Additive manufacturing (AM) is an innovative and sustainable technique that offers a possibility to produce complex 3D structures. The AM products can be found in many industrial fields, including aerospace, healthcare, automotive and defence [1]. AM is a particularly promising solution, especially for ceramic materials when conventional manufacturing approaches fail [2]. Ceramic materials can be fabricated using various 3D printing techniques such as stereolithography, direct ink writing, and inkjet printing. Two types of feedstock material are used for the AM of advanced ceramics: ceramic powder with a binder and polymer-derived ceramics (PDCs). This work uses PDCs, as their ease of processability makes them an outstanding class of materials for AM, since they are processed as organic components. After the desired geometric structure has been printed, the organic component is converted into a functional ceramic via a pyrolysis process [3].

Inkjet printing is the method of choice in this work, as it is a typical AM method, which allows a wide range of low-viscous liquids or suspensions to be deposited. Furthermore, a large number of inks can be printed in parallel, depending on the printing device. The 3D structures are created layer by layer using a drop-on-demand (DOD) approach, whereby droplets are generated by a piezoelectric actuator and ejected onto e.g. a substrate [4].

Polyorganosilazane was used as a precursor material for PDCs in the work. The formulated ink meets the requirement of the inkjet printer with respect to the rheological and surface properties. The ink was printed with different resolutions on silicon wafer (Figure 1) and formed homogeneous green-bodies after UV curing. Subsequently, the thin films were pyrolyzed at 970 °C in an inert atmosphere, resulting in the formation of defect-free amorphous ceramic coatings. 

These coatings display chemical and oxidation resistance, good adhesion and high temperature stability. The progress of the crosslinking process and the structure of the final ceramic was investigated in detail using FTIR spectroscopy. The results reveal that crosslinking was mainly induced by free-radical polymerisation and the final ceramic formed was silicon carbonitride (SiCN(O)). The decomposition and pyrolysis processes were studied by means of thermogravimetric analysis. The layer thicknesses range from 0.2 µm to 2 µm. Possible applications of these thin-film might be interlayer dielectrics in MEMS applications or high-temperature protective layers.

References
[1] M. Dadkhah; J.-M. Tulliani; A. Saboori; L. Iuliano; Journal of European Ceramic Society, 2023, 15, 6635–6664.
[2] M. Abdelkader; S. Petrik; D. Nestler; M. Fijalkowski; Ceramics, 2024, 7, 68–85.
[3] J. Han; C. Liu; R.L. Bradford-Vialva; D.A. Klosterman; Materials, 2023, 16 (13), 4636.
[4] B. Derby; Engineering, 2015, 1, 113–123.