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Effect of Oxygen Partial Pressure on the Phase Stability of Copper–Iron Delafossites at Elevated Temperatures
摘要： Oxide-based materials are promising candidates for use in high temperature thermoelectric generators. While their thermoelectric performance is inferior to commonly used thermoelectrics, oxides are environmentally friendly and cost-effective. In this study, Cu-based delafossites (CuFeO2), a material class with promising thermoelectric properties at high temperatures, were investigated. This work focuses on the phase stability of CuFeO2 with respect to the temperature and the oxygen partial pressure. For this reason, classical material characterization methods, such as scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction, were combined in order to elucidate the phase composition of delafossites at 900 ?C at various oxygen partial pressures. The experimentally obtained results are supported by the theoretical calculation of the Ellingham diagram of the copper–oxygen system. In addition, hot-stage X-ray diffraction and long-term annealing tests of CuFeO2 were performed in order to obtain a holistic review of the phase stability of delafossites at high temperatures and varying oxygen partial pressure. The results support the thermoelectric measurements in previous publications and provide a process window for the use of CuFeO2 in thermoelectric generators.
关键词： high temperature thermoelectric materials,delafossite,thermoelectric generator (TEG),phase stability,Ellingham diagram
更新于2025-09-19 17:15:36
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Superconducting Filter Based on Split Ring Resonator Structures
摘要： A design of high-temperature superconducting (HTS) bandpass filter (BPF) based on split ring resonator (SRR) structures is presented in this paper. The SRR has been considered as a classical element for metamaterials and exhibits characteristics of subwavelength resonator, hence can aid in the compact design of filters. Filter has been simulated and optimized using Sonnet software. The measured results of the filter have good consistency with the simulated results and show good band pass characteristics. The center frequency of the filter measured at 70K was 2.515GHz, the rectangle coefficient was 1.22, and the insertion loss was 0.1dB at the center frequency.
关键词： high-temperature superconducting,bandpass filter,split ring resonator,metamaterial
更新于2025-09-19 17:15:36
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Prognostic phenotypic and genotypic factors associated with photodynamic therapy response in patients with age-related macular degeneration
摘要： Background: This study aimed to demonstrate the phenotypic and genotypic factors associated with photodynamic therapy (PDT) for age-related macular degeneration (AMD). Methods: The study included 149 patients with exudative AMD treated by PDT. Eight phenotypic factors and ten genotypic factors for three single nucleotide polymorphisms (SNPs; rs800292, rs1061170, rs1410996) in the complement factor H (CFH) gene, rs 11200638-SNP in the high temperature requirement A-1 (HTRA1) gene, two SNPs (rs699947, rs2010963) in the vascular endothelial growth factor (VEGF) gene, and four SNPs (rs12948385, rs12150053, rs9913583, rs1136287) in the pigment epithelium-derived factor (PEDF) gene were evaluated. Results: A significant association with best-corrected visual acuity change was demonstrated in the greatest linear dimension, presence or absence of pigment epithelial detachment, and HTRA1-rs11200638 genotype statistically (P=3.67×10-4, 1.95×10-2, 1.24×10-3, respectively). Best-corrected visual acuity in patients with AA genotype of HTRA1-rs11200638 significantly decreased compared with that in patients with GG genotype (P=1.33×10-3). Logistic regression analyses demonstrated HTRA1-rs11200638 genotype was most strongly associated with best-corrected visual acuity outcome from baseline at 12 months after photodynamic therapy (P=4.60×10-3; odds ratio 2.363; 95% confidence interval 1.303–4.285). Conclusion: The HTRA1-rs11200638 variant showed the most significant association. Therefore, this variant may be used as a prognostic factor to estimate the PDT response with significant predictive power.
关键词： pigment epithelial detachment,photodynamic therapy,phenotypic and genotypic factors,greatest linear dimension,high temperature requirement A-1,age-related macular degeneration
更新于2025-09-19 17:15:36
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Effect of oxygen on degradation of defects on ta-C coatings deposited by filtered arc deposition
摘要： Among diamond-like carbon (DLC) coatings, tetrahedral amorphous carbon (ta-C) coatings show particularly high thermal stability and oxidation resistance due to their high sp3 content and hydrogen-free structure. On the other hand, it is well known that high-temperature annealing leads to degradation of the ta-C structure, resulting in a release of stress, decrease of hardness, increase in surface roughness, and transformation of the coating nature. Although optical observation is a powerful candidate for imaging the surface conditions of ta-C coatings, strong light emission due to high temperature prevents the acquisition of clear images. In this paper, we establish a novel in situ observation method using environment scanning electron microscopy (ESEM), which allows us to view ta-C surface defects and droplets at 650°C. A heater embedded in the ESEM increased the temperature on ta-C coatings to 650°C at gas pressure of 120 Pa. Using a variety of gas conditions including ambient air, dry nitrogen, or dry oxygen, we clarified the effect of the gases on the degradation of the defects. In a dry oxygen atmosphere, defects grew dramatically with annealing time, whereas nitrogen caused no significant transformation to ta-C surfaces. Raman spectroscopy analysis revealed significant structural change in one type of defect, while no noticeable Raman shift was detected in the other type. A focused ion beam created a cross-section of an annealed defect on the ta-C coating. Subsequently, energy dispersive X-ray spectroscopy (EDS) revealed the characteristics of defect growth; one type of defect was associated with a droplet on the interlayer, and the other with graphitization due to oxidization of ta-C on the droplets.
关键词： oxidation mechanism,droplet,ta-C coating,surface defect,high temperature
更新于2025-09-19 17:15:36
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Computed tomography dataset analysis for stereotaxic neurosurgery navigation
摘要： First-ever 28 nm embedded split-gate MONOS (SG-MONOS) ?ash macros have been developed to increase memory capacity embedded in micro controller units and to improve performance over wide junction temperature range from C to 170 C as demanded strongly in automotive uses. Much attention has been paid to the degradation of the reliability characteristics along with the process shrinkage. Temperature-adjusted word-line overdrive scheme improves random read access frequency by 15% and realizes both of 6.4 GB/s read throughput by 200 MHz no-wait random access of code ?ash macros and more than ten times longer TDDB lifetime of WL drivers. Temperature-adaptive step pulse erase control (TASPEC) improves the TDDB lifetime of dielectric ?lms between metal interconnect layers by three times. TASPEC is particularly useful for a data ?ash macro with one million rewrite cycles. Source-side injection (SSI) program with negative back-bias voltage achieves 63% reduction of program pulse time and, consequently, realizes 2.0 MB/s write throughput of code ?ash macros. A spread spectrum clock generation and a clock phase shift technique are introduced for charge pump clock generation in order to suppress EMI noise due to high write throughput of code ?ash macros, and peak power of EMI noise is reduced by 19 dB.
关键词： high-temperature operation,time dependent dielectric breakdown,Automotive application,high reliability,spread spectrum clock generation,word-line over-drive,split-gate MONOS(SG-MONOS),embedded ?ash memory,Fast random read operation
更新于2025-09-19 17:13:59
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Optimization of the areas of solar collectors and photovoltaic panels in liquid desiccant air-conditioning systems using solar energy in isolated low-latitude islands
摘要： The climate conditions of high temperature and humidity in isolated low-latitude islands lead to high energy consumption of air-conditioning throughout the year. Since the area of island is limited and the supply of conventional energy is difficult, the solar radiation acts as an excellent energy resource for solar air-conditioning. Therefore, an important challenge is to optimize the ratio of the area of the solar collectors and photovoltaic panels to ensure the indoor air is maintained within a comfortable range. In this work, a solar-powered liquid desiccant air-conditioning system is considered as a suitable system, and the working principle of the air-conditioning system and the physico-mathematical models of the subsystems were determined. The energy consumption of the proposed system was compared with that of a conventional cooling dehumidification system under different fresh air loads and heat to humidity load ratios. When the installed area is limited, the ratio of the areas of the collector to photovoltaic panel under different load conditions is optimized. Furthermore, the influence of indoor air design parameters on the required installed area of the system was analyzed. The results provide a basis for the application of solar-powered liquid desiccant air-conditioning system in isolated low-latitude islands.
关键词： Intense solar radiation,Photovoltaic panel area,Solar-powered liquid desiccant air-conditioning systems,Solar collector area,High temperature,High humidity
更新于2025-09-19 17:13:59
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Thermally-stable low-loss polymer dielectrics enabled by attaching crosslinkable antioxidant to polypropylene
摘要： Polymer dielectrics with low loss and high-temperature tolerance are extremely desirable as electrical energy storage materials for advanced electronics and electrical power applications. They can allow fast switching rates during power conversion and therefore achieve high power densities without thermal issues. Here we explore polypropylene (PP), the state of the art dielectric polymer, and present an innovative approach to substantially improve the thermal stability and concurrently reduce the dielectric loss of PP. In particular, crosslinkable antioxidant groups, hindered phenol (HP), are incorporated into PP via well-controlled chemical synthesis. The grafted HP can simultaneously serve as radical scavenger and crosslinker, thereby constraining thermally decomposed radicals and charge transport in the synthesized PP-HP copolymer. As a result, the upper-temperature limit of PP-HP is greatly extended to 190 ?C and the electrical loss is even gradually reduced upon thermal annealing. The copolymer after heating under 190 ?C exhibits better dielectric properties than the PP without any thermal treatment. The experimental results indicate that the PP-HP copolymers are promising materials for high temperature, low loss, and high voltage dielectric applications.
关键词： energy storage,crosslinking,hindered phenol antioxidants,functionalized polypropylene,high-temperature low-loss dielectrics,electrical leakage current
更新于2025-09-19 17:13:59
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Defect-free Laser Powder Bed Fusion of Ti-48Al-2Cr-2Nb with a high temperature inductive preheating system
摘要： In the industrial panorama, Laser Powder Bed Fusion systems enable the near net shaping of metal powders into complex geometries with unique design features. This makes the technology appealing for many industrial applications, which require high performance materials combined with lightweight design, lattice structures and organic forms. However, many of the alloys that would be ideal for the realisation of these functional components are classified as difficult to weld due to their cracking sensitivity. γ-TiAl alloys are currently processed via Electron Beam Melting to produce components for energy generation applications. The Electron Beam Melting process provides crack-free processing thanks to the preheating stages between layers, but lacks geometrical precision. The use of laser powder bed fusion could provide the means for higher precision, and therefore an easier post-processing stage. However, industrial Laser Powder Bed Fusion systems employ resistive heating elements underneath the base plate which do not commonly reach the high temperatures required for the processing of γ-TiAl alloys. Thus, elevated temperature preheating of the build part and control over the cooling rate after the deposition process is concluded are amongst the features which require further investigations. In this work, the design and implementation of a novel inductive high temperature Laser Powder Bed Fusion system to process Ti-48Al-2Cr-2Nb is presented. Specimens were built with preheating at 800 °C and the cooling rate at the end of the build was controlled at 5 °C/min. Crack formation was suppressed and apparent density in excess of 99 % was achieved.
关键词： High Temperature,Preheating,TiAl,Laser Powder Bed Fusion,Energy generation
更新于2025-09-19 17:13:59
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A high power laser facility to conduct annealing tests at high temperature
摘要： The knowledge of material properties and their behavior at high temperatures is of crucial importance in many fields. For instance, annealing phenomena occurring during the thermomechanical processing of materials, such as recrystallization, have long been recognized as being both of scientific interest and technological importance. Different methods are currently used to study annealing phenomena and submit metals to heat loads. In this work, we present the design and the development of a laser-based facility for annealing tests. This experimental setup enables studies at the laboratory scale with great flexibility to submit samples to various spatial and temporal heating profiles. Due to the possibility of having optical access to the sample, laser heating can be combined with several non-contact diagnostics such as infrared imaging to control and analyze the temperature gradients. As a case study, we present a set of experiments performed to study the recrystallization kinetics of tungsten. We demonstrate that samples can be heated linearly with heating rate up to ～2000 K/s, at temperatures above 2000 K, for seconds or hours, with typical errors in the temperature measurement of around 1% that depend mainly on the determination of sample emissivity. Such studies are of crucial interest in the framework of nuclear fusion since the international thermonuclear experimental reactor nuclear reactor will operate with a full-W divertor.
关键词： tungsten,laser annealing,nuclear fusion,high temperature,recrystallization
更新于2025-09-19 17:13:59
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revealed by spatially and angle-resolved photoemission spectroscopy
摘要： Nematicity, where rotational symmetry is broken while translational symmetry is conserved, is prevalent in high-temperature superconductors. In particular, nematic quantum critical point has been universally found near the optimum doping of the superconducting dome of several iron-based superconductor families. In such a regime, evidence for strong nematic ?uctuations have been observed. As the precursor to this order, nematic ?uctuations emerge before nematicity, providing favorable ground to study how nematic order modi?es the electronic structure in the absence of structural distortion. Here we use spatially resolved angle-resolved photoemission spectroscopy to investigate the correlation between the onset of nematic ?uctuations and electronic structure in an optimally doped BaFe2(As1?xPx )2 (x ～ 0.3) superconductor. We reveal a strong spatially varying anisotropy of the Fermi surface on a length scale of tens of microns with strong correlation between the changes in the hole and electron Fermi pockets, consistent with the variations expected in the presence of ?uctuating nematic order. These results provide direct evidence for spatial nematic ?uctuations in the optimal doping regime of iron-based superconductors.
关键词： iron-based superconductors,high-temperature superconductors,angle-resolved photoemission spectroscopy,nematicity,Fermi surface
更新于2025-09-19 17:13:59