Binding Energies Of Mn Research Articles

A Comparison of Ferrite Growth Kinetics under Denitriding and Decarburizing Conditions

Recent years have seen an increasing emphasis on the identification of transitions in growth modes during the diffusional decomposition of austenite to ferrite in Fe-C-X alloys. Of particular interest are transitions between the extremes of non-partitioned growth represented by the ParaEquilibrium (PE) and local equilibrium negligible partition limits. Identification of such transitions requires high-quality measurements of ferrite growth kinetics, and recent uses of the decarburization approach have allowed access to very high-precision growth kinetic measurements. However, one of the limitations of the decarburization approach is that the lower limit of its applicability is the eutectoid temperature and this has so far compromised its usefulness to probe the temperature dependence of kinetic transitions. In this contribution, analogous denitriding studies have been performed that allow access to much lower temperatures than are possible using decarburization. It is shown that the kinetics of ferrite growth in the Fe-N-Mn system become closer to the PE limit as the temperature is lowered. The growth kinetic data are interpreted quantitatively in the framework of the Zurob et al. model that includes diffusional dissipation due to Mn diffusion across the migrating interface. Furthermore, comparisons are made between decarburization and denitriding in Fe-Mn alloys of the same Mn content at the same temperature. The interface velocities are much faster under denitriding conditions, and this allows inferences to be made about the effect of the interface velocity on dissipation and contact conditions. It is also suggested that the binding energy of Mn to the migrating interface may be slightly higher in the Fe-C-Mn system than in the Fe-N-Mn system, and it is speculated that this is due to the strong segregation of C to the interface and the associated co-segregation of Mn.

Effects of Fe addition on the structure and catalytic performance of mesoporous Mn/Al–SBA-15 catalysts for the reduction of NO with ammonia

Mesoporous Al–SBA-15 has been synthesized by a hydrothermal method and used as a support for Mn/Al–SBA-15, Fe/Al–SBA-15, and Mn–Fe/Al–SBA-15 catalysts. XRD, N2 sorption, XPS, H2-TPR and activity tests have been used to assess the properties of catalysts. The Mn–Fe/Al–SBA-15 catalyst exhibited a higher SCR activity than Mn/Al–SBA-15 or Fe/Al–SBA-15 due to a synergistic effect between Mn and Fe. After the addition of Fe, the binding energy of Mn 2p3/2 on Mn–Fe/Al–SBA-15(573) decreased by about 0.4eV and the Mn4+/Mn3+ ratio decreased to 1.10. The appropriate Mn4+/Mn3+ ratio may have a great effect on the reduction of NO over Mn–Fe/Al–SBA-15(573) catalyst.

X-ray photoemission study in Re0.7Ca0.3MnO3 epitaxial films

We have performed the x-ray photoemission experiments in the colossal magnetoresistive manganites Re0.7Ca0.3MnO3 with Re=La, Pr, and Nd in order to study the Re dependence of electronic structures in this system. The samples are epitaxial films grown on LaAlO3 substrates with pulsed laser deposition system. It is found that the binding energies of Mn 2p3/2 are 641.7 and 643.1 eV for La0.7Ca0.3MnO3 and Nd0.7Ca0.3MnO3, respectively. The shift of this energy level is related to the change in bond angle and/or bond length between Mn and oxygen. Moreover, two lines of O 1s core level are assigned as Mn–O (530 eV) and Re–O (533 eV). The intensity ratio of these two lines in Nd0.7Ca0.3MnO3 is different from those in La0.7Ca0.3MnO3 and Pr0.7Ca0.3MnO3, suggesting that the ion redistribution between Re–O and Mn–O sites occurs with the Re substitution in these films.

Influence of the preparation conditions on the synthesis, structure and thermal properties of LaSrCo1-xMnxO4

A series of LaSrCo1-xMnxO4 (x=0.1, 0.3, 0.5) mixed oxides with a perovskite-type structure were successfully synthesized at fairly low temperatures in air by the decompositon of amorphous citric and ethylene diamine tetraacetic acid complexes. The obtained mixed oxides were characterized by means of XRD, BET, DTA, DTG, XPS analyses. The results show that the precursor can be completely decomposed into oxide at temperatures below 500?C. The decomposed species equisisted of LaSrCo1-xMnxO4 mixed oxides and formed a perovskite-type structure after calcination at 650?C for 6h. The influence of the calcination temperature on the particle size, the microstrain density and the specific surface area was much more significant than that of the calcination time. The intensity of the characteristic peak of Co2+ decresed with increasing manganese content in the LaSrCo1-xMnxO4 (x=0.1, 0.3, 0.5) mixed oxides. The binding energies of Mn 2p3/2 in the mixed oxides reveal that themanganese wasmainly in the Mn3+ state, which indicates that the influence of the calcination temperature and Mn content on the binding energies of Mn 2p3/2 was very weak.

Behaviour of manganese in InP compared with other impurities of 3d transition metals

A series of InP single crystals doped with Mn, Fe, Ti and Ni with two levels of doping, (i) larger (heavy doping); and (ii) smaller (light doping) than the background doping were grown using the Czochralski technique. The crystals were studied by infrared absorption spectroscopy at liquid helium temperatures and by temperature dependent Hall measurements. Absorption spectra indicate a special electron configuration of Mn bound with a shallow hole and on regular partly occupied 3d shells of Fe and Ti. Binding energies of Mn, Fe and Ti were determined by temperature dependent Hall measurements on the first type of sample. Electron mobility of the second type of sample shows a large decline at low temperatures in the cases of Fe, Ti and Ni doping in comparison with the undoped samples. No such difference was observed in the case of Mn doping. The reduction of mobility demonstrates large electron scattering on transition metal ions with partly occupied d-shells.

ESCA and thermodynamic studies of alkali metal ion exchange reactions on an α-MnO2 phase with the tunnel structure

A manganic acid cation-exchange material with the 2×2 type tunnel structure was synthesized by decomposition of a mixture of 80 mol% MnCO3 and 20 mol% (CH3)3COK at 530°C, followed by leaching out any other residual ionic impurities using 1M HNO3. Its chemical composition was represented by H1.7Mn8O15.01. The theoretical ion exchange capacity was 2.49 mmol g−1, assuming that all the H+s are exchangeable. The binding energies of Mn 2p1/2 and Mn 2p3/2 levels were not shifted upon alkali cation exchange of this material. This is clear evidence that no redox process is associated with the cation exchange. The plot of the corrected selectivity coefficient in logarithmic scale vs. the charge fraction M was linear in a small range of the charge fraction up to 0.1. This suggests that each cation resides in a similar chemical environment at this concentration level within the tunnel. The slope was −40 for Li+/H+ exchange, −46 for Na+/H+ exchange, −108 for K+/H+ exchange, −72 for Rb+/H+ exchange, and −60 for Cs+/H+ exchange. The corrected selectivity coefficient at infinitesimal exchange increased in the order Li<Na<CsK≈Rb at 30–60°C, indicating that the largest hydrated cation is the least selective and cations having the same dimension as the tunnel size are the most selective. Thermodynamic functions were evaluated for the hypothetical ion-exchange reaction with the least steric hindrance.

Synthesis and Magnetic Properties of (Mg6-xAlx)MnO8 (0 ≤ x ≤ 0.3)

Murdochite-type (Mg6-xAlx)MnO8 (0 ≤ x ≤ 0.3) was synthesized at 1073 K using a solid state reaction. The cell constants of (Mg6-xAlx)MnO8 monotonously decrease with increasing x. From the results of the magnetic measurement, both low-spin and high-spin states of Mn3+ ions coexist. The binding energy of Mn 2p3/2 determined from XPS measurement is independent of the composition. But the full width at haft maximum (FWHM) of the Mn 2p3/2 peak increases with increasing x . The presence of both low-spin and high-spin slates of the Mn3+ ion causes an increase of the FWHM of the Mn 2p3/2 peak.