刚性聚合物修饰BaTiO3纳米线及其复合物介电和储能性能研究

Dielectric ceramic particles/polymer composites possess advantages such as high dielectric constant, low dielectric loss, high breakdown strength and flexibility, which are promising in developing renewable energy storage sources with high energy storage density and high power. At present, it is difficult to further increase the energy storage density of the composites and the effects of the interfaces on dielectric and energy storage properties are still needed to be clarified. This project plans to synthesize BaTiO3 nanofibers (BT NFs) with high quality and high aspect ratios via hydrothermal method. Surface modification of BT NFs by a kind of rigid liquid crystal polymer, i.e. PMPCS, is proposed for the first time, taking advantage of the rigidity and orientation properties of PMPCS to precisely control the modification layer, which provide a feasible technical route to quantitatively establish the relationship between the interface effects and the composites properties. 3D direct writing technique is applied to control the alignment of BT NFs in polymer matrix and prepare for the composite film with designed fine structures. With the aid of FEM tool, the effects of key factors, such as BT NFs’ aspect radios, alignments and the thickness of the modifier layer, on the dielectric and energy storage properties of such composites will be clarified, resulting in significant improvement of the energy storage density. The outcomes from this study will contribute to the knowledge of materials science, and offer a guideline for further development and applications of the dielectric composites.

介电陶瓷颗粒/聚合物复合材料兼具高介电常数、低损耗、高抗击穿电场和柔韧性等优点，为发展高储能密度、高功率的可再生能源储能器件提供了新的前景。如何提高该类复合材料的储能密度、厘清界面效应对介电和储能特性的影响是当前亟需解决的难题。本项目通过水热法合成性能优异、长径比可控的钛酸钡纳米线；首次提出采用刚性液晶高分子 (PMPCS)修饰纳米线表面，利用这类聚合物的刚性和自取向精确地控制纳米线表面的修饰剂层，为定量阐明界面效应与复合物性能的本质联系提供了技术基础；采用3D直写成型技术控制纳米线在聚合物基体中的分布形态并制备精细结构可控的复合物膜；结合有限元分析，获得纳米线长径比、分布形态、修饰剂层厚度等关键因素与复合物介电和储能性能的相关性，实现该类复合材料储能密度的大幅提高。本项目的研究丰富了材料科学的知识体系，为推动介电复合材料的发展和应用提供了科学依据和指导。

介电陶瓷颗粒/聚合物复合材料为发展高储能密度、高功率的可再生能源储能器件提供了新的前景。如何提高该类复合材料的储能密度、厘清界面效应对介电和储能特性的影响是当前亟需解决的难题。本项目通过水热法合成性能优异、长径比可控的BaTiO3纳米线，提出采用刚性液晶高分子修饰纳米线表面，利用这类聚合物的刚性和自取向精确地控制纳米线表面的修饰剂层，为定量阐明界面效应与复合物性能的本质联系提供了技术基础；采用3D直写成型技术控制纳米线在聚合物基体中的分布形态并制备精细结构可控的复合物膜；结合有限元分析，获得纳米线长径比、分布形态、修饰剂层厚度等关键因素与复合物介电和储能性能的相关性，实现储能密度的大幅提高。主要内容有:.(1) 采用两步水热法合成BaTiO3纳米线，采用原位活性聚合的方法，将PMPCS接枝包覆在BaTiO3纳米线表面，形成核-壳结构的纳米填料与P(VDF-HFP)复合。结果表明，PMPCS修饰后的BaTiO3纳米线在聚合物基体中的分散性和相容性得到改善；复合材料在1kHz下的相对介电常数随填料含量的增加逐渐由6.9增加到22.5，同时介电损耗小于0.05，当BaTiO3@PMPCS纳米线含量为5.0 vol%时，复合材料在300 kV/m电场下有效能量密度为7.5 J/cm3。.(2) 将含氟液晶高分子PTFMPCS包覆在BaTiO3纳米线表面，利用液晶高分子刚性的特点，通过改变分子量制备了不同PTFMPCS层厚度的BaTiO3核壳纳米结构，并与PVDF复合；结果表明，PTFMPCS厚度为14.8nm时比为9.2nm时所制备的复合材料具有更高的介电常数、抗击穿电场值和能量密度。PTFMPCS厚度为14.8nm时，5.0vol.% BaTiO3@PTFMPCS纳米线含量的复合材料在466kV/m电场下放电能量密度达到14.64 J/cm3。.(3) 应用3D直写方法实现BaTiO3纳米线填料沿复合材料面内平行取向，结果表明，相比BaTiO3纳米线无规排列的复合材料，BaTiO3纳米线定向排列的复合材料具有更高的抗击穿电场值和储能密度。含有5.0vol%定向排列和无规分布BaTiO3纳米线的P(VDF-CTFE)复合物材料的最大有效储能密度为分别为14.52 J/cm3和9.34 J/cm3，有效能量密度提高了55.46%。