高储能PVDF基介电复合薄膜材料的研究

发布时间：2018-04-21 00:03

本文选题：聚偏氟乙烯 + 纳米复合材料　；参考：《北京化工大学》2017年博士论文

【摘要】：近年来,为应对能源短缺和能源利用率较低等问题,世界上许多国家的研究人员都致力于开发新型的储能和能量转换装置。由此,介电电容器由于其高功率密度、抗循环老化、性能稳定等优点成为研究热点。目前,传统陶瓷材料具有很高的介电常数,但是其制备工艺复杂、体积大且不耐高压。而聚合物介电材料机械性能好、易于加工且击穿场强高,但是通常介电常数较低。因此,研究和制备具备高介电常数和击穿场强、低介电损耗的聚合物基介电复合材料具有非常重要的意义。本论文以聚偏氟乙烯(PVDF)基聚合物为基体,研究了不同填料的尺寸与形貌、有机-无机界面及有机填料对复合膜介电行为的影响,并分析了相应机理,建立结构-性能的构效关系,设计并制备了高储能低损耗的介电复合材料。本论文的主要研究内容如下:1.利用水热法制备了 SnO2颗粒,粒径5-7 nm。基于渗流理论,构建了 SnO2/PVDF纳米复合膜,在103Hz下介电常数高达320,与PVDF基体相比提高了近40倍,而介电损耗小于0.8;根据线性拟合的结果,介电行为符合渗流模型;SnO2纳米颗粒具有较宽的禁带宽度,同时,纳米级的SnO2与PVDF形成的界面形成更多的电子散射和势阱,阻止了载流子的传输,能够有效地保持一定的击穿场强。2.水热法制备了钛酸钠纳米管,管径8-10 nm,管长300-500 nm,并与聚偏氟乙烯-三氟乙烯-三氟氯乙烯(PVDF-TrFE-CTFE)复合成膜。采用双向和单向电滞回线测试探索复合膜的介电损耗机制,提出外部和内部电导损耗共同构成了介电材料的介电损耗。当测试频率为10 Hz时,双向电滞回线有上移现象,证明存在与填料之间和填料与聚合物基体之间的外部电导损耗的存在。利用单向电滞回线对复合膜进行测试,在100 Hz以上,其外部电导损耗不明显,但仍然存在非线性的介电损耗,证明了存在于填料内部的内部电导损耗的存在。3.利用Stober法制备了不同壳厚的Ag@SiO2核壳结构填料,Ag核大小40-55 nm,SiO2壳层厚度分别为5 nm,10 nm和20nm。由于填料的核壳型结构使得复合膜界面极化的增强,从而提高了介电常数,最高达到31;同时复合膜保持了较低的介电损耗,小于0.05。介电常数随SiO2壳厚的增加而下降,而击穿场强增高;在加入少量Ag@SiO2时,击穿场强得到了提高,最高达到346 MV/m。测试结果证明SiO2壳层作为良好的绝缘层能够降低漏电流,提高薄膜的击穿场强。同时,薄膜的介电行为能够通过Si02壳层厚度进行调控。4.用化学剥离法制备了层数较少的氮化硼纳米片(BNNS)填料,并与PVDF-TrFE-CTFE复合,研究了 BNNS的最佳填充量;当BNNS填量为12wt%时,介电性能最好,能量释放密度为7.1J/cm3;由于BNNS的宽禁带宽度和高击穿场强,介电薄膜的的击穿场强得到提高,达到610 MV/m,BNNS的加入降低了复合材料的晶粒尺寸,从而提高了放电效率(84%)。在此基础上,对纳米钛酸钡(BT)用多巴胺进行表面修饰,制备了以BNNS和BT为填料的三相介电复合材料。利用BNNS的高击穿场强和钛酸钡的高介电常数,三相复合膜的介电性能得到显著提升,介电常数最高达到76。当钛酸钡掺杂量为20 wt %、BNNS掺杂量为12 wt %时,三相介电薄膜的能量释放密度最高达到13.3 J/cm3,同时放电效率为72 %。5.利用逐步加成聚合法制备了芳香聚硫脲(ArPTU)介电薄膜,由于ArPTU的非晶相极性聚合物结构,分子链中的偶极子能够及时响应电场变化,使得ArPTU具备很低的介电损耗(0.0067),同时具备很高的击穿场强(746 MV/m)和能量释放效率(大于90 %); ArPTU的加入改变了复合介电薄膜晶体结构和电阻率,使得复合膜的晶粒尺寸变小,晶面间距变大,有利于PVDF-TrFE-CTFE分子链中偶极子的自由转动,降低了电滞损耗,从而提高了击穿场强和能量释放密度。复合膜能量释放密度在700 MV/m电场下达到19.2 J/cm3,同时,放电效率仍大于85 %。
[Abstract]:In recent years, in order to cope with the shortage of energy and the low utilization rate of energy, researchers in many countries of the world are committed to developing new energy storage and energy conversion devices. Thus, dielectric capacitors have become a research hotspot because of their high power density, anti cycle aging, and stable performance. Dielectric constant, but its preparation process is complex, large and not resistant to high pressure. The polymer dielectric material has good mechanical properties, easy to process and high breakdown field, but usually has low dielectric constant. Therefore, it is very important to study and prepare polymer based dielectric composites with high dielectric constant and breakdown field and low dielectric loss. In this paper, polyvinylidene fluoride (PVDF) based polymer was used as the matrix to study the size and morphology of different fillers, the effect of organic inorganic interface and organic filler on the dielectric behavior of the composite membrane. The corresponding mechanism was analyzed, the structure performance relationship was established, and the high energy storage and low loss dielectric composites were designed and prepared. The main contents are as follows: 1. SnO2 particles were prepared by hydrothermal method. The particle size 5-7 nm. was based on the percolation theory, and the SnO2/PVDF nanocomposite membrane was constructed. The dielectric constant was up to 320 under 103Hz, and the dielectric loss was less than 0.8 compared with the PVDF matrix. The dielectric behavior accorded with the percolation model and SnO2 nanoscale according to the linear fitting results. The grain has a wider band width. At the same time, the nano scale SnO2 and PVDF formed more electron scattering and potential well, and prevented the carrier transmission. It can effectively maintain a certain breakdown field strength.2. hydrothermal method to prepare sodium titanate nanotube, the diameter of 8-10 nm, the length of 300-500 nm, and polyvinylidene fluoride three fluoroethylene - three fluorine chloride The dielectric loss mechanism of the composite film is explored by a two-way and unidirectional hysteresis loop test. It is suggested that the dielectric loss of the dielectric material is formed by the external and internal conductance losses. When the test frequency is 10 Hz, the bidirectional hysteresis loop has the upward movement. It is proved that there exists between the filler and the filler and the polymer base. The external conductance loss exists between the bodies. The composite membrane is tested by one-way hysteresis loop, and the external conductance loss is not obvious at 100 Hz, but the nonlinear dielectric loss still exists. It is proved that the existence of internal conductance loss exists in the filler.3. by using the Stober method to prepare the Ag@SiO2 shell structure with different shell thickness. Packing, the size of Ag core is 40-55 nm, the thickness of SiO2 shell is 5 nm, 10 nm and 20nm. increase the interface polarization of the composite membrane because of the core shell structure of the packing, thus the dielectric constant is increased to up to 31, while the composite film keeps low dielectric loss, and the dielectric constant decreases with the increase of the SiO2 shell thickness, and the breakdown field strength increases. When a small amount of Ag@SiO2 is added, the breakdown field strength is improved and the maximum 346 MV/m. test results show that the SiO2 shell as a good insulating layer can reduce the leakage current and improve the breakdown field of the film. At the same time, the dielectric behavior of the thin film can be regulated by the thickness of the Si02 shell and the chemical peeling method of.4. has been prepared by the chemical peeling method. Boron nanoscale (BNNS) filler and composite with PVDF-TrFE-CTFE have been used to study the optimum filling amount of BNNS. When BNNS is 12wt%, the dielectric property is best and the energy release density is 7.1J/cm3. The breakdown field of the dielectric thin film is enhanced by the width of the band gap and the high breakdown field strength of BNNS, and the strength of the dielectric thin film is increased to 610 MV/m, and the addition of BNNS reduces the composite material. The grain size of the material increases the discharge efficiency (84%). On the basis of the surface modification of the nanometer barium titanate (BT), the dielectric properties of the three phase dielectric composites with BNNS and BT as filler are prepared. The dielectric properties of the three phase composite films are greatly improved by using the high breakdown field strength of BNNS and the high permittivity of barium titanate. Up to 76. when the doping amount of barium titanate is 20 wt% and the BNNS doping amount is 12 wt%, the energy release density of the three phase dielectric thin films is up to 13.3 J/cm3, and the discharge efficiency is 72%.5., and the aromatic polythiourea (ArPTU) dielectric thin film is prepared by the stepwise addition polymerization method, because of the amorphous phase polymer structure of ArPTU and the couple in the molecular chain. The ArPTU has very low dielectric loss (0.0067), high breakdown field strength (746 MV/m) and energy release efficiency (greater than 90%). The addition of ArPTU changes the crystal structure and resistivity of the composite dielectric thin film, which makes the grain size of the composite film smaller and the space between the crystal larger, which is beneficial to the PVDF-T. The free rotation of dipoles in the rFE-CTFE molecular chain reduces the hysteresis loss and increases the breakdown field strength and the energy release density. The energy release density of the composite membrane reaches 19.2 J/cm3 under the 700 MV/m electric field, while the discharge efficiency is still more than 85.

【学位授予单位】：北京化工大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB383.2

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