Enhanced strength and toughness

The strength and toughness of both ceramics and metals can be enormously enhanced if they are made out of nanoscale crystallites rather than the usual micron-sized grains. This effect is already widely exploited to make superior ceramics and tungsten carbide-cobalt composites. Ceramics made from nanoscale TiO2 particles not only sinter together even at 600°C, but also possess enhanced strength and toughness. There is a similar effect in metal systems. Nanocrystalline copper, for example, is up to five times stronger than ordinary copper. In this case, the explanation relies upon the observation that deformation in metals is generally carried by lattice defects called dislocations, and nanoscale copper crystals are actually too small to even contain dislocations. Aluminum also shows the same effect. A process called as equiangular extrusion is used to refine the grain size of the aluminum into the nanoscale, so that it will be hard and lose the ductility. Similar behavior is exhibited by gold.