Investigation of the states of water and OH groups on the surface of silica

The states of water and OH groups on the surface of amorphous nanosilica with heat treatment at different temperature for hours were studied by thermogravimetry (TG), differential scanning calorimetry (DSC) and Fourier-transform infrared (FT-IR) spectroscopy. The physically adsorbed water, OH groups oil surface and OH groups below surface were removed mainly at 343. 709, and 1210 K, respectively. With the increasing temperature in DSC curves, the physically adsorbed water was removed firstly: secondly OH groups on surface were dehydrated; lastly were OH groups below the surface. In a wide temperature the dehydration of the three kinds of water took place at the same time. According to the surface ran e g, the H(2)O density and OH group density on surface were obtained. For the sample with-area and TG results, out heat treatment, the physically adsorbed water and OH groups on surface were 9.80 and 8.20 nm(-2). respectively. And the physically adsorbed water and OH groups of the sample with heat treatment at 1273 K were about 0 and 2.50 nm(-2), respectively. (C) 2008 Elsevier B.V. All rights reserved.