Molten thermoelectric alloy expressed as (Bi, Sb).sub.2 (Te, Se).sub.3 is rapidly cooled at 10.sup.4 to 10.sup.6 .degree. K/second so as to crystallize the thermoelectric alloy, and powder of the thermoelectric alloy is hot pressed under the pressure equal to or greater than 400 kgf/cm.sup.2 at 200 degrees to 400 degrees in centigrade for a time period between {(-T/5)+90} minutes and 150 minutes or at 400 degrees to 500 degrees in centigrade for a time period between 5 minutes and 150 minutes so as to increase the figure of merit by virtue of the strain left in the crystal and/or micro crystal grain.
A thermoelectric semiconductor is formed of a sintered semiconductor layer and metal layers arranged on sides of opposite end faces of the sintered semiconductor layer. These metal layers are to inhibit a reaction between the sintered semiconductor layer and solder layers through which electrodes are joined to the sintered semiconductor layer. The sintered semiconductor layer and the metal layers have been obtained beforehand by integrally sintering a semiconductor powder layer and metal sheets arranged on sides of opposite end faces of the semiconductor powder layer.
Thermoelectric material is produced through a process sequence including a liquid quenching, a primary solidification such as a hot pressing or extrusion and an upset forging; although the C-planes of the crystal grains are directed in parallel to the direction in which the force is exerted on flakes during the hot pressing/extrusion, the a-axes are randomly directed; the a-axes are oriented in a predetermined direction through the upset forging; this results in improvement of electric resistivity without reduction in the figure of merit.
A process for producing a thermoelectric material based on two or more elements selected in the group constituted by Bi, Sb, Te and Se, which process comprises: i. an alloying step wherein determined amounts of the elements Bi, Sb, Te or Se are mixed until an homogenous powdered alloy is obtained; ii. an extrusion step of the powdered homogenous alloy obtained in the preceding step. The elements Bi, Sb, Te or Se being preferably mechanically mixed in an homogenous powdered alloy. The thermoelectric material, which are obtainable by this process, exhibits improved thermoelectric and mechanical properties and are therefore suitable, for example, as cooler, as temperature stabilizer in a electronic device or as power generator.
The present invention relates to catheters for selectively cooling or warming tissue within a patient's vasculature. The present invention utilizes novel heat exchanging devices, which reside inside the catheter body for selectively altering the temperature of fluid that flows through the catheter shaft. In addition, the present invention utilizes novel pumping devices, which reside within a patient's vasculature for withdrawing oxygenated blood into the catheter body where heat exchange occurs across a heat transfer interface for selective cooling or warming of the blood occurs. The present invention can be used in a multiplicity of medical disciplines where it is advantageous to selectively alter the temperature of tissue, including beating heart applications, as well as stopped heart medical interventions.
A method includes operating the refrigeration system in a cooling mode wherein a space is conditioned, and also includes transferring heat from a heat-transfer circuit to a thermoelectric device to a refrigeration circuit. A method further includes operating the refrigeration system in a defrost mode of operation including transferring heat through the thermoelectric device to the heat-transfer circuit to a heat exchanger.
