Study of the structural evolution of copper-doped porous silica gels

Porous silica gels have been prepared by the sol-gel method using tetraetho xysilane (TEOS), ethanol and water with two dopants, CuCl and CuSO4, with d ifferent copper contents (1 and 5 mol%). The samples were prepared as monol ithic shapes, dried at 110 degrees C for 24 h and heat treated at 500, 900 and 1100 degrees C. Their structural evolution was studied by gas absorptio n, X-ray diffraction and X-ray absorption spectroscopy. All samples showed a stable structure of pores up to 900 degrees C and a strong densification process at 1100 degrees C. For temperatures lower than 500 degrees C, an am orphous material was formed, and the crystalline phases of cristobalite, qu artz, cuprite and tenorite were determined after heat treatment at 900 degr ees C. CuO was formed in the pores of samples doped with CuCl heated at 900 and 1100 degrees C. In the pores of samples doped with CuSO4, CuO was form ed at 900 degrees C and Cu2O at 1100 degrees C, (C) 2000 Elsevier Science L td. All rights reserved.