کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1333222 | 979070 | 2010 | 11 صفحه PDF | دانلود رایگان |
First-principles techniques have been employed to study the reactivity of water into a calcium aluminosilicate glass. In addition to the well known hydrolysis reactions Si–O–Si+H2O→Si–OH+Si–OHSi–O–Si+H2O→Si–OH+Si–OH and Si–O–Al+H2O→Si–OH+Al–OHSi–O–Al+H2O→Si–OH+Al–OH, a peculiar mechanism is found, leading to the formation of an AlO3–H2O entity and the breaking of Al–O–Si bond. In the glass bulk, most of the hydrolysis reactions are endothermic. Only a few regular sites are found reactive (i.e. in association with an exothermic reaction), and in that case, the hydrolysis reaction leads to a decrease of the local disorder in the amorphous vitreous network. Afterwards, we suggest that ionic charge compensators transform into network modifiers when hydrolysis occurs, according to a global process firstly suggested by Burnham in 1975. Our theoretical computations provide a more general model of the first hydrolysis steps that could help to understand experimental data and water speciation in glasses.
Graphical AbstractReactivity within glass bulk: structures obtained after hydrolyses reactions (endothermic and exothermic processes) and mechanisms involving Si–OH, Al–OH, Si–OH–Al groups within aluminosilicates glasses (through ab initio molecular dynamics): formation of the Si–OH–Al entity coupled with an H exchange—Frédéric Bouyer and Grégory Geneste.Figure optionsDownload as PowerPoint slide
Journal: Journal of Solid State Chemistry - Volume 183, Issue 12, December 2010, Pages 2786–2796