發(fā)布時間：2018-05-10 10:13

  本文選題：磁流變彈性體 + 顆粒結構　； 參考：《山東科技大學》2017年碩士論文

【摘要】：磁流變彈性體(magnetorheological elastomers, MRE)是將微米級鐵磁性顆粒分散于液態(tài)高分子聚合物中,在外加磁場作用下發(fā)生磁流變效應,顆粒磁化并形成有序鏈狀結構,在保持磁場作用的同時聚合物固化而形成的彈性固體。鏈狀結構能夠作為導電通道使得MRE具有導電性。與普通的導電高分子復合材料相比,MRE具有電阻小、制備簡單、變化參數(shù)多等優(yōu)點,存在較高的實用價值。本文對MRE的制備工藝和顆粒結構進行了分析,對外界壓力、工作磁場、溫度等影響MRE導電性能的因素進行了研究。通過分析MRE對組成材料的性能要求,確立了 MRE的基本制備工藝。以羰基鐵粉作為分散相、硅橡膠作為基體材料,制備了不同顆粒體積比的MRE樣品。通過實驗觀察了 MRE樣品的內(nèi)部微觀結構,分析了固化磁場強度和顆粒體積比對鏈狀結構的影響。在顆粒結構分析的基礎上分析了 MRE的導電機理,驗證了基于隧道電流和傳導電流組合的MRE導電機理模型。在電場強度較小時,傳導電流起主要作用。隧道電流在電場強度較大時起主要作用,而且由于隧道電流的作用,MRE的電導率與電場強度之間存在明顯的非線性關系。基于Hertz接觸理論和MRE的導電機理模型推導了 MRE壓敏特性理論模型。對MRE的導電性和壓敏特性開展了實驗分析,測試結果與理論模型預測符合的很好。開展了外加磁場對MRE導電性能影響的研究。基于磁化顆粒的偶極子模型,分析了相鄰顆粒的相互作用磁場力。磁場力導致顆粒間導流面積發(fā)生變化,從而影響MRE的磁敏效應。設計實驗裝置對MRE電阻率與磁感應強度的關系進行了研究。研究結果表明MRE的電阻率隨著磁場強度的增大而減小,當磁場強度再繼續(xù)增大電阻率下降趨勢逐漸趨于緩和,最后達到平穩(wěn)狀態(tài)。以MRE的導電機理為理論基礎,對MRE的導電性能受溫度的影響進行了分析。MRE導電填料和基體材料熱膨脹率的不同,隨著溫度的升高顆粒間間隙發(fā)生變化,進而影響MRE的導電性能。對MRE進行溫度特性實驗研究,發(fā)現(xiàn)MRE表現(xiàn)出明顯的溫度效應,隨著溫度的升高MRE的導電性減弱。
[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.
【學位授予單位】：山東科技大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O631.23;TB34

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