Lightweight and robust SiO₂f/SiO₂ composites with superior dielectric properties via three-dimensional woven spacer technique

Abstract

Lightweight, high-strength ceramic matrix composites with excellent dielectric properties are in great demand in strategic fields such as aerospace and wireless communication. Herein, a three-dimensional (3D) spacer SiO₂_f/SiO₂ composite with high porosity in the thickness direction was fabricated by combining 3D woven spacer quartz fabric with SiO₂ through a sol-gel process. As a result, the porous SiO₂_f/SiO₂ composite with a 3D woven spacer structure (SiO₂_f/SiO₂-3DWSS) exhibits a low volume density of 0.71 g/cm³, yet it can support over 30,000 times its own weight without any damage. Additionally, the as-produced SiO₂_f/SiO₂-3DWSS demonstrates an ultra-low dielectric constant (ε = 1.67), dielectric loss (tan δ = 7.2 × 10⁻³), and a high electromagnetic (EM) wave transmission coefficient (|T|² = 98.35 %). Furthermore, the dielectric properties of SiO₂_f/SiO₂-3DWSS demonstrate low sensitivity to temperature fluctuations, with the dielectric constant and dielectric loss changing by only 0.39 % and 7.54 %, respectively, when the ambient temperature reaches 400 °C. Simulations further reveal the advantage of SiO₂_f/SiO₂-3DWSS over solid structures in EM wave transmission. This work proposes a promising strategy for the design of advanced ceramic matrix composites characterized by lightweight properties and enhanced wave transmission.