Fabrication of a helical tubular pore in YSZ ceramics by the superplastically foaming method

We have already proposed and demonstrated novel ceramic foams named "superplastically foamed ceramics" utilizing the superplastic deformation. Since almost all the processes are carried out in solid phase, figure and the location of the foaming agent can be controllable, leading to desired patterning of closed pore in a fully densified ceramics. We have already demonstrated two-dimensional (2D) pore patterning through the superplastically foaming method. In the present study, we aim to fabricate helical tubular pore in zirconia based ceramics as a typical 3D patterned pore. As a foaming agent, SiC powders were used with a form of thin sheet based on methylcellulose aqueous solution followed by drying. A core cylindrical matrix compact was first fabricated using Φ 10 steel die and the liner foaming agent was attached to make helical pattern. The patterned core matrix was placed in Φ 14 or Φ 15 steel die and pressed together with the filled matrix powder. The resultant powder compact was heat treated at 1600°C for 8h for sintering followed by foaming to give a ceramics with 3D tubular pore. Continuous upheaval reflecting the tubular pore was clearly observed on the side wall of the cylinder and helical tubular pore with different pitch can be fabricated.