How many are there? or actually, that have been made and are for sale commercially.
I’m not really sure of the answer to your question, but we investigated the use of metal foams in a particular application; the company we worked with made metal foams by dipping open-cell polymer foam in a powdered metal slurry, and then firing the resulting cake. This process burned away the polymer and sintered the powdered metal, leaving a metal foam. Seems to me that making metal foams this way could be applied to any number of different metals. Googling led me to this site, which appears to be an industry group of metal foam makers. That might be of some help to you.
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