CN115415656A - Method for connecting skutterudite thermoelectric material with Fe-Cr-Mo/W as barrier layer and copper electrode - Google Patents
Method for connecting skutterudite thermoelectric material with Fe-Cr-Mo/W as barrier layer and copper electrode Download PDFInfo
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- CN115415656A CN115415656A CN202211138051.1A CN202211138051A CN115415656A CN 115415656 A CN115415656 A CN 115415656A CN 202211138051 A CN202211138051 A CN 202211138051A CN 115415656 A CN115415656 A CN 115415656A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
- B23K20/001—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating by extrusion or drawing
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- B23K1/00—Soldering, e.g. brazing, or unsoldering
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K1/00—Soldering, e.g. brazing, or unsoldering
- B23K1/20—Preliminary treatment of work or areas to be soldered, e.g. in respect of a galvanic coating
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- B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
- B23K20/14—Preventing or minimising gas access, or using protective gases or vacuum during welding
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- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
- B23K20/16—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating with interposition of special material to facilitate connection of the parts, e.g. material for absorbing or producing gas
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Abstract
A method for connecting a skutterudite thermoelectric material with a copper electrode by taking Fe-Cr-Mo/W as a barrier layer relates to a method for connecting a thermoelectric material with an electrode. The method aims to solve the problems of element diffusion and low strength of a welding joint in the process of connecting the skutterudite and the copper electrode. According to the invention, the barrier layer raw material is smelted and then is subjected to suction casting in a water-cooling copper mold for rapid solidification, the non-equilibrium solidification principle is innovatively adopted to greatly improve the solid solubility of large-size Mo/W elements in the Fe-Cr alloy, reduce element diffusion, reduce the residual stress of the joint and improve the strength of the joint. The method for connecting the skutterudite and the copper electrode by adopting the methods of diffusion welding, brazing, nano silver sintering and the like is convenient to operate, flexible in process, capable of selecting a proper method according to actual use requirements and low in cost.
Description
Technical Field
The invention relates to a method for connecting a skutterudite thermoelectric material and a copper electrode by taking Fe-Cr-Mo/W as a barrier layer.
Background
Skutterudite (CoSb) 3 ) Is one of the thermoelectric materials with the highest conversion efficiency in the middle temperature range (room temperature is 600 ℃), and has excellent mechanical property and thermal stability. However, the preparation of reliable solder joints between skutterudite and electrodes is an indispensable step in the fabrication of thermoelectric devices.
At present, because skutterudite and a copper electrode joint have a serious element diffusion problem, the conversion efficiency of a device in a service process is sharply reduced, and the use effect is influenced. Meanwhile, due to the difference of the thermal expansion coefficients of the welded joints, the joint connection strength is too low, and the use of the device is severely restricted. At present, all materials of the anti-diffusion barrier layer which can be used for the skutterudite thermoelectric material are pure metals and alloys thereof, but because the melting point of Sb element in the skutterudite thermoelectric material is only 630 ℃, the Sb element can react with most metal elements to form intermetallic compounds, the interface resistance is increased, and the joint strength is reduced.
At present, no barrier layer metal material capable of meeting the long-term service requirement of the skutterudite thermoelectric material exists. Therefore, it is very important to design a method for realizing a reliable connection between the skutterudite thermoelectric material and the copper electrode for a long period of time.
Disclosure of Invention
The invention provides a method for connecting a skutterudite thermoelectric material and a copper electrode by taking Fe-Cr-Mo/W as a barrier layer, aiming at solving the problems that element diffusion is easy to occur between the skutterudite and the copper electrode and the strength of a welding joint is low in the existing connection process of the skutterudite and the copper electrode.
The method for connecting the skutterudite thermoelectric material and the copper electrode by taking Fe-Cr-Mo/W as the barrier layer comprises the following steps:
1. firstly, cutting a skutterudite thermoelectric material, then sequentially carrying out abrasive paper step-by-step grinding, polishing, alcohol ultrasonic cleaning and acetone ultrasonic cleaning on the to-be-treated surface of the skutterudite thermoelectric material, and then placing the to-be-treated surface in an inert gas atmosphere for storage; polishing and ultrasonically cleaning the surface to be welded of the copper electrode, drying to obtain the copper electrode to be welded, and storing in inert atmosphere;
2. weighing raw materials according to the atomic percentage of the barrier layer, putting the raw materials into a vacuum arc melting furnace for arc melting, and then performing suction casting on the raw materials into a water-cooled copper mold for rapid solidification to obtain a supersaturated solid solution barrier layer ingot with uniform components; sequentially cutting the supersaturated solid solution barrier layer cast ingot into sheets, polishing, cleaning and blow-drying to obtain barrier layer sheets for later use;
the barrier layer consists of 10 to 19.9 atomic percent of Cr, 0.1 to 10 atomic percent of Mo or W and the balance of Fe, and the sum of the atomic percent of the Cr and the Mo and the atomic percent of the Cr and the W is 20 percent; the sum of the atomic percentages of Cr and Mo and the atomic percentages of Cr and W are 20 percent, so that the welding line can be prevented from cracking;
the rapid solidification rate is at least 1000 ℃/min;
3. placing the barrier layer slice between the skutterudite thermoelectric material processed in the step one and the surface to be welded of the copper electrode to be welded for assembly, and obtaining a connecting piece to be welded; the connecting piece to be welded is 1 x 10 -4 -5×10 -3 And (3) simultaneously applying welding pressure of 10-30MPa in a vacuum environment of Pa, heating to 550-650 ℃, maintaining the temperature and the pressure for 3-30min, and then slowly cooling to room temperature to complete the connection of the skutterudite thermoelectric material and the copper electrode.
The other method for connecting the skutterudite thermoelectric material with the Fe-Cr-Mo/W as the barrier layer and the copper electrode is carried out according to the following steps:
1. weighing raw materials according to the atomic percentage of the barrier layer, putting the raw materials into a vacuum arc melting furnace for arc melting or vacuum induction melting, and then performing suction casting on the raw materials into a water-cooled copper mold for rapid solidification to obtain a supersaturated solid solution barrier layer ingot with uniform components; cutting the supersaturated solid solution barrier layer cast ingot into slices, polishing, cleaning and blow-drying in sequence to obtain barrier layer slices for later use; polishing and ultrasonically cleaning the surface to be welded of the copper electrode, drying to obtain the copper electrode to be welded, and storing in inert atmosphere;
the barrier layer consists of 10 to 19.9 atomic percent of Cr, 0.1 to 10 atomic percent of Mo or W and the balance of Fe, and the sum of the atomic percent of the Cr and the Mo and the atomic percent of the Cr and the W is 20 percent; the sum of the atomic percentages of Cr and Mo and Cr and W is 20%, so that the weld joint can be prevented from cracking;
the rapid solidification rate is at least 1000 ℃/min;
2. placing the barrier layer slice in a graphite mould filled with the thermoelectric material powder of skutterudite to be welded, covering the thermoelectric material powder of skutterudite with the barrier layer slice, carrying out hot-pressing sintering on the barrier layer and the thermoelectric material powder, and cooling along with a furnace to obtain the thermoelectric material with the barrier layer; then cutting, polishing step by step, cleaning to obtain a thermoelectric material to be welded, and storing in an inert gas environment for later use; the hot-pressing sintering process parameters are determined according to factors such as the type of the thermoelectric material;
the particle size of the thermoelectric material powder is not more than 10 μm;
3. placing a layer of brazing filler metal between the barrier layer of the thermoelectric material to be welded and the copper electrode, wherein the barrier layer of the thermoelectric material to be welded faces the surface to be welded of the copper electrode, so as to obtain a part to be welded, and performing brazing; or arranging nano silver soldering paste between the barrier layer of the thermoelectric material to be welded and the copper electrode obtained in the step two, enabling the barrier layer of the thermoelectric material to be welded to face the surface to be welded of the copper electrode to obtain a piece to be welded, and performing solid-phase sintering.
The invention has the beneficial effects that:
1. the existing barrier layer is not rapidly solidified, and only element content change is taken as a research point, so that alloy added by Mo/W elements with large volume fraction cannot be obtained, a large amount of compounds are inevitably generated in the alloy, metal brittleness of the barrier layer is caused, and joint strength is reduced. The invention innovatively adopts the non-equilibrium solidification principle to greatly improve the solid solubility of large-size Mo/W elements in Fe-Cr alloy, causes the lattice constant of the Fe-Cr alloy to be obviously increased, occupies the original Cr atom position, increases the lattice distortion, and causes the difficulty in moving adjacent atoms, in addition, the Mo/W elements do not react with elements in the skutterudite thermoelectric material, other atoms only can bypass MoW during diffusion, and the element diffusion distance is increased, thereby reducing the element diffusion degree and obviously reducing the element diffusion rate. And because Cr-Mo/W elements can be infinitely dissolved, the thermal expansion coefficient of the Fe-Cr alloy can be linearly adjusted, so that the residual stress of the joint is reduced, and the strength of the joint is improved.
Therefore, according to the method for connecting the skutterudite thermoelectric material and the copper electrode by taking Fe-Cr-Mo/W as the barrier layer, the novel supersaturated diffusion-preventing barrier layer is obtained by rapidly cooling through unbalanced solidification, so that the phenomenon that element diffusion is easy to occur between the skutterudite and the copper electrode in the existing soldering connection process of the skutterudite and the copper electrode is effectively reduced, and the problem of low strength of a welding joint is solved. The skutterudite and the barrier layer are connected with good interface bonding, no crack is generated, the shear strength of the joint at room temperature can reach 20MPa, the diffusion of interface elements is very little, the thickness of an interface reaction layer is less than 5 mu m, and the contact resistance and the contact thermal resistance at the welding joint are both small.
2. The method can adopt methods such as diffusion welding, brazing, nano silver sintering and the like to connect the skutterudite and the copper electrode, is convenient to operate, has flexible process, can select a proper method according to actual use requirements, and has lower cost.
3. The invention prepares the barrier layer into a sheet, then connects the skutterudite thermoelectric material with the copper electrode, realizes one-step diffusion connection, has simple and convenient operation, can obtain a welding joint by only one furnace, can realize low-temperature connection and high-temperature service, and has a thinner interface reaction layer.
4. The invention sinters the barrier layer and the thermoelectric material powder together and then connects the barrier layer and the thermoelectric material with the copper electrode, and then adopts soldering/nano silver solid phase sintering and the like to connect the electrodes, so that the thermoelectric device with various structures can be prepared and assembled more conveniently and flexibly without being restricted by a diffusion welding clamp.
Drawings
FIG. 1 is an SEM image of the FeCrMo alloy barrier layer/skutterudite thermoelectric material interface of example 1.
Detailed Description
The technical scheme of the invention is not limited to the specific embodiments listed below, and any reasonable combination of the specific embodiments is included.
The first embodiment is as follows: the method for connecting the skutterudite thermoelectric material and the copper electrode with Fe-Cr-Mo/W as the barrier layer in the embodiment comprises the following steps:
1. firstly, cutting a skutterudite thermoelectric material, then sequentially carrying out abrasive paper step-by-step grinding, polishing, alcohol ultrasonic cleaning and acetone ultrasonic cleaning on the to-be-treated surface of the skutterudite thermoelectric material, and then placing the to-be-treated surface in an inert gas atmosphere for storage; polishing and ultrasonically cleaning the surface to be welded of the copper electrode, drying to obtain the copper electrode to be welded, and storing in inert atmosphere;
2. weighing raw materials according to the atomic percentage of the barrier layer, putting the raw materials into a vacuum arc melting furnace for arc melting, and then performing suction casting on the raw materials into a water-cooled copper mold for rapid solidification to obtain a supersaturated solid solution barrier layer ingot with uniform components; cutting the supersaturated solid solution barrier layer cast ingot into slices, polishing, cleaning and blow-drying in sequence to obtain barrier layer slices for later use;
the barrier layer consists of 10 to 19.9 atomic percent of Cr, 0.1 to 10 atomic percent of Mo or W and the balance of Fe, and the sum of the atomic percent of the Cr and the Mo and the atomic percent of the Cr and the W is 20 percent;
the rapid solidification rate is at least 1000 ℃/min;
3. placing the barrier layer slice between the skutterudite thermoelectric material processed in the step one and the surface to be welded of the copper electrode to be welded for assembly, and obtaining a connecting piece to be welded; the connecting piece to be welded is 1 x 10 -4 -5×10 -3 And (3) simultaneously applying welding pressure of 10-30MPa in a vacuum environment of Pa, heating to 550-650 ℃, maintaining the temperature and the pressure for 3-30min, and then slowly cooling to room temperature to complete the connection of the skutterudite thermoelectric material and the copper electrode.
The embodiment has the following beneficial effects:
1. the existing barrier layer is not rapidly solidified, and only element content change is taken as a research point, so that alloy added by Mo/W elements with large volume fraction cannot be obtained, a large amount of compounds are inevitably generated in the alloy, metal brittleness of the barrier layer is caused, and joint strength is reduced. The embodiment innovatively adopts the non-equilibrium solidification principle to greatly improve the solid solubility of large-size Mo/W elements in the Fe-Cr alloy, so that the lattice constant of the Fe-Cr alloy is obviously increased, the original Cr atom positions are occupied, the lattice distortion is increased, and the difficulty in moving adjacent atoms is caused. And because Cr-Mo/W elements can be infinitely dissolved, the thermal expansion coefficient of the Fe-Cr alloy can be linearly adjusted, so that the residual stress of the joint is reduced, and the strength of the joint is improved.
Therefore, according to the method for connecting the skutterudite thermoelectric material and the copper electrode, which uses Fe-Cr-Mo/W as the barrier layer, a novel supersaturated diffusion-preventing barrier layer is obtained by non-equilibrium solidification and rapid cooling, so that the phenomenon that element diffusion easily occurs between the skutterudite and the copper electrode in the existing soldering connection process of the skutterudite and the copper electrode is effectively reduced, and the problem of low strength of a welding joint is solved. The skutterudite and the barrier layer are connected with good interface bonding, no crack is generated, the joint shear strength at room temperature can reach 20MPa, the diffusion of interface elements is very little, the thickness of an interface reaction layer is less than 5 mu m, and the contact resistance and the contact thermal resistance at the welding joint are both small.
2. The method can be used for connecting the skutterudite and the copper electrode by adopting methods such as diffusion welding, brazing, nano silver sintering and the like, is convenient to operate, has flexible process, can select a proper method according to actual use requirements, and has lower cost.
3. According to the embodiment, the barrier layer is prepared into a thin sheet, and then the skutterudite thermoelectric material is connected with the copper electrode, so that one-step diffusion connection is realized, the operation is simple and convenient, a welding joint can be obtained by only one furnace, low-temperature connection and high-temperature service can be realized, and the interface reaction layer is thin.
The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: step one, the ultrasonic cleaning time of the alcohol is 10min; the ultrasonic cleaning time of acetone is 10min.
The third concrete implementation mode: the first difference between the present embodiment and the specific embodiment is: and the raw material in the second step is pure Fe, pure Cr, pure Mo, pure W, crMo or CrW.
The fourth concrete implementation mode: the first difference between the present embodiment and the specific embodiment is: step two, the electric arc melting process comprises the following steps: the electric arc melting current is 130A, the arc is initiated for 20s each time, the materials are turned over once by a material spoon after each time, and the melting is repeated for at least 5 times.
The fifth concrete implementation mode is as follows: the first difference between the present embodiment and the specific embodiment is: and step two, the thickness of the barrier layer sheet is 100-300 mu m.
The sixth specific implementation mode: the method for connecting the skutterudite thermoelectric material and the copper electrode with Fe-Cr-Mo/W as the barrier layer in the embodiment comprises the following steps:
1. weighing raw materials according to the atomic percentage of the barrier layer, putting the raw materials into a vacuum arc melting furnace for arc melting or vacuum induction melting, and then carrying out suction casting on the raw materials into a water-cooling copper mold for rapid solidification to obtain a supersaturated solid solution barrier layer ingot with uniform components; cutting the supersaturated solid solution barrier layer cast ingot into slices, polishing, cleaning and blow-drying in sequence to obtain barrier layer slices for later use; polishing and ultrasonically cleaning the surface to be welded of the copper electrode, drying to obtain the copper electrode to be welded, and storing in inert atmosphere;
the barrier layer consists of 10 to 19.9 atomic percent of Cr, 0.1 to 10 atomic percent of Mo or W and the balance of Fe, and the sum of the atomic percent of the Cr and the Mo and the atomic percent of the Cr and the W is 20 percent;
the rapid solidification rate is at least 1000 ℃/min;
2. placing the barrier layer slice in a graphite mould filled with the thermoelectric material powder of skutterudite to be welded, covering the thermoelectric material powder of skutterudite with the barrier layer slice, carrying out hot-pressing sintering on the barrier layer and the thermoelectric material powder, and cooling along with a furnace to obtain the thermoelectric material with the barrier layer; then cutting, polishing step by step, cleaning to obtain a thermoelectric material to be welded, and storing in an inert gas environment for later use; the hot-pressing sintering process parameters are determined according to factors such as the type of the thermoelectric material;
the particle size of the thermoelectric material powder is not more than 10 μm;
3. placing a layer of brazing filler metal between the barrier layer of the thermoelectric material to be welded and the copper electrode, wherein the barrier layer of the thermoelectric material to be welded faces the surface to be welded of the copper electrode, so as to obtain a part to be welded, and performing brazing; or arranging nano silver soldering paste between the barrier layer of the thermoelectric material to be welded and the copper electrode obtained in the step two, enabling the barrier layer of the thermoelectric material to be welded to face the surface to be welded of the copper electrode to obtain a piece to be welded, and performing solid-phase sintering.
1. The existing barrier layer is not rapidly solidified, and only element content change is taken as a research point, so that alloy added by Mo/W elements with large volume fraction cannot be obtained, a large amount of compounds are inevitably generated in the alloy, metal brittleness of the barrier layer is caused, and joint strength is reduced. The embodiment innovatively adopts the non-equilibrium solidification principle to greatly improve the solid solubility of large-size Mo/W elements in the Fe-Cr alloy, so that the lattice constant of the Fe-Cr alloy is obviously increased, the original Cr atom positions are occupied, the lattice distortion is increased, and the difficulty in moving adjacent atoms is caused. And because Cr-Mo/W elements can be infinitely mutually dissolved, the thermal expansion coefficient of the Fe-Cr alloy can be linearly adjusted, so that the residual stress of the joint is reduced, and the strength of the joint is improved.
Therefore, according to the method for connecting the skutterudite thermoelectric material and the copper electrode, which uses Fe-Cr-Mo/W as the barrier layer, a novel supersaturated diffusion-preventing barrier layer is obtained by non-equilibrium solidification and rapid cooling, so that the phenomenon that element diffusion easily occurs between the skutterudite and the copper electrode in the existing soldering connection process of the skutterudite and the copper electrode is effectively reduced, and the problem of low strength of a welding joint is solved. The skutterudite and the barrier layer are connected with good interface bonding, no crack is generated, the joint shear strength at room temperature can reach 20MPa, the diffusion of interface elements is very little, the thickness of an interface reaction layer is less than 5 mu m, and the contact resistance and the contact thermal resistance at the welding joint are both small.
2. The method can be used for connecting the skutterudite and the copper electrode by adopting methods such as diffusion welding, brazing, nano silver sintering and the like, is convenient to operate, has flexible process, can select a proper method according to actual use requirements, and has lower cost.
3. According to the embodiment, the barrier layer and the thermoelectric material powder are sintered together and then connected with the copper electrode, the barrier layer and the thermoelectric material are connected firstly, and then the electrodes are connected by brazing/nano silver solid phase sintering and the like, so that the thermoelectric devices with various structures can be prepared and assembled more conveniently and flexibly without being limited by a diffusion welding clamp.
The seventh concrete implementation mode: the sixth embodiment is different from the specific embodiment in that: step one, the electric arc melting process comprises the following steps: the electric arc melting current is 130A, the arc is initiated for 20s each time, the materials are turned over once by a material spoon after each time, and the melting is repeated for at least 5 times.
The specific implementation mode is eight: the sixth embodiment is different from the specific embodiment in that: in the first step, the raw materials are pure Fe, pure Cr, pure Mo, pure W, crMo or CrW.
The specific implementation method nine: the sixth embodiment is different from the specific embodiment in that: step three, the solid phase sintering process comprises the following steps: under a vacuum of 1X 10 -4 -5×10 -3 Under Pa, applying pressure of 0.5-10MPa to the workpiece to be welded, heating to 200-500 deg.C, maintaining for 5-30min, and cooling with the furnace.
The detailed implementation mode is ten: the sixth embodiment is different from the sixth embodiment in that: the brazing process in the third step comprises the following steps: under a vacuum of 1X 10 -4 -5×10 -3 Heating to 650-700 ℃ at a heating rate of 5-15 ℃/min under Pa, keeping the temperature for 3-10min, and cooling along with the furnace at a cooling rate of 2-10 ℃/min.
The concrete implementation mode eleven: the sixth embodiment is different from the sixth embodiment in that: and step three, the brazing filler metal is Ag-Cu-In-Sn or Ag-Cu-In-Ti or CuSn10.5PNi2.
The specific implementation mode twelve: the sixth embodiment is different from the sixth embodiment in that: step one, the thickness of the slice is 100-300 μm.
Example 1
In this example, the method for connecting the skutterudite thermoelectric material and the copper electrode using Fe-Cr-Mo/W as the barrier layer was performed according to the following steps:
1. firstly, cutting a skutterudite thermoelectric material, then sequentially carrying out abrasive paper step-by-step grinding, polishing, alcohol ultrasonic cleaning for 10min and acetone ultrasonic cleaning for 10min on the to-be-treated surface of the skutterudite thermoelectric material, and then placing the to-be-treated surface in a nitrogen atmosphere for storage; polishing and ultrasonically cleaning the surface to be welded of the copper electrode, drying to obtain the copper electrode to be welded, and storing in inert atmosphere;
2. weighing raw materials according to the atomic percentage of the barrier layer, putting the raw materials into a vacuum arc melting furnace for arc melting, and then performing suction casting on the raw materials into a water-cooled copper mold for rapid solidification to obtain a supersaturated solid solution barrier layer ingot with uniform components; cutting the supersaturated solid solution barrier layer cast ingot into slices, polishing, cleaning and blow-drying in sequence to obtain barrier layer slices for later use;
the barrier layer is composed of 15% of Cr, 5% of Mo and the balance of Fe according to atom percentage;
the raw materials are pure Fe, pure Cr and pure Mo;
the electric arc melting process comprises the following steps: the electric arc melting current is 130A, the arc is initiated for 20s each time, the materials are turned over once by a material spoon after each time, and the melting is repeated for 5 times;
the speed of the rapid solidification is 1000 ℃/min;
the barrier layer sheet has a thickness of 300 μm;
3. placing the barrier layer slice between the skutterudite thermoelectric material processed in the step one and the surface to be welded of the copper electrode to be welded for assembly, and obtaining a connecting piece to be welded; the connecting piece to be welded is 1 x 10 -4 -5×10 -3 And (3) simultaneously applying welding pressure of 10MPa in a vacuum environment of Pa, heating to 600 ℃, keeping the temperature and the pressure for 10min, and then slowly cooling to room temperature at the speed of 5 ℃/min to complete the connection of the skutterudite thermoelectric material and the copper electrode.
FIG. 1 is a FeCrMo alloy barrier layer in example 1SEM picture of/skutterudite thermoelectric material interface, from left to right in the figure, is FeCrMo barrier layer and skutterudite thermoelectric material. FIG. 1 can show that the joint interface is well bonded, and the reaction layer is small and uniform in thickness. The supersaturated solid solution barrier layer with large volume fraction of Mo/W elements added is prepared by a rapid solidification method based on the non-equilibrium solidification principle, the expansion coefficient is linearly adjustable, and the element barrier effect is good. After the aging test at 550 ℃ for 600 hours, the joint reaction layer is not more than 25 mu m, and the interfacial resistivity is less than 4 mu omega cm 2 The shear strength of the joint can reach 18MPa.
Example 2
In this example, the method for connecting the skutterudite thermoelectric material with the Fe-Cr-Mo/W barrier layer and the copper electrode is performed according to the following steps:
1. weighing raw materials according to the atomic percentage of the barrier layer, putting the raw materials into a vacuum arc melting furnace for arc melting or vacuum induction melting, and then performing suction casting on the raw materials into a water-cooled copper mold for rapid solidification to obtain a supersaturated solid solution barrier layer ingot with uniform components; cutting the supersaturated solid solution barrier layer cast ingot into slices, polishing, cleaning and blow-drying in sequence to obtain barrier layer slices for later use; polishing and ultrasonically cleaning the surface to be welded of the copper electrode, drying to obtain the copper electrode to be welded, and storing in inert atmosphere;
the barrier layer is composed of 15 atomic% of Cr, 5 atomic% of W and the balance of Fe; the raw materials are pure Fe, pure Cr and pure W;
the electric arc melting process comprises the following steps: the electric arc melting current is 130A, the arc is initiated for 20s each time, the materials are turned over once by a material spoon after each time, and the melting is repeated for 5 times;
the speed of the rapid solidification is 1000 ℃/min;
the thickness of the thin slice is 300 mu m;
2. placing the barrier layer slice in a graphite mould filled with the thermoelectric material powder of skutterudite to be welded, covering the thermoelectric material powder of skutterudite with the barrier layer slice, carrying out hot-pressing sintering on the barrier layer and the thermoelectric material powder, and cooling along with a furnace to obtain the thermoelectric material with the barrier layer; then cutting, polishing step by step, cleaning to obtain a thermoelectric material to be welded, and storing in an inert gas environment for later use; the hot-pressing sintering process parameters are determined according to factors such as the type of thermoelectric materials;
the particle size of the thermoelectric material powder is 8-10 mu m;
the skutterudite thermoelectric material powder component is La 0.8 Ti 0.1 Ga 0.1 Fe 3.3 Co 0.7 Sb 12 The sintering process comprises the following steps: rapidly heating to 650 ℃ at a speed of 100 ℃/min under Ar gas atmosphere, preserving heat for 10min at a pressure of 60MPa, and then slowly cooling to room temperature at a speed of 5 ℃/min;
3. arranging nano silver soldering paste between the barrier layer of the thermoelectric material to be welded and the copper electrode obtained in the step two, enabling the barrier layer of the thermoelectric material to be welded to face the surface to be welded of the copper electrode to obtain a piece to be welded, and performing solid-phase sintering;
the solid phase sintering process comprises the following steps: under vacuum degree of 5X 10 -3 Under Pa, applying 5MPa pressure to a workpiece to be welded, heating to 500 ℃, preserving heat for 10min, and cooling along with the furnace;
in the embodiment, the thermoelectric material is connected with the supersaturated solid solution barrier layer by one-time hot-pressing sintering, and then the thermoelectric material is connected with the Cu electrode by solid-phase sintering by adopting the nano-silver soldering paste, so that the reliable connection between the thermoelectric material and the Cu electrode is realized, and the element diffusion between the thermoelectric material and the Cu is effectively blocked; the obtained joint has shear strength up to 17MPa, and contact resistance less than 5 mu omega cm after aging at 550 ℃ for 600h 2 。
Claims (10)
1. A method for connecting a skutterudite thermoelectric material and a copper electrode by taking Fe-Cr-Mo/W as a barrier layer is characterized in that: the method for connecting the skutterudite thermoelectric material with the Fe-Cr-Mo/W as the barrier layer and the copper electrode comprises the following steps:
1. firstly, cutting a skutterudite thermoelectric material, then sequentially carrying out abrasive paper step-by-step grinding, polishing, alcohol ultrasonic cleaning and acetone ultrasonic cleaning on the to-be-treated surface of the skutterudite thermoelectric material, and then placing the to-be-treated surface in an inert gas atmosphere for storage; polishing and ultrasonically cleaning the surface to be welded of the copper electrode, drying to obtain the copper electrode to be welded, and storing in inert atmosphere;
2. weighing raw materials according to the atomic percentage of the barrier layer, putting the raw materials into a vacuum arc melting furnace for arc melting, and then performing suction casting on the raw materials into a water-cooled copper mold for rapid solidification to obtain a supersaturated solid solution barrier layer ingot with uniform components; cutting the supersaturated solid solution barrier layer cast ingot into slices, polishing, cleaning and blow-drying in sequence to obtain barrier layer slices for later use;
the barrier layer consists of 10 to 19.9 atomic percent of Cr, 0.1 to 10 atomic percent of Mo or W and the balance of Fe, and the sum of the atomic percent of the Cr and the Mo and the atomic percent of the Cr and the W is 20 percent;
the rapid solidification rate is at least 1000 ℃/min;
3. placing the barrier layer slice between the skutterudite thermoelectric material processed in the step one and the surface to be welded of the copper electrode to be welded for assembly, and obtaining a connecting piece to be welded; the connecting piece to be welded is 1 x 10 -4 -5×10 -3 And (3) simultaneously applying welding pressure of 10-30MPa in a vacuum environment of Pa, heating to 550-650 ℃, maintaining the temperature and the pressure for 3-30min, and then slowly cooling to room temperature to complete the connection of the skutterudite thermoelectric material and the copper electrode.
2. The method for connecting a skutterudite thermoelectric material using Fe-Cr-Mo/W as a barrier layer to a copper electrode according to claim 1, wherein: step one, the ultrasonic cleaning time of the alcohol is 10min; the ultrasonic cleaning time of acetone is 10min.
3. The method for connecting a skutterudite thermoelectric material using Fe-Cr-Mo/W as a barrier layer with a copper electrode according to claim 1, wherein: and the raw material in the second step is pure Fe, pure Cr, pure Mo, pure W, crMo or CrW.
4. The method for connecting a skutterudite thermoelectric material using Fe-Cr-Mo/W as a barrier layer to a copper electrode according to claim 1, wherein: step two, the electric arc melting process comprises the following steps: the electric arc melting current is 130A, the arc is initiated for 20s each time, the materials are turned over once by a material spoon after each time, and the melting is repeated for at least 5 times.
5. The method for connecting a skutterudite thermoelectric material using Fe-Cr-Mo/W as a barrier layer to a copper electrode according to claim 1, wherein: and step two, the thickness of the barrier layer sheet is 100-300 mu m.
6. A method for connecting a skutterudite thermoelectric material and a copper electrode by taking Fe-Cr-Mo/W as a barrier layer is characterized in that: the method for connecting the skutterudite thermoelectric material with the Fe-Cr-Mo/W as the barrier layer and the copper electrode comprises the following steps:
1. weighing raw materials according to the atomic percentage of the barrier layer, putting the raw materials into a vacuum arc melting furnace for arc melting or vacuum induction melting, and then performing suction casting on the raw materials into a water-cooled copper mold for rapid solidification to obtain a supersaturated solid solution barrier layer ingot with uniform components; cutting the supersaturated solid solution barrier layer cast ingot into slices, polishing, cleaning and blow-drying in sequence to obtain barrier layer slices for later use; polishing and ultrasonically cleaning the surface to be welded of the copper electrode, drying to obtain the copper electrode to be welded, and storing in inert atmosphere;
the barrier layer consists of 10 to 19.9 atomic percent of Cr, 0.1 to 10 atomic percent of Mo or W and the balance of Fe, and the sum of the atomic percent of Cr and Mo and the atomic percent of Cr and W is 20 percent;
the rapid solidification rate is at least 1000 ℃/min;
2. placing the barrier layer slice in a graphite mould filled with the thermoelectric material powder of skutterudite to be welded, covering the thermoelectric material powder of skutterudite with the barrier layer slice, carrying out hot-pressing sintering on the barrier layer and the thermoelectric material powder, and cooling along with a furnace to obtain the thermoelectric material with the barrier layer; then cutting, polishing step by step, cleaning to obtain a thermoelectric material to be welded, and storing in an inert gas environment for later use; the hot-pressing sintering process parameters are determined according to factors such as the type of the thermoelectric material;
the particle size of the thermoelectric material powder is not more than 10 μm;
3. placing a layer of brazing filler metal between the barrier layer of the thermoelectric material to be brazed and the copper electrode, wherein the barrier layer of the thermoelectric material to be brazed faces the surface to be brazed of the copper electrode to obtain a part to be brazed; or arranging nano silver soldering paste between the barrier layer of the thermoelectric material to be welded and the copper electrode obtained in the step two, enabling the barrier layer of the thermoelectric material to be welded to face the surface to be welded of the copper electrode to obtain a piece to be welded, and performing solid-phase sintering.
7. The method for connecting a skutterudite thermoelectric material using Fe-Cr-Mo/W as a barrier layer with a copper electrode according to claim 6, wherein: step one, the electric arc melting process comprises the following steps: the electric arc melting current is 130A, the arc is initiated for 20s each time, the materials are turned over once by a material spoon after each time, and the melting is repeated for at least 5 times.
8. The method for connecting a skutterudite thermoelectric material using Fe-Cr-Mo/W as a barrier layer to a copper electrode according to claim 6, wherein: in the first step, the raw materials are pure Fe, pure Cr, pure Mo, pure W, crMo or CrW.
9. The method for connecting a skutterudite thermoelectric material using Fe-Cr-Mo/W as a barrier layer to a copper electrode according to claim 6, wherein: the solid phase sintering process comprises the following steps: under a vacuum of 1X 10 -4 -5×10 -3 And (3) under Pa, applying pressure of 0.5-10MPa to the to-be-welded part, heating to 200-500 ℃, preserving heat for 5-30min, and cooling along with the furnace.
10. The method for connecting a skutterudite thermoelectric material using Fe-Cr-Mo/W as a barrier layer to a copper electrode according to claim 6, wherein: the brazing process in the third step comprises the following steps: under a vacuum of 1X 10 -4 -5×10 -3 Heating to 650-700 ℃ at a heating rate of 5-15 ℃/min under Pa, keeping the temperature for 3-10min, and cooling along with the furnace at a cooling rate of 2-10 ℃/min.
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