摘要:
采用羟乙基纤维素(HEC)和导电炭黑并添加山梨醇增湿剂制备碳湿敏膜,研究了膜在偏离结露区的非线性感湿特性和导电机理.扫描电镜脱测到,膜中炭黑粒子形成网链状的空问导电结构;2%炭黑含量使膜的导电通路处于渗流区,膜电阻在80%RH附近对湿度有较强的非线性特件.分析I-V曲线认为,是导电网链中炭黑粒子的间距使膜电阻对湿度变化和测量电压的变化都非常敏感,非线性感湿特性与导电机理密切相关.复阻抗谱表明,碳湿敏样品在33%RH时只出现与炭黑体电阻有关的半圆弧,在80%RH时出现与炭黑粒界电阻有关的第二个半圆弧,92%RH时的复阻抗谱是以上两个半圆弧外加接近45°角的拖尾,拖尾部分对应膜与电极之间水分子引起的极化作用.
Abstract:
The nonlinear sensing property and electric mechanism of carbon humidity-sensitive membranes under investigation were manufactured by using hydroxyethyl cellulose (HEC), carbon black (CB) and humidizer sorbitol. Microstructures examined by scanning electronic microscopy (SEM) show that, an effective carbon black electric network in humidity-sensing membrane would make the membrane' s resistance to have strong nonlinear property near 80% RH; so that the amount of 2wt% carbon black is in the proximity of the electric percolation threshold. The voltage-current characteristic suggested that the nonlinear sensing property and electric mechanism of the carbon humidity membranes are closely related. Particularly, impedance spectroscopy of sample at 92% RH was made up by two semi-circular arcs and a straight tail near 45° angle. The membrane's equivalent circuit was three RC circuits in series that corresponds to the contributions of the carbon bulk resistance, CB-grain-boundary resistance and electrode contact resistance, respectively.
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