Translated Abstract
Ionic Polymer-Metal Composite (IPMC) is a kind of ionic electro-active polymer, which is soft, light-mass and of large deformation, and shows great potential in science and engineering fields. For lack of understanding on the large deformation mechanisms, there exist many complicated deformation phenomena of IPMC that are difficult to be explained. To solve these problems, it is deeply explored the large deformation mechanisms and proposed a multi-physical model in this dissertation.To fully understand the complicated deformation behaviors of IPMC, based on combination of fabrication technique steps, a series of IPMC samples with typical electrodes were prepared. The structure morphologies of IPMC, especially electrodes, were captured by SEM, the influence of electrode morphologies on the elastic modulus and electrode conductivity was analyzed by experiments. The dielectric properties of the typical IPMC samples were investigated by a broad frequency dielectric spectrometer. The results indirectly proved that the cation migration among clusters is the main relaxation mechanism at low frequency. Then the electromechanical responses of the samples were measured using a self-made test platform. The ways how the conductivity, dielectric modulus and elastic modulus affect the deformation quantitatively were explained well, and the linearity of the current and displacement with the voltage also obtained. Subsequently the deformation of IPMC in air with reduction of water content was measured, in which a few abnormal phenomena were explained using deformation that was due to air-drying by combining the static/dynamic water content of IPMC in air. To explore the actuation mechanisms of IPMC, breaking through from the relaxation properties, a series of comparative experiments were performed, including comparing the deformation properties of Nafion-IPMC with the inner water phases and their proportions under variable water contents, and comparing the deformation properties of Flemion-IPMC with the inner water phases and their proportions under variable water contents. A more general deformation theory was presented, which was main characterized by: (1)The proportion of free water in IPMC is the critical for the relaxation. (2)From the similarities and differences between Flemion and Nafion based IPMC, the third deformation process existed in the former, the slow anode deformation, is the result of thee slow dissociation and migration of the weak acid in Flemion.A multi-physical model were established based on experiments, which mainly focused on three points, the transport process of cation and water, the strain/stress field induced by the gradient mass distribution and various eigen stresses in IPMC. Considering integrality of transport mechanisms and mensurability of model parameters, by comparing previous thermal irreversible process, frictional and NP models, an improved transport equation was proposed based on general Nernst-Planck (NP) equation theory and was simplified for numerical analysis further. The equation emphasizes the pressure induced convection. Based on a cluster model a complete mechanical model was set up using the way of micromechanics from the viewpoint of swelling theory. Combined the transport and mechanical equations, an integrated multi-physical model was obtained finally to expatiate the physical processes in IPMC sensor and actuator. Using a basic model that only included hydrostatic pressure, numerical simulation proved that the pressure induced convection show great influence not only on the distribution of water but also on that of cation after taking into account hydration effect. Finally, based on dimensionless form of the model, the properties of hydrostatic pressure, osmotic pressure, electrostatic stress and capillary pressure were investigated, especially their properties with the total water content decline. Combined with numeric simulation, the complicated relaxation deformation of IPMC was well explained. The above mentioned researches and conclusions are of significance to the design, fabrication, control and modification of IPMC actuator and sensor.
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