29SiMASNMR investigation on silica glass prepared by the drying control chemical additives method

Porous Materials

“…The dilution of alkoxides in the carrier solvent affects the hydrolysis and condensation reaction rates, uniformity and equilibrium of the process [52]. In addition to methanol and ethanol, other solvents such as acetone, acetonitrile, dioxane, formamide, glycerol and dimethylformamide, which may affect rate of hydrolysis and condensation, surface tension, pore size distribution etc., were used [64][65][66][67][68][69][70][71][72][73][74][75][76][77]. Among these solvents, formamide has been extensively used as a drying control chemical additive to prepare monoliths.…”

“…73 Processing stages for fabricating dry gels and glasses. Reproduced with permission from[163] © 1990 Elsevier Science, NL.…”

Highly Thermally Stable and Transparent WO3–SiO2 Gasochromic Films Obtained by an Automated Printing Method

“…To analyze the structure of SiO 2 , liquid-state 29 Si NMR for the sols was performed, and the results are shown in Figure a. The data show peaks mainly at approximately −101.9 ppm and −111.1 ppm, which are assigned to the Q 3 structure and Q 4 structure of Si, respectively. , The structures of Q 1, Q 2 , Q 3 , and Q 4 are shown in Figure b . For the WO 3 –tSiO 2 sol, the peak for the Q 3 structure with only one terminal (OH) left is much higher than that for Q 4 , indicating that OH bonds remain following completion of the hydrolysis and condensation process, which agrees with the results that the hydrolysis speeds for the four OR­(−CH 2 CH 3 ) groups of the SiO 4 tetrahedron are different. , In contrast, for the WO 3 –aSiO 2 sol, there are mainly Q 4 structures, which means that the hydrolysis processes in all four directions of the SiO 4 tetrahedron are completed before condensation, resulting in a high degree of cross-linking and highly porous morphology, which is consistent with its discrete cluster microstructures .…”

“…The data show peaks mainly at approximately −101.9 ppm and −111.1 ppm, which are assigned to the Q 3 structure and Q 4 structure of Si, respectively. 41,42 The structures of Q 1, Q 2 , Q 3 , and Q 4 are shown in Figure 4b. 43 For the WO 3 −tSiO 2 sol, the peak for the Q 3 structure with only one terminal (OH) left is much higher than that for Q 4 , indicating that OH bonds remain following completion of the hydrolysis and condensation process, which agrees with the results that the hydrolysis speeds for the four OR(−CH 2 CH 3 ) groups of the SiO 4 tetrahedron are different.…”

Silica Monoliths Templated on L3 Liquid Crystal

“…Solid-state 29 Si NMR spectra, recorded on a Varian (Palo Alto, CA) 400 MHz NMR spectrometer at 79 MHz with magic angle spinning and proton decoupling, was used to quantify the degree of condensation within the silica network . The delay between pulses was set to 100 s, and a small flip angle pulse was used to obtain quantitative spectra.…”