Controlling the hardness and wear resistance of opaque white glaze by addition of halloysite clay in the composition

The effect of adding 0.1, 0.3, 0.6, 1.0, and 2.0 wt.% halloysite clay, which calcined and uncalcined form, was studied on the glossy opaque glaze hardness and mechanical properties. Since the most significant disadvantage of opaque glazes is low hardness, halloysite particles with higher toughness were added to glazes to increase this property. Since more stable halloysite tubes were obtained after the calcination process, both calcined and uncalcined halloysite additions were made to see the effect of calcination, and the obtained results were examined. Detailed technological, mechanical and microstructural characterization studies were done on glazed samples. In addition, the change in the melting behavior of the glaze and the glassy phase viscosity of the addition of halloysite was also examined and interpreted considering hot stage microscope analyses. Compared to standard glossy opaque glaze, almost all the halloysite added samples displayed similar optical properties but higher hardness, surface wear resistance, and fracture toughness values. Among the case studies, the 2% halloysite addition by weight (uncalcined and calcined form) showed the highest mechanical properties.