Iron-rich Particles Research Articles

Sustainable recycling of pure aluminum from waste chips under supergravity-enhanced separation: A cleaning process

Large quantities of chips containing high levels of aluminum are always inevitably produced during machining process of aluminum products, which is a valuable renewable resource. In this paper, an environmental-friendly method for direct and continuous recovery of same-level recycled Al from waste chips under supergravity-induced was proposed. The oxide film covering the surface of the molten Al-chips was easily disrupted under super-gravity, and subsequently almost all of Al melt detached from the oxide film and flowed rapidly through the microporous ceramic foam filter, with a yield ratio of more than 97 %. During this process, all fine broken oxide-film particles and large amounts of primary iron-rich particles in the melt were captured in the complex channels of the filter, resulting in clean 1xxx series recycled Al with free inclusions and impurity iron content of less than 0.28 wt%. In addition, a sustainable process and a continuous centrifugal unit for recycling aluminum chips were designed, the economic and environmental advantages of which demonstrate the feasibility of sustainable regeneration of aluminum chip resources on an industrial scale via supergravity technique.

Seasonal euxinia in a coastal basin: Impact on sedimentary molybdenum enrichments and isotope signatures

Eutrophication and global warming are leading to increased deoxygenation of coastal waters worldwide. To predict future trajectories of oxygen loss, insight into the intensity and temporal dynamics of past coastal deoxygenation is essential. Here, we assess the use of sedimentary molybdenum (Mo) enrichments and isotopic signatures (δ98Mo) as redox proxies in sediments of a seasonally euxinic coastal basin (Scharendijke, Lake Grevelingen, the Netherlands). Strong drawdown of dissolved Mo (from ∼100 to ∼60 nmol L−1) was observed in the euxinic bottom waters from July to September in 2021, coinciding with sedimentary enrichment of Mo (with peak values up to 19 ppm). A mass balance for Mo indicates that both deposition of Mo in the form of particles and diffusion of dissolved Mo into the sediment account for this Mo enrichment. The δ98Mo composition of suspended matter in the euxinic waters (0.30 to −1.95 ‰) is in line with isotopic fractionation during formation of thiomolybdates, and removal of Mo by sulfur- and/or iron-rich particles. The δ98Mo composition of the bottom water increases from 2.42 to 3.16 ‰ throughout the euxinic period, thereby further supporting preferential uptake of light Mo isotopes during sulfidation in the water column and near the sediment-water interface. The exceptionally high sedimentation rate at this site (>13 cm yr−1) allows seasonal variations in sedimentary enrichments to be preserved in the sedimentary record. Notably, sediment δ98Mo values peak during the summer euxinic period, reaching 1.28 ‰ in 2021 and as high as 2.15 ‰ in 2020. The 2020 value is close to the mean ocean value of 2.3 ‰, implying that sediments overlain by seasonally and permanently euxinic bottom waters can record the same isotopic signatures for Mo. Further work is needed to determine the potential role of diagenesis in altering δ98Mo records on time scales of months to several years.

Iron Trace Elements Concentration in PM10 and Alzheimer's Disease in Lima, Peru: Ecological Study.

Alzheimer's disease (AD) has been linked to air pollution, especially particulate matter (PM). PM comprises various elements, including iron-rich particles that may reach the brain through inhalation. Lima, Peru is one of the most polluted cities in Latin America, with a high rate of AD. The study aims to evaluate the association between iron (Fe) trace elements in PM10 and AD cases in Lima, Peru. This retrospective ecological study used monthly Fe concentration data from the Peruvian Ministry of Health. AD cases (ICD-10-G30) and dementia in AD cases (DAD, ICD-10-F00) were obtained from the Peruvian CDC. Fe trace element data were available for six districts in Lima for the years 2017-2019 and 2022. Cases were standardized based on ≥60-year-old populations of each district. Hierarchical mixed-effects models of Gaussian and negative binomial families were constructed to evaluate both outcomes jointly (AD + DAD) and separately (AD, and DAD). A sensitivity analysis was conducted by excluding data from Lima's downtown district. In the complete model, log-Fe concentration was associated with a higher rate of AD + DAD and DAD, and with a higher IRR for the three outcomes. After controlling for other metals, a higher DAD rate was observed (β-coeff = 6.76, 95%CI 0.07; 13.46, p = 0.048), and a higher IRR for AD + DAD (1.55, 95%CI 1.09; 2.20, p = 0.014) and DAD (1.83, 95%CI 1.21; 2.78, p = 0.004). The association was not significant in the sensitivity analysis. In conclusion, exposure to Fe through PM10 inhalation may be associated with the presence of AD in Lima.

Preparation and characterization of highly catalytic and corrosion resistant Fe–Ti–O magnetorheological composite powders

Magnetorheological finishing (MRF) is one of the candidate technologies for the efficient polishing of single crystal silicon carbide (SiC). It is of great importance to improve the efficiency of MRF and reduce the costs by improving the catalytic activity and corrosion resistance of iron-based magnetic particles while maintaining the magnetic properties. In this work, α-Fe2O3 and TiH2 powders were used as raw materials, and Fe–Ti–O composite powders for MRF were prepared by three processes: ball milling + reduction (R1), ball milling + calcination (R2) and ball milling + calcination + reduction (R3). The effects of TiH2 content (5 wt%-15 wt%) on the phase composition, microstructure, catalytic activity and corrosion resistance of the composite powders were investigated. The results demonstrated that submicron α-Fe2O3/TiH2 mixed powders with uniform composition were obtained by ball milling. Compared to the powders prepared by the R1 and R2 routes, the Fe–Ti–O composite powders prepared by the R3 were composed of Fe2TiO4 particles (500–800 nm) and iron-rich particles (30–200 nm). The iron-rich particles were uniformly distributed on the surface of the agglomerated Fe2TiO4 spheres, forming a unique "Ferrero" structure. When the TiH2 content was 15 wt%, the Fe–Ti–O composite powders exhibited the required saturation magnetization (Ms) for MRF (61.0 emu/g), the highest catalytic activity and the best corrosion resistance.

Seasonal euxinia in a coastal basin: Impact on sedimentary molybdenum enrichments and isotope signatures

Eutrophication and global warming are leading to increased deoxygenation of coastal waters worldwide. To predict future trajectories of oxygen loss, insight into the intensity and temporal dynamics of past coastal deoxygenation is essential. Here, we assess the use of sedimentary molybdenum (Mo) enrichments and isotopic signatures (δ98Mo) as redox proxies in sediments of a seasonally euxinic coastal basin (Scharendijke, Lake Grevelingen, the Netherlands). Strong drawdown of dissolved Mo (from ~100 to ~60 nmol L−1) was observed in the euxinic bottom waters from July to September in 2021, coinciding with sedimentary enrichment of Mo (with peak values up to 19 ppm). A mass balance for Mo indicates that both deposition of Mo in the form of particles and diffusion of dissolved Mo into the sediment account for this Mo enrichment. The δ98Mo composition of suspended matter in the euxinic waters (0.30 to −1.95 ‰) is in line with isotopic fractionation during formation of thiomolybdates, and removal of Mo by sulfur- and/or iron-rich particles. The δ98Mo composition of the bottom water increases from 2.42 to 3.16 ‰ throughout the euxinic period, thereby further supporting preferential uptake of light Mo isotopes during sulfidation in the water column and near the sediment-water interface. The high sedimentation rate at this site (>13 cm yr−1) allows seasonal variations in sedimentary enrichments to be preserved in the sedimentary record. Notably, sediment δ98Mo values peak during the summer euxinic period, reaching 1.28 ‰ in 2021 and as high as 2.15 ‰ in 2020. The 2020 value is close to the mean ocean value of 2.3 ‰, implying that sediments overlain by seasonal and permanently euxinic bottom waters can record the same isotopic signatures for Mo. Further work is needed to determine the potential role of diagenesis in altering δ98Mo records on time scales of months to several years.

Enhancing iron biogeochemical cycling for canga ecosystem restoration: insights from microbial stimuli.

The microbial-induced restoration of ferruginous crusts (canga), which partially cover iron deposits and host unique ecosystems, is a promising alternative for reducing the environmental impacts of the iron mining industry. To investigate the potential of microbial action to accelerate the reduction and oxidation of iron in substrates rich in hematite and goethite, four different microbial treatments (water only as a control - W; culture medium only - MO; medium + microbial consortium - MI; medium + microbial consortium + soluble iron - MIC) were periodically applied to induce iron dissolution and subsequent precipitation. Except for W, all the treatments resulted in the formation of biocemented blocks. MO and MI treatments resulted in significant goethite dissolution, followed by precipitation of iron oxyhydroxides and an iron sulfate phase, due to iron oxidation, in addition to the preservation of microfossils. In the MIC treatment, biofilms were identified, but with few mineralogical changes in the iron-rich particles, indicating less iron cycling compared to the MO or MI treatment. Regarding microbial diversity, iron-reducing families, such as Enterobacteriaceae, were found in all microbially treated substrates. However, the presence of Bacillaceae indicates the importance of fermentative bacteria in accelerating the dissolution of iron minerals. The acceleration of iron cycling was also promoted by microorganisms that couple nitrate reduction with Fe(II) oxidation. These findings demonstrate a sustainable and streamlined opportunity for restoration in mining areas.

Regenerative braking system effectively reduces the formation of brake wear particles

Brake wear particles (BWPs) are considered one of the most significant non-exhaust particle emission sources from motor vehicles. Previous studies have primarily focused on BWPs from conventional fuel vehicles (CFVs), with limited research available on BWPs from new energy vehicles (NEVs). We developed an independent BWP emission testing system applicable to NEVs and conducted BWP emission tests on representative NEVs and CFVs under various testing cycles via a chassis dynamometer. The BWP emission characteristics of the NEVs equipped with regenerative braking system significantly differed from those of gasoline vehicles. For transient emission characteristics, gasoline vehicles exhibited higher peak concentrations during brake events than brake drag events, while those with regenerative braking exhibited the opposite feature. Under continuous braking, the concentration of ultrafine particles emitted by NEVs was reduced by more than 3 orders of magnitude compared to gasoline vehicles. In terms of single-particle morphology, BWPs could be mainly divided into three categories: carbonaceous particles, iron-rich particles, and mixed metal particles. We obtained realistic emission characteristics of BWPs from NEVs, which could provide data support and a scientific basis for the formulation of relevant emission standards and control measures in the future.

Measuring magnetic susceptibility of particulate matter collected on filters

The magnetic susceptibility (κ) of particulate matter (PM) is a useful tool in estimation concentration of iron-rich particles and provides useful information on the emission sources and pathways of spread of PM in the atmosphere. However, there is currently no established protocol for measuring the magnetic susceptibility of PM collected on filters used in standard monitoring of PM concentration. This paper presents a step-by-step process for collecting PM on filters in automatic samplers and measuring their κ. The procedure outlines requirements for data quality, measurement uncertainty, exposure time and conditions, and the amount of material collected on the filters. The study analyzed a 2-year dataset of magnetic susceptibility measurements by MFK-1 kappabridge (Agico, Czech Republic) for PM10 and PM2.5 collected at two locations, Warsaw and Cracow, in Poland using low-volume PM samplers. By strictly following the procedure for conditioning filters, measuring magnetic susceptibility and mass of PM, the study found that it is possible to obtain repeatable data with good measurement accuracy and acceptable errors. This makes magnetic susceptibility an additional reliable parameter for tracking of emission sources of iron-rich particles. Successful implementation of this magnetic method as a standard procedure for monitoring PM in addition to the PM mass collected on filters could be used to analyze sources of emission of Fe-particles and their contribution to the PM mass, especially in urban and industrial environments.

Aerosol high water contents favor sulfate and secondary organic aerosol formation from fossil fuel combustion emissions

Fine-particle pollution associated with high sulfate and secondary organic aerosol (SOA) contents still occurs in winter, despite considerable reductions in precursor emissions in China. The chemical mechanisms involved are consistently acknowledged to be linked with aerosol water but remain poorly understood. Here, we present findings demonstrating that the synergistic effect of elevated aerosol water content and particles originating from fossil fuel combustion significantly enhanced the rapid formation of sulfate and SOAs under high humidity conditions during winter in northern China. The presence of high aerosol water content promoted the aging process of particles containing elemental carbon (EC) and facilitated the formation of SOAs. Evidence from single particles reveals an increased potential for SOA formation from primary organic aerosols (POAs) originating from fossil fuel combustion, in the presence of increasing aerosol water. Under conditions of relative humidity exceeding 85%, the multiphase oxidation of SO2 by in-particle nitrite/nitrous acid, generated through reactions involving aged EC-containing and iron-rich particles, as well as aqueous-phase formation of hydroxymethanesulfonate (HMS), led to a substantial increase in sulfate production. This study emphasizes the critical role of aerosol water in the aerosol chemistry concerning sulfate and SOAs, highlighting the urgent necessity to mitigate primary emissions from fossil fuel combustion.

Morphological, Mineralogical, and Biochemical Characteristics of Particulate Matter in Three Size Fractions (PM10, PM2.5, and PM1) in the Urban Environment.

Air pollution in megacities is increasing due to the dense population index, increasing vehicles, industries, and burning activities that negatively impact human health and climate. There is limited study of air pollution in many megacities of the world including Pakistan. Lahore is a megacity in Pakistan in which the continuous investigation of particulate matter is very important. Therefore, this study investigates particulate matter in three size fractions (PM1, PM2.5, and PM10) in Lahore, a polluted city in south Asia. The particulate matter was collected daily during the winter season of 2019. The average values of PM1, PM2.5, and PM10 were found to be 102.00 ± 64.03, 188.31 ± 49.21, and 279.73 ± 75.04 μg m-3, respectively. Various characterization techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX) were used. FT-IR and XRD techniques identified the minerals and compounds like quartz, peroxides, calcites and vaterite, feldspar group, kaolinite clay minerals, chrysotile, vaterite, illite, hematite, dolomite, calcite, magnesium phosphate, ammonium sulfate, calcium iron oxide, gypsum, vermiculite, CuSO4, and FeSO4. Morphology and elemental composition indicated quartz, iron, biological particles, carbonate, and carbonaceous particles. In addition, various elements like C, O, B, Mg, Si, Ca, Cl, Al, Na, K, Zn, and S were identified. Based on the elemental composition and morphology, different particles along with their percentage were found like carbonaceous- (38%), biogenic- (14%), boron-rich particle- (14%), feldspar- (10%), quartz- (9%), calcium-rich particle- (5%), chlorine-rich particle- (5%), and iron-rich particle (5%)-based. The main sources of the particulate matter included vehicular exertion, biomass consumption, resuspended dust, biological emissions, activities from construction sites, and industrial emissions near the sampling area.

The Curie line in protoplanetary disks and the formation of Mercury-like planets

In laboratory experiments, we heated chondritic material up to 1400 K in a hydrogen atmosphere. Mössbauer spectroscopy and magnetometry reveal that, at high temperatures, metallic iron forms from silicates. The transition temperature is about 1200 K after 1 h of tempering, likely decreasing to about 1000 K for longer tempering. This implies that in a region of high temperatures within protoplanetary disks, inward drifting solids will generally be a reservoir of metallic iron. Magnetic aggregation of iron-rich matter then occurs within the magnetic field of the disk. However, the Curie temperature of iron, 1041 K, is a rather sharp discriminator that separates the disk into a region of strong magnetic interactions of ferromagnetic particles and a region of weak paramagnetic properties. We call this position in the disk the Curie line. Magnetic aggregation will be turned on and off here. On the outer, ferromagnetic side of the Curie line, large clusters of iron-rich particles grow and might be prone to streaming instabilities. To the inside of the Curie line, these clusters dissolve, but that generates a large number density that might also be beneficial for planetesimal formation by gravitational instability. One way or the other, the Curie line may define a preferred region for the formation of iron-rich bodies.

Immobile Iron-Rich Particles Promote Arsenic Retention and Regulate Arsenic Biotransformation in Treatment Wetlands.

Remediation of arsenic (As)-contaminated wastewater by treatment wetlands (TWs) remains a technological challenge due to the low As adsorption capacity of wetland substrates and the release of adsorbed As to pore water. This study investigated the feasibility of using immobile iron-rich particles (IIRP) to promote As retention and to regulate As biotransformation in TWs. Iron-rich particles prepared were immobilized in the interspace of a gravel substrate. TWs with IIRP amendment (IIRP-TWs) achieved a stable As removal efficiency of 63 ± 4% over 300 days, while no As removal or release was observed in TWs without IIRP after 180 days of continuous operation. IIRP amendment provided additional adsorption sites and increased the stability of adsorbed As due to the strong binding affinity between As and Fe oxides. Microbially mediated As(III) oxidation was intensified by iron-rich particles in the anaerobic bottom layer of IIRP-TWs. Myxococcus and Fimbriimonadaceae were identified as As(III) oxidizers. Further, metagenomic binning suggested that these two bacterial taxa may have the capability for anaerobic As(III) oxidation. Overall, this study demonstrated that abiotic and biotic effects of IIRP contribute to As retention in TWs and provided insights into the role of IIRP for the remediation of As contamination.

Elastoplastic analysis of AA7075-O aluminum sheet by hybrid micro-scale representative volume element modeling with really-distributed particles and in-situ SEM experimental testing

• Presents a novel computationally-efficient reconstruction of 3D RVE model of second-phase particle-strengthened AA7075-O sheet with real distribution of particles based on FIB-SEM techniques. • Three types of second-phase particles (i.e., irregularly-shaped iron-rich particle Al 3 Fe, elliptically-shaped particle MgZn 2 , and needle-like particle CuAl 2 ) are determined using SEM-based EDS and EBSD techniques. • Presents a systematic study of the overall elastic-plastic response by developing and applying a hybrid experimental analysis and computational modeling framework. • Good agreement is observed in the comparison of RVE results with that of in-situ SEM tensile tests, indicating that the real 3D microstructure-based RVE models can accurately predict the plastic deformation and interfacial failure evolution in AA7075-O sheet. This paper addresses the challenge of reconstructing randomly distributed second-phase particle-strengthened microstructure of AA7075-O aluminum sheet material for computational analysis. The particle characteristics in 3D space were obtained from focused ion beam and scanning electron microscopy (FIB-SEM) and SEM-based Electron Backscatter Diffraction/Energy Dispersive X-ray Spectrometry (EBSD/EDS) techniques. A theoretical framework for analysis of elastic-plastic deformation of such 3D microstructures is developed. Slip-induced shear band formation, void initiation, growth and linkage at large plastic strains during uniaxial tensile loading were investigated based on reconstructed 3D representative volume element (RVE) models with real-distribution of particles and the results compared with experimental observations. In-situ SEM interrupted tension tests along transverse direction (TD) and rolling direction (RD), employing microscopic-digital image correlation (μ-DIC) technique, were carried out to investigate slip bands, micro-voids formation and obtain microstructural strain maps. The resulting local strain maps were analyzed in relation to the experimentally observed plastic flow localization, failure modes and local stress maps from simulations of RVE models. The influences of particle size, shape, orientation, volume fraction as well as matrix-particle interface properties on local plastic deformation, global stress-strain/strain-hardening curves and interfacial failure mechanisms were studied based on 3D RVE models. When possible, the model results were compared with in-situ tensile test data. In general, good agreement was observed, indicating that the real 3D microstructure-based RVE models can accurately predict the plastic deformation and interfacial failure evolution in AA7075-O aluminum sheet.

Study of the growth mechanism of ε-Fe2O3 crystals in Chinese sauce glaze replications

The ferric oxide ε-Fe2O3 has recently been at the center of interest of scientists to understand its physical properties and find efficient methods of synthesis. In parallel to those studies, ε-Fe2O3 was discovered in several ancient brown and black glazed ware produced in different Chinese kilns and time periods. The ubiquity of such phase in ancient glaze in spite of its low stability could be a very interesting indicator to understand both the traditional manufacturing of ancient Chinese glaze and the growth of ε-Fe2O3 in a glassy matrix. This study is based on a set of glazed samples taken out from the kiln at different stages of the firing. Analyses show that ε-Fe2O3 crystals begin to grow at high-temperature at the beginning of the cooling stage. The growth continues through iron ion pumping from the glaze. The iron depletion of the glaze causes the dissolution of iron rich particles, which were formed during the heating and ion diffusion from deeper in the glaze. Al-substitution in ε-Fe2O3 was observed, with a higher Al concentration in more developed crystals. Ti- and Mg-substitutions were also highlighted. A set of equation is proposed to model the formation process.

EFFECT OF INCLUSIONS ON THE SOFTENING MECHANISM OF Al 1235 ALLOY DURING THERMAL DEFORMATION

The effect of inclusions on the softening mechanism of a pure aluminum alloy is studied with TEM, EDAX and SAED. Oxide inclusions and iron-rich second-phase particles are the main inclusions in Al 1235 alloy. The phase of iron-rich particles in the alloy is phase AlFe3 with a lattice constant of 5.79 and crystal band axis of Š 231Æ. During thermal deformation, coarser inclusions in the alloy are beneficial to the nucleation of dynamic recrystallization, but they have a great effect on the separation of the alloy matrix. Nucleation and growth of dynamic-recrystallization grains are restricted by finer inclusions, reducing the possibility of aluminum-matrix fracture. The preferred places for dynamic-recrystallization nucleation include boundaries at the intersection of three grains, the dislocation plug area, the surface of the coarse oxide inclusions or the coarse second-phase inclusions.

Effects of Heat Treatment on Microstructure and Mechanical Properties of AlSi10Mg Fabricated by Selective Laser Melting Process

AlSi10Mg is the most widely additively manufactured and commercialized aluminum alloy and has been used in this study to analyze the effect of heat treatment on its microstructure and mechanical properties. Although research indicates AlSi10Mg parts produced by selective laser melting have characteristically very fine microstructures, there is a need for more intensive study to comprehend the effect of heat treatment on the mechanical properties of this alloy by analyzing its microstructure. In this study, AlSi10Mg specimens heat-treated at varying temperatures were analyzed by optical and electron microscopes. Micro-indentation hardness and tensile tests were performed to evaluate mechanical properties while considering the specimen build orientation. Observation shows that it is nearly impossible to completely dissolve the evolved second phase silicon-rich particles, which may have significant effects on the mechanical characteristics. Electron microscopy images show the evolution of iron-rich particles in the Al matrix, which may have a significant influence on the mechanical properties of the alloy.

Computational Elastic Analysis of AA7075-O using 3D-Microstructrure-Based-RVE with Really-distributed Particles

AA7075 is of special interest amongst aluminum alloys for structural applications in automotive and aerospace industries because of its higher strength. Due to advances in experimental and numerical analysis tools, there is much interest amongst researchers in developing analytical and computational methods to calculate the effective material properties of AA7075 alloy based of its complex microstructure. This paper presents a novel computationally-efficient reconstruction of three-dimensional microstructure of representative volume element model with real distribution of particles using focused ion beam equipped with scanning electron microscopy techniques and specialized computer software to investigate the mechanical properties of AA7075-O sheet. As part of material microstructure characterization for computational analysis, particle identification and chemical characterization of the AA7075-O sheet are also investigated by scanning electron microscopy-based energy dispersive X-ray spectroscopy and electron back-scatter diffraction analysis. The results show that there are three main types of particles that exist in AA7075-O sheet, i.e., irregularly-shaped iron-rich particle Al3Fe, elliptically-shaped particle MgZn2, and needle-like particle CuAl2. The spatial distribution of these particles in AA7075-O sheet from a set of scanning electron microscopy images are utilized to reconstruct RVE models in a finite element analysis environment and analyzed with periodic boundary condition and kinematically uniform boundary condition. Also, a comparison of RVE results with that of modified rule of mixtures is presented. It is shown that the particular boundary conditions have almost no influence over the effective elastic properties when the RVE size is 10 um × 10 um × 10 um and volume fraction of particle is large. Also, the modified rule of mixtures predictions of elastic properties generally well match with the trends of RVE-based computational results, which implies the validity of simpler modified rule of mixtures approach.

Characterization of a Chromium-Bearing Carbon Steel Electric Arc Furnace Slag after Magnetic Separation to Determine the Potential for Iron and Chromium Recovery

This study investigates the potential to recover iron and chromium from a chromium-bearing carbon steel Electric Arc Furnace (EAF) slag. This slag contains indeed about 30 wt.% Fe and 2.5 wt.% Cr. However, the minerals are intergrown at small scale (<100 µm) and iron and chromium are mostly contained in spinel phases which makes the separation challenging. Several methods including Mössbauer spectroscopy, X-ray Diffraction, Scanning Electron Microscopy (SEM) and electron microprobe analysis were used in order to fully characterize the products obtained after a low-intensity magnetic separation of this carbon steel EAF slag, with the objective to define a pre-treatment process allowing the recovery of iron-rich particles and of a chromium-upgraded fraction. The results show that even if the magnetic separation seems to be not efficient in a first approach for producing an iron-rich/chromium-poor fraction, this fraction can be obtained by adding an attrition step which means that some separation mechanisms still occurred during the magnetic separation. However, it was not possible to produce a chromium-rich fraction. The main bottleneck for reaching a good separation is most probably the very fine liberation size of the iron and chromium bearing minerals.

Uncovering the Growth Kinetics of Atmospheric Corrosion Pits in Aluminum

Understanding how the local kinetics of atmospheric corrosion damage are controlled by environment and microstructure remains a central challenge in the field. Conventional approaches such as mass-change studies provide little insight into the growth kinetics of individual pits. To overcome the challenges of observing pit evolution in-situ, the current study employed laboratory-based X-ray computed microtomography (XCT) to directly observe pitting in-situ over months of exposure. This approach enabled direct observation of how the growth kinetics and morphology of individual pits evolved. Atmospheric corrosion damage in Al wires of various purities, including 99.99% Al and 1100 Al, exposed to chloride salts in humid air was studied. Initial studies suggested that most pits grow at a linear rate until pit repassivation. Following repassivation, no further growth was observed. Subsequent studies at higher temporal resolutions indicated that, in some cases, growth rate is non-linear. A corrosion-driven drying mechanism appears to lead to pit death in both cases. Pit growth occurred at significantly faster rates in samples containing second-phase, Iron-rich particles. Droplet size also played an important role in pit growth kinetics. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

Uncovering the Growth Kinetics of Atmospheric Corrosion Pits in Aluminum Using X-Ray Computed Tomography

Understanding how the local kinetics of atmospheric corrosion damage are controlled by environment and microstructure remains a central challenge in the field. Conventional approaches such as mass-change studies provide little insight into the growth kinetics of individual pits. To overcome the challenges of observing pit evolution in-situ, the current study employed laboratory-based X-ray computed microtomography (XCT) to directly observe pitting in-situ over months of exposure. This approach enabled direct observation of how the growth kinetics and morphology of individual pits evolved. Atmospheric corrosion damage in Al wires of various purities, including 99.99% Al and 1100 Al, exposed to chloride salts in humid air was studied. Initial studies suggested that most pits grow at a linear rate until pit repassivation. Following repassivation, no further growth was observed. Subsequent studies at higher temporal resolutions indicated that, in some cases, growth rate is non-linear. A corrosion-driven drying mechanism appears to lead to pit death in both cases. Pit growth occurred at significantly faster rates in samples containing second-phase, Iron-rich particles. Droplet size also played an important role in pit growth kinetics. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.