Resilient Si3N4@SiO2 nanowire aerogels for high-temperature electromagnetic wave transparency and thermal insulation

Abstract

With the development of aerospace technology, the Mach number of aircraft continues to increase, which puts forward higher performance requirements for high-temperature wave-transparent materials. Silicon nitrides have excellent mechanical properties, high-temperature stability, and oxidation resistance, but their brittleness and high dielectric constant impede their practical applications. Herein, by employing a template-assisted precursor pyrolysis method, we prepared a class of Si3N4@SiO2 nanowire aerogels (Si3N4@SiO2 NWAGs) that are assembled by Si3N4@SiO2 nanowires with diameters ranging from 386 to 631 nm. Si3N4@SiO2 NWAGs have low density of 12–31 mg∙cm−3, specific surface area of 4.13 m2∙g−1, and average pore size of 68.9 μm. Mechanical properties characterization shows that the aerogels exhibit reversible compressibility from 60% compressive strain and good fatigue resistance even when being compressed 100 times at set strain of 20%. The aerogels also show good thermal insulation performance (0.032 W·m−1∙K−1 at room temperature), ablation resistance (butane blow torch), and high-temperature stability (maximum service temperature in air over 1200 ℃). The dielectric constant and loss of the aerogels are 1.02–1.06 and 4.3×10−5–1.4×10−3 at room temperature, respectively. The combination of good mechanical, thermal, and dielectric properties makes Si3N4@SiO2 NWAGs promising ultralight wave-transparent and thermally insulating materials for applications at high temperatures.

Keywords

• electromagnetic wave transparency
• resilient ceramic aerogels
• high-temperature stability
• fire resistance
• high-temperature resistance