Search Results (154)

The high concentrations of heavy metals in electroplating sludge (ES) result in its dual properties as both hazardous waste and a potential secondary resource. Effective strategies are urgently needed for the simultaneous detoxification and utilization of ES. In this study, a sustainable strategy for co-melting of ES and coal gasification slag (CGS) was proposed. By optimizing the mass ratio of ES to CGS (m(ES)/m(CGS) = 1) and adding 7.5 wt% B₂O₃, a low-temperature vitrification system was established at 1250 °C, enabling the recovery of 97.31 ± 0.61% Cu, 99.17 ± 0.43% Ni, and 81.84 ± 0.33% Fe in the alloy phase within 90 min. Melt structure analysis indicated that CaO and [BO₃] promoted the depolymerization of the silicate network, facilitating the amorphous phase transition and enhancing fluidity. Meanwhile, residual carbon from CGS functioned as a reductant, reducing metal minerals in the mixture to form alloys that were simultaneously separated during co-melting. Compared with the raw sample, heavy metals in the vitrified product were effectively immobilized, exhibiting low risk of heavy metal leaching. Furthermore, high-value-added glass-ceramic materials were successfully prepared from the vitrified product. Therefore, the proposed strategy could serve as a sustainable solution for the treatment of ES and CGS. Full article

Background/Objectives: Dihydroquercetin (DHQ), also known as taxifolin, is a natural flavonoid which has anti-inflammatory and wound-healing biological effects. One of the main limitations for developing formulations with DHQ is its low solubility in water at room temperature. One of the high-potential co-formers for increasing its solubility is l-lysine, which has an aliphatic amino group in the side radical capable of entering into intermolecular interactions with the phenolic hydroxyl groups of DHQ. Methods: Several modifications were obtained using grinding, drying, and lyophilization methods. Subsequent evaluation was conducted using a combination of physicochemical and biological analytical methods. Results: Obtained modifications could be described as very easily soluble substances. The absence of the formation of new covalent bonds between the compounds during the formation of such systems was established. The glass transition effect was detected at 64 °C for the obtained films. It is important to note that as a result of studying the cytotoxic properties of the objects, a decrease in cytotoxicity was established during lyophilization of the mechanical mixture of the initial components. For these lyophilizates, the IC50 value was 0.025 mg/mL, 0.068 mg/mL, 0.145 mg/mL, and 0.288 mg/mL for the 3T3, HEK293, Caco-2, and HUVEC cell lines, respectively. Conclusions: Co-amorphous systems of DHQ and l-lysine in the form of films and lyophilizates were obtained and described. These objects may be interesting from the point of view of increasing the solubility of natural flavonoids, which solves one of the main problems in developing drugs based on them. Full article

The physico-chemical and electrophysical properties of carbon coke obtained by coking composite mixtures of pitches isolated from coal tar coking plants of JSC “Shubarkol Komir” and “Qarmet” are investigated. The component composition of the initial resins and the obtained pitches was determined by gas–liquid chromatography methods. The purpose of this study was to identify the patterns of influence of the composition of composite mixtures of pitches isolated from coal tar coking plants of JSC “Shubarkol Komir” and “Qarmet”, as well as heat treatment parameters (temperature 800–1000 °C, duration 4–6 h), on the thermophysical and electrophysical properties of electrode coke, with the determination of optimal conditions for obtaining a material combining low ash content and high carbon content. It was found that the content of phenols and paraffins in the resin of “Shubarkol Komir” is approximately 25% of each component. It is shown that the properties of the final coke depend on the ratio of the mixed pitches (1:1, 1:2, 2:1) and coking conditions (temperature 800–1000 °C, duration 4–6 h). Optimal characteristics (minimal ash content of 0.4%, maximal carbon content of 97.75%) were achieved with a pitch ratio of 1:2 and a temperature of 1000 °C for 6 h. A specific heat capacity in the range of 298–448 K was measured calorimetrically for this sample, where a type II phase transition was detected at 373 K. Electrophysical measurements in the range of 293–483 K revealed a complex temperature dependence of the resistance characteristic of a semiconductor with two sections of a narrow band gap (~0.67 eV and ~0.55 eV). The novelty of the work consists in a comprehensive study of composite mixtures of coal tar pitches and the influence of heat treatment parameters on the formation of thermophysical and electrophysical properties of electrode coke. For the first time, signs of a type II phase transition have been identified for this type of coke material and gigantic permittivity values (up to 10⁹) have been recorded, indicating its potential as a functional carbon material. Full article

Characterized by its low melting temperature of 138 °C, the eutectic Sn-58Bi solder expands the melting temperature range of interconnect joints in electronic packaging, making it widely used in multi-level packaging processes. However, its reliability at higher current densities poses a challenge. This paper employs a hybrid process combining laser soldering and hot-air reflow to fabricate Cu/Sn-58Bi/Cu solder joints in ball grid array (BGA) structures. Through mechanical testing under current loading, the effects of increasing current density (0 A/cm², 0.85 × 10³ A/cm², 1.70 × 10³ A/cm², 2.55 × 10³ A/cm², 3.40 × 10³ A/cm², 4.25 × 10³ A/cm²) were studied systematically. Results indicate that the shear strength decreases markedly with increasing current density, exhibiting a reduction of approximately 5.63% to 95.75%. This degradation is initiated by the overall temperature increase and material softening due to Joule heating. It is further exacerbated by the loss of the non-thermal electron wind’s strengthening contribution, which weakens as the dominant thermal impact escalates with current density. Fracture mode transitions from ductile failure within the solder matrix to a ductile-brittle mixture at the solder/IMC interface, with the transition initiating at 3.40 × 10³ A/cm². Finite element simulations reveal that current crowding in Sn-rich regions and at the solder/IMC interface induces localized Joule heating and thermomechanical strain, which jointly drive the degradation in shear strength and the shift in fracture path. Full article

Fiber reinforcement is a promising solution to several problems, however, the impact of fiber characteristics on the mechanical behavior and reinforcement mechanisms of asphalt mixtures remains unclear. Therefore, two distinct forms of basalt fiber—chopped basalt fiber (CBF) and flocculent basalt fiber (FBF)—were employed. A comprehensive experimental program was conducted, encompassing macroscopic and microscopic analyses through semi-circular bending tests integrated with digital image correlation, four-point bending fatigue tests, and dynamic modulus tests. Results indicate that both fiber types significantly improve crack resistance, with FBF demonstrating superior performance. Compared with the ordinary mixture, the flexibility index and fracture energy of the FBF-reinforced asphalt mixture increased by 59.7% and 30.6%, respectively. Fibers exert a crack-bridging effect, delaying the transition of the crack propagation stage by 1.25–2.21 s and reducing the crack propagation rate by 39.6–55.4%. Although fatigue life decreased with increasing strain levels, basalt fibers substantially enhanced fatigue resistance, with FBF-reinforced asphalt mixture achieving 20–40% higher N_f,50 values than CBF. Dynamic modulus tests revealed that fibers reduce modulus at low temperatures while increasing it at high temperatures, with more pronounced reinforcement effects observed in high-frequency regions. These findings underscore the importance of fiber morphology in optimizing asphalt mixture design and provide a theoretical basis for optimizing fiber-reinforced pavement materials to achieve long-term durability under complex environmental and traffic load conditions. Full article

This study presents a dual-phase lanthanum manganite ceramic composite based on a mixture of equal weight ratios of La_0.7Ca_0.2Sr_0.1MnO₃ and La_0.7Ca_0.25Sr_0.05MnO₃ designed to enhance the magnetocaloric effect (MCE) of individual compounds, under a low magnetic field (≤18 kOe). X-ray diffraction (XRD) analysis revealed the coexistence of two orthorhombic manganite phases corresponding to the individual compounds, with no secondary phases detected. Temperature-dependent magnetization measurements in the composite evidenced two Curie temperatures at 286.8 K and 307.6 K, reflecting the effect of Ca²⁺ and Sr²⁺ concentrations. Arrott plots and β parameters confirmed that the phase transition is of second order. Although the maximum magnetic entropy change (ΔS_M) of the composite is slightly lower than that of the individual manganite phases, its relative cooling power (RCP) reaches 188.82 J·kg⁻¹, with an extended operational temperature window (OTW) of approximately 85 K, spanning from around 243 K to 328 K. This broad OTW enables efficient operation over a wider temperature range compared to similar materials, such as the individual La_0.7Ca_0.2Sr_0.1MnO₃ and La_0.7Ca_0.25Sr_0.05MnO₃ compounds, which exhibit an RCP of 55.24 and 65.12 J·kg⁻¹, respectively, under a comparable magnetic field (~18 kOe). The improved magnetocaloric performance is attributed to interfacial exchange coupling and strain-mediated effects that broaden the ΔS_M response and generate a non-additive RCP. These results demonstrate that interphase coupling and microstructural tuning effectively broaden the operating temperature range for magnetic refrigeration under moderate fields, making this composite a strong candidate for practical cooling applications. Full article

UHPC has been found to have excellent freeze–thaw durability in cold regions. Previous UHPC testing performed has mostly focused on concrete with compressive strength above 21 ksi (145 MPa). In this study, testing was conducted to determine at what strength level concrete transitions to provide excellent freeze–thaw (F–T) performance. Non-proprietary concrete samples were made for freeze–thaw durability from four different concrete mixture designs: 12–15 ksi, 15–18 ksi, 18–21 ksi, and 21+ ksi (83–145+ MPa), and these were tested according to ASTM C666, using 1.5% steel fibers. The samples were made for three different curing regimens: limewater curing in a fog room, simulated precast curing, and steam curing. Low-temperature differential scanning calorimetry (DSC) and mercury intrusion porosimetry (MIP) tests were carried out to reveal the freeze–thaw mechanism of the concrete samples. All mixtures with compressive strength above 15 ksi (103 MPa) performed excellent in freeze–thaw testing with no damage seen. Steam curing was found to negatively affect the freeze–thaw performance at the lowest strength level tested. Full article

Polybutylene succinate (PBS), as one of the most promising multi-application polymer, still suffers from low toughness, poor miscibility, and high crystallinity. Blending with starch is an effective strategy to improve the properties of PBS, but the compatibility and dispersity between starch and PBS still need to be optimized. In this study, mechanical ball milling was carried out to synthesize esterified starch and the subsequent PBS/esterified starch blend. The FT-IR and XPS analyses confirmed the existence of molecular interactions between PBS and esterified starch. SEM images showed a homogeneous surface for the PBS/esterified starch blend, highlighting the favorable compatibility and good dispersion of starch within the PBS matrix. TGA, DSC, and VSP tests indicated that the introduction of esterified starch into PBS lowered the thermal transition temperatures, thereby enhancing the processability. WCA measurements displayed that the water contact angle of the PBS/esterified starch blends gradually decreased with increasing esterified starch content, proving the improved hydrophilicity of PBS/esterified starch blends. Mechanical testing indicated that incorporating 5 wt% esterified starch into PBS significantly improved the tensile strength to 36.35 ± 2.16 MPa and the breaking elongation to 27.18 ± 5.08%, surpassing those of the pure PBS, PBS/esterified starch mixture, and PBS/starch blend. Our study indicates that mechanical ball milling is an efficient method to improve the properties of PBS composites. Full article

The use of molybdenum-based alloys as materials for components operating under high temperatures and significant mechanical loads is widely recognized due to their excellent mechanical properties. However, their low high-temperature resistance remains a critical limitation, which can be effectively mitigated by applying protective coatings. In this study, we investigate the influence of a two-step coating process on the properties and performance of the TZM molybdenum alloy. In the first step, pack cementation was performed. Simultaneous surface saturation with aluminum and silicon, a process known as aluminosiliconizing, was conducted at 1000 °C for 6 h. The saturating mixture comprised powders of aluminum, silicon, aluminum oxide, and ammonium chloride. The second step involved the application of a pre-ceramic coating based on polyhydrosiloxane modified with silicon and boron. This treatment effectively eliminated pores and cracks within the coating. Thermodynamic calculations were carried out to evaluate the likelihood of aluminizing and siliconizing reactions under the applied conditions. Aluminosiliconizing of the TZM alloy resulted in the formation of a protective layer 20–30 µm thick. The multiphase structure of this layer included intermetallics (Al₆₃Mo₃₇, MoAl₃), nitrides (Mo₂N, AlN, Si₃N₄), oxide (Al₂O₃), and a solid solution α-Mo(Al). Subsequent treatment with silicon- and boron-modified polyhydrosiloxane led to the development of a thicker surface layer, 130–160 µm in thickness, composed of crystalline Si, amorphous SiO₂, and likely amorphous boron. A transitional oxide layer ((Al,Si)₂O₃) 5–7 µm thick was also observed. The resulting coating demonstrated excellent structural integrity and chemical inertness in an argon atmosphere at temperatures up to 1100 °C. High-temperature stability at 800 °C was observed for both coating types: aluminosiliconizing, and aluminosiliconizing followed by the pre-ceramic coating. Moreover, additional oxide layers of SiO₂ and B₂O₃ formed on the two-step coated TZM alloy during heating at 800 °C for 24 h. These layers acted as an effective barrier, preventing the evaporation of the substrate material. Full article

Compact nuclear reactor systems usually use helium–xenon (He-Xe) mixtures as coolants. Tight-lattice rod-bundled channels, serving as primary core configurations in compact nuclear reactor designs, exhibit quasi-triangular cross-sections where fluid dynamics substantially deviate from circular tube behavior. This study evaluates the applicability of turbulence models and turbulent Prandtl number (Pr_t) models in quasi-triangular channels through systematic numerical simulations. The results demonstrate that the Transition SST model accurately resolves flow dynamics and turbulence development in helium–xenon mixtures, while implementing Pr_t models significantly enhances temperature prediction accuracy. Among the evaluated models, the Weigand model achieves optimal performance by dynamically adapting Pr_t values across flow regimes. Further refinements targeting parameters governing near-wall Pr_t distribution are identified as critical pathways for improving numerical simulation precision of low-Prandtl-number fluids in geometrically complex nuclear systems. Full article

The demand for clean energy to improve waste valorization and enhance resource utilization efficiency has been increasingly recognized in the last few years. In this context, the co-carbonization of different waste streams, aiming at solid fuel production, appears as a potential strategy to address the challenges of the energy transition and divert waste from landfills. In this work, refuse-derived fuel (RDF) samples were subjected to the co-carbonization process with low-quality animal fat waste in different proportions to assess the synergistic effect of the mixture on producing chars with enhanced fuel properties. Dry (DC) and hydrothermal carbonization (HTC) tests were conducted at 425 °C and 300 °C, respectively, with a residence time of 30 min. The RDF sample and produced chars with different animal fat incorporation were analyzed for their physical, chemical, and fuel properties. The results demonstrated that increasing the fat proportion in the samples leads to an increase in mass yield and apparent density of the produced chars. Furthermore, char samples with higher fat addition presented a proportional increase in high heating value (HHV). The highest values for the HHV corresponded to the char samples produced with 30% fat incorporation for both carbonization techniques (27.9 MJ/kg and 32.9 MJ/kg for dry and hydrothermal carbonization, respectively). Fat addition also reduced ash content, improved hydrophobicity in hydrochars, and lowered ignition temperature, although additional washing was necessary to reduce chlorine to acceptable levels. Furthermore, fat incorporation reduced concentrations of elements linked to slagging and fouling. Overall, the results demonstrate that incorporating 30% fat into RDF during DC or HTC is the most effective condition for producing chars with improved physical, chemical, and fuel properties, enhancing their potential as alternative solid fuels. Full article

In the quest for greener alternatives to conventional organic solvents, Deep Eutectic Solvents (DESs) have gained significant attention due to their sustainability, biodegradability, and tunability. The use of water as an active and genuine component has recently led to the emergence of water-based DESs (wb-DESs). Here, a careful experimental characterization was performed on choline acetate (ChAc)/water mixtures across a range of water:ChAc molar ratios (n = 2–6). Differential Scanning Calorimetry (DSC) revealed glass transitions between 150 and 180 K, with no first-order transitions, leading to a classification of these mixtures as Low Transition-Temperature Mixtures (LTTMs). Physicochemical measurements, including density, viscosity, electrical conductivity, and refractive index, were conducted over a broad temperature range. NMR analyses provided insights into dynamics and solvation environments, with ¹H T1_slow relaxation times reaching their lowest value at n = 2, consistent with the formation of a strong hydrogen-bonding network. The n = 2 mixture was further investigated using Small and Wide-Angle X-ray Scattering (S-WAXS) and ab initio molecular dynamics (AIMD). These studies, jointly with ¹H NMR choline diffusion coefficient, directly challenge previous claims of the existence of aggregation phenomena in wb-DES. The simulation revealed a well-organized solvation structure, where acetate and water synergistically stabilize the choline cation through a cooperative hydrogen-bonding network. These findings highlight the impact and significance of an integrated physicochemical study in guiding the rational development of new sustainable systems, such as wb-DESs. Full article

Ultrafine fibers from poly(3-hydroxybutyrate) (PHB) and polyvinylpyrrolidone (PVP) and their blends with different component ratios in the range of 0/100 to 100/0 wt.% were obtained, and their structure and dynamic properties were studied. The polymers were obtained via electrospinning in solution mode. The structure, morphology, and segmental dynamic behavior of the fibers were determined using optical microscopy, SEM, EPR, DSC, and IR spectroscopy. The low-temperature maximum on the DSC endotherms provided information on the state of the PVP hydrogen bond network, which made it possible to determine the enthalpies of thermal destruction of these bonds. The PHB/PVP fiber blend ratio significantly affected the structural and dynamic parameters of the system. Thus, at low concentrations of PVP (up to 9%) in the structure of ultra-fine fibers, the distribution of this polymer occurs in the form of tiny particles, which are crystallization centers, which causes a significant increase in the degree of crystallinity (χ) activation energy (E_act) and slowing down of molecular dynamics (τ). At higher concentrations of PVP, loose interphase layers were formed in the system, which caused a decrease in these parameters. The strongest changes in the concentration of hydrogen bonds occurred when PVP was added to the composition from 17 to 50%, which was due to the formation of intermolecular hydrogen bonds both in PVP and during the interaction of PVP and PHB. The diffusion coefficient of water vapor in the studied systems (D) decreased as the concentration of glassy PVP in the composition increased. The concentration of the radical decreased with an increase in the proportion of PVP, which can be explained by the glassy state of this polymer at room temperature. A characteristic point of the 50/50% mixture component ratio was found in the region where an inversion transition of PHB from a dispersion material to a dispersed medium was assumed. The conducted studies made it possible for the first time to conduct a comprehensive analysis of the effect of the component ratio on the structural and dynamic characteristics of the PHB/PVP fibrous material at the molecular scale. Full article

The effects of different carrier agents—pea protein (PP), rice protein (RP), bean protein (BP), whey protein (WP), and maltodextrin (MT, as a control)—on pitaya juice encapsulation via spray drying were evaluated. Juice and carrier mixtures (30% w/v) were dried at 150 °C, and the resulting powders were analyzed for water activity (aw), hygroscopicity (Hg), water solubility (WSI), bulk density (BD), glass transition temperature (Tg), water absorption (WAI), antioxidant activity (AA), total polyphenol content (TPC), total betalain (TB) content, and TB stability. Vegetable proteins showed promising results, significantly impacting the protein content, Hg content, WAI, WSI, AA, TPC, and TB content and resulting in high Tg values. PP showed the best results, with high betalain retention (>30%), high TPC and AA, high protein levels, and low Hg, similarly to MT. WP had the highest TB, AA, and TPC but the lowest Tg (47.21 °C), thus reducing stability. Encapsulates obtained with plant protein-based wall materials presented high Tg (>58 °C); low aw, WSI, and Hg; high protein contents >40%; and adequate retention of bioactive compounds, with low degradation rate constants and long half-lives. Overall, plant proteins are promising alternatives to traditional carriers, offering improved stability and functionality in encapsulated products. Full article

In the present work, we describe the use of the potentially tridentate ligand pyridine-2-amidoxime (NH₂paoH) in Fe-Co chemistry. The 1:1:3 Fe^III(NO₃)₃·9H₂O/Co^II(ClO₄)₂·6H₂O/NH₂paoH reaction mixture in MeOH gave complex [Co^III₂Fe^III(NH₂pao)₆](ClO₄)₂(NO₃) (1) in ca. 55% yield, the cobalt(II) being oxidized to cobalt(III) under the aerobic conditions. The same complex was isolated using cobalt(II) and iron(II) sources, the oxidation now taking place at both metal sites. The structure of 1 contains two structurally similar, crystallographically independent cations [Co^III₂Fe^III(NH₂pao)₆]³⁺ which are strictly linear by symmetry. The central high-spin Fe^III ion is connected to each of the terminal low-spin Co^III ions through the oximato groups of three 2.1110 (Harris notation) NH₂pao⁻ ligands, in such a way that the six O atoms are bonded to the octahedral Fe^III center ({Fe^IIIO₆} coordination sphere). Each terminal octahedral Co^III ions is bonded to six N atoms (three oximato, three 2-pyridyl) from three NH₂pao⁻ groups ({Co^IIIN₆} coordination sphere). The IR and Raman spectra of the complex are discussed in terms of the coordination mode of the organic ligand, and the non-coordinating nature of the inorganic ClO₄⁻ and NO₃⁻ counterions. The UV/VIS spectrum of the complex in EtOH shows the two spin-allowed d-d transitions of the low-spin 3d⁶ cobalt(III) and a charge-transfer NH₂pao⁻ → Fe^III band. The δ and ΔΕ_Q ⁵⁷Fe-Mössbauer parameter of 1 at 80 K show the presence of an isolated high-spin Fe^III center. Variable-temperature (1.8 K–300 K) and variable-field (0–7 T) magnetic studies confirm the isolated character of Fe^III. A critical discussion of the importance of NH₂paoH and its anionic forms (NH₂pao⁻, NHpao²⁻) in homo- and heterometallic chemistry is also attempted. Full article