Design of Pastes for Direct Ink Writing of Zirconia Parts with Medical Applications

Abstract

Direct ink writing (DIW) is an extrusion additive manufacturing (AM) technique in which inks are extruded through a nozzle and then deposited layer-by-layer. This technology allows 3D printing many different materials such as ceramics, metals, food, etc. In this work, the performance of zirconia pastes is addressed. The pastes are composed of yttria stabilized zirconia (YSZ) powder and a polymeric binder. Ceramic content is a mix of two components: A and B. Both the total content of ceramic and the content of component A in the paste are varied, according to a 32 design of experiments. The paste was characterized regarding Densification (%) and Elastic modulus G’ (Pa). A new parameter w3/G’ is defined to evaluate the viscosity of the inks. In the tests, the ceramic percentage is limited by the pressing force of the plunger that will be used to extrude the pastes. On the other hand, the binder concentration is also limited, because it requires to be in a gel form in order to be properly extruded. The results showed that Densification depends mainly on ceramic content, while the w3/G’ parameter is related to percentage of component A. In this work, the properties of the pastes prior to 3D printing are assessed. However, in the future, the pastes will be used to extrude complex parts with medical applications. AM extrusion processes constitute a possible way to overcome the difficulties to obtain complex geometries with conventional methods such as machining, in which zirconia parts can break due to their brittleness. Thus, the results of this work will help to manufacture complex shapes with porous areas in zirconia, when the DIW technology is employed.