Preparation method of MgAl2O4-Al2O3 (at) C composite material

Abstract

The invention belongs to the technical field of refractory materials, and discloses a preparation method of a MgAl2O4-Al2O3 (at) C composite material, which comprises the following steps: mixing magnesite clinker micropowder, metal aluminum powder and deionized water in proportion, and stirring and heating under a water bath condition to prepare a Mg (OH) 2-AlOOH mixed solution; adding a polyvinyl alcohol solution into the mixed solution and stirring; sequentially adding the spherical graphite powder and the additive, and continuously stirring; finally, adding a gelling agent solution to prepare precursor gel; and calcining the precursor gel under the condition of a reducing atmosphere, so as to obtain the MgAl2O4-Al2O3 (at) C composite material. The raw materials which are low in cost and easy to obtain are adopted, the cost is low, the process is simple, the prepared MgAl2O4-Al2O3 (at) C composite material has excellent wettability, the defects that graphite in refractory castable is poor in hydrophilicity and prone to oxidation at high temperature are overcome, and the MgAl2O4-Al2O3 (at) C composite material can be widely applied to preparation of carbon sources in the field of carbon-containing refractory materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of refractories, and particularly relates to a preparation method of MgAl2O4-Al2O3@C composite materials. Background Art

[0002] Graphite is widely used in refractories due to its unique advantages, significantly improving the slag erosion resistance and thermal shock resistance of refractories. However, the poor hydrophilicity of graphite and its disadvantage of being easily oxidized at high temperatures limit its application in refractories, especially in castables. To solve this problem, researchers have used the surface coating method to modify graphite, forming a single-phase or multi-phase coating layer on the surface of graphite to improve its oxidation resistance and hydrophilicity.

[0003] Among them, for the patented technology "A modified graphite-based composite material, its preparation method and application" (CN119092741A), graphite powder, polyethylenedioxythiophene, and a solvent are taken and mixed evenly to obtain graphite powder with polyethylenedioxythiophene attached to its surface; then modified graphene, carbon nanotubes, epoxy resin, methyl methacrylate, and tert-butyl perbenzoate are added and mixed evenly to obtain a mixed slurry; and then a modified graphite-based composite material is prepared through a hot pressing process. This method involves processes such as pickling, drying, and hot pressing sintering, with complex operating processes. At the same time, expensive chemical products such as polyethylenedioxythiophene and methyl methacrylate are used in the reaction, resulting in high costs.

[0004] For the patented technology "A high thermal conductivity spherical sulfonated polyether ether ketone / graphite core-shell structure filler and its preparation method" (CN110684512A), sulfonated polyether ether ketone is prepared by nucleophilic substitution reaction after mixing fluorenone, sulfonated fluorenone, and hydroquinone, softened and dried to remove moisture, and then the sulfonated polyether ether ketone is cut using a spherical mold to obtain spherical sulfonated polyether ether ketone particles with different particle size dimensions; finally, the spherical sulfonated polyether ether ketone and micron-sized graphite are subjected to electrostatic adsorption to prepare a high thermal conductivity spherical sulfonated polyether ether ketone / graphite core-shell structure filler with sulfonated polyether ether ketone as the core and micron-sized graphite as the shell. This method requires steps such as nucleophilic substitution reaction and electrostatic adsorption, with a long operation time and complex processes.

[0005] For the patented technology "A preparation process of a copper / graphite core-shell structure" (CN104707997A), a copper / graphite core-shell structure material is prepared by direct current magnetron sputtering and radio frequency plasma enhanced chemical vapor deposition methods. This method requires high-end equipment such as an ultra-high vacuum facing target magnetron sputtering instrument, resulting in high costs. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a method for preparing a MgAl2O4-Al2O3@C composite material. The present invention prepares an AlOOH solution by hydrating sintered magnesia fine powder to form Mg(OH)2 and the boehmite process of metallic aluminum powder; adding spherical graphite powder and an additive and stirring, and finally adding a gelling agent to prepare a precursor gel, and then heat-treating under a reducing atmosphere to obtain the MgAl2O4-Al2O3@C composite material, improving the disadvantages of poor hydrophilicity of graphite and easy oxidation at high temperatures, and solving the problem that it is difficult to apply in unshaped refractory castables.

[0007] To achieve the above object, the technical solution of the present invention is as follows: A method for preparing a MgAl2O4-Al2O3@C composite material, comprising the following steps: Step 1: Based on parts by weight of the raw material addition amount, mix 20 - 48 parts of sintered magnesia fine powder and 18 - 34 parts of metallic aluminum powder with deionized water at a material: water mass ratio of 1:5 - 13, and stir and heat at 80 - 100 °C in a water bath for 1 - 5 h to prepare a Mg(OH)2-AlOOH mixed solution with a concentration of 0.5 - 2.5 g / ml; Step 2: Add 10 - 30 parts of a polyvinyl alcohol solution with a concentration of 0.05 - 0.25 g / ml to the solution obtained in Step 1, and continue stirring for 0.5 - 2.5 h; Step 3: Then sequentially add 5 - 25 parts of spherical graphite powder and 1 - 5 parts of an additive and continue stirring for 0.5 - 2.5 h; finally add 1 - 5 parts of a gelling agent solution with a concentration of 0.05 - 0.25 g / ml to prepare a precursor gel; Step 4: Calcinate the precursor gel at 1300 °C - 1500 °C for 1 - 5 h under a reducing atmosphere to obtain the MgAl2O4-Al2O3@C composite material.

[0008] The purity of the sintered magnesia fine powder > 98%, and the particle size ≤ 1 μm.

[0009] The purity of the metallic aluminum powder > 98%, and the particle size ≤ 1 μm.

[0010] The purity of the spherical graphite powder > 98%, and the particle size ≤ 10 μm.

[0011] The additive is one or more of analytical pure ferric nitrate, chemical pure ferric nitrate, and industrial pure ferric nitrate, with a purity > 99.9%.

[0012] The gelling agent is one or more of analytical pure borax, chemical pure borax, and industrial pure borax, with a purity > 99.9%.

[0013] The present invention is applied to the preparation of carbon sources in the field of carbon-containing refractories.

[0014] Among them, in the present invention, an AlOOH solution is prepared by the hydration of sintered magnesia fine powder to form Mg(OH)₂ and the boehmite process of metallic aluminum powder; with the assistance of a polyvinyl alcohol solution, these coated particles are fixed on the graphite surface through a gelatinization reaction; meanwhile, under a reducing atmosphere condition, along with the decomposition of boehmite and the CO formed during the addition process, a certain CO partial pressure is formed; according to the thermodynamic conditions of the Mg-Al-O-C system, the regulation of the O₂ and CO partial pressures in its environment contributes to the formation of MgAl₂O₄-Al₂O₃.

[0015] The present invention uses the magnesia hydration and boehmite processes to prepare a mixed coating layer of Mg(OH)₂ and AlOOH on the graphite surface, controls the degree of hydration and boehmite process according to the stirring time, introduces additives to promote the combination of active MgO and Al₂O₃ to form a spinel coating layer during the high-temperature action process, increases the connection between particles by regulating the degree of magnesia hydration, the boehmite process and the addition amount of additives. When the surface of the newly formed particles is in a metastable state, it can react with the gas in the environment, and the specific surface area of the newly formed particles relatively increases, and the activity is improved, thereby realizing the integrity of the coating layer.

[0016] In addition, in carbon-containing unshaped refractory materials, the poor wettability of graphite will lead to uneven dispersion of graphite in them, which will lead to uneven distribution of thermal stress in the product and cause cracks. The wetting angle of the present invention is 10 - 35°; thus, the binding ability between the graphite interface and water is improved.

[0017] The beneficial effects of the present invention are as follows: The present invention conducts the hydration and boehmite processes on sintered magnesia fine powder and metallic aluminum powder under a water bath condition, then adds graphite, polyvinyl alcohol solution and additives and stirs them, and prepares a precursor through a gelling agent; the precursor is heat-treated under a reducing atmosphere condition to obtain a MgAl₂O₄-Al₂O₃@C composite material; the raw materials used in the present invention are easily available, non-toxic, environmentally friendly, the operation process is simple, and the prepared MgAl₂O₄-Al₂O₃@C composite material has excellent wettability, improves the problems of poor hydrophilicity and easy oxidation of graphite in refractory castables, and can be widely used in the preparation of carbon sources in the field of carbon-containing refractory materials. Description of the Drawings

[0018] Figure 1 SEM photograph of the MgAl₂O₄-Al₂O₃@C composite material prepared in Example 1. Detailed Embodiments

[0019] The present invention will be further described in detail below with reference to specific embodiments. A preparation method of an MgAl2O4-Al2O3@C composite material provided by an embodiment of the present invention, the raw material addition amount is in parts by weight, the purity of the sintered magnesite fine powder > 98%, the particle size ≤ 1 μm; the purity of the metallic aluminum powder > 98%, the particle size ≤ 1 μm; the purity of the spherical graphite powder > 98%, the particle size ≤ 10 μm.

[0020] Example 1

[0021] A preparation method of an MgAl2O4-Al2O3@C composite material, comprising the following steps: Step 1: Mix 20 parts of sintered magnesite fine powder and 18 parts of metallic aluminum powder with deionized water at a mass ratio of 1:5, and stir and heat at 80 - 85 °C in a water bath for 4 - 5 h to prepare a Mg(OH)2-AlOOH mixed solution; Step 2: Add 10 parts of a polyvinyl alcohol solution with a concentration of 0.2 - 0.25 g / ml to the mixed solution obtained in Step 1, and continue stirring for 0.5 - 1 h; Step 3: Then sequentially add 5 parts of spherical graphite powder and 1 part of additive and continue stirring for 0.5 - 1 h; finally add 1 part of a gelling agent solution with a concentration of 0.2 - 0.25 g / ml to prepare a precursor gel; Step 4: Calcinate the precursor gel at 1300 °C - 1350 °C for 4 - 5 h under a reducing atmosphere condition; thus obtaining the MgAl2O4-Al2O3@C composite material.

[0022] The additive used in this example is analytical pure ferric nitrate, and the gelling agent is industrial pure borax.

[0023] Example 2

[0024] A preparation method of an MgAl2O4-Al2O3@C composite material, comprising the following steps: Step 1: Mix 27 parts of sintered magnesite fine powder and 22 parts of metallic aluminum powder with deionized water at a mass ratio of 1:7, and stir and heat at 85 - 90 °C in a water bath for 3 - 4 h to prepare a Mg(OH)2-AlOOH mixed solution; Step 2: Add 15 parts of a polyvinyl alcohol solution with a concentration of 0.15 - 0.2 g / ml to the solution obtained in Step 1, and continue stirring for 1 - 1.5 h; Step 3: Then sequentially add 10 parts of spherical graphite powder and 2 parts of additive and continue stirring for 1 - 1.5 h; finally add 2 parts of a gelling agent solution with a concentration of 0.15 - 0.2 g / ml to prepare a precursor gel; Step 4: Calcinate the precursor gel at 1350 °C - 1400 °C for 3 - 4 h under a reducing atmosphere condition; thus obtaining the MgAl2O4-Al2O3@C composite material.

[0025] The additive used in this example is analytical pure ferric nitrate, and the gelling agent is chemically pure borax.

[0026] Example 3

[0027] A preparation method of MgAl2O4-Al2O3@C composite material includes the following steps: Step 1: Mix 34 parts of sintered magnesite fine powder and 26 parts of metallic aluminum powder with deionized water at a mass ratio of 1:9, and stir and heat at 80-100 °C in a water bath for 2-3 h to prepare a Mg(OH)2-AlOOH mixed solution; Step 2: Add 20 parts of a polyvinyl alcohol solution with a concentration of 0.1-0.15 g / ml to the solution obtained in Step 1, and continue to stir for 1.5-2 h; Step 3: Then sequentially add 15 parts of spherical graphite powder and 3 parts of additive and continue to stir for 1.5-2 h; finally, add 3 parts of a gelling agent solution with a concentration of 0.1-0.15 g / ml to prepare a precursor gel; Step 4: Calcinate the precursor gel at 1400 °C - 1450 °C for 2-3 h under a reducing atmosphere condition; thus, the MgAl2O4-Al2O3@C composite material is obtained.

[0028] The additive used in this example is industrial pure ferric nitrate, and the gelling agent is analytical pure borax.

[0029] Example 4

[0030] A preparation method of MgAl2O4-Al2O3@C composite material includes the following steps: Step 1: Mix 41 parts of sintered magnesite fine powder and 30 parts of metallic aluminum powder with deionized water at a mass ratio of 1:13, and stir and heat at 80-100 °C in a water bath for 0.5-2.5 h to prepare a Mg(OH)2-AlOOH mixed solution; Step 2: Add 30 parts of a polyvinyl alcohol solution with a concentration of 0.05-0.1 g / ml to the solution obtained in Step 1, and continue to stir for 2-2.5 h; Step 3: Then sequentially add 25 parts of spherical graphite powder and 5 parts of additive and continue to stir for 2-2.5 h; finally, add 5 parts of a gelling agent solution with a concentration of 0.05-0.1 g / ml to prepare a precursor gel; Step 4: Calcinate the precursor gel at 1450 °C - 1500 °C for 1-2 h under a reducing atmosphere condition; thus, the MgAl2O4-Al2O3@C composite material is obtained.

[0031] The additive used in this example is chemically pure ferric nitrate, and the gelling agent is chemically pure borax.

[0032] The performance indexes such as the contact angle test of the samples prepared in Examples 1-4 and the oxidation weight loss rate after the samples are burned are shown in the following table:

[0033] The preparation method of this MgAl2O4-Al2O3@C composite material has non-toxic, harmless and easily available raw materials, so it requires a low production cost; only three steps of water bath, gelatinization and heat treatment are needed, and the preparation process is simple. As can be seen from the above table, the MgAl2O4-Al2O3@C composite material prepared by this preparation method has excellent wettability and high-temperature oxidation resistance.

[0034] The parts not detailed in the present invention are prior arts. The above embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. Within the scope of the present invention defined by the appended claims, various changes in form, details or equivalents made using the present invention specification are within the protection scope of the present invention.

Claims

1. A method for preparing a MgAl2O4-Al2O3@C composite material, characterized in that: The following steps are involved: Step 1: The raw material addition amount is calculated by weight: 20-48 parts of sintered magnesia powder and 18-34 parts of metal aluminum powder are mixed with deionized water at a material: water mass ratio of 1:5-13, and stirred and heated in a water bath at 80-100°C for 1-5 hours to prepare a Mg(OH)2-AlOOH mixed solution with a concentration of 0.5-2.5 g / ml; Step 2: Add 10 to 30 parts of a polyvinyl alcohol solution having a concentration of 0.05 to 0.25 g / ml to the solution obtained in step 1, and continue stirring for 0.5 to 2.5 hours; Step 3: Add 5 to 25 parts of spherical graphite powder and 1 to 5 parts of additives in sequence and continue stirring for 0.5 to 2.5 hours; finally, add 1 to 5 parts of a gelling agent solution with a concentration of 0.05 to 0.25 g / ml to prepare a precursor gel; Step 4: calcine the precursor gel at 1300°C~1500°C for 1~5h under reducing atmosphere conditions; thus, the MgAl2O4-Al2O3@C composite material is obtained.

2. The method for preparing a MgAl2O4-Al2O3@C composite material according to claim 1, characterized in that: The purity of sintered magnesia powder is greater than 98%, and the particle size is ≤1μm.

3. The method for preparing a MgAl2O4-Al2O3@C composite material according to claim 1, characterized in that: The purity of the metal aluminum powder is >98% and the particle size is ≤1μm.

4. The method for preparing a MgAl2O4-Al2O3@C composite material according to claim 1, characterized in that: The purity of spherical graphite powder is greater than 98%, and the particle size is ≤10μm.

5. The method for preparing a MgAl2O4-Al2O3@C composite material according to claim 1, characterized in that: The additive is one or more of analytical pure ferric nitrate, chemical pure ferric nitrate and industrial pure ferric nitrate, with a purity of more than 99.9%.

6. The method for preparing a MgAl2O4-Al2O3@C composite material according to claim 1, characterized in that: The gelling agent is one or more of analytical pure borax, chemical pure borax and industrial pure borax, with a purity of more than 99.9%.

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