Search Results (900)

The interface between high-performance thermoelectric materials and electrodes critically governs the conversion efficiency and long-term reliability of thermoelectric generators under high-temperature operation. Here, we propose Al_xCoCrFeNi high-entropy alloys (HEA) as barrier layers to bond Cu-W electrodes with p-type skutterudite (p-SKD) thermoelectric materials. The HEA/p-SKD interface exhibited excellent chemical bonding with a stable and controllable reaction layer, forming a dense, defect-free (Fe,Ni,Co,Cr)Sb phase (thickness of ~2.5 μm) at the skutterudites side. The interfacial resistivity achieved a low value of 0.26 μΩ·cm² and remained at 7.15 μΩ·cm² after aging at 773 K for 16 days. Moreover, the interface demonstrated remarkable mechanical stability, with an initial shear strength of 88 MPa. After long-term aging for 16 days at 773 K, the shear strength retained 74 MPa (only 16% degradation), ranking among the highest reported for thermoelectric materials/metal joints. Remarkably, the joint maintained a shear strength of 29 MPa even after 100 continuous thermal cycles (623–773 K), highlighting its outstanding thermo-mechanical stability. These results validate the Al_xCoCrFeNi high-entropy alloys as an ideal interfacial material for thermoelectric generators, enabling simultaneous optimization of electrical and mechanical performance in harsh environments. Full article

In this study, we present a comprehensive theoretical analysis of modifications in the physical and chemical properties of MoSe₂ upon the introduction of substitutional transition metal impurities, specifically, Ti, V, Cr, Fe, Co, Ni, Cu, W, Pd, and Pt. Wet systematically calculated the adsorption enthalpies for various representative analytes, including O₂, H₂, CO, CO₂, H₂O, NO₂, formaldehyde, and ethanol, and further evaluated their free energies across a range of temperatures. By employing the formula for probabilities, we accounted for the competition among molecules for active adsorption sites during simultaneous adsorption events. Our findings underscore the importance of integrating temperature effects and competitive adsorption dynamics to predict the performance of highly selective sensors accurately. Additionally, we investigated the influence of temperature and analyte concentration on sensor performance by analyzing the saturation of active sites for specific scenarios using Langmuir sorption theory. Building on our calculated adsorption energies, we screened the catalytic potential of doped MoSe₂ for CO₂-to-methanol conversion reactions. This paper also examines the correlations between the electronic structure of active sites and their associated sensing and catalytic capabilities, offering insights that can inform the design of advanced materials for sensors and catalytic applications. Full article

This article provides a comprehensive overview of recent studies concerning laser heat treatment (LHT) of structural and tool steels, with particular attention to the 21NiCrMo2 steel used for carburized gear wheels. Analysis includes the influence of critical laser processing conditions—including power output, motion speed, spot size, and focusing distance—on surface microhardness, hardening depth, and microstructure development. The findings indicate that the energy density is the dominant factor that affects the outcomes of LHT. Optimal results, in the form of a high surface microhardness and a sufficient depth of hardening, were achieved within the energy density range of 80–130 J/mm², allowing for martensitic transformation while avoiding defects such as melting or cracking. At densities below 50 J/mm², incomplete hardening occurred with minimal microhardness improvement. On the contrary, densities exceeding 150–180 J/mm² caused surface overheating and degradation. For carburized 21NiCrMo2 steel, the most effective parameters included 450–1050 W laser power, 1.7–2.5 mm/s scanning speed, and 2.0–2.3 mm beam diameter. The review confirms that process control through energy-based parameters allows for reliable prediction and optimization of LHT for industrial applications, particularly in components exposed to cyclic loads. Full article

Background: The waist–calf circumference ratio (WCR) is an index that combines waist and calf circumference measurements, offering a potentially effective method for evaluating the imbalance between abdominal fat and leg muscle mass in older adults. Objective: To assess the association between WCR and indicators of body composition, muscle strength, and physical performance in community-dwelling older women. Methods: This was a cross-sectional study involving 133 older women (≥65 years) from an urban-marginal community in Guayaquil, Ecuador. The WCR was categorized into quartiles (Q1: 2.07–2.57; Q2: 2.58–2.75; Q3: 2.76–3.05; Q4: 3.06–4.76). Body indicators included fat-free mass (FFM), skeletal muscle mass (SMM), appendicular muscle mass (ASM), appendicular muscle mass index (ASMI), visceral fat (VF), fat mass (FM), and fat mass index (FMI). Handgrip strength (HGS) and the Short Physical Performance Battery test (SPPB) score were used to assess muscle strength and function, respectively. Results: The median age of the participants was 75 [IQR: 65–82] years. The mean WCR was 2.92 ± 0.93. Statistically significant associations were found between WCR and VF (p < 0.001), WCR and SMM (p = 0.039), and WCR and ASM (p = 0.016). Regarding muscle function, WCR was associated with HGS (p = 0.025) and SPPB score (p = 0.029). Conclusions: A significant association was observed between WCR and body composition, and muscle strength and function in older women. Full article

Bcakground: The deepithelialized free gingival graft (DGG) technique provides high-quality connective tissue grafts (CTGs) with predictable outcomes for recession coverage. This study evaluates a novel method of free gingival graft (FGG) deepithelialization using an Er,Cr:YSGG laser (LDEE) for treating multiple gingival recessions. Methods: A split-mouth study was conducted on 46 (n = 46) recessions in nine patients (23 per test and control group). Sites were randomized. Full-thickness palatal grafts were harvested with a scalpel. In the test group (LDEE), deepithelialization was performed extraorally using an Er,Cr:YSGG laser (2780 nm; 2.5 W, 83.3 mJ, 30 Hz, 600 µm tip). In the control group (DEE), a 15c scalpel was used. All CTGs were applied using the modified coronally advanced tunnel (TUN) technique. Clinical parameters—recession depth (RD), keratinized tissue width (KT), gingival thickness (GT), pocket depth (PD), clinical attachment loss (CAL), pink esthetic score (PES), approximal plaque index (API), mean root coverage (MRC), and complete root coverage (CRC)—were assessed at baseline (T0), 3 months (T1), and 6 months (T2). Results: Both LDEE and DEE groups showed significant improvements in RD, KT, GT, PD, and CAL over time (p < 0.001). At T1 and T2, KT was significantly higher in the LDEE group (T1: 3.73 ± 0.72 mm; T2: 3.98 ± 0.76 mm) compared to the DEE group (T1: 3.21 ± 0.61 mm; T2: 3.44 ± 0.74 mm; p < 0.05). Other parameters (RD, GT, PD, CAL) showed no statistically significant intergroup differences at any time point (p > 0.05). After 6 months, MRC was 95% and CRC 82.6% for LDEE, compared to 94.8% and 82.6% for DEE (p > 0.05). PES scores were similar between groups at all time points (p > 0.05). Conclusions: Both laser- and scalpel-deepithelialized grafts effectively treated gingival recessions. LDEE combined with TUN resulted in significantly greater KT width compared to DEE + TUN. Full article

Objectives: The aim of this study was to determine the differential temperature produced on ceramic implants using laser irradiation on a pulsed setting of intrabony defects in vitro. Methods: A ceramic (Zr) dental implant (Zeramex, 4.8 × 12 mm) was placed into a bovine bone block. A three-wall intrabony defect (6 × 4 × 3 mm) was created to mimic an osseous peri-implant defect. Thermocouples were placed on the apical and coronal areas to measure temperature changes (∆T) during 60 s of laser irradiation. The bovine block was heated to 37 °C, and the defect walls were irradiated with the CO₂ and Er,Cr:YSGG laser. The settings used were pulsed mode for both lasers, with 30 Hz and 1.5 W for the Er,Cr:YSGG laser and 70 Hz and 2 W for the CO₂ laser. The same laser settings were repeated at room temperature (RT, 23 °C). Twenty trials were performed for each experimental group at room and body temperature for assessment of ∆T. Paired t-test were used to compare the measurements between 37 °C and 23 °C for the Er,Cr:YSGG, and CO₂ laser, respectively. Results: The CO₂ laser resulted in the highest ∆T (°C) at the coronal (15.22 ± 0.28/8.82 ± 0.21) and apical (5.84 ± 0.14/2.30 ± 0.28) level when this laser was used in both room temperature and body temperature, respectively. The highest ∆T (°C) for the Er,Cr:YSGG laser at body temperature at the coronal thermocouple was 7.64 ± 0.55, while for the CO₂ laser, at body temperature was 8.82 ± 0.21. Conclusion: Within the limitations of our study, the use of CO₂ laser and Er,Cr:YSGG laser on peri-implant defects generally appears to be safe in treating peri-implant defects around zirconia implants in vitro. Full article

An analysis of the working surfaces of cylindrical gears after scuffing shock tests allowed for the assessment of the effect of loading conditions on the form of damage to the tooth surfaces. Unlike the method of scuffing under severe conditions, where loading is applied gradually, the presented tests employed direct maximum loading—shock loading—without prior lapping of the gears under lower loads. This loading method significantly increases the vulnerability of the analyzed components to scuffing, enabling an evaluation of their limit in terms of operational properties. To identify the changes and the types of the teeth’s working surface damage, the following microscopy techniques were applied: scanning electron microscopy (FE-SEM) with EDS microanalyzer, optical interferential profilometry (WLI), atomic force microscope (AFM), and optical microscopy. The results allowed us to define the characteristic damage mechanisms and assess the efficiency of the applied DLC coatings when it comes to resistance to scuffing in shock scuffing conditions. Tribological tests were performed by means of an FZG T-12U gear test rig in a power circulating system to test cylindrical gear scuffing. The gears were made from 18CrNiMo7-6 steel and 35CrMnSiA nano-bainitic steel and coated with W-DLC/CrN. Full article

Background/Objectives: In this study, we aimed to evaluate probiotics’ clinical efficacy and safety in adults with chronic rhinosinusitis (CRS), and summarize mechanistic evidence related to mucosal immunity and microbiota modulation. Methods: We performed a systematic review and random-effects meta-analysis. MEDLINE, Embase, Scopus, Web of Science, and the Cochrane Library were searched until May 2025. Eligibility: Randomized controlled trials (RCTs) and mechanistic studies investigating probiotics (any strain, dose, or administration route) in adults with CRS were eligible. Primary outcomes included changes in Sino-Nasal Outcome Test (SNOT-20/22) scores and CRS relapse rates. Secondary outcomes were adverse events and mechanistic endpoints. Results: Six studies (four RCTs, n = 337; two mechanistic studies) met the inclusion criteria. Probiotics did not significantly improve SNOT scores compared with the placebo, but trended in that direction (pooled mean difference—2.70; 95% CI −7.12 to 1.72; I² = 0%). Furthermore, probiotic use was associated with a non-significant trend towards fewer CRS relapses (risk ratio 0.41; 95% CI 0.16–1.04; p = 0.06; I² = 48%). Adverse events were mild and comparable to the placebo (risk ratio 0.87; 95% CI 0.33–2.34). Mechanistic data indicated that intranasal Lactococcus lactis W136 might downregulate type 1 inflammatory pathways and modestly increase microbiome diversity. Subgroup analyses (by route, duration, and CRS subtype) revealed no statistically significant effect modifiers, though mechanistic insights suggest possible differences in efficacy based on the CRS endotype and delivery method. Conclusions: Probiotics appear safe and may provide a small, non-significant improvement in CRS symptoms; emerging evidence of reduced relapse rates warrants further investigation through larger, endotype-stratified trials utilizing targeted probiotic strains and optimized delivery methods. Full article

This article presents a review of the composition optimization progress of nickel-based single crystal (SC) superalloy design in recent years in order to obtain better high-temperature performance for the development of the aviation industry. The influence of alloying elements on the creep resistance, microstructure characteristics, oxidation resistance, castability, density, and cost of superalloys is analyzed and discussed. In order to obtain better high-temperature performance, the content of refractory elements (Ta + Re + W + Mo) and Co was increased gradually. The addition of Ru was added in the fourth-generation nickel-based SC superalloy to stabilize the microstructures and suppress the precipitation of the topologically close-packed (TCP) phase. However, the content of the antioxidant element Cr significantly decreased, while the synergistic effect of Al, Cr, and Ta received more attention. Therefore, synergistic effects should also receive more attention to meet the practical needs of reducing the content of refractory elements to reduce costs and density in future single crystal alloy designs without compromising critical performance. Full article

This study introduces an advanced strategy for improving microbial fuel cell (MFC) performance in hexavalent chromium (Cr(VI)) wastewater treatment. A high-performance nano-iron sulfide (nano-FeS) hybridized biocathode was developed by regulating glucose concentration and applying an external voltage. The combination of a glucose concentration of 1000 mg/L and a 0.2 V applied voltage greatly promoted the in situ biosynthesis of nano-FeS, resulting in smaller particle sizes and increased quantities within the biocathode, leading to enhanced electrochemical performance. The MFC with the hybridized biocathode exhibited the highest power density (43.45 ± 1.69 mW/m²) and Cr(VI) removal rate (3.99 ± 0.09 mg/L·h), outperforming the control by 29% and 71%, respectively. The improvements were attributed to the following processes. (1) Nano-FeS provided additional active sites that enhanced electron transfer and electrocatalytic activity, reducing cathode passivation; (2) it protected microorganisms by reducing Cr(VI) toxicity, promoting redox-active substance enrichment and antioxidant enzyme secretion, which maintained microbial activity; (3) the biocathode selectively enriched electroactive and Cr(VI)-reducing bacteria (such as Brucella), fostering a stable and symbiotic microbial community. This study highlights the promising potential of regulating carbon source and external voltage to boost nano-FeS biosynthesis, offering a sustainable and efficient strategy for MFC-based Cr(VI) wastewater treatment with practical implications. Full article

In this study, chromium ferrite (FeCr; CrFe₂O₄) nanoparticles supported on activated carbon (AC), obtained from agricultural olive mill solid waste, were synthesized via a simple hydrothermal process. The structural, morphological, optical, and chemical properties of the FeCr/AC composite were characterized using XRD, SEM, EDX, DRS, BET, and FTIR techniques. The FeCr/AC composite was applied as a heterogeneous photo-Fenton catalyst for the degradation of methylene blue (MB) dye in an aqueous solution under 25 W visible-light LED irradiation. Critical operational factors, such as FeCr/AC dosage, pH, MB concentration, and H₂O₂ levels, were optimized. Under optimal conditions, 97.56% of MB was removed within 120 min of visible-light exposure, following pseudo-first-order kinetics. The composite also exhibited high efficiency in degrading methyl orange dye (95%) and tetracycline antibiotic (88%) within 180 min, with corresponding first-order rate constants of 0.0225 min⁻¹ and 0.0115 min⁻¹, respectively. This study highlights the potential of FeCr/AC for treating water contaminated with dyes and pharmaceuticals, in line with the Sustainable Development Goals (SDGs) for water purification. Full article

The unique structures and properties of natural organisms provide abundant inspiration for surface modification research in materials science. In this paper, the tribological advantages of radial ribs found on shell surfaces were combined with laser cladding to address challenges in material surface strengthening. Laser cladding technology was used to fabricate bionic units on the surface of 20CrMnTi steel. The alloy powder consisted of a Ni-based alloy with added WC particles. The influence of laser power (1.0 kW–3.0 kW) on the dimensions, microstructure, hardness, surface roughness, and tribological properties of the bionic units was investigated to enhance the tribological performance of the Ni60/WC bionic unit. The microstructure, phase composition, hardness, and tribological behavior of the bionic units were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), a microhardness tester, and a wear tester. Experimental results show that the dimensions of the bionic units increased with laser power. However, beyond a certain threshold, the growth rate of the width and height gradually slowed due to heat conduction and edge cooling effects. The microstructure primarily consisted of equiaxed and dendritic crystals, with grain refinement observed at higher laser powers. The addition of WC resulted in average hardness values of 791 HV_0.2, 819 HV_0.2, 835 HV_0.2, and 848 HV_0.2 across the samples. This enhancement in hardness was attributed to dispersion strengthening and grain refinement. Increasing the laser power also reduced the surface roughness of the bionic units, though excessively high laser power led to a roughness increase. The presence of WC altered the wear mechanism of the bionic units. Compared to the wear observed in the N60 sample, the wear amount of the WC-containing samples decreased by 73.7%, 142.1%, 157.5%, and 263.1%, respectively. Hard WC particles played a decisive role in enhancing tribological performance of the bionic unit. Full article

The paper shows the effect of using a lubricant in the form of an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF₆), on the tribological properties of a hydrogenated diamond-like coating (DLC) doped with tungsten a-C:H:W. The coatings were deposited on 100Cr6 steel by plasma-enhanced chemical vapor deposition PECVD. Tribological tests were carried out on a TRB³ tribometer in a rotary motion in a ball–disc combination. 100Cr6 steel balls were used as a counter-sample. Friction and wear tests were carried out for discs made of 100Cr6 steel and 100Cr6 steel discs with a DLC coating. They were performed under friction conditions with and without lubrication under 10 N and 15 N loads. The ionic liquid BMIM-PF₆ was used as a lubricant. Coating thickness was observed on a scanning microscope, and the linear analysis of chemical composition on the cross-section was analyzed using the EDS analyzer. The confocal microscope with an interferometric mode was used for analysis of the geometric structure of the surface before and after the tribological tests. The contact angle of the samples for distilled water, diiodomethane and ionic liquid was tested on an optical tensiometer. The test results showed good cooperation of the DLC coating with the lubricant. It lowered the coefficient of friction in comparison to steel about 20%. This indicates the synergistic nature of the interaction: DLC coating–BMIM-PF₆ lubricant–100Cr6 steel. Full article

Many components in industry are subjected to high loads during operation and therefore often do not reach their intended service life. Conventional steels frequently do not provide sufficient protection against wear and corrosion. One solution is to coat these components using methods like thermal spraying to apply cermet coatings such as Cr₃C₂-NiCr or WC-Co-Cr. In light of increasingly strict environmental regulations, more eco-friendly alternatives are needed, especially ones that use little or no Cr, Ni, Co, or W. Another alternative is the recycling of powder materials, which is the focus of this research project. This study investigated whether filter dust from an HVOF system could be used to develop a new coating suitable for use in applications requiring resistance to wear and corrosion. This is challenging as the filter dusts have heterogeneous compositions and irregular particle sizes. Nevertheless, this recycled material, referred to as “Green Cermets” (GCs), offers previously untapped potential that may also be of ecological interest. An established WC-Co-Cr coating served as a reference. In addition to friction wear and corrosion resistance, the study also examined particle size distribution, hardness, microstructure, and susceptibility to crack formation at the interface and inside the coating. Even though the results revealed a diminished performance of the GC coatings relative to the conventional WC-CoCr, they may still be applicable in various industrial applications. Full article

Na₀.₈₉Co_0.90Me_0.10O₂ (Me = Cr, Ni, Mo, W, Pb, and Bi) ceramic samples were prepared using a solid-state reaction method, and their crystal structure, microstructure, and electrical, thermal, and thermoelectric properties were investigated. The effect of the nature of the doping metal (Me = Cr, Ni, Mo, W, and Bi) on the structure and properties of layered sodium cobaltite Na_0.89CoO₂ was analyzed. The largest Seebeck coefficient (616 μV/K at 1073 K) and figure-of-merit (1.74 at 1073 K) values among the samples studied were demonstrated by the Na_0.89Co_0.9Bi_0.1O₂ solid solution, which was also characterized by the lowest value of the dimensionless relative self-compatibility factor of about 8% within the 673–873 K temperature range. The obtained results demonstrate that doping of layered sodium cobaltite by transition and heavy metal oxides improves its microstructure and thermoelectric properties, which shows the prospectiveness of the used doping strategy for the development of new thermoelectric oxides with enhanced thermoelectric characteristics. It was also shown that samples with a higher sodium content (Na:Co = 0.89:1) possessed higher chemical and thermal stability than those with a lower sodium content (Na:Co = 0.55:1), which makes them more suitable for practical applications. Full article