Method for connecting skutterudite thermoelectric material and electrode by using high-entropy alloy and low-expansion-coefficient particle composite barrier layer

Abstract

The invention discloses a method for connecting a skutterudite thermoelectric material and an electrode by using a high-entropy alloy and low-expansion-coefficient particle composite barrier layer, and relates to a method for connecting the skutterudite thermoelectric material and the electrode. The method aims at solving the problems that an existing conductive connector for connecting a skutterudite thermoelectric material and an electrode through a barrier layer is large in thermal stress and prone to cracking. The method comprises the steps that composite powder of high-entropy alloy and low-expansion-coefficient particles is prepared through a mechanical mixing method; and preparing the high-entropy alloy and low-thermal-expansion-coefficient particle composite barrier layer by adopting a sintering method. And then the barrier layer, the skutterudite thermoelectric material and the electrode are connected into a conductive joint through a diffusion welding or brazing method. The materials of the low-expansion-coefficient reinforced particles comprise but are not limited to low-expansion metal particles, graphite and the like; the components of the high-entropy alloy matrix material comprise, but are not limited to, an Al-Co-Cr-Fe-Ni system, an Fe-Co-Ni-Cu system, an Hf-Nb-Ta-Ti-Zr system and the like. The skutterudite thermoelectric material and the electrode are connected through the composite barrier layer of the high-entropy alloy and the low-expansion-coefficient particles, and the obtained conductive connector has high mechanical strength, a low-resistance interface and excellent thermal stability at the same time. The method is suitable for connecting the skutterudite thermoelectric material and the electrode.

Description

Technical Field

[0001] The present invention relates to a method for connecting skutterudite thermoelectric materials and electrodes. Background Art

[0002] Thermoelectric materials are semiconductor materials that can directly convert thermal energy and electrical energy. Due to their unique high efficiency and environmental friendliness, they have significant economic benefits in fields such as thermoelectric power generation, refrigeration and heating, medical equipment, and new energy vehicles. Among them, skutterudite thermoelectric materials have significant advantages in the medium-temperature range and are also one of the thermoelectric materials with the most practical application potential. When a thermoelectric device composed of a skutterudite thermoelectric material and an electrode works in a service environment, there are a series of problems such as severe interfacial element reaction and diffusion, inconsistent thermal expansion coefficients, and large interfacial resistance, which seriously affect the conversion efficiency and mechanical reliability of the thermoelectric device. These problems limit the development of skutterudite thermoelectric materials in practical applications. Therefore, it poses a great challenge to the connection method of skutterudite thermoelectric materials and electrodes.

[0003] High-entropy alloys are a new type of multi-element (five or more elements) alloy material. Due to their unique low system free energy, lattice distortion effect, and diffusion retardation effect, they are expected to be applied in the barrier connection layer between skutterudite thermoelectric materials and electrodes. However, when using traditional high-entropy alloys as the barrier connection layer to connect skutterudite thermoelectric materials and electrodes, microcracks or even cracks often occur in the conductive joints. This is mainly because the thermal expansion coefficient of the high-entropy alloy is higher than that of the skutterudite thermoelectric material, resulting in mechanical stress in the conductive joints. And because the plasticity of the high-entropy alloy is poorer than that of pure metals, it is difficult to relieve the thermal stress generated during the welding and connection process of the conductive joints through the plastic deformation of the high-entropy alloy barrier connection layer itself, resulting in cracks in the joints and seriously affecting the mechanical connection strength of the conductive joints.

[0004] Composite materials are new materials composed of two or more materials with different properties, which can integrate the characteristics of multiple materials, providing a solution to the above problems. The composite material obtained by adding low-expansion coefficient strengthening particles to the high-entropy alloy matrix material can, while having the high-entropy effect of the high-entropy alloy, change its thermal expansion coefficient to be consistent with that of the skutterudite thermoelectric material by adjusting the proportion of the low-expansion coefficient strengthening particles. Currently, there is no report on the successful connection of skutterudite thermoelectric materials and electrodes using a composite barrier layer composed of a high-entropy alloy matrix material and low-expansion coefficient strengthening particles, and the obtained conductive joints having high mechanical strength, low-resistance interfaces, and excellent thermal stability in the service environment. Summary of the Invention

[0005] The present invention aims to solve the problem that the existing conductive joints connecting skutterudite thermoelectric materials and electrodes using a barrier layer have high mechanical stress and are prone to cracking, and proposes a method for connecting skutterudite thermoelectric materials and electrodes using a composite barrier layer of high-entropy alloy and low-expansion coefficient particles.

[0006] The method for connecting skutterudite thermoelectric materials and electrodes using a composite barrier layer of high-entropy alloy and low-expansion coefficient particles in the present invention is carried out according to the following steps:

[0007] Prepare a composite powder of high-entropy alloy and low-thermal expansion coefficient particles using a mechanical mixing method; use this composite powder to prepare a composite barrier layer of high-entropy alloy and low-thermal expansion coefficient particles on the surface of the electrode or on the surface of the skutterudite thermoelectric material using a sintering method; then stack the obtained electrode and skutterudite thermoelectric material, with the composite barrier layer of high-entropy alloy and low-expansion coefficient particles facing inward, to obtain a workpiece to be welded; perform diffusion welding on the workpiece to be welded;

[0008] Alternatively, prepare a composite powder of high-entropy alloy and low-thermal expansion coefficient particles using a mechanical mixing method; use this composite powder to prepare a composite barrier layer of high-entropy alloy and low-thermal expansion coefficient particles on the surface of the skutterudite thermoelectric material using a sintering method; stack the electrode and skutterudite thermoelectric material, with the composite barrier layer of high-entropy alloy and low-expansion coefficient particles facing inward, and place a filler metal between the skutterudite thermoelectric material and the electrode to obtain a workpiece to be welded; perform brazing on the workpiece to be welded;

[0009] The above-mentioned low-expansion coefficient strengthening particle materials include but are not limited to low-expansion metal particles (such as W or Mo), ceramic particles, graphite, graphene, or carbon nanotubes, etc.;

[0010] The above-mentioned high-entropy alloy matrix material components include but are not limited to Al x Co y Cr z Fe m Ni n system, Fe x Co y Ni z Cr m Mn n system, Fe x Co y Ni z Cu m system, Mo x Co y Cr z Fe m Ni n system, Hf x Nb y Ta z Ti m Zrn Department, Nb x Ti y V z Zr m Department, Mo x Nb y Re z Ta m W n System; where x, y, z, m, and n take values ​​from 0 to 2.

[0011] The above-mentioned mechanical mixing methods include but are not limited to ball milling, ultrasonic mixing, resonance mixing, etc.

[0012] The above-mentioned sintering methods include but are not limited to hot pressing sintering, spark plasma sintering, laser cladding, electron beam cladding, high-energy beam 3D printing, etc.

[0013] The principles and beneficial effects of the present invention are:

[0014] The present invention innovatively uses a composite material composed of a high entropy alloy matrix material and low expansion coefficient reinforcement particles as a barrier connection layer between the skutterudite thermoelectric material and the electrode. Unlike the traditional barrier connection layer, the composite barrier connection layer utilizes the changes in the types and proportions of different materials between the high entropy alloy and the low thermal expansion particles, and can flexibly and accurately regulate the thermal expansion coefficient of the intermediate layer, so that it can be thermomechanically matched with the skutterudite thermoelectric material, reduce the mechanical stress of the conductive joint, and thus obtain a conductive joint with high mechanical connection strength. At the same time, the high entropy effect is used to effectively curb the mutual diffusion of interface elements between the skutterudite thermoelectric material and the electrode conductive joint, and reduce the interface resistance of the conductive joint.

[0015] The reason for achieving compatibility of thermal expansion coefficients and high mechanical connection strength is that the present invention uses a composite material composed of a high entropy alloy matrix material and low expansion coefficient reinforcing particles as a barrier connection layer between a skutterudite thermoelectric material and an electrode, and can accurately control the thermal expansion coefficient of the composite barrier connection layer by adjusting the proportion of the low expansion coefficient reinforcing particles and changing the type of the low expansion coefficient reinforcing particles, thereby achieving matching of the thermal expansion coefficients among the composite barrier connection layer, the skutterudite thermoelectric material and the electrode, reducing the mechanical thermal stress caused by the incoordination of the thermal expansion coefficients in the conductive joint between the skutterudite thermoelectric material and the electrode, preventing the conductive joint from cracking or even breaking, thereby improving the interface connection strength and mechanical reliability of the conductive joint.

[0016] Since the matrix material of the composite barrier connection layer is a high-entropy alloy, the low system free energy, lattice distortion effect, and diffusion retardation effect brought about by its high-entropy effect can effectively inhibit the mutual diffusion of interface elements of the conductive joint and improve the thermal stability of the joint. Because of the low system free energy, the high-entropy alloy exhibits excellent phase stability. Even in a high-temperature environment, the phases composed of the high-entropy alloy can still maintain the stability of the microstructure and do not undergo phase transformation reactions, thereby improving the thermal stability of the joint. In addition, the lattice distortion effect can increase the resistance of atomic diffusion in the lattice, and the diffusion retardation effect can reduce the speed of atomic diffusion. Even in a high-temperature environment, the speed of atomic diffusion is still small, thereby reducing the vacancies at the diffusion interface, effectively curbing the mutual diffusion of interface elements of the conductive joint, reducing the increase in interface resistance caused by the diffusion of interface elements, and improving the electrical properties of the conductive joint.

[0017] The present invention uses mechanical mixing and sintering methods to prepare a composite barrier layer of a high-entropy alloy and low-expansion coefficient particles, realizing the direct welding of skutterudite thermoelectric materials and metal or alloy electrodes. By precisely controlling the types and proportions of the high-entropy alloy and low-thermal-expansion particles, high mechanical reliability, high thermal stability, and low interface resistance of the conductive joint are simultaneously achieved. The process control is simple and suitable for large-scale production. Brief Description of the Drawings

[0018] Figure 1 is a photograph of the joint structure obtained in Example 1; Detailed Embodiments

[0019] The technical solution of the present invention is not limited to the following specific embodiments listed, but also includes any reasonable combination between the specific embodiments.

[0020] Detailed Embodiment 1: The method for connecting skutterudite thermoelectric materials and electrodes using a composite barrier layer of a high-entropy alloy and low-expansion coefficient particles is carried out according to the following steps:

[0021] Use mechanical mixing methods to prepare a composite powder of a high-entropy alloy and low-thermal-expansion coefficient particles; use this composite powder to prepare a composite barrier layer of a high-entropy alloy and low-thermal-expansion coefficient particles on the surface of the electrode or on the surface of the skutterudite thermoelectric material by sintering methods; then stack the obtained electrode and skutterudite thermoelectric material with the composite barrier layer of the high-entropy alloy and low-expansion coefficient particles facing inward to obtain the workpiece to be welded; perform diffusion welding on the workpiece to be welded;

[0022] Alternatively, a composite powder of a high-entropy alloy and low-thermal-expansion-coefficient particles is prepared by a mechanical mixing method; a composite barrier layer of the high-entropy alloy and the low-thermal-expansion-coefficient particles is prepared on the surface of the skutterudite thermoelectric material by using the composite powder through a sintering method; an electrode and the skutterudite thermoelectric material are stacked with the composite barrier layer of the high-entropy alloy and the low-thermal-expansion-coefficient particles facing inward, and a filler metal is placed between the skutterudite thermoelectric material and the electrode to obtain a workpiece to be soldered; the workpiece to be soldered is soldered.

[0023] The above low-thermal-expansion-coefficient strengthening particle materials include but are not limited to low-expansion metal particles (such as W or Mo), ceramic particles, graphite, graphene, or carbon nanotubes, etc.

[0024] The above high-entropy alloy matrix material components include but are not limited to Al x Co y Cr z Fe m Ni n system, Fe x Co y Ni z Cr m Mn n system, Fe x Co y Ni z Cu m system, Mo x Co y Cr z Fe m Ni n system, Hf x Nb y Ta z Ti m Zr n system, Nb x Ti y V z Zr m system, Mo x Nb y Re z Ta m W n system; where x, y, z, m, and n take values from 0 to 2.

[0025] The above mechanical mixing methods include but are not limited to ball milling, ultrasonic mixing, resonance mixing, etc.

[0026] The above sintering methods include but are not limited to hot pressing sintering, spark plasma sintering, laser cladding, electron beam cladding, high-energy beam 3D printing, etc.

[0027] This embodiment innovatively uses a composite material composed of a high entropy alloy matrix material and low expansion coefficient reinforcement particles as a barrier connection layer between the skutterudite thermoelectric material and the electrode. Unlike the traditional barrier connection layer, the composite barrier connection layer utilizes the changes in the types and proportions of different materials between the high entropy alloy and the low thermal expansion particles, and can flexibly and accurately control the thermal expansion coefficient of the intermediate layer, so that it can be thermomechanically matched with the skutterudite thermoelectric material, reduce the mechanical stress of the conductive joint, and thus obtain a conductive joint with high mechanical connection strength. At the same time, the high entropy effect is used to effectively curb the mutual diffusion of interface elements between the skutterudite thermoelectric material and the electrode conductive joint, and reduce the interface resistance of the conductive joint.

[0028] The reason for achieving compatibility of thermal expansion coefficients and high mechanical connection strength is that the present invention uses a composite material composed of a high entropy alloy matrix material and low expansion coefficient reinforcing particles as a barrier connection layer between a skutterudite thermoelectric material and an electrode, and can accurately control the thermal expansion coefficient of the composite barrier connection layer by adjusting the proportion of the low expansion coefficient reinforcing particles and changing the type of the low expansion coefficient reinforcing particles, thereby achieving matching of the thermal expansion coefficients among the composite barrier connection layer, the skutterudite thermoelectric material and the electrode, reducing the mechanical thermal stress caused by the incoordination of the thermal expansion coefficients in the conductive joint between the skutterudite thermoelectric material and the electrode, preventing the conductive joint from cracking or even breaking, thereby improving the interface connection strength and mechanical reliability of the conductive joint.

[0029] Since the base material of the composite barrier connection layer is a high entropy alloy, the low system free energy, lattice distortion effect and diffusion hysteresis effect brought by its high entropy effect can effectively inhibit the mutual diffusion of the interface elements of the conductive joint and improve the thermal stability of the joint. Because the low system free energy makes the high entropy alloy show excellent phase stability, even in a high temperature environment, the phase composed of the high entropy alloy can still maintain the stability of the microstructure and will not undergo phase change reaction, thereby improving the thermal stability of the joint. In addition, the lattice distortion effect can increase the resistance of atomic diffusion in the lattice, and the diffusion hysteresis effect can reduce the speed of atomic diffusion. Even in a high temperature environment, the speed of atomic diffusion is still small, thereby reducing the vacancies at the diffusion interface, which can effectively curb the mutual diffusion of the interface elements of the conductive joint, reduce the increase of interface resistance caused by the diffusion of interface elements, and improve the electrical properties of the conductive joint.

[0030] This embodiment adopts mechanical mixing and sintering methods to prepare a composite barrier layer of high entropy alloy and low thermal expansion coefficient particles, realizes direct welding of skutterudite thermoelectric materials and metal or alloy electrodes, and simultaneously realizes high mechanical reliability, high thermal stability and low interface resistance of the conductive joint through precise control of the types and proportions of high entropy alloy and low thermal expansion particles. The process control is simple and suitable for large-scale production.

[0031] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that the above-mentioned electrode is a metal electrode or an alloy electrode;

[0032] The material of the metal electrode is Cu, Ni, Fe, Co or Cr;

[0033] The material of the alloy electrode is a Cu-based alloy, a Ni-based alloy, an Fe-based alloy, a Co-based alloy, or a Cr-based alloy;

[0034] The Cu-based alloy is CuW or CuMo, etc.; the Ni-based alloy is NiW, NiMo or NiCr, etc.; the Fe-based alloy is FeW, FeMo, FeCr or FeCoNi, etc.; the Co-based alloy is CoW, CoMo, CoCr, CoNi or CoFe, etc.; the Cr-based alloy is CrW, CrMo, CrCoNi or CrFeNi, etc.

[0035] Specific Embodiment 3: The difference between this embodiment and Specific Embodiment 1 or 2 is that the material of the above-mentioned low expansion coefficient strengthening particles includes, but is not limited to, low expansion metal particles (such as W or Mo), ceramic particles, graphite, graphene or carbon nanotubes, etc.

[0036] Specific Embodiment 4: The difference between this embodiment and any one of Specific Embodiments 1 to 3 is that the composition of the above-mentioned high entropy alloy matrix material includes, but is not limited to, Al x Co y Cr z Fe m Ni n system, Fe x Co y Ni z Cr m Mn n system, Fe x Co y Ni z Cu m system, Mo x Co y Cr z Fe m Ni n system, Hf x Nb y Ta z Ti m Zr n system, Nb x Ti y V z Zr m system, Mo x Nb y Re z Ta m W nsystem; where x, y, z, m, and n take values from 0 to 2.

[0037] Specific Embodiment Five: The difference between this embodiment and any one of Embodiments One to Four is that the above mechanical mixing method includes, but is not limited to, ball milling, ultrasonic mixing, resonance mixing, etc.

[0038] Specific Embodiment Six: The difference between this embodiment and any one of Embodiments One to Five is that the above sintering method includes, but is not limited to, hot press sintering, spark plasma sintering, laser cladding, electron beam cladding, high-energy beam 3D printing, etc.

[0039] Specific Embodiment Seven: The difference between this embodiment and any one of Embodiments One to Six is that the thickness of the above high-entropy alloy and low-expansion coefficient particle composite barrier layer is 1 to 500 μm.

[0040] Specific Embodiment Eight: The difference between this embodiment and any one of Embodiments One to Seven is that the formula of the above skutterudite thermoelectric material is R r T t X x , in the formula: R is one or more elements of alkali metals, alkaline earth metals, rare earth metals, or Group III elements; T is one or more elements of Cr, Mn, Fe, Co, Ni, Ru, Os, Rh, Ir, Pt, or Au; X is one or more elements of P, As, Sb, Bi, Se, Te, Si, Ge, Sn, Ga, or In; 0 < r ≤ 1, t = 4, 11.8 ≤ x ≤ 12.4.

[0041] Specific Embodiment Nine: The difference between this embodiment and any one of Embodiments One to Eight is that the above brazing process is as follows: Brazing is carried out in a heating furnace, and the atmosphere of the heating furnace is a vacuum or an inert gas protection atmosphere, where the inert gas includes, but is not limited to, argon, helium, or nitrogen, etc.; When welding, a pressure not less than 0.003 MPa can be applied to the workpiece to be welded or no pressure is applied. First, it is heated to not less than 500 °C and held for more than 1 min, and then cooled to room temperature.

[0042] Specific Embodiment Ten: The difference between this embodiment and any one of Embodiments One to Nine is that the above diffusion welding process is as follows: Diffusion welding is carried out in a heating furnace, and the atmosphere of the heating furnace is a vacuum or an inert gas protection atmosphere, where the inert gas includes, but is not limited to, argon, helium, or nitrogen, etc.; When welding, a pressure not less than 5 MPa is applied to the workpiece to be welded. First, it is heated to not less than 500 °C and held for more than 1 min, and then cooled to room temperature.

[0043] Specific Embodiment Eleven: The difference between this embodiment and any one of Embodiments One to Ten is that the filler metal used in the above brazing process is an Ag-based filler metal or an Al-based filler metal with a liquidus temperature greater than 500 °C.

[0044] Example 1:

[0045] The method for connecting the skutterudite thermoelectric material and the electrode by using the composite barrier layer of the high-entropy alloy and the low-expansion coefficient particles is carried out according to the following steps:

[0046] Use the ball milling method to prepare the composite powder of the high-entropy alloy and the low thermal expansion coefficient particles; use this composite powder to prepare the composite barrier layer of the high-entropy alloy and the low thermal expansion coefficient particles on the surface of the electrode by hot pressing sintering method, and then stack the obtained electrode and the skutterudite thermoelectric material, with the composite barrier layer of the high-entropy alloy and the low expansion coefficient particles facing inward to obtain the workpiece to be welded; carry out diffusion welding on the workpiece to be welded;

[0047] The above skutterudite thermoelectric material is Yb 0.4 Co4Sb 12 , and the electrode is a CuW electrode;

[0048] The above low-expansion coefficient strengthening particle material is W, with a purity of >99% and a volume fraction of 40%;

[0049] The above high-entropy alloy matrix material composition is Al x CoCrFeNi; where x is 0.1;

[0050] The thickness of the above composite barrier layer of the high-entropy alloy and the low-expansion coefficient particles is 340μm;

[0051] The above diffusion welding process is as follows: Diffusion welding is carried out in a heating furnace, and the atmosphere of the heating furnace is an Ar gas protection atmosphere, with an Ar gas pressure of -0.5 Mpa; the pressure applied to the workpiece to be welded during welding is 60 Mpa. First, heat it to 700°C at a speed of 110°C / min, 50°C / min, and 25°C / min and hold for 10 min, then cool it to 300°C at a speed of 5°C / min, and then cool it to room temperature with the furnace.

[0052] Figure 1 is a photo of the joint structure obtained in Example 1; as Figure 1 shown, Yb 0.4 Co4Sb 12 The joint between the skutterudite thermoelectric material and the CuW alloy electrode is well combined, without any interface defects. The composite barrier layer Al 0.1 CoCrFeNi-40%W of the high-entropy alloy and the low-expansion coefficient particles effectively blocks the diffusion of Cu element in the electrode into the skutterudite, and at the same time, the filling atoms Yb and Sb elements in the skutterudite base material are effectively blocked on the Yb 0.4 Co4Sb 12 skutterudite thermoelectric material side. After testing, the contact resistivity of the joint is 1.2 μΩ·cm 2, the shear strength of the joint is 41 MPa. After annealing at 550 °C for 120 h, the joint is well bonded, and the contact resistivity of the joint is less than 2 μΩcm 2 , the shear strength of the joint is 35 MPa.

[0053] Example 2:

[0054] The method for connecting skutterudite thermoelectric materials and electrodes using a composite barrier layer of high-entropy alloy and low thermal expansion coefficient particles is carried out according to the following steps:

[0055] Prepare a composite powder of high-entropy alloy and low thermal expansion coefficient particles using the ball milling method; use this composite powder to prepare a composite barrier layer of high-entropy alloy and low thermal expansion coefficient particles on the electrode surface by hot pressing sintering method, and then stack the obtained electrode and skutterudite thermoelectric material, with the composite barrier layer of high-entropy alloy and low thermal expansion coefficient particles facing inward to obtain the workpiece to be welded; perform diffusion welding on the workpiece to be welded;

[0056] The above skutterudite thermoelectric material is La 0.8 Ga 0.1 Ti 0.1 Fe 3.3 Co4Sb 12 , and the electrode is a CuW electrode;

[0057] The above low thermal expansion coefficient strengthening particle material is W, with a purity of >99% and a volume fraction of 40%;

[0058] The above high-entropy alloy matrix material composition is Al x CoCrFeNi; where x is 0.3;

[0059] The thickness of the above composite barrier layer of high-entropy alloy and low thermal expansion coefficient particles is 340 μm;

[0060] The above diffusion welding process is as follows: Diffusion welding is carried out in a heating furnace, the atmosphere of the heating furnace is an Ar gas protection atmosphere, and the Ar gas pressure is -0.5 Mpa; the pressure applied to the workpiece to be welded during welding is 60 Mpa. First, heat it to 650 °C at a speed of 125 °C / min, 50 °C / min, and 25 °C / min and hold for 10 min, then cool it to 300 °C at a speed of 5 °C / min, and then cool it to room temperature with the furnace.

[0061] After testing, the joint between the La 0.8 Ga 0.1 Ti 0.1 Fe 3.3 Co4Sb 12 skutterudite thermoelectric material and the CuW alloy electrode is well bonded, and the contact resistivity of the joint is about 1.1 μΩcm 2, the shear strength of the joint is 39 MPa. After annealing at 550 °C for 120 h, the joint is well combined, and the contact resistivity of the joint is lower than 2 μΩ·cm 2 , the shear strength of the joint is 34 MPa.

[0062] Example 3:

[0063] The method for connecting skutterudite thermoelectric materials and electrodes using a composite barrier layer of high-entropy alloy and low-expansion coefficient particles is carried out according to the following steps:

[0064] Use the ball milling method to prepare a composite powder of high-entropy alloy and low-thermal expansion coefficient particles; use this composite powder to prepare a composite barrier layer of high-entropy alloy and low-thermal expansion coefficient particles on the surface of the skutterudite thermoelectric material by hot pressing sintering method. Stack the electrode and the skutterudite thermoelectric material with the composite barrier layer of high-entropy alloy and low-expansion coefficient particles facing inward, and place BAg56CuZnSn filler metal between the skutterudite thermoelectric material and the electrode to obtain the workpiece to be welded; perform brazing on the workpiece to be welded;

[0065] The above-mentioned skutterudite thermoelectric material is Yb 0.4 Co4Sb 12 , and the electrode is a CuW electrode;

[0066] The above-mentioned low-expansion coefficient strengthening particle material is W, with a purity of >99% and a volume fraction of 40%;

[0067] The above-mentioned high-entropy alloy matrix material composition is Al x CoCrFeNi; where x is 0.1;

[0068] The thickness of the above-mentioned composite barrier layer of high-entropy alloy and low-expansion coefficient particles is 300 μm;

[0069] The above-mentioned brazing process is as follows: Use a tube furnace equipment for heating, in an Ar gas atmosphere, the pressure applied to the workpiece to be welded during welding is 5 MPa. First, heat it to 680 °C at a rate of 30 °C / min and hold for 2 min, then cool it to 100 °C at a rate of 5 °C / min, and then cool it to room temperature with the furnace.

[0070] After testing, the joint between the Yb 0.4 Co4Sb 12 skutterudite thermoelectric material and the CuW alloy electrode is well combined without any interfacial defects. The composite barrier layer of high-entropy alloy and low-expansion coefficient particles Al 0.1 CoCrFeNi-40%W effectively blocks the diffusion of Cu element in the electrode to the skutterudite. At the same time, the filling atoms Yb and Sb elements in the skutterudite base material are effectively blocked on the Yb 0.4 Co4Sb 12 skutterudite thermoelectric material side, and the contact resistivity of the joint is about 1.5 μΩ·cm2 The shear strength of the joint is 42 MPa. After annealing at 550 °C for 600 h, the joint is well-bonded, and the contact resistivity of the joint is lower than 3 μΩ·cm. 2 The shear strength of the joint is 33 MPa.

[0071] Example 4:

[0072] The method for connecting skutterudite thermoelectric materials and electrodes using a composite barrier layer of high-entropy alloy and low thermal expansion coefficient particles is carried out according to the following steps:

[0073] Prepare a composite powder of high-entropy alloy and low thermal expansion coefficient particles by ball milling; use this composite powder to prepare a composite barrier layer of high-entropy alloy and low thermal expansion coefficient particles on the surface of the skutterudite thermoelectric material by hot pressing sintering. Stack the electrode and the skutterudite thermoelectric material with the composite barrier layer of high-entropy alloy and low thermal expansion coefficient particles facing inward, and place BAg56CuZnSn solder between the skutterudite thermoelectric material and the electrode to obtain the workpiece to be welded; perform brazing on the workpiece to be welded.

[0074] The above skutterudite thermoelectric material is La 0.8 Ga 0.1 Ti 0.1 Fe 3.3 Co4Sb 12 , and the electrode is a CuMo electrode;

[0075] The above low thermal expansion coefficient strengthening particle material is W, with a purity of >99% and a volume fraction of 40%;

[0076] The composition of the above high-entropy alloy matrix material is Al x CoCrFeNi; where x is 0.5;

[0077] The thickness of the above composite barrier layer of high-entropy alloy and low thermal expansion coefficient particles is 300 μm;

[0078] The above brazing process is as follows: heat using a tube furnace equipment, in an Ar gas atmosphere, the pressure applied to the workpiece to be welded during welding is 5 MPa. First, heat to 680 °C at a rate of 30 °C / min and hold for 2 min, then cool to 100 °C at a rate of 5 °C / min, and then cool to room temperature with the furnace.

[0079] After testing, the joint between the La 0.8 Ga 0.1 Ti 0.1 Fe 3.3 Co4Sb 12 skutterudite thermoelectric material and the CuMo alloy electrode is well-bonded, and the contact resistivity of the joint is 1.8 μΩ·cm. 2, the shear strength of the joint is 38 MPa. After annealing at 550 °C for 600 h, the joint is well bonded and the contact resistivity of the joint is less than 3 μΩ·cm 2 , the shear strength of the joint is 31 MPa.

Claims

1. A method for connecting a skutterudite thermoelectric material and an electrode using a composite barrier layer of a high entropy alloy and low expansion coefficient particles, characterized in that: The method proceeds as follows: A composite powder of a high entropy alloy and low thermal expansion coefficient particles is prepared by a mechanical mixing method; a composite barrier layer of a high entropy alloy and low thermal expansion coefficient particles is prepared on the surface of an electrode by a sintering method using the composite powder, or a composite barrier layer of a high entropy alloy and low thermal expansion coefficient particles is prepared on the surface of a skutterudite thermoelectric material; then the obtained electrode and the skutterudite thermoelectric material are stacked, with the composite barrier layer of the high entropy alloy and low thermal expansion coefficient particles facing inward, to obtain a workpiece to be welded; and diffusion welding is performed on the workpiece to be welded; Alternatively, a composite powder of a high entropy alloy and low thermal expansion coefficient particles is prepared by a mechanical mixing method; a composite barrier layer of a high entropy alloy and low thermal expansion coefficient particles is prepared on the surface of a skutterudite thermoelectric material by a sintering method using the composite powder; an electrode and a skutterudite thermoelectric material are stacked, with the composite barrier layer of the high entropy alloy and low thermal expansion coefficient particles facing inward, a brazing material is placed between the skutterudite thermoelectric material and the electrode, to obtain a workpiece to be welded; and the workpiece to be welded is brazed; The material of the low expansion coefficient reinforcement particles includes but is not limited to low expansion metal particles (W or Mo, etc.), ceramic particles, graphite, graphene or carbon nanotubes, etc.; The above high entropy alloy matrix material composition includes but is not limited to Al x Co y Cr z Fe m Ni n Department, Fe x Co y Ni z Cr m Mn n Department, Fe x Co y Ni z Cu m Department, Mo x Co y Cr z Fe m Ni n Department, Hf x Nb y Ta z Ti m Zr n Department, Nb x Ti y V z Zr m Department, Mo x Nb y Re z Ta m W n System; where x, y, z, m, and n are values ​​ranging from 0 to 2; The mechanical mixing methods include but are not limited to ball milling, ultrasonic mixing, resonance mixing, etc.; The above-mentioned sintering methods include but are not limited to hot pressing sintering, spark plasma sintering, laser cladding, electron beam cladding, high-energy beam 3D printing, etc.

2. The method for connecting skutterudite thermoelectric material and electrode by using a composite barrier layer of high entropy alloy and low expansion coefficient particles according to claim 1, characterized in that: The electrode is a metal electrode or an alloy electrode.

3. The method for connecting skutterudite thermoelectric material and electrode by using a composite barrier layer of high entropy alloy and low expansion coefficient particles according to claim 2, characterized in that: The metal electrode is made of Cu, Ni, Fe, Co or Cr; the alloy electrode is made of Cu-based alloy, Ni-based alloy, Fe-based alloy, Co-based alloy or Cr-based alloy.

4. The method for connecting skutterudite thermoelectric material and electrode by using a composite barrier layer of high entropy alloy and low expansion coefficient particles according to claim 3, characterized in that: The Cu-based alloy is CuW or CuMo, etc.; the Ni-based alloy is NiW, NiMo or NiCr, etc.; the Fe-based alloy is FeW, FeMo, FeCr or FeCoNi, etc.; the Co-based alloy is CoW, CoMo, CoCr, CoNi or CoFe, etc.; the Cr-based alloy is CrW, CrMo, CrCoNi or CrFeNi, etc.

5. The method for connecting skutterudite thermoelectric material and electrode by using a composite barrier layer of high entropy alloy and low expansion coefficient particles according to claim 1, characterized in that: The thickness of the high entropy alloy and low expansion coefficient particle composite barrier layer is 1 to 500 μm.

6. The method for connecting skutterudite thermoelectric material and electrode by using a composite barrier layer of high entropy alloy and low expansion coefficient particles according to claim 1, characterized in that: The molecular formula of the skutterudite thermoelectric material is R r T t X x , wherein: R is one or more elements of alkali metal, alkaline earth metal, rare earth metal or third main group element; T is one or more elements of Cr, Mn, Fe, Co, Ni, Ru, Os, Rh, Ir, Pt or Au; X is one or more elements of P, As, Sb, Bi, Se, Te, Si, Ge, Sn, Ga or In; 0﹤r≤1, t=4, 11.8≤x≤12.

4.

7. The method for connecting skutterudite thermoelectric material and electrode by using a composite barrier layer of high entropy alloy and low expansion coefficient particles according to claim 1, characterized in that: The diffusion welding process is as follows: the diffusion welding is carried out in a heating furnace, the atmosphere of the heating furnace is a vacuum or inert gas protective atmosphere, wherein the inert gas includes but is not limited to argon, helium or nitrogen, etc.; during welding, a pressure of not less than 5Mpa is applied to the workpiece to be welded, first heated to not less than 500°C and kept warm for more than 1 minute, and then cooled to room temperature.

8. The method for connecting skutterudite thermoelectric material and electrode by using a composite barrier layer of high entropy alloy and low expansion coefficient particles according to claim 1, characterized in that: The brazing process is as follows: the brazing is carried out in a heating furnace, the atmosphere of the heating furnace is a vacuum or inert gas protective atmosphere, wherein the inert gas includes but is not limited to argon, helium or nitrogen, etc.; during welding, a pressure of not less than 0.003MPa or no pressure is applied to the workpiece to be welded, firstly heated to not less than 500°C and kept warm for more than 1 minute, and then cooled to room temperature.

9. The method for connecting skutterudite thermoelectric material and electrode by using a composite barrier layer of high entropy alloy and low expansion coefficient particles according to claim 1, characterized in that: The solder used in the soldering process is an Ag-based solder or an Al-based solder with a liquidus temperature greater than 500°C.

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