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This study explores the synthesis of AZ61 alloy composite powders with Co-Ni additives using high-energy ball milling (HEBM). The powders are extensively characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) to analyze their morphology, composition, structure, and bonding. The hydrogen storage capacity of the powders is measured using a Sievert's-type system revealing diverse capacities. For AZ61 alloy with Ni additive (2 µm), it absorbs 90% of the capacity in 410 s, showing an activation energy of 91.46 kJmol−1 and displays Mg 2 NiH 4 as an intermediate. On the other hand, AZ61 alloy with Co additive requires 576 s to absorb 90% of the capacity, showing an activation energy of 117.23 kJmol−1 and Mg 2 CoH 5 as an intermediate. When a mixture of Ni and Co is added to AZ61 alloy, it achieves 90% capacity absorption in 300 s. In the absence of additives, AZ61 alloy (15 µm) reaches 90% capacity absorption in 1600 s. The incorporation of additives significantly reduces the activation energy. A correlation between longer absorption times and larger activation energies provides valuable insights into the storage kinetics and activation energy associated with the hydrogen absorption/desorption process. [Display omitted] • The addition of Ni, Co, and a mixture of Ni and Co to the AZ61 alloy enhances its hydrogen storage capacity compared to the alloy without additives. • The hydrogen storage capacities of the AZ61 alloy with Ni, Co, and Ni-Co additives were measured to be 4.5 wt%, 5.316 wt%, and 5.14 wt%, respectively. • The presence of specific reaction intermediates, such as Mg 2 NiH 4 and Mg 2 CoH 5 , was confirmed through XRD patterns, indicating their role in the hydrogen absorption process and promoting reversibility and cycle stability. • The activation energy for hydrogen absorption in the AZ61 alloy with Co additive was found to be 117.23 kJ/mol while that of Ni was 91.46 kJ/mol. • Kinetics to achieve 90% capacity: AZ61 alloy with Ni additive requiring 410 s, the alloy with Co additive requiring 576 s, the alloy with Ni and Co mixture requiring 300 s, and the alloy without additives requiring 1600 s. These results highlight the influence of additive composition on the kinetics of hydrogen absorption. [ABSTRACT FROM AUTHOR]

In this study, commercial AZ31 Mg alloys were processed by equal channel angular pressing (ECAP) to study the effects of processing route and numbers of passes on hydrogen storage properties of AZ31 alloys. Furthermore, Mg-based metal matrix composites (MMCs) were fabricated by gravimetric casting of AZ31 alloy, activated carbon and Ni to investigate the effect of additives on hydrogen storage properties. The results indicated that kinetics of hydrogen uptake increased with the increasing number of pass. AZ31 processed by ECAP route B c with 8 passes had hydrogen capacity of 7.0 wt%, and demonstrated the highest grain refinement and the fastest hydrogen absorption kinetics. With the addition of 5 wt% of activated carbon and 0.5 wt% Ni, the hydrogen sorption kinetics of MMCs was enhanced and was comparable to that of the AZ31 processed by ECAP with 8 passes; however, in exchange for the improved kinetics, the hydrogen storage capacity was lowered to 6.3 wt%. To enhance hydrogen absorption kinetics, adding catalysts in the casting process could be more efficient than post-casting ECAP treatment if saving processing time is the priority. [ABSTRACT FROM AUTHOR]

We studied the hydrogen storage properties of commercial AZ31 and AZ91 magnesium alloys with refined microstructure. Various processing techniques, such as equal channel angular pressing (ECAP) and high energy ball milling (HEBM), were utilized to modify the microstructure and phase composition of the alloys. X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical digital microscopy (ODM) were utilized to characterise the microstructure and phase transformations during the hydrogen absorption/desorption processes. The isothermal kinetics are measured by a Sieverts'-type apparatus at the temperature of 350 ℃. In the ECAP process, the AZ31 alloy had a slightly higher storage capacity and faster absorption kinetics, absorbing 6.0 wt% (6.6 wt% - maximum) of hydrogen in less than 12 min. In the HEBM process, AZ91 absorbed 6.5 wt% of hydrogen and desorbed it in 347 ± 13 s, a faster rate than AZ31. The pressure–composition isotherms of all studied alloys at a temperature of 300 °C were determined. The processed alloys exhibited no pressure hysteresis. The microstructure of bulk samples and the morphology of prepared powders were shown to affect their hydrogenation behaviour. The activation energies for hydrogen desorption were 119 ± 2 kJ/mol for AZ31 alloy processed by ECAP and 128 ± 3 kJ/mol for AZ91 alloy processed by HEBM, which are significantly lower than the activation energy values of pure Mg hydride. • Hydrogen storage properties of commercial AZ31 and AZ91 alloys are studied. • The ECAP and HEBM processes were employed to enhance hydrogen storage performance. • Both processes significantly improved the kinetic and thermodynamics properties. • The processed alloys exhibited no pressure hysteresis • The activation energies reduced to 119 ± 5 kJ/mol for AZ31-ECAP and 128 ± 5 kJ/mol for AZ91-HEBM. [ABSTRACT FROM AUTHOR]

The process engineering of Mg alloys is nevertheless compromised due to their relatively poor mechanical properties. To address some of these difficulties, metal-matrix composites (MMCs) of Mg-alloys have been investigated for sometime. In the present work, small amounts (up to 1 wt%) of WS 2 nanotubes are mixed with Mg-alloy (AZ31) using melt-stirring process above 700 °C. The new MMC nanocomposites exhibit much superior mechanical properties vis a vis the pristine alloy. Metallographic investigation demonstrates that the average grain size has been reduced in inverse proportion to the added amounts of nanotubes up to 1 wt%. Physical considerations suggest that the main mechanism responsible for the reinforcement effect lies in the mismatch between the thermal expansion coefficients of the metal and the nanotubes. This mismatch induced large density of dislocations in the grain boundaries in the vicinity of the nanotube-matrix interface, which obstruct the crack propagation. [ABSTRACT FROM AUTHOR]

Magnesium is the lightest metal and is extensive in the structural application. The metal matrix composites are developed to improve the strength of magnesium alloys. In this research, AZ91 alloy reinforced with 1 wt% WS 2 was produced using stir casting process. The composite was homogenized for 24 h at 410 °C and subsequently aged for 10 h at 200 °C. The severe plastic deformation was performed using equal channel angular pressing (ECAP). The phase composition was analyzed using X-ray diffraction techniques. The microstructure, fractography, and mechanical properties of ECAPed composites have been investigated using scanning electron microscope, and universal testing machines, respectively. The results indicate that B-phases are present in the form of particles inside and at grain boundaries in annealed composites, which are refined to needle-shaped precipitates at grain boundaries, and grains size is refined to 0.2 μm after 4passes of ECAP. Microhardness and tensile yield strength are proportional to the number of passes, and 20.45% and 103.5% are increased respectively after 4pass. The UTS was found to be maximum (324.8 MPa) for 4P WS 2 /AZ91. Fractography analysis revealed that plastic fracture in annealed and elastic-plastic fracture occurred after 4P WS 2 /AZ91 MMC. • WS 2 /AZ91 (MMCs) were manufactured by stir casting method and subsequently annealed are deformed by ECAP. • ECAP effects on microstructure and mechanical behavior of WS 2 /AZ91 MMCs have been investigated. • The relation between number of passes and strength has been established. • The investigations reveal that 4pass-WS 2 /AZ91 exhibits maximum hardness and ultimate tensile strength. [ABSTRACT FROM AUTHOR]

In this work, AZ91 magnesium alloy reinforced with a low fraction (0–1) wt.% tungsten disulfide(WS 2) microparticles have been fabricated using stir casting method. Effects of WS 2 microparticles on mechanical properties, microstructure, and their correlation have been analyzed. The microstructure of composites has been investigated by scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffractometer. Results indicate that density, hardness, ultimate tensile strength (UTS), and tensile ductility have a direct relation with reinforcement (WS 2) contents and has optimal value for 0.6 wt% WS 2 /AZ91 composites then slightly decrease afterward. The UTS and hardness of 0.6 wt%WS 2 /AZ91 were increased by 23.23% and 10.65% respectively with respect to monolithic AZ91. The ultimate compressive strength(UCS) is directly related with WS 2 concentration and 10.07% enhancement in UCS for 1 wt%WS 2 /AZ91 composites have been noted. The trend is interlinked with density and hardness of composites. SEM images depict, WS 2 micro-particles suppress β-Mg 17 Al 12 precipitates, refine the microstructure and enhance the grain size resulting in an increase in mechanical properties. The improvement in microstructure and mechanical properties is attributed to the dispersion of WS 2 particles which hinder the grain growth. The increase in porosity has causes the decrease in mechanical behavior of 1 wt%WS 2 /AZ91. Twin boundary fracture has been found major fracture phenomenon in fractured WS 2 /AZ91 surfaces. • WS 2 /AZ91 metal matrix composites have been manufacture by stir casting method. • Density and porosity of WS 2 /AZ91 composites has been assessed. • Mechanical behavior under compression and tension has been analyzed. • Effect of WS 2 on microstructure has been investigated. • Fracture behavior of composites has been studied. [ABSTRACT FROM AUTHOR]

Abstract We developed a simple room-temperature synthetic route that achieves well-crystallized Pb 100− x Ag x Se alloy thin films by chemical bath deposition (CBD). The strategy provides a new paradigm to synthesize Ag doped PbSe thin films in one-step. We show that uniform distributed Pb 100− x Ag x Se thin films can be produced, whose crystal structure, morphology, and optical properties could be tailored with Ag concentration. With increasing x , both the shape and size of crystals are changing. Besides, the growth mechanism transits from cluster to ion by ion (IBI). The optical band gap (E g) of the thin films is found to linearly increase with x values, from 0.26 eV to 0.31 eV. The density of states (DOS) and energy band structure of Pb 100− x Ag x Se are calculated using the first principle method. The calculation shows that Se 4p hybrids with Ag 4d at the valance band maximum, and the contribution to the conduction band minimum is mainly from Pb 6p and Ag 5s. The energy band gap shows the same tendency with Ag concentration as that in the experiment. Highlights • Pb 100− x Ag x Se alloy thin films were chemically fabricated in one-step. • Both crystallite size and growth mechanism depend on Ag composition. • E g of the Pb 100− x Ag x Se thin films could be tailored by x. • CASTEP calculation shows the same tendency for E g with experiments. [ABSTRACT FROM AUTHOR]

Abstract: Hf1−x Ta x Fe2 pseudobinary alloy with x =0.18 was prepared. It was found to crystallize in C14 type Laves phase structure examined by X-ray diffraction (XRD). Mössbauer spectra at varied temperatures show there are two transition temperatures, one for paramagnetic (PM) to antiferromagnetic (AFM) state at about 330K, and the other for AFM to ferromagnetic (FM) state at about 180K. In the latter transition, spin reorientation is observed. The spin of Fe magnetic moment at 6h is along c axis in AFM state while lie close to ab-plane in FM state. No magnetic interaction at 2a site is found in AFM state but FM. The hyperfine field anisotropy at 6h site in FM state is also analyzed. [Copyright &y& Elsevier]