Although
a tremendous amount of research and development activities has been devoted to this
topic in the past decade,early research on nanomaterials dates back to the 1960s
when chemical flame furnaces were used to produce particles smaller than one
micron(1 micron=10-6 m = 10 3 nm)in size. the early applications of nanoma-terials
were as chemical catalysts and pigments,Metallurgists have always been
aware that by refining the grain structure of a metal to ultrafine (submicron)levels,
its strength and hardness increases significantly in comparison to the coarse-grained
(micron-size)bulk metal,For example, nanostructured pure copper has a yield
strength six times that of coarse-grained copper.