A SiGe thermoelectric device for a space heap thermoelectric power source and a preparation method thereof

Abstract

The present invention discloses a SiGe thermoelectric device for a space nuclear power generator and a preparation method thereof. The thermoelectric device has a sandwich structure, including: insulating plates arranged in parallel on the outer layer of the thermoelectric device, conductive layers arranged in parallel on the inner side of the insulating plates, transition layers arranged in parallel on the inner side of the conductive layers, a plurality of thermocouple arms between two transition layers, and a heat insulation layer between the thermocouple arms; the method uses a diffusion welding method to weld the thermocouple arms and the electrode graphite layers. The SiGe thermoelectric device provided by the present invention can withstand high-temperature environments and has a compact structure. The preparation method uses a diffusion welding method to connect the two-end electrodes and the thermocouple materials, ensuring that both the hot end and the cold end of the prepared thermoelectric device have a relatively high operating temperature. The SiGe thermoelectric device provided by the present invention can be used for a space nuclear power generator.

Description

Technical Field

[0001] The present invention belongs to the field of thermoelectric devices, and particularly relates to a SiGe thermoelectric device for a space reactor thermoelectric power source and a preparation method thereof. Background Art

[0002] In deep space exploration missions, space reactor thermoelectric power sources have become one of the ideal power sources for deep space detectors due to their strong environmental adaptability, no vibration, and long lifespan. A thermoelectric device is an energy conversion device that uses the Seebeck effect to convert the thermal energy output by the reactor and conducted by the heat pipe into electrical energy. It has the advantages of being static, vibration-free, maintenance-free, high reliability, and long lifespan, and is the core component of a space reactor thermoelectric power source. Since the temperature of a space reactor thermoelectric power source is relatively high, the thermoelectric device used for a space reactor thermoelectric power source must also be a high-temperature thermoelectric device, requiring the hot end temperature of the thermoelectric device in contact with the heat pipe of the space reactor thermoelectric power source to withstand up to 800°C to 1000°C, and the cold end temperature to reach above 400°C.

[0003] SiGe thermoelectric devices are one of the existing high-temperature thermoelectric devices with the highest technology maturity and the best performance. Although their materials can be applicable to high temperatures of 1000°C, the device preparation process affects the thermal stability of the interface between their SiGe materials and electrodes and the operating temperature of the device. Currently, the main preparation methods for SiGe thermoelectric devices include: the direct brazing electrode method, the hot-end diffusion welding - cold-end brazing method, or the method of preparing a transition layer on the SiGe surface and then brazing the electrodes. Among these methods, for the SiGe thermoelectric devices prepared by the direct brazing electrode method, the applicable temperatures of their cold and hot ends are both lower than 800°C, which is obviously not applicable to a space reactor thermoelectric power source. If they are used in a space reactor thermoelectric power source for a long time, serious interfacial reactions will occur in the device, resulting in the disconnection and fracture of the electrodes from the SiGe; for the SiGe thermoelectric devices prepared by the hot-end diffusion welding - cold-end brazing method, there are problems such as complex processes, non-compact structures, and relatively low applicable temperatures at the cold end, which are also not applicable to a space reactor thermoelectric power source; for the SiGe thermoelectric devices prepared by the method of preparing a transition layer on the SiGe surface and then brazing the electrodes, the interfacial composition of the prepared thermoelectric devices is complex, the thermal stability needs to be verified, additional thermal insulation materials need to be filled between the thermocouple arms, and the device structure is not compact. Obviously, the thermoelectric devices prepared by the above methods cannot be used for a space reactor thermoelectric power source at around 1000°C due to their unsatisfactory high-temperature thermal stability or non-compact structures, or there is room for improvement.

[0004] Therefore, there is an urgent need for a new SiGe thermoelectric device for a space reactor thermoelectric power source and a preparation method thereof. The SiGe thermoelectric device prepared by this method has a compact structure, strong high-temperature adaptability, and can be used for a space reactor thermoelectric power source. Summary of the Invention

[0005] In view of this, the present invention provides a SiGe thermoelectric device for a space nuclear power source and a preparation method thereof. The SiGe thermoelectric device prepared by this method has a compact structure and strong high-temperature adaptability, and can be used for a space nuclear power source.

[0006] To achieve this purpose, the present invention adopts the following technical solutions: A SiGe thermoelectric device for a space nuclear power source, the thermoelectric device has a sandwich structure, including: two insulating plates arranged in parallel at the outermost layer of the thermoelectric device, two conductive layers arranged in parallel inside the insulating plates, two transition layers arranged in parallel inside the conductive layers, a plurality of thermocouple arms between the two transition layers, and a heat insulation layer between the thermocouple arms;

[0007] The material of the conductive layer is tungsten, and the material of the transition layer is graphite. The conductive layer and the transition layer are connected to form the electrodes of the thermoelectric device, and the electrodes are composed of a plurality of discontinuous electrode blocks;

[0008] The thermocouple arms include P-type thermocouple arms and N-type thermocouple arms. The P-type thermocouple arms and N-type thermocouple arms are arranged at intervals, and a heat insulation layer is filled between adjacent thermocouple arms. The material of the thermocouple arms is SiGe;

[0009] Each electrode block at both ends of the thermocouple arms is connected to a thermocouple pair composed of a P-type thermocouple arm and an N-type thermocouple arm, and the electrode block at one end of the thermocouple arm is staggered from the electrode opposite to it at the other end of the thermocouple arm by one thermocouple arm arrangement.

[0010] Preferably, the thermoelectric device includes at least two pairs of thermocouple pairs composed of P-type thermocouple arms and N-type thermocouple arms.

[0011] Preferably, the insulating plate is aluminum nitride.

[0012] Preferably, the heat insulation layer is inorganic glue.

[0013] A preparation method of a SiGe thermoelectric device for a space nuclear power source, the method includes:

[0014] S1: Prepare electrodes composed of tungsten conductive layers and graphite transition layers, and use a mold to connect the tungsten conductive layers and graphite transition layers into one body;

[0015] S2: Bond SiGe thermocouple arms with inorganic glue, wherein the P-type thermocouple arms and N-type thermocouple arms are arranged at intervals, and an inorganic glue heat insulation layer is filled between adjacent thermocouple arms to form a SiGe thermocouple arm array;

[0016] S3: Adopt a diffusion welding method to weld two electrodes formed by connecting tungsten conductive layers and graphite transition layers to both ends of the SiGe thermocouple arm array respectively;

[0017] S4: Cut the electrodes connected to both ends of the SiGe thermocouple arm array into electrode blocks, and connect any one electrode block to a thermocouple pair composed of a P-type thermocouple arm and an N-type thermocouple arm;

[0018] S5: Bond an insulating plate on the outer surface of the tungsten conductive layer to form a SiGe device.

[0019] Preferably, when preparing the tungsten conductive layer and the graphite transition layer in step S1, nickel powder is added between the two layers.

[0020] Preferably, in step S3, the temperature used in the diffusion welding method is 1100 °C to 1300 °C, the pressure is 10 to 25 MPa, and the time is 10 to 30 minutes.

[0021] Preferably, the method used for electrode cutting in step S4 is wire cutting.

[0022] The beneficial effects of the present invention are as follows: The preparation method of the SiGe thermoelectric device for space reactor thermoelectric power generation provided by the present invention enables both the hot end and the cold end of the thermoelectric device to withstand high-temperature environments, and has a compact structure. This preparation method connects the thermocouple material with the hot-end electrode and the cold-end electrode simultaneously by diffusion welding, ensuring that the prepared thermoelectric device is applicable to relatively high temperatures. The SiGe thermoelectric device provided by the present invention can be used for space reactor thermoelectric power generation. Description of the Drawings

[0023] Figure 1 It is a schematic structural diagram of the SiGe thermoelectric device for space reactor thermoelectric power generation in the embodiment of the present invention;

[0024] Figure 2 It is a performance curve of the SiGe thermoelectric device for space reactor thermoelectric power generation prepared in the embodiment of the present invention;

[0025] In the figure: 1. Insulating plate 2. Conductive layer 3. Transition layer 4. P-type thermocouple arm 5. N-type thermocouple arm 6. Heat insulation layer. Detailed Embodiments

[0026] Those of ordinary skill in the art will realize that the embodiments described herein are for helping the reader understand the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific deformations and combinations that do not depart from the essence of the present invention based on the technical revelations disclosed in the present invention, and these deformations and combinations are still within the protection scope of the present invention.

[0027] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0028] As an embodiment, as Figure 1The SiGe thermoelectric device for a space nuclear heat source thermoelectric power supply as shown, the thermoelectric device having a sandwich structure, comprising: two insulating plates 1 arranged in parallel on the outer layer of the thermoelectric device, two conductive layers 2 arranged in parallel inside the insulating plates 1, two transition layers 3 arranged in parallel inside the conductive layers 2, a plurality of thermocouple arms sandwiched between the two transition layers 3, and a heat insulation layer 6 located between the thermocouple arms;

[0029] The above-mentioned conductive layer 2 and the transition layer 3 are connected as a whole, the material of the conductive layer 2 is tungsten, the material of the transition layer 3 is graphite, the conductive layer 2 and the transition layer 3 form the electrodes of the thermoelectric device, and the electrodes are cut into a plurality of discontinuous electrode blocks;

[0030] The thermocouple arms include P-type thermocouple arms 4 and N-type thermocouple arms 5, the P-type thermocouple arms 4 and the N-type thermocouple arms 5 are arranged at intervals, a heat insulation layer 6 is filled between adjacent thermocouple arms, the material of the thermocouple arms is SiGe, the heat insulation layer 6 is an inorganic glue, which plays the roles of mechanical support, heat insulation and electrical insulation, and each electrode block at both ends of the thermocouple arms is connected to a thermocouple pair composed of a P-type thermocouple arm 4 and an N-type thermocouple arm 5, and the electrode block at one end of the thermocouple arm is staggered from the opposite electrode by the arrangement of one thermocouple arm, as Figure 1 shown, all the thermocouple arms and the electrodes are connected in a folded strip shape;

[0031] The above-mentioned thermoelectric device includes at least two pairs of thermocouple pairs composed of P-type thermocouple arms and N-type thermocouple arms.

[0032] The material of the above-mentioned insulating plate 1 is aluminum nitride.

[0033] A preparation method of a SiGe thermoelectric device for a space nuclear heat source thermoelectric power supply, the method comprising:

[0034] S1: Prepare electrodes composed of tungsten conductive layers and graphite transition layers, and use a mold to connect the tungsten conductive layers and the graphite transition layers as a whole;

[0035] S2: Bond SiGe thermocouple arms with inorganic glue, wherein the P-type thermocouple arms and the N-type thermocouple arms are arranged at intervals, and the inorganic glue filled between adjacent thermocouple arms becomes a heat insulation layer after curing, forming a SiGe thermocouple arm array;

[0036] S3: Adopt a diffusion welding method to weld the electrodes formed by connecting the tungsten conductive layers and the graphite transition layers to both ends of the SiGe thermocouple arm array respectively;

[0037] The specific process is: place the electrodes, the SiGe thermocouple arm array, and the electrodes in a mold from bottom to top, place them in a diffusion welding furnace, heat and pressurize them to connect the SiGe thermocouple arms with the electrodes, the diffusion welding temperature is 1100°C to 1300°C, the pressure is 10 to 25 MPa, and the time is 10 to 30 minutes;

[0038] S4: Cut the electrodes connected to both ends of the SiGe thermocouple arm array into electrode blocks. Any one electrode block is connected to a thermocouple pair composed of a P-type thermocouple arm and an N-type thermocouple arm. The wire cutting method can be selected as the cutting method.

[0039] S5: Bond an insulating board on the outer surface of the tungsten conductive layer to form a SiGe device.

[0040] Embodiment

[0041] Taking a thermoelectric device including 3 pairs of SiGe thermocouple arms and having a series circuit inside as an example, the specific implementation manner of the present invention will be specifically described as follows:

[0042] (1) Prepare a tungsten / graphite electrode. The size of the tungsten sheet is 10 mm × 15 mm × 0.5 mm, and the size of the graphite sheet is 10 mm × 15 mm × 2 mm. Place the tungsten sheet, nickel powder, and graphite sheet in a graphite mold from bottom to top, and sinter them in a vacuum hot-pressing sintering furnace at 1400 °C and 20 MPa for 20 minutes to obtain a tungsten / graphite electrode.

[0043] (2) Alternately arrange 3 N-type SiGe thermocouple arms and 3 P-type SiGe thermocouple arms in the order of N-SiGe / P-SiGe / N-SiGe / P-SiGe / N-SiGe / P-SiGe. Use a high-temperature resistant inorganic adhesive to bond between every two thermocouple arms to form a SiGe thermocouple arm array. The size of the thermocouple arm is 2 mm in thickness, 10 mm in width, and 8 mm in height, and the gap between the thermocouple arms is 0.5 mm.

[0044] (3) Place the tungsten / graphite electrode, SiGe thermocouple arm array, and tungsten / graphite electrode in a graphite mold from bottom to top in sequence. The graphite side of the electrode is in contact with the upper and lower surfaces of the SiGe array. In a vacuum hot-pressing sintering furnace, press and connect them at 1200 °C and 20 MPa for 20 min to connect the electrode with SiGe and form a combination of tungsten / graphite electrode - SiGe thermocouple arm array - tungsten / graphite electrode.

[0045] (4) For the tungsten / graphite electrode - SiGe thermocouple arm array - tungsten / graphite electrode combination after welding in the previous step, use a wire cutting machine to cut the hot-end electrode and the cold-end electrode to form the designed circuit in the device.

[0046] (5) Use a high-temperature resistant inorganic adhesive to bond an aluminum nitride insulating board on the electrode surface.

[0047] In the SiGe thermoelectric device prepared in this embodiment, when the hot-end temperature is 800 °C and the cold-end temperature is 300 °C, the output electric power is about 1.2 W@3A, as Figure 2 shown. Before and after heat treatment at 927 °C for 300 hours, the internal resistance of the device is 46 mΩ and remains unchanged.

Claims

1. A preparation method of a SiGe thermoelectric device for a space thermoelectric power generation device using a thermoelectric pile, characterized in that The thermoelectric device has a sandwich structure, including: two insulating plates arranged in parallel on the outermost layer of the thermoelectric device, two conductive layers arranged in parallel inside the insulating plates, two transition layers arranged in parallel inside the conductive layers, a plurality of thermocouple arms between the two transition layers, and a heat insulation layer between the thermocouple arms; The material of the conductive layer is tungsten, and the material of the transition layer is graphite. The conductive layer and the transition layer are connected to form the electrodes of the thermoelectric device, and the electrodes are composed of a plurality of discontinuous electrode blocks; The thermocouple arms include P-type thermocouple arms and N-type thermocouple arms. The P-type thermocouple arms and N-type thermocouple arms are arranged at intervals, and a heat insulation layer is filled between adjacent thermocouple arms. The material of the thermocouple arms is SiGe; Each electrode block at both ends of the thermocouple arms is connected to a thermocouple pair composed of a P-type thermocouple arm and an N-type thermocouple arm, and the electrode block at one end of the thermocouple arm is staggered from the electrode opposite to it at the other end of the thermocouple arm by one thermocouple arm arrangement; The method includes: S1: Prepare an electrode composed of a tungsten conductive layer and a graphite transition layer, and use a mold to connect the tungsten conductive layer and the graphite transition layer into one body; S2: Bond the SiGe thermocouple arms with an inorganic glue, where the P-type thermocouple arms and N-type thermocouple arms are arranged at intervals, and an inorganic glue heat insulation layer is filled between adjacent thermocouple arms to form a SiGe thermocouple arm array; S3: Adopt the diffusion welding method to weld the two electrodes formed by connecting the tungsten conductive layer and the graphite transition layer to the two ends of the SiGe thermocouple arm array respectively; connect the thermocouple material to the hot-end electrode and the cold-end electrode simultaneously by the diffusion welding method; S4: Cut the electrodes connected to both ends of the SiGe thermocouple arm array into electrode blocks, and any one electrode block is connected to a thermocouple pair composed of a P-type thermocouple arm and an N-type thermocouple arm; S5: Bond an insulating plate on the outer surface of the tungsten conductive layer to form a SiGe device.

2. The preparation method of the SiGe thermoelectric device for the space nuclear thermal power source according to claim 1, characterized in that, The thermoelectric device includes at least two pairs of thermocouple pairs composed of P-type thermocouple arms and N-type thermocouple arms.

3. The preparation method of the SiGe thermoelectric device for the space nuclear thermoelectric power source according to claim 1, characterized in that, The insulating plate is aluminum nitride.

4. The method for preparing a SiGe thermoelectric device for a space reactor temperature difference power supply according to claim 1, characterized in that: The heat insulation layer is an inorganic glue.

5. The preparation method of the SiGe thermoelectric device for the space nuclear thermoelectric power source according to claim 1, wherein, When preparing the tungsten conductive layer and the graphite transition layer in step S1, nickel powder is added between the two layers.

6. The preparation method of the SiGe thermoelectric device for the space nuclear heat power source according to claim 1, characterized in that In step S3, the temperature used in the diffusion welding method is 1100°C to 1300°C, the pressure is 10 to 25 MPa, and the time is 10 to 30 minutes.

7. The preparation method of the SiGe thermoelectric device for space nuclear heat power generation according to claim 1, characterized in that The method used for electrode cutting in step S4 is wire cutting.

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