MELTING-THERMODYNAMIC CHARACTERISTICS OF Fe, Co, Ni MAGNETIC NANOCRYSTALS

Abstract

A simplified model that describes the size and shape dependence of melting thermodynamics of full free nanocrystals was established. Critical sizes of Fe, Co, Ni magnetic nanocrystals when the crystals keep their crystallinity were calculated and the corresponding minimum melting temperature was predicted. Theoretical predictions were consistent with experimental results.

Thermal stability of Fe, Co, Ni metal nanoparticles

“…Based on the definition of surface-to-volume atomic ratio α , there should be a direct relationship among the values of α for nanoparticles, nanowires and nanofilms with the same size R. For nanoparticles, R means the normal radius; for nanowires, R denotes the radius of the cross section; and for nanofilms, R represents half the value of the thickness. Accordingly it is deduced that for different low-dimensional systems, α is in the ratio of sphere α : wire α : film α = 3:2:1, where sphere α , wire α and film α are the surface-tovolume atomic ratio for nanoparticles, nanowires and nanofilms, respectively [19,20]. Then the above thermodynamic formulae for particles can be extended to describe the properties of corresponding wires or films, for example, from Eqs.…”

“…Also, the interface thermodynamics is somehow not highlighted. Therefore, based on our previous work in metal nanocrystals [13,[19][20][21][22][23], a simplified thermodynamic model covering both size and shape effects on metal nanoparticles has been established. For melting thermodynamics, melting temperature and critical size will be mainly discussed.…”