Influence of Water on the Preparation of Thick Mesoporous Silica Coatings by the Electrophoretic Deposition Method

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

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

“…Only low quantities of silica were deposited from dehydrated acetone, in comparison to both that containing water and the EFE, which was attributed to the low zeta potential in this solvent. 20),27) On the one hand, when acetone containing 1 wt % of water was used, an almost comparable amount of deposit was obtained as in the case of EFE. The energy efficiency of the deposition from these two solvents was calculated from the quantities of silica deposited and the current densities.…”

Electrophoretic deposition of mesoporous silica powder synthesized by spray-drying method

“…We found that it was possible to prepare uniform MPS coatings on a aluminum substrate by controlling the amount of water in acetone as the EPD bath. 16) In this study, we synthesized an MPS powder by spray-drying method 17) and formed thick coatings on an aluminum substrate by EPD. In order to confirm the possibility of controlling the amount of MPS powder deposited on the substrate, namely, the coating thickness, we investigated the dispersion stability of the EPD bath, and the influence of the EPD condition on the coating thickness.…”