Arc Melting Research Articles

Optimizing Hydrogen Storage Pathways in Ti–Al Alloys through Controlled Oxygen Addition

In the present study, we aimed to destabilize the Ti–Al system with nonmetallic oxygen. The synthesis of α‐(Ti, Al)[O] starting from TiO2, Ti, and Al was carried out through the arc melting method, resulting in three different oxygen content levels, 3.4, 10, and 20 at%. The room temperature activation of α‐(Ti, Al)[O] was not successful, and the activation was performed at 300°C under 5 MPa H2 pressure. The structural changes after hydrogenation (maximum absorption capacity of 3.74 wt% hydrogen) arose from the transformation of α‐(Ti, Al)[O] to cubic (Ti, Al)[O]Hx (c‐(Ti, Al)[O]Hx); nonetheless, they recovered their original lattice parameters, which are meaningfully larger than those of α‐Ti, after dehydrogenation. The hydrogen storage capacities for various α‐(Ti, Al)[O] compositions generally decreased with increasing oxygen (3.4 and 10 at%) and aluminum content in the alloy. In contrast, for the compositions with a higher oxygen content of 20 at%, the hydrogen storage capacity slightly increased as the Al concentration increased: Ti0.790Al0.010O0.200 absorbed 2.91 wt% hydrogen, whereas Ti0.767Al0.033O0.200 absorbed 3.04 wt% hydrogen. The thermogravimetric analysis showed that samples with 20 at% O released hydrogen at lower temperatures even though the major phase after hydrogenation is c‐(Ti, Al)[O]Hx regardless of the oxygen content.

Study on corrosion resistance of CoCrFeNiTi0.2Mox high entropy alloy in acidic and alkaline solutions

Using vacuum arc melting, a new alloy called CoCrFeNiTi0.2Mox (x=0, 0.1, 0.3) was made. We tested corrosion resistance in acidic and alkaline environments by using electrochemical methods. The consequences substantiated that the corrosion resistance of the alloy improved in terms of solvents and molybdenum content, despite some variation in the polarization curves. In 1 mol/L sulfuric acid, the polarization curve of high entropy alloy shows activation, activation-passivation, and passivation stages, and in 1 mol/L caustic soda solution, the polarization curve of CoCrFeNiTi0.2Mox alloys directly changes from the vital polarization region to the passivation region.

Mechanical and Tribological Performance of AlCrFeCuNi-(Vx) HEAs Synthesized via Arc Melting technique

The AlCrFeCuNi-(Vx) High Entropy Alloy (HEA) was created via arc-melting and casting processes. The influence of vanadium (V) on the Nano mechanical behaviour, microstructural development, as well as the wear performance of the produced HEAs was examined. Notable improvements to the Nano hardness of the HEAs were evident with an increase in V content from 1at% to 5at%. The addition of V altered the frictional behaviour of the HEA with an increased coefficient of friction as V is increased. The addition of V also greatly affected the microstructural orientation of the HEA, exhibiting signs of homogenization as V content increased.

A study on the first hydrogenation behavior of TiFe0.9Cr0.1 hydrogen storage alloy with the laves phase

This study investigated the first hydrogenation behavior of TiFe-based hydrogen storage alloy with the laves phase. A TiFe0.9Cr0.1 alloy was prepared through vacuum arc melting, and it had a dual-phase microstructure with B2 and laves phases. The first hydrogenation kinetics was measured by applying a hydrogen pressure of 40 bar at 30 °C, where the alloy absorbed hydrogen without thermal activation. The first hydrogenation kinetics was divided into three sections to understand the first hydrogenation behavior, and each section was analyzed using a solid–gas reaction model. The model's goodness of fit was evaluated by fitting each section. In the early hydrogen absorption stage, a surface-controlled mechanism (Chemisorption model) was analyzed to be the most dominant. In the second stage, where hydrogen was quickly absorbed, an interface-controlled mechanism (CV3D model) was most suitable. In the last hydrogen absorption stage, where hydrogen absorption was saturated, a diffusion-controlled mechanism (GB3D model) was most suitable.

Effects of Al addition on the microstructure and mechanical properties of AlxCoCrFeNi2.1 high-entropy alloys

To investigate the effect of Al content on the microstructure evolution and properties of AlxCoCrFeNi2.1 high-entropy alloys, the AlxCoCrFeNi2.1 high-entropy alloys (=0.5, 0.8, 1.0, 1.2 and 1.5) were prepared by vacuum arc melting. The results show that all the designed alloys are composed of single face-centered cubic (FCC) and ordered body-centered cubic (B2) phases. With the increase of Al content, the volume fraction of FCC phase decreases while that of B2 phase increases. In addition, the increasing Al content leads to the sequential increase of the hardness and yield strength of the alloys, while both the plasticity and compressive strength decrease. And the corresponding wear rate decreases from 312.9 × 10−5 mm2 N−1 to 55.3 × 10−5 mm2 N−1. It is revealed that the wear mechanism transforms from initially dominant abrasive wear with adhesive wear as a supplement to the mechanism dominated by adhesive wear with abrasive wear as a supplement, and finally to the oxidation wear plus abrasive wear. The experimental results show that the Al1.2CoCrFeNi2.1 alloy has the most excellent comprehensive performance, with an average hardness of 441 HV, compression ratio of 36.4%, compressive strength of 2618 MPa and wear rate of 68.0 × 10−5 mm2 N−1.

Microstructural Evolution of High-Entropy Intermetallic Compounds during Detonation Spraying

This study aims at investigating the feasibility of depositing quality coatings from various high-entropy intermetallic compounds (HEICs) using detonation spraying (DS). Four different HEIC coatings, namely (NbTaVCrTi)Al3, (NbTaVNiFe)Al3, (NbTaVZrHf)Al3, and (FeNiCoCrMn)(MoCr), were prepared by DS on low alloy steel substrates. The HEIC powders were first prepared by arc melting followed by ball milling and then used as reinforcement particles to deposit HEIC coatings. Elemental segregation was observed for all the as-cast samples. Powders with average particle sizes of about ~25 µm for (NbTaVCrTi)Al3, ~22 µm for (NbTaVNiFe)Al3, ~34 µm for (NbTaVZrHf)Al3, and ~18 µm for (FeNiCoCrMn)(MoCr) were obtained. (NbTaVCrTi)Al3, (NbTaVNiFe)Al3, and (NbTaVZrHf)Al3 HEICs exhibited a nearly single D022 (TaAl3 type) structure, while (FeNiCoCrMn)(MoCr) exhibited a single D8b (FeCr type) structure. Dense coatings consisted of a lamellar microstructure and sound bonding with the substrate, and low porosity was obtained for all the samples. Crystal structures of the HEIC samples were highly retained during DS, whereas all the samples underwent some degree of oxidation. Microhardness values of 745 HV for (NbTaVCrTi)Al3, 753 HV for (NbTaVNiFe)Al3, and 862 HV for (NbTaVZrHf)Al3 were obtained, which are significantly higher than the microhardness of the substrate (~140 HV). Among all the samples, (FeNiCoCrMn)(MoCr) exhibited the highest microhardness values of about 1047 HV.

Tailoring microstructures and properties in Co-free FeNiCrCuAl high entropy alloys by Al addition

In this study, a series of Co-free FeNiCrCuAlx (x = 0.1, 0.3, 0.5, 0.8 and 1.0) high entropy alloys (HEAs) were developed by vacuum arc melting and casting method in high-purity argon atmosphere. The effects of Al addition on the microstructure and properties were investigated using X-ray diffraction, scanning electron microscopy, Vickers hardness tester, tensile test, wear test and electrochemical experiment. It was found that with the increase in the large atomic-sized Al content, the closely-packed FCC structure was destabilized for a transition to the loosely-packed BCC structure at x = 0.3. As x increased up to 1.0, the structure was mainly composed of BCC phase. The hardness of HEAs was enhanced by the influence of the contiguous atomic planes in BCC structures due to the relatively lower inter-planar spacing and higher lattice friction for dislocation motion, with the potential to increase the yield strength of the HEAs by 93.5 %. The friction coefficient decreased with increasing Al content, as indicated by stable profiles of Al0.8 and Al1.0 under progressive wear in comparison to those of Al0.1, Al0.3 and Al0.5 while the associated minimal wear depth and lower capacity for debris accumulation of the higher Al content HEAs confirmed their superior wear resistance. As FeNiCrCuAl0.5 presented the most superior corrosion resistance due to high resistance to ionic transport via the steady oxide film and the indication of a comparatively wider capacitive semicircle, undue Al additions would not be beneficial to improving plasticity or enhance corrosion resistance. Thus, FeNiCrCuAlx HEAs with Al contents in the range of 0.5–1.0 were found to possess optimized comprehensive properties, and can be suitably recommended as nuclear structural materials. This study will shed light on advancing the development of cutting-edge HEAs.

Effect of industrial grade raw materials and its associated impurities on first hydrogenation of BCC solid solution alloys

This study explores the effects of using industrial-grade raw materials on the hydrogen storage properties of body-centered cubic (BCC) solid solution alloys. Industrial scrap metals were chosen as the raw material, and the desired alloys were synthesized using a vacuum arc melting furnace. Instead of using pure vanadium (V), different inexpensive industrial substitutes such as low-grade vanadium (V), vanadium nitride (VN), vanadium oxide (VO), and ferrovanadium (FeV) were utilized. The crystal structure, morphology, first hydrogenation, thermodynamics, and cyclability of the prepared alloys were analyzed by using XRD, SEM-EDS, and XPS methods. The crystal structure and morphology analysis revealed multiphase alloys in all the prepared alloys and a Ti rich third phase in the VN sample, which was absent otherwise. The first hydrogenation was performed at room temperature under a hydrogen pressure of 2 MPa without any prior heat treatment. The VO alloy displayed negligible hydrogen absorption during first hydrogenation, while the V, VN, and FeV alloys showed maximum hydrogen storage capacities of 3.49 wt%, 2.47 wt%, and 2.18 wt%, respectively. The presence of oxygen hinders the activation of the VO alloy and requires two activation cycles to activate the sample. A short-term cyclability analysis showed a reversible hydrogen storage capacity of 2 wt%. The change in enthalpy of hydrogen absorption and desorption for V alloy were calculated to be −36.73 ± 8.6 and 57.34 ± 8.3 kJ/mol H2, respectively. One of the prominent advantages of utilizing scrap raw materials was the substantial reduction in overall raw material costs, which saw an impressive 95% decrease when compared to using pure raw materials. These results highlight the economic benefits of incorporating recovered industrial scrap into hydrogen storage alloys.

Estimation of magnetocaloric effect in multicomponent material Gd0.2Tb0.2Dy0.2Ho0.2Er0.2Ni2: Exploring high-entropy design

Polycrystalline rare earth intermetallic compound Gd0.2Tb0.2Dy0.2Ho0.2Er0.2Ni2 has been synthesized by arc melting and it has MgCu2-type cubic crystal structure at 300 K (space group Fd-3m). Magnetization measurement on arc-melted Gd0.2Tb0.2Dy0.2Ho0.2Er0.2Ni2 reveals a paramagnetic to ferromagnetic transition at ∼32 K (TC). The TC is close to the average value of the ferromagnetic transition temperatures of the end member GdNi2, TbNi2, DyNi2, HoNi2 and ErNi2 compounds. Using the field-dependent magnetization data measured around TC, isothermal magnetic entropy change (ΔSm) has been estimated. A maximum value of ΔSmmax = −14.3 J kg−1 K−1 is obtained at 27.5 K for 5 T field change. This value is significant when compared to that in the parent RNi2 (R = Gd, Tb, Dy, Ho and Er) compounds. The multicomponent compound Gd0.2Tb0.2Dy0.2Ho0.2Er0.2Ni2 has also been prepared by melt-spinning under inert atmosphere. The melt-spun sample shows granular microstructure with an average grain size of ∼1 µm. It is found that the bulk magnetic properties are almost retained in the melt-spun sample and the magnetocaloric effect is nearly equal to that in arc-melted Gd0.2Tb0.2Dy0.2Ho0.2Er0.2Ni2. The relative cooling power is large and is about 568 J kg−1 and 531 J kg−1 for 5 T field change for the arc-melted and melt-spun Gd0.2Tb0.2Dy0.2Ho0.2Er0.2Ni2 samples respectively.

Anodic Oxidation and Corrosion Resistance of Ta-Containing High Entropy Alloys

Stainless steels are corrosion resistant, but pitting corrosion sometimes occurs in chloride solutions. Anodic oxidation is one of the effective methods to increase the pitting corrosion resistance. However, unlike valve metals, stainless steels are difficult to improve pitting corrosion resistance by anodic oxidation. In this study, Fe-based alloys containing valve metals were fabricated to investigate anodic oxidation and corrosion resistance.Equimolar CrFeNbNiTa and (CrFeTa)30(NbNi)5 alloys were fabricated by arc melting, and pure metals of Cr, Fe, Nb, Ni, and Ta were used as raw materials. After casting, the ingots were heat-treated at 1200 ℃ for 2 h (furnace-cooling) and cut into 2 mm thick sheets. After that, the specimen surfaces were polished up to 1 μm with a diamond paste. The microstructures were observed using an optical microscope and a scanning electron microscope. The chemical compositions and elemental distributions of the specimens were analyzed by energy dispersive X-ray spectroscopy. Potentiodynamic polarization was performed in 1 M H2SO4. As a reference, Type 304 stainless steel was used.The equimolar CrFeNbNiTa alloy was composed of two phases. One was Cr- and Fe-rich and the other was Nb- and Ni-rich. The (CrFeTa)30(NbNi)5 alloy was a single phase. In the potentiodynamic polarization measurements, the current densities of oxygen evolution reaction of equimolar CrFeTaNbNi and (CrFeTa)30(NbNi)5 alloys were lower than that of Type 304 stainless steel. Moreover, the passive current densities of equimolar CrFeTaNbNi and (CrFeTa)30(NbNi)5 alloys were higher than that of Type 304 stainless steel.

Boron Enhanced Complex Concentrated Silicides – A bridge between lightweight, oxidation-resistant Refractory Metal Silicides and Refractory Complex Concentrated Alloys

This study presents the Boron Enhanced Complex Concentrated Silicides (BECCSs) as a novel category of high-temperature materials derived from the high entropy concept. Using a quaternary MoNbTaW equiatomic alloy as a starting point, four new alloy compositions were designed in a multi-step process oriented towards reducing the density of the material. By incorporating different combinations of Ti, Si, and B, the phase composition of the materials was altered from a BCC solid solution to a multi-phase structure consisting of BCC solid solution and various intermetallics (silicides, borides, and borosilicides). The suggested modification of the alloy composition led to a significant decrease in density, reaching down to 6.87 g/cm3. All four alloys were fabricated by the arc melting technique, while their microstructure and room temperature mechanical properties were evaluated by SEM/EDS/EBSD and micro-indentation methods. The results of structural characterization enabled the identification of specific phase constituents. Consequently, it was established that the transition from BCC solid solutions to silicides/borides based alloys results in a significant increase in hardness, achieving up to 1200 HV (13 GPa).

Influence of platinum content (X) in the LaNi5PtX catalyst and reaction conditions on the properties of ferromagnetic Ni-filled CNTs

This research highlights the synthesis of carbon nanostructures using the catalytic chemical vapor deposition (CCVD) method, a hybrid process combining chemical vapor deposition (CVD) and Gas-Solid Heterogeneous Catalysis (GSHC). Intermetallic catalysts, LaNi5Ptx (x = 0, 0.05, 0.5, 1.0), were fabricated through an arc melting procedure to serve as templates for the catalytic conversion of carbon precursors into solid materials. These catalysts, featuring the ferromagnetic transition metal Ni, tend to aggregate into larger particles, reducing the rate of hydrocarbon cracking at the catalyst surface. Rare earth metals like Lanthanum were introduced to form an alloy with a higher melting point to prevent thermal aggregation. Additionally, Pt was incorporated to modify the catalytic properties of the alloy. The study primarily explores the impact of catalyst composition on carbon nanotube (CNT) production. The introduction of platinum content to the catalyst influences the rate at which Ni is filled. The research aimed to alter the catalyst's composition by varying platinum doping in the Pauli paramagnetic lanthanum nickel alloy (LaNi5) to understand the growth mechanism and morphological variations of Ni-filled CNTs. Platinum and lanthanum oxides significantly influence nickel filling in CNTs, resulting in an increased filling rate as the catalyst's Pt content varies from 0 to 1.0. However, higher Pt doping content disrupts the CNT structure with spontaneous nickel encapsulation.

Mechanism of interstitial atoms on oxidation and fracture of niobium‑silicon alloys

To investigate the effect of interstitial atoms on high-temperature oxidation behavior and fracture room-temperature fracture toughness of niobium‑silicon alloys. The Nb-16Si-24Ti-xC-yB (x = 1, 2; y = 5, 10) alloys were prepared by arc melting. Results show that the addition of C and B elements shifts solidification path to hypereutectic direction and promotes the generation of coarse silicide and lamellar Nb5Si3-Nbss eutectic structure. TiB2 appears in 1C10B and 2C10B alloy as primary phase. The KQ value of 1C5B alloy reaches 12.30 MPa·m1/2 and increased by 95.5% compared to Nb-16Si-24Ti alloy. The surfaces of alloys do not generate stable oxide layer which could defense oxidation effectively. However, the increase of silicide and the obstructive effect of interstitial atoms on inward diffusion of O atoms improves the oxidation resistance of 1C10B and 2C10B alloy. The existence of interstitial atoms reduces the internal stress of oxide film and improves the integrity of oxide layers.

Thermoelectric Transport of a Novel Zr‐Based Half‐Heusler High‐Entropy Alloy

The high‐entropy concept, extensively studied in alloys and ceramics, has produced intriguing results, but its use in thermoelectric materials is still in its infancy. This study introduces a pioneering high‐entropy half‐Heusler (hH) alloy, ZrTiNiFeSnSb, synthesized via arc melting and heat treatment. Phonon scattering from multiple elements significantly reduces the lattice thermal conductivity of the alloy, which decreases to a minimum of 3.5 Wm−1 K−1 (700 K) in this material. The experimental thermal data matches the density functional theory calculations for phonon dispersion, phonon group velocity, and Grüneisen parameters. This demonstrates that crystal distortion induced anharmonicity slows the alloy's phonon heat transport, which is suitable for thermoelectric applications. Notably possessing elevated electrical conductivity and a moderate Seebeck coefficient, this high‐entropy hH alloy emerges as a promising thermoelectric material for energy harvesting.

Crystal structure change in magnetocaloric compounds (Er,Nd)2Fe17

Numerous research studies have documented materials exhibiting a significant magnetocaloric effect (MCE) at elevated temperatures. However, there is a scarcity of materials displaying both intriguing MCE and a second-order transition phase from a ferromagnetic state to a paramagnetic state at approximately 300 K. In this current study, we provide an account of the structural, magnetic, and magnetocaloric characteristics of the (Er,Nd)2Fe17 system. (Er,Nd)2Fe17 compound was prepared by arc melting under high pure argon and homogenized at 1073K to minimize the amount of other possible impurity phases. X-ray diffraction (XRD) coupled with Rietveld analysis with FullProf computer code was used for the structural study. This compound crystallizes in the rhombohedral Th2Zn17 and Th2Ni17 type structure.the Er2−xNdxFe17 compounds adopt the hexagonal Th2Ni17-structure type and extends for x = 0, 0.4, 0.7, while for x = 1.75, 1.85 and 2 adopts the rhombohedral Th2Zn17-structure type. Hence, the temperature dependence of the magnetization is determined. The Curie temperature increases from 294K to 335K after the total Er substitution by Nd. The magnetic entropy changes ΔSM, and the relative cooling power and temperature-averaged entropy change (TEC) are reported. Based on these results, the compounds under investigation exhibit an intriguing magnetocaloric effect in the vicinity of room temperature.

Study on magnetic and structural properties of Fe65Co35 soft magnetic alloy prepared by arc melting and subsequent annealing

Fe65Co35 based soft magnetic alloys (SMAs) have been gaining attention for their superior magnetic features and playing significant roles in composite permanent magnets, magnetic storage and automotive electrification technologies. In the present work, the Fe65Co35 alloy were produced by arc melting with subsequent annealing. The effects of arc melting and annealing upon the structural and magnetic properties of the soft magnetic phase of the alloy Fe65Co35 have been investigated. The variation in magnetic and microstructural characteristics with melting and annealing have been observed using the X-ray diffractometer (XRD), scanning electron microscope (SEM), and the vibrating sample magnetometer (VSM). The XRD patterns verified the existence of the Fe65Co35 alloy. After melting and annealing, the alloy surface morphologies were examined using SEM. In this approach, the Fe65Co35 alloy was annealed at 600 °C for 4 h in an argon environment which resulted in the highest saturation magnetization of 237 emu/g and the lowest coercivity of 31 Oe. The rise in saturation magnetization was attributed to the removal of impurities, during the melting and annealing process.

Magnificent tensile strength and ductility synergy in a NiCoCrAlTi high-entropy alloy at elevated temperature

The study reported a novel L12-strengthening NiCoCrAlTi high-entropy alloy (HEA) with an outstanding synergy of tensile strength and ductility at both ambient and high temperatures. The HEA was prepared by arc melting and cold-rolling, followed by isothermal aging at designed precipitation temperatures to achieve coexistence of recrystallized and non-recrystallized grains. Transmission electron microscopy (TEM) characterization revealed a high density of rod-like and spheroidal L12 precipitates distributing in the micro/nanograins and non-recrystallized regions in the annealed specimens. The yield stress, ultimate tensile stress, and ductility of the HEA were ∼1300 MPa, 1610 MPa, and 14 % at room temperature, respectively. Such excellent mechanical properties of ∼1060 MPa, 1271 MPa, and 25 % were maintained to 600 °C, which was superior to most reported HEAs and Co- and Ni-based superalloys to date. Systematic TEM analysis unveiled at low strain, the deformation mechanism was mainly controlled by dislocations and stacking faults (SFs). With the increase in strain, the deformation mode gradually transferred to dislocations, deformation twins (DTs), and SFs. Moreover, the complex interaction between SFs and L12 precipitates, including the shearing and blocking effects, was frequently observed, contributing to the high tensile strength. Thus, the extremely high tensile strength and sustained ductility at 600 °C mainly originate from the cooperation among interaction between L12 precipitation and dislocations and extensive SFs, DTs, immobile Lomer-Cottrell (L-C) locks formed from interactions between SFs and SFs/DTs, hierarchical SFs/DTs networks, as well as hetero-deformation-induced strengthening. Such a unique deformation mechanism breaks the strength-ductility trade-off of the HEA at high temperatures.

Influence of alloying elements and composition on microstructure and mechanical properties of Cu-Si, Cu-Ag, Cu-Ti, and Cu-Zr alloys

This study aims to quantitatively compare the effects of alloying elements on the microstructures and mechanical properties of Cu–Si, Cu–Ag, Cu–Ti, and Cu–Zr binary alloys over an alloying content range up to 2 wt%. The alloys were produced using vacuum arc melting, followed by homogenization and cold-rolling into plates. Subsequently, the annealing response of the cold-rolled plates was examined over a temperature range of 200–700 °C. The as-cast alloys show distinct microstructural features attributable to the alloying elements. Following the homogenization and cold-rolling processes, substantial microstructural transformations were observed. The analysis of mechanical properties revealed that solid solution hardening played a dominant role in increasing strength in Cu–Si alloys. Cu–Ag alloys displayed a minor increase in strength with alloying content, implying the influence of Cu–Ag precipitates on strength. Conversely, Cu–Ti and Cu–Zr alloys demonstrated remarkable strength improvements due to the presence of intermetallic precipitates and grain size reduction. While all other alloys displayed an inverse relationship between strength and elongation with increasing alloying content, the Cu-Si alloys exhibited a simultaneous enhancement of both strength and elongation. This effect can be attributed to the twinning-induced plasticity, brought about by the reduction of stacking fault energy in Cu through the addition of Si.

Effect of Ti0.9Zr0.1Mn1.5V0.3 alloy catalyst on hydrogen storage kinetics and cycling stability of magnesium hydride

As a high-capacity hydrogen storage material, MgH2 still has the problem of high operating temperature and slow reaction kinetics. In this work, an TiMn2-based Laves phase alloy (Ti0.9Zr0.1Mn1.5V0.3, denoted as Ti–Mn) was first synthesized by arc melting and then employed to regulate the hydrogen storage properties of MgH2, with the carbon nanotubes (CNTs) as an aid agent to facilitate the hydrogen diffusion and heat transfer. It was shown that the introduction of Ti–Mn/CNTs can remarkably improve the hydrogen storage properties of MgH2. The MgH2 + 10 wt% Ti–Mn + 1 wt% CNTs composite has an initial dehydrogenation temperature of 195 °C and can absorb hydrogen at room temperature. As for the kinetics, it can release 6.1 wt% H2 in 5 min at 300 °C, and absorb 4.8 wt% H2 in 10 min at 150 °C. It still has a reversible capacity of 6.2 wt% after 100 cycles. Combination of Ti–Mn alloy and CNTs is more effective than Ti–Mn alloy or CNTs alone for regulating MgH2. Ti–Mn/CNTs does not alter the overall thermodynamics of MgH2. However, local destabilization of Mg–H bonds induced by the MgH2/Ti–Mn interfaces was observed experimentally and confirmed theoretically, which partially contributes to the enhanced hydrogen storage of MgH2. In addition, the active transition metals contained in the alloy was believed to accelerate the hydrogen dissociation and delivery during the hydrogen storage process. This work not only achieves the synergistic improvement of hydrogen storage of MgH2 by combination of Ti–Mn alloy and CNTs, but also presents the local destabilization mechanism to explain the improved hydrogen storage of MgH2 by Ti–Mn alloy experimentally and theoretically.

Exploration of synthesis route and effect of Ni-doping on thermoelectric performance of CoSb3

CoSb3-based materials have surfaced as promising contenders for mid-temperature thermoelectric (TE) applications owing to their low cost and stability. The current work focuses on designing three different synthesis routes and their comparison to find out the most suitable route for synthesizing pristine CoSb3. The designed synthesis routes are direct spark plasma sintering (SPS), conventional furnace melting followed by SPS, and arc melting followed by SPS. Based on structural and transport characterizations, the synthesis route of arc melting followed by SPS was handpicked amongst the three different synthesis routes. The key benefit of this synthesis route is the massive reduction in synthesis time and efforts without compromising the TE performance. Finally, to analyze the effectiveness of the optimized synthesis route, Ni-doped CoSb3 alloys were also synthesized, and the properties were studied. The effect of “Ni doping” on TE properties of CoSb3 alloys, resulted in n-type conduction, and an enhanced figure-of-merit (ZT) ∼0.61 at around 870 K for optimized composition Ni0.07Co0.93Sb3.