Preparation of aerogel beryllium borate with supercritical carbon dioxide drying

A supercritical carbon dioxide drying technique was developed to prepare na nometer particulate materials. The technique consists of preparation of an aqueous gel, filtering, washing, replacement of the water in the gel with a mixture solvent of n-butanol and ligroin and supercritical carbon dioxide drying. The product was characterized with TEM, XRD and X-ray small-angle s cattering. The results indicated that an amorphous aerogel of the beryllium berate was obtained with this technique. The diameter of the product parti cles was about 7 nm. Isopropyl alcohol supercritical drying was also used t o prepare aerogel beryllium berate, where recrystallization took place due to the high critical temperature of isopropanol. (C) 2001 Elsevier Science S.A. All rights reserved.