Flux particle size and composition effects on the evolution of sanitaryware vitreous body

Experimental Procedure A combination of three industrial flux compositions (sodium fedspar > 67 wt.%, potassium feldspar > 69 wt.% and a 1:1 mix of them) and two particle size distributions (d50 ? 45 and 75 ?m) have been used to prepare sanitaryware slips (flux amount about 25 wt.%). Samples have been fired up to 1200 °C, and then characterized in terms of water absorption, density, X-ray diffraction (at ambient and HT conditions) and micro-structure occurrence by Scanning Electron Microscopy. Results Despite of the small differences in the samples, some trends have been observed. Water absorption and interconnected porosity (obtained by density measurements) are minimized if sodium feldspar is used, suggesting a better densification, in agreement with [1]. The same effect is achieved by decreasing the flux particle size, which leads to a higher reactivity of the starting slip, in keeping with [2]. The application of RIR-Rietveld method [3] to powder diffraction patterns shows that also differences in phase composition are present: in particular, the highest glass content has been observed if the smallest flux particle size is used, in combination with a sodium bearing feldspar. Moreover, observations from HT-powder diffraction experiments (thermal range 900-1100°C) do not yield significant differences in the feldspar thermal decomposition as a function of flux composition and particle size. References [1] Das & Dana (2003) Termochimica Acta, 406, 199-206. [2] Alves, Melchiades & Boschi (2012) Journal of European Ceramic Society, 32, 2095-2102. [3] Gualtieri (2000) Journal of Applied Crystallography, 33, 267-278.