New developments in Additive Manufacturing Technologies (AMT) enlarge their fields of applications. Therefore, also the demands on the properties of 3D-printed objects increase which makes it necessary to develop and optimize advanced materials which are suitable for additive manufacturing.
One of the fields of application is tissue engineering, where scaffolds are used to treat bone defects. Among others, Tricalcium Phosphate (TCP) is used as ceramic bone substitute material to build up those scaffolds. At TU Wien a lithography based AMT system was developed, which relies on the Digital Light Processing (DLP) Technology. The system enables the fabrication of ceramic parts which excel in resolution, precision and surface quality. In a first step the objects are printed out of a photopolymerizable slurry, which is highly filled with ceramic particles. Afterwards, in a thermal processing step, the organic matrix is burned out and the ceramic particles are sintered together to obtain a dense ceramic body.
Good mechanical properties in the final ceramic structure can only be obtained if size and number of defects are minimized during all processing steps. Since a suspension consisting of ceramic particles filled in a reactive organic liquid is used, the long term stabilization and homogenous dispersion of particles in the fluid is of crucial importance for the final part properties. Furthermore, the composition (reactive and non-reactive constituents) of the organic components and the mechanical properties of the resulting green bodies are important factors.
Increasing the molecular weight of the organic components and/or the solid loading increases the viscosity of the slurry, which is beneficial for the long term stability of suspensions. However, viscosity should not exceed 20 Pa.s which is taken as the processing limit for the utilized 3D printers. Through selecting a proper dispersing agent the ceramic particles are well dispersed and the viscosity can be adjusted to fit the processing window. For this work, the maximum solid loading was 50 vol%. The achieved density of the sintered TCP parts is 88 % of the theoretical density. The biaxial bending strength is 32 MPa.