Freeform 3D Printing of Pure Ceramics

Current additive manufacturing (AM) processes (namely layer-by-layer processes requiring UV curing) are not suitable for ceramics due to low production efficiency and inherently low laser absorption characteristics. We propose a new process for AM of polymer-derived ceramic (PDC) parts based on direct three-dimensional printing of low viscosity (~800 cP, ~13-time less viscous than honey) preceramic polymers (without the need for UV-curing agents) in a pseudoplastic (thixotropic) fluid as the support bath. A custom-made 3D printer is used to support the printing process and coordinates are added to g-code files to specify part geometries. The specially designed support bath maintains the geometry of the printed part during one-step high temperature curing (~160 °C). The final pyrolyzed ceramic is fully dense without apparent porosity and with characteristic flexural strength of ~260 MPa. Three-point flexural tests were performed to mechanically characterize samples, and cross-sections of fractured samples were imaged using scanning electron microscopy (SEM). The polymer-to-ceramic transformation was investigated by differential scanning calorimetry / thermal gravimetric analysis (DSC / TGA) and a rheometer was used to measure rheological properties of the support bath. The process is low-cost, does not require any modification of the preceramic polymer for UV or optical curing, and is scalable. Applications are anticipated for AM of ceramic components and sensors in extreme environments in which high temperatures and corrosion are to be expected. Overall, there are numerous benefits of our project. The first and foremost would be cost and time efficiency. Relative to conventional manufacturing methods of ceramics, our process is much less expensive and takes much less time to produce a finished ceramic product. Secondly, the process of manufacturing such intricate structures through conventional methods can be tedious and prone to error. With our method, complex structures can be produced accurately and efficiently while being applied to unprecedented applications. As such, ceramics are particularly useful in aerospace applications. Aerospace vehicles used in both the defense and space industries are subjected to extreme environments where weight and working temperatures are extremely important. Ceramics are lightweight, resistant to high temperatures and corrosion, and offer comparable mechanical properties to their metal alloy counterparts. Additionally, they can be used to sufficiently insulate onboard microelectronic components and reduce / absorb vibrations produced from the outside environment that could potentially stress and fatigue the vehicle. Ceramics are necessary in society’s most prominent industries, with other important applications including gas turbine blades, high-performance braking systems, and bulletproof armor, among others.