The dynamic development of three-dimensional printing techniques, observed in recent years, is related to the need for the production of complex and precise elements without the use of expensive casting moulds and cutting tools. Additive manufacturing methods allow to obtain products with relatively smooth surfaces and high accuracy of dimensional mapping. Several 3D printing methods utilize UV light to cure layer by layer dispersions containing resins (or monomers), photoinitiators and ceramic powders. Shaping ceramic materials by additive manufacturing is still a big challenge for researchers. Unfortunately, the ceramic powder particles scatter and absorb UV radiation which significantly reduces the cure depth. Therefore, the ceramic powder should have a refractive index similar to the used resin. In order to improve the fracture toughness of ceramics, ceramic-metal composites are commonly used. Even a small addition of the metallic particles, such as nickel or molybdenum which are capable of plastic deformation, can significantly improve the mechanical properties of the single-phase ceramic materials. The aim of the research was to obtain alumina ceramics and composites with the addition of nickel and molybdenum by UV-assisted 3D shaping, including digital light processing. An important step was the preparation of Al₂O₃-based photocurable ceramic suspensions of certain features. The rheological properties of the slurries were determined and the cure depth of the suspensions with the addition of various photoinitiators was measured. The printing parameters (such as UV exposure time, light intensity and the single layer height) were also matched. The obtained green bodies were subjected to pressureless sintering at 1550°C and the properties of the composites (shrinkage after sintering, density, Vickers hardness, fracture toughness) were examined. The microstructure of sintered bodies was analyzed by using scanning electron microscope, followed by EDS and XRD. The results have shown that even the small content of the metallic phase (0.5 vol%) causes the increase in fracture toughness of single-phase alumina (by 36-40%).

Acknowledgements:
Research was funded by POB Technologie Materia?owe of Warsaw University of Technology within the Excellence Initiative: Research University (IDUB) programme.