Ethylene, carbon layers

The cooled mixture is transferred to a 3-1. separatory funnel, and the ethylene dichloride layer is removed. The aqueous phase is extracted three times with a total of about 500 ml. of ether. The ether and ethylene chloride solutions are combined and washed with three 100-ml. portions of saturated aqueous sodium carbonate solution, which is added cautiously at first to avoid too rapid evolution of carbon dioxide. The non-aqueous solution is then dried over anhydrous sodium carbonate, the solvents are distilled, and the remaining liquid is transferred to a Claisen flask and distilled from an oil bath under reduced pressure (Note 5). The aldehyde boils at 78° at 2 mm. there is very little fore-run and very little residue. The yield of crude 2-pyrrolealdehyde is 85-90 g. (89-95%), as an almost water-white liquid which soon crystallizes. A sample dried on a clay plate melts at 35 0°. The crude product is purified by dissolving in boiling petroleum ether (b.p. 40-60°), in the ratio of 1 g. of crude 2-pyrrolealdehyde to 25 ml. of solvent, and cooling the solution slowly to room temperature, followed by refrigeration for a few hours. The pure aldehyde is obtained from the crude in approximately 85% recovery. The over-all yield from pyrrole is 78-79% of pure 2-pyrrolealdehyde, m.p. 44 5°. 

Most of the ethylene that interacts with Ru(001) at 323 K produces a nondesorbable carbon layer. This result is similar to that for the interaction of C2H4 with Ni, which produces a surface carbide at temperatures between about 300-600 K (14). SIMS results suggest, however, the presence of small amounts of molecularly adsorbed ethylene, acetylenic and other hydrocarbon complexes in addition to the nondesorbable carbon layer. 

The formation of several volatile carbon hydrides in the hydrogen-graphite reaction between 360 and 800° was reported by Breisacher and Marx (138). The formation of ethane, ethylene, propylene, and even butane suggests that the edge of the carbon layers became hydrogenated in the first step of this reaction. The results were discussed on the basis of a mechanism proposal by Zielke and Gorin (139). 

A typical lithium-ion cell consists of a positive electrode composed of a thin layer of powdered metal oxide (e.g., LiCo02) mounted on aluminum foil and a negative electrode formed from a thin layer of powdered graphite, or certain other carbons, mounted on a copper foil. The two electrodes are separated by a porous plastic film soaked typically in LiPFe dissolved in a mixture of organic solvents such as ethylene carbonate (EC), ethyl methyl carbonate (EMC), or diethyl carbonate (DEC). In the charge/ discharge process, lithium ions are inserted or extracted from the interstitial space between atomic layers within the active materials. 

As already mentioned, salt-containing liquid solvents are typically used as electrolytes. The most prominent example is LiPF6 as a conductive salt, dissolved in a 1 1 mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) as 1 molar solution. It should be mentioned that this electrolyte is not thermodynamically stable in contact with lithium or, for example, LiC6. Its success comes from the fact that it forms an extremely stable passivation layer on top of the electrode, the so-called solid-electrolyte interface (SEI) [35], Key properties of such SEI layers are high Li+ and very low e conductivity - that is, they act as additional electrolyte films, where the electrode potential drops to a level the liquid electrolyte can withstand [36],... 

Figure 18. Galvanostatic discharge curves at room temperature and at 0.1 mA cm for layered cobalt and nickel oxides, and spinel manganese oxide in ethylene carbonate-diethyl carbonate-LiN(CF3S02)2 [134] (by permission of Elsevier Seience S.A. S. Megahed, B. Scrosati, J. Power...

Naji, A., Ghanbaja, J., Humbert, B., Willmann, P., and Billaud, D. (1996). Electroreduction of graphite in LiC104-ethylene carbonate electrolyte. Characterization of the passivating layer by transmission electron microscopy and Fourier-transform infrared spectroscopy. J. Power Some., 63, 33—9. 

Most of the ethylene that interacts with an Ru(OOl) surface at 323 K produces a nondesorbable carbon layer. 

Thermal desorption of CO, Auger electron spectroscopy, and temperature programmed oxidation all show that the carbon layer 1) is Immobile below 550 K 2) forms a more densely packed surface phase at temperatures of 550-1150 K and 3) dissolves into the bulk at 1350 K. SIMS measurements of isotope mixing in the ions confirm formation of dense-phase (graphitic) islands after heating the carbon layer to 923 K. SIMS spectra also demonstrate that at 520 K, CO dissociates on Ru(OOl). The oxygen-free carbon layer that forms behaves similarly to the carbon from ethylene. Both SIMS and thermal desorption results show no positive interaction between adsorbed CO and D but significant attraction between and C formed by CO dissociation. 

Carbon Layers From Ethylene. Carbon coverage as a function of ethylene exposure at 323 K has been determined previously by recording the amount of CO desorbed during TPO XU Half monolayer (M.L.) coverage by carbon requires about 2 Langmuirs (L) of C H, while 1.1 monolayer coverage corresponds to 15 L. Molecular species removed... 

CO Thermal Desorption. On a clean Ru(OOl) surface, 9 L of CO induces saturation coverage by molecular CO. When this dose of CO is applied to a surface preexposed to C H at 323 K, the CO uptake is diminished but not completely blocked by the carbon layer. The CO uptake is still 90% of the saturation value when the carbon coverage is 1/4 M.L. and falls to 1/4 of the saturation value after 15 L preexposure to ethylene. 

For Case A, the peak area ratio of 25 to (24 + 26) goes from 0.75 at 435 K to nearly 1 at 818 K. The substantial isotope mixing at low temperature shows that molecular emission of intact C2 from the original ethylene molecule does not occur. It is interesting, however, that the isotope mixing is not complete at the lower annealing temperatures. This suggests that proximity of the parent carbons is preserved at low temperature and supports the conclusion that the carbon layer is immobile at temperatures below about 550 K. 

It follows that d ln gni/[d(dAi is a minimum when din m/d(dAm (j>) = 0, that is, when = Nd- The inner layer capacity curve calculated with the parameters chosen previously for the two-state system and with a low value of U p is also shown in fig. 10.24. As predicted, a minimum occurs at the position of the maximum on the curve for the two-state system. At charge densities sufficiently far from the minimum, maxima are observed. The three-state model is able to account for inner layer capacity curves in a variety of solvents such as methanol, ethylene carbonate, and dimethylformamide [35]. 

Styrene/butadiene polymer food-contact articles, interior core layer Ethylene/carbon monoxide copolymer food-contact articles, multilaminate Ethylene/carbon monoxide copolymer food-contact coating copolymer, metal Sodium 2-sulfoethyl methacrylate food-contact coatings Glyceryl rosinate Methyl rosinate Pentaerythrityl rosinate food-contact polymers Iron oxides... 

Because of a high barrier for the reaction leading to oligo(ethylene carbonate) formation, this reaction is expected to be slnggish with a low yield. It is consistent with the formation of a thin passivation layer on the cathode surface. Poly(ethylene carbonate) formation on cathode surfaces as a result of the oxidation-induced decomposition of an EC-based electrolyte was also recently suggested from experimental studies [46]. 

Graphites can be used alone as smoke suppressants giving a heat insulation effect but, for some applications, the expanded carbon layers are too unstable and other FRs, such as zinc borate, APP or ethylene diamine phosphate, can be used as stabilisers, to give a good span of properties and applications. 

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