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TEOS Nafion/silica membranes

Ren et al. also reported that the water uptake by the membrane containing oxide is higher than that by the pristine Nafion (Ren et al. 2005). Nafion-silica man-branes have been prepared employing several methods by casting mixtures such as silica powder, diphenylsilicate (DPS), sol-gel reaction with tetraethylorthosilicate (TEOS), followed by solution casting of the Nafion solution, phosphotungstic acid (PTA)-doped composite silica/Nafion/PTA, and silica oxide (Wang et al. 2007). [Pg.414]

Mixing Solutions. Nafion/Si02 membranes also can be prepared using Nafion solutions and silicon alkoxides. The mixed solution is cast into shallow containers and dried at ambient temperature. This procedure allows the incorporation of continuously increasing amounts of sihca. Since the composites are formed from a mixed solution, instead of a Nafion film, the silica phase is not restricted to the clusters ofNafion. Transparent but brittle films are obtained when TEOS is used, showing a lamellar structure by transmission electron microscopy (TEM). When part of the TEOS is substituted by 1,1,3,3-tetramethyl-l, 3-diethoxy disiloxane (TMDES), phase separation, higher flexibility and higher ionic conductivity are observed (Zoppi, 1997, 1998). [Pg.1505]

Nation /Silica System Jungetal. [174] have reported the synthesis of a Nafion /silica composite membrane obtained via the sol-gel acid catalysis of tetraethoxysilane (TEOS) in a Nafion 115 membrane (equivalent weight = 1100). The amount of TEOS impregnated in the membrane varied with the reaction time. These authors noted that the water absorption of the composite membrane increased... [Pg.83]

In the case of Si02/Nafion composites the Nafion membrane is swollen in water and methanol and immersed in a methanol solution of silicon tetraetoxysilane (TEOS). Thus, the TEOS hydrolysis take place inside the membrane and the amount of formed Si02 inside the membrane depends on the impregnation time. Einally the membrane is dried at high temperature to remove trapped volatiles and promote further silica network condensation [32]. [Pg.128]


See other pages where TEOS Nafion/silica membranes is mentioned: [Pg.252]    [Pg.1075]    [Pg.802]    [Pg.21]    [Pg.242]    [Pg.1074]    [Pg.1074]    [Pg.1082]    [Pg.411]    [Pg.241]    [Pg.246]    [Pg.253]    [Pg.227]    [Pg.1082]    [Pg.368]    [Pg.381]    [Pg.382]    [Pg.223]   
See also in sourсe #XX -- [ Pg.316 , Pg.317 ]




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