Preparation and crystallization of hollow α-Fe2O3 microspheres following the gas-bubble template method

L. De Los Santos Valladares, L. León Félix, S. M. Espinoza Suarez, A. G. Bustamante Dominguez, T. Mitrelias, S. Holmes, N. O. Moreno, J. Albino Aguiar, C. H.W. Barnes

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10 Scopus citations

Abstract

In this work we report the formation of hollow α-Fe2O3 (hematite) microspheres by the gas-bubble template method. This technique is simple and it does not require hard templates, surfactants, special conditions of atmosphere or complex steps. After reacting Fe(NO3)3.9H2O and citric acid in water by sol-gel, the precursor was annealed in air at different temperatures between 180 and 600 °C. Annealing at 550 and 600 °C generates bubbles on the melt which crystallize and oxidizes to form hematite hollow spheres after quenching. The morphology and crystal evolution are studied by means of X-ray diffraction and scanning electron microscopy. We found that after annealing at 250-400 °C, the sample consist of a mixture of magnetite, maghemite and hematite. Single hematite phase in the form of hollow microspheres is obtained after annealing at 550 and 600 °C. The crystallization and crystal size of the hematite shells increase with annealing temperature. A possible mechanism for hollow sphere formation is presented.

Original languageEnglish
Pages (from-to)21-27
Number of pages7
JournalMaterials Chemistry and Physics
Volume169
DOIs
StatePublished - 1 Feb 2016
Externally publishedYes

Bibliographical note

Funding Information:
This work was supported by the Engineering and Physical Science Research Council (EPSRC No. EP/J003638/1). The work in Peru has been supported by the Ministry of Production of Peru through the program "Programa Nacional de Innovación para la Competitividad y Productividad" (Innóvate Perú project No. ECIP-1- P-069-14). The work in Brazil was supported by CNPq (307552/ 2012-8), CAPES (PNPD-230.007518/2011-11) and FACEPE (APQ- 0589-1.05/08).

Funding Information:
This work was supported by the Engineering and Physical Science Research Council (EPSRC No. EP/J003638/1 ). The work in Peru has been supported by the Ministry of Production of Peru through the program “Programa Nacional de Innovación para la Competitividad y Productividad” (Innóvate Perú project No. ECIP-1-P-069-14 ). The work in Brazil was supported by CNPq ( 307552/2012-8 ), CAPES ( PNPD-230.007518/2011-11 ) and FACEPE ( APQ-0589-1.05/08 ).

Publisher Copyright:
© 2015 Published by Elsevier B.V.

Keywords

  • Crystal growth
  • Magnetic materials
  • Nanostructures
  • Oxides
  • X-ray diffraction

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