Surface modifications of boron nitride nanosheets for poly(vinylidene fluoride) based film capacitors: advantages of edge-hydroxylation
Surface modifications of boron nitride nanosheets for poly(vinylidene fluoride) based film capacitors: advantages of edge-hydroxylation
复制标题
用于聚偏二氟乙烯薄膜电容器的氮化硼纳米片的表面改性：边缘羟基化的优点
DOI：
10.1039/c9ta00616h
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发表时间：
2019-04-07
影响因子：
11.9
通讯作者：
Fu, Qiang
中科院分区：
文献类型：
--
作者：
Wu, Lingyu;Wu, Kai;Fu, Qiang
氮化硼纳米片（BNNS）是赋予聚合物高击穿强度（E-b）和储能密度（U-e）的理想候选者。采用包括非共价或共价键合在内的表面修饰来改善它们在聚合物基体中的分散性，但通常它们的介电性能较差。关键是在不牺牲优异介电性能的情况下提高它们在聚合物中的相容性，这仍然是一个巨大的挑战。在本研究中，设计了三种方法来修饰聚偏氟乙烯 (PVDF) 中的 BNNS，以进行比较研究。第一个涉及非共价聚多巴胺 (PDA) 涂层 (PDA-BNNS)；晶格保存完好，但引入了额外的 PDA。第二种方法是通过硝酸（HNO3）氧化进行基底羟基化（BOH-BNNSs），羟基（-OH）主要位于基底面，从而严重破坏面内晶体。第三种是通过球磨进行边缘羟基化（EOH-BNNS），在边界处调节-OH基团；因此，基本保持了完整的基础晶体。非常有趣的是，三种表面改性方法中 BNNS 在 PVDF 基体中的分散、界面相互作用和取向或多或少相似，但 E-b 的增强却截然不同。 PDA-BNNS 和 BOH-BNNS 填充的 PVDF 纳米复合材料的 E-b 表现出有限的增强，而与 PVDF/BNNSs 纳米复合材料相比，EOH-BNNS 填充的 PVDF 纳米复合材料的 E-b 大大提高（约 146.6%）。因此，边缘羟基化可以赋予PVDF/EOH-BNNS纳米复合材料令人印象深刻的E-b (585 kV mm(-1))和U-e (16.23 J cm(-3))。因为PDA的低E-b和BOH-BNNSs（2.73 eV）的带隙能量（E-g）降低都是实现高E-b的缺点。相反，如果在边界处调节-OH基团，则可以获得保存完好的基础晶格，这使得EOH-BNNS不仅表现出更好的色散和界面相互作用，而且保留了更高的E-g（5.76 eV）。这项研究证明了在首次进行表面改性时保持 BNNS 完整晶格的重要性。我们的研究为BNNS的表面改性和制备具有优异性能的聚合物基电容器提供了指导。
Boron nitride nanosheets (BNNSs) are ideal candidates to endow polymers with high breakdown strength (E-b) and energy storage density (U-e). Surface modifications, including non-covalent or covalently bonding, are adopted to improve their dispersion in polymer matrix, but, usually, they suffer from inferior dielectric properties. The key is to improve their compatibility within polymer without sacrificing excellent dielectric properties, which remains to be a great challenge. In this study, three methods were designed to modify BNNSs within poly(vinylidene fluoride) (PVDF) for a comparative study. The first one involves a non-covalent polydopamine (PDA) coating (PDA-BNNSs); the crystal lattice was well-preserved, but additional PDA was introduced. The second method involves basal hydroxylation via nitric acid (HNO3) oxidation (BOH-BNNSs) with hydroxyl groups (-OH) mainly located at the basal plane, thus, seriously damaging the in-plane crystal. The third one is edge-hydroxylation via ball-milling (EOH-BNNSs) with -OH groups being regulated at the boundary; thus, integrated basal crystal is largely maintained. It was very interesting to find that the dispersion, interfacial interaction and orientation of BNNSs in PVDF matrix are more or less similar for all three surface-modification methods, but the enhancement of E-b is very different. PDA-BNNS and BOH-BNNS filled PVDF nanocomposites exhibited a limited enhancement of E-b, while a greatly improved E-b (approximate to 146.6%) was observed for EOH-BNNS filled PVDF nanocomposites in comparison with that of PVDF/BNNSs nanocomposites. Therefore, edge-hydroxylation could endow PVDF/EOH-BNNS nanocomposites with impressive E-b (585 kV mm(-1)) and U-e (16.23 J cm(-3)). Because the low E-b of PDA and the decreased band gap energy (E-g) of BOH-BNNSs (2.73 eV) are both disadvantages for achievement of high E-b. Inversely, well-preserved basal crystal lattices could be obtained if -OH groups are regulated at the boundary, which makes EOH-BNNSs not only display better dispersion and interfacial interaction but also retain higher E-g (5.76 eV). This study demonstrates the importance of maintaining an integrated crystal lattice of BNNSs when exposed to surface modification for the first time. Our study provides guidance for surface-modification of BNNSs and preparation of polymer-based capacitors with excellent performance.