solid parts made from tantalum carbide, hafnium carbide, or binderless tungsten carbide?

Hello Al(l),
I've searched all over google (web, images, groups, even froogle) and
I have not found any information suggesting that the materials in my
subject line exist in a form other than as a grit or as an exotic
coating.
I've tried a local university's library, and amazon.com and found
nothing on the topic of making solid parts of HfC, WC, or TaC.
Surely these materials would extend the search for HPHT materials in
temperatures at least a thousand degrees higher than what is possible
with a cemented carbide like WC.
Do you think these superlative materials be worth the trouble to
fabricate?
-Scott
Reply to
aSkeptic
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As you are no doubt aware the limited atomic mobility in these covalently bonded ceramics makes solid state sintering a difficult endeavor without the presence of a liquid phase. Binderless cemented carbides have been synthesized in bulk form with increased hardness and corrosion resistance, however, this has been only achieved through specialized powder synthesis, pulverizing and mixing techniques combined with sintering at unusually high temperatures under specific sintering atmospheres ultimately utilizing techniques more advanced/exotic/extreme as hot isostatic pressing. The links below are two manufacturers I know that commercially produce binderless tungsten carbides, and one of the links describes their patented process. I know that some of the other carbides are used to enhance the properties of WC, but I am not aware of bulk HfC or TaC products. You might shoot a question to the guys at Boride if you are really curious. These carbides do have some unique properties, however, they still tend to oxidize at temperatures not much above 1000C unless a protective atmosphere can be used.
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Reply to
Ceraboy
Thank you Ceraboy and Al!
This is exactly what I was looking for!
-Scott
P.S Al, have you heard about aragonite? It is a polymorph of calcite that is metastable at STP, supposidly stable at about 5000 bar. The most interesting thing about it is that aragonite is also made in certain biological processes, at STP! Life can sidestep HPHT synthesis!
Reply to
aSkeptic

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