CN114664477B - Preparation method of copper-based flexible composite material - Google Patents
Preparation method of copper-based flexible composite material Download PDFInfo
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- CN114664477B CN114664477B CN202210351815.9A CN202210351815A CN114664477B CN 114664477 B CN114664477 B CN 114664477B CN 202210351815 A CN202210351815 A CN 202210351815A CN 114664477 B CN114664477 B CN 114664477B
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- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/20—Conductive material dispersed in non-conductive organic material
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- H—ELECTRICITY
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- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/20—Conductive material dispersed in non-conductive organic material
- H01B1/24—Conductive material dispersed in non-conductive organic material the conductive material comprising carbon-silicon compounds, carbon or silicon
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- H—ELECTRICITY
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Abstract
The invention belongs to the technical field of flexible electronic printing, and particularly relates to copper-based conductive ink, a preparation method thereof, a copper-based flexible composite material and application thereof. The invention provides copper-based conductive ink, which comprises the following components in percentage by mass: 0.1 to 0.7 percent of graphene/copper composite material, 52.1 to 59.1 percent of nano copper, 2 to 5 percent of binder and 38 to 43 percent of organic solvent. The copper-based flexible composite material prepared by the copper-based conductive ink provided by the invention contains the graphene/copper composite material, when the copper-based flexible composite material is subjected to external force, cracks are generated among sintered nano copper tissues, and when the cracks are expanded to the graphene/copper composite material, the further expansion of the cracks can be prevented due to the strong mechanical property of the graphene, so that the fatigue resistance of the copper-based flexible composite material is improved, and further, the flexible circuit prepared by the copper-based flexible composite material is ensured to have lower resistivity change rate.
Description
Technical Field
The invention belongs to the technical field of flexible electronic printing, and particularly relates to a preparation method of a copper-based flexible composite material.
Background
The flexible printed electronic technology is an electronic manufacturing technology based on a printing principle and is widely applied to the fields of flexible touch screen panels, sensors, power electronic packages, flexible circuits, solar cells and the like. The flexible printed electronic material for flexible printed electronic technology is obtained by depositing conductive ink on the surface of a substrate and then sintering. Nano metal has the characteristics of low sintering temperature, strong conductivity, strong flexibility and the like, and becomes one of important materials of conductive ink. Silver (Ag) and gold (Au) have excellent conductivity and stability, and nano-silver conductive ink and nano-gold conductive ink are ideal choices for preparing flexible printed electronic materials, however, silver and gold are expensive and are not suitable for large-scale use in industrial production. The development of the flexible printed electronic material with low price, good conductivity and fatigue resistance has great significance for promoting the industrialization of flexible printed electronics.
Copper has conductivity inferior to silver, which has the best conductivity, but its price is only one percent of silver, so nano-copper conductive ink is one of the most promising metallic materials in flexible printed electronic materials. However, nano copper has strong oxidation tendency, and fatigue resistance of the nano copper is reduced after oxidation, so that the resistivity of a formed flexible circuit is rapidly increased after long-time working, and the flexible circuit cannot stably work for a long time, thereby preventing the application of copper in flexible printed electronics.
Disclosure of Invention
In view of the above, the invention provides a preparation method of a copper-based flexible composite material, and the copper-based flexible composite material prepared by the copper-based conductive ink provided by the invention has higher fatigue resistance.
In order to solve the technical problems, the invention provides copper-based conductive ink which comprises the following components in percentage by mass:
preferably, the average particle size of the nano copper is 20-100 nm;
the mass ratio of graphene to copper in the graphene/copper composite material is 5.8-6.2:1.
Preferably, the binder comprises polyvinylpyrrolidone or sodium carboxymethylcellulose;
the organic solvent includes an alcohol solvent.
The invention also provides a preparation method of the copper-based conductive ink, which comprises the following steps:
and mixing the graphene/copper composite material, nano copper, a binder and an organic solvent to obtain the copper-based conductive ink.
Preferably, the mixing is ball milling;
the ball-milling ball-material ratio is 2-3:1;
the ball for ball milling is an agate ball, and the agate ball is an agate ball with the diameter of 5mm and an agate ball with the diameter of 8 mm;
the mass ratio of the agate balls with the diameter of 8mm to the agate balls with the diameter of 5mm is 15.8-16.2:3.
Preferably, the rotation speed of the ball milling is 380-420 r/min; the ball milling time is 7-9 h.
The invention provides a copper-based flexible composite material, which comprises a base material and a copper-based composite material deposited on the surface of the base material;
the copper-based composite material is obtained by sintering the copper-based conductive ink prepared by the technical scheme or the preparation method.
Preferably, the sintering temperature is 300-330 ℃; the sintering time is 15-40 min.
Preferably, the substrate comprises polyimide or polyvinyl alcohol.
The invention also provides application of the copper-based flexible composite material as a flexible printed electronic material.
The invention provides copper-based conductive ink, which comprises the following components in percentage by mass: 0.1 to 0.7 percent of graphene/copper composite material, 52.1 to 59.1 percent of nano copper, 2 to 5 percent of binder and 38 to 43 percent of organic solvent. The copper-based conductive ink provided by the invention contains the graphene/copper composite material, and the graphene/copper composite material is contained in the copper-based flexible composite material when the copper-based flexible composite material is used for preparing the copper-based flexible composite material, so that cracks can be generated among sintered nano copper tissues when the copper-based flexible composite material is subjected to external force, and when the cracks are expanded to the graphene/copper composite material, the cracks can be prevented from further expansion due to the strong mechanical property of the graphene, so that the fatigue resistance of the copper-based flexible composite material is improved, and further, the flexible circuit prepared from the copper-based flexible composite material is ensured to have a lower resistivity change rate.
Drawings
FIG. 1 is a schematic flow chart of a process for preparing a copper-based flexible composite;
FIG. 2 is an SEM image of a copper-based flexible composite material prepared in example 1;
FIG. 3 is a graph showing the resistivity histogram of the copper-based flexible composite materials prepared in examples 1 to 3 and comparative example 1;
FIG. 4 is a schematic diagram of a fatigue test;
fig. 5 is a fatigue line graph of the copper-based flexible composite materials prepared in examples 1 to 3 and comparative example 1.
Detailed Description
The invention provides copper-based conductive ink, which comprises the following components in percentage by mass:
in the invention, the copper-based conductive ink comprises 0.1 to 0.7% of graphene/copper composite material, preferably 0.5 to 0.6% by mass. In the invention, the mass ratio of graphene to copper in the graphene/copper composite material is preferably 5.8-6.2:1, and more preferably 6:1. In the invention, the graphene/copper composite material is preferably prepared according to the following steps:
mixing graphene, potassium permanganate and concentrated sulfuric acid, and performing an oxidation reaction to obtain graphene oxide;
mixing the graphene oxide, an activating agent, a buffering agent, a complexing agent, a copper source and water for ultrasonic treatment to obtain copper ion-loaded graphene oxide;
and mixing the graphene oxide loaded with copper ions with a reducing agent, and carrying out a reduction reaction to obtain the graphene/copper composite material.
According to the invention, graphene, potassium permanganate and concentrated sulfuric acid are mixed, and oxidation reaction is carried out to obtain graphene oxide. In the invention, the mass ratio of the graphene to the potassium permanganate is preferably 1:4.3-4.7, and more preferably 1:4.5. In the invention, the volume ratio of the mass of the graphene to the concentrated sulfuric acid is preferably 5 g:18-22 mL, and more preferably 5g:20mL. In the present invention, the mixing is preferably performed in an ice-water bath, and the mixing is preferably performed under stirring for a period of preferably 18 to 22 minutes, more preferably 20 minutes. The invention has no special requirement on the stirring rotation speed, and can be uniformly mixed. In the present invention, the oxidation reaction is performed during the mixing. In the invention, the stirring ensures that the oxidation reaction is uniformly and fully carried out; hydroxyl or carboxyl functional groups are inserted into the surface of graphene in the oxidation reaction process, so that the graphene is oxidized.
In the present invention, the oxidation reaction preferably further comprises:
mixing the oxidation reaction system with hydrogen peroxide, and performing chemical reaction to obtain manganese sulfate;
mixing the system after chemical reaction with hydrochloric acid aqueous solution, and centrifuging to obtain a solid;
and mixing the solid with water, and freeze-drying to obtain the graphene oxide.
The invention mixes the oxidation reaction system with hydrogen peroxide to carry out chemical reaction to obtain manganese sulfate. The present invention is not particularly limited as long as the mixing can be uniformly performed. In the invention, the chemical reaction is that hydrogen peroxide and potassium permanganate react in an acidic environment to generate manganese sulfate to remove the potassium permanganate remained after the oxidation reaction. The invention has no special requirement on the dosage of the hydrogen peroxide, and only needs to fully react the residual potassium permanganate in the oxidation reaction.
After manganese sulfate is obtained, the system after chemical reaction and hydrochloric acid aqueous solution are mixed and then are subjected to centrifugal treatment to obtain solid. In the present invention, the mass concentration of the aqueous hydrochloric acid solution is preferably 8 to 12%, more preferably 10%. The present invention is not particularly limited as long as the mixture is uniform. In the invention, the graphene oxide has good dispersibility in water, and the addition of the aqueous hydrochloric acid solution is favorable for separating the graphene oxide from water. In the present invention, the number of times of the centrifugation is preferably 5 to 7 times, more preferably 6 times. The invention has no special requirement on the rotation speed of the centrifugal treatment, and only needs to realize solid-liquid separation. In the invention, the centrifugal treatment process is preferably carried out under ultrasonic conditions, and the power of the ultrasonic waves is preferably 110-130W, more preferably 120W; the frequency of the ultrasonic wave is preferably 38-42 KHz, more preferably 40KHz; the time of the ultrasonic wave is preferably 55 to 65 seconds, more preferably 58 to 60 seconds. In the invention, the ultrasonic waves can wash away dirt adsorbed on the surface of the graphene oxide.
After the solid is obtained, the graphene oxide is obtained by mixing the solid with water and freeze-drying the mixture. In the present invention, the water is preferably deionized water. In the present invention, the ratio of the mass of the solid to the volume of water is preferably 1 mg/0.8 to 1.2mL, more preferably 1 mg/1 mL. In the present invention, the temperature of the freeze-drying is preferably 30 to 50 ℃, more preferably 40 to 45 ℃; the time for the freeze-drying is preferably 46 to 50 hours, more preferably 47 to 48 hours. In the invention, the addition of water during the freeze-drying process can enable graphene oxide to be dispersed in water without generating a large amount of aggregation.
In the invention, after graphene oxide is obtained, the graphene oxide, an activating agent, a buffering agent, a complexing agent, a copper source and water are mixed for ultrasonic treatment, so that the copper ion-loaded graphene oxide is obtained. In the present invention, the mixing preferably includes the steps of:
firstly mixing graphene oxide with part of water to obtain a graphene oxide solution;
mixing an activating agent, a buffering agent, a complexing agent, a copper source and the rest of water for the second time to obtain a mixed solution;
and thirdly mixing the graphene oxide solution and the mixed solution.
According to the invention, graphene oxide and part of water are mixed for the first time to obtain a graphene oxide solution. In the present invention, the water is preferably deionized water. In the present invention, the mass concentration of the graphene oxide solution is preferably 0.8 to 1.2mg/mL, more preferably 1mg/mL. The present invention is not particularly limited as long as the mixing can be uniformly performed.
In the present invention, the first mixed product is preferably subjected to a first ultrasonic treatment, and the power of the first ultrasonic treatment is preferably 110-130W, more preferably 120W; the frequency of the first ultrasonic treatment is preferably 38-42 KHz, more preferably 40KHz; the time of the first ultrasonic treatment is preferably 55 to 65 minutes, more preferably 58 to 60 minutes.
In the invention, the first ultrasonic treatment preferably disperses graphene oxide, which is beneficial to plating more copper on each piece of graphene oxide.
The invention mixes the activator, buffer, complexing agent, copper source and the rest water to obtain mixed solution. In the present invention, the activator is preferably nickel sulfate; the buffer is preferably boric acid; the complexing agent is preferably citric acid; the copper source is preferably copper sulfate. In the present invention, the mass concentration of the activator in the mixed solution is preferably 0.8 to 1g/L, more preferably 0.9g/L; the mass concentration of the buffer in the mixed solution is preferably 28-32 g/L, more preferably 30g/L; the mass concentration of the complexing agent in the mixed solution is preferably 18-22 g/L, more preferably 20g/L; the mass concentration of the copper source in the mixed solution is preferably 8 to 12g/L, more preferably 10g/L. The invention has no special requirement on the second mixing mode, so long as the second mixing mode can be uniformly mixed.
After the graphene oxide solution and the mixed solution are obtained, the graphene oxide solution and the mixed solution are subjected to third mixing. In the present invention, the temperature of the third mixture is preferably 48 to 52 ℃, more preferably 50 ℃. The third mixing mode is not particularly limited in the present invention, as long as the third mixing mode can be uniformly mixed.
In the present invention, the power of the ultrasonic treatment is preferably 110 to 130W, more preferably 120W; the frequency of the ultrasonic treatment is preferably 38-42 KHz, more preferably 40KHz; the time of the ultrasonic treatment is preferably 1.8 to 2.2 hours, more preferably 2 hours.
The invention can effectively improve the dispersibility of copper ions and Graphene Oxide (GO) in a copper source in an aqueous solution system by ultrasonic energy, and can provideSufficient vibration performance to promote copper ions (Cu 2+ ) Reacts with oxygen-containing functional groups (hydroxyl or carboxyl) on the surface of graphene oxide. Notably, the oxygen-containing functional groups on the surface of the graphene oxide can provide a large number of pinning points for the deposition of copper ions under the action of electrostatic adsorption so as to form GO-Cu 2+ A composite system. When Cu is 2+ The agglomeration of the GO sheets can be effectively hindered while the surface of the GO is uniformly nucleated and grown, because the attractive force between the GO sheets can be obviously reduced after the copper particles are introduced.
After the graphene oxide carrying the copper ions is obtained, the graphene oxide carrying the copper ions is mixed with a reducing agent, and a reduction reaction is carried out to obtain the graphene/copper composite material. In the present invention, the reducing agent is preferably sodium hypophosphite. In the invention, the reducing agent reduces graphene oxide to reduced graphene oxide, and simultaneously reduces part of copper ions to copper atoms; the residual copper ions are combined with graphene on the surface of the graphene to form C-O-Cu bonds to form substances similar to copper oxide or cuprous oxide structures. In the invention, the mass concentration of the reducing agent in the mixed solution obtained by mixing the graphene oxide loaded with copper ions and the reducing agent is preferably 38-42 g/L, and more preferably 40g/L. In order to facilitate operation, the invention directly adds the reducing agent into the system of ultrasonic treatment after the graphene oxide, the activating agent, the buffering agent, the complexing agent, the copper source and the water are mixed. The invention preferably mixes graphene oxide, an activating agent, a buffering agent, a complexing agent, a copper source and water before adding a reducing agent, and then sequentially stirs and heats the ultrasonic treatment system. In the present invention, the stirring time is preferably 0.8 to 1.2 hours, more preferably 1 hour. The invention has no special requirement on the stirring rotation speed, and can be uniformly mixed. In the present invention, the temperature after the temperature rise is preferably 58 to 62 ℃, more preferably 60 ℃.
In the present invention, the mixing of the copper ion-loaded graphene oxide and the reducing agent is preferably performed under stirring for a period of preferably 28 to 32 minutes, more preferably 30 minutes. The stirring speed is not particularly limited, as long as the stirring speed can be uniformly mixed.
In the present invention, the temperature of the reduction reaction is preferably room temperature, and the temperature of the room temperature is preferably 20 to 30 ℃, more preferably 23 to 25 ℃; the time of the reduction reaction is preferably 10 to 14 hours, more preferably 12 hours. In the present invention, the reduction reaction is preferably performed under a stationary condition.
In the present invention, the reduction reaction preferably further comprises: carrying out solid-liquid separation on the system of the reduction reaction; and washing and drying the solid obtained by solid-liquid separation in sequence.
In the present invention, the solid-liquid separation is preferably suction filtration. In the present invention, the washing solvent is preferably water; the number of times of washing is preferably 4 to 8 times, more preferably 6 to 7 times. In the present invention, the drying is preferably freeze-drying, and the temperature of the freeze-drying is preferably 20 to 50 ℃, more preferably 30 to 40 ℃; the time for the freeze-drying is preferably 46 to 50 hours, more preferably 48 to 49 hours.
In the invention, the graphene/copper composite material is black.
In the invention, the copper-based conductive ink comprises 52.1 to 59.1 percent of nano copper, preferably 54 to 58 percent of nano copper by mass percent. In the present invention, the average particle diameter of the nano copper is preferably 20 to 100nm, more preferably 30 to 90nm. In the present invention, the method for preparing nano copper preferably includes the steps of:
dissolving polyvinylpyrrolidone and copper sulfate pentahydrate in diethylene glycol to obtain a precursor solution;
sodium hypophosphite is dissolved in diethylene glycol to obtain a reducer solution;
and mixing the precursor solution and the reducing agent solution, and carrying out a reduction reaction to obtain the nano copper.
According to the invention, polyvinylpyrrolidone and copper sulfate pentahydrate are dissolved in diethylene glycol to obtain a precursor solution. In the invention, the mass ratio of the polyvinylpyrrolidone to the copper sulfate pentahydrate is preferably 1:1.8 to 2.2, more preferably 1:2. In the invention, the volume ratio of the mass of the polyvinylpyrrolidone to the diethylene glycol is preferably 1 g:58-62 mL, and more preferably 1g:60mL. The invention has no special requirement on the dissolution, and the dissolution can be completed.
Sodium hypophosphite is dissolved in diethylene glycol to obtain a reducer solution. In the present invention, the mass ratio of the sodium hypophosphite to the diethylene glycol is preferably 48g:290 to 310mL, more preferably 48g:300mL. The invention has no special requirement on the dissolution, so long as the dissolution is complete.
After the precursor solution and the reducing agent solution are obtained, the precursor solution and the reducing agent solution are mixed for reduction reaction, and the nano copper is obtained. In the present invention, the mixing is preferably adding a reducing agent solution to the precursor solution. The reducing agent solution is preferably heated to 100 ℃ prior to mixing. In the present invention, the temperature of the reduction reaction is preferably 90 to 110 ℃, more preferably 100 ℃; the time of the reduction reaction is preferably 4 to 6 minutes, more preferably 5 minutes. In the present invention, the reduction reaction is preferably accompanied by stirring, and the stirring is preferably magnetic stirring. In the present invention, the magnetic stirring is preferably performed in a magnetic stirrer. In the present invention, the reduction reaction preferably further comprises:
cooling the system after the reduction reaction, and performing first centrifugal treatment to obtain a solid;
and soaking the solid in an aqueous solution of formic acid and ethanol, and sequentially washing and drying after solid-liquid separation to obtain the nano copper.
The invention cools the system after the reduction reaction and then carries out the first centrifugal treatment to obtain the solid. In the present invention, the temperature after cooling is preferably room temperature, and the temperature of the room temperature is preferably 20 to 30 ℃, more preferably 23 to 25 ℃. The cooling mode is not particularly required, so long as the required temperature can be reached. In the present invention, the first centrifugal treatment is preferably preceded by mixing the post-reduction reaction system with water; the water is preferably deionized water. In the present invention, the volume ratio of the system after the reduction reaction to water is preferably 2:05 to 2, more preferably 2:1 to 1.5. In the present invention, the rotational speed of the first centrifugal treatment is preferably 4500 to 5500r/min, more preferably 5000r/min; the time of the first centrifugation is preferably 4 to 6 minutes, more preferably 5 minutes.
After the solid is obtained, the nano copper is obtained by soaking the solid in an aqueous solution of formic acid and ethanol, and sequentially washing and drying after solid-liquid separation. The invention preferably further comprises a first washing of the solid before soaking the solid in the aqueous solution of formic acid and ethanol; the first washing solvent is preferably deionized water; the number of times of the first washing is preferably 3.
In the present invention, the mass percentage of the aqueous solution of formic acid and ethanol is preferably 1.8 to 2.2%, more preferably 2%. In the present invention, the soaking time is preferably 14 to 16 minutes, more preferably 15 minutes. In the invention, the methanolic acid-ethanol solution can remove the oxide layer on the surfaces of the nano copper particles, so that the purity of the nano copper is improved.
In the present invention, the washing solvent is preferably absolute ethanol; the number of times of washing is preferably 2. In the present invention, the washing is preferably followed by solid-liquid separation, and the solid-liquid separation is preferably centrifugation, and the present invention has no special requirement for the centrifugation, as long as the solid-liquid separation can be achieved.
In the present invention, the drying temperature is preferably 45 to 55 ℃, more preferably 50 ℃; the drying time is preferably 11 to 13 hours, more preferably 12 hours.
In the invention, the graphene/copper composite material and nano copper are used as conductive filler together; the mass ratio of the graphene/copper composite material to the nano copper is preferably 98-99.5:1, and more preferably 99:1.
In the present invention, the copper-based conductive ink includes 2 to 5% of a binder, preferably 3 to 4% by mass. In the present invention, the binder preferably includes polyvinylpyrrolidone or sodium carboxymethyl cellulose, more preferably polyvinylpyrrolidone.
In the present invention, the copper-based conductive ink comprises 38 to 43% of an organic solvent, preferably 40 to 42% by mass. In the present invention, the organic solvent preferably includes an alcohol solvent; the alcohol solvent preferably comprises diethylene glycol or ethanol, more preferably diethylene glycol; the ethanol is preferably absolute ethanol.
The invention also provides a preparation method of the copper-based conductive ink, which comprises the following steps:
and mixing the graphene/copper composite material, nano copper, a binder and an organic solvent to obtain the copper-based conductive ink.
In the present invention, the mixing is preferably ball milling; the ball-milling ball material ratio is preferably 2-3:1; the ball for ball milling is preferably an agate ball, and the agate ball is preferably an agate ball with the diameter of 5mm and an agate ball with the diameter of 8 mm; the mass ratio of the agate balls with the diameter of 8mm to the agate balls with the diameter of 5mm is preferably 15.8-16.2:3, and more preferably 16:3.
In the invention, the rotating speed of the ball milling is preferably 380-420 r/min, more preferably 390-400 r/min; the time of the ball milling is preferably 7 to 9 hours, more preferably 8 hours. In the present invention, the ball mill is preferably operated in such a manner that clockwise rotation and counterclockwise rotation are alternately performed, and the time of the alternate rotation is preferably 25 to 35 minutes, more preferably 30 minutes.
In the invention, the copper-based conductive ink is in a viscous gel state.
A copper-based flexible composite material, comprising a substrate and a copper-based composite material deposited on the surface of the substrate;
the copper-based composite material is obtained by sintering the copper-based conductive ink prepared by the technical scheme or the preparation method.
In the present invention, the substrate preferably includes polyimide or polyvinyl alcohol, more preferably polyimide.
In the present invention, the preparation method of the copper-based flexible composite material preferably comprises the following steps:
and depositing copper-based conductive ink on the surface of the substrate, and sintering to obtain the copper-based flexible composite material.
In the present invention, the deposition is preferably a screen printing method. In the present invention, the thickness of the conductive ink layer obtained by depositing the copper-based conductive ink is preferably 55 to 70 μm. The invention has no special requirement on the deposition pattern, and the deposition pattern is designed according to the requirement. In the present invention, the deposited pattern is a circle having a diameter of 20 mm.
In the present invention, the post-deposition preferably further includes: drying the substrate on which the copper-based conductive ink is deposited; the drying is preferably vacuum drying; the drying temperature is preferably 58-62 ℃, more preferably 60 ℃; the drying time is preferably 7 to 9 hours, more preferably 8 hours. In the present invention, the organic solvent volatilizes during the drying process.
In the present invention, the sintering temperature is preferably 300 to 330 ℃, more preferably 330 ℃; the sintering time is preferably 15 to 40 minutes, more preferably 25 to 30 minutes. In the present invention, the heating rate to the sintering temperature is preferably 9 to 11 ℃/min, more preferably 10 ℃/min. In the present invention, the sintering is preferably performed under a reducing atmosphere, which is preferably hydrogen; the purity of the hydrogen gas is preferably 99.99%. In the present invention, the sintering is preferably performed in a tube furnace.
In the present invention, copper atoms on the nano copper surface continuously move and aggregate to form a continuous structure at a high temperature during the sintering process.
In the present invention, the sintered material preferably further comprises: the sintered product is cooled. In the present invention, the temperature after cooling is preferably room temperature, and the temperature of the room temperature is preferably 20 to 30 ℃, more preferably 23 to 25 ℃. In the present invention, the sintering is preferably performed in a tube furnace, and the cooling is preferably performed in a water-cooled area; the water cooling area is preferably externally connected with the outside of the tube furnace.
The flow of the preparation of the copper-based flexible composite material is shown in the figure 1, and specifically comprises the following steps: oxidizing graphene into graphene oxide, and then plating copper to obtain copper ion-loaded graphene oxide; reducing the graphene oxide loaded with copper ions to obtain a graphene/copper composite material; reducing the copper sulfate pentahydrate into nano copper; ball milling is carried out on the graphene/copper composite material, the nano copper binder and the organic solvent, so as to obtain graphene/copper composite material-nano copper conductive ink; and depositing the graphene/copper composite material-nano copper conductive ink on the surface of the substrate, and sintering to obtain the graphene/copper composite material-nano copper flexible film.
In the invention, the conductive component of the copper-based flexible composite material is graphene/copper composite material and nano copper.
The invention also provides application of the copper-based flexible composite material as a flexible printed electronic material. In the present invention, the flexible printed electronic material is used for preparing a flexible touch screen panel, a sensor, a power electronic package, a flexible circuit, or a solar cell.
The technical solutions provided by the present invention are described in detail below in conjunction with examples for further illustrating the present invention, but they should not be construed as limiting the scope of the present invention.
Example 1
Mixing 0.5g of graphene, 2.25g of potassium permanganate and 20mL of concentrated sulfuric acid in an ice-water bath under stirring to perform oxidation reaction for 20min; mixing the mixed solution obtained by mixing with hydrogen peroxide to perform chemical reaction to remove potassium permanganate remained by oxidation reaction, mixing the solution after chemical reaction with HCl aqueous solution with the mass concentration of 10%, and performing centrifugal treatment (with the accompanying power of 120W and the frequency of 40 KHz) for 60s; repeating the centrifugal treatment for 6 times; mixing the solid obtained by centrifugal treatment with deionized water (the volume ratio of the solid to the deionized water is 1mg:1 mL), and freeze-drying the mixture in a freeze dryer at 40 ℃ for 48 hours to obtain graphene oxide;
dissolving nickel sulfate (activating agent), boric acid (buffering agent), citric acid (complexing agent) and copper sulfate (copper source) in deionized water to obtain a mixed solution; mixing graphene oxide with deionized water, and performing ultrasonic treatment for 1h under the condition that the power is 120W and the frequency is 40KHz to obtain a graphene oxide solution with the mass concentration of 1g/L;
mixing the mixed solution and graphene oxide solution (nickel sulfate mass concentration is 0.9g/L, boric acid mass concentration is 30g/L, citric acid mass concentration is 20g/L, copper sulfate mass concentration is 10g/L, and graphene oxide mass concentration is 1 g/L), and performing ultrasonic treatment for 2 hours under the condition that the temperature is 50 ℃ and the power is 120W and the frequency is 40KHz to obtain copper ion-loaded graphene oxide;
stirring a solution which is subjected to ultrasonic treatment for 2 hours under the condition that the temperature is 50 ℃ and the power is 120W and the frequency is 40KHz for 1 hour, heating to 60 ℃, mixing with sodium hypophosphite (the mass concentration of the sodium hypophosphite after mixing is 40 g/L), stirring for 30 minutes, standing for 12 hours at 25 ℃, carrying out suction filtration, washing the solid obtained by suction filtration for 6 times by using water, and freeze-drying for 48 hours at 40 ℃ to obtain the graphene/copper composite material;
5g of polyvinylpyrrolidone (PVP) and 10g of copper sulfate pentahydrate were dissolved in 300mL of diethylene glycol (DEG) to obtain a precursor solution; 48g of sodium hypophosphite is dissolved in 300mL of diethylene glycol (DEG) to obtain a reducer solution; heating (with stirring) the reducer solution to 100 ℃, adding the reducer solution into the precursor solution, carrying out heat preservation and stirring for 5min in a magnetic stirrer, cooling to 25 ℃, mixing with deionized water (the volume ratio of the cooled solution to the deionized water is 2:1), and centrifuging for 5min at a rotation speed of 5000r/min; washing the solid obtained by centrifugation with deionized water for three times, soaking the soil body obtained by washing in 2% formic acid-ethanol solution for 15min, washing with water-ethanol for two times (by utilizing centrifugal solid-liquid separation), and vacuum drying the solid obtained by centrifugation at 50 ℃ for 12h to obtain nano copper with the average particle size of 50 nm;
grinding 0.1% of graphene/copper composite material, 56.9% of nano copper, 3% of polyvinylpyrrolidone and 40% of diethylene glycol for 8 hours according to the rotation speed of 400r/min (the rotation mode is that the copper-based conductive ink alternately rotates in a clockwise rotation 30min and then anticlockwise rotation 30 min) by mass percentage; wherein the grinding balls are agate balls with the diameter of 5mm and the diameter of 8mm, and the ball-to-material ratio is 3:1; the mass ratio of the agate balls with the diameter of 8mm to the agate balls with the diameter of 5mm is 16:3h;
taking polyimide as a substrate, depositing copper-based conductive ink on the surface of the polyimide substrate by using a screen printing method, and then vacuum drying at 60 ℃ for 8 hours; wherein the deposited pattern is a circle with a diameter of 20mm, and the thickness of the deposited copper-based conductive ink layer is 60 mu m; and placing the product after vacuum drying in a tube furnace, introducing 99.99% pure hydrogen, heating to 330 ℃ at a heating rate of 10 ℃/min, sintering for 30min, pushing the product into an external water cooling area of the tube furnace, and cooling to 25 ℃ to obtain the copper-based flexible composite material.
Example 2
Graphene/copper composites and nano-copper were prepared as in example 1;
the copper-based conductive ink was prepared according to the method of example 1, except that the graphene/copper composite material was 0.5% by mass and the nano copper was 56.5% by mass;
a copper-based flexible composite was prepared as in example 1, except that the copper-based conductive ink prepared in example 2 was used.
Comparative example 1
A copper-based flexible composite material was prepared according to the method of example 1, except that no graphene/copper composite material was added and only nano copper was used as a conductive filler.
Comparative example 2
Graphene/copper composites and nano-copper were prepared as in example 1;
the copper-based conductive ink was prepared according to the method of example 1, except that the graphene/copper composite material was 1% by mass and the nano copper was 56% by mass;
a copper-based flexible composite was prepared in the same manner as in example 1, except that the copper-based conductive ink prepared in comparative example 2 was used.
Scanning electron microscope detection is carried out on the copper-based flexible composite material prepared in the embodiment 1, and an SEM (scanning electron microscope) diagram is shown in FIG. 2. From fig. 2, it can be seen that the graphene sheets are uniformly distributed around the nano copper in a sheet shape, wherein the arrow indicates the graphene sheets; it can also be seen from fig. 2 that some of the graphene is incorporated into the copper structure while being bound to copper.
The copper-based flexible composites prepared in examples 1 to 2 and comparative examples 1 to 2 were examined for resistivity according to the following methods, and the results are shown in table 1.
The method for detecting the resistivity comprises the following steps:
the resistivity of the copper-based flexible composite material was measured using a four-probe method. The test instrument is a high and low resistance tester (HG 2511) and a Hexapa four-probe test probe (HPS 58003); firstly, testing the sheet resistance R of the copper-based flexible composite material by using a high and low resistance tester and four HERBA probes, then observing the cross section of the copper-based flexible composite material by adopting a scanning electron microscope after cold inlaying, storing SEM pictures and measuring the film thickness W by using Image J software; the resistivity of the copper-based flexible composite can be calculated by equation 1:
ρ＝R·W·F SP f (D/S). F (W/S) equation 1;
wherein ρ -resistivity (μΩ·cm);
r is sheet resistance (mΩ), a low resistance tester measurement;
s-average probe spacing (mm);
w-sample thickness (. Mu.m);
F SP -probe pitch correction factor (F value on four probe qualifiers);
f (D/S) -a sample diameter correction factor, related to the shape of the sample;
-a sample thickness correction factor related to the sample thickness.
Calculated F SP F (D/S). F (W/S) has a value of 1/pi.
TABLE 1 resistivity of copper-based Flexible composite materials prepared in examples 1-2 and comparative examples 1-2
| Examples | Resistivity (mu omega cm) |
| Example 1 | 18.2 |
| Example 2 | 18.7 |
| Comparative example 1 | 19.2 |
| Comparative example 2 | 35.6 |
The resistivity bar graphs of the copper-based flexible composites prepared in examples 1 to 2 and comparative examples 1 to 2 are plotted in conjunction with table 1, as shown in fig. 3. It can be seen from a combination of table 1 and fig. 3 that the copper-based flexible composite material provided by the invention has a lower resistivity.
The fatigue resistance of the copper-based flexible composite materials prepared in examples 1 to 2 and comparative examples 1 to 2 was measured according to the following method, the resistivity of the samples after the fatigue test was measured, and the resistivity increase rate of the samples after the fatigue test was calculated, the results of which are shown in Table 2. Wherein the resistivity increase rate of the sample after the fatigue test is the ratio of the difference between the resistivity of the sample after the fatigue test and the resistivity of the sample before the fatigue test to the resistivity of the sample before the fatigue test.
The method for testing the fatigue resistance performance is as follows
The fatigue test schematic diagram is shown in fig. 4, the center of the copper-based flexible composite material is taken as a center point, two ends of a base material at a position 10mm away from the center point are fixed, one end of the base material is fixed at the movable end, the other end of the base material is fixed at the movable end, the movable end compresses at a frequency of 1Hz, the cycle period is 100 times, and the resistance of a sample is measured after each cycle period is finished until the compression bending cycle is 1000 times. Radius of curvature r=5 mm, substrate movement distance d L ＝10mm
The letter meaning in fig. 4 is:
r—radius of curvature (mm);
l-sample length (mm);
h s -substrate thickness (mm);
d L -distance of movement (mm).
TABLE 2 resistivity increase rate of samples after fatigue test of copper-based flexible composite materials prepared in examples 1 to 2 and comparative examples 1 to 2
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Fatigue line diagrams of the copper-based flexible composite materials prepared in examples 1 to 2 and comparative examples 1 to 2 were plotted in combination with the data of table 2, as shown in fig. 5. As can be seen from fig. 5 and table 2, as the content of the graphene/copper composite material increases, the resistivity increase rate of the copper-based flexible composite material is significantly reduced after the fatigue resistance test, and when the content of the graphene/copper composite material is 0, the resistivity increase rate is 294.6%; when the content of the graphene/copper composite material is 0.5%, the resistivity increase rate is 46.7%.
Referring to fig. 3 and 5, it can be seen that the copper-based flexible composite material prepared by using the copper-based conductive ink added with the graphene/copper composite material has lower resistivity and good fatigue resistance.
Although the copper-based composite material prepared in comparative example 2 has a lower resistivity increase rate (has good fatigue resistance), the resistivity is higher, which is nearly double that of the copper-based composite material using only nano copper as the conductive filler.
Although the foregoing embodiments have been described in some, but not all, embodiments of the invention, it should be understood that other embodiments may be devised in accordance with the present embodiments without departing from the spirit and scope of the invention.
Claims (1)
1. The preparation method of the copper-based flexible composite material is characterized by comprising the following steps:
mixing 0.5g of graphene, 2.25g of potassium permanganate and 20mL of concentrated sulfuric acid in an ice-water bath under stirring to perform oxidation reaction for 20min; mixing the mixed solution obtained by mixing with hydrogen peroxide to perform chemical reaction to remove potassium permanganate remained by oxidation reaction, mixing the solution after chemical reaction with HCl aqueous solution with the mass concentration of 10%, and performing centrifugal treatment for 60s, wherein the accompanying power is 120W and the frequency is 40KHz; repeating the centrifugal treatment for 6 times; mixing the solid obtained by centrifugal treatment with deionized water, and freeze-drying for 48 hours at 40 ℃ in a freeze dryer to obtain graphene oxide; the mass of the solid and the volume ratio of deionized water were 1mg to 1mL;
dissolving nickel sulfate, boric acid, citric acid and copper sulfate in deionized water to obtain a mixed solution; mixing graphene oxide with deionized water, and performing ultrasonic treatment for 1h under the condition that the power is 120W and the frequency is 40KHz to obtain a graphene oxide solution with the mass concentration of 1g/L;
mixing the mixed solution and the graphene oxide solution, and performing ultrasonic treatment for 2 hours under the condition that the temperature is 50 ℃ and the power is 120W and the frequency is 40KHz, so as to obtain the graphene oxide loaded with copper ions; wherein the mass concentration of nickel sulfate is 0.9g/L, the mass concentration of boric acid is 30g/L, the mass concentration of citric acid is 20g/L, the mass concentration of copper sulfate is 10g/L, and the mass concentration of graphene oxide is 1g/L;
stirring a solution which is subjected to ultrasonic treatment for 2 hours under the conditions of 50 ℃ and 120W frequency of 40KHz for 1 hour, heating to 60 ℃ and mixing and stirring sodium hypophosphite for 30 minutes, standing for 12 hours at 25 ℃ after mixing, carrying out suction filtration, washing a solid obtained by suction filtration for 6 times by using water, and freeze-drying at 40 ℃ for 48 hours to obtain a graphene/copper composite material;
5g of polyvinylpyrrolidone and 10g of copper sulfate pentahydrate are dissolved in 300mL of diethylene glycol to obtain a precursor solution; 48g of sodium hypophosphite is dissolved in 300mL of diethylene glycol to obtain a reducer solution; heating the reducer solution to 100 ℃, adding the reducer solution into the precursor solution, carrying out heat preservation and stirring for 5min in a magnetic stirrer, cooling to 25 ℃, mixing with deionized water, centrifuging for 5min at a rotating speed of 5000r/min, and cooling to obtain a volume ratio of the solution to the deionized water of 2:1; washing the solid obtained by centrifugation with deionized water for three times, soaking the soil body obtained by washing in 2% formic acid-ethanol solution for 15min, washing with water-ethanol for two times, and vacuum drying the solid obtained by centrifugation at 50 ℃ for 12h to obtain nano copper with the average particle size of 50 nm;
grinding 0.5% of graphene/copper composite material, 56.5% of nano copper, 3% of polyvinylpyrrolidone and 40% of diethylene glycol for 8 hours according to the condition that the rotating speed is 400r/min to obtain copper-based conductive ink; wherein the grinding balls are agate balls with the diameter of 5mm and the diameter of 8mm, and the ball-to-material ratio is 3:1; the mass ratio of the agate balls with the diameter of 8mm to the agate balls with the diameter of 5mm is 16:3h;
taking polyimide as a substrate, depositing copper-based conductive ink on the surface of the polyimide substrate by using a screen printing method, and then vacuum drying at 60 ℃ for 8 hours; wherein the deposited pattern is a circle with a diameter of 20mm, and the thickness of the deposited copper-based conductive ink layer is 60 mu m; and placing the product after vacuum drying in a tube furnace, introducing 99.99% pure hydrogen, heating to 330 ℃ at a heating rate of 10 ℃/min, sintering for 30min, pushing the product into an external water cooling area of the tube furnace, and cooling to 25 ℃ to obtain the copper-based flexible composite material.
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| CN113293424A (en) * | 2021-05-20 | 2021-08-24 | 哈尔滨工业大学 | Graphene/copper composite powder and preparation method thereof, graphene/copper composite material and preparation method and application thereof |
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| CN107513311A (en) * | 2017-08-28 | 2017-12-26 | 厦门大学 | Antioxidant copper-graphene composite conductive ink and preparation method thereof |
| CN108231241A (en) * | 2018-01-19 | 2018-06-29 | 林荣铨 | The preparation and its application of a kind of medium temperature graphene/copper composite conducting slurry |
| CN110212176A (en) * | 2019-05-16 | 2019-09-06 | 南京工业大学 | Preparation method of graphene/molybdenum disulfide nanosphere/carbon black composite material |
| CN111393910A (en) * | 2020-05-11 | 2020-07-10 | 南昌航空大学 | Composite nano-copper conductive ink, preparation method thereof and conductive device |
| CN113293424A (en) * | 2021-05-20 | 2021-08-24 | 哈尔滨工业大学 | Graphene/copper composite powder and preparation method thereof, graphene/copper composite material and preparation method and application thereof |
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