Synthesis and characterization of α-MnO₂ nanowires: Self-assembly and phase transformation to β-MnO₂ microcrystals

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• 作者：Xiong Zhang ; Wensheng Yang ; Junjiao Yang ; David G. Evans
• 关键词：A1. Crystal morphology ; A1. Low-dimensional structure ; A2. Hydrothermal crystal growth ; B1. Nanomaterials ; B1. Oxide
• 刊名：Journal of Crystal Growth
• 出版年：2008
• 出版时间：1 February 2008
• 年：2008
• 卷：310
• 期：3
• 页码：716-722
• 全文大小：833 K

文摘

Single-crystalline α-MnO₂ nanowires and β-MnO₂ microcrystals have been synthesized by a hydrothermal method. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and simultaneous thermogravimetry–mass spectrometry (TG–MS). The effects of varying the hydrothermal reaction times and the initial reactant concentrations on the morphology and crystalline structures of the final products have been investigated. It was found that at high reactant concentrations, the α-MnO₂ nanowires formed initially became self-assembled into bundles and subsequently underwent a phase transformation to β-MnO₂ microcrystals on prolonging the hydrothermal treatment. At low reactant concentrations, however, β-MnO₂ microcrystals were formed even after short hydrothermal reaction times. A possible mechanism for the oriented attachment of the α-MnO₂ nanowires and subsequent phase transformation to β-MnO₂ microcrystals has been suggested.