Elastic Strain Effects On The Supercapacitors Of Nanofilms

Elastic Strain Engineering?ESE?is a promising research field combined with material science,physics and chemistry,which is aimed at applying the elastic strain to the functional material in order to modify its physical and chemical properties.Because the traditional method is difficult to apply large elastic strain to the nanomaterials,the present research mainly concentrated upon elastic-strain effect on core-shell nanoparticles and epitaxial nanofilms.There is a new design idea that the large elastic strain produced by the substrate baesd on martensitic transformation will be applied to the functional nanofilms which can not be grown epitaxially.In this dissertation,FeNiC alloy and NiTiNb shape memory alloy and were selected as the substrate to impose the relative larger elastic strain to the Fe₂O₃ and MnO₂ semiconducting nanofilms,Differential scanning calorimetry?DSC?and thermal dilatation measurement were used to study the phase transformation behavior of the substrate.Scanning electron microscopy?SEM?were used to characterize the surface morphology of the films.X-ray diffraction were utilized to measure the substrate.For supercapacitors,electrochemical analytical techniques including Cyclic Voltammetry?CV?and Chronopotentiometry?CP?were used for clarifying the elastic strain effects on the supercapacitor activity of MnO₂ and Fe₂O₃ nanofilms.The main conclusions obtained here are as follows:?1?Through the preparation of different thickness of the MnO₂ semiconductor film,in the 1M/L Na₂SO₄ electrolyte,in the 0⁰.9 V voltage window,the electrochemical test found that with the thickness of the film increases,the areal specific capacitance increases continuously,but the volume specific capacitance reach the maximum value at 90 nm,about 129 mF/cm²?m.For the same thickness of the MnO₂ semiconductor film,with the anodization current density increases,the specific capacitance gradually increased.?2?The tensile and compressive strains were applied to the MnO₂ nanofilms by the two-way shape memory effect of the TiNiNb memory alloy matrix.In the 1M/L Na₂SO₄ electrolyte,in the voltage window of 0⁰.9 V,the electrochemical test found that the compressive strain increased its supercapacitor specific capacitance by about 20%,while the tensile strain reduced its supercapacitor specific capacitance by about 30%.?3?The semiconducting film comprised of Fe₂O₃ was tensile-strained biaxially by the means of surface relief of FeNiC alloy substrate,which lead to decrease in the specific capacitance.