稳态强磁场下PVDF基磁电复合材料的微结构调控及耦合机制研究

The magnetoelectric properties of the poly(vinylidene fluoride) (PVDF) based 0-3 magnetoelectric composite materials is closely related with the content and distribution of the magnetoelectric phase as well as the coupling effect of the PVDF and functional phase. This project makes use of the strong force on the magnetic functional powder by applying a high steady magnetic field to arrange the spatial distribution of the magnetoelectric composite powders which show good mobility in the molten PVDF during the themoforming process and have a core-shell( lead zirconate titanate/cobalt ferrite) structure that exhibits good magnetoelectric coupling effect. In addition, the surface of the functional powder is modified to strengthen the interface physical adsorption and promote the precipitation of the β-PVDF phase induced by forming interface bond, which enhances the coupling effect of the PVDF and functional phase. Moreover, the functional powders driven by the high steady magnetic field move towards a certain direct which can induce orientation β-PVDF phase because of the strong coupling effect, and further strengthen the interface coupling of the PVDF andfunctional phase. In short, the functional powders with directional arrangement and the ferroelectric β-PVDF phase which exhibits high degree of orientation reflect the achievement of the unity of high content functional phase, high interfacial coupling effect and high orientation, which contributes to reduce the polarization voltage and improve the magnetoelectric performance. The implementation of this project has a role in promoting the level of the research on high-performance flexible magnetoelectric composite.

聚偏氟乙烯（PVDF）基0-3型磁电复合材料的磁电性能和磁电功能相含量、分布及其与PVDF耦合效应密切相关。项目以芯-壳结构（锆钛酸铅/铁酸钴）纳米线作为功能相，利用热成型过程中PVDF熔融状态下纳米线的可动性，借助稳态强磁场对磁性材料的强作用力进行空间分布调控；对纳米线进行表面修饰，利用带电基团与PVDF分子链的化学键合作用增强界面耦合效应，诱导PVDF铁电β相并使其有序排列，增强PVDF压电性，发挥PVDF既作粘合剂又做压电相的双重功能；稳态强磁场驱动的纳米线通过强界面耦合对PVDF产生定向拉力作用，进一步促进β相产生，提高压电性能，提升界面耦合强度；稳态强磁场下纳米线定向排布、铁电β相PVDF高取向及纳米线与PVDF界面高效耦合实现了PVDF高压电相、高取向性、强界面耦合的统一，降低了极化电压，提高了磁电性能。项目研究将促进稳态强磁场大科学装置在功能材料制备新方法方面发挥积极作用。

PVDF基磁电复合材料是一种能够实现磁电性能转换的材料，目前已成为功能材料领域一个研究热点。为了实现 PVDF粘合作用和压电作用的双重功能，提升界面有效耦合度，增强复合材料磁电效应，本基金从微结构调控出发，探究了磁场对PVDF基复合材料性能的改善作用。首先制备了稳态磁场预处理的PVDF/CoFe2O4复合材料，研究了磁场作用下不同CoFe2O4的掺杂含量和磁场强度对PVDF析晶行为的影响，结果表明5 wt%掺杂量CoFe2O4纳米颗粒可以提高PVDF中β相的含量至84%，400Oe的稳态磁场可进一步提高β至95%；接着制备了PVDF/(PZT)/TD磁电复合材料，并研究了热压过程中施加诱导磁场对复合材料的影响，结果表明复合材料的磁电转换系数在200 Oe达到最大值82.5 mV·cm-1·Oe-1，比无磁场诱导提高了40%以上；然后制备了三层结构的(TD+PVDF)/(PZT+PVDF)/(TD+PVDF) (TPT)磁电复合材料，并探究了热压过程中施加磁场对磁电系数的影响，结果表明层厚比为2:3:2的TPT磁电复合材料的磁电系数αME为2556.61 mV·cm-1·Oe-1，相比0-3型材料提升了30倍以上，当热压过程中施加的磁场大小为300 Oe，谐振频率在75 kHz附近时，αME取得最大值3051.67 mV·cm-1·Oe-1，比无磁场时的αME增加了19%；进一步将CoFe2O4与PZT用静电纺丝工艺制成核壳结构的纳米线，分散到PVDF基质中制成复合材料，并研究了在热压过程中膜Y轴方向的磁场对复合材料储能特性的影响，结果表明当磁场大小为600 Oe时，储能密度达到最大，为2.8 J/cm3；最后将掺Mn的PZT纳米线分散到PVDF基质中制得了1-3型复合材料，并将复合材料在强磁场下热处理，探究了不同磁场强度、处理时间、处理温度对复合材料性能的影响，结果表明当磁场强度为7.875T，处理时间为20 min，处理温度为140℃时，样品极化强度达到最大，110 MV/m下为1.8 μC/cm-2。该基金对促进我国高性能磁电复合材料的研发和应用推广具有重要的理论及实际意义。