Rhenium diboride
Crystal structure | |||||||
---|---|---|---|---|---|---|---|
__ Re 6+ __ B 3− | |||||||
General | |||||||
Surname | Rhenium diboride | ||||||
Ratio formula | ReB 2 | ||||||
Brief description |
shiny silver solid |
||||||
External identifiers / databases | |||||||
|
|||||||
properties | |||||||
Molar mass | 207.829 g mol −1 | ||||||
Physical state |
firmly |
||||||
Melting point |
2400 ° C |
||||||
safety instructions | |||||||
|
|||||||
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . |
Rhenium diboride (ReB 2 ) is an artificially produced crystalline solid. It consists of the elements rhenium and boron and has a hardness comparable to that of diamond . In experiments it was possible to scratch diamond with rhenium diboride, from which it can be concluded that this substance has a higher hardness than diamond in at least one crystallographic direction (the c-axis).
History and manufacture
Rhenium diboride is a compound that does not occur in nature and was first synthesized in the 1960s. Its extremely high hardness was first discovered by a group of scientists led by Hsiu-Ying Chung from the University of California, Los Angeles , and published in 2007. It is produced by heating the powders of the two starting elements in a vacuum , enclosed in quartz glass, to 950–1000 ° C. for a period of five days. This creates rhenium diboride as a black powder. The reaction of rhenium and boron in the arc , on the other hand, leads to shiny metal pellets.
In contrast to the production of artificial diamond or cubic boron nitride , no great pressure is required here. This makes the production process cheaper and less complicated.
properties
The compression modulus of rhenium diboride is 360 G Pa and is therefore close to the 442 GPa measured for diamond. At temperatures between 4.5 K and 6.3 K the substance becomes superconducting ; the trirhenium boride (Re 3 B) has this property at approx. 4.7 K.
Web links
- What scratches the diamond throne .
- Synthesis of Ultra-Incompressible Superhard Rhenium Diboride at Ambient Pressure .
Individual evidence
- ↑ Appearance and metallic luster of ReB 2 ( English ) Daily Science News. April 20, 2007. Archived from the original on October 8, 2007. Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved July 4, 2012.
- ↑ AI Portnoi, VM Romashov: phase diagram of the system rhenium-boronic . In: Powder Metallurgy and Metal Ceramics , Volume 7, 1968, Number 2, pp. 112-114, doi: 10.1007 / BF00774302
- ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
- ^ SJ La Placa, B. Post: The crystal structure of rhenium diboride . In: Acta Cryst. 1962, 15, pp. 97-99
- ^ HY Chung et al .: Synthesis of ultra-incompressible superhard rhenium diboride at ambient pressure . In: Science , Vol. 316, 2007, pp. 436-439
- ↑ Rhenium diboride: diamond hard without pressure . In: Spektrumdirekt , edition April 20, 2007, p. 8
- ↑ G. K. Strukowa, V. F. Degtyareva, D. V. Shovkun, V. N. Zverev, V. M. Kiiko, A. M. Ionov, A. N. Chaika: Superconductivity in the Re-B system . (PDF; 63 kB) February 1, 2008. Accessed July 4, 2012.