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When quantum dots meet blue phase liquid crystal elastomers:visualized full-color and mechanically-switchable circularly polarized luminescence

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Light(Science & Applications) 2024年第6期13卷 1210-1220页

作者： Shan Li Yuqi Tang Qingyan Fan Ziyuan Li Xinfang Zhang Jingxia Wang Jinbao Guo Quan Li Key Laboratory of Carbon Fibers and Functional Polymers Ministry of Educationand College of Materials Science and EngineeringBeijing University of Chemical Technology100029BeijingChina Institute of Advanced Materials and School of Chemistry and Chemical Engineering Southeast UniversityNanjing211189China Materials Science Graduate Program Kent State UniversityKentOH44242USA CAS Key Laboratory of Bio-Inspired Materials and Interfacial Sciences Technical Institute of Physics and ChemistryChinese Academy of Sciences100190BeijingChina

Polymer-based circularly polarized luminescence(CPL)materials with the advantage of diversified structure,easy fabrication,high thermal stability,and tunable properties have garnered considerable ***,adequate and precise tuning over CPL in polymer-based materials remains challenging due to the difficulty in regulating chiral ***,visualized full-color CPL is achieved by doping red,green,and blue quantum dots(QDs)into reconfigurable blue phase liquid crystal elastomers(BPLCEs).In contrast to the CPL signal observed in cholesteric liquid crystal elastomers(CLCEs),the chiral 3D cubic superstructure of BPLCEs induces an opposite CPL ***,this effect is entirely independent of photonic bandgaps(PBGs)and results in a high glum value,even without matching between PBGs and the emission bands of ***,the lattice structure of the BPLCEs can be reversibly switched via mechanical stretching force,inducing on-off switching of the CPL signals,and these variations can be further fixed using dynamic disulfide bonds in the ***,the smart polymer-based CPL systems using the BPLCEs for anti-counterfeiting and information encryption have been demonstrated,suggesting the great potential of the BPLCEs-based CPL active materials.

关键词： circular quantum crystal

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Cr is not an acceptor in β−Ga2O3

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Physical Review materials 2025年第5期9卷 054606-054606页

作者： Cassandra Remple Benjamin L. Dutton Joel B. Varley John S. McCloy Matthew D. McCluskey Materials Science & Engineering Program Washington State University Pullman Washington 99164-2711 USA Department of Physics and Astronomy Washington State University Pullman Washington 99164-2814 USA Institute of Materials Research Washington State University Pullman Washington 99164-2711 USA Lawrence Livermore National Laboratory Livermore California 94551-0808 USA

The intensity of red Cr3+ photoluminescence (PL) in monoclinic gallium oxide (β−Ga2O3) is suppressed by n-type conductivity, an effect that has been attributed to a Cr deep acceptor level in the bandgap. In n-type material, such an acceptor level would be occupied, resulting in the Cr2+ oxidation state and the absence of Cr3+ PL. To test this model, n-type β−Ga2O3 crystals co-doped with Cr and Zr (a donor) were grown from the melt. The samples show Cr3+ optical absorption bands and a high free-electron concentration of 4×1018cm−3. If Cr were an acceptor, then it would be fully compensated and therefore would not exhibit the Cr3+ optical signature. Hybrid functional calculations indicate that Cr occupies the substitutional octahedral Ga(II) site and that the Cr2+ state is energetically unfavorable, i.e., Cr is not an acceptor. Weak Cr3+ PL was observed in the Cr/Zr co-doped samples. The quenching of PL may be caused by a transfer of energy to free electrons, a nonradiative process that would reduce the emission intensity.

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Skin Layer at the Actin-Gel Surface: Quenched Protein Membranes form Flat, Crumpled, and Tubular Morphologies

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Physical Review Letters 2004年第1期93卷 018101-018101页

作者： L. S. Hirst C. R. Safinya Materials & Physics Departments Biomolecular Science and Engineering Program University of California

We report the discovery of a hierarchically structured skin layer formed at the surface of an isotropic gel of filamentous actin bundles at high molar ratios of α-actinin, an actin cross-linker, to globular actin. Confocal microscopy has elucidated the full, micron scale 3D structure. The protein skin layer, composed of a directed network of bundles, exhibits flat, crumpled, tubelike and pleated multitubular morphologies, resulting from stresses due to the underlying gel. The skin layer, which readily detaches, constitutes a model anisotropic solid membrane with stress-induced, quenched disorder.

关键词： .actinin actin laments isotropic gel Skin Layer Protein Membranes network of bundles

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Phase selection during directional solidification of peritectic alloys

Phase selection during directional solidification of peritec...

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作者： Lograsso, T.A. Fuh, B.C. Trivedi, R. Materials and Engineering Physics Program Ames Laboratory Ames IA 50014 Ames Laboratory United States Department of Energy Materials Science and Engineering Iowa State University Ames IA 50011

Directional solidification studies have been conducted using Pb-Bi peritectic alloys over a wide range of compositions, temperature gradients, and growth velocities to characterize the primary α- to primary β-phase transitions, which have been observed at both very low and very high velocities. The critical conditions for these transitions correspond to the simultaneous growth of the α and β phases at or close to a single isotherm. The low velocity transition occurs under very specific conditions of composition, temperature gradient, and growth velocity. Since the transition conditions are composition dependent, they change continuously under terrestrial conditions where rejected solute is convectively mixed into the liquid. Detailed experimental studies have been carried out to examine the phase selection in the immediate vicinity of the critical velocity for the α to β transition, and the effect of convection on this transition is examined experimentally in the Pb-Bi system. The dynamic condition, at which both phases are present at the same isotherm, was shown to depend not only on velocities, temperature gradients, and bulk (nominal) alloy compositions, but also on the volume fractions of solid. A quantitative expression for the α- to β-phase transition condition was obtained by using the boundary layer model of fluid flow, which showed good agreement with the experimental results. It is shown that the transition occurs at the volume fraction where the bulk composition reaches the critical composition value predicted by the diffusive model. The modification in the microstructure map for the trailing planar or nonplanar β phase is discussed.

关键词： Lead alloys

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Microstructure-property relationships in ultra-hard AlMgB14

Microstructure-property relationships in ultra-hard AlMgB14

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2005 International Conference on Powder Metallurgy and Particulate materials, PowderMet 2005

作者： Peters, Justin S. Cook, Bruce A. Harringa, Joel L. Russell, Alan M. Kracher, Alfred Materials and Engineering Physics Program Ames Laboratory USDOE Ames IA 50011 United States Department of Materials Science and Engineering Iowa State University Ames IA 50011 United States

ISBN: (纸本)0976205726

AlMgB14 based composites have many potential applications in industry, but better understanding of the mechanisms responsible for high hardness and wear resistance is required for the implementation of this technology. This study was performed to determine if the results of electron probe microanalysis (EPMA) could be correlated with the observed variations in local hardness and toughness. The relationship between microstructure and hardness in AlMgB14 was investigated to improve the processing of this ultra-hard ceramic and its related composites. High-energy milling and subsequent hot-pressing of the powders produced dense composites with high hardness, but inconsistencies in powder processing and microstructure have led to variations in hardness. The morphology of the microstructure and distribution of O and Fe containing impurities were compared to the local hardness.

关键词： Microstructure

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Influence of DC hollow cathode H2 and CH4/H2 plasma processing conditions on the hydrophobic behavior of Carbon Fiber Paper used as Gas Diffusion Barrier Layer 20

Influence of DC hollow cathode H2 and CH4/H2 plasma processi...

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20th World Hydrogen Energy Conference, WHEC 2014

作者： Lumban, Carmencita Ramos, Henry Materials Science and Engineering Program College of Science University of the Philippines-Diliman Philippines Plasma Physics Laboratory National Institute of Physics University of the Philippines-Diliman Philippines

Significant improvement on the hydrophobicity of the Carbon Fiber Paper (CFP) Gas Diffusion Barrier Layer used in PEM Fuel Cell was achieved using DC Hollow Cathode Plasma Technique. Influence of the plasma processing conditions such as H2 and CH4/H2 gas mixture, gas flow rates, processing time, and discharge current were identified. To quantify the hydrophobicity, water contact angle (θw) measurements via sessile drop method were conducted. As-received untreated CFP and vacuum treated CFP formed no contact angle and both exhibited θw =0. After H2 plasma treatment at 50 sccm and 26 mA discharge, the CFP yield θw= 108.45°. At 50 sccm H2 flow rate and varying CH4 flow rate (5 sccm-20 sccm), measured θw values range from 107.71° to 137.25°. SEM images revealed etching of the CFP surface for the H2 treated samples. Partial etching and deposition effects were observed upon addition of CH4. This was attributed to the polymerization of hydrocarbon compounds accompanied by ion etching. AFM analysis revealed a significant difference between the surface rms roughness of the etched surfaces obtained with H2 only and CH4/H2 plasma. Using Micro-Raman Spectroscopy, intensity, position and FWHM of the D band peak at 1350 cm-1 and G band peak at 1585 cm-1 of the untreated CFP were compared against the plasma processed CFP substrates.

关键词： Hydrophobicity

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High temperature corrosion of materials in supercritical water and liquid lead-alloy environments

High temperature corrosion of materials in supercritical wat...

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Interfacial Electrochemistry and Chemistry in High Temperature Media - 212th ECS Meeting

作者： Sridharan, K. Chen, Y. Tan, L. Machut, M. Kruizenga, A. Ren, X. Allen, T.R. Department of Engineering Physics University of Wisconsin Madison United States Materials Science Program University of Wisconsin Madison United States

ISBN: (纸本)9781605603124

The Supercritical Water-cooled Reactor (SCWR) and Lead-cooled Fast Reactor (LFR) are among the six reactor concepts identified by the Generation IV initiative for the next generation nuclear reactors. materials degradation due to corrosion is a significant issue in both supercritical water and molten lead (-alloy) environments, particularly at the intended higher temperatures of application. In supercritical water, corrosion of ferritic and austenitic steels and Inconel alloys occurs mainly by the growth of an oxide layer on the surface. In molten lead (-alloy), corrosion can occur by dissolution of the material, oxidation, or by the penetration of liquid metal into the material primarily along the grain boundaries. Surface treatment of ferritic steels by the incorporation of thin film of oxidation-resistant materials has been shown to mitigate corrosion in these aggressive environments. Grain boundary engineering (GBE) reduces spallation of oxide layers in austenitic steels in supercritical water environment. © The Electrochemical Society.

关键词： Ferrite

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Numerical Analysis of QCW-Laser-Based Spot-Beam Crystallization of Si Films

Numerical Analysis of QCW-Laser-Based Spot-Beam Crystallizat...

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SID Symposium, Seminar, and Exhibition 2017, Display Week 2017

作者： Pann, Wenkai Song, Ruobing Suresh, Akhilesh K. Wong, Vernon K. Yu, Miao Choi, Insung Im, James S. Program in Materials Science and Engineering Department of Applied Physics and Applied Mathematics Columbia University New YorkNY United States

ISBN: (纸本)9781510848757

We are in the process of developing a new laser annealing method referred to as Spot-Beam Crystallization (SBC). The SBC method, which is potentially well suited for manufacturing advanced ultra-high-resolution AMOLED displays, is most effectively implemented using ultra-high- frequency quasi-continuous-wave (QCW) pulsed lasers. Conceptually and physically, this QCW-laser-based SBC (Q- SBC) approach builds on a thermally additive utilization of multiple short-lived ultra-high-frequency pulses, achieved via overlapped scanning of a small spot beam to incrementally and gradually heat and melt the beam-irradiated region. Using an updated version of a previously developed numerical program, we have carried out a simulation-based investigation to quantitatively examine and evaluate the basic tenets of the approach relevant specifically to partial-melting-based "ELA- like" crystallization of small-columnar-grained polycrystalline Si films using the Q-SBC method. The results from the effort to date as reported in this paper (1) largely confirm and validate the viability of the Q-SBC approach, and (2) suggest some specific directions for optimal development of the Q-SBC equipment and process. © 2017 SID.

关键词： Continuous wave lasers

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Epitaxial growth following crystal nucleation in laser-quenched Si filins on SiO2

Epitaxial growth following crystal nucleation in laser-quenc...

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2015 MRS Spring Meeting

作者： Wong, Vemon K. Chitu, A.M. Limanov, A.B. Im, James S. Program in Materials Science and Engineering Department of Applied Physics and Applied Mathematics Columbia University New YorkNY United States

ISBN: (纸本)9781510826267

We have investigated the solidified microstructure of nucleation-generated grains obtained via complete melting of Si films on SiO2 at high nucleation temperatures. This was achieved using a high-temperature-capable hot stage in conjunction with excimer laser irradiation. As predicted by the direct-growth model that considers (1) the evolution in the temperature of the solidifying interface and (2) the subsequent modes of growth (consisting of amorphous, defective, and epitaxial) as key factors, we were able to observe the appearance of "normal" grains that possess a single-crystal core area. These grains, which are in contrast to previously reported flower-shaped grains that fully make up the microstructure of the solidified films obtained via irradiation at lower preheating temperatures (and amongst which these "normal" grains emerge), indicate that epitaxial growth of nucleated crystals must have taken place within the grains. We discuss the implications of our findings regarding (1) the validity of the direct-growth model, (2) the nature of the heterogeneous nucleation mechanism, and (3) the alternative explanations and assumptions that have been previously employed in order to explain the microstructure of Si films obtained via nucleation and growth within the complete melting regime. © 2015 materials Research Society.

关键词： Silica

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Spectral evolution of nonlinear excitations in a quasi-one-dimensional charge density wave material

Spectral evolution of nonlinear excitations in a quasi-one-d...

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Laser Science, LS_2019

作者： Kim, S.S. Leicht, J.A. Dexheimer, S.L. Materials Science and Engineering Program Department of Physics and Astronomy Washington State University PullmanWA99164-2814 United States

We follow the spectral evolution and vibrational dynamics as an initially generated exciton in a quasi-one-dimensional charge density wave system localizes and then undergoes charge transfer to form a soliton/antisoli... 详细信息

ISBN: (纸本)9781943580675

关键词： Charge transfer

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