Backscattered Electron Imaging Research Articles

Experimental determination of Fe–Mg interdiffusion in orthopyroxene as a function of Fe content

We have measured the dependence of the Fe–Mg interdiffusion coefficient, DFe-Mg, on the ferrosilite component in orthopyroxene, which so far has not been experimentally calibrated. Diffusion couples, consisting of approximately 1 µm thin-films were deposited by pulsed laser ablation on orthopyroxene crystals of En91Fs9 composition. Diffusion experiments were carried out at atmospheric pressure in vertical gas mixing furnaces (CO-CO2) at temperatures between 950 and 1100 °C at constant fO2 = 10–7 Pa. Using a focused ion beam-scanning electron microscope (FIB-SEM), FIB-foils were cut from diffusion couples before and after annealing. Diffusion profiles were extracted by using combined backscattered electron (BSE) imaging and energy dispersive X-ray (EDXS) mapping on FIB-foils which allowed to resolve concentration gradients within 20 nm. The microstructure of the diffusion experiments was investigated using transmission electron microscopy (TEM). Using this method, we obtained the first experimentally determined data on the dependence of DFe-Mg on the ferrosilite content in orthopyroxene at different temperatures, appearing to increase with increasing a temperature. For the temperature range (950 – 1100 °C), log fO2 = -7 Pa, along [001] in the composition Fs9, the log DFe-Mg yields the following Arrhenius equation:DFe-Mg[m2/s]=3.8·10-9exp[-261.07±24[kJ/mol]/(R/T[K])]\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D_{Fe - Mg} [m^2 /s] = 3.8 \\cdot 10^{ - 9} \\exp [ - 261.07 \\pm 24[kJ/mol]/(R/T[K])]$$\\end{document}The effect of XFe on DFe-Mg, given by D(XFe)=D(XFe=0.09)·10m(XFe-0.09),\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D(X_{Fe} ) = D(X_{Fe} = 0.09) \\cdot {10}^{m (X_{Fe} - 0.09)},$$\\end{document} can be calculated by the following parameterization where m follows a linear regression of m on temperature: m=-2.711·104/T(K)+23.5408\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m = - 2.711 \\cdot 10^4 /T(K) + 23.5408$$\\end{document}By considering the DFe-Mg dependence on XFe, the timescales of natural processes obtained from modelling the compositional zoning of natural crystal may considerably differ from previously estimated timescales.

Exploring synergistic effects and hydration mechanisms in metakaolin-blended cement system with varying metakaolin and wollastonite content

The quest for sustainable construction practices has led to a growing interest in reducing cement consumption, with supplementary cementitious materials emerging as a promising solution. While reactive admixtures have been extensively studied, there is a noticeable research gap regarding inert admixtures, a critical component of cementitious systems. This paper introduces a novel metakaolin-blended cement system, optimizing the metakaolin, wollastonite, and ground quartz ratios to enhance microstructure and performance. Within this complex quaternary system, we conduct a comprehensive investigation, including assessments of compressive strength, setting times, heat release during hydration, R3 test. Furthermore, we explore hydration products and microstructure through thermogravimetric analysis, X-ray diffraction, backscattered electron imaging, and mercury intrusion porosimetry. The results indicate the influence of wollastonite on clinker reactions and hydration. Although wollastonite slightly increases meso-scale pores, its fibrous shape enhances the overall microstructure. Substituting 50% of metakaolin with wollastonite not only enhances the pozzolanic reactivity but also leads to improved long-term strength. Moreover, the synergistic effect of wollastonite and metakaolin allows for precise tailoring setting times and modulate hydration kinetics, thereby enhancing the overall performance of the cementitious system.

The role of supplementary cementitious materials and fiber reinforcements in enhancing the sulfate attack resistance of SCC/ECC composite systems

The purpose of this study is to investigate the effects of sulfate exposure on the mechanical behavior of fresh-to-fresh composite systems (CS), incorporating self-compacting concrete (SCC) in compression and engineered cementitious composites (ECC) in tension. ECCs were designed based on various supplementary cementitious materials (SCM) such as low and high calcium fly ash, slag and reinforcing fibers such as PVA and steel fibers. Repeated cycles of immersion in concentrated sodium sulfate solution were followed by drying at high temperatures (80 °C). After 90 and 180 days of cyclic exposure, the mechanical properties including flexural, compressive and tensile bond strength and mass change were evaluated. To investigate microstructural deterioration and reaction product concentration, SEM-EDS and backscattered electron imaging were used to examine sulfate profiles at the interfacial zone between SCC and ECC. Composite samples demonstrated excellent physico-mechanical resilience. The incorporation of low calcium fly ash and slag was observed to have a beneficial impact on residual mechanical properties in long-term exposures, along with the de-passivation capacity of the reinforcing fibers. No physical de-bonding was observed in any CS, however phase assemblages revealed high concentrations of reaction products in the SCC layers near the interfacial bond with the ECC layers.

Quantitative analysis of sintered NdFeB backscattered electron images based on a general large model

The macroscopic performance of magnets is determined by their microscopic structure, quantifying the microscopic image of magnets is of great importance for studying its performance. Backscattered electron images of sintered NdFeB magnets contain information about the size, morphology, and distribution of grains and the grain boundary phases. Traditional methods for quantifying images involve labor-intensive manual measurements, digital image processing with complex contour extraction algorithms, and convolutional neural network algorithms that require extensive image data labeling. In this study, we introduced a general vision large model called Segment Anything Model(SAM) for image segmentation. SAM enables rapid and accurate segmentation of grains and grain boundary phases without the need for complex algorithms and tedious data labeling. From the segmented mask images, we extracted various data related to the performance of magnets, including the centroid positions, perimeter, area, sphericity, roughness, and principal axis directions of all grains. We also obtained information on the distances and angles between adjacent grains and the relevant parameters affecting magnet performance, such as the number and volume of grain boundary phases. We conducted comprehensive quantification of the backscattered images for three different magnets and provided reasonable explanations for the differences in magnet performance. This model offers superior speed and accuracy in image quantification compared to traditional algorithms and can be used for the rapid analysis of large datasets. It represents an essential method and trend for the quantification of image data in the future.

Plagioclase as archive of the incremental assembly of the Quxu batholith, South Tibet: Implication for the nature of magma reservoir

The formation of magma reservoir and resultant construction of large batholith are increasingly recognized as long-term incremental processes. Here we employed back-scattered electron and cathodoluminescence images, in-situ major and trace elements, and Sr isotopes of plagioclase for five lithological groups from the Quxu complex batholith (south Tibet), which shed new light on the nature and incremental construction processes of batholith. Our results show that plagioclases display diverse textures and show systematic differences in geochemistry and Sr isotopes for different lithologies, indicating that their host rocks originated from multiple magma sources and/or underwent distinct magmatic processes. Plagioclases in Group I granodiorites and Group III mafic dykes and mafic magmatic enclaves exhibit comparable textural features (e.g., resorption and sieved textures) and share similar Sr (< 1500 ppm) and Ba (< 200 ppm) contents, and 87Sr/86Sr ratios (ISr) (0.7035–0.7050) at given lower An (20–50) values, suggesting that they were evolved from similar mafic magma sources. The significant variations in An (20–90), Sr and Ba contents of plagioclase in Group III indicate both fractional crystallization and magma mixing. Plagioclases in Group II monzogranites have a similar An ranges to Group I but higher Sr (900–2200 ppm) contents and ISr (mostly 0.7045 to 0.7066) values, suggesting that they formed from partial melting of juvenile mafic crust without significant mantle contribution. Plagioclases in Group IV granodiorites and Group V monzogranites exhibit higher Sr (500–3000 ppm) contents than other groups at given An values. Their ISr values fall within the range of Group II, indicating a similar magma source. Abundant plagioclases displaying normal and oscillatory zonings in them implies that fractional crystallization occurred, while the presence of typical glomerocrysts in Group V indicates mush disaggregation. The simulation results of the trace elements indicate that the different lithologies of the Quxu batholith represent different states of magma reservoirs, corresponding to crystal mushes with varying degrees of extracted melts. The incremental growth processes of lager batholith operate as an open system, in which magma convection, mixing and recharge, crystal accumulation, recycling and reaction with melts, and mush disaggregation commonly occur.

Phosphorus fractions and speciation in an alkaline, manured soil amended with alum, gypsum, and Epsom salt.

Snowmelt runoff is a dominant pathway of phosphorus (P) losses from agricultural lands in cold climatic regions. Soil amendments effectively reduce P losses from soils by converting P to less soluble forms; however, changes in P speciation in cold climatic regions with fall-applied amendments have not been investigated. This study evaluated P composition in soils from a manured field with fall-amended alum (Al2(SO4)3·18H2O), gypsum (CaSO4·2H2O), or Epsom salt (MgSO4·7H2O) using three complementary methods: sequential P fractionation, scanning electron microscopy with energy-dispersive X-rays (SEM-EDX) spectroscopy, and P K-edge X-ray absorption near-edge structure spectroscopy (XANES). Plots were established in an annual crop field in southern Manitoba, Canada, with unamended and amended (2.5 Mg ha-1) treatments having four replicates in 2020 fall. Soil samples (0-10cm) taken from each plot soon after spring snowmelt in 2021 were subjected to P fractionation. A composite soil sample for each treatment was analyzed using SEM-EDX and XANES. Alum- and Epsom salt-treated soils had significantly greater residual P fraction with a higher proportion of apatite-like P and a correspondingly lower proportion of P sorbed to calcite (CaCO3) than unamended and gypsum-amended soils. Backscattered electron imaging of SEM-EDX revealed that alum- and Epsom salt-amended treatments had P-enriched microsites frequently associated with aluminum (Al), iron (Fe), magnesium (Mg), and calcium (Ca), which was not observed in other treatments. Induced precipitation of apatite-like species may have been responsible for reduced P loss to snowmelt previously reported with fall application of amendments.

Pronounced cortical porosity and sex-specific patterns of increased bone and osteocyte lacunar mineralization characterize the human distal fibula with aging

The high occurrence of distal fibula fractures among older women suggests a potential link to impaired bone health. Here we used a multiscale imaging approach to investigate the microarchitecture, mineralization, and biomechanics of the human distal fibula in relation to age and sex. Micro-computed tomography was performed to analyze the local volumetric bone mineral density and various microarchitectural parameters of the trabecular and the cortical compartment. Bone mineral density distribution and osteocyte lacunar parameters were quantified using quantitative backscattered electron imaging in periosteal, endocortical, and trabecular regions. Additionally, cortical hardness and Young's modulus were assessed by nanoindentation. While cortical porosity strongly increased with age independent of sex, trabecular microarchitecture remained stable. Notably, nearly half of the specimens showed non-bony hypermineralized tissue located at the periosteum, similar to that previously detected in the femoral neck, with no consistent association with advanced age. Independent of this finding, cortical and trabecular mineralization, i.e., mean calcium content, as well as endocortical tissue hardness increased with age in males but not females. Importantly, we also observed mineralized osteocyte lacunae that increased with age specifically in females. In conclusion, our results indicate that skeletal aging of the distal fibula is signified not only by pronounced cortical porosity but also by an increase in mineralized osteocyte lacunae in females. These findings may provide an explanation for the increased occurrence of ankle fractures in older women.

An Edge Detection Algorithm for SEM Images of Multilayer Thin Films

In processing multilayer thin film materials, scanning electron microscopy (SEM) is commonly employed for observation. In images of SEM, backscattered electron (BSE) images is particularly suitable for distinguishing different components and layers of the films. However, at high magnification levels, BSE images often have blurriness and noise, leading to low edge sharpness. This study proposes a method for improving the integrity and accuracy of the edges. First, we segment the image into different contrast regions using the masking algorithm. Second, we enhance the images in separate regions by the enhancement algorithm. Finally, we combine the regions by logical operations. In instantiation, we implement our approach on SEM-BSE images. It was found that the edges are significantly sharpened through the assessment of the edge evaluation algorithm.

Gamma-enhancement of reflected light images as a routine method for assessment of compositional heterogeneity in common low-reflectance Fe-bearing minerals

Abstract Incorporation of impurity elements into minerals impacts on their physical properties (e.g., reflectance, hardness, and electrical conductivity) but the quantitative relationships between these features and compositional variation remain inadequately constrained. Prior work has shown that gamma-enhancement of reflected light images represents a simple yet powerful tool to assess the compositional heterogeneity of single pyrite crystals as it can enhance subtle differences in reflectance between distinct domains with different minor element concentrations. This study extends the gamma correction method to several other common Fe-bearing minerals, magnetite, garnet, wolframite, and tetrahedrite-tennantite, which all have far lower reflectance than pyrite. Gamma-enhanced optical images reveal clear variations in reflectance that are either systematic with increased minor element concentration as the change in gray value on backscatter electron (BSE) images (in the case of magnetite, garnet, and tetrahedrite-tennantite) or contrasting (as in pyrite), yielding a convincing linkage between reflectance variation and compositional heterogeneity. Reflectance variation is an expression of the distribution of the average effective number of free electrons on the mineral surface that can re-emit light when excited by visible light. Gamma-enhanced images can reveal compositional heterogeneity in minerals such as wolframite where small atomic mass differences between substituting elements (Mn and Fe, in the case of wolframite) are virtually impossible to observe as a variation of gray values on BSE images. Results also demonstrate that Fe-rich domains in these minerals can be expected to have higher reflectance than Fe-poor domains whenever Fe is a major constituent. The greater reflectance is attributed to Fe ions having a greater effective number of free electrons than many other elements (e.g., Co, Ni, Si, Ca, Al, Mg, Mn, and As). The research highlights the utility of gamma correction as an inexpensive tool for routine evaluation of compositional heterogeneity in common Fe-bearing minerals, potentially obviating the necessity of a microbeam platform to correlate textures and composition.

Alterations in compositional and cellular properties of the subchondral bone are linked to cartilage degeneration in hip osteoarthritis

ObjectiveThe subchondral bone is an emerging regulator of osteoarthritis (OA). However, knowledge of how specific subchondral alterations relate to cartilage degeneration remains incomplete. MethodFemoral heads were obtained from 44 patients with primary OA during total hip arthroplasty and from 30 non-OA controls during autopsy. A multiscale assessment of the central subchondral bone region comprising histomorphometry, quantitative backscattered electron imaging, nanoindentation, and osteocyte lacunocanalicular network characterization was employed. ResultsIn hip OA, thickening of the subchondral bone coincided with a higher number of osteoblasts (controls: 3.7±4.5 mm-1, OA: 16.4±10.2 mm-1, age-adjusted mean difference 10.5 mm-1 [95% CI 4.7 to 16.4], p<0.001) but a similar number of osteoclasts compared to controls (p=0.150). Furthermore, higher matrix mineralization heterogeneity (CaWidth, controls: 2.8±0.2 wt%, OA: 3.1±0.3 wt%, age-adjusted mean difference 0.2 wt% [95% CI 0.1 to 0.4], p=0.011) and lower tissue hardness (controls: 0.69±0.06 GPa, OA: 0.67±0.06 GPa, age-adjusted mean difference -0.05 GPa [95% CI -0.09 to -0.01], p=0.032) were detected. While no evidence of altered osteocytic perilacunar/canalicular remodeling in terms of fewer osteocyte canaliculi was found in OA, specimens with advanced cartilage degeneration showed a higher number of osteocyte canaliculi and larger lacunocanalicular network area compared to those with low-grade cartilage degeneration. Multiple linear regression models indicated that several subchondral bone properties, especially osteoblast and osteocyte parameters, were closely related to cartilage degeneration (R2 adjusted=0.561, p<0.001). ConclusionSubchondral bone properties in OA are affected at the compositional, mechanical, and cellular levels. Based on their strong interaction with cartilage degeneration, targeting osteoblasts/osteocytes may be a promising therapeutic OA approach. Data and materials availabilityAll data are available in the main text or the supplementary materials.

Effects of carbon content on precipitate evolution and crack susceptibility in additively manufactured IN738LC

Hot cracking is a major bottleneck preventing the additive manufacturing community from adopting precipitation-strengthened nickel-base superalloys, such as the IN738LC. Prior literature demonstrates the beneficial outcome of increasing the carbon content within IN738LC to alleviate its hot cracking problem. However, the effect of carbon content on the gamma prime precipitation and grain recrystallization was not fully addressed. Here, we fabricated five sample sets of IN738LC with different carbon contents and subjected these samples to two separate heat treatment processes. The precipitate and grain evolution were monitored under the backscattered electron imaging and electron backscattered diffraction studies. While the carbon addition could assist in addressing the hot cracking problem, horizontal delamination cracks were detected during the fabrication of large samples when the overall carbon content was above 0.4 wt.%, highlighting the need for care when introducing carbon for the purpose of resolving hot cracking.

Petrogenesis of a new type of intrusive shergottite: olivine-gabbro Northwest Africa 13227

Petrologic investigations of martian meteorite Northwest Africa (NWA) 13227 indicate it is an olivine-gabbroic shergottite, a relatively new shergottite group, which differs from previously described gabbroic shergottites due to relatively high quantities of olivine. NWA 13227 is comprised of phenocrystic, oscillatory-zoned pyroxene and olivine, set in a matrix of maskelynite, Fe-Cr-Ti oxides, phosphates, and sulfides. It displays gabbroic and poikilitic textures in 2D from back-scattered electron images, and in 3D from X-ray Computed Tomography (XCT) imaging, suggesting affinities to both poikilitic and gabbroic shergottites. Measured εHf and εNd values of bulk rock (-19.7 and −5.9, respectively) and its chondrite-normalized La/Yb ratio of 1.13 indicate the specimen is derived from a mantle reservoir relatively enriched in incompatible trace elements and is similar to that which produced most ‘enriched shergottites.’ Based on the Ti/Al ratio of pyroxene, phosphorous zoning in olivine, and minor components in phosphates and oxides, we infer that NWA 13227 began crystallizing under reducing conditions of QFM–2.6 and temperatures of ∼ 1100 °C, consistent with conditions in Mars’ lower crust/upper mantle. The sample finished crystallizing at or near the surface under redox conditions between QFM–0.5 to QFM–0.1 and temperatures of ∼ 850 °C. The volatile element compositions in apatite indicate that NWA 13227 experienced degassing during the last stages of crystallization. The timing of crystallization is estimated at 225 Ma ± 50 Ma using a Lu-Hf and Sm-Nd source versus age model.

Sequential Bayesian-optimized graphene synthesis by direct solar-thermal chemical vapor deposition

This work reports the use of a high-flux solar simulator that mimics the solar spectrum and a cold-wall CVD reactor to demonstrate the feasibility of utilizing a renewable energy resource in synthesizing graphene under various conditions. A parametric study of process parameters was conducted using a probabilistic approach. Gaussian process regression serves as a surrogate to establish a prior for Bayesian optimization, and an information acquisition function is employed to identify conditions that yield high-quality products. Backscattered electron images and Raman mapping were used to assess the effects of growth conditions on graphene characteristic sizes, film quality, and uniformity. We report the synthesis of high-quality single-layer graphene (SLG) and AB-stacked bilayer graphene films in a one-step, short-time process with ID/IG\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$I_{D}/I_{G}$$\\end{document} ratios of 0.21 and 0.14, respectively. Electron diffraction analysis shows peak intensities that resemble SLG and AB-bilayer graphene with up to 5 and 20 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upmu }$$\\end{document}m grain sizes, respectively. The optical transmissivities of SLG and AB-bilayer graphene fall between 0.959–0.977 and 0.929–0.953, whereas the sheet resistances measured by a 4-point probe with 1 mm spacing are 15.5 ± 4.6 and 3.4 ± 1.5 kΩ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Omega$$\\end{document}/sq, respectively. Further scale-up of the optimized graphene growth area was achieved by flattening the insolation profile, leading to spatial uniformity up to 13 mm in radius. Direct solar capture for CVD synthesis enable a practical and sustainable option for synthesizing graphene films applicable for photonic and electronic applications.

Significant impact of TiO2 purity on the phase structure and electrical properties of BiFeO3–BaTiO3 lead‐free piezoelectric ceramics

AbstractIn many studies, the properties of BiFeO3–BaTiO3 (BF–BT) ceramics vary greatly using different raw reagents, which makes it challenging to obtain reliable and repeatable properties of BF–BT‐based devices. In this work, 0.7BiFeO3–0.3BaTiO3 (0.7BF–0.3BT) ceramics were fabricated by a conventional solid‐phase synthesis using TiO2 reagents with varied purities of 98%, 99%, 99.9%, and 99.99%, respectively. The phase structure, microstructure, ferroelectric, and piezoelectric properties were comprehensively studied. All compositions of the ceramics exhibit a pseudo‐cubic phase perovskite structure, and the fraction of the rhombohedral phase increases with increasing the TiO2 purity. Additionally, backscattered electron images and energy‐dispersive spectroscopy revealed an obvious core–shell structure within grains. In particular, the 0.7BF–0.3BT ceramics prepared with 98% purity TiO2 exhibited superior ferroelectric and piezoelectric properties, d33 ∼ 220 pC/N and ∼ 230 pm/V. The ceramics prepared with higher purity TiO2 suffered from severe leakage conduction, which can be well addressed by adding excess TiO2. Our work reveals the importance of different grades of purity TiO2 on the electrical properties of BF–BT ceramics.

Comparison of large-volume 3D reconstruction using plasma FIB-SEM and X-ray CT.

We demonstrated large-volume three-dimensional (3D) reconstruction using plasma-focused ion beam-scanning electron microscopy (PFIB-SEM). We successfully reconstructed a 750 μm (W) × 143 μm (H) × 310 μm (D) volume at a resolution of 200 nm/pix from 1550 SEM backscattered electron images of a Li-ion battery cathode sheet. The PFIB-SEM system was found to be capable of acquiring and reconstructing larger volume 3D datasets than X-ray computed tomography, and with higher resolution and contrast.

Electrodeposition of Dy and its grain boundary diffusion behavior of sintered NdFeB magnets

This paper presents the electrodeposition of a Dy layer onto the surface of sintered NdFeB magnets to serve as a diffusion source. Subsequently, the sintered NdFeB magnets were subjected to grain boundary diffusion treatment through electrochemical deposition at the solution temperature of 45 °C and the solution pH (hydrogenii) of 4.0. The results indicated that the coercivity of the Dy-diffused magnet increased from 1073 kA/m to 1418 kA/m compared to the original magnet after annealing at a primary diffusion heat treatment temperature of 900 °C for 6 h and subjected to the same secondary tempering heat treatment at 500 °C for 2 h, while the remanence remained relatively unaffected. SEM (Scanning Electron Microscopy) revealed that the Dy coating exhibited a compact and flat surface with a small grain size. Energy spectrum analysis confirmed a relatively uniform distribution of Dy elements in the electrodeposition coating, without any significant agglomeration. SEM-EDS (Scanning Electron Microscopy-Energy Dispersive Spectrometer) line scan demonstrated that the diffused Dy elements along the grain boundary phase primarily concentrated in the grain boundary phase itself and the epitaxial layer of the main grains. BSE (Backscattered Electron imaging) revealed the presence of a thin and continuous grain boundary phase structure between the main phases following grain boundary diffusion. XRD (X-ray diffraction) analysis demonstrated a general shift toward higher angles in the main peak of NdFeB after Dy diffusion. The remarkable increase in coercivity of the diffused Dy magnets can be attributed to the optimization of microstructure, grain boundary phase composition, and the formation of the (Dy,Nd)2Fe14B structure. The coercivity mechanism in diffusion Dy magnets was still governed by a nucleation reversal mechanism, as supported by the Kronmüller-Plot curve fitting. Tafel tests have revealed that Dy-diffused magnets have a much higher corrosion resistance with a more positive equilibrium potential, Ecorr, and a lower corrosion current density, Icorr.

Structural and compositional data for childrenite from the Homolka granite, Czech Republic

Abstract. Members of the childrenite–eosphorite series, ideally (Fe1−xMnx)AlPO4(OH)2⋅H2O, from the highly evolved Homolka granite, in the southern Czech Republic, were characterized using a multi-analytical approach. They occur as anhedral grains, up to ∼0.2 mm in size, associated with quartz, muscovite, albite, and K-feldspar. Tiny inclusions of probable uraninite have been observed. Backscattered electron images reveal a patchy zoning of these members of the childrenite–eosphorite series, related to an uneven distribution of Fe and Mn. On the basis of electron microprobe analysis, the average composition of the studied material is (Fe0.68Mn0.28Ca0.03)Σ0.99Al0.96(P1.04Si0.01)Σ1.05O4.00(OH)2.09⋅0.91H2O, thus corresponding to childrenite. Unit-cell parameters of this species are a=6.9226(9), b=10.4081(13), c=13.3957(17) Å. Its crystal structure was refined in the space group Cmca down to R1=0.0295 on the basis of 602 unique reflections with Fo&gt;4σ(Fo) and 66 refined parameters. The crystal structure analysis agrees with the results of electron microprobe analysis and suggests that, in the studied material, Fe occurs in the divalent oxidation state only. Crystal structure data are also consistent with the Raman spectrum collected on the same grain that was structurally characterized, confirming the occurrence of PO4 groups only in childrenite.

Selective Visualization of Martensite in Bainitic Steel Using Backscattered Electron Images and Phase Fraction Evaluation Using Machine Learning

Selective Visualization of Martensite in Bainitic Steel Using Backscattered Electron Images and Phase Fraction Evaluation Using Machine Learning

Influence of Heat Treatment on Elinvar Properties of a 40NiCrTiAl Alloy

This study investigates the effect of heat treatment on the microstructure and Elinvar properties of a cold-rolled 40NiCrTiAl alloy. This study utilizes optical microscopy, scanning electron microscopy backscattered electron imaging, secondary electron imaging, and energy-dispersive X-ray spectroscopy analysis to observe the precipitation behavior and determine the composition within the material. The results show that the 40NiCrTiAl Elinvar alloy at aging temperatures of 600-700°C, spherical precipitates appear within the grains. At approximately 700°C and with an aging time of around 2 hours, the precipitate volume reaches a peak, and the Young’s modulus and Elastic modulus temperature coefficient also reach their respective peaks. These elastic performance indicators exhibit a strong linear relationship with the degree of precipitate formation. These findings are important for a deeper understanding of the application potential and performance optimization of this Elinvar alloy.

Tetrad Effect of Rare Earth Element Fractionation in Zircon from the Pegmatite of the Adui Massif, Middle Urals

The zircon from the pegmatite of the Adui granitic massif displays the unique the rare earth element (REE) distribution spectrum with the tetrad effect in REE fractionation. The tetrad effect often occurs in granitoid rocks, but it is rarely encountered in minerals, e.g., zircon. Fluid saturated with volatiles, water and trace elements is a factor responsible for the tetrad effect in the zircon. The detailed isotopic-geochemical study of the zircon has revealed several zones differing in internal structure (in the back-scattered electron (BSE) image), composition and REE distribution. The zones indicate changes in the crystallization environment provoked by the evolution of the pegmatite-forming melt. They occur as the gradually growing changes in composition from the unaltered zones that are light-colored in BSE to the altered zones that are dark-colored in BSE. The unaltered zones are consistent in composition and geochemical features with magmatic zircons. The high content of trace (U, Th, REE) and volatile elements (F, Cl) in water suggests its crystallization from the fluid-saturated magmatic melt. The altered zircon zones occur as recrystallized zones with high content of non-formula elements (Y, Ca, Sr, Nb, P), a non-differentiated REE distribution spectrum and an absent Ce anomaly. These features are consistent with those of hydrothermal-metasomatic zircon.