Papers by Keyword: Hydrogen Storage Kinetics

Abstract: In order to obtain a nanocrystalline and amorphous structure in the Mg2Ni-type alloy, the melt spinning technology has been used to prepare the Mg20Ni8M2 (M = Co, Cu) hydrogen storage alloys. The microstructures of the alloys were characterized by XRD, SEM and HRTEM. The effects of the melt spinning on the gaseous and electrochemical hydrogen storage kinetics of the alloys were investigated. The results indicate that the as-spun (M = Co) alloys display a nanocrystalline and amorphous structure as spinning rate grows to 20 m/s, while the as-spun (M = Cu) alloys hold an entire nanocrystalline structure even if a limited spinning rate is applied, suggesting that the substitution of Co for Ni facilitates the glass formation in the Mg2Ni-type alloy. The melt spinning remarkably ameliorates the gaseous hydriding and dehydriding kinetics of the alloys. As the spinning rate is raised from 0 (As-cast was defined as the spinning rate of 0 m/s) to 30 m/s, the hydrogen absorption saturation ratio ( ), a ratio of the hydrogen absorption capacity in 5 min to the saturated hydrogen absorption capacity, are enhanced from 80.43% to 94.38% for the (M = Co) alloy and from 56.72% to 92.74% for the (M = Cu) alloy. The hydrogen desorption ratio ( ), a ratio of the hydrogen desorption capacity in 20 min to the saturated hydrogen absorption capacity of the alloy, are increased from 24.52% to 51.67% for the (M = Co) alloy and from14.89% to 40.37% for the (M = Cu) alloy. Furthermore, the high rate discharge ability (HRD) and the hydrogen diffusion coefficient (D) of the alloys notably mount up with the growing of the spinning rate.

Abstract: In order to obtain a nanocrystalline and amorphous structure in the Mg2Ni-type alloy, the melt spinning was applied to fabricate the Mg20Ni7M3 (M=Co, Cu) hydrogen storage alloys. The microstructures of the alloys were characterized by XRD, SEM and HRTEM. The effects of the melt spinning on the gaseous and electrochemical hydrogen storage kinetics of the alloys were investigated. The results indicate that the as-spun (M=Co) alloys display a nanocrystalline and amorphous structure as spinning rate grows to 20 m/s, while the as-spun (M=Cu) alloys hold an entire nanocrystalline structure even if a limited spinning rate is applied, suggesting that the substitution of Co for Ni facilitates the glass formation in the Mg2Ni-type alloy. The melt spinning remarkably ameliorates the gaseous hydriding and dehydriding kinetics of the alloys. The hydrogen absorption ratio ( ) and hydrogen desorption ratio ( ) are enhanced from 81.9% to 94.7% and from 34.9% to 57.3% for the (M=Co) alloy, and from 57.2% to 92.8% and from 21.6% to 49.6% for the (M=Cu) alloy by raising spinning rate from 0 (as-cast was defined as the spinning rate of 0 m/s) to 30 m/s. Furthermore, the high rate discharge ability (HRD), the limiting current density (IL) and the hydrogen diffusion coefficient (D) of the alloys notably increase with the growing of the spinning rate.

Abstract: In order to obtain a nanocrystalline and amorphous structure in the Mg2Ni-type alloy, the Ni in Mg2Ni alloy has been partially substituted by M (M=Co, Cu), and the melt spinning has been used to fabricate the Mg20Ni10-xMx (M=Co, Cu; x=0-4) hydrogen storage alloys. The microstructures of the alloys were characterized by XRD, SEM and HRTEM. The effects of substituting Ni with M (M=Co, Cu) on the gaseous and electrochemical hydrogen storage kinetics of the as-spun alloys were investigated. The results indicate that the as-spun (M=Co) alloys display a nanocrystalline and amorphous structure, while the as-spun (M=Cu) alloys hold an entire nanocrystalline structure, suggesting 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 exerts a trifling impact on the hydriding kinetics of the alloys, but it renders a marked enhancement of dehydriding capacity and kinetics. Furthermore, the measurements of the high rate discharge ability (HRD) and the hydrogen diffusion coefficient (D) as well as the electrochemical impedance spectra (EIS) of the alloys exhibit that the electrochemical kinetics of the as-spun (30 m/s) alloys is significantly ameliorated by substituting Ni with M (M=Co, Cu).

Abstract: It has come to light that the Mg₂Ni-type alloy with a nanocrystalline/amorphous structure possesses superior hydrogen storage kinetics. The Mg₂Ni-type Mg₂₀Ni_10-xM_x (M=Cu, Co; x=0, 4) hydrogen storage alloys were synthesized by a melt-spinning technique. The microstructures of the as-cast and spun alloys were characterized by XRD, SEM and HRTEM. The gaseous and electrochemical hydrogen storage kinetics of the alloys was measured. The results show that whatever spinning rate the as-spun (M=Cu) alloys hold an entire nanocrystalline structure. As spinning rate approaches to 20 m/s, the as-spun (M=Co) alloys display a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni facilitates the glass formation in the Mg₂Ni-type alloy. Furthermore, such substitution results in the formation of secondary phases Mg₂Cu and MgCo₂ instead of changing the major phase of Mg₂Ni. The melt spinning markedly improves the gaseous and electrochemical hydrogen storage kinetics of the alloys. The hydrogen absorption ratio (R₅^a ), hydrogen desorption ratio (R₂₀^d ) and the high rate discharge ability (HRD) notably mount up with the growing of the spinning rate.

Abstract: 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).

Abstract: In order to improve the gaseous hydrogen storage kinetics of the Mg2Ni-type alloys, Ni in the alloy was partially substituted by M (M=Cu, Co). Melt-spinning technology was used for the preparation of the Mg20Ni10-xMx (M=Cu, Co; 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 results show that the as-spun (M=Cu) alloys hold a typical nanocrystalline structure, whereas the as-spun (M=Co) alloys display 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=Cu, Co) 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. As the M (M=Cu, Co) content increase from 0 to 4, the hydrogen desorption ratio ( ) is enhanced from 27.7% to 58.9% for the as-spun (30 m/s) alloy (M=Cu), and from 27.7% to 70.2% for the as-spun (30 m/s) alloy (M=Co).

Abstract: In this paper, melt-spinning technology was used for preparing Mg₂₀Ni_10-xCo_x (x = 0, 1, 2, 3, 4) hydrogen storage alloys. The influences of both the Co substitution and the melt spinning on the the physical and electrochemical hydrogen storage kinetics of the alloys were investigated. The XRD, SEM and TEM characterization exhibits that the as-spun Co-free alloy holds a typical nanocrystalline structure, whereas the as-spun alloys substituted by Co display a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni facilitates the glass formation in the Mg₂Ni-type alloy. The Co substitution gives rise to forming secondary phase MgCo₂ without altering the Mg₂Ni major phase of the alloys. The measurement of the physical and electrochemical hydrogen storage kinetics of the alloys shows that both the melt spinning and the substitution of Co for Ni markedly improve the physical hydriding and dehydriding kinetics and the electrochmeical kinetics (HRD) of the alloys.

Abstract: The nanocrystalline and amorphous Mg₂Ni_1-xCo_x (x=0, 0.1, 0.2, 0.3, 0.4) alloys were prepared by melt-spinning technique. The structures of the alloys were studied by XRD, SEM and HRTEM. The hydrogen absorption and desorption kinetics and the high rate discharge ability (HRD) of the alloys were measured. The results show that the as-spun Co-free alloy holds a typical nanocrystalline structure, whereas the as-spun alloys containing Co display 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 Co for Ni evidently improves the hydriding and dehydriding kinetics and the HRD of the alloys. With an increase in the amount of Co substitution from 0 to 0.4, the HRD value rises from 52.9% to 60.3% for the as-cast alloy, and from 65.9% to 76.0% for the as-spun (30 m/s) alloy.

Abstract: 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 Co. Melt-spinning technology was used for the preparation of the Mg20Ni10-xCox (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 the as-spun Co-free alloy holds a typical nanocrystalline structure, whereas the as-spun alloys substituted by Co display a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni facilitates the glass formation in the Mg2Ni-type alloy. Both the melt spinning and the substitution of Co for Ni evidently ameliorate the hydriding and dehydriding kinetics and the HRD of the alloys. With an increase in the spinning rate from 0 (As-cast was defined as spinning rate of 0 m/s) to 30 m/s, the hydrogen absorption saturation ratio ( ) of the Co4 alloy grows from 77.1 to 93.5 wt.%, the hydrogen desorption ratio ( ) from 54.5% to 70.2%, the HRD from 60.3% to 76.0%, respectively.

Abstract: 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.