Synthesis of Preceramic Precursor Based on Organic Aluminum Salts for Stereolithographic 3D Printing of Corundum Ceramics

Abstract: 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.