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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]

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.

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]