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Functionalization of Graphite and Graphene
Published in Titash Mondal, Anil K. Bhowmick, Graphene-Rubber Nanocomposites, 2023
Akash Ghosh, Simran Sharma, Anil K. Bhowmick, Titash Mondal
As shown in Figure 4.1a, graphene demonstrates a hexagonal lattice. Ideally, the lattice system of graphene cannot be classified as a Bravais lattice. Typically, the lattice system of graphene is considered as a fusion of two triangular lattices wherein the one individual carbon atom is linked to three other neighboring carbon atoms with carbon single bond carbon distance of 0.142 nm. This forms the two-dimensional crystal, which is of P6mm plane group. The structural rigidity is attributed to the formation of sigma bonds, due to the interaction of three half-filled valence orbitals, thereby leaving a half-filled orbital in an uncoupled state. These uncoupled orbitals result in the formation of a pi-cloud as shown in Figure 4.1b.
Graphene from Rice Husk
Published in Amir Al-Ahmed, Inamuddin, Graphene from Natural Sources, 2023
Hosam M. Saleh, Amal I. Hassan
In 2004, a group of scientists from the University of Manchester in the United Kingdom discovered graphene, which ushered in a global revolution in scientific study. Graphene is a cross-linked carbon sheet made up of sp2-hybridized [4]. Graphene's most notable features of thermal and electrical conductivity are because of its hexagonal lattice structure [5]. Chemically, graphene comprises a single element, carbon isotope C-12, which has four free electrons, which facilitates formatting bonds with other atoms. Graphene takes part in many chemical reactions as a reactant, an electron donor, or an oxidizing agent (electron acceptor). It directly results from graphene's electron structure, which gives it an electron affinity and an ionization potential of about 4.6 eV [6]. Because of its 2D crystals, it has novel electronic and mechanical properties, high electronic mobility, structural flexibility, and the ability to be tuned from p-type to n-type by applying gate voltage [7].
Introduction to Graphene
Published in Yaser M. Banadaki, Safura Sharifi, Graphene Nanostructures, 2019
Yaser M. Banadaki, Safura Sharifi
Graphene has a honeycomb-like hexagonal lattice, as shown in Fig. 1.2a. As such, the carbon atoms form strong a covalent bonds by three in-plane sp2-hybridized orbitals, whereas the fourth bond is a π bond in z-direction [12]. The electron in this bond can move freely in the delocalized π-electronic system referred as the π-band and π*-bands [13]. The lattice structure of graphene made out of two interpenetrating triangular lattices results in a unit cell consisting of two atoms, as shown in Fig. 1.2b. The lattice vectors can be written as follows: a1→=acc2(3,3),a2→=acc2(3,−3)
Current trends in additively manufactured (3D printed) energy absorbing structures for crashworthiness application – a review
Published in Virtual and Physical Prototyping, 2022
Chukwuemeke William Isaac, Fabian Duddeck
Other shape configuration 3D printed lattices that have been configured as energy absorbers are the multi-circular lattice (Wang et al. 2021), hexagonal lattice (Dong and Fan 2022), octahedral lattice (Bai et al. 2020), cubic lattice (Wang et al. 2021; Wang et al. 2020; Shen et al. 2016) and hollow-walled lattice (Noronha et al. 2021). The hexagonal lattice is a similitude of the honeycomb structure. When subjected to in-plane loading, no outstanding energy absorption results were obtained. With out-of-plane compression, the initial peak force can be very high, and the CLE is not as competitive as for other energy absorbers. A buckling orientation systemic solution can be adopted to lower the initial peak force and consequently lead to increment in the CLE of the hexagonal lattice structure. The hexagonal lattice with this buckling orientation pattern can achieve maximum SEA when subjected to quasi-static in-plane loading condition. However, under out-of-plane loading condition, the crushing parameters such as the SEA and MCL can become decreased compared to those of the conventional hexagon lattice.
Image hiding technique using a pseudo hexagonal structure approach
Published in International Journal of Computers and Applications, 2019
Image processing applications like image rotation, edge detection etc. in hexagonal lattice have already been discussed by many researchers. Middleton and Sivaswamy [19] proposed an edge detection method in a hexagonal image processing frame work. In this work the authors conclude that the hexagonal frame work gives better results for edge detection. Vidya et al. [20,21] also analyzed the performance of edge detection on hexagonal sampling grid. Comparisons of image alignment on hexagonal and square lattices were performed by Shima et al. [22]. Azam et al. [23] were proposed Discrete Cosine Transform based method for face recognition in hexagonal images. Wavelet based image compression in hexagonal domain was proposed by Jeevan K.M. and Krishnakumar S in the paper titled ‘Compression of images represented in hexagonal lattice using wavelet and gabor filter’ [24]. In all these works, the authors confirmed that, the hexagonal representation gives better results.
Low-cost synthesis of high-quality graphene in do-it-yourself CVD reactor
Published in Automatika, 2018
Graphene [1] is material composed entirely of carbon atoms arranged in the two-dimensional hexagonal lattice structure. Due to its one-atom thickness (approximately 3 Angstrom) it is the thinnest material available. In addition, the strong bonds between carbon atoms result in thermodynamic stability of graphene sheets [2] even when suspended in air. Graphene has exceptional mechanical and thermal properties. The Young’s modulus is 1 TPa, the tensile strength reaches a value of 100 GPa, while the thermal conductivity is 5000 W/mK [3]. From an electrical engineering point of view, a graphene is actually a zero-gap semiconductor material that supports ballistic transport [4] accompanied with very high charge mobility of 200,000 cm2/V [5] and the sheet resistance of 125 Ω-1 [6]. Particularly interesting is the fact that graphene can be viewed as a plasmonic material with the plasma frequency in the THz band [7]. In principle, plasma frequency can be tuned electrically, by changing electrochemical potential [8]. This interesting property was used in recent proposals of various THz and optical metamaterial-inspired structures such as absorbers [9], antennas [10], single-atom thick waveguides [11], reflectors [12], and lenses [13]. In addition, there have been several attempts to use non-linear electromagnetic properties of the graphene, in order to construct high-speed THz modulators [14]. Of course, all of these interesting engineering applications presume that there is a reliable and affordable graphene synthesis technology.