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Ionic Polymer-Metal Nanocomposite; Multiscale Simulation, Fabrication and Mechanical Characterization

Ozmaian, Masoumeh | 2014

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 45423 (48)
  4. University: Sharif University of Technology
  5. Department: Institute for Nanoscience & Nanotechnology
  6. Advisor(s): Naghdabadi, Reza; Irajizad, Azam; Ejtehadi, Mohammad Reza
  7. Abstract:
  8. Ionic polymer metal nanocomposites (IPMNCs) are among the advance materials which have been widely used recently as smart materials. These nanocomposites, which are made of polymeric layers (Nafion) plated by metallic or non-metallic conductive electrodes, show large deformations under low applied voltages. The advance materials like these nanocomposites have resolved the problems of the conventional actuators and helped in producing accurate systems.
    Several methods have been used to predict the behavior of IPMNCs which any of them consider some simplifying assumptions. In these materials physical phenomena happen at the molecular scale and deformations observed at the large scale. Thus, it is necessary to use multiscale methods to study their behavior which have not been used widely in this field. The main aim of this project is to propose a model based on analytical equations and atomistic simulation to predict the mechanical and physical behavior of IPMNCs and Nafion membrane. The experimental measurements have also implemented to verify the results predicted by theoretical method and calibrate the characteristic features of IPMNCs. In this thesis, a hierarchical multiscale framework based on molecular simulation and analytical equations is developed. This model is used to predict the macroscopic equivalent behavior and local physical properties of the polymeric membrane using the water gradient profile across the thickness, induced curvature of the membrane, distribution of permittivity and conductance. This method can be also generalized to other smart materials which work based on water gradient across them. We have also studied the bending deformation of a beam made of IPMNC by non linear electroelastic method. The experimental results of measuring the deflection and forces are also used to calibrate the electroelastic parameters. In the molecular dynamics simulation part, many physical properties of the polymeric membrane are investigated. The molecular dynamic simulation results show that by applying uniaxial loading, the diffusion coefficient of water molecules increases. This effect helps to improve the efficiency of devices made of Nafion. We have also estimated the glass transition temperature of hydrated Nafion using the simulation results and theories of glass transition. The effect of water content on this temperature is also considered. Most of the results obtained from this research are useful in the most applications of IPMNCs such as actuators, sensors and fuel cells.
  9. Keywords:
  10. Smart Materials ; Molecular Dynamic Simulation ; Ionic Polymer-Metal Nanocomposite ; Multiscale Method ; Nonlinear Electroelastic Method

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