Abstract

Dual phase (Hf,Ta,Ti,W,Zr)B2-(Hf,Ta,Ti,W,Zr)C high entropy ultra-high temperature ceramics were processed from commercial diboride and carbide powders with and without SiC additions. A 30-min hold at a maximum temperature of 1850 °C in spark plasma sintering resulted in a relative density of ∼95 %, which increased to ∼100 % with the addition of 7.5 wt.% SiC. The compositions did not reach chemical equilibrium under the given sintering conditions resulting in an inhomogeneous distribution of transition metals in both the boride and carbide phases. The addition of SiC improved densification by inhibiting grain growth, which reduced the grain size from 9.0 ± 4.2 μm without SiC to 5.6 ± 2.5 μm with SiC. The addition of SiC also improved both microhardness and fracture toughness. Microhardness at the maximum indentation load of 10 N increased from 20.3 ± 0.6 GPa without SiC to 22.6 ± 0.6 GPa with SiC, while indentation fracture toughness increased from 2.2 ± 0.3 MPa m1/2 to 4.0 ± 0.9 MPa m1/2. The room temperature thermal conductivity of the dual phase high entropy ceramic was ∼15 W/(m.K) due to the high entropy effect which increased to ∼22 W/(m.K) with the addition of SiC. The addition of SiC enhanced densification, inhibited grain growth, improved mechanical properties, and increased thermal conductivity of the dual phase high entropy system.

Department(s)

Materials Science and Engineering

Comments

United States - India Educational Foundation, Grant 2990 FNPDR/2023

Keywords and Phrases

High entropy ceramics; Silicon carbide; Spark plasma sintering; Ultra-high temperature ceramics

International Standard Serial Number (ISSN)

0272-8842

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2024 Elsevier, All rights reserved.

Publication Date

01 Jan 2024

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