Molten Salt Techniques: Volume 3

ISBN-13: 9781461290315 / Angielski / Miękka / 2012 / 368 str.

Robert J. Gale; D. G. Lovering

Opis

The physicist Kamerlingh Onnes, who was the first to liquify helium (1908), had written on the walls of his laboratory in Leiden: "From measur- ing to knowing." As true as this is at very low temperatures, it is just as applicable at the high temperatures of molten salts. Only on the basis of exact measurements by a plethora of experimental methods can any real understanding be reached of both classes of liquids. In both temperature ranges experimental difficulties are much greater than those encountered around ambient temperature. Molten salts often present a formidable challenge to the experimen- talist, for example, because of corrosion and other materials problems. Applications of molten salts were for a long time based on empirical knowledge alone. This was true for the first application of molten salts in 1807, when Davy obtained sodium and potassium by electrolysis of the molten hydroxides. For 100 years the winning of aluminum has been based on the very nearly simultaneous invention by Hall and Heroult (1886) of the electrolysis of molten cryolite. The process, though essentially unchanged, has since been perfected owing to an improvement in our understanding of what actually happens, based on difficult measurements ofthe many variables. However, even now there are gaps in our knowledge.

Spis treści

1. Introduction.- References.- 2. Actinides.- 1. Introduction.- 1.1. Perspective.- 1.2. Historical Availability of Actinides.- 1.3. Current Availability of Actinides.- 2. Special Enclosures Required for Actinides.- 2.1. Health and Safety Standards.- 2.2. Benchtop and Chemical Hood Enclosures.- 2.3. Glovebox Enclosures.- 2.4. Remote Handling.- 3. Materials Problems.- 3.1. Irradiation Degradation of Materials.- 3.2. Container Compatibility at High Temperatures.- 4. Microtechniques.- 5. Techniques for Purification of Multigram Quantities of Actinides and Their Salts.- 5.1. Aqueous Methods of Purification.- 5.2. Pyrochemical Preparative Chemistry.- 5.3. Final Steps of Purification.- 6. Metal Preparation and Purification.- 6.1. Reduction by Metal Vapor.- 6.2. Pressure Vessel or “Bomb” Reduction.- 6.3. Ambient Pressure Reduction of Actinide Salts.- 6.4. Pyrochemical Purification of Actinide Metals.- 7. Physical Properties Measurements.- 7.1. Melting Points and Phase Relationships.- 7.2. Other Physical Properties of Actinide Salts.- 8. Absorption Spectra.- 9. Electrochemistry.- 9.1. Conductance Measurements.- 9.2. Electromotive Force Measurements.- 10. Summary.- References.- 3. Cryolite Systems.- 1. Introduction.- 1.1. General.- 1.2. Physical Properties of Cryolite.- 1.3. Uses of Cryolite.- 2. Container Materials.- 2.1. Graphite.- 2.2. Boron Nitride.- 2.3. Metals.- 3. Preparative Techniques.- 3.1. Commercial Cryolite.- 3.2. Preparation of Aluminum Fluoride.- 3.3. Purification of Alkali Metal Fluorides.- 4. The Study of Thermodynamic and Physicochemical Properties.- 4.1. Vapor Pressure.- 4.2. Electrical Conductivity.- 4.3. Density.- 4.4. Surface Tension.- 4.5. Viscosity.- 5. Electrodes in Molten Cryolite.- 5.1. General.- 5.2. Gas Electrodes.- 5.3. Oxide Electrodes.- 5.4. Metal Electrodes.- 5.5. Conclusion.- 6. Spectroscopy in Molten Cryolite.- 6.1. General.- 6.2. The Windowless Cell.- 6.3. The Diamond-Windowed Cell.- 7. Miscellaneous Techniques.- 7.1. Removing Cryolite.- 7.2. Cryolite Mixtures.- 7.3. Laboratory Furnaces.- 8. Conclusion.- References.- 4. Reference Electrodes for Molten Electrolytes.- 1. Introduction.- 2. Theoretical Principles.- 2.1. Electrode Potentials and Potential Scales.- 2.2. Cell Types, Half-Cells, and Standard States.- 2.3. Significance of the Electrolyte-Junction Potentials.- 2.4. Types of Reference Electrodes.- 2.5. Special Features of Molten Salts and Their Importance for Molten-Salt Reference Electrodes.- 2.6. Standard Electromotive-Force Series of Molten Salts.- 3. Principles of Reference Electrode Construction and Application.- 3.1. Construction and Use of Molten Salt Reference Electrodes.- 3.2. Stability of Reference Electrodes.- 3.3. Interaction between Reference Electrode and Instrumentation.- 4. Description of Reference Electrodes.- 4.1. Chlorides, Bromides, Iodides.- 4.2. Chloroaluminates.- 4.3. Fluorides.- 4.4. Cryolites.- 4.5. Nitrates.- 4.6. Carbonates.- 4.7. Sulfates.- 4.8. Hydroxides.- References.- 5. Neutron Diffraction.- 1. Introduction.- 2. Molten Salt Structure.- 2.1. Structure Factors.- 2.2. Small-Angle Neutron Scattering (SANS).- 3. Neutron or X-Ray Diffraction.- 3.1. Combination of Neutron and X-Ray Data.- 3.2. Scattering Experiment.- 4. Samples Amenable to Neutron Diffraction Study.- 5. Sample Preparation.- 5.1. Isotope Exchange.- 5.2. Sample Drying.- 6. Sample Containers.- 7. Furnaces.- 8. Neutron Beam Facilities.- 8.1. Diffractometers.- 8.2. Experiment Time Scales.- 9. Data Analysis.- 9.1. Introduction.- 9.2. Magnetic Scattering.- 10. Melts Studied Using Neutron Diffraction.- 10.1. Melts of the Type MX.- 10.2. Melts of the Type MX2.- 10.3. Binary Melts.- 10.4. Melts Discussion.- 11. Summary.- References.- 6. Dry Boxes and Inert Atmosphere Techniques.- 1. Introduction.- 2. Equipment.- 2.1. Glove Bags.- 2.2. Glove Boxes.- 2.3. Transfer Ports for Enclosures.- 2.4. Gas Sources and Purification Systems.- 2.5. Accessories.- 3. Operation.- 3.1. Startup Procedures.- 3.2. Maintaining the Inert Atmosphere.- 3.3. Monitoring the Atmosphere.- 4. Common Operations Conducted inside Dry Boxes.- 4.1. Weighing and Volumetric Operations.- 4.2. Electrochemical Measurements.- 4.3. Spectroscopic Measurements.- References.