Out-of-oven rapid synthesis of entropy stabilized oxides using radio frequency heating

Abstract

Entropy stabilized oxides (ESOs) are a new class of stable hybrids and single phase metal oxides made from multiple ions with material properties somewhere between the constituent oxides, or occasionally entirely new properties. One of the limitations of ESOs is their energy-intensive fabrication process, which has resulted in slow development and scale-up of new ESOs. In this work, we present a novel energy-efficient ESO synthesis method that uses the ability of carbonaceous materials to heat rapidly in response to radio frequency (RF) fields in 1–200 MHz range. Using carbon fibers and graphene as RF susceptors, synthesis of (Mg0·2Co0·2Ni0·2Cu0·2Zn0.2)O is achieved through RF-initiated combustion synthesis with heating rates of 203 °C/s at 20 W of input power. This method reduces the formation time of ESOs to less than a minute, allowing for much more efficient fabrication. The corresponding morphology and composition of the as-synthesized ESO-carbon fiber and ESO-graphene were studied using extensive spectroscopy and characterization. Additionally, single carbon fibers coated with ESO were tested for tensile strength and modulus; little change in mechanical properties was observed as compared to pristine fibers. This work opens an exciting frontier for the rapid synthesis of ESO-carbon composites using RF heating as a non-contact, rapid, and efficient manufacturing process.

Keywords

• RF heating
• ESOs
• ESO-Carbon composites
• Oxides
• Entropy stabilized oxides