Pressureless solid-state sintering of SiC ceramics prepared by material extrusion 3D printing

In this study, high-strength dense silicon carbide ceramics were successfully prepared via material extrusion 3D printing in combination with pressureless solid-state sintering, in which a polyethylene/wax synergistic binder system was applied to material extrusion 3D printing. Samples of different binder components were prepared by adjusting the ratios of high-density polyethylene (HDPE), low-density polyethylene (LDPE), and paraffin wax (PW). Owing to the good synergy between HDPE/LDPE and PW, a uniform polymer skeleton network was formed in the HL21P sample, demonstrating the best rheological properties and printing quality. After sintering, the HL21P sample possessed the highest density of 3.06 g/cm 3 and the lowest open porosity of 0.4%, along with an optimal flexural strength of 397±29 MPa and elastic modulus of 345±29 GPa. Additionally, the optimal composition HL21P sample still possesses a flexural strength of 382 MPa after sintering at 1700°C. This research addresses the high-temperature failure of SiC ceramics fabricated via the prevalent reaction sintering method in the field of 3D-printed SiC ceramics, attributed to the presence of free silicon. It also demonstrates the importance of polyethylene and paraffin synergy in forming a polymeric skeletal network, enabling the production of SiC ceramics through 3D printing and pressureless sintering.