Wollastonite as a Flux for Ceramics Bodies

Wollastonite is a calcium silicate mineral natural or synthetic. Commercial wollastonite starts to melt at about 1450°C and can not be considered a "flux" as alkali feldspar. For this function, it depends on the reaction with other raw materials. Faced with this, came the goal of this work which was to investigate the mechanism of action of wollastonite as a ceramic flux. The use of wollastonite in ceramic bodies was investigated by analysis of its reactivity with other materials such as quartz, kaolin, talc and feldspar. It was analyzed the technological properties of the final parts, especially in relation to the firing temperature, phase formation and technological properties (mechanical strength, porosity, etc.). The results of this characterization showed that the technical properties of the parts are developed according to commercial porcelain products.

X-ray diffraction and SEM/EDX studies on technological evolution of the oxide-fluoride ceramic flux for submerged arc-surfacing

The ceramic flux for submerged arc-surfacing with main component composition MgO (10.0 wt. %)-Al2O3 (25.0 wt. %)-SiO2 (40.0 wt. %)-CaF2 (25.0 wt. %) was prepared in a disk dryer-granulator using a sodium/potassium silicate solution as a binder. X-ray powder diffraction (XRPD) collected at r.t. identified ?- phase of quartz, Al2O3, MgO and CaF2 of the initial components in the samples taken after granulation and subsequent annealing at 600 ?C. In contrast to the low temperature annealing, anorthite (CaAl2Si2O8) is the main phase in the composition of the samples remelted at 1500 ?C and quenched subsequently. Chemical analysis performed by means of scanning electron microscopy with energy-dispersive X-ray spectroscopy analysis (SEM/EDX) detects that the grains of the remelted samples possess the same Ca : Al : Si elemental ratio as anorthite. High temperature X-ray diffraction (HTXRD) was used to examine structural transformation in the solid at 600 ?C < T < 1200 ?C and stages of thermal evolution of ceramic flux were determined. The ceramic flux melts completely at the temperature above 1350 ?C. The intensity pattern of the flux melt was obtained by X-ray diffraction of scattered X-rays at 1450 ?C. After calculating the structure factor (SF), the radial distribution function (RDF) was evaluated and used to calculate the structural basicity of the flux melt.