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Enhancing the oxidation resistance of nanocrystalline high-entropy AlCuCrFeMn alloys by the addition of tungsten by Sheetal Kumar Dewangan;Devesh Kumar; Ashutosh Sharma;Byungmin Ahn;Vinod Kumar Journal of Materials Research and Technology-JMR&T 2022, 21(0); https://doi.org/10.1016/j.jmrt.2022.11.078 Abstract The isothermal oxidation behavior of multi-component high entropy alloys (HEAs), namely AlCuCrFeMn, AlCuCrFeMnW0.05, AlCuCrFeMnW0.1, and AlCuCrFeMnW0.5, was investigated and the behavior of the oxide layer was analyzed. All four HEAs were synthesized via mechanical alloying (MA) and consolidated by spark plasma sintering (SPS). The samples were oxidized in the air atmosphere at a temperature of 500 °C for 50 h. Based on the thermogravimetric result, the oxidation rate of the materials decreased with the increase of W content, and the values of parabolic constants were on a level similar to those observed in Ni–Al superalloys. However, higher content of W improves the continuity and internal position of the WO3 scale, which leads to increased oxidation resistance. Throughout the oxidation process, the composition of the phases of all materials changed significantly. The triple-thick oxide layer formed of Al2O3, Cr2O3, and WO3, developed in HEAs, has been carefully studied using the XPS technique. Keywords: High-entropy alloyOxide resistanceNanocrystallinePowder metallurgy
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Quasiresonant diffusion of wave packets in one-dimensional disordered mosaic lattices by Ba Phi Nguyen;Duy Khuong Phung;Kihong Kim Physical Review B 2022, 106(13); https://doi.org/10.1103/PhysRevB.106.134204 Abstract We investigate numerically the time evolution of wave packets incident on one-dimensional semi-infinite lattices with mosaic modulated random on-site potentials, which are characterized by the integer-valued modulation period κ and the disorder strength W. For Gaussian wave packets with the central energy E0 and a small spectral width, we perform extensive numerical calculations of the disorder-averaged time-dependent reflectance, 〈R(t)〉, for various values of E0, κ, and W. We find that the long-time behavior of 〈R(t)〉 obeys a power law of the form t−γ in all cases. In the presence of the mosaic modulation, γ is equal to 2 for almost all values of E0, implying the onset of the Anderson localization, while at a finite number of discrete values of E0 dependent on κ, γ approaches 3/2, implying the onset of the classical diffusion. This phenomenon is independent of the disorder strength and arises in a quasiresonant manner such that γ varies rapidly from 3/2 to 2 in a narrow energy range as E0 varies away from the quasiresonance values. We deduce a simple analytical formula for the quasiresonance energies and provide an explanation of the delocalization phenomenon based on the interplay between randomness and band structure and the node structure of the wave functions. We explore the nature of the states at the quasiresonance energies using a finite-size scaling analysis of the average participation ratio and find that the states are neither extended nor exponentially localized, but critical states.
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Development of the adaptive pattern synthesis method for accurate structured illumination by InYoung Park;Jonghee Yoon Optics and Lasers in Engineering 2022, 161(0); https://doi.org/10.1016/j.optlaseng.2022.107342 Abstract Structured illumination, which projects a predefined spatially varying intensity pattern, has been widely used in a variety of applications, including 3D shape estimation, optical property estimation, and super-resolution imaging. The precision of the structured illumination method is determined by the accuracy of the illumination pattern captured by the detector; however, acquiring images of the precise pattern is difficult due to distortion and nonlinear response in the imaging system. We proposed an adaptive pattern synthesis method that could overcome projecting system distortion and the system's nonlinear response. The proposed method consists of four steps: estimation of the geometric transformation matrix between the structured illumination unit and detector, estimation of the detector's intensity lookup table, and synthesis of the corrected patterns. Furthermore, by measuring the 3D printed target and tissue-mimicking phantom, the proposed method demonstrated its ability to improve the accuracy of phase shift profilometry and spatial frequency domain imaging. It does not require fine alignment or optical system details because all procedure is performed by projecting digital patterns and its measurement without calibration targets. The proposed method could be applied to any optical technique that uses structured illumination to improve accuracy and performance, making it useful in both academic and industrial applications. Keywords Structured illuminationSpatial frequency domain imagingPhase shift profilometryAdaptive opticsPattern correction
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Surface activated zinc-glutarate for the copolymerization of CO2 and epoxides by Yongmoon Yang;Jong Doo Lee;Yeong Hyun Seo;Ju-Hyung Chae;Sohee Bang;Yeon-Joo Cheong;Bun Yeoul Lee;In-Hwan Lee;Seung Uk Son;Hye-Young Jang Dalton Transactions 2022, 51(0); https://doi.org/10.1039/D2DT03007A Abstract Zinc-glutarate (ZnGA) is a promising catalyst that can form polymers from CO2 and epoxides, thereby contributing to the development of CO2 utilization technologies and future sustainability. One of the obstacles to commercializing ZnGA in polymer industries is its low catalytic activity. In this study, we introduced activated two-dimensional (2D) ZnGA to improve its catalytic activity in polymerization. The morphology-controlled 2D ZnGA was treated with H3Co(CN)6, and a porous granular-type Co-modified ZnGA (Co-ZnGA) was prepared. The morphology of 2D ZnGA is a prerequisite for the activation by H3Co(CN)6. The catalytic properties of Co-ZnGA were evaluated by copolymerization of various epoxides and CO2, and exhibited catalytic activity of 855, 1540, 1190, and 148 g g-cat−1 with propylene oxide, 1,2-epoxyhexane, 1,2-epoxybutane, and styrene oxide, respectively. This study provided a new strategy using 2D ZnGA instead of conventional ZnGA for increasing the catalytic activity in CO2 polymerization.
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Recent defect passivation drifts and role of additive engineering in perovskite photovoltaics by Ali Hassan;Zhijie Wang, Yeong Hwan Ahn;Muhammad Azam;Abbas Ahmad Khan;Umar Farooq;Muhammad Zubair;Yu Cao Nano Energy 2022, 101(0); https://doi.org/10.1016/j.nanoen.2022.107579 Abstract Rapid progress in the efficiency of hybrid lead halide perovskite photovoltaics surpassed the semiconductor thin-film solar cells such as CdTe (cadmium telluride), CZTS (copper zinc tin sulfide), and CIGS (copper indium gallium selenide) within a decade. Furthermore, low-cost solution processibility demonstrated the immense potential of perovskite solar cells (PSCs) as an alternative to commercially available light-harvesting materials. Despite the fast-track development in perovskite photovoltaic technology, several drawbacks are mainly linked with defects, including undercoordinated ions, band offsets, grain boundaries, photocurrent hysteresis, and environmental instability: restraint the industrialization of perovskite photovoltaics. Herein, we present the comprehensive knowledge of the source, nature, correlation with photophysical properties, and overlapping effects of these defects. The defects are categorized based on their energy levels within the conduction and valence bands, such as deep or shallow level defects, and their dimensionality (e.g., point defects such as vacancies, dislocation, grain boundaries, and cracks are regarded as zero-, one-, two-, and three-dimensional defects). Furthermore, we developed the fundamental understanding of defect-mediated, nonradiative recombination, ion migration, carrier trapping, and their cross-link with device performance and photocurrent hysteresis. Besides, an overview of topical defect passivation strategies on perovskite absorber, materials interface, charge transport layers, surface passivation, contact passivation, and additive engineering has been spotlighted. Finally, based on past and present defect healing drifts, we have summarized and recommended suggestions for next-generation PSCs, which will pave the way for swift industrialization. Keywords Perovskite solar cellsEnergy harvestingAdditive engineeringDefect passivationPhotovoltaics
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Acceleration of Singlet Oxygen Evolution by Superoxide Dismutase Mimetics in Lithium–Oxygen Batteries. by Joo-Eun Kim;Hyun-Wook Lee;Won-Jin Kwak Advanced Functional Materials 2022, 32(52); https://doi.org/10.1002/adfm.202209012 Abstract Side reactions caused by reactive oxygen species (e.g., superoxide and singlet oxygen) are limiting factors in the lithium–oxygen batteries (LOBs). Superoxide dismutase mimetics (SODms), which suppress superoxide-triggered side reactions by accelerating the disproportionation reaction during discharge, are introduced as soluble additives in the LOBs. However, although SODms promote the disproportionation reaction, which is the main pathway for singlet oxygen evolution, the correlation between SODms and singlet oxygen has not been verified. Here, 4-carboxy-TEMPO is selected as a representative SODm that effectively promotes the disproportionation reaction and chemically verifies acceleration of singlet oxygen evolution. Furthermore, by using quencher, it is reported that the release of singlet oxygen evolved by the SODm is decreased. Because this study closely examines the relationship between the additives and singlet oxygen, it is believed that this study provides an important reference for the development of additives for the practical application of LOBs.
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[논문] Sheetal Kumar Dewangan - Enhancing the oxidation resistance of nanocrystalline high-entropy AlCuCrFeMn alloys by th 위치 확인