Author: admin
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Examples of Industrial Electrolytic Processes
Industrial electrolytic processes consume about 6% of the total electrical generating capacity of the United States, and represent the principal or only method for producing several important products. This section provides a brief summary of some important industrial applications. Synthesis of Inorganic ChemicalsElectrolytic production of chlorine and sodium hydroxide, introduced earlier in this chapter, represents…
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Design of Electrochemical Reactors for Industrial Applications
The process of designing an industrial electrochemical system is multifaceted, typically specialized to the application, and iterative. Our description is limited and focuses on the key trade-off between size and efficiency. This balance, illustrated in Figure 14.6, dominates the design process. Economic considerations are at the heart of the design of industrial electrolytic processes. As…
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Voltage Losses and the Polarization Curve
In this section, we examine the different polarizations or voltage losses present in typical electrolytic cells. The analysis is largely the same as for any electrochemical cell. Again, the objective is to establish the relationship between the potential of the cell and the current density. Recall from Chapter 4 for an electrolytic cell, (4.58b)We again…
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Performance Measures
This section describes three performance measures that are useful for industrial electrolytic systems. We begin with the faradaic efficiency, which is the ratio of the product mass to the amount that could be obtained based on the current and Faraday’s law, as was introduced previously in Chapter 1. It can be written as (14.1) where mi is the mass…
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Overview of Industrial Electrolysis
The purpose of industrial electrolysis is to use electrical energy to convert raw materials into desired products. This conversion of raw materials takes place in an electrochemical reactor. Since energy is added, the electrochemical cells used are electrolytic rather than galvanic. Hence, the term industrial electrolysis is used to describe these processes. Just two electrolytic processes, the…
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Resistive Substrates
Up to this point we have assumed that the material being plated is highly conductive and essentially at a single potential; in other words, we have assumed that the conductivity of the material is sufficiently high that the potential gradient accompanying current flow in the material is very small and can be neglected. There are…
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Impact of Side Reactions
Side reactions are reactions that do not directly contribute to the formation of the desired deposit. For the deposition of metals from aqueous solutions, the most common side reaction is electrolysis of water or reduction of hydrogen ions, which results in the evolution of hydrogen gas at the cathodic potentials needed for deposition. The portion…
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Impact of Current Distribution
In the above discussion, we have implicitly characterized deposition by a single overpotential and rate for the surface of interest. In practice, however, the rate varies over the surface of the piece being plated, as illustrated schematically in Figure 13.12. To avoid the problems associated with deposition under mass-transport control, practical systems typically operate at…
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Additives
Additives have been and continue to be a critical component of industrial plating baths. Most additive work has been done empirically, although recent years have seen increased fundamental understanding of these complex systems. A detailed treatment of additive effects is left to more specialized texts. Instead, we provide just a brief introduction to this important…
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Deposit Morphology
Description of the deposition process rapidly becomes more complex as we move from the isolated nuclei of initial growth to interacting growth sites and, finally, coalescence and layer growth. The fundamental processes described above, however, provide a basis for understanding the deposit morphologies that are observed in practice. They also help us to understand ways…