Polyacrylonitrile-derived carbon nanofibers/carbon foams containing closed microspheres

Abstract

Lightweight materials with favorable mechanical, electromagnetic interference (EMI) shielding and thermal insulation performance are highly desirable for applications in harsh environments. Polyacrylonitrile (PAN)-derived carbon nanofibers/carbon foams containing hollow closed microspheres have been developed, and their balanced multifunction is noteworthy. The addition of CNFs resulted in a gradual enhancement of the specific compressive strength of carbon foams, reaching a maximum value of 26.6 MPa·cm³·g⁻¹ with content of 3 wt.% CNFs, improved by as much as 62%, compared to that of pristine carbon foam. Additionally, the fracture toughness exhibited the maximum fracture energy absorption of 118.6 MJ‧m⁻³ at 3 wt.% CNFs. The appropriate amount of CNFs and hollow carbon microspheres resulted in effective toughening and strengthening of carbon foams. Incorporation of CNFs into carbon foams also resulted in an improvement in their electromagnetic shielding performance, with a maximum EMI-shielding effectiveness of 65.8 dB. Reflection loss was the main contributor to electromagnetic shielding efficiency. Furthermore, carbon foams presented remarkable high-temperature thermal insulation, with a minimum thermal conductivity of merely 0.509 W·m⁻¹·K⁻¹ at 800 °C. They exhibited the ability to withstand the butane flame ablation at 1000 °C, which substantiated the potential of carbon foams for aerospace applications.