针对纳米氧化镁/环氧树脂复合电介质的高温介电响应特性展开研究,测试了其热失重曲线和在120~200℃的宽频介电谱.实验结果表明:复合介质的最大热失重速率随着纳米氧化镁掺杂量的增加先上升后下降,并在掺杂量为2%时达到最大值;复合介质工频下的相对介电常数随掺杂量的变化规律与最大热失重速率类似,并在不同的温度区间出现了两个松弛过程,分别对应热离子极化导致的δ松弛和偶极子转向极化导致的α松弛.通过模量谱计算发现,掺杂0.1%的纳米氧化镁导致载流子跃迁的平均势垒升高,随着掺杂量的进一步增加,平均势垒开始降低;而转向极化的活化能则在掺杂量为2%时达到最低.纳米粒子和环氧树脂基体之间形成的交互区是影响高温介电性能的主要原因.
In order to study the dielectric response characteristics of nano-MgO/EP composite dielectrics at high temperature, their thermogravimetric curves and broadband dielectric spectra ranged from 120 ℃to 200 ℃ were tested. The results show that with the increase of nanoparticle content, the maximum mass loss rate of the nano-MgO/EP composite dielectrics increases at first and then decreases, and it reaches the maximum value when the nano-MgO content is 2%. The relative dielectric constant of the dielectrics under power frequency has similar change law with the maximum mass loss rate, and there is two relaxation process at different temperature region in the dielectric spectra, which correspond to the relaxation caused by thermionic polarization and the relaxation caused by dipole orientation polarization. The calculation results of modulus spectrum indicate that the average barrier of carrier transition increas-es after adding 0.1% of nano-MgO in the dielectrics, and it decreases with the increase of nano-MgO content. The activation energy of orientation polarization reaches the minimum value when nano-MgO con-tent is 2%. The interaction zone between nanoparticles and epoxy resin matrix is the main reason affect-ing the dielectric characteristics at high temperature.
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