Search

Mg3Sb2 compounds were synthesized via low-temperature solid-state reaction (SSR) and ball milling (BM), respectively, followed by spark plasma sintering (SPS) process. The effects of possible sintering pressure-induced orientation in the SPS process have been investigated in terms of the microstructure and thermoelectric transport properties. The results indicate that BM technique causes more severe Mg loss than pure SSR method, leading to distinct Sb phase existing in the product after SPS consolidation process. On the contrary, a single phase of Mg3Sb2 is easily obtained with the combination of SSR and SPS techniques. Besides, these BM-SPS and SSR-SPS samples exhibit the similar microstructure as well as the same electrical and thermal transport properties parallel or perpendicular to the direction of sintering pressure. The study suggests that SSR method embodies the advantages of both the composition control and the orientation elimination in Mg3Sb2 compound as compared to BM method with the specific parameters in the current work. This investigation is quite favorable for this material fabrication and the future application of thermoelectric modules and devices. [ABSTRACT FROM AUTHOR]

The diffusion bonding between Ti and Ni was investigated in the presence and absence of an imposed electric current. Bonding was carried out over the temperature range of 873-1123 K and the current density range of 255-350 A/cm. The formation and sequence of evolution of the three intermetallic phases, TiNi, TiNi, and TiNi, were investigated and discussed in light of calculations of Gibbs free energies of formation and interfacial energies associated with their nucleation. Within the experimental times and in the presence of a current, the growth of the three phases was parabolic. The evolution of the TiNi phase required an incubation period, while the relatively high growth rate of TiNi suggests the possibility of another mechanism. The growth of all phases was enhanced by the application of a direct current, with no apparent dependence on its direction. [ABSTRACT FROM AUTHOR]