摘 要

随着科技的发展和环保意识的提高，人类对环境污染以及能源短缺问题的关注程度越来越高。压电材料作为实现机械能与电能相互转换的材料得到了快速的发展。其中NaNbO₃由于不含有毒物质铅以及其可以与锆钛酸铅(PZT)压电陶瓷相比逆的压电性能而备受关注。压电聚合物聚偏氟乙烯(PVDF)由于具有柔性、质轻以及化学性质稳定等特点成为制备柔性纳米发电机常用的基体材料。静电纺丝由于兼具对聚合物的拉伸和电场极化作用，是制备较高β晶含量PVDF纳米纤维的理想方法。通过在PVDF中引入NaNbO₃制备柔性、高压电性能的纳米发电机，可以为便携式电子器件供电以及人体机械能采集奠定基础。

本论文针对水热法制备NaNbO₃纳米材料，并将NaNbO₃纳米材料引入到PVDF中制备高性能纳米发电机这一过程开展研究，通过尝试不同条件制备不同形貌的NaNbO₃纳米材料，旨在探明NaNbO₃形貌的影响因素以及NaNbO₃在水热反应过程中的变化规律；通过静电纺丝制备NaNbO₃/PVDF薄膜并构建纳米发电机，进一步研究NaNbO₃掺杂对静电纺丝PVDF纳米纤维微观形貌、结构及宏观压电性能的影响，并综合讨论NaNbO₃提升PVDF压电性能的作用机理，为设计和发展高性能压电器件提供理论依据和基础。本论文的主要研究成果如下：

(1)通过水热法成功制备纳米立方体与纳米棒两种结构的NaNbO₃纳米材料。X射线衍射(XRD)以及扫描电子显微镜(SEM)表明，较长的水热反应时间有利于制备立方体结构的NaNbO₃纳米材料，制备NaNbO₃纳米立方体的最佳条件为在15 ^oC/min的升温速率下升温至150 ^oC后保温8 h；较低的升温速率有利于制备纳米棒结构的NaNbO₃纳米材料，制备NaNbO₃纳米棒的最佳条件为在1 ^oC/min的升温速率下升温至150 ^oC后保温4 h，并通过在600 ^oC的空气氛围下煅烧2 h以保证无中间产物NaNb₂O₆·H₂O。

(2)将合成的NaNbO₃纳米材料加入至PVDF，通过静电纺丝制备NaNbO₃/PVDF复合薄膜。红外光谱(FTIR)与差式扫描量热分析(DSC)表明NaNbO₃的加入有利于PVDF中α相转变为β相。当NaNbO₃纳米立方体的添加量为9 wt%时，NaNbO₃/PVDF复合薄膜的β相含量最高为88.2%。

(3)将NaNbO₃/PVDF复合薄膜制备柔性纳米发电机，其压电性能均优于PVDF薄膜制备的纳米发电机。通过NaNbO₃纳米立方体制备的纳米发电机的压电性能优于NaNbO₃纳米棒。其中NaNbO₃纳米立方体的添加量为9 wt%的纳米发电机的压电性能最优，开路电压为2.79 V、短路电流为0.75 μA。

关键词：NaNbO₃；PVDF；水热法；压电性能；纳米发电机

Abstract

　　With the development of science and technology and the improvement of environmental protection awareness, people are paying more and more attention to environmental pollution and energy shortage. As a material which realize the conversion between mechanical energy and electrical energy, piezoelectric materials have developed rapidly. NaNbO₃ has attracted much attention due to its non-toxic and lead-free properties, and its piezoelectric properties are similar to the ones of PZT piezoelectric ceramics. Piezoelectric polymer polyvinylidene fluoride (PVDF) is a common matrix material for flexible nanogenerators due to its flexibility, light weight and stable chemical properties. Electrostatic spinning is an ideal method for preparing PVDF nanofibers with high β phase content due to tensile effect and electric field polarization. By introducing NaNbO₃ into PVDF to produce flexible nanogenerator with high voltage output, it can lay a foundation for power supply of portable electronic devices and mechanical energy collection of human body.

In this paper, NaNbO₃ nanomaterials were prepared via hydrothermal method, and the NaNbO₃ nanomaterials were introduced into PVDF to prepare high-performance nanogenerator. We tried to prepare NaNbO₃ nanomaterials with different morphologies under different conditions, and explored the influence factors of NaNbO₃ morphologies and the change regularities of NaNbO₃ in the hydrothermal process. NaNbO₃/PVDF thin film was prepared via electrostatic spinning and then the nanogenerator was constructed. NaNbO₃ was doped on PVDF, and the influence of microstructure, structure and macroscopic piezoelectric properties of PVDF nanofiber was further studied, then the mechanism of NaNbO₃ improving the piezoelectric properties of PVDF was comprehensively discussed to provide a theoretical basis for the design and development of high-performance piezoelectric devices. The main research results of this paper are as follows:

　　(1) NaNbO₃ nanomaterials with nanocube and nanorod structures were successfully prepared via hydrothermal method. X ray diffraction (XRD) and scanning electron microscope (SEM) results indicated that the long hydrothermal time was conducive for the preparation of NaNbO₃ nanomaterials with cubic structure. The optimal condition for the preparation of NaNbO₃ nanocube was to heat the raw material up to 150 ^oC at a heating rate of 15 ^oC/min for 8 h. The low heating rate is conducive for the preparation of NaNbO₃ nanorods with nanorods structure. The best condition for the preparation of NaNbO₃ nanorods is to heat the raw material up to 150 ^oC at the heating rate of 1 ^oC/min for 4 h, and calcinate them at 600 ^oC for 2 h to ensure the absence of intermediate NaNb₂O₆·H₂O.

　　(2) NaNbO₃/PVDF composite films were prepared via electrostatic spinning with PVDF containing NaNbO₃ nanomaterials. Infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) results showed that NaNbO₃ could facilitate the conversion from α phase to β phase in PVDF. When adding 9 wt% NaNbO₃ nanocube to PVDF, the content of β phase in NaNbO₃/PVDF composite film was up to 88.2%.

　　(3) The piezoelectric properties of NaNbO₃/PVDF composite film are better than those of PVDF composite film. The piezoelectric properties of nanogenerators prepared through NaNbO₃ nanocube are better than the ones through NaNbO₃ nanorod. The NaNbO₃ nanocube with an additive amount of 9 wt% had the best piezoelectric performance, with the open circuit voltage of 2.79 V and the short circuit current of 0.75 μA.

Keywords：NaNbO₃, PVDF, Hydrothermal method, Piezoelectric properties, Nanogenerator

目 录

第1章 绪论 2