Ultrasonic sprayed hollow ceramic/carbon microspheres function as thermal insulation, ablative resistance, and electromagnetic shielding materials

Hollow ceramic/carbon microspheres (HCCMs) have widespread applications for thermal insulation and ablative resistance materials in aerospace areas, attributed to their multiple advantages such as low density, low thermal conductivity, oxidation and high-temperature resistance. In this work, we fabricated HCCMs with diameters around 18-242 mu m by the ultrasonic spray method, using mixed solutions of poly(acrylonitrile) (PAN), polyvinyl pyrrolidone (PVP), and preceramic polymers as starting materials. After optimizing the morphology of HCCMs, we introduced them as fillers into phenolic resin (PR). By adjusting the ratio between HCCMs and PR, the optimal properties were obtained at a loading content of 30 wt% of HCCMs. The density of as-obtained PR composite was 0.70 g/cm3, the thermal conductivity was 0.27 W/(m & sdot;K), and the maximum electromagnetic shielding effectiveness was 76.30 dB at the frequency of 8-12 GHz. This work develops a powerful approach to fabricating HCCMs, and demonstrates their typical application as fillers in PR to improve thermal insulation, electromagnetic shielding, and ablative resistance performance.