Effects of solvent debinding on the microstructure and properties of 3D-printed alumina ceramics

Solvents assist in the debinding of stereolithography-based 3D-printed alumina green bodies. The green bodies subsequently undergo thermal debinding and sintering to obtain alumina ceramics. In this study, several solvents were tested, including polyethylene glycol, oxalic acid, ammonium hydroxide, ethyl alcohol, methyl methacrylate, butyl acetate, dimethyl carbonate, methanol, ethyl acetate, and sec-butyl alcohol. The tested solvents during the debinding process showed different effects on microstructure and properties of 3D-printed alumina ceramics due to the variable aspects of their solubility toward the binders. The microstructure of the samples changed significantly after green bodies underwent solvent debinding, thermal debinding, and sintering, leading to loose spongy structures, porous aggregates, and compact structures, respectively. Shrinkage, bulk density, and open porosity changed slightly due to the debinding function of different solvents. Polyethylene glycol-impregnated samples displayed the minimum shrinkage in length direction (5.3%). Ethyl alcohol-impregnated sample showed minimum shrinkage in width (4.8%) and height (11.5%) directions. Ammonium hydroxide-impregnated samples exhibited minimum bulk density (2.8 g/cm³) and maximum open porosity (28.3%). Dimethyl carbonate-impregnated samples presented minimum flexural strength (32.6 MPa), and oxalic acid-impregnated samples revealed maximum flexural strength (63.4 MPa). In sum, the as-obtained ceramics would be used as ceramic cores for hollow blades in aircraft engines due to their high open porosity and moderate flexural strength.