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采用γ-缩水甘油醚氧丙基三甲氧基硅烷(KH560)对氮化硼纳米片(BNNS)进行表面改性,然后将其掺入环氧树脂基体中,制备了环氧树脂/功能化氮化硼纳米片(EP/BNNS-KH560)复合材料。对功能化氮化硼纳米片的结构及形貌进行测定,并对EP/BNNS-KH560复合材料的性能进行研究。结果表明:BNNS表面成功接枝KH560,在透射电子显微镜下展现出透明薄层结构;宽能级间隙的BNNS-KH560填料的加入可以保持复合材料的高电绝缘性、优异的介电性能和力学性能,使其热稳定性提高,并能在环氧树脂基体中形成良好的导热通道,有效改善复合材料的导热性能。当复合材料中BNNS-KH560质量分数为20%时,复合材料的导热系数可达到0.51 W/(m·K)。 相似文献
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With the continuous improvement of current levels in power systems,the demands on the breaking capacity requirements of vacuum circuit breakers are getting higher and higher.The breaking capacity of vacuum breakers is determined by cathode spots,which provide electrons and metal vapor to maintain the arc.In this paper,experiments were carried out on two kinds of transverse magnetic field (TMF) contacts in a demountable vacuum chamber,the behavior of the cathode spots was recorded by a high-speed charge-coupled device (CCD) video camera,and the characteristics of the cathode spots were analyzed through the image processing method.The phenomenon of cathode spot groups and the star-shaped pattern of the spots were both discovered in the experiment.The experimental results show that with the condition of TMF contacts the initial expansion speed of cathode spots is influenced by some parameters,such as the tested current,contact gap,the structure of the contact,the contact diameter,the number of slots,etc.In addition,the influence of the magnetic field on the formation of the cathode spot groups,the distribution,and the dynamic characteristics of the cathode spots were analyzed.It is concluded that the characteristics of the cathode spots are due to the effect of the magnetic field on the near-cathode plasma.The study of the characteristics of cathode spots in this paper would be helpful in the exploration of the physical process of vacuum arcs,and would be of guiding significance in optimizing the design of vacuum circuit breakers. 相似文献
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为了降低电力系统局部放电造成的损耗,设计了一种局部放电系统信号单元电路设计及其实验测试。利用ACDCA引脚产生高低电平来实现对三极管导通状态的调控,根据继电器开关状态确定直流或交流的耦合电路。利用ATTA引脚来产生高低电平,从而对三极管的导通状态进行口控制,并调整继电器开关来达到不同的衰减程度。研究结果表明,通过FPGA技术对局部放电测试系统进行处理可以调节A/D转换模块的放电信号分析,并实现对数据信息的快速采集与提取。在很长测试区间内,采用局部放电测试系统都可以实现良好可重复性。 相似文献