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1
Woellner, Cristiano Francisco, Pedro Alves da Silva Autreto i Douglas S. Galvao. "One Side-Graphene Hydrogenation (Graphone): Substrate Effects". MRS Advances 1, nr 20 (2016): 1429–34. http://dx.doi.org/10.1557/adv.2016.196.
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ABSTRACTRecent studies on graphene hydrogenation processes showed that hydrogenation occurs via island growing domains, however how the substrate can affect the hydrogenation dynamics and/or pattern formation has not been yet properly investigated. In this work we have addressed these issues through fully atomistic reactive molecular dynamics simulations. We investigated the structural and dynamical aspects of the hydrogenation of graphene membranes (one-side hydrogenation, the so called graphone structure) on different substrates (graphene, few-layers graphene, graphite and platinum). Our results also show that the observed hydrogenation rates are very sensitive to the substrate type. For all investigated cases, the largest fraction of hydrogenated carbon atoms was for platinum substrates. Our results also show that a significant number of randomly distributed H clusters are formed during the early stages of the hydrogenation process, regardless of the type of substrate. These results suggest that, similarly to graphane formation, large perfect graphone-like domains are unlikely to be formed. These findings are especially important since experiments have showed that cluster formation influences the electronic transport properties in hydrogenated graphene.
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Murav’ev, V. V., i V. M. Mishchenka. "Ab-initio simulation of hydrogenated graphene properties". Doklady BGUIR 19, nr 8 (1.01.2022): 5–9. http://dx.doi.org/10.35596/1729-7648-2021-19-8-5-9.
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Ab-initio simulation of hydrogenated graphene properties was performed. At present, graphene is considered one of the most promising materials for the formation of new semiconductor devices with good characteristics. Graphene has been the subject of many recent investigations due to its peculiar transport, mechanical and others properties [1]. The chemical modification of graphene named as graphane has recently entered the investigation as a possible candidate to solve problems connected with the lack of a graphene bandgap. Graphane is a compound material consisting of two-dimensional graphene bonded by some atoms of hydrogen. The investigation shows that graphane has the three valley Г-М-K band structure with the Г valley, which has the smallest energy gap between the conductivity zone and the valence zone. The calculation of relative electron masses and non-parabolic coefficients in Г, М and K valleys was performed. Based on the obtained characteristics, it is possible to implement a statistical multi-particle Monte Carlo method to determine the characteristics of electron transfer in heterostructure semiconductor devices. A research on modified graphene structures is important for fundamental science and technological applications in high-speed transistor structures operating in the microwave and very high frequency ranges.
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Qu, Li-Hua, Xiao-Long Fu, Chong-Gui Zhong, Peng-Xia Zhou i Jian-Min Zhang. "Equibiaxial Strained Oxygen Adsorption on Pristine Graphene, Nitrogen/Boron Doped Graphene, and Defected Graphene". Materials 13, nr 21 (4.11.2020): 4945. http://dx.doi.org/10.3390/ma13214945.
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We report first-principles calculations on the structural, mechanical, and electronic properties of O2 molecule adsorption on different graphenes (including pristine graphene (G–O2), N(nitrogen)/B(boron)-doped graphene (G–N/B–O2), and defective graphene (G–D–O2)) under equibiaxial strain. Our calculation results reveal that G–D–O2 possesses the highest binding energy, indicating that it owns the highest stability. Moreover, the stabilities of the four structures are enhanced enormously by the compressive strain larger than 2%. In addition, the band gaps of G–O2 and G–D–O2 exhibit direct and indirect transitions. Our work aims to control the graphene-based structure and electronic properties via strain engineering, which will provide implications for the application of new elastic semiconductor devices.
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Lee, Ji, Sung Kwon, Soonchul Kwon, Min Cho, Kwang Kim, Tae Han i Seung Lee. "Tunable Electronic Properties of Nitrogen and Sulfur Doped Graphene: Density Functional Theory Approach". Nanomaterials 9, nr 2 (15.02.2019): 268. http://dx.doi.org/10.3390/nano9020268.
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We calculated the band structures of a variety of N- and S-doped graphenes in order to understand the effects of the N and S dopants on the graphene electronic structure using density functional theory (DFT). Band-structure analysis revealed energy band upshifting above the Fermi level compared to pristine graphene following doping with three nitrogen atoms around a mono-vacancy defect, which corresponds to p-type nature. On the other hand, the energy bands were increasingly shifted downward below the Fermi level with increasing numbers of S atoms in N/S-co-doped graphene, which results in n-type behavior. Hence, modulating the structure of graphene through N- and S-doping schemes results in the switching of “p-type” to “n-type” behavior with increasing S concentration. Mulliken population analysis indicates that the N atom doped near a mono-vacancy is negatively charged due to its higher electronegativity compared to C, whereas the S atom doped near a mono-vacancy is positively charged due to its similar electronegativity to C and its additional valence electrons. As a result, doping with N and S significantly influences the unique electronic properties of graphene. Due to their tunable band-structure properties, the resulting N- and S-doped graphenes can be used in energy and electronic-device applications. In conclusion, we expect that doping with N and S will lead to new pathways for tailoring and enhancing the electronic properties of graphene at the atomic level.
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Liu, Li, i Chang Chun Zhou. "Preparation and Application of Grapheme". Applied Mechanics and Materials 670-671 (październik 2014): 127–29. http://dx.doi.org/10.4028/www.scientific.net/amm.670-671.127.
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Graphene is a kind of new carbon material with isomer. Its basic structure is composed of six carbon atoms in closed loop structure. In order to make graphene with excellent properties in practical application, people have proposed various methods of preparing grapheme. Graphene shows promising applications in solar cell. This paper introduced preparation and applications of graphene in the high-tech fields.
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Rozhkov, M. A., A. L. Kolesnikova, I. Hussainova, M. A. Kaliteevskii, T. S. Orlova, Yu Yu Smirnov, I. S. Yasnikov, L. V. Zhigilei, V. E. Bougrov i A. E. Romanov. "Evolution of Dirac Cone in Disclinated Graphene". REVIEWS ON ADVANCED MATERIALS SCIENCE 57, nr 2 (1.07.2018): 137–42. http://dx.doi.org/10.1515/rams-2018-0057.
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Abstract Graphene crystals, containing arrays of disclination defects, are modeled and their energies are calculated using molecular dynamics (MD) simulation technique. Two cases are analyzed in details: (i) pseudo-graphenes, which contain the alternating sign disclination ensembles and (ii) graphene with periodic distribution of disclination quadrupoles. Electronic band structures of disclinated graphene crystals are calculated in the framework of density functional theory (DFT) approach. The evolution of the Dirac cone and magnitude of band gap in the band structure reveal a dependence on the density of disclination quadrupoles and alternating sign disclinations. The electronic properties of graphene with disclination ensembles are discussed.
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Colmiais, Ivo, Vitor Silva, Jérôme Borme, Pedro Alpuim i Paulo M. Mendes. "Extraction of Graphene’s RF Impedance through Thru-Reflect-Line Calibration". Micromachines 14, nr 1 (14.01.2023): 215. http://dx.doi.org/10.3390/mi14010215.
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Graphene has unique properties that can be exploited for radiofrequency applications. Its characterization is key for the development of new graphene devices, circuits, and systems. Due to the two-dimensional nature of graphene, there are challenges in the methodology to extract relevant characteristics that are necessary for device design. In this work, the Thru-Reflect-Line (TRL) calibration was evaluated as a solution to extract graphene’s electrical characteristics from 1 GHz to 65 GHz, where the calibration structures’ requirements were analyzed. It was demonstrated that thick metallic contacts, a low-loss substrate, and a short and thin contact are necessary to characterize graphene. Furthermore, since graphene’s properties are dependent on the polarization voltage applied, a backgate has to be included so that graphene can be characterized for different chemical potentials. Such characterization is mandatory for the design of graphene RF electronics and can be used to extract characteristics such as graphene’s resistance, quantum capacitance, and kinetic inductance. Finally, the proposed structure was characterized, and graphene’s resistance and quantum capacitance were extracted.
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Wang, Xuan Lun, i Wei Jiu Huang. "Fabrication and Characterization of Graphene/Polyimide Nanocomposites". Advanced Materials Research 785-786 (wrzesień 2013): 138–44. http://dx.doi.org/10.4028/www.scientific.net/amr.785-786.138.
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Graphene/polyimide nanocomposites with different weight loadings were prepared by a solution compounding technique. Graphene was synthesized from graphite oxide that was fabricated by the Hummers method. X-ray diffraction (XRD), ultraviolet visible (UV-vis) spectra and simultaneous thermal analysis were used for the microstructure analysis of the graphenes. Graphenes with single layer structure were synthesized successfully and had good solubility in water or other polar solvents due to a few functional groups on the graphene carbons. Graphenes have good thermal stability. Mechanical and tribological properties were studied for the graphene/polyimide composites. The composites have excellent strength and toughness with very small graphene loading level and the addition of graphene decreased the friction coefficient and wear rate of the composites.
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RAO, C. N. R., K. S. SUBRAHMANYAM, H. S. S. RAMAKRISHNA MATTE i A. GOVINDARAJ. "GRAPHENE: SYNTHESIS, FUNCTIONALIZATION AND PROPERTIES". Modern Physics Letters B 25, nr 07 (20.03.2011): 427–51. http://dx.doi.org/10.1142/s0217984911025961.
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Graphenes with varying number of layers can be synthesized by different strategies. Thus, single-layer graphene is obtained by the reduction of single layer graphene oxide, CVD and other methods besides micromechanical cleavage. Few-layer graphenes are prepared by the conversion of nanodiamond, arc-discharge of graphite and other means. We briefly present the various methods of synthesis and the nature of graphenes obtained. We then discuss the various properties of graphenes. The remarkable property of graphene of quenching fluorescence of aromatic molecules is shown to be associated with photo-induced electron transfer, on the basis of fluorescence decay and time-resolved transient absorption spectroscopic measurements. The interaction of electron donor and acceptor molecules with few-layer graphene samples has been discussed. Decoration of metal nano-particles on graphene sheets and the resulting changes in electronic structure are examined. Few-layer graphenes exhibit ferromagnetic features along with antiferromagnetic properties, independent of the method of preparation. Graphene-like MoS 2 and WS 2 have been prepared by chemical methods, and the materials are characterized by electron microscopy, atomic force microscopy (AFM) and other methods. Boron nitride analogues of graphene have been obtained by a simple chemical procedure starting with boric acid and urea and have been characterized by various techniques.
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RAO, C. N. R., K. S. SUBRAHMANYAM, H. S. S. RAMAKRISHNA MATTE, URMIMALA MAITRA, KOTA MOSES i A. GOVINDARAJ. "GRAPHENE: SYNTHESIS, FUNCTIONALIZATION AND PROPERTIES". International Journal of Modern Physics B 25, nr 30 (10.12.2011): 4107–43. http://dx.doi.org/10.1142/s0217979211059358.
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Graphenes with varying number of layers can be synthesized by different strategies. Thus, single-layer graphene is obtained by the reduction of single layer graphene oxide, CVD and other methods besides micromechanical cleavage. Few-layer graphenes are prepared by the conversion of nanodiamond, arcdischarge of graphite and other means. We briefly present the various methods of synthesis and the nature of graphenes obtained. We then discuss the various properties of graphenes. The remarkable property of graphene of quenching fluorescence of aromatic molecules is shown to be associated with photo-induced electron transfer, on the basis of fluorescence decay and time-resolved transient absorption spectroscopic measurements. The interaction of electron donor and acceptor molecules with few-layer graphene samples has been discussed. Decoration of metal nano-particles on graphene sheets and the resulting changes in electronic structure are examined. Few-layer graphenes exhibit ferromagnetic features along with antiferromagnetic properties, independent of the method of preparation. Graphene-like MoS 2 and WS 2 have been prepared by chemical methods, and the materials are characterized by electron microscopy, atomic force microscopy (AFM) and other methods. Boron nitride analogues of graphene have been obtained by a simple chemical procedure starting with boric acid and urea and have been characterized by various techniques.
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Ooi, Kelvin J. A., i Dawn T. H. Tan. "Nonlinear graphene plasmonics". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 473, nr 2206 (październik 2017): 20170433. http://dx.doi.org/10.1098/rspa.2017.0433.
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The rapid development of graphene has opened up exciting new fields in graphene plasmonics and nonlinear optics. Graphene's unique two-dimensional band structure provides extraordinary linear and nonlinear optical properties, which have led to extreme optical confinement in graphene plasmonics and ultrahigh nonlinear optical coefficients, respectively. The synergy between graphene's linear and nonlinear optical properties gave rise to nonlinear graphene plasmonics, which greatly augments graphene-based nonlinear device performance beyond a billion-fold. This nascent field of research will eventually find far-reaching revolutionary technological applications that require device miniaturization, low power consumption and a broad range of operating wavelengths approaching the far-infrared, such as optical computing, medical instrumentation and security applications.
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Nair, Aparna V., i B. Manoj. "Tailoring of Energy Band Gap inGraphene-like System by Fluorination". Mapana - Journal of Sciences 18, nr 1 (1.01.2019): 55–66. http://dx.doi.org/10.12723/mjs.48.4.
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Fluorinated grapheme has a two-dimensional layer structure with a wide band gap. In the present study, Fluoro Graphene (FG) is obtained from Graphene Oxide (GO) through a deoxyfluorination reaction with the aid of Diethylaminosulphurtrifluoride (DAST). The FT-IR exhibited a peak at 1216 cm-1 and the shoulder at 1312 cm-1 were ascribed to the stretching vibration of covalent C–F bonds and C–F2 bonds, respectively. Surface morphology revealed a leafy structure in GO and a rocky structure in FG. The EDS analysis confirmed the fluorination of the graphitic structure. The TEM analysis confirmed the formation of a mixed structure of graphene and carbon dots. The results of structural, morphological and electrical properties of both graphene oxide and fluorographene show the possibility of using these samples as electronic/electrochemical devices in future.
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Xiao, Zhen Hui, Shui Sheng Wu, Yan Lin Sun, Yu Lin Zhao i Ya Ming Wang. "Microwave-Hydrothermal Synthesis and Characterization of Graphene". Advanced Materials Research 602-604 (grudzień 2012): 917–20. http://dx.doi.org/10.4028/www.scientific.net/amr.602-604.917.
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Graphene was synthesized by microwave-hydrothermal chemical reduction of graphite oxide using hydrazine hydrate as the reducing agent. Graphene was characterized using X-ray diffraction, UV-visible spectrum, FT-IR spectrum and scanning electron microscopy. Results indicated that the as-prepared graphene was wrinkled and comprised fewer graphenes with a highly crystalline structure.
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Dąbrowski, Igor Jakub, Patrycja Magdalena Nogas, Tadeusz Kałdoński, Barbara Nasiłowska i Małgorzata Djas. "Application of graphene materials in tribology — analysis of state of the problem and the preliminary research". Bulletin of the Military University of Technology 68, nr 2 (28.06.2019): 81–108. http://dx.doi.org/10.5604/01.3001.0013.3006.
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Present publication describes one of the most interesting materials discovered in recent years, which is graphene. This paperwork contains information about graphene’s structure, properties, applications and methods of synthesis. The special attention has been given to tribological applications of graphene structures, including the usage of the graphene itself in the composite materials, protective integuments, and additives to lubricants (oils, greases). This publication was based on the information and research results published in the international articles and preliminary researches realized at the Military University of Technology as well. The research results concern the changes of basic lubricants’ parameters, which contain different amount of graphene oxide (or comparatively of hexagonal boron nitride). The results obtained during the tests indicate that graphene oxide could improve lubricating abilities of oils and greases. Keywords: tribology, lubricants, graphene, graphene oxide.
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Mavrinskii, Viktor, i Evgeniy A. Belenkov. "Ab Initio Calculations of New α-L<sub>5-7a</sub> and β-L<sub>5-7a</sub> Graphyne Polymorphic Varieties". Materials Science Forum 1049 (11.01.2022): 180–85. http://dx.doi.org/10.4028/www.scientific.net/msf.1049.180.
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Calculations of the structural and energy parameters, band structure and density of electronic states of new structural varieties of graphyne have been performed by the density functional theory method. The initial structure of the nine polymorphs was theoretically constructed on the basis of the 5-7a graphene layer. As a result of the calculations, the structure of only five graphyne layers was found to be stable: α-L5-7a, β1-L5-7a, β2-L5-7a, β3-L5-7a and β4-L5-7a. The structure of layers γ1-L5-7a, γ2-L5-7a, and γ3-L5-7a is transformed into the structure of graphene layers by geometric optimization, and the graphyne layer γ4-L5-7a is transformed sp+sp2 layer L3-6-13. The sublimation energy of the stable graphyne polymorphs varies from 6.66 to 6.78 eV/atom. The density of electronic states at the Fermi energy level for all α-L5-7a and β-L5-7a layers of graphyne is different from zero, so the new graphyne polymorphs should have metallic properties.
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Liu, Jingran, Huasong Qin i Yilun Liu. "Multi-Scale Structure–Mechanical Property Relations of Graphene-Based Layer Materials". Materials 14, nr 16 (23.08.2021): 4757. http://dx.doi.org/10.3390/ma14164757.
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Pristine graphene is one of the strongest materials known in the world, and may play important roles in structural and functional materials. In order to utilize the extraordinary mechanical properties in practical engineering structures, graphene should be assembled into macroscopic structures such as graphene-based papers, fibers, foams, etc. However, the mechanical properties of graphene-based materials such as Young’s modulus and strength are 1–2 orders lower than those of pristine monolayer graphene. Many efforts have been made to unveil the multi-scale structure–property relations of graphene-based materials with hierarchical structures spanning the nanoscale to macroscale, and significant achievements have been obtained to improve the mechanical performance of graphene-based materials through composition and structure optimization across multi-scale. This review aims at summarizing the currently theoretical, simulation, and experimental efforts devoted to the multi-scale structure–property relation of graphene-based layer materials including defective monolayer graphene, nacre-like and laminar nanostructures of multilayer graphene, graphene-based papers, fibers, aerogels, and graphene/polymer composites. The mechanisms of mechanical property degradation across the multi-scale are discussed, based on which some multi-scale optimization strategies are presented to further improve the mechanical properties of graphene-based layer materials. We expect that this review can provide useful insights into the continuous improvement of mechanical properties of graphene-based layer materials.
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First, Phillip N., Walt A. de Heer, Thomas Seyller, Claire Berger, Joseph A. Stroscio i Jeong-Sun Moon. "Epitaxial Graphenes on Silicon Carbide". MRS Bulletin 35, nr 4 (kwiecień 2010): 296–305. http://dx.doi.org/10.1557/mrs2010.552.
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AbstractThis article reviews the materials science of graphene grown epitaxially on the hexagonal basal planes of SiC crystals and progress toward the deterministic manufacture of graphene devices. We show that the growth of epitaxial graphene on Si-terminated SiC(0001) differs from growth on the C-terminated SiC(0001) surface, resulting in, respectively, strong and weak coupling to the substrate and to successive graphene layers. Monolayer epitaxial graphene on either surface displays the expected electronic structure and transport characteristics of graphene, but the non-graphitic stacking of multilayer graphene on SiC(0001) determines an electronic structure much different from that of graphitic multilayers on SiC(0001). This materials system is rich in subtleties, and graphene grown on the two polar faces of SiC differs in important ways, but all of the salient features of ideal graphene are found in these epitaxial graphenes, and wafer-scale fabrication of multi-GHz devices already has been achieved.
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Taufantri, Yudha, Irdhawati Irdhawati i Ida Ayu Raka Astiti Asih. "Sintesis dan Karakterisasi Grafena dengan Metode Reduksi Grafit Oksida Menggunakan Pereduksi Zn". Jurnal Kimia VALENSI 2, nr 1 (31.05.2016): 17–23. http://dx.doi.org/10.15408/jkv.v2i1.2233.
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Graphene is a thin material, has a hexagonal two-dimentional lattice and is considered as an interesting material for adsorption process. Nowadays, graphene has been known as a potential material for diverse application, such as adsorbent. In this study graphene was synthesized from graphite. Furthermore, graphene was applied for adsorption of dichloro diphenyl trichloroethane (DDT). Graphene was synthesized by Hummer’s method using hydrothermal and reduced by Zn. The samples were characterized by Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD) methods. The results of the XRD showed graphene structure in the 2θ, appeared at 23.9369 with interlayer spacing was about 3.71763 Å, compared with graphite oxide structure in the 2θ appeared at 11.2055 with interlayer spacing was about 7.89649 Å. The results of SEM analysis showed graphene has one layer with planar hexagonal structure and seems transparent whose single layer and multi layers. The graphene adsorption was analyzed by using the UV-Visible spectrophotometer. The results indicated the surface area of graphene was shown as 46.8563 m2/g. The amount of DDT adsorbed by graphene during 15 minutes was 7.5859 mg/g. This adsorption mechanism of DDT and graphene might be due to π-π and hydrogen interactions. Keywords: Adsorption, dichloro diphenyl trichloroethane (DDT), graphena. DOI: http://dx.doi.org/10.15408/jkv.v2i1.2233
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Yang, Jun, Julietraja Konsalraj i Arul Amirtha Raja Raja S. "Neighbourhood Sum Degree-Based Indices and Entropy Measures for Certain Family of Graphene Molecules". Molecules 28, nr 1 (25.12.2022): 168. http://dx.doi.org/10.3390/molecules28010168.
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A topological index (TI) is a real number that defines the relationship between a chemical structure and its properties and remains invariant under graph isomorphism. TIs defined for chemical structures are capable of predicting physical properties, chemical reactivity and biological activity. Several kinds of TIs have been defined and studied for different molecular structures. Graphene is the thinnest material known to man and is also extremely strong while being a good conductor of heat and electricity. With such unique features, graphene and its derivatives have found commercial uses and have also fascinated theoretical chemists. In this article, the neighbourhood sum degree-based M-polynomial and entropy measures have been computed for graphene, graphyne and graphdiyne structures. The proper analytical expressions for these indices are derived. The obtained results will enable theoretical chemists to study these exciting structures further from a structural perspective.
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Zhou, Qingxiao, Weiwei Ju, Xiangying Su, Yongliang Yong, Xiaohong Li, Zhibing Fu i Chaoyang Wang. "Adsorption sensitivity of graphane decorated with B, N, S, and Al towards HCN: a first-principles study". RSC Advances 7, nr 69 (2017): 43521–30. http://dx.doi.org/10.1039/c7ra08579f.
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The geometric structure, adsorption energy, electronic structure, and magnetic properties of hydrogenated graphene (graphane) with the adsorption of a HCN molecule were investigated by first-principles calculations.
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Slepchenkov, Michael M., Pavel V. Barkov i Olga E. Glukhova. "Electronic and Electrical Properties of Island-Type Hybrid Structures Based on Bi-Layer Graphene and Chiral Nanotubes: Predictive Analysis by Quantum Simulation Methods". Coatings 13, nr 5 (22.05.2023): 966. http://dx.doi.org/10.3390/coatings13050966.
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Hybrid structures based on graphene and carbon nanotubes (CNTs) are one of the most relevant modern nanomaterials for applications in various fields, including electronics. The variety of topological architectures of graphene/CNT hybrids requires a preliminary study of their physical properties by in silico methods. This paper is devoted to the study of the electronic and electrical properties of graphene/CNT hybrid 2D structures with an island topology using the self-consistent charge density functional-based tight-binding (SCC-DFTB) formalism and the Landauer–Buttiker formalism. The island-type topology is understood as the atomic configuration of a graphene/CNT hybrid film, in which the structural fragments of graphene and nanotubes form “islands” (regions of the atomic structure) with an increased density of carbon atoms. The island-type graphene/CNT hybrid structures are formed by AB-stacked bilayer graphene and (6,3)/(12,8) chiral single-walled carbon nanotubes (SWCNT). The bilayer graphene is located above the nanotube perpendicular to its axis. Based on the binding energy calculations, it is found that the atomistic models of the studied graphene/SWCNT hybrid structures are thermodynamically stable. The peculiarities of the band structure of graphene/SWCNT (6,3) and graphene/SWCNT (12,8) hybrid structures are analyzed. It is shown that the electronic properties of graphene/SWCNT hybrid structures are sensitive to the orientation and size of the graphene layers with respect to the nanotube surface. It is found that an energy gap of ~0.1 eV opens in the band structure of only the graphene/SWCNT (6,3) hybrid structure, in which the graphene layers of the same length are arranged horizontally above the nanotube surface. We revealed the electrical conductivity anisotropy for all considered atomistic models of the graphene/SWCNT (12,8) hybrid structure when bilayer graphene sheets with different sizes along the zigzag and armchair directions are located at an angle with respect to the nanotube surface. The obtained knowledge is important to evaluate the prospects for the potential application of the considered atomic configurations of graphene/SWCNT hybrid structures with island-type topology as connecting conductors and electrodes in electronic devices.
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Ghaffar, A., M. Umair, Majeed A. S. Alkanhal i Y. Khan. "Dispersion characteristics of surface plasmon polaritons in a graphene–plasma–graphene waveguide structure". Canadian Journal of Physics 100, nr 2 (luty 2022): 123–28. http://dx.doi.org/10.1139/cjp-2019-0642.
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Theoretical investigations are carried out to study surface wave propagation for a graphene parallel-plate waveguide structure filled with isotropic plasma. The extended wave propagation theory is used. The Kobo formula is used to determine graphene conductivity. Maxwell’s equations (differential form) are used to solve the analytical problem. It is concluded that surface wave propagation can be tuned and controlled by tuning the plasma parameters (plasma frequency and collisional frequency) as well as chemical potential and relaxation time of graphene. Furthermore, the effect of plasma frequency and collisional frequency on the wave attenuation is discussed, and the effect of graphene’s chemical potential, plasma frequency, and collisional frequency on propagation length are also analyzed. The normalized field distribution of plasma medium is also studied. These results may lead to potential applications in optical sensing, communication, and plasma-based optical integrated devices in the gigahertz frequency regime.
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Pumera, Martin, i Zdeněk Sofer. "Towards stoichiometric analogues of graphene: graphane, fluorographene, graphol, graphene acid and others". Chemical Society Reviews 46, nr 15 (2017): 4450–63. http://dx.doi.org/10.1039/c7cs00215g.
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Zhumabekov, A. Zh, A. E. Sadykova i E. V. Seliverstova. "Nitrided Silicon-Carbon Coatings Structure and Properties". Bulletin of the Karaganda University. "Physics" Series 98, nr 2 (30.06.2020): 18–23. http://dx.doi.org/10.31489/2020ph2/18-23.
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In this paper, planar structures of various configurations based on TiO2 and graphene oxide are synthesized. Using SEM, it is shown that graphene oxide forms an insular film both on the surface and under the TiO2 layer during deposition. As well as SEM images show that TiO2 nanoparticles on the surface of graphene oxide are distributed as evenly as on the surface of FTO glass. The absorption spectra of synthesized films are a combination of the absorption curves of the original components. In this case, there is a shift of the absorption band of the planar structure nanocomposite to the longwave region. It is shown that in planar ensembles, the photoelectrochemical activity of films is higher only for the first lighting cycle. Research shows that the amount of graphene oxide affects not only the optical and photoelectrochemical properties, but also the electrical parameters. The latter, in turn, show that the resistance decreases by 1.3 times in the planar structure of graphene oxide with 30 layers. It was found that in planar structures of nanocomposite materials, the location of graphene oxide also affects the overall properties of the material. Research shows that the best indicators of photoinduced current generation are registered for the FTO/GO/TiO2 structure. Thus, a nanocomposite material in a planar structure based on TiO2 and graphene oxide depends on the architecture of the location and deposited volume of graphene oxide.
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Jung, Yeon Wook, Seung Geun Jo, Hae-In Moon, Young Won Kim, Yujin Shin, Gil-Ryeong Park i Jung Woo Lee. "A Study on Graphene Structure Control Using Ammonia Gas for a Highly Sensitive Pressure Sensor". Korean Journal of Metals and Materials 60, nr 3 (5.03.2022): 206–12. http://dx.doi.org/10.3365/kjmm.2022.60.3.206.
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Graphene has been used in various fields because of its excellent mechanical, optical, electrical, and thermal properties. However, its intrinsic low sensitivity to pressure limits its sensor applications. To overcome this drawback, many researchers have tried to improve the sensitivity by controlling the defects on the graphene, but have yet to report a significant increase in sensitivity compared to the pristine graphene. Herein, we fabricated a graphene-based highly sensitive pressure sensor by flowing ammonia gas during chemical vapor deposition. The ammonia gas assisted the generation of nano-sized defects due to nitrogen doping in the graphene lattice, as well as macro-sized cracks in the graphene layer, due to the corrosion of the Cu surface. We regulated the concentration ratio of ammonia gas and methane gas during the graphene synthesis, which controlled the crack generation. These cracks weakened the in-plane force of the networks in the geometric structure of the graphene, thereby allowing them to deform more easily under external force, and changing the resistance of the sensor dramatically. As a result, the sensitivity of the pressure sensor increased about 10,000 times higher than that of the pristine graphene. These results suggest that controlling defects to improve graphene’s mechanical sensitivity provides a promising route to pressure sensor applications.
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NAEEM, Nida, Mudassar ABBAS i Mumtaz Hasan MALIK. "GRAPHENE/GRAPHENE OXIDE BASED COATINGS FOR ADVANCED TEXTILE APPLICATIONS". TEXTEH Proceedings 2019 (5.11.2019): 148–52. http://dx.doi.org/10.35530/tt.2019.31.
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Today, graphene oxide has been significantly used in many technological sectors, medical sectors as well in textiles due to its abundant applications and dominant characteristics. Graphene oxide is basically a mono layered material synthesized by the oxidation of graphite by the addition of multiple functional groups containing oxygen such as alcohols, carboxylic acids and epoxides and presenting a 2-diamentional honeycomb structure. On the textile surfaces the grapheme oxide can be applied through Pad dry-cure, Dip dry-cure and Spray coating methods. However, the most appropriate method is dipping of the fabric into the graphene suspension and the process is followed by drying and curing techniques. Initially, the fabric swatches have been cut out in a suitable size according to the padder or adjustments on the machine can also be done. 100% pure cotton, polyester, cotton polyester blend, silk, aramids and acrylics have been used as a substrate for the application of graphene to imparts different functional properties. The oxygen content is reduced resulting the increase in the interlayer spacing’s well as functionalization. The oxygen containing groups have been removed with the repossession of the conjugated structure. The reduced graphene oxide has the higher strength as well as high electrical and thermal conductivity which effect the final performance of a materials.
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Steinbauer, Miloslav, Roman Pernica, Jiri Zukal, Radim Kadlec, Tibor Bachorec i Pavel Fiala. "MODELING ELECTROMAGNETIC NANOSTRUCTURES AND EXPERIMENTING WITH NANOELECTRIC ELEMENTS TO FORM PERIODIC STRUCTURES". Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska 10, nr 4 (20.12.2020): 4–14. http://dx.doi.org/10.35784/iapgos.2383.
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We discuss the numerical modeling of electromagnetic, carbon-based periodic structures, including graphene, graphane, graphite, and graphyne. The materials are suitable for sub-micron sensors, electric lines, and other applications, such as those within biomedicine, photonics, nano- and optoelectronics; in addition to these domains and branches, the applicability extends into, for example, microscopic solutions for modern SMART elements. The proposed classic and hybrid numerical models are based on analyzing a periodic structure with a high repeatability, and they exploit the concept of a carbon structure having its fundamental dimension in nanometers. The models can simulate harmonic and transient processes; are capable of evaluating the actual random motion of an electric charge as a source of spurious signals; and consider the parameters of harmonic signal propagation along the structure. The results obtained from the analysis are utilizable for the design of sensing devices based on carbon periodic structures and were employed in experiments with a plasma generator. The aim is to provide a broader overview of specialized nanostructural modeling, or, more concretely, to outline a model utilizable in evaluating the propagation of a signal along a structure’s surface.
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Gilbert, S. Matt, Adam Molnar, Donez Horton-Bailey, Helen Y. Yao i Alex Zettl. "Strain-controlled Graphene-Polymer Angular Actuator". MRS Advances 4, nr 40 (2019): 2161–67. http://dx.doi.org/10.1557/adv.2019.276.
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ABSTRACTWe demonstrate a suspended graphene-(poly(methyl methacrylate) (PMMA) polymer angular displacement actuator enabled by variable elastic modulus of the perforated stacked structure. Azimuthal flexures support a central disc-shaped membrane, and compression of the membrane can be used to control the rotation of the entire structure. Irradiating the PMMA on graphene stack with 5 kV electrons in a convention scanning electron microscope reduces the elastic modulus of the PMMA and allows graphene’s built in strain to dominate and compress the flexures, thus rotating the actuator.
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NAJI, S., A. BELHAJ, H. LABRIM, A. BENYOUSSEF i A. EL KENZ. "ELECTRONIC STRUCTURE OF GRAPHENE AND GERMANENE BASED ON DOUBLE HEXAGONAL STRUCTURE". Modern Physics Letters B 27, nr 29 (15.11.2013): 1350212. http://dx.doi.org/10.1142/s0217984913502126.
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In this paper, we study the electronic structure of monolayer materials based on a double hexagonal geometry with (1×1) and [Formula: see text] superstructures. Inspired from the two-dimensional root system of an exceptional Lie algebra called G2, this hexagonal atomic configuration involves two hexagons of unequal side length at angle 30°. The principal unit hexagonal cell contains twelve atoms instead of the usual configuration involving only six ones relying only on the (1×1) superstructure. Using ab initio calculations based on FPLO9.00-34 code, we investigate numerically the graphene and the germanene with the double hexagonal geometry. In particular, we find that the usual electronic properties and the lattice parameters of such materials are modified. More precisely, the lattice parameters are increased. It has been shown that, in the single hexagonal geometry, the grapheme and the germanene behave as a gapless semiconductor and a semi-metallic, respectively. In double hexagonal geometry however, both materials becomes metallic.
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Sun, Zhanshan, Yuejun Zheng i Yunqi Fu. "Graphene-Based Spatial Light Modulator Using Metal Hot Spots". Materials 12, nr 19 (21.09.2019): 3082. http://dx.doi.org/10.3390/ma12193082.
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Here, we report a graphene-based electric field enhancement structure achieved by several adjacent metal nanoribbons which form the hot spots of the electric field and thus promote the absorption of the single layered graphene below the hot spots. Based on the tunability of the graphene’s Fermi level, the absorption rate can be modulated from near 100% to 35% under low electrostatic gating, leading to a 20 dB modulation depth of reflectance. Compared with the existing near infrared spatial light modulators such as optical cavities integrated with graphene and other structures utilizing patterned or highly doped graphene, our design has the advantages of strong optical field enhancement, low power dissipation and high modulation depth. The proposed electro-optic modulator has a promising potential for developing optical communication and exploiting big data interaction systems.
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Davydov, V. N. "The recurrent relations for the electronic band structure of the multilayer graphene". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 474, nr 2220 (grudzień 2018): 20180439. http://dx.doi.org/10.1098/rspa.2018.0439.
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The structure of the electronic energy bands for stacked multilayer graphene is developed using the tight-binding approximation (TBA). The spectra of the Dirac electrons are investigated in vicinity of the Brillouin zone minima. The electron energy dependence on quasi-momentum is established for an arbitrary number of the graphene layers for multilayer graphene having even number of layers N = 2 n , ( n = 2, 3, 4, …) with the Bernal stacking ABAB … AB; or for odd number of layers N = 2 n + 1, ( n = 1, 2, 3, …) with stacking ABAB … A. It is shown that four non-degenerate energy branches of the electronic energy spectrum are present for any number of layers. Degeneracy is considered of graphene-like energy branches with linear dispersion law. Dependences of such branches number and their degeneracy are found on number of layers. The recurrent relations are obtained for the electronic band structure of the stacked ABA…, ABC… and AAA… multilayer graphene. The flat electronic bands are obtained for ABC-stacked multilayer graphene near the K -point at the Fermi level. Such an approach may be useful in the study of multivarious aspects of graphene's physics and nanotechnologies. Also paper gives new hints for deeper studies of graphite intercalation compounds.
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Wu, Gao Li, Li Li Wu, Jun Hong Jin, Sheng Lin Yang i Guang Li. "Structure and Electrochemical Performance of Melamine/Graphene Aerogel Composite for Supercapacitors". Materials Science Forum 898 (czerwiec 2017): 1844–49. http://dx.doi.org/10.4028/www.scientific.net/msf.898.1844.
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Melamine/graphene (GO/MF) aerogel composite was prepared through a simple one-step hydrothermal route, freeze-drying, and subsequent carbonization with graphene oxide (GO) and melamine resin. The structure, morphology and electrochemical performance of the composites were characterized by SEM, TEM, XRD-ray, Raman spectroscopy, and electrochemical tests. GO/MF aerogel possessed 3D porous structure and enlarged surface like aerogel materials for efficient ionic diffusion and transport. Melamine resin was used as N-doping agent, and the electrochemical performance of GO//MF was improved effectively. GO/MF aerogel shows a higher capacitance of 106 F/g at a current density of 0.1 A/g comparing to reduce graphen oxide (rGO). Not only the macroporous structure but also the N-doping agent had a significant impact on the capacitive behavior of graphene. These results provide a new method to prepare high performance electrode material as supercapacitors.
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Fu, Ruimin, i Mingfu Zhu. "Synthesis and Characterization of Structure of Fe3O4@Graphene Oxide Nanocomposites". Advanced Composites Letters 25, nr 6 (listopad 2016): 096369351602500. http://dx.doi.org/10.1177/096369351602500604.
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Nowadays, the hummers method for preparation of graphene oxide (GO) was improved. The grapheme oxide @ Fe3O4 magnetic nanocomposites were synthesized by co-precipitation method. After analysing the morphology and structure of obtained nanocomposites by X-ray diffraction (XRD), transmission electron microscope (TEM) and Fourier transform infrared (FT-IR) spectroscopy, the result was shown as follows. The particle size of Fe3O4 in nanocomposites is 30 nm. Many functional groups are found in grapheme oxide, and such groups could be used to bind with the drug. In the test for magnetic properties, the nanocomposites gathered rapidly in the vicinity of the permanent magnet. The nanocomposites, with high superparamagnetism, can be used in the following applications: drug targeting transports, drug carrier, and diagnosis assistant system.
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Duong, Dinh Loc, Si Young Lee, Seong Kyu Kim i Young Hee Lee. "Graphene/ferroelectrics/graphene hybrid structure: Asymmetric doping of graphene layers". Applied Physics Letters 106, nr 24 (15.06.2015): 243104. http://dx.doi.org/10.1063/1.4922448.
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Velasco, Andres, Yu Kyoung Ryu, Assia Hamada, Alicia de Andrés, Fernando Calle i Javier Martinez. "Laser-Induced Graphene Microsupercapacitors: Structure, Quality, and Performance". Nanomaterials 13, nr 5 (21.02.2023): 788. http://dx.doi.org/10.3390/nano13050788.
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Laser-induced graphene (LIG) is a graphenic material synthesized from a polymeric substrate through point-by-point laser pyrolysis. It is a fast and cost-effective technique, and it is ideal for flexible electronics and energy storage devices, such as supercapacitors. However, the miniaturization of the thicknesses of the devices, which is important for these applications, has still not been fully explored. Therefore, this work presents an optimized set of laser conditions to fabricate high-quality LIG microsupercapacitors (MSC) from 60 µm thick polyimide substrates. This is achieved by correlating their structural morphology, material quality, and electrochemical performance. The fabricated devices show a high capacitance of 22.2 mF/cm2 at 0.05 mA/cm2, as well as energy and power densities comparable to those of similar devices that are hybridized with pseudocapacitive elements. The performed structural characterization confirms that the LIG material is composed of high-quality multilayer graphene nanoflakes with good structural continuity and an optimal porosity.
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Wang, Jingang, Xijiao Mu i Mengtao Sun. "The Thermal, Electrical and Thermoelectric Properties of Graphene Nanomaterials". Nanomaterials 9, nr 2 (6.02.2019): 218. http://dx.doi.org/10.3390/nano9020218.
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Graphene, as a typical two-dimensional nanometer material, has shown its uniqueapplication potential in electrical characteristics, thermal properties, and thermoelectric propertiesby virtue of its novel electronic structure. The field of traditional material modification mainlychanges or enhances certain properties of materials by mixing a variety of materials (to form aheterostructure) and doping. For graphene as well, this paper specifically discusses the use oftraditional modification methods to improve graphene’s electrical and thermoelectrical properties.More deeply, since graphene is an atomic-level thin film material, its shape and edge conformation(zigzag boundary and armchair boundary) have a great impact on performance. Therefore, thispaper reviews the graphene modification field in recent years. Through the change in the shape ofgraphene, the change in the boundary structure configuration, the doping of other atoms, and theformation of a heterostructure, the electrical, thermal, and thermoelectric properties of graphenechange, resulting in broader applications in more fields. Through studies of graphene’s electrical,thermal, and thermoelectric properties in recent years, progress has been made not only inexperimental testing, but also in theoretical calculation. These aspects of graphene are reviewed inthis paper.
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Rabchinskii, Maxim K., Vladimir V. Shnitov, Maria Brzhezinskaya, Marina V. Baidakova, Dina Yu Stolyarova, Sergey A. Ryzhkov, Svyatoslav D. Saveliev i in. "Manifesting Epoxide and Hydroxyl Groups in XPS Spectra and Valence Band of Graphene Derivatives". Nanomaterials 13, nr 1 (21.12.2022): 23. http://dx.doi.org/10.3390/nano13010023.
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The derivatization of graphene to engineer its band structure is a subject of significant attention nowadays, extending the frames of graphene material applications in the fields of catalysis, sensing, and energy harvesting. Yet, the accurate identification of a certain group and its effect on graphene’s electronic structure is an intricate question. Herein, we propose the advanced fingerprinting of the epoxide and hydroxyl groups on the graphene layers via core-level methods and reveal the modification of their valence band (VB) upon the introduction of these oxygen functionalities. The distinctive contribution of epoxide and hydroxyl groups to the C 1s X-ray photoelectron spectra was indicated experimentally, allowing the quantitative characterization of each group, not just their sum. The appearance of a set of localized states in graphene’s VB related to the molecular orbitals of the introduced functionalities was signified both experimentally and theoretically. Applying the density functional theory calculations, the impact of the localized states corresponding to the molecular orbitals of the hydroxyl and epoxide groups was decomposed. Altogether, these findings unveiled the particular contribution of the epoxide and hydroxyl groups to the core-level spectra and band structure of graphene derivatives, advancing graphene functionalization as a tool to engineer its physical properties.
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Najim, Abdelhafid, Omar Bajjou, Mustapha Boulghallat, Khalid Rahmani i Lhouceine Moulaoui. "DFT study on electronic and optical properties of graphene under an external electric field". E3S Web of Conferences 336 (2022): 00006. http://dx.doi.org/10.1051/e3sconf/202233600006.
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The paper investigates the electronic and optical properties of graphene, under the external electric field (Eext) according to perpendicular direction, using density functional theory (DFT). Applying the Eext to the graphene sheet modifies its electronic and optical properties, including the band gap energy, total density of states (TDOS), absorption coefficient, dielectric function, and refractive index. Graphene’s band gap is opened by the application of Eext to its structure. As a result of the effect of Eext on graphene layer, its absorption coefficient increases in the ultraviolet (UV) range and decreases in the visible range. We found that the electronic and optical properties of graphene material, can be altered by a perpendicular excitation applied to its structure.
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Zhang, Pei Chao, i Ying Hui Zhou. "Influence of Support Structure on the Ultraviolet Photoluminescence Enhancement from Graphene/ZnO Hybrid Structures". Key Engineering Materials 748 (sierpień 2017): 132–36. http://dx.doi.org/10.4028/www.scientific.net/kem.748.132.
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Novel application of graphene combined with light emitting materials has been proposed recently due to the plasmonic effects of graphene. Here, we report our investigations on the structural and optical properties of two graphene/ZnO hybrid structures that fabricated based on different ZnO supports. Plasmon-enhanced ultraviolet photoluminescence has been observed from both samples. The combined Raman and photoluminescence studies suggest a strong interaction between ZnO and graphene, which is affected by the surface structures of ZnO. Our results develop insights about the influence of ZnO supports on the PL enhancement and interfacial coupling in graphene/ZnO hybrid structures, which provides a reference for the design and fabrication of optoelectronic devices with high efficiency.
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Williams, Michael D., i Dennis W. Hess. "Effect of Growth Morphology on the Electronic Structure of Epitaxial Graphene on SiC". Graphene 02, nr 01 (2013): 55–59. http://dx.doi.org/10.4236/graphene.2013.21008.
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Glukhova O. E. i Slepchenkov M. M. "Graphene/nanotube quasi-1D structures in strong electric fields". Physics of the Solid State 64, nr 5 (2022): 571. http://dx.doi.org/10.21883/pss.2022.05.53519.264.
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In silico studies of the behavior of graphene/nanotube quasi-one-dimensional (1D) structures with covalent bonded graphene and nanotube in strong electric fields with a strength of 10^7-108 V/cm have been carried out. The atomic structure, band structure, electron transmission function, electrical conductivity, and regularity of the electronic structure changes in strong fields have been studied. It is found that the electron transmission function of quasi-1D structures has an intensity peak at the Fermi level in contrast to nanotubes and graphene. As a result of quantum molecular dynamics modeling, the regularities of deformation of the atomic framework and its destruction under the action of ponderomotive force have been established. We have found a critical value of the strength at which the electric field detaches the graphene from the tube. It is ~2·108 V/cm. A further increase leads to the detachment of graphene from the tube with its simultaneous destruction. Keywords: graphene/nanotube structures, electrical conductivity, ponderomotive force, strong electric fields.
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Lee, Chi Ho, Byeongsun Jun i Sang Uck Lee. "Theoretical evaluation of the structure–activity relationship in graphene-based electrocatalysts for hydrogen evolution reactions". RSC Advances 7, nr 43 (2017): 27033–39. http://dx.doi.org/10.1039/c7ra04115b.
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We systematically analyzed the relationship between structure and electrocatalytic activity of heteroatom-doped graphenes (GXs, where G and X represent graphene and the heteroatom dopant) for the hydrogen evolution reaction (HER).
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Karimi, Samira, Emna Helal, Giovanna Gutierrez, Nima Moghimian, Milad Madinehei, Eric David, Mazen Samara i Nicole Demarquette. "A Review on Graphene’s Light Stabilizing Effects for Reduced Photodegradation of Polymers". Crystals 11, nr 1 (22.12.2020): 3. http://dx.doi.org/10.3390/cryst11010003.
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Graphene, the newest member of the carbon’s family, has proven its efficiency in improving polymers’ resistance against photodegradation, even at low loadings equal to 1 wt% or lower. This protective role involves a multitude of complementary mechanisms associated with graphene’s unique geometry and chemistry. In this review, these mechanisms, taking place during both the initiation and propagation steps of photodegradation, are discussed concerning graphene and graphene derivatives, i.e., graphene oxide (GO) and reduced graphene oxide (rGO). In particular, graphene displays important UV absorption, free radical scavenging, and quenching capabilities thanks to the abundant π-bonds and sp2 carbon sites in its hexagonal lattice structure. The free radical scavenging effect is also partially linked with functional hydroxyl groups on the surface. However, the sp2 sites remain the predominant player, which makes graphene’s antioxidant effect potentially stronger than rGO and GO. Besides, UV screening and oxygen barriers are active protective mechanisms attributed to graphene’s high surface area and 2D geometry. Moreover, the way that graphene, as a nucleating agent, can improve the photostability of polymers, have been explored as well. These include the potential effect of graphene on increasing polymer’s glass transition temperature and crystallinity.
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Speyer, Lucie, Océane Louppe, Sébastien Fontana, Sébastien Cahen i Claire Hérold. "Toward the control of graphenic foams". Pure and Applied Chemistry 89, nr 4 (24.05.2017): 565–77. http://dx.doi.org/10.1515/pac-2016-1117.
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AbstractGraphene-based materials are extensively studied, due to their excellent properties and their wide range of possible applications. Attention has recently been paid to three-dimensional-like graphenic structures, such as crumpled graphene sheets and graphenic foams: these kinds of materials can combine the properties of graphene associating high surface area and porosity, what is particularly interesting for energy or catalysis applications. Most of the synthesis methods leading to such structures are based on graphite oxide exfoliation and re-assembly, but in this work we focus on the preparation of graphenic foams by a solvothermal-based process. We performed a solvothermal reaction between ethanol and sodium at 220°C, during 72 h, under 200 bar, followed by a pyrolysis under nitrogen flow. An extended study of the influence of the temperature (800°C–900°C) of pyrolysis evidences an unexpected strong effect of this parameter on the characteristics of the materials. The optimal conditions provide multi-layer graphene (10 layers) foam with a surface area of 2000 m2·g−1. This work is an important step for the understanding of the mechanisms of the thermal treatment. Post-treatments in different experimental conditions are performed in order to modulate the structure and properties of the graphenic foams.
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Baimova, Julia, Polina Polyakova i Stepan Shcherbinin. "Effect of the Structure Morphology on the Mechanical Properties of Crumpled Graphene Fiber". Fibers 9, nr 12 (15.12.2021): 85. http://dx.doi.org/10.3390/fib9120085.
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Crumpled graphene fiber is a promising structure to be a graphene precursor to enhance the production and mechanical properties of various carbon fibers. The primary goal of the present work is to study the crumpled graphene of different morphologies using molecular dynamics simulations to find the effect of the structural peculiarities on the mechanical properties, such as the tensile strength, elastic modulus, and deformation characteristics. Mono- and poly-disperse structures are considered under uniaxial tension along two different axes. As it is found, both structures are isotropic and stress–strain curves for tension along different directions are very similar. Young’s modulus of crumpled graphene is close, about 50 and 80 GPa; however, the strength of the polydisperse structure is bigger at the elastic regime. While a monodisperse structure can in-elastically deform until high tensile strength of 90 GPa, structure analysis showed that polydisperse crumpled graphene fiber pores appeared two times faster than the monodisperse ones.
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An, Yu Min, Xing Hong Zhang, Wen Bo Han, Ping Hu, Gui Qing Chen i Guang Dong Zhao. "Interface of Graphene/ZrB2 Ceramics Structure by Molecular Dynamics Simulation". Key Engineering Materials 655 (lipiec 2015): 82–86. http://dx.doi.org/10.4028/www.scientific.net/kem.655.82.
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With honeycomb lattice ofsp2hybridized carbon atoms, graphene has demonstrated excellent electrical and mechanical properties. One of its promising applications is to fabricate graphene-ceramic composite to improve the mechanical properties. In order to quantify the strength between graphene-ZrB2interactions, molecular dynamic method was utilized to simulate typical interface of graphene/ZrB2ceramic structure. Berendsen method was used to control the temperature and pressure during the whole simulation process. Universal potential function was employed to simulate the force filed between graphene and ZrB2structure. The binding structures of graphene/ZrB2(0001) interface were analyzed in detail and the bonding energy of the interface was calculated. The influence of numbers of graphene layer and sandwich structures on the bonding energy of interface is discussed. The study helped to understand the influence of graphene on mechanical properties of ZrB2ceramic.
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Kuanyshbekov, T., Zh Sagdollin, E. Zhasasynov, N. Kaiyrbekov, K. Akatan, S. Kabdrakhmanova, N. Kantai, Zh Tolepov, M. Tulegenova i M. Beisebekov. "SYNTHESIS OF COMPOSITE MEMBRANE BASED ON GRAPHENE OXIDE AND NANOSTARCH". NNC RK Bulletin, nr 3 (28.09.2022): 94–99. http://dx.doi.org/10.52676/1729-7885-2022-3-94-99.
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Intensive research of nanocomposites contributes to the development of new materials in the fields of medicine, nanoelectronics, high dielectric materials, energy, biotechnology and information technology. Therefore, the synthesis of new materials by modifying of grapheme oxide with nanostarch and the study of its properties are of great interest. In this study, nanocomposite membrane was synthesized by modifying of graphene oxide in a 1:1 volume ratio with nanostarch and their chemical structures were studied by fourier-transform infrared spectroscopy and ultraviolet spectroscopy. The results of the study showed the absorption of the etheric bond C=O in the ultraviolet spectrum at full length was 243 nm. The infrared spectrum showed new etheric bonds O=C-OH at a wavelength of 1150 cm-1. The scanning electron microscopy analysis indicates that grapheme oxide is homogeneously coated by starch, it means that nanostarch was successfully polymerized on the surfaces of graphene oxide nanosheets and formed sandwich-like structures. The X-Ray diffraction analysis indicatedthat the crystalline structure changes to amorphous to a certain extent due to the ester bond formed between graphene oxide and starch. The electrical properties showed the resistivity of the initial graphene oxide was ρ = 5.53·103 Ohm·m and after its modification by starch, the resistivity of the graphene oxide/starch membrane increased by 2 orders, which was equal to 2.59·105 Ohm·m. According to the results, high dielectric materials are very important in electrical and electronics engineering. Therefore, there is no doubt that there will be great interest in this field.
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Ghosh, Ankita, i Soma Samaddar'. "Review on Graphene Nanoparticle Composites". International Journal of Chemical and Environmental Sciences 3, nr 1 (1.10.2021): 46–66. http://dx.doi.org/10.15864/268963821834540191.
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In recent years, graphene has attracted atlcntion. Grapheneis a thick planar sheet of Sp2 bonded carbon atoms. Its lattice is honey comb structure. Graphene is one of the most rising material due to its various fascinatingl properties. From recent study it is proved that graphene based composites with different nanoparticle show extensive applielltion. In this review we focus on recent developement in the synthetic approach, properties and the facilities of use of graph nanoparticle comosites. The advantages of graphene-nanupartide composites are specifically observed in catalytic reactions, electrochemical sensing, detection by surface enhanced Raman spectroscopy, purification of waterusing adsurbent and other applications are discussed here.
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Kang, Je, TaeGyeong Lim, Myeong Hee Jeong i Ji Won Suk. "Graphene Papers with Tailored Pore Structures Fabricated from Crumpled Graphene Spheres". Nanomaterials 9, nr 6 (30.05.2019): 815. http://dx.doi.org/10.3390/nano9060815.
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Graphene papers have great potential for various applications, such as electrodes in energy storage devices, protective coating, and desalination, because of their free-standing structure, flexibility, and chemical tunability. The inner structures of the graphene papers can affect their physical properties and device performance. Here, we investigated a way to fabricate graphene papers from crumpled reduced graphene oxide (rGO) spheres. We found that ultrasonication was useful for tailoring the morphology of the crumpled graphene spheres, resulting in a successful fabrication of graphene papers with tunable inner pore structures. The fabricated graphene papers showed changes in mechanical and electrical properties depending on their pore structures. In addition, the tailored pore structures had an influence on the electrochemical performance of supercapacitors with the fabricated graphene papers as electrode materials. This work demonstrates a facile method to fabricate graphene papers from crumpled rGO powders, as well as a fundamental understanding of the effect of the inner pore structures in mechanical, electrical, and electrochemical characteristics of graphene papers.
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Machado, L. D., P. A. S. Autreto i D. S. Galvao. "Graphyne Oxidation: Insights From a Reactive Molecular Dynamics Investigation". MRS Proceedings 1549 (2013): 53–58. http://dx.doi.org/10.1557/opl.2013.941.
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ABSTRACTGraphyne is a generic name for a family of carbon allotrope two-dimensional structures where sp2 (single and double bonds) and sp (triple bonds) hybridized states coexists. They exhibit very interesting electronic and mechanical properties sharing some of the unique graphene characteristics. Similarly to graphene, the graphyne electronic properties can be modified by chemical functionalization, such as; hydrogenation, fluorination and oxidation. Oxidation is of particular interest since it can produce significant structural damages.In this work we have investigated, through fully atomistic reactive molecular dynamics simulations, the dynamics and structural changes of the oxidation of single-layer graphyne membranes at room temperature. We have considered α, β, and γ-graphyne structures. Our results showed that the oxidation reactions are strongly site dependent and that the sp-hybridized carbon atoms are the preferential sites to chemical attacks. Our results also showed that the effectiveness of the oxidation (estimated from the number of oxygen atoms covalently bonded to carbon atoms) follows the α, β, γ-graphyne structure ordering. These differences can be explained by the fact that for α-graphyne structures the oxidation reactions occur in two steps: first, the oxygen atoms are trapped at the center of the large polygonal rings and then they react with the carbon atoms composing of the triple bonds. The small rings of γ-graphyne structures prevent these reactions to occur. The effectiveness of β-graphyne oxidation is between the α- and γ-graphynes.