微秒脉冲电场频率对氮化硼纳米片取向程度及复合材料电热性能的影响

Effect of Frequency of Microsecond Pulsed Electric Field on Orientation of BNNSs and Electrical and Thermal Properties of Composites

纳秒脉冲电场(电场强度大于200kV/mm)已用于诱导填料的取向排列,以制备高热导率的聚合物基薄膜(120~250μm)复合物。但由于需要极高的纳秒脉冲电压,因此对块状复合物的研究很少。该文采用脉宽1μs、电场仅为11.76kV/mm的微秒脉冲电压制备厚度为1.7mm的块状复合物,研究频率对氮化硼纳米片(BNNSs)取向程度及复合材料热导率的影响。用断面扫描电镜(SEM)和X射线衍射峰(XRD)表征纳米片的取向程度。结果表明,纳米片的取向度和复合材料的热导率随着频率的增加而增加,但在较高频率下其增加速率明显降低。当微秒脉冲电场频率为100Hz时,热导率为0.588W/(m·K),是未施加电场的复合材料的两倍以上。此外,测量了纯环氧树脂和复合材料的交流击穿场强,结果表明,微秒脉冲电场下制备的取向型复合材料的交流击穿性能优于纯环氧树脂。

Nanosecond pulsed electric fields over 200 kV/mm have been used for filler alignment in polymer-based thin film(120~250μm) composites to improve their thermal conductivity, but little research has been performed on bulk composites because of the requirement of an extremely high nanosecond pulsed voltage. In this paper, a microsecond pulsed voltage, whose pulse width was 1μs, and electric field was only11.76 kV/mm, was adopted for the first time to prepare bulk composites of 1.7 mm. Effects of frequency on orientation and thermal conductivity of composites were studied. The degree of orientation was determined based on cross-sectional scanning electron microscopy(SEM) and X-ray diffraction(XRD) peaks. The results show that the orientation degree and thermal conductivity increase with the increasing frequency, but the increase rate is lower under higher frequencies. The thermal conductivity under 100 Hz is 0.588 W/mK,which is more than twice that of composites without application of electric field(0.286 W/mK).Additionally, AC breakdown strength was measured, the results show that after BNNSs orientation, the composites still have better AC breakdown performance than pure epoxy resin.