Ultra-low-electric power electrophoretic deposition by using non-flammable hydrofluoroether

Abstract

A relative dielectric constant of a solvent is important for the electrophoretic deposition (EPD) suspension, and when the electrical resistance of the solvent is high, a large quantity of material is expected to be deposited. In this study, ethylperfluorobutylether (EFE), which is a kind of hydrofluoroether, was applied as the solvent for preparing a particle suspension for the EPD. EFE has the advantages of being polar, non-flammable, and having high electrical insulation properties. Silica powder was selected as the deposition material. When EFE is used, unlike when acetone-based EPD suspension was used, the amount deposited remains the same, but power consumption is 1/2,000 or less. Depending on conditions, power consumption is reducible even to 1/200,000. Thus, highly efficient EPD with ultra power saving ability was achieved. In addition, this process is extremely safe as EFE is nonflammable, removing the hazard of ignition. As the specific gravity of EFE is large, sedimentation of inorganic particles is slow; therefore, the dispersibility is excellent, and highly uniform coatings can be obtained. Unlike water-based EPD suspensions, the application of a high voltage is possible. In the present study, the deposition behavior was no different from that for conventional EPD, being controllable by varying the applied voltage, deposition time, and particle concentration.

Ultra-Low-Power Electrophoretic Deposition of Silica Powder with Nonflammable Organic Solvent

“…The zeta potential of the silica particles was measured at 25°C with an electrophoretic light-scattering spectrophotometer (Zetasizer-nano ZS, Malvern Instruments Ltd, Worcestershire, UK). EPD experiments were performed as described below [1]. First, silica powder was dried through heat treatment at 120°C for 3 h, and then allowed to cool to room temperature under a dry atmosphere, which was achieved by using silica gel in a desiccator.…”

“…Various types of ceramic powders can be deposited by electrophoretic deposition (EPD), so it has been attracting increasing interest as a ceramic processing technique. The charge of the particles and electrophoresis is considered in general as follows [1]: The electrical double layer between the solution and the particles is related to particle charging. When the thickness of the electrical double layer (1/κ) is sufficiently small relative to the particle diameter (α) or the particle diameter is sufficiently large (κα>1), the electrophoretic mobility, u e (m 2 /s•V), follows Smoluchowski's eq.…”

“…We have already reported nonflammable organic solvents that can be applied to EPD [1,12], which are hydrofluoroethers (HFE). This means the possibility of EPD with the safe application of a high voltage.…”

“…This means the possibility of EPD with the safe application of a high voltage. In initial investigations on the HFE series in EPD, ethyl-perfluorobutyl ether (EFE) was used as the solvent for the EPD suspension [1].The molecular formula of EFE is C 4 F 9 OC 2 H 5 , and its boiling point is 76 °C, which is suitable for EPD applications. The relative dielectric constant of EFE is 7.35, and its density is 1.43 g/cm 3 , which is 1.4 times that of water and around 1.75 times that of alcohol or acetone.…”