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In this work, we studied phase composition, hydrogen desorption kinetics and microstructural topology of hydrogen-sorbing composite materials prepared by ball milling under hydrogen of the powders of Mg89Ni11 eutectic alloy without and with additive of graphene-like material (GLM). It was shown that in both cases the reproducible fast desorption kinetics were achieved after the fifth dehydrogenation—re-hydrogenation cycle. Using transmission electron microscopy, selected area electron diffraction, and the effect of MgH2 radiolysis it was found that after seven hydrogenation–dehydrogenation cycles the material retains a highly dispersed microstructure: in the regions with a cross-sectional area of 1 micron in the size there are grains of Mg and Mg2Ni hydride-forming phases that are in direct contact, that favors the hydrogen sorption performance of the material. [ABSTRACT FROM AUTHOR]

Multicaloric stacks consisting of a magnetocaloric film on a piezoelectric substrate promise improved caloric properties as the transition temperature can be controlled by both magnetic and electric fields. We present epitaxially grown magnetocaloric Ni-Mn-Ga-Co thin films on ferroelectric Pb(Mg1/3Nb2/3)0.72Ti0.28O3 substrates. Structure and microstructure of two samples, being in the austenitic and martensitic state at room temperature, are investigated by X-ray diffraction in two- and four-circle geometry and by atomic force microscopy. In addition, high temperature magnetometry was performed on the latter sample. The combination of these methods allows separating the influence of epitaxial growth and martensitic transformation. A preferential alignment of twin boundaries is observed already in the as-deposited state, which indicates the presence of prestress, without applying an electric field to the substrate. A temperature-magnetic field phase diagram is presented, which demonstrates the inverse magnetocaloric effect of the epitaxial Ni-Mn-Ga-Co film. [ABSTRACT FROM AUTHOR]

The formation of metastable γ-MgH 2 upon application of ultra-high pressure and its dehydrogenation properties were studied. Magnesium-nickel alloy (14 wt.% Ni) was hydrogenated and compressed at ultra-high pressures of 2.5 and 4 GPa. The phase composition and desorption properties of the products were investigated. Powder X-ray diffraction indicated that some α-MgH 2 converted to γ-MgH 2 during compression. This resulted in the onset of hydrogen desorption at 60 °C under vacuum. Our findings thus show that application of ultra-high pressure can facilitate the formation of γ-MgH 2 , which has a lower dehydrogenation temperature (≤200 °C) than α-MgH 2 , which desorbs at temperatures above 300 °C. The metastable phase possessed a high hydrogen storage capacity of at least 4.5 wt.%. These properties revealed the potential of γ-MgH 2 as a future hydrogen storage material. • An innovative way was used to produce metastable MgH 2 in Mg-Ni by ultra-high pressure. • Some α-MgH 2 was converted to γ-MgH 2 during compression. • γ-MgH2 was able to desorb hydrogen at a low temperature of 60 °C under vacuum. • γ-MgH2 demonstrates its potential as a future hydrogen storage material. [ABSTRACT FROM AUTHOR]

Ab initio total-energy density functional theory is used to investigate the low temperature (LT) monoclinic form of Mg[sub 2]NiH[sub 4]. The calculated minimum energy geometry of LT Mg[sub 2]NiH[sub 4] is close to that determined from neutron diffraction data, and the NiH[sub 4] complex is close to a regular tetrahedron. The enthalpies of the phase change to high temperature (HT) pseudo-cubic Mg[sub 2]NiH[sub 4] and of hydrogen absorption by Mg[sub 2]Ni are calculated and compared with experimental values. LT Mg[sub 2]NiH[sub 4] is found to be a semiconductor with an indirect band gap of 1.4 eV. The optical dielectric function of LT Mg[sub 2]NiH[sub 4] differs somewhat from that of the HT phase. A calculated thin film transmittance spectrum is consistent with an experimental spectrum. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract Mg 80– x Ni 20 Y x (x = 0–7) alloys were successfully prepared by using the vacuum induction melting method. The structural characterizations of the alloys were performed by using X-ray diffraction, scanning electron microscope, transmission electron microscope and X-ray photoelectron spectroscopy measurements. The effects of yttrium content on the microstructure and hydrogen storage properties of the as-cast alloys were investigated. The alloys are composed of a primary phase of Mg 2 Ni, lamella eutectic composites of Mg + Mg 2 Ni, and some amount of YNi 3. The YNi 3 has completely transformed into in situ formed nanoscale YH 2 and YH 3 , with the formation of Mg 2 NiH 4. Pulverization of the alloy particles was observed during the hydrogen absorption and desorption cycles. However, the phase composition remains unchanged even after 20 hydrogenation cycles. Yttrium addition significantly improved the hydrogen-absorption kinetic performance of the alloy. In addition, pressure-composition-temperature measurements indicated that the entropy and enthalpy changes for the formation and decomposition of MgH 2 and Mg 2 NiH 4 gradually decreased with the increase of yttrium content. Highlights • YNi 3 , Mg 2 Ni and lamella eutectic Mg + Mg 2 Ni phases were observed in the alloys. • YNi 3 fully decomposed, with the formation of nanometer YH 2 and Mg 2 NiH 4. • Increasing Y content significantly improves the hydrogen absorption kinetics. • The decomposition peak temperature was reduced from 586 K to 523 K. • Δ H and Δ S of the Mg/MgH 2 and Mg 2 Ni/Mg 2 NiH 4 transformations decreased. [ABSTRACT FROM AUTHOR]

Abstract In the present work, nanocrystalline Mg 2 Ni with an average size of 20–50 nm was prepared via ball milling of a 2MgH 2 Ni powder followed by compression under a pressure of 280 MPa. The phase component, microstructure, and hydrogen sorption properties were characterized by using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), pressure-composition-temperature (PCT) and synchronous thermal analyses (DSC/TG). Compared to the non-compressed 2MgH 2 Ni powder, the compressed 2MgH 2 Ni pellet shows lower dehydrogenation temperature (290 °C) and a single-phase Mg 2 Ni is obtained after hydrogen desorption. PCT measurements show that the nanocrystalline Mg 2 Ni obtained from dehydrogenated 2MgH 2 Ni pellet has a single step hydrogen absorption and desorption with fairly low absorption (−57.47 kJ/mol H 2) and desorption (61.26 kJ/mol H 2) enthalpies. It has very fast hydrogen absorption kinetics at 375 °C with about 3.44 wt% hydrogen absorbed in less than 5 min. The results gathered in this study show that ball milling followed by compression is an efficient method to produce Mg-based ternary hydrides. Highlights • Single phase Mg 2 Ni was prepared from ball milled 2MgH 2 Ni compressed pellet. • Enthalpies of hydrogenation/dehydrogenation of Mg 2 Ni/Mg 2 NiH 4 were −57.47 kJ/mol H 2 and 61.26 kJ/mol H 2 respectively. • Nanocrystalline Mg 2 Ni hydrogen absorption was very fast and absorbed 3.44 wt% hydrogen in less than 5 min. [ABSTRACT FROM AUTHOR]

Highlights • The Mg 85 Ni 15 -0.2 wt.% Ti and Mg 68 Ti 9 Ni 23 alloys were produced by casting. • The Mg 85 Ni 15 -0.2 wt.% Ti alloy had hydrogen storage capacity of 5.22 wt.% at 653 K. • Intersection of initial hydriding curves for different temperatures were discussed. • The dehydrogenation activation energies of the two alloys were much lower than MgH 2. • The hydrogenation enthalpy of Mg 85 Ni 15 -0.2 wt.% Ti was 5KJ/mol lower than MgH 2. Abstract The as-cast Mg 85 Ni 15 -0.2 wt.% Ti and Mg 68 Ti 9 Ni 23 alloys were produced with vacuum induction levitation melting furnace. The Mg 85 Ni 15 -0.2 wt.% Ti alloy had a reversible hydrogen storage capacity of 5.22 wt.% at 653 K. Intersection of hydrogen absorption curves at different temperatures, which could be found during the initial hydrogenation process, indicated two competed kinetic mechanism took part in the original hydrogenation. Pressure-composition isothermal (PCI) curves showed two pressure plateaus for all applied temperatures. The enthalpies, obtained by PCI data, of hydrogenation for these two alloys were estimated to be about 5 kJ/mol lower than MgH 2. Results of Kissinger plots, based on DSC data, showed the activation energy of dehydrogenation were 51.69 kJ/mol and 57.75 kJ/mol, which were much lower than pure MgH 2 , for Mg 85 Ni 15 -0.2 wt.% Ti and Mg 68 Ti 9 Ni 23 alloys, respectively. [ABSTRACT FROM AUTHOR]

In this article, the isothermal hydrogenation curves of hypo-eutectic Mg–6Ni–3Cu (at. %) alloy under various temperatures and applied hydrogen pressures are fitted by Johnson-Mehl-Avrami equation. The hydrogenation behavior and its dependence on absorption conditions are investigated, as different from that of pure Mg. A three-stage hydrogenation behavior is illustrated and an extra absorption process (Stage III) resulted from H dissolution or the hydride formation in boundaries appears when the hydrogen pressure reaches a critical value. Due to the same role of increased Δ P and decreased Δ T on hydride nucleation driving force and their opposite impacts on H diffusion, temperature and hydrogen pressure are influencing the absorption process differently. As the great H permeability in Mg–Mg 2 Ni–Mg 2 Cu eutectic, more hydrogen is absorbed under larger hydrogenation driving force, rather than hydrogen uptake deficit. It is revealed that the reaction order η corresponding to H diffusing in thin MgH 2 layer is larger than that in thick MgH 2 shell, which can preliminarily identify the hydrogenation behavior after MgH 2 impinging around primary Mg (Stage II). [ABSTRACT FROM AUTHOR]

A study of the magnetocaloric effect (MCE) in the ferromagnetic Heusler alloys Ni50Mn37+xSb13-x (x=0,0.5,1) has been carried out through magnetization measurements. An inverse magnetocaloric effect was observed in the vicinity of the first order martensitic transition. A maximum positive magnetic entropy change of ΔSm≈19 J/kg K at approximately 297 K for a magnetic field change of 5 T was observed. It is demonstrated that the martensitic transformation temperature, and the corresponding ΔSm, can be tuned through a slight variation in composition. [ABSTRACT FROM AUTHOR]

The precipitation mechanism of nano-sized and micro-sized Mg 2 Ni particles during hydrogen-induced decomposition of 18R-type long period stacking ordered phase is investigated. Nano-sized Mg 2 Ni particles adhere to YH 2 particles inside grains, while micro-sized Mg 2 Ni particles form at grain boundaries due to the segregation of Ni atoms. The interface energies are predicted to be 1.108–1.263 J/m 2 for Mg/Mg 2 Ni, 1.389 J/m 2 for YH 2 /Mg 2 Ni, and 1.536 J/m 2 for YH 2 /Mg, indicating that the adhesion of nano-sized Mg 2 Ni to YH 2 reduces the total energy of the system. The negative segregation energy of −0.194 eV proves that the segregation of Ni atoms is energetically favorable. [ABSTRACT FROM AUTHOR]

Nanocrystalline La 1.5 Mg 0.5 Ni 7 alloy has been synthesized by mechanical alloying and heat treatment (850 °C) and a 20–50 μm fraction of its particles has been encapsulated with three kinds of Ni-based coatings: (i) electroless Ni P, 1 μm thick, (ii) magnetron sputtered Ni, 0.087 μm thick and (iii) magnetron sputtered Ni, 0.29 μm thick. The electrochemical charge/discharge multicycling of powder composite electrodes has been carried out in view of material potential usefulness for Ni/MH x batteries. The nanocrystalline La 1.5 Mg 0.5 Ni 7 alloy exhibits four times lower capacity fade as compared to a microcrystalline LaNi 5 reference compound. Modification of La 1.5 Mg 0.5 Ni 7 particle surface with comparatively thick layer of electroless Ni P coating deteriorates electrode corrosion behavior and worsens kinetics of hydrogen electrosorption due to unsatisfactory adhesion of the coating to the Mg-containing substrate. Corrosion protection of the La 1.5 Mg 0.5 Ni 7 nanomaterial by magnetron sputtered Ni films depends on average film thickness. Relatively thick (0.29 μm) sputtered Ni film limits corrosion degradation and stabilizes exchange current density of H 2 O/H 2 system. Particle modification by Ni encapsulation does not affect the hydrogen diffusivity. Effective diffusion coefficient of hydrogen for La 1.5 Mg 0.5 Ni 7 nanocrystalline material, irrespectively of surface modification, is close to 2·10 −10  cm 2 s −1 . [ABSTRACT FROM AUTHOR]

Porous hollow Mg 0.6 Ni 0.4 O has been fabricated by simple solvothermal method and removed the template by calcining. Afterward, taking advantage of liquid infiltration method, we have successfully synthesized hollow Mg 0.6 Ni 0.4 O/S as positive material for Li-S battery with a sulfur loading of 59.9 wt%. Porous hollow structure not only promoted the electron transfer, but also mitigated the expansion of element sulfur in the process of charging and discharging. Under a current density of 200 mA g −1 , the reversible capacity was up to 912 mAh g −1 after 65 cycles with a high rate performance, coulombic efficiency and a capacity retention of 98%. Especially, at a higher current density of 4000 mA g −1 , the reversible capacity maintained at 174.5 mAh g −1 after 500 cycles. The excellent electrochemical performance was owe to Mg 0.6 Ni 0.4 O alleviating polysulfide dissolution in electrolyte and had unique catalytic effect on the Li/S redox reactions. [ABSTRACT FROM AUTHOR]

Mg 2 Ni has drawn attention due to its high reaction rates, good reversibility, and possibility to be applied as a negative electrode in the Ni-MH (metal hydride) batteries. Mg 2 Ni samples were prepared by sintering under Ar in a stainless-steel crucible at 823 K. Johnson-Mehl equation for nucleation and growth mechanism was applied to the behaviors of hydriding and dehydriding reactions of Mg 2 Ni. At 571 K under 30 bar H 2 , the activation of the Mg 2 Ni sample was completed at the number of cycles of three (n = 3). At n = 3, hydrided fractions of the sample were 0.51 (1.92 wt% H) at 0.50 min and 0.90 (3.38 wt% H) at 2.00 min. Reverse temperature dependences of the initial hydriding rate and the quantity of hydrogen absorbed for 60 min appeared from 571 K to 620 K. Hydriding and dehydriding reactions progressed by the nucleation and growth mechanism and could be expressed by the Johnson-Mehl equation. [ABSTRACT FROM AUTHOR]

It is crucial to understand the compositional dependence of the bandgap of the Ni1-xMgxO alloy as it is a promising bandgap-tunable material for ultraviolet (UV) and deep-UV photodetectors. However, the dependence of the bandgap of this material on the Mg content, x, is still a subject of debate, as the experimentally measured optical bandgap of Ni1-xMgxO is 2-3 eV lower than that of pure MgO (7.77 eV), in contrast to that predicted by conventional bandgap bowing theories. Here, we demonstrate that the Ni1-xMgxO alloy has two bandgaps: (i) the Ni-3d bandgap Eg 3d, i.e., the bandgap between the valence band (O 2p) and Ni-3d(eg) bands, where the charge-transfer (CT) transition energy weakly depends on the Mg content and (ii) the alloy bandgap ..., i.e., the bandgap between the valence band and the conduction band of the Ni1-xMgxO alloy, which is related to the Ni 4s/Mg 3s states; the alloy bandgap obeys the conventional bandgap bowing model. The Ni1-xMgxO absorption spectra at low Mg contents are difficult to deconvolute because the electronic bands originating from the Ni-3d bands and the alloy conduction band overlap. The band structure described above elucidates the anomalous characteristics of the bandgap of Ni1-xMgxO, i.e., most of the optical bandgap values reported so far are smaller than the expected value corresponding to the transition from the valence band to the alloy conduction band because they were evaluated based on the absorption due to the O 2p-Ni 3d(eg) CT transition. [ABSTRACT FROM AUTHOR]

To investigate the effect of microstructure on the better de-/hydrogenation property of Mg-based alloy, hypo-eutectic Mg-8Ni (at. %) alloy and hyper-eutectic Mg-15Ni alloy are prepared by metallurgy method. The phase constitutions and microstructures are characterized by XRD and SEM/EDS. Mg-8/15Ni alloy is composed of primary Mg/Mg 2 Ni and eutectic Mg-Mg 2 Ni. In isothermal sorption test, Mg-15Ni alloy shows preferable activation performance and faster de-/hydrogenation rates than Mg-8Ni alloy. The respective hydrogen uptake capacity in 165min is 5.62 wt% and 5.76 wt% H 2 at 300 °C 3 MPa. Intersections of Mg-Mg 2 Ni eutectic phase boundaries with particle surface provide excellent sites and paths for the dissociation and permeation of hydrogen. The de-/hydrogenation enthalpy and entropy values are determined by PCI measurement. Based on the DSC curves at different heating rates, the desorption behavior of Mg-8/15Ni hydride is revealed and the respective activation energy is calculated to be 134.67 kJ mol −1 and 88.34 kJ mol −1 H 2 by Kissinger method. Synergic dehydrogenation occurs in eutectic MgH 2 -Mg 2 NiH 4 , which facilitates the primary MgH 2 in Mg-8Ni hydride to decompose at a lower temperature. The rapid H diffusion and synergic effect in eutectic MgH 2 -Mg 2 NiH 4 collectively contribute to the lower dehydrogenation energy barrier of Mg-15Ni hydride. [ABSTRACT FROM AUTHOR]

Effects of Mn doping on the hydrogen adsorption and diffusion on the Mg 2 Ni (010) surface are studied using first-principles density functional theory. The results show that the Mg 2 Ni (010) surface becomes more uneven and the thermodynamical stability of Mg 2 Ni (010) system is lowered after Mn doping. Analysis of the hydrogen adsorption energies on the pure and Mn-doped Mg 2 Ni (010) surfaces shows that Mn-doped Mg 2 Ni (010) surface has more sites for hydrogen to adsorb stably. Further calculation of the hydrogen diffusion indicates that the substitution of Mg with Mn lowers the energy barrier for hydrogen to diffuse from the (010) surface to the subsurface. [ABSTRACT FROM AUTHOR]

The present study investigates the thermal stability of binary geopolymers prepared with fly ash and high magnesium nickel slag (HMNS). TGA, XRD and SEM techniques are adopted to investigate the chemical composition and microstructure of the binder gel phase exposed to high temperatures. The results show that incorporating HMNS mitigates dehydration induced mass loss and volume shrinkage of the geopolymer samples between room temperature and 250 °C, and increases their residual strengths when exposed to high temperatures between 600 °C and 800 °C. The key role that HMNS substitution of improving the thermal stability of geopolymers is associated with the formation of sodium-alumina(magnesia)-silica hydrate (N-A(M)-S-H) gel phase, which turns to be a less porous microstructure after thermal exposure when compared with the N-A-S-H gel phase, which is formed in the pure fly ash sample. The binary geopolymers exhibit higher residual strengths and better maintaining of volume stability in the range from 250 °C to 550 °C compared to Portland cements. However, both the geopolymer and Portland cement show severer volume shrinkage after exposure of 600 °C, because of the viscous sintering of geopolymer gels and the decomposition of cement hydration products, respectively. [ABSTRACT FROM AUTHOR]

The present study investigates the thermal stability of binary geopolymers prepared with fly ash and high magnesium nickel slag (HMNS). TGA, XRD and SEM techniques are adopted to investigate the chemical composition and microstructure of the binder gel phase exposed to high temperatures. The results show that incorporating HMNS mitigates dehydration induced mass loss and volume shrinkage of the geopolymer samples between room temperature and 250 °C, and increases their residual strengths when exposed to high temperatures between 600 °C and 800 °C. The key role that HMNS substitution of improving the thermal stability of geopolymers is associated with the formation of sodium-alumina(magnesia)-silica hydrate (N-A(M)-S-H) gel phase, which turns to be a less porous microstructure after thermal exposure when compared with the N-A-S-H gel phase, which is formed in the pure fly ash sample. The binary geopolymers exhibit higher residual strengths and better maintaining of volume stability in the range from 250 °C to 550 °C compared to Portland cements. However, both the geopolymer and Portland cement show severer volume shrinkage after exposure of 600 °C, because of the viscous sintering of geopolymer gels and the decomposition of cement hydration products, respectively. [ABSTRACT FROM AUTHOR]

The cycle stability of La-Mg-Ni based alloys in a gas–solid reaction system was investigated in this work. Both partial substitutions of La and Ni by Ce and Al, respectively, improved the cycle stability of La (0.65−x) Ce x Ca 1.03 Mg 1.32 Ni (9−y) Al y alloys. Although the addition of Al reduced the hydrogen storage capacity significantly, it is still important to be included in the system for its superior property in improving the cycle life. Hence, two optimized samples with a small addition of Al (y = 0.10) were used to compare with the cycle life of CaNi 5 . It was found that the Ce and Al added samples have a better hydrogen capacity retention than that of samples without element substitution; and their overall hydrogen storage capacity was still higher than that of CaNi 5 . We also found that heat treatment used in this study did not fully recover the hydrogen storage capability of La-Mg-Ni based alloy to its original storage capacity. A probable reason was the heat treatment used in this study could only recover the degradation caused by the disproportionation to some extent, but the treatment was unable to reverse the degradation caused by decrepitation. [ABSTRACT FROM AUTHOR]

A (La,Mg) 5 Ni 19 single-phase La 0.78 Mg 0.22 Ni 3.73 alloy with superior overall electrochemical properties has been prepared by step-wise annealing the as-cast alloy sample. The as-cast alloy is composed of 2H-/3R-type (La,Mg) 2 Ni 7 and (La,Mg) 5 Ni 19 main phases as well as (La,Mg)Ni 3 and LaNi 5 minor phases. During step-wise annealing process, (La,Mg)Ni 3 and LaNi 5 minor phases are first consumed to form (La,Mg) 2 Ni 7 and (La,Mg) 5 Ni 19 phases at 800–850 °C. Then the 3R-type (La,Mg) 2 Ni 7 phase transforms to (La,Mg) 5 Ni 19 phase at 900 °C, followed by the transformation of 2H-type (La,Mg) 2 Ni 7 phase to (La,Mg) 5 Ni 19 phase which is completed at 950 °C, producing the alloy with (La,Mg) 5 Ni 19 single phase. The (La,Mg) 5 Ni 19 single-phase alloy possesses good structural stability and strong resistance against pulverization and corrosion/oxidation during repeated charge/discharge cycling, achieving a cycle life of above 400 cycles, nearly three times that of the as-cast alloy. Meanwhile, the (La,Mg) 5 Ni 19 -phase alloy electrode exhibits outstanding kinetics performance with a high rate dischargeability of 62.4% at 1500 mA g −1 compared with 51.2% of the as-cast alloy. The (La,Mg) 5 Ni 19 single-phase alloy is considered a promising potential electrode material for high-power and long-lifetime Ni/MH batteries. [ABSTRACT FROM AUTHOR]

The melt-spun alloys of La–Mg–Ni–Co–Al-based AB 2 -type La 0.8− x Ce 0.2 Y x MgNi 3.4 Co 0.4 Al 0.1 ( x = 0, 0.05, 0.1, 0.15, 0.2) were prepared in this work. The influences of Y content and spinning rate on structures and electrochemical hydrogen storage properties of the alloys were studied systematically. The measurement made by XRD and SEM reveal that the experimental samples contain LaMgNi 4 as principal phase (∼80 wt.%) and LaNi 5 as secondary phase. The variations of Y content and spinning rate cause an obvious variation of the phase abundance of the alloys without changing the phase composition. Namely, the fraction of LaMgNi 4 phase will increase and the fraction of LaNi 5 phase decrease with Y content and spinning rate growing. Furthermore, the displacement of La by Y and melt spinning result in the alloy grains clearly refined. The electrochemical tests show that the displacement of La by Y and melt spinning remarkably ameliorate the discharging potential performances of the as-spun alloys. The discharge capacity of the as-spun (15 m/s) alloys decreases from 377.6 to 357.2 mAh/g with Y content increasing from 0 to 0.2. However, it rises firstly and declines later with spinning rate increasing. The as-spun alloys exhibit admirable activation capability as reaching the maximum discharge capacity with only one cycling. The electrochemical kinetics of the alloys, involving the charge transfer rate, hydrogen diffusion coefficient ( D ), high rate discharge property (HRD) and limiting current density ( I L ), augment firstly and decline later with the Y content and spinning rate increasing. The Y replacement for La and melt-spinning could greatly improve the as-spun alloys with their cycle stabilities, and the positive influence of Y replacing La and melt-spinning on the cycling stability is attributed to the enhancement of the anti-pulverization, anti-corrosion, and anti-oxidation abilities. The capacity retaining rate of 150th cycle ( S 150 ) of the as-spun (15 m/s) alloys grows from 76.5% to 92.4% with x increasing from 0 to 0.2. [ABSTRACT FROM AUTHOR]

The focus of this work is on exploring the effect of cooling rate on the microstructure and hardness of the Mg 80 Ni 10 Gd 10 alloy which is known for its potential hydrogen storage capability. A series of chart is displayed to compare the mechanical and transport properties with commercial Mg-based alloys, Mg-based metallic glasses and low density high entropy alloys. We outline the interest of this alloy composition for the development of new light metal high entropy alloy with multifunctionality. [ABSTRACT FROM AUTHOR]

The effect of vanadium doping on the kinetics and thermodynamics of hydrogenation–dehydrogenation process of Mg 2 Ni have been investigated. Two samples, Mg 2 Ni-5 wt.% V and Mg 2 Ni-10 wt.% vanadium were prepared by ball milling process. The hydrogenation–dehydrogenation kinetics along with pressure–composition isotherm (PCT) of vanadium doped and pure-Mg 2 Ni samples were studied. The sample Mg 2 Ni-5 wt.% V has shown improved hydrogenation–dehydrogenation kinetics with extended plateau region as compared to pure-Mg 2 Ni under similar conditions. Marginal changes in the enthalpies of hydrogenation–dehydrogenation have been observed on vanadium addition. The improved properties could be beneficial for the viable commercial applications of Mg 2 Ni as a negative electrode of metal-hydride batteries and as a material for hydrogen storage. [ABSTRACT FROM AUTHOR]

First-principles calculations have been used to study the hydrogen adsorption and diffusion in both hexagonal Mg 2 Ni surface and bulk Mg 2 Ni, and the hydrogen diffusion rate in bulk Mg 2 Ni is evaluated. The calculation shows that the adsorption energies on Mg 2 Ni (100) surface are much higher than in bulk Mg 2 Ni. For hydrogen diffusing from Mg 2 Ni (100) surface to subsurface, three diffusion pathways have been studied, and the lowest energy barrier is found to be 0.64 eV. To study the hydrogen atom diffusion in bulk Mg 2 Ni, nine possible diffusion paths have been considered. The results show hydrogen diffusion from Ni Ni bridge sites to the most nearby Mg Ni bridges site is energetically more favorable than the other paths. The energy barrier of this process is 0.34eV, which is close to experimental data of 0.28 ± 0.04 eV. The temperature dependence of the jump rates has been investigated in some details using harmonic transition state theory and semi-classically corrected harmonic transition state theory. The calculated diffusion constant is in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

On the basis of catalytic actions of transition metals and rare earth metals on Mg-based hydrogen storage alloys and aiming at alleviating the adverse influence of Mg oxidation, Mg-Ni-Ce alloys with different Ni and Ce contents were prepared by near equilibrium solidification. A new 18R-type long-period stacking ordered phase (LPSO) was formed coherently with Mg, Ni-substituted Mg 12 Ce and Mg 2 Ni in Mg-rich Mg-Ni-Ce ternary alloys. Distinct from the reported LPSO structures in other Mg-based alloys, in which the LPSO structures were fundamentally long period stacking variants of hexagonal close-packed structure of Mg, the LPSO structure found in the present work was a variant of Mg 12 Ce. Nanocrystalline alloys were obtained by high-energy ball milling the as-cast alloys. Nanocrystals of Mg, Mg 2 Ni and Mg 12 Ce with grain size in the range of 3–5 nm were observed in ball milled samples. The activation performance, isothermal hydrogenation behavior and anti-oxidation properties of the ball milled samples were systematically investigated and corresponding mechanisms were discussed based on detailed microstructural characteristics. CeH 2.73 was formed after hydrogenation and spontaneously transformed into CeO 2 during air exposure. The anti-oxidation properties of Mg-based hydrogen storage alloy were substantially improved with the addition of Ce by forming CeH 2.73 /CeO 2 composite. [ABSTRACT FROM AUTHOR]

Rechargeable ion batteries based on the intercalation of multivalent ions are attractive due to their high energy density and structural stability. Surface of cathode materials plays an important role for the electrochemical performance of the rechargeable ion batteries. In this work we calculated surface energies of (001), (110) and (111) facets with different terminations in spinel MgMn 2 O 4 and MgNi 0.5 Mn 1.5 O 4 cathodes. Results showed clearly that atomic reconstruction occurred due to surface relaxation. The surface energies for the (001), (110) and (111) surfaces of the MgNi 0.5 Mn 1.5 O 4 were 0.08, 0.13 and 0.11 J/m 2 , respectively, whereas those of the Ni-doped MgMn 2 O 4 showed less dependence on the surface structures. [ABSTRACT FROM AUTHOR]

This work presents the characterization and contribution of neutron and gamma components to the absorbed dose in a zero power nuclear reactor. A dosimetric method based on Fricke gel was implemented to evaluate the separation between dose components in the mixed field. The validation of this proposed method was performed by means of direct measurements of neutron flux in different positions using Au and Mg-Ni activation foils. Monte Carlo simulations were conversely performed using the MCNP main code with a dedicated subroutine to incorporate the exact complete geometry of the nuclear reactor facility. Once nuclear fuel elements were defined, the simulations computed the different contributions to the absorbed dose in specific positions inside the core. Thermal/epithermal contributions of absorbed dose were assessed by means of Fricke gel dosimetry using different isotopic compositions aimed at modifying the sensitivity of the dosimeter for specific dose components. Clear distinctions between gamma and neutron capture dose were obtained. Both Monte Carlo simulations and experimental results provided reliable estimations about neutron flux rate as well as dose rate during the reactor operation. Simulations and experimental results are in good agreement in every positions measured and simulated in the core. [ABSTRACT FROM AUTHOR]

Ball-milled Mg-Ni powder has been cold-compacted and subsequently processed by severe shear deformation under high-pressure torsion. The effect of high pressure torsion on morphology and microstructure of the disk-shape samples has been characterized by scanning electron microscopy and X-ray diffraction, respectively. In order to achieve partially hydrogenated and dehydrogenated states of deformed samples, the hydrogen uptake or release was interrupted at 25%, 50% and 75% hydrogen contents in a Sieverts' type apparatus. In this paper we present the characterization of the microstructure during a full absorption-desorption cycle of the nanocrystalline Mg–Ni alloy. [ABSTRACT FROM AUTHOR]

Mg and its alloys are very attractive for hydrogen generation via hydrolysis because their hydrolysis reaction occurs in neutral seawater instead of the alkaline water necessary for the hydrolysis of Al and its alloys. The hydrogen generation rate from the hydrolysis of Mg is proportional to the corrosion rate of Mg to Mg 2+ . Mg powder, though producing a high reaction rate in the hydrolysis, causes explosive dangers when in contact with air or moisture. However, Bulk Mg such as plate and sheet exhibits an extremely low hydrogen generation rate. To overcome the disadvantage, Mg–Ni alloys were designed to form an electrochemically noble phase (Mg 2 Ni) along grain boundaries (G.B.), and hence to significantly accelerate the hydrolysis rate by causing a galvanic and intergranular corrosion between the noble Mg 2 Ni and Mg matrix. In particular, the Mg–2.7Ni alloy among the designed Mg–Ni alloys exhibits the highest hydrogen generation rate (23.8 ml min −1 g −1 ) that is 1300 times faster than that of pure Mg. Furthermore, it was demonstrated that PEMFC stably produced 7.3 W for 20 min when it is operated by the hydrogen generated from the hydrolysis of 2 g Mg–2.7Ni alloy, that is, equivalent to 1.215 KWh/Kg-Mg–2.7Ni alloy. [ABSTRACT FROM AUTHOR]

Microstructure and texture evolutions during tensile and compression deformation of an as-extruded Mg–11Gd–4.5Y–1Nd–1.5Zn–0.5Zr (wt%) alloy have been investigated using in-situ synchrotron radiation diffraction and subsequent microscopy. The alloy consists of 〈 10 1 ¯ 0 〉 fiber texture, { 11 2 ¯ 0 }[0001] and { 11 2 ¯ 0 }〈 10 1 ¯ 0 〉 texture components prior to deformation. The texture evolves from [0001] to 〈 10 1 ¯ 0 〉 in tension, but from 〈 10 1 ¯ 0 〉 to [0001] in compression. The evolution of texture is attributed to the activity of the tensile twinning and non-basal 〈 a 〉 type slip. The tendency of texture evolution depends on the favorable texture component for the activation of above deformation modes. The grain refinement, Mg 5 (Gd, Y, Nd) and LPSO phases, and the texture contribute to the improvement in strength. [ABSTRACT FROM AUTHOR]

With the aim to decrease temperature and improve the kinetics of decomposition of the MgH stoichiometric hydride, we study the possibility of its complex alloying with 3 at.% Al + 3 at.% Ni + 7 at.% Ti performed with the help of mechanochemical synthesis. It is shown that, as a result of the addition of Al, Ni, and Ti to magnesium, the thermal resistance of the MgH hydride phase of the mechanical alloy obtained by the reactive mechanical alloying decreases and, hence, the temperature of the onset of hydrogen desorption decreases from 320°C (for MgH without Al, Ni, and Ti) to 280°C. We do not detect any decrease in the equilibrium temperature of the onset of hydrogen desorption under its constant pressure of 1 bar in a reactor, which may serve as an indication of the loss of thermodynamic stability of MgH as a result of mechanical alloying. It is shown that the kinetics of hydrogen desorption of the MgH phase of the mechanical alloy is mainly improved by alloying with Ni and Ti, whereas the contribution of Al is negligible. [ABSTRACT FROM AUTHOR]

We present a brief survey of works on the structure and hydrogen-sorption properties of some R-Mg-Ni alloys. It is shown that R-Mg-Ni alloys can be regarded as promising electrode materials for Ni/MH rechargeable batteries. Main attention is focused on the analysis of the properties of RMgNi alloys. The relationship between the composition of these alloys, character of isotherms, and electrochemical characteristics is discussed. [ABSTRACT FROM AUTHOR]

The effects of the Ni addition on the microstructures of Mg-2Gd-xNi (at.%, x = 0, 0.25, 0.5 and 1) alloys were systematically investigated. A series of two-phase Mg-Gd-Ni alloys consisting of long period stacking ordered (LPSO) phase and α-Mg were obtained. The LPSO phase presented block-like shape and was distributed between α-Mg dendrite arms. Its volume fraction was found to be proportional to the Ni content, ranging from 0 to ∼40% with the Ni content increasing from 0 to 1 at.%. After a heat treatment at 500 °C for 100 h, the LPSO phase experienced a structure transformation from 18R to 14H but was hardly dissolved into the α-Mg matrix, which evidenced a high thermal stability. The mechanism for the effects of the Ni addition on the formation of the LPSO phase was discussed. [ABSTRACT FROM AUTHOR]

Fast capacity degradation is a significant drawback hindering La–Mg–Ni-based alloys from wide application as anode electrode materials of nickel metal hydride batteries. Herein, the effect of Pr element on the phase structure and cycling stability of La 0.8− x Pr x Mg 0.2 Ni 3.4 Al 0.1 ( x = 0, 0.1, 0.2 and 0.3) alloys is investigated. All the alloys contain (La,Mg) 2 Ni 7 and (La,Mg) 5 Ni 19 main phases as well as LaNi 5 minor phase. It is found that Pr tends to form [AB 5 ] subunits more than [A 2 B 4 ] subunits, thus increasing the content of (La,Mg) 5 Ni 19 phase with higher [AB 5 ]/[A 2 B 4 ] ratio in sacrifice of (La,Mg) 2 Ni 7 phase. The increased (La,Mg) 5 Ni 19 phase network with good structural stability increases the anti-pulverization and anti-amorphization resistance of the alloys. After 100 charge/discharge cycles, part of the superlattice phases in La 0.6 Mg 0.2 Ni 3.4 Al 0.1 alloy decomposes into amorphous phase and LaNi 5 phase, leading to the decrease in superlattce phase abundance; while little amorphization is observed for La 0.6 Pr 0.2 Mg 0.2 Ni 3.4 Al 0.1 alloy and its phase contents remain almost unchanged. Correspondingly La 0.6 Pr 0.2 Mg 0.2 Ni 3.4 Al 0.1 alloy electrode has a slighter oxidation degree after 100 cycles in alkaline electrolyte and exhibits good electrochemical cycling stability with a discharge capacity of 340 mAh g −1 and a cycling stability of 90.7% at the 100 th cycle. [ABSTRACT FROM AUTHOR]

Mg 0.6 Ni 0.4 O hollow nanofibers were prepared by electrospinning technique and subsequent thermal treatment. The as-prepared Mg 0.6 Ni 0.4 O hollow nanofibers were used as an additive to prepare sulfur/Mg 0.6 Ni 0.4 O composite cathodes. Their crystalline phase and morphologies were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The SEM observation revealed that the sulfur morphology was changed by the Mg 0.6 Ni 0.4 O addition, from smooth to rough agglomerated particles. The initial discharge profiles and cyclic voltammetry tests demonstrated the hollow nanofibers of Mg 0.6 Ni 0.4 O can not only contribute to reducing the dissolution of polysulfides into electrolytes, but also improve the electrochemical reaction kinetics during charge–discharge process. In addition, the hollow nanofibers of Mg 0.6 Ni 0.4 O ensure short diffusion distance for Li + on interaction in charge–discharge cycles. The effect of the Mg 0.6 Ni 0.4 O hollow nanofibers heat treatment temperature on the S/Mg 0.6 Ni 0.4 O cycling performance was also investigated. As a result, the cathode with Mg 0.6 Ni 0.4 O hollow nanofibers calcined at 700 °C exhibited 910 mAh g −1 of initial capacity and keeping the remaining capacity of 554 mAh g −1 over 20 cycles. [ABSTRACT FROM AUTHOR]

In this present study, fine elemental nickel particles were incorporated into commercially pure magnesium matrix using blend-press-sinter powder metallurgy technique avoiding ball milling. The nickel reinforcement particles dispersion was reasonably uniform with good matrix-reinforcement interfacial integrity. The small volume fraction of elemental nickel particle reinforcement refined grain morphology and significantly improved the hardness and tensile strength of the magnesium matrix without affecting the yield strength. However, ductility was adversely affected. The reinforcement changed fracture mode of magnesium matrix from pseudo-ductile to brittle mode dominated by nickel particle fracture. [ABSTRACT FROM AUTHOR]

Our earlier study Yartys et al. (2015) showed that at high hydrogen pressures, hexagonal MgNi 2 undergoes a hydrogen assisted phase transition into the orthorhombic MoSi 2 -type structure. Here we report on a combined high resolution synchrotron and neutron diffraction investigation of the crystal structure of MgNi 2 D 3 , and ab initio calculation of its electronic structure that revealed the nature of the metal–hydrogen bonding. The diffraction data (293 and 1.8 K) are well described with a Cmca unit cell with H atoms filling the deformed octahedra Mg 4 Ni 2 and the positions within the buckled nets –Ni–H–Ni–H– penetrating through the structure. DFT and phonon calculations showed that the Cmca structure of MgNi 2 D 3 is the most stable, both from the electronic structure and the lattice dynamical arguments. The Bader charge analysis indicates an electronic transfer from Mg (−1.59e − ) to Ni (+0.21e − ), H1 (+0.55e − ) and H2 (+0.31e − ). The phonon dispersion curves of MgNi 2 H 3 show positive frequencies, indicating that the structure is mechanically stable. The calculated gross heat of formation for the Cmca phase of MgNi 2 H 3 is −37.3 kJ/mol-H 2 , which makes it more stable by 3 kJ/mol-H 2 than the prototype structures tested in Yartys et al. (2015). The stability of the Cmca crystal structure of MgNi 2 H 3 is enhanced by the formation of the directional Ni–H covalent bonds supplemented by the electron transfer from Mg to both Ni and H. The heat capacity as a function of temperature is obtained by phonon calculation in the quasi-harmonic approximation. [ABSTRACT FROM AUTHOR]

Herein, a way to generate mono- and bi-metallic copper and/or nickel nanoparticles by the direct reduction of Mg(Ni)CuAl-layered double hydroxide (LDH) precursors is reported. Cu and Ni with various molar ratios (0:1, 1:4, 1:1, 4:1 and 1:0) were substituted in the MgAl brucite-like sheets during synthesis. Studies on the evolution of LDH structures under H 2 reduction of as-synthesized samples at different temperatures (30–550 °C) followed by in situ XRD evidenced the high reducibility of copper cations. The metallic phases generated during reduction of LDHs were dependent on the chemical composition of the sample. The corresponding TEM images display small, very well-dispersed metallic nanoparticles. A positive effect of nickel cations on the dispersion and thermostability of metallic copper phase was also observed, especially with increasing Ni content. For instance, metallic particle sizes of 6.5 and 3.3 nm were calculated for the NPs generated by reduction at 500 °C of MgCuAl and MgNiCuAl (Ni:Cu = 1:1), respectively. Outstanding results for the hydrogenation of cinnamaldehyde in liquid phase were obtained on Cu-rich materials that are able to generate metallic active sites even after reduction at temperature as low as 150 °C. Due to the difficulty to detect the metallic phases generated after reduction at 150 °C by usual techniques (e.g., TPR, in situ XRD and TEM), Cu 0 was put in evidence by the dissociative chemisorption of N 2 O. [ABSTRACT FROM AUTHOR]

This work focuses on microstructure and electrochemical hydrogen storage properties of La-doped Mg 2 Ni alloys. The alloys with nominal compositions of Mg 2 Ni 1 − x La x ( x = 0, 0.1, 0.3, 0.5) were prepared via metallurgical smelting and melt-spun on a rotating copper wheel. The scanning electron microscope, X-ray diffraction, differential scanning calorimetry and transition electron microscope, galvanostatic charging/discharging and other electrochemical measurements were employed to investigate. The results show that the increasing of La content and melt-spinning speed favors the formation of Mg–Ni–La amorphous/nanocrystalline alloys. It is found that the melt-spun ribbons display increased discharge capacities and superior cycle stabilities compared to the as-cast alloys with and without La. The potentiodynamic polarization results indicate that melt-spun La-doped Mg 2 Ni ribbons possess more positive corrosion potential E corr and exhibit relatively high corrosion resistance against the alkaline solution. The mechanism for electrochemical hydrogenation/dehydrogenation has been proposed based on the effect of microstructures on the mass/charge transfer process for electrode electrochemical reaction. [ABSTRACT FROM AUTHOR]

In this contribution we have studied magnetisation of Mg/Ni multilayers (MLs) to characterise the alloing effect near interfaces. The layered structure was characterised by standard X-ray diffraction. The MLs were deposited by UHV magnetron sputtering onto naturally oxidised Si(100) substrates. Results showed, that due to Mg-Ni alloy formation near interfaces the magnetizations of the MLs were strongly reduced. Effective "dead" Ni layer thickness was estimated as 1.2 nm at room temperature (RT). Furthermore, hydrogen absorption kinetics at a pressure of about 1000 mbar was studied at RT in Pd covered Mg/Ni MLs using four-point resistivity measurements. Results showed that the fastest initial rise in resistance in the first 9 s was observed for dNi = 3:5 nm. [ABSTRACT FROM AUTHOR]

Multiphase La MgNi alloys are synthesized by induction melting. The crystalline structures of all phases in the alloys are determined with X-ray diffraction. The La MgNi electrodes with nickel as a binder and electrical conductor are prepared and their charge-discharge characteristics are studied. The influence of homogenizing annealing and mechanical grinding on the discharge capacity and cyclic stability of the metal hydride (MH) electrodes is shown. The best electrochemical parameters are observed for powdered as-cast alloys. [ABSTRACT FROM AUTHOR]

The present study investigated the removal of calcium from sulfate solutions containing magnesium and nickel using aqueous two phase systems (ATPS) at room temperature. In an attempt to evaluate the application range of this separation method, batch scale tests (bottom/top phase weight = 1) were carried out using synthetic test solutions at two concentration levels (low and high). The test solution of high concentration used as the bottom phase consisted of a solution containing [Ca] = 0.44 g·L − 1 , [Mg] = 1.42 g·L − 1 and [Ni] = 80.0 g·L − 1 , whose concentration level is similar to those typically found in high pressure acid leach liquors. The test solution of low concentration used as the bottom phase consisted of a solution of sodium tartrate in which a given volume of the solution of high concentration was added, resulting in a dilution of approximately 80 fold. The performance of some cationic extractants (Cyanex 272, 1N2N and PAN) at changing concentrations and the effect of the pH of the aqueous system (1, 6 and 11) were investigated in the dilute condition. This study found that, when ATPS operated in at least 3 contact stages, it proved to be a highly efficient and selective method to separate calcium from magnesium and nickel, using no extractant and at low pH values (around 1–2) for both dilute and concentrated solutions. The extraction of nickel depends on the pH and the type/concentration of extractant, while the extraction of magnesium was not affected by the studied operating variables. [ABSTRACT FROM AUTHOR]

Mg 2 Ni intermetallics are processed using three different routes to produce three different microstructural features: annealing at high temperature for coarse grain formation, severe plastic deformation through high-pressure torsion (HPT) for nanograin formation, and HPT processing followed by annealing for the introduction of stacking faults. It is found that both grain boundaries and stacking faults are significantly effective to activate the Mg 2 Ni intermetallics for hydrogen storage at 423 K (150 °C). The hydrogenation kinetics is also considerably enhanced by the introduction of large fractions of grain boundaries and stacking faults while the hydrogenation thermodynamics remains unchanged. This study shows that, similar to grain boundaries and cracks, stacking faults can act as quick pathways for the transportation of hydrogen in the hydrogen storage materials. [ABSTRACT FROM AUTHOR]

Structural changes in multiphase La 0.8 Mg 0.2 Ni 3.5 alloy during hydrogen absorption/desorption cycles were studied in this work. XRD and TEM characterizations confirm that transformation from crystallinity to amorphous viz. hydrogen induced amorphization (HIA) of both (La,Mg) 2 Ni 7 and (La,Mg) 5 Ni 19 phases has occurred after 100 repeated cycles. In addition, P-C-T plateau is found to become slope and narrow, indicating that degradation of the hydrogen storage capacity comes with partial amorphization in the cyclic process. In order to comprehend the mechanism of HIA in the La–Mg–Ni compounds, hydrogenation processes from low to high hydrogen pressure at various temperatures were adopted and the structural evolution was investigated. Two kinds of crystalline La–Mg–Ni based hydrides are found to present successively, but transformation to amorphous subsequently takes place with the hydrogen concentration increased. Structural changes of the alloy are almost the same and no disproportion of the La–Mg–Ni phases is detected when hydrogenated at both the room and elevated temperatures. However, amorphization of the La–Mg–Ni phases becomes more severe as the charging temperature decreased. HIA of the La–Mg–Ni phases is thus considered to be non-thermally activated, which is launched directly by distortion of the lattice with hydrogen concentration increased. Furthermore, it is established that HIA of (La,Mg) 2 Ni 7 phase is more liable to occur but hard to recrystallize compared with that of (La,Mg) 5 Ni 19 compound. The structural stability towards HIA of various compounds in the multiphase La 0.8 Mg 0.2 Ni 3.5 alloy is then believed to be as follows: LaNi 5 > (La,Mg) 5 Ni 19 > (La,Mg) 2 Ni 7 . [ABSTRACT FROM AUTHOR]

Synthesizing 2Mg–9Ni–Y catalyst was investigated by mechanical alloying of Mg, Ni, and Y elemental powder mixture and subsequent heat treatment. Accordingly, effects of milling time, process control agent (PCA) type (stearic acid and toluene), and heat treatment time on the powder microstructure, phase composition, and powder morphology were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and laser particle size analyzer (LPSA). Results showed that particle size of the samples prepared by toluene were smaller than those of the samples prepared by stearic acid. Also, it was found that the ternary Mg 2 Ni 9 Y compound was not formed by mechanical milling alone. This intermetallic compound was partially formed after the heat treatment of ball milled powders for 8 h at 800 °C. Effect of toluene on powder particle was higher than that of stearic acid. According to XRD patterns, it seems that the amount of formed Mg 2 Ni 9 Y in the samples which were ball milled for 15 h using stearic acid and subsequently heat treated at 800 °C for 8 h was more than the powders that used toluene in the same conditions. Furthermore, results of hydrogen desorption tests of MgH 2 doped with 10 wt% sample prepared by toluene after the desorption time of 2500 s at 300 °C showed that it desorbed 1 wt% more hydrogen than MgH 2 doped with 10 wt% sample prepared by acid stearic. [ABSTRACT FROM AUTHOR]

Mg0:95Ni0:05Ti0:98Zr0:02O3 ceramics was prepared via conventional solid-state mixed-oxide route. The phase, microstructure and microwave dielectric properties of the sintered samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and a vector network analyzer. The microstructure comprised of circular and elongated plate-like grains. The semi quantitative analysis (EDS) of the circular and elongated grains revealed the existence of Mg0:95Ni0:05T2O5 as a secondary phase along with the parent Mg0:95Ni0:05Ti0:98Zr0:02O3 phase, which was consistent with the XRD findings. In the present study, εr ~17.1, Qufo~195855 ± 2550 GHz and τf ~ -46 ppm/K was achieved for the synthesized Mg0:95Ni0:05Ti0:98Zr0:02O3 ceramics sintered at 1325 °C for 4 h. [ABSTRACT FROM AUTHOR]

In this study, phase transformation and electrochemical properties of super-stacking La 0.70 Mg 0.30 Ni 3.3 alloys obtained by annealing the induction melting samples were systematically studied. XRD and Rietveld refinement results show that the as-cast alloy consists of LaNi 5 , La 4 MgNi 19 , La 3 MgNi 14 , La 2 MgNi 9 and LaMgNi 4 phases, and the gradual rising annealing temperature effectively increases La 3 MgNi 14 phase abundance via phase transformations. At 1123 K, LaNi 5 and LaMgNi 4 are eliminated, transforming to super-stacking phases. Further increase the temperature to 1173 K, partial La 4 MgNi 19 and La 2 MgNi 9 phases transform to La 3 MgNi 14 phase and La 4 MgNi 19 phase is depleted completely at 1223 K, resulting in La 3 MgNi 1 4 as the main phase and La 2 MgNi 9 as the surplus phase. Electrochemical results show that increasing abundance of La 3 MgNi 14 phase makes a significant improvement on the discharge capacity of the alloy electrode, enhancing from 370 to 401 mAh g −1 . And ascribing to the formation of La 4 MgNi 19 phase, the high rate dischargeability ( HRD 1800 ) of the alloy electrode is ameliorated by 10%. Based on the phase transformation, purposeful controlling the alloy phase composition by annealing could efficiently improve the electrochemical properties of the super-stacking metal hydride alloys. [ABSTRACT FROM AUTHOR]

Superior catalytic effects of multi-walled carbon nanotube supported titania synthesized by the sol–gel method on hydrogen storage of a Mg–Ni alloy were investigated. The excellent hydrogen storage properties were obtained: absorbed 5.60 wt% H2 within 60 s at 373 K and released 6.08 wt% H2 within 600 s at 553 K. [ABSTRACT FROM AUTHOR]

The reversible hydrogen storage capacity and structural features against cycle numbers of SmMgNi 4 compound prepared by the combination of ball-milling with sintering are investigated systematically in this work. It is found that the structure of SmMgNi 4 with an exchange between Sm and Mg by 13% has a good stability without occurrence of hydrogen-induced amorphization and phase decomposition upon multiple cycling. However, about 16% capacity loss is still observed at the early stages of hydrogen ab-/desorption cycles at 298 K. The increase in lattice strain caused by the accumulation of dislocations is believed to be responsible for the capacity degradation of SmMgNi 4 . [ABSTRACT FROM AUTHOR]