Characterizations of interface and microstructure of nanolayered materials

It is known that microstructure will essentially determine the properties of materials. In nanolayered materials, besides the microstructure of each constituent, the interface will play an increasingly important role at smaller layer thickness. A straight forward explanation is that the volume fraction of atoms along layer interfaces will become significant at layer thickness of 10 nm or less. Furthermore, atoms around layer interface may possess different properties compared with that of the same atoms in bulk materials due to a different chemical bonding environment.

Given the important role of layer interfaces, it is crucial to understand the microstructure and especially interface of these nanolayered materials at nanometer and even atomic length scale. Transmission electron microscopy is one of the best techniques to study these problems. Extraordinary amount of useful information can be obtained from microscopy studies, such as accurate measurement of layer thickness (± 0.5 nm), crystal structure, texture and phases of each layer. The characteristics of layer interface can also be determined, such as a coherent interface between Cu and Ni, incoherent interface between Cu and Mo, interface roughness and mixing of different atoms along interfaces.

Bright field TEM micrograph of Cu/304 stainless steel multilayers with a layer thickness of 10nm.

Diffraction pattern of these multilayer thin films indicating a mixture of face-centered-cubic and body-centered-cubic structures of 304 stainless steel.

References

“Strengthening mechanisms in nanostructured copper/304 stainless steel multilayers”, Journal of Materials Research, 18 (2003) 1600. (PDF)