Synthesis and structural evolution of dual-boron-source-modified polysilazane derived SiBCN ceramics

Here, we demonstrated a novel synthesis of a polyborosilazane (PBSN) precursor using hydroboration and aminolysis reaction synergies to modify polysilazane (PSN). Specifically, borane-tetrahydrofuran and boron trichloridehexane were used as dual boron sources, which not only reacted with Si Vi and Si N H functionality respectively to modify multiple active sites of PSN resulting in boron-rich silicon boron carbide nitride (SiBCN) ceramics, but also improved controllability on composition, molecular structure, as well as final features. The resulting structures were characterized by FTIR, solid-state 11B and 29Si magic-angle spinning NMR and inductively coupled plasma emission spectral (ICP) analysis. These polymers were found to be structurally complex networks composed of tri-coordinate BCxN3-x and tetra-coordinate BCxN4-x bridges. The resulting polyborosilazanes contained similar to 11 wt% higher boron contents than that in the starting polymer. The structural evolution of the resulting polymers was evaluated by means of XPS, FTIR and XRD, and TGA-DSC-QMS was utilized to detail the precursor-to-ceramic conversion.