Paste backward extrusion process as a suitable method for fabrication of sodium beta-alumina electrolyte closed-end tubes

In this study, paste backward extrusion is introduced for fabrication of sodium beta-alumina electrolyte closed-end tubes (with a wall thickness of 1 mm and external diameter of 8.0 mm). For this purpose, the two-piece extrusion die was designed and extrudable water-based paste was prepared by using sodium beta-alumina powder, polyvinyl pyrrolidone, as a binder, and ethylene glycol as a plasticizer. The effect of solvent content on the rheological parameters of the paste and the ram extrusion velocity on the liquid phase separation are investigated. The results indicate that the optimum solvent content for making the extrudable paste is in the range of 30–35 wt-%, and the liquid phase separation is obviously occurred when the ram velocity is lower than 1.2 mm s−1. It was also shown that by using backward extrusion, and by applying optimum conditions, closed-end tubes with high density (about 97%) and good surface quality could be fabricated successfully.