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

Abstract

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.