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High-Temperature Analysis of GaN-based MQW Photodetector for Optical Galvanic Isolations in High-Density Integrated Power Modules
摘要： The InGaN/GaN MQW structure is demonstrated as a possible solution for high-temperature photodiode applications. High temperature spectral and noise analysis of InGaN/GaN MQW structure are performed for the potential integration as a detector in future power electronics applications. The spectral response was measured under photovoltaic and bias modes for the temperature range of 77 - 800 K. A peak spectral responsivity of 27.0 mA/W at 440 nm at 500 K is recorded. The peak external quantum efficiency of the device was calculated to be in the range of 5 - 8 % in the temperature range 77 - 800 K. The photodetector sensitivity of the structure is quantified using the material figure of merit parameter, D* for different temperature and biased voltages. A peak detectivity of 4 x 108 cmHz1/2W-1 is observed at 800 K with zero bias at 440 nm.
关键词： quantum well devices,power electronics,High-temperature,photodiode,optocouplers
更新于2025-09-16 10:30:52
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Investigation of hydrogen production potential of the LASER inertial confinement fusion fission energy (LIFE) engine
摘要： The main purpose of this paper is to research of the time-dependent hydrogen production possibility of the Laser Inertial Con?nement Fusion Fission Energy (LIFE) engine using steam methane reforming (SMR), sulfureiodine (SeI) thermochemical water splitting and high temperature electrolysis (HTE) cycles. The fuel zone of the LIFE engine contains 90 vol % Flibe coolant and 10 vol% TRISO coated minor actinides. Firstly, to examine the time-dependent hydrogen generation potential of this reactor, the time-dependent neutronic performance of the reactor has been performed with using the MCNP neutron transport code. As a result of neutronic calculations, tritium production (TBR), energy multiplication factor (M) and fuel burnup (BU) values have been computed. Secondly, the total power required for SMR, SeI and HTE cycle process have been calculated by using the time dependent energy multiplication factor obtained from the neutronic results. Depending on this total power, the change of hydrogen production with operation time in the LIFE engine has been investigated. As a result of the calculations, it has been found that the LIFE engine has a good both neutronic performance and hydrogen production by SMR, SeI and HTE cycle process.
关键词： Minor actinides,SeI cycle,LIFE engine,Steam methane reforming,Hydrogen,High temperature electrolysis
更新于2025-09-16 10:30:52
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Large-scale synthesis of crystalline g-C <sub/>3</sub> N <sub/>4</sub> nanosheets and high-temperature H <sub/>2</sub> sieving from assembled films
摘要： Poly(triazine imide) (PTI), a crystalline g-C3N4, hosting two-dimensional nanoporous structure with an electron density gap of 0.34 nm, is highly promising for high-temperature hydrogen sieving because of its high chemical and thermal robustness. Currently, layered PTI is synthesized in potentially unsafe vacuum ampules in milligram quantities. Here, we demonstrate a scalable and safe ambient pressure synthesis route leading to several grams of layered PTI platelets in a single batch with 70% yield with respect to the precursor. Solvent exfoliation under anhydrous conditions led to single-layer PTI nanosheets evidenced by the observation of triangular g-C3N4 nanopores. Gas permeation studies confirm that PTI nanopores can sieve He and H2 from larger molecules. Last, high-temperature H2 sieving from PTI nanosheet–based membranes, prepared by the scalable filter coating technique, is demonstrated with H2 permeance reaching 1500 gas permeation units, with H2/CO2, H2/N2, and H2/CH4 selectivities reaching 10, 50, and 60, respectively, at 250°C.
关键词： PTI,high-temperature,nanosheets,crystalline g-C3N4,hydrogen sieving
更新于2025-09-16 10:30:52
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EXPRESS: Two-Dimensional Temperature Measurement in a High Temperature and Pressure Combustor Using Computed Tomography Tunable Diode Laser Absorption Spectroscopy (CT-TDLAS) with a Wide-Scanning Laser at 1335–1375 nm
摘要： Tunable diode laser absorption spectroscopy (TDLAS) technology is a developing method for temperature and species concentration measurements with the features of non-contact, high precision, high sensitivity, etc. The difficulty of two-dimensional (2D) temperature measurement in actual combustors has not yet been solved because of pressure broadening of absorption spectra, optical accessibility, etc. In this study, the combination of computed tomography (CT) and TDLAS with a wide scanning laser at 1335–1375 nm has been applied to a combustor for 2D temperature measurement in high temperature of 300–2000 K and high pressure of 0.1–2.5 MPa condition. An external cavity type laser diode with wide wavelength range scanning at 1335–1375 nm was used to evaluate the broadened H2O absorption spectra due to the high temperature and high pressure effect. The spectroscopic database in high temperature of 300–2000 K and high pressure of 0.1–5.0 MPa condition has been revised to improve the accuracy for temperature quantitative analysis. CT reconstruction accuracy was also evaluated in different cases, which presented the consistent temperature distribution between CT reconstruction and assumed distributions. The spatial and temporal distributions of temperature in the high temperature and high pressure combustor were measured successfully by CT-TDLAS using the revised spectroscopic database.
关键词： high temperature and high pressure field,TDLAS,computed tomography,2D,Two-dimensional temperature measurement,combustion,CT,tunable diode laser absorption spectroscopy
更新于2025-09-12 10:27:22
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High-Temperature Analysis of GaN-based Blue LEDs for Future Power Electronic Applications
摘要： Commercial gallium-nitride-based blue light-emitting diodes (LEDs), primarily fabricated for lighting applications, are evaluated at high temperatures (up to 700 K) for possible integration as an optocoupler emitter in high-density power electronic modules. The temperature- and injection-current-dependent internal quantum efficiency and current-voltage characteristics of the blue LEDs are studied. The internal quantum efficiency (IQE) is extracted integrated electroluminescence (EL) intensity at different temperatures using the ABC model. The presented method helps evaluate the optimized injection current density to achieve minimum deviation in LED IQE at a broader range of operating temperatures. As per the ABC model, the LED can operate at 700 K with an IQE of 58.50% when it operates at a current density of 2A/cm2. The results show that for a temperature range of 77 – 700 K, the minimum deviation of IQE occurs when the injected current density is between 1 to 10 A/cm2. Normalized external quantum efficiency (EQE) of the device at different temperatures were also extracted using the ABC model.
关键词： quantum efficiency,high-density power module,electroluminescence,optocoupler,high-temperature optoelectronics,galvanic isolation
更新于2025-09-12 10:27:22
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High‐Temperature Optical Characterization of GaN‐Based LEDs for Future Power Electronic Modules
摘要： High-temperature optical analysis of three different InGaN/GaN MQW LED structures (peak wavelength λp = 448nm, 467 nm & 515nm) is conducted for possible integration as an optocoupler emitter in high-density power electronic modules. The commercially available LEDs, primarily used in the display (λp = 467 nm & 515nm) and lighting (λp = 448nm) applications, are studied and compared to evaluate if they can satisfy the light output requirements in the optocouplers at high temperatures. The temperature- and intensity-dependent electroluminescence (T-IDEL) measurement technique is used to study the internal quantum efficiency (IQE) of the LEDs. All three LEDs exhibits above 70 % IQE at 500 K, and stable operation at 800 K without flickering or failure. At 800K, a promising IQE of above 40 % is observed for blue for display (λp = 467 nm) and green for display (λp = 515nm) samples. Blue for light (λp = 448nm) sample shows 24 % IQE at 800 K.
关键词： high-temperature optoelectronics,high-density power modules,optocouplers,quantum efficiency
更新于2025-09-12 10:27:22
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Laser modification of high-pressure high-temperature nanodiamonds
摘要： Micro-thin semitransparent films of purified high pressure high temperature nanodiamonds were produced on a glass substrate. A focused 632.8 nm He-Ne laser irradiation is shown to cause an emission of light in the green region of the optical spectrum accompanied with laser-induced blackening of the obtained films. Possible mechanisms of the observed phenomenon are discussed.
关键词： optical spectrum,laser modification,nanodiamonds,sp2-carbon,sp3-carbon,high-pressure high-temperature
更新于2025-09-12 10:27:22
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A Study of Laser Beam Welding, Gas Tungsten Arc Welding and High Temperature Brazing Processes on Micro hardness and Tensile Strength of AISI Type 316 Stainless Steel
摘要： Thin wall joints for elevated temperature (~550 °C) applications can be prepared by Laser Beam Welding (LBW), Gas Tungsten Arc Welding (GTAW) and High Temperature Brazing (HTB) methods. The joints have been made and tests such as helium leak test (HLT), micro hardness test and tensile test were carried out. A study has been performed on these joining techniques to recognize the suitable method for high temperature applications. No observable leak was identified during HLT. Microstructures shows dissimilarity in solidification morphology due to disparity in heat sources. It has been identified that the joint made by brazing process having higher micro hardness value. Further, it has been observed that LBW joints have better mechanical properties than GTAW joints and HTB joints.
关键词： GTAW,Micro hardness,AISI 316 stainless steels,Tensile properties,High temperature brazing,Microstructures,Nd:YAG Laser
更新于2025-09-12 10:27:22
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Anomalous doping evolution of nodal dispersion revealed by <i>in situ</i> ARPES on continuously doped cuprates
摘要： We study the systematic doping evolution of nodal dispersions by in situ angle-resolved photoemission spectroscopy on the continuously doped surface of a high-temperature superconductor Bi2Sr2CaCu2O8+x and reveal that the nodal dispersion has three fundamentally different segments separated by two kinks, located at ～10 meV and roughly 70 meV, respectively. These three segments have different band velocities and different doping dependence. In particular, in the underdoped region the velocity of the high-energy segment increases monotonically as the doping level decreases and can even surpass the bare band velocity. We propose that electron fractionalization is a possible cause for this anomalous nodal dispersion and may even play a key role in the understanding of exotic properties of cuprates.
关键词： electron fractionalization,high-temperature superconductors,nodal dispersion,ARPES,cuprates
更新于2025-09-12 10:27:22
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[IEEE 2018 48th European Microwave Conference (EuMC) - Madrid (2018.9.23-2018.9.27)] 2018 48th European Microwave Conference (EuMC) - Dispersion of THz Modes Localized on Layered Superconductor Controlled by DC Magnetic Field
摘要： Being materials that support terahertz waves propagation, layered superconductors attract great attention of many researchers. The Josephson plasma modes localized on a slab of layered superconductor can possess an anomalous dispersion. The possibility of anomalous dispersion manipulation opens wide perspectives for applications. One of the tools that can flexibly change the electromagnetic properties of layered superconductors is the external DC magnetic field. The effect of the DC magnetic field on the spectrum of the localized modes is a subject of the present paper. We present the derivation and analysis of the dispersion relations and discuss some interesting corollaries such as resonant amplification of wave transmission induced by the internal excitation of the localized modes and the possibility of the internal reflection of the localized modes controlled by the external DC magnetic field.
关键词： high-temperature superconductors,electromagnetic fields,Terahertz metamaterials,Josephson junctions
更新于2025-09-12 10:27:22