This study focused on uncovering the relationship among nanofiller, crystallization behavior, and dielectric property of polymer composites. The effects of carbon nanofibers (CNFs) and heat treatment on the crystalline structures and dielectric properties of the semi‐crystalline polymers were analyzed by using high density polyethylene (HDPE) as a matrix, which is a representative of non‐polar polymer and contains only one crystal structure. The experimental results showed that the degree of crystallinity, size distribution of crystallity, and relative amount of different crystal planes in the HDPE matrix were changing due to the addition of CNFs. With the increase of CNF loading, the dielectric constant, dielectric loss and AC conductivity of the HDPE composites were increased, presenting a typical percolation characteristic, and the dependence of the dielectric constant on frequency became more obvious. All kinds of electronic transmission, polarization effect, and relaxation behaviors in CNF/HDPE composite system were deeply analyzed. After heat treatment, the degree of crystallinity of HDPE composites was decreased with the enhanced cooling rate. For the CNF/HDPE composites with nanofiller content slightly higher than the percolation threshold, the significant increase of the dielectric constant and the dramatical reduction of the dielectric loss over a wide frequency range were realized simultaneously through rapid cooling treatment. The research indicated that a general commercial polymer material with excellent dielectric properties, which exhibited a high dielectric constant and a low dielectric loss, can be obtained by a simple technical approach different from traditional fabrication method of threshold composites.

中文翻译：

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基于受控结晶获得碳纳米纤维复合材料的理想介电性能

这项研究的重点是揭示聚合物复合材料的纳米填料，结晶行为和介电性能之间的关系。以高密度聚乙烯（HDPE）为基质，分析了碳纳米纤维（CNF）和热处理对半结晶聚合物的晶体结构和介电性能的影响，该基质是非极性聚合物的代表，仅包含一种晶体结构。实验结果表明，由于添加了CNF，HDPE基体中的结晶度，结晶度的大小分布以及不同晶面的相对数量发生了变化。随着CNF载荷的增加，HDPE复合材料的介电常数，介电损耗和交流电导率增加，呈现出典型的渗流特性，介电常数对频率的依赖性变得更加明显。深入分析了CNF / HDPE复合体系中的各种电子传输，极化效应和弛豫行为。热处理后，HDPE复合材料的结晶度随着冷却速率的增加而降低。对于纳米填料含量略高于渗滤阈值的CNF / HDPE复合材料，通过快速冷却处理，可以同时实现介电常数的显着提高和介电损耗在很宽的频率范围内的显着降低。研究表明，具有优异介电性能的通用商业聚合物材料具有高介电常数和低介电损耗，