Synthesis and characterization of high entropy (TiVNbTaM) ₂AlC (M = Zr, Hf) ceramics

Abstract

The high-entropy design of MAX phases is expected to confer superior properties, but its study was hindered by the complex synthesis method and limited purity of samples. In this work, two noteworthy types of high-entropy MAX phase structural ceramics, high-entropy (TiVNbTaM) 2 AlC (M = Zr, Hf), were designed and prepared by the in-situ synthesis using spark plasma sintering (SPS). The microstructure and lattice parameters of sintered samples were determined. Compared with the single-component MAX phases, the highly pure high-entropy (TiVNbTaZr) 2 AlC sample had good physical and mechanical properties, including electrical conductivity of 0.

Understanding the Role of 1/2 ⟨110⟩ Dislocations in Deformation Mechanisms of Single-Crystal High-Entropy Carbide Ceramics from Machine Learning Force Field Simulations

“…For example, (Ti 0.2 Zr 0.2 Nb 0.2 Hf 0.2 Ta 0.2 )C exhibits excellent thermal stability at elevated temperatures. In comparison, (La 0.2 Sm 0.2 Er 0.2 Yb 0.2 Y 0.2 ) 2 CexO 3 + 2 x has a thermal expansion coefficient of approximately 9.04–13.12 × 10 –6 K –1 , while (Ti, Zr, Hf)­B 2 shows a coefficient of about 8.7 × 10 –6 K –1 , and (TiVNbTaZr) 2 AlC has a coefficient around 3.65 × 10 –6 K –1 . Although the thermal expansion coefficient of HECCs lies within these values, their unique properties still provide exceptional performance, making them highly suitable for ultrahigh-temperature applications where thermal stability and resistance to thermal shock are critical.…”