In Situ Catalytic Encapsulation of Core-Shell Nanoparticles Having Variable Shell Thickness: Dielectric and Energy Storage Properties of High-Permittivity Metal Oxide Nanocomposites
In Situ Catalytic Encapsulation of Core-Shell Nanoparticles Having Variable Shell Thickness: Dielectric and Energy Storage Properties of High-Permittivity Metal Oxide Nanocomposites
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DOI：
10.1021/cm1009493
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发表时间：
2010-09-28
影响因子：
8.6
通讯作者：
Marks, Tobin J.
中科院分区：
文献类型：
--
作者：
Li, Zhong;Fredin, Lisa A.;Marks, Tobin J.
通过逐层甲基铝氧烷包覆工艺制备了具有不同Al 2 O3壳层厚度的氧化铝包覆的高介电常数BaTiO 3和ZrO 2核壳纳米粒子。随后的单中心茂金属催化剂[外消旋-乙烯-双茚基]二氯化锆（EBIZrCl 2）的化学吸附活化这些Al 2 O3-封装的纳米粒子，然后通过丙烯加成，提供0-3金属氧化物-全同立构聚丙烯纳米复合材料。通过X射线衍射、透射电子显微镜、扫描电子显微镜、差示扫描量热法、原子力显微镜和拉曼光谱分析了纳米复合材料的微观结构。原位聚合过程产生在聚烯烃基质中均匀分散的纳米颗粒。电测量表明，作为填料纳米粒子的浓度增加，纳米复合材料的有效介电常数增加，提供高达6.2的介电常数值。这种复合材料的有效介电常数可以通过Maxwell-Garnett形式主义使用有效介质理论预测，用于低于0.06的纳米颗粒的体积分数（nu（f））。该纳米复合材料在10（5）V/cm的电场下具有类似于10（-7）-10（-9）A/cm（2）的漏电流密度，并且在100 Hz-1 MHz的频率范围内具有非常低的介电损耗。增加Al 2 O3壳层厚度可以显著抑制这些纳米复合材料的漏电流和高场介电损耗。
Aluminum oxide encapsulated high-permittivity (epsilon) BaTiO3 and ZrO2 core-shell nanoparticles having variable Al2O3 shell thicknesses were prepared via a layer-by-layer methylaluminoxane coating process. Subsequent chemisorptive activation of the single-site metallocene catalyst [rac-ethylene-bisindenyl]zirconium dichloride (EBIZrCl2) on these Al2O3-encapsulated nanoparticles, followed by propylene addition, affords 0-3 metal oxide-isotactic polypropylene nanocomposites. Nanocomposite microstructure is analyzed by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, differential scanning calorimetry, atomic force microscopy, and Raman spectroscopy. The in situ polymerization process yields homogeneously dispersed nanoparticles in a polyolefin matrix. Electrical measurements indicate that as the concentration of the filler nanoparticles increases, the effective permittivity of the nanocomposites increases, affording epsilon values as high as 6.2. The effective permittivites of such composites can be predicted by the Maxwell-Garnett formalism using the effective medium theory for volume fractions (nu(f)) of nanoparticles below 0.06. The nanocomposites have leakage current densities of similar to 10(-7)-10(-9) A/cm(2) at an electric field of 10(5) V/cm, and very low dielectric loss in the frequency range 100 Hz-1 MHz. Increasing the Al2O3 shell thickness dramatically suppresses the leakage current and high field dielectric loss in these nanocomposites.