A preceramic precursor based on the adduct of diisobutylaluminum hydride and acrylonitrile was synthesized and tested for producing aluminum nitride ceramics by stereolithographic 3D printing. Experiments showed that the interaction of diisobutylaluminum hydride with acrylonitrile leads to formation of an imine adduct as well as substitution products in which the isobutyl fragment is transferred to the acrylonitrile molecule. Photopolymerization of a polymeric precursor based on the aluminoimine and 1,6-hexanediol diacrylate yielded a macroporous aluminum nitride ceramic. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) confirmed formation of aluminum nitride at temperatures from 1000°C; the most intensive mass loss occurred up to 1100°C, and removal of thermolysis products of the diacrylate took place in the 300–500°C range. The significant mass loss (78%) inherent to preceramic precursors, and the associated linear shrinkage, remain problems. The substantial reduction in linear dimensions did not disrupt the macroporous structure of the printed part, however residual carbon was observed in the fired ceramic. The results demonstrate the promise of using aluminoimines and products of their oligomerization for stereolithographic ceramic fabrication; however, further study and process optimization are required to achieve lower firing shrinkage and reduced residual carbon.
Leontiev et al. (Wed,) studied this question.