Refractory metals

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

the 4th subgroup ( titanium , zirconium and hafnium )
the 5th subgroup ( vanadium , niobium and tantalum )
the 6th subgroup ( chromium , molybdenum and tungsten ).

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.

literature

Michael Binnewies, Maik Finze, Manfred Jäckel, Peer Schmidt, Helge Willner, Geoff Rayner-Canham: General and Inorganic Chemistry . 3. Edition. Springer-Verlag, Berlin 2016, ISBN 978-3-662-45067-3 , pp. 775 f ., Doi : 10.1007 / 978-3-662-45067-3 .

swell

whs-special metals : refractory metals

Federal Ministry of Agriculture, Forestry, Environment and Water Management (Ed.): Federal Waste Management Plan 2011 . tape 2 . Vienna 2011, p. 343 ( PDF ).

Dierk Raabe: Melt metallurgical production and cold forming of a copper-niobium-silver in situ composite material . Ed .: Max Planck Institute for Iron Research. ( PDF ).

Individual evidence

↑ ^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).
↑ 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).
↑ 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).
^ 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).

[Kirsten_Bobzin-1] Kirsten Bobzin: Surface technology for mechanical engineering . John Wiley & Sons, 2013, ISBN 978-3-527-68149-5 ( limited preview in Google Book Search).

[Michael_Haschke,_Jörg_Flock-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).

[Serope_Kalpakjian,_Steven_R._Schmid,_Ewald_Werner-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).

[E._M._Savitskii-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).