Gaphene/silver composite material and preparation method thereof

Abstract

A method for preparing graphene/silver composite material is provided. A reduction agent and silver nitrate are added successively into a graphene oxide solution; silver powder obtained by reduction is directly combined with graphene oxide in the solution, so as to preliminarily obtain graphene oxide/silver composite powder; graphene/silver composite powder is then obtained through drying and reducing; a graphene/silver composite block material, a graphene/silver composite wire material and a graphene/silver composite belt material are able to be obtained by powder metallurgy, hot-extruding and rolling techniques. According to the composite material of the present invention, graphene is dispersed uniformly, and interface bonding between a matrix and an enhanced body is sufficient, leading to excellent physical performance of the composite material. Meanwhile, the method of the present invention is simple and processes are easy to control, which is conducive to large-scale production and application.

Claims

1-10. (canceled)

11. A method for preparing a graphene/silver composite material, comprising steps of: 1) preparing a silver nitrate solution and a reduction agent, respectively; 2) mixing the reduction agent with a graphene oxide aqueous solution, then adding the silver nitrate solution while stirring; wherein silver nitrate is reduced to silver micro-particles and a small amount of nano-particles, and graphene oxide is adsorbed by the silver particles, so as to form a graphene oxide/silver suspension; 3) washing the graphene oxide/silver suspension obtained in the step 2) for several times by centrifugation method, then freeze-drying to obtain graphene oxide/silver composite powder; 4) preforming the graphene oxide/silver composite powder obtained in the step 3), then reducing in hydrogen to obtain graphene/silver composite powder; and 5) molding and sintering the graphene/silver composite powder obtained in the step 4) by powder metallurgy techniques, so as to obtain the graphene/silver composite material.

12. The method, as recited in claim 11, wherein in the step 1), the reduction agent is selected from a group consisting of ascorbic acid, glucose, citric acid and oxalic acid.

13. The method, as recited in claim 11, wherein in the step 2), the graphene oxide is single-layer or few-layer graphene oxide prepared by a Hummers method; a mixing order of the graphene oxide aqueous solution, the reduction agent and the silver nitrate solution is: mixing the graphene oxide aqueous solution with the reduction agent, then mixing a mixture obtained with the silver nitrate solution; after mixing the graphene oxide aqueous solution with the reduction agent, the graphene oxide is partially reduced by the reduction agent; the reduction agent is excessively added, so as to completely reduce silver ions.

14. The method, as recited in claim 13, wherein a concentration of the reduction agent and a concentrate of the silver nitrate solution are both 0.1-0.5 mol/L; a mass concentration of the graphene oxide aqueous solution is 0.7-1.2%; a total content of the graphene oxide in the composite material is 0.5-6 wt %.

15. The method, as recited in claim 11, further comprising a step 6) after the step 5): extruding the graphene/silver composite material obtained in the step 5) by hot-extruding technique and charcoal protection which prevents oxidization, wherein the material is further densified to form a graphene/silver composite wire.

16. The method, as recited in claim 12, further comprising a step 6) after the step 5): extruding the graphene/silver composite material obtained in the step 5) by hot-extruding technique and charcoal protection which prevents oxidization, wherein the material is further densified to form a graphene/silver composite wire.

17. The method, as recited in claim 13, further comprising a step 6) after the step 5): extruding the graphene/silver composite material obtained in the step 5) by hot-extruding technique and charcoal protection which prevents oxidization, wherein the material is further densified to form a graphene/silver composite wire.

18. The method, as recited in claim 14, further comprising a step 6) after the step 5): extruding the graphene/silver composite material obtained in the step 5) by hot-extruding technique and charcoal protection which prevents oxidization, wherein the material is further densified to form a graphene/silver composite wire.

19. The method, as recited in claim 15, further comprising a step 7) after the step 6): rolling the graphene/silver composite wire obtained in the step 6) by rolling technique, so as to obtain graphene/silver composite belt, wherein the graphene is further orientation-distributed in the silver matrix, which improves a reinforcement effect of graphene.

20. The method, as recited in claim 16, further comprising a step 7) after the step 6): rolling the graphene/silver composite wire obtained in the step 6) by rolling technique, so as to obtain graphene/silver composite belt, wherein the graphene is further orientation-distributed in the silver matrix, which improves a reinforcement effect of graphene.

21. The method, as recited in claim 17, further comprising a step 7) after the step 6): rolling the graphene/silver composite wire obtained in the step 6) by rolling technique, so as to obtain graphene/silver composite belt, wherein the graphene is further orientation-distributed in the silver matrix, which improves a reinforcement effect of graphene.

22. The method, as recited in claim 18, further comprising a step 7) after the step 6): rolling the graphene/silver composite wire obtained in the step 6) by rolling technique, so as to obtain graphene/silver composite belt, wherein the graphene is further orientation-distributed in the silver matrix, which improves a reinforcement effect of graphene.

23. The method, as recited in claim 19, wherein in the step 6), a hot-extruding temperature is 400-600 C., an extruding ratio is 20-60; in the step 7), a thickness of the graphene/silver composite belt material obtained by rolling is 0.1-1 mm.

24. The method, as recited in claim 20, wherein in the step 6), a hot-extruding temperature is 400-600 C., an extruding ratio is 20-60; in the step 7), a thickness of the graphene/silver composite belt material obtained by rolling is 0.1-1 mm.

25. The method, as recited in claim 21, wherein in the step 6), a hot-extruding temperature is 400-600 C., an extruding ratio is 20-60; in the step 7), a thickness of the graphene/silver composite belt material obtained by rolling is 0.1-1 mm.

26. The method, as recited in claim 22, wherein in the step 6), a hot-extruding temperature is 400-600 C., an extruding ratio is 20-60; in the step 7), a thickness of the graphene/silver composite belt material obtained by rolling is 0.1-1 mm.

27. The method, as recited in claim 11, wherein an adding amount of the graphene oxide is 0.5-6 wt % with a balance of silver; the silver powder prepared by reduction is spheroid with a particle size of 0.1-5 m.

28. The method, as recited in claim 12, wherein an adding amount of the graphene oxide is 0.5-6 wt % with a balance of silver; the silver powder prepared by reduction is spheroid with a particle size of 0.1-5 m.

29. The method, as recited in claim 13, wherein an adding amount of the graphene oxide is 0.5-6 wt % with a balance of silver; the silver powder prepared by reduction is spheroid with a particle size of 0.1-5 m.

30. The method, as recited in claim 14, wherein an adding amount of the graphene oxide is 0.5-6 wt % with a balance of silver; the silver powder prepared by reduction is spheroid with a particle size of 0.1-5 m.

31. A graphene/silver composite material prepared by a method as recited in claim 11.

32. A graphene/silver composite material prepared by a method as recited in claim 26.

33. The graphene/silver composite material, as recited in claim 31, wherein a resistivity thereof is 1.5-1.7, a relative conductivity IACS (International Annealed Copper Standard) is 106-108%; a density is 10.32-10.4 g/cm.sup.3; a Vickers hardness is 80-115; a tensile strength is 185-195 MPa; and an elongation is 40-45%.

34. The graphene/silver composite material, as recited in claim 32, wherein a resistivity thereof is 1.5-1.7, a relative conductivity IACS (International Annealed Copper Standard) is 106-108%; a density is 10.32-10.4 g/cm.sup.3; a Vickers hardness is 80-115; a tensile strength is 185-195 MPa; and an elongation is 40-45%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 is a diagram of a method for preparing a graphene/silver composite material according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0040] The embodiments of the present invention will be described in detail, and the following examples give a detailed description and a specific operation. However, the scope of the present invention is not limited to the following embodiments.

[0041] Referring to FIG. 1, a diagram of a method for preparing a graphene/silver composite material according to a preferred embodiment of the present invention is illustrated, wherein graphene/silver composite material is able to be prepared by executing processes in sequence, or selecting part of the processes according to application requirements.

Embodiment 1

[0042] According to embodiment 1, basic operation processes for preparing the graphene/silver composite material are as follows:

[0043] I) Material Composition of the Graphene/Silver Composite Material

[0044] Main compounds of the graphene/silver composite material are silver metal and graphene. The silver metal is prepared by chemical reduction, which has a particle size of 0.1-5 m and an amount of 94 wt % in the composite material. A graphene raw material is single-layer or few-layer graphene oxide prepared by a Hummers method, which has an amount of 6 wt % in the composite material.

[0045] II) Basic Steps for Preparing the Graphene/Silver Composite Material (as Shown in FIG. 1)

[0046] 1) respectively preparing a 0.1 mol/L silver nitrate solution and a 0.1 mol/L ascorbic acid solution (or a solution selected form a group consisting of glucose, citric acid and oxalic acid);

[0047] 2) adding graphene oxide into deionized water, and ion-mixing for 0.5 h, so as to evenly disperse the graphene oxide and obtain a graphene oxide solution with a concentration of 0.7%;

[0048] 3) mixing 2.5 L the ascorbic acid solution with 183.6 g the graphene oxide solution, and ion-mixing for 5-10 min, then adding 2 L the silver nitrate solution into a mixture obtained and keeping ion-mixing; wherein silver nitrate is reduced to silver particles by ascorbic acid, and graphene oxide is adsorbed by silver powder, so as to form a graphene oxide/silver suspension;

[0049] 4) centrifugal-washing the graphene oxide/silver suspension for 5-10 times, then freeze-drying for obtaining graphene oxide/silver composite powder;

[0050] 5) pre-forming the graphene oxide/silver composite powder, then heating at 500 C. for 2 h with hydrogen atmosphere for reducing, so as to obtain graphene/silver composite powder; and

[0051] 6) molding the graphene/silver composite powder by isostatic pressing techniques, so as to obtain the graphene/silver composite block material; sintering the block material in a sintering furnace at 700 C. for 5 h with the hydrogen atmosphere, so as to obtain the highly-densified graphene/silver composite material.

Embodiment 2

[0052] Different from the embodiment 1, the embodiment 2 further adapts a hot-extruding step for obtaining a graphene/silver composite wire material.

[0053] According to embodiment 2, basic operation processes for preparing the graphene/silver composite wire material are as follows:

[0054] I) Material Composition of the Graphene/Silver Composite Wire Material

[0055] Main compounds of the graphene/silver composite material are silver metal and graphene. The silver metal is prepared by chemical reduction, which has a particle size of 0.1-5 m and an amount of 97 wt % in the composite material. A graphene raw material is single-layer or few-layer graphene oxide prepared by a Hummers method, which has an amount of 3 wt % in the composite material.

[0056] II) Basic Steps for Preparing the Graphene/Silver Composite Wire Material (as Shown in FIG. 1)

[0057] 1) respectively preparing a 0.25 mol/L silver nitrate solution and a 0.25 mol/L ascorbic acid solution;

[0058] 2) adding graphene oxide into deionized water, and ion-mixing for 0.5 h, so as to evenly disperse the graphene oxide and obtain a graphene oxide solution with a concentration of 0.9%;

[0059] 3) mixing 2.5 L the ascorbic acid solution with 178.5 g the graphene oxide solution, and ion-mixing for 5-10 min, then adding 2 L the silver nitrate solution into a mixture obtained and keeping ion-mixing; wherein silver nitrate is reduced to silver particles by ascorbic acid, and graphene oxide is adsorbed by silver powder, so as to form a graphene oxide/silver suspension;

[0060] 4) centrifugal-washing the graphene oxide/silver suspension for 5-10 times, then freeze-drying for obtaining graphene oxide/silver composite powder;

[0061] 5) pre-forming the graphene oxide/silver composite powder, then heating at 500 C. for 2 h with hydrogen atmosphere for reducing, so as to obtain graphene/silver composite powder;

[0062] 6) molding the graphene/silver composite powder by isostatic pressing techniques, so as to obtain the graphene/silver composite block material; sintering the block material in a sintering furnace at 700 C. for 5 h with the hydrogen atmosphere; and

[0063] 7) hot-extruding a highly-densified graphene/silver composite material obtained by powder metallurgy with an extruding temperature of 600 C. and an extruding ratio of 40, so as to obtain the graphene/silver composite wire material. After performance testing, it was found that a resistivity of the material is 1.52, a density is 10.32 g/cm.sup.3, a Vickers hardness is 100, a tensile strength is 192 MPa, and an elongation is 43%.

Embodiment 3

[0064] Different from the embodiment 2, the embodiment 3 further adapts annealing and rolling steps for obtaining a graphene/silver composite belt material.

[0065] According to embodiment 3, basic operation processes for preparing the graphene/silver composite belt material are as follows:

[0066] I) Material Composition of the Graphene/Silver Composite Belt Material

[0067] Main compounds of the graphene/silver composite material are silver metal and graphene; wherein raw materials and amounts of the silver metal and the graphene are the same as the embodiment 2.

[0068] II) Basic Steps for Preparing the Graphene/Silver Composite Belt Material (as Shown in FIG. 1)

[0069] 1) respectively preparing a 0.25 mol/L silver nitrate solution and a 0.25 mol/L ascorbic acid solution;

[0070] 2) adding graphene oxide into deionized water, and ion-mixing for 0.5 h, so as to evenly disperse the graphene oxide and obtain a graphene oxide solution with a concentration of 0.9%;

[0071] 3) mixing 2.5 L the ascorbic acid solution with 178.5 g the graphene oxide solution, and ion-mixing for 5-10 min, then adding 2 L the silver nitrate solution into a mixture obtained and keeping ion-mixing; wherein silver nitrate is reduced to silver particles by ascorbic acid, and graphene oxide is adsorbed by silver powder, so as to form a graphene oxide/silver suspension;

[0072] 4) centrifugal-washing the graphene oxide/silver suspension for 5-10 times, then freeze-drying for obtaining graphene oxide/silver composite powder;

[0073] 5) pre-forming the graphene oxide/silver composite powder, then providing reduction treatment, so as to obtain graphene/silver composite powder;

[0074] 6) molding the graphene/silver composite powder by isostatic pressing techniques, so as to obtain the graphene/silver composite block material; sintering the block material in a sintering furnace at 700 C. for 5 h with the hydrogen atmosphere;

[0075] 7) hot-extruding a highly-densified graphene/silver composite material obtained by powder metallurgy with an extruding temperature of 600 C. and an extruding ratio of 40, so as to obtain the graphene/silver composite wire material;

[0076] 8) annealing the graphene/silver composite wire material at 350 C. for 2 h; and

[0077] 9) rolling the annealed graphene/silver composite wire material with rolling techniques for obtaining the graphene/silver composite belt material with a thickness of 0.1 mm. After performance testing, it was found that a resistivity of the material is 1.51, a density is 10.34 g/cm.sup.3, a Vickers hardness is 115. Different from the embodiment 2, the resistivity of the graphene/silver composite material is slightly decreased after rolling, while the hardness is significantly increased.

Embodiment 4

[0078] Different from the embodiment 3, the embodiment 4 adapts different mass proportions of a silver matrix and a graphene reinforcement body, so as to adjust process parameters according to different formulation.

[0079] According to embodiment 4, basic operation processes for preparing a graphene/silver composite material are as follows:

[0080] I) Material Composition of the Graphene/Silver Composite Belt Material

[0081] Main compounds of the graphene/silver composite material are silver metal and graphene. The silver metal is prepared by chemical reduction, which has a particle size of 0.1-5 m and an amount of 99.5 wt % in the composite material. A graphene raw material is single-layer or few-layer graphene oxide prepared by a Hummers method, which has an amount of 0.5 wt % in the composite material.

[0082] II) Basic Steps for Preparing the Graphene/Silver Composite Material (as Shown in FIG. 1)

[0083] 1) respectively preparing a 0.5 mol/L silver nitrate solution and a 0.5 mol/L ascorbic acid solution;

[0084] 2) adding graphene oxide into deionized water, and ion-mixing for 0.5 h, so as to evenly disperse the graphene oxide and obtain a graphene oxide solution with a concentration of 1.2%;

[0085] 3) mixing 2.5 L the ascorbic acid solution with 44.6 g the graphene oxide solution, and ion-mixing for 5-10 min, then adding 2 L the silver nitrate solution into a mixture obtained and keeping ion-mixing; wherein silver nitrate is reduced to silver particles by ascorbic acid, and graphene oxide is adsorbed by silver powder, so as to form a graphene oxide/silver suspension;

[0086] 4) centrifugal-washing the graphene oxide/silver suspension for 5-10 times, then freeze-drying for obtaining graphene oxide/silver composite powder;

[0087] 5) pre-forming the graphene oxide/silver composite powder, t then heating at 350 C. for 5 h with hydrogen atmosphere for reducing, so as to obtain graphene/silver composite powder;

[0088] 6) molding the graphene/silver composite powder by isostatic pressing techniques, so as to obtain the graphene/silver composite block material; sintering the block material in a sintering furnace at 800 C. for 5 h with the hydrogen atmosphere;

[0089] 7) hot-extruding a highly-densified graphene/silver composite material obtained by powder metallurgy with an extruding temperature of 400 C. and an extruding ratio of 20, so as to obtain the graphene/silver composite wire material; wherein after performance testing, it was found that a resistivity of the material is 1.6, a density is 10.37 g/cm.sup.3, a Vickers hardness is 80, a tensile strength is 185 MPa, and an elongation is 42%; different from the embodiment 2, the Vickers hardness and the tensile strength are slightly decreased after decreasing the amount of the graphene;

[0090] 8) annealing the graphene/silver composite wire material at 380 C. for 2 h; and

[0091] 9) rolling the annealed graphene/silver composite wire material with rolling techniques for obtaining the graphene/silver composite belt material with a thickness of 0.5 mm. After performance testing, it was found that a resistivity of the material is 1.55, a density is 10.37 g/cm.sup.3, a Vickers hardness is 110. The resistivity of the graphene/silver composite material is slightly decreased after rolling, while the hardness is significantly increased.

[0092] It should be understood that the above-described embodiments are merely part of all embodiments of the present invention. According to the present invention, the graphene/silver composite material includes all applicable forms, such as changing a preparation formulation of the silver matrix, and other combinations of silver salts and reducing agent solutions. The formulation of the final composite material should be designed based on application requirements.

[0093] It will thus be seen that the objects of the present invention have been fully and effectively accomplished. Its embodiments have been shown and described for the purposes of illustrating the functional and structural principles of the present invention and is subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.