自供能柔性多铁性磁电复合薄膜的结构构筑与性能调控

Due to their unique collective physical properties and rapid magnetoelectric response, multiferroic composite film with the co-existence of ferroelectricity and ferromagnetism have a great potential in new and smart self-powering device applications. Aimed to uncovering giant multiferroic response, a tailored electric-active polymer-based composite film is developed which is consisting of high-order inorganic magnetostrictive and organic piezoelectric components. In particular, a viable processing technique will be explored for the fabrication of high-performance multiferroic polymer composite film. The proposed magnetic-field-assisted electrospinning is a non-invasive and efficient process. Moreover, this viscoelastic state processing and extra field- induced method provides us an unprecedented opportunity to dramatically enhance the magnetoelectric (ME) response of the flexible composite film. Therefore, the alignment of the 1-D ferromagnetism under the magnetic field will yield large magnetostriction, while the preferential formation of the polar crystalline phase of the ferroelectric polymers in electrospinning will result in greatly increased piezoelectricity. Detailed and systematic characterization of the resulting structures and properties will be carried out to gain fundamental insight into key relationships between material-structure-process-properties. We also plan to exploit unique mechanisms and phenomena in the multifunctional materials such as the interfacial coupling effect which becomes significant as the size of constituents is reduced to nanometer scales to enhance the cross-coupled responses. Furthermore, our preliminary studies have demonstrated a strong coupling of molecularly engineered ferroelectric polymers and ferromagnetic inorganics, thus opening an exciting research arena where various electro- and magneto-active nanostructures can be judiciously assembled and processed to exhibit colossal collective properties.

铁电基元与铁磁基元共存的多铁性薄膜，具有优异的巨磁电耦合性能以及快速、高效的多信号响应，在军事、信息、传感等领域具有令人瞩目的发展前景，为自供能技术的实现提供了可能。为探明铁磁基元的有序性、铁电基元的结晶结构以及两相界面对多铁性薄膜磁-力-电耦合效应的影响，本课题以聚偏氟乙烯及其共聚物为铁电基体、以生长于一定长度碳纳米管的铁氧体作为铁磁基元，采用磁场辅助静电纺丝技术以及高分子类橡胶态加工方法，制备一类铁磁基元在铁电基体中高度有序排列的柔性磁电复合薄膜。通过磁场诱导调控铁磁基元的高度有序结构，温度外力协同增强功能基元的磁-力-电耦合效应，以外加电场诱导铁电基元的结晶过程，阐明功能基元有序程度及界面结构对多铁性薄膜磁电耦合性能的影响规律，建立通过外场诱导-结构调控-加工协同-性能优化制备自供能多铁性磁电复合薄膜的新技术与新方法，为多功能材料的结构设计以及性能调控提供新途径。

柔性多铁性磁电复合薄膜具有自供能、快响应的特性，可实现磁能、机械能、电能等多种能量相互转化，在无源驱动、自供能系统、可穿戴器件领域具有重要的应用前景。本课题采用溶剂热法制备了室温超顺磁CoFe2O4纳米粒子，其平均粒径为6.5nm，饱和磁化强度为35emu/g；通过静电纺丝和高温煅烧技术制备了CoFe2O4纳米纤维，平均直径控制在150~250nm，在室温下为铁磁性，饱和磁化强度可达87emu/g；采用模板法和原位生长技术，分别以氧化多壁碳纳米管（sCNT）和磺化芳纶（s-PPTA）为模板，制备了一维结构的sCNT-CoFe2O4和s-PPTA/CoFe2O4磁性纳米纤维，其饱和磁化强度最高可达58emu/g。为调控磁性纳米材料与基体的界面结构，采用1H,1H,2H,2H-全氟辛基三乙氧基硅烷（POTS）对磁性纳米材料进行氟化改性，制备了负载大量柔性短链的氟化磁性纳米材料（统称为fMNMs）。以聚偏氟乙烯及其共聚物（统称为cPVDF）为铁电基体，采用溶液流延法和静电纺丝技术制备了cPVDF/fMNMs复合膜，辅助外加电场和外加磁场调控了fMNMs在cPVDF基体中的有序排布，探究了fMNMs的结构、取向程度、有序排列对cPVDF基体的结晶结构的影响；以温度和外力调控cPVDF的结晶结构和两相界面，系统分析温度及外力作用下cPVDF基体的结晶程度、晶型、晶粒尺寸以及铁电与铁磁基元相界面结构对cPVDF-sMNLs/cPVDF薄膜铁电性能、铁磁性能以及磁-力-电耦合效应的影响，所制备的复合薄膜的磁电耦合系数可达39.5mV·cm-1·Oe-1。以cPVDF/fMNMs为功能材料，搭建了力-电、磁-力-电响应器件，实现了cPVDF/fMNMs在拉伸、弯曲、卷绕等条件下的力电耦合，磁场存在下信号强度提高40%，为无源智能器件研制提供了理论基础和器件原型，实现了项目预期与研究目标。该项目在国家自然科学基金的支持下，取得了一系列有价值的研究成果，共发表学术研究论文17篇，参加学术会议论文12人次，授权国家发明专利5项，培养了3名博士研究生和9名硕士研究生，完成了项目预期的研究指标。