Surface roughness improvement of near net shaped alumina by EPD

The high surface roughness of thick and dense alumina deposits prepared by long-term electrophoretic deposition (EPD) caused by surface inhomogeneities could be eliminated by changing the suspension composition or EPD parameters. This work is aimed at the influence of the suspension composition, more precisely on the increase of electrical conductivity through indifferent electrolyte (lithium chloride) addition and its effect on the surface roughness. At first, the electrical conductivity was adjusted by the various amounts of the stabilisers of mono-, di- and trichloroacetic acid in the range of 0.85–21.25 wt%. It was demonstrated that deposits prepared from these suspensions were several millimetres thick, dense with a relatively low surface roughness (Ra ≈ 10 μm) only when the electrical conductivity was higher than 4 μS/cm. If a portion of the stabiliser was replaced with indifferent electrolyte, it resulted in the significantly smoother surface with a roughness Ra ≈ 2 μm preserving all other benefits. Suggested optimization represents a useful novel approach for the preparation of dense, thick and near net-shaped alumina deposits with low surface roughness via EPD.