Preparation method for enhancing combination between ceramic glaze of glass-lined reaction kettle by using carbon nano tube

Abstract

The invention relates to the technical field of porcelain glaze, and discloses a preparation method for combining porcelain glaze of a carbon nano tube enhanced glass-lined reaction kettle, which comprises the following steps: firstly, preparing a carbon nano tube aqueous dispersion, slowly dropwise adding the carbon nano tube aqueous dispersion into a surfactant solution to obtain a positively charged carbon nano tube aqueous dispersion, adding glaze powder into a negative ion solution, and uniformly stirring to obtain the carbon nano tube enhanced glass-lined reaction kettle porcelain glaze. And fully mixing the glaze particles with negative charges to obtain glaze slip, carrying out centrifugal filtration to obtain preliminarily modified glaze particles, carrying out gradient pre-heating in an aerobic environment to obtain pre-calcined glaze particles, placing the pre-calcined glaze particles in calcination equipment, carrying out oxygen-isolated calcination, and in order to discharge pores in the sintered glaze particles, raising the temperature in the furnace again to enhance the fluidity of the glaze particles. The preparation method comprises the following steps: preparing a glaze block, preparing a vacuum environment by using a vacuum pump, recovering to a normal-pressure environment, stopping heating to obtain the glaze block with tightly combined inside, and finally grinding and crushing the glaze block in grinding equipment with the particle size capable of being adjusted according to downstream application requirements.

Description

Technical Field

[0001] The present invention relates to a preparation method for enhancing the bonding between carbon nanotubes and porcelain enamel of an enameled glass-lined reactor, belonging to the technical field of porcelain enamel. Background Art

[0002] An enameled glass-lined reactor is a composite material product in which a glaze containing silicon dioxide is lined on the inner surface of a steel container and adheres to the metal surface after high-temperature calcination, and is widely used in industrial fields such as chemical industry, medicine, and petroleum. According to the different component ratios of the porcelain enamel, it can be divided into primer glaze and topcoat glaze. The primer glaze is the porcelain enamel that tightly binds the fired porcelain layer to the steel body, and its component ratio increases the content of the adhesion agent to enhance the bonding force between the porcelain layer and the steel body. The component ratio of the topcoat glaze increases the content of the corrosion-resistant components, so that the fired outer enamel layer has high corrosion resistance. Therefore, chipping caused by reasons such as sharp temperature changes or external impacts often occurs at the detachment between the primer glaze and the topcoat glaze.

[0003] Due to its perfect bonding structure, carbon nanotubes exhibit excellent mechanical properties and chemical stability, and can effectively improve the comprehensive performance of materials.

[0004] Patent CN202211724122.6 discloses a preparation method for a carbon nanotube-reinforced composite ceramic coating. The light metal substrate is immersed in an electrolyte for thermoelectrochemical oxidation treatment to in-situ grow a ceramic film layer on the surface of the light metal substrate. Among them, the electrolyte contains CNT modified by an anionic surfactant. When the light metal is oxidized, the modified CNT migrates towards the ceramic coating direction, improving the depth and uniformity of the fusion of CNT and the ceramic coating, thereby improving the mechanical properties of the ceramic film layer.

[0005] However, from the publicly available technologies, this type of technology makes the modified CNT migrate towards the ceramic coating direction through thermoelectrochemical oxidation treatment, and cannot guarantee the fusion depth of CNT and the ceramic coating. In the present invention, the glaze particles and carbon nanotubes first have an active bonding tendency and then are deeply fused during the calcination process to obtain modified glaze powder for the enamel process, which can strengthen the bonding between the topcoat glaze and the primer glaze, thereby improving the mechanical properties of the ceramic film layer and reducing the occurrence of chipping. Summary of the Invention

[0006] In order to solve the above problems, the present invention proposes a preparation method for enhancing the bonding between carbon nanotubes and porcelain enamel of an enameled glass-lined reactor:

[0007] 1. Mix carbon nanotubes, deionized water, and a dispersant, adjust the pH of the mixture to 7 with a pH regulator, seal it, and obtain an aqueous carbon nanotube dispersion through ultrasonic dispersion. The mass ratio of the carbon nanotubes, deionized water, and the dispersant is 0.1 - 10:100:0.05 - 1. The aspect ratio of the carbon nanotubes is 500 - 1000. The dispersant is one or any combination of sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, and sodium dodecyl sulfate. The pH regulator is an aqueous solution of a basic substance with a mass concentration of 2%. The basic substance is one or any combination of potassium hydroxide, sodium hydroxide, and calcium hydroxide. The power of the ultrasonic dispersion is 500 - 2000 W, and the time is 0.5 - 10 h;

[0008] 2. Add a cationic surfactant to deionized water at a mass ratio of 0.1 - 20:100 to obtain a surfactant solution. The cationic surfactant is one or any combination of cetyltrimethylammonium bromide, dodecylamine hydrochloride, and cetylpyridinium chloride. Slowly add the aqueous carbon nanotube dispersion obtained in step 1 to the surfactant solution, and stir at room temperature for 12 - 24 h to allow the surfactant to adsorb on the surface of the carbon nanotubes through non-covalent interactions. After stirring, separate the carbon nanotubes adsorbed with the surfactant by centrifugation, wash with deionized water to remove the unadsorbed surfactant, and repeat step 1 to obtain an aqueous carbon nanotube dispersion with a positive charge;

[0009] 3. Add the ground glaze powder to be modified to a solution containing a large amount of negative ions at a mass ratio of 0.1 - 20:100, stir and soak for 2 - 4 h to exchange the cations on the surface of the glaze particles with negative ions, so that the surface of the glaze particles is negatively charged. The negative ion solution is one or any combination of sodium phosphate, potassium phosphate, and calcium phosphate, and the concentration of phosphate ions is 0.1 - 0.5 mol / L. After soaking, separate the glaze particles by centrifugation, wash with deionized water to remove the residual negative ion solution on the surface, and obtain negatively charged glaze particles;

[0010] 4. Put the aqueous carbon nanotube dispersion with a positive charge obtained in step 2 and the negatively charged glaze particles obtained in step 3 into a blender at a mass ratio of 50 - 100:100 and mix well for 0.5 - 5 h to make the carbon nanotubes adsorb more firmly on the surface of the glaze particles through the attraction of positive and negative charges, and obtain a glaze slurry;

[0011] 5. Centrifuge and filter the glaze slurry obtained in step 4, and dry it in a vacuum oven for 0.5 - 12 h to obtain preliminarily modified glaze particles;

[0012] 6. Under aerobic conditions, place the preliminarily modified glaze particles obtained in step 5 in a temperature of 70% T1 for preheating, with a heating duration of 30 min - 300 min, and then heat up to T1 + (T2 - T1) / 2, and keep the temperature for 3 min - 7 min to remove amorphous carbon while trying to retain the carbon nanotubes. The temperature T1 is the oxidation temperature of amorphous carbon, and the temperature T2 is the oxidation temperature of carbon nanotubes, obtaining the pre-calcined glaze particles;

[0013] 7. Place the pre-calcined glaze particles obtained in step 6 in a calcination device. Before heating, first introduce a protective gas into the furnace to discharge the air in the furnace and then heat the system. When the temperature in the furnace reaches 110% of the viscous flow state temperature of the glaze particles and is maintained for 0.1 - 0.5 h, the carbon nanotubes adsorbed on the surface of the glaze particles penetrate into the interior of the viscous flow state glaze particles. Due to the irregular shape of the glaze particles, several glaze particles sinter together under the action of high temperature to form micro-pores. To discharge the pores in the sintered glaze particles, raise the temperature in the furnace to 120% of the viscous flow state temperature of the glaze particles and maintain it for 0.1 - 0.5 h to enhance the fluidity of the glaze particles, and connect a vacuum pump to an air outlet of the calcination device, close the other intake valves, start the vacuum pump to work. When the pressure in the calcination device reaches 0.1 - 1000 Pa and is maintained for 0.5 - 10 h, the vacuum pump stops working, returns to the normal pressure environment, and stops heating, allowing it to cool naturally. The viscous flow state glaze particles gradually solidify to form a glaze block with a tightly combined interior;

[0014] 8. Place the glaze block obtained in step 7 in a grinding device for grinding and pulverizing, and its particle size can be adjusted according to the requirements of downstream applications;

[0015] The beneficial effects of the present invention are as follows: Through the mutual attraction of opposite charges, the positively charged carbon nanotubes and the negatively charged glaze particles have active binding properties, avoiding the oxidation consumption caused by high-temperature calcination in an aerobic environment during the compounding process of carbon nanotubes and glaze particles. Adopting an oxygen-isolated calcination method, through gradient heating and calcination, the carbon nanotubes adsorbed on the surface are deeply fused with the glaze particles when the glaze particles are in a viscous flow state, and raising the temperature again enhances the fluidity of the viscous flow state glaze particles, which helps to discharge the pores inside the glaze block. To further reduce the existence of internal bubbles, a vacuum environment is created using a vacuum pump, which is beneficial to achieving the purpose of improving the quality of the glaze block. The glaze powder obtained by secondary grinding has carbon nanotubes penetrating into its interior, realizing the feasibility of calcination of the attached glaze in an aerobic environment under industrial production conditions. The modified glaze powder can be used to enhance the bonding strength between the base glaze and the top glaze, and between the base glaze and the metal matrix, thereby reducing the occurrence of porcelain peeling and reducing cost losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of the operation process of the preparation method for enhancing the bonding between carbon nanotubes and porcelain enamel in a glass-lined reaction kettle according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] The technical solutions in the present invention will be clearly and completely described below in conjunction with the accompanying drawings. The following is known as one example:

[0018] 1. Mix carbon nanotubes, deionized water, and a dispersant, adjust the pH of the mixture to pH = 7 with a pH regulator, seal it, and obtain an aqueous carbon nanotube dispersion through ultrasonic dispersion. The mass ratio of the carbon nanotubes, deionized water, and the dispersant is 1:100:0.5. The aspect ratio of the carbon nanotubes is 500. The dispersant is made by mixing 50% sodium dodecylbenzenesulfonate and 50% sodium dodecylsulfonate. The pH regulator is a 2% potassium hydroxide aqueous solution by mass concentration. The power of the ultrasonic dispersion is 1000 W and the time is 5 h.

[0019] 2. Add a cationic surfactant to deionized water at a mass ratio of 1:100 to obtain a surfactant solution. The cationic surfactant is cetyltrimethylammonium bromide. Slowly drip the aqueous carbon nanotube dispersion obtained in step 1 into the surfactant solution, and stir at room temperature for 12 h to allow the surfactant to adsorb on the surface of the carbon nanotubes through non-covalent interactions. After stirring, separate the carbon nanotubes adsorbed with the surfactant by centrifugation, wash with deionized water to remove the unadsorbed surfactant, and repeat step 1 to obtain an aqueous carbon nanotube dispersion with a positive charge.

[0020] 3. Add the ground glaze powder to be modified to a solution containing a large amount of negative ions at a mass ratio of 1:100, stir and soak for 2 h to allow the cations on the surface of the glaze particles to exchange with the negative ions, so that the surface of the glaze particles is negatively charged. The negative ion solution is a sodium phosphate solution with a phosphate ion concentration of 0.5 mol / L. After soaking, separate the glaze particles by centrifugation, wash with deionized water to remove the residual negative ion solution on the surface, and obtain negatively charged glaze particles.

[0021] 4. Put the aqueous carbon nanotube dispersion with a positive charge obtained in step 2 and the negatively charged glaze particles obtained in step 3 into a blender at a mass ratio of 1:2 and mix well for 1 h to allow the carbon nanotubes to adsorb more firmly on the surface of the glaze particles through the attraction of positive and negative charges, and obtain a glaze slurry.

[0022] 5. Centrifuge and filter the glaze slurry obtained in step 4, and place it in a vacuum oven to dry for 5 h to obtain preliminarily modified glaze particles.

[0023] 6. Preheat the preliminarily modified glaze particles obtained in step 5 in an aerobic environment at a temperature of 70% T1 for 100 min, and then heat up to T1 + (T2 - T1) / 2 and keep it warm for 4 min to remove amorphous carbon and try to retain the carbon nanotubes as much as possible. The temperature T1 is 450 °C and the temperature T2 is 530 °C to obtain pre-calcined glaze particles.

[0024] 7. Place the pre-calcined glaze particles obtained in step 6 into a calcination device. Before heating, introduce a protective gas into the furnace to exhaust the air in the furnace and then heat the system. When the temperature in the furnace reaches 1150 °C and is maintained for 0.1 h, the carbon nanotubes adsorbed on the surface of the glaze particles penetrate deep into the viscous-flow glaze particles. Due to the irregular shape of the glaze particles, several glaze particles sinter together under the action of high temperature to form tiny pores. To discharge the pores in the sintered glaze particles, raise the temperature in the furnace to 1250 °C and maintain it for 0.1 h to enhance the fluidity of the glaze particles. Connect a vacuum pump to an air outlet of the calcination device, close the other intake valves, and start the vacuum pump. After the pressure in the calcination device reaches 100 Pa and is maintained for 0.5 h, stop the vacuum pump, restore to the atmospheric pressure environment, and stop heating to allow it to cool naturally. The viscous-flow glaze particles gradually solidify to form a glaze block with a tightly bonded interior.

[0025] 8. Place the glaze block obtained in step 7 into a grinding device for grinding and pulverization, and its particle size can be adjusted according to the requirements of downstream applications.

Claims

1. The preparation method for enhancing the bonding between the enamel and the carbon nanotube-reinforced glass-lined reactor is as follows: Mix carbon nanotubes, deionized water, and a dispersant, adjust the pH of the mixed solution to 7 with a pH regulator, seal it, and obtain an aqueous carbon nanotube dispersion through ultrasonic dispersion. The mass ratio of the carbon nanotubes, deionized water, and the dispersant is 0.1 - 10:100:0.05 - 1. The aspect ratio of the carbon nanotubes is 500 - 1000. The dispersant is one or any combination of sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, and sodium dodecyl sulfate. The pH regulator is an aqueous solution of an alkaline substance with a mass concentration of 2%. The alkaline substance is one or any combination of potassium hydroxide, sodium hydroxide, and calcium hydroxide. The power of the ultrasonic dispersion is 500 - 2000W, and the time is 0.5 - 10h. Add a cationic surfactant to deionized water according to a mass ratio of 0.1 - 20:100 to obtain a surfactant solution. The cationic surfactant is one or any combination of cetyltrimethylammonium bromide, dodecylamine hydrochloride, and cetylpyridinium chloride. Slowly drip the aqueous carbon nanotube dispersion into the surfactant solution, stir at room temperature for 12 - 24h, and after stirring, separate the carbon nanotubes adsorbed with the surfactant by centrifugation, wash with deionized water to remove the unadsorbed surfactant, and repeat the carbon nanotube dispersion step to obtain a positively charged aqueous carbon nanotube dispersion. Add the ground enamel powder to be modified to a solution containing a large amount of negative ions according to a mass ratio of 0.1 - 20:100, stir and soak for 2 - 4h, so that the surface of the enamel particles is negatively charged. The negative ion solution is one or any combination of sodium phosphate, potassium phosphate, and calcium phosphate, and the concentration of phosphate ions is 0.1 - 0.5mol / L. After soaking, separate the enamel particles by centrifugation, wash with deionized water to remove the residual negative ion solution on the surface, and obtain negatively charged enamel particles. Put the positively charged aqueous carbon nanotube dispersion and the negatively charged enamel particles into a mixer according to a mass ratio of 50 - 100:100 and mix well for 0.5 - 5h to obtain an enamel slurry. Centrifuge and filter the enamel slurry, and dry it in a vacuum oven for 0.5 - 12h to obtain preliminarily modified enamel particles. In an aerobic environment, place the preliminarily modified enamel particles in a temperature of 70%T1 for preheating, with a preheating duration of 30min - 300min, and then heat up to T1+(T2 - T1) / 2, with a holding duration of 3min - 7min. The temperature T1 is the amorphous carbon oxidation temperature, and the temperature T2 is the carbon nanotube oxidation temperature, to obtain pre-calcined enamel particles. Place the pre-calcined enamel particles in a calcination device. Before heating, first introduce a protective gas into the furnace to exhaust the air in the furnace and then heat the system. When the temperature in the furnace reaches 110% of the viscous flow temperature of the enamel particles and is maintained for 0.1 - 0.5h, due to the irregular shape of the enamel particles, several enamel particles will sinter together under the action of high temperature to form micro-pores. To discharge the pores in the sintered enamel particles, raise the temperature in the furnace to 120% of the viscous flow temperature of the enamel particles and maintain it for 0.1 - 0.5 h to enhance the fluidity of the glaze particles, connect the vacuum pump to an air outlet of the calcination equipment, close the remaining inlet valves, start the vacuum pump, stop the vacuum pump after the pressure in the calcination equipment reaches 0.1 - 1000 Pa and is maintained for 0.5 - 10 h, restore to the atmospheric pressure environment, stop heating, and let it cool naturally. The viscous - flow - state glaze particles gradually solidify to form a glaze block with tightly - bound interior; place the glaze block in a grinding equipment for grinding and crushing, and its particle size can be adjusted according to the requirements of downstream applications.

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