Physico-Chemical nanomaterials science

Equilibrium states in nano-scale binary metallic materials and equilibium curves in the two-phase region of the phase diagram
A.S. Shirinyan 1, Y.S. Bilogorodskyy2, G. Wilde3 and Makara V.A. 1,4

1 “Physical-chemical materials science” center of National Academy of Sciences of Ukraine, Prospect Nauki, 46, Kyiv-03039, Ukraine
E-mail: aramshirinyan@ukr.net
2 Research and Education Institution “Cherkasy Regional Center of works with students”, Smelianska street, 132, 18029, Cherkasy, Ukraine
3 Institut für Materialphysik, Westfälische Wilhelms-Universität, Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
4 Department of Metals Physics, Faculty of Physics, Kyiv National University named after T.Shevchenko, vul. Volodymyrska 61, 01601, Kyiv, Ukraine

Surface and volume confinement effects need to be taken into account into the description of phase changes in nanoscale systems [1]. In our investigation a modified Gibbsian thermodynamics approach has been suggested to describe: i) the solidification of a nano-sized liquid alloy droplet, ii) melting of a nano-sized solid particle and iii) the equilibrium states in the two-phase region of the phase diagram. Cu-Ni has been chosen as a model system. This description shows for the first time the occurrence of melting and solidification loops at the size-dependent temperature-composition phase diagram for the isolated Cu-Ni nanosystem, showing two-phase equilibrium states for droplet / particle radii of 25nm, 40nm and 80nm, i.e. well within the size domain of nanoparticles that are e.g. used for applications in additive manufacturing [2]. Results lead to the new "melting loop" and "solidification loop" concepts concerning the phase diagram [3]. 

1.	Shirinyan A. S., Wautelet M. Phase separation in nanoparticles // Nanotechnology.-2004.-15.-P. 1720–1731.
2.	Shirinyan A., Wilde G., Bilogorodskyy Y.S. Solidification loops in the phase diagram of nanoscale alloy particles: from a specific example towards a general vision // Journal of Materials Science.-2018.-53.-P. 2859–2879.
3.	Shirinyan A. Two-phase equilibrium states in individual Cu-Ni nanoparticles: size, depletion and hysteresis effect // Beilstein Journal of Nanotechnology.-2015.-6.-P. 1811-1820.