Development of Aqueous Sol‐Gel Method for Synthesis of Nanostructured SiO 2 ‐BaO Powder for Use in Dental Composite Resins

Abstract

SiO 2 -BaO composite powders are known to use as filler materials in dental composite resins. Sol-gel method for synthesis of glass, ceramics, bioceramics and glass-ceramics has received much attention in recent years. However, for the synthesis of multicomponent systems from single metal alkoxides, chemical homogeneity is of great importance. Different hydrolysis rates of individual alkoxides may result in chemical inhomogeneity that leads to the formation of undesired crystalline phases. To overcome these limitations, several approaches have been attempted, including matching of hydrolysis rates by chemical modifications of alkoxides, or synthesis of multication alkoxides, or partial prehydrolysis of an alkoxide. The objective of the present work is to develop an efficient and cost-effective sol-gel route for synthesis of nanostuctured multicomponent ceramic powders. Here the sol-gel method has been modified by using metal formates instead of metal alkoxides, and water as reaction medium instead of alcohol. In this paper we describe the aqueous sol-gel synthesis of powders of SiO 2 -BaO containing 5, 10, and 15 mol.% BaO which can be used as filler in dental composite resins. Barium formate and tetraethoxysilane were used as starting materials, and water was used as the reaction medium instead of conventionally used alcohol. The gels were calcined at 600, 800, and 1000°C and characterized by X-ray powder diffraction, IR spectroscopy, DTA, thermogravimetry, and transmission electron microscopy. The method is shown to provide homogeneous, nanostructured powders at comparatively low temperatures and offers the potential of a simpler and cost effective route than other reported methods.