When I retire I intend to work on unobtainium and non-expandium I have some metal matrix ideas in mind.... I may resort some ideas found in text written by the legendary Merlin... magician and alchemist of legend

A current material that is similiar to non-expanidium is abresist lined piping.... the stuff does not expand hardly at all... it can be lined with a variety of materials the one I looked at was volcanic basalt!