Functional Coatings: Sol-gels

Functional Coatings: Sol-gels

Thin and transparent coatings with tailor mad functionalities can be mad with the sol-gel functional coating technology. Sol-gel coatings are prepared by hydrolysis and condensation of metal alkoxides or organosilanes and optional organic precursors. They can be tailored with properties ranging from hard and brittle solely inorganic coatings to more flexible inorganic organic hybrid coatings, respectively exemplified in Figure 1 and Figure 2.

Inorganic CoatingFigure 1. A hard, brittle and solely inorganic coating

Org Hybrid Coating Figure 2. A more flexible inorganic organic hybrid coating

 

The organic moiety of organosilanes can be non-reactive or can contribute to further cross-linking as exemplified in Figure 3.

Epoxysilanes 

Figure 3. Reaction between an epoxysilane and an amino functionalized silane

Sol-gel coatings are applied by standard methods such as spray-coating and are widely used due to their excellent adhesion to metals and their high chemical and wear resistance. Typical film thicknesses reach from a few nm to a few μm. The low thickness makes them extremely interesting for enhancing heat exchangers where good heat transfer is required in combination with other properties such as low adhesion if ice, improved bubble formation, antifouling, etc.