Shi Xiaoling, Cao Maosheng, Fang Xiaoyong
School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China.
J Nanosci Nanotechnol. 2011 Aug;11(8):6953-8. doi: 10.1166/jnn.2011.4252.
Large-scale beta-MnO2/SiO2 core-shell nanorods were synthesized by hydrolysis process. The product was characterized by XRD, EDS, SEM and TEM. The thickness of the SiO2 shell layer is about 3 nm approximately 5 nm, which can be tuned by changing the amount of tetraethyl orthosilicate (TEOS) and the reaction time. The dielectric properties of the synthesized core-shell nanorods at the temperature range from 373 K to 773 K in X-band were investigated in detail and the mechanism of the dielectric response was discussed. The dielectric loss of the SiO2-coated MnO2 nanorods at 773 K was about twice than that at 373 K. The high dielectric loss is mainly attributed to the interfacial polarization and the electromagnetic impedance match between the SiO2 shell layer and MnO2 core layer. The quantitative formula between the permittivity of beta-MnO2/SiO2 core-shell nanorods and the thickness of the SiO2 shell is established, which can be used to tune the dielectric properties of the core-shell nanorods through controlling the thickness of the SiO2 shell layer.
通过水解法合成了大规模的β-MnO₂/SiO₂核壳纳米棒。采用X射线衍射（XRD）、能谱分析（EDS）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）对产物进行了表征。SiO₂壳层的厚度约为3纳米至5纳米，可通过改变正硅酸乙酯（TEOS）的用量和反应时间进行调节。详细研究了合成的核壳纳米棒在X波段373 K至773 K温度范围内的介电性能，并讨论了介电响应机制。SiO₂包覆的MnO₂纳米棒在773 K时的介电损耗约为373 K时的两倍。高介电损耗主要归因于界面极化以及SiO₂壳层与MnO₂核层之间的电磁阻抗匹配。建立了β-MnO₂/SiO₂核壳纳米棒介电常数与SiO₂壳层厚度之间的定量公式，可通过控制SiO₂壳层厚度来调节核壳纳米棒的介电性能。
