Nanodielectics: How does the presence of interfaces influence behaviour?

Nanocomposites are composed of host and guest materials in general. They should be fabricated so that they may be endowed with superb performances of the guest filler materials, while keeping original performances of the host materials. In general, inorganic materials are excellent in optical, electrical, mechanical and thermal properties, while organic materials are superb in light weight, flexibility, and processability. Such performances for both materials can be transferred, complementarily, to nanocomposites. Furthermore, novel performances that neither of them holds by nature will possibly appear in newly fabricated nanocomposites. There are three kinds of combination as for hosts and guests, i.e. inorganic-inorganic, inorganic-organic, and organic-organic composite systems. The materials that attract most attention to-date are nanocomposites that consist of organic polymers as host and inorganic substances as guest. This field was pioneered by the successful invention of polyamide/organic clay nanocomposites in 1990´s. Much attention was directed toward mechanical and optical properties in the beginning. Furthermore, recent investigation is oriented also to performances including gas barrier, lubrication, thermal endurance, heat radiation, electrical conductivity, electrical insulation, aiming at drastic changes in such performances that are expected to appear by controlling material structures in nanometer scale in self-assembly mode. Investigation of various polymer nanocomposites has been intensively made on permittivity, loss tangent, electrical conductivity, space charge, TSC, dielectric breakdown, treeing breakdown (short time breakdown and treeing V-t characteristics), partial discharge (PD) resistance, electroluminescence and any other relevant characteristics. It is now recognized that all the performances as indicated above show the superiority of nanocomposites to conventional composites and especially the improvement of PD resistance, the prolon- ation of treeing lifetime, and the suppression of space charge formation are most prominent among them as nanocomposites. New application innovation for power apparatus is certainly expected through polymer nanocomposites.