The contribution of IR Fourier spectroscopy to the investigation of the state of surface modes and molecular interactions occurring on adsorption of various compounds onto silica surfaces was demonstrated by the analyses of the FT-IR spectra of various amorphous and crystalline silicas with specific surface area ranging from 1 to 1000 m2 3456789101112g"1, such as quartz fiber (QF), silica gel, aerosil, and silicalite. Thus, the Si-OH• • -Si silanol group pairs were found to represent those H-perturbed silanol groups of highly hydroxylated amorphous silica surfaces which initiate dehydration and/or dehydroxylation processes at room temperatures. Microporosity and surface permeability of "hydrophobous" QF with a specific surface area of 1-5 m2 g-1 cause a tenacious retention by QF of molecular adsorbed water varied on chemical modifications of QF. Hydrophilic sites of silicalites, if any, are largely represented by residual alkali cations being doped on synthesis of silicalite. Adsorption of small amounts of triethylamine onto amorphous superpure silica surfaces causes acid-base type interactions of varying strength with Si-OH groups up to the formation of a surface chemical compound (Et3HN)+(Si-0)~s table under vacuum to over 773 K.
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