23-01-2013, 11:38 AM
NEW METHOD FOR METAL COATING
NEW METHOD.ppt (Size: 1.25 MB / Downloads: 145)
Introduction and Overview
It is well known that mechanical processing, such as high pressure and shear deformation, ball milling, etc., can create defects and change the atomic structure, it can be used to influence the speed, direction and extent of physical and chemical changes in and between solids, between solids and liquids as well as solids and gases.
Mechanochemistry investigates the principles of chemical interactions and conversions in solids under mechanical influence.
Theoretical and Applied Mechanochemistry
Practical Applications. Mechanochemical methods were utilized
to prepare carbides, sulfides, amorphous and nanocrystalline materials,
superconductive materials etc. Mechanochemical processing is simple,
environmental friendly, and can be scaled up to tonnage quantities.
The chemical changes take place in the solid state form without a need
for solvents or high temperature.
Theory. In spite of simplicity of practical realization the theoretical
description of ball milling-induced chemical reactions is a difficult
problem due to the complex combination of interrelated processes
on several length and time scales. There is no common theory that
could explain the available data and orient future investigations and
the development of applications. Further progress in this area requires
better fundamental knowledge of the mechanisms of the relevant
chemical interaction and the role of mechanical activation in these
processes.
Deposition of Metallic Coatings (Cr, Cu) on the Steel and Al
Metal coatings formed due to the mechanical alloying. For the Cr or Cu coatings, Cr or Cu powders were used only, The mechanism of coating formation is offered based on the theory of solids’ deformation and dislocation theory. Coating-specimen bonding strength is of cold-welding nature, as was shown by our experiments.
The coating is formed when initial oxide compounds containing to-be-coated-metals are mechanochemically reduced: the Steel-Cr2O3 -H2 system is used for Cr coating on the Al.
Conclusions for DLC Films Deposition
Several DLC films on the steel and Al specimens have been deposited and investigated. The presence of broad D and G resonance peaks on the Raman spectra along with the high microhardness indicate that the films have developed the microstructure typical for DLC films.
The thickness from 100 nm to 300nm was recorded. It was suggested that the method introduced allow to manage aromatic microstructure of the precursors thus providing opportunity to regulate microstructure during the deposition process.
CONCLUSIONS
A key aspect of the proposed technology is the fact that mechanochemical processing is simple, economically profitable and environmentally friendly. The chemical changes take place in the solid-state form without a need for complicated solvents or high temperature.
The authors’ believe that the method presented can form the basis of an efficient technological coating process, holding good prospects for such applications as e.g. corrosion/erosion protective coating on pipes and steel and aluminum sheet..