Wavelength Dispersive Spectroscopy Research Articles

Brittle initiation of dissolution–precipitation creep in plagioclase-rich rocks: insights from the Bergen arcs, Norway

The initiation of ductile shear zones commonly occurs spatially associated with fluid-rock reactions along brittle precursors. In many cases the relative timing of fracturing, fluid infiltration, reaction, and recrystallisation is unclear, making it difficult to disentangle mechanisms of shear zone initiation from subsequent deformation and recrystallisation. Here we present the study of the transition from a dry plagioclase-diopside-garnet-scapolite host granulite-facies lithology to (1) a low strain amphibolite-facies rock, and (2) a transition from low strain to high strain amphibolite-facies lithologies. Hydration of the granulite-facies precursor at amphibolite-facies conditions produces an assemblage comprised dominantly of plagioclase-amphibole-zoisite-clinozoisite-kyanite-scapolite-quartz. Detailed study of plagioclase chemistry and microstructures across these two transitions using Electron Backscatter Diffraction (EBSD) and Wavelength Dispersive Spectrometry (WDS) allows us to assess the degree of coupling between deformation and fluid-rock reaction across the outcrop. Plagioclase behaves dominantly in a brittle manner at the hydration interface and so the initial weakening of the rock is attributed to grain size reduction caused by fracture damage and fluid infiltration at amphibolite-facies conditions. Extensive fracturing-induced grain size reduction locally increases permeability and allows for continuing plagioclase and secondary mineral growth during shear. Based on plagioclase microstructures, such as, an inherited but dispersed crystallographic preferred orientation (CPO), truncation of chemical zoning, and the dominance of fine (5–150 µm), slightly elongate, polygonal grains we conclude that deformation is dominantly facilitated by dissolution–precipitation creep assisted by grain boundary sliding in the shear zone.

Corrosion behaviors of single-layer and double-layer nickel alloy coatings fabricated by arc spraying and high-velocity oxy-fuel

This study investigates single-layer and double-layer thermally sprayed nickel alloy coatings (bond and top coatings). Ni-5 wt% Al and Ni-20 wt% Cr, were used as bond coatings, whereas highly alloyed Ni-based coatings, Hastelloy C276 or Inconel 625, were used as top coatings. Arc spraying (A) and high-velocity oxy-fuel (HVOF) techniques were used to create the coatings on a 304 stainless steel substrate. The samples were studied by performing potentiodynamic polarization tests in a 20 vol% H2SO4 solution at room temperature. The scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) and wavelength dispersive X-ray spectroscopy (WDS) techniques were used to investigate the microstructure and chemical composition of the coatings. The arc sprayed coatings are composed of a lamellar microstructure with low porosities, unmelted particles, and high oxides at the intersplats. A uniform and compact coating with minimal oxides and porosity was achieved for all coatings via HVOF technique. In single-layer coatings, arc spray coating surpasses HVOF coating owing to its oxide layers, which impede sulfuric solution penetration and bolster resistance against electrolyte infiltration. Double-layer coatings, comprising a bonding layer and a top coating, effectively alleviate microgalvanic corrosion between layers when using the same thermal spray method.

Fabrication of americium containing transmutation targets

An innovative, dust-free method for producing (U,Am)O2-x targets without the generation of Am-contaminated liquid waste has been successfully demonstrated in the Fuel Materials Laboratories at SCK CEN. The method comprises the fabrication of porous uranium oxide microspheres through internal gelation, using starch as a pore-former, and a single-step Am(NO3)3 aqueous solution infiltration process. Various samples containing targeted Am contents of 5, 10, 20, or 30 mol% were prepared. The concentration of the Am(III) stock solution was confirmed by ICP-MS and no other Am species than Am3+ were distinguished by UV–Vis spectrophotometry. The microstructural investigations revealed that the density of the porous host microspheres was approximately 65 %TD, with 30 vol% accessible porosity, suitable for an efficient infiltration. Microstructural analysis using SEM-EDS was performed on the sintered microspheres. Unexpectedly, EDS analysis was found to be incompatible due to detector interference from the 60 keV gamma-rays emitted by the sample. Therefore, examination of cross-sectioned (U,Am)O2-x microspheres was performed using wavelength dispersive spectrometry (WDS), which was unaffected by the soft gamma ray emission. A homogeneous mixing of Am and U was observed, without the formation of agglomerates with distinct doping levels. From the periphery to the center of the microspheres a radial gradient in Am content was observed, indicating a slight enrichment of Am on the surface of the microspheres. Overall, the nominal Am concentration was in very good agreement with the targeted content.

Physical simulation of the underclad heat affected zone in a reactor pressure vessel to study intergranular cracking

Underclad cracking in nuclear pressure vessels was of significant concern in the 1970s and 1980s before mitigating adjustments were made both to steel compositions and manufacturing practice. Unfortunately, the cracking mechanisms are still not well understood, and this can undermine confidence when changes to cladding operations are under consideration. In this work, Charpy-sized test coupons of 18MND5 steel were subject to a range of thermal cycles that can be experienced by the substrate immediately adjacent to the interface with the overlay. The Charpy test results are considered in combination with analysis of the samples through field emission gun (FEG) scanning electron microscopy (SEM) and wavelength dispersive X-ray spectroscopy (WDXS). The findings suggest that the heat affected zone subject to the coarse grained plus intercritical thermal cycle, before post weld heat treatment, has a peculiar and potentially brittle microstructure. However, in a steel with no obvious macrosegregation, no clear evidence of intergranular cracking in the early stages of the post weld heat treatment could be found. The second part of the work focuses on the effects of segregation regions in large forgings, more specifically ghost lines, on the tendency for underclad cracking. Ghost line regions that subsequently form a coarse grained heat affected zone (CGHAZ), and are then heated to just under the A1 temperature, seem to be the most prone to intergranular cracking. Cracking susceptibility appears to be associated with elevated concentrations of alloying and impurity elements at grain boundaries.

Additive manufacturing of high nitrogen austenitic steel using shell-core strategy

Laser Powder Bed Fusion/Metal (PBF-LB/M) is a promising technology for industrial applications, but challenges such as long process times remain. Innovations such as the shell-core approach aim to address this by creating a dense shell around a minimally exposed powder core, significantly reducing processing times, with full densification and property adjustments achieved by subsequent hot isostatic pressing (HIP). This study focuses on the fabrication of shell-core samples using a powder mixture of austenitic steel and Si3N4 to produce high nitrogen steel PBF-LB/M components, which are otherwise difficult to produce due to the limited nitrogen solubility in the melt. PBF-LB/M induces Si3N4 decomposition, resulting in Si and N loss through laser-powder interaction. Si3N4 particles in the still powdered regions serve as a source of N enrichment during HIP, circumventing the limitations of nitrogen solubility in the melt and exploiting the higher solubility in the solid. After HIP, energy dispersive spectrometry and electron backscatter diffraction reveal a fully austenitic matrix with Si diffusion seams mainly in non-laser-exposed areas. The Si3N4 dissolution during HIP contributes to an interstitial dissolved N content of about 0.189 mass%, which, together with the higher Si content, increases hardness. Wavelength dispersive spectrometry (WDS) and nanoindentation line scans show decreasing Si and N concentrations from core to shell, resulting in reduced (nano)hardness in the shell. This innovative approach demonstrates the potential to produce AM components with enhanced properties by overcoming the limitations of nitrogen solubility in the steel melt during PBF-LB/M.

Antibiofilm Properties and Demineralization Suppression in Early Enamel Lesions Using Dental Coating Materials.

This study aimed to investigate the effects of dental coating materials on Streptococcus mutans biofilm formation. The test materials were PRG Barrier Coat (PRG), BioCoat Ca (BioC), and FluorDental Jelly (FluorJ). Bovine enamel specimens were demineralized to mimic early enamel lesions. The biofilm was developed on a specimen treated with one of the materials by using a modified Robbins device flow-cell system. Scanning electron and fluorescence confocal laser scanning microscopy, viable and total cell counts, and gene expression assessments of the antibiofilm were performed. Ion incorporation was analyzed using a wavelength-dispersive X-ray spectroscopy electron probe microanalyzer. All materials allowed biofilm formation but reduced its volume. FluorJ was the only material that inhibited biofilm accumulation and had a bactericidal effect, revealing 0.66 log CFU in viable cells and 1.23 log copy reduction in total cells compared with the untreated group after 24 h of incubation. The ions released from PRG varied depending on the element. BioC contributed to enamel remineralization by supplying calcium ions while blocking the acid produced from the biofilm. In summary, the dental coating materials physically prevented acid attacks from the biofilm while providing ions to the enamel to improve its mechanical properties.

A new neodymium complex on renewable magnetic biochar nanoparticles as an environmentally friendly, recyclable and efficient nanocatalyst in the homoselective synthesis of tetrazoles.

Inexpensive, stable, selective, and recyclable nanocatalysts, waste regeneration, and utilization of safe and available solvents are of interest and important factors in laboratory science and industrial applications of green chemistry. Therefore, herein, biochar nanoparticles (BNPs) were synthesized through chicken manure pyrolysis as a novel method for waste recycling. Then, in order to improve their recyclability, the obtained BNPs were magnetized using magnetic nickel nanoparticles. Then, the surface of the biochar magnetic nanoparticles (BMNPs) was modified by (3-chloropropyl)trimethoxysilane (3-CPTMS) and further a novel neodymium Schiff-base complex was immobilized on the surface of the modified BMNPs, denoted as Nd-Schiff-base@BMNPs. The obtained supported neodymium complex was used as a practical, selective, biocompatible, commercial, and reusable heterogeneous nanocatalyst. The biochar support of this nanocatalyst was formed from pyrolysis of chicken manure; therefore, it is cheap, economically viable, green and also compatible with the principles of green chemistry. Nd-Schiff-base@BMNPs acts selectively in organic reactions and also it can easily be recovered using an external magnet and reused, which is compatible with the principles of green chemistry. This nanocatalyst was characterized by wavelength-dispersive X-ray spectroscopy (WDX), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), inductively coupled plasma (ICP), and N2 adsorption-desorption (BET method) techniques. In the next step, the catalytic utilization of Nd-Schiff-base@BMNPs was investigated in the homoselective synthesis of 5-substituted 1H-tetrazole compounds from [3 + 2] cycloaddition of sodium azide (NaN3) and organo-nitriles in PEG-400 as a green solvent. Utilizing PEG-400 as a solvent offers various advantages, e.g. cheap, readily available, and environmentally friendly solvent as well as rapid separation and high purity of products. Therefore, this work is fully compatible with the principles of green chemistry.

Visualizing the Effect of Temperature on Carbonate Salt Production in CO2 Electrolysis

Carbon dioxide (CO2) electrolysis is a novel and promising technology to tackle anthropogenic climate change by reducing our dependency on fossil fuels and creating a sustainable carbon cycle. However, current CO2 electrolysis suffers from low CO2 reduction reaction (CO2RR) selectivity and rapid gas diffusion electrode (GDE) degradation and flooding due to carbonate precipitation. As the hydrophilic precipitate accumulates in the porous structure of the cathode GDE, the liquid anolyte invades the pores, blocking the catholyte from reaching the catalyst layer. This effect promotes the adverse hydrogen evolution reaction and thus decreases the CO2RR selectivity (1). Current literature focuses on limiting carbonate precipitate formation as opposed to understanding the factors affecting its growth (2). While carbonate precipitation is dependent on the specific electrolyte in a flow cell, the impact of parameters, such as operating temperature and GDE porosity, on the nature of carbonate precipitation still need to be investigated (3).In this study, we examine the relationship between cell temperature with carbonate precipitate accumulation. A zero-gap alkaline membrane electrode assembly (MEA) was used with potassium carbonate as the anolyte and humidified CO2 as the catholyte. Electrochemical impedance spectroscopy was used to calculate the activation, ohmic, and mass transport losses of the cell before and after a constant current density phase where faradaic efficiency was measured to quantify the CO2RR selectivity degradation due to salt accumulation. Furthermore, to characterize precipitate growth, the cathode GDEs were imaged before and after electrochemical testing using scanning electron microscopy (SEM) and wavelength dispersive spectroscopy (WDS). To quantify precipitate-driven flooding over operation time, identical MEAs were imaged using operando X-ray synchrotron radiography over a range of temperatures. Through-plane images of the operating cell were processed to find the electrolyte thickness in the cathode GDE as a function of time. Radiography results revealed progressive, cyclical flooding as well as preferential gas pathways. Moreover, after four hours of constant current operation and at a cell temperature of 60℃, the catalyst layer exhibited large amounts of uniformly distributed precipitates, while the GDE contained large, localized precipitate crystals. This indicates that at high temperatures, carbonate precipitates significantly block the catalyst layer and cause flooding into the substrate layer. This work provides new insight into the effect of temperature on carbonate precipitate buildup, deepening the understanding of the mechanism responsible for precipitate degradation. M. E. Leonard, L. E. Clarke, A. Forner-Cuenca, S. M. Brown, and F. R. Brushett, ChemSusChem, 13 (2020).Y. Xu et al., ACS Energy Lett, 6, 809–815 (2021).E. R. Cofell, U. O. Nwabara, S. S. Bhargava, D. E. Henckel, and P. J. A. Kenis, ACS Appl Mater Interfaces, 13, 15132–15142 (2021).

Monitoring Copper Ion Leaching from a Metalloporphyrin-Based Cathode for Rechargeable Magnesium Batteries

Great efforts are being undertaken to characterize the fundamental processes of solid electrolyte interphase (SEI) formation, degradation, and initial conditioning steps of battery electrode materials, including organic electrode materials.[1] Imaging techniques, such as focused ion beam / scanning electron microscopy (FIB/SEM) tomography in combination with element mapping using energy- and wavelength-dispersive X-ray spectroscopy are employed to gain insight into distribution, interconnectivity, and porosity of active materials as well as electrolyte penetration and their influence on degradation processes after longer cycling times.[2] Additionally, electrochemical impedance spectroscopy[3] and anodic stripping voltammetry[4] are used to shed light on those processes. The metalloporphyrin-based material [5,15-bis(ethynyl)-10,20-diphenylporphinato]copper(II) (CuDEPP) has been used as an interesting material for cathodes and anodes of various battery chemistries. These materials undergo initial self-conditioning by electro-polymerization for monovalent ions. With respect to multivalent ions, like magnesium, this polymerization is far less pronounced and an exchange of the copper from the CuDEPP by magnesium ions appears to be occurring.[5] Gaining insight into this trans- or demetallation process induced by parameters like the electrochemical driving force during galvanostatic cycling is a complex analytical challenge.We report the use of Hg ultramicroelectrodes and anodic stripping voltammetry as a sensitive strategy to detect copper ion leaching from metalloporphyrin-based CuDEPP composite electrodes. We demonstrate in-situ/intermittent monitoring of copper ion release during the initial self-conditioning step of the active material while galvanostatic cycling of the battery electrode in dimethoxy ethane. This method could be used to assess the release of an ionic species from complex systems, like composite battery electrodes.

Micro-scale structural and chemical characterisation of deformed rocks with simultaneous in-situ synchrotron X-ray fluorescence and backscatter diffraction mapping

In-situ measurements of structural and chemical information on deformed rocks are required to understand microphysical deformation mechanisms, the relative timing of tectono-metamorphic events, and the interplay between deformation, fluid flow, and mineral reactions. Scanning-electron microscopy is commonly used for this purpose, because it can provide compositional information (via energy- or wavelength-dispersive spectroscopy and backscattered electron imaging) and crystallographic orientation data (via electron backscatter diffraction) for large fractions of thin sections down to nanometre resolution. However, elemental and crystal-structural data are usually acquired independently, introducing the need for registration of maps with different information and increasing instrument time. In addition, measuring element concentrations to levels below 1000 ppm increases acquisition times significantly, rendering the mapping of centimetre-scale areas with micrometre-resolution or below time-costly. Here, we introduce an alternative method using coeval synchrotron X-ray fluorescence microscopy (XFM) and X-ray backscatter diffraction mapping (XBDM) for the rapid acquisition of structural and compositional information down to the ppb level on whole rock sections with a spatial resolution down to ∼1 μm per pixel. We illustrate the principles of XFM/XBDM mapping on a sample of granitic mylonite. As example for the scientific potential of the new method, it is shown that the Ti distribution in quartz and feldspar can be accurately correlated with physical structure. A discussion of the limitations and opportunities of XFM/XBDM mapping for studying deformed rocks concludes this article.

RbEr2AsS7: A Rubidium-Containing Erbium Sulfide Thioarsenate(III) with (S2)2− Ligands According to RbEr2S(S2)[AsS2(S2)

The new rubidium-containing erbium sulfide thioarsenate(III) with the structured formula RbEr2S(S2)[AsS2(S2)] was obtained from the syntheses of elemental erbium (Er), arsenic sesquisulfide (As2S3) and rubidium sesquisulfide (Rb2S3) with elemental sulfur (S) at 773 K as transparent, orange, needle-shaped crystals. RbEr2AsS7 crystallizes monoclinically in the space group C2/c with a = 2339.86(12) pm, b = 541.78(3) pm, c = 1686.71(9) pm and β = 93.109(3) ° for Z = 8. The crystal structure features complex [AsS2(S2)]3− anions with two S2− anions and a (S2)2− disulfide dumbbell coordinating end-on as ligands for each As3+ cation. Even outside the ligand sphere of As3+, S2− and (S2)2− can be found as sulfide anions. Two distinct Er3+ cations are surrounded by either nine or seven sulfur atoms. The [ErS9] polyhedra are corner- and face-connected, while the [ErS7] units share common edges, both building chains along [010]. These different chains undergo edge connectivity with each other, resulting in the formation of corrugated layers, which are held together by Rb+ in chains of condensed [RbS9] polyhedra. So, a three-dimensional network is generated, offering empty channels along [010] apt to take up the As3+ lone-pair cations. Wavelength-dispersive X-ray spectroscopy verified a molar Rb:Er:As:S ratio of approximately 1:2:1:7 and diffuse reflectance spectroscopy showed the typical f–f transitions of Er3+, while the optical band gap was found to be 2.42 eV.

Real-time observation of polarization dependence of soft x-ray absorption spectrum during chemical reaction under near-ambient pressure conditions.

The real-time observation of the polarization dependence of soft x-ray absorption spectra during chemical reactions is realized by combining the fluorescence-yield wavelength-dispersive x-ray absorption spectroscopy technique with a 10Hz switching between horizontal and vertical polarizations. The soft x-ray absorption spectra for boththe horizontal and vertical polarizations are recorded every 100ms with a time difference of 50ms, which enables the real-time observation of changes in the anisotropic structure around the surface. The technique is applied to the oxidation reaction of a cobalt thin film under an air pressure of up to 25Pa, and it is suggested that an anisotropic structure appears during the growth of the cobalt oxide species. By using the developed technique, it is expected that the changes in the anisotropic structures, such as molecular orientations, are observed during chemical reactions under near-ambient pressure conditions, which gives a deeper insight into the understanding of the reaction mechanism.

Real-time observation of intermediate species in electrochemical oxygen evolution reactions on CoOx through soft X-ray absorption spectroscopy

Real-time monitoring of oxygen species during the oxygen evolution reaction (OER) on cobalt oxide, one of the major OER electrocatalysts, was achieved through operando observation using wavelength-dispersive X-ray absorption spectroscopy (XAS) at the oxygen K-edge. The XAS spectra were collected every 3 s during electrode potential sweeping for the OER, and oxygen intermediate species related to the rate-determining step of the OER were detected just below the onset potential. Moreover, the cobalt L-edge XAS results demonstrate that the Co3O4 species dominates the surface of the electrode at a relatively high potential region, where the OER occurs. The present technique has significant potential for application in the analysis of solid–liquid interfaces, whose fundamental understanding is useful for further improvement of electrocatalysis.

Chemical Composition Effects on the Microstructure and Hot Hardness of NiCrSiFeB Self-Fluxing Alloys Manufactured via Gravity Casting

Ni-Cr-Si-Fe-B self-fluxing alloys are commonly used in hardfacing applications; in addition, they are subjected to conditions of wear, corrosion, and high temperatures, but are not used in casting applications. In this work, gravity casting is presented as a potential manufacturing route for these alloys. Three alloys with different chemical compositions were investigated with a focus on microstructure characterization, solidification path, and strengthening mechanisms. Phases and precipitates were characterized using a field emission scanning electron microscope employing energy-dispersive X-ray spectroscopy, wavelength dispersive spectroscopy, and electron backscatter diffraction. Nano- and microhardness indentations were performed at different phases to understand their contribution to the overall hardness of the studied alloys. Hardness measurements were performed at room temperature and high temperature (650 °C). The borides and carbides were the hardest phases in the microstructure, thus contributing significantly to the overall hardness of the alloys. Additional hardening was provided by the presence of hard Ni3B eutectics; however, there was also a small contribution from the solid solution hardening of the γ-Ni dendrites in the high-alloy-grade sample. The amount and size of the different phases and precipitates depended mainly on the contents of the Cr, C, and B of the alloy.

Novel strategy toward color-tunable and glow-in-the-dark colorless smart natural wooden window

Smart windows that use photochromic colorless wooden materials are an intriguing and urgent area of research. Herein, we create afterglow transparent woods with UV-induced photochromic capability. Infiltrating a lignin-modified wood (LMW) with a solution of methyl acrylate (MA) and rare-earth strontium aluminum oxide (SrAl2O4: Eu2+, Dy3+; SAOED) yielded afterglow and photochromic translucent wood. Preparing photoluminescent transparent wood effectively requires dispersing SAOED phosphor nanoparticles (NPs) in pre-polymerized MA without clumping. CIE (Commission Internationale de ĺEclairage) Lab colorimetric studies indicated that this transparent timber substrate changed color from colorless in daylight to greenish when exposed to ultraviolet rays. Micrographs taken using a transmission electron microscope (TEM) were analyzed to learn more about the morphology of the synthesized SAOED NPs. Different characterization techniques were applied on the photochromic translucent wood samples, including scanning electron microscopy (SEM), energy-dispersive X-ray analyzer (EDX), hardness properties, wavelength-dispersive X-ray fluorescent spectroscopy (WD-XRF), and absorption and emission spectroscopy. Absorption maximum wavelength was detected at 365 nm. Both 436 nm and 517 nm were observed as emission wavelengths in the developed photoluminescence wood. The results displayed that the manufactured transparent wood introduced superior protection from UV radiation and superhydrophobic activity. UV light triggered a rapid and reversible photochromic reaction in the transparent luminous wood.

The Impact of Various Superalloys on the Oxidation Performance of Nanocrystalline Coatings at High Temperatures

Nanocrystalline coatings with the same chemical composition as an N5 superalloy were prepared on K38 and N5 superalloys by magnetron sputtering. The effect of different superalloys on the high temperature oxidation behavior of nanocrystalline coatings was investigated through oxidation kinetics, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and wavelength dispersive spectrometry (WDS). The results indicated that K38-N5 had better oxidation resistance than N5-N5 due to the diffusion of Zr from the K38 superalloy into the oxide scale. In addition, no interdiffusion occurred in the K38 superalloy. The formation of Ta-rich phases in the Al2O3 scale leads to decrease the oxidation resistance of nanocrystalline coatings. However, the presence of Zr inhibits the formation of Ta-rich phases.

Identification method for dental alloy type using a cosine similarity program: A preliminary investigation.

Although dental evidence is frequently used for the identification of unidentified persons, information about the many types of alloys used in prosthetics is not utilized. If the type of alloy can be identified from a small amount of material, the scope of the search could be narrowed. In this experiment, a method was investigated for identifying the alloy type using 3 kinds of cutting points (a white point and 2 types of silicone points). Wavelength-dispersive X-ray spectroscopy (WDS) was used for elemental analysis. The elements were translated into multidimensional vectors, and the cosine similarity was calculated to compare vectors of the WDS results and vectors of the official data of alloys. According to the results, cosine similarity showed a concordance of more than 0.8. The developed program is expected to be useful as a method for identifying alloy types using only a small amount of grinding dust.

Incorporation of antimony-bearing mining wastes into clinker Portland raw feed: The difficulty of Sb analysis in calcium silicates.

Within the global trend to valorise various mineral wastes as substituents in Portland cement clinker raw feed, mining wastes are promising candidates. However, they might still contain high levels of metallic elements. Their fate in the kiln is not always understood as well as their incorporation within the various clinker's phases. This is especially the case for antimony. Its in situ microanalysis by the means of energy-dispersive spectroscopy is tricky since several of its L lines (Lα1 = 3604,72eV, Lα2 = 3595,32eV) overlap with calcium lines (Kα1 = 3691,68eV, Kα2 = 3688,09eV). Hence, at low concentrations, it is not possible to visualise its characteristics peaks. Increasing the counting rate by increasing the acceleration current results in the generation of spurious sum peaks, rendering the analysis not viable. Wavelength dispersive spectroscopy (i.e. electron microprobe) allows a better spectral resolution and quantification of Sb in the clinker phases. In a Portland cement clinker doped with 1% of Sb-bearing mining waste, the Sb2O3 content in belite and alite is in the 0.2-0.4wt.% range as well as for C3A; in C4AF the content is higher, from 1.4wt.% to 2wt.%. However, there are microstructural evidence that Sb forms blebs from less than 1 μm in diameter up to 10 μm, included in calcium silicates. Hence, its incorporation in the lattice of calcium silicates is dubious. However, for ferrites and aluminates there is no microstructural evidence for remaining Sb-bearing phases, suggesting a direct incorporation in crystal lattices.

A comparative study of in-situ alloying in laser powder bed fusion for the stainless steel X2CrNiMoN20-10-3

This paper compares, for the first time, laser powder bed fusion (PBF-LB/M) processing of a powder mixture (PM), also known as in-situ alloying, with that of a pre-alloyed (PA) powder from gas atomization with the same chemical composition, using the example of X2CrNiMoN20-10-3 ferritic-austenitic stainless steel. The focus is on the differences in the microstructure formation mechanisms during PBF-LB/M between PM and PA using different energy inputs, in order to gain new insights into the process transferability of in-situ alloying to the processing of pre-alloyed powders. The microstructure investigations are carried out using electron backscattered diffraction (EBSD), energy dispersive (EDS) as well as wavelength dispersive X-ray spectrometry (WDS), X-ray diffraction (XRD) and magneto-inductive method (Feritscope®). The microstructures of samples produced from PM and PA differ significantly in terms of the resulting ferritic and austenitic phase fractions, so that a ferritic-austenitic microstructure forms for PM, while the PA is predominantly austenitic. The differences are mainly based on the increased chemical inhomogeneities for the PM in comparison to the PA state, which are discussed based on EDS map analysis through spatial statistics. With increasing energy input, the chemical homogeneity of the PM approaches that of the PA, but it cannot reach it even with maximum energy input. The formation of a ferritic-austenitic microstructure in the case of the PM leads to the formation of a finer microstructure compared to single-phase PA steel resulting in higher hardness of PBF-LB/M-built PM.

Role of oxygen potential in dopant solubility in ferrite magnets: Enhanced Zn solubility and magnetization in La–Zn co-substituted magnetoplumbite-type strontium ferrite

To improve the performance of magnetoplumbite-type (M-type) AFe12O19 (A = Sr, Ba, Pb,…) hard ferrite magnets, such as the remanent magnetization and the coercivity, it is effective to dope transition metal elements at the Fe site. Substitution of nonmagnetic Zn, which preferentially occupies a minority-spin site in the ferrimagnets, is expected to increase magnetization. However, the solubility of Zn is limited to approximately 2–3% of Fe when synthesized in air. The solubility of divalent transition-metal substituents achieved by simultaneous substitution with trivalent cations on the A-site is often limited due to the auto reduction of Fe3+ to Fe2+. In this study, La–Zn co-substituted M-type strontium ferrites, Sr1−xLaxFe12−yZnyO19, were synthesized under different oxygen pressures of pO2 = 0.2, 1, and 10 atm, and the phase equilibrium and chemical composition were established by X-ray diffraction and wavelength dispersive X-ray spectroscopy. At pO2 = 10 atm, Sr-free La–Zn co-substituted ferrite, LaFe11.25Zn0.75O19, and single phases with actual compositions (x, y) = (0.42, 0.33) and (0.50, 0.45) were obtained for the first time. The single-phase samples exhibited a 5–9% higher saturation magnetization compared to non-doped SrFe12O19 at room temperature. Together with the coercivity enhancement by Co2+ substitution, oxygen potential control is a promising strategy to tune both coercivity and magnetization in future ferrite magnets.