Search Results (46,621)

This study examines the microspherical high-calcium fly ash (HCFA) and the high-strength binder material based on it by method of scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS). The composition of 568 individual microspheres of the initial HCFA was determined and presented as ternary diagrams CaO–Al₂O₃–SiO₂ and CaO–FeO–SiO₂. The binder specimens have a compressive strength of 24–82 MPa at a curing time of 3–300 days. Their strength is close to that of CEM I 42.5N cement specimens with a curing time of up to 28 days, but exceeds it with a curing time of up to 300 days. The SEM-EDS method showed that the predominant composition of hydration products is concentrated in the high-calcium region of the CaO–Al₂O₃–SiO₂ diagram with a CaO content of 60–80%. The SiO₂ content in them is 15–30%, and their composition includes 1–15% Al₂O₃ and 5–14% FeO. It follows that the predominant products that provide the strength of the binder are calcium silicate hydrates with a CaO/SiO₂ ratio of 1.7 to 4.2. The results contribute to the data for development of models for predicting the effect of HCFA on the properties of composite binders. Full article

This study investigates the dielectric relaxation and conduction mechanisms in $S{e}_{90}S{n}_{6}P{b}_4$ chalcogenide glassy material, which is of interest for applications in phase-change memory devices, optical memory, and thermoelectric sensors. Despite previous studies on chalcogenide glasses, the conduction mechanisms at varying temperatures and the role of correlated barrier hopping (CBH) remain unclear. Using impedance spectroscopy in the frequency range 1 Hz–1 MHz at temperatures from 288 K to 318 K, the real ($Z\prime$) and imaginary ($Z″$) parts of the complex impedance were recorded. The sample was also characterized by X-ray diffraction (XRD) to confirm its glassy nature, and X-ray photoelectron spectroscopy (XPS) to determine the surface chemical composition and oxidation states of the elements. Peaks in $Z″$ at each temperature were used to evaluate the relaxation time τ, revealing thermally activated processes with an activation energy of 0.62 eV. Nyquist plots showed semicircular behavior with decreasing radii at higher temperatures, indicating enhanced d.c. conductivity with an activation energy of 0.63 eV. A.C. conductivity analysis demonstrated frequency-dependent behavior consistent with the CBH model, with hopping energy calculated as 0.32 eV. The dielectric loss increased with temperature and decreased with frequency, stabilizing above 250 Hz at 318 K. These findings provide new insights into the dielectric and conduction properties of $S{e}_{90}S{n}_{6}P{b}_4$ glasses, supporting their optimization for practical electronic applications. Full article

Indigenous clays are widely used for facial skincare in South Africa, yet their suitability for cosmetic incorporation remains poorly characterised, particularly with respect to elemental safety. This study assessed two traditionally applied clays for acne-prone skin (Umcako and Ibomvu) using a multi-analytical workflow encompassing colorimetry, scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), pH measurement, in vitro sun protection factor (SPF) estimation, X-ray fluorescence (XRF), and inductively coupled plasma mass spectrometry (ICP-MS) of clay leachates. XRD showed both materials to be kaolinite-dominated, with higher kaolinite content in Umcako (92.5 wt%) than in Ibomvu (77.3 wt%); SEM revealed characteristic overlapping pseudo-hexagonal platelets, and FT-IR did not indicate prominent organic functional groups under the conditions tested. The clays were mildly acidic (pH 4.23–4.48), aligning with physiological skin pH, but exhibited low photoprotective performance when assessed alone (SPF ≈ 2.5–2.6). Elemental screening identified nutritionally relevant trace minerals but also detected regulated or sensitising metals, with Ibomvu showing elevated bulk Pb (53 ± 12 ppm), Ni (126 ± 71 ppm) and Zn (72 ± 26 ppm), while Umcako contained elevated bulk Cr (460 ± 140 ppm) and Pb (18 ± 6 ppm). Overall, although Umcako and Ibomvu display physicochemical properties compatible with clay-based cosmetic products, their heavy metal burden, together with the potential for dermal exposure highlighted by leachate analysis, indicates that purification, batch-to-batch monitoring and regulatory risk assessment are essential before safe cosmetic use. Full article

MgCr2O4 nanospinel samples were synthesized using a modified Pechini method, followed by controlled calcination. The resulting materials were evaluated in terms of crystal structure, particle morphology, and optical and electronic properties. Their oxidative activity towards the degradation of organic dyes was investigated via photocatalysis, Fenton-like, and photon-Fenton-like processes. Various analytical techniques were employed to characterize the samples, including X-ray diffraction (XRD) with Rietveld refinements, infrared (IR) spectroscopy, UV–Vis spectroscopy, colorimetry, and transmission and high-resolution transmission electron microscopy (TEM/HRTEM). Structural characterization revealed that MgCr2O4 crystallized after calcination at 600 ${}^{\circ }$C, and Rietveld refinements confirmed cubic Fd-3m symmetry. IR spectra confirmed the short-range order through the presence of vibrational modes assigned to CrO6^2- octahedra. UV–Vis spectroscopy indicated mixed Cr valences (Cr³+/Cr⁶+) for samples calcined at temperatures below 900 ${}^{\circ }$C, with Cr⁶+ eliminated at higher temperatures, confirmed by electron paramagnetic resonance (EPR) spectroscopy. This suggests that an oxidation reaction occurred due to oxygen vacancies in the lattice. Optical bandgap (Eg) increased with temperature. Samples calcined at low temperatures were dark green and became more saturated at temperatures above 900 ${}^{\circ }$C, suggesting photoresponse to visible light, as indicated by the Eg values. The oxidative activity of the nanospinels in degrading the dyes methylene blue (MB) and rhodamine B (RhB) under visible light depended on the nature of the dye, the catalyst concentration, and the use of H2O2 in the process to improve the formation of hydroxyl radicals (•OH), as confirmed by photohydroxylation of terephthalic acid (TA). The highest degradation rate was observed in the photo-Fenton-like process, with 96% and 97% degradation of RhB and MB dyes in 60 min, reaching a kinetic rate constant (${\mathit{K}}_{app}$) of 0.055 min${}^{-1}$ and 0.051 min${}^{-1}$, respectively. This study highlights the importance of controlling various parameters to promote the formation of reactive oxygen species (ROS) required for oxidative degradation by nanospinels. Full article

Advances in polysaccharide-based polymer matrices have expanded the possibilities for developing controlled-release systems for bioactive compounds. This study evaluated the effect of incorporating maltodextrin (0, 1, 3, and 5% w/w) into films composed of thermoplastic starch (5%) and chitosan (2%) was evaluated with the aim of improving their structural, thermal, mechanical, and surface properties. The films were obtained by solvent casting and characterized by XRD, TGA-DSC, FTIR, SEM, contact angle, and mechanical analysis. X-ray diffraction revealed greater organization in sample TPS-CH-M3 compared with TPS-CH-M0 (23,316.7) and TPS-CH-M5 (18,941.4), indicating a balanced semicrystalline structure. Thermal analyses showed an increase in the glass transition temperature from 63.0 °C to 72.6 °C and a shift in the main degradation step from 308 °C to 311 °C, indicating greater thermal stability. The contact angle decreased from 89.5° to 74°, confirming increased hydrophilicity. SEM micrographs revealed a homogeneous surface in TPS-CH-M0 and controlled roughness in TPS-CH-M3. Mechanical tests recorded the highest tensile strength (12.5 MPa) and elongation (18%) for TPS-CH-M3. FTIR spectra revealed physical interactions without the formation of new chemical bands, while colorimetry showed an increase in yellow hue, suggesting potential applications related to photosensitive materials. Overall, the incorporation of 3% maltodextrin optimized the functional properties of the matrices for potential controlled-release applications. Full article

We report the synthesis and single-crystal X-ray structures of three novel (Z)-5-arylidene-3-phenylrhodanine derivatives, differing in the substituents on the benzylidene fragment (two methoxy groups (compound I), a dioxine ring (compound II), or a dioxole ring (compound III)). Despite the overall similarity of the molecules, their supramolecular architectures were found out to be strikingly different. The results of intermolecular interactions in those structures are investigated via Hirshfeld surface, molecular electrostatic potential surface and non-covalent interaction analyses. The fine modulation of the arylidene substituent can switch the primary intermolecular synthon from weak S···S bonding to n···π* interactions, offering new possibilities for crystal engineering of rhodanine-based materials. Full article

In this study, NiO/ZnO heterojunction materials were prepared by calcining metal–organic frameworks (MOFs). The structural and morphological characteristics of the NiO/ZnO composite were investigated using various characterization methods, including X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. Gas-sensing tests showed that at the operating temperature of 190 °C, the NiO/ZnO heterojunction (with a molar ratio of 1:1) exhibited the highest response value (R_a/R_g = 201.7) and good selectivity toward 100 ppm n-propanol. Compared to pure ZnO and NiO, the response of NiO/ZnO was significantly improved (ZnO: 6, NiO: 14.6), with increases of 33.5-fold and 13.8-fold, respectively. The response and recovery times were 92 and 30 s, respectively. Additionally, to enable rapid identification of n-propanol gas concentrations, this study developed and validated a method by training and predicting response curves using a random forest algorithm, achieving identification of n-propanol gas at different concentrations (2–100 ppm) within 7 s. Finally, the enhanced sensing performance was mainly attributed to the formation of the interfacial p-n heterojunction between NiO and ZnO, together with increased surface active sites, oxygen vacancies, and chemisorbed oxygen species. Full article

A multi-analytical investigation was carried out to elucidate the deterioration processes affecting the stone materials of the Arca di Cansignorio della Scala in Verona (Italy) and to characterize the surviving traces of its original polychrome and gilded decoration. The study combined macroscopic mapping, stratigraphic sampling, optical microscopy (OM), environmental scanning electron microscopy coupled with energy-dispersive X ray spectroscopy (ESEM-EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and ion chromatography (IC). The monument, predominantly carved from Candoglia marble, exhibits three principal weathering patterns: (i) rain washed areas affected by marble decohesion, (ii) grey deposits corresponding to dirt accumulation areas; and (iii) sulphation-induced black crusts developed in dirt wetting areas. In addition, severe mechanical deterioration was found to be associated with early twentieth-century structural consolidation interventions involving embedded iron bars, whose corrosion-driven volumetric expansion generated vertical cracking. Stratigraphic and microanalytical investigations revealed the presence of original azurite-based polychromy, proteinaceous and lipidic binding media, lead white preparatory layers, and multiple applications of gold leaf. The analytical results highlight the complex interplay between environmental exposure, atmospheric pollution, the incompatibility of materials introduced during past restorations campaigns. Furthermore, they contribute to a better understanding of the composition, execution techniques and preservation state of the surviving decorative layers, providing a scientific basis for future conservation strategies. Full article

Grey cast iron brake discs remain standard in automotive braking systems due to their favourable thermal conductivity and mechanical strength. However, increasingly stringent environmental regulations, including Euro 7, necessitate enhanced surface durability to reduce particulate emissions and mitigate corrosion-related degradation. In this context, laser metal deposition (LMD) offers a promising route to engineer wear-resistant coating systems with tailored microstructures. This study investigates phase formation and microstructural evolution in a 316L/430L-WC multilayer coating deposited on grey cast iron (GJL) brake discs and subjected to brake-shock testing to replicate thermomechanical load cycles representative of real braking conditions. X-ray diffraction (XRD) performed on the interlayer region between the 316L and 430L-WC layers revealed clear evidence of σ-phase formation, indicating intermetallic transformations facilitated by thermal cycling. Microstructural characterization using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) identified localized enrichment of Cr- and Fe-rich regions that support the XRD-based interpretation of σ-phase development. These results provide insights into phase transformations and elemental diffusion in LMD-fabricated brake-disc coatings. The findings advance the understanding of thermally induced transformations in multilayer steel systems and support the optimization of LMD coatings for high-temperature and wear-intensive applications through advanced analytical evaluation. Full article

This study presents the first detailed mineralogical characterization of rare earth element (REE) enrichment (up to 1.39 wt% TREO (total rare earth oxide)) within the regolith overlying the Doradilla tin-skarn prospect, northern New South Wales, Australia. The REE mineralogy was investigated using petrography, field-emission scanning electron microscopy (FE-SEM), electron microprobe analysis (EPMA), micro-X-ray fluorescence (µ-XRF) elemental mapping, and laser Raman spectroscopy. Hydrated REE phosphate minerals are identified as the dominant REE hosts within the regolith. Raman spectroscopy confirms the presence of water in both rhabdophane and churchite. Three compositionally distinct rhabdophane populations are identified, including one La-dominant and two Y-rich groups, whereas churchite-(Y) represents the only HREE-enriched phase identified. The predominance of hydrated REE phosphates within the regolith highlights the importance of secondary phosphate minerals as major REE hosts within the Doradilla profile. This study emphasizes the need for detailed mineral characterization when studying REEs in previously undescribed settings. Furthermore, the results demonstrate that regolith developed over tin-skarn protoliths may host compositionally diverse and REE-enriched phosphate assemblages. With growing global demand for REEs, a greater understanding of REE mineralization in underexplored geological settings is increasingly important. Full article

The use of waste eggshell as a support material for nickel catalysts in the dry reforming of methane (DRM) aims to enhance hydrogen production while controlling catalyst deactivation caused by carbon deposition. Catalyst samples were prepared by wet impregnation and characterized by N₂ adsorption–desorption measurements, X-ray diffractometry (XRD), thermogravimetric analysis (TGA), temperature-programmed reduction, desorption of CO₂ and oxidation (H₂-TPR, CO₂-TPD and TPO), and scanning electron microscopy (SEM). Catalyst activity experiments were conducted at temperatures ranging from 500 to 750 °C, with both reduced and unreduced samples, utilizing a 1.5:1 mixture of CH₄ and CO₂ in a fixed-bed reactor, accompanied by online gas chromatography for analysis. By employing a low calcination temperature (500 °C), the integrity of the eggshell support was maintained. The Ni20 catalyst, with an intermediate nickel loading, exhibited the highest CH₄ (24.5%) and CO₂ (60.5%) conversion and showed minimal carbon formation. Notably, the basicity of the eggshell support contributed to the suppression of carbon deposition, as evidenced by the TPO and SEM analyses. The results suggest that the inherent basicity of the eggshell enhances catalyst resistance to coking while also contributing to the mitigation of eggshell waste. Full article

B-site ordering of Li-modified Pb_0.95Li_0.05(Yb_1/2Nb_1/2)O₃ (PLYN) ceramics can be changed by duration during sintering. In this paper, the conventional solid-state reaction method was employed to prepare antiferroelectric perovskite Li-substituted PLYN ceramics. Crystal structure evolution dependence of sintering time was investigated using X-ray diffraction (XRD), Raman spectroscopy, and dielectric response. Two dielectric anomalies responses, attributed to the transition from B-site order to disorder and antiferroelectric-paraelectric phase transition depend on B-site ordering. The high-temperature dielectric relaxation associated with charged carries (oxygen-vacancy hopping) was characterized by isothermal electric modulus and universal dielectric response. Impedance spectroscopy was used to uncover the relationship between defect type and the oxygen partial pressure (pO₂) dependence on sintering time in PLYN systems. These findings provide new insights into the interplay among B-site ordered phase structure, dielectric response, and defect types. Full article

The present work investigates the combined effect of precursor source and solvent on the structural, morphological, and optical properties of ZnO thin films prepared by the spin-coating technique. Three precursor sources (zinc acetate dihydrate, zinc chloride, and zinc nitrate hexahydrate) and four solvents (ethanol, 2-methoxyethanol, 2-propanol, and 1-methoxy-2-propanol) were systematically explored. X-ray diffraction analysis confirms that all films crystallize in the hexagonal wurtzite structure, with a pronounced (002) preferential orientation for zinc acetate-derived and most of the zinc chloride-derived films. Scanning electron microscopy reveals that both precursor and solvent strongly influence surface morphology. Zinc acetate yields smoother and more compact films, zinc chloride promotes larger hexagonal grains, and zinc nitrate leads to relatively porous structures. Among the solvents, 2-methoxyethanol produces the most uniform and dense films regardless of the precursor. Optical measurements show that transmittance is highly dependent on synthesis conditions, reaching up to 90% in the visible range for zinc acetate-based films, particularly with 2-methoxyethanol. The optical band gap varies between 3.20 and 3.37 eV, reflecting differences in crystallinity and defect density. Overall, these results highlight the key role of precursor–solvent interactions in tailoring ZnO thin film properties for optoelectronic applications. Full article

The blue, white, and black glazed areas of nineteen Nevers earthenware pieces bearing a date or precisely datable between 1589 and 1865 were for the first time analyzed by X-ray fluorescence spectroscopy at the Musée de la faïence et des Beaux-Arts-‘Frédéric Blandin’ in the city of Nevers by pXRF in order to categorize the raw materials and recipes used. The semi-quantitative signal comparison of major elements and impurities such as rubidium, strontium and zirconium shows the use of the same raw materials except for six artifacts. At least three types of cobalt, characterized by association with copper, nickel, and manganese, are observed. Different blacks (with manganese or bismuth) are observed. A comparison is made between the classification obtained with chemometry (z-score, PCA, and dendrograms of similarity) and a reasoned analysis of ternary diagrams based on the signal of the most characteristic elements. This preliminary work demonstrates the potential provided for the categorization of enameled ceramics and their dating through non-invasive on-site semi-quantitative elemental analyses. No important advantages were observed for the chemometric procedure: the same conclusions are obtained by quantitative comparisons of the XRF data, but the chemometric procedures allow a clear visualization of the main conclusions. Full article

Energetic materials face dual challenges of enhancing detonation performance and replacing toxic lead-based formulations. Triazole-based energetic potassium salts typically struggle to achieve simultaneous high-density and excellent detonation properties. Herein, a novel gem-dinitro-functionalized 1,2,3-triazole energetic salt, tripotassium 4,5-bis(gem-dinitromethyl)-2H-1,2,3-triazolate (3K₃BNOT·4H₂O), was rationally designed and synthesized via a six-step mild route using diaminomaleonitrile as the starting material. The structure was fully characterized by IR, NMR, elemental analysis, and single-crystal X-ray diffraction (SC-XRD). 3K₃BNOT·4H₂O crystallizes in the triclinic system (space group P-1) and forms a three-dimensional K-O/K-N ionic coordination network, delivering an ultra-high anhydrous crystal density of 2.077 g·cm⁻³ at 193K. It exhibits a peak decomposition temperature of 183.8 °C (10 °C·min⁻¹), impact sensitivity of 5 J, and friction sensitivity of 60 N (standard BAM methods). The calculated detonation velocity and pressure reach 8836 m·s⁻¹ and 28.6 GPa, respectively, outperforming the classical explosive RDX. This work provides a structural analysis of triazole-based energetic potassium salt hydrates, and 3K₃BNOT·4H₂O shows structural potential as a high-energy energetic material; its initiating performance needs further experimental verification. Full article