The Fountain of Discordia - 16-6-2009 at 14:44
Just as a point of curiosity, I was wondering if there were any metallic compounds, not including alloys.
not_important - 16-6-2009 at 15:37
Intermetallic compounds, well known. Gold-aluminum, "purple gold", causes failures in wiring. Many amalgams contain compounds of mercury with other
metals. Alloys of copper also are or contain intermetallic compounds, zinc and tin both form such. Nitinol is a nickel-titanium alloy with shape
memory, other such alloys are copper-aluminium-nickel and copper-zinc-nickel compounds. A number of superconductive alloys are intermetallics.
Several metallic elements can be considered to be a compound of the element in several different valencies.
Do a Web search for "intermetallic"
bfesser - 16-6-2009 at 20:36
Isn't an amalgam by definition an alloy of mercury? So that should be all, not many, right?
not_important - 16-6-2009 at 21:03
Alloys are mixtures of metals, intermetallic compounds could be considered subsets of alloys where definite compounds are formed, typically with
distintly different properties than with simple mixtures.
For example consider Li3Bi. Two low melting metals, Bi @ 271 C and Li @ 99, but Li3Bi melts at 1145 C. When the elents are heated together they
react exothermically, raising the reaction mass from a few hundred degrees to 1500 C or so.
You can makes alloys with more Bi or Li in them than in Li3Bi, this act more like an alloy of Li and 'LiBi' or Bi and 'LiBi' with a continuous smooth
change in melting point and so on. (there is a slight eutectic of 243 C at 14% Bi). Similarly you can make amalgams that have an excess of Hg or the
other metal, but in many cases there exists one or more distinct compounds with definite ratios of the two.
Pyrovus - 16-6-2009 at 23:45
There are also a few ionic compounds as well - for instance, gold is fairly electronegative and will in combination with suitably electropositive
elements such as caesium form salts along the lines of Cs(+)Au(-). Also there are zintl salts, which contain anions consisting of clusters of metal
atoms, such as Pb9(4-)
[Edited on 17-6-2009 by Pyrovus]
unionised - 17-6-2009 at 11:03
It may be a matter of definition, but so far all the candidates have been compounds of metals so it's fair to describe them as alloys which would
exclude them from the original question.
Something like the tungsten bronzes might be closer, but even that is mainly a mixture of metals.
This stuff
http://en.wikipedia.org/wiki/Polythiazyl
looks like a metal and conducts like one too.
I think there are other examples, but none spring to mind.