CN108441668B - Silver-tungsten electric contact material and preparation method thereof - Google Patents
Silver-tungsten electric contact material and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a silver-tungsten electrical contact material, which adopts silver as a matrix material, tungsten as a first enhanced phase, graphene as a second enhanced phase and nickel as a third enhanced phase. The invention also relates to a preparation method of the silver-tungsten electrical contact material, which comprises the following steps: preparing silver/graphene oxide/nickel composite powder by a chemical method; mixing metal tungsten powder with the silver/graphene oxide/nickel composite powder to obtain silver/tungsten/graphene oxide/nickel composite powder; and reducing the silver/tungsten/graphene oxide/nickel composite powder to obtain silver/tungsten/graphene/nickel composite powder, and preparing the electric contact material by a powder metallurgy technology or a preform compression molding and air pressure infiltration technology. The invention improves the interface bonding quality of silver and tungsten due to the introduction of nickel; due to the introduction of the graphene, the fusion welding resistance of the material is improved, the high-temperature oxidation condition of tungsten is reduced, the contact resistance is reduced, the method is simple to operate, the process is easy to control, and the large-scale production is easy to realize.
Description
Technical Field
The invention relates to a preparation method of an electric contact composite material in the technical field of materials, in particular to a novel silver-tungsten electric contact material and a preparation method thereof.
Background
Silver-tungsten composite materials are one of the electrical contact materials widely used at present. Because the mechanical property and the electric contact property of pure silver are insufficient, in order to meet the use requirement of the electric contact material, other reinforcements are added to prepare the silver-based electric contact material by compounding with the silver. Tungsten is widely used as an optimal reinforcement for high current silver-based electrical contact materials. However, tungstate is generated in the process of switching on and off of a large current by the silver-tungsten material, and the tungstate is an electrical poor conductor, so that the contact resistance of the contact is increased, the temperature rise of the contact is increased, and finally fusion welding of the contact is caused to cause switch failure. The poor wettability of silver to tungsten leads to poor material interface bonding, which causes the increase of interface resistance and the reduction of material performance.
Graphene has attracted attention as a new carbon due to its excellent electrical conductivity, thermal conductivity, and high strength. Although the research development of the graphene reinforced metal matrix composite material is slow, the excellent electrical conductivity, thermal conductivity and mechanical properties of the graphene bring a great revolution to the improvement of the properties of the metal matrix composite material. The combination of the graphene and the traditional reinforcement is also a key for the significant breakthrough of the graphene, and the defects of the traditional material are made up by using certain properties of the graphene, so that the traditional material is optimized and improved.
The Chinese patent with publication number CN 105798319A provides a method and a device for preparing a silver-tungsten electrical contact material, which applies an in-situ synthesis method to prepare raw material powder of the silver-tungsten electrical contact, and the powder preparation engineering comprises the working procedures of material preparation, replacement reaction, separation, drying and reduction; and sintering to obtain the silver-tungsten composite material. The electric contact material is obtained, wherein the silver powder has uniform particle size, small particle size and easy regulation, and the silver powder and the tungsten particle film layer form compact combination. The invention does not improve the interface combination of silver and tungsten essentially, but directly compounds silver and tungsten, only changes the compound mode, and the prepared silver and tungsten material still has the problem of poor density. Meanwhile, the welding resistance of the silver-tungsten material is not improved.
The Chinese patent with the publication number of CN 104480335B provides a preparation method of a silver-tungsten contact material. Mixing silver powder and tungsten powder, placing the obtained silver-tungsten mixed powder, high-purity nickel balls and water in a ball mill for ball milling, and drying, annealing, forming and infiltrating the obtained ball-milled silver-tungsten mixed powder. The invention puts the silver-tungsten mixed powder, the high-purity nickel balls and the water into a ball mill according to a specific proportion to perform ball milling for a specific time, thereby not only enabling the mixing of the silver powder and the tungsten powder to be more uniform, but also realizing the simultaneous ball milling and the introduction of nickel elements, and enabling the nickel lost by the ball milling on the high-purity nickel balls to be uniformly covered on the surfaces of tungsten particles, thereby achieving the purpose of effectively improving the wettability of the silver on the tungsten. The invention patent considers the interface bonding of silver and tungsten, but still has some problems. According to the invention, the ball milling medium is water, the high-purity nickel balls are abraded by the hard particle tungsten in the ball milling process to obtain the micro-nano nickel powder, the micro-nano nickel powder is oxidized in the water by high temperature generated in the ball milling process to generate nickel oxide, and the nickel oxide and the tungsten cannot be combined, so that the tungsten particles covered by the nickel cannot be obtained. In addition, an interface improving element nickel is introduced in a grinding ball mode, the obtained nickel particles are irregular in shape, the nickel content is extremely difficult to control, the requirements in the field of electric contact cannot be met, and the nickel particles cannot be stably produced and applied in a large scale.
Therefore, the production process means with good interface combination, good fusion welding resistance, environmental protection, low cost and good controllability is used for realizing the preparation of the high-performance silver-tungsten electric contact material, and has important industrial upgrading value.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a novel silver-tungsten electric contact material based on chemical synthesis, powder metallurgy and liquid phase infiltration technologies and a preparation method thereof.
According to the invention, silver is used as a base material, tungsten is used as a first reinforcing phase, graphene is used as a second reinforcing phase, and nickel is used as a third reinforcing phase, so that the composite reinforced silver-tungsten electric contact material with high density, good conductivity, strong fusion welding resistance and low contact resistance is prepared. Meanwhile, the method is simple, the process controllability is good, the cost is low, the large-scale production is easy to realize, and the silver-tungsten electric contact material is uniform in tissue and stable in performance.
According to a first aspect of the present invention, there is provided a silver-tungsten electrical contact material, the material using silver as a matrix material, tungsten as a first reinforcing phase, graphene as a second reinforcing phase, and nickel as a third reinforcing phase, wherein:
the mass percentage of the tungsten is 12 wt% -85 wt%;
the mass percentage of the graphene is 0.1-8 wt%;
the mass percentage of the nickel is 0.5-3 wt%;
the balance being silver.
According to a second aspect of the present invention, there is provided a method for preparing the silver-tungsten electrical contact material, including:
preparing silver/graphene oxide/nickel composite powder by a chemical method;
mixing metal tungsten powder with the silver/graphene oxide/nickel composite powder to obtain silver/tungsten/graphene oxide/nickel composite powder;
reducing the silver/tungsten/graphene oxide/nickel composite powder to obtain silver/tungsten/graphene/nickel composite powder, wherein the addition amount of tungsten powder accounts for 12-85 wt% of the total mass of the silver/tungsten/graphene/nickel composite powder;
when the mass percentage of tungsten in the silver/tungsten/graphene/nickel composite powder is 12 wt% -25 wt%, preparing a silver/tungsten/graphene/nickel electric contact material by a powder metallurgy technology;
when the mass percentage of tungsten in the silver/tungsten/graphene/nickel composite powder is more than 25 wt% and less than or equal to 85 wt%, preparing the silver/tungsten/graphene/nickel electric contact material, namely the silver-tungsten electric contact material, by performing preform compression molding and air pressure infiltration technologies.
Preferably, the preparation of the silver/graphene oxide/nickel composite powder by using a chemical method refers to:
mixing a silver nitrate solution and a nickel nitrate solution to obtain a silver nitrate-nickel nitrate mixed solution;
mixing an ascorbic acid solution with a graphene oxide solution to obtain an ascorbic acid-graphene oxide mixed solution;
and mixing the silver nitrate-nickel nitrate mixed solution with the ascorbic acid-graphene oxide mixed solution to obtain silver/graphene oxide/nickel composite powder.
More preferably, the silver/graphene oxide/nickel composite powder prepared by the chemical method has one or more of the following characteristics:
-the concentration of the silver nitrate solution and the nickel nitrate solution are both 0.05mol/L-2 mol/L;
-the concentration of the ascorbic acid solution is between 0.05mol/L and 2 mol/L;
-the mass concentration of the graphene oxide solution is 2-2.5%;
the addition amount of the graphene oxide accounts for 0.1-8 wt% of the total mass of the final silver-tungsten electric contact material.
More preferably, the silver nitrate-nickel nitrate mixed solution is mixed with the ascorbic acid-graphene oxide mixed solution, wherein:
the silver nitrate and the nickel nitrate are reduced by ascorbic acid, nickel is partially or completely coated on the surface of the silver powder, and the coated powder is deposited on the surface of the graphene to obtain a suspension of the silver/graphene oxide/nickel composite powder, and the suspension is settled, washed and dried to obtain pure silver/graphene oxide/nickel composite powder.
More preferably, the addition amount of the nickel accounts for 0.5-3 wt% of the total mass of the final silver-tungsten electric contact material.
Preferably, the metal tungsten powder is mixed with the silver/graphene oxide/nickel composite powder, wherein:
putting the silver/graphene oxide/nickel composite powder and tungsten powder into an alcohol medium by a planetary ball milling method, performing ball milling and mixing, drying and sieving to obtain the silver/tungsten/graphene oxide/nickel composite powder.
Preferably, the silver/tungsten/graphene oxide/nickel composite powder is subjected to reduction treatment, wherein:
and (3) placing the silver/tungsten/graphene oxide/nickel composite powder in hydrogen or hydrogen mixed gas atmosphere for reduction treatment, removing oxygen-containing groups on the surface of graphene oxide, and improving the conductivity of the composite material.
More preferably, the reduction treatment, wherein: the heating temperature is 350-700 ℃, and the heating time is 2-6 hours.
Preferably, when the mass content of tungsten in the silver/tungsten/graphene/nickel composite powder is 12 wt% -25 wt%, the silver/tungsten/graphene/nickel composite powder is pressed and molded, and is sintered at 800-900 ℃ for 8-16 hours in the presence of hydrogen, so that the silver/tungsten/graphene/nickel composite material is finally obtained.
When the mass content of tungsten in the silver/tungsten/graphene/nickel composite powder is 26 wt% -85 wt%, performing preform pressing on the silver/tungsten/graphene/nickel composite powder to obtain a silver/tungsten/graphene/nickel framework structure, sintering the framework structure at 600-800 ℃ for 5-8 hours, wherein the sintering atmosphere is hydrogen; and (2) placing the sintered framework on a silver infiltration sheet, and carrying out air pressure infiltration at the heating temperature of 900-950 ℃ for 4-8 hours, wherein the sintering process is vacuum sintering, argon or helium rare gas is used in the air pressure infiltration stage, the infiltration temperature is 980-1100 ℃, and the gas pressure is 100MPa-1GPa, so that the silver/tungsten/graphene/nickel composite material is finally obtained.
Firstly, preparing silver/graphene oxide/nickel composite powder by a chemical method, and then mixing metal tungsten powder with the silver/graphene oxide/nickel composite powder, wherein when the mass fraction of tungsten in the composite powder is 12-25 wt%, the powder is subjected to reduction treatment and powder metallurgy technology to prepare a silver/tungsten/graphene/nickel electric contact material; when the mass fraction of tungsten in the composite powder is more than 25 wt% and less than or equal to 85 wt%, the powder is subjected to reduction treatment, preform compression molding and air pressure infiltration technology to prepare the silver/tungsten/graphene/nickel electric contact material. The silver/tungsten/graphene/nickel material maintains the original performance of the traditional silver tungsten, the interface bonding quality of the silver tungsten is improved due to the introduction of nickel, meanwhile, the fusion welding resistance of the material is improved due to the introduction of graphene, the high-temperature oxidation condition of tungsten is reduced, and the contact resistance is reduced.
According to the invention, the addition amounts of tungsten, graphene and nickel and the morphology particle size of the silver matrix can be conveniently controlled, preferably, the addition amount of tungsten is 12-85 wt%, and the addition amount of graphene oxide is 0.1-8 wt%. The addition amount of the nickel is 0.5 to 3 weight percent, and the balance is silver. The novel silver-tungsten electric contact material prepared by the invention obviously reduces and stabilizes the contact resistance of the traditional silver-tungsten material, and effectively improves the fusion welding resistance of the traditional silver-tungsten material. The invention can be well applied to the requirements of high-current application.
Compared with the prior art, the invention has the following beneficial effects:
(1) the nickel is added by a chemical reduction method, the nickel content is controllable in appearance, meanwhile, the nickel is dispersed in a matrix more uniformly and finely, and is partially or completely coated on the surface of silver particles.
(2) The graphene is added, so that the contact resistance of the electric contact material is favorably reduced, the defects that the contact resistance of the traditional silver-tungsten material is large and unstable are overcome, meanwhile, the generation of tungsten oxide and silver tungstate can be inhibited due to the existence of the graphene, and the reliability of the electric contact material is improved.
(3) When the tungsten content is 26-85 wt%, the invention adopts a gas pressure infiltration method. Compared with the traditional pressureless infiltration method, the electric contact material with higher density can be obtained, thereby improving the yield of the material and various performance indexes of the material.
By adopting the technical scheme of the invention, the novel silver-tungsten electric contact material (silver/tungsten/graphene/nickel) with excellent performance can be prepared by the mutual matching of the technologies such as chemical synthesis, powder metallurgy, liquid-phase infiltration and the like. Compared with the traditional silver-tungsten electric contact material, the electric service life of the silver/tungsten/graphene/nickel electric contact material is improved by 20-30%, and the contact resistance is reduced by 5-15%.
The invention realizes the preparation of the novel high-performance silver-tungsten electric contact material by a production process means with environmental protection, low cost and good controllability, and has not only important industrial value but also wide high-end application prospect.
Drawings
FIG. 1 is a flow chart illustrating the preparation of a preferred embodiment of the present invention having a tungsten content of 12 wt% to 25 wt%;
FIG. 2 is a flow chart of the preparation of a preferred embodiment of the present invention having a tungsten content of greater than 25 wt% and less than or equal to 85 wt%.
Detailed Description
The technical solutions of the present invention are further described below, and the following description is only for understanding the technical solutions of the present invention and is not intended to limit the scope of the present invention, which is defined by the claims.
As shown in fig. 1, the figure is a flow chart of the preparation process of the silver-tungsten electrical contact material with a tungsten content of 12 wt% to 25 wt%, and the preparation process of the silver-tungsten electrical contact material can be performed sequentially according to the flow chart, or individual steps of the preparation process can be selected according to actual application requirements.
As shown in fig. 2, which is a flow chart of the preparation process of the silver-tungsten electrical contact material with a tungsten content of greater than 25 wt% and less than or equal to 85 wt%, the preparation process of the silver-tungsten electrical contact material may be performed sequentially according to the flow chart, or may be selected to perform individual steps according to actual application requirements.
In the invention, the silver-tungsten electrical contact material is silver/tungsten/graphene/nickel electrical contact material, wherein the tungsten content can be preferably 25 wt% -65 wt%; the content of the graphene can be preferably 1 wt% -5 wt%, and is further preferably 3 wt% -5 wt%; the content of the nickel may be preferably 1.2 wt% to 3 wt%, and more preferably 1.2 wt% to 1.5 wt%.
Example 1
The embodiment provides a preparation method of a silver/tungsten/graphene/nickel electrical contact material, which comprises the following operation steps:
i) Material composition of silver/tungsten/graphene/Nickel electric contact Material
The silver/tungsten/graphene/nickel electric contact material mainly comprises metal silver, metal tungsten, graphene and metal nickel, wherein the content of tungsten is 12 wt%, the content of graphene is 0.1 wt%, the content of nickel is 0.5 wt%, and the balance is silver.
II) basic procedure for preparing silver/tungsten/graphene/nickel electrical contact materials (see the flow chart in the attached figure 1)
1) Preparing 0.1mol/L silver nitrate solution, 0.1mol/L nickel nitrate solution and 0.1mol/L ascorbic acid solution (or one or more of glucose, citric acid or oxalic acid).
2) According to the composition of the material, a certain amount of ascorbic acid solution is mixed with a graphene oxide solution with the mass concentration of 2%, and the mixture is uniformly stirred.
3) Mixing the mixed solution obtained in the step 1) and the mixed solution obtained in the step 2) with mechanical stirring or magneton stirring. And reducing the silver nitrate and the nickel nitrate by ascorbic acid, growing and depositing on the surface of the graphene oxide to generate a silver/graphene oxide/nickel suspension, settling, centrifugally washing and drying the silver/graphene oxide/nickel suspension to obtain the silver/graphene oxide/nickel composite powder.
4) The method is characterized in that a planetary ball mill (or a high-energy ball mill/V-shaped mixer) is used, the grinding balls adopt agate balls, the grinding pot adopts an agate pot, and the ball-material ratio is 5: 1, mixing the obtained silver/graphene oxide/nickel composite powder with a certain amount of tungsten powder for 8 hours to obtain the silver/tungsten/graphene oxide/nickel composite powder.
5) And (2) heating and reducing the silver/tungsten/graphene oxide/nickel composite powder for 2 hours at 400 ℃ in a hydrogen atmosphere to obtain the silver/tungsten/graphene/nickel composite powder, wherein the tungsten content is 12 wt%, the graphene content is 0.1 wt%, the nickel content is 0.5 wt%, and the balance is silver.
6) And pressing and molding the silver/tungsten/graphene/nickel composite powder by using a compression molding technology to obtain a silver/tungsten/graphene/nickel blank, placing the blank in a sintering furnace, and sintering at 870 ℃ for 13 hours in a hydrogen atmosphere to obtain the highly compact silver/tungsten/graphene/nickel composite material.
Example 2
The main differences from example 1 are: in this example 2, the tungsten content is 25 wt%, the graphene content is 3 wt%, the nickel content is 1.5 wt%, and the balance is silver.
The preparation of the silver/tungsten/graphene/nickel electrical contact material of the embodiment comprises the following operation steps:
i) Material composition of silver/tungsten/graphene/Nickel electric contact Material
The silver/tungsten/graphene/nickel electric contact material mainly comprises the following components of metal silver, metal tungsten, graphene and metal nickel, wherein the content of tungsten is 25 wt%, the content of graphene is 3 wt%, the content of nickel is 1.5 wt%, and the balance is silver.
II) basic procedure for preparing silver/tungsten/graphene/nickel electrical contact material (see the process flow in the attached figure 1)
1) Preparing 0.2mol/L silver nitrate solution, 0.2mol/L nickel nitrate solution and 0.2mol/L citric acid solution.
2) According to the composition of the material, a certain amount of citric acid solution is mixed with a graphene oxide solution with the mass concentration of 1.8%, and the mixture is uniformly stirred.
3) Mixing the mixed solution obtained in the step 1) and the mixed solution obtained in the step 2) with mechanical stirring or magneton stirring. And reducing the silver nitrate and the nickel nitrate by using citric acid, growing and depositing on the surface of the graphene oxide to generate a silver/graphene oxide/nickel suspension, settling, centrifugally washing and drying the silver/graphene oxide/nickel suspension to obtain the silver/graphene oxide/nickel composite powder.
4) And (3) mixing the obtained silver/graphene oxide/nickel composite powder with a quantitative tungsten powder by using a V-shaped mixer (or a high-energy ball mill/a planetary ball mill) for 10 hours to obtain the silver/tungsten/graphene oxide/nickel composite powder.
5) And (2) heating and reducing the silver/tungsten/graphene oxide/nickel composite powder for 2.5 hours at 420 ℃ in a hydrogen atmosphere to obtain the silver/tungsten/graphene/nickel composite powder, wherein the tungsten content is 25 wt%, the graphene content is 3 wt%, the nickel content is 1.5 wt%, and the balance is silver.
6) And pressing and molding the silver/tungsten/graphene/nickel composite powder by using a compression molding technology to obtain a silver/tungsten/graphene/nickel blank, placing the blank in a sintering furnace, and sintering for 16 hours at 900 ℃ in a hydrogen atmosphere to obtain the highly compact silver/tungsten/graphene/nickel composite material.
Example 3
This embodiment 3 provides a preparation method of a silver/tungsten/graphene/nickel electrical contact material, including the following steps:
i) Material composition of silver/tungsten/graphene/Nickel electric contact Material
The silver/tungsten/graphene/nickel electric contact material mainly comprises metal silver, metal tungsten, graphene and metal nickel, wherein the content of tungsten is 26 wt%, the content of graphene is 1 wt%, the content of nickel is 1.2 wt%, and the balance is silver.
II) basic procedure for preparing silver/tungsten/graphene/nickel electrical contact material (see the process flow in the attached figure 2)
1) Preparing 1mol/L silver nitrate solution, 1mol/L nickel nitrate solution and 1mol/L ascorbic acid solution.
2) According to the composition of the material, a certain amount of ascorbic acid solution is mixed with a graphene oxide solution with the mass concentration of 2%, and the mixture is uniformly stirred.
3) Mixing the mixed solution obtained in the step 1) and the mixed solution obtained in the step 2) with mechanical stirring. And reducing the silver nitrate and the nickel nitrate by ascorbic acid, growing and depositing on the surface of the graphene oxide to generate a silver/graphene oxide/nickel suspension, settling, centrifugally washing and drying the silver/graphene oxide/nickel suspension to obtain the silver/graphene oxide/nickel composite powder.
4) A planetary ball mill is used, the grinding balls adopt agate balls, the grinding pot adopts an agate pot, and the ball material ratio is 4: 1, mixing the obtained silver/graphene oxide/nickel composite powder with a certain amount of tungsten powder for 7 hours to obtain the silver/tungsten/graphene oxide/nickel composite powder.
5) And (3) heating and reducing the silver/tungsten/graphene oxide/nickel composite powder for 2 hours at 400 ℃ in a hydrogen atmosphere to obtain the silver/tungsten/graphene/nickel composite powder.
6) And pressing the silver/tungsten/graphene/nickel composite powder into a preform framework by using a compression molding technology to obtain a silver/tungsten/graphene/nickel preform, placing the preform in a sintering furnace, and sintering at 700 ℃ for 5 hours in a hydrogen atmosphere to obtain the silver/tungsten/graphene/nickel composite preform with pores.
7) Placing the preform in step 6) in a graphite mold, which is in strict conformity with the shape and size of the preform, while placing the silver infiltrated sheet on the bottom of the preform. And (3) placing the die in an infiltration furnace, heating at 900 ℃ for 6 hours in a vacuum state, heating to 1050 ℃ after heat preservation for 6 hours, filling argon into the furnace when the temperature is reached, wherein the air pressure is 100MPa, and carrying out air pressure infiltration for 0.5 hour to finally obtain the silver/tungsten/graphene/nickel composite material.
Example 4
The main differences from example 3 are: in this example, the tungsten content of the product is 65 wt%, the graphene content is 5 wt%, the nickel content is 3 wt%, and the balance is silver.
In the preparation of the silver/tungsten/graphene/nickel electrical contact material in this embodiment, the operation steps are as follows:
i) Material composition of silver/tungsten/graphene/Nickel electric contact Material
The silver/tungsten/graphene/nickel electric contact material mainly comprises metal silver, metal tungsten, graphene and metal nickel, wherein the content of tungsten is 65 wt%, the content of graphene is 5 wt%, the content of nickel is 3 wt%, and the balance is silver.
II) basic procedure for preparing silver/tungsten/graphene/nickel electrical contact material (see the process flow in the attached figure 2)
1) Preparing 2mol/L silver nitrate solution, 2mol/L nickel nitrate solution and 2mol/L ascorbic acid solution.
2) According to the composition of the material, a certain amount of ascorbic acid solution is mixed with a graphene oxide solution with the mass concentration of 2.5%, and the mixture is uniformly stirred.
3) Mixing the mixed solution obtained in the step 1) and the mixed solution obtained in the step 2) with mechanical stirring. And reducing the silver nitrate and the nickel nitrate by ascorbic acid, growing and depositing on the surface of the graphene oxide to generate a silver/graphene oxide/nickel suspension, settling, centrifugally washing and drying the silver/graphene oxide/nickel suspension to obtain the silver/graphene oxide/nickel composite powder.
4) A planetary ball mill is used, the grinding balls adopt agate balls, the grinding pot adopts an agate pot, and the ball material ratio is 6: 1, mixing the obtained silver/graphene oxide/nickel composite powder with a certain amount of tungsten powder for 9 hours to obtain the silver/tungsten/graphene oxide/nickel composite powder.
5) And (3) heating and reducing the silver/tungsten/graphene oxide/nickel composite powder for 2.5 hours at 450 ℃ in a hydrogen atmosphere to obtain the silver/tungsten/graphene/nickel composite powder.
6) And pressing the silver/tungsten/graphene/nickel composite powder into a preform framework by using a compression molding technology to obtain a silver/tungsten/graphene/nickel preform, placing the preform in a sintering furnace, and sintering at 800 ℃ for 6 hours in a hydrogen atmosphere to obtain the silver/tungsten/graphene/nickel composite preform with pores.
7) Placing the preform in step 6) in a graphite mold, which is in strict conformity with the shape and size of the preform, while placing the silver infiltrated sheet on the bottom of the preform. And (3) placing the die in an infiltration furnace, heating the die for 7 hours at 950 ℃ in a vacuum state, heating the die to 1100 ℃ after the heat preservation for 7 hours, filling argon into the furnace when the temperature is reached, wherein the air pressure is 0.5GPa, and carrying out air pressure infiltration for 0.5 hour to finally obtain the silver/tungsten/graphene/nickel composite material.
It should be understood that the above examples are only some embodiments of the present invention, and the silver-tungsten electrical contact material of the present invention includes all systems suitable for the product, such as changing the content of the silver and other elements in the matrix, or using other silver salt solutions in combination with reducing agents, and the graphene, nickel reinforcement and tungsten reinforcement can be any other addition method, and the formulation of the final composite material can be designed according to the actual application requirements.
While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.
Claims (10)
1. A silver-tungsten electrical contact material is characterized in that: the material adopts silver as a matrix material, tungsten as a first reinforcing phase, graphene as a second reinforcing phase and nickel as a third reinforcing phase, wherein:
the mass percentage of the tungsten is 12 wt% -85 wt%;
the mass percentage of the graphene is 0.1-8 wt%;
the mass percentage of the nickel is 0.5-3 wt%;
the balance being silver;
the silver-tungsten electric contact material is prepared by the following method:
preparing silver/graphene oxide/nickel composite powder by a chemical method, wherein nickel is partially or completely coated on the surface of the silver powder, and the coated powder is deposited on the surface of graphene;
mixing metal tungsten powder with the silver/graphene oxide/nickel composite powder to obtain silver/tungsten/graphene oxide/nickel composite powder;
reducing the silver/tungsten/graphene oxide/nickel composite powder to obtain silver/tungsten/graphene/nickel composite powder, wherein the addition amount of tungsten powder accounts for 12-85 wt% of the total mass of the silver/tungsten/graphene/nickel composite powder;
when the mass percentage of tungsten in the silver/tungsten/graphene/nickel composite powder is 12 wt% -25 wt%, preparing a silver/tungsten/graphene/nickel electric contact material by a powder metallurgy technology;
when the mass percentage of tungsten in the silver/tungsten/graphene/nickel composite powder is more than 25 wt% and less than or equal to 85 wt%, preparing the silver/tungsten/graphene/nickel electric contact material, namely the silver-tungsten electric contact material, by performing preform compression molding and air pressure infiltration technologies.
2. A method for preparing the silver-tungsten electrical contact material of claim 1, which is characterized by comprising the following steps: the method comprises the following steps:
preparing silver/graphene oxide/nickel composite powder by a chemical method;
mixing metal tungsten powder with the silver/graphene oxide/nickel composite powder to obtain silver/tungsten/graphene oxide/nickel composite powder;
reducing the silver/tungsten/graphene oxide/nickel composite powder to obtain silver/tungsten/graphene/nickel composite powder, wherein the addition amount of tungsten powder accounts for 12-85 wt% of the total mass of the silver/tungsten/graphene/nickel composite powder;
when the mass percentage of tungsten in the silver/tungsten/graphene/nickel composite powder is 12 wt% -25 wt%, preparing a silver/tungsten/graphene/nickel electric contact material by a powder metallurgy technology;
when the mass percentage of tungsten in the silver/tungsten/graphene/nickel composite powder is more than 25 wt% and less than or equal to 85 wt%, preparing the silver/tungsten/graphene/nickel electric contact material, namely the silver-tungsten electric contact material, by performing preform compression molding and air pressure infiltration technologies.
3. The method for preparing the silver-tungsten electrical contact material according to claim 2, wherein the method comprises the following steps: the silver/graphene oxide/nickel composite powder prepared by the chemical method is prepared by the following steps:
mixing a silver nitrate solution and a nickel nitrate solution to obtain a silver nitrate-nickel nitrate mixed solution;
mixing an ascorbic acid solution with a graphene oxide solution to obtain an ascorbic acid-graphene oxide mixed solution;
and mixing the silver nitrate-nickel nitrate mixed solution with the ascorbic acid-graphene oxide mixed solution to obtain silver/graphene oxide/nickel composite powder.
4. The method for preparing the silver-tungsten electrical contact material according to claim 3, wherein the method comprises the following steps: has one or more of the following characteristics:
-the concentration of the silver nitrate solution and the nickel nitrate solution are both 0.05mol/L-2 mol/L;
-the concentration of the ascorbic acid solution is between 0.05mol/L and 2 mol/L;
-the mass concentration of the graphene oxide solution is 2-2.5%;
the addition amount of the graphene oxide accounts for 0.1-8 wt% of the total mass of the final silver-tungsten electric contact material.
5. The method for preparing the silver-tungsten electrical contact material according to claim 3, wherein the method comprises the following steps: mixing the silver nitrate-nickel nitrate mixed solution with the ascorbic acid-graphene oxide mixed solution, wherein:
the silver nitrate and the nickel nitrate are reduced by ascorbic acid, nickel is partially or completely coated on the surface of the silver powder, and the coated powder is deposited on the surface of the graphene to obtain a suspension of the silver/graphene oxide/nickel composite powder, and the suspension is settled, washed and dried to obtain pure silver/graphene oxide/nickel composite powder.
6. The method for preparing the silver-tungsten electrical contact material according to claim 5, wherein the method comprises the following steps: wherein the addition amount of the nickel accounts for 0.5-3 wt% of the total mass of the final silver-tungsten electric contact material.
7. The method for preparing the silver-tungsten electrical contact material according to claim 2, wherein the method comprises the following steps: mixing metal tungsten powder with the silver/graphene oxide/nickel composite powder, wherein:
putting the silver/graphene oxide/nickel composite powder and tungsten powder into an alcohol medium by a planetary ball milling method, performing ball milling and mixing, drying and sieving to obtain the silver/tungsten/graphene oxide/nickel composite powder.
8. The method for preparing the silver-tungsten electrical contact material according to claim 2, wherein the method comprises the following steps: carrying out reduction treatment on the silver/tungsten/graphene oxide/nickel composite powder, wherein:
and (3) placing the silver/tungsten/graphene oxide/nickel composite powder in hydrogen or hydrogen mixed gas atmosphere for reduction treatment, removing oxygen-containing groups on the surface of graphene oxide, and improving the conductivity of the composite material.
9. The method for preparing the silver-tungsten electrical contact material according to claim 8, wherein the method comprises the following steps: the reduction treatment, wherein: the heating temperature is 350-700 ℃, and the heating time is 2-6 hours.
10. The method for preparing a silver-tungsten electrical contact material according to any one of claims 2 to 9, wherein: when the mass content of tungsten in the silver/tungsten/graphene/nickel composite powder is 12 wt% -25 wt%, the silver/tungsten/graphene/nickel composite powder is pressed and molded, and is sintered at 800-900 ℃ for 8-16 hours in the presence of hydrogen, so that the silver/tungsten/graphene/nickel composite material is finally obtained;
when the mass content of tungsten in the silver/tungsten/graphene/nickel composite powder is 26 wt% -85 wt%, performing preform pressing on the silver/tungsten/graphene/nickel composite powder to obtain a silver/tungsten/graphene/nickel framework structure, sintering the framework structure at 600-800 ℃ for 5-8 hours, wherein the sintering atmosphere is hydrogen; and (2) placing the sintered framework on a silver infiltration sheet, and carrying out air pressure infiltration at the heating temperature of 900-950 ℃ for 4-8 hours, wherein the sintering process is vacuum sintering, argon or helium rare gas is used in the air pressure infiltration stage, the infiltration temperature is 980-1100 ℃, and the gas pressure is 100MPa-1GPa, so that the silver/tungsten/graphene/nickel composite material is finally obtained.
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