Study On Forming And Controlling Of Ag₂Ga Nanoneedle Using Phase Field Model

Due to its unique mechanical,electronic and optical properties,Ag₂Ga nanoneedles are widely used in electromechanical,optical,biological and other important areas.At present,the fabrication methods of Ag₂Ga nanoneedles at home and abroad are mostly based on self-assembly method.However,this method is difficult to precisely control the fabrication process and there are some contingencies in the results.At the same time,there is no study to explain the formation mechanism of Ag₂Ga nanoneedles.Compared with the self-assembly experimental method,the phase field method can simulate any microstructure evolution process within the allowable microscale and study the evolution process of the microstructure more effectively from the energetics.In this paper,we propose a new method to study the forming and control of Ag₂Ga nanoneedles based on the phase field model,we will discuss the changes of microstructure during the forming process of Ag₂Ga nanoneedles,explain the forming mechanism which will provide the theoretical basis for the forming process of Ag₂Ga nanoneedles.The main contents of this paper are as follows:?1?Study the mathematical model of Ag₂Ga nanoneedles in the forming process,establish a three-dimensional phase field model based on the atomic diffusion mechanism in the Ag-Ga contact reaction process.Then,analyze the energy variations of each phase in the model detailed.According to the Cahn-Hilliard theory,the governing equations for the microstructure evolution of Ag,Ga and Ag₂Ga are derived respectively.Then obtain the numerical solution of these governing equations by using the semi-implicit Fourier spectrum method and the second-order backward difference method.?2?Simulate the forming process of Ag₂Ga nanoneedles.The governing equations were programmed by C language to simulate the microstructure evolution characteristics of Ag,Ga and Ag2 Ga and then summarize the forming mechanism.Analyze the variation of the length and diameter of Ag₂Ga nanoneedles with time,and then summarize the changing rule about the aspect ratio of Ag₂Ga nanoneedles.?3?Study the effects of different surface energy coefficients on the Ag₂Ga nano-needles tip morphologies.Summarize the law of Ag₂Ga nanoneedles tip morphological changes through the simulation results of three surface energy coefficients.Meanwhile,study the effect of Ag₂Ga nanoneedles tip morphologies by change the direction of the external force on the end of Ag.Analyze the Ag₂Ga nanoneedle tips morphologies under two different directions of external force of vertical and parallel Ag-Ga interfaces,which will provide a new direction for controlling the processing of Ag₂Ga nanoneedles with different tip morphologies.