SI-29 SOLID-STATE NMR-STUDY OF MESOPOROUS M41S MATERIALS

Si-29 NMR T-1 relaxation times of M41S materials have been measured us ing the saturation recovery pulse sequence and T-CP and T-1 rho relaxa tion times measured using variable contact time Si-29 CP NMR. T-1 rela xation times are considerably shorter for Q(3) silicon atoms than Q(4) silicon atoms, and optimum conditions for recording quantitative spec tra are reported. On this basis accurate Q(3)/Q(4) silicon atom ratios are determined and a modified mechanism of silicate condensation is p roposed. Relaxation rates are compared with those of amorphous silica gels.