MnO_2 powder with self-grown core-shell structure Was prepared by hydrothermal synthesis using(NH_4)_2S_2O_8 as the oxidizing agent and MnSO_4·H_2O as the Mn source.The composition,crystal shape,morphology,magnetic characteristic and thermal stability of the samples were characterized by powder X-ray diffraction(XRD),transmission electron microscopy(TEM),scanning electron microscopy(SEM),vibrating sample magnetometry(VSM) and thermogravimetric analysis(TG,DTA),respectively.In addition,the electromagnetic properties and microwave loss mechanism of MnO_2 specimens are discussed based on the tested electromagnetic parameters,such as the dielectric constant and permeability.The results show that MnO_2 powders have a self-grown core-shell structure with diameters of 3～5μm,the real and the imaginary part of the complex relative permittivity are 8.40～5.35 and 2.66～2.07,respectively,whereas the real and imaginary part of the complex permeability are as small as 1.04～1.14 and 0.03～0.21,respectively.Finally,the microwave loss mechanism and the thermally stable performance of MnO_2 withcore-shell structure are suggested.%采用水热合成法,以(NH_4)_2S_2O_8作氧化剂,以MnSO_4·H_2O为锰源,制备了自生核壳结构MnO_2:粉体.利用x射线粉末衍射、扫描电子显微镜、透射电子显微镜、振动样品磁强计和热重分析对产物进行成分、晶型、形貌、磁性能和热稳定性分析,并通过电磁参数的测试对产物的电磁特性以及电磁波损耗机制进行阐述.结果表明:所制得粉体是直径3～5μm的核壳结构海胆球形MnO_2,其复介电常数实部在8.40～5.35,虚部在2.66～2.07;复磁导率实部和虚部都很小,分别在1.04～1.14和0.03～0.21范围内.最后分析了核壳结构MnO_2的电磁波损耗机制以及热稳定性能.
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