Magnesium-aluminum spinel@corundum powder based on low-temperature synthesis and preparation method thereof

Abstract

The application relates to a low-temperature synthesis-based magnesia-alumina spinel corundum powder and a preparation method thereof. The technical scheme is as follows: taking magnesium citrate and magnesium sulfate heptahydrate as magnesium sources, tabular corundum micro powder as an alumina source, and magnesium chloride hexahydrate as a molten salt medium. The magnesium citrate and the magnesium sulfate heptahydrate are mixed and then added into deionized water to obtain solution A after stirring; the tabular corundum micro powder is added into the solution A to obtain mixture B after stirring and drying; the magnesium chloride hexahydrate is mixed with the mixture B to obtain mixture C after stirring. The mixture C is pressed into a shape, heated to 1000-1300 DEG C under the condition of a flowing protective atmosphere in a high-temperature tube furnace, kept warm, and cooled with the furnace; the mixture C is broken, washed with deionized water, washed with isopropyl alcohol again, and dried to obtain the low-temperature synthesis-based magnesia-alumina spinel corundum powder. The low-temperature synthesis-based magnesia-alumina spinel corundum powder prepared by the application has a complete coating structure, high bonding strength, excellent erosion resistance and high purity.

Description

Technical Field

[0001] This invention belongs to the field of corundum powder technology. Specifically, it relates to a magnesium aluminum spinel@corundum powder synthesized at low temperature and its preparation method. Background Technology

[0002] Corundum is an oxide material with high temperature resistance, high strength, and resistance to acids and alkalis, and is widely used in the preparation of alumina refractories. However, slag from steel smelting can severely corrode the corundum in refractories. MgAl2O4, on the other hand, is the only stable oxide in the Al2O3–MgO binary system, possessing excellent erosion resistance and thermal shock resistance. It is often used to replace magnesia-chrome sand in the manufacture of magnesia-alumina spinel bricks or in the production of ladle castables. Its unique spinel crystal structure can absorb various metal ions.

[0003] Zhu Fangdi et al. (Zhu Fangdi, Dai Yajie, Yan Wen, et al. Effects of spinel-coated aggregate on thermal shock resistance and cement clinker erosion resistance of magnesia-alumina refractories. [J]. Journal of the Chinese Ceramic Society. 51(03)(2023)658-668) pointed out that a spinel-coated magnesia aggregate was prepared by physical mixing of fused magnesia aggregate and fine magnesia-alumina spinel powder. The main process is to use pulp waste liquid to combine the aggregate with fine magnesia-alumina spinel powder, and then dry it to obtain spinel-coated magnesia aggregate. However, there are still many pores between magnesia-alumina spinel and magnesia aggregate, the coating is incomplete, the bonding strength between magnesia-alumina spinel and fused magnesia is low, and it is easy to fall off.

[0004] Qu et al. (Jiaoyang Qu, Donghai Ding, Guoqing Xiao, et al. Preparation of CaCO3 coated corundum aggregates by dip-coating and heat treatment and its effects on the properties and microstructures of Al2O3–MgO castables.[J].Ceramics International.48(2022)5174-5186) pointed out that CaCO3 coated corundum aggregates can be prepared by using citric acid solution and light calcium carbonate to prepare a precursor solution, then adding plate-shaped corundum aggregates to the precursor solution for a period of time, and then heat-treating at 430℃ for 3h. However, the use of this coated aggregate in refractory materials will increase the Ca content, thereby reducing the erosion resistance of corundum refractory materials.

[0005] Ding et al. (Donghai Ding, Lihua Lv, Guoqing Xiao, et al. One-step synthesis of in situ multilayer graphene containing MgAl2O4 spinel composite powders.[J].Ceramics International.45(2019)6209-6215) prepared MgAl2O4 / C powder at 1400℃ using magnesium citrate and alumina as raw materials via a carbon-embedded sintering method, but the product purity was low.

[0006] Singh et al. (Subhash Singh, Kaushik Pal. Influence of surface morphology and UFG on damping and mechanical properties of composite reinforced with spinel MgAl2O4–SiC core-shell microcomposites.[J].MaterialsCharacterization.123(2017)244-255) prepared MgAl2O4-coated SiC microcomposites using the sol-gel method. The process involved first preparing a transparent solution using magnesium nitrate hexahydrate and aluminum nitrate nonahydrate, then adding SiC powder to form a sol, and finally heating the sol to obtain a gel, which was then heat-treated at 1000℃ under argon for 12 hours to obtain the final product. However, the bonding strength between the matrix and the coating layer was low, and the MgAl2O4-coated structure was prone to cracking. Summary of the Invention

[0007] The present invention aims to overcome the shortcomings of existing technologies and provides a simple method for preparing magnesium aluminum spinel@corundum powder based on low-temperature synthesis. The magnesium aluminum spinel@corundum powder prepared by this method has a complete coating structure, high bonding strength, excellent erosion resistance and high purity.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] Step 1: Mix 60-80 wt% magnesium sulfate heptahydrate and 20-40 wt% magnesium citrate to obtain mixture A.

[0010] Step 2: Add the mixture A to the deionized water at a mass ratio of 12.5 to 50 to 100, and stir at 30 to 40°C for 1 to 4 hours to obtain solution A.

[0011] Step 3: Add the tabular corundum micro powder to the solution A at a mass ratio of 1 to 10 to 100, stir for 1 to 4 hours, and dry to obtain mixture B.

[0012] Step 4: Mix the mixture B and magnesium chloride hexahydrate at a mass ratio of 100:20-50 and stir for 1-4 hours to obtain mixture C.

[0013] Step 5: Press the mixture C under 5-20 MPa conditions, then place the formed blank in a high-temperature tube furnace, and heat it to 1000-1300℃ at a rate of 3-6℃ / min under a flowing protective atmosphere, hold it at that temperature for 2-5 hours, and allow it to cool naturally in the furnace; crush it, wash it 3-6 times with deionized water, then wash it 2-5 times with isopropanol, and dry it to obtain magnesium aluminum spinel@corundum powder based on low-temperature synthesis.

[0014] The purity of the magnesium sulfate heptahydrate is ≥99.5%, and the particle size is ≤1mm.

[0015] The magnesium citrate has a purity of ≥99% and a particle size of ≤0.1mm.

[0016] The tabular corundum micro powder has an Al2O3 content ≥99.5wt% and a particle size ≤0.074μm.

[0017] The purity of the magnesium chloride hexahydrate is ≥99%, and the particle size is ≤1mm.

[0018] The protective atmosphere for the flow is argon or nitrogen.

[0019] The purity of the isopropanol is ≥99.9%.

[0020] By adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0021] This invention uses plate-shaped corundum micro powder, magnesium sulfate heptahydrate, and magnesium citrate as the main raw materials, and magnesium chloride hexahydrate as the molten salt medium. The materials are mixed, dried, ball-milled, and pressed into shape. Under a flowing protective atmosphere, the temperature is raised to 1000-1300℃ at 3-6℃ / min and held for 2-5 hours, followed by natural cooling in the furnace. The product is then crushed, washed, and dried to obtain magnesium aluminum spinel@corundum powder based on low-temperature synthesis. The process is simple.

[0022] This invention uses an impregnation-loading method combined with a molten salt method to prepare magnesium aluminum spinel@corundum powder based on low-temperature synthesis. Due to the liquid phase environment generated by the molten salt medium, the formation temperature of MgAl2O4 is reduced, and MgAl2O4 is uniformly formed on the surface of corundum in the liquid phase environment, with a complete coating structure.

[0023] This invention employs a low-temperature synthesis method to prepare magnesium aluminum spinel@corundum powder using an impregnation-loading combined with molten salt method. MgAl2O4 is uniformly generated on the corundum surface at a relatively low temperature, and the MgAl2O4 coating layer chemically bonds with the corundum matrix, resulting in high bonding strength.

[0024] This invention utilizes magnesium sulfate heptahydrate and magnesium citrate in deionized water to prepare a solution that can be effectively loaded onto the surface of tabular corundum. Based on the fact that the low-temperature synthesized magnesium aluminum spinel@corundum powder is insoluble in water, while the selected molten salt medium is soluble in water and does not contain other metal ions, the obtained low-temperature synthesized magnesium aluminum spinel@corundum powder is easy to separate from the molten salt, and the product has high purity.

[0025] This invention utilizes a combination of impregnation loading and molten salt method to prepare magnesium aluminum spinel@corundum powder based on low-temperature synthesis. Magnesium aluminum spinel and corundum have small differences in their coefficients of thermal expansion, resulting in good stability under high-temperature operating conditions. The magnesium aluminum spinel coating layer can effectively absorb other metal ions in the slag to form a composite spinel, ensuring the integrity of the low-temperature synthesized magnesium aluminum spinel@corundum powder while significantly improving its corrosion resistance.

[0026] Therefore, the magnesium aluminum spinel@corundum powder prepared by this invention based on low-temperature synthesis has a complete coating structure, high bonding strength, excellent erosion resistance and high purity. Attached Figure Description

[0027] Figure 1 The XRD pattern of a magnesium aluminum spinel@corundum powder prepared by low-temperature synthesis according to the present invention;

[0028] Figure 2 for Figure 1 The image shown is a BSE diagram of the profile of magnesium aluminum spinel@corundum powder synthesized at low temperature.

[0029] Figure 3 for Figure 2 The BSE diagram shown corresponds to the EDS surface distribution of element O.

[0030] Figure 4 for Figure 2 The BSE diagram shown corresponds to the EDS surface distribution of the Al element.

[0031] Figure 5 for Figure 2 The BSE diagram shown corresponds to the EDS surface distribution of Mg. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of protection thereof.

[0033] A magnesium aluminum spinel@corundum powder synthesized at low temperature and its preparation method. The preparation method described in this specific embodiment is as follows:

[0034] Step 1: Mix 60-80 wt% magnesium sulfate heptahydrate and 20-40 wt% magnesium citrate to obtain mixture A.

[0035] Step 2: Add the mixture A to the deionized water at a mass ratio of 12.5 to 50 to 100, and stir at 30 to 40°C for 1 to 4 hours to obtain solution A.

[0036] Step 3: Add the tabular corundum micro powder to the solution A at a mass ratio of 1 to 10 to 100, stir for 1 to 4 hours, and dry to obtain mixture B.

[0037] Step 4: Mix the mixture B and magnesium chloride hexahydrate at a mass ratio of 100:20-50 and stir for 1-4 hours to obtain mixture C.

[0038] Step 5: Press the mixture C under 5-20 MPa conditions, then place the formed blank in a high-temperature tube furnace, and heat it to 1000-1300℃ at a rate of 3-6℃ / min under a flowing protective atmosphere, hold it at that temperature for 2-5 hours, and allow it to cool naturally in the furnace; crush it, wash it 3-6 times with deionized water, then wash it 2-5 times with isopropanol, and dry it to obtain magnesium aluminum spinel@corundum powder based on low-temperature synthesis.

[0039] The protective atmosphere for the flow is argon or nitrogen.

[0040] In this specific implementation:

[0041] The purity of the magnesium sulfate heptahydrate is ≥99.5%, and the particle size is ≤1mm.

[0042] The magnesium citrate has a purity of ≥99% and a particle size of ≤0.1mm.

[0043] The tabular corundum micro powder has an Al2O3 content ≥99.5wt% and a particle size ≤0.074μm.

[0044] The purity of the magnesium chloride hexahydrate is ≥99%, and the particle size is ≤1mm.

[0045] The purity of the isopropanol is ≥99.9%.

[0046] The details will not be repeated in the examples.

[0047] Example 1

[0048] A magnesium aluminum spinel@corundum powder synthesized at low temperature and its preparation method. The preparation method described in this embodiment is as follows:

[0049] Step 1: Mix 60 wt% magnesium sulfate heptahydrate and 40 wt% magnesium citrate to obtain mixture A.

[0050] Step 2: Add the mixture A to the deionized water at a mass ratio of 12.5:100, and stir at 30°C for 1 hour to obtain solution A.

[0051] Step 3: Add the tabular corundum micro powder to the solution A at a mass ratio of 1:100, stir for 1 hour, and dry to obtain mixture B.

[0052] Step 4: Mix the mixture B and magnesium chloride hexahydrate at a mass ratio of 100:20 and stir for 1 hour to obtain mixture C.

[0053] Step 5: Press the mixture C under 5 MPa, then place the formed blank in a high-temperature tube furnace, and heat it to 1000℃ at a rate of 3℃ / min under a flowing protective atmosphere, hold it at that temperature for 2 hours, and let it cool naturally in the furnace; crush it, wash it three times with deionized water, then wash it twice with isopropanol, and dry it to obtain magnesium aluminum spinel@corundum powder based on low-temperature synthesis.

[0054] The protective atmosphere being flowed is argon.

[0055] Example 2

[0056] A magnesium aluminum spinel@corundum powder synthesized at low temperature and its preparation method. The preparation method described in this embodiment is as follows:

[0057] Step 1: Mix 65 wt% magnesium sulfate heptahydrate and 35 wt% magnesium citrate to obtain mixture A.

[0058] Step 2: Add the mixture A to the deionized water at a mass ratio of 25:100, and stir at 33°C for 2 hours to obtain solution A.

[0059] Step 3: Add the tabular corundum micro powder to the solution A at a mass ratio of 4:100, stir for 2 hours, and dry to obtain mixture B.

[0060] Step 4: Mix the mixture B and magnesium chloride hexahydrate at a mass ratio of 100:30 and stir for 2 hours to obtain mixture C.

[0061] Step 5: Press the mixture C under 10 MPa, then place the formed blank in a high-temperature tube furnace, and heat it to 1100℃ at a rate of 4℃ / min under a flowing protective atmosphere, hold it at that temperature for 3 hours, and allow it to cool naturally in the furnace; crush it, wash it 4 times with deionized water, then wash it 3 times with isopropanol, and dry it to obtain magnesium aluminum spinel@corundum powder based on low-temperature synthesis.

[0062] The protective atmosphere being flowed is argon.

[0063] Example 3

[0064] A magnesium aluminum spinel@corundum powder synthesized at low temperature and its preparation method. The preparation method described in this embodiment is as follows:

[0065] Step 1: Mix 70 wt% magnesium sulfate heptahydrate and 30 wt% magnesium citrate to obtain mixture A.

[0066] Step 2: Add the mixture A to the deionized water at a mass ratio of 37.5:100, and stir at 36°C for 3 hours to obtain solution A.

[0067] Step 3: Add the tabular corundum micro powder to the solution A at a mass ratio of 7:100, stir for 3 hours, and dry to obtain mixture B.

[0068] Step 4: Mix the mixture B and magnesium chloride hexahydrate at a mass ratio of 100:40 and stir for 3 hours to obtain mixture C.

[0069] Step 5: Press the mixture C under 15 MPa, then place the formed blank in a high-temperature tube furnace, and heat it to 1200°C at a rate of 5°C / min under a flowing protective atmosphere, hold it at that temperature for 4 hours, and allow it to cool naturally in the furnace; crush it, wash it 5 times with deionized water, then wash it 4 times with isopropanol, and dry it to obtain magnesium aluminum spinel@corundum powder based on low-temperature synthesis.

[0070] The protective atmosphere being flowed is nitrogen.

[0071] Example 4

[0072] A magnesium aluminum spinel@corundum powder synthesized at low temperature and its preparation method. The preparation method described in this embodiment is as follows:

[0073] Step 1: Mix 80 wt% magnesium sulfate heptahydrate and 20 wt% magnesium citrate to obtain mixture A.

[0074] Step 2: Add the mixture A to the deionized water at a mass ratio of 50:100, and stir at 40°C for 4 hours to obtain solution A.

[0075] Step 3: Add the tabular corundum micro powder to solution A at a mass ratio of 10:100, stir for 4 hours, and dry to obtain mixture B.

[0076] Step 4: Mix the mixture B and magnesium chloride hexahydrate at a mass ratio of 100:50 and stir for 4 hours to obtain mixture C.

[0077] Step 5: Press the mixture C under 20 MPa, then place the formed blank in a high-temperature tube furnace, and heat it to 1300℃ at a rate of 6℃ / min under a flowing protective atmosphere, hold it at that temperature for 5 hours, and let it cool naturally in the furnace; crush it, wash it 6 times with deionized water, then wash it 5 times with isopropanol, and dry it to obtain magnesium aluminum spinel@corundum powder based on low-temperature synthesis.

[0078] The protective atmosphere being flowed is nitrogen.

[0079] This specific implementation method has the following advantages compared with the prior art:

[0080] This specific embodiment uses tabular corundum micro powder, magnesium sulfate heptahydrate, and magnesium citrate as the main raw materials, and magnesium chloride hexahydrate as the molten salt medium. The materials are mixed, dried, ball-milled, and pressed into shape. Under a flowing protective atmosphere, the temperature is raised to 1000-1300℃ at 3-6℃ / min and held for 2-5 hours, and then naturally cooled with the furnace. The product is then crushed, washed, and dried to obtain magnesium aluminum spinel@corundum powder based on low-temperature synthesis. The process is simple.

[0081] The magnesium aluminum spinel@corundum powder prepared according to this specific embodiment based on low-temperature synthesis is shown in the attached figure: Figure 1 The image shows the XRD pattern of the magnesium aluminum spinel@corundum powder prepared in Example 3 based on low-temperature synthesis. Figure 2 for Figure 1 The image shown is a BSE diagram of the profile of magnesium aluminum spinel@corundum powder synthesized at low temperature. Figure 3 for Figure 2 The BSE diagram shown corresponds to the EDS surface distribution of element O. Figure 4 for Figure 2 The BSE diagram shown corresponds to the EDS surface distribution of the Al element. Figure 5 for Figure 2 The BSE diagram shown corresponds to the EDS surface distribution of Mg. From Figure 1It can be seen that the main phases of the low-temperature synthesized magnesium aluminum spinel@corundum powder are Al2O3 and MgAl2O4. The MgAl2O4 diffraction peak is strong, and there are no XRD diffraction peaks for other substances, indicating that the prepared low-temperature synthesized magnesium aluminum spinel@corundum powder has high purity and well-developed MgAl2O4. Figure 2 It can be seen that the corundum matrix of the low-temperature synthesized magnesium aluminum spinel@corundum powder is tightly bonded to the magnesium aluminum spinel coating layer without cracks; from Figure 3 and Figure 4 It can be seen that O and Al are distributed throughout the low-temperature synthesized magnesium aluminum spinel@corundum powder, and the two elements overlap in the central region, proving that the central region of the low-temperature synthesized magnesium aluminum spinel@corundum powder is corundum; from Figure 5 It can be seen that the Mg element is distributed in a ring and overlaps with the O and Al elements, completely encapsulating the particles, proving that the MgAl2O4 coating structure of the tabular corundum powder is complete.

[0082] In this specific embodiment, magnesium aluminum spinel@corundum powder based on low-temperature synthesis is prepared by impregnation loading combined with molten salt method. Due to the liquid phase environment generated by magnesium chloride hexahydrate, the formation temperature of MgAl2O4 is reduced, and MgAl2O4 is uniformly formed on the surface of corundum in the liquid phase environment, with a complete coating structure.

[0083] This specific embodiment uses a low-temperature synthesized magnesium aluminum spinel@corundum powder prepared by impregnation loading combined with molten salt method. MgAl2O4 is uniformly generated on the corundum surface at a low temperature, and the MgAl2O4 coating layer chemically bonds with the corundum matrix, resulting in high bonding strength.

[0084] In this specific embodiment, magnesium sulfate heptahydrate and magnesium citrate are used to prepare a solution that can be effectively loaded onto the surface of tabular corundum. Since the low-temperature synthesized magnesium aluminum spinel@corundum powder is insoluble in water, and the selected molten salt medium is soluble in water and does not contain other metal ions, the obtained low-temperature synthesized magnesium aluminum spinel@corundum powder is easy to separate from the molten salt and the product has high purity.

[0085] This specific embodiment uses a low-temperature synthesized magnesium aluminum spinel@corundum powder prepared by impregnation loading combined with molten salt method. The difference in thermal expansion coefficient between magnesium aluminum spinel and corundum is small, and it has good stability under high-temperature use conditions. The magnesium aluminum spinel coating layer can effectively absorb other metal ions in the slag to form composite spinel, ensuring the integrity of the corundum refractory material and improving its erosion resistance.

[0086] Therefore, the magnesium aluminum spinel@corundum powder prepared by this invention based on low-temperature synthesis has a complete coating structure, high bonding strength, excellent erosion resistance, and high purity.

Claims

1. A method for preparing a low-temperature synthesis-based magnesia-alumina spinel@corundum powder, characterized by The steps of the preparation method are: Step one, mixing 60-80wt% of magnesium sulfate heptahydrate and 20-40wt% of magnesium citrate to obtain a mixture A; Step two, adding the mixture A into deionized water according to a mass ratio of the mixture A:deionized water of 12.5-50:100, stirring at 30-40℃ for 1-4h to obtain a solution A; Step three, adding tabular corundum micropowder into the solution A according to a mass ratio of the tabular corundum micropowder:solution A of 1-10:100, stirring for 1-4h, and drying to obtain a mixture B; Step four, mixing the mixture B with magnesium chloride hexahydrate according to a mass ratio of the mixture B:magnesium chloride hexahydrate of 100:20-50, stirring for 1-4h to obtain a mixture C; Step five, pressing the mixture C under a pressure of 5-20MPa, placing the formed green body in a high-temperature tube furnace, heating at a rate of 3-6℃ / min to 1000-1300℃ under a flowing protective atmosphere, maintaining the temperature for 2-5h, and naturally cooling down with the furnace; crushing, washing with deionized water for 3-6 times, washing with isopropanol for 2-5 times, and drying to obtain the low-temperature synthesized magnesium aluminate spinel@corundum powder.

2. The method for preparing low-temperature synthesis-based magnesio-alumina spinel@corundum powder according to claim 1, characterized in that, The purity of the magnesium sulfate heptahydrate is ≥99.5%, and the particle size is ≤1mm.

3. The method for preparing low-temperature synthesis-based magnesio-aluminate spinel@corundum powder according to claim 1, characterized in that, The purity of the magnesium citrate is ≥99%, and the particle size is ≤0.1mm.

4. The method for preparing low-temperature synthesis-based magnesio-aluminate spinel@corundum powder according to claim 1, characterized in that, The Al2O3 content of the tabular corundum micropowder is ≥99.5wt%, and the particle size is ≤0.074μm.

5. The method for preparing low-temperature synthesis-based magnesio-aluminate spinel@corundum powder according to claim 1, characterized in that, The purity of the magnesium chloride hexahydrate is ≥99%, and the particle size is ≤1mm.

6. The method for preparing low-temperature synthesis-based magnesio-aluminate spinel@corundum powder according to claim 1, characterized in that, The flowing protective atmosphere is argon or nitrogen.

7. The method for preparing low-temperature synthesis-based magnesio-aluminate spinel@corundum powder according to claim 1, characterized in that, The purity of the isopropanol is ≥99.9%.

8. A low temperature synthesis based magnesia-alumina spinel@corundum powder, characterized by The low-temperature synthesized magnesium aluminate spinel@corundum powder is prepared according to the preparation method of the low-temperature synthesized magnesium aluminate spinel@corundum powder in any one of claims 1-7.

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