Abstract
Hollow silica fibre reinforced BN–Si3N4 matrix composites (SiO2f/BN–Si3N4 composites) were fabricated by repeated infiltration and pyrolysis from a hybrid precursor. The effects of pyrolysis time on densification behaviour, mechanical properties, dielectric properties and microstructures of the composites were investigated. With increasing pyrolysis time, the density of SiO2f/BN–Si3N4 composites increases, the elastic modulus increases accordingly; however, the flexural strength and the dielectric properties decrease. The composites prepared at 400°C with the pyrolysis time of 1 h exhibit a maximum flexural strength of 132·4 MPa, a low dielectric constant of 2·78 and a low loss angle tangent value of 1·4 × 10–3. The high performance of the composites results from the good state of the silica fibres, controlled fibre/matrix interfacial microstructures, high purity hollow silica fibres with excellent dielectric properties and low density non-carbon nitride matrix. The calculation results of dielectric performance show that the composites prepared with the pyrolysis time of 1 h have broadband transmission properties.