טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentDubrovski Oles
SubjectFlexural Wave Assisted Electropolishing
DepartmentDepartment of Chemical Engineering
Supervisor Dr. Ofer Manor
Full Thesis textFull thesis text - English Version


Abstract

Previous experimental studies showed that the electropolishing of copper may be enhanced by twofold following the excitation of the polished anode by 80 KHz and 1 MHz frequency vibration. The vibration was further found to support the formation of periodic dents in the anode. We use theory to show that the vibration enhances the transport of ions through a layer of viscous liquid that appears near the anode during the electropolishing process and is the main diffusion barrier to the transport of ions from the anode to the bulk of the electrolyte in the electrochemical cell. The vibration supports acoustic flow, convecting ions and deforming the viscous layer. Weak ion convection and small deformation of the viscous layer that are associated with low vibrational power alter the ion transport flux to support the formation of dents. This regime of ion transport does appear to add substantial contribution to the efficiency of the electropolishing process. Higher vibrational power renders the Pecl ́et number, Pe, which gives the ratio between the convective and diffusive fluxes of ions in the viscous layer, large. In this limit we find an appreciable contribution to the efficiency of the electropolishing process from the vibration, in accordance to previous experimental findings. The enhancement in the efficiency of the electropolishing processes is measured by the increased flux of ions through the viscous layer. It is quantified by the expression 2 Pe1/2 h0 k / p3/2 in which h0 is the apparent thickness of the viscous layer at rest and k is the wavenumber of the vibration in the anode. Moreover, we find that the convection of ions supports the formation of periodic dents in the anode.