具有优异抗氧化性的非等摩尔(Hf,Zr,Ta,W)B_(2)高熵二硼化物

Non-equimolar(Hf,Zr,Ta,W)B_(2)high-entropy diborides enable superior oxidation resistance

开发具有优异抗氧化性能的高熵二硼化物对于扩展其在极端环境中的潜在应用至关重要.本文通过调控W含量首次制备出了具有优异抗氧化性能的非等摩尔(Hf,Zr,Ta,W)B_(2)高熵二硼化物.采用机器学习对材料氧化深度进行了量化分析,发现制备的(Hf_(0.28)Zr_(0.28)Ta_(0.28)W_(0.15))B_(2)样品在1473–1773 K温度范围内具有优异的抗氧化性能,这主要是因为适量的WO_(3)可以有效抑制B_(2)O_(3)的挥发.此外,由于Hf和Zr元素的优先氧化以及氧化产物的扩散激活能差异,1773 K下生成的产物层形成了一个四层结构.通过计算的相稳定性图以及氧原子与不同金属吸附位点之间的吸附能和电荷转移,进一步证明了Hf和Zr元素的优先氧化.具有优异抗氧化性能的非等摩尔(Hf_(0.28)Zr_(0.28)Ta_(0.28)W_(0.15))B_(2)高熵二硼化物在超高温结构材料领域具有潜在的应用前景.

Developing superior oxidation resistance of high-entropy diborides is critical for extending their potential applications in harsh environments.Herein,we developed non-equimolar(Hf,Zr,Ta,W)B_(2)high-entropy diborides with superior oxidation resistance by adjusting W contents for the first time.The as-fabricated(Hf_(0.28)Zr_(0.28)Ta_(0.28)W_(0.15))B_(2)samples are predicted to possess superior oxidation resistance at 1473–1773 K through the oxidation depth quantitative analysis obtained by machine learning,which is attributed to the reason that the moderate WO_(3)can effectively inhibit the volatilization of B_(2)O_(3).Furthermore,a four-layered structure is found in the generated product layers at 1773 K,which is due to the preferential oxidation of Hf and Zr elements at low oxygen partial pressure and the different diffusion activation energies of oxide products.The preferential oxidation of Hf and Zr elements is further demonstrated by the computational phase stability diagrams,and oxygen adsorption energies and charge transfer between oxygen atoms and different metal adsorption sites via first-principles calculations.Such superior performance endows(Hf_(0.28)Zr_(0.28)Ta_(0.28)W_(0.15))B_(2)with potential applications as ultrahigh-temperature structural materials.