The interesting hybrid properties of ceramics and metals induced by unique nano-laminated structures make the M_(n+1)AX n(MAX)phase attractive as a potential protective coating for vital structural compo-nents in hars...The interesting hybrid properties of ceramics and metals induced by unique nano-laminated structures make the M_(n+1)AX n(MAX)phase attractive as a potential protective coating for vital structural compo-nents in harsh systems.However,an extremely narrow phase-forming region makes it difficult to prepare MAX phase coatings with high purity,which is required to obtain coatings with high-temperature anti-oxidation capabilities.This work describes the dependence of the phase evolution in deposited M-Al-C(M=Ti,V,Cr)coatings as a function on temperature using in-situ X-ray diffraction analysis.Compared to V_(2)AlC and Cr_(2)AlC MAX phase coatings,the Ti_(2)AlC coating displayed a higher phase-forming tempera-ture accompanied by a lack of any intermediate phases before the appearance of the Ti_(2)AlC MAX phase.The results of the first-principle calculations correlated with the experience in which Ti_(2)AlC exhibited the largest formation energy and density of states.The effect of the phase compositions of these three MAX phase coatings on mechanical properties were also investigated using ex-situ Vickers and nano-indenter tests,demonstrating the improved mechanical properties with good stability at high temperatures.These findings provide a deeper understanding of the phase-forming mechanism of MAX phase coatings to guide the preparation of high-purity MAX phase coatings and the optimization of MAX phase coatings with expected intermediate phases such as Cr_(2)C,V_(2)C etc.,as well as their application as protective coat-ings in temperature-related harsh environments.展开更多
Surface-modified Zr-based alloy(ZIRLO)claddings with advanced ceramic coatings are increasingly required for accident-tolerant fuel(ATF)systems in light-water reactors.Cr_(2)AlC MAX phase coatings are promising for th...Surface-modified Zr-based alloy(ZIRLO)claddings with advanced ceramic coatings are increasingly required for accident-tolerant fuel(ATF)systems in light-water reactors.Cr_(2)AlC MAX phase coatings are promising for this purpose owing to their remarkable properties combining radiation/oxidation/corrosion resistance.However they are suffering from weak interface compatibility to ZIRLO substrate and poor structural densities for long-term services.Herein,we fabricated densely high-purity Cr_(2)AlC MAX phase coatings with uniquely designed Cr/CrC_(x)interfacial layers.The oxidation behavior of the coatings was focused under steam environments at 1000–1200℃.Results showed that Cr_(2)AlC coatings exhibited an oxidation mass gain of 8.9 mg/cm^(2)and an oxide thickness of 680 nm after oxidation at 1200℃ for 30 min,which were about 10%and 0.5%of ZIRLO substrate,respectively.Based on microstructural evolutions,the embedded interfacial layers significantly suppressed the rapid diffusion of Al in Cr_(2)AlC coatings to the substrate and the premature delamination of oxidized coatings.Particularly,the formed oxides were identified as dense yet pure α-Al_(2)O_(3),which endowed the protection against further oxidation and excellent resistance to high-temperature steam corrosion.展开更多
The Cr_(2)AlC MAX phase offers a remarkable combination of excellent electrical conductivity and hot corrosion resistance in extremely harsh environments.However,the strong trade-off between hardness and toughness is ...The Cr_(2)AlC MAX phase offers a remarkable combination of excellent electrical conductivity and hot corrosion resistance in extremely harsh environments.However,the strong trade-off between hardness and toughness is rather limited by its nanolaminate structure for desired applications.Taking the solid solution strengthening and gradient hardening synergy,in this work,high-purity Cr_(2)AlC coatings with various Mo solid solutions were successfully fabricated via a hybrid sputtering technique followed by subsequent annealing.Interestingly,gradually changing the Mo concentration in the(Cr_(1−x)Mo_(x))_(2)AlC(x=0.05–0.24)coating enabled a hierarchical structure responsible for gradient refinement of the crystal grain size,and the solid solution of Mo atoms at Cr sites and the gradient variation in the Mo content were confirmed via the atomic-resolution transmission electron microscopy(TEM)characterization.Compared with those of the pristine Cr_(2)AlC coating,the nanoindentation hardness and toughness values of H/E and H_(3)/E_(2) for the hierarchical(Cr_(1−x)Mo_(x))_(2)AlC coating were enhanced by approximately 26%,12%,and 57%,respectively.On the basis of comprehensive experiments and ab initio simulations,the reasons behind this observation were mainly attributed to the synergistic effect of Mo occupancy with strong bonding at the Cr site and the strengthening of grain refinement induced by the gradient Mo concentration in the(Cr_(1−x)Mo_(x))_(2)AlC coating.These findings not only reveal the underlying mechanism for the Mo solid solution in the Cr_(2)AlC coating but also offer a new concept for developing ultrahigh-strength ductility materials for the laminar MAX phase.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos.52025014,52171090,52101109,U22A20111).
文摘The interesting hybrid properties of ceramics and metals induced by unique nano-laminated structures make the M_(n+1)AX n(MAX)phase attractive as a potential protective coating for vital structural compo-nents in harsh systems.However,an extremely narrow phase-forming region makes it difficult to prepare MAX phase coatings with high purity,which is required to obtain coatings with high-temperature anti-oxidation capabilities.This work describes the dependence of the phase evolution in deposited M-Al-C(M=Ti,V,Cr)coatings as a function on temperature using in-situ X-ray diffraction analysis.Compared to V_(2)AlC and Cr_(2)AlC MAX phase coatings,the Ti_(2)AlC coating displayed a higher phase-forming tempera-ture accompanied by a lack of any intermediate phases before the appearance of the Ti_(2)AlC MAX phase.The results of the first-principle calculations correlated with the experience in which Ti_(2)AlC exhibited the largest formation energy and density of states.The effect of the phase compositions of these three MAX phase coatings on mechanical properties were also investigated using ex-situ Vickers and nano-indenter tests,demonstrating the improved mechanical properties with good stability at high temperatures.These findings provide a deeper understanding of the phase-forming mechanism of MAX phase coatings to guide the preparation of high-purity MAX phase coatings and the optimization of MAX phase coatings with expected intermediate phases such as Cr_(2)C,V_(2)C etc.,as well as their application as protective coat-ings in temperature-related harsh environments.
基金financially supported by the National Natural Science Foundation of China(52171090,U22A20111)the National Science Fund for Distinguished Young Scholars of China(52025014)the Municipal Natural Science Foundation of Ningbo(2023J410,2022J305)
文摘Surface-modified Zr-based alloy(ZIRLO)claddings with advanced ceramic coatings are increasingly required for accident-tolerant fuel(ATF)systems in light-water reactors.Cr_(2)AlC MAX phase coatings are promising for this purpose owing to their remarkable properties combining radiation/oxidation/corrosion resistance.However they are suffering from weak interface compatibility to ZIRLO substrate and poor structural densities for long-term services.Herein,we fabricated densely high-purity Cr_(2)AlC MAX phase coatings with uniquely designed Cr/CrC_(x)interfacial layers.The oxidation behavior of the coatings was focused under steam environments at 1000–1200℃.Results showed that Cr_(2)AlC coatings exhibited an oxidation mass gain of 8.9 mg/cm^(2)and an oxide thickness of 680 nm after oxidation at 1200℃ for 30 min,which were about 10%and 0.5%of ZIRLO substrate,respectively.Based on microstructural evolutions,the embedded interfacial layers significantly suppressed the rapid diffusion of Al in Cr_(2)AlC coatings to the substrate and the premature delamination of oxidized coatings.Particularly,the formed oxides were identified as dense yet pure α-Al_(2)O_(3),which endowed the protection against further oxidation and excellent resistance to high-temperature steam corrosion.
基金supported by the National Science Found for Distinguished Young Scholars of China(No.52025014)the Zhejiang Provincial Postdoctoral Science Foundation(No.ZJ2023106)+1 种基金the Zhejiang Provincial Natural Science Foundation(No.LQ24E01005)the Key R&D Program of Ningbo(No.2024Z096).
文摘The Cr_(2)AlC MAX phase offers a remarkable combination of excellent electrical conductivity and hot corrosion resistance in extremely harsh environments.However,the strong trade-off between hardness and toughness is rather limited by its nanolaminate structure for desired applications.Taking the solid solution strengthening and gradient hardening synergy,in this work,high-purity Cr_(2)AlC coatings with various Mo solid solutions were successfully fabricated via a hybrid sputtering technique followed by subsequent annealing.Interestingly,gradually changing the Mo concentration in the(Cr_(1−x)Mo_(x))_(2)AlC(x=0.05–0.24)coating enabled a hierarchical structure responsible for gradient refinement of the crystal grain size,and the solid solution of Mo atoms at Cr sites and the gradient variation in the Mo content were confirmed via the atomic-resolution transmission electron microscopy(TEM)characterization.Compared with those of the pristine Cr_(2)AlC coating,the nanoindentation hardness and toughness values of H/E and H_(3)/E_(2) for the hierarchical(Cr_(1−x)Mo_(x))_(2)AlC coating were enhanced by approximately 26%,12%,and 57%,respectively.On the basis of comprehensive experiments and ab initio simulations,the reasons behind this observation were mainly attributed to the synergistic effect of Mo occupancy with strong bonding at the Cr site and the strengthening of grain refinement induced by the gradient Mo concentration in the(Cr_(1−x)Mo_(x))_(2)AlC coating.These findings not only reveal the underlying mechanism for the Mo solid solution in the Cr_(2)AlC coating but also offer a new concept for developing ultrahigh-strength ductility materials for the laminar MAX phase.
