Search Results (10,823)

This study investigates the effects of aluminum and nitrogen content on the microstructure, mechanical properties, and tribological performance of high-entropy coatings based on (TiCrAl_ₓNbY)N_y systems. Using a hybrid magnetron sputtering technique, both metallic and nitride coatings were synthesized and evaluated. Increasing the aluminum concentration led to a transition from a crystalline to a nanocrystalline and nearly amorphous (NC/A) structure, with the TiAl_0.5CrNbY sample (11.8% Al) exhibiting the best balance of hardness (6.8 GPa), elastic modulus (87.1 GPa), and coefficient of friction (0.64). The addition of nitrogen further enhanced these properties, transitioning the coatings to a denser fine-grained FCC structure. The HN2 sample (45.8% nitrogen) displayed the highest hardness (21.8 GPa) but increased brittleness, while the HN1 sample (32.9% nitrogen) provided an optimal balance of hardness (14.3 GPa), elastic modulus (127.5 GPa), coefficient of friction (0.60), and wear resistance (21.2 × 10⁻⁶ mm³/Nm). Electrochemical impedance spectroscopy revealed improved corrosion resistance for the HN1 sample due to its dense microstructure. Overall, the (TiAl_0.5CrNbY)N_0.5 coating achieved the best performance for friction applications, such as break and clutch systems, requiring high coefficients of friction, high wear resistance, and durability. Full article

One of the most effective methods to limit the mechanical vibrations of bladed disks is the use of friction damping at mechanical joint interfaces. Unfortunately, dedicated tests to assess the impact of mistuning and the effectiveness of friction dampers are uncommon. This paper presents an original design of an academic demonstrator to perform an experimental analysis of the dynamic response of a tip-free bladed disk with under-platform dampers (UPDs) , including an identification of intrinsic and contact mistuning introduced by the UPDs. The 48-blade disk was tested in a vacuum spinning rig by using permanent magnets. Vibration measurements were performed with the Blade Tip-Timing system. Tests were simulated using the Policontact tool, which predicted the average experimental nonlinear response in the presence of UPD, confirming the tool’s ability to capture the general nonlinear dynamic behavior of the mistuned bladed disk. This study presents a novel approach combining experimental Blade Tip Timing (BTT) with numerical simulations using Policontact (ver. 3.0) software and a model update based on experimental evidence to validate nonlinear dynamic responses. It distinguishes between intrinsic and contact mistuning effects, providing new insights into their impact on bladed disk vibrations. Additionally, a comparison of aluminum and steel UPDs reveals that steel offers a 26% greater damping efficiency due to its higher density and preload, significantly improving vibration reduction. Full article

Industrial CO₂ emissions contribute to pollution and greenhouse effects, highlighting the importance of carbon capture. Potassium carbonate (K₂CO₃) is an effective CO₂ absorbent, yet its liquid-phase absorption faces issues like diffusion resistance and corrosion risks. In this work, the solid adsorbents were developed with K₂CO₃ immobilized on the selected porous supports. Al₂O₃ had an optimum CO₂ adsorption capacity of 0.82 mmol g⁻¹. After further optimization of its pore structure, the self-prepared support Al₂O₃-2, which has an average pore diameter of 11.89 nm and a pore volume of 0.59 cm³ g⁻¹, achieved a maximum CO₂ adsorption capacity of 1.12 mmol g⁻¹ following K₂CO₃ impregnation. Additionally, the relationship between support structure and CO₂ adsorption efficiency was also analyzed. The connectivity of the pores and the large pore diameter of the support may play a key role in enhancing CO₂ adsorption performance. During 10 cycles of testing, the K₂CO₃-based adsorbents demonstrated consistent high CO₂ adsorption capacity with negligible degradation. Full article

We examined the effectiveness of metal-exchanged phosphomolybdic acid salts in converting levulinic acid, derived from biomass, into valuable products (alkyl levulinate). We prepared salts of phosphomolybdic acid using different metals (Fe³⁺, Al³⁺, Zn²⁺, Cu²⁺, Mn²⁺, Ni²⁺, and Co²⁺). The influence of metal cations on the conversion and selectivity of the reactions was assessed. We found that the salts prepared with iron and aluminum phosphomolybdate were the most effective catalysts for the esterification of levulinic acid with methanol, with the conversion and selectivity tending towards 100% after 6 h of reaction at a temperature of 323 K. The effect of catalyst loading and its recovery and reuse was evaluated; the results from the reaction using aluminum phosphomolybdate remained similar for four cycles of use. The influence of temperature on conversion and selectivity was investigated between 298 and 353 K. The reactivity of different alcohols with a carbon chain size of C1-C4 was assessed and conversions above 65% were obtained for all alcohols tested under the conditions evaluated, except for tert-butyl alcohol. These catalysts are a promising alternative to the traditional soluble and corrosive Brønsted acid catalysts. The superior performance of these catalysts was ascribed to the higher pH decline triggered by the hydrolysis of these metal cations. Full article

To enhance the sustainability of construction and meet the sector’s environmental agenda, it is essential to comprehensively scrutinize the environmental, social, and economic impacts of construction projects from the project’s design stage. Such assessment is of utmost importance to minimize the impacts of both new construction and rehabilitation projects and is particularly critical during the selection of building materials and construction solutions. This work reports improvements in functionality and user-friendliness of an eco-design tool (UAveiroGreenBuilding) targeting the construction/rehabilitation sector and previously developed within our research group. The optimized version of the eco-design tool underwent validation through the assessment of competitive window frame materials (e.g., wood, PVC, and aluminum) for potential implementation in a rehabilitation project. Windows with PVC frames were identified as the preferred window configuration due to their superior environmental performance and favorable economic profile. Additionally, a digital communication interface was developed to connect the eco-design tool with building information modeling (BIM) projects, achieved through a routine integrated using a Dynamo application. Such successful integration not only streamlined and expedited the data transfer process by obviating the need for manual input but it also enabled the storage of environmental data throughout the life cycle of the project using a simple and reliable data storage protocol. Full article

Background: Trigeminal neuralgia (TN) is a disease that causes severe pain that can seriously affect the quality of life. This study aimed to compare the effectiveness of two different low-level laser therapies (LLLT) as alternatives to medical treatment to reduce pain and improve the quality of life in patients with TN. Methods: A total of 45 patients were randomly divided into 3 groups. In the first group, a new-generation diode laser (GRR laser) was applied at predetermined points in the trigeminal nerve line. In the second group, a low-level neodymium-doped yttrium aluminum garnet (Nd:YAG) laser was applied along the affected nerve line. The placebo group received the same protocol with a Nd:YAG laser without the device switched on. The scores were recorded pre- and post-treatment using the Brief Pain Inventory-Facial (BPI-facial) scale. Results: A statistically significant difference was found between the pre- and post-treatment values of all four variables in the GRR laser, Nd:YAG laser, and placebo groups. When the post-treatment values were compared, statistically significant differences were found between the groups in pain frequency, pain intensity, and interference in facial-specific activities, but no differences were found in general activities. Conclusions: Both LLLTs can be considered alternative treatment modalities for TN, but the GRR laser treatment was more effective than the Nd:YAG laser treatment in reducing pain and improving the quality of life in patients with TN. Full article

This minireview presents some unusual but encouraging examples of lignocellulosic-based adhesives and coatings used for metals, glass, and some other difficult-to-adhere materials. The reactions and applications presented are as follows. (i) The reactions of tannins and wood lignin with phosphate salts, in particular triethylphosphate, to adhere and join steel and aluminum to Teflon, in particular for non-stick frying pans. These adhesive coatings have been shown to sustain the relevant factory industrial test of 410 °C for 11 min and, moreover, to present a 50% material loss even at 900 °C for 5 min. (ii) Non-isocyanate polyurethanes (NIPU) based on glucose and sucrose as coatings of steel and glass. These were obtained by the carbonation of carbohydrates through reaction with the inexpensive dimethyl carbonate followed by reaction with a diamine; all materials used were bio-sourced. Lastly, (iii) the use of citric acid-based adhesive coupled with any hydroxyl groups carrying material for coating metals is also described. These three approaches give a clear indication of the possibilities and capabilities of biomaterials in this field. All these are presented and discussed. Full article

To reduce vehicle weight and improve energy efficiency, automotive manufacturers are increasingly using aluminum body panels. However, the traditional joining method, Resistance Spot Welding (RSW), presents challenges like weld porosity and electrode degradation when used with aluminum. These issues have driven the industry to explore alternative, more effective methods for joining aluminum in vehicle manufacturing such as Refill Friction Stir Spot Welding (RFSSW). This research reports on a comparison of the microstructure and mechanical properties of welds made with RSW and RFSSW in AA6061-T4 automotive sheets. This comparison includes CT scanning, optical and SEM imaging, statistical microscopy, hardness testing, tensile testing, and fatigue testing. The results showed that RFSSW produced fully consolidated welds with a refined, equiaxed grain structure that outperformed RSW’s dendritic grain structure by as much as 73% in tensile testing and 2600% in fatigue testing. These results suggest that future designs utilizing RFSSW could incorporate fewer joints, reducing processing time, energy consumption, and tool wear. Cost studies also found that RFSSW consumes 2.5% of the energy that RSW does per joint, demonstrating that RFSSW is positioned as the preferred method for joining aluminum automotive sheets. Full article

A Raman and IR study of AlCl₃-based ethereal solutions is here presented and aims at identifying the [AlCl₂]⁺ cation, which has been so far unambiguously characterized by ²⁷Al NMR spectrometry. To do that, experimental–theoretical vibrational spectroscopy was so employed, and the data are interpreted successfully. As a known amount of water is added to the tetrahydrofuran (THF)-containing electrolyte, a Raman band at 271 cm⁻¹ has its intensity increased along with the most intense band of [AlCl₄]⁻, and such behavior is also seen for a band at 405 cm⁻¹ in the IR spectra. New bands at around 420 and 400 cm⁻¹ are observed in both Raman and IR spectra for the tetraglyme (G4)-based systems. The [AlCl₂(THF)₄]⁺ complex, in the cis and trans forms, is present in the cyclic ether, while the cis-[AlCl₂(G4)]⁺ isomer is identified in the acyclic one. Full article

The novel crosslinked composite polymer electrolyte (CPE) was developed and investigated using polytetrahydrofuran (PTHF) and polyethyleneglycol diacrylate (PEGDA), incorporating lithium aluminum titanium phosphate (LATP) particles and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. Composite polymer electrolytes (CPEs) for solid-state lithium-ion batteries (LIBs) were synthesized by harnessing the synergistic effects of PTHF crosslinking and the addition of LATP ceramics, while systematically varying the film composition and LATP content. CPEs containing 15 wt% LATP (PPL15) demonstrated improved mechanical strength and electrochemical stability, achieving a high conductivity of 1.16 × 10⁻⁵ S·cm⁻¹ at 80 °C, outperforming conventional PEO-based polymer electrolytes. The CPE system effectively addresses safety concerns and mitigates the rapid degradation typically associated with polyether electrolytes. The incorporation of PEGDA not only enhances mechanical stability but also facilitates lithium salt dissociation and ion transport, leading to a uniform microstructure free from agglomerated particles. The temperature-dependent ionic conductivity measurements indicated optimal performance at lower LATP concentrations, highlighting the impact of ceramic particle agglomeration onion transport pathways. These findings contribute to advancing solid-state battery systems toward practical application. Full article

The ability of the cement to release calcium ions, which participate in the remineralization of dentin by forming apatite which improves root canal sealing with time, is of particular importance. Five recently introduced calcium-silicate commercial dental cements were investigated with a view to the influence of the physicochemical characteristics on the possibility of releasing calcium ions in an aqueous medium. Two hybrid calcium-silicate cements in the form of a paste-like ready mix (BioCal^® Cap and TheraCal LC) and three calcium-silicate cements consisting of two components—powder and liquid (Harvard MTA Universal, Rootdent, and BioFactor) were subjected to powder XRD, SEM, and EDS for detailed examination. The cements were immersed in water for 28 days and the phase composition and morphology of the cements before and after soaking were studied. The total calcium release for each cement was determined by ICP-OES. BioFactor and BioCal^® Cap release the highest amount of calcium ions, while the lowest release is registered with Rootdent and TheraCal LC. The PDT treatment of BioFactor does not influence substantially the calcium release. The impact of the elemental and phase composition on the calcium release and calcium carbonate formation was discussed. A reciprocal relation between the aluminum content and the quantity of the released calcium has been found. Full article

Piezoelectric micromachined ultrasonic transducers (PMUTs) have been widely applied in distance sensing applications. However, the rapid movement of miniature robots in complex environments necessitates higher ranging capabilities from sensors, making the enhancement of PMUT sensing distance critically important. In this paper, a scandium-doped aluminum nitride (ScAlN) PMUT based on a flexurally suspended membrane is proposed. Unlike the traditional fully clamped design, the PMUT incorporates a partially clamped membrane, thereby extending the vibration displacement and enhancing the output sound pressure. Experimental results demonstrate that at a resonant frequency of 78 kHz, a single PMUT generates a sound pressure level (SPL) of 112.2 dB at a distance of 10 mm and achieves a high receiving sensitivity of 12.3 mV/Pa. Distance testing reveals that a single PMUT equipped with a horn can achieve a record-breaking distance sensing range of 11.2 m when used alongside a device capable of simultaneously transmitting and receiving ultrasound signals. This achievement is significant for miniaturized and integrated applications that utilize ultrasound for long-range target detection. Full article

Organic/silicon hybrid solar cells have attracted much interest due to their cheap fabrication process and simple device structure. A category of organic substances, Dibenzothiophene–Spirobifluorene–Dithiophene (DBBT-mTPA-DBT), comprises dibenzo [d,b] thiophene and 3-(3-methoxyphenyl)-6-(4-methoxyphenyl)-9H-Carbazole, which function as electron donors. In contrast, methanone is an electron acceptor, with an ∆Est of 3.19 eV. This work focused on hybrid solar cells based on the guest–host phenomena of DBBT-mTPA-DBT and CBP. Using a Si/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) hybrid solar cell with an ultra-thin Dibenzothiophene–Spirobifluorene–Dithienothiophene (DBBT-mTPA-DBT) interlayer between Si and Al led to a PCE of 17.5 ± 2.5%. The DBBT-mTPA-DBT interlayer substantially improved the Si/Al interface, reducing contact resistance from 6.5 × 10⁻¹ Ω·cm² to 3.5 × 10⁻² Ω·cm². This improvement increases electron transport efficiency from silicon to aluminum and reduces carrier recombination. The solar cell containing the DBBT-mTPA-DBT/Al double-layer cathode shows a 10.85% increase in power conversion efficiency relative to the standard Al cathode device. Full article

This review examines hydrogen embrittlement (HE) in precipitation-hardenable aluminum alloys, focusing on the role of precipitates as hydrogen traps. It covers hydrogen entry mechanisms, the effects of microstructural features such as dislocations and grain boundaries, and secondary phase evolution during heat treatment. The interaction between hydrogen and precipitates, including the role of coherent and incoherent interfaces, is analyzed in view of the impact on HE susceptibility. Various techniques used to assess the interaction between hydrogen and aluminum alloys are also compared. The goal is to summarize the state-of-the-art understanding of the microstructural factors influencing the resistance of aluminum alloys to HE. Full article

The increasing production of solid waste and the scarcity of natural aggregates as a matter of fact have made waste recycling a necessity. One such waste, which is generated in large quantities, is slag. However, slag from incineration plants may contain harmful elements that adversely affect the physical, chemical and mechanical properties of cement composites. This study presents laboratory research results on the effect of slag from the Poznan Municipal Waste Thermal Conversion Plant (Poland) on the physicochemical properties of cement composites. The samples were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It was shown that the slag analyzed contained significant amounts of aluminum, which had a direct effect on the structure of the concrete. An example of this influence is the release of hydrogen during reactions, which causes swelling and cracking of the concrete and reduces its mechanical strength. The authors emphasize that waste aggregate (slag) can be effectively used in the production of concrete after appropriate processing that reduces the risk of adverse effects. Full article