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17 pages, 2829 KiB  
Article
Apparatus and Experiments Towards Fully Automated Medical Isotope Production Using an Ion Beam Accelerator
by Abdulaziz Yahya M. Hussain, Aliaksandr Baidak, Ananya Choudhury, Andy Smith, Carl Andrews, Eliza Wojcik, Liam Brown, Matthew Nancekievill, Samir De Moraes Shubeita, Tim A. D. Smith, Volkan Yasakci and Frederick Currell
Instruments 2025, 9(3), 18; https://doi.org/10.3390/instruments9030018 - 18 Jul 2025
Viewed by 261
Abstract
Zirconium-89 (89Zr) is a widely used radionuclide in immune-PET imaging due to its physical decay characteristics. Despite its importance, the production of 89Zr radiopharmaceuticals remains largely manual, with limited cost-effective automation solutions available. To address this, we developed an automated [...] Read more.
Zirconium-89 (89Zr) is a widely used radionuclide in immune-PET imaging due to its physical decay characteristics. Despite its importance, the production of 89Zr radiopharmaceuticals remains largely manual, with limited cost-effective automation solutions available. To address this, we developed an automated system for the agile and reliable production of radiopharmaceuticals. The system performs transmutations, dissolution, and separation for a range of radioisotopes. Steps in the production of 89Zr-oxalate are used as an exemplar to illustrate its use. Three-dimensional (3D) printing was exploited to design and manufacture a target holder able to include solid targets, in this case an 89Y foil. Spot welding was used to attach 89Y to a refractory tantalum (Ta) substrate. A commercially available CPU chiller was repurposed to efficiently cool the metal target. Furthermore, a commercial resin (ZR Resin) and compact peristaltic pumps were employed in a compact (10 × 10 × 10 cm3) chemical separation unit that operates automatically via computer-controlled software. Additionally, a standalone 3D-printed unit was designed with three automated functionalities: photolabelling, vortex mixing, and controlled heating. All components of the assembly, except for the target holder, are housed inside a commercially available hot cell, ensuring safe and efficient operation in a controlled environment. This paper details the design, construction, and modelling of the entire assembly, emphasising its innovative integration and operational efficiency for widespread radiopharmaceutical automation. Full article
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14 pages, 2761 KiB  
Article
Electrochemical Properties of Soluble CuCl·3TU Coordination Compound and Application in Electrolysis for Copper Foils
by Wancheng Zhao, Fangquan Xia and Dong Tian
Chemistry 2025, 7(4), 114; https://doi.org/10.3390/chemistry7040114 - 18 Jul 2025
Viewed by 278
Abstract
As the crucial current collector for lithium-ion batteries (LIBs), electrolytic copper foils are generally manufactured by electrodeposition in acidic copper sulfate solution. However, there are many disadvantages for traditional electrolytic copper foils, such as coarse grains, insufficient mechanical properties, and high energy consumption. [...] Read more.
As the crucial current collector for lithium-ion batteries (LIBs), electrolytic copper foils are generally manufactured by electrodeposition in acidic copper sulfate solution. However, there are many disadvantages for traditional electrolytic copper foils, such as coarse grains, insufficient mechanical properties, and high energy consumption. In order to improve the performances of electrolytic copper foil, a novel cuprous electrodeposition system was developed in this study. A soluble cuprous coordination compound was synthesized. In addition, XPS, FT-IR spectrum, as well as single-crystal X-ray diffraction illustrated that thiourea coordinated with Cu(I) through S atom and therefore stabilized Cu(I) by the formation of CuCl·3TU. Importantly, the corresponding electrochemical behaviors were investigated. In aqueous solution, two distinct reduction processes were demonstrated by linear sweep voltammetry (LSV) at rather negative potentials, including the reduction of adsorbed state and non-adsorbed state. Moreover, the observed inductive loops in electrochemical impedance spectroscopy further confirmed the adsorption phenomenon. More significantly, the designed cuprous electrodeposition system could contribute to low energy consumptions during electrolysis. and produce ultrathin nanocrystalline copper foils with appropriate roughness. Consequently, the electrolysis method based on CuCl·3TU could provide an improved approach for copper foils manufacturing in advanced LIBs fabrication. Full article
(This article belongs to the Section Electrochemistry and Photoredox Processes)
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16 pages, 912 KiB  
Article
Environmental Impact Assessment of Heat Storage System in Rock-Bed Accumulator
by Mateusz Malinowski, Stanisław Bodziacki, Stanisław Famielec, Damian Huptyś, Sławomir Kurpaska, Hubert Latała and Zuzanna Basak
Energies 2025, 18(13), 3360; https://doi.org/10.3390/en18133360 - 26 Jun 2025
Viewed by 243
Abstract
The use of a rock-bed accumulator for a short-term heat storage and air exchange in a building facility is an economical and energy-efficient technological solution to balance and optimize the energy supplied to the facility. Existing scientific studies have not addressed, as yet, [...] Read more.
The use of a rock-bed accumulator for a short-term heat storage and air exchange in a building facility is an economical and energy-efficient technological solution to balance and optimize the energy supplied to the facility. Existing scientific studies have not addressed, as yet, the environmental impacts of using a rock bed for heat storage. The purpose of the research is the environmental life cycle assessment (LCA) of a heat storage system in a rock-bed accumulator supported by a photovoltaic installation. The boundaries of the analyzed system include manufacturing the components of the storage device, land preparation for the construction of the accumulator, the entire construction process, including transportation of materials, and its operation in cooperation with a horticultural facility (foil tunnel) during one growing season, as well as the photovoltaic installation. The functional unit in the analysis is 1 square meter of rock-bed accumulator surface area. SimaPro 8.1 software and Ecoinvent database were used to perform the LCA, applying the ReCiPe model to analyze environmental impact. The analysis showed the largest negative environmental impact occurs during raw materials extraction and component manufacturing (32.38 Pt). The heat stored during one season (April to October) at a greenhouse facility reduces this negative impact by approx. 7%, mainly due to the reduction in the use of fossil fuels to heat the facility. A 3 °C increase in average air temperature results in an average reduction of 0.7% per year in the negative environmental impact of the rock-bed thermal energy storage system. Full article
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15 pages, 2341 KiB  
Article
Roll-to-Roll (R2R) High-Throughput Manufacturing of Foil-Based Microfluidic Chips for Neurite Outgrowth Studies
by Nihan Atak, Martin Smolka, Anja Haase, Alexandra Lorenz, Silvia Schobesberger, Stephan Ruttloff, Christian Wolf, Ana Ayerdi-Izquierdo, Peter Ertl, Nerea Briz Iceta, Jan Hesse and Martin Frauenlob
Micromachines 2025, 16(6), 713; https://doi.org/10.3390/mi16060713 - 16 Jun 2025
Viewed by 1986
Abstract
Microfluidic devices have emerged as a pivotal in vitro technology for axon outgrowth studies, facilitating the separation of the cell body from the neurites by geometric constraints. However, traditional microfabrication techniques fall short in terms of scalability for large-scale production, hindering widespread application. [...] Read more.
Microfluidic devices have emerged as a pivotal in vitro technology for axon outgrowth studies, facilitating the separation of the cell body from the neurites by geometric constraints. However, traditional microfabrication techniques fall short in terms of scalability for large-scale production, hindering widespread application. This study presents the development of foil-based cell culture chips, made of polyethylene terephthalate and in-house formulated ultraviolet curable liquid resin by high-throughput roll-to-roll (R2R) manufacturing. Here, two microchannel designs were tested to optimize manufacturing quality and assess the neurite outgrowth behavior. The fabricated neuron-foil chips demonstrated biocompatibility and supported neurite outgrowth within microchannels under static cell culture conditions. Furthermore, fluidic flow, oriented either perpendicular or parallel to the microchannel direction, was applied to enhance the biological reproducibility within the neuron-foil chips. These findings suggest that R2R manufacturing offers a promising approach for the high-throughput production of biocompatible microfluidic devices, advancing their potential application in modeling neurological diseases within the biomedical industry. Full article
(This article belongs to the Section B2: Biofabrication and Tissue Engineering)
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17 pages, 17692 KiB  
Article
An Exploration of Manufacturing Technology to Refine the Grain Size and Improve the Properties of Welded TA1 Titanium Plates for Cathode Rollers
by Lin Qi, Jing Hu, Dayue Wang, Jingyi Gu, Weiju Jia, Xulong An and Wei Wei
Coatings 2025, 15(6), 687; https://doi.org/10.3390/coatings15060687 - 6 Jun 2025
Viewed by 477
Abstract
Electrolytic copper foil is one of the core materials in the fields of electronics, communications, and power. The cathode roller is the key component of the complete set of electrolytic copper foil equipment, and the quality of the titanium cylinder of the cathode [...] Read more.
Electrolytic copper foil is one of the core materials in the fields of electronics, communications, and power. The cathode roller is the key component of the complete set of electrolytic copper foil equipment, and the quality of the titanium cylinder of the cathode roller directly determines the quality of the electrolytic copper foil. There typically exists a longitudinal weld on the surface of the cathode roller’s titanium cylinder sleeve manufactured by the welding method, which leads to the degradation of the quality of the electrolytic copper foil. Refining the grains in the weld zone and the heat-affected zone to close to those of the base material is a key solution for the manufacturing of welded cathode rollers. In order to effectively modify the microstructure and obtain an optimal refining effect in the weld zone of a TA1 cathode roller, a novel composite technology consisting of low-energy and fewer-pass welding combined with multi-pass rolling deformation and vacuum annealing treatment was primarily explored for high-purity TA1 titanium plates in this study. The microstructure of each area of the weld was observed using the DMI-3000M optical microscope, and the hardness was measured using the HVS-30 Vickers hardness tester. The research results show that the microstructure of each area of the weld can be effectively refined by using the novel composite technology of low-energy and fewer-pass welding, multi-pass rolling deformation, and vacuum annealing treatment. Among the explored experimental conditions, the optimal grain refinement effect is obtained with a V-shaped welding groove and four passes of welding with a welding current of 90 A and a voltage of 8–9 V, followed by 11 passes of rolling deformation with a total deformation rate of 45% and, finally, vacuum annealing at 650 °C for 1 h. The grain size grades in the weld zone and the heat-affected zone are close to those of the base material, namely grade 7.5~10, grade 7.5~10, and grade 7.5~10 for the weld zone, heat-affected zone, and base material, respectively. Meanwhile, this technology can also refine the grains of the base material, which is conducive to improving the overall mechanical properties of the titanium plate. Full article
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19 pages, 6105 KiB  
Article
Polylactic Acid and Polyhydroxybutyrate as Printed Circuit Board Substrates: A Novel Approach
by Zahra Fazlali, David Schaubroeck, Maarten Cauwe, Ludwig Cardon, Pieter Bauwens and Jan Vanfleteren
Processes 2025, 13(5), 1360; https://doi.org/10.3390/pr13051360 - 29 Apr 2025
Cited by 1 | Viewed by 913
Abstract
This study presents a novel approach to manufacture a rigid printed circuit board (PCB) using sustainable polymers. Current PCBs use a fossil-fuel-based substrate, like FR4. This presents recycling challenges due to its composite nature. Replacing the substrate with an environmentally friendly alternative leads [...] Read more.
This study presents a novel approach to manufacture a rigid printed circuit board (PCB) using sustainable polymers. Current PCBs use a fossil-fuel-based substrate, like FR4. This presents recycling challenges due to its composite nature. Replacing the substrate with an environmentally friendly alternative leads to a reduction in negative impacts. Polylactic acid (PLA) and Polyhydroxybutyrate (PHB) biopolymers are used in this study. These two biopolymers have low melting points (130–180 °C, and 170–180 °C, respectively) and cannot withstand the high temperature soldering process (up to 260 °C for standard SAC (SnAgCu, tin/silver/copper) lead free solder processes). Our approach for replacing the PCB substrate is applying the PLA/PHB carrier substrate at the end of the PCB manufacturing process using injection molding technology. This approach involves all the standard PCB processes, including wet etching of the Cu conductors, and component assembly with SAC solder on a thin flexible polyimide (PI) foil with patterned Cu conductors and then overmolding the biopolymer onto the foil to create a rigid base. This study demonstrates the functionality of two test circuits fabricated using this method. In addition, we evaluated the adhesion between the biopolymer and PI to achieve a durable PCB. Moreover, we performed two different end-of-life approaches (debonding and composting) as a part of the end-of-life consideration. By incorporating biodegradable materials into PCB standard manufacturing, the CO2 emissions and energy consumption are significantly reduced, and installation costs are lowered. Full article
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18 pages, 10927 KiB  
Article
Study on the Formation and Evolution Mechanism of Pinhole in Aluminum Foil for the Lithium-Ion Battery Soft Packaging
by Kai Zhang, Wei Chen, Zhehang Fan, Xiaohu Chen, Changle Xiao, Yunan Chen, Yinhui Xu, Ruian Ni and Hongyan Wu
Coatings 2025, 15(4), 472; https://doi.org/10.3390/coatings15040472 - 16 Apr 2025
Viewed by 714
Abstract
As the crucial core material in aluminum–plastic-laminated films, aluminum foil serves as a barrier and shaping element for lithium-ion battery soft packaging. However, its thinness, measuring only tens of microns, makes it susceptible to the formation of pinholes during the manufacturing process, which [...] Read more.
As the crucial core material in aluminum–plastic-laminated films, aluminum foil serves as a barrier and shaping element for lithium-ion battery soft packaging. However, its thinness, measuring only tens of microns, makes it susceptible to the formation of pinholes during the manufacturing process, which can significantly impact the barrier performance and properties of the aluminum–plastic-laminated film. The morphology and composition of foreign particles that lead to pinholes were analyzed using scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS). Additionally, the formation mechanism and evolution law of pinholes were investigated using a laser scanning confocal microscope (LSCM). The results revealed that foreign particles responsible for pinholes originated from the inclusions in the aluminum alloy melt, filter aid particles from rolling oil, and environmental dust particles. To address this issue, potential strategies for controlling foreign particles were proposed. These included purifying the aluminum alloy melt, filtering the rolling oil, and maintaining a clean production environment. The simulated experiments showed that foreign particles were gradually embedded in the aluminum matrix during plastic deformation, leading to damage in the aluminum matrix. When the cumulative rolling reduction ratio exceeded 38%, the aluminum foil and foreign particles began to separate along the rolling direction, resulting in the formation of pinholes. The mechanism of uncoordinated deformation between foreign particles and aluminum foil was elaborated in detail. In addition, the simulation experiment indicated that once the cumulative reduction ratio surpassed 50%, the aspect ratio of the pinhole increased rapidly. When the cumulative reduction ratio increased to 83%, the pinhole began to gradually heal. Consequently, a quantitative relationship model between the pinhole area and the rolling reduction ratio was constructed. The pinhole evolution model enables a rough prediction of the actual pinhole area change and meets the requirements for engineering applications. This research provides both engineering applications and theoretical prediction approaches that can aid in the production of high-quality aluminum foil for lithium-ion battery soft packaging. Full article
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10 pages, 4748 KiB  
Article
Fragmentation of Cu2O Oxides Caused by Various States of Stress Resulting from Extreme Plastic Deformation
by Małgorzata Zasadzińska
Materials 2025, 18(8), 1736; https://doi.org/10.3390/ma18081736 - 10 Apr 2025
Viewed by 444
Abstract
The development of microelectronics results in higher demand for copper microwires and thin foils. Higher demand requires conducting research to obtain knowledge on the influence of extreme plastic deformation on materials’ susceptibility to plastic processing without the loss of coherence. One of the [...] Read more.
The development of microelectronics results in higher demand for copper microwires and thin foils. Higher demand requires conducting research to obtain knowledge on the influence of extreme plastic deformation on materials’ susceptibility to plastic processing without the loss of coherence. One of the key factors contributing to rupture during the plastic deformation of copper is the presence of micrometer-sized, eutectic Cu2O oxides, which are weakly bound to the copper matrix. These oxides are formed during the metallurgical stage of wire rod copper manufacturing. Copper wire rod of the ETP (electrolytic tough pitch) grade was subjected to wire drawing followed by cold-rolling. Applying different states of stress during plastic deformation (wire drawing, cold-rolling, and upsetting) made it possible to specify the conditions required for Cu2O oxides’ fragmentation due to the extreme total deformation. Qualitative and quantitative analyses of the Cu2O oxides’ evolution and fragmentation as the plastic deformation progressed were the main focus of this paper. It was determined that major fragmentation occurred during the initial stages of plastic deformation. Applying further extreme deformation or changing the state of stress during plastic deformation did not facilitate the continuation of fragmentation. It was only their shape that was becoming elongated. Full article
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21 pages, 2081 KiB  
Article
Translation of COVID-19 Serology Test on Foil-Based Lateral Flow Chips: A Journey from Injection Molding to Scalable Roll-to-Roll Nanoimprint Lithography
by Pakapreud Khumwan, Stephan Ruttloff, Johannes Götz, Dieter Nees, Conor O’Sullivan, Alvaro Conde, Mirko Lohse, Christian Wolf, Nastasia Okulova, Janine Brommert, Richard Benauer, Ingo Katzmayr, Nikolaus Ladenhauf, Wilfried Weigel, Maciej Skolimowski, Max Sonnleitner, Martin Smolka, Anja Haase, Barbara Stadlober and Jan Hesse
Biosensors 2025, 15(4), 229; https://doi.org/10.3390/bios15040229 - 4 Apr 2025
Viewed by 801
Abstract
Lateral flow tests (LFTs) had a pivotal role in combating the spread of the SARS-CoV-2 virus throughout the COVID-19 pandemic thanks to their affordability and ease of use. Most of LFT devices were based on nitrocellulose membrane strips whose industrial upscaling to billions [...] Read more.
Lateral flow tests (LFTs) had a pivotal role in combating the spread of the SARS-CoV-2 virus throughout the COVID-19 pandemic thanks to their affordability and ease of use. Most of LFT devices were based on nitrocellulose membrane strips whose industrial upscaling to billions of devices has already been extensively demonstrated. Nevertheless, the assay option in an LFT format is largely restricted to qualitative detection of the target antigens. In this research, we surveyed the potential of UV nanoimprint lithography (UV-NIL) and extrusion coating (EC) for the high-throughput production of disposable capillary-driven, foil-based tests that allow multistep assays to be implemented for quantitative readout to address the inherent lack of on-demand fluid control and sensitivity of paper-based devices. Both manufacturing technologies operate on the principle of imprinting that enables high-volume, continuous structuring of microfluidic patterns in a roll-to-roll (R2R) production scheme. To demonstrate the feasibility of R2R-fabricated foil chips in a point-of-care biosensing application, we adapted a commercial chemiluminescence multiplex test for COVID-19 antibody detection originally developed for a capillary-driven microfluidic chip manufactured with injection molding (IM). In an effort to build a complete ecosystem for the R2R manufacturing of foil chips, we also recruited additional processes to streamline chip production: R2R biofunctionalization and R2R lamination. Compared to conventional fabrication techniques for microfluidic devices, the R2R techniques highlighted in this work offer unparalleled advantages concerning improved scalability, dexterity of seamless handling, and significant cost reduction. Our preliminary evaluation indicated that the foil chips exhibited comparable performance characteristics to the original IM-fabricated devices. This early success in assay translation highlights the promise of implementing biochemical assays on R2R-manufactured foil chips. Most importantly, it underscores the potential utilization of UV-NIL and EC as an alternative to conventional technologies for the future development in vitro diagnostics (IVD) in response to emerging point-of-care testing demands. Full article
(This article belongs to the Special Issue Biosensing Technologies in Medical Diagnosis)
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18 pages, 14690 KiB  
Article
Influence of the Oscillation Parameters Amplitude and Frequency on the Microstructure of Laser-Welded Thin Nitinol Foils
by Danka Katrakova-Krüger, Sabine Weichert and Christoph Hartl
J. Manuf. Mater. Process. 2025, 9(2), 32; https://doi.org/10.3390/jmmp9020032 - 23 Jan 2025
Viewed by 988
Abstract
Laser welding has become well established for joining Ni-Ti-based shape memory alloys and extends the manufacturability of highly functional components with complex geometries. Published studies on the effect of laser welding on alterations to microstructure and properties of these alloys, however, mainly deal [...] Read more.
Laser welding has become well established for joining Ni-Ti-based shape memory alloys and extends the manufacturability of highly functional components with complex geometries. Published studies on the effect of laser welding on alterations to microstructure and properties of these alloys, however, mainly deal with conventional component dimensions and linear laser beam movement. In view of the increasing importance of microtechnology, research into joining of thin-walled Ni-Ti components is therefore of interest. At the same time, studies comparing oscillating and linear beam movement on other materials and the authors’ own work on Ni-Ti materials suggest that oscillating beam movement has a more favorable effect on alterations in material properties and microstructure. Therefore, laser welding of foils made of Ni55/Ti45 with 125 µm thickness was systematically analyzed using a fiber laser and circular oscillation. Amplitude A and frequency f were varied from 0 to 200 µm and 0 to 2000 Hz, respectively. Microstructural analysis showed that by increasing the frequency, grain refinement could be achieved up to a certain value of f. An increasing amplitude led to decreasing hardness values of the weld seam, while the influence of f was less pronounced. The analysis of the weld material using chip calorimetry (Flash DSC) revealed that the beam oscillation had fewer effects on the change in transformation points compared to a linear beam movement. Full article
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20 pages, 4123 KiB  
Article
RFID Unpacked: A Case Study in Employing RFID Tags from Item to Pallet Level
by Ethan Claucherty, Danielle Cummins and Bahar Aliakbarian
Electronics 2025, 14(2), 278; https://doi.org/10.3390/electronics14020278 - 11 Jan 2025
Viewed by 1985
Abstract
As the use of passive ultra-high frequency (UHF) radio frequency identification (RFID) tags continues to surge in supply chain management, it becomes crucial to optimize their application at various levels of packaging to ensure reliability. These packaging levels play a pivotal role in [...] Read more.
As the use of passive ultra-high frequency (UHF) radio frequency identification (RFID) tags continues to surge in supply chain management, it becomes crucial to optimize their application at various levels of packaging to ensure reliability. These packaging levels play a pivotal role in achieving maximum readability and widespread adoption within the industry. This research paper aims to determine the most suitable passive UHF RFID tag for consumer goods filled with liquid and wrapped in foil packaging. In this study, two distinct RFID tags from separate manufacturers were evaluated. The research focused on critical factors such as reader height, distance, and item configuration across different packaging levels (item, case, and pallet). The results demonstrated that the packaging configuration impacts the readability of RFID tags at each packaging level. Through rigorous testing, it was found that achieving a tag readability rate higher than 99.7% is feasible and readability can be optimized by adjusting the reader position, packaging configuration, and tag design. The optimized configuration and testing platform developed in this study can be used for comparable products in other supply chains such as consumer goods, pharmaceuticals, and food. The results of this study emphasize RFID’s potential to revolutionize supply chain management. Full article
(This article belongs to the Special Issue RFID Technology and Its Applications)
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14 pages, 10429 KiB  
Article
Studies of Thermal Conductivity of Graphite Foil-Based Composite Materials
by Vladimir A. Shulyak, Nikolai S. Morozov, Roman A. Minushkin, Viktor Yu. Gubin, Dmitriy V. Vakhrushin, Alexandra V. Gracheva, Ildar Kh. Nigmatullin, Sergei N. Chebotarev and Viktor V. Avdeev
Materials 2025, 18(2), 233; https://doi.org/10.3390/ma18020233 - 8 Jan 2025
Cited by 2 | Viewed by 1149
Abstract
We have proposed and developed a method for measuring the thermal conductivity of highly efficient thermal conductors. The measurement method was tested on pure metals with high thermal conductivity coefficients: aluminum (99.999 wt.% Al) and copper (99.990 wt.% Cu). It was demonstrated that [...] Read more.
We have proposed and developed a method for measuring the thermal conductivity of highly efficient thermal conductors. The measurement method was tested on pure metals with high thermal conductivity coefficients: aluminum (99.999 wt.% Al) and copper (99.990 wt.% Cu). It was demonstrated that their thermal conductivities at a temperature of T = 22 ± 1 °C were <λAl> = 243 ± 3 W/m·K and <λCu> = 405 ± 4 W/m·K, which was in good agreement with values reported in the literature. Artificial graphite (ρG1 = 1.8 g/cm3) and natural graphite (ρG2 = 1.7 g/cm3) were used as reference carbon materials; the measured thermal conductivities were <λG1> = 87 ± 1 W/m·K and <λG2> = 145 ± 3 W/m·K, respectively. It is well established that measuring the thermal conductivity coefficient of thin flexible graphite foils is a complex metrological task. We have proposed to manufacture a solid rectangular sample formed by alternating layers of thin graphite foils connected by layers of ultra-thin polyethylene films. Computer modelling showed that, for equal thermal conductivities of solid products made of compacted thermally exfoliated graphite and products made of a composite material consisting of 100 layers of thin graphite foil and 99 layers of polyethylene, the differences in temperature fields did not exceed 1%. The obtained result substantiates our proposed approach to measuring thermal conductivity of flexible graphite foil by creating a multi-layer composite material. The thermal conductivity coefficient of such a composite at room temperature was <λGF> = 184 ± 6 W/m·K, which aligns well with measurements by the laser flash method. Full article
(This article belongs to the Section Carbon Materials)
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20 pages, 1132 KiB  
Article
Photodiode Signal Patterns: Unsupervised Learning for Laser Weld Defect Analysis
by Erkan Caner Ozkat
Processes 2025, 13(1), 121; https://doi.org/10.3390/pr13010121 - 5 Jan 2025
Viewed by 1308
Abstract
Laser welding, widely used in industries such as automotive and aerospace, requires precise monitoring to ensure defect-free welds, especially when joining dissimilar metallic thin foils. This study investigates the application of machine learning techniques for defect detection in laser welding using photodiode signal [...] Read more.
Laser welding, widely used in industries such as automotive and aerospace, requires precise monitoring to ensure defect-free welds, especially when joining dissimilar metallic thin foils. This study investigates the application of machine learning techniques for defect detection in laser welding using photodiode signal patterns. Supervised models, including Support Vector Machine (SVM), k-Nearest Neighbors (kNN), and Random Forest (RF), were employed to classify weld defects into sound welds (SW), lack of connection (LoC), and over-penetration (OP). SVM achieved the highest accuracy (95.2%) during training, while RF demonstrated superior generalization with 83% accuracy on validation data. The study also proposed an unsupervised learning method using a wavelet scattering one-dimensional convolutional autoencoder (1D-CAE) network for anomaly detection. The proposed network demonstrated its effectiveness in achieving accuracies of 93.3% and 87.5% on training and validation datasets, respectively. Furthermore, distinct signal patterns associated with SW, OP, and LoC were identified, highlighting the ability of photodiode signals to capture welding dynamics. These findings demonstrate the effectiveness of combining supervised and unsupervised methods for laser weld defect detection, paving the way for robust, real-time quality monitoring systems in manufacturing. The results indicated that unsupervised learning could offer significant advantages in identifying anomalies and reducing manufacturing costs. Full article
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14 pages, 8037 KiB  
Article
Highlighting Free-Recovery and Work-Generating Shape Memory Effects at 80r-PET Thermoformed Cups
by Ștefan-Dumitru Sava, Bogdan Pricop, Mihai Popa, Nicoleta-Monica Lohan, Elena Matcovschi, Nicanor Cimpoeșu, Radu-Ioachim Comăneci and Leandru-Gheorghe Bujoreanu
Polymers 2024, 16(24), 3598; https://doi.org/10.3390/polym16243598 - 23 Dec 2024
Viewed by 904
Abstract
The paper starts by describing the manufacturing process of cups thermoformed from extruded foils of 80% recycled PET (80r-PET), which comprises heating, hot deep drawing and cooling. The 80r-PET foils were heated up to 120 °C, at heating rates of the order of [...] Read more.
The paper starts by describing the manufacturing process of cups thermoformed from extruded foils of 80% recycled PET (80r-PET), which comprises heating, hot deep drawing and cooling. The 80r-PET foils were heated up to 120 °C, at heating rates of the order of hundreds °C/min, and deep drawn with multiple punchers, having a depth-to-width ratio exceeding 1:1. After puncher-assisted deformation, the cups were air blown away from the punchers, thus being “frozen” in the deformed state. Due to the high cooling rate, most of the polymer’s structure reached a rigid, glassy state, the internal stresses that tended to recover the flat undeformed state were blocked and the polymer remained in a temporary cup form. When heating was applied, glass transition occurred, and the polymer reached a rubbery state and softened. This softening process released the blocked internal stresses and the polymer tended to recover its flat permanent shape. This relative volume contraction quantitatively describes the shape memory effect (SME) which can be obtained either with free recovery (FR-SME) or with work generation (WG-SME) when the cups lifted their bottoms with different loads placed inside them. The paper discusses the results obtained by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), room-temperature tensile failure tests (TENS) and scanning electron microscopy (SEM). The DSC charts emphasized a glass transition, responsible for SME occurrence. The DMA thermograms and the TENS curves revealed that there are slight differences between the storage modulus and the tensile strains of the specimens cut on longitudinal, transversal, or 45° to the film rolling direction. The SEM micrographs enabled to observe structural differences between the specimens cut parallelly and transversally to the film’s rolling direction. The thermoformed cups were heated on a special experimental setup, which enabled the determination of FR-SME and WG-SME after applying different maximum temperatures and loads placed into the cups, respectively. Full article
(This article belongs to the Special Issue Additive Manufacturing of Polymer Based Materials)
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15 pages, 3667 KiB  
Article
Intercalation of Large Flake Graphite with Fuming Nitric Acid
by Vladimir A. Shulyak, Nikolai S. Morozov, Vera S. Makhina, Kristina E. Klyukova, Alexandra V. Gracheva, Sergei N. Chebotarev and Viktor V. Avdeev
C 2024, 10(4), 108; https://doi.org/10.3390/c10040108 - 20 Dec 2024
Cited by 1 | Viewed by 1723
Abstract
In this work, the possibilities of introducing nitric acid molecules with a solution concentration of 75–98% into graphite matrices in the form of synthetic quasi-monocrystal graphite and natural graphite of four different farcical compositions were determined in order to identify factors of the [...] Read more.
In this work, the possibilities of introducing nitric acid molecules with a solution concentration of 75–98% into graphite matrices in the form of synthetic quasi-monocrystal graphite and natural graphite of four different farcical compositions were determined in order to identify factors of the acid concentration and graphite size on the production process and properties of graphite foil. The actual stage of graphite intercalation in the resulting compound was determined by X-ray diffraction analysis (XRD). The differences in the temporal patterns of the intercalation process for different intercalation stages (from 2 to 5) are demonstrated. The obtained acid solutions were used in the manufacturing of flexible graphite foil from natural graphite of four different particle size distributions. The mass characteristics of the intermediate and final products were determined as the graphite was treated with these solutions. The actual difference in the characteristics of the raw materials and intermediate synthetic products was recorded by measuring the electrical conductivity of the final material, graphite foil. Analysis of the results has shown that a decrease in the acid concentration of a solution leads to an increase in the intercalation stage. Weight gains due to the formation of oxygen-containing groups and the introduction of water and acid were reduced by this effect, whereas the yield of the final product (thermally expanded graphite) increased. Foil made of thermally expanded graphite obtained from intercalated compounds of high stages had greater electrical conductivity. An improvement in the conductive properties of the material implies that there should be fewer defects in its structure. Full article
(This article belongs to the Special Issue Carbon Functionalization: From Synthesis to Applications)
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