Generative shaping and material-forming (GSM) enables structure engineering of complex-shaped Li4SiO4 ceramics based on 3D printing of ceramic/polymer precursors

Abstract

Vat photopolymerization (VPP) 3D printing of ceramics normally uses ceramic slurries directly made of the target ceramic powder. It may become challenging when the ceramic powders are difficult-to-make and thus are expensive or rarely accessible. We have previously proposed a generative shaping and material-forming (GSM) 3D printing strategy, which involves the use of low-cost multi-component inorganic ceramic precursors as powder sources. The shaping of complex structures was realized through VPP, followed by reaction sintering to form the target ceramic material. In the current study, as a step further, ceramic (Li 2 CO 3 ) and polymer (methyl polysiloxane) combined precursors were employed as an alternative material source for the first time to go through the 3D printing and reaction sintering processes, complementing the application range of the proposed GSM strategy. The slurry formulation and printability, the sinterability of the printed parts and the microstructures and mechanical performance of the sintered parts were characterized and optimized in accordance with the ingredient contents, particularly the stoichiometric ratios of Si:Li in the precursors. As a result, complex-structured Li 4 SiO 4 ceramics with high purity were fabricated based on the use of Li 2 CO 3 ceramic and Si-rich polymer as precursors. Through the advanced characterization and analysis of material phase and microstructural evolution, it was found that the fabricated complex-structured Li 4 SiO 4 ceramics based on a precursor slurry with a solid content of 40 vol%, a Si:Li ratio of 1:2.5, and a sintering temperature of 850 ℃ showed a high phase purity of 97.23% and a compressive strength of 15.24 ± 0.33 MPa, with a skeleton’s relative density of 65.31% is achieved. The results showed greatly enhanced strength at much higher porosities, which might be advantageous and beneficial to structure engineering for mechanical enhancement and the improvement of tritium release effectiveness. Compared with the previous study using multi-component ceramic powder precursors, the ceramics prepared in this study exhibited enhanced microstructural stability and higher phase purity with an advantageously lower sintering temperature. Further analysis revealed that compared with the high temperature solid-state reaction of multi-component ceramic powder precursors, the involvement of the Si-rich polymer precursor enabled the more efficient and complete synthesis of Li 4 SiO 4 as a result of the accelerated covering and cleavage of Si–O–Si bonds on the Li 2 CO 3 particles at a much lower temperature. The present work suggests that the GSM strategy using combined ceramic and polymer precursors as proposed in this study is a promising alternative method to produce high quality Li 4 SiO 4 components with complex structures. • Our GSM strategy is extended to 3D printing using ceramic/polymer precursors. • Slurry formulation and printability, sinterability of parts and microstructures of sintered parts were characterized. • High material phase purity and strength for the skeleton were achieved with lower sintering temperature. • Improved strength by GSM enabled structure engineering with complete synthesis/rearrangement of material/microstructures.