One-step thermal oxidation synthesis of large-area Mn 3 O 4 nanoflakes at low temperature in air atmosphere
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Rare Met. DOI 10.1007/s12598-014-0389-x
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One-step thermal oxidation synthesis of large-area Mn3O4 nanoflakes at low temperature in air atmosphere Ming-Long Zhong*, Bin Yang, Cheng-Jun Guo, Hai-Ping Huang, Bai-Xiong Liu, Hui-Ping Liu
Received: 5 August 2013 / Revised: 30 December 2013 / Accepted: 2 September 2014 Ó The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg 2014
Abstract Single-crystalline Mn3O4 nanoflakes were grown on manganese sheets by one-step thermal oxidation process at 360–500 °C in ambient atmosphere. The samples were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), Raman and transmission electron microscope (TEM). The nanoflakes with a size of 15–20 nm in thickness, *60 nm in width, and *210 nm in length are obtained at 360 °C for 24 h. A surface diffusion mechanism is proposed to explain the growth of manganese oxide nanostructures via thermal oxidation, which includes two steps: manganese oxide (MnO/Mn3O4) layers form firstly, and then Mn3O4 nanostructures grow above the upper metal oxide layer to form multi-layered structures, MnO/Mn3O4/Mn3O4–nanoflakes. The nucleation and growth of Mn3O4 nanostructures are related to the surface energy and different growth rates along different crystal directions, which are controlled by the diffusion of the metal and gas molecule. Keywords Mn3O4; Nanostructure; Thermal oxidation; Growth mechanism
nanoscale devices. 1D metal oxide nanostructures have growing interest due to their special shapes, compositions, and chemical and physical properties, which are widely used in catalysis, sensors, optoelectronic, and electronic devices and energy production areas [1–5]. Among the metal oxides, manganese oxides are important materials due to their wide range of applications in ion exchange, catalytic, electrochemical, and magnetic properties [1–4]. In addition, Mn3O4 is the most stable oxide of manganese, and in the current research field, it is used in catalysts [5], rechargeable batteries [6], electrochemical capacitors [7], and magneto-electronic [8] devices. Moreover, Mn3O4 is particularly used as main sources of manganese ferrite materials [9]. Many methods were adopted to get 1D Mn3O4 nanostructures, including solvothermal/hydrothermal [10, 11], vacuum calcining precursors [12], vapor phase growth [13], thermal decomposition [14], ultrasonic, microwave, and gamma irradiation [15–17], and chemical liquid homogeneous precipitation [18]. In this paper, a novel and a very simple non-catalytic one-step process pathway was introduced for the synthesis of single-crystalline Mn3O4 nanoflakes by directly heating the manganese substrates in ambient condition. The growth mechanism was also discussed.
1 Introduction One-dimensional (1D) nanomaterials, such as nanowires, nanobelts, nanoflakes, and nanowalls are expected to play an important role as interconnects and functional units in fabricating electronic, optoelectronic, and electromechanical
M.-L. Zhong*, B. Yang, C.-J. Guo, H.-P.
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