Upcoming Events

Computational Materials Science in Pb-free Solders and Nanoparticles

November 8, 2012 2:00PM to 3:00PM
Presenter 
Hyuck Mo Lee, KAIST, Korea
Location 
Building 440, Room A105-106
Type 
Colloquium
Series 
CNM Nanoscience Colloquium
Abstract:
With the aid of phase diagrams and phase equilibria obtained from computational thermodynamics, the designing of Pb-free Sn-based solders for low-temperature, mid-temperature and high-temperature applications due to increasing environmental and health concerns over the use of lead has been successful and this approach also proved very useful in studying the interfacial reactions at the solder joints. Some of their examples are presented.

When the nanotechnology is applied to the lead-free solder alloys, they may result in synthesis of Sn-based nanoparticles. A various size of bimetallic or unary nanoparticles were synthesized and they were eventually used in inkjet printing. The eutectic composition shift was observed in nano-sized particles as compared with bulk alloys. By controlling the size and eutectic composition, a significant melting temperature depression was achieved, which was beneficial to the low temperature printed electronics.

The nano phase diagram of the corresponding material systems were obtained using molecular dynamics simulations. It revealed that apart from the melting temperature depression the structure of the solid-state nanoparticles changed in relation to the composition and size. Additionally, the density functional theory calculations were performed to explore the CO oxidation of the nanoparticles. Among various determinant factors for catalytic performance, CO and O2 co-adsorption was calculated in critical compositions. In this way, their alloying effect on the catalytic properties was investigated.