Electron Backscatter Research Articles

High-Resolution Cathodoluminescence Images of Igneous and Metamorphic Monazite.

Monazite is one of the most important dating accessory minerals for deciphering geological processes. The growth history of monazite can be identified by its internal structure; thus, high-resolution imaging is necessary for in situ U-Th-Pb dating. In this study, cathodoluminescence (CL) techniques were optimized via the key parameters of working distance, accelerating voltage, and beam current and were then applied to monazites from igneous and metamorphic rocks. The CL images of igneous monazites show concentric oscillatory zoning, whereas those of metamorphic monazites clearly show homogeneous, patchy, or core-rim structures. CL imaging is a more effective approach than back-scattered electron (BSE) imaging for the observation of the internal structure of monazite and may yield additional information. CL can add to the interpretation of X-ray maps and the two techniques that may complement each other. The CL spectra of monazite consist of broad peaks and sets of narrow emission rare earth element 3+ (REE3+) peaks (Gd3+, Tb3+, Dy3+, and Sm3+). The microstructures observed via CL imaging techniques can show a certain relationship between light REE (LREE) and U, Th, and Si in some igneous monazites and heavy REE (HREE) variation in some metamorphic monazites.

Influence of the Graphene Oxide on the Pore-Throat Connection of Cement Waste Rock Backfill.

The pore-throat characteristics significantly affect the consolidated properties, such as the mechanical and permeability-related performance of the cementitious composites. By virtue of the nucleation and pore-infilling effects, graphene oxide (GO) has been proven as a great additive in reinforcing cement-based materials. However, the quantitative characterization reports of GO on the pore-throat connection are limited. This study applied advanced metal intrusion and backscattered electron (BSE) microscopy scanning technology to investigate the pore-throat connection characteristics of the cement waste rock backfill (CWRB) specimens before and after GO modification. The results show that the microscopic pore structure of CWRB is significantly improved by the GO nanosheets, manifested by a decrease in the total porosity up to 31.2%. With the assistance of the GO, the transfer among internal pores is from large equivalent pore size distribution to small equivalent pore size distribution. The fitting relationship between strength enhancement and pore reinforcement efficiency under different pore-throat characteristics reveals that the 1.70 μm pore-throat owns the highest correlation in the CWRB specimens, implying apply GO nanosheets to optimizing the pore-throat under this interval is most efficient. Overall, this research broadens our understanding of the pore-throat connection characteristics of CWRB and stimulates the potential application of GO in enhancing the mechanical properties and microstructure of CWRB.

Effects of sufficient carbonation on the strength and microstructure of CO2-cured concrete

To maximize its potential in capturing CO2, concretes with various water-to-binder (w/b) ratios underwent a sufficient carbonation through CO2 curing in this study. The variations in the compressive strength and microstructure of concrete were examined. Thermogravimetric analysis (TGA), scanning electron microscopy (SEM) with backscatter electrons (BSE), and mercury injection porosimeter (MIP) were employed to investigate the amount of CO2 captured by concrete, the changes in the microstructure of cement hydrates and interface transition zone (ITZ), and the pore structure, respectively. The results indicate that the amount of CO2 captured by concrete can be increased through two aspects: (1) an increase in carbonation depth, and (2) an increase in the CO2 uptake per unit mass of cement paste. Additionally, the compressive strengths of concrete at the ages of 28 and 56 days show a significant improvement, and this differs from existing studies in which CO2 curing primarily improves the compressive strength at early age. The porosity deceases due to a reduction in the volume of pores with a diameter less than 50 nm. An increase in the degree of cement reaction results in a denser ITZ. The pH of concrete decreases to about 8.9, which means that CO2-cured concrete with a sufficient carbonation could be applied in moderate or low humidity environments.

Bone structure and composition in a hyperglycemic, obese, and leptin receptor-deficient rat: Microscale characterization of femur and calvarium.

Metabolic abnormalities, such as diabetes mellitus and obesity, can impact bone quantity and/or bone quality. In this work, we characterize bone material properties, in terms of structure and composition, in a novel rat model with congenic leptin receptor (LepR) deficiency, severe obesity, and hyperglycemia (type 2 diabetes-like condition). Femurs and calvaria (parietal region) from 20-week-old male rats are examined to probe bones formed both by endochondral and intramembranous ossification. Compared to the healthy controls, the LepR-deficient animals display significant alterations in femur microarchitecture and in calvarium morphology when analyzed by micro-computed X-ray tomography (micro-CT). In particular, shorter femurs with reduced bone volume, combined with thinner parietal bones and shorter sagittal suture, point towards a delay in the skeletal development of the LepR-deficient rodents. On the other hand, LepR-deficient animals and healthy controls display analogous bone matrix composition, which is assessed in terms of tissue mineral density by micro-CT, degree of mineralization by quantitative backscattered electron imaging, and various metrics extrapolated from Raman hyperspectral images. Some specific microstructural features, i.e., mineralized cartilage islands in the femurs and hyper-mineralized areas in the parietal bones, also show comparable distribution and characteristics in both groups. Overall, the altered bone microarchitecture in the LepR-deficient animals indicates compromised bone quality, despite the normal bone matrix composition. The delayed development is also consistent with observations in humans with congenic Lep/LepR deficiency, making this animal model a suitable candidate for translational research.

Germ-Free C57BL/6 Mice Have Increased Bone Mass and Altered Matrix Properties but Not Decreased Bone Fracture Resistance.

The gut microbiome impacts bone mass, which implies a disruption to bone homeostasis. However, it is not yet clear how the gut microbiome affects the regulation of bone mass and bone quality. We hypothesized that germ-free (GF) mice have increased bone mass and decreased bone toughness compared with conventionally housed mice. We tested this hypothesis using adult (20- to 21-week-old) C57BL/6J GF and conventionally raised female and male mice (n = 6-10/group). Trabecular microarchitecture and cortical geometry were measured from micro-CT of the femur distal metaphysis and cortical midshaft. Whole-femur strength and estimated material properties were measured using three-point bending and notched fracture toughness. Bone matrix properties were measured for the cortical femur by quantitative back-scattered electron imaging and nanoindentation, and, for the humerus, by Raman spectroscopy and fluorescent advanced glycation end product (fAGE) assay. Shifts in cortical tissue metabolism were measured from the contralateral humerus. GF mice had reduced bone resorption, increased trabecular bone microarchitecture, increased tissue strength and decreased whole-bone strengththat was not explained by differences in bone size, increased tissue mineralization and fAGEs, and altered collagen structure that did not decrease fracture toughness. We observed several sex differences in GF mice, most notably for bone tissue metabolism. Male GF mice had a greater signature of amino acid metabolism, and female GF mice had a greater signature of lipid metabolism, exceeding the metabolic sex differences of the conventional mice. Together, these data demonstrate that the GF state in C57BL/6J mice alters bone mass and matrix properties but does not decrease bone fracture resistance. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Quantitative study on the influence of fly ash content, saturation degree and interface transition zone on the permeability of cement-based materials

The interfacial transition zone (ITZ) and fly ash content affect the transmission performance of concrete by altering its pore structure, while varying water content also has distinct effects on transport characteristics. Therefore, this paper investigates the effects of ITZ, fly ash content, and saturation degree on the gas transport performance of concrete materials through gas penetration tests, mercury injection tests, scanning electron microscopy (SEM), and backscattered electron (BSE) imaging. The influences of these factors on the intrinsic permeability of concrete materials are quantitatively analyzed through methods such as parallel test comparative analysis, regression analysis, function fitting, and fixed parameter analysis. The results indicate that the incorporation of fly ash can refine the pore structure of concrete, but it also leads to an increase in intrinsic permeability. The relationship between saturation degree of concrete and intrinsic permeability conforms to an exponential function. Under the same volume fraction, the intrinsic permeability of ITZ is hundreds of thousands of times higher than that of mortar matrix.

Cementitious phase quantification using deep learning

This study investigates deep learning-based backscattered electron (BSE) image segmentation as a novel approach to automatise phase quantification of cementitious materials and estimate their degree of hydration and porosity. The case study was on Portland cement paste that hydrated from 1 day to 2 years. The initial findings suggest that using arbitrary thresholds for phase segmentation, a strong correlation can be established between the results from BSE image analysis, quantitative XRD, and EDS/BSE, particularly for samples with a hydration age >28 days. The second part demonstrates the success of automated image segmentation that relies on learning the material composition from a meticulously analysed image database, which can then predict the content of numerous other images within seconds. This novel approach can turn the analysis of cementitious materials' phase composition from a tedious process that requires specialised equipment and expertise into a routine test for quality control.

Molecular beam epitaxy and crystal structure of majority a-plane-oriented and substrate-strained Mn3Sn thin films grown directly on sapphire (0001)

The Kagome antiferromagnet Mn3Sn has garnered much attention due to the presence of exciting properties such as anomalous Hall and Nernst effects. This paper discusses the synthesis of crystalline Mn3Sn thin films, prepared on Al2O3 (0001) substrates at 453±5°C using molecular beam epitaxy. The growth is monitored in situ using reflection high energy electron diffraction and measured ex situ using x-ray diffraction, Rutherford back-scattering, and cross-sectional scanning transmission electron microscopy. Our analysis shows the in-plane lattice constants of a1,M=4.117±0.027 Å and a2,M=4.943±0.033 Å, which is a very unexpected result when compared to the bulk a-plane Mn3Sn. This indicates a strain in the film and makes it challenging to provide a straightforward explanation. In an effort to explain our results, we discuss two possible orientation relationships between the Mn3Sn films and the sapphire substrates. Samples prepared under these conditions appear to have smooth surfaces locally, but overall the film has a 3D island morphology. First-principles calculations provide atomic models of the Mn3Sn (112¯0) lattice on Al2O3 (0001) high symmetry sites, indicating that the L3-R90° is the most stable configuration. A detailed discussion of the experimental data and theoretical results, as well as strain effects, is provided.

Accelerated mineral bio-carbonation of coarse residue kimberlite material by inoculation with photosynthetic microbial mats

Microbiological weathering of coarse residue deposit (CRD) kimberlite produced by the Venetia Diamond Mine, Limpopo, South Africa enhanced mineral carbonation relative to untreated material. Cultures of photosynthetically enriched biofilm produced maximal carbonation conditions when mixed with kimberlite and incubated under near surface conditions. Interestingly, mineral carbonation also occurred in the dark, under water-saturated conditions. The examination of mineralized biofilms in ca. 150 µm-thick-sections using light microscopy, X-ray fluorescence microscopy (XFM) and backscatter electron—scanning electron microscopy-energy dispersive x-ray spectrometry demonstrated that microbiological weathering aided in producing secondary calcium/magnesium carbonates on silicate grain boundaries. Calcium/magnesium sulphate(s) precipitated under vadose conditions demonstrating that evaporites formed upon drying. In this system, mineral carbonation was only observed in regions possessing bacteria, preserved within carbonate as cemented microcolonies. 16S rDNA molecular diversity of bacteria in kimberlite and in natural biofilms growing on kimberlite were dominated by Proteobacteria that are active in nitrogen, phosphorus and sulphur cycling. Cyanobacteria based enrichment cultures provided with nitrogen & phosphorus (nutrients) to enhance growth, possessed increased diversity of bacteria, with Proteobacteria re-establishing themselves as the dominant bacterial lineage when incubated under dark, vadose conditions consistent with natural kimberlite. Overall, 16S rDNA analyses revealed that weathered kimberlite hosts a diverse microbiome consistent with soils, metal cycling and hydrocarbon degradation. Enhanced weathering and carbonate-cemented microcolonies demonstrate that microorganisms are key to mineral carbonation of kimberlite.

Absence of Weak Localization Effects in Strontium Ferromolybdate

Sr2FeMoO6-δ (SFMO) double perovskite is a promising candidate for room-temperature spintronic applications, since it possesses a half-metallic character (with theoretically 100% spin polarization), a high Curie temperature of about 415 K and a low-field magnetoresistance (LFMR). The magnetic, resistive and catalytic properties of the double perovskite SFMO are excellent for spintronic (non-volatile memory), sensing, fuel cell and microwave absorber applications. However, due to different synthesis conditions of ceramics and thin films, different mechanisms of electrical conductivity and magnetoresistance prevail. In this work, we consider the occurrence of a weak localization effect in SFMO commonly obtained in disordered metallic or semiconducting systems at very low temperatures due to quantum interference of backscattered electrons. We calculate the quantum corrections to conductivity and the contribution of electron scattering to the resistivity of SFMO. We attribute the temperature dependence of SFMO ceramic resistivity in the absence of a magnetic field to the fluctuation-induced tunneling model. We also attribute the decreasing resistivity in the temperature range from 409 K to 590 K to adiabatic small polaron hopping and not to localization effects. Neither fluctuation-induced tunneling nor adiabatic small polaron hopping favors quantum interference. Additionally, we demonstrate that the resistivity upturn behavior of SFMO cannot be explained by weak localization. Here, the fitted model parameters have no physically meaningful values, i.e., the fitted weak localization coefficient (B′) was three orders of magnitude lower than the theoretical coefficient, while the fitted exponent (n) of the electron–electron interaction term (CnTn) could not be assigned to a specific electron-scattering mechanism. Consequently, to the best of our knowledge, there is still no convincing evidence for the presence of weak localization in SFMO.

Evaluation of residual stress reproducibility and orientation dependent fatigue crack growth in powder bed fusion stainless steel

The complex thermal gradients of additive manufacturing (AM) result in residual stress and distinctive grain morphologies that influence mechanical performance and contribute to concern regarding the fatigue properties of AM parts. In this study, residual stress, microstructure, and fatigue crack growth rate (FCGR) results were compared in AM Type 304L stainless steel produced by laser powder bed fusion (PBF) on different systems using similar process parameters. Residual stress measured in the build direction was remarkably consistent in all PBF builds. Backscatter electron large area images revealed similar grain morphologies in the different builds, all of which exhibited elongated grains in the build direction and inhomogeneous grain size and shape. Fatigue crack growth investigated both parallel and perpendicular to the build direction revealed higher measured crack growth rates in the near-threshold regime in both orientations of the PBF material compared to wrought material. The difference in near-threshold fatigue crack growth rates is attributed primarily to the influence of processing-induced residual stress quantified by the residual stress intensity factor. These values revealed consistent FCGR effects in each orientation across specimens extracted from different builds and were then used to reveal a convergence of the corrected FCGR data of all PBF and wrought specimens.

Multiscale (microscopic to remote sensing) preliminary exploration of auriferous-uraniferous marbles: A case study from the Egyptian Nubian Shield

Since their recent first record within the Egyptian Nubian Shield, auriferous and uraniferous marbles (Au = 0.98–2.76 g/t; U = 133–640 g/t) have rarely been addressed, despite not only their probable economic importance but also the fact that it is a new genetic style of gold and uranium mineralization in the Nubian Shield rocks. This is mainly attributed to the inadequate localization of these marbles within harsh terrains, as well as the cost and time spent with conventional fieldwork for their identification compared to the main lithological components of the Nubian Shield. On the contrary, remote sensing and machine learning techniques save time and effort while introducing reliable feature identification with reasonable accuracy. Consequently, the current research is an attempt to apply the well-known machine learning algorithm (Support vector Machine—SVM) over Sentinel 2 remote sensing data (with a spatial resolution of up to 10 m) to delineate the distribution of auriferous-uraniferous marbles in the Barramiya-Daghbagh district (Eastern Desert of Egypt), as a case study from the Nubian Shield. Towards better results, marbles were accurately distinguished utilizing ALOS PRISM (2.5 m) pan-sharpened Sentinel 2 data and well-known exposures during fieldwork. With an overall accuracy of more than 90%, a thematic map for auriferous-uraniferous marbles and the major rock units in the Barramiya-Daghbagh district was produced. Marbles are spatially related to ophiolitic serpentinite rocks, as consistent with their genesis within the Neoproterozoic oceanic lithosphere. Field and petrographic investigations have confirmed the newly detected Au and U-bearing zones (impure calcitic to impure dolomitic marbles in Wadi Al Barramiya and Wadi Daghbagh areas and impure calcitic marble in Gebel El-Rukham area). Additionally, X-ray diffraction (XRD), back-scattered electron images (BSEIs), and Energy Dispersive X-ray spectroscopy (EDX) results were integrated to verify our remote sensing results and petrographic investigations. Different times of mineralization are indicated, ranging from syn-metamorphism (gold in Wadi Al Barramiya and Gebel El-Rukham) to post-metamorphism (gold in Wadi Daghbagh and uranium in all locations). Based on the application of geological, mineralogical, machine learning and remote sensing results for the construction of a preliminary exploration model of the auriferous-uraniferous marble in the Egyptian Nubian Shield, we recommend a detailed exploration of Au and U-bearing zones in Barramiya-Dghbagh district and applying the adopted approach to other districts of similar geological environments.

Hydration and microstructure of cement paste mixed with seawater – An advanced investigation by SEM-EDS method

This study aimed to investigate the microstructural hydration features of Portland cement incorporating with natural seawater (SW). Special attention was paid to characterizing the pore structure, hydrated and anhydrous phases using microscopy techniques, such as secondary electron (SE), backscattered electron (BSE) imaging and energy dispersive spectrometry (EDS) mapping. Through the utilization of algorithms, information extracted from these methods underwent self-corrected, denoising, and imaging calibration, which significantly contributed to the calculation of pore volume, identification and segmentation of various phases, and quantitative characterization. By leveraging the chemical and spatial information from EDS mapping, highly detailed distribution maps of the different cement phases could be obtained, surpassing the conventional BSE grayscale segmentation method in phase identification. Statistical analysis revealed that the deviation of the phase quantification was reduced when using a magnification of 250 times. Higher content of hydrate phases with lower porosity can be observed in SW samples exhibited a higher content of hydrate phases with lower porosity, indicating a stimulated hydration effect. However, accurately determining hydrate phases with small crystal sizes, such as ettringite, necessitated an increase in mapping resolution. Therefore, the use EDS mapping for quantification of various cement phases in submicroscopic and microscopic characterization is both feasible and promising.

Small but Diverse SEM Image Dataset: Impact of Image Augmentation on the Performance of AlexNet

To this date, scanning electron microscope has produced among the most complex and diverse images at nanoscale resolution. The highly magnified images of backscattered electrons reflected from the surface of samples are non-uniformed, even for the same class of images. The study investigates the impact of having a small but diverse dataset on the performance of AlexNet. A total of 160 samples from EUDAT Collaborative Database Infrastructure is used for the study. Compared to the use of new non-augmented samples to increase the size of dataset, image augmentation has been significantly improved classification performance and generalization ability of the AlexNet.

High-Resolution Characterization of Deformation Induced Martensite in Large Areas of Fatigued Austenitic Stainless Steel Using Deep Learning

This paper aims to demonstrate a novel technique enabling the accurate visualization and fast mapping of deformation-induced α′-martensite produced during cyclic straining of a metastable austenitic stainless steel, refined by reversion annealing to different grain sizes. The technique is based on energy and angular separation of the signal electrons in a scanning electron microscope (SEM). Collection of the inelastic backscattered electrons emitted under high take-off angles from a sample surface results in the acquisition of micrographs with high sensitivity to structural defects, such as dislocations, grain boundaries, and other imperfections. The areas with a high density of lattice imperfections reduce the penetration depth of the primary electrons, and simultaneously affect the signal electrons leaving the specimen. This results in an increase in the inelastic backscattered electrons yielded from the vicinity of α′-martensite, and a bright halo surrounds this phase. The α′-martensite phase can thus be separated from the austenitic matrix in SEM micrographs. In this work, we propose a deep learning method for a precise α′-martensite mapping within a large area. Various deep learning-based methods have been tested, and the best result measured by both Dice loss and IoU scores has been achieved using the U-Net architecture extended by the ResNet encoder.

Structural Aspects of the Formation of Multilayer Composites from Dissimilar Materials upon High-Pressure Torsion.

A multi-metal composite was consolidated from the Ti50Ni25Cu25 and Fe50Ni33B17 alloys by room-temperature high-pressure torsion (HPT). The structural research methods used in this study were X-ray diffractometry, high-resolution transmission electron microscopy, scanning electron microscopy with an electron microprobe analyzer in the mode of backscattered electrons, and the measurement of indentation hardness and modulus of the composite constituents. The structural aspects of the bonding process have been examined. The method of joining materials using their coupled severe plastic deformation has been established to play a leading role in the consolidation of the dissimilar layers upon HPT.

Microstructural Evolution and Deformation Behavior of a Solution-Treated Ti-Al-Mo-Fe Metastable Beta Titanium Alloy during Room-Temperature Deformation

Beta titanium (β-Ti) alloys have been widely used in aerospace and biomedical implants due to their specific strengths, low elastic modulus, and their resistance to corrosion. As β titanium alloy is a novel metastable, Ti-2Al-9.2Mo-2Fe (wt.%) alloy is essential to understand microstructural evolution and deformation behavior at room temperature to improve the strength–ductility balance. The deformation behavior and microstructural evolution of the Ti-2Al-9.2Mo-2Fe alloy during room-temperature deformation has been investigated via electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI). It was found that the β-solution-treated alloy exhibited a single β phase with a lower β stability. However, the α/β-solution-treated alloy exhibited a layered structure, consisting of fine α + β grain layers and coarse β grain layers, and the β in the coarse grain layer had a lower stability, but the β in the fine grain layer had a higher stability owing to the coexistence of α. The β-solution-treated alloy was mainly deformed via {332}<113> deformation twinning, thus showing very high ductility; uniform elongation of approximately 35%. The α/β-solution-treated alloy was deformed via two mechanisms, namely {332}<113> deformation twinning in the coarse grain layers and dislocation slip in the fine grain layers. The α/β-solution-treated alloy exhibited high strength with a lower ductility due to the small amount of deformation twinning.

Long-term effects of canagliflozin treatment on the skeleton of aged UM-HET3 mice.

Sodium glucose cotransporter-2 inhibitors (SGLT2is) promote urinary glucose excretion and decrease plasma glucose levels independent of insulin. Canagliflozin (CANA) is an SGLT2i, which is widely prescribed, to reduce cardiovascular complications, and as a second-line therapy after metformin in the treatment of type 2 diabetes mellitus. Despite the robust metabolic benefits, reductions in bone mineral density (BMD) and cortical fractures were reported for CANA-treated subjects. In collaboration with the National Institute on Aging (NIA)-sponsored Interventions Testing Program (ITP), we tested skeletal integrity of UM-HET3 mice fed control (137 mice) or CANA-containing diet (180ppm, 156 mice) from 7 to 22months of age. Micro-computed tomography (micro-CT) revealed that CANA treatment caused significant thinning of the femur mid-diaphyseal cortex in both male and female mice, did not affect trabecular bone architecture in the distal femur or the lumbar vertebra-5 in male mice, but was associated with thinning of the trabeculae at the distal femur in CANA-treated female mice. In male mice, CANA treatment is associated with significant reductions in cortical bone volumetric BMD by micro-CT, and by quantitative backscattered scanning electron microscopy. Raman microspectroscopy, taken at the femur mid-diaphyseal posterior cortex, showed significant reductions in the mineral/matrix ratio and an increased carbonate/phosphate ratio in CANA-treated male mice. These data were supported by thermogravimetric assay (TGA) showing significantly decreased mineral and increased carbonate content in CANA-treated male mice. Finally, the sintered remains of TGA were subjected to X-ray diffraction and showed significantly higher fraction of whitlockite, a calcium orthophosphate mineral, which has higher resorbability than hydroxyapatite. Overall, long-term CANA treatment compromised bone morphology and mineral composition of bones, which likely contribute to increased fracture risk seen with this drug.

Zircon and Garnet U–Pb Ages of the Longwan Skarn Pb–Zn Deposit in Guangxi Province, China and Their Geological Significance

Garnet is the most common alteration mineral in skarn-type deposits, and the geochronological research on it can limit the mineralization age. The Longwan Pb–Zn deposit, situated within the Fozichong Pb–Zn ore field in Guangxi, lacks precise geochronological data, limiting the in-depth comprehension of its genesis and tectonic setting. This study employs LA-ICP-MS U–Pb dating of garnets developed in the skarn orebody and zircons in the associated granitic porphyry to determine the deposit’s mineralization age. Backscatter electron images and electron probe microanalysis reveal common zonation characteristics in garnets from the Longwan Pb–Zn deposit, with dominant end-member compositions of Andradite and Grossular. The values of U concentrations range from 1.8 ppm to 3.7 ppm, and a garnet U–Pb age of 102.6 ± 1.9 Ma was obtained, consistent with the zircon U–Pb age of 102.1 ± 1.2 Ma from the granite porphyry within the deposit. The Longwan Pb–Zn deposit formed during the late Early Cretaceous as a skarn deposit resulting from contact metasomatism between the granite porphyry and the host rock. The deposit likely formed in response to the Neo-Tethys plate subducting beneath the South China continent during the Cretaceous, followed by a retreat during the Late Cretaceous. The Cenxi-Bobai Fault experienced reactivation under the extensional tectonic regime induced by the Neo-Tethys Ocean’s retreat, leading to a series of magmatic activities along the NE-trending direction within the Fault. The Longwan Pb–Zn deposit formed during the processes of magma emplacement and contact metasomatic reactions with the country rock.

Identification and Elemental Impurity Analysis of Heterogeneous Morphologies in Uranium Oxides Synthesized from Uranyl Fluoride Precursors.

The surface morphology characteristics of postenrichment deconversion products in the nuclear fuel cycle are important for producing nuclear fuel pellets. They also provide the first opportunity for a microstructural signature after conversion to gaseous uranium hexafluoride (UF6). This work synthesizes uranium oxides from uranyl fluoride (UO2F2) starting solutions by the wet ammonium diuranate route and a modification of the dry route. Products are reduced under a nitrogen/hydrogen atmosphere, with and without water vapor in the reducing environment. The crystal structures of the starting materials and resulting uranium oxides are characterized by powder X-ray diffraction. Scanning electron microscopy (SEM) and focused ion beam SEM with energy-dispersive X-ray spectroscopy (EDX) are used to investigate microstructural properties and quantify fluorine impurity concentrations. Heterogeneous distributions of fluorine with unique morphology characteristics were identified by backscatter electron imaging and EDX; these regions had elevated concentrations of fluorine impurities relating to the incomplete reduction of UO2F2 to UO2 and may provide a novel nuclear forensics morphology signature for nuclear fuel and U metal precursors.