Papers by Keyword: Monolayer

Abstract: Bilayer graphene has been widely studied in recent years due to its intriguing physical properties and potential engineering applications. Here, we report on the stability measurements of isotope-labeled bilayer graphene with different stacking sequences. The results showed evidence of different defect intensity after the Ar plasma treatment. We found that the AB stacked bilayer graphene shows better stability when compared to twisted bilayer and monolayer graphene. However, for the protection of the under layer graphene, the twisted bilayer graphene showed better results. Our work demonstrates that the stability of bilayer graphene strongly depends on the layer stacking sequence.

Abstract: Recently, two-dimensional (2D) material developed rapidly and provided a wide application on the anode of the batteries, reducing the adverse effect of traditional ion batteries such as low capacity, short cycle life, slow charging and poor safety mainly coming from the use of graphite anode. The current report investigates the anode performances of phosphorus, a new 2D material in electrochemistry field, with monolayer and bilayer structure for Li ion batterys (LIBs) through density functional theory (DFT) calculations and gives a comparison on the Li ion valences, binding energies and open-circuit voltages between the two structures. The results indicate that bilayer phosphorus perform better as a novel anode due to the stronger adhesion to Li and lower barrier for ion diffusion. Furthermore, our research results illustrate a broad application prospect on the new anode inventions as well as reducing useless consumption on the batteries by the practice of bilayer phosphorus anode.

Abstract: In this study, We demonstrate mono and few layers MoS₂ samples on the SiO₂(270nm)/Si substrate from bulk MoS₂ crystal by micromechanical exfoliation technique. We have systematically studied Atomic Force Microscopy, Raman and PL properties of mono and few layer MoS₂ on the SiO₂(270nm)/Si substrate. First, we find that the number of layer values dependent the Raman and PL emission. First, Raman intensity area ratio of the MoS₂ E¹_2g, A_1g and 2LA modes to that area of the Si substrate increased linear with increasing number of layers MoS₂. Second, Normalized PL intensity area of the (A) peak decreased linear with increasing number of layers MoS₂. The value of those graphs is a method to understand the number of layers the exfoliated MoS₂.

Abstract: There is the need to determine the process capability of available and novel carbon fibre (CF) roving with minimal material and reproducible procedures in the field of research and development of continuous fibre reinforced composites and structural components, as well as to identify the power delivery in thermoplastic laminate constructions. The innovative TFW procedure with the appropriate system technology allows the production of piece size variable unidirectional (UD) prepreg in a continuous sequential process of spiral winding. A flexible surface design, resulting in the partial fixation of a single highly spread CF roving on fine nonwoven fabric. By defined accumulating of composite components, the fibre volume content (FVC) is adjustable and correspond to the level of spreading and to the grammage of nonwoven fabric. Minimum single layer thickness promote compound homogeneity and thereby allow the generation of greatest possible degrees of freedom in load-oriented structural design of CF-reinforced thermoplastic lightweight products in the laboratory staff.

Abstract: Influence of Fe-Si-Al-C alloy cooling rate on its phase composition, structure and microhardness is shown based on metallographic investigations, electron microscopy and x-ray diffraction analysis. It was determined that the structure will change from dendrite to grained, size of structure elements will decrease, quantity and size of secondary phases precipitations will decrease when cooling rate changes from 103 to 107 K/s. The metastable phases such as primary ferrite, austenite and complex carbides are formed in cooling rate range. The volume ratio of main phases changes in favor of primary ferrite with cooling rate increasing. Hardening of the material occurs more than twice. Hardening is due to the interaction of solid-solution hardening, grain boundary hardening and dispersive hardening by secondary phases particles. The maximum hardening is achieved during formation of the alloy in molten pool at electron-beam melting. The alloy in this case contains 80 vol. % of austenite with dendrite similar structure and precipitations of carbide and silicocarbide phases. It can be assumed than such structure will be formed from the alloy with investigated composition at additive manufacturing.

Abstract: As an oxidized form of graphene, graphene oxide has a variety of oxygen-containing groups together with a laminar structure, showing great potential in various engineering applications. In this work, on the basis of the top-down fabrication principle, superhydrophilic graphene oxide nanosheets with a uniform sheet size of ~50 nm diameter and 0.7 nm thickness were prepared by the modified Hummers method, and using microcrystalline graphite as the carbon source. After chemical oxidation, the obtained graphene oxide nanosheets had a great amount of C-O-C, C-OH and C=O groups and its water contact angle was ~3.9°. This result offers a facile strategy to fabricate superhydrophilic and monolayer graphene oxide nanosheets with well-defined morphology.

Abstract: We investigated the change of optical second harmonic generation (SHG) intensity during In/Si (111) interface formation. It was proved that Si (111)2×2-In reconstruction is formed by one monolayer of In on silicon surface.

Abstract: Water/toluene interfacial self-assembly of nanostructures is a powerful bottom-up approach for film fabrication because of the low cost and high efficiency, and it is a simple and universal method for almost all low-dimensional nanostructures. The method involved adding alcohol and then toluene (here the dispersant was itself alcohol, only toluene was added) into SiO₂ nanoparticle dispersion, and then a large quantity of distilled water was rapidly poured into the mixed system. Simultaneously, nanoparticles in the dispersion were extracted to the water/toluene interface, forming a thin film with a nearly perfect hexagonal close packed phase. Large-area nanoparticle monolayer films (e.g., more than 20 cm²) could be prepared in less than 1 min. The close-packed structures of these thin films were verified by a field emission scanning electron microscopy (FESEM, Hitachi S-4800, Japan). We also investigated the whole process of forming the films and found out the mechanism of water-induced interfacial assembly. As for the specific kinetic mechanism of the fabrication process, it is expected to further study in later time.

Abstract: The Ag nanoparticles was prepared by reduction of silver nitrate with sodium citrate, and the APS monolayers was self-assembled with 3-Aminopropyltrimethoxysilane (APS) on the monocrystalline silicon surface. Then, Ag/APS molecular self-assembled film was formed with Ag nanoparticles and APS membrane by liquid method. The chemical structure and morphology of the Ag nanoparticles and self-assembled film were investigated by AFM, XRS and IR. Meanwhile, the friction performances of self-assembled film was also investigated. The results shown that the Ag nanoparticle have the morphology of spherical particles with an average particle size of ca. 65 nm in diameter which were successful assembled on the surface of APS film and partially oxidized into Ag₂O. The friction coefficient of the Ag-APS molecular self-assembled film has been decreased with the assembled time extened while the wear rate has improved.

Abstract: ~50 μm single crystal graphene with hexagonal flower shape was synthesized on copper foils by low pressure chemical vapor deposition (LPCVD). The strong influence of Cu foils annealing on suppressing the nucleation of graphene was observed. Scanning electron microscopy (SEM), Optical microscopy (OM), and Raman spectrum showed that single crystal graphene as grown was monolayer with high quality. Suppressing nucleation through an annealing procedure offers an promising way to grow large-scale single crystal graphene controllably.