Morphology and Structural Stability of Bismuth-Gadolinium Co-Doped Ceria Electrolyte Nanopowders

The reduction of the sintering temperature of doped ceria ceramics remains an open challenge for their real exploitation as electrolytes for intermediate temperature solid oxide fuel cell (IT-SOFCs) at the industrial level. In this work, we have used Bi (0.5 and 2 mol %) as the sintering aid for Gd (20 mol %)-doped ceria. Nano-sized powders of Bi/Gd co-doped ceria were easily synthesized via a simple and cheap sol-gel combustion synthesis. The obtained powders showed high sinterability and very good electrochemical properties. More importantly, even after prolonged annealing at 700 °C, both of the powders and of the sintered pellets, no trace of structural modifications, phase instabilities, or Bi segregation appeared. Therefore, the use of a small amount of Bi can be taken into account for preparing ceria-based ceramic electrolytes at low sintering temperatures.

Compressive Fracture Behavior of Bi-added Ni50Mn28Ga22 Ferromagnetic Shape Memory Alloys

ABSTRACTIn order to develop NiMnGa/polymer composite materials, a production of single-crystal-like NiMnGa particles is important and should be developed for better quality. Although mechanical pulverization is a promising method by utilizing intrinsic intergranular brittleness of NiMnGa polycrystalline ingots, the amount of lattice defects introduced during mechanical crushing needs to be minimized. This must be achieved by enhancement of intergranular brittleness of NiMnGa particles. In this study, the effect of Bi addition on the compressive fracture behavior of polycrystalline Ni50Mn28Ga22 was investigated where Bi was expected to be segregated to the grain boundaries in NiMnGa, similar to Bi segregation to the grain boundaries in Ni. It was found that only intergranular fracture was observed in Ni50Mn28Ga22 polycrystals with 0.3 at.% Bi addition, although a mixture of intergranular and transgranular fracture was observed in Bi-free Ni50Mn28Ga22 polycrystal. Microalloying of Bi into NiMnGa enhances intergranular embrittlement. A number of spherical particles of Bi were confirmed on the fractured surface of Bi-doped NiMnGa polycrystals. The formation of Bi particles is a proof of the grain boundary segregation of Bi in NiMnGa.

A Replaceable Lead-Free Solder for Sn-37Pb

In this paper, a new kind of Sn-Bi lead-free solder was fabricated via rapid solidification method by adding a series of microelements which can optimize the properties of Sn-Bi solder. When the solder was manufactured by Single Roller Melt Spinning Process, the faster the cooling rate is, the better the effect of restraining Bi segregation is. When the melt spinning rate was up to 1000 rpm, it had the best result. The effects of microelements on the melting characteristics, microstructure and properties of the new solder were also systemically studied. The results show that when the added content of Ag is 0.7%, Cu 0.3%, Ge 0.1%, In 0.5% and Sb 0.5%, the microstructure of the solder is fine, the extent of Bi segregation obviously decreases and the mechanical property is similar to that of Sn-37Pb solder. The melting point of the new solder is close to that of the Sn-37Pb solder. The mechanical and soldering properties are also similar to that of it.