A. Yakymovych, C. Kaptay, H. Flandorfer, J. Bernardi, S. Schwarz, H. Ipser:
"The nano heat effect of replacing macro-particles by nano-particles in drop calorimetry: the case of core/shell metal/oxide nano-particles";
Experimental results are presented here obtained by a drop calorimetric method, in which Ni and Cu
particles, both in bulk and nanosized form, were dropped into a liquid Sn-3.8Ag-0.7Cu solder alloy
(in wt%). The molar enthalpies of mixing of the liquid (Sn-3.8Ag-0.7Cu)-Ni(Cu) alloys were measured. An
extra exothermic heat effect is observed when dropping nano-particles instead of macro-particles. This
is partly due to the loss of the large surface area and the corresponding large surface enthalpy of the
nano-particles before their dissolution in the liquid alloy. However, a large additional exothermic heat
effect was also found in the case of Cu-nano-particles, due to the exchange chemical reaction between
the Cu2O shell of the nano-particles and liquid Sn; this is caused by the fact that the Cu-nano-particles
are core-shell particles with an inner metallic Cu core and an outer Cu2O shell. This effect is less
significant for Ni nano-particles which have a thinner oxide shell.
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