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Opal and calcium carbonate are thought to regulate the biological pump's transfer of organic carbon to the deep ocean. A global sediment trap database exhibits large regional variations in the organic carbon flux associated with opal flux. These variations are well‐explained by upper ocean silicate concentrations, with high opal 'ballasting' in the silicate‐deplete tropical Atlantic Ocean, and low ballasting in the silicate‐rich Southern Ocean. A plausible, testable hypothesis is that opal ballasting varies because diatoms grow thicker frustules where silicate concentrations are higher, carrying less organic carbon per unit opal. The observed pattern does not fully emerge in an advanced ocean biogeochemical model when diatom silicification is represented using a single global parameterization as a function of silicate and iron. Our results suggest a need for improving understanding of currently modeled processes and/or considering additional parameterizations to capture the links between elemental cycles and future biological pump changes. Plain Language Summary: Opal, or hydrated silica, is taken up in the surface ocean by diatoms to construct their protective frustules. Another plankton type, coccolithophores, generate protective platelets from calcium carbonate. These two minerals, and thereby plankton types, play major roles in the global carbon cycle. The 'biological carbon pump' transfers carbon from the upper ocean to the ocean's depths, where it can stay for millenia. This process has influenced past atmospheric carbon dioxide concentrations and could also do so in the future. The transfer of carbon to the deep ocean is partially regulated by the amount of 'ballast' minerals in sinking particles, especially opal and calcium carbonate, which are denser and cause particles to sink faster and/or protect organic carbon from microbial consumption. We show that unlike calcium carbonate, opal's ballasting effect varies a great deal between different regions of the ocean. The variation in opal ballasting is well‐explained by the upper‐ocean concentration of silicate between these regions. This suggests a simple explanation: when silicate concentrations are high, diatoms grow thick frustules which actually results in lower carbon sinking per unit opal. Capturing this ballasting–silicate relationship in carbon cycle models may improve their ability to predict future biogeochemical cycles and climate. Key Points: Opal ballasting varies by more than a factor of six across ocean regions; calcium carbonate ballasting is uniformSilicate concentration predicts opal ballasting which suggests that the latter varies with diatom frustule thicknessThis emergent relationship's absence from a sophisticated biogeochemical model indicates it holds useful information for constraining models [ABSTRACT FROM AUTHOR]

Alkaline iron (Fe) batteries are attractive due to the high abundance, low cost, and multiple valent states of Fe but show limited columbic efficiency and storage capacity when forming electrochemically inert Fe3O4 on discharging and parasitic H2 on charging. Herein, sodium silicate is found to promote Fe(OH)2/FeOOH against Fe(OH)2/Fe3O4 conversions. Electrochemical experiments, operando X‐ray characterization, and atomistic simulations reveal that improved Fe(OH)2/FeOOH conversion originates from (i) strong interaction between sodium silicate and iron oxide and (ii) silicate‐induced strengthening of hydrogen‐bond networks in electrolytes that inhibits water transport. Furthermore, the silicate additive suppresses hydrogen evolution by impairing energetics of water dissociation and hydroxyl de‐sorption on iron surfaces. This new silicate‐assisted redox chemistry mitigates H2 and Fe3O4 formation, improving storage capacity (199 mAh g−1 in half‐cells) and coulombic efficiency (94 % after 400 full‐cell cycles), paving a path to realizing green battery systems built from earth‐abundant materials. [ABSTRACT FROM AUTHOR]

Copper tailings are a common byproduct of copper production, containing high levels of heavy metals which are released into the environment. Conventional methods have historically prioritized copper recovery, and often overlooking the leaching of other valuable elements. However, the rising demand for nonferrous metals necessitates understanding their leaching behavior from copper tailings. This study examined the atmospheric leaching of Cu, Fe, Pb, Zn, and CuO from a polymetallic tailing ore. Leaching recoveries of 63.5% for Cu, 97.5% for CuO, 1% for Fe, and 100% for Zn were achieved under the optimum conditions of 0.5 M sulfuric acid concentration, 25% solids percentage, 65°C, stirring speed of 100rpm, particle size of 75 µm within 30 minutes. Results indicated that the dissolution of oxide minerals such as CuO and ZnO was significant; however, copper sulfides need oxidant to be dissolved. In this condition, iron oxides and silicates were partially reacted by sulfuric acid, and Pb-bearing minerals formed lead sulfate. The presence of iron and lead-bearing minerals in the leaching residue was confirmed by XRF, XRD, and SEM analyses, and was in agreement with the information displayed in the Eh-pH diagrams. [ABSTRACT FROM AUTHOR]

Ferromagnesian silicates are the dominant constituents of the Earth's mantle, which comprise more than 80% of our planet by volume. To interpret the low shear-velocity anomalies in the lower mantle, we need to construct a reliable transformation diagram of ferromagnesian silicates over a wide pressure-temperature (P-T) range. While MgSiO3 in the perovskite structure has been extensively studied due to its dominance on Earth, phase transformations of iron silicates under the lower mantle conditions remain unresolved. In this study, we have obtained an iron silicate phase in the perovskite (Pv) structure using synthetic fayalite (Fe2SiO4) as the starting material under P-T conditions of the lower mantle. Chemical analyses revealed an unexpectedly high Fe/Si ratio of 1.72(3) for the Pv phase in coexistence with metallic iron particles, indicating incorporation of about 25 mol% Fe2O3 in the Pv phase with an approximate chemical formula (Fe2+ 0.75Fe3+ 0.25)(Fe3+ 0.25Si0.75)O3. We further obtained an iron silicate phase in the postperovskite (PPv) structure above 95 GPa. The calculated curves of compressional (VP) and shear velocity (VS) of iron silicate Pv and PPv as a function of pressure are nearly parallel to those of MgSiO3, respectively. To the best of our knowledge, the iron silicate Pv and PPv are the densest phases among all the reported silicates stable at P-T conditions of the lower mantle. The high ferric iron content in the silicate phase and the spin-crossover of ferric iron at the Si-site above ~55 GPa should be taken into account in order to interpret the seismic observations. Our results would provide crucial information for constraining the geophysical and geochemical models of the lower mantle. [ABSTRACT FROM AUTHOR]

Primary phases in iron-rich chemical sedimentary rocks are important archives of seawater geochemistry throughout the Precambrian. The record of seawater chemistry, however, is obscured by post-depositional changes that occur during diagenesis, metamorphism, and modern weathering. Recent studies have identified silica-cemented horizons in some Archean and Paleoproterozoic iron formation that may preserve reduced, texturally early mineral phases, which may inform interpretations of oxygen dynamics preceding atmospheric oxygen accumulation before the ~2.3 Ga Great Oxidation Event (GOE). However, fewer investigations focus on silica-cemented horizons in Paleoproterozoic iron formation deposited after the GOE, a period where oxygen levels are poorly constrained. Here, we present petrographic observations, scanning electron microscopy, electron microprobe analysis, and Raman spectroscopy of iron mineral phases preserved within silica-cemented horizons of the ~1.9 Ga Biwabik Iron Formation (Minnesota, U.S.A.) to constrain texturally early iron formation mineralogy from this crucial post-GOE interval. Based on textural relationships, the iron silicate greenalite is identified as the earliest-forming iron silicate mineral preserved within silica-cemented horizons. The magnesium- and aluminum-rich iron silicates chamosite and stilpnomelane are preserved proximal to fine-grained, non-silicified horizons, suggesting local geochemical exchange during early diagenesis. The presence of well preserved, early-forming silicates containing predominantly ferrous iron may indicate reducing conditions at the sediment-water interface during deposition of the Biwabik Iron Formation. More definitively, future studies using iron silicate mineralogy as seawater geochemistry proxies should consider preservation by silica cementation, in addition to the efects of local geochemical exchange during diagenesis. [ABSTRACT FROM AUTHOR]

This study conducts low-vacuum sulfidation to form a sulfidation layer on the serpentinite-derived magnesium iron silicate, thereby enhancing its electrochemical properties. Results show (Mg,Fe)2SiO4 calcined at 900 °C has the best crystallinity, and the cubic FeS2 is synthesized on the surface of the orthorhombic magnesium iron silicate (MFS). Two distinct charge plateaus can be distinguished during the first charge process, and the discharge capacities increased significantly. This study confirms that the surface FeS2 layer provides extra ion pathways, allowing more lithium/magnesium ions to be extracted and inserted in the serpentinite-derived magnesium iron silicate. Accordingly, the serpentinite electrode boasts straightforward exploitation with low-cost advantages and potential. [ABSTRACT FROM AUTHOR]

Banded iron formations (BIF) are chemically precipitated sediments that can record Archean ocean geochemistry. BIFs are laminated silica- and iron-rich deposits that host a range of iron(II, III) minerals, including hematite, magnetite, siderite, greenalite, minnesotaite, and stilpnomelane. This diverse mineralogical assemblage reflects secondary mineralization reactions due to diagenesis and/or post-depositional alteration. While petrographic observations of BIFs sparingly contain the iron silicate greenalite, recent evidence of greenalite nanoparticles preserved in early-mineralizing BIF chert suggest this mineral was a primary phase in BIF progenitor sediments. Therefore, it is critical to investigate the formation and alteration of greenalite to constrain the Archean ocean environment and help unravel post-depositional processes. To examine how iron silicates precipitate and then crystallize and/or transform during diagenesis, we simulated these two processes under Archean ocean conditions. We first precipitated a poorly ordered Fe-rich serpentine with subsidiary ferrihydrite at neutral pH by performing in situ Fe(II) oxidation experiments at 25 °C in the presence of silica. Subjected to simulated diagenesis at 80 °C, the rudimentary Fe-phyllosilicate transformed into a crystalline phyllosilicate characterized as 30% cronstedtite and 70% greenalite accompanied by magnetite and persistent ferrihydrite. At temperatures ≤150 °C, we continued to observe ferrihydrite, increased magnetite formation, and elevated incorporation of Mg into the phyllosilicate as it further recrystallized into Mg-greenalite. Our findings demonstrate a possible formation mechanism of early silicates through partial Fe(II) oxidation and support petrographic observations that magnetite likely mineralizes during diagenesis. Additionally, we suggest that Mg contents in BIF iron phyllosilicates could serve as a tracer for diagenesis, with Mg signaling phyllosilicate-fluid interactions at elevated temperatures. Ultimately, our experiments help reveal how initial iron-silica coprecipitates are altered during diagenesis, providing novel insights into the interpretation of greenalite and magnetite in ancient BIF assemblages. [ABSTRACT FROM AUTHOR]

The ore deposits obtained from Dunoka, Amankwo and Umuakpo in Lejja Nsukka were found to be iron silicate in nature. They were analysedby XRD, XRF, AAS and the ores were found to contain 60.59% Fe, 64.81%Fe and 64.67%Fe respectively. These ores when compared to those iron ore producing nations, they were classified as medium-grade iron ore. Other elements like titanium, magnesium and manganese were present and could be mined for commercial use. Chemical analysis of the ore samples showed that traces of phosphorous of = 0.0079% and were free from the deleterious elements, sulphur and arsenic. [ABSTRACT FROM AUTHOR]

Soft sensors are mathematical models that estimate the value of a process variable that is difficult or expensive to measure directly. They can be based on first principle models, data-based models, or a combination of both. These models are increasingly used in mineral processing to estimate and optimize important performance parameters such as mill load, mineral grades, and particle size. This study investigates the development of a data-driven soft sensor to predict the silicate content in iron ore reverse flotation concentrate, a crucial indicator of plant performance. The proposed soft sensor model employs a dataset obtained from Kaggle, which includes measurements of iron and silicate content in the feed to the plant, reagent dosages, weight and pH of pulp, as well as the amount of air and froth levels in the flotation units. To reduce the dimensionality of the dataset, Principal Component Analysis, an unsupervised machine learning method, was applied. The soft sensor model was developed using three machine learning algorithms, namely, Ridge Regression, Multi-Layer Perceptron, and Random Forest. The Random Forest model, created with non-reduced data, demonstrated superior performance, with an R-squared value of 96.5% and a mean absolute error of 0.089. The results suggest that the proposed soft sensor model can accurately predict the silicate content in the iron ore flotation concentrate using machine learning algorithms. Moreover, the study highlights the importance of selecting appropriate algorithms for soft sensor developments in mineral processing plants. [ABSTRACT FROM AUTHOR]

Lithium iron silicate (Li 2 FeSiO 4) has high theoretical capacity of 332 mAh∙g-1 upon full extraction of two lithium ions, which is accompanied by high delithiation potential and large volume change. Sulfur modification could be an effective approach for stabilizing Li 2 FeSiO 4 cathodes. A series of carbon-coated Li 2 FeSiO 4 samples were prepared through a hydrothermal and solid-state reaction route at a fixed sucrose content (14 wt% carbon) with varying amounts of sublimed sulfur at 5, 10, 15, 20 and 25 at%. The crystal structures, chemical compositions, microstructures and electrochemical performances of the differently sulfur-modified Li 2 FeSiO 4 /C were systematically investigated. The sulfur-carbon co-modifications and possible existing chemical states of sulfur are discussed in terms of the surface and near-bulk modifications. It was found that all the samples exhibited a monoclinic P 2 1 structural Li 2 FeSiO 4 , while the sulfur contents over 10 at% formed impure phases such as iron sulfides (Fe 1-x S) and lithium metasilicate (Li 2 SiO 3). Furthermore, three types of sulfur states could be found when sulfur and carbon were added simultaneously into Li 2 FeSiO 4. The surfaces were predominated by S–C and S–O–C, indicating the sulfur-carbon co-modification, which would reduce the resistance at the solid/electrode interface (SEI) but increase the charge transfer resistance. Near the bulk, the enhanced interactions between sulfur and iron S–Fe(−S) or sulfur and silicon S–Si(−O) may lead to the formation of possible impurities or oxygen substitution by sulfur. The former is detrimental as the effective sulfur amount is reduced, while the latter is beneficial to improve specific capacity and cycle stability. The overall performance of sulfur-carbon co-modified sample is influenced complicatedly by the sulfur content. The best initial discharge capacity of 152.3 mAh∙g-1 was obtained with 5 at% sulfur modification, while the best overall performance, showing a typical warm-up response and good cycle stability, was observed with 15 at% sulfur modification. [ABSTRACT FROM AUTHOR]

Dissolved Oxygen (DO) plays a key role in reactive processes and microbial dynamics in the critical zone. Recent observations showed that fractures can provide rapid pathways for oxygen penetration in aquifers, triggering unexpected biogeochemical processes. In the shallow subsurface, DO reacts with electron donors, such as Fe2+ coming from mineral dissolution. Yet, little is known about the factors controlling the spatial heterogeneity and distribution of oxygen with depth. Here we present a reduced analytical model describing the coupled evolution of DO and Fe2+ as a function of fluid travel time in silicate catchments. Our model, validated from fully resolved reactive transport simulations, predicts a linear decay of DO with time, followed by a rapid non‐linear increase of Fe2+ concentrations up to a far‐from‐equilibrium steady‐state. The relative effects of geological and hydrological forcings are quantified through a Damköhler number (Da) and a lithological number (Λ). We use this framework to investigate the depth distribution of DO and Fe2+ in two catchments with similar environmental contexts but contrasted hydrochemical properties. We show that hydrochemical differences are explained by small variations in Da but orders of magnitude variations in Λ. Therefore, we demonstrate that the hydrological and geological drivers controlling hydrochemistry in silicate catchments can be discriminated by analyzing jointly the O2 and Fe2+ evolution with depth. These findings provide a new conceptual framework to understand and predict the evolution of DO in modern groundwater, which plays an important role in critical zone processes. Plain Language Summary: Dissolved Oxygen (DO) is involved in important biogeochemical reactions, such as the aerobic respiration of microbes, rock‐weathering or contaminant degradation. The general view is that the deeper subsurface of continents is mostly anoxic. However, recent observations have shown that cracks in rocks can allow oxygen to reach deeper down, thus extending deeper the influence of oxygen in reactions. Here, we present a modeling framework validated with field data to understand and predict the hydrological and geological controls on DO evolution in silicate catchments, shedding new light on its influence on rock‐weathering and microbial life in the continents. Key Points: We derive a reduced analytical model to predict the depth distribution of dissolved O2 and Fe2+ in silicate catchmentsThe theory, validated from a reactive transport model, quantifies the hydrological and geological controls through two dimensionless numbersWe use this framework to analyze and explain the O2/Fe2+ distributions in two sites with contrasted chemical properties [ABSTRACT FROM AUTHOR]

Utilizing iron silicate copper slag as supplementary cementitious material (SCM) is a means to improve resource efficiency and lower the carbon dioxide emissions from cement production. Despite multiple studies on the performance of these slags in SCM applications, the variations in cooling procedure, grinding, and methods for evaluating reactivity limit the ability to assess the influence of chemical composition on reactivity from the literature data. In this study, a methodology was developed to synthesize iron silicate slags, which were then evaluated for their inherent reactivity using the R3 calorimeter-based experiments. The results demonstrated that laboratory-scale granulation produced the same reactivity as industrially granulated slag. Furthermore, a synthesized triplicate sample showed high repeatability. Based on these two aspects, this method can be used to systematically study the influence of chemical composition on the inherent reactivity of iron silicate slags while producing results that are directly translatable to industrial slags. [ABSTRACT FROM AUTHOR]

The first samples collected by the Mars 2020 mission represent units exposed on the Jezero Crater floor, from the potentially oldest Séítah formation outcrops to the potentially youngest rocks of the heavily cratered Máaz formation. Surface investigations reveal landscape‐to‐microscopic textural, mineralogical, and geochemical evidence for igneous lithologies, some possibly emplaced as lava flows. The samples contain major rock‐forming minerals such as pyroxene, olivine, and feldspar, accessory minerals including oxides and phosphates, and evidence for various degrees of aqueous activity in the form of water‐soluble salt, carbonate, sulfate, iron oxide, and iron silicate minerals. Following sample return, the compositions and ages of these variably altered igneous rocks are expected to reveal the geophysical and geochemical nature of the planet's interior at the time of emplacement, characterize martian magmatism, and place timing constraints on geologic processes, both in Jezero Crater and more widely on Mars. Petrographic observations and geochemical analyses, coupled with geochronology of secondary minerals, can also reveal the timing of aqueous activity as well as constrain the chemical and physical conditions of the environments in which these minerals precipitated, and the nature and composition of organic compounds preserved in association with these phases. Returned samples from these units will help constrain the crater chronology of Mars and the global evolution of the planet's interior, for understanding the processes that formed Jezero Crater floor units, and for constraining the style and duration of aqueous activity in Jezero Crater, past habitability, and cycling of organic elements in Jezero Crater. Plain Language Summary: Here we provide a narrative of sample collection and associated in situ rover observations for the rocks collected by the Perseverance rover to provide a preliminary description of the first samples of the Mars 2020 mission. These rocks collected in Jezero Crater represent the first samples from Mars with a known geologic context, the first collected with the potential to be returned to Earth for laboratory analysis, and the first cores from rock outcrops on another planet. Remote and proximal analyses indicate that all crater floor outcrops investigated are igneous in origin. Laboratory analyses of these rocks will be useful to study the planet's interior at the time of emplacement, characterize martian magmatism, and place timing constraints on geologic processes, both in Jezero Crater and more widely on Mars. All collected rocks have interacted with water and contain secondary geochemical and mineralogical evidence that can be used to understand aqueous environments in the crater and the potential conditions of habitability for ancient life on Mars. Key Points: Nine samples, consisting of four pairs of rock cores and a tube of atmospheric gas, were collected from the floor of Jezero Crater, MarsIn situ observations of crater floor outcrops, used as proxies for the samples, reveal aqueously altered igneous lithologiesPerseverance will leave one sample from each pair at the Three Forks depot and retain a second to be cached with future samples [ABSTRACT FROM AUTHOR]

Iron tailings (ITS), as solid decay absolved afterward beneficiation, are adverse to the environment. ITS to prepare zinc‐containing mesoporous silicate (MAO‐Zn) by a calcination‐crystallization method are used. An admixture of ammonium polyphosphate (APP) and MAO‐Zn can solve the problem of poor flame retardancy in rigid polyurethane foam (RPUF), giving them higher thermal stability and lower heat release. The total heat release rate and smoke factor values exhibited by RPUF‐3 are 24.52 MJ m−2 and 234.29 MW m−2 respectively, a decrease of 38.45% and 29.60% respectively compared to pure RPUF. Lower combustible and toxic gas release intensities are in RPUF‐3. Meanwhile, RPUF‐3 possesses enhanced compactness char residue with higher graphitization degree, endowing RPUF‐3 with excellent fire observed performance. This work demonstrates the potential of ITS in the fire retardancy field. [ABSTRACT FROM AUTHOR]

Purpose: Biochar and silicate-enriched steel-slag, as agricultural and industrial waste materials, are used to improve soil physicochemical properties and soil fertility; however, there are few studies on the effects of their combined application to paddy fields on the formation of root Fe plaque. Materials and methods: We tested the effects of four application rates (0, 300, 600 and 900 kg ha−1) of biochar-based silicate fertilizer (BSF) to early and late rice on root Fe plaque formation. Results and discussion: Application of BSF increased soil total carbon and total nitrogen concentrations in late rice, and total phosphorus concentrations were increased by 47.03% at the jointing stage and 27.73% at the mature growth stage of early rice following application of BSF at 600 kg ha−1. The three application treatments all significantly increased the abundance of soil iron-reducing bacteria (IRB) in late rice, and application of 600 kg of BSF ha−1 increased IRB abundance by 52.16% and 66.59% at the jointing and mature growth stage, respectively. Both IRB abundance and IP concentration were positively correlated with Fe(II) and negatively correlated with Fe(III) in late rice. Soil Fe(II) concentration was positively correlated with water content, whereas Fe(III) concentration was negatively correlated. Conclusions: Our study demonstrated that moderate inputs of BSF (600 kg ha−1) increased soil Fe reduction and subsequently promoted the formation of more soluble Fe(II) and iron plaque formation through soil fluidity and Fe(II) movement to roots. We suggest that the application of BSF to dry–wet rice paddies may contribute to reduction of agricultural pollution, improvement in soil conditions, and production of sustainable healthy food crops. [ABSTRACT FROM AUTHOR]

The study aims experimentally investigate how to obtain a ferrosilicon alloy using iron silicate - fayalite generated after flotation enrichment of slag in pyrometallurgical production of copper. This material contains about 46 % iron and about 27 % silicon dioxide. Due to its dispersed structure, fayalite is first sintered. The article describes mathematical and physical modeling of the agglomeration and ore thermal process for the production of ferrosilicon. The main fraction of the obtained agglomerate (57,60 %) is over 15 mm. In the electric arc furnace, the time for refining the agglomerate tap to tap is 40 - 60 minutes. The obtained alloy yield is 46 %. In the three melts, the silicon content in the alloy averaged 44 %, meeting the ferrosilicon standard. [ABSTRACT FROM AUTHOR]

Mineral specific surface area (SSA) increases as primary minerals weather and restructure into secondary phyllosilicate, oxide, and oxyhydroxide minerals. SSA is a measurable property that captures cumulative effects of many physical and chemical weathering processes in a single measurement and has meaningful implications for many soil processes, including water-holding capacity and nutrient availability. Here we report our measurements of SSA and mineralogy of two 21 m deep SSA profiles at two landscape positions, in which the emergence of a very small mass percent (<0.1 %) of secondary oxide generated 36 %–81 % of the total SSA in both drill cores. The SSA transition occurred near 3 m at both locations and did not coincide with the boundary of soil to weathered rock. The 3 m boundary in each weathering profile coincides with the depth extent of secondary iron oxide minerals and secondary phyllosilicates. Although elemental depletions in both profiles extend to 7 and 10 m depth, the mineralogical changes did not result in SSA increase until 3 m depth. The emergence of secondary oxide minerals at 3 m suggests that this boundary may be the depth extent of oxidation weathering reactions. Our results suggest that oxidation weathering reactions may be the primary limitation in the coevolution of both secondary silicate and secondary oxide minerals. We value element depletion profiles to understand weathering, but our finding of nested weathering fronts driven by different chemical processes (e.g., oxidation to 3 m and acid dissolution to 10 m) warrants the recognition that element depletion profiles are not able to identify the full set of processes that occur in weathering profiles. [ABSTRACT FROM AUTHOR]

The presence of organic matter in carbonaceous chondrites provides valuable information about the early composition of the Solar System. Although they are considered primitive, the majority of these chondrites have undergone secondary processes subsequent to their formation. These processes, such as aqueous alteration, have altered their composition. The effect of aqueous alteration on minerals is well known, but the effect on organic matter and/or on an organo-mineral system have been little studied. Here, we report experimental results devoted to investigate the chemical evolution of a hypothetical initial chondritic material subjected to hydrothermal alteration under reducing conditions at low-temperature. The mixtures consist of different anhydrous minerals (peridot, feldspar, troilite) together with hexamethylenetetramine (HMT) chosen as a model molecule inherited from the interstellar grains. After different times at 80 °C, the large molecular diversity formed is highly influenced by the presence and the nature of the minerals, as highlighted in particular by the evolution of the amide produced. The presence of minerals in the mixture appears to influence the reactivity of the system more through the formation of salts and chelates than through surface adsorption mechanisms. The most pronounced effect is observed in the presence of troilite, both in the degradation of HMT and in the abundance of amides formed. The study of the mutual influence of minerals and organic matter, and their intrinsic transformations in the media during the processes, could help to understand about the origin of organic molecules observed in carbonaceous chondrites. • Organic composition in carbonaceous chondrites may result from aqueous alteration. • We made chondritic analogs with hexamethylenetetramine and non-hydrated minerals. • Mineral type, pH, red-ox and complexation influence the organic diversity formed. • Mixing minerals shows a synergistic effect on molecular complexity. • Minerals can impact organics in carbonaceous chondrites during aqueous alteration. [ABSTRACT FROM AUTHOR]

• Phosphonate additives demonstrate variable stabilization effectiveness for ferric silicate. • Phosphonates act as chelators/ligands for Fe3+ ions, and thus, "turn off" their catalytic effect in silica polycondensation. • The silica precipitates that form in the presence of Fe3+ ions are Fe3+-absorbed amorphous silica, with variable Fe3+ content. • Phosphonate entrapment into the precipitates occurs as a result of Fe-induced formation of sparingly soluble Fe−phosphonate "complexes". The formation, precipitation, and deposition of the so-called "iron silicate" in geothermal waters have been among the problematic issues in some geothermal installations. Our approach aims to systematically study the influence of phosphonate-based chemical additives on the formation of precipitates in the presence of both silicate and ferric (Fe3+) ions. The selection of this type of antiscalants was based on their extraordinary affinity for metal ions in general, and in particular for ferric cations. For this purpose, various phosphonate additives that possess diverse chemical structures and variable numbers of functional groups have been systematically evaluated. These additives are PBTC (2-phosphonobutane-1,2,4-tricarboxylic acid), HEDP (hydroxyethylidene-1,1-diphosphonic acid), AMP (amino- tris (methylenephosphonic acid)), HDTMP (hexamethylenediamine- tetrakis (methylenephosphonic acid)), DTPMP (diethylenetriamine- pentakis (methylene phosphonic acid)) and BHMTPAMP (bis-hexamethylenetriamine- pentakis (methylenephosphonic acid)). Experiments were conducted in solutions containing silicate (150 ppm, expressed as SiO 2) and iron (150 ppm, as Fe) at pH 7.0. The phosphonate additives used were found to act as stabilizing agents, most likely by complexing the Fe3+cations, thereby preventing ferric silicate formation. The experimental design included a plethora of physicochemical parameters, such as antiscalant concentration, salinity, and temperature. Based on the generated experimental data, numerous functional insights have been generated, contributing to a more complete and comprehensive understanding of the mechanism of ferric silicate control. [Display omitted] [ABSTRACT FROM AUTHOR]

• Ferric silicate precipitation is pH-dependent. • Ferric silicate precipitates can be described as Fe-loaded amorphous silica. • Ferric silicate is an amorphous precipitate with variable Fe:Si molar ratios. • Its solubility increases with temperature. The interest in the utilization of geothermal energy has increased exponentially in the past few decades, and researchers internationally are currently focusing on improving harvesting methods and promoting it due to its numerous benefits compared to traditional energy sources. Corrosion and scaling are two of the significant problems in modern geothermal industry that occur during the harvesting of geothermal energy. Scaling occurs due to the variety of anions and cations that the majority of geothermal reservoir waters contain. High levels of dissolved Fe3+ and silicate ions cause the formation of the elusive "iron silicate", the latter term usually referring to ferric silicate. Its identity, as it is formed in geothermal waters, differs from its geological counterparts. Usually, deposits that contain Fe and Si are referred to as "iron silicate", revealing very little about its true identity. This research is focused on revealing the true nature of the so-called "ferric silicate", performing a series of synthesis experiments under various conditions that take into account iron and silicate concentrations (at the supersaturation regime), solution pH, temperature and different sources of iron. Although solutions containing 150 ppm silicate (no ferric) are stable and do not undergo any polycondensation at pH = 7.0, the presence of ferric induces variable silicate loss from solution. Its severity is enhanced as the ferric concentration increases. Ferric loss from solution in the presence of silicate ions is also severe, regardless of the silicate concentration. Both silicate and ferric loss from solution are pH-dependent processes, with a maximum observed around pH = 7.0. This loss is accompanied by precipitate formation, which is corroborated by turbidity measurements. The solubility of ferric silicate (under the conditions studied) increases with temperature. There is a roughly 4-fold solubility increase when the temperature is increased from 25 °C up to 220 °C. However, enhanced ferric incorporation into the final precipitate was observed at higher temperatures. The ferric silicate precipitates were characterized by several techniques, such as powder XRD, ATR-IR, SEM, and EDS, and showed that ferric silicate is an amorphous precipitate with variable Fe:Si atom ratios and a random Fe distribution throughout the solid. These results can serve as a roadmap for ferric silicate precipitation, taking into account the water chemistry of a specific scale-forming brine. [Display omitted] [ABSTRACT FROM AUTHOR]

Most iron meteorites formed in planetary cores during differentiation, but the IIE iron meteorites have chemical and physical features that are inconsistent with this origin. By combining mineral chemistry, mineral modes and three-dimensional petrography, we reconstruct the bulk chemistry of the felsic silicate-bearing Miles IIE iron meteorite and demonstrate that the silicate inclusion compositions are similar to partial melts produced experimentally from an H chondrite composition. We use the reconstructed bulk composition, mineralogy and thermodynamic modelling to show that melting above ∼1200°C under reducing conditions formed metal (Fe-Ni alloy) and felsic silicate partial melts. Upon cooling, the melts crystallized Mg-rich pyroxenes, Na- and K-rich feldspars, and tridymite. Importantly, this mechanism enriches cosmochemically volatile elements (i.e., those with a 50% condensation temperature of ∼430–830°C, like Na and K) to the level found in the felsic silicate inclusions. The presence of crystallographically disordered srilankite (only stable above 1160°C) and an absence of Widmanstätten texture require both high peak temperatures and rapid cooling, which cannot be explained by core formation. Instead they point to small melt volumes, a transient heat pulse, and small thermal mass, and imply efficient physical segregation of silicate and metallic melts through buoyancy separation followed by rapid cooling that arrested the separation of metal and silicate liquid phases. In situ 207Pb/206Pb age of 4542.3 ± 4.0 Ma in Zr-oxide and phosphate minerals dates the melting event that formed the silicate inclusions. This age aligns with the earliest ages found in other IIE iron meteorite silicates and requires a heating event ∼25 million years after the solar system formed. We found 39Ar/40Ar ages of 3495 ± 52 Ma (low-T) and 4303 ± 7 Ma (high-T) in a K-feldspar grain, with the 3495 Ma age aligning with later thermal events recorded in other IIE iron meteorites. Dating reveals the complex petrogenetic and thermal history of Miles and the IIE iron meteorites. This is the first IIE iron meteorite found to record evidence of heating at 4.5 and 3.5 Ga likely from impact events. We propose that high-velocity impact(s) into an iron-rich, porous chondritic parent body at ∼4.54 Ga produced immiscible metal and silicate melts that cooled rapidly and trapped low density silicate inclusions within high density metal. Other IIE irons that formed at lower peak temperatures (900–1000°C) contain chondritic silicate inclusions and relict chondrules, supporting this conceptual model. This petrogenesis is consistent with thermodynamic modelling, experimental data and the wide range of peak temperatures and cooling rates observed in the IIE iron meteorites. [ABSTRACT FROM AUTHOR]

[Display omitted] Most metal sites and some non-metallic sites such as carbon and nitrogen are usually considered to be traditional active sites during peroxymonosulfate (PMS) activation. However, as an important non-metallic element, the actual role of silicon (Si) in PMS activation still remains unclear. In this work, taking iron silicate (FeSi) as an example, the role of the Si region in PMS activation was clearly revealed. The experiments and density functional theory (DFT) calculation results showed that besides the traditional Fe sites, the Si also played a non-negligible role during PMS activation. In FeSi containing oxygen vacancies (Ovac), Fe-Si was the active site instead of Fe-Fe. The Bard charge results implied that the presence of Ovac tuned the electronic properties of FeSi, making the Si participate in PMS activation. This work deepened understanding of the role of Si in silicates for PMS activation and provided a theoretical basis for the development of excellent Si-based catalysts. [ABSTRACT FROM AUTHOR]

The Earth's iron-rich core contains light elements. Studying the interaction of multiple light elements with iron and silicates during core–mantle segregation process in early Earth evolution has become important. In-situ X-ray diffraction and imaging observations of the iron–silicate–water–sulfur system at 5–10 GPa, up to approximately 1900°C, were used to elucidate sequential reactions: phase transformation and hydrogenation of iron, and formation of iron sulfide and silicates. The newly constructed X-ray imaging system achieved spatial resolution of approx. 10 μm for this study to show iron blob formation and motion. Sulfur distorted the iron blob shape and affected blob growth during heating by reducing the interfacial energy between molten iron and silicates. Light elements in the molten iron and the remaining silicate grains affected core–mantle segregation in the primitive Earth as temperatures increased. Carbon and silicon were incorporated into liquid Fe during later processes at higher temperatures. [ABSTRACT FROM AUTHOR]

The improved description of the planets' interior is provided. We examine the modified gravity effects on the Earth-like planets composed of the iron core and silicate mantle. We confirm that the mass–radius relations as well as density profiles differ with respect to the commonly adopted Newtonian models. [ABSTRACT FROM AUTHOR]

We present a study of photochemical hazes of exoplanet atmospheres based on a self-consistent model including haze microphysics, disequilibrium chemistry, and radiative feedbacks. We derive the haze properties required to match Hubble Space Telescope observations of 10 hot-Jupiters. HAT-P-12b, HD-189733b, HD-209458b, and WASP-6b require haze mass fluxes between 5 × 10−15 and 9 × 10−12 g cm−2 s−1 to match the observations. WASP-12b and WASP-19b with equilibrium temperatures above 2000 K are incompatible with the presence of haze and are better fitted by heavy metals. HAT-P-1b and WASP-31b do not show clear evidence for the presence of hazes with upper mass fluxes of 10−15 and 10−16 g cm−2 s−1, respectively, while WASP-17b and WASP-39b present an upper mass flux limit of 10−16 g cm−2 s−1. We discuss the implications of the self-consistent model and we derive upper limits for the haze abundances based on photochemistry results. Our results suggest HCN as the main haze precursor up to 1300 K effective temperatures and CO above. Our derived haze mass fluxes based on the fit to the observations are consistent with the photochemistry with formation yields up to ∼6.4 per cent. Disequilibrium chemistry has negligible impact on the spectra considering the low-resolution observations used but impacts the chemical composition and temperature profiles. We find that hazes produce hotter upper atmosphere temperatures with a detectable impact on the spectra. Clouds may have implications for interpreting the transit spectra of HD-209458b, WASP-31b, and WASP-39b. Nevertheless, the presence of silicate and iron clouds is expected in all studied atmospheres except WASP-12b and WASP-19b. [ABSTRACT FROM AUTHOR]

Iron–manganese silicate (IMS) was synthesized by chemical coprecipitation and used as a catalyst for ozonating acrylic acid (AA) in semicontinuous flow mode. The Fe-O-Mn bond, Fe-Si, and Mn-Si binary oxide were formed in IMS on the basis of the results of XRD, FTIR, and XPS analysis. The removal efficiency of AA was highest in the IMS catalytic ozonation processes (98.9% in 15 min) compared with ozonation alone (62.7%), iron silicate (IS) catalytic ozonation (95.6%), and manganese silicate catalytic ozonation (94.8%). Meanwhile, the removal efficiencies of total organic carbon (TOC) were also improved in the IMS catalytic ozonation processes. The IMS showed high stability and ozone utilization. Additionally, H2O2 was formed in the process of IMS catalytic ozonation. Electron paramagnetic resonance (EPR) analysis and radical scavenger experiments confirmed that hydroxyl radicals (•OH) were the dominant oxidants. Cl−, HCO3−, PO43−, Ca2+, and Mg2+ in aqueous solution could adversely affect AA degradation. In the IMS catalytic ozonation of AA, the surface hydroxyl groups and Lewis acid sites played an important role. [ABSTRACT FROM AUTHOR]

The thermodynamics and kinetics of the reduction of iron silicate (fayalite), generated as a result of flotation processes in the production of copper concentrates, were studied. Three reducing agents were used - coke, charcoal, and graphite, in ratios to the stoichiometrically calculated amounts of reducer: 1: 1.5; 1: 2; 1: 2.5. The free Gibbs energy in the temperature range from 973 K to 1040 K was determined experimentally and the corresponding equations for ΔG = f(T) were derived. The kinetic parameters were determined using thermogravimetric and differential methods at temperatures up to 1273 K. The results showed that the reduction process using coke went through three stages, and using charcoal - two stages. The reactions that took place were of the first order. Carbonated reduction of iron silicate occurred in the kinetic region. The highest values of the apparent activation energy were obtained as 67.83 kJ mol-1 when using coke (1257 K), and when using graphite - 60.29 kJ mol-1 at 1318 K. The lowest values of the activating energy 36 kJ mol-1 were observed with a charcoal reducer in the temperature range 966-1573 K. [ABSTRACT FROM AUTHOR]

Infrared-active optical phonons were studied in olivine LiFePO4 oriented single crystals by means of both rotating analyzer and rotating compensator spectroscopic ellipsometry in the spectral range between 50 and 1400 cm-1. The eigenfrequencies, oscillator strengths, and broadenings of the phonon modes were determined from fits of the anisotropic harmonic oscillator model to the data. Optical phonons in a heterosite FePO4 crystal were measured from the delithiated ab-surface of the LiFePO4 crystal and compared with the phonon modes of the latter. Good agreement was found between experimental data and the results of solid-state hybrid density functional theory calculations for the phonon modes in both LiFePO4 and FePO4. [ABSTRACT FROM AUTHOR]

The transformation of olivine during the conversion of CO2 to light hydrocarbons activated by mechanochemical treatments at different impact frequencies was studied by a combination of several complementary characterization methods including X-ray diffraction, Raman and 57Fe Mössbauer spectroscopy. Several olivine samples were studied as a function of the milling time, indicating the gradual transformation of FeII-containing olivine into new FeIII-containing weathering products including iron oxides, magnesium iron carbonates and silicates. The results presented here complement those of a previous study on the weathering process of olivine promoted by mechanochemical activation, by demonstrating the role of the redox activity of the iron species during the activation process. These additional spectroscopic results allow us to thoroughly understand the complex weathering mechanism and to correlate it with the efficiency of the CO2 conversion and storage properties of mechanochemically activated olivine. [ABSTRACT FROM AUTHOR]

The zinc in the fayalite slag of copper smelters, in which Zn-containing raw materials are used, is mainly found to be in oxidic phases, such as glassy iron silicate. During the slag water granulation process, the molten slag is heated, whereby the granulated slag achieves varying granulation temperatures. Therefore, in this study, we aimed to characterize and assess the leaching behavior of a synthesized Fe-saturated (FeX,Zn(1−X))2SiO4 system to understand the dependance of the zinc leaching behavior on the parameters of the ZnO content (1–10 wt.%) and granulation temperature (1300 or 1400 °C). It was found that the Zn leaching increased with the increasing Zn content and granulation temperature, using both batch and static pH leaching methods. Zn leaching was further increased at pH 5 using diluted nitric acid under oxidation conditions. Among the oxides in the samples—fayalite, spinel, and glass—glass was found to contribute to Zn leaching, owing to its weathering during pH-titration. [ABSTRACT FROM AUTHOR]

The application of fluxed pellets in iron making industry has attracted considerable attention because of the better metallurgical properties than acid pellets and environmental friendliness compared to sinters. However, fluxed pellets with different binary basicity (CaO/SiO2) exhibited significant differences in phase composition, microstructure and consolidation mechanism. These differences mainly stemmed from the influence of calcium-containing substances in fluxed pellets. Herein, the theoretical investigation discovered the calcium-containing substances from fluxed pellets, including calcium iron silicate, calcium silicate and complex calcium ferrite (SFCA), which determined the properties of fluxed pellets. Microstructure analysis revealed that the calcium-containing substances filled between hematite particles were used as a binding phase to assist in pellets' consolidation. Furthermore, the calcium-containing binding phase formed in the low-basicity (0.4–1.0) pellets was mainly composed of the calcium iron silicate glassy phase, while the binding phase of the high-basicity (1.0–1.2) pellets was dominated by SFCA belonging to SiO2-Fe2O3-CaO-Al2O3 multivariate system. In comparison, SFCA exhibited better crystallinity and reducibility than calcium iron silicate. Within the roasting temperature range of 1200–1250 °C, the increase of basicity contributed to the fluxed pellets obtaining better strength. To sum up, fluxed pellets with SFCA as the main calcium-containing binding phase can be obtained by increasing the basicity above 1.0–1.2, which was imperative for further improving the physical and metallurgical properties of fluxed pellets. [ABSTRACT FROM AUTHOR]

High-capacity and high-voltage cathode materials are required to meet the increasing demand for energy density in Li ion batteries. Lithium iron silicate (Li2FeSiO4) is a cathode material with a high theoretical capacity of 331 mAh·g−1. However, its poor conductivity and low Li ion diffusion coefficient result in poor capability, hindering practical applications. Morphology has an important influence on the properties of materials, and nanomaterials with hollow structures are widely used in electrochemical devices. Herein, we report a novel hollow hemispherical Li2FeSiO4 synthesized by a template-free hydrothermal method with the addition of ascorbic acid. The hollow hemispherical Li2FeSiO4 consisted of finer particles with a shell thickness of about 80 nm. After carbon coating, the composite was applied as the cathode in Li ion batteries. As a result, the hollow hemispherical Li2FeSiO4/C exhibited a discharge capacity as high as 192 mAh·g−1 at 0.2 C, and the average capacities were 134.5, 115.5 and 93.4 mAh·g−1 at 0.5, 1 and 2 C, respectively. In addition, the capacity increased in the first few cycles and then decayed with further cycling, showing a warm-up like behavior, and after 160 cycles the capacities maintained 114.2, 101.6 and 79.3 mAh·g−1 at 0.5, 1 and 2 C, respectively. Such a method of adding ascorbic acid in the hydrothermal reaction can effectively synthesize hollow hemispherical Li2FeSiO4 with the enhanced electrochemical performance. [ABSTRACT FROM AUTHOR]

According to most sources, the type locality for the hydrous iron silicate mineral hisingerite is Riddarhyttan, Västmanland, Sweden, first reported in 1828. However, it was described by A.F. Cronstedt as early as 1751 from Väster Silvberg, Dalarna (under the name "kolspeglande järnmalm"), and in 1810 by W. Hisinger from the Gillinge iron mine, Södermanland ("svart stenart", later "gillingit"). J. Berzelius introduced the presently valid species name (originally spelt "hisingrit") in 1819. Potential type materials are preserved by the Swedish Museum of Natural History, from Gillinge and Riddarhyttan. A Hisinger specimen from Gillinge has recently been analysed and was shown to contain associated potassic-hastingsite, magnetite and fayalite that explain the previously observed aluminium contents and high density for "gillingit", compared to pure hisingerite. [ABSTRACT FROM AUTHOR]

We report a combined conventional Mössbauer and synchrotron Nuclear Resonant Inelastic X-ray Scattering (NRIXS) study of a series of basalt, andesite, dacite, and rhyolite glasses at temperatures ranging from 5 to 1223 K. These glasses were synthesized under controlled oxygen fugacities and span a wide range of Fe3+/Fe tot ratios. As expected from theory, we find that in these glasses, the inverse of the Lamb-Mössbauer factor (the recoil-free fraction) correlates linearly with the fraction of the conventional Mössbauer spectrum that can be ascribed to Fe3+. Extrapolating the linear relationships to pure Fe3+ and Fe2+ endmembers yields a ratio for the Lamb-Mössbauer factors C of Fe3+ and Fe2+ of 1.203 ± 0.017 (1σ), with no clear dependence on the chemical composition of the glass. We show that the materials studied follow the harmonic approximation up to 1223 K for olivine and 773 K for basaltic glass, allowing us to extrapolate C in temperature. The temperature-dependence of C is well approximated by the formula C = 1.203 ± 0.033 T / 300 over the temperature range 50–750 K. This calibration is used to correct previous redox ratio determinations. We investigate how chemical composition and iron redox state influence the mean force constant of iron in glasses, a key driver of Fe isotopic fractionation during magma generation and differentiation. As previously documented by Dauphas et al. (2014), we find clear correlation between bond strength and iron redox ratio that is secondarily modulated by coordination effects in more alkali-rich felsic magmas. New data on simplified glass compositions reveal that network modifiers, notably K and Na, seem to exert an important control on Fe2+ bond strengths. The refined ratio of Mössbauer factors for Fe2+ and Fe3+ is used to improve on calibrations of iron redox state in geological glasses using XANES spectroscopy. We reevaluate the Fe3+/Fe tot ratio of MORBs based on previously published XANES and Mössbauer data. 0.087 ± 0.005 [ABSTRACT FROM AUTHOR]

We report on the mineralogy, petrology, and oxygen isotopic compositions of ferroan olivine–pyroxene‐normative cryptocrystalline chondrules (Fe‐CCs) in CH chondrites and discuss their origin and the origin of other components in the genetically related CH and CB chondrites. There are two kinds of Fe‐CCs: (1) compositionally uniform (Fe/[Fe+Mg] = 0.17–0.34) chondrules with euhedral Fe, Ni‐metal grains and (2) metal‐free chemically zoned (Fe/[Fe+Mg] = 0.05–0.4) chondrules surrounded by ferroan olivine (Fa44−62) rims; the Fe/(Fe+Mg) ratio increases toward the rims. Both types contain low CaO and Al2O3 (<0.04 wt%), but relatively high contents of MnO and Cr2O3 (up to 1 wt%). Compositionally uniform euhedral Fe, Ni‐metal grains are Ni‐rich (9–20 wt%) and have subsolar Co/Ni ratio. There is a positive correlation between iron content in the metal grains and Fe/(Fe+Mg) ratio in silicate portion of their host chondrules. Some Fe‐CCs experienced postcrystallization solid‐state reduction of ferroan silicates to metallic iron. Ferroan cryptocrystalline chondrules and olivine rims have similar oxygen isotopic compositions (interchondrule Δ17O ranges from ~ −2‰ to 2‰), which are slightly 16O‐depleted relative to those of magnesian olivine–pyroxene‐normative cryptocrystalline chondrules (Mg‐CCs; Δ17O ~ −2‰) commonly observed in CBs and CHs. We suggest that the Fe‐CCs and Mg‐CCs formed in the impact plume under different redox conditions (~IW−1 and ~IW−3, respectively), which may have been controlled by heterogeneous distribution of water‐bearing phases (water ice, hydrated materials) in the collided bodies and/or in the disk. We propose the following impact plume scenario for the origin of Fe‐CCs: (1) condensation of ferromagnesian silicate melt around Fe, Ni‐metal melt droplets from a highly oxidized portion of the plume; (2) crystallization of euhedral metal grains from the supercooled ferromagnesian silicate melt followed by its solidification; (3) condensation of ferroan olivine rims around solidified Fe‐CCs; (4) high‐temperature annealing of Fe‐CCs and their rims in the plume accompanied by Fe‐Mg interdiffusion between ferroan olivine rims and their host chondrules. Subsequently, some Fe‐CC experienced solid‐state reduction to various degrees, possibly in the reduced portions of gaseous plume. The impact plume‐produced or reprocessed components in CBs and CHs include Ca,Al‐poor magnesian and ferroan cryptocrystalline chondrules; Ca,Al‐rich skeletal olivine chondrules; isotopically uniform, 26Al‐poor 16O‐depleted (Δ17O ~ −15 to −5‰) igneous CAIs surrounded by igneous forsterite rims; chemically zoned and unzoned Fe,Ni‐metal grains; and metal‐sulfide nodules. These objects are dominant in CBs and abundant in CHs. The CH chondrites also contain other high‐temperature chondritic components, which avoided processing in the plume and most likely predate the plume event: 26Al‐poor and 26Al‐rich, mostly 16O‐rich CAIs (Δ17O ~ −40 to −10‰) surrounded by Wark–Lovering rims, and porphyritic chondrules (magnesian [type I], ferroan [type II], and Al‐rich) showing a range of Δ17O (from ~ −10 to ~ +5‰). Some of these components appear to have been melted in the plume. We conclude that CH and CB chondrites contain multiple generations of chondrules and refractory inclusions formed by different mechanisms at different times and different regions of the protoplanetary disk, consistent with the hypothesis of Wasson and Kallemeyn (1990). [ABSTRACT FROM AUTHOR]

Limestone fluxed iron ore pellets are reduced in CO-rich atmosphere generally accompanied by swelling behavior. If the reduction swelling index (RSI) exceeds the normal range (≥20%), it will seriously hinder the stable and anterograde production of iron making. To better guide the industrial production, the effect of binary basicity (CaO/SiO 2) on the reduction swelling behavior and mechanism of limestone fluxed iron ore pellets was investigated. Meanwhile, X-ray diffraction technique was used to analyze the phase transformation in pellets with different basicity during the reduction process, and the microstructures of different substances were examined by SEM-EDS. The above researches confirmed that the crystal volume expansion caused by crystal structure transformation during hematite (α-Fe 2 O 3) reduced to maghemite (γ-Fe 2 O 3) was the fundamental reason for the swelling of limestone fluxed pellets. Low basicity (0.4–0.8) amplified the volume expansion produced in this process, while high basicity (1.0–1.2) reversed it. This inconsistency stemmed from the difference in the composition of binding phase. Compared with calcium iron silicate in low basicity pellets, complex calcium ferrite (SFCA) as the binding phase of high basicity pellets had excellent reducibility, which promoted uniform reduction rate of high basicity pellets. The increased of SFCA content i reduced the quantities of hematite and effectively inhibited swelling of pellets. From this investigation, increasing the basicity above 1.0 to promote the formation of SFCA was an effective way for decreasing the reduction swelling index of limestone fluxed pellets. [Display omitted] • Crystal volume expansion was fundamental reason for fluxed iron pellets swelling. • Calcium iron silicate intensified inconsistency of fluxed iron pellets swelling. • The increase of internal stress in low basicity pellet leaded to abnormal swelling. • SFCA formation reduced hematite content and total swelling index of fluxed pellets. • SFCA showed excellent reducibility, making high basicity pellets swelling uniformly. [ABSTRACT FROM AUTHOR]

Although the seismic properties of polycrystalline olivine have been the subject of systematic and comprehensive study at seismic frequencies, the role of orthopyroxene as the major secondary phase in the shallow parts of the Earth's upper mantle has so far received little attention. Accordingly, we have newly prepared three synthetic melt‐free polycrystalline specimens containing different proportions of olivine (Ol, Fo90) and orthopyroxene (Px, En90) by hot pressing precursor powders produced with the solution‐gelation method at 1,200°C and 300 MPa. The resulting specimens (of Ol95Px5, Ol70Px30, and Ol5Px95 phase proportions) were mechanically tested by torsional forced‐oscillation from 1,300 or 1,200–400°C during staged cooling under a confining pressure of 200 MPa. Within the observational window (1–1,000 s), the shear modulus and dissipation vary monotonically with period and temperature for each of the tested specimens. There is no evidence of the superimposed high‐temperature dissipation peak reported by Sundberg and Cooper (2010, https://doi.org/10.1080/14786431003746656) for an Ol60Px40 specimen derived from natural precursor material and containing ∼1.5% melt. The forced‐oscillation data for each specimen are well‐described by a model based on an extended Burgers‐type creep function. The findings suggest that an olivine‐based model for high‐temperature viscoelasticity in upper mantle olivine requires only modest adjustment of the unrelaxed shear modulus to accommodate the role of orthopyroxene. Plain Language Summary: Olivine is the most abundant mineral phase in the Earth's upper mantle, and accordingly seismic wave speeds and attenuation within polycrystalline olivine have been studied systematically in laboratory. However, orthopyroxene, the second major phase in the upper mantle, has received less attention. In this study, we applied oscillating torque at the periods of seismic waves to synthetic olivine‐orthopyroxene samples with different phase proportions at temperatures ranging from 1,300 or 1,200°C down to 400°C. We found that, regardless of the difference in phase proportions, the strain‐energy dissipation in each of the three samples increases smoothly with increasing period and temperature, accompanied by systematic relaxation of the rigidity or shear modulus. In particular, the behavior of the sample containing 30% orthopyroxene is essentially indistinguishable from that of the sample with 95% olivine and 5% orthopyroxene. We therefore conclude that variation only of the (high‐frequency) unrelaxed modulus is needed to accommodate the role of orthopyroxene in olivine‐based seismological models. Key Points: Viscoelastic behavior of olivine‐orthopyroxene mixtures is relatively insensitive to variation of orthopyroxene concentrationAn olivine‐based viscoelasticity model requires adjustment only of the unrelaxed shear modulus to accommodate the role of ≤30% orthopyroxeneA dissipation peak and enhanced dispersion observed in a previous study of an olivine‐orthopyroxene specimen are now plausibly attributed to melt squirt [ABSTRACT FROM AUTHOR]

The layered iron silicate cronstedtite was encountered in ore veins in the exploration shaft mined in the Neoproterozoic black shale-hosted pyrite-manganese deposit near Litošice (Eastern Bohemia, Czech Republic) around 1955. It forms up to 2 mm thick black double or single bands in symmetrically zoned hydrothermal veins cutting shales. The specimens selected from available material were studied by single-crystal X-ray diffraction using the four-circle diffractometer with an area detector. The chemical composition of some of the specimens was determined by the electron probe microanalysis (EPMA) in the WDS mode. Furthermore, a polished section of the ore material with cronstedtite bands was prepared, and the mineral association was analyzed with the aid of back-scattered electron (BSE) images. The interpretation of reciprocal space (RS) sections produced by the diffractometer software allowed the determination of OD subfamilies (Bailey's groups) A, B, C, D, and polytypes. The 1T polytype (subfamily C), a = 5.52, c = 7.12 Å, space group P31m, is the most abundant in the occurrence. In rare cases, it forms oriented crystal associations (allotwins) with the 1M polytype (subfamily A), a = 5.52 Å, b = 9.55, c = 7.136 Å, ß = 104.4°, space group Cm. Fully disordered allotwinned crystals of the A + C subfamilies were found, too. In addition, few allotwins of the polytype 2H1 (subfamily D) with a small amount of 2H2, were identified. Unit cell parameters are a = 5.49, c = 14.21 Å, space groups are P63cm (2H1), and P63 (2H2). EPMA-WDS of selected crystals of prevailing 1T polytype revealed elevated contents of Mn (0.19-0.62 apfu) and low contents of Mg (up to 0.13 apfu) and Cl (up to 0.05 apfu), respectively. More rare 2H1 (+ 2H2) polytypes show elevated contents of Mg in the range of 0.19-0.62 apfu and distinctly lower Mn (up to 0.07 apfu) and Cl contents (up to 0.01 apfu). The BSE images reveal that cronstedtite bands are associated with multiple generations of carbonates (rhodochrosite, siderite, rarely magnesite and calcite), quartz, opal, pyrite and carbonate-fluorapatite. Intense metasomatic replacement of cronstedtite by opal and siderite appeared especially around the center of the studied vein. [ABSTRACT FROM AUTHOR]

Fe-implanted Si-wafers have been oxidized at 900 °C and 1100 °C in order to investigate the behaviour of Fe atoms at the growing SiO2/Si interface and the impact on the integrity of microelectronic devices of an involuntary Fe contamination before or during the oxidation process. As-implanted and oxidized wafers have been characterized using secondary ion mass spectroscopy, atom probe tomography, and high-resolution transmission electron microscopy. Experimental results were compared to calculated implantation profiles and simulated images. Successive steps of iron disilicide precipitation and oxidation were evidenced during the silicon oxidation process. The formation of characteristic pyramidal-shaped defects, at the SiO2/Si interface, was notably found to correlate with the presence of β-FeSi2 precipitates. Taking into account the competitive oxidation of these precipitates and of the surrounding silicon matrix, dynamic mechanisms are proposed to model the observed microstructural evolution of the SiO2/Si interface, during the growth of the silicon oxide layer. [ABSTRACT FROM AUTHOR]

Sedimentary rock deposits provide the best records of (bio)geochemical cycles in the ancient ocean. Studies of these sedimentary archives show that greenalite, an Fe(II) silicate with low levels of Fe(III), was an early chemical precipitate from the Archean ocean. To better understand the formation of greenalite, we explored controls on iron silicate precipitation through experiments in simulated Archean seawater under exclusively ferrous conditions or supplemented with low Fe(III). Our results confirm a pH-driven process promoting the precipitation of iron-rich silicate phases, and they also reveal an important mechanism in which minor concentrations of Fe(III) promote the precipitation of well-ordered greenalite among other phases. This discovery of an Fe(III)-triggering iron silicate formation process suggests that Archean greenalite could represent signals of iron oxidation reactions, potentially mediated by life, in circumneutral ancient seawater. [ABSTRACT FROM AUTHOR]

The design and preparation of electrode materials with excellent performance is particularly important due to the current global scarcity of energy supplies, especially those using sustainable and renewable materials. In this work, it is first proposed to apply iron silicate (FeSi), which is synthesized using environmentally friendly biomass as a raw material, as an electrode material for supercapacitors (SCs). FeSi is derived from the calcination of reed leaves (RLs) in combination with a hydrothermal method, and spherical FeSi retains the porosity of the RL precursors and shows remarkable electrochemical performance. The specific capacitance of FeSi as a SC electrode can reach 575 F g−1 at 0.5 A g−1 in the voltage window from −1 to −0.5 V. Simultaneously, the FeSi electrode exhibits favorable cycling stability with 76% capacitance retention after 10 000 cycles and outstanding electrical conductivity. This finding provides a novel method of preparing a kind of untapped electrode material, porous FeSi nanoparticles derived from RLs, and the resulting FeSi material shows enormous potential for energy storage via high-performance SCs. [ABSTRACT FROM AUTHOR]

We developed a promoted iron based catalyst that converts 20% more CO to diesel than the unpromoted counterparts. The synthesis involves a non-hydrolytic sol-gel method (NHSG) and 0.04 g g−1 copper and 0.02 g g−1 potassium as promoters. The iron catalyst supports included cerium and zirconium metallosilicates and Catalox and Dispal commercial aluminum oxides from Sasol. At 325 ∘C and 20 bar, CO conversion over the Fe/Ce/SiO 2 -K,Cu, exceeded 85% while at the same conditions it was only 68% over the unpromoted catalyst. Fe/Zr/SiO 2 -K,Cu converted less CO than the cerium-silicate (75%) but the unpromoted zirconium-silicate only converted 43% of the CO. The conversion and selectivity of the Catalox was about the same as the cerium-silicate, while the Dispal performance was equivalent to the zirconium-silicate. This study also highlights the importance of support and promoters in FTS, demonstrates the potential of the NHSG method to synthesize promoted iron catalysts with various supports and lays the foundation for developing efficient and stable catalysts for converting syngas to hydrocarbons. [Display omitted] • Promoters (Cu and K) on iron metallosilicates increase CO conversion by 20% • Iron on cerium silicate support converts 85% of CO vs 75% for iron zirconium silicate • Metallosilicates are more active than aluminum oxides supports and equally stable • Promoted aluminum oxide supported iron catalyst converts 88% of CO at 325 ∘C • C 7+ selectivity is higher for metallosilicates compared to aluminum oxide at 300 ∘C [ABSTRACT FROM AUTHOR]

Silicate fertilizer derived from iron slag (hereafter, silicate fertilizer) as a soil amendment has been added to Korean and Japanese rice paddies to improve soil pH and supply nutrients to the crop. However, the consequences of silicate fertilizer application to soil organic carbon (SOC) stocks remain unclear. Hypothetically, silicate fertilizer might deplete SOC by increasing soil pH and stimulating microbial activity or increase SOC by improving rice productivity and biomass. To investigate this, we first quantified the relationship between plant-available silicate (SiO 2) and soil organic matter concentrations using national soil survey data. We found a highly positive correlation between the two parameters, suggesting that long-term silicate fertilizer application might promote SOC sequestration. We then examined the effect of silicate fertilizer and lime (CaCO 3) addition on soil respiration for 30 days under flooded conditions. Both materials increase soil pH but affect soil respiration in different ways: respiration increased significantly with lime but decreased significantly with silicate fertilizer application. This demonstrates that silicate fertilizer simultaneously improves pH while minimizing C loss through soil respiration. Finally, in a field study spanning two years, we ascertained the impact of silicate fertilizer (1.5 Mg ha-1) on annual SOC stock changes under rice cropping. Silicate fertilizer application increased net primary production (NPP) of rice plants by around 20% over control plots that did not receive silicate but decreased respired C loss by 16–20%. As a result, silicate fertilizer application increased the SOC stock by 0.96–1.1 Mg C ha−1 year−1 over the control. Our findings show that iron slag-based silicate fertilizer can promote C sequestration in soil organic matter while simultaneously improving soil properties and rice productivity. [Display omitted] • Available SiO 2 and SOM concentrations have a high positive correlation using a national soil survey. • Silicate fertilizer (SF) application decreased soil respiration compared with lime. • SF addition markedly increased the NPP of rice plants by around 20% over control. • SF application decreased respired C loss by around 18% over control. • SF application increased the SOC stock by 0.96–1.1 Mg C ha−1 year−1 over the control. [ABSTRACT FROM AUTHOR]

Hydrogen (H) is considered to be one of the candidates for light elements in the Earth's core, but the amount and timing of delivery have been unknown. We investigated the effects of sulfur (S), another candidate element in the core, on deuteration of iron (Fe) in iron–silicate–water system up to 6–12 GPa, ~ 1200 K using in situ neutron diffraction measurements. The sample initially contained saturated water (D2O) as Mg(OD)2 in the ideal composition (Fe–MgSiO3–D2O) of the primitive Earth. In the existence of water and sulfur, phase transitions of Fe, dehydration of Mg(OD)2, and formation of iron sulfide (FeS) and silicates occurred with increasing temperature. The deuterium (D) solubility (x) in iron deuterides (FeDx) increased with temperature and pressure, resulting in a maximum of x = 0.33(4) for the hydrous sample without S at 11.2 GPa and 1067 K. FeS was hardly deuterated until Fe deuteration had completed. The lower D concentrations in the S-containing system do not exceed the miscibility gap (x < ~ 0.4). Both H and S can be incorporated into solid Fe and other light elements could have dissolved into molten iron hydride and/or FeS during the later process of Earth's evolution. [ABSTRACT FROM AUTHOR]

Dissolution and solubility of palladium in iron silicate melts saturated with alumina–iron spinel at 1300°C has been measured using an equilibration-drop quenching technique combined with electron probe microanalysis and laser ablation–inductive coupled plasma–mass spectrometry analysis from polished sections. Composition of the resulting Fe-Pd alloy allowed estimation of the activity of palladium at different oxygen partial pressures, and, thus, the solubilities of palladium in the studied slags in conditions typical of copper and nickel smelting as well as slag cleaning at pO2=10-5 to 10-10 atm. The mechanism of palladium dissolution in the studied iron silicate slags was oxidation by formation of the monovalent oxide species PdO0.5 over the entire oxygen activity range of this study. Testing the applicability of the various palladium isotopes for quantitative analyses of Pd in these types of matrices resulted in a good fit of measured concentrations of 104Pd and 105Pd with interference-corrected 106Pd and 108Pd. [ABSTRACT FROM AUTHOR]

Chemical gardens, which are self‐organizing, abiotic, inorganic precipitates in far‐from‐equilibrium systems, are of interest for prebiotic chemistry/origin of life research and, under certain reaction systems, can be considered hydrothermal vent analogs. While the presence of different additives to chemical gardens, including phosphate and amino acids, have been explored, the reactivity of organic molecules in chemical garden systems is not well understood. Here we explored the reactivity of two metabolically important alpha‐keto acids (pyruvic acid and glyoxylic acid) and ammonia in the presence of iron‐silicate chemical gardens. While reactivity was not observed in the case of pyruvic acid, we found that glyoxylic acid formed alpha‐hydroxy acids and amino acids. We found that the observed organic reactivity can be attributed to the silicate in the exterior solution as opposed to the solid iron‐containing chemical garden structure. These results have implications for the reactivity of hydrothermal vent chimneys and their surrounding environments in iron‐ and silica‐rich systems. [ABSTRACT FROM AUTHOR]

Olivine, a ferromagnesian orthosilicate, is the most abundant mineral in Earth's upper mantle and is stable down to the olivine-wadsleyite phase transition, which defines the 410 km depth mantle transition zone. Olivine also occurs in crustal environments in metamorphic and hydrothermal rocks and is expected to be the major mineral constituent of the Martian and Venusian mantles. The olivine atomic structure is also used in materials science to manufacture lithium batteries. Like any other crystalline solid, including minerals, olivine never occurs with a perfect crystalline structure: defects in various dimensions are ubiquitous, from point, line, and planar defects to three-dimensional (3-D) inclusions. In this contribution, I review the current state of the art of defects in olivine and several implications for key processes occurring in Earth's mantle. Intrinsic and extrinsic point defects are detailed, exemplifying the astonishing diversity of atomic impurities in mantle-derived olivine. Linear defects, one of the key defect types responsible for ductile deformation in crystalline solids, are examined in light of recent progress in 3-D transmission electron microscopy, which has revealed an important diversity of dislocation slip systems. I summarize the principal characteristics of interface defects in olivine: the free surface, grain and interface boundaries, and internal planar defects. As the least-studied defects to date, interface defects represent an important challenge for future studies and are the main application of numerical simulation methods in materials science. I provide an overview of melt, fluid, and mineral inclusions, which are widely studied in volcanology and igneous petrology. Special attention is given to new crystalline defects that act as deformation agents: disclinations (rotational defects) and the potential occurrence of disconnections in olivine, both of which are expected to occur along or near grain boundaries. Finally, I detail outstanding questions and research directions that will further our understanding of the crystalline specificities and paradoxes of olivine and olivine-rich rocks and ultimately their implications for the dynamics of Earth's upper mantle. [ABSTRACT FROM AUTHOR]

The structures of a series of Na2O–FeO–Fe2O3–SiO2 melts with Si/Fe = 1, 2, or 3 have been characterized via synchrotron X-ray total scattering using aerodynamic levitation, a containerless technique, paired with laser heating. The melt structure has been simulated using empirical potential structure refinement (EPSR) based on X-ray scattering data and molecular dynamics (MD) simulations with effective partial charge potentials. Pair distribution functions and coordination numbers of cations in the melt were obtained from the data refinement and from the MD simulations. Iron redox and accompanying density were modeled for each composition assuming either (1) oxidized (all Fe3+) or (2) reduced (some Fe2+) to the level predicted for the Ar levitator environment from a literature model. The actual redox of the melts appears to be intermediate, with some Fe2+ but not as much as assumed from the literature model of redox. Comparison of EPSR and MD models at the same redox conditions indicates generally good agreement, and precise values of coordination numbers depend sensitively on the assumptions for cutoff lengths. Stepwise cooling of each melt in the series resulted in formation of magnetite on the free surface of the sample, but no silica-containing crystalline phases were observed. This study provides a comprehensive assessment of coupled factors (composition, redox, density) needed to assess high-temperature in situ structural measurements of simplified iron silicates. [ABSTRACT FROM AUTHOR]