Manganese Enrichment Research Articles

Effects of vacuum heating in AISI 410 and AISI 321 stainless steels' surface layer revealed by SIMS/GDMS depth profile analysis

AbstractVacuum annealing of steels is employed for out‐gassing elements, surface activation and in different production purposes. Such procedure was applied for chromium–nickel AISI 321 and chromium AISI 410 stainless steels used in aviation technologies.Depth profile analysis of the samples annealed in vacuum for 120 min. in 750 and 950 °C was performed by using two methods: SIMS and glow discharge mass spectrometry (GDMS). SIMS data were obtained with a 5 keV Ar+ ion gun. In GDMS analyzer, d.c. glow discharge was induced by 1.5 kV d.c. voltage in 1 mbar Ar pressure.Analyses of AISI 321 samples annealed in 750 °C show enrichment of titanium, chromium and manganese in the depth range of 150 nm, and depletion in iron and nickel within this range. The sample treated in 950 °C shows mainly Ti enrichment into 300 nm depth. Vacuum heating of AISI 410 steel sample in 750 °C causes formation of 150‐nm‐thick surface layer enriched in Cr and Mn and depleted in Fe. In turn, 950 °C treatment results in only some increasing of Mn and Ni concentration within 70 nm distance from the surface.The results obtained by SIMS and GDMS confirm each other. However, higher depth profile resolution was obtained by GDMS due to the lower sputtering energy (1.5 kV glow discharge) and due to the use of multidirectional ion bombardment instead of unidirectional bombardment by ion beam in the SIMS method. Copyright © 2010 John Wiley & Sons, Ltd.

Carbon‐Induced Ordering in Manganese‐Rich Austenite — A Density‐Functional Total‐Energy and Chemical‐Bonding Study

AbstractDensity‐functional theory‐based total‐energy calculations have been performed in order to discover possible local atomic ordering effects in manganese‐rich austenite phases. For manganese contents of 25 and 50% we found a thermochemical driving force that should lead to a manganese enrichment of the immediate proximity of the carbon atom. The energy lowers almost linearly from a pure iron‐ to a pure manganese‐coordinated carbon atom with an energy difference between the two M6 octahedra (M = Fe, Mn) of ca. 0.34 eV (33 kJ/mol) for both antiferromagnetic and nonmagnetic structures. This very effect and the energy differences are almost independent of (a) the manganese concentration, (b) the carbon concentration, and (c) the magnetic state. A comprehensive bonding analysis yields that the effect is caused by the destabilization of the carbon atom's surrounding metal–metal bonds which come out larger for iron than for manganese. The size of the energy differences indicate a strong tendency for carbon‐induced short‐range ordering.

Soils Reveal Widespread Manganese Enrichment from Industrial Inputs

It is well-known that metals are emitted to the air by human activities and subsequently deposited to the land surface; however, we have not adequately evaluated the geographic extent and ecosystem impacts of industrial metal loading to soils. Here, we demonstrate that atmospheric inputs have widely contaminated soils with Mn in industrialized regions. Soils record elemental fluxes impacting the Earth's surface and can be analyzed to quantify inputs and outputs during pedogenesis. We use a mass balance model to interpret details of Mn enrichment by examining soil, bedrock, precipitation, and porefluid chemistry in a first-order watershed in central Pennsylvania, USA. This reveals that ∼ 53% of Mn in ridge soils can be attributed to atmospheric deposition from anthropogenic sources. An analysis of published data sets indicates that over half of the soils surveyed in Pennsylvania (70%), North America (60%), and Europe (51%) are similarly enriched in Mn. We conclude that soil Mn enrichment due to industrial inputs is extensive, yet patchy in distribution due to source location, heterogeneity of lithology, vegetation, and other attributes of the land surface. These results indicate that atmospheric transport must be considered a potentially critical component of the global Mn cycle during the Anthropocene.

Austenite stabilization through manganese enrichment

A model is proposed to predict austenite stabilization through manganese partitioning between ferrite and austenite. The model predicts retained austenite fractions as a function of intercritical annealing temperature based on equilibrium phase fractions and solute contents. Thermodynamic data are used to calculate the Ms temperature of the enriched austenite in order to predict fresh martensite formation upon cooling to room temperature. An intercritical annealing temperature resulting in the greatest retained austenite fraction is predicted which correlates to some experimental observations.

Chemical speciation of redox sensitive elements during hydrocarbon leaching in the Junggar Basin, Northwest China

Bleaching related to seepage of petroleum fluids and subsurface migration of crude oil and natural gas can alter the chemical and mineralogical properties of rocks, while concurrently depleting hydrocarbon reservoirs. Mud volcanoes constitute one type of petroleum seepage present in several areas on the southern margin of the Junggar Basin in the Xinjiang Uygur Autonomous Region, NW China. The results of XRD, XRF, XANES, and Mössbauer spectroscopy on rock samples collected from areas affected by these mud volcanoes revealed an enrichment of certain minerals and elements, as well changes in mineralogical, molecular, or ionic carrier (“species”). After bleaching, reddish sedimentary rocks showed depletion in silica and enrichment of calcium, magnesium, manganese, and iron. Other elements, including aluminum, potassium, sodium, and titanium, were largely unchanged. Reduced iron and sulfur compounds predominated in the bleached rocks, producing changes in color from the original reddish into green, deep gray, and black. Iron and calcium were associated with carbonates, indicating carbonation of these elements during the bleaching processes. Manganese also appeared to be associated with carbonate, though not with sulfate even though sulfate was present in the bleached rocks. Alkaline conditions were apparently the dominant because reduced manganese would have been absent under acidic condition. The alteration of certain minerals, clay minerals in particular, was also observed in bleached rocks, the alteration of smectite-group minerals to chlorite and muscovite, for example. Mineralogical and geochemical changes in rocks bleached by hydrocarbon fluids could provide a better overall understanding of bleaching processes, and may have applications in surface geochemical exploitation and remote imaging.

Depth Resolved XRF and XAS for Enrichment and Oxidation of Mn on Surface of Annealed Fe-Mn Alloys

Alloying elements added to steel for improving surface properties such as corrosion resistance are often enriched to the surface of the alloys during annealing at high temperatures. Their behavior depends on difference in their chemical characters and the condition of annealing. In this study, nondestructive depth-resolved analysis of amount distribution and chemical state of alloying element by using X-ray fluorescence analysis (XRF) technique in combination with X-ray absorption spectroscopy (XAS) in order to characterize the enrichment and oxidation of manganese on the surface layers of an Fe-Mn alloy annealed under low oxygen partial pressure. The experiments were carried out using a two-dimensional detector with geometrical arrangement of grazing exit in detection of fluorescence X-ray emitted from sample surface. The results showed that manganese was enriched to surface layers of the Fe-Mn alloys during annealing at high temperatures and formed as manganese oxide. The preferential oxidation of manganese by annealing under low oxygen partial pressure is considered the driving force for their enrichment on the alloy surface.

Invertebrates control metals and arsenic sequestration as ecosystem engineers

Organic sediments are known to be a significant sink of inorganic elements in polluted freshwater ecosystems. Hence, we investigated the role of invertebrate shredders (the freshwater shrimp Gammarus pulex L.) in metal and arsenic enrichment into organic partitions of sediments in a wetland stream at former uranium mining site. Metal and metalloid content in leaf litter increased significantly during decomposition, while at the same time the carbon content decreased. During decomposition, G. pulex as a ecosystem engineer facilitated significantly the enrichment of magnesium (250%), manganese (560%), cobalt (310%), copper (200%), zinc (43%), arsenic (670%), cadmium (100%) and lead (1340%) into small particle sizes. The enrichments occur under very high concentrations of dissolved organic carbon. Small particles have high surface area that results in high biofilm development. Further, the highest amounts of elements were observed in biofilms. Therefore, invertebrate shredder like G. pulex can enhance retention of large amounts of metal and arsenic in wetlands.

Microstructural Evolution during Gas Tungsten Arc, Laser and Resistance Spot Welding of Al-Containing Transformation Induced Plasticity (TRIP) Steel

In this work, the microstructural evolution of aluminum containing commercial grade TRIP steels during gas tungsten arc (GTA), Laser beam (LB) and resistance spot (RS) welding have been studied. Microstructural analysis was carried out using optical and scanning electron microscopy. Results show that fusion zones of welded TRIP steels contain complex inclusions with similar size distribution. The energy dispersive spectroscopy analysis of inclusions indicated that these inclusions are primarily oxides of aluminum with epitaxial enrichment of manganese and phosphorous. The fusion lines of GTA and LB welded aluminum containing TRIP steel contain a zone of polygonal ferrite with a size of about 200 m and 50 m respectively. It is found that aluminum partitioned from the liquid weld to the solidified delta ferrite in the fusion line causing enrichment and resulting in ferrite stabilisation. This ferrite zone was not found in the case of resistance spot welded samples due to faster cooling rates.

Characterization of Manganese Oxide-Enriched Surface Layers of Fe-Mn Alloys

Alloying elements are added to steel for improving surface properties such as corrosion resistance. The alloying elements exhibit different chemical characters, and they are often enriched to the surface of the alloys during annealing at high temperatures. In this study, depth-resolved X-ray absorption spectroscopy (XAS) measurements were carried out using a two-dimensional detector with geometrical arrangement of grazing exit in detection of fluorescence X-ray emitted from sample surface, in order to characterize the enrichment and oxidation of manganese on the surface layers of an Fe-Mn alloy annealed under low oxygen partial pressure. This technique facilitates non-destructive measurement for characterizing the compositional distribution of manganese in the depth direction. The results showed that manganese was enriched to surface layers of the Fe-Mn alloys during annealing at high temperatures and formed as manganese oxide. The preferential oxidation of manganese by annealing under low oxygen partial pressure is considered the driving force for their enrichment on the alloy surface.

Enrichment and depletion of alloying elements in surface layers of iron base alloys annealed under different conditions

Abstract X-ray photoelectron spectroscopy (XPS), electron microprobe microanalysis (EPMA), and secondary ion mass spectrometry (SIMS) have been used for analyzing the chemical composition in surface layers of iron-base alloys. Samples analyzed in this study were a ferritic Fe–Mn alloy annealed under low partial pressure of oxygen and an austenitic Fe–Mn–Si–Cr alloy annealed under vacuum. The XPS results showed that manganese was enriched and oxidized while iron was metallic in the surface layer of the Fe–Mn alloy annealed under a low partial pressure of oxygen. The EPMA results showed that manganese was depleted while chromium was enriched in the surface layer of the Fe–Mn–Si–Cr alloy annealed under vacuum. The SIMS depth profiles coupled with the EPMA results indicated that the enrichment of chromium in the surface layer improves the oxidation resistance of the alloy. The enrichment and depletion of manganese in the surface layer is discussed on the basis of the thermodynamic properties of the iron–manganese system.

Trace and minor elements in sphalerite: A LA-ICPMS study

Sphalerite is an important host mineral for a wide range of minor and trace elements. We have used laser-ablation inductively coupled mass spectroscopy (LA-ICPMS) techniques to investigate the distribution of Ag, As, Bi, Cd, Co, Cu, Fe, Ga, Ge, In, Mn, Mo, Ni, Pb, Sb, Se, Sn and Tl in samples from 26 ore deposits, including specimens with wt.% levels of Mn, Cd, In, Sn and Hg. This technique provides accurate trace element data, confirming that Cd, Co, Ga, Ge, In, Mn, Sn, As and Tl are present in solid solution. The concentrations of most elements vary over several orders of magnitude between deposits and in some cases between single samples from a given deposit. Sphalerite is characterized by a specific range of Cd (typically 0.2–1.0 wt.%) in each deposit. Higher Cd concentrations are rare; spot analyses on samples from skarn at Baisoara (Romania) show up to 13.2 wt.% (Cd 2+ ↔ Zn 2+ substitution). The LA-ICPMS technique also allows for identification of other elements, notably Pb, Sb and Bi, mostly as micro-inclusions of minerals carrying those elements, and not as solid solution. Silver may occur both as solid solution and as micro-inclusions. Sphalerite can also incorporate minor amounts of As and Se, and possibly Au (e.g., Magura epithermal Au, Romania). Manganese enrichment (up to ∼4 wt.%) does not appear to enhance incorporation of other elements. Sphalerite from Toyoha (Japan) features superimposed zoning. Indium-sphalerite (up to 6.7 wt.% In) coexists with Sn-sphalerite (up to 2.3 wt.%). Indium concentration correlates with Cu, corroborating coupled (Cu +In 3+) ↔ 2Zn 2+ substitution. Tin, however, correlates with Ag, suggesting (2Ag +Sn 4+) ↔ 3Zn 2+ coupled substitution. Germanium-bearing sphalerite from Tres Marias (Mexico) contains several hundred ppm Ge, correlating with Fe. We see no evidence of coupled substitution for incorporation of Ge. Accordingly, we postulate that Ge may be present as Ge 2+ rather than Ge 4+. Trace element concentrations in different deposit types vary because fractionation of a given element into sphalerite is influenced by crystallization temperature, metal source and the amount of sphalerite in the ore. Epithermal and some skarn deposits have higher concentrations of most elements in solid solution. The presence of discrete minerals containing In, Ga, Ge, etc. also contribute to the observed variance in measured concentrations within sphalerite.

Microstructural Development during Welding of Silicon- and Aluminum-Based Transformation-Induced Plasticity Steels—Inclusion and Elemental Partitioning Analysis

Microstructural development in gas tungsten arc (GTA) welded silicon- and aluminum-based transformation-induced plasticity (TRIP) steels was studied by optical and electron microscopy. The fusion zone (FZ) of both welds contained complex inclusions. Energy-dispersive spectroscopic (EDS) analysis on these inclusions showed that the center of the inclusions contained oxides of silicon and aluminum in silicon- and aluminum-based steels, respectively. Epitaxial enrichment of manganese, sulfur, and phosphorous was found on the oxides in the inclusions, resulting in depletion of solutes in solid solution and thereby reducing the stability of austenite in the fusion zone. The fusion line of aluminum-based steel weldments contained higher amounts of allotriomorphic ferrite than silicon-based steel weldments due the partitioning of aluminum at the fusion line during solidification. The retained austenite (RA) contents in the heat-affected zones (HAZs) and FZs of both TRIP steels were found to be about 8 and 4 pct by volume, respectively.

Uptake and removal of mineral nutrients by rice plants from seeds subjected to preplanting air thermal heating and manganese enrichment

Preplanting treatment of seeds by heating and enriching them with manganese increases rice grain yield by 4.0–7.8 cwt/ha. Plants from such seeds take up and accumulate more nitrogen, phosphorus, and potassium. In this case, their harvest removal increases but expenditures on the formation of 1 cwt grain don’t increase, which indicates the efficient use of nutrients.

Short Term Oxidation of Stainless Steels during Final Annealing

Two ferritic AISI 430 and AISI 441 and two austenitic AISI 304 and AISI 316L stainless steels were submitted to short term oxidation in a complex atmosphere 3% O2, 16% H2O, 8% CO2, 73% N2 to simulate phenomena occurring during the rapid furnace annealing taking place after the final cold rolling. This thermal sequence is devoted to metallurgical aims but generates undesirable oxides which have to be further pickled. Temperature of the furnace was set to the values used in industrial practice: 900°C for 430, 1060°C for 441 and 1120°C for both austenitics. Six different oxidation durations were used between 30 and 300 s. For the shortest times, sample temperature was not constant and heating rate depended on sample thickness. Oxide thickness measured by GDOS was shown to increase monotonically for all grades whereas mass change measurements exhibited initial mass losses for the austenitic grades. XRD and Raman spectroscopy were used for phase characterisation and confirmed the increase of the ratio chromia/haematite with increasing annealing time. Enrichment of manganese (MnCr2O4), silicon (SiO2) and boron (B-containing oxide) at the external (Mn) and internal (Si, B) interfaces was observed on the GDOS profiles (boron for austenitic grades only). Manganese spinel was responsible for blocking chromium (VI) volatilisation after a certain time, and interface oxides for hindering chromium transfer from the steel to the oxide scale. Ferritic grades behaved the same, except that no boron enrichment was detected. Besides, stabilised 441 exhibited Ti and Nb enrichments as oxides at both internal and external interfaces. External TiO2-NbO2 solid solution was assumed to be hardly dissolved in acidic pickling baths. All these results were consistent with the different pickling behaviours of the materials.

Surface segregation of interstitial manganese inGa1−xMnxAsstudied by hard x-ray photoemission spectroscopy

The effects of low-temperature annealing and oxidation of the dilute magnetic semiconductor ${\text{Ga}}_{1\ensuremath{-}x}{\text{Mn}}_{x}\text{As}$ are studied by photoemission spectroscopy in the hard x-ray regime (HAXPES), with special attention to the depth profile of both concentration and chemical state of manganese. Annealing of ${\text{Ga}}_{1\ensuremath{-}x}{\text{Mn}}_{x}\text{As}$ in air at $190\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$ for up to 150 h leads to an enrichment of manganese at the surface accompanied by an increase in the native oxide layer. These observations are consistently explained by thermally activated surface segregation of interstitial Mn and its subsequent passivation by oxidation, thereby confirming a recently suggested mechanism for an enhancement of the Curie temperature upon annealing.

Influence of surface contaminations on the hydrogen storage behaviour of metal hydride alloys

Hydrogen storage in metal hydrides is a promising alternative to common storage methods. The surface of a metal hydride plays an important part in the absorption of hydrogen, since important partial reaction steps take place here. The development of surface contaminations and their influence on hydrogen absorption is examined by means of absorption experiments and surface analysis, using X-ray photoelectron spectroscopy (XPS), thermal desorption mass spectrometry (TDMS) and secondary neutral mass spectrometry (SNMS), in this work. All investigations were carried out on a modern AB(2) metal hydride alloy, namely Ti(0.96)Zr(0.04)Mn(1.43)V(0.45)Fe(0.08). Surface analysis (SNMS, XPS) shows that long-term air storage (several months) leads to oxide layers about 15 nm thick, with complete oxidation of all main alloy components. By means of in situ oxygen exposure at room temperature and XPS analysis, it can be shown that an oxygen dose of about 100 Langmuirs produces an oxide layer comparable to that after air storage. Manganese enrichment (segregation) is also clearly observed and is theoretically described here. This oxide layer hinders hydrogen absorption, so an activation procedure is necessary in order to use the full capacity of the metal hydride. This procedure consists of heating (T = 120 degrees C) in vacuum and hydrogen flushing at pressures like p = 18 bar. During the activation process the alloy is pulverized to particles of approximately 20 microm through lattice stretches. It is shown that this pulverization of the metal hydride (creating clean surface) during hydrogen flushing is essential for complete activation of the material. Re-activation of powder contaminated by small doses of air (p approximately 0.1 bar) does not lead to full absorption capacity. In ultrahigh vacuum, hydrogen is only taken up by the alloy after sputtering of the surface (which is done in order to remove oxide layers from it), thus creating adsorption sites for the hydrogen. This is shown by TDMS measurements with and without sputtering and oxygen exposure.

Organic-rich and manganese sedimentation during the Cenomanian–Turonian boundary event in the Outer Carpathian basins; a new record from the Skole Nappe, Poland

Upper Cenomanian–Lower Turonian strata in the Spława section of the Skole Nappe, Outer Carpathians, Poland, provide a detailed palaeoenvironmental record of the oceanic anoxic event (OAE-2) from a deep-water basin below the CCD at the northern margin of the Western Tethys. The OAE-2 succession consists of black, parallel-laminated radiolarian shales, enriched in organic matter of mainly marine origin (TOC up to 8%). Organic carbon isotope variations, together with microfossil datum events allowed to correlate the studied organic-rich facies with other black shale successions along the Outer Carpathians and other areas of the Western Tethys. The mean values of sedimentation rate (3.5–5.5 mm/kyr) and organic matter accumulation rate (0.5 g/m 2/year), calculated for the OAE-2 interval in the Outer Carpathian basins, are comparable to the values from other deep-water marginal basins in the Western Tethys. The average redox-sensitive trace metal contents and their enrichment factors, indicate water column anoxia in the Outer Carpathian basins, intensified during the interval of the largest shift in δ 13C values. The periods of bottom anoxia were interrupted by intervals of variable Eh conditions with sedimentation of hemipelagic green shales, including poor agglutinated foraminiferal assemblages. An increase in productivity of organic and siliceous plankton during the OAE-2 is documented, based on increased values of silica and barium enrichments. This closely corresponds to an interval of the largest positive stable carbon isotope excursion, related to the beginning of the largest sea level rise, linked with intensive coastal upwelling. Extremely low sedimentation rate or even hiatuses and the increase in deep-water circulation causing basin oxygenation resulted in precipitation of two ferromanganese layers. Their formation was related to changes in hydrodynamic conditions at the basin floor, expressed by precipitation of Fe–Mn carbonates. Some chemical indices seem to suggest that the primary metal enrichments could be related to hydrothermal activity. However, the concentrations of some elements show also on hydrogenic to diagenetic influences in these metalliferous sediments. The precipitation of these Fe–Mn sediments was probably synchronous with the manganese enrichment across the C–T transition recorded in other Western Tethyan basins and in the adjacent epicontinental seas.

Effect of Manganese Incorporation Manner on an Iron-Based Catalyst for Fischer-Tropsch Synthesis

A systematic study was undertaken to investigate the effects of the manganese incorporation manner on the textural properties, bulk and surface phase compositions, reduction/carburization behaviors, and surface basicity of an iron-based Fischer-Tropsch synthesis (FTS) catalyst. The catalyst samples were characterized by N 2 physisorption, X-ray photoelectron spectroscopy (XPS), H 2 (or CO) temperature-programmed reduction (TPR), CO 2 temperature-programmed desorption (TPD), and Mössbauer spectroscopy. The FTS performance of the catalysts was studied in a slurry-phase continuously stirred tank reactor (CSTR). The characterization results indicated that the manganese promoter incorporated by using the coprecipitation method could improve the dispersion of iron oxide, and decrease the size of the iron oxide crystallite. The manganese incorporated with the impregnation method is enriched on the catalyst's surface. The manganese promoter added with the impregnation method suppresses the reduction and carburization of the catalyst in H 2, CO, and syngas because of the excessive enrichment of manganese on the catalyst surface. The catalyst added manganese using the coprecipitation method has the highest CO conversion (51.9%) and the lowest selectivity for heavy hydrocarbons (C 12+).

Manganese Abnormity in Holocene Sediments of the Bohai Sea

Manganese abnormity has been observed in the Holocene sediments of the mud area of Bohai Sea. On the basis of grain size, chemical composition, heavy mineral content and accelerator mass spectrometry (AMS) MC dating of foraminifer, relationships between manganese abnormity and sedimentation rates, material source, hydrodynamic conditions are probed. Manganese abnormity occurred during the Middle Holocene when sea level and sedimentation rates were higher than those at present Sedimentary hiatus was not observed when material sources and hydrodynamic conditions were quite similar. Compared with the former period, the latter period showed a decrease in reduction environment and an inclination toward oxidation environment with high manganese content, whereas provenance and hydrodynamic conditions showed only a slight change. From the above observations, it can be concluded that correlation among manganese abnormity, material source, and hydrodynamic conditions is not obvious. Redox environment seems to be the key factor for manganese enrichment, which is mainly related to marine authigenic process.

Neogene weathering and supergene manganese enrichment in subtropical South China: An 40Ar/ 39Ar approach and paleoclimatic significance

Deep weathering profiles and associated supergene Mn-oxides deposits are widely distributed in South China. However, data on their ages are not available until most recently. 40Ar/ 39Ar laser incremental heating analysis of potassium-bearing supergene Mn-oxides collected from four weathering profiles in the Qinzhou–Fangcheng Mn belt, Guangxi Province, South China, provides, for the first time, numerical constraints on timing of weathering and supergene Mn enrichment. Thirty-eight of 42 cryptomelane grains yield well-defined plateau (36 grains) or pseudo plateau (2 grains) ages ranging from 17.6 ± 0.5 Ma to 4.71 ± 0.08 Ma (2 σ). The results, when combined with data from Mn-oxides deposits from the adjacent Guangdong and Hunan Provinces, document a protracted history of weathering and supergene Mn enrichment, spanning from the earliest Miocene to the latest Pliocene in South China. This indicates that warm and humid climatic conditions conducive to intense weathering and secondary mineralization prevailed across South China during the whole Neogene. The climatic conditions inferred from weathering geochronology are consistent with sedimentary records and fossil floral and fauna associations from Cenozoic inland and marginal sea basins of South China. The weathering geochronology data also provide temporal constraints on the initiation and intensification of the East Asian monsoon that has been the cause for the South China's humid climate.