Mn Content Research Articles

Continuous-Flow Synthesis of Zn1-xMnxS Nanoparticles at Ambient Conditions.

With its large direct band gap and good chemical stability, ZnS is suitable for many applications, including light-emitting diodes, panel displays, and photodetection. Here, nanoparticles of ZnS are synthesized phase pure under ambient conditions by precipitation in a simple and scalable continuous-flow reactor. Furthermore, different degrees of Zn substitution with Mn have been investigated, Zn1-xMnxS, with x = 0.05, 0.19, and 0.25 according to X-ray fluorescence measurements. The products are analyzed with multitemperature synchrotron powder X-ray diffraction (PXRD) and X-ray total scattering. The analysis reveals phase-pure synthesis products with the sphalerite structure and crystallite sizes in the range of 3.8-4.7 nm in agreement with scanning transmission electron microscopy. Only Zn0.75Mn0.25S shows traces of Mn3O4, indicating that x = 0.25 is above the substitution limit as the impurity appears. Substitution of Zn with Mn in the nanoparticles is confirmed by energy-dispersive X-ray spectroscopy, as well as an observed decrease in the band gap, decrease in the sphalerite-to-wurtzite phase transition temperature, and increase in the unit cell dimensions with increasing Mn content. Based on the modeling of the PXRD Rietveld refined atomic displacement parameters, the Debye temperature for ZnS and Zn0.95Mn0.05S is determined to be 322 ± 13 and 394 ± 22 K, respectively.

Mathematical optimization of multilinear and artificial neural network regressions for mineral composition of different tea types infusions

The objective of this study was to investigate the change in mineral composition depending on tea variety, tea concentration, and steeping time. Four different tea varieties, black Ceylon (BC), black Turkish (BT), green Ceylon (GC), and green Turkish (GT), were used to produce teas at concentrations of 1, 2, and 3%, respectively. These teas were produced using 7 different steeping times: 2, 5, 10, 20, 30, 45, and 60 min. It was also aimed to optimize the regression equations utilizing these factors to identify parameters conducive to maximizing Zn, K, Cu, Mg, Ca, Na, and Fe levels; minimizing Al content, and maintaining Mn level at 5.3 mg/L. The optimal conditions for achieving a Mn content of 5.3 mg/L in black Turkish tea entailed steeping at a concentration of 1.94% for 11.4 min. Variations in K and Mg levels across teas were inconsistent with those observed for other minerals, whereas variations in Al, Cu, Fe, Mn, Na, and Zn levels exhibited a close relationship. Overall, mineral levels in tea can be predicted through regression analysis, and by mathematically optimizing the resultant equations, the requisite conditions for tea production can be determined to achieve maximum, minimum, or target mineral values.

Distribution and risk assessment of nutrients and heavy metals from sediments in the world-class water transfer projects

South-to-North Water Diversion Project, a globally renowned engineering feat, aims to address water supply issues. The sediments within reservoirs play a pivotal role in natural ecosystems, not only as habitats for diverse biota but also as repositories of heavy metals, organic matter, and other contaminants. These sediments serve as a critical interface between sediment and water bodies. This comprehensive analysis focused on the spatial patterns of nutrients, organic matter, and heavy metals in the surface layer and profiles of reservoirs, exploring their interconnectedness. Leveraging the integrated pollution index, organic pollution index, potential ecological risk index, and geo-accumulation index, an ecological risk assessment was performed. The key findings are as follows: (i) Along the Middle Route of the South-to-North Diversion Project, the nutrient and organic matter contents in sediments tends to rise with distance from the Danjiangkou Reservoir, with the TN and TC contents increasing by 2.35- and 3.05-fold, respectively. (ii) As the sediment depth increases, the carbon, nitrogen, phosphorus, and organic matter contents exhibit varying degrees of decline, with average decreases of 62.38%, 67.47%, 17.56%, and 41.83% for TN, TC, TP, and OM, respectively. (iii) Among the eight heavy metals, only manganese (Mn) and zinc (Zn) in the Yahekou Reservoir showed moderate pollution levels, according to the geo-accumulation index. The Mn content within the surface sediments of the six reservoirs ranges from 550 to 1837 mg/kg (average, 1019.5 ± 548.3 mg/kg), whereas the Zn content ranges from 89 to 360 mg/kg (average, 156.5 ± 101.6 mg/kg). (vi) Total phosphorus (TP) and total nitrogen (TN) emerged as the primary pollutants in surface sediments. Comprehensive nitrogen and phosphorus pollution assessment revealed that the surface sediment of Danjiangkou Reservoir is mildly polluted, while Baiguishan and Jiangang Reservoirs are moderately polluted, and the rest are heavily contaminated. For the Yahekou and Chaohe Reservoirs, the average pollutant content indicates moderate pollution, while the remaining reservoirs show mild pollution levels.Graphical

Assessment of Human Health Risk Caused by Heavy Metals in Kiln Dust from Coal-Fired Clay Brick Factories in Türkiye

AbstractHeavy metal (HM) pollution from natural processes and different anthropogenic activities pose significant human and environmental health risks because of their stability, non-degradable properties, and high toxicity. HM released into the air in the form of dust can enter the human body via ingestion, inhalation, and dermal contact. Keeping in mind the significance of estimating the risk from HM in different environments, the carcinogenic and non-carcinogenic health risks to workers caused by HM in kiln dust (KD) samples collected from coal-fired clay brick factories in the Western Black Sea Region of Türkiye were assessed for the first time in this study. The concentrations of major and minor oxides and HMs in the collected KD samples were analyzed using energy-dispersive X-ray fluorescence spectrometry. The average concentrations of Fe, Mn, Cr, Ni, V, Zn, Cu, As, Co and Pb analyzed in thirty-three KD samples were determined as 65444, 768, 251, 249, 248, 122, 60, 52, 42 and 16 mg/kg dw, respectively. The average levels of Ni, As, Cr, Co and Cu exceed the maximum contaminant levels recommended in the Turkish Regulation on Control of Soil Pollution. Carcinogenic and non-carcinogenic human health risk assessments for workers via three exposure pathways were carried out, estimating the hazard index (HI) and total carcinogenic risk (TCR) index, respectively. The HI values (< 1) revealed no possible non-carcinogenic health risk due to exposure to all HMs in the studied KD samples. The average TCR value revealed that the potential cancer risks for Ni, As, Cr, and Pb were slightly above the safe limit and required monitoring and further investigation for these HMs.

Spatial-temporal distribution and eutrophication evaluation of nutrients and trace metals in summer surface seawater of Yantai Sishili Bay, China

Due to coastal development expansion, an increasing influx of pollutants enters the sea through riverine input and land runoff, threatening coastal ecosystems and posing a risk of eutrophication. In this study, trace metals (Fe, Mn, Cu, and Zn), and nutrients (constituents of N, P, and Si) were assessed in the summer surface seawater of Yantai Sishili Bay (YSB), Northern China focusing on the determination of concentration, spatial-temporal distribution and sources identification, while exploring their correlations. It also aimed to clarify the eutrophication status and evaluate the linear relationships between eutrophication, trace metals, and nutrients in YSB. Over three years (2021–2023), the total dissolved concentrations of Fe, Mn, Cu, and Zn ranged from 4.79–26.71, 0.19–6.41, 0.26–1.53, and 0.74–13.12 µg/L, respectively. Concurrently, nutrient concentrations including NO2-, NO3-, NH4+, PO43-, and DSi exhibited a range of 0.37–11.66, 2.04–178.30, 1.69–70.01, 0.02–16.68, and 0.02–0.71 µg/L respectively. These concentrations revealed a gradual decrease from nearshore to offshore and the temporal variation also showed significant patterns from year to year, indicating distinct regional variations. The primary contributors to the trace metals and nutrients in the study region were recognized as external contributions stemming from natural, anthropogenic, and atmospheric deposition through correlation and principal component analysis. More specifically, riverine input and coastal farming contributed large amounts of nutrients to coastal waters, threatening a potential risk of eutrophication. The eutrophication evaluation expressed below the mild eutrophication level and was far lower than the other global and Chinese bays. The linear correlation between eutrophication and trace metals revealed a weak positive correlation but a significant correlation with nutrients. Despite the absence of significant eutrophication in the bay, potential risks were identified due to identifiable sources of nutrient and trace metal inputs. The findings provided insights to guide efforts in preventing and mitigating coastal eutrophication, as well as nutrient and trace metal pollution, in coastal cities.

Assessing the health risks of dermal exposure to heavy metals dust among nail salon technicians.

Nail salon technicians are susceptible to potential exposure to a diverse array of hazardous chemicals in the form of dust or vapors. One of the main routes of exposure is dermal contact. The aim of present study was to health risk assessment of dermal exposure to dust containing heavy metals in nail salon technicians. Dust sampling was done on the work surface of 20 available nail salon technicians. The concentration of five metals including cadmium, lead, chromium, nickel, and manganese were determined using ICP-MS. Afterwards, the United States Environmental Protection Agency (USEPA) guideline was used to estimate the potential health risks, including carcinogenic and non-carcinogenic risks, associated with the analyzed metals. Results indicated the mean concentrations of Pb, Cd, Ni, Cr and Mn were 0.7953±0.4373, 0.0952±0.0264, 0.7666±0.8629, 0.4900±0.5994 and 1.134±0.4736, respectively. The hazard quotient (HQ) of all metals was within the permissible value, while hazard index (HI) was greater than 1. The probability of cancer risk (CR) resulting from dermal exposure to Ni, Cd and Cr exceeded the acceptable risk levels (10-6-10-4), but CR calculated for Pb was less than allowable value. Implementation of engineering controls such as downdraft vented nail tables and portable source capture systems is necessary. Besides, the use of personal protective equipment such as disposable nitrile gloves, N95 respirator masks, and ensuring proper training on safe work practices is recommended.

Distribution of Heavy Metals in the Surrounding Mining Region of Kizhnica in Kosovo

This study investigated the distribution of heavy metals in agricultural soils in the vicinity of three large mining landfills of the Kizhnica mine in the Republic of Kosovo. The mining sector is one of the most important sectors of Kosovo’s economic development, and the Kizhnica mine is one of the most important ore producers in Kosovo. Besides the positive aspects, the development of production also has some negative side effects, such as the generation of industrial waste and the possible contamination of surrounding areas, including agricultural land. Therefore, ten sampling sites were selected in the vicinity of the Kizhnica mine. These sites were characterized and assessed as the most important due to the anthropogenic impact of mineral processing and open-tailing waste deposits in Kizhnica. The concentration of Pb, Zn, Cu, As, Cd, Ni, Mn and Sb in the selected samples was determined using inductively coupled plasma–optical emission spectrometry. The data obtained were used to create geochemical maps and calculate the contamination factor, pollution load index and geoaccumulation index. Cluster analysis, Pearson correlation coefficient and air spatial distribution patterns using the air dispersion model were used to evaluate within the area. The results showed that heavy metal levels are influenced by the anthropogenic nature of pollution, confirming a current ecological threat from mining activities in the region. In order to improve waste management, reduce the hazardous impacts of mining and contribute to the sustainable development of the region, the potential reuse of the deposited waste material in the construction industry is proposed.

Investigation of Irradiation Hardening and Effectiveness of Post-Irradiation Annealing on the Recovery of Tensile Properties of VVER-1000 Realistic Welds Irradiated in the LYRA-10 Experiment

Assessing the embrittlement and hardening of reactor pressure vessel steels is critical for the extension of the service lifetime of nuclear power plants. This paper summarises the tensile test results on the irradiation behaviour of realistic VVER-1000 welds from the STRUMAT-LTO project. The welds were irradiated at the HFR (Petten, the Netherlands) to a fluence of up to 1.087 × 1020 n·cm−2, and their irradiation hardening was studied by means of tensile testing. The four grades, with different Mn and Ni contents, show different hardening behaviours. The highest degree of irradiation hardening is observed for the weld that has the highest combined Ni + Mn content. The results show that there is a synergetic effect of Mn and Ni on the irradiation hardening behaviour of the VVER-1000 welds. Besides irradiation hardening, the effectiveness of post-irradiation annealing treatments on the recovery of the tensile properties is studied in the present work. Post-irradiation annealing treatments conducted at 418 °C and at 475 °C proved to be effective for three of the four investigated welds. For the realistic weld with the highest combined Ni + Mn, only the annealing at 475 °C led to the complete recovery of the tensile properties.

Statuary Qualities of White and Black Göktepe Identified in the Hispanic Valdetorres de Jarama Marble Collection

This paper focuses on the role of the most common mineralogical techniques applied to the identification of the different statuary qualities in white, grey, and black Göktepe marble. For this purpose, the case of a Roman sculpture marble collection from the rural villa of Valdetorres de Jarama (central Iberia), dating to the 4th century AD, is presented. The mythological statuary, combining white, grey, and black marbles, is one of the most outstanding marble collections in the Aphrodisian style found in Hispania. The analytical results (achieved through Petrography, Cathodoluminescence, C and O isotopes, and Sr and Mn concentration) support the identification of two varieties of “black” Göktepe, traditionally referred to as bigio morato and bigio antico, as well as the best statuary quality of white Göktepe. In addition, the analytical identification of other Asiatic marbles in the Valdetorres collection, a white coarse-grain originally from the quarries of Aphrodisias city, and one small piece identified as Carian red from Iasos, corroborates the already suggested strong connection existing between artists and the stone material they chose for their works. Finally, the identification carried out on the marble of the bases that served as seats for the sculptures is noteworthy, as it is a white marble of lower quality whose analytical characteristics are consistent with the Microasiatic marble of Denizli. The use of these exotic and exceptional raw materials confirms the taste for luxury and decorative richness in Late Antique Hispanic rural villae and contributes to a better understanding of the distribution of Aphrodisian production and trade networks with the Western Roman provinces.

GIS- and Multivariate-Based Approaches for Assessing Potential Environmental Hazards in Some Areas of Southwestern Saudi Arabia

Soil contamination is a major issue that endangers the ecology in most countries. Total concentrations of As, Cd, Co, Cr, Cu, Mn, Ni, Pb, VFe, and Zn were determined by analyzing soil samples from 32 surface soil samples in southwest Saudi Arabia, including certain areas of Al-Baha. Kriging techniques were used to create maps of the distribution of metal. To assess the levels of soil contamination in the research area, principal component analysis (PCA), contamination factors (CF), and pollution load index were used. The results show the stable model gave the best fit to the As and Zn semivariograms. The circular model fits the Cd, Co, and Ni semivariograms the best, while the exponential model fits the Cr, V, and Fe semivariograms the best. For Ni and Pb, respectively, spherical and Gaussian models are fitted. The findings demonstrated two clusters containing different soil heavy metal concentrations. According to the data, there were two different pollution levels in the research region: 36.58% of it is strongly contaminated, while 63.41% of it has a moderate level of contamination (with average levels of these metals 5.28 ± 5.83, 0.81 ± 0.19, 18.65 ± 6.22, 45.15 ± 23.25, 60.55 ± 23.74, 972.30 ± 223.50, 33.45 ± 14.11, 10.05 ± 5.13, 84.15 ± 30.72, 97.40 ± 30.05, and 43,245.00 ± 8942.95 mg kg−1 for As, Cd, Co, Cr, Cu, Mn, Ni, Pb, V, Fe, and Zn, respectively). The research area’s poor management practices are reflected in the current results, which raised the concentration of harmful elements in the soil’s surface layers. Ultimately, the outcomes of pollution concentration and spatial distribution maps could aid in informing decision-makers when creating suitable heavy metal mitigation strategies.

Remediation of AMD based on hydrogeochemical zonation: A typical metal mine in China

Mining activities disrupt the natural oxidative balance underground, increasing the oxidation of metal sulfides like pyrite. This process leads to the formation of highly acidic mine drainage (AMD) with elevated concentrations of iron (Fe) and sulfate (SO42−). However, generic plugging and backfilling methods, when applied without considering the specific post-mining oxidative environments of different metal mines, often yields minimal results. To clarify the distribution of the underground redox environment after mining of a metal mine in Dexing, China, fifteen water samples from flood and dry periods, as well as fifteen borehole samples, were collected for hydrogeological and chemical analysis. For the first time, the study proposed that the redox zone could be identified and delineated through vertical analysis of water storage media, mineral composition, and hydrochemical characteristics. A hydrogeochemical cause model was constructed, revealing that AMD formation primarily occurs in oxidative and transition zones. Based on the redox zone characteristics of the study area, actual engineering sealing was performed on the oxidation and transition zones of cavity No. 23. As a result, the pH increased from 2.5 before remediation to 4.5, indicating a reduction in acidity. The concentrations of SO42− and Fe significantly decreased, reducing from 1360.0 mg/L and 147.0 mg/L before treatment to 726.0 mg/L and 23.6 mg/L after treatment; the total decrease amounting to 46.6 % and 84.0 %, respectively. The concentrations of Mn and Cu similarly, decreased by 10.7 % and 15.6 %, respectively. This study provides a novel approach and valuable reference for the refined identification and classification of redox zones after metal mine exploitation, as well as for the targeted plugging and treatment of cavities that produce AMD.

Assessing background levels of trace elements in soils of Mato Grosso (Brazil) for environmental and food security

The State of Mato Grosso, Brazil, presents a great diversity of soils and landscapes, and many areas of agriculture and mining. However, the natural content of trace elements in the soil are still little known, which represents a great gap for studies and/or regulations concerning soil and food security. This study proposes to establishing quality reference values ​​(QRVs) for trace elements in Mato Grosso soils. Soil sampling was carried out to cover the geodiversity of soils in this region, considering geology, geomorphology, lithology, pedology and biomes, in addition to summarizing the data available in the literature to form the database for this study. The soil was analyzed for the contents of Fe, Mn, Cu, Zn, Ni, Cr, Ba, Pb, As, Cd and Hg, according to the USEPA 3051A methodology. Trace element results based on soil geodiversity contributed to a general description of how levels of these elements may be related to the environmental factors studied. The levels of main elements related to the environmental factors were Mn and Zn to geology; Mn, Cr, Ba, Zn, As and Cd to geomorphology; Mn to lithology; Mn and Cr to pedology; and Mn, As, Cd and Hg to the biome. It was not possible to propose QRVs grouped by environmental factors for the State of Mato Grosso, especially due to the large territorial extension covered. Thus, the QRVs were proposed in the 90th percentile, in mg kg−1, as follows: Fe 23,128; Mn 351; Cu 16.50; Zn 29.24; Ni 8.86; Cr 52.73; Ba 84.45; Pb 13.42; As 7.60; Cd 0.87; and Hg 0.10. Mercury, Cd, and As levels require careful regional monitoring, as some environments, such as the Amazon biome, may present naturally high levels, and small alterations in the bioavailability of such elements might represent a risk to health or the environment.

Differential root nutrient‐acquisition strategies underlie biogeochemical niche separation between grasses and forbs across grassland biomes

Abstract Plant nutrient composition is a reliable tool to identify plant ecological strategies and niche differentiation. Here, we aimed to (i) reveal the potential physiological mechanisms governing distinct foliar nutrient compositions among coexisting grassland species and (ii) clarify the role of taxonomy and environmental conditions in these compositions. At the local (grassland) scale, we measured root morphological and physiological traits, photosynthetic parameters and foliar concentrations of six macronutrients (N, P, S, K, Ca and Mg) and four micronutrients (Fe, Mn, Zn and Cu) across 18 coexisting species. At the regional scale, foliar macro‐ and micronutrient concentrations of 76 site‐species combinations of grasses and forbs across temperate meadow, typical, desert and saline grasslands were measured in Inner Mongolia. At the national scale, we collected the data on foliar macronutrient concentrations of 513 site‐species combinations across grasslands in Xinjiang, Qinghai‐Tibet and Inner Mongolia of China. Compared with forbs, grasses had 3.9 times higher root branching intensity, but 58% and 48% lower root carboxylate exudation and leaf transpiration rate. These distinct nutrient acquisition and transport strategies led to lower foliar nutrient (N, P, Ca, Mg and Mn) concentrations in grasses than forbs at the local scale. Most foliar micronutrient concentrations did not differ between grasses and forbs at the regional scale, whereas macronutrient concentrations were higher in forbs than grasses regardless of the grassland type at both the regional and national scales. All macronutrient concentrations exhibited stronger phylogenetic conservatism and less environmental control than micronutrients. The biogeochemical niche segregation (Euclidean distance based on PCA score of foliar macronutrient concentrations) between sympatric grasses and forbs was lower in meadow grassland than in the typical, desert and saline grasslands. Our results suggest that diverse nutrient acquisition and transport strategies can underlie the distinct foliar nutrient compositions between grasses and forbs. The linkage between potential physiological mechanisms and biogeochemical niche differentiation of grasses and forbs will advance our understanding of plant species coexistence and adaptive strategy. Read the free Plain Language Summary for this article on the Journal blog.

Structural, morphological, and optical investigations of Mn-doped LaAlO3 perovskite obtained by microwave-assisted combustion and rapid calcination at low temperature

In this work, LaAlO3 perovskite was doped with 1, 2, 3, 5, 8, and 13 mol% of Mn using the microwave-assisted combustion method. The powders produced were heat treated at 700 °C and 900 °C for 10 min in an adapted microwave oven and then characterized by Thermogravimetric analysis (TG/DTG) and Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD) and Rietveld refinement, X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR), Raman, Ultraviolet–Visible Reflectance (UV–Vis), Field Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-ray Spectroscopy (EDS). The materials produced doped with the highest concentration of Mn (13 %) showed a single-phase reduced crystallite size compared to the pure sample. The unit cell volumes increased compared to the pure material, while the oxidation state of the dopant was mainly Mn3+. The refinement data for the volume of the different polyhedral that comprise the LaAlO3 unit cell revealed a local change at both sites, which may also indicate Mn substitution at the A site. The heat treatment temperature did not change significantly, demonstrating the method's efficiency in producing perovskites at temperatures and times below those reported in the literature. The morphology observed was porous and irregular agglomerates, and the bandgap was 2.90 eV.

Dynamics of Fe, Mn, and potentially harmful elements under reducing conditions in iron ore tailings after dam collapse in the Doce River basin-Brazil: flooded and non-flooded rice cultivations.

Potentially harmful element (PHE) bioavailability is important to environmental contamination and must be checked under several soil conditions. This study aimed to assess Fe, Mn, and PHE uptake by rice (Oryza sativa) grown on flooded and non-flooded Fe tailings collected from the Doce River basin after its collapse in Brazil. After 65days of sowing, shoots and roots were harvested to determine PHE concentrations. The mean concentrations of Mn in shoots and Fe in the roots of rice grown on the flooded tailings were 2140mgkg-1 and 15,219mgkg-1, respectively. Mn was extensively translocated from roots to shoots (translocation factor (TF) = 2). Conversely, Fe accumulated in roots (TF = 0.015) and caused morphological damage to this rice organ. The application of macro and micronutrients lessened Fe toxicity in the roots of rice cultivated on the flooded tailings. The flooding of tailings influenced more Fe accumulation than Mn accumulation by rice plants. The PHE Ag, As, Cd, Ni, Hg, Pb, and Sb exhibited low total concentrations (maximum of 9mgkg-1 for Ni and a minimum of 0.2mgkg-1 for Cd, Hg, and Sb), and it was not observed an increase in their availability under tailings flooding conditions.

Biodegradation, Antibacterial Performance, and Cytocompatibility of a Novel ZK30-Cu-Mn Biomedical Alloy Produced by Selective Laser Melting.

In the present study, an antibacterial biomedical magnesium (Mg) alloy with a low biodegradation rate was designed, and ZK30-0.2Cu-xMn (x = 0, 0.4, 0.8, 1.2, and 1.6 wt%) was produced by selective laser melting, which is a widely applied laser powder bed fusion additive manufacturing technology. Alloying with Mn evidently influenced the grain size, hardness, and biodegradation behavior. On the other hand, increasing Mn content to 0.8 wt% resulted in a decrease of biodegradation rate which is attributed to the decreased grain size and relatively protective surface layer of manganese oxide. Higher Mn contents increased the biodegradation rate attributed to the presence of the Mn-rich particles. Taken together, ZK30-0.2Cu-0.8Mn exhibited the lowest biodegradation rate, strong antibacterial performance, and good cytocompatibility.

Effects of the dietary supplementation of manganese on growth, skeletal development, oxidative stress and bone metabolism related genes in gilthead seabream (Sparus aurata) larvae

Manganese (Mn) is an essential element necessary for normal growth, antioxidant defense and maintaining bone health. Knowledge about the effects of dietary Mn levels in gilthead seabream (Sparus aurata) larvae performance is still scarce. To determine the effects of dietary Mn levels on growth, survival, skeletal development and expression of antioxidant and bone metabolism related genes, gilthead seabream larvae were fed six experimental microdiets supplemented with manganese sulfate monohydrate (MnSO4.H2O) (contained 6.3, 39, 75, 79, 200 and 270 mg Mn/kg diet). After 26 days of feeding, dietary Mn levels had no effect on larval survival. However, larvae fed the non-supplemented diet (6.3 mg Mn/kg) showed signs of Mn deficiency, including growth reduction, low whole body Mn content, lower expression of mnsod, runx2, oc, and reduced bone mineralization. The poor vertebral body mineralization and low bone relative gene expression in seabream larvae was related to a marked increase in the number of fish with total skeletal anomalies and anomalies of the caudal vertebrae region. On the contrary, larvae fed with Mn supplemented diet up to 270 mg Mn/kg showed increased growth and whole body Mn content, up-regulated mnsod, runx2, alp, opn and oc expression, as well as increased bone mineralization, and reduced number of fish with skeletal anomalies. Therefore, the findings suggest that adequate dietary Mn supplementation positively influences the growth, skeletal development, and antioxidant defense of gilthead seabream larvae, preventing the manifestation of Mn deficiency-related issues.

Dynamic transition of internal oxides during high dew point heat treatment in Fe-2.4Mn-0.4Si-0.13 C alloy

The origin of the dynamic transition of internal oxides was clarified in Fe-2.4Mn-0.4Si-0.13C-based steel during decarburization annealing at 1073K. High dew point with H2 gas leads to the formation of deep decarburized ferrite layers containing grain boundary internal oxides. Microstructural characterization reveals the oxide transition from Mn2SiO4 to α-SiO2 at the tip of the internal oxidation layer and from α-SiO2 to Mn2SiO4 at the middle range of the internal oxidation layer. The dynamic transition between Mn2SiO4 and α-SiO2 is understood by the depletion in Mn contents and change of oxygen content, which change the normalized driving force of both oxides. The study gives a detailed mechanism of internal oxide formation and growth in multi-phase steel during high dew point annealing. Impact statementDuring high dew-point decarburization annealing, the fluctuation of Mn contents affects the driving force to form an internal oxide, resulting in the dynamic transition between Mn2SiO4 and α-SiO2.

Corrosion Resistance of FeCrMnxAlCu High-Entropy Alloys in 0.5 M H2SO4 Solution

In this study, FeCrMnxAlCu high-entropy alloys with varying Mn contents (x = 2.0, 1.5, 1.0, 0.5, and 0) were prepared using a vacuum arc melting furnace. The phase structure and microstructure of the alloys before and after corrosion were characterized via X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The corrosion resistance of the alloys in a 0.5M H2SO4 solution was comprehensively evaluated through potentiodynamic polarization, electrochemical impedance spectroscopy, immersion tests, white light interferometry, and X-ray photoelectron spectroscopy. Microstructural characterization results revealed that the FeCrMnxAlCu high-entropy alloys exhibited mixed FCC and BCC phase structures and featured typical dendritic and interdendritic regions. Corrosion tests indicated that as the Mn content decreased, the corrosion resistance of the high-entropy alloys improved, and the corrosion type transitioned from dendritic to interdendritic. Among these alloys, the FeCrAlCu high-entropy alloy exhibited the highest corrosion resistance, with the highest positive corrosion potential (Ecorr = −0.11V), the lowest corrosion current density (Icorr = 1.02 × 10−5 A∙cm2), minimal corrosion depth, and the lowest corrosion rate (0.1592mm/y). After corrosion, a composite oxide protective film was formed on the alloy surface, effectively hindering further penetration of the H2SO4 solution and exhibiting excellent corrosion resistance.

Preparation of high-strength and high-ductility medium Mn steel with chemistry heterogeneous via a two-step intercritical annealing process

Recently, the retained austenite (RA) with chemically heterogeneous has attracted great attention in medium Mn steel. In this work, we designed a two-step intercritical annealing (TIA) heat treatment process to prepare high-strength medium Mn steel with the chemical composition of Fe–0.20C–8.0Mn–1.6Si–1.3Al (wt.%). Compared with the normal intercritical annealing (IA) heat treatment process, the TIA process can not only increase the volume fraction of RA but also obtain the RA with inhomogeneous Mn distribution. Meanwhile, it was found that the Mn content on the outer side of this structured RA was higher than that on the inner side, forming a nanoscale Mn-enriched layer on the outer side of RA, which played a significant role in improving the stability of RA. Finally, we used the TIA process to obtain medium Mn steel with an ultimate tensile strength (UTS) of 1611.83 MPa, a total elongation (TE) of 45.02%, and a product of strength and elongation (PSE) of 72.56 GPa·%, which achieves a superior combination of high strength and high ductility in medium Mn steel.