Structural and functional thick ceramic coatings by electrophoretic deposition (original) (raw)

Preparation of ceramic thin films by electrospray of ceramic suspensions

Conference Record of the 2000 IEEE Industry Applications Conference. Thirty-Fifth IAS Annual Meeting and World Conference on Industrial Applications of Electrical Energy (Cat. No.00CH37129), 2000

An electrostatic atomization technique has been developed to generate ultra-fine spray of ZrOl and Sic ceramic suspensions in a range of a few micrometers with a narrow size distribution. The aim of this work i s to generate fine spray of ceramic suspensions for preparation of uniform thin films of these ceramic materials on substrates. Compared to some other thin film deposition techniques, such as Chemical vapour deposition (CVD), physical vapour deposition (PVD) and plasma spray (PS) etc. the thin film deposition process using electrostatic atomization is not only cheap but also controllable. Preliminary results have shown that for low through-put atomization, the cone-jet is the most suitable method to produce a fine charged aerosol with a narrow size distribution, which is crucial to produce uniform thin films. It was found that the droplet size of the spray is in the range of a few micrometers with a narrow size distribution and that droplet size and spray current obey theoretical prediction of scaling law. The prepared Z r 0 2 and SIC thin films were observed to be homogenous with a particle size less than 10pm.

Electrostatic Sol–Spray Deposition of Nanostructured Ceramic Thin Films

Journal of Aerosol Science, 1999

Electrospraying has been developed into an electrostatic spray deposition technique for the deposition of ceramic thin "lms. The cone-jet spraying mode appears to be the most preferable for this purpose, and the domain where the cone-jet mode exists was found to depend strongly on the nozzle design. A nozzle with a large diameter and a tilted outlet widens the windows for both the applied high DC voltage and the #ow rates of a precursor liquid keeping the cone-jet mode intact. The results of three nozzle designs are compared, one of which has been selected for feeding two di!erent precursor liquids simultaneously. With three relevant sols as precursor liquids, nanostructured thin "lms of ZnO, ZrO , and Al O have been deposited. Their morphologies are dependent on the preparation of the precursor sols and the deposition temperature. Highly porous "lms were obtained by using a high deposition temperature and a sol prepared from a metal alkoxide or a metal acetate.

Layered ceramic composites via control of electrophoretic deposition kinetics

Journal of The European Ceramic Society, 2013

The article summarises optimisation of electrophoretic deposition of alumina and zirconia from concentrated isopropanolic suspensions stabilised by monochloracetic acid. Method for in situ monitoring of deposited mass was developed and experimentally checked. Prediction of electrophoretic deposition kinetics was based on the voltage drop measurement and electrophoretic mobility estimation from experimental kinetics data. It was shown that voltage change during electrophoretic deposition did not affect relative density of the deposited layers in the laminates prepared. For this purpose a method of the relative density measurement using the microscopic measurement of relative shrinkage of individual layers was developed. Accuracy of the method was confirmed by comparison with shrinkage measurement using high temperature dilatometry. Adopting obtained results the alumina/zirconia laminate with precise control of layers thicknesses and final densities was prepared.

Forming and Microstructure Control of Ceramics by Electrophoretic Deposition (EPD)

KONA Powder and Particle Journal, 2010

Electrophoretic deposition (EPD) is one of the colloidal processes during in ceramic production and has gained significant interest because of the high versatility of its use with different materials including nanopar ticles and its cost-ef fectiveness requiring simple equipment. Of the major parameters for ceramic processing involving the EPD, preparation of the suspensions and application methods of electric fields are particularly important factors that affect the microstructure. At the beginning of this review, we introduce the fundamental aspects of the EPD processing. We then focus on the following four points: (1) the stability of the Pb(Zr,Ti)O2 /ethonol suspension by the addition of phosphate esters and its influence on the subsequent EPD process, (2) the stability of a TiO2/(2-propanal 2.4 pentanedione) suspension, which is a suspension without dispersants, (3) the film performance of the pulsed direct current EPD using an aqueous suspension, and (4) the laminated textured ceramics by EPD in a strong magnetic field.

Electrophoretic Deposition of Lead Zirconate Titanate Ceramics

Journal of the American Ceramic Society, 2004

The formation of thick PZT films via electrophoretic deposition (EPD) was studied. The colloidal suspension of a nano-sized PZT powder dispersed in ethanol was prepared using a phosphate ester (PE) as a dispersant. The amount of PE addition on the stability of the PZT suspension has been investigated by measuring the pH and conductivity of the suspension, deposition weight and the relative density of the PZT green compacts. The effect of the applied voltage on the relative green density was also determined as a function of the wt% PE. The composition and microstructure of the sintered PZT ceramics were characterized by XRD and SEM. The electrical properties of the PZT ceramics were also investigated.

Electrophoretic deposition applied to thick metal–ceramic coatings

Surface and Coatings Technology, 2002

Electrophoretic deposition was used to fabricate thick (04 mm) metal-ceramic deposits from a non-aqueous slurry of nickel and alumina particles. A high solid volume in the slurry was identified as the primary parameter for depositing thick cermet coatings rather than the applied electric potential or ionic additive concentration. Ionic additives (MgCl , AlCl , etc.) were found 2 3 to adequately suspend the alumina particles and provide rapid deposition rates. The nickel particles proved to be more difficult to suspend in solution, thereby sacrificing control of the deposition composition. The use of small (3.0 mm) particles and continuously pumping the slurry alleviated the suspension problems but small electric potentials ((100 Vycm) were required to avoid the formation of rough, columnar deposits on the depositing electrode.

Dense, bubble-free ceramic deposits from aqueous suspensions by electrophoretic deposition

Journal of Materials Research, 2001

The characteristics of electrophoretic deposition (EPD) of positively charged particles onto a cathode were investigated using aqueous alumina and zirconia suspensions. The deposition was performed using several kinds of metal substrates at different current densities. For most substrate materials, a large number of macropores appeared in the deposit, and their size increased with the current density due to gas bubble formation. However, no macropores were formed in the deposit on a palladium substrate, regardless of the current density. The green density and sintering properties of the EPD deposits on a palladium substrate from aqueous suspensions were the same as from slip casting. Bubble-free zirconia/alumina laminate composites were also fabricated by EPD from aqueous suspensions.

Tailoring of Nano- and Microstructure in Biomimetically Synthesized Ceramic Films

2006

A novel ceramic thin film deposition approach through which inorganic materials were deposited on a functionalized organic matrix from aqueous media at low temperatures was studied. This process is analogous to the natural biomineralization process. Specifically, nanostructured ZrO 2 and TiO 2 thin films were deposited at about 70°C by the hydrolysis of Zr(SO 4) 2 and TiCl 4 aqueous precursor solutions, respectively, on silicon substrates coated with phosphonate-terminated selfassembled monolayers (SAMs). The as-deposited oxide films consisted of nanocrystallites of tetragonal ZrO 2 and anatase phase TiO 2 in size of 5-10 nm, while some amorphous phases existed as well. The principal mechanism for the formation of the films seems to be homogeneous nucleation of the bulk precipitates and their aggregation behavior in supersaturated solution. Different from the previous results, the ZrO 2 and TiO 2 films could also be deposited on bare silicon substrates without any SAMs, under the same conditions used for deposition on SAMs. The Derjaguin, Landau, Verwey and Overbeek (DLVO) theory was applied to disclose the mechanisms for the formation of the oxide films in the media of aqueous precursor solutions. The interactions of particlesubstrate, particle-deposited film, and particle-particle all exhibit negative minimal energies, indicating that the initial and subsequent continuous depositions on SAM and bare silicon, as well as particle aggregation, are thermodynamically favorable. In addition, the differences among the amplitudes of the minimal interaction energies may, however, reflect some preference of the deposition on SAMs to that on bare silicon. In an effort to evaluate mechanical integrity of the asdeposited ceramic films, the intrinsic elastic moduli of the as-deposited ceramic films were determined by using dynamic nanoindentations. Dye leak tests suggest that the as-deposited ceramic films, especially the TiO 2 films, enhance significantly the hermeticity performance of the device coatings.