交联聚乙烯电缆绝缘中的导电和非导电型电树枝

研究发现,交联聚乙烯中存在导电型、非导电型和混合型三种电树枝,分别对应于不同的生长机理,主要取决于介质的聚集态和施压频率等。实验表明,均匀结晶态中的电树枝为导电型,非均匀结晶态大球晶界面的电树枝为非导电型;频率会促进非导电型电树枝的发展,但对导电型电树枝的引发与生长不产生显著影响。非导电型电树,会缓慢发展成为混合型。研究分析证实,空间电荷限制下的树枝尖端微击穿是深入到晶体中的导电型电树枝缓慢发展的主要过程,局部高温高压气体沿晶界弱区迅速膨胀、树枝通道中的局部放电和电荷复合等是非导电型电树枝发展的主要过程。

交联聚乙烯电缆中非导电型电树枝的自愈现象

为研究交联聚乙烯(XLPE)电缆中非导电型电树枝的自愈机制,对XLPE薄片试样进行了非导电型电树枝的老化与自愈实验。实验发现,在电树引发初期断开电源一段时间后,浅色非导电型电树枝消失,产生了自愈现象。通过构建非导电型电树枝生长及自愈模型,分析了非导电型电树枝的生长和自愈机制。结果表明:在电树枝引发初期,由于Maxwell应力、局部放电、电荷注入抽出以及场致发光等作用,导致XLPE分子链发生断裂并气化,从而使得电树枝快速生长。当外施电压去除后,贮存在电树枝周围XLPE材料中的弹性势能逐渐释放,电树枝直径减小,通道内壁XLPE分子链相互重叠交错,使得电树枝通道消失,从而产生自愈现象。

非导电型各向同性手性介质中非线性旋光的宏观理论

采用经典电磁场理论描述非导电型各向同性手性介质，研究了圆偏振抽运光作用下线偏振信号光的非线性旋光现象．给出了非线性旋光角的解析表达式．

Study on Improving Storage Stability of Marine Engine Oil

According to the conductivity test results,it is found that oil conductivity increases with an increasing additive content,and the turbidity of engine oil is also augmented with an increasing additive content.After testing the turbidity and stability of oils containing the typical conventional calcium sulfonate,the overbased calcium sulfonate and the mixture of the above two calcium sulfonates,the results show that at the same amount of additives used,the oil with a higher turbidity demonstrated a worse stability.A nonionic dispersant that was added into lube oils at a definite concentration could improve the detergent compatibility.For this reason,the sediment volume in three kinds of oils all decreased obviously,resulting in successful improvement of storage stability of marine engine oils.