磁流变弹性体导电特性研究

发布时间：2018-05-10 10:13

本文选题：磁流变弹性体 + 颗粒结构　；参考：《山东科技大学》2017年硕士论文

【摘要】：磁流变弹性体(magnetorheological elastomers, MRE)是将微米级铁磁性颗粒分散于液态高分子聚合物中,在外加磁场作用下发生磁流变效应,颗粒磁化并形成有序链状结构,在保持磁场作用的同时聚合物固化而形成的弹性固体。链状结构能够作为导电通道使得MRE具有导电性。与普通的导电高分子复合材料相比,MRE具有电阻小、制备简单、变化参数多等优点,存在较高的实用价值。本文对MRE的制备工艺和颗粒结构进行了分析,对外界压力、工作磁场、温度等影响MRE导电性能的因素进行了研究。通过分析MRE对组成材料的性能要求,确立了 MRE的基本制备工艺。以羰基铁粉作为分散相、硅橡胶作为基体材料,制备了不同颗粒体积比的MRE样品。通过实验观察了 MRE样品的内部微观结构,分析了固化磁场强度和颗粒体积比对链状结构的影响。在颗粒结构分析的基础上分析了 MRE的导电机理,验证了基于隧道电流和传导电流组合的MRE导电机理模型。在电场强度较小时,传导电流起主要作用。隧道电流在电场强度较大时起主要作用,而且由于隧道电流的作用,MRE的电导率与电场强度之间存在明显的非线性关系。基于Hertz接触理论和MRE的导电机理模型推导了 MRE压敏特性理论模型。对MRE的导电性和压敏特性开展了实验分析,测试结果与理论模型预测符合的很好。开展了外加磁场对MRE导电性能影响的研究。基于磁化颗粒的偶极子模型,分析了相邻颗粒的相互作用磁场力。磁场力导致颗粒间导流面积发生变化,从而影响MRE的磁敏效应。设计实验装置对MRE电阻率与磁感应强度的关系进行了研究。研究结果表明MRE的电阻率随着磁场强度的增大而减小,当磁场强度再继续增大电阻率下降趋势逐渐趋于缓和,最后达到平稳状态。以MRE的导电机理为理论基础,对MRE的导电性能受温度的影响进行了分析。MRE导电填料和基体材料热膨胀率的不同,随着温度的升高颗粒间间隙发生变化,进而影响MRE的导电性能。对MRE进行温度特性实验研究,发现MRE表现出明显的温度效应,随着温度的升高MRE的导电性减弱。
[Abstract]:Magnetorheological elastomer (MREs) is a kind of magnetorheological elastomer (MREs), which disperses micron ferromagnetic particles in liquid polymer. The magneto-rheological effect occurs under the action of external magnetic field, and the particles magnetize and form an ordered chain structure. An elastic solid formed when the polymer is solidified while maintaining the magnetic field. Chain structure can be used as a conductive channel to make MRE electrical conductivity. Compared with conventional conductive polymer composites, MRE has the advantages of low resistance, simple preparation and varied parameters, so it has high practical value. In this paper, the preparation process and particle structure of MRE are analyzed, and the factors affecting the conductivity of MRE, such as external pressure, working magnetic field and temperature, are studied. The basic preparation process of MRE was established by analyzing the performance requirements of MRE. MRE samples with different particle volume ratios were prepared by using carbonyl iron powder as dispersion phase and silicone rubber as matrix material. The microstructure of MRE samples was observed experimentally and the effects of solidified magnetic field strength and particle volume ratio on the chain structure were analyzed. Based on the analysis of particle structure, the conductive mechanism of MRE is analyzed, and the conduction mechanism model of MRE based on the combination of tunneling current and conduction current is verified. When the electric field intensity is small, the conduction current plays a major role. The tunneling current plays a major role when the electric field intensity is high, and there is an obvious nonlinear relationship between the conductivity of MRE and the electric field intensity due to the effect of tunnel current. Based on the Hertz contact theory and the conductive mechanism model of MRE, the theoretical model of MRE varistor characteristics is derived. The electrical conductivity and varistor characteristics of MRE are analyzed experimentally, and the results are in good agreement with the theoretical model. The effect of external magnetic field on the conductivity of MRE was studied. Based on the dipole model of magnetized particles, the interaction magnetic field force of adjacent particles is analyzed. The magnetic field force changes the conductivity area between particles, which affects the magnetic sensitivity of MRE. The relationship between MRE resistivity and magnetic induction intensity was studied by designing an experimental device. The results show that the resistivity of MRE decreases with the increase of magnetic field intensity, and the decreasing trend of resistivity decreases gradually with the further increase of magnetic field intensity, and finally reaches a stable state. Based on the conductive mechanism of MRE, the influence of temperature on the conductivity of MRE was analyzed. The difference of thermal expansion ratio between conductive filler and matrix material was analyzed. The gap between particles changed with the increase of temperature, which affected the conductivity of MRE. The experimental study on the temperature characteristics of MRE shows that the temperature effect of MRE is obvious and the conductivity of MRE weakens with the increase of temperature.
【学位授予单位】：山东科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O631.23;TB34

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