Characterization and Microstructural Evolution of Continuous BN Ceramic Fibers Containing Amorphous Silicon Nitride

Area of Science:

• Materials Science
• Ceramic Engineering
• Nanotechnology

Background:

• Boron nitride (BN) and silicon nitride (Si3N4) are advanced ceramic materials with unique properties.
• Developing composite fibers offers synergistic benefits for enhanced performance.
• Controlling microstructure is crucial for optimizing mechanical properties.

Purpose of the Study:

• To fabricate BN/Si3N4 composite ceramic fibers using hybrid precursors.
• To investigate the effect of varying Si3N4 content on microstructure and properties.
• To determine the optimal composition for amorphous BN/Si3N4 ceramics and core-shell structures.

Main Methods:

• Hybrid precursors: poly(tri(methylamino)borazine) (PBN) and polycarbosilane (PCS).
• Fabrication: melt-spinning, curing, decarburization (1000 °C, NH3), and pyrolysis (1600 °C, N2).
• Characterization: Analysis of microstructure, tensile strength, and Young's modulus at varying Si3N4 content (5-25 wt%).

Main Results:

• Si3N4 crystallization was suppressed below 25 wt% at 1600 °C, yielding amorphous BN/Si3N4 composites.
• Mean tensile strength and Young's modulus increased with Si3N4 content.
• A distinct BN (shell)/Si3N4 (core) structure formed at 25 wt% Si3N4.

Conclusions:

• Amorphous BN/Si3N4 composite ceramic fibers can be successfully fabricated.
• Si3N4 content significantly influences the microstructure and mechanical properties of BN fibers.
• The study demonstrates a pathway to tailor BN/Si3N4 composites for specific applications.