tailieunhanh - handbook of extractive metallurgy 3 Part 7

Tham khảo tài liệu 'handbook of extractive metallurgy 3 part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 1416 Handbook of Extractive Metallurgy 87. H. Stuart F. Heisterkamp The Niobium Market -A Perspective Proceedings of International Symposium on Tantalum and Niobium Tantalum-Nio- bium International Study Center Brussels Belgium 1988 pp. 71-89. 29 Tantalum Klaus Andersson Karlheinz Reichert Rudiger Wolf Occurrence. 1418 Extraction and Processing of Ore Obtaining Ta-Nb Concentrates from Tin Processing Tantalum Metallic Semifinished Tantalum Powder for Capacitors . 1422 Other Uses .-J. 1422 Economic Introduction Tantalum has the electronic structure Is2 1rpẫ isíp6dìữ tâp6 0 4 5s2p6 ỉ 6s2 which accounts for its principal oxidation states 2 and 5 . There are two naturally occurring isotopes lslTa and the weakly radioactive isotope 180Ta half-life ca. 1013 years . Ạ large number of artificial radioactive isotopes are also known. History Tantalum was discovered by Ekeberg in 1802 1-2 . The discovery and history of tantalum and niobium are closely linked. The two elements usually occur together. Properties The physical properties of tantalum are as follows 1-7 Crystal structure Lattice constant Density Melting point Boiling point Heat of fusion Heat of vaporization at 3273 K Specific heat capacity at 20 C Linear coefficient ofthermal expansion at 20 C Thermal conductivity at 20 C Specific electrical conductivity xio 6 1 K- . at 20 C flr cm-1 Superconductivity K Temperature coefficient 0-100 C The effect of temperature on electrical and thermal conductivity has been accurately determined 3 . The mechanical properties of the metal are strongly dependent on its purity structure and crystal defects as is .

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