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The kinetic of the ageing process of 3 pyrogenic silica samples, exhibiting increasing surface areas (Wacker N20, T30 and T40), was followed through gravimetric measurements, during about 1000h at 22.5°C, under different relative humidities (RH) from 62% up to100%. Silanol chemical titration, and IR spectroscopy were also called on to evidence the change of the surface chemistry induced by the ageing...
In the present study, we have examined the influence of the aging process under controlled relative humidity on the surface properties of 3 silicas samples of increasing specific surface area. Both comparison of the specific surface areas, determined using either nitrogen (BET) or cetyltrimethylamonium bromide (CTAB), and the surface nanoroughness indexes, determined by size exclusion inverse gas...
The study of the aging of synthetic pyrogenic silicas, in the presence of a water containing atmosphere was led on two pyrogenic silicas, having respectively a specific surface area of around 200m 2 /g (N20) and 300m 2 /g (T30) were aged under a relative humidity (RH) of 94% at 25°C. The evolution of their surface properties was followed by gravimetry and immersion microcalorimetry...
The interaction of water with pyrogenic silica samples, modified by a controlled partial silylation with dimethyldichlorosilane, was studied by microcalorimetry, at 20°C, 25°C and 30°C. Whatever the coverage ratio was, the heat of immersion in water does not vary significantly with the temperature, except one sample corresponding to a high grafting ratio that exhibit a high temperature dependence...
The specific surface area of silicas samples modified by controlled silylation with dimethyldichlorosilane were assessed by inverse gas chromatography at finite concentration, using isopropanol and water as probes. If isopropanol assesses the whole residual free silica surface, water addresses only the more hydrophilic sites, present at the silica surface. It was also established that the heat of...
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