Papers by Author: Sang Soo Chee

Abstract: SnO₂ powders were prepared using a modified polyol synthesis method and subsequent calcinations. Well-dispersed spherical 2SnO∙(H₂O) particles could be synthesized at room temperature through the modified polyol method using tin (II) 2-ethylhexanoate as the precusor, 1,2-propanediol as the solvent, PVP as the capping agent, and sodium borohydride as the reducing agent. The 2SnO∙(H₂O) nanoparticles agglomerated to form larger particles during the drying step, and most of these larger nanoparticles coalesced with one another. Finally, these 2SnO∙(H₂O) nanoparticles were successfully transformed into the SnO₂ phase by calcination for 1 h at 500 °C.

Abstract: The transient liquid-phase sintering behavior of micro-Zn/nano-Sn-3.0Ag-0.5Cu (SAC) pastes was examined at a temperature of 190 °C as a function of the volume of ultrafine (~12.4 nm) SAC nanoparticles present. SAC nanoparticles have lower melting point drop than the bulk SAC particles. Although successful linkage at the interface between all Zn particles was not accomplished in all sintered samples, the number of linkages increased marginally with a decrease in the SAC content. As a result, the electrical resistivity of the sintered samples decreased with the decrease in the SAC content; however, the resistivities were still very high in all samples. Microstructural observations indicated that the observed results were mainly due to the short lifespan of the liquid phase caused by the coarsening of SAC nanoparticles during heating.

Abstract: Tin nanoparticles were synthesized through compulsive reduction using a Tin(II) 2-ethylhexanoate precursor, and the effect of reductant (sodium borohydride) amount on the size distribution of the particles was surveyed. Issues caused by the absence of a capping agent (polyvinyl pyrrolidone) were similarly examined. An excessive amount of dissolved sodium borohydride caused variations in the tin nanoparticle sizes, from a few nanometers to several tens of nanometers. The formation of abnormally large particles was attributed to the vigorous coagulation among smaller tin particles. In the tin nanoparticles synthesized without polyvinyl pyrrolidone, an exceptionally wide size distribution was observed owing to irregularly coagulated and aggregated large particles.