CN116813386B - Self-healing high-oxygen-resistance high-temperature-oxidation-prevention composite coating for aluminum electrolysis carbon anode and preparation method thereof - Google Patents

Abstract

The invention discloses a self-healing high oxygen barrier and high temperature oxidation resistant composite coating for aluminum electrolytic carbon anode and a preparation method, belonging to the technical field of aluminum electrolytic carbon anode anti-oxidation coating. The composite coating includes a bonding transition layer, a self-healing glass oxygen barrier layer, a sealing layer and a high temperature corrosion resistant ceramic layer; the invention adopts a brushing or spraying method to uniformly apply a multi-layer coating on the surface of the aluminum electrolytic carbon anode in batches under room temperature conditions, and can be cured at room temperature; the protective layer is sintered at 400-800°C to form a bonding transition layer, a self-healing glass oxygen barrier layer, a sealing layer and a high temperature corrosion resistant ceramic layer in situ. The self-healing high oxygen barrier and high temperature oxidation resistant composite coating prepared by the invention can extend the anode pole replacement cycle by more than 2 days and has a low cost of raw materials, is suitable for industrial production, has a dense coating, good anti-oxidation effect, can withstand temperatures above 900°C for a long time, and has stable physical and chemical properties; it has broad application prospects in the field of aluminum electrolytic carbon anode anti-oxidation.

Description

A self-healing high-oxygen-barrier high-temperature oxidation-resistant composite coating for aluminum electrolysis carbon anode and its preparation method

Technical Field

The invention relates to the technical field of anti-oxidation coatings for aluminum electrolytic carbon anodes, and in particular to a self-healing high-oxygen-barrier and high-temperature-oxidation-resistant composite coating for aluminum electrolytic carbon anodes and a preparation method thereof.

Background Art

In recent years, my country's aluminum industry has developed rapidly, and my country's aluminum production ranks among the top in the world. At present, the aluminum electrolysis industry adopts the cryolite-alumina molten salt electrolysis method, in which the carbon anode is an indispensable part of the electrolytic aluminum production process, and its production cost accounts for more than 15% of the total cost. Therefore, the consumption of anode carbon blocks is an important production technical indicator for measuring electrolytic aluminum production. In the aluminum electrolysis process, 333 kg of carbon should be consumed for every ton of aluminum produced in theory, but 460 to 500 kg is consumed in actual production. In the aluminum electrolysis process, the consumption of anode carbon blocks mainly includes electrochemical consumption, residual anode carbon consumption and chemical consumption. Among them, electrochemical consumption and residual anode carbon consumption are inevitable in the production process, while chemical consumption is the additional consumption caused by the oxidation reaction of carbon anode with oxygen under high temperature conditions, which can be reduced by effective means. With the implementation of the national energy-saving and emission-reduction policies, low-consumption production and operation has become an inevitable trend in the aluminum electrolysis industry. Reducing the oxidation consumption of carbon anodes is an effective way to reduce the cost of aluminum electrolysis. It is also one of the effective measures to solve the energy consumption indicators of the aluminum electrolysis industry's "carbon peak and carbon neutrality" policy.

Studies have shown that preparing a dense high-temperature resistant and anti-oxidation coating on the surface of the carbon anode can prevent oxygen from entering and reacting with the carbon anode, which is an effective method to reduce the oxidation consumption of the carbon anode. Among them, the coatings published in patent application numbers CN202210070662.0, CN201710041749.4, CN201911310797.4, and CN201911337979.0 have a large difference in thermal expansion coefficient between the coating and the carbon anode, which produces thermal stress and easily leads to cracks in the coating. Moreover, the self-healing performance is poor and the cracks cannot be self-healed. The presence of cracks in the coating will lead to a deterioration in the anti-oxidation performance of the coating. The coatings published in patent applications No. CN201510442632.8 and CN201710081675.7 are prepared using a large amount of low-melting-point boride and other substances. The coatings have poor corrosion resistance under high temperature conditions. Corrosion will cause the coatings to fall off, affecting their long-term antioxidant properties. At the same time, new impurities will be introduced into the electrolyte, affecting the electrolyte environment. The coating published in patent application No. 201810363913.8 uses aluminum ash slag to prepare the coating, which makes the coating composition difficult to control and complex, and has poor antioxidant effect.

In order to solve the problems existing in the above-mentioned carbon anode high temperature resistant and anti-oxidation coating, a coating with self-healing, high oxygen barrier, high temperature resistance, corrosion resistance and oxidation resistance is developed to reduce carbon anode oxidation consumption, reduce _CO2 emissions, and promote carbon neutrality in the aluminum electrolysis industry, which has greater economic and social effects.

Summary of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a self-healing high-oxygen-barrier and high-temperature-oxidation-resistant composite coating for aluminum electrolysis carbon anode and a preparation method thereof.

The technical solution of the present invention is: a self-healing high oxygen barrier and high temperature oxidation resistant composite coating for aluminum electrolytic carbon anode and a preparation method thereof, wherein the composite structure includes a bonding transition layer, a self-healing glass oxygen barrier layer, a sealing layer and a high temperature and corrosion resistant ceramic layer.

Furthermore, the raw materials of the bonding transition layer are composed of the following components in terms of mass percentage: 60-95% of a main component and 5-40% of a bonding agent, and the sum of the mass percentages of the above components is 100%.

Furthermore, the raw materials of the self-healing glass oxygen barrier layer are composed of the following components by mass percentage: 60-85% of a main component, 15-35% of a binder, and 5-10% of an auxiliary sintering agent, and the sum of the mass percentages of the above components is 100%.

Furthermore, the raw materials of the sealing layer are composed of the following components in terms of mass percentage: 50-70% of a main component, 10-35% of a binder, and 5-15% of an auxiliary sintering agent, and the sum of the mass percentages of the above components is 100%.

Furthermore, the raw materials of the high temperature resistant and corrosion resistant ceramic layer are composed of the following components by mass percentage: 75-90% of main component, 5-20% of binder, 5-10% of auxiliary sintering agent, and the sum of the mass percentages of the above components is 100%.

Furthermore, main components of the bonding transition layer are silicon carbide, silicon boride and silicon carbon nitrogen.

Furthermore, main components of the self-healing glass oxygen barrier layer are silicon dioxide, aluminum oxide and boron carbide.

Furthermore, main components of the sealing layer are silicon dioxide, aluminum oxide, boron carbide, boron oxide and calcium oxide.

Furthermore, the main components of the high temperature resistant and corrosion resistant ceramic layer are silicon dioxide, aluminum oxide and boric acid.

Furthermore, the binder is prepared by mixing one or more of polyvinyl alcohol, methyl cellulose, water glass, polyacrylamide, silane coupling agent and bentonite with water in a mass ratio of (1-5): (10-50).

Furthermore, the auxiliary sintering agent is one or both of titanium dioxide and aluminum powder.

The method for preparing the aluminum electrolytic carbon anode self-healing high oxygen barrier and high temperature oxidation resistant composite coating provided by the present invention comprises the following specific steps:

(1) Preparation of liquid binder: one or more of polyvinyl alcohol, methyl cellulose, water glass, polyacrylamide, silane coupling agent and bentonite are mixed with deionized water, and stirred evenly after ultrasonic treatment to obtain a liquid binder; wherein the mass fraction of deionized water is 40 to 90 wt %, and the mass fraction of one or more of polyvinyl alcohol, sodium carboxymethyl cellulose, water glass, polyacrylamide, silane coupling agent and bentonite is 10 to 60 wt %;

(2) Mixing solid phase powder: weigh the main components and auxiliary sintering agent raw materials in order according to the bonding transition layer, self-healing glass oxygen barrier layer, sealing layer and high temperature resistant and corrosion resistant ceramic layer, and mix the solid powders of each layer of coating evenly by mechanical mixing to obtain a solid mixture of each coating;

(3) Preparation of slurry: The solid mixture of different coatings is evenly dispersed in the respective liquid binders to obtain the coating slurry of each coating layer;

(4) Application of composite coating: applying the bonding transition layer slurry to the surface of the carbon anode by a slurry brush plating method, and drying in an oven to obtain a bonding transition layer; applying the self-healing glass oxygen barrier layer slurry to the surface of the carbon anode with a bonding transition layer by a slurry brush plating method, and drying in an oven to obtain a self-healing glass oxygen barrier layer; applying the sealing layer slurry to the surface of the carbon anode with a bonding transition layer and a self-healing glass oxygen barrier layer by a slurry brush plating method, and drying in an oven to obtain a sealing layer; applying the high temperature and corrosion resistant ceramic layer slurry to the surface of the carbon anode with a bonding transition layer, a self-healing glass oxygen barrier layer and a sealing layer by a slurry brush plating method, and drying in an oven to obtain a high temperature and corrosion resistant ceramic layer;

(5) Curing of the composite coating: The composite coating is further cured in a constant temperature drying oven or drying room at a curing temperature of 105-120°C and a curing time of 8-12 hours;

(6) Calcination of the composite coating: The carbon anode coated with the composite coating is calcined and then cooled in the furnace; after the calcination, an anti-oxidation coating having a multi-layer structure of an adhesive transition layer, a self-healing glass oxygen barrier layer, a sealing layer and a high-temperature and corrosion-resistant ceramic layer can be formed in situ on the surface of the coating.

Furthermore, the mixing preparation of the liquid phase binder in step (1) is carried out using a magnetic stirrer at a stirring rate of 300 to 500 rpm for a time of 0.5 to 1 h.

Furthermore, the coating slurry is mixed and prepared in step (3) using a magnetic stirrer at a stirring rate of 100 to 500 rpm for 1 to 3 hours.

Furthermore, in step (4), the drying temperature is 60-90° C., and the drying time is 2-4 hours.

Furthermore, in step (6), the calcination temperature is 400-800° C., and the calcination time is 2-4 hours.

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

1. The coating prepared by the present invention has good adhesion and can be coated on the surface of the carbon anode by brushing or spraying. At the same time, the preparation process is simple, the raw material price is low, and the economic conditions are better.

2. The coating prepared by the present invention can be sintered at 400-800°C to form a dense anti-oxidation coating, wherein the oxygen barrier layer can generate a fluid and dense glass layer in situ to prevent oxygen penetration and carbon anode oxidation, and has a good anti-oxidation effect. At the same time, due to its fluidity, it can self-heal and repair coating cracks.

3. The coating prepared by the present invention, wherein the high temperature resistant and corrosion resistant ceramic layer can generate a dense alumina ceramic layer in situ after sintering, which can hinder the corrosion of the glass layer by the electrolytic cell environment, protect the stability of the glass layer and prevent the coating from polluting the electrolyte.

4. The coating prepared by the present invention can withstand a temperature of more than 900°C for a long time and has stable physical and chemical properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the structure of the composite coating prepared by the present invention.

FIG. 2 is a weight change curve of the carbon anode of the composite coating prepared by the present invention after oxidation at 900° C. for 96 hours.

FIG3 shows the macroscopic morphology of the carbon anode of the composite coating prepared by the present invention after drying and 96h oxidation.

FIG. 4 is an XRD curve of the composite coating prepared by the present invention after drying.

FIG. 5 is an XRD curve of the composite coating prepared by the present invention after oxidation for 96 hours.

FIG6 is an XRD curve of the oxygen barrier layer prepared by the present invention after calcination.

FIG. 7 shows the surface morphology of the oxygen barrier layer prepared by the present invention after calcination.

DETAILED DESCRIPTION

The present invention is further described in detail below in conjunction with specific embodiments.

Example

A self-healing high-oxygen-barrier high-temperature oxidation-resistant composite coating for aluminum electrolysis carbon anode and a preparation method thereof, comprising the following steps:

(1) Preparation of liquid binder: Sodium silicate, polyvinyl alcohol, bentonite and deionized water were weighed in a mass ratio of 1:1:1:45, respectively. The water glass, polyvinyl alcohol and bentonite were ultrasonically treated and then stirred to obtain a mixture. The mixture was then mixed with deionized water under a magnetic stirring rate of 400 rpm and mechanical stirring was maintained for 1 h to obtain a liquid binder.

(2) Mixing solid phase powders: According to the mass ratio of bentonite to silicon carbide of 1:15, weigh silicon carbide to obtain a bonding transition layer solid phase powder; according to the mass ratio of bentonite to self-healing glass oxygen barrier layer solid phase powder of 1:15, weigh the self-healing glass oxygen barrier layer solid phase powder, the mass percentage of which is 35% silicon dioxide, 5% aluminum oxide, 50% boron carbide, 5% titanium dioxide, and 5% aluminum powder; according to the mass ratio of bentonite to sealing layer solid phase powder of 1:6, weigh the sealing layer solid phase powder, the mass percentage of which is 55% silicon dioxide, 20% aluminum oxide, 10% boron carbide, 5% titanium dioxide, and 10% aluminum powder; according to the mass ratio of bentonite to high temperature and corrosion resistant ceramic layer solid phase powder of 1:12, weigh the high temperature and corrosion resistant ceramic layer solid phase powder, the mass percentage of which is 5% silicon dioxide, 80% aluminum oxide, 5% boric acid, 5% titanium dioxide, and 5% aluminum powder; the solid phase powders of each coating are mixed evenly to obtain their own solid phase mixtures for use.

(3) Preparation of slurry: A magnetic stirrer was used to evenly disperse the solid mixture of different coatings in their respective liquid binders. The magnetic stirring speed was 500 rpm and the stirring time was 2 h to obtain slurry of each coating layer.

(4) Application of composite coating: The bonding transition layer slurry is applied to the surface of the carbon anode by a slurry brush plating method, and the mixture is dried in an oven at 80°C for 2 hours to obtain a bonding transition layer; the self-healing glass oxygen barrier layer slurry is applied to the surface of the carbon anode with a bonding transition layer by a slurry brush plating method, and the mixture is dried in an oven at 80°C for 2 hours to obtain a self-healing glass oxygen barrier layer; the sealing layer slurry is applied to the surface of the carbon anode with a bonding transition layer and a self-healing glass oxygen barrier layer by a slurry brush plating method, and the mixture is dried in an oven at 80°C for 2 hours to obtain a sealing layer; the high-temperature and corrosion-resistant ceramic layer slurry is applied to the surface of the carbon anode with a bonding transition layer, a self-healing glass oxygen barrier layer and a sealing layer by a slurry brush plating method, and the mixture is dried in an oven at 80°C for 2 hours to obtain a high-temperature and corrosion-resistant ceramic layer.

(5) Drying of the composite coating: The composite coating is further dried in a drying oven at 120°C for 10 hours.

(6) Calcination of the composite coating: The carbon anode after the coating is dried is heated to 700°C at a rate of 5°C/min and kept at this temperature for 4 h to obtain the composite coating, as shown in FIG1 .

Antioxidation performance test: the temperature was raised from room temperature to 900℃ at a rate of 5℃/min, kept at 900℃ for 24h, then cooled with the furnace, taken out and weighed, and repeated 3 times to calculate the average value. After weighing, the constant temperature oxidation at 900℃ was continued, and the total oxidation time accumulated was 96h. The test data obtained is shown in curve 1 of Figure 2. The weight loss rate of the carbon anode coated with the composite coating after 96h oxidation was only 0.56%.

As shown in Figure 3, a1 and a2 are the macroscopic morphology of the composite coating after drying and 96h oxidation, respectively. The cracks in the coating can heal by themselves at high temperature and the coating remains intact after 96h oxidation.

After the obtained composite coating and oxygen barrier layer slurry were dried and calcined, X-ray diffraction test analysis (XRD) was performed, and the obtained data are shown in Figures 4, 5 and Curve 1 in Figure 6. After calcination, the oxygen barrier layer forms an amorphous glass layer, which can effectively prevent oxygen from entering and reacting with the carbon anode. The phase of the composite coating remains stable after oxidation for 96 hours.

The surface morphology of the oxygen barrier layer after calcination was observed using a scanning electron microscope (SEM), as shown in Figure 7a. The coating is dense and continuous without holes or cracks.

Example

A self-healing high-oxygen-barrier high-temperature oxidation-resistant composite coating for aluminum electrolysis carbon anode and a preparation method thereof, comprising the following steps:

(1) Preparation of liquid binder: Sodium silicate, methyl cellulose, bentonite and deionized water were weighed in a mass ratio of 1:1:1:45, respectively. The water glass, methyl cellulose and bentonite were ultrasonically treated and then stirred to obtain a mixture. The mixture was then mixed with deionized water under a magnetic stirring rate of 300 rpm and mechanical stirring was maintained for 1 h to obtain a liquid binder.

(2) Mixing solid phase powders: According to the mass ratio of bentonite to silicon carbide of 1:15, weigh silicon carbide to obtain a bonding transition layer solid phase powder; according to the mass ratio of bentonite to self-healing glass oxygen barrier layer solid phase powder of 1:15, weigh the self-healing glass oxygen barrier layer solid phase powder, the mass percentage of which is 35% silicon dioxide, 5% aluminum oxide, 50% boron carbide, 5% titanium dioxide, and 5% aluminum powder; according to the mass ratio of bentonite to sealing layer solid phase powder of 1:6, weigh the sealing layer solid phase powder, the mass percentage of which is 65% silicon dioxide, 10% aluminum oxide, 15% boron carbide, 5% titanium dioxide, and 5% aluminum powder; according to the mass ratio of bentonite to high temperature and corrosion resistant ceramic layer solid phase powder of 1:12, weigh the high temperature and corrosion resistant ceramic layer solid phase powder, the mass percentage of which is 5% silicon dioxide, 80% aluminum oxide, 5% boric acid, 5% titanium dioxide, and 5% aluminum powder; the solid phase powders of each coating are mixed evenly to obtain their own solid phase mixtures for use.

(3) Preparation of slurry: A magnetic stirrer was used to evenly disperse the solid mixture of different coatings in their respective liquid binders. The magnetic stirring speed was 300 rpm and the stirring time was 3 h to obtain slurry of each coating layer.

(4) Application of composite coating: The bonding transition layer slurry is applied to the surface of the carbon anode by a slurry brush plating method, and the mixture is dried in an oven at 70°C for 1.5 h to obtain a bonding transition layer; the self-healing glass oxygen barrier layer slurry is applied to the surface of the carbon anode with a bonding transition layer by a slurry brush plating method, and the mixture is dried in an oven at 70°C for 1.5 h to obtain a self-healing glass oxygen barrier layer; the sealing layer slurry is applied to the surface of the carbon anode with a bonding transition layer and a self-healing glass oxygen barrier layer by a slurry brush plating method, and the mixture is dried in an oven at 70°C for 1.5 h to obtain a sealing layer; the high-temperature and corrosion-resistant ceramic layer slurry is applied to the surface of the carbon anode with a bonding transition layer, a self-healing glass oxygen barrier layer and a sealing layer by a slurry brush plating method, and the mixture is dried in an oven at 70°C for 1.5 h to obtain a high-temperature and corrosion-resistant ceramic layer.

(5) Drying of the composite coating: The composite coating is further dried in a drying oven at 120°C for 8 hours.

(6) Calcination of the composite coating: The carbon anode after the coating is cured is heated to 800°C at a rate of 5°C/min and kept at this temperature for 3 h to obtain the composite coating, as shown in FIG1 .

Antioxidation performance test: the temperature was raised from room temperature to 900℃ at a rate of 5℃/min, kept at 900℃ for 24h, then cooled with the furnace, taken out and weighed, and repeated 3 times to calculate the average value. After weighing, the constant temperature oxidation at 900℃ was continued, and the total oxidation time accumulated was 96h. The test data obtained is shown in curve 2 of Figure 1. The weight loss rate of the carbon anode coated with the composite coating after 96h oxidation was only 0.50%.

As shown in Figure 3, b1 and b2 are the macroscopic morphology of the composite coating after drying and 96h oxidation, respectively. The cracks in the coating can heal by themselves at high temperature and the coating remains intact after 96h oxidation.

After the slurry is dried and calcined, the obtained composite coating and oxygen barrier layer are analyzed by X-ray diffraction (XRD), and the obtained data are shown in Figures 4, 5 and Curve 2 in Figure 6. After calcination, the oxygen barrier layer forms an amorphous glass layer, which can effectively prevent oxygen from entering and reacting with the carbon anode. The phase of the composite coating remains stable after oxidation for 96 hours.

The surface morphology of the oxygen barrier layer after calcination was observed using a scanning electron microscope (SEM), as shown in Figure 7b. The coating is dense and continuous without holes or cracks.

Example

A self-healing high-oxygen-barrier high-temperature oxidation-resistant composite coating for aluminum electrolysis carbon anode and a preparation method thereof, comprising the following steps:

(1) Preparation of liquid binder: Water glass, silane coupling agent, bentonite and deionized water were weighed in a mass ratio of 1:1:1:45, respectively. The water glass, silane coupling agent and bentonite were ultrasonically treated and then stirred to obtain a mixture. The mixture was then mixed with deionized water under a magnetic stirring rate of 400 rpm and mechanical stirring was maintained for 0.5 h to obtain a liquid binder.

(2) Mixing solid phase powders: According to the mass ratio of bentonite to silicon carbide of 1:15, weigh silicon carbide to obtain a bonding transition layer solid phase powder; according to the mass ratio of bentonite to self-healing glass oxygen barrier layer solid phase powder of 1:15, weigh the self-healing glass oxygen barrier layer solid phase powder, the mass percentage of which is 35% silicon dioxide, 5% aluminum oxide, 50% boron carbide, 5% titanium dioxide, and 5% aluminum powder; according to the mass ratio of bentonite to sealing layer solid phase powder of 1:6, weigh the sealing layer solid phase powder, the mass percentage of which is 60% silicon dioxide, 10% aluminum oxide, 15% boron carbide, 5% calcium oxide, 5% titanium dioxide, and 5% aluminum powder; according to the mass ratio of bentonite to high temperature and corrosion resistant ceramic layer solid phase powder of 1:12, weigh the high temperature and corrosion resistant ceramic layer solid phase powder, the mass percentage of which is 5% silicon dioxide, 80% aluminum oxide, 5% boric acid, 5% titanium dioxide, and 5% aluminum powder; the solid phase powders of each coating are mixed evenly to obtain their own solid phase mixtures for use.

(3) Preparation of slurry: A magnetic stirrer was used to evenly disperse the solid mixture of different coatings in their respective liquid binders. The magnetic stirring speed was 400 rpm and the stirring time was 2 h to obtain slurry of each coating layer.

(4) Application of composite coating: The bonding transition layer slurry is applied to the surface of the carbon anode by a slurry brush plating method, and the mixture is dried in an oven at 85°C for 2 hours to obtain a bonding transition layer; the self-healing glass oxygen barrier layer slurry is applied to the surface of the carbon anode with a bonding transition layer by a slurry brush plating method, and the mixture is dried in an oven at 85°C for 2 hours to obtain a self-healing glass oxygen barrier layer; the sealing layer slurry is applied to the surface of the carbon anode with a bonding transition layer and a self-healing glass oxygen barrier layer by a slurry brush plating method, and the mixture is dried in an oven at 85°C for 2 hours to obtain a sealing layer; the high-temperature and corrosion-resistant ceramic layer slurry is applied to the surface of the carbon anode with a bonding transition layer, a self-healing glass oxygen barrier layer and a sealing layer by a slurry brush plating method, and the mixture is dried in an oven at 85°C for 2 hours to obtain a high-temperature and corrosion-resistant ceramic layer.

(5) Drying of the composite coating: The composite coating is further dried in a drying oven at 120°C for 12 hours.

(6) Calcination of the composite coating: The carbon anode after the coating is cured is heated to 850°C at a rate of 5°C/min and kept at this temperature for 4 h to obtain the composite coating, as shown in FIG1 .

Antioxidation performance test: the temperature was raised from room temperature to 900℃ at a rate of 5℃/min, kept at 900℃ for 24h, then cooled with the furnace, taken out and weighed, and repeated 3 times to calculate the average value. After weighing, the constant temperature oxidation at 900℃ was continued, and the total oxidation time accumulated was 96h. The test data obtained is shown in curve 3 of Figure 1. The weight loss rate of the carbon anode coated with the composite coating after 96h oxidation was only 0.58%.

As shown in Figure 3, c1 and c2 are the macroscopic morphology of the composite coating after drying and 96h oxidation, respectively. The cracks in the coating can heal by themselves at high temperature and the coating remains intact after 96h oxidation.

After the slurry is dried and calcined, the obtained composite coating and oxygen barrier layer are analyzed by X-ray diffraction test (XRD), and the obtained data are shown in Figures 4, 5 and Curve 3 in Figure 6. After calcination, the oxygen barrier layer forms an amorphous glass layer, which can effectively prevent oxygen from entering and reacting with the carbon anode. The phase of the composite coating remains stable after oxidation for 96 hours.

The surface morphology of the oxygen barrier layer after calcination was observed using a scanning electron microscope (SEM), as shown in Figure 7c. The coating is dense and continuous without holes or cracks.

Example

A self-healing high-oxygen-barrier high-temperature oxidation-resistant composite coating for aluminum electrolysis carbon anode and a preparation method thereof, comprising the following steps:

(1) Preparation of liquid binder: Sodium silicate, polyacrylamide, bentonite and deionized water were weighed in a mass ratio of 1:1:1:45, respectively. The water glass, polyacrylamide and bentonite were ultrasonically treated and then stirred to obtain a mixture. The mixture was then mixed with deionized water under a magnetic stirring rate of 350 rpm and mechanical stirring was maintained for 1 h to obtain a liquid binder.

(2) Mixing solid phase powders: According to the mass ratio of bentonite to silicon carbide of 1:15, weigh silicon carbide to obtain a bonding transition layer solid phase powder; according to the mass ratio of bentonite to self-healing glass oxygen barrier layer solid phase powder of 1:15, weigh the self-healing glass oxygen barrier layer solid phase powder, the mass percentage of which is 40% silicon dioxide, 5% aluminum oxide, 45% boron carbide, 5% titanium dioxide, and 5% aluminum powder; according to the mass ratio of bentonite to sealing layer solid phase powder of 1:6, weigh the sealing layer solid phase powder, the mass percentage of which is 60% silicon dioxide, 5% aluminum oxide, 10% boron carbide, 15% boron oxide, 5% titanium dioxide, and 5% aluminum powder; according to the mass ratio of bentonite to high temperature and corrosion resistant ceramic layer solid phase powder of 1:12, weigh the high temperature and corrosion resistant ceramic layer solid phase powder, the mass percentage of which is 5% silicon dioxide, 80% aluminum oxide, 5% boric acid, 5% titanium dioxide, and 5% aluminum powder; the solid phase powders of each coating are mixed evenly to obtain their own solid phase mixtures for use.

(6) Calcination of the composite coating: The carbon anode after the coating is cured is heated to 750°C at a rate of 5°C/min and kept at this temperature for 4 h to obtain the composite coating, as shown in FIG1 .

Antioxidation performance test: the temperature was raised from room temperature to 900℃ at a rate of 5℃/min, kept at 900℃ for 24h, then cooled with the furnace, taken out and weighed, and repeated 3 times to calculate the average value. After weighing, the constant temperature oxidation at 900℃ was continued, and the total oxidation time accumulated was 96h. The test data obtained is shown in curve 4 of Figure 1. The weight loss rate of the carbon anode coated with the composite coating after 96h oxidation was only 0.52%.

As shown in Figure 3, d1 and d2 are the macroscopic morphology of the composite coating after drying and 96h oxidation, respectively. The cracks in the coating can heal by themselves at high temperature and the coating remains intact after 96h oxidation.

After the slurry is dried and calcined, the obtained composite coating and oxygen barrier layer are analyzed by X-ray diffraction test (XRD), and the obtained data are shown in Figures 4, 5 and Curve 4 in Figure 6. After calcination, the oxygen barrier layer forms an amorphous glass layer, which can effectively prevent oxygen from entering and reacting with the carbon anode. The phase of the composite coating remains stable after oxidation for 96 hours.

The surface morphology of the oxygen barrier layer after calcination was observed using a scanning electron microscope (SEM), as shown in Figure 7d. The coating is dense and continuous without holes or cracks.

The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or simple replacements that are not conceived through creative work should be included in the protection scope of the present invention.

Claims (3)

1. The preparation method of the self-healing high-oxygen-resistance high-temperature oxidation-prevention composite coating of the aluminum electrolysis carbon anode comprises the following steps:

(1) Preparation of liquid phase binder: according to the mass ratio of 1:1:1:45, respectively weighing water glass, polyvinyl alcohol, bentonite and deionized water, carrying out ultrasonic treatment on the water glass, the polyvinyl alcohol and the bentonite, uniformly stirring to obtain a mixture, and then mixing the mixture with the deionized water under the condition that the magnetic stirring rate is 400 rpm, and keeping mechanical stirring for 1h to obtain a liquid-phase binder;

(2) Mixing solid phase powder: according to the mass ratio of bentonite to silicon carbide of 1:15, weighing silicon carbide to obtain solid phase powder of the bonding transition layer; according to the mass ratio of bentonite to self-healing glass oxygen barrier solid phase powder of 1:15, weighing solid phase powder of the self-healing glass oxygen barrier layer, wherein the solid phase powder comprises the following components in percentage by mass of 35% of silicon dioxide, 5% of aluminum oxide, 50% of boron carbide, 5% of titanium dioxide and 5% of aluminum powder; according to the mass ratio of bentonite to solid phase powder of the sealing layer of 1:6, weighing solid phase powder of the sealing and filling layer, wherein the solid phase powder comprises 55 mass percent of silicon dioxide, 20 mass percent of aluminum oxide, 10 mass percent of boron carbide, 5 mass percent of titanium dioxide and 10 mass percent of aluminum powder; according to the mass ratio of bentonite to the solid phase powder of the high temperature resistant and corrosion resistant ceramic layer of 1:12, weighing solid phase powder of the high temperature resistant and corrosion resistant ceramic layer, wherein the solid phase powder comprises the following components in percentage by mass of 5% of silicon dioxide, 80% of aluminum oxide, 5% of boric acid, 5% of titanium dioxide and 5% of aluminum powder; uniformly mixing the solid phase powder of each coating to obtain respective solid phase mixture for standby;

(3) Preparation of the slurry: uniformly dispersing solid mixtures of different coatings in respective liquid phase binders by adopting a magnetic stirrer, wherein the magnetic stirring speed is 500 rpm, and the stirring time is 2 hours, so as to obtain slurry of each layer of coating;

(4) Coating of a composite coating: coating the slurry of the bonding transition layer on the surface of the carbon anode by adopting a slurry brush plating method, and drying in an oven at 80 ℃ for 2 hours to obtain the bonding transition layer; coating the slurry of the self-healing glass oxygen barrier layer on the surface of the carbon anode with the bonding transition layer by adopting a slurry brush plating method, and drying in an oven at 80 ℃ for 2 hours to obtain the self-healing glass oxygen barrier layer; coating the sealing layer slurry on the surface of a carbon anode with a bonding transition layer and a self-healing glass oxygen barrier layer by adopting a slurry brush plating method, and drying in an oven at 80 ℃ for 2 hours to obtain a sealing layer; coating the slurry of the high-temperature-resistant and corrosion-resistant ceramic layer on the surface of the carbon anode with the bonding transition layer, the self-healing glass oxygen-blocking layer and the sealing layer by adopting a slurry brush plating method, and drying in an oven at 80 ℃ for 2 hours to obtain the high-temperature-resistant and corrosion-resistant ceramic layer;

(5) Drying of the composite coating: continuously drying the composite coating in a drying oven at 120 ℃ for 10 hours;

(6) Roasting the composite coating: and heating the carbon anode with the dried coating to 700 ℃ at a speed of 5 ℃/min, and preserving the heat for 4 hours to obtain the composite coating.

2. The preparation method of the self-healing high-oxygen-resistance high-temperature oxidation-prevention composite coating of the aluminum electrolysis carbon anode comprises the following steps:

(1) Preparation of liquid phase binder: according to the mass ratio of 1:1:1:45, respectively weighing water glass, methylcellulose, bentonite and deionized water, carrying out ultrasonic treatment on the water glass, the methylcellulose and the bentonite, uniformly stirring to obtain a mixture, and then mixing the mixture with the deionized water under the condition that the magnetic stirring rate is 300 rpm, and keeping mechanical stirring for 1h to obtain a liquid-phase binder;

(2) Mixing solid phase powder: according to the mass ratio of bentonite to silicon carbide of 1:15, weighing silicon carbide to obtain solid phase powder of the bonding transition layer; according to the mass ratio of bentonite to self-healing glass oxygen barrier solid phase powder of 1:15, weighing solid phase powder of the self-healing glass oxygen barrier layer, wherein the solid phase powder comprises the following components in percentage by mass of 35% of silicon dioxide, 5% of aluminum oxide, 50% of boron carbide, 5% of titanium dioxide and 5% of aluminum powder; according to the mass ratio of bentonite to solid phase powder of the sealing layer of 1:6, weighing solid phase powder of the sealing and filling layer, wherein the solid phase powder comprises 65 mass percent of silicon dioxide, 10 mass percent of aluminum oxide, 15 mass percent of boron carbide, 5 mass percent of titanium dioxide and 5 mass percent of aluminum powder; according to the mass ratio of bentonite to the solid phase powder of the high temperature resistant and corrosion resistant ceramic layer of 1:12, weighing solid phase powder of the high temperature resistant and corrosion resistant ceramic layer, wherein the solid phase powder comprises the following components in percentage by mass of 5% of silicon dioxide, 80% of aluminum oxide, 5% of boric acid, 5% of titanium dioxide and 5% of aluminum powder; uniformly mixing the solid phase powder of each coating to obtain respective solid phase mixture for standby;

(3) Preparation of the slurry: uniformly dispersing solid mixtures of different coatings in respective liquid phase binders by adopting a magnetic stirrer, wherein the magnetic stirring speed is 300 rpm, and the stirring time is 3 hours, so as to obtain slurry of each layer of coating;

(4) Coating of a composite coating: coating the slurry of the bonding transition layer on the surface of the carbon anode by adopting a slurry brush plating method, and drying in an oven at 70 ℃ for 1.5 hours to obtain the bonding transition layer; coating the slurry of the self-healing glass oxygen barrier layer on the surface of the carbon anode with the bonding transition layer by adopting a slurry brush plating method, and drying in an oven at 70 ℃ for 1.5 hours to obtain the self-healing glass oxygen barrier layer; coating the sealing layer slurry on the surface of a carbon anode with a bonding transition layer and a self-healing glass oxygen barrier layer by adopting a slurry brush plating method, and drying in an oven at 70 ℃ for 1.5 hours to obtain a sealing layer; coating the slurry of the high-temperature-resistant and corrosion-resistant ceramic layer on the surface of the carbon anode with the bonding transition layer, the self-healing glass oxygen-blocking layer and the sealing layer by adopting a slurry brush plating method, and drying in an oven at 70 ℃ for 1.5 hours to obtain the high-temperature-resistant and corrosion-resistant ceramic layer;

(5) Drying of the composite coating: continuously drying the composite coating in a drying oven at 120 ℃ for 8 hours;

(6) Roasting the composite coating: and heating the carbon anode after the coating is solidified to 800 ℃ at a speed of 5 ℃/min, and preserving heat for 3 hours to obtain the composite coating.

3. The preparation method of the self-healing high-oxygen-resistance high-temperature oxidation-prevention composite coating of the aluminum electrolysis carbon anode comprises the following steps:

(1) Preparation of liquid phase binder: according to the mass ratio of 1:1:1:45, respectively weighing water glass, a silane coupling agent, bentonite and deionized water, carrying out ultrasonic treatment on the water glass, the silane coupling agent and the bentonite, uniformly stirring to obtain a mixture, and then mixing the mixture with the deionized water under the condition that the magnetic stirring rate is 400 rpm, and keeping mechanical stirring for 0.5h to obtain a liquid-phase binder;

(2) Mixing solid phase powder: according to the mass ratio of bentonite to silicon carbide of 1:15, weighing silicon carbide to obtain solid phase powder of the bonding transition layer; according to the mass ratio of bentonite to self-healing glass oxygen barrier solid phase powder of 1:15, weighing solid phase powder of the self-healing glass oxygen barrier layer, wherein the solid phase powder comprises the following components in percentage by mass of 35% of silicon dioxide, 5% of aluminum oxide, 50% of boron carbide, 5% of titanium dioxide and 5% of aluminum powder; according to the mass ratio of bentonite to solid phase powder of the sealing layer of 1:6, weighing solid phase powder of the sealing layer, wherein the solid phase powder comprises 60 mass percent of silicon dioxide, 10 mass percent of aluminum oxide, 15 mass percent of boron carbide, 5 mass percent of calcium oxide, 5 mass percent of titanium dioxide and 5 mass percent of aluminum powder; according to the mass ratio of bentonite to the solid phase powder of the high temperature resistant and corrosion resistant ceramic layer of 1:12, weighing solid phase powder of the high temperature resistant and corrosion resistant ceramic layer, wherein the solid phase powder comprises the following components in percentage by mass of 5% of silicon dioxide, 80% of aluminum oxide, 5% of boric acid, 5% of titanium dioxide and 5% of aluminum powder; uniformly mixing the solid phase powder of each coating to obtain respective solid phase mixture for standby;

(3) Preparation of the slurry: uniformly dispersing solid mixtures of different coatings in respective liquid phase binders by adopting a magnetic stirrer, wherein the magnetic stirring speed is 400 rpm, and the stirring time is 2 hours, so as to obtain slurry of each layer of coating;

(4) Coating of a composite coating: coating the slurry of the bonding transition layer on the surface of the carbon anode by adopting a slurry brush plating method, and drying in an oven at 85 ℃ for 2 hours to obtain the bonding transition layer; coating the slurry of the self-healing glass oxygen barrier layer on the surface of the carbon anode with the bonding transition layer by adopting a slurry brush plating method, and drying in an oven at 85 ℃ for 2 hours to obtain the self-healing glass oxygen barrier layer; coating the sealing layer slurry on the surface of a carbon anode with a bonding transition layer and a self-healing glass oxygen barrier layer by adopting a slurry brush plating method, and drying in an oven at 85 ℃ for 2 hours to obtain a sealing layer; coating the slurry of the high-temperature-resistant and corrosion-resistant ceramic layer on the surface of the carbon anode with the bonding transition layer, the self-healing glass oxygen-blocking layer and the sealing layer by adopting a slurry brush plating method, and drying in an oven at 85 ℃ for 2 hours to obtain the high-temperature-resistant and corrosion-resistant ceramic layer;

(5) Drying of the composite coating: continuously drying the composite coating in a drying oven at 120 ℃ for 12 hours;

(6) Roasting the composite coating: and heating the carbon anode after the coating is solidified to 850 ℃ at a speed of 5 ℃/min, and preserving heat for 4 hours to obtain the composite coating.