Bright Yellowish-Red Pigment Based on Hematite/Alumina Composites with a Unique Porous Disk-like Structure

Hideki Hashimoto; Jun Kiyohara; Arisa Isozaki; Yuya Arakawa; Tatsuo Fujii; Jun Takada; Hirofumi Inada; Taigo Takaishi; Hidetaka Asoh

doi:10.1021/acsomega.9b04297

Bright Yellowish-Red Pigment Based on Hematite/Alumina Composites with a Unique Porous Disk-like Structure

ACS Omega. 2020 Feb 21;5(8):4330-4337. doi: 10.1021/acsomega.9b04297. eCollection 2020 Mar 3.

Authors

Hideki Hashimoto¹, Jun Kiyohara¹, Arisa Isozaki¹, Yuya Arakawa², Tatsuo Fujii³, Jun Takada³, Hirofumi Inada², Taigo Takaishi², Hidetaka Asoh¹

Affiliations

¹ Department of Applied Chemistry, School of Advanced Engineering, Kogakuin University, 2665-1 Nakano, Hachioji, Tokyo 192-0015, Japan.
² Kyoto Municipal Institute of Industrial Technology and Culture, 91 Chudojiawatacho Kyoto, Shimogyo-ku, Kyoto 600-8815, Japan.
³ Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Kita-ku, Okayama 700-8530, Japan.

Abstract

Inspired by a bacteriogenic, iron-based oxide material and a traditional Japanese red pigment, a bright yellowish-red pigment was prepared by heating an Al-containing iron oxyhydroxide precursor. The obtained red pigment had a unique porous disk-like structure, comprising Al-substituted hematite particles and crystalline alumina nanoparticles. Although these disk-like structures loosely gathered to form an aggregate in powder, they can be easily dispersed into a single, disk-like structure by simple ultrasonic irradiation. The powder exhibited a bright yellowish-red color and high thermostability, making it attractive as a coloring material for various industrial products needing a bright-red color, high weather resistance, and durability. Quantitative color measurements revealed extremely high L*, a*, and b* values that are much greater than those of commercially available hematite. The thermostability test showed that even after exposure to high temperatures, the pigment retained the red color, indicating its high thermostability. The unique microstructure should be strongly related to the bright yellowish-red color and the high thermostability of the developed red pigment.