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

Abstract

Porous silica gels have been prepared by sol-gel method using tetraethoxysilane (TEOS), ethanol and water with two dopants, CuCl and CuSO4, with different copper contents (1 and 5 mol degree centigrades). The samples were prepared as monolithic shapes, dried at 110 degree centigrades for 24 h and heat treated at 500, 900 and 1100 degree centigrades. Their structural evolution was studied by gas absorption, X-ray diffraction and X-ray absorption spectroscopy. All samples showed a stable structure of pores up to 900 degree centigrades and a strong densification process at 1100 degree centigrades. For temperatures lower than 500 degree centigrades, an amorphous material was formed, and the crystalline phases of cristobalite, quartz, cuprite and tenorite were determined after heat treatment at 900 degree centigrades.