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,...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 Co- ffee 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.展开更多
This work proposed a strategy of indirectly inducing uniform microarc discharge by controlling the content and distribution ofβ-Mg_(17)Al_(12)phase in AZ91D Mg alloy.Two kinds of nano-particles(ZrO_(2)and TiO_(2))wer...This work proposed a strategy of indirectly inducing uniform microarc discharge by controlling the content and distribution ofβ-Mg_(17)Al_(12)phase in AZ91D Mg alloy.Two kinds of nano-particles(ZrO_(2)and TiO_(2))were designed to be added into the substrate of Mg alloy by friction stir processing(FSP).Then,Mg alloy sample designed with different precipitated morphology ofβ-Mg_(17)Al_(12)phase was treated by microarc oxidation(MAO)in Na_(3)PO_(4)/Na2SiO3electrolyte.The characteristics and performance of the MAO coating was analyzed using scanning electron microscopy(SEM),energy dispersive spectrometer(EDS),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),contact angle meter,and potentiodynamic polarization.It was found that the coarseα-Mg grains in extruded AZ91D Mg alloy were refined by FSP,and theβ-Mg_(17)Al_(12)phase with reticular structure was broken and dispersed.The nano-ZrO_(2)particles were pinned at the grain boundary by FSP,which refined theα-Mg grain and promoted the precipitation ofβ-Mg_(17)Al_(12)phase in grains.It effectively inhibited the“cascade”phenomenon of microarcs,which induced the uniform distribution of discharge pores.The MAO coating on Zr-FSP sample had good wettability and corrosion resistance.However,TiO_(2)particles were hardly detected in the coating on TiFSP sample.展开更多
A designed Mg_(88.7)Ni_(6.3)Y_(5)hydrogen storage alloy containing 14H type LPSO(long-period stacking ordered)and ternary eutectic structure was prepared by regulating the alloy composition and casting.The hydrogen st...A designed Mg_(88.7)Ni_(6.3)Y_(5)hydrogen storage alloy containing 14H type LPSO(long-period stacking ordered)and ternary eutectic structure was prepared by regulating the alloy composition and casting.The hydrogen storage performance of the alloy was improved by adding nano-flower-like TiO_(2)@C catalyst.The decomposition of the LPSO structure during hydrogenation led to the formation of plenty of nanocrystals which provided abundant interphase boundaries and activation sites.The nanoscale TiO_(2)@C catalyst was uniformly dispersed on the surface of alloy particles,and the"hydrogen overflow''effect of TiO_(2)@C accelerated the dissociation and diffusion of hydrogen on the surface of the alloy particles.As a result,the in-situ endogenous nanocrystals of the LPSO structure decomposition and the externally added flower-like TiO_(2)@C catalyst uniformly dispersed on the surface of the nanoparticles played a synergistic catalytic role in improving the hydrogen storage performance of the Mg-based alloy.With the addition of the TiO_(2)@C catalyst,the beginning hydrogen desorption temperature was reduced to 200℃.Furthermore,the saturated hydrogen absorption capacity of the sample was 5.32 wt.%,and it reached 4.25 wt.%H_(2) in 1 min at 200℃and 30 bar.展开更多
The development of superconducting joining technology for reacted magnesium diboride(MgB_(2))conductors remains a critical challenge for the advancement of cryogen-free MgB_(2)-based magnets for magnetic resonance ima...The development of superconducting joining technology for reacted magnesium diboride(MgB_(2))conductors remains a critical challenge for the advancement of cryogen-free MgB_(2)-based magnets for magnetic resonance imaging(MRI).Herein,the fabrication of superconducting joints using reacted carbon-doped multifilament MgB_(2)wires for MRI magnets is reported.To achieve successful superconducting joints,the powder-in-mold method was employed,which involved tuning the filament protection mechanism,the powder compaction pressure,and the heat treatment condition.The fabricated joints demonstrated clear superconducting-to-normal transitions in self-field,with effective magnetic field screening up to 0.5 T at 20 K.To evaluate the interface between one of the MgB_(2)filaments and the MgB_(2)bulk within the joint,serial sectioning was conducted for the first time in this type of superconducting joint.The serial sectioning revealed space formation at the interface,potentially caused by the volume shrinkage associated with the MgB_(2)formation or the combined effect of the volume shrinkage and the different thermal expansion coefficients of the MgB_(2)bulk,the filament,the mold,and the sealing material.These findings are expected to be pivotal in developing MgB_(2)superconducting joining technology for MRI magnet applications through interface engineering.展开更多
The hydrolysis of MgH_(2) delivers high hydrogen capacity(15.2 wt%),which is very attractive for real-time hydrogen supply.However,the formation of a surface passivation Mg(OH)_(2) layer and the large excess of H_(2)O...The hydrolysis of MgH_(2) delivers high hydrogen capacity(15.2 wt%),which is very attractive for real-time hydrogen supply.However,the formation of a surface passivation Mg(OH)_(2) layer and the large excess of H_(2)O required to ensure complete hydrolysis are two key challenges for the MgH_(2) hydrolysis systems.Now,a low-cost method is reported to synthesize MgH_(2)@Mg(BH_(4))_(2) composite via ball-milling MgH_(2) with cheap and widely available B_(2)O_(3)(or B(OH)_(3)).By adding small amounts of B_(2)O_(3),the in-situ formed Mg(BH_(4))_(2) could significantly promote the hydrolysis of MgH_(2).In particular,the MgH_(2)–10 wt%B_(2)O_(3) composite releases 1330.7 mL·g^(−1) H_(2)(close to 80%theoretical hydrogen generation H_(2))in H_(2)O and 1520.4 mL·g^(−1) H_(2)(about 95%)in 0.5 M MgCl_(2) in 60 min at 26℃ with hydrolysis rate of 736.9 mL·g^(−1)·min^(−1) and 960.9 mL·g^(−1)·min^(−1) H_(2) during the first minute of the hydrolysis,respectively.In addition,the MgCl_(2) solution allows repeated use by filtering and exhibits high cycle stability(20 cycles),therefore leading to much reduced capacity loss caused by the excess H_(2)O.We show that by introducing B_(2)O_(3) and recycling the 0.5 M MgCl_(2) solution,the system hydrogen capacity can approach 5.9 wt%,providing a promising hydrogen generation scheme to supply hydrogen to the fuel cells.展开更多
A partial substitution of Ni by Cu has been carried out in order to improve the hydrogen storage characteristics of the Mg2Ni-type alloys. The nanocrystalline Mg20Ni10-xCux (x = 0, 1, 2, 3, 4) alloys are synthesized b...A partial substitution of Ni by Cu has been carried out in order to improve the hydrogen storage characteristics of the Mg2Ni-type alloys. The nanocrystalline Mg20Ni10-xCux (x = 0, 1, 2, 3, 4) alloys are synthesized by the melt-spinning technique. The structures of the as-cast and spun alloys have been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM). The electrochemical performances were evaluated by an automatic galvanostatic system. The hydrogen absorption and desorption kinetics of the alloys were determined by using an automatically controlled Sieverts apparatus. The results indicate that the substitution of Cu for Ni does not alter the major phase Mg2Ni. The Cu substitution significantly ameliorates the electrochemical hydrogen storage performances of alloys, involving both the discharge capacity and the cycle stability. The hydrogen absorption capacity of alloys has been observed to be first increase and then decrease with an increase in the Cu contents. However, the hydrogen desorption capacity of the alloys exhibit a monotonous growth with an increase in the Cu contents.展开更多
In order to improve the gaseous and electrochemical hydrogen storage kinetics of the M2Nitype alloy, the elements Cu and Nd were added in the alloy. The nanocrystalline and amorphous Mg2Ni-type alloys with the composi...In order to improve the gaseous and electrochemical hydrogen storage kinetics of the M2Nitype alloy, the elements Cu and Nd were added in the alloy. The nanocrystalline and amorphous Mg2Ni-type alloys with the composition of（Mg24Ni10Cu2）100-xNdx（x = 0, 5, 10, 15, 20） were prepared by melt spinning technology. The effects of Nd content on the structures and hydrogen storage kinetics of the alloys were investigated. The characterization by X-ray diffraction（XRD）, transmission electron microscopy（TEM） and scanning electron microscopy（SEM） reveals that all the as-cast alloys hold multiphase structures, containing Mg2Ni-type major phase as well as some secondary phases Mg6Ni, Nd5Mg41, and Nd Ni, whose amounts clearly grow with increasing Nd content. Furthermore, the as-spun Nd-free alloy displays an entire nanocrystalline structure, whereas the as-spun Nd-added alloys hold a mixed structure of nanocrystalline and amorphous structure and the amorphization degree of the alloys visibly increases with the rising of the Nd content, suggesting that the addition of Nd facilitates the glass forming in the Mg2Ni-type alloy. The measurement of the hydrogen storage kinetics indicates that the addition of Nd significantly improves the gaseous and electrochemical hydrogen storage kinetics of the alloys. The addition of Nd enhances the diffusion ability of hydrogen atoms in the alloy, but it impairs the charge-transfer reaction on the surface of the alloy electrode, which makes the high rate discharge ability（HRD） of the alloy electrode fi rst mount up and then go down with the growing of Nd content.展开更多
The element Ni in the Mg2Ni alloy is partially substituted by M（M = Cu, Co, Mn） in order to ameliorate the electrochemical hydrogen storage performances of Mg2Ni-type electrode alloys. The nanocrystalline and amorph...The element Ni in the Mg2Ni alloy is partially substituted by M（M = Cu, Co, Mn） in order to ameliorate the electrochemical hydrogen storage performances of Mg2Ni-type electrode alloys. The nanocrystalline and amorphous Mg20Ni10-xMx（M = None, Cu, Co, Mn; x = 0-4） alloys were prepared by melt spinning. The effects of the M（M = Cu, Co, Mn） content on the structures and electrochemical hydrogen storage characteristics of the as-cast and spun alloys were comparatively studied. The analyses by XRD, SEM and HRTEM reveal that all the as-cast alloys have a major phase of Mg2Ni but the M（M = Co, Mn） substitution brings on the formation of some secondary phases, MgCo2 and Mg for the（M = Co） alloy, and Mn Ni and Mg for the（M = Mn） alloy. Besides, the as-spun（M = None, Cu） alloys display an entirely nanocrystalline structure, whereas the as-spun（M = Co, Mn） alloys hold a nanocrystalline/amorphous structure, suggesting that the substitution of M（M = Co, Mn） for Ni facilitates the glass formation in the Mg2Ni-type alloys. The electrochemical measurements indicate that the variation of M（M = Cu, Co, Mn） content engenders an obvious effect on the electrochemical performances of the as-cast and spun alloys. To be specific, the cyclic stabilities of the alloys augment monotonously with increasing M（M = Cu, Co, Mn） content, and the capacity retaining rate（S20） is in an order of（M = Cu） 〉（M = Co） 〉（M = Mn） 〉（M = None） for x≤1 but changes to（M = Co） 〉（M = Mn） 〉（M = Cu） 〉（M = None） for x≥2. The discharge capacities of the as-cast and spun alloys always grow with the rising of M（M = Co, Mn） content but first mount up and then go down with increasing M（M = Cu） content. Whatever the M content is, the discharge capacities are in sequence：（M = Co） 〉（M = Mn） 〉（M = Cu） 〉（M = None）. The high rate discharge abilities（HRDs） of all the alloys grow clearly with rising M（M = Cu, Co） content except for（M = Mn） alloy, whose HRD has a maximum value with varying M（M = Mn） content. Furthermore, for the as-cast alloys, the HRD is in order of（M = Co） 〉（M = Mn） 〉（M = Cu） 〉（M = None）, while for the as-spun（20 m·s^-1） alloys, it changes from（M = Co） 〉（M = Mn） 〉（M = Cu） 〉（M = None） for x = 1 to（M = Cu） 〉（M = Co） 〉（M = None） 〉（M = Mn） for x = 4.展开更多
In order to improve the electrochemical hydrogen storage performance of the Mg2Ni-type electrode alloys, Mg in the alloy was partially substituted by La, and the nanocrystalline and amorphous Mg2Ni-type Mg20-xLaxNi10 ...In order to improve the electrochemical hydrogen storage performance of the Mg2Ni-type electrode alloys, Mg in the alloy was partially substituted by La, and the nanocrystalline and amorphous Mg2Ni-type Mg20-xLaxNi10 (x=0, 2) alloys were synthesized by melt-spinning technique. The microstructures of the as-spun alloys were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical hydrogen storage properties of the experimental alloys were tested. The results show that no amorphous phase is detected in the as-spun Mg20Ni10 alloy, but the as-spun Mg18La2Ni10 alloy holds a major amorphous phase. As La content increases from 0 to 2, the maximum discharge capacity of the as-spun (20 m/s) alloys rises from 96.5 to 387.1 mA·h/g, and the capacity retaining rate (S20) at the 20th cycle grows from 31.3% to 71.7%. Melt-spinning engenders an impactful effect on the electrochemical hydrogen storage performances of the alloys. With the increase in the spinning rate from 0 to 30 m/s, the maximum discharge capacity increases from 30.3 to 135.5 mA·h/g for the Mg20Ni10 alloy, and from 197.2 to 406.5 mA·h/g for the Mg18La2Ni10 alloy. The capacity retaining rate (S20) of the Mg20Ni10 alloy at the 20th cycle slightly falls from 36.7% to 27.1%, but it markedly mounts up from 37.3% to 78.3% for the Mg18La2Ni10 alloy.展开更多
In order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys,Ni in the alloy is substituted by element Co. The nanocrystalline and amorphous Mg2Ni-type Mg2Ni1-xCox (x=0,0.1,0.2,0.3,0.4) alloys w...In order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys,Ni in the alloy is substituted by element Co. The nanocrystalline and amorphous Mg2Ni-type Mg2Ni1-xCox (x=0,0.1,0.2,0.3,0.4) alloys were synthesized by melt-spinning technique. The structures of the as-cast and spun alloys were studied with an X-ray diffractometer (XRD) and a high resolution transmission electronic microscope (HRTEM). An investigation on the thermal stability of the as-spun alloys was carried out with a differential scanning calorimeter (DSC). The hydrogen absorption and desorption kinetics of the alloys were measured with an automatically controlled Sieverts apparatus. The results demonstrate that the substitution of Co for Ni does not alter the major phase of Mg2Ni but results in the formation of secondary phase MgCo2. No amorphous phase is detected in the as-spun Co-free alloy,but a certain amount of amorphous phase is clearly found in the as-spun Co-containing alloys. The substitution of Co for Ni exerts a slight influence on the hydriding kinetics of the as-spun alloy. However,it dramatically enhances the dehydriding kinetics of the as-cast and spun alloys. As Co content (x) increases from 0 to 0.4,the hydrogen desorption capacity increases from 0.19% to 1.39% (mass fraction) in 20 min for the as-cast alloy,and from 0.89% to 2.18% (mass fraction) for the as-spun alloy (30 m/s).展开更多
Nanocrystalline Mg2Ni-type alloys with nominal compositions of Mg20Ni10–xCux(x=0,1,2,3,4,mass fraction,%) were synthesized by rapid quenching technique.The microstructures of the as-cast and quenched alloys were char...Nanocrystalline Mg2Ni-type alloys with nominal compositions of Mg20Ni10–xCux(x=0,1,2,3,4,mass fraction,%) were synthesized by rapid quenching technique.The microstructures of the as-cast and quenched alloys were characterized by XRD,SEM and HRTEM.The electrochemical hydrogen storage performances were tested by an automatic galvanostatic system.The hydriding and dehydriding kinetics of the alloys were measured using an automatically controlled Sieverts apparatus.The results show that all the as-quenched alloys hold the typical nanocrystalline structure and the rapid quenching does not change the major phase Mg2Ni.The rapid quenching significantly improves the electrochemical hydrogen storage capacity of the alloys,whereas it slightly impairs the cycling stability of the alloys.Additionally,the hydrogen absorption and desorption capacities of the alloys significantly increase with rising quenching rate.展开更多
基金Funded by National Natural Science Foundations of China(Nos.51161015 and 50961009)Natural Science Foundation of Inner Mongolia,China(Nos.2011ZD10 and 2010ZD05)Higher Education Science Research Project of Inner Mongolia,China(No.NJzy08071)
文摘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 Co- ffee 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.
基金funded by China Postdoctoral Science Foundation(No.2021M700569)Chongqing Postdoctoral Science Foundation(No.7 cstc2021jcyj-bshX0087)。
文摘This work proposed a strategy of indirectly inducing uniform microarc discharge by controlling the content and distribution ofβ-Mg_(17)Al_(12)phase in AZ91D Mg alloy.Two kinds of nano-particles(ZrO_(2)and TiO_(2))were designed to be added into the substrate of Mg alloy by friction stir processing(FSP).Then,Mg alloy sample designed with different precipitated morphology ofβ-Mg_(17)Al_(12)phase was treated by microarc oxidation(MAO)in Na_(3)PO_(4)/Na2SiO3electrolyte.The characteristics and performance of the MAO coating was analyzed using scanning electron microscopy(SEM),energy dispersive spectrometer(EDS),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),contact angle meter,and potentiodynamic polarization.It was found that the coarseα-Mg grains in extruded AZ91D Mg alloy were refined by FSP,and theβ-Mg_(17)Al_(12)phase with reticular structure was broken and dispersed.The nano-ZrO_(2)particles were pinned at the grain boundary by FSP,which refined theα-Mg grain and promoted the precipitation ofβ-Mg_(17)Al_(12)phase in grains.It effectively inhibited the“cascade”phenomenon of microarcs,which induced the uniform distribution of discharge pores.The MAO coating on Zr-FSP sample had good wettability and corrosion resistance.However,TiO_(2)particles were hardly detected in the coating on TiFSP sample.
基金partially supported by the National Key R&D Program of China(No.2020YFA0406204)the National Natural Science Foundation of China(No.52201265)+1 种基金Shaanxi Province Key Project of Research and Development Plan,China(No.2023-YBGY-294,No.2023KXJ-060)the Doctoral Scientific Research Starting Foundation of Shaanxi University of Science and Technology,China(No.2016GBJ-02)。
文摘A designed Mg_(88.7)Ni_(6.3)Y_(5)hydrogen storage alloy containing 14H type LPSO(long-period stacking ordered)and ternary eutectic structure was prepared by regulating the alloy composition and casting.The hydrogen storage performance of the alloy was improved by adding nano-flower-like TiO_(2)@C catalyst.The decomposition of the LPSO structure during hydrogenation led to the formation of plenty of nanocrystals which provided abundant interphase boundaries and activation sites.The nanoscale TiO_(2)@C catalyst was uniformly dispersed on the surface of alloy particles,and the"hydrogen overflow''effect of TiO_(2)@C accelerated the dissociation and diffusion of hydrogen on the surface of the alloy particles.As a result,the in-situ endogenous nanocrystals of the LPSO structure decomposition and the externally added flower-like TiO_(2)@C catalyst uniformly dispersed on the surface of the nanoparticles played a synergistic catalytic role in improving the hydrogen storage performance of the Mg-based alloy.With the addition of the TiO_(2)@C catalyst,the beginning hydrogen desorption temperature was reduced to 200℃.Furthermore,the saturated hydrogen absorption capacity of the sample was 5.32 wt.%,and it reached 4.25 wt.%H_(2) in 1 min at 200℃and 30 bar.
基金the Japan Society for the Promotion of Science(JSPS)KAKENHI Grant Number JP18F18714Cryogenic Station,Research Network and Facility Services Division,National Institute for Materials Science(NIMS),Japansupported by the ARC Linkage Project(LP200200689)。
文摘The development of superconducting joining technology for reacted magnesium diboride(MgB_(2))conductors remains a critical challenge for the advancement of cryogen-free MgB_(2)-based magnets for magnetic resonance imaging(MRI).Herein,the fabrication of superconducting joints using reacted carbon-doped multifilament MgB_(2)wires for MRI magnets is reported.To achieve successful superconducting joints,the powder-in-mold method was employed,which involved tuning the filament protection mechanism,the powder compaction pressure,and the heat treatment condition.The fabricated joints demonstrated clear superconducting-to-normal transitions in self-field,with effective magnetic field screening up to 0.5 T at 20 K.To evaluate the interface between one of the MgB_(2)filaments and the MgB_(2)bulk within the joint,serial sectioning was conducted for the first time in this type of superconducting joint.The serial sectioning revealed space formation at the interface,potentially caused by the volume shrinkage associated with the MgB_(2)formation or the combined effect of the volume shrinkage and the different thermal expansion coefficients of the MgB_(2)bulk,the filament,the mold,and the sealing material.These findings are expected to be pivotal in developing MgB_(2)superconducting joining technology for MRI magnet applications through interface engineering.
基金supported by the Basic and Applied Basic Research Foundation of Guangdong Province(No.2022A1515011832 and 2021A1515110676)supported by GDAS’Project of Science and Technology Development(2022GDASZH-2022010104,2022GDASZH-2022030604-04).
文摘The hydrolysis of MgH_(2) delivers high hydrogen capacity(15.2 wt%),which is very attractive for real-time hydrogen supply.However,the formation of a surface passivation Mg(OH)_(2) layer and the large excess of H_(2)O required to ensure complete hydrolysis are two key challenges for the MgH_(2) hydrolysis systems.Now,a low-cost method is reported to synthesize MgH_(2)@Mg(BH_(4))_(2) composite via ball-milling MgH_(2) with cheap and widely available B_(2)O_(3)(or B(OH)_(3)).By adding small amounts of B_(2)O_(3),the in-situ formed Mg(BH_(4))_(2) could significantly promote the hydrolysis of MgH_(2).In particular,the MgH_(2)–10 wt%B_(2)O_(3) composite releases 1330.7 mL·g^(−1) H_(2)(close to 80%theoretical hydrogen generation H_(2))in H_(2)O and 1520.4 mL·g^(−1) H_(2)(about 95%)in 0.5 M MgCl_(2) in 60 min at 26℃ with hydrolysis rate of 736.9 mL·g^(−1)·min^(−1) and 960.9 mL·g^(−1)·min^(−1) H_(2) during the first minute of the hydrolysis,respectively.In addition,the MgCl_(2) solution allows repeated use by filtering and exhibits high cycle stability(20 cycles),therefore leading to much reduced capacity loss caused by the excess H_(2)O.We show that by introducing B_(2)O_(3) and recycling the 0.5 M MgCl_(2) solution,the system hydrogen capacity can approach 5.9 wt%,providing a promising hydrogen generation scheme to supply hydrogen to the fuel cells.
文摘A partial substitution of Ni by Cu has been carried out in order to improve the hydrogen storage characteristics of the Mg2Ni-type alloys. The nanocrystalline Mg20Ni10-xCux (x = 0, 1, 2, 3, 4) alloys are synthesized by the melt-spinning technique. The structures of the as-cast and spun alloys have been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM). The electrochemical performances were evaluated by an automatic galvanostatic system. The hydrogen absorption and desorption kinetics of the alloys were determined by using an automatically controlled Sieverts apparatus. The results indicate that the substitution of Cu for Ni does not alter the major phase Mg2Ni. The Cu substitution significantly ameliorates the electrochemical hydrogen storage performances of alloys, involving both the discharge capacity and the cycle stability. The hydrogen absorption capacity of alloys has been observed to be first increase and then decrease with an increase in the Cu contents. However, the hydrogen desorption capacity of the alloys exhibit a monotonous growth with an increase in the Cu contents.
基金Funded by the National Natural Science Foundations of China(Nos.51161015 and 51371094)
文摘In order to improve the gaseous and electrochemical hydrogen storage kinetics of the M2Nitype alloy, the elements Cu and Nd were added in the alloy. The nanocrystalline and amorphous Mg2Ni-type alloys with the composition of（Mg24Ni10Cu2）100-xNdx（x = 0, 5, 10, 15, 20） were prepared by melt spinning technology. The effects of Nd content on the structures and hydrogen storage kinetics of the alloys were investigated. The characterization by X-ray diffraction（XRD）, transmission electron microscopy（TEM） and scanning electron microscopy（SEM） reveals that all the as-cast alloys hold multiphase structures, containing Mg2Ni-type major phase as well as some secondary phases Mg6Ni, Nd5Mg41, and Nd Ni, whose amounts clearly grow with increasing Nd content. Furthermore, the as-spun Nd-free alloy displays an entire nanocrystalline structure, whereas the as-spun Nd-added alloys hold a mixed structure of nanocrystalline and amorphous structure and the amorphization degree of the alloys visibly increases with the rising of the Nd content, suggesting that the addition of Nd facilitates the glass forming in the Mg2Ni-type alloy. The measurement of the hydrogen storage kinetics indicates that the addition of Nd significantly improves the gaseous and electrochemical hydrogen storage kinetics of the alloys. The addition of Nd enhances the diffusion ability of hydrogen atoms in the alloy, but it impairs the charge-transfer reaction on the surface of the alloy electrode, which makes the high rate discharge ability（HRD） of the alloy electrode fi rst mount up and then go down with the growing of Nd content.
基金Funded by the National Natural Science Foundations of China(Nos.51161015,51371094)Natural Science Foundation of Inner Mongolia,China(No.2011ZD10)
文摘The element Ni in the Mg2Ni alloy is partially substituted by M（M = Cu, Co, Mn） in order to ameliorate the electrochemical hydrogen storage performances of Mg2Ni-type electrode alloys. The nanocrystalline and amorphous Mg20Ni10-xMx（M = None, Cu, Co, Mn; x = 0-4） alloys were prepared by melt spinning. The effects of the M（M = Cu, Co, Mn） content on the structures and electrochemical hydrogen storage characteristics of the as-cast and spun alloys were comparatively studied. The analyses by XRD, SEM and HRTEM reveal that all the as-cast alloys have a major phase of Mg2Ni but the M（M = Co, Mn） substitution brings on the formation of some secondary phases, MgCo2 and Mg for the（M = Co） alloy, and Mn Ni and Mg for the（M = Mn） alloy. Besides, the as-spun（M = None, Cu） alloys display an entirely nanocrystalline structure, whereas the as-spun（M = Co, Mn） alloys hold a nanocrystalline/amorphous structure, suggesting that the substitution of M（M = Co, Mn） for Ni facilitates the glass formation in the Mg2Ni-type alloys. The electrochemical measurements indicate that the variation of M（M = Cu, Co, Mn） content engenders an obvious effect on the electrochemical performances of the as-cast and spun alloys. To be specific, the cyclic stabilities of the alloys augment monotonously with increasing M（M = Cu, Co, Mn） content, and the capacity retaining rate（S20） is in an order of（M = Cu） 〉（M = Co） 〉（M = Mn） 〉（M = None） for x≤1 but changes to（M = Co） 〉（M = Mn） 〉（M = Cu） 〉（M = None） for x≥2. The discharge capacities of the as-cast and spun alloys always grow with the rising of M（M = Co, Mn） content but first mount up and then go down with increasing M（M = Cu） content. Whatever the M content is, the discharge capacities are in sequence：（M = Co） 〉（M = Mn） 〉（M = Cu） 〉（M = None）. The high rate discharge abilities（HRDs） of all the alloys grow clearly with rising M（M = Cu, Co） content except for（M = Mn） alloy, whose HRD has a maximum value with varying M（M = Mn） content. Furthermore, for the as-cast alloys, the HRD is in order of（M = Co） 〉（M = Mn） 〉（M = Cu） 〉（M = None）, while for the as-spun（20 m·s^-1） alloys, it changes from（M = Co） 〉（M = Mn） 〉（M = Cu） 〉（M = None） for x = 1 to（M = Cu） 〉（M = Co） 〉（M = None） 〉（M = Mn） for x = 4.
基金Projects(50871050, 50961009) supported by the National Natural Science Foundation of ChinaProject(2010ZD05) supported by the Natural Science Foundation of Inner Mongolia, ChinaProject(NJzy08071) supported by the Higher Education Science Research Project of Inner Mongolia, China
文摘In order to improve the electrochemical hydrogen storage performance of the Mg2Ni-type electrode alloys, Mg in the alloy was partially substituted by La, and the nanocrystalline and amorphous Mg2Ni-type Mg20-xLaxNi10 (x=0, 2) alloys were synthesized by melt-spinning technique. The microstructures of the as-spun alloys were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical hydrogen storage properties of the experimental alloys were tested. The results show that no amorphous phase is detected in the as-spun Mg20Ni10 alloy, but the as-spun Mg18La2Ni10 alloy holds a major amorphous phase. As La content increases from 0 to 2, the maximum discharge capacity of the as-spun (20 m/s) alloys rises from 96.5 to 387.1 mA·h/g, and the capacity retaining rate (S20) at the 20th cycle grows from 31.3% to 71.7%. Melt-spinning engenders an impactful effect on the electrochemical hydrogen storage performances of the alloys. With the increase in the spinning rate from 0 to 30 m/s, the maximum discharge capacity increases from 30.3 to 135.5 mA·h/g for the Mg20Ni10 alloy, and from 197.2 to 406.5 mA·h/g for the Mg18La2Ni10 alloy. The capacity retaining rate (S20) of the Mg20Ni10 alloy at the 20th cycle slightly falls from 36.7% to 27.1%, but it markedly mounts up from 37.3% to 78.3% for the Mg18La2Ni10 alloy.
基金Project(2006AA05Z132) supported by the National High-tech Research and Development Program of ChinaProjects(50871050, 50961009) supported by the National Natural Science Foundation of China+1 种基金Project(2010ZD05) supported by the Natural Science Foundation of Inner Mongolia, ChinaProject(NJzy08071) supported by the High Education Science Research Program of Inner Mongolia, China
文摘In order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys,Ni in the alloy is substituted by element Co. The nanocrystalline and amorphous Mg2Ni-type Mg2Ni1-xCox (x=0,0.1,0.2,0.3,0.4) alloys were synthesized by melt-spinning technique. The structures of the as-cast and spun alloys were studied with an X-ray diffractometer (XRD) and a high resolution transmission electronic microscope (HRTEM). An investigation on the thermal stability of the as-spun alloys was carried out with a differential scanning calorimeter (DSC). The hydrogen absorption and desorption kinetics of the alloys were measured with an automatically controlled Sieverts apparatus. The results demonstrate that the substitution of Co for Ni does not alter the major phase of Mg2Ni but results in the formation of secondary phase MgCo2. No amorphous phase is detected in the as-spun Co-free alloy,but a certain amount of amorphous phase is clearly found in the as-spun Co-containing alloys. The substitution of Co for Ni exerts a slight influence on the hydriding kinetics of the as-spun alloy. However,it dramatically enhances the dehydriding kinetics of the as-cast and spun alloys. As Co content (x) increases from 0 to 0.4,the hydrogen desorption capacity increases from 0.19% to 1.39% (mass fraction) in 20 min for the as-cast alloy,and from 0.89% to 2.18% (mass fraction) for the as-spun alloy (30 m/s).
基金Project(2007AA03Z227) supported by High-tech Research and Development Program of ChinaProjects(50871050,50701011) supported by the National Natural Science Foundation of China+1 种基金Project(200711020703) supported by the Natural Science Foundation of Inner Mongolia,ChinaProject(NJzy08071) supported by High Education Science Research Project of Inner Mongolia,China
文摘Nanocrystalline Mg2Ni-type alloys with nominal compositions of Mg20Ni10–xCux(x=0,1,2,3,4,mass fraction,%) were synthesized by rapid quenching technique.The microstructures of the as-cast and quenched alloys were characterized by XRD,SEM and HRTEM.The electrochemical hydrogen storage performances were tested by an automatic galvanostatic system.The hydriding and dehydriding kinetics of the alloys were measured using an automatically controlled Sieverts apparatus.The results show that all the as-quenched alloys hold the typical nanocrystalline structure and the rapid quenching does not change the major phase Mg2Ni.The rapid quenching significantly improves the electrochemical hydrogen storage capacity of the alloys,whereas it slightly impairs the cycling stability of the alloys.Additionally,the hydrogen absorption and desorption capacities of the alloys significantly increase with rising quenching rate.
