An investigation of color development by means of the factorial design in wall tile glazes with ferrochromium fly ash

Abstract

In tile manufacturing; generally different glazes with 1-15 wt% pigment and dye are used to obtain aesthetic properties. It can be said that pigment and dyes are the most expensive raw materials in glaze production due to its high costs limits. Ferrochromium fly ashes are a waste material obtained from the manufacturing of ferrochromium alloy. It mainly consists of chrome, ferric oxides, CaO and also MgO and Al2O3. This study outlines a novel approach in formulating tile glaze production as coloring agent. With this aim factorial design of experiment is used for defining the main factors on color formation. These factors are calcination temperature of fly ash, amount of fly ash and type of glaze. Ferrochromium fly ash is calcined at 1000, 1100 and 1160°C for 6 h and added at 1-4 wt% to transparent, opaque and matt glaze compositions. Glazed wall tiles were sintered at 1145°C for 30 min. For comparison of the colorimetric parameters (L*, a*, b*) of glazes spectrometer is used. The crystalline phases of the obtained glazed samples and fly ashes which calcined at different temperatures and different type glazes are evaluated by X-ray diffraction and scanning electron microscopy (SEM, EDS), respectively. Different brown tones are observed related to zinc iron chromite spinel crystal structure in glazed wall tiles. The most effective factors are determined by factorial design as amount of fly ash for L* parameter, and glaze type for a*, b* parameters.