Nanocomposites are an interesting class of material, which have applications, e.g., as hard, wear resistant and low friction coatings. We have studied nanocomposites of nanocrystalline metal carbide particles (nc-MeC) embedded in an amorphous matrix of carbon (a-C). This type of systems (nc-MeC/a-C) have large potential for tailoring, including such aspects as choice of carbide, particle size, and relative amount of matrix phase.
In this paper we introduce a concept of controlling the distribution of carbon between the matrix and carbide phase. This concept is built on alloying the nc-MeC/a-C nanocomposite with a second metal. Depending on the carbide forming abilities of this third element it will be more or less energetically favorable to form a separate matrix phase. This concept is explored in a number of systems, including Ti-FeC, Ti-Al-C and Ti-Cu-C, where we have combined experiments and simulations. Samples have been deposited using non-reactive dc-magnetron sputtering and analyzed using XPS. Simulations were performed using DFT-methods.
We have shown that this concept of alloying can be used to improve properties of coatings, such as a reduction of friction from 0.3 without alloying to 0.05 with alloying, due to an increased surface graphitization. We see this alloying as a more general concept, which should be applicable to other systems than those studied up to now, and which can be further developed into a standard tool in the design of new nanocomposites.
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