Preparation of Free Standing Alumina Thick Film by Electrophoretic Deposition Using Formed Carbon Powder as Electrode

Abstract

Electrophoretic deposition (EPD) is an attractive powder forming method in which charged particles in a liquid are forced to migrate to an electrode by applied DC electric field and deposit to form a thick film. As an application of the EPD method, a free standing α-alumina thick film was prepared by the EPD using formed carbon powder as an electrode and following firing. The formed carbon electrode was prepared by uniaxial pressing of graphite or graphite/carbon black mixed powder, added with some binder. A commercial α-alumina powder with the median diameter of 0.6 μm was dispersed into ethanol, which contained HCl to enhance its dispersibility, and used for the EPD. After the deposition, the electrode was fired in the furnace with flowing air. For the successful preparation of the alumina thick film, the selection of the binder added to the electrode is important. When paraffin was used as a binder, the alumina deposit was broken into small pieces during heating because the electrode largely expands during heating. On the other hand, when polyvinyl alcohol (PVA) or polyvinyl butyral (PVB) was used, the deposit was sintered into a continuous thick film. The surface of the thick film has a characteristic micrometer-scale uneven texture, which is transferred from the surface of the carbon electrode. This microtexture can be easily controlled by altering the surface texture of the electrode, for example by changing the starting carbon material. As the shape of the formed carbon electrode is easily changed, alumina thick film components with various shapes can be prepared by this method. In this study, an alumina thick film on which some letters were patterned, and a wavy shaped alumina thick film were successively prepared.