Graphite, liquid phases

Whereas superaeid (HF/BF3, HF/SbF, HF/TaF FS03FI/SbF3, etc.)-eatalyzed hydroearbon transformations were first explored in the liquid phase, subsequently, solid aeid eatalyst systems, sueh as those based on Nafion-H, longer-chain perfluorinated alkanesulfonic acids, fluorinated graphite intercalates, etc. were also developed and utilized for heterogeneous reactions. The strong acidic nature of zeolite catalysts was also successfully explored in cases such as FI-ZSM-5 at high temperatures. 

Fig. 5. A growth model of a nanocapsule partially filled with a crystallite of rare-earth carbide (RCj for R = Y, La,. . . , Lu R,C4 for R = Sc) (a) R-C alloy particles, which may be in a liquid or quasi-liquid phase, are formed on the surface of a cathode (b) solidification (graphitizalion) begins from the surface of a particle, and R-enriched liquid is left inside (c) graphite cage outside equilibrates with RCj (or R3C4 for R = Sc) inside.

Intermolecular forces are responsible for the existence of several different phases of matter. A phase is a form of matter that is uniform throughout in both chemical composition and physical state. The phases of matter include the three common physical states, solid, liquid, and gas (or vapor), introduced in Section A. Many substances have more than one solid phase, with different arrangements of their atoms or molecules. For instance, carbon has several solid phases one is the hard, brilliantly transparent diamond we value and treasure and another is the soft, slippery, black graphite we use in common pencil lead. A condensed phase means simply a solid or liquid phase. The temperature at which a gas condenses to a liquid or a solid depends on the strength of the attractive forces between its molecules. 

As we saw in Section 5.1, a single substance can exist in different phases, or physical forms. The phases of a substance include its solid, liquid, and gaseous forms and its different solid forms, such as the diamond and graphite phases of carbon. In one case—helium—two liquid phases are known to exist. The conversion of a substance from one phase into another, such as the melting of ice, the vaporization of water, and the conversion of graphite into diamond, is called a phase transition (recall Section 6.11). 

Use the phase diagram for carbon in Exercise 8.14 (a) to describe the phase transitions that carbon would undergo if compressed at a constant temperature of 2000 K from 100 atm to 1 X 106 atm (b) to rank the diamond, graphite, and liquid phases of carbon in order of increasing density. 

The second processing step consisted of salt decomposition with the subsequent reduction to pure metal. The method of chemical deposition of metal salts from the water salt solution with the subsequent reduction to pure metal by liquid phase reducer has been applied to prepare graphite-tin CMs. In this case tin chloride was used for impregnation and potassium tetrahydroborate was used as liquid phase reducer. 

Above the eutectic temperature in the iron-FcsC system (1130°C)12, growth of large graphite plates and flakes occurs from the liquid phase. Carbon precipitates in the form of highly ordered graphite crystals from molten iron supersaturated with carbon. The Raman spectrum for chlorination at 1200°C is shown in Fig. 2c. A very strong and narrow... 

Fig. 2.1 Top-down synthesis methods, (a) Micromechanical cleavage (b) ion intercalation (c) graphite oxide (d) liquid-phase exfoliation.

Fig. 2.4 Typical Raman spectra of (a) graphite, with peaks labeled as discussed in the text (b) graphene (liquid-phase exfoliated). Inset Evolution of 2D-band with increasing layer numbers [120],...

Y. Hernandez, V. Nicolosi, M. Lotya, F.M. Blighe, Z. Sun, S. De, et ah, High-yield production of graphene by liquid-phase exfoliation of graphite, Nature Nanotechnology, 3 (2008) 563-568. 

M. Lotya, Y. Hernandez, P.J. King, R.J. Smith, V. Nicolosi, L.S. Karlsson, et ah, Liquid phase production of graphene by exfoliation of graphite in surfactant/water solutions, Journal of the American Chemical Society, 131 (2009) 3611-3620. 

Organic Adsorbents. (a) Organic crystal compounds (e.g., benzophenone on firebrick, anthraquinone on graphitized carbon black, phthalic anhydride and/or phthalic acid isomers on Chromo-sorb G). (b) Liquid phases below their melting point (e.g.,... 

Brooks, J. D. and Taylor, G. H. The formation of graphitizing carbons from the liquid phase. Carbon 3, 185 (1965) (see also the Extended Abstracts of the 12th Biennial Conference on Carbon , Am. Carbon Soc., 1975). 

The successful conversion of graphite to diamond involves crystallizing the diamond from a liquid melt. The solvent most often used is nickel metal, or alloys of nickel with other ferrous metals. The reason for this success can be seen by referring to Figure 15.7, the binary (solid + liquid) phase diagram for (nickel + carbon).u8 We note from the figure that (Ni + C) forms a simple... 

Graphite 300 Light hydrocarbons, H2S, S02, CH3SH, sour gas Often modified with small quantities (1.5-5%) of conventional liquid phases requires oxygen-free carrier... 

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