Tailoring electrostatic surface potential and adsorption capacity of porous ceramics by silica-assisted sintering

In this study, we apply silica-assisted sintering to develop porous yttria stabilized zirconia (YSZ) ceramics with tailored electrostatic surface potential and adsorption capacity as a promising alternative to chemical functionalization. The porous bodies were formed by partial sintering at 1050 degrees C and were investigated regarding the influence of admixtures of silica particles on sintering behavior, microstructural evolution and the resulting mechanical and surface properties of the material, particularly the surface potential. With increasing silica concentration, the sintering mechanism was gradually changed from solid state to liquid phase sintering, due to the wetting of YSZ by liquid silica and a resulting inhibition of mass transport, particle growth and diffusion-induced densification. Most importantly, due to the silica layer development, the isoelectric point (IEP) of the YSZ/silica material surfaces was systematically shifted towards the IEP of silica from pH 9.4 to 1.2 resulting in a more pronounced negative surface potential at neutral pH. The relationship between surface IEP and silica concentration was mathematically described using the IEPs of the starting materials, the YSZ particle radius and the glass layer thickness. This estimation allows us to tailor the surface coverage of the YSZ matrix with silica as well as the resulting electrostatic surface potential. We further demonstrate how the applied processing route can be effectively used to develop ceramics with specified adsorption capacities for protein immobilization for use in filtration, bioprocessing or biomaterial applications. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of Acta Materialia Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)