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Seeking materials with high melting temperature and structural stability

model of a high-entropy carbide HEC-16

A high-entropy carbide HEC-16: MoNbTaVWC5 that forms a single phase with spark plasma sintering. It was designed, synthesized, and tested using MGI-facilitated strategies. See

Credit: Duke University

What is the highest melting temperature material one can conceive, and how would you make it? That deceptively simple question is actually unimaginably complicated. Materials that are able to maintain their load-bearing capability to the very highest temperatures in extreme environments will enable technological achievements such as advanced manufacturing tooling and leading edges for hypersonic aerospace vehicles. But understanding the factors that influence interatomic bonding and then harnessing the controlling physical mechanisms to deliver such materials has been elusive until now. A multidisciplinary university research initiative award supported by the Office of Naval Research is applying integrated computational materials engineering (ICME)-based and MGI-based approaches to design ultrahigh-temperature ceramics (UTHCs) with enhanced hardness to meet this challenge.

The project is focused on UHTCs, also called high-entropy ceramics, by combining carbon, nitrogen, and boron with refractory metals (Hf, Mo, Nb, Ta, Ti, V, W, and Zr) to produce complex atomic structures that are predicted to be harder and have higher melting temperatures than previously known ceramics. The team is using the automatic FLOW (AFLOW) repository with a partial occupation method to rapidly generate distinct quasirandom unit cell configurations and screen them for synthesizability and stability at elevated temperature. Then employing accelerated synthesis and analysis techniques, the team of materials scientists and engineers has demonstrated several compositions with a Vickers hardness up to 50% higher than those predicted by a simple rule-of-mixtures calculation.

This promising result illustrates that materials discovery of combinatorially complicated systems like this can only be accomplished in a sufficiently fast and affordable way with ICME and MGI concepts.

Created September 2, 2021