STRUCTURAL CHARACTERIZATION of ACID and BASE-CATALYZED SILICA XEROGELS

In this study, silica xerogels were synthesized by the sol gel method using TEOS (tetraethyl orthosilicate), ethanol, water and sulfuric acid as acidic catalyst and ammonia as basic catalyst. The structural characterizations of the synthesized acid-catalyzed silica xerogels (ACXs) and base-catalyzed silica xerogels (BCXs) were investigated by thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) and N2 adsorption and desorption techniques. It was seen from TGA analyzes that the thermal decomposition process of silica xerogels consists of two steps. The SEM images show that the solid skeletal phase of ACXs has a globular morphology with primary particles that are joined together to form agglomerates. In contrast, SEM images of the BCXs indicate a hierarchical morphology with the clusters of these agglomerates organized into larger spherical particles. The pore size distributions (PSD) of ACXs and BCXs samples show a main peak in the micropore and micro-mesopore regions, respectively. © 2019 Yildiz Technical University. All Rights Reserved.