中文摘要：

利用太赫兹时域光谱技术和电导测量研究了多壁碳纳米管/高密度聚乙烯（MWNTs/HDPE）复合体系的光电性质.直流电导率结果表明,复合体系的逾渗阈值在5%左右;交流电导率则随频率的变化出现一个拐点,拐点的位置与颗粒浓度以及导电颗粒的存在状态密切相关.加入碳纳米管后,复合体系在太赫兹波段的吸收系数和折射率均有很大的提高.通过假定在此波段导电颗粒在聚合物中的介电行为类似于偶极子的弛豫,利用Cole-Cole理论对复合材料的介电性质进行了解释.

英文摘要：

Conductive composites were prepared by filling high density polyethylene （HDPE） with various amounts of multi-walled carbon nanotubes （MWNTs） and were characterized by using a terahertz time-domain spectroscopy （THz-TDS） setup assisted with conductivity measurements. The direct current （dc） conductivity measurement indicated that the percolation threshold was about 5% in volume fraction. The frequence and filler concentration dependences of alternating current （ac） conductivity were investigated and the results could be understood with the polarization effects between clusters, anomalous diffusion within the clusters as well as the percolating structures. With increasing the MWNT particles, the absorption coefficient and refractive index all increased at THz band due to the increase of the charge carrier density. The experimental data were analyzed with Cole-Cole formula of dipole relaxation under the assumption that conductive particles dispersed in the matrix behaved like dipoles and contributed mainly to the dielectric loss in the THz frequency range.