Fabrication and properties of borazine derived boron nitride matrix wave-transparent composites reinforced by 2.5 dimensional fabric of Si–N–O fibers

The fabrication of a 2.5 dimensional silicon oxynitride fiber fabric reinforced boron nitride matrix (2.5 D Si–N–Of/BN) composites through borazine infiltration and pyrolysis routine is reported. The Si–N–O fiber exhibited an amorphous structure with high composition uniformity. The borazine-to-ceramic conversion completed at 1200 °C and generated hydrogen-free turbostratic BN ceramic. Both the density and crystalline degree of the derived BN products increased with the elevating of pyrolysis temperature. The average bending and tensile strength of the 1200 °C fabricated 2.5 D Si–N–Of/BN composites were 127.4 MPa and 78.3 MPa, respectively. Considerable fiber pull-out was observed throughout the fractured surfaces, which was mainly attributed to the appropriate bonded fiber/matrix interfaces and the relative low elastic modulus of the matrix. Meanwhile, the composites displayed low dielectric constant and loss tangent values of 3.37 and 0.0031, as well as a low thermal conductivity of 1.04 W m−1 K−1.