Probe Microanalysis Research Articles

Allanite-(Sm), CaSm(Al2Fe2+)(Si2O7)(SiO4)O(OH), the third samarium mineral from Jordanów Śląski, Lower Silesia, Poland

Abstract Allanite-(Sm), the third samarium mineral to be discovered, was studied using electron microprobe analysis and single-crystal X-ray diffraction. It is isostructural with monoclinic epidote-supergroup minerals and belongs to the allanite group. The mineral was found in a granitic pegmatite in a serpentine quarry near Jordanów Śląski in Lower Silesia, SW Poland. It occurs as subhedral to anhedral crystals with sizes of up to ~150 μm accompanied by allanite-(Nd), allanite-(Y), clinozoisite, hingganite-(Y), and xenotime-(Y). Allanite-(Sm) is yellowish-brown and shows a white streak, a vitreous luster, and a Mohs hardness of ~6. It is brittle, with conchoidal fracture and imperfect cleavage. The calculated density is 3.842 g·cm-3, and the calculated mean refractive index is close to 1.737. The holotype crystal contains (in wt%) 33.08(11) SiO2, 0.08(3) TiO2, 21.15(9) Al2O3, 0.45(6) Sc2O3, 0.48 Fe2O3(calc.), 0.02(1) V2O3, 2.49(31) Y2O3, 0.18(4) La2O3, 0.95(9) Ce2O3, 0.34(6) Pr2O3, 3.52(31) Nd2O3, 6.12(23) Sm2O3, 0.06(2) EuO, 3.25(21) Gd2O3, 0.34(2) Tb2O3, 0.94(7) Dy2O3, 0.15(4) Ho2O3, 0.16(3) Er2O3, 0.07(6) Tm2O3, 0.06(4) Yb2O3, 0.28(4) MnO, 8.38 FeO(calc.), 0.13(2) MgO, 13.71(15) CaO, and 1.95 H2O(+)calc.; the total is 98.04. The empirical EPMA + SREF formula is A1(Ca0.966Mn0.022Fe2+0.010)Σ0.998A2(Ca0.372Sm0.192Y0.121Nd0.114Gd0.098Ce0.032Dy0.028Pr0.011Tb0.010La0.006Er0.005Ho0.004Eu0.002Tm0.002Yb0.002)Σ0.998M1Al0.998M2Al0.998M3(Fe2+0.628Al0.275Sc0.036Fe3+0.033Mg0.018T i0.005V3+0.002)Σ0.998(T1–T3Si3.012O11)O(OH), the simplified formula is Ca(Sm,REE,Ca)Al2(Fe2+,Al,Fe3+)(Si2O7)(SiO4)O(OH), and the ideal formula is CaSm(Al2Fe2+)(Si2O7)(SiO4)O(OH), which requires (in wt.%) SiO2—30.37, Al2O3—17.18, Sm2O3—29.38, FeO—12.11, CaO—9.45, and H2O—1.52; the total is 100. Allanite-(Sm) is monoclinic, space-group P21/m, with the following unit-cell parameters: a = 8.8923(6), b = 5.7005(3), c = 10.1280(8) Å, β = 115.445(9)º, V = 463.59(6) Å3, Z = 2, and a : b : c = 1.5599 : 1 : 1.7767. The T site is exclusively occupied by Si, the A1 site is occupied by Ca and Mn, and the A2 site is mainly occupied by rare earth elements (REE), of which Sm is dominant. The M1 and M2 sites are occupied by Al and the M3 site by divalent cations, of which Fe2+, characteristic of allanite-type species, is dominant. Allanite-(Sm) and the associated allanite-(Y), allanite-(Nd), and hingganite-(Y) are secondary minerals precipitated from Ca-rich hydrothermal fluid during the metasomatic alteration of the Jordanów Śląski pegmatite. They accumulated REE released by the alteration of nearby xenotime-(Y). The disequilibrium rapid crystallization of REE-selective allanite and hingganite structures in an environment strongly enriched in heavy REE (HREE) relative to light REE (LREE), as well as small-scale heterogeneities in REE abundances in the fluid, resulted in the crystallization of exotic allanite species, including allanite-(Sm).

Chemical classification of spherules recovered from the Pacific Ocean site of the CNEOS 2014-01-08 (IM1) bolide

We have conducted an extensive towed-magnetic-sled survey during the period of June 14–28, 2023, over the seafloor about 85 km north of Manus Island, Papua New Guinea, centered around the calculated path of the bolide CNEOS 2014-01-08 (IM1). We found about 850 spherules of diameter 0.1–1.3 mm in our samples. The samples were analyzed by micro-XRF, Electron Probe Microanalyzer and ICP Mass spectrometry. Here we report major and trace element compositions of the samples and classify spherules based on that analysis. We identified 78 % of the spherules as primitive, in that their compositions have not been affected by planetary differentiation. We divided these into four groups, three of which correspond to previously described cosmic spherule types. Spherules in the fourth group, comprising 22 % of the collection, appear to all reflect planetary igneous differentiation and are all different from previously described spherules. We call them D-type spherules. At least five of the D-type spherules are suggested to be terrestrial in origin, although many spherules exhibit elemental ratios that are distinct from known planetary bodies and their origins are undetermined. A subset of the D-spherules show an excess of Be, La and U, by up to three orders of magnitude relative to the solar system standard of CI chondrites. Detailed mass spectrometry of 12 of these “BeLaU”-type spherules, the population of which may constitute up to ∼10 % of our entire collected sample, suggests that they are derived from material formed by planetary igneous fractionation. Their chemical composition is unlike any known solar system material. We compare these compositions to known differentiated bodies in the solar system and find them similar to those of evolved planetary materials–with lunar KREEP the closest in terms of its trace element enrichment pattern, but unusual in terms of their elevated CI-normalized incompatible elements. The “BeLaU”-type spherules reflect a highly differentiated, extremely evolved composition of an unknown source.

Hydrothermal activity near the Permian–Triassic transition in the south‐western Ordos Basin, China: Evidence from carbonate cementation in Upper Permian sandstones

ABSTRACTCarbonate cementation in the Upper Permian sandstones informs the timing and temperature of hydrothermal activity in the south‐western Ordos Basin. This study presents a detailed examination of these hydrothermally influenced carbonate cements, constraining their age, carbonate diagenesis and relationship with regional geodynamic evolution. Sedimentological analyses demonstrate the development of deltaic plain and front sand bodies in the study area, which resulted in interbeds of volcanic matrix‐rich sandstones with matrix‐free sandstones. Petrography and electron microprobe analysis reveal four carbonate mineral growth phases of matrix‐free sandstones in the following sequence; scarce pure siderite, scarce Mg‐rich siderite, abundant blocky calcite and moderately abundant grain‐replacing calcite. The fluid inclusion data show anomalies of homogenization temperature of blocky carbonate cements during early diagenesis, over a wide range of ca 148 to 228°C. In addition, blocky carbonate cements show low δ13C (−5.9 to −13.1‰ Vienna PeeDee Belemnite) and δ18O (clustered tightly from −12.4 to −14.6‰ Vienna PeeDee Belemnite) values, interpreted to result from elevated temperatures during cementation, associated with activation of basement faults and concomitant hydrothermal fluid intrusion triggered by oceanic crust subduction in the south‐west margin of the Ordos Basin. Using in situ calcite U–Pb geochronology, the timing of hydrothermal activity was constrained to ca 247.0 ± 11 to 248.2 ± 4.7 Ma. This work provides a case study for applying intergranular calcite U–Pb dating to determine the absolute timing of fluid flow in sedimentary basins, offering tremendous potential to capture snapshots of various diagenetic evolution stages in sediments. The proposed diagenetic model can also provide new insights and understanding regarding hydrothermally influenced sediments. More importantly, hydrothermal activity may have commenced earlier than previously thought. The North Qinling Orogen uplift and associated Mianlue oceanic crust subduction may have begun at the Permian–Triassic transition with a protracted hydrothermal event in the south‐western Ordos Basin.

Fabrication and Characterization of Ce3+-Doped Lithium Alumino-Silicate Scintillating Glass-Ceramic and Fiber.

Ce3+-doped lithium alumino-silicate (Li-Al-Si) scintillating glass was prepared using a melting method and crystallized via heat treatment. X-ray diffraction and transmission electron microscopy confirmed the presence of nanocrystals in the materials. Radioluminescence spectra, obtained by X-ray excitation, and luminescence spectra, obtained by 338 nm excitation, showed that the luminescence intensity increased after crystallization. The glass was combined with pure silica as the inner cladding to fabricate a hybrid fiber core using a melt-in-tube technique. The composition of the fiber core was examined using an electron probe microanalyzer. The glass fiber produced strong blue luminescence under UV excitation. After a micro-crystallizing heat treatment of the hybrid fiber at 850 °C in a reducing atmosphere, a Ce3+-doped lithium alumino-silicate glass-ceramic scintillating hybrid fiber was obtained. The nanocrystal structure of the fiber core was examined using micro-Raman spectroscopy. Excitation and luminescence spectra of the hybrid fiber before and after micro-crystallization were measured using microspectrofluorimetry. The results demonstrated that the fiber remained luminous after micro-crystallization. Hence, this work provides a new way to prepare scintillating glass-ceramic hybrid fibers for neutron detection.

The High-Cycle Tensile-Shear Fatigue Properties and Failure Mechanism of Resistance Spot-Welded Advanced High-Strength Steel with a Zn Coating.

Advanced high-strength steels (AHSSs) with Zn coatings are commonly joined by the resistance spot welding (RSW) technique. However, Zn coatings could possibly cause the formation of liquid metal embrittlement (LME) cracks during the RSW process. The role of a Zn coating in the tensile-shear fatigue properties of a welding joint has not been systematically explored. In this study, the fatigue properties of tensile-shear RSW joints for bare and Zn-coated advanced high-strength steel (AHSS) specimens were comparatively studied. In particular, more severe LME cracks were triggered by employing a tilted welding electrode because much more stress was caused in the joint. LME cracks had clearly occurred in the Zn-coated steel RSW joints, as observed via optical microscopy. On the contrary, no LME cracks could be found in the RSW joints prepared with the bare steel sheets. The fatigue test results showed that the tensile-shear fatigue properties remained nearly unchanged, regardless of whether bare or Zn-coated steel was used for the RSW joints. Furthermore, Zn mapping adjacent to the crack initiation source was obtained by an electron probe micro-analyzer (EPMA), and it showed no segregation of the Zn element. Thus, the failure of the RSW joints with the Zn coating had not initiated from the LME cracks. It was concluded that the fatigue cracks were initiated by the stress concentration in the notch position between the two bonded steel sheets.

Spectroscopic Analysis of Nigerian Gem-grade Yellow Garnet Varieties and their Color Differences

Background: Research on yellow garnets of different shades regarding their varieties, colors, as well as chemical states, and contents of coloring ions is somewhat lacking. Spectroscopic analyses are expected to enrich the research methods and data on yellow garnets and explore a scientific path for enhancing their colors. Methods: A series of analyses, such as X-ray diffraction, infrared spectroscopy, ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, and electron microprobe analyses, have been performed on the garnet crystal samples. Results: X-ray diffraction analysis and infrared spectral analysis have shown yellow and tawny garnets to be spessartite garnets; UV–visible spectral analysis has shown the yellow sample to have stronger absorption peaks at 408, 421, and 430 nm than the tawny sample. Electron microprobe and X-ray photoelectron spectroscopy analyses have shown both spessartite garnet samples to contain the same elements, including Si, O, Al, Ca, Mn, and Fe. Among them, the coloring elements, Mn and Fe, have been found to be identical in terms of type, chemical state, lattice occupancy, and coordination environment, but with different mass percentages. Conclusion: The color differences between yellow-shaded spessartite garnets from Nigeria have not been found to arise from differences in the types of coloring elements, their valance states, or coordination environments. Instead, the concentration of coloring ions Mn2+ and Fe2+ has been identified as the crucial factor. Controlling the concentrations is the key scientific direction for improving the colors of these yellow-toned spessartite garnets. conclusion: The color differences between yellow-shaded spessartite garnets from Nigeria do not arise from differences in the types of coloring elements, their valance states, or coordination environments. Instead, the concentration of coloring ions Mn2+and Fe2+ is identified as the crucial factor. Controlling the concentrations is the key scientific direction for improving the colors of these yellow-toned spessartite garnets.

Diagenetic and hydrothermal events revealed by an Ediacaran dolomite breccia from the Araras-Alto Paraguai basin, southern Amazon Craton

The establishment of extensive carbonate platforms characterized the Ediacaran period during CaCO3 oversaturation events and the exceptional creation of accommodation space associated with the aftermath of the Marinoan glaciation (∼635 Ma). Carbonate deposits in the Araras Group record the early Ediacaran period, stage 1, in the Amazon Craton. The Serra do Quilombo Formation is an intermediate unit characterized by heavily fractured and faulted dolomites, as well as the presence of dolomite-cemented breccias (CB) overlying thick limestone packages associated with diagenetic and hydrothermal modifications. These features are commonly attributed to structurally controlled hydrothermal dolomitization (HTD) and are of significant economic importance as hydrocarbon reservoirs and Mississippi Valley-type (MVT) lead-zinc mineralization hosts. This study aims to unravel the origin of cemented breccias and the diagenetic/burial processes within the unit, focusing on dolomitization processes. Dolomite samples were analyzed using petrographic, scanning electron microscopy, microprobe, micro-Raman, cathodoluminescence, and isotopic analyses (δ13C, δ18O, 87Sr/86Sr) to unravel their burial history. CBs are sub-vertical to sub-horizontal bodies with complex geometries, generally cutting bedding at high angles, indicating hydrofracturing processes related to vertical flows of hydrothermal fluids (hydraulic breccia) and present the typical cockade texture of expansion breccias in dilatational faults. The substitutive matrix RD1 is the main constituent of the Serra Quilombo Formation, its low correlation between δ13C and δ18O (R2 = 0.009), the well-preserved fabric, and the similarity with the isotopic values (C and Sr) documented for Ediacaran carbonates, suggest that the syndepositional dolomitization. The first generation of dolomite cement (DC1) and the last phase of dolomitic cementation (saddle dolomite - SD) occur, filling pores, CBs, and fractures. The cockade texture of the breccias evidences a low precipitation rate or a pause in precipitation between DC1 and SD. Concurrently, DC1 has isotopic signals of δ18O = −4.34 ± 1.32‰ (n = 18) and 87Sr/86Sr = 0.708831 (n = 2), while SD has values of δ18O = −9.57 ± 2.51‰ (n = 15) and 87Sr/86Sr = 0.711464 (n = 3). The large isotopic fractionation between DC1 and SD suggests different dolomitizing fluids. This relationship shows an increase in 87Sr in the fluid as the temperature increases; moreover, the enrichment in 87Sr of the fluid is explained by the interaction of this fluid with rocks from the crystalline basement. Thus, the main conduit for the ascent of this radiogenic fluid would be faults with deep roots spatially close to tectonically active zones. Lastly, the presence of tectonic stylolites cutting cemented breccias and rotated zebra-like strata-bound structures suggests that brecciation occurred before the installation of fragile post-Ordovician transtensional structures, preceding the establishment of Paleozoic Basins on the South American Platform.

Structural, morphological, and chemical composition of ternary ZrHfN thin films deposited by reactive co-magnetron sputtering

This study focuses on a deposited ternary zirconium hafnium nitride (ZrHfN) thin film prepared using the reactive co-magnetron sputtering technique. The effect of the nitrogen (N2) flow rate on the films' structural, morphological, and chemical composition was investigated. The gracing-incidence X-ray diffraction (GIXRD) showed that all ZrHfN thin films exhibited a crystalline face-centered cubic structure with a strong (111) orientation. With increasing the N2 flow rate, the film's crystallography changed based on thermodynamic theory. The films demonstrated uniformity and homogeneity in their ternary nitride composition, as confirmed by transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDS) mapping and electron probe microanalyzer (EPMA). Chemical state analysis using X-ray photoelectron spectroscopy (XPS) indicated the presence of both nitride and oxynitride species in all samples. Notably, the atomic concentration of the main elements (Zr, Hf, and N) remained relatively stable over the controlled N2 flow rate range. However, the N2 flow rate played a crucial role in forming hafnium nitride and oxynitride chemical states, whereas it did not significantly influence the Zr phases, dominated by Zr oxides. Additionally, the hardness of the ternary ZrHfN thin films exhibited enhancement comparable to typical ternary nitrides.

Effects of rare earth modifying inclusions on the nucleation mechanism and mechanical properties of MC5 roller steel

The effect of Ce treatment on the inclusions and mechanical properties of MC5 roller steel after solidification and annealing process was investigated. The implementation was observed by thermodynamic calculation, Electron Probe Micro-Analyzer and high-temperature confocal laser scanning microscopy (HT-CLSM). The results showed that as rare earth content increase, the inclusions were effectively modified into cerium oxide (Ce-O) and cerium sulfide (Ce-O-S); Compared with 0 RE steel, eliminating the proportion of inclusions larger than 5 μm by 14% and 22%; the average size decreased to 3.60 μm and 2.30 μm. Subsequently. CLSM was used to observe the aggregation, separation and agglomeration behavior of MgAlO4 inclusions and alloy elements on the surface of molten steel. Moreover. the ultimate tensile strength and yield strength of MC5 roller steel with Ce treatment increased by 12.6% and 34%. The addition of rare earths could improve the of MC5 roller steel, it provides effective reference value for subsequent industrial experiments.

The Yadovitaya fumarole, Tolbachik volcano: A comprehensive mineralogical and geochemical study and driving factors for mineral diversity

Active volcanic fumaroles are one of the most spectacular natural objects in terms of mineral diversity. The Great Tolbachik Fissure Eruption (GTFE) (Kamchatka) fumaroles are renowned for its exceptional number of mineral species. The total number of minerals that have been reliably identified from this particular locality exceeds 400, which is approximately 6.5 % of all known minerals to date. In this study, we employ a comprehensive approach (bulk chemistry, microprobe analysis, powder X-ray diffraction, HR X-ray computed tomography, and 34S, 18O, and 65Cu isotope measurements) to study the distribution of primary exhalation and secondary mineral assemblages and to reveal the driving factors responsible for the unique mineral diversity in the Yadovitaya fumarole. High oxygen fugacity, the interaction of minerals with atmospheric oxygen and water from seasonal precipitation (leading to abundant hydrated mineral associations), temperature conditions controlling the spatial distribution of mineral-forming components, gas-rock interactions, and basaltic scoria morphology perfect for the crystallization of various minerals are some of the factors revealed. The combination of these factors caused a stepwise mineralization resulting in 12 zones of the Yadovitaya fumarole with characteristic mineral assemblages. The described mineralogy of the Yadovitaya fumarole demonstrates a consistent spatial evolution of fumarolic mineral assemblages that vary in complexity, chemistry, and interaction patterns with the surrounding environment. The examination of mineralogical and geochemical data yields novel insights into the active volcanic systems that are associated with the formation of distinct oxidation-type fumaroles.

Characterization and potential toxicity of asbestiform erionite from Gawler Downs, New Zealand

Abstract Erionite is the name for a zeolite mineral series originating from diagenesis or hydrothermal alteration of volcanic rocks. The particular erionite “species” is based on the dominant extra-framework cation, erionite-Ca, erionite-K, or erionite Na. Irrespective of the species, erionite can display a fibrous/asbestiform morphology and has been linked with cases of malignant mesothelioma, a disease typically associated with asbestos exposure. Characterization of new discoveries of erionite is therefore important to assess any potential exposure hazards. This study describes a new asbestiform erionite from vesicles within the Upper Cretaceous Mt. Somers Volcanics Group (MSVG), Canterbury, New Zealand. The erionite is within the Hinds River Dacite, the youngest unit within the MSVG at Gawler Downs, ~100 km west of Christchurch, in the foothills of the Southern Alps. A multi-analytical approach was taken to analyze the sample which included micro-Raman spectroscopy, thermogravimetric analysis, electron microscopy, electron microprobe analysis, and X-ray powder diffraction with the Rietveld method. Results confirmed the mineral as fibrous erionite-K. The chemical composition of the mineral is unique due to the presence of higher levels of Mg. While Fe was also identified, this was due to smectite flakes occurring on the surface of the erionite fibers. According to the World Health Organization (WHO) respirable mineral fiber definition, where length ≥5 μm, width ≤3 μm, and aspect ratio (L/w) ≥3:1, the Gawler Downs erionite fibers are respirable, while the fibers themselves exceed respirable thickness. In addition to morphology, a value for the potential toxicity model was computed to be 2.28 for the Gawler Downs erionite. This is similar to those of other carcinogenic erionites from Karain, Turkey (2.33), and Nevada, U.S.A. (2.28). Taken together, results indicate Gawler Downs erionite represents an environmental hazard. Nevertheless, further investigation is required to determine potential environmental exposure pathways by which erionite may become airborne and assess the actual environmental risk in the Gawler Downs area.

Influence of cerium addition and redox state on silicate structure and viscosity

AbstractThe viscosities of Ce‐free and Ce‐bearing (∼1.3 mol%, ∼6.5 wt.% Ce2O3) soda lime silicate (window glass) melts were measured with respect to oxidation state. Experiments were performed isothermally using a concentric‐cylinder viscometer on melts equilibrated with successively reducing CO–CO2 gas mixtures within a gas tight vertical tube furnace at 1 atm. Viscosity measurement and sampling were performed at the end of each melt reduction step. Further, viscosities in the glass transition temperature range were estimated using the shift factor method applied to glass transition temperature values determined using differential scanning calorimetry (DSC) measurements on quenched glasses. The Ce speciation at each stepwise melt reduction was probed using Ce L3‐edge X‐ray absorption near‐edge structure (XANES) spectroscopy, while structural information upon Ce addition and reduction was provided by Raman spectroscopy. The viscosities of these materials remain constant at this level of Ce addition and do not vary significantly with redox state at high temperature. Conversely, viscosity values in the glass transition temperature range increase upon both Ce addition and reduction. Our analysis, based on the glass composition analyses obtained via electron probe microanalyzer (EPMA), viscosity calculations, and observations of silicate structural changes, leads to the conclusion that the observed viscosity increase around the glass transition temperature is explained by the high ionic field strength of Ce ions as well as the polymerization behavior of the silicate matrix occurring during reduction of Ce. Because of its low concentration, resulting from its low solubility, Ce redox changes exert only minimal effects on the viscosity of this melt.

Lazerckerite, Ag3.75Pb4.5(Sb7.75Bi4)S24, from Kutná Hora, Czech Republic: a new Sb–Bi member of the andorite branch of the lillianite homologous series

Abstract. Lazerckerite, ideally Ag3.75Pb4.5(Sb7.75Bi4)S24, is a new mineral species found in medieval mine dumps of the historic Ag–Pb–Zn Kutná Hora ore district, Czech Republic. The mineral is associated with other Sb–Bi lillianite homologues (terrywallaceite, gustavite, holubite) and Ag,Bi-bearing galena, most frequently as grain aggregates and replacement rims of earlier Ag–Pb–Bi minerals, growing together in aggregates of up to 0.6×0.3 mm. Lazerckerite is opaque, is steel grey in colour, and has a metallic lustre; the calculated density is 5.920 g cm−3. In reflected light lazerckerite is greyish white, and bireflectance and pleochroism are weak with grey tints. Anisotropy is weak to moderate with grey to bluish-grey rotation tints. Internal reflections are not observed. Electron microprobe analyses yielded the empirical formula, based on 44 apfu, (Ag3.61Cu0.04)Σ3.65(Pb4.55Fe0.01Cd0.01)Σ4.57(Sb7.87Bi3.75)Σ11.62(S24.15Se0.01)Σ24.16. Its unit cell parameters are a=13.2083(9), b=19.4595(8), c=8.4048(13), β=90.032(7)°, V=2160.3(4) Å3, space group P21/c, and Z=2. The structure of lazerckerite contains two Pb sites (Pb1 and Pb2) in bicapped trigonal prismatic coordination, 8 independent octahedral sites, and 13 distinct sulfur positions. Four of the octahedral sites are mixed (Sb,Bi) and (Bi,Sb) sites, one is a mixed (Ag,Bi) site, and one is a mixed (Sb,Pb) site. The new mineral belongs to the andorite branch of the lillianite homologous series with N=4 and is a new addition to the group of Sb–Bi mixed members of the series. Lazerckerite is defined as a lillianite homologue with the three following requirements: N=4, L (Ag++ (Bi3+, Sb3+) ↔ 2 Pb2+ substitution) ≈ 90 %–95 %, and approximately one-third of atom percentage of antimony is replaced by bismuth (Bi/(Bi+Sb) ≈ 0.30–0.38). The new mineral has been approved by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association (IMA 2022-113) and named after Lazarus Ercker, the supreme Royal Bergmeister of the Kingdom of Bohemia and the Master of Prague Mint.

Microstructural evolution and diffusion mechanism of MCrAlY coated nickel-based superalloy turbine blades after serviced for 47,000 h

The large-sized industrial gas turbine blades exhibit non-uniform microstructural degradation in various parts due to ultra-long term service in high-temperature and high-pressure environments. Determination of degradation behavior at critical locations is important for the safety of gas turbine and blades refurbishment program. The microstructure characterization on the surface and interface of MCrAlY coated Ni-based superalloy blades have been studied. The microstructure evolution near the coating/ substrate interface was studied by scanning electron microscope (SEM) and the difference in degradation of the main precipitates at several locations were quantified. Surface oxidation and interfacial diffusion were analyzed through energy dispersive spectrum (EDS) and electron probe microanalyzer (EPMA) to clarify the influence of elemental diffusion on microstructure. The results indicated that regional microstructure evolution influenced by the spatial structural characteristics of the blades. The migration of Ni, Al, Cr, and Co dominated the diffusion mechanism during service, and reconstructed the microstructure of the coating/substrate interface and surface.

Optimization design and interface characteristics research of high damping NiTi - Nickel-Aluminum Bronze functional gradient composite coating additively manufactured by high-speed laser-directed energy deposition

The near-equatomic NiTi shape memory alloy demonstrates exceptional damping performance due to its distinctive low-temperature self-cooperative martensitic internal friction. This study successfully fabricated NiTi-NAB (Nickel-Aluminium bronze shape memory alloy) functionally graded composite coatings with excellent metallurgical bonding between layers on Q235 steel substrates by designing an appropriate interlayer structure and employing the high-speed laser-directed energy deposition (LDED). Through comprehensive evaluation of the composite coating's performance and the numerical simulations of heat transfer within the molten pool, we elucidated the impact of process parameter levels on the microstructure and phase transformation characteristics of the NiTi alloy coating (NTC). The phase composition and phase interface characteristics of the NTC surface and bonding interface were analyzed using an electron probe microanalyzer and transmission electron microscopy, while dynamic thermomechanical analysis was employed to evaluate the damping performance of the NTC. The results indicate that an optimal parameter combination area still exists within the NTC-LDED process parameter window, even with equal laser energy density. Insufficient parameter levels can lead to an increase of micro-defects within the NTC, consequently causing a deterioration in both the cohesion and deformation resistance of the coating. Excessively high parameter levels can lead to significant element loss and residual stress, which in turn contributes to an increase in microcracks within the coating. A considerable quantity of reaction product mixture phases was formed at the interface between NTC and NAB, tending to align coherently with the NAB phase interface. The NTC, prepared with optimal process parameters, exhibits exceptional damping performance with a damping ratio of 0.498 at internal friction equilibrium, rendering it highly promising for applications in surface erosion protection for fluid machinery.

Rotherkopfite, KNa2(Fe2+2.5Ti4+1.5)Fe2+(Si4O12)2, a new neptunite-group mineral without essential lithium, from Rother Kopf, Eifel volcanic fields, Germany

Abstract. Rotherkopfite, KNa2(Fe2.52+Ti1.54+)Fe2+(Si4O12)2, is a new member of the neptunite group, from Rother Kopf, Roth, near Gerolstein, Eifel volcanic fields, Rhineland-Palatinate, Germany. It is found in cavities in a quartz–sanidine xenolith embedded in a vesicular alkaline basalt and is associated with fluorophlogopite and an amphibole supergroup mineral that is zoned from potassic-magnesio-fluoro-arfvedsonite on the exterior to potassic-fluoro-richterite in the core. It is presumed to have formed as the result of contact metasomatism of the xenolith by the alkaline basalt melt. Rotherkopfite occurs as brownish-red equant or tabular crystals, up to about 0.2 mm in maximum dimension. The mineral has a light-orange streak, a vitreous lustre, a Mohs hardness of ∼4.5, a brittle tenacity, a curved fracture and a density of 3.20(2) g cm−3. Optically, rotherkopfite crystals are biaxial (+), with α=1.668(5), β=1.678(5), γ=1.720(5) (white light) and 2V(meas) = 53.2(6)°. The empirical formula from electron microprobe analyses, secondary ion mass spectrometry and structure refinement is (K0.87Na0.20)Σ1.07(Na1.99Ca0.01)Σ2.00M1+M2(Fe1.662+Ti1.48Mg0.79Mn0.02)Σ3.95M3(Fe0.642+Li0.16Ti0.15Al0.01)Σ0.96(Si8.00O24). Rotherkopfite is monoclinic with space group C2/c and unit-cell parameters a=16.4599(17), b=12.5457(6), c=10.0487(7) Å, β=115.669(7)°, V=1870.3(3) Å3 and Z=4. The crystal structure (R1=0.0268 for 1324 reflections with I>2σI) is based on two interwoven three-dimensional frameworks: (1) a silicate framework made up of pyroxene-like chains of corner-sharing SiO4 tetrahedra and (2) an octahedral framework made up of chains of edge-sharing metal–oxygen octahedra. The two interwoven frameworks are bound to one another by corner sharing. K and Na are hosted in channels in the combined framework.

A supervised machine learning procedure for EPMA classification and plotting of mineral groups

An analytical method to automatically characterize rock samples for geological or petrological purposes is here proposed, by applying machine learning approach (ML) as a protocol for saving experimental times and costs.Proper machine learning algorithms, applied to automatically acquired microanalytical data (i.e., Electron Probe Micro Analysis, EPMA), carried out with a SEM-EDS microprobe on randomly selected areas from a petrographic polished thin section, are trained, used, tested, and reported.Learning and Validation phases are developed with literature mineral databases of electron microprobe analyses on 15 main rock-forming mineral groups. The Prediction phase is tested using an eclogite rock from the Western Alps, considered as an unknown sample: randomly selected areas are acquired as backscattered images whose intervals of gray levels, appropriately set in the gray level histogram, allow the automated particle mineral separation: automated separating Oxford Instruments Aztec Feature ® packages and a mineral plotting software are applied for mineral particle separation, crystal chemical formula calculation and plotting.Finally, a microanalytical analysis is performed on each separated mineral particle. The crystal chemical formula is calculated, and the final classification plots are automatically produced for any determined mineral. The final results show good accuracy and analytical ease and assess the proper nature of the unknown eclogite rock sample. Therefore, the proposed analytical protocol is especially recommended in those scenarios where a large flow of microanalytical data is automatically acquired and needs to be processed.

Evaluating the mechanism and the capacitive properties of nickel boride electrodes for supercapacitor applications

This study investigates the electrochemical properties of nickel boride electrodes produced via a novel molten salt boron diffusion method; known as cathodic reduction and thermal diffusion-based boriding (CRTD-Bor). Pure nickel substrates with two different geometries (i.e. flat and foam) were borided in the borax-based electrolyte. The presence of nickel borides, composed of NiB, Ni4B3 and Ni2B with the order locations from the surface towards the matrix, was confirmed by X-ray diffractometry (XRD) and scanning electron microscopy (SEM) attached with electron probe microanalyzer (EPMA). The electrochemical behaviors of the produced electrodes were inspected through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), as well as impedance spectroscopy (EIS). The areal capacitances of the electrodes were calculated as 478 and 1385 mF/cm2 for flat and foam samples, respectively after the 2000th cycle of CV at 10 mV/s scan rate. The reaction kinetic followed the mixed-controlled model according to the Trasatti approach. The capacitive contribution (Co) measured in flat samples was 71 %; whereas, it was found as 40.6 % in the foam-shaped electrodes. Additionally, the mechanism behind the faradaic reactions was explored through X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR) which were conducted both before and after the CV experiments. The obtained results showed that the possible mechanism was related to the formation of NiO bonds due to the oxygen saturation in the defective regions of the surfaces during electrochemical testing. Moreover, the importance of the electrode geometry on the performance was determined by the fact that the porous structure leads to more energy storage and favors a fast charge-discharge trend.

Increase in elastic and hardness anisotropy of titanium with oxygen uptake due to high temperature oxidation: A multimodal framework using high speed nanoindentation mapping

Titanium and its alloys combine an important mechanical anisotropy and a high capacity to dissolve oxygen. The detailed evolution of the elastic compliance of titanium as a function of its oxygen content is only partially known, despite its importance in structural applications. Here, high speed nanoindentation mapping (HSNM) was conducted on a grade 2 commercially pure titanium (CP-Ti) to probe elastic and hardness anisotropy as well as property evolution as a function of the oxygen content within Ti using pre-oxidized specimens. The oxygen concentration investigated ranged from 600 ppm to 20% atomic. Pre-oxidation of the CP-Ti was performed at 700 °C for 100 h under air to create a gradient of oxygen content within the metal, denoted oxygen-rich layer (ORL). Local oxygen content was quantified using microprobe analyses (EPMA) and crystal orientation using electron backscattered diffraction (EBSD). Reduced modulus and hardness maps were obtained on the pre-oxidized sample within the ORL and far from the ORL using large but highly resolved nanoindentation technique in continuous stiffness measurement (CSM) mode. Data merging techniques were used on this multi-modal dataset to statistically link local mechanical properties to chemical and crystal orientation information. Oxygen insertion in the Ti lattice was found to significantly increase the hardness and elastic moduli of titanium and was correlated to orientation of the c-axis of the α-Ti as a function of the nanoindentation loading direction. Using the Vlassak and Nix theory, it was possible to identify the evolution of the Cij terms of the stiffness matrix as a function of the oxygen content up to 20% at. in O.

Effect of elemental composition and phase transformation on lithium leaching behavior of micas in calcination-acid leaching process

Lithium (Li)-bearing clays have emerged as new types of Li resources. The structure and elemental composition of clay minerals play a crucial role in determining the Li leaching efficiency. The elemental composition and structural transformation of Li-bearing mica from Inner Mongolia (IMS) and Jiangxi (JS), China, were studied during the calcination-leaching process by using X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR) and electron microprobe analysis (EMPA). The findings indicate that Mica is the predominant Li-bearing mineral in both IMS and JS. Notably, the IMS mica contains a significantly higher concentration of fluorine compared to the JS mica. Fluorine exerts a minor inhibitory effect on Li leaching, whereas the hydroxyl group (OH) significantly inhibits the leaching of Li from mica. The removal of residual oxygen atoms post-dehydroxylation is crucial to extract Li from mica. Both defluorination and dehydroxylation reactions occur within the temperature range of 800 °C to 900 °C. When calcined at 900 °C, the IMS mica was transformed into sanidine, while the JS mica was transformed into microcline. The acid leaching of products calcined at this temperature represents a process that further disrupts the residual mica structure and facilitates a cation exchange reaction.