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Organisationseinheit der BAM
Capsule summary
THE MATERIALS
Manufacturers can use preceramic polymers to produce ceramic components in a range of compositions using a variety of additive manufacturing technologies. Preceramic polymers even can overcome some of the problems that are intrinsic to additive manufacturing in general.
THE APPLICATION
Modifying the composition, molecular architecture, and molecular weight of preceramic polymers allows adaptation of these materials to specific processing requirements of individual additive manufacturing technologies.
THE OPPORTUNITY
Further development of new additive manufacturing technologies, in addition to improvement of existing technologies, will enable manufacturing of advanced ceramic components with enhanced mechanical characteristics and new functional properties.
A new approach for fabrication of ceramic components with inner channels is proposed, as a result of the combination of two additive and one subtractive manufacturing processes. In this project, porcelain parts are manufactured by the Layerwise Slurry Deposition (LSD) process, meanwhile end milling and Direct Ink Writing (DIW) are applied to create channels on the surface of the deposited ceramic. Unique to the LSD process is the Formation of a freestanding powder bed with a mechanical strength comparable to conventional slip casted ceramic green bodies. Combining these three processes allows the manufacturing of ceramic objects containing an internal path of ink, which in this case was a graphite-based ink that can be further eliminated by heat treatment to obtain a porcelain object embedded with channels. The results show the capabilities of this method and its potential to fabricate not only parts with inner channels, but also multi-material and multi-functional components (such as integrated electronic circuits).
In this work, we demonstrated that the hardystonite (Ca2ZnSi2O7) bioceramics can be produced withhigh phase purity, starting from different preceramic polymers and suitable fillers (precursors for CaOand ZnO) after heating at 1200◦C in air. Open-celled hardystonite foams were easily prepared from a filler-containing silicone resin using hydrazine as foaming agent. The fabrication of cellular structures using a preceramic polymer and fillers was possible because the polymeric melt allowed for the entrapment of the gases generated by the decomposition of hydrazine, and the simultaneous cross-linking of the preceramic polymer enabled the retention of the foam structure. Samples with a well-developed hierarchical porous structure, with an open porosity ranging from ∼65 to ∼81 vol% and an average cell window size ranging from 150 to 500 µm were produced. The hardystonite components possessed a compressive strength ranging from ∼1.4 to ∼2.1 MPa.
Recently, additive manufacturing of ceramics has achieved the maturity to be transferred from scientific laboratories to industrial applications. At the same time, research is progressing to expand the boundaries of this field into the territory of novel materials and applications. This feature issue addresses current progress in all aspects of additive manufacturing of ceramics, from parts design to feedstock selection, from technological development to characterization of printed components.
Advanced ceramics printed with photon-based additive manufacturing deals with anisotropic mechanical properties from the layer-by-layer manufacturing. Motivated by the success in using highly filled transparent slurries containing nanoparticles for powder-based two-photon-polymerization (2PP) for advanced ceramic printing, this works approach is the transfer to Xolography, a volumetric additive manufacturing technology based on linear two-photon excitation and without recoating steps. This paper reports the results of a preliminary investigation optimizing the photocurable slurry to the requirements of Xolography in terms of transparency, over a significantly larger mean free path, compared to 2PP. A feedstock filled with 70 % weight fraction of ceramic particles (∼30 vol%) exhibiting an exceptionally high degree of transparency in the relevant wavelength range of 400–800 nm was prepared from 5 nm zirconia nanoparticles. The high transparency of the photocurable slurry is attributed to the near-monomodal particle size distribution of the zirconia nanoparticles used.