Abstract
In this paper we report, for the first time, a new approach for synthesis of high quality faceted microcrystalline coatings of molybdenum (Mo), tungsten (W), their carbides and composites. These studies are carried out using Hot Filament Chemical Vapor Deposition (HF-CVD) method wherein parent materials (Mo and/or W) are taken in the form of wires (~0.5 mmdia) and are heated to a high temperature (TF ~ 1500 - 2000 C), in ambient of “oxygen (O2) diluted hydrogen (H2) gas”. Due to high filament temperature (TF), a series of pyrolytic reactions take place. Firstly, the gasification of wire material (Mo and/or W) occurs in the form of its oxide. The oxide molecules reach the substrate which is kept underneath the filament assembly. Secondly, molecular hydrogen gets dissociated into atomic hydrogen and subsequently reaches the substrate to react with oxide molecules, finally leading to the precipitation of a pure metal. This method can also be used, in situ, to convert metallic coatings into their carbides and/or composites. The method offers many other attractive features, which can not be rendered by the conventionalCVD/PVDmethods. The results are discussed in terms of temperature induced “Red-ox” reactions.
Highlights
Since materials play a central role in different technologies, there has been a tremendous increase in the activity of “materials research”
In a given deposition experiment, the different types of substrates are kept “side-by-side” on the substrate holder so that these get processed at almost identical processing conditions
The method is primarily based upon temperature induced “Red-ox reactions”
Summary
Since materials play a central role in different technologies, there has been a tremendous increase in the activity of “materials research”. In view of a new trend of “collapsing dimentions” in modern technologies, the subject of “materials coatings” has received a prime importance to form new materials. Novelty of these new materials refers to a multi-parametric restrictions on different physical/chemical properties, so as to be suitable in given type of application/s. Various types of newer physical/ chemical methods have been devised for synthesis of coatings of various types. Some of these methods are matured enough to routinely achieve the objective, while on the other hand newer methods/ concepts are still being proposed to synthesize required types of materials coatings
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