CN103681952B - Preparation process of molybdenum/platinum/silver layered metal matrix composites for space vehicles - Google Patents

Abstract

The present invention relates to a kind of preparation technology of spacecraft solar battery array sheet of interconnect molybdenum/platinum/silver laminar metal matrix composite.Step is the pre-treatment of molybdenum paper tinsel, Mo metallic surface electroplatinizing, molybdenum/platinum plating sample annealing, molybdenum/platinum layer shape annealed sample surface electrical are silver-plated and the annealing of molybdenum/platinum/silver plating sample, molybdenum/platinum/silver laminar metal matrix composite surface topography scanning electron microscopic observation, test along the Auger spectroscopy analysis of the degree of depth and resistance spot welding hot strength.The invention enables molybdenum/platinum, platinum/silver-colored interface that diffusion occurs to infiltrate, thus metallurgical binding is realized on molybdenum/platinum, platinum/silver-colored interface, obtain the molybdenum/platinum/silver laminar metal matrix composite with high interfacial bonding strength, high welding hot strength, hot strength of welding when itself and the resistance spot welding of solar battery sheet single-point is 324 gram forces (gf), has exceeded the weld strength index that GJB GJB2602-1996 specifies.

Description

Preparation process of molybdenum/platinum/silver layered metal matrix composites for space vehicles

technical field

The invention relates to a preparation process of a molybdenum/platinum/silver layered metal-based composite material for a space vehicle solar battery array interconnection sheet.

Background technique

The power supply system of space vehicles (including satellites, spacecraft and space stations, etc.) is composed of solar arrays as power generation devices, battery packs as energy storage devices, and power control devices required for power distribution systems. The solar array generates electricity during bright periods in Earth orbit, powering the spacecraft's electrical loads and charging the battery pack.

The solar cell array is composed of a large number of solar cells, which are mounted on the solar panel in an orderly manner, and use the photoelectric effect of the solar cell to convert the incident sunlight radiation into electrical energy. Although each cell contributes a small current and voltage, a large number of cells can be properly connected in series and parallel to provide the current and voltage required by the spacecraft load. Continuously.

A considerable part of the spacecraft is operating in low earth orbit (LowEarthOrbit-LEO, the orbital altitude is between 200Km and 1000Km). The interconnection sheet used will be subjected to the influence of atomic oxygen, thermal cycle, micrometeorite and space debris and ultraviolet radiation in this orbit, among which the impact of atomic oxygen and thermal cycle is the most serious. In this kind of space environment, the interconnection sheet often has cracks, oxidative erosion, and deformation and shedding. In the slightest, the output power of the solar cell array decreases, and in severe cases, the battery array is completely destroyed, resulting in the failure of the space vehicle. To improve the on-orbit reliability and lifespan of LEO spacecraft, the use of new molybdenum/platinum/silver layered composite materials with high resistance to atomic oxygen erosion, low thermal expansion and excellent electrical conductivity will be one of the keys.

Chinese patent CN201110008862.5 discloses a molybdenum/silver layered metal matrix composite material and preparation process for solar cell interconnect sheets, mainly using ion implantation method, injecting silver ions into molybdenum metal foil test pieces, and then electroplating silver to obtain molybdenum/silver Silver layered metal matrix composites. It should be pointed out that although the molybdenum/silver layered metal matrix composite material solves the problems of high interfacial bonding strength, thermal fatigue resistance, excellent solderability and electrical conductivity of the interconnection sheet, it has been proved that the interconnection sheet has excellent resistance to corrosion. Oxidation to bear the problem of LEO atomic oxygen erosion can be satisfied by adding a platinum metal layer between molybdenum-silver to prepare a molybdenum/platinum/silver layered composite material.

There are several difficulties in the preparation technology of molybdenum/platinum/silver layered composites: Although molybdenum-platinum is a solid solution system, there are five metal intermediate phases ( Phase Mo ₆ Pt, Phase Mo ₃ Pt, Phase Mo ₃ Pt, Phase MoPt, phase Mo ₆ Pt ₂ ), coupled with the extremely low surface activity of molybdenum foil, it is difficult to obtain a molybdenum/platinum bonding interface with high bonding strength and good ductility; Although the platinum-silver system is a solid solution system, so far there has been considerable controversy over the phase diagram of platinum-silver binary alloys in the academic circles, which makes it difficult to confirm the reasonable microstructure and formulate the annealing process; The thermal expansion coefficients of molybdenum, platinum and silver metals are quite different (the thermal expansion coefficient of molybdenum is about 5.2 10 ^-6 /K ^-1 , the thermal expansion coefficient of platinum is about 9.0 10 ^-6 /K ^-1 , the thermal expansion coefficient of silver is about 19.2 10 ^-6 /K ^-1 ), the thermal stress is difficult to control.

Contents of the invention

The purpose of the present invention is to provide a preparation process of a molybdenum/platinum/silver layered metal matrix composite material for solar cell array interconnection sheets of space vehicles, so as to improve the life and reliability of LEO space vehicles on orbit. Cyanide-free electroplating + multiple annealing techniques were used to realize the metallurgical bonding of the interface between molybdenum/platinum/silver, and finally a molybdenum/platinum/silver layered metal matrix composite material was prepared, which met the performance requirements. The prepared molybdenum/platinum/silver layered metal matrix composite material can meet the requirements of the national military standard GJB2602-1996 with the resistance spot welding strength of the space gallium arsenide solar cell.

The preparation process of the molybdenum/platinum/silver layered metal matrix composite material for solar cell array interconnect sheet provided by the present invention mainly includes the following steps:

1) Pretreatment of molybdenum metal foil. The pretreatment of molybdenum foil is very important to obtain high-strength molybdenum/platinum/silver interfacial bonding. The pre-treatment includes the steps of molybdenum foil degreasing, cleaning, etching, and ultrasonic cleaning. The molybdenum foil is immersed in the etching solution for etching, and then immersed in deionized water after etching, then placed in deionized water for ultrasonic cleaning, and dried after ultrasonic cleaning.

2) The surface of molybdenum metal is electroplated with platinum. In this step, a direct current electroplating device is used to electroplate platinum, the temperature of the electroplating solution is 80-85°C, and a molybdenum/platinum electroplating sample is obtained after electroplating.

Platinum electroplating solution composition and process parameters are as follows:

Disodium hydrogen phosphate 140g/LpH 7-7.5

Diammonium hydrogen phosphate 40g/L Current density 4-4.5A·dm ^-2

Chloroplatinic acid 0.5308g/L electroplating time 3.5-4h

Sodium dodecyl sulfonate 0.01g/L electroplating temperature 80-85

3) Annealing of molybdenum/platinum plating samples (the first atmosphere protection annealing). This step is mainly to place the molybdenum electroplated platinum sample obtained in the previous step under argon protection for 900-950 Annealing was performed for 3.5-4 hours, and a molybdenum/platinum layered annealed sample was obtained after annealing.

4) The molybdenum/platinum layered annealed sample surface was electroplated with silver. In this step, a direct current electroplating device is used to electroplate silver, and a molybdenum/platinum/silver electroplating sample is obtained after electroplating.

The composition and process parameters of the electroplating silver solution are:

Sodium thiosulfate 250g/LpH 6.5~8

Potassium metabisulfite 45g/L Current density 0.40-0.45A·dm ^-2

Ammonium acetate 150g/L electroplating time 20-25min

Silver nitrate 45g/L electroplating temperature 18～35

Thiosemicarbazide 0.8g/L

5) Annealing of molybdenum/platinum/silver plating samples (the second atmosphere protection annealing).

This step is mainly to place the molybdenum/platinum/silver plating sample obtained in the previous step under argon protection at 700~750 Annealing is carried out for 4-4.5 hours, and the molybdenum/platinum/silver layered metal matrix composite material is finally obtained after annealing.

The present invention carries out following test:

1) Scanning electron microscope (SEM) observation of the surface morphology of the molybdenum/platinum plating sample obtained after platinum plating on the molybdenum surface;

2) SEM observation of the surface morphology of the molybdenum/platinum layered annealed sample obtained after the first atmosphere protection annealing after platinum plating on the molybdenum surface;

3) SEM observation of the surface morphology of molybdenum/platinum/silver layered metal matrix composites;

4) Compositional Auger spectroscopy (AES) analysis of molybdenum/platinum/silver layered metal matrix composites along the depth;

5) Resistance spot welding tensile strength test of molybdenum/platinum/silver layered metal matrix composites and space gallium arsenide solar cells.

The molybdenum/platinum/silver layered composite material of the present invention is an advanced layered structure composite material prepared by using molybdenum metal as the matrix, silver metal as the surface layer, platinum metal as the middle layer, and the metallurgical combination of the three on the interface. Among them, molybdenum metal is resistant to high temperature and can maintain high strength at high temperature. At the same time, the low thermal expansion coefficient makes molybdenum have good thermal shock resistance, good electrical conductivity and wear resistance; silver metal has good weldability (molybdenum has relatively poor weldability) and electrical conductivity; while platinum metal In addition to being used as an intermediate layer to achieve layered composites of mutually insoluble molybdenum and silver metals, it can also take advantage of its excellent oxidation resistance to bear atomic oxygen erosion. Therefore, the molybdenum/platinum/silver layered composite material has the characteristics of thermal shock resistance, good electrical conductivity and welding performance, and is resistant to atomic oxygen corrosion, non-ferromagnetic, and is very suitable for bearing alternating thermal loads and atomic oxygen. Eroded LEO spacecraft.

The invention provides a preparation process of a molybdenum/platinum/silver layered metal-based composite material for a space vehicle solar cell array interconnection sheet. Platinum plating on the surface of molybdenum metal + atmosphere protection annealing, molybdenum/platinum surface silver plating + atmosphere protection annealing and other technologies make the interface of molybdenum/platinum and platinum/silver diffuse and infiltrate, so as to realize metallurgy on the interface of molybdenum/platinum and platinum/silver Combined, a molybdenum/platinum/silver layered metal matrix composite material with high interfacial bonding strength and high welding tensile strength was obtained, and the welding tensile strength when it was single-point resistance spot welded with solar cells was 324 grams of force (gf ), exceeding the 150gf welding strength index stipulated in the national military standard GJB2602-1996.

Description of drawings

Figure 1: Schematic diagram of the structure of the molybdenum/platinum/silver layered metal matrix composite material in the present invention.

Fig. 2: The schematic diagram of electroplating platinum device in the present invention.

Fig. 3: The schematic diagram of electroplating silver device in the present invention.

Figure 4: SEM image of surface morphology observation of molybdenum/platinum electroplating sample obtained after electroplating platinum on the surface of molybdenum in the present invention.

Fig. 5: SEM image of the surface morphology observation of the molybdenum/platinum layered annealed sample obtained after the first atmosphere protection annealing after the molybdenum surface is electroplated with platinum in the present invention.

Fig. 6: SEM image of surface morphology observation of molybdenum/platinum/silver layered metal matrix composite material in the present invention.

Figure 7: Compositional AES spectra of molybdenum/platinum/silver layered metal matrix composites along depth.

Fig. 8: Schematic diagram of testing the welding strength of molybdenum/platinum/silver layered metal matrix composites in the present invention.

Fig. 9: Test curve of tensile strength of molybdenum/platinum/silver layered metal matrix composite material and space gallium arsenide solar cell resistance spot welding in the present invention.

detailed description

The present invention is described in detail in conjunction with the embodiments and accompanying drawings.

Fig. 1 is a schematic diagram of the structure of molybdenum/platinum/silver layered metal matrix composites, in which, 1-matrix metal is molybdenum metal with a thickness of 12 ; 2 - middle layer metal, platinum metal, thickness 0.5 ;3-Surface metal, silver, thickness 5 .

The specific implementation steps are as follows:

1. Degreasing and cleaning the molybdenum metal surface

Will be cleaned with alcohol 180mm long Width 120mm The molybdenum metal foil with a thickness of 15 μm is completely immersed in 1L degreasing solution (50mL of 37% concentrated hydrochloric acid+50mL of 98% concentrated sulfuric acid+distilled water) for 3 minutes, then taken out and immersed in deionized water for 5 minutes for cleaning, and the cleaning is carried out 3 times.

2. Molybdenum metal surface etching

Soak the molybdenum foil that has been degreased and cleaned with deionized water in 1L of etching solution (150mL of 37% concentrated hydrochloric acid + 150mL of 98% concentrated sulfuric acid + distilled water + 80g of chromium trioxide) and etch for 10 minutes, take it out and immerse it in deionized water Soak for 15 minutes, then take out and soak in deionized water for ultrasonic cleaning for 25 minutes (ultrasonic frequency 50Hz, temperature 30 ), after ultrasonic cleaning, take it out and dry it for later use.

3. Preparation of electroplating platinum solution

First, dissolve 140g of disodium hydrogen phosphate in 200mL of deionized water, stir to make it all dissolve into a disodium hydrogen phosphate solution; then dissolve 40g of diammonium hydrogen phosphate with 500mL of deionized water into a diammonium hydrogen phosphate solution; Dissolve 1 g of chloroplatinic acid (containing 0.2 g of platinum in total) with 100 mL of deionized water to form a chloroplatinic acid solution.

Mix the prepared disodium hydrogen phosphate solution and diammonium hydrogen phosphate solution, add the chloroplatinic acid solution and stir to mix evenly; then add 0.01g sodium dodecylsulfonate to dissolve them all, and finally add deionized water to 1L.

4. Platinum plating on the surface of molybdenum metal

Electroplating was performed using the DC electroplating device shown in Figure 2. In the figure, 4-DC power supply, 5-milliampere meter, 6-platinum metal plate anode, 7-molybdenum metal test piece, 8-plating tank (made of transparent inorganic glass), 9-plating solution, 10-constant temperature water bath.

Platinum electrode (anode) area is 1cm 1cm, the distance from the plating sample is 3.5cm. The electroplating current density was 4A·dm ^-2 , the electroplating time was 3.5 hours, and the temperature of the electroplating solution was controlled at 85°C with a constant temperature water bath.

After the electroplating finished, the molybdenum/platinum electroplating sample was obtained, soaked in deionized water for 15 minutes, blotted dry with filter paper, hung it in the air for 12 hours, put it into a vacuum oven at 60 temperature and 10 ^-1 Pa vacuum for 90 minutes.

5. The first atmosphere protection annealing

The molybdenum/platinum electroplated sample was subjected to argon protection annealing in an annealing furnace at 900° C. for 4 hours. The annealing process is as follows: increase the temperature at a rate of 5 °C per minute to 250 °C, hold at 250 °C for 10 minutes, then increase the rate of temperature at 6.5 °C per minute to 900 °C, and keep at 900 °C for 4 hours. Cooling, the way of cooling is to cool with the furnace.

After annealing, a molybdenum/platinum layered annealed sample was obtained.

6. Silver plating on the surface of molybdenum/platinum layered annealed sample

(1) Preparation of electroplating silver solution

First, dissolve 250g of sodium thiosulfate in 300mL of deionized water, stir to make it all dissolve into a sodium thiosulfate solution; then dissolve 45g of silver nitrate and 45g of potassium metabisulfite in 250mL of deionized water to form a silver nitrate solution and potassium metabisulfite solution, pour the potassium metabisulfite solution into the silver nitrate solution under the condition of stirring, after the cloudy solution of silver metabisulfite is generated, immediately add the solution slowly into the sodium thiosulfate solution to make the silver ions Combining with sodium thiosulfate to produce a slightly yellow clear liquid;

Add 150 g of ammonium acetate to the above-mentioned yellowish clear liquid, and after standing still, add 0.8 g of thiosemicarbazide to dissolve it completely, and finally dilute to 1 L with deionized water. The pH value of the prepared silver plating solution is between 6.5 and 8.

(2) Silver plating

The surface of the molybdenum/platinum layered annealed sample was electroplated with silver using the DC electroplating device shown in Figure 3 . In the figure, 11 - DC power supply, 12 - mA meter, 13 - silver metal plate anode, 14 - molybdenum/platinum layered annealing sample, 15 - plating tank (made of transparent inorganic glass), 16 - plating solution.

The silver electrode (anode) has an area of 10cm 10cm, the silver electrode is 5.5cm away from the sample (cathode). The electroplating current density is 0.45A·dm ^-2 , the electroplating time is 25min, and the electroplating temperature is 25 .

After electroplating finishes, obtain molybdenum/platinum/silver electroplating sample, soak with deionized water for 15 minutes and blot dry with filter paper, hang to air for 12 hours, put into vacuum oven at 60 temperature and 10 ^-1 Pa vacuum for 90 minutes.

7. The second atmosphere protection annealing

The above-mentioned molybdenum/platinum/silver electroplating sample was subjected to argon protection annealing in an annealing furnace at 700° C. for 4 hours. The annealing process is as follows: increase the temperature at a rate of 5 °C per minute to 250 °C, keep it at 250 °C for 10 minutes, then increase the rate of temperature at 6.5 °C per minute to 700 °C, and keep it at 700 °C for 4 hours. Cooling, the way of cooling is to cool with the furnace.

After the annealing, the molybdenum/platinum/silver layered metal matrix composite material is finally obtained.

8. SEM observation of the surface morphology of molybdenum/platinum layered annealed samples

Figure 4 is the surface morphology of the molybdenum/platinum electroplating sample. From Figure 4, it can be seen that a layer of dense and uniform platinum layer is coated on the surface of the molybdenum metal; /Platinum layered annealed sample surface topography, it can be seen that the platinum layer grains grow uniformly after annealing, and the surface of the platinum-coated layer is smooth and dense.

9. SEM observation of surface morphology of molybdenum/platinum/silver layered metal matrix composites

Figure 6 is the SEM image of the surface morphology of the molybdenum/platinum/silver layered metal matrix composite material. From Figure 6, it can be seen that the surface is covered with a uniform and dense silver layer, and the composite material forms a whole.

10. Composition AES analysis along the depth of molybdenum/platinum/silver layered metal matrix composites

Figure 7 is the composition AES spectrum of the molybdenum/platinum/silver layered metal matrix composite material along the depth. It can be seen that the molybdenum-platinum and platinum-silver interfaces have diffused to form a metallurgical bond.

11. Welding tensile strength test of molybdenum/platinum/silver layered metal matrix composites

The welding tensile strength test process is shown in Figure 8. The specific process is to weld the molybdenum/platinum/silver layered metal matrix composite material test piece on the space gallium arsenide solar cell by single point resistance spot welding, and then stretch it from The solar cells fall off, and the tensile load is 45% of that of the sample. .

According to the characteristics of the structure of molybdenum/platinum/silver layered metal matrix composites (see Figure 1), the tensile test results of the welding of silver metal on the surface of the composite material and space gallium arsenide solar cells not only reflect the relationship between the composite material and solar energy. The strength of the welding head between the cells also reflects the interface strength between molybdenum/platinum/silver.

Accompanying drawing 9 is test result. The results show that the welding (interface) strength of single-point resistance spot welding is 324 grams force (gf), which meets the national military standard and the index requirements put forward by aerospace users (the national military standard GJB2602-1996 stipulates that the index is 150gf, which meets the requirements of space vehicles. requirements.

Claims (10)

1. a preparation technology for solar battery array sheet of interconnect molybdenum/platinum/silver laminar metal matrix composite, comprises the following steps:

1) molybdenum paper tinsel deoiled, clean, etch, the pre-treatment of Ultrasonic Cleaning;

2) adopt direct current electrode position device to Mo metallic surface electroplatinizing, obtain molybdenum/platinum plating sample;

3) previous step is obtained molybdenum electroplatinizing sample to carry out annealing under first time inert atmosphere protection and obtain molybdenum/platinum layer shape annealed sample;

4) adopt direct current electrode position device silver-plated to molybdenum/platinum layer shape annealed sample surface electrical, obtain molybdenum/platinum/silver plating sample;

5) previous step is obtained molybdenum/platinum/silver plating sample to carry out the annealing of second time inert atmosphere protection, finally obtain molybdenum/platinum/silver laminar metal matrix composite.

2. a preparation technology for solar battery array sheet of interconnect molybdenum/platinum/silver laminar metal matrix composite, comprises the following steps:

1) the carrying out of molybdenum paper tinsel deoiled, clean, etch and Ultrasonic Cleaning pre-treatment, it is characterized in that:

2) adopt direct current electrode position device, with platinum electrode as anode, molybdenum as negative electrode, at Mo metallic surface electroplatinizing, obtain molybdenum/platinum plating sample;

3) 900-950 under argon shield molybdenum/platinum plating sample is carried out to first time atmosphere protection annealing 3.5 ~ 4 hours, obtains molybdenum/platinum layer shape annealed sample after annealing;

4) adopt direct current electrode position device, with fine silver plate as anode, molybdenum/platinum layer shape annealed sample as negative electrode, carry out electrosilvering, obtain molybdenum/platinum/silver and electroplate sample;

5) by molybdenum/platinum/silver plating sample 700-750 under argon shield carry out second time atmosphere protection annealing 4 ~ 4.5 hours, after annealing, finally obtain molybdenum/platinum/silver laminar metal matrix composite.

3., according to the preparation technology described in claim 1 or 2, it is characterized in that the structure of described composite material is the layer structure of silver-platinum-molybdenum-platinum-Yin, platinum is the intermediate metal layer between molybdenum and silver; Molybdenum-platinum and platinum-Yin interface all diffuse to form metallurgical binding.

4., according to the preparation technology described in claim 1 or 2, it is characterized in that in described composite material, Mo substrate layer thickness is 12 , platinum middle layer thickness is 0.5 , silver-colored skin depth is 5 .

5. according to the preparation technology described in claim 1 or 2, it is characterized in that described electroplatinizing solution composition and technological parameter as follows:

Sodium hydrogen phosphate 140g/LpH value 7-7.5

Diammonium hydrogen phosphate 40g/L current density 4-4.5Adm ^-2

Chloroplatinic acid 0.5308g/L electroplating time 3.5-4h

Dodecyl sodium sulfate 0.01g/L electroplating temperature 80-85 .

6., according to the preparation technology described in claim 1 or 2, it is characterized in that described plating silver solution composition and technological parameter are:

Sodium thiosulfate 250g/LpH value 6.5 ~ 8

Potassium metabisulfite 45g/L current density 0.40-0.45Adm ^-2

Ammonium acetate 150g/L electroplating time 20-25min

Silver nitrate 45g/L electroplating temperature 18 ~ 35

Thiosemicarbazide 0.8g/L.

7. according to preparation technology according to claim 2, it is characterized in that annealing process described in step 3) is: rise to 250 DEG C with 5 DEG C of heating rates per minute, 250 DEG C of insulations 10 minutes, then 900 DEG C are risen to 6.5 DEG C of heating rates per minute, 4 hours are incubated at 900 DEG C, start cooling after insulation terminates, cooling method is cool with stove.

8. according to preparation technology according to claim 2, it is characterized in that annealing process described in step 5) is: rise to 250 DEG C with 5 DEG C of heating rates per minute, 250 DEG C of insulations 10 minutes, then 700 DEG C are risen to 6.5 DEG C of heating rates per minute, 4 hours are incubated at 700 DEG C, start cooling after insulation terminates, cooling method is cool with stove.

9. solar battery array sheet of interconnect molybdenum/platinum/silver laminar metal matrix composite that the preparation technology described in claim 1 or 2 obtains.

10., according to solar battery array sheet of interconnect molybdenum/platinum/silver laminar metal matrix composite according to claim 9, it is characterized in that this composite material and the space gallium arsenide solar cell sheet hot strength of welding when carrying out single-point resistance spot welding is 324 gram forces.