Surface-fluorinated graphite

Charge-discharge behavior of surface-fluorinated graphite... 

Table 4 shows the compositions of surface-fluorinated graphite samples, obtained by elemental analysis, and surface compositions calculated from the peak areas of... 

Binding energies of X-ray photoelectron spectra of surface-fluorinated graphite samples... 

A further advantageous modification of electrodes is claimed by Watanabe [154] for the Central Glass Co. Ltd. which uses anodes coated with a composite layer of nickel containing a dispersed eutectoid of PTFE particles or fluorinated graphite particles. The low surface energy nickel based composite is said to improve the yield of perfluorooctanesulphonyl fluoride to 40.5 % in ECF. 

In equation 5, C is amorphous carbon and CF2 changes to many perfluorocarbons, such as CF4, C2F6, etc., by secondary reactions. The surface coverage of graphite fluoride on the anode depends on the relative reaction rates of equations 4 and 5. Equation 6 has been introduced to analyze the wettability of the carbon surface with graphite fluoride formed on it.2 It shows the relationship between the fraction of effective surface for equation 3 per unit surface area of carbon (a) and the contact angle (0) of a fluorine gas bubble on the surface of the carbon electrode.2... 

The hydrophobic nature of F-treated graphite can be evaluated from contact-angles of liquid droplets. The surface free-energy can be reduced from 50 mJ m-2 to as low as 7 mJ m-2 after exposure to NF3 or SF6 rf plasmas. A significant coverage of surface fluorination is achieved for exposure times of 10-15 min under an NF3 plasma, yielding water contact angle of 115° [91], In some case this value has been found to exceed that of PTFE [92]. 

Composition and structure changes of graphite by surface fluorination... 

In order to increase the reaction rate and capacity, some methods to modify the surface structure and composition were recently attempted [42-49], They are surface oxidation [42-45] and surface fluorination [46-48] of graphite and carbon, and metal coating to carbon surface [49], These show that surface modifications are useful techniques to improve the electrochemical characteristics of graphite and carbon. 

Fig. 14. Charge-discharge curves of original graphite, surface fluorinated samples (10th cycle).-- ...

In this contribution it is shown that local density functional (LDF) theory accurately predicts structural and electronic properties of metallic systems (such as W and its (001) surface) and covalently bonded systems (such as graphite and the ethylene and fluorine molecules). Furthermore, electron density related quantities such as the spin density compare excellently with experiment as illustrated for the di-phenyl-picryl-hydrazyl (DPPH) radical. Finally, the capabilities of this approach are demonstrated for the bonding of Cu and Ag on a Si(lll) surface as related to their catalytic activities. Thus, LDF theory provides a unified approach to the electronic structures of metals, covalendy bonded molecules, as well as semiconductor surfaces. 

We have shown that local density functional (LDF) theory provides a methodology that allows a unified theoretical/computational study of such diverse systems as bulk W and its surface, graphite, the ethylene, fluorine, and DPPH... 

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