Skutterudite thermoelectric material / electrode high-thermal-stability welding method based on metal ceramic composite barrier layer

Abstract

The invention discloses a skutterudite thermoelectric material / electrode high-thermal-stability welding method based on a metal ceramic composite barrier layer, and relates to a connecting method for a skutterudite-based thermoelectric material and a metal electrode. The invention aims to solve the problems that severe element diffusion exists between skutterudite and a metal electrode, so that the strength and interface resistance of the skutterudite are increased, the strength of a welding joint is low, and the service life is shortened. The metal ceramic composite phase is used as the diffusion barrier layer, the connection strength is high, the connector resistance is low, the thickness of the reaction layer is slowly increased under long-term service, and therefore good mechanical performance and using performance are kept. The composition and proportion of the whole barrier layer can be regulated and controlled by selecting different refractory metals and ceramics, the type, thickness and distribution mode of the interface reaction layer can be controlled by controlling the welding temperature and the heat preservation time, and then the strength and heat / electricity transport performance of a welding joint are controlled.

Description

Technical Field

[0001] The invention relates to a skutterudite thermoelectric material / electrode welding method. Background Art

[0002] Thermoelectric materials are an important class of materials that have the function of converting heat and electricity. Using the Seebeck effect and the Peltier effect, these materials are widely used in temperature difference power generation and thermoelectric refrigeration. As a representative of medium-temperature thermoelectric materials, skutterudite thermoelectric materials (hereinafter referred to as SKD) have a service temperature range of 300°C to 600°C. Due to their good thermoelectric and mechanical properties, they have great potential for practical applications.

[0003] The last step in manufacturing thermoelectric devices is to connect the thermoelectric material to the metal electrode, but there is a violent element diffusion between the cobaltite and the metal electrode, which increases its strength and interface resistance and greatly reduces its service life. There is currently no barrier layer metal material that can meet the long-term service requirements of cobaltite thermoelectric materials. Therefore, it is very important to design a method to achieve long-term and reliable connection between cobaltite thermoelectric materials and metal electrodes.

[0004] A conventional metal barrier layer will produce a brittle phase after being connected to skutterudite. The addition of refractory metals can reduce the proportion of the brittle phase to a certain extent, but the connection strength is often low due to different thermal expansion coefficients. If other metals are added, they will react with skutterudite, resulting in a deterioration in the overall diffusion barrier effect. In general, the reaction layer between the added barrier layer and skutterudite has a higher interface resistivity than the parent material, but its strength is lower than that of the parent material, so reducing the thickness of the reaction layer is the core purpose of the barrier layer. Therefore, it is of great practical significance to invent a reliable connection method for skutterudite-based thermoelectric materials and metal electrodes. Summary of the invention

[0005] The present invention aims to solve the problem that there is a violent element diffusion between skutterudite and the metal electrode, which increases the strength and interface resistance thereof, and thus leads to low strength of the welded joint and reduced service life.

[0006] The high thermal stability welding method of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer of the present invention is carried out according to the following steps:

[0007] 1. First, hot-pressing and sintering the skutterudite thermoelectric material and the barrier layer to obtain the skutterudite with a pre-barrier layer; the surface of the barrier layer in the skutterudite with the pre-barrier layer is the surface to be welded, and the surface to be welded of the skutterudite with the pre-barrier layer and the surface to be welded of the metal electrode are pre-treated respectively; finally, the treated skutterudite with the pre-barrier layer and the metal electrode are stored in an oxygen-free or inert atmosphere;

[0008] The preparation method of the skutterudite with a pre-set barrier layer is as follows: a layer of skutterudite powder is spread in a graphite mold, a layer of metal-ceramic composite barrier layer powder is spread on the skutterudite powder, and finally hot-pressing and sintering is performed;

[0009] The hot pressing sintering process is: under a vacuum environment, the applied pressure is 40-70 MPa, the temperature is raised to 650-760°C at a rate of 10-20°C / min and kept at this temperature for 5-30 minutes, and then cooled to room temperature at a rate of 20-50°C / min;

[0010] The metal-ceramic composite barrier layer powder is a mixture of refractory metal powder and ceramic powder; the refractory metal powder is one or more of Mo, V, Zr, Nb, Ta, Re, and Ti; the ceramic powder is M x Si y 、M x N y 、M x O y One or more of, wherein M is one or more of Ti, Zr, Mg, Al, K, Ca, Zn, and Mn; the molar percentage of the refractory metal powder in the metal-ceramic composite barrier layer powder is 60%-90%;

[0011] 2. Assemble the skutterudite with a pre-set barrier layer and the metal electrode, with the surface to be welded of the skutterudite with the pre-set barrier layer facing the surface to be welded of the metal electrode, place a brazing material between the surface to be welded of the skutterudite with the pre-set barrier layer and the surface to be welded of the electrode, obtain a workpiece to be welded, and finally weld; the welding process is: in a vacuum degree of 5×10 -3 In a vacuum brazing furnace below Pa, heat to 600-700℃ at a rate of 10-20℃ / min and keep warm for 5-30min, then cool to room temperature at a rate of 10-50℃ / min.

[0012] The metal-ceramic composite barrier layer powder in the present invention is mixed with refractory metal powder and ceramic powder, and a metal-ceramic composite phase is formed after hot pressing and sintering. The metal-ceramic composite phase as a barrier layer has no serious interface reaction with the skutterudite-based thermoelectric material and the metal electrode during the welding process, and the element diffusion diffuses slowly in the metal-ceramic composite phase. At the same time, compared with the existing Ti barrier layer, the overall proportion of the brittle reaction layer of the metal-ceramic composite phase of the present invention is reduced, and the reaction layer is also thinned as a whole. The high thermal expansion coefficient of the ceramic in the metal-ceramic composite phase adjusts the overall thermal expansion coefficient, and the connection strength is relatively high. The addition of ceramics also avoids the problem that other metals adjust the thermal expansion coefficient and react with skutterudite, and does not destroy the overall diffusion resistance effect. Therefore, the connection strength of the metal-ceramic composite phase used as the diffusion barrier layer of the present invention is high, the joint resistance is low, and the thickness of the reaction layer increases slowly under long-term service. After testing, the thickness of the reaction layer only increases from 9.5μm to 14.5μm after annealing for 135h, so good mechanical properties and performance are maintained. The present invention can adjust the composition and proportion of the overall barrier layer by selecting different refractory metals and ceramics, and can control the type, thickness and distribution of the interface reaction layer by controlling the welding temperature and insulation time, thereby controlling the strength and heat / electricity transport performance of the welded joint.

[0013] Another method for high thermal stability welding of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer of the present invention is carried out according to the following steps:

[0014] 1. First, hot-press and sinter the skutterudite powder into skutterudite, and hot-press and sinter the metal-ceramic composite barrier layer powder into a pre-set barrier layer; then pre-treat the to-be-welded surface of the skutterudite, the to-be-welded surface of the metal electrode, and the two surfaces of the pre-set barrier layer; finally, store the treated skutterudite, the metal electrode, and the pre-set barrier layer in an oxygen-free or inert atmosphere;

[0015] The process of hot-pressing and sintering skutterudite powder into skutterudite is as follows: in a vacuum environment, applying a pressure of 40-70 MPa, heating to 650-760° C. at a rate of 10-20° C. / min and keeping the temperature for 5-30 min, and then cooling to room temperature at a rate of 20-50° C. / min;

[0016] The process of hot-pressing and sintering the metal-ceramic composite barrier layer powder into the preset barrier layer is as follows: in a vacuum environment, the applied pressure is 40-70 MPa, the temperature is raised to 650-760°C at a rate of 10-20°C / min and kept at that temperature for 5-30 minutes, and then cooled to room temperature at a rate of 20-50°C / min;

[0017] The metal-ceramic composite barrier layer powder is a mixture of refractory metal powder and ceramic powder; the refractory metal powder is one or more of Mo, V, Zr, Nb, Ta, Re, and Ti; the ceramic powder is M xSi y 、M x N y 、M x O y One or more of, wherein M is one or more of Ti, Zr, Mg, Al, K, Ca, Zn, and Mn; the molar percentage of the refractory metal powder in the metal-ceramic composite barrier layer powder is 60%-90%;

[0018] 2. Placing the pre-set barrier layer between the surface to be welded of the skutterudite and the surface to be welded of the metal electrode to obtain the welded parts, and finally welding them; the welding process is: in a vacuum degree of 5×10 -3 In a vacuum brazing furnace below 1.5 MPa, apply a pressure of 5-20 MPa, heat to 600-700°C at a rate of 10-20°C / min and keep warm for 5-30 minutes, then cool to room temperature at a rate of 10-50°C / min.

[0019] The metal-ceramic composite barrier layer powder in the present invention is mixed with refractory metal powder and ceramic powder, and a metal-ceramic composite phase is formed after hot pressing and sintering. The metal-ceramic composite phase as a barrier layer has no serious interface reaction with the skutterudite-based thermoelectric material and the metal electrode during the welding process, and the element diffusion diffuses slowly in the metal-ceramic composite phase. At the same time, compared with the existing Ti barrier layer, the overall proportion of the brittle reaction layer of the metal-ceramic composite phase of the present invention is reduced, and the reaction layer is also thinned as a whole. The high thermal expansion coefficient of the ceramic in the metal-ceramic composite phase adjusts the overall thermal expansion coefficient, and the connection strength is relatively high. The addition of ceramics also avoids the problem that other metals adjust the thermal expansion coefficient and react with skutterudite, and does not destroy the overall diffusion resistance effect. Therefore, the present invention uses the metal-ceramic composite phase as a diffusion barrier layer with high connection strength, low joint resistance, and slow growth of the reaction layer thickness under long-term service. After testing, the reaction layer thickness only increases from 8.5μm to 15.5μm after annealing for 135h, so it maintains good mechanical properties and performance. The present invention can adjust the composition and proportion of the overall barrier layer by selecting different refractory metals and ceramics, and can control the type, thickness and distribution of the interface reaction layer by controlling the welding temperature and insulation time, thereby controlling the strength and heat / electricity transport performance of the welded joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a SEM image of the welding interface of the metal-ceramic composite phase / skutterudite thermoelectric material obtained in Example 1;

[0021] Figure 2 This is a SEM image of the welding interface in the metal-ceramic composite phase / skutterudite thermoelectric material obtained in Example 1 after annealing for 135 hours. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any reasonable combination of the specific implementation modes.

[0023] Specific implementation method 1: The method for high thermal stability welding of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer in this implementation method is carried out according to the following steps:

[0024] 1. First, hot-pressing and sintering the skutterudite thermoelectric material and the barrier layer to obtain the skutterudite with a pre-barrier layer; the surface of the barrier layer in the skutterudite with the pre-barrier layer is the surface to be welded, and the surface to be welded of the skutterudite with the pre-barrier layer and the surface to be welded of the metal electrode are pre-treated respectively; finally, the treated skutterudite with the pre-barrier layer and the metal electrode are stored in an oxygen-free or inert atmosphere;

[0025] The preparation method of the skutterudite with a pre-set barrier layer is as follows: a layer of skutterudite powder is spread in a graphite mold, a layer of metal-ceramic composite barrier layer powder is spread on the skutterudite powder, and finally hot-pressing and sintering is performed;

[0026] The hot pressing sintering process is: under a vacuum environment, the applied pressure is 40-70 MPa, the temperature is raised to 650-760°C at a rate of 10-20°C / min and kept at this temperature for 5-30 minutes, and then cooled to room temperature at a rate of 20-50°C / min;

[0027] The metal-ceramic composite barrier layer powder is a mixture of refractory metal powder and ceramic powder; the refractory metal powder is one or more of Mo, V, Zr, Nb, Ta, Re, and Ti; the ceramic powder is M x Si y 、M x N y 、M x O y One or more of, wherein M is one or more of Ti, Zr, Mg, Al, K, Ca, Zn, and Mn; the molar percentage of the refractory metal powder in the metal-ceramic composite barrier layer powder is 60%-90%;

[0028] 2. Assemble the skutterudite with a pre-set barrier layer and the metal electrode, with the surface to be welded of the skutterudite with the pre-set barrier layer facing the surface to be welded of the metal electrode, place a brazing material between the surface to be welded of the skutterudite with the pre-set barrier layer and the surface to be welded of the electrode, obtain a workpiece to be welded, and finally weld; the welding process is: in a vacuum degree of 5×10 -3 In a vacuum brazing furnace below Pa, heat to 600-700℃ at a rate of 10-20℃ / min and keep warm for 5-30min, then cool to room temperature at a rate of 10-50℃ / min.

[0029] In this embodiment, the metal-ceramic composite barrier layer powder is mixed with refractory metal powder and ceramic powder, and a metal-ceramic composite phase is formed after hot pressing and sintering. The metal-ceramic composite phase as a barrier layer has no serious interface reaction with the cobalt-based thermoelectric material and the metal electrode during the welding process, and the element diffusion is slow in the metal-ceramic composite phase. At the same time, compared with the existing Ti barrier layer, the overall proportion of the brittle reaction layer of the metal-ceramic composite phase in this embodiment is reduced, and the reaction layer is also thinned as a whole. The high thermal expansion coefficient of the ceramic in the metal-ceramic composite phase adjusts the overall thermal expansion coefficient, and the connection strength is relatively high. The addition of ceramics also avoids the problem that other metals adjust the thermal expansion coefficient and react with cobalt, and does not destroy the overall diffusion resistance effect. Therefore, in this embodiment, the connection strength of the metal-ceramic composite phase as a diffusion barrier layer is high, the joint resistance is low, and the thickness of the reaction layer increases slowly under long-term service. After testing, the thickness of the reaction layer only increases from 9.5μm to 14.5μm after annealing for 135h, so good mechanical properties and performance are maintained. This embodiment can adjust the composition and proportion of the overall barrier layer by selecting different refractory metals and ceramics, and can control the type, thickness and distribution of the interface reaction layer by controlling the welding temperature and insulation time, thereby controlling the strength and heat / electricity transport properties of the welded joint.

[0030] Specific implementation method 2: The difference between this implementation method and specific implementation method 1 is that the pretreatment process described in step 1 is: the surface to be welded is grinded, polished, cleaned and dried step by step with metallographic sandpaper in sequence; ethanol or acetone is used for cleaning.

[0031] Specific implementation method three: This implementation method is different from specific implementation methods one or two in that: the thickness of the barrier layer in step one is 20-200 μm.

[0032] Specific implementation method 4: This implementation method is different from any one of specific implementation methods 1 to 3 in that: the metal electrode in step 1 is Cu, Cu-based alloy, Ni, Ni-based alloy, Fe or Fe-based alloy.

[0033] Specific implementation mode 5: This implementation mode is different from any one of specific implementation modes 1 to 4 in that: the solder in step 2 is a copper-based solder paste.

[0034] Specific implementation method 6: The method for high thermal stability welding of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer in this implementation method is carried out according to the following steps:

[0035] 1. First, hot-press and sinter the skutterudite powder into skutterudite, and hot-press and sinter the metal-ceramic composite barrier layer powder into a pre-set barrier layer; then pre-treat the to-be-welded surface of the skutterudite, the to-be-welded surface of the metal electrode, and the two surfaces of the pre-set barrier layer; finally, store the treated skutterudite, the metal electrode, and the pre-set barrier layer in an oxygen-free or inert atmosphere;

[0036] The process of hot-pressing and sintering skutterudite powder into skutterudite is as follows: in a vacuum environment, applying a pressure of 40-70 MPa, heating to 650-760° C. at a rate of 10-20° C. / min and keeping the temperature for 5-30 min, and then cooling to room temperature at a rate of 20-50° C. / min;

[0037] The process of hot-pressing and sintering the metal-ceramic composite barrier layer powder into the preset barrier layer is as follows: in a vacuum environment, the applied pressure is 40-70 MPa, the temperature is raised to 650-760°C at a rate of 10-20°C / min and kept at that temperature for 5-30 minutes, and then cooled to room temperature at a rate of 20-50°C / min;

[0038] The metal-ceramic composite barrier layer powder is a mixture of refractory metal powder and ceramic powder; the refractory metal powder is one or more of Mo, V, Zr, Nb, Ta, Re, and Ti; the ceramic powder is M x Si y 、M x N y 、M x O y One or more of, wherein M is one or more of Ti, Zr, Mg, Al, K, Ca, Zn, and Mn; the molar percentage of the refractory metal powder in the metal-ceramic composite barrier layer powder is 60%-90%;

[0039] 2. Placing the pre-set barrier layer between the surface to be welded of the skutterudite and the surface to be welded of the metal electrode to obtain the welded parts, and finally welding them; the welding process is: in a vacuum degree of 5×10 -3 In a vacuum brazing furnace below 1.5 MPa, apply a pressure of 5-20 MPa, heat to 600-700°C at a rate of 10-20°C / min and keep warm for 5-30 minutes, then cool to room temperature at a rate of 10-50°C / min.

[0040] In this embodiment, the metal-ceramic composite barrier layer powder is mixed with refractory metal powder and ceramic powder, and a metal-ceramic composite phase is formed after hot pressing and sintering. The metal-ceramic composite phase as a barrier layer has no serious interface reaction with the cobalt-based thermoelectric material and the metal electrode during the welding process, and the element diffusion diffuses slowly in the metal-ceramic composite phase. At the same time, compared with the existing Ti barrier layer, the overall proportion of the brittle reaction layer of the metal-ceramic composite phase in this embodiment is reduced, and the reaction layer is also thinned as a whole. The high thermal expansion coefficient of the ceramic in the metal-ceramic composite phase adjusts the overall thermal expansion coefficient, and the connection strength is relatively high. The addition of ceramics also avoids the problem that other metals adjust the thermal expansion coefficient and react with cobalt, and does not destroy the overall diffusion resistance effect. Therefore, in this embodiment, the connection strength of the metal-ceramic composite phase as a diffusion barrier layer is high, the joint resistance is low, and the thickness of the reaction layer increases slowly under long-term service. After testing, the thickness of the reaction layer only increases from 8.5μm to 15.5μm after annealing for 135h, so good mechanical properties and performance are maintained. This embodiment can adjust the composition and proportion of the overall barrier layer by selecting different refractory metals and ceramics, and can control the type, thickness and distribution of the interface reaction layer by controlling the welding temperature and insulation time, thereby controlling the strength and heat / electricity transport properties of the welded joint.

[0041] Specific implementation method seven: The difference between this implementation method and specific implementation method six is ​​that: the pretreatment process described in step one is: the surface to be welded is grinded, polished, cleaned and dried step by step with metallographic sandpaper in sequence; ethanol or acetone is used for cleaning.

[0042] Specific implementation eight: This implementation differs from specific implementation six or seven in that: the thickness of the barrier layer in step one is 20-200 μm.

[0043] Specific implementation method 9: This implementation method is different from any one of specific implementation methods 6 to 8 in that: the metal electrode in step 1 is Cu, Cu-based alloy, Ni, Ni-based alloy, Fe or Fe-based alloy.

[0044] Specific implementation method ten: This implementation method is different from any one of specific implementation methods six to nine in that: the solder in step two is a copper-based solder paste.

[0045] Embodiment 1:

[0046] The high thermal stability welding method of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer in this embodiment is carried out according to the following steps:

[0047] 1. First, hot-pressing and sintering the skutterudite thermoelectric material and the barrier layer to obtain the skutterudite with a pre-barrier layer; the surface of the barrier layer in the skutterudite with the pre-barrier layer is the surface to be welded, and the surface to be welded of the skutterudite with the pre-barrier layer and the surface to be welded of the metal electrode are pre-treated respectively; finally, the treated skutterudite with the pre-barrier layer and the metal electrode are stored in an inert atmosphere;

[0048] The pretreatment process is: grinding, polishing, cleaning and drying the surface to be welded with metallographic sandpaper step by step; ethanol is used for cleaning;

[0049] The preparation method of the skutterudite with a pre-set barrier layer is as follows: a layer of skutterudite powder is spread in a graphite mold, and then a layer of metal-ceramic composite barrier layer powder is spread on the skutterudite powder, and finally hot pressing and sintering is performed; the hot pressing and sintering process is as follows: in a vacuum environment, the pressure applied is 40MPa, the temperature is increased to 750°C at a rate of 10°C / min and kept at this temperature for 15min, and then cooled to room temperature at a rate of 20°C / min;

[0050] The metal-ceramic composite barrier layer powder is formed by mixing refractory metal powder and ceramic powder; the refractory metal powder is Ti and Nb, and the molar percentage of Ti in the metal-ceramic composite barrier layer powder is 70%, and the molar percentage of Nb is 20%;

[0051] The barrier layer has a thickness of 200 μm;

[0052] The metal electrode is a copper tungsten electrode with a thickness of 2 mm;

[0053] 2. Assemble the skutterudite with a pre-set barrier layer and the metal electrode, with the surface to be welded of the skutterudite with the pre-set barrier layer facing the surface to be welded of the metal electrode, place a brazing material between the surface to be welded of the skutterudite with the pre-set barrier layer and the surface to be welded of the electrode, obtain a workpiece to be welded, and finally weld; the welding process is: in a vacuum degree of 5×10 -3 In a vacuum brazing furnace below Pa, the temperature is raised to 675°C at a rate of 10°C / min and kept at this temperature for 15 minutes, and then cooled to room temperature at a rate of 10°C / min; the brazing material is a copper-based brazing paste.

[0054] This embodiment uses Ti-Nb-TiSi2 as a barrier layer between the skutterudite thermoelectric material and the metal electrode to prevent element diffusion. It can effectively prevent the Sb element in the skutterudite from reacting with the electrode to form a large amount of intermetallic compounds, and the joint has good thermal stability. Figure 1 This is a SEM image of the Ti-Nb-TiSi2 barrier layer / skutterudite thermoelectric material interface obtained in Example 1. Figure 1 It can be seen that the reaction layer of the joint is thin and the element barrier effect is good. Figure 2This is the SEM image of the welding interface in the metal-ceramic composite phase / skutterudite thermoelectric material obtained in Example 1 after annealing for 135 hours. After annealing at 550°C for 135 hours, the thickness of the reaction layer only increased from 9.5 μm to 14.5 μm.

[0055] Embodiment 2:

[0056] The high thermal stability welding method of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer of the present invention is carried out according to the following steps:

[0057] 1. First, hot-press and sinter the skutterudite powder into skutterudite, and hot-press and sinter the metal-ceramic composite barrier layer powder into a pre-set barrier layer; then pre-treat the to-be-welded surface of the skutterudite, the to-be-welded surface of the metal electrode, and the two surfaces of the pre-set barrier layer; finally, store the treated skutterudite, the metal electrode, and the pre-set barrier layer under an inert atmosphere;

[0058] The pretreatment process is: grinding, polishing, cleaning and drying the surface to be welded with metallographic sandpaper step by step; ethanol is used for cleaning;

[0059] The process of hot-pressing and sintering skutterudite powder into skutterudite is as follows: in a vacuum environment, applying a pressure of 40 MPa, heating to 750° C. at a rate of 10° C. / min and keeping the temperature for 15 minutes, and then cooling to room temperature at a rate of 20° C. / min;

[0060] The process of hot-pressing and sintering the metal-ceramic composite barrier layer powder into the preset barrier layer is as follows: in a vacuum environment, the applied pressure is 40 MPa, the temperature is raised to 750° C. at a rate of 10° C. / min and kept at that temperature for 15 minutes, and then cooled to room temperature at a rate of 20° C. / min;

[0061] The metal-ceramic composite barrier layer powder is formed by mixing refractory metal powder and ceramic powder; the refractory metal powder is Ti and Nb, and the molar percentage of Ti in the metal-ceramic composite barrier layer powder is 70%, and the molar percentage of Nb is 20%;

[0062] The barrier layer has a thickness of 200 μm;

[0063] The metal electrode is a copper tungsten electrode with a thickness of 2 mm;

[0064] 2. Placing the pre-set barrier layer between the surface to be welded of the skutterudite and the surface to be welded of the metal electrode to obtain the welded parts, and finally welding them; the welding process is: in a vacuum degree of 5×10 -3 Pa or less, applying a pressure of 5MPa, heating to 675°C at a rate of 10°C / min and keeping the temperature for 15min, and then cooling to room temperature at a rate of 10°C / min; the brazing material is copper-based brazing paste;

[0065] This embodiment uses Ti-Nb-TiSi2 as a barrier layer between the skutterudite thermoelectric material and the metal electrode to prevent element diffusion, effectively blocking the Sb element in the skutterudite from reacting with the electrode to form a large amount of intermetallic compounds, the joint has good thermal stability, the reaction layer of the joint is thin, and the element barrier effect is good. After annealing at 550°C for 135h, the thickness of the reaction layer only increases from 8.5μm to 15.5μm.

Claims

1. A method for high thermal stability welding of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer, characterized in that: The high thermal stability welding method of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer is carried out according to the following steps:

1. First, hot-pressing and sintering the skutterudite thermoelectric material and the barrier layer to obtain the skutterudite with a pre-barrier layer; the surface of the barrier layer in the skutterudite with the pre-barrier layer is the surface to be welded, and the surface to be welded of the skutterudite with the pre-barrier layer and the surface to be welded of the metal electrode are pre-treated respectively; finally, the treated skutterudite with the pre-barrier layer and the metal electrode are stored in an oxygen-free or inert atmosphere; The preparation method of the skutterudite with a pre-set barrier layer is as follows: a layer of skutterudite powder is spread in a graphite mold, a layer of metal-ceramic composite barrier layer powder is spread on the skutterudite powder, and finally hot-pressing and sintering is performed; The hot pressing sintering process is: under a vacuum environment, the applied pressure is 40-70 MPa, the temperature is raised to 650-760°C at a rate of 10-20°C / min and kept at this temperature for 5-30 minutes, and then cooled to room temperature at a rate of 20-50°C / min; The metal-ceramic composite barrier layer powder is a mixture of refractory metal powder and ceramic powder; the refractory metal powder is one or more of Mo, V, Zr, Nb, Ta, Re, and Ti; the ceramic powder is M x Si y 、M x N y 、M x O y One or more of, wherein M is one or more of Ti, Zr, Mg, Al, K, Ca, Zn, and Mn; the molar percentage of the refractory metal powder in the metal-ceramic composite barrier layer powder is 60%-90%; 2. Assemble the skutterudite with a pre-set barrier layer and the metal electrode, with the surface to be welded of the skutterudite with the pre-set barrier layer facing the surface to be welded of the metal electrode, place a brazing material between the surface to be welded of the skutterudite with the pre-set barrier layer and the surface to be welded of the electrode, obtain a workpiece to be welded, and finally weld; the welding process is: in a vacuum degree of 5×10 -3 In a vacuum brazing furnace below Pa, heat to 600-700℃ at a rate of 10-20℃ / min and keep warm for 5-30min, then cool to room temperature at a rate of 10-50℃ / min.

2. The method for high thermal stability welding of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer according to claim 1, characterized in that: The pretreatment process described in step 1 is: grinding, polishing, cleaning and drying the surface to be welded in sequence with metallographic sandpaper; cleaning is carried out using ethanol or acetone.

3. The method for high thermal stability welding of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer according to claim 1, characterized in that: The thickness of the barrier layer in step 1 is 20-200 μm.

4. The method for high thermal stability welding of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer according to claim 1, characterized in that: The metal electrode in step 1 is Cu, Cu-based alloy, Ni, Ni-based alloy, Fe or Fe-based alloy.

5. The method for high thermal stability welding of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer according to claim 1, characterized in that: The solder described in step 2 is copper-based solder paste.

6. A method for high thermal stability welding of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer, characterized in that: The high thermal stability welding method of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer is carried out according to the following steps:

1. First, hot-press and sinter the skutterudite powder into skutterudite, and hot-press and sinter the metal-ceramic composite barrier layer powder into a pre-set barrier layer; then pre-treat the to-be-welded surface of the skutterudite, the to-be-welded surface of the metal electrode, and the two surfaces of the pre-set barrier layer; finally, store the treated skutterudite, the metal electrode, and the pre-set barrier layer in an oxygen-free or inert atmosphere; The process of hot-pressing and sintering skutterudite powder into skutterudite is as follows: in a vacuum environment, applying a pressure of 40-70 MPa, heating to 650-760° C. at a rate of 10-20° C. / min and keeping the temperature for 5-30 min, and then cooling to room temperature at a rate of 20-50° C. / min; The process of hot-pressing and sintering the metal-ceramic composite barrier layer powder into the preset barrier layer is as follows: in a vacuum environment, the applied pressure is 40-70 MPa, the temperature is raised to 650-760°C at a rate of 10-20°C / min and kept at that temperature for 5-30 minutes, and then cooled to room temperature at a rate of 20-50°C / min; The metal-ceramic composite barrier layer powder is a mixture of refractory metal powder and ceramic powder; the refractory metal powder is one or more of Mo, V, Zr, Nb, Ta, Re, and Ti; the ceramic powder is M x Si y 、M x N y 、M x O y One or more of, wherein M is one or more of Ti, Zr, Mg, Al, K, Ca, Zn, and Mn; the molar percentage of the refractory metal powder in the metal-ceramic composite barrier layer powder is 60%-90%; 2. placing a pre-set barrier layer between the surface of the skutterudite to be welded and the surface of the metal electrode to be welded to obtain a welded part, and finally welding; The welding process is as follows: in a vacuum degree of 5×10 -3 In a vacuum brazing furnace below 1.5 MPa, apply a pressure of 5-20 MPa, heat to 600-700°C at a rate of 10-20°C / min and keep warm for 5-30 minutes, then cool to room temperature at a rate of 10-50°C / min.

7. The method for high thermal stability welding of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer according to claim 6, characterized in that: The pretreatment process described in step 1 is: grinding, polishing, cleaning and drying the surface to be welded in sequence with metallographic sandpaper; cleaning is carried out using ethanol or acetone.

8. The method for high thermal stability welding of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer according to claim 6, characterized in that: The thickness of the barrier layer in step 1 is 20-200 μm.

9. The method for high thermal stability welding of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer according to claim 6, characterized in that: The metal electrode in step 1 is Cu, Cu-based alloy, Ni, Ni-based alloy, Fe or Fe-based alloy.

10. The method for high thermal stability welding of skutterudite thermoelectric material / electrode based on metal-ceramic composite barrier layer according to claim 6, characterized in that: The solder described in step 2 is copper-based solder paste.

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