Dielectric properties and Fourier transform IR analysis of MCM-48, Al-MCM-48 and Ti-MCM-48 mesoporous materials

Broad-band dielectric spectroscopy was used to investigate the dielectric p roperties of the mesoporous materials MCM-48, Al-MCM-48 and Ti-MCM-48. The samples were examined in the frequency range from 20 Hz to 1 MHz and in the temperature range from -100 to 250 degrees C. The dielectric relaxation of the materials has a complex nonexponential behavior with some common featu res for all the samples. The dielectric spectroscopy and Fourier transform IR measurements identified the relaxation process related to percolation of H+ ions associated with silanol groups and water adsorbed in the materials . The non-Debye behavior of the macroscopic dipole correlation functions re lated to the percolation process allowed us to extract the fractal dimensio ns of the paths of excitation transfer within the porous medium, and the po rosity of each sample was estimated.