Search Results (2,687)

Zinc–tin oxide (ZTO) thin films (ZnO)_x(SnO₂)_1−x with different material composition x (0 < x < 1) are deposited by spin coating on glass substrates at room temperature. The Differential Scanning Calorimetry (DSC) data of the precursor compounds show gradual phase transitions up to 480 °C. These data are used for an appropriate regime for thermal annealing of the layers. X-ray photoelectron spectroscopy (XPS) data show mixed oxide compound formation in states Zn²⁺, Sn⁴⁺ and O^2- of the constituents. Optical investigation manifests high transmittance above 80% in the visible spectral range and an optical band gap of 3.3–3.7 eV. The work functions vary between 4.1 eV and 5 eV, depending on the annealing, with deviations less than 1% for surface 1 mm² scans. Stack devices ITO/ZTO/metal with different metal contacts are formed. The I–V (current–voltage) measurements of the fabricated stacks exhibit Ohmic or nonlinear behavior, depending on the material composition and the work function levels. Full article

This study explores, for the first time, the application of electrospun biobased poly(butylene 2,5-furanoate) (PBF) and poly(pentamethylene 2,5-furanoate) (PPeF) mats in biomedical and drug delivery fields, through a careful investigation of their structure–property relationship. PBF mats, with a glass transition temperature (T_g) of 25–30 °C and an as-spun crystallinity of 18.8%, maintained their fibrous structure (fiber diameter ~1.3 µm) and mechanical properties (stiffness ~100 MPa, strength ~4.5 MPa, strain at break ~200%) under treatment in physiological conditions (37 °C, pH 7.5). In contrast, PPeF mats, being amorphous with a T_g of 14 °C, underwent significant densification, with geometrical density increasing from 0.68 g/cm³ to 1.07 g/cm³, which depressed the specific (i.e., normalized by density) mechanical properties. DSC analysis revealed that the treatment promoted crystallization in PBF (reaching 45.9% crystallinity), while PPeF showed limited, but interestingly not negligible, structural reorganization. Both materials promoted good cell adhesion and were biocompatible, with lactate dehydrogenase release not exceeding 20% after 48 h. The potential of PBF mats for drug delivery was evaluated using dexamethasone. The mats exhibited a controlled drug release profile, with ~10% drug release in 4 h and ~50% in 20 h. This study demonstrates the versatility of these biopolyesters in biomedical applications and highlights the impact of polymer structure on material performance. Full article

Waterborne polyurethane cationomer coatings modified with 1,3-bis(3(3-(propoxy-2-ol-)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide)-3-propyloxy))tetramethyldisiloxane (TMDS–AGE–DOPA) containing phosphorus and silicon atoms were obtained. Their structures were confirmed by Fourier transform infrared (FTIR) spectroscopy. The effect of TMDS–AGE–DOPA on thermal properties, flame retardancy, and surface characteristics (gloss, contact angle, surface free energy), as well as performance properties (hardness, impact resistance), was investigated. A coupled TG-FTIR technique was employed for evolved gas analysis. Thermal stability decreased with the addition of the modifier, while the glass transition temperature increased from −19 to 25 °C. The modifier improved the flame retardancy of the material by shifting the peak temperature of the heat release rate (T_PHRR) to lower values. The gloss of the coatings was very high (>90 GU at all angles studied), although it decreased with increasing modifier content. The presence of phosphorus moieties from the modifier enhanced hydrophilicity, raising surface free energy (SFE) from 37.9 to 44.0 mJ/m². The coatings are soft materials with a Persoz hardness in the range of 0.05–0.32. The modifier increased hardness but reduced impact strength. The obtained cationomers can be applied as environmentally friendly coatings on hydrophilic surfaces such as textiles, glass, or wood. Full article

Background: Patients with no-option chronic limb-threatening ischemia (NoCLTI), lacking suitable distal arteries for conventional revascularization, face major limb amputation. The 1-year mortality rate after major amputation is 48.3%, increasing to 70.9% in 3 years. Open deep venous arterialization (DVA) offers a promising alternative for limb salvage, achievable through open, endovascular, or hybrid approaches. We aim to provide a comprehensive, step-by-step guide to performing open DVA in NoCLTI patients, addressing preoperative and postoperative considerations as well as the technical details of the procedure. Methods: Patient selection for open DVA focuses on individuals with NoCLTI at high risk for amputation. Preoperative assessments include evaluating risk factors, determining limb threat severity using the Wound, Ischemia, and foot Infection (WIfI) score, and mapping anatomical patterns via the Global Limb Anatomic Staging System (GLASS). The procedure involves identifying the target artery using Doppler ultrasound, performing microdissection to expose the artery and vein, ligating proximal vein branches, and creating a side-to-side anastomosis. Venous valves are disrupted with a valvulotome to allow antegrade flow. A proximal bypass graft may be applied if necessary. Results: Postoperatively, patients are monitored for 2–4 days with frequent Doppler assessments. Anticoagulation therapy begins with a heparin drip, transitioning to oral agents and/or dual antiplatelet therapy. Wound care includes deferred debridement for 2–4 weeks and may involve negative-pressure therapy. Follow-up involves weekly visits for the first month, and then at 3 months, and every 6 months thereafter, with surveillance using transcutaneous oxygen measurement, the toe–brachial index, and arterial duplex ultrasound. Conclusions: Open DVA represents a viable limb salvage option for patients with NoCLTI, potentially avoiding major amputations and improving quality of life. Success depends on careful patient selection, a meticulous surgical technique, and comprehensive postoperative care. Full article

In recent years, the employment of rejuvenators and warm mix asphalt (WMA) additives for reclaimed asphalt pavement (RAP) has been recognized as a popular approach to increase the recycling rate of waste materials and promote the sustainable development of pavement engineering. However, the composition of warm mix recycled asphalt binder is complicated, and the microstructural changes brought about by the rejuvenators and WMA additives are critical in determining its macroscopic mechanical properties. This research focuses on the atomic modeling of the rejuvenators and WMA additives diffusion behavior of the warm mix recycled asphalt binder. The objective is to reveal the thermodynamic performance and diffusion mechanism of the WMA binder under the dual presence of rejuvenators and WMA additives. Three types of mutual diffusion systems (Aged and oil + virgin + wax, Aged + virgin + wax, and Aged and oil + virgin) were established, respectively, for a comparative investigation of the glass transition temperature, viscosity, thermodynamics, free volume, and diffusion behavior. The results indicate a 44.27% and 31.33% decrease in the glass transition temperature and apparent viscosity, respectively, after the incorporation of 5% oil rejuvenators in the Aged + virgin + wax asphalt binder, demonstrating the improved cracking resistance and construction workability. The presence of the RAP binder and organic WMA additives raised the cohesion of the asphalt binder and decreased self-healing ability and free volume, and these detrimental influences can be offset by the introduction of rejuvenators. The combined use of rejuvenators and organic WMA additives remarkably enhanced the de-agglomeration to asphaltenes, stimulated the activity of aged RAP macromolecular components, and ultimately improved the blending efficiency of virgin binders with the overall structure of RAP binders. Full article

Mg₇₂Zn₂₇Pt₁ and Mg₇₂Zn₂₇Cu₁ metallic glasses were produced using a melt-spinner. Their crystallization kinetics were investigated during annealing with five heating rates using DSC. Amorphous Mg₇₂Zn₂₇Pt₁ crystallized in the form of one and Mg₇₂Zn₂₇Cu₁ crystallized in the form of two exothermic crystallization peaks. It was noticed that the glass transition, the onset crystallization and the crystallization peak temperatures were strongly heating-rate-dependent. The addition of Pt and Cu increased the stability compared to that of binary Mg-Zn glass, and especially so with Pt, due to its higher melting point and different atom size to those of Mg and Zn. The activation energies were calculated using six model-free methods: the Kissinger, Ozawa–Flynn–Wall, Boswell, Tang, Augis–Bennett and Gao–Wang methods. The Augis–Bennett and Gao–Wang methods allow for the calculation of only the activation energy at the crystallization peak but they are the only ones that consider $T_x$ or $dx/dT$. For Mg₇₂Zn₂₇Pt₁, the calculated values fluctuate in the ranges 114.60–117.99 kJ/mol, 102.46–105.98 kJ/mol and 71.16–98.62 kJ/mol for $E_g$, $E_x$ and $E_p$, respectively, whereas, for Mg₇₂Zn₂₇Cu₁, the calculated values are in the ranges of 98.51–101.77 kJ/mol, 95.15–98.51 kJ/mol and 55.15–93.34 kJ/mol for $E_g$, $E_x$ and $E_p$, respectively. Both alloys are meta-stable in the amorphous state and crystallization occurs spontaneously. The Kissinger, Ozawa–Flynn–Wall, Tang and Boswell methods give similar values for the activation energy. The Gao–Wang method significantly underestimates values compared to other methods. The Augis–Bennett method shows much lower values for the local activation energy. Considering the ease of their formulas, best convergence and widespread use in the literature, the Kissinger and Ozawa–Flynn–Wall methods will work very well for any comparison. Full article

Aceclofenac (ACF), a non-steroidal anti-inflammatory drug, was obtained in its amorphous state by cooling from melt. The glass transition was investigated using dielectric and calorimetric techniques, namely, dielectric relaxation spectroscopy (DRS), thermally stimulated depolarization currents (TSDC), and conventional and temperature-modulated differential scanning calorimetry (DSC and TM-DSC). The dynamic behavior in both the glassy and supercooled liquid states revealed multiple relaxation processes. Well below the glass transition, DRS was able to resolve two secondary relaxations, γ and β, the latter of which was also detectable by TSDC. The kinetic parameters indicated that both processes are associated with localized motions within the molecule. The main (α) relaxation was clearly observed by DRS and TSDC, and results from both techniques confirmed a non-Arrhenian temperature dependence of the relaxation times. However, the glass transition temperature (T_g) extrapolated from DRS data significantly differed from that obtained via TSDC, which in turn showed reasonable agreement with the calorimetric T_g (T_g-DSC = 9.2 °C). The values of the fragility index calculated by the three experimental techniques converged in attributing the character of a moderately fragile glass former to ACF. Above the α relaxation, TSDC showed a well-defined peak. In DRS, after “removing” the high-conductivity contribution using ε’ derivative analysis, a peak with shape parameters α_HN = β_HN = 1 was also detected. The origin of these peaks, found in the full supercooled liquid state, has been discussed in the context of structural and dynamic heterogeneity. This is supported by significant differences observed between the FTIR spectra of the amorphous and crystalline samples, which are likely related to aggregation differences resulting from variations in the hydrogen bonds between the two phases. Additionally, the pronounced decoupling between translational and relaxational motions, as deduced from the low value of the fractional exponent x = 0.72, derived from the fractional Debye–Stokes–Einstein (FDSE) relationship, further supports this interpretation. Full article

Using 3D-printed (3DPd) polymers and their composites as shape memory materials in various smart engineering applications has raised the demand for such functionally graded sustainable materials. This study aims to investigate the viscoelastic, shape memory, and fracture toughness properties of the epoxy-based ultraviolet (UV)-curable resin. A UV-based DLP (Digital Light Processing) printer was employed for the 3D printing (3DPg) epoxy-based structures. The effect of the hydrothermal accelerated ageing on the various properties of the 3DPd components was examined. The viscoelastic performance in terms of glass transition temperature (T_g), storage modulus, and loss modulus was evaluated. The shape memory polymer (SMP) performance with respect to shape recovery and shape fixity (programming the shape) were calculated through dynamic mechanical thermal analysis (DMTA). DMTA is used to reveal the molecular mobility performance through three different regions, i.e., glass region, glass transition region, and rubbery region. The shape-changing region (within the glass transition region) between the T_g value from the loss modulus and the T_g value from the tan(δ) was analysed. The temperature memory behaviour was investigated for flat and circular 3DPd structures to achieve sequential deployment. The critical stress intensity factor values of the single-edge notch bending (SENB) specimens have been explored for different crack inclination angles to investigate mode I (opening) and mixed-mode I/III (opening and tearing) fracture toughness. This study can contribute to the development of highly complex shape memory 3DPd structures that can be reshaped several times with large deformation. Full article

This research studied the recycling of borosilicate glass wastes from damaged laboratory glassware. The luminescent glasses were prepared by doping glass waste powder with rare earth ions, namely, dysprosium ions (Dy³⁺) and samarium ions (Sm³⁺), as well as co-doping with Dy³⁺ and Sm³⁺ at a concentration of 2% by weight. The sintering process was conducted in a microwave oven for a duration of 15 min. The photoluminescence spectra of the doped glasses were obtained under excitation at 401 nm and 388 nm. The results showed that the emission characteristics depended on the doping concentrations of Dy³⁺ and Sm³⁺ and the excitation wavelengths. Upon excitation at 401 nm, the co-doped glasses exhibited the maximum emission peak of Sm³⁺ at 601 nm (yellowish and orange region in the CIE chromaticity diagram) due to the energy transition from ⁴G_5/2 to ⁶H_7/2. When excited at 388 nm, however, the emission spectra of the co-doped glasses were similar to the characteristic emission peaks of Dy³⁺ (white region in the CIE chromaticity diagram), but the peak position exhibits a red shift. This could be attributed to an increase in the amount of non-bridging oxygens (NBOs) by co-doping. Full article

Perovskite solar cells (PSCs) have emerged as a promising photovoltaic technology, yet their stability under environmental stressors remains a critical challenge. This study examines the substrate-dependent degradation mechanisms of perovskite films and evaluates the role of methylammonium chloride (MACl) incorporation. Devices fabricated on ITO and glass substrates exhibited markedly different stability behaviors under high-humidity conditions. ITO substrates delayed the phase transition from the black α-phase to the yellow δ-phase due to stronger substrate–film interactions and reduced defect densities, while glass substrates facilitated rapid degradation through moisture infiltration and grain boundary instability. MACl incorporation enhanced the initial crystallinity and optoelectronic properties of the perovskite films, as evidenced by superior power conversion efficiency and photon absorption. However, residual MACl under humid conditions introduced structural instability, particularly on glass substrates. To address these challenges, a fully coated ITO structure, referred to as the Island Type design, was proposed. This structure eliminates exposed glass regions, leveraging the stabilizing properties of ITO to suppress moisture infiltration and prolong device durability. The findings provide a comprehensive understanding of the interplay between substrate properties and material composition in PSC stability and highlight the potential of structural optimizations to balance efficiency and durability for commercial applications. Full article

Background: It is generally accepted that water as a plasticizer can decrease the glass transition temperatures (T_gs) of amorphous drugs and drug delivery systems, resulting in physical instabilities. However, a recent study has reported an anti-plasticizing effect of water on amorphous lidocaine (LID). In co-amorphous systems, LID might be used as a co-former to impair the plasticizing effect of water. Method: Flurbiprofen (FLB) was used to form a co-amorphous system with a mole fraction of LID of 0.8. The effect of water on the stability of co-amorphous FLB-LID upon hydration was investigated. The crystallization behaviors of anhydrous and hydrated co-amorphous FLB-LID systems were measured by an isothermal modulated differential scanning calorimetric (iMDSC) method. The relaxation times of the co-amorphous FLB-LID system upon hydration were measured by a broadband dielectric spectroscopy (BDS), and the differences in Gibbs free energy (ΔG) and entropy (ΔS) between the amorphous and crystalline phases were determined by differential scanning calorimetry (DSC). Results: It was found that the crystallization tendency of co-amorphous FLB-LID decreased with the addition of water. Molecular mobility and thermodynamic factors were both investigated to explain the difference in crystallization tendencies of co-amorphous FLB-LID upon hydration. Conclusions: The results of the study showed that LID could be used as an effective co-former to decrease the crystallization tendency of co-amorphous FLB-LID upon hydration by enhancing the entropic (ΔS) and thermodynamic activation barriers (TΔS)³/ΔG²) to crystallization. Full article

This work investigates nanostructured Ho_0.5Ca_0.5MnO₃, considered a model system of the Ln_0.5Ca_0.5MnO₃ series of manganites with perovskite structures featuring small lanthanide (Ln) ions half-substituted by Ca ions. Here, we propose a modified hybrid sol–gel–solid-state approach to produce multiple samples with a single batch, obtaining very high crystalline quality and ensuring the same chemical composition, with an average particle size in the range 39–135 nm modulated on-demand by a controlled calcination process. Our findings evidence that, provided the crystalline structure is preserved, the charge-ordering transition can be observed even at the nanoscale. Additionally, this research explores the presence of glassy phenomena, which are commonly seen in this class of materials, to enhance our understanding beyond simplistic qualitative observations. Comprehensive characterization using DC and AC magnetometry, along with relaxation and aging measurements, reveals that the complex dynamics typical of glassy phenomena emerge only at the nanoscale and are not visible in the bulk counterpart. Nevertheless, the analysis confirms that even the sample with the smallest nanoparticles cannot be intrinsically classified as canonical spin glass. Full article

Epoxy-terminated hyperbranched polymers (EHBPs) are a class of macromolecular polymers with a hyperbranched structure containing epoxy groups. They possess characteristics such as low viscosity, high functionality, and thermal stability, which endow them with broad application potential in materials science and chemical engineering. This study uses epoxidized soybean oil (ESO) as the raw material, which undergoes ring-opening reactions with glycerol and is esterified with 2,2-bis(hydroxymethyl)propionic acid (DMPA) to obtain epoxy soybean oil polyol (EGD) with a high hydroxyl value. Subsequently, four types of EHBPs are synthesized by incorporating epichlorohydrin (ECH) in mass ratios of 1:3, 1:4, 1:5, and 1:6 under strong alkaline conditions. The product structure is characterized using FT–IR and GPC. The degree of branching of EGD is calculated using ¹H NMR and ¹³C NMR spectroscopy. The epoxy value of EHBPs is tested using the hydrochloric acid–acetone method, and the water contact angle, adhesion properties, rheological properties, and thermal properties of the EHBPs are also evaluated. The results show that the degree of branching of EGD is 0.45. The epoxy values of the EHBPs are 0.73, 0.79, 0.82, and 0.89 mol/100g, respectively. As the epoxy value and molecular weight of the epoxy hyperbranched polymers (EHBPs) increase, the water contact angle and adhesion strength of the EHBPs rise progressively and the viscosity decreases. Additionally, the glass transition temperature increases with the increase in the epoxy value. These epoxy hyperbranched polymers with low viscosity and high adhesion strength offer a promising approach for modifying surface coatings or formulating adhesives. Full article

To design bioactive glass compositions with optimal thermal, mechanical, and bioactive properties as coatings on Ti6Al4V metallic implants, we investigated phosphosilicate bioactive glasses based on the 6P55 composition. SiO₂ was substituted with B₂O₃ to improve adhesion to the metallic implants and physical properties. This substitution significantly altered the glass structure and is hypothesized to improve adhesion. Computational and experimental methods revealed that boron substitution introduced BO₃ and BO₄ units, disrupted the Si-O network, and formed non-bridging oxygens (NBOs), resulting in a decrease in density and glass transition temperature (T_g). These changes were attributed to boron’s dual role as a network former and modifier, influencing coordination environments and connectivity. Thermal and structural analyses showed that optimal boron levels improved thermal expansion and network flexibility, which are critical for coating applications. By integrating molecular dynamics simulations and experimental techniques, this study provides valuable insights into tailoring glass compositions for enhanced performance on metallic substrates. Full article

This study addresses the limitations of traditional polyimides (PIs) in high-frequency and high-temperature soft electronic applications, and then introducing trifluoromethylbenzene (TFMB) into the molecular structure and employing various diamines as connecting components to solve the bottleneck. The innovative molecular design enhances thermal, mechanical, and dielectric properties, overcoming challenges in balancing these performances. The optimized fluorinated PI (TPPI50) exhibits exceptional properties, including a glass transition temperature of 402 °C, thermal decomposition temperature of 563 °C, tensile strength of 232.73 MPa, elongation at break of 26.26%, and dielectric constant of 2.312 at 1 MHz with a dielectric loss as low as 0.00676. These improvements are attributed to the unique synergy between TFMB’s fluorinated groups, which reduce molecular polarization, and the biphenyl structure, which reinforces chain stability. Compared to conventional PIs, TPPI50 demonstrates superior comprehensive performance, making it highly suitable for soft circuits, high-frequency signal transmission, and advanced applications such as wearable devices and biosensors. This study provides a robust framework for industrial applications, offering a path to next-generation soft electronics with enhanced reliability and performance. Full article