Search Results (15,987)

This study deals with the long-running challenge of joining similar and dissimilar materials using composite-to-composite and composite-to-metal joints. This research was conducted to evaluate the effects of surface morphology and surface treatments on the mechanical performance of adhesively bonded joints used for the aircraft industry. A two-segment, commercially available, toughened epoxy was chosen as the adhesive. Unidirectional carbon fiber prepreg and aluminum 2021-T3 alloys were chosen for the composite and metal panels, respectively. Surface treatment of the metal included corrosion elimination followed by a passive surface coating of Alodine^®. A combination of surface treatment methods was used for the composite and metal specimens, including detergent cleaning, plasma exposure, and sandblasting. The shear strength of the single-lap adhesive joint was evaluated according to the ASTM D1002. Ultraviolet (UV) and plasma exposure effects were studied by measuring the water contact angles. The test results showed that the aluminum adherent treated with sandblasting, detergent, and UV irradiation resulted in the strongest adhesive bonding of the composite-to-composite panels, while the composite-to-metal sample cleaned only with detergent resulted in the least bonding strength. The failure strain of the composite-to-composite bonding was reduced by approximately 50% with only sandblasting. However, extended treatment did not introduce additional brittleness in the adhesive joint. The bonding strength of the composite-to-composite panel improved by approximately 35% with plasma treatment alone because of the better surface functionalization and bonding strength. In the composite-to-aluminum bonding process, exposing the aluminum surface to UV resulted in 30% more joint strength compared to the Alodine^® coating, which suggests the origination of higher orders of magnitude of covalent groups from the surface. A comparison with published results found that the joint strengths in both similar and dissimilar specimens are higher than most other results. Detailed observations and surface analysis studies showed that the composite-to-composite bonding mainly failed due to adhesive and cohesive failures; however, failure of the composite-to-aluminum bonding was heterogeneous, where adhesive failure occurred on the aluminum side and substrate failure occurred on the composite side. Full article

Due to the chemical composition and structure of the target tissue, autologous bone grafting remains the gold standard for orthopedic applications worldwide. However, ongoing advancements in alternative grafting materials show that 3D-printed synthetic biomaterials offer many advantages. For instance, they provide high availability, have low clinical limitations, and can be designed with a chemical composition and structure comparable to the target tissue. This study aimed to compare the influences of particle size and sintering temperature on the mechanical properties and biocompatibility of calcium phosphate (CaP) gyroid scaffolds. CaP gyroid scaffolds were fabricated by 3D printing using powders with the same chemical composition but different particle sizes and sintering temperatures. The physicochemical characterization of the scaffolds was performed using X-ray diffractometry, scanning electron microscopy, and microtomography analyses. The immortalized human mesenchymal stem cell line SCP-1 (osteoblast-like cells) and osteoclast-like cells (THP-1 cells) were seeded on the scaffolds as mono- or co-cultures. Bone cell attachment, number of live cells, and functionality were assessed at different time points over a period of 21 days. Improvements in mechanical properties were observed for scaffolds fabricated with narrow-particle-size-distribution powder. The physicochemical analysis showed that the microstructure varied with sintering temperature and that narrow particle size distribution resulted in smaller micropores and a smoother surface. Viable osteoblast- and osteoclast-like cells were observed for all scaffolds tested, but scaffolds produced with a smaller particle size distribution showed less attachment of osteoblast-like cells. Interestingly, low attachment of osteoclast-like cells was observed for all scaffolds regardless of surface roughness. Although bone cell adhesion was lower in scaffolds made with powder containing smaller particle sizes, the long-term function of osteoblast-like and osteoclast-like cells was superior in scaffolds with improved mechanical properties. Full article

Due to population growth and global technological development, energy consumption has increased exponentially. The global energy crisis opens up many hotly debated topics regarding energy generation and consumption. Not only is energy production in short supply due to limited energy resources but efficient and sustainable storage has become a very important goal. Currently, there are energy storage devices such as batteries, capacitors, and super-capacitors. Supercapacitors or electrochemical capacitors can be very advantageous replacements for batteries and capacitors because they can achieve higher power density and energy density characteristics. The evolution and progress of society demand the use of innovative and composite nanostructured metal oxide materials, which fulfill the requirements of high-performance technologies. This review mainly addresses the synthesis techniques and properties of 2D and 3D metal oxide nanostructured materials, especially based on Ti, Fe, Ga, and Sn ions, electrochemical methods used for the characterization and application of 2D, and 3D nanostructured metal oxide structures in electrochemical storage systems of energy. Full article

This research investigated the sound insulation performance of 3D woven hybrid fabric-reinforced composites using natural fibers, such as jute, along with E-glass and biomass derived from agro-waste, e.g., coffee husk and waste palm fiber. The composites made from pure E-glass, pure jute, and hybrid glass–jute configurations were tested for sound absorbance at frequencies of 1000 Hz and 10,000 Hz. A sound insulation chamber was used for measuring the sound reduction levels. Results show that the sound insulation performance of the panels was remarkably enhanced with composites containing natural fiber reinforcements. The jute-based composites provided the maximum insulation of sound, with waste palm fiber fillers in particular. At a frequency of 10,000 Hz, a noise reduction reaching 44.9 dB was observed. The highest sound absorption was observed in the 3D woven jute composites with the additive of waste palm fiber, which outperformed the other samples. When comparing the effect of coffee husk and palm fiber as biomass fillers, both exhibited notable improvements in sound insulation, but the palm fiber generally performed better across different samples. Although panels containing palm fiber additives appeared to reduce sound more than those containing coffee husk, statistical analysis revealed no significant difference between the two, indicating that both are efficient and eco-friendly fillers for soundproofing applications. One-way analysis of variance (ANOVA) confirmed the significance of the effect of reinforcing structures and biofillers on acoustic performance. This study demonstrated the possibility of using sustainable green materials for soundproofing applications within various industries. Full article

Chemical warfare agents (CWAs) are known as poor man’s bombs because of their small lethal dose, cheapness, and ease of production. Therefore, the highly sensitive and rapid detection of CWAs at room temperature (RT = 25 °C) is essential. In this paper, we have developed a resistive semiconductor sensor for the highly sensitive detection of CWAs at RT. The gas-sensing material is SnS₂/rGO nanosheets (NSs) prepared by hydrothermal synthesis. The lower detection limits of the SnS₂/rGO NSs-based gas sensor were 0.05 mg/m³ and 0.1 mg/m³ for the typical chemical weapons sarin (GB) and sulfur mustard (HD), respectively. The responsivity can reach −3.54% and −10.2% in 95 s for 1.0 mg/m³ GB, and in 47 s for 1.0 mg/m³ HD. They are 1.17 and 2.71 times higher than the previously reported Nb-MoS₂ NSs-based gas sensors, respectively. In addition, it has better repeatability (RSD = 6.77%) and stability for up to 10 weeks (RSD = 20.99%). Furthermore, to simplify the work of later researchers based on the detection of CWAs by two-dimensional transition metal sulfur compounds (2D-TMDCs), we carried out calculations of the SnS₂ NSs-based and SnS₂/rGO NSs-based gas sensor-adsorbing CWAs. Detailed comparisons are made in conjunction with experimental results. For different materials, it was found that the SnS₂/rGO NSs-based gas sensor performed better in all aspects of adsorbing CWAs in the experimental results. Adsorbed CWAs at a distance smaller than that of the SnS₂ NSs-based gas sensor in the theoretical calculations, as well as its adsorption energy and transferred charge, were larger than those of the SnS₂ NSs-based gas sensor. For different CWAs, the experimental results show that the sensitivity of the SnS₂/rGO NSs-based gas sensor for the adsorption of GB is higher than that of HD, and accordingly, the theoretical calculations show that the adsorption distance of the SnS₂/rGO NSs-based gas sensor for the adsorption of GB is smaller than that of HD, and the adsorption energy and the amount of transferred charge are larger than that of HD. This regularity conclusion proves the feasibility of adsorption of CWAs by gas sensors based on SnS₂ NSs, as well as the feasibility and reliability of theoretical prediction experiments. This work lays a good theoretical foundation for subsequent rapid screenings of gas sensors with gas-sensitive materials for detecting CWAs. Full article

Background and objectives: Nephrocalcinosis (NC) is a common condition characterized by the deposition of calcium salts in the kidneys of very preterm infants due to tubular immaturity, intensive treatment and nutritional supplements. However, optimal vitamin D supplementation remains unclear. In most patients, NC spontaneously resolves within the first year of life, but long-term kidney function data are lacking. The aim was to study nephrocalcinosis in very preterm infants, assess risk factors and evaluate vitamin D’s impact during the first month with a 2-year follow-up. Material and Methods: This was a prospective observational study conducted over a 3-year period in infants with a gestational age of less than 32 weeks. The patients’ data were compared between the NC and control groups based on kidney ultrasound results at discharge. In the first month, the mean vitamin D intake from all sources as well as biochemical markers of calcium metabolism were collected. Patients diagnosed with NC were referred to a pediatric nephrologist after discharge. Results: NC was found in 35% of a cohort of 160 infants, more common in those with a gestational age <28 weeks. Risk factors were associated with higher morbidity and necessary treatment. At 28 days, serum 25-hydroxy vitamin D levels differed between NC and control groups (p < 0.05). The NC group with GA ≥ 28 weeks had higher vitamin D intake (p < 0.05), hypercalciuria and calcium/creatinine ratio (p < 0.01) and lower parathyroid hormone levels (p < 0.05). Follow-up showed resolution in 70% at 12 months and 90% at 24 months. Conclusions: The prevalence of NC in very preterm infants is significant, associated with lower maturity and higher morbidity. Careful vitamin D supplementation and biochemical monitoring of Ca metabolism from the first month of life should support bone health and limit the risk of nephrocalcinosis. Due to the high incidence of NC in very preterm infants, long-term follow-up is essential. Full article

The automatic inspection of belt conveyors gathers increasing attention in the mining industry. The utilization of mobile robots to perform the inspection allows increasing the frequency and precision of inspection data collection. One of the issues that needs to be solved is the location of inspected objects, such as, for example, conveyor idlers in the vicinity of the robot. This paper presents a novel approach to analyze the 3D LIDAR data to detect idler frames in real time with high accuracy. Our method processes a point cloud image to determine positions of the frames relative to the robot. The detection algorithm utilizes density histograms, Euclidean clustering, and a dimension-based classifier. The proposed data flow focuses on separate processing of single scans independently, to minimize the computational load, necessary for real-time performance. The algorithm is verified with data recorded in a raw material processing plant by comparing the results with human-labeled objects. The proposed process is capable of detecting idler frames in a single 3D scan with accuracy above 83%. The average processing time of a single scan is under 22 ms, with a maximum of 75 ms, ensuring that idler frames are detected within the scan acquisition period, allowing continuous operation without delays. These results demonstrate that the algorithm enables the fast and accurate detection and localization of idler frames in real-world scenarios. Full article

Magnetic two-dimensional (2D) materials have garnered significant attention for their potential to revolutionize 2D spintronics due to their unique magnetic properties. However, their air-sensitivity and highly insulating nature of the magnetic semiconductors present substantial challenges for device fabrication with effective contacts. In this study, we introduce a polycarbonate (PC)-assisted transfer method that effectively forms van der Waals (vdW) contacts with 2D materials, streamlining the fabrication process without the need for additional lithography. This method is particularly advantageous for air-sensitive magnetic materials, as demonstrated in Fe₃GeTe₂. It also ensures excellent interface contact quality and preserves the intrinsic magnetic properties in magnetic semiconductors like CrSBr. Remarkably, this method achieves a contact resistance four orders of magnitude lower than that achieved with traditional thermally evaporated electrodes in thin-layer CrSBr devices and enables the observation of sharp magnetic transitions similar to those observed with graphene vdW contacts. Compatible with standard dry-transfer processes and scalable to large wafer sizes, our approach provides a straightforward and effective solution for developing complex magnetic heterojunction devices and expanding the applications of magnetic 2D materials. Full article

Through molecular dynamics methods, composite models built with a large scale were employed to investigate the effects of different reinforcements, which were different from those used in most of the similar studies, where only a graphene nanosheet (GNS) or a rigid spherical particle was embedded in a metal matrix. Here, 27 GNSs or diamond particles were placed in the empty spaces between Al particles with random directions. Then, Al matrix composites were prepared by modeling a sintering process. Structural analysis and tensile modeling were carried out on the sintered composites. The results indicate that the density of the Al–graphene composite was higher and increased with growth in the size of the reinforcements, although the Al–graphene system required more heating time to achieve densification. Bigger GNSs were likely to increase the pore volume of the composite. Meanwhile, larger GNSs were also more beneficial for grain refinement, leading to growth in the ratio of Al atoms at grain boundaries. The greater impact of GNSs on the inner structure was not just derived from their high specific surface area, and this impact was enlarged if drawn as a function of the weight fraction rather than the surface area. However, tensile processes revealed that two-dimensional (2D) materials seemed to have no clear impact on the direct strengthening effect, and anisotropy could not be observed in the large-scale models. The biggest GNSs even led to reductions in both the tensile strength and ductility of the Al–graphene composite, which coincided with some experimental reports. The evolution of the inner structures indicated that GNSs have the same role as diamond particles in dislocation accumulation and crack propagation. The major advantage of GNSs is their ability to improve the densification and grain refinement of the metal matrix composite (MMC). Full article

Aims: this study aims to investigate the impact of simulated skin color and the use of fiducial markers on the accuracy of 3D facial scans, comparing two types of structured light scanners under constant ambient lighting conditions. Materials and Methods: Three mannequins with different skin colors—black, white, and pink—were scanned using two light based hand-held scanners (infrared light and blue-light). Each mannequin was scanned with and without fiducial markers placed on defined anatomical landmarks. A total of one hundred thirty-two scans were performed and converted into standard tessellation language (STL) files. STL files from each scanner were compared to their respective control scans using point cloud comparison software. Accuracy was evaluated based on root mean square (RMS) values. Descriptive statistics summarized the data, and a t-test was performed to assess differences in RMS values between scans with and without fiducial markers for each scanner type. Results: The infrared light scanner showed the highest accuracy for the white mannequin, as evidenced by lower RMS values compared to the pink and black mannequins. Adding fiducial markers significantly enhanced scan accuracy for the pink and black mannequins. The blue-light scanner achieved accuracy for the white and pink mannequins comparable to that of the infrared scanner. However, it was unable to scan the black mannequin, even with the use of markers. Conclusions: Within the limitations of this study, simulated skin color significantly affects the accuracy of facial 3D scans. Scans of lighter (white) tones demonstrate higher accuracy compared to darker tones. Fiducial markers enhance the accuracy for an infrared scanner; however, a blue-light scanner is unable to capture dark simulated skin, even with the addition of fiducial markers. Full article

A host–guest-based fluorescent composite with a large Stokes shift was synthesized by intercalating 2,2′-(thiophene-2,5-diyl)bis(benzo[d]oxazol-6-amine) (BBTA) into the nanochannels of zeolite L (ZL) and sealing the pores with (3-aminopropyl)triethoxysilane (APTES). To confirm the orientation of the amino groups in BBTA, a single crystal of 2,5-bis(6-nitrobenzo[d]oxazol-2-yl)thiophene (BBTN) was grown and examined by X-ray crystallography. The evidence of successful intercalation of BBTA into the nanochannels of ZL was provided by fluorescence spectrometry, gas sorption and fluorescence microscopy. BBTA showed a Stokes shift of 6641 cm⁻¹ (157 nm) in ethanol and 4611 cm⁻¹ (93 nm) in toluene. The BBTA-ZL composite (BBTA-ZL-s) showed a Stokes shift of 5677 cm⁻¹ (123 nm) in toluene, and 5450 cm⁻¹ (124 nm) in ethanol. In addition, the degree of loading was determined and stability against leaching was confirmed. We report the synthesis of this novel composite dye material with potential applications where free dyes are not applicable and which retains a large Stokes shift, independent of its chemical environment. Full article

Nanomaterials can significantly improve the analytical performance of optical sensors for environmental pollutants. Two-dimensional (2D) molybdenum sulfide (MoS₂) exhibits some unique physicochemical properties, such as strong light–matter interactions, bandgap tunability, and high carrier mobility, which are beneficial for constructing flexible optoelectronic devices. In this review, the principle and classification of 2D MoS₂-based photodetectors (PDs) are introduced, followed by a discussion about the physicochemical properties of 2D MoS₂, as well as the structure–property relationships of 2D MoS₂-based photoactive materials for PDs to understand the modulation strategies for enhancing the photodetection performance. Furthermore, we discuss significant advances in the surface modification and functionalization of 2D MoS₂ for developing high-performance PDs, particularly focusing on synthesis pathways, modification strategies, and underlying physiochemical mechanisms for enhanced photodetection capabilities. Finally, conclusions and research perspectives on resolving significant bottlenecks or remaining challenges are offered based on recent developments in 2D MoS₂-based PDs. Full article

As part of the Horizon 2020 InfraROB project aimed at enhancing road safety through innovative robotic solutions, a compact autonomous vehicle has been developed to repair asphalt potholes. Central to this system is a 3D printer capable of extruding a novel cold-asphalt mixture, specifically designed for patching road surfaces. The printer is mounted on a small robot that autonomously navigates to potholes, while the human operator controls the operation from a secure location outside the traffic area. The system’s development involved several key steps: designing the repair mixture, constructing the 3D printer for mixture extrusion, implementing a photogrammetric technique to accurately measure pothole geometry for printing, and integrating the extrusion system with the robotic platform. Two preliminary tests were conducted in controlled environments at Sapienza University of Rome to check the reliability of calculation of the amount of material needed to fill in the potholes. Finally, the entire procedure was tested on an Italian motorway, demonstrating the system’s functionality without encountering operational issues. Full article

Flexible energy storage devices have attracted wide attention as a key technology restricting the vigorous development of wearable electronic products. However, the practical application of flexible batteries faces great challenges, including the lack of good mechanical toughness of battery component materials and excellent adhesion between components, resulting in battery performance degradation or failure when subjected to different types of deformation. It is imperative to develop flexible batteries that can withstand deformation under different conditions and maintain stable battery performance. This paper reviews the latest research progress of flexible lithium batteries, from the research and development of new flexible battery materials, advanced preparation processes, and typical flexible structure design. First, the types of key component materials and corresponding modification technologies for flexible batteries are emphasized, mainly including carbon-based materials with flexibility, lithium anode materials, and solid-state electrolyte materials. In addition, the application of typical flexible structural designs (buckling, spiral, and origami) in flexible batteries is clarified, such as 3D printing and electrospinning, as well as advanced fabrication techniques commonly used in flexible materials and battery components. Finally, the limitations and coping strategies in the practical application of flexible lithium batteries are discussed, which provides new ideas for future research. Full article

This study aims to investigate the outcomes of carbonaceous products, derived from the decomposition of the components of vehicular brake materials, under high-temperature wear tests. Pin-on-disc (PoD) wear tests were conducted by using cast iron discs against pins made of commercially available low-steel friction material. Tests were carried out at different temperatures: 155 °C, 200 °C, 250 °C, and 300 °C. The characterization of the sliding plateaus on worn pin surfaces was based on X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. It was noted that at temperatures above 200 °C, the thermal degradation of the inorganic resin, used as a material binder, occurs. An interesting observation was recorded at 300 °C; the brake pin material’s friction curve showed higher stability despite having an excessive wear rate. However, the brake pin’s specific wear coefficient was higher at this temperature than was observed in the other friction tests. A detailed study of the friction plateaus on the worn-out pins at 300 °C revealed that the decomposed carbon resin product, i.e., the distorted graphite, was widespread over the surface of the pin. Lubricant stabilization can be expected, as established by the observed values of the coefficient of friction (CoF), retaining values within the 0.4–0.6 range, even at high temperatures. Other friction material components may have contributed to the formation of this ubiquitous carbonaceous interface film. Full article