COLOR CHARACTERISTICS AND PROPERTIES OF HIGH-TEMPERATURE CERAMIC PIGMENTS, OBTAINED BY UTILIZATION OF BIO-WASTE

Abstract

The subject of this study are high-temperature pigments from the aluminum-silicon system. For their preparation, both pure starting raw materials and biowaste were used – ash from oxidized rice husks, containing 94.47% SiO₂. Cobalt, copper and nickel oxides were introduced as colorants in the batches. The quantities of the materials were weighed with an accuracy of 0.1 g, then they were mixed and homogenized dry in a Pulverisette-6 planetary mill. The high-temperature firing of the pigments was carried out in a NaberTherm furnace, in an air atmosphere at a final temperature of 1450°C, with a 2-hour isothermal hold. The X-ray phase analysis performed shows that the main phases in all compositions are mullite and corundum. It has been proven that when NiO is introduced into the batches in both series, nickel spinel is also obtained, i.e. nickel shows a strong tendency to form spinel. It has been established that copper ions, in turn, tend to form solid solutions with mullite. Some of them are included in the crystal lattice of mullite, defect it and thus promote the formation of mullite. In terms of color characteristics, the best indicators are those of the compositions with the chromophore cobalt. This chromophore ensures the production of pigments with a saturated blue color. In pigments obtained with the addition of oxidized rice husks as a source of SiO₂, the amount of blue color is b* = -28.2, and in pigments obtained from pure raw materials, the amount of blue color is b* = -31.1.