Comprehensive anodic dissolution

The strange anodic polarization behaviors (negative difference effect, lower apparent valence, low anodic dissolution efficiency, low anodic polarization resistance and poor passivity ) are closely associated with the AHE process which is further related to the onset of localized corrosion or pitting . A comprehensive anodic dissolution model can be employed to understand these. 

According to the comprehensive anodic dissolution model, the further anodic reaction (1.32) is a potential-dependent electrochemical process which can become faster at a more positive polarization potential. This means that y will increase and therefore n should also increase as the potential becomes more positive. This prediction has been experimentally verified n starting at 1.2 approached a value of 1.8 after the anodic polarization potential was more positive than -1 V/NHE (Perrault, 1978). Because the hydrogen production reactions in the anodic process cannot fully stop at anodic potentials, n cannot reach its theoretical value of 2, which is also consistent with experimental observation (Perrault, 1978). 

Electroplating. The second-largest appHcation for nickel chemicals is as electrolytes ia nickel electroplating (qv). In ordinary plating systems, nickel present ia the electrolyte never forms on the finished workpiece the latter results from dissolution and transfer from nickel anodes. Decorative nickel plating is used for automobile bumpers and trim, appHances, wire products, flatware, jewelry, and many other consumer items. A comprehensive review of nickel electroplating has been compiled (164). 

Based on an extensive investigation of the anodic i-V relations, dissolution valence, and PS morphology on a large matrix of silicon substrates, Beale el proposed a rather comprehensive model on the formation of PS. This was the first model that analyzed the i-V characteristics and correlated them with the current conduction mechanisms associated with silicon substrates of different types and doping concentrations. 

Three comprehensive books on porous silicon have been published, wherein detailed information can be found related to silicon anodization (Canham 1997 Lehman 2002 Sailor 2012a). The topics covered include dissolution chemistries and the dependences of porosity, pore morphology, and pore size distribution on various parameters (e.g., wafer type/doping, electrolyte composition, current density, time) additionally, different types of electrochemical cells are discussed (Lehman 2002 Sailor 2012a), as well as some of the more practical aspects related to anodization (Sailor 2012a e.g., wafer preparation, equipment and instrumentation, health and safety). The reader is referred to these references for essential background reading. 

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