Organically modified silicates and ceramics as two-phasic systems : synthesis and processing

Based on the concept of controlling the particle size by the surface free energy, the growth of sol-gel derived nanoparticles (Al2O3, TiO2, ZrO2) has been investigated in presence of molecules with binding ability to the growing particles. The investigations show that the use of silanes, carboxylic acid or â-diketones allows to replace electrostatic sol stabilisation by steric sol stabilisation and through this, high solid content sols can be obtained. The introduction of these sols into organic or ormocer type of matrices leads to nano composites with degrees of filling up to 40 wt.-% without agglomeration and with high optical quality. Already developed TiO2 containing bulk materials, ultrahard coatings on plastic and adhesives for fiber to chip coupling are examples for the usefulness of this alternative sol-gel route. The nanocomposite materials show interesting mechanical and thermomechanical properties such as high hardness or low thermal expansion compared to unfilled systems.