Microstructural analysis of the effects of poly(ethylene glycol) on an acid catalyzed sol-gel derived ceramic material

Ceramic materials have been derived from an acid catalyzed sol-gel process. The addition of different molecular weights and concentrations of polyethylene glycol (PEG) to the sol mixture modifies the phase behaviour of the sol-gel process. The resulting gel is burned at 973 K to make porous ceramic materials. Nitrogen adsorption-desorption isotherms are used to assess the effects of PEG on the internal structure of the burned ceramic material. These isotherms indicate an extensive pore network exists consisting of micropores and mesopores. In the micropore region of the isotherms, the alpha(S)-plot analysis reveals changes in specific primary micropore volumes, specific total pore volumes, specific external surface areas and specific SPE surface area when PEG is added in the sol-gel process. The average pore width and the overall mesopore size distribution curves shift to higher pore size values and ranges on addition of PEG to the sol-gel mixture. The presence of PEG during the sol-gel process leads to an apparent narrowing of the micropore size distribution. The results of this work clearly indicate that the molecular weight and the concentration of a polymer, such as PEG, influences the eventual internal structure of a ceramic after burning.