阅读说明：本技术 一种宽波段光学吸收剂及涂层制备方法 (Broadband optical absorbent and coating preparation method ) 是由 朴明星 李朝龙 王啸 史浩飞 于 2021-07-02 设计创作，主要内容包括：本发明公开一种宽波段光学吸收剂及涂层的制备方法。以纳米级金属氧化物为核材料,在其表面沉积一层石墨烯墙作为壳材料,从而得到石墨烯墙包覆的核壳型复合金属氧化物粉体。基于花瓣状微观结构的石墨烯墙的巨大的比表面积,通过有效增加辐射波在涂层内部的反射吸收次数,可以有效提高涂层的吸收特性。同时,通过与金属氧化物的协同作用,可以进一步提升涂层从可见光到红外波段的光学吸收特性。本发明利用微波等离子体增强化学气相沉积技术制备具有花瓣状微观结构的石墨烯墙,可以有效缩短生长石墨烯墙的时间,提高单位时间的产量。本发明制备的石墨烯墙包覆的核壳型复合金属氧化物粉体可以作为一种新型高效的光学吸收剂进行推广和应用。(The invention discloses a preparation method of a broadband optical absorbent and a coating. The method comprises the following steps of taking a nano-scale metal oxide as a core material, and depositing a layer of graphene wall on the surface of the nano-scale metal oxide as a shell material, thereby obtaining the graphene wall-coated core-shell composite metal oxide powder. The huge specific surface area of the graphene wall based on the petal-shaped microstructure can effectively improve the absorption characteristic of the coating by effectively increasing the reflection and absorption times of the radiation wave in the coating. Meanwhile, the optical absorption characteristic of the coating from visible light to infrared bands can be further improved through the synergistic effect of the metal oxide. The method utilizes the microwave plasma enhanced chemical vapor deposition technology to prepare the graphene wall with the petal-shaped microstructure, can effectively shorten the time for growing the graphene wall and improve the yield in unit time. The core-shell composite metal oxide powder coated by the graphene wall prepared by the invention can be popularized and applied as a novel high-efficiency optical absorbent.)

1. A method for preparing a broadband optical absorbent is characterized by comprising the following steps:

weighing the metal chloride and hexamethylenetetramine, dissolving in a solvent for reaction;

separating the precipitate generated in the step 1) to obtain nano-scale metal hydroxide powder;

placing the metal hydroxide powder obtained in the step 2) in a reactor, wherein the interior of the reactor is in an oxygen-free environment; introducing mixed gas of inert gas and hydrogen into the reactor, opening a microwave generating device, carrying out microwave treatment on the metal hydroxide powder in the reactor, fully reacting and cooling to obtain nanoscale metal powder;

maintaining an oxygen-free environment in the reactor, introducing a mixed gas of inert gas, hydrogen and carbon source gas into the reactor, and opening a microwave generating device to enable the nano-scale metal powder to continue to react to obtain the core-shell type composite metal powder coated by the graphene wall;

and 5, placing the core-shell composite metal powder coated by the graphene wall in an atmospheric environment, introducing inert gas, opening a microwave generating device, and reacting the core-shell composite metal powder coated by the graphene wall to form the core-shell composite metal oxide powder coated by the graphene wall, so as to obtain the broadband optical absorbent.

2. The method of claim 1, wherein the step of preparing the broadband optical absorber comprises:

in the step 1, the mass ratio of the metal chloride to the hexamethylenetetramine is (2-5) to 24, and the mass ratio of the metal chloride (mmol) to the volume of the solvent (mL) is (2-5) to 400;

the metal chloride is one of cobalt chloride, nickel chloride and ferric chloride, or a mixture of two or more of the cobalt chloride, the nickel chloride and the ferric chloride.

3. The method of claim 1, wherein the step of preparing the broadband optical absorber comprises: and step 3), the reactor is a quartz tube and a quartz boat (5-10 g of metal hydroxide is placed in the quartz boat once in the experiment), and the reactor is vacuumized for 10-20 min to keep the oxygen-free environment in the quartz tube.

4. The method of claim 1, wherein the step of preparing the broadband optical absorber comprises: in the step 4, an oxygen-free environment in the reactor is maintained, when argon and hydrogen mixed gas is introduced into the reactor, the flow rate of the argon gas is controlled to be 100-200 sccm, the flow rate of the hydrogen is controlled to be 50-100 sccm, a carbon source gas methane for growing the graphene wall is introduced, the flow rate of the methane gas is controlled to be 40-80 sccm, a microwave generating device is started, the microwave working frequency is 2450MHz, the output power is 700-1000W, the reaction time is maintained for 20-40 min, then the hydrogen and the carbon source gas are stopped, and the core-shell composite metal powder coated by the graphene wall is obtained after the carbon source gas and the hydrogen are cooled to room temperature in the argon atmosphere.

5. The method of claim 1, wherein the step of preparing the broadband optical absorber comprises: and step 5, introducing argon gas when the graphene wall-coated core-shell composite metal powder is placed in an atmospheric environment, controlling the flow rate to be 100-200 sccm, opening a microwave generating device, controlling the microwave working frequency to be 2450MHz, outputting the power to be 700-1000W, and keeping the reaction time for 20-40 min, thereby obtaining the graphene wall-coated core-shell composite metal oxide powder.

6. A method for preparing a broadband optical absorption coating by using the absorbent of any one of claims 1 to 5, which is characterized in that: adding the broadband optical absorbent into organic silicon resin to disperse the organic silicon resin; and adding tetrabutyl titanate and uniformly mixing to obtain the coating slurry for spraying. The organic silicon resin is methyl vinyl silicon resin or methyl phenyl silicon resin.

7. The method of claim 6, wherein the step of preparing the broadband optical absorption coating comprises: the mass ratio of the broadband optical absorbent to the organic silicon resin to the tetrabutyl titanate is (1-2) to (20-40) to (1-2).

8. A method of making a broadband optical absorbing coating according to claim 6 or 7, characterized in that: after the broadband optical absorbent is added into the organic silicon resin, the organic silicon resin is dispersed for 1-3 hours at the rotating speed of 5000-10000 rpm through a high-speed stirrer, and then tetrabutyl titanate is added and mixed uniformly.

9. A method of producing a broadband optical absorbing coating according to claim 7 or 8, characterized in that: and spraying the coating slurry onto the surface of the base material, wherein the spraying thickness is 30-60 mu m, placing the base material at room temperature for 5-8 h, and then placing the base material into an oven at 80-100 ℃ for heating and curing for 1-3 h to obtain the coating with excellent absorption performance in the ultra-wide band from visible light to infrared wave.

10. An absorbent or coating prepared by the method of any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of materials, and particularly relates to a preparation method of a broadband optical absorbent and a coating from visible light to infrared bands.

Background

According to the basic black body concept set forth by kirchhoff and the law of black body radiation created by planck, an ideal absorptive coating can absorb all light rays radiated onto the surface of a material, with no reflection and no transmission. The high-absorption coating can effectively reduce the unfavorable reflection of the surface of the material, can absorb the discrete light rays on the surface of the material to the maximum extent, and has important application value in the fields of novel thermoelectric sensors, thermal detectors, optical instrument structural parts, solar energy conversion devices and the like. The coatings for the production of highly absorbing coatings are generally composed of an optical absorber as binder and a binder as carrier. The optical absorbent has the function of improving the optical absorption performance of the coating, and the carrier binder enables the coating to be firmly adhered to the surface of the substrate, so that the optical absorbent is a core functional material of the absorption coating and has an important influence on improving the optical absorption performance of the coating. The absorption index of the existing light absorbent changes along with the wavelength change of radiation waves, so that the absorption of the material presents certain selectivity, and the performance and the application range are influenced.

Disclosure of Invention

The invention aims to provide a preparation method of a broadband optical absorbent, which is characterized by comprising the following steps:

weighing metal chloride and hexamethylenetetramine, dissolving in a solvent for reaction;

separating the precipitate generated in the step 1) to obtain nano-scale metal hydroxide powder;

placing the metal hydroxide powder obtained in the step 2) in a reactor, wherein the interior of the reactor is in an oxygen-free environment; introducing mixed gas of inert gas and hydrogen into the reactor, opening a microwave generating device, carrying out microwave treatment on the metal hydroxide powder in the reactor, fully reacting and cooling to obtain nanoscale metal powder;

maintaining an oxygen-free environment in the reactor, introducing a mixed gas of inert gas, hydrogen and carbon source gas into the reactor, and opening a microwave generating device to enable the nano-scale metal powder to continue to react to obtain the core-shell type composite metal powder coated by the graphene wall;

and 5, placing the core-shell composite metal powder coated by the graphene wall in an atmospheric environment, introducing inert gas, opening a microwave generating device, and reacting the core-shell composite metal powder coated by the graphene wall to form the core-shell composite metal oxide powder coated by the graphene wall, so as to obtain the broadband optical absorbent.

Further, in the step 1, the mass ratio of the metal chloride to the hexamethylenetetramine is (2-5) to 24, and the mass ratio of the metal chloride (mmol) to the volume of the solvent (mL) is (2-5) to 400;

further, in the step 1), the metal chloride is one of cobalt chloride, nickel chloride and ferric chloride, or a mixture of two or more of cobalt chloride, nickel chloride and ferric chloride;

further, in the step 1), the solvent is a mixture of deionized water and absolute ethyl alcohol, and the volume ratio of the deionized water to the absolute ethyl alcohol is 9: 1;

further, in the step 1), the deionized water is first-stage pure water with the resistance not less than 10 Ω m; further, in the step 1), after adding a solvent into metal chloride and hexamethylenetetramine, stirring for 15-30 min by a magnetic stirrer until the precursor powder is completely dissolved, then transferring to a three-neck flask, heating the mixed solution to 90-120 ℃ under the magnetic stirring state, and keeping the temperature for reacting for 1-3 h; ,

further, in the step 2), collecting the precipitate in a vacuum filtration mode, alternately washing the precipitate with deionized water and absolute ethyl alcohol for 3 times respectively, and drying the precipitate in an oven at the temperature of 60-80 ℃ for 5-8 hours to obtain nano-scale metal hydroxide powder, wherein the obtained metal hydroxide comprises one or two or more mixed metal hydroxides of cobalt hydroxide, nickel hydroxide and iron hydroxide;

further, in the step 3), the reactor is a quartz tube and a quartz boat (5-10 g of metal hydroxide is put into the quartz boat once during the experiment), and the reactor is vacuumized for 10-20 min to keep the oxygen-free environment in the quartz tube.

Further, in the step 3), when a mixed gas of argon and hydrogen is introduced, controlling the flow rate of the argon at 100-200 sccm and the flow rate of the hydrogen at 100-200 sccm, opening a microwave generating device after introducing the mixed gas for 10-20 min, controlling the microwave working frequency at 2450MHz, outputting the power at 700-1000W, keeping the reaction time for 20-30 min, then closing a hydrogen source, and cooling to room temperature in an argon atmosphere to obtain nano-scale metal powder, including metal cobalt, metal nickel, metal iron and mixed metal powder of two or three of the metal cobalt, the metal nickel and the metal iron;

further, in the step 4), an oxygen-free environment in the reactor is maintained, when argon and hydrogen mixed gas is introduced into the reactor, the flow rate of the argon gas is controlled to be 100-200 sccm, the flow rate of the hydrogen is controlled to be 50-100 sccm, carbon source gas methane for growing the graphene wall is introduced, the flow rate of the methane gas is controlled to be 40-80 sccm, a microwave generating device is started, the microwave working frequency is 2450MHz, the output power is 700-1000W, the reaction time is maintained for 20-40 min, then the hydrogen and the carbon source gas are closed, and the reaction is cooled to the room temperature in the argon atmosphere, so that the graphene wall-coated core-shell composite metal powder is obtained;

further, in the step 5), when the core-shell composite metal oxide powder coated by the graphene wall is placed in an atmospheric environment, argon is introduced, the flow rate is controlled to be 100-200 sccm, a microwave generating device is opened, the microwave working frequency is 2450MHz, the output power is 700-1000W, and the reaction time is kept for 20-40 min, so that the core-shell composite metal oxide powder coated by the graphene wall is obtained; the invention claims a preparation method of a coating adopting the broadband optical absorbent, which is characterized by comprising the following steps: adding the broadband optical absorbent into organic silicon resin to disperse the organic silicon resin; and adding tetrabutyl titanate and uniformly mixing to obtain the coating slurry for spraying. The organic silicon resin is methyl vinyl silicon resin or methyl phenyl silicon resin.

Furthermore, the mass ratio of the broadband optical absorbent, the organic silicon resin and the tetrabutyl titanate is (1-2) to (20-40) to (1-2).

Further, after the broadband optical absorbent is added into the organic silicon resin, dispersing for 1-3 hours at the rotating speed of 5000-10000 rpm by a high-speed stirrer, and then adding tetrabutyl titanate to mix uniformly;

further, spraying the coating slurry onto the surface of the base material, wherein the spraying thickness is 30-60 microns, placing the base material at room temperature for 5-8 hours, and then placing the base material into an oven at 80-100 ℃ for heating and curing for 1-3 hours to obtain the coating with excellent absorption performance in the ultra-wide waveband from visible light to infrared wave.

The invention also claims the absorbent or coating prepared by the method.

It is worth to be noted that graphene, as a two-dimensional planar crystal structure with a honeycomb structure composed of a single layer of carbon atoms, has unique physicochemical properties including good electrical and thermal conductivity, excellent mechanical properties, a huge specific surface area, and the like. Meanwhile, C-C bond in graphene has high radiation emissivity, which can reach 0.95. The two-dimensional graphene and other low-dimensional materials are compounded to form a microstructure with rich interfaces, so that the two-dimensional graphene can permeate into coating materials to form a new interface, the reflection of incident light waves in the coating is improved, and the absorption performance of the coating is effectively improved.

The invention utilizes a homogeneous precipitation method to prepare metal hydroxide with nano-scale size and uniform size distribution, and reduces the metal hydroxide in a microwave plasma-assisted reduction mode to obtain nano-scale metal particles. The hydrogen plasma obtained by microwave discharge contains not only high-temperature electrons but also various hydrogen ions (H)⁺,H₂ ⁺,H₃ ⁺,H^-) And hydrogen atoms and hydrogen molecules in ground and electronically excited states. The high temperature electrons couple almost all energy to hydrogen gas through inelastic collisions, so that the reduction activity of the hydrogen plasma is much higher than the energy of the thermal motion average kinetic energy of the hydrogen molecules. Therefore, the method for preparing the micron-submicron metal particles by the microwave plasma-assisted reduction technology is more energy-saving and efficient. On the basis, by a microwave plasma enhanced chemical vapor deposition technology and by regulating and controlling the proportion and the flow rate between carbon source gas and hydrogen, uniform and stable graphene walls with petal-shaped structures grow on the surfaces of metal particles. Compared with the traditional chemical vapor deposition technology, the microwave plasma enhanced chemical vapor deposition technology can effectively shorten the time for growing the graphene wall, improve the yield in unit time and finally utilize the generated argonThe heat released in the gas plasma process oxidizes the metal particles as a core material to obtain corresponding metal oxide microparticles.

According to the core-shell composite metal oxide powder coated by the graphene wall, on one hand, the graphene wall has a huge specific surface, and the two-dimensional layered structure of the graphene wall can improve the inner interface of the coating and effectively increase the reflection and absorption times of radiation waves in the coating; meanwhile, the graphene wall can effectively reduce the refractive index of the coating by reducing the density of the coating, so that the absorption characteristic of the coating is further improved. On the other hand, the metal oxide particles with micron-submicron size destroy the inherent chemical bonds in the original substance, so that the average distance between the basic microscopic particles in the particles is increased, the number of particles in unit volume is obviously reduced, the absorption index and the refractive index can be reduced to improve the transmission depth of heat radiation, and the absorption rate and the emissivity of the material are effectively improved. The composite filler is added into the organic silicon film-forming resin, so that the optical absorption characteristic of the coating in the visible light to infrared band is effectively improved by utilizing the synergistic effect of the graphene wall and the nano metal oxide.

Drawings

FIG. 1: scanning electron microscope photos of the core-shell type composite cobalt oxide powder coated by the graphene wall prepared in the invention;

FIG. 2: the invention relates to a wide-waveband optical absorption coating photo taking core-shell type composite cobalt oxide powder coated by a graphene wall as a light absorber;

FIG. 3: according to the invention, the integrating sphere reflectivity of a coating taking the core-shell type composite cobalt oxide powder coated by the graphene wall as a light absorbent in a visible light-near infrared band of 0.4-2 mu m is increased;

FIG. 4: according to the invention, the mirror reflectivity of the coating with the core-shell type composite cobalt oxide powder coated by the graphene wall as the light absorbent is 60 degrees of a middle and far infrared band of 2-20 microns. .

Detailed Description

The present invention is further illustrated by the following examples, but it should not be construed that the scope of the above-described subject matter is limited to the following examples. Various substitutions and alterations can be made without departing from the technical idea of the invention and the scope of the invention is covered by the present invention according to the common technical knowledge and the conventional means in the field.

Example 1:

the invention aims to provide a light absorbent with wide-band absorption characteristics from visible light to infrared band and a preparation method of a coating thereof, which is characterized by comprising the following steps: 1) weighing 4mmol of cobalt chloride and 48mmol of hexamethylenetetramine, and dissolving in 800ml of mixed solvent consisting of deionized water and absolute ethyl alcohol, wherein the volume ratio of the deionized water to the absolute ethyl alcohol is 9: 1; stirring for 15min by a magnetic stirrer until the precursor powder is completely dissolved, transferring the precursor powder into a three-neck flask, heating the mixed solution to 90 ℃ under the magnetic stirring state, and keeping the temperature for reacting for 1 h;

2) collecting the precipitate obtained in the step 1) by a vacuum filtration mode, alternately washing the precipitate with deionized water and absolute ethyl alcohol for 3 times respectively, and drying the precipitate in a drying oven at the temperature of 60 ℃ for 5 hours to obtain nano cobalt hydroxide powder;

3) weighing 10g of the cobalt hydroxide obtained in the step 2), putting the cobalt hydroxide into a quartz boat, and vacuumizing for 10min to keep the oxygen-free environment in the quartz tube. Then introducing mixed gas of argon and hydrogen, controlling the flow rate of the argon at 100sccm and the flow rate of the hydrogen at 100sccm, introducing the mixed gas for 10min, then opening a microwave generating device, controlling the microwave working frequency at 2450MHz, outputting the power at 700W, keeping the reaction time for 20min, then closing a hydrogen source, and cooling to room temperature in the argon atmosphere to obtain the nano-scale metal cobalt powder;

4) introducing argon and hydrogen mixed gas, controlling the flow rate of the argon gas to be 100sccm and the flow rate of the hydrogen to be 50sccm, introducing carbon source gas methane for growing the graphene wall, controlling the flow rate of the methane to be 40sccm, opening a microwave generating device, controlling the microwave working frequency to be 2450MHz, outputting the power of 700W, keeping the reaction time for 20min, then closing the hydrogen and the methane, and cooling to the room temperature in the argon atmosphere, thereby obtaining the core-shell type composite metal cobalt powder coated by the graphene wall;

5) introducing argon gas in an atmospheric environment, controlling the flow rate at 100sccm, opening a microwave generating device, controlling the microwave working frequency at 2450MHz and the output power at 700W, and keeping the reaction time for 20min to obtain the graphene wall-coated core-shell composite cobalt oxide powder;

6) weighing 1g of core-shell type composite cobalt oxide powder coated by the graphene wall prepared in the step 5), adding the core-shell type composite cobalt oxide powder into 20g of methyl vinyl silicone resin, dispersing for 1h at the rotating speed of 5000rpm by using a high-speed stirrer, and then adding 1g of tetrabutyl titanate to mix uniformly;

7) spraying the coating slurry obtained in the step 6) on the surface of a base material, wherein the spraying thickness is 50 microns, placing the base material at room temperature for 8 hours, and placing the base material in an oven at 80 ℃ for heating and curing for 1 hour to obtain the coating with excellent absorption performance in the ultra-wide wave band from visible light to infrared wave.

The average integrating sphere reflectivity of the coating in a visible light-near infrared band of 0.4-2 mu m is 0.014, and the 60-degree specular reflectivity in a middle and far infrared band of 2-20 mu m is not more than 0.013.

Example 2:

1) weighing 4mmol of nickel chloride and 48mmol of hexamethylenetetramine, and dissolving in 800ml of mixed solvent consisting of deionized water and absolute ethyl alcohol, wherein the volume ratio of the deionized water to the absolute ethyl alcohol is 9: 1; stirring for 15min by a magnetic stirrer until the precursor powder is completely dissolved, transferring the precursor powder into a three-neck flask, heating the mixed solution to 100 ℃ under the magnetic stirring state, and keeping the temperature for reacting for 1 h;

2) collecting the precipitate obtained in the step 1) by a vacuum filtration mode, alternately washing the precipitate with deionized water and absolute ethyl alcohol for 3 times respectively, and drying the precipitate in a 60 ℃ drying oven for 5 hours to obtain nano-grade nickel hydroxide powder;

3) weighing 10g of nickel hydroxide obtained in the step 2), putting into a quartz boat, and vacuumizing for 10min to keep the oxygen-free environment in the quartz tube. Then introducing mixed gas of argon and hydrogen, controlling the flow rate of the argon at 100sccm and the flow rate of the hydrogen at 100sccm, introducing the mixed gas for 10min, then opening a microwave generating device, controlling the microwave working frequency at 2450MHz, outputting the power at 700W, keeping the reaction time for 20min, then closing a hydrogen source, and cooling to room temperature in the argon atmosphere to obtain the nano-scale metallic nickel powder;

4) introducing argon and hydrogen mixed gas, controlling the flow rate of the argon gas to be 100sccm and the flow rate of the hydrogen to be 50sccm, introducing carbon source gas methane for growing the graphene wall, controlling the flow rate of the methane to be 40sccm, opening a microwave generating device, controlling the microwave working frequency to be 2450MHz, outputting the power of 700W, keeping the reaction time for 20min, then closing the hydrogen and the methane, and cooling to the room temperature in the argon atmosphere, thereby obtaining the core-shell type composite metallic nickel powder coated by the graphene wall;

5) introducing argon gas in an atmospheric environment, controlling the flow rate at 100sccm, opening a microwave generating device, controlling the microwave working frequency at 2450MHz and the output power at 700W, and keeping the reaction time for 20min to obtain the graphene wall-coated core-shell composite nickel oxide powder;

6) weighing 1g of the core-shell type composite nickel oxide powder coated by the graphene wall prepared in the step 5), adding the core-shell type composite nickel oxide powder into 20g of methyl vinyl silicone resin, dispersing for 1h at the rotating speed of 5000rpm by using a high-speed stirrer, and then adding 1g of tetrabutyl titanate to mix uniformly;

7) spraying the coating slurry obtained in the step 6) on the surface of a base material, wherein the spraying thickness is 50 microns, placing the base material at room temperature for 8 hours, and placing the base material in an oven at 80 ℃ for heating and curing for 1 hour to obtain the coating with excellent absorption performance in the ultra-wide wave band from visible light to infrared wave.

The average integrating sphere reflectivity of the coating in a visible light-near infrared band of 0.4-2 mu m is 0.013, and the mirror reflectivity of a middle and far infrared band of 2-20 mu m at 60 degrees is not more than 0.012.

Example 3:

1) weighing 4mmol of ferric chloride and 48mmol of hexamethylenetetramine, and dissolving in 800ml of mixed solvent consisting of deionized water and absolute ethyl alcohol, wherein the volume ratio of the deionized water to the absolute ethyl alcohol is 9: 1; stirring for 15min by a magnetic stirrer until the precursor powder is completely dissolved, transferring the precursor powder into a three-neck flask, heating the mixed solution to 110 ℃ under the magnetic stirring state, and keeping the temperature for reacting for 1 h;

2) collecting the precipitate obtained in the step 1) by a vacuum filtration mode, alternately washing the precipitate with deionized water and absolute ethyl alcohol for 3 times respectively, and drying the precipitate in a 60 ℃ drying oven for 5 hours to obtain nanoscale ferric hydroxide powder;

3) weighing 10g of ferric hydroxide obtained in the step 2), putting into a quartz boat, and vacuumizing for 10min to keep the oxygen-free environment in the quartz tube. Then introducing mixed gas of argon and hydrogen, controlling the flow rate of the argon at 100sccm and the flow rate of the hydrogen at 100sccm, introducing the mixed gas for 10min, then opening a microwave generating device, controlling the microwave working frequency at 2450MHz, outputting the power at 700W, keeping the reaction time for 20min, then closing a hydrogen source, and cooling to room temperature in the argon atmosphere to obtain the nanoscale metallic iron powder;

4) introducing argon and hydrogen mixed gas, controlling the flow rate of the argon gas to be 100sccm and the flow rate of the hydrogen to be 50sccm, introducing carbon source gas methane for growing the graphene wall, controlling the flow rate of the methane to be 40sccm, opening a microwave generating device, controlling the microwave working frequency to be 2450MHz, outputting the power of 700W, keeping the reaction time for 20min, then closing the hydrogen and the methane, and cooling to the room temperature in the argon atmosphere, thereby obtaining the core-shell type composite metallic iron powder body coated by the graphene wall;

5) introducing argon gas in an atmospheric environment, controlling the flow rate at 100sccm, opening a microwave generating device, controlling the microwave working frequency at 2450MHz and the output power at 700W, and keeping the reaction time for 20min to obtain the graphene wall-coated core-shell composite iron oxide powder;

6) weighing 1g of the core-shell type composite iron oxide powder coated by the graphene wall prepared in the step 5), adding the core-shell type composite iron oxide powder into 20g of methyl phenyl silicone resin, dispersing for 1h at the rotating speed of 5000rpm by using a high-speed stirrer, and then adding 1g of tetrabutyl titanate to mix uniformly;

7) spraying the coating slurry obtained in the step 6) on the surface of a base material, wherein the spraying thickness is 50 microns, placing the base material at room temperature for 8 hours, and placing the base material in an oven at 80 ℃ for heating and curing for 1 hour to obtain the coating with excellent absorption performance in the ultra-wide wave band from visible light to infrared wave.

The average integrating sphere reflectivity of the coating in a visible light-near infrared band of 0.4-2 mu m is 0.013, and the 60-degree specular reflectivity of a middle and far infrared band of 2-20 mu m is not more than 0.013.

Example 4:

the invention aims to provide a light absorbent with wide-band absorption characteristics from visible light to infrared band and a preparation method of a coating thereof, which is characterized by comprising the following steps:

1) weighing 2mmol of cobalt chloride, 2mmol of nickel chloride and 48mmol of hexamethylenetetramine, and dissolving in 800ml of mixed solvent consisting of deionized water and absolute ethyl alcohol, wherein the volume ratio of the deionized water to the absolute ethyl alcohol is 9: 1; stirring for 15min by a magnetic stirrer until the precursor powder is completely dissolved, transferring the precursor powder into a three-neck flask, heating the mixed solution to 100 ℃ under the magnetic stirring state, and keeping the temperature for reaction for 2 h;

2) collecting the precipitate obtained in the step 1) by vacuum filtration, alternately washing the precipitate with deionized water and absolute ethyl alcohol for 3 times respectively, and drying the precipitate in a drying oven at the temperature of 60 ℃ for 5 hours to obtain nano cobalt hydroxide/nickel hydroxide composite powder;

3) weighing 10g of the cobalt hydroxide/nickel hydroxide composite powder obtained in the step 2), putting the powder into a quartz boat, and vacuumizing for 10min to keep the oxygen-free environment in the quartz tube. Then introducing mixed gas of argon and hydrogen, controlling the flow rate of the argon at 100sccm and the flow rate of the hydrogen at 100sccm, after introducing the mixed gas for 10min, opening a microwave generating device, controlling the microwave working frequency at 2450MHz and the output power at 700W, keeping the reaction time for 20min, then closing a hydrogen source, and cooling to room temperature in the argon atmosphere to obtain the nano-scale metal cobalt/nickel composite powder;

4) introducing argon and hydrogen mixed gas, controlling the flow rate of the argon gas to be 100sccm and the flow rate of the hydrogen to be 50sccm, introducing carbon source gas methane for growing the graphene wall, controlling the flow rate of the methane to be 40sccm, opening a microwave generating device, controlling the microwave working frequency to be 2450MHz, outputting the power of 700W, keeping the reaction time for 20min, then closing the hydrogen and the methane, and cooling to the room temperature in the argon atmosphere, thereby obtaining the core-shell type metal cobalt/nickel composite powder coated by the graphene wall;

5) introducing argon gas in an atmospheric environment, controlling the flow rate at 100sccm, opening a microwave generating device, controlling the microwave working frequency at 2450MHz and the output power at 700W, and keeping the reaction time for 20min, thereby obtaining the graphene wall-coated core-shell cobalt oxide/nickel oxide composite powder;

6) weighing 0.5g of the graphene wall-coated core-shell cobalt oxide/nickel oxide composite powder prepared in the step 5), adding the core-shell cobalt oxide/nickel oxide composite powder into 10g of methyl phenyl silicone resin, dispersing the core-shell cobalt oxide/nickel oxide composite powder for 1 hour at the rotating speed of 5000rpm by using a high-speed stirrer, and then adding 0.5g of tetrabutyl titanate to mix uniformly;

7) spraying the coating slurry obtained in the step 6) on the surface of a base material, wherein the spraying thickness is 50 microns, placing the base material at room temperature for 8 hours, and placing the base material in an oven at 80 ℃ for heating and curing for 1 hour to obtain the coating with excellent absorption performance in the ultra-wide wave band from visible light to infrared wave.

The average integrating sphere reflectivity of the coating in a visible light-near infrared band of 0.4-2 mu m is 0.012, and the mirror reflectivity of 60 degrees in a middle and far infrared band of 2-20 mu m is not more than 0.014.

Example 5:

the invention aims to provide a light absorbent with wide-band absorption characteristics from visible light to infrared band and a preparation method of a coating thereof, which is characterized by comprising the following steps:

1) weighing 2mmol of cobalt chloride, 2mmol of nickel chloride, 2mmol of ferric chloride and 48mmol of hexamethylenetetramine, and dissolving in 800ml of mixed solvent consisting of deionized water and absolute ethyl alcohol, wherein the volume ratio of the deionized water to the absolute ethyl alcohol is 9: 1; stirring for 20min by a magnetic stirrer until the precursor powder is completely dissolved, transferring the precursor powder into a three-neck flask, heating the mixed solution to 110 ℃ under the magnetic stirring state, and keeping the temperature for reaction for 2 h;

2) collecting the precipitate obtained in the step 1) by vacuum filtration, alternately washing the precipitate with deionized water and absolute ethyl alcohol for 3 times respectively, and drying the precipitate in a drying oven at the temperature of 60 ℃ for 5 hours to obtain nano-scale cobalt hydroxide/nickel hydroxide/iron hydroxide composite powder;

3) weighing 10g of the cobalt hydroxide/nickel hydroxide/ferric hydroxide composite powder obtained in the step 2), putting the powder into a quartz boat, and vacuumizing for 10min to keep the oxygen-free environment in the quartz tube. Then introducing mixed gas of argon and hydrogen, controlling the flow rate of the argon at 100sccm and the flow rate of the hydrogen at 100sccm, after introducing the mixed gas for 10min, opening a microwave generating device, controlling the microwave working frequency at 2450MHz and the output power at 700W, keeping the reaction time for 20min, then closing a hydrogen source, and cooling to room temperature in the argon atmosphere to obtain nano-scale metal cobalt/nickel/iron composite powder;

4) introducing argon and hydrogen mixed gas, controlling the flow rate of the argon gas to be 100sccm and the flow rate of the hydrogen to be 100sccm, introducing carbon source gas methane for growing the graphene wall, controlling the flow rate of the methane to be 40sccm, opening a microwave generating device, controlling the microwave working frequency to be 2450MHz, outputting the power of 700W, keeping the reaction time for 20min, then closing the hydrogen and the methane gas, and cooling to the room temperature in the argon atmosphere, thereby obtaining the core-shell type metal cobalt/nickel/iron composite powder coated by the graphene wall;

5) introducing argon gas in an atmospheric environment, controlling the flow rate at 100sccm, opening a microwave generating device, controlling the microwave working frequency at 2450MHz, outputting power at 700W, and keeping the reaction time for 20min, thereby obtaining the graphene wall-coated core-shell cobalt oxide/nickel oxide/iron oxide composite powder;

6) weighing 0.5g of the graphene wall-coated core-shell cobalt oxide/nickel oxide/iron oxide composite powder prepared in the step 5), adding the powder into 10g of methyl phenyl silicone resin, dispersing the powder for 1h at the rotating speed of 5000rpm by using a high-speed stirrer, and then adding 0.5g of tetrabutyl titanate to mix uniformly;

7) spraying the coating slurry obtained in the step 6) on the surface of a base material, wherein the spraying thickness is 50 microns, placing the base material at room temperature for 8 hours, and placing the base material in an oven at 80 ℃ for heating and curing for 1 hour to obtain the coating with excellent absorption performance in the ultra-wide wave band from visible light to infrared wave.

The average integrating sphere reflectivity of the coating in a visible light-near infrared band of 0.4-2 mu m is 0.012, and the 60-degree specular reflectivity of a middle and far infrared band of 2-20 mu m is not more than 0.013.