Defect-rich flexible TiO2 nanofibers enabled by ultrafast microwave CO2 plasma torch sintering for electromagnetic wave absorption

A novel method combining electrospinning with microwave CO 2 plasma torch sintering produces flexible TiO 2 nanofibers. • The TiO 2 fibers achieve excellent electromagnetic wave absorption with an RL min of −44.8 dB and an EAB max of 6.0 GHz. • Radar cross-section simulations of flexible TiO 2 nanofibers demonstrated a maximum reduction of 28.15 dB·m 2 . Flexible oxide nanofibers are attractive for conformal electromagnetic wave (EMW) absorption, yet rapid ceramic crystallization without sacrificing bendability remains challenging. Here, we report an ultrafast route that couples molecularly regulated electrospinning with atmospheric-pressure microwave CO 2 plasma torch sintering to fabricate flexible, defect-rich TiO 2 nanofibers. The chelated titanium sol enables continuous electrospinning, while plasma treatment at 8 kW converts precursor fibers into TiO 2 within 3 min. Multiphysics simulations reveal localized electromagnetic-thermal field coupling mechanism and a plasma core temperature approaching 7000 K, which explains the rapid precursor-to-TiO 2 conversion and the formation of nanocrystalline/amorphous interfaces under ultrafast heating-cooling conditions. Electron paramagnetic resonance and X-ray photoelectron spectroscopy confirm abundant oxygen-vacancy-related paramagnetic centers and weak surface Ti 3+ species, while transmission electron microscopy and off-axis electron holography reveal nanocrystalline/amorphous interfaces and interfacial charge accumulation. Furthermore, the obtained TiO 2 nanofibers achieve a minimum reflection loss (RL min ) of −44.8 dB at 1.8 mm and a maximum effective absorption bandwidth (EAB max ) of 6 GHz at 2.1 mm. Radar cross-section (RCS) simulations further show a maximum reduction of 28.15 dB·m 2 , indicating potential application for advanced microwave absorption. This work establishes microwave CO 2 plasma torch sintering as a rapid strategy for flexible oxide nanofibers and clarifies how plasma-induced defects and interfaces enhance EMW dissipation. Download: Download high-res image (377KB) Download: Download full-size image