炭黑含量对太赫兹脉冲在HDPE中传播的影响

Effect of Carbon Black Content on the Propagation of Terahertz Pulse in HDPE

太赫兹时域光谱非常适用于聚合物材料或制品的无损检测。聚乙烯燃气管道中通常含有少量炭黑,炭黑的加入会改变材料的介电性能从而影响太赫兹脉冲在其中的传播。为揭示其影响机理,本文制备了炭黑体积分数为0~2.06%的高密度聚乙烯/炭黑样品并采集其太赫兹光谱。结果发现,随着炭黑含量的增加,太赫兹脉冲传播的相位延迟增加,透射强度下降,同时计算得到的材料在太赫兹波段的折射率、吸收系数及介电常数均随炭黑含量呈上升趋势。由德拜弛豫模型可知样品的直流电导率和弛豫强度与炭黑含量呈现正相关线性关系。对上述现象进行理论分析得出材料的介电常数变化是由于其中的载流子浓度变化及载流子弛豫行为所致。

Terahertz time-domain spectroscopy was very suitable for non-destructive testing of polymer materials or products.Polyethylene gas pipelines typically contained a small amount of carbon black,which could alter the dielectric properties of the material and affect the propagation of terahertz pulses.In order to reveal its influencing mechanism,high-density polyethylene/carbon black samples with a carbon black volume fraction of 0~2.06%were prepared and their terahertz spectra were collected.The results show that as the carbon black content increases,the phase delay of terahertz pulse propagation increases,and the transmission intensity decreases.At the same time,the calculated refractive index,absorption coefficient and dielectric constant of the material in the terahertz band show an upward trend with the carbon black contents.According to the Debye relaxation model,the direct current conductivity and relaxation strength of the sample exhibit a positive linear relationship with the carbon black content.Theoretical analysis of the above phenomena reveals that the change in dielectric constant of the material is due to changes in carrier concentration and carrier relaxation behavior.