Preparation, microstructure, and color tone of microtubule material composed of hematite/amorphous-silicate nanocomposite from iron oxide of bacterial origin

Hideki Hashimoto, Hiroshi Asaoka, Takuya Nakano, Yoshihiro Kusano, Hiromichi Ishihara, Yasunori Ikeda, Makoto Nakanishi, Tatsuo Fujii, Tadanori Yokoyama, Nanao Horiishi, Tokuro Nanba, Jun Takada

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

By heating an amorphous iron oxide produced by Leptothrix ochracea, an iron-oxidizing bacterium species, at 600-1100°C in air for 2 h, vivid red-colored powdered materials including α-Fe 2O 3 (hematite) and amorphous silicate with high thermostability were prepared which offer potential for use as overglaze enamels on porcelain. The precise color tone of the materials greatly depends on the heat-treatment temperature. The most strikingly beautiful sample, heat-treated at 800°C, is light yellowish-red in color (L* = 47.3, a* = 34.1, and b* = 34.6), has a unique microstructure, and does not fade in color even with reheating at 800°C, which is the firing temperature for overglaze enamel on porcelain. The sample primarily consists of crystalline hematite particles ∼40 nm in diameter with slightly longer axis unit-cell parameters than those of pure hematite. The particles are covered with amorphous silicate phase ∼5 nm in thickness and are intricately interconnected into microtubules with an average diameter of 1.26 μm. The attractive color of this material is due to the following structural features: small particle size (∼40 nm), nanocomposite of hematite and amorphous silicate, and a microtubule structure that inhibits aggregation of individual hematite particles and microtubules.

Original languageEnglish
Pages (from-to)639-643
Number of pages5
JournalDyes and Pigments
Volume95
Issue number3
DOIs
Publication statusPublished - Dec 1 2012

Keywords

  • Amorphous silicate
  • Biogenous iron oxides
  • Hematite
  • Iron-oxidizing bacteria
  • Microtubule
  • Nanocomposite

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Process Chemistry and Technology

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