Pure MnS Research Articles

Effect of Crucible Material for Ingot Casting on Detrimental Non‐Metallic Inclusions and the Resulting Mechanical Properties of 18CrNiMo7‐6 Steel

The steel 18CrNiMo7‐6 (AISI 4317) is treated in three different crucibles based on carbon‐bonded alumina. Non‐metallic inclusions in the steel are characterized by means of optical microscopy and scanning electron microscopy. Strength, ductility, and dynamic fracture toughness of the steel are evaluated at different temperatures. Furthermore, fatigue lifetimes in the very high cycle regime are determined. The treatment in a carbon‐bonded alumina (A–C) crucible resulted in a relatively high inclusion content involving a high number of duplex inclusions consisting of MnS and Si–Al–O. In contrast, less but large pure MnS inclusions are observed when the steel is treated in carbon‐bonded alumina‐zirconia‐titania crucibles – with or without a coating of carbon nanotubes (AZT–C–n and AZT–C). The steel treated in the A–C crucible exhibits the highest strength and fatigue lifetime, but the lowest energy dissipation. The relatively low inclusion content in the AZT–C treated steel results in high energy dissipation during tensile deformation. However, large MnS inclusions in the AZT–C and AZT–C–n treated steels act as crack initiation sites and reduce the fatigue lifetime. The dynamic fracture toughness is not affected by the different melt treatments. This result is explained by cell‐like structures within the material that are characterized by a lower strength and an increased concentration of MnS inclusions.

The Relationship Between MnS Precipitation and the Induced Nucleation Effect of Ti-Bearing Inclusions

Abstract The relationship between MnS precipitation and the induced nucleation effect of Ti-bearing inclusions has been analyzed using SEM and EDS. In comparison with a non-treated sample, it can be seen that the Ti treatment leads to the oxide evolution from Al-Mn-Si-O to Ti-Al-Si-Mn-O. Moreover, it was found that sulfur congregates around both types of oxide, which is attributed to the MnS precipitation. As for pure MnS, its proportion in the total inclusion decreases when a Ti treatment is performed. EDS line analysis suggested that a Mn depletion zone (MDZ) occurs in the Fe matrix surrounding Ti-Al-Si-Mn-O. It does not occur surrounding Al-Mn-Si-O in the comparison sample. This difference leads to different microstructures. The intragranular acicular ferrites (IAFs) are only observed in the Ti-treated sample. Further analysis indicated that this microstructure is induced by Ti-Al-Si-Mn-O inclusions. In the same sample, the similar induced nucleation effect and a MDZ could not be found surrounding pure MnS. This comparison suggests that the formation of the MDZ may be independent of a MnS precipitation.

Characterization of MnS Particles in Heavy Rail Steels Using Different Methods

Characterization of the MnS particles in continuous casting (CC) blooms and rolled rails of U75V steel using the methods of traditional two-dimensional (2D) microscope observation, three-dimensional (3D) micro-CT detection, and electrolytic extraction is performed. MnS particles from the surface to the interior, inside of columnar dendritic zone, and the equiaxed zone of the CC bloom are discussed. The morphology of MnS changes from elliptical and spherical near the surface of bloom to strip-like, petal-like, polyhedral, and irregular in the center of bloom gradually. The size of both pure MnS particles and complex inclusions which consist of a MnS outer layer and an oxide core increase from the edge to the center of bloom. However, MnS is elongated along the rolling direction during rolling process. The morphology of the cross section of the elongated MnS particles presents as globular and flaggy shape in the head and bottom of rail, and spindle shape in the waist of rail. The precipitation of MnS particles is studied on the basis of thermodynamics, the calculating results show that MnS particles are generated towards the end of solidification (solid fraction fS = 0.94), the amount of MnS particles are affected by the initial concentration of Mn and S in molten steel during solidification.

Effects of Ti–Mg Complex Inclusions on Acicular Ferrite Nucleation

Abstract The alloys of Ti and Mg are added in molten carbon structural steel in sequence to reveal their influence on features of inclusion and microstructure. Compared with non-treated steel, it is found that they leads to the formation of Ti-Mg-O inclusion and reduction in portion of pure MnS. Experimental results indicate that average inclusion size in treated steel significantly decreases and its number per unit volume increases by 48 %. Moreover, the margin mole ratio of Mg/Ti in all Ti-Mg-O inclusions is larger than 2, which hints they are more complex than single assumption of MgTi2O4. After etching, intragranular acicular ferrite (IAF) microstructure is observed. EDS line analysis suggests that Mn-depletion zone exists in steel matrix, which is proposed to explain the IAF nucleation effect induced by Ti-Mg-O inclusions. Through comparison with only Mg-treated sample, the refinement of inclusion and increase in portion of pure MnS due to Ti adding are revealed.

Thermodynamics of Complex Sulfide Inclusion Formation in Ca-Treated Al-Killed Structural Steel

Controlling the morphology of the sulfide inclusion is of vital importance in enhancing the properties of structural steel. Long strip-shaped sulfides in hot-rolled steel can spherize when, instead of the inclusion of pure single-phase MnS, the guest is a complex sulfide, such as an oxide-sulfide duplex and a solid-solution sulfide particle. In this study, the inclusions in a commercial rolled structural steel were investigated. Spherical and elongated oxide-sulfide duplex as well as single-phase (Mn,Ca)S solid solution inclusions were observed in the steel. A thermodynamic equilibrium between the oxide and sulfide inclusions was proposed to understand the oxide-sulfide duplex inclusion formation. Based on the equilibrium solidification principle, thermodynamic discussions on inclusion precipitation during the solidification process were performed for both general and resulfurized structural steel. The predicted results of the present study agreed well with the experimental ones.

In Situ Synthesis of MnS Hollow Microspheres on Reduced Graphene Oxide Sheets as High-Capacity and Long-Life Anodes for Li- and Na-Ion Batteries.

Uniform MnS hollow microspheres in situ crystallized on reduced graphene oxide (RGO) nanosheets via a facile hydrothermal method. The MnS/RGO composite material was used as the anode for Na-ion batteries for the first time and exhibited excellent cycling performance, superior specific capacity, and great cycle stability and rate capability for both Li- and Na-ion batteries. Compared with nonencapsulated pure MnS hollow microspheres, these MnS/RGO nanocomposites demonstrated excellent charge-discharge stability and long cycle life. Li-ion storage testing revealed that these MnS/RGO nanocomposites deliver high discharge-charge capacities of 640 mAh g(-1) at 1.0 A g(-1) after 400 cycles and 830 mAh g(-1) at 0.5 A g(-1) after 100 cycles. The MnS/RGO nanocomposites even retained a specific capacity of 308 mAh g(-1) at a current density of 0.1 A g(-1) after 125 cycles as the anode for Na-ion batteries. The outstanding electrochemical performance of the MnS/RGO composite attributed to the RGO nanosheets greatly improved the electronic conductivity and efficiently mitigated the stupendous volume expansion during the progress of charge and discharge.

Remarkably Improved Electrode Performance of Bulk MnS by Forming a Solid Solution with FeS – Understanding the Li Storage Mechanism

Transition metal compounds based on conversion reactions are promising electrode materials for lithium‐ion batteries due to their higher lithium storage capacity compared with currently available commercial battery electrodes. Most of the studies on these materials in the literature focus on transition metal oxides and fluorides, and not much work on transition metal sulphides has been reported, partially due to their relatively poor electrochemical performance. Here, synthesis and characterization of a series of solid solution FexMn1‐xS (x = 0.2, 0.5, 0.8) monosulphide compounds is reported. Interestingly, hexagonal FeS and cubic MnS can form a solid solution of FexMn1‐xS (x < 0.57). It is demonstrated that the lithium storage voltage can be tuned by changing the Fe concentration in the FexMn1‐xS matrix; meanwhile, the discharge‐charge coulombic efficiency and cycle stability of FexMn1‐xS are greatly enhanced in comparison with that of pure MnS. A half cell using Fe0.5Mn0.5S as electrode material achieves a high first cycle coulombic efficiency of 78.0% and a high reversible capacity of ca. 477 mAh g−1 after 35 cycles, while for pure MnS the first cycle coulombic efficiency is only 45.9% and the capacity rapidly fades to ≈200 mAh g−1 after 15 cycles. Although the solid solution state of Fe0.5Mn0.5S cannot be retained during conversion reaction as indicated by X‐ray diffraction (XRD), X‐ray absorption spectroscopy (XAS), and transmission electron microscopy (TEM), the initial discharge “polarization”, which has been considered as one of the major hurdles for conversion reaction, can be significantly reduced by this type of material design. In addition, the size and distribution of the nucleated nanophases might also be altered by the initial solid solution state of Fe0.5Mn0.5S, contributing to the improved electrochemical performance reported here.

MnS / 카본나노튜브 복합체의 합성과 리튬 전기화학적 거동

A simple synthetic process is demonstrated for the preparation of MnS/carbon nanotube (CNT) composites for Li ion battery electrodes. CNTs were initially treated using a strong acid solution to generate carboxylate ions (-COO?) on their surfaces. The MnS/CNT composites were synthesized by a polyvinyl-pyrrolidone-assisted hydrothermal method in the presence of as-functionalized CNTs. The phase and morphology of the MnS/CNT composites and pure MnS microspheres were characterized using X-ray diffraction and high-resolution transmission electron microscopy. Furthermore, the Li electroactivity levels of the MnS/CNT composites and MnS microspheres were investigated using cyclic voltammetry and galvanostatic cycling. The MnS/CNT composite electrodes showed higher specific capacities exceeding 365 mA h g -1 at a C/10 current rate and enhanced cyclic performance compared to pure MnS microspheres.

Effects of alloying elements, microstructure, and inclusions on hydrogen induced cracking of X120 pipeline steel in wet H2S sour environment

AbstractHydrogen induced cracking (HIC) behavior of X120 pipeline steel with different amounts of Mn and Al was investigated using NACE standard TM0284‐2005 and back‐scattered electron imaging (BSE). The results demonstrated that inclusions and microstructure play significant roles in HIC susceptibility in X120 steels. The more the area and volume fraction of inclusions in the steel, the more the steel is susceptible to HIC. Three types of inclusions exist in the tested X120 steel and they play different roles in cracking. The critical size resulting in HIC cracks for pure MnS inclusions or mixed inclusions (inclusion clusters mainly composed of two or three different phases and compounds) of Mn/Al ratio >1 is smaller than that of pure Al2O3 inclusions or mixed inclusions of Mn/Al ratio <1. No HIC crack was observed at inclusions enriched in Si. The microstructure containing lath bainite and martensite/austenite (M/A) microconstituents is more susceptible to HIC than that with granular bainite and ferrite.

Correlation Analysis of MnS Inclusion Composition Using Original Position Statistic Distribution Analysis

In the process of Original Position Statistic Distribution Analysis, many abnormal higher spark signals exist. They are believed as inclusion signals. Analyzing the time sequence and position of the abnormal spark, It is found that the higher spark signals for S and Mn will appear simultaneously . The reason is that MnS inclusion caused the element concentration enrichment at these zone. Mixing some pure MnS crystal in pure iron powder and pressed by Heat Isostatic Pressing technology, reference samples of MnS inclusion were made . Criteria of abnormal higher spark signals for Mn and S is the measured value from the “blank sample ”.After analyzing the spark behavior of these reference samples using OPA instrument, we can calculate the MnS inclusion concentration through such method. steel samples were analyzed and results is satisfactory.

Structure and photoluminescence studies on ZnS:Mn nanoparticles

ZnS:Mn was produced in nanocrystalline form by a chemical method using polyvinylpyroledone as a chemical capping agent. Mn was stoichiometrically substituted for Zn in ZnS. The manganese (Mn) concentration was varied over its whole solid solution limit in ZnS, i.e., from 0 to 40%. In the high concentration regime this material formed may be thus written as nanocrystalline (Zn, Mn)S. The material formed is thus a wide gap diluted magnetic semiconductor. The characterized material was in powder form. X-ray diffraction was used to estimate the crystallite size and to confirm formation of the material in single phase. The average crystallite size obtained was about 2 nm. The material remained cubic over the whole Mn solid solution range. The room temperature photoluminescence (PL) when deconvoluted using a Gaussian fit showed two extra peaks in nanocrystalline ZnS:Mn when compared to pure nanocrystalline ZnS, which had only two peaks. Mn incorporation significantly enhanced the PL intensity in nanocrystalline ZnS:Mn (400–850 nm range) thereby suggesting Mn2+ induced PL. The red shift of the two new peaks with increase in Mn2+ concentration can be attributed to the change in band structure due to the formation of ZnS:Mn alloy. These extra peaks were due to (a) various Mn2+ transitions in the ZnS host, (b) related to S as the nearest neighbor of Mn2+ ion in the nanocrystallite (due to the high concentration of Mn2+), or (c) Mn–Mn interactions at high Mn concentrations. However, our prepared pure MnS samples did not show any photoluminescence at room temperature. So it is concluded that the observed PL is Mn2+ induced in the nanocrystalline ZnS host.

The effect of hydrogen on the defect structure of manganous sulfide and on the sulfidation rate of manganese

The effect of the presence of various possible hydrogen species in MnS on the concentration of its native defects and on the parabolic rate constant for the sulfidation of Mn at high temperatures is examined. This allows to resolve the discrepancy between the experimental values of the rate constant for the sulfidation of manganese in H 2-H 2S mixtures and those calculated on the basis of the defect structure of pure MnS. It is concluded that the most likely form of hydrogen doping is due to the simultaneous presence of two species, i.e., the proton interstitials and the hydride ions in substitutional sulfur sites.

Tracer diffusion of Mn in α-MnS and α-(Mn,Cr)S

By a radioactive tracer method the bulk self-diffusivity of 54Mn in α-MnS was determined in the temperature range 873 K to 973 K. The effect was determined of doping the manganese sulphide with chromium. As expected the diffusivity of Mn is increased by the increase of vacancy concentration caused by Cr 3+ ions. Accordingly, the growth of mixed sulphide (Mn,Cr)S in sulphidation of high temperature alloys is much faster than in the case of pure MnS growth.

Evidence for possible linkage between genetic markers and affective disorders

Studies of the underlying components of affective disorders are particularly difficult because of the confounding effects of both genetic and environmental factors. Linkage analysis is a useful tool in delineating the etiology of affective disorders, as it is unlikely that linkage between behavioral traits and blood group polymorphisms could result from environmental effects. The present study used the robust Haseman and Elston sibpair method to analyze linkage between 24 genetic markers and affective disorder in 34 nuclear families from 25 pedigrees (195 people). The probands were ascertained as part of the ongoing NIMH Collaborative Depression Study. Indications of linkage between familial pure depressive disease and MNS and depression spectrum disease and ORM were found, as had been previously suggested. There was also suggestive evidence for linkage between the latter and GC. Results are discussed in terms of methodological differences with previous studies.

On the Mn-MnS phase diagram

Using a DTA technique the melting point of pure MnS has been determined to 1655 ± 5°C. The monotectic temperature in the Mn-MnS system was found to be 1570 ± 5°C. With these new data a thermodynamic analysis of the Mn-MnS system was carried out applying a pre-viously developed thermodynamic model.

Optical Spectra of Exchange Coupled Mn++ Ion Pairs in ZnS:MnS

The optical spectra of several ZnS:MnS (1 to 10 mole%) mixed crystals were obtained at temperatures from 4.2° to 300°K. A concentration dependence was found which proved that certain bands were due to pairs of Mn++ ions in nearest-neighbor cation sites. Temperature—dependent absorption bands were found which were interpreted to give an interionic exchange integral in the ground state of —9 cm—1 in the spin—spin Hamiltonian H = —2JS1·S2. This agrees with the value obtained from the analysis of the susceptibility of pure MnS. The narrow bands due to transitions to the 4A1, 4E(G) states were shown to fit an isotropic spin—spin coupling law with J = +6 cm—1 for each state. The inversion of sign from the ground state is not fully understood. The selection rules for the transitions do not follow those for the total spin (ΔS = 0).