Hierarchically-porous metallic scaffolds via 3D extrusion and reduction of oxide particle inks with salt space-holders

3D ink-extrusion of powders followed by sintering is an emerging additive manufacturing method capable creating metallic microlattices. Here, we study the creation hierarchically porous Fe or Ni scaffolds extrusion 0/90° lattices from inks consisting fine oxide (Fe2O3 NiO, < 3 µm), coarse space-holder particles (CuSO4, 45 µm) and a polymer binder within solvent. After leaching debinding lattices, step densifies created reduction with H2, while maintaining larger pores templated printed struts. The resulting exhibit hierarchical porosity: (i) open submillimeter channels lattice between struts; (ii) micropores (5–50 struts, particles; (iii) closed submicron micropore walls, incomplete metal microparticles reduction. While channel porosity defined geometry, strut controlled temperature, finest removed first. Sintering at 873–1373 K for 1 h leads to porosities 38–19% in 59–29% Ni. In situ synchrotron X-ray tomography reveals kinetics evolution upon debinding, H2 metal, which, combined, lead ~50% shrinkage as compared state. are not eliminated remain but they shrink surrounding matrix (e.g., 40% 30% 1173 h).