Abstract
The molecular dynamics method was used to study the processes of melting and crystallization of nickel nanoparticles and the influence of carbon impurities on these processes. The influence of the particle size and concentration of carbon atoms, which were initially randomly distributed in the volume of a nickel particle, was considered. The particle diameter varied from 1.5 to 12 nm, and the concentration of carbon atoms varied from 0 to 10 at.%. It has been shown that the melting and crystallization temperatures are inversely proportional to the particle diameter: as the particle size decreases and, accordingly, the free surface fraction increases, the temperatures of melting during heating and crystallization during cooling decrease. The presence of an impurity of carbon atoms reduces both the melting point and the crystallization temperature ‒ by approximately 150 K in the presence of 10 at.% carbon. Carbon atoms often formed clusters consisting of several carbon atoms in the metal. Such clusters distorted the nickel crystal lattice around them, which led to earlier melting of the metal near the carbon clusters. At cooling from the melt at a rate of 1012 K/s, the particle crystallized with the formation of a nanocrystalline structure containing a high density of grain boundaries and other defects. Impurity carbon atoms, especially carbon clusters, were fixed primarily at grain boundaries and triple junctions.
Published Version
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