Experimental pipe, maybe.
An example of the element Niobium

This is vapor-deposited niobium from some sort of CVD reaction. Unlike the other sample of vapor-deposited niobium, this one was performed on a large heated surface or large-diameter electrode, thus the pipe-like nature of it. In fact, there's a good-to-high probability that this experiment was performed in order to test the possibility of making niobium pipe (used in chemical and nuclear reactors, for example, as well as other demanding applications such as rocket engines) by a simple vapor-deposition process where the outer surface could simply be lathed to size, rather than by painstakingly rolling it in to appropriately sized foil, fabricating it into a tube shape and then joining it by electron-beam welding, where especially the final step is very expensive and time-consuming. I doubt the as-deposited niobium in this case would have possessed the homogeneity and microstructure necessary to give niobium its ideal mechanical properties, but would be nifty to say the least if it worked.