Action film formation

The formation of passivating films on lithium in contact with liquid or soluble cathodic reagents is a prerequisite for the construction of a practical cell. The film acts in the same way as a separator, preventing further direct chemical reaction of lithium and the cathodic reagent. However, film formation involving the action of S02, SOCl2, etc. on lithium is considerably more complex and may produce much more severe voltage delay characteristics than in the case of insoluble cathodes described above. 

Considering these results, the main difference between the antiwear action of the ZDDP soft-core RMs and the hard-core RMs is clear. In the case of ZDDP soft-core RMs, the anti wear film formation requires that chemical reactions occur between the additive and the metallic surfaces. In the case of hard-core RMs, the mineral material (CaC03) is directly introduced to the sliding contact and undergoes small physicochemical changes during the film build-up. Consequently no chemical reaction with the substrate surfaces is required. 

The joint synergistic action of solid hydrophobic particles and liquid drops of an apolar oil [19,20,67,85,86] have been explained on the basis of the model defoaming action of solid particles (rupture of asymmetric film - formation of a bridge and its detachment from the foam film). Dippenaar reasons that mineral oils increase the effectiveness of the defoaming action of particles and this is associated with the increase in the contact angle... 

The film formation and thickening actions of povidone, and sometimes also its ability to form complexes with active ingredients, keep the solution in the eye for a longer time,increasing its therapeutic effect. Pilocarpine [86], timolol [166] and... 

Hoy (27) has examined some factors that influence the efficiency of coalescing aids. An important factor is the distribution of solvent between aqueous and polymer phases at the critical time during film formation. Water-soluble solvents may be lost from the coating through wicking action into the substrate. 

The mechanisms of the toxic actions of zinc remain obscure, though in-vitro (but not in-vivo) experiments have shown an inhibitory effect on respiration of the liver, kidney, and gills (Tort et al. 1984). Zinc exerts cytotoxic effects on fibroblastic cell lines of fishes which is stronger than those of copper or nickel but weaker than that of cadmium (Babich et al. 1986). Metallothio-nein induction occurs obviously also in fish (Roch and McCarter 1986). At high zinc concentrations (25 mg L ), necrosis of the hepatic cells and a veil-like film formation on the gills has been observed, affecting the respiration and blood circulation (Wong et al. 1977). 

Chemical vapour deposition (CVD) processes have become a very important group of film-formation methods. Basically CVD is a material synthesis in which constituents of the vapour phase react chemically to form thin solid films as a solid-phase reaction product which condenses on the substrate. The reaction should take place very near to or on the substrate surface (heterogeneous reactions) and not in the gas phase to avoid powdery deposits. Activation of the reaction can be performed by various means such as the application of heat, high-frequency electrical fields, light or X-ray radiation, electric arc, electron bombardment or catalytic action of the substrate surface. A marked influence of the process parameters such as sub-... 

Film formation occurs via evaporation of water from the paint film and coalescence of the high molecular mass binders the release of water takes place relatively quickly (physical drying). The minimum film-forming temperature depends on the chemical structure of the polymers. Film formation can be facilitated by the addition of organic solvents (e.g., alcohols, butylglycol ethers) or by the action of heat. 

Despite the large number of studies on the tribo-chemistry of ZnDTP reported in the literature, several points regarding the antiwear action of ZnDTP are stUl unclear and under discussion. Two open questions concern the kinetics of the trihofilm formation and the relative roles of tribochemical and thermal processes. Film formation in the presence of Zn DTP also occurs at lower apparent temperatures due to flash temperatures induced by the metal-metal contact itself [39,41]. The dependence of the ZnDTP decomposition rate on the temperature has been also described in the Uterature and considered one of the most important features in the anti-wear film formation mechanism [10]. 

Fleischmann et al [22] compared benzotriazole and 2-mercaptobenzoxazole as inhibitors of copper corrosion in KCl solutions containing low concentrations of cyanide. Benzotriazole proved to be an ineffective inhibitor in cyanide media, while 2-mercaptobenzoxazole remained effective. SERS showed that cyanide, revealed by a broad band centred at 2090 cm displaced benzotriazole from the Cu surface, whereas 2-mercaptobenzoxazole displaced adsorbed cyanide. A synergetic inhibition of Cu corrosion by benzotriazole and benzylamine, both in chloride and chloride/cyanide media, was also shown [22]. As SERS showed that benzylamine had not been adsorbed, its beneficial effect was ascribed to an improved film formation. Subsequent 4or measurements showed that benzotriazole, MBO, 2-mercaptobenzothiazole and 2-mercaptobenzimidazole were all effective inhibitors of copper corrosion in neutral chloride solutions, but the inhibition efficiency of benzotriazole was decreased at pH 1-2 [23]. SERS spectra showed that, at pH 7, benzotriazole and its anionic form were coadsorbed and Cl was excluded from the interface. However, at pH < 2 undissociated benzotriazole and CH were coadsorbed, such that Cu underwent corrosion. In contrast, the anion from 2-mercaptobenzothiazole was the only adsorbed species at pH between 7 and 2 only at pH 1 was the neutral 2-mercaptobenzothiazole molecule detected. Competitive adsorption experiments showed that the inhibitive action of benzotriazole and 2-mercaptobenzothiazole in neutral/acid media could be explained in terms of adsorption strength. 

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