Polyborosilazane with Broadly Tunable Boron Content for SiBCN Ceramics

Area of Science:

• Materials Science
• Ceramic Engineering
• Inorganic Chemistry

Background:

• High-temperature durability of silicon boron carbon nitride (SiBCN) ceramics is crucial for many applications.
• Existing synthesis methods, like single-source routes, limit boron content due to borane (BH3) constraints.
• Controlling boron concentration is key to tailoring SiBCN ceramic properties.

Purpose of the Study:

• To develop a novel synthesis route for SiBCN ceramics with a wide range of boron concentrations.
• To investigate the effect of varying boron content on the structural and thermal properties of SiBCN ceramics.
• To explore the potential of boron-rich SiBCN ceramics for enhanced functional properties, such as neutron shielding.

Main Methods:

• Synthesized carborane-substituted polyborosilazanes using a one-pot reaction between polysilazanes and decaborododecahydrodiacetonitrile complexes.
• Varied the molar ratios of reactants to achieve boron content from approximately 0 to 40.00 wt %.
• Analyzed ceramic yields, crystallization behavior (onset temperature, phase formation), and thermal stability.

Main Results:

• Achieved high ceramic yields (50.92-90.81 wt %) with tunable boron content.
• SiBCN ceramics began crystallizing at 1200 °C, with boron carbide (B4C) appearing as a new phase at higher boron concentrations.
• Increased boron content inhibited Si3N4 crystallization and raised the SiC crystallization temperature, while the B4C phase enhanced thermal stability and neutron-shielding capabilities.

Conclusions:

• The developed one-pot synthesis method effectively produces SiBCN ceramics with significantly enhanced boron content.
• The presence of boron, particularly as B4C, positively impacts thermal stability and neutron absorption properties.
• This research offers a promising pathway for designing advanced polyborosilazanes with tailored properties for demanding applications.