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arXiv 2024年

作者： Pant, Nick Armitage, Rob Kioupakis, Emmanouil Applied Physics Program University of Michigan Ann ArborMI48109 United States Department of Materials Science & Engineering University of Michigan Ann ArborMI48109 United States Lumileds LLC San JoseCA95131 United States

Significant effort has been devoted toward mitigating polarization fields in nitride LEDs, as they are viewed as detrimental to light emission, albeit with limited success for red emission. Here, we show that such fields can unusually enhance the optical oscillator strength of red-emitting nitride quantum wells. This insight is enabled by machine-learned models trained on multi-scale quantum-mechanical simulations, which allow for a global exploration of the quantum-well design space at greatly reduced computational cost. Larger polarization fields correlate with higher wave-function overlaps for red emission, a consequence of the quantum-confined Stark effect enabling thinner quantum wells. This finding has implications for designing efficient red nitride LEDs, which are crucial for miniaturizing polychromatic LED pixels to the micron scale for extended-reality and biomedical applications. More broadly, this work highlights the power of machine learning in accelerating the discovery of unconventional paradigms for semiconductor design. Copyright © 2024, The Authors. All rights reserved.

关键词： Semiconductor quantum wells

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A Robust Bendable Irox Thin Film Via Mild Alkaline Solution Process for Neuron Stimulating Electrodes

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SSRN 2023年

作者： Tso, Kuang-Chih Chan, Tzu-Ying Yu, Tsung-Chun Pan, Shih-Chin Chu, Chao-Yi Chen, San-Yuan Lee, Jyh-Fu Ohta, Jun Wu, Pu-Wei Chen, Po-Chun Graduate Program of Accelerator Light Source National Yang Ming Chiao Tung University Hsinchu300 Taiwan Division of Materials Science Graduate School of Science and Technology Nara Institute of Science Technology Takayama Ikoma Nara8916-5 Japan Department of Materials Science and Engineering National Yang Ming Chiao Tung University Hsinchu300 Taiwan Institute of Materials Science and Engineering National Taipei University of Technology Taipei106 Taiwan National Synchrotron Radiation Research Center Hsinchu300 Taiwan

We demonstrate a unique chemical formula to deposit hydrous iridium oxide thin film on a platinum-coated polyimide substrate. In a mild alkaline solution, the iridium (III) precursor undergoes the ligand exchange and hydrolysis reaction to become the iridium (III) dimers that are physically adsorbed on the substrate for subsequent heterogeneous condensation and growth of amorphous hydrous iridium oxide thin film. Both UV-Vis and X-ray absorption spectroscopy (XAS) are employed to determine the reaction steps involved. The chemical nature and crystallinity of the hydrous iridium oxide thin film are investigated by XAS, X-ray photon spectroscopy, and X-ray diffraction. The hydrous iridium oxide thin film reveals an impressive normalized charge storage capacity (CSC) of 0.3 mC/cm2-nm and a low impedance (80.5 Ω) at 1k Hz. In addition, in bending test of 3,000 cycles, the hydrous iridium oxide thin film retains 91.2% of its initial normalized CSC without any physical crack and delamination. The cell viability test suggests negligible bio-toxicity. Our results provide a solid evidence of fabricating a robust flexible electrode for neural interfaces for potential use in implantable electronic devices. © 2023, The Authors. All rights reserved.

关键词： Iridium compounds

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Stable Cycling of Sodium All-Solid-State Batteries with High-Capacity Cathode Presodiation

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Advanced Energy materials 2025年

作者： Tang, Wei Xu, Dapeng Wu, Junlin Lee, Dong Ju Fuqua, Alexander Li, Feng Jeon, Yuju Bian, Wenjuan Chen, Zheng Aiiso Yufeng Li Department of Chemical and Nano Engineering University of California La Jolla San DiegoCA92093 United States Program of Materials Science and Engineering University of California La Jolla San DiegoCA92093 United States Energy and Environment Science and Technology Idaho National Laboratory Idaho FallsID83415 United States Sustainable Power and Energy Center University of California La Jolla San DiegoCA92093 United States

Sodium all-solid-state batteries (NaSSBs) with an alloy-type anode (e.g., Sn and Sb) offer superior capacity and energy density compared to hard carbon anode. However, the irreversible loss of Na+ at the alloy anode during the initial cycle results in diminished capacity and stability, impairing full-cell performance. This study presents an easy-to-implement cathode presodiation strategy by employing a Na-rich material to address these challenges. Leveraging the high theoretical capacity and suitable voltage window, Na2S is chosen as the Na donor, which is activated by creating a mixed electron-ion conducting network, delivering a high capacity of 511.7 mAh g−1. By adding a small amount (i.e., 3 wt.%) of Na2S to the cathode composite, a NaCrO2 || Sn full cell demonstrated capacity improvement from 90.8 to 118.2 mAh g−1 (based on cathode mass). The capacity-balanced full cell can thus cycle to more than 300 times with >90% capacity retention. This work provides a practical solution to enhance the full-cell performance and advance the transformation from half-cell to full-cell applications of NaSSBs. © 2025 Wiley-VCH GmbH.

关键词： Solid-State Batteries

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Heat Transfer Coefficients of Moving Particle Beds from Flow-Dependent Particle Bed Thermal Conductivity and Near-Wall Resistance

arXiv

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arXiv 2024年

作者： Adapa, Sarath R. Zhang, Xintong Feng, Tianshi Zeng, Jian Chung, Ka Man Albrecht, Kevin J. Ho, Clifford K. Madden, Dimitri A. Chen, Renkun Department of Mechanical and Aerospace Engineering University of California La Jolla San DiegoCA92093 United States Program in Materials Science and Engineering University of California La Jolla San DiegoCA92093 United States Concentrating Solar Technologies Department Sandia National Laboratories 1515 Eubank Blvd. SE AlbuquerqueNM87123 United States

Accurate determination of heat transfer coefficients for flowing packed particle beds is essential to the design of particle heat exchangers, and other thermal and thermochemical processes. While such dense granular flows mostly fall into the well-known plug-flow regime, the discrete nature of granular materials alters the thermal transport processes in both the near-wall and bulk regions of flowing particle beds from their stationary counterparts. As a result, heat transfer correlations based on the stationary particle bed thermal conductivity could be inadequate for flowing particles in a heat exchanger. Most earlier works have achieved a reasonable agreement with experiments by treating granular heat transfer media as a plug-flow continuum with a near-wall thermal resistance in series. However, the thermophysical properties of the continuum were often obtained from measurements on stationary beds owing to the difficulty of flowing bed measurements. In this work, it was found that the properties of a stationary bed are highly sensitive to the method of particle packing and there is a decrease in the particle bed thermal conductivity and increase in the near-wall thermal resistance, measured as an effective air gap thickness, on the onset of particle flow. These variations in the thermophysical properties of stationary and flowing particle beds can lead to errors in heat transfer coefficient calculations. Therefore, the heat transfer coefficients for granular flows were calculated using experimentally determined flowing particle bed thermal conductivity and near-wall air gap for ceramic particles - CARBO CP 40/100 (mean diameter=275 µm), HSP 40/70 (404 µm) and HSP 16/30 (956 µm);at velocities of 5-15 mm·s-1;and temperatures of 300-650 ºC. The thermal conductivity and air gap values for CP 40/100 and HSP 40/70 were further used to calculate heat transfer coefficients across different particle bed temperatures and velocities for different parallel-plate heat exchange

关键词： Heat transfer coefficients

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Revealing the EuCd2As2 Semiconducting Band Gap via n-type La-Doping

arXiv

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arXiv 2024年

作者： Nelson, Ryan A. King, Jesaiah Cheng, Shuyu Williams, Archibald J. Jozwiak, Christopher Bostwick, Aaron Rotenberg, Eli Sasmal, Souvik Kao, I-Hsuan Tiwari, Aalok Jones, Natalie R. Cai, Chuting Martin, Emma Dolocan, Andrei Shi, Li Kawakami, Roland Heremans, Joseph P. Katoch, Jyoti Goldberger, Joshua E. Department of Chemistry and Biochemistry The Ohio State University ColumbusOH43210 United States Department of Physics The Ohio State University ColumbusOH43210 United States Department of Mechanical and Aerospace Engineering The Ohio State University ColumbusOH43210 United States Department of Materials Science and Engineering The Ohio State University ColumbusOH43210 United States Department of Physics Carnegie Mellon University PittsburghPA15213 United States Materials Science and Engineering Program The University of Texas AustinTX78712 United States Department of Mechanical Engineering The University of Texas AustinTX78712 United States Advanced Light Source E.O. Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Texas Materials Institute The University of Texas AustinTX78712 United States

EuCd2As2 has attracted considerable interest as one of the few magnetic Weyl semimetal candidate materials, although recently there have been emerging reports that claim it to have a semiconducting electronic structure. To resolve this debate, we established the growth of n-type EuCd2As2 crystals, to directly visualize the nature of the conduction band using angle resolve photoemission spectroscopy (ARPES). We show that La-doping leads to n-type transport signatures in both the thermopower and Hall effect measurements, in crystals with doping levels at 2-6 x 1017 e- cm-3. Both p-type and n-type doped samples exhibit antiferromagnetic ordering at 9 K. ARPES experiments at 6 K clearly show the presence of the conduction band minimum at 0.8 eV above the valence band maximum, which is further corroborated by the observation of a 0.71 – 0.72 eV band gap in room temperature diffuse reflectance absorbance measurements. Together these findings unambiguously show that EuCd2As2 is indeed a semiconductor with a substantial band gap and not a topological semimetal. © 2024, CC BY.

关键词： Photoelectron spectroscopy

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Decoding the Roles of Amyloid-β (1-42)’s Key Oligomerization Domains toward Designing Epitope-Specific Aggregation Inhibitors

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JACS Au 2023年第4期3卷 1065-1075页

作者： Im, Dongjoon Kim, Soohyeong Yoon, Gyusub Hyun, Da Gyeong Eom, Yu-Gon Lee, Ye Eun Sohn, Chang Ho Choi, Jeong-Mo Kim, Hugh I. Department of Chemistry Korea University Seoul 02841 South Korea Center for Proteogenome Research Korea University Seoul 02841 South Korea Single Cell Analysis Laboratory Korea University Seoul 02841 South Korea Department of Chemistry Pusan National University Busan 46241 South Korea Center for Nanomedicine Institute for Basic Science (IBS) Seoul 03722 South Korea Graduate Program in Nanobiomedical Engineering Advanced Science Institute Yonsei University Seoul 03722 South Korea Chemistry Institute for Functional Materials Pusan National University Busan 46241 South Korea

Fibrillar amyloid aggregates are the pathological hallmarks of multiple neurodegenerative diseases. The amyloid-β (1-42) protein, in particular, is a major component of senile plaques in the brains of patients with Alzheimer’s disease and a primary target for disease treatment. Determining the essential domains of amyloid-β (1-42) that facilitate its oligomerization is critical for the development of aggregation inhibitors as potential therapeutic agents. In this study, we identified three key hydrophobic sites (¹⁷LVF¹⁹³²IGL³⁴, and ⁴¹IA⁴²) on amyloid-β (1-42) and investigated their involvement in the self-assembly process of the protein. Based on these findings, we designed candidate inhibitor peptides of amyloid-β (1-42) aggregation. Using the designed peptides, we characterized the roles of the three hydrophobic regions during amyloid-β (1-42) fibrillar aggregation and monitored the consequent effects on its aggregation property and structural conversion. Furthermore, we used an amyloid-β (1-42) double point mutant (I41N/A42N) to examine the interactions between the two C-terminal end residues with the two hydrophobic regions and their roles in amyloid self-assembly. Our results indicate that interchain interactions in the central hydrophobic region (¹⁷LVF¹⁹) of amyloid-β (1-42) are important for fibrillar aggregation, and its interaction with other domains is associated with the accessibility of the central hydrophobic region for initiating the oligomerization process. Our study provides mechanistic insights into the self-assembly of amyloid-β (1-42) and highlights key structural domains that facilitate this process. Our results can be further applied toward improving the rational design of candidate amyloid-β (1-42) aggregation inhibitors. © 2023 The Authors. Published by American Chemical Society.

关键词： aggregation conformation inhibitors oligomers peptides and proteins

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Effect of Order of Addition and Precursor/Reductor Ratio on Direct Synthesis of TiO2 Nanoparticles: Synthesis, Characterization, and Photocatalytic Performance

SSRN

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SSRN 2022年

作者： Goulart, Silviany de Souza Pereira, Mariana Benetti, Renata Martins Bellettini, Gécica Cardoso Elyseu, Fábio Dal-Bó, Alexandre Gonçalves Bernardin, Adriano Michael Graduate Program on Materials Science and Engineering Universidade do Extremo Sul Catarinense Santa Catarina Criciúma88806-000 Brazil Ceramic Materials Group Parque Científico e Tecnológico Santa Catarina Criciúma88807-420 Brazil

Titanium dioxide (TiO2) is the most used semiconductor for heterogeneous photocatalysis. However, there is a limitation of its application, since TiO2 is activated only under ultraviolet radiation. Sunlight has only about 5% of UV radiation and, consequently, there are limitations for the application and commercialization of this semiconductor. The present study aimed to obtain nanostructured TiO2 powders for photocatalysis under UV light by a direct synthesis route, obtaining anatase and rutile phases without further heat treatment. A 2k factorial experimental design was used to evaluate the effect of the order of addition of precursors and their ratio on the synthesis of NPs. TiO2 nanoparticles with large surface area were synthesized via controlled precipitation method. The NPs were characterized by XRD, DSC/TG, FTIR, BET, DLS, ELS, UV-Vis, FESEM-EDS, and photocatalytic activity test. The commercial TiO2 NP P25 was used as standard photocatalyst for comparison with the obtained samples. The surface area measured by the BET method for the synthesized samples was approximately three to five times higher when compared to P25. The photoactivity of the synthesized samples and P25 were determined for the degradation of the methylene blue and rhodamine B dyes under UVA radiation. The results showed that the synthesized samples have an efficiency equivalent to the P25 sample. The synthesis of nanoparticles via the controlled precipitation method using only two reagents proved to be a viable and promising route. The method does not require heat treatment for titanium dioxide crystallization and is still capable of producing a mixture of ideal phases to delay the recombination of the photogenerated electron-hole pair, contributing to the increase of the photocatalytic efficiency. © 2022, The Authors. All rights reserved.

关键词： Titanium dioxide

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Evaluation of Automatic Microstructural Analysis of Energy Dispersive Spectroscopy (EDS) Maps via a Python-Based Data Processing Framework 240

Evaluation of Automatic Microstructural Analysis of Energy D...

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240th ECS Meeting

作者： Batool, Mariah O. Godoy, Andres Birnbach, Martin Dekel, Dario R Jankovic, Jasna Institute of Materials Science University of Connecticut 97 North Eagleville Road StorrsCT06269-3136 United States Department of Materials Science and Engineering University of Connecticut 97 North Eagleville Road StorrsCT06269-3136 United States Wolfson Department of Chemical Engineering Nancy and Stephen Grand Technion Energy Program Israel Institute of Technology Haifa3200003 Israel

ISBN: (纸本)9781607685395

Computer-aided data acquisition, analysis and interpretation have been employed in various research areas generating useful information. Among these, image processing is most often implemented for post-processing of material characterization data. However, to tackle ambiguity of multi-component materials analysis, spectral data analysis can be used instead. The current study introduces a unique Python-based data processing method for in-depth analysis of energy dispersive spectroscopy (EDS) elemental maps to analyze agglomerate size distribution, average area of each component and their overlap. The framework developed in this study is applied to examine interaction of Cerium (Ce) and Palladium (Pd) particles in membrane electrode assembly (MEA) of Anion-Exchange Membrane Fuel Cell (AEMFC) and investigate if this approach can be utilized to predict the fuel cell's electrochemical behavior. The study concludes that the developed framework is a promising method for automatic data extraction and can be beneficial for use in a variety of clean energy applications. © 2021 ECS - The Electrochemical Society.

关键词： Python

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Exfoliated MXene nanosheet by double layer forces for preparing magnetic adsorbents of toxic metal ions and recycling with hyperthermic effect

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Separation and Purification Technology 2024年 349卷

作者： Chen, Chih-Wei Chang, Chi-Jung Liaw, Shien-Kuei Lu, Chien-Hsing Chen, Jem-Kun Department of Materials Science and Engineering National Taiwan University of Science and Technology 43 Sec. 4 Keelung Road Taipei106 Taiwan Division of Neurosurgery Department of Surgery Chi Mei Medical Center Tainan710 Taiwan Department of Chemical Engineering Feng Chia University 100 Wenhwa Road Seatwen Taichung40724 Taiwan Department of Electronic and Computer Engineering National Taiwan University of Science and Technology Taipei10607 Taiwan Department of Obstetrics and Gynecology Taichung Veterans General Hospital Taichung40705 Taiwan Institute of Biomedical Sciences Ph.D. Program in Translational Medicine and Rong-Hsing Research Center for Translational Medicine National Chung-Hsing University Taichung940227 Taiwan

The conventional etching method for exfoliating MXene using hydrofluoric acid solution is time-consuming and inefficient in productivity. A double layer force is generated through polarization among the heterogeneous layers of MXene due to their different dielectric properties. The exfoliated MXene by the polarization method in an acidic solution was employed to synthesize magnetic MXene (MXFe) with Fe3O4 nanoparticles. MXFe was coated on polyacrylonitrile microspheres (PANs) as precursors (PAN@MXFe) by Pickering emulsion polymerization. The core@shell polyvinyltetrazole@MXFe (PVT@MXFe) was obtained as the adsorbent after subsequent cyano-tetrazole conversion of PAN@MFs for the removal of toxic metal ions. The maximum adsorption capacities of Hg(II) on the MXFe and PVT@MXFe coating 2 wt% of MXFe were 579 and 324 mg/g, respectively, indicating the high use efficiency of MXFe. At 8.5 kHz of high frequency, hyperthermia occurs on the PVT@MXFe, facilitating the desorption of the toxic metal ions from the adsorbents. Compared with reuse using an acidic solution, the PVT@MXFe can be reused repeatedly 10 times without obvious damage under the AMF. Our proposed polarization exfoliation method not only provides a novel methodology to exfoliate MXene but also develops an ideal adsorbent for universal adsorption, simple separation, stable regeneration, and low secondary pollution. © 2024 Elsevier B.V.

关键词： Synthesis (chemical)

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Acoustic Sensing for Investigating Critical Heat Flux Enhancement During Pool Boiling on Electrodeposited Copper Foams

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SSRN 2023年

作者： Pandey, Hari Mehrabi, Hamed Williams, Amanda Mira-Hernández, Carolina Coridan, Robert Henry Hu, Han Department of Mechanical Engineering University of Arkansas FayettevilleAR72701 United States Materials Science and Engineering Program University of Arkansas FayettevilleAR72701 United States Universidad Pontificia Bolivariana Medellín Colombia Department of Chemistry and Biochemistry University of Arkansas FayettevilleAR72701 United States

Nano-engineered structured boiling surfaces have shown great promise in the improvement of heat dissipation performance in thermal management applications. Electrodeposited copper foams have attracted lots of scientific and engineering interest owing to their multi-tier structures. In this study, hierarchical copper foams with ultra-wicking properties were fabricated using cathodic deposition at different pH, including both acidic (pH 0) and basic (pH 10 and 12) solutions. Pendant droplet wicking tests and pool boiling experiments were performed to characterize the wicking flux and the critical heat flux (CHF) of the fabricated copper foams, respectively. The high-speed optical images were analyzed to examine the effect of surface wickability on bubble dynamics. The CHF enhancement mechanism in hierarchical copper foams was investigated by characterizing the acoustic emissions (AE) generated during wicking and boiling vapor dynamics. The results show that base-deposited copper foams (pH 10 and 12) yield higher wicking flux and higher boiling CHF than acid-deposited copper foam (pH 0) due to smaller dendrites and crystallites. The effect of the surface structures on bubble dynamics is probed by analyzing the maximum bubble size, bubble count, and the power and dominant frequency of vapor fraction at varying heat fluxes from high-speed videos. The results reveal no significant differences between tested surfaces (polished copper and copper foams deposited at pH 0, 10, and 12) when the heat flux is kept the same. Additionally, acoustic emissions were used to understand the CHF enhancement mechanisms in different copper foam structures. While investigating the AE data, the results show consistent acoustic signatures between wicking and boiling, that is, a smaller AE amplitude is observed for higher wicking flux and higher CHF. Initiation of CHF during pool boiling was a prime source for AE and these were recognized with AE parametric study. Combing the optical and acous

关键词： Heat flux

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