The formation mechanisms and growth kinetics of Al3 Ni and Al3Ni2 in Ni-Al diffusion couple prepared by electrodeposition of Ni on Al substrate were investigated. The nickel coating with 20 μm thickness was applied o...The formation mechanisms and growth kinetics of Al3 Ni and Al3Ni2 in Ni-Al diffusion couple prepared by electrodeposition of Ni on Al substrate were investigated. The nickel coating with 20 μm thickness was applied on 6061 aluminum alloy by direct current electroplating. The samples were then heat-treated for different durations at 450, 500 and 550 °C under argon atmosphere. The intermetallic phases were identified by means of scanning electron microscopy（SEM）, energy dispersive spectrometry（EDS） and X-ray diffraction（XRD）. The results showed that the formation of intermetallic phases consisted of two important steps. The first step was the lateral growth of intermetallic phase from separate sites, resulting in the formation of a continuous layer. The second step was the growth of the continuous intermetallic layer in the direction perpendicular to the interface. However, excessive increase in thickness of intermetallic phases led to the detachment of reaction products, i.e., Al3 Ni and Al3Ni2, from the substrate. It was also observed that aluminum was the dominant diffusing element during Al3 Ni growth, while nickel diffusion was dominant during Al3Ni2 growth. The growth kinetics of both Al3 Ni and Al3Ni2 phases obeyed a parabolic law.展开更多
Instantaneous reactions of Al,Mn,Zn,Zr and Y with Ni by mixing the prepared Mg-8Al-0.4Mn,Mg-6Zn-2Y-0.5Zr and Mg-0.6Ni melts were investigated in this work to reveal the underlying mechanisms of their effects on the re...Instantaneous reactions of Al,Mn,Zn,Zr and Y with Ni by mixing the prepared Mg-8Al-0.4Mn,Mg-6Zn-2Y-0.5Zr and Mg-0.6Ni melts were investigated in this work to reveal the underlying mechanisms of their effects on the removal of Ni impurity.The results indicate three Ni-containing intermetallics,namely Al_(4)NiY,Al_(4)Ni(Y,Zr)and Al_(31)Ni_(2)Mn_(6).The former two phases present lath-like and have a relatively larger size(>20μm in length)than the latest one which is granular with the diameter of∼120 nm.This illustrates that Al and Y(/Zr)can efficiently remove Ni by forming Al_(4)NiY or Al_(4)Ni(Y,Zr)which would precipitate to the bottom of the melt.Furthermore,adding Y into Mg-Al based alloys can simultaneously remove Fe and Ni,which contributes their excellent corrosion resistance.Finally,this paper proposes two methods helped to efficiently remove Ni for both Mg-Al based alloys and Al-free Mg alloys,and both of them are also benefit to improve alloys’strength.展开更多
Enhancing the stability of Pt-based electrocatalysts for the sluggish cathodic oxygen reduction reaction(ORR)is critical for proton exchange membrane fuel cells(PEMFCs).Herein,high-entropy intermetallic(HEI)L1_(2)-Pt(...Enhancing the stability of Pt-based electrocatalysts for the sluggish cathodic oxygen reduction reaction(ORR)is critical for proton exchange membrane fuel cells(PEMFCs).Herein,high-entropy intermetallic(HEI)L1_(2)-Pt(FeCoNiCuZn)3is designed for durable ORR catalysis.Benefiting from the unique HEI structure and the enhanced intermetallic phase stability,Pt(FeCoNiCuZn)3/C nanoparticles demonstrate significantly improved stability over Pt/C and PtCu_(3)/C catalysts.The Pt(FeCoNiCuZn)3/C exhibits a negligible decay of the half-wave potential during 30,000 potential cycles from 0.6 to 1.0 V,whereas Pt/C and PtCu_(3)/C are negatively shifted by 46 and 36 m V,respectively.Even after 10,000 cycles at potential up to 1.5 V,the mass activity of Pt(FeCoNiCuZn)3/C still shows~70%retention.As evidenced by the structural characterizations,the HEI structure of Pt(FeCoNiCuZn)3/C is well maintained,while PtCu_(3)/C nanoparticles undergo severe Cu leaching and particle growth.In addition,when assembled Pt(FeCoNiCuZn)3/C as the cathode in high-temperature PEMFC of 160℃,the H_(2)-O_(2)fuel cell delivers almost no degradation even after operating for 150 h,demonstrating the potential for fuel cell applications.This work provides a facile design strategy for the development of high-performance ultrastable electrocatalysts.展开更多
A novel approach to produce an intermetallic composite coating was put forward.The microstructure,microhardness,and dry-sliding wear behavior of the composite coating were investigated using X-ray diffraction （XRD）,...A novel approach to produce an intermetallic composite coating was put forward.The microstructure,microhardness,and dry-sliding wear behavior of the composite coating were investigated using X-ray diffraction （XRD）,scanning electron microscopy （SEM）,energy dispersive spectrum （EDS） analysis,microhardness test,and ball-on-disc wear experiment.XRD results indicate that some new phases FeAl,Fe0.23Ni0.77Al,and Ni3Al exit in the composite coating with the Al2O3 addition.SEM results show that the coating is bonded with carbon steel metallurgically and exhibits typical rapid directional solidification structures.The Cr7C3 carbide and intermetallic compounds co-reinforced composite coating has a high average hardness and exhibits an excellent wear resistance under dry-sliding wear test compared with the Cr7C3 carbide-reinforced composite coating.The formation mechanism of the intermetallic compounds was also investigated.展开更多
In this study, cold spraying（CS） was used to deposit a mixture of nickel-coated graphite and 40 vol.% Al powder（Ni-Gr/Al） on a steel substrate aiming to effectively preserve a certain volume fraction of graphite i...In this study, cold spraying（CS） was used to deposit a mixture of nickel-coated graphite and 40 vol.% Al powder（Ni-Gr/Al） on a steel substrate aiming to effectively preserve a certain volume fraction of graphite in the deposited Ni-Gr/Al composite coating. The microstructure of the as-sprayed coating and the effect of post-spray heat-treatment（PSHT） temperatures on the in-situ formation of Ni-Al intermetallic phases in coating were studied. The tribological behaviors of the as-sprayed coating and the PSHTed coating under 450？C were tested at 25？C, while the as-sprayed coating was tested at 450？C for comparison.As a result, the Ni-Gr particles showed a homogenous distribution in the coating. The multilayer Ni-Al intermetallics-coated graphite/Al composite coating was achieved in situ after the PSHT of 450？C, where the graphite did decompose at 550？C leaving big pores in the coating. The coefficients of friction（COF）of the CSed coating and the PSHTed coating were measured at 450？C as well as 25？C, which showed a similar tendency, much higher than that of the CSed coating tested at 25？C. The lubrication phase（graphite） improved the formation of a graphite film during sliding friction and decreased the COF, while the hard Ni-Al intermetallic phases contributed to the increase of COF.展开更多
Pt-based catalysts are the typical industrial catalysts for propane dehydrogenation(PDH),which still suffer from insufficient lo ng-term durability due to the structu ral instability and coke deposition.A commercial ...Pt-based catalysts are the typical industrial catalysts for propane dehydrogenation(PDH),which still suffer from insufficient lo ng-term durability due to the structu ral instability and coke deposition.A commercial γ-Al_(2)O_(3) supported thermally robust sub-nanometer Pt2In3intermetallic catalyst with atomically ordered structure and rigorously separated Pt single atoms was fabricated,which showed outstanding robustness in 240 h long-term operation at 600℃ with the deactivation rate constant kdas low as0.00078 h^(-1), ranking among the lowest reported values.Based on various in situ characterizations and theoretical calculations,it was proved that the catalyst stability not only resulted from the separated Pt single-atom sites but also significantly affected by the distance of adjacent Pt atoms.An increasing distance to 3.25 A in the Pt_(2)In_(3)could induce a weak π-adsorption configuration of propylene on Pt sites,which facilitated the desorption of propylene and restrained the side reactions like coking.展开更多
We describe a novel mechanism for the synthesis of a stable high-entropy alloy powder from an otherwise immiscible Mg-Ti rich metallic mixture by employing high-energy mechanical milling.The presented methodology expe...We describe a novel mechanism for the synthesis of a stable high-entropy alloy powder from an otherwise immiscible Mg-Ti rich metallic mixture by employing high-energy mechanical milling.The presented methodology expedites the synthesis of amorphous alloy powder by strategically injecting entropic disorder through the inclusion of multi-principal elements in the alloy composition.Predictions from first principles and materials theory corroborate the results from microscopic characterizations that reveal a transition of the amorphous phase from a precursor intermetallic structure.This transformation,characterized by the emergence of antisite disorder,lattice expansion,and the presence of nanograin boundaries,signifies a departure from the precursor intermetallic structure.Additionally,this phase transformation is accelerated by the presence of multiple principal elements that induce severe lattice distortion and a higher configurational entropy.The atomic size mismatch of the dissimilar elements present in the alloy produces a stable amorphous phase that resists reverting to an ordered lattice even on annealing.展开更多
The development of electrocatalysts for the oxygen reduction reaction(ORR) that bears high selectivity,exceptional activity,and long-term stability is crucial for advancing various green energy technologies.Intermetal...The development of electrocatalysts for the oxygen reduction reaction(ORR) that bears high selectivity,exceptional activity,and long-term stability is crucial for advancing various green energy technologies.Intermetallics composed of platinum and transition metals are considered to be promising candidates for this purpose.However,they typically face challenges such as unfavorable intrinsic activity and a propensity for particle aggregation,diminishing their ORR performance.Against this backdrop,we present our findings on a N-doped carbon confined Pt_(3)Co intermetallic doped with p-block metal tin(Pt_(3)Co_(x)Sn_(1-x)/NC).The introduction of Sn induces lattice strain due to its larger atomic size,which leads to the distortion of the Pt_(3)Co lattice structure,while the coupling of carbon polyhedra inhibits the particle aggregation.The optimized Pt_(3)Co_(0.8)Sn_(0.2)/NC catalyst demonstrates an impressive half-wave potential of 0.86 V versus RHE,surpassing both Pt_(3)Co/NC and Pt_(3)Sn/NC catalysts.Moreover,the Pt_(3)Co_(0.8)Sn_(0.2)/NC exhibits a mass-specific activity as high as 1.4 A mg_(Pt)^(-1),ranking it in the top level among the intermetallicsbased ORR electrocatalysts.When further employed as a cathode material in a self-assembled zinc-air battery,it shows stable operation for over 80 h.These results underscore the significant impact of lattice strain engineering through the strategic doping of p-block metal in the carbon-confined Pt_(3)Co intermetallic,thereby enhancing the catalytic efficiency for the ORR.展开更多
Porous intermetallics show potential in the field of filtration and separation as well as in the field of catalysis.Herein,porous Ti Fe2intermetallics were fabricated by the reactive synthesis of elemental powders.The...Porous intermetallics show potential in the field of filtration and separation as well as in the field of catalysis.Herein,porous Ti Fe2intermetallics were fabricated by the reactive synthesis of elemental powders.The phase transformation and pore formation of porous TiFe2intermetallics were investigated,and its corrosion behavior and hydrogen evolution reaction(HER)performance in alkali solution were studied.Porous TiFe2intermetallics with porosity in the range of 34.4%-56.4%were synthesized by the diffusion reaction of Ti and Fe elements,and the pore formation of porous TiFe2intermetallic compound is the result of a combination of the bridging effect and the Kirkendall effect.The porous TiFe2samples exhibit better corrosion resistance compared with porous 316L stainless steel,which is related to the formation of uniform nanosheets on the surface that hinder further corrosion,and porous TiFe2electrode shows the overpotential of 220.6 and 295.6 mV at 10 and 100 mA·cm-2,suggesting a good catalytic performance.The synthesized porous Fe-based intermetallic has a controllable pore structure as well as excellent corrosion resistance,showing its potential in the field of filtration and separation.展开更多
Intermetallic formation in sludge during magnesium(Mg)melting,holding and high pressure die casting practices is a very important issue.But,very often it is overlooked by academia,original equipment manufacturers(OEM)...Intermetallic formation in sludge during magnesium(Mg)melting,holding and high pressure die casting practices is a very important issue.But,very often it is overlooked by academia,original equipment manufacturers(OEM),metal ingot producers and even die casters.The aim of this study was to minimize the intermetallic formation in Mg sludge via the optimization of the chemistry and process parameters.The Al8Mn5 intermetallic particles were identified by the microstructure analysis based on the Al and Mn ratio.The design of experiment(DOE)technique,Taguchi method,was employed to minimize the intermetallic formation in the sludge of Mg alloys with various chemical compositions of Al,Mn,Fe,and different process parameters,holding temperature and holding time.The sludge yield(SY)and intermetallic size(IS)was selected as two responses.The optimum combination of the levels in terms of minimizing the intermetallic formation were 9 wt.%Al,0.15 wt.%Mn,0.001 wt.%(10 ppm)Fe,690℃ for the holding temperature and holding at 30 mins for the holding time,respectively.The best combination for smallest intermetallic size were 9 wt.%Al,0.15 wt.%Mn,0.001 wt.%(10 ppm)Fe,630℃ for the holding temperature and holding at 60 mins for the holding time,respectively.Three groups of sludge factors,Chemical Sludge(CSF),Physical Sludge(PSF)and Comprehensive Sludge Factors(and CPSF)were established for prediction of sludge yields and intermetallic sizes in Al-containing Mg alloys.The CPSF with five independent variables including both chemical elements and process parameters gave high accuracy in prediction,as the prediction of the PSF with only the two processing parameters of the melt holding temperature and time showed a relatively large deviation from the experimental data.The Chemical Sludge Factor was primarily designed for small ingot producers and die casters with a limited melting and holding capacity,of which process parameters could be fixed easily.The Physical Sludge Factor could be used for mass production with a single type of Mg alloy,in which the chemistry fluctuation might be negligible.In large Mg casting suppliers with multiple melting and holding furnaces and a number of Mg alloys in production,the Comprehensive Sludge Factor should be implemented to diminish the sludge formation.展开更多
The Li-CO_(2) battery has been under the spotlight of future battery technologies since it can achieve CO_(2)utilization and energy conversion simultaneously.However,its advancement is hampered by poor energy efficien...The Li-CO_(2) battery has been under the spotlight of future battery technologies since it can achieve CO_(2)utilization and energy conversion simultaneously.However,its advancement is hampered by poor energy efficiency and limited reversibility due to the sluggish kinetics of the CO_(2) reduction and evolution reactions.Herein,a multiscale nanoporous interpenetrating phase nanohybrid of RuAl intermetallic and Cu_(2)O(MP-Cu_(2)O/RuAl) was carved by driving synchronous phase and microstructure evolutions through dealloying of one RuCuAl master alloy.The built-in RuAl intermetallic and Cu_(2)O closely stack to form abundant nano-interfaces with revolutionized electronic structure,The theoretical simulations reveal that the Cu_(2)O/RuAl interface can distinctly reduce the energy barrier of the Li_(2)CO_(3) decomposition reaction,The interconnected pore channels with large surface area can enhance catalytic site accessibility,mass transfer,and uniform deposition of the discharge products.In situ differential electrochemical mass spectrometry discloses that the CO_(2)-to-electron ratio during charging coincides with the theoretical value of 3/4,demonstrating the high efficacy of MP-Cu_(2)O/RuAl in achieving the recycling of CO_(2).The dealloying protocol provides an affordable platform to empower transition metal oxides into high-efficiency electrocatalysts by hybridizing with metallic nano-sponge for advancing the application of Li-CO_(2)batteries.展开更多
The long-range periodically ordered atomic structures in intermetallic nanoparticles(INPs)can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction...The long-range periodically ordered atomic structures in intermetallic nanoparticles(INPs)can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction(ORR)compared to the disordered atomic structures in ordinary solid-solution alloy NPs.Accordingly,through a facile and scalable synthetic method,a series of carbon-supported ultrafine Pt_3Co_(x)Mn_(1-x)ternary INPs are prepared in this work,which possess the"skin-like"ultrathin Pt shells,the ordered L1_(2) atomic structure,and the high-even dispersion on supports(L1_(2)-Pt_3Co_(x)Mn_(1-x)/~SPt INPs/C).Electrochemical results present that the composition-optimized L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C exhibits the highest electrocata lytic activity among the series,which are also much better than those of the pristine ultrafine Pt/C.Besides,it also has a greatly enhanced electrochemical stability.In addition,the effects of annealing temperature and time are further investigated.More importantly,such superior ORR electrocatalytic performance of L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C are also well demonstrated in practical fuel cells.Physicochemical characterization analyses further reveal the major origins of the greatly enhanced ORR electrocata lytic performance:the Pt-Co-Mn alloy-induced geometric and ligand effects as well as the extremely high L1_(2) atomic-ordering degree.This work not only successfully develops a highly active and stable ordered ternary intermetallic ORR electrocatalyst,but also elucidates the corresponding"structure-function"relationship,which can be further applied in designing other intermetallic(electro)catalysts.展开更多
The ductility of TiAl intermetallics can be improved through stabilizing the ductile β phase.New β-stabilized Ti-45Al-xFe-yMo（x,y=1,2,3,4） alloys were designed through adding the β stabilizing elements Fe and Mo....The ductility of TiAl intermetallics can be improved through stabilizing the ductile β phase.New β-stabilized Ti-45Al-xFe-yMo（x,y=1,2,3,4） alloys were designed through adding the β stabilizing elements Fe and Mo.The microstructural evolution and deformation behavior of the Ti-45Al-xFe-yMo alloys were investigated.The results show that the amount of β（B2） phase is increased with the increase of alloying elements.Mo shows a higher capability for stabilizing the β phase than Fe.In the optimized Ti-45Al-3Fe-2Mo alloy,the grains are significantly refined to about 12 μm,and this alloy shows a very good hot ductility at the elevated temperature.展开更多
Porous Ni3Al intermetallics were fabricated by elemental powder reactive synthesis method, using carbamide powders as space holders. Corrosion behavior of porous Ni3Al intermetallics was investigated in a 6 mol/L KOH ...Porous Ni3Al intermetallics were fabricated by elemental powder reactive synthesis method, using carbamide powders as space holders. Corrosion behavior of porous Ni3Al intermetallics was investigated in a 6 mol/L KOH solution using electrochemical methods and immersion test. Effect of porous structures on the corrosion behavior of the porous Ni3Al intermetallics was studied. The results indicate that the porous Ni3Al intermetallics with higher porosities suffer more serious corrosion than the ones with lower porosities because the complicated interconnected porous structures and the large true surface areas exist in the samples with a higher porosity. But the corrosion rates of the porous Ni3Al intermetallics are not proportional to the true surface areas. The reason is that the pore size, pore size distribution and pore shape of the porous Ni3Al intermetallics change with the increasing porosity. All the porous Ni3Al intermetallics with different porosities exhibit excellent corrosion resistance in a strong alkali solution.展开更多
The tortuosity factor is the most critical parameter for the pore characteristic of porous materials. The tortuosity factor for porous FeAl intermetallics was studied based on the Darcy law and Hagen-Poiseuille equati...The tortuosity factor is the most critical parameter for the pore characteristic of porous materials. The tortuosity factor for porous FeAl intermetallics was studied based on the Darcy law and Hagen-Poiseuille equation. Porous stainless steel with the same pore structure parameter as porous FeAl was fabricated by powder metallurgy method for comparison. The results show that the tortuosity factor of porous FeAl intermetallics is smaller than that of porous stainless steel when their pore structure parameters are the same. The average tortuosity factor is 2.26 for the porous FeAl material and 2.92 for the porous stainless steel, calculated by Hagen-Poiseuille equation. The reason of the different tortuosity factors for porous FeAl and porous stainless steel was also explored through studying the pore formation mechanisms of the two types of porous materials.展开更多
The crystal structures,compositions and phase relations of the intermetallics of Mg-Zn-Ce system in the Mg-rich corner at 400 ℃ were identified through equilibrium alloy method.For Mg-Zn-Ce system,there is a linear t...The crystal structures,compositions and phase relations of the intermetallics of Mg-Zn-Ce system in the Mg-rich corner at 400 ℃ were identified through equilibrium alloy method.For Mg-Zn-Ce system,there is a linear ternary compound（T phase）,whose chemical formula is（Mg1-xZnx）11Ce.The range of Zn content in T phase is from 9.6% to 43.6%（molar fraction）.The crystal structure of T phase is C-centered orthorhombic lattice with lattice parameters of a=0.96-1.029 nm,b=1.115-1.204 nm,c=0.940-1.015 nm.And the lattice parameters of T phase are decreasing a little with increasing Zn content.According to the results of composition and crystal structure,the maximal solubility of Zn in Mg12Ce is about 7.8%（molar fraction）,and the chemical formula of the solid solution can be identified as（Mg1-xZnx）12Ce.The isothermal section of Mg-Zn-Ce system in Mg-rich corner at 400 ℃ was constructed.展开更多
Experimental studies were conducted on the tensile behaviors and fracture modes of TiAl（Ti-46.5Al-2Nb-2Cr） alloys with near gamma（NG） equiaxed and near lamellar（NL） microstructures over a temperature range from ...Experimental studies were conducted on the tensile behaviors and fracture modes of TiAl（Ti-46.5Al-2Nb-2Cr） alloys with near gamma（NG） equiaxed and near lamellar（NL） microstructures over a temperature range from room temperature to 840 ℃ and a strain rate range of 0.001-1 350 s-1.The results indicate that the alloys are both temperature and strain rate dependent and they have a similar dependence.The dynamic strength is higher than the quasi-static strength but almost insensitive to high strain rate range of 320-1 350 s-1.The brittle-to-ductile transition temperature（BDTT） increases with increasing strain rates.NG TiAl yields obviously,while NL TiAl does not.Below BDTT,as the temperature increases,the fracture modes of the two alloys change from planar cleavage fracture to a mixture of transgranular and intergranular fractures,and finally to totally intergranular fracture.展开更多
Formation and sedimentation of Fe-rich intermetallics were studied in a commercial Al-Si-Cu-Fe alloy with extra additions of Mn. It is found that the introduction of extra Mn is an effective approach to lower the Fe l...Formation and sedimentation of Fe-rich intermetallics were studied in a commercial Al-Si-Cu-Fe alloy with extra additions of Mn. It is found that the introduction of extra Mn is an effective approach to lower the Fe level in the equilibrium liquid phase after sedimentation of solid Fe-rich phase at a temperature between its liquidus and solidus. The higher Mn/Fe mass ratio results in the lower Fe content in the retained alloy, during which Mn is also consumed and settled at the bottom of the melt as solid Fe-rich intermetallics. Therefore, the final Fe content in the alloy can be controlled by the Mn content and the holding temperature of the melt. The results confirmed a good agreement of the theoretical calculation and the experimental test with a specially designed 50 mm cylindrical casting. The sedimentation of Fe-rich intermetallics in the Al-Si-Cu-Fe alloy is completed at 600 °C after 10 min. The reduction of Fe content in the retained alloy is 31.4% when m（Mn）/m（Fe）=0.5 and 53.3% when m（Mn）/m（Fe）=1.0 in comparison with that in the original alloy. The settled Fe-rich intermetallics were identified as α-Al15（Fe,Mn）3Si2, which provided the lower balanced Fe concentration in the melt in comparison with other Fe-rich intermetallics.展开更多
文摘The formation mechanisms and growth kinetics of Al3 Ni and Al3Ni2 in Ni-Al diffusion couple prepared by electrodeposition of Ni on Al substrate were investigated. The nickel coating with 20 μm thickness was applied on 6061 aluminum alloy by direct current electroplating. The samples were then heat-treated for different durations at 450, 500 and 550 °C under argon atmosphere. The intermetallic phases were identified by means of scanning electron microscopy（SEM）, energy dispersive spectrometry（EDS） and X-ray diffraction（XRD）. The results showed that the formation of intermetallic phases consisted of two important steps. The first step was the lateral growth of intermetallic phase from separate sites, resulting in the formation of a continuous layer. The second step was the growth of the continuous intermetallic layer in the direction perpendicular to the interface. However, excessive increase in thickness of intermetallic phases led to the detachment of reaction products, i.e., Al3 Ni and Al3Ni2, from the substrate. It was also observed that aluminum was the dominant diffusing element during Al3 Ni growth, while nickel diffusion was dominant during Al3Ni2 growth. The growth kinetics of both Al3 Ni and Al3Ni2 phases obeyed a parabolic law.
基金This work was supported by the National Natural Science Foundation of China under grants no.11804030the Scientific and Technological Developing Scheme of Jilin Province under grants no.20200801048GH.
文摘Instantaneous reactions of Al,Mn,Zn,Zr and Y with Ni by mixing the prepared Mg-8Al-0.4Mn,Mg-6Zn-2Y-0.5Zr and Mg-0.6Ni melts were investigated in this work to reveal the underlying mechanisms of their effects on the removal of Ni impurity.The results indicate three Ni-containing intermetallics,namely Al_(4)NiY,Al_(4)Ni(Y,Zr)and Al_(31)Ni_(2)Mn_(6).The former two phases present lath-like and have a relatively larger size(>20μm in length)than the latest one which is granular with the diameter of∼120 nm.This illustrates that Al and Y(/Zr)can efficiently remove Ni by forming Al_(4)NiY or Al_(4)Ni(Y,Zr)which would precipitate to the bottom of the melt.Furthermore,adding Y into Mg-Al based alloys can simultaneously remove Fe and Ni,which contributes their excellent corrosion resistance.Finally,this paper proposes two methods helped to efficiently remove Ni for both Mg-Al based alloys and Al-free Mg alloys,and both of them are also benefit to improve alloys’strength.
基金supported by the National Natural Science Foundation(22279036)the Innovation and Talent Recruitment Base of New Energy Chemistry and Device(B21003)。
文摘Enhancing the stability of Pt-based electrocatalysts for the sluggish cathodic oxygen reduction reaction(ORR)is critical for proton exchange membrane fuel cells(PEMFCs).Herein,high-entropy intermetallic(HEI)L1_(2)-Pt(FeCoNiCuZn)3is designed for durable ORR catalysis.Benefiting from the unique HEI structure and the enhanced intermetallic phase stability,Pt(FeCoNiCuZn)3/C nanoparticles demonstrate significantly improved stability over Pt/C and PtCu_(3)/C catalysts.The Pt(FeCoNiCuZn)3/C exhibits a negligible decay of the half-wave potential during 30,000 potential cycles from 0.6 to 1.0 V,whereas Pt/C and PtCu_(3)/C are negatively shifted by 46 and 36 m V,respectively.Even after 10,000 cycles at potential up to 1.5 V,the mass activity of Pt(FeCoNiCuZn)3/C still shows~70%retention.As evidenced by the structural characterizations,the HEI structure of Pt(FeCoNiCuZn)3/C is well maintained,while PtCu_(3)/C nanoparticles undergo severe Cu leaching and particle growth.In addition,when assembled Pt(FeCoNiCuZn)3/C as the cathode in high-temperature PEMFC of 160℃,the H_(2)-O_(2)fuel cell delivers almost no degradation even after operating for 150 h,demonstrating the potential for fuel cell applications.This work provides a facile design strategy for the development of high-performance ultrastable electrocatalysts.
文摘A novel approach to produce an intermetallic composite coating was put forward.The microstructure,microhardness,and dry-sliding wear behavior of the composite coating were investigated using X-ray diffraction （XRD）,scanning electron microscopy （SEM）,energy dispersive spectrum （EDS） analysis,microhardness test,and ball-on-disc wear experiment.XRD results indicate that some new phases FeAl,Fe0.23Ni0.77Al,and Ni3Al exit in the composite coating with the Al2O3 addition.SEM results show that the coating is bonded with carbon steel metallurgically and exhibits typical rapid directional solidification structures.The Cr7C3 carbide and intermetallic compounds co-reinforced composite coating has a high average hardness and exhibits an excellent wear resistance under dry-sliding wear test compared with the Cr7C3 carbide-reinforced composite coating.The formation mechanism of the intermetallic compounds was also investigated.
基金financial support from the program of China Scholarship Council (No. 201404490058)Marie-Curie (No. 268696)+2 种基金the National Key Research and Development Program of China (No. 2016YFE0701203)the National Natural Science Foundation of China (No. 51574196)the 111 Project (No. B08040)
文摘In this study, cold spraying（CS） was used to deposit a mixture of nickel-coated graphite and 40 vol.% Al powder（Ni-Gr/Al） on a steel substrate aiming to effectively preserve a certain volume fraction of graphite in the deposited Ni-Gr/Al composite coating. The microstructure of the as-sprayed coating and the effect of post-spray heat-treatment（PSHT） temperatures on the in-situ formation of Ni-Al intermetallic phases in coating were studied. The tribological behaviors of the as-sprayed coating and the PSHTed coating under 450？C were tested at 25？C, while the as-sprayed coating was tested at 450？C for comparison.As a result, the Ni-Gr particles showed a homogenous distribution in the coating. The multilayer Ni-Al intermetallics-coated graphite/Al composite coating was achieved in situ after the PSHT of 450？C, where the graphite did decompose at 550？C leaving big pores in the coating. The coefficients of friction（COF）of the CSed coating and the PSHTed coating were measured at 450？C as well as 25？C, which showed a similar tendency, much higher than that of the CSed coating tested at 25？C. The lubrication phase（graphite） improved the formation of a graphite film during sliding friction and decreased the COF, while the hard Ni-Al intermetallic phases contributed to the increase of COF.
基金financially supported by the DNL Cooperation Fund,CAS (DNL202002)the National Natural Science Foundation of China (22102180)+3 种基金the CAS Project for Young Scientists in Basic Research,(YSBR-022)the Key Research Program of Frontier Sciences,CAS (ZDBS-LY-7012)Liao Ning Revitalization Talents Program (XLYC2007070)the Fundamental Research Funds for the Central Universities (20720220009)。
文摘Pt-based catalysts are the typical industrial catalysts for propane dehydrogenation(PDH),which still suffer from insufficient lo ng-term durability due to the structu ral instability and coke deposition.A commercial γ-Al_(2)O_(3) supported thermally robust sub-nanometer Pt2In3intermetallic catalyst with atomically ordered structure and rigorously separated Pt single atoms was fabricated,which showed outstanding robustness in 240 h long-term operation at 600℃ with the deactivation rate constant kdas low as0.00078 h^(-1), ranking among the lowest reported values.Based on various in situ characterizations and theoretical calculations,it was proved that the catalyst stability not only resulted from the separated Pt single-atom sites but also significantly affected by the distance of adjacent Pt atoms.An increasing distance to 3.25 A in the Pt_(2)In_(3)could induce a weak π-adsorption configuration of propylene on Pt sites,which facilitated the desorption of propylene and restrained the side reactions like coking.
基金supported in part by the National Science Foundation(NSF)award#CMMI-1944040。
文摘We describe a novel mechanism for the synthesis of a stable high-entropy alloy powder from an otherwise immiscible Mg-Ti rich metallic mixture by employing high-energy mechanical milling.The presented methodology expedites the synthesis of amorphous alloy powder by strategically injecting entropic disorder through the inclusion of multi-principal elements in the alloy composition.Predictions from first principles and materials theory corroborate the results from microscopic characterizations that reveal a transition of the amorphous phase from a precursor intermetallic structure.This transformation,characterized by the emergence of antisite disorder,lattice expansion,and the presence of nanograin boundaries,signifies a departure from the precursor intermetallic structure.Additionally,this phase transformation is accelerated by the presence of multiple principal elements that induce severe lattice distortion and a higher configurational entropy.The atomic size mismatch of the dissimilar elements present in the alloy produces a stable amorphous phase that resists reverting to an ordered lattice even on annealing.
基金Natural Science Foundation of Jiangsu Province (BK20210735)National Natural Science Foundation of China (52201269, 52302296)+4 种基金Collaborative Innovation Center of Suzhou Nano Science and Technologythe 111 Projectthe Suzhou Key Laboratory of Functional Nano and Soft MaterialsJiangsu Key Laboratory for Carbon-Based Functional Materials & Devicesthe funding from the Gusu leading talent plan for scientific and technological innovation and entrepreneurship (ZXL2022487)。
文摘The development of electrocatalysts for the oxygen reduction reaction(ORR) that bears high selectivity,exceptional activity,and long-term stability is crucial for advancing various green energy technologies.Intermetallics composed of platinum and transition metals are considered to be promising candidates for this purpose.However,they typically face challenges such as unfavorable intrinsic activity and a propensity for particle aggregation,diminishing their ORR performance.Against this backdrop,we present our findings on a N-doped carbon confined Pt_(3)Co intermetallic doped with p-block metal tin(Pt_(3)Co_(x)Sn_(1-x)/NC).The introduction of Sn induces lattice strain due to its larger atomic size,which leads to the distortion of the Pt_(3)Co lattice structure,while the coupling of carbon polyhedra inhibits the particle aggregation.The optimized Pt_(3)Co_(0.8)Sn_(0.2)/NC catalyst demonstrates an impressive half-wave potential of 0.86 V versus RHE,surpassing both Pt_(3)Co/NC and Pt_(3)Sn/NC catalysts.Moreover,the Pt_(3)Co_(0.8)Sn_(0.2)/NC exhibits a mass-specific activity as high as 1.4 A mg_(Pt)^(-1),ranking it in the top level among the intermetallicsbased ORR electrocatalysts.When further employed as a cathode material in a self-assembled zinc-air battery,it shows stable operation for over 80 h.These results underscore the significant impact of lattice strain engineering through the strategic doping of p-block metal in the carbon-confined Pt_(3)Co intermetallic,thereby enhancing the catalytic efficiency for the ORR.
基金financially supported by the National Natural Science Foundation of China(No.51971251)。
文摘Porous intermetallics show potential in the field of filtration and separation as well as in the field of catalysis.Herein,porous Ti Fe2intermetallics were fabricated by the reactive synthesis of elemental powders.The phase transformation and pore formation of porous TiFe2intermetallics were investigated,and its corrosion behavior and hydrogen evolution reaction(HER)performance in alkali solution were studied.Porous TiFe2intermetallics with porosity in the range of 34.4%-56.4%were synthesized by the diffusion reaction of Ti and Fe elements,and the pore formation of porous TiFe2intermetallic compound is the result of a combination of the bridging effect and the Kirkendall effect.The porous TiFe2samples exhibit better corrosion resistance compared with porous 316L stainless steel,which is related to the formation of uniform nanosheets on the surface that hinder further corrosion,and porous TiFe2electrode shows the overpotential of 220.6 and 295.6 mV at 10 and 100 mA·cm-2,suggesting a good catalytic performance.The synthesized porous Fe-based intermetallic has a controllable pore structure as well as excellent corrosion resistance,showing its potential in the field of filtration and separation.
基金Meridian Lightweight Technologies Inc.,Strathroy,Ontario Canadathe University of Windsor,Windsor,Ontario,Canada for supporting this workpart of a large project funded by Meridian Lightweight Technologies,Inc.
文摘Intermetallic formation in sludge during magnesium(Mg)melting,holding and high pressure die casting practices is a very important issue.But,very often it is overlooked by academia,original equipment manufacturers(OEM),metal ingot producers and even die casters.The aim of this study was to minimize the intermetallic formation in Mg sludge via the optimization of the chemistry and process parameters.The Al8Mn5 intermetallic particles were identified by the microstructure analysis based on the Al and Mn ratio.The design of experiment(DOE)technique,Taguchi method,was employed to minimize the intermetallic formation in the sludge of Mg alloys with various chemical compositions of Al,Mn,Fe,and different process parameters,holding temperature and holding time.The sludge yield(SY)and intermetallic size(IS)was selected as two responses.The optimum combination of the levels in terms of minimizing the intermetallic formation were 9 wt.%Al,0.15 wt.%Mn,0.001 wt.%(10 ppm)Fe,690℃ for the holding temperature and holding at 30 mins for the holding time,respectively.The best combination for smallest intermetallic size were 9 wt.%Al,0.15 wt.%Mn,0.001 wt.%(10 ppm)Fe,630℃ for the holding temperature and holding at 60 mins for the holding time,respectively.Three groups of sludge factors,Chemical Sludge(CSF),Physical Sludge(PSF)and Comprehensive Sludge Factors(and CPSF)were established for prediction of sludge yields and intermetallic sizes in Al-containing Mg alloys.The CPSF with five independent variables including both chemical elements and process parameters gave high accuracy in prediction,as the prediction of the PSF with only the two processing parameters of the melt holding temperature and time showed a relatively large deviation from the experimental data.The Chemical Sludge Factor was primarily designed for small ingot producers and die casters with a limited melting and holding capacity,of which process parameters could be fixed easily.The Physical Sludge Factor could be used for mass production with a single type of Mg alloy,in which the chemistry fluctuation might be negligible.In large Mg casting suppliers with multiple melting and holding furnaces and a number of Mg alloys in production,the Comprehensive Sludge Factor should be implemented to diminish the sludge formation.
基金financially National Natural Science Foundation of China (52201254)Natural Science Foundation of Shandong Province (ZR2023ME155, ZR2023ME085)+4 种基金project of “20 Items of University” of Jinan (202228046)Taishan Scholar Project of Shandong Province (tsqn202306226)Scientific Research Foundation for New Talents in University of Jinan (16010089104)Introducing Major Universities and Research Institutions to Jointly Build Innovative Carrier Project of Jining City (2023DYDS022)support provided by the Shandong Province Laboratory of Technology and Equipment for Molecular Diagnosis。
文摘The Li-CO_(2) battery has been under the spotlight of future battery technologies since it can achieve CO_(2)utilization and energy conversion simultaneously.However,its advancement is hampered by poor energy efficiency and limited reversibility due to the sluggish kinetics of the CO_(2) reduction and evolution reactions.Herein,a multiscale nanoporous interpenetrating phase nanohybrid of RuAl intermetallic and Cu_(2)O(MP-Cu_(2)O/RuAl) was carved by driving synchronous phase and microstructure evolutions through dealloying of one RuCuAl master alloy.The built-in RuAl intermetallic and Cu_(2)O closely stack to form abundant nano-interfaces with revolutionized electronic structure,The theoretical simulations reveal that the Cu_(2)O/RuAl interface can distinctly reduce the energy barrier of the Li_(2)CO_(3) decomposition reaction,The interconnected pore channels with large surface area can enhance catalytic site accessibility,mass transfer,and uniform deposition of the discharge products.In situ differential electrochemical mass spectrometry discloses that the CO_(2)-to-electron ratio during charging coincides with the theoretical value of 3/4,demonstrating the high efficacy of MP-Cu_(2)O/RuAl in achieving the recycling of CO_(2).The dealloying protocol provides an affordable platform to empower transition metal oxides into high-efficiency electrocatalysts by hybridizing with metallic nano-sponge for advancing the application of Li-CO_(2)batteries.
基金supported by the National Key Research and Development Program of China(2021YFB4001301)the Science and Technology Commission of Shanghai Municipality(21DZ1208600)the Oceanic Interdisciplinary Program of Shanghai Jiao Tong University(SL2021ZD105)。
文摘The long-range periodically ordered atomic structures in intermetallic nanoparticles(INPs)can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction(ORR)compared to the disordered atomic structures in ordinary solid-solution alloy NPs.Accordingly,through a facile and scalable synthetic method,a series of carbon-supported ultrafine Pt_3Co_(x)Mn_(1-x)ternary INPs are prepared in this work,which possess the"skin-like"ultrathin Pt shells,the ordered L1_(2) atomic structure,and the high-even dispersion on supports(L1_(2)-Pt_3Co_(x)Mn_(1-x)/~SPt INPs/C).Electrochemical results present that the composition-optimized L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C exhibits the highest electrocata lytic activity among the series,which are also much better than those of the pristine ultrafine Pt/C.Besides,it also has a greatly enhanced electrochemical stability.In addition,the effects of annealing temperature and time are further investigated.More importantly,such superior ORR electrocatalytic performance of L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C are also well demonstrated in practical fuel cells.Physicochemical characterization analyses further reveal the major origins of the greatly enhanced ORR electrocata lytic performance:the Pt-Co-Mn alloy-induced geometric and ligand effects as well as the extremely high L1_(2) atomic-ordering degree.This work not only successfully develops a highly active and stable ordered ternary intermetallic ORR electrocatalyst,but also elucidates the corresponding"structure-function"relationship,which can be further applied in designing other intermetallic(electro)catalysts.
基金Project(2011CB605505) supported by the National Basic Research Program of ChinaProject(2011JQ002) supported by the Fundamental Research Funds for the Central Universities,ChinaProject supported by the Open-End Fund for the Valuable and Precision Instruments of Cental South University,China
文摘The ductility of TiAl intermetallics can be improved through stabilizing the ductile β phase.New β-stabilized Ti-45Al-xFe-yMo（x,y=1,2,3,4） alloys were designed through adding the β stabilizing elements Fe and Mo.The microstructural evolution and deformation behavior of the Ti-45Al-xFe-yMo alloys were investigated.The results show that the amount of β（B2） phase is increased with the increase of alloying elements.Mo shows a higher capability for stabilizing the β phase than Fe.In the optimized Ti-45Al-3Fe-2Mo alloy,the grains are significantly refined to about 12 μm,and this alloy shows a very good hot ductility at the elevated temperature.
基金Project(2009CB623406)supported by the National Basic Research Program of ChinaProject(12JJ4044)supported by the Natural Science Foundation of Hunan Province,ChinaProject(13C902)supported by the Scientific Research Fund of Hunan Provincial Education Department,China
文摘Porous Ni3Al intermetallics were fabricated by elemental powder reactive synthesis method, using carbamide powders as space holders. Corrosion behavior of porous Ni3Al intermetallics was investigated in a 6 mol/L KOH solution using electrochemical methods and immersion test. Effect of porous structures on the corrosion behavior of the porous Ni3Al intermetallics was studied. The results indicate that the porous Ni3Al intermetallics with higher porosities suffer more serious corrosion than the ones with lower porosities because the complicated interconnected porous structures and the large true surface areas exist in the samples with a higher porosity. But the corrosion rates of the porous Ni3Al intermetallics are not proportional to the true surface areas. The reason is that the pore size, pore size distribution and pore shape of the porous Ni3Al intermetallics change with the increasing porosity. All the porous Ni3Al intermetallics with different porosities exhibit excellent corrosion resistance in a strong alkali solution.
基金Project (2009CB623406) supported by the National Basic Research Program of ChinaProjects (50825102, 50721003, 51071178) supported by the National Natural Science Foundation of China+1 种基金Project (11JJ4036) supported by the Natural Science Foundation of Hunan Province, ChinaProject supported by the Central South University Free Exploring Project, China
文摘The tortuosity factor is the most critical parameter for the pore characteristic of porous materials. The tortuosity factor for porous FeAl intermetallics was studied based on the Darcy law and Hagen-Poiseuille equation. Porous stainless steel with the same pore structure parameter as porous FeAl was fabricated by powder metallurgy method for comparison. The results show that the tortuosity factor of porous FeAl intermetallics is smaller than that of porous stainless steel when their pore structure parameters are the same. The average tortuosity factor is 2.26 for the porous FeAl material and 2.92 for the porous stainless steel, calculated by Hagen-Poiseuille equation. The reason of the different tortuosity factors for porous FeAl and porous stainless steel was also explored through studying the pore formation mechanisms of the two types of porous materials.
基金Project(N110323017) supported by the Fundamental Research Funds for the Central Universities,ChinaProject(E2010001390) supported by the Natural Science Foundation of Hebei Province,China
文摘The crystal structures,compositions and phase relations of the intermetallics of Mg-Zn-Ce system in the Mg-rich corner at 400 ℃ were identified through equilibrium alloy method.For Mg-Zn-Ce system,there is a linear ternary compound（T phase）,whose chemical formula is（Mg1-xZnx）11Ce.The range of Zn content in T phase is from 9.6% to 43.6%（molar fraction）.The crystal structure of T phase is C-centered orthorhombic lattice with lattice parameters of a=0.96-1.029 nm,b=1.115-1.204 nm,c=0.940-1.015 nm.And the lattice parameters of T phase are decreasing a little with increasing Zn content.According to the results of composition and crystal structure,the maximal solubility of Zn in Mg12Ce is about 7.8%（molar fraction）,and the chemical formula of the solid solution can be identified as（Mg1-xZnx）12Ce.The isothermal section of Mg-Zn-Ce system in Mg-rich corner at 400 ℃ was constructed.
基金Projects(10902106,90505002)supported by the National Natural Science Foundation of China
文摘Experimental studies were conducted on the tensile behaviors and fracture modes of TiAl（Ti-46.5Al-2Nb-2Cr） alloys with near gamma（NG） equiaxed and near lamellar（NL） microstructures over a temperature range from room temperature to 840 ℃ and a strain rate range of 0.001-1 350 s-1.The results indicate that the alloys are both temperature and strain rate dependent and they have a similar dependence.The dynamic strength is higher than the quasi-static strength but almost insensitive to high strain rate range of 320-1 350 s-1.The brittle-to-ductile transition temperature（BDTT） increases with increasing strain rates.NG TiAl yields obviously,while NL TiAl does not.Below BDTT,as the temperature increases,the fracture modes of the two alloys change from planar cleavage fracture to a mixture of transgranular and intergranular fractures,and finally to totally intergranular fracture.
基金financial support from TSB (UK) under project No. 101172the EPSRC (UK) and Jaguar Cars Ltd. (UK) for financial support under the grant for the EPSRC Centre-LiME
文摘Formation and sedimentation of Fe-rich intermetallics were studied in a commercial Al-Si-Cu-Fe alloy with extra additions of Mn. It is found that the introduction of extra Mn is an effective approach to lower the Fe level in the equilibrium liquid phase after sedimentation of solid Fe-rich phase at a temperature between its liquidus and solidus. The higher Mn/Fe mass ratio results in the lower Fe content in the retained alloy, during which Mn is also consumed and settled at the bottom of the melt as solid Fe-rich intermetallics. Therefore, the final Fe content in the alloy can be controlled by the Mn content and the holding temperature of the melt. The results confirmed a good agreement of the theoretical calculation and the experimental test with a specially designed 50 mm cylindrical casting. The sedimentation of Fe-rich intermetallics in the Al-Si-Cu-Fe alloy is completed at 600 °C after 10 min. The reduction of Fe content in the retained alloy is 31.4% when m（Mn）/m（Fe）=0.5 and 53.3% when m（Mn）/m（Fe）=1.0 in comparison with that in the original alloy. The settled Fe-rich intermetallics were identified as α-Al15（Fe,Mn）3Si2, which provided the lower balanced Fe concentration in the melt in comparison with other Fe-rich intermetallics.
