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A Thesis on the Constitution of Alloys of Thorium with Certain Transition Metals. , by J.R. Thomson Submitted for the Degree Of

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A Thesis on the Constitution of Alloys of Thorium with Certain Transition Metals. , by J.R. Thomson Submitted for the Degree Of A thesis on The constitution of alloys of thorium with certain transition metals. , by J.R. Thomson submitted for the degree of Doctor of Philosophy in the University of London. Department of Metallurgy, Imperial College of Science August, 1963. and Technology, Prince Consort Road, London, S.W.7. 1. SUMMARY The behaviour of the transition series of elements has long been of interest and the position of thorium in group 4A of the periodic table near to the beginning of a possible 'actinide' series of elements has made a know- ledge of its properties and alloying behaviour of especial interest from the theoretical point of view. In the present work, the physical properties and electron theory of the transition metals and their alloys have been reviewed. Factors affecting the formation of intermetallic compounds have also been reviewed and their applications to some specific types of crystal structure discussed. The phase diagrams of six binary alloy systems of thorium with the metals ruthenium, rhodium, palladium, osmium, iridium and platinum have been investigated in the temperature range 1000°C - 1500°C, mainly by x-ray and metallographic methods. Solid solubility of thorium in palladium has been observed and intermetallic compounds occur in each system. The crystal structures of 15 of these compounds, embracing 7 structure types, have been determined while the structures of 5 other compounds have been confirmed. In several cases additional information about the latter compounds has been obtained. 2. In general, the results are in agreement with alloy theory although the solubility of thorium in palladium would not be predicted by current theories. There are several points of similarity between the present systems but the constitution of Th-Pd alloys is often different from that of the other five systems. The thorium-rich eutectic compositions and temperatures show a general correlation with the melting points of the component phases similar to that reported for eutectics formed by magnesium, the rare earths, uranium and plutonium. Available results on the structures of the intermetallic compounds have been discussed in relation to other compounds with the same structures and the phase diagrams have been compared with the available information on several other alloy systems of the group 8 metals. The structures of compounds con- taining less than 50% group 8 element tend to be character- istic of the other element and size factors tend to be important in determining which structures will occur. With more than 50% group 8 element, size factors are still important but the structures can often tolerate a much wider range of radius ratio. 3. The Constitution of Alloys of Thorium with certain Transition Metals. Summary. List of contents. List of tables. List of figures. 1.Introduction. 2.Literature review. 2.1. The transition elements. 2.1.1. Physical properties. 2.1.2. The electron theory of the transition metals. 2.1.2.1. Collective electron theories. 2.1.2.2. Localised wave-function approach. 2.2. Factors affecting the formation of intermetallic compounds. 2.2.1. General. 2.2.2. Th7Fe3 (D 102) structure. 2.2.3. CuA12 (C 16) structure. 2.2.4. CrB (Bf) structure. 2.2.5. Ni2In (B 82) structure. 2.2.6. Laves phases MgZn2 (C 14), MgCu2 (C 15) and MgNi2 (C 36). 2.2.7. (L 12) structure. Cu3Au 2.2.8. TiNi3 (D024) structure. 2.2.9. CaZn5 (D 2d) structure. 4. 2.3. Alloys of the transition metals. 2.3.1. Solid solutions. 2.3.2. Alloys of intermediate composition. 2.3.3. Alloys of the platinum metals. 2.3.4. Alloys of thorium. 2.3.5. Other work on the systems under investigation. 3.Experimental methods. 3.1. Alloy preparation. 3.2. Heat treatment. 3.3. Thermal analysis. 3.4. Metallographic preparation. 3.5. Hardness. 3.6. X-ray techniques. 4. Results. 4.1. The thorium-ruthenium system. 4.1.1. The phase diagram. 4.1.2. The crystal structure of Th7Ru3. 4.1.3. The crystal structure of ThRu. 4.1.4. The crystal structure of ThRu2. 4.2. The thorium-rhodium system. 4.2.1. The phase diagram. 4.2.2. The crystal structure of 0-ThRh2. 4.2.3. The crystal structure of ThRh3. 4.3. The thorium-palladium system. 4.3.1. The phase diagram. 4.3.1.1. Alloys of 0-75% palladium. 4.3.1.2. Alloys of 75-100% palladium. 5. 4.3.2. The crystal structure of Th2Pd. 4.3.3. The crystal structure of Th3Pd5. 4.3.4. The crystal structure of ThPd3. 4.3.5. The crystal structure of ThPd4. 4.4. The thorium-osmium system. 4.4.1. The phase diagram. 4.5. The thorium-iridium system. 4.5.1. The phase diagram. 4.5.2. The crystal structure of ThIr5. 4.6. The thorium-platinum system. 4.6.1. The phase diagram. 5. Discussion. 5.1. The phase diagrams. 5.1.1. Accuracy of the results. 5.1.2. Points of similarity between the systems. 5.1.3. The thorium-rich eutectic temperatures. 5.1.4. Melting points of the compounds. 5.1.5. Age-hardening behaviour and the lattice parameter of thorium. 5.2. The intermetallic compounds. 5.2.1. Compounds of the type Th7X3. 5.2.2. Compounds of the type Th2X. 5.2.3. ThX compounds with the CrB (Bf) structure. 5.2.4. The compounds Th3Pd5 and Th3Pt5 5.2.5. The compound p-ThRh2. 5.2.6. The Laves phases (AB2). 6. 5.2.7. Compounds of the type ThX3. 5.2.7.1. Compounds with the Cu3Au (I, 12) struAure. 5.2.7.2. Compounds with the TiNi3 (D024) structure. 5.2.8. Compounds of the type ThX5. 5.2.9. The types of crystal structure observed. 5.3. Comparison with expectations. 5.4. Comparison with other alloy systems. 5.4.1. Alloys of thorium with iron, cobalt and nickel. 5.4.2. Alloys of titanium, zirconium and hafnium with group 8 metals. 5.4.3. Alloys of uranium and plutonium with group 8 metals. 5.4.4. Alloys of lanthanum and cerium with group 8 metals. 5.5. The behaviour of palladium in intermetallic systems. 5.5.1. General. 5.5.2. Thorium-palladium alloys. 6.Suggestions for further work. 7.Conclusions. 7.1. The thorium-ruthenium system. 7.2. The thorium-rhodium system. 7.3. The thorium-palladium system. 7.4. The thorium-osmium system. 7.5. The thorium-iridium system. 7.6. The thorium-platinum system. 7.7. Crystal structures of the compounds. 7.8. General. 7 Appendix 1. Acknowledgements. References. Tables. Appendix 2. Figures. 8. LIST OF TABLES Table 1. Classification of atoms with respect to their electron transfer properties. 2. Comparison of observed and calculated sin2 0 values and line intensities for Th7Ru3. 3. Interatomic distances in Th7X compounds. 3 4. X-ray data for compounds. Th7x3 5. Comparison of observed and calculated sin26 values for Th7Rh3, Th70s3' Th71r and 3 Th Pt . 7 3 6. Comparison of observed and calculated sin26 values and line intensities for ThRu. 7. Structural data for ThX compounds having the ) structure. CrB(Bf 8. Comparison of observed and calculated sin26 values and line intensities for ThRh. 9. Comparison of observed and calculated sin26 values and line intensities for ThIr. 10. Comparison of observed and calculated sin26 values and line intensities for ThPt. 11. Interatomic distances in ThX compounds. 12. Comparison of observed and calculated sin26 values and line intensities for ThRu2. 13. Comparison of observed and calculated sin26 values and line intensities for ThOs2 and ThIr2. 9. Table 14. Interatomic distances in ThX2 compounds. 15. Comparison of observed and calculated sin26 values and line intensities for p-ThRh2. 16. Comparison of observed and calculated sin26 values and line intensities for cubic ThRh3. 17. Comparison of observed and calculated sin; values and line intensities for tetragonal ThRh3. 18. Phases identified in Pd-Th alloys. 19. Hardness of Pd-Th alloys after homogenising for 4 days at 1000°C. 20. Comparison of observed and calculated sin26 values and line intensities for Th2Pd. 21. Comparison of observed and calculated sin26 values and line intensities for Th Pd 3 5 22. Comparison of observed and calculated sin26 values for Th3Pt5. 23. Comparison of observed and calculated sin26 values and line intensities for ThPd 3 (75% p alladium). 24. Comparison of observed and calculated sin26 values and line intensities for ThPd4 (80% palladium). 10. Table 25. Comparison of singe values for alloys of 66-83% iridium. 26. Comparison of observed and calculated singe values and line intensities for ThIr5. 27. Summary of closest interatomic distances in A°. 11. LIST OF FIGURES Figure 1. The thorium-ruthenium system. 2. The thorium-rhodium system. 3. The thorium-palladium system. 4. The thorium-osmium system. 5. The thorium-iridium system. 6. The thorium-platinium system. 7. Eutectic temperature vs melting point of the compound. 8. Eutectic composition vs melting point of the compound. 9. Eutectic temperature vs mean electron concen- tration. 10. Interatomic distances between unlike atoms in Th2X compounds. 12. 1. Introduction In recent years the development of new branches of technology has called for many new materials; this has led to commercial interest in a number of metals which occur in the transition series of the periodic classification and also in the so-called heavy metals thorium, uranium and plutonium. The increased availability of these metals in relatively pure form and the desirability of improving their properties has led to a study of many of their alloy systems. Thorium is of interest in the nuclear energy field since it has a naturally occurring radioisotope Th232.
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