Thermal behavior and coloration study of silica-coated α-Fe ₂O ₃ and β-FeOOH nanocapsules

This manuscript reports characterization of the colorations and thermal behaviors of the silica-coated α-Fe ₂O ₃ and β-FeOOH nanocapsules. Prepared β-FeOOH and α-Fe ₂O ₃ nanoparticles were coated with silica using tetraethylorthosilicate (TEOS) and cetyltrimethyl-ammonium bromide (CTAB) as a surface modifier for the comparison of physical properties of both samples. XRD patterns of the silica-coated β-FeOOH and α-Fe ₂ by ₃ nanoparticles were heated to 1000 °C, show a hematite (α-Fe ₂O ₃) structure. The silica-coated ev -FeOOH nanoparticles became almost entirely hollow at 1000 °C due to their volume reduction. In addition, the coloration values of the transformation nano capsule α-Fe ₂O ₃ are lower than those of the silica-coated a-Fe ₂O ₃ nanostructures. On the other hand, the silica-coated α-Fe ₂ 10 ₃ nanoparticles retained their colorations and shapes after being heated to 1000 °C. The morphologies, crystal structures and colorations of the as prepared samples were analyzed by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction and CIE colorimeter.