Nanoscaled Powders for Coatings

Abstract

Particles with a diameter from 1 to 100 nm are commonly known as nanoparticles. They can be distinguished from their corresponding bulk solid form by the size of their surface area in relation to their weight. When this ratio exceeds a particular value, a change in the physical and optical properties can be observed and the material behaves differently from its corresponding bulk solid form. This was already recognized in the early 90’s by Gleiter et al. [1] for nanoscaled metal clusters. Since then many metal, metal oxide and nitride nanoscaled systems have been studied. Nanoparticles have a high surface energy with specific surface area & 250m2/g and tend therefore to build agglomerates consisting of hundreds of nanoparticles, which usually cannot be separated by chemical, physical or mechanical forces. Such agglomerates behave like bulk material made of micrometer size particles and lose the unique properties of nanoscaled particles. The sol-gel method is one of the most powerful processes to circumvent this tendency and to allow the preparation of new materials containing dispersed nanoparticles. Such systems, called Nanomers ®, are interesting for the preparation of ceramics with improved properties but especially for the production of hybrid coatings which can be densified by polymerizing the organic network at low temperature opening the way to new applications.