TY - JOUR
T1 - Preparation and crystallization of hollow α-Fe2O3 microspheres following the gas-bubble template method
AU - Valladares, L. De Los Santos
AU - León Félix, L.
AU - Espinoza Suarez, S. M.
AU - Bustamante Dominguez, A. G.
AU - Mitrelias, T.
AU - Holmes, S.
AU - Moreno, N. O.
AU - Albino Aguiar, J.
AU - Barnes, C. H.W.
PY - 2016/2/1
Y1 - 2016/2/1
N2 - © 2015 Published by Elsevier B.V. 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.
AB - © 2015 Published by Elsevier B.V. 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.
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U2 - 10.1016/j.matchemphys.2015.11.021
DO - 10.1016/j.matchemphys.2015.11.021
M3 - Article
SN - 0254-0584
SP - 21
EP - 27
JO - Materials Chemistry and Physics
JF - Materials Chemistry and Physics
ER -