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Pressure, Temperature, and Thickness Dependence of CO2-Induced Devitrification of Polymer Films

Physical Review Letters 2003年第17期91卷 175503-175503页

作者： Joseph Q. Pham Stephen M. Sirard Keith P. Johnston Peter F. Green Graduate Program in Materials Science and Engineering University of Texas at Austin Austin Texas 78712 USA Department of Chemical Engineering and Texas Materials Institute University of Texas at Austin Austin Texas 78712 USA

The glass transition temperature is known to increase with decreasing film thickness h for sufficiently thin poly(methyl methacrylate) films supported by silicon oxide substrates. We show that this system undergoes a CO2 pressure-induced devitrification transition, Pg, which is film thickness dependent, Pg(h)=ΔPg+Pgbulk. Pgbulk is the bulk glass transition and ΔPg can be positive or negative depending on T and P. The phenomenon of retrograde vitrification, wherein the polymer exhibits a rubbery-to-glassy-to-rubbery transition upon changing temperature isobarically, is also shown to occur in this system and it is film thickness dependent.

关键词： Polymethyl methacrylates

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Accuracy of DFT computed oxygen-vacancy formation energies and high-throughput search of solar thermochemical water-splitting compounds

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Physical Review materials 2023年第6期7卷 065403-065403页

作者： Bianca Baldassarri Jiangang He Xin Qian Emanuela Mastronardo Sean Griesemer Sossina M. Haile Christopher Wolverton Graduate Program in Applied Physics Northwestern University Evanston Illinois USA Department of Materials Science and Engineering Northwestern University Evanston Illinois USA

The enthalpy change involved in metal oxide reduction is a key quantity in various processes related to energy conversion and storage and is of particular interest for computational prediction. Often this prediction involves the simulation of a high-temperature reduction process with a 0-K methodology like density functional theory (DFT), and it is not infrequent for the high temperature and 0-K stable crystal structures to differ. This introduces a conundrum with regard to the choice of crystal structure to utilize in the computation, with approaches in the literature varying and experimental validation remaining scarce. In this work, we address both the crystal structure conundrum and the experimental validation, and then apply the insights we gain to guide a high-throughput search for new materials for solar thermochemical water-splitting applications. By computing the DFT+U oxygen-vacancy formation energy (ΔEvf) of a selection of ABO3 compounds and comparing different crystal structures for each composition, we highlight the issues that arise when the structure utilized in the computation is dynamically unstable at 0 K, namely the presence of an artificial lowering of ΔEvf, and the lack of convergence of ΔEvf with cell size. We solve these limitations by identifying and employing a suitable surrogate dynamically stable structure. We then validate the predictive power of our calculations against appositely generated experimental measurements of reduction enthalpy for a series of Hubbard U values, finding an accuracy ranging between 0.2–0.6 eV/O. In light of such conclusions, we revise and expand a previous a high-throughput DFT study on ABO3 perovskite oxides. We provide a list of candidate STCH materials, highlight trends with redox-active cation and structural distortion, and identify Mn4+, Mn3+, and Co3+ as the most promising redox-active cations.

关键词： Energy applications First-principles calculations Hydrogen energy

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Fabrication of graphene by electrochemical exfoliation in alkaline electrolytes

Fabrication of graphene by electrochemical exfoliation in al...

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作者： Chang, Li-Chung Hsieh, Yu-Chi Chen, Yong-Min Wu, Pu-Wei Lee, Jyh-Fu Graduate Program for Science and Technology of Accelerator Light Source China Department of Materials Science and Engineering National Chiao Tung University Hsin-Chu 30010 Taiwan Taiwan National Synchrotron Radiation Research Center Hsin-Chu 30076 Taiwan Taiwan

ISBN: (纸本)9781607685395

Fabrication of graphene was demonstrated by electrochemical exfoliation of graphite in an ammonium hydroxide solution. The processing parameter of applied voltage was optimized to accomplish graphene productivity and desired chemical composition. Images from the atomic force microscopy showed graphene sheets with lateral sizes of several hundred nanometers. Images from the transmission electron microscopy indicated the existence of stacked graphene sheets with thickness of a few graphene layers. Raman spectroscopy confirmed variation of assynthesized graphene and bulk graphite. X-ray photoemission spectroscopy suggested the formation of graphene oxide at large voltage. © 2014 The Electrochemical Society.

关键词： Graphene

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Study of Silicon Nitride Etched by Cyclic Atomic Layer Etching

Study of Silicon Nitride Etched by Cyclic Atomic Layer Etchi...

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2022 IET International Conference on engineering Technologies and Applications, IET-ICETA 2022

作者： Yang, Tsung-Ying Kuo, Mei-Yan Chang, Edward-Yi National Yang Ming Chiao Tung University International College of Semiconductor Technology Hsinchu Taiwan National Yang Ming Chiao Tung University Graduate Program for Nanotechnology Department of Materials Science and Engineering Hsinchu Taiwan

ISBN: (数字)9781665491389

ISBN: (纸本)9781665491389

In this work, cyclic atomic layer etching (ALE) was used to etch silicon nitride (SiN) to find its working conditions. To understand the mechanism behind it, we tested the ALE adsorption effect and the removal effect of the ALE working window. Also, we made a comparison with the etching RMS of normal etching ICP and showed that ALE has better etch flatness. This demonstrates that ALE has a potential ability to become a reliable and stable etching technology in the future. © 2022 IEEE.

关键词： Silicon nitride

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Synchrotron X-ray scattering studies of star-shape polymers

Synchrotron X-ray scattering studies of star-shape polymers

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2007 NSTI Nanotechnology Conference and Trade Show - NSTI Nanotech 2007

作者： Jin, S. Higashihara, T. Jin, K.S. Yoon, J. Heo, K. Kim, J. Kim, K.-W. Hirao, A. Ree, M. BK21 Program Polymer Research Institute Pohang University of Science and Technology Pohang 790-784 Korea Republic of Polymeric and Organic Materials Department Graduate School of Science and Engineering Tokyo Institute of Technology Tokyo 152-8552 Japan

Shapes and structures of star-polystyrenes bearing 6 to 57-arms were in detail investigated in good and theta solvents by small-angle X-ray scattering with synchrotron radiation sources.

ISBN: (纸本)1420063766

Shapes and structures of star-polystyrenes bearing 6 to 57-arms were in detail investigated in good and theta solvents by small-angle X-ray scattering with synchrotron radiation sources.

关键词： Polystyrenes

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Preparation of CdSe/ZnS quantum Dots-PEG-b-PAMA conjugate and application for immunohistochemistry

Preparation of CdSe/ZnS quantum Dots-PEG-b-PAMA conjugate an...

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Transactions - 7th World Biomaterials Congress

作者： Nakamae, M. Takahashi, T. Ishii, T. Nagasaki, Y. Kataoka, K. Preventure Program JST Department of Materials Science Tokyo University of Science Yamazaki2641 Noda 278-8510 Japan Department of Matereals Science Graduate School of Engineering University of Tokyo Hongo 7-3-1 Bunkyo-ku Tokyo 113-8656 Japan

ISBN: (纸本)1877040193

The stable dispersion of quantum dot nanoparticles (QD) in aqueous solution using polymers containing poly(ethylene glycol) (PEG) segment was investigated. It was found that using PEG/poly(2-N,N-dimethylaminoethyl methacrylate) (PEG-b-PAMA) enables stabilization of QD in aqueous phase. The photochemical characteristics of the PEG-modified QD were found to be almost same as unmodified QD. It was observed that as he PEG/PAMA block copolymer-modified QDs possess PEG tethered chains on the surface, it is highly dispersion stable in aqueous media and also showed non-fouling character.

关键词： Semiconductor quantum dots

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Resonant photonic structures in porous silicon for biosensing 9

Resonant photonic structures in porous silicon for biosensin...

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Frontiers in Biological Detection: From Nanosensors to Systems IX

作者： Zhao, Yiliang Rodriguez, Gilberto A. Graham, Yasmin M. Cao, Tengfei Gaur, Girija Weiss, Sharon M. Interdisciplinary Graduate Program in Materials Science Vanderbilt University NashvilleTN37235 United States Department of Electrical Engineering and Computer Science Vanderbilt University NashvilleTN37235 United States Department of Mechanical Engineering University of Maryland Baltimore County BaltimoreMD21250 United States

ISBN: (数字)9781510606043

ISBN: (纸本)9781510606036

The formation of resonant photonic structures in porous silicon leverages the benefit of high surface area for improved molecular capture that is characteristic of porous materials with the advantage of high detection sensitivity that is a feature of resonant optical devices. This review provides an overview of the biosensing capabilities of a variety of resonant porous silicon photonic structures including microcavities, Bloch surface waves, ring resonators, and annular Bragg resonators. Detection sensitivities > 1000 nm/RIU are achieved for small molecule detection. The challenge of detecting molecules that approach and exceed the pore diameter is also addressed. © 2017 SPIE.

关键词： Porous silicon

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Low-temperature spin Seebeck effect in nonmagnetic vanadium dioxide

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Physical Review B 2024年第2期110卷 024415-024415页

作者： Renjie Luo Tanner J. Legvold Liyang Chen Henry Navarro Ali C. Basaran Deshun Hong Changjiang Liu Anand Bhattacharya Ivan K. Schuller Douglas Natelson Department of Physics and Astronomy Applied Physics Graduate Program Rice Quantum Institute Department of Physics and Center for Advanced Nanoscience Materials Science Division Department of Electrical and Computer Engineering Department of Materials Science and NanoEngineering

The spin Seebeck effect (SSE) is sensitive to thermally driven magnetic excitations in magnetic insulators. Vanadium dioxide in its insulating low-temperature phase is expected to lack magnetic degrees of freedom, as vanadium atoms are thought to form singlets upon dimerization of the vanadium chains. Instead, we find a paramagnetic SSE response in VO2 films that grows as the temperature decreases below 50 K. The field and temperature-dependent SSE voltage is qualitatively consistent with a general model of paramagnetic SSE response and inconsistent with triplet spin transport. Quantitative estimates find a spin Seebeck coefficient comparable in magnitude to that observed in strongly magnetic materials. The microscopic nature of the magnetic excitations in VO2 requires further examination.

关键词： Spin Seebeck effect Paramagnets Strongly correlated systems

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Direct Scaffold-Coupled Electrical Stimulation of Chondrogenic Progenitor Cells through Graphene Foam Bioscaffolds to Control the Mechanical Properties of Graphene Foam-Cell Composites

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ACS Applied materials and Interfaces 2025年 2025 May 20页

作者： Sawyer, Mone’t Semodji, Amevi Nielson, Olivia Rektor, Attila Burgoyne, Hailey Eppel, Michael Eixenberger, Josh Montenegro-Brown, Raquel Nelson, Miranda L. Lujan, Trevor J. Estrada, David Biomedical Engineering Doctoral Program Boise State University Boise 83725 ID United States Department of Chemical and Biological Engineering University of Idaho Moscow 83844 ID United States Micron School for Materials Science and Engineering Boise State University Boise 83725 ID United States Biomolecular Sciences Graduate Program Boise State University Boise 83725 ID United States Department of Physics Boise State University Boise 83725 ID United States Center for Advanced Energy Studies Boise State University Boise 83725 ID United States Idaho National Laboratory Idaho Falls 83401 ID United States

Osteoarthritis, a major global cause of pain and disability, is driven by the irreversible degradation of hyaline cartilage in the joints. Cartilage tissue engineering presents a promising therapeutic avenue, but success hinges on replicating the native physiological environment to guide cellular behavior and generate tissue constructs that mimic natural cartilage. Although electrical stimulation has been shown to enhance chondrogenesis and extracellular matrix production in two-dimensional (2D) cultures, the mechanisms underlying these effects remain poorly understood, particularly in three-dimensional (3D) models. Here, we report that direct scaffold-coupled electrical stimulation applied to 3D graphene foam bioscaffolds significantly enhances the mechanical properties of the resulting graphene foam-cell constructs. Using custom 3D-printed electrical stimulus chambers, we applied biphasic square impulses (20, 40, 60 mVpp at 1 kHz) for 5 min daily over 7 days. Stimulation at 60 mVpp increased the steady-state energy dissipation and equilibrium modulus by approximately 65 and 25%, respectively, as compared with unstimulated controls. 60 mVpp stimulation also yielded the highest cell density among stimulated samples. In addition, our custom chambers facilitated full submersion of the hydrophobic graphene foam in media, leading to enhanced cell attachment and integration across the scaffold surface and within its hollow branches. To assess this cellular integration, we employed colocalized confocal fluorescence microscopy and X-ray microCT imaging enabled by colloidal gold nanoparticle and fluorophore staining, which allowed visualization of cell distribution within the opaque scaffold’s internal structure. These findings highlight the potential of a direct scaffold-coupled electrical stimulus to modulate the mechanical properties of engineered tissues and offer insights into the emergent behavior of cells within conductive 3D bioscaffolds. © 2025 The Authors. Publish

关键词： dynamic mechanical analysis electrical stimulation graphene foam MicroCT volumetric analysis

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Using 4D-STEM to Map 3D Morphologies of 2D materials

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Microscopy and microanalysis : the official journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada 2023年第1期29卷 262-263页

作者： Mireles, Adan Shi, Chuqiao Park, Jeongwon Shin, Bongki Sung, Suk Hyun Ophus, Colin Hovden, Robert Kang, Kibum Han, Yimo Applied Physics Graduate Program Smalley-Curl Institute Rice University Houston TX United States Department of Materials Science and NanoEngineering Rice University Houston TX United States Department of Materials Science and Engineering Korea Advanced Institute of Science and Technology (KAIST) Daejeon South Korea Department of Materials Science and Engineering University of Michigan Ann Arbor MI United States National Center for Electron Microscopy Molecular Foundry Lawrence Berkeley National Laboratory Berkeley CA United States

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