Electrophoretic packing structure from aqueous nanoparticle suspension in pulse DC charging

Nanoparticle layers were deposited on a substrate of submillimeter-sized stainless steel wire. The layers were produced from an aqueous TiO2 suspension by pulse direct current (DC) electrophoretic deposition. The electro-sterically stabilized suspension was prepared by beads-milling process with TiO2 powders and an anionic surfactant as starting materials. The solid concentration of the prepared suspensions was 7.5 and 30 wt% concentration with average particle sizes of 10 and 50 nm, respectively. To examine the deposited layer structure, a cross-section was spontaneously cleaved perpendicular to the substrate starting from the inner layer towards the outer layer by applying a heat treatment technique. The state of particle inside the layer deposited by pulse DC charging was compared with the one prepared by conventional DC charging from the aspects of morphology and size distributions. More uniform particle layers can be obtained using the pulse DC charging compared to those of the conventional DC. By using pulse DC, a relatively high volume density of the deposited structure (up to 0.35 kg/m3 at 1.3 V/cm) can be obtained.