Structural evolution of silica sols modified with formamide
نویسندگان
چکیده
منابع مشابه
SPINNABILITY OF SILICA SOLS Structural and rheological criteria
29Si NMR spectroscopy of concentrated silicate sols, prepared by acid-catalyzed hydrolysis of TEOS in ethanol with H20/Si ratios, r -1.5 or 1.7, followed by alcohol evaporation, shows that the polysilicate species responsible for spinnability are not simple rigid-rod, ladder polymers or linear polymers. Instead a distribution of silicate species is observed consistent with the products of a sta...
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By destabilization of quasi-monodisperse silica sols, fractal clusters can be obtained. Solvent evacuation gives a porous solid with fractal structure. Structural investigations of these colloidal aerogels by small-angle neutron scattering are presented, and compared to similar observations in concentrated sols and xerogels. An investigation of the vibrational modes of these materials by inelas...
متن کاملPreparation of Silica by Sol-Gel Method Using Formamide
In this work we obtained microporous and mesoporous silica gels by sol-gel processing. Tetraethylortosilicate (TEOS) was used as precursor. Nitric acid and hydrofluoric acid were used as catalysts. In order to study the affect of formamide as drying additive, we used a molar ratio alkoxide/formamide of 1/1. The performance of formamide in obtaining crack-free gels was evaluated through monolith...
متن کاملIdentification of self- and cross-condensation products in organically modified silica sols by 29Si and 170 NMR
High resolution 295i and 170 NMR spectroscopy has been used to identify selfand cross-condensation products in sols prepared from tetraethoxysilane (TEOS) and organically modified triethoxysilanes (RTES, where R is a methyl, ethyl or phenyl group). The sols were prepared by the acid catalyzed hydrolysis of TEOS and RTES with H20/Si mole ratios of 0.15, 0.3 or 0.5. Resonance assignments were mad...
متن کاملDynamic and structural correlations in nanocomposites of silica with modified surface and carboxylated nitrile rubber.
Distinct affinities between the organic and inorganic phases were observed in nanocomposites prepared through a colloidal route with carboxylated nitrile rubber and modified silica nanoparticles, which resulted in variable mechanical properties and improved thermal stability. Nanoparticles with modified surface affected the macromolecular arrangements of the elastomeric matrix, changing the fin...
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ژورنال
عنوان ژورنال: Materials Research
سال: 2001
ISSN: 1516-1439
DOI: 10.1590/s1516-14392001000300006