Volume instability of porous solids: part 2: dissolution of porous silica glass in sodium hydroxide

Dimensional changes of porous 96% silica glass have been determined during exposure to aqueous NaOH solution. Depending on the thickness of the specimen (1, 3, 4, or 8 mm) and the concentration of the alkali (0.1, 0.4, 0.8, 1.6, 3.2 and 6.4 M), either expansion or contraction or both were observed, the maximum being 0.7%. The features of the extension curves cannot yet be fully explained, but the results suggest that dissolution of glass leads to expansion and that surface reaction and chemisorption lead to contraction. The presence of CaCl[2] in the solution in 1M concentration significantly retards dissolution and expansion.Les variations dimensionnelles d'un verre de silice poreux \ue0 96% ont \ue9t\ue9 d\ue9termin\ue9es lors de l'exposition \ue0 une solution aqueuse de NaOH. Selon l'\ue9paisseur de l'\ue9chantillon (1, 3, 4 ou 8 mm) et la concentration de l'alcali (0,1, 0,4, 0,8, 1, 6, 3,2 et 6,4 moles), on a pu observer une expansion ou une contraction, dont le maximum a atteint 0,7%. La forme des courbes d'expansion ne peut pas encore \ueatre compl\ue8tement expliqu\ue9e, mais les r\ue9sultats semblent indiquer que la dissolution du verre conduit \ue0 une expansion et que la r\ue9action en surface et l'adsorption chimique conduisent \ue0 une contraction. La pr\ue9sence de CaCl[2] dans la solution \ue0 la concentration de 1 mole retarde nettement la dissolution et l'expansion.Peer reviewed: YesNRC publication: Ye