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
Bulk Mg-based hydrogen storage materials have the potential to provide a low-cost solution to diversify energy storage and transportation.Compared to nano powders which require handling and processing under hydrogen o...Bulk Mg-based hydrogen storage materials have the potential to provide a low-cost solution to diversify energy storage and transportation.Compared to nano powders which require handling and processing under hydrogen or an inert gas atmosphere,bulk Mg-based alloys are safer and are more oxidation re-sistant.Conventional methods and existing infrastructures can be used to process and handle these ma-terials.However,bulk Mg alloys have smaller specific surface areas,resulting in slower hydrogen sorp-tion kinetics,higher equilibrium temperatures,and enthalpies of hydride formation.This work reviews the effects of the additions of a list of alloying elements and the use of innovative processing meth-ods,e.g.,rapid solidification and severe plastic deformation processes,to overcome these drawbacks.The challenges,advantages,and weaknesses of each method and future perspectives for the development of Mg-based hydrogen storage materials are discussed.展开更多
Hydrogen energy is expected to be an“ideal fuel”in the era of decarbonization.The discovery,de-velopment,and modification of high-performance hydrogen storage materials are the keys to the fu-ture development of sol...Hydrogen energy is expected to be an“ideal fuel”in the era of decarbonization.The discovery,de-velopment,and modification of high-performance hydrogen storage materials are the keys to the fu-ture development of solid-state hydrogen storage and hydrogen energy utilization.Magnesium hydride(MgH_(2)),with its high hydrogen storage capacity,abundant natural reserves,and environmental friend-liness,has been extensively researched.Herein,we briefly summarize the typical structure and hy-drogenation/dehydrogenation reaction mechanism of MgH_(2)and provide a comprehensive overview of strategies to effectively tune the thermodynamics and kinetics of Mg-based materials,such as alloy-ing,nanosizing,the introduction of additives,and composite modification.With substantial efforts,great achievements have been achieved,such as lower absorption/desorption temperatures and better cy-cling stability.Nonetheless,some pivotal issues remain to be addressed,such as unfavorable hydro-genation/dehydrogenation factors,harsh conditions,slow kinetics,incomplete dehydrogenation,low hy-drogen purity,expensive catalysts,and a lack of valid exploration of mechanisms in the hydrogena-tion/dehydrogenation process.Lastly,some future development prospects of MgH_(2)in energy-efficient conversion and storage have been presented,including advanced manufacturing ways,stabilization of nanostructures,the introduction of additives combined with structural modification,and utilization of advanced characterization techniques.展开更多
The Curie temperatures(T_(C))of La_(0.7)Ce_(0.3)Fe_(13-x-y)Mn_(x)Si_(y)compounds that are hydrogenated to saturation are raised to near room temperature.The age stability was inves-tigated for the fully hydrogenated L...The Curie temperatures(T_(C))of La_(0.7)Ce_(0.3)Fe_(13-x-y)Mn_(x)Si_(y)compounds that are hydrogenated to saturation are raised to near room temperature.The age stability was inves-tigated for the fully hydrogenated La_(0.7)Ce_(0.3)Fe_(11.5-x)Mn_(x)Si_(1.5) compounds.This result indicates that the H content will slowly decrease in the hydrides,leading to a decrease in T_(C).However,no age splitting is observed after the hydrides are held at room temperature for two years,indicating the excellent age stability of the hydrides.Further structural analysis by neutron diffrac-tion shows that Mn atoms preferentially substitute Fe in the 96i sites.The T_(C)of La_(0.7)Ce_(0.3)Fe_(11.55-y)Mn_(y)Si_(1.45)hydrides can be adjusted to the desired working temperature by regulating Mn content based on the linear relationship between T_(C)and Mn content.Moreover,the La_(0.7)Ce_(0.3)Fe_(11.55-y)Mn_(y)Si_(1.45)hydrides exhibit a giant magnetic entropy change of 15 J·kg^(-1)·K^(-1) under a low magneticfield change of 0-1 T.As a result,the giant magnetocaloric effect,linearly adjustable T_(C),and excel-lent age stability make the La_(0.7)Ce_(0.3)Fe_(11.55-y)Mn_(y)Si_(1.45)hydrides be one of the ideal candidates for room temperature magnetic refrigerants.展开更多
Recent reports of the superconductivity in hydrides of two different families(covalent lattice,as in SH3 and clathrate-type H-cages containing La and Y atoms,as in LaH10 and YH6)have revealed new families of high-Tc m...Recent reports of the superconductivity in hydrides of two different families(covalent lattice,as in SH3 and clathrate-type H-cages containing La and Y atoms,as in LaH10 and YH6)have revealed new families of high-Tc materials with Tc’s near room temperature values.These findings confirm earlier expectations that hydrides may have very high Tc’s due to the fact that light H atoms have very high vibrational frequencies,leading to high Tc values within the conventional Bardeen–Cooper–Schrieffer phonon mechanism of superconductivity.However,as is pointed out by Ashcroft,it is important to have the metallic hydrogen“alloyed”with the elements added to it.This concept of a metallic alloy containing a high concentration of metal-like hydrogen atoms has been instrumental in finding new high-Tc superhydrides.These new superhydride“roomtemperature”superconductors are stabilized only at very high pressures above 100 GPa,making the experimental search for their superconducting properties very difficult.We will review the current experimental and theoretical results for LaH10−x and YH6−x superhydrides.展开更多
Complex aluminum hydrides have been widely studied as potential hydrogen storage materials but also,for some time now, for electrochemical applications. This review summarizes the crystal structures of alkali and alka...Complex aluminum hydrides have been widely studied as potential hydrogen storage materials but also,for some time now, for electrochemical applications. This review summarizes the crystal structures of alkali and alkaline earth aluminum hydrides and correlates structure properties with physical and chemical properties of the hydride compounds. The crystal structures of the alkali metal aluminum hydrides change significantly during the stepwise dehydrogenation. The general pathway follows a transformation of structures built of isolated [AlH4]- tetrahedra to structures built of isolated [Al H6]3- octahedra.The crystal structure relations in the group of alkaline earth metal aluminum hydrides are much more complicated than those of the alkali metal aluminum hydrides. The structures of the alkaline earth metal aluminum hydrides consist of isolated tetrahedra but the intermediate structures exhibit chains of cornershared octahedra. The coordination numbers within the alkali metal group increase with cation sizes which goes along with an increase of the decomposition temperatures of the primary hydrides. Alkaline earth metal hydrides have higher coordination numbers but decompose at slightly lower temperatures than their alkali metal counterparts. The decomposition pathways of alkaline metal aluminum hydrides have not been studied in all cases and require future research.展开更多
The Meissner effect,magnetic field expulsion,is a hallmark of superconductivity.Associated with it,superconductors exclude applied magnetic fields.Recently,Minkov et al.[Nat.Commun.13,3194(2022)]presented experimental...The Meissner effect,magnetic field expulsion,is a hallmark of superconductivity.Associated with it,superconductors exclude applied magnetic fields.Recently,Minkov et al.[Nat.Commun.13,3194(2022)]presented experimental results reportedly showing“definitive evidence of the Meissner effect”in sulfur hydride and lanthanum hydride under high pressure,and Eremets et al.[J.Supercond.Nov.Magn.35,965(2022)]argued that“the arguments against superconductivity(in hydrides)can be either refuted or explained.”Instead,we show here that the evidence presented in those papers does not support the case for superconductivity in these materials.Together with experimental evidence discussed in earlier papers,we argue that this strongly suggests that hydrides under pressure are not high-temperature superconductors.展开更多
The structures and properties of Y-substituted Mg<sub>2</sub>Ni alloys and the corresponding hydrides are investigated by a first-principles plane-wave pseudopotential method within density functional theo...The structures and properties of Y-substituted Mg<sub>2</sub>Ni alloys and the corresponding hydrides are investigated by a first-principles plane-wave pseudopotential method within density functional theory. Results show that Mg<sub>2</sub>Ni has the best structural stability when Y atom occupies the Mg(6f) lattice sites. The calculated enthalpies of formation for Mg<sub>2</sub>Ni, Mg<sub>2</sub>NiH<sub>4</sub> and Mg<sub>15</sub>YNi<sub>8</sub>H<sub>32</sub> are -51.612, -64.667 and -62.554 kJ/mol, respectively. It is implied that the substitution of Y alloying destabilizes the stability of the hydrides. Moreover, the dissociated energies of H atoms are decreased significantly, indicating that Y alloying benefits the improvement of the dehydrogenating properties of Mg<sub>2</sub>Ni hydrides. The calculation and analysis of the electronic structures suggest that there is a stronger interaction between H and Ni atoms than the interaction between H and Mg atoms in Mg<sub>2</sub>NiH<sub>4</sub>. However, the Ni-H bond is weakened by the substitution of Y. Therefore, the substitution is an effective technique to decrease the structural stability of the hydrides and benefit for hydrogen storage.展开更多
Although rare-earth metals have increasingly received attention for use in the storage and transportation of the tritium used in nuclear fusion reactions,they still face great challenges,such as the effect of helium o...Although rare-earth metals have increasingly received attention for use in the storage and transportation of the tritium used in nuclear fusion reactions,they still face great challenges,such as the effect of helium on the mechanical properties of different erbium hydrides.In this work,first principles are used to study the mechanical properties(elastic constants,Young's modulus,transverse shear modulus and bulk modulus)of different erbium hydrides exposed to helium.The Young's modulus,the transverse shear modulus and the bulk modulus are given based on the elastic constants calculated according to first principles.It is found that the mechanical properties of all three erbium hydrides decrease in the presence of helium,and the decline of the mechanical properties of ErH_3 is the most serious.To explain the reason for the decrease in the mechanical properties,the densities of the states of erbium hydrides are calculated.During the calculations,helium embrittlement is not found and the ductility of the erbium hydrides improves following the production of helium at the helium concentrations considered in this work.展开更多
The high pressure behaviors of Th_4H_（15） and ThH_2 are investigated by using the first-principles calculations based on the density functional theory（DFT）. From the energy–volume relations, the bct phase of ThH_...The high pressure behaviors of Th_4H_（15） and ThH_2 are investigated by using the first-principles calculations based on the density functional theory（DFT）. From the energy–volume relations, the bct phase of ThH_2 is more stable than the fcc phase at ambient conditions. At high pressure, the bct ThH_2 and bcc Th_4H（15） phases are more brittle than they are at ambient pressure from the calculated elastic constants and the Poisson ratio. The thermodynamic stability of the bct phase ThH_2 is determined from the calculated phonon dispersion. In the pressure domain of interest, the phonon dispersions of bcc Th_4H（15） and bct ThH_2 are positive, indicating the dynamical stability of these two phases, while the fcc ThH_2 is unstable. The thermodynamic properties including the lattice vibration energy, entropy, and specific heat are predicted for these stable phases. The vibrational free energy decreases with the increase of the temperature, and the entropy and the heat capacity are proportional to the temperature and inversely proportional to the pressure. As the pressure increases, the resistance to the external pressure is strengthened for Th_4H_（15） and ThH_2.展开更多
The magnetocrystalline anisotropies of RFe10V2 (R=Y, Tb, Dy, Ho and Er) and their hydrides were studied by X-ray diffraction, magnetization and a.c. susceptibility measurements. The uniaxial anisotropy of Fe-sublattic...The magnetocrystalline anisotropies of RFe10V2 (R=Y, Tb, Dy, Ho and Er) and their hydrides were studied by X-ray diffraction, magnetization and a.c. susceptibility measurements. The uniaxial anisotropy of Fe-sublattice and R-sublattice with positive second order Stevens αJ in RFe10V2 compounds is weakened by hydrogenation, while that of R-sublattice with negative αJ (Er) enhanced. Such a change of anisotropy causes planar-easy magnetic structures in RFe10V2 (R=Tb and Dy) at room temperature and induces spin reorientation in HoFe10V2 after hydrogenation. The change of anisotropy of R-sublattice after hydrogenation may be owed to a decrease of the second order crystalline coefficient.展开更多
Here,we study the hydride formation in a metastable Ti-33Zr-22Hf-11Ta(at.%)refractory high entropy alloy(RHEA).Deviating to non-equiatomic compositions of RHEAs promotes the formation of transformation-induced plastic...Here,we study the hydride formation in a metastable Ti-33Zr-22Hf-11Ta(at.%)refractory high entropy alloy(RHEA).Deviating to non-equiatomic compositions of RHEAs promotes the formation of transformation-induced plasticity where the body-centered cubic phase transforms to hexagonal close-packed(HCP)phase.It is found that the phase transformation capability assists the hydride formation due to the low solubility of hydrogen within the HCP phase.In this study,hydrogen is charged via electrochemical polishing and the corresponding phase transformation is activated in the metastable RHEAs.The newly formed HCP phase interacts with hydrogen to form a face-centered cubic hydride verified by electron energy loss spectroscopy.This work provides a primary exploration of the formation of compositionally complex metal hydrides in the metastable RHEAs,which are potential candidates for future hydrogen storage material design.展开更多
Metal hydrides (MeH) on solid surfaces, i.e., surface MeH, are ubiquitous but criticalspecies in heterogeneous catalysis, and their intermediate roles have been proposed innumerous reactions such as (de)hydrogenation ...Metal hydrides (MeH) on solid surfaces, i.e., surface MeH, are ubiquitous but criticalspecies in heterogeneous catalysis, and their intermediate roles have been proposed innumerous reactions such as (de)hydrogenation and alkanes activation, etc., however, thedetailed spectroscopic characterizations remain challenging. Solid-state nuclear magnetic resonance (ssNMR) spectroscopy has become a powerful tool in surface studies, asit provides access to local structural characterizations at atomic level from multipleviews, with comprehensive information on chemical bonding and spatial structures. Inthis review, we summarized and discussed the latest research developments on thesuccessful application of ssNMR to characterize surface MeH species on solid catalystsincluding supported single-site heterogeneous catalysts, bulk metal oxides and metalmodified zeolites. We also discussed the opportunities and challenges in this field, aswell as the potential application/development of state-of-the-art ssNMR technologies toenable further exploration of metal hydrides in heterogeneous catalysis.展开更多
Hydrogen has been widely considered as a clean energy carrier that bridges the energy producers and energy consumers in an efficient and safe way for a sustainable society.Hydrogen can be stored in a gas,liquid and so...Hydrogen has been widely considered as a clean energy carrier that bridges the energy producers and energy consumers in an efficient and safe way for a sustainable society.Hydrogen can be stored in a gas,liquid and solid states and each method has its unique advantage.Though compressed hydrogen and liquefied hydrogen are mature technologies for industrial applications,appropriate measures are necessary to deal with the issues at high pressure up to around 100 MPa and low temperature at around 20 K.Distinct from those technologies,storing hydrogen in solid-state hydrides can realize a more compact and much safer approach that does not require high hydrogen pressure and cryogenic temperature.In this review,we will provide an overview of the majormaterial groups that are capable of absorbing and desorbing hydrogen reversibly.The main features on hydrogen storage properties of each material group are summarized,together with the discussion of the key issues and the guidance of materials design,aiming at providing insights for new material development as well as industrial applications.展开更多
Mg–RE(Dy,Gd,Y)alloys show promising for being developed as biodegradable medical applications.It is found that the hydride REH_(2) could be formed on the surface of samples during their preparations with water cleani...Mg–RE(Dy,Gd,Y)alloys show promising for being developed as biodegradable medical applications.It is found that the hydride REH_(2) could be formed on the surface of samples during their preparations with water cleaning.The amount of formed hydrides in Mg–RE alloys is affected by the content of RE and heat treatments.It increases with the increment of RE content.On the surface of the alloy with T4 treatment the amount of formed hydride REH_(2) is higher.In contrast,the amount of REH2 is lower on the surfaces of as-cast and T6-treated alloys.Their formation mechanism is attributed to the surface reaction of Mg–RE alloys with water.The part of RE in solid solution in Mg matrix plays an important role in influencing the formation of hydrides.展开更多
Introduction It is well known that organometallic hydrides of rare earth metals are the catalysts and reducing reagents for the catalysis polymerization of alkenes and the catalysis hydrogenation of alkenoalkynes. The...Introduction It is well known that organometallic hydrides of rare earth metals are the catalysts and reducing reagents for the catalysis polymerization of alkenes and the catalysis hydrogenation of alkenoalkynes. There are four methods for the syntheses of organometallic hydrides of rare earth metals:（1） the thermal atomization of metals, i.e., the interaction of a rare earth metal with alkenes with a terminal alkyne;（2） the Ln—Cσ bond is broken with H;;（3） metal-展开更多
We report the lithium ionic conductivities of closo –type complex hydrides synthesized from various molar ratios of lithium borohydride(LiBH4) and decaborane(B10H14) as starting materials. The prepared closo –type c...We report the lithium ionic conductivities of closo –type complex hydrides synthesized from various molar ratios of lithium borohydride(LiBH4) and decaborane(B10H14) as starting materials. The prepared closo –type complex hydrides comprised [B12H12]^2-, [B11H11]^2-, and [B10H10]^2- complex anions. In addition, increasing the LiBH4 content in the starting materials increased the amounts of [B11H11]^2- and [B10H10]^2-, leading to an improved ion conductivity of the prepared sample. The present study offers useful insights into strategies for controlling the complex anion composition in emerging solid electrolytes of closo-type complex hydrides at the molecular level, and improving their ionic conductivities.展开更多
The α alloy Ti-2Al-2.5Zr and near α alloy Ti-4Al-2V were hydrogenated to various levels. The morphology, orientation relation （OR）, and habit plane of the hydrides were studied by means of transmission electron mi...The α alloy Ti-2Al-2.5Zr and near α alloy Ti-4Al-2V were hydrogenated to various levels. The morphology, orientation relation （OR）, and habit plane of the hydrides were studied by means of transmission electron microscopy （TEM）. It was found that in the two alloys most of the precipitates are δ-hydrides which have fcc structure with the lattice parameter a = 0.44 nm. Two basic orientation relationships and habit planes of the precipitates are determined. Twin structure was observed in both alloys.展开更多
The influence of the surface state of the graphite furnace atomizer on the atomization of hydrides has been studied by means of surface film coating and quantum chemistry CN-DO/2 calculations. The results of the study...The influence of the surface state of the graphite furnace atomizer on the atomization of hydrides has been studied by means of surface film coating and quantum chemistry CN-DO/2 calculations. The results of the study prove that the atomization of AsH3, SbH3 and BiH3 in the graphite furnace atomizer is not a simple gas phase pyrolytic process, but a surface catalysis pyrolytic process.展开更多
Known as one of the most promising application of metal hydride(MH),the MH compressor can afford hydrogen with high pressure and high purity.Two AB5 type multi-component hydrogen storage alloys and vanadium are studie...Known as one of the most promising application of metal hydride(MH),the MH compressor can afford hydrogen with high pressure and high purity.Two AB5 type multi-component hydrogen storage alloys and vanadium are studied for the purpose of high pressure compression.A compact compression system has been built.Each designed small-size reactor contains seven special stainless-steel pipes.The single stage compressor can improve the hydrogen pressure from 2 up to 35 MPa with the hydrogen desorbed per unit mass of 207.8 mL/g.The two-stage compression can output hydrogen with pressure of 38 MPa steadily in whole 5.7 mol hydrogen output flow.However,its hydrogen desorbed per unit mass was only computed to 106.9 mL/g as a result of two reactors used in the cycle and the output mass of hydrogen increased less.展开更多
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.
基金supported by the Australian Research Council (No.LP160100690)a Japan Society for the Promotion of Science (JSPS)Postdoctoral Fellowship for Research in Japan (Standard) (No.P22739)supported by an Aus-tralian Government Research Training Program (RTP)Scholarship.
文摘Bulk Mg-based hydrogen storage materials have the potential to provide a low-cost solution to diversify energy storage and transportation.Compared to nano powders which require handling and processing under hydrogen or an inert gas atmosphere,bulk Mg-based alloys are safer and are more oxidation re-sistant.Conventional methods and existing infrastructures can be used to process and handle these ma-terials.However,bulk Mg alloys have smaller specific surface areas,resulting in slower hydrogen sorp-tion kinetics,higher equilibrium temperatures,and enthalpies of hydride formation.This work reviews the effects of the additions of a list of alloying elements and the use of innovative processing meth-ods,e.g.,rapid solidification and severe plastic deformation processes,to overcome these drawbacks.The challenges,advantages,and weaknesses of each method and future perspectives for the development of Mg-based hydrogen storage materials are discussed.
基金supported by the National Natu-ral Science Foundation of China(Nos.U20A20237,51863005,52271205,51871065,51971068,and 52101245)the Scientific Research and Technology Development Program of Guangxi(Nos.AA19182014,AD17195073,AA17202030-1,AB21220027,and 2021AB17045)+2 种基金National Natural Science Foundation of Guangxi Province(Nos.2021GXNSFBA075057,2018GXNSFDA281051,2014GXNSFAA118401,and 2013GXNSFBA019244)the Scientific Research and Technology Development Program of Guilin(Nos.20210102-4 and 20210216-1)Guangxi Bagui Scholar Founda-tion,Guilin Lijiang Scholar Foundation,Guangxi Collaborative Innovation centre of Structure and Property for New Energy and Materials,Guangxi Advanced Functional Materials Foundation and Application Talents Small Highlands,Chinesisch-Deutsche Kooperationsgruppe(No.GZ1528).
文摘Hydrogen energy is expected to be an“ideal fuel”in the era of decarbonization.The discovery,de-velopment,and modification of high-performance hydrogen storage materials are the keys to the fu-ture development of solid-state hydrogen storage and hydrogen energy utilization.Magnesium hydride(MgH_(2)),with its high hydrogen storage capacity,abundant natural reserves,and environmental friend-liness,has been extensively researched.Herein,we briefly summarize the typical structure and hy-drogenation/dehydrogenation reaction mechanism of MgH_(2)and provide a comprehensive overview of strategies to effectively tune the thermodynamics and kinetics of Mg-based materials,such as alloy-ing,nanosizing,the introduction of additives,and composite modification.With substantial efforts,great achievements have been achieved,such as lower absorption/desorption temperatures and better cy-cling stability.Nonetheless,some pivotal issues remain to be addressed,such as unfavorable hydro-genation/dehydrogenation factors,harsh conditions,slow kinetics,incomplete dehydrogenation,low hy-drogen purity,expensive catalysts,and a lack of valid exploration of mechanisms in the hydrogena-tion/dehydrogenation process.Lastly,some future development prospects of MgH_(2)in energy-efficient conversion and storage have been presented,including advanced manufacturing ways,stabilization of nanostructures,the introduction of additives combined with structural modification,and utilization of advanced characterization techniques.
基金financially supported by the National Key Research and Development Program of China (No. 2017YFB0702704)the National Science Foundation of China (No. 51571018)。
文摘The Curie temperatures(T_(C))of La_(0.7)Ce_(0.3)Fe_(13-x-y)Mn_(x)Si_(y)compounds that are hydrogenated to saturation are raised to near room temperature.The age stability was inves-tigated for the fully hydrogenated La_(0.7)Ce_(0.3)Fe_(11.5-x)Mn_(x)Si_(1.5) compounds.This result indicates that the H content will slowly decrease in the hydrides,leading to a decrease in T_(C).However,no age splitting is observed after the hydrides are held at room temperature for two years,indicating the excellent age stability of the hydrides.Further structural analysis by neutron diffrac-tion shows that Mn atoms preferentially substitute Fe in the 96i sites.The T_(C)of La_(0.7)Ce_(0.3)Fe_(11.55-y)Mn_(y)Si_(1.45)hydrides can be adjusted to the desired working temperature by regulating Mn content based on the linear relationship between T_(C)and Mn content.Moreover,the La_(0.7)Ce_(0.3)Fe_(11.55-y)Mn_(y)Si_(1.45)hydrides exhibit a giant magnetic entropy change of 15 J·kg^(-1)·K^(-1) under a low magneticfield change of 0-1 T.As a result,the giant magnetocaloric effect,linearly adjustable T_(C),and excel-lent age stability make the La_(0.7)Ce_(0.3)Fe_(11.55-y)Mn_(y)Si_(1.45)hydrides be one of the ideal candidates for room temperature magnetic refrigerants.
基金V.S.acknowledges support fromthe Thousand Talent Program by the State Council of the People’s Republic of China.Portions of this work were performed at GeoSoilEnviroCARS(The University of Chicago,Sector 13)Advanced Photon Source(APS),Argonne National Laboratory.GeoSoilEnviroCARS is supported by the National Science Foundation-Earth Sciences(Grant No.EAR-1634415)Department of Energy-GeoSciences(Grant No.DE-FG02-94ER14466).This research used resources from the Advanced Photon Source,a U.S.Department of Energy(DOE)Office of the Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No.DEAC02-06CH11357.I.T.and A.G.acknowledge support from the Ministry of Science and Higher Education of the Russian Federation within the State assignment of the FSRC“Crystallography and Photonics”of RAS in part of the high-pressure structural experiments and from the Russian Science Foundation(Project No.19-12-00414)in part of the high-pressure studies of superconductivity.A.G.acknowledges the use of the facilities of the Center for Collective Use“AcceleratorCenter for NeutronResearch of the Structure of Substance and Nuclear Medicine”of the INR RAS.
文摘Recent reports of the superconductivity in hydrides of two different families(covalent lattice,as in SH3 and clathrate-type H-cages containing La and Y atoms,as in LaH10 and YH6)have revealed new families of high-Tc materials with Tc’s near room temperature values.These findings confirm earlier expectations that hydrides may have very high Tc’s due to the fact that light H atoms have very high vibrational frequencies,leading to high Tc values within the conventional Bardeen–Cooper–Schrieffer phonon mechanism of superconductivity.However,as is pointed out by Ashcroft,it is important to have the metallic hydrogen“alloyed”with the elements added to it.This concept of a metallic alloy containing a high concentration of metal-like hydrogen atoms has been instrumental in finding new high-Tc superhydrides.These new superhydride“roomtemperature”superconductors are stabilized only at very high pressures above 100 GPa,making the experimental search for their superconducting properties very difficult.We will review the current experimental and theoretical results for LaH10−x and YH6−x superhydrides.
文摘Complex aluminum hydrides have been widely studied as potential hydrogen storage materials but also,for some time now, for electrochemical applications. This review summarizes the crystal structures of alkali and alkaline earth aluminum hydrides and correlates structure properties with physical and chemical properties of the hydride compounds. The crystal structures of the alkali metal aluminum hydrides change significantly during the stepwise dehydrogenation. The general pathway follows a transformation of structures built of isolated [AlH4]- tetrahedra to structures built of isolated [Al H6]3- octahedra.The crystal structure relations in the group of alkaline earth metal aluminum hydrides are much more complicated than those of the alkali metal aluminum hydrides. The structures of the alkaline earth metal aluminum hydrides consist of isolated tetrahedra but the intermediate structures exhibit chains of cornershared octahedra. The coordination numbers within the alkali metal group increase with cation sizes which goes along with an increase of the decomposition temperatures of the primary hydrides. Alkaline earth metal hydrides have higher coordination numbers but decompose at slightly lower temperatures than their alkali metal counterparts. The decomposition pathways of alkaline metal aluminum hydrides have not been studied in all cases and require future research.
文摘The Meissner effect,magnetic field expulsion,is a hallmark of superconductivity.Associated with it,superconductors exclude applied magnetic fields.Recently,Minkov et al.[Nat.Commun.13,3194(2022)]presented experimental results reportedly showing“definitive evidence of the Meissner effect”in sulfur hydride and lanthanum hydride under high pressure,and Eremets et al.[J.Supercond.Nov.Magn.35,965(2022)]argued that“the arguments against superconductivity(in hydrides)can be either refuted or explained.”Instead,we show here that the evidence presented in those papers does not support the case for superconductivity in these materials.Together with experimental evidence discussed in earlier papers,we argue that this strongly suggests that hydrides under pressure are not high-temperature superconductors.
文摘The structures and properties of Y-substituted Mg<sub>2</sub>Ni alloys and the corresponding hydrides are investigated by a first-principles plane-wave pseudopotential method within density functional theory. Results show that Mg<sub>2</sub>Ni has the best structural stability when Y atom occupies the Mg(6f) lattice sites. The calculated enthalpies of formation for Mg<sub>2</sub>Ni, Mg<sub>2</sub>NiH<sub>4</sub> and Mg<sub>15</sub>YNi<sub>8</sub>H<sub>32</sub> are -51.612, -64.667 and -62.554 kJ/mol, respectively. It is implied that the substitution of Y alloying destabilizes the stability of the hydrides. Moreover, the dissociated energies of H atoms are decreased significantly, indicating that Y alloying benefits the improvement of the dehydrogenating properties of Mg<sub>2</sub>Ni hydrides. The calculation and analysis of the electronic structures suggest that there is a stronger interaction between H and Ni atoms than the interaction between H and Mg atoms in Mg<sub>2</sub>NiH<sub>4</sub>. However, the Ni-H bond is weakened by the substitution of Y. Therefore, the substitution is an effective technique to decrease the structural stability of the hydrides and benefit for hydrogen storage.
基金This work was supported by the National Natural Science Foundation of China(Grant No.11804046 and No.61505023).
文摘Although rare-earth metals have increasingly received attention for use in the storage and transportation of the tritium used in nuclear fusion reactions,they still face great challenges,such as the effect of helium on the mechanical properties of different erbium hydrides.In this work,first principles are used to study the mechanical properties(elastic constants,Young's modulus,transverse shear modulus and bulk modulus)of different erbium hydrides exposed to helium.The Young's modulus,the transverse shear modulus and the bulk modulus are given based on the elastic constants calculated according to first principles.It is found that the mechanical properties of all three erbium hydrides decrease in the presence of helium,and the decline of the mechanical properties of ErH_3 is the most serious.To explain the reason for the decrease in the mechanical properties,the densities of the states of erbium hydrides are calculated.During the calculations,helium embrittlement is not found and the ductility of the erbium hydrides improves following the production of helium at the helium concentrations considered in this work.
基金Project supported by the Long-Term Subsidy Mechanism from the Ministry of Finance and the Ministry of Education of China
文摘The high pressure behaviors of Th_4H_（15） and ThH_2 are investigated by using the first-principles calculations based on the density functional theory（DFT）. From the energy–volume relations, the bct phase of ThH_2 is more stable than the fcc phase at ambient conditions. At high pressure, the bct ThH_2 and bcc Th_4H（15） phases are more brittle than they are at ambient pressure from the calculated elastic constants and the Poisson ratio. The thermodynamic stability of the bct phase ThH_2 is determined from the calculated phonon dispersion. In the pressure domain of interest, the phonon dispersions of bcc Th_4H（15） and bct ThH_2 are positive, indicating the dynamical stability of these two phases, while the fcc ThH_2 is unstable. The thermodynamic properties including the lattice vibration energy, entropy, and specific heat are predicted for these stable phases. The vibrational free energy decreases with the increase of the temperature, and the entropy and the heat capacity are proportional to the temperature and inversely proportional to the pressure. As the pressure increases, the resistance to the external pressure is strengthened for Th_4H_（15） and ThH_2.
文摘The magnetocrystalline anisotropies of RFe10V2 (R=Y, Tb, Dy, Ho and Er) and their hydrides were studied by X-ray diffraction, magnetization and a.c. susceptibility measurements. The uniaxial anisotropy of Fe-sublattice and R-sublattice with positive second order Stevens αJ in RFe10V2 compounds is weakened by hydrogenation, while that of R-sublattice with negative αJ (Er) enhanced. Such a change of anisotropy causes planar-easy magnetic structures in RFe10V2 (R=Tb and Dy) at room temperature and induces spin reorientation in HoFe10V2 after hydrogenation. The change of anisotropy of R-sublattice after hydrogenation may be owed to a decrease of the second order crystalline coefficient.
基金W.J.Lu is grateful for financial support from the open research fund of Songshan Lake Materials Laboratory(No.2021SLABFK05)the Shenzhen Science and Technology Program(No.JCYJ20210324104404012).
文摘Here,we study the hydride formation in a metastable Ti-33Zr-22Hf-11Ta(at.%)refractory high entropy alloy(RHEA).Deviating to non-equiatomic compositions of RHEAs promotes the formation of transformation-induced plasticity where the body-centered cubic phase transforms to hexagonal close-packed(HCP)phase.It is found that the phase transformation capability assists the hydride formation due to the low solubility of hydrogen within the HCP phase.In this study,hydrogen is charged via electrochemical polishing and the corresponding phase transformation is activated in the metastable RHEAs.The newly formed HCP phase interacts with hydrogen to form a face-centered cubic hydride verified by electron energy loss spectroscopy.This work provides a primary exploration of the formation of compositionally complex metal hydrides in the metastable RHEAs,which are potential candidates for future hydrogen storage material design.
基金the National Natural Science Foundation of China(Grant Nos.21902158,21773230,91945302)the National Key R&D Program of China(No.2021YFA1502803)LiaoNing Revitalization Talents Program(XLYC1807207),DICP I202104.
文摘Metal hydrides (MeH) on solid surfaces, i.e., surface MeH, are ubiquitous but criticalspecies in heterogeneous catalysis, and their intermediate roles have been proposed innumerous reactions such as (de)hydrogenation and alkanes activation, etc., however, thedetailed spectroscopic characterizations remain challenging. Solid-state nuclear magnetic resonance (ssNMR) spectroscopy has become a powerful tool in surface studies, asit provides access to local structural characterizations at atomic level from multipleviews, with comprehensive information on chemical bonding and spatial structures. Inthis review, we summarized and discussed the latest research developments on thesuccessful application of ssNMR to characterize surface MeH species on solid catalystsincluding supported single-site heterogeneous catalysts, bulk metal oxides and metalmodified zeolites. We also discussed the opportunities and challenges in this field, aswell as the potential application/development of state-of-the-art ssNMR technologies toenable further exploration of metal hydrides in heterogeneous catalysis.
基金support by the program of studying/visiting abroad(No.450404).
文摘Hydrogen has been widely considered as a clean energy carrier that bridges the energy producers and energy consumers in an efficient and safe way for a sustainable society.Hydrogen can be stored in a gas,liquid and solid states and each method has its unique advantage.Though compressed hydrogen and liquefied hydrogen are mature technologies for industrial applications,appropriate measures are necessary to deal with the issues at high pressure up to around 100 MPa and low temperature at around 20 K.Distinct from those technologies,storing hydrogen in solid-state hydrides can realize a more compact and much safer approach that does not require high hydrogen pressure and cryogenic temperature.In this review,we will provide an overview of the majormaterial groups that are capable of absorbing and desorbing hydrogen reversibly.The main features on hydrogen storage properties of each material group are summarized,together with the discussion of the key issues and the guidance of materials design,aiming at providing insights for new material development as well as industrial applications.
文摘Mg–RE(Dy,Gd,Y)alloys show promising for being developed as biodegradable medical applications.It is found that the hydride REH_(2) could be formed on the surface of samples during their preparations with water cleaning.The amount of formed hydrides in Mg–RE alloys is affected by the content of RE and heat treatments.It increases with the increment of RE content.On the surface of the alloy with T4 treatment the amount of formed hydride REH_(2) is higher.In contrast,the amount of REH2 is lower on the surfaces of as-cast and T6-treated alloys.Their formation mechanism is attributed to the surface reaction of Mg–RE alloys with water.The part of RE in solid solution in Mg matrix plays an important role in influencing the formation of hydrides.
文摘Introduction It is well known that organometallic hydrides of rare earth metals are the catalysts and reducing reagents for the catalysis polymerization of alkenes and the catalysis hydrogenation of alkenoalkynes. There are four methods for the syntheses of organometallic hydrides of rare earth metals:（1） the thermal atomization of metals, i.e., the interaction of a rare earth metal with alkenes with a terminal alkyne;（2） the Ln—Cσ bond is broken with H;;（3） metal-
基金supported by METX,JSPS KAKENHI (Grant numbers, 16K0 676 6, 17H0 6519, 17K18972, 18H01727, and JP18H05513)Collaborative Research Center on Energy Materials in IMR (E-IMR)Target Project 4 of WPI-AIMR, Tohoku University
文摘We report the lithium ionic conductivities of closo –type complex hydrides synthesized from various molar ratios of lithium borohydride(LiBH4) and decaborane(B10H14) as starting materials. The prepared closo –type complex hydrides comprised [B12H12]^2-, [B11H11]^2-, and [B10H10]^2- complex anions. In addition, increasing the LiBH4 content in the starting materials increased the amounts of [B11H11]^2- and [B10H10]^2-, leading to an improved ion conductivity of the prepared sample. The present study offers useful insights into strategies for controlling the complex anion composition in emerging solid electrolytes of closo-type complex hydrides at the molecular level, and improving their ionic conductivities.
文摘The α alloy Ti-2Al-2.5Zr and near α alloy Ti-4Al-2V were hydrogenated to various levels. The morphology, orientation relation （OR）, and habit plane of the hydrides were studied by means of transmission electron microscopy （TEM）. It was found that in the two alloys most of the precipitates are δ-hydrides which have fcc structure with the lattice parameter a = 0.44 nm. Two basic orientation relationships and habit planes of the precipitates are determined. Twin structure was observed in both alloys.
文摘The influence of the surface state of the graphite furnace atomizer on the atomization of hydrides has been studied by means of surface film coating and quantum chemistry CN-DO/2 calculations. The results of the study prove that the atomization of AsH3, SbH3 and BiH3 in the graphite furnace atomizer is not a simple gas phase pyrolytic process, but a surface catalysis pyrolytic process.
基金the National Natural Science Foundation of China(No.50776094)the National High Technology Research and Development Program(863)of China(No.2006AA05Z135)
文摘Known as one of the most promising application of metal hydride(MH),the MH compressor can afford hydrogen with high pressure and high purity.Two AB5 type multi-component hydrogen storage alloys and vanadium are studied for the purpose of high pressure compression.A compact compression system has been built.Each designed small-size reactor contains seven special stainless-steel pipes.The single stage compressor can improve the hydrogen pressure from 2 up to 35 MPa with the hydrogen desorbed per unit mass of 207.8 mL/g.The two-stage compression can output hydrogen with pressure of 38 MPa steadily in whole 5.7 mol hydrogen output flow.However,its hydrogen desorbed per unit mass was only computed to 106.9 mL/g as a result of two reactors used in the cycle and the output mass of hydrogen increased less.
