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Graphene: A Brief Overview
Published in Ruquan Ye, James M. Tour, Laser-Induced Graphene, 2020
For the translation of the laboratory discovery of graphene to products, graphene needs to be cost-effectively manufactured on a larger scale, and 3D structures are no exception. So far, there have been many methods for preparation of 3D graphene foams, including chemical vapor deposition (CVD), mechanical exfoliation from graphite, liquid phase exfoliation, wet-chemistry redox processes, and others, followed by 3D structuring [9]. Each of the methods has its own advantages in the preparation of graphene of different grades at varied costs, which is an important advancement toward the commercialization of graphene. In general, the cost of CVD-growth graphene is higher, and the quality of the graphene is also higher, which can find applicability in advanced technologies such as flexible electronics, photonics, transistors, and future devices [8]. Exfoliations by means of chemical or electrochemical processes produce lower-grade graphene, but they are the most popular approaches for the preparation of graphene on a large scale [12, 13]. The exfoliated process from graphite usually affords FLG or graphene nanoplatelets (GNPs), and this material in 3D foams has found use in composites, catalysis, and heat dissipation platforms. Here we will introduce some conventional methods that have been reported for the synthesis of 3D graphene.
Graphene-based Porous Materials for Advanced Energy Storage in Supercapacitors
Published in Ranjusha Rajagopalan, Avinash Balakrishnan, Innovations in Engineered Porous Materials for Energy Generation and Storage Applications, 2018
Zhong-Shuai Wu, Xiaoyu Shi, Han Xiao, Jieqiong Qin, Sen Wang, Yanfeng Dong, Feng Zhou, Shuanghao Zheng, Feng Su, Xinhe Bao
3D graphene hybrid frameworks usually refer to macroporous interconnected graphene-based network structure with intriguing properties of graphene nanosheets and intriguing features of individual components. Graphene foams (GFs), as typical 3D macroscopic graphene architecture, possess high surface area, excellent conductivity, low weight density and strong mechanical strength, which are impressive in electronic devices, environmental engineering and biomedical sciences fields (Jiang and Fan 2014). Normally, GFs and its derivatives can be obtained by hydrothermal method, chemical reduction method, template-directed chemical vapor deposition (CVD) method or their combination. GFs incorporated with metal oxides or polymers are intensively developed for high-performance electrodes for pseudocapacitors.
Synthesis of Graphene Nanosheets
Published in Ling Bing Kong, Carbon Nanomaterials Based on Graphene Nanosheets, 2017
Ling Bing Kong, Freddy Boey, Yizhong Huang, Zhichuan Jason Xu, Kun Zhou, Sean Li, Wenxiu Que, Hui Huang, Tianshu Zhang
Both the GO and graphene materials were made into solid foams from their colloidal suspensions, by using a freeze-drying method, as demonstrated in Fig. 2.89 (a) and (b). Their SEM images are shown in Fig. 2.89 (c) and (d), respectively. The foams exhibited an ultra-hollow framework structure, consisting of the large nanosheets. The graphene foam could be further purified by annealing in an inert atmosphere. The annealed graphene foam was highly conductive, but still behaving like a sponge with high elasticity and flexibility. It was found that the nanosheets were highly cross-linked after the thermal annealing. The suspensions could also be filtrated to make GO and graphene papers with high electrical conductivities [205].
Scientific worth of polymer and graphene foam-based nanomaterials
Published in Journal of the Chinese Advanced Materials Society, 2018
Graphene is a nanoallotrope of carbon consisting of single layer of hexagonally arranged carbon atoms. Graphene has gained academic and industrial interest owing to transparency, heat and electricity conduction, nonlinear diamagnetism, etc.[21,22] Doping of graphene has been used as an effective way to enhance the electronic, mechanical, and thermal properties for electrochemical sensors, electronic devices, transistor, supercapacitor, transparent conductor, etc.[23,24] Graphene has also been used as a biocompatible biomaterial in biosensor, imaging, drug delivery, and tissue engineering.[25] Recently, carbon-based sponge-like structures have high porosity, flexibility, and deformation stability.[26,27] Graphene foam is an open-cell foam consisting of single-layer of graphene nanosheet (Figure 1). Foam-like graphene nanostructures possess high flexibility, porosity, and robustness. 3D porous low-density assemblies also have high electrical conductivity, thermal conductivity, electron mobility, elasticity, stiffness, and large internal surface area.[28] These properties render graphene foams important in sensors, actuators, catalytic supports, adsorption, and compression tolerant electrodes for supercapacitors. However, it is challenging to synthesize the porous foams with large surface areas, high flexibility, ultrahigh compressibility, as well as robustness.[29] Various techniques have been used to fabricate 3D foams, for example, self-assembly method can form macroscopic free-standing graphene foam with adjustable electrical conductivity and air-similar density. The 3D interconnected graphene networks fabricated from 2D graphene nanosheet may open ways for superlight high-performance nanomaterial.[30]
On hygrothermal wave dispersion characteristics of embedded graphene foam
Published in Waves in Random and Complex Media, 2022
As graphene foam examples, Yang and Chen [36] reported the preparation of GF excited with magnetite nanoparticles and its usage for the adsorption of oil and organic solvents. Li and Sun [37] studied thermal transport behavior of graphene foam. They found out that highly porous free-standing graphene foam indicates an abnormal characteristic in such a way that graphene foam’s thermal property gets greater with temperature above room temperature. Coarse grain molecular dynamics simulation (CGMDS) was carried out by Wangand Zhang [38] to explore the mechanical behavior of GF. The acoustic performance of thermos-acoustic sound generating devices made of bi-layer graphene and graphene foam was analyzed by Lee and Jang [39]. Energy dissipation capability of graphene foam was investigated by Wang and Pan [40] based on CGMDS. The Chebyshev–Ritz method is implemented by Wang and Teng [41] to analyze natural frequency of circular and annular three-dimensional GF (3D-GF) plates under various boundary conditions. Wang and Liu [42] investigated free vibration and stability analyses of polymeric shells reinforced with 3D-GFs utilizing Navier and Galerkin method. Bending and stability characteristics of plates consist of 3D-GFs based on the two-variable refined plate theory are explored by Wang and Zhang [43]. Later, Wang and Zhao [44] have just studied vibration, bending and buckling of 3D-GF beams on the basis of the SSDT by using Navier’s method and Rayleigh–Ritz method. Sound radiation and sound transmission loss responses of porous 3D-GF plate based on refined plate theory were presented by Kumar and Gunasekaran [45]. By seeking in literature, it can be found obviously that no investigation on wave propagation analysis of porous graphene foam (PGF) beam lying on an elastic medium exposed to hygrothermal environment has not been reported yet.
Synthesis, experimental testing and multi-scale modelling of graphene foam/epoxy composite
Published in Mechanics of Advanced Materials and Structures, 2023
Sajedeh Khosravani, Mohammad Homayoune Sadr, Erasmo Carrera, Alfonso Pagani
Most graphene/polymer composites are prepared by in situ polymerization and solution mixing methods, but the problem is that graphene sheets tend to agglomerate due to the strong van der Waals forces, which reduces networking [5]. Consequently, the dispersion of the reinforcement in the polymer matrix and the expected properties are not achieved. So graphene is challenged for use in the macro dimension. There are many methods such as surface functionalization of graphene sheets or polymer matrix chains, graphene surface modification, graphene alignment in polymer, and exfoliation of graphene sheets to improve the dispersion of graphene sheets within the matrix [6, 7]. However, none of them can still significantly improve the agglomeration problem, and some of them alter the inherent properties of graphene. On the other hand, an efficient way of dispersing graphene sheets in the polymer matrix in the form of three-dimensional graphene hydrogel, graphene aerogel, and thin-film plates have been introduced to solve the dispersion problem [8, 9]. Three-dimensional graphene is an excellent way to reduce two-dimensional graphene problems. These materials have advanced a lot due to their high performance, such as open porosity, lightweight, high pore connection, large surface area, remarkable strength, etc. [10]. Graphene foam is one of the carbon foam structures that consists of several graphene sheets and pores. Graphene foam (sometimes called three-dimensional monolayer graphene or sponge graphene) is a new material presented in 2011 [11]. In experimental methods for synthesizing graphene foam, the principle is to remove the force between the graphene sheets in the graphite. However, for production of it, there are many methods such as template directing, cross-linking, chemical vapor deposition, and in situ reduction assembly [12], but some efficient methods are still being improved.