Structural study of the effect of mineral additives on the transparency, stability, and aging of silicate gels

Abstract

The objective of this work is to evaluate to structural evolution of silicate gel in function of time and mineral additives. A comparison between fresh and aged silicate gel synthesized by silica and potassium hydroxide was carried out using FTIR, Raman and 29 Si MAS-NMR spectroscopies. Then, different additives such as NaOH, AlOOH, Li2B4O7 and HCl were incorporated in the silica solution. Their effect on the aspect, transparency, Q n polymerization and stability of silicate gels was studied. The structural study has shown that the quantification of Q n species is difficult using FTIR and Raman spectroscopy because of the existence of several contributions in the same spectral region of silicate species. More precise informations were given by 29 Si NMR spectroscopy which has demonstrated the increase of Q 3 species in the detriment of Q 4 revealing the depolymerization of the structure over time. The study of effect of additives reveals that HCl, AlOOH and Li2B4O7 do not permit to improve the stability of the gel due to the formation of several networks. However, promising results of stability and transparency were obtained using NaOH with a molar ratio of former to modifier of 2.52.

Novel Organochlorinated Xerogels: From Microporous Materials to Ordered Domains

“…The minor signal detected in the POSS, T 2 , is related to the presence of partially open cages (T 7 ). The proportion of Q species has also been associated with the FTIR spectra, with reports that Q 2 , Q 3 , and Q 4 species present their asymmetric Si–O–Si stretching vibration mode at different frequencies (1000–1030, 1100, and 1150–1200 cm −1 , respectively) [ 46 , 47 ] and that the aforementioned polycyclic structures ((SiO) 4 and T 8 cages) are related to bands at 1090 and 1150 cm −1 , respectively [ 48 ]. It can therefore be concluded that the presence of these structures in the materials is consistent with the increase in T 3 , Q 3 , and Q 4 species when the amount of precursor is larger and with the shoulder at 1150 cm −1 observed in the FTIR spectra ( Figure S1 ).…”

The Effect of External Electron Irradiation on the Properties of Simulated Borosilicate Glass from PDC MCC

“…Слабый пик при 630 см -1 может быть отнесен к четырехчленным кольцам связанных между собой пар Si 2 O 7 и B 2 O 7 , подобно наблюдаемым в структуре данбурита [21] . Частотный диапазон 900-1200 см -1 соответствует симметричным валентным колебаниям концевых групп кремний-кислородных тетраэдров SiO 4 (так называемый параметр Q n , где n -число мостиковых атомов кислорода) [22] . В спектрах КР исследованных стекол полосы около 1100 и 990 см -1 связываются с Q 3 и Q 2 соответственно .…”