The oxidation and interdiffusion behavior of a novel AlCoCrFeNiY bond coat deposited on a directionally solidified Ni-based superalloy were systematically studied at 1050,1100 and 1150°C,and compared with a conve...The oxidation and interdiffusion behavior of a novel AlCoCrFeNiY bond coat deposited on a directionally solidified Ni-based superalloy were systematically studied at 1050,1100 and 1150°C,and compared with a conventional NiCoCrAlY coating deposited on the same substrate.The AlCoCrFeNiY bond coat exhibits lower oxide growth rates due to its large columnar grains and low Al activity at the oxide scale/bond coat interface.Meanwhile,AlCoCrFeNiY has higher resistance to oxide spallation than NiCoCrAlY,which is attributed to the formation of a clean and defect-free metal/oxide interface.Significant interdiffusion occurs across the AlCoCrFeNiY/superalloy substrate interface.Our experimental evidence and thermody-namic modelling suggest that Fe accelerates interdiffusion and destabilizes theγ’phase,thereby causing the formation of a thick andγ’-depleted interdiffusion zone.In addition,the AlCoCrFeNiY bond coat un-dergoes more Al depletion and subsequentβtoγtransformation compared with NiCoCrAlY.Based on the findings in this work,a novel AlCoCrFeNiY/NiCoCrAlY double-layer bond coat was designed,tested and validated to achieve optimal balance between oxidation and interdiffusion.展开更多
Pure metal Fe films with thickness of about 100nm were deposited on Si （100） substrates by DC magnetron sputtering. Annealing was subsequently performed in a vacuum furnace in the temperature range of 600-1000℃ for...Pure metal Fe films with thickness of about 100nm were deposited on Si （100） substrates by DC magnetron sputtering. Annealing was subsequently performed in a vacuum furnace in the temperature range of 600-1000℃ for 2h. The samples were characterized by means of Rutherford backscattering （RBS） with 3MeV carbon ions. The RBS data were fitted with SIMNRA 6.0, and the results show the atomic interdiffusion in Fe/Si systems. The microstructures and crystal structures were characterized by scanning electron microscope and X-ray diffrac- tion. The effects of annealing on atomic interdiffusion, silicide formation, and microstructures in Fe/Si systems were analyzed.展开更多
The effect of high magnetic field on the atomic interdiffusion in Ni-Cu system was studied using the Cu/Ni/Cu diffusion couples. During the atomic interdiffusion in Ni-Cu system, it was found that the interdiffusion c...The effect of high magnetic field on the atomic interdiffusion in Ni-Cu system was studied using the Cu/Ni/Cu diffusion couples. During the atomic interdiffusion in Ni-Cu system, it was found that the interdiffusion coefficients increased with the increase of molar fraction of Ni atoms in the interdiffusion zones when the couples were annealed with or without the magnetic field. It was noted that all corresponding interdiffusion coefficients under the magnetic field are smaller than those without the magnetic field. The results demonstrate that the magnetic field retards the atomic interdiffusion in Ni-Cu system. This retardation is achieved through reducing the frequency factors but not changing the interdiffusion activation energies.展开更多
MCrAlY(M=Ni and/or Co)overlay coating is widely used as a protective coating against high temperature oxidation and corrosion.However,due to its big difference in chemical composition with the underlying superalloy,el...MCrAlY(M=Ni and/or Co)overlay coating is widely used as a protective coating against high temperature oxidation and corrosion.However,due to its big difference in chemical composition with the underlying superalloy,elements interdiffusion occurs inevitably.One of the direct results is the formation of interdiffusion zone(IDZ)and secondary reaction zone(SRZ)with a high density of fine topological closed-packed phases(TCPs),weakening dramatically the mechanical properties of the alloy substrate.It is by now the main problem of modern high-temperature metallic coatings,but there are still hardly any reports studying the formation,growth and transformation of IDZ and SRZ in deep,as well as the precipitation of TCPs.In this work,a typical NiCrAlY coating is deposited by arc ion plating on a single-crystal superalloy N5.Elements interdiffusion between them and its relationship on microstructure were clarified.Cr rather than Al from the coating diffuses into the alloy at high temperatures and segregates immediately beneath their interface,contributing largely to the formation of IDZ.Simultaneously,diffusion of Ni from the deep alloy to IDZ leads to the formation and continuous expansion of SRZ.展开更多
High-temperature chromium(Cr)-zirconium(Zr)interdiffusion commonly occurs in Cr-coated zircaloys applied for enhanced accident-tolerant fuel(ATF)claddings.Such interdiffusion changes the interfacial microstructure and...High-temperature chromium(Cr)-zirconium(Zr)interdiffusion commonly occurs in Cr-coated zircaloys applied for enhanced accident-tolerant fuel(ATF)claddings.Such interdiffusion changes the interfacial microstructure and thus the fracture mechanism of the coating under external loading.In this study,the interdiffusion behavior in a magnetron sputtered Cr coating deposited on a Zr-4 alloy was studied in a vacuum environment at 1160C.In addition,the effect of interdiffusion on the microcracking behavior of the Cr coating was determined by in situ three-point bending tests.The experimental results show that the interdiffusion behavior resulted in the formation of a ZrCr2 layer,accompanied by the consumption of Cr coating and interfacial roughening.The growth of the diffusion layer followed a nearly parabolic law with respect to annealing time,and the residual stress of the annealed coating decreased with increasing annealing time.Under external loading,a large number of cracks were generated in the brittle interlayer,and some interfacial cracks were formed and grew at the ZrCr2/Zr-4 interface.Despite the remarkable microcracks in the ZrCr2 layer,the vacuum-annealed Cr coating has significantly fewer cracks than the original coating,mainly because of the recrystallization of the coating during annealing.展开更多
NiCrAlY coatings are widely applied on various alloy components to enhance oxidation and/or corrosion resistance at high temperatures.However,elements interdiffusion occurs between them due to composition difference.A...NiCrAlY coatings are widely applied on various alloy components to enhance oxidation and/or corrosion resistance at high temperatures.However,elements interdiffusion occurs between them due to composition difference.Although various diffusion barriers(DBs)are reported,this problem is still far from completely solved as most ceramic barriers suffer from poor adherence,while the metallic barriers play a limited role.In this study,NiCrAlY coating was deposited onto a second-generation single-crystal superalloy by arc ion plating.A novel simple method is provided to address elements interdiffusion.By pre-oxidation at a moderate temperature,a thin scale of Ni(Co)O forms at the alloy surface.It transforms to be an alumina/NiCoCr alloy/alumina sandwich by an in-situ reaction with the overlaying NiCrAlY coating and the alloy substrate at high service temperatures,which offers good barrier ability in conjunction with strong adhesion.In the presence of such an alumina/alloy/alumina DB,the NiCrAlY coating provides high resistance to oxidation and scale spallation for the alloy substrate.展开更多
To reveal the influence of substrate/coating interdiffusion on the cyclic oxidation property of a metallic coating, cyclic oxida- tion behavior of an EB-PVD CoCrAIY coating on directionally solidified Ni-based superal...To reveal the influence of substrate/coating interdiffusion on the cyclic oxidation property of a metallic coating, cyclic oxida- tion behavior of an EB-PVD CoCrAIY coating on directionally solidified Ni-based superalloy DZ125 at 1 050℃ is investigated. The 40 μm thick CoCrA1Y coating has a cyclic oxidation life of around 160 h, and the oxidation constant is 1.915× 10^-7 mg4.cm^-8.s-1. However, severe spallation of the oxides containing Co, Cr, Ni, Ta and Ti occurs with longer cyclic oxidation. The degradation in oxidation resistance for the coating is related to the depletion of A1 due to the oxide spallation and interdiffu- sion. Severe interdiffusion between the coating and underlying substrate occurs at 1 050 ℃. The composition of the substrate has an important effect on the thermal cycling lifetime of the coating. The influencing mechanism is discussed.展开更多
To refrain the interdiffusion of elements while holding good oxidation resistance,a(Ni,Pt)Al/Ni composite coating was prepared by sequential treatments of electroplating Ni and Pt and successive gaseous aluminization....To refrain the interdiffusion of elements while holding good oxidation resistance,a(Ni,Pt)Al/Ni composite coating was prepared by sequential treatments of electroplating Ni and Pt and successive gaseous aluminization.In comparison with normal(Ni,Pt)Al coating,high-temperature performance of the composite coating was evaluated in isothermal oxidation test at 1100℃.Both the two coatings exhibited good resistance against high-temperature oxidation,but the interdiffusion of elements between composite coating and single-crystal(SC)superalloy substrate was greatly relieved,in which the thickness of secondary reaction zone(SRZ)and the amount of precipitated topologically close-packed phase in the SC alloy matrix were significantly decreased.Mechanisms responsible for delaying rate of coating degradation and SRZ growth/propagation are discussed.展开更多
Delafossite CuFeO_(2) is a promising photocathode material for cost-efficiently photoelectrochemical(PEC)water splitting,but the unfavorable conductivity and fast recombination dynamics of photogenerated carriers limi...Delafossite CuFeO_(2) is a promising photocathode material for cost-efficiently photoelectrochemical(PEC)water splitting,but the unfavorable conductivity and fast recombination dynamics of photogenerated carriers limit its PEC activity for water reduction.Here,we developed a heterostructure photocathode consisting of the Cu-doped NiO(Cu:NiO)hole selective layer(HSL)and Ni-doped CuFeO_(2)(Ni:CuFeO_(2))active layer by simply annealing a homogeneous Cu-Fe oxalate layer grown on the Ni film deposited on the fluorine doped tin oxide(FTO)substrate.The obtained heterostructure of Cu:NiO/Ni:CuFeO_(2) with enhanced charge carrier transportability and high-quality interface greatly promotes the separation of photogenerated carriers.Accordingly,the Cu:NiO/Ni:CuFeO_(2) photocathode exhibits a high photocurrent density of~0.9 mA·cm^(-2 )at 0.2 V(vs.reversible hydrogen electrode,RHE),outperforming most of the reported bare CuFeO_(2) photocathodes in the literature.And the photocurrent density can be further improved to 1.2 mA·cm^(-2) after decorating NiSx cocatalyst.展开更多
To investigate the interdiffusion behavior of Ge-modified silicide coatings on an Nb–Si-based alloy substrate,the coating was oxidized at 1250°C for 5,10,20,50,or 100 h.The interfacial diffusion between the(Nb,X...To investigate the interdiffusion behavior of Ge-modified silicide coatings on an Nb–Si-based alloy substrate,the coating was oxidized at 1250°C for 5,10,20,50,or 100 h.The interfacial diffusion between the(Nb,X)(Si,Ge)_2(X = Ti,Cr,Hf) coating and the Nb–Si based alloy was also examined.The transitional layer is composed of(Ti,Nb)_5(Si,Ge)_4 and a small amount of(Nb,X)_5(Si,Ge)_3.With increasing oxidation time,the thickness of the transitional layer increases because of the diffusion of Si from the outer layer to the substrate,which obeys a parabolic rate law.The parabolic growth rate constant of the transitional layer under oxidation conditions is 2.018 μm×h^(-1/2).Moreover,the interdiffusion coefficients of Si in the transitional layer were determined from the interdiffusion fluxes calculated directly from experimental concentration profiles.展开更多
Interdiffusion in the Fe203-TiO2 system was investigated by the diffusion couple method in the temperature range of 1323 to 1473 K. The diffusion concentration curves of Ti4＋ cations were obtained by electron probe m...Interdiffusion in the Fe203-TiO2 system was investigated by the diffusion couple method in the temperature range of 1323 to 1473 K. The diffusion concentration curves of Ti4＋ cations were obtained by electron probe microanalysis, according to which the Boltzmann-Matano method optimized by Broeder was used to calculate the interdiffusion coeffi- cients. The interdiffusion coefficients almost increased linearly with the mole fraction of Ti4＋ cations increasing, and they were in the range of 10-12-10-11cm2-s-1. The increase of temperature could also lead to the increase of the interdiffusion coefficients at a constant concentration of Ti4＋ cations. It was also found that the thickness growth of the diffusion layer obeyed the parabolic rate law.展开更多
The interdiffusion interface microstructures and composition evolution of Ni-Al-Cr/Ni-Al-Cr layered alloys under different temperature gradients were studied using phase-field simulation.A precipitate-free zone forms ...The interdiffusion interface microstructures and composition evolution of Ni-Al-Cr/Ni-Al-Cr layered alloys under different temperature gradients were studied using phase-field simulation.A precipitate-free zone forms near the interface of the layered alloys,and the interface does not move with time under temperature gradients.When Cr concentrations in the alloy layers are different,Al diffuses from a low-to high-temperature region,whereas Cr from a high-to low-temperature region.The width of the precipitate-free zone changes from 0.5 to 2.5μm as the temperature gradient changes fromΔT=0.625 K·μm^(−1) to 1.250 K·μm^(−1);the width of the interdiffusion zone is also enlarged.Additionally,the temperature gradient promotes the interdiffusion of elements through the interface.In contrast,when the initial Al concentration is different in the alloy layers,an uphill diffusion of Al occurs,which is driven by the chemical potential of Al.展开更多
Interdiffusion coefficients at 950℃ and 1050℃ are calculated by Wagner analysis method as a function of composition of β-NiAI phase. The β-NiAI phase is formed by pack cementation on surface of superalloy. Results...Interdiffusion coefficients at 950℃ and 1050℃ are calculated by Wagner analysis method as a function of composition of β-NiAI phase. The β-NiAI phase is formed by pack cementation on surface of superalloy. Results of the calculation show that interdiffusion coefficients in β-NiAI phase strongly depend on the compositions and vary over several orders of magnitude. Compared with the interdiffusion coefficients in the stoichiometric β-NiAI phase, the interdiffusion coefficients in β-NiAI phase formed on superalloy is obviously small, probably due to the composition, complicated microstructure and precipitates. However, it could be seen clearly that the shapes of the diffusivity curves are very similar to each other. The similarity of the diffusion curves and the difference between interdiffusion coefficients imply that the compositions, microstructures and precipitates of superalloy have a distinctly adverse effect on the interdiffusion of Ni and Al atoms during aluminization, but do not change the essential characteristics of β-NiAI phase.展开更多
A repeated interdiffusion method is described for phase-stable and high-quality （FA,MA）PbI3 film. The crys- tallization and growth of the perovskite films can be well controlled by adjusting the reactant concentrati...A repeated interdiffusion method is described for phase-stable and high-quality （FA,MA）PbI3 film. The crys- tallization and growth of the perovskite films can be well controlled by adjusting the reactant concentrations. With this method, dense, smooth perovskite films with large crystals have been obtained. Finally, a PCE of 16.5% as well as a steady-state efficiency of 16.3% is achieved in the planar perovskite solar cell.展开更多
The miscibility of poly（vinyl chloride）/poly（n-butyl methacrylate） （PVC/PnBMA） blend and the interdiffusion kinetics of PVC/PnBMA laminates have been investigated by differential scanning calorimetry （DSC） and...The miscibility of poly（vinyl chloride）/poly（n-butyl methacrylate） （PVC/PnBMA） blend and the interdiffusion kinetics of PVC/PnBMA laminates have been investigated by differential scanning calorimetry （DSC） and atomic force microscopy （AFM）, respectively. This blend exhibited a lower critical solution temperature behavior. Below 120 ℃, DSC results showed each blend with different PVC contents exhibited only a single glass transition temperature which increased with PVC content, indicating that PVC and PnBMA were miscible. After PVC/PnBMA laminates were annealed at different temperature for different time, a smooth cross-section across interface was prepared by ultramicrotoming. Combined with topography and phase images of tapping mode AFM, the relative concentration profile, interface width and the relationship between interface width and annealing time could be obtained. In a regime of rubbery/rubbery interdiffusion, the diffusion obeyed a typical Fickian Case-I behavior where the interface width was proportional to the square root of annealing time. The mutual diffusion coefficient was in good agreement with that obtained from DSC and positron annihilation lifetime spectroscopy. However, in the regime of glassy/rubbery interdiffusion, the diffusion followed a typical Case-II behavior where the interface width was proportional to annealing time. These results imply that AFM is a reliable and powerful tool for the investigation of polymer/polymer interdiffusion at a level of polymer chain size.展开更多
The effect of interaction among γ′ ordered domains on the interdiffusion process in γ＋γ′ and γ＋γ′/γ＋γ′ diffusion couples is investigated by using the phase-field method, in which bulk free energy and mob...The effect of interaction among γ′ ordered domains on the interdiffusion process in γ＋γ′ and γ＋γ′/γ＋γ′ diffusion couples is investigated by using the phase-field method, in which bulk free energy and mobility are linked with thermodynamic and kinetic databases. Simulated results show that the interaction among γ′ ordered domains has great influence on the microstructure, the interdiffnsion velocity and the volume fraction ofγ′ phase on both sides of the diffusion couples.展开更多
In accordance with the definition of diffusivity, the origin of coordinate system of the original diffusion equation is set at a point in the solvent material. Kirkendall revealed that Cu atoms, Zn atoms and vacancies...In accordance with the definition of diffusivity, the origin of coordinate system of the original diffusion equation is set at a point in the solvent material. Kirkendall revealed that Cu atoms, Zn atoms and vacancies move simultaneously in the interdiffusion region. This indicates that the original diffusion equation is a moving coordinate system for the experimentation system outside the diffusion region. The diffusion region space which means vacancies and interstices among atoms plays an important role in the diffusion phenomena. The theoretical equation of the Kirkendall effect is reasonably obtained as a shift between coordinate systems of the diffusion equation. The situation is similar to the well-known Doppler effect in the wave equation. Boltzmann transformed the original diffusion equation of a binary system into the nonlinear ordinary differential equation in accordance with the parabolic law. In the previous works, the solutions of the diffusion equation transformed by Boltzmann were analytically obtained and we found that the well-known Darken equation is mathematically wrong. In the present study, we found that the so-called intrinsic diffusivity corresponds in appearance to the physical solution obtained previously. However, the intrinsic diffusivity itself conceived in the diffusion research history is essentially nonexistent.展开更多
The nonlinear diffusion equation for a binary system interdiffusion was analytically solved in the previous work. The theoretical relation of Kirkendall effect was also derived in the previous work. These new results ...The nonlinear diffusion equation for a binary system interdiffusion was analytically solved in the previous work. The theoretical relation of Kirkendall effect was also derived in the previous work. These new results have not yet been concretely applied to actual diffusion problems. In the present work, it is revealed that the previous results reproduce the experimental concentration profile by taking account of the movement of diffusion region space. It is thus actually confirmed that any problems of binary system interdiffusion can be solved by the new analytical method if even diffusivities of self-diffusion and impurity diffusion in the materials concerned are given. The method for solving interdiffusion problems of many elements system, which is extremely important for the development of new useful materials, is also reasonably discussed. Further, it is revealed that the concept of intrinsic diffusion is unsuitable for the diffusion theory. The fundamental theory of diffusion discussed here will be useful for analyzing actual diffusion problems in future.展开更多
A novel NiAlTa blade tip protective coating is designed and its oxidation,hot corrosion,and interdiffusion with DD5 single-crystal superalloys are investigated.NiAlTa coatings exhibit low oxidation rates.The dragging ...A novel NiAlTa blade tip protective coating is designed and its oxidation,hot corrosion,and interdiffusion with DD5 single-crystal superalloys are investigated.NiAlTa coatings exhibit low oxidation rates.The dragging effect of Ta on Al hinders the external diffusion of Al.Ta that accumulates at the Al_(2)O_(3)grain boundaries reduces the internal diffusion of O by combining or reacting with it.NaCl aggravates the hot corrosion through self ustaining cycles of chlorination/oxidation.β-NiAl phase fails first as a diffusion channel for the corrosive medium.Significant element interdiffusion occurs.An interdiffusion zone and a secondary reaction zone are formed.Interdiffusion changes the percentage of elements,causing a phase transition of the coating.The volume change caused by the phase transition induces bulging and cracking of the oxide film.Furthermore,the oxidation,hot corrosion,and interdiffusion mechanisms are discussed.展开更多
Precise determination of cation diffusivity in garnet can provide critical information for quantitatively understanding the timescales and thermodynamics of various geological processes,but very few studies have been ...Precise determination of cation diffusivity in garnet can provide critical information for quantitatively understanding the timescales and thermodynamics of various geological processes,but very few studies have been performed for Fe-Mn interdiffusion.In this study,Fe-Mn interdiffusion rates in natural single crystals of Mn-bearing garnet with 750 ppm H2O are determined at 6 GPa and 1273-1573 K in a Kawai-type multi-anvil apparatus.Diffusion profiles were acquired by electron microprobe and fitted using Boltzmann-Matano equation.The experimental results show that the Fe-Mn interdiffusion coefficient(DFe-Mn)slightly decreases with increasing XFe.The experimentally determined DFe-Mn in Mn-bearing garnet can be fitted by the Arrhenius equation:DFe-Mn(m2/s)=D0XFenexp(-E*/RT),where E*=(1-XFe)E*Mn+XFeE*Fe,D0=8.06-6.04+9.87×10-9 m2/s,E*Mn=248±27 KJ/mol,E*Fe=226±59 KJ/mol,n=-1.36±0.51.The comparing the present results with previous experimental data suggest that water can greatly enhance the DFe-Mn in garnet.Our results indicate that the time required for homogenization of the compositional zoning of a garnet is much shorter than previously thought.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.52201082 and 51971139)the Science Center for Gas Turbine Project(No.P2022-A-I-002-001)+1 种基金the Shanghai Sailing Program(No.22YF1419200)sponsored by the Chenguang Program supported by Shanghai Education Development Foundation and Shanghai Municipal Education Commission(No.21CGA10).
文摘The oxidation and interdiffusion behavior of a novel AlCoCrFeNiY bond coat deposited on a directionally solidified Ni-based superalloy were systematically studied at 1050,1100 and 1150°C,and compared with a conventional NiCoCrAlY coating deposited on the same substrate.The AlCoCrFeNiY bond coat exhibits lower oxide growth rates due to its large columnar grains and low Al activity at the oxide scale/bond coat interface.Meanwhile,AlCoCrFeNiY has higher resistance to oxide spallation than NiCoCrAlY,which is attributed to the formation of a clean and defect-free metal/oxide interface.Significant interdiffusion occurs across the AlCoCrFeNiY/superalloy substrate interface.Our experimental evidence and thermody-namic modelling suggest that Fe accelerates interdiffusion and destabilizes theγ’phase,thereby causing the formation of a thick andγ’-depleted interdiffusion zone.In addition,the AlCoCrFeNiY bond coat un-dergoes more Al depletion and subsequentβtoγtransformation compared with NiCoCrAlY.Based on the findings in this work,a novel AlCoCrFeNiY/NiCoCrAlY double-layer bond coat was designed,tested and validated to achieve optimal balance between oxidation and interdiffusion.
文摘Pure metal Fe films with thickness of about 100nm were deposited on Si （100） substrates by DC magnetron sputtering. Annealing was subsequently performed in a vacuum furnace in the temperature range of 600-1000℃ for 2h. The samples were characterized by means of Rutherford backscattering （RBS） with 3MeV carbon ions. The RBS data were fitted with SIMNRA 6.0, and the results show the atomic interdiffusion in Fe/Si systems. The microstructures and crystal structures were characterized by scanning electron microscope and X-ray diffrac- tion. The effects of annealing on atomic interdiffusion, silicide formation, and microstructures in Fe/Si systems were analyzed.
基金Project(2011CB012803) supported by the National Basic Research Program of ChinaProject(NCET-10-0278) supported by Program for New Century Excellent Talents in University,China
文摘The effect of high magnetic field on the atomic interdiffusion in Ni-Cu system was studied using the Cu/Ni/Cu diffusion couples. During the atomic interdiffusion in Ni-Cu system, it was found that the interdiffusion coefficients increased with the increase of molar fraction of Ni atoms in the interdiffusion zones when the couples were annealed with or without the magnetic field. It was noted that all corresponding interdiffusion coefficients under the magnetic field are smaller than those without the magnetic field. The results demonstrate that the magnetic field retards the atomic interdiffusion in Ni-Cu system. This retardation is achieved through reducing the frequency factors but not changing the interdiffusion activation energies.
基金the National Natural Science Foundation of China Nos.51671053 and 51801021the Ministry of Industry and Information Technology Project No.MJ-2017-J-99)。
文摘MCrAlY(M=Ni and/or Co)overlay coating is widely used as a protective coating against high temperature oxidation and corrosion.However,due to its big difference in chemical composition with the underlying superalloy,elements interdiffusion occurs inevitably.One of the direct results is the formation of interdiffusion zone(IDZ)and secondary reaction zone(SRZ)with a high density of fine topological closed-packed phases(TCPs),weakening dramatically the mechanical properties of the alloy substrate.It is by now the main problem of modern high-temperature metallic coatings,but there are still hardly any reports studying the formation,growth and transformation of IDZ and SRZ in deep,as well as the precipitation of TCPs.In this work,a typical NiCrAlY coating is deposited by arc ion plating on a single-crystal superalloy N5.Elements interdiffusion between them and its relationship on microstructure were clarified.Cr rather than Al from the coating diffuses into the alloy at high temperatures and segregates immediately beneath their interface,contributing largely to the formation of IDZ.Simultaneously,diffusion of Ni from the deep alloy to IDZ leads to the formation and continuous expansion of SRZ.
基金the Guangdong Major Project of Basic and Applied Basic Research(No.2019B030302011)National Natural Science Foundation of China(Nos.52005523,U2032143,11902370)+3 种基金International Sci&Tech Cooperation Program of GuangDong Province(No.2019A050510022)Key Research Project of GuangDong Province(Nos.2019B010943001 and 2017B020235001)China Postdoctoral Science Foundation(Nos.2019M653173 and 2019TQ0374)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(No.2021qntd12).
文摘High-temperature chromium(Cr)-zirconium(Zr)interdiffusion commonly occurs in Cr-coated zircaloys applied for enhanced accident-tolerant fuel(ATF)claddings.Such interdiffusion changes the interfacial microstructure and thus the fracture mechanism of the coating under external loading.In this study,the interdiffusion behavior in a magnetron sputtered Cr coating deposited on a Zr-4 alloy was studied in a vacuum environment at 1160C.In addition,the effect of interdiffusion on the microcracking behavior of the Cr coating was determined by in situ three-point bending tests.The experimental results show that the interdiffusion behavior resulted in the formation of a ZrCr2 layer,accompanied by the consumption of Cr coating and interfacial roughening.The growth of the diffusion layer followed a nearly parabolic law with respect to annealing time,and the residual stress of the annealed coating decreased with increasing annealing time.Under external loading,a large number of cracks were generated in the brittle interlayer,and some interfacial cracks were formed and grew at the ZrCr2/Zr-4 interface.Despite the remarkable microcracks in the ZrCr2 layer,the vacuum-annealed Cr coating has significantly fewer cracks than the original coating,mainly because of the recrystallization of the coating during annealing.
基金financially supported by the National Natural Science Foundation of China(No.51671053)the Natural Science Foundation of Liaoning Province of China(No.2019-ZD-0264)the Ministry of Industry and Information Technology Project(No.MJ-2017-J-99)。
文摘NiCrAlY coatings are widely applied on various alloy components to enhance oxidation and/or corrosion resistance at high temperatures.However,elements interdiffusion occurs between them due to composition difference.Although various diffusion barriers(DBs)are reported,this problem is still far from completely solved as most ceramic barriers suffer from poor adherence,while the metallic barriers play a limited role.In this study,NiCrAlY coating was deposited onto a second-generation single-crystal superalloy by arc ion plating.A novel simple method is provided to address elements interdiffusion.By pre-oxidation at a moderate temperature,a thin scale of Ni(Co)O forms at the alloy surface.It transforms to be an alumina/NiCoCr alloy/alumina sandwich by an in-situ reaction with the overlaying NiCrAlY coating and the alloy substrate at high service temperatures,which offers good barrier ability in conjunction with strong adhesion.In the presence of such an alumina/alloy/alumina DB,the NiCrAlY coating provides high resistance to oxidation and scale spallation for the alloy substrate.
基金National Natural Science Foundation of China (50731001, 51071013, 51001032)National Basic Research Program of China (2010CB631200)
文摘To reveal the influence of substrate/coating interdiffusion on the cyclic oxidation property of a metallic coating, cyclic oxida- tion behavior of an EB-PVD CoCrAIY coating on directionally solidified Ni-based superalloy DZ125 at 1 050℃ is investigated. The 40 μm thick CoCrA1Y coating has a cyclic oxidation life of around 160 h, and the oxidation constant is 1.915× 10^-7 mg4.cm^-8.s-1. However, severe spallation of the oxides containing Co, Cr, Ni, Ta and Ti occurs with longer cyclic oxidation. The degradation in oxidation resistance for the coating is related to the depletion of A1 due to the oxide spallation and interdiffu- sion. Severe interdiffusion between the coating and underlying substrate occurs at 1 050 ℃. The composition of the substrate has an important effect on the thermal cycling lifetime of the coating. The influencing mechanism is discussed.
基金financially supported by the National Natural Science Foundation of China (Nos.51671202 and 51301184)the "Liaoning BaiQianWan Talents" Program
文摘To refrain the interdiffusion of elements while holding good oxidation resistance,a(Ni,Pt)Al/Ni composite coating was prepared by sequential treatments of electroplating Ni and Pt and successive gaseous aluminization.In comparison with normal(Ni,Pt)Al coating,high-temperature performance of the composite coating was evaluated in isothermal oxidation test at 1100℃.Both the two coatings exhibited good resistance against high-temperature oxidation,but the interdiffusion of elements between composite coating and single-crystal(SC)superalloy substrate was greatly relieved,in which the thickness of secondary reaction zone(SRZ)and the amount of precipitated topologically close-packed phase in the SC alloy matrix were significantly decreased.Mechanisms responsible for delaying rate of coating degradation and SRZ growth/propagation are discussed.
基金financially supported by the National Key Research and Development Program of China(No.2021YFA1500800)the National Natural Science Foundation of China(Nos.51825204,52072377,521888101 and 51402199)+6 种基金the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2020192)the International Partnership Program of Chinese Academy of Sciences(No.174321KYSB20200005)China Postdoctoral Science Foundation(No.2017M621137)Liaoning Revitalization Talents Program(No.XLYC2007193)the Natural Science Foundation of Liaoning Province(Nos.2021-MS-014 and 2021NLTS1210)the University Innovation Talent Foundation of Liaoning Province(No.LR2018074)the State Key Laboratory of Fine Chemicals,Dalian University of Technology(No.KF1708)。
文摘Delafossite CuFeO_(2) is a promising photocathode material for cost-efficiently photoelectrochemical(PEC)water splitting,but the unfavorable conductivity and fast recombination dynamics of photogenerated carriers limit its PEC activity for water reduction.Here,we developed a heterostructure photocathode consisting of the Cu-doped NiO(Cu:NiO)hole selective layer(HSL)and Ni-doped CuFeO_(2)(Ni:CuFeO_(2))active layer by simply annealing a homogeneous Cu-Fe oxalate layer grown on the Ni film deposited on the fluorine doped tin oxide(FTO)substrate.The obtained heterostructure of Cu:NiO/Ni:CuFeO_(2) with enhanced charge carrier transportability and high-quality interface greatly promotes the separation of photogenerated carriers.Accordingly,the Cu:NiO/Ni:CuFeO_(2) photocathode exhibits a high photocurrent density of~0.9 mA·cm^(-2 )at 0.2 V(vs.reversible hydrogen electrode,RHE),outperforming most of the reported bare CuFeO_(2) photocathodes in the literature.And the photocurrent density can be further improved to 1.2 mA·cm^(-2) after decorating NiSx cocatalyst.
基金financially supported by the National Natural Science Foundation of China(No.51431003)the Joint Funds of the National Natural Science Foundation of China(No.U1435201)
文摘To investigate the interdiffusion behavior of Ge-modified silicide coatings on an Nb–Si-based alloy substrate,the coating was oxidized at 1250°C for 5,10,20,50,or 100 h.The interfacial diffusion between the(Nb,X)(Si,Ge)_2(X = Ti,Cr,Hf) coating and the Nb–Si based alloy was also examined.The transitional layer is composed of(Ti,Nb)_5(Si,Ge)_4 and a small amount of(Nb,X)_5(Si,Ge)_3.With increasing oxidation time,the thickness of the transitional layer increases because of the diffusion of Si from the outer layer to the substrate,which obeys a parabolic rate law.The parabolic growth rate constant of the transitional layer under oxidation conditions is 2.018 μm×h^(-1/2).Moreover,the interdiffusion coefficients of Si in the transitional layer were determined from the interdiffusion fluxes calculated directly from experimental concentration profiles.
基金financially supported by the National Natural Science Foundation of China (No. 51090384)
文摘Interdiffusion in the Fe203-TiO2 system was investigated by the diffusion couple method in the temperature range of 1323 to 1473 K. The diffusion concentration curves of Ti4＋ cations were obtained by electron probe microanalysis, according to which the Boltzmann-Matano method optimized by Broeder was used to calculate the interdiffusion coeffi- cients. The interdiffusion coefficients almost increased linearly with the mole fraction of Ti4＋ cations increasing, and they were in the range of 10-12-10-11cm2-s-1. The increase of temperature could also lead to the increase of the interdiffusion coefficients at a constant concentration of Ti4＋ cations. It was also found that the thickness growth of the diffusion layer obeyed the parabolic rate law.
基金financially supported by the National Natural Science Foundation of China(No.51571122)the Fundamental Research Funds for the Central Universities(No.30921013107)。
文摘The interdiffusion interface microstructures and composition evolution of Ni-Al-Cr/Ni-Al-Cr layered alloys under different temperature gradients were studied using phase-field simulation.A precipitate-free zone forms near the interface of the layered alloys,and the interface does not move with time under temperature gradients.When Cr concentrations in the alloy layers are different,Al diffuses from a low-to high-temperature region,whereas Cr from a high-to low-temperature region.The width of the precipitate-free zone changes from 0.5 to 2.5μm as the temperature gradient changes fromΔT=0.625 K·μm^(−1) to 1.250 K·μm^(−1);the width of the interdiffusion zone is also enlarged.Additionally,the temperature gradient promotes the interdiffusion of elements through the interface.In contrast,when the initial Al concentration is different in the alloy layers,an uphill diffusion of Al occurs,which is driven by the chemical potential of Al.
文摘Interdiffusion coefficients at 950℃ and 1050℃ are calculated by Wagner analysis method as a function of composition of β-NiAI phase. The β-NiAI phase is formed by pack cementation on surface of superalloy. Results of the calculation show that interdiffusion coefficients in β-NiAI phase strongly depend on the compositions and vary over several orders of magnitude. Compared with the interdiffusion coefficients in the stoichiometric β-NiAI phase, the interdiffusion coefficients in β-NiAI phase formed on superalloy is obviously small, probably due to the composition, complicated microstructure and precipitates. However, it could be seen clearly that the shapes of the diffusivity curves are very similar to each other. The similarity of the diffusion curves and the difference between interdiffusion coefficients imply that the compositions, microstructures and precipitates of superalloy have a distinctly adverse effect on the interdiffusion of Ni and Al atoms during aluminization, but do not change the essential characteristics of β-NiAI phase.
基金supported by the National Key Basic Research Program (No.2012CB932903)Natural Science Foundation of China (Nos. 51402348,51421002,91433205,21173260,11474333 and 91233202)
文摘A repeated interdiffusion method is described for phase-stable and high-quality （FA,MA）PbI3 film. The crys- tallization and growth of the perovskite films can be well controlled by adjusting the reactant concentrations. With this method, dense, smooth perovskite films with large crystals have been obtained. Finally, a PCE of 16.5% as well as a steady-state efficiency of 16.3% is achieved in the planar perovskite solar cell.
基金supported by the Major International (Regional) Joint Research Project of the National Natural Science Foundation of China (No. 51210004)the National Natural Science Foundation of China (No. 50903035)Chinese Ministry of Education (NCET-11-0174)
文摘The miscibility of poly（vinyl chloride）/poly（n-butyl methacrylate） （PVC/PnBMA） blend and the interdiffusion kinetics of PVC/PnBMA laminates have been investigated by differential scanning calorimetry （DSC） and atomic force microscopy （AFM）, respectively. This blend exhibited a lower critical solution temperature behavior. Below 120 ℃, DSC results showed each blend with different PVC contents exhibited only a single glass transition temperature which increased with PVC content, indicating that PVC and PnBMA were miscible. After PVC/PnBMA laminates were annealed at different temperature for different time, a smooth cross-section across interface was prepared by ultramicrotoming. Combined with topography and phase images of tapping mode AFM, the relative concentration profile, interface width and the relationship between interface width and annealing time could be obtained. In a regime of rubbery/rubbery interdiffusion, the diffusion obeyed a typical Fickian Case-I behavior where the interface width was proportional to the square root of annealing time. The mutual diffusion coefficient was in good agreement with that obtained from DSC and positron annihilation lifetime spectroscopy. However, in the regime of glassy/rubbery interdiffusion, the diffusion followed a typical Case-II behavior where the interface width was proportional to annealing time. These results imply that AFM is a reliable and powerful tool for the investigation of polymer/polymer interdiffusion at a level of polymer chain size.
基金Project supported by the National Natural Science Foundation of China (Grant No 50401013)the National Defense Preresearch Foundation of China (Grant No 9140A12020108HK0333)
文摘The effect of interaction among γ′ ordered domains on the interdiffusion process in γ＋γ′ and γ＋γ′/γ＋γ′ diffusion couples is investigated by using the phase-field method, in which bulk free energy and mobility are linked with thermodynamic and kinetic databases. Simulated results show that the interaction among γ′ ordered domains has great influence on the microstructure, the interdiffnsion velocity and the volume fraction ofγ′ phase on both sides of the diffusion couples.
文摘In accordance with the definition of diffusivity, the origin of coordinate system of the original diffusion equation is set at a point in the solvent material. Kirkendall revealed that Cu atoms, Zn atoms and vacancies move simultaneously in the interdiffusion region. This indicates that the original diffusion equation is a moving coordinate system for the experimentation system outside the diffusion region. The diffusion region space which means vacancies and interstices among atoms plays an important role in the diffusion phenomena. The theoretical equation of the Kirkendall effect is reasonably obtained as a shift between coordinate systems of the diffusion equation. The situation is similar to the well-known Doppler effect in the wave equation. Boltzmann transformed the original diffusion equation of a binary system into the nonlinear ordinary differential equation in accordance with the parabolic law. In the previous works, the solutions of the diffusion equation transformed by Boltzmann were analytically obtained and we found that the well-known Darken equation is mathematically wrong. In the present study, we found that the so-called intrinsic diffusivity corresponds in appearance to the physical solution obtained previously. However, the intrinsic diffusivity itself conceived in the diffusion research history is essentially nonexistent.
文摘The nonlinear diffusion equation for a binary system interdiffusion was analytically solved in the previous work. The theoretical relation of Kirkendall effect was also derived in the previous work. These new results have not yet been concretely applied to actual diffusion problems. In the present work, it is revealed that the previous results reproduce the experimental concentration profile by taking account of the movement of diffusion region space. It is thus actually confirmed that any problems of binary system interdiffusion can be solved by the new analytical method if even diffusivities of self-diffusion and impurity diffusion in the materials concerned are given. The method for solving interdiffusion problems of many elements system, which is extremely important for the development of new useful materials, is also reasonably discussed. Further, it is revealed that the concept of intrinsic diffusion is unsuitable for the diffusion theory. The fundamental theory of diffusion discussed here will be useful for analyzing actual diffusion problems in future.
基金financially supported by the Strategic Priority Research Program of the Chinese Academy of Sciences,Grant(No.XDB 047010204)Liaoning Key Laboratory of Aero-engine Material Tribology for both financial and facility support
文摘A novel NiAlTa blade tip protective coating is designed and its oxidation,hot corrosion,and interdiffusion with DD5 single-crystal superalloys are investigated.NiAlTa coatings exhibit low oxidation rates.The dragging effect of Ta on Al hinders the external diffusion of Al.Ta that accumulates at the Al_(2)O_(3)grain boundaries reduces the internal diffusion of O by combining or reacting with it.NaCl aggravates the hot corrosion through self ustaining cycles of chlorination/oxidation.β-NiAl phase fails first as a diffusion channel for the corrosive medium.Significant element interdiffusion occurs.An interdiffusion zone and a secondary reaction zone are formed.Interdiffusion changes the percentage of elements,causing a phase transition of the coating.The volume change caused by the phase transition induces bulging and cracking of the oxide film.Furthermore,the oxidation,hot corrosion,and interdiffusion mechanisms are discussed.
基金supported by the National Natural Science Foundation of China (41973056,41773056)Key Research Program of Frontier Sciences of CAS (ZDBS-LY-DQC015)to B.Zhang+1 种基金the Fundamental Research Funds for the Central Universities (K20210168)Data presented as part of this study are available from Zenodo (https://doi.org/10.5281/zenodo.7080353).
文摘Precise determination of cation diffusivity in garnet can provide critical information for quantitatively understanding the timescales and thermodynamics of various geological processes,but very few studies have been performed for Fe-Mn interdiffusion.In this study,Fe-Mn interdiffusion rates in natural single crystals of Mn-bearing garnet with 750 ppm H2O are determined at 6 GPa and 1273-1573 K in a Kawai-type multi-anvil apparatus.Diffusion profiles were acquired by electron microprobe and fitted using Boltzmann-Matano equation.The experimental results show that the Fe-Mn interdiffusion coefficient(DFe-Mn)slightly decreases with increasing XFe.The experimentally determined DFe-Mn in Mn-bearing garnet can be fitted by the Arrhenius equation:DFe-Mn(m2/s)=D0XFenexp(-E*/RT),where E*=(1-XFe)E*Mn+XFeE*Fe,D0=8.06-6.04+9.87×10-9 m2/s,E*Mn=248±27 KJ/mol,E*Fe=226±59 KJ/mol,n=-1.36±0.51.The comparing the present results with previous experimental data suggest that water can greatly enhance the DFe-Mn in garnet.Our results indicate that the time required for homogenization of the compositional zoning of a garnet is much shorter than previously thought.
