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Focused Session at Central Metallurgical Research and Development Institute (CMRDI) |
Novel Properties of Nanomaterials
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Metallic Nanoparticles and Films for Plasmonic Applications
Paras N Prasad
University at Buffalo, the State University of New York
Buffalo, New York 14260-3000, USA
Metallic nanostructures have drawn a considerable attention recently because of their prospective applicants to a wide range of areas such as catalysis, sensing, optical technology as well as cancer therapy. Examples of metallic nanostructures are: metallic nanoparticles, nanorods, metallic nanoshells and nanoscales thick films. A metallic-electric boundary on the nanoscale produces considerable changes in the optical properties giving rise to a new type of resonance called plasmon or surface plasmon resonance which are localized near the boundary between the metal nanostructure and the surrounding dielectric. This field of nanoplasmonic is rapidly growing worldwide. The plasmonic resonance produces enhanced electromagnetic field at the interface. This enhanced field can be used for metal-dielectric interface-sensitive optical interaction that form a powerful basis for optical sensing, nanoscales lithographic printing and nanoscales localized optical imaging. A new application of plasmonics is to use a close-packed array of metallic nanoparticles for confinement and guiding of an electromagnetic wave as plasmon through a waveguide much smaller in a cross-section than the wavelength of light.
This talk will discuss the concepts, methods of preparation and some selected applications of metallic nanoparticles and films.
Analysis of Nanoparticles using XPS with External Stimuli
Sefik Suzer
Bilkent University, Ankara 06800, Turkey
X-ray Photoelectron Spectroscopy, XPS, due to the perfect match of its probe length (1-10 nm) to the size of the nanoparticles, chemical specificity, and susceptibility to electrical charges, is ideally suited for harvesting chemical, physical and electrical information from nanosized surface structures. In addition, as we have demonstrated recently, by recording the XPS spectra while applying external d.c. and/or pulsed voltage stimuli, it is also possible to control the extent of charging and extract various information related with dielectric properties of nanosized structures. Implementation of the technique and application to analysis of bare and core-shell type of nanoparticles consisting of metallic, semiconductiong, and insulating materials will be presented.
Electrochemical preparation of Nanoporous Catalysts
F. M. Al Kharafi, B, F. M. Bayoumi and B. G. Ateya
Kuwait University, Safat 1360 Kuwait
The selective electrochemical dissolution of the active component of an alloy (dealloying) leaves the alloy surface enriched in the more noble component such as platinum, gold, silver or copper. The process leads to instability of the surface and eventually to the formation of a nanoporous structure that is rich in the more noble component. It is affected by the compositions of the electrochemical potential which drives the selective dissolution reaction. The objective of this paper is to present the fundamental aspects of this process and to discuss the results obtained from several systems.
Nano-Particle Molybdate Based Anti-corrosion Thin Films for Aluminum Alloys
Abdel Salam Hamdy(a), A. A. Ismail(b), D. P. Butt(c) and A. K. Ismail(b)
(a)Department of Surface Treatment & Corrosion Control,
Central Metallurgical R & D Institute, CMRDI, P.O. Box: 87, Helwan, Cairo, Egypt.
E-mail: asalam85@yahoo.com
(b)Department of Nanotechnology, Central Metallurgical R & D Institute,
CMRDI, P.O. Box: 87, Helwan, Cairo, Egypt
(c)Department of Materials Science, University of Florid, USA
Chromate conversion coatings have been widely applied for the corrosion protection of aluminum alloys. However, the waste containing Cr6+ has many limitations due to the environmental consideration and health hazards. Molybdate are among the proposed alternatives to chromating. Series of specimens were prepared under the following conditions a) As polished, b) directly treated with molybdate, c) etched, d) oxide thickened and, e) etching followed by oxide thickening. After surface preparation, the specimens were dipped in molybdate solution prepared via sol gel method. Electrochemical Impedance Spectroscopy (EIS) and polarization measurements have been used to evaluate the coating performance in 3.5% NaCl. The optimum conditions under which molybdate treatments can provide good corrosion protection to the aluminum substrate were determined. The surface morphologies of the treated samples were investigated using SEM and EDS. Optical microscope was also used to investigate the occurrence of pitting corrosion. The surface preparation prior to molybdate treatment was found to have a marked effect on the corrosion protection of AA6061 T6. Generally, molybdate treatments improve the corrosion resistance due to formation of highly protective molybdenum oxides. According to the EIS and polarization measurements, a combination between etching and oxide thickening prior to molybdate treatment plays an important role on the corrosion protection mechanism.
