In order to ameliorate the electrochemical cycle stability of the RE-Mg-Ni based A2B7-type electrode alloys, the Mg content in the alloy was reduced and La in the alloy was partially substituted by Sm. The La0.8-xSmxM...In order to ameliorate the electrochemical cycle stability of the RE-Mg-Ni based A2B7-type electrode alloys, the Mg content in the alloy was reduced and La in the alloy was partially substituted by Sm. The La0.8-xSmxMg0.2Ni3.15Co0.2Al0.1Si0.05 （x=0, 0.1, 0.2, 0.3, 0.4） elec-trode alloys were fabricated by casting and annealing. The microstructures of the as-cast and annealed alloys were characterized by XRD and SEM. The electrochemical hydrogen storage characteristics of the as-cast and annealed alloys were measured. The results revealed that all of the experimental alloys mainly consisted of two phases： （La,Mg）2Ni7 phase with the hexagonal Ce2Ni7-type structure and LaNi5 phase with the hexagonal CaCu5-type structure. As Sm content grew from 0 to 0.4, the discharge capacity and the high rate discharge ability （HRD） first in-creased and then decreased for the as-cast and annealed alloys, whereas the capacity retaining rate （S100） after 100 cycles increased continuously.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 Mg2oNi10 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
For the purpose of improving the electrochemical cycle stability of the La-Mg-Ni based A2BT-type electrode alloys, both reducing Mg content and substituting La with Pr were adopted. The Lao.8-xPrxMg0.2Ni3.15Co0.2A10.1...For the purpose of improving the electrochemical cycle stability of the La-Mg-Ni based A2BT-type electrode alloys, both reducing Mg content and substituting La with Pr were adopted. The Lao.8-xPrxMg0.2Ni3.15Co0.2A10.1Si0.05 （x=0, 0.1, 0.2, 0.3, 0.4） electrode alloys were fabricated by casting and annealing. The investigation on the structures and electrochemical performances of the alloys was performed. The obtained results reveal that the as-cast and annealed alloys comprise two major phases, （La, Mg）2Ni7 phase with the hexagonal Ce2NiT-type structure and LaNi5 phase with the hexagonal CaCus-type structure, as well as a little residual LaNi3 phase. It is also found that the addition of Pr element observably affects the electrochemical hydrogen storage characteristics of the alloys, just as the discharge capacity and high rate discharge ability （HRD） first rise then fall with the growing of Pr content, and among all the alloys, the as-cast and annealed （x=0.3） alloys generate the largest discharge capacities of 360.8 and 386.5 mA.h/g, respectively. Additionally, the electrochemical cycle stability of all the alloys markedly grows with the increase of Pr content. The capacity retaining rate （S100） at the 100th charging and discharging cycle is enhanced from 64.98% to 77.55% for the as-cast alloy, and from 76.60% to 95.72% for the as-annealed alloy by rising Pr content from 0 to 0.4. Furthermore, the substitution of Pr for La results in first increase and then decrease in the hydrogen diffusion coefficient （D）, the limiting current density （IL） as well as the electrochemical impedance.展开更多
A partial substitution of Ni by Mn was implemented in order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys. The nanocrystalline and amorphous MgzNi-type Mg2Nil-xMnx （x=0, 0. 1, 0.2, 0.3, ...A partial substitution of Ni by Mn was implemented in order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys. The nanocrystalline and amorphous MgzNi-type Mg2Nil-xMnx （x=0, 0. 1, 0.2, 0.3, 0.4） alloys were synthesized by the melt-spinning technique. The structures of the as-cast and spun alloys were studied by X-ray diffractometry （XRD）, scanning electron microscopy （SEM） and high resolution transmission electron microscopy （HRTEM）. The hydrogen absorption and desorption kinetics of the alloys were measured with an automatically controlled Sieverts apparatus. The results show that the as-spun Mn-free alloy holds a typical nanocrystalline structure, whereas the as-spun alloys containing Mn display a nanocrystalline and amorphous structure, confirming that the substitution of Mn for Ni intensifies the glass forming ability of the Mg2Ni-type alloy. The hydrogen absorption and desorption capacities and kinetics of the alloys increase with increasing the spinning rate, for which the nanocrystalline and amorphous structure produced by the melt spinning is mainly responsible. The substitution of Mn for Ni evidently improves the hydrogen desorption performance. The hydrogen desorption capacities of the as-cast and spun alloys rise with the increase in the percentage of Mn substitution.展开更多
The Bayan Obo iron ore contains valuable metallic elements such as niobium and rare earth elements. However, developing appropriate metallurgical processes to achieve effective dephosphorization of Nb-bearing hot meta...The Bayan Obo iron ore contains valuable metallic elements such as niobium and rare earth elements. However, developing appropriate metallurgical processes to achieve effective dephosphorization of Nb-bearing hot metal meanwhile retaining Nb in the steel products remains a challenge. We carried out a thermodynamic study on dephosphorization of Nbbearing hot metal and investigated the effects of the initial [C] content and the dephosphorization temperature on oxidation behaviors of [Nb] and [P]. In particular, we focused on thermodynamic analysis of dephosphorization of Nb-bearing hot metal with highly basic BaO-based slag. The results showed that the highly basic BaO-based slag system is more suitable for dephosphorization under oxidative conditions, and increasing the [C] content favors dephosphorization of Nb-bearing hot metal without oxidizing [Nb]. Moreover, the values of equilibrium oxygen activity for oxidation reactions of [Nb] and [P] are increased as the dephosphorization temperature increases. Considering the hot metal containing 0.02% of [Nb] in Baotou Steel, thermodynamic calculations indicated that the content of [P] can be reduced to 0.02%–0.05% and [Nb] remains unoxidized when dephosphorization occurs at the cconditions of T=1573–1673 K, [C]=4.0%, [Nb]=0.02%, aP2O5=10-24, aNb2O5=10-10.展开更多
Melting method was used to obtain La2Mg17 alloy, and then Ni powder was added by mechanical alloying method. The kinetics of hydriding process and electrochemical properties of La2Mg17-X wt.%Ni （x=0, 50, 100, 150, 20...Melting method was used to obtain La2Mg17 alloy, and then Ni powder was added by mechanical alloying method. The kinetics of hydriding process and electrochemical properties of La2Mg17-X wt.%Ni （x=0, 50, 100, 150, 200） composites were investigated. X-ray diffraction （XRD） and scanning electron microscopy （SEM） analyses showed that the crystal structure of composite alloy gradually transformed into amorphous phase by the effect of ball milling and Ni powders. The research of hydrogen absorption properties found that La2Mg17-50 wt.%Ni reached the highest hydrogen absorption than other alloys with more addition of Ni content, reached to 5.796 wt.% at 3 MPa, and up to 5.229 wt.% merely in 2 min, which revealed that the amorphous phase reduced the H occupation of the lattice clearance, resulting in the decline of hydrogen absorption capacity. The electrochemical tests indicated that the maximum discharge capacity increased to 353.1 mAh/g at 30 ℃, however, the cycle stability decreased considerably./~ series of ki- netic measurements demonstrated that the controlling steps of electrochemical process of La2Mg17-x wt.%Ni alloys transferred from hydrogen diffusion on alloy bulk （x=50, 100） to hydrogen diffusion on both alloy bulk and surface （x=150, 200）.展开更多
Hysteresis loops,energy products and magnetic moment distributions of perpendicularly oriented Nd2Fe(14)B/α-Fe exchange-spring multilayers are studied systematically based on both three-dimensional(3D)and one-dimensi...Hysteresis loops,energy products and magnetic moment distributions of perpendicularly oriented Nd2Fe(14)B/α-Fe exchange-spring multilayers are studied systematically based on both three-dimensional(3D)and one-dimensional(1D)micromagnetic methods,focused on the influence of the interface anisotropy.The calculated results are carefully compared with each other.The interface anisotropy effect is very palpable on the nucleation,pinning and coercive fields when the soft layer is very thin.However,as the soft layer thickness increases,the pinning and coercive fields are almost unchanged with the increment of interface anisotropy though the nucleation field still monotonically rises.Negative interface anisotropy decreases the maximum energy products and increases slightly the angles between the magnetization and applied field.The magnetic moment distributions in the thickness direction at various applied fields demonstrate a progress of three-step magnetic reversal,i.e.,nucleation,evolution and irreversible motion of the domain wall.The above results calculated by two models are in good agreement with each other.Moreover,the in-plane magnetic moment orientations based on two models are different.The 3D calculation shows a progress of generation and disappearance of vortex state,however,the magnetization orientations within the film plane calculated by the 1D model are coherent.Simulation results suggest that negative interface anisotropy is necessarily avoided experimentally.展开更多
The effect of Eu3＋ ion doping in the La sites of single-crystal La4/3Srs/3Mn2O7 was investigated. Electron spin resonance （ESR） was applied to La4/3Sr5/3Mn2O7 and （Lao.8Euo.2）4/3Sr5/3Mn2O7 single crystals. A phas...The effect of Eu3＋ ion doping in the La sites of single-crystal La4/3Srs/3Mn2O7 was investigated. Electron spin resonance （ESR） was applied to La4/3Sr5/3Mn2O7 and （Lao.8Euo.2）4/3Sr5/3Mn2O7 single crystals. A phase separation and phase transitions were observed from the ESR spectra data. Between 350 K and 300 K, both paramagnetic resonance （PMR） and anisotropic ferromagnetic resonance （FMR） lines were observed in the ab plane and the c axis direction, suggesting a coexistence of the paramagnetic （PM） phase and the ferromagnetic （FM） phase. The magnetization measurement reveals a spin-glass-like behavior in single-crystal （Lao.8Euo.2）4/3 Sr5/3Mn2O7 below the temperature of spin freezing Tf （- 29.5 K）.展开更多
The magnetic and electrical properties of nonmagnetic Ga＋3 ion substitution for Mn site are investigated in the bilayer manganite La1.2Sr1.8Mn2-xGaxO7. When the Mn is substituted by Ga, the ferromagnetic property obv...The magnetic and electrical properties of nonmagnetic Ga＋3 ion substitution for Mn site are investigated in the bilayer manganite La1.2Sr1.8Mn2-xGaxO7. When the Mn is substituted by Ga, the ferromagnetic property obviously weakens, the magnetic transition temperature decreases and a spin-glass behaviour occurs at low temperature. Meanwhile, doping causes the resistivity to dramatically increase, the metal-insulator transition temperature to disappear, and a greater magneto-resistance effect to occur at low temperature. These effects result from the fact that Ga substitution dilutes the magnetic active Mn-O-Mn network and weakens the double exchange interaction, and further suppresses ferromagnetic ordering and metallic conduction.展开更多
基金Project supported by National Natural Science Foundations of China (51161015 and 50961009)National High Technology Research and Development Program of China (2011AA03A408)Natural Science Foundations of Inner Mongolia,China (2011ZD10 and 2010ZD05)
文摘In order to ameliorate the electrochemical cycle stability of the RE-Mg-Ni based A2B7-type electrode alloys, the Mg content in the alloy was reduced and La in the alloy was partially substituted by Sm. The La0.8-xSmxMg0.2Ni3.15Co0.2Al0.1Si0.05 （x=0, 0.1, 0.2, 0.3, 0.4） elec-trode alloys were fabricated by casting and annealing. The microstructures of the as-cast and annealed alloys were characterized by XRD and SEM. The electrochemical hydrogen storage characteristics of the as-cast and annealed alloys were measured. The results revealed that all of the experimental alloys mainly consisted of two phases： （La,Mg）2Ni7 phase with the hexagonal Ce2Ni7-type structure and LaNi5 phase with the hexagonal CaCu5-type structure. As Sm content grew from 0 to 0.4, the discharge capacity and the high rate discharge ability （HRD） first in-creased and then decreased for the as-cast and annealed alloys, whereas the capacity retaining rate （S100） after 100 cycles increased continuously.
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 Mg2oNi10 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Projects(51161015,50961009) supported by the National Natural Science Foundation of ChinaProject(2011AA03A408) supported by the National High Technology Research and Development Program of ChinaProjects(2011ZD10,2010ZD05) supported by the Natural Science Foundation of Inner Mongolia,China
文摘For the purpose of improving the electrochemical cycle stability of the La-Mg-Ni based A2BT-type electrode alloys, both reducing Mg content and substituting La with Pr were adopted. The Lao.8-xPrxMg0.2Ni3.15Co0.2A10.1Si0.05 （x=0, 0.1, 0.2, 0.3, 0.4） electrode alloys were fabricated by casting and annealing. The investigation on the structures and electrochemical performances of the alloys was performed. The obtained results reveal that the as-cast and annealed alloys comprise two major phases, （La, Mg）2Ni7 phase with the hexagonal Ce2NiT-type structure and LaNi5 phase with the hexagonal CaCus-type structure, as well as a little residual LaNi3 phase. It is also found that the addition of Pr element observably affects the electrochemical hydrogen storage characteristics of the alloys, just as the discharge capacity and high rate discharge ability （HRD） first rise then fall with the growing of Pr content, and among all the alloys, the as-cast and annealed （x=0.3） alloys generate the largest discharge capacities of 360.8 and 386.5 mA.h/g, respectively. Additionally, the electrochemical cycle stability of all the alloys markedly grows with the increase of Pr content. The capacity retaining rate （S100） at the 100th charging and discharging cycle is enhanced from 64.98% to 77.55% for the as-cast alloy, and from 76.60% to 95.72% for the as-annealed alloy by rising Pr content from 0 to 0.4. Furthermore, the substitution of Pr for La results in first increase and then decrease in the hydrogen diffusion coefficient （D）, the limiting current density （IL） as well as the electrochemical impedance.
基金Projects(50871050,50961001) supported by the National Natural Science Foundation of ChinaProject(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A partial substitution of Ni by Mn was implemented in order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys. The nanocrystalline and amorphous MgzNi-type Mg2Nil-xMnx （x=0, 0. 1, 0.2, 0.3, 0.4） alloys were synthesized by the melt-spinning technique. The structures of the as-cast and spun alloys were studied by X-ray diffractometry （XRD）, scanning electron microscopy （SEM） and high resolution transmission electron microscopy （HRTEM）. The hydrogen absorption and desorption kinetics of the alloys were measured with an automatically controlled Sieverts apparatus. The results show that the as-spun Mn-free alloy holds a typical nanocrystalline structure, whereas the as-spun alloys containing Mn display a nanocrystalline and amorphous structure, confirming that the substitution of Mn for Ni intensifies the glass forming ability of the Mg2Ni-type alloy. The hydrogen absorption and desorption capacities and kinetics of the alloys increase with increasing the spinning rate, for which the nanocrystalline and amorphous structure produced by the melt spinning is mainly responsible. The substitution of Mn for Ni evidently improves the hydrogen desorption performance. The hydrogen desorption capacities of the as-cast and spun alloys rise with the increase in the percentage of Mn substitution.
基金Item Sponsored by Inner Mongolia Natural Science Foundation of China(2011MS0726)Inner Mongolia University of Science and Technology Innovation Foundation of China(2009NC016)Inner Mongolia Key Laboratory for Utilization of Bayan Obo Multi-metallic Resources Foundation of China(BO-13-003)
文摘The Bayan Obo iron ore contains valuable metallic elements such as niobium and rare earth elements. However, developing appropriate metallurgical processes to achieve effective dephosphorization of Nb-bearing hot metal meanwhile retaining Nb in the steel products remains a challenge. We carried out a thermodynamic study on dephosphorization of Nbbearing hot metal and investigated the effects of the initial [C] content and the dephosphorization temperature on oxidation behaviors of [Nb] and [P]. In particular, we focused on thermodynamic analysis of dephosphorization of Nb-bearing hot metal with highly basic BaO-based slag. The results showed that the highly basic BaO-based slag system is more suitable for dephosphorization under oxidative conditions, and increasing the [C] content favors dephosphorization of Nb-bearing hot metal without oxidizing [Nb]. Moreover, the values of equilibrium oxygen activity for oxidation reactions of [Nb] and [P] are increased as the dephosphorization temperature increases. Considering the hot metal containing 0.02% of [Nb] in Baotou Steel, thermodynamic calculations indicated that the content of [P] can be reduced to 0.02%–0.05% and [Nb] remains unoxidized when dephosphorization occurs at the cconditions of T=1573–1673 K, [C]=4.0%, [Nb]=0.02%, aP2O5=10-24, aNb2O5=10-10.
基金Project supported by National Natural Science Foundation of China(51161015)National Science Foundation of Inner Mongolia,China(2011ZD10)
文摘Melting method was used to obtain La2Mg17 alloy, and then Ni powder was added by mechanical alloying method. The kinetics of hydriding process and electrochemical properties of La2Mg17-X wt.%Ni （x=0, 50, 100, 150, 200） composites were investigated. X-ray diffraction （XRD） and scanning electron microscopy （SEM） analyses showed that the crystal structure of composite alloy gradually transformed into amorphous phase by the effect of ball milling and Ni powders. The research of hydrogen absorption properties found that La2Mg17-50 wt.%Ni reached the highest hydrogen absorption than other alloys with more addition of Ni content, reached to 5.796 wt.% at 3 MPa, and up to 5.229 wt.% merely in 2 min, which revealed that the amorphous phase reduced the H occupation of the lattice clearance, resulting in the decline of hydrogen absorption capacity. The electrochemical tests indicated that the maximum discharge capacity increased to 353.1 mAh/g at 30 ℃, however, the cycle stability decreased considerably./~ series of ki- netic measurements demonstrated that the controlling steps of electrochemical process of La2Mg17-x wt.%Ni alloys transferred from hydrogen diffusion on alloy bulk （x=50, 100） to hydrogen diffusion on both alloy bulk and surface （x=150, 200）.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFB0700900)the National Natural Science Foundation of China(Grant Nos.51571126 and 51861030)+1 种基金the Inner Mongolia Autonomous Region Natural Science Foundation of China(Grant No.2019MS01002)the Inner Mongolia Innovative Research Team of China(Grant No.3400102)。
文摘Hysteresis loops,energy products and magnetic moment distributions of perpendicularly oriented Nd2Fe(14)B/α-Fe exchange-spring multilayers are studied systematically based on both three-dimensional(3D)and one-dimensional(1D)micromagnetic methods,focused on the influence of the interface anisotropy.The calculated results are carefully compared with each other.The interface anisotropy effect is very palpable on the nucleation,pinning and coercive fields when the soft layer is very thin.However,as the soft layer thickness increases,the pinning and coercive fields are almost unchanged with the increment of interface anisotropy though the nucleation field still monotonically rises.Negative interface anisotropy decreases the maximum energy products and increases slightly the angles between the magnetization and applied field.The magnetic moment distributions in the thickness direction at various applied fields demonstrate a progress of three-step magnetic reversal,i.e.,nucleation,evolution and irreversible motion of the domain wall.The above results calculated by two models are in good agreement with each other.Moreover,the in-plane magnetic moment orientations based on two models are different.The 3D calculation shows a progress of generation and disappearance of vortex state,however,the magnetization orientations within the film plane calculated by the 1D model are coherent.Simulation results suggest that negative interface anisotropy is necessarily avoided experimentally.
基金supported by the National Natural Science Foundation of China(Grant Nos.11164019 and 11064008)the Inner Mongolia Natural ScienceFoundation,China(Grant Nos.NJZZ11166,NJZY10163,NJZY12202,2011MS0101,2011MS0108,and 2009MS0101)
文摘The effect of Eu3＋ ion doping in the La sites of single-crystal La4/3Srs/3Mn2O7 was investigated. Electron spin resonance （ESR） was applied to La4/3Sr5/3Mn2O7 and （Lao.8Euo.2）4/3Sr5/3Mn2O7 single crystals. A phase separation and phase transitions were observed from the ESR spectra data. Between 350 K and 300 K, both paramagnetic resonance （PMR） and anisotropic ferromagnetic resonance （FMR） lines were observed in the ab plane and the c axis direction, suggesting a coexistence of the paramagnetic （PM） phase and the ferromagnetic （FM） phase. The magnetization measurement reveals a spin-glass-like behavior in single-crystal （Lao.8Euo.2）4/3 Sr5/3Mn2O7 below the temperature of spin freezing Tf （- 29.5 K）.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50862007)the Inner Mongolia Natural Science Foundation of China (Grant No. 2009MS0101)
文摘The magnetic and electrical properties of nonmagnetic Ga＋3 ion substitution for Mn site are investigated in the bilayer manganite La1.2Sr1.8Mn2-xGaxO7. When the Mn is substituted by Ga, the ferromagnetic property obviously weakens, the magnetic transition temperature decreases and a spin-glass behaviour occurs at low temperature. Meanwhile, doping causes the resistivity to dramatically increase, the metal-insulator transition temperature to disappear, and a greater magneto-resistance effect to occur at low temperature. These effects result from the fact that Ga substitution dilutes the magnetic active Mn-O-Mn network and weakens the double exchange interaction, and further suppresses ferromagnetic ordering and metallic conduction.
