Fe Ratio Research Articles

Magmatic (Cr-Ni-PGE) and secondary/hydrothermal (emerald-peridot-rodingite-nephrite jade) mineralization associated with mafic-ultramafic rock complexes of Pakistan

Mafic magmatism has repeatedly taken place in Pakistan throughout its geologic history from the earliest Proterozoic to Recent. Much of it, however, does not have associated metallic mineralization. This paper concerns mineralization associated with mafic-ultramafic plutonic rock occurrences in the western- and northern suture zones of Pakistan, which demarcate the collision boundary between the northwestern Indian plate and Eurasian blocks. We discuss the petrology of the ophiolites and basaltic magma-related chromite deposits, showings of PGE and Ni minerals, and secondary mineral deposits (emerald and peridot gems, rodingite, and nephrite jade) associated with mafic-ultramafic complexes of the two suture zones. Chromite with high Cr#s (68 to 85) occurs in fair quantity and is mostly considered to be genetically related to basaltic magma of subduction-related environments. PGE and nickeliferous minerals are insignificant in quantity; PGE's are formed by a higher degree of partial melting and melt-rock reaction, whereas Ni-sulphides are the product of serpentinization of the ultramafic rocks. Emerald occurs in several localities in the ISZ, whereas the peridot has so far been reported from only one locality. Emerald is associated with Mg-carbonate ± quartz ± fuchsite ± talc ± serpentine, and peridot (Fo 89-92 ) is associated with chrysotile ± magnesite ± talc ± magnetite ± ludwigite. Both are formed via hydrothermal alteration of ultramafic rocks through the introduction of hydrous fluids incorporating CO 2 , Be, B, K, Al, and possibly Na. In view of the undeformed nature of the emerald and peridot and the 23 Ma age of emerald formation, the mineralization appears to post-date deformation and may be of Late Oligocene-Early Miocene age. The metasomatising fluids were either derived from the subducting Indian plate crust underneath the Kohistan arc or were related to 23-26 Ma silicic magmatism in this area of the NW Indian plate. The nephrite jade in the ophiolite mélange is hosted in serpentinites and has disseminated grains of chrome spinel with elevated Fe/(Mg + Fe) ratios (0.10–0.18), implying low-grade metamorphism of ultramafic rocks (protolith of serpentinite) with loss of Al and introduction of SiO 2 during accompanying metasomatism. The rodingite in Dargai ophiolite could have formed by the action of seawater channeled through fractures and cracks in rocks. However, their mineral assemblages indicate that they formed as a result of the influx of Ca, Al, and Na-bearing hydrothermal fluids related to the intrusion of gabbros/sheeted dykes in the serpentinized ultramafic rocks, resulting in Ca-metasomatism.

Influence of FexOy and Al2O3 Contents on the Thermal Stability of Iron Ore-Waste Fibers: Key Mechanisms and Control.

Traditional rock wool fibres are susceptible to crystallization and pulverization. To mitigate this, glass fibres were produced from iron ore waste (IOW). When the ratio of Fe2+ and Fe3+ is 1:3 and the Al2O3 content is 10 wt.%, increasing the FexOy content enhances the thermal stability.At an FexOy content of 17-19% and an Al2O3 content of 10-13%, the glass transition temperature (Tg) peaked. Increasing the FexOy content from 10% to 20% enhanced the stability of Si-O and Al-O bonds and increased bridged oxygen, stabilizing the structure. Here, Fe2+ balances structural charges, while Fe3+ replaces some Al atoms in the network. When the Al2O3 content is 10-13% and the FexOy content is 17-19%, the thermal stability of the IOW rock glass reaches its optimal level. At 20% FexOy content, the structure becomes three-dimensional and cyclic, increasing polymerization. Consequently, incorporating FexOy alongside a 10% Al2O3 content improves thermal stability, supporting the development of high-stability rock wool from IOW. This approach also enhances the refractory properties of rock wool fibres within the FexOy-Al2O3-SiO2-MgO-CaO system.

Recovery of phosphorus from chemical-enhanced phosphorus removal sludge: Influence of sodium sulfide dosage on phosphorus fractionation, sludge dewaterability, and struvite product

Despite the potential of sodium sulfide (Na2S) for phosphorus (P) recovery from iron-phosphate waste, the underlying mechanism regarding its impact on P conversion and product quality has not been well addressed. In this study, the effects of Na2S addition on P release and recovery from a chemical-enhanced phosphorus removal (CEPR) sludge during anaerobic fermentation were systematically investigated. The results revealed that the effective mobilization of P bound to Fe (Fe–P) by Na2S dominated the massive P release from the CEPR sludge, while the organic P (OP) release was not significantly enhanced during anaerobic fermentation. Due to the rapid reaction of Na2S with Fe–P and the prevention of Fe(II)–P precipitation by excess S2−, the Fe–P was decreased by 9.7%, 15.2% and 24.9% at S:Fe molar ratios of 0.3, 0.5 and 1, respectively. After anaerobic fermentation, the released P mainly existed as soluble phosphate (SP), P bound to Ca (Ca–P) and P bound to Al (Al–P). The nitrogen and P contents in the fermentation supernatant significantly increased with higher S:Fe ratios, facilitating the efficient recovery of P as high-purity struvite. However, the increased Na2S dosage deteriorated the sludge dewaterability because of the dissolution of hydrophilic extracellular polymeric substances and the looser secondary structure of proteins. Comprehensively considering the P recovery, sludge dewaterability and economic cost, the optimal Na2S dosage was determined at the S:Fe ratio of 0.3. These findings provide novel insights into the role of Na2S in P recovery as struvite from CEPR sludge.

Copper migration and enrichment in the mantle wedge: Insights from orogenic peridotites and pyroxenites

The refertilized mantle wedge is an important source of ore-forming metals in subduction-related Cu–Au deposits. However, the source and migration of Cu in the mantle wedge are poorly constrained. Here, we present a combined study of the Cu elemental and isotopic compositions (δ65Cu) as well as Fe3+/∑Fe ratios on a well-characterized suite of the Mg-lherzolites, Fe-rich peridotites and pyroxenites from the Bohemian Massif in a Variscan subduction zone. The Mg-lherzolites represent melting residues moderately affected by metasomatism of slab-derived melts/fluids. The Fe-rich peridotites and pyroxenites are, respectively, results of Mg-lherzolite-melt reaction and crystalline products of evolved melts in the lithospheric mantle.The peridotites and pyroxenites display higher Fe3+/∑Fe ratios (0.14–0.56) than the cratonic peridotites and mid-ocean ridge basalts, indicating that the mantle wedge was oxidized by slab-derived components. The Mg-lherzolites have relatively low Cu contents (7.35–39.6 μg/g) and normal mantle-like δ65Cu values (−0.13 to 0.26 ‰), suggesting an insignificant slab-to-mantle wedge Cu transfer. In contrast, the Fe-rich peridotites and pyroxenites have variable but overall high Cu contents (37.0–513 μg/g) and heavier δ65Cu values (up to 0.83 ‰). These signatures are ascribed to secondary sulfide precipitation from the evolved Cu- and 65Cu-enriched melts, which were produced by reaction of Mg-lherzolites with subduction-related oxidative SiO2‐undersaturated basaltic melts. Such melt-peridotite reaction at high oxygen fugacity can cause the partial oxidative decomposition of primary sulfides in peridotites with the preferential release of 65Cu into the evolved melts. Our results thus demonstrate that oxidative melt-rock reaction can result in the Cu migration, redistribution and its local enrichment in the mantle wedge, which may serve as an important source of Cu for subduction-related porphyry copper deposits.

Corrosion behavior of Cr/RE alloyed rebar in carbonated simulated concrete pore solutions with chloride ions

This study investigated the effect of the addition of Cr and RE microalloying regarding the steel rebar's resistance to corrosion in the co-existence of carbonation and chloride ions using electrochemical tests, scanning electron microscopy and confocal laser scanning microscopy. The best corrosion resistance of the Cr/RE microalloying rebar was found by the reduction in corrosion rates and the diminution of the rust layer. And during the initial stages of localized corrosion, the corrosion pits' depth was minimized, showing lateral expansion trends, which was supported by confocal laser scanning microscopy. Additionally, XPS analysis revealed that Cr/RE microalloying rebar can change the structure of the surface oxide film with a higher Fe(II)/Fe(III) ratio, which enhanced the surface oxide film's protective qualities.

Elevated Water Oxidation by Cation Leaching Enabled Tunable Surface Reconstruction.

Water electrolysis is one promising and eco-friendly technique for energy storage, yet its overall efficiency is hindered by the sluggish kinetics of oxygen evolution reaction (OER). Therefore, developing strategies to boost OER catalyst performance is crucial. With the advances in characterization techniques, an extensive phenomenon of surface structure evolution into an active amorphous layer was uncovered. Surface reconstruction in a controlled fashion was then proposed as an emerging strategy to elevate water oxidation efficiency. In this work, Cr substitution induces the reconstruction of NiFexCr2-xO4 during cyclic voltammetry (CV) conditioning by Cr leaching, which leads to a superior OER performance. The best-performed NiFe0.25Cr1.75O4 shows a ~1500 % current density promotion at overpotential η=300 mV, which outperforms many advanced NiFe-based OER catalysts. It is also found that their OER activities are mainly determined by Ni : Fe ratio rather than considering the contribution of Cr. Meanwhile, the turnover frequency (TOF) values based on redox peak and total mass were obtained and analysed, and their possible limitations in the case of NiFexCr2-xO4 are discussed. Additionally, the high activity and durability were further verified in a membrane electrode assembly (MEA) cell, highlighting its potential for practical large-scale and sustainable hydrogen gas generation.

Elevated Water Oxidation by Cation Leaching Enabled Tunable Surface Reconstruction

AbstractWater electrolysis is one promising and eco‐friendly technique for energy storage, yet its overall efficiency is hindered by the sluggish kinetics of oxygen evolution reaction (OER). Therefore, developing strategies to boost OER catalyst performance is crucial. With the advances in characterization techniques, an extensive phenomenon of surface structure evolution into an active amorphous layer was uncovered. Surface reconstruction in a controlled fashion was then proposed as an emerging strategy to elevate water oxidation efficiency. In this work, Cr substitution induces the reconstruction of NiFexCr2‐xO4 during cyclic voltammetry (CV) conditioning by Cr leaching, which leads to a superior OER performance. The best‐performed NiFe0.25Cr1.75O4 shows a ~1500 % current density promotion at overpotential η=300 mV, which outperforms many advanced NiFe‐based OER catalysts. It is also found that their OER activities are mainly determined by Ni : Fe ratio rather than considering the contribution of Cr. Meanwhile, the turnover frequency (TOF) values based on redox peak and total mass were obtained and analysed, and their possible limitations in the case of NiFexCr2‐xO4 are discussed. Additionally, the high activity and durability were further verified in a membrane electrode assembly (MEA) cell, highlighting its potential for practical large‐scale and sustainable hydrogen gas generation.

Enhanced mineralization of bisphenol A by electric arc furnace slag: Fenton-like oxidation

Bisphenol A (BPA) aqueous solution was treated through a heterogeneous Fenton-like oxidation process with electric arc furnace slag (EAFS), a waste product from an Argentinian steel processing plant, as the catalyst. SEM/EDS, XRD, and Mössbauer spectroscopy characterization revealed a significant presence of Fe and minor amounts of Cu and Mn in EAFS, known to play active roles in the Fenton-like reactions. The predominant crystalline form of iron in EAFS was magnesiowüstite, accompanied by minor amounts of hematite, magnetite, maghemite, and metallic iron. Batch Fenton-like oxidation experiments were conducted under acidic conditions (pH 2.8–3), examining the effect of temperature (25, 50, and 70 °C) and catalyst load (0.1, 0.5, and 1 g/L) on BPA degradation and mineralization over 180 min. BPA was completely degraded within the first minutes, while mineralization levels improved from 40% to an outstanding 70% as the temperature increased from 25 to 70 °C. The catalyst gradually lost its activity after five cycles at 25 °C, but raising the temperature up to 70 °C allowed maintaining mineralization levels between 70 and 50% over ten cycles. The oxidation process involved a combined Fenton-like homogeneous/heterogeneous mechanism, and deactivation was linked to a lower leaching of active cations over the cycles, reduction of the Fe(II)/Fe(III) ratio in the iron phases, and blocking of active sites by adsorption of reaction intermediates. EAFS demonstrated an exceptional performance in the Fenton-like oxidation of BPA. The utilization of this type of industrial waste materials represents a promising technological alternative that could benefit both steel processing and water treatment plants.

Accelerating the dissolution and transformation of detrimental Fe-rich intermetallics in recycled Al-Mg-Si alloy by homogenization and hot deformation

The plate-like Fe-rich intermetallics in recycled Al-Mg-Si alloys dramatically degrade the mechanical properties, which has to be minimized to obtain the high-performance components. Previous finding of using Mn to neutralize the harmful Fe have proven to be effective at a Mn:Fe ratio of 2:1 in order to convert detrimental β-Al5FeSi (β-Fe) plates into less harmful α-Al₁₅(Fe, Mn)₃Si₂ (α-Fe) scripts. However, excess amount of Mn will inevitably introduce large fraction of intermetallic particles which reduce the ductility of alloy. In this study, we propose a new process which utilize both homogenization and hot deformation processes to achieve dissolution and transformation of detrimental Fe-rich intermetallics. The transformation mechanisms with limited Mn addition (Mn:Fe Ratio≈1) have been uncovered. After homogenization for 10 h, the percentage of β-Fe decreases from 1.13% to 0.87%. After 30% hot deformation, it further decreases to 0.45% and the elongation is increased by 55.97%. If we combine the hot deformation 30% with cold deformation by 20%, it will eventually decrease to 0.25%, achieving complete conversion from β-Fe to α-Fe, and the tensile strength is increased by 42.15%. To uncover the transformation mechanisms of Fe-rich intermetallics, 3D distribution of Fe-rich intermetallics and microporosity have been quantified as a function of processing conditions by using X-ray computed tomography (XCT), demonstrating that the new approach can make use of the Fe tolerable recycled Al alloys to achieve high strength and ductility.

Ferric Iron in Eclogitic Garnet and Clinopyroxene from the V. Grib Kimberlite Pipe (NW Russia): Evidence of a Highly Oxidized Subducted Slab

Abstract Estimates of oxygen fugacity of eclogitic rocks are linked to the redox evolution of the oceanic protolith during subduction and its residence in the lithospheric mantle, and, based on knowledge of pressures and temperatures, allow modelling of the speciation of volatile elements and diamond (or graphite) versus carbonate stability. To date, the oxygen fugacity of mantle eclogites has been shown to vary between −6 (Kasai, Congo and Udachnaya, Siberia) and −0.1 (Udachnaya, Siberia) log units (relative to the fayalite–magnetite–quartz buffer, FMQ), linked to the low Fe3+ contents of garnets. In this study, we investigated the Fe oxidation state of coexisting garnet and clinopyroxene hand-picked out of 17 diamond-free high-MgO and low-MgO mantle eclogites (dated at 2.84 Ga) from the Grib kimberlite pipe (East-European platform). Measured Fe3+/∑Fe values range between 0.03 and 0.19 for garnet and 0.18–0.38 for clinopyroxene, the former being higher than what was measured previously in garnets equilibrated at mantle conditions. The Fe3+/∑Fe of the reconstructed bulk rock ranges between 0.10 and 0.15 for high-MgO eclogites and 0.10 and 0.24 for low-MgO eclogites (with uncertainties of ± 0.02 and ± 0.03 in both cases). Thermobarometric calculations result in equilibration pressures and temperatures of 3.0–5.2 (± 0.4) GPa and 720–1050 (± 60) °C for both high-MgO and low-MgO eclogites, slightly lower than previous P–T estimates of mantle eclogites from the Udachnaya kimberlite pipe (Siberian craton). At these conditions, ∆logfo2 (FMQ) calculated using the available oxythermobarometric model varies from −1.7 to −0.6 log units for high-MgO eclogites and from −2.9 to 0.9 log units for low-MgO eclogites. Samples recording ∆logfo2 (FMQ) ≤ −1 log units overlap with North Slave, West Africa and Udachnaya eclogites, with no difference among eclogite types. The average values of −1.2 (± 0.4) log units for high-MgO and −0.6 (± 1.1) log units for low-MgO eclogites suggest different redox conditions of basaltic protoliths during subduction worldwide. Previous geochemical studies on the same rock samples reported evidence of cryptic metasomatism in both garnet and clinopyroxene that we demonstrate being not recorded by their major elements, while modal metasomatism evidenced by the presence of phlogopite as a product of interaction with a kimberlitic melt only affects the MgO of the bulk rock. Therefore, we suggest that high Fe3+/∑Fe ratios for garnet (> 0.10) and for reconstructed bulk rocks in the case of both low-MgO and high-MgO samples cannot be due to metasomatic interaction with an oxidized fluid, but rather are the consequence of Fe3+ redistribution in an unusually oxidized mafic protolith upon metamorphism. Our results highlight the redox variability of eclogites of Archaean age at conditions more oxidized than present-day mid-ocean ridge basalts (MORBs) and imply an oxidizing nature of the convective mantle source where magma was formed with consequent speciation of C in the form of carbonate fluid explaining, therefore, the lack of eclogitic diamonds in V. Grib kimberlite pipe.

Garnet Geochemistry of Pertek Skarns (Tunceli, Turkey) and U-Pb Age Findings

The Fe skarn and vein-type Cu mineralization types are common in the Eastern Taurus Mountains. This study aims to determine the U-Pb geochronology of garnets of varying sizes within the skarn zone developed at the quartz diorite–marble contact zone in Ayazpınar, Pertek District, Tunceli Province, Turkey. Additionally, this study aims to determine the age of the skarnization and the types of inclusion minerals in the garnets. Faulting and magma emplacement along the thrust plane caused mineralization in the Eastern Taurus Mountains, especially at the marble and quartz diorite contact zone between the cities of Elazığ and Tunceli. The greenish garnets found in the Ayazpınar deposit are characteristic of distal skarns, while red or brown Pertek garnets are observed in the proximal skarns. The garnets typically feature a core–rim texture. The cores of the garnet crystals are large, reddish in color, and have a high REE (Ce, Pr) content. Moreover, the cores have higher Fe and lower Al ratios, alongside higher La, Ce, and Pr contents, than the rims. We propose that the compositional differences between the rims and the cores reflect the transition from oxidized REE- and Fe3+-rich liquids to liquids with lower REE and Fe3+ contents, producing the differences in the garnet colors. Green garnets show lower REE contents than brown garnets with Fe-rich cores. The skarn under study includes the following successively formed zones: diorite → epidote skarn → garnet–magnetite → pyrite–garnet–magnetite → calcite carbonate. Diopside, magnetite, and hematite, including small grains, are surrounded or enveloped by garnets. The U-Pb age of the mineralization is 74.1 ± 5 Ma, indicating that the mineralization occurred concurrently with the intrusion settlement.

Tailoring Electrochemical Water Oxidation Activity from the Isostructural Series of Alkaline‐Stable Bimetallic Fe,Ni‐Azolate Metal–Organic Frameworks

AbstractIncorporating electrocatalytic active sites into the reticular framework allows for the design of novel catalytic structures promoting desired catalytic reactions with efficient mass transfer. However, to fully exploit the advantages of such a framework, it is crucial to ensure the electrochemical stability of the material. In this context, alkaline‐stable bimetallic MxNi2‐xCl2BTDD (M = Fe, Co) metal–organic frameworks (MOFs) are employed as electrocatalysts for alkaline water oxidation reaction (WOR) to understand the correlation between secondary metal incorporation and catalytic activity changes. For a specific Fe ratio within the MOF, the optimal catalytic activity is achieved at an overpotential of 315 mV at a WOR current density of 10 mA cm−2geo. Based on its well‐defined crystal structure and uniformly arranged metal nodes, which are not limited to specific facets, the cooperative electrocatalytic mechanism during the faradaic WOR process is investigated through operando Raman spectroscopy and density functional theory calculations. These results enable the interpretation of the electrochemical WOR mechanism based on MOF, providing a further fundamental understanding of electrocatalytic activity in bimetallic systems.

WITHDRAWN: Optimization of Thermochemical Stability of La-based/Zr-based Dual-Phase Composites for Oxygen Transport Membranes via Computational Thermodynamics

The current investigation deploys a computational thermodynamics approach to develop new materials for dual-phase composites. The chemical stability of (La0.9Sr0.1)0.95CrxFe1-xO3-δ and (La0.8Sr0.2)0.95CrxFe1-xO3-δ (x=0.5, 0.7, 0.8, and 0.9) with three fluorite phases of 8YSZ, 10Sc1YSZ, and 10Sc1CeSZ has been examined. The changes in the Sr-content and the Cr: Fe ratio in the perovskite phase have also been investigated under oxidizing and reducing atmospheres at elevated temperatures. The results show that SrZrO3 as the dominant secondary phase together with limited formations of (La0.5Zr0.5)O1.75 and La2O3. The experimental results have been incorporated into simulations performed by computational thermodynamics. Involved mechanisms to improve the chemical stability have been discussed based on correlations between the content of dopants and applied conditions. The results promote knowledge for the development of ceramic-based dual-phase composite membranes.

Remediation of diesel contaminated soil by using activated persulfate with Fe3O4 magnetic nanoparticles: effect and mechanisms.

In this study, Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) were assessed for their ability to enhance the activity of persulfate (PS). Various controlling factors including PS dosages, initial pH, water-soil ratio, ratio of Fe2+, and Fe3O4 MNPs to PS were considered in both the Fe2+/PS system and the Fe3O4 MNPs/PS system. Results showed that the Fe3O4 MNP-activated PS system exhibited high processing efficiency owing to the gradual release of Fe2+. This process occurred in a wide pH range (5-11), attributed to the synergistic action of sulfate radicals (SO4-·) and hydroxyl radicals (OH·) under alkaline conditions, effectively mitigating soil acidification. The ratio of Fe3O4 MNPs to PS and water-soil ratio significantly influenced the degradation rate with the highest petroleum hydrocarbon degradation rate exceeding 80% (82.31%). This rate was 3.1% higher than that achieved by the Fe2+/PS system under specific conditions: PS dosage of 0.05 mol/L, Fe3O4 MNPs to PS ratio of 1:10, water-soil ratio of 2:1, and initial pH of 11. Meanwhile, oxidant consumption in the Fe3O4 MNPs/PS system was halved compared to the Fe2+/PS system due to the slow release of Fe2+ and less ineffective consumption of SO4-·. Mechanistically, the possible degradation process was divided into three parts: the initial chain reaction, the proliferating chain reaction, and the terminating chain reaction. The introduction of Fe3O4 MNPs accelerated the degradation rate of pentadecane, heneicosane, eicosane, tritetracontane, and 9-methylnonadecane.

XPS Investigation of Magnetization Reduction Behavior and Kinetics of Oolitic Hematite in Gas-Based Roasting

Magnetization reduction roasting is an important method for the utilization of oolitic magnetite. In this study, the magnetization reduction behavior and kinetics of oolitic hematite in gas-based roasting were systematically investigated by X-ray photoelectron spectroscopy (XPS). The results revealed that under optimal roasting conditions of 650 °C, a roasting time of 60 min, and a CO concentration of 30%, the magnetization reduction rate of the roasted product reached 44.34%. Furthermore, the weak magnetic separation concentrate presented a TFe of 58.09% and a concentrate iron recovery of 94.3%. The results of the XPS spectrum indicated that the peak area ratio (Fe2+/Fe3+) gradually increased with an increase in roasting temperature, roasting time, and CO concentration, while over-reduction occurred when the roasting temperature exceeded 750 °C. The investigation of magnetization roasting kinetics for varying particle sizes demonstrated that the magnetization reduction process is controlled by chemical reaction, with a corresponding activation energy range of 42.96 kJ/mol to 63.29 kJ/mol, indicating the particle size has little effect on the magnetization reduction of oolitic hematite.

Investigation of borate glasses reinforced with iron (III) oxide [Fe2O3]: Preparation, physical, UV–Vis properties and γ-ray attenuation efficacy

Five samples of borate glasses reinforced with various ratios of Fe3+ ions with chemical formula (60-X)B2O3–10ZnO–10CdO–5Li2O–15Na2O-XFe2O3: (0.0 (Fe-0.0) ≤ X ≤ 1 (Fe-1.0) mol%) were prepared using the melt-quenching technique. The structure, physical, optical characteristics, and γ-ray attenuation properties of the prepared Fe-X glasses have been investigated. The amorphous state of Fe-X glasses confirmed by XRD observations. Density (ρglass) of the Fe-X glasses increased from 3.21 g cm−3 to 3.91 g cm−3. Molar volume (Vm) gradually reduced from 18.87 cm3/mol to 15.35 cm3/mol with increasing Fe2O3 content in the glass network from 0.0 to 1.0 mol%. The color of Fe-X glasses changed from yellow to brown according to the absorption bands located at around 385–412 nm and 407–429 nm within the visible spectrum. The indirect optical band gap (Eg) decreased from 3.37 eV to 2.78 eV, while the linear refractive index (no) increased from 2.31 to 2.45. Mass- (MAC) and linear- (LAC) attenuation coefficients increased as Fe3+ ions increased in the glass network. The Fe-1.0 sample with highest Fe2O3 content possessed the lowest values of half-value layer (HVL) and mean free path (MFP) shielding parameters. Results revealed that the suggested glass compositions can be applied in optical and radiation protection fields.

The Success of Fabrication of Pure SmFe2 Phase Film with Outstanding Perpendicular Magnetic Anisotropy.

This study used DC magnetron sputtering technology to fabricate Sm-Fe films and systematically investigated the phase transition behavior of Sm-Fe films with different Fe ratios. It was found that at higher Fe content, the films consisted of Sm2Fe17 or SmFe7 phases; as Fe content decreased, the films were mainly composed of SmFe3 or SmFe2 phases; at higher Sm content, the films primarily consisted of Sm phase. Sm is prone to volatilization at high temperatures, so Ta was used as a capping layer to effectively suppress Sm volatilization, successfully synthesizing pure SmFe2 phase films at a nearly 1:2 ratio. The magnetic properties and magnetostrictive behavior of the SmFe2 films were investigated, revealing that pure-phase SmFe2 films exhibit good perpendicular magnetic anisotropy and magnetostriction properties. The larger stress along the perpendicular-to-film direction, resulting from the absence of substrate-induced constraints, contributes to the excellent perpendicular magnetic anisotropy of the films. This study successfully synthesized pure-phase SmFe2 films and discovered a new method for fabricating perpendicularly anisotropic films. The research findings are of great significance for the efficient synthesis of desired films with high phase formation temperatures containing volatile elements.

Iron dissolution from Patagonian dust in the Southern Ocean: under present and future conditions

Although the input of desert dust as a key source of trace metals in the Southern Ocean (SO) has been previously studied, the dissolution process of metals in surface waters, particularly iron (Fe), remain poorly understood. Given the crucial role of Fe in primary production and the biological carbon pump in the SO, we focused on experimental estimations of Fe dissolution from Patagonian dust, the primary natural dust source in the SO. Our study considered both current and projected future conditions, encompassing sea-surface warming, acidification, increased photosynthetically active radiation, and doubled dust inputs. Through controlled laboratory experiments using filtered SO seawater, conducted over 7 days, we assessed changes in particulate Fe (pFe) concentrations, Fe redox speciation (Fe(II)/Fe(III)), and in the mineralogy of Fe-bearing dust in abiotic condition. The predominant minerals in the dust included quartz and aluminosilicates, with silicon (Si), aluminum (Al), and Fe as the major elements. No significant alterations in the mineralogy and the elemental composition of the dust were recorded during the dissolution experiments, neither under present nor under projected future conditions. The particulate Fe(II)/Fe(III) ratio remained consistently at 0.25 during the experiments, unaffected by changed conditions. Consequently, changes in environmental conditions in the SO would therefore not significantly alter the mineralogy and redox speciation of pFe in the Patagonian dust. On the contrary, pFe exhibited a dissolution rate of 3.8% and 1.6% per day under present and future conditions, respectively. The environmental changes anticipated for 2100 in the SO will likely to result in a decrease in the dissolution rate of pFe. Thus, even though a doubling of dust input by 2100 is anticipated, it will unlikely provide significantly more dissolved Fe (dFe) in seawater in the SO. Consequently, the future intensification of Patagonian dust inputs may not alleviate the Fe limitation in the SO.

Enthalpy of mixing of solid solution rhomboclase – Indium-substituted rhomboclase (H3O) Fe1−xInx(SO4)2·nH2O

Solid solution of rhomboclase [nominally (H3O) Fe(SO4)2·3H2O] with Fe-In substitution was synthesized by coprecipitation and hydrothermal treatment and investigated by chemical, X-ray diffraction, and thermodynamic analysis in this study. The solid solution is continuous over the whole stoichiometric range despite significant differences in ionic radii between Fe3+ and In3+. Enthalpy of formation of rhomboclase and enthalpies of mixing of solid solution rhomboclase – indium-substituted rhomboclase were determined by acid-solution calorimetry in 5 mol·dm−1 HCl at T = 298.15 K and p = 1 bar. The actual compositions of the studied synthetic end members are (H3O)0.798Fe(SO4)1.899·3.078H2O (rhomboclase with molecular mass of 308.8719 g·mol−1) and (H3O)1.067In(SO4)2.034·3.017H2O (indium-substituted rhomboclase with molecular mass of 384.8377 g·mol−1). The enthalpies of mixing were obtained for a series of four indium-incorporating rhomboclase synthetic samples with molar In/(In + Fe) ratios of 0.115, 0.226, 0.537, and 0.733. The enthalpy of formation from elements in their standard state at T = 298.15 K and p = 1 bar obtained in this study by thermochemical cycle for (H3O)0.798Fe(SO4)1.899·3.078H2O is: ΔfH298.15°=-2815.2±2.8 kJ·mol−1. Mean measured enthalpies of dissolution for (H3O)0.798Fe(SO4)1.899·3.078H2O and (H3O)1.067In(SO4)2.034·3.017H2O are: ΔdissH°=14.47±0.42 kJ·mol−1 and -6.68±0.27 kJ · mol−1, respectively. Enthalpies of mixingΔmixH° have small positive values and can be fitted by a regular solid solution model with a mixing parameter W=4.26±0.32 kJ·mol−1.

Unveiling the growth mechanism of FeSeTe films by pulsed laser deposition technique

The superconductivity of FeSeTe films, deposited by the pulsed laser deposition (PLD), is extremely sensitive to the preparation conditions. Hence, it is necessary to study the growth mechanism and reveal the key factors affecting the superconductivity of FeSeTe films. Among all the preparation conditions, the substrate temperature ( Ts ) is one of the most critical one because it can alter the diffusion and nucleation of deposited atoms, as well as subsequent secondary volatilization. In this study, we prepared a series of FeSeTe films deposited on CaF2 substrates with Ts ranging from 25 ∘C to 700 ∘C. It is found that the growth mechanism of the FeSeTe films deposited at different Ts is determined by the competition between crystallization and volatilization, and the Ts can serve as an effective means to regulate the (Se+Te):Fe ratio of the FeSeTe films. The superconductivity of the FeSeTe films is co-modulated by the crystallinity and composition. In addition, the Ts can greatly affect the pinning mechanism of the FeSeTe films by introducing the fine nonstoichiometric particles, local chemical inhomogeneity and planar defects. This work facilitates the further performance improvement and practical applications of FeSeTe superconducting films, and is of reference for the FeSeTe film prepared by other deposition methods.