AVS 53rd International Symposium
    Advanced Surface Engineering Thursday Sessions
       Session SE-ThA

Paper SE-ThA9
Dimensional Attributes of Enhancements in Nanocrystalline Ta-V Layered Structures

Thursday, November 16, 2006, 4:40 pm, Room 2007

Session: Hard and Nanocomposite Coatings: Synthesis, Structure, and Properties
Presenter: A.F. Jankowski, Univ. California - Lawrence Livermore National Laboratory
Correspondent: Click to Email
The scaling of structure to the micro- and nano-scale is a known method of enhancing the physical properties of many materials. For example, the strength and hardness of nanocrystalline metals and laminates can be increased several fold. At present, we evaluate how the dimensional attribute of nanoscale affects the mechanical properties of body-centered-cubic Ta and V thin films. The samples for this study are prepared by magnetron sputter deposition and characterized using the methods of x-ray diffraction, transmission electron microscopy, and nanoindentation. Systematic increases in hardness, for example, are measured to a factor of ten or more above the comparative value of fully annealed samples. To asses underlying structural origin, single and layered structures of each metal are evaluated separately as well as in the form of layered structures. That is we examine Ta, Ta/Ta, V, V/V, and Ta/V films as deposited on silicon substrates. At small layer-pair spacings, as 3 nm, it is found that strained layered superlattices are formed in Ta/V. Dimensional attributes of the nanoscale effects are considered in accounting for the origin of mechanical property enhancements in all these Ta and V nanostructured materials. Specifically, we assess the nanoscale features that are parallel versus perpendicular to the growth plane of the films, i.e. the relative effects of grain size versus the layer pair spacing. Although layer spacing is commonly associated with the effects of superlattice distortions in correlating effects of elastic properties, it is seen that grain size is a dominant contributor to plastic deformation associated with strength and hardness in the Ta-V films. This work was performed under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.