Electron Microprobe Research Articles

Karlseifertite, Pb(Ga2Ge)(AsO4)2(OH)6, a new dussertite-group mineral, from Tsumeb, Namibia

Abstract. Karlseifertite (IMA 2024-007, International Mineralogical Association), Pb(Ga2Ge)(AsO4)2(OH)6, is a new member of the dussertite group, from Tsumeb, Namibia. It is a secondary oxidation-zone mineral found on fracture surfaces in germanite–chalcocite ore. Karlseifertite occurs in rosettes of thin, yellow, hexagonal plates up to about 0.2 mm in diameter and usually less than 0.01 mm thick. The mineral has a pale-yellow streak, subadamantine lustre, Mohs hardness of ∼ 4, brittle tenacity, irregular fracture, perfect cleavage on {001} and a calculated density of 4.993 g cm−3. Optically, karlseifertite crystals are uniaxial (+), with ω=1.890(5) and ε=1.894(calc) (white light). The empirical formula from electron probe microanalyses is Pb0.992+(Ga1.603+Ge0.684+Fe0.573+Al0.123+)Σ2.97[(As0.765+S0.156+W0.096+)Σ1.00O4]2(OH0.99)6. Karlseifertite is trigonal with space group R3‾m and unit-cell parameters a=7.2814(7), c=17.1077(12) Å, V=785.50(15) Å3 and Z=3. The mineral has an alunite-supergroup structure (R1=0.0591 for 248 reflections with I>2σI).

Enhancing the stability of soil contaminated with fluoride through the utilization of pristine and aluminium-impregnated biochar: a comprehensive mechanistic approach.

The effect of trivalent metal-modified biochar on the stability and mitigation of fluoride ions (F-) in contaminated soils remains largely unexplored, despite biochar's extensive application in F--contaminated soil. The mineral metal-modified biochar has the potential to serve as an efficient solution for soil contaminated with F-. In this study, pristine-pinecone biochar (P-BC) and AlCl3-modified pinecone biochar (A-BC) were synthesized and then utilized to remediate the soil that had been contaminated with F-. Both P-BC and A-BC efficiently immobilized F- within the contaminated soil. Further examinations through sequential extraction procedure and subsequent analysis using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and elemental dot mapping demonstrated a transformation of F- into a more stable state by A-BC treatment of the contaminated soil. This implies that A-BC may possess the capacity to function as an efficient ameliorant for immobilizing F- within the soil.

Use of carbon black powder for surface treatment of stainless steel substrates via a low-cost CO2 laser

Nowadays, AISI 304 stainless steel plays a crucial role in industry. However, stainless steel exhibits limited wear resistance as it is used in parts with relative motion. Laser treatment emerges as a promising approach to improve its superficial properties. Using a laser as a heat source presents unique properties for heating surfaces, as the first atomic layers of the material absorb the radiation from the laser beam. In this study, we used a low-cost 100 W CO2 laser with carbon black powder to treat the surface of AISI 304 steels. In addition, the reflectance of irradiation on steel is 90%. We used carbon black powder as a photo-absorbing material for radiation to overcome this obstacle. The characterization included field emission gun–scanning electron microscopy, energy dispersive x ray, microhardness, and pin-on reciprocation tribometer. The results showed a significant increase in surface hardness after laser treatment compared to the untreated substrate at a magnitude of 3.8 times. Elemental mapping analysis revealed carbon's presence on the substrate's surface. In addition to increasing surface hardness, we observed a decrease in the friction coefficient of the laser-treated samples compared to the reference substrate. Finally, it could be concluded that carbon black powder had a triple function; it acted as a photo-absorbent material, a carbon source to increase surface hardness, and a solid lubricant. These results show the predictions of using a low-cost CO2 laser with carbon black powder as an efficient, versatile, and fast alternative.

Folic acid-conjugated bovine serum albumin-coated selenium-ZIF-8 core/shell nanoparticles for dual target-specific drug delivery in breast cancer.

Methotrexate (MTX), a frequently used chemotherapeutic agent, has limited water solubility, leading to rapid clearance even in local injections. In the present study, we developed folic acid-conjugated BSA-stabilized selenium-ZIF-8 core/shell nanoparticles for targeted delivery of MTX to combat breast cancer. FT-IR, XRD, SEM, TEM, and elemental mapping analysis confirmed the successful formation of FA-BSA@MTX@Se@ZIF-8. The developed nano-DDS had a mean diameter, polydispersity index, and zeta potential of 254.8nm, 0.17, and - 16.5 mV, respectively. The release behavior of MTX from the nanocarriers was pH-dependent, where the cumulative release percentage at pH 5.4 was higher than at pH 7.4. BSA significantly improved the blood compatibility of nanoparticles so that after modifying their surface with BSA, the percentage of hemolysis decreased from 12.67 to 5.12%. The loading of methotrexate in BSA@Se@ZIF-8 nanoparticles reduced its IC50 on 4T1 cells from 40.29µg/mL to 16.54µg/mL, and by conjugating folic acid on the surface, this value even decreased to 12.27µg/mL. In vivo evaluation of the inhibitory effect in tumor-bearing mice showed that FA-BSA@MTX@Se@ZIF-8 caused a 2.8-fold reduction in tumor volume compared to the free MTX, which is due to the anticancer effect of selenium nanoparticles, the pH sensitivity of ZIF-8, and the presence of folic acid on the surface as a targeting agent. More importantly, histological studies and animal body weight monitoring confirmed that developed nano-DDS does not have significant organ toxicity. Taking together, the incorporation of chemotherapeutics in folic acid-conjugated BSA-stabilized selenium-ZIF-8 nanoparticles may hold a significant impact in the field of future tumor management.

The effect of Bi3+ doping on the structural, magnetic, dielectric, optical, and photocatalytic efficiency of Mg-Ni ferrite nanoparticles

Ferrite nanoparticles with the general formula Mg0.7Ni0.3BixFe2-xO4 (MNB) (0 ≤ x ≤ 0.1, Δx = 0.02) were prepared by the citrate combustion method. X-ray diffraction (XRD) results confirmed the spinel single-phase with crystallite size varied from 30.68 to 43.74 ± 0.01 nm. Scanning electron microscopes with elemental mapping conformed to the nano-nature of the MNB samples with all the constituents present without secondary elements. The sample Mg0.7Ni0.3Bi0.02Fe1.98O4 has the highest saturation magnetization of 31.06 ± 0.01 emu g−1. The sample Mg0.7Ni0.3Bi0.08Fe1.92O4 has the lowest coercivity of 31.06 ± 0.01 G. The high-frequency response of the MNB nanoferrites allows them to be used at frequencies around 6.48± 0.01–6.87± 0.01 GHz. The nanoferrite Mg0.7Ni0.3Bi0.1Fe1.9O4 has notable dielectric parameters at 300 K and 50 Hz: the highest dielectric constant (747.93 with enhancing ratio 371%) and the highest conductivity (26.14 μ(Ω.m)−1 with enhancing ratio 288%). The Mg0.7Ni0.3Bi0.08Fe1.92O4 sample has a loss of 8.65 with an enhancing ratio of 56.79% compared to the loss of the pristine Mg0.7Ni0.3Fe2O4 sample of 15.23. Diffuse reflectance (DR) spectroscopy showed an irregular trend for the band gap values with increasing Bi3+ content, where the nanoferrite Mg0.7Ni0.3Bi0.1Fe1.9O4 had the lowest energy gap of 2 eV. The sample Mg0.7Ni0.3Bi0.1Fe1.9O4 exhibited the maximum photodegradation efficiency (96.16%) for rhodamine B (RhB) dye, with outstanding stability after five cycles (96.16, 95.92, 95.71, 95.56, and 95.23%, respectively). The current work has shown the capability to customize ferrite MNB for soft ferrite applications and to eliminate hazardous RhB from water.

Eco-Friendly Carbon Nanotubes Reinforced with Sodium Alginate/Polyacrylic Acid for Enhanced Adsorption of Copper Ions: Kinetics, Isotherm, and Mechanism Adsorption Studies.

This study investigates the removal efficiency of Cu2+ from wastewater using a composite hydrogel made of carbon nanotubes (CNTs), sodium alginate (SA), and polyacrylic acid (PAA) prepared by free radical polymerization. The CNTs@SA/PAA hydrogel's structure and properties were characterized using SEM, TEM, FTIR, XRD, rheology, DSC, EDS, elemental mapping analysis, and swelling. The adsorption performance for Cu2+ was tested in batch adsorption experiments, considering the pH, dosage, initial concentration, and contact time. The optimal conditions for Cu2+ removal were pH 5.0, an adsorbent dosage of 500 mg/L, and a contact time of 360 min. The adsorption followed pseudo-second order kinetics. Isotherm analyses (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Sips, Toth, and Khan) revealed that the Freundlich isotherm best described the adsorption, with a maximum capacity of 358.52 mg/g. A thermodynamic analysis indicated that physical adsorption was the main interaction, with the spontaneity of the process also demonstrated. This study highlights the high efficiency and environmental friendliness of CNT@SA/PAA composites for Cu2+ removal from wastewater, offering a promising approach for water treatment.

Nanoarchitectonics of vanadium nanoparticles decorated mesoporous carbon nitride in photocatalytic systems: A study on ethylbenzene oxidation reaction

In this work, we have described the synthesis of vanadium (V) nanoparticles (NPs) anchored on mesoporous graphitic carbon nitride (V@mpg-C3N4) and their uses in photocatalytic ethylbenzene oxidation to the respective acetophenones. The mpg-C3N4 serves as the support for the decoration of V NPs, through a simple impregnation method. Various advanced techniques, such as XRD, UV–vis spectrometry, HRTEM, HAADF-STEM, AC-STEM, elemental mapping, and BET surface area analysis, were employed for the characterization of V@mpg-C3N4. The detailed characterization studies reveal that the V@mpg-C3N4 catalyst has a medium band gap (2.78 eV), a high surface area (76.7 m2g−1), and a mesoporous nature. The V@mpg-C3N4 photocatalysts demonstrated excellent performance in the light-assisted oxidation of ethylbenzene, achieving over 99 % conversion and selectivity for acetophenone in an environmentally friendly solvent (water) using a domestic light source (50 W white light). This developed synthesis strategy will be useful for synthesizing various noble and non-noble metal-based catalysts and their applications in organic transformation and environmental remediation.

The glass from the arrabal of Arrixaca (Murcia, 12th-13th centuries)

This article presents an assemblage of 36 glass samples excavated in the urban site of San Esteban, part of the arrabal of Arrixaca (Murcia) (in al-Andalus, an arrabal was a relatively dense urbanised area outside the city walls) in contexts securely dated to the 12th and early 13th century, spanning the rule of Ibn Mardanīš, and the early period of Almohad domination in the city. The samples were analysed by electron microprobe (EMPA) for major and minor elements and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for trace elements. The results are examined within the context of glass production, circulation, and consumption in al-Andalus and the Islamicate Mediterranean more broadly. The results show that some of the glasses found in San Esteban-Arrixaca may have been imported from other Islamicate regions (Egypt and Mesopotamia), but that the vast majority can be related to previously recognised compositional Iberian glass groups. At the same time, the identification of several fragments of production waste and raw glass suggest that some glass-working facility may have existed in the vicinity of San Esteban-Arrixaca. The compositional evidence also indicates that recycling (including of imported glass objects) may have been a fairly common practice in Andalusi glassmaking, but it is suggested that some of the usual chemical markers of recycling may, in the case of al-Andalus and perhaps also elsewhere in the medieval Mediterranean, be the result of the cross-breeding of glass- and glaze-making activities.

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).

Enhanced hypersensitive (5D0→7F2) transition characteristics of Eu3+ doped β-Ga2O3 microrods

Exploring and realizing the luminescence characteristics of rare earth metal (RE) ions doped gallium oxide (Ga2O3) is crucial for developing optoelectronic device applications. The current research used the solid-state reaction approach to synthesize Ga2O3 microrods doped with various europium (Eu3+) concentrations (0.1, 0.2, 0.3, 0.5, 0.75, and 1 mol). X-ray diffraction (XRD) and Raman spectral analyses confirm the monoclinic structure of β-Ga2O3. The intensity of the Raman phonon modes decreased and a peak shift was observed for Eu:β-Ga2O3. The electron microscopy (SEM, TEM) images depicted a nearly uniform distribution of microrods for undoped and Eu:β-Ga2O3 samples. The interplanar distance (d = 0.290 nm, 0.561 nm, and 0.433 nm), from HR-TEM images, corresponding to (0 0 4), (1 0 0), and (1 0 2) crystallographic orientations confirm the monoclinic structure of β-Ga2O3. The elemental mapping images showed a nearly homogeneous Ga, O, and Eu distribution. The UV–visible diffuse reflectance spectroscopy (UV-DRS) showed a notable reduction in the bandgap as the Eu3+ concentration increased. The emission spectra of Eu: β-Ga2O3 microrods showed a narrow red emission at 612 nm (5D0 → 7F2), which relates to the 5D0 → 7Fj (j = 0, 1, 2, 3) energy level arising from an intra-4f transition of Eu3+ ions upon 394 and 465 nm excitation. The red emission was found to increase with Eu content up to 0.5 mol.%. A quenching of emission due to the multipole–multipole interactions was obtained beyond 0.5 mol.% of Eu. The absolute quantum yield (η) calculated for Eu: β-Ga2O3 (0.5 mol.%) was 3.82 %. The luminescence decay curve using the bi-exponential fit and the average lifetime (τ) of the Eu: β-Ga2O3 (0.5 mol.%) was found to be ∼0.172 ms. CIE chromaticity and correlated color temperature analyses of Eu:β-Ga2O3 microrods yielded a red emission with a superior color purity (93 %). The obtained results suggest that Eu:β-Ga2O3 (0.5 wt.%) microrods could be one of the potential candidates for red light sources.

Non-destructive visualisation and in situ quantification of micronutrient mobilisation in germinating rice grains using synchrotron-based X-ray fluorescence microscopy

Maintaining micronutrient availability in germinating rice tissues is crucial for seedling vigour and agronomic performance. However, current methods for visualising micronutrient dynamics often require destructive sample preparation. Here we report that synchrotron-based X-ray fluorescence microscopy (XFM) could enable non-destructive, in situ visualisation and quantification of zinc (Zn) mobilisation in intact, germinating rice grains. Using XFM on whole grains of salt-tolerant Pokkali and salt-sensitive Nipponbare varieties, we generated high-resolution elemental maps revealing the spatiotemporal distribution of Zn and other micronutrients. Direct quantification by seed volume using element association window proved inaccurate due to tissue heterogeneity. However, normalisation by areal density showed Zn accumulation was highest in the embryo, followed by the aleurone layer and shoots. Zn was initially localised in the aleurone layer and embryo, with subsequent mobilisation to developing shoots and roots during germination. Calcium was predominantly detected in the hull, while potassium was enriched in growing roots and shoots. This non-destructive XFM method provides unprecedented insights into real-time micronutrient fluxes during rice germination, offering a powerful tool for studying nutrient dynamics in diverse contexts such as biofortification, stress responses, and varietal differences. Our findings contribute to understanding the mechanisms underlying micronutrient allocation during early seedling development, with potential applications in improving rice nutritional quality and seedling establishment.

Machine learning-assisted design of refractory high-entropy alloys with targeted yield strength and fracture strain

In order to improve the traditional “trial and error” material design method, machine learning-yield strength and machine learning-fracture strain models are incorporated into one system to predict yield strength and fracture strain in refractory high-entropy alloys (RHEAs) under compression. The ML-yield strength model and ML-fracture strain model achieve excellent predictions (R2 = 0.942, RMSE=0.35) and (R2 = 0.892, RMSE=0.41) in the testing set, respectively. Based on the machine learning model, Nb0.22Ta0.22Ti0.24V0.23W0.09, Nb0.24Ta0.22Ti0.26V0.04W0.24, Nb0.26Ta0.24Ti0.21V0.24W0.05, and Nb0.18Ta0.26Ti0.22V0.21W0.13 RHEAs in the Nb-Ta-Ti-V-W RHEA system were screened and synthesized. The yield strength (1915 MPa, 1983 MPa) of the Nb0.22Ta0.22Ti0.24V0.23W0.09 and Nb0.24Ta0.22Ti0.26V0.04W0.24 RHEAs are higher than that (1689 MPa) of the NbTaTiVW RHEA. The unfractured Nb0.18Ta0.26Ti0.22V0.21W0.13 and Nb0.26Ta0.24Ti0.21V0.24W0.05 RHEAs under compression exhibit superior performance than the fracture strain (16.6 %) of the NbTaTiVW RHEA. The mixing enthalpy of RHEAs is negatively correlated with the yield strength, whereas a negative relationship exists between electronegativity difference and fracture strain through the SHAP analysis. Decreasing the mixing enthalpy and increasing the electronegativity difference promote the formation of the precipitated phase. The electron probe microanalysis reveals that the differences in mechanical properties (yield strength and fracture strain) in the NbTaTiVW RHEAs primarily stem from the fraction of the precipitated phase.

Characterization of (Zr,Ti)B2-SiC composites obtained by hot press sintering of ZrB2-SiC-TiO2 powder mixtures

The ability to enhance mechanical and oxidation properties for severe environmental applications has led to substantial academic interest in multiphase ultra-high temperature ceramics (UHTC). The purpose of this work is to study the in-situ solid solution formation of (Zr,Ti)B2 from ZrB2 and TiO2 in a ZrB2-SiC composite using hot pressing reaction sintering. For this, a mixture of 10, 20, and 30 % vol% SiC with ZrB2 was mixed with 2.0 wt% TiO2. Hot pressing sintering was performed with a load of 20 MPa at a final temperature of 1850 °C/30 min in an argon atmosphere. The microstructures, crystalline phases, densities, mechanical properties, and oxidation resistance of the composites were examined and compared with ZrB2-SiC samples lacking TiO2. In samples where TiO2 was added, the matrix grain size slightly decreased, the fracture mode was mainly intergranular, and the SiC grain morphology changed the aspect ratio to be more equiaxed. The solid solution (Zr,Ti)B2 was produced, and it was demonstrated by EDS elemental map images and the XRD analysis that Ti atoms incorporate into the ZrB2 crystalline structure. The development of solid solutions showed no impact on relative densities or Vickers hardness. However, the solid solution formation favored an improvement in fracture toughness, probably owing to the smaller matrix grain size and intergranular fracture mode. Samples exhibiting (Zr,Ti)B2 formation presented lower oxidation resistance than undoped samples in the same oxidizing condition.

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.

Destinezite: physicochemical and calorimetric study

Destinezite (Fe3+ Al0.02)(PO4)0.99(SO4)0.90(OH)1.20 ⋅ 5.97H2O (Czech Republic) has been studied by thermal and electron-microprobe analyses, X-ray powder diffraction, IR, Raman, and Mössbauer spectroscopy. The enthalpy of formation of destinezite Fe3 +(PO4)(SO4)(OH)⋅6H2O from the elements ∆fH0(298.15 K) = −4258 ± 12 kJ/mol was determined by the method of solution calorimetry in melt lead borate 2PbO ⋅ B2O3 on a Calvet microcalorimeter Setaram (France). The value of its absolute entropy S0(298.15 K) = 462.0 J/(mol⋅K) was estimated, the entropy of formation ∆fS0(298.15 K) = −2054 J/(mol⋅K) and the Gibbs energy of formation from the elements ∆fG0(298.15 K) = −3646 kJ/mol.

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.

Exploring constituent redistribution in irradiated U-19Pu-14Zr fuel via electron probe microanalysis

The phenomena of constituent redistribution, wherein a previously homogeneous metallic fuel forms discrete, radially concentric compositional zones upon irradiation was investigated by examining an irradiated U-19Pu-14Zr fuel (where numbers represent wt. %) with a burnup of 11.5 at.% with electron probe microanalysis (EPMA) and quadruple inductively coupled plasma mass spectroscopy (Q-ICP-MS).EPMA-generated U, Pu, and Zr compositional data obtained from a diameter traverse of the sample was converted to mass and was used to: 1) compare the overall fuel element analysis results between the two methods, 2) determine the number of compositionally distinct zones forming as a result of constituent redistribution; and 3) quantify the post-irradiation loss or gain of U, Pu, and Zr atoms in each distinct compositional zone.Weight percent concentrations of U, Pu, and Zr for the overall cross section compare favorably between the two analytical methods, suggesting that the spatially resolved EPMA analysis complements bulk chemical analysis.Among the four identified compositional zones, post-irradiation quantification of U, Pu, and Zr elemental atom content changes shows that the quantity of U atoms lost from the innermost zone is slightly less than the quantity of U atoms gained by the middle two zones, and the quantity of Zr atoms lost from the high-U third zone is slightly less than is gained by the two innermost zones. Pu is lost from all four zones, although the innermost zone and the high-U third zone lose a significantly higher percentage (> 22 %) of their initial Pu atoms than the other two zones. For all three elements, EPMA cannot distinguish between atoms lost due to transport to a different zone from atoms lost due to nuclear processes; however, the insight gained from using this process can be used to experiment with new modeling techniques to predict constituent redistribution in U-Pu-Zr fuels.

Pressure–Temperature–Time Evolution of a Polymetamorphic Paragneiss With Pseudomorphs After Jadeite From the HP–UHP Gneiss‐Eclogite Unit of the Variscan Erzgebirge Crystalline Complex, Germany

ABSTRACTA quartz‐rich paragneiss from the Variscan Erzgebirge Crystalline Complex (ECC) was studied in detail because of abundant millimetre‐sized and clearly oriented pseudomorphs after a sodic mineral interpreted to have been jadeite. This mineral, or pseudomorphs after it, is rarely found in extensive high‐pressure (HP)–ultrahigh‐pressure (UHP) terranes worldwide despite reported pressure–temperature (P–T) conditions suitable for the formation of jadeite in common paragneisses and orthogneisses. In the studied rock, which contains abundant large and oriented potassic white mica flakes and minor millimetre‐sized garnet grains, the pseudomorphs consist of clusters of small albite grains with thin phengitic muscovite flakes in between. X‐ray maps for Ca and Mg in garnet demonstrate that an early generation of this mineral (Gt1) was corroded and subsequently overgrown by a Ca‐richer generation (Gt2). White mica is phengite with maximum Si contents of 3.42 atoms per formula unit. P–T conditions of 0.85 GPa and 650°C and 1.7 GPa and 660°C were derived for the formation of Gt1 and Gt2 rim + Si‐rich phengite, respectively, using pseudosection modelling. The latter conditions representing the pressure peak experienced by the paragneiss are compatible with the original presence of jadeite and possibly paragonite as well. This metamorphic peak occurred at 338.4 ± 2.3 (2σ) Ma based on in situ dating of monazite grains with the electron microprobe. A single monazite age of 386.4 ± 10.5 (2σ) Ma is related to the formation of Gt1. Thus, a Late Devonian metamorphism is suggested here for the first time to have occurred in ECC gneisses before the major HP event in the Early Carboniferous. Furthermore, the study demonstrates that the eclogite‐facies gneisses of the Gneiss‐Eclogite Unit of the ECC experienced peak pressures of not more than 2 GPa in contrast to recent proposals of an extensive UHP area in this unit. In addition, it is suggested that the localized occurrence of UHP rocks surrounded by other lithologies otherwise lacking evidence for UHP conditions should be interpreted with caution with respect to their regional extent and significance.

Transition Metal-Promoted LDH-Derived CoCeMgAlO Mixed Oxides as Active Catalysts for Methane Total Oxidation

A series of M(x)CoCeMgAlO mixed oxides with different transition metals (M = Cu, Fe, Mn, and Ni) with an M content x = 3 at. %, and another series of Fe(x)CoCeMgAlO mixed oxides with Fe contents x ranging from 1 to 9 at. % with respect to cations, while keeping constant in both cases 40 at. % Co, 10 at. % Ce and Mg/Al atomic ratio of 3 were prepared via thermal decomposition at 750 °C in air of their corresponding layered double hydroxide (LDH) precursors obtained by coprecipitation. They were tested in a fixed bed reactor for complete methane oxidation with a gas feed of 1 vol.% methane in air to evaluate their catalytic performance. The physico-structural properties of the mixed oxide samples were investigated with several techniques, such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), elemental mappings, inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction under hydrogen (H2-TPR) and nitrogen adsorption–desorption at −196 °C. XRD analysis revealed in all the samples the presence of Co3O4 crystallites together with periclase-like and CeO2 phases, with no separate M-based oxide phase. All the cations were distributed homogeneously, as suggested by EDX measurements and elemental mappings of the samples. The metal contents, determined by EDX and ICP-OES, were in accordance with the theoretical values set for the catalysts’ preparation. The redox properties studied by H2-TPR, along with the surface composition determined by XPS, provided information to elucidate the catalytic combustion properties of the studied mixed oxide materials. The methane combustion tests showed that all the M-promoted CoCeMgAlO mixed oxides were more active than the M-free counterpart, the highest promoting effect being observed for Fe as the doping transition metal. The Fe(x)CoCeMgAlO mixed oxide sample, with x = 3 at. % Fe displayed the highest catalytic activity for methane combustion with a temperature corresponding to 50% methane conversion, T50, of 489 °C, which is ca. 40 °C lower than that of the unpromoted catalyst. This was attributed to its superior redox properties and lowest activation energy among the studied catalysts, likely due to a Fe–Co–Ce synergistic interaction. In addition, long-term tests of Fe(3)CoCeMgAlO mixed oxide were performed, showing good stability over 60 h on-stream. On the other hand, the addition of water vapors in the feed led to textural and structural changes in the Fe(3)CoCeMgAlO system, affecting its catalytic performance in methane complete oxidation. At the same time, the catalyst showed relatively good recovery of its catalytic activity as soon as the water vapors were removed from the feed.

Synthesis of Trimanganese Tetraoxide (Mn3O4) as a promising electrode and Photocatalyst for the degradation of Rhodamine B dye

The article involves the facile bio-synthesis of Manganese (III) Oxide (Mn3O4) nanoparticles (NPs) using Curry leaf (Murraya Koenigii) extract as an efficacious chelating agent. The prepared NPs were subjected to various characterization methods such as Powder X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray (EDX) Analysis, Transmission Electron Microscopy (TEM), Fourier Transform Infrared analysis (FTIR), Ultra Violet spectroscopy study (UV–Vis), Cyclic Voltammetry (CV) and Vibrating Sample Magnetometer (VSM) to study the crystalline structure, morphology, optical properties, electrochemical activity and magnetic property of the sample. The XRD result proved the crystallinity of the sample having crystallite size around 15 nm with tetragonal structure. The absorption band observed at 612 cm−1 indicates the Mn-O stretching modes of tetrahedral sites in FTIR analysis of the prepared sample which confirmed the formation of Mn3O4 NPs. Using SEM and TEM techniques, the surface morphology and NPs size were examined. The composition and distribution of the NPs was verified using EDX spectrum and elemental mapping. Using the UV–Visible spectroscopy, the energy band gap (Eg) for the NPs was computed and calculated as 2.34 eV. The Mn3O4 NPs evinced a specific capacitance of 276 Fg-1 at 10 mV/s scan rate. This result proposes that the obtained Mn3O4 NPs can be used as a suitable electrode mainly for supercapacitor applications. VSM study revealed the paramagnetic behavior of the synthesized Mn3O4 NPs. The synthesized Mn3O4 NPs exhibited moderate antibacterial activity with gram positive bacteria such as Staphylococcus aureus, Streptococcus pneumoniae, and gram negative bacteria such as Klebsiella pneumoniae, with the inhibition zones of 12, 10, and 9 mm respectively. Photo catalytic degradation study was carried out for Rhodamine B (RhB) dye, which showed a strong characteristic absorption peak nearly at 554 nm with 94 % of degradation efficiency.