CN111392717B - Preparation method of concentrated graphene oxide solution and heat conducting film - Google Patents
Preparation method of concentrated graphene oxide solution and heat conducting film Download PDFInfo
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- CN111392717B CN111392717B CN202010218000.4A CN202010218000A CN111392717B CN 111392717 B CN111392717 B CN 111392717B CN 202010218000 A CN202010218000 A CN 202010218000A CN 111392717 B CN111392717 B CN 111392717B
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Abstract
The invention discloses a preparation method of a concentrated graphene oxide solution and a heat conducting film. One specific embodiment of the preparation method of the concentrated graphene oxide solution comprises the following steps: forming negative charges on the surface of graphene oxide in the graphene oxide aqueous solution; utilizing metal salt to colloidize the graphene oxide aqueous solution with negative charges to form metal-doped graphene oxide colloid; and concentrating and separating the metal-doped graphene oxide colloid to obtain a metal-doped graphene oxide aqueous solution, namely the concentrated graphene oxide solution. According to the embodiment of the invention, the concentration of the graphene oxide is improved by preparing the metal-doped graphene oxide aqueous solution; the method solves the problems that the concentration of graphene oxide is low and is difficult to improve in the prior art. Utilize concentrated graphene oxide solution to make the heat conduction membrane, not only can reduce the energy consumption of later stage water treatment, can greatly improve the vertical thermal conductivity of heat conduction membrane moreover to obtain high coefficient of thermal conductivity's heat conduction membrane.
Description
Technical Field
The invention relates to the technical field of material preparation, in particular to a preparation method of a concentrated graphene oxide solution and a heat-conducting film.
Background
In solid materials, phonons and electrons are the key pathways for heat transfer. The thermal conductivity of metals depends mainly on the electron transfer process at high concentration, while silver metal has the highest thermal conductivity (K429W/mK) among all metals, but this thermal conductivity is still not ideal in practical applications. The thermal conductivity of the nonmetal mainly depends on the propagation rate of phonons, the thermal conductivity of different elements is greatly different, and the thermal conductivity of the same element is greatly different due to different lattice arrangements, such as diamond and graphite, so that how to obtain a thermal conductive material with more excellent performance from the nonmetal material still has great challenges.
Graphene is a two-dimensional material, carbon atoms are arranged in a hexagon and connected with each other to form a carbon molecule, the structure of the graphene is very stable, and the thickness of single-layer graphene is only one carbon atom, namely 0.335nm, and the graphene is the thinnest material. The theoretical thermal conductivity coefficient of the graphene is as high as 5300W/mK, the graphene is a material with the highest natural thermal conductivity coefficient, meanwhile, the unique single-layer structure endows the graphene with ultrahigh flexibility, and the graphene is more likely to become a thermal conductive material with ultrahigh thermal conductivity and ultrahigh flexibility due to the unique properties.
Graphene is oxidized by concentrated acid/strong oxidant, and hydroxyl, carbonyl, carboxyl, epoxy bond and other groups are generated on the surface of the graphene to form graphene oxide. The graphene oxide has strong hydrophilicity due to a large amount of oxygen-containing functional groups on the surface, so that the stability of the graphene oxide dispersed in water is very good. However, the graphene oxide has strong stability in water, so that the concentration of the graphene oxide in an aqueous solution is difficult to increase by a conventional method, and thus the practical use of the graphene oxide has a limitation which is difficult to overcome.
Application number 201610404290.5 discloses a preparation method of a graphene-nano copper composite film, which comprises the steps of obtaining an electrodeposited graphene oxide film by an electrophoretic deposition method, obtaining the graphene-nano copper composite film by high-temperature annealing treatment, and finally obtaining the graphene-nano copper composite heat-conducting film by a hot-pressing technology. The thermal conductivity coefficient of the thermal conductive film obtained by the method is about 600W/mK, the longitudinal thermal conductivity coefficient is about 3W/mK, the thermal conductivity coefficient is low, and the practical application is difficult.
Application number 201610327285.9 discloses a method for preparing a titanium metal-graphene composite heat conducting film by spraying graphene oxide on the surface of a copper foil, drying, compacting, stripping to obtain a graphene oxide film, then transferring the graphene oxide film to a vacuum condition for titanium ion plating on the surface of the graphene oxide film, and spraying an insulating material. The product has transverse heat conductivity of 600-1800W/mK and longitudinal heat conductivity of about 3W/mK, but has harsh preparation process conditions and higher cost, and is not favorable for scale-up production.
The existing heat conducting film is usually prepared by a method of coating graphene oxide to form a film, but because the concentration of a graphene oxide aqueous solution is lower than 0.8%, a large amount of energy is consumed to evaporate redundant water in the film forming process, so that the energy consumption for preparing the graphene film is too high, and the thickness of the graphene film is also thinner due to the lower concentration, so that the heat conducting flux of the graphene film cannot meet the current 5G heat dissipation application. In addition, the high thermal conductivity of graphene is mainly embodied in the plane, but the thermal conductivity perpendicular to the graphene plane is low, so that the overall thermal conductivity and heat dissipation capability of graphene is weak.
Disclosure of Invention
In view of this, embodiments of the present invention provide a preparation method of a concentrated graphene oxide solution, which can effectively increase the concentration of graphene oxide, so as to solve one or more problems in the prior art.
In order to achieve the above object, a first aspect of embodiments of the present invention provides a preparation method of a concentrated graphene oxide solution, where the preparation method includes the following steps: forming negative charges on the surface of graphene oxide in the graphene oxide aqueous solution; utilizing metal salt to colloidize the graphene oxide aqueous solution with negative charges to form metal-doped graphene oxide colloid; and concentrating and separating the metal-doped graphene oxide colloid to obtain a metal-doped graphene oxide aqueous solution, namely the concentrated graphene oxide solution.
Further, the forming negative charges on the surface of the graphene oxide in the graphene oxide aqueous solution comprises: and carrying out ultraviolet irradiation on the graphene oxide aqueous solution by using an ultraviolet lamp so as to form negative charges on the surface of the graphene oxide in the graphene oxide aqueous solution.
Further, the colloidizing the graphene oxide aqueous solution with negative charges by using a metal salt to form a metal-doped graphene oxide colloid, comprising: and fully mixing the metal salt and the graphene oxide aqueous solution with negative charges so as to colloidize the graphene oxide aqueous solution with negative charges by using the metal salt to form a metal-doped graphene oxide colloid.
Further, the step of concentrating and separating the metal-doped graphene oxide colloid to obtain a concentrated graphene oxide solution includes: crystallizing the metal-doped graphene oxide colloid at low temperature, heating for crystal elimination, and concentrating to obtain a mixed solution; centrifuging the mixed solution to remove supernatant to obtain a precipitate; and stirring the precipitation solution to uniformly disperse the metal-doped graphene oxide in water to obtain a concentrated graphene oxide solution.
Further, the power of the ultraviolet lamp used for ultraviolet irradiation is 300-500W, and the wavelength is 280-380 nm; the ultraviolet irradiation time is 5-50 min.
Further, the metal salt is a soluble metal salt; furthermore, the metal salt is one or more of metal nitrate and metal chloride; further, the mass ratio of the metal salt to the graphene oxide is 1:10000-1: 1000.
Further, the stirring speed in the full mixing process is 600r/min, and the stirring time is 10-100 min.
Further, the low-temperature crystallization temperature is-10 ℃ to-20 ℃, and the low-temperature crystallization time is 12-24 h; furthermore, the temperature-rising crystal elimination is to eliminate the crystal by natural temperature rise at normal temperature.
In a second aspect, the present invention provides a method for preparing a thermal conductive film from the concentrated graphene oxide solution according to the first aspect, where the method includes: coating the concentrated graphite oxide solution on a substrate; drying the substrate coated with the concentrated graphene oxide solution in an oven, and stripping to obtain a metal graphene oxide film; and graphitizing the metal graphene oxide film at 1500-2300 ℃, and then rolling to obtain the heat-conducting film.
A third aspect of the embodiments of the present invention provides a thermally conductive film produced by the method for producing a thermally conductive film according to the second aspect of the embodiments of the present invention.
Compared with the prior art, the embodiment of the invention at least has the following beneficial effects:
1. according to the embodiment of the invention, firstly, a large amount of negative charges are generated on the surface of graphene oxide in a graphene oxide aqueous solution in an ultraviolet irradiation mode, then metal ions in metal salt are combined with the negative charges on the surface of the graphene oxide to generate a metal-doped graphene oxide colloid, and finally, the metal-doped graphene oxide colloid is crystallized at a low temperature and then crystallized at a high temperature to obtain the metal-doped graphene oxide aqueous solution, so that the concentration of the graphene oxide is improved by preparing the metal-doped graphene oxide aqueous solution; the method solves the problems that the concentration of graphene oxide is low and is difficult to improve in the prior art.
2. According to the embodiment of the invention, the heat conducting film is prepared by using the concentrated graphene oxide, so that the drying time in the preparation process of the heat conducting film can be shortened, and the energy consumption of later-stage water treatment is saved; but also can effectively adjust the thickness of heat conduction membrane through changing concentrated oxidation graphite alkene concentration, improve the heat conductivity.
3. The preparation method of the heat-conducting film in the embodiment of the invention is simple, low in cost, strong in applicability and suitable for industrial production.
Drawings
FIG. 1 is an SEM photograph of a thermally conductive film in example 1 of the present invention;
FIG. 2 is an SEM photograph of a thermally conductive film in example 2 of the present invention;
FIG. 3 is an SEM photograph of a thermally conductive film in example 3 of the present invention;
fig. 4 is an SEM image of the heat conductive film in example 4 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
In a first aspect, an embodiment of the present invention provides a preparation method of a concentrated graphene oxide solution, where the preparation method includes the following steps: s101, forming negative charges on the surface of graphene oxide in a graphene oxide aqueous solution; s102, colloidizing the graphene oxide aqueous solution with negative charges by using metal salt to form metal-doped graphene oxide colloid; s103, concentrating and separating the metal-doped graphene oxide colloid to obtain a metal-doped graphene oxide aqueous solution, namely the concentrated graphene oxide solution.
The embodiment of the invention does not limit the specific implementation modes of the three processes of negative charge formation, gelatinization and concentration and separation, as long as the concentrated graphene oxide solution can be obtained.
According to the embodiment of the invention, negative charges are formed on the surface of graphene oxide in a graphene oxide aqueous solution, then metal ions in metal salt are fully combined with the negative charges to enable the graphene oxide aqueous solution to be gelatinized, and finally the metal-doped graphene oxide aqueous solution is obtained through concentration and separation. According to the embodiment of the invention, the concentration of the graphene oxide is improved by preparing the metal-doped graphene oxide aqueous solution.
In a further embodiment, forming negative charges on the surface of graphene oxide in the graphene oxide aqueous solution comprises: and carrying out ultraviolet irradiation on the graphene oxide aqueous solution by using an ultraviolet lamp so as to form negative charges on the surface of the graphene oxide in the graphene oxide aqueous solution.
According to the embodiment of the invention, ultraviolet irradiation is carried out on the graphene oxide aqueous solution, so that a large amount of negative charges can be formed on the surface of the graphene oxide in the graphene oxide aqueous solution.
In a further embodiment, the colloidizing of the graphene oxide aqueous solution having negative charges with a metal salt to form a metal-doped graphene oxide colloid comprises: and fully mixing the metal salt and the graphene oxide aqueous solution with negative charges so as to colloidize the graphene oxide aqueous solution with negative charges by using the metal salt to form a metal-doped graphene oxide colloid.
After the metal salt and the graphene oxide with negative charges are fully mixed, the metal ions and the negative charges can be spontaneously combined, so that a colloidization process is realized.
In a further embodiment, in order to enable concentration of the metal-doped graphene oxide, the metal-doped graphene oxide colloid is concentrated and separated to obtain a concentrated graphene oxide solution, which includes: crystallizing the metal-doped graphene oxide colloid at low temperature, heating for crystal elimination, and concentrating to obtain a mixed solution; centrifuging the mixed solution to remove supernatant to obtain a precipitate; and stirring the precipitation solution to uniformly disperse the metal-doped graphene oxide in water to obtain a concentrated graphene oxide solution.
The metal-doped graphene oxide colloid formed after the colloid is converted into a uniform dispersion liquid state, and then dispersoids in the dispersion liquid can be effectively dissolved in partial water through a low-temperature crystallization and temperature rise crystallization mode, so that a suspension liquid is formed; and finally, removing the supernatant through centrifugal separation to obtain a concentrated graphene oxide solution.
In a further embodiment, the power of the ultraviolet lamp used for ultraviolet irradiation is 300-500W (e.g. 300, 350, 400, 450 or 500W, etc.), and the wavelength is 280-380nm (e.g. 280, 300, 350 or 380nm, etc.).
In further embodiments, the time of the ultraviolet irradiation is 5-50min (e.g., 5, 10, 20, 30, 45, or 50min, etc.).
In a further embodiment, in order to enable the metal ions in the metal salt to effectively combine with the negative charges on the surface of the graphene oxide; preferably, the metal salt is a soluble metal salt, for example, the metal salt is one or more of a metal nitrate, a metal chloride, and the like. In a further embodiment, the mass ratio of the metal salt to the graphene oxide is 1:10000-1:1000 (e.g., 1:10000, 1:5000, 1:4000, 1:3000, 1:2000, or 1:1000, etc.), and the addition of an excess amount of the metal salt can facilitate the negative charges on the surface of the graphene oxide to be sufficiently bound by the metal ions.
In a further embodiment, the stirring speed during the intensive mixing is 600-.
In a further embodiment, in order to enable the graphene oxide to be effectively concentrated, the low-temperature crystallization temperature is-10 ℃ to-20 ℃ (for example, -10 ℃, 15 ℃ or-20 ℃, and the like), and the low-temperature crystallization time is 12 to 24 hours (for example, 12, 15, 20 or 24 hours and the like); in a further embodiment, the temperature-rising decrystallization is performed by naturally raising the temperature at normal temperature to eliminate crystallization.
In a second aspect, the present invention provides a method for preparing a thermal conductive film from the concentrated graphene oxide solution according to the first aspect, where the method includes: coating the concentrated graphite oxide solution on a substrate; drying the substrate coated with the concentrated graphene oxide solution in an oven, and stripping to obtain a metal graphene oxide film; graphitizing the metal graphene oxide film at 1500-2300 ℃ and then rolling to obtain the heat-conducting film.
In the prior art, since the graphene oxide concentration is too low, a large amount of energy is consumed for drying treatment at a later stage in the process of preparing the thermally conductive film to remove moisture in the thermally conductive film, and since the graphene oxide concentration is too low, it is also difficult to change the graphene oxide concentration by a conventional method to adjust the thickness of the thermally conductive film. According to the embodiment of the invention, the heat conducting film is prepared by adopting the concentrated graphene oxide, so that the drying time can be shortened, the energy consumption can be saved, and the thickness of the heat conducting film can be effectively adjusted.
The metal ion that combines in the concentrated oxidation graphite alkene solution of this embodiment stops between oxidation graphite alkene's layer, and among the graphitization processing process, metallic element can realize the overlap joint between oxidation graphite alkene layer and the layer at high temperature in-process to improve the longitudinal thermal conductivity of heat conduction membrane.
According to the embodiment of the invention, the concentration of the graphene oxide is improved by using a method of forming colloid by combining positive and negative charges; the heat conducting membrane prepared by the concentrated graphene oxide solution shortens the drying treatment time and saves the energy consumption of the later water treatment; the longitudinal thermal conductivity of the heat-conducting film is greatly improved by utilizing the synergistic effect of metal and graphene oxide.
A third aspect of the embodiments of the present invention provides a thermally conductive film produced by the method for producing a thermally conductive film according to the second aspect of the embodiments of the present invention.
It is further noted that any range recited herein includes the endpoints and any values therebetween and any subranges subsumed therein or any values therebetween unless otherwise specified.
The longitudinal thermal conductivity of the heat-conducting film is tested by adopting a relaxation-resistant LFA467 HT type laser thermal conductivity coefficient measuring instrument.
Example 1
The preparation method of the concentrated graphene oxide solution comprises the following steps: and (3) carrying out ultraviolet irradiation on the graphene oxide aqueous solution with the mass concentration of 1% for 5min by adopting an ultraviolet lamp with the power of 350W and the ultraviolet wavelength of 280-380nm, so that a large amount of negative charges are generated on the surface of the graphene oxide, and the graphene oxide aqueous solution with the negative charges is obtained. Adding ferric nitrate into the graphene oxide aqueous solution with negative charges, and stirring at the speed of 600r/min for 10min to fully combine iron ions in the system with the negative charges on the surface of the graphene oxide to generate iron-doped graphene oxide colloid; wherein the mass ratio of the ferric nitrate to the graphene oxide is 1: 10000. Crystallizing the iron-doped graphene oxide colloid at a low temperature of-10 ℃ for 12h, naturally heating at a normal temperature, and removing ice crystals to generate a mixed solution; centrifuging the mixed solution for 10min to remove supernatant to obtain precipitate; and ultrasonically stirring the precipitation solution for 0.5h to obtain an iron-doped graphene oxide aqueous solution with the mass concentration of 3%, namely the concentrated graphene oxide solution.
The preparation method of the heat-conducting film comprises the following steps: continuously coating the concentrated graphene oxide solution on a PET (polyethylene terephthalate) substrate by using a coating machine, drying the PET substrate coated with the concentrated graphene oxide solution in a tunnel oven, peeling, and rolling to obtain an iron-doped graphene oxide film; graphitizing the iron-doped graphene oxide film at 1500 ℃, and then rolling to obtain the heat-conducting film. The metal iron realizes the lapping effect among the longitudinal graphene oxide layers of the heat-conducting film in the graphitization treatment process, so that the longitudinal thermal conductivity is improved. The longitudinal thermal conductivity of the heat conducting film is 15W/mK.
Fig. 1 is an SEM image of the heat conductive film in example 1 of the present invention. As shown in fig. 1, the structure of the heat conductive film of the embodiment of the present invention is orderly arranged, and the thickness of the heat conductive film is 20 μm.
Example 2
The preparation method of the concentrated graphene oxide solution comprises the following steps: and (3) carrying out ultraviolet irradiation on the graphene oxide aqueous solution with the mass concentration of 1% for 15min by adopting an ultraviolet lamp with the power of 350W and the ultraviolet wavelength of 280-380nm, so that a large amount of negative charges are generated on the surface of the graphene oxide, and the graphene oxide aqueous solution with the negative charges is obtained. Adding copper nitrate into the graphene oxide aqueous solution with negative charges, and stirring at the speed of 600r/min for 30min to fully combine copper ions in the system with the negative charges on the surface of the graphene oxide to generate a copper-doped graphene oxide colloid; wherein the mass ratio of the copper nitrate to the graphene oxide is 3: 10000. Crystallizing the copper-doped graphene oxide colloid at a low temperature of-12 ℃ for 15h, naturally heating at a normal temperature, and removing ice crystals to generate a mixed solution; centrifuging the mixed solution for 20min to remove supernatant to obtain precipitate; and ultrasonically stirring the precipitation solution for 1h to obtain an iron-doped graphene oxide aqueous solution with the mass concentration of 5%, namely the concentrated graphene oxide solution.
The preparation method of the heat-conducting film comprises the following steps: continuously coating the concentrated graphene oxide solution on a PET (polyethylene terephthalate) substrate by using a coating machine, drying the PET substrate coated with the concentrated graphene oxide solution in a tunnel oven, peeling, and rolling to obtain a copper-doped graphene oxide film; graphitizing the copper-doped graphene oxide film at 1700 ℃, and then rolling to obtain the heat-conducting film. The metal copper realizes the lapping effect among the longitudinal graphene oxide layers of the heat conducting film in the graphitization treatment process, so that the longitudinal thermal conductivity is improved. The longitudinal thermal conductivity of the heat conducting film is 20W/mK.
Fig. 2 is an SEM image of the heat conductive film in example 2 of the present invention. As shown in fig. 2, the structure of the heat conductive film of the embodiment of the present invention is orderly arranged, and the thickness of the heat conductive film is 60 μm.
Example 3
The preparation method of the concentrated graphene oxide solution comprises the following steps: and (3) carrying out ultraviolet irradiation on the graphene oxide aqueous solution with the mass concentration of 1% for 30min by adopting an ultraviolet lamp with the power of 350W and the ultraviolet wavelength of 280-380nm, so that a large amount of negative charges are generated on the surface of the graphene oxide, and the graphene oxide aqueous solution with the negative charges is obtained. Adding silver nitrate into the graphene oxide aqueous solution with negative charges, and stirring at the speed of 600r/min for 60min to fully combine silver ions in the system with the negative charges on the surface of the graphene oxide to generate a silver-doped graphene oxide colloid; wherein the mass ratio of silver nitrate to graphene oxide is 6: 10000. Crystallizing the iron-doped graphene oxide colloid at a low temperature of-15 ℃ for 20h, naturally heating at a normal temperature, and removing ice crystals to generate a mixed solution; centrifuging the mixed solution for 30min to remove supernatant to obtain precipitate; and ultrasonically stirring the precipitation solution for 3 hours to obtain a silver-doped graphene oxide aqueous solution with the mass concentration of 7%, namely the concentrated graphene oxide solution.
The preparation method of the heat-conducting film comprises the following steps: continuously coating the concentrated graphene oxide solution on a PET (polyethylene terephthalate) substrate by using a coating machine, drying the PET substrate coated with the concentrated graphene oxide solution in a tunnel oven, peeling, and rolling to obtain a silver-doped graphene oxide film; graphitizing the silver-doped graphene oxide film at 2000 ℃, and then rolling to obtain the heat-conducting film. The metal silver realizes the lapping effect among the longitudinal graphene oxide layers of the heat conducting membrane in the graphitization treatment process, so that the longitudinal thermal conductivity is improved. The longitudinal thermal conductivity of the heat conducting film is 28W/mK.
Fig. 3 is an SEM image of the heat conductive film in example 3 of the present invention. As shown in fig. 3, the structure of the heat conductive film of the embodiment of the invention is orderly arranged, and the thickness of the heat conductive film is 150 μm.
Example 4
The preparation method of the concentrated graphene oxide solution comprises the following steps: and (3) carrying out ultraviolet irradiation on the graphene oxide aqueous solution with the mass concentration of 1% for 50min by adopting an ultraviolet lamp with the power of 350W and the ultraviolet wavelength of 280-380nm, so that a large amount of negative charges are generated on the surface of the graphene oxide, and the graphene oxide aqueous solution with the negative charges is obtained. Adding silver nitrate into the graphene oxide aqueous solution with negative charges, and stirring at the speed of 600r/min for 100min to fully combine silver ions in the system with the negative charges on the surface of the graphene oxide to generate a silver-doped graphene oxide colloid; wherein the mass ratio of silver nitrate to graphene oxide is 1: 1000. Crystallizing the iron-doped graphene oxide colloid at a low temperature of-20 ℃ for 24h, naturally heating at a normal temperature, and removing ice crystals to generate a mixed solution; centrifuging the mixed solution for 60min to remove supernatant to obtain precipitate; and ultrasonically stirring the precipitation solution for 6 hours to obtain an iron-doped graphene oxide aqueous solution with the mass concentration of 10%, namely the concentrated graphene oxide solution.
The preparation method of the heat-conducting film comprises the following steps: continuously coating the concentrated graphene oxide solution on a PET (polyethylene terephthalate) substrate by using a coating machine, drying the PET substrate coated with the concentrated graphene oxide solution in a tunnel oven, peeling, and rolling to obtain a silver-doped graphene oxide film; graphitizing the silver-doped graphene oxide film at 2300 ℃, and then rolling to obtain the heat-conducting film. The metal silver realizes the lapping effect among the longitudinal graphene oxide layers of the heat conducting membrane in the graphitization treatment process, so that the longitudinal thermal conductivity is improved. The longitudinal thermal conductivity of the heat conducting film is 35W/mK.
Fig. 4 is an SEM image of the heat conductive film in example 4 of the present invention. As shown in fig. 4, the structure of the heat conductive film of the embodiment of the invention is orderly arranged, and the thickness of the heat conductive film is 200 μm.
In the description herein, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (12)
1. A preparation method of a concentrated graphene oxide solution is characterized by comprising the following steps:
forming negative charges on the surface of graphene oxide in the graphene oxide aqueous solution;
utilizing metal salt to colloidize the graphene oxide aqueous solution with negative charges to form metal-doped graphene oxide colloid;
crystallizing the metal-doped graphene oxide colloid at low temperature, heating for crystal elimination, concentrating and separating to obtain a metal-doped graphene oxide aqueous solution, namely a concentrated graphene oxide solution;
the forming negative charges on the surface of graphene oxide in the graphene oxide aqueous solution comprises: and carrying out ultraviolet irradiation on the graphene oxide aqueous solution by using an ultraviolet lamp so as to form negative charges on the surface of the graphene oxide in the graphene oxide aqueous solution.
2. The preparation method according to claim 1, wherein the colloidizing the graphene oxide aqueous solution with negative charges by using the metal salt to form a metal-doped graphene oxide colloid comprises:
and fully mixing the metal salt and the graphene oxide aqueous solution with negative charges so as to colloidize the graphene oxide aqueous solution with negative charges by using the metal salt to form a metal-doped graphene oxide colloid.
3. The preparation method according to claim 1, wherein the concentrating and separating the metal-doped graphene oxide colloid to obtain the metal-doped graphene oxide aqueous solution comprises:
crystallizing the metal-doped graphene oxide colloid at low temperature, heating for crystal elimination, and concentrating to obtain a mixed solution;
centrifuging the mixed solution to remove supernatant to obtain a precipitate;
and stirring the precipitation solution to uniformly disperse the metal-doped graphene oxide in water to obtain a metal-doped graphene oxide aqueous solution.
4. The method as claimed in claim 1, wherein the power of the ultraviolet lamp used for the ultraviolet irradiation is 300-500W, and the wavelength is 280-380 nm; the ultraviolet irradiation time is 5-50 min.
5. The method of claim 2, wherein the metal salt is a soluble metal salt.
6. The method according to claim 5, wherein the metal salt is one or more of a metal nitrate and a metal chloride.
7. The preparation method according to claim 5, wherein the mass ratio of the metal salt to the graphene oxide is 1:10000-1: 1000.
8. The method as claimed in claim 2, wherein the stirring speed during the thorough mixing process is 600-1000r/min, and the stirring time is 10-100 min.
9. The preparation method of claim 3, wherein the temperature of the low-temperature crystallization is-10 ℃ to-20 ℃, and the time of the low-temperature crystallization is 12 to 24 hours.
10. The preparation method according to claim 9, wherein the temperature-rising decrystallization is natural temperature-rising decrystallization at normal temperature.
11. A method for preparing a thermal conductive film using the concentrated graphene oxide solution according to any one of claims 1 to 10, comprising:
coating the concentrated graphene oxide solution on a substrate;
drying the substrate coated with the concentrated graphene oxide solution in an oven, and stripping to obtain a metal graphene oxide film;
and graphitizing the metal graphene oxide film at 1500-2300 ℃, and then rolling to obtain the heat-conducting film.
12. The heat conductive film according to claim 11.
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