Search Results (2,512)

We present a first-principles investigation of the layered ternary manganese tellurides ${\mathrm{MgMnTe}}_2$, ${\mathrm{Mg}}_3{\mathrm{MnTe}}_4$, and ${\mathrm{MgMn}}_3{\mathrm{Te}}_4$ using density functional theory with GGA and meta-GGA functionals. The optimized tetragonal structures (space group No. 115) satisfy the Born elastic stability criteria, with the structural derivatives exhibiting enhanced ductility. Unlike analogous alkali-based half-metals, these systems emerge as ferromagnetic semiconductors featuring substantial energy gaps in both spin channels. The calculated total spin magnetic moments are strict integers ($5 {\mathrm{\mu }}_{\mathrm{B}}$ for ${\mathrm{MgMnTe}}_2$ and ${\mathrm{Mg}}_3{\mathrm{MnTe}}_4$; $15 {\mathrm{\mu }}_{\mathrm{B}}$ for ${\mathrm{MgMn}}_3{\mathrm{Te}}_4$), driven predominantly by localized Mn d-states. Although advanced meta-GGA functionals modulate the magnitude of the predicted band gaps, the overarching electronic topology and magnetic character remain highly consistent. Ultimately, their calculated elastic response and intrinsic ferromagnetic semiconducting behavior identify these phases as candidates for further theoretical and experimental investigation for spintronic applications. Full article

Manganese is a raw material of increasing strategic importance owing not only to its fundamental role in steel production but also to its use in battery technologies, chemical processes, environmental applications, and advanced industrial fields. With the ongoing energy transition, the growing demand for battery-grade manganese has made it increasingly important to reassess the geological, mineralogical, and geochemical characteristics of manganese occurrences that are known from limited data. In this study, the manganese mineralization observed in the Kulu–Kozanlı area of Central Anatolia was investigated using field observations, ore microscopy, XRD, SEM–EDS, major oxide and trace element geochemistry, and spatial data based on sampling locations. Major oxide and trace element data indicate that manganese enrichment is not homogeneous and is concentrated in specific zones. The results of Spearman correlation, PCA, HCA, and factor analysis reveal a clear opposition between MnO and SiO₂, whereas MnO tends to increase together with Cu, Ba, V, Ga, and Sr. XRD, SEM–EDS, and ore microscopy findings show that the mineralization is mainly represented by a Mn oxide/oxyhydroxide assemblage composed of manganite and pyrolusite, with local braunite. When all findings are evaluated together, the Kulu manganese mineralization is interpreted as a lithologically heterogeneous Mn mineralization associated with radiolarite/chert and carbonate–cherty levels within the Dereköy ophiolitic mélange and consistent with hydrothermal influence. Full article

Heterogeneous photocatalysis has attracted attention as an effective method for the degradation of a wide range of organic contaminants. Despite the growing interest in ceria- and manganese oxide-based photocatalysts, CeO₂/Na-birnessite heterostructures remain largely unexplored. Therefore, CeO₂/Na-birnessite composite materials were synthesized by a hydrothermal method and investigated for photocatalytic water treatment. XRD and WPPF analyses confirmed the coexistence of fluorite-type CeO₂ and layered Na-birnessite, while an additional hausmannite phase was detected in the Mn-rich samples. SEM, TEM and EDS analyses revealed close spatial contact between ceria nanoparticles and layered birnessite structures. The mixed samples exhibited higher specific surface areas than the pure oxides, reaching up to 121.7 m² g⁻¹ for the 50Mn:50Ce composition. UV–Vis DRS showed enhanced visible-light absorption with increasing manganese content. Photocatalytic activity was evaluated through Rhodamine B degradation under UV irradiation at solution pH values below and above the point of zero charge (pH_pzc = 6.46) determined for the 50Mn:50Ce sample. Significantly higher photocatalytic activity was observed at pH 7.5, where the 50Mn:50Ce sample achieved more than 90% Rhodamine B degradation after only 20 min of irradiation. These results suggest that photocatalytic performance depends on the combined effect of high specific surface area and surface charge control. Full article

Radioactive and chemical contamination of aquatic systems remains a key environmental concern in areas affected by historical nuclear testing. The objective of this study was a comprehensive geochemical and ecotoxicological screening assessment of bottom sediments in the Shagan River, which partially flows through the Balapan test site within the Semipalatinsk test site. This 2 km stretch is potentially affected by groundwater discharge hydraulically connected to the Atomnoye Lake retaining zone. A total of 21 bottom sediment samples were collected over a 2 km stretch, and their elemental composition was determined using inductively coupled plasma mass spectrometry (ICP-MS). Bottom sediment quality was assessed using the geoaccumulation index (Igeo) and ecotoxicological criteria, including the threshold effect concentration (TEC), probable effect concentration (PEC), least impact level (LEL), and high impact level (SEL). The results revealed significant spatial heterogeneity in the element distribution and local geochemical anomalies. Manganese (Mn) and molybdenum (Mo) corresponded to the Igeo index category of severe contamination, while zinc (Zn) demonstrated an extremely high contamination level (Igeo = 6), exceeding the PEC threshold by 16 times. Mn concentrations also exceeded the SEL by 15 times. These results provide a baseline geochemical profile for a previously understudied and ecologically sensitive section of the Shagan River, identifying zones of local geochemical enrichment in bottom sediments and laying the foundation for further hydrogeochemical, mineralogical, granulometric, and ecotoxicological studies. Full article

The depletion of high-grade manganese ore reserves, accompanied by the progressive decline in ore quality, has intensified concerns regarding the supply of suitable manganese raw materials for Kazakhstan’s ferroalloy industry. Under these conditions, the development of efficient processing technologies for iron manganese ores characterized by low Mn/Fe ratios and complex mineralogical compositions has become increasingly important. This review examines current pyrometallurgical approaches for the processing of iron manganese ores, including carbothermic reduction roasting followed by magnetic separation, reduction smelting for the production of rich manganese slag, and hydrogen-based selective reduction followed by magnetic separation. Particular attention is given to the mineralogical and chemical characteristics of Kazakhstan’s iron manganese ores, which significantly limit their direct utilization in conventional ferromanganese production processes. The advantages and limitations of these technologies are critically evaluated in terms of metal recovery, Mn/Fe upgrading efficiency, energy requirements, environmental performance, and industrial applicability. The comparative analysis identifies reduction smelting as the most suitable route for Kazakhstan’s iron manganese ores under current technological conditions. This conclusion is primarily supported by the low Mn/Fe ratios, elevated iron contents, and complex mineralogical associations characteristic of the major Kazakhstan deposits, which limit the efficiency of solid-state reduction followed by magnetic separation. During smelting, the original mineral structure is destroyed, and iron and manganese are separated directly between the liquid metal and slag phases. Published studies report iron recoveries exceeding 95%, MnO recovery to the slag of approximately 94.6%, and Mn/Fe ratios above 15 in the resulting rich manganese slag. In addition, the process produces two potentially marketable products-cast iron and rich manganese slag-and can be integrated more readily into Kazakhstan’s existing ferroalloy production infrastructure. Therefore, reduction smelting currently represents the most technologically mature and practically feasible route for the comprehensive utilization of Kazakhstan’s iron manganese resources. Full article

Selective laser melting (SLM) can effectively suppress metallurgical defects inherent to conventional manufacturing; however, subsequent aging treatments essential for engineering applications introduce secondary precipitates that alter the electrochemical homogeneity of the matrix. The underlying mechanism by which such precipitation behavior governs corrosion resistance remains elusive. In this study, a Fe-30Mn-8Al-1.5C-2.5Ni steel was investigated to elucidate the corrosion morphology and electrochemical behavior of the as-built, 450 °C-aged, and 750 °C-aged specimens during immersion in a 3.5 wt.% NaCl solution. The results demonstrate that the inherent Mn microsegregation and high-density subgrain boundaries induced by SLM trigger preferential localized anodic dissolution on the surface of the as-built sample, culminating in the formation of a loose, porous manganese oxide product layer. Aging treatment at 450 °C induces extensive precipitation of κ-carbides within grain interiors and along grain boundaries, accompanied by localized depletion of Al and Mn at the phase interfaces. A pronounced micro-galvanic coupling established between the κ-carbides and the adjacent Al-depleted zones directly compromises the continuity of the passive film, thereby further deteriorating the corrosion resistance. In contrast, aging at 750 °C relieves the residual stress and eliminates the as-built elemental microsegregation. The resulting compositional homogenization of the matrix reduces the localized electrochemical driving force, which promotes a uniform reaction of Al at the surface to construct a continuous, compact Al-rich passive film, thereby sustaining the highest charge-transfer resistance during long-term immersion. This work elucidates the correlation among the intrinsic defects of SLM, aging-induced solute-depleted zones, κ-carbide precipitation, and localized micro-galvanic corrosion, providing a fundamental basis for tailoring the microstructure and corrosion resistance of additively manufactured lightweight steels. Full article

Selenium (Se) is a beneficial element that enhances plant antioxidant capacity, improves fruit quality, and contributes to the biofortification of horticultural crops. However, information regarding its effects on mineral nutrient balance and antioxidant metabolism in pomegranate remains limited. This study investigated the effects of foliar selenium (Se) application on fruit yield, mineral nutrient balance, antioxidant metabolism, and fruit quality of pomegranate (Punica granatum L.) cv. ‘Malas Saveh’ during the 2022 and 2023 growing seasons under orchard conditions in Iran. Trees were treated with sodium selenate at different concentrations using a randomized complete block design. In 2022, Se was applied at 0, 2, 4, and 6 mg L⁻¹, while in 2023, based on the results of the first-year screening phase, the concentration range was expanded to 0, 6, 8, and 10 mg L⁻¹ to further investigate plant responses to higher Se levels. Foliar Se application significantly increased fruit yield, fruit number, and Se accumulation in both leaves and fruits, confirming the effectiveness of Se biofortification. Selenium treatments also improved the nutritional composition of pomegranate fruits by increasing the concentrations of nitrogen (N), phosphorus (P), potassium (K), iron (Fe), and zinc (Zn), whereas manganese (Mn) concentrations declined, suggesting an antagonistic interaction between Se and Mn uptake. Significant improvements were observed in fruit quality traits, including soluble solids content, titratable acidity, vitamin C, total phenolics, anthocyanins, and antioxidant activity. The 6 mg L⁻¹ treatment in 2022 and the 8–10 mg L⁻¹ treatments in 2023 resulted in the most pronounced physiological and biochemical responses, with 10 mg L⁻¹ showing no further significant improvement for several key traits. Selenium application also enhanced the antioxidant defense system through increased activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), phenylalanine ammonia-lyase (PAL), and ascorbate peroxidase (APX), while reducing hydrogen peroxide (H₂O₂), malondialdehyde (MDA), and membrane ion leakage. Principal component analysis further confirmed the strong positive association between higher Se concentrations and improved mineral and biochemical characteristics. Overall, foliar Se application effectively enhanced pomegranate productivity, nutritional quality, antioxidant capacity, and physiological performance, highlighting its potential as a sustainable agronomic practice for the production of high-quality Se-enriched fruits. Full article

This article describes the mineralogical and geochemical features of the Marsyaty Mn–Fe sedimentary deposit in the Northern Urals (Russia). Oolitic ironstones of the deposit are localized in the Cenomanian coastal sandstones. Manganese ores (carbonate and carbonate–oxide types) lies within the Lower Paleocene siliciclastic sediments and are separated from the oolitic ironstone (iron oxide and iron carbonate types) by a polymictic gravelite bed. Authigenic Fe³⁺ oxyhydroxides (goethite and ferrihydrite), chamosite/berthierine and late siderite predominate in the ironstones; kaolinite, apatite, perhamite, calcite and dolomite are minor constituents. Rhodochrosite and rancieite are the major minerals of the manganese ore; Mn-dominated phyllosilicates (parsettensite? and caryopilite?) are rare. Both ore types contain authigenic glauconite, montmorillonite, sulfides (sphalerite/wurtzite, galena, and pyrite), gibbsite/boehmite and REE phosphates. Both ore types contain detrital quartz, ilmenite, zircon, monazite, epidote, titanite, muscovite and feldspars. The δ¹³C_carb value (VPDB) varies from −18.5 to −23.3 in both ironstone types and from −10.0 to −41.0 ‰ in the manganese ore. The negative C isotopic composition and numerous organic remains indicate the involvement of microbial processes in the formation of both types of carbonate ores. The Fe and Mn ores belong to one transgression–regression sedimentation cycle and formed consecutively during the evolution of the West Siberian basin. A unique feature of the Marsyaty deposit includes two ore formation stages within a limited area and over a relatively short geological period: the accumulation of (i) oolitic ironstones enriched in Mn first and then (ii) manganese ores only. Full article

The co-contamination of manganese ions (Mn²⁺) and ammonia nitrogen (NH₄⁺) caused by the stockpiling of manganese residue poses a serious threat to the ecological environment. In this study, a series of the composite was prepared from red mud, bentonite, and corn straw via oxygen-limited pyrolysis. The effects of pyrolysis temperature and raw material ratio on the material properties were investigated, and the synergistic remediation performance of the composites for Mn²⁺ and NH₄⁺ in manganese residue-contaminated soil was evaluated through a 180-day soil column experiment. The results showed that the composite prepared with a raw material ratio of 1:1:1 at a pyrolysis temperature of 700 °C exhibited the largest specific surface area and the most developed pore structure, achieving a Mn²⁺ removal rate of 92.72% ± 0.85% in aqueous solution. In the soil column experiment, the material prepared at 700 °C gave the highest immobilization rate for soil Mn²⁺ (96.22% ± 0.5%), whereas the combined addition of materials prepared at 700 °C and 500 °C achieved the best removal efficiency for NH₄⁺ (99.33% ± 0.23%). Mechanistic studies revealed that the stabilization of Mn²⁺ is primarily attributable to alkaline precipitation and mineral lattice solid solution induced by the composite, leading to the formation of stable spinel phases (e.g., (Fe,Mn)₃O₄) and insoluble manganese phosphate-carbonate salts. The removal of NH₄⁺ is proposed to proceed via adsorptive enrichment by the porous structure and Fe⁰-mediated Fenton-like catalytic oxidation, ultimately converting NH₄⁺ to N₂ gas. The 180-day monitoring results demonstrated that the remediation effect continuously increased over time, indicating good long-term stability of the composite. This study provides an efficient, low-cost functional material derived from solid waste for the remediation of manganese residue-contaminated soil and offers a theoretical basis for the synergistic resource utilization of multiple solid wastes. Full article

The ecological risks brought by sulfadiazine (SDZ) residues in the environment have put forward requirements for efficient antibiotic treatment technologies. In this study, biogenic manganese oxides (BMOs) were synthesized using the bacterium Stenotrophomonas maltophilia DT1, and a BMO/syringaldehyde (SYR) system was constructed for SDZ degradation to investigate its performance, mechanism, and potential application. Results showed that the DT1-synthesized BMO contained Mn (II/III/IV) and defect-related oxygen species, which enabled the BMO to participate in SYR activation and SDZ transformation. A total of 99.67% of 10 mg/L SDZ was removed within 3 h under optimized conditions. Humic acid and most environmental ions had no significant interference with the system, except for slight inhibition by Fe³⁺ and Mn²⁺. Three degradation pathways of SDZ were elucidated through the identification of five transformation products and density functional theory calculations. ECOSAR toxicity prediction and growth inhibition of Escherichia coli revealed that the degradation products exhibited significantly reduced toxicity. Furthermore, the BMO exhibited 4.41–17.47 times higher SYR-mediated SDZ transformation efficiency than chemically synthesized manganese oxide (CMO) and showed good performance in reuse tests and real water matrices. This study provides an efficient and eco-friendly green technology for the remediation of SDZ pollution in aquatic environments and provides potential support for the removal of refractory pollutants mediated by BMO. Full article

Porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae (Mhp) are major contributors to the porcine respiratory disease complex. Although PCV2-Mhp bivalent inactivated vaccines are useful for simultaneous disease control, their immunogenicity may be improved by adjuvant optimization. This study evaluated a composite adjuvant consisting of porcine interleukin-2 (IL-2), IL-4, IL-6 and MnJ(beta), a colloidal manganese adjuvant, in an initial murine immunogenicity model. Thirty female Kunming mice were assigned to three groups (n = 10/group): bivalent antigen plus IL-2/IL-4/IL-6/MnJ(beta), bivalent antigen plus MnJ(beta), or phosphate-buffered saline. Body weight, complete blood count, peripheral blood T- and B-cell subsets, PCV2-specific IgG and Mhp-specific indirect hemagglutination titers were monitored after primary and booster immunization. The composite formulation did not suppress body-weight gain or induce sustained abnormalities in erythrocyte- or platelet-related indices. WBC, neutrophil, lymphocyte and monocyte counts were elevated in group A at days 7 and 28 post-primary immunization, indicating transient immune activation. Day-56 flow cytometry indicated increased CD19+IgM-IgD- B-cell and effector/memory T-cell-associated responses. PCV2-specific IgG increased from day 14 onward. At day 56, the OD450 value in group A reached 1.532 ± 0.006, compared with 1.095 ± 0.004 in group C1 and 0.102 ± 0.002 in group C2, corresponding to approximately 1.40-fold and 15.09-fold higher levels than the MnJ(beta)-adjuvanted and PBS control groups, respectively. Mhp-specific IHA titers were also maintained at high levels after booster immunization; at day 56, group A showed a log2 endpoint titer of 13.00 ± 0.00, corresponding to a GMT of 1:8192, whereas group C1 showed a log2 endpoint titer of 12.00 ± 0.00, corresponding to a GMT of 1:4096, and group C2 remained negative. These results indicate that the IL-2/IL-4/IL-6/MnJ(beta) composite adjuvant demonstrates potential for improving antibody and peripheral lymphocyte responses to PCV2-Mhp bivalent antigen, but protective efficacy must be confirmed in target-species challenge studies. Full article

High lithium and manganese oxides (HLMs), also known as lithium- and manganese-rich oxides (LMR), are an alternative to the state-of-the-art (SoA) cathode materials for Li-ion battery cells due to their high specific capacity, working potential, and potential elimination of cobalt from their composition. Nevertheless, they are claimed to undergo accelerated capacity and potential fade. In this work, an extensive electrochemical characterization is conducted while revisiting the most relevant literature on HLM. The classical galvanostatic cycling is used to conduct differential voltage and incremental capacity analyses, while impedance spectroscopy and galvanostatic intermittent titration techniques are applied to complement this test. The results are complemented with online electrochemical mass spectrometry and postmortem characterization. Loss of anode active material is identified as the main degradation mechanism, aggravated by potential slippage. Moreover, the hypotheses on degradation mechanisms are further confirmed by changing the voltage cutoffs of the cells, limiting the Li₂MnO₃ activation. The results are benchmarked with SoA LiNi_0.8Mn_0.1Co_0.1O₂-based cells with a promising balance for HLM in some cases. This work serves as a guide to assist in the interpretation (and avoid misinterpretation) of the results with Li-ion batteries consisting of HLM electrodes. Full article

The escalating demand for sustainable metallurgical practices necessitates innovative approaches to manganese production. The smelting–aluminothermic reduction of hydrogen pre-reduced manganese ores in a direct current (DC) arc furnace offers a resilient and sustainable trajectory for optimizing manganese recovery efficiencies while minimizing waste generation under low-carbon operating conditions. This study presents a comparison of smelting–aluminothermic reduction of two Mn ores pre-reduced with hydrogen using two distinct approaches, namely, a packed-bed vertical retort and a plasma rotary furnace. A 200 kW DC arc furnace was used for smelting. The scope of this assessment integrates technical, environmental, and operational metrics of smelting–aluminothermic reduction. For partial process energy estimation, the considered metrics are power stability metrics, specific energy requirement, and load factor/power-on time. The metrics considered for material are reductant efficiency, elemental accountability, elemental recovery, elemental deportment, and slag-to-metal ratio. For process sustainability, refractory and electrode consumption were considered. The environmental indicators considered include CO₂-equivalent emissions per ton of product, dust and particulate emissions, NO_x/SO_x emissions. This research provides critical insights into the viability and environmental advantages of hydrogen pre-reduction coupled with smelting–aluminothermic reduction for cleaner manganese production. Full article

Magnetization roasting followed by magnetic separation can upgrade ferruginous manganese raw materials, but its efficiency depends on the iron phase state after roasting. This study clarified the phase state and distribution of iron in magnetic and non-magnetic products obtained from ferruginous manganese ore and concentrate after magnetization roasting and dry magnetic separation. The materials were roasted at 600–650 °C using Shubarkol coal as a solid reducing agent and then separated at a magnetic field strength of 1.2 kOe. Chemical analysis, X-ray diffraction, and Mössbauer spectroscopy were used to relate separation results to iron phase states. The Mn/Fe ratio in the non-magnetic products increased from 3.92 to 10.87 for the ore and from 2.98 to 23.99 for the concentrate, while 76.25% and 88.26% of iron were transferred to the corresponding magnetic fractions. Mössbauer spectroscopy showed that magnetite-type spinel components, including Fe₃O₄ and substituted (Fe_1−xM_x)₃O₄, were mainly associated with the magnetic products. Hematite-like and paramagnetic Fe³⁺/Fe²⁺ components were also detected, indicating incomplete conversion of iron-bearing phases into magnetite-type spinels. The Mössbauer-area-weighted fraction of iron in magnetite-type spinel phases was 76.5% for the ore and 64.36% for the concentrate. These results explain the different separation behavior after roasting–magnetic treatment. Full article

Manganese can provide strong solid-solution strengthening in austenite, thereby effectively enhancing the strength and toughness of Fe-based coatings. However, the underlying mechanism remains unclear. In this study, building on previously developed high-strength, hard Fe-based alloy coatings produced via laser cladding, the influence of Mn content on the microstructural evolution and mechanical properties is systematically investigated using XRD, SEM, TEM, microhardness testing, and a reciprocating friction and wear testing machine. The results show that the coatings fabricated from three iron-based alloy powders are primarily composed of a martensitic matrix, retained austenite, and various MxC-type eutectic carbides (such as MC, M₂C, M₆C). With increasing Mn content, the MC-type carbides gradually change from a blocky morphology to a fishbone-like structure, while the originally fishbone-like M₆C-type carbides first become blocky and eventually turn into fine granules. Meanwhile, the sizes of all three types of carbides are refined. Especially, after the addition of Mn, dispersed second-phase particles (Mn-Si-O) precipitate in the coatings. The coating with 2.0 wt.% Mn exhibits the best comprehensive mechanical properties: an average microhardness of 925 ± 8 HV_0.5 and a minimum wear rate of 0.78 × 10⁻⁶ mm³/N·m. Full article