纳米碳纤维掺杂量与取向对纳米碳纤维/乙烯-醋酸乙烯酯复合材料介电性能的影响

通过微波法化学镀镍对纳米碳纤维(CNFs)进行表面改性,采用熔融共混法将表面改性的CNFs与乙烯-醋酸乙烯酯(EVA)复合制备CNFs/EVA复合材料,在模压交联过程中对复合材料施加磁场,使表面镀镍的CNFs在复合材料基体中沿磁场方向取向;用场发射扫描电子显微镜(FE-SEM),透射电子显微镜(TEM)和X射线衍射仪(XRD)观察表面改性前后CNFs表面形貌和结构、复合材料内部微观结构及取向情况;用宽频介电谱仪与阻抗谱仪对复合材料进行介电谱测试,研究了CNFs的取向与掺杂量对复合材料介电性能的影响,并用四探针法测量复合材料的体电阻率。研究结果表明,掺杂量和是否取向对复合材料介电性能影响较大;CNFs掺杂质量分数为0.5%时,取向复合材料相对介电常数最低,施加磁场取向不会增加复合材料的介电损耗,少量掺杂即可大幅降低复合材料的体电阻率。

Effect of Carbon Nanofibers Incorporation Concentration and Orientation on Dielectric Properties in Carbon Nanofibers/Ethylene-vinyl Acetate Copolymer Composites

The carbon nanofibers(CNFs) were surface-modificated by microwave assisted chemical nickel plating.The CNFs/EVA(ethylene-vinyl acetate) composites were prepared by melt-compounding of the modified CNFs and EVA resin.The magnetic field was used during the moulding process and CNFs oriented along the magnetic field direction.The morphology and structure of surface-modificated CNFs,microstructure and orientation of composites were analyzed by field-emission scanning electron microscopy(FE-SEM),transmission electron microscopy(TEM),and X-ray diffraction(XRD).The dielectric properties of CNFs/EVA nanocomposites with different CNFs concentration and orientation were tested by broadband dielectric spectrometer and impedance spectrometer and the volume resistivity of composites was measured by four-probe method.It is found that CNFs incorporation concentration and orientation have evident effects on the dielectric property of the composites.When the CNFs incorporation concentration was 0.5%(mass concentration),the dielectric constant of the oriented composites was the lowest.The orientation of CNFs in EVA matrix did not increase the dielectric loss of the nanocomposites.A little corporation could reduce the volume resistivity of composites significantly.