.2)O1.9 (CGO) were electrophoretically deposited on Ni foils and Ni-yttria stabilized zirconia substrates prepared by tape casting. It was demonstrated that the ethyl alcohol‐phosphate ester‐polyvinyl butyral system is an eAective solvent‐dispersant‐binder system for electrophoretic deposition of these materials. The influence of dispersant, binder and current density on deposition eAciency and deposit morphology was studied. The microstructure of the deposits was examined by electron microscopy. The proposed solvent‐ dispersant‐binder medium for electrophoretic deposition of LSGM, LSCF, YSZ and CGO has important advantages and implications in fuel cell design. # 2000 Elsevier Science Ltd. All rights reserved.

Cellulose Nanocrystal Aerogels as Universal 3D Lightweight Substrates for Supercapacitor Materials

Chemically cross-linked cellulose nanocrystal aerogels represent a versatile and universal substrate on which to prepare lightweight hybrid materials. In situ incorporation of polypyrrole nanofibers, polypyrrole-coated carbon nanotubes, and manganese dioxide nanoparticles in the aerogels gives flexible 3D supercapacitor devices with excellent capacitance retention, low internal resistance, and fast charge-discharge rates.

Electrophoretic and electrolytic deposition of ceramic coatings on carbon fibers

Abstract Alumina, zirconia, titania, lead zirconate titanate, hydroxyapatite and chemically bonded ceramics in the system CaO-SiO 2 -P 2 O 5 were deposited via electrophoretic or/and electrolytic deposition methods on individual carbon fibers, bundles and felts, which served as cathodic substrates. Experimental conditions were determined for formation of uniform deposits of controlled thickness. After burning out of carbon fibers the corresponding ceramic replicas can be obtained. The possibility to form multilayer alumina/zirconia hollow fibers with sharp interfaces between alumina and zirconia layers has been demonstrated. Obtained coatings and fibers were studied by SEM. Experimental results obtained by electrophoretic and electrolytic deposition methods were compared.

Electrochemical deposition of ceria and doped ceria films

Abstract Cathodic electrodeposition of CeO 2 and Ce 1− x Gd x O 2− y was performed from aqueous and mixed ethyl alcohol-water solutions of CeCl 3 and GdCl 3 on Ni foil and Ni–yttria stabilized zirconia substrates. The influence of hydrogen peroxide on the electrodeposition process was studied. Electrochemical intercalation of poly(diallyldimethylammonium chloride) into the deposits was demonstrated and the mechanism of intercalation is discussed. The experimental results indicate that the polymer acts as a binder, providing better adhesion of the organoceramic deposits and reducing cracking while allowing for film formation on porous substrates. The deposits were studied by X-ray diffraction, thermogravimetric analysis and scanning electron microscopy.

Electrolytic and electrophoretic deposition of CeO2 films

Abstract Cerium oxide films of thickness 0.1–300 μm were deposited on Ni substrates via cathodic electrolytic and electrophoretic deposition. The films were studied by X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. Experimental results obtained by both deposition methods are compared. The influence of deposition parameters and additives on deposition yields and film morphologies is studied and discussed.

Electrodeposition of ceramic films from non-aqueous and mixed solutions

The preparation of films of TiO2, ZrO2 and PbZrO3 by electrodeposition from N,N-dimethylformamide solution, has been performed. A new method of cathodic electrodeposition of ceramic films via peroxoprecursors has been proposed and demonstrated on the deposition of TiO2. The effect of thermal treatment on the phase content of the obtained films and the influence of the solvent used on the deposition process and film morphology were studied.

Electrophoretic deposition of electrolyte materials for solid oxide fuel cells

Electrophoretic deposition of electrolyte materials for solid oxide fuel cells, including La0.8Sr0.2Ga0.875Mg0.125O3−x, yttria stabilized zirconia and (Ce0.8Gd0.2)O1.9, was studied under various experimental conditions. The use of phosphate ester as a dispersant and poly (vinyl butyral) as a binder enabled high deposition rate and formation of crack-free, adherent deposits. Electrodeposition rates were quantified in experiments performed at constant current and constant voltage modes from suspensions in ethanol, isopropanol and mixed ethanol—isopropanol solvents. The microstructure of as prepared and sintered deposits was studied by electron microscopy. The bath composition was optimized to enable formation of dense deposits.