Magnesia carbon brick based on rare earth modification and preparation method thereof

Abstract

The invention relates to the technical field of refractory materials, in particular to a magnesia carbon brick based on rare earth modification and a preparation method of the magnesia carbon brick, which are used for solving the problems of poor corrosion resistance and flexural strength of the existing magnesia carbon brick at high temperature, and by matching multi-stage particles and fine powder, close packing is realized, the volume density and normal-temperature strength of a brick body are improved, and the service life of the brick body is prolonged. The porosity is reduced, and erosion of alkaline slag can be effectively resisted; the additive is added, so that the toughness, stripping resistance and high-temperature breaking strength of the material are improved; the carbon source provides excellent thermal shock resistance and non-wettability, and the microcosmic toughness of the material is improved; the rare earth oxide forms a compact and high-viscosity protective layer on the surface of the brick body, so that the corrosion resistance, the high-temperature breaking strength and the stability are improved; the antioxidant provides gradient protection; the thermal shock resistance, the mechanical shock resistance and the erosion resistance of the material are improved by adding the adhesive; the paint forms a coating on the surface of a green brick, and corrosion resistance is improved.

Description

Technical Field

[0001] This invention relates to the field of refractory materials technology, specifically to a rare earth-modified magnesia-carbon brick and its preparation method. Background Technology

[0002] In the field of refractory materials, magnesia-carbon bricks are widely used due to their excellent high-temperature resistance and good oxidation resistance, especially in the steel industry. Magnesia-carbon bricks are usually made by mixing magnesia and graphite in a certain proportion and adding an appropriate amount of binder. The use of this type of brick ensures good thermal stability and improves its mechanical strength in high-temperature environments.

[0003] However, magnesia-carbon bricks also have some shortcomings in practical applications. For example, they have poor corrosion resistance at high temperatures, and carbonaceous materials are prone to volatilization at high temperatures. When used in high-temperature and corrosive environments for a long time, their strength is prone to decrease. This not only affects the performance but also increases maintenance costs, thus affecting the performance and service life of magnesia-carbon bricks.

[0004] Therefore, this invention provides a rare earth-modified magnesia-carbon brick and its preparation method, aiming to optimize material performance through reasonable processes and technologies, which is of great significance to the field of refractory materials. Summary of the Invention

[0005] In order to overcome the above-mentioned technical problems, the purpose of this invention is to provide a rare earth-modified magnesia-carbon brick and its preparation method: solving the problems of poor corrosion resistance and flexural strength of existing magnesia-carbon bricks at high temperatures.

[0006] The objective of this invention can be achieved through the following technical solutions: In a first aspect, this application provides a rare earth-modified magnesia-carbon brick, comprising the following components by weight: The mixture contains 70-80 parts of fused magnesia granules, 5-10 parts of fused magnesia fine powder, 15-20 parts of carbon source, 1-3 parts of rare earth oxides, 5-10 parts of coating, 2-5 parts of additives, 2-5 parts of antioxidant, 0.1-0.5 parts of catalyst, and 4-6 parts of binder. The fused magnesia particles include fused magnesia particles of four different sizes: 3-5mm, 1-3mm, ≤1mm, and ≤0.075mm, with a mass ratio of 15-25g:30-35g:15-20g:10-15g.

[0007] In a preferred embodiment of the present invention, the particle size of the fused magnesia fine powder is 1-2 μm.

[0008] In a preferred embodiment of the present invention, the carbon source is one or more of the following: modified coal tar pitch and graphite, semi-reinforcing furnace black, general-purpose furnace black, spray carbon black, high abrasion resistant furnace black, fast-pressed furnace black, flake graphite, and petroleum pitch.

[0009] In a preferred embodiment of the present invention, the rare earth oxide is one or more of the following: La2O3, Nd2O3, Sc2O3, Sm2O3, HfO2, Y2O3, and CeO2, with a particle size <0.088 mm.

[0010] In a preferred embodiment of the present invention, the coating is prepared by mixing and stirring deionized water and Y2O3 powder with a particle size of 32-36μm in a ratio of 10mL:90g.

[0011] In a preferred embodiment of the present invention, the antioxidant is one or more of Si powder, Al powder, B4C and ZrB2.

[0012] In a preferred embodiment of the present invention, the catalyst is one of nano-metal powder and metal salt; the nano-metal powder is one of Co powder, Ni powder and Fe powder; the metal salt is one of Co(NO3)2•6H2O, Ni(NO3)2•6H2O and Fe(NO3)3•9H2O.

[0013] In a preferred embodiment of the present invention, the additive is prepared by the following steps: Step a1: Phenol, plant polyphenols, rare earth metal compounds, sodium hydroxide, and deionized water were added to a three-necked flask equipped with a stirrer and thermometer. The mixture was stirred in a 45°C water bath for 20-30 min, then heated to 55-70°C. Formaldehyde solution was added, and the reaction was allowed to proceed for 20-30 min. The temperature was then raised to 90°C, and the mixture was refluxed for 1 h. Methylphenyl dimethoxysilane was added, and the reaction was continued at 90°C for 1 h. The mixture was then transferred to a 70°C, 0.1 MPa vacuum drying oven for reduced pressure concentration. Anhydrous ethanol was added, and the mixture was stirred for 30 min to obtain the precursor. Step a2: Add magnesium powder, tetrahydrofuran, and chlorotrimethoxysilane to a three-necked flask equipped with a stirrer and thermometer. Purge with nitrogen and mix and stir for 30 min in an ice-water bath at 0-5℃. Add (4-bromophenylethynyl)trimethylsilane and react for 24 h in a water bath at 45℃ in the dark. Centrifuge and retain the supernatant. Extract with n-pentane and rotary evaporate at 45℃ to obtain the intermediate product. Add KOH and anhydrous methanol to a beaker and mix and stir for 30 min. Add the intermediate product and react for 12 h in the dark at 25℃. Centrifuge and extract the supernatant with n-pentane. Rotary evaporate at 40℃ and wash with n-hexane 2-3 times to obtain the modifier. Step a3: Place the alumina fiber in a constant temperature drying oven at 150℃ and dry for 5 hours, then allow it to cool naturally to 25℃. Add the modifier, tetrahydrofuran, methanol, n-pentane, and N,N-dimethylformamide to a three-necked flask equipped with a stirrer and thermometer, mix and stir for 15 minutes, then immerse the alumina fiber in the flask and seal for 1 hour. Remove the fiber. Add the silaneyne resin and acetone to a beaker and mix and stir for 15 minutes. Immerse the impregnated alumina fiber in the beaker for 5-10 minutes, then remove the solvent using a vacuum drying oven at 45℃ to obtain the alumina fiber preform. Step a4: Place the alumina fiber preform in a mold, and impregnate the alumina fiber preform with the precursor using vacuum-assisted impregnation technology. Let it stand for 5-10 minutes, and then use a programmed curing process. First, keep it at 90℃ for 1 hour, then raise the temperature to 120℃ and keep it at 1 hour, then raise the temperature to 150℃ and keep it at 2 hours, and finally raise the temperature to 180℃ and cure for 2 hours. Transfer it to a forced-air drying oven at 40-60℃ and keep it at that temperature for 24-48 hours, then raise the temperature to 80-100℃ and keep it at that temperature for 12-24 hours. Let it cool naturally to 25℃, then grind it in a mortar for 1-2 hours. Finally, sieve it through a 325-mesh sieve to obtain the additive.

[0014] In a preferred embodiment of the present invention, the ratio of phenol, plant polyphenol, rare earth metal compound, sodium hydroxide, deionized water, formaldehyde solution, methylphenyldimethoxysilane, and anhydrous ethanol in step a1 is 90-100g: 10-30g: 5-15g: 9-10g: 500-600mL: 200-300mL: 15-30mL: 100-200mL; the plant polyphenol is one of lignin, tannin, and cashew nut shell oil; the rare earth metal compound is one of DyCl3, LaCl3, and Eu(NO3)3; and the formaldehyde solution has a mass fraction of 37%.

[0015] In a preferred embodiment of the present invention, the ratio of magnesium powder, tetrahydrofuran, chlorotrimethoxysilane, (4-bromophenylethynyl)trimethylsilane, KOH and anhydrous methanol in step a2 is 0.3-0.5g: 10-20mL: 10-15mL: 2-3g: 0.5-1g: 10-15mL.

[0016] In a preferred embodiment of the present invention, the ratio of alumina fiber, modifier, tetrahydrofuran, methanol, n-pentane, N,N-dimethylformamide, silaneyne resin and acetone in step a3 is 10g:1-3g:50mL:50-100mL:50-100mL:50-100mL:5-15g:50-100mL.

[0017] In a preferred embodiment of the present invention, the ratio of the alumina fiber preform to the precursor in step a4 is 10g:300-500mL.

[0018] In a preferred embodiment of the present invention, the modified coal tar pitch is prepared by the following steps: Coal tar pitch and composite modifier are added to a three-necked flask equipped with a stirrer, thermometer, condenser, and heating mantle. The heating mantle is turned on, and the temperature is raised to 80-90°C at a rate of 5-10°C / min. The temperature is maintained and the mixture is stirred at 100-200 r / min for 1-2 hours. The temperature is then raised to 100°C, and the mixture is stirred at 300-500 r / min for 30 minutes. The temperature is then raised to 150°C at a rate of 2°C / min, and the mixture is kept at a constant temperature for 1 hour. The mixture is then allowed to cool naturally to 25°C. Phenolic resin is added, and the temperature is raised to 100°C. The mixture is stirred for 30 minutes, and the temperature is raised to 180°C at a rate of 5°C / min. The mixture is kept at a constant temperature for 1 hour, and the mixture is allowed to cool naturally to 25°C to obtain modified coal tar pitch.

[0019] In a preferred embodiment of the present invention, the ratio of coal tar pitch, composite modifier, and phenolic resin is 80-100g: 5-15g: 10g; the composite modifier is obtained by mixing polyethylene glycol PEG-800, divinylbenzene, and polystyrene GR1551 in a ratio of 1-5g: 1-6mL: 1-3g; and the phenolic resin is of type P83190.

[0020] In a preferred embodiment of the present invention, the adhesive is prepared by the following steps: Phenol, Tween-80, silicone oil, formaldehyde solution, and molybdic acid were added to a three-necked flask equipped with a stirrer and thermometer. The mixture was stirred at 40-50°C for 30 minutes. A catalyst was added, and the mixture was heated to 80-100°C and refluxed for 2-4 hours. The pH was adjusted to 7 with sodium carbonate solution. Carboxylated nitrile latex was added, and the mixture was stirred for 10-15 minutes. The mixture was then dehydrated under vacuum at 60-90°C and 0.08-0.09 MPa. Ethylene glycol was added, and the mixture was stirred for 30 minutes to obtain the binder.

[0021] In a preferred embodiment of the present invention, the ratio of phenol, Tween-80, silicone oil, formaldehyde solution, molybdic acid, catalyst, carboxylated nitrile latex, and ethylene glycol is 100g:1g:75mL:75-100mL:3g:1-3mL:15-20mL:10-20mL; the catalyst is concentrated hydrochloric acid with a mass fraction of 37%; the formaldehyde solution has a mass fraction of 37%; and the sodium carbonate solution has a mass fraction of 10%.

[0022] Secondly, this application provides a method for preparing rare earth-modified magnesia-carbon bricks, comprising the following steps: Step 1: Weigh out the following components by weight: 70-80 parts of fused magnesia granules, 5-10 parts of fused magnesia fine powder, 15-20 parts of carbon source, 1-3 parts of rare earth oxides, 5-10 parts of coating, 2-5 parts of additives, 2-5 parts of antioxidant, 0.1-0.5 parts of catalyst, 0.1-0.5 parts of hexamethylenetetramine, 5 parts of ethylene glycol, 5 parts of anhydrous ethanol, and 4-6 parts of binder. Step 2: Mix fused magnesia particles, additives, and antioxidants for 3-5 minutes, wet with a mixture of ethylene glycol and anhydrous ethanol, mix for another 3-5 minutes, add rare earth oxides, fused magnesia fine powder, carbon source, catalyst, hexamethylenetetramine, and binder, mix for 5-10 minutes, transfer to a tablet press with a pressure of 150-250 MPa, press and shape, hold pressure for 2-5 minutes, after pressing and shape, dip into the coating, dry at 40-60℃ for 1-2 hours, place in a muffle furnace, heat to 200-600℃ at a heating rate of 3-5℃ / min, hold for 1 hour, continue heating to 800-1000℃, hold for 1 hour, continue heating to 1550℃, hold for 2 hours, and naturally cool to 25℃ to obtain rare earth modified magnesia-carbon bricks.

[0023] The beneficial effects of this invention are: This invention discloses a rare-earth-modified magnesia-carbon brick and its preparation method. The method involves mixing fused magnesia particles, additives, and antioxidants, wetting them with a mixture of ethylene glycol and anhydrous ethanol, mixing again, adding rare-earth oxides, fine fused magnesia powder, a carbon source, a catalyst, hexamethylenetetramine, and a binder, mixing again, transferring the mixture to a tablet press for molding, then coating it with a coating material, drying it, and finally heat-treating it in a muffle furnace with carbon embedded in the surface. After cooling, the resulting rare-earth-modified magnesia-carbon brick is obtained. The use of multi-level particles and fine powder achieves close packing, increasing the brick's bulk density and room-temperature strength, while reducing porosity, effectively resisting the erosion of alkaline slag. Additives are added to improve the toughness, anti-stripping properties, and high-temperature flexural strength of the material; carbon sources provide excellent thermal shock resistance and non-wetting properties, improving the microscopic toughness of the material; rare earth oxides form a dense, high-viscosity protective layer on the surface of the brick, improving corrosion resistance, high-temperature flexural strength, and stability; antioxidants provide gradient protection; catalysts are added to generate carbon nanotubes in situ, improving the high-temperature mechanical properties of magnesia-carbon bricks; binders are added to improve the thermal shock resistance, mechanical impact resistance, and erosion resistance of the material; coatings form a dense, high-melting-point yttrium oxide coating on the surface of the brick blank, directly contacting the slag and delaying the erosion of the brick body by the slag.

[0024] In the preparation of rare earth-modified magnesium-carbon bricks, additives were first prepared. Phenol and formaldehyde reacted under the alkaline catalyst NaOH to generate hydroxymethylphenol. Plant polyphenols contain multiple phenolic hydroxyl groups and benzene rings, which react with multiple formaldehyde molecules, introducing higher cross-linking points into the phenolic resin network, making the three-dimensional resin network more dense and robust. Hydroxymethylphenols underwent a condensation reaction to form phenolic resin. The added methylphenyl dimethoxysilane hydrolyzed to generate silanol, which underwent a co-condensation reaction with the phenolic hydroxyl groups on the phenolic resin chain to form Si-OC covalent bonds. Silanols also self-condensed to form a Si-O-Si network. Rare earth metal compounds... Encased in a polymer network, the Si-O bonds exhibit extremely high chemical and thermal stability, effectively resisting the chemical erosion of molten slag. The integrated rare earth elements transform into high-melting-point rare earth oxides at high temperatures or react with molten slag to form high-melting-point rare earth silicates, forming a dense barrier layer on the material surface and delaying slag penetration and erosion. Magnesium powder undergoes a Grignard reaction with chlorotrimethoxysilane to generate a Grignard reagent, which then undergoes nucleophilic addition with (4-bromophenylethynyl)trimethylsilane, attaching the trimethoxysilane group to the phenylethynyl backbone. Under the action of KOH / methanol, the terminal trimethylsilane protecting group is removed, yielding the modifier. Its methoxysilane end can hydrolyze and form a strong Si-O-Al covalent bond with the hydroxyl groups on the surface of alumina fibers. The highly reactive phenylacetylene group at the other end can undergo a co-crosslinking reaction with silanarylene resin and precursor resin under curing and high temperature conditions, improving the toughness of the composite material and preventing brittle fracture. Through physical impregnation and solvent evaporation processes, the modifier chemically bonds to the fiber surface. Alumina fibers, as the skeleton of the preform, possess extremely high high-temperature flexural strength and modulus. The modifier treatment ensures a strong chemical bond between the fiber and the matrix. Further bonding occurs between the precursor and silanarylene resin during the stepped temperature curing process. The cross-linking reaction forms a highly cross-linked three-dimensional network structure. The programmed drying process removes the solvent while shrinking and strengthening the network structure. Phenolic resin, silane-modified inorganic network, and silaneyne resin are cured together to form an organic-inorganic interpenetrating network. After high-temperature carbonization, a multiphase composite material composed of nano-carbon, SiC, rare earth oxides, and alumina fibers is generated. Alumina fibers act as a reinforcing skeleton, providing the main load-bearing and toughening effects. SiC and nano-carbon fill the spaces between the fibers, serving as a strong and tough matrix that provides extremely high high-temperature flexural strength and hardness. The rare earth phase is dispersed in the matrix, improving the material's corrosion resistance.

[0025] In the preparation of rare-earth modified magnesia-carbon bricks, modified coal tar pitch was first prepared. Polyethylene glycol (PEG) mainly served as a compatibilizer and plasticizer; its long-chain ether structure interspersed between the macromolecules of coal tar pitch, improving the mixing uniformity of the components. Divinylbenzene, containing two unsaturated double bonds, formed a robust three-dimensional cross-linked network between the aromatic macromolecules of coal tar pitch through free radical polymerization under heating conditions, transforming the thermoplastic coal tar pitch into a thermosetting resin. This prevented it from melting and flowing during subsequent carbonization, allowing it to maintain its shape and improving the residual carbon rate. Polystyrene, as a polymer blending modifier, has a benzene ring structure that has good compatibility with coal tar pitch, enabling physical blending and... It can undergo grafting reactions, increasing the molecular weight and viscosity of the system and strengthening the three-dimensional network. The added phenolic resin is a thermosetting resin with high residual carbon. During the heating process, the phenolic resin itself is further cross-linked and cured. Its molecular chains interpenetrate with the coal tar pitch network that has been cross-linked with divinylbenzene. After modification, the resulting coal tar pitch has a higher residual carbon rate and optimized carbon structure when used as a binder and carbon source for magnesia-carbon bricks, forming a continuous and stable carbon skeleton. The modified carbon structure is more compact and has fewer pores, which physically hinders the inward diffusion of oxygen and makes it less susceptible to oxidation. The strengthened carbon network can more effectively block the penetration of molten slag and improve corrosion resistance.

[0026] In the preparation of rare-earth-modified magnesia-carbon bricks, a binder was first prepared. Phenol and formaldehyde under the action of concentrated hydrochloric acid underwent an electrophilic substitution condensation reaction to generate thermoplastic phenolic resin. In an acidic reaction environment, molybdate ions coordinated with the phenolic hydroxyl groups of the phenolic resin, introducing molybdenum into the molecular structure of the resin. After neutralizing the reaction system, carboxyl-based nitrile rubber latex was added. The carboxyl-based nitrile rubber particles in the latex and the phenolic resin formed a physical blend under stirring. Under vacuum dehydration and heat treatment, the hydroxymethyl groups of the phenolic resin and the carboxyl groups on the nitrile rubber chains underwent an esterification reaction to form chemical bonds. Ethylene glycol was used as a diluent and stabilizer to prevent resin crystallization and adjust the viscosity of the binder. After carbonization in the magnesia-carbon bricks, this binder formed a high-performance... The carbon-bonded phase, a high-strength carbon network catalyzed by molybdate, possesses higher strength and modulus, improving high-temperature flexural strength. After high-temperature carbonization, carboxylated nitrile rubber leaves behind carbonized residues with good toughness and high strength, which can effectively bridge and passivate microcracks. Through the "pull-out effect," it consumes the energy of crack propagation, thereby endowing the carbon-bonded phase with excellent toughness and significantly improving the material's thermal shock resistance and mechanical impact resistance. The introduced molybdenum element will be converted into molybdenum oxide at high temperatures. In the reducing atmosphere of magnesia-carbon bricks and in the presence of carbon and metal additives, it reacts to generate high-melting-point molybdenum carbide or molybdenum borides and silicides, which have extremely high hardness, melting point, and chemical inertness. Dispersed in the carbon-bonded phase, it can greatly hinder the penetration and erosion of slag, thereby improving corrosion resistance. Attached Figure Description

[0027] The invention will now be further described with reference to the accompanying drawings.

[0028] Figure 1 This is a schematic diagram showing the corrosion resistance test results of rare earth modified magnesia-carbon bricks in Examples 1-3 and Comparative Examples 1-3 of this invention.

[0029] Figure 2 This is a schematic diagram showing the high-temperature flexural strength test results of rare earth modified magnesia-carbon bricks in Examples 1-3 and Comparative Examples 1-3 of this invention. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1: This embodiment describes a method for preparing rare earth-modified magnesia-carbon bricks, including the following steps: Step S1: Add 90g phenol, 10g tannin, 5g DyCl3, 9g sodium hydroxide and 500mL deionized water to a three-necked flask equipped with a stirrer and thermometer. Mix and stir in a 45℃ water bath for 20min. Raise the temperature to 55℃, add 200mL of 37% formaldehyde solution, react for 20min, raise the temperature to 90℃, reflux for 1h, add 15mL of methylphenyldimethoxysilane, and continue to react at 90℃ for 1h. Transfer to a 70℃, 0.1MPa vacuum drying oven for reduced pressure concentration, add 100mL of anhydrous ethanol, mix and stir for 30min to obtain the precursor. Step S2: Add 0.3g magnesium powder, 10mL tetrahydrofuran, and 10mL trichlorotrimethoxysilane to a three-necked flask equipped with a stirrer and thermometer. Purge with nitrogen and mix and stir for 30min in an ice-water bath at 0℃. Add 2g (4-bromophenylethynyl)trimethylsilane and react for 24h in a water bath at 45℃ in the dark. Centrifuge and retain the supernatant. Extract with n-pentane and rotary evaporate at 45℃ to obtain the intermediate product. Add 0.5g KOH and 15mL anhydrous methanol to a beaker and mix and stir for 30min. Add the intermediate product and react for 12h in the dark at 25℃. Centrifuge and extract the supernatant with n-pentane. Rotary evaporate at 40℃ and wash three times with n-hexane to obtain the modifier. Step S3: Place 10g of alumina fiber in a constant temperature drying oven at 150℃ and dry for 5 hours, then allow it to cool naturally to 25℃. Add 1g of modifier, 50mL of tetrahydrofuran, 50mL of methanol, 50mL of n-pentane, and 50mL of N,N-dimethylformamide to a three-necked flask equipped with a stirrer and thermometer, mix and stir for 15 minutes, then immerse the alumina fiber in the flask and seal for 1 hour before removing it. Add 5g of silaneyne resin and 50mL of acetone to a beaker, mix and stir for 15 minutes, then immerse the impregnated alumina fiber in the beaker for 5 minutes. Remove the solvent using a vacuum drying oven at 45℃ to obtain the alumina fiber preform. Step S4: Place 10g of alumina fiber preform into a mold, use vacuum-assisted impregnation technology, impregnate the alumina fiber preform with 300mL of precursor, let stand for 5min, use programmed curing, first keep at 90℃ for 1h, raise the temperature to 120℃ and keep for 1h, raise the temperature to 150℃ and keep for 2h, finally raise the temperature to 180℃ and cure for 2h, transfer to a 40℃ forced-air drying oven, keep at 40℃ for 24h, raise the temperature to 80℃ and keep for 12h, cool naturally to 25℃, grind in a mortar for 1h, and sieve through a 325 mesh sieve to obtain the additive; Step S5: Add 80g of coal tar pitch and 5g of composite modifier to a three-necked flask equipped with a stirrer, thermometer, condenser, and heating mantle. Turn on the heating mantle and heat to 80°C at a rate of 5°C / min. Stir at 100r / min for 1 hour at a constant temperature. Continue heating to 100°C and stir at 300r / min for 30 minutes. Heat to 150°C at a rate of 2°C / min and react at a constant temperature for 1 hour. Allow to cool naturally to 25°C. Add 10g of phenolic resin, heat to 100°C, mix and stir for 30 minutes. Heat to 180°C at a rate of 5°C / min and react at a constant temperature for 1 hour. Allow to cool naturally to 25°C to obtain modified coal tar pitch. The composite modifier is obtained by mixing polyethylene glycol PEG-800, divinylbenzene, and polystyrene GR1551 in a ratio of 1g:1mL:1g. Step S6: Add 100g phenol, 1mL Tween-80, 75mL silicone oil, 3g 37% formaldehyde solution and 1mL molybdic acid to a three-necked flask equipped with a stirrer and thermometer. Stir at 40℃ for 30min. Add 15mL 37% concentrated hydrochloric acid, heat to 80℃, reflux for 2h. Adjust the pH to 7 with 10% sodium carbonate solution. Add carboxylated nitrile latex, mix and stir for 10min. Dehydrate under vacuum at 60℃ and 0.08MPa. Add 10mL ethylene glycol, mix and stir for 30min to obtain the adhesive. Step S7: Weigh out 70 parts by weight of fused magnesia granules, 5 parts by weight of fused magnesia fine powder, 15 parts by weight of carbon source, 1 part by weight of La2O3 with a particle size <0.088mm, 5 parts by weight of coating, 2 parts by weight of additive, 2 parts by weight of Si powder, 0.1 parts by weight of Ni powder, 0.1 parts by weight of hexamethylenetetramine, 5 parts by weight of ethylene glycol, 5 parts by weight of anhydrous ethanol, and 4 parts by weight of binder; the fused magnesia granules include fused magnesia granules of three particle sizes, namely 3mm, ≤1mm and ≤0.075mm, with a mass ratio of 15g:45g:10g; the fused magnesia fine powder has a particle size of 1μm; the carbon source is a mixture of modified coal tar pitch and graphite in a mass ratio of 1g:3g; the coating is a mixture of deionized water and Y2O3 powder with a particle size of 32μm in a dosage ratio of 10g:90g. Step S8: Mix fused magnesia particles, additives, and antioxidants for 3 minutes, wet with a mixture of ethylene glycol and anhydrous ethanol, mix for another 3 minutes, add fused magnesia fine powder, carbon source, rare earth oxides, catalyst, hexamethylenetetramine, and binder, mix for 5 minutes, transfer to a 150MPa tablet press for pressing and molding, hold pressure for 2 minutes, after pressing and molding, dip into the coating, dry at 40℃ for 1 hour, place in a muffle furnace, heat to 200℃ at a heating rate of 3℃ / min, hold for 1 hour, continue heating to 800℃, hold for 1 hour, continue heating to 1550℃, hold for 2 hours, and naturally cool to 25℃ to obtain rare earth modified magnesia-carbon bricks.

[0032] Example 2: This embodiment describes a method for preparing rare earth-modified magnesia-carbon bricks, including the following steps: Step S1: Add 95g phenol, 20g tannin, 10g DyCl3, 9.5g sodium hydroxide and 550mL deionized water to a three-necked flask equipped with a stirrer and thermometer. Mix and stir in a 45℃ water bath for 25min. Raise the temperature to 60℃, add 250mL of 37% formaldehyde solution, react for 25min, raise the temperature to 90℃, reflux for 1h, add 25mL of methylphenyldimethoxysilane, and continue to react at 90℃ for 1h. Transfer to a 70℃, 0.1MPa vacuum drying oven for reduced pressure concentration, add 150mL of anhydrous ethanol, mix and stir for 30min to obtain the precursor. Step S2: Add 0.4g magnesium powder, 15mL tetrahydrofuran, and 13mL chlorotrimethoxysilane to a three-necked flask equipped with a stirrer and thermometer. Purge with nitrogen and mix and stir for 30min in an ice-water bath at 3℃. Add 2.5g (4-bromophenylethynyl)trimethylsilane and react for 24h in a water bath at 45℃ in the dark. Centrifuge and retain the supernatant. Extract with n-pentane and rotary evaporate at 45℃ to obtain the intermediate product. Add 0.8g KOH and 13mL anhydrous methanol to a beaker and mix and stir for 30min. Add the intermediate product and react for 12h in the dark at 25℃. Centrifuge and extract the supernatant with n-pentane. Rotary evaporate at 40℃ and wash three times with n-hexane to obtain the modifier. Step S3: Place 10g of alumina fiber in a constant temperature drying oven at 150℃ and dry for 5 hours, then allow it to cool naturally to 25℃. Add 2g of modifier, 50mL of tetrahydrofuran, 75mL of methanol, 75mL of n-pentane, and 75mL of N,N-dimethylformamide to a three-necked flask equipped with a stirrer and thermometer, mix and stir for 15 minutes, then immerse the alumina fiber in the flask, seal for 1 hour, and remove. Add 10g of silaneyne resin and 75mL of acetone to a beaker, mix and stir for 15 minutes, then immerse the impregnated alumina fiber in the beaker for 8 minutes. Remove the solvent using a vacuum drying oven at 45℃ to obtain the alumina fiber preform. Step S4: Place 10g of alumina fiber preform into a mold, use vacuum-assisted impregnation technology, impregnate the alumina fiber preform with 400mL of precursor, let stand for 8min, use programmed curing, first keep at 90℃ for 1h, raise the temperature to 120℃ and keep for 1h, raise the temperature to 150℃ and keep for 2h, finally raise the temperature to 180℃ and cure for 2h, transfer to a 50℃ forced-air drying oven, keep at 36h, raise the temperature to 90℃ and keep for 18h, cool naturally to 25℃, grind in a mortar for 1.5h, and sieve through a 325 mesh sieve to obtain the additive; Step S5: Add 90g of coal tar pitch and 10g of composite modifier to a three-necked flask equipped with a stirrer, thermometer, condenser, and heating mantle. Turn on the heating mantle and heat to 85°C at a rate of 8°C / min. Stir at 150r / min for 1.5h at a constant temperature. Continue heating to 100°C and stir at 400r / min for 30min. Heat to 150°C at a rate of 2°C / min and react at a constant temperature for 1h. Allow to cool naturally to 25°C. Add 10g of phenolic resin, heat to 100°C, mix and stir for 30min, heat to 180°C at a rate of 5°C / min, and react at a constant temperature for 1h. Allow to cool naturally to 25°C to obtain modified coal tar pitch. The composite modifier is obtained by mixing polyethylene glycol PEG-800, divinylbenzene, and polystyrene GR1551 in a ratio of 3g:3mL:2g. Step S6: Add 100g phenol, 1.5mL Tween-80, 85mL silicone oil, 3g 37% formaldehyde solution and 2mL molybdic acid to a three-necked flask equipped with a stirrer and thermometer. Stir at 45℃ for 30min. Add 18mL 37% concentrated hydrochloric acid, heat to 90℃, reflux for 3h. Adjust the pH to 7 with 10% sodium carbonate solution. Add carboxylated nitrile latex, mix and stir for 13min. Dehydrate under vacuum at 75℃ and 0.08MPa. Add 15mL ethylene glycol, mix and stir for 30min to obtain the adhesive. Step S7: Weigh out 75 parts by weight of fused magnesia granules, 8 parts by weight of fused magnesia fine powder, 18 parts by weight of carbon source, 2 parts by weight of La2O3 with a particle size <0.088mm, 8 parts by weight of coating, 3 parts by weight of additive, 3 parts by weight of Si powder, 0.3 parts by weight of Ni powder, 0.3 parts by weight of hexamethylenetetramine, 5 parts by weight of ethylene glycol, 5 parts by weight of anhydrous ethanol, and 5 parts by weight of binder; the fused magnesia granules include fused magnesia granules of four different sizes, namely 4mm, 2mm, ≤1mm and ≤0.075mm, with a mass ratio of 20g:33g:18g:13g; the fused magnesia fine powder has a particle size of 1.5μm; the carbon source is a mixture of modified coal tar pitch and graphite in a mass ratio of 2g:5g; the coating is a mixture of deionized water and Y2O3 powder with a particle size of 34μm in a dosage ratio of 10mL:90g. Step S8: Mix fused magnesia particles, additives, and antioxidants for 4 minutes, wet with a mixture of ethylene glycol and anhydrous ethanol, mix for another 4 minutes, add fused magnesia fine powder, carbon source, rare earth oxides, catalyst, hexamethylenetetramine, and binder, mix for 8 minutes, transfer to a 200MPa tablet press for pressing and molding, hold for 3 minutes, after pressing and molding, dip into a coating, dry at 50℃ for 1.5 hours, place in a muffle furnace, heat to 400℃ at a heating rate of 4℃ / min, hold for 1 hour, continue heating to 900℃, hold for 1 hour, continue heating to 1550℃, hold for 2 hours, and naturally cool to 25℃ to obtain rare earth modified magnesia-carbon bricks.

[0033] Example 3: This embodiment describes a method for preparing rare earth-modified magnesia-carbon bricks, including the following steps: Step S1: Add 100g phenol, 30g tannin, 15g DyCl3, 10g sodium hydroxide and 600mL deionized water to a three-necked flask equipped with a stirrer and thermometer. Mix and stir in a 45℃ water bath for 30min. Raise the temperature to 70℃, add 300mL of 37% formaldehyde solution, react for 30min, raise the temperature to 90℃, reflux for 1h, add 30mL of methylphenyldimethoxysilane, and continue to react at 90℃ for 1h. Transfer to a 70℃, 0.1MPa vacuum drying oven for reduced pressure concentration, add 200mL of anhydrous ethanol, mix and stir for 30min to obtain the precursor. Step S2: Add 0.5g magnesium powder, 20mL tetrahydrofuran, and 15mL chlorotrimethoxysilane to a three-necked flask equipped with a stirrer and thermometer. Purge with nitrogen and mix and stir for 30min in an ice-water bath at 5℃. Add 3g (4-bromophenylethynyl)trimethylsilane and react for 24h in a water bath at 45℃ in the dark. Centrifuge and retain the supernatant. Extract with n-pentane and rotary evaporate at 45℃ to obtain the intermediate product. Add 1g KOH and 15mL anhydrous methanol to a beaker and mix and stir for 30min. Add the intermediate product and react for 12h in the dark at 25℃. Centrifuge and extract the supernatant with n-pentane. Rotary evaporate at 40℃ and wash three times with n-hexane to obtain the modifier. Step S3: Place 10g of alumina fiber in a constant temperature drying oven at 150℃ and dry for 5 hours, then allow it to cool naturally to 25℃. Add 3g of modifier, 50mL of tetrahydrofuran, 100mL of methanol, 100mL of n-pentane, and 100mL of N,N-dimethylformamide to a three-necked flask equipped with a stirrer and thermometer, mix and stir for 15 minutes, then immerse the alumina fiber in the flask and seal for 1 hour. Remove the flask. Add 15g of silaneyne resin and 100mL of acetone to a beaker and mix and stir for 15 minutes. Immerse the impregnated alumina fiber in the beaker for 10 minutes, then remove the solvent using a vacuum drying oven at 45℃ to obtain the alumina fiber preform. Step S4: Place 10g of alumina fiber preform into a mold, use vacuum-assisted impregnation technology, impregnate the alumina fiber preform with 500mL of precursor, let stand for 10min, use programmed curing, first keep at 90℃ for 1h, raise the temperature to 120℃ and keep for 1h, raise the temperature to 150℃ and keep for 2h, finally raise the temperature to 180℃ and cure for 2h, transfer to a 60℃ forced-air drying oven, keep at 60℃ for 48h, raise the temperature to 100℃ and keep for 24h, cool naturally to 25℃, grind in a mortar for 2h, and sieve through a 325 mesh sieve to obtain the additive; Step S5: Add 100g of coal tar pitch and 15g of composite modifier to a three-necked flask equipped with a stirrer, thermometer, condenser, and heating mantle. Turn on the heating mantle and heat to 90°C at a rate of 10°C / min. Stir at 200r / min for 2 hours at a constant temperature. Continue heating to 100°C and stir at 500r / min for 30 minutes. Heat to 150°C at a rate of 2°C / min and react at a constant temperature for 1 hour. Allow to cool naturally to 25°C. Add 10g of phenolic resin, heat to 100°C, mix and stir for 30 minutes. Heat to 180°C at a rate of 5°C / min and react at a constant temperature for 1 hour. Allow to cool naturally to 25°C to obtain modified coal tar pitch. The composite modifier is obtained by mixing polyethylene glycol PEG-800, divinylbenzene, and polystyrene GR1551 in a ratio of 5g:6mL:3g. Step S6: Add 100g phenol, 2mL Tween-80, 100mL silicone oil, 3g 37% formaldehyde solution and 3mL molybdic acid to a three-necked flask equipped with a stirrer and thermometer. Stir at 50℃ for 30min. Add 20mL 37% concentrated hydrochloric acid, heat to 100℃ and reflux for 4h. Adjust the pH to 7 with 10% sodium carbonate solution. Add carboxylated nitrile latex and mix and stir for 15min. Dehydrate under vacuum at 90℃ and 0.09MPa. Add 20mL ethylene glycol and mix and stir for 30min to obtain the adhesive. Step S7: Weigh out 80 parts by weight of fused magnesia granules, 10 parts by weight of fused magnesia fine powder, 20 parts by weight of carbon source, 3 parts by weight of La2O3 with a particle size <0.088mm, 10 parts by weight of coating, 5 parts by weight of additive, 5 parts by weight of Si powder, 0.5 parts by weight of Ni powder, 0.5 parts by weight of hexamethylenetetramine, 5 parts by weight of ethylene glycol, 5 parts by weight of anhydrous ethanol, and 6 parts by weight of binder; the fused magnesia granules include fused magnesia granules of four different sizes, namely 5mm, 3mm, ≤1mm and ≤0.075mm, with a mass ratio of 25g:35g:20g:15g; the fused magnesia fine powder has a particle size of 2μm; the carbon source is a mixture of modified coal tar pitch and graphite in a mass ratio of 3g:6g; the coating is a mixture of deionized water and Y2O3 powder with a particle size of 36μm in a dosage ratio of 10mL:90g. Step S8: Mix fused magnesia particles, additives, and antioxidants for 5 minutes, wet with a mixture of ethylene glycol and anhydrous ethanol, mix for another 5 minutes, add fused magnesia fine powder, carbon source, rare earth oxides, catalyst, hexamethylenetetramine, and binder, mix for 10 minutes, transfer to a 250MPa tablet press and press into shape, hold pressure for 5 minutes, after pressing and coating, dry at 60℃ for 2 hours, place in a muffle furnace, heat to 600℃ at a heating rate of 5℃ / min, hold for 1 hour, continue heating to 1000℃, hold for 1 hour, continue heating to 1550℃, hold for 2 hours, and naturally cool to 25℃ to obtain rare earth modified magnesia-carbon bricks.

[0034] Comparative Example 1: This comparative example illustrates a method for preparing rare-earth modified magnesia-carbon bricks, comprising the following steps: Step S1: Weigh out 75 parts by weight of fused magnesia granules, 8 parts by weight of fused magnesia fine powder, 18 parts by weight of carbon source, 2 parts by weight of La2O3 with a particle size <0.088mm, 8 parts by weight of coating, 3 parts by weight of Si powder, 0.3 parts by weight of Ni powder, 0.3 parts by weight of hexamethylenetetramine, 5 parts by weight of ethylene glycol, 5 parts by weight of anhydrous ethanol, and 5 parts by weight of phenolic resin; the fused magnesia granules include fused magnesia granules of four different sizes, namely 4mm, 2mm, ≤1mm and ≤0.075mm, with a mass ratio of 20g:33g:18g:13g; the fused magnesia fine powder has a particle size of 1.5μm; the carbon source is a mixture of coal tar pitch and graphite in a mass ratio of 2g:5g; the coating is a mixture of deionized water and Y2O3 powder with a particle size of 34μm in a dosage ratio of 10mL:90g. Step S2: Mix fused magnesia particles and Si powder for 4 min, wet with a mixture of ethylene glycol and anhydrous ethanol, mix for another 4 min, add fused magnesia fine powder, carbon source, La2O3, Ni powder, hexamethylenetetramine and binder, mix for 8 min, transfer to a 200 MPa tablet press and press into shape, hold pressure for 3 min, after pressing and coating, dry at 50℃ for 1.5 h, put into a muffle furnace, heat to 400℃ at a heating rate of 4℃ / min, hold for 1 h, continue to heat to 900℃, hold for 1 h, continue to heat to 1550℃, hold for 2 h, and naturally cool to 25℃ to obtain rare earth modified magnesia-carbon bricks.

[0035] Comparative Example 2: This comparative example illustrates a method for preparing rare-earth modified magnesia-carbon bricks, comprising the following steps: Step S1: Add 95g phenol, 20g tannin, 10g DyCl3, 9.5g sodium hydroxide and 550mL deionized water to a three-necked flask equipped with a stirrer and thermometer. Mix and stir in a 45℃ water bath for 25min. Raise the temperature to 60℃, add 250mL of 37% formaldehyde solution, react for 25min, raise the temperature to 90℃, reflux for 1h, add 25mL of methylphenyldimethoxysilane, and continue to react at 90℃ for 1h. Transfer to a 70℃, 0.1MPa vacuum drying oven for reduced pressure concentration, add 150mL of anhydrous ethanol, mix and stir for 30min to obtain the precursor. Step S2: Add 0.4g magnesium powder, 15mL tetrahydrofuran, and 13mL chlorotrimethoxysilane to a three-necked flask equipped with a stirrer and thermometer. Purge with nitrogen and mix and stir for 30min in an ice-water bath at 3℃. Add 2.5g (4-bromophenylethynyl)trimethylsilane and react for 24h in a water bath at 45℃ in the dark. Centrifuge and retain the supernatant. Extract with n-pentane and rotary evaporate at 45℃ to obtain the intermediate product. Add 0.8g KOH and 13mL anhydrous methanol to a beaker and mix and stir for 30min. Add the intermediate product and react for 12h in the dark at 25℃. Centrifuge and extract the supernatant with n-pentane. Rotary evaporate at 40℃ and wash three times with n-hexane to obtain the modifier. Step S3: Place 10g of alumina fiber in a constant temperature drying oven at 150℃ and dry for 5 hours, then allow it to cool naturally to 25℃. Add 2g of modifier, 50mL of tetrahydrofuran, 75mL of methanol, 75mL of n-pentane, and 75mL of N,N-dimethylformamide to a three-necked flask equipped with a stirrer and thermometer, mix and stir for 15 minutes, then immerse the alumina fiber in the flask, seal for 1 hour, and remove. Add 10g of silaneyne resin and 75mL of acetone to a beaker, mix and stir for 15 minutes, then immerse the impregnated alumina fiber in the beaker for 8 minutes. Remove the solvent using a vacuum drying oven at 45℃ to obtain the alumina fiber preform. Step S4: Place 10g of alumina fiber preform into a mold, use vacuum-assisted impregnation technology, impregnate the alumina fiber preform with 400mL of precursor, let stand for 8min, use programmed curing, first keep at 90℃ for 1h, raise the temperature to 120℃ and keep for 1h, raise the temperature to 150℃ and keep for 2h, finally raise the temperature to 180℃ and cure for 2h, transfer to a 50℃ forced-air drying oven, keep at 36h, raise the temperature to 90℃ and keep for 18h, cool naturally to 25℃, grind in a mortar for 1.5h, and sieve through a 325 mesh sieve to obtain the additive; Step S5: Weigh out 75 parts by weight of fused magnesia granules, 8 parts by weight of fused magnesia fine powder, 18 parts by weight of carbon source, 2 parts by weight of La2O3 with a particle size <0.088mm, 8 parts by weight of coating, 3 parts by weight of additive, 3 parts by weight of Si powder, 0.3 parts by weight of Ni powder, 0.3 parts by weight of hexamethylenetetramine, 5 parts by weight of ethylene glycol, 5 parts by weight of anhydrous ethanol, and 5 parts by weight of phenolic resin; the fused magnesia granules include fused magnesia granules of four different sizes, namely 4mm, 2mm, ≤1mm and ≤0.075mm, with a mass ratio of 20g:33g:18g:13g; the fused magnesia fine powder has a particle size of 1.5μm; the carbon source is a mixture of coal tar pitch and graphite in a mass ratio of 2g:5g; the coating is a mixture of deionized water and Y2O3 powder with a particle size of 34μm in a dosage ratio of 10mL:90g. Step S6: Mix fused magnesia particles, additives, and Si powder for 4 min, wet with a mixture of ethylene glycol and anhydrous ethanol, mix for another 4 min, add La2O3, fused magnesia fine powder, carbon source, Ni powder, hexamethylenetetramine, and binder, mix for 8 min, transfer to a 200 MPa tablet press for pressing and molding, hold for 3 min, after pressing and molding, dip into a coating, dry at 50℃ for 1.5 h, place in a muffle furnace, heat to 400℃ at a heating rate of 4℃ / min, hold for 1 h, continue heating to 900℃, hold for 1 h, continue heating to 1550℃, hold for 2 h, and naturally cool to 25℃ to obtain rare earth modified magnesia-carbon bricks.

[0036] Comparative Example 3: This comparative example illustrates a method for preparing rare-earth modified magnesia-carbon bricks, comprising the following steps: Step S1: Add 90g of coal tar pitch and 10g of composite modifier to a three-necked flask equipped with a stirrer, thermometer, condenser, and heating mantle. Turn on the heating mantle and heat to 85°C at a rate of 8°C / min. Stir at 150r / min for 1.5h at a constant temperature. Continue heating to 100°C and stir at 400r / min for 30min. Heat to 150°C at a rate of 2°C / min and react at a constant temperature for 1h. Allow to cool naturally to 25°C. Add 10g of phenolic resin, heat to 100°C, mix and stir for 30min, heat to 180°C at a rate of 5°C / min, and react at a constant temperature for 1h. Allow to cool naturally to 25°C to obtain modified coal tar pitch. The composite modifier is obtained by mixing polyethylene glycol PEG-800, divinylbenzene, and polystyrene GR1551 in a ratio of 3g:3mL:2g. Step S2: Add 100g phenol, 1.5mL Tween-80, 85mL silicone oil, 3g 37% formaldehyde solution and 2mL molybdic acid to a three-necked flask equipped with a stirrer and thermometer. Stir at 45℃ for 30min. Add 18mL 37% concentrated hydrochloric acid, heat to 90℃, reflux for 3h. Adjust the pH to 7 with 10% sodium carbonate solution. Add carboxylated nitrile latex, mix and stir for 13min. Dehydrate under vacuum at 75℃ and 0.08MPa. Add 15mL ethylene glycol, mix and stir for 30min to obtain the adhesive. Step S3: Weigh out 75 parts by weight of fused magnesia granules, 8 parts by weight of fused magnesia fine powder, 18 parts by weight of carbon source, 2 parts by weight of La2O3 with a particle size <0.088mm, 8 parts by weight of coating, 3 parts by weight of Si powder, 0.3 parts by weight of Ni powder, 0.3 parts by weight of hexamethylenetetramine, 5 parts by weight of ethylene glycol, 5 parts by weight of anhydrous ethanol, and 5 parts by weight of binder; the fused magnesia granules include fused magnesia granules of four different sizes, namely 4mm, 2mm, ≤1mm and ≤0.075mm, with a mass ratio of 20g:33g:18g:13g; the fused magnesia fine powder has a particle size of 1.5μm; the carbon source is a mixture of modified coal tar pitch and graphite in a mass ratio of 2g:5g; the coating is a mixture of deionized water and Y2O3 powder with a particle size of 34μm in a dosage ratio of 10mL:90g. Step S4: Mix fused magnesia particles and Si powder for 4 min, wet with a mixture of ethylene glycol and anhydrous ethanol, mix for another 4 min, add La2O3, fused magnesia fine powder, carbon source, Ni powder, hexamethylenetetramine and binder, mix for 8 min, transfer to a 200 MPa tablet press and press into shape, hold pressure for 3 min, after pressing and coating, dry at 50℃ for 1.5 h, put into a muffle furnace, heat to 400℃ at a heating rate of 4℃ / min, hold for 1 h, continue to heat to 900℃, hold for 1 h, continue to heat to 1550℃, hold for 2 h, and cool naturally to 25℃ to obtain rare earth modified magnesia-carbon bricks.

[0037] The corrosion resistance of the rare earth-modified magnesia-carbon bricks prepared in Examples 1-3 and Comparative Examples 1-3 was tested by the alkali vapor method in the standard GB / T14983-2008 "Test Method for Alkali Resistance of Refractory Materials". Type 1: The surface is black and undamaged, and the fracture surface is only eroded by 1-4mm; Category 2: The surface is black with severe edge and corner damage and small cracks. The entire fracture is grayish-black, with only a small amount of the core remaining uncorroded. Category 3: The surface is black with obvious cracks, the edges and corners are severely damaged, and the entire fracture surface is black. The high-temperature flexural strength of magnesia-carbon bricks at 1400℃ was tested according to standard GB / T 3002-2017 "Test Method for High-Temperature Flexural Strength of Refractory Materials"; the test results are as follows. Figure 1-2 As shown: In Examples 1-3, the amount of additives and rare earth oxides gradually increases, resulting in a denser distribution of reinforcing fibers, a more complete microscopic composite material network, and more significant toughening and reinforcing effects. Rare earth oxides are directly used as functional fillers, and the increased amount leads to more rare earth atoms accumulating at the MgO grain boundaries, more effectively eliminating impurity phases such as low-melting-point silicates, making the grain boundaries more stable and stronger at high temperatures. More rare earth oxides react with the intruding slag to generate a high-melting-point, high-viscosity rare earth silicate protective layer, enhancing corrosion resistance. Optimization of carbon source quality: The increased ratio of modified coal tar pitch to graphite results in a higher quality carbon-bonded phase, a stronger carbon network, and enhanced high-temperature strength.

[0038] Comparing Example 2 with Comparative Example 1, it can be seen that: Comparative Example 1 lacks additives, modified coal tar pitch, and binders, and uses brittle glassy carbon formed by ordinary phenolic resin and ordinary coal tar pitch as the binding phase, and there is no reinforcing skeleton. Example 2 uses additives, and the rare earth elements in the additives and the molybdenum in the binder can generate a high-melting-point protective phase at high temperatures, actively resisting slag penetration. The alumina fibers in the additives provide a fiber toughening effect, which can effectively bridge and prevent crack propagation. The molybdate in the binder catalyzes the generation of higher-strength "graphite-like" carbon. Together, the two construct a strong and tough carbon composite binding phase. The carbon network of Comparative Example 1 is fragile and easily oxidized.

[0039] Comparing Example 2 with Comparative Example 2, it can be seen that: Comparative Example 2 used additives but did not use modified coal tar pitch or binder. Although Comparative Example 2 has reinforcing fibers, the quality of the carbon-bonded phase that wraps the fibers is poor. The carbon-bonded phase formed by ordinary coal tar pitch and phenolic resin is fragile and porous, and cannot effectively transfer stress to the fibers, resulting in weak high-temperature flexural strength. The carbon-bonded phase of Comparative Example 2 itself has weak oxidation and erosion resistance. Slag and alkaline vapors can easily corrode the fragile carbon matrix, resulting in poor corrosion resistance.

[0040] Comparing Example 2 with Comparative Example 3, it can be seen that: Comparative Example 3 used an optimized carbon source and binder, but lacked additives. Comparative Example 3 lacked a fiber toughening mechanism. The carbon-bonded phase itself has high strength, but it is a brittle material. Once microcracks are generated, they will rapidly propagate and lead to fracture. The alumina fibers in Example 2 can effectively pin cracks and deflect crack paths. Through processes such as fiber pull-out, a large amount of energy is absorbed, resulting in higher flexural strength and better toughness. Due to the lack of fiber toughening, Comparative Example 3 is more prone to macroscopic cracks and structural spalling under the combined effects of thermal stress and chemical corrosion, resulting in weaker corrosion resistance.

[0041] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0042] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in this application, they should all fall within the protection scope of the present invention.

Claims

1. A rare earth-modified magnesia-carbon brick, characterized in that, Includes the following components by weight: The mixture contains 70-80 parts of fused magnesia granules, 5-10 parts of fused magnesia fine powder, 15-20 parts of carbon source, 1-3 parts of rare earth oxides, 5-10 parts of coating, 2-5 parts of additives, 2-5 parts of antioxidant, 0.1-0.5 parts of catalyst, and 4-6 parts of binder. The adhesive is prepared by the following steps: Phenol, Tween-80, silicone oil, formaldehyde solution and molybdic acid are mixed and stirred, a catalyst is added, the mixture is heated to reflux, the pH is adjusted with sodium carbonate solution, carboxylated nitrile latex is added, mixed and stirred, vacuum dehydrated, ethylene glycol is added, and mixed and stirred to obtain the adhesive.

2. The rare earth-modified magnesia-carbon brick according to claim 1, characterized in that, The ratio of phenol, Tween-80, silicone oil, formaldehyde solution, molybdic acid, catalyst, carboxylated nitrile latex, and ethylene glycol is 100g:1g:75mL:75-100mL:3g:1-3mL:15-20mL:10-20mL; the catalyst is concentrated hydrochloric acid with a mass fraction of 37%; the formaldehyde solution has a mass fraction of 37%; and the sodium carbonate solution has a mass fraction of 10%.

3. The rare earth-modified magnesia-carbon brick according to claim 1, characterized in that, The fused magnesia particles include four particle sizes: 3-5 mm, 1-3 mm, ≤1 mm, and ≤0.075 mm, with a mass ratio of 15-25 g: 30-35 g: 15-20 g: 10-15 g. The fine fused magnesia powder has a particle size of 1-2 μm. The catalyst is one of nano-metal powder and metal salt. The nano-metal powder is one of Co powder, Ni powder, and Fe powder. The metal salt is one of Co(NO3)2•6H2O, Ni(NO3)2•6H2O, and Fe(NO3)3•9H2O.

4. A rare earth-modified magnesia-carbon brick according to claim 1, characterized in that, The carbon source is one or more of the following: modified coal tar pitch and graphite, semi-reinforcing furnace black, general furnace black, spray carbon black, high abrasion resistant furnace black, fast-pressed furnace black, flake graphite, and petroleum asphalt; the rare earth oxide is one or more of the following: La2O3, Nd2O3, Sc2O3, Sm2O3, HfO2, Y2O3, and CeO2 with a particle size <0.088mm; the coating is prepared by mixing deionized water and Y2O3 powder with a particle size of 32-36μm at a ratio of 10mL:90g; the antioxidant is one or more of the following: Si powder, Al powder, B4C, and ZrB2.

5. A rare-earth-modified magnesia-carbon brick according to claim 1, characterized in that, The additive is prepared by the following steps: Step a1: Phenol, plant polyphenols, rare earth metal compounds, sodium hydroxide and deionized water are mixed and stirred, formaldehyde solution is added, the mixture is refluxed, methylphenyldimethoxysilane is added, the mixture is reacted at a constant temperature, concentrated under reduced pressure, anhydrous ethanol is added, and the mixture is stirred to obtain the precursor. Step a2: Add magnesium powder, tetrahydrofuran, and chlorotrimethoxysilane to a three-necked flask and stir. Add (4-bromophenylethynyl)trimethylsilane and react. Centrifuge, retain the supernatant, extract, and rotary evaporate to obtain the intermediate product. Mix KOH and anhydrous methanol, stir, add the intermediate product and react. Centrifuge, extract, rotary evaporate, and wash to obtain the modifier. Step a3: Dry and cool the alumina fibers; mix and stir the modifier, tetrahydrofuran, methanol, n-pentane and N,N-dimethylformamide, impregnate the alumina fibers, seal and remove; mix and stir the silanyl yne resin and acetone, impregnate the alumina fibers, remove the solvent to obtain the alumina fiber preform. Step a4: Impregnate the alumina fiber preform with the precursor, let it stand, cure, cool, grind, and sieve to obtain the additive.

6. A rare-earth-modified magnesia-carbon brick according to claim 5, characterized in that, The ratio of phenol, plant polyphenols, rare earth metal compounds, sodium hydroxide, deionized water, formaldehyde solution, methylphenyl dimethoxysilane, and anhydrous ethanol in step a1 is 90-100g: 10-30g: 5-15g: 9-10g: 500-600mL: 200-300mL: 15-30mL: 100-200mL; the plant polyphenols are one of lignin, tannin, and cashew nut shell oil; The rare earth metal compound is one of DyCl3, LaCl3, and Eu(NO3)3; the formaldehyde solution has a mass fraction of 37%; the ratio of magnesium powder, tetrahydrofuran, chlorotrimethoxysilane, (4-bromophenylethynyl)trimethylsilane, KOH, and anhydrous methanol in step a2 is 0.3-0.5g: 10-20mL: 10-15mL: 2-3g: 0.5-1g: 10-15mL.

7. A rare-earth-modified magnesia-carbon brick according to claim 5, characterized in that, In step a3, the ratio of alumina fiber, modifier, tetrahydrofuran, methanol, n-pentane, N,N-dimethylformamide, silaneyne resin, and acetone is 10g:1-3g:50mL:50-100mL:50-100mL:50-100mL:5-15g:50-100mL; in step a4, the ratio of alumina fiber preform to precursor is 10g:300-500mL.

8. A rare-earth-modified magnesia-carbon brick according to claim 1, characterized in that, The modified coal tar pitch is prepared by the following steps: Coal tar pitch and composite modifier are added to a three-necked flask, the heating mantle is turned on, the temperature is increased and stirred, and the mixture is allowed to cool naturally. Phenolic resin is then added, the temperature is increased, the mixture is stirred and stirred, and the mixture is allowed to cool naturally to obtain modified coal tar pitch.

9. A rare-earth-modified magnesia-carbon brick according to claim 8, characterized in that, The ratio of coal tar pitch, composite modifier, and phenolic resin is 80-100g: 5-15g: 10g; the composite modifier is obtained by mixing polyethylene glycol PEG-800, divinylbenzene, and polystyrene GR1551 in a ratio of 1-5g: 1-6mL: 1-3g; the phenolic resin is of type P83190.

10. A method for preparing rare earth-modified magnesia-carbon bricks as described in any one of claims 1-9, characterized in that, Includes the following steps: Step 1: Weigh out the following components by weight: 70-80 parts of fused magnesia granules, 5-10 parts of fused magnesia fine powder, 15-20 parts of carbon source, 1-3 parts of rare earth oxides, 5-10 parts of coating, 2-5 parts of additives, 2-5 parts of antioxidant, 0.1-0.5 parts of catalyst, 0.1-0.5 parts of hexamethylenetetramine, 5 parts of ethylene glycol, 5 parts of anhydrous ethanol, and 4-6 parts of binder. Step 2: Mix fused magnesia particles, additives, and antioxidants, wet with a mixture of ethylene glycol and anhydrous ethanol, mix again, add rare earth oxides, fused magnesia fine powder, carbon source, catalyst, hexamethylenetetramine, and binder, mix again, transfer to a tablet press to press into shape, dip into a coating after pressing, dry, sinter in a muffle furnace, and cool naturally to obtain rare earth modified magnesia-carbon bricks.

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