为了研究不同纳米添加物对聚酰亚胺(polyimide,PI)电气性能的影响,采用原位聚合法制备了纯PI薄膜、PI质量分数10%的PI/SiO_2和PI/Al_2O_3纳米复合薄膜,测试其电导率(表面、体积电导率)、介电频谱、方波脉冲下的局部放电以及耐电晕性能,...为了研究不同纳米添加物对聚酰亚胺(polyimide,PI)电气性能的影响,采用原位聚合法制备了纯PI薄膜、PI质量分数10%的PI/SiO_2和PI/Al_2O_3纳米复合薄膜,测试其电导率(表面、体积电导率)、介电频谱、方波脉冲下的局部放电以及耐电晕性能,并用SEM观察击穿点周围的表面形貌。结果表明:PI/SiO_2膜的电导率大于PI/Al_2O_3膜,其中表面电导率是PI/Al_2O_3膜的6倍;PI/Al_2O_3膜、PI/SiO_2膜、PI膜的介电常数依次降低;PI/SiO_2膜和纯PI膜的介电损耗角正切值(tanδ)随频率的增加先减小后增大,PI/Al_2O_3膜的tanδ值在6 k Hz后最大;由于空间电荷弛豫,PI/Al_2O_3膜的tanδ值在0.02Hz左右出现了一个峰值;另外,因为电荷扩散能力不同,PI/SiO_2膜、PI/Al_2O_3膜以及PI膜的局部放电起始电压和耐电晕时间依次减小,而局部放电的平均幅值则依次增大;电晕放电使得3种薄膜表面都形成了很多微孔、裂纹,纳米复合薄膜表面出现块状物。研究结果表明:复合薄膜中界面体积分数和纳米粒子极性,是造成PI/SiO_2薄膜和PI/Al_2O_3薄膜电气性能差异的主要原因。展开更多
Due to the biological risks of using the conventional lubricants,the vegetable oils have been considered nowadays.Besides,to improve the tribological properties of the vegetable oils in various applications like metal...Due to the biological risks of using the conventional lubricants,the vegetable oils have been considered nowadays.Besides,to improve the tribological properties of the vegetable oils in various applications like metal forming processes,nanoparticles have been used as additives.This research evaluated the lubrication performance of the Al2O3 and TiO2 nanoparticles dispersed in rapeseed oil during the parallel tubular channel angular pressing (PTCAP) process.The experimental PTCAP tests have been fulfilled under three lubrication conditions and the comparison between the PTCAP processed tubes has been performed in terms of the maximum forming force,surface roughness,and microhardness.The experimental results indicate that adding the mentioned nanoparticles has caused at least a 50% reduction in the maximum deformation load.Moreover,a remarkable decrement in the surface roughness of the formed tubes has been obtained.展开更多
文摘为了研究不同纳米添加物对聚酰亚胺(polyimide,PI)电气性能的影响,采用原位聚合法制备了纯PI薄膜、PI质量分数10%的PI/SiO_2和PI/Al_2O_3纳米复合薄膜,测试其电导率(表面、体积电导率)、介电频谱、方波脉冲下的局部放电以及耐电晕性能,并用SEM观察击穿点周围的表面形貌。结果表明:PI/SiO_2膜的电导率大于PI/Al_2O_3膜,其中表面电导率是PI/Al_2O_3膜的6倍;PI/Al_2O_3膜、PI/SiO_2膜、PI膜的介电常数依次降低;PI/SiO_2膜和纯PI膜的介电损耗角正切值(tanδ)随频率的增加先减小后增大,PI/Al_2O_3膜的tanδ值在6 k Hz后最大;由于空间电荷弛豫,PI/Al_2O_3膜的tanδ值在0.02Hz左右出现了一个峰值;另外,因为电荷扩散能力不同,PI/SiO_2膜、PI/Al_2O_3膜以及PI膜的局部放电起始电压和耐电晕时间依次减小,而局部放电的平均幅值则依次增大;电晕放电使得3种薄膜表面都形成了很多微孔、裂纹,纳米复合薄膜表面出现块状物。研究结果表明:复合薄膜中界面体积分数和纳米粒子极性,是造成PI/SiO_2薄膜和PI/Al_2O_3薄膜电气性能差异的主要原因。
文摘Due to the biological risks of using the conventional lubricants,the vegetable oils have been considered nowadays.Besides,to improve the tribological properties of the vegetable oils in various applications like metal forming processes,nanoparticles have been used as additives.This research evaluated the lubrication performance of the Al2O3 and TiO2 nanoparticles dispersed in rapeseed oil during the parallel tubular channel angular pressing (PTCAP) process.The experimental PTCAP tests have been fulfilled under three lubrication conditions and the comparison between the PTCAP processed tubes has been performed in terms of the maximum forming force,surface roughness,and microhardness.The experimental results indicate that adding the mentioned nanoparticles has caused at least a 50% reduction in the maximum deformation load.Moreover,a remarkable decrement in the surface roughness of the formed tubes has been obtained.
