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The graphene microchannel heat sinks have attracted extensive attention due to its high cooling efficiency in microelectric devices. The interfacial thermal resistance (ITR) between graphene as the bottom layer of microchannel and water is one of the key factors of its good working performance. In this paper, the impacts of structure defects in graphene surfaces on ITR of the graphene–water interface are investigated using molecular dynamic simulations. The results indicate that graphene layer with different types of structure defects shows different variation trends of ITR as the defect concentration or temperature increases. A peak ITR reduction of nearly 30% is generated with the Stone‐Wales defect of 2%. Finally, the density of phonon states and interfacial binding energy analysis are performed to verify the correctness of the simulation results. The present work expands the understanding of structure defects effect on thermal transport in graphene microchannel. [ABSTRACT FROM AUTHOR]

Radiation effects at cryogenic temperature are investigated in two radiation-tolerant Fluorine-doped single-mode fibers originating from two different manufacturers. This paper presents measurements at room temperature (297 K) and at cryogenic temperature (16 K) of the radiation induced attenuation at 1312 nm and 1570 nm for both fibers. In addition to the massive increase of the optical attenuation at 16 K, the fiber is found to be in a frozen state where thermal bleaching and defect recombination no longer occurs. However, a long-term recovery, including the heating of the fiber from cryogenic temperature to room temperature, anneals a large amount of the defects created and brings the fiber back to almost its initial performance. [ABSTRACT FROM PUBLISHER]

Introduction. The main work objective is systematization and analysis of structural defects of vacuum ion-plasma coatings; on this basis, their classification principles are developed and given in the paper. Another important part of the work is the experimental study on one of the specific defects of coatings, which the authors propose to call “defect of substructural origin”.Materials and Methods. PVD coatings of various nitride and metal systems 1.5-9.0 μm thick were used as an object of the research. Coatings were applied in vacuum installations using arc and magnetron evaporators. The research results were obtained by high resolution electron microscopy, energy dispersive analysis and indentation.Results. Various types of defects in ion-vacuum coatings are presented as the research results. They include discontinuities, deformation of crystallites, and structural inhomogeneity. The principles of their systematization are validated. It is proposed to classify defects into droplet, substructural, and growth defects (depending on the causes of their nucleation), as well as regular and stochastic ones (depending on their distribution in the coating volume). The study of “substructural defects”, classified by the authors as stochastic, is given special consideration. These micrometric defects are shaped like a cylinder with a conical “head”. Their main axle is oriented perpendicular to the surface of the coating. They can be “extruded” (tore away) by the coating. The paper validates the dislocation mechanism of their nucleation and the helicoid growth principle. Conclusions. The inference is summarized that the proposed systematization of defects in ion-plasma coatings has the character of an intermediate result of research in this scientific area. At this, the “substructural defects” do not have a fatal effect on the structure and properties of the coating due to a small size.

In the investigations reported in this paper, focus is made on structure defects in a triple compoundsemiconductor ZnGeP. The effects of secondary-phase inclusions (ZnP) on optical material characteristics are demonstrated. The variation in the positions of dislocation chains and single dislocations in the bulk of ZnGeP is addressed. [ABSTRACT FROM AUTHOR]

Abstract The graphene microchannel heat sinks have attracted extensive attention due to its high cooling efficiency in microelectric devices. The interfacial thermal resistance (ITR) between graphene as the bottom layer of microchannel and water is one of the key factors of its good working performance. In this paper, the impacts of structure defects in graphene surfaces on ITR of the graphene–water interface are investigated using molecular dynamic simulations. The results indicate that graphene layer with different types of structure defects shows different variation trends of ITR as the defect concentration or temperature increases. A peak ITR reduction of nearly 30% is generated with the Stone‐Wales defect of 2%. Finally, the density of phonon states and interfacial binding energy analysis are performed to verify the correctness of the simulation results. The present work expands the understanding of structure defects effect on thermal transport in graphene microchannel.

High-entropy quasicrystals contain both multiple principal alloying elements and complex crystal structures, in contrast to usual high-entropy alloys that have simple crystal structures; however, microstructures of high-entropy quasicrystal-related phases have seldom been revealed. In this paper, we report complex domains of approximants of high-entropy decagonal quasicrystal (HE-DQC) in Al 20 Si 20 Mn 20 Fe 20 Ga 20 alloy, investigated by spherical aberration-corrected scanning transmission electron microscopy at atomic-level resolution. Importantly, a phase transition from HE-DQC to a (1/0, 2/1)–type orthorhombic approximant, with a = 0.73 nm, b = 1.23 nm, c = 2.24 nm, was revealed. We found that multi-point nucleations and growth of the oriented hexagonal structural blocks and phason flips of the basic structural blocks lead to this phase transition. This study benefits understanding of the formation of periodic structures in HE-DQC. • Complex domains in Al 20 Si 20 Mn 20 Fe 20 Ga 20 alloy were studied by spherical aberration-corrected STEM. • A phase transition from HE-DQC to (1/0, 2/1) orthorhombic approximant was revealed. • The multi-point nucleations, growth, and phason flips lead to the phase transition. [ABSTRACT FROM AUTHOR]

Adsorption‐based cooling is an energy‐efficient renewable‐energy technology that can be driven using low‐grade industrial waste heat and/or solar heat. Here, we report the first exploration of fluorocarbon adsorption using porous covalent organic polymers (COPs) for this cooling application. High fluorocarbon R134a equilibrium capacities and unique overall linear‐shaped isotherms are revealed for the materials, namely COP‐2 and COP‐3. The key role of mesoporous defects on this unusual adsorption behavior was demonstrated by molecular simulations based on atomistic defect‐containing models built for both porous COPs. Analysis of simulated R134a adsorption isotherms for various defect‐containing atomistic models of the COPs shows a direct correlation between higher fluorocarbon adsorption capacities and increasing pore volumes induced by defects. Combined with their high porosities, excellent reversibility, fast kinetics, and large operating window, these defect‐containing porous COPs are promising for adsorption‐based cooling applications. [ABSTRACT FROM AUTHOR]

A series of Ce‐Mn‐Ox catalysts synthesized under different hydrothermal conditions were evaluated by catalytic removal of toluene. The results of characterization showed that the contents of oxygen vacancies and active species in catalysts were crucial for the catalytic oxidation process. The concentration of Ce3+, Mn3+, and adsorbed oxygen associated with structural defects in Ce‐Mn‐Ox catalysts could be controlled by hydrothermal conditions, which were considered to promote redox capacity and improve catalytic oxidation performance. In addition, suitable synthetic conditions could increase the SBET and Vp of catalysts. Among the prepared catalysts, CM‐100 showed the best catalytic performance due to the generation of more defective oxygen and active species (Ce3+, Mn3+, and surface‐adsorbed oxygen). In addition, the CM‐100 catalyst showed satisfactory water resistance and stability. [ABSTRACT FROM AUTHOR]

To understand the relation between different nanostructures and thermal properties, a simple yet effective model is in demand for characterizing the underlying phonons and electrons scattering mechanisms. Herein, we make a systematic review on the newly developed thermal reffusivity theory. Like electrical resistivity which has been historically used as a theory for analyzing structural domain size and defect levels of metals, the thermal reffusivity can also uncover phonon behavior, structure defects and domain size of materials. We highlight that this new theory can be used for not only metals, but also nonmetals, even for amorphous materials. From the thermal reffusivity against temperature curves, the Debye temperature of the material and the ideal thermal diffusivity of single perfect crystal can be evaluated. From the residual thermal reffusivity at the 0 K limit, the structural thermal domain (STD) size of crystalline and amorphous materials can be obtained. The difference of white hair and normal black hair from heat conduction perspective is reported for the first time. Loss of melanin results in a worse thermal protection and a larger STD size in the white hair. By reviewing the different variation of thermal reffusivity against decreasing temperature profiles, we conclude that they reflected the structural connection in the materials. Ultimately, the future application of thermal reffusivity theory in studying 2D materials and amorphous materials is discussed. [ABSTRACT FROM AUTHOR]

Nanocrystalline Li1.14Ni0.18Mn0.62O2 cathode materials are synthesized by a molten salt method using KCl as the molten agent. The influence of the sintering temperature and the mass ratio of KCl to Li1.14Ni0.18Mn0.62O2 on the structure and electrochemical performance are investigated. The sintering temperature can markedly affect the formation of the layered structure and the content of stacking faults. The amount of KCl influences the cation ordering of the materials. The ratios of Li+/Ni2+ replacement for the materials obtained at 800 °C with a KCl amount of R=4, 8, and 12 [ R= m(KCl)/ m(Li1.14Ni0.18Mn0.62O2)] are 16.51, 8.39, and 4.46 %, respectively. A lower steric hindrance-related to a better cationic ordering-is obtained when the amount of KCl is increased, which is in agreement with the tendency of the Li+ diffusion coefficient. This study demonstrates a new approach to control the Li+/Ni2+ replacement in lithium-rich layered cathode materials to improve their electrochemical performance. [ABSTRACT FROM AUTHOR]

The present study deals with how stochastic stackings of tetrahedral/octahedral phengitic sheets bearing diverse cation distributions affect diffraction signals and the structural inferences therefrom derived. The interest for such minerals is dictated by that the stability of phengite polytypes, their cation distributions and P/ T conditions of crystallization are related to each other. We focus our attention on layers' probabilistic sequences that preserve the topology of the polytypes 2 M(SG: C2/ c) and 3 T(SG: P312). Neutron diffraction intensities are modelled by a Monte Carlo approach and then used as artificial experimental data for conventional structure refinements that yield the occupancy factors in the fourfold (Si, Al) and sixfold (Al, Mg) coordination sites of 2 M and 3 T. The cation ordering from structure refinement tallies with the one of the 'average structure' of a stochastic stacking, but it can significantly differ from those of the individual tetrahedral/octahedral sheets. For instance, sheets having ordered cation arrangements can lead to a stochastic structure which is supposed to bear a fully disordered cation partitioning according to structure refinement. This affects the configuration entropy contributions: the values obtained by conventional refinements can deviate from the correct ones up to 30 %. The analysis of the equivalent reflection intensities brings to light the anomalies hinting at the occurrence of such stacking disorder (using modelled reflections, the mean ratio between standard deviation and average intensity of symmetry equivalent reflections is ideally 0 for perfect crystal structures, but it can amount up to 6 in stochastically disordered phengites). However, taking into account the instrumental uncertainties and the deviations from ideality of actual crystals, such phenomena are very difficult to be detected experimentally. [ABSTRACT FROM AUTHOR]

The spectra of optical absorption, luminescence excitation and photoluminescence in the range of 200-750 nm in the Cu-Cd-photochromic glasses were measured. As a matrix of photochromic glass the sodium-borosilicate glass was used. The absorption within the UV wavelength range (200-300 nm) is connected to various structural defects of the matrix glass. The changes of the optical absorption and photoluminescence excitations resulting from the UV radiation in the Cu-Cd-photochromic glasses have been analysed. It was noticed the share of the matrix glass structure components in creation of the colour centers stable of room temperature. [ABSTRACT FROM AUTHOR]