不同结构碳黑填充的复合体系的太赫兹时域光谱研究

利用熔融共混、压片的方法制备了两种不同结构的碳黑(乙炔碳黑和高结构碳黑)填充的高密度聚乙烯复合材料,并利用太赫兹时域光谱研究了复合体系在太赫兹波段的介电性质.研究发现,随着频率的增加,体系的吸收系数逐渐增大而折射率则逐渐降低;在相同的频率下,吸收系数和折射率均随颗粒浓度的增加而增大;与乙炔碳黑相比,相同浓度的高结构碳熙填充的复合体系具有较大的吸收系数和较低的折射率,这与碳黑的颗粒结构以及颗粒间的团聚状态是紧密相关的.假定复合体系的介电损耗是由碳黑颗粒内部载流子的极化和聚乙烯基体的界面极化所导致的,利用双德拜模型对实验结果进行了解释,分别得到了两种极化模式所对应的弛豫时间和弛豫强度等信息.

THz time-domain spectroscopic study of composites filled with different carbon black

Composites were prepared by filling high density polyethylene (HDPE) with acetylene black (AC-CB) and high-structure CB (HG-CB), respectively. Optical properties of the composites were characterized with terahertz time-domain spectroscopy (THz-TDS). It was found that as frequency increases the absorption coefficients of the composites increase whereas the refractive indexes decrease. Both the absorption coefficient and refractive index increase with increasing the particle concentration. The HG-CB filled composites have larger absorption coefficient but smaller refractive index compared with that of the AC-CB composites at the same particle concentration. These phenomena are related to the different particulate structures and aggregate structures of the CB particles. Assuming that the dielectric loss in THz frequency range is mainly attributed to the electron transport within the conductive clusters and the interfacial polarization of HDPE, the information of relaxation time and relaxation strength was obtained through fitting the experimental results to two-Debye theory of dipole relaxation.