Microstructure, Mechanical and Dielectric Properties of Si₃N₄-BN Composites with Different Porosities

Abstract:

Si₃N₄-BN composites were prepared by die-pressing and precursor infiltration and pyrolysis (PIP) route using borazine as the precursor. The composition, microstructure, mechanical, and dielectric properties of the composites with different porosities were investigated. With the adoption of starch as pore forming substance, drawn the Si₃N₄ preform from the liquid precursor borazine and decrease the pressure during curing, the porosity of the Si₃N₄-BN composites were effectively increased. Along with the increase of the porosity of the composites, the mechanical properties were decreased and the dielectric properties were improved. With 20 wt.% starch and drawn Si₃N₄ preform from borazine before curing, the density, porosity, flexural strength and elastic modulus of the composites were 1.70 g·cm^-3, 29.78%, 48.05MPa and 32.45GPa, respectively. The dielectric constants and loss tangents were 4.20~4.44 and 0.48~3.42×10^-3 at the frequency 7~ 18GHz. Composites with various dielectric and mechanical properties can be designed and prepared according to the application needs.

• Periodical: Materials Science Forum (Volume 816)
• Pages: 40-47
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.816.40
• Online since: April 2015
• Authors: Kun Liu, Chang Rui Zhang*, Bin Li, Si Qing Wang, Feng Cao
• Keywords: Borazine, Boron Nitride, Composites, Dielectric, Gel-Casting, Porous Materials, Silicon Nitride

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