Magnesite-chromite-containing magnesia-chromite refractory and method for producing the same

Abstract

This invention relates to the field of refractory materials technology, specifically a magnesia-chromium refractory material containing magnesia and chromite, and its preparation method, comprising the following components: chromite particles, fine magnesia powder, modified magnesia, phenolic resin powder, sodium tripolyphosphate, and magnesium stearate. The phosphate groups grafted onto the modified silica surface are pre-adsorbed and complexed with Cr. 3+ / Al 3+ Metal ions are gradually released as the pH of the system increases during the simultaneous dropwise addition of alkali solution, resulting in controlled and uniform co-precipitation of metal ions on the surface of modified LDH nanosheets. This leads to the in-situ construction of a uniformly thick, lattice-continuous gradient spinel coating layer on the magnesia surface. Cr is used... 3+ / Al 3+ Synergistic deposition significantly improves thermal shock resistance. Silicate groups in the modified LDH are converted in situ into magnesium aluminum silicate during high-temperature calcination, achieving interfacial chemical bonding.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, specifically a magnesia-chromium refractory material containing magnesia sand and chromite and its preparation method. Background Technology

[0002] Magnesia-chrome refractories are widely used in the lining of high-temperature equipment such as converters, electric furnaces, and ladles in steel smelting due to their excellent resistance to alkaline slag erosion and thermal shock stability. Traditional magnesia-chrome bricks are mainly prepared by mechanically mixing magnesia and chromite, but this leads to uneven distribution of chromium at the microscale, forming chromium-rich islands and chromium-poor areas, resulting in unstable performance and significant differences in local slag resistance. Existing technologies attempt to deposit Cr₂O₃ or Cr(OH)₃ on the surface of MgO through chemical precipitation; however, the thickness and uniformity of the chromium layer are difficult to control, and the low interfacial bonding energy between MgO and Cr₂O₃ leads to easy peeling during high-temperature cycling. Summary of the Invention

[0003] (1) Technical problems to be solved

[0004] The purpose of this invention is to provide a magnesium-chromium refractory material containing magnesia and chromite and its preparation method, in order to solve the problems that when Cr2O3 or Cr(OH)3 is deposited on the surface of MgO by chemical precipitation, the thickness and uniformity of the chromium layer are difficult to control, the bonding force between the deposited layer and the substrate is weak, and it is easy to peel off at high temperature.

[0005] (2) Technical solution

[0006] To achieve the above objectives, on the one hand, the present invention provides a magnesia-chromium refractory material containing magnesia sand and chromite, comprising the following components in parts by weight: 35-45 parts chromite particles, 15-25 parts fine magnesia sand powder, 15-25 parts modified magnesia, 2-5 parts phenolic resin powder, 0.2-0.6 parts sodium tripolyphosphate, and 0.1-0.2 parts magnesium stearate;

[0007] The modified magnesium oxide is a powder obtained by high-temperature calcination of MgO precursor powder coated with Cr-Al induced by modified LDH and modified silica.

[0008] Furthermore, the preparation method of the modified magnesium oxide includes the following steps:

[0009] S11. Modified LDH and modified silica were ultrasonically dispersed in anhydrous ethanol, heated in an oil bath, and stirred under nitrogen protection. The resulting reaction solution was centrifuged to collect the solid, washed with anhydrous ethanol, and dried under vacuum to obtain the first compound.

[0010] S12. The first compound is ultrasonically dispersed in deionized water to obtain a dispersion; magnesium oxide powder is dispersed in deionized water, sodium hexametaphosphate is added, ultrasonic treatment is performed, dilute hydrochloric acid is added to adjust the pH while stirring, the dispersion is slowly added dropwise, stirring is continued, stirring is stopped and the mixture is allowed to stand, the supernatant is decanted, and deionized water is added to obtain the second compound.

[0011] S13. Dissolve Cr(NO3)3·9H2O and Al(NO3)3·9H2O in deionized water to obtain a metal salt solution; heat the second compound, and simultaneously add the metal salt solution and NaOH solution while stirring, continue stirring and aging, raise the temperature for aging, collect the solid product by centrifugation, wash with deionized water and anhydrous ethanol, vacuum dry, calcine in stages, grind the sintered powder to obtain modified magnesium oxide.

[0012] Furthermore, the segmented calcination in S13 is divided into two stages: an organic matter removal stage, in which the temperature is increased to 550°C at 3°C / min and held for 2 hours; and a gradient spinelization and silicate formation stage, in which the temperature is increased to 1350°C at 5°C / min and held for 4 hours.

[0013] Furthermore, the mass ratio of the modified LDH to the modified silica is 1.5 to 2:1; the mass ratio of the first compound to magnesium oxide powder is 1:20 to 25.

[0014] Furthermore, the method for preparing the modified LDH includes the following steps:

[0015] S21. Dissolve Mg(NO3)2·6H2O and Al(NO3)3·9H2O in deionized water to obtain a salt solution; dissolve NaOH and Na2SiO3·9H2O in deionized water, add sodium citrate, stir well to obtain an alkali-silicon mixed solution;

[0016] S22. The salt solution and the alkali-silicon mixed solution were simultaneously and slowly added dropwise to deionized water. Under nitrogen protection, the mixture was stirred and aged. The resulting reaction solution was centrifuged to collect the precipitate, which was then washed with deionized water and anhydrous ethanol to obtain a wet gel.

[0017] S23. The wet gel was ultrasonically dispersed in anhydrous ethanol, and 3-carboxypropyltrimethoxysilane was added dropwise. Under nitrogen protection, the reaction was refluxed. The resulting reaction solution was centrifuged to collect the solid, washed with anhydrous ethanol, vacuum dried, and ground to obtain modified LDH.

[0018] Furthermore, the method for preparing the modified silica includes the following steps:

[0019] S31. Hexadecyltrimethylammonium bromide was dissolved in a mixed solvent of anhydrous ethanol and deionized water, concentrated ammonia was added, and the mixture was stirred until homogeneous. Tetraethyl orthosilicate was slowly added dropwise, and the reaction was continued. The resulting reaction solution was centrifuged to collect the precipitate, which was washed alternately with anhydrous ethanol and deionized water, dried, and calcined in a muffle furnace to obtain mesoporous silica.

[0020] S32. Mesoporous silica was ultrasonically dispersed in anhydrous toluene. Under nitrogen protection, γ-glycidoxypropyltrimethoxysilane was added and the mixture was refluxed. The resulting reaction solution was centrifuged to collect the solid, which was washed successively with anhydrous toluene, acetone, and anhydrous ethanol, and then dried under vacuum to obtain the third compound.

[0021] S33. The third compound was dispersed in anhydrous ethanol, triethylamine was added, and an aqueous solution of phosphoric acid was slowly added dropwise under nitrogen protection. The reaction was stirred, and the resulting reaction solution was centrifuged to collect the solid. The solid was washed with deionized water and anhydrous ethanol and dried under vacuum to obtain modified silica.

[0022] On the other hand, based on the same inventive concept, the present invention also provides a method for preparing a magnesia-chromium refractory material containing magnesia sand and chromite, applicable to the aforementioned magnesia-chromium refractory material containing magnesia sand and chromite, comprising the following steps:

[0023] S1. Place chromite particles, magnesia powder, and modified magnesium oxide in a mixer, stir and mix well, add phenolic resin powder, stir and mix well, continue to add sodium tripolyphosphate and magnesium stearate, continue stirring, sieve, and obtain refractory material.

[0024] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0025] 1. Phosphate groups grafted onto the surface of modified silica pre-adsorb and complex Cr 3+ / Al 3+ Metal ions are gradually released as the pH of the system increases during the simultaneous addition of alkali solution, enabling controlled and uniform co-precipitation of metal ions on the surface of modified LDH nanosheets. Through staged calcination, a gradient spinel coating layer with uniform thickness and continuous lattice is constructed in situ on the surface of magnesia.

[0026] 2. This invention uses Cr 3+ / Al 3+ Synergistic deposition, Al 3+ First, it bonds firmly with the MgO matrix, and then, through a gradual structural change, it bonds with Cr. 3+ By integrating the chromium layer with the substrate, the problem of poor adhesion between the chromium layer and the substrate is solved. Furthermore, by controlling the deposition and diffusion, a continuous compositional gradient is constructed from Al-rich on the inside to Cr-rich on the outside. Correspondingly, the coefficient of thermal expansion also transitions continuously from the inside to the outside, greatly improving the thermal shock resistance of the final refractory material.

[0027] 3. During the high-temperature calcination process, MgO and Al2O3 generated from the decomposition of modified LDH react with the intercalated silicate and the silicate in the residual modified silica to form magnesium aluminum silicate in situ. This silicate phase is distributed at the grain boundaries of the gradient spinel layer and penetrates to the interface with the MgO matrix, playing a dual role as a liquid phase sintering binder and a crack bridging toughening phase, thus achieving interfacial chemical bonding. Attached Figure Description

[0028] Figure 1 This is a photograph of the modified magnesium oxide prepared in Example 1 of the present invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0030] Example 1: This example discloses a magnesia-chromium refractory material containing magnesia sand and chromite, comprising the following components in parts by weight: 40 parts chromite particles, 20 parts fine magnesia sand powder, 20 parts modified magnesium oxide, 3.5 parts phenolic resin powder, 0.4 parts sodium tripolyphosphate, and 0.15 parts magnesium stearate.

[0031] The modified magnesium oxide is a powder obtained by high-temperature calcination of MgO precursor powder coated with Cr-Al induced by modified LDH and modified silica.

[0032] The method for preparing the modified magnesium oxide includes the following steps:

[0033] S11. 0.3 g of modified LDH and 0.15 g of modified silica were ultrasonically dispersed in 150 mL of anhydrous ethanol, heated in an oil bath at 75 °C, and stirred for 6 h under nitrogen protection. The resulting reaction solution was centrifuged to collect the solid, washed with anhydrous ethanol, and dried under vacuum at 60 °C for 6 h to obtain the first compound.

[0034] S12. Disperse 0.5g of the first compound in 50mL of deionized water by ultrasonication to obtain a dispersion; disperse 10g of magnesium oxide powder in 200mL of deionized water, add 0.02g of sodium hexametaphosphate, sonicate for 30min, adjust the pH to 8.8 with dilute hydrochloric acid while stirring, slowly add the dispersion dropwise at 40℃ with stirring, continue stirring for 2h, stop stirring and let stand for 20min, decant the supernatant, add deionized water to obtain the second compound;

[0035] S13. Dissolve 4g Cr(NO3)3·9H2O and 1.41g Al(NO3)3·9H2O in 50mL of deionized water to obtain a metal salt solution; heat the second compound to 55℃, and simultaneously add the metal salt solution and 2mol / L NaOH solution while stirring. Continue stirring and aging at 55℃ for 90min, then raise the temperature to 70℃ and keep it at that temperature for 3h for aging. Centrifuge the obtained product to collect the solid, wash it with deionized water and anhydrous ethanol at 60℃, vacuum dry it at 60℃ for 24h, calcine it in stages, and grind the sintered powder to obtain modified magnesium oxide.

[0036] The segmented calcination in S13 is divided into two stages: the organic matter removal stage, in which the temperature is increased to 550℃ at 3℃ / min and held for 2 hours; and the gradient spinelization and silicate formation stage, in which the temperature is increased to 1350℃ at 5℃ / min and held for 4 hours.

[0037] It should be noted that, as Figure 1 The image shown is a physical picture of the modified magnesium oxide prepared in Example 1 of the present invention. The modified magnesium oxide must be calcined at high temperature during the preparation process to generate magnesium aluminum silicate. This silicate phase plays a dual role as a liquid phase sintering binder and a crack bridging toughening phase, thereby achieving interfacial chemical bonding.

[0038] The mass ratio of modified LDH to modified silica is 2:1; the mass ratio of the first compound to magnesium oxide powder is 1:20.

[0039] The method for preparing the modified LDH includes the following steps:

[0040] S21. Dissolve 7.69g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O in 80mL of deionized water to obtain a salt solution; dissolve 3.2g NaOH and 2.84g Na2SiO3·9H2O in 80mL of deionized water, add 0.5g sodium citrate, stir well to obtain an alkali-silicon mixed solution;

[0041] S22. The salt solution and the alkali-silicon mixed solution were simultaneously and slowly added dropwise to 100 mL of deionized water at the same rate of about 2 mL / min. Under nitrogen protection, the mixture was stirred and aged at 60 °C for 24 h. The resulting reaction solution was centrifuged to collect the precipitate, which was then washed with deionized water and anhydrous ethanol to obtain a wet gel.

[0042] S23. The wet gel was ultrasonically dispersed in 200 mL of anhydrous ethanol, and 1.5 mL of 3-carboxypropyltrimethoxysilane was added dropwise. The mixture was refluxed at 78 °C for 8 h under nitrogen protection. The solid obtained from the reaction solution was collected by centrifugation, washed with anhydrous ethanol, dried under vacuum at 60 °C for 12 h, and ground to obtain modified LDH.

[0043] The method for preparing the modified silica includes the following steps:

[0044] S31. Dissolve 1.0 g of hexadecyltrimethylammonium bromide in a mixed solvent of 160 mL anhydrous ethanol and 60 mL deionized water, add 8 mL of 28% concentrated ammonia, stir until homogeneous, slowly add 10 mL of tetraethyl orthosilicate, and continue the reaction for 24 h. Centrifuge the resulting reaction solution to collect the precipitate, wash it alternately with anhydrous ethanol and deionized water, dry it, and place it in a muffle furnace to heat it to 550 °C at 2 °C / min and calcine it for 5 h to obtain mesoporous silica.

[0045] S32. 1.0 g of mesoporous silica was ultrasonically dispersed in 100 mL of anhydrous toluene. Under nitrogen protection, 2 mL of γ-glycidoxypropyltrimethoxysilane was added, and the mixture was refluxed at 110 °C for 12 h. The resulting reaction solution was centrifuged to collect the solid, which was washed successively with anhydrous toluene, acetone, and anhydrous ethanol, and dried under vacuum at 80 °C for 6 h to obtain the third compound.

[0046] S33. The third compound was dispersed in 50 mL of anhydrous ethanol, triethylamine was added, and 0.6 mL of 85% phosphoric acid aqueous solution was slowly added dropwise under nitrogen protection. The mixture was stirred at 80 °C for 16 h. The solid obtained from the reaction solution was collected by centrifugation, washed with deionized water and anhydrous ethanol, and dried under vacuum to obtain modified silica.

[0047] The method for preparing a magnesia-chromium refractory material containing magnesia sand and chromite includes the following steps:

[0048] S1. Place chromite particles, magnesia powder, and modified magnesium oxide in a mixer, stir and mix well, add phenolic resin powder, stir and mix well, continue to add sodium tripolyphosphate and magnesium stearate, continue stirring, sieve, and obtain refractory material.

[0049] It should be noted that the refractory material prepared by this invention can be used after pressing and high-temperature firing. The firing process is divided into three stages: the binder removal stage, in which the temperature is increased at 1~2℃ / min, held at 200℃ for 3 hours, held at 450℃ for 2 hours, and then increased to 600℃; the structure formation stage, in which the temperature is increased at 3℃ / min, held at 1050℃ for 2 hours, held at 1250℃ for 2 hours, and then increased to 1350℃; and the densification and welding stage, in which the temperature is increased at 1℃ / min to 1650℃, held for 4~6 hours, and finally cooled to room temperature in the furnace.

[0050] Example 2: This example is based on Example 1, but differs from Example 1 in that it discloses a magnesia-chromium refractory material containing magnesia sand and chromite, comprising the following components in parts by weight: 35 parts chromite particles, 15 parts fine magnesia sand powder, 15 parts modified magnesium oxide, 2 parts phenolic resin powder, 0.2 parts sodium tripolyphosphate, and 0.1 parts magnesium stearate.

[0051] The other components and preparation methods are the same as in Example 1.

[0052] Example 3: This example is based on Example 1, but differs from Example 1 in that it discloses a magnesia-chromium refractory material containing magnesia sand and chromite, comprising the following components in parts by weight: 45 parts chromite particles, 25 parts fine magnesia sand powder, 25 parts modified magnesium oxide, 5 parts phenolic resin powder, 0.6 parts sodium tripolyphosphate, and 0.2 parts magnesium stearate.

[0053] The other components and preparation methods are the same as in Example 1.

[0054] Example 4: This example is based on Example 1, but differs from Example 1 in that the mass ratio of modified LDH to modified silica is 1.5:1; and the mass ratio of the first compound to magnesium oxide powder is 1:25.

[0055] The other components and preparation methods are the same as in Example 1.

[0056] Comparative Example 1: This comparative example is based on Example 1, but differs from Example 1 in that the silicate ions in the modified LDH described in this comparative example are replaced by carbonate ions.

[0057] The method for preparing the modified LDH includes the following steps:

[0058] S21. Dissolve 7.69g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O in 80mL of deionized water to obtain a salt solution; dissolve 3.2g NaOH and 1.06g Na2CO3 in 80mL of deionized water to obtain an alkaline solution.

[0059] S22. The salt solution and the alkaline solution were simultaneously and slowly added dropwise to 100 mL of deionized water at the same rate of about 2 mL / min. Under nitrogen protection, the mixture was stirred and aged at 60 °C for 24 h. The resulting reaction solution was centrifuged to collect the precipitate, which was then washed with deionized water and anhydrous ethanol to obtain a wet gel.

[0060] S23. The wet gel was ultrasonically dispersed in 200 mL of anhydrous ethanol, and 1.5 mL of 3-carboxypropyltrimethoxysilane was added dropwise. Under nitrogen protection, the mixture was refluxed at 78 °C for 8 h. The resulting reaction solution was centrifuged to collect the solid, washed with anhydrous ethanol, dried under vacuum at 60 °C for 12 h, and ground to obtain modified LDH.

[0061] The other components and preparation methods are the same as in Example 1.

[0062] Comparative Example 2: This comparative example is based on Example 1, but differs from Example 1 in that the modified silica in this comparative example does not have phosphate groups grafted onto it.

[0063] The method for preparing the modified silica includes the following steps:

[0064] S31. Dissolve 1.0 g of hexadecyltrimethylammonium bromide in a mixed solvent of 160 mL anhydrous ethanol and 60 mL deionized water, add 8 mL of 28% concentrated ammonia, stir until homogeneous, slowly add 10 mL of tetraethyl orthosilicate, and continue the reaction for 24 h. Centrifuge the resulting reaction solution to collect the precipitate, wash it alternately with anhydrous ethanol and deionized water, dry it, and place it in a muffle furnace to heat it to 550 °C at 2 °C / min and calcine it for 5 h to obtain mesoporous silica.

[0065] S32. 1.0 g of mesoporous silica was ultrasonically dispersed in 100 mL of anhydrous toluene. Under nitrogen protection, 2 mL of γ-glycidoxypropyltrimethoxysilane was added, and the mixture was refluxed at 110 °C for 12 h. The resulting reaction solution was centrifuged to collect the solid, which was washed successively with anhydrous toluene, acetone, and anhydrous ethanol, and then vacuum dried at 80 °C for 6 h to obtain modified silica.

[0066] The other components and preparation methods are the same as in Example 1.

[0067] Comparative Example 3: This comparative example is based on Example 1, but differs from Example 1 in that the modified magnesium oxide in this comparative example does not contain modified LDH.

[0068] The method for preparing the modified magnesium oxide includes the following steps:

[0069] S11. 0.5 g of modified silica was ultrasonically dispersed in 50 mL of deionized water to obtain a dispersion; 10 g of magnesium oxide powder was dispersed in 200 mL of deionized water, 0.02 g of sodium hexametaphosphate was added, and the mixture was ultrasonically treated for 30 min. Under stirring, dilute hydrochloric acid was added to adjust the pH to 8.8. The dispersion was slowly added dropwise at 40 °C with stirring. Stirring was continued for 2 h. Stirring was stopped and the mixture was allowed to stand for 20 min. The supernatant was discarded, and deionized water was added to obtain the fourth compound.

[0070] S12. Dissolve 4g Cr(NO3)3·9H2O and 1.41g Al(NO3)3·9H2O in 50mL of deionized water to obtain a metal salt solution; heat the fourth compound to 55℃, and simultaneously add the metal salt solution and 2mol / L NaOH solution while stirring. Continue stirring and aging at 55℃ for 90min, then raise the temperature to 70℃ and keep it at that temperature for 3h for aging. Centrifuge the obtained product to collect the solid, wash it with deionized water and anhydrous ethanol at 60℃, vacuum dry it at 60℃ for 24h, calcine it in stages, and grind the sintered powder to obtain modified magnesium oxide.

[0071] The other components and preparation methods are the same as in Example 1.

[0072] Comparative Example 4: This comparative example is based on Example 1, but unlike Example 1, the modified magnesium oxide in this comparative example does not contain modified silicon dioxide.

[0073] The method for preparing the modified magnesium oxide includes the following steps:

[0074] S11. 0.5 g of modified LDH was ultrasonically dispersed in 50 mL of deionized water to obtain a dispersion; 10 g of magnesium oxide powder was dispersed in 200 mL of deionized water, 0.02 g of sodium hexametaphosphate was added, and the mixture was ultrasonically treated for 30 min. Under stirring, dilute hydrochloric acid was added to adjust the pH to 8.8. The dispersion was slowly added dropwise at 40 °C with stirring, and stirring was continued for 2 h. After stirring was stopped, the mixture was allowed to stand for 20 min, the supernatant was discarded, and deionized water was added to obtain the fifth compound.

[0075] S12. Dissolve 4g Cr(NO3)3·9H2O and 1.41g Al(NO3)3·9H2O in 50mL of deionized water to obtain a metal salt solution; heat the fifth compound to 55℃, and simultaneously add the metal salt solution and 2mol / L NaOH solution while stirring. Continue stirring and aging at 55℃ for 90min, then raise the temperature to 70℃ and keep it at that temperature for 3h for aging. Centrifuge the obtained product to collect the solid, wash it with deionized water and anhydrous ethanol at 60℃, vacuum dry it at 60℃ for 24h, calcine it in stages, and grind the sintered powder to obtain modified magnesium oxide.

[0076] The other components and preparation methods are the same as in Example 1.

[0077] Comparative Example 5: This comparative example is based on Example 1, but differs from Example 1 in that the modified magnesium oxide described in this comparative example does not contain Al(NO3)3·9H2O.

[0078] The method for preparing the modified magnesium oxide includes the following steps:

[0079] S11. 0.3 g of modified LDH and 0.15 g of modified silica were ultrasonically dispersed in 150 mL of anhydrous ethanol, heated in an oil bath at 75 °C, and stirred for 6 h under nitrogen protection. The resulting reaction solution was centrifuged to collect the solid, washed with anhydrous ethanol, and dried under vacuum at 60 °C for 6 h to obtain the first compound.

[0080] S12. Disperse 0.5g of the first compound in 50mL of deionized water by ultrasonication to obtain a dispersion; disperse 10g of magnesium oxide powder in 200mL of deionized water, add 0.02g of sodium hexametaphosphate, sonicate for 30min, adjust the pH to 8.8 with dilute hydrochloric acid while stirring, slowly add the dispersion dropwise at 40℃ with stirring, continue stirring for 2h, stop stirring and let stand for 20min, decant the supernatant, add deionized water to obtain the second compound;

[0081] S13. Dissolve 5.32 g Cr(NO3)3·9H2O in 50 mL of deionized water to obtain a metal salt solution; heat the second compound to 55 °C, and simultaneously add the metal salt solution and 2 mol / L NaOH solution while stirring. Continue stirring and aging at 55 °C for 90 min, then raise the temperature to 70 °C and keep it at that temperature for 3 h for aging. Centrifuge the obtained product to collect the solid, wash it with deionized water and anhydrous ethanol at 60 °C, vacuum dry it at 60 °C for 24 h, calcine it in stages, and grind the sintered powder to obtain modified magnesium oxide.

[0082] The other components and preparation methods are the same as in Example 1.

[0083] Comparative Example 6: This comparative example is based on Example 1, but differs from Example 1 in that the refractory modified magnesium oxide described in this comparative example is not modified and is pure magnesium oxide powder.

[0084] The other components and preparation methods are the same as in Example 1.

[0085] Comparative Example 7: This comparative example is based on Example 1, but differs from Example 1 in that the refractory material described in this comparative example does not contain modified magnesium oxide.

[0086] The other components and preparation methods are the same as in Example 1.

[0087] Experimental verification:

[0088] Experiment 1:

[0089] (1) Modified magnesium oxide was dispersed in epoxy resin insert, cured and polished to obtain a smooth surface containing the complete cross-section of the particles, and the sample was obtained. The interfacial bonding force (shear strength) between the modified magnesium oxide powder coating layer and the matrix was tested using a nanoindenter.

[0090] (2) The modified magnesium oxide of the examples and comparative examples were dry-pressed into cylindrical blocks of regular size under the same pressure. All samples were degummed and pre-fired under the same conditions. The thermal expansion behavior of the samples at 25~1400℃ was tested using a high-temperature thermomechanical analyzer.

[0091] Table 1. Test results of interfacial bonding strength and thermal expansion behavior between modified magnesium oxide powder and matrix:

[0092]

[0093] Table 1 shows the test results of the interfacial bonding force and thermal expansion behavior between the modified magnesium oxide powder and the matrix. The interfacial shear strength of the examples all exceeded that of the comparative examples, with modified LDH and modified silica playing a key role in enhancing the interfacial bonding. Meanwhile, the coefficient of thermal expansion of the examples changed continuously without abrupt changes, indicating that their gradient structure allows for a continuous transition in thermal expansion, buffering thermal stress and providing good thermal matching.

[0094] Experiment 2: The refractory materials prepared in the examples and comparative examples were pressed into shapes, dried in an oven, and fired in an air atmosphere tunnel kiln. The firing process was divided into three stages: the binder removal stage, in which the temperature was increased at 1~2℃ / min, held at 200℃ for 3 hours, held at 450℃ for 2 hours, and then increased to 600℃; the structure formation stage, in which the temperature was increased at 3℃ / min, held at 1050℃ for 2 hours, held at 1250℃ for 2 hours, and then increased to 1350℃; and the densification and welding stage, in which the temperature was increased at 1℃ / min to 1650℃, held for 4~6 hours, and finally cooled to room temperature with the furnace to obtain the sample.

[0095] (1) The bulk density and apparent porosity of the sample were tested in accordance with GB / T 2997.

[0096] (2) Test the compressive strength of the specimen at room temperature according to GB / T 5072.

[0097] (3) Test the high-temperature flexural strength of the specimen according to GB / T 3002.

[0098] (4) Test the thermal shock resistance of the specimens according to GB / T 30759.

[0099] (5) Test the slag erosion resistance of the sample according to the static crucible method.

[0100] Table 2. Basic properties of refractory materials:

[0101]

[0102] Table 2 shows the basic properties of the refractory materials. As can be seen from the table, the properties of the refractory materials prepared by the present invention have been improved, and Example 3 is the best solution.

[0103] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A magnesia-chromium refractory material containing magnesia sand and chromite, characterized in that, The composition includes the following components in parts by weight: 35-45 parts chromite particles, 15-25 parts fine magnesia powder, 15-25 parts modified magnesium oxide, 2-5 parts phenolic resin powder, 0.2-0.6 parts sodium tripolyphosphate, and 0.1-0.2 parts magnesium stearate. The modified magnesium oxide is a powder obtained by high-temperature calcination of MgO precursor powder coated with Cr-Al induced by modified LDH and modified silica. The method for preparing the modified magnesium oxide includes the following steps: S11. Modified LDH and modified silica were ultrasonically dispersed in anhydrous ethanol, heated in an oil bath, and stirred under nitrogen protection. The resulting reaction solution was centrifuged to collect the solid, washed with anhydrous ethanol, and dried under vacuum to obtain the first compound. S12. The first compound is ultrasonically dispersed in deionized water to obtain a dispersion; magnesium oxide powder is dispersed in deionized water, sodium hexametaphosphate is added, ultrasonic treatment is performed, dilute hydrochloric acid is added to adjust the pH while stirring, the dispersion is slowly added dropwise, stirring is continued, stirring is stopped and the mixture is allowed to stand, the supernatant is decanted, and deionized water is added to obtain the second compound. S13. Dissolve Cr(NO3)3·9H2O and Al(NO3)3·9H2O in deionized water to obtain a metal salt solution; heat the second compound, and simultaneously add the metal salt solution and NaOH solution while stirring, continue stirring and aging, raise the temperature and age, collect the solid product by centrifugation, wash with deionized water and anhydrous ethanol, vacuum dry, calcine in stages, grind the sintered powder to obtain modified magnesium oxide; The method for preparing the modified LDH includes the following steps: S21. Dissolve Mg(NO3)2·6H2O and Al(NO3)3·9H2O in deionized water to obtain a salt solution; dissolve NaOH and Na2SiO3·9H2O in deionized water, add sodium citrate, stir well to obtain an alkali-silicon mixed solution; S22. The salt solution and the alkali-silicon mixed solution were simultaneously and slowly added dropwise to deionized water. Under nitrogen protection, the mixture was stirred and aged. The resulting reaction solution was centrifuged to collect the precipitate, which was then washed with deionized water and anhydrous ethanol to obtain a wet gel. S23. The wet gel was ultrasonically dispersed in anhydrous ethanol, and 3-carboxypropyltrimethoxysilane was added dropwise. Under nitrogen protection, the reaction was refluxed. The resulting reaction solution was centrifuged to collect the solid, washed with anhydrous ethanol, vacuum dried, and ground to obtain modified LDH. The method for preparing the modified silica includes the following steps: S31. Hexadecyltrimethylammonium bromide was dissolved in a mixed solvent of anhydrous ethanol and deionized water, concentrated ammonia was added, and the mixture was stirred until homogeneous. Tetraethyl orthosilicate was slowly added dropwise, and the reaction was continued. The resulting reaction solution was centrifuged to collect the precipitate, which was washed alternately with anhydrous ethanol and deionized water, dried, and calcined in a muffle furnace to obtain mesoporous silica. S32. Mesoporous silica was ultrasonically dispersed in anhydrous toluene. Under nitrogen protection, γ-glycidoxypropyltrimethoxysilane was added and the mixture was refluxed. The resulting reaction solution was centrifuged to collect the solid, which was washed successively with anhydrous toluene, acetone, and anhydrous ethanol, and then dried under vacuum to obtain the third compound. S33. The third compound was dispersed in anhydrous ethanol, triethylamine was added, and an aqueous solution of phosphoric acid was slowly added dropwise under nitrogen protection. The reaction was stirred, and the resulting reaction solution was centrifuged to collect the solid. The solid was washed with deionized water and anhydrous ethanol and dried under vacuum to obtain modified silica.

2. The magnesia-chromium refractory material containing magnesia sand and chromite according to claim 1, characterized in that, The segmented calcination in S13 is divided into two stages: the organic matter removal stage, in which the temperature is increased to 550℃ at 3℃ / min and held for 2 hours; and the gradient spinelization and silicate formation stage, in which the temperature is increased to 1350℃ at 5℃ / min and held for 4 hours.

3. The magnesia-chromium refractory material containing magnesia sand and chromite according to claim 1, characterized in that, The mass ratio of modified LDH to modified silica is 1.5~2:1; the mass ratio of the first compound to magnesium oxide powder is 1:20~25.

4. A method for preparing a magnesia-chromium refractory material containing magnesia sand and chromite, applied to the preparation of a magnesia-chromium refractory material containing magnesia sand and chromite as described in any one of claims 1 to 3, characterized in that, The method includes the following steps: S1. Place chromite particles, magnesia powder, and modified magnesium oxide in a mixer, stir and mix well, add phenolic resin powder, stir and mix well, continue to add sodium tripolyphosphate and magnesium stearate, continue stirring, sieve, and obtain refractory material.

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