Search Results (4,409)

The work develops methods for synthesizing complex salts: [Co(NH₃)₆]₂(CrO₄)₃, [Co(NH₃)₆](CrO₄)(NO₃), [Co(NH₃)₆](CrO₄)Cl·3H₂O, [Co(NH₃)₆]₂(Cr₂O₇)₃·5H₂O, [Co(NH₃)₆](Cr₂O₇)(NO₃)·H₂O and [Co(NH₃)₆](Cr₂O₇)Cl·H₂O. The compounds were characterized by PXRD, IR and elemental analysis. It was demonstrated that mixed-anion complex salts ([Co(NH₃)₆](CrO₄)(NO₃) or [Co(NH₃)₆](CrO₄)Cl·3H₂O) form in the [Co(NH₃)₆]³⁺/(CrO₄)²⁻ system depending on the counterion of hexaamminecobalt(III), [Co(NH₃)₆](NO₃)₃ or [Co(NH₃)₆]Cl₃, respectively. Conversely, it was more difficult to obtain mixed-anion complexes in the [Co(NH₃)₆]³⁺/(Cr₂O₇)²⁻ system. Thus, to obtain [Co(NH₃)₆](Cr₂O₇)Cl·H₂O an excess of chloride ions in the solution is required. At the same time, when the initial dichromate solution is acidified, the complex [Co(NH₃)₆]₂(Cr₂O₇)₃·5H₂O is formed, exhibiting structural polymorphism: the crystal structure changes without altering the chemical composition when stored in a closed container. The process of thermal decomposition of all synthesized complex compounds in an inert atmosphere has been studied. The final product of the thermolysis of most compounds at a temperature of 600 °C is a nanoscale single-phase solid solution Co(Co_1−xCr_x)₂O₄ with a spinel structure (with crystallite sizes of no more than 15 nm), where the metal ratio corresponds to that of the initial complex salt. The smallest crystallite size (3–4 nm) was obtained through the thermolysis of [Co(NH₃)₆](CrO₄)Cl. Full article

Class III aminotransferases represent a structurally and functionally unique subgroup. However, the contribution of specific loop elements to their active-site architecture and cofactor-dependent structural transitions remain underexplored. We elucidated the structural framework underlying the catalytic function of class III fold Pyridoxal 5′-phosphate-dependent aminotransferase from the Antarctic bacterium Hymenobacter sp. PAMC 26554 (HyAT), and report its crystal structure at 2.31 Å resolution. The structure revealed a canonical class III fold organized as a functional homotetramer. Structural analysis identified a proline-containing motif (P-x-P) within the α10-α11 loop, which induces intrinsic disorder at the active-site entrance in the apo-form and revealed that a cooperative disorder-to-order transition is requisite for active-site assembly upon cofactor binding. We propose that this flexible loop region may be involved in modulating substrate access. Notably, this proline motif was conserved in homologs from Hyperthermophiles, despite the cold-adapted nature of HyAT. This convergence implies a common evolutionary strategy where the geometric constraints of proline are exploited to decouple local active-site dynamics from global scaffold stability, thereby addressing the stability–activity trade-off across diverse thermal environments. Our findings provide new molecular insights into the structural dynamics of class III aminotransferases and highlight evolutionary strategies for tuning enzyme flexibility in extreme environments. Full article

Due to the high saturated fat content, increasing cost, and supply instability of cocoa butter (CB), the development of structured lipid systems with improved nutritional profiles and suitable technological functionality has received increasing attention. This study aimed to optimize a coriander seed oil-based oleogel (COG) using a D-optimal mixture design and evaluate its potential as a structured lipid phase for dark chocolate formulation. The effects of coriander seed oil, monoglycerides, candelilla wax, xanthan gum, and polyglycerol polyricinoleate (PGPR) on the physicochemical, rheological, and mechanical properties of the oleogel were investigated. The optimized COG formulation exhibited a maximum crystallization temperature of 30.159 °C, enhanced viscoelastic characteristics, and a stable three-dimensional lipid network. The optimized oleogel retained substantial amounts of bioactive compounds, including α-tocopherol, phenolic compounds, flavonoids, and linalool, together with antioxidant activity, and showed a lower accumulation of primary oxidation products during storage than the non-structured oil. Dark chocolate prepared with the optimized oleogel (COG-Ch) was evaluated in comparison with cocoa butter-based chocolate (CB-Ch) in terms of thermal behavior, rheological properties, texture, and storage-related whitening changes. Although COG-Ch showed comparable onset and maximum melting temperatures and a lower increase in whiteness index during storage at 35 °C, significant differences remained in melting enthalpy, hardness, and several rheological parameters compared with CB-Ch. These differences reflect the distinct lipid organization and crystallization behavior of the oleogel system. Therefore, the developed coriander seed oil oleogel should be considered a promising structured lipid phase for chocolate applications rather than a complete functional equivalent of cocoa butter. Further investigations involving sensory evaluation, crystal polymorphism analysis, microstructural characterization, and comprehensive oxidative stability assessment are required to determine its broader applicability in chocolate manufacturing. Full article

Co-based oxides are commonly introduced into porous ceramic membranes to add catalytic activity, but their attachment at the atomic scale remains unclear. We examined a buried Co₃O₄/Al₂O₃ interface formed by sol–gel deposition and thermal conversion. Site-specific focused-ion-beam (FIB) lift-out, scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy (STEM-EDS), and high-resolution transmission electron microscopy (HRTEM) were used to access and characterize the interface. A Co-rich spinel-type domain with a (111) lattice spacing was observed next to Al₂O₃(012). The observations guided density functional theory (DFT) initial models. After structural relaxation, substrate-O-mediated Co-O contacts emerged from both starting geometries: the O-bridged-start model exhibited eight contacts across four Co sites, whereas the non-bridged-start model developed three contacts around one Co site. Around the Co-O-Al linkages, there is a clear manifertation of the interface polarization and charge redistribution, indicated by charge-density-difference and Bader analyses. In both models, projected density of states (PDOS) showed coupling between Co 3d and O 2p states, while integrated crystal orbital Hamilton population (ICOHP) analysis further indicated that O atoms retained Al-O bonds while forming occupied-state Co-O bonds. These results support a representative, laterally distributed Co-O-Al motif as an atomic-scale pathway for chemically attaching the functional oxide to porous alumina. Full article

Ultrawide bandgap (UWBG) semiconductors are destined to become the foundation for next-generation power and radio-frequency (RF) electronic devices. Their superior qualities such as high thermal conductivity, strong critical electric field, and robust mechanical and radiation hardness are driving continuous and widespread research. Amongst the UWBG materials, aluminum nitride (AlN) is highly attractive due to its direct ultrawide bandgap of about 6.2 eV, resulting in one of the highest Baliga’s and Johnson’s figures of merit. Equally important as its properties are material availability and growth methods capable of producing large-diameter substrates. In this work we report on bulk growth of 100 mm AlN crystals using the physical vapor transport (PVT) technique. The thermal gradients were simulated and tailored to obtain adequate thermal stresses, resulting in substrates with narrow X-ray rocking curves and dislocation densities in the range of 10²–10⁵ cm⁻². In addition, the room-temperature thermal conductivity measured in two directions, perpendicular and parallel to the c-axis, was confirmed to be 300 W m⁻¹ K⁻¹. AlN substrates also demonstrated high UV transparency with absorption coefficients as low as 10 cm⁻¹ at 265 nm wavelength. These results, along with the availability of 100 mm substrates, demonstrate that AlN is ready for further exploration and development for the power and RF electronics industry. Full article

Poly(L-lactic acid) (PLLA) nanofibers are promising materials for biomedical and packaging applications; however, their inherent brittleness limits applications requiring both stiffness and ductility. Here, α- and β-chitin, differing in molecular packing and hydrogen-bonding characteristics, were incorporated into electrospun PLLA nanofibers at a PLLA/chitin mass ratio of 10:1. Both chitin types enhanced the mechanical properties of PLLA, increasing tensile strength by 1.4- and 1.6-fold and Young’s modulus to 83.7 and 79.7 MPa for PLLA/α-chitin and PLLA/β-chitin, respectively. PLLA/α-chitin exhibited higher yield strength and more uniform fiber morphology, whereas PLLA/β-chitin showed substantially greater ductility and toughness with pronounced necking behavior. Thermal, spectroscopic, and diffraction analyses revealed distinct structural responses associated with the two chitin forms. α-Chitin produced a constrained hydrogen-bonded environment that restricted PLLA chain mobility. In contrast, β-chitin preserved greater chain mobility and promoted a more heterogeneous local molecular environment. Despite its lower overall crystallinity, PLLA/β-chitin exhibited a distinct secondary melting feature, suggesting localized chain organization and a limited nucleation effect rather than enhanced bulk crystallization. These findings demonstrate that chitin structure provides a practical design parameter for balancing stiffness and toughness in PLLA nanofiber composites, broadening their potential applications in the biomedical and packaging fields. Full article

The 7075-T6 aluminum alloy exhibits excellent specific strength due to the presence of precipitated η′ phase, but its surface mechanical performance under demanding conditions is often limited. In this study, a horizontal cylindrical magnetron sputtering system was used to deposit TiN coatings on the surface of 7075-T6 aluminum alloy to enhance its surface mechanical properties and structural performance. The effects of deposition temperature, substrate bias voltage, and N₂/Ar flow ratio on the microstructure, surface morphology, phase composition, hardness, and residual stress of the coatings were systematically investigated. The results showed that at 80 °C, enhanced lateral atomic diffusion promoted the transformation of the coating growth mode from coarse columnar crystals to dense quasi-layered structures. The surface roughness decreased from 0.193 μm at room temperature to 0.077 μm, the (111) preferred orientation significantly increased, the hardness reached 383 HV, and the compressive stress was −2.8 GPa. However, when the temperature was raised to 120 °C, grain coarsening and TiN/7075Al interface thermal mismatch stress dominated, and the hardness decreased by approximately 19.3%. At −80 V bias, the atomic impact effect produced by ion bombardment made the coating densified optimally, with the lowest surface roughness of 0.068 μm, a hardness of 377 HV, and a compressive stress of −3.1 GPa; at −150 V, excessive bombardment led to severe re-sputtering and lattice distortion, resulting in a compressive stress of −6.8 GPa and a hardness of 351 HV. When N₂/Ar = 10/25, the reaction sputtering kinetics and chemical thermodynamic conditions reached the optimal balance, achieving the highest diffraction peak signal-to-noise ratio and the narrowest full width at half maximum. These results reveal the temperature-dependent competitive relationship between thermally activated coating densification and thermal mismatch-induced structural degradation, providing insights into the optimization of TiN coating deposition parameters on aluminum alloys. Full article

This study presents the effect of gamma rays of up to 2000 kGy on the chemical structure and the physical properties of a poly(butylene terephthalate) (PBT). PBT is an important engineering polymer, tougher than PET, that can be upgraded by radiation crosslinking with the addition of crosslinkers. Previous studies found in the literature provided very limited data about the effect of ionizing radiation on pure PBT. No gel was produced, and the changes in molecular weight with the increase in dose were in agreement with the results found in the literature, with a decrease until 1000 kGy dose when chain scission predominated and a slight increase at higher doses when crosslinking became significant. Proton NMR analysis was used for the first time in PBT to determine the changes in chemical species, mainly the appearance of terminal butyl groups and aromatic carboxylic groups coming from the rupture of the ester linkage. Both thermal and mechanical properties were explained by the scission of the chains in the amorphous phase and at the boundaries of the crystallites, and the crosslinking in the amorphous phase. The thermal parameter most affected by irradiation was the crystallization temperature, which increased when chain scission was predominant up to a 1000 kGy dose and decreased at higher doses when crosslinking became significant. Stress and strain at break suffered a continuous decrease with dose until PBT became fragile at high dose, with a faster decrease in strain at break from the 1000 kGy dose, when crosslinking became significant. Full article

Metal–organic framework (MOF) powders possess remarkable adsorption capabilities, yet their practical application is severely hampered by poor processability, difficult recovery, and high mass-transfer resistance. Here, we report a green and rapid two-stage strategy for constructing UiO-66-NH₂ self-assembled aerogels with a bimodal micro-/mesoporous architecture. A brief thermal pretreatment (130 °C, 3 h) is used solely for precursor activation, after which the critical MOF crystallization and in situ self-assembly are driven under ambient conditions via ultrasonic cavitation (900 W, 15–60 min). This protocol simultaneously drives the nucleation, crystallization, and self-assembly of UiO-66-NH₂ nanocrystals into a monolithic, self-supporting architecture, thereby replacing the conventional prolonged high-temperature solvothermal MOF crystallization with a rapid room-temperature process. The sonication time critically governs the structural evolution, transforming initially amorphous aggregates into well-defined regular octahedral nanocrystals that form an interconnected framework. The optimized aerogel (UNA-T60) exhibits an exceptional specific surface area (1196.9 m² g⁻¹) and a synergistic bimodal pore structure comprising intrinsic micropores and intercrystalline mesopores. This architecture enables rapid mass transfer and active-site accessibility, resulting in a maximum Congo Red (CR) adsorption capacity of 660.56 mg g⁻¹, with kinetics conforming to the pseudo-second-order model (R² > 0.999). The robust monolithic structure endows the material with outstanding reusability, retaining 90.8% of its initial adsorption capacity after four regeneration cycles. This work presents a paradigm-shifting approach for the sustainable fabrication of pure MOF aerogels, offering a promising solution for advanced dye wastewater treatment. Full article

Recent research has shown that Cu atoms can incorporate into the L1₂₋Al₃Sc precipitates in Al-Cu-Sc alloys, forming Al_3−xCu_xSc compounds that serve as effective hydrogen traps. Nevertheless, the Cu-induced modifications to the stability and mechanical properties of these precipitates have not yet been systematically quantified. In this work, first-principles calculations are performed to systematically investigate the crystal structures, phase stability, elastic properties, and thermodynamic behavior of Al_3−xCu_xSc (x = 0, 1, 2, 3) compounds. Structural optimizations are carried out for all compositions, and the formation enthalpies, elastic constants, polycrystalline moduli, and Debye temperatures are derived from the computed total energies and stress–strain relationships. The calculations reveal that Al₂CuSc and AlCu₂Sc adopt tetragonal structures rather than the cubic L1₂-type symmetry found in Al₃Sc and Cu₃Sc, indicating a composition-driven structural transition. The formation enthalpy becomes progressively less negative with increasing Cu content, implying a reduction in thermodynamic driving force for compound formation. The computed elastic properties further show that Cu substitution decreases the bulk-to-shear modulus ratio and the Vickers hardness, while simultaneously enhancing the ductility of the material. Additionally, the Debye temperature exhibits a monotonic and rapid decrease from Al₃Sc to Cu₃Sc, reflecting a significant softening of the lattice vibrational spectra upon Cu alloying. These quantitative theoretical results provide a comprehensive basis for understanding the compositional dependence of the mechanical and thermal responses of Cu-modified Al₃Sc precipitates. Full article

Mt. Guntur (West Java, Indonesia) has remained in surface repose since its last significant eruption in 1847 CE. Nevertheless, persistent volcano-tectonic seismicity and seismic tomographic anomalies indicate the possible presence of an active, melt-bearing magmatic system beneath the volcano. This study examines whole-rock geochemistry, high-resolution mineral chemistry, quantitative textural analysis (Crystal Size Distribution; CSD), and geothermobarometry of the youngest eruptive products to reconstruct the subvolcanic architecture. The results delineate a vertically extensive transcrustal plumbing system, consisting of a shallow, crystal-rich reservoir (1.0–3.0 kbar; approximately 3.5–11 km) and a deeper staging zone (approximately 3.0–3.5 kbar; 11–13 km, assuming an average crustal density of 2.7 g/cm³). This configuration spatially corresponds with seismic Low Velocity Zones (LVZs) and high-attenuation anomalies identified at 5–8 km depth in previous geophysical studies. Textural and micro-analytical data demonstrate a marked shift in magmatic dynamics over time. The mature GL-18 unit (>50 vol% crystallinity) records prolonged, closed-system fractional crystallization within a stable reservoir. It represents differentiated magma confined within a rigid crystal framework. In contrast, the younger basaltic units (GL-17, GL-11, GL-10) exhibit evidence of active disruption driven by successive mafic recharge events. These recharges largely replaced the resident interstitial melt, as indicated by primitive mineral compositions and distinct textural features that reflect pulsed thermal perturbations. The historical 1847 CE GL-17 eruption reached its final pre-eruptive equilibration at shallow depths (less than 1.5 kbar; approximately 1110–1125 °C), where the primitive magma was thermally buffered by cooler, partially crystallized portions of the resident reservoir. These findings classify Mt. Guntur as a system with Potentially Active Magmatic Storage (PAMS). Although persistent magmatic heat sustains regional geothermal fields, ongoing recharge dynamics suggest a continued potential for future volcanic unrest. As petrology alone cannot predict eruptions, a multidisciplinary monitoring framework that integrates continuous geophysical, deformation, and gas observations is necessary to mitigate risks in the Garut Basin. Full article

The article presents the results of a study of the properties of a new pyrochlore (Bi_2.7Mg_0.46Ni_0.70Sb₂O_10+Δ) using X-ray powder diffraction analysis, high-temperature X-ray powder diffraction and thermal analysis, diffuse reflectance spectroscopy, impedance spectroscopy, and X-ray spectroscopy methods (XPS, NEXAFS). The Ni/Mg codoped bismuth stibate pyrochlore was synthesized using the solid-phase method. The best results of the Rietveld structure refinement were achieved for the disordered pyrochlore model (sp. gr. Fd-3m:2, a = 10.47574(6) Å). The results of modeling the cation distribution over crystallographic positions are presented. The thermal expansion coefficient (TEC) of pyrochlore increases monotonically from 6.8 × 10⁻⁶ °C⁻¹ (30 °C) to 9.8 × 10⁻⁶ °C⁻¹ (810 °C). Above 1080 °C, thermal dissociation of pyrochlore occurs with the formation of (Mg/Ni)Sb₂O₆ and two cubic phases. At temperatures below 200 °C, the sample exhibits primarily capacitive impedance. The sample capacitance (~17 pF) is independent of temperature and frequency up to 200 °C. The high-frequency relative permittivity and dielectric loss tangent are 30.5 and 5 × 10⁻⁴ (24 °C, 5 × 10⁴ Hz). The activation energy for conductivity is 0.99 eV. The analysis of NEXAFS and XPS spectra allowed for the determination of the charge state of the metal cations: Bi + (3-δ), Sb + (5-δ), Ni/Mg + 2. Full article

This study examines the luminescence performance of two single-crystal scintillators under X-ray excitation, as a function of temperature. Two identical cubic samples of bismuth germanate (Bi₄Ge₃O₁₂-BGO) and barium fluoride (BaF₂) crystals are irradiated by a medical-type X-ray source, and their luminescence output is collected and measured while they are heated from room temperature up to 174 °C. The luminescence efficiencies of BGO and BaF₂ scintillators decreased by 87.5% and 79.48%, respectively, with increasing temperature. BGO showed higher luminescence efficiency results in most of the examined temperature range; however, BaF₂ minimized the differences at temperatures approaching 174 °C. The combination of economic accessibility and thermal performance at higher temperatures renders BaF₂ a good choice for harsh environments and large-scale applications where budget and durability are as critical as performance. Full article

Background: Hot-melt extrusion (HME) is a scalable pharmaceutical technology increasingly relevant to flexible manufacturing, including small-batch production, personalized dosage-form development, and potential use in pharmacy compounding. When translated into compounding practice, however, HME introduces a risk that routine quality-control methods available in pharmacies may be insufficient to reliably assess the stability of extrusion-based preparations. Methods: Granules containing 50% (w/w) darunavir were prepared by HME at 70 and 90 °C using a previously developed polymeric premix. Samples were stored for 24 months under ambient conditions. During storage, routine quality attributes were evaluated, including appearance, particle size distribution, loss on drying, disintegration time, content uniformity, and assay. Solid-state changes were investigated using differential scanning calorimetry (DSC) and X-ray diffraction (XRD), with a reference PEG-associated darunavir sample prepared and characterized for comparative analysis. Changes in drug release and darunavir content were assessed by dissolution testing and HPLC analysis, respectively. Results: Granules produced at both extrusion temperatures retained acceptable routine quality attributes throughout the 24-month storage period. No substantial changes were detected by visual inspection, pharmacopoeial tests, or UV assay. However, DSC revealed a new thermal event after storage, while XRD showed the formation of a new crystalline phase. Comparison with the reference PEG-associated sample supported the assignment of this phase as a PEG-associated crystalline phase of darunavir. Importantly, this transformation occurred even though the routine quality attributes evaluated in pharmacy compounding practice remained unchanged. Dissolution profiles differed between samples tested immediately after preparation and after long-term storage, with a more pronounced overall difference for granules produced at 90 °C, whereas HPLC confirmed comparable darunavir content in all investigated samples. Discussion: Our results show that routine compounding quality control can meet conventional acceptance criteria while failing to detect API solid-state changes in the investigated HME-derived system. In the PEG-containing matrix, amorphous darunavir undergoes storage-induced crystallization, forming a PEG-associated crystalline phase consistent with its known affinity for polyol-containing media. Conclusions: Acceptable routine quality attributes do not necessarily reflect the solid-state stability of APIs in HME-based formulations. These results highlight the need for solid-state risk assessment when developing extrusion-based systems intended for pharmacy compounding and other personalized manufacturing models in which routine quality control may not include advanced solid-state characterization. Full article

The edge-defined film-fed growth (EFG) method is the dominant industrial technique for producing large-area β-Ga₂O₃ single-crystal substrates, but thermal stress-induced dislocation generation remains a critical barrier. This work presents a coupled thermo-mechanical finite-element framework for thermal-stress management in EFG-grown β-Ga₂O₃. The central methodological contribution is a 500-sample gradient-boosting surrogate sensitivity analysis ($R^2=0.955$, mean absolute error (MAE) $=11.3$ MPa) that quantitatively decomposes thermal-stress variance into controllable process factors and irreducible material-property uncertainties. The physical foundation comprises two enabling elements: (i) the full 21-component monoclinic Voigt stiffness matrix with explicit crystal–model coordinate mapping, for which the orthotropic model is rigorously shown to be exact in 2D plane strain through an exact kinematic theorem showing that the 2D plane-strain results of prior orthotropic EFG analyses are unaffected by the coupling terms, while the monoclinic formulation provides the essential foundation for future 3D studies; and (ii) a dimensionless and numerical justification for omitting melt convection, which enables 100% solver convergence (500/500 Latin hypercube samples) with stress errors < 1.5 MPa. Afterheater temperature $T_{\mathrm{AH}}$ is the leading controllable parameter (35.9%), nearly tied with the elastic constant $C_{33}$ (35.5%), followed by the thermal-expansion component ${\alpha }_c$ (15.9%). Elevating $T_{\mathrm{AH}}$ from 1900 K to 1950 K reduces the peak von Mises stress by ∼29% (COMSOL Multiphysics 6.2-verified); the 2D plane-strain baseline anchors the surrogate analysis at ${\sigma }_{max}=223$ MPa, while the afterheater-free 3D configuration gives ${\sigma }_{max}=187$ MPa at the crystal periphery near the solid–liquid interface. The isotropic approximation underestimates peak stress by 39.6%, confirming that directional anisotropy is essential for quantitatively reliable thermal stress prediction in monoclinic oxide crystals. Full article