Rapid Synthesis of Entropy Stabilized Oxides Using Radio Frequency Heating

Entropy-stabilized oxides (ESOs) represent an exciting new category of hybrid materials and single-phase metal oxides, composed of multiple ions, exhibiting material characteristics that lie between those of their constituent oxides or occasionally showcasing entirely novel properties. One drawback of ESOs is their energy expensive manufacturing process, which has hindered the pace of their development and scaling. In this study, we introduce an innovative, energy-efficient method for synthesizing ESOs. This approach leverages the rapid heating capability of carbonaceous materials when exposed to radio frequency (RF) fields within the 1–200 MHz range. By employing carbon fibers and graphene as RF susceptors, we successfully achieved the synthesis of (MgCoNiCuZn)_0.2O through RF-triggered combustion synthesis, achieving heating rates of 203°C/s with a 20 W input power. This technique reduces the ESO formation time to less than a minute, significantly enhancing fabrication efficiency. The morphology and composition of the resultant ESO-carbon fiber and ESO-graphene composites were comprehensively examined using spectroscopy and characterization techniques. Moreover, single carbon fibers coated with ESO underwent testing for tensile strength and modulus, revealing minimal changes in mechanical properties compared to pristine fibers. In this study, for the first time, a new method for producing ESO-carbon composites has been demonstrated using out-of-oven electromagnetic heating using radio frequencies in the range of 1–200 MHz at low input power (less than 25 W).