The thermoelectric generating device can convert the heat flow due to temperature difference into electric energy by the Seebeck effect. In general, electric power can be obtained by alternately arranging N type thermoelectric elements and P type thermoelectric elements and connecting upper and lower staggered electrodes (π type structure).
However, the generation capacity due to Seebeck effect is low, and even bismuth-telluride thermoelectric elements widely used at the present time are at most about 200 μV / K. Therefore, it is necessary to arrange hundreds of π structures, but the π structure is complicated, poor mass productivity, and there is a problem of increasing the internal resistance due to being connected in series.
The nickel material and aluminum material can be directly bonded by applying temperature and pressure . Using this feature, two nickel plates with a thickness of 0.2 mm, a length of 30 mm and a width of 15 mm and three aluminum plates were alternately laminated and directly bonded. An anodized film of 1 μm is formed on the surface of the aluminum plate, and the oxide film is peeled off by 5 mm from the end portion by polishing. Direct bonding was performed by holding for 40 minutes under the conditions of a pressure of 7.6 MPa, a temperature of 600 ° C. and a degree of vacuum of 0.4 Kpa. By selectively forming an anodic oxide film on the surface of aluminum and using it as a mask, it is possible to selectively and directly bond them. Since only the aluminum portion from which the anodized film has been removed is bonded, if it is slightly pulled, it peels off, and five layers accordion type structure can be produced.
It was found that by adding a temperature difference of 73 ° C to this device, electric power of maximum 20 μW can be obtained.
Hiroshi Sato, Tetsuro Yanaseko, and Hiroshi Asanuma, "Accordion type thermoelectric power generation device using the metal direct bonding technology (Conference Presentation)," Proc. SPIE 10601, Smart Materials and Nondestructive Evaluation for Energy Systems IV, 106010C (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 05, 2018; Published: 3 April 2018); https://doi.org/10.1117/12.2300778.5763109676001.
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