カオリンから群青顔料の合成における反応メカニズム

Abstract

The reaction mechanism in synthesis of ultramarine blue with kaolin, sulfur, sodium carbonate, silica and rosin was investigated by a thermal analysis, a powder X-ray diffraction analysis and a Raman scattering. The mixture of the raw materials was calcined at 820 °C for 5 hours (heating rate：0.1 °C/min.) to form the ultramarine green, which was the intermediate products of the ultramarine blue. The ultramarine blue was finally prepared with the oxidation of the ultramarine green at 500 °C. In the calcination process, the sodium sulfides were generated by the reductive reaction of sodium carbonate, sulfur and rosin at 400∼500 °C, and the NaAlSiO4 was formed by the synthesis of anhydrous amorphous kaolin and the sodium sulfides at about 600 °C. And, the ultramarine green begun to form at near 700 °C with the reaction of the NaAlSiO4 and the sodium sulfides. In the oxidation process, the sulfur atoms was generated from the oxidation of the sodium sulfides which excessively existed in the ultramarine green, the sulfur atoms transformed the (S2-) ions of the ultramarine green into the (S3-) ions. And these reactions caused the ultramarine green to convert the ultramarine blue. The lattice parameter of ultramarine green was increased during the oxidation.