单词 | niobium |
释义 | ni·o·bi·um ![]() n. Symbol Nb A silvery, soft, rare, ductile metallic element that occurs chiefly in columbite-tantalite and is used in steel alloys, arc welding, and superconductive materials. Atomic number 41; atomic weight 92.906; melting point 2,477°C; boiling point 4,744°C; specific gravity 8.57; valence 2, 3, 5. See Periodic Table. [After NIOBE (so called because it is extracted from tantalite).] |
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