MEASUREMENTS OF SPATIAL TEMPORAL STRUCTURES IN PRECIPITATED IRON SULFATE

Current pulses may cause an unusual spatial-temporal structure in precipitated films on iron electrode surfaces produced in sulfuric acid solutions. The precipitated films show an arrangement of cells resembling those found in convection at fluid-fluid interfaces. This phenomenon is the result of macroscopic fluid flow induced by interfacial tension gradients generated by the chemical kinetics of metal dissolution. The fluid motion induced by surface tension variation accelerates the aggregation of particles into a preferential square cell geometry which was observed on the samples prepared using a freeze-drying technique. Both the square pattern cell sizes and the interfacial tension variation have an identical functional dependence on sulfuric acid concentration.