High wave transmittance and low thermal conductivity Y--SiAlON porous ceramics for high-temperature radome applications

With the development of hypersonic vehicle technology, ceramic-based radome materials are highly demanded due to their high operating temperatures, good dielectric properties, and high mechanical properties. Although alpha-SiAlON is an ideal material for radome applications, its intrinsic low transmittance and high thermal conductivity limit its applications. Herein, we prepared Y-alpha-SiAlON porous ceramics through tert-butanol (TBA) gel-casting using the self-synthesized a-SiAlON powder. The Y-alpha-SiAlON porous ceramics exhibited a uniform micron-level connected pore structure with the porosity (P) of 44.2%- 58.6%. The real part of permittivity (epsilon') was 3.13-4.18 (8.2-12.4 GHz), which decreased significantly with the increasing porosity. The wave transmittance ( | T |(2)) of the sample with porosity of 58.6% could exceed 80% in the thickness range of 6-10 mm. The thermal conductivity was maintained at a low level of 1.38-2.25 W center dot m(-1)center dot K-1 owing to the introduction of the pore structure. The flexural strength was 44.73-88.33 MPa, which may be increased by rod-like alpha-SiAlON grains. The results indicate that the prepared Y-alpha-SiAlON porous ceramics meet the requirements of high-temperature wave-transmitting materials for radome applications.