Table of contents for Fundamental aspects of electrometallurgy / edited by Konstantin I. Popov, Stojan S. Djokic, and Branimir N. Grgur.


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1. WHAT IS ELECTROMETALLURGY           .........................     1
1.1  Further Readings  .........................................  3
2. DEFINITIONS, PRINCIPLES AND CONCEPTS ................             5
2.1  Basic Facts  ..............................................  5
2.1.1 Electrodes and electrochemical reactions, cell and circuit ....  5
2.1.2 The electrochemical double layer and possible
electrochemical reactions ..........  .....................  6
2.2 Self Driving Cells ........................................   7
2.2.1 The Nemst equation and energy producing cells ...........  7
2.2.2 Cementation ........................................   10
2.3 Electrolysis .........................................       10
2.3.1 Decomposition voltage ...........................       10
2.3.2 A cell with an insoluble anode . ..................     11
2.3.3 A cell with a soluble anode ............................  13
2.3.4 Current efficiency ....................................  14
2.3.5 Faraday's law .......................................   14
2.3.6 The current density-overpotential relationships ...........  14
2.3.6.1 Basic equations ............... ................  14
2.3.6.2 Some approximations ..........................  17
2.3.7 The cell voltage ..........    .....................    19
2.3.8 Specific energy consumption ...........................  20
2.4 Some Aspects of Electrocrystallization ........................  20
2.5 Conclusions .............................................    26
2.6 Further Readings .........................................   26
3. SURFACE MORPHOLOGY OF METAL ELECTRODEPOSITS ..                   29
3.1 Thin Compact Surface Metal Films ..........................  30
3.1.1 Crystallization overpotential ...........................  31



3.1.2 The nucleation exclusion zones ........ .................  34
3.1.2.1 Basic definitions .......  ...... ................  34
3.1.2.2 Physical simulation .................  ..........  36
3.1.3 Nucleation rate and deposition overpotential .............  38
3.1.4 Deposition from simple salt solutions ...................  41
3.1.5 Deposition from complex salt solutions ..................  43
3.1.6 Deposition in the presence of adsorbed additives ..........  44
3.1.6.1 Inorganic compounds  ...........      .........  44
3.1.6.2 Organic compounds     .....................      45
3.1.7 Conclusions             ..    .................................  47
3.2 Thick Compact Metal Electrodeposits ........................  49
3.2.1 Coarse surfaces ......................................  49
3.2.1.1 Mathematical models ........................     49
3.2.1.2 Physical simulation ............................  54
3.2.1.3 Real systems .............   .... ..............  56
3.2.1.3.1 Optimum current density for compact metal
deposition  ............................  56
3.2.1.3.2 Cauliflower like forms ................  57
3.2.1.3.3 Carrot like forms ........ ..............  59
3.2.2 Smooth surfaces .....................................   61
3.2.2.1  Basic  facts  ........ ...... .....................  61
3.2.2.2 Model of leveling .............   ............   63
3.2.2.3 Quantitative treatment ............ .............  65
3.2.3 Bright surfaces  .  .............. .....................  66
3.2.3.1  Silver mirror  ........... .......... ..............  66
3.2.3.2 Electropolished surfaces .......................  67
3.2.3.3 Electrodeposited surfaces .......................  71
3.2.3.4  Conclusions  ........... ............... .....  72
3.3 Disperse Deposits ..................................          72
3.3.1 Spongy deposits ....................................    72
3.3.1.1 Mathematical model ...........................   72
3.3.1.2  Physical model  ......................... .....  74
3.3.1.3 Real systems ..................................  76
3.3.2 Dendritic deposits .................................  78
3.3.2.1 Mathematical model ...........................   78
3.3.2.2 Physical simulation .................................  82
3.3.2.3 Real systems ................  ...........       83
3.3.3 Powdered deposits ......     ..........................  89
3.3.4 Granular deposits ........... ....   ...............    92
3.3.5  Whisker deposits  ................... ..................  93
3.3.6 Conclusions .........................................   95
3.4 Further Readings ...................  .......... .  ...... ..  95



4. THE CURRENT DISTRIBUTION IN ELECTROCHEMICAL
CELLS  ....................................................  101
4.1 Two Equal Plane Parallel Electrodes Arrangement ..............  103
4.1.1 Ohmic resistance of the cell .........................  103
4.1.2 The very edge ohmic resistance ........................  106
4.1.3  The edge effect ......................................  108
4.1.4 The depth of the penetration of a current line between
the electrode edges and the cell side walls ............... 109
4.1.4.1 Mathematical model ...............................  109
4.1.4.2 Cell voltage-current density dependencies ..........  111
4.1.4.3 Determination of the current density distribution ....  115
4.1.5 Quantitative treatment ................................  118
4.1.5.1 Calculation of the cell voltage-current density
distribution dependences ........................  119
4.1.5.2 The critical current density for dendritic growth
initiation  at the  edges  ..........................  122
4.2 Cells with Low Anode Polarisation ..........................  124
4.2.1 The dependence of the current density at the tip of a
stationary wire electrode on the current density in the middle
of the electrode .... ..............................  124
4.2.2 Experimental evidence ................................  127
4.2.2.1 The effect of ohmic resistance .... ................. 127
4.2.2.2 Deposition in the presence of strongly adsorbed
organic additives (effect of increased cathodic Tafel
slope)  .......................................  129
4.2.2.3 Deposition from a complex salt solution (effect of
exchange current density) .......................  131
4.3 Corner Weakness Phenomena in Electroforming ................  133
4.3.1  Ohmic controlled deposition  .......................... .  133
4.3.2 Mixed activation - diffusion - ohmic controlled deposition ...  136
4.3.3 Activation - diffusion controlled deposition ...............  140
4.4  Conclusions  .............................................  141
4.5  Further Readings  .........................................  142
5. ELECTRODEPOSITION AT A PERIODICALLY CHANGING
RATE   .....................................................   145
5.1  Basic Definitions  .........................................  145
5.1.1  Reversing current  ....................................  145
5.1.2  Pulsating  current .....................................  146
5.1.3 Alternating current superimposed on direct current .........  148



5.1.4 Pulsating overpotential ................................  148
5.2 Surface Concentration of Depositing Ions in the Periodic
Condition ........................    ................     149
5.2.1 Electrodeposition with periodically changing rate in the
millisecond range  ...................   .................  149
5.2.2 Capacitance effects ....................................  154
5.2.3 Reversing current in the second range ..................  156
5.3 Prevention of the Formation of Spongy Deposits and the Effect on
Dendritic Particles .......................................  158
5.4 Compact Deposits ........................................   161
5.4.1 Surface film  .......................................  161
5.4.2 Electrode surface coarsening .........................  163
5.5 Current Density and Morphology Distribution on a Macroprofile ..  169
5.6 Conclusions .....................................           172
5.7 Further Readings .........................................  172
6. ELECTROW    INNING  ........................................   175
6.1 Theoretical Aspects of Electrowinning ..........................  175
6.2 Theoretical Aspects of Zinc Electrowinning ...................  176
6.2.1 Technological scheme of zinc electrowinning .............  177
6.3 Further Readings .........................................  180
7. ELECTROREFINING       .....................................    181
7.1 Theoretical Aspects of Electrorefining .............................  181
7.1.1 Selectivity of metal dissolution and deposition ............  182
7.2 Theoretical Aspect of Copper Electrorefining ..................  183
7.2.1 Technological scheme of copper electrorefining ........  186
7.2.1.1 Refining of the electrolyte .......................  188
7.2.1.2 Processing of the anodic slime ...................  188
7.3 Further Readings .......................................   189
8. OPTIMUM CONDITIONS FOR ELECTROPLATING ...........              191
8.1 Cementation and Deposition from the Complex Salt Solutions ....  191
8.2 The Porosity of Metal Electrodeposits ........................  192
8.3 The Condition for the Deposition of a Coating with a Minimum
Porosity  ................ ................................. 195
8.4   Further Readings  ..........  .....  ...................... 196



9. ELECTROPLATING AND SURFACE FINISHING ..............            197
9.1 Electrodeposition of Alloys ................................  197
9.2 Electrodeposition of Composite Materials .................... 210
9.3 Electroforming ........................................    216
9.4 Electroplating from Non-Aqueous Electrolytes ...............  219
9.5 Electroplating from Room Temperature Molten Salts ........... 223
9.6 Electropolishing .........................................  226
9.7 Electromachining ........................................  233
9.8 Electrochemical Oxidation of Metals ........................  236
9.9 Further Readings ..........................................  243
10. METAL DEPOSITION WITHOUT AN EXTERNAL
CURRENT ...................        .....................        249
10.1  Basic Definitions  ..................................... ..  250
10.1.1 Displacement deposition ................... ......... 250
10.1.2 Contact deposition ................................  251
10.1.3 Autocatalytic deposition .................... ... . 251
10.2 Solutions for Electroless Deposition ......................  252
10.3 Mechanistic Aspects of Electroless Deposition .................. 259
10.3.1 The atomic hydrogen mechanism .....................  259
10.3.2 The hydride ion mechanism  ......................... ......  260
10.3.3 The electrochemical mechanism ...................... 261
10.3.4 Metal hydroxide mechanism  .... ...   ............... .....  263
10.3.5 The universal mechanism  ........................ 265
10.4 Applications and Properties of Electroless Deposited Films ...... 266
10.4.1 Metallization of non-conductive surfaces ...............  267
10.4.2 Electroless deposition of composite coatings ........... 267
10.4.3 Electroless deposition of gold .........................  268
10.4.4 Electroless deposition of other metals ..................  269
10.5 Further Readings ........................................  270
11. ELECTRODEPOSITION OF METALS FROM MOLTEN SALTS                  271
11.1 Ionically Conducting Melts ................................  273
11.2 Electrochemical Studies in Electrodeposition from Molten Salts ..  275
11.2.1 Electrolysis of alumina-cryolite melts .............. ... . 276
11.3 The Anode Effect ........................................  286
11.4 Nonconsumable Anode Materials in Molten Salts
Electrodeposition  ........................................  287
11.5  Further Readings  ........................................ 289



12. ENVIRONMENTAL ISSUES ................................. 291
12.1 Environmental Concerns in the Electrowinning and Electrorefining
from Aqueous Solutions .................................. 292
12.2 Environmental Concerns in the Molten Salts Electrolysis ........ 293
12.3 Environmental Concerns in the Electroplating Technologies ...... 294
12.4   Further Readings  ........................................  299








Library of Congress subject headings for this publication: Electrometallurgy