Enhanced hydrogen storage properties of NaBH4–Mg(BH4)2 composites by NdF3 addition

As two important members of complex hydrides, Mg(BH₄)₂ and NaBH₄ have a high gravimetric capacity (14.9 and 10.8 ​wt%, respectively). In this study, the Mg(BH₄)₂ was synthesized by the ion exchange method. Afterwards, the Mg(BH₄)₂ and NaBH₄ composites with different amounts (30, 40 and 50 ​wt%) of NdF₃ were prepared by mechanical milling. Effects of the NdF₃ on the microstructural evolution and hydrogen storage properties were investigated. The results show that NdF₃ catalyst can significantly improve the dehydrogenation kinetics of the eutectic composites of NaBH₄–Mg(BH₄)₂. The onset hydrogen desorption temperature of the composites is about 88.6 ​°C, which is about 110 ​°C lower than that of Mg(BH₄)₂ and NaBH₄ composites. Mg(BH₄)₂–NaBH₄-0.5NdF₃ composites can released 5.2 ​wt% H₂ at 250 ​°C within 30 ​min, and the dehydrogenation capacity is significantly higher than that of Mg(BH₄)₂–NaBH₄ composites. The analysis of the dehydrogenation mechanism reveals that NdF₃ takes participate in the reaction to generate NaMgF₃ to promote the dehydrogenation reaction process of the composites.     

Improvement in hydrogen storage performance of Mg by mechanical grinding with molten salt etching Ti3C2Clx

Mg-based materials are currently a hot research topic as hydrogen storage materials due to their considerable theoretical hydrogen storage capacity. However, the kinetic performance of hydrogen absorption and desorption of Mg is too slow and requires high temperature, which seriously hinders the application of this material. MXene is a new type of two-dimensional material with significant role in improving thermodynamics and kinetics. In this experiment, a two-dimensional layered MXene containing Cl functional group was prepared by molten salt etching using the Ti-containing MAX phase as the raw material. Then different ratios of Ti₃C₂Cl_x were uniformly dispersed onto the surface of Mg by high energy ball milling. The samples were characterized by hydrogen absorption and desorption kinetics, SEM, XRD, XPS, and DSC to investigate the effect of Ti₃C₂Cl_x on the hydrogen absorption and desorption performance of Mg. The onset hydrogen absorption temperature can be reduced to room temperature and the hydrogen release temperature is reduced by 200 ​°C by doping Ti₃C₂Cl_x. And there is also 5.4 ​wt% hydrogen storage in the isothermal hydrogen absorption test at 400 ​°C. The results of DSC demonstrate that the E_a of Mg+15 ​wt% Ti₃C₂Cl_x was reduced by 12.6% compared to pristine Mg. The ΔH is almost invariable. The results of XPS show that the presence of multivalent Ti promotes electron transfer and thus improves the conversion between Mg²⁺/Mg and H⁻/H. This study provides a guideline for further improving the hydrogen absorption and desorption performance of Mg-based hydrogen storage materials.     

Microstructure and electrical conductivity of 10% Yb-doped SrCeO3 ceramics

As a candidate material for hydrogen separation, Yb-doped SrCeO₃ has attracted increasing attention in recent decades. In the present study, Yb-doped SrCe_0.9Yb_0.1O_3-α ceramics were prepared by the dry pressing and sintering approach, with the microstructure evolution and the micro morphology investigated. It was indicated that the ceramics sintered in air were of a pure perovskite structure, and that the sintering temperature had a significant effect on the growth of ceramic grains. The average grain size increased from 1 ​μm to 10 ​μm with an increase in sintering temperature from 1300 to 1500 ​°C. Further investigation of the thermodynamics and kinetics of grain growth revealed that the grain boundary diffusion was the main driving force of grain growth during solid phase sintering, with a grain growth index of 4 and an activation energy of approximately 61.23 ​kJ ​mol⁻¹. These results illustrate an obvious tendency of grain size growth. By electrochemical workstation with different atmospheres the effects of sintering temperature on the conductivity were characterized in the temperature range of 700–900 ​°C. The electrical conductivities σ of SrCe_0.9Yb_0.1O_3-α ceramics in different atmospheres were as follows: σ(wet hydrogen) ​> ​σ(dry hydrogen) ​> ​σ(dry air) ​> ​σ(wet air). In the test atmosphere containing water and hydrogen the conductivity of protons increased with increasing temperature because of the protons jump between lattices in the form of interstitial hydrogen ions or bare protons.     

Corrosion resistance and thermal stability of sputtered Fe44Al34Ti7N15 and Al61Ti11N28 thin films for prospective application in oil and gas industry

Fe-and Al-based thin-film metallic glass coatings (Fe₄₄Al₃₄Ti₇N₁₅ and Al₆₁Ti₁₁N₂₈) were fabricated using magnetron co-sputtering technique, and their corrosion performances compared against wrought 316L stainless steel. The results of GI-XRD and XPS analyses demonstrated amorphous structure and oxide layer formation on the surface of the fabricated thin films, respectively. The potentiodynamic (PD) polarization test in chloride-thiosulfate (NH₄Cl ​+ ​Na₂S₂O₃) solution revealed lower corrosion current (I_corr) (0.42 ​± ​0.02 ​μA/cm² and 0.086 ​± ​0.001 ​μA/cm² Vs. 0.76 ​± ​0.05 ​μA/cm²), lower passivation current (I_pass) (1.45 ​± ​0.03 ​μA/cm² and 1.83 ​± ​0.07 ​μA/cm² Vs. 1.98 ​± ​0.04 ​μA/cm²), and approximately six-fold higher breakdown potential (E_bd) for Fe- and Al-based coatings than those of wrought 316L stainless steel. Electrochemical Impedance Spectroscopy (EIS) of both films showed 4- and 2-fold higher charge transfer resistance (R_ct), 7- and 2.5-times higher film resistance (R_f), lower film capacitance values (Q_f) (10 ​± ​2.4 ​μS-s^acm^-2, and 5.41 ​± ​0.8 ​μS-s^acm^-2 Vs. 18 ​± ​2.21 ​μS-s^acm^-2), and lower double-layer capacitance values (Q_dl) (31.33 ​± ​4.74 ​μS-s^acm^-2, and 15.3 ​± ​0.48 ​μS-s^acm^-2 Vs. 43 ​± ​4.23 ​μS-s^acm^-2), indicating higher corrosion resistance of the thin films. Cyclic Voltammetry (CV) scan exhibited that the passive films formed on the Fe- and Al-based coatings were more stable and less prone to pitting corrosion than the wrought 316L stainless steel. The surface morphology of both films via SEM endorsed the CV scan results, showing better resistance to pitting corrosion. Furthermore, the thermal analysis via TGA and DSC revealed the excellent thermal stability of the thin films over a wide temperature range typically observed in oil-gas industries.     

Dehydrogenation and reaction pathway of Perovskite-Type NH4Ca(BH4)3

Perovskite-type borohydride, NH_4Ca(BH_4)_3, is considered as a promising hydrogen storage material due to its high gravimetric hydrogen capacity(15.7 wt%). In this work, the dehydrogenation performance and reaction pathway of NH_4Ca(BH_4)_3 have been systematically investigated. It is found that the initial decomposition temperature is only 65 °C, suggesting a low thermodynamic stability of NH4Ca(BH4)3. The desorption kinetics conducted by differential scanning calorimetry(DSC) indicates that the activation energy of decomposition is about 226.1 k J/mol. The dehydrogenation pathway of NH_4Ca(BH_4)_3 characterized by fourier-transform infrared spectroscopy(FTIR) and solid-state nuclear magnetic resonance(NMR) shows a stepwise decomposition process,in which the initial dehydrogenation is due to destabilization of H~+ in NH4 and H-in BH4 followed by the subsequent dehydrogenation steps arising from the decomposition of homologous NH_3BH_3 and the final decomposition of Ca(BH_4)_2 at a high temperature, respectively.     

Ameliorating mechanical properties and reducing anisotropy of as-extruded Mg-1.0Sn-0.5Ca alloy via Al addition

Effects of Al addition to a Mg–Sn–Ca ternary alloy on its microstructure and tensile properties after extrusion were studied via extrusion of Mg-1.0Sn-0.5Ca-xAl (x ​= ​0, 0.8, 2.4 ​wt%) sheets and analysis of the extruded materials. The results showed that Al addition not only refined the grain size (from 9.8 ​± ​0.7 ​μm to 8.3 ​± ​0.4 ​μm and 7.6 ​± ​0.5 ​μm) but also accelerated the generation of more second phase (from 0.98 to 1.72 and 4.32%). Except for the CaMgSn and Mg₂Ca in Mg-1.0Sn-0.5Ca alloy, new phase (Mg, Al)₂Ca appeared after Al addition. The addition of Al into Mg–Sn–Ca alloy induced the textural variation from an initially ED-split double-peaked texture to a weakened texture, i.e., divergent elliptical texture, due to the effect of particle stimulated nucleation. This eventually contributed to the improvement of mechanical anisotropy as well as the higher Hc value and n-value. For the strain hardening behavior when tension along the TD, the prolonged stage Ⅱ of Al-modified alloys was closely connected with the additional TD textural components, accelerating the activation of more basal slip. The decreased θⅢ0 in stage Ⅲ of Al-modified alloys is beneficial to the grain refinement and the emergence of more second phase.     

Towards understanding the influence of Mg content on phase transformations in the La3-xMgxNi9 alloys by in-situ neutron powder diffraction study

The present work is focused on the studies of the phase-structural transformations in the La_3-xMg_xNi₉ (x ​= ​1.0, 1.1 and 1.2) alloys as active materials of negative electrodes in the Nickel-Metal Hydride (Ni/MH) batteries. The phase equilibria and phase-structural transformations in the alloys were probed by in situ neutron powder diffraction (NPD) at the temperatures ranging from 300 ​K to 1273 ​K using the measurements of the equilibrated alloys at 8 setpoint temperatures of 300, 973, 1073, 1123, 1173, 1223, 1248 and 1273 ​K.Prepared by induction melting initial alloys were found to be multi-phase structured, containing up to 6 individual intermetallic compounds with different stoichiometric compositions. With the increase of the temperature and holding time, various transformations took place in the studied alloys. These included the formations and transformations of super-stacking intermetallics with variable ratios (La ​+ ​Mg)/Ni, 1:3, 2:7 and 5:19.With increasing temperatures, several systematic changes took place. (a) Abundances of (La,Mg)₂Ni₄ AB₂ and (La,Mg)Ni₃ AB₃ type intermetallics gradually decreased before they melted/decomposed above 1073 ​K; (b) The (La,Mg)₂Ni₇ A₂B₇ type intermetallics began to decrease in abundances above 1123 ​K; (c) The transformation in the (La,Mg)₅Ni₁₉ intermetallics from 3R to 2H proceeded above 1223 ​K.The increase of Mg content had no obvious influence on (La,Mg)₂Ni₄ and (La,Mg)₂Ni₇ phases, and corresponding reactions R1 and R3 took place at the same temperatures as in the La–Ni system. However, with increasing Mg content the melting point of (La,Mg)₅Ni₁₉ phase increased while the melting point of the (La,Mg)Ni₃ phase it decreased, leading to the variation of the reaction temperatures of the corresponding processes.The present study will assist in optimizing phase-structural composition of the alloys in the La–Mg–Ni system which contain Mg-modified layered structures by tailoring the high temperature annealing conditions.     

Effect of Mn content on the microstructure and mechanical properties of Mg–6Li–4Zn-xMn alloys

The as-cast Mg–6Li–4Zn-xMn alloys were prepared and extruded at 280 ​°C with an extrusion ratio of 25:1. The effects of Mn content on the microstructure and mechanical properties of Mg–6Li–4Zn-xMn alloys were investigated in this study. The XRD results show that Mg–6Li–4Zn–xMn alloys consisted of α-Mg (hcp) ​+ ​β-Li (bcc) duplex structured matrix, MgLi₂Zn and Mn phases. The grains of the extruded Mg–6Li–4Zn–xMn alloys were refined by dynamic recrystallization during the extrusion process. The EBSD results show that the extruded alloys had basal textures. The grain size of the extruded alloys decreased while the basal texture was strengthened with the increasing Mn addition. The TEM results show that a large amount of nanoscale Mn precipitates existed in the extruded Mg–6Li–4Zn–1.2Mn alloy, which can effectively inhibit the dynamic recrystallized (DRXed) grains growth during the hot extrusion and is beneficial to the improvement of mechanical properties. Mg–6Li–4Zn–1.2Mn alloy in this research possesses the best mechanical properties with the ultimate tensile strength and yield strength of 321 ​MPa, 250 ​MPa, respectively.     

Synthesis and characterization of nano-hydroxyapatite added with magnesium obtained by wet chemical precipitation

Biogenic hydroxyapatites from mammalian bones naturally contain traces of ions, like Mg, which play a vital role in the bone remodeling process. In this way, synthetic hydroxyapatites should include this kind of mineral. In this work, hydroxyapatite added with Mg was synthesized by wet precipitation using (NH₄)H₂PO₄, Ca(NO₃)₂.4H₂O, and Mg(NO₃)₂.6H₂O (0, 0.032, 0.061, and 0.123 ​M). Inductively coupled plasma and X-ray diffraction evidenced the Mg inclusion in the hydroxyapatite lattice in the same levels reported for natural hydroxyapatites. The calcination at 600 ​°C was performed to remove the reaction by-products, but it also gave rise to physicochemical changes as the coalescence and crystals recrystallization. It produced, in turn, an improvement in the crystalline quality, according to Raman analysis. Despite those physicochemical changes, all the samples remained nanometric according to scanning electron microscopy imaging.     

FeCo-based mesoporous carbon shells modified N-doped porous carbon spheres for oxygen reduction reaction

FeCo-based non-noble metal electrocatalysts (NNMEs) of FeCo/MCS-NPCS was fabricated by immobilization of hemin on mesoporous carbon shells modified N-doped porous carbon spheres (MCS-NPCS). The obtained FeCo/MCS-NPCS exhibits a half-wave potential (E_1/2) of 0.851 ​V versus the reversible hydrogen electrode (vs. RHE) and a limited-diffusion current density (J_L) of 5.45 ​mA ​cm⁻². In addition, FeCo/MCS-NPCS shows comparable oxygen reduction reaction (ORR) performances to 20 ​wt% Pt/C in terms of E_1/2 and J_L and better electrochemical properties, including the methanol tolerance and durability in alkaline solution. Such outstanding electrochemical activities of FeCo/MCS-NPCS can be ascribed to Fe and/or Co-based nitrides and carbides as well as N-doped carbon matrixes modified with mesoporous carbon shells. This research introduces a promising path to design and synthesize highly efficient FeCo–N–C electrocatalysts towards ORR.     

Synthesis of amorphous SeP2/C composite by plasma assisted ball milling for high-performance anode materials of lithium and sodium-ion batteries

To promote substantially the performances of red phosphorous (P) anode for lithium and sodium-ion batteries, a simple plasma assisted milling (P-milling) method was used to in-situ synthesize SeP₂/C composite. The results showed that the amorphous SeP₂/C composite exhibits the excellent lithium and sodium storage performances duo to the small nano-granules size and complete combination of selenium (Se) and phosphorous (P) to generate Se–P alloy phase. It was observed that inside the granules of SeP₂/C composite the nanometer size of the SeP₂ particles ensured the fast kinetics for Li⁺ and Na⁺ ​transfer, and the amorphous carbon wrapping the SeP₂ particles relieved volume expansion during lithium/sodium storage processes and enhances electric conductivity. Therefore, the SeP₂/C electrode retained reversible capacities of 700 ​mA ​h ​g⁻¹ at 2 ​A ​g⁻¹ after 500 cycles and 400 ​mA ​h ​g⁻¹ at 0.5 ​A ​g⁻¹ after 400 cycles as anode for LIBs and SIBs, respectively. The result proves that the amorphous SeP₂/C composite can be a new type of anode material with great potential for lithium and sodium-ion batteries.     

Improvement on hydrogen generation properties of Zr(BH_4)_4·8NH_3

Hydrolysis of Zr(BH_4)_4·8NH_3 in deionized water can generate high purity hydrogen at room temperature.However, the sluggish hydrolysis kinetics of Zr(BH_4)_4·8NH_3 hinders its practical use. To improve its hydrogen generation properties, the effects of magnetic stirring, changing hydrolysis solution and tuning the ammonia coordination number on the hydrolysis properties of Zr(BH_4)_4·8NH_3 were investigated. Results show that both changing hydrolysis solution and tuning the ammonia coordination number can enhance the hydrolysis kinetics.The hydrolysis kinetics properties of Zr(BH_4)_4·8NH_3 were significantly improved in MgCl_2 and CoCl_2 solutions.The Zr(BH_4)_4·8NH_3(x ≤ 8) samples were synthesized by a ball-milling method with different ammonization time(10, 60 and 180 min). Both the hydrolysis kinetics and hydrogen yield of Zr(BH_4)_4·8NH_3(x ≤ 8) were enhanced as the ammonia coordination number(x) decreased. Thus, tuning ammonia coordination number is an effective way to control the hydrolysis properties of Zr(BH_4)_4·8NH_3(x ≤ 8).     

Large specific surface area S-doped Fe–N–C electrocatalysts derived from Metal–Organic frameworks for oxygen reduction reaction

It is highly desired but challenging to develop platinum group metal-free electrocatalysts for oxygen reduction reaction (ORR), which can promote the commercialization of fuel cell technology. To achieve this target, we report a one-step doping method to prepare S-doped Fe–N–C catalysts using zeolite imidazole framework (ZIF-8) and iron (III) thiocyanate (Fe(SCN)₃) as precursor. Different from conventional doping approach, i.e. physical mixing, Fe(SCN)₃ is in-situ added during ZIF-8 formation which would encapsulate Fe(SCN)₃ molecules inside ZIF-8 to avoid structure destruction and create potential replacement of Zn ions by Fe ions to form uniform Fe–N₄ complexes. As a result, the prepared S-doped Fe–N–C catalysts own large specific surface areas with a maximum value of 1326 ​m² ​g⁻¹ and a dual-scale porous structure that benefits mass transport. Significantly, the composition-optimized catalyst exhibits superior ORR activity in both 0.1 ​M HClO₄ electrolyte and 0.1 ​M KOH electrolyte, in which the half-wave potential reaches 0.81 ​V and 0.92 ​V (vs. RHE), respectively. Remarkable stability is also attained, which loses 2 ​mV only after 10000 potential cycles in O₂-saturated 0.1 ​M HClO₄ and remains almost constant in O₂-saturated 0.1 ​M KOH, surpassing commercial Pt/C catalyst in both acidic and alkaline medium.     

Binder- and conductive additive-free Ga2O3 nanowires as a self-healing anode for lithium storage

High-capacity anode materials have stimulated much attention to developing high-performance lithium-ion batteries. However, high-capacity anode materials commonly suffer from the pulverization matter that greatly hinders their practical applications, especially in terms of the high proportion of active materials. In this work, a Ga₂O₃ nanowire electrode is synthesized by thermal evaporation and immediately used as an anode without the aid of binders and conductive additives. The 3D interconnected architecture of the Ga₂O₃ nanowire electrode shortens lithium diffusion lengths and expedites reaction kinetics. The Ga₂O₃ nanowires exhibit high elasticity and a self-healing ability which is inherited from metallic Ga formed during the electrochemical transition process, thus circumventing the formidable pulverization issue to a certain extent. Benefiting from the unique structural, mechanical, and chemical attributes, the as-grown Ga₂O₃ nanowire electrode gives a high initial lithiation capacity of 1462 mAh g⁻¹ under a current density of 0.1 ​A ​g⁻¹. It delivers good cyclic stability with a reversible capacity of 445 mAh g⁻¹ after 200 cycles at 0.5 ​A ​g⁻¹. Furthermore, the investigation of lithium storage behaviors indicates the high rate capability of Ga₂O₃ nanowires. This paper contributes to understanding binder- and conductive additive-free electrodes consisting of high-capacity active materials from various viewpoints.     

Hydrogen absorption-desorption characteristic of (Ti0.85Zr0.15)1.1Cr1-xMoxMn based alloys with C14 Laves phase

The microstructure and hydrogen absorption-desorption characteristic of (Ti_0.85Zr_0.15)_1.1Cr_1-xMo_xMn (x ?= ?0.05, 0.1, 0.15, 0.2 ?at.%) alloys were investigated. The results showed that the corresponding alloys were determined as a single phase of C14-type Laves structure. With the increase of Mo content, the maximum and reversible hydrogen absorption capacity decreased, the slope factor H_f increased. Among the studied alloys, (Ti_0.85Zr_0.15)_1.1Cr_0.95Mo_0.05Mn had the best overall properties for practical application of hydrogen storage materials. The maximum and reversible hydrogen storage capacity were 1.76 ?wt% and 1.09 ?wt%, the slope factor H_f was 0.51, and its dissociation enthalpy (ΔH_d) and entropy change (ΔS_d) were 23.1 ?kJ ?mol^?1H₂, 93.8J ?K^?1mol^?1H₂ at 303K, respectively. By studying the dissociation pressures of the synthesized metal hydrides, it was found that Mo had a special effect on the dissociation pressure of Ti–Zr–Cr–Mo–Mn alloys. Among the four alloys, (Ti_0.85Zr_0.15)_1.1Cr_0.95Mo_0.05Mn alloy had the largest hydrogen absorption capacity and the fastest hydrogen desorption rate, which can meet the commercialization demand of hydrogen fuel cell hydrogen supply system.     

Hydrogen absorption-desorption cycle decay mechanism of palladium nanoparticle decorated nitrogen doped graphene

As a hydrogen storage material, palladium nanoparticle decorated nitrogen doped graphene (Pd/N-rGO) has drawn much attention owing to its high absorption capacity at moderate conditions. However, its hydrogen absorption-desorption cycle performance, which is essential for their practical application, has been rarely studied. In this paper, a simple and convenient high temperature thermal reduction method was used to synthesize nitrogen-doped graphene decorated with Pd nanoparticles (Pd/N-rGO). Taken it as a representative, the hydrogen absorption-desorption cycle performance of Pd/N-rGO was investigated. The results showed that after three cycles the hydrogen storage capacity dropped from 2.9 ​wt% to 0.8 ​wt% at 25 ​°C and 4 ​MPa pressure. It was found that the palladium nanoparticles shed from Pd/N-RGO sheet after cycle performance test, and then agglomerated. These phenomena will weaken the hydrogen spillover effect, leading to the decrease of hydrogen storage capacity. Meanwhile, decreased defects reduce the hydrogen absorption sites, which will thus deteriorate the hydrogen storage capacity.     

Reversible hydrogenation of AB2-type Zr–Mg–Ni–V based hydrogen storage alloys

The development of hydrogen energy is hindered by the lack of high-efficiency hydrogen storage materials. To explore new high-capacity hydrogen storage alloys, reversible hydrogen storage in AB₂-type alloy is realized by using A or B-side elemental substitution. The substitution of small atomic-radius element Zr and Mg on A-side of YNi₂ and partial substitution of large atomic-radius element V on B-side of YNi₂ alloy was investigated in this study. The obtained ZrMgNi₄, ZrMgNi₃V, and ZrMgNi₂V₂ alloys remained single Laves phase structure at as-annealed, hydrogenated and dehydrogenated states, indicating that the hydrogen-induced amorphization and disproportionation was eliminated. From ZrMgNi₄ to ZrMgNi₂V₂ with the increase of the degree of vanadium substitution, the reversible hydrogen storage capacity increased from 0.6 ?wt% (0.35H/M) to 1.8 ?wt% (1.0H/M), meanwhile the lattice stability gradually increased. The ZrMgNi₂V₂ alloy could absorb 1.8 ?wt% hydrogen in about 2 ?h ?at 300 ?K under 4 ?MPa H₂ pressure and reversibly desorb the absorbed hydrogen in approximately 30 ?min ?at 473 ?K without complicated activation process. The prominent properties of ZrMgNi₂V₂ elucidate its high potential for hydrogen storage application.     

Effects of heat treatment on microstructure and mechanical properties of SLMed Sc-modified AlSi10Mg alloy

The influence of heat treatments on the microstructures and mechanical properties of the selective laser melting manufactured AlSi10Mg alloy modified with Sc was systematically investigated. The results showed that the addition of Sc element introduced primary Al₃Sc, which increased the heterogeneous nucleation during the solidification of AlSi10Mg alloy, and then the ultrafine network eutectic structure was obtained, and hence the tensile strength was improved significantly (nearly 23 ​%). During the heat treatment process, the network eutectic structure transformed from continuous to discontinuous, and the grain refinement was weakened with an increasing heating temperature, both of which affected the mechanical properties of the Sc modified AlSi10Mg alloy. The tensile strength decreased from 438 ​± ​10 ​MPa for the Sc-modified alloy to 208 ​± ​6 ​MPa, while the fracture strain significantly increased from 6 ​± ​0.2 ​% to 30.2 ​± ​1.2 ​% when the Sc-modified alloy was heat-treated at 325 ​°C for 12 ​h. It has been found that the desirable microstructure and mechanical properties of SLM Sc-modified AlSi10Mg alloy can be realized by controlling the heat treatment process parameters.     

Mechanical behaviors of extruded Mg alloys with high Gd and Nd content

The influence of alloying elements and heat treatment on the microstructure and mechanical behaviors of extruded Mg–Gd–Nd ternary alloys was investigated in this study. The grain sizes dramatically decreased after extrusion, and the particles which distributed in Mg matrix had great effect on the grain size. The grain sizes of extruded alloys decreased from 26 to 5 ​μm with the alloying content increasing. The mechanical test results show that both Gd and Nd had positive effect on the hardness, yield strength and Young's modulus. The ultimate tensile strength (UTS) was enhanced by Gd content, decreased with Nd content. The elongation of alloys was lower with higher alloying elements. Those extruded alloys were aged for 200 ​h in 200 ​°C. The Young's moduli were decreased by ageing treatment. Combined with microstructure study, the part of the reinforcement which identified as Mg₅(Gd/Nd) was dissolved in Mg matrix. Nd element obviously has influence on the solubility of Gd in Mg alloys.     

Catalytic effect of a novel MgC_(0.5)Co_3 compound on the dehydrogenation of MgH_2

The application of magnesium hydride(MgH_2) is limited due to the high reaction temperature and slow kinetics during dehydrogenation. In order to ameliorate the dehydrogenation property of MgH_2, MgC_(0.5)Co_3 compound with induction and catalytic effects was introduced into the Mg/MgH_2 system via ball-milling and hydriding combustion methods in present study. Compared to the pure MgH_2,the initial hydrogen desorption temperature of MgH_2–MgC_(0.5)Co_3 composite lowered to 237°C, decreasing by 141°C. At 325°C the MgH_2–MgC_(0.5)Co_3 composite could release 4.38 wt% H_2 within 60 min, which is 4.5 times the capacity of hydrogen released by as milled-MgH_2. Besides, the hydrogen desorption activation energy of the MgH_2–MgC_(0.5)Co_3 composite was dramatically reduced to 126.7 ± 1.4 k J/mol. It was observed that MgC_(0.5)Co_3 was chemically stable and no chemical transformation occurred after cycling, which not only inhibited the nucleation and growth of composite particles, but also had a positive effect on the hydrogen desorption reaction of MgH_2 due to its catalytic effect.This study may provide references for designing and synthesizing Mg–C–Co alloy compound for the Mg-based hydrogen storage area.