In our new approach-thermoplastic 3D printing-a high-filled ceramic suspension based on thermoplastic binder systems is used to produce dense ceramic components by additive manufacturing. Alumina (67 vol%) and zirconia (45 vol%) suspensions were prepared by ball milling at a temperature of about 100°C to adjust a low viscosity. After the preparation the suspension solidified at cooling. For the sintered samples (alumina at 1600°C, zirconia at 1500°C), a density of about 99% and higher was obtained. FESEM studies of the samples' cross section showed a homogenous microstructure and a very good bond between the single printed layers.

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Technical ceramics are widely used for industrial and research applications, as well as for consumer goods. Today, the demand for complex geometries with diverse customization options and favorable production methods is increasing continuously. With fused filament fabrication (FFF), it is possible to produce large and complex components quickly with high material efficiency. In FFF, a continuous thermoplastic filament is melted in a heated nozzle and deposited below. The computer-controlled print head is moved in order to build up the desired shape layer by layer. Investigations regarding printing of metals or ceramics are increasing more and more in research and industry. This study focuses on additive manufacturing (AM) with a multi-material approach to combine a metal (stainless steel) with a technical ceramic (zirconia: ZrO 2 ). Combining these materials offers a broad variety of applications due to their different electrical and mechanical properties. The paper shows the main issues in preparation of the material and feedstock, device development, and printing of these composites. Video LinkThe video component of this article can be found at https://www.jove.com/video/57693/ 12 . Three different suspension-based AM techniques are qualified to allow the AM of ceramic-ceramic as well as metalceramic components. The utilization of suspension-based AM techniques promises improved component performance in comparison to powder- Journal of Visualized Experiments

Abstract

In our study, we investigated the additive manufacturing (AM) of ceramic-based functionally graded materials (FGM) by the direct AM technology thermoplastic 3D printing (T3DP). Zirconia components with varying microstructures were additively manufactured by using thermoplastic suspensions with different contents of pore-forming agents (PFA), which were co-sintered defect-free. Different materials were investigated concerning their suitability as PFA for the T3DP process. Diverse zirconia-based suspensions were prepared and used for the AM of single- and multi-material test components. All of the samples were sintered defect-free, and in the end, we could realize a brick wall-like component consisting of dense (<1% porosity) and porous (approx. 5% porosity) zirconia areas to combine different properties in one component. T3DP opens the door to the AM of further ceramic-based 4D components, such as multi-color, multi-material, or especially, multi-functional components.

An additive manufacturing technology is applied to obtain functionally graded ceramic parts. This technology, based on digital light processing/ stereolithography, is developed within the scope of the CerAMfacturing European research project. A three-dimensional (3-D) hemi-maxillary bone-like structure is 3-D printed using custom aluminum oxide polymeric mixtures. The powders and mixtures are fully analyzed in terms of rheological behavior in order to ensure proper material handling during the printing process. The possibility to print functionally graded materials using the Admaflex technology is explained in this document. Field-emission scanning electron microscopy (FESEM) show that the sintered aluminum oxide ceramic part has a porosity lower than 1% and no remainder of the original layered structure is found after analysis.

In our study we investigated the additive manufacturing (AM) of ceramic-based 11 Functionally Graded Materials (FGM) by the direct AM technology Thermoplastic 3D-Printing 12 (T3DP). Zirconia components with a varying microstructure were additively manufactured by 13 using thermoplastic suspensions with different contents of pore forming agents (PFA) and were co-14 sintered defect-free. 15 Different materials were investigated concerning their suitability as PFA for the T3DP process. 16 Different zirconia-based suspensions were prepared and used for AM of single-and multi-material 17 test components. All samples were sintered defect-free and in the end we could realize a brick wall-18 like component consisting of dense (<1% porosity) and porous (approx. 5% porosity) zirconia areas 19 to combine different properties in one component. 20 The T3DP opens the door to AM of further ceramic-based 4D-components like multi-color or multi-21 material, especially multi-functional components. 22