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排序方式: 共有574条查询结果,搜索用时 46 毫秒
81.
Michele Serri Giuseppe Cucinotta Lorenzo Poggini Giulia Serrano Philippe Sainctavit Judyta Strychalska-Nowak Antonio Politano Francesco Bonaccorso Andrea Caneschi Robert J. Cava Roberta Sessoli Luca Ottaviano Tomasz Klimczuk Vittorio Pellegrini Matteo Mannini 《Advanced materials (Deerfield Beach, Fla.)》2020,32(24):2000566
Magnetic crystals formed by 2D layers interacting by weak van der Waals forces are currently a hot research topic. When these crystals are thinned to nanometric size, they can manifest strikingly different magnetic behavior compared to the bulk form. This can be the result of, for example, quantum electronic confinement effects, the presence of defects, or pinning of the crystallographic structure in metastable phases induced by the exfoliation process. In this work, an investigation of the magnetism of micromechanically cleaved CrCl3 flakes with thickness >10 nm is performed. These flakes are characterized by superconducting quantum interference device magnetometry, surface-sensitive X-ray magnetic circular dichroism, and spatially resolved magnetic force microscopy. The results highlight an enhancement of the CrCl3 antiferromagnetic interlayer interaction that appears to be independent of the flake size when the thickness is tens of nanometers. The estimated exchange field is 9 kOe, representing an increase of ≈900% compared to the one of the bulk crystals. This effect can be attributed to the pinning of the high-temperature monoclinic structure, as recently suggested by polarized Raman spectroscopy investigations in thin (8–35 nm) CrCl3 flakes. 相似文献
82.
83.
Vaz Isabela C. F. Macchi Carlos Eugenio Somoza Alberto Rocha Leandro S. R. Longo Elson Cabral Luis da Silva Edison Z. Simões Alexandre Zirpoli Zonta Giulia Malagù Cesare Desimone P. Mariela Ponce Miguel Adolfo Moura Francisco 《Journal of Materials Science: Materials in Electronics》2022,33(15):11632-11649
Journal of Materials Science: Materials in Electronics - This study reports the electrical properties of Nd-doped cerium oxide (CeO2) films synthesized by microwave assisted hydrothermal using a... 相似文献
84.
85.
Paolo Massimo Buscema Giulia Massini Marco Fabrizi Marco Breda Francesca Della Torre 《Computational Intelligence》2018,34(1):310-344
This research has 6 fundamental aims: (i) to present a modified version of Taylor's interpolation, one that is more effective and faster than the original; (ii) outline the capability of artificial neural networks (ANNs) to perform an optimal functional approximation of the digital elevation model reconstruction from a satellite map, using a small and independent sample of Global Positioning System observations; (iii) demonstrate experimentally how ANNs outperform the traditional and most used algorithm for the height interpolation (Taylor's interpolation); (iv) introduce a new ANN, the Conic Net, able to outperform the results of the classic and more known multilayer perceptron; (v) determine that Conic Nets, even when using Taylor's modified interpolation as input features, are able to optimally approximate the heights with one order of magnitude more than the original satellite map; and (vi) make evident the possibility to interpolate the DEM heights through an ANN, which learns a data set of known points. 相似文献
86.
Battistuzzi G Borsari M Di Rocco G Leonardi A Ranieri A Sola M 《Chembiochem : a European journal of chemical biology》2005,6(4):692-696
The L12E, L12K, Q88E, and Q88K variants of spinach plastocyanin have been electrochemically investigated. The effects of insertion of net charges near the metal site on the thermodynamics of protonation and detachment from the copper(I) ion of the His87 ligand have been evaluated. The mutation-induced changes in transition enthalpy cannot be explained by electrostatic considerations. The existence of enthalpy/entropy (H/S) compensation within the protein series indicates that solvent-reorganization effects control the differences in transition thermodynamics. Once these compensating contributions are factorized out, the resulting modest differences in transition enthalpies turn out to be those that can be expected on purely electrostatic grounds. Therefore, this work shows that the acid transition in cupredoxins involves a reorganization of the H-bonding network within the hydration sphere of the molecule in the proximity of the metal center that dominates the observed transition thermodynamics and masks the differences that are due to protein-based effects. 相似文献
87.
Mixed‐Conducting Perovskites as Cathode Materials for Protonic Ceramic Fuel Cells: Understanding the Trends in Proton Uptake
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Reihaneh Zohourian Rotraut Merkle Giulia Raimondi Joachim Maier 《Advanced functional materials》2018,28(35)
The proton uptake of 18 compositions in the perovskite family (Ba,Sr,La)(Fe,Co,Zn,Y)O3‐δ, perovskites, which are potential cathode materials for protonic ceramic fuel cells (PCFCs), is investigated by thermogravimetry. Hydration enthalpies and entropies are derived, and the doping trends are explored. The uptake is found to be largely determined by the basicity of the oxide ions. Partial substitution of Zn on the B‐site strongly enhances proton uptake, while Co substitution has the opposite effect. The proton concentration in Ba0.95La0.05Fe0.8Zn0.2O3‐δ is found to be 10% per formula unit at 250 °C, 5.5% at 400 °C, and 2.3% at 500 °C, which are the highest values reported so far for a mixed‐conducting perovskite exhibiting hole, proton, and oxygen vacancy transport. A comprehensive set of thermodynamic data for proton uptake in (Ba,Sr,La)(Fe,Co,Zn,Y)O3‐δ is determined. Defect interactions between protons and holes partially delocalized from the B‐site transition metal to the adjacent oxide ions decrease the proton uptake. From these results, guidelines for the optimization of PCFC cathode materials are derived. 相似文献
88.
Nanoporous Si as an efficient thermoelectric material 总被引:1,自引:0,他引:1
Room-temperature thermoelectric properties of n-type crystalline Si with periodically arranged nanometer-sized pores are computed using a combination of classical molecular dynamics for lattice thermal conductivity and ab initio density functional theory for electrical conductivity, Seebeck coefficient, and electronic contribution to the thermal conductivity. The electrical conductivity is found to decrease by a factor of 2-4, depending on doping levels, compared to that of bulk due to confinement. The Seebeck coefficient S yields a 2-fold increase for carrier concentrations less than 2 x 10(19) cm(-3), above which S remains closer to the bulk value. Combining these results with our calculations of lattice thermal conductivity, we predict the figure of merit ZT to increase by 2 orders of magnitude over that of bulk. This enhancement is due to the combination of the nanometer size of pores which greatly reduces the thermal conductivity and the ordered arrangement of pores which allows for only a moderate reduction in the power factor. We find that while alignment of pores is necessary to preserve power factor values comparable to those of bulk Si, a symmetric arrangement is not required. These findings indicate that nanoporous semiconductors with aligned pores may be highly attractive materials for thermoelectric applications. 相似文献
89.
Friddle RW Lemieux MC Cicero G Artyukhin AB Tsukruk VV Grossman JC Galli G Noy A 《Nature nanotechnology》2007,2(11):692-697
Carbon nanotubes display a consummate blend of materials properties that affect applications ranging from nanoelectronic circuits and biosensors to field emitters and membranes. These applications use the non-covalent interactions between the nanotubes and chemical functionalities, often involving a few molecules at a time. Despite their wide use, we still lack a fundamental understanding and molecular-level control of these interactions. We have used chemical force microscopy to measure the strength of the interactions of single chemical functional groups with the sidewalls of vapour-grown individual single-walled carbon nanotubes. Surprisingly, the interaction strength does not follow conventional trends of increasing polarity or hydrophobicity, and instead reflects the complex electronic interactions between the nanotube and the functional group. Ab initio calculations confirm the observed trends and predict binding force distributions for a single molecular contact that match the experimental results. Our analysis also reveals the important role of molecular linkage dynamics in determining interaction strength at the single functional group level. 相似文献