A material is called a nano-object when one, two or three external dimensions of it are present in nanoscale. This includes nanoparticles, i.e. nano-objects with all three external dimensions on the nanoscale. Nano-platelets are nano-objects with one external dimension on the nanoscale, and two much larger external dimensions. Nanofibers have two similar external dimensions on the nanoscale, and a third external dimension that is much larger than the other two dimensions.
These definitions were developed in 2008 by the Technical Committee ISO/TC 229 “Nanotechnologies” in collaboration with the Technical Committee CEN/TC 352 “Nanotechnologies”.
Nanoparticles can be of different chemical nature. Both inorganic and organic nanoparticles are known. They can consist of only one element, i.e. metal or carbon or of compounds like oxides, nitrides, etc. Nanocomposites are understood to be composite materials that have at least one component in the form of a nano-object. Nanoparticles often build clusters of aggregates or agglomerates. By contrast to aggregates, agglomerates can be ground into the primary grains through optimal mixing. Therefore, their shape can be very inconsistent and they may take a wide variety of forms which has considerable influence on their properties. In principle, because of their enormous surface-to-mass ratio nanoparticles behave completely different than larger composites.
