Flexible and ultrathin SiO(C)N nanofiber films with broadband electromagnetic wave absorption/transmission and effective thermal insulation
Topic(s) : Material science
Co-authors :
Li ZHAOCHEN (CHINA)Abstract :
With the rapid development of electronic information technology, sophisticated electronics face the influence of complex electromagnetic (EM) environments, putting forward higher requirements for the dielectric properties of materials. At the same time, some avionic devices also bear the severe high temperature environment. It is urgent to develop novel ceramic materials integrating electromagnetic function, thermal insulation, and high-temperature stability. With their large aspect ratio, high porosity, high temperature resistance, low density, and good dielectric properties, the SiC/Si3N4 nanofiber aerogels are considered strong candidates but challenged by weak dielectric tunability, large insulation thickness, and instability above 1300°C. Microstructure control and composition design are the keys to overcoming these shortages.
In this work, based on the polymer-derived ceramic method and electrospinning process, SiO(C)N nanofiber films with nanoscale diameters (100–300 nm), good alignment, flexibility, lightweight, and ultrathin thickness (0.2–0.5 mm) were synthesized. By managing the C and N element contents, various types of films showed wide adjusting ranges of permittivity (2–14) and dielectric loss (0–1.2), realizing the EM wave absorption-transmission adjustability. Among them, the polycrystalline SiOCN nanofiber films represented an ultra-broad effective absorption bandwidth (EAB, more than 90% of EM wave can be absorbed) of 8.93 GHz (covering 9.07–18 GHz), while the amorphous SiON nanofiber films exhibited good EM wave transparency (wave transmission coefficient T above 0.9 in 2–18 GHz). The prepared films revealed low thermal conductivity (40–70 mW·m-1K-1), fire resistance (withstand butane flames around 1300°C), and effectively thermal insulation (a temperature difference of about 1000°C in 1 mm thick). The SiO(C)N nanofiber films also had high temperature stability at 1500°C, with the weight gaining less than 1% in inert gas and 7% in air.
The effects of microstructure and composition on multiple functions were studied in detail. For EM wave absorption, the aligned nanofibers provide a conductive network for conductive loss, while the doped N element benefits polarization loss and impedance matching. For EM wave transmission, the release of the C element contributes to the decrease in permittivity. For thermal insulation, heat can be conducted along nanofibers in the in-plane direction and insulated by porous structures in the through-thickness direction. For high temperature stability, the multielement phase can remain in amorphous states at high temperatures (1300–1500°C). The prepared SiO(C)N nanofiber films show the potential to be applied in harsh environments in aerospace, communication fields, fire protection fields, and so on. What’s more, the SiO(C)N nanofibers meet wide application prospects as added absorbers and thermal managers in various ceramic matrices for designing multifunctional ceramic matrix composites.
In this work, based on the polymer-derived ceramic method and electrospinning process, SiO(C)N nanofiber films with nanoscale diameters (100–300 nm), good alignment, flexibility, lightweight, and ultrathin thickness (0.2–0.5 mm) were synthesized. By managing the C and N element contents, various types of films showed wide adjusting ranges of permittivity (2–14) and dielectric loss (0–1.2), realizing the EM wave absorption-transmission adjustability. Among them, the polycrystalline SiOCN nanofiber films represented an ultra-broad effective absorption bandwidth (EAB, more than 90% of EM wave can be absorbed) of 8.93 GHz (covering 9.07–18 GHz), while the amorphous SiON nanofiber films exhibited good EM wave transparency (wave transmission coefficient T above 0.9 in 2–18 GHz). The prepared films revealed low thermal conductivity (40–70 mW·m-1K-1), fire resistance (withstand butane flames around 1300°C), and effectively thermal insulation (a temperature difference of about 1000°C in 1 mm thick). The SiO(C)N nanofiber films also had high temperature stability at 1500°C, with the weight gaining less than 1% in inert gas and 7% in air.
The effects of microstructure and composition on multiple functions were studied in detail. For EM wave absorption, the aligned nanofibers provide a conductive network for conductive loss, while the doped N element benefits polarization loss and impedance matching. For EM wave transmission, the release of the C element contributes to the decrease in permittivity. For thermal insulation, heat can be conducted along nanofibers in the in-plane direction and insulated by porous structures in the through-thickness direction. For high temperature stability, the multielement phase can remain in amorphous states at high temperatures (1300–1500°C). The prepared SiO(C)N nanofiber films show the potential to be applied in harsh environments in aerospace, communication fields, fire protection fields, and so on. What’s more, the SiO(C)N nanofibers meet wide application prospects as added absorbers and thermal managers in various ceramic matrices for designing multifunctional ceramic matrix composites.