Preparation method and application of aluminum ion deposition-phytic acid complex modified carbon nanotubes

Abstract

The application discloses a preparation method and application of aluminum ion deposition-phytic acid complex modified carbon nanotubes. 3+ The method adopts a preparation process of "aluminum ion deposition and phytic acid complexing", first allows Al 3+ Through the chemical deposition or electro-deposition method, a stable aluminum ion deposition layer is uniformly deposited on the surface of the carboxylated carbon nanotube, Al 3+ Then, the complexing reaction is carried out with phytic acid, aluminum phytate is generated and firmly coated on the surface of the carbon nanotube, a composite structure of "carbon nanotube core-aluminum ion electro-deposition layer-phytic acid aluminum shell" is formed, the interface bonding force of the carbon nanotube and the aluminum phytate is significantly improved, and the problems of the existing carbon nanotube agglomeration, uneven aluminum ion deposition, weak interface bonding of the carbon nanotube and the aluminum phytate, poor synergism of the flame-retardant and corrosion-resistant properties and the like are solved.

Description

Technical Field

[0001] This invention relates to the technical field of functional composite material preparation, and more specifically, to a method for preparing aluminum ion deposition-phytic acid complexation modified carbon nanotubes and their application. Background Technology

[0002] With increasingly stringent environmental regulations, halogen-free, low-toxicity, and highly efficient flame-retardant and corrosion-resistant materials have become the mainstream trend in the industry. Phytic acid, as a natural and renewable organophosphate compound, is widely available and environmentally friendly. The phytic acid-aluminum complex formed by phytic acid and aluminum ions exhibits excellent flame-retardant and corrosion-inhibiting properties, and is halogen-free and low-toxicity, effectively replacing traditional halogenated flame retardants and toxic corrosion-resistant fillers. For example, CN120040701A discloses a water-based flame-retardant polyurethane resin and its preparation method, which utilizes phytic acid to form a stable chelate with aluminum ions in aluminum hydroxide. This allows phytic acid and aluminum ions to tightly bind together, forming coordinate bonds. Under the coordination effect of phytic acid and aluminum ions, during combustion, the alumina produced during the thermal decomposition of aluminum ions can combine with the carbonized char layer of phytic acid, better preventing the transfer of heat and oxygen, thus improving flame retardancy.

[0003] Most existing composite materials incorporate carbon nanomaterials to enhance their mechanical properties and corrosion protection, such as carbon nanotubes (CNTs). However, carbon nanotubes, due to their smooth surface and lack of active groups, are prone to aggregation, and their inherent conductivity poses a risk of accelerated electrochemical corrosion or electrostatic accumulation leading to fire when directly applied to flame-retardant and corrosion-resistant systems. To improve the synergistic effect of carbon nanomaterials and flame retardants, CN114656828B describes a flame-retardant polyurea for new energy battery boxes and its preparation method. This method involves first mixing phytic acid and aminated carbon nanotubes for a grafting reaction to obtain phytic acid-grafted carbon nanotubes. Then, using lanthanum hydroxide as the core and the phytic acid-grafted carbon nanotubes as the shell, lanthanum hydroxide is uniformly dispersed within the phytic acid-grafted carbon nanotubes as a flame retardant. This overcomes the shortcomings of uneven dispersion of synergistic flame retardants and improves the deficiencies of lanthanum hydroxide, such as high surface polarity, strong hydrophilicity, easy aggregation, and low flame-retardant efficiency. This method improves the dispersibility of phytic acid and carbon nanotubes by grafting carbon nanotubes with phytic acid. However, in the flame retardant system of carbon nanotubes and aluminum phytate, the composite of aluminum phytate and carbon nanotubes has defects such as uneven complexation of aluminum ions and phytic acid and weak interfacial bonding between carbon nanotubes and aluminum phytate. For example, when carbon nanotubes and aluminum phytate are composited by simple physical mixing, the interfacial bonding between the two is easily loose, and their respective performance advantages cannot be fully utilized. This leads to uneven dispersion, poor performance synergy, and even detachment during subsequent processing, which limits its application in high-end functional materials. Summary of the Invention

[0004] The main technical problem to be solved by the present invention is that the existing materials have shortcomings such as weak interfacial bonding force and uneven aluminum ion complexation when carbon nanotubes are combined with aluminum phytate, resulting in uneven dispersion and poor synergy between flame retardant and anti-corrosion properties. The present invention provides a method for preparing aluminum ion deposition-phytate complexation modified carbon nanotubes.

[0005] Another technical problem solved by this invention is to provide applications of modified carbon nanotubes prepared based on the method.

[0006] The objective of this invention is achieved through the following technical solution: A method for preparing aluminum ion deposition-phytic acid complexation modified carbon nanotubes, comprising the following steps: S1. Preparation of carboxylated carbon nanotubes: Carbon nanotubes were added to an acid solution, heated and stirred, washed and dried to obtain carboxylated carbon nanotubes.

[0007] S2. Preparation of carbon nanotube dispersion: Carboxylated carbon nanotubes and dispersant were added to deionized water and dispersed evenly to obtain carbon nanotube dispersion.

[0008] S3, Aluminum Ion Deposition: A soluble aluminum salt solution is added to a carbon nanotube dispersion, and an aluminum ion-modified carbon nanotube dispersion is obtained through chemical deposition or electrodeposition, thereby carboxylating the -COO groups on the surface of the carbon nanotubes. - With Al 3+ Electrostatic adsorption occurs, with -OH reacting with Al. 3+ Coordination bonds are formed to ensure that the aluminum ion deposition layer is firmly attached to the surface of carbon nanotubes. At the same time, the hollow structure of carbon nanotubes can be used to load some aluminum ions inside the tubes, further improving the subsequent complexation effect and performance synergy.

[0009] S4. Phytic acid complexation modification: A complexation promoter and phytic acid are added to the aluminum ion deposition modified carbon nanotube dispersion. The phytic acid reacts with the Al atoms deposited on the surface of the carbon nanotubes. 3+ A complexation reaction occurs, generating aluminum phytate which firmly coats the surface of carbon nanotubes, forming a composite structure of "carbon nanotube core - aluminum ion deposition layer - aluminum phytate shell". Phytic acid and aluminum ions form a stable aluminum phytate coating layer through ion exchange and complexation. At the same time, the hydroxyl and phosphate groups of phytic acid can form hydrogen bonds with the carboxyl groups on the surface of carbon nanotubes, further strengthening the interfacial bonding.

[0010] S5. Post-treatment: Centrifuge to collect the precipitate, wash and obtain aluminum ion deposition-phytic acid complex modified carbon nanotubes.

[0011] Furthermore, the raw materials include: 0.5 to 5 parts by weight of carbon nanotubes, 3 to 15 parts by weight of soluble aluminum salts, 2 to 10 parts by weight of phytic acid, 0.1 to 2 parts by weight of dispersant, and 0.05 to 1 part by weight of complexation promoter.

[0012] Furthermore, the carbon nanotubes are multi-walled carbon nanotubes with a diameter of 1~20nm, a length of 1~10μm, and an aspect ratio ≥1000.

[0013] Furthermore, the acid solution is a mixture of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1. After carboxylation pretreatment, the carbon nanotubes have a surface carboxyl content of 1.5~3.5 mmol / g. The carboxylated carbon nanotubes have a negative charge on their surface, which can adsorb aluminum ions through electrostatic interaction, providing a stable "anchor point" for aluminum ion deposition. At the same time, their surface hydroxyl groups can also form coordination with aluminum ions, further enhancing the deposition effect.

[0014] Further, the dispersant includes one or more of sodium dodecylbenzenesulfonate (SDBS), polyethylene glycol, Tween-80, and polyvinylpyrrolidone. Preferably, the dispersant is sodium dodecylbenzenesulfonate, which can effectively disperse carbon nanotubes and prevent their aggregation, while not affecting the deposition of aluminum ions and the subsequent complexation reaction of phytic acid.

[0015] Further, the soluble aluminum salt includes one or more of aluminum nitrate, aluminum chloride, and aluminum sulfate. Preferably, the soluble aluminum salt is aluminum nitrate nonahydrate (Al(NO3)3·9H2O) with a purity ≥99%, which can rapidly dissociate Al in aqueous solution. 3+ Furthermore, no residual impurities remain after high-temperature decomposition, ensuring that the flame-retardant and corrosion-resistant properties of the composite material are not affected by impurities.

[0016] Furthermore, the complexation promoter is one or more of triethanolamine and sodium citrate, which can promote the deposition of Al on the surface of carbon nanotubes. 3+ The complexation reaction with phytic acid accelerates the reaction rate and improves the stability of the complexation product, ensuring that aluminum phytate is uniformly coated on the surface of carbon nanotubes to form a dense protective layer. By strengthening the binding strength between phytic acid and aluminum ions through a complexation promoter and drawing on the complexation mechanism of aluminum ions with phosphates, the corrosion resistance and flame retardant durability of the composite material are further improved.

[0017] Furthermore, the heating temperature in S1 is 60~80℃, and the stirring time is 2~4h.

[0018] Further, the chemical deposition includes adjusting the pH value to 4.0-6.0 with a pH adjuster, and stirring at a constant temperature of 25-90°C for 2-3 hours, Al 3+ A uniform aluminum ion deposition layer can be formed by electrostatic adsorption and coordination on the surface of carboxylated carbon nanotubes.

[0019] Furthermore, the pH adjuster is one or more of ammonia, urea, and sodium hydroxide, preferably ammonia with a concentration of 25-28 wt%, used to adjust the pH value of the system and promote Al 3+The deposition on the surface of carbon nanotubes provides a suitable pH environment for the subsequent complexation reaction of phytic acid and aluminum ions.

[0020] Furthermore, the electrodeposition includes electrodeposition using a three-electrode system in a solution containing carboxylated carbon nanotubes, a dispersant, an electrolyte, and a soluble aluminum salt. A platinum sheet is used as the counter electrode, a saturated calomel electrode as the reference electrode, and the carbon nanotube dispersion as the working electrode. The electrodeposition potential is controlled at -1.2 to -0.8 V, the electrodeposition temperature at 25 to 40 °C, and the electrodeposition time at 30 to 90 min, so that Al... 3+ Under the action of an electric field, aluminum ion electrodeposition is oriented and uniformly deposited on the surface of carbon nanotubes to obtain an aluminum ion electrodeposition modified carbon nanotube dispersion.

[0021] Furthermore, the complexation reaction temperature in S4 is 50~85℃, and the reaction time is 2~4h.

[0022] The carbon nanotubes prepared by the above method can be used in polymer adhesives, metal protective coatings, and engineering plastics.

[0023] Compared with existing technologies, the beneficial effects are: This invention employs a preparation process of "aluminum ion deposition followed by phytic acid complexation," first allowing Al... 3+ A stable aluminum ion deposition layer is formed by uniformly depositing carboxylated carbon nanotubes on their surface through electrostatic adsorption and coordination or by electric field orientation. This layer then undergoes a complexation reaction with phytic acid, significantly enhancing the interfacial bonding between the carbon nanotubes and aluminum phytate, thus avoiding the problems of loose bonding and easy detachment. Simultaneously, the hollow structure of the carbon nanotubes is used to load some aluminum ions, further strengthening the synergistic effect. The aluminum ion deposition layer used in this invention can serve as a "transition layer," effectively dispersing the carbon nanotubes and solving their aggregation problem, while simultaneously providing sufficient Al for phytic acid complexation. 3+ Active sites allow phytic acid to react with Al. 3+ The complexation is more uniform, resulting in a denser aluminum phytate shell. Combined with the effect of the complexation promoter, the stability of the complexation product is further improved, giving full play to the flame retardant and corrosion inhibitory properties of aluminum phytate. At the same time, the mechanical reinforcement and physical shielding effect of carbon nanotubes are fully demonstrated, achieving synergistic effect among the three. Drawing on the protection concept of endogenous precipitants, the composite material can form a stable protective layer through interfacial interaction in corrosive environments, improving corrosion resistance and durability.

[0024] The dense aluminum phytate shell in this invention can effectively encapsulate carbon nanotubes, completely eliminating the risk of electrochemical corrosion and electrostatic fire caused by their conductivity. At the same time, the insolubility and chemical stability of aluminum phytate, combined with the protective effect of the aluminum ion deposition layer, further improve the water resistance, chemical corrosion resistance and corrosion resistance of the composite material, and can maintain excellent performance in complex corrosive environments such as acids, alkalis and salts.

[0025] This invention features a simple preparation process requiring no complex equipment. Utilizing an aqueous system, it is environmentally friendly and cost-effective. All raw materials are common and readily available reagents, and process parameters are easily controlled, facilitating large-scale production. Simultaneously, it avoids complex surface modification processes, reducing production costs while minimizing damage to the carbon nanotube structure and preserving its excellent mechanical and shielding properties. The modified carbon nanotubes prepared by this invention can be widely applied in polymer adhesives, metal protective coatings, engineering plastics, and other fields. Adding 1-5% by weight of the substrate can significantly improve the material's mechanical strength, flame retardancy, and corrosion resistance. It is particularly suitable for high-end applications requiring strong interfacial bonding and performance stability, such as protective coatings for large equipment like aircraft, ships, and high-speed trains, as well as new energy fields like battery plates, demonstrating broad application prospects. Attached Figure Description

[0026] Figure 1 It is made of pure carbon nanotubes.

[0027] Figure 2 It is carbon oxide nanotubes.

[0028] Figure 3 It is a phytic acid-aluminum modified carbon nanotube. Detailed Implementation

[0029] The following examples further explain and clarify the invention, but the specific examples do not limit the invention in any way.

[0030] Example 1 This embodiment provides a method for preparing aluminum ion deposition-phytic acid complexation modified carbon nanotubes, the steps of which include: S1. Preparation of carboxylated carbon nanotubes: 0.5 parts by weight of multi-walled carbon nanotubes with a diameter of 1~5 nm and a length of 1~5 μm were added to a mixed acid (volume ratio of concentrated sulfuric acid to concentrated nitric acid 3:1), heated and stirred in a water bath at 60°C for 2 h, cooled to room temperature, and washed with deionized water by centrifugation until the pH of the supernatant was 7. The supernatant was then dried at 80°C for 4 h to obtain carboxylated carbon nanotubes. S2, Preparation of carbon nanotube dispersion: The carboxylated carbon nanotubes obtained in S1 and 0.1 parts by weight of SDBS were added to 50 parts by weight of deionized water and ultrasonically dispersed at 300W for 30 min to obtain a uniform and stable carbon nanotube dispersion. S3, Aluminum Ion Deposition: A solution of 3 parts by weight of aluminum nitrate nonahydrate dissolved in 10 parts by weight of deionized water was slowly added dropwise to the carbon nanotube dispersion. The mixture was stirred for 1 hour, then the pH was adjusted to 4.0 with 25 wt% ammonia. The mixture was then stirred at 25°C for 2 hours to allow the aluminum ion to deposit. 3+ Aluminum ion deposition modified carbon nanotube dispersion was obtained by uniformly depositing aluminum ions on the surface of carbon nanotubes. S4. Phytic acid complexation modification: Add 0.05 parts by weight of triethanolamine and 2 parts by weight of phytic acid to the aluminum ion deposition modified carbon nanotube dispersion, stir for 30 min, adjust the pH of the system to 5.0 with 25 wt% ammonia water, and stir at 50℃ for 2 h to allow the Al deposited on the surface of the carbon nanotubes to form a complex. 3+ It undergoes a complexation reaction with phytic acid; S5. Post-treatment: The reaction solution of S4 was centrifuged at 3000 rpm, the precipitate was collected, washed three times with deionized water, dried at 80℃ for 6 h, and pulverized to obtain aluminum ion deposition-phytic acid complex modified carbon nanotubes.

[0031] Example 2 This embodiment provides a method for preparing aluminum ion deposition-phytic acid complexation modified carbon nanotubes, the steps of which include: S1. Preparation of carboxylated carbon nanotubes: 3 parts by weight of multi-walled carbon nanotubes with a diameter of 5~10nm and a length of 3~8μm were added to a mixed acid (volume ratio of concentrated sulfuric acid to concentrated nitric acid 3:1), heated and stirred in a water bath at 70℃ for 3h, cooled to room temperature, and washed with deionized water by centrifugation until the pH of the supernatant was 7. The supernatant was then dried at 90℃ for 5h to obtain carboxylated carbon nanotubes. S2. Preparation of carbon nanotube dispersion: The carboxylated carbon nanotubes obtained in step S1 and 1 part by weight of SDBS were added to 75 parts by weight of deionized water and ultrasonically dispersed at 450W for 45min to obtain a uniform and stable carbon nanotube dispersion. S3, Aluminum Ion Deposition: A solution of 9 parts by weight of aluminum nitrate nonahydrate dissolved in 15 parts by weight of deionized water was slowly added dropwise to the carbon nanotube dispersion. The mixture was stirred for 1.5 hours, then the pH was adjusted to 5.0 with 25 wt% ammonia. The mixture was then stirred at 30°C for 2.5 hours to allow the aluminum ion to deposit. 3+ Aluminum ion deposition modified carbon nanotube dispersion was obtained by uniformly depositing aluminum ions on the surface of carbon nanotubes. S4. Phytic acid complexation modification: 0.5 parts by weight of triethanolamine and 6 parts by weight of phytic acid were added to the aluminum ion deposition modified carbon nanotube dispersion, stirred for 35 min, and the pH of the system was adjusted to 6.0 with 25 wt% ammonia water. The mixture was then stirred at 70℃ for 3 h to allow the Al deposited on the surface of the carbon nanotubes to form a complex. 3+ It undergoes a complexation reaction with phytic acid; S5. Post-treatment: The reaction solution was centrifuged at 4000 rpm, the precipitate was collected, washed 4 times with deionized water, dried at 90℃ for 7 h, and then pulverized to obtain aluminum ion deposition-phytic acid complex modified carbon nanotubes.

[0032] Example 3 This embodiment provides a method for preparing aluminum ion deposition-phytic acid complexation modified carbon nanotubes, the steps of which include: S1. Preparation of carboxylated carbon nanotubes: 5 parts by weight of multi-walled carbon nanotubes with a diameter of 10~20nm and a length of 5~10μm were added to a mixed acid (volume ratio of concentrated sulfuric acid to concentrated nitric acid 3:1), heated and stirred in a water bath at 80℃ for 4h, cooled to room temperature, and washed with deionized water by centrifugation until the pH of the supernatant was 7. The supernatant was dried at 100℃ for 6h to obtain carboxylated carbon nanotubes. S2. Preparation of carbon nanotube dispersion: The carboxylated carbon nanotubes obtained in step S1 and 2 parts by weight of SDBS were added to 100 parts by weight of deionized water and ultrasonically dispersed at 600W for 60min to obtain a uniform and stable carbon nanotube dispersion. S3, Aluminum Ion Deposition: A solution of 15 parts by weight of aluminum nitrate nonahydrate dissolved in 20 parts by weight of deionized water was slowly added dropwise to the carbon nanotube dispersion. The mixture was stirred for 2 hours, then the pH was adjusted to 6.0 with 25 wt% ammonia. The mixture was then stirred at 90°C for 3 hours to allow Al³⁺ to deposit. + Aluminum ion deposition modified carbon nanotube dispersion was obtained by uniformly depositing aluminum ions on the surface of carbon nanotubes. S4. Phytic acid complexation modification: Add 1 part by weight of sodium citrate and 10 parts by weight of phytic acid to the aluminum ion deposition modified carbon nanotube dispersion, stir for 40 min, adjust the pH of the system to 7.0 with 25 wt% ammonia water, and stir at 85℃ for 4 h to allow the Al deposited on the surface of the carbon nanotubes to form a complex. 3+ It undergoes a complexation reaction with phytic acid; S5. Post-treatment: The reaction solution was centrifuged at 5000 rpm, the precipitate was collected, washed 5 times with deionized water, dried at 100℃ for 8 hours, and then pulverized to obtain aluminum ion deposition-phytic acid complex modified carbon nanotubes.

[0033] Example 4 This embodiment provides a method for preparing aluminum ion deposition-phytic acid complexation modified carbon nanotubes, the steps of which include: S1. Preparation of carboxylated carbon nanotubes: 0.5 parts by weight of multi-walled carbon nanotubes with a diameter of 1~5 nm and a length of 1~5 μm were added to a mixed acid (volume ratio of concentrated sulfuric acid to concentrated nitric acid 3:1), heated and stirred in a water bath at 60°C for 2 h, cooled to room temperature, and washed with deionized water by centrifugation until the pH of the supernatant was 7. The supernatant was then dried at 80°C for 4 h to obtain carboxylated carbon nanotubes. S2. Preparation of carbon nanotube electrodeposition solution: The carboxylated carbon nanotubes obtained in step S1, 0.1 parts by weight of SDBS, and 0.5 parts by weight of sodium sulfate were added to 50 parts by weight of deionized water and ultrasonically dispersed at 300W for 30 min. Then, 3 parts by weight of aluminum nitrate nonahydrate were added and stirred until completely dissolved. The pH of the system was adjusted to 3.5 with 25wt% ammonia water to obtain a uniform and stable carbon nanotube electrodeposition solution. S3. Aluminum ion electrodeposition: The carbon nanotube electrodeposition solution is poured into the electrodeposition tank. A three-electrode system is used, with a platinum sheet as the counter electrode, a saturated calomel electrode as the reference electrode, and the carbon nanotube dispersion as the working electrode. The electrodeposition potential is controlled at -1.2V, the electrodeposition temperature at 25℃, and the electrodeposition time at 30min, so that Al... 3+ A dispersion of aluminum ion-modified carbon nanotubes was obtained by directional electrodeposition on the surface of carbon nanotubes. S4. Phytic acid complexation modification: Add 0.05 parts by weight of triethanolamine and 2 parts by weight of phytic acid to the aluminum ion electrodeposition modified carbon nanotube dispersion, stir for 30 min, adjust the pH of the system to 5.0 with 25 wt% ammonia water, and stir at 30℃ for 2 h to allow the Al ions electrodeposited on the surface of the carbon nanotubes to form a complex. 3+ It undergoes a complexation reaction with phytic acid; S5. Post-treatment: The reaction solution was centrifuged at 3000 rpm, the precipitate was collected, washed three times with deionized water, dried at 80℃ for 6 h, and then pulverized to obtain aluminum ion electrodeposition-phytic acid complex modified carbon nanotubes.

[0034] Example 5 This embodiment provides a method for preparing aluminum ion deposition-phytic acid complexation modified carbon nanotubes, the steps of which include: S1. Preparation of carboxylated carbon nanotubes: 3 parts by weight of multi-walled carbon nanotubes with a diameter of 5~10nm and a length of 3~8μm were added to a mixed acid (volume ratio of concentrated sulfuric acid to concentrated nitric acid 3:1), heated and stirred in a water bath at 70℃ for 3h, cooled to room temperature, and washed with deionized water by centrifugation until the pH of the supernatant was 7. The supernatant was then dried at 90℃ for 5h to obtain carboxylated carbon nanotubes. S2. Preparation of carbon nanotube electrodeposition solution: The carboxylated carbon nanotubes obtained in step S1, 1 part by weight of SDBS, and 1.5 parts by weight of sodium sulfate were added to 75 parts by weight of deionized water and ultrasonically dispersed at 450W for 45 min. Then, 9 parts by weight of aluminum nitrate nonahydrate were added and stirred until completely dissolved. The pH of the system was adjusted to 4.5 with 25wt% ammonia water to obtain a uniform and stable carbon nanotube electrodeposition solution. S3. Aluminum ion electrodeposition: The carbon nanotube electrodeposition solution is poured into the electrodeposition tank. A three-electrode system is used, with a platinum sheet as the counter electrode, a saturated calomel electrode as the reference electrode, and the carbon nanotube dispersion as the working electrode. The electrodeposition potential is controlled at -1.0V, the electrodeposition temperature at 30℃, and the electrodeposition time at 60min, so that Al... 3+ A dispersion of aluminum ion-modified carbon nanotubes was obtained by directional electrodeposition on the surface of carbon nanotubes. S4. Phytic acid complexation modification: 0.5 parts by weight of triethanolamine and 6 parts by weight of phytic acid were added to the aluminum ion electrodeposition modified carbon nanotube dispersion, stirred for 35 min, and the pH of the system was adjusted to 6.0 with 25 wt% ammonia water. The mixture was then stirred at 40℃ for 3 h to allow the Al ions electrodeposited on the surface of the carbon nanotubes to form a complex.3+ It undergoes a complexation reaction with phytic acid; S5. Post-treatment: The reaction solution was centrifuged at 4000 rpm, the precipitate was collected, washed 4 times with deionized water, dried at 90℃ for 7 h, and then pulverized to obtain aluminum ion electrodeposition-phytic acid complex modified carbon nanotubes.

[0035] Example 6 This embodiment provides a method for preparing aluminum ion deposition-phytic acid complexation modified carbon nanotubes, the steps of which include: S1. Preparation of carboxylated carbon nanotubes: 5 parts by weight of multi-walled carbon nanotubes with a diameter of 10~20nm and a length of 5~10μm were added to a mixed acid (volume ratio of concentrated sulfuric acid to concentrated nitric acid 3:1), heated and stirred in an 80℃ water bath for 4h, cooled to room temperature, and washed with deionized water by centrifugation until the pH of the supernatant was 7. The supernatant was dried at 100℃ for 6h to obtain carboxylated carbon nanotubes. S2. Preparation of carbon nanotube electrodeposition solution: The carboxylated carbon nanotubes obtained in step S1, 2 parts by weight of SDBS, and 3 parts by weight of sodium sulfate were added to 100 parts by weight of deionized water and ultrasonically dispersed at 600W for 60min. Then, 15 parts by weight of aluminum nitrate nonahydrate were added and stirred until completely dissolved. The pH of the system was adjusted to 5.5 with 25wt% ammonia water to obtain a uniform and stable carbon nanotube electrodeposition solution. S3. Aluminum ion electrodeposition: The carbon nanotube electrodeposition solution is poured into the electrodeposition tank. A three-electrode system is used, with a platinum sheet as the counter electrode, a saturated calomel electrode as the reference electrode, and the carbon nanotube dispersion as the working electrode. The electrodeposition potential is controlled at -0.8V, the electrodeposition temperature at 40℃, and the electrodeposition time at 90min, so that Al... 3+ A dispersion of aluminum ion-modified carbon nanotubes was obtained by directional electrodeposition on the surface of carbon nanotubes. S4. Phytic acid complexation modification: Add 1 part by weight of sodium citrate and 10 parts by weight of phytic acid to the aluminum ion electrodeposition modified carbon nanotube dispersion, stir for 40 min, adjust the pH of the system to 7.0 with 25 wt% ammonia water, and stir at 50℃ for 4 h to allow the Al ions electrodeposited on the surface of the carbon nanotubes to form a complex. 3+ It undergoes a complexation reaction with phytic acid; S5. Post-treatment: The reaction solution was centrifuged at 5000 rpm, the precipitate was collected, washed 5 times with deionized water, dried at 100℃ for 8 hours, and then pulverized to obtain aluminum ion electrodeposition-phytic acid complex modified carbon nanotubes.

[0036] In the above embodiments, aluminum chloride and aluminum sulfate are used as soluble aluminum salts, and polyethylene glycol and Tween-80 are used as dispersants, both of which can achieve the purpose of this invention.

[0037] Comparative Example 1 This comparative example provides an aluminum ion-phytic acid complex-modified carbon nanotube, which has the same process as Example 1, except that in this comparative example, phytic acid is first grafted onto carbon nanotubes and then complexed with aluminum ions.

[0038] The modified carbon nanotubes prepared in Examples 1-6 and Comparative Example 1 were added to polyamide at a content of 0.3% wt, respectively, and carbon nanotube / polyamide composites were prepared by in-situ polymerization. The performance of the obtained composites was tested, and the performance test results are shown in Table 1 below:

[0039] As shown in Table 1 above, compared to the comparative example, the modified carbon nanotubes prepared by the "aluminum ion deposition followed by phytic acid complexation" process of this invention exhibit stronger interfacial bonding strength, significantly improving the material's mechanical strength and flame retardant properties. Simultaneously, the use of aluminum electrodeposition more effectively strengthens the interfacial bonding between carbon nanotubes and aluminum phytate, improving the uniformity and density of aluminum ion deposition, achieving a synergistic effect of mechanical enhancement, flame retardancy, and corrosion resistance, while also improving the material's performance stability to meet the application requirements of high-end functional materials. Furthermore, the material exhibits excellent salt spray resistance, maintaining good protective effects in complex corrosive environments, meeting the application requirements of high-strength, high-corrosion-resistant materials.

[0040] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing aluminum ion deposition-phytic acid complexation modified carbon nanotubes, characterized in that the steps include... include: S1. Preparation of carboxylated carbon nanotubes: Carbon nanotubes were added to an acid solution, heated and stirred, washed and dried to obtain carboxylated carbon nanotubes; S2. Preparation of carbon nanotube dispersion: Carboxylated carbon nanotubes and dispersant were added to deionized water and dispersed evenly to obtain carbon nanotube dispersion; S3, Aluminum ion deposition: A soluble aluminum salt solution is added to the carbon nanotube dispersion, and aluminum ion deposition modified carbon nanotube dispersion is obtained by chemical deposition or electrodeposition. S4. Phytic acid complexation modification: A complexation promoter and phytic acid are added to the aluminum ion deposition modified carbon nanotube dispersion to carry out a complexation reaction, generating aluminum phytate and firmly coating the surface of carbon nanotubes, forming a composite structure of "carbon nanotube core - aluminum ion deposition layer - aluminum phytate shell". S5. Post-treatment: Centrifuge to collect the precipitate, wash and obtain aluminum ion deposition-phytic acid complex modified carbon nanotubes.

2. The method for preparing aluminum ion deposition-phytic acid complexation modified carbon nanotubes according to claim 1, characterized in that, The raw materials include: 0.5-5 parts by weight of carbon nanotubes, 3-15 parts by weight of soluble aluminum salts, 2-10 parts by weight of phytic acid, 0.1-2 parts by weight of dispersant, and 0.05-1 parts by weight of complexation promoter.

3. The method for preparing aluminum ion deposition-phytic acid complexation modified carbon nanotubes according to claim 1, characterized in that, The dispersant includes one or more of sodium dodecylbenzenesulfonate, polyethylene glycol, Tween-80, and polyvinylpyrrolidone.

4. The method for preparing aluminum ion deposition-phytic acid complexation modified carbon nanotubes according to claim 1, characterized in that, The soluble aluminum salt includes one or more of aluminum nitrate, aluminum chloride, and aluminum sulfate.

5. The method for preparing aluminum ion deposition-phytic acid complexation modified carbon nanotubes according to claim 1, characterized in that, The complexation promoter is one or more of triethanolamine and sodium citrate.

6. The method for preparing aluminum ion deposition-phytic acid complexation modified carbon nanotubes according to claim 1, characterized in that, The heating temperature described in S1 is 60~80℃, and the stirring time is 2~4h.

7. The method for preparing aluminum ion deposition-phytic acid complexation modified carbon nanotubes according to claim 1, characterized in that, The chemical deposition process involves adjusting the pH value to 4.0-6.0 with a pH adjuster and stirring at a constant temperature of 25-90°C for 2-3 hours.

8. The method for preparing aluminum ion deposition-phytic acid complexation modified carbon nanotubes according to claim 1, characterized in that, The electrodeposition was performed using a three-electrode system, with a platinum sheet as the counter electrode, a saturated calomel electrode as the reference electrode, and a carbon nanotube dispersion as the working electrode. The electrodeposition potential was controlled at -1.2 to -0.8 V, the electrodeposition temperature at 25 to 40 °C, and the electrodeposition time at 30 to 90 min.

9. The method for preparing aluminum ion deposition-phytic acid complexation modified carbon nanotubes according to claim 1, characterized in that, The complexation reaction temperature described in S4 is 50~85℃, and the reaction time is 2~4h.

10. The carbon nanotubes prepared by the method according to any one of claims 1 to 9, characterized in that, The carbon nanotubes are used in polymer adhesives, metal protective coatings, and engineering plastics.

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