SUPSI University develops hybrid AM process for complex ceramics

During the last 20 years, the Hybrid Materials Laboratory (HM Lab) of the University of Applied Sciences and Arts of Southern Switzerland (SUPSI) has been conducting cutting-edge research on ceramics. In 2019, the HM Lab head Professor Alberto Ortona already illustrated the potential that porous 3D prints possess for ceramic materials. Now, one of Professor Ortona’s doctoral candidates at the University of Padua, Marco Pelanconi, has successfully defended his Ph.D. thesis in this very research area.

A novel hybrid AM process

As his dissertation project, Pelanconi optimized the process to produce complex ceramic architectures through additive manufacturing. The approach involves the 3D printing of polymeric preforms with high microporosity through selective laser sintering (SLS), combined with infiltration with preceramic polymers. Then, pyrolysis is used to obtain a polymer-to-ceramic conversion at around 1000°C. Final densification is performed via molten silicon infiltration to achieve ceramic parts with high density.

Porosity control with open parameters

The Sintratec Kit – the world’s first and only assembly kit in the field of SLS – took center stage in Marco Pelanconi’s research thanks to the 3D printer’s open parameters. “The Kit allowed us to change a lot of printing parameters, including powder surface temperature, layer thickness, laser speed, hatching spacing, and more, making it easy to control the porosity of the 3D printed parts,” said Pelanconi. By varying these factors, the material engineer at SUPSI University was able to achieve an ideal porosity (crucial for further infiltration) and thus a high part quality.

Complex ceramic architectures

To illustrate how this method could be used for especially complex shapes, Pelanconi’s research focused on two cylindrical porous structures with different topologies: a rotated cube and a gyroid. After printing with Sintratec PA12 and subsequent conversion into ceramics, the resulting parts exhibited outstanding mechanical and thermal properties. They maintained their pristine shape without distortion or macrocracks, despite a shrinkage of ~25%. According to Pelanconi, their impressive biaxial strength of 165 MPa could still be increased through further process optimization.

Potential for a multitude of industries

“These classes of materials offer unmatched thermo-mechanical properties that cannot be provided by steels, such as high-temperature resistance, high oxidation resistance, high thermal shock resistance, and high strength,” said Pelanconi. Therefore, ceramics are well suited to be used in extreme environments, for example, in heat exchangers, catalyst supports, thermal storage, burners, or aerospace. This innovative approach, carried out by Marco Pelanconi within the HM Lab, could be exploited by the high-tech industry thanks to the many different ceramic materials obtainable from a wide range of preceramic polymers.