Talk:Rhenium diboride

Ionic or covalent?
I think the thing about it being as hard as a diamond is odd, because it is an ionic compound and ionic compounds aren't that strong. Can anyone with a degree in Chemistry elucidate me on why this is true? -Lordgilman 00:55, 22 April 2007 (UTC)


 * Who said it's ionic? ReB2 has lots of short covalent bonds, and that's what makes it hard. Not all metal-nonmetal compounds have to be ionic, you know. Consider the electronegativities: 1.9 for Re and 2.04 for B. The covalent bonds aren't even that polar. —Keenan Pepper 07:36, 22 April 2007 (UTC)

borazon
This article mentions the harder substances ultrahard fullerite and aggregated diamond nanorods but not Borazon. Which is harder? --Use the force (Talk * Contribs) 03:18, 30 November 2007 (UTC)

ReB2 is harder than boron nitride and harder than diamond in one direction (but not in the other two). However, it's not as cheap as the article suggests, since rhenium costs nearly three hundred dollars an ounce. That probably needs to be mentioned, no? Scythe33 (talk) 21:54, 5 January 2008 (UTC)

Actual hardness values are not reported in this Wiki article. Check the original Science article, ultra-high hardness was only measured at low indentation loads, which are subject to the "indentation size effect" which results in artificially high readings. The asymptotic value appears to be around 30 GPa, which is by no means soft, but not in the ultra-hard range. I'm not absolutely certain, but if it helps, I believe Borazon is a trade name for cubic boron nitride and should have a hardness around 45-50 GPa. Solazy (talk) 21:06, 3 September 2008 (UTC)

Incorrect discovery citation
The first portion of the article describing the discovery of rhenium diboride is incorrect. The first publication on ReB2 was in 1962 by Sam La Placa and Ben Post whom published the crystal structure in Acta Crystallographer.

The reference: The crystal structure of rhenium diboride. La Placa, Sam; Post, Ben. Acta Cryst. (1962), 15, 97-9.

129.59.119.219 (talk) 22:10, 29 January 2008 (UTC)

Updating the article
I have a very recent article from Sichuan University (published in the journal Advanced Materials) on the properties of rhenium diboride, I intend to udate the article based on this. Aksel89 (talk) 04:34, 15 February 2009 (UTC)