Gold in cyanide tailings from Shandong Province is mainly encapsulated by hematite and magnetite at distribution rates of 76.49 % and 10.88 %, respectively.Chlorination-reduction one-step roasting of cyanide tailings ...Gold in cyanide tailings from Shandong Province is mainly encapsulated by hematite and magnetite at distribution rates of 76.49 % and 10.88 %, respectively.Chlorination-reduction one-step roasting of cyanide tailings was conducted under the following conditions： calcium chloride dosage of 6 %, bituminous coal dosage of 30 %, calcium oxide dosage of 10 %（all dosages are vs.the mass of cyanide tailings） at 1000 ℃ of roasting temperature. X-ray diffraction（XRD）, scanning electron microscopy（SEM）, and chemical-phase analysis were performed to investigate the effects of iron phase transformation on the high-temperature chlorination of gold.Results indicate that the lattice structure of hematite undergoes expansion, pulverization, and reorganization when hematite is reduced to magnetite, which leads to42.03 % gold exposure, and the high-temperature chlorination rate of gold is 41.17 % at the same time. The structure of wustite formed by the reduction in magnetite is porous and loose, and thus 44.02 % of gold is exposed. The high-temperature chlorination rate of gold is increased by41.98 percentage points. When wustite is reduced to metallic iron, 4.42 % of gold is exposed, and the hightemperature chlorination rate of gold is increased by3.38 percentage points. Accordingly, the high-temperature chlorination of gold mainly occurs in two stages, in which Fe_2O_3 is reduced to Fe_3O_4, and Fe_3O_4 is reduced to Fe_xO finally.展开更多
Clay minerals from different Cretaceous stratigraphic successions of Egypt were investigated using XRD, DTA, dissolution analysis (DCB), IR, M*issbauer and X-band Electron Spin Resonance (ESR) spectroscopies. The puri...Clay minerals from different Cretaceous stratigraphic successions of Egypt were investigated using XRD, DTA, dissolution analysis (DCB), IR, M*issbauer and X-band Electron Spin Resonance (ESR) spectroscopies. The purity of the samples and the degree of structural order were determined by XRD. The location of Fe in the octahedral sheet is characterized by absorption bands at ～875 cm\+\{-1\} assigned as Al-OH-Fe which is present after chemical dissolution of free iron. The M*issbauer spectra of these clays show two doublets with isomer shift and quadrupole splitting typical of octahedral coordinated Fe\+\{3+\}, in addition to third doubler with hyperfine parameter typical of Fe\+\{2+\} in the spectra of Abu-Had kaolinite (H) sample. 6-lines magnetic hyperfine components which are consistent with those of hematite are confirmed in the spectra of both Isel and Rish kaolinite samples. Goethite was confirmed by both IR and DTA. Multiple nature of ESR of these clays suggested structural Fe in distorted octahedral symmetry and as non-structural Fe. Little dispersion and low swelling indices as well as incomplete activation of investigated montmorillonite samples by NaCO\-3 appear to be due to incomplete disaggregation of montmorillonite particles. This can be explained by the ability of Fe-gel to aggregate the montmorillonite into pseudo-particles and retard the rigid-gel structure. However, extraction of this ferric amorphous compound by dithonite treatment recovers the surface properties of the montmorillonite samples. On the other hand, amounts and site occupation of Fe associated with kaolinite samples show a negative correlation with the parameters used to describe the degree of crystalline perfection, color, brightness and vitrification range of these kaolinite samples.展开更多
The preparation of sulfoaluminate cementitious materials(SCM)is a promising way to massively utilize solid wastes.Iron phases are significant in SCM system but the thermodynamic data of some key minerals,such as6 CaO&...The preparation of sulfoaluminate cementitious materials(SCM)is a promising way to massively utilize solid wastes.Iron phases are significant in SCM system but the thermodynamic data of some key minerals,such as6 CaO·Al2 O3·2 Fe2 O3(C6 AF2)and 6 CaO·2 Al2 O3·Fe2 O3(C6 A2 F),are missing,which greatly hinders the SCM optimization in a theoretical way.This work,for the first time,calculated the standard formation enthalpy,Gibbs free energy of formation,entropy and molar heat capacity for C6 AF2 and C6 A2 F and lowered the errors to the least with the reference of C4 AF data in the literature.By building the function diagram of Gibbs free energy changes with temperature for the basic iron phase formation reactions with the obtained thermodynamic data,it is proved that the formation likeliness of C6 AF2 is higher than that of C6 A2 F,as is accordant to the literatures and verifies the correctness of obtained data.This work provides a good theoretical foundation to optimize SCM mineral system and to study relevant mechanism deeply.展开更多
Clay minerals from different Cretaceous stratigraphic successions of Egypt were investigated using XRD, DTA, dissolution analysis (DCB), IR, Mssbauer and X\|ray Electron Spin Resonance (ESR) spectroscopes. The purity ...Clay minerals from different Cretaceous stratigraphic successions of Egypt were investigated using XRD, DTA, dissolution analysis (DCB), IR, Mssbauer and X\|ray Electron Spin Resonance (ESR) spectroscopes. The purity of the samples and the degree of their structural order were determined by XRD. The location of Fe in the octahedral sheet is characterized by absorption bands at ～875cm\+\{-1\} assigned as Al\|OH\|Fe which persist after chemical dissolution of free iron. The Mssbauer spectra of these clays show two doublets with isomer shift and quadrupole splitting typical of octahedrally coordinated Fe\+\{3+\}, in addition to third doublet with hyperfine parameter typical of Fe\+\{2+\} in the spectra of Abu\|Had kaolinite (H) sample. Six\|lines magnetic hyperfine components which are consistent with those of hematite are confirmed in the spectra of both Isel and Rish kaolinite samples. Goethite was confirmed by both IR and DTA. Multiple nature of ESR of these clays suggested structural Fe in distorted octahedral symmetry as well as non\|structural Fe.\; Little dispersion and low swelling indices as well as incomplete activation of the investigated montmorillonite samples by NaCO\-3 appear to be due to incomplete disaggregation of montmorillonite particles. This can be explained by the ability of Fe\|gel to aggregate the montmorillonite into pseudo\|particles and retard the rigid\|gel structure. However, extraction of this ferric amorphous compound by dithonite treatment recovers the surface properties of the montmorillonite samples.\; On the other hand, the amount and site occupation of Fe associated with kaolinite samples show an inverse correlation with the parameters used to describe the degree of crystallinity perfection, color, brightness and vitrification range of these kaolinite samples.展开更多
It is well known that the magnetic properties such as the Curie temperature Tmag <sub>C and the mean magnetic moment β of ordered compounds have different values from those of the disordered solutions. For inst...It is well known that the magnetic properties such as the Curie temperature Tmag <sub>C and the mean magnetic moment β of ordered compounds have different values from those of the disordered solutions. For instance, both Tmag c and β of the Ni3Pt （L12） and NiPt （L10） and Tmag <sub>c of the CoPt （L10） and CoPt3 （L12） ordered compounds are strongly depressed due to the ordering compared with those of the metastable disordered Ni-Pt and Co-Pt alloys. On the other hand, the γ’-FeNi3 （L12） and the α’-FeCo （B2） ordered compounds have higher Tmag <sub>c and β values comparing with the disordered solution phases, γ （A1） and α （A2）, respectively. In consequence, the stability of the ordered phase is depressed or enhanced due to the interaction between the chemical and magnetic ordering caused by the decrease or increase of Tmag <sub>c and β values. The purpose of this study is to investigate the effect of the interaction between the chemical and the magnetic ordering on the phase equilibria in the Fe-X（X=Al, Co, Ni, Rh, Si） binary systems.The Gibbs energy of the α（A2）, γ（A1） and liquid phases is described by a sub-regular solution approximation. The ordering contribution to the Gibbs energy ,ΔGorder <sub>m, and deviations of magnetic properties, ΔTmag <sub>c and Δβ, of the ordered compounds, FeAl （B2）, Fe3Al （D03）, FeCo （B2）, FeRh （B2）, FeSi （B2）, Fe3Si （D03） and FeNi3 （L12） is introduced by the split compound energy formalism. Effect of the interaction between the chemical ordering, B2, D03 and L12 and the magnetic ordering on the phase equilibria will be discussed according to the calculated phase diagrams of the Fe-X binary systems.展开更多
The difference of conductivity between primary iron-rich phases and aluminum melt has been used to separate them by electromagnetic force (EMF) which is induced by imposing a direct electric current and a steady magne...The difference of conductivity between primary iron-rich phases and aluminum melt has been used to separate them by electromagnetic force (EMF) which is induced by imposing a direct electric current and a steady magnetic field in molten Al-Si alloy. Theoretical analysis and experiments on self-designed electromagnetic separation indicates that primary needle-like β phases are difficult to separate; while primary α iron-rich phases can be separated by electromagnetic separation. Primary iron-rich phases have been removed from the melt successfully when the molten metal flows horizontally through separation channel. The iron content is reduced from 1.13% to 0.41%.展开更多
This paper provides an investigation of the phase transition and spalling characteristic induced during shock loading and unloading in the pure iron and the FeMnNi alloy. The impact for the pure iron is symmetric and ...This paper provides an investigation of the phase transition and spalling characteristic induced during shock loading and unloading in the pure iron and the FeMnNi alloy. The impact for the pure iron is symmetric and with the same-thickness for both the flyer and the target plate. It is found that an abnormal multiple spalling happens in the pure iron sample as the pressure exceeds the α- ε transition threshold of 13 GPa. In the symmetric and same-thickness impact and reverse impact experiments of the FeMnNi alloy, two abnormal tension regions occur when the pressure exceeds the α - ε transition threshold of 6.3 GPa, and the reverse phase transition s - ~ begins below 4.2 GP. The experimental process is simulated successfully from the non-equilibrium mixture phase and Boettger＇s model. Such abnormal spalling phenomena are believed to relate to the shocked α - ε phase transition. The possible reasons for the abnormal multiple spalling, which occurs during the symmetric and same-thickness impact experiments of pure iron and FeMnNi alloy, are discussed.展开更多
The phenomenon of phase separation into antiferromagnetic（AFM） and superconducting（SC） or normal-state regions has great implication for the origin of high-temperature（high-T_c） superconductivity. However, the o...The phenomenon of phase separation into antiferromagnetic（AFM） and superconducting（SC） or normal-state regions has great implication for the origin of high-temperature（high-T_c） superconductivity. However, the occurrence of an intrinsic antiferromagnetism above the T_c of（Li,Fe）OHFe Se superconductor is questioned. Here we report a systematic study on a series of（Li,Fe）OHFe Se single crystal samples with T_c up to ～41 K. We observe an evident drop in the static magnetization at T_（afm） ～ 125 K, in some of the SC（T_c 38 K, cell parameter c■9.27 ？） and non-SC samples. We verify that this AFM signal is intrinsic to（Li,Fe）OHFe Se. Thus, our observations indicate mesoscopic-to-macroscopic coexistence of an AFM state with the normal（below T_（afm）） or SC（below T_c） state in（Li,Fe）OHFe Se. We explain such coexistence by electronic phase separation, similar to that in high-T_c cuprates and iron arsenides. However, such an AFM signal can be absent in some other samples of（Li,Fe）OHFe Se, particularly it is never observed in the SC samples of T_c 38 K, owing to a spatial scale of the phase separation too small for the macroscopic magnetic probe. For this case, we propose a microscopic electronic phase separation. The occurrence of two-dimensional AFM spin fluctuations below nearly the same temperature as T_（afm）, reported previously for a（Li,Fe）OHFe Se（T_c ～ 42 K） single crystal, suggests that the microscopic static phase separation reaches vanishing point in high T_c（Li,Fe）OHFe Se. A complete phase diagram is thus established. Our study provides key information of the underlying physics for high-T_c superconductivity.展开更多
The effect of F,K,and Na on the solid phase reaction of the Baiyunebo iron ore was investigated by differential thermal analysis （DTA） and X-ray diffraction（XRD）.It has been identified that alkaline elements K and...The effect of F,K,and Na on the solid phase reaction of the Baiyunebo iron ore was investigated by differential thermal analysis （DTA） and X-ray diffraction（XRD）.It has been identified that alkaline elements K and Na in the Baiyunebo ore instigate the formation of low melting point compounds Na2SiO3 and Na2O·Fe2O3 and the generation of molten state in the solid phase sintering.Element F in the Baiyunebo ore facilitates the formation of cuspidine compound 3CaO·2SiO2·CaF2 in the solid phase reaction.The cuspidine compound is kept in solid as one of the final products through the entire sintering process due to its high melting point.In the sintering process,CaF2and SiO2 react with CaO first and form 3CaO·2SiO2·CaF2 and 3CaO·2SiO2,so the formation of ferrites,Na2O·Fe2O3,and 2CaO·Fe2O3 is inhibited.展开更多
Gangue existing states largely affect the high-temperature characteristics of iron ores. Using a micro-sintering method and scan- ning electron microscopy, the effects of gangue content, gangue type, and gangue size o...Gangue existing states largely affect the high-temperature characteristics of iron ores. Using a micro-sintering method and scan- ning electron microscopy, the effects of gangue content, gangue type, and gangue size on the assimilation characteristics and fluidity of liquid phase of five different iron ores were analyzed in this study. Next, the mechanism based on the reaction between gangues and sintering mate- dais was unraveled. The results show that, as the SiO2 levels increase in the iron ores, the lowest assimilation temperature （LAT） decreases, whereas the index of fluidity of liquid phase （IFL） increases. Below 1.5wt%, Al2O3 benefits the assimilation reaction, but higher concentra- tions proved detrimental. Larger quartz particles increase the SiO2 levels at the local reaction interface between the iron ore and CaO, thereby reducing the LAT. Quartz-gibbsite is more conductive to assimilation than kaolin. Quartz-gibbsite and kaolin gangues encourage the forma- tion of liquid-phase low-Al2O3-SFCA with high IFL and high-Al2O3-SFCA with low IFL, respectively.展开更多
Electromagnetic separation of the iron-rich phase inclusions from Al alloy was investigated. The influencing parameters including magnetic induction density, the section shape of the separating channel and the length ...Electromagnetic separation of the iron-rich phase inclusions from Al alloy was investigated. The influencing parameters including magnetic induction density, the section shape of the separating channel and the length of influential loop of the metal melt on the separation efficiency of iron-rich phase inclusions were studied. The results show that when the proper magnetic induction density (B=0.3T) is applied, rectangle separating channel is used, and the influential loop of the metal melt is long, high separating efficiency of the iron-rich phase inclusions can be obtained.展开更多
A new method has been proposed to prepare Mg-A1-Si master alloys by utilizing scrap AI-Si-Fe alloys with higher Fe levels, which aims to segregate Fe from AI-Si-Fe alloys by Mg melt. The segregation be- haviors, micro...A new method has been proposed to prepare Mg-A1-Si master alloys by utilizing scrap AI-Si-Fe alloys with higher Fe levels, which aims to segregate Fe from AI-Si-Fe alloys by Mg melt. The segregation be- haviors, microstructure morphology and evolution mechanism of iron-rich phases in Mg-A1-Si alloy melts were studied, after AI-14Si-4Fe （wt%） alloys were added and dissolved completely. In the Mg-A1-Si alloys, iron has very little solubility and tends to combine with other elements to form intermetallic phases, which grow into a deposition layer due to the higher density. During the cooling and solidifying process of Mg-A1-Si melts, the needle-like AlsSiFe phase in AI-14Si-4Fe alloy evolved into blocky AI5Fe2 and Al0.7Fe3Si0.3 phases. Besides, the Fe levels of the Mg-AI-Si master alloys were reduced to 0.017 wt% from nominal content of 0.164 wt%. Based on the above results, this work carried out a semi-quantitative phase- compositions analysis for the deposition layer by relative intensity ratio （RIR） method, and evolution mechanism of the iron-rich phases had also been discussed. This study has paved a new way to regen- erate the scrap AI-Si-Fe alloys, which has a great significance of promoting the recycling of aluminum resources.展开更多
Background: Magnetic resonance imaging (MRI) is the best imaging examination to evaluate abnormal iron deposition in the brain. Although phase of susceptibility weighted imaging (SWI) and R2* values have been used to ...Background: Magnetic resonance imaging (MRI) is the best imaging examination to evaluate abnormal iron deposition in the brain. Although phase of susceptibility weighted imaging (SWI) and R2* values have been used to probe iron deposition in Alzheimer’s disease (AD) brain, no study has exploited both techniques for quantification of iron deposition in AD. Purpose: Use phase and R2* to evaluate iron changes in AD brain. Investigate the correlation of two methods with the severity of cognitive impairment in AD patients.Materials and methods: Twenty-three patients with AD and eighteen normal controls underwent SWI and multi-echo gradient recalled-echo (GRE) imaging on a 3T MR scanner. The phase values from SWI and R2* values calculated from multi-echo GRE imaging of bilateral hippocampus, globus pallidus, putamen, caudate nucleus, thalamus, substantia nigra, red nucleus and dentate nucleus were evaluated. Results: In AD group, the phase values of bilateral hippocampus, globus pallidus, caudate nucleus, substantia nigra and left putamen were significantly lower than the control group. The R2* values of bilateral hippocampus, caudate nucleus, putamen and right globus pallidus were significantly higher than the control group. The phase and R2* values of the left putamen had the most significant correlation with mini-mental state examination (MMSE) scores in AD patients. Conclusion: The SWI phase value and R2* value can be used as effective methods to study the abnormality of iron deposition in AD brain, wherein phase had advantages in small brain structure. Phase value showed a higher correlation coefficient with MMSE scores, moreover the iron deposition of left putamen has a close relationship with the progression of AD.展开更多
Catalytic activity and selectivity of prepared catalysts (Fe2O3/ and Fe2O3/AC(KOH)) were investigated for liquid phase aerobic oxidation of primary and secondary alcohols, in a batch reactor, using solvent free condit...Catalytic activity and selectivity of prepared catalysts (Fe2O3/ and Fe2O3/AC(KOH)) were investigated for liquid phase aerobic oxidation of primary and secondary alcohols, in a batch reactor, using solvent free condition and/or eco-friendly solvents. The catalysts were characterized by SEM, EDX, XRD, FTIR, TGA/DTA, and surface area and pore size analysis. Experimental data revealed that Fe2O3/AC(KOH) was an efficient catalyst for the oxidation (dehydrogenation) of alcohol while was found to show catalytic activity for both dehydration and dehydrogenation of alcohols. The catalysts were recycled by simple filtration, and used several times without any loss of catalytic activity.展开更多
The graphite phase has been extracted from the nodular cast iron to measure the concentration of trace element in it. The impurity phase was removed from the extracted matter by dissolving it with HCl and HCl+H<sub...The graphite phase has been extracted from the nodular cast iron to measure the concentration of trace element in it. The impurity phase was removed from the extracted matter by dissolving it with HCl and HCl+H<sub>2</sub>O<sub>2</sub> to get the pure graphite phase. PIXE measurements were performed with thick targets of the pure graphite phase. Differences in the trace element concentrations between the graphite phase and the matrix have been observed. The effect of Ti and As in graphite phase on the nodularization rate and the mechanical properties have been studied.展开更多
In this work,we present a new and fast method to obtain the single phase YFeO(YIG,cubic) and YFeO(YIP, orthorhombic) nanocrystals based on hydrothermal technique. The influence of initial Y/Fe mole ratio and calcinati...In this work,we present a new and fast method to obtain the single phase YFeO(YIG,cubic) and YFeO(YIP, orthorhombic) nanocrystals based on hydrothermal technique. The influence of initial Y/Fe mole ratio and calcination temperature on the nature, purity, phase structure, and morphology of the product was investigated by X-ray diffraction(XRD), Fourier-transform infrared(FT-IR) spectroscopy,energy-dispersive(EDX) X-ray spectroscopy, and field emission scanning electron microscopy(FESEM).The results show that the transformation of the as-synthesized YIG from amorphous to orthorhombic and finally to cubic phase occurs with the increase of annealing temperature. On this basis, the pure cubic phase YIG can be obtained by calcination(at 1100℃) of the precursor which is prepared using the hydrothermal treatment of mole ratio of Y:Fe = 1:1.5 exposure to an ammonia atmosphere. Also, the initial Y/Fe mole ratio of 1:1 and calcination temperature of 1000 ℃ are the optimal conditions to form single-phase nanocrystalline YIP. Further, vibrating sample magnetometry(VSM) measurements illustrate the average magnetic saturation, coercivity and remanence of 2.73 and 15.00 emu/g, 42.74 and40.02 Oe, and 1.65 and 4.30 emu/g for YIP and YIG nanocrystals, revealing their soft ferromagnetic character.展开更多
基金financially supported by the National Natural Science Foundation of China (No. 51474018)
文摘Gold in cyanide tailings from Shandong Province is mainly encapsulated by hematite and magnetite at distribution rates of 76.49 % and 10.88 %, respectively.Chlorination-reduction one-step roasting of cyanide tailings was conducted under the following conditions： calcium chloride dosage of 6 %, bituminous coal dosage of 30 %, calcium oxide dosage of 10 %（all dosages are vs.the mass of cyanide tailings） at 1000 ℃ of roasting temperature. X-ray diffraction（XRD）, scanning electron microscopy（SEM）, and chemical-phase analysis were performed to investigate the effects of iron phase transformation on the high-temperature chlorination of gold.Results indicate that the lattice structure of hematite undergoes expansion, pulverization, and reorganization when hematite is reduced to magnetite, which leads to42.03 % gold exposure, and the high-temperature chlorination rate of gold is 41.17 % at the same time. The structure of wustite formed by the reduction in magnetite is porous and loose, and thus 44.02 % of gold is exposed. The high-temperature chlorination rate of gold is increased by41.98 percentage points. When wustite is reduced to metallic iron, 4.42 % of gold is exposed, and the hightemperature chlorination rate of gold is increased by3.38 percentage points. Accordingly, the high-temperature chlorination of gold mainly occurs in two stages, in which Fe_2O_3 is reduced to Fe_3O_4, and Fe_3O_4 is reduced to Fe_xO finally.
文摘Clay minerals from different Cretaceous stratigraphic successions of Egypt were investigated using XRD, DTA, dissolution analysis (DCB), IR, M*issbauer and X-band Electron Spin Resonance (ESR) spectroscopies. The purity of the samples and the degree of structural order were determined by XRD. The location of Fe in the octahedral sheet is characterized by absorption bands at ～875 cm\+\{-1\} assigned as Al-OH-Fe which is present after chemical dissolution of free iron. The M*issbauer spectra of these clays show two doublets with isomer shift and quadrupole splitting typical of octahedral coordinated Fe\+\{3+\}, in addition to third doubler with hyperfine parameter typical of Fe\+\{2+\} in the spectra of Abu-Had kaolinite (H) sample. 6-lines magnetic hyperfine components which are consistent with those of hematite are confirmed in the spectra of both Isel and Rish kaolinite samples. Goethite was confirmed by both IR and DTA. Multiple nature of ESR of these clays suggested structural Fe in distorted octahedral symmetry and as non-structural Fe. Little dispersion and low swelling indices as well as incomplete activation of investigated montmorillonite samples by NaCO\-3 appear to be due to incomplete disaggregation of montmorillonite particles. This can be explained by the ability of Fe-gel to aggregate the montmorillonite into pseudo-particles and retard the rigid-gel structure. However, extraction of this ferric amorphous compound by dithonite treatment recovers the surface properties of the montmorillonite samples. On the other hand, amounts and site occupation of Fe associated with kaolinite samples show a negative correlation with the parameters used to describe the degree of crystalline perfection, color, brightness and vitrification range of these kaolinite samples.
基金Supported by the Program for National Key R&D Plan(2017YFC0703100).
文摘The preparation of sulfoaluminate cementitious materials(SCM)is a promising way to massively utilize solid wastes.Iron phases are significant in SCM system but the thermodynamic data of some key minerals,such as6 CaO·Al2 O3·2 Fe2 O3(C6 AF2)and 6 CaO·2 Al2 O3·Fe2 O3(C6 A2 F),are missing,which greatly hinders the SCM optimization in a theoretical way.This work,for the first time,calculated the standard formation enthalpy,Gibbs free energy of formation,entropy and molar heat capacity for C6 AF2 and C6 A2 F and lowered the errors to the least with the reference of C4 AF data in the literature.By building the function diagram of Gibbs free energy changes with temperature for the basic iron phase formation reactions with the obtained thermodynamic data,it is proved that the formation likeliness of C6 AF2 is higher than that of C6 A2 F,as is accordant to the literatures and verifies the correctness of obtained data.This work provides a good theoretical foundation to optimize SCM mineral system and to study relevant mechanism deeply.
文摘Clay minerals from different Cretaceous stratigraphic successions of Egypt were investigated using XRD, DTA, dissolution analysis (DCB), IR, Mssbauer and X\|ray Electron Spin Resonance (ESR) spectroscopes. The purity of the samples and the degree of their structural order were determined by XRD. The location of Fe in the octahedral sheet is characterized by absorption bands at ～875cm\+\{-1\} assigned as Al\|OH\|Fe which persist after chemical dissolution of free iron. The Mssbauer spectra of these clays show two doublets with isomer shift and quadrupole splitting typical of octahedrally coordinated Fe\+\{3+\}, in addition to third doublet with hyperfine parameter typical of Fe\+\{2+\} in the spectra of Abu\|Had kaolinite (H) sample. Six\|lines magnetic hyperfine components which are consistent with those of hematite are confirmed in the spectra of both Isel and Rish kaolinite samples. Goethite was confirmed by both IR and DTA. Multiple nature of ESR of these clays suggested structural Fe in distorted octahedral symmetry as well as non\|structural Fe.\; Little dispersion and low swelling indices as well as incomplete activation of the investigated montmorillonite samples by NaCO\-3 appear to be due to incomplete disaggregation of montmorillonite particles. This can be explained by the ability of Fe\|gel to aggregate the montmorillonite into pseudo\|particles and retard the rigid\|gel structure. However, extraction of this ferric amorphous compound by dithonite treatment recovers the surface properties of the montmorillonite samples.\; On the other hand, the amount and site occupation of Fe associated with kaolinite samples show an inverse correlation with the parameters used to describe the degree of crystallinity perfection, color, brightness and vitrification range of these kaolinite samples.
文摘It is well known that the magnetic properties such as the Curie temperature Tmag <sub>C and the mean magnetic moment β of ordered compounds have different values from those of the disordered solutions. For instance, both Tmag c and β of the Ni3Pt （L12） and NiPt （L10） and Tmag <sub>c of the CoPt （L10） and CoPt3 （L12） ordered compounds are strongly depressed due to the ordering compared with those of the metastable disordered Ni-Pt and Co-Pt alloys. On the other hand, the γ’-FeNi3 （L12） and the α’-FeCo （B2） ordered compounds have higher Tmag <sub>c and β values comparing with the disordered solution phases, γ （A1） and α （A2）, respectively. In consequence, the stability of the ordered phase is depressed or enhanced due to the interaction between the chemical and magnetic ordering caused by the decrease or increase of Tmag <sub>c and β values. The purpose of this study is to investigate the effect of the interaction between the chemical and the magnetic ordering on the phase equilibria in the Fe-X（X=Al, Co, Ni, Rh, Si） binary systems.The Gibbs energy of the α（A2）, γ（A1） and liquid phases is described by a sub-regular solution approximation. The ordering contribution to the Gibbs energy ,ΔGorder <sub>m, and deviations of magnetic properties, ΔTmag <sub>c and Δβ, of the ordered compounds, FeAl （B2）, Fe3Al （D03）, FeCo （B2）, FeRh （B2）, FeSi （B2）, Fe3Si （D03） and FeNi3 （L12） is introduced by the split compound energy formalism. Effect of the interaction between the chemical ordering, B2, D03 and L12 and the magnetic ordering on the phase equilibria will be discussed according to the calculated phase diagrams of the Fe-X binary systems.
文摘The difference of conductivity between primary iron-rich phases and aluminum melt has been used to separate them by electromagnetic force (EMF) which is induced by imposing a direct electric current and a steady magnetic field in molten Al-Si alloy. Theoretical analysis and experiments on self-designed electromagnetic separation indicates that primary needle-like β phases are difficult to separate; while primary α iron-rich phases can be separated by electromagnetic separation. Primary iron-rich phases have been removed from the melt successfully when the molten metal flows horizontally through separation channel. The iron content is reduced from 1.13% to 0.41%.
基金Project supported by the National Science Foundations of China (Grant Nos. 10776032 and 10902102)Science Foundation of China Academy of Engineering Physics (Grant Nos. 20060104 and 2009B0201014)
文摘This paper provides an investigation of the phase transition and spalling characteristic induced during shock loading and unloading in the pure iron and the FeMnNi alloy. The impact for the pure iron is symmetric and with the same-thickness for both the flyer and the target plate. It is found that an abnormal multiple spalling happens in the pure iron sample as the pressure exceeds the α- ε transition threshold of 13 GPa. In the symmetric and same-thickness impact and reverse impact experiments of the FeMnNi alloy, two abnormal tension regions occur when the pressure exceeds the α - ε transition threshold of 6.3 GPa, and the reverse phase transition s - ~ begins below 4.2 GP. The experimental process is simulated successfully from the non-equilibrium mixture phase and Boettger＇s model. Such abnormal spalling phenomena are believed to relate to the shocked α - ε phase transition. The possible reasons for the abnormal multiple spalling, which occurs during the symmetric and same-thickness impact experiments of pure iron and FeMnNi alloy, are discussed.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2017YFA0303003,2016YFA0300300 and 2015CB921000the National Natural Science Foundation of China under Grant Nos 11574370,11474338,11674374 and 61501220+1 种基金the Strategic Priority Research Program and Key Research Program of Frontier Sciences of the Chinese Academy of Sciences under Grant Nos QYZDY-SSW-SLH001,QYZDY-SSW-SLH008 and XDB07020100the Beijing Municipal Science and Technology Project under Grant No Z161100002116011
文摘The phenomenon of phase separation into antiferromagnetic（AFM） and superconducting（SC） or normal-state regions has great implication for the origin of high-temperature（high-T_c） superconductivity. However, the occurrence of an intrinsic antiferromagnetism above the T_c of（Li,Fe）OHFe Se superconductor is questioned. Here we report a systematic study on a series of（Li,Fe）OHFe Se single crystal samples with T_c up to ～41 K. We observe an evident drop in the static magnetization at T_（afm） ～ 125 K, in some of the SC（T_c 38 K, cell parameter c■9.27 ？） and non-SC samples. We verify that this AFM signal is intrinsic to（Li,Fe）OHFe Se. Thus, our observations indicate mesoscopic-to-macroscopic coexistence of an AFM state with the normal（below T_（afm）） or SC（below T_c） state in（Li,Fe）OHFe Se. We explain such coexistence by electronic phase separation, similar to that in high-T_c cuprates and iron arsenides. However, such an AFM signal can be absent in some other samples of（Li,Fe）OHFe Se, particularly it is never observed in the SC samples of T_c 38 K, owing to a spatial scale of the phase separation too small for the macroscopic magnetic probe. For this case, we propose a microscopic electronic phase separation. The occurrence of two-dimensional AFM spin fluctuations below nearly the same temperature as T_（afm）, reported previously for a（Li,Fe）OHFe Se（T_c ～ 42 K） single crystal, suggests that the microscopic static phase separation reaches vanishing point in high T_c（Li,Fe）OHFe Se. A complete phase diagram is thus established. Our study provides key information of the underlying physics for high-T_c superconductivity.
基金supported by the National Natural Science Foundation of China(No.50664006)
文摘The effect of F,K,and Na on the solid phase reaction of the Baiyunebo iron ore was investigated by differential thermal analysis （DTA） and X-ray diffraction（XRD）.It has been identified that alkaline elements K and Na in the Baiyunebo ore instigate the formation of low melting point compounds Na2SiO3 and Na2O·Fe2O3 and the generation of molten state in the solid phase sintering.Element F in the Baiyunebo ore facilitates the formation of cuspidine compound 3CaO·2SiO2·CaF2 in the solid phase reaction.The cuspidine compound is kept in solid as one of the final products through the entire sintering process due to its high melting point.In the sintering process,CaF2and SiO2 react with CaO first and form 3CaO·2SiO2·CaF2 and 3CaO·2SiO2,so the formation of ferrites,Na2O·Fe2O3,and 2CaO·Fe2O3 is inhibited.
基金financially supported by the Fundamental Research Funds for the Central Universities of China(No.FRF-MP-12-003B)
文摘Gangue existing states largely affect the high-temperature characteristics of iron ores. Using a micro-sintering method and scan- ning electron microscopy, the effects of gangue content, gangue type, and gangue size on the assimilation characteristics and fluidity of liquid phase of five different iron ores were analyzed in this study. Next, the mechanism based on the reaction between gangues and sintering mate- dais was unraveled. The results show that, as the SiO2 levels increase in the iron ores, the lowest assimilation temperature （LAT） decreases, whereas the index of fluidity of liquid phase （IFL） increases. Below 1.5wt%, Al2O3 benefits the assimilation reaction, but higher concentra- tions proved detrimental. Larger quartz particles increase the SiO2 levels at the local reaction interface between the iron ore and CaO, thereby reducing the LAT. Quartz-gibbsite is more conductive to assimilation than kaolin. Quartz-gibbsite and kaolin gangues encourage the forma- tion of liquid-phase low-Al2O3-SFCA with high IFL and high-Al2O3-SFCA with low IFL, respectively.
基金Foundation item: project (59774017) supported by NationalNatureScience Found, China project (G199906490-4) supported by Na-tionalKey FundamentalResearch and Developing Program, China
文摘Electromagnetic separation of the iron-rich phase inclusions from Al alloy was investigated. The influencing parameters including magnetic induction density, the section shape of the separating channel and the length of influential loop of the metal melt on the separation efficiency of iron-rich phase inclusions were studied. The results show that when the proper magnetic induction density (B=0.3T) is applied, rectangle separating channel is used, and the influential loop of the metal melt is long, high separating efficiency of the iron-rich phase inclusions can be obtained.
基金supported by the National Natural Science Foundation of China(No.512711101)the National Basic Research Program of China (No.2012CB825702)
文摘A new method has been proposed to prepare Mg-A1-Si master alloys by utilizing scrap AI-Si-Fe alloys with higher Fe levels, which aims to segregate Fe from AI-Si-Fe alloys by Mg melt. The segregation be- haviors, microstructure morphology and evolution mechanism of iron-rich phases in Mg-A1-Si alloy melts were studied, after AI-14Si-4Fe （wt%） alloys were added and dissolved completely. In the Mg-A1-Si alloys, iron has very little solubility and tends to combine with other elements to form intermetallic phases, which grow into a deposition layer due to the higher density. During the cooling and solidifying process of Mg-A1-Si melts, the needle-like AlsSiFe phase in AI-14Si-4Fe alloy evolved into blocky AI5Fe2 and Al0.7Fe3Si0.3 phases. Besides, the Fe levels of the Mg-AI-Si master alloys were reduced to 0.017 wt% from nominal content of 0.164 wt%. Based on the above results, this work carried out a semi-quantitative phase- compositions analysis for the deposition layer by relative intensity ratio （RIR） method, and evolution mechanism of the iron-rich phases had also been discussed. This study has paved a new way to regen- erate the scrap AI-Si-Fe alloys, which has a great significance of promoting the recycling of aluminum resources.
文摘Background: Magnetic resonance imaging (MRI) is the best imaging examination to evaluate abnormal iron deposition in the brain. Although phase of susceptibility weighted imaging (SWI) and R2* values have been used to probe iron deposition in Alzheimer’s disease (AD) brain, no study has exploited both techniques for quantification of iron deposition in AD. Purpose: Use phase and R2* to evaluate iron changes in AD brain. Investigate the correlation of two methods with the severity of cognitive impairment in AD patients.Materials and methods: Twenty-three patients with AD and eighteen normal controls underwent SWI and multi-echo gradient recalled-echo (GRE) imaging on a 3T MR scanner. The phase values from SWI and R2* values calculated from multi-echo GRE imaging of bilateral hippocampus, globus pallidus, putamen, caudate nucleus, thalamus, substantia nigra, red nucleus and dentate nucleus were evaluated. Results: In AD group, the phase values of bilateral hippocampus, globus pallidus, caudate nucleus, substantia nigra and left putamen were significantly lower than the control group. The R2* values of bilateral hippocampus, caudate nucleus, putamen and right globus pallidus were significantly higher than the control group. The phase and R2* values of the left putamen had the most significant correlation with mini-mental state examination (MMSE) scores in AD patients. Conclusion: The SWI phase value and R2* value can be used as effective methods to study the abnormality of iron deposition in AD brain, wherein phase had advantages in small brain structure. Phase value showed a higher correlation coefficient with MMSE scores, moreover the iron deposition of left putamen has a close relationship with the progression of AD.
文摘Catalytic activity and selectivity of prepared catalysts (Fe2O3/ and Fe2O3/AC(KOH)) were investigated for liquid phase aerobic oxidation of primary and secondary alcohols, in a batch reactor, using solvent free condition and/or eco-friendly solvents. The catalysts were characterized by SEM, EDX, XRD, FTIR, TGA/DTA, and surface area and pore size analysis. Experimental data revealed that Fe2O3/AC(KOH) was an efficient catalyst for the oxidation (dehydrogenation) of alcohol while was found to show catalytic activity for both dehydration and dehydrogenation of alcohols. The catalysts were recycled by simple filtration, and used several times without any loss of catalytic activity.
文摘The graphite phase has been extracted from the nodular cast iron to measure the concentration of trace element in it. The impurity phase was removed from the extracted matter by dissolving it with HCl and HCl+H<sub>2</sub>O<sub>2</sub> to get the pure graphite phase. PIXE measurements were performed with thick targets of the pure graphite phase. Differences in the trace element concentrations between the graphite phase and the matrix have been observed. The effect of Ti and As in graphite phase on the nodularization rate and the mechanical properties have been studied.
基金financial support of this work from University of Kashan by Grant No. 363030/12
文摘In this work,we present a new and fast method to obtain the single phase YFeO(YIG,cubic) and YFeO(YIP, orthorhombic) nanocrystals based on hydrothermal technique. The influence of initial Y/Fe mole ratio and calcination temperature on the nature, purity, phase structure, and morphology of the product was investigated by X-ray diffraction(XRD), Fourier-transform infrared(FT-IR) spectroscopy,energy-dispersive(EDX) X-ray spectroscopy, and field emission scanning electron microscopy(FESEM).The results show that the transformation of the as-synthesized YIG from amorphous to orthorhombic and finally to cubic phase occurs with the increase of annealing temperature. On this basis, the pure cubic phase YIG can be obtained by calcination(at 1100℃) of the precursor which is prepared using the hydrothermal treatment of mole ratio of Y:Fe = 1:1.5 exposure to an ammonia atmosphere. Also, the initial Y/Fe mole ratio of 1:1 and calcination temperature of 1000 ℃ are the optimal conditions to form single-phase nanocrystalline YIP. Further, vibrating sample magnetometry(VSM) measurements illustrate the average magnetic saturation, coercivity and remanence of 2.73 and 15.00 emu/g, 42.74 and40.02 Oe, and 1.65 and 4.30 emu/g for YIP and YIG nanocrystals, revealing their soft ferromagnetic character.
