You mean ceramics? There are so many to chose from, and most are unusable for one reason or another. The leading candidate being investigated is carborundum (

You mean ceramics? There are so many to chose from, and most are unusable for one reason or another. The leading candidate being investigated is carborundum (silicon carbide). It doesn't corrode in molten salt, it low appetite for neutrons, is reasonably easy to manufacture, conducts heat fairly well. It's even mentioned in the video.