magnetic alloy neodymium-iron-boron has been produced by co-deposition from a molten salt. A wide range of compounds—from electronic and photonic materials such as gallium arsenide and cadmium telluride to wear-resistant materials such as tungsten carbide to electron emitters such as Ianthanum hexaboride—have been deposited. Opportunities exist to develop new nonaqueous chemistries to extend the window of electrochemical potential and thereby give greater access to highly reactive materials.
Electrolysis is a nonequilibrium process that has the capability of generating nonequilibrium structures such as coatings, epitaxial layers, or powders. Compositionally modulated structures such as that illustrated in Figure 4.9 are readily produced electronically.
Electrodeposition is carried out at or near room temperature in aqueous and organic electrolytes, at elevated temperatures in molten salts, and at low temperatures in cryogenic liquids. Cryogenic electroprocessing offers a new window of opportunity in a temperature region in which kinetic processes occur at rates quite different from those that occur at room temperatures or elevated temperatures, providing new opportunities for achieving metastable structures.
Two important themes cut across all four of the elements of materials science and engineering. The first is the importance of instrumentation in performing and controlling synthesis and processing; characterizing structure, composition, and properties; and analyzing performance (see Appendix D). The second is the increasing importance of analysis and modeling (see Appendix E), which, together with increased computational abilities and judicious experimentation, are helping to make materials science and engineering increasingly quantitative.
The instrumentation used in materials science and engineering has become increasingly sophisticated and expensive. The cost of analytical instruments such as electron microscopes ranges from $50,000 to $850,000, and the cost of dedicated process equipment, such as MBE and ion implantation equipment, is in the range of $1 million to $2 million. Furthermore, these costs are rising rapidly, at well above the rate of inflation. With the increasing use of powerful computers to simulate the synthesis and processing, structure and composition, properties, and performance of materials, instrumentation has become important for theoretical as well as experimental materials research. Cost-effectiveness rules out having such facilities at every institution, making new sharing mechanisms a necessity.