Effect of a static magnetic field on the preparation of MnOOH and Mn3O4 by a hydrothermal process

Abstract

In this paper, manganese oxides/oxyhydroxides were prepared by a low-temperature hydrothermal process in a static magnetic field. The products were analyzed with XRD, TEM, HRTEM and VSM. Single-crystalline nanowires (20 nm in diameter and 1 μm in length) of MnOOH were obtained under zero magnetic fields. However, some cubic particles of Mn₃O₄ were formed when a static magnetic field was applied. Furthermore, the quantity of Mn₃O₄ increased with the increase of the magnetic flux density. Quantitative thermodynamic calculation results showed that the magnetic Gibbs energy would change the direction of the chemical reaction to obtain Mn₃O₄.