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Search Results (2,109)

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Keywords = laser stability

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14 pages, 3905 KiB  
Article
Stability of Ultrafast Laser-Induced Stress in Fused Silica and Ultra-Low Expansion Glass
by Carolyn C. Hokin and Brandon D. Chalifoux
Photonics 2025, 12(8), 778; https://doi.org/10.3390/photonics12080778 (registering DOI) - 1 Aug 2025
Abstract
Stress fields imparted with an ultrafast laser can correct low spatial frequency surface figure error of mirrors through ultrafast laser stress figuring (ULSF): the formation of nanograting structures within the bulk substrate generates localized stress, creating bending moments that equilibrize via wafer deformation. [...] Read more.
Stress fields imparted with an ultrafast laser can correct low spatial frequency surface figure error of mirrors through ultrafast laser stress figuring (ULSF): the formation of nanograting structures within the bulk substrate generates localized stress, creating bending moments that equilibrize via wafer deformation. For ULSF to be used as an optical figuring process, the ultrafast laser generated stress must be effectively permanent or risk unwanted figure drift. Two isochronal annealing experiments were performed to measure ultrafast laser-generated stress stability in fused silica and Corning ultra-low expansion (ULE) wafers. The first experiment tracked changes to induced astigmatism up to 1000 °C on 25.4 mm-diameter wafers. Only small changes were measured after each thermal cycle up to 500 °C for both materials, but significant changes were observed at higher temperatures. The second experiment tracked stress changes in fused silica and ULE up to 500 °C but with 4 to 16× higher signal-to-noise ratio. Change in trefoil on 100 mm-diameter wafers was measured, and the induced stress in fused silica and ULE was found to be stable after thermal cycling up to 300 °C and 200 °C, respectively, with larger changes at higher temperatures. Full article
(This article belongs to the Special Issue Advances in Ultrafast Laser Science and Applications)
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14 pages, 2107 KiB  
Article
Optimal Coherence Length Control in Interferometric Fiber Optic Hydrophones via PRBS Modulation: Theory and Experiment
by Wujie Wang, Qihao Hu, Lina Ma, Fan Shang, Hongze Leng and Junqiang Song
Sensors 2025, 25(15), 4711; https://doi.org/10.3390/s25154711 - 30 Jul 2025
Viewed by 127
Abstract
Interferometric fiber optic hydrophones (IFOHs) are highly sensitive for underwater acoustic detection but face challenges owing to the trade-off between laser monochromaticity and coherence length. In this study, we propose a pseudo-random binary sequence (PRBS) phase modulation method for laser coherence length control, [...] Read more.
Interferometric fiber optic hydrophones (IFOHs) are highly sensitive for underwater acoustic detection but face challenges owing to the trade-off between laser monochromaticity and coherence length. In this study, we propose a pseudo-random binary sequence (PRBS) phase modulation method for laser coherence length control, establishing the first theoretical model that quantitatively links PRBS parameter to coherence length, elucidating the mechanism underlying its suppression of parasitic interference noise. Furthermore, our research findings demonstrate that while reducing the laser coherence length effectively mitigates parasitic interference noise in IFOHs, this reduction also leads to elevated background noise caused by diminished interference visibility. Consequently, the modulation of coherence length requires a balanced optimization approach that not only suppresses parasitic noise but also minimizes visibility-introduced background noise, thereby determining the system-specific optimal coherence length. Through theoretical modeling and experimental validation, we determined that for IFOH systems with a 500 ns delay, the optimal coherence lengths for link fibers of 3.3 km and 10 km are 0.93 m and 0.78 m, respectively. At the optimal coherence length, the background noise level in the 3.3 km system reaches −84.5 dB (re: rad/√Hz @1 kHz), representing an additional noise suppression of 4.5 dB beyond the original suppression. This study provides a comprehensive theoretical and experimental solution to the long-standing contradiction between high laser monochromaticity, stability and appropriate coherence length, establishing a coherence modulation noise suppression framework for hydrophones, gyroscopes, distributed acoustic sensing (DAS), and other fields. Full article
(This article belongs to the Section Optical Sensors)
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25 pages, 7101 KiB  
Article
Study on the Influence of Ultrafast Laser Welding Parameters on Glass Bonding Performance
by Aowei Xing, Ziwei Li, Tianfeng Zhou, Zhiyuan Huang, Weijia Guo and Peng Liu
Micromachines 2025, 16(8), 888; https://doi.org/10.3390/mi16080888 - 30 Jul 2025
Viewed by 146
Abstract
Glass enjoys a wide range of applications thanks to its superior optical properties and chemical stability. Conventional glass bonding techniques suffer from low efficiency, limited precision, and high cost. Moreover, for multilayer glass bonding, repeated alignment is often required, further complicating the process. [...] Read more.
Glass enjoys a wide range of applications thanks to its superior optical properties and chemical stability. Conventional glass bonding techniques suffer from low efficiency, limited precision, and high cost. Moreover, for multilayer glass bonding, repeated alignment is often required, further complicating the process. These limitations have become major constraints on the advancement of microfluidic chip technologies. Laser bonding of microfluidic chips offers high precision and efficiency. This research first uses an ultrafast laser system to investigate how processing parameters affect weld morphology, identifying the optimal parameter range. Then, this paper proposes two methods for ultrafast-laser bonding of multilayer glass with different thicknesses and performs preliminary experiments to demonstrate their feasibility. The research in this paper could expand the fabrication method of microfluidic chips and lay a foundation for the wider application of microfluidic chips. Full article
(This article belongs to the Special Issue Ultra-Precision Micro Cutting and Micro Polishing)
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23 pages, 3795 KiB  
Article
Structural Analysis of the Newly Prepared Ti55Al27Mo13 Alloy by Aluminothermic Reaction
by Štefan Michna, Jaroslava Svobodová, Anna Knaislová, Jan Novotný and Lenka Michnová
Materials 2025, 18(15), 3583; https://doi.org/10.3390/ma18153583 - 30 Jul 2025
Viewed by 131
Abstract
This study presents the structural and compositional characterisation of a newly developed Ti55Al27Mo13 alloy synthesised via aluminothermic reaction. The alloy was designed to overcome the limitations of conventional processing routes for high–melting–point elements such as Ti and Mo, enabling the formation of a [...] Read more.
This study presents the structural and compositional characterisation of a newly developed Ti55Al27Mo13 alloy synthesised via aluminothermic reaction. The alloy was designed to overcome the limitations of conventional processing routes for high–melting–point elements such as Ti and Mo, enabling the formation of a complex, multi–phase microstructure in a single high–temperature step. The aim was to develop and characterise a material with microstructural features expected to enhance wear resistance, oxidation behaviour, and thermal stability in future applications. The alloy is intended as a precursor for composite nanopowders and surface coatings applied to aluminium–, magnesium–, and iron–based substrates subjected to mechanical and thermal loading. Elemental analysis (XRF, EDS) confirmed the presence of Ti, Al, Mo, and minor elements such as Si, Fe, and C. Microstructural investigations using laser confocal and scanning electron microscopy revealed a heterogeneous structure comprising solid solutions, eutectic regions, and dispersed oxide and carbide phases. Notably, the alloy exhibits high hardness values, reaching >2400 HV in Al2O3 regions and ~1300 HV in Mo– and Si–enriched solid solutions. These results suggest the material’s substantial potential for protective surface engineering. Further tribological, thermal, and corrosion testing, conducted with meticulous attention to detail, will follow to validate its functional performance in target applications. Full article
(This article belongs to the Section Metals and Alloys)
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21 pages, 6163 KiB  
Article
Residual Stress and Corrosion Performance in L-PBF Ti6Al4V: Unveiling the Optimum Stress Relieving Temperature via Microcapillary Electrochemical Characterisation
by Lorenzo D’Ambrosi, Katya Brunelli, Francesco Cammelli, Reynier I. Revilla and Arshad Yazdanpanah
Metals 2025, 15(8), 855; https://doi.org/10.3390/met15080855 - 30 Jul 2025
Viewed by 207
Abstract
This study aims to determine the optimal low-temperature stress relieving heat treatment that minimizes residual stresses while preserving corrosion resistance in Laser Powder Bed Fusion (L-PBF) processed Ti6Al4V alloy. Specifically, it investigates the effects of stress relieving at 400 °C, 600 °C, and [...] Read more.
This study aims to determine the optimal low-temperature stress relieving heat treatment that minimizes residual stresses while preserving corrosion resistance in Laser Powder Bed Fusion (L-PBF) processed Ti6Al4V alloy. Specifically, it investigates the effects of stress relieving at 400 °C, 600 °C, and 800 °C on microstructure, residual stress, and electrochemical performance. Specimens were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical techniques. A novel microcapillary electrochemical method was employed to precisely assess passive layer stability and corrosion behaviour under simulated oral conditions, including fluoride contamination and tensile loading. Results show that heat treatments up to 600 °C effectively reduce residual stress with minimal impact on corrosion resistance. However, 800 °C treatment leads to a phase transformation from α′ martensite to a dual-phase α + β structure, significantly compromising passive film integrity. The findings establish 600 °C as the optimal stress-relieving temperature for balancing mechanical stability and electrochemical performance in biomedical and aerospace components. Full article
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21 pages, 4865 KiB  
Article
Impact of Laser Power and Scanning Speed on Single-Walled Support Structures in Powder Bed Fusion of AISI 316L
by Dan Alexander Gallego, Henrique Rodrigues Oliveira, Tiago Cunha, Jeferson Trevizan Pacheco, Oksana Kovalenko and Neri Volpato
J. Manuf. Mater. Process. 2025, 9(8), 254; https://doi.org/10.3390/jmmp9080254 - 30 Jul 2025
Viewed by 184
Abstract
Laser beam powder bed fusion of metals (PBF-LB/M, or simply L-PBF) has emerged as one of the most competitive additive manufacturing technologies for producing complex metallic components with high precision, design freedom, and minimal material waste. Among the various categories of additive manufacturing [...] Read more.
Laser beam powder bed fusion of metals (PBF-LB/M, or simply L-PBF) has emerged as one of the most competitive additive manufacturing technologies for producing complex metallic components with high precision, design freedom, and minimal material waste. Among the various categories of additive manufacturing processes, L-PBF stands out, paving the way for the execution of part designs with geometries previously considered unfeasible. Despite offering several advantages, parts with overhang features require the use of support structures to provide dimensional stability of the part. Support structures achieve this by resisting residual stresses generated during processing and assisting heat dissipation. Although the scientific community acknowledges the role of support structures in the success of L-PBF manufacturing, they have remained relatively underexplored in the literature. In this context, the present work investigated the impact of laser power and scanning speed on the dimensioning, integrity and tensile strength of single-walled block type support structures manufactured in AISI 316L stainless steel. The method proposed in this work is divided in two stages: processing parameter exploration, and mechanical characterization. The results indicated that support structures become more robust and resistant as laser power increases, and the opposite effect is observed with an increment in scanning speed. In addition, defects were detected at the interfaces between the bulk and support regions, which were crucial for the failure of the tensile test specimens. For a layer thickness corresponding to 0.060 mm, it was verified that the combination of laser power and scanning speed of 150 W and 500 mm/s resulted in the highest tensile resistance while respecting the dimensional deviation requirement. Full article
(This article belongs to the Special Issue Recent Advances in Optimization of Additive Manufacturing Processes)
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27 pages, 2602 KiB  
Article
Folate-Modified Albumin-Functionalized Iron Oxide Nanoparticles for Theranostics: Engineering and In Vitro PDT Treatment of Breast Cancer Cell Lines
by Anna V. Bychkova, Maria G. Gorobets, Anna V. Toroptseva, Alina A. Markova, Minh Tuan Nguyen, Yulia L. Volodina, Margarita A. Gradova, Madina I. Abdullina, Oksana A. Mayorova, Valery V. Kasparov, Vadim S. Pokrovsky, Anton V. Kolotaev and Derenik S. Khachatryan
Pharmaceutics 2025, 17(8), 982; https://doi.org/10.3390/pharmaceutics17080982 - 30 Jul 2025
Viewed by 298
Abstract
Background/Objectives: Magnetic iron oxide nanoparticles (IONPs), human serum albumin (HSA) and folic acid (FA) are prospective components for hybrid nanosystems for various biomedical applications. The magnetic nanosystems FA-HSA@IONPs (FAMs) containing IONPs, HSA, and FA residue are engineered in the study. Methods: [...] Read more.
Background/Objectives: Magnetic iron oxide nanoparticles (IONPs), human serum albumin (HSA) and folic acid (FA) are prospective components for hybrid nanosystems for various biomedical applications. The magnetic nanosystems FA-HSA@IONPs (FAMs) containing IONPs, HSA, and FA residue are engineered in the study. Methods: Composition, stability and integrity of the coating, and peroxidase-like activity of FAMs are characterized using UV/Vis spectrophotometry (colorimetric test using o-phenylenediamine (OPD), Bradford protein assay, etc.), spectrofluorimetry, dynamic light scattering (DLS) and electron magnetic resonance (EMR). The selectivity of the FAMs accumulation in cancer cells is analyzed using flow cytometry and confocal laser scanning microscopy. Results: FAMs (dN~55 nm by DLS) as a drug delivery platform have been administered to cancer cells (human breast adenocarcinoma MCF-7 and MDA-MB-231 cell lines) in vitro. Methylene blue, as a model photosensitizer, has been non-covalently bound to FAMs. An increase in photoinduced cytotoxicity has been found upon excitation of the photosensitizer bound to the coating of FAMs compared to the single photosensitizer at equivalent concentrations. The suitability of the nanosystems for photodynamic therapy has been confirmed. Conclusions: FAMs are able to effectively enter cells with increased folate receptor expression and thus allow antitumor photosensitizers to be delivered to cells without any loss of their in vitro photodynamic efficiency. Therapeutic and diagnostic applications of FAMs in oncology are discussed. Full article
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15 pages, 4667 KiB  
Article
Longitudinal High-Resolution Imaging of Retinal Sequelae of a Choroidal Nevus
by Kaitlyn A. Sapoznik, Stephen A. Burns, Todd D. Peabody, Lucie Sawides, Brittany R. Walker and Thomas J. Gast
Diagnostics 2025, 15(15), 1904; https://doi.org/10.3390/diagnostics15151904 - 29 Jul 2025
Viewed by 215
Abstract
Background: Choroidal nevi are common, benign tumors. These tumors rarely cause adverse retinal sequalae, but when they do, they can lead to disruption of the outer retina and vision loss. In this paper, we used high-resolution retinal imaging modalities, optical coherence tomography [...] Read more.
Background: Choroidal nevi are common, benign tumors. These tumors rarely cause adverse retinal sequalae, but when they do, they can lead to disruption of the outer retina and vision loss. In this paper, we used high-resolution retinal imaging modalities, optical coherence tomography (OCT) and adaptive optics scanning laser ophthalmoscopy (AOSLO), to longitudinally monitor retinal sequelae of a submacular choroidal nevus. Methods: A 31-year-old female with a high-risk choroidal nevus resulting in subretinal fluid (SRF) and a 30-year-old control subject were longitudinally imaged with AOSLO and OCT in this study over 18 and 22 months. Regions of interest (ROI) including the macular region (where SRF was present) and the site of laser photocoagulation were imaged repeatedly over time. The depth of SRF in a discrete ROI was quantified with OCT and AOSLO images were assessed for visualization of photoreceptors and retinal pigmented epithelium (RPE). Cell-like structures that infiltrated the site of laser photocoagulation were measured and their count was assessed over time. In the control subject, images were assessed for RPE visualization and the presence and stability of cell-like structures. Results: We demonstrate that AOSLO can be used to assess cellular-level changes at small ROIs in the retina over time. We show the response of the retina to SRF and laser photocoagulation. We demonstrate that the RPE can be visualized when SRF is present, which does not appear to depend on the height of retinal elevation. We also demonstrate that cell-like structures, presumably immune cells, are present within and adjacent to areas of SRF on both OCT and AOSLO, and that similar cell-like structures infiltrate areas of retinal laser photocoagulation. Conclusions: Our study demonstrates that dynamic, cellular-level retinal responses to SRF and laser photocoagulation can be monitored over time with AOSLO in living humans. Many retinal conditions exhibit similar retinal findings and laser photocoagulation is also indicated in numerous retinal conditions. AOSLO imaging may provide future opportunities to better understand the clinical implications of such responses in vivo. Full article
(This article belongs to the Special Issue High-Resolution Retinal Imaging: Hot Topics and Recent Developments)
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13 pages, 1723 KiB  
Article
Molecular Fractionation Induced by Viscosity-Driven Segregative Phase Separation Behavior of Gum Arabic/Hydroxypropyl Methylcellulose
by Lingyu Han, Cunzhi Zhang, Nuo Dong, Jixin Yang, Qiuyue Zheng, Xiaobo Zhang, Ronggang Liu, Jijuan Cao and Bing Hu
Foods 2025, 14(15), 2642; https://doi.org/10.3390/foods14152642 - 28 Jul 2025
Viewed by 178
Abstract
Segregative phase separation technology demonstrates substantial potential for precise molecular fractionation in food and biomaterial applications. The investigation elucidates the causal relationship between viscosity variations and phase separation dynamics, which govern molecular fractionation in GA/HPMC composite systems. By conducting a comparative analysis of [...] Read more.
Segregative phase separation technology demonstrates substantial potential for precise molecular fractionation in food and biomaterial applications. The investigation elucidates the causal relationship between viscosity variations and phase separation dynamics, which govern molecular fractionation in GA/HPMC composite systems. By conducting a comparative analysis of two GA subtypes (CGA and SGA) and three HPMC grades with controlled viscosity gradients, we utilized gel permeation chromatography-multi-angle laser light scattering (GPC-MALLS) coupled with rheological characterization to elucidate the critical relationship between continuous phase viscosity and fractionation efficiency. Notably, increasing HPMC viscosity significantly intensified phase separation, resulting in selective enrichment of arabinogalactan-protein complexes: from 6.3% to 8.5% in CGA/HPMC systems and from 27.3% to 36.5% in SGA/HPMC systems. Further mechanistic investigation revealed that elevated HPMC viscosity enhances thermodynamic incompatibility while slowing interfacial mass transfer, synergistically driving component redistribution. These findings establish a quantitative viscosity–fractionation relationship, offering theoretical insights for optimizing GA/HPMC systems in emulsion stabilization, microencapsulation, and functional biopolymer purification via viscosity-mediated phase engineering. Full article
(This article belongs to the Section Food Physics and (Bio)Chemistry)
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16 pages, 1865 KiB  
Article
pH-Controlled Yeast Protein Precipitation from Saccharomyces cerevisiae: Acid-Induced Denaturation for Improved Emulsion Stability
by Laura Riedel, Nico Leister and Ulrike S. van der Schaaf
Foods 2025, 14(15), 2643; https://doi.org/10.3390/foods14152643 - 28 Jul 2025
Viewed by 174
Abstract
In the search for alternative protein sources, single cell proteins have gained increasing attention in recent years. Among them, proteins derived from yeast represent a promising but still underexplored option. To enable their application in food product design, their techno-functional properties must be [...] Read more.
In the search for alternative protein sources, single cell proteins have gained increasing attention in recent years. Among them, proteins derived from yeast represent a promising but still underexplored option. To enable their application in food product design, their techno-functional properties must be understood. In order to investigate the impact of precipitation pH on their emulsion-stabilizing properties, yeast proteins from Saccharomyces cerevisiae were isolated via precipitation at different pH (pH 3.5 to 5) after cell disruption in the high-pressure homogenizer. Emulsions containing 5 wt% oil and ~1 wt% protein were analyzed for stability based on their droplet size distribution. Proteins precipitated at pH 3.5 stabilized the smallest oil droplets and prevented partitioning of the emulsion, outperforming proteins precipitated at higher pH values. It is hypothesized that precipitation under acidic conditions induces protein denaturation and thereby exposes hydrophobic regions that enhance adsorption at the oil–water interface and the stabilization of the dispersed oil phase. To investigate the stabilization mechanism, the molecular weight of the proteins was determined using SDS-PAGE, their solubility using Bradford assay, and their aggregation behavior using static laser scattering. Proteins precipitated at pH 3.5 possessed larger molecular weights, lower solubility, and a strong tendency to aggregate. Overall, the findings highlight the potential of yeast-derived proteins as bio-surfactants and suggest that pH-controlled precipitation can tailor their functionality in food formulations. Full article
(This article belongs to the Section Nutraceuticals, Functional Foods, and Novel Foods)
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18 pages, 3199 KiB  
Article
Geomechanical Basis for Assessing Open-Pit Slope Stability in High-Altitude Gold Mining
by Farit Nizametdinov, Rinat Nizametdinov, Denis Akhmatnurov, Nail Zamaliyev, Ravil Mussin, Nikita Ganyukov, Krzysztof Skrzypkowski, Waldemar Korzeniowski, Jerzy Stasica and Zbigniew Rak
Appl. Sci. 2025, 15(15), 8372; https://doi.org/10.3390/app15158372 - 28 Jul 2025
Viewed by 247
Abstract
The development of mining operations in high-altitude regions is associated with a number of geomechanical challenges caused by increased rock fracturing, adverse climatic conditions, and high seismic activity. These issues are particularly relevant for the exploitation of gold ore deposits, where the stability [...] Read more.
The development of mining operations in high-altitude regions is associated with a number of geomechanical challenges caused by increased rock fracturing, adverse climatic conditions, and high seismic activity. These issues are particularly relevant for the exploitation of gold ore deposits, where the stability of open-pit slopes directly affects both safety and extraction efficiency. The aim of this study is to develop and practically substantiate a comprehensive approach to assessing and ensuring slope stability, using the Bozymchak gold ore deposit—located in a high-altitude and seismically active zone—as a case study. The research involves the laboratory testing of rock samples obtained from engineering–geological boreholes, field shear tests on rock prisms, laser scanning of pit slopes, and digital geomechanical modeling. The developed calculation schemes take into account the structural features of the rock mass, geological conditions, and the design contours of the pit. In addition, special bench excavation technologies with pre-shear slotting and automated GeoMoS monitoring are implemented for real-time slope condition tracking. The results of the study make it possible to reliably determine the strength characteristics of the rocks under natural conditions, identify critical zones of potential collapse, and develop recommendations for optimizing slope parameters and mining technologies. The implemented approach ensures the required level of safety. Full article
(This article belongs to the Special Issue Latest Advances in Rock Mechanics and Geotechnical Engineering)
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18 pages, 4836 KiB  
Article
Deep Learning to Analyze Spatter and Melt Pool Behavior During Additive Manufacturing
by Deepak Gadde, Alaa Elwany and Yang Du
Metals 2025, 15(8), 840; https://doi.org/10.3390/met15080840 - 28 Jul 2025
Viewed by 375
Abstract
To capture the complex metallic spatter and melt pool behavior during the rapid interaction between the laser and metal material, high-speed cameras are applied to record the laser powder bed fusion process and generate a large volume of image data. In this study, [...] Read more.
To capture the complex metallic spatter and melt pool behavior during the rapid interaction between the laser and metal material, high-speed cameras are applied to record the laser powder bed fusion process and generate a large volume of image data. In this study, four deep learning algorithms are applied: YOLOv5, Fast R-CNN, RetinaNet, and EfficientDet. They are trained by the recorded videos to learn and extract information on spatter and melt pool behavior during the laser powder bed fusion process. The well-trained models achieved high accuracy and low loss, demonstrating strong capability in accurately detecting and tracking spatter and melt pool dynamics. A stability index is proposed and calculated based on the melt pool length change rate. Greater index value reflects a more stable melt pool. We found that more spatters were detected for the unstable melt pool, while fewer spatters were found for the stable melt pool. The spatter’s size can affect its initial ejection speed, and large spatters are ejected slowly while small spatters are ejected rapidly. In addition, more than 58% of detected spatters have their initial ejection angle in the range of 60–120°. These findings provide a better understanding of spatter and melt pool dynamics and behavior, uncover the influence of melt pool stability on spatter formation, and demonstrate the correlation between the spatter size and its initial ejection speed. This work will contribute to the extraction of important information from high-speed recorded videos for additive manufacturing to reduce waste, lower cost, enhance part quality, and increase process reliability. Full article
(This article belongs to the Special Issue Machine Learning in Metal Additive Manufacturing)
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20 pages, 14936 KiB  
Article
Viscosity, Morphology, and Thermomechanical Performance of Attapulgite-Reinforced Bio-Based Polyurethane Asphalt Composites
by Haocheng Yang, Suzhou Cao, Xinpeng Cui, Zhonghua Xi, Jun Cai, Zuanru Yuan, Junsheng Zhang and Hongfeng Xie
Polymers 2025, 17(15), 2045; https://doi.org/10.3390/polym17152045 - 26 Jul 2025
Viewed by 370
Abstract
Bio-based polyurethane asphalt binder (PUAB) derived from castor oil (CO) is environmentally friendly and exhibits extended allowable construction time. However, CO imparts inherently poor mechanical performance to bio-based PUAB. To address this limitation, attapulgite (ATT) with fibrous nanostructures was incorporated. The effects of [...] Read more.
Bio-based polyurethane asphalt binder (PUAB) derived from castor oil (CO) is environmentally friendly and exhibits extended allowable construction time. However, CO imparts inherently poor mechanical performance to bio-based PUAB. To address this limitation, attapulgite (ATT) with fibrous nanostructures was incorporated. The effects of ATT on bio-based PUAB were systematically investigated, including cure kinetics, rotational viscosity (RV) evolution, phase-separation microstructures, dynamic mechanical properties, thermal stability, and mechanical performance. Experimental characterization employed Fourier transform infrared spectroscopy, Brookfield viscometry, laser scanning confocal microscopy, dynamic mechanical analysis, thermogravimetry, and tensile testing. ATT incorporation accelerated the polyaddition reaction conversion between isocyanate groups in polyurethane (PU) and hydroxyl groups in ATT. Paradoxically, it reduced RV during curing, prolonging allowable construction time proportionally with clay content. Additionally, ATT’s compatibilizing effect decreased bitumen particle size in PUAB, with scaling proportionally with clay loading. While enhancing thermal stability, ATT lowered the glass transition temperature and damping properties. Crucially, 1 wt% ATT increased tensile strength by 71% and toughness by 62%, while maintaining high elongation at break (>400%). The cost-effectiveness and significant reinforcement capability of ATT make it a promising candidate for producing high-performance bio-based PUAB composites. Full article
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13 pages, 8086 KiB  
Article
Flexible FLIG-Based Temperature Sensor Enabled by Femtosecond Laser Direct Writing for Thermal Monitoring in Health Systems
by Huansheng Wu, Cong Wang, Linpeng Liu and Ji’an Duan
Sensors 2025, 25(15), 4643; https://doi.org/10.3390/s25154643 - 26 Jul 2025
Viewed by 338
Abstract
In this study, a facile and mask-free femtosecond laser direct writing (FLDW) approach is proposed to fabricate porous graphene (FLIG) patterns directly on polyimide (PI) substrates. By systematically adjusting the laser scanning spacing (10–25 μm), denser and more continuous microstructures are obtained, resulting [...] Read more.
In this study, a facile and mask-free femtosecond laser direct writing (FLDW) approach is proposed to fabricate porous graphene (FLIG) patterns directly on polyimide (PI) substrates. By systematically adjusting the laser scanning spacing (10–25 μm), denser and more continuous microstructures are obtained, resulting in significantly enhanced thermal sensitivity. The optimized sensor demonstrated a temperature coefficient of 0.698% °C−1 within the range of 40–120 °C, with response and recovery times of 10.3 s and 20.9 s, respectively. Furthermore, it exhibits remarkable signal stability across multiple thermal cycles, a testament to its reliability in extreme conditions. Moreover, the sensor was successfully integrated into a 3D-printed robotic platform, achieving both contact and non-contact temperature detection. These results underscore the sensor’s practical adaptability for real-time thermal sensing. This work presents a viable and scalable methodology for fabricating high-performance FLIG-based flexible temperature sensors, with extensive application prospects in wearable electronics, electronic skin, and intelligent human–machine interfaces. Full article
(This article belongs to the Special Issue State of the Art in Wearable Sensors for Health Monitoring)
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15 pages, 8574 KiB  
Article
Hydrogen Embrittlement Resistance of an Optimized Additively Manufactured Austenitic Stainless Steel from Recycled Sources
by Mattia Cabrioli, María Silva Colmenero, Matteo Vanazzi, Luisa E. Mondora, Gianluca Acquistapace, Fabio Esposito and Michela Giovanardi
Corros. Mater. Degrad. 2025, 6(3), 34; https://doi.org/10.3390/cmd6030034 - 26 Jul 2025
Viewed by 161
Abstract
In the framework of hydrogen production and storage for clean energy generation, the resistance to hydrogen embrittlement of a newly developed austenitic stainless steel is presented. Gas-atomized metal powders prepared from secondary-sourced metals were employed to manufacture test specimens with Laser Powder Bed [...] Read more.
In the framework of hydrogen production and storage for clean energy generation, the resistance to hydrogen embrittlement of a newly developed austenitic stainless steel is presented. Gas-atomized metal powders prepared from secondary-sourced metals were employed to manufacture test specimens with Laser Powder Bed Fusion (LPBF) technology. After machining and exposure to a controlled, pressurized hydrogen atmosphere at high temperature, the effect of hydrogen charging on the mechanical performance under static and dynamic conditions was investigated. The stabilizing effect of the optimized chemical composition is reflected in the absence of degradation effects on Yield Stress (YS), Ultimate Tensile Stress (UTS), and fatigue life observed for specimens exposed to hydrogen. Moreover, despite a moderate reduction in the elongation at fracture observed by increasing the hydrogen charging time, ductility loss calculated as Relative Reduction of Area (RRA) remains substantially unaffected by the duration of exposure to hydrogen and demonstrates that the austenitic steel is capable of resisting hydrogen embrittlement (HE). Full article
(This article belongs to the Special Issue Hydrogen Embrittlement of Modern Alloys in Advanced Applications)
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