Nano/micro-structured polymer-derived SiBCN ceramics via two-photon lithography

Printed microstructures face challenges when their applications require excellent mechanical strength and chemical stability at high temperatures. To maximize the service temperatures of printed microstructures, this study introduces a printable ceramic precursor for deriving SiBCN microstructures. The precursor possesses a high photosensitivity and high ceramic yield (76 wt%) because of the graft of acrylate and an increase of crosslinking degree, which is achieved by functionalizing polyborosilazane with 2-Isocyanatoethyl acrylate via nucleophilic addition reaction. The composition and chemical structure of the precursor and ceramic have been meticulously characterized. Moreover, a kinetics model has been established to describe the weight loss in pyrolysis, illuminating that the polymer-to-ceramic conversion is a diffusion-mediated growth process. Through two-photon lithography and pyrolysis, the photosensitive precursor can directly lead to SiBCN nano/microstructures with complex shapes and submicron (linewidth: ∼700 nm) features, which are the smallest SiBCN structures reported to date. At these microscales, it is revealed that shrinkage during pyrolysis is anisotropic and surface-area dependent and that the printed SiBCN micropillars can have an exceptional compressive strength of 3.59 ± 0.08 GPa. The potential applications of printed SiBCN microstructures were explored, including high-temperature embossing stamps for microlens and structural-color fabrication.