Preparation and spectroscopy of aluminosilicate films deposited on graphite surfaces via an anhydrous sol-gel route

Anhydrous aluminosilicate sols with Al : Si molar ratio ranging from 1 : 10 to 1 : 5 were prepared by a two-step anhydrous sol-gel process, in which t etraethoxysilane (TEOS) is pre-hydrolysed by formic acid, followed by addit ion of aluminium ethoxide. Unlike the case of aqueous sol-gel routes, where the Si-O-Al network homogeneity is greatly restricted by precipitation of Al(OH)(3), this anhydrous route yields clear, homogeneous sols. The sol for mation and densification processes were investigated by infrared spectrosco py and X-ray powder diffraction (XRD) techniques, and the existence of Al-O -Si linkages was confirmed. To demonstrate an application of the anhydrous sol-gel process, aluminosilicate films were deposited onto graphite surface s by dip coating and densified at 800 degreesC under nitrogen, and their pr otective effect was evaluated.