An understanding of the nucleation mechanism involved in the sonoelectrochemical synthesis of copper from sulfate bath is reported here. These explanations include the analysis of sono-chronoamperometric current transients and atomic force microscopy. The results indicate that ultrasound induces secondary nucleation by breakage of the existing primary nuclei in addition to the primary nucleation. The understanding of the sonoelectrochemical mechanisms clarifies a few unclear issues. It could possibly allow for the better design of sonoelectrochemical synthesis.Cavitation, the irradiation of liquid with high intensity ultrasound, as a means of altering the crystallization process has been reported for many systems. 1,2 It is at the solid-liquid interface that electrochemical techniques may be employed to detect the possible influence of sonication on electrochemical nucleation and growth of clusters. Cluster formation of N ions, however, is connected initially with an increase in the Gibbs energy of the system and proceeds as an energy fluctuation system expression 3-5Both the terms are functions of the size of the cluster N. The first term is associated with the degree of supersaturation, the state of unstable equilibrium, and the second term takes into consideration the total energy excess due to the creation of interfaces when a nucleus appears on the electrode surface. Thus, the interrelation between the supersaturation ͑⌬͒ and the size of the critical nucleus ͑N crit ͒ decides the lowest Gibbs energy of the phase formation ͑⌬G crit ͒ and the highest rate ͓J = A j exp͑−⌬G crit /BT͔͒ of cluster formation. Different approaches have been established for the estimation of the parameters depending upon the size of the clusters. If adsorption, diffusion, and binding of the clusters are not the limiting factors ͑for sufficiently large clusters͒, then ⌬G crit has a value ofSmall crystals with a dominant effect of binding energies of adatom with substrate as well as bulk phase may have an expression for ⌬G critHence, irrespective of the size of the initial critical nuclei, the increase in supersaturation explicitly follows a decreasing N crit trend. Ultrasound capable of creating zones of extremely high level localized supersaturation 6 should set off the nucleation process. In the process of growth, however, high indexed surface zones are transformed into atomically smooth equilibrium faces. Further phase formation needs the formation of steps or irregularities on the substrate's surface for nucleation. Crystal fragmentation by ultrasound may create new steps on the defect-free crystal face to further supplement the crystallization process. Though a limited literature exists on the aspects of ultrasound-induced secondary nucleation, there is an urgent need for information particularly related to electrochemical phenomena. Thus, ultrasonic energy is believed to stimulate a biphasic nucleation sequence, i.e., primary ͑on the native substrate͒ and secondary ͑on the existing primary clusters͒. 1,2The purpose of this artic...
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