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Design of additively manufactured multi-material ceramics
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School of Engineering |
Master's thesis
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en
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84
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Monolithic implant designs made from bioactive ceramic materials are difficult to realize, as their mechanical properties are insufficient to withstand the forces exerted on them during operation. A multi-material ceramic implant involving a stronger bioinert ceramic could offer a potential solution for bone replacement applications. However, the joining of the two ceramic parts is challenging due to their different shrinking behaviour during the sintering process. This thesis investigated different joining methods to overcome this challenge.
The method of sinter-joining was selected for the experiments, which creates a press-fit between the connecting interfaces of the parts. The approach was tested on a material combination of hydroxyapatite and yttria-stabilised zirconia. Data from high-temperature dilatometric measurements was used to predict the shrinking rate of the parts to design the press-fit. The parts were co-sintered to 1300°C. Two joining mechanisms, namely the adapted reverse design and the wedge-design were proposed and evaluated. The results showed that the press-fit was achieved in both cases. The findings suggest that the wedge-design is more reliable than the adapted reverse design.
The wedge-design was incorporated into two distinct implant models using various computer-aided design software, and the workflow was introduced. The implants were manufactured and evaluated. The results showed that the press-fit was not achieved, and an angular deformation was formed on the zirconia parts. The findings suggest that the non-uniform wall thickness within the parts caused warping during sintering.