Abstract

This manuscript reports on compared color evolution about phase transformation of alpha-FeOOH@SiO_2 and beta-FeOOH@SiO_2 pigments. Prepared alpha-FeOOH and beta-FeOOH were coated with silica for enhancing thermal properties and coloration of both samples. To study phase and color of alpha-FeOOH and beta-FeOOH, we prepared nano sized iron oxide hydroxide pigments which were coated with SiO_2 using tetraethylorthosilicate and cetyltrimethyl-ammonium bromide as a surface modifier. The silica-coated both samples were calcined at high temperatures (300, 700 and 1000°C) and characterized by scanning electron microscopy, CIE L*a*b* color parameter measurements, transmission electron microscopy and UV-vis spectroscopy. The yellow alpha-FeOOH and beta-FeOOH was transformed to alpha-Fe_2O_3 with red, brown at 300, 700°C, respectively.

• Keywords: alpha-FeOOH;beta-FeOOH;Pigment;Phase transformation;Silica coating;