CN113073221A

CN113073221A - Graphene modification method of metal

Info

Publication number: CN113073221A
Application number: CN202010006480.8A
Authority: CN
Inventors: 曾为霖; 施养明; 洪启航
Original assignee: Amazing Cool Technology Co ltd
Current assignee: Amazing Cool Technology Co ltd
Priority date: 2020-01-03
Filing date: 2020-01-03
Publication date: 2021-07-06
Anticipated expiration: 2040-01-03
Also published as: CN113073221B

Abstract

The invention provides a graphene modification method of metal, which comprises the following steps: providing metal powder, graphene powder and an adhesive, wherein the metal powder comprises a plurality of metal particles, the graphene powder comprises a plurality of graphene micro-sheets, each graphene micro-sheet comprises a plurality of connected graphene molecules, and each graphene molecule is connected with a stearic acid functional group through a mixed layer track sp3 bond; mixing metal powder and graphene powder adhesive, generating heat by friction, enabling each mixed layer rail domain sp3 bond connected with each stearic acid functional group to absorb heat and then breaking, and enabling each graphene molecule to be in key joint with other graphene molecules through the broken mixed layer rail domain sp3 bond so as to enable each metal particle to be coated by the graphene molecule; sintering the metal particles to fuse the metal particles into a metal body and the graphene molecules are combined in the metal body in a three-dimensional network form.

Description

Graphene modification method of metal

Technical Field

The invention relates to a graphene metal composite material, in particular to a graphene modification method of metal.

Background

At present, the preparation and application of silicon carbide and aluminum oxide reinforced copper-based composite materials tend to be mature, but the comprehensive performance and the actual demand of the composite materials have a certain distance, and graphene has excellent mechanical property, thermal property and electrical property, so that the graphene is one of the most ideal reinforcements for preparing heat-conducting composite materials. However, research on graphene-reinforced copper-aluminum-based composite materials is still in the beginning stage, and related research work is urgently needed. How to uniformly disperse graphene into a copper-aluminum substrate and form a good contact interface between the graphene and metal is a key problem in research.

Furthermore, in the existing modification technology, a tackifier is generally added to the organic material to increase the viscosity of the material so as to fix different organic materials; inorganic materials are generally in an ionic state with broken bonds in solution, so reagent is generally added to fix different inorganic materials by bonding. However, the characteristics of organic materials and inorganic materials are different, and there is no good method for fixing organic materials and inorganic materials. Therefore, the organic graphene and the inorganic metal are not easily uniformly combined.

In view of the above, the present inventors have made extensive studies and studies to solve the above problems in combination with the application of the above prior art, and as a result, the present inventors have improved the present invention.

Disclosure of Invention

The invention provides a graphene modification method for metal, which can uniformly distribute graphene in metal.

The invention provides a graphene modification method of metal, which comprises the following steps: providing metal powder, graphene powder and an adhesive, wherein the metal powder comprises a plurality of metal particles, the adhesive comprises a wax material, the graphene powder comprises a plurality of graphene micro-sheets, each graphene micro-sheet comprises a plurality of connected graphene molecules, each graphene molecule comprises six carbon elements which are connected in a ring shape, one carbon element of each graphene molecule is connected with a stearic acid functional group through a mixed layer orbital sp3 bond, the adhesive comprises 0.5-2 wt% of a coupling agent and 5-20 wt% of a dispersing agent, the coupling agent is one of titanate and an organic chromium complex, and the dispersing agent is one of methyl amyl alcohol, polyacrylamide and fatty acid polyglycol ester; mixing metal powder and a graphene powder adhesive to form a powder raw material, heating by mixing friction to ensure that each layer mixing track sp3 bond connected with each stearic acid functional group absorbs heat and then is broken, separating the stearic acid functional group from each graphene molecule, and then bonding each graphene molecule with other graphene molecules through the broken layer mixing track sp3 bond to ensure that each metal particle is coated by each graphene molecule; sintering the metal particles to fuse the metal particles into a metal body and the graphene molecules are combined in the metal body in a three-dimensional network form.

According to the graphene modification method, the initial blank comprises the metal particles and the graphene micro-sheets which are uniformly mixed, and each graphene micro-sheet is coated by the solid adhesive to adhere the metal particles.

The graphene modification method further comprises the following steps: heating the powder raw material to melt the powder raw material into a liquid mixed raw material, wherein the liquid mixed raw material comprises metal powder, a liquid adhesive and graphene powder; injecting the liquid mixed raw material into a mould for injection molding and curing to form a primary blank; and removing the adhesive in the blank to form a dewaxed semi-finished product, firstly, carrying out solvent dewaxing on the blank to remove part of the adhesive, so as to form a gap in the dewaxed semi-finished product, and then carrying out thermal dewaxing, wherein the thermal dewaxing temperature is between 140 ℃ and 170 ℃, and in the step f, sintering the dewaxed semi-finished product to fuse the metal particles into a metal body.

The graphene modification method of the invention is used for sintering and dewaxing the semi-finished product in a nitrogen or hydrogen thermal sintering mode.

In the graphene modification method, the solvent dewaxing is to immerse the initial blank into a solution to dissolve the adhesive. The hot dewaxing heat-treats the green stock to vaporize the adhesive.

The graphene modification method provided by the invention is used for sintering metal particles in a vacuum hot-pressing sintering manner.

According to the graphene modification method, the metal body is aluminum or copper.

According to the graphene modification method of the metal, each metal particle is a dendritic electrolytic copper particle. The powder raw materials are mixed by planetary stirring. The weight percentage of the graphene powder in the powder raw material is less than 5%.

In summary, in the method for modifying metal graphene according to the present invention, graphene is added when metal powder is mixed with an adhesive, a mixture of metal, adhesive and graphene is formed after mixing and granulation, and after injection molding and dewaxing, the metal powder and graphene are combined in a sintering stage, so as to improve the heat transfer coefficient.

Drawings

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings. Like reference numerals refer to like parts throughout the drawings, and the drawings are not intended to be drawn to scale in actual dimensions, emphasis instead being placed upon illustrating the principles of the invention.

FIG. 1 is a flow chart of a method for graphene modification of metals in accordance with a preferred embodiment of the present invention;

FIG. 2 is a schematic diagram of a powder raw material in a graphene modification method of a metal according to a preferred embodiment of the present invention;

FIG. 3 is a schematic diagram of an injection molding step in a graphene modification method of metal according to a preferred embodiment of the present invention;

FIG. 4 is a schematic diagram of an initial blank in a graphene modification method of a metal according to a preferred embodiment of the present invention;

FIG. 5 is a schematic diagram of a dewaxing semi-finished product in a graphene modification method of metals according to a preferred embodiment of the present invention;

FIG. 6 is a schematic diagram of a graphene metal composite according to a preferred embodiment of the present invention;

FIG. 7 is a schematic representation of graphene;

fig. 8 is a schematic of functionalized graphene.

Reference numerals:

10 powdered raw material

20 liquid mixing of raw materials

30 initial blank

40 dewaxing semi-finished product

50 the product

100 metal particles

100a metal body

200 graphene nanoplatelets

300 adhesive

400 mould

a to f.

Detailed Description

Referring to fig. 1 to 6, a graphene metal composite and a method for manufacturing the same are provided in the preferred embodiment of the present invention. In this embodiment, the method for modifying graphene with metal of the present invention at least comprises the following steps:

in step a, a metal powder (metal powder), a graphene powder (graphene powder) and an adhesive 300(binder) are provided, wherein the metal powder is aluminum powder or copper powder. Wherein the metal powder comprises a plurality of metal particles 100 (aluminum particles or copper particles, preferably dendritic electrolytic copper particles), the graphene powder comprises a plurality of graphene micro-slabs 200, and each graphene micro-slab 200 comprises a plurality of graphene molecules connected as shown in fig. 7. Referring to fig. 1, 7 and 8, the graphene nanoplatelets (as shown in fig. 7) are modified with functional groups to become functionalized graphene (as shown in fig. 8). In the present embodiment, the functional group is preferably an oxygen-containing functional group, such as stearic acid, which bonds to one of the carbon atoms of the graphene through a mixed layer orbital sp3 bond. Each graphene molecule comprises six carbon atoms connected in a ring shape, and one of the carbon atoms of each graphene molecule is connected with a functional group by a mixed layer orbital sp3 bond as shown in fig. 8. The adhesive 300 is mainly a wax material including paraffin wax, microcrystalline wax or acryl wax, etc., and is generally composed of a low molecular weight thermoplastic polymer or oil. The adhesive 300 contains 0.5-2 wt% of titanate or organic chromium complex as a coupling agent for fixing materials. The adhesive 300 contains 5-20 wt% of a dispersant, which can be methyl amyl alcohol, polyacrylamide or fatty acid polyglycol ester, so that the material can be uniformly dispersed.

In step b, the metal powder, the graphene powder and the adhesive 300 provided in step a are subjected to a mixing and granulation (mixing and granulation) process to form a powder raw material 10. The mixing granulation is to uniformly mix the metal powder, the graphene powder and the adhesive 300, so that the metal particles 100 and the graphene nanoplatelets 200 in the powder raw material 10 can be dispersed in the dispersing agent and coated by the adhesive 300 respectively. Specifically, since the specific gravity difference between the graphene and the metal is considerable, it is necessary to mix the graphene nanoplatelets 200 in a planetary stirring manner while stirring the graphene and the metal in different directions so as to uniformly distribute the graphene nanoplatelets 200 in the powder raw material 10. And 10 weight percent of the graphene powder in the powder feedstock is preferably less than 5% to avoid agglomeration. The functionalized graphene increases the dispersibility of the graphene nanoplatelets 200 in the metal powder and the adhesive 300 in step b. Because a certain amount of functional groups enter the graphene nanoplatelets 200, the graphene nanoplatelets 200 have the same charges, and when the graphene nanoplatelets 200 have the functional groups, electrostatic repulsion is generated between the same charges, so that the graphene nanoplatelets 200 are repelled and separated from each other and can be uniformly dispersed in the dispersing agent and the adhesive 300. In the mixing process of the step b, the functionalized graphene nanoplatelets 200 rub to generate heat energy, so that the sp3 bond of the mixed layer containing the oxygen functional group is broken in an endothermic way, and the oxygen functional group is separated. Therefore, the carbon atoms bonded with the oxygen-containing functional groups can be immediately bonded with other broken mixed-layer orbital sp3 bonds in the graphene nanoplatelets 200 again, so that the graphene nanoplatelets 200 are connected in a planar shape and cover the metal particles 100 to form spheres.

Specifically, the coupling agent is added into the mixture of graphene and metal to assist organic graphene and inorganic metal to bond with each other, and the dispersant is added to disperse the graphene enough to avoid agglomeration. Furthermore, the inorganic material is generally in an ionic state and has a bonding force in the mixture, and the coupling agent can also assist the dispersion in the inorganic material of the dispersant. Titanate or organic chromium complex both have the characteristic of strong peripheral electronic bonding force, can strengthen the bonding strength of graphene and metal, and titanate has the advantage of light weight, and organic chromium complex has side and can form more bonds. And selecting different solid dispersing agent materials and adding methyl amyl alcohol as a dispersing agent corresponding to the graphene materials in different states, adding polyacrylamide as a dispersing agent in a liquid material, and adding fatty acid polyglycol ester as a dispersing agent in a gaseous material.

The sintered metal particles 100 may be sintered by a vacuum hot press sintering method in which in the sintering step f subsequent to the step b, the liquid mixed raw material 20 is injected into a mold 400 as shown in fig. 3, the liquid mixed raw material 20 is pressurized by the mold 400 and sintered at 700 ℃ for 1 hour in vacuum, and the metal particles 100 of aluminum or copper can be sintered. Sintering at lower temperatures is facilitated by the mold 400 pressurizing the liquid feedstock mixture 20 to increase its density.

The metal particles 100 are sintered by vacuum hot pressing sintering, so that the metal particles 100 are melted and combined with each other to form a metal body 100a, and the adhesive 300 is vaporized and removed, since the graphene nanoplatelets 200 are not melted and have a boiling point much higher than that of the metal particles 100 and the adhesive 300, the structure is not damaged during heat treatment, and the graphene nanoplatelets 200 are uniformly distributed in the metal body 100 a. Depending on the metal particles 100 (aluminum or copper), the sintered metal body 100a may be aluminum or copper. Thereby, a finished product 50 of the graphene metal composite material of the present invention is manufactured as shown in fig. 6.

The sintered metal particles 100 may also be cold pressed and hot sintered. The method comprises two steps of cold press molding (c-e) and sintering (f), wherein the cold press step comprises the following two steps.

In step c, continuing with step b, heating the powder raw material 10 to melt it into a liquid mixed raw material 20; the liquid raw material mixture 20 includes metal powder, a liquid adhesive 300, and graphene powder.

In step d, following step c, the liquid blend 20 is injected into a mold 400 as shown in fig. 3 and solidified into a green part 30 as shown in fig. 4 by cold isostatic pressing; the blank 30 includes uniformly mixed metal particles 100 and graphene nanoplatelets 200, and each graphene nanoplatelet 200 is coated with a solid adhesive 300 to bond the metal particles 100.

As shown in fig. 5, in step e, following step d, the blank 30 is dewaxed to remove the adhesive 300 from the blank 30 to form a dewaxed semi-finished product 40(brown part). The dewaxing mode can be thermal dewaxing (thermal dewaxing) or solvent dewaxing (water/solvent dewaxing). The thermal dewaxing is to perform a heat treatment on the primary blank 30, and an inert gas is used as a flowing medium, and the temperature is increased to crack and vaporize the adhesive 300, and the adhesive is carried out from the medium. Vacuum dewaxing uses high temperature and high vacuum to evaporate the adhesive 300 and then carry the molecules out by distillation. Solvent dewaxing utilizes a solvent to dissolve the adhesive 300. The thermal dewaxing and the solvent dewaxing may be performed in parallel, and the adhesive 300 is partially solvent dewaxed from the blank 30, so that a gap is formed in the dewaxed semi-finished product 40, and then the thermal dewaxing is performed, thereby facilitating the high temperature gas to decompose and discharge the remaining adhesive 300 through the gap. In step e, the temperature of the thermal dewaxing step is preferably lower than the melting point of the metal particles 100 and higher than the melting point or boiling point of the adhesive 300, and the environment is heated to 140-170 ℃, so that the structure is not damaged during the heat treatment because the graphene nanoplatelets 200 are not melted and have a much higher boiling point than the metal particles 100 and the adhesive 300.

In the sintering step f, step e is continued, the dewaxed semi-finished product 40 is sintered by thermal sintering in nitrogen or hydrogen to melt the metal particles 100 and combine them into a metal body 100a, the ambient operating temperature is heated to 1050 ℃ for sintering for 1 hour when the metal particles 100 are copper, and the ambient operating temperature is heated to 600 ℃ for sintering for 1 hour when the metal particles 100 are aluminum. Since the graphene nanoplatelets 200 are not melted and have a boiling point much higher than that of the metal particles 100 and the adhesive 300, the structure is not damaged during the heat treatment, and the graphene nanoplatelets 200 are uniformly distributed in the metal body 100 a. The metal body 100a is aluminum or copper. Thereby, a finished product 50 of the graphene metal composite material of the present invention is manufactured as shown in fig. 6.

Referring to fig. 6, the graphene metal composite product 50 of the present invention is manufactured by the aforementioned manufacturing method, and the graphene metal composite of the present invention includes a metal body 100a and a plurality of graphene micro-sheets 200 embedded in the metal body 100 a. The metal body 100a is aluminum or copper, and the graphene nanoplatelets 200 are uniformly distributed in the metal body 100 a.

In summary, in the method for modifying metal graphene according to the present invention, the graphene powder is added when the metal powder is mixed with the adhesive 300, and after mixing and granulation, a mixture of the metal particles 100, the graphene nanoplatelets 200 and the adhesive 300 is formed, and after injection molding and dewaxing, the mixture is sintered, so that the graphene nanoplatelets 200 originally coated with the metal particles 100 in a sphere arrangement form in the finished product 50 form a three-dimensional network of connected spheres, which are combined in the metal body 100a, thereby increasing the heat transfer coefficient of the finished product 50. The heat transfer coefficient of the metal piece is increased by the graphene, and compared with the case that pure metal is used as a heat transfer medium, the graphene metal composite material can be configured to be smaller as the heat transfer medium under the condition of the same total heat transfer amount. Furthermore, the graphene nanoplatelets 200 are arranged regularly by adding the functional groups, so that the heat energy is more uniformly dispersed in the graphene nanoplatelets compared with the heat energy of the conventional inert machine dispersion structure, and the graphene nanoplatelets have more excellent heat conduction efficiency.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and other equivalent variations using the spirit of the present invention should fall within the scope of the present invention.

Claims

1. A method for modifying graphene of a metal, comprising:

a) providing a metal powder, a graphene powder and an adhesive, wherein the metal powder comprises a plurality of metal particles, the adhesive comprises a wax material, the graphene powder comprises a plurality of graphene micro-sheets, each graphene micro-sheet comprises a plurality of connected graphene molecules, each graphene molecule comprises six carbon elements which are connected in a ring shape, one of the carbon elements of each graphene molecule is connected with a stearic acid functional group through a mixed layer orbital sp3 bond, the adhesive comprises 0.5-2% by weight of a coupling agent and 5-20% by weight of a dispersing agent, the coupling agent is one of titanate and organic chromium complex, and the dispersing agent is one of methyl amyl alcohol, polyacrylamide and fatty acid polyglycol ester;

b) mixing the metal powder, the graphene powder and the adhesive to form a powder raw material, wherein mixing friction heat causes each layer-mixing track sp3 bond connected with each stearic acid functional group to absorb heat and then break, after the stearic acid functional groups are separated from each graphene molecule, each graphene molecule is bonded with other graphene molecules through the broken layer-mixing track sp3 bond, so that each metal particle is coated by each graphene molecule;

f) sintering the metal particles to fuse the metal particles into a metal body, wherein the graphene molecules are combined in the metal body in a three-dimensional net shape.

2. The method of claim 1, further comprising the step between steps b and f:

c) heating the powder raw material to melt the powder raw material into a liquid mixed raw material, wherein the liquid mixed raw material comprises the metal powder, the liquid adhesive and the graphene powder;

d) injecting the liquid mixed raw material into a mould for injection molding and curing to form a primary blank; and

e) removing the adhesive in the blank to form a dewaxed semi-finished product, firstly, solvent dewaxing the blank to remove part of the adhesive to form a gap in the dewaxed semi-finished product, and then, carrying out thermal dewaxing at a temperature of 140-170 ℃,

wherein sintering the dewaxed intermediate product in step f fuses the metal particles into the metal body.

3. The method of claim 2, wherein in step d, the initial blank comprises the metal particles and the graphene nanoplatelets uniformly mixed, and each graphene nanoplatelet is coated with the solid adhesive to bond the metal particles.

4. The method of claim 2, wherein the dewaxed intermediate product is sintered by nitrogen or hydrogen thermal sintering in step f.

5. The method of claim 2, wherein in step e, the solvent dewaxing immerses the blank in a solution to dissolve the adhesive.

6. The method of claim 2, wherein in step e, the thermal dewaxing thermally treats the green stock to vaporize the adhesive.

7. The method of claim 1, wherein the metal body is aluminum or copper.

8. The method of claim 1, wherein the metal particles are sintered by vacuum hot pressing sintering in step f.

9. The method of graphene modification of a metal according to claim 1, wherein each of said metal particles is a dendritic electrolytic copper particle.

10. The method of claim 1, wherein the powder material is mixed by planetary stirring.

11. The method of claim 1, wherein the graphene powder is present in an amount of less than 5% by weight of the powder feedstock.