Rhenium Diboride

Description

Rhenium diboride (ReB2) is a synthetic superhard material. It was first synthesized in 1962 and re-emerged recently due to hopes of achieving high hardness comparable to that of diamond. However, the ultrahigh hardness has not been confirmed.
The production method of this material does not involve high pressures as with other hard synthetic materials, such as cubic boron nitride, which makes production cheap. However, rhenium itself is an expensive metal.
The compound is formed from a mixture of rhenium, noted for its resistance to high pressure, and boron, which forms short, strong covalent bonds with rhenium.
Chemical Formulas: ReB2

Specifications

Molar Mass (g/mol.)	207.83l
Density (g/cm3)	12.7
Tap Density (g/cm3)
Freezing Point (°C)
Melting Point (°C)	2400
Specific Surface Area (m2/g)
Thermal Conductivity (W/cm·K)
Knoop Hardness (1200 kgf/mm2)
Crystal Structure	hexagonal
Solubility In Water	none
Appearance	black powder

General Properties:

1) Two factors contribute to ReB2's great hardness: a high density of valence electrons and an abundance of short covalent bonds. In chemistry valence electrons are the Electrons contained in the outermost or valence, Electron shell of an Atom. Rhenium has one of the highest valence electron densities of any transition metal (476 electrons/nm3, compare to 572 electrons/nm3 for osmium and 705 electrons/nm3 for diamond. Osmium is a Chemical element that has the symbol Os and Atomic number 76 The addition of boron requires only a 5% expansion of the rhenium lattice, because the small boron atoms fill the existing spaces between the rhenium atoms. Furthermore, the electronegativities of rhenium and boron are close enough. " Electronegativity " is the opposite of " Electropositivity," which describes an element's ability to donate electrons 9 and 2. 04 on the Pauling scale) that they form covalent bonds in which the electrons are shared almost equally. " Electronegativity " is the opposite of " Electropositivity," which describes an element's ability to donate electrons.
2) Although ReB2 is harder than diamond along certain directions, it exhibits considerable anisotropy because of its hexagonal layered structure. Anisotropy (pronounced with stress on the third syllable), is the property of being directionally dependent as opposed to Isotropy, which means homogeneity.

Synonyms

Rhenium boride, B2Re, rhenium diboride, rhenium boron, Re-B, rhenium boride, 99.5% (metals basis), metal boride, CAS# 12355-99-6.

Chemical Properties

Up to 99.999%

Physical Properties

Powder, ingot, lump, chunk, target

Typical Applications

1) Cutting and polishing tools
2) Wear resistant coatings
3) Corrosion resistant coatings
4) Industrial abrasive

Packaging

Varies. Usually to customer specification.