Contact type thermoelectric device and preparation process thereof

Abstract

The invention discloses a contact type thermoelectric device and a preparation process thereof, and belongs to the technical field of thermoelectric conversion device manufacturing. The contact type thermoelectric device mainly comprises a hot end part, a positioning compression piece, a thermoelectric material and a cold end part. The preparation process of the contact type thermoelectric device mainly comprises the steps of preparation of a hot end part, preparation of a thermoelectric material part, preparation of a cold end part, design and preparation of a positioning compression part, overall preparation of the contact type thermoelectric device and assembly of a thermoelectric power generation system containing the contact type thermoelectric device. According to the contact type thermoelectric device, the electrode of the device hot end part and the thermoelectric material are in pressure contact, welding flux is omitted, a traditional welding process is replaced, and the service temperature of the thermoelectric device is greatly increased. According to the preparation process of the contact type thermoelectric device, the thermoelectric device is prevented from being in the environments of overhigh welding temperature, non-uniform heating and the like for a long time in the preparation process, and the performance degradation of the thermoelectric material is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of thermoelectric conversion device manufacturing, in particular to a contact type thermoelectric device and a preparation process thereof. Background Art

[0002] With the intensification of energy crisis and environmental problems, improving energy efficiency based on traditional energy has become one of the focus issues of governments and scientists. Since most of the wasted energy is mainly waste heat resources, exploring and fully utilizing waste heat resources is considered to be one of the most promising new energy technologies. Thermoelectric devices have gradually been valued by various countries due to their ability to directly convert heat energy and electrical energy. In addition, thermoelectric devices have the advantages of simple structure, high reliability, no moving components, no noise generation, and miniaturization, and have broad application prospects in waste heat recovery.

[0003] Thermoelectric devices are composed of individual thermoelectric particles. In a hot and cold temperature difference environment, thermoelectric devices will generate thermoelectric potential and thermoelectric current in the device loop due to the Seebeck effect of thermoelectric particles. Thermoelectric materials are mainly divided into three types according to the working temperature: room temperature thermoelectric materials (300K~500K), medium temperature thermoelectric materials (500K~900K), and high temperature thermoelectric materials (>900K). At present, Bi2Te3 thermoelectric materials in the room temperature domain have been widely used. In my country, the waste heat resource structure is that medium temperature waste heat (473K~773K) and high temperature waste heat (>773K) account for a large proportion. It is difficult to recycle medium and high temperature waste heat resources using room temperature Bi2Te3 thermoelectric materials (the best performance temperature is below 573K). However, the medium and high waste heat resource temperature range is exactly the best working temperature range of medium and high temperature thermoelectric materials. Therefore, medium and high temperature thermoelectric materials have a wide range of application potential. The process of preparing medium and high temperature thermoelectric materials into devices is particularly important in research.

[0004] Bi2Te3 thermoelectric materials in the room temperature domain are generally prepared into thermoelectric devices using the reflow soldering method. Since the soldering temperature of the reflow soldering method is generally lower than 573K (much lower than the hot end operating temperature of medium and high temperature thermoelectric devices), the connection between the hot end of medium and high temperature thermoelectric devices and thermoelectric materials cannot be made using the reflow soldering method. At present, colleges and research institutes generally use traditional brazing alloy methods to connect the hot end of medium and high temperature thermoelectric devices and thermoelectric materials. However, during the brazing process, the temperature is too high and the heating is uneven, resulting in performance degradation of thermoelectric materials, element diffusion between interfaces, and residual thermal stress in welding. Therefore, there is currently a lack of mature preparation processes for medium and high temperature thermoelectric devices. How to achieve low-temperature connection and high-temperature service of devices is the focus of current research. Summary of the invention

[0005] The object of the present invention is to provide a contact type thermoelectric device and a preparation process thereof to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solution: a contact type thermoelectric device.

[0007] The device is arranged in order from top to bottom into several parts: a hot end part, a positioning compression part, a thermoelectric material, and a cold end part, wherein the hot end part is divided into a hot end assembly, the thermoelectric material is a thermoelectric material assembly, and the cold end part is divided into a cold end assembly. The hot end part includes a hot end ceramic substrate and a foam metal electrode fixed on the hot end ceramic substrate, and one end of the foam metal electrode is coated with a conductive paste layer. The cold end part includes a cold end ceramic substrate and a copper electrode fixed on the cold end ceramic substrate, and a low-temperature solder layer is coated on the copper electrode, wherein the cold end part has two copper electrodes welded with wires. The copper electrode of the cold end part is connected to one end of the thermoelectric material by low-temperature solder welding, and the cold end part of the thermoelectric material is embedded in one end of the positioning compression part, and the hot end part is embedded in the other end of the positioning compression part.

[0008] When the contact thermoelectric device is used, it can be directly attached to the cold and hot sources. The hot-end ceramic substrate is attached to the heat source plane, and the cold-end metal-clad ceramic substrate is attached to the cold source plane. A load is applied to the heat source, and the heat source applies a load to the hot-end ceramic substrate and pushes the hot-end ceramic substrate toward the thermoelectric material. The foam metal electrode on the hot-end ceramic substrate gradually contacts the high-temperature end of the thermoelectric material and is compressed. After the hot and cold temperature difference is established, the contact thermoelectric device can be put into service and tested.

[0009] The present invention adds a positioning compression member. In the actual assembly process of the contact device, the hot end ceramic substrate and the thermoelectric material are prone to misalignment, which causes the foam metal electrode on the hot end ceramic substrate to be misaligned with the thermoelectric material. Therefore, in the present invention, a corresponding positioning compression member is designed and prepared for the thermoelectric device, wherein the main force-bearing and deforming part of the positioning compression member adopts a rectangular cross-sectional structure design with a large aspect ratio (b / h). The advantage of this design is that when the frame is subjected to loads in different directions, there will be different sizes of bending section coefficients. When a uniform load is applied to the hot end ceramic substrate of the contact thermoelectric device, the positioning compression member is compressed and deformed. At this time, the bending section coefficient of the force-bearing and deformed part is small. Only a very small uniform load is applied to the hot end ceramic substrate to make the force-bearing and deformed part produce a large deflection, so that the hot end foam metal electrode can be close to the thermoelectric material and fully contact. When a load component appears perpendicular to the device compression direction due to the generation of a small inclination during compression, the bending section coefficient of the force-bearing and deformed part is large. Therefore, only when the load component is large can the hot end ceramic substrate and the thermoelectric material be misaligned. Therefore, the positioning compression member can effectively prevent the hot end ceramic substrate and the thermoelectric material from being misaligned due to the load component.

[0010] The present invention adopts foam metal electrodes to replace traditional metal electrodes. In the actual device preparation process, due to the influence of factors such as the cutting and electroplating process of the thermoelectric material preparation, each thermoelectric material column will have a size difference. When the metal electrode and the thermoelectric material are used to prepare a contact thermoelectric device, a large gap is formed between the rigid thermoelectric material and the rigid metal electrode. These gaps make it impossible for the thermoelectric material and the metal electrode to form a fitted state. When working under the condition of pressure external load, these gaps will not only lead to the generation of excessive concentrated stress, but also generate a large thermal resistance and even cause the device to be short-circuited. At the same time, due to the difference in thermal expansion coefficients between n-type thermoelectric materials and p-type thermoelectric materials, when the thermoelectric device works in a high temperature environment, the difference in thermal expansion will further aggravate the generation of gaps between the thermoelectric material and the metal electrode. Therefore, in order to achieve complete fitting of the contact thermoelectric device electrode and the thermoelectric material, the present invention optimizes the traditional metal electrode into a foam metal electrode. The electrical and thermal conductivity of metal foam materials are comparable to those of metals of the same type. When metal foam is compressed, the internal pores gradually shrink and are compacted, which makes up for the difference in the size of thermoelectric material columns caused by factors such as the preparation, cutting and electroplating process of thermoelectric materials, ensures that the metal foam fits the thermoelectric material, and avoids the generation of large gaps. Not only that, taking the common copper foam and copper in the market as an example, the elastic modulus of the compacted copper foam is between tens of megapascals and hundreds of megapascals, while the elastic modulus of copper is about 100-130GPa. The elastic modulus of copper foam is much smaller than that of copper. Therefore, metal foam can reduce the impact of the gap caused by the difference in thermal expansion coefficients between n-type thermoelectric materials and p-type thermoelectric materials on device performance. Not only that, due to the porous structure of metal foam materials, the material will not extend to the surroundings when compressed. The zero Poisson's ratio characteristic of copper foam allows it to be better used in the narrow space of thermoelectric devices.

[0011] In the present invention, a conductive paste layer is added between the foam metal electrode and the thermoelectric material. In a contact thermoelectric device, although the foam metal material and the thermoelectric material can be completely fitted on a macroscopic level, a solid-solid contact interface will be formed at the junction of the materials. Microscopically, due to the rough surface of the thermoelectric material and the porous structure of the foam metal, the two material surfaces can only be effectively contacted at a small number of protrusions. There are tiny gaps between other uncontacted surfaces, which are generally filled with air. When current or heat flow passes through, the actual contact will increase a part of the additional transfer resistance compared to the ideal contact. This part of the resistance is the contact resistance and contact thermal resistance. The contact thermal resistance will cause temperature discontinuity at the interface when heat flow passes through; and the contact resistance will cause an increase in the internal resistance of the thermoelectric device. Therefore, the contact effect will cause the performance of the thermoelectric power generation device to deteriorate. In order to reduce the tiny gap between the two materials and lower the resistance of the device contact interface, the present invention adds a conductive paste layer between the contact interface of the foam metal electrode and the thermoelectric material. The conductive paste can effectively squeeze out the air in the tiny gap, reduce the tiny gap between the two materials, increase the actual contact area of ​​the surfaces of the two materials, reduce the contact resistance and contact thermal resistance, and optimize the performance of the contact thermoelectric device.

[0012] Another technical solution proposed by the present invention is to provide a process for preparing a contact thermoelectric device, comprising the following steps: S1: Preparation of the hot end part: First, prepare the foam metal material and use a dicing machine to cut the foam metal into foam metal electrodes. Then prepare the hot end ceramic substrate and use a high temperature resistant thermal conductive glue and a mold to adhere the prepared foam metal electrode to the hot end ceramic substrate. Finally, use screen printing to print the conductive paste on the surface of the foam metal electrode (the contact surface with the thermoelectric material), and finally take out the prepared hot end part for use.

[0013] S2: Preparation of thermoelectric material parts: prepare thermoelectric material ingots, slice them, then pickle and electroplate the sheet materials with nickel, electroplate them on the surface to form a barrier layer, and then cut them into particles to obtain n-type and p-type thermoelectric material particles respectively.

[0014] S3: Preparation of the cold end part: First, prepare the cold end metal-clad ceramic substrate (composed of a cold end ceramic substrate and a metal electrode), then print a low-temperature solder layer by screen printing, and finally take out the prepared cold end part for use.

[0015] S4: Design and preparation of positioning compression parts: First, the auxiliary part is divided into three parts from top to bottom, the upper frame part, the compression part, and the lower frame part. The lower frame part is designed with a groove for placing the cold-end metal-clad ceramic substrate. The depth of the groove should be smaller than the cold-end ceramic substrate of the cold-end part, and the length and width of the groove should be slightly larger than the length and width of the cold-end ceramic substrate. The thickness of the lower frame part does not exceed the total height of the cold-end ceramic substrate plus the metal electrode. A wire groove is opened at the corresponding position on one side of the lower frame part to facilitate the wire to pass through during later assembly. Correspondingly, the upper frame part is designed with a groove for placing the hot-end ceramic substrate. The depth of the groove of the upper frame part should be smaller than the hot-end ceramic substrate of the hot-end part, and the length and width of the groove should be slightly larger than the length and width of the hot-end ceramic substrate. The thickness of the upper frame part is consistent with that of the lower frame part. The total height of the compression part is designed to be greater than the sum of the height of the thermoelectric material and the thickness of the foam metal electrode. The structure of the compression part is torsion-resistant and easy to compress after design and simulation preparation. The compression part leaves sufficient space at the wire position to facilitate the wire to pass through.

[0016] S5: Overall preparation of contact thermoelectric device: put the prepared cold end part into the welding mold, alternately fill the prepared n-type and p-type thermoelectric material particles through the mold, and then put it on the welding table for reflow welding, so that the thermoelectric material can be welded on the cold end part, and then weld the wire. Pass the wire of the cold end part through the positioning compression part, and nest the cold end part in the groove of the lower end frame part of the positioning compression part, and then nest the hot end part in the groove of the upper end frame part of the positioning compression part (the conductive paste layer of the hot end part faces the thermoelectric material), and prepare the contact thermoelectric device.

[0017] S6: Assembly of the temperature difference power generation system containing contact thermoelectric devices: Spread the prepared contact thermoelectric devices evenly on the cooling panel, cover the heat source panel on the contact thermoelectric devices, and use bolts to connect and fix the cooling panel and the heat source panel, so that the cooling panel and the heat source panel apply enough pressure to the contact thermoelectric devices to allow the foam metal electrode to be in complete contact with the high-temperature end of the thermoelectric material.

[0018] The contact thermoelectric device preparation process provided by the present invention uses pressure contact between the electrode and the thermoelectric material at the hot end of the device, and the solder is eliminated to replace the traditional welding process. The traditional welding process uses a brazing alloy method to prepare medium and high temperature thermoelectric devices. The welding temperature is too high and the heating is uneven, which will lead to problems such as performance attenuation of thermoelectric materials, element diffusion between interfaces, and residual thermal stress of welding. The pressure contact method can effectively avoid the above problems. In the preparation process of the contact thermoelectric device, only a relatively low temperature reflow soldering method is used (the thermoelectric material is connected to the cold end part, and the welding temperature is generally less than 573K). The damage to the material caused by high temperature and uneven heating is avoided during the whole process of device preparation, so that the device can exert its original performance. In addition, since the pressure contact method eliminates the solder (the solder will be molten when working for a long time at too high a temperature, resulting in a decrease in device performance or even failure), the device failure caused by the melting of the solder is avoided, and the contact thermoelectric device can be operated in a higher temperature difference environment, exerting the performance that the thermoelectric material should have, and broadening the application scenarios of thermoelectric devices.

[0019] Compared with the prior art, the contact thermoelectric device and the process for preparing the contact thermoelectric device of the present invention have at least the following innovative features and beneficial effects: The contact thermoelectric device of the present invention comprises a hot-end ceramic substrate, a foam metal electrode, a conductive paste layer, a positioning compression member, a thermoelectric material, a low-temperature solder layer, a cold-end metal-clad ceramic substrate, and a wire, and a product contact thermoelectric device is obtained. The device has the following innovations: 1. The device uses a positioning compression member to achieve precise alignment of the foam metal electrode and the thermoelectric material, avoiding the misalignment of the foam metal electrode and the particles; 2. The addition of the foam metal can make the electrode and the thermoelectric material fit completely on a macro scale, avoiding the generation of an excessive gap when the two materials contact each other. At the same time, the influence of the gap caused by the difference in thermal expansion coefficients between the n-type thermoelectric material and the p-type thermoelectric material on the performance of the device is reduced; 3. The high-temperature end electrode adopts foam metal, and the material has excellent electrical conductivity and thermal conductivity. The porous structure makes the foam metal material have the characteristic of zero Poisson's ratio, which ensures that the foam metal material will not deform in a direction perpendicular to the load when the device is pressurized; 4. A conductive paste layer is added between the foam metal electrode and the thermoelectric material, which reduces the contact resistance and contact thermal resistance of the contact thermoelectric device and improves the conversion performance of the contact thermoelectric device.

[0020] The contact thermoelectric device of the present invention has the following beneficial effects: 1. Under the action of pressure load, the performance of the contact thermoelectric device is close to or even better than the conventionally welded thermoelectric devices of the same specifications currently on the market; 2. Since the pressure contact type is used instead of the welding type between the high-temperature end and the thermoelectric material, the service temperature of the thermoelectric device can be greatly improved, broadening the application scenarios of the thermoelectric device.

[0021] The contact thermoelectric device preparation process of the present invention includes the preparation of the hot end part, the preparation of the thermoelectric material part, the preparation of the cold end part, the design and preparation of the positioning compression part, and the overall preparation of the contact thermoelectric device. The process has the following innovations: 1. The pressure contact method is used between the hot end of the thermoelectric device and the thermoelectric material instead of the traditional welding method, eliminating the solder; 2. In the process of preparing the contact thermoelectric device, only the reflow soldering method with a relatively low temperature is used (the thermoelectric material is connected to the cold end part, and the welding temperature is generally less than 573K), realizing low-temperature preparation and high-temperature service.

[0022] The contact thermoelectric device preparation process of the present invention has the following beneficial effects: 1. It avoids the thermoelectric device being in an environment of excessively high welding temperature, uneven heating, etc. for a long time during the preparation process, thereby reducing the performance attenuation of the thermoelectric material caused by element diffusion between the welding interface and residual thermal stress of welding; 2. It eliminates the high-temperature welding process for connecting the hot end of the thermoelectric device and the thermoelectric material, thereby realizing the economical, rapid, and batch preparation of contact thermoelectric devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the three-dimensional structure of a contact thermoelectric device; Figure 2 It is a schematic diagram of the explosion structure of the contact thermoelectric device; Figure 3 It is a schematic diagram of the hot end part of the contact thermoelectric device; Figure 4 It is a schematic diagram of the cold end structure of the contact thermoelectric device; Figure 5 It is a schematic diagram of pressing the contact thermoelectric device; Figure 6 A temperature difference power generation system containing contact thermoelectric devices; Figure 7 Schematic diagram of the change of device internal resistance with temperature difference; Figure 8 Schematic diagram of device power changing with temperature difference; Fig. 9 Schematic diagram of device conversion efficiency changing with temperature difference; In the figure: 1, hot end part; 11, hot end ceramic substrate; 12, foam metal electrode; 13, conductive paste layer; 2, positioning compression member; 3, thermoelectric material; 31, n-type thermoelectric material; 32, p-type thermoelectric material; 4, cold end part; 41, cold end ceramic substrate; 42, metal electrode; 43, wire; 44, cold end metal-coated ceramic substrate; 45, low-temperature solder; 5, heat source panel; 6, cooling panel Figure 4 In the middle, e is the welding point; Figure 5N is the applied load, the left side of Figure Ⅰ represents before compression, and the right side of Figure Ⅱ represents after compression; Figure 6 Where N represents the applied load and A represents the contact thermoelectric device; Figure 7 a1 is the contact type which can operate stably under 400K temperature difference; a2 is the conventional type which has the solder melting and circuit breaking; Figure 8 b1 is 0.94W; b2 is 0.87W; Fig. 9 In the figure, c1 is the conversion efficiency of 5.6%; c2 is the efficiency dropped sharply due to reaching the material limit; and c3 is the efficiency of 5.26%. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Embodiment: In this embodiment, the foam metal, the cold end metal-clad ceramic substrate of the cold end part, and the conductive paste are respectively made of commonly available foam copper, cold end copper-clad ceramic substrate, and conductive copper paste on the market.

[0026] Please refer to Figure 1-2 This embodiment provides a contact thermoelectric device, which includes a hot end portion, a positioning compression member, a thermoelectric material, and a cold end portion arranged in sequence from top to bottom. Please refer to Figure 3 The hot end part of the contact thermoelectric device provided in this embodiment includes a conductive copper paste layer, a foam copper electrode, and a hot end ceramic substrate arranged in sequence from top to bottom. The positioning compression member provided in this embodiment is divided into an upper frame part, a compression part, and a lower frame part arranged in sequence from top to bottom for the convenience of subsequent introduction. Please refer to Figure 4 The cold end portion of the contact thermoelectric device provided in this embodiment includes a low-temperature solder layer, a wire, and a cold-end copper-clad ceramic substrate arranged in sequence from top to bottom.

[0027] Please refer to Figure 5-6, a temperature difference power generation system including contact thermoelectric devices. When the contact thermoelectric device is used, it can be directly attached to the cold and hot sources, the hot end ceramic substrate is attached to the heat source plane, and the cold end copper-clad ceramic substrate is attached to the cold source plane. A load is applied to the heat source, and the heat source applies a load to the hot end ceramic substrate and pushes the hot end ceramic substrate to move toward the thermoelectric material. The foam copper electrode on the hot end ceramic substrate gradually contacts the thermoelectric material and is compressed. After the hot and cold temperature difference is established, the contact thermoelectric device can be put into service and tested.

[0028] The complete contact thermoelectric device is prepared through the following process flow: S1: Preparation of the hot end part: First, prepare the foam copper electrode. Use a dicing machine to cut the foam copper material into 17 foam copper electrodes with a cross-section of 2mm×4.8mm. Then prepare a hot end ceramic substrate with a specification of 20mm×20mm×1mm. Use a high-temperature resistant thermal conductive adhesive and use a mold to adhere the prepared foam copper electrode to the hot end ceramic substrate. Finally, use screen printing to print the copper conductive paste on the foam metal surface (the contact surface with the thermoelectric material) with a printing thickness of 0.1mm. Finally, take out the prepared hot end part for use. Figure 3 shown.

[0029] Furthermore, in the preparation process of the hot end part of the embodiment of the present application, the selected foam copper specifications are 130ppi pore size, 97 porosity, 500 surface density, and 2mm thickness.

[0030] Furthermore, in the preparation process of the hot end part of the embodiment of the present application, the hot end ceramic substrate material selected is an alumina ceramic sheet with good thermal conductivity and high strength.

[0031] Furthermore, the copper conductive paste selected in the preparation process of the hot end part of the embodiment of the present application has good compatibility with the foam copper electrode, and the copper conductive paste has the same electrical and thermal conductivity as copper, can withstand a high temperature of 1100°C and has good chemical stability.

[0032] S2: Preparation of thermoelectric materials: Prepare Φ30mm n-Bi2Te3 and p-Bi2Te3 thermoelectric material ingots, slice them using a diamond wire saw, and obtain two Φ30mm×5mm thin sheets. Then, pickle the two sheet materials in a 5% H2So4 solution for 30s. Then, place the pickled materials in a NiSo4 electrolyte for nickel electroplating, with an electroplating voltage of 1.5V and a plating time of 20min to form a barrier layer on the material. Finally, place them in a diamond wire saw and cut them into 1.7mm×1.7mm×5mm particles to obtain n-Bi2Te3 and p-Bi2Te3 thermoelectric material particles.

[0033] S3: Preparation of cold end: First, prepare a 20mm×20mm×1mm cold end copper-clad ceramic substrate, and then print a 0.1mm thick low-temperature solder layer using a screen printing process. The solder is a lead-free tin-bismuth solder paste. Finally, take out the prepared cold end for use. Figure 4 shown.

[0034] S4: Design and preparation of positioning compression parts: 3D printing technology is used for preparation, and HP nylon material is selected. Its overall size is 22mm×22mm×9.6mm. The size of the upper frame part is 22mm×22mm×1.3mm, and its groove size is 20.2mm×20.2mm×0.8mm. Correspondingly, the size of the lower frame part is 22mm×22mm×1.3mm, and its groove size is 20.2mm×20.2mm×0.8mm, and two wire grooves are opened at the corresponding position on the side of the wire, and the center of the wire groove is 14mm apart. The structure of the compression part is designed in a "Y" shape, and the compression part is torsion-resistant and easy to compress after structural design.

[0035] S5: Overall preparation of contact thermoelectric device: put the prepared cold end part into the welding mold, fill the prepared n-Bi2Te3 and p-Bi2Te3 thermoelectric material particles alternately through the mold, and then put it on the welding table for reflow welding. The welding conditions are 248.3N pressure, 200℃, and the welding time is 5min, so that the thermoelectric material can be welded on the cold end part, and then weld the wire. Then pass the wire of the cold end part through the positioning compression part, and nest the cold end part in the groove of the lower frame part of the positioning compression part, and nest the hot end part in the groove of the upper frame part of the positioning compression part (the conductive paste layer of the hot end part faces the thermoelectric material), and prepare a contact thermoelectric device, such as Figure 1 and Figure 2 shown.

[0036] S6: Assembly of the temperature difference power generation system containing contact thermoelectric devices: Spread the prepared contact thermoelectric devices evenly on the cooling panel, cover the heat source panel on the contact thermoelectric devices, and use bolts to connect and fix the cooling panel and the heat source panel, so that the cooling panel and the heat source panel apply enough pressure to the contact thermoelectric devices to allow the foam copper electrode to be in complete contact with the high-temperature end of the thermoelectric material.

[0037] Test Example 1: A contact thermoelectric device was prepared according to the process provided in the embodiment. A thermoelectric test was performed on the device. The thermoelectric test system includes a test pressurized mold, a heat source, a cold source, a test circuit, and a vacuum box. The test process is as follows: the device is placed in a test pressurized mold for assembly and pressurization. The compression diagram is shown in FIG. Figure 5Then put the assembled mold into the vacuum box, and then connect the device to the test circuit. Then seal the vacuum box and evacuate it. Adjust the temperature difference between the hot source and the cold source. After the hot and cold ends reach the specified temperature difference and stabilize, record the data of the test circuit. The temperature difference range tested this time is 50K-400K, and the data is recorded every 50K, with a total of 8 data points. The test results are as follows: Figure 7-9 As shown by the black line, Figure 7 (a) is the temperature difference-resistance curve, which shows the change of the resistance of the device with the temperature difference; Figure 8 (b) is the temperature difference-power curve, which shows the change of the output power of the device with the temperature difference; Fig. 9 (c) is the conversion efficiency-power curve. The black line shows how the conversion efficiency of the contact device changes with temperature difference, which is also the most important indicator for evaluating the quality of the device.

[0038] Test Example 2: Conventional welded thermoelectric devices were prepared for test control, and conventional welded thermoelectric devices were tested. The thermoelectric test system includes a test pressurized mold, a heat source, a cold source, a test circuit, and a vacuum box. The test process is: the device is placed in the test pressurized mold for assembly and pressurization, and then the assembled mold is placed in the vacuum box, and then the device is connected to the test circuit. The vacuum box is then sealed and evacuated, and the temperature difference between the heat source and the cold source is adjusted. After the hot and cold ends reach the specified temperature difference and stabilize, the test circuit data is recorded. The temperature difference range tested this time is 50K-400K, and data points are recorded every 50K, with a total of 8 data points. The test results are as follows Figure 7-9 As shown by the red line, Figure 7 It is the temperature difference-resistance curve, which shows the change of the resistance of the device with the temperature difference; Figure 8 is the temperature difference-power curve, which shows the change of the output power of the device with the temperature difference; Fig. 9 This is the conversion efficiency-power curve. The red line shows how the conversion efficiency of conventional soldered devices changes with temperature difference.

[0039] From the test results, it can be seen that the maximum power of conventional welded thermoelectric devices is 0.87W at a temperature difference of 300K, and the conversion efficiency of conventional welded thermoelectric devices is 5.26%. And when the temperature difference of conventional welded thermoelectric devices is greater than 300K, the conventional welded thermoelectric devices have the phenomenon of solder melting and device short circuit, so the 350K and 400K data points are not collected, which also shows that conventional welded thermoelectric devices are not suitable for long-term operation in an environment with too high temperature.

[0040] The test results show that the power of the contact thermoelectric device prepared by this process is 0.940W at a temperature difference of 300K, and the conversion efficiency of the device reaches a maximum of 5.6% at this time, indicating that the performance of the contact thermoelectric device under the same temperature difference condition is close to or even higher than that of the conventional welded thermoelectric device. Although the conversion efficiency drops sharply after the temperature difference of 350K because the temperature has reached the limit conversion efficiency of the thermoelectric material of the embodiment, Figure 8 The device power is still rising steadily at this time, indicating that the contact thermoelectric device prepared by this process can indeed be used in a higher temperature environment. This process lays the foundation for the subsequent application of thermoelectric materials in the medium and high temperature domain. Therefore, according to the test, it can be seen that according to the process provided in the embodiment of the present application, a thermoelectric device with thermoelectric performance that meets the requirements can be effectively prepared.

[0041] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A process for preparing a contact thermoelectric device, characterized in that: The preparation process comprises the following steps: S1: preparing a hot end component, wherein the preparation process is as follows: S11, preparing a foam metal material, and using a dicing machine to cut the foam metal into foam metal electrodes; S12, preparing a hot end ceramic substrate (11), and using a thermal conductive adhesive to adhere the prepared foam metal electrode (12) to the hot end ceramic substrate (11) through a mold; S13, printing a conductive paste (13) on the surface of the foam metal electrode (12) through screen printing to obtain a prepared hot end component (1), and taking it out for use; S2: preparing a thermoelectric material assembly, wherein the preparation process is as follows: S21, preparing a thermoelectric material ingot, slicing the ingot to form a sheet-shaped thermoelectric material ingot; S22, microetching the surface of the sheet-shaped thermoelectric material ingot and electroplating nickel to form a barrier layer on the surface of the sheet-shaped thermoelectric material ingot; S23, cutting the electroplated thermoelectric material ingot into particles to obtain n-type thermoelectric material (31) particles and p-type thermoelectric material (32) particles for later use; S3: preparing a cold end assembly, wherein the preparation process is as follows: S31, preparing a cold end metal-clad ceramic substrate (44), wherein the cold end metal-clad ceramic substrate (44) comprises a cold end ceramic substrate (41) and a metal electrode (42); S32, printing a low-temperature solder layer (45) on the cold end metal-clad ceramic substrate (44) by a screen printing process, thereby obtaining a cold end assembly for standby use; S4: preparing a positioning compression member (2), wherein the specific process is as follows: the positioning compression member comprises an upper frame, a compression frame and a lower frame from top to bottom; the lower frame is provided with a groove 1 for placing a cold-end metal-coated ceramic substrate (44), the depth of the groove 1 is less than the thickness of the cold-end ceramic substrate (41), and the length and width of the groove 1 are greater than the length and width of the cold-end ceramic substrate (41), the thickness of the lower frame is less than the sum of the heights of the cold-end ceramic substrate (41) and the metal electrode (42), and a wire groove is provided on one side of the lower frame for placing a wire (43); the upper frame is provided with a groove 2 for placing a hot-end ceramic substrate (11), the depth of the groove 2 is less than the thickness of the hot-end ceramic substrate (11) of the hot-end assembly (1), and the length and width of the groove 2 are greater than the length and width of the hot-end ceramic substrate (11); the height of the compression frame is greater than the sum of the height of the thermoelectric material (3) and the thickness of the foam metal electrode (12); S5: preparing a contact thermoelectric device, the specific process of which is as follows: S51, placing the prepared cold end component (4) into a welding mold, alternately filling the prepared n-type thermoelectric material (31) particles and p-type thermoelectric material (32) particles through the mold, and one end of the thermoelectric material (3) particles is in contact with the low-temperature solder layer (45) in the cold end component; S52, welding, welding the thermoelectric material component (3) to the metal electrode (42) of the cold end component (4) through the low-temperature solder layer (45), and welding the wire (43) to the metal electrode (42); S53, passing the wire (43) of the cold end component (4) through the positioning compression member (2), and nesting the cold end component (4) in the groove 1 of the lower end frame; S54, nesting the hot end component (1) in the groove 2 of the upper end frame component, and the conductive paste layer of the hot end component is close to the thermoelectric material component, to obtain a contact thermoelectric device; S6: Assembling the contact thermoelectric device and the temperature difference power generation system, wherein the assembly process is as follows: S61, evenly laying the prepared contact thermoelectric device on the cooling panel (6), and covering the heat source panel (5) on the contact thermoelectric device; S62, connecting and fixing the cooling panel (6) and the heat source panel (5) with bolts, wherein the cooling panel (6) and the heat source panel (5) exert pressure on the contact thermoelectric device, and the foam metal electrode (12) contacts the high-temperature end of the thermoelectric material component (3).

2. The process for preparing a contact thermoelectric device according to claim 1, characterized in that: The specific process of preparing the hot end component is as follows: first, prepare the foam copper electrode, and use a dicing machine to cut the foam copper material into 17 foam copper electrodes with a cross-section of 2mm×4.8mm; then prepare a hot end ceramic substrate with a specification of 20mm×20mm×1mm, use a high-temperature resistant thermal conductive adhesive, and use a mold to adhere the prepared foam copper electrode to the hot end ceramic substrate; finally, use screen printing to print copper conductive paste on the surface of the foam metal, which is in contact with the thermoelectric material, and the printing thickness of the foam metal surface is 0.1mm, and finally the prepared hot end component is taken out for use.

3. The process for preparing a contact thermoelectric device according to claim 2, characterized in that: The selected foam copper specifications are 130ppi pore size, 97 porosity, 500 surface density, and 2mm thickness; the selected hot end ceramic substrate material is alumina ceramic sheet.

4. The process for preparing a contact thermoelectric device according to claim 1, characterized in that: Preparation of the thermoelectric material component: prepare Φ30mm n-Bi2Te3 and p-Bi2Te3 thermoelectric material ingots, slice them respectively using a diamond wire cutting machine to obtain two Φ30mm×5mm thin sheets, and put the two sheet materials into a 5% H2So4 solution for pickling for 30s; put the pickled materials into a NiSo4 electrolyte for nickel electroplating, with an electroplating voltage of 1.5V and an electroplating time of 20min to form a barrier layer on the outer surface of the material; put the electroplated materials into a diamond wire cutting machine and cut them into 1.7mm×1.7mm×5mm particles to obtain n-Bi2Te3 and p-Bi2Te3 thermoelectric material particles.

5. The process for preparing a contact type thermoelectric device according to claim 1, characterized in that: The cold end component is prepared as follows: first, a 20mm×20mm×1mm cold end copper-clad ceramic substrate is prepared, and a 0.1mm thick low-temperature solder layer is printed by screen printing, wherein the solder is lead-free tin-bismuth solder paste; finally, the prepared cold end component is taken out for use.

6. The process for preparing a contact type thermoelectric device according to claim 1, characterized in that: The positioning compression member (2) is prepared as follows: the upper frame, the compression frame and the lower frame are all prepared by 3D printing technology; the overall size of the positioning compression member is 22 mm×22 mm×9.6 mm; the size of the upper frame is 22 mm×22 mm×1.3 mm, and the size of its groove 2 is 20.2 mm×20.2 mm×0.8 mm; the size of the lower frame is 22 mm×22 mm×1.3 mm, and the size of its groove 1 is 20.2 mm×20.2 mm×0.8 mm, and two wire grooves are opened at corresponding positions on one side of the wire, and the centers of the wire grooves are 14 mm apart in the middle of the span.

7. The process for preparing a contact thermoelectric device according to claim 1, characterized in that: The overall preparation of the contact thermoelectric device is as follows: the prepared cold end component is placed in a welding mold, and the prepared n-Bi2Te3 and p-Bi2Te3 thermoelectric material particles are alternately filled in through the welding mold, and then it is placed on a welding table for reflow welding. The welding conditions are 248.3N pressure, 200°C, and the welding time is 5 minutes, so that the thermoelectric material can be welded on the cold end part, and then the wire is welded; then the wire of the cold end component is passed through the positioning compression part, and the cold end component is nested in the groove 1 of the lower end frame of the positioning compression part, and the hot end component is nested in the groove 2 of the upper end frame part of the positioning compression part, so as to prepare the contact thermoelectric device.

8. A contact type thermoelectric device, which is applied to the preparation process of a contact type thermoelectric device according to any one of claims 1 to 7, characterized in that: The contact thermoelectric device comprises a hot end component (1), a positioning compression component (2), a thermoelectric material component (3) and a cold end component (4); the thermoelectric material component (3) is placed in the positioning compression component (2), the hot end component (1) and the cold end component (4) are respectively nested at two ends of the positioning compression component (2), and the hot end component (1) is close to the high-temperature end of the thermoelectric material component (3).

9. A contact type thermoelectric device according to claim 8, characterized in that: The hot end component (1) comprises a hot end ceramic substrate (11) and a foam metal electrode (12) adhered to the hot end ceramic substrate (11), one side of the foam metal electrode (12) is in contact with the high temperature end of the thermoelectric material component (3), and one end of the foam metal electrode (12) is coated with a conductive paste layer (13); The cold end component (4) comprises a cold end ceramic substrate (41) and a metal electrode (42) fixed on the cold end ceramic substrate (41), the metal electrode (42) being coated with a low temperature solder layer (45), wherein the cold end component (4) has two metal electrodes (42) on which wires (43) are welded; the metal electrode (42) of the cold end component (4) is welded to one end of the thermoelectric material component (3) via the low temperature solder (45).

10. A contact type thermoelectric device according to claim 9, characterized in that: The contact-type thermoelectric devices are equidistantly distributed between the cooling panel (6) and the heat source panel (5), and the cooling panel (6) and the heat source panel (5) are connected and fixed by bolts.

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