Film preparation by inorganic-organic sol-gel synthesis

Film formation by sol-gel techniques is an advantageous method to abtain inorganic coatings. The sol-gel process allows the preparation of prepolymers with suitable viscosities to use various coating techniques like dipping, spraying and spin-on coating. The main disadvantage is the shrinkage of the gel layer during drying or sintering which leads to cracks with layer thicknesses more than some micrometers. The introduction of organics, causing a decrease of the network connectivity and increasing relaxation ability can help to overcome densification problems. Moreover, in some cases, hardness or abrasion resistance are not too much affected by organics. In these cases, the organics can be left within the inorganic network. The possibilities of inorganic-organic processing techniques will be discussed and examples for film formations will be given. (ISC)