Synthesis and characterization of Sn-rich Ni–Sb–Sn nanosolders

Nano-crystalline samples of pure Sn and of Sn-rich ternary Ni–Sb–Sn alloys, with compositions ranging from 80 to 97.5 at% Sn and a Ni to Sb molar ratio of 1:1, were synthesized by reduction of stoichiometric metal chloride solutions with NaBH4 at 0 °C in alkaline medium. The particle sizes of the obtained alloys, measured by TEM/SEM, were found to be in the range of 40–350 nm. A relative decrease in melting temperature of up to 15 °C was observed for these alloys compared to a bulk sample. A sample with 95 at% Sn was subjected to heat treatment at 180 °C for various time periods up to 5.0 h to study particles with well defined average sizes between 50 and 135 nm. The melting temperatures of the annealed samples were found to increase progressively with increasing particle size. At the same time, the excess surface energy of these heat treated samples was measured as a function of particle size using a Calvet-type calorimeter. From the differences of the (H573–H299) values between nano and bulk samples, the excess enthalpies for nano-sized samples were derived to be between 18.8 ± 1.9 and 0.8 ± 1.4 kJ g−1 for particle sizes between 50 and 135 nm.

► Nano-crystalline samples of pure Sn and of Sn-rich ternary Ni–Sb–Sn alloys were synthesized by chemical reduction. ► They were characterized by TEM/SEM, XRD, DSC, and calorimetry. ► Melting temperatures were found to decrease with decreasing particle size, whereas the excess surface energy was found to increase with decreasing particle size.