CN113563773A - Preparation method of graphene heat dissipation coating - Google Patents
Preparation method of graphene heat dissipation coating Download PDFInfo
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- CN113563773A CN113563773A CN202110845517.0A CN202110845517A CN113563773A CN 113563773 A CN113563773 A CN 113563773A CN 202110845517 A CN202110845517 A CN 202110845517A CN 113563773 A CN113563773 A CN 113563773A
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D133/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Coating compositions based on derivatives of such polymers
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- C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
- C09D5/08—Anti-corrosive paints
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- C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
- C09D7/40—Additives
- C09D7/60—Additives non-macromolecular
- C09D7/61—Additives non-macromolecular inorganic
- C09D7/62—Additives non-macromolecular inorganic modified by treatment with other compounds
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
- F21V29/00—Protecting lighting devices from thermal damage; Cooling or heating arrangements specially adapted for lighting devices or systems
- F21V29/50—Cooling arrangements
- F21V29/70—Cooling arrangements characterised by passive heat-dissipating elements, e.g. heat-sinks
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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- F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
- F21V29/00—Protecting lighting devices from thermal damage; Cooling or heating arrangements specially adapted for lighting devices or systems
- F21V29/85—Protecting lighting devices from thermal damage; Cooling or heating arrangements specially adapted for lighting devices or systems characterised by the material
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K2201/00—Specific properties of additives
- C08K2201/011—Nanostructured additives
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
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- F21Y2115/00—Light-generating elements of semiconductor light sources
- F21Y2115/10—Light-emitting diodes [LED]
Abstract
The invention discloses a preparation method of a graphene heat dissipation coating. According to the invention, firstly, the unstable ammonium carbonate of intercalation is heated by an electric arc method to open a graphite sheet layer to form an accordion-type expanded graphite form, then the accordion-type expanded graphite form is added into a mixed aqueous solution of oxalic acid and potassium ferrate, and the graphite sheet layer is enabled to have a small amount of oxygen-containing functional groups under the high-pressure working environment of a high-pressure homogenizer, so that the graphene nanoplatelets have certain hydrophilicity and are easy to disperse and compatible with a heat dissipation coating system, and the graphene nanoplatelets and other raw materials are used together to prepare the heat dissipation coating. The coating can be directly coated on the surface of an object to be cooled or accelerated in heat conduction, the coating automatically radiates heat to the atmospheric space or the internal space of the object by the emissivity of more than 0.91 epsilon and the infrared wave long wave band, the heat exchange is accelerated, the surface and internal temperature of the object is reduced, and the comparison of the heat radiation of a heat source of an iron plate at 100 ℃ and the working temperature of a 9W power LED lamp shows that: the graphene heat dissipation coating can be effectively reduced by 4-8 ℃.
Description
Technical Field
The invention relates to the technical field of heat dissipation coatings, and particularly relates to a preparation method of a graphene heat dissipation coating.
Background
With the development of current electronic technology, electronic components of devices such as mobile phones and computers generate much heat during operation, and in order to dissipate heat as quickly as possible, a metal heat sink is usually added, because metal has a high thermal conductivity, and common materials include copper, aluminum or aluminum alloy. However, the emissivity of the metal surface is low, and the heat collected on the metal surface is difficult to dissipate without convective heat transfer. The improvement of the heat radiation efficiency of the metal surface by the coating technology is an important way to improve the heat radiation performance of the metal material, and the heat radiation coating is widely concerned today in the rapid development of the electronic industry.
The emissivity of most coatings is very high and very close. The emissivity of the thermal infrared imager to the coating can be set to be 0.95, the emissivity of the coatings made of the same materials and different colors is very close, and the error does not exceed the measurement precision range generally. Therefore, the technical challenges of heat-dissipating coatings have focused not only on increasing the emissivity, but also on reducing the thermal resistance of the coating, including reducing the contact resistance between the coatings and the thermal resistance of the coating material itself. The method for realizing the low thermal resistance of the coating comprises two aspects: the heat conductivity coefficient of the coating is improved, and a heat conduction functional body with high performance and high structure is used; the mechanical property of the coating is improved, and the thickness of the coating is reduced, so that the coating can meet the requirements of good adhesive force, good flexibility resistance, good impact resistance, good compactness and the like when being thin.
Graphene is a novel two-dimensional material composed of a single layer of carbon atoms, and has the highest thermal conductivity (5300W/mK), the highest mechanical strength (130GPa, the theoretical Young modulus of 1TPa) and the high carrier mobility (2.5 x 10) of the known materials5cm2V-1s-1) Good flexibility and low density, etc., are observedIs the most promising new type of heat conducting material. In the aspect of heat dissipation coating, different from the traditional heat conduction filler, in the coating component composition, the graphene macro material can be assembled by single-layer graphene through molecular level lap joint, and meanwhile, the high heat conduction and super flexibility characteristics of the graphene are inherited, so that the coating is a different choice from the traditional carbon heat conduction filler of the heat dissipation coating. Graphene has a definite application prospect in the heat dissipation coating, and in a graphene heat dissipation coating system, the dispersibility of a graphene material and the compatibility of the system are important factors which are not negligible. In the existing graphene preparation process and heat dissipation coating technical route, the stable dispersibility of the hydrophobic and oleophobic material graphene in the system is easily ignored, so that the expected effect of the graphene heat dissipation coating cannot be achieved in use.
Disclosure of Invention
In order to solve the problems, the invention provides a preparation method of a graphene heat-dissipation coating, which comprises the steps of heating intercalation unstable ammonium carbonate by an electric arc method to open a graphite sheet layer to form an accordion-type expanded graphite form (worm graphite precursor), adding the expanded graphite form into a mixed aqueous solution of oxalic acid and potassium ferrate, and enabling the graphite sheet layer to have a small amount of oxygen-containing functional groups under the high-pressure working environment of a high-pressure homogenizer, so that the graphene microchip has certain hydrophilicity and is easy to disperse and compatible with a heat-dissipation coating system. The modified graphene nanoplatelets are dispersed and compatible with a water-based paint system, so that the heat dissipation efficiency of the heating matrix coating is effectively improved, and the adhesion, water resistance, corrosion resistance and impact resistance of the coating are improved.
The technical scheme of the invention is as follows: a preparation method of a graphene heat dissipation coating is characterized by comprising the following steps:
(1) pretreatment of vermicular graphite
Adding the vermicular graphite into an ammonium carbonate aqueous solution, soaking for 1-3h, filtering, drying, pressing the vermicular graphite into blocks by using a laminating machine, and then carrying out electric arc heating and puffing treatment for 10-20min to obtain a vermicular graphite treatment precursor;
(2) preparation of graphene nanoplatelets
Adding the worm graphite treatment precursor into a mixed aqueous solution of oxalic acid and potassium ferrate to prepare a mixed material, stirring, and then carrying out shearing and stripping treatment in a high-pressure homogenizing device to obtain hydrophilic graphene nanoplatelets;
(3) preparation of graphene heat dissipation coating
And (3) stirring and mixing the hydrophilic graphene nanoplatelets prepared in the step (2) and other components of the heat dissipation coating uniformly, mechanically sanding, and filtering to obtain the graphene heat dissipation coating.
Further, the graphene heat dissipation coating in the step (3) comprises the following components in parts by weight: 15-30 parts of graphene micro-sheets, 1-2 parts of conductive carbon black, 1-3 parts of carbon nano-tubes, 40-60 parts of aqueous polyurethane dispersion liquid, 1-2 parts of defoaming agent and 1-3 parts of dispersing agent. When the titanium dioxide is used for preparing the gray black heat dissipation coating, the components and the parts by weight are as follows: 15-20 parts of graphene micro-sheets, 10-15 parts of titanium dioxide, 1-3 parts of carbon nano-tubes, 40-55 parts of aqueous polyurethane dispersion liquid, 1-2 parts of defoaming agent and 1-3 parts of dispersing agent.
Further, the mechanical sanding process in the step (3) is as follows: stirring in the stirring reaction kettle, after the materials are uniformly mixed, leading the power pump into a sand mill, circulating the materials through the power pump, mechanically sanding for 1-2h, and filtering with a 325-mesh filter screen to obtain the graphene heat dissipation coating.
Further, the step (2) of shear peeling treatment is as follows: and mechanically stirring, pumping the mixed material into a high-pressure homogenizing device through a transmission pump for material shearing and stripping treatment, wherein the working pressure of the high-pressure homogenizing device is 40-60MPa, the working temperature is 15-35 ℃, the two devices carry out material circulation treatment through a power pump, the material treatment time is 1-2h, a discharge valve is opened, a filter screen is used for filtering, washing and vacuum drying are carried out, and the hydrophilic graphene microchip is obtained. Preferably, the material filtration adopts 1500-.
Preferably, the purity of the vermicular graphite in the step (1) is more than or equal to 99 percent, the expansion ratio is 500-600ml/g, the particle size of the raw material is 100-325 meshes, and the solid content of the ammonium carbonate aqueous solution is 10-25 percent.
Preferably, in the filtering in the step (1), a screen with 325 and 1500 meshes is selected; the drying adopts a blowing drying mode, the drying temperature is 60-80 ℃, and the electric arc heating temperature is 400-600 ℃.
Preferably, in the step (2), the content of potassium ferrate in the mixed aqueous solution of oxalic acid and potassium ferrate is 1-5g/L, the content of oxalic acid is 1-5g/L, and the mass fraction of graphene nanoplatelets in the prepared graphene nanoplatelet mixed material is 1-3 wt%.
Preferably, the solid content of the aqueous polyurethane dispersion liquid in the step (3) is 30-50 wt%, and the solid content of the prepared graphene heat dissipation coating is 55-70 wt%. The aqueous polyurethane dispersion can be one or a combination of more of aqueous acrylic resin, aqueous epoxy resin, aqueous polyurethane and aqueous organic silicon resin.
Preferably, the dispersant in the step (3) can be one or a mixture of several of non-ionic fatty acid ethylene oxide adduct, polyethylene glycol type polyol and polyethyleneimine derivative, and the defoaming agent can be one or a mixture of several of aqueous system silicone polyether siloxane, fluorine modified polysiloxane and polyolefin.
The invention also discloses a coating method of the graphene heat dissipation coating, which specifically comprises the following steps: the metal substrate is subjected to oil and rust removal pretreatment, the heat dissipation coating is diluted by deionized water, the construction mode adopts air spraying, the spraying pressure is 0.3-0.5Mpa, the construction environment temperature is 15-35 ℃, the relative humidity is 45-75% RH, the coated substrate is sent into an oven at 80 ℃ for fast drying for 5min, and is transferred to an oven at 150 ℃ for 30min for coating setting, and the coating thickness is 0.5 mm.
Preferably, the dilution ratio of the heat dissipation coating and the deionized water is 1:0.25-0.35, and the construction viscosity of the diluted heat dissipation coating is 20-45s/15-35 ℃ (NK, 2# cup).
The invention develops a coating which takes a graphene nano material as a main heat conducting filler, radiates object heat in a radiation mode or accelerates heat conduction. The graphene nanoplatelets are heated by an electric arc method to intercalate unstable ammonium carbonate so as to open the graphite sheet layers, and thus, an accordion-type expanded graphite form (a worm graphite precursor) is formed. The potassium ferrate contains FeO4 2-The central atom Fe exists in hexavalent range, and the standard electrode potential under the acidic condition is respectively E0 FeO4 2-/Fe3+＝2.20V，E0FeO4 2-/Fe(OH)30.72V, very oxidizing. The temporary stable state of the mixed aqueous solution of oxalic acid and potassium ferrate can quickly react to release CO in the high-pressure working environment of a high-pressure homogenizer2、O2And oxidizing part of the graphite sheet layer to enable the graphite sheet layer to have a small amount of oxygen-containing functional groups, and the graphene nanoplatelets have certain hydrophilicity and are easy to disperse and compatible with a heat dissipation coating system. The performance indexes of the graphene heat dissipation coating prepared by the prepared graphene nanoplatelets and other raw materials are shown in the following table 1.
Table 1 graphene heat dissipation coating detection performance table
| Serial number | Inspection item | Test results | Basis of |
| 1 | Nonvolatile content,% [ (150. + -.2). degree.C./1 h/about 2g] | 40-55 | GB/T 1725-2007 |
| 2 | Viscosity, mPas | 0.14-0.28×103 | GB/T 2794-2013 |
| 3 | Drying for (dry) min [ (80 + -2) deg.C/10 min] | Has dried | GB/T1728- |
| 4 | Hundred lattice test, grade | 1-2 | GB/T 9286-1998 |
| 5 | Film hardness | HB | GB/T 6739-2006 |
| 6 | Thermal conductivity, W/mK | ＞3 | ASTM E1461 |
| 7 | Acid resistance ( |
No abnormality | GB/T9274- |
| 8 | Alkali resistance (immersed in 10% NaOH solution for 168h) | No abnormality | GB/T9274-1988A method |
| 9 | Abrasion resistance (500g/500r, grinding wheel type: CS-10) | 0.003-0.005 | GB/T 1768-2006 |
| 10 | Heat resistance [ (250 +/-3) DEG C/24 h] | Slight discoloration | GB/T 1735-2009 |
| 11 | Infrared reflectivity (emission band 2-13.5 μm) | 0.91-0.93 | GJB5023.2-2003 |
The invention has the beneficial effects that: the graphene heat dissipation coating prepared by the invention is a water-based heat dissipation coating, is green and environment-friendly, and is suitable for commercial and industrial large-scale production. The coating can be directly coated on the surface of an object to be cooled or accelerated in heat conduction, the coating can automatically radiate heat to the atmosphere space or the internal space of the object by the emissivity of more than 0.91 epsilon and the infrared wave long wave band, so that the heat exchange is accelerated, the surface and internal temperature of the object is reduced, the heat exchange rate is improved, and the comparison of the heat source cooling effect of the iron plate at 100 ℃ and the working temperature of the 9W power LED lamp shows that: the graphene heat dissipation coating can be effectively reduced by 4-8 ℃.
Drawings
FIG. 1 is an SEM image of an expanded graphite (vermicular graphite) precursor;
fig. 2 is a graphene nanoplatelet SEM image;
FIG. 3 is a graphene nanoplatelet TEM image;
fig. 4 is a graphene nanoplatelet Raman image;
fig. 5 is a pictorial view of an iron plate coated with a graphene heat dissipation coating;
FIG. 6 is a comparison graph of the heat dissipation effect of a 100 ℃ iron plate;
fig. 7 is a graph showing the temperature drop of a heat source at 100 ℃ of graphene heat-dissipating paint-coated iron plates according to examples and comparative examples 1 to 5;
FIG. 8 is a comparison graph of the heat dissipation effect of an LED lamp with 9W power;
FIG. 9 is a graph of the normal operating temperature drop of 9W power LED lamps of examples and comparative examples 1-5.
Detailed Description
The following are specific examples of the present invention and further describe the technical solutions of the present invention, but the scope of the present invention is not limited to these examples. All changes, modifications and equivalents that do not depart from the spirit of the invention are intended to be included within the scope thereof. The carbon nano tube used in the embodiment is a nano TNNF-6 model product in the middle age, the diameter is 10-20nm, the length is 5-20um, and the specific surface area is more than 120m2(ii) multi-walled carbon nanotubes; the conductive carbon black is a Delong carbon black DL-10 type product, the particle size is 25nm, and the oil absorption value is 220 +/-15 ml/g.
Example 1:
(1) pretreatment process of vermicular graphite
Adding 40 parts of vermicular graphite with the purity of 99 percent, the expansion ratio of 600ml/g and the raw material particle size of 100 meshes into an ammonium carbonate aqueous solution with the solid content of 15 percent for soaking for 3 hours, filtering the material by using a 325-mesh screen mesh filter screen, drying the material by using an air blowing drying box at the temperature of 80 ℃, pressing the vermicular graphite into blocks by using a laminating machine, heating the blocks by electric arc to 600 ℃, performing expansion treatment for 20 minutes to obtain a vermicular graphite treatment precursor, wherein an SEM image is shown in figure 1, and a graphene nano-micro sheet is heated by an electric arc method to intercalate unstable ammonium carbonate so as to open graphite sheets to form an accordion-type expanded graphite form;
(2) process preparation of graphene nanoplatelets
Adding 30 parts of the treated worm graphite material into a mixed aqueous solution of oxalic acid and potassium ferrate with 5g/L of potassium ferrate and 5g/L of oxalic acid to prepare a mixed material with 3 wt% of graphene nanoplatelets.
Mechanically stirring for 30min, pumping the materials into a high-pressure homogenizing device through a material conveying pump, controlling the pressure at 60MPa and the working temperature at 25 ℃, carrying out material shearing and stripping treatment, carrying out material circulation treatment on the two devices through a power pump, carrying out material treatment for 2h, opening a discharge valve, filtering through a 1500-mesh filter screen, washing, and carrying out vacuum drying at 70 ℃ to obtain hydrophilic graphene nanoplatelets; the SEM image, TEM image and Raman image are shown in the sequence of fig. 2-4, and can be seen from fig. 2: the graphene microchip has good separation effect and extremely low impurity ion content, and as can be seen from fig. 3: the exfoliation process does not form the defective structure of the graphene sheets, as can be seen in fig. 4: the graphene nanoplatelets have high single-layer rate and good product quality.
(3) Process preparation of graphene heat dissipation coating
The formula (parts by weight) is as follows: 30 parts of graphene microchip, 2 parts of conductive carbon black, 3 parts of carbon nanotube, 60 parts of 40% aqueous polyurethane/acrylic resin (the mass ratio of the two is 1:3) mixed dispersion, 2 parts of polyethylene glycol defoamer and 3 parts of polyether siloxane dispersant.
The raw materials are sequentially added into a stirring reaction kettle, mechanical stirring is carried out for 30min, after materials are uniformly mixed, a power pump is guided into a sand mill, the materials are circulated through the power pump, mechanical sand milling treatment is carried out for 2h, a 325-mesh filter screen is used for filtering, the graphene heat dissipation coating is obtained, and the solid content of the graphene heat dissipation coating is 64%.
(4) Graphene heat dissipation coating process
The iron plate is subjected to oil and rust removal pretreatment, the heat dissipation coating is diluted by deionized water according to the proportion of 1:0.25, the heat dissipation coating is coated in an air spraying mode, the spraying pressure is 0.4Mpa, the construction environment temperature is 20 ℃, the relative humidity is 45% RH, the coated base material is sent into an oven at 80 ℃ for quick drying for 5min, the coated base material is transferred to an oven at 150 ℃ for drying for 30min for coating setting, the thickness of the coating is 0.5mm, and the picture of the product is shown in figure 5.
Comparative example 1: step (1) without impregnating with an aqueous ammonium carbonate solution
The pretreatment process of the vermicular graphite in the step (1) comprises the following steps: 40 parts of vermicular graphite with the purity of 99 percent, the expansion ratio of 600ml/g and the raw material particle size of 100 meshes are pressed into blocks by a laminating machine, and arc heating and puffing treatment is carried out for 20min to obtain the vermicular graphite treatment precursor.
The rest of the procedure was the same as in example 1.
Comparative example 2: step (2) does not use oxalic acid and potassium ferrate
And (2) preparing the graphene nanoplatelets by a process: adding 30 parts of the processed worm graphite material into deionized water to prepare a graphene microchip mixed material with the solid content of 3 wt%, mechanically stirring for 30min, pumping the material into ultrahigh-pressure homogenizing equipment through a material conveying pump to perform material shearing and stripping treatment, performing material circulation treatment on the two equipment through a power pump for 2h, opening a discharge valve, filtering through a 1500-mesh filter screen, washing, and performing vacuum drying at 70 ℃ to obtain the graphene microchip.
The rest of the procedure was the same as in example 1.
Comparative example 3:
the pretreatment process of step (1) was not performed on the vermicular graphite, as in comparative example 2.
Comparative example 4:
the same as example 1 is otherwise applied, except that the treatment in steps (1) and (2) is not performed, and the untreated vermicular graphite is directly used in step (3) to prepare the heat-dissipating coating.
Comparative example 5: step (3) without using carbon nanotubes
The formula (in parts by weight) of the step (3) is as follows: 35 parts of graphene microchip, 60 parts of 40% aqueous polyurethane/acrylic resin mixed dispersion, 2 parts of defoaming agent and 3 parts of dispersing agent. The rest is the same as example 1.
Test example 1: comparison of heat dissipation effects of iron plates at 100 ℃
The experimental process comprises the following steps: fixing a square iron plate with the thickness of 50mm multiplied by 50mm to the center of a heating source of constant-temperature heat dissipation tester equipment, wherein the heat source is a square heating module with the thickness of 10mm multiplied by 10mm, adjusting the power of the equipment to stabilize the temperature of the heating source to 100 ℃, recording the temperature of the iron plate close to the position of the heat source every minute, and recording 20 groups of temperature data; after the square iron plate is treated by the graphene heat dissipation coating process in example 1 (the coating thickness is 0.5mm), the above test operation is also performed, 20 groups of temperature data are recorded, and the heat dissipation effect of the iron plate at 100 ℃ is compiled by taking numbers at different points and comparing with fig. 6. Wherein the control iron plate is represented by dots (●) and the graphene coated iron plate is represented by square dots (■). The experimental results are shown in fig. 6, where the graphene-coated iron plate can reduce the surface temperature by 6 ℃ on average.
In addition, 5 square iron plates are taken to repeat the test operation, 20 groups of temperature data of each iron plate are recorded, and the average value of the temperature of each iron plate is calculated; then, after the graphene heat dissipation coating processes in comparative examples 1 to 5 were respectively performed, the above test operation was similarly performed, 20 sets of temperature data of each iron plate coated with the heat dissipation coating were recorded, the average temperature value of each coated iron plate was calculated, and the difference between the average temperature value of each iron plate and the average temperature value after the heat dissipation coatings in comparative examples 1 to 5 were respectively coated was further calculated (the difference was also calculated in example 1), so that a heat source temperature drop diagram of 100 ℃ shown in fig. 7 was obtained. As shown in FIG. 7, the surface temperature of the comparative examples 1 to 5, which is decreased by 5 to 6 ℃ on average, can be decreased by the 100 ℃ heat source temperature drop, and the temperature decrease effect of the example 1 is significantly better than that of the comparative examples 1 to 5. The effect of comparative example 2 is the worst, and probably, after the vermicular graphite is compacted in step (1) of comparative example 2, the swelling and the exfoliation of the vermicular graphite cannot be realized in step (2) without oxalic acid and potassium ferrate.
Test example 2: comparison of heat dissipation effects of 9W power LED lamps
The experimental process comprises the following steps: buying an LED illuminating lamp with 220V power and 9W power for European and ordinary illumination, electrifying for 3 hours under normal illumination, and tracking and monitoring the change curve of the LED position temperature in 3 hours by using a temperature detector; the radiating fins of the LED illuminating lamp are taken out, the radiating fins are assembled after being processed by the graphene radiating coating process (the coating thickness is 0.5mm) in the embodiment 1, the radiating fins are normally illuminated and electrified for 3 hours, and the change curve of the LED position temperature in 3 hours is tracked and monitored by a temperature detector. The experimental results are shown in fig. 8, from which it can be seen that the graphene coated LED heat sink temperature decreases by 5 ℃.
In addition, 5 LED illuminating lamps with 220V of European general illumination and 9W of power are taken to repeat the test operation, the change curve of the LED position temperature in 3 hours is tracked and monitored by a temperature detector, and the average value of the temperature of each LED illuminating lamp is calculated; then, after the graphene heat dissipation coatings in comparative examples 1 to 5 are respectively coated, the above test operation is performed in the same way, the temperature detector tracks and monitors the change curve of the LED position temperature in 3 hours, calculates the average temperature value of each LED illuminating lamp coated with the heat dissipation coatings, and further calculates the difference between the average temperature value of each LED illuminating lamp and the average temperature value after the heat dissipation coatings in comparative examples 1 to 5 are respectively coated (the difference is also calculated in example 1), so as to obtain the operating temperature drop of the LED lamp as shown in fig. 9, as can be seen from fig. 9: the temperature of the core heating area can be averagely reduced by 4.5-5 ℃, and the temperature reduction effect of the embodiment 1 is superior to that of the comparative examples 2-5.
In conclusion, comparison of the heat source heat dissipation effect of the iron plate at 100 ℃ and the working temperature of the 9W power LED lamp shows that: the graphene heat dissipation coating can be effectively cooled by 4.5-6.0 ℃. In addition, compared with comparative examples 1-4, in the embodiment 1 of the present invention, the modified graphene processed in steps (1) and (2) is adopted, and the surface modification part contains oxygen functional groups, such that the hydrophilic effect enables the graphene to be well dispersed in the material components, and the hydrophilic groups can be effectively combined with the water-based resin and the dispersant system in the dispersed component by the similar compatibility principle, thereby facilitating the reduction of graphene agglomeration and the enhancement of material system dispersion.
In another embodiment of the present invention, an aqueous polyurethane dispersion or an aqueous acrylic resin dispersion may be used in place of the aqueous polyurethane/acrylic resin mixed dispersion of example 1, and the rest is the same as example 1.
In another embodiment of the present invention, the grey black heat dissipation coating can be prepared by adding titanium dioxide, and the formula (parts by weight) of step (3) is: 20 parts of graphene nanoplatelets, 10 parts of titanium dioxide, 2 parts of conductive carbon black, 3 parts of carbon nanotubes, 60 parts of 40% aqueous polyurethane/acrylic resin mixed dispersion, 2 parts of a defoaming agent and 3 parts of a dispersing agent. The rest is the same as example 1.
Claims (10)
1. A preparation method of a graphene heat dissipation coating is characterized by comprising the following steps:
(1) pretreatment of vermicular graphite
Adding the vermicular graphite into an ammonium carbonate aqueous solution for dipping, filtering and drying, pressing the vermicular graphite into blocks by using a laminating machine, and then carrying out electric arc heating and puffing treatment to obtain a vermicular graphite treatment precursor;
(2) preparation of graphene nanoplatelets
Adding the worm graphite treatment precursor prepared in the step (1) into a mixed aqueous solution of oxalic acid and potassium ferrate to prepare a mixed material, and then carrying out shearing and stripping treatment in a high-pressure homogenizing device to obtain hydrophilic graphene nanoplatelets;
(3) preparation of graphene heat dissipation coating
And (3) stirring and mixing the hydrophilic graphene nanoplatelets prepared in the step (2) and other components of the heat dissipation coating uniformly, mechanically sanding, and filtering to obtain the graphene heat dissipation coating.
2. The method for preparing graphene heat dissipation coating according to claim 1,
the graphene heat dissipation coating in the step (3) comprises the following components in parts by weight: 15-30 parts of graphene micro-sheets, 1-2 parts of conductive carbon black, 1-3 parts of carbon nano-tubes, 40-60 parts of aqueous polyurethane dispersion liquid, 1-2 parts of defoaming agent and 1-3 parts of dispersing agent.
3. The method for preparing graphene heat dissipation coating according to claim 1,
the graphene heat dissipation coating in the step (3) comprises the following components in parts by weight: 15-20 parts of graphene micro-sheets, 10-15 parts of titanium dioxide, 1-3 parts of carbon nano-tubes, 40-55 parts of aqueous polyurethane dispersion liquid, 1-2 parts of defoaming agent and 1-3 parts of dispersing agent.
4. The method for preparing the graphene heat dissipation coating as claimed in claim 2 or 3,
the solid content of the aqueous polyurethane dispersion liquid is 30-50 wt%; the aqueous polyurethane dispersion liquid is one or a combination of more of aqueous acrylic resin, aqueous epoxy resin, aqueous polyurethane and aqueous organic silicon resin.
5. The method for preparing the graphene heat dissipation coating as claimed in any one of claims 1 to 3,
the mechanical sanding treatment in the step (3) is as follows: stirring in the stirring reaction kettle, after the materials are uniformly mixed, leading the power pump into a sand mill, circulating the materials through the power pump, mechanically sanding for 1-2h, and filtering with a 325-mesh filter screen to obtain the graphene heat dissipation coating.
6. The method for preparing the graphene heat dissipation coating as claimed in any one of claims 1 to 3,
the shearing and stripping treatment in the step (2) comprises the following steps: mechanically stirring, pumping the mixed material into a high-pressure homogenizing device through a transmission pump for material shearing and stripping treatment, wherein the working pressure of a high-pressure homogenizing machine is 40-60MPa, the working temperature is 15-35 ℃, the two devices are used for material circulating treatment through a power pump, the material treatment time is 1-2h, a discharge valve is opened, a filter screen is used for filtering, washing and vacuum drying are carried out, and hydrophilic graphene nanoplatelets are obtained; the material filtration adopts a 1500-plus 5000-mesh filter screen, and the vacuum drying temperature of the material is 50-70 ℃.
7. The method for preparing the graphene heat dissipation coating as claimed in any one of claims 1 to 3,
in the step (1), the purity of the vermicular graphite is more than or equal to 99 percent, the expansion ratio is 500-600ml/g, the particle size of the raw material is 100-325 meshes, and the solid content of the ammonium carbonate aqueous solution is 10-25 percent;
in the filtering in the step (1), a filter screen of 325-1500 meshes is selected as the filter screen; the drying adopts a blowing drying mode, the drying temperature is 60-80 ℃, and the electric arc heating temperature is 400-600 ℃.
8. The method for preparing the graphene heat dissipation coating as claimed in any one of claims 1 to 3,
in the step (2), the content of potassium ferrate in the oxalic acid and potassium ferrate mixed aqueous solution is 1-5g/L, the content of oxalic acid is 1-5g/L, and the mass fraction of graphene nanoplatelets in the prepared graphene nanoplatelet mixed material is 1-3 wt%.
9. The graphene heat dissipation coating prepared by the preparation method of any one of claims 1 to 3.
10. The method of claim 9, wherein the graphene thermal dissipation coating is applied,
carrying out oil and rust removal pretreatment on a metal substrate, diluting a heat dissipation coating with deionized water, adopting an air spraying mode in a construction mode, wherein the spraying pressure is 0.3-0.5Mpa, the construction environment temperature is 15-35 ℃, the relative humidity is 45-75% RH, sending the coated substrate into an oven at 80 ℃, quickly drying for 5min, transferring to an oven at 150 ℃ for 30min, and carrying out coating setting, wherein the thickness of a coating is 0.5 mm;
the dilution ratio of the heat dissipation coating to the deionized water is 1:0.25-0.35, and the construction viscosity of the diluted heat dissipation coating is 20-45s/15-35 ℃.
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