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SSRN 2024年

作者： Giglio, Roman Shattique, Muhammad Rubaiet Dede, Ercan M. Narumanchi, Sreekant Asheghi, Mehdi Goodson, Kenneth E. Palko, James W. Department of Mechanical Engineering University of California MercedCA United States Materials and Biomaterials Science and Engineering Graduate Program University of California MercedCA United States Toyota Research Institute of North America Ann ArborMI United States National Renewable Energy Laboratory GoldenCO United States Department of Mechanical Engineering Stanford University StanfordCA United States

High performance electronics are continuously demanding cooling of higher heat fluxes. Phase change cooling, including pool boiling, is a useful approach to address this challenge, however competition between liquid and vapor flows generally limit the heat fluxes that can be dissipated. Here a manifold structure formed from metallic mesh is introduced to control the disposition of liquid and vapor phases above a boiling surface enhanced with a porous structure. Copper mesh forms defined liquid flow paths using capillary action to guide and distribute liquid evenly over the heated surface and open channels to facilitate vapor escape. The manifold performance is characterized in pool boiling with water above a laser textured aluminum nitride heat dissipation surface with pin fin structures having heights of 110 µm and spacing of 30 µm with a heated area of 5 mm x 5 mm. Maximum heat flux of 490W/cm is reached with the manifold in the pool boiling configuration, representing a 64% increase over the porous surface alone. Maximum superheat found for the manifold is 36 K, which is 14 K higher than the porous surface without manifold. Factors limiting performance of the manifold are analyzed. Based on variation of manifold geometry and numerical simulation, the primary limitation to heat flux is found to be viscous resistance to liquid flow in the manifold mesh. The increased superheat is attributed to partial flooding of the boiling surface as indicated by reduction in superheat using external suction. Similar systems and structures for enhanced two-phase cooling are compared. © 2024, The Authors. All rights reserved.

关键词： Heat flux

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Laser Processed Aluminum Nitride Structures for Enhanced Two-Phase Cooling

SSRN

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SSRN 2024年

作者： Giglio, Roman Shattique, Muhammad Rubaiet Md. Dede, Ercan M. Narumanchi, Sreekant Asheghi, Mehdi Goodson, Kenneth E. Palko, James W. Department of Mechanical Engineering University of California MercedCA United States Materials and Biomaterials Science and Engineering Graduate Program University of California MercedCA United States Toyota Research Institute of North America Ann ArborMI United States National Renewable Energy Laboratory GoldenCO United States Department of Mechanical Engineering Stanford University StanfordCA United States

The demand for higher heat flux cooling is increasing as the use of power electronics continues to expand. Two-phase cooling approaches that are tightly integrated into electronic packages offer potential for high performance. Here we describe a method to produce microscale pillars directly in aluminum nitride using UV laser ablation that is compatible with existing substrates for power electronics packaging and offers high precision and short production time. The resulting structures show significantly enhanced performance in pool boiling compared to unmodified surfaces. Effectiveness in two-phase cooling is investigated in terms of critical heat flux, heat transfer coefficient, and thermal resistance. The micropillar structures achieve a maximum critical heat flux of 299 W/cm2 and heat transfer coefficients up to 20 W/cm2 K for cooled areas of 0.25 cm2 in deionized water. Performance is attributed to the effective capillary rewetting of the surface during boiling and increased surface area. Corrosion of the aluminum nitride surface by the water working fluid is observed and contributes to a slow degradation of the measured heat transfer coefficient. The potential for simple processing routes to allow tight integration of two-phase cooling of electronics more generally is considered. © 2024, The Authors. All rights reserved.

关键词： Heat flux

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CsPbBr3nanocrystals plasmonic distributed Bragg reflector waveguide laser

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Applied Physics Letters 2023年第7期122卷 1-6页

作者： Ahmad Kamal, Ahmad Syazwan Lin, Cheng-Chieh Wang, Zhiyu Xing, Di Lee, Yang-Chun Chen, Mu-Hsin Ho, Ya-Lun Chen, Chun-Wei Delaunay, Jean-Jacques School of Engineering The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo113-8656 Japan School of Mechanical Engineering Engineering Campus Universiti Sains Malaysia Pulau Pinang14300 Malaysia Universiti Sains Malaysia Pulau Pinang11900 Malaysia Taiwan International Graduate Program National Taiwan University and Academia Sinica No. 1 Sec. 4 Roosevelt Rd Taipei10617 Taiwan Department of Materials Science and Engineering National Taiwan University No. 1 Sec. 4 Roosevelt Rd. Taipei10617 Taiwan Academia Sinica No. 128 Sec. 2 Academia Rd. Taipei11529 Taiwan National Taiwan University No. 1 Sec. 4 Roosevelt Rd. Taipei10617 Taiwan

The recent development of perovskite-based lasers showcased the outstanding optical properties of the material such as high absorption coefficient and high quantum yield. The lasers were demonstrated in the form of nanowires and nanoplates, which are difficult to be integrated on a chip in the form of high-density arrays due to the difficulties in positioning them on the chip. The solution to this problem should be to use the well-known lithography process in the fabrication process of the lasers. In this work, we demonstrate several perovskite-based plasmonic lasers that were fabricated by using the lithographic in-mold patterning method that relies on the electron beam lithography process. The lasers utilized CsPbBr3 perovskite nanocrystals as the gain material and plasmonic distributed Bragg reflector grating structure as the optical feedback provider to achieve a low lasing threshold of 42.5 μJ/cm2 with a linewidth of 0.6 nm (FWHM) at room temperature. The use of the lithographic process in the fabrication of the lasers makes it possible to fabricate and integrate them on a chip in a relatively high-density manner, so that they can be used extensively in quantum optics and on-chip integrated photonics applications. © 2023 Author(s).

关键词： Perovskite

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High-value utilization of CO_(2) to synthesize sulfur-doped carbon nanofibers with excellent capacitive performance

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International Journal of Minerals,Metallurgy and materials 2020年第12期27卷 1666-1677页

作者： Meng-jun Hu Ming-zhu Yin Li-wen Hu Peng-jie Liu Shuo Wang Jian-bang Ge College of Materials Science and Engineering Chongqing UniversityChongqing 400044China Chongqing Key Laboratory of Vanadium-Titanium Metallurgy and Advanced Materials Chongqing UniversityChongqing 400044China Nuclear Engineering Program Department of Mechanical EngineeringVirginia Polytechnic Institute and State UniversityBlacksburgVirginia 24061USA

Carbon nanofiber(CNF)is considered a promising material due to its excellent physical and chemical *** paper proposes a novel way to transform CO_(2) into heteroatom-doped CNFs,with the introduction of Fe,Co,and Ni as *** the electrolyte containing Ni O,Co2O3,and Fe_(2)O_(3) was employed,sulfur-doped CNFs in various diameters were *** the introduction of Fe catalyst,the obtained sulfur-doped CNFs showed the smallest and tightest diameter *** obtained sulfur-doped CNFs had high gravimetric capacitance(achieved by SDG-Fe)that could reach 348.5 F/g at 0.5 A/g,excellent cycling stability,and good rate *** comparison purposes,both Fe and nickel cathodes were tested,where the active metal atom at their surface could act as *** these two situations,sulfur-doped graphite sheet and sulfur-doped graphite quasi-sphere were the main products.

关键词： carbon dioxide capture electrochemical conversion carbon fiber molten salt

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Improved gas-phase infrared analysis of nitrobenzene using nanoporous silica preconcentrator

Improved gas-phase infrared analysis of nitrobenzene using n...

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Optical Sensors, Sensors 2021 - Part of OSA Optical Sensors and Sensing Congress 2021

作者： Day, Coco Hutter, Tanya Department of Chemistry University of Cambridge Lensfield Road CambridgeCB2 1EW United Kingdom Department of Mechanical Engineering Materials Science and Engineering Program Texas Materials Institute The University of Texas at Austin AustinTX78712 United States

Gas-phase infrared (IR) is often insufficiently sensitive to detect low-vapor-pressure explosives. A nanoporous silica preconcentrator was used to achieve a three-fold sensitivity enhancement of gas-phase IR for nitro... 详细信息

ISBN: (纸本)9781557528209

关键词： Nitrobenzene

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Achieving Near-Intrinsic Exciton Linewidth at Room Temperature in Monolayer WS2 Coupled with a Mie Resonator

Achieving Near-Intrinsic Exciton Linewidth at Room Temperatu...

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Conference on Lasers and Electro-Optics (CLEO)

作者： Jie Fang Kan Yao Yuebing Zheng Materials Science & Engineering Program and Texas Materials Institute The University of Texas at Austin Austin TX USA Walker Department of Mechanical Engineering The University of Texas at Austin Austin TX USA

Strong multiparticle interactions at room temperature (RT) lead to broadened homogeneous exciton linewidths in 2D semiconductors, degrading the quality of excitonic mode and emission. By coupling a Mie resonator with ... 详细信息

ISBN: (数字)9781957171050

ISBN: (纸本)9781665466660

关键词： Couplings Laser theory Excitons Semiconductor lasers Kelvin Lasers and electrooptics Laser modes

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Corner cutting connects chiral colorimetry to net electric flux in lossless all-dielectric metasurfaces

arXiv

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arXiv 2024年

作者： Haddadin, Zaid Nguyen, Anna M.Y. Poulikakos, Lisa V. Department of Electrical & Computer Engineering UC San Diego La Jolla CA92093-0021 United States Department of Mechanical & Aerospace Engineering UC San Diego La Jolla CA92093-0021 United States Program of Materials Science & Engineering UC San Diego La Jolla CA92093-0021 United States

All-dielectric metasurfaces can produce structural colors, but the most advantageous design criteria are still being investigated. This work numerically studies how the two-dimensional shape of nanoparticles affects the colorimetric response under circularly polarized light (CPL) to develop a sensor distinguishing CPL orientations. Using lossless dielectric materials (silicon nitride on silicon dioxide), we achieve far-field dichroism by modifying oblong nanoparticles into L-shaped structures through corner cuts. This design suppresses one electric dipole under CPL illumination, leading to differential colorimetric responses. We link these responses to a decoupling effect in the near-field net electric flux. Our findings provide design guidelines for all-dielectric, lossless colorimetric sensors of chiral light. Copyright © 2024, The Authors. All rights reserved.

关键词： Silicon nitride

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Polarization-Tunable Colorimetric Metasurfaces for All-Optical and Non-Destructive Structural Characterization of Polymeric Nanofibers

arXiv

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arXiv 2025年

作者： Kirya, Paula Hochberg, Justin D. Kim, Han Sol Haddadin, Zaid Bordy, Samantha Byun, Jiuk Pokorski, Jonathan K. Poulikakos, Lisa V. Department of Mechanical and Aerospace Engineering UC San Diego La Jolla CA United States Aiiso Yufeng Li Family Department of Chemical and Nano Engineering UC San Diego La Jolla CA United States Department of Electrical and Computer Engineering UC San Diego La Jolla CA United States Program in Materials Science and Engineering UC San Diego La Jolla CA United States

Metasurfaces have pioneered significant improvements in sensing technology by tailoring strong optical responses to weak signals. When designed with anisotropic subwavelength geometries, metasurfaces can tune responses to varying polarization states of light. Leveraging this to quantify structural alignment in fibrous materials unveils an alternative to destructive characterization methods. This work introduces metasurface-enhanced polarized light microscopy (Meta-PoL), which employs polarization-tunable, guided-mode-resonant colorimetric metasurfaces to characterize molecular and bulk alignment of poly(Ε-caprolactone) (PCL) nanofibers in a far-field configuration. PCL nanofibers drawn at 0%, 400%, and 900% ratios were interfaced with the studied metasurfaces. Metasurface resonances coinciding with the intrinsic drawn nanofiber resonances – confirmed by Stokes Polarimetry – produced the strongest colorimetric enhancement, resultant from alignment-specific nanofiber reflectivity. The enhancement degree corresponded with molecular and bulk alignments for each draw ratio, as measured through differential scanning calorimetry and scanning electron microscopy, respectively. Thus, Meta-PoL presents an all-optical, non-destructive, and quantitative measurement of nanofiber alignment. Copyright © 2025, The Authors. All rights reserved.

关键词： Differential scanning calorimetry

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In-situ Atomic-scale Observations of Disconnection Dynamics at the Metal/Oxide Interfaces

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Microscopy and Microanalysis 2022年第S1期28卷 150-151页

作者： Liang, Zhilu Wang, Jianyu Sun, Xianhu Chen, Xiaobo Zakharov, Dmitri N Zhou, Guangwen Department of Mechanical Engineering & Materials Science and Engineering Program State University of New York at Binghamton Binghamton NY USA Center for Functional Nanomaterials Brookhaven National Laboratory Upton NY USA

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Anomalous elastic softening in ferroelectric hafnia under pressure

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Physical Review B 2025年第6期111卷 064106-064106页

作者： Alejandro Alvarez Niaz Abdolrahim Sobhit Singh Materials Science Program University of Rochester Rochester New York 14627 USA Department of Mechanical Engineering University of Rochester Rochester New York 14627 USA Laboratory for Laser Energetics University of Rochester Rochester New York 14627 USA Center for Coherence and Quantum Optics University of Rochester Rochester New York 14627 USA

This study employs first-principles density-functional theory (DFT) calculations to explore the elastic and mechanical properties of ferroelectric hafnia (HfO2) in its polar orthorhombic Pca21 phase under varying hydrostatic pressure conditions up to 30 GPa. Utilizing a plane-wave basis set and Perdew-Burke-Ernzerhof generalized-gradient approximation for solids in our DFT calculations, we investigate both pure and yttrium-substituted HfO2. Our findings reveal an anomalous reduction in the C33 component of the elastic tensor with increasing pressure, which becomes significant above 15 GPa and signals a potential pressure-driven structural phase transition at higher pressure. The analysis of atomic displacements under pressure sheds light on the unusual mechanical behavior and phase stability of this material. Additionally, we observe a transition from an indirect band gap to a direct band gap with increasing pressure, which could have significant implications for optical applications. The effects of yttrium substitution on the mechanical and electronic properties are further examined, revealing that yttrium substitution softens the elastic response of this material and reduces the electronic band gap. These results enhance our understanding of elastic and mechanical responses of ferroelectric hafnia and its potential for applications in microelectronics, piezoelectric devices, and nonvolatile ferroelectric random-access memories. Further experimental validation is recommended to confirm our predictions and explore the practical implications of the observed phase transitions and electronic behavior of the ferroelectric hafnia under high-pressure conditions.

关键词： Ferroelectricity

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