Universidad Nacional Autónoma de México - CNyN

1st International Symposium on Nanoscience and Nanomaterials
usually different from their single metal counterparts and they significantly vary as a function of composition
and particle size. The enhanced properties of bimetallic metal catalysts are generally attributed to either
ensemble or ligand effects although other factors related to particle size effects and matrix effects, have been
invoked. Some examples about the preparation of Au-Ag catalysts supported on TiO, by a new method based
on deposition-precipitation, their characterization and catalytic activity in the reaction of CO oxidation will be
shown [1]. Another way to overcome the deactivation process is to produce oxygen vacancies on the surface
of the support particles. These oxygen vacancies generate crystalline defects that work as pinning centers for
the gold particles. The steps on the surface of the support particles are also crystalline defects that could work
as pinning centers for the gold particles. Theoretical calculations have demonstrated that the gold particles
bind stronger to a defect-rich surface than to a defect-deficient surface and that a significant charge transfer
occurs from the titania support to the Au particles, which could explain the catalytic activity of the Au
particles for the oxidation of CO. To illustrate this kind of systems, the characterization, catalytic performance
and stability in the CO oxidation reaction of Au/TiO 2 and Au/Y-TiO 2 will be discussed [2]. The Y-TiO 2
supports were prepared by the sol-gel method and the Au supported nanoparticles were obtained from the
DP–Urea process.
[1] A. Sandoval, A. Aguilar, C. Louis, A. Traverse, R. Zanella, J. Catal. 281 (2011) 40-49.
[2] R. Zanella, V. Rodríguez-González, Y. Arzola, A. Moreno-Rodríguez, ACS Catalysis 2 (2012) 1-11.
PLENARY X
FUNDAMENTAL PROPERTIES OF TM NITRIDES: DESIGN STRATEGIES FOR GROWTH OF
SELF-ORGANIZED NITRIDE NANOSTRUCTURES
Joseph E. Greene
Departments of Materials Science, Physics, and the Materials Research Laboratory
University of Illinois, Urbana, Illinois, USA
Physics Department, Linköping University, Linköping, Sweden
Mat. Sci. Dept, National Taiwan University of Science & Technology, Taipei, Taiwan
Cubic TM nitrides have wide single phase compound fields which can be exploited. We show results
for vacancy hardening (not associated with film strain) in 3d group-IV TiN x (001): the hardness H of epitaxial
layers increases dramatically, while the elastic modulus E and the relaxed lattice constant decrease linearly, as
x is decreased from 1.0 to 0.67. Over the same x range, the resistivity (x) increases from 13 to 192 -cm
due to electron scattering from N vacancies. In contrast, H(x), E(x), and (x) for 5d group-V TaN x (001)
remain constant due primarily to the presence of isoelectronic antisites. While TiN and TaN are metallic, 3d
group-III ScN(001) is a transparent semiconductor with an indirect Γ-X gap of 1.3 eV and a direct X-point
gap of 2.4 eV. Reflectivity measurements from Sc 1-x Ti x N(001) layers show TiN is strongly reflecting up to the
reflectance edge at ћ e = 2.3 eV, ScN is transparent, and e x 0.5 . Thus, hard decorative coatings with a wide
palette of colors can be obtained. The extreme range of materials properties available in TM nitrides and
related systems can be enhanced through the formation of self-organized superhard nanostructures consisting
of commensurate nanolamellae, nanocolumns, nanospheres, and nanopipes. Self-organization strategies
include controlled phase separation, surface-induced spinodal decomposition, surface segregation-induced
renucleation, strain-induced roughening, surface anisotropy, and dynamic resputter yield amplification. As a
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