^57Fe Mossbauer spectroscopic study was carried out on the organic rich sedimentary samples collected at different depth intervals from newly drilled test well Chinnewala Tibba-1（CT-1） located in Jaisalmer Petrolife...^57Fe Mossbauer spectroscopic study was carried out on the organic rich sedimentary samples collected at different depth intervals from newly drilled test well Chinnewala Tibba-1（CT-1） located in Jaisalmer Petroliferous basin India. It is found that iron is mainly distributed in high spin Fe^3＋and Fe^2＋ state in clay minerals. The plot of Fe^2＋/（Fe^2＋＋ Fe^3＋） indicates the presence of poor redox conditions in the samples.Results obtained are also compared with those already reported in the literature. This comparison shows that there may exist a correlation between prospecting of the basin, the redox environment in sediments and the nature of iron bearing minerals distributed in the sedimentary sequence.展开更多
We calculate level densities for ^56,57 Fe nuclei using BCS hamiltonian with inclusion of pairing interaction. The results of calculations show that the step structure observed experimentally has been supported by mic...We calculate level densities for ^56,57 Fe nuclei using BCS hamiltonian with inclusion of pairing interaction. The results of calculations show that the step structure observed experimentally has been supported by microscopic theory, Also the S-shaped energy and entropy as function of temperature have been obtained in theoretical calculations. Structures in the curves are interpreted as fingerprints of breaking Cooper pairs and quenching of pairing correlations.展开更多
Nanostructured Fe70Si20Cr10 alloy was produced by high energy planetary ball milling, starting from elemental powders. The structural, microstructural and magnetic properties of the milled powders were characterized b...Nanostructured Fe70Si20Cr10 alloy was produced by high energy planetary ball milling, starting from elemental powders. The structural, microstructural and magnetic properties of the milled powders were characterized by X-ray diffraction, scanning electron microscopy, vibrating sample magnetometer and 57Fe M6ssbauer. After 5 h of milling, it is observed the formation of a bcc solid solutions ~t-Fe （Si, Cr）. Its grain size decreases with increasing milling time attaining 20 nm after 15 h of milling time. Analysis of M6ssbauer spectra shows an increasing broad magnetic component when the milling time increases. Its mean hyperfme field is about 25.5 T at 15 h of milling. M-H hysteresis loop curves reveal a room temperature ferromagnetic behaviour with a saturation magnetisation reaching 143 emu/g after 15 hours of milling, which is 20% lower than that of bulk iron; i.e., 1800 emu/g, due to effect of alloying elements after the formation of ct-Fe （Si, Cr） solid solution.展开更多
This review summarizes the recent advances on the application of ^(57)Fe Mössbauer spectrometry to study the magnetic and phase characteristics of Nd–Fe–B-based permanent magnets. First of all, the hyperfine st...This review summarizes the recent advances on the application of ^(57)Fe Mössbauer spectrometry to study the magnetic and phase characteristics of Nd–Fe–B-based permanent magnets. First of all, the hyperfine structures of the Ce_(2)Fe_(14)B,(Ce,Nd)_(2)Fe_(14)B and MM_(2)Fe_(14)B phases are well-defined by using the model based on the Wigner-Seitz analysis of the crystal structure. The results show that the isomer shift δ and the quadrupole splitting öEQ of those 2:14:1 phases show minor changes with the Nd content, while the hyperfine field Bhfincreases monotonically with increasing Nd content and its value is influenced by the element segregation and phase separation in the 2:14:1 phase. Then, the hyperfine structures of the low fraction secondary phases are determined by the ^(57)Fe Mössbauer spectrometry due to its high sensitivity. On this basis,the content, magnetic behavior, and magnetization of the REFe_(2) phase, the amorphous grain boundary(GB) phase, and the amorphous worm-like phase, as well as their effects on the magnetic properties, are systematically studied.展开更多
Temperature dependence of the hyperfine field of Fe nanocrystalline in SiO2matrix prepared by using an ion implantation and subsequent heat treatment can not be described by a formula for the isolated Fe nanocrystalli...Temperature dependence of the hyperfine field of Fe nanocrystalline in SiO2matrix prepared by using an ion implantation and subsequent heat treatment can not be described by a formula for the isolated Fe nanocrystalline.The large stresses or chemical bond force to which interface atoms may be subjected lead to increase effective anisotropic constant. In addition a little concentration of oxygen atoms contained in the crystalline might enhance the hyperfine field.展开更多
基金The project was supported by the National Key Basic Research Project of China(973)(2010CB833103)Scientific Research Key Program of Beijing Municipal Commission of Education,China(KM201010005019)~~
文摘^57Fe Mossbauer spectroscopic study was carried out on the organic rich sedimentary samples collected at different depth intervals from newly drilled test well Chinnewala Tibba-1（CT-1） located in Jaisalmer Petroliferous basin India. It is found that iron is mainly distributed in high spin Fe^3＋and Fe^2＋ state in clay minerals. The plot of Fe^2＋/（Fe^2＋＋ Fe^3＋） indicates the presence of poor redox conditions in the samples.Results obtained are also compared with those already reported in the literature. This comparison shows that there may exist a correlation between prospecting of the basin, the redox environment in sediments and the nature of iron bearing minerals distributed in the sedimentary sequence.
文摘We calculate level densities for ^56,57 Fe nuclei using BCS hamiltonian with inclusion of pairing interaction. The results of calculations show that the step structure observed experimentally has been supported by microscopic theory, Also the S-shaped energy and entropy as function of temperature have been obtained in theoretical calculations. Structures in the curves are interpreted as fingerprints of breaking Cooper pairs and quenching of pairing correlations.
文摘Nanostructured Fe70Si20Cr10 alloy was produced by high energy planetary ball milling, starting from elemental powders. The structural, microstructural and magnetic properties of the milled powders were characterized by X-ray diffraction, scanning electron microscopy, vibrating sample magnetometer and 57Fe M6ssbauer. After 5 h of milling, it is observed the formation of a bcc solid solutions ~t-Fe （Si, Cr）. Its grain size decreases with increasing milling time attaining 20 nm after 15 h of milling time. Analysis of M6ssbauer spectra shows an increasing broad magnetic component when the milling time increases. Its mean hyperfme field is about 25.5 T at 15 h of milling. M-H hysteresis loop curves reveal a room temperature ferromagnetic behaviour with a saturation magnetisation reaching 143 emu/g after 15 hours of milling, which is 20% lower than that of bulk iron; i.e., 1800 emu/g, due to effect of alloying elements after the formation of ct-Fe （Si, Cr） solid solution.
基金Project supported by the Zhejiang Provincial Natural Science Foundation of China(Grant Nos.LY20E010002,LR18E010001,and LD19E010001)the National Natural Science Foundation of China(Grant Nos.U1704253 and 51801047)+2 种基金Liaoning Revitalization Talents Program(Grant No.XLYC1807177)the Key Research and Development plan of Zhejiang Province,China(Grant No.2020C05014)Ten Thousand Talents Plan of Zhejiang Province,China(Grant No.2018R52003)。
文摘This review summarizes the recent advances on the application of ^(57)Fe Mössbauer spectrometry to study the magnetic and phase characteristics of Nd–Fe–B-based permanent magnets. First of all, the hyperfine structures of the Ce_(2)Fe_(14)B,(Ce,Nd)_(2)Fe_(14)B and MM_(2)Fe_(14)B phases are well-defined by using the model based on the Wigner-Seitz analysis of the crystal structure. The results show that the isomer shift δ and the quadrupole splitting öEQ of those 2:14:1 phases show minor changes with the Nd content, while the hyperfine field Bhfincreases monotonically with increasing Nd content and its value is influenced by the element segregation and phase separation in the 2:14:1 phase. Then, the hyperfine structures of the low fraction secondary phases are determined by the ^(57)Fe Mössbauer spectrometry due to its high sensitivity. On this basis,the content, magnetic behavior, and magnetization of the REFe_(2) phase, the amorphous grain boundary(GB) phase, and the amorphous worm-like phase, as well as their effects on the magnetic properties, are systematically studied.
文摘Temperature dependence of the hyperfine field of Fe nanocrystalline in SiO2matrix prepared by using an ion implantation and subsequent heat treatment can not be described by a formula for the isolated Fe nanocrystalline.The large stresses or chemical bond force to which interface atoms may be subjected lead to increase effective anisotropic constant. In addition a little concentration of oxygen atoms contained in the crystalline might enhance the hyperfine field.
