High-Entropy Boride-Oxide Multiphase Composite

Harder than partially stabilized zirconia

A thermodynamically designed multiphase ceramic composite made from B₄C and nine transition metal oxides, stabilized by Y₂O₃, combining high hardness, high modulus, and high toughness.

Qian, Yang · Qi, Liu · Liang, Xu · Liu, Jingjing · Ji, Wei · Xie, Jingjing · Wang, Weimin · Zhengyi, Fu · Zou, Ji

Journal of Materials Science and Technology 2027

Specifications

Vickers hardness

{'zh': '23.07', 'en': '23.07'} GPa

Young's modulus

{'zh': '384.42', 'en': '384.42'} GPa

Fracture toughness

{'zh': '5.71', 'en': '5.71'} MPa m1/2

Flexural strength

{'zh': '570.80', 'en': '570.80'} MPa

Advantages

Hardness outperforms zirconia ceramics

With optimized Y₂O₃ content, the composite reached a Vickers hardness (4.9 N) of 23.07 GPa, significantly superior to conventional oxide ceramics.

Toughness and strength exceed most high-entropy borides

Fracture toughness of 5.71 MPa·m¹ᐟ² and flexural strength of 570.80 MPa surpass most typical high-entropy boride ceramics.

Toughening mechanism is tunable

The extent of tetragonal-(Hf, Zr)O₂ phase transformation during crack propagation, and hence toughness, can be tuned by adjusting Y₂O₃ content.

Applications

• Advanced structural ceramics：Replace partially stabilized zirconia with higher hardness for load-bearing and wear-resistant structural parts.
• Wear-resistant mechanical parts：High hardness combined with adequate toughness extends service life of parts under friction.
• Aerospace thermal protection materials：High-melting-point constituents and good mechanical properties suit demanding thermal protection systems.
• High-temperature structural materials：Maintains structural and mechanical stability at high temperatures for load-bearing components.