Latest advances in lithography-based additive manufacturing of non-oxide ceramics
SCHWENTENWEIN M. 1, LALE A. 1, PROCHASKA T. 1
1 Lithoz GmbH, Vienna, Austria
While lithographic additive manufacturing (AM) of oxide ceramics is already well established, the use of non-oxide ceramics for this particular printing approach is still less matured. One main reason for that is the higher light absorption and refractive index that non-oxide ceramic powders often exhibit. These properties make it more difficult for light to penetrate into suspensions based on non-oxide ceramics and consequently, pose a significant challenge for the successful shaping of these material by lithography-based AM techniques.
This contribution mainly focuses on the advances concerning AM of aluminum nitride and silicon nitride ceramics. By using a variation of vat photopolymerization, the so-called lithography-based ceramic manufacturing (LCM) process, which is an AM process that relies on the selective curing of a photocurable ceramic suspension using digital light processing (DLP) and by developing bespoke, highly reactive binder systems it was possible to print these nitride ceramics with high green density and homogeneity. These green parts were then thermally post-processed to give dense and defect-free ceramic components. The used debinding and sintering processes were without pressure assistance. The resulting nitride ceramic components exhibited the same thermal and mechanical properties as from parts made by conventional manufacturing (isostatic pressing). With a relative density of higher than 99.8 %, a hardness of 1500 and a biaxial bending strength of 760 MPa the tested silicon nitride composition is exactly at eye-level with its conventionally processed analogue (hardness of 1500 and biaxial bending strength of 770 MPa). For aluminum nitride components with a thermal conductivity of >200 W/m.K could be successfully obtained. These material properties in combination with the high precision of the LCM process allow the production of highly complex components that have not been feasible before and that are fully functional. Thus, beside the printing process and the properties of the ceramic material, this presentation will also give an outlook on the status of first use cases where the applications of AM of non-oxide ceramics is currently benchmarked and evaluated.