Refractory metals

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Refractory metals (Latin: refractarius = stubborn, stubborn) are the refractory , base metals

Refractory metals are relatively resistant to corrosion at room temperature due to their passivation (for example, tungsten is not soluble in hydrofluoric acid / hydrofluoric acid or in aqua regia , but only in mixtures of hydrofluoric and nitric acid ). The recovery of the refractory metals is made more difficult by the fact that they easily react with many non-metals at high temperatures .

Advantages for many technical applications of refractory metals are their high melting point , their low coefficient of thermal expansion and their conductivities for heat and electrical current, which are higher than those of steel .

Due to the body-centered cubic lattice structure , refractory metals show a transition from ductile to brittle material behavior at low temperatures . Recent studies have shown that the brittle behavior at temperatures below the Debye temperature is mainly due to contamination. In contrast, ultra-pure crystals of tantalum, niobium and hafnium can be easily deformed even at the lowest temperatures.



Individual evidence

  1. a b Kirsten Bobzin: Surface technology for mechanical engineering . John Wiley & Sons, 2013, ISBN 978-3-527-68149-5 ( limited preview in Google Book Search).
  2. Michael Haschke, Jörg Flock: X-ray fluorescence analysis in laboratory practice . John Wiley & Sons, 2017, ISBN 978-3-527-80880-9 , pp. 190 ( limited preview in Google Book Search).
  3. Serope Kalpakjian, Steven R. Schmid, Ewald Werner: materials engineering . Pearson Deutschland GmbH, 2011, ISBN 978-3-86894-006-0 , p. 214 ( limited preview in Google Book search).
  4. ^ EM Savitskii: Physical Metallurgy of Refractory Metals and Alloys . Springer Science & Business Media, 2012, ISBN 978-1-4684-1572-8 ( limited preview in Google book search).