微观浓度场对银生长形貌的调控作用

Role of micro-concentration field on morphology of silver particles

利用原位光学显微镜和计算模拟技术研究了材料生长界面微观浓度场对材料结构演化的影响。在电沉积法制备银颗粒中,通过调控电位在电解液中生成氧化银胶体粒子。在外加电场作用下胶体粒子在溶液中运动,进而带动溶质的定向迁移;通过外加电场控制胶体粒子迁移速度,调控生长界面溶质浓度分布。随胶体粒子迁移速度增加,界面传质增强,颗粒生长前沿扩散层变薄,浓度梯度变大,银颗粒形貌由球状纳米晶变为对称枝晶结构,生长速度由10μm2/s增大到60μm2/s。最后结合格子Boltzmann模拟结果,验证了界面浓度场对银颗粒形貌演化的调控作用。

To reveal the role of interface micro-concentration distribution on the evolution of materials structure,silver crystallization was investigated by the in-situ optical microscopy and lattice Boltzmann simulations.Silver particles were synthesized by electrodeposition,in which silver oxide colloid particles were generated as the byproducts.The migration velocity of colloid particles in the electrolyte was regulated by the electric field.With the increase of migration velocity of colloid particle,mass transfer increased,the diffusion layer in the front of the growth became thinner,and the concentration gradient became sharper.As a result,the morphology of silver particles changed from spherical nanocrystals to symmetrical dendrites,and the growth rate increased from 10μm2/s to 60μm2/s simultaneously.Finally,it was proposed that the micro-concentration field in the diffusion layer is the main mechanism dominating the evolution of particle morphology,which was verified by the lattice Boltzmann simulation of convection diffusion and phase transition.