6.1 Nanoparticles 103 Table 6.1 The ontology of nanodispersions State of the nano-objects Matrix Solid Liquid Gaseous a Other Solid Nanocomposite a Nanosuspension c Aerosol Liquid ­ Nanoemulsion Aerosol Gaseous Nanofoam b Nanofoam b ­ materials falling into this category are nano-alloys, metal­matrix composites, etc. b These materials may be described with the adjective "nanoporous" (or, in French, using the noun "nanoporeux"). c Nanofluids are included here (Section 6.5.4). surface area of an aggregate is significantly smaller than the sum of the surface areas of the individual objects prior to aggregation). In terms of interaction ener- gies (Figure 4.4), the particles in an agglomerate are separated by a distance ` 1 , and those in an aggregate by a distance ` 0 . If a material comprises two or more distinct phases, if one or more dimensions