Investigation of surface-modified anhydrous borax utilisation in raw glazes

Abstract

This study aims to determine the feasibility of preparing ceramic glaze using a surface-modified borate, which contributes boron to the composition without the need of a fritting process. In this context, surface modification of anhydrous borax powders (ABP) with magnesium stearate (MgSt) via dry powder coating is investigated. The surface modification of ABP with MgSt is optimised by employing modifier dosage of 0.5, 1, and 2 wt% and coating periods of 30, 60, and 120 min. The resulting powders are comparatively characterised via wettability, solubility, and dispersibility tests. The structural changes in surface-treated ABP are investigated using X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR) analyses. The results indicate that ABP surface could be switched from hydrophilic (17°) to hydrophobic (115°), its water solubility decreased from 40% to 10%, and a coating yield of approximately 74% was achieved with MgSt dosage of 1 wt% at a processing period of 2 h. Furthermore, FT-IR and XPS results indicated that MgSt is mainly coated over the surface of ABP via physical adsorption rather than chemical bonding. The glaze containing surface-treated ABP that was fired at 1050 °C, demonstrated complete melting and surface coverage without defects. Thus, effective dry coating as a single-step approach could be applied to obtain surface-modified ABP, which offers controlled solubility in glaze suspensions with improved dispersibility and excellent glaze coverage of the surfaces.