Bi-Ag Alloys Research Articles

Thermal and Tensile Properties of Bi-Ag Alloys

This study investigated the microstructure and properties of Bi-Ag alloys, a novel Pb-free solder for high-temperature applications. The results show that Bi-Ag alloys exhibited a nonequilibrium solidification feature and a considerably large undercooling. An increase in the Ag content effectively raised the tensile strength. However, the elongation in a decreasing order was hypereutectic Bi-11Ag, pure Bi, and then eutectic Bi-2.5Ag. The fracture mode was significantly affected by microstructural characteristics and the strain rate.

Thermodynamics-Aided Alloy Design and Evaluation of Pb-free Solders for High-Temperature Applications

High temperature solders that will not be affected in the subsequent thermal treatment are required in the step soldering process of multi-chip module (MCM) packaging. High-Pb solder alloys such as 95Pb–5Sn (numbers are all in mass% unless specified otherwise) are currently being used for this purpose. However, the development of the Pb-free solder alloy for high temperature applications is needed due to environmental issues. The solder alloys of Bi–Ag, Sn–Sb and Au–Sb–Sn systems are considered as candidates in this study. Aided by thermodynamic calculations, several specific compositions have been chosen and they were investigated in terms of melting behavior, electrical resistivity, wetting angle and hardness. The Bi–Ag alloy exhibited poor electro-conductivity while the Sn–Sb system had low melting temperatures. The ternary Au–Sn–Sb solder alloy shows prospects for high temperature applications in spite of poor wetting properties.

Recovery of hydrogen from hydrogen sulfide with metals or metal sulfides

The following two types of reactions were investigated for the recovery of hydrogen from hydrogen sulfide: Type 1 H 2S → H 2 + S 0, Type 2 H 2S + O 2 → H 2 + SO 2 Each type of reaction is constructed by a two-step cycle, in which H 2S is reacted with metal or metal sulfide and then the resulting sulfide undergoes thermal decomposition or oxidation. Ag 2S, FeS, Co 9S 8, Ni 3S 2, and the double sulfide CuFeS 2 were examined in the former type of reaction, while Ag, Cu, Ni, liquid Pb, and liquid BiAg alloy were used as an intermediate in the latter.

Electric field gradients created by near neighbour impurity atoms in a cubic silver host

The electric quadrupole interactions produced by near neighbour impurity atoms of Cu, Au, Zn, In, Sn and Bi on111Cd probe nuclei in a cubic Ag lattice were studied by the TDPAC method. The effects of the type of impurity and its concentration have been investigated. The results show the presence of a high-frequency interactionvQh superimposed to a smeared out low frequencyvQl. The high frequency interaction, in the range 20 to 600 MHz, is attributed to impurity atoms located in nearest neighbour sites, while the low frequency interaction, in the range 2 to 12 MHz, is generated by impurities distributed at various different atomic distances from the probe nuclei. BothvQh andvQl increase with impurity concentration leaving the ratiovQh/vQl almost constant. The results show that the high frequencyvQh is linearly dependent on the solute valence, and a logarithmic function of the impurity concentration, in the range 0.5 to 4.5 at. %. Large size effects have been observed in CuAg and BiAg alloys. Instead for ZnAg and SnAg, thevQh andvQl variation is attributed basically to charge effects.