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Electrochemistry of Porous Carbon-Based Materials
Published in Antonio Doménech-Carbó, Electrochemistry of Porous Materials, 2021
Recently, a lot of new carbon materials have been introduced in the electrochemistry world—from boron-doped diamond electrodes to fullerenes; from carbon black, porous carbons, and carbon fiber electrodes to carbon nanotubes (CNTs) [2]. Glassy carbon (or vitreous carbon) is routinely used in electrochemistry. It is produced by thermal degradation of selected organic polymers followed by carbonization at temperatures ca. 1800 °C and constitutes a widely used working electrode. Graphene—discovered in 2004 [3]—and its derivatives [4] are making a profound impact in science and technology. Several properties of carbons (for precise definitions of different types of carbons, see Ref. [5]) make these materials of particular interest for electrochemical applications; carbon materials are relatively inert in contact with most electrolytes while retaining a high degree of surface activity and admitting different functionalization/derivatization procedures. Novel porous carbon materials have attracted attention for their use as adsorbents, gas storage and catalyst support, and electrode materials in supercapacitors, batteries, fuel cells, and separation techniques based on electro-sorption, etc. [6].
Application of 3D Porous Graphene in Emission Electronics: New Atomistic Model and Numerical Estimations
Published in Olga E. Glukhova, 2D and 3D Graphene Nanocomposites, 2019
Olga E. Glukhova, Michael M. Slepchenkov
Optimization of the nanostructure in the large box was carried out for a long time. From the resulting structure, a cubic fragment with dimensions 5 × 5 × 5 nm was cut out and periodic boundary conditions were set. Despite the fact that glass-like carbon is not a periodic structure, we had to introduce a supercell to study the properties of this interesting material. Such a fragment in a small periodic box is shown in Fig. 5.2a. The structure represents an unordered mixture of carbon nanostructures whose atoms are in the state of sp-, sp2-, and sp3 hybridization. Since the atomic grid of the periodic box is chaotic, the translation of the box made the material isotropic in correspondence with the real situation. The view of the box structure corresponded with the structure after 15 ps of optimization at the temperature of 1300 K. After that, the structure was again optimized and insignificantly contracted in all directions. During this process, the density of the structure increased. It was done to achieve the required density corresponding to similar porous carbons of type II glass carbon. In Ref. [6], its value equals to 1.42 g/cm3. The density of our glassy carbon model is 1.22 g/cm3 with the dimensions of the cubic cell 4 × 4 × 4 nm. The number of atoms in the supercell is 3918. The size of the box is typical for the modeling of porous glassy carbon since the pore sizes for type II glass carbon are 0.25–2.00 nm as shown by Harris [9, 10].
Polymers
Published in Bryan Ellis, Ray Smith, Polymers, 2008
Applications: Synthetic carbons from graphite are used as special electrodes. Carbon materials form good inert impermeable lining materials for chemical apparatus and nuclear reactors. With carbon-fibre reinforcement they may be used as structural materials for large-scale apparatus in the chemical industry e.g. for heat exchangers. Glassy carbon has found application in several high-technology areas: as compressor wheels for turbo blowers, melting crucibles, vacuum vaporisation boats for metal deposition coatings, spinning nozzles, precision bearings and spot- welding electrodes. Glassy carbon is also used in medical implants: electrodes for heart pacemakers, artificial cardiac valves and bile ducts. Phenolic resins are included in the composition of heat shield laminates for spacecraft. They form a sacrificial ablative coating able to withstand the temp. shock of 140008 during re-entry in the earth's atmosphere
Electrochemical reduction of halogenated organic contaminants using carbon-based cathodes: A review
Published in Critical Reviews in Environmental Science and Technology, 2023
Jacob F. King, William A. Mitch
In addition to conventional carbon materials (e.g., graphite, glassy carbon), electrodes can be fashioned from black carbons, which include biochars and activated carbons. While properties of black carbons have been reviewed recently (Pignatello et al., 2017), aspects relevant to electrodes are summarized here. Biochars are produced by heating cellulosic (e.g., grasses) or lignin-containing (e.g., hardwood) materials under anoxic conditions (i.e., pyrolysis) at temperatures ranging from 300-900 °C. Increasing pyrolysis temperatures drive off hydrogen and oxygen, forming saturated carbon bonds and aromatic rings (Table 1) (Klüpfel et al., 2014; Lattao et al., 2014; W. Xu et al., 2013). At the same time, increasing pyrolysis temperature led to fusion of aromatic rings to form micrographitic regions, with the mean number of carbons in micrographitic regions increasing from 8 to 76 as the pyrolysis temperature increased from 300-700 °C for maple wood (Cao et al., 2012). Graphite itself features extended graphene sheets with minimal H (1.6% by weight) and O (<0.01% by weight) content (Table 1) (W. Xu et al., 2013).
Co-production of hydrogen and carbon nanotubes by catalytic cracking of waste cooking oil model compound over Ni-Cu/Al-KCC-1
Published in Environmental Technology, 2023
Songyuan Hao, Hong Yuan, Huiliang Zhou
Figure 11 presents the Raman spectra of the CNTs deposited on the different catalysts. The signal at 1580 cm−1 was assigned to the G-band that is associated with the tangential stretching modes of sp2 hybridised carbon in graphite layers with a high degree of crystalline order. The signal at 1320 cm−1 was attributed to the D-band associated with sp3 hybridised carbon in disordered graphite or glassy carbon [35]. The 2D signal at 2690 cm−1 was related to the degree of CNT purity. The ratios of the intensity of the D peak to the G peak (ID/IG) for the various samples were all less than 1, demonstrating that the CNTs deposited on each catalyst were highly crystalline with a significant degree of graphitisation.
Research progress of spectra and properties of ultrahard carbon materials at high pressure and high temperature
Published in Functional Diamond, 2022
Zhiqiang Hou, Haikuo Wang, Yao Tang, Jiakun Wu, Chao Wang, Zhicai Zhang, Xiaoping Ouyang
Glassy carbon is an amorphous carbon allotrope containing nearly 100% sp2 bonding at ambient conditions [67]. Compressing glassy carbon to 44 GPa or higher pressure at room temperature in a DAC observed complete conversion of sp2 bonding and formed a new carbon allotrope with a fully sp3-bonded amorphous structure, but the transition was reversible upon releasing pressure [6]. Used the glassy carbon ball as an indenter, its strength could reach up to 130 GPa with a confining pressure of 60 GPa. Such an extremely large stress difference (>70 GPa) has never been observed in any material besides diamond, indicating this high-pressure carbon allotrope possesses the high hardness (above 40 GPa) and diamondlike strength. The extreme pressure-hardening behavior of this phase may be used as a second stage anvil or as a gasket material which hardens with pressure.