Structure-directing agent auxiliary protection etching USY zeolite-based ultra-black coating with high vacuum adsorption capacity and controllable preparation method thereof

Abstract

The invention discloses a structure-directing agent auxiliary protection etching USY zeolite-based ultra-black coating with high vacuum adsorption capacity and a controllable preparation method thereof, and belongs to the field of special functional coatings. The invention aims to solve the problems that a zeolite adsorption coating is low in adsorption capacity in an extreme environment and a microporous structure limits diffusion. The coating comprises a functional filler and a binder, the functional filler is composed of structure-directing agent auxiliary protection etching zeolite powder and ball-milled carbon black, the binder is silica sol, and the composite coating is formed through a spraying process. The graded USY zeolite with a high specific surface, high crystallinity and a complete microporous structure is obtained through a structure-directing agent auxiliary protection etching strategy, the problem that zeolite micropores limit diffusion is solved, and meanwhile, the limitation of damage to a zeolite framework structure by a conventional etching method is broken through. The method has very wide application prospects in the fields of air purification, sewage treatment, pollution protection and the like.

Description

Technical Field

[0001] The present invention belongs to the field of special functional coatings. Specifically, it relates to a structure-directing agent-assisted protected etching USY zeolite-based super black coating with a high vacuum adsorption capacity and a controllable preparation method thereof. The present invention has very broad application prospects in the fields of air purification, sewage treatment, aerospace and military industries, pollution protection, etc. Background Art

[0002] The materials used in spacecraft will release organic molecules in a vacuum environment, which will cause serious pollution to the sensitive surfaces of precision payloads. This will reduce the performance of spacecraft hardware and shorten the service life of spacecraft. With the increasingly strict requirements for the quality and reliability of spacecraft, it is urgent to control space molecular pollution. At present, the effective solution for pollution control is the adsorption method. As a new type of adsorption material, the molecular adsorption coating can be directly sprayed on the inner surface of the spacecraft, which has the advantages of good effect and no power consumption. However, the zeolite functional filler in the molecular adsorption coating has a single microporous structure (<2 nm), which greatly limits the diffusion of larger pollutant molecules, and may cause problems such as reduced adsorption efficiency and pore blockage, seriously affecting the actual use of the adsorption coating. Therefore, it is of great significance to regulate the pore structure of zeolite molecular sieves through modification treatment.

[0003] Etching is an important means to regulate the framework structure of zeolite molecular sieves. It can form additional mesoporous structures by removing silicon atoms and aluminum atoms from the zeolite framework. The hierarchical pore structure greatly promotes the mass transfer and diffusion of molecular pollutants. The traditional etching methods are acid etching and alkali etching. The mesopores introduced by the acid etching method during the selective dealumination process are isolated and cannot create an interconnected mesoporous system, which is likely to cause the destruction and collapse of the zeolite framework structure. Alkali etching can generate interconnected mesopores in zeolites, which will be beneficial to the adsorption and diffusion of macromolecular pollutants. However, alkali etching has a higher degree of damage to the zeolite framework structure. Zeolites treated with alkaline solutions usually show a decrease in micropore volume and crystallinity. Summary of the Invention

[0004] In the existing molecular adsorption coatings, the microporous structure of zeolites is restricted by diffusion, and the adsorption capacity needs to be further improved. Although the traditional etching methods can generate mesoporous structures, they will cause damage to the microporous framework structure. The present invention aims to solve the problems of low adsorption capacity of zeolite adsorption coatings in extreme environments and diffusion limited by microporous structures, and provides a controllable preparation method for a structure-directing agent-assisted protected etching USY zeolite coating with a high vacuum adsorption capacity. Through the structure-directing agent-assisted protected etching strategy, hierarchical USY zeolites with a high specific surface area, high crystallinity and a complete microporous structure are obtained, solving the problem of diffusion limited by zeolite micropores, and at the same time breaking through the limitation of the conventional etching method on the destruction of the zeolite framework structure.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The present invention provides a structure-directing agent-assisted protected etching molecular sieve adsorption and thermal control multifunctional coating, which has both adsorption performance and thermal control performance. The coating includes two parts: functional fillers and a binder. The functional fillers are composed of structure-directing agent-assisted protected etching zeolite powder and carbon black after ball milling, and the binder is silica sol. The composite coating is formed by a spraying process.

[0007] In the present invention, the controllable preparation method of the structure-directing agent-assisted protected etching USY zeolite-based super black coating with high vacuum adsorption capacity includes the following steps:

[0008] Step 1: Immerse the USY zeolite molecular sieve with an amine-based structure-directing agent, filter and separate, and place it at room temperature until it reaches a dry state;

[0009] Step 2: Then add it to a low-concentration NaOH aqueous solution, carry out an etching reaction under stirring at a certain temperature, centrifuge, wash with hot distilled water, dry, grind, and mix evenly with nano-scale carbon black powder to obtain a mixed powder;

[0010] Step 3: Add a small amount of deionized water to the silica sol, stir magnetically at room temperature until uniform, add the mixed powder in batches and slowly, and continue to stir for a period of time to obtain a slurry;

[0011] Step 4: Then coat it on the surface of the substrate and heat it for curing to obtain the coating.

[0012] Further defined, the amine-based structure-directing agent in Step 1 is n-propylamine, butylamine, diethylamine or diisopropylamine.

[0013] Further defined, the impregnation treatment in Step 1 is about 40 minutes.

[0014] Further defined, the nano-carbon black powder in Step 2 is prepared by the following steps:

[0015] The nano-carbon black powder was prepared by ball milling method. First, 5.0 g of carbon black and 40 g of zirconia microspheres were put into the ball milling tank, and nitrogen gas was continuously introduced for 20 min (nitrogen gas was used as the protective gas) to prevent the carbon black from being oxidized during the grinding process. Set the parameters of the ball mill, the ball milling speed was 700 r / min, the single ball milling time was 10 min, the single ball milling rest time was 5 min, and 15 min constituted a ball milling cycle, and 40 cycles were set. Considering that the carbon black powder forms agglomerates during grinding, the ball milling should be stopped every 2 h, and the agglomerates attached to the surrounding of the ball milling tank should be scraped off. Under intense grinding, the carbon black particles were gradually ground into nano-powder. After grinding, the prepared nano-scale carbon black powder was collected and stored, and then mixed with the modified zeolite molecular sieve powder and silica sol to prepare a slurry. The optimal ball milling time was 10 h.

[0016] Further defined, in step 2, the concentration of the NaOH aqueous solution was 0.1 mol / L to 0.4 mol / L; the preparation steps were as follows: accurately weigh sodium hydroxide and water, add sodium hydroxide to water, and stir and dissolve it fully at 70 °C for standby to obtain the NaOH aqueous solution.

[0017] Further defined, in step 2, it was added to the low-concentration NaOH aqueous solution according to the mass ratio of liquid to solid of 20.

[0018] Further defined, in step 2, the etching reaction temperature was 4 °C - 70 °C, which could be an ice-water bath at 4 °C, or room temperature at 25 °C, as well as high temperatures at 50 °C and 70 °C, and the time was 20 min to 30 min. The number of etching reactions could be adjusted according to actual needs.

[0019] Further defined, in step 2, the temperature of the hot distilled water was 353 K.

[0020] Further defined, in step 2, the black pigment used could be carbon black, iron chromite black or copper chromite black.

[0021] Further defined, in step 2, the mass ratio of the ground USY zeolite to carbon black was 0.2 / 0.8 to 0.8 / 0.2.

[0022] Further defined, in step 3, the mass ratio of the mixed powder obtained in step 2 to silica sol was controlled at 7.5 / 50 to 45 / 50.

[0023] Further defined, the coating substrate used in step 4 could be a metal substrate such as aluminum alloy; it could also be a resin substrate or an organic-inorganic composite substrate; when using an aluminum alloy thin plate as the substrate, the surface of the substrate could be polished with 500-mesh sandpaper, and then ultrasonically cleaned with absolute ethanol for 30 min.

[0024] Further limit, in step 4, the coating preparation process used includes but is not limited to spraying, brushing, scraping, spin coating and other processes. By adjusting process parameters such as spraying pressure, spraying speed and gun distance, zeolite coatings with different morphological structures can be prepared.

[0025] Further limit, in step 4, the coating can be composed of multiple layers, and the coating thickness is 50 microns - 300 microns.

[0026] The present invention provides a coating prepared by any of the above methods.

[0027] The present invention provides a structure-directing agent-assisted protection etching USY zeolite-based super black coating with high vacuum adsorption capacity and its controllable preparation method. The present invention adopts a structure-directing agent-assisted protection etching strategy to precisely control the zeolite pore structure to generate mesopores while protecting the zeolite framework through the action of an organic structure-directing agent, obtaining a zeolite with a high specific surface area, high crystallinity and a complete microporous structure. The zeolite modified by the method of the present invention has a three-dimensionally connected hierarchical confined pore structure, thus solving the problem of restricted diffusion in zeolite micropores and breaking through the limitation of the destruction of the zeolite framework structure by conventional etching methods.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention precisely controls the zeolite pore structure by a structure-directing agent-assisted protection etching method, constructs a three-dimensionally connected hierarchical confined pore structure to promote diffusion, the pore structure matching promotes pollutant adsorption, and effectively absorbs trapped sunlight through the synergistic effect of USY zeolite molecular sieve material and nano carbon black, achieving the synergistic effect of adsorption and light absorption functions.

[0030] The present invention adopts a structure-directing agent-assisted protection etching strategy to modify USY zeolite molecular sieve, avoiding the destruction of the zeolite framework structure and obtaining a hierarchical USY zeolite with a high specific surface area, high crystallinity and a complete microporous structure.

[0031] The present invention precisely controls the zeolite pore structure by a structure-directing agent-assisted protection etching method, and the constructed coating has a three-dimensionally connected hierarchical confined pore structure, which is conducive to the mass transfer and diffusion of pollutants and enhances the adsorption capacity of the coating for molecular pollutants.

[0032] The rough micro-nano surface structure and porous composite structure formed by combining the etched USY zeolite molecular sieve material, nano carbon black powder and silica sol binder of the present invention are synergistically matched to effectively absorb trapped sunlight and have good light absorption performance.

[0033] In order to further understand the features and technical content of the present invention, please refer to the following detailed description of the present invention and the attached drawings. However, the attached drawings are only for reference and illustration purposes and are not used to limit the present invention. Description of the Drawings

[0034] Figure 1 It is the SEM image of the USY zeolite molecular sieve without being impregnated with a structure-directing agent and etched with sodium hydroxide in Example 1;

[0035] Figure 2 It is the SEM image of the etched zeolite molecular sieve USY zeolite molecular sieve prepared by the method of Example 1;

[0036] Figure 3 It is the XRD pattern of the etched zeolite molecular sieve USY zeolite molecular sieve prepared by the method of Example 1;

[0037] Figure 4 It is the nitrogen isothermal adsorption-desorption curve of the etched zeolite molecular sieve prepared by the method of Example 1;

[0038] Figure 5 It is the SEM image of the etched zeolite molecular adsorption coating prepared by the method of Example 1;

[0039] Figure 6 It is the test result of the ultraviolet-visible spectrometer of the etched zeolite molecular adsorption coating prepared by the method of Example 1;

[0040] Figure 7 It is the test result of the Fourier transform infrared absorption spectrum of the etched zeolite molecular adsorption coating prepared by the method of Example 1;

[0041] Figure 8 It is the physical diagram before and after the adhesion test experiment of the etched zeolite molecular adsorption coating prepared by the method of Example 1. Detailed Embodiments

[0042] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, and at the same time do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made. These all belong to the protection scope of the present invention.

[0043] Example 1: In this example, a controllable preparation method of a structure-directing agent-assisted protected etched USY zeolite-based super-black coating with a high vacuum adsorption capacity is achieved through the following steps:

[0044] Step (1) Preparation of nano-carbon black powder

[0045] The nano-carbon black powder was prepared by ball milling method. First, 5.0 g of carbon black and 40 g of zirconia microspheres were put into a ball milling jar, and nitrogen gas was continuously introduced for 20 min to prevent the carbon black from being oxidized during the grinding process. The parameters of the ball mill were set. The ball milling speed was 700 r / min, the single ball milling time was 10 min, the single ball milling rest time was 5 min, and 15 min constituted a ball milling cycle. 40 cycles were set. Considering that the carbon black powder forms agglomerates during grinding, the ball milling should be stopped every 2 h, and the total ball milling time was 8 h. The agglomerates attached to the surrounding of the ball milling jar were scraped off. Under intense grinding, the carbon black particles were gradually ground into nano-powder. After grinding, the prepared nano-scale carbon black powder was collected and stored, and then mixed with the modified zeolite molecular sieve powder and silica sol to prepare a slurry.

[0046] Step (2) Treating USY zeolite molecular sieve with structure-directing agent

[0047] 5 g of USY zeolite molecular sieve was fully impregnated with 20 g of the amine structure-directing agent n-propylamine. The mixture of zeolite molecular sieve and structure-directing agent was slowly stirred with a glass rod for 30 minutes, and then separated by filtration. After separation, it was left at room temperature for 5 minutes and turned into dry powder. The amine structure-directing agent can be reused.

[0048] Step (3) Structure-directing agent-assisted sodium hydroxide etching of USY zeolite molecular sieve

[0049] Accurately weigh 0.8 g of sodium hydroxide and add it to 99.2 g of water (the molar concentration of sodium hydroxide is 0.2 mol / L). The sodium hydroxide aqueous solution was stirred at 70 °C until fully dissolved for standby. Accurately weigh 5.0 g of the structure-directing agent-impregnated USY zeolite and add it to the sodium hydroxide aqueous solution (the mass ratio of liquid to solid is 20). Under the assistance of the structure-directing agent, the etching reaction was carried out with stirring at 1800 r / min under the condition of 70 °C. After the reaction for 30 minutes, solid-liquid separation was immediately carried out by centrifugation, and it was thoroughly washed 3 - 5 times with preheated hot distilled water at 353 K to remove sodium hydroxide and n-propylamine in the solution to obtain a solid etching product. The etching product was dried at 373 K for 6 hours and ground to obtain zeolite powder.

[0050] Step (4) Preparation of the slurry for spraying the molecular adsorption coating

[0051] 7.5 g of the zeolite powder obtained in step (3), 7.5 g of carbon black powder and silica sol were accurately weighed in a certain proportion. 5 g of deionized water was added to 50 g of silica sol, and it was magnetically stirred at 1200 r / min at room temperature for 30 min to mix evenly. In order to prevent the zeolite from being added too fast and resulting in poor dispersion or agglomeration, the USY zeolite and carbon black powder should be fully ground and mixed evenly, and then added to the diluted silica sol in batches 10 times slowly, and stirring was continued for 3 hours.

[0052] (5) Spraying and curing of the adsorption coating

[0053] In this embodiment, an aluminum alloy thin plate is used as the substrate. The surface of the substrate is polished with 500-mesh sandpaper, and then ultrasonically cleaned with absolute ethanol for 30 min. The slurry used for spraying is added to the liquid storage tank of the ultrasonic-assisted thermal spraying device. The ultrasonic power is adjusted to 1000 W, and ultrasonic action is carried out for 25 min. By using the cavitation effect of ultrasonic waves, the further uniform mixing of the slurry is promoted. The spraying diluent is sprayed on the surface of the aluminum alloy substrate. Spraying conditions: the nozzle diameter is 2.5 mm, the liquid supply pressure is 0.6 Mpa, the moving speed of the spray gun is 120 cm / s, and the spraying distance is 20 cm. To prevent cracking caused by poor coating adhesion, the multi-spraying method is used to prepare the coating. The spraying interval is 5 min each time, and the coating is made after spraying about 15 times. The obtained hierarchical USY zeolite adsorption coating is placed in a vacuum oven for programmed heating and curing to ensure a strong adhesion between the adsorption coating and the substrate and prevent the coating from cracking. The specific heating conditions are as follows: first, heat up to 100 °C at a rate of 2 °C / min and hold for 1 h, and then heat up to 120 °C at a rate of 1 °C / min and hold for 8 h, and a molecular adsorption coating with good performance can be obtained.

[0054] The test results of the scanning electron microscope of the USY zeolite used in this embodiment are as Figure 1 shown. The surface of the unetched zeolite presents a smooth structure, but the regular edges and corners are irregular and present an approximate spherical structure.

[0055] The test results of the scanning electron microscope of the structure-directing agent-assisted sodium hydroxide-etched zeolite obtained in this embodiment are as Figure 2 shown. The surface of the etched molecular sieve presents a porous structure, and the original regular edges and corners of the zeolite are etched.

[0056] The XRD test results of the structure-directing agent-assisted sodium hydroxide-etched zeolite obtained in this embodiment are as Figure 3 shown. By comparing the diffraction peak positions of the etched zeolite with the USY zeolite characterization card and the original, it can be seen that they basically coincide, indicating that it has the crystal structure of the original USY zeolite. And compared with the unprotected etched zeolite, the former has good crystallinity and is less damaged by sodium hydroxide.

[0057] The test result graph of the 77.3K nitrogen adsorption-desorption isotherm of the structure-directing agent-assisted sodium hydroxide-etched zeolite obtained in this embodiment is as Figure 4As shown, obvious hysteresis loops appear in the etched zeolite in the range of p / p0 from 0.6 to 0.8, indicating its mesoporous structure. The hierarchical pore structure of micropores - mesopores is beneficial to the transport and diffusion of molecular substances. According to the BET method calculation, although its specific surface area decreases, after protected etching, the mesopores increase while minimizing the sacrifice of micropores. The etched hierarchical USY zeolite with more obvious mesopores is beneficial to the absorption of pollutants.

[0058] The test results of the scanning electron microscope of the structure - directing agent - assisted etched molecular sieve adsorption thermal control coating obtained in this example are as Figure 5 shown. The surface of the coating is a hierarchical porous rough structure, which is beneficial to the adsorption of spatial molecular pollutants.

[0059] The test results of the ultraviolet - visible spectrometer of the structure - directing agent - assisted etched molecular sieve adsorption thermal control coating obtained in this example are as Figure 6 shown. After calculation, in the wavelength range of 200 - 2500 nm, the average solar absorptance is 97.03%.

[0060] The Fourier transform infrared absorption spectrum test of the structure - directing agent - assisted etched molecular sieve adsorption thermal control coating obtained in this example is as Figure 7 shown. After calculation, in the wavelength range of 2 - 16 μm, the average emissivity of this coating reaches 95.43%.

[0061] For the adhesion test of the adsorption coating obtained in this example, according to the tape peeling method specified in 4.6.4 of GJB 2704A - 2006 "General Specification for Spacecraft Thermal Control Coatings", the coating is bonded and peeled to further screen the binder composition. Specifically, use a tape with a peeling strength of 2 N / cm - 4 N / cm, stick it tightly to the middle area of the coating, not less than 3 mm from the edge, pull up one end of the tape by hand, and make the tape form a 90° angle with the surface, and slowly (about 5 mm / s) pull the tape away from the surface to observe whether there is peeling of the coating. Figure 8 By comparison, after the tape is pulled away, the silicate binder coating after the test shows phenomena such as cracking and powder falling, while the silica sol binder coating shows no cracking, powder falling and other phenomena after the tape is pulled away, and has excellent interfacial adhesion.

[0062] The test results of the pollutant adsorption amount of the structure - directing agent - assisted etched molecular sieve adsorption thermal control coating obtained in this example are shown in Table 1, and the pollutant adsorption amount after modification is significantly improved.

[0063] Table 1

[0064]

[0065] The specific embodiments of the present invention have been described above. It should be noted that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which does not affect the essence of the present invention.

Claims

1. A controllable preparation method for USY zeolite-based ultra-black coating assisted by structure-directing agent with high vacuum adsorption, characterized in that: The following steps are involved: Step 1, impregnating USY zeolite molecular sieve with an amine structure directing agent, filtering and separating, and placing at room temperature until it reaches a dry state; Step 2, then add it to a low concentration NaOH aqueous solution, etch it under stirring and at a certain temperature, centrifuge it, wash it with hot distilled water, dry it, grind it, and mix it evenly with the nano-scale carbon black powder to obtain a mixed powder; Step 3: Add a small amount of deionized water to the silica sol, stir it magnetically at room temperature until it is uniform, slowly add the mixed powder in batches, continue stirring for a period of time, and obtain a slurry; Step 4: After coating on the surface of the substrate, heat and cure to obtain the coating.

2. The method according to claim 1, characterized in that: The amine structure directing agent is n-propylamine, butylamine, diethylamine or diisopropylamine.

3. The method according to claim 1, characterized in that: The concentration of the NaOH aqueous solution is 0.1 mol / L to 0.4 mol / L.

4. The method according to claim 1, characterized in that: The mass ratio of liquid to solid is 20, and the etching reaction temperature is 4°C-70°C, and the time is 20min-30min.

5. The method according to claim 1, characterized in that: The temperature of hot distilled water is 353K.

6. The method according to claim 1, characterized in that: The mass ratio of the ground USY zeolite to the carbon black powder is 0.2 / 0.8 to 0.8 / 0.2; the mass ratio of the mixed powder to the silica sol is controlled at 7.5 / 50 to 45 / 50.

7. The method according to claim 1, characterized in that: The base material is metal, resin, or organic-inorganic composite material.

8. The method according to claim 1, characterized in that: The coating is carried out by spraying, brushing, scraping or spin coating.

9. The method according to claim 1, characterized in that: The coating thickness is 50 microns to 300 microns.

10. A coating prepared by the method according to any one of claims 1 to 9.

Images