Evaporation of Free PbS Nanoparticles: Evidence of the Kelvin Effect

Abstract

The size-dependent evaporation of free-spherical PbS nanoparticles has been investigated by in-flight sintering of size-classified aerosols. The temperature (T(ev)) at which the particle size decreases due to evaporation is found to be size dependent and decreases with decreasing particle size. A linear relationship between the evaporation temperature and the inverse of the particle size is obtained as is the case with size-dependent melting of nanoparticles. This gives a direct evidence of the Kelvin effect and allows one to estimate the surface energy of nanoparticles. The surface energy of PbS nanoparticles has been found to be 2.45 J m(2).

Thermal stability of gas phase magnesium nanoparticles

“…23 In addition, as Fig. 3͑c͒ indicates, the areal percentage of Mg loss in different sized nanoparticles shows that with sizes Ͻ20 nm the loss is much faster than with sizes larger than 20 nm.…”

“…The latter shows that the driving force for evaporation is much higher in case of nanoparticles than for bulk Mg. 22,23 The ratio of the vapor pressure of 10-50 nm Mg nanoparticles based on Eq. ͑1͒ at 300°C after inserting realistic values for Mg ͑bulk; using ␥ = 0.63 J / m 2 at 300°C͒ shows that the driving force for Mg evaporation for 10 nm nanoparticles is more than 13 orders of magnitude higher than a nanoparticle with size of 50 nm.…”

“…The size dependence can be readily understood on the basis of the Kelvin equation, leading to an increased driving force for evaporation with decreasing particle size, as already explained above. 22,23 …”

Surface Energy and Wetting in Island Films

“…As follows from relations (24) and (25), at t = const the relation of maximum film deflection δ to the droplet base radius r will be different for cases with prevailing deformation of bending (δ ~ r Experimental relations δ(r) for the Sn/C system at t = 10 nm (Figure 12) corroborate this conclusion. It is apparent from the chart that the linear dependence δ(r) is observed at δ < t on the coordinates "r 3 -δ," and at δ > t -on the coordinates "r -δ.…”

“…Available experimental data, for example, [8,9,24,25], offer contradictory conclusions regarding the sign of the size dependence of the surface energy of small particles.…”