Glasses surface reactions

Many of the examples concerning mineral and ceramic surfaces can be used equally well to illustrate information, measurements and proces.ses for glass surfaces. The reader will find it useful to consider examples under the same headings in Sections 4 and 5 in conjunction with those presented in this section. The studies discussed here have been selected to illustrate proces.ses that have some generality in glass surface reactions and modifications. 

The silanization reaction has been used for some time to alter the wetting characteristics of glass, metal oxides, and metals [44]. While it is known that trichlorosilanes polymerize in solution, only very recent work has elucidated the mechanism for surface reaction. A novel FTIR approach allowed Tripp and Hair to prove that octadecyl trichlorosilane (OTS) does not react with dry silica. 

Arsine, AsHs, is formed when many As-containing compounds are reduced with nascent hydrogen and its decomposition on a heated glass surface to form a metallic mirror formed the basis of Marsh s test for the element. The low-temperature reduction of AsCls with LiAlH4 in diethyl ether solution gives good yields of the gas as does the dilute acid hydrolysis of many arsenides of electropositive elements (Na, Mg, Zn, etc.). Similar reactions yield stibine, e.g. ... 

Active halogen groups were bonded to a glass surface by nonhydrolyzable links using the reactions set out in Scheme (40) ... 

Less clearly recognizable as scavenging, but in principle the same thing, is the evident reaction of glass surfaces with carrier-free species. While this phenomenon has been studied widely in radiochemistry, adsorption on the walls of glass vessels has been more of a nuisance to be avoided. Harbottle... 

When the product of a reaction is purified and isolated, some of it is inevitably lost during the collection process. Gases may escape while being pumped out of a reactor. Liquids adhere to glass surfaces, making it impossible to transfer every drop of a liquid product. Likewise, it is impossible to scrape every trace of a solid material from a reaction vessel. 

Surface modification reactions are used to improve the wettability of glass surfaces by polar stationary phases and to Improve the extent of deactivation by sllylation" [138-146,166]. Miaaiuua procedures have been investigated but only a few are in use. Of these, the most important reactions are etching by hydrogen chloride, leaching with aqueous hydrochloric acid, formation of whiskers and solution deposition of a layer of solid particles. Because of the high purity and thinness of the... 

Immobilization on glass surfaces can be carried out by either routes [5] or [6] in Scheme 2 both yielding the immobilized complex (1), reaction [5] being the procedure most commonly used. 

Douglas, R.W. and El-Shamy, T.M.M. (1967). Reactions of glasses with aqueous solutions. Journal of the American Ceramic Society 50 1-8. Douglas, R.W. and Isard, J.O. (1949). The action of water and of sulphur dioxide on glass surfaces. Journal of the Society of Glass Technologists 33 289-335. 

In spite of their relevance to air pollution and to the combustion of sulphur-contaminated fuels, kinetic data for the homogeneous decomposition of S03 are practically non-existent. The thermal decomposition is dominated by a heterogeneous component, even in clean silica vessels390 reactions of S03 at a glass surface are evident even at room temperature380. The kinetics of approach to the equilibrium... 

Mass fluxes of alkali elements transported across the solid-solution interfaces were calculated from measured decreases in solution and from known surface areas and mineral-to-solution weight-to-volume ratios. Relative rates of Cs uptake by feldspar and obsidian in the batch experiments are illustrated in Figure 1. After initial uptake due to surface sorption, little additional Cs is removed from solution in contact with the feldspars. In contrast, parabolic uptake of Cs by obsidian continues throughout the reaction period indicating a lack of sorption equilibrium and the possibility of Cs penetration into the glass surface. 

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