(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。
(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。
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
第1章 绪论 2