Featuring low density and high specific strength, magnesium(Mg) alloys have attracted wide interests in the fields of portable devices and automotive industry. However, the active chemical and electrochemical properti...Featuring low density and high specific strength, magnesium(Mg) alloys have attracted wide interests in the fields of portable devices and automotive industry. However, the active chemical and electrochemical properties make them susceptible to corrosion in humid, seawater, soil,and chemical medium. Various strategies have revealed certain merits of protecting Mg alloys. Therein, engineering self-repairing coatings is considered as an effective strategy, because they can enable the timely repair for damaged areas, which brings about long-term protection for Mg alloys. In this review, self-repairing coatings on Mg alloys are summarized from two aspects, namely shape restoring coatings and function restoring coatings. Shape restoring coatings benefit for swelling, shrinking, or reassociating reversible chemical bonds to return to the original state and morphology when coatings broken;function self-repairing coatings depend on the release of inhibitors to generate new passive layers on the damaged areas. With the advancement of coating research and to fulfill the demanding requirements of applications, it is an inevitable trend to develop coatings that can integrate multiple functions(such as stimulus response, self-repairing, corrosion warning,and so on). As a novel carrier and barrier, porous solids, especially covalent organic frameworks(COFs), have been respected as the future development of self-repairing coatings on Mg alloys, due to their unique, diverse structures and adjustable functions.展开更多
Cast Cr Co Ni Alx(x=0-1.2) medium-entropy alloys(MEAs) were produced by arc melting and flip cast to investigate the alloying effect of Al addition on the microstructure, phase constituent and mechanical properties. T...Cast Cr Co Ni Alx(x=0-1.2) medium-entropy alloys(MEAs) were produced by arc melting and flip cast to investigate the alloying effect of Al addition on the microstructure, phase constituent and mechanical properties. The crystal structure changes from an initial face-centered cubic(FCC) to duplex FCC and body-centered cubic(BCC) and finally a single BCC with increasing Al content. In the duplex region, FCC and BCC phases form under a eutectic reaction in the interdendrite region. In the single BCC region, the dendrites transform to ordered B2 and disordered A2 BCC phases resulting from spinodal decomposition. Corresponding to their phase constituents, yield strength increases accompanied with an elongation reduction with increasing Al addition. A very interesting phenomenon of very weak ordered FCC(001) spots appearing in Al-0.4 alloy was observed, indicating a local ordering of FCC phase. The changes of fracture surfaces after the tensile deformation are also corresponding to the variations in mechanical properties.展开更多
Ultrafine nano-scale Cu2Sb alloy confined in a three-dimensional porous carbon was synthesized using NaCl template-assisted vacuum freeze-drying followed by high-temperature sintering and was evaluated as an anode for...Ultrafine nano-scale Cu2Sb alloy confined in a three-dimensional porous carbon was synthesized using NaCl template-assisted vacuum freeze-drying followed by high-temperature sintering and was evaluated as an anode for sodium-ion batteries(SIBs)and potassium-ion batteries(PIBs).The alloy exerts excellent cycling durability(the capacity can be maintained at 328.3 mA·h·g^(-1) after 100 cycles for SIBs and 260 mA·h·g^(-1) for PIBs)and rate capability(199 mA·h·g^(-1) at 5 A·g^(-1) for SIBs and 148 mA·h·g^(-1) at 5 A·g^(-1) for PIBs)because of the smooth electron transport path,fast Na/K ion diffusion rate,and restricted volume changes from the synergistic effect of three-dimensional porous carbon networks and the ultrafine bimetallic nanoalloy.This study provides an ingenious design route and a simple preparation method toward exploring a high-property electrode for K-ion and Na-ion batteries,and it also introduces broad application prospects for other electrochemical applications.展开更多
Microstructure and mechanical properties of non-equiatomic(CuNi)_(100-x)Co_(x)(x=15,20,25 and 30,at.%)medium-entropy alloys(MEAs)prepared by vacuum arc-melting were investigated.Results show that all the as-cast MEAs ...Microstructure and mechanical properties of non-equiatomic(CuNi)_(100-x)Co_(x)(x=15,20,25 and 30,at.%)medium-entropy alloys(MEAs)prepared by vacuum arc-melting were investigated.Results show that all the as-cast MEAs exhibit dual face-centered cubic(fcc)solid-solution phases with identical lattice constant,showing typical dendrite structure consisting of(Ni,Co)-rich phase in dendrites and Cu-rich phase in inter-dendrites.The positive enthalpy of mixing among Cu and Ni-Co elements is responsible for the segregation of Cu.With the increase of Co content,the volume fraction of(Ni,Co)-rich phase increases while the Cu-rich phase decreases,resulting in an increment of yield strength and a decrement of elongation for the(CuNi)_(100-x)Co_(x) MEAs.Nano-indentation test results show a great difference of microhardness between the two fcc phases of the MEAs.The measured microhardness value of the(Ni,Co)-rich phase is almost twofold as compared to that of the Cu-rich phase in all the(CuNi)_(100-x)Co_(x) MEAs.During the deformation of the MEAs,the Cu-rich phase bears the main plastic strain,whereas the(Ni,Co)-rich phase provides more pronounced strengthening.展开更多
The spontaaleous infiltration aald wetting behaviors of a Zr-based alloy melt on porous a SiC ceramic plate were studied using tile sessile drop metilod by continuous heating and holding for 1800 s at different temper...The spontaaleous infiltration aald wetting behaviors of a Zr-based alloy melt on porous a SiC ceramic plate were studied using tile sessile drop metilod by continuous heating and holding for 1800 s at different temperatures in a high-vacuum furnace. The results showed that tile Zr-based alloy melt could pastly infiltrate tile porous SiC substrate without pressure due to tile effect of capillary pressure. Wettability and infiltration rates increased witil increasing temperature, and interracial reaction products (ZrC0.7 and TiC) were detected in tile Zr-based alloy/SiC ceramic system, likely because of tile reaction of tile active elements Zr and Ti witil elemental C. Furtilelinore, tile redundant ele- ment Si diffused into tile alloy melt.展开更多
Porous aluminum alloys produced by the metal-gas eutectic method or GASAR process need to be performed under a certain pressure of hydrogen, and to carry over melt to a tailor-made apparatus that ensures directional s...Porous aluminum alloys produced by the metal-gas eutectic method or GASAR process need to be performed under a certain pressure of hydrogen, and to carry over melt to a tailor-made apparatus that ensures directional solidif ication. Hydrogen is driven out of the melt, and then the quasi-cylindrical pores normal to the solidif ication front are usually formed. In the research, the effects of processing parameters(saturation pressure, solidif ication pressure, temperature, and holding time) on the pore structure and porosity of porous aluminum alloys were analyzed. The mechanical properties of Al-Mg alloys were studied by the compressive tests, and the advantages of the porous structure were indicated. By using the GASAR method, pure aluminum, Al-3wt.%Mg, Al-6wt.%Mg and Al-35wt.%Mg alloys with oriented pores have been successfully produced under processing conditions of varying gas pressure, and the relationship between the f inal pore structure and the solidif ication pressure, as well as the inf luences of Mg quantity on the pore size, porosity and mechanical properties of AlMg alloy were investigated. The results show that a higher pressure of solidif ication tends to yield smaller pores in aluminum and its alloys. In the case of Al-Mg alloys, it was proved that with the increasing of Mg amount, the mechanical properties of the alloys sharply deteriorate. However, since Al-3%Mg and Al-6wt.%Mg alloys are ductile metals, their porous samples have greater compressive strength than that of the dense samples due to the existence of pores. It gives the opportunity to use them in industry at the same conditions as dense alloys with savings in weight and material consumption.展开更多
A series of as-cast lightweight multicomponent alloys Al(86-x)Mg10Zn2Cu2Six(x=0,0.3,0.6,0.9,1.2 at.%)were prepared by a vacuum induction furnace with a steel die.With the addition of Si,the reticular white Al-Cu phase...A series of as-cast lightweight multicomponent alloys Al(86-x)Mg10Zn2Cu2Six(x=0,0.3,0.6,0.9,1.2 at.%)were prepared by a vacuum induction furnace with a steel die.With the addition of Si,the reticular white Al-Cu phase deposited were gradually replaced by the gray eutectic Mg-Si phase,while the compressive strength of the alloys increases first and then decreases slowly.It is particularly noteworthy that the compression plasticity also exhibits this trend.When the Si content is 0.9 at.%,the compressive strength reaches its maximum at 779.11 MPa and the compressive plasticity reaches 20.91%.The effect of the addition of Si on the serration behavior of alloy was also studied;we found that the addition of Si introduces a new MgSi phase,and with the change of Si is significantly affects the morphology of the precipitated phase,which affects the serration behavior of the alloys.The comprehensive mechanical properties of the alloy are optimal at the critical point where the serration behavior disappears.In this work,we have provided a method and a composition for the preparation of a low-cost,high-strength,lightweight medium-entropy alloys.展开更多
High-entropy alloys(HEAs)and medium-entropy alloys(MEAs)have attracted a great deal of attention for developing nuclear materials because of their excellent irradiation tolerance.Herein,formation and evolution of radi...High-entropy alloys(HEAs)and medium-entropy alloys(MEAs)have attracted a great deal of attention for developing nuclear materials because of their excellent irradiation tolerance.Herein,formation and evolution of radiation-induced defects in Ni Co Fe MEA and pure Ni are investigated and compared using molecular dynamics simulation.It is observed that the defect recombination rate of ternary Ni Co Fe MEA is higher than that of pure Ni,which is mainly because,in the process of cascade collision,the energy dissipated through atom displacement decreases with increasing the chemical disorder.Consequently,the heat peak phase lasts longer,and the recombination time of the radiation defects(interstitial atoms and vacancies)is likewise longer,with fewer deleterious defects.Moreover,by studying the formation and evolution of dislocation loops in Ni-Co-Fe alloys and Ni,it is found that the stacking fault energy in Ni-Co-Fe decreases as the elemental composition increases,facilitating the formation of ideal stacking fault tetrahedron structures.Hence,these findings shed new light on studying the formation and evolution of radiation-induced defects in MEAs.展开更多
Lotus-type porous Mg-1 wt.% Mn-xZn(x = 0 wt.%, 1 wt.% and 2 wt.%) alloys were fabricated by metal–gas eutectic unidirectional solidification(the Gasar method). Effects of Zn addition and the fabrication process on th...Lotus-type porous Mg-1 wt.% Mn-xZn(x = 0 wt.%, 1 wt.% and 2 wt.%) alloys were fabricated by metal–gas eutectic unidirectional solidification(the Gasar method). Effects of Zn addition and the fabrication process on the porosity, pore diameter and microstructure of the porous Mg alloys were investigated. Zn addition from 0 wt.% to 1 wt.% and 2 wt.% to the Mg-1 wt.% Mn alloy decreased the porosity from41.2% to 36.9% and 35.8%, respectively, with the same preparation processing. In the lotus-type porous Mg-1 wt.%Mn-1 wt.%Zn alloy, the porosities and average pore diameters changed with hydrogen pressures from 0.1 to 0.6 MPa. Conical areas that were rich in elemental Zn existed below the directional pores, and precipitates were also found in conical areas. Homogeneous directional pores existed in the lower portion of the ingot, and coarser directional pores and finer non-directional pores formed in the upper part. A theoretical model of the change in porosity with hydrogen pressure agreed well with the calculated porosities in the steady bubble growing area. The compressive strength of Mg-1 wt.Mn-Zn alloys can be increased by around 20 MPa through rising Zinc content from 1 wt.% to 2 wt.%, which basically linearly decline with the increasing of porosity. This work provides the basis for Gasar Mg-Zn-Mn alloy synthesis in biological applications and shows that the Gasar process is a promising method to fabricate Mg-Zn-Mn alloys with directional pores and a controllable pore structure.展开更多
Porous Al-Mg alloys with different nominal compositions were successfully fabricated via elemental powder reactive synthesis, and the phase composition, pore structure, and corrosion resistance were characterized with...Porous Al-Mg alloys with different nominal compositions were successfully fabricated via elemental powder reactive synthesis, and the phase composition, pore structure, and corrosion resistance were characterized with X-ray diffractometer, scanning electron microscope and electrochemical analyzer. The volume expansion ratio, open porosity and corrosion resistance in 3.5%(mass fraction) Na Cl aqueous solution of the alloys increase at first and then decrease with the increase of Mg content. The maxima of volume expansion ratio and open porosity are 18.3% and 28.1% for the porous Al-56%Mg(mass fraction) alloy, while there is the best corrosion resistance for the porous Al-37.5% Mg(mass fraction) alloy. The pore formation mechanism can be explained by Kirkendall effect, and the corrosion resistance can be mainly affected by the phase composition for the porous Al-Mg alloys. They would be of the potential application for filtration in the chloride environment.展开更多
Ti-Ni porous alloy was made from titanium and nickel powder mixture in equiatomic composition by combustion synthesis technique (self-propagation high temperature synthesis). The result analyzed by SEM and XRD shows t...Ti-Ni porous alloy was made from titanium and nickel powder mixture in equiatomic composition by combustion synthesis technique (self-propagation high temperature synthesis). The result analyzed by SEM and XRD shows that the alloy possesses high porosity (50%~70%), and mainly consists of TiNi phase as well as rare Ti_2Ni and TiNi_3 transition phase. Then it was activated, cracked and used as sorbent for hydrogen isotope separation. Through experiment investigation, it was discovered that the alloy is able to absorb hydrogen in very large quantities in the lattice thereof, but deuterium only very slightly or not at all, at temperatures up to 623 K, especially at temperatures from about 323 to 423 K. According to this characteristic, the Ti-Ni porous alloys may replace noble metal palladium(Pd) as used for hydrogen isotope separation and purification. Study illustrated that the technology would have a promising engineering application, such as being used for reprocessing Tokamak exhaust gases and producing high purity deuterium.展开更多
Porous Fe-Sialloys with different nominalcompositions ranging from Fe-10wt% Sito Fe-50wt% Siwere fabricated through a reactive synthesis of Fe and Sielementalpowder mixtures.The effects of Sicontents on the pore struc...Porous Fe-Sialloys with different nominalcompositions ranging from Fe-10wt% Sito Fe-50wt% Siwere fabricated through a reactive synthesis of Fe and Sielementalpowder mixtures.The effects of Sicontents on the pore structure of porous Fe-Sialloy were investigated in detail.The results showed that the open porosity,gas permeability and maximum pore size of the porous Fe-Sialloys increased with increasing Sicontents,indicating that the porosity and pore size can be tailored by changing the Sicontents.The pore structure parameter including the open porosity,gas permeability,maximum pore size obeyed the HagenPoiseuille formula with the constant G=0.035 m^(-1_Pa^(-1)s^(-1) for the reactively synthesized porous Fe-Sialloys.The mechanicalproperty of the porous Fe-Sialloys showed applicability in the filtration industries.展开更多
Sn/Sb based alloy anodes have attracted considerable interest as electrodes for next-generation high performance Li-ion batteries (LIBs) owing to their high theoretical capacities. And fabricate porous structure is an...Sn/Sb based alloy anodes have attracted considerable interest as electrodes for next-generation high performance Li-ion batteries (LIBs) owing to their high theoretical capacities. And fabricate porous structure is an effective way to improve materials’ cycling performance. Here, we developed nanoporous SnSb alloy ribbon (NP-SnSb) through a melt-spinning/chemical-etching process and took it as electrode of LIB directly. Being of self-supported and binder free, the NP-SnSb shows a total outperformance over its nonporous counterparts both in cycling performance and kinetic characteristic. Besides, considering the melt-spinning/chemical-etching synthetic process is high-through-put and simple, the ribbon kind of alloy anodes have strong potential application for LIBs research.展开更多
Designing strong, yet ductile, and body-centered cubic(BCC) medium-entropy alloys(MEAs) remains to be a challenge nowadays.In this study, the strength–ductility trade-off of Ni_(0.6)CoFe_(1.4)MEAs was tackled via int...Designing strong, yet ductile, and body-centered cubic(BCC) medium-entropy alloys(MEAs) remains to be a challenge nowadays.In this study, the strength–ductility trade-off of Ni_(0.6)CoFe_(1.4)MEAs was tackled via introducing a BCC + face-centered cubic(FCC) dual-phase microstructure. Ni_(0.6)CoFe_(1.4)Nbx(x = 0, 0.05, 0.08, 0.10, and 0.15, in molar ratio) MEAs were prepared using vacuum induction melting. Results show that the new alloy is composed of BCC plus FCC dual phases featuring a network-like structure, and the BCC phase is the main phase in this alloy system. Moreover, the Nb0.10 MEA shows high strength and respectable tensile ductility, representing the best combination of the strength and fracture elongation among the alloys studied here. The remarkable strength of the Nb0.10 MEA is attributed to the combined effect of the solid solution strengthening, the precipitation hardening effect and the interface strengthening effect.展开更多
A novel inorganic-organic layer with outstanding corrosion resistance in a 3.5wt.% NaCl solution was fabricated by taking advantage of the unique interactions between coumarin (COM) molecules and the porous layer form...A novel inorganic-organic layer with outstanding corrosion resistance in a 3.5wt.% NaCl solution was fabricated by taking advantage of the unique interactions between coumarin (COM) molecules and the porous layer formed on Mg alloy. To achieve this aim, the AZ31 Mg alloy coated via microarc oxidation (MAO) coating was placed in an ethanolic solution of COM for 6 and 12 h at 25 ℃. By reducing the surface area exposed to the corrosive species, the donor-acceptor complexes produced by the particular interactions between the COM and MAO surface would successfully prevent the corrosion of Mg alloy substrate. The MAO layer would provide the ideal sites for the charge-transfer-induced physical and chemical locking, leading to uneven organic layer nucleation and crystal growth with a thatch-like structure. To evaluate the formation mechanism of such hybrid composites and highlight the key bonding modes between the COM and MAO, theoretical simulations were conducted.展开更多
The oxygen reduction reaction(ORR)electrocatalytic activity of Pt-based catalysts can be significantly improved by supporting Pt and its alloy nanoparticles(NPs)on a porous carbon support with large surface area.Howev...The oxygen reduction reaction(ORR)electrocatalytic activity of Pt-based catalysts can be significantly improved by supporting Pt and its alloy nanoparticles(NPs)on a porous carbon support with large surface area.However,such catalysts are often obtained by constructing porous carbon support followed by depositing Pt and its alloy NPs inside the pores,in which the migration and agglomeration of Pt NPs are inevitable under harsh operating conditions owing to the relatively weak interaction between NPs and carbon support.Here we develop a facile electrospinning strategy to in-situ prepare small-sized PtZn NPs supported on porous nitrogen-doped carbon nanofibers.Electrochemical results demonstrate that the as-prepared PtZn alloy catalyst exhibits excellent initial ORR activity with a half-wave potential(E_(1/2))of 0.911 V versus reversible hydrogen electrode(vs.RHE)and enhanced durability with only decreasing 11 mV after 30,000 potential cycles,compared to a more significant drop of 24 mV in E_(1/2)of Pt/C catalysts(after 10,000 potential cycling).Such a desirable performance is ascribed to the created triple-phase reaction boundary assisted by the evaporation of Zn and strengthened interaction between nanoparticles and the carbon support,inhibiting the migration and aggregation of NPs during the ORR.展开更多
The L1_(2)-strengthened Co_(34)Cr_(32)Ni_(27)Al_(4)Ti_(3)medium-entropy alloy(MEA)with precipitations of grain boundaries has been developed through selective laser melting(SLM)followed by cold rolling and annealing,e...The L1_(2)-strengthened Co_(34)Cr_(32)Ni_(27)Al_(4)Ti_(3)medium-entropy alloy(MEA)with precipitations of grain boundaries has been developed through selective laser melting(SLM)followed by cold rolling and annealing,exhibiting excellent strength-ductility synergy.The as-printed alloy exhibits low yield strength(YS)of~384 MPa,ultimate tensile strength(UTS)of~453 MPa,and uniform elongation(UE)of 1.5%due to the existence of the SLM-induced defects.After cold rolling and annealing,the YS,UTS,and UE are significantly increased to~739 MPa,~1230 MPa,and~47%,respectively.This enhancement primarily originates from the refined grain structure induced by cold rolling and annealing.The presence of coherent sphericalγ'precipitates(L1_(2)phases)and Al/Ti-rich precipitates at the grain boundaries,coupled with increased lattice defects such as dislocations,stacking faults,and ultrafine deformation twins,further contribute to the property’s improvement.Our study highlights the potential of SLM in producing high-strength and ductile MEA with coherent L1_(2)nanoprecipitates,which can be further optimized through subsequent rolling and annealing processes.These findings offer valuable insights for the development of high-performance alloys for future engineering applications.展开更多
Incorporating four cations into a single-phase oxide is beneficial for maintaining structural stability during Li+insertion/desertion because of the produced entropy-dominated phase stabilization effects. However,medi...Incorporating four cations into a single-phase oxide is beneficial for maintaining structural stability during Li+insertion/desertion because of the produced entropy-dominated phase stabilization effects. However,medium-entropy oxides exhibit inherently poor electron and ion conductivity. As such, in this work, a single-phase medium-entropy oxide of Ni_(x)Cu_(y)CozMn_(1-x-y-z)O(named as NCCM@oxides(H_(2))) is prepared by modified-NiCuCoMn alloy through the epitaxial-growing-based self-combustion and hydrogen reduction. During hydrogen reduction, some Cu ions are reduced to elemental Cu(defined as Cu^(0)),which is distributed among the metal oxides, while generating extensive oxygen vacancies around Cu. The synergetic effect between nanoporous metal-core oxide-shell structure and enriched oxygen/Cu^(0) vacancies greatly enhances the electronic/ionic conductivity. In addition, the lattice of single-phase quaternary metal oxides has the configuration entropy stability, which enables the rock-salt structure to remain stable during repeated conversion reactions. Benefiting from the above-mentioned merits, the anodeforLi-ionbatterieswithentropy-stabled NCCM@oxides(H_(2)) composite shows a high specific capacity of 699 mAh·g^(-1) at 0.1 A·g^(-1) and ultra-stable cycling stability, which maintains 618 and 489 mAh·g^(-1) at 0.1 and 1.0 A·g^(-1) after 200 cycles, respectively. This is the first use of this novel and simple strategy for modifying medium-entropy oxides, which paves the way for the development of high-entropy oxides as high-performance electrodes.展开更多
Rational designing of one-dimensional(1D)magnetic alloy to facilitate electromagnetic(EM)wave attenuation capability in low-frequency(2-6 GHz)microwave absorption field is highly desired but remains a significant chal...Rational designing of one-dimensional(1D)magnetic alloy to facilitate electromagnetic(EM)wave attenuation capability in low-frequency(2-6 GHz)microwave absorption field is highly desired but remains a significant challenge.In this study,a composite EM wave absorber made of a FeCoNi medium-entropy alloy embedded in a 1D carbon matrix framework is rationally designed through an improved electrospinning method.The 1D-shaped FeCoNi alloy embedded composite demonstrates the high-density and continuous magnetic network using off-axis electronic holography technique,indicating the excellent magnetic loss ability under an external EM field.Then,the in-depth analysis shows that many factors,including 1D anisotropy and intrinsic physical features of the magnetic medium-entropy alloy,primarily contribute to the enhanced EM wave absorption performance.Therefore,the fabricated EM wave absorber shows an increasing effective absorption band of 1.3 GHz in the low-frequency electromagnetic field at an ultrathin thickness of 2 mm.Thus,this study opens up a new method for the design and preparation of high-performance 1D magnetic EM absorbers.展开更多
基金the financial support from the National Natural Science Foundation of China (Nos.52204389,U19A2084 and 52234009)the National Key Research and Development Program (No.2022YFE0122000)Program for the Central University Youth Innovation Team。
文摘Featuring low density and high specific strength, magnesium(Mg) alloys have attracted wide interests in the fields of portable devices and automotive industry. However, the active chemical and electrochemical properties make them susceptible to corrosion in humid, seawater, soil,and chemical medium. Various strategies have revealed certain merits of protecting Mg alloys. Therein, engineering self-repairing coatings is considered as an effective strategy, because they can enable the timely repair for damaged areas, which brings about long-term protection for Mg alloys. In this review, self-repairing coatings on Mg alloys are summarized from two aspects, namely shape restoring coatings and function restoring coatings. Shape restoring coatings benefit for swelling, shrinking, or reassociating reversible chemical bonds to return to the original state and morphology when coatings broken;function self-repairing coatings depend on the release of inhibitors to generate new passive layers on the damaged areas. With the advancement of coating research and to fulfill the demanding requirements of applications, it is an inevitable trend to develop coatings that can integrate multiple functions(such as stimulus response, self-repairing, corrosion warning,and so on). As a novel carrier and barrier, porous solids, especially covalent organic frameworks(COFs), have been respected as the future development of self-repairing coatings on Mg alloys, due to their unique, diverse structures and adjustable functions.
基金financially supported by the National Nature Science Foundation of China(51775204 and 51604222)the Analytical and Testing Center,HUSTChina Postdoctoral Science Foundation Funded Project
文摘Cast Cr Co Ni Alx(x=0-1.2) medium-entropy alloys(MEAs) were produced by arc melting and flip cast to investigate the alloying effect of Al addition on the microstructure, phase constituent and mechanical properties. The crystal structure changes from an initial face-centered cubic(FCC) to duplex FCC and body-centered cubic(BCC) and finally a single BCC with increasing Al content. In the duplex region, FCC and BCC phases form under a eutectic reaction in the interdendrite region. In the single BCC region, the dendrites transform to ordered B2 and disordered A2 BCC phases resulting from spinodal decomposition. Corresponding to their phase constituents, yield strength increases accompanied with an elongation reduction with increasing Al addition. A very interesting phenomenon of very weak ordered FCC(001) spots appearing in Al-0.4 alloy was observed, indicating a local ordering of FCC phase. The changes of fracture surfaces after the tensile deformation are also corresponding to the variations in mechanical properties.
基金financially supported by the National Natural Science Foundation of China(Nos.51871046,51902046,52071073,51874079,51571054,51771046,and 51674068)the Natural Science Foundation of Liaoning Province,China(No.201602257)+2 种基金Natural Science Foundation of Hebei Province,China(Nos.E2019501097,E2018501091,E2020501004)the Science and Technology Project of Hebei Province,China(No.15271302D)the Fundamental Research Funds for the Central Universities,China(Nos.N182304017,N182304015,N172302001,N172304044).
文摘Ultrafine nano-scale Cu2Sb alloy confined in a three-dimensional porous carbon was synthesized using NaCl template-assisted vacuum freeze-drying followed by high-temperature sintering and was evaluated as an anode for sodium-ion batteries(SIBs)and potassium-ion batteries(PIBs).The alloy exerts excellent cycling durability(the capacity can be maintained at 328.3 mA·h·g^(-1) after 100 cycles for SIBs and 260 mA·h·g^(-1) for PIBs)and rate capability(199 mA·h·g^(-1) at 5 A·g^(-1) for SIBs and 148 mA·h·g^(-1) at 5 A·g^(-1) for PIBs)because of the smooth electron transport path,fast Na/K ion diffusion rate,and restricted volume changes from the synergistic effect of three-dimensional porous carbon networks and the ultrafine bimetallic nanoalloy.This study provides an ingenious design route and a simple preparation method toward exploring a high-property electrode for K-ion and Na-ion batteries,and it also introduces broad application prospects for other electrochemical applications.
基金supported by the Key-Area Research and Development Program of Guangdong Province(Grant No.2018B090905002)the National Natural Science Foundation of China(Grant No.52103360)the Basic Research Foundation of Guangzhou City(Grant No.201804020071).
文摘Microstructure and mechanical properties of non-equiatomic(CuNi)_(100-x)Co_(x)(x=15,20,25 and 30,at.%)medium-entropy alloys(MEAs)prepared by vacuum arc-melting were investigated.Results show that all the as-cast MEAs exhibit dual face-centered cubic(fcc)solid-solution phases with identical lattice constant,showing typical dendrite structure consisting of(Ni,Co)-rich phase in dendrites and Cu-rich phase in inter-dendrites.The positive enthalpy of mixing among Cu and Ni-Co elements is responsible for the segregation of Cu.With the increase of Co content,the volume fraction of(Ni,Co)-rich phase increases while the Cu-rich phase decreases,resulting in an increment of yield strength and a decrement of elongation for the(CuNi)_(100-x)Co_(x) MEAs.Nano-indentation test results show a great difference of microhardness between the two fcc phases of the MEAs.The measured microhardness value of the(Ni,Co)-rich phase is almost twofold as compared to that of the Cu-rich phase in all the(CuNi)_(100-x)Co_(x) MEAs.During the deformation of the MEAs,the Cu-rich phase bears the main plastic strain,whereas the(Ni,Co)-rich phase provides more pronounced strengthening.
基金the financial support from the National Natural Science Foundation of China(No.51401131)the China's Manned Space Station Project(No.TGJZ800–2–RW024)
文摘The spontaaleous infiltration aald wetting behaviors of a Zr-based alloy melt on porous a SiC ceramic plate were studied using tile sessile drop metilod by continuous heating and holding for 1800 s at different temperatures in a high-vacuum furnace. The results showed that tile Zr-based alloy melt could pastly infiltrate tile porous SiC substrate without pressure due to tile effect of capillary pressure. Wettability and infiltration rates increased witil increasing temperature, and interracial reaction products (ZrC0.7 and TiC) were detected in tile Zr-based alloy/SiC ceramic system, likely because of tile reaction of tile active elements Zr and Ti witil elemental C. Furtilelinore, tile redundant ele- ment Si diffused into tile alloy melt.
基金financially supported by Liaoning BaiQianWan Talents Program(No.2011921065)
文摘Porous aluminum alloys produced by the metal-gas eutectic method or GASAR process need to be performed under a certain pressure of hydrogen, and to carry over melt to a tailor-made apparatus that ensures directional solidif ication. Hydrogen is driven out of the melt, and then the quasi-cylindrical pores normal to the solidif ication front are usually formed. In the research, the effects of processing parameters(saturation pressure, solidif ication pressure, temperature, and holding time) on the pore structure and porosity of porous aluminum alloys were analyzed. The mechanical properties of Al-Mg alloys were studied by the compressive tests, and the advantages of the porous structure were indicated. By using the GASAR method, pure aluminum, Al-3wt.%Mg, Al-6wt.%Mg and Al-35wt.%Mg alloys with oriented pores have been successfully produced under processing conditions of varying gas pressure, and the relationship between the f inal pore structure and the solidif ication pressure, as well as the inf luences of Mg quantity on the pore size, porosity and mechanical properties of AlMg alloy were investigated. The results show that a higher pressure of solidif ication tends to yield smaller pores in aluminum and its alloys. In the case of Al-Mg alloys, it was proved that with the increasing of Mg amount, the mechanical properties of the alloys sharply deteriorate. However, since Al-3%Mg and Al-6wt.%Mg alloys are ductile metals, their porous samples have greater compressive strength than that of the dense samples due to the existence of pores. It gives the opportunity to use them in industry at the same conditions as dense alloys with savings in weight and material consumption.
基金The authors would like to thank the National Science Foundation of China(NSFC,Grants 51671020)Dongguan Yi’an Technology Co.,Ltd.for the financial support.
文摘A series of as-cast lightweight multicomponent alloys Al(86-x)Mg10Zn2Cu2Six(x=0,0.3,0.6,0.9,1.2 at.%)were prepared by a vacuum induction furnace with a steel die.With the addition of Si,the reticular white Al-Cu phase deposited were gradually replaced by the gray eutectic Mg-Si phase,while the compressive strength of the alloys increases first and then decreases slowly.It is particularly noteworthy that the compression plasticity also exhibits this trend.When the Si content is 0.9 at.%,the compressive strength reaches its maximum at 779.11 MPa and the compressive plasticity reaches 20.91%.The effect of the addition of Si on the serration behavior of alloy was also studied;we found that the addition of Si introduces a new MgSi phase,and with the change of Si is significantly affects the morphology of the precipitated phase,which affects the serration behavior of the alloys.The comprehensive mechanical properties of the alloy are optimal at the critical point where the serration behavior disappears.In this work,we have provided a method and a composition for the preparation of a low-cost,high-strength,lightweight medium-entropy alloys.
基金financially supported by the National Natural Science Foundation of China(Grant No.11775074)the Science and Technology Program of Hunan Province,China(Grant No.2019TP1014)
文摘High-entropy alloys(HEAs)and medium-entropy alloys(MEAs)have attracted a great deal of attention for developing nuclear materials because of their excellent irradiation tolerance.Herein,formation and evolution of radiation-induced defects in Ni Co Fe MEA and pure Ni are investigated and compared using molecular dynamics simulation.It is observed that the defect recombination rate of ternary Ni Co Fe MEA is higher than that of pure Ni,which is mainly because,in the process of cascade collision,the energy dissipated through atom displacement decreases with increasing the chemical disorder.Consequently,the heat peak phase lasts longer,and the recombination time of the radiation defects(interstitial atoms and vacancies)is likewise longer,with fewer deleterious defects.Moreover,by studying the formation and evolution of dislocation loops in Ni-Co-Fe alloys and Ni,it is found that the stacking fault energy in Ni-Co-Fe decreases as the elemental composition increases,facilitating the formation of ideal stacking fault tetrahedron structures.Hence,these findings shed new light on studying the formation and evolution of radiation-induced defects in MEAs.
基金National Natural Science Foundation of China(51771101)。
文摘Lotus-type porous Mg-1 wt.% Mn-xZn(x = 0 wt.%, 1 wt.% and 2 wt.%) alloys were fabricated by metal–gas eutectic unidirectional solidification(the Gasar method). Effects of Zn addition and the fabrication process on the porosity, pore diameter and microstructure of the porous Mg alloys were investigated. Zn addition from 0 wt.% to 1 wt.% and 2 wt.% to the Mg-1 wt.% Mn alloy decreased the porosity from41.2% to 36.9% and 35.8%, respectively, with the same preparation processing. In the lotus-type porous Mg-1 wt.%Mn-1 wt.%Zn alloy, the porosities and average pore diameters changed with hydrogen pressures from 0.1 to 0.6 MPa. Conical areas that were rich in elemental Zn existed below the directional pores, and precipitates were also found in conical areas. Homogeneous directional pores existed in the lower portion of the ingot, and coarser directional pores and finer non-directional pores formed in the upper part. A theoretical model of the change in porosity with hydrogen pressure agreed well with the calculated porosities in the steady bubble growing area. The compressive strength of Mg-1 wt.Mn-Zn alloys can be increased by around 20 MPa through rising Zinc content from 1 wt.% to 2 wt.%, which basically linearly decline with the increasing of porosity. This work provides the basis for Gasar Mg-Zn-Mn alloy synthesis in biological applications and shows that the Gasar process is a promising method to fabricate Mg-Zn-Mn alloys with directional pores and a controllable pore structure.
基金Project(IRT_14R48)supported by the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of ChinaProjects(51271158,51272158,51401175,51504213)supported by the National Natural Science Foundation of China+2 种基金Project([2009]17)supported by the Changjiang Scholar Incentive Program,ChinaProject(CX2015B224)supported by the Hunan Provincial Innovation Foundation for Postgraduate,ChinaProject(2015WK3021)supported by the Hunan Provincial Key Research Program,China
文摘Porous Al-Mg alloys with different nominal compositions were successfully fabricated via elemental powder reactive synthesis, and the phase composition, pore structure, and corrosion resistance were characterized with X-ray diffractometer, scanning electron microscope and electrochemical analyzer. The volume expansion ratio, open porosity and corrosion resistance in 3.5%(mass fraction) Na Cl aqueous solution of the alloys increase at first and then decrease with the increase of Mg content. The maxima of volume expansion ratio and open porosity are 18.3% and 28.1% for the porous Al-56%Mg(mass fraction) alloy, while there is the best corrosion resistance for the porous Al-37.5% Mg(mass fraction) alloy. The pore formation mechanism can be explained by Kirkendall effect, and the corrosion resistance can be mainly affected by the phase composition for the porous Al-Mg alloys. They would be of the potential application for filtration in the chloride environment.
文摘Ti-Ni porous alloy was made from titanium and nickel powder mixture in equiatomic composition by combustion synthesis technique (self-propagation high temperature synthesis). The result analyzed by SEM and XRD shows that the alloy possesses high porosity (50%~70%), and mainly consists of TiNi phase as well as rare Ti_2Ni and TiNi_3 transition phase. Then it was activated, cracked and used as sorbent for hydrogen isotope separation. Through experiment investigation, it was discovered that the alloy is able to absorb hydrogen in very large quantities in the lattice thereof, but deuterium only very slightly or not at all, at temperatures up to 623 K, especially at temperatures from about 323 to 423 K. According to this characteristic, the Ti-Ni porous alloys may replace noble metal palladium(Pd) as used for hydrogen isotope separation and purification. Study illustrated that the technology would have a promising engineering application, such as being used for reprocessing Tokamak exhaust gases and producing high purity deuterium.
基金Funded by the National Natural Science Foundation of China(51071178)the Natural Science Foundation of Hunan Province,China(12JJ4044)the State Science and Technology Support Program(2012BAC02B05)
文摘Porous Fe-Sialloys with different nominalcompositions ranging from Fe-10wt% Sito Fe-50wt% Siwere fabricated through a reactive synthesis of Fe and Sielementalpowder mixtures.The effects of Sicontents on the pore structure of porous Fe-Sialloy were investigated in detail.The results showed that the open porosity,gas permeability and maximum pore size of the porous Fe-Sialloys increased with increasing Sicontents,indicating that the porosity and pore size can be tailored by changing the Sicontents.The pore structure parameter including the open porosity,gas permeability,maximum pore size obeyed the HagenPoiseuille formula with the constant G=0.035 m^(-1_Pa^(-1)s^(-1) for the reactively synthesized porous Fe-Sialloys.The mechanicalproperty of the porous Fe-Sialloys showed applicability in the filtration industries.
文摘Sn/Sb based alloy anodes have attracted considerable interest as electrodes for next-generation high performance Li-ion batteries (LIBs) owing to their high theoretical capacities. And fabricate porous structure is an effective way to improve materials’ cycling performance. Here, we developed nanoporous SnSb alloy ribbon (NP-SnSb) through a melt-spinning/chemical-etching process and took it as electrode of LIB directly. Being of self-supported and binder free, the NP-SnSb shows a total outperformance over its nonporous counterparts both in cycling performance and kinetic characteristic. Besides, considering the melt-spinning/chemical-etching synthetic process is high-through-put and simple, the ribbon kind of alloy anodes have strong potential application for LIBs research.
基金financially supported by the National Natural Science Foundation of China (No. 51571118)。
文摘Designing strong, yet ductile, and body-centered cubic(BCC) medium-entropy alloys(MEAs) remains to be a challenge nowadays.In this study, the strength–ductility trade-off of Ni_(0.6)CoFe_(1.4)MEAs was tackled via introducing a BCC + face-centered cubic(FCC) dual-phase microstructure. Ni_(0.6)CoFe_(1.4)Nbx(x = 0, 0.05, 0.08, 0.10, and 0.15, in molar ratio) MEAs were prepared using vacuum induction melting. Results show that the new alloy is composed of BCC plus FCC dual phases featuring a network-like structure, and the BCC phase is the main phase in this alloy system. Moreover, the Nb0.10 MEA shows high strength and respectable tensile ductility, representing the best combination of the strength and fracture elongation among the alloys studied here. The remarkable strength of the Nb0.10 MEA is attributed to the combined effect of the solid solution strengthening, the precipitation hardening effect and the interface strengthening effect.
基金This work was supported by the National Research Foundation of Korea(NRF)funded by the Korean government(MSIT)(No.2022R1A2C1006743).
文摘A novel inorganic-organic layer with outstanding corrosion resistance in a 3.5wt.% NaCl solution was fabricated by taking advantage of the unique interactions between coumarin (COM) molecules and the porous layer formed on Mg alloy. To achieve this aim, the AZ31 Mg alloy coated via microarc oxidation (MAO) coating was placed in an ethanolic solution of COM for 6 and 12 h at 25 ℃. By reducing the surface area exposed to the corrosive species, the donor-acceptor complexes produced by the particular interactions between the COM and MAO surface would successfully prevent the corrosion of Mg alloy substrate. The MAO layer would provide the ideal sites for the charge-transfer-induced physical and chemical locking, leading to uneven organic layer nucleation and crystal growth with a thatch-like structure. To evaluate the formation mechanism of such hybrid composites and highlight the key bonding modes between the COM and MAO, theoretical simulations were conducted.
基金This work was financially supported by National Key Research and Development Program(2018YFB1502503).
文摘The oxygen reduction reaction(ORR)electrocatalytic activity of Pt-based catalysts can be significantly improved by supporting Pt and its alloy nanoparticles(NPs)on a porous carbon support with large surface area.However,such catalysts are often obtained by constructing porous carbon support followed by depositing Pt and its alloy NPs inside the pores,in which the migration and agglomeration of Pt NPs are inevitable under harsh operating conditions owing to the relatively weak interaction between NPs and carbon support.Here we develop a facile electrospinning strategy to in-situ prepare small-sized PtZn NPs supported on porous nitrogen-doped carbon nanofibers.Electrochemical results demonstrate that the as-prepared PtZn alloy catalyst exhibits excellent initial ORR activity with a half-wave potential(E_(1/2))of 0.911 V versus reversible hydrogen electrode(vs.RHE)and enhanced durability with only decreasing 11 mV after 30,000 potential cycles,compared to a more significant drop of 24 mV in E_(1/2)of Pt/C catalysts(after 10,000 potential cycling).Such a desirable performance is ascribed to the created triple-phase reaction boundary assisted by the evaporation of Zn and strengthened interaction between nanoparticles and the carbon support,inhibiting the migration and aggregation of NPs during the ORR.
基金This work is supported by the National Natural Science Foundation of China(Nos.51971180,52271037,and 51971179)the Guangdong Provincial Science and Technology Program,China(No.2019B090905009)+2 种基金the Shaanxi Provincial Science and Technology Program,China(No.2023-JC-ZD-23)the Foreign Senior Talents Program of Guangdong Province,China,and the Fundamental Research Funds for the Central Universities of China(No.D5000230131)the Shenzhen Fundamental Research Program(Grant No.JCYJ20210324122203010).The authors would like to express their sincere gratitude to Dr.W.Loeser and Dr.V.Y.Zadorozhnyy for invaluable discussion.
文摘The L1_(2)-strengthened Co_(34)Cr_(32)Ni_(27)Al_(4)Ti_(3)medium-entropy alloy(MEA)with precipitations of grain boundaries has been developed through selective laser melting(SLM)followed by cold rolling and annealing,exhibiting excellent strength-ductility synergy.The as-printed alloy exhibits low yield strength(YS)of~384 MPa,ultimate tensile strength(UTS)of~453 MPa,and uniform elongation(UE)of 1.5%due to the existence of the SLM-induced defects.After cold rolling and annealing,the YS,UTS,and UE are significantly increased to~739 MPa,~1230 MPa,and~47%,respectively.This enhancement primarily originates from the refined grain structure induced by cold rolling and annealing.The presence of coherent sphericalγ'precipitates(L1_(2)phases)and Al/Ti-rich precipitates at the grain boundaries,coupled with increased lattice defects such as dislocations,stacking faults,and ultrafine deformation twins,further contribute to the property’s improvement.Our study highlights the potential of SLM in producing high-strength and ductile MEA with coherent L1_(2)nanoprecipitates,which can be further optimized through subsequent rolling and annealing processes.These findings offer valuable insights for the development of high-performance alloys for future engineering applications.
基金financially supported by the National Natural Science Foundation of China (Nos. 52271011, 52102291 and 51701142)。
文摘Incorporating four cations into a single-phase oxide is beneficial for maintaining structural stability during Li+insertion/desertion because of the produced entropy-dominated phase stabilization effects. However,medium-entropy oxides exhibit inherently poor electron and ion conductivity. As such, in this work, a single-phase medium-entropy oxide of Ni_(x)Cu_(y)CozMn_(1-x-y-z)O(named as NCCM@oxides(H_(2))) is prepared by modified-NiCuCoMn alloy through the epitaxial-growing-based self-combustion and hydrogen reduction. During hydrogen reduction, some Cu ions are reduced to elemental Cu(defined as Cu^(0)),which is distributed among the metal oxides, while generating extensive oxygen vacancies around Cu. The synergetic effect between nanoporous metal-core oxide-shell structure and enriched oxygen/Cu^(0) vacancies greatly enhances the electronic/ionic conductivity. In addition, the lattice of single-phase quaternary metal oxides has the configuration entropy stability, which enables the rock-salt structure to remain stable during repeated conversion reactions. Benefiting from the above-mentioned merits, the anodeforLi-ionbatterieswithentropy-stabled NCCM@oxides(H_(2)) composite shows a high specific capacity of 699 mAh·g^(-1) at 0.1 A·g^(-1) and ultra-stable cycling stability, which maintains 618 and 489 mAh·g^(-1) at 0.1 and 1.0 A·g^(-1) after 200 cycles, respectively. This is the first use of this novel and simple strategy for modifying medium-entropy oxides, which paves the way for the development of high-entropy oxides as high-performance electrodes.
基金supported by the National Natural Science Foundation of China(Nos.51725101,11727807,51672050,61790581,22088101)the Ministry of Science and Technology of China(973 Project Nos.2018YFA0209102 and 2021YFA1200600)Infrastructure and Facility Construction Project of Zhejiang Laboratory.
文摘Rational designing of one-dimensional(1D)magnetic alloy to facilitate electromagnetic(EM)wave attenuation capability in low-frequency(2-6 GHz)microwave absorption field is highly desired but remains a significant challenge.In this study,a composite EM wave absorber made of a FeCoNi medium-entropy alloy embedded in a 1D carbon matrix framework is rationally designed through an improved electrospinning method.The 1D-shaped FeCoNi alloy embedded composite demonstrates the high-density and continuous magnetic network using off-axis electronic holography technique,indicating the excellent magnetic loss ability under an external EM field.Then,the in-depth analysis shows that many factors,including 1D anisotropy and intrinsic physical features of the magnetic medium-entropy alloy,primarily contribute to the enhanced EM wave absorption performance.Therefore,the fabricated EM wave absorber shows an increasing effective absorption band of 1.3 GHz in the low-frequency electromagnetic field at an ultrathin thickness of 2 mm.Thus,this study opens up a new method for the design and preparation of high-performance 1D magnetic EM absorbers.