Shockwave fabrication of thermoelectric materials

Abstract

The explosive consolidation of semiconductor powders results in thermoelectric materials having reduced thermal conductivity without a concurrent reduction in electrical conductivity and thereby allows the construction of thermoelectric generators having improved conversion efficiencies of heat energy to electrical energy.

1 . A method for manufacturing thermoelectric elements from a conductive or semiconductive powder comprising the steps of
 green compacting said powder into a tube,   applying a surrounding explosive force to the outside of said tube so as to bond said powder into a solid body without the occurrence of melting or crystallization, and   machining said solid body to produce said thermoelectric elements.   
     
     
         2 . The method of  claim 1  wherein said powder has a significant proportion of elements whose largest dimensional size is less than 20 nanometers. 
     
     
         3 . The method of  claim 1  wherein said powder is made up of a mixture of elemental powders in the stochiometric ratio that is desired in the final product. 
     
     
         4 . The method of  claim 1  wherein said powder is green compacted in layers separated by metallic electrodes. 
     
     
         5 . The method of  claim 4  wherein said thermoelectric elements are produced by cutting said solid body apart at the electrodes, thereby producing thermoelectric elements that are attached to electrical conductors on either side. 
     
     
         6 . The method of  claim 1  wherein said powder is loaded into said tube in layers of materials having variable properties, thereby resulting in a functionally graded thermoelectric element. 
     
     
         7 . A method for the consolidation of thermoelectric powders by an external explosive force so that the resulting bonded structure has a high density of dislocations and grain boundaries, thereby reducing thermal conductivity and resulting in an enhanced thermoelectric material. 
     
     
         8 . The method of  claim 7  wherein said thermoelectric powders include a significant proportion of particles with a size in all dimensions of less than 20 nanometers. 
     
     
         9 . The method of  claim 7  wherein said thermoelectric powders contain significant proportions of the elements taken from the group including bismuth, tellurium, antimony and selenium.