SiO2-B2O3 xerogels: The problem of boron leaching

Borosilicate materials are of interest for many technological applications. Whereas sol-gel techniques are well suited for the preparation of these materials, the nominal concentration of boron is often not maintained, and a considerable amount of boron is lost during the preparation procedure. In this work we deal with the synthesis of borosilicate systems in order to analyse the problem of the boron loss. Different sol-gel precursors of B₂O₃ were explored and organically modified silicon alcoxide were tested, in addition P₂O₅ co-doping was proposed. IR spectroscopy, differential Scanning Calorimetry, Thermogravimetry and ICP-OES analyses were performed. Sol-gel synthesis of SiO₂-B₂O₃ xerogels with a high boron content (> 18 wt.%) was successfully obtained by employing trimethoxyboroxine and 3-aminopropyltriethoxysilane.