Search Results (2,795)

Reactive co-sputtering was applied to deposit TaN-(Ag,Cu) nanocomposite films on Si and tool steels. Prior to post-deposition annealing, the films were deposited with TaN cap (diffusion barrier) layers in various thicknesses in order to slow down the nucleation and growth of emerging Ag and Cu particles. The thickness of the cap layers was set at 5, 10, 20, or 50 nm. The films were then annealed using Rapid Thermal Annealing (RTA) at 400 °C to induce the nucleation and growth of Ag and Cu nanoparticles. These films’ surface morphologies and structures were examined. The samples were tested for their anti-wear and antibacterial behaviors against Gram-positive S. aureus and Gram-negative E. coli, with a variation in cap layer thickness. It is found that, through the application of TaN cap layers, the out-diffusion of Ag and Cu atoms may be slowed down. The surface concentrations of Ag and Cu might decrease from 35 at.% and 17 at.% to 18 at.% and 6 at.%, respectively, when the cap layer thickness increases to 50 nm (after being annealed for 12 min). The diffusion mechanism is proposed to explain the formation of nanoparticles on the surface through boundary diffusion. Antibacterial behaviors against both bacteria, as well as tribological properties, could still be effective but become less significant with an increase in the cap layer thickness. The antibacterial efficiency after 3 h testing decreased from 99% to 5% and 8% against E. coli and S. aureus, respectively. At 12 h, all the samples reached >99% antibacterial efficiency, despite the variation in cap thickness. For sliding wear, the wear rate was doubled when the cap thickness increased to 50 nm (when the normal load was 1 N). On the other hand, the difference was minor when the normal load was changed to 5 N. The sliding lifetime of the samples was studied using a tribometer. The total lifetime may increase with an increase in the cap thickness. The wear is found to be due to the oxidation of Ag and Cu nanoparticles, which results in the loss of low coefficient behaviors. Full article

The sustainability of Arctic ecosystems that are extremely vulnerable is contingent upon the state of cryosoils. Understanding the principles of ecosystem stability in permafrost conditions, particularly under external natural or human-induced influences, necessitates an examination of the thermal and moisture regimes of the seasonally thawed soil layer. The study concentrated on the variability in the soil’s thermophysical properties in Central Siberia’s permafrost zone (the northern part of Krasnoyarsk Region, Taimyr, Russia). In the industrially affected area of interest, we evaluated and contrasted the differences in the thermophysical properties of soils between two opposing types of landscapes. On the one hand, these are soils that are characteristic of the natural landscape of flat shrub tundra, with a well-developed moss–lichen cover. An alternative is the soils in the landscape, which have exhibited significant degradation in the vegetation cover due to both natural and human-induced factors. The heat-insulating properties of background areas are controlled by the layer of moss and shrubs, while its disturbance determines the excessive heating of the soil at depth. In comparison to the background soil characteristics, degradation of on-ground vegetation causes the active layer depth of the soils to double and the temperature gradient to decrease. With respect to depth, we examine the changes in soil temperature and heat flow dynamics (q, W/m²). The ranges of thermal conductivity (λ, W/(m∙K)) were assessed using field-measured temperature profiles and heat flux values in the soil layers. The background soil was discovered to have lower thermal conductivity values, which are typical of organic matter, in comparison to the soil of the transformed landscape. Thermal diffusivity coefficients for soil layers were calculated using long-term temperature monitoring data. It is shown that it is possible to use an adjusted model of the thermal conductivity coefficient to reconstruct the dynamics of moisture content from temperature dynamics data. A satisfactory agreement is shown when the estimated ($W_{calc}$, %) and observed ($W_{exp}$, %) moisture content values in the soil layer are compared. The findings will be employed to regulate the effects on landscapes in order to implement sustainable nature management in the region, thereby preventing the significant degradation of ecosystems and the concomitant risks to human well-being. Full article

Particle accelerators are powerful tools in fundamental research, medicine, and industry that provide high-energy beams that can be used to study matter and to enable advanced applications. The state-of-the-art particle accelerators are fundamentally constructed from superconducting radio-frequency (SRF) cavities, which act as resonant structures for the acceleration of charged particles. The performance of such cavities is governed by inherent superconducting material properties such as the transition temperature, critical fields, penetration depth, and other related parameters and material quality. For the last few decades, bulk niobium has been the preferred material for SRF cavities, enabling accelerating gradients on the order of ~50 MV/m; however, its intrinsic limitations, high cost, and complicated manufacturing have motivated the search for alternative strategies. Among these, sputter-deposited superconducting thin films offer a promising route to address these challenges by reducing costs, improving thermal stability, and providing access to numerous high-T_c superconductors. This review focuses on progress in sputtered superconducting materials for SRF applications, in particular Nb, NbN, NbTiN, Nb₃Sn, Nb₃Al, V₃Si, Mo–Re, and MgB₂. We review how deposition process parameters such as deposition pressure, substrate temperature, substrate bias, duty cycle, and reactive gas flow influence film microstructure, stoichiometry, and superconducting properties, and link these to RF performance. High-energy deposition techniques, such as HiPIMS, have enabled the deposition of dense Nb and nitride films with high transition temperatures and low surface resistance. In contrast, sputtering of Nb₃Sn offers tunable stoichiometry when compared to vapour diffusion. Relatively new material systems, such as Nb₃Al, V₃Si, Mo-Re, and MgB₂, are just a few of the possibilities offered, but challenges with impurity control, interface engineering, and cavity-scale uniformity will remain. We believe that future progress will depend upon energetic sputtering, multilayer architectures, and systematic demonstrations at the cavity scale. Full article

Objective: The objective of this study was to clarify the connection between BTX-A injections and local changes in skin temperature and to assess the correlation between post-BTX-A injection facial vascular hyperthermia and subcutaneous adipose tissue thickness (SAT) in the frontal area using thermography. Methods: The study involved 30 patients (mean age 42 ± 0.5 years; 18 women, 12 men). Facial skin temperature was measured via thermography (Thermo GEAR G30) before, immediately after, and 20 min after subcutaneous injection of BTX-A with hemagglutinin complex, gelatin (6 mg), and maltose monohydrate (12 mg). SAT development was graded by combined visual-palpation assessment. Statistical analysis included Student’s t-test and the Mann–Whitney U-test. Results: Biphasic thermal response: immediately post-injection: Significant decrease in min (−1.1 °C) and mean (−0.3 °C) facial temperatures (p < 0.05); 20 min post-injection: pronounced increase in mean (+1.5 °C), max (+1.3 °C), and min (+1.6 °C) temperatures (p < 0.001), attributed to BTX-A-induced vasodilation and local inflammation. Subjects with pronounced SAT exhibited significantly higher baseline temperatures (Me = 33.1 °C vs. 29.8 °C; p < 0.001) and more intense hyperthermic responses (+1.6 °C mean increase vs. +1.1 °C in low-SAT group; p < 0.001). Pronounced SAT was predominantly female (10/15; p < 0.05) and linked to higher BMI (33.3% overweight vs. 0% in low-SAT; *p = 0.036*). Conclusions: SAT thickness is a key determinant of post-BTX-A vascular hyperthermia, with pronounced SAT predicting stronger reactions. Practical Recommendation: Targeted local hypothermia (+4 °C to +8 °C for 5–7 min post-injection, adjustable by SAT thickness) mitigates hyperemia, edema, hematoma risk, and potential toxin diffusion, especially in high-SAT individuals. Full article

Thermal barrier coatings (TBCs) extend gas-turbine blade lifetime by improving high-temperature oxidation resistance and mechanical performance. We investigated the microstructural evolution, TGO growth, and Al depletion in air-plasma-sprayed (APS) single-layer YSZ top coat over a NiCrCoAlY bond coat on Ni-based superalloy circular plates, heat treated isothermally at 850 °C and 1000 °C for 50–5000 h. Cross-sectional SEM/EDS analysis showed TGO quadratic thickening kinetics at both temperatures, reaching ~10 µm at 1000 °C/5000 h, the growth rate of which was ~5.8 times higher than at 850 °C. On top of the single-layer TGO of Al₂O₃ observed from the onset, a NiCrCo oxide layer appeared and grew from ≥500 h at 850 °C, with increasing growth rate and cracking. The layer configuration of the YSZ top coat, the TGO of Al₂O₃, and the bond coat (comprising β-NiAl and γ-NiCr) on top of GTD111, showed an Al concentration gradient in the bond coat starting at 850 °C for 250 h, which intensified with increased duration and temperature. The decrease in Al concentration in the bond coat and the growth of TGO are due to the dissolution of β-NiAl and subsequent Al diffusion to the Al₂O₃ TGO. Full article

A sheet-type sinter-bonding material was developed to form thermally stable and highly heat-conductive joints suitable for wide-bandgap (WBG) semiconductor dies and high-heat-flux devices, and its bonding characteristics were investigated. To enhance the cost-competitiveness of the bonding material, Ag-coated Cu (Cu@Ag) particles were employed as fillers instead of conventional Ag particles. To facilitate accelerated sintering, a bimodal particle size distribution comprising several micron- and submicron-sized particles was adopted by synthesizing and mixing both size ranges. For sheet fabrication, a decomposable resin was used as the essential binder component, which could be removed during the bonding process via thermal decomposition. This approach enabled the formation of a sintered bond line composed entirely of Cu@Ag particles. Thermogravimetric and differential thermal analyses revealed that the decomposition of the resin in the sheet occurred within the temperature range of 290–340 °C. Consequently, sinter-bonding conducted at 350 °C and 370 °C exhibited significantly superior bondability compared to bonding at 330 °C. In particular, sinter-bonding at 350 °C for just 60 s resulted in a highly densified joint microstructure with a low porosity of 7.6% and high shear strength exceeding 25 MPa. The formation of the bond line was initiated by sintering between the outer Ag shells of the adjacent particles. However, with increasing bonding time or temperature, sintering driven by Cu diffusion from the particle cores to the outer Ag shells, particularly in the submicron-sized particles, was progressively enhanced. These results obtained from the fabricated sheet-type materials demonstrate that, even with the use of resin, rapid solid-state sintering between filler particles combined with the removal of resin through decomposition enables the formation of a metallic bond line with excellent thermal conductivity. Full article

Cu₂S has wide-ranging applications in the energy field, particularly as electrode materials and components of energy storage devices. However, the migration of copper ions is prone to component segregation and copper precipitation, impairing long-term thermal stability and service performance. Ce₂S₃ not only possesses the unique 4f electron layer structure of Ce but also has high thermal stability and chemical inertness. Here, we report for the first time that the thermal stability and mechanical properties of Cu₂S can be significantly enhanced by introducing the dispersed phase Ce₂S₃. Thermogravimetry—differential scanning calorimetry (TG-DSC) results show that the addition of 6 wt% Ce₂S₃ improves the thermal stability of Cu₂S sintered at 400 °C. X-ray diffraction (XRD) results indicate that the crystal structure of Cu₂S gradually transforms to tetragonal Cu_1.96S and orthorhombic Cu_1.8S phase at 400 °C with the increase of Ce₂S₃ addition. Scanning electron microscopy (SEM) results show that the particle size gradually decreased with the increase of Ce₂S₃ amount, indicating that the Ce₂S₃ addition increased the reactivity. The Ce content in Cu₂S increased gradually with the increase of Ce₂S₃ amount at 400–600 °C. The 7 wt% Ce₂S₃-Cu₂S exhibits paramagnetic behavior with a saturation magnetization of 1.2 µ_B/Ce. UV-Vis analysis indicates that the addition of Ce₂S₃ can reduce the optical energy gap and enrich the band structure of Cu₂S. With increasing addition of Ce₂S₃ and rising sintering temperature, the density of Ce₂S₃-Cu₂S gradually increases, and the hardness of Ce₂S₃-Cu₂S increases by 52.5% at 400 °C and by 34.2% at 600 °C. The friction test results show that an appropriate addition amount of Ce₂S₃ can increase the friction coefficients of Cu₂S. Ce₂S₃ modification offers a novel strategy to simultaneously enhance the structural and service stability of Cu₂S by regulating Cu ion diffusion and suppressing compositional fluctuations. Full article

In this article, the mechanism of relaxation polarization currents occurring at a constant temperature (isothermal process) in crystals with ionic-molecular chemical bonds (CIMBs) in an alternating electric field was investigated. Methods of the quasi-classical kinetic theory of dielectric relaxation, based on solutions of the nonlinear system of Fokker–Planck and Poisson equations (for the blocking electrode model) and perturbation theory (by expanding into an infinite series in powers of a dimensionless small parameter) were used. Generalized nonlinear mathematical expressions for calculating the complex amplitudes of relaxation modes of the volume-charge distribution of the main charge carriers (ions, protons, water molecules, etc.) were obtained. On this basis, formulas for the current density of relaxation polarization (for transient processes in a dielectric) in the k-th approximation of perturbation theory were constructed. The isothermal polarization currents are investigated in detail in the first four approximations (k = 1, 2, 3, 4) of perturbation theory. These expressions will be applied in the future to compare the results of theory and experiment, in analytical studies of the kinetics of isothermal ion-relaxation (in crystals with hydrogen bonds (HBC), proton-relaxation) polarization and in calculating the parameters of relaxers (molecular characteristics of charge carriers and crystal lattice parameters) in a wide range of field parameters (0.1–1000 MV/m) and temperatures (1–1550 K). Asymptotic (far from transient processes) recurrent formulas are constructed for complex amplitudes of relaxation modes and for the polarization current density in an arbitrary approximation k of perturbation theory with a multiplicity r by the polarizing field (a multiple of the fundamental frequency of the field). The high degree of reliability of the theoretical results obtained is justified by the complete agreement of the equations of the mathematical model for transient and stationary processes in the system with a harmonic external disturbance. This work is of a theoretical nature and is focused on the construction and analysis of nonlinear properties of a physical and mathematical model of isothermal ion-relaxation polarization in CIMB crystals under various parameters of electrical and temperature effects. The theoretical foundations for research (construction of equations and working formulas, algorithms, and computer programs for numerical calculations) of nonlinear kinetic phenomena during thermally stimulated relaxation polarization have been laid. This allows, with a higher degree of resolution of measuring instruments, to reveal the physical mechanisms of dielectric relaxation and conductivity and to calculate the parameters of a wide class of relaxators in dielectrics in a wide experimental temperature range (25–550 K). Full article

This study investigated the effects of silver doping, natural ageing, and thermal-induced oxidation on the surface chemistry, morphology, and thermal performance of copper thin films. Ag is used as a doping element in Cu because, in bulk materials it usually refines microstructures, leading to increased hardness and mechanical strength through mechanisms such as solid solution strengthening and twinning. In this work was also used due to its oxidation resistance. Thin films of pure and silver-doped copper (Cu_2Ag and Cu_4Ag) were deposited by RF magnetron sputtering and characterized as-deposited, naturally aged, at room temperature and humidity for one year, and thermally treated at 200 °C, in air. The characterization included X-ray photoelectron spectroscopy (XPS), Atomic Force microscopy (AFM), and thermal analysis, specifically thermal conductivity (λ), thermal diffusivity (α), and thermal capacity (ρ.Cp). Surface XPS analysis revealed changes in copper and silver oxidation states after natural aging and annealing. AFM revelead that the incorporation of silver and heat treatment altered the surface roughness and morphology. Thermal analysis found that for lower silver concentrations, the thermal conductivity increased, but aging and annealing had varying effects depending on the silver content. The Cu_4Ag film showed the best thermal stability after natural ageing. Overall, the results suggest that carefully controlled silver doping can enhance the thermal stability of copper thin films for applications where aging is a concern, such as microelectronics. Full article

Deep coalbed methane (CBM) resources possess significant potential. However, their development is challenged by geological characteristics such as high in situ stress and low permeability. Furthermore, existing production strategies often prove inadequate. In order to achieve long-term stable production of deep coalbed methane reservoirs and increase their final recoverable reserves, it is urgent to construct a scientific and reasonable drainage system. This study focuses on the deep CBM reservoir in the Daning-Jixian Block of the Ordos Basin. First, a thermal–hydraulic–mechanical (THM) multi-physics coupling mathematical model was constructed and validated against historical well production data. Then, the model was used to forecast production. Finally, key control measures for enhancing well productivity were identified through production strategy adjustment. The results indicate that controlling the bottom-hole flowing pressure drop rate at 1.5 times the current pressure drop rate accelerates the early-stage pressure drop, enabling gas wells to reach the peak gas production earlier. The optimized pressure drop rates for each stage are as follows: 0.15 MPa/d during the dewatering stage, 0.057 MPa/d during the gas production rise stage, 0.035 MPa/d during the stable production stage, and 0.01 MPa/d during the production decline stage. This strategy increases peak daily gas production by 15.90% and cumulative production by 3.68%. It also avoids excessive pressure drop, which can cause premature production decline during the stable phase. Consequently, the approach maximizes production over the entire life cycle of the well. Mechanistically, the 1.5× flowing pressure drop offers multiple advantages. Firstly, it significantly shortens the dewatering and production ramp-up periods. This acceleration promotes efficient gas desorption, increasing the desorbed gas volume by 1.9%, and enhances diffusion, yielding a 39.2% higher peak diffusion rate, all while preserving reservoir properties. Additionally, this strategy synergistically optimizes the water saturation and temperature fields, which mitigates the water-blocking effect. Furthermore, by enhancing coal matrix shrinkage, it rebounds permeability to 88.9%, thus avoiding stress-induced damage from aggressive extraction. Full article

This study reports the development and optimization of a Melissa officinalis oil-based nanoemulgel for transdermal delivery using a Design-of-Experiments (DoE) approach. A Central Composite Design (CCD) was applied to optimize Tween 80 concentration and homogenization time, resulting in a nanoemulsion with a droplet size of 127.31 nm, PDI of 17.7%, and zeta potential of −25.0 mV, indicating good colloidal stability. FTIR analysis confirmed the presence of functional groups such as O–H, C=O, and C–O–C, supporting the oil’s phytochemical richness and therapeutic potential. DSC analysis revealed enhanced thermal stability and successful encapsulation, while SEM imaging showed a uniform and spherical microstructure. The drug release followed Higuchi kinetics (R² = 0.900), indicating diffusion-driven release, with the Korsmeyer–Peppas model (n = 0.88) suggesting anomalous transport. Antibacterial studies showed inhibition of Staphylococcus aureus (MIC = 250 µg/mL) and Escherichia coli (MIC = 500 µg/mL). In vivo anti-inflammatory testing demonstrated significant edema reduction (p < 0.05) using a carrageenan-induced rat paw model. These results support the potential of Melissa nanoemulgel as a stable and effective topical therapeutic for inflammatory and microbial skin disorders. Full article

Hybrid polysaccharide-based aerogels offer significant potential as advanced drug delivery platforms due to their tunable structure, high porosity, and biocompatibility. In this study, aerogel microparticles were synthesized using alginate, pectin, carrageenan, and their hybrid formulations via an emulsion–gelation technique followed by supercritical fluid CO₂ extraction. The resulting aerogels exhibit mesoporous structures with specific surface areas ranging from 324 to 521 m²/g and pore volumes between 1.99 and 3.75 cm³/g. Comprehensive characterization (SEM, gas sorption, XRD, TGA, DSC, and FTIR) confirmed that hybridization improved morphological uniformity and thermal stability compared to single polymer aerogels. Ibuprofen was used as a model drug to evaluate loading efficiency and release kinetics. Among all formulations, the alginate/carrageenan (2:1) hybrid showed the highest drug loading efficiency (93.5%) and a rapid release profile (>90% within 15 min), closely matching the performance of commercial ibuprofen tablets. Drug release followed Fickian diffusion, as confirmed by the Korsmeyer–Peppas model (R² > 0.99). These results highlight the potential of hybrid polysaccharide aerogels as vehicles for drug delivery and other fast-acting therapeutic applications. Full article

Microstructural analysis of hot-compressed magnesium alloys is crucial for understanding the plastic formability of magnesium alloys during thermo-mechanical processing. Thermal compression tests and finite element simulations were conducted on a low rare-earth (RE) Mg-1.8Nd-0.4Zr-0.3Ca alloy. Multiple microstructural characterization techniques were employed to analyze slip systems, twinning mechanisms, dynamic recrystallization (DRX), and precipitate phases in the hot-compressed alloy. The results demonstrated that the equivalent strain distribution within compressed specimens exhibits heterogeneity, with a larger equivalent strain in the core. After thermal compression, the original microscopic structure formed a necklace-like structure. The primary DRX mechanisms comprise continuous dynamic recrystallization (CDRX), twin-induced dynamic recrystallization (TDRX), and particle-stimulated nucleation (PSN). Pyramidal slip and recrystallization constitute primary contributors to peak texture weakening and tilting. Mg₄₁Nd₅ and α-Zr phases enhanced dislocation density by impeding dislocation motion and promoting cross-slip activation. Hot compression provided the necessary thermal activation energy and stress conditions for solute atom diffusion and clustering, triggering dynamic precipitation of Mg₄₁Nd₅ phases. Full article

Externally governed hydrogel swelling is a highly convenient yet inherently challenging process, as it requires both responsive materials and appropriately tuned external stimuli. In this work, for the first time, the influence of simultaneous action of external physical fields—ultrasound (US) and microwave heating (MW), combined with cooling—on the isothermal swelling kinetics of poly(methacrylic acid) (PMAA) hydrogel was investigated and compared with swelling under conventional thermal heating (TH) under isothermal conditions. Swelling kinetics were monitored over a temperature range of 248–318 K, under simultaneous cooling with either US, MW, or TH. The well-established Peppas model was used to determine swelling kinetics parameters, revealing a significant acceleration in the swelling process under MW (up to 48.8 times at 313 K), as well as different water penetrating mechanisms (non-Fickian diffusion) compared to TH and US (Super-case II). Additionally, it was demonstrated that the swelling conversion curves could be mathematically described using a “shrinking boundary surfaces” model. Isothermal swelling constants and the corresponding kinetic parameters (activation energy E_a and pre-exponential factor ln A) were calculated. The results confirmed that external physical fields significantly influence the thermal activation and swelling behavior of PMAA xerogels, offering insight into field-responsive transport processes in hydrogel networks. Full article

Carmustine (BCNU) is a powerful alkylating agent primarily used in the chemotherapeutic treatment of malignant brain tumors. However, its clinical application faces significant constraints due to its lipophilicity, low thermal stability, and rapid degradation in physiological environments. To tackle these challenges, our research aimed at the development and detailed characterization of α-cyclodextrin (α-CD) inclusion complexes (ICs) with BCNU employing three different synthesis techniques: co-grinding, cryomilling, and co-precipitation. The selected synthetic methods displayed variations dependent on the technique used, affecting the efficiency, inclusion ratios, and drug-loading capacities, with co-precipitation achieving the most favorable complexation parameters. Structural elucidation through ¹H NMR chemical shifts analysis indicated that only partial inclusion of BCNU occurred within α-CD in ICs produced via co-grinding, while cryomilling and co-precipitation allowed for complete inclusion. Multimodal spectroscopic analyses (FT-IR, UV-Vis, ¹³C CP MAS NMR, and ESI-MS) further substantiated the effective encapsulation of BCNU within α-CD, and systematic solubility assessments via Job’s continuous variation and the Benesi-Hildebrand method revealed a 1:1 host-guest stoichiometry. The ICs obtained were evaluated for BCNU release in vitro at pH levels of 4, 5, 6.5, and 7.4. The mechanism of BCNU drug release was determined to be Fickian diffusion, with the highest cumulative release noted in the acidic microenvironment. These findings collectively validate the effectiveness of α-CD as a functional excipient for the modulation of BCNU’s physicochemical properties through non-covalent complexation. This strategy shows potential for increasing the stability and solubility of BCNU, which may enhance its therapeutic effectiveness in the treatment of brain tumors. Full article