CN113845110A - Graphene oxide for anticorrosive paint, preparation method of graphene oxide, and anticorrosive paint - Google Patents
Graphene oxide for anticorrosive paint, preparation method of graphene oxide, and anticorrosive paint Download PDFInfo
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- C01—INORGANIC CHEMISTRY
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- C01B32/15—Nano-sized carbon materials
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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
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Abstract
The invention provides graphene oxide with low oxidation degree and low defect and application thereof in anticorrosive paint. By regulating and controlling the oxidation degree and other properties of the graphene oxide, the graphene oxide with high barrier property and high dispersibility can be obtained, and the anti-corrosion property of the coating is further improved by using the graphene oxide as a coating component. According to the invention, the graphene oxide and the related high-performance graphene anticorrosive paint can be obtained by using a preparation method with simple process and low cost, and the application prospect is more definite. The anticorrosive paint can be widely applied to various occasions such as ship corrosion prevention, bridge corrosion prevention, water wind power equipment corrosion prevention and the like.
Description
Technical Field
The invention belongs to the field of functional materials, and particularly relates to graphene oxide with low oxidation degree and low defects, a preparation method of the graphene oxide, and an anticorrosive coating containing the graphene oxide.
Background
Corrosion is the oxidation that occurs as a result of exposure of the metal to air. In high humidity environments, such as oceans and islands in the sea, corrosion is more severe. According to relevant statistics, the economic loss caused by corrosion accounts for about 3-5% of GDP of each country every year, and is far greater than the sum of natural disasters and various accident losses. In china, the total cost of corrosion including the loss due to corrosion and the corrosion protection investment in 2014 is over 2.1 trillion renminbi. Such dramatic losses have led to an increasing demand for high performance anticorrosive coatings.
Graphene was discovered in 2004 by the laboratory micromechanical exfoliation method of costandin norworth and anderley geiger, university of manchester, uk (Novoselov, K.S.&Geim, A.K.et al.electric field effect in atomic thin carbon films science 306, 666-. It is a compound consisting of carbon atoms in sp2The planar two-dimensional thin film material with hexagonal honeycomb lattice and only one carbon atom thickness formed by hybrid orbitals is gradually attracting attention in the field of paint and the like as the thinnest nanometer material so far due to the excellent mechanical property and super high diameter-thickness ratio, especially the high barrier capability to various substances which are easy to cause corrosion, such as water, oxygen, chloride ions and the like. However, when the graphene is added into the anticorrosive paint, due to unreasonable oxygen element/carbon element ratio, too high content of hydrophilic groups such as-COOH, or insufficient peeling, too thick lamella thickness, or a large number of defects on the lamellar structure, the barrier capability of the graphene on substances such as water in the actual anticorrosive paint coating is lower than expected, and the corrosion resistance effect is not ideal; or due to the fact that graphene is not easy to disperse, local agglomeration is serious, the mechanical property and the corrosion resistance of the anticorrosive paint cannot be improved, pores are generated in the anticorrosive paint coating, and the pores, a corrosion medium and a base material metal plate form a micro battery to accelerate corrosion. In addition, the graphene has numerous performance parameters and is expensive, and how to obtain graphene suitable for coating application through a low-cost process is still a difficulty in the current stage in obtaining the graphene anticorrosive coating with low addition and high anticorrosive performance.
In patent document 1, graphite with different sheet diameters is oxidized by a Hummers method to obtain corresponding graphene oxide with different sheet diameters, and the graphene oxide is added into an anticorrosive coating, wherein the large-size graphene oxide shows lower corrosion current and corrosion rate. Although the correlation between the size of graphene oxide and the corrosion resistance is proposed, the degree of oxidation of graphene oxide and the influence of oxygen-containing groups and the like on the corrosion resistance are not considered.
Non-patent document 1 discloses the anticorrosion effect of graphene oxide with different oxidation degrees after being added into a water-based epoxy zinc-rich coating. The graphene oxide system with low oxidation degree, less oxygen-containing groups and no carboxyl peak in an infrared spectrogram shows high corrosion resistance. However, the content of carboxyl groups is not clarified in the document, and the correlation between the graphene oxide performance and the performance of the aqueous anticorrosive coating due to the low oxidation degree is not studied.
Research on the properties of graphene or graphene oxide itself has been a focus of much attention.
Non-patent document 2 discloses a method of treating graphene oxide with ultraviolet irradiation to change its structure, thereby affecting the performance of the graphene oxide. The content of oxygen-containing groups in the graphene oxide can be reduced by performing ultraviolet treatment on the graphene oxide prepared by the improved Hummers method for a certain intensity and time. However, while reducing, the problem of local crystallite formation of graphene oxide lamellae, leading to increased thickness of the lamellae agglomerates.
Patent document 2 discloses a method for producing high-quality graphene on a large scale. 95-98 wt% of sulfuric acid and the like are used as oxidants, potassium permanganate and the like are used as intercalation agents, and the graphene with low defect and high conductivity is obtained by a method of multiple mild oxidation intercalation and multiple high-temperature stripping of graphite. The patent does not disclose specific performance parameters of the prepared graphene, and the preparation method is very complicated.
Patent document 3 proposes a method for preparing expandable graphite by using medium-low carbon fine flake graphite as a raw material, low-concentration sulfuric acid (30-85 wt%) as an intercalating agent and potassium permanganate as an oxidizing agent. Although the oxidation conditions are mild, the graphite peak in the XRD spectrum of the product still exists, and graphene oxide and graphene cannot be obtained.
Documents of the prior art
Patent document
Patent document 1: CN106118364A
Patent document 2: CN102452649A
Patent document 3: CN106185882A
Non-patent document
Non-patent document 1: chenzhong Hua, Liqing and He chang. Influence of the oxidation degree and content of graphene on the corrosion resistance of the water-based zinc powder coating is disclosed in coating industry, No. 6, pages 35-41, 2019;
non-patent document 2: waldo Robert Gallegos-Perez, Ana Cecilia Reynosa-Mart i nez et al effect of UV radiation on the structure of graphene oxide in water and its immunity on cytotoxicity and As (III) adsorption. Chemosphere Volume,249,12160,2020.
Disclosure of Invention
In order to solve the problems, the invention provides the graphene oxide with low oxidation degree and low defect, and the graphene oxide can obviously improve the performance of the anticorrosive paint.
The invention aims to provide graphene oxide with low oxidation degree and low defects. The graphene oxide has a low oxidation degree, and is represented by an oxygen element/carbon element molar ratio of 0.23-0.40. The method for measuring the molar ratio of oxygen element to carbon element may be an elemental analysis method. Compared with the conventional graphene oxide, the graphene oxide has the oxygen element/carbon element molar ratio of less than 0.40, is favorable for avoiding the lamella defect caused by high oxidation degree, and better realizes the blocking effect on water and the like; compared with the conventional graphene, the graphene oxide has the oxygen element/carbon element molar ratio of more than 0.23, and is beneficial to improving the dispersion performance and avoiding agglomeration. The molar ratio of oxygen element/carbon element may be more preferably 0.25 to 0.35 in order to balance low defects and high barrier properties at a low oxidation level and high dispersibility at a high oxidation level.
The graphene oxide according to the present invention has a content of-COOH groups of 0to 0.01 wt% based on the entire mass of the graphene oxide, as measured by a Boehm titration method. The low content of the hydrophilic group-COOH group can improve the barrier effect of graphene oxide on water and the like. the-COOH group content may be further preferably 0to 0.005% by weight in order to achieve a higher barrier effect.
The thickness of the graphene oxide is 0.5-10.0 nanometers. The method of measuring the thickness may be atomic force microscopy. Under the condition that the thickness is more than 10 nanometers, the barrier advantage of the graphene two-dimensional material in terms of high aspect ratio cannot be exerted, but the situation that the thickness is less than 0.5 nanometers due to the limitation of the molecular size of the six-membered carbon ring of the graphene oxide per se is difficult to realize. In order to make graphene oxide have higher barrier performance, the thickness of graphene oxide may be further preferably 0.5 to 2.5 nm.
As the graphene oxide provided by the invention, due to the damage of strong acid to a carbon-carbon six-membered ring structure in the oxidation process, intrinsic defects consisting of carbon atoms not hybridized with sp2 orbitals on the graphene oxide and externally introduced defects caused by non-carbon atoms covalently bonded with the carbon atoms of the graphene oxide exist. The defect degree of the whole graphene oxide can be characterized by the proportion of D/G in a Raman spectrum. The G peak is a main characteristic peak of the graphene-related material, is caused by in-plane vibration of sp2 carbon atoms, and appears at 1580cm-1Nearby. The D peak is generally considered as a disordered vibrational peak of the graphene-related material, and is used to characterize structural defects or edges in the graphene-related material. Therefore, the larger the D/G ratio, the lower the sheet regularity of the graphene-based material and the more defects. The graphene oxide of the present invention has a low oxidation degree, and thus has an appropriate oxidation degree and an appropriate barrier property, and the ratio of D/G in a raman spectrum may preferably be 0.4 to 0.7. In order to make the graphene oxide less defective and have higher barrier properties, the ratio of D/G may be further preferably 0.4 to 0.6.
In addition, in the graphene oxide of the present invention, since the incorporation of a heteroatom increases defects and deteriorates barrier properties, the nitrogen element content is preferably 0 wt%. The method of testing for elemental nitrogen may be elemental analysis.
The graphene oxide has the sheet diameter of 5-50 mu m, and is easy to agglomerate when the sheet diameter is too large, and has poor barrier effect when the sheet diameter is too small. In order to make the graphene oxide have better dispersibility and higher barrier property, the sheet diameter may be further preferably 10 to 30 μm.
As a method for producing graphene oxide with a low degree of oxidation and low defects according to the present invention, a production method including the steps of: the mild oxidation of graphite by sulfuric acid and potassium permanganate with the concentration of 87-92 wt% can also be realized by the mild oxidation of graphene and the like.
It is known that after sulfuric acid is mixed with potassium permanganate, brown potassium permanganate and sulfuric acid react as shown in the following formula (1) to convert into green manganese heptaoxide with stronger oxidizability and poorer stability.
2KMnO4+H2SO4＝Mn2O7+H2O+2KHSO4Formula (1)
When the concentration of the sulfuric acid is higher than 92 wt%, the mixed system of potassium permanganate and sulfuric acid is green, which indicates that the potassium permanganate is completely converted into green manganese dioxide. When the system is used for oxidizing graphite, an oxidant in the system is manganese dioxide, and the graphite is oxidized to the degree similar to that of graphene oxide prepared by a conventional Hummers method. When the concentration of the sulfuric acid is lower than 87 wt%, a mixed system of potassium permanganate and sulfuric acid is brown, and the green color of manganese pentoxide is not presented, and when the system oxidizes graphite, due to the existence of only potassium permanganate with weak oxidizing property, graphene oxide with sufficient oxidation stripping cannot be obtained. When the concentration of the sulfuric acid is 87-92 wt%, the mixed system of the potassium permanganate and the sulfuric acid is dark green, which shows that the potassium permanganate in the system is partially converted into green manganese dioxide, and the mixed system of the potassium permanganate and the manganese dioxide is formed. When the system is used for oxidizing graphite, the two oxidants are blended, so that the oxidation can be carried out mildly. In order to provide the graphene oxide obtained by the reaction with a desirable balance of properties, the sulfuric acid concentration may be further preferably 88 to 90 wt%.
In particular, when the mass ratio of the amount of sulfuric acid to potassium permanganate in a sulfuric acid solution having a concentration of 87 to 92 wt% is 2 to 50, graphene oxide having a low degree of oxidation and high reproducibility and stable performance can be obtained. In order to make the graphene oxide obtained by the reaction have ideal comprehensive performance, the mass ratio of the sulfuric acid in the sulfuric acid solution with the concentration of 87-92 wt% to the potassium permanganate can be further preferably 5-20.
Another object of the present invention is to provide an anticorrosive coating containing the above graphene oxide. In the anticorrosive paint, the content of the graphene oxide in the solid components of the paint is preferably 0.01-0.50 wt%. The content of the graphene oxide is more than 0.01 wt%, so that the graphene oxide can form an effective blocking channel in the coating; in addition, the content of graphene oxide is 0.50 wt% or less, which can prevent the graphene oxide from agglomerating in the coating material. The addition amount of the graphene oxide may be further preferably 0.05 to 0.20 wt% for better balance of cost and corrosion resistance.
In the invention, in order to represent the barrier effect and the anticorrosion effect of the graphene oxide, two main parameters of water transmittance and salt spray resistant time are adopted. The characterization of the barrier and preservative effects is not limited to these two parameters, however, and can be performed using other parameters familiar to those skilled in the art.
The water permeability can be measured by forming the coating material into a film and then filtering the film under reduced pressure.
The salt spray resistant time can be measured in a neutral salt spray test box according to the national standard GB/T1771-2007.
The invention provides graphene oxide with low oxidation degree and low defect, a preparation method thereof and an anticorrosive coating. The graphene oxide with high barrier property and high dispersibility can be obtained by regulating and controlling the oxidation degree and other properties of the graphene oxide, and further the graphene oxide can be used as a coating component to improve the corrosion resistance of the coating. According to the invention, the graphene oxide and the related high-performance graphene anticorrosive paint can be obtained by using a preparation method with simple process and low cost, and the application prospect is more definite. The anticorrosive paint can be widely applied to various occasions such as ship corrosion prevention, bridge corrosion prevention, water wind power equipment corrosion prevention and the like.
Detailed Description
The present invention is further illustrated by the following examples, which are intended to be purely exemplary and are not intended to limit the scope of the invention.
1. Raw materials
(1) Anticorrosive paint with 70 wt% of zinc powder and curing agent: purchased from Hangzhou Saibao chemical Co., Ltd, and used directly.
(2) Graphite: different discs were purchased from Alfa Aesar and used as received.
(3) Other reagents
Deionized water: and (4) self-making.
Sulfuric acid: the 98 wt% concentration was purchased from national pharmaceutical products chemical Co., Ltd, and diluted to a desired concentration for use.
Potassium permanganate, 0.05mol/L NaHCO3Standard solution, methyl red, 0.05mol/L HCl standard solution, hydrogen peroxide: all purchased from chemical reagents of national drug group, Ltd.
2. Method for determining the relevant properties in the examples according to the invention and in the comparative examples:
(1) molar ratio of oxygen element to carbon element of graphene oxide: elemental analyzer (ElementarVario EL Cube Germany)
The graphene oxide was vacuum dried at 60 ℃ for 12 hours before testing. After the mass fractions of the respective elements C, O, S were measured, the oxygen element/carbon element molar ratio was calculated by the following formula (2).
The measurement was performed 3 times, and the average value was obtained.
(2) Content of — COOH group of graphene oxide: boehm titration method
Accurately weighing 3 parts of the graphene oxide sample which is about 200 mg by using an electronic balance, and recording the real weight.
The samples were placed in conical flasks each having a capacity of 300mL to conduct a parallel experiment. NaHCO with the concentration of 0.05mol/L is added325mL of the standard solution was stirred for 24 hours. The mouth of the conical flask is covered by filter paper, so that the carbon dioxide gas generated by reaction is prevented from remaining in the flask. Then filtered and washed thoroughly with deionized water and all filtrates were collected. And titrating the unreacted alkali liquor in the filtrate to an end point by using 0.05mol/L HCl standard solution by using methyl red as an end point indicator.
The content of-COOH groups in graphene oxide was calculated according to formula (3), and the average of 3 parallel samples was taken.
In the formula, VbDeionized water blank (mL); Δ V3In order to correct the theoretical indication end point of methyl red to the HCl standard solution volume correction value of the theoretical end point of acid-base titration,
ΔV3＝(NaHCO3volume + HCl volume) ([ H ]+]R-[H+]NaHCO3) HCl concentration formula (4)
[H+]R＝10-5mol/L, is the proton concentration of the end point indicated by methyl red theory; [ H ]+]NaHCO3Titration of NaHCO for HCl3The theoretical end point of proton concentration.
(3) Thickness of graphene oxide: atomic force microscope (Shimadzu SPM-8100FM Japan)
Dispersing graphene oxide in deionized water to prepare 0.1 wt% dispersion liquid, performing ultrasonic treatment for 30min, sucking the dispersion liquid drop on a mica sheet by using a liquid transfer device, and performing a test after drying. The measurement was performed 3 times, and the average value was obtained.
(4) Ratio of D/G in raman spectrum of graphene oxide: raman spectrometer (Bruker Senterra R200-L Germany)
Dispersing graphene oxide in deionized water to prepare 0.1 wt% dispersion liquid, performing ultrasonic treatment for 10min, sucking the dispersion liquid drop on a silicon wafer by using a liquid transfer device, and performing a test after air drying. The measurement was performed 3 times, and the average value was obtained.
(5) Nitrogen content of graphene oxide: elemental analyzer (ElementarVario EL Cube Germany)
The graphene oxide was vacuum dried at 60 ℃ for 12 hours before testing. The measurement was performed 3 times, and the average value was obtained.
(6) Sheet diameter of graphene oxide: scanning electron microscope (JEOL JSM-6700F Japan)
Samples from different regions were selected, measured 50 times and averaged.
(7) The content of graphene oxide in the solid components of the coating is as follows: calculated by the following formula (5)
(8) Coating thickness: paint film thickness meter (TIME TT220 Chinese)
And (4) after the thickness gauge is reset to zero, placing the dried coating sample under the probe of the gauge for measurement. Different areas on the coating sample were selected and measured 10 times, and the average value was taken.
(9) Water permeability of the coating: calculated by the following formula (6)
Test samples: the coating was peeled off from the PET base film and cut into a size of a circular filter paper having a diameter of 53 mm.
The test method comprises the following steps: the filter paper-sized coating was placed in a vacuum filtration apparatus, and water was passed through the filter under a vacuum of 30 Torr. The water passage weight W was recorded for a predetermined time t and calculated according to the following formula (6). The measurement was performed 3 times in parallel, and the average value was obtained.
(10) Salt spray resistance: neutral salt fog test box (HAIDA HD-E808-120 China)
The test method comprises the following steps: coating the paint on the steel plate subjected to sand blasting according to the national standard GB/T1771-2007, scratching the surface of the paint after the paint is dried, and uninterruptedly testing 5 parallel samples in a neutral salt spray test box. The salt spray resistance of the coating is indicated by the time the coating foams, peels off or scratches rust for more than 2 mm.
Example 1
Preparing graphene oxide:
in an ice-water bath at 0 ℃, 5g of graphite with the sheet diameter of 15 microns is slowly added into a beaker filled with 21g of sulfuric acid with the concentration of 87 wt%, graphene is slowly added under the stirring condition, 2g of potassium permanganate is slowly added after the graphene is uniformly stirred, and then the temperature is kept at about 0 ℃ for continuous stirring for 2 hours. And then moving the beaker to a warm water bath at about 35 ℃ to continue stirring for 30 minutes, then diluting the reaction system with 200 ml of deionized water, and adding a proper amount of 5% hydrogen peroxide until no gas is generated in the system. Washing the graphene oxide powder with deionized water for many times until the graphene oxide powder is neutral, and drying a filter cake in a freeze dryer at the temperature of-50 ℃ to obtain the graphene oxide.
Specific properties of graphene oxide are shown in table 1.
Preparing a coating containing graphene oxide:
1g of graphene oxide is added into an anticorrosive coating with the zinc powder content of 70 wt%, so that the graphene oxide content in the anticorrosive coating is 2 wt%. And then mixing the mixture with a curing agent, and spraying the mixture on a PET base film to prepare a sample for testing water permeability, or spraying the mixture on a steel plate subjected to sand blasting to prepare a sample for testing salt spray resistance. Both coatings had a thickness of 60 microns.
Specific properties of the graphene oxide-containing coating are shown in table 1.
Examples 2 to 6, comparative examples 1 and 2
The same operation as in example 1 was carried out while changing the sulfuric acid concentration or the mass ratio of the amounts of sulfuric acid and potassium permanganate used in the sulfuric acid solution in example 1 to obtain graphene oxide and a coating layer containing the graphene oxide as shown in table 1.
TABLE 1
As shown in table 1, it can be seen from the combination of examples 1 to 6 and comparative examples 1 to 2 that, when the molar ratio of oxygen element/carbon element is 0.23 to 0.40, the content of — COOH group relative to the entire mass of the graphene oxide measured by Boehm titration is 0to 0.01 wt%, and the thickness of the graphene oxide is 0.5 to 10.0 nm, the water transmittance or the salt spray time resistance of the coating layer containing the graphene oxide is far superior to that of the coating layer containing the graphene oxide which does not satisfy the above conditions.
Examples 7 to 12
Graphene oxide and a coating layer containing the graphene oxide shown in table 2 were obtained in the same manner as in example 1, except that the concentration of sulfuric acid, the mass ratio of the amounts of sulfuric acid and potassium permanganate used in the sulfuric acid solution, or the sheet diameter of graphite in example 1 was changed.
TABLE 2
As shown in table 2, in examples 1 to 3 and examples 7 to 8, it is understood that the water permeability of the coating layer increases as the molar ratio of oxygen element/carbon element of graphene oxide increases; the salt spray resistance time is increased and then shortened along with the increase of the molar ratio of the oxygen element to the carbon element of the graphene oxide. This is because the increase of the molar ratio of oxygen element/carbon element makes the graphene oxide show stronger hydrophilicity, which results in poor water barrier effect, but at the same time, the dispersibility of the graphene oxide in the coating can be improved, thereby improving the salt spray resistance time of the coating. When the molar ratio of the oxygen element to the carbon element is 0.25-0.35, the coating containing the graphene oxide has the best salt spray resistance.
As shown in table 2, combining examples 2, 4 and examples 9 to 11, it can be seen that the water permeability of the coating layer increases as the-COOH group content of graphene oxide increases; the salt spray resistance time is shortened. This is because the-COOH group serves as a hydrophilic group, and an increase in the content significantly increases the hydrophilicity of graphene oxide, which results in a poor barrier effect against water, and thus shortens the salt spray resistance time of the coating layer. When the-COOH group content is 0to 0.005, the graphene oxide-containing coating layer has the best salt spray resistance.
As shown in table 2, it is known from the combination of examples 2, 5, 6 and 12 that the increase in the thickness of the graphene oxide results in the deterioration of the water-blocking effect of the graphene oxide, and further shortens the salt spray resistance time of the coating. When the thickness of the graphene oxide is 0.5-2.5 nanometers, the coating containing the graphene oxide has the best salt spray resistance.
Examples 13 to 15
The same operations as in example 1 were carried out while changing the graphite flake diameter, the sulfuric acid concentration, or the mass ratio of the amounts of sulfuric acid and potassium permanganate used in the sulfuric acid solution in example 1 to obtain graphene oxide and a coating layer containing the graphene oxide as shown in table 3.
TABLE 3
As shown in table 3, combining example 2 and examples 13 to 15, it can be seen that the water transmittance of the coating layer increases as the ratio of D/G in the raman spectrum of graphene oxide increases; the salt spray resistance time is shortened. This is because the increase in the ratio of D/G in the raman spectrum is due to the increase in defects on the graphene oxide sheet layer, which results in a poor barrier effect against water, thereby shortening the salt spray resistance time of the coating. When the ratio of D/G in the Raman spectrum of the graphene oxide is 0.4-0.6, the coating containing the graphene oxide has the best salt spray resistance.
Example 16
The same raw materials, raw material ratios, and operations as in example 2 were carried out, but only 10g of nitric acid having a concentration of 68 wt% was mixed with sulfuric acid, thereby obtaining graphene oxide and a coating layer containing the graphene oxide as shown in table 4.
Examples 17 to 21
The same operations as in example 1 were carried out while changing the graphite flake diameter, the sulfuric acid concentration, or the mass ratio of the amounts of sulfuric acid and potassium permanganate used in the sulfuric acid solution in example 1 to obtain graphene oxides and coatings containing the graphene oxides as shown in table 4.
TABLE 4
As shown in table 4, it is understood from the combination of example 2 and example 16 that the nitrogen element as a heteroatom of the graphene oxide material increases defects and deteriorates barrier properties when introduced, thereby shortening the salt spray resistance time of the coating layer.
As shown in table 4, it can be seen from the combination of example 2 and examples 17 to 21 that the water permeability of the coating layer decreases and then increases as the sheet diameter of graphene oxide increases; the salt spray resistance time is firstly improved and then shortened along with the increase of the sheet diameter of the graphene oxide. This is because the increase in the sheet diameter of graphene oxide can improve the water-barrier effect of graphene oxide, but if the sheet diameter is too large, the graphene oxide itself may easily agglomerate. When the sheet diameter of the graphene oxide is 10-30 microns, the coating containing the graphene oxide has the best salt spray resistance.
Examples 22 to 29
Graphene oxide and a coating layer containing the graphene oxide as shown in table 5 were obtained in the same manner as in example 1, except that the concentration of sulfuric acid or the mass ratio of the amount of sulfuric acid to potassium permanganate used in the sulfuric acid solution in example 1 was changed.
TABLE 5
As shown in Table 5, it is understood by combining examples 2, 22 to 24 and comparative examples 1 to 2 that the concentration of sulfuric acid is 87 to 92 wt%, which contributes to obtaining graphene oxide having the characteristics of the present invention. Particularly, when the concentration of the sulfuric acid is 88-90 wt%, the coating containing the obtained graphene oxide has the best salt spray resistance.
As shown in table 5, it is understood from the combination of example 2 and examples 25 to 29 that when the mass ratio of the amount of sulfuric acid to potassium permanganate in the sulfuric acid solution is 2 to 50, graphene oxide having the characteristics of the present invention can be obtained. Particularly, when the mass ratio of the dosage of sulfuric acid to potassium permanganate in the sulfuric acid solution is 5-20, the coating containing the obtained graphene oxide has the best salt spray resistance.
Examples 30to 35 and comparative example 3
Using the graphene oxide obtained in example 2, the content of the graphene oxide added to the anticorrosive paint was adjusted to obtain a coating layer containing the graphene oxide as shown in table 6.
TABLE 6
As shown in table 6, when example 2, examples 30to 35 and comparative example 3 were combined, the water transmittance and the salt spray resistance time of the coating layer containing graphene oxide according to the present invention were higher than those of the coating layer containing no graphene oxide, but the performance was rather deteriorated when the amount of graphene oxide was too high. This is because when the graphene oxide content is too low, the graphene oxide cannot form an effective blocking channel in the coating; with the increase of the content of the graphene oxide, a blocking channel is gradually formed, the blocking effect on water is enhanced, and the salt spray resistant time of the coating is prolonged; however, when the amount of graphene oxide added is too large, agglomeration is easily formed in the coating. Therefore, the water permeability of the coating is firstly reduced and then increased along with the increase of the content of the graphene oxide in the coating; the salt spray resistance time is firstly increased and then shortened along with the increase of the content of the graphene oxide in the coating. When the content of the graphene oxide is 0.01-0.5 wt%, the coating containing the obtained graphene oxide has the best salt spray resistance.
Claims (8)
1. The graphene oxide for the anticorrosive paint is characterized in that: an oxygen element/carbon element molar ratio of 0.23 to 0.40, a-COOH group content of 0to 0.01 wt% relative to the entire mass of the graphene oxide as measured by Boehm's titration, and a thickness of the graphene oxide of 0.5 to 10.0 nm.
2. The graphene oxide for anticorrosive paint according to claim 1, characterized in that: the ratio of D/G of the graphene oxide in a Raman spectrum is 0.4-0.7.
3. The graphene oxide for anticorrosive paint according to claim 1, characterized in that: in the graphene oxide, the content of nitrogen element is 0 wt%.
4. The graphene oxide for anticorrosive paint according to claim 1, characterized in that: the sheet diameter of the graphene oxide is 5-50 μm.
5. A preparation method of graphene oxide for an anticorrosive paint according to any one of claims 1 to 4, characterized by comprising: oxidizing the graphite by using sulfuric acid with the concentration of 87-92 wt% and potassium permanganate.
6. The method for preparing graphene oxide for anticorrosive paint according to claim 5, characterized in that: the mass ratio of the sulfuric acid to the potassium permanganate in the sulfuric acid solution with the concentration of 87-92 wt% is 2-50.
7. An anticorrosive paint is characterized in that: comprising the graphene oxide of any one of claims 1-4.
8. The anticorrosive paint according to claim 7, characterized in that: the content of the graphene oxide in the solid component of the coating is 0.01-0.50 wt%.
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