Fig. 5: Periodic helical structures via embedded printing of F127-niobia ink.
From: Hierarchically ordered porous transition metal compounds from one-pot type 3D printing approaches
a A helix in ethanol after removal from the support matrix used for embedded printing. b–d Visualizing the elastic behavior of a hybrid helix by compressing (left pointing arrow) and releasing (right pointing arrow) in ethanol. e,f Picking a hybrid helix out with tweezers (refraction causes apparent misalignment). g Oxide helix after calcination in air to 450 °C (inset: view along helical axis). h Nitride helix after heat treatment to 950 °C in different environments. The helices in (a, g, h) and (b–f) were printed with radii of 2 and 3 mm, respectively. (i) WAXS profiles of hybrid, oxide, and nitride helices. Grey and black ticks represent relative intensities and corresponding q positions of peaks of NbN (PDF #01-089-5007) and NbC (PDF #03-065-8781), respectively. j Nitrogen adsorption (solid line) and desorption (dashed line) curves of mesoporous oxide (heat treated under air to 450 °C) and nitride-type (heat treated to 550 °C under ammonia and subsequently to 750 °C in carburizing gas) helices, and k corresponding pore size distributions derived from the BJH model. Same color scheme in (i) applies to (j, k).
