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Online Monitoring of Aluminum Electrolytic Capacitors in Photovoltaic Systems by Magnetoresistive Sensors
摘要： Due to the environmental concerns and new energy policies, worldwide expectations for energy production utilizing photovoltaic (PV) systems are increasing significantly. The aluminum electrolytic capacitor (AEC) is extensively used in filtering application for power electronic converters in PV systems since they can achieve the highest energy density with the lowest cost. However, the lifetime of an AEC is limited due to the electrolyte vaporization. The degradation of AECs challenges the efficiency and reliability of a PV system. Therefore, the health-monitoring of AECs is indispensable for the PV systems to operate reliably. In this paper, an online AEC-monitoring scheme based on magnetic-field sensing is proposed for PV systems under various working conditions. The AEC-monitoring technique using the equivalent series resistance (ESR) and capacitance (C) as the health indicators were developed for the power electronic converters in PV systems. The proposed methodology considering the voltage drops on C can improve the accuracy in ESR-estimation and achieve the estimation of C. The simulation results with Simulink verified that the proposed method was capable of estimating the health indicators accurately over various levels of solar irradiance and ambient temperature. The tunneling magnetoresistive (TMR) sensors were pre-calibrated from -25 to 100 oC for implementation in PV systems. The experimental results proved that TMR sensors could measure the current of AECs effectively to achieve the precise estimations of the health indicators using the proposed technique. This technique is non-invasive, compact, and cost-effective since it can be realized with the TMR sensors or other MR sensors.
关键词： Aluminum electrolytic capacitor,tunneling magnetoresistive sensor,PV system,condition monitoring
更新于2025-09-12 10:27:22
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Grain refining in weld metal using short-pulsed laser ablation during CW laser welding of 2024-T3 aluminum alloy
摘要： The 2024 aluminum alloy is used extensively in the aircraft and aerospace industries because of its excellent mechanical properties. However, the weldability of 2024 aluminum alloy is generally low because it contains a high number of solutes, such as copper (Cu), magnesium (Mg), and manganese (Mn), causing solidification cracking. If high speed welding of 2024 aluminum alloy without the use of filler is achieved, the applicability of 2024 aluminum alloys will expand. Grain refining is one of the methods used to prevent solidification cracking in weld metal, although it has never been achieved for high-speed laser welding of 2024 aluminum alloy without filler. Here, we propose a short-pulsed, laser-induced, grain-refining method during continuous wave laser welding without filler. Bead-on-plate welding was performed on a 2024-T3 aluminum alloy at a welding speed of 1 m min?1 with a single mode fiber laser at a wavelength of 1070 nm and power of 1 kW. Areas in and around the molten pool were irradiated with nanosecond laser pulses at a wavelength of 1064 nm, pulse width of 10 ns, and pulse energy of 430 mJ. The grain-refinement effect was confirmed when laser pulses were irradiated on the molten pool. The grain-refinement region was formed in a semicircular shape along the solid–liquid interface. Results of the vertical section indicate that the grain-refinement region reached a depth of 1 mm along the solid–liquid interface. The Vickers hardness test results demonstrated that the hardness increased as a result of grain refinement and that the progress of solidification cracking was suppressed in the grain refinement region.
关键词： grain refinement,short pulsed laser,laser welding,laser ablation,2024 aluminum alloy,hot cracking,dendrite fragmentation
更新于2025-09-12 10:27:22
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Lossy Mode Resonance Generation on Sputtered Aluminum-Doped Zinc Oxide Thin Films Deposited on Multimode Optical Fiber Structures for Sensing Applications in the 1.55 μm Wavelength Range
摘要： In this work, we demonstrated lossy mode resonance (LMR) generation in optical fiber structures based on multimode fibers coated with aluminum-doped zinc oxide (AZO) films. AZO thin films were deposited by using radio frequency magnetron sputtering. In order to exhibit the usefulness of the LMR effect for sensing applications in optical fiber based systems, the deposition conditions of the AZO film coatings were set to obtain the second LMR order within the 1.55 μm wavelength range. An optical transmission configuration setup was used to investigate the LMR effect on fiber structures based on the use of no-core and cladding-removed multimode fibers coated with AZO films synthesized from metallic sputtering targets with different proportions of Zn:Al, 92:8% and 98:2%, at atomic concentrations. The optical and electrical/chemical features of the AZO films were characterized with UV–vis and XPS spectroscopy, respectively. The optical response of the proposed sensing configuration to refractive index (RI) variations was experimentally demonstrated. For the best approach, the sensitivity of wavelength displacement to RI variations on the liquid surrounding media was found to be 1214.7 nm/RIU.
关键词： multimode fiber,lossy mode resonance,optical fiber sensors,reactive RF magnetron sputtering,aluminum-doped zinc oxide
更新于2025-09-12 10:27:22
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Comparative Study on Welding Characteristics of Laser-CMT and Plasma-CMT Hybrid Welded AA6082-T6 Aluminum Alloy Butt Joints
摘要： Laser-CMT (Cold Metal Transfer) and plasma-CMT hybrid welding are two promising alternative joining technologies for traditional Metal-Inert-Gas (MIG) welding of the aluminum alloy joints in the high speed trains manufacturing industry. In this work, a comparative study on the weld formation, microstructure, micro-hardness, and mechanical properties of the butt joints in the two welding methods was conducted. The results indicate that the overall quality of the laser-CMT and plasma-CMT welds were good, especially of the laser-CMT hybrid weld, and the laser-CMT hybrid welding process needed a lower heat input. The width of the partially melted zone of the laser-CMT hybrid weld was narrower than that in the plasma-CMT hybrid weld. Micro-hardness test results show that two distinct softening regions were identi?ed in the heat a?ected zone, and the micro-hardness values of each zone in the laser-CMT hybrid weld were lower than that in the plasma-CMT hybrid weld. The tensile strength of the laser-CMT hybrid welded joints was higher than that of the plasma-CMT hybrid welded joints, which could reach up to 79.4% and 73.7% of the base materials, respectively. All the fractures occurred in the softening region and exhibited a ductile shear fracture with a shear angle of approximately 45. The fractographs manifested that the laser-CMT and plasma-CMT hybrid welded joints presented ductile fracture and ductile-brittle fracture features, respectively.
关键词： laser-CMT hybrid welding,mechanical property,aluminum alloy,microstructure,plasma-CMT hybrid welding
更新于2025-09-11 14:15:04
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Interface Microstructure and Nanoindentation Characterization of Laser Offset Welded 5052 Aluminum to Press-Hardened Steel Using a Brass Interlayer
摘要： Laser o?set welding of 5052 aluminum to press-hardened steel using a brass interlayer was carried out. The cross-sectioned macrostructure and tensile strength were governed by varying the thickness of the brass interlayer. The maximum tensile strength reached 56.4 MPa when the thickness of brass interlayer was 0.05 mm. Subsequently, the interface microstructure, the nanoindentation characterization, and the fracture behavior were evaluated experimentally by means of scanning electron microscopy (SEM), energy-dispersive X-ray spectrometer (EDS), and micro-X-ray di?raction (micro-XRD), respectively. It was found that the intermetallic compound (IMC) layer at the interface consisted of an Fe2Al5 layer and an FeAl layer, and the estimated nanohardness of Fe2Al5, FeAl, and Fe3Al were 16.11 GPa, 9.48 GPa, and 4.13 GPa, respectively. The fracture of the joint with the 0.05 mm brass interlayer was a mixture of cleavage fracture and intergranular fracture, while that of the joint with the 0.1 mm brass interlayer exhibited the characterization of a major dendrite arm, leaving a metallurgical connected zone consisting of the Al2Cu and the α-Al phase.
关键词： laser o?set welding,aluminum,press-hardened steel,brass interlayer,nanoindentation,interface microstructure
更新于2025-09-11 14:15:04
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Effect of Hot Isostatic Pressing on Al-10%Si-0.4%Mg Alloy Fabricated by Selective Laser Melting; レーザ積層造形により作製したAl-10%Si-0.4%Mg合金における熱間等方加圧処理の影響;
摘要： In this study, we investigated the effects of hot isostatic pressing (HIP) on the mechanical properties of an Al-10%Si-0.4%Mg alloy fabricated by selective laser melting (SLM). In addition, the effect of internal porosity on the mechanical properties of the alloy was also investigated. After the HIP, the internal porosity of the alloy decreased, while its elongation to failure (EL) improved significantly. However, the 0.2% proof stress (PS) and the tensile strength (TS) of the HIPed alloy were significantly lower than those of the as-built state. This can be attributed to the microstructural changes that occurred at elevated temperatures during the HIP. In addition, the PS and TS of the as-built alloy decreased with an increase in the internal porosity. On the other hand, in the case of the HIPed alloy, the PS and TS were not affected by the internal porosity. However, EL was sensitive to the internal porosity. The EL of the HIPed alloy decreased with an increase in its initial internal porosity. This is because the diffusion bonding during the HIP was imperfect owing to the presence of oxidized scales. Hence, it is imperative to optimize the laser irradiation conditions for the fabrication of aluminum alloy by SLM.
关键词： aluminum alloy,selective laser melting (SLM),hot isostatic pressing (HIP),additive manufacturing (AM),internal porosity
更新于2025-09-11 14:15:04
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Aluminum with dispersed nanoparticles by laser additive manufacturing
摘要： While laser-printed metals do not tend to match the mechanical properties and thermal stability of conventionally-processed metals, incorporating and dispersing nanoparticles in them should enhance their performance. However, this remains difficult to do during laser additive manufacturing. Here, we show that aluminum reinforced by nanoparticles can be deposited layer-by-layer via laser melting of nanocomposite powders, which enhance the laser absorption by almost one order of magnitude compared to pure aluminum powders. The laser printed nanocomposite delivers a yield strength of up to 1000 MPa, plasticity over 10%, and Young’s modulus of approximately 200 GPa, offering one of the highest specific Young’s modulus and specific yield strengths among structural metals, as well as an improved specific strength and thermal stability up to 400 °C compared to other aluminum-based materials. The improved performance is attributed to a high density of well-dispersed nanoparticles, strong interfacial bonding between nanoparticles and Al matrix, and ultrafine grain sizes.
关键词： mechanical properties,aluminum,laser additive manufacturing,thermal stability,nanoparticles
更新于2025-09-11 14:15:04
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Infrared-laser based characterization of the pyroelectricity in AlScN thin-films
摘要： A measurement system for characterization of the pyroelectricity in thin- and thick-films is introduced. The system is based on a quantum-cascade infrared laser that stimulates the temperature within the sample film with variable modulation frequencies up to 120 kHz. As model material system we choose Scandium-doped Aluminum Nitride (AlScN) due to its promising piezo- and dielectric behavior as well as CMOS compatibility. We measured the pyro-electric response and its temperature characteristics. The transverse effective piezoelectric coefficient e31 is derived from the measurement of the longitudinal effective piezoelectric modulus d33 and we discuss the contribution of piezoelectric clamping to the measured pyroelectric response. Our findings are important for integration of AlScN films on exposed membranes for dense and sensitive infrared detectors.
关键词： Pyroelectric,AlScN,Piezoelectric,Aluminum-scandium-nitride
更新于2025-09-11 14:15:04
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Effect of post heat treatment on the phase composition and strength of laser welded joints of an Al–Mg–Li alloy
摘要： In the present work, the effects of laser beam welding and post-weld heat treatment on the phase composition and mechanical properties of the 1424 alloy (Al–Mg–Li) joints were investigated. Holding the joints at a certain temperature was followed by quenching and artificial aging. The structural studies were carried out using electron microscopy, conventional X-ray diffractometry, and synchrotron radiation diffractometry. The heat treatment conditions were optimized to favor the formation of strengthening phases in the welds, the presence of which imparted mechanical strength to the joints. For the first time, 1424 Al alloy joints with a weld strength of σuts = 500 MPa have been obtained; this value of strength was achieved by applying post-weld annealing followed by quenching and artificial aging.
关键词： X-ray diffraction,Aluminum-lithium alloy,Laser welding,Electron microscopy,Synchrotron radiation,Mechanical properties
更新于2025-09-11 14:15:04
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Dye-Sensitized Solar Cells Using Aluminum-Doped Zinc Oxide/Titanium Dioxide Photoanodes in Parallel
摘要： In this study, both zinc oxide (ZnO) nanorods and aluminum-doped zinc oxide (AZO) nanosheets were deposited by hydrothermal growth on ?uorine-doped tin oxide (FTO) glass. After a photoanode was added to ZnO nanorods or AZO nanosheets, the photovoltaic conversion e?ciency (PCE) increased due to improved electron transport and enhanced dye absorption. The improvement in electron transport was veri?ed by electrochemical impedance spectroscopy (EIS), and the increase in dye absorption was veri?ed by ultraviolet-visible spectroscopy. Both of these factors facilitated an increase in PCE. Parameters for dye-sensitized solar cells (DSSCs) using ZnO nanorods/TiO2 and AZO nanosheets/TiO2 photoanodes were tested and the results were recorded using EIS. The results indicated that the addition of the ZnO nanorods increased the short-circuit current density (Jsc) from 9.07 mA/cm2 to 10.91 mA/cm2, the open circuit voltage (Voc) from 0.68 V to 0.70 V, and the PCE from 3.70% to 4.73%, respectively. When the DSSCs were produced in a parallel silver-grid device, the results showed that PCE could be increased from 3.67% to 4.04% due to the reduction in connection resistance.
关键词： titanium dioxide (TiO2),dye-sensitized solar cells (DSSCs),parallel connection,aluminum-doped zinc oxide (AZO)
更新于2025-09-11 14:15:04