Designing ultra-thin high entropy oxide nanofibers with electrospinning method

High entropy oxides (HEOs) have emerged as significant nanomaterials due to their unique structural and functional properties. In this study, the suitability of the electrospinning method to produce HEO fibers with high surface area and diameters below 100 nm was investigated. In this study, the effects of solution composition, precursor concentration, processing parameters, and calcination temperature on fiber morphology and phase formation were systematically investigated. Electrospinning parameters, polymer concentration, and precursor content were varied to analyze their influence on fiber diameter. In addition, thermal treatments were applied to induce phase transformations and stabilize the high entropy oxide (HEO) phase. The results showed that increasing PAN concentration significantly increased fiber diameter, with 5 wt%, 7 wt%, and 10 wt% PAN solutions producing fibers with diameters of 204 nm, 322 nm, and 666 nm, respectively. Reducing the HEO content from 50 wt% to 45 wt% reduced the fiber diameter by 23 %, while further reductions had a more moderate effect. Adding ethyl acetate (EAc) further reduced the fiber diameter, reaching 133 nm at 10 wt% EAc. Using a 22G needle also contributed to finer fibers of 111 nm compared to the 19G needle. After calcination at 600 degrees C, a rock-salt structured R-HEO phase formed, the fiber diameter decreased to 58 nm, and the crystal size ranged from 5to12nm.