前驱体法制备Mn_2O_3空心橄榄形结构及形貌演化

利用苹果酸还原高锰酸钾以水热合成方法制备了具有橄榄形貌的纳米结构MnCO3前驱体,通过600℃焙烧MnCO3前驱体得到橄榄形Mn2O3.以扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、热重-差热分析(TG-DTA)等方法对产物的形貌和结构进行了表征.考察了MnCO3前驱体微观形貌随水热反应时间的演变:当水热反应时间为2h时得到具有橄榄形形貌的MnCO3前驱体,空心结构的壁比较厚;当水热反应时间延长到6h时得到的MnCO3前驱体仍然具有橄榄形形貌,壁变薄;当反应时间延长到24h时得到的MnCO3前驱体仍然具有橄榄形形貌,并且壁非常薄.我们推测在Ostwald熟化机理作用下,空心橄榄形MnCO3前驱体随着反应时间的延长其壁逐渐由160nm演化为30nm.

Synthesis of Mn2O3 with a Hollow Olive Shape and Its Morphology Evolution

Permanganic potassium was reduced by malic acid under hydrothermal conditions without a template or additives and olive-shaped MnCO₃ particles were obtained. After the MnCO₃ precursor was calcined at 600 °C for 3 h, Mn₂O₃ was obtained and the olive-shape morphology was maintained. The products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetry-differential thermal analysis (TG-DTA). The effect of hydrothermal reaction time on the morphology of the products was studied. A MnCO₃ precursor with hollow olive morphology and thick wall was obtained when the reaction time was 2 h. When the reaction time was increased to 6 h, the wall of the hollow olive-shaped particles became thinner. When the reaction time was increased to 24 h the wall thickness of the MnCO₃ precursor with the hollow olive morphology was about 30 nm. Because of the Ostwald-Ripening effect, the morphology of the MnCO₃ precursor gradually evolved from thick-wall hollow olive to thin-wall hollow olive by increasing the reaction time.