Multiscale Simulation and Evaluation of Mechanical and Electromechanical Sensing Materials for Extreme Pressure Applications

Li, Meng
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With more and more exhausted near surface and shallow water gas and oil fields, the natural resources are now being extracted at even greater depths. Data distortion, loss of circulation, stuck pipe, and problems related to well measurement are even more likely happen when drilling in high pressure and high temperature (HPHT) deep wells. Easy drilling wells are no longer common. By conducting a survey on the sensors from five petroleum and sensor companies, the shortages of current commercial sensors were summarized, and the microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS) based sensors were found to be the prospected extreme pressure sensors.

Over the past decade, the significant development in manufacturing technology enables to obtain small-scale materials in various forms such as thin films, nanowires, nanotubes, and nanoparticles. The extensive use of microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS) in sensors enforces the importance of nanotechnology as one of the major trends in future. The small-scale ferroelectric materials in MEMS/NEMS have a wide range of potential industrial applications. Intensive experimental and computational efforts have been made recently to understand the performance of small-scale ferroelectrics in external fields. Due to the quantum effects, small-scale materials show significant differences in mechanical, thermal, electrical, magnetic, or optical properties when compared with their corresponding bulk state. At the nanoscale, even a slight atomic displacement could strongly affect the properties of the material, leading to critical malfunction of devices in some cases. Thus, a reliable design of small-scale devices requires a better understanding of the behaviors of the small scale materials. At the nanoscale, the mechanical response of nanoparticle is largely affected by the particle size. To assess the size effect (e.g., nanoparticle's volume, cross-sectional area, and length) of the nanoparticle, the Bcc iron nanoparticles under compressive loading was simulated to study its mechanical behaviors. The atomistic field theory and the Finnis-Sinclair model were applied in this case. Through the atomistic potential-based method, the mechanical responses were analyzed in different sizes. To further investigate the electromechanical properties of small size ferroelectrics in external fields, the multiscale simulation and shell model were adopted in the simulation. In this study, the deformation process and the ferroelectricity of nanostructures PbTiO3 were investigated. The polarization was switched 180° in an electric field, and the polarization was rotated 90° by under mechanical loading. The phase transition processes and the coupling effect of electrical and mechanical fields were observed. The pressure could reduce perovskite material's ferroelectricity at the nanoscale. The fracture behavior of perovskite BaTiO3 nanoparticles with dependence on size and atomic structure has been investigated. Atomic structure and atomic size were played important roles in the fracture process and breaking position of a ferroelectric nanoparticle subjected to uniaxial tension.

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Electromechanical, Material, Mechanical, Pressure, Simulation
Electrical and Computer Engineering