Changes in the glaze characteristics and moderate antibacterial activity of ceramic tile glazes with the addition of ZnO

Abstract

Zinc glaze forms a glossy surface or exhibits the characteristics of a crystalline glaze owing to the precipitation of fan shaped crystals, depending on the ZnO content. In this study, we fabricated tile specimens by adding 5-20 wt.% ZnO to commercial tile glaze and analyzed the changes in their surface characteristics, crystalline phase, microstructure, and ion dissolution. The effects of such changes on the antibacterial activity of the glaze were also analyzed. When the ZnO content exceeded 10 wt.%, the gloss of the glaze decreased, whereas the surface roughness and contact angle increased because the willemite crystalline phase generated in the glaze grew as it was exposed to the surface. In the glazes, reactive oxygen species (ROS) were not detected, irrespective of the ZnO content. As the ZnO content increased, the Zn ion dissolution increased, causing a change in the total dissolved ion concentration of the glaze. Furthermore, apart from the changes in the other characteristics of the analyzed glaze specimens, the antibacterial activity against S. aureus and E. co/i was found to increase with the Zn ion dissolution. As reported previously, zinc ion dissolution is apparently the major cause of the antibacterial activity exhibited by these glazes.