Cesium was incorporated into silica matrix by direct mixture of cesium chloride into the casting solution formed by water and tetramethylorthosilicate. The casting solutions were prepared with cesium content ranging from 0.035 to 4.9 wt.%. For structural characterization the techniques of nitrogen sorption, mercury pycnometry, thermogravimetric analysis (TGA), differential thermal analysis (DTA) and X-ray diffraction were employed. Specific surface area, pore-size distribution and bulk density of the gels were obtained by nitrogen sorption (BET) and mercury pycnometry. The pore morphology was inferred through curves of nitrogen-sorption hysteresis. After drying and heat treatment, the gels obtained with hydrofluoric (HF) as catalyst remained unbroken, The specific surface area of the silica gels decreases in the presence of cesium. The shape of curves of nitrogen-sorption hysteresis did not change with the cesium content studied. The presence of cesium makes the pore-size distribution narrower. Gels obtained with 1. 1 wt.% Cs (content in casting solution) and treated at two dwell temperature (500 + 800 degreesC) show the indication of a lower cesium leaching. (C) 2001 Elsevier Science B.V. All rights reserved.
