Rhenium diboride

Crystal structure
__ Re 6+      __ B 3−
General
Surname	Rhenium diboride
Ratio formula	ReB 2
Brief description	shiny silver solid
External identifiers / databases
CAS number 12355-99-6 Wikidata Q425164
properties
Molar mass	207.829 g mol −1
Physical state	firmly
Melting point	2400 ° C
safety instructions
GHS hazard labeling no classification available
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, ReB ₂

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.

${\displaystyle \mathrm {Re+2\ B\ {\xrightarrow[{(Lichtbogen)}]{950-1000^{\circ }C}}\ ReB_{2}} }$

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

1. ↑ 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. 
2. ↑ 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
3. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
4. ^ SJ La Placa, B. Post: The crystal structure of rhenium diboride . In: Acta Cryst. 1962, 15, pp. 97-99
5. ^ HY Chung et al .: Synthesis of ultra-incompressible superhard rhenium diboride at ambient pressure . In: Science , Vol. 316, 2007, pp. 436-439
6. ↑ Rhenium diboride: diamond hard without pressure . In: Spektrumdirekt , edition April 20, 2007, p. 8
7. ↑ 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.