Surface reactivity and electrophoretic deposition of ZrO₂–MgO mechanical mixture

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 ZrO₂ 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 ZrO₂–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.