CN113789109A - Fluorine and boron double-doped graphene/alkyd resin composite coating and preparation method thereof - Google Patents

Fluorine and boron double-doped graphene/alkyd resin composite coating and preparation method thereof Download PDF

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CN113789109A
CN113789109A CN202110975475.2A CN202110975475A CN113789109A CN 113789109 A CN113789109 A CN 113789109A CN 202110975475 A CN202110975475 A CN 202110975475A CN 113789109 A CN113789109 A CN 113789109A
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alkyd resin
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郑玉婴
张�杰
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Fuzhou University
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Abstract

The invention discloses a fluorine and boron double-doped graphene/alkyd resin composite coating and a preparation method thereof. Due to the change of the energy band structure, the electrical conductivity of the graphene after double doping of fluorine and boron is obviously reduced, so that the corrosion promoting activity of the graphene is effectively inhibited. And due to the introduction of fluorine atoms, the surface energy of the graphene is greatly reduced. After the fluorine and boron double-doped graphene is dispersed in the alkyd resin, the obtained fluorine and boron double-doped graphene/alkyd resin composite coating has excellent antibacterial property, hydrophobicity and corrosion resistance.

Description

Fluorine and boron double-doped graphene/alkyd resin composite coating and preparation method thereof
Technical Field
The invention belongs to the technical field of solvent coatings, and particularly relates to a fluorine and boron double-doped graphene/alkyd resin composite coating which is remarkably improved in corrosion resistance.
Background
The alkyd resin is low in price, excellent in weather resistance, durable in gloss, strong in adhesive force, flexible in paint film and resistant to friction, so that the alkyd resin is widely used as a matrix resin of an anticorrosive paint. However, alkyd resins inevitably leave a large number of structural defects in the coating layer during the drying and curing process due to the volatilization of the solvent, resulting in poor corrosion resistance of the coating layer. In order to improve the corrosion resistance of alkyd resin paint, it is an effective way to mix a barrier anticorrosive filler into the paint. In recent years, graphene of monoatomic thickness has become an ideal filler in the field of corrosion protection due to its excellent permeation resistance, stable chemical inertness, thermal stability, and the like. However, graphene also has excellent conductivity. Although the graphene has great application potential in the fields of photoelectron and the like, the graphene causes serious harm in the field of corrosion prevention. Since a corrosive galvanic cell will form in the graphite-metal substrate-NaCl solution system when the coating is damaged, or when corrosive media penetrate to the graphene-metal substrate contact points when immersed in seawater for a long time. Since highly conductive graphene is chemically inert, it will act as a cathode in a corrosive galvanic cell, while relatively active metal substrates such as magnesium, aluminum, iron, copper, etc. will act as anodes to accelerate corrosion.
However, most of the conventional methods for suppressing the graphene corrosion promotion effect use an insulating material (e.g., SiO)2，ZrO2Etc.) to encapsulate the graphene, avoiding direct contact of the graphene with the metal substrate. Although this method can avoid the formation of a corrosion primary battery, since the thickness of the graphene is significantly increased after the graphene is encapsulated, the increase in thickness will result in the reduction of the barrier efficiency of the graphene. Because the smaller the thickness of the graphene is, the more the number of the formed lap joints is, the longer the permeation path of the corrosive medium is, and the better the corrosion resistance is. The thickness of the graphene is increased, so that the number of overlapping layers is reduced under the same coating thickness, the compactness of the composite coating is correspondingly reduced, and the anti-corrosion performance improving capability is reduced.
In view of this, it is an urgent need to solve the problem of the art to provide a strategy for reducing the conductivity of graphene to inhibit the corrosion promoting activity of graphene, and simultaneously maintaining the requirement of graphene monoatomic thickness to maximize the anticorrosion performance of the composite coating, and to apply the strategy to alkyd resin anticorrosive coatings.
Disclosure of Invention
The invention provides a preparation method of a fluorine and boron double-doped graphene/alkyd resin composite coating, aiming at the problems of a large number of structural defects, poor hydrophobicity, poor barrier property and the like left in the drying and curing process of the existing alkyd resin coating. Fluoroboric acid is used as a doping agent, and fluorine atoms and boron atoms are introduced on a graphene basal plane while graphene oxide is reduced by utilizing the high-temperature and high-pressure conditions of hydrothermal reaction, so that the fluorine and boron double-doped graphene with the thickness of an ultrathin monoatomic layer is prepared. Due to the change of the energy band structure, the electrical conductivity of the graphene after double doping of fluorine and boron is obviously reduced, so that the corrosion promoting activity of the graphene is effectively inhibited. And due to the introduction of fluorine atoms, the surface energy of the graphene is greatly reduced. After the fluorine and boron double-doped graphene is dispersed in the alkyd resin, the ultrathin fluorine and boron double-doped graphene forms a compact lap joint layer in the alkyd resin to improve the barrier property of the composite coating, and the fluorine atom doping improves the hydrophobicity and antibacterial property of the composite coating, so that the corrosion resistance of the composite coating is obviously enhanced.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of fluorine and boron double-doped graphene/alkyd resin composite coating uses fluoroboric acid as a doping agent, is beneficial to the high-temperature and high-pressure condition of hydrothermal reaction, reduces graphene oxide, and simultaneously dopes fluorine atoms and boron atoms on a graphene basal plane, so that fluorine and boron double-doped graphene is obtained. And uniformly dispersing the fluorine-boron double-doped graphene/alkyd resin composite coating into alkyd resin to obtain the fluorine-boron double-doped graphene/alkyd resin composite coating.
The preparation method of the fluorine and boron double-doped graphene/alkyd resin composite coating specifically comprises the following steps:
step S1 preparation of graphene oxide:
firstly, 1g of flake graphite is added into a 500mL beaker, 90mL of concentrated sulfuric acid and 10 mL of phosphoric acid are added, and ultrasonic treatment is carried out for 5min after stirring for 5 min. It was then stirred in a 35 ℃ water bath and 6g of potassium permanganate were slowly added thereto over a period of 5 min. Continuously stirring the mixture at 35 ℃ for reacting for 4 hours, and then heating the mixture to 50 ℃ for continuously reacting for 15 min. 200mL of ice water was slowly added to the beaker and stirring was continued for 5 min. Next, a 30wt% hydrogen peroxide solution was added dropwise until the solution turned golden yellow and no bubbles were generated. Then 50mL of 10wt% dilute hydrochloric acid was added. And finally, centrifugally washing with deionized water until the supernatant is neutral, and freeze-drying the product to obtain the graphene oxide.
Step S2, preparation of fluorine and boron double-doped graphene:
firstly, 160mg of graphene oxide is added into a 100mL beaker, 80mL of deionized water is added, and ultrasound is carried out for 30min to obtain a uniform dispersion liquid. Then 2g of fluoroboric acid (40 wt% aqueous solution) was added and dispersed uniformly by sonication for 1 min. Then transferring the dispersion liquid into a 100mL high-pressure reaction kettle with a polytetrafluoroethylene inner container, and keeping the dispersion liquid at 180 ℃ for 30 hours to carry out hydrothermal reaction. After the reaction is finished, the reaction product is naturally cooled to room temperature. And finally, filtering the product by using a microporous filter membrane, repeatedly washing the product by using deionized water, and freeze-drying the product to obtain the fluorine and boron double-doped graphene.
Step S3 preparation of the fluorine and boron double-doped graphene/alkyd resin composite coating:
firstly, 8mL of dimethylbenzene and 2mL of n-butanol are taken, then fluorine and boron double-doped graphene is added, and the ultrasonic treatment is carried out for 30 min. Then weighing alkyd resin, adding the alkyd resin into the dispersion, and stirring until the alkyd resin is completely dissolved. Adding cobalt drier, and stirring for 30 min. Finally, the composite coating was coated on a Q235 steel plate with a 50 μm wire coater and dried at room temperature for 7 days.
The mass ratio of the crystalline flake graphite to the potassium permanganate in the step S1 is 1: 6.
the volume ratio of the concentrated sulfuric acid to the phosphoric acid in the step S1 is 9: 1.
the concentration of the graphene oxide dispersion liquid in step S2 is 2 mg/mL.
The mass ratio of the graphene oxide to the fluoroboric acid in the step S2 is 1: 5.
in step S3, the volume ratio of xylene to n-butanol is 8: 2.
in the step S3, the addition amount of the fluorine and boron double-doped graphene is 0-100 mg.
The mass ratio of the alkyd resin (CAS number: 63148-69-6) to the cobalt drier (CAS number: 136-52-7) described in step S3 is 20: 1.
the invention has the following remarkable advantages:
1. according to the invention, the improved Hummers method is adopted to prepare the graphene oxide, phosphoric acid with stronger corrosion effect is added in a reaction system, and the large-size thick-layer flake graphite can be more effectively oxidized and exfoliated into light and thin graphene oxide with smaller size. The obtained graphene oxide has high oxidation degree, is easy to obtain single-layer graphene oxide by ultrasonic stripping, and the high oxidation degree is beneficial to subsequent doping of fluorine atoms and boron atoms.
2. According to the method, the fluorine atoms and the boron atoms are doped on the basal plane of the graphene while the graphene oxide is reduced by utilizing the hydrothermal reaction high-temperature and high-pressure conditions. The reaction is synthesized in one step, and the operation is simple.
3. The fluorine and boron double-doped graphene prepared by the invention effectively changes the energy band structure of the graphene, so that the zero-band-gap conductive graphene is changed into the low-conductivity doped graphene, and the corrosion promotion effect of the graphene is effectively inhibited.
4. The fluorine and boron double-doped graphene prepared by the method has an ultrathin structure with a single atom thickness, and can improve the corrosion resistance of the composite coating to the maximum extent.
5. After the fluorine and boron double-doped graphene/alkyd resin composite coating prepared by the invention is formed into a film, a compact lap joint structure is formed in a coating, the diffusion path of a corrosive medium is greatly prolonged, and the corrosion resistance of the composite coating is remarkably enhanced.
6. The fluorine and boron double-doped graphene/alkyd resin composite coating prepared by the invention has extremely low surface energy after film forming, and can remarkably improve the hydrophobicity and antibacterial property of a composite coating.
Drawings
Fig. 1 is an SEM image of fluorine, boron double-doped graphene;
FIG. 2 is an EDS energy spectrum of fluorine and boron double-doped graphene;
fig. 3 is an SEM image of boron-doped graphene;
fig. 4 is an EDS energy spectrum of boron-doped graphene;
fig. 5 is an SEM image of fluorine doped graphene;
fig. 6 is an EDS energy spectrum of fluorine-doped graphene;
FIG. 7 is a graph showing the water contact angle of pure alkyd resin;
FIG. 8 is a graph of 0.5wt% graphene// alkyd water contact angle;
FIG. 9 is a water contact angle diagram of 0.5wt% boron doped graphene/alkyd resin;
FIG. 10 is a water contact angle diagram of 0.5wt% fluorine doped graphene/alkyd resin;
FIG. 11 is a graph of water contact angle for 0.5wt% fluorine, boron double doped graphene// alkyd resin;
FIG. 12 is a water contact angle diagram of 1.0wt% fluorine and boron double doped graphene// alkyd resin.
Detailed Description
In order to make the present invention more comprehensible, the technical solutions of the present invention are further described below with reference to specific embodiments, but the present invention is not limited thereto.
Example 1
(1) Preparing graphene oxide:
firstly, 1g of flake graphite is added into a 500mL beaker, 90mL of concentrated sulfuric acid and 10 mL of phosphoric acid are added, and ultrasonic treatment is carried out for 5min after stirring for 5 min. It was then stirred in a 35 ℃ water bath and 6g of potassium permanganate were slowly added thereto over a period of 5 min. Continuously stirring the mixture at 35 ℃ for reacting for 4 hours, and then heating the mixture to 50 ℃ for continuously reacting for 15 min. 200mL of ice water was slowly added to the beaker and stirring was continued for 5 min. Next, a 30wt% hydrogen peroxide solution was added dropwise until the solution turned golden yellow and no bubbles were generated. Then 50mL of 10wt% dilute hydrochloric acid was added. And finally, centrifugally washing with deionized water until the supernatant is neutral, and freeze-drying the product to obtain the graphene oxide.
(2) Preparing fluorine and boron double-doped graphene:
firstly, 160mg of graphene oxide is added into a 100mL beaker, 80mL of deionized water is added, and ultrasound is carried out for 30min to obtain a uniform dispersion liquid. Then 2g of fluoroboric acid (40 wt% aqueous solution) was added and dispersed uniformly by sonication for 1 min. The dispersion was transferred to a 100mL autoclave containing a Teflon liner and held at 180 ℃ for 30 h. After the reaction is finished, the reaction product is naturally cooled to room temperature. And finally, filtering the product by using a microporous filter membrane, repeatedly washing the product by using deionized water, and freeze-drying the product to obtain the fluorine and boron double-doped graphene.
(3) Preparing 0.5wt% of fluorine and boron double-doped graphene/alkyd resin composite coating:
firstly, 8mL of dimethylbenzene and 2mL of n-butanol are taken, then 100mg of fluorine and boron double-doped graphene is added, and ultrasonic treatment is carried out for 30 min. Then 20g of alkyd resin was weighed into the dispersion and stirred until the alkyd resin was completely dissolved. Then 1g of cobalt drier is added and stirred for 30 min. Finally, the composite coating was coated on a Q235 steel plate with a 50 μm wire coater and dried at room temperature for 7 days.
Example 2
(1) Preparing graphene oxide:
firstly, 1g of flake graphite is added into a 500mL beaker, 90mL of concentrated sulfuric acid and 10 mL of phosphoric acid are added, and ultrasonic treatment is carried out for 5min after stirring for 5 min. It was then stirred in a 35 ℃ water bath and 6g of potassium permanganate were slowly added thereto over a period of 5 min. Continuously stirring the mixture at 35 ℃ for reacting for 4 hours, and then heating the mixture to 50 ℃ for continuously reacting for 15 min. 200mL of ice water was slowly added to the beaker and stirring was continued for 5 min. Next, a 30wt% hydrogen peroxide solution was added dropwise until the solution turned golden yellow and no bubbles were generated. Then 50mL of 10wt% dilute hydrochloric acid was added. And finally, centrifugally washing with deionized water until the supernatant is neutral, and freeze-drying the product to obtain the graphene oxide.
(2) Preparing fluorine and boron double-doped graphene:
firstly, 160mg of graphene oxide is added into a 100mL beaker, 80mL of deionized water is added, and ultrasound is carried out for 30min to obtain a uniform dispersion liquid. Then 2g of fluoroboric acid (40 wt% aqueous solution) was added and dispersed uniformly by sonication for 1 min. The dispersion was transferred to a 100mL autoclave containing a Teflon liner and held at 180 ℃ for 30 h. After the reaction is finished, the reaction product is naturally cooled to room temperature. And finally, filtering the product by using a microporous filter membrane, repeatedly washing the product by using deionized water, and freeze-drying the product to obtain the fluorine and boron double-doped graphene.
(3) 1.0wt% of fluorine and boron double-doped graphene/alkyd resin composite coating:
firstly, 8mL of dimethylbenzene and 2mL of n-butanol are taken, 200mg of fluorine and boron double-doped graphene is added, and the ultrasonic treatment is carried out for 30 min. Then 20g of alkyd resin was weighed into the dispersion and stirred until the alkyd resin was completely dissolved. Then 1g of cobalt drier is added and stirred for 30 min. Finally, the composite coating was coated on a Q235 steel plate with a 50 μm wire coater and dried at room temperature for 7 days.
Example 3
(1) Preparing graphene oxide:
firstly, 1g of flake graphite is added into a 500mL beaker, 90mL of concentrated sulfuric acid and 10 mL of phosphoric acid are added, and ultrasonic treatment is carried out for 5min after stirring for 5 min. It was then stirred in a 35 ℃ water bath and 6g of potassium permanganate were slowly added thereto over a period of 5 min. Continuously stirring the mixture at 35 ℃ for reacting for 4 hours, and then heating the mixture to 50 ℃ for continuously reacting for 15 min. 200mL of ice water was slowly added to the beaker and stirring was continued for 5 min. Next, a 30wt% hydrogen peroxide solution was added dropwise until the solution turned golden yellow and no bubbles were generated. Then 50mL of 10wt% dilute hydrochloric acid was added. And finally, centrifugally washing with deionized water until the supernatant is neutral, and freeze-drying the product to obtain the graphene oxide.
(2) Preparing the hydrothermal reduction graphene oxide:
firstly, 160mg of graphene oxide is added into a 100mL beaker, 80mL of deionized water is added, and ultrasound is carried out for 30min to obtain a uniform dispersion liquid. The dispersion was then transferred to a 100mL autoclave containing a polytetrafluoroethylene liner and held at 180 ℃ for 30 h. After the reaction is finished, the reaction product is naturally cooled to room temperature. And finally, filtering the product by using a microporous filter membrane, repeatedly washing the product by using deionized water, and freeze-drying the product to obtain the hydrothermal reduction graphene oxide.
(3) Preparation of 0.5wt% graphene/alkyd resin composite coating:
firstly, taking 8mL of dimethylbenzene and 2mL of n-butanol, then adding 100mg of hydrothermal reduction graphene oxide, and carrying out ultrasonic treatment for 30 min. Then 20g of alkyd resin was weighed into the dispersion and stirred until the alkyd resin was completely dissolved. Then 1g of cobalt drier is added and stirred for 30 min. Finally, the composite coating was coated on a Q235 steel plate with a 50 μm wire coater and dried at room temperature for 7 days.
Example 4
(1) Preparing graphene oxide:
firstly, 1g of flake graphite is added into a 500mL beaker, 90mL of concentrated sulfuric acid and 10 mL of phosphoric acid are added, and ultrasonic treatment is carried out for 5min after stirring for 5 min. It was then stirred in a 35 ℃ water bath and 6g of potassium permanganate were slowly added thereto over a period of 5 min. Continuously stirring the mixture at 35 ℃ for reacting for 4 hours, and then heating the mixture to 50 ℃ for continuously reacting for 15 min. 200mL of ice water was slowly added to the beaker and stirring was continued for 5 min. Next, a 30wt% hydrogen peroxide solution was added dropwise until the solution turned golden yellow and no bubbles were generated. Then 50mL of 10wt% dilute hydrochloric acid was added. And finally, centrifugally washing with deionized water until the supernatant is neutral, and freeze-drying the product to obtain the graphene oxide.
(2) Preparing boron-doped graphene:
firstly, 160mg of graphene oxide is added into a 100mL beaker, 80mL of deionized water is added, and ultrasound is carried out for 30min to obtain a uniform dispersion liquid. Then 0.8g of boric acid was added and dispersed uniformly by sonication for 1 min. The dispersion was transferred to a 100mL autoclave containing a Teflon liner and held at 180 ℃ for 30 h. After the reaction is finished, the reaction product is naturally cooled to room temperature. And finally, filtering the product by using a microporous filter membrane, repeatedly washing the product by using deionized water, and freeze-drying the product to obtain the boron-doped graphene.
(3) Preparation of 0.5wt% boron-doped graphene/alkyd resin composite coating:
firstly, 8mL of dimethylbenzene and 2mL of n-butanol are taken, then 100mg of boron-doped graphene is added, and ultrasonic treatment is carried out for 30 min. Then 20g of alkyd resin was weighed into the dispersion and stirred until the alkyd resin was completely dissolved. Then 1g of cobalt drier is added and stirred for 30 min. Finally, the composite coating was coated on a Q235 steel plate with a 50 μm wire coater and dried at room temperature for 7 days.
Example 5
(1) Preparing graphene oxide:
firstly, 1g of flake graphite is added into a 500mL beaker, 90mL of concentrated sulfuric acid and 10 mL of phosphoric acid are added, and ultrasonic treatment is carried out for 5min after stirring for 5 min. It was then stirred in a 35 ℃ water bath and 6g of potassium permanganate were slowly added thereto over a period of 5 min. Continuously stirring the mixture at 35 ℃ for reacting for 4 hours, and then heating the mixture to 50 ℃ for continuously reacting for 15 min. 200mL of ice water was slowly added to the beaker and stirring was continued for 5 min. Next, a 30wt% hydrogen peroxide solution was added dropwise until the solution turned golden yellow and no bubbles were generated. Then 50mL of 10wt% dilute hydrochloric acid was added. And finally, centrifugally washing with deionized water until the supernatant is neutral, and freeze-drying the product to obtain the graphene oxide.
(2) Preparing fluorine-doped graphene:
firstly, 160mg of graphene oxide is added into a 100mL beaker, 80mL of deionized water is added, and ultrasound is carried out for 30min to obtain a uniform dispersion liquid. Then 2g of hydrofluoric acid (40 wt% aqueous solution) was added and dispersed uniformly by sonication for 1 min. The dispersion was transferred to a 100mL autoclave containing a Teflon liner and held at 180 ℃ for 30 h. After the reaction is finished, the reaction product is naturally cooled to room temperature. And finally, filtering the product by using a microporous filter membrane, repeatedly washing the product by using deionized water, and freeze-drying the product to obtain the fluorine-doped graphene.
(3) Preparation of 0.5wt% fluorine-doped graphene/alkyd resin composite coating:
firstly, 8mL of dimethylbenzene and 2mL of n-butanol are taken, then 100mg of fluorine-doped graphene is added, and ultrasonic treatment is carried out for 30 min. Then 20g of alkyd resin was weighed into the dispersion and stirred until the alkyd resin was completely dissolved. Then 1g of cobalt drier is added and stirred for 30 min. Finally, the composite coating was coated on a Q235 steel plate with a 50 μm wire coater and dried at room temperature for 7 days.
Example 6
(1) Preparing the pure alkyd resin composite coating:
firstly, taking 8mL of dimethylbenzene and 2mL of n-butanol, then weighing 20g of alkyd resin, adding into the mixed solvent, and stirring until the alkyd resin is completely dissolved. Then 1g of cobalt drier is added and stirred for 30 min. Finally, the composite coating was coated on a Q235 steel plate with a 50 μm wire coater and dried at room temperature for 7 days.
Performance testing
The salt water resistance and the acid and alkali resistance of the paint film are measured according to the national standard GB/T1763-79 (89) method for measuring the chemical reagent resistance of the paint film, and the chemical reagent resistance of the paint film is expressed by the phenomenon of change of the surface of the paint film after the specified test time is reached. Preparing 3.5wt% NaCl solution, 5wt% HCl solution and 5wt% NaOH solution. Three paint film samples which are completely dried and maintained for 7 days are respectively put into three solutions with constant temperature of 25 +/-1 ℃, and 2/3 of the length of each sample plate is soaked in the solutions. When the soaking time of the sample plate is finished, the sample plate is taken out of the solution, the water on the surface of the sample plate is absorbed by using filter paper, the sample plate is visually inspected, and whether the phenomena of discoloration, light loss, wrinkling, bubbling, rusting, falling off and the like exist or not is recorded.
Results of Performance testing
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Figure 406063DEST_PATH_IMAGE002
As shown in table 1, the results of the corrosion resistance of pure alkyd resin, 0.5wt% graphene/alkyd resin, 0.5wt% boron-doped graphene/alkyd resin, 0.5wt% fluorine, boron-double-doped graphene/alkyd resin, and 1.0wt% fluorine, boron-double-doped graphene/alkyd resin are shown, respectively. When 0.5wt% of fluorine and boron double-doped graphene/alkyd resin coating sample is soaked in 3.5wt% of NaCl solution for testing, the coating is not affected within 720 h. Whereas the pure alkyd resin coating failed after 168h of soaking. In addition, when tested in 5.0wt% HCl and 5.0wt% NaOH solutions, the 0.5wt% fluorine and boron double doped graphene/alkyd coating samples did not change during soaking for 192h and 144h, respectively, with a slight decrease in coating gloss. The pure alkyd resin coating sample completely fell off after being soaked in 5.0wt% HCl and 5.0wt% NaOH solutions for 24h and 18h, respectively. For the 0.5wt% boron-doped graphene/alkyd resin sample, the corrosion promotion effect of graphene is weakened due to the reduced conductivity of graphene, so that the corrosion prevention performance of the sample is better than that of pure alkyd resin and 0.5wt% graphene/alkyd resin in the solution of 5.0wt% HCl, 5.0wt% NaOH and 3.5wt% NaCl. And the 0.5wt% fluorine-doped graphene/alkyd resin shows better corrosion resistance than pure alkyd resin, 0.5wt% graphene/alkyd resin and 0.5wt% boron-doped graphene/alkyd resin, because the fluorine-doped graphene can not only reduce the conductivity of the graphene, but also improve the hydrophobic property, so that the anti-permeability performance of the composite coating to the solution can be obviously improved. However, 0.5wt% fluorine-doped graphene/alkyd resin is inferior to the corrosion resistance of 0.5wt% fluorine, boron double-doped graphene/alkyd resin and 1.0wt% fluorine, boron double-doped graphene/alkyd resin, because fluoroboric acid is more easily doped on the surface of graphene than hydrofluoric acid under the same doping monomer quality, which can be obtained by comparing the results of the description with fig. 2, fig. 4 and fig. 6. And the 1.0wt% fluorine and boron double-doped graphene/alkyd resin has poor dispersibility due to too high content of fluorine and boron double-doped graphene, and the excellent barrier property of the resin cannot be fully exerted, so that the 1.0wt% fluorine and boron double-doped graphene/alkyd resin shows slightly poorer corrosion resistance than the 0.5wt% fluorine and boron double-doped graphene/alkyd resin. In conclusion, the 0.5wt% fluorine and boron double-doped graphene/alkyd resin composite coating shows the optimal different corrosion resistance in the solution of 5.0wt% HCl, 5.0wt% NaOH and 3.5wt% NaCl.
And (3) performance characterization:
fig. 1 is an SEM image of fluorine and boron double-doped graphene: fig. 1 shows that the fluorine and boron double-doped graphene is a folded two-dimensional layered structure.
Fig. 2 is an EDS energy spectrum of fluorine and boron double-doped graphene: as can be seen from fig. 2, the fluorine and boron double-doped graphene contains C, O, F, B atoms. Wherein the doped elements F and BThe point sites are uniformly distributed on the surface of the fluorine and boron double-doped graphene in a higher density. Because F, B atoms are connected by covalent bonds, after bond breaking at high temperature, they all carry a lone electron and are easy to dope to the surface of graphene, which shows that F, B atom doping has a mutual assistance effect. If F, B double doping source is replaced, for example, ammonium fluoroborate is used, N atoms are introduced during doping, and the doping of N atoms increases the conductivity, which is contrary to the original intention of reducing the conductivity of graphene to inhibit the corrosion promotion effect of graphene. Furthermore, fluoroboric acid (HBF)4) The F, B atomic mass percentage is as high as 98.86%, which is the ideal fluorine and boron double doping source. Fig. 2 demonstrates the successful synthesis of fluorine and boron double-doped graphene with higher doping amount.
Fig. 3 is an SEM image of boron-doped graphene: it can be seen from fig. 3 that the boron-doped graphene also exhibits a folded two-dimensional layered structure.
Fig. 4 is an EDS energy spectrum of boron-doped graphene: from fig. 4, it can be seen that the boron-doped graphene contains C, O, B atoms. Wherein the doped B element sites are distributed on the surface of the boron-doped graphene at a lower density. Boric acid (H)3BO3) The mass ratio of the B atoms is 17.74%, the ratio is low, and the doping amount is low. In the case of replacement of boron sources, e.g. boron oxide (B)2O3The mass ratio of B atoms is 31.43%), and the doping effect is theoretically improved. In this example, boric acid was used as the boron source because acids were used for uniformity. Fig. 4 demonstrates the successful synthesis of boron doped graphene, but with a lower doping level.
Fig. 5 is an SEM image of fluorine-doped graphene: fig. 5 shows that the fluorine-doped graphene also has a folded two-dimensional layered structure.
Fig. 6 is an EDS energy spectrum of fluorine-doped graphene: as can be seen from fig. 6, the fluorine-doped graphene contains C, O, F atoms. Wherein the doped F element sites are distributed on the surface of the fluorine-doped graphene in a lower density. Hydrofluoric acid (HF, F at 95.00 atomic mass%) is present as a weak acid, and F is often F-Doping in the form of ions due to F in this case-The ions are in a saturated state, so F-Ion doping on graphene surfaceThe effect is not ideal enough. If the fluorine source is replaced, e.g. F2This will have a better effect. But F2Is a gas, has high toxicity and extremely strong corrosiveness, is difficult to control in the experiment and production process, is easy to generate danger, and is considered to be safe by F2As a fluorine source is not a desirable choice. Fig. 6 demonstrates the successful synthesis of fluorine doped graphene, but with a lower doping level.
FIG. 7 is a graph of water contact angle of pure alkyd resin: the water contact angle was 61.2 °.
FIG. 8 is a graph of 0.5wt% graphene// alkyd water contact angle: the water contact angle was 68.4 °.
Fig. 9 is a water contact angle diagram of 0.5wt% boron doped graphene/alkyd resin: the water contact angle was 65.3 °.
Fig. 10 is a water contact angle diagram of 0.5wt% fluorine doped graphene/alkyd resin: the water contact angle is 83.2 degrees, compared with pure alkyd resin, the contact angle is obviously increased, and the hydrophobic property is improved.
FIG. 11 is a water contact angle diagram of 0.5wt% fluorine, boron double doped graphene// alkyd resin: the water contact angle is 92.3 degrees, compared with pure alkyd resin, the water contact angle is obviously increased, and excellent hydrophobic performance (the contact angle is more than 90 degrees) is shown.
FIG. 12 is a water contact angle diagram of 1.0wt% fluorine, boron double doped graphene// alkyd resin: the water contact angle was 86.5 °.
The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.

Claims (10)

1. A preparation method of fluorine and boron double-doped graphene/alkyd resin composite paint is characterized by comprising the following steps: fluoroboric acid is used as a doping agent, and fluorine atoms and boron atoms are doped on a graphene basal plane together while reducing graphene oxide, so that fluorine and boron double-doped graphene is obtained and uniformly dispersed in alkyd resin, and the fluorine and boron double-doped graphene/alkyd resin composite coating is obtained.
2. The preparation method of the fluorine and boron double-doped graphene/alkyd resin composite coating according to claim 1, characterized by comprising the following steps: the method specifically comprises the following steps:
step S1 preparation of graphene oxide:
firstly, adding flake graphite into a beaker, adding concentrated sulfuric acid and phosphoric acid, stirring and ultrasonically treating, then placing the flake graphite into a 35 ℃ water bath kettle for stirring, slowly adding potassium permanganate into the flake graphite, continuously stirring for reaction, heating to 50 ℃ for continuous reaction for 15min, slowly adding ice water, continuously stirring, then dropwise adding 30wt% of hydrogen peroxide solution until the solution becomes golden yellow and no bubble is generated, then adding 10wt% of dilute hydrochloric acid, finally centrifugally washing with deionized water until the supernatant is neutral, and freeze-drying the product to obtain graphene oxide;
step S2, preparation of fluorine and boron double-doped graphene:
firstly, mixing the graphene oxide deionized water obtained in the step (1) and performing ultrasonic treatment to obtain uniform dispersion liquid, then adding a fluoboric acid solution, performing ultrasonic dispersion to be uniform, transferring the mixture into a high-pressure reaction kettle with a polytetrafluoroethylene inner container to perform hydrothermal reaction, naturally cooling to room temperature after the reaction is finished, finally filtering a product by using a microporous filter membrane, repeatedly washing by using deionized water, and freeze-drying the product to obtain fluorine and boron double-doped graphene;
step S3 preparation of the fluorine and boron double-doped graphene/alkyd resin composite coating:
firstly, taking dimethylbenzene and n-butyl alcohol, then adding fluorine and boron double-doped graphene, carrying out ultrasonic treatment for 30min, then weighing alkyd resin, adding the alkyd resin into the dispersion, stirring until the alkyd resin is completely dissolved, then adding a cobalt drier, and stirring for 30min to obtain the fluorine and boron double-doped graphene/alkyd resin composite coating.
3. The preparation method of the fluorine and boron double-doped graphene/alkyd resin composite coating according to claim 2, characterized by comprising the following steps: the mass ratio of the crystalline flake graphite to the potassium permanganate in the step S1 is 1: 6, the volume ratio of the concentrated sulfuric acid to the phosphoric acid is 9: 1.
4. the preparation method of the fluorine and boron double-doped graphene/alkyd resin composite coating according to claim 2, characterized by comprising the following steps: the concentration of the graphene oxide dispersion liquid in step S2 is 2 mg/mL.
5. The preparation method of the fluorine and boron double-doped graphene/alkyd resin composite coating according to claim 2, characterized by comprising the following steps: the mass ratio of the graphene oxide to the fluoroboric acid in the step S2 is 1: 5.
6. the preparation method of the fluorine and boron double-doped graphene/alkyd resin composite coating according to claim 2, characterized by comprising the following steps: the hydrothermal reaction condition in step S2 is reaction at 180 ℃ for 30 h.
7. The preparation method of the fluorine and boron double-doped graphene/alkyd resin composite coating according to claim 2, characterized by comprising the following steps: in step S3, the volume ratio of xylene to n-butanol is 8: 2.
8. the preparation method of the fluorine and boron double-doped graphene/alkyd resin composite coating according to claim 2, characterized by comprising the following steps: in the step S3, the addition amount of the fluorine and boron double-doped graphene is 0.1-100 mg.
9. The preparation method of the fluorine and boron double-doped graphene/alkyd resin composite coating according to claim 2, characterized by comprising the following steps: the mass ratio of the alkyd resin to the cobalt drier in the step S3 is 20: 1.
10. a fluorine and boron double-doped graphene/alkyd resin composite coating prepared by the preparation method of any one of claims 1 to 9.
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