Abstract
Ink formulation is one of the main challenges with ceramic 3D printing. Here, we present a new, reactive-colloidal hybrid ink for 3D printing by robocasting of BaTiO3-based ceramics. The hybrid ink combines a titanium isopropoxide-based sol-gel base with a colloidal dispersion of powder, here demonstrated with BaTiO3 both as the sol-gel (by reaction of titanium isopropoxide and barium oxide) and colloidal (by addition of BaTiO3 powder) parts. Addition of glycerol was necessary to avoid fast precipitation and poor dispersion of BaTiO3 from the reaction of BaO and Ti-isopropoxide. With a solid loading of 40 vol% BaTiO3, 10 mm tall structures could be printed with minimal deformation from slumping. The BaTiO3 shows good piezo-, ferro- and dielectric properties after sintering, with a piezoelectric charge coefficient (d33 = 159 pC/N) in the range commonly reported for BaTiO3. The hybrid inks developed in this work are therefore suitable for robocasting of BaTiO3-based electroceramics.
Highlights
Additive Manufacturing (AM) technologies, or 3D printing, have in the previous years been at the centre of attention for the development of three dimensional ceramic-based objects [1,2,3,4,5,6,7]
The ink exhibits relatively high yield stress, which means the ink does not flow at pressures lower than this value, and a shear-thinning behaviour illustrated by the shape of the flow curve
The presence of particles in the hybrid inks (HI) ink is believed to be Ba(OH)2 mixed with some remaining BaO due to rapid precipitation between barium oxide particles and the titanium isopropoxide
Summary
Additive Manufacturing (AM) technologies, or 3D printing, have in the previous years been at the centre of attention for the development of three dimensional ceramic-based objects [1,2,3,4,5,6,7]. The ink must (1) exhibit a shear thinning behaviour to flow through a small nozzle when low air pressure is applied, (2) have sufficiently high yield stress (σy) so the object does not collapse under its own weight ( called slumping), without external contribution (temperature assisted drying, curing etc ...). Such rheological behaviour is called “Herschel-Buckley” and is approximated with the following equation:.
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