Nb-Si based alloys have the greatest potential to replace nickel-based superalloys and become a new gen-eration ultra-high temperature structural material with service temperature of 1200-1400℃ due to their high melt...Nb-Si based alloys have the greatest potential to replace nickel-based superalloys and become a new gen-eration ultra-high temperature structural material with service temperature of 1200-1400℃ due to their high melting point,high stiffness,low density,and attractive specific mechanical properties at elevated temperatures.This article reviewed the recent progress in the development of Nb-Si based refractory al-loys.Special attention was paid to the property characteristics,preparation techniques,alloying effects,oxidation resistance and fabrication of Nb-Si based alloy components.Thereafter,the trend of develop-ment in the future was forecasted,including:Optimization of the composition and microstructure of Nb-Si based alloys to achieve a balance of mechanical properties;Comprehensive properties evaluation for Nb-Si based alloys to accumulate sufficient data for engineering applications;Development of practical preparation technology for Nb-Si based alloy components with complex shapes;New multilayer compos-ite coatings for Nb-Si based alloy;Joining technology of Nb-Si alloy to itself and to superalloy.展开更多
Surface engineering technology is a suitable method for coatings on the metal surfaces or performing surface modification treatment, which can improve corrosion resistance and biocompatibility of metals. In this resea...Surface engineering technology is a suitable method for coatings on the metal surfaces or performing surface modification treatment, which can improve corrosion resistance and biocompatibility of metals. In this research, corrosion behavior of Nb coating on H2SO4 and HNO3 treated AISI stainless steel 316L （SS） was evaluated. Nb coating was carried out using physical vapor deposition process on the SS. Characterization techniques including scanning electron microscopy （SEM） and energy dispersive X-ray （EDX） technique were used to investigate the microstructure and morphology of the coated and treated SS. Electrochemical potentiodynamic tests were performed in two types of physiological solutions and compared with the pristine SS specimens. Cyclic polarization tests were performed to evaluate resistivity against pitting. Experimental results indicate that Nb coating and surface treatment of the SS had a positive effect on improvement of corrosion behavior. The decrease in corrosion current densities was significant for coated and treated specimens. The corrosion current density was much lower than the values obtained for pristine specimens.展开更多
Multifunctional photocatalytic and thermochromic composites consisting of fluorine-doped vanadium dioxide(F-VO_(2))and niobium-doped TiO_(2)(NTO)were prepared by a simple physical mixing.The composites exhibited a hig...Multifunctional photocatalytic and thermochromic composites consisting of fluorine-doped vanadium dioxide(F-VO_(2))and niobium-doped TiO_(2)(NTO)were prepared by a simple physical mixing.The composites exhibited a higher thermochromic activity and nitrogen oxide(NO_(x))decomposition activity than that of pristine VO_(2)/NTO.Both VO_(2) and NTO materials were synthesized using an environmentally friendly soft chemical solvothermal/hydrothermal process,which produced NTO nanoparticles with a controllable morphology and particle size by changing the ratio of ethanol and acetic acid sol-vent.F-VO_(2)/NTO showed a better multifunctionality of thermochromic and photocatalytic activities than those of VO_(2)/NTO samples.The coexistence coating films showed a better effect on thermochromic and deNO_(x)(NO_(x) reduction)activity than those of double-sided films for F-VO_(2)/NTO samples.The best thermochromic and photocatalytic activities obtained from sample F-VO_(2)/NTO 60 showed the ΔT_(1500 nm)[difference of transmittance(ΔT)at the wavelength of 1500 nm under 25°C and 95°C]of up to 29.5%and deNO_(x) activity of up to 40%at λ>290 nm under mercury lamp irradiation.The use of F-VO_(2)/NTO coexistence coating films showed the appropriateness for multifunctional materials.展开更多
The high-temperature oxidation-resistant MoSi2 coating on the Nb substrate was prepared by slurry firing. The structure, compositions and phase distribution of the coating and the relationship between these features a...The high-temperature oxidation-resistant MoSi2 coating on the Nb substrate was prepared by slurry firing. The structure, compositions and phase distribution of the coating and the relationship between these features and the oxidation resistance of the coating were investigated by SEM, EDS and XRD. The results indicate that the interface between the coating and the substrate has metallurgic combination, and a transitional layer is formed by diffusion. The multi-layer structure improves the oxidation resistance of the coating. The method of slurry firing to prepare the high-temperature MoSi2 coating on Nb is feasible. The SiO2 scale, which is formed on the surface of the coating by the self-oxidation of MoSi2, prevents the further diffusion of oxygen.展开更多
Fe-based bulk metallic glasses(BMGs)with high boron content have potential application as a coating material used in the framework for storing spent nuclear fuels to support their safe long-term disposal.The high glas...Fe-based bulk metallic glasses(BMGs)with high boron content have potential application as a coating material used in the framework for storing spent nuclear fuels to support their safe long-term disposal.The high glass forming ability(GFA)and large supercooled liquid region are therefore required for such Fe-based BMGs in either the glassy powder fabrication or the subsequent coating spraying.In order to meet these requirements,the influence of Nb content on the GFA of Fe_(57)Cr_(10)Zr_(8)B_(18)Mo_(7-x)Nb_(x)(x=1-5,at.%)alloys was investigated,as Nb has positive roles in GFA and thermal stability of BMGs.The results indicate that a fully amorphous phase in the as-cast samples with 3 mm in diameter is obtained for both the Fe_(57)Cr_(10)Zr_(8)B_(18)Mo_(5)Nb_(2) and Fe_(57)Cr_(10)Zr_(8)B_(18)Mo_(4)Nb_(3) alloys.The corresponding supercooled liquid regions of the two BMGs are 78 K and 71 K,respectively.The mechanism for improving their GFA was analyzed based on the principle of metal solidification,the parameters for glass formation and thermal properties of the alloys.The compression strength and Vicker’s hardness of the two BMGs are 1,950 MPa and 1,310 HV,2,062 MPa and 1,180 HV,respectively.The developed BMGs with high B content,good GFA,and very high hardness can be used as coating materials to the framework for spent nuclear fuels.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.U2141205,52175369,52005465,51775525,51771006,51875541)the National Science and Technol-ogy Major Projects(No.2019-VII-0016-0156)the Foundation of Equipment Pre-research Area(No.JZX7Y20210262400501).
文摘Nb-Si based alloys have the greatest potential to replace nickel-based superalloys and become a new gen-eration ultra-high temperature structural material with service temperature of 1200-1400℃ due to their high melting point,high stiffness,low density,and attractive specific mechanical properties at elevated temperatures.This article reviewed the recent progress in the development of Nb-Si based refractory al-loys.Special attention was paid to the property characteristics,preparation techniques,alloying effects,oxidation resistance and fabrication of Nb-Si based alloy components.Thereafter,the trend of develop-ment in the future was forecasted,including:Optimization of the composition and microstructure of Nb-Si based alloys to achieve a balance of mechanical properties;Comprehensive properties evaluation for Nb-Si based alloys to accumulate sufficient data for engineering applications;Development of practical preparation technology for Nb-Si based alloy components with complex shapes;New multilayer compos-ite coatings for Nb-Si based alloy;Joining technology of Nb-Si alloy to itself and to superalloy.
基金support of this research by Isfahan University of technology
文摘Surface engineering technology is a suitable method for coatings on the metal surfaces or performing surface modification treatment, which can improve corrosion resistance and biocompatibility of metals. In this research, corrosion behavior of Nb coating on H2SO4 and HNO3 treated AISI stainless steel 316L （SS） was evaluated. Nb coating was carried out using physical vapor deposition process on the SS. Characterization techniques including scanning electron microscopy （SEM） and energy dispersive X-ray （EDX） technique were used to investigate the microstructure and morphology of the coated and treated SS. Electrochemical potentiodynamic tests were performed in two types of physiological solutions and compared with the pristine SS specimens. Cyclic polarization tests were performed to evaluate resistivity against pitting. Experimental results indicate that Nb coating and surface treatment of the SS had a positive effect on improvement of corrosion behavior. The decrease in corrosion current densities was significant for coated and treated specimens. The corrosion current density was much lower than the values obtained for pristine specimens.
基金This research was financially supported by the JSPS KAKENHI[Grant-in-Aid for Scientific Research on Innovative Areas“Mixed Anion”(Grant No.16H06439)]the Cooperative Research Program of“Network Joint Research Center for Materials and Devices”the Dynamic Alliance for Open Innovations Bridging Human,Environment,and Materials.
文摘Multifunctional photocatalytic and thermochromic composites consisting of fluorine-doped vanadium dioxide(F-VO_(2))and niobium-doped TiO_(2)(NTO)were prepared by a simple physical mixing.The composites exhibited a higher thermochromic activity and nitrogen oxide(NO_(x))decomposition activity than that of pristine VO_(2)/NTO.Both VO_(2) and NTO materials were synthesized using an environmentally friendly soft chemical solvothermal/hydrothermal process,which produced NTO nanoparticles with a controllable morphology and particle size by changing the ratio of ethanol and acetic acid sol-vent.F-VO_(2)/NTO showed a better multifunctionality of thermochromic and photocatalytic activities than those of VO_(2)/NTO samples.The coexistence coating films showed a better effect on thermochromic and deNO_(x)(NO_(x) reduction)activity than those of double-sided films for F-VO_(2)/NTO samples.The best thermochromic and photocatalytic activities obtained from sample F-VO_(2)/NTO 60 showed the ΔT_(1500 nm)[difference of transmittance(ΔT)at the wavelength of 1500 nm under 25°C and 95°C]of up to 29.5%and deNO_(x) activity of up to 40%at λ>290 nm under mercury lamp irradiation.The use of F-VO_(2)/NTO coexistence coating films showed the appropriateness for multifunctional materials.
基金Project(20010533003) supported by the Special Research Foundation of PhD Study
文摘The high-temperature oxidation-resistant MoSi2 coating on the Nb substrate was prepared by slurry firing. The structure, compositions and phase distribution of the coating and the relationship between these features and the oxidation resistance of the coating were investigated by SEM, EDS and XRD. The results indicate that the interface between the coating and the substrate has metallurgic combination, and a transitional layer is formed by diffusion. The multi-layer structure improves the oxidation resistance of the coating. The method of slurry firing to prepare the high-temperature MoSi2 coating on Nb is feasible. The SiO2 scale, which is formed on the surface of the coating by the self-oxidation of MoSi2, prevents the further diffusion of oxygen.
基金the Liaoning Joint Fund of NSFC(No.U1908219)Natural Science Foundation of Liaoning(No.2020-KF-14-03)National Key Research and Development Program of China(No.2019YFB2006501)。
文摘Fe-based bulk metallic glasses(BMGs)with high boron content have potential application as a coating material used in the framework for storing spent nuclear fuels to support their safe long-term disposal.The high glass forming ability(GFA)and large supercooled liquid region are therefore required for such Fe-based BMGs in either the glassy powder fabrication or the subsequent coating spraying.In order to meet these requirements,the influence of Nb content on the GFA of Fe_(57)Cr_(10)Zr_(8)B_(18)Mo_(7-x)Nb_(x)(x=1-5,at.%)alloys was investigated,as Nb has positive roles in GFA and thermal stability of BMGs.The results indicate that a fully amorphous phase in the as-cast samples with 3 mm in diameter is obtained for both the Fe_(57)Cr_(10)Zr_(8)B_(18)Mo_(5)Nb_(2) and Fe_(57)Cr_(10)Zr_(8)B_(18)Mo_(4)Nb_(3) alloys.The corresponding supercooled liquid regions of the two BMGs are 78 K and 71 K,respectively.The mechanism for improving their GFA was analyzed based on the principle of metal solidification,the parameters for glass formation and thermal properties of the alloys.The compression strength and Vicker’s hardness of the two BMGs are 1,950 MPa and 1,310 HV,2,062 MPa and 1,180 HV,respectively.The developed BMGs with high B content,good GFA,and very high hardness can be used as coating materials to the framework for spent nuclear fuels.
