Corrosion-resistant aerogel and processing technology thereof

Abstract

The invention discloses corrosion-resistant aerogel and a processing technology thereof.The processing technology comprises the following steps that graphene oxide dispersion liquid and a metal organic framework precursor ZIF-67 are mixed, metal salt is cobalt salt, the mass ratio of graphene oxide to metal salt is 1: 0.5-1: 2, and homogeneous sol is formed through ultrasonic treatment. After the composite aerogel is soaked in strong acid HCl with the pH value of 1 and strong alkali NaOH with the pH value of 14 for 7 days, the mass loss rate is smaller than 5%, meanwhile, the porosity is kept to be larger than or equal to 95%, the compressive strength is kept to be larger than or equal to 1.5 MPa, and the industrial problems that traditional aerogel collapses in a structure and degrades in performance in a corrosive medium are solved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of aerogels, in particular to a corrosion-resistant aerogel and a processing technology thereof. BACKGROUND

[0002] Currently, the most commonly used in the market is micro-arc oxidation coating. It is a treatment technology widely used on the surfaces of aluminum alloy, titanium alloy and magnesium alloy and other materials in recent years, and has strong wear resistance, high temperature resistance and good corrosion resistance. Although the micro-arc oxidation coating has achieved good application effect in some fields, there are still some obvious shortcomings poor structural stability, traditional silicon-based aerogels Si-O-Si skeleton hydrolysis occurs in strong acid / alkali environment, resulting in collapse of pore structure, and organic aerogels (such as phenolic resin-based) are resistant to weak acid, but ester bond rupture occurs in strong alkali, resulting in increased density and reduced porosity.

[0003] Conventional silane coatings (such as perfluorooctyltriethoxysilane) can only temporarily delay corrosion, and the coating falls off after long-term soaking, and the corrosion medium penetrates into the interior.

[0004] At the same time, some inorganic reinforcing phases are added, such as adding ceramic particles Although the mechanical strength is improved, the introduction of phase interface defects accelerates electrochemical corrosion, resulting in pitting perforation. Therefore, it is urgent to design a corrosion-resistant aerogel and a processing technology to solve the above problems. SUMMARY

[0005] The purpose of the present application is to provide a corrosion-resistant aerogel and a processing technology to solve the above problems in the prior art.

[0006] In order to achieve the above purpose, the present application provides the following technical scheme: A preparation method of a corrosion-resistant composite aerogel, comprising the following steps: (1) mixing graphene oxide dispersion liquid and metal organic framework precursor ZIF-67, the metal salt is cobalt salt, the mass ratio of graphene oxide to metal salt is 1:0.5-1:2, and homogeneous sol is formed by ultrasonic treatment; (2) adding polytetrafluoroethylene nanofiber with a diameter of 50-200 nm to the sol of step (1), the addition amount is 10%-30% of the mass of graphene oxide, and the mixture is poured into a mold after stirring; (3) gradient freeze-drying: first stage, pre-freezing at-20 DEG C for 2 h, second stage, deep freezing at-50 DEG C for 4 h, third stage, freeze-drying under the conditions of vacuum degree less than or equal to 10 Pa and-80 DEG C for 24 h, to form a multi-level pore structure wet gel; (4) The wet gel is placed in a tube furnace and carbonized at 800-1000℃ for 2 h at a rate of 5℃ / min under argon atmosphere to obtain a carbide-reinforced composite aerogel; (5) The carbonized aerogel is immersed in an ethanol solution of perfluorooctyltriethoxysilane with a concentration of 2 wt% and treated with hydrophobicity at 60℃ for 6 h to obtain a corrosion-resistant aerogel with a porosity of ≥95% and a mass loss rate of <5% after being immersed in an HCl solution with a pH of 1 and a NaOH solution with a pH of 14 for 7 days.

[0007] Preferably, the metal-organic framework precursor in step (1) is ZIF-8 or ZIF-67, and the metal salt is selected from zinc salt or cobalt salt. The composite of the metal salt and graphene oxide enhances the stability of the framework through π-π stacking and coordination bonding, so that the compression strength attenuation rate of the aerogel is <10% after being exposed to a salt spray environment (5 wt% NaCl, 35℃) for 240 h.

[0008] Preferably, the polytetrafluoroethylene nanofiber in step (2) is pretreated by plasma, specifically treated at a power of 100 W for 10 min under an oxygen atmosphere to generate carboxyl groups on the surface, thereby enhancing the hydrogen bonding force with graphene oxide and improving the toughness of the aerogel with a breaking strain of >15%.

[0009] Preferably, the temperature reduction program of the gradient freeze-drying in step (3) is optimized as follows: the first stage is -10℃ for 1 h to form micrometer-sized macropores, the second stage is -30℃ for 2 h to form sub-micrometer-sized transition pores, and the third stage is -50℃ for 3 h to form nanometer-sized micropores, thereby obtaining a bimodal structure with a gradient distribution of pore sizes of 1 nm-50 μm and a thermal conductivity of ≤0.025 W / (m·K).

[0010] Preferably, boron trimethyl ester vapor is introduced during the carbonization process in step (4) and is introduced at a flow rate of 0.5 L / min under argon carrier flow to dope boron elements into the carbon framework to form B-C bonds to inhibit high-temperature oxidation, thereby improving the thermal stability of the aerogel by >40% in an air atmosphere at 600℃.

[0011] Preferably, the hydrophobic treatment in step (5) adopts a two-step method: first, immerse in a 5 wt% methytrimethoxysilane ethanol solution to form a bottom hydrophobic film, and then spray a nano-silicon dioxide / fluorocarbon resin composite emulsion with a particle size of 100 nm to form a micro-nano hierarchical rough structure, so that the contact angle is ≥160°.

[0012] Preferably, rare earth oxide nanoparticles, including lutetium oxide or yttrium oxide , the additive amount is 1%~5% of the mass of graphene oxide, the rare earth ion fills the grain boundary to inhibit the penetration of corrosive medium, and the aerogel in 3.5 wt% NaCl seawater is improved by more than 50% in the electrochemical impedance modulus value.

[0013] A kind of corrosion-resistant composite aerogel, density is 0.05~0.1 g / cm³, specific surface area is ≥500 m² / g, and surface load manganese-based / precious metal Pt, Au nanoparticles, particle size is 5~20 nm, in the presence of persulfate can catalyze degradation organic dye, such as methylene blue, 30 min degradation rate is >95%.

[0014] Preferably, its microstructure is a dome-shaped polyhedral unit, unit size is 20~100 μm, cell wall is composed of graphene nanosheet, thickness is 1~3 nm and cobalt carbide nanocrystal, particle size is 10~30 nm staggered stacking, compressive strength is ≥1.5 MPa, elastic recovery rate is >99%.

[0015] Preferably, as a corrosion-resistant thermal insulation coating of offshore platform heat pipe, the coating thickness is 5~10 mm, after 12 months of use in 150℃ steam environment, the corrosion rate of the substrate carbon steel is <0.01 mm / a.

[0016] In the above technical solution, the corrosion-resistant aerogel and its processing process provided by the application, after soaking in strong acid HCl with pH=1 and strong base NaOH environment with pH=14 for 7 days, the mass loss rate is <5%, while the porosity is ≥95% and the compressive strength is ≥1.5 MPa, solving the industry problem of traditional aerogel structure collapse and performance attenuation in corrosive medium. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art according to these drawings.

[0018] Figure 1 The figure shows the steps of the processing process of the corrosion-resistant aerogel and its processing process. DETAILED DESCRIPTION

[0019] In order to make those skilled in the art better understand the technical solutions of the present application, the following will further introduce the present application in combination with the drawings.

[0020] As Figure 1 shown, the preparation method of the corrosion-resistant composite aerogel provided by the embodiment of the present application comprises the following steps: (1) mixing the graphene oxide dispersion liquid with metal organic framework precursor ZIF-67, the metal salt is cobalt salt, the mass ratio of graphene oxide to metal salt is 1:0.5-1:2, and a homogeneous sol is formed by ultrasonic treatment; (2) adding polytetrafluoroethylene nanofiber with a diameter of 50-200 nm to the sol of step (1), the addition amount is 10%-30% of the mass of graphene oxide, and then pouring into a mold after stirring; (3) gradient freeze-drying: first stage, pre-freezing at-20℃ for 2 h, second stage, deep-freezing at-50℃ for 4 h, and third stage, freeze-drying under the conditions of a vacuum degree of≤10 Pa and-80℃ for 24 h, to form a wet gel with a hierarchical pore structure; (4) placing the wet gel in a tube furnace, carbonizing at 800-1000℃ at a rate of 5℃ / min under an argon atmosphere for 2 h to obtain a carbide reinforced composite aerogel; (5) immersing the carbonized aerogel in an ethanol solution of perfluorooctyltriethoxysilane with a concentration of 2 wt%, and then performing hydrophobic treatment at 60℃ for 6 h, to finally obtain a corrosion-resistant aerogel, the porosity of which is≥95%, and the mass loss rate is<5% after being immersed in an HCl solution with pH=1 and an NaOH solution with pH=14 for 7 days.

[0021] Preferably, in step (1), the metal organic framework precursor is ZIF-8 or ZIF-67, and the metal salt is selected from zinc salt or cobalt salt, and the combination of graphene oxide and the metal salt enhances the skeleton stability through π-π stacking and coordination bonding, so that the compression strength attenuation rate of the aerogel is<10% after being exposed to a salt spray environment (5 wt% NaCl, 35℃) for 240 h.

[0022] Preferably, in step (2), the polytetrafluoroethylene nanofiber is pretreated by plasma, specifically, the surface of the nanofiber is treated by plasma under an oxygen atmosphere at a power of 100 W for 10 min, so that carboxyl groups are generated on the surface of the nanofiber, and the hydrogen bond binding force between the nanofiber and graphene oxide is enhanced, thereby improving the toughness of the aerogel, and the breaking strain is>15%.

[0023] Preferably, in step (3), the temperature decreasing procedure of the gradient freeze-drying is optimized as follows: first stage, maintaining at-10℃ for 1 h to form micrometer-sized large pores, second stage, maintaining at-30℃ for 2 h to form sub-micrometer-sized transition pores, and third stage, maintaining at-50℃ for 3 h to form nanometer-sized micropores, so that a bimodal structure with a gradient distribution of pore sizes of 1 nm-50 μm is finally obtained, and the thermal conductivity is≤0.025 W / (m·K).

[0024] Preferably, in step (4), trimethyl borate vapor is introduced during the carbonization process, and the boron element is doped into the carbon skeleton under the carrier of argon gas at a flow rate of 0.5 L / min, so that B-C bonds are formed to inhibit high-temperature oxidation, and the thermal stability of the aerogel is improved by>40% in an air atmosphere at 600℃.

[0025] Preferably, the hydrophobic treatment in step (5) adopts a two-step method: first, immerse in a 5 wt% methytrimethoxysilane ethanol solution to form a bottom hydrophobic film, and then spray a nano-silica / fluorocarbon resin composite emulsion with a particle size of 100 nm to form a micro-nano hierarchical rough structure, so that the contact angle is ≥160°.

[0026] Preferably, rare earth oxide nanoparticles, including lutetium oxide or yttrium oxide , are added to the sol in step (1), and the addition amount is 1%~5% of the mass of graphene oxide. The penetration of corrosive media is inhibited by filling the grain boundaries with rare earth ions, so that the electrochemical impedance modulus of the aerogel in seawater 3.5 wt% NaCl is increased by >50%.

[0027] A corrosion-resistant composite aerogel has a density of 0.05~0.1 g / cm³, a specific surface area of ≥500 m² / g, and a surface loaded with manganese-based / precious metal Pt, Au nanoparticles with a particle size of 5~20 nm, which can catalyze the degradation of organic dyes such as methylene blue in the presence of persulfate, with a degradation rate of >95% in 30 min.

[0028] Preferably, its microstructure is a dome-shaped polyhedral unit with a unit size of 20~100 μm, and the cell wall is composed of graphene nanosheets with a thickness of 1~3 nm and cobalt carbide nanocrystals with a particle size of 10~30 nm stacked alternately, with a compressive strength of ≥1.5 MPa and an elastic recovery rate of >99%.

[0029] Preferably, as a corrosion-resistant and heat-insulating coating for ocean platform heat pipes, the coating has a thickness of 5~10 mm, and after 12 months of use in a 150℃ steam environment, the corrosion rate of the carbon steel substrate is <0.01 mm / a. Example 1

[0030] A method for preparing a corrosion-resistant composite aerogel, comprising the following steps: (1) Mix graphene oxide dispersion liquid with metal organic framework precursor ZIF-67, the metal salt is cobalt salt, and the mass ratio of graphene oxide to metal salt is 1:0.5~1:2, and ultrasonic treatment to form a homogeneous sol; (2) Add polytetrafluoroethylene nanofibers with a diameter of 50~200 nm to the sol of step (1), and the addition amount is 10%~30% of the mass of graphene oxide, and after stirring, pour into a mold; (3) Gradient freeze-drying: first stage, pre-freeze at -20℃ for 2 h, second stage, deep freeze at -50℃ for 4 h, third stage, freeze-drying under the conditions of vacuum degree ≤10 Pa and -80℃ for 24 h, to form a multi-level porous structure wet gel; (4) The wet gel is placed in a tube furnace, and carbonized at 800-1000℃ for 2 h under argon atmosphere at a rate of 5℃ / min to obtain carbide reinforced composite aerogel; (5) The carbonized aerogel is immersed in an ethanol solution of perfluorooctyltriethoxysilane with a concentration of 2 wt%, and hydrophobic treated at 60℃ for 6 h to obtain a corrosion-resistant aerogel, which has a porosity of ≥95% and a mass loss rate of <5% after being immersed in an HCl solution with a pH of 1 and a NaOH solution with a pH of 14 for 7 days. Example 2

[0031] This example is further limited based on Example 1. In step (1), the metal organic framework precursor is ZIF-8 or ZIF-67, and the metal salt is selected from zinc salt or cobalt salt. The composite of the metal salt and graphene oxide enhances the stability of the framework through π-π stacking and coordination bond, so that the compression strength attenuation rate of the aerogel is <10% after being exposed to a salt spray environment (5 wt% NaCl, 35℃) for 240 h. In step (2), the polytetrafluoroethylene nanofiber is subjected to plasma pretreatment, specifically, the surface of the nanofiber is treated in an oxygen atmosphere at a power of 100 W for 10 min to generate carboxyl groups, thereby enhancing the hydrogen bond binding force with graphene oxide and improving the toughness of the aerogel, with a breaking strain of >15%. In step (3), the cooling program of the gradient freeze-drying is optimized as follows: the first stage is to maintain at -10℃ for 1 h to form micrometer-sized large pores, the second stage is to maintain at -30℃ for 2 h to form sub-micrometer-sized transition pores, and the third stage is to maintain at -50℃ for 3 h to form nanometer-sized micropores, so that a bimodal structure with a gradient distribution of pore sizes of 1 nm-50 μm is finally obtained, and the thermal conductivity is ≤0.025 W / (m·K). In step (4), trimethyl borate vapor is introduced during the carbonization process, and is introduced at a flow rate of 0.5 L / min under argon carrier flow, so that boron is doped into the carbon framework to form B-C bonds to inhibit high-temperature oxidation, and the thermal stability of the aerogel is improved by >40% in an air atmosphere at 600℃. In step (5), the hydrophobic treatment adopts a two-step method: first, the nanofiber is immersed in an ethanol solution of methyltrimethoxysilane with a concentration of 5 wt% to form a bottom hydrophobic film, and then nano-silicon dioxide / fluorocarbon resin composite emulsion with a particle size of 100 nm is sprayed to form a micro-nano hierarchical rough structure, so that the contact angle is ≥160°. In step (1), rare earth oxide nanoparticles, including lutetium oxide Lu2O3 or yttrium oxide Y2O3, are added to the sol, and the addition amount is 1%-5% of the mass of the graphene oxide. The rare earth ions fill the grain boundaries to inhibit the penetration of corrosive media, so that the electrochemical impedance modulus of the aerogel is improved by >50% in seawater with a NaCl concentration of 3.5 wt%. Example 3

[0032] The corrosion-resistant composite aerogel has a density of 0.05-0.1 g / cm3, a specific surface area of greater than or equal to 500 m2 / g, and a surface loaded with manganese-based / gold Pt, Au nanoparticles with a particle size of 5-20 nm, and can catalyze degradation of organic dyes, such as methylene blue, in the presence of persulfate, with a degradation rate of greater than 95% in 30 min; the microstructure is a dome-shaped polyhedral unit with a unit size of 20-100 μm, the cell wall is composed of graphene nanosheets with a thickness of 1-3 nm and cobalt carbide nanocrystals with a particle size of 10-30 nm, which are staggered and stacked; the compressive strength is greater than or equal to 1.5 MPa, and the elastic recovery rate is greater than 99%; as a corrosion-resistant and heat-insulating coating for a heat pipe of a marine platform, the coating has a thickness of 5-10 mm, and after 12 months of use in a 150℃ steam environment, the corrosion rate of the carbon steel substrate is less than 0.01 mm / a.

[0033] The above has described certain exemplary embodiments of the present application by way of illustration only, and it is obvious to those skilled in the art that the described embodiments can be modified in various ways without departing from the spirit and scope of the present application. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present application.

Claims

1. A method for preparing a corrosion-resistant composite aerogel, characterized in that: The following steps are involved: (1) Mixing graphene oxide dispersion with metal organic framework precursor ZIF-67, where the metal salt is cobalt salt and the mass ratio of graphene oxide to metal salt is 1:0.5~1:2, and ultrasonic treatment is performed to form a homogeneous sol; (2) Adding polytetrafluoroethylene nanofibers with a diameter of 50 to 200 nm and an amount of 10% to 30% of the mass of graphene oxide to the sol in step (1), stirring and then injecting into a mold; (3) Gradient freeze drying: the first stage is pre-freezing at -20 °C for 2 h, the second stage is deep freezing at -50 °C for 4 h, and the third stage is freeze drying at -80 °C for 24 h under vacuum ≤10 Pa to form a wet gel with a multi-level porous structure; (4) The wet gel was placed in a tubular furnace and heated to 800-1000°C at a rate of 5°C / min under an argon atmosphere for carbonization for 2 h to obtain a carbide-reinforced composite aerogel; (5) The carbonized aerogel was immersed in a 2 wt% ethanol solution of perfluorooctyltriethoxysilane at 60 °C for hydrophobic treatment for 6 h, and finally a corrosion-resistant aerogel was obtained with a porosity of ≥95%. The mass loss rate was less than 5% after immersion in a pH = 1 HCl solution and a pH = 14 NaOH solution for 7 days.

2. The preparation method according to claim 1, wherein: In step (1), the metal organic framework precursor is ZIF-8 or ZIF-67, and the metal salt is zinc salt or cobalt salt. The composite with graphene oxide enhances the skeleton stability through π-π stacking and coordination bonds, so that the compression strength decay rate of the aerogel is less than 10% after exposure to a salt spray environment (5 wt% NaCl, 35°C) for 240 h.

3. The preparation method according to claim 1, wherein: In step (2), the polytetrafluoroethylene nanofibers are plasma pretreated, specifically at a power of 100 W for 10 min in an oxygen atmosphere, so that carboxyl groups are generated on their surface, which enhances the hydrogen bonding strength with graphene oxide, thereby improving the toughness of the aerogel and the fracture strain is greater than 15%.

4. The preparation method according to claim 1, wherein: The cooling program of step (3) gradient freeze-drying was optimized as follows: the first stage was maintained at -10°C for 1 h to form micron-sized macropores, the second stage was maintained at -30°C for 2 h to form submicron-sized transitional pores, and the third stage was maintained at -50°C for 3 h to form nanoscale micropores. Finally, a bimodal structure with a gradient pore size distribution of 1 nm to 50 μm was obtained, and the thermal conductivity was ≤0.025 W / (m·K).

5. The preparation method according to claim 1, wherein: In step (4), trimethyl borate vapor is introduced into the carbonization process at a rate of 0.5 L / min under an argon carrier flow to dope boron into the carbon skeleton, forming BC bonds to inhibit high-temperature oxidation, thereby improving the thermal stability of the aerogel by more than 40% in an air atmosphere at 600°C.

6. The preparation method according to claim 1, wherein: Step (5) hydrophobic treatment adopts a two-step method: first, immerse in 5 wt% methyltrimethoxysilane ethanol solution to form a bottom hydrophobic film, and then spray nano-silica / fluorocarbon resin composite emulsion with a particle size of 100 nm to form a micro-nano graded rough structure so that the contact angle is ≥160°.

7. The preparation method according to claim 1, wherein: Rare earth oxide nanoparticles, including lutetium oxide Lu2O3 or yttrium oxide Y2O3, are added to the sol in step (1). The addition amount is 1% to 5% of the mass of graphene oxide. The rare earth ions fill the grain boundaries to inhibit the penetration of the corrosive medium, so that the electrochemical impedance modulus of the aerogel in 3.5 wt% NaCl seawater is increased by more than 50%.

8. A corrosion-resistant composite aerogel, characterized by: Prepared by the method of any one of claims 1 to 7, having a density of 0.05-0.1 g / cm³, a specific surface area ≥500 m² / g, and surface-loaded manganese-based / noble metal Pt and Au nanoparticles with a particle size of 5-20 nm. In the presence of persulfate, it can catalytically degrade organic dyes, such as methylene blue, with a degradation rate of >95% in 30 min.

9. The composite aerogel according to claim 8, characterized in that: Its microstructure is a dome-shaped multicellular unit with a unit size of 20~100 μm. The cell wall is composed of graphene nanosheets with a thickness of 1~3 nm and cobalt carbide nanocrystals with a particle size of 10~30 nm. The compressive strength is ≥1.5 MPa and the elastic recovery rate is >99%.

10. Use of the composite aerogel according to claims 8-9, characterized in that: As an anti-corrosion and thermal insulation coating for thermal pipelines on offshore platforms, the coating thickness is 5~10 mm. After 12 months of use in a 150°C steam environment, the corrosion rate of the base carbon steel is less than 0.01 mm / a.

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