Surface reactivity and electrophoretic deposition of ZrO2-MgO mechanical mixture

Abstract

Electrophoretic deposition (EPD) is a precision technique useful for obtaining high quality ceramic bodies with controlled dimensions and smooth coatings. The electrophoretic deposition rate is highly dependent on the surface chemistry of the powders, especially when dealing with multi-component systems. The objective of this work is to study the surface reactivity of both ZrO 2 and MgO in ethanol suspension to provide experimental benchmarks to control EPD of a ZrO2-3 wt% MgO mechanical mixture (Z3M) in ethanol. Infrared spectroscopy (FTIR) showed that ZrO2 surface spontaneously reacts with ethanol, generating negative electrophoretic mobility of the particles (-0.07 × 10-8 V-1 s-1) measured by Electroacoustic Sonic Amplitude (ESA). MgO surface also spontaneously reacted with ethanol, but a positive electrophoretic mobility was observed in this case (0.26 × 10-8 V-1 s-1). Scanning Electron Microscopy of Z3M dried from ethanol suspension showed that MgO particles were located around the ZrO2 particles, forming composite agglomerates, probably due to the electrostatic attraction between MgO and ZrO2 particles. Homogeneous deposits could be obtained from EPD of Z3M ethanol suspensions. Mercury intrusion porosimetry showed that the ZrO 2-MgO green deposited bodies using different voltages had similar pores diameters distributions, indicating that the ZrO2-MgO agglomerates are not affected by the increasing deposition rates. © Springer Science+Business Media, LLC 2007.