Quantitative µ-CT Analysis of Scale Topology Formed During Oxidation of High SiMo Cast Iron
Not provided.
Metallurgy & Metallurgical Engineering↗
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Spectroscopic investigations on structural incorporation pathways of FeIII into zeolite frameworks in cement-relevant environments
Fe{sup III}-containing aluminosilicate zeolites are present in cement-relevant and natural environments. Although Fe{sup III} is known to occur in framework tetrahedral sites where it substitutes isomorphically Al{sup III}O{sub 4} or in extra-framework octahedral sites as free Fe(H{sub 2}O){sub 6}{sup 3+}, the structural incorporation process of Fe{sup III} into different sites is little known. We aim to discern feasible pathways of Fe{sup III} incorporation using hydrothermal synthesis methods and synchrotron-based spectroscopic analyses. Results showed that introducing either Fe{sup 3+} or Fe{sub 2}O{sub 3}·xH{sub 2}O initially during zeolite nucleation did not lead to Fe{sup III} incorporation into the zeolites but only Fe{sub 2}O{sub 3}·xH{sub 2}O prevailed in both cases. However, Fe(NO{sub 3}){sub 3}, FeCl{sub 3}, and Fe{sub 2}O{sub 3}·xH{sub 2}O affected the kind of zeolite formed. A feasible pathway to incorporate tetrahedral Fe{sup III} in the zeolite framework was to introduce firstly Fe{sup III} in the cage of faujasite-Y followed by a phase transformation to chabazite. This study facilitates understanding of Fe{sup III} uptake in zeolites and of Fe{sup III} functional sites that can contribute to immobilization of contaminants.
36 MATERIALS SCIENCE↗
Quantitative assessment of the influence of external magnetic field on clustering of nano-Fe3O4 particles in cementitious paste
In view of active rheology control of cementitious materials, nano-Fe{sub 3}O{sub 4} can be added as responsive particles. Following the concept of magnetorheological fluids, it is assumed that magnetic nanoparticles will form chains or clusters in cementitious paste following magnetic field lines. A quantitative experimental validation of this assumption is presented herein. The clustering of nano-Fe{sub 3}O{sub 4} particles under magnetic fields is studied by mapping iron (Fe) element distribution in cementitious paste using energy dispersive X-ray spectroscopy. By means of image analysis, the Fe-element patterns are quantified by the deviation of Fe-elements in a unit area from the mean value expected in case of a uniform distribution, as expressed by coefficient of variation (COV). The magneto-rheological responses of cementitious pastes are evaluated using small amplitude oscillatory shear technique. Results show that the magneto-rheological effect exhibits a linear relationship with the relative change of COV, providing a quantitative validation of magnetic clustering in cementitious paste.
36 MATERIALS SCIENCE↗
Effect of ZnO on the whiteness of white Portland cement clinker
The addition of ZnO to significantly improve the Hunter whiteness of white Portland cement (WPC) clinkers is introduced in this paper. The effects of ZnO on the whiteness of WPC were studied by chroma analysis, X-ray diffraction (XRD), the Rietveld method, hydration heat measurements and SEM-EDS. The results showed that adding ZnO increased the visible light reflectance, increased the brightness (L{sup ⁎}), and reduced the yellowness (b{sup ⁎}) of WPC clinker with high Fe{sub 2}O{sub 3}. Therefore, ZnO can increase the whiteness of WPC clinker. Zn was mainly distributed in the amorphous phase and unquantifiable crystalline phase (ACn), and then dissolved in the silicate phase. ZnO stabilized R-C{sub 3}S, reduced the crystallization of C{sub 3}A, and increased the ACn content. ZnO increased the amount of Fe in the ACn and minerals, thereby reducing the formation of C{sub 4}AF and improving whiteness. ZnO increased the accumulated heat of hydration but prolonged the induction period. This method provides a new approach for the WPC industry to broaden sources of raw materials and improve product quality.
36 MATERIALS SCIENCE↗
Labile Fe(III) supersaturation controls nucleation and properties of product phases from Fe(II)-catalyzed ferrihydrite transformation
We report Fe(II)-catalyzed ferrihydrite (Fh) transformation to more crystalline iron (oxyhydr)oxide phases is a widely occurring geochemical process which has been extensively studied as a function of Fe(II)/Fh ratios at fixed Fh loadings. However, recent isolation of an intermediate Fe(III) species resulting from Fe(II)-Fh contact that facilitates transformation by dissolution/reprecipitation suggests that the kinetics and properties of product phases will instead depend mostly on its rate of accumulation to a critical concentration, consistent with principles in the classical nucleation theory (CNT). This suggests a dependence both on the loading of Fe(II) on the surface, which controls the rate of labile Fe(III) formation, as well as the available volume of solution, which also impacts how fast it can achieve its critical concentration to nucleate product phases. To specifically examine the latter effect, here we studied transformation of 15 mg Fh in 1 mM FeSO 4 solutions at pH 7.2 in batch suspensions of 30 mL, 150 mL, and 450 mL volumes. Time-dependent concentrations of aqueous Fe(II), surface-associated Fe(II), and resulting labile Fe(III) were monitored along with bulk solids characterization as a function of time. Transmission electron microscopy (TEM) was used to visualize the evolution of phases at identical locations on TEM grids. The collective results show that the rates of Fh loss and emergence of product lepidocrocite (Lp) and goethite (Gt) as well as their phase proportions, nucleation mode and morphological properties depend directly on the rate of accumulation of the labile Fe(III) precursor to its critical concentration, which in our experiments was controlled simply by varying the available volume of solution into which it enters. Statistical analyses of TEM image data suggest that while both heterogeneous and homogeneous nucleation occurred in all experiments, the former was increasingly favored at lower Fh/solution ratio due to its lower nucleation barrier being more favorable at attendant lower supersaturations of Fe(III).
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Consistent Controls on Trace Metal Micronutrient Speciation in Wetland Soils and Stream Sediments
Trace metal are essential for microbially-mediated biogeochemical processes occurring in anoxic wetland soils and stream bed sediments, but low availability of these elements may inhibit anaerobic element cycling and transformations. Solid-phase speciation is likely a critical control on trace metal availability but has seen limited study in anoxic systems having concentrations similar to geological background levels, where metal limitations may be most prevalent. We have investigated trace metal concentrations and solid-phase speciation in three freshwater subsurface aquatic systems: marsh wetland soils, riparian wetland soils, and the sediments of a streambed. These systems displayed low solid-phase trace metal concentrations, generally at or below geological background levels, which generally followed the trend Zn > Cu ≈ Ni > Co and showed no correlation with major element compositions. All soils and sediments were dominated by quartz but varied in clay mineralogy as well as the organic matter, total sulfur, and total iron contents. X-ray absorption near-edge structure (XANES) spectroscopy shows that sulfur speciation in both wetlands is dominated by organic sulfur. Elemental sulfur and iron sulfides together made up <25% of the sulfur in the wetland soils, but the distribution between inorganic and organic forms was reversed in the stream sediments. Ferrous and ferric iron in clay minerals were common species identified by both XANES and extended X-ray absorption fine structure (EXAFS) spectroscopies at all sites. Iron(III) oxides were substantial components in all but the marsh wetland soils. Quantitative analysis of copper, nickel, and zinc XANES spectra revealed similar metal speciation across all sites. Copper speciation was dominated by sulfides, adsorbed species, and minor amounts of copper bound to organic matter; no metallic copper was detected. Nickel speciation also varied little and was dominated by nickel in clay mineral octahedral sheets and nickel sulfide, with adsorbed species also present. Zinc speciation was slightly more varied, with the marsh wetland soils and stream bed sediments containing adsorbed species, zinc associated with clay mineral structures, and zinc bound to reduced sulfur groups on organic matter, whereas the riparian wetland soils lacked clay-associated zinc but contained zinc sulfide. Trace metals bound to reduced sulfur occurred at every site, with a greater sulfur-bound fraction for copper. The fractional abundance of sulfur-bound species showed no relationship with soil or sediment total sulfur content, which varied by two orders of magnitude. More broadly, the observations in this study suggest that trace metal speciation in freshwater wetland soils and stream sediments is consistently dominated by a small set of recurring components which are distinct for each metal. Furthermore, this may represent a general geochemical phenomenon in anoxic soils and sediments containing trace metals at background concentrations (as low as 3 µg g -1 ) that was not predicted from systems that are contaminated with or naturally-enriched in copper, nickel, or zinc.
54 ENVIRONMENTAL SCIENCES↗
The role of Ca-bridged organic matter in an alkaline soil, as revealed by multimodal chemical imaging
Mineral–organic matter (OM) studies have predominantly focused on acidic soils that are abundant in iron (Fe) oxides and aluminum (Al) oxides. We have probed mineral–OM interactions in an alkaline or calcareous soil of the Aridisols class. Unlike the role of Fe and Al, the role of Ca-minerals (particularly calcite), which are ubiquitous in alkaline soils, in OM sequestration is not well understood. Multiple recent model studies with aqueous Ca2+ or synthetic calcite and a suite of OM compounds have shown Ca-OM assemblages to be spatially correlated with calcite at the microscale. To study the chemical state of both Ca and Fe and their competing role in soil organic matter (SOM) stabilization, we performed laboratory characterization using x-ray diffraction, Mössbauer spectroscopy, x-ray photoelectron spectroscopy, scanning electron microscopy, and scanning transmission electron microscopy, alongside synchrotron-based microscale chemical imaging using scanning transmission x-ray microscopy combined with near-edge x-ray absorption fine structure. Ca mineral–organic associations were found to be ubiquitous in this system and are likely critical for understanding SOM stabilization/degradation in alkaline soils. From our findings on mineralogy, speciation, and the nature of Ca-OM bridging, we identified differences in C and Ca chemistry based on the relative location of OM to Ca minerals. The OM near the calcite crystal was enriched in lipid and protein moieties, Ca-OM next to Fe minerals displayed a strong contribution from aromatic compounds, while on the surface of microbes, the carbonate was believed to be of microbial in origin, as also suggested by preliminary works reporting on the formation of amorphous calcite or nano-calcite. In Ca-OM admixed with carbonate, it was difficult to distinguish Ca-associated OM from amorphous calcite or nano-calcite.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Ferrous iron enhances arsenic sorption and oxidation by non-stoichiometric magnetite and maghemite
Abstract not provided
Gubler, Reto↗
Direct Methane Oxidation by Copper- and Iron-Dependent Methane Monooxygenases
Not provided.
Chemistry↗
Toward Accelerated Activation of Fe-ZSM-5 in Methane Dehydroaromatization
Not Available
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
A Critical Review on the Multiple Roles of Manganese in Stabilizing and Destabilizing Soil Organic Matter
Not Available
54 ENVIRONMENTAL SCIENCES↗
Redox Potentials of Magnetite Suspensions under Reducing Conditions
Not Available
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Irreversible Trace Metal Binding to Goethite Controlled by the Ion Size
The dynamics of trace metals at mineral surfaces influence their fate and bioaccessibility in the environment. Trace metals on iron (oxyhydr)oxide surfaces display adsorption–desorption hysteresis, suggesting entrapment after aging. However, desorption experiments may perturb the coordination environment of adsorbed metals, the distribution of labile Fe(III), and mineral aggregation properties, influencing the interpretation of labile metal fractions. Here, in this study, we investigated irreversible binding of nickel, zinc, and cadmium to goethite after aging times of 2–120 days using isotope exchange. Dissolved and adsorbed metal pools exchange rapidly, with half times <90 min, but all metals display a solid-associated fraction inaccessible to isotope exchange. The size of this nonlabile pool is the largest for nickel, with the smallest ionic radius, and the smallest for cadmium, with the largest ionic radius. Spectroscopy and extractions suggest that the irreversibly bound metals are incorporated in the goethite structure. Rapid exchange of labile solid-associated metals with solution demonstrates that adsorbed metals can sustain the dissolved pool in response to biological uptake or fluid flow. Trace metal fractions that irreversibly bind following adsorption provide a contaminant sequestration pathway, limit the availability of micronutrients, and record metal isotope signatures of environmental processes.
58 GEOSCIENCES↗
Short-Term Inhibition and Long-Term Enhancement of Irreversible Trace Metal Binding to Goethite in Multi-Metal Systems
Iron (oxyhydr)oxide minerals are important sorbents of trace metals in aquatic environments. Adsorption–desorption hysteresis has been documented for trace metals after aging, suggesting that they become incorporated over time. We previously found that ion size controls the extent of irreversible metal binding of single metals to goethite. In this study, we evaluate how the presence of multiple metals influences irreversible binding. Mixed Ni–Zn and Ni–Cd solutions were aged with goethite at pH 7 for 2 days, 30 days, and 60 days, after which isotope exchange experiments were performed to assess the lability of the adsorbed metal pools. After 2 days of aging, Ni and Cd in mixed-metal systems were more labile than in single-metal systems, indicating that competitive adsorption may partially block irreversible binding on short time scales. After 60 days, all three metals had larger irreversibly bound fractions than in single-metal systems. X-ray absorption near-edge structure (XANES) spectroscopy indicates that irreversibly bound fractions correlate with incorporation into goethite. This study demonstrates that pools of coadsorbed metals are bioaccessible on a time scale of minutes. Cooperative effects promote the structural sequestration of even large trace metals, causing reactive transport models to likely overpredict metal mobility. Long-term metal entrapment processes hinder micronutrient availability, impact contaminant sequestration and critical mineral recovery, and yield complex pathways through which metal solubilization may be enhanced or hindered during redox cycling.
58 GEOSCIENCES↗
Particle-Scale Reduction Analysis of CuFeMnO 4 with Hydrogen for Chemical Looping Combustion
In this work CuFeMnO 4 (copper iron manganese oxide) oxygen carrier was characterized using DSC/TGA, in-situ XRD, and SEM-EDS to gain a clear elucidation of the chemical looping combustion (CLC) reactions with H2 which is a component of synthesis gas. A reaction model which best described the experimental TGA reaction data was selected from the analysis. Intrinsic rate of reaction parameters obtained from the study could be used for designing a reactor for scale-up. A model with combined contributions from nucleation and growth model and dimensional phase boundary model was found to exhibit the best correlation with the experimental data. The analysis provided validation of intrinsic reaction rates and other rate parameters.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Controlled Release of Hydrogen Isotopes from Hydride-Magnetic Nanomaterials
In this work, hydrogen isotopes in the form of protium and deuterium were rapidly desorbed from magnetic-hydride iron oxide-palladium (Fe 2 O 3 -Pd) hybrid nanomaterials using an alternating magnetic field (AMF). Palladium, a hydride material with a well-known hydrogen isotope effect, was deposited on Fe 2 O 3 magnetic nanoparticle support by solution chemistries and used as a hydrogen isotope storage component. The morphological, structural, optical, and magnetic studies reveal that the Fe 2 O 3 -Pd nanoparticles (NPs) are hybrid structures exhibiting both hydrogen isotope storage (Pd) and magnetic (Fe 2 O 3 ) properties. The hydrogen isotope sorption/desorption behavior of metal hydride-magnetic nanomaterials was assessed by isothermal pressure-composition response curves (isotherms). The amount and rate of hydrogen isotope gas release was tuned by simply adjusting the strength of the magnetic field strength applied. Protium and deuterium displayed a similar loading capacity, namely H/M 0.55 and H/M=0.45, but different plateau pressures. Significant differences in the kinetics of release for protium and deuterium during magnetic heating were observed. A series of magnetically induced charge-discharge cycling experiments were conducted showing that this is a highly reproducible and robust process
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Multiscale Mechanical Characterization of Mineral-Reinforced Wood Cell Walls
Studying the multiscale mechanics of bio-based composites offers unique perspectives on underlying structure–property relations. Cellular materials, such as wood, are highly organized, hierarchical assemblies of load-bearing structural elements that respond to mechanical stimuli at the microscopic, mesoscopic and macroscopic scale. In this study, we modified oak wood with nanocrystalline ferrihydrite, a widespread ferric oxyhydroxide mineral, and characterized the resulting mechanical properties of the composite at various levels of organization. Ferrihydrite nanoparticles were deposited inside the wood cell wall by an in situ chemical reaction, resulting in increased stiffness and hardness of the functionalized secondary cell wall, as evidenced by region-specific nanoindentation tests under an electron microscope. Chemically modified and pristine wood samples were characterized by using atomic force microscopy in the bimodal frequency modulation mode, which produced topographical images from the cellular ultrastructure with high lateral resolution and localized nanomechanical information across distinct cell wall layers. In conclusion, despite mineral reinforcement at the cell wall level, the macroscopic fracture behavior examined through three-point flexural testing remained unchanged upon modification, as cell–cell adhesion could be impaired by harsh chemical conditions.
Cells↗
Scaling of the strange-metal scattering in unconventional superconductors
Marked evolution of properties with minute changes in the doping level is a hallmark of the complex chemistry that governs copper oxide superconductivity as manifested in the celebrated superconducting domes and quantum criticality taking place at precise compositions. The strange-metal state, in which the resistivity varies linearly with temperature, has emerged as a central feature in the normal state of copper oxide superconductors. The ubiquity of this behaviour signals an intimate link between the scattering mechanism and superconductivity. However, a clear quantitative picture of the correlation has been lacking. In this study we report the observation of precise quantitative scaling laws among the superconducting transition temperature (T c ), the linear-in-T scattering coefficient (A 1 ) and the doping level (x) in electron-doped copper oxide La 2-x Ce x CuO 4 (LCCO). High-resolution characterization of epitaxial composition-spread films, which encompass the entire overdoped range of LCCO, has enabled us to systematically map its structural and transport properties with unprecedented accuracy and with increments of Δx = 0.0015. Additionally, we have uncovered the relations T c ~ (x c - x) 0.5 ~ (A 1 $\square$ ) 0.5 , where x c is the critical doping in which superconductivity disappears and A 1 $\square$ is the coefficient of the linear resistivity per CuO 2 plane. The striking similarity of the T c versus A 1 $\square$ relation among copper oxides, iron-based and organic superconductors may be an indication of a common mechanism of the strange-metal behaviour and unconventional superconductivity in these systems.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗