We report an experimental investigation on the effects of thermal treatments at different temperatures (room—1270 K) and for different duration (0–75 h) on amorphous silica nanoparticles (fumed silica) in powder tabletform. Three types of fumed silica are considered, comprising nearly spherical particles of 40 nm, 14 nmand 7 nmmean diameter. The experimental techniques used here are Raman and infrared absorption (IR) spectroscopytogether with atomic force microscopy (AFM). Raman and IR spectra indicate that the structure of nanometersilica particles is significantly differentwith respect to that of a bulk silica glass. In particular, themain differencesregard the positions of the IR band peaked at about 2260 cm−1, the Raman R-band peaked at about 440 cm−1 andthe intensity of the D1 and the D2 Raman lines, related to the populations of 4- and 3-membered rings,respectively. Our data also indicate that, under thermal treatments, the structure of fumed silica samples issignificantly changed, gradually relaxing towards that pertaining to ordinary bulk silica. These changes areinterpreted here on the basis of the morphological information provided by the AFM measurements andassuming a two-shell structure for the fumed silica primary particles.
|Numero di pagine||5|
|Rivista||Journal of Non-Crystalline Solids|
|Stato di pubblicazione||Published - 2011|
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