Elucidation of a reaction mechanism is the most critical aspect for designing electrodes for highperformance secondary batteries.Herein,we investigate the sodium insertion/extraction into an iron fluoride hydrate(FeF_...Elucidation of a reaction mechanism is the most critical aspect for designing electrodes for highperformance secondary batteries.Herein,we investigate the sodium insertion/extraction into an iron fluoride hydrate(FeF_(3)·0.5H_(2)O)electrode for sodium-ion batteries(SIBs).The electrode material is prepared by employing an ionic liquid 1-butyl-3-methylimidazolium-tetrafluoroborate,which serves as a reaction medium and precursor for F^(-)ions.The crystal structure of FeF_(3)·0.5H_(2)O is observed as pyrochlore type with large open 3-D tunnels and a unit cell volume of 1129A^(3).The morphology of FeF_(3)·0.5H_(2)O is spherical shape with a mesoporous structure.The microstructure analysis reveals primary particle size of around 10 nm.The FeF_(3)·0.5H_(2)O cathode exhibits stable discharge capacities of 158,210,and 284 mA h g^(-1) in three different potential ranges of 1.5-4.5,1.2-4.5,and 1.0-4.5 V,respectively at 0.05 C rate.The specific capacities remained stable in over 50 cycles in all three potential ranges,while the rate capability was best in the potential range of 1.5-4.5 V.The electrochemical sodium storage mechanism is studied using X-ray absorption spectroscopy,indicating higher conversion at a more discharged state.Ex-situ M?ssbauer spectroscopy strengthens the results for reversible reduction/oxidation of Fe.These results will be favorable to establish high-performance cathode materials with selective voltage window for SIBs.展开更多
In search of an experimental route to produce linear arrays of spins without the use of nanotechnological tools, we have doped Nb<sub>28</sub>O<sub>70</sub> with small amounts of transition met...In search of an experimental route to produce linear arrays of spins without the use of nanotechnological tools, we have doped Nb<sub>28</sub>O<sub>70</sub> with small amounts of transition metal oxides (TM;in this case Fe<sub>2</sub>O<sub>3</sub>) or rare-earth oxides<sub>3</sub>, and investigated the location of the alien metal (Fe in this case) in the structure. Previous AC magnetic susceptibility measurements at low temperatures have been consistent with the formation of arrays of TM magnetic moments along the widely spaced columns parallel to the crystallographic b-axis in the Nb<sub>28</sub>O<sub>70</sub> structure. To obtain further details about the TM distribution, the previous investigation has been extended now to include a room-temperature Mössbauer spectroscopic analysis of the Fe-doped material. The data are consistent with the presence of low-spin Fe<sup>3+</sup> ions in both octahedral and tetrahedral coordinations of oxygens, and confirm (as suggested in the previous work) that Fe also interchanges positions with Nb ions located at tetrahedrally coordinated sites in the columns of the structure.展开更多
In search of an experimental route to produce linear arrays of spins without the use of nanotechnological tools, we have doped Nb<sub>28</sub>O<sub>70</sub> with small amounts of transition met...In search of an experimental route to produce linear arrays of spins without the use of nanotechnological tools, we have doped Nb<sub>28</sub>O<sub>70</sub> with small amounts of transition metal oxides (TM;in this case Fe<sub>2</sub>O<sub>3</sub>) or rare-earth oxides<sub>3</sub>, and investigated the location of the alien metal (Fe in this case) in the structure. Previous AC magnetic susceptibility measurements at low temperatures have been consistent with the formation of arrays of TM magnetic moments along the widely spaced columns parallel to the crystallographic b-axis in the Nb<sub>28</sub>O<sub>70</sub> structure. To obtain further details about the TM distribution, the previous investigation has been extended now to include a room-temperature Mössbauer spectroscopic analysis of the Fe-doped material. The data are consistent with the presence of low-spin Fe<sup>3+</sup> ions in both octahedral and tetrahedral coordinations of oxygens, and confirm (as suggested in the previous work) that Fe also interchanges positions with Nb ions located at tetrahedrally coordinated sites in the columns of the structure.展开更多
The Dounan manganese deposit is a typical large-scale marine sedimentary manganese deposit of the Middle Triassic in China. The metallogenic environment and change process directly dictate the migration, enrichment, a...The Dounan manganese deposit is a typical large-scale marine sedimentary manganese deposit of the Middle Triassic in China. The metallogenic environment and change process directly dictate the migration, enrichment, and precipitation of Mn. To better understand its metallogenetic environment, a detailed study was undertaken involving field observation, mineralogical and geochemical and M?ssbauer spectroscopic analyses. The major findings are as follows:(1) Lithofacies paleogeography, sedimentary structural characteristics, and geochemical indexes indicate that the deposits were formed in an epicontinental marine sedimentary basin environment of normal salinity;(2) there were three ore phases including Mn oxides, Mn carbonates, and mixed Mn ores. The ore minerals found were braunite, manganite, Ca-rhodochrosite, manganocalcite, and kutnahorite. Petrographic and mineralogical information indicates that the metallogenic environment was a weakly alkaline and weakly oxidized to weakly reduced environment, and the mineralization occurred near the redox interface;(3) the V/(V + Ni)ratios, δCe and Fe^(2+)/Fe^(3+) found in profiles of Baigu and Gake ore sections show that the redox conditions of the ore-forming environment were continuously changing; and(4) three Fe species, α-Fe_2O_3, para-Fe^(3+), and para-Fe^(2+),were found in hematite and clay mineral samples using M?ssbauer spectrum analysis. The presence and distribution of these Fe species indicate that the deposit was formed in a typical sedimentary environment during the mineralization process. In summary, our study showed that redox was a key factor controlling the mineralization of the Dounan manganese deposit. Our results have led us to the conclusion that transgression and regression caused fluctuations in sea level, which in turn caused the change of the redox environment. M?ssbauer spectroscopy is an effective tool for studying the redox conditions of the paleoenvironment in which sedimentary manganese deposits were formed.展开更多
The emission Mssbauer Spectroscopy in cotnbination with transmission electron microscope was used to study NiTi shape memory alloy. The damage and the precipitated phase in NiTi alloy have heen discussed.
用DSC技术和M ssbauer谱研究了颗粒弥散的快凝Al Fe V Si Nd合金薄带中纳米相的转变和相变动力学·结果表明 :快凝Al Fe V Si Nd纳米合金在加热过程中亚稳的Al8Fe4Nd相向α Al13 (Fe ,V) 3 Si相转变 ,并用Avrami公式计算了Al8Fe4Nd...用DSC技术和M ssbauer谱研究了颗粒弥散的快凝Al Fe V Si Nd合金薄带中纳米相的转变和相变动力学·结果表明 :快凝Al Fe V Si Nd纳米合金在加热过程中亚稳的Al8Fe4Nd相向α Al13 (Fe ,V) 3 Si相转变 ,并用Avrami公式计算了Al8Fe4Nd相的分解激活能Eα 为 1 61± 0 1 2eV·研究表明亚稳相Al8Fe4Nd向α Al13 (Fe,V) 3 Si相转变的过程是由原子体扩散和原位扩散共同控制的·展开更多
Ball milling for long time （such as 10, 20, and 30 h） can transform Fe84.94Si9,68A15.38 alloy powders with irregular shapes into flakes. X-ray diffraction （XRD） and M6ssbauer measurements have proven that the unmi...Ball milling for long time （such as 10, 20, and 30 h） can transform Fe84.94Si9,68A15.38 alloy powders with irregular shapes into flakes. X-ray diffraction （XRD） and M6ssbauer measurements have proven that the unmilled particles and the flakes obtained by milling for 10 h have the same D03-type superlattice structure. The flakes obtained by milling for 20 h and 30 h have the same disorder a-Fe（Si, A1） structure. There are more than 6 absorption peaks in the transmis- sion MSssbauer spectra （TMSs） for the particles with D03-type superlattice structure, which can be fitted with 5 sextets representing 5 different Fe-site environments. However, only 6 TMS absorption peaks have been found for particles with a disorder a-Fe（Si, A1） structure, which can be fitted with the distributions of M6ssbauer parameters （Bhf, isomer shift）. The TMS results show that the flaky particles have a stronger tendency to possess the planar magnetic anisotropy. As the result, the flakes have larger microwave permeability values than particles with irregular shapes. The conversion electron M6ssbauer spectra （CEMSs） also show the significantly different Fe-sites environments between the alloy surface and the inside.展开更多
The structural evolution of Fe-doped TiO2 by high-energy ball milling was investigated by X-ray diffraction and Mǒssbauer spectroscopy, The results show that the original anatase-TiO2 transforms to srilankite-type an...The structural evolution of Fe-doped TiO2 by high-energy ball milling was investigated by X-ray diffraction and Mǒssbauer spectroscopy, The results show that the original anatase-TiO2 transforms to srilankite-type and rutile-type during ball milling. Iron atoms are preferable to dissolve in rutile-TiO2 and there are two relative doublets appearing in Mǒssbauer spectra. A doublet is found in the condition of Fe atoms dissolved in srilankite TiO2 lattice. Mǒssbauer spectra show that the composition distribution is nonuniform in TiO2 during the mechanical alloying with Fe atoms rich at the interface or surface of TiO2 crystalline.展开更多
In this paper, an overview of the theory of Mössbauer effect is covered, and the main hyperfine interactions parameters which affect the shape of the resultant Mössbauer spectrum are explained and il...In this paper, an overview of the theory of Mössbauer effect is covered, and the main hyperfine interactions parameters which affect the shape of the resultant Mössbauer spectrum are explained and illustrated as well. In principle, Mössbauer effect applies to any and all nuclides, but in practice, certain ideal properties are desirable;that is, the conditions for recoil-free emission and absorption of gamma rays must be optimized. Therefore, briefly discussed in this review, one of the most commonly used for practical and fundamental studies the 151Eu Mössbauer isotope. Also, the intermediate valence phenomena and their theoretical treatments are briefly discussed.展开更多
Natural magnetic black sands are known from several sites often located in areas of volcanic origin. Their elemental and mineral composition provides information on the geology of their territory and depends on severa...Natural magnetic black sands are known from several sites often located in areas of volcanic origin. Their elemental and mineral composition provides information on the geology of their territory and depends on several factors occurred during their formation. A sample of black sand was collected on the seashore of the island of Mayotte in the Indian Ocean and its magnetic part was investigated by means of energy dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (XRD), and MÖssbauer spectroscopy at room temperature. The mineral composition is dominantly magnetite, in good agreement with samples collected in other sites of volcanic origin. Contrary to pure magnetite, a relevant fraction of Ti was detected by EDS. The 16% Ti and 1% Mn content increase the magnetite lattice parameter to 8.4312 (25) Å. The broadening of XRD lines pointed towards a significant degree of disorder. This was confirmed by MÖssbauer spectroscopy and is attributed to the presence of Ti replacing Fe in the magnetite lattice. The presence of Ti modifies the local magnetic field on the Fe sites, leading to a broader and more complex MÖssbauer transmission spectrum with respect to the one of pure magnetite. To study the effect of temperature, samples were heated for 12 hours to 600°C and 800°C in argon and to 1000°C in air. Annealing in argon did not improve the crystallinity while annealing in air caused a complete decomposition of magnetite into hematite and pseudobrookite.展开更多
Mixed-oxide nanostructures of the type xGd<sub>2</sub>O<sub>3</sub>-(1-x)α-Fe<sub>2</sub>O<sub>3</sub> (x=0.1, 0.3, 0.5 and 0.7) were synthesized by mechanochemical act...Mixed-oxide nanostructures of the type xGd<sub>2</sub>O<sub>3</sub>-(1-x)α-Fe<sub>2</sub>O<sub>3</sub> (x=0.1, 0.3, 0.5 and 0.7) were synthesized by mechanochemical activation for ball milling times of 0, 2, 4, 8 and 12 hours. The systems were subsequently analyzed by Mӧssbauer spectroscopy, X-ray powder diffraction (XRPD), magnetic measurements and optical diffuse reflectance spectroscopy. The magnetic hyperfine field was studied as function of ball milling time for all sextets involved and found to be consistent with the formation of a limited solid solution in the systems investigated. The end-product was the gadolinium perovskite, represented by a doublet whose abundance was derived as function of the milling time. The XRPD patterns recorded for the equimolar composition were dominated by the diffraction peaks of GdFeO<sub>3</sub> after 12 hours of milling. The hysteresis loops were recorded at 300 and 5 K in an applied magnetic field of 5 T and were interpreted as a superposition of paramagnetic behavior of gadolinium oxide and weak ferromagnetic behavior of hematite and gadolinium perovskite. The Morin transition of hematite was inferred from zero-field-cooling-field-cooling (ZFC-FC) curves measured with a magnetic field of 200 Oe in the 5-300 K temperature range and was found to depend on the ball milling time. Optical diffuse reflectance spectra showed that the compounds were semiconductors with an optical band gap of 2.1 eV.展开更多
基金supported by the Basic Science Research Program of the National Research Foundation(NRF)of South Koreafunded by the Ministry of Science&ICT and Future Planning(NRF-2020M3H4A3081889)KIST Institutional Program of South Korea(Project Nos.2E31860)。
文摘Elucidation of a reaction mechanism is the most critical aspect for designing electrodes for highperformance secondary batteries.Herein,we investigate the sodium insertion/extraction into an iron fluoride hydrate(FeF_(3)·0.5H_(2)O)electrode for sodium-ion batteries(SIBs).The electrode material is prepared by employing an ionic liquid 1-butyl-3-methylimidazolium-tetrafluoroborate,which serves as a reaction medium and precursor for F^(-)ions.The crystal structure of FeF_(3)·0.5H_(2)O is observed as pyrochlore type with large open 3-D tunnels and a unit cell volume of 1129A^(3).The morphology of FeF_(3)·0.5H_(2)O is spherical shape with a mesoporous structure.The microstructure analysis reveals primary particle size of around 10 nm.The FeF_(3)·0.5H_(2)O cathode exhibits stable discharge capacities of 158,210,and 284 mA h g^(-1) in three different potential ranges of 1.5-4.5,1.2-4.5,and 1.0-4.5 V,respectively at 0.05 C rate.The specific capacities remained stable in over 50 cycles in all three potential ranges,while the rate capability was best in the potential range of 1.5-4.5 V.The electrochemical sodium storage mechanism is studied using X-ray absorption spectroscopy,indicating higher conversion at a more discharged state.Ex-situ M?ssbauer spectroscopy strengthens the results for reversible reduction/oxidation of Fe.These results will be favorable to establish high-performance cathode materials with selective voltage window for SIBs.
文摘In search of an experimental route to produce linear arrays of spins without the use of nanotechnological tools, we have doped Nb<sub>28</sub>O<sub>70</sub> with small amounts of transition metal oxides (TM;in this case Fe<sub>2</sub>O<sub>3</sub>) or rare-earth oxides<sub>3</sub>, and investigated the location of the alien metal (Fe in this case) in the structure. Previous AC magnetic susceptibility measurements at low temperatures have been consistent with the formation of arrays of TM magnetic moments along the widely spaced columns parallel to the crystallographic b-axis in the Nb<sub>28</sub>O<sub>70</sub> structure. To obtain further details about the TM distribution, the previous investigation has been extended now to include a room-temperature Mössbauer spectroscopic analysis of the Fe-doped material. The data are consistent with the presence of low-spin Fe<sup>3+</sup> ions in both octahedral and tetrahedral coordinations of oxygens, and confirm (as suggested in the previous work) that Fe also interchanges positions with Nb ions located at tetrahedrally coordinated sites in the columns of the structure.
文摘In search of an experimental route to produce linear arrays of spins without the use of nanotechnological tools, we have doped Nb<sub>28</sub>O<sub>70</sub> with small amounts of transition metal oxides (TM;in this case Fe<sub>2</sub>O<sub>3</sub>) or rare-earth oxides<sub>3</sub>, and investigated the location of the alien metal (Fe in this case) in the structure. Previous AC magnetic susceptibility measurements at low temperatures have been consistent with the formation of arrays of TM magnetic moments along the widely spaced columns parallel to the crystallographic b-axis in the Nb<sub>28</sub>O<sub>70</sub> structure. To obtain further details about the TM distribution, the previous investigation has been extended now to include a room-temperature Mössbauer spectroscopic analysis of the Fe-doped material. The data are consistent with the presence of low-spin Fe<sup>3+</sup> ions in both octahedral and tetrahedral coordinations of oxygens, and confirm (as suggested in the previous work) that Fe also interchanges positions with Nb ions located at tetrahedrally coordinated sites in the columns of the structure.
基金supported by the Natural Science Foundation of China(NSFC No.41376080)the 12th Five-Year Plan project of the State Key Laboratory of Ore-deposit Geochemistry,Chinese Academy of Sciences(SKLODG-ZY125-08)
文摘The Dounan manganese deposit is a typical large-scale marine sedimentary manganese deposit of the Middle Triassic in China. The metallogenic environment and change process directly dictate the migration, enrichment, and precipitation of Mn. To better understand its metallogenetic environment, a detailed study was undertaken involving field observation, mineralogical and geochemical and M?ssbauer spectroscopic analyses. The major findings are as follows:(1) Lithofacies paleogeography, sedimentary structural characteristics, and geochemical indexes indicate that the deposits were formed in an epicontinental marine sedimentary basin environment of normal salinity;(2) there were three ore phases including Mn oxides, Mn carbonates, and mixed Mn ores. The ore minerals found were braunite, manganite, Ca-rhodochrosite, manganocalcite, and kutnahorite. Petrographic and mineralogical information indicates that the metallogenic environment was a weakly alkaline and weakly oxidized to weakly reduced environment, and the mineralization occurred near the redox interface;(3) the V/(V + Ni)ratios, δCe and Fe^(2+)/Fe^(3+) found in profiles of Baigu and Gake ore sections show that the redox conditions of the ore-forming environment were continuously changing; and(4) three Fe species, α-Fe_2O_3, para-Fe^(3+), and para-Fe^(2+),were found in hematite and clay mineral samples using M?ssbauer spectrum analysis. The presence and distribution of these Fe species indicate that the deposit was formed in a typical sedimentary environment during the mineralization process. In summary, our study showed that redox was a key factor controlling the mineralization of the Dounan manganese deposit. Our results have led us to the conclusion that transgression and regression caused fluctuations in sea level, which in turn caused the change of the redox environment. M?ssbauer spectroscopy is an effective tool for studying the redox conditions of the paleoenvironment in which sedimentary manganese deposits were formed.
文摘The emission Mssbauer Spectroscopy in cotnbination with transmission electron microscope was used to study NiTi shape memory alloy. The damage and the precipitated phase in NiTi alloy have heen discussed.
文摘用DSC技术和M ssbauer谱研究了颗粒弥散的快凝Al Fe V Si Nd合金薄带中纳米相的转变和相变动力学·结果表明 :快凝Al Fe V Si Nd纳米合金在加热过程中亚稳的Al8Fe4Nd相向α Al13 (Fe ,V) 3 Si相转变 ,并用Avrami公式计算了Al8Fe4Nd相的分解激活能Eα 为 1 61± 0 1 2eV·研究表明亚稳相Al8Fe4Nd向α Al13 (Fe,V) 3 Si相转变的过程是由原子体扩散和原位扩散共同控制的·
基金supported by the National Key Basic Research Program of China(Grant No.2010CB334702)the China National Funds for Distinguished Young Scientists(Grant No.51025208)+1 种基金the International Collaboration Project of Sichuan Province,China(Grant Nos.2011HH0001 and 2012JQ0053)the Program for New Century Excellent Talents in Universities,China(Grant No.NCET-11-0060)
文摘Ball milling for long time （such as 10, 20, and 30 h） can transform Fe84.94Si9,68A15.38 alloy powders with irregular shapes into flakes. X-ray diffraction （XRD） and M6ssbauer measurements have proven that the unmilled particles and the flakes obtained by milling for 10 h have the same D03-type superlattice structure. The flakes obtained by milling for 20 h and 30 h have the same disorder a-Fe（Si, A1） structure. There are more than 6 absorption peaks in the transmis- sion MSssbauer spectra （TMSs） for the particles with D03-type superlattice structure, which can be fitted with 5 sextets representing 5 different Fe-site environments. However, only 6 TMS absorption peaks have been found for particles with a disorder a-Fe（Si, A1） structure, which can be fitted with the distributions of M6ssbauer parameters （Bhf, isomer shift）. The TMS results show that the flaky particles have a stronger tendency to possess the planar magnetic anisotropy. As the result, the flakes have larger microwave permeability values than particles with irregular shapes. The conversion electron M6ssbauer spectra （CEMSs） also show the significantly different Fe-sites environments between the alloy surface and the inside.
文摘The structural evolution of Fe-doped TiO2 by high-energy ball milling was investigated by X-ray diffraction and Mǒssbauer spectroscopy, The results show that the original anatase-TiO2 transforms to srilankite-type and rutile-type during ball milling. Iron atoms are preferable to dissolve in rutile-TiO2 and there are two relative doublets appearing in Mǒssbauer spectra. A doublet is found in the condition of Fe atoms dissolved in srilankite TiO2 lattice. Mǒssbauer spectra show that the composition distribution is nonuniform in TiO2 during the mechanical alloying with Fe atoms rich at the interface or surface of TiO2 crystalline.
文摘In this paper, an overview of the theory of Mössbauer effect is covered, and the main hyperfine interactions parameters which affect the shape of the resultant Mössbauer spectrum are explained and illustrated as well. In principle, Mössbauer effect applies to any and all nuclides, but in practice, certain ideal properties are desirable;that is, the conditions for recoil-free emission and absorption of gamma rays must be optimized. Therefore, briefly discussed in this review, one of the most commonly used for practical and fundamental studies the 151Eu Mössbauer isotope. Also, the intermediate valence phenomena and their theoretical treatments are briefly discussed.
文摘Natural magnetic black sands are known from several sites often located in areas of volcanic origin. Their elemental and mineral composition provides information on the geology of their territory and depends on several factors occurred during their formation. A sample of black sand was collected on the seashore of the island of Mayotte in the Indian Ocean and its magnetic part was investigated by means of energy dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (XRD), and MÖssbauer spectroscopy at room temperature. The mineral composition is dominantly magnetite, in good agreement with samples collected in other sites of volcanic origin. Contrary to pure magnetite, a relevant fraction of Ti was detected by EDS. The 16% Ti and 1% Mn content increase the magnetite lattice parameter to 8.4312 (25) Å. The broadening of XRD lines pointed towards a significant degree of disorder. This was confirmed by MÖssbauer spectroscopy and is attributed to the presence of Ti replacing Fe in the magnetite lattice. The presence of Ti modifies the local magnetic field on the Fe sites, leading to a broader and more complex MÖssbauer transmission spectrum with respect to the one of pure magnetite. To study the effect of temperature, samples were heated for 12 hours to 600°C and 800°C in argon and to 1000°C in air. Annealing in argon did not improve the crystallinity while annealing in air caused a complete decomposition of magnetite into hematite and pseudobrookite.
文摘Mixed-oxide nanostructures of the type xGd<sub>2</sub>O<sub>3</sub>-(1-x)α-Fe<sub>2</sub>O<sub>3</sub> (x=0.1, 0.3, 0.5 and 0.7) were synthesized by mechanochemical activation for ball milling times of 0, 2, 4, 8 and 12 hours. The systems were subsequently analyzed by Mӧssbauer spectroscopy, X-ray powder diffraction (XRPD), magnetic measurements and optical diffuse reflectance spectroscopy. The magnetic hyperfine field was studied as function of ball milling time for all sextets involved and found to be consistent with the formation of a limited solid solution in the systems investigated. The end-product was the gadolinium perovskite, represented by a doublet whose abundance was derived as function of the milling time. The XRPD patterns recorded for the equimolar composition were dominated by the diffraction peaks of GdFeO<sub>3</sub> after 12 hours of milling. The hysteresis loops were recorded at 300 and 5 K in an applied magnetic field of 5 T and were interpreted as a superposition of paramagnetic behavior of gadolinium oxide and weak ferromagnetic behavior of hematite and gadolinium perovskite. The Morin transition of hematite was inferred from zero-field-cooling-field-cooling (ZFC-FC) curves measured with a magnetic field of 200 Oe in the 5-300 K temperature range and was found to depend on the ball milling time. Optical diffuse reflectance spectra showed that the compounds were semiconductors with an optical band gap of 2.1 eV.
