Re: metals that don't form carbides?

From: aSkeptic (scott_at_yannitell.com)
Date: 06/06/04 

Date: 6 Jun 2004 00:24:39 -0700

jjedwab@ulb.ac.be (jacques jedwab) wrote in message news:<jjedwab-2708561345070001@geochim-mac2.ulb.ac.be>...
> In article <dde6cfc4.0406031852.781a4128@posting.google.com>,
> scott@yannitell.com (aSkeptic) wrote:
>
> > Hi sci.materials,
> >
> > From my searching on the topic of carbides on google, I have found
> > that most metals will form a carbide. There are peculiar ommisions
> > though. I have not found information on, and cannot determine if these
> > could exist:
> >
> > gold carbide
> > rhenium carbide
> > gallium carbide
> >
> > Are there metals that will never form a carbide even in highly
> > pressurized or heated enviroments?
>
> The word "never" should be avoided in this field:
> -Au combines with C into a very unstable carbide. The trick is to start
> with the good precursor,
> -Berzelius once wrote that Pt could not form a synthetic carbide,
> -Goldschmidt wrote that TaC is impossible as a natural compound,
> -the characterization of some metal/graphite intercalation compounds is
> sometimes very difficult,
> -the field is strongly influenced by possible technological outlooks, and
> unpromising topics are sometimes left aside,
> -...
>
> You should explore the footnotes of classical treatises, the Journal of
> Less-common Metals, Moissan's papers, etc., rather that the data found on
> the web, which are highly selective in what concerns "footnotes".
>
> The story of Moissan's failures and successes is enlightening: the finding
> of the good crucible material and the craftsman able to carve it were
> decisive.
>
> J.J.

I did what you said, good advice. I think I understand the answer now.
I went to OU's library and picked up a translated russian treasie on
the subject of carbides.

The gold, sliver, and copper carbides cannot be made directly from
only carbon and the intended metal. A precursor is needed for it to
form. They are very unstable (not typical of a carbide).

Gallium carbide is not possible! (acording to a 30 year old text), but
Galium alloyed (probably the wrong term in this case) with annother
metal could form a carbide.

I should have taken my notebook.

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