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The present investigation aims to synthesize a novel (AlCuCoFeMnNi)3O4 type high entropy spinel oxide through the sol‐gel and investigate the effect of different carbon‐based additives on charge storage performance. The formation of the inverse spinel phase of [B(AB)O4] type inverse spinel phase was confirmed through the detailed x‐ray diffraction analysis of the synthesized sample. The synthesized spinel phase was indexed with the space group of Fd−3m and has a lattice parameter of 8.2697 Å. The synthesized high entropy oxide (HEO) phase Ni, Co, and Fe coexists in +2 and +3 states. At the same time, Cu in +2 state, Al in +3 state, and Mn in +3 and +4 states confirmed through x‐ray photoelectron spectroscopy. The electrochemical charge storage performance of synthesized HEO was measured through the three‐electrode setup in 2 M KOH aqueous electrolyte solution in two different potential windows, such as −0.2 to 0.4 V and 0.0 to 0.5 V. Different carbon‐based conducting materials such as acetylene black, reduced graphene oxide (RGO), and carbon particles obtained from 10‐hour ball‐milling of used dry cell carbon electrode (CP). The charge storage mechanism changes from electrochemical double layer capacitance to pseudocapacitive type as the potential window varies from −0.2 to 0.4 to 0 to 0.5 V. The value of specific capacitance for an electrode made of HEO with acetylene black, RGO, and CP was found to be 32.67, 7.50, and 4.58 F/g and 30.68, 16.33, and 9.05 F/g in the potential window of −0.2 to 0.4 V and 0 to 0.5 V at a scan rate of 5 mV/s, respectively. The cyclic performance of the developed three electrodes was measured at a scan rate of 100 mV/s for 1000 cycles, and it was found to be 94%, 98%, and 99% for electrodes made of HEO with acetylene black, RGO, and CP, respectively. [ABSTRACT FROM AUTHOR]

Soft magnetic high entropy alloys (HEAs) have great potential to be used as industrial material because of their good magnetic properties and balanced mechanical, electrical, and corrosion resistance properties. To further optimize high saturation magnetization (Ms) along with other functional properties, it is critical to understand the effect of Mn, Cu, and Al on the magnetic properties and phase evolution of FeCoNi-based magnetic HEAs. In the present study, a combinatorial approach is adopted to optimize the magnetic properties of Co35 Fe10Ni30Ti20M5 (M = Mn, Cu, and Al) HEA through the variation of a single alloying element and its effects on the phase evolution, microstructure, and magnetic properties. Co35Fe10Ni30Ti20Mn5, Co35Fe10Ni30Ti20Cu5, and Co35 Fe10Ni30Ti20Al5 high entropy alloys were synthesized through mechanical alloying, and the as-synthesized HEAs were comprised of fcc and bcc solid solution phases. The as-synthesized Co35Fe10Ni30Ti20Mn5, Co35Fe10Ni30Ti20Cu5, and Co35Fe10Ni30Ti20Al5 HEAs have the value of saturation magnetization (Ms)- 81, 85 & 79 emu/g and coercivity (Hc)- 18, 28 & 27 Oe respectively. The phase stability of the developed alloys was also investigated through vacuum annealing at 700°C for 2 h duration. After vacuum annealing, both the Ms and Hc increased to 90 emu/g & 37 Oe, 105 emu/g & 43 Oe, and 104 emu/g & 46 Oe, respectively, for Mn, Cu, and Al – containing Co35Fe10Ni30Ti20M5 (M = Mn, Cu, and Al) HEAs. The present study provides a detailed insight into how the variation of a single alloying element and the annealing temperature significantly affect the magnetic properties of CoFeNiTi-based HEA. [ABSTRACT FROM AUTHOR]

The aim of the present study is to investigate the effect of synthesis routes on phase evolution, microstructure, change in ionic state and their co‐relation with electrochemical charge storage, and magnetic properties of novel (CuNiFeMnCo)3O4 high entropy spinel oxide (HESO). We successfully synthesized novel (CuNiFeMnCo)3O4 HESO through two different synthesis methods, that is, sol‐gel and reverse coprecipitation methods abbreviated as SA‐1 and SA‐2, respectively. The XRD analysis for both samples reveals the formation of inverse spinel phase (space group Fd‐3m) with the lattice constant of 8.3602 and 8.2502 Å for SA‐1 and SA‐2, respectively. The sample synthesized through the sol‐gel method possessed porous morphology, whereas the sample synthesized through the reverse coprecipitation method had spherical particles. The x‐ray photoelectron spectroscopy confirmed the presence of +2 and +3 ionic states for Fe, Ni, and Co, while Cu has a + 2 state and Mn exist in +3 and +4 states for both the synthesized samples. The ionic states of all cations remain invariant irrespective of the synthesis methods. However, the concentration of oxygen vacancy is significantly different for samples synthesized through different routes. Both the HESO electrodes show the electrochemical double‐layer capacitive type behavior in 2 M KOH electrolytic solution. The value of maximum specific capacitance is 38.46 and 34.24 F/g at a scan rate of 5 mV/s for SA‐1 and SA‐2, respectively. Moreover, the electrodes have capacity retention of 90 and 99% for 1000 cycles at a scan rate of 50 mV/s for SA‐1 and SA‐2, respectively. The magnetic property of the synthesized HESO samples was also investigated, and the found values of magnetization and coercivity are 1.79 emu/g and 54.9 Oe and 8.5 emu/g and 67.69 Oe for SA‐1 and SA‐2, respectively. [ABSTRACT FROM AUTHOR]

The novel (CuNiZnAlFe)3O4 type nanocrystalline High Entropy Oxide (HEO) was synthesized through the sol‐gel method with combustion at 350°C for 1 h duration. The XRD analysis reveals the formation of inverse spinel [B(AB)O4] type phase indexed with the space group of Fd‐3 m confirmed through the Rietveld Refinement of the XRD data. The lattice constant for the synthesized spinel phase was found to be 8.2453°A. The Scanning Electron Microscope of the synthesized HEO confirms the flakes‐like morphology with porous microstructure. The Energy Dispersive X‐ray (EDX) analysis and elemental mapping confirm the homogeneous distribution of the cations over the selected region. It was found that Fe and Ni are in the +3 and +2 states, other cations, Cu and Zn, are in the +2 states, and Al is in the +3 confirmed through the X‐ray photoelectron Spectroscopy. The electrochemical performance was studied in three electrodes in a 2 M KOH aqueous electrolyte. The specific capacitance value was 2.02, 1.58, 1.24, 1.06, 0.87, 0.71, and 0.65 F/g at scan rates of 5, 10, 20, 30, 50, 80, and 100 mV/s, respectively. The low value of specific capacitance was observed due to the stable ionic structure of the inverse spinel phase. The magnetization behavior of the sample is also investigated. The M‐H loop of the (CuNiZnAlFe)3O4 HEO sample exhibits a ferrimagnetic nature. [ABSTRACT FROM AUTHOR]

A mixture of spinel and rock-salt phase was synthesized for (Cu-Zn-Ni-Mg-Fe)O HEO High Entropy Oxide (HEO) through the modified solid-state synthesis and studied for the dielectric properties. Three different (Cu-Zn-Ni-Mg-Fe)O HEO samples were synthesized by the variation of synthesis parameters, i.e., 10 hour (hr) ball-milling followed by sintering at 1050 °C for 20 hr (10BM-HEO-20), 20 hr ball-milling followed by sintering at 1050 °C for 20 hr (20BM-HEO-20) and sintering for 10 hr (20BM-HEO-10) separately. The synthesized samples were studied for the effect of synthesis parameters on phase evolution and their correlation with dielectric properties. The volume phase fraction for the spinel and rock-salt phase changed with the variation of the synthesis parameters. The value of dielectric constant decreased for the sample 10 BM-HEO-20, 20BM-HEO-20 and 20 BM-HEO-10 HEOs due to the synergistic effect of decrease in particle size, volume phase fraction of spinel phase as well as more distorted unit cells of spinel HEO phase. The value of dielectric loss is in decreasing trend for 10BM-HEO-20, 20BM-HEO-20 and 20BM-HEO-10 samples. The value of the dispersion factor for 10BM-HEO-20, 20BM-HEO-20, and 20BM-HEO-10 are found to be 1.839, 2.313, and 2.156, respectively. The present study provides insight the dielectric properties of HEO can be tuned broadly by the change in the synthesis parameters. [ABSTRACT FROM AUTHOR]

• A novel Co 35 Cr 5 Fe 20 Ni 20 Ti 20 HEA was synthesized through MA. • Co 35 Cr 5 Fe 20 Ni 20 Ti 20 HEA exhibits mixture FCC and BCC Phase. • Synthesized Co 35 Cr 5 Fe 20 Ni 20 Ti 20 HEA has low H c. • 200 °C annealed Co 35 Cr 5 Fe 20 Ni 20 Ti 20 HEA has high Ms. • Found Ms for annealed Co 35 Cr 5 Fe 20 Ni 20 Ti 20 HEA is highest for CoCrFeNiTi based HEA. A novel Co 35 Cr 5 Fe 20 Ni 20 Ti 20 high entropy alloy (HEA) is synthesized through mechanical alloying (MA). The synthesized HEA is comprised of mixture of FCC and BCC phases and exhibits soft magnetic properties with M s = 46 emu/g and H c = 15 Oe. After annealing at 200 °C, the value of Ms is increased approximately two times and coercivity remains the same to as synthesized HEA. The found value of Ms (81 emu/g) is the highest value of Ms for the CoCrFeNiTi-based HEA, reported so far. [ABSTRACT FROM AUTHOR]

Highlights • Effect of annealing condition on magnetic properties of TiFeNiCrMn HEA is investigated. • FCC, BCC and a minor sigma phase has been evolved for in synthesized TiFeNiCrCo HEA. • Synthesized HEA was annealed under vacuum and open air at 500 and 700 oC. • Oxide (Mn 2 O 3) and a spinel type (Fe,Ti) 3 O 4 phases are evolved after open air annealing. • Spinel phase formation in HEAs open new area for magnetic properties of HEAs. Graphical abstract (a) Volume fraction of formed phases in different samples (b) Ms. and Hc of samples (1,2,3,4,5 represents the SA-1, SA-2, SA-3, SA-4 and SA-5 respectively. Abstract An equiatomic CrFeMnNiTi high entropy alloy (HEA) was synthesized through mechanical alloying (MA) technique. The synthesized HEA consists of FCC, BCC and a minor σ-phase. In order to investigate the phase evolution and magnetic characteristics, the synthesized HEA was annealed under different conditions (vacuum and open air) at two different temperatures (500 and 700 °C). After vacuum annealing at 500 and 700 °C the volume fraction of FCC and BCC phases are changed. However, after open air annealing, the volume fraction of synthesized phases (FCC and BCC) is altered effectively along with the formation of an oxide (Mn 2 O 3) and a spinel type (Fe,Ti) 3 O 4 phase. The synthesized sample exhibits ferromagnetic characteristic and the value of saturation magnetization (Ms) and coercivity (Hc) are found to be 13.39 emu/g (A-m2/kg) and 162.2Oe (12.9 × 103 A/m) respectively. After annealing in vacuum and open air at 700 °C the value of Ms. is found to be 2.95 and 11.63 emu/g (A-m2/kg) respectively. Open air annealed sample at 500 °C shows better magnetic characteristics with Ms = 32.85 emu/g (A-m2/kg) and Hc = 159.34Oe (12.67 × 103 A/m) as compared to the synthesized and annealed samples. The enhanced value of Ms for open air annealed HEA at 500 °C corresponds to increase in the volume fraction of BCC phase and the formation of Mn 2 O 3 and (Fe,Ti) 3 O 4 spinel phase. The effect of annealing conditions on the phase formation and their correlation with magnetic characteristic are discussed and described in detail. [ABSTRACT FROM AUTHOR]

The report describes the effect of elemental addition (Mn and Co) on the phase evolution and magnetic properties of equiatomic TiFeNiCr based high entropy alloys (HEAs). HEAs were synthesized through mechanical alloying (MA) of constituent elements for different milling duration. XRD analysis confirms that simple solid solution of face cantered cubic structure is formed for all the three selected HEAs. Double FCC and a sigma phase are evolved for TiFeNiCr and TiFeNiCrMn HEAs. However, for TiFeNiCrCo HEA single FCC phase is formed. Synthesized HEAs show soft magnetic characteristics and the value of saturation magnetization increases as the content of magnetic element increases. Moreover, the investigation also describes the effect of annealing on phase evolution and magnetic properties of synthesized HEAs. The value of saturation magnetization altered for annealed TiFeNiCrM (M = Mn, Co) HEAs. [ABSTRACT FROM AUTHOR]

The unfavorable de/re-hydrogenation aspects of high storage capacity material, Mg can be overcome by synthesis of composites with known intermetallic hydrogen storage alloys. In this work, a new additive, ZrFe 2 H x intermetallic hydride, is used to synthesize MgH 2 –ZrFe 2 H x nanocomposite by reactive mechanical milling technique. Also this report describes the comparison of hydrogen sorption behavior of MgH 2 –ZrFe 2 and MgH 2 –ZrFe 2 H x nanocomposites. It is found that the composite containing ZrFe 2 and ZrFe 2 H x leads to decrease in desorption temperature from 410 °C (for MgH 2 ) to 350 and 290 °C respectively. The activation energy for rehydrogenation of composite is found to be ∼61 kJ/mol. This is lowered by 30 kJ/mol compared to the pristine milled MgH 2 (92 kJ/mol). Thus, the results show significant improvement of hydrogenation behavior with the addition of ZrFe 2 H x . Reasons for better catalytic activity achieved by using ZrFe 2 H x have been put forwarded. Based on the present studies it can be suggest that the use of hydride version instead of the parent intermetallic phase for synthesizing the composite with MgH 2 has a distinct advantage in improving the hydrogenation behavior of MgH 2 . [ABSTRACT FROM AUTHOR]

Abstract: The present study deals with the microstructural changes with respect to the addition of Ti and their correlation with hydrogen storage characteristics of (Zr69.5Al7.5Cu12Ni11)100− x Ti x (x =0, 4 and 12) quasicrystalline alloys. The grain size of quasicrystals decreases with addition of Ti. It has been found that the alloy with x =0 absorbed 1.20 wt. %, whereas the alloys with x =4 and 12 absorbed 1.38 wt. % and 1.56 wt. % of hydrogen respectively. Hydrogenation was found to exhibit a significant effect on the structure/microstructure and microhardness behavior of (Zr69.5Al7.5Cu12Ni11)100− x Ti x quasicrystalline alloys. Variation in the microhardness behavior has been discussed based on a structure–property correlation. [Copyright &y& Elsevier]

The aim of the present investigation is to synthesize mixed sodium potassium alanate (K2NaAlH6) and to explore its hydrogen sorption characteristics. K2NaAlH6 is synthesized through ball milling of KH and NaAlH4 in the molar ratio 2:1 under hydrogen pressure of 10 bar. The temperature programmed desorption experiment shows that the synthesized K2NaAlH6 has peak desorption temperature of ∼352°C and reveals appreciable rehydrogenation kinetics under 6 bar hydrogen pressure at 300°C. The investigations are also focused on the catalytic effect of carbon nanostructures (CNS) namely, the graphene sheet (GS) and single wall carbon nanotube (SWCNT) and titanium halides (TiCl3 and TiF3) on K2NaAlH6. In the case of graphene and SWCNT catalyzed K2NaAlH6, the peak desorption temperature gets reduced to ∼347°C and ∼341°C respectively. The catalytic effects of CNS and titanium halide on K2NaAlH6 are also compared in the investigation. Between the two types of catalysts, halides are found to be better than CNS and out of the two halides, TiF3 is found to be the best catalyst for hydrogen sorption in K2NaAlH6. The peak desorption temperature decreases significantly from 352°C to ∼324°C for TiF3 catalyzed K2NaAlH6. Thus, the desorption activation energy reduces drastically from 124.43 kJ/mol (synthesized K2NaAlH6) to 88.05 kJ/mol for TiF3 catalyzed K2NaAlH6. [ABSTRACT FROM AUTHOR]

The effect of different carbon nanostructures specifically carbon nanotubes (CNTs) and carbon nanofibers (CNFs) on the improvement of the de/re-hydrogenation characteristics of a Mg(NH2)2/LiH mixture have been studied. Amongst CNTs and CNFs, the improvement in the hydrogenation properties for the Mg(NH2)2/LiH mixture is higher when CNFs are used as a catalyst. Investigations are also focused on the deployment of two different types of CNF (a) CNF1 (synthesized using a ZrFe2 catalyst) and (b) CNF2 (synthesized using a LaNi5 catalyst). The results show that CNF2 is better. The maximum decomposition temperature for the pristine Mg(NH2)2/LiH mixture is found to be ∼250 °C, which is reduced to ∼180 and ∼150 °C for the sample mixed with 4 wt% of multi-walled carbon nanotubes (MWCNTs) and CNF2 respectively. The activation energy for the dehydrogenation reaction is found to be 74 and 68 kJ mol−1 for the samples mixed with MWCNT and CNF2 respectively, whereas the activation energy for the dehydrogenation reaction of the pristine Mg(NH2)2/LiH mixture is 97 kJ mol−1. The catalytic activity and the de/re-hydrogenation characteristics of the Mg(NH2)2/LiH mixture mixed with different carbon nanostructures are described and discussed. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, we have investigated the combined effect of different transition metals such as Ti, Fe and Ni on the de/rehydrogenation characteristics of nano MgH2. Mechanical milling of MgH2 with 5 wt% each of Ti, Fe and Ni for 24 h at 12 atm of H2 pressure lead to the formation of nano MgH2-Ti5Fe5Ni5. The decomposition temperature of nano MgH2-Ti5Fe5Ni5 is lowered by 90 °C as compared to nano MgH2 alone. It is also found that the nano MgH2-Ti5Fe5Ni5 absorbs 5.3 wt% within 15 min at 270 °C and 12 atm hydrogen pressures. However, nano MgH2 reabsorbs only 4.2 wt% under identical condition. An interesting result of the present study is that mechanical milling of MgH2 separately with Fe and Ni besides refinement in particle size also leads to the formation of alloys Mg2NiH4 and Mg2FeH6 respectively. On the other hand, when MgH2 is mechanically milled together with Ti, Fe and Ni, the dominant result is the formation of nano particles of MgH2. Moreover the activation energy for dehydrogenation of nano MgH2 co-catalyzed with Ti, Fe and Ni is 45.67 kJ/mol which is 35.71 kJ/mol lower as compared to activation energy of nano MgH2 (81.34 kJ/mol). These results are one of the most significant in regard to improvement in de/rehydrogenation characteristics of known MgH2 catalyzed through transition metal elements. [Copyright &y& Elsevier]

Abstract: The effect of carbon nanofibres (CNFs) on the de/re-hydrogenation characteristics of 1:2 magnesium amide (Mg(NH2)2) and lithium hydride (LiH) mixture is investigated. It is found that the desorption as well as absorption characteristic of the 1:2 Mg(NH2)2/LiH mixture is improved with admixing of different shaped (planar and helical) CNFs separately. The different shaped CNFs were synthesized through catalytic decomposition of acetylene gas over LaNi5 alloy. The synthesized CNFs contain Ni-metal nano particles. Among two different types of nanofibres namely planar carbon nanofibres (PCNFs) and helical carbon nanofibres (HCNFs), the later was found to act as a better catalyst. The decomposition temperature of the pristine Mg(NH2)2/LiH mixture is ∼250 °C, reduced to 150 and 140 °C for the PCNF and HCNF admixed Mg(NH2)2/LiH mixture respectively. The activation energy for dehydrogenation reaction was found to ∼97.2 kJ/mol, which is further reduced to ∼67 and ∼65 kJ/mol for the PCNF and HCNF admixed Mg(NH2)2/LiH mixture respectively. The lowering of decomposition temperature and enhancement in desorption kinetics, with admixing of different shaped CNFs are described and discussed. [Copyright &y& Elsevier]

Abstract: In this paper, we describe and discuss the synthesis, structural-microstructural and hydrogen storage behaviour of three AB2 type storage materials namely (a) ZrFe2, (b) Zr(Fe0.75V0.25)2 and (c) Zr(Fe0.5V0.5)2. These alloys were synthesied by radio frequency induction melting in argon atmosphere. X-ray diffraction and transmission electron microscope have been employed for structural and microstructural characterizations. The XRD study reveals that the lattice constants and the unit cell volume of ZrFe2, Zr (Fe0.75V0.25)2, Zr(Fe0.5V0.5)2 alloys, which has C14 type hexagonal Laves phase. The Surface morphology and elemental composition of these alloys were investigated by scanning electron microscope and energy dispersive X-ray analysis. The pressure composition isotherms of these alloys were investigated at room temperature and pressure ranges of 0–100 atm respectively, measured through a fully computerized PCI apparatus. As we increase the concentration of V (substituted for Fe), the total hydrogen storage capacities increased up to 1.45 wt%. This capacity is achieved in Zr(Fe0.5V0.5)2 alloy, while the reversible hydrogen storage capacity decreases due to the formation of a stable hydride phase. It has been found that the lattice constants increase with higher vanadium concentration. This is indicating that the majority of vanadium atoms reside in the B-site. The broader X-ray diffraction peaks observed in Zr(Fe0.5V0.5)2 alloy indicates a higher degree of disorder for alloys with the higher V-content. The yet another interesting feature observed in our present study is that the plateau pressure remains well below 1 atm for all the compositions. [Copyright &y& Elsevier]

In the present investigation, the formation and stability of icosahedral phase in Al70-xGaxPd17Mn13 alloys has been explored using X-ray diffraction, scanning, transmission electron microscopy and energy dispersive X-ray analysis. Cast alloys and melt-spun ribbons with x = 2.5, 5, 7.5, 10, 12.5, 15 and 20 have been investigated. In both cases, the alloys up to 5 at% Ga exhibit the formation of pure icosahedral phase. However, for x ≥5 at% Ga content, the cast alloy exhibits the formation of multiphase material, consisting of an icosahedral phase along with AlPd-type B2 and ξ' crystalline (orthorhombic structure with unit cell a = 23.5 Å, b = 16.6 Å and c = 12.4 Å) phases. In the case of the melt spun ribbon for x = 5 at% Ga, only an icosahedral phase has been found, but for 15 > x > 5 at% Ga, an icosahedral phase is the majority phase with AlPd-type B2 phase being the minority component. For x = 15 at% Ga, a Al3Pd2-type hexagonal phase together with a small amount of quasicrystalline phase is formed. However, for x = 20, only a hexagonal Al3Pd2 phase results. [ABSTRACT FROM AUTHOR]

Abstract: The present study deals with the microstructural changes with respect to the processing parameter (quenching rate) and their correlation with hydrogen storage characteristics of Ti45Zr38Ni17 quasicrystalline alloys. The ribbons of the alloy have been synthesized at different quenching rates obtained through different wheel speeds (35, 40, 45 and 50 m/s) and investigated for their hydrogen storage characteristics. The lower cooling rate obtained through low wheel speed (35 m/s) produces, i-phase grains whose size ranges from 300-350 nm, whereas higher cooling rates obtained through high wheel speed (45 and 50 m/s) promote the formation of grains with size ranges from 100-150 nm in Ti45Zr38Ni17 ribbons. It has been found that the ribbons synthesized at 35 m/s absorbed ∼2.0 wt%, whereas ribbons synthesized at 50 m/s absorbed ∼2.84 wt. % of hydrogen. Thus the hydrogen storage capacity of ribbon increases for the ribbons produced at higher quenching rate. One of the salient features of the present study is that the improvement of hydrogen storage capacity obtained through higher quenching rates (∼45 to 50 m/s wheel speed) leading to the formation of lower grain size. [Copyright &y& Elsevier]

Abstract: In the present study, we have investigated the effect of vanadium and its compounds (V, V2O5 and VCl3) on desorption characteristics of 1:2 magnesium amide (Mg(NH2)2) and lithium hydride (LiH) mixture. The hydrogen storage characteristics of 1:2 Mg(NH2)2/LiH mixture gets enhanced with admixing of V, V2O5 and VCl3 separately. The VCl3 has been found to be the most effective followed by V and V2O5. The activation energy for dehydrogenation process of 1:2 Mg(NH2)2/LiH mixture with and without catalyst has been evaluated using a method suggested by Ozawa et al. . Based on the experimental results, schematic reaction scheme for decomposition of Mg(NH2)2 in the presence of VCl3 has also been proposed. [Copyright &y& Elsevier]

Abstract: We have investigated the ball-milling (5–45h) followed by dehydrogenation kinetics of LiNH2–MgH2 mixture. A new result of ball-milling reveals the formation of Mg(NH2)2 for mixtures ball-milled for more than 15h. The desorption kinetics has been found to improve appreciably by increasing the duration of milling from 5 to 45h. This enhancement is attributed to formation of Mg(NH2)2 during this process. It was found that the Mg(NH2)2 form through the reaction 2LiNH2 +MgH2 →Mg(NH2)2 +2LiH. The phase and microstructural characterizations have been done through X-ray diffraction, IR-spectrometry, transmission and scanning electron microscopy. Correlation between particle size and hydrogenation behavior has also been investigated. [Copyright &y& Elsevier]

The present study deals with the use of ZrFe 2 for the formation of pure phase of hydrogen storage material Mg(NH 2 ) 2 /LiH. Since ZrFe 2 is harder than the starting material LiNH 2 and MgH 2 , pulverization effect produced by ZrFe 2 assists in the synthesis of pure phase. The formation of pure Mg(NH 2 ) 2 /LiH has been examined by XRD and confirmed by FTIR. The catalytic effect of ZrFe 2 has been found to improve significantly the de/rehydrogenation characteristic of Mg(NH 2 ) 2 /LiH. The ZrFe 2 catalyzed Mg(NH 2 ) 2 /LiH shows good recyclability. The activation energy of ZrFe 2 catalyzed Mg(NH 2 ) 2 /LiH was found to be 74.80 kJ/mol which is better than several other reported studies using different catalysts. Based on experimental results, a viable mechanism for dehydrogenation of Mg(NH 2 ) 2 in the presence of ZrFe 2 has also been proposed. [ABSTRACT FROM AUTHOR]

• The influence of Fe/Ni content on structural and magnetic behavior is studied for Co 35 Cr 5 Fe 20−x Ni 20+x Ti 20 HEAs. • The mixture of the fcc, and a minor R-phase are evolved for all the synthesized HEAs. • The coercivity decreased more than five times to the initial value after the heat treatment. • Annealed Co 35 Cr 5 Fe 10 Ni 30 Ti 20 HEA exhibits excellent soft magnetic properties Ms = 78.01 emu/g and extremely low Hc = 1.7 Oe • The found coercivity is the lowest value of coercivity reported so far for the case of magnetic HEAs. The design and development of excellent soft magnetic materials are fascinating research areas in materials science. A series of Co 35 Cr 5 Fe 20−x Ni 20+x Ti 20 (x = 5, 10, 15) High Entropy Alloys (HEAs) were synthesized through mechanical alloying (MA) technique and heat-treated at two different temperatures at 200 °C and 700 °C for 2 h. The XRD analysis confirmed that the HEAs comprised of face-centered cubic (fcc) phase and a minor fraction of an intermetallic R-phase at as-synthesized and annealed state. SEM-EDS observation confirmed the homogeneous compositional distribution and showed that after annealing at 700 °C, tiny spherical particles precipitated over the large grains. The synthesized HEAs showed soft magnetic behavior with low coercivity (12–16 Oe). However, the coercivity decreased more than five times to the initial value after the annealing at 700 °C. Co 35 Cr 5 Fe 10 Ni 30 Ti 20 HEA annealed at 700 °C shows excellent soft magnetic properties with a high value of Ms (78.01 emu/g) and an extremely low value of Hc (1.7 Oe). The found value of the coercivity is the lowest value of the coercivity reported so far for the case of magnetic CoCrFeNiTi based HEAs. In addition, the present work provides a novel design strategy for the development of magnetic HEAs with excellent magnetic softness. [ABSTRACT FROM AUTHOR]

The present paper explores the enhancement in hydrogen sorption behavior of MgH2 with TiO2 nanoparticles. The catalytic effect of TiO2 nanoparticles with different sizes (7, 25, 50, 100 and 250 nm) were used for improving the sorption characteristics of MgH2. The MgH2 catalyzed with 50 nm of TiO2 exhibited the optimum catalytic effect for hydrogen sorption behavior. The desorption temperature of MgH2 catalyzed through 50 nm TiO2 was found to be 310 degrees C. This is 80 degrees C lower as compared to MgH2 having a desorption temperature of 390 degrees C. It was noticed that the dehydrogenated MgH2 catalyzed with 50 nm TiO2 reabsorbed 5.1 wt% of H2 within 6 minutes at temperature and pressure of 250 degrees C and 50 atm, respectively. The 50 nm TiO2 catalyst lowered the absorption activation energy of MgH2 from - 92 to - 52.7 kJ mol(-1).