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Effect of Static Magnetic Field on the Evolution of Residual Stress and Microstructure of Laser Remelted Inconel 718 Superalloy
摘要： As a typical additive manufacturing technique, direct energy deposition is restricted from further application due to the presence of residual stress and the structural deformation. Thus, minimizing the residual stress plays a crucial role in additive manufacturing. In this work, a transverse static magnetic field is introduced in the laser remelting of Inconel 718 superalloy to investigate the effects on residual stress and microstructural change. The x-ray diffraction technique was used to examine the residual stress variation. Optical microscope and scanning electron microscope were applied to observe the microstructure evolution. It was found that the compressive residual stress of the remelted region was notably reduced from 392.50 to 315.45 MPa under the effect of the magnetic field of 0.55 T. Furthermore, it was observed that the average dendrite spacing was reduced by about 32% under the magnetic field. During the laser remelting process, the imposed electromagnetic force minimized the flow field within the molten pool, inhibiting the heat transfer and minimizing the cooling rate. These directly reduced the residual stresses. Based on research findings, the magnetic field can be a potential method to eliminate the residual stress in laser additive manufacturing components.
关键词： laser direct deposition,static magnetic field,Inconel 718 superalloy,laser remelting,residual stress,thermoelectric magnetic force
更新于2025-09-23 15:21:01
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Investigation of photovoltaic thermoelectric air-conditioning system for room application under tropical climate
摘要： Photovoltaic thermoelectric air-conditioning system (PT A/C) system could be a greater option compared to conventional A/C system as it is Freon-free and absence of moving parts. This study investigated the cooling and dehumidification performance of a PT A/C that is solely powered by solar energy under tropical climate conditions. The system is built with 9 pieces of thermoelectric to provide cooling for a test chamber of 3.6 m3 volume. The effect of input current on the system’s cooling and moisture removal rate were investigated and results showed that 5 A is the optimum current level, providing an average of 181 W cooling capacity and 0.14 ltr/hour of moisture removal rate at the given ambient conditions. During the operation, indoor temperature of the test chamber was 4 °C lower than the unconditioned chamber and 7.7 °C compared to the ambient temperature. Whereas the indoor relative humidity varies between 58~83 %. Furthermore, for a 12 hours operation, the system consumes 1.45 kWh of energy, and delivered temperature between 23.8 to 27.8 oC at 5 A.
关键词： Air-conditioning,Cooling,Relative humidity,Thermoelectric
更新于2025-09-23 15:21:01
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[IEEE 2020 IEEE 33rd International Conference on Micro Electro Mechanical Systems (MEMS) - Vancouver, BC, Canada (2020.1.18-2020.1.22)] 2020 IEEE 33rd International Conference on Micro Electro Mechanical Systems (MEMS) - Monolithic Integration of Plasmonic Meta-Material Absorber with CMOS-MEMs Infrared Sensor for Responsivity Enhancement and Human Detection Application
摘要： This study integrates monolithically a metal-insulator-metal-based plasmonic metamaterial absorber (PMA) with a thermoelectric (TE) infrared (IR) sensor using standard TSMC CMOS platform. The proposed design extends the strip-via releasing hole structure in [1] to further integrate MIM absorber with TE IR sensor. Such design exhibits three merits: (1) the line width requirement of MIM absorber is achieved by CMOS process, (2) the absorption peaks of MIM absorbers can be modulated by pattern designs in the epsilon-near-pole region, and (3) the MIM absorbers can be designed to broaden the absorption spectrum of IR sensor. In application, the absorption spectrum of IR sensor is designed within 8-14μm in this study for human detection application. Measurement result demonstrates the integration of MIM absorber and IR sensor can achieve 21% improvement and the measured absorption spectrum matches with simulation.
关键词： CMOS-MEMS,human detection,thermoelectric infrared sensor,responsivity enhancement,plasmonic metamaterial absorber
更新于2025-09-23 15:21:01
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Experimental analysis of a photovoltaic/thermoelectric generator using cobalt oxide nanofluid and phase change material heat sink
摘要： Nowadays, photovoltaic panels have been known as effective devices to harness solar energy. These panels mainly convert the UV and visible areas of the solar spectrum into electricity and the rest of the energy is dissipated. One of the favorable methods to take advantage of such dissipated heat is to combine thermoelectric generators (TEG) utilizing the IR area of the solar radiation with photovoltaic panels. Having the different and opposite impact on the efficiency of thermal photovoltaic cells (PV/T) and thermoelectric generators (TEG), the system operating temperature appears as a critical parameter in the productivity of a PV/T-TEG hybrid unit. In the present study, a novel heat sink for a PV/T-TEG hybrid system is introduced. The effectiveness of simultaneous usage of the Co3O4/water nanofluid and the improved phase change material (paraffin wax/Alumina powder) as a cooling method on the performance of the PV/T-TEG is examined throughout an experimental study. Then, the overall electrical, thermal and exergy efficiency of such a system is compared to the units with divers working fluids including water and 0.25%, 0.5%, and 1% nanofluid and the unit consisting of 1% nanofluid with non-enhanced PCM cooling method. The results reveal that using 1% nanofluid with enhanced PCM, as a cooling method, would improve the overall electrical efficiency by 12.28% compared to water cooling technique. Also, an increase of 11.6% in the exergy efficiency of the PV/T-TEG is observed in comparison with PV/T-TEG with the water cooling method. Hence, it could be concluded that the combination of this unit could contribute to harnessing solar energy more efficiently, compared to solo photovoltaic panels.
关键词： Photovoltaic thermal,Solar energy,Nanofluid,Thermoelectric generator,Phase change material
更新于2025-09-23 15:21:01
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Experimental study for the application of different cooling techniques in photovoltaic (PV) panels
摘要： This article contains the experimental investigations of different cooling methods used for photovoltaic (PV) panels. Phase change material (PCM), thermoelectric (TE) and aluminum fins were chosen as the cooling methods. The CaCl2·6H2O is chosen as one of the PCM which is widely used in the cooling of PVs and the other is the PCM with melting temperature above the surface temperature of the PV panel. By using TE material in different numbers (6, 8 and 12) and aluminum fins in different layouts, surface temperatures and output powers of PV panels were compared. It is observed that the PCM which is not chosen appropriately has insulation feature in the PV panel and enhances the temperature of the panel and decreases the output power. When the most successful cooling methods were tested under the same environmental conditions, PV with fin system produced the highest power generation of 47.88 W while PV with PCM and TEM produced the lowest power generation of 44.26 W.
关键词： Thermoelectric module,Photovoltaic,Fin,Cooling,Phase change material
更新于2025-09-23 15:21:01
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Photo-Thermoelectric Conversion of Plasmonic Nanohole Array
摘要： Plasmonic photo-thermoelectric conversion offers an alternative photodetection mechanism that is not restricted by semiconductor bandgaps. Here, we report a plasmonic photodetector consisting of an ultra-thin silver film with nanohole array, whose photodetection mechanism is based on thermoelectric conversion triggered by plasmonic local heating. The detector exhibits a maximum photocurrent at the wavelength of the surface plasmon polaritons, determined by the periodicity of the nanoholes. Hence, the response wavelength of the detector can be controlled via the morphological parameters of the nanohole pattern. The contribution of plasmonic local heating to thermoelectric conversion is verified experimentally and numerically, enabling discussion on the mechanisms governing light detection. These results provide a starting point for the development of other nanoscale photodetectors.
关键词： plasmon,photodetector,silver film,plasmonic local heat,thermoelectric conversion,nanohole
更新于2025-09-23 15:21:01
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-type PbTe from first principles
摘要： We present an ab initio study that identifies the main electron-phonon scattering channels in n-type PbTe. We develop an electronic transport model based on the Boltzmann transport equation within the transport relaxation time approximation, fully parametrized from first-principles calculations that accurately describe the dispersion of the electronic bands near the band gap. Our computed electronic mobility as a function of temperature and carrier concentration is in good agreement with experiments. We show that longitudinal optical phonon scattering dominates electronic transport in n-type PbTe, while acoustic phonon scattering is relatively weak. We find that scattering due to soft transverse optical phonons is by far the weakest scattering mechanism, due to the symmetry-forbidden scattering between the conduction band minima and the zone center soft modes. Soft phonons thus play the key role in the high thermoelectric figure of merit of n-type PbTe: they do not degrade its electronic transport properties although they strongly suppress the lattice thermal conductivity. Our results suggest that materials like PbTe with soft modes that are weakly coupled with the electronic states relevant for transport may be promising candidates for efficient thermoelectric materials.
关键词： electron-phonon scattering,transport relaxation time approximation,thermoelectric materials,Boltzmann transport equation,n-type PbTe
更新于2025-09-23 15:21:01
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Thermal stability study of transition metal perovskite sulfides
摘要： Transition metal perovskite chalcogenides, a class of materials with rich tunability in functionalities, are gaining increased attention as candidate materials for renewable energy applications. Perovskite oxides are considered excellent n-type thermoelectric materials. Compared to oxide counterparts, we expect the chalcogenides to possess more favorable thermoelectric properties such as lower lattice thermal conductivity and smaller band gap, making them promising material candidates for high temperature thermoelectrics. Thus, it is necessary to study the thermal properties of these materials in detail, especially thermal stability, to evaluate their potential. In this work, we report the synthesis and thermal stability study of five compounds, a-SrZrS3, b-SrZrS3, BaZrS3, Ba2ZrS4, and Ba3Zr2S7. These materials cover several structural types including distorted perovskite, needle-like, and Ruddlesden–Popper phases. Differential scanning calorimeter and thermogravimetric analysis measurements were performed up to 1200 °C in air. Structural and chemical characterizations such as X-ray diffraction, Raman spectroscopy, and energy dispersive analytical X-ray spectroscopy were performed on all the samples before and after the heat treatment to understand the oxidation process. Our studies show that perovskite chalcogenides possess excellent thermal stability in air at least up to 550 °C.
关键词： differential scanning calorimeter,thermoelectric materials,Transition metal perovskite chalcogenides,thermal stability,thermogravimetric analysis,Raman spectroscopy,Ruddlesden–Popper phases,X-ray diffraction,energy dispersive analytical X-ray spectroscopy
更新于2025-09-23 15:21:01
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Three-Layer Detection Pixel of Single-Photon Thermoelectric Detector Based on Rare-Earth Hexaborides
摘要： The results of computer simulation of heat propagation processes in the three-layer detection pixel of single-photon thermoelectric detector after the absorption of single photons with the energies 0.5–4.13 eV are presented. The various geometries of the detection pixel consisting of rare-earth hexaborides are considered. The lanthanum hexaboride (LaB6) is chosen as the absorber material, and for the materials of thermoelectric sensor the cerium (CeB6) and lanthanum–cerium (La0.99Ce0.01) B6 hexaborides are chosen. The problem is solved to achieve the high system efficiency of thermoelectric detector for the detection of photons in the wavelength range from the UV to the near IR. The computer modeling was carried out based on the equation of heat propagation from the limited volume with the use of three-dimensional matrix method for differential equations. It is shown that a single-photon thermoelectric detector with a three-layer detection pixel made only of hexaborides will have the gigahertz count rate, high-energy resolution, and detection efficiency exceeding 90%. Taking into account the advantages of the three-layer detection pixel compared to the single-layer it can be argued that the three-layer detection pixel of the thermoelectric detector has the great prospects to solve a number of single-photon detection tasks.
关键词： rare-earth hexaborides,thermoelectric detector,photon
更新于2025-09-23 15:21:01
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Probing of Thermal Transport in 50-nm Thick PbTe Nanocrystal Film by Time-Domain Thermoreflectance
摘要： Bottom-up fabrication of thermoelectric (TE) materials from colloidal nanocrystal (NC) building blocks can substantially increase their TE efficiency, e.g., by reducing lattice thermal conductivity. In this work, 10-nm spherical phase-pure oleate-capped PbTe NCs with narrow size distribution were synthesized and employed to fabricate 50-nm thick films on insulating SiO2/Si substrates. The spin-coating, with subsequent ligand exchange procedure, was applied to enhance coupling interactions between the NCs. Using dark conductivity measurements, we confirmed the semiconducting behavior and the Schottky-type electrical field-dependent conductivity mechanism in the resultant thin films. The thermal transport in the thin-film was probed by means of a time-domain thermoreflectance (TDTR) method. For this purpose, we used a customized state-of-the-art system based on a picosecond thermoreflectance instrument, which enables area-selective analysis with spatial resolution down to 5 μm. The results show that as-fabricated PbTe NC films exhibit ultralow thermal conductivity of 0.9 W m–1 K–1 at 300 K. The transport property findings suggest potential in the proposed quick and cost-effective spin-coating strategy for bottom-up fabrication of nanostructured TE films from high-quality colloidal NC building blocks.
关键词： colloidal nanocrystals,spin-coating,thermoelectric materials,thermal conductivity,time-domain thermoreflectance,PbTe
更新于2025-09-23 15:21:01