Figure 5.

TEM (top) and SEM (bottom) images of particles detected at the machining center (a) and foundry (b) sites. For both sites, particles with different morphologies are observed including spherical and cubic (blue arrows) nanoparticles. At least four populations of spherical particle are observed including: very small nanoparticles, less than 10 nm (red arrows); small nanoparticles, less than 100 nm (yellow arrows); larger nanoparticles, approximately 100nm (green arrows) and very larger particles which are hundreds of nanometers in size or micrometers in size (purple arrows).