Size Effect of Boron Nitride Nanosheets on Dielectric Properties of BNNSs/P(VDF-HFP) Composite Films
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摘要: 通过球磨法制备了两种不同片径大小的氮化硼纳米片（BNNSs），并采用溶液刮膜的方式制备了BNNSs与聚偏氟乙烯-六氟丙烯（P（VDF-HFP））的复合薄膜BNNSs/P（VDF-HFP）。通过介质耐压测试仪与宽频电介质谱仪测试了复合薄膜的击穿强度和介电常数，揭示了BNNSs的片径大小对复合薄膜介电性能的影响。结果表明，大片径纳米片的晶格结构更完善且在P（VDF-HFP）中的取向度更高，在复合薄膜中能形成更完善的绝缘网络，从而能有效阻止复合薄膜发生电导及电力学击穿。与小片径纳米片复合薄膜相比，大片径纳米片复合薄膜具有更高的击穿强度。Abstract: Boron nitride nanosheets (BNNSs) is an insulating material with high breakdown strength (800 kV/mm), which is an ideal candidate for the enhancement of breakdown strength of polymer-based composites. Generally, the lateral size of BNNSs has a significant influence on thermal conductivity and mechanical properties of composites. Thus, it is worthy to further study the size effect of BNNSs on dielectric properties of composites. In this study, edge-hydroxylated BNNSs with large lateral size (l-BNNSs) and small lateral size (s-BNNSs) were respectively added into poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) to prepare BNNSs/P(VDF-HFP) composite films. The breakdown strength and dielectric constant of the composite films are tested by dielectric strength tester and broadband dielectric spectrometer to reveal the size effect of BNNSs on dielectric properties of polymer-based film capacitors. Due to the better crystal lattice of l-BNNSs and higher degree of in-plane orientation compared with s-BNNSs, the insulating network of l-BNNSs/P(VDF-HFP) composite film is more compact and perfect, which can effectively prevent the occurrence of conduction and electrical breakdown in composite films. When the mass fraction of BNNSs is 10%, P(VDF-HFP)/l-BNNSs composite films reach the highest breakdown strength (644 kV/mm). Compared with s-BNNSs/P(VDF-HFP) composite films, the breakdown strength of l-BNNSs/P(VDF-HFP) composite films has an increase of 7.65%.
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Key words:
- boron nitride nanosheet /
- breakdown strength /
- energy density
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图 1 （a）s-BNNSs和（b）l-BNNSs的SEM图；根据SEM图统计得到的（c）s-BNNSs和（d）l-BNNSs的片径大小统计图
Figure 1. SEM images of (a) s-BNNSs and (b) l-BNNSs; Statistical analysis of the lateral size of a set of (c) s-BNNSs and (d) l-BNNSs based on the result of SEM image
图 2 样品的（a）TGA曲线；（b）FT-IR谱图和（c）XPS谱图；（d）s-BNNSs和（e）l-BNNSs的B1s分谱
Figure 2. (a) TGA curves, (b) FT-IR spectra and (c) XPS wide spectra of samples; B1s core level of (d) s-BNNSs and (e) l-BNNSs
图 3 BNNSs/P(VDF-HFP)复合薄膜的
$ {E}_{\mathrm{b}} $ 与填料含量的关系Figure 3. Breakdown strength of BNNSs/P(VDF-HFP) composite films as functions of BNNSs content
图 4 s-BNNSs和l-BNNSs的UV光谱转变曲线（曲线拟合得到的直线在hv轴上的截距即为
$ {E}_{\rm{g}} $ ）Figure 4. Transformation curves of UV spectra of s-BNNSs and l-BNNSs (The hν axis intercept in the image is
$ {E}_{\rm{g}} $ )
图 5 （a）BNNSs及（b）BNNSs/P（VDF-HFP）复合薄膜的XRD谱图（虚线：l-BNNSs /P（VDF-HFP），实线：s-BNNSs/P(VDF-HFP））
Figure 5. XRD spectra of (a) BNNSs and (b) BNNSs/P(VDF-HFP) composite films (Dotted lines: l-BNNSs/P(VDF-HFP); solid lines: s-BNNSs/P(VDF-HFP))
图 6 BNNSs/P(VDF-HFP)复合薄膜的SEM图（x（BNNSs）=10%）
Figure 6. SEM images of BNNSs/P(VDF-HFP) composite films (x(BNNSs)=10%)
图 7 （a）s-BNNSs/P(VDF-HFP)和（b）l-BNNSs/P(VDF-HFP)复合薄膜的
$ {\varepsilon }_{\mathrm{r}} $ 和介电损耗；复合薄膜的（c）$ {\varepsilon }_{\mathrm{r}} $ 和介电损耗以及（d）$ {U}_{\mathrm{e}} $ 的总结和对比Figure 7. Dielectric constant and dielectric loss of (a) s-BNNSs/P(VDF-HFP) and (b) l-BNNSs/P(VDF-HFP) composite films; Summary and comparison of (c) dielectric constant and dielectric loss and (d)
$ {U}_{\mathrm{e}} $ of composite films -
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