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Storage is a challenging issue that cuts across distribution, delivery, and safe end-uses of hydrogen as fuel. All the fuel cell vehicles are equipped with inefficient and unsafe high-pressure hydrogen cylinders. It is well known that storing such a highly flammable gas at high pressure is not safe. Only hydrogen can be stored safely as a form of metal hydrides, and all the investigated metal hydrides are inefficient in one way or another. Four essential hydrogen parameters for solid-state storage for fuel cell applications are high volumetric storage capacity, excellent heat transfer, and recharge time and feasible charging discharging temperatures. The available metal tanks have good gravimetric storage capacity but did not satisfy the prescribed criterion for good volumetric capacity necessary for mobile applications. Recently, some promising reports are published on the hydrogen storage properties of newly discovered High Entropy Alloys (HEAs). HEAs provide vast composition selection freedom for the formation of favorable simple solid solution phase for hydrogen storage. The four core effects of these alloys may also play a vital role in hydrogen storage properties. Here we reviewed and summarized the published results on hydrogen storage properties of HEAs to date. We underlined different essential aspects for the future development of HEAs as hydrogen storage materials. This review article discusses and describes the perspectives of HEAs in regards to the hydrogen storage applications of these alloys and will provide insight into the future development of hydrogen storage HEAs. • Provide detailed, information on the different aspects of hydrogen storage properties of HEAs. • Discuss basic properties (definition and core effects) of HEAs regarding hydrogen storage properties. • Discuss benefits of HEAs over conventional alloys in regards to HS properties. • Underlined different aspects that have importance on the future development of hydrogen storage HEAs for applications. [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 TiO 2 nano particles on the hydrogenation characteristics of promising Li-Mg-N-H hydrogen storage system. The effect of different particle size of TiO 2 (200, 25 and 7 nm) on de/re-hydrogenation characteristics of Mg(NH 2 ) 2 /LiH mixture has been investigated. Desorption kinetics of Li-Mg-N-H system with 25 nm TiO 2 gets enhanced upto ∼25% as compared to the pristine material kinetics at 453 K (180 °C). The report also deals mechanistic approach for hydrogen release from Li-Mg-N-H system in the presence of TiO 2 nanoparticles through XPS analysis of catalyzed sample at various stages of reaction. The XPS analysis confirms that during dehydrogenation nitrogen atom present in Li-Mg-N-H system share their lone pair electrons to Ti (present in TiO 2 ) and provides an alternate decomposition path which has lower activation energy for dehydrogenation. [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]

The present investigations are focused on the effect of different Ti-based catalysts (Ti, TiO 2 , TiCl 3 and TiF 3 ) on de/re-hydrogenation characteristics of nanocrystalline MgH 2 . Desorption temperature of milled MgH 2 lowers from 380 to 350, 340, 310 and 260 °C with the addition of Ti, TiO 2, TiCl 3 and TiF 3 respectively. The rehydrogenation characteristics are also improved through the deployment of Ti-based catalysts. Among all Ti based additives, TiF 3 is found to be the most effective catalyst for hydrogen sorption from nano MgH 2 . The better catalytic effect of TiF 3 over other Ti-based catalyst can be explained on the basis of temperature programmed reduction (TPR) studies. TPR experiments performed for different Ti additives, reveals that there is no oxidation/reduction reaction below 400 °C except for TiF 3 . The TPR profile of TiF 3 shows some oxidation/reduction reaction exhibits at 200 °C. In order to further improve the sorption characteristics and cyclability of TiF 3 catalyzed nano MgH 2 , we have investigated the effect of SWCNTs in MgH 2 +TiF 3 sample. De/rehydrogenation characteristics reveal the synergistic effect of SWCNTs and TiF 3 in MgH 2 +TiF 3 sample. The details of the improvement in sorption behavior of MgH 2 –TiF 3 in presence of SWCNTs are described and discussed. [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 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]

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]

In this report, a modified solid-state synthesis technique is optimized to synthesize a single spinel phase for a novel (CuNiTiZnFe) 3 O 4 High Entropy Oxide (HEO) and studied for magnetic behavior. Three different approaches were adopted for the synthesis of pure spinel HEO. In the first approach, The initial mixture of constituent oxides was admixed, and sintered at 1050 °C for 20 h. For the second and third approaches, the mixture of constituent oxides was ball-milled for 2 h, and 10 h separately, followed by sintering at 1050 °C for 20 h. A small amount of undiffused constituent oxide peaks are present in both the first and second approaches. However, the sample synthesis through 10 h milling followed by sintering has single spinel (CuNiTiZnFe) 3 O 4 HEO phase. The single spinel HEO phase formation was confirmed through the le-Bail refinement. The lattice parameter for the well-fitted XRD pattern is 8.415161 A°. Further, the investigation was focused on the magnetic behavior of the single spinel HEO phase. The value of magnetization and coercivity is 16.11 emu/g and 10.66 Oe, respectively. The synthesized HESO has typical ferrimagnetic nature and has the second-highest value of Ms reported so far for HEOs. The ionic states of different cations present in the (CuNiTiZnFe) 3 O 4 HESO were also investigated through X-ray photoelectron Spectroscopy. XPS analysis reveals that Fe and Ni are in the +3 and + 2 states, Cu and Zn are in the +2 states, and Ti is in the +4 states. [ABSTRACT FROM AUTHOR]

The present study reports the synthesis of a novel (Al 0·2 Co 0·2 Fe 0·2 Ni 0·2 Ti 0.2) 3 O 4 high entropy oxide (HEO) through the solid-state reaction method and its structural, dielectric, electric, and magnetic properties. For the first time, a cumulative study of dielectric, electric, and magnetic properties of the spinel HEO has been investigated in detail. The obtained HEO has a single-phase spinel structure with Fd-3m space group, confirmed through X-ray diffraction and Raman spectroscopy techniques. Moreover, Raman spectroscopic analysis also confirms that the synthesized spinel HEO is an inverse spinel. The dielectric and magnetic characterizations reveal a better dielectric permittivity of ε ′ = 35 at 1 MHz and high saturation magnetization Ms = 8.58 emu/g with low magnetic coercivity. The leakage current characteristics studied in terms of J-E curves indicate an ohmic conduction mechanism at a low electric field. Moreover, the high dielectric permittivity with resistive switching behavior (observed in the J-E curve) indicates its potential application in resistive switching memory devices, which have better functionality and enhanced scalability. [Display omitted] • Novel single-phase inverse spinel structured (Al 0.2 Co 0.2 Fe 0.2 Ni 0.2 Ti 0.2) 3 O 4 HEO is synthesized by the solid-state method. • Cumulative study of dielectric, electric, and magnetic properties of the spinel HEO reported for the first time. • Synthesized HEO showed resistive switching behavior in the J-E curve and yielded better dielectric and magnetic properties. [ABSTRACT FROM AUTHOR]

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 present investigation describes the hydrogen storage properties of 2:1 molar ratio of MgH 2 –NaAlH 4 composite. De/rehydrogenation study reveals that MgH 2 –NaAlH 4 composite offers beneficial hydrogen storage characteristics as compared to pristine NaAlH 4 and MgH 2 . To investigate the effect of carbon nanostructures (CNS) on the de/rehydrogenation behavior of MgH 2 –NaAlH 4 composite, we have employed 2 wt.% CNS namely, single wall carbon nanotubes (SWCNT) and graphene nano sheets (GNS). It is found that the hydrogen storage behavior of composite gets improved by the addition of 2 wt.% CNS. In particular, catalytic effect of GNS + SWCNT improves the hydrogen storage behavior and cyclability of the composite. De/rehydrogenation experiments performed up to six cycles show loss of 1.50 wt.% and 0.84 wt.% hydrogen capacity in MgH 2 –NaAlH 4 catalyzed with 2 wt.% SWCNT and 2 wt.% GNS respectively. On the other hand, the loss of hydrogen capacity after six rehydrogenation cycles in GNS + SWCNT (1.5 + 0.5) wt.% catalyzed MgH 2 –NaAlH 4 is diminished to 0.45 wt.%. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with how the Hydrogen Energy may play a crucial role in taking care of the environmental scenario/climate change. The R&D efforts, at the Hydrogen Energy Center, Banaras Hindu University have been described and discussed to elucidate that hydrogen is the best option for taking care of the environmental/climate changes. All three important ingredients for hydrogen economy, i.e., production, storage and application of hydrogen have been dealt with. As regards hydrogen production, solar routes consisting of photoelectrochemical electrolysis of water have been described and discussed. Nanostructured TiO2 films used as photoanodes have been synthesized through hydrolysis of Ti[OCH(CH3)2]4. Modular designs of TiO2 photoelectrode-based PEC cells have been fabricated to get high hydrogen production rate (∼10.35lh−1 m−2). However, hydrogen storage is a key issue in the success and realization of hydrogen technology and economy. Metal hydrides are the promising candidates due to their safety advantage with high volume efficient storage capacity for on-board applications. As regards storage, we have discussed the storage of hydrogen in intermetallics as well as lightweight complex hydride systems. For intermetallic systems, we have dealt with material tailoring of LaNi5 through Fe substitution. The La(Nil − x Fe x )5 (x =0.16) has been found to yield a high storage capacity of ∼2.40wt%. We have also discussed how CNT admixing helps to improve the hydrogen desorption rate of NaAlH4. CNT (8mol%) admixed NaAlH4 is found to be optimum for faster desorption (∼3.3wt% H2 within 2h). From an applications point of view, we have focused on the use of hydrogen (stored in intermetallic La–Ni–Fe system) as fuel for Internal Combustion (IC) engine-based vehicular transport, particularly two and three-wheelers. It is shown that hydrogen used as a fuel is the most effective alternative fuel for circumventing climate change. [Copyright &y& Elsevier]

• 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]