Size effect on melting of small particles

Abstract

A phenomenological theory of the size dependence of the melting temperature of small crystalline particles is offered. Fluctuations and deviation of the crystals form from the equilibrium one are shown to produce a considerable effect on the melting of small particles. An experimental study of the melting of small particles of Sn, Pb, Bi, and In in island films is carried out. The fraction of the melted particles is determined by the curves of temperature dependence for integral intensity of one of the reflexes of the electron diffraction pattern. The results obtained by the authors are easy to describe with the thermodynamic theory taking into account the effect of fluctuations and nonequilibrium habit.

In-situ observation and the thermodynamical analysis of the melting process of In particles embedded in an Al matrix

“…These intermediate stages of melt-ing in the particle smaller than 100 À have not been observed. The difference of the melting process between particles larger than 100 À and those smaller than 100 À is also suggested by the relation between superheating temperature (AT) and reciprocal length of the {100} facet separation (1/L) [8] as shown in figure 5. A Ts of the particles smaller than 100 À are on the straight line through the original point with a slop A TL = 2000 À K. The straight line, however, could not be drawn for the A Ts of the particles larger then 100 Å.…”

“…The melting of microcrystals at temperatures below the bulk melting temperature was first demonstrated by Takagi [2]. The experimental and theoretical works after the Takagi's work have pointed out an important role of the properties of the surface and interface [3][4][5] in the melting phenomenon of microcrystals. In order to reveal the role of the interfaces during the melting process on In particles embedded in an Al matrix, an in-situ heating experiment in a high resolution/high voltage electron microscope was performed [6].…”

Surface Energy and Wetting in Island Films

“…It is common knowledge that melting temperature of small particles, thin metal, and alloy films is a function of size [6,7,22,[27][28][29][30][31][32][33][34][35][36]. When considered in terms of thermodynamics, there exist several models to describe the size dependence of melting temperature of small particles [27]; however, as the quantitative analysis of experimental data shows, the triple point model proves to be the most feasible.…”

“…These values agree well with available literature data on σ s for bulk samples obtained by other methods. data [6,7,22,[31][32][33][34][35][36] (the dotted lines are extrapolation of dependencies σ l (T) to the area of supercooling state) -creep data [5], ⊕ -small particles evaporation data [7], -data for Fe [39] …”

“…Analysis of known methods for the determination of the wetting contact angles θ shows that the use of traditional methods [1,40] for studying wetting in ultradispersed systems is quite limited. In view of these, new methods [41,42] were developed that allowed to investigate wetting in ultradispersed systems with different types of contact interaction (i.e., applicable both at θ < 90°, and for [6,7,22,[31][32][33][34][35][36] (the dotted lines are extrapolation of dependencies σ l (T) to the area of supercooling state) ■ -creep data [5], ⊕ -small particles evaporation data [7], □ -data for Fe [39] It is evident that there is a common tendency observed for all of the preceding metals manifested in the fact that the values of σ s have nonlinear temperature dependence. With relative temperatures below T/T s ≤ (0.85-0.9) the temperature coefficient for these metals becomes approximately constant and makes module (0.3-0.4) mJ/m 2 K (Figure 4).…”