Surface films structure

Electrochemical deposition of lithium usually forms a fresh Li surface which is exposed to the solution phase. The newly formed surface reacts immediately with the solution species and thus becomes covered by surface films composed of reduction products of solution species. In any event, the surface films that cover these electrodes have a multilayer structure [49], resulting from a delicate balance among several types of possible reduction processes of solution species, dissolution-deposition cycles of surface species, and secondary reactions between surface species and solution components, as explained above. Consequently, the microscopic surface film structure may be mosaiclike, containing different regions of surface species. The structure and composition of these surface films determine the morphology of Li dissolution-deposition processes and, thus, the performance of Li electrodes as battery anodes. Due to the mosaic structure of the surface... 

Layer-by-layer atomic composition of the films was determined by Auger spectroscopy (PHI-660 Perkin Elmer) after five second ion-beam cleaning of the films surface. Films structure was investigated by scanning (SEM) and transmission electron microscopy (TEM). 

Tn 1922 Adam (I) published the third paper in his extraordinary series on surface film structure. He observed that fatty acid monolayers greatly expanded on alkaline subphases. He also suggested that fatty acid anions desorbed or dissolved from the monolayer into the alkaline subphase. In 1933 he and Miller (2) showed that the composition of the subphase buffer significantly affected the monolayer thus palmitic and stearic acid monolayers were more condensed on 2N sodium hydroxide than on 2N potassium hydroxide. The expansion, desorption, and cation selectivity of ionizing monolayers are the subjects of this investigation. 

The material of interest is dissolved in a volatile solvent, spread on the surface and allowed to evaporate. As the sweep moves across, compressing the surface, the pressure is measured providing t versus the area per molecule, a. Care must be taken to ensure complete evaporation [1] and the film structure may depend on the nature of the spreading solvent [78]. When the trough area is used to calculate a, one must account for the area due to the meniscus [79]. Barnes and Sharp [80] have introduced a remotely operated barrier drive mechanism for cleaning the water surface while maintaining a closed environment. 

Uchida M, Tanizaki T, Gda T and Ka]iyama T 1991 Control of surface chemical-structure and functional property of Langmuir-Blodgett-film composed of new polymerizable amphiphile with a sodium-sulfonate Maoromoieouies 24 3238-43... 

The anodes are generally not of pure metals but of alloys. Certain alloying elements serve to give a fine-grained structure, leading to a relatively uniform metal loss from the surface. Others serve to reduce the self-corrosion and raise the current yield. Finally, alloying elements can prevent or reduce the tendency to surface film formation or passivation. Such activating additions are necessary with aluminum. 

Sputtered Neutral Mass Spectrometry (SNMS) is the mass spectrometric analysis of sputtered atoms ejected from a solid surface by energetic ion bombardment. The sputtered atoms are ionized for mass spectrometric analysis by a mechanism separate from the sputtering atomization. As such, SNMS is complementary to Secondary Ion Mass Spectrometry (SIMS), which is the mass spectrometric analysis of sputtered ions, as distinct from sputtered atoms. The forte of SNMS analysis, compared to SIMS, is the accurate measurement of concentration depth profiles through chemically complex thin-film structures, including interfaces, with excellent depth resolution and to trace concentration levels. Genetically both SALI and GDMS are specific examples of SNMS. In this article we concentrate on post ionization only by electron impact. 

Macroscopic heterogeneities, e.g. crevices, discontinuities in surface films, bimetallic contacts etc. will have a pronounced effect on the location and the kinetics of the corrosion reaction and are considered in various sections throughout this work. Practical environments are shown schematically in Fig. 1.3, which also serves to emphasise the relationship between the detailed structure of the metal, the environment, and external factors such as stress, fatigue, velocity, impingement, etc. 

Secondly, crystal defects might be expected to affect the corrosion behaviour of metals which owe their corrosion resistance to the presence of thin passive or thick protective films on their surface. The crystal defects and structural features discussed in Section 20.4 might, in principle, be expected to affect the thickness, strength, adhesion, porosity, composition, solubility, etc. of these surface films, and hence, in turn, the corrosion behaviour of the filmed metal surfaces. Clearly, this is the more common situation in practice. 

Influence of Structure on Surface Films—Pitting Corrosion... 

So far the structure of pure metals has been discussed with reference to bulk characteristics and continuous crystals. However, corrosion is essentially a surface phenomenon and it is necessary to consider how the structure and defects already described interact with free surfaces. At this stage it is convenient to consider only a film-free metal surface, although of course in most corrosion phenomena the presence of surface films is of the utmost importance. Furthermore, it is at free surfaces that the hard sphere model of metals... 

According to the depth profile of lithium passivated in LiAsF6 / dimethoxyethane (DME), the SEI has a bilayer structure containing lithium methoxide, LiOH, Li20, and LiF [21]. The oxide-hydroxide layer is close to the lithium surface and there are solvent-reduction species in the outer part of the film. The thickness of the surface film formed on lithium freshly immersed in LiAsF /DME solutions is of the order of 100 A. 

It has been proposed recently [28] that static friction may result from the molecules of a third medium, such as adsorbed monolayers or liquid lubricant confined between the surfaces. The confined molecules can easily adjust or rearrange themselves to form localized structures that are conformal to both adjacent surfaces, so that they stay at the energy minimum. A finite lateral force is required to initiate motion because the energy barrier created by the substrate-medium system has to be overcome, which gives rise to a static friction depending on the interfacial substances. The model is consistent with the results of computer simulations [29], meanwhile it successfully explains the sensitivity of friction to surface film or contamination. 

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