Bulk Non-Equilibrium Materials by Shockwave Consolidation

ABSTRACT: Phase 1 research will validate an approach for material synthesis that combines mechanical alloying with explosive powder consolidation to produce bulk materials with novel properties. The main advantage to the approach is that it can be applied to diverse material systems, including the creation of alloys with otherwise insoluble constituents. An additional advantage is that it has a straightforward path for scale up to industrial levels of production. In Phase 1, elemental powders of bismuth, antimony and tellurium will be mechanically alloyed, both with and without inert nanoinclusions, to produce a powder with particles that are in a highly non-equilibrium state. Explosive powder consolidation will allow the imposition of dynamic pressures in excess of 10 GPa to accomplish densification and interparticle bonding without the attendant grain growth and loss of non-equilibrium features that occur with other powder metallurgy approaches. A series of post-consolidation heat treatments for the step restoration of the material to the equilibrium state allows a characterization of bulk properties as a function of departure from equilibrium. The specific application addressed in Phase 1 is the development of high performance p-type thermoelectric material, a choice that not only has immediate market potential but that also allows microstructural assessment through measurements of bulk quantities such as thermopower, electrical conductivity and thermal conductivity. BENEFIT: Non-equilibrium materials produced by shockwave synthesis may exhibit unique properties such as increased ductility, higher strength and higher melting point. A specific application that will benefit is in the production of thermoelectric materials where the high incidence of grain boundaries and lattice defects will reduce thermal conductivity and increase the figure-of-merit, Z. A higher Z thermoelectric material has an immediate home in generation and Peltier heat pumping applications.