A method for preparing nanocarbon and secondary doped polyaniline composite material

Abstract

The invention provides a method for preparing a nano-carbon and secondary doped polyaniline composite material, and relates to the technical field of polyaniline composite materials. The method comprises the following steps: adding an intrinsic polyaniline-graphene composite material and an intrinsic polyaniline-carbon nanotube composite material to a 1 mol / L doping acid solution in a mass ratio of 1:1, and adopting a polyaniline secondary doping method to prepare a composite material of graphene, carbon nanotubes and secondary doped polyaniline, thereby solving the problems of agglomeration and dispersion of polyaniline and having excellent corrosion inhibition performance; the product morphology is more uniform, and the nanofibers are more unified; the product morphology is improved by controlling the ratio of graphene to aniline and the ratio of carbon nanotubes to aniline; the polyaniline wraps the carbon nanotubes and neatly arranges them on the surface of the graphene; the size is uniform, and the fiber length reaches more than 800 nm; the agglomeration problem of the graphene and carbon nanotubes themselves is avoided, and various performances of the product are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polyaniline composite materials, in particular to a method for preparing a composite material of nano-carbon and secondary doped polyaniline. Background Art

[0002] Currently, most research on anti-corrosion coatings, both domestically and internationally, focuses on reducing VOC emissions through water-based coatings. However, the overall anti-corrosion performance of water-based coatings is inferior to that of oil-based coatings. Water has a high surface tension, and contaminants in the coating system can cause craters in the coating. Furthermore, the evaporation of water as a solvent increases the likelihood of coating defects.

[0003] Solvent-free epoxy coatings eliminate the need for organic volatile solvents as a dispersion medium during their manufacture and application. This reduces air pollution from organic volatile solvents and the likelihood of coating defects. Furthermore, their excellent wet adhesion ensures durability in harsh corrosive environments. Furthermore, a single coat of solvent-free epoxy coating can achieve a higher effective film thickness, significantly reducing the number of application coats and lowering construction costs. Therefore, solvent-free coatings offer significant advantages and broad application prospects in the corrosion protection field.

[0004] However, solvent-free epoxy coatings have high viscosity and difficult construction due to their lack of solvents. This study explored the performance comparison of coatings made by mixing different epoxy resins and curing agents. The approach involved selecting the epoxy resin and curing agent, and then selecting pigments and fillers to achieve a coating with not only good physical properties but also excellent corrosion resistance.

[0005] Polyaniline (PAI), a conductive polymer made from the monomer aniline, is easy to synthesize, chemically stable, and possesses diverse structures. It is widely used, particularly in metal corrosion protection. However, PAI's application also faces urgent challenges, such as poor dispersibility and film tightness, which severely impact its corrosion resistance.

[0006] Carbon nanotubes and graphene are currently hot topics in the research of nanocarbon materials. Carbon nanotubes have excellent electrical conductivity, mechanical strength and toughness; graphene has excellent mechanical, optical, thermal and barrier properties. Carbon nanotubes and graphene have been widely used in capacitor materials, energy storage, seawater desalination, solar cells, and also have broad application prospects in the field of corrosion protection. Studies have shown that adding carbon-based materials to polyaniline can improve its electrical conductivity, while also improving its electrochemical and mechanical properties. The field has always hoped to prepare new materials with excellent corrosion resistance by compounding carbon nanotubes or graphene with secondary doped polyaniline, but conventional compounding methods cannot avoid the self-agglomeration of carbon nanotubes and graphene. The effect of the resulting composite material is worse than that of the product prepared by polyaniline and carbon nanotubes or graphene separately, and it cannot achieve the purpose of enhancing its corrosion resistance. Summary of the Invention

[0007] The present invention provides a method for preparing a composite material of nanocarbon and secondary doped polyaniline. The method adopts the secondary doping method of polyaniline to prepare a graphene and carbon nanotube composite material based on the secondary doped polyaniline, which can achieve the effect of 1+1+1>3, thereby solving the agglomeration and dispersion problems of polyaniline and avoiding the self-agglomeration problem of carbon nanotubes and graphene.

[0008] The present invention provides a method for preparing a composite material of nanocarbon and secondary doped polyaniline, comprising:

[0009] (1) Taking two equal volumes of 1 mol / L doping acid solutions, respectively adding aniline-graphene mixture and ammonium persulfate, wherein the molar ratio of the aniline-graphene mixture to the ammonium persulfate is 0.8:1, and uniformly mixing the two with a magnetic stirrer for 1 to 2 hours, placing them at room temperature and allowing them to stand for 20 to 26 hours, and washing the obtained product with ethanol and deionized water to neutrality, and drying and grinding to obtain a primary doped polyaniline-graphene composite material; wherein the mass ratio of aniline to graphene in the aniline-graphene mixture is 15 to 25:1;

[0010] (2) adding excess ammonia water to the primary doped polyaniline-graphene composite material for dedoping, stirring with a magnetic stirrer for 1 to 2 hours, standing at room temperature for 20 to 26 hours, washing the obtained product with ethanol and deionized water until neutral, and finally drying and grinding to obtain an intrinsic polyaniline-graphene composite material;

[0011] (3) taking two equal volumes of 1 mol / L doped acid solutions, adding aniline-carbon nanotube mixture and ammonium persulfate respectively, wherein the molar ratio of aniline-carbon nanotube mixture to ammonium persulfate is 0.8:1, and uniformly mixing the two with a magnetic stirrer for 1 to 2 hours, placing them at room temperature and allowing them to stand for 20 to 26 hours, washing the obtained product with ethanol and deionized water until neutral, drying and grinding to obtain a primary doped polyaniline-carbon nanotube composite material; wherein the mass ratio of aniline to carbon nanotubes in the aniline-carbon nanotube mixture is 15 to 25:1;

[0012] (4) adding excess ammonia water to the primary doped polyaniline-carbon nanotube composite material for dedoping, stirring with a magnetic stirrer for 1 to 2 hours, standing at room temperature for 20 to 26 hours, washing the obtained product with ethanol and deionized water until neutral, and finally drying and grinding to obtain an intrinsic polyaniline-carbon nanotube composite material;

[0013] (5) The intrinsic polyaniline-graphene composite material and the intrinsic polyaniline-carbon nanotube composite material were added to a 1 mol / L doped acid solution in a mass ratio of 1:1, mixed and stirred, and allowed to stand for 20 to 26 hours. They were then filtered and washed with ethanol and deionized water in turn until neutral, and finally dried and ground to obtain a composite material of graphene, carbon nanotubes and secondary doped polyaniline.

[0014] Optionally, the mass ratio of aniline to graphene in the aniline-graphene mixture is equal to the mass ratio of aniline to carbon nanotubes in the aniline-carbon nanotube mixture.

[0015] Optionally, the mass ratio of aniline to graphene in the aniline-graphene mixture is 18 to 22:1, and the mass ratio of aniline to carbon nanotubes in the aniline-carbon nanotube mixture is 18 to 22:1.

[0016] Optionally, the mass ratio of aniline to graphene in the aniline-graphene mixture is 20:1, and the mass ratio of aniline to carbon nanotubes in the aniline-carbon nanotube mixture is 20:1.

[0017] Optionally, the doping acid solution is one of an inorganic acid solution, an organic acid solution and a composite acid, and the molar concentration ratio of the inorganic acid to the organic acid in the composite acid is 1:1 to 1:6.

[0018] Optionally, the organic acid is a mixture of one or more of formic acid, acetic acid, propionic acid, butyric acid, octanoic acid, adipic acid, oxalic acid, malonic acid, succinic acid, tartaric acid, benzoic acid, phenylacetic acid, perchloric acid, sulfuric acid, phosphoric acid, hydrochloric acid, and molybdic acid, and the inorganic acid is perchloric acid, sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, molybdic acid, etc. The organic acid is mainly a mixture of one or more of acetic acid, oxalic acid, citric acid, tartaric acid, tannic acid, p-toluenesulfonic acid, phytic acid, and tannic acid.

[0019] Optionally, the corrosion inhibition efficiency of the prepared composite material of graphene, carbon nanotubes and secondary doped polyaniline is greater than 78%, and the impedance value of the prepared composite material of graphene, carbon nanotubes and secondary doped polyaniline is greater than 1500Ω*cm2.

[0020] Optionally, the corrosion inhibition efficiency of the prepared composite material of graphene, carbon nanotubes and secondary doped polyaniline is greater than 80%, and the impedance value of the prepared composite material of graphene, carbon nanotubes and secondary doped polyaniline is greater than 1800Ω*cm2.

[0021] Optionally, the fiber length of the prepared composite material of graphene, carbon nanotubes and secondary doped polyaniline is greater than 800 nm.

[0022] Optionally, the fiber length of the prepared composite material of graphene, carbon nanotubes and secondary doped polyaniline is greater than 850 nm.

[0023] The present invention has the following beneficial technical effects:

[0024] The present invention provides a method for preparing a nano-carbon and secondary doped polyaniline composite material. The method comprises the following steps: adding an intrinsic polyaniline-graphene composite material and an intrinsic polyaniline-carbon nanotube composite material into a 1 mol / L doping acid solution in a mass ratio of 1:1, and adopting a polyaniline secondary doping method to prepare a composite material of graphene, carbon nanotubes and secondary doped polyaniline, thereby solving the agglomeration and dispersion problems of polyaniline and having excellent corrosion inhibition performance; the composite material product of the graphene, carbon nanotubes and secondary doped polyaniline after secondary mixing and doping has a better morphology. The nanofibers are more uniform, and the product morphology is better by controlling the ratio of graphene to aniline and the ratio of carbon nanotubes to aniline. The carbon nanotubes wrapped with polyaniline are neatly arranged on the surface of graphene with uniform size, and the fiber length reaches more than 800nm. The composite material of graphene, carbon nanotubes and secondary doped polyaniline is prepared by the method of secondary doping of polyaniline, which avoids the agglomeration problem of graphene and carbon nanotubes themselves and effectively improves the various performances of the product, which is better than the performance of the product obtained by single doping or secondary doping of graphene or carbon nanotubes. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 Schematic diagram of scanning electron microscopy of polyaniline products with different doping states in a perchloric acid system according to an embodiment of the present invention;

[0027] Figure 2 Schematic diagram of a scanning electron microscope of a composite material of graphene, carbon nanotubes and secondary doped polyaniline in a perchloric acid system according to an embodiment of the present invention;

[0028] Figure 3 Schematic diagram of a transmission electron microscope of a composite material of graphene and / or carbon nanotubes and secondary doped polyaniline according to an embodiment of the present invention;

[0029] Figure 4 Polarization curves of products with different doping states according to an embodiment of the present invention;

[0030] Figure 5The impedance spectrum equivalent circuit diagram of an embodiment of the present invention;

[0031] Figure 6 Impedance diagrams of products with different doping states according to an embodiment of the present invention;

[0032] Figure 7 Polarization curves and AC impedance diagrams of products with different doping states according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings. It is apparent that the embodiments described are only some, not all, of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0034] The present invention provides a method for preparing a composite material of nanocarbon and secondary doped polyaniline, comprising:

[0035] (1) Taking two equal volumes of 1 mol / L doping acid solutions, respectively adding aniline-graphene mixture and ammonium persulfate, wherein the molar ratio of the aniline-graphene mixture to the ammonium persulfate is 0.8:1, and uniformly mixing the two with a magnetic stirrer for 1 to 2 hours, placing them at room temperature and allowing them to stand for 20 to 26 hours, and washing the obtained product with ethanol and deionized water to neutrality, and drying and grinding to obtain a primary doped polyaniline-graphene composite material; wherein the mass ratio of aniline to graphene in the aniline-graphene mixture is 15 to 25:1;

[0036] (2) adding excess ammonia water to the primary doped polyaniline-graphene composite material for dedoping, stirring with a magnetic stirrer for 1 to 2 hours, standing at room temperature for 20 to 26 hours, washing the obtained product with ethanol and deionized water until neutral, and finally drying and grinding to obtain an intrinsic polyaniline-graphene composite material;

[0037] (3) taking two equal volumes of 1 mol / L doped acid solutions, adding aniline-carbon nanotube mixture and ammonium persulfate respectively, wherein the molar ratio of aniline-carbon nanotube mixture to ammonium persulfate is 0.8:1, and uniformly mixing the two with a magnetic stirrer for 1 to 2 hours, placing them at room temperature and allowing them to stand for 20 to 26 hours, washing the obtained product with ethanol and deionized water until neutral, drying and grinding to obtain a primary doped polyaniline-carbon nanotube composite material; wherein the mass ratio of aniline to carbon nanotubes in the aniline-carbon nanotube mixture is 15 to 25:1;

[0038] (4) adding excess ammonia water to the primary doped polyaniline-carbon nanotube composite material for dedoping, stirring with a magnetic stirrer for 1 to 2 hours, standing at room temperature for 20 to 26 hours, washing the obtained product with ethanol and deionized water until neutral, and finally drying and grinding to obtain an intrinsic polyaniline-carbon nanotube composite material;

[0039] (5) The intrinsic polyaniline-graphene composite material and the intrinsic polyaniline-carbon nanotube composite material were added to a 1 mol / L doped acid solution in a mass ratio of 1:1, mixed and stirred, and allowed to stand for 20 to 26 hours. They were then filtered and washed with ethanol and deionized water in turn until neutral, and finally dried and ground to obtain a composite material of graphene, carbon nanotubes and secondary doped polyaniline.

[0040] Furthermore, the mass ratio of aniline to graphene in the aniline-graphene mixture is equal to the mass ratio of aniline to carbon nanotubes in the aniline-carbon nanotube mixture. Preferably, the mass ratio of aniline to graphene in the aniline-graphene mixture is 18 to 22:1, and the mass ratio of aniline to carbon nanotubes in the aniline-carbon nanotube mixture is 18 to 22:1. By controlling the ratio of graphene to aniline and the ratio of carbon nanotubes to aniline within this range, the product morphology is improved, with polyaniline-coated carbon nanotubes neatly arranged on the graphene surface, achieving uniform size and fiber length exceeding 800 nm.

[0041] Optionally, the mass ratio of aniline to graphene in the aniline-graphene mixture is 20:1, and the mass ratio of aniline to carbon nanotubes in the aniline-carbon nanotube mixture is 20:1.

[0042] Optionally, the doping acid solution is one of an inorganic acid solution, an organic acid solution and a composite acid, and the molar concentration ratio of the inorganic acid to the organic acid in the composite acid is 1:1 to 1:6.

[0043] The doping acid solution used in the embodiments of the present invention is one of an inorganic acid solution, an organic acid solution, and a composite acid. The molar concentration ratio of the inorganic acid to the organic acid in the composite acid is between 1:1 and 1:6. Organic acids include, but are not limited to, formic acid, acetic acid, propionic acid, butyric acid, octanoic acid, adipic acid, oxalic acid, malonic acid, succinic acid, tartaric acid, benzoic acid, phenylacetic acid, perchloric acid, sulfuric acid, phosphoric acid, hydrochloric acid, and molybdic acid, or a mixture thereof. Preferably, the embodiments of the present invention use a tartaric acid solution. Furthermore, the preparation method of the embodiments of the present invention may also use a composite acid formed by combining an organic acid and an inorganic acid. The composite acid used in the embodiments of the present invention is primarily a mixture of an inorganic acid and an organic acid. The inorganic acids primarily include perchloric acid, sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, and molybdic acid. The organic acids primarily include acetic acid, oxalic acid, citric acid, tartaric acid, tannic acid, p-toluenesulfonic acid, phytic acid, and tannic acid. The composite acid has a molar concentration ratio of the inorganic acid to the organic acid between 1:1 and 1:6.

[0044] The composite material of graphene, carbon nanotubes, and secondary doped polyaniline prepared using the preparation method of the embodiment of the present invention has a corrosion inhibition efficiency greater than 78%, an impedance value greater than 1500Ω*cm2, and a fiber length greater than 800nm. The composite material of graphene, carbon nanotubes, and secondary doped polyaniline prepared using the optimal ratio can have a corrosion inhibition efficiency greater than 80%, an impedance value greater than 1800Ω*cm2, and a fiber length greater than 850nm.

[0045] refer to Figure 1 As shown, the morphology characterization results of polyaniline and other products using perchloric acid as the doping acid Figure 1 As shown, from Figure 1 -a It can be seen that the first-doped polyaniline product has a large number of agglomeration phenomena and eventually becomes nanoparticles. Compared with the first-doped polyaniline, the second-doped polyaniline product ( Figure 1 -b) The agglomeration phenomenon is significantly improved, forming a stick structure. The length of the nanofibers increases to about 600nm and the diameter increases to 200nm. This is because the introduction of anions during the secondary doping process also promotes the regrowth of the polyaniline molecular chain, and the morphology also grows from granular to stick structure. Figure 1 -c is a multi-walled carbon nanotube with a clustered structure. Figure 1 -d and Figure 1-e correspond to the single-doped polyaniline and carbon nanotube composite material (wherein the mass ratio of carbon nanotubes CNTs: aniline ANI = 1:15) and the secondary-doped polyaniline / carbon nanotube composite material (the mass ratio of carbon nanotubes CNTs: aniline ANI = 1:15). It can be clearly seen from the figure that the polyaniline molecular chain has obvious growth, the fiber uniformity is good, and the arrangement is more compact. Figure 1 -f shows the multi-layered sheet structure of graphene and a large number of wrinkles on the surface. Figure 1 -g and Figure 1 -h correspond to the primary doped polyaniline and graphene composite material (the mass ratio of graphene RGO: aniline ANI = 1:20) and the secondary doped polyaniline and graphene composite material (the mass ratio of graphene RGO: aniline ANI = 1:20), respectively. Figure 1 -g, it can be seen that a small amount of polyaniline is attached to the surface of graphene, and the fiber length is relatively short and agglomerated. Figure 1 -h, it can be seen that the agglomeration phenomenon of secondary doped graphene polyaniline has been improved, and a large amount of polyaniline is attached to the graphene. The product morphology is the best under this ratio, but at this time, the graphene still has agglomeration phenomenon.

[0046] Figure 2 The following is a scanning electron microscope image of the composite material of graphene, carbon nanotubes and secondary doped polyaniline in a perchloric acid system. It can be seen that the morphological changes caused by adding different ratios of carbon nanotubes and graphene are different. Figure 2 -a to Figure 2 -c, control the ratio of graphene to aniline to be 1:20, change the ratio of carbon nanotubes, Figure 2 -a The mass ratio of carbon nanotubes to aniline is 1:25; Figure 3 -b The mass ratio of carbon nanotubes to aniline = 1:20; Figure 2 -c carbon nanotubes: aniline mass ratio = 1:15, by comparison we can see that Figure 2 -a The wrinkles of graphene can be vaguely seen, and a small amount of polyaniline is attached to the surface of graphene; Figure 2 -b formed a network structure with the best product morphology. Graphene played a good template role. The fiber length could reach about 850nm with the best morphology. Figure 2 In -c, polyaniline is neatly arranged on the graphene surface, playing an excellent barrier role.

[0047] From the perspective of the composite materials of graphene, carbon nanotubes and secondary doped polyaniline, graphene RGO retains the original lamellar structure, and graphene RGO can play a good template role at a ratio of 1:20. Aniline is adsorbed on the graphene surface through adsorption, intermolecular forces, and π-π conjugation. However, since the hybridized polyaniline molecules and carbon nanotubes are too similar in morphology, the difference between the two cannot be identified under a scanning electron microscope. Therefore, the material with the best effect when the graphene ratio is 1:20 was selected for transmission electron microscopy testing.

[0048] refer to Figure 3 As shown, Figure 3 -a, Figure 3 -b and Figure 3 -c are transmission electron microscope images of aniline PANI, carbon nanotubes CNTs, graphene, and carbon nanotubes and secondary doped polyaniline composites, Figure 3 -a is pure polyaniline. It can be seen that polyaniline is stick-shaped, short and thick. Figure 3 -b is pure carbon nanotubes, which are hollow tubes with long and slender shapes. Figure 3 -c is a magnified observation of the composite material of graphene, carbon nanotubes and secondary doped polyaniline. The carbon nanotubes wrapped with polyaniline are successfully attached to the graphene surface, and the morphology of the carbon nanotubes is complete. Graphene plays a good template role, proving that under the doped acid system, when the mass ratio of aniline to graphene in the aniline-graphene mixture is 20:1 and the mass ratio of aniline to carbon nanotubes in the aniline-carbon nanotube mixture is 20:1, the product morphology is optimal. The carbon nanotubes CNTs wrapped with polyaniline (PANI) are neatly arranged on the graphene surface with uniform size, which effectively avoids the agglomeration of polyaniline, graphene and carbon nanotubes. The fiber length reaches 850nm. The prepared composite material of graphene, carbon nanotubes and secondary doped polyaniline has the best performance.

[0049] The electrochemical performance analysis and comparison results of the graphene and carbon nanotubes and secondary doped polyaniline composites prepared in the embodiment of the present invention are shown in Table 1 below, where CNTs1:15 RGO1:5 means that the mass ratio of aniline to carbon nanotubes in the aniline-carbon nanotube mixture is 15:1, and the mass ratio of aniline CNTs to graphene RGO in the aniline-graphene mixture is 5:1.

[0050] Table 1 Polarization curve fitting results

[0051]

[0052] Figure 4Table 1 shows the polarization curves of different products. The fitting results of the polarization curves are shown in Table 2. The corrosion potential and corrosion current are obtained by fitting the Tafel polarization curves. The corrosion inhibition effects of different products on the steel surface are obtained by comparing them with those of bare steel. Figure 4 -a can be seen that when the mass ratio of carbon nanotubes CNTs and aniline ANI is controlled to be 1:15 and the ratio of graphene RGO to aniline ANI is changed, as the amount of RGO gradually decreases, the corrosion current will gradually decrease. When the ratio of RGO to ANI is 1:20, the corrosion current reaches the minimum value. At this time, the corrosion resistance of the product reaches the best, and the corrosion inhibition efficiency reaches 78.68%. When the amount of RGO is further reduced, the corrosion current begins to increase gradually. This is because the morphology of the product changes after adding different amounts of RGO. When the ratio of RGO to ANI is 1:25, the RGO content is low and cannot play a good template role. The polyaniline agglomeration phenomenon is not changed, and the corrosion current is relatively high. When the amount of RGO is gradually increased, RGO begins to play a barrier role and provides a good template for polyaniline, allowing PANI wrapped with CNTs to grow evenly on RGO, with the largest specific surface area and sufficient electrode interaction, which greatly plays the passivation role of PANI.

[0053] from Figure 4 As can be seen in Figure 2-b, when the ratio of graphene RGO to aniline ANI is controlled at 1:20 and the ratio of carbon nanotubes CNTs to aniline ANI is changed, the corrosion current begins to gradually decrease as the amount of CNTs is gradually reduced. When the ratio of CNTs to ANI is 1:20, the corrosion current reaches a minimum value, at which point the product's corrosion resistance reaches its optimal value, with a corrosion inhibition efficiency of 81.79%. When the amount of CNTs is further reduced, the corrosion current begins to increase. This is because the addition of different amounts of CNTs changes the product morphology. When the CNTs ratio is 1:20, the CNTs act as a good template, and the PANI grown on the CNT surface has a uniform morphology, which effectively prevents agglomeration and maximizes the specific surface area, maximizing the passivation effect of the PANI.

[0054] Table 2 Electrochemical impedance spectroscopy fitting results

[0055]

[0056] The equivalent circuit diagram of the electrode system of the embodiment of the present invention is as follows Figure 5 As shown, Rs represents the internal resistance of the solution, Qc represents the polyaniline film capacitance, Rp represents the polyaniline film resistance, Qdl represents the dual capacitance at the metal surface and the polyaniline film, and Rt represents the passivation film resistance generated by the reaction of polyaniline and metal.

[0057] Table 2 shows the impedance results obtained by fitting the ZsimpleWin software for different doping products. When the ratio of CNTs to ANI is 1:20 and the ratio of RGO to ANI is 1:20, the fitting result is 1893.6Ω. Figure 6 As shown, at this time the impedance arc radius is the largest, the impedance value is the highest, and the anti-corrosion effect is the best.

[0058] Table 3 Polarization curve fitting results

[0059]

[0060]

[0061] Figure 7 Table 3 shows the polarization curves and electrochemical impedance spectroscopy of different products. Figure 7 -a and Table 3 show that compared with bare steel, the corrosion potential of PANI and products with different doping states has shifted negatively to a certain extent, and the corrosion current has gradually decreased. All products have shown different degrees of anti-corrosion effect. The cathode polarization slope is much greater than the anodic polarization slope, which proves that the cathode reaction resistance of the product in 3.5% sodium chloride solution is large, the water molecule film of the double electric layer is relatively complete, the metal atoms are more difficult to dissolve, and the effect on the cathode oxygen absorption reaction is more significant. When the RGO ratio is 1:20 and the CNTs ratio is 1:20, RGO plays a good template role. The PANI grown on the surface of CNTs has a uniform morphology, which solves the agglomeration phenomenon very well, has the largest specific surface area, and maximizes the passivation effect of PANI.

[0062] Table 4 AC impedance fitting results

[0063]

[0064] Table 4 shows the AC impedance fitting results of different products obtained by ZsimpleWin software. Figure 7-b and Table 4 clearly show that the impedance arc radius of the doped polyaniline with different ratios is larger than that of bare steel, and the impedance values ​​are significantly improved, proving that the products of polyaniline all have a certain anti-corrosion effect. The impedance arc of the secondary doped product is significantly better than that of the primary doped product. This is because more functional acid ions are released during the secondary doping, which changes the morphological characteristics of the polyaniline. Among them, the impedance arc radius of the secondary doping with RGO at a ratio of 1:20 and CNTs at a ratio of 1:20 is significantly better than that of other ratios. The impedance arc radius is the best and the impedance value is the largest. The fitted impedance value is 1893.6Ω, further proving that polyaniline at this ratio can form a denser metal passivation film on the metal surface, giving full play to the density of RGO and the shielding effect of CNTs, thereby slowing the corrosion rate of the metal and providing stronger protection for the metal surface.

[0065] Through the above product morphology and electrochemical performance analysis, the following conclusions were drawn:

[0066] (1) The composite materials of graphene, carbon nanotubes and secondary doped polyaniline prepared by the secondary doping method have more uniform morphology and more uniform nanofibers. The product morphology is best when the ratio of RGO to ANI is 1:20 and the ratio of CNTs to ANT is 1:20. PANI wraps CNTs and arranges them neatly on the graphene surface with uniform size. The fiber length reaches 850nm.

[0067] (2) Through the analysis of Tafel curve and electrochemical impedance diagram, it can be concluded that polyaniline with different ratios has a certain anti-corrosion effect on metals. When the ratio of RGO to ANI is 1:20 and the ratio of CNTs to ANI is 1:20, the anti-corrosion effect of the composite material of graphene, carbon nanotubes and secondary doped polyaniline prepared by the polyaniline secondary doping method is significantly better than that of products with other ratios. The corrosion current is the lowest, the corrosion inhibition efficiency reaches 81.79%, and the impedance value is 1893.6Ω.

[0068] (3) The use of polyaniline secondary doping to prepare composite materials of graphene, carbon nanotubes, and secondary doped polyaniline can avoid the agglomeration of nanomaterials and effectively improve the various properties of the product, which is better than either single doping or secondary doping of the same composite material alone. This is a breakthrough in preparing composite materials of graphene / carbon nanotubes simultaneously with polyaniline, and the product performance is significantly lower than the composite products of graphene alone or carbon nanotubes alone with polyaniline.

[0069] The present invention provides a method for preparing a nano-carbon and secondary doped polyaniline composite material. The method comprises the following steps: adding an intrinsic polyaniline-graphene composite material and an intrinsic polyaniline-carbon nanotube composite material into a 1 mol / L doping acid solution in a mass ratio of 1:1, and adopting a polyaniline secondary doping method to prepare a composite material of graphene, carbon nanotubes and secondary doped polyaniline, thereby solving the agglomeration and dispersion problems of polyaniline and having excellent corrosion inhibition performance; the composite material product of the graphene, carbon nanotubes and secondary doped polyaniline after secondary mixing and doping has a better morphology. The nanofibers are more uniform, and the product morphology is better by controlling the ratio of graphene to aniline and the ratio of carbon nanotubes to aniline. The carbon nanotubes wrapped with polyaniline are neatly arranged on the surface of graphene with uniform size, and the fiber length reaches more than 800nm. The composite material of graphene, carbon nanotubes and secondary doped polyaniline is prepared by the method of secondary doping of polyaniline, which avoids the agglomeration problem of graphene and carbon nanotubes themselves and effectively improves the various performances of the product, which is better than the performance of the product obtained by single doping or secondary doping of graphene or carbon nanotubes.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a composite material of nanocarbon and secondary doped polyaniline, characterized in that: The method comprises: (1) Two equal volumes of 1 mol / L doped acid solution were added to an aniline-graphene mixture and ammonium persulfate, respectively, wherein the molar ratio of the aniline-graphene mixture to the ammonium persulfate was 0.8:

1. The two were uniformly mixed with a magnetic stirrer for 1-2 h, and allowed to stand at room temperature for 20-26 h. The obtained product was washed with ethanol and deionized water until neutral, and then dried and ground to obtain a primary doped polyaniline-graphene composite material; wherein the mass ratio of aniline to graphene in the aniline-graphene mixture was 20:1; (2) Adding excess ammonia water to the primary doped polyaniline-graphene composite material for dedoping, stirring with a magnetic stirrer for 1-2 h, and standing at room temperature for 20-26 h. The obtained product is washed with ethanol and deionized water until neutral, and finally dried and ground to obtain the intrinsic polyaniline-graphene composite material; (3) Take two equal volumes of 1 mol / L doped acid solution and add aniline-carbon nanotube mixture and ammonium persulfate respectively, wherein the molar ratio of aniline-carbon nanotube mixture to ammonium persulfate is 0.8:1, and mix the two evenly with a magnetic stirrer for 1-2 h. Place them at room temperature and let them stand for 20-26 h. The obtained product is washed with ethanol and deionized water to neutrality, and then dried and ground to obtain a primary doped polyaniline-carbon nanotube composite material; wherein the mass ratio of aniline to carbon nanotubes in the aniline-carbon nanotube mixture is 20:1; (4) Adding excess ammonia water to the primary doped polyaniline-carbon nanotube composite material for dedoping, stirring with a magnetic stirrer for 1-2 h, and standing at room temperature for 20-26 h. The obtained product is washed with ethanol and deionized water until neutral, and finally dried and ground to obtain the intrinsic polyaniline-carbon nanotube composite material; (5) The intrinsic polyaniline-graphene composite material and the intrinsic polyaniline-carbon nanotube composite material were added to a 1 mol / L doped acid solution in a mass ratio of 1:1, mixed and stirred, and then allowed to stand for 20 to 26 h. They were then filtered and washed with ethanol and deionized water in sequence until neutral. Finally, they were dried and ground to obtain a nanocarbon and secondary doped polyaniline composite material, wherein the nanocarbon and secondary doped polyaniline composite material is a composite material of graphene, carbon nanotubes and secondary doped polyaniline, and the mass ratio of aniline to graphene in the aniline-graphene mixture is equal to the mass ratio of aniline to carbon nanotubes in the aniline-carbon nanotube mixture.

2. The method according to claim 1, characterized in that The doping acid solution is one of an inorganic acid solution, an organic acid solution and a composite acid, and the molar concentration ratio of the inorganic acid to the organic acid in the composite acid is 1:1 to 1:

6.

3. The method according to claim 2, characterized in that The organic acid is one or more of formic acid, acetic acid, propionic acid, butyric acid, octanoic acid, adipic acid, oxalic acid, malonic acid, succinic acid, tartaric acid, benzoic acid, phenylacetic acid, and perchloric acid; the inorganic acid is one or more of sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, and molybdic acid.

4. The method according to claim 1, wherein The corrosion inhibition efficiency of the prepared nanocarbon and secondary doped polyaniline composite material is greater than 78%, and the impedance value of the prepared nanocarbon and secondary doped polyaniline composite material is greater than 1500Ω*cm 2 .

5. The method according to claim 1, wherein The corrosion inhibition efficiency of the prepared nano-carbon and secondary doped polyaniline composite material is greater than 80%, and the impedance value of the prepared nano-carbon and secondary doped polyaniline composite material is greater than 1800 Ω*cm2.

6. The method according to claim 1, characterized in that The fiber length of the prepared nano-carbon and secondary doped polyaniline composite material is greater than 800 nm.

7. The method according to claim 1, characterized in that The fiber length of the prepared nano-carbon and secondary doped polyaniline composite material is greater than 850nm.

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