BORON NITRIDE-NANOTUBE–SILICON NITRIDE COMPOSITES FOR HIGH TEMPERATURE RADOME APPLICATIONS

Abstract

High-temperature radomes necessitate a number of design constraints, including the need for stability at high temperatures while maintaining a low dielectric constant to minimize signal loss. The addition of boron nitride nanotubes to a conventional silicon nitride system represents a potential to lower the dielectric constant while not sacrificing other material properties. This study investigates the manufacturing processes needed, as well as the mechanical properties of zero- to 3-volume-loaded boron nitride nanotube loaded silicon nitride. Successful hot pressing of silicon nitride-boron nitride nanotube composites was performed, reaching densities of up to 97.2% of theoretical. 4-point bend testing was performed, as well as impulse excitation testing and fracture surface micrography. An average decrease in flexural strength from 660 MPa to 558 MPa was observed between silicon nitride and silicon nitride- 3 vol% boron nitride nanotube composite samples. An investigation of BNNT dispersion within the part was conducted, which showed strong dispersion. The results suggest that the combined system shows promise in the field of radome materials but may require further study.