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

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