Hydrogen Storage Kinetics Of Alloys Research Articles

Hydrogen storage properties of amorphous and nanocrystalline (Mg24Ni10Cu2)100-xNdx (x = 0–20) alloys

The as-cast and spun (Mg24Ni10Cu2)100-xNdx (x = 0–20) alloys were prepared in this experiment to study their hydrogen storage performances. The alloys were tested on composition, structure, de-/hydriding kinetics and electrochemical property in many ways including XRD, SEM, TEM, Sieverts apparatus and automatic galvanostatic system. It was found that each as-cast alloy is multi-phased, including Mg2Ni-type major phase and some second phases of Mg6Ni, Nd5Mg41 and NdNi, the proportion of which obviously increases with Nd content rising. After being melt spinning, the structure of no-Nd-added alloy is nanocrystalline, while the Nd-added alloy holds an amorphous and nanocrystalline structure, whose amorphization degree rises significantly with Nd content increasing. The hydrogen storage kinetics of alloys can be improved by the addition of Nd significantly. Besides, adding Nd results in the electrochemical discharge capacity of the as-spun alloy augments at first and declines later as well as cycle stability.

An Investigation on Hydrogen Storage Kinetics of the Nanocrystalline and Amorphous LaMg12-type Alloys Synthesized by Mechanical Milling

Nanocrystalline and amorphous LaMg12-type LaMg11Ni + x wt% Ni (x = 100, 200) alloys were synthesized by mechanical milling. Effects of Ni content and milling time on the gaseous and electrochemical hydrogen storage kinetics of as-milled alloys were investigated systematically. The electrochemical hydrogen storage properties of the as-milled alloys were tested by an automatic galvanostatic system. And the gaseous hydrogen storage properties were investigated by Sievert apparatus and a differential scanning calorimeter (DSC) connected with a H2 detector. Hydrogen desorption activation energy of alloy hydrides was estimated by using Arrhenius and Kissinger methods. It is found that the increase of Ni content significantly improves the gaseous and electrochemical hydrogen storage kinetic performances of as-milled alloys. Furthermore, as ball milling time changes, the maximum of both high rate discharge ability (HRD) and the gaseous hydriding rate of as-milled alloys can be obtained. But the hydrogen desorption kinetics of alloys always increases with the extending of milling time. Moreover, the improved gaseous hydrogen storage kinetics of alloys are ascribed to a decrease in the hydrogen desorption activation energy caused by increasing Ni content and milling time.

Improved hydrogen storage kinetics of nanocrystalline and amorphous Pr-Mg-Ni-based PrMg12-type alloys synthesized by mechanical milling

In this paper, the nanocrystalline and amorphous PrMg11Ni + x wt.% Ni (x = 100, 200) alloys were synthesized by mechanical milling. The gaseous and electrochemical hydrogen storage performances were studied in detail. The results reveal that increasing Ni content facilitates the glass forming of the alloys, and it significantly improves the gaseous and electrochemical hydrogen storage kinetics performance. Furthermore, milling time varying significantly affects the hydrogen storage properties of the alloys. The hydrogen capacity of the alloys first increases and then decreases with milling time prolonged. The hydriding rate and high-rate discharge ability (HRD) of the as-milled alloys have maximum values with milling time varying. But dehydriding rate always increases with milling time prolonged. The improved gaseous hydrogen storage kinetics of alloys are convinced to be ascribed to a reduction in hydrogen desorption activation energy caused by increasing Ni content and prolonging milling time.

Hydrogen Storage Characteristics of Nanocrystalline and Amorphous Nd-Mg-Ni-Based NdMg12-Type Alloys Synthesized via Mechanical Milling

In this study, Mg was partially substituted by Ni with the intent of improving the hydrogen storage kinetics performance of NdMg12-type alloy. Mechanical milling technology was adopted to fabricate the nanocrystalline and amorphous NdMg11Ni + x wt pct Ni (x = 100, 200) alloys. The effects of Ni content and milling duration on the microstructures and hydrogen storage kinetics of as-milled alloys have been systematically investigated. The structures were characterized by XRD and HRTEM. The electrochemical hydrogen storage properties were tested by an automatic galvanostatic system. Moreover, the gaseous hydrogen storage properties were investigated by Sievert apparatus and a differential scanning calorimeter connected with a H2 detector. Hydrogen desorption activation energy of alloy hydrides was estimated by using Arrhenius and Kissinger methods. The results reveal that the increase of Ni content dramatically ameliorates the gaseous and electrochemical hydrogen storage kinetics performance of the as-milled alloys. Furthermore, high rate discharge ability (HRD) reach the maximum value with the variation of milling time. The maximum HRDs of the NdMg11Ni + x wt pct Ni (x = 100, 200) alloys are 80.24 and 85.17 pct. The improved gaseous hydrogen storage kinetics of alloys via increasing Ni content and milling time can be attributed to a decrease in the hydrogen desorption activation energy.

Hydrogen storage kinetics of nanocrystalline and amorphous NdMg12-type alloy–Ni composites synthesized by mechanical milling

Abstract Nanocrystalline and amorphous NdMg11Ni + x wt.% Ni (x = 100, 200) composites were synthesized by mechanical milling, and their gaseous and electrochemical hydrogen storage kinetic performances were systematically investigated. Hydrogen absorption and desorption properties were investigated by means of a Sievert apparatus and a differential scanning calorimeter connected with an H2 detector. Electrochemical hydrogen storage kinetics of the as-milled alloys were tested by an automatic galvanostatic system. Results show that increasing Ni content significantly improves gaseous and electrochemical hydrogen storage kinetics. The improved gaseous hydrogen storage kinetics of the alloys are ascribed to the decrease in hydrogen desorption activation energy caused by increasing Ni content and milling time.

An investigation on hydrogen storage thermodynamics and kinetics of Nd–Mg–Ni-based alloys synthesized by mechanical milling

In order to improve the hydrogen storage kinetics of NdMg12-type alloy, the Mg in the alloy was partially substituted by Ni, and mechanical milling technology was used to fabricate the nanocrystalline and amorphous NdMg11Ni + x wt.% Ni (x = 100, 200) alloys. Effects of Ni content and milling time on the gaseous hydrogen storage thermodynamics and kinetics of alloys were investigated systematically. The structures of as-cast and milled alloys were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscope (HRTEM). The pressure-composition isotherms (P-C-T) and the hydrogen absorption and desorption kinetics of the as-milled alloys were measured by an automatically controlled Sievert's apparatus and a differential scanning calorimetry (DSC) (SDT-Q600) with a H2 detector. Thermodynamic parameters (ΔH and ΔS) for the hydrogen absorption and desorption of alloys were calculated from Van't Hoff equation. Hydrogen desorption activation energy of alloy hydride was also estimated by using Arrhenius and Kissinger methods. It is found that the variation of Ni content brings on a slight effect on the thermodynamic properties of the alloys, but it significantly improves the hydrogen absorption and desorption kinetics. The improved gaseous hydrogen storage kinetics of alloys are considered to be ascribed to a decrease in hydrogen desorption activation energy caused by increasing Ni content and prolonging milling time.

Influences of substituting Ni with M (M=Cu, Co, Mn) on gaseous and electrochemical hydrogen storage kinetics of Mg20Ni10 alloys

In this work, a comprehensive comparison regarding the impacts of M (M=Cu, Co, Mn) substitution for Ni on the structures and the hydrogen storage kinetics of the nanocrystalline and amorphous Mg20Ni10−xMx (M=Cu, Co, Mn; x=0–4) alloys prepared by melt spinning has been carried out. The analysis of XRD and TEM reveals that the as-spun (M=None, Cu) alloys display an entire nanocrystalline structure, whereas the as-spun (M=Co, Mn) alloys hold a mixed structure of nanocrystalline and amorphous structure when M content x=4, indicating that the substitution of M (M=Co, Mn) for Ni facilitates the glass formation in the Mg2Ni-type alloy. Besides, all the as-spun alloys have a major phase of Mg2Ni but M (M=Co, Mn) substitution brings on the formation of some secondary phases, MgCo2 and Mg phases for M=Co as well as MnNi and Mg phases for M=Mn. Based upon the measurements of the automatic Sieverts apparatus and the automatic galvanostatic system, the impacts engendered by M (M=Cu, Co, Mn) substitution on the gaseous and electrochemical hydrogen storage kinetics of the alloys appear to be evident. The gaseous hydriding kinetics of the alloys first rises and then declines with the growing of M (M=Cu, Co, Mn) content. Particularly, the M (M= Mn) substitution results in a sharp drop in the hydriding kinetics when x=4. The M (M=Cu, Co, Mn) substitution ameliorates the dehydriding kinetics dramatically in the order (M=Co)>(M=Mn)>(M=Cu). The electrochemical kinetics of the alloys visibly grows with M content rising for (M=Cu, Co), while it first increases and then declines for (M=Mn).

Gaseous and electrochemical hydrogen storage kinetics of as-quenched nanocrystalline and amorphous Mg2Ni-type alloys

The nanocrystalline and amorphous Mg2Ni-type Mg2Ni1−xCox (x = 0, 0.1, 0.2, 0.3, 0.4) alloys were synthesized by melt quenching technology. The structures of the as-cast and quenched alloys were characterized by XRD, SEM and HRTEM. The gaseous hydrogen storage kinetics of the alloys was measured using an automatically controlled Sieverts apparatus. The alloy electrodes were charged and discharged with a constant current density in order to investigate the electrochemical hydrogen storage kinetics of the alloys. The results demonstrate that the substitution of Co for Ni results in the formation of secondary phases MgCo2 and Mg instead of altering the major phase Mg2Ni. No amorphous phase is detected in the as-quenched Cofree alloy, however, a certain amount of amorphous phase is clearly found in the as-quenched alloys substituted by Co. Furthermore, both the rapid quenching and the Co substitution significantly improve the gaseous and electrochemical hydrogen storage kinetics of the alloys, for which the notable increase of the hydrogen diffusion coefficient (D) along with the limiting current density (IL) and the obvious decline of the electrochemical impedance generated by both the Co substitution and the rapid quenching are basically responsible.

Investigation on Gaseous and Electrochemical Hydrogen Storage Kinetics of As-Quenched Nanocrystalline Mg2Ni-type Alloys

Abstract In order to improve the gaseous and electrochemical hydrogen storage kinetics of the Mg 2 Ni-type alloys, Ni in the alloy was partially substituted by element Cu. Rapid quenching technology was used for the preparation of the Mg 2 Ni 1- x Cu x ( x = 0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys. The structures of the as-cast and quenched alloys were characterized by XRD, SEM and TEM. The gaseous hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the as-quenched alloys was tested by an automatic galvanostatic system. The results show that all the as-quenched alloys hold an entire nanocrystalline structure and are free of amorphous phase. The substitution of Cu, instead of changing the major phase Mg 2 Ni, leads to a visible refinement of the grains of the as-cast alloys. Furthermore, both the rapid quenching treatment and Cu substitution significantly improve the gaseous and electrochemical hydrogen storage kinetics of the alloys. As the quenching rate grows from 0 (as-cast is defined as quenching rate of 0 m/s) to 30 m/s, the hydrogen absorption saturation ratio in 5 min, for the Mg 2 Ni 0.7 Cu 0.3 alloy, increases from 57.2% to 92.8%, the hydrogen desorption ratio in 20 min from 21.6% to 49.6%, the high rate discharge ability (HRD) from 40.6% to 73.1%, the hydrogen diffusion coefficient ( D ) from 1.02×10 −11 to 4.08×10 −11 cm 2 /s and the limiting current density ( I L ) from 113.0 to 715.3 mA/g.

Improved Physical and Electrochemical Hydrogen Storage Kinetics of the As-Spun Mg<sub>2</sub>Ni-Type Alloys by Substituting Ni with M (M=Co, Cu)

In order to improve the physical and electrochemical hydrogen storage kinetics of the Mg2Ni-type alloys, Ni in the alloy was partially substituted by M (M=Co, Cu). Melt-spinning technology was used for the preparation of the Mg20Ni10-xMx (M=Co, Cu; x=0, 1, 2, 3, 4) hydrogen storage alloys. The structures of the as-cast and spun alloys are characterized by XRD, SEM and TEM. The physical and electrochemical hydrogen storage kinetics of the alloys is measured. The results show that the as-spun (M=Cu) alloys hold an entire nanocrystalline structure, whereas the as-spun (M=Co) alloys exhibit a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni facilitates the glass formation in the Mg2Ni-type alloy. The substitution of M (M=Co, Cu) for Ni engenders an insignificant effect on the hydrogen absorption kinetics of the alloys, but it markedly ameliorates the hydrogen desorption kinetics of the alloys and the high rate discharge ability. With an increase of the M (M=Co, Cu) content from 0 to 4, the hydrogen desorption ratio ( ) is enhanced form 20.0% to 65.43% for the as-spun (20 m/s) alloy (M=Co), and from 20.0% to 52.88% for the as-spun (20 m/s) alloy (M=Cu).

Gaseous and Electrochemical Hydrogen Storage Kinetics of as-Spun Nanocrystalline Mg<sub>20</sub>Ni<sub>10-x</sub>Cu<sub>x</sub> (x = 0-4) Alloys

In order to improve the gaseous and electrochemical hydrogen storage kinetics of the Mg2Ni-type alloys, Ni in the alloy was partially substituted by element Cu. Melt-spinning technology was used for the preparation of the Mg20Ni10-xCux (x = 0, 1, 2, 3, 4) hydrogen storage alloys. The structures of the as-cast and spun alloys are characterized by XRD, SEM and TEM. The gaseous hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the as-spun alloys is tested by an automatic galvanostatic system. The results show that all the as-spun alloys hold an entire nanocrystalline structure and are free of amorphous phase. The substitution of Cu for Ni, instead of changing the major phase Mg2Ni, leads to a visible refinement of the grains of the as-cast alloys. Furthermore, both the melt spinning treatment and Cu substitution significantly improve the gaseous and electrochemical hydrogen storage kinetics of the alloys.

Enhanced hydrogen storage kinetics of nanocrystalline and amorphous Mg 2N-type alloy by substituting Ni with Co

In order to improve the hydrogen storage kinetics of the Mg 2Ni-type alloys, Ni in the alloy was partially substituted with element Co. The Mg 2Ni-type Mg 2Ni 1- x Co x ( x=0, 0.1, 0.2, 0.3, 0.4) alloys were fabricated by melt-spinning technique. The structures of the as-spun alloys were characterized by XRD and TEM. The gaseous and electrochemical hydrogen storage kinetics of the alloys was measured. The results show that the substitution of Co for Ni notably enhances the glass forming ability of the Mg 2Ni-type alloy. The amorphization degree of the alloys visibly increases with rising of Co content. Furthermore, the substitution of Co for Ni significantly improves the hydrogen storage kinetics of the alloys. With an increase in the amount of Co substitution from 0 to 0.4, the hydrogen absorption saturation ratio of the as-spun (15 m/s) alloy increases from 81.2% to 84.9%, the hydrogen desorption ratio from 17.60% to 64.79%, the hydrogen diffusion coefficient increases from 1.07×10 −11 to 2.79×10 −11 cm 2/s and the limiting current density increases from 46.7 to 191.7 mA/g, respectively.