Fundamental Aspects of ELECTROCRYSTALLIZATION

This monograph is an attempt to present in a concise manner those aspects of the electrolytic growth of crystals considered to be of basic mechanistic significance. The accent has been put consistently on the understanding of the physical models of the processes discussed. Out of the extensive amount of information in this field, the authors have tried to abstract those systems which can be considered central, and which can, therefore, be related to the basic concepts connected with the electrodeposition of metals. In particular, stress has been laid upon consideration of atomic movements -of ions and molecules in solution, of adsorbed substances on the surface of metals, of steps on a growing crystal. Although the main stress is upon the physical picture, a number of derivations have been presented in detail. It is assumed that the reader is familiar to some degree with the concepts of electrodics; in particular, frequent reference is made to models of the electrical double layer at the metal­ solution interface and the transfer of charged species across it.

1 Retrospect.- 1. The First Contributions.- 2. Earlier Concepts.- 2 Perspective.- 3 Methods of Investigation.- 1. Electrochemical Methods.- 2. Optical Methods.- 3. Surface and Solution Preparation.- 4 Basic Models of the Atomic Movements Which Lead to Deposition.- 1. A Definition.- 2. Mechanism of Interfacial Charge Transfer.- 3. The Alternative Paths for Metal Deposition.- 4. What Happens to the Hydration Sheath During the Atomic Movements Between Arrival in the Double Layer and Building into the Lattice?.- 5. Is Charge Transfer to all Types of Sites on the Metal Surface Equally Probable?.- 6. Can “Two-Electron Transfers” Take Place?.- 7. Adatom or Adion?.- 8. Path and Rate-Determining Step in Deposition: Theoretical Indications.- 5 Transients.- 1. Origin of Transient Measurements in Metal Deposition Studies.- 2. The Mehl and Bockris Analysis.- 3. Better Approximations in the Analysis of Transients.- 6 Discussion of Some Basic Questions Concerning Path and Rate-Determining Step.- 1. The Charge-Transfer Step.- 2. The Two Paths: Via the Surface or Directly to Kink Sites.- 3. The Generality of Rate Control by the Charge-Transfer Step at High Current Densities.- 4. Under Surface-Diffusion Control, Deposition Does Take Place Preferentially Near a Growth Site.- 7 Deposition and Dissolution Kinetics as a Function of the Initial Substrate.- 1. Variation of the Activity of a Surface with Time.- 2. The Effect of the Potential Dependence of the Activity of the Emergent Dislocations on the Kinetics of Deposition.- 3. The Effect of Change of Concentration of Emergent Dislocations in the Initial Substrate.- 8 Why Do Some Crystals Grow in Filamentary Shapes?.- 1. Crystal Growth, Dendritic Growth, and the Study of the Mechanism of Electrocrystallization.- 2. Facts about Dendritic Growth on Electrodes.- 3. Mechanism of Dendritic Growth.- 9 Mechanistic Aspects of Morphology.- 1. Preliminary Observations.- 2. Some Forms Observed.- 3. The Potential Dependence of the Growth Form.- 4. Impurity Effects on Morphology.- 5. Texture.- 10 Kinematics of Step Propagation.- 1. A Necessary Methodology.- 2. Microsteps.- 3. Macrosteps.- 4. Facts of Macrostep Movements.- 5. Determination of the Origin of Microsteps.- 6. The Instability of Bunches of Microsteps in the Absence of Impurities.- 7. Impurity Adsorption Theory of Bunching.- 8. Mechanism of the Propagation and Fading of Macrosteps.- 11 Effect of Adsorbed Substances upon Electrocrystallization.- 1. Facts.- 2. Adsorption of Inhibitors at Electrified Interfaces.- 3. Thermodynamics and Kinetics of Adsorption.- 4. Mechanisms of Inhibition.- 12 The Theory of the Electrochemical Leveling and Brightening of Surfaces.- 1. Factors Affecting Current Distribution.- 2. Leveling.- 3. Bright Electrocrystallization.- 13 Electrocrystallization and Crystallization from the Gas Phase.- 14 Prospects.- References.