Electromechanical Coupling Properties With Surface/Interface Effect Of Nanoscale Materials

Nanoscale piezoelectric materials with excellent piezoelectric and semiconducting properties are widely used in sensors, resonators, transistors. They show a broad application prospect in biological treatment systems, micro-nano electromechanical systems, selfpowered micro-nano systems, which greatly promote the development of nanotechnology. Compared with macroscopic materials, nanoscale piezoelectric materials have higher property in conversion and stronger performance in electromechanical coupling. But due to their large ratio of surface area to volume, there is a huge potential difference between surface atoms and internal atoms. This character leads to higher surface atomic activity, making surface/interface effect of nanoscale materials more significant. So the surface/interface effect on the performance of the electromechanical coupling can not be ignored. Based on the electro-elastic surface/interface theory and the specific analysis methods, the electromechanical coupling properties with surface/interface effect of piezoelectric materials are investigated in the paper. The main research contents are as follows:Combined with the G-M theory, the electro-elastic coupling surface/interface model and conformal mapping method, the surface/interface effect on the electromechanical responses around a nanoscale elliptical piezoelectric inclusion embedded in an infinite piezoelectric matrix under far-field loading with an arbitrary angle is studied. Different material constants, load angles, elliptical shapes are adopted to analyze the surface/interface effect on the electromechanical coupling properties, which can improve overall performance by optimizing the inclusion shape and material.Combined with the electro-elastic coupling surface/interface model and wave theory, the multiple scattering of anti-plane shear wave in multilayer nanoscale piezoelectric materials is investigated. The analytic solutions of stress and electric field can be obtained by wave function expansion method and potential functions of each layer in the nanoscale cylinder. Different material constants, numbers of layer, layer thickness, incident wave numbers are adopted to study the surface/interface effect on electromechanical coupling properties. It is shown that the interface material selection has a significant impact on the stress and electric field of each layer.Combined with the electro-elastic coupling surface/interface model, conformal mapping method and Laurent series, the electromechanical response of infinite piezoelectric matrix with a coated nanoscale inclusion of arbitrary shape under anti-plane mechanical and in-plane electric loadings is studied. Different material constants of interfaces, inclusion shapes are adopted to study the surface/interface effect on electromechanical coupling properties. It is found that there is a big difference of the stress and electric field among different shapes, and the surface/interface effect on circular inclusion is relatively small while on the external layer interface, the surface/interface effect on stress and electric fields is large.Combined with the Goodier’s theoretical analysis method, the G-M theory and electro-elastic coupling surface/interface model, an infinite piezoelectric matrix containing spherical nanoscale piezoelectric inclusions under a uniform electric field is studied, and the surface/interface effect on the electromechanical coupling properties is also analyzed. The results show that different impact factors exhibit different effects on the stress, electric field of the matrix and inclusions.Combined with the magneto-electro-elastic coupling surface/interface theory, conformal mapping method and series expansion, the magneto-electro-mechanical response of magneto-electro-elastic materials under far fields and eigenfields is studied. An infinite piezoelectric matrix containing nanoscale piezomagnetic inclusion of arbitrary shape is taken for example. With the surface/interface effect, the influence of interfacial material constants, inclusion shapes on the stress, electric displacement, magnetic flux is also analyzed. The numerical results show that the elastic factor effect on the stress is the maximum, and the piezomagnetic factor effect is the minimum. For the electric displacement, the piezoelectric factor effect is greater than the elastic factor second. The piezomagnetic factor nearly shows no effects. The magnetic flux is only influenced by piezomagnetic factor. Under different shapes of inclusion, the stress, electric displacement and magnetic flux are also obviously different considering the surface/interface effect.ZnO nanowires are prepared on FTO conductive glass substrates and ITO flexible conductive film substrates with two-step method at low temperature through hydrothermal method and electrochemical deposition method. The tests are also explored by scanning electron microscope(SEM) and ultraviolet and visible spectrum(UV). The controllable growth of ZnO nanowires is realized. The conclusion can lay the foundation for producing electricity by vibration and the mechanical energy transform to electrical energy.