Synthesis of preceramic precursor based on organic aluminum salts for stereolithographic 3D printing of corundum ceramics

Variants for the synthesis of aluminum acrylates, including substituted hydroxoacrylates, as well as an adduct of aluminum isopropylate with allylamine, were tested to develop a mixture that can be formed by photopolymerization, followed by annealing while maintaining the shape of the ceramic, for further use in molding using stereolithographic 3D printing. By photopolymerization of a polymer precursor based on an acrylate suspension of in situ synthesized alumoxane Al(OH)2(ООСН2СН=СН2), corundum ceramics of a given shape were prepared. The inhomogeneity of the polymer precursor does not prevent its use in technology. A significant percentage of weight loss during heat treatment of the polymer precursor suggests its possible use as a binder when filled with dispersed aluminum oxide powder. The highest shrinkage of a ceramic product occurs in the range of 200–400°C; it is necessary to develop a special program for heating up the product to the sintering temperature to minimize the consequences of severe shrinkage. When a molded product is heat treated in an inert atmosphere, the shrinkage is less than when annealed in air, since pyrolysis leaves behind a large amount of amorphous carbon. Annealing such ceramics with amorphous carbon in a nitrogen atmosphere is promising for carrying out the carbonitridization process in the preparation of aluminum nitride and oxynitride.