Diffusion-controlled alloying of single-phase multi-principal transition metal carbides with high toughness and low thermal diffusivity

Abstract

Multicomponent alloying has displayed extraordinary potential for producing exceptional structural and functional materials. However, the synthesis of single-phase, multiprincipal covalent compounds remains a challenge. Here we present a diffusioncontrolled alloying strategy for the successful realization of covalent multi-principal transition metal carbides (MPTMCs) with a single face-centered cubic (FCC) phase. The increased interfacial diffusion promoted by the addition of a nonstoichiometric compound leads to rapid formation of the new single phase at much lower sintering temperature.Direct atomic-level observations via scanning transmission electron microscopy demonstrate that MPTMCs are composed of a single phase with a random distribution of all cations, which holds the key to the unique combinations of improved fracture toughness, superior Vickers hardness, and extremely lower thermal diffusivity achieved in MPTMCs. The present discovery provides a promising approach toward the design and synthesis of next-generation high-performance materials.

Review of high entropy ceramics: design, synthesis, structure and properties

“…55,56 4. 33 , (Hf-Ta-Zr-Nb)C, 60 and equal-molar TiN 0.3 /VC/NbC/TiC/TaC/Mo 2 C/WCs, 61 based on STEM-EDS and HAADF images.…”

“…By tting the PDF prole using the PDF gui code with an ideal FCC structural model and a random atomic arrangement, they concluded that the HEC carbide was a well-dened single phase with negligible lattice distortion. 61 The local distortion can also be indirectly detected by electron paramagnetic resonance (EPR), which exploits the physical properties of unpaired electrons in materials, e.g. electrons of transition metal ions.…”

Thermophysical and mechanical properties of novel high‐entropy metal nitride‐carbides

“…The multicomponent metal nitride‐carbides are of interest for a wide range of applications because of the attractive chemical and physical properties of individual component, such as extreme hardness, high thermal conductivity, low chemical reactivity, and so on. In the recent past, some multicomponent metal nitride‐carbides have been successfully fabricated and investigated 18‐20 . However, they cannot be defined as high‐entropy nitride‐carbides in that their metallic or nonmetallic elements are far from four principal elements or near‐equiatomic ratios or at least with each element being between 5 and 35 at.%.…”

Critical role of cationic local stresses on the stabilization of entropy‐stabilized transition metal oxides

“…Following the aforementioned work, the idea of entropy stabilization was extended to covalently bonded ceramics in recent times. For instance, several single‐phase multicomponent metal diborides and metal carbide systems were synthesized, the synthesized ceramic structures had ultra‐high temperature properties coupled with low values of thermal conductivity . The concept of entropy stabilization was further used to synthesize more complex spinel, perovskite and fluorite crystal structures .…”