Corrosion nanostructured materials

Thin metalhc fihns play an important role in diverse fields of applications, with special emphasis on micro- and nanoelectronics for which the metals Al, Cu, Ag, Au, Ti and W are essential Additional fields of commercial interests are electrodes as well as reflective, corrosion-resistant, oxidation-resistant and abrasion-resistant coatings . Noble metals (periods 5 and 6 of groups 8-11 of the periodic table of the elements) are of special interest due to their manifold application in heterogeneous catalysis. Other metals used in specialized industrial applications or as components of more complex materials such as metal alloys are Ni, Pd, Pt, Ag and Au. For example, FePt-based nanostructured materials are excellent candidates for future high-density magnetic recording media . ... 

Nickel containing scales exhibit higher conductivity because of the presence of trivalent nickel ions, which introduce vacancies in the lattice of the scale. Therefore, nickel-based coating can lead to superior conductivity and good protection provided that it is alloyed properly with corrosion resistant elements. Cobalt has a lower solubility in molten carbonate and electroless Co has been successfully used for a variety of corrosion-resistant applications. Electroless plating of Ni-Co gives rise to deposition of uniform layers of nanostructured material, which would result in better protection of the substrate. 

The combination of the processes of the severe plastic deformation of the surface with their physical-chemical treatment can provide the unique opportunity of the controlled formation of nano-sized grain structure for the strength and corrosion stability increasing. By applying both surface plastic deformation and nitriding process simultaneously nanostructured material could be determined. This kind of surface treatment related to refinement of grain could be helpful for considerable modification of material service properties. 

CORDIS (2003) NMP-2003-3.4.2.2-2 Development of Nanostructured Materials. Integrated Project, Advanced Environmentally Friendly Multilimctional Corrosion Protection by Nanotechnology. 

Chapter 1 provides an overview of the current rmderstanding of the problem of corrosion. The chapter also provides a brief introduction to nanomaterials in this context. Chapter 2 discusses corrosion basics with referetrce to nanostmctured materials. Chapter 3 addresses theoretical aspects of grain size reduction on corrosion with a model example and comparison with experimental resirlts of nanocrystalline zirconium and its alloys. Chapter 4 provides a good accoimt of the relevant electrochemical aspects of nanostructured materials. The nature of passive film and its correlation with nanocrystallization are explained. Chapter 5 gives a good description of fabrication of electrodeposited nanostructured materials. 

Enhancement of corrosion resistance can bring huge dividends, as nanostructured materials are also superior in mechanical and electronic properties. Nanostructured metals, which are expected to be stronger, harder and tougher, can provide very hard coatings that are more resistant to corrosion, useful for applications in defense armor, aerospace components, constraction equipment, medical devices, sports equipment, etc. Efforts are focused on the commercialization of nanostractured alloys (steel, cobalt alloys, etc.) as well as nanostroctured bulk metals (Cu, Ni, Zr, Ti, etc.). A number of leading research and development institutes and companies... 

Abstract Electrodeposition is a weU-known conventional surface modification method to improve the surface characteristics, decorative and functional, of a wide variety of materials. Now, electrodeposition is emerging as an accepted versatile technique for the preparation of nanomaterials. Work done in this direction is discussed in this chapter. The basics of electrodeposition are introduced, then the electrodeposition of nanomaterials using special techniques for reducing grain size. Methods such as pulse and pulse reverse current deposition, template-assisted deposition and use of additives and grain refiners are explained with suitable examples. Deposition of nanostructured metals, alloys, metal matrix composites, multilayers and biocompatible materials reported in the literature are discussed. Finally, there is a discussion of the improved corrosion resistance of electrodeposited nanostructured materials, quoting results reported in Uterature. 

Electrodeposition is a versatile technique for the production of nanostructured materials with lower capital investment, higher production rates and few shape and size limitations. Electrodeposited nanomaterials such as nanostractured metals, alloys and metal matrix composites have proven successful in providing superior corrosion resistance of substrate materials compared with the corresponding microstmctured materials. 

The concepts and basic approach used in studies of electrical fluctuations in corrosion processes proved to be very successful as well in mechanistic studies of electrode reactions taking place at materials covered by passivating films. A typical example is the electrochemical dissolution of silicon. From an analysis of the noise characteristics of this process, it has been possible to identify many features as well as the conductivity of the nanostructures of porous silicon being formed on the original silicon surface. 

Wang, Heli he has worked at the National Renewable Energy Laboratory (NREL) in the United States. He received a Ph.D. in corrosion science and materials chemistry from the Helsinki University of Technology in Finland. From 1998, he had worked with nanostructured semiconductors of metal oxides at the Department of Physical Chemistry, Uppsala University, Sweden. His research work has been in materials, electrochemistry, photoelectrochemistry, as well as fuel cell components. 

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