Enhanced thermal stability and corrosion resistance of novel high-entropy spinels in cryolite-alumina molten salt applications

Abstract

The development of spinel oxide materials with high thermal stability and corrosion resistance is essential for thermochemical reactions, particularly in aluminum electrolysis. This study presents the structural design of a family of high-entropy spinels (HESs) with a stable cubic spinel structure (Fd3‾m), specifically formulated as (Cr5/12 Mn5/12 Fe5/12 Co3/8 Y3/8)3O4, (Y = Ni, Cu, or Zn). Our results demonstrate that these high-entropy spinels significantly outperform conventional NiFe₂O₄, exhibiting superior corrosion resistance and thermal properties. Specifically, we observe lower high-temperature weight loss (0.24 %–0.74 % at 1000 °C), reduced thermal conductivity (1.810–2.258 W m−1 K−1 at room temperature), and lower thermal expansion coefficients (8.2 - 10.7 × 10−6 K−1 from 400 °C to 800 °C), while maintaining comparable specific heat capacities (0.51–0.55 J g−1 K−1). Corrosion testing at 800 °C for 20 h in a KF3-AlF3-Al2O3 molten salt environment shows a corrosion layer thickness of less than 150 μm, with minimal corrosion product formation. These findings not only advance our understanding of material properties under extreme conditions but also pave the way for the development of next-generation materials for thermochemical applications, specifically aimed at improving the efficiency of aluminum electrolysis. Show more