We report a theoretical investigation into superconductivity within the MAXH_(6) quaternary hydride system using first-principles calculations,where M and A denote alkali and alkaline earth elements,respectively,and X...We report a theoretical investigation into superconductivity within the MAXH_(6) quaternary hydride system using first-principles calculations,where M and A denote alkali and alkaline earth elements,respectively,and X represents transition metal elements.Systematic analysis of electronic band structures,phonon dispersions,and electron-phonon coupling reveals that substitution of MA binary metal combinations and X metal atoms can create favorable conditions for superconductivity.Mapping of superconducting critical temperatures,combined with dynamical stability analysis through phonon calculations,identifies ten superconducting candidates at ambient pressure.Among these,LiNaAgH_(6) exhibits nearly-free-electron behavior reminiscent of monovalent electron superconductors.It demonstrates exceptional superconducting properties with electron–phonon coupling λ=2.707,which yields a superconducting transition temperature T_(c) of 206.4 K using the Allen–Dynes formula.Its structural analogs MgNaPdH_(6),LiMgPdH_(6),LiMgAgH_(6),LiMgAuH_(6) all exhibit superconducting transition temperatures above 110 K.These findings advance our fundamental understanding of superconductivity in quaternary hydrides and provide guidance for rational design of new high-temperature superconducting materials.展开更多
La-Mg-Ni-based hydrogen storage alloys with superlattice structures are the new generation anode material for nickel metal hydride(Ni-MH)batteries owing to the advantages of high capacity and exceptional activation pr...La-Mg-Ni-based hydrogen storage alloys with superlattice structures are the new generation anode material for nickel metal hydride(Ni-MH)batteries owing to the advantages of high capacity and exceptional activation properties.However,the cycling stability is not currently satisfactory enough which plagues its application.Herein,a strategy of partially substituting La with the Y element is proposed to boost the capacity durability of La-Mg-Ni-based alloys.Furthermore,phase structure regulation is implemented simultaneously to obtain the A5 B19-type alloy with good crystal stability specifically.It is found that Y promotes the phase formation of the Pr5 Co19-type phase after annealing at 985℃.The alloy containing Y contributes to the superior rate capability resulting from the promoted hydrogen diffusion rate.Notably,Y substitution enables strengthening the anti-pulverization ability of the alloy in terms of increasing the volume match between[A_(2)B_(4)]and[AB5]subunits,and effectively enhances the anti-corrosion ability of the alloy due to high electronegativity,realizing improved long-term cycling stability of the alloy from 74.2%to 78.5%after cycling 300 times.The work is expected to shed light on the composition and structure design of the La-Mg-Ni-based hydrogen storage alloy for Ni-MH batteries.展开更多
Dinitrogen fixation is one of the key reactions in chemistry, which is closely associated with food, environment, and energy. It has been recently recognized that the hydride materials containing negatively charged hy...Dinitrogen fixation is one of the key reactions in chemistry, which is closely associated with food, environment, and energy. It has been recently recognized that the hydride materials containing negatively charged hydrogen(H~-) show promises for Nfixation and hydrogenation to ammonia. Herein, we report that rare earth metal hydrides such as lanthanum hydride can also fix Neither by heating to 200 °C or ball milling under ambient Npressure and temperature. The Nfixation by lanthanum hydride may proceed via an intermediate lanthanum hydride-nitride(La-H-N) structure to form the final lanthanum nitride product. The hydride ion functions as an electron donor, which provides electrons for Nactivation possibly mediated by the lanthanum atoms. It is observed that N–H bond is not formed during the Nfixation process, which is distinctly different from the alkali or alkaline earth metal hydrides. The hydrolysis of La-H-N to ammonia is feasible using water as the hydrogen source. These results provide new insights into the nitrogen fixation by hydride materials and more efforts are needed for the development of rare earth metal-based catalysts and/or nitrogen carriers for ammonia synthesis processes.展开更多
Yttrium hydride(YH_(x))is a highly promising neutron moderator material for nuclear reactors,known for its exceptional thermal stability and high hydrogen content.This study investigated the sintering mechanism and mi...Yttrium hydride(YH_(x))is a highly promising neutron moderator material for nuclear reactors,known for its exceptional thermal stability and high hydrogen content.This study investigated the sintering mechanism and microstructural evolution of YH_(x)monoliths processed by spark plasma sintering(SPS),with the effects of temperature,duration,and pressure.The results indicate that the sintering process can be divided into five stages:formation of sintering necks,rapid densification,anti-densification,recrystallization,and grain growth.The anti-densification behavior is attributed to hydrogen desorption,phase transformation-induced volumetric contraction,and vacancy coalescence from hydrogen migration,leaving residual pores and lattice defects.Furthermore,increasing the sintering temperature and duration promotes recrystallization and grain growth,whereas elevated pressure effectively suppresses grain boundary migration.This research establishes fundamental processing-structure correlations critical for optimizing YHx moderators in nuclear applications.展开更多
Magnesium hydride(MgH_(2))was highly regarded for its substantial hydrogen storage capacity of up to 7.6 wt%,but its commercial application was hindered by the high operating temperatures and slow kinetics.In this stu...Magnesium hydride(MgH_(2))was highly regarded for its substantial hydrogen storage capacity of up to 7.6 wt%,but its commercial application was hindered by the high operating temperatures and slow kinetics.In this study,the successful synthesis of the layered Ti_(2)NbC_(2) has significantly enhanced the hydrogen storage performance of MgH_(2).MgH_(2)+5 wt%Ti_(2)NbC_(2) began to release hydrogen at 190℃ and started to absorb hydrogen at room temperature.At a constant temperature of 275℃,complete hydrogen release was achieved in just 250 s,up to 6.9 wt%.At 150℃,the absorption of hydrogen reached 6.59 wt%within 200 s,and the hydrogen absorption activation energy was reduced to 41.517±3.981 kJ·mol^(−1),significantly improving the kinetic performance.Moreover,the composite material still exhibited excellent cyclic stability after 20 cycles at 275℃.In the process of hydrogen de/absorption of Ti_(2)NbC_(2) with MgH_(2),active substances Nb-H and Ti-H were generated in situ,which effectively weakened the Mg-H bond and acted as efficient“hydrogen pumps”to accelerate the re/dehydrogenation of MgH_(2).The unique layered structure and hydrogen affinity of Ti_(2)NbC_(2) provided an effective transfer channel for hydrogen migration,which was key to the excellent hydrogen storage performance of the MgH_(2)+Ti_(2)NbC_(2).展开更多
Catalytic doping is one of the economic and efficient strategies to optimize the operating temperature and kinetic behavior of magnesium hydride(MgH_(2)).Herein,efficient regulation of electronic and structural rearra...Catalytic doping is one of the economic and efficient strategies to optimize the operating temperature and kinetic behavior of magnesium hydride(MgH_(2)).Herein,efficient regulation of electronic and structural rearrangements in niobium-rich nickel oxides was achieved through precise compositional design and niobium cation functionalized doping,thereby greatly enhancing its intrinsic catalytic activity in hydrogen storage systems.As the niobium concentration increased,the Ni-Nb catalysts transformed into a mixed state of multi-phase nanoparticles(composed of nickel and niobium-rich nickel oxides)with smaller particle size and uniform distribution,thus exposing more nucleation sites and diffusion channels at the MgH_(2)/Mg interface.In addition,the additional generation of active Ni-Nb-O mixed phase induced numerous highly topical disordered and distorted crystalline,promoting the transfer and reorganization of H atoms.As a result,a stable and continuous multi-phase/component synergistic catalytic microenvironment could be constructed,exerting remarkable enhancement on MgH_(2)’s hydrogen storage performance.After comparative tests,Ni_(0.7)Nb_(0.3)-doped MgH_(2) presented the optimal low-temperature kinetics with a dehydrogenation activation energy of 78.8 kJ·mol^(−1).The onset dehydrogenation temperature of MgH_(2)+10 wt%Ni_(0.7)Nb_(0.3) was reduced to 198℃ and 6.18 wt%H_(2) could be released at 250℃ within 10 min.In addition,the dehydrogenated MgH_(2)–NiNb composites absorbed 4.87 wt%H_(2) in 10 min at 125℃ and a capacity retention rate was maintained at 6.18 wt%even after 50 reaction cycles.In a word,our work supplies fresh insights for designing novel defective-state multiphase catalysts for hydrogen storage and other energy related field.展开更多
Hydrogen,as a cheap,clean,and cost-effective secondary energy source,performs an essential role in optimizing today’s energy structure.Magnesium hydride(Mg H_(2))represents an attractive hydrogen carrier for storage ...Hydrogen,as a cheap,clean,and cost-effective secondary energy source,performs an essential role in optimizing today’s energy structure.Magnesium hydride(Mg H_(2))represents an attractive hydrogen carrier for storage and transportation,however,the kinetic behavior and operating temperature remain undesirable.In this work,a dual-phase multi-site alloy(Ms A)anchored on carbon substrates was designed,and its superior catalytic effects on the hydrogen storage properties of MgH_(2) were reported.Mechanism analysis identified that multi-site Fe Ni_(3)/Ni Cu nanoalloys synergistically served as intrinsic drivers for the striking de/hydrogenation performance of the MgH_(2)-Ms A systems.Concretely,the unique multi-metallic site structure attached to the surface of MgH_(2)provided substantial reversible channels and accessible active sites conducive to the adsorption,activation,and nucleation of H atoms.In addition,the coupling system formed by FeNi_(3) and NiCu dual-phase alloys further enhanced the reactivity between Mg/MgH_(2) and H atoms.Hence,the onset dehydrogenation temperature of Mg H_(2)+5 wt%Ms A was reduced to 195℃ and the hydrogen desorption apparent activation energy was reduced to 83.6 k J/mol.5.08 wt%H_(2) could be released at 250℃ in 20 min,reaching a high dehydrogenation rate of 0.254 wt%H_(2)/min,yet that for MgH_(2) at a higher temperature of 335℃ was only 0.145 wt%H_(2)/min.Then,the dehydrogenated Mg H_(2)-Ms A sample could absorb hydrogen from room temperature(30℃)and charge 3.93 wt%H_(2) at 100℃ within20 min under 3.0 MPa H_(2) pressure.Benefiting from carbon substrates,the 5 wt%Ms A doped-MgH_(2) could still maintain 6.36 wt%hydrogen capacity after 20 cycles.In conclusion,this work provides experimental rationale and new insights for the design of efficient catalysts for magnesium-based solid-state hydrogen storage materials.展开更多
As a highly reactive reaction intermediate,surface gallium hydride(Ga–H)has garnered significant attention due to its critical role in various catalytic reactions.However,the detailed experimental characterization of...As a highly reactive reaction intermediate,surface gallium hydride(Ga–H)has garnered significant attention due to its critical role in various catalytic reactions.However,the detailed experimental characterization of this unique species remains challenging.Recently,we have demonstrated that solid-state NMR can be an effective tool for studying surface Ga–H.In this work,we report a comparative solid-state NMR study on H_(2) activation over different Ga_(2)O_(3) polymorphs,specificallyα-,β-andγ-Ga_(2)O_(3).^(1)H solid-state NMR enabled the identification of Ga–H species formed on all the three samples following high-temperature H_(2) treatment.The characteristic ^(1)H NMR signals of Ga–H species are resolved using J-coupling-based double-resonance NMR methods,revealing highly similar lineshapes of Ga–H for all the Ga_(2)O_(3) samples.This suggests potentially similar surface Ga–H configurations among different Ga_(2)O_(3) polymorphs.In addition,the local hydrogen environments on the oxide surfaces are further explored using two-dimensional(2D)^(1)H–^(1)H homonuclear correlation spectra,revealing multiple spatially proximate Ga–H and Ga–H/–OH pairs on different Ga_(2)O_(3) polymorphs.These findings provide insights into the potential mechanism of H_(2) dissociation.Overall,this work offers new perspectives on the local structure of surface Ga–H on Ga_(2)O_(3),and the analytical approach presented here can be further extended to the study of other Ga-based catalysts and other metal hydride species.展开更多
MgH_(2) has been extensively studied as one of the most ideal solid hydrogen storage materials.Nevertheless,rapid capacity decay and sluggish hydrogen storage kinetics hamper its practical application.Herein,a Ni/C na...MgH_(2) has been extensively studied as one of the most ideal solid hydrogen storage materials.Nevertheless,rapid capacity decay and sluggish hydrogen storage kinetics hamper its practical application.Herein,a Ni/C nano-catalyst doped MgH_(2)(MgH_(2)–Ni/C)shows an improved hydrogen absorption kinetics with largely reduced activation energy.Particularly,the MgH_(2)–Ni/C displays remarkable cycling stability,which maintains a high capacity of 6.01 wt.%(98.8%of initial capacity)even after 50 full hydrogen ab/desorption cycles,while the undoped MgH_(2) counterpart retains only 85.2%of its initial capacity.Detailed microstructure characterizations clearly reveal that particle sintering/growth accounts primarily for the deterioration of cycling performance of undoped MgH_(2).By comparison,MgH_(2)–Ni/C can maintain a stable particle size with a growing porous structure during long-term cycling,which effectively increases the specific surface of the particles.A novel carbon-induced-porosity stabilization mechanism is proposed,which can stabilize the proportion of rapid hydrogen absorption process,thus dominating the excellent cycling performance of MgH_(2)–Ni/C.This study provides new insights into the cycling stability mechanism of carbon-containing Mg-based hydrogen storage materials,thus promoting their practical applications.展开更多
To modify the stable thermodynamics and poor kinetics of magnesium hydride(MgH_(2))for solid-state hydrogen storage,MIL-100(Fe)was in situ fabricated on the surfaces of TiO_(2)nano-sheets(NS)by a self-assembly method,...To modify the stable thermodynamics and poor kinetics of magnesium hydride(MgH_(2))for solid-state hydrogen storage,MIL-100(Fe)was in situ fabricated on the surfaces of TiO_(2)nano-sheets(NS)by a self-assembly method,and the prepared TiO_(2)NS@MIL-100(Fe)presents an excellent catalytic effect on MgH_(2).The MgH_(2)+7wt.%TiO_(2)NS@MIL-100(Fe)composite can release hydrogen at 200℃,achieving a decrease of 150℃ compared to pure MgH_(2).Besides,the activation energy of dehydrogenation is decreased to 70.62 kJ/mol and 4 wt.%H_(2) can be desorbed within 20 min at a low temperature of 235℃.Under conditions of 100℃ and 3 MPa,MgH_(2)+7wt.%TiO_(2)NS@MIL-100(Fe)absorbs 5 wt.%of H_(2) in 10 min.Surprisingly,6.62 wt.%reversible capacity is maintained after 50 cycles.The modification mechanism is confirmed that the presence of oxygen vacancies and the synergistic effect of multivalent titanium in TiO_(2)NS@MIL-100(Fe)greatly enhance the kinetic and thermodynamic properties of MgH_(2).展开更多
Catalytic doping of magnesium hydride(MgH_(2))to improve its hydrogen ab/desorption kinetic properties is considered to be an effective and feasible method.In solid-phase catalysis,the extent of contact between the ca...Catalytic doping of magnesium hydride(MgH_(2))to improve its hydrogen ab/desorption kinetic properties is considered to be an effective and feasible method.In solid-phase catalysis,the extent of contact between the catalyst and the substrate determines the catalytic reaction in a great sense.With large specific surface area and abundant active sites,two-dimensional(2D)nanomaterials are promising catalysts for MgH_(2)via providing numerous pathways for the diffusion and dissociation of hydrogen.In this regard,2D NiMn-based layered double hydroxide and layered metallic oxide(LMO)are designed and introduced into MgH_(2)to improve its hydrogen storage properties.Simultaneous enhancement in interfacial contact,desorption temperature and kinetics are achieved.The MgH_(2)+9wt%Ni3Mn-LMO composites begin to discharge hydrogen at only 190℃and 6.10wt%H_(2)could be charged in 600 s at 150℃.The activation energy for de/hydrogenation is reduced by 42.43%and 46.56%,respectively,compared to pure MgH_(2).Even at a low operating temperature of 235℃,the modified system was still able to release 4.44wt%H_(2)in an hour,which has rarely been reported in previous studies.Microstructure observations and density functional theory calculations revealed that first,the hydrogen pumping effect of Mg_(2)Ni/Mg_(2)NiH_(4) promotes the adsorption and desorption of hydrogen molecules on the surface of MgH_(2),second,MnOx drew electrons from Mg_(2)Ni,producing a new Density of State structure with a lower d-bond center.This unique change further strengthens the Mg_(2)Ni/Mg_(2)NiH_(4) pump effect on MgH_(2).Our work indicates that the application of 2D metal-based catalysts is a feasible and promising approach towards MgH_(2)for solid-state hydrogen storage to meet technical and scientific requirements.展开更多
Ternary hydrides, with their superior chemical and structural flexibility over binary systems, open up new avenues for advancing high-performance superconductor research. The Y-Ca-H system is a promising candidate for...Ternary hydrides, with their superior chemical and structural flexibility over binary systems, open up new avenues for advancing high-performance superconductor research. The Y-Ca-H system is a promising candidate for high-temperature superconductors, as both Im3m YH_(6) and Im3m CaH_(6) exhibit similar structures and excellent superconducting properties, while Y and Ca atoms possess close atomic radii and electronegativities.Here, we report the successful synthesis of Im3m(Y, Ca)H_(6) achieving a maximum superconducting transition temperature(T_(c)) approximately 224 K at 155 GPa through five independent high-temperature and high-pressure experiments. Remarkably, the T_(c) of Im3m(Y, Ca)H_(6) remains highly stable(ΔT_(c) ≤ 1 K) during decompression between 148 and 165 GPa, significantly outperforming binary Im3m CaH_(6) and Im3m YH_(6). The enhanced superconducting properties may stem from the cooperative chemical template effect of Y and Ca atoms near the s-d border, which significantly reinforces H lattice stability and thus maintains superior superconductivity.This study highlights the potential of multicomponent cooperative effects in designing hydride superconductors,offering new insights for achieving high-T_(c) hydrides at lower pressures in the future.展开更多
Dibenzyltoluene(DBT)is a prospective liquid organic hydrogen carrier(LOHC)with low cost and high theoretical hydrogen storage capacity(6.2 wt%).However,the wide application of DBT is severely restricted by expensive n...Dibenzyltoluene(DBT)is a prospective liquid organic hydrogen carrier(LOHC)with low cost and high theoretical hydrogen storage capacity(6.2 wt%).However,the wide application of DBT is severely restricted by expensive noble catalysts.In this work,a new Mg-based metal hydride hydrogenation catalyst,which is composed of MgH_(2),Mg_(2)NiH_(4) and LaH_(3) micro-nano-particles.展开更多
Rare earth-Mg-Ni-based superlattice structure alloys have garnered recognition as promising materials for hydrogen storage.However,their application is impeded by suboptimal cycling longevity.The novel AB_(4)-type all...Rare earth-Mg-Ni-based superlattice structure alloys have garnered recognition as promising materials for hydrogen storage.However,their application is impeded by suboptimal cycling longevity.The novel AB_(4)-type alloy emerges as an attractive candidate,distinguished by its good structure stability,high rate capability,and long-term durability.Herein,we designed an AB_(4)-type La_(0.6)0Sm_(0.22)Mg_(0.18)Ni_(4.09)Al_(0.09)Mn_(0.10)alloy that manifests superior electrochemical performance.The obtained AB_(4)-type single-phase alloy delivers a high discharge capacity of 375.2 mAh·g^(-1)and features outstanding discharge ability at high rates,maintaining 121 mAh·g^(-1)even at a discharge rate of 6C.The excellent high-rate discharge performance can be attributed to its fast charge transfer and hydrogen diffusion kinetics.Moreover,the AB_(4)-type alloy maintains a capacity retention of 84.5%after 200 cycles and retains 55.7%of its capacity retention even after 500 cycles.This work provides a good alternative to hydrogen storage alloy with high power and long cycling durability performance for nickel metal hydride batteries.展开更多
In this work,the hydrogen sorption properties of the LiBH4-Mg2NiH4 composite system with the molar ratio 2:2.5 were thoroughly investigated as a function of the applied temperature and hydrogen pressure.To the best of...In this work,the hydrogen sorption properties of the LiBH4-Mg2NiH4 composite system with the molar ratio 2:2.5 were thoroughly investigated as a function of the applied temperature and hydrogen pressure.To the best of our knowledge,it has been possible to prove experimentally the mutual destabilization between LiBH4 and Mg2NiH4.A detailed account of the kinetic and thermodynamic features of the dehydrogenation process is reported here.展开更多
The Mg-Ni hydride was prepared by hydriding combustion synthesis under a high magnetic field. The dehydriding kinetics of the hydrides was measured under the isothermal and non-isothermal conditions. A model was appli...The Mg-Ni hydride was prepared by hydriding combustion synthesis under a high magnetic field. The dehydriding kinetics of the hydrides was measured under the isothermal and non-isothermal conditions. A model was applied to analyzing the kinetics behavior of Mg-Ni hydride. The calculation results show that the theoretical value and the experimental data can reach a good agreement, especially in the case of non-isothermal dehydriding. The rate-controlling step is the diffusion of hydrogen atoms in the solid solution. The sample prepared under magnetic field of 6 T under the isothermal condition can reach the best performance. The similar tendency was observed under the non-isothermal condition and the reason was discussed.展开更多
In order to optimize the dehydriding process for producing nanocrystalline Mg alloy powders by hydriding-dehydriding treatment,nano-structured as-hydrided Mg-3%Al-1%Zn(AZ31 Mg)(mass fraction)alloy powders were thermal...In order to optimize the dehydriding process for producing nanocrystalline Mg alloy powders by hydriding-dehydriding treatment,nano-structured as-hydrided Mg-3%Al-1%Zn(AZ31 Mg)(mass fraction)alloy powders were thermally dehydrided at various temperatures from 275 to 375℃.The kinetics of hydrogen desorption was examined by hydrogen discharge measurement during dehydriding.The microstructure of the as-hydrided and the subsequently fully dehydrided alloy powders was investigated by X-ray diffraction analysis(XRD)and transmission electron microscopy(TEM),respectively.Both the desorption kinetics and the grain size of the alloy after complete dehydriding were found to be strongly dependent on the processing temperature.The higher the temperature,the faster the desorption,and the more significant the grain growth.When the desorption temperature was raised from 300 to 375℃,the time to achieve complete dehydriding was shortened from 190 to 20 min,and the average grain size increased correspondingly from 20 to 58 nm.展开更多
In order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys,Ni in the alloy is substituted by element Co. The nanocrystalline and amorphous Mg2Ni-type Mg2Ni1-xCox (x=0,0.1,0.2,0.3,0.4) alloys w...In order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys,Ni in the alloy is substituted by element Co. The nanocrystalline and amorphous Mg2Ni-type Mg2Ni1-xCox (x=0,0.1,0.2,0.3,0.4) alloys were synthesized by melt-spinning technique. The structures of the as-cast and spun alloys were studied with an X-ray diffractometer (XRD) and a high resolution transmission electronic microscope (HRTEM). An investigation on the thermal stability of the as-spun alloys was carried out with a differential scanning calorimeter (DSC). The hydrogen absorption and desorption kinetics of the alloys were measured with an automatically controlled Sieverts apparatus. The results demonstrate that the substitution of Co for Ni does not alter the major phase of Mg2Ni but results in the formation of secondary phase MgCo2. No amorphous phase is detected in the as-spun Co-free alloy,but a certain amount of amorphous phase is clearly found in the as-spun Co-containing alloys. The substitution of Co for Ni exerts a slight influence on the hydriding kinetics of the as-spun alloy. However,it dramatically enhances the dehydriding kinetics of the as-cast and spun alloys. As Co content (x) increases from 0 to 0.4,the hydrogen desorption capacity increases from 0.19% to 1.39% (mass fraction) in 20 min for the as-cast alloy,and from 0.89% to 2.18% (mass fraction) for the as-spun alloy (30 m/s).展开更多
A partial substitution of Ni by Mn was implemented in order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys. The nanocrystalline and amorphous MgzNi-type Mg2Nil-xMnx （x=0, 0. 1, 0.2, 0.3, ...A partial substitution of Ni by Mn was implemented in order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys. The nanocrystalline and amorphous MgzNi-type Mg2Nil-xMnx （x=0, 0. 1, 0.2, 0.3, 0.4） alloys were synthesized by the melt-spinning technique. The structures of the as-cast and spun alloys were studied by X-ray diffractometry （XRD）, scanning electron microscopy （SEM） and high resolution transmission electron microscopy （HRTEM）. The hydrogen absorption and desorption kinetics of the alloys were measured with an automatically controlled Sieverts apparatus. The results show that the as-spun Mn-free alloy holds a typical nanocrystalline structure, whereas the as-spun alloys containing Mn display a nanocrystalline and amorphous structure, confirming that the substitution of Mn for Ni intensifies the glass forming ability of the Mg2Ni-type alloy. The hydrogen absorption and desorption capacities and kinetics of the alloys increase with increasing the spinning rate, for which the nanocrystalline and amorphous structure produced by the melt spinning is mainly responsible. The substitution of Mn for Ni evidently improves the hydrogen desorption performance. The hydrogen desorption capacities of the as-cast and spun alloys rise with the increase in the percentage of Mn substitution.展开更多
The precipitation process of zirconium hydrides induced by stress and strain was investigated by means of electron microscopy in-situ.The precipitating hydrides induced by stress were found to be γ phase with orienta...The precipitation process of zirconium hydrides induced by stress and strain was investigated by means of electron microscopy in-situ.The precipitating hydrides induced by stress were found to be γ phase with orientation relationship of (110)_γ‖(110)_(αZr),(001)_γ‖ (0001)_(αZr) between γ-hydrides and surrounding matrix.The growth rate of γ-hydrides which was much faster along [110] direction brought them in taper shape.After fracture of y-hydrides,a new one will precipitate at the tip of cracks.This is the essential process of hydrogen-induced delayed cracking in Zircaloy.The precipitating hydrides induced by strain were found to be δ phase with both orientation relationships of(111)_δ‖(0001)_(αZr),(110)_δ‖ (110)_(αZr) or (010)_δ‖(0001)_(αZr),(001)_δ‖(110)_(αZr)between δ-hydride and surrounding matrix.The δ-hydrides become much finer as the strain rate increased.展开更多
基金supported by the National Key R&D Program of China (Grant No.2022YFA1403201)the National Natural Science Foundation of China (Grant Nos.12125404,T2495231,123B2049,and 12204138)+9 种基金the Advanced MaterialsNational Science and Technology Major Project (Grant No.2024ZD0607000)the Natural Science Foundation of Jiangsu Province (Grant Nos.BK20233001 and BK20253009)the Jiangsu Funding Program for Excellent Postdoctoral Talent (Grant No.2024ZB002)the China Postdoctoral Science Foundation (Grant No.2025M773331)the Fundamental and Interdisciplinary Disciplines Breakthrough Plan of the Ministry of Education of Chinathe AI&AI for Science program of Nanjing UniversityArtificial Intelligence and Quantum physics (AIQ) program of Nanjing Universitythe Fundamental Research Funds for the Central Universitiesthe Natural Science Foundation of Nanjing University of Posts and Telecommunications(Grant Nos.NY224165,NY220038,and NY219087)the Hua Li Talents Program of Nanjing University of Posts and Telecommunications。
文摘We report a theoretical investigation into superconductivity within the MAXH_(6) quaternary hydride system using first-principles calculations,where M and A denote alkali and alkaline earth elements,respectively,and X represents transition metal elements.Systematic analysis of electronic band structures,phonon dispersions,and electron-phonon coupling reveals that substitution of MA binary metal combinations and X metal atoms can create favorable conditions for superconductivity.Mapping of superconducting critical temperatures,combined with dynamical stability analysis through phonon calculations,identifies ten superconducting candidates at ambient pressure.Among these,LiNaAgH_(6) exhibits nearly-free-electron behavior reminiscent of monovalent electron superconductors.It demonstrates exceptional superconducting properties with electron–phonon coupling λ=2.707,which yields a superconducting transition temperature T_(c) of 206.4 K using the Allen–Dynes formula.Its structural analogs MgNaPdH_(6),LiMgPdH_(6),LiMgAgH_(6),LiMgAuH_(6) all exhibit superconducting transition temperatures above 110 K.These findings advance our fundamental understanding of superconductivity in quaternary hydrides and provide guidance for rational design of new high-temperature superconducting materials.
基金the financial support by the National Nat-ural Science Foundation of China(Nos.52201282,52071281,52371239)the China Postdoctoral Science Foundation(No.2023M742945)+4 种基金Hebei Provincial Postdoctoral Science Foundation(No.B2023003023)the Science Research Project of Hebei Education Department(No.BJK2022033)the Natural Science Foundation of Hebei Province(No.C2022203003)the Inner Mongolia Science and Technology Major Project(No.2020ZD0012)the Baotou Science and Technology Planning Project(No.XM2022BT09).
文摘La-Mg-Ni-based hydrogen storage alloys with superlattice structures are the new generation anode material for nickel metal hydride(Ni-MH)batteries owing to the advantages of high capacity and exceptional activation properties.However,the cycling stability is not currently satisfactory enough which plagues its application.Herein,a strategy of partially substituting La with the Y element is proposed to boost the capacity durability of La-Mg-Ni-based alloys.Furthermore,phase structure regulation is implemented simultaneously to obtain the A5 B19-type alloy with good crystal stability specifically.It is found that Y promotes the phase formation of the Pr5 Co19-type phase after annealing at 985℃.The alloy containing Y contributes to the superior rate capability resulting from the promoted hydrogen diffusion rate.Notably,Y substitution enables strengthening the anti-pulverization ability of the alloy in terms of increasing the volume match between[A_(2)B_(4)]and[AB5]subunits,and effectively enhances the anti-corrosion ability of the alloy due to high electronegativity,realizing improved long-term cycling stability of the alloy from 74.2%to 78.5%after cycling 300 times.The work is expected to shed light on the composition and structure design of the La-Mg-Ni-based hydrogen storage alloy for Ni-MH batteries.
基金the financial support from the National Key R&D Program of China(2021YFB4000401)the National Natural Science Foundation of China(Grant Nos.21922205,21872137,22109158,and 51801197)+2 种基金the Youth Innovation Promotion Association CAS(Grant Nos.2018213,2019189,2022180)the Liaoning Revitalization Talents Program(Grant Nos.XLYC2007173,XLYC2002076)the K.C.Wong Education Foundation(Grant No.GJTD-2018-06)。
文摘Dinitrogen fixation is one of the key reactions in chemistry, which is closely associated with food, environment, and energy. It has been recently recognized that the hydride materials containing negatively charged hydrogen(H~-) show promises for Nfixation and hydrogenation to ammonia. Herein, we report that rare earth metal hydrides such as lanthanum hydride can also fix Neither by heating to 200 °C or ball milling under ambient Npressure and temperature. The Nfixation by lanthanum hydride may proceed via an intermediate lanthanum hydride-nitride(La-H-N) structure to form the final lanthanum nitride product. The hydride ion functions as an electron donor, which provides electrons for Nactivation possibly mediated by the lanthanum atoms. It is observed that N–H bond is not formed during the Nfixation process, which is distinctly different from the alkali or alkaline earth metal hydrides. The hydrolysis of La-H-N to ammonia is feasible using water as the hydrogen source. These results provide new insights into the nitrogen fixation by hydride materials and more efforts are needed for the development of rare earth metal-based catalysts and/or nitrogen carriers for ammonia synthesis processes.
基金supported by the Frontier Science Key Program of the Chinese Academy of Sciences(No.QYZDY-SSW-JSC016)Chinese Academy of Sciences President’s International Fellowship Initiative(No.2024VMA0012).
文摘Yttrium hydride(YH_(x))is a highly promising neutron moderator material for nuclear reactors,known for its exceptional thermal stability and high hydrogen content.This study investigated the sintering mechanism and microstructural evolution of YH_(x)monoliths processed by spark plasma sintering(SPS),with the effects of temperature,duration,and pressure.The results indicate that the sintering process can be divided into five stages:formation of sintering necks,rapid densification,anti-densification,recrystallization,and grain growth.The anti-densification behavior is attributed to hydrogen desorption,phase transformation-induced volumetric contraction,and vacancy coalescence from hydrogen migration,leaving residual pores and lattice defects.Furthermore,increasing the sintering temperature and duration promotes recrystallization and grain growth,whereas elevated pressure effectively suppresses grain boundary migration.This research establishes fundamental processing-structure correlations critical for optimizing YHx moderators in nuclear applications.
基金supported by the National Natural Science Foundation of China(No.52201255)the Natural Science Foundation of Jiangsu Province(No.BK20210884)the Innovation and Entrepreneurship Program of Jiangsu Province(No.JSSCBS20211007).
文摘Magnesium hydride(MgH_(2))was highly regarded for its substantial hydrogen storage capacity of up to 7.6 wt%,but its commercial application was hindered by the high operating temperatures and slow kinetics.In this study,the successful synthesis of the layered Ti_(2)NbC_(2) has significantly enhanced the hydrogen storage performance of MgH_(2).MgH_(2)+5 wt%Ti_(2)NbC_(2) began to release hydrogen at 190℃ and started to absorb hydrogen at room temperature.At a constant temperature of 275℃,complete hydrogen release was achieved in just 250 s,up to 6.9 wt%.At 150℃,the absorption of hydrogen reached 6.59 wt%within 200 s,and the hydrogen absorption activation energy was reduced to 41.517±3.981 kJ·mol^(−1),significantly improving the kinetic performance.Moreover,the composite material still exhibited excellent cyclic stability after 20 cycles at 275℃.In the process of hydrogen de/absorption of Ti_(2)NbC_(2) with MgH_(2),active substances Nb-H and Ti-H were generated in situ,which effectively weakened the Mg-H bond and acted as efficient“hydrogen pumps”to accelerate the re/dehydrogenation of MgH_(2).The unique layered structure and hydrogen affinity of Ti_(2)NbC_(2) provided an effective transfer channel for hydrogen migration,which was key to the excellent hydrogen storage performance of the MgH_(2)+Ti_(2)NbC_(2).
基金financial supports from the National Key R&D Program of China(2023YFB3809103)the National Natural Science Foundation of China(U23A20128).
文摘Catalytic doping is one of the economic and efficient strategies to optimize the operating temperature and kinetic behavior of magnesium hydride(MgH_(2)).Herein,efficient regulation of electronic and structural rearrangements in niobium-rich nickel oxides was achieved through precise compositional design and niobium cation functionalized doping,thereby greatly enhancing its intrinsic catalytic activity in hydrogen storage systems.As the niobium concentration increased,the Ni-Nb catalysts transformed into a mixed state of multi-phase nanoparticles(composed of nickel and niobium-rich nickel oxides)with smaller particle size and uniform distribution,thus exposing more nucleation sites and diffusion channels at the MgH_(2)/Mg interface.In addition,the additional generation of active Ni-Nb-O mixed phase induced numerous highly topical disordered and distorted crystalline,promoting the transfer and reorganization of H atoms.As a result,a stable and continuous multi-phase/component synergistic catalytic microenvironment could be constructed,exerting remarkable enhancement on MgH_(2)’s hydrogen storage performance.After comparative tests,Ni_(0.7)Nb_(0.3)-doped MgH_(2) presented the optimal low-temperature kinetics with a dehydrogenation activation energy of 78.8 kJ·mol^(−1).The onset dehydrogenation temperature of MgH_(2)+10 wt%Ni_(0.7)Nb_(0.3) was reduced to 198℃ and 6.18 wt%H_(2) could be released at 250℃ within 10 min.In addition,the dehydrogenated MgH_(2)–NiNb composites absorbed 4.87 wt%H_(2) in 10 min at 125℃ and a capacity retention rate was maintained at 6.18 wt%even after 50 reaction cycles.In a word,our work supplies fresh insights for designing novel defective-state multiphase catalysts for hydrogen storage and other energy related field.
基金financial supports from the National Key R&D Program of China(No.2020YFA0406204)the National Natural Science Foundation of China(No.51801078)。
文摘Hydrogen,as a cheap,clean,and cost-effective secondary energy source,performs an essential role in optimizing today’s energy structure.Magnesium hydride(Mg H_(2))represents an attractive hydrogen carrier for storage and transportation,however,the kinetic behavior and operating temperature remain undesirable.In this work,a dual-phase multi-site alloy(Ms A)anchored on carbon substrates was designed,and its superior catalytic effects on the hydrogen storage properties of MgH_(2) were reported.Mechanism analysis identified that multi-site Fe Ni_(3)/Ni Cu nanoalloys synergistically served as intrinsic drivers for the striking de/hydrogenation performance of the MgH_(2)-Ms A systems.Concretely,the unique multi-metallic site structure attached to the surface of MgH_(2)provided substantial reversible channels and accessible active sites conducive to the adsorption,activation,and nucleation of H atoms.In addition,the coupling system formed by FeNi_(3) and NiCu dual-phase alloys further enhanced the reactivity between Mg/MgH_(2) and H atoms.Hence,the onset dehydrogenation temperature of Mg H_(2)+5 wt%Ms A was reduced to 195℃ and the hydrogen desorption apparent activation energy was reduced to 83.6 k J/mol.5.08 wt%H_(2) could be released at 250℃ in 20 min,reaching a high dehydrogenation rate of 0.254 wt%H_(2)/min,yet that for MgH_(2) at a higher temperature of 335℃ was only 0.145 wt%H_(2)/min.Then,the dehydrogenated Mg H_(2)-Ms A sample could absorb hydrogen from room temperature(30℃)and charge 3.93 wt%H_(2) at 100℃ within20 min under 3.0 MPa H_(2) pressure.Benefiting from carbon substrates,the 5 wt%Ms A doped-MgH_(2) could still maintain 6.36 wt%hydrogen capacity after 20 cycles.In conclusion,this work provides experimental rationale and new insights for the design of efficient catalysts for magnesium-based solid-state hydrogen storage materials.
基金financially supported by the National Key R&D Program of China(No.2021YFA1502803)the National Natural Science Foundation of China(Nos.22325405,22372160,22432005 and 22321002)Dalian Science and Technology Talent Innovation Program(No.2024RG009).
文摘As a highly reactive reaction intermediate,surface gallium hydride(Ga–H)has garnered significant attention due to its critical role in various catalytic reactions.However,the detailed experimental characterization of this unique species remains challenging.Recently,we have demonstrated that solid-state NMR can be an effective tool for studying surface Ga–H.In this work,we report a comparative solid-state NMR study on H_(2) activation over different Ga_(2)O_(3) polymorphs,specificallyα-,β-andγ-Ga_(2)O_(3).^(1)H solid-state NMR enabled the identification of Ga–H species formed on all the three samples following high-temperature H_(2) treatment.The characteristic ^(1)H NMR signals of Ga–H species are resolved using J-coupling-based double-resonance NMR methods,revealing highly similar lineshapes of Ga–H for all the Ga_(2)O_(3) samples.This suggests potentially similar surface Ga–H configurations among different Ga_(2)O_(3) polymorphs.In addition,the local hydrogen environments on the oxide surfaces are further explored using two-dimensional(2D)^(1)H–^(1)H homonuclear correlation spectra,revealing multiple spatially proximate Ga–H and Ga–H/–OH pairs on different Ga_(2)O_(3) polymorphs.These findings provide insights into the potential mechanism of H_(2) dissociation.Overall,this work offers new perspectives on the local structure of surface Ga–H on Ga_(2)O_(3),and the analytical approach presented here can be further extended to the study of other Ga-based catalysts and other metal hydride species.
基金supported by the National Natural Science Foundation of China(Nos.22279111,51971195,and 11935004)the Natural Science Foundation of Hebei Province(No.B2020203037)Subsidy for Hebei Key Laboratory of Applied Chemistry after Operation Performance(No.22567616H).
文摘MgH_(2) has been extensively studied as one of the most ideal solid hydrogen storage materials.Nevertheless,rapid capacity decay and sluggish hydrogen storage kinetics hamper its practical application.Herein,a Ni/C nano-catalyst doped MgH_(2)(MgH_(2)–Ni/C)shows an improved hydrogen absorption kinetics with largely reduced activation energy.Particularly,the MgH_(2)–Ni/C displays remarkable cycling stability,which maintains a high capacity of 6.01 wt.%(98.8%of initial capacity)even after 50 full hydrogen ab/desorption cycles,while the undoped MgH_(2) counterpart retains only 85.2%of its initial capacity.Detailed microstructure characterizations clearly reveal that particle sintering/growth accounts primarily for the deterioration of cycling performance of undoped MgH_(2).By comparison,MgH_(2)–Ni/C can maintain a stable particle size with a growing porous structure during long-term cycling,which effectively increases the specific surface of the particles.A novel carbon-induced-porosity stabilization mechanism is proposed,which can stabilize the proportion of rapid hydrogen absorption process,thus dominating the excellent cycling performance of MgH_(2)–Ni/C.This study provides new insights into the cycling stability mechanism of carbon-containing Mg-based hydrogen storage materials,thus promoting their practical applications.
基金financial support from the National Natural Science Foundation of China(No.51801078).
文摘To modify the stable thermodynamics and poor kinetics of magnesium hydride(MgH_(2))for solid-state hydrogen storage,MIL-100(Fe)was in situ fabricated on the surfaces of TiO_(2)nano-sheets(NS)by a self-assembly method,and the prepared TiO_(2)NS@MIL-100(Fe)presents an excellent catalytic effect on MgH_(2).The MgH_(2)+7wt.%TiO_(2)NS@MIL-100(Fe)composite can release hydrogen at 200℃,achieving a decrease of 150℃ compared to pure MgH_(2).Besides,the activation energy of dehydrogenation is decreased to 70.62 kJ/mol and 4 wt.%H_(2) can be desorbed within 20 min at a low temperature of 235℃.Under conditions of 100℃ and 3 MPa,MgH_(2)+7wt.%TiO_(2)NS@MIL-100(Fe)absorbs 5 wt.%of H_(2) in 10 min.Surprisingly,6.62 wt.%reversible capacity is maintained after 50 cycles.The modification mechanism is confirmed that the presence of oxygen vacancies and the synergistic effect of multivalent titanium in TiO_(2)NS@MIL-100(Fe)greatly enhance the kinetic and thermodynamic properties of MgH_(2).
基金supports from the National Key R&D Program of China(2020YFA0406204)the National Natural Science Foundation of China(Grant No 51801078).
文摘Catalytic doping of magnesium hydride(MgH_(2))to improve its hydrogen ab/desorption kinetic properties is considered to be an effective and feasible method.In solid-phase catalysis,the extent of contact between the catalyst and the substrate determines the catalytic reaction in a great sense.With large specific surface area and abundant active sites,two-dimensional(2D)nanomaterials are promising catalysts for MgH_(2)via providing numerous pathways for the diffusion and dissociation of hydrogen.In this regard,2D NiMn-based layered double hydroxide and layered metallic oxide(LMO)are designed and introduced into MgH_(2)to improve its hydrogen storage properties.Simultaneous enhancement in interfacial contact,desorption temperature and kinetics are achieved.The MgH_(2)+9wt%Ni3Mn-LMO composites begin to discharge hydrogen at only 190℃and 6.10wt%H_(2)could be charged in 600 s at 150℃.The activation energy for de/hydrogenation is reduced by 42.43%and 46.56%,respectively,compared to pure MgH_(2).Even at a low operating temperature of 235℃,the modified system was still able to release 4.44wt%H_(2)in an hour,which has rarely been reported in previous studies.Microstructure observations and density functional theory calculations revealed that first,the hydrogen pumping effect of Mg_(2)Ni/Mg_(2)NiH_(4) promotes the adsorption and desorption of hydrogen molecules on the surface of MgH_(2),second,MnOx drew electrons from Mg_(2)Ni,producing a new Density of State structure with a lower d-bond center.This unique change further strengthens the Mg_(2)Ni/Mg_(2)NiH_(4) pump effect on MgH_(2).Our work indicates that the application of 2D metal-based catalysts is a feasible and promising approach towards MgH_(2)for solid-state hydrogen storage to meet technical and scientific requirements.
基金supported by the National Key R&D Program of China (Grant No.2022YFA1405500)the National Natural Science Foundation of China (Grant No.52372257)。
文摘Ternary hydrides, with their superior chemical and structural flexibility over binary systems, open up new avenues for advancing high-performance superconductor research. The Y-Ca-H system is a promising candidate for high-temperature superconductors, as both Im3m YH_(6) and Im3m CaH_(6) exhibit similar structures and excellent superconducting properties, while Y and Ca atoms possess close atomic radii and electronegativities.Here, we report the successful synthesis of Im3m(Y, Ca)H_(6) achieving a maximum superconducting transition temperature(T_(c)) approximately 224 K at 155 GPa through five independent high-temperature and high-pressure experiments. Remarkably, the T_(c) of Im3m(Y, Ca)H_(6) remains highly stable(ΔT_(c) ≤ 1 K) during decompression between 148 and 165 GPa, significantly outperforming binary Im3m CaH_(6) and Im3m YH_(6). The enhanced superconducting properties may stem from the cooperative chemical template effect of Y and Ca atoms near the s-d border, which significantly reinforces H lattice stability and thus maintains superior superconductivity.This study highlights the potential of multicomponent cooperative effects in designing hydride superconductors,offering new insights for achieving high-T_(c) hydrides at lower pressures in the future.
基金supported by the National Key R&D Program of China(No.2023YFB3809100)the Youth Fund Project of Grinm(No.SKHT10422023060280).
文摘Dibenzyltoluene(DBT)is a prospective liquid organic hydrogen carrier(LOHC)with low cost and high theoretical hydrogen storage capacity(6.2 wt%).However,the wide application of DBT is severely restricted by expensive noble catalysts.In this work,a new Mg-based metal hydride hydrogenation catalyst,which is composed of MgH_(2),Mg_(2)NiH_(4) and LaH_(3) micro-nano-particles.
基金supported by the Natural Science Foundation of China(Nos.52201282 and 52371239)the Natural Science Foundation of Hebei Province(No.E2024203037)+1 种基金the Basic Innovation Research Project in Yanshan University(2022LGZD004)Baotou Science and Technology Planning Project(No.XM2022BT09).
文摘Rare earth-Mg-Ni-based superlattice structure alloys have garnered recognition as promising materials for hydrogen storage.However,their application is impeded by suboptimal cycling longevity.The novel AB_(4)-type alloy emerges as an attractive candidate,distinguished by its good structure stability,high rate capability,and long-term durability.Herein,we designed an AB_(4)-type La_(0.6)0Sm_(0.22)Mg_(0.18)Ni_(4.09)Al_(0.09)Mn_(0.10)alloy that manifests superior electrochemical performance.The obtained AB_(4)-type single-phase alloy delivers a high discharge capacity of 375.2 mAh·g^(-1)and features outstanding discharge ability at high rates,maintaining 121 mAh·g^(-1)even at a discharge rate of 6C.The excellent high-rate discharge performance can be attributed to its fast charge transfer and hydrogen diffusion kinetics.Moreover,the AB_(4)-type alloy maintains a capacity retention of 84.5%after 200 cycles and retains 55.7%of its capacity retention even after 500 cycles.This work provides a good alternative to hydrogen storage alloy with high power and long cycling durability performance for nickel metal hydride batteries.
基金supported by the Danish Council for Strategic Research via HyFillFast
文摘In this work,the hydrogen sorption properties of the LiBH4-Mg2NiH4 composite system with the molar ratio 2:2.5 were thoroughly investigated as a function of the applied temperature and hydrogen pressure.To the best of our knowledge,it has been possible to prove experimentally the mutual destabilization between LiBH4 and Mg2NiH4.A detailed account of the kinetic and thermodynamic features of the dehydrogenation process is reported here.
基金Project(51464008) supported by the National Natural Science Foundation of ChinaProject(KY[2012]004) supported by the Key Laboratory Item of Education Office in Guizhou Province,China
文摘The Mg-Ni hydride was prepared by hydriding combustion synthesis under a high magnetic field. The dehydriding kinetics of the hydrides was measured under the isothermal and non-isothermal conditions. A model was applied to analyzing the kinetics behavior of Mg-Ni hydride. The calculation results show that the theoretical value and the experimental data can reach a good agreement, especially in the case of non-isothermal dehydriding. The rate-controlling step is the diffusion of hydrogen atoms in the solid solution. The sample prepared under magnetic field of 6 T under the isothermal condition can reach the best performance. The similar tendency was observed under the non-isothermal condition and the reason was discussed.
基金Project(50574034)supported by the National Natural Science Foundation of ChinaProject(20060213016)supported by Doctoral Education Fund of Ministry of Education of China
文摘In order to optimize the dehydriding process for producing nanocrystalline Mg alloy powders by hydriding-dehydriding treatment,nano-structured as-hydrided Mg-3%Al-1%Zn(AZ31 Mg)(mass fraction)alloy powders were thermally dehydrided at various temperatures from 275 to 375℃.The kinetics of hydrogen desorption was examined by hydrogen discharge measurement during dehydriding.The microstructure of the as-hydrided and the subsequently fully dehydrided alloy powders was investigated by X-ray diffraction analysis(XRD)and transmission electron microscopy(TEM),respectively.Both the desorption kinetics and the grain size of the alloy after complete dehydriding were found to be strongly dependent on the processing temperature.The higher the temperature,the faster the desorption,and the more significant the grain growth.When the desorption temperature was raised from 300 to 375℃,the time to achieve complete dehydriding was shortened from 190 to 20 min,and the average grain size increased correspondingly from 20 to 58 nm.
基金Project(2006AA05Z132) supported by the National High-tech Research and Development Program of ChinaProjects(50871050, 50961009) supported by the National Natural Science Foundation of China+1 种基金Project(2010ZD05) supported by the Natural Science Foundation of Inner Mongolia, ChinaProject(NJzy08071) supported by the High Education Science Research Program of Inner Mongolia, China
文摘In order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys,Ni in the alloy is substituted by element Co. The nanocrystalline and amorphous Mg2Ni-type Mg2Ni1-xCox (x=0,0.1,0.2,0.3,0.4) alloys were synthesized by melt-spinning technique. The structures of the as-cast and spun alloys were studied with an X-ray diffractometer (XRD) and a high resolution transmission electronic microscope (HRTEM). An investigation on the thermal stability of the as-spun alloys was carried out with a differential scanning calorimeter (DSC). The hydrogen absorption and desorption kinetics of the alloys were measured with an automatically controlled Sieverts apparatus. The results demonstrate that the substitution of Co for Ni does not alter the major phase of Mg2Ni but results in the formation of secondary phase MgCo2. No amorphous phase is detected in the as-spun Co-free alloy,but a certain amount of amorphous phase is clearly found in the as-spun Co-containing alloys. The substitution of Co for Ni exerts a slight influence on the hydriding kinetics of the as-spun alloy. However,it dramatically enhances the dehydriding kinetics of the as-cast and spun alloys. As Co content (x) increases from 0 to 0.4,the hydrogen desorption capacity increases from 0.19% to 1.39% (mass fraction) in 20 min for the as-cast alloy,and from 0.89% to 2.18% (mass fraction) for the as-spun alloy (30 m/s).
基金Projects(50871050,50961001) supported by the National Natural Science Foundation of ChinaProject(2010ZD05) supported by the Natural Science Foundation of Inner Mongolia,ChinaProject(NJzy08071) supported by the High Education Science Research Program of Inner Mongolia,China
文摘A partial substitution of Ni by Mn was implemented in order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys. The nanocrystalline and amorphous MgzNi-type Mg2Nil-xMnx （x=0, 0. 1, 0.2, 0.3, 0.4） alloys were synthesized by the melt-spinning technique. The structures of the as-cast and spun alloys were studied by X-ray diffractometry （XRD）, scanning electron microscopy （SEM） and high resolution transmission electron microscopy （HRTEM）. The hydrogen absorption and desorption kinetics of the alloys were measured with an automatically controlled Sieverts apparatus. The results show that the as-spun Mn-free alloy holds a typical nanocrystalline structure, whereas the as-spun alloys containing Mn display a nanocrystalline and amorphous structure, confirming that the substitution of Mn for Ni intensifies the glass forming ability of the Mg2Ni-type alloy. The hydrogen absorption and desorption capacities and kinetics of the alloys increase with increasing the spinning rate, for which the nanocrystalline and amorphous structure produced by the melt spinning is mainly responsible. The substitution of Mn for Ni evidently improves the hydrogen desorption performance. The hydrogen desorption capacities of the as-cast and spun alloys rise with the increase in the percentage of Mn substitution.
文摘The precipitation process of zirconium hydrides induced by stress and strain was investigated by means of electron microscopy in-situ.The precipitating hydrides induced by stress were found to be γ phase with orientation relationship of (110)_γ‖(110)_(αZr),(001)_γ‖ (0001)_(αZr) between γ-hydrides and surrounding matrix.The growth rate of γ-hydrides which was much faster along [110] direction brought them in taper shape.After fracture of y-hydrides,a new one will precipitate at the tip of cracks.This is the essential process of hydrogen-induced delayed cracking in Zircaloy.The precipitating hydrides induced by strain were found to be δ phase with both orientation relationships of(111)_δ‖(0001)_(αZr),(110)_δ‖ (110)_(αZr) or (010)_δ‖(0001)_(αZr),(001)_δ‖(110)_(αZr)between δ-hydride and surrounding matrix.The δ-hydrides become much finer as the strain rate increased.
