Calcium carbonate-carbon nanotube co-coated magnesium calcium-based refractory and method for preparing the same

Abstract

This invention relates to a calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. The technical solution involves adding a single-element catalyst or compound precursor to a magnesium-calcium refractory material and stirring until homogeneous, resulting in a magnesium-calcium refractory material with one or more of Fe, Co, and Ni surface-loaded. The waste oil and the magnesium-calcium refractory material with one or more of Fe, Co, and Ni surface-loaded are placed in an atmosphere furnace at a mass ratio of 1:1 to 5. Under an inert atmosphere, the temperature is increased to 500 to 1000°C at a rate of 2 to 10°C / min, and the reaction is carried out for 0.5 to 5 hours. The furnace is then cooled to obtain the calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material. This invention features a simple process, controllable operation, low pyrolysis temperature requirements, and high safety. The resulting product exhibits superhydrophobicity, good hydration resistance, high coating layer bonding strength, and good high-temperature resistance.

Description

Technical Field

[0001] This invention belongs to the technical field of magnesium-calcium refractory materials. Specifically, it relates to a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes, and its preparation method. Background Technology

[0002] Magnesia-calcium refractories are alkaline refractories with numerous excellent properties, including high refractoriness, resistance to alkaline slag erosion, thermodynamic stability, high-temperature vacuum stability, and the ability to purify molten steel. They are commonly used in continuous casting tundishes, cement kiln firing zones, and furnace linings. However, the free CaO in these refractories readily reacts with water to form Ca(OH)₂, releasing a large amount of heat and causing significant volume expansion. This leads to the complete pulverization of the magnesia-calcium refractories, posing significant challenges to production, storage, and use, and severely restricting their development and application. Therefore, how to inhibit calcium oxide hydration remains a pressing technical challenge in the field of magnesia-calcium refractories.

[0003] To address this issue, there are currently three main methods for improving the hydration resistance of magnesia-calcium refractories: (1) calcination method: This method uses high-temperature calcination (>1800℃) or secondary calcination. However, the calcination method has high temperature requirements, complex preparation process, and high production cost; (2) additive method: This method improves the hydration resistance of magnesia-calcium refractories by adding sintering aids through different sintering mechanisms. However, adding additives often affects the performance of the material, especially its high-temperature performance; excessive addition will further increase production costs; (3) surface treatment method: This method involves covering the material surface with an organic or inorganic protective layer to isolate air, etc. However, if the protective layer is too thick, it will cause the material volume to increase and reduce the material performance; the bonding strength of the coating layer is not high and it is easy to fall off; the organic coating layer is easy to volatilize into toxic substances at high temperatures, polluting the environment. Therefore, those skilled in the art are constantly developing new technologies:

[0004] The patented technology, "A Method for Preparing Hydration-Resistant CaO Sand" (CN104860688B), involves adding zircon powder to CaO sand, mixing it thoroughly, pressing it into balls or blocks, and then quenching it at a temperature range of 1250–1900℃ to obtain CaO sand. While the resulting CaO sand exhibits improved hydration resistance, the calcination temperature is excessively high, and the addition of zircon powder inevitably lowers the melting point of the CaO sand, leading to a decline in its high-temperature performance.

[0005] Reference I (Xu T, Su Y, Shi T, et al. Improving hydration resistance of MgO-CaOceramics by in situ synthesized CaZrO3 coatings prepared using a non-hydrolytic sol[J].Ceramics International,2021,47(2):2165-2171) prepared CaZrO3 coatings by immersing MgO-CaO ceramics in a 0.6 mol / L non-aqueous solution of ZrO2 and then calcining at 1600℃ for 2 h. The results showed that the hydration weight gain of the modified samples was reduced by 30-50% compared with the raw materials. However, due to the high processing temperature and the high price of ZrO2, there is a problem of high production cost.

[0006] The patented technology, "A Hydration-Resistant Magnesium-Calcium Sand and Its Preparation Method" (CN106495665B), involves cooling magnesium-calcium sand sintered by high-temperature calcination to a temperature of 100–300°C, then continuously spraying organosilicon resin onto the surface of the magnesium-calcium sand, followed by cooling to room temperature to obtain hydration-resistant magnesium-calcium sand. The prepared hydration-resistant magnesium-calcium sand exhibits good hydration resistance due to the organosilicon resin coating that isolates it from air. However, the organic matter releases toxic gases during high-temperature use, polluting the environment.

[0007] Reference II (CHEN M, ITO S, YAMAGUCHIA. Carbonation of CaO clinkers and improvement of their hydration resistance[J]. Journal of the Ceramic Society of Japan, 2002, 110(1282):512-517) describes carbonation of hydrated CaO material by passing CO2 through it, thus coating the surface of the CaO material with a calcium carbonate anti-hydration layer. The resulting anti-hydration CaO material showed no obvious hydration after 7 days at 70℃ / 90% relative humidity, but rapid hydration occurred after 7 days. This indicates that the calcium carbonate coating layer has good anti-hydration performance in a short period of time, but a single coating layer cannot provide long-lasting and stable anti-hydration performance. Furthermore, the calcium carbonate coating layer still has shortcomings such as excessive thickness, low bonding strength, and looseness. Summary of the Invention

[0008] The present invention aims to overcome the defects of the prior art and provides a method for preparing calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory materials that is simple in process, low in production cost, low in energy consumption and environmentally friendly. The calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory materials prepared by this method have superhydrophobicity, excellent hydration resistance, high coating layer bonding strength and good high temperature resistance under service conditions.

[0009] To achieve the above objectives, the technical solution adopted by the present invention comprises the following steps:

[0010] Step 1: Add the elemental catalyst or compound precursor to the magnesium-calcium refractory material and stir until homogeneous to obtain a magnesium-calcium refractory material with one or more of Fe, Co and Ni on its surface.

[0011] The elemental catalyst is one or more of iron powder, cobalt powder, and nickel powder;

[0012] The precursor of the compound is one of nitrate, chloride, and oxide.

[0013] The nitrate is one or more of ferric nitrate, cobalt nitrate, and nickel nitrate;

[0014] The chloride salt is one or more of ferric chloride, cobalt chloride, and nickel chloride;

[0015] The oxide is one or more of iron oxide, cobalt oxide, and nickel oxide.

[0016] The amount of the elemental catalyst added is 0.5 to 10 wt% of the magnesium-calcium refractory material, and the amount of the compound precursor added is 0.5 to 10 wt% of the magnesium-calcium refractory material containing one or more of Fe, Co and Ni.

[0017] Step 2: According to the mass ratio of waste oil to one or more of the magnesium-calcium refractory materials of Fe, Co and Ni on the surface, the waste oil and the magnesium-calcium refractory materials on the surface are mixed at 1:1 to 5 and placed in an atmosphere furnace; under inert atmosphere conditions, the temperature is raised to 500 to 1000°C at a rate of 2 to 10°C / min, and the reaction is carried out for 0.5 to 5 hours. The mixture is then cooled with the furnace to obtain a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes.

[0018] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 140-160° and a hydration weight gain rate of 0.29-4% after being placed at 70°C and 85% relative humidity for 24 hours.

[0019] The method of addition is one of adsorption, dissolution, mixing, coating, and coprecipitation.

[0020] The magnesia-calcium refractory material is a refractory material containing magnesium oxide and calcium oxide, and it can be either magnesia-calcium refractory powder or magnesia-calcium refractory product. Wherein:

[0021] The calcium oxide content of the magnesium-calcium refractory powder is 20-80 wt%, and the particle size of the magnesium-calcium refractory powder is one of the following: less than 3 mm, less than 5 mm and greater than or equal to 3 mm, and less than 50 mm and greater than or equal to 5 mm.

[0022] Magnesia-calcium refractory products refer to refractory products with a certain shape and size made through molding, sintering or other processing techniques. The porosity of magnesium-calcium refractory products is 2-70%, and the calcium oxide content is 20-80 wt%. The size of magnesium-calcium refractory products is one of the following: less than 100 mm and greater than or equal to 50 mm, less than 170 mm and greater than or equal to 100 mm, and less than 240 mm and greater than or equal to 170 mm.

[0023] The waste oil is one of the following: vegetable oil, fossil biomass oil, or animal fat.

[0024] The inert gas is one of nitrogen, argon, and helium; the purity of the inert gas is 99%.

[0025] By adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0026] 1. This invention involves adding a single-element catalyst or compound precursor to a magnesium-calcium refractory material, then placing it in an atmosphere furnace with waste oil, heating it to 500–1000°C in an inert atmosphere, reacting for 0.5–5 hours, and then cooling it with the furnace to obtain a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes. Therefore, this invention has advantages such as simple process flow, controllable operation, low required pyrolysis temperature, and high safety.

[0027] This invention uses magnesia-calcium sand with in-situ generated carbon nanotubes as raw material to prepare a calcium carbonate-carbon nanotube co-coated magnesia-calcium refractories. This magnesia-calcium refractories offer excellent thermal shock resistance and slag corrosion resistance. This is because carbon is a highly chemically stable element with good resistance to most acidic and alkaline substances. Furthermore, the addition of carbon can form carbon-containing compounds, which possess high thermal stability and corrosion resistance, thereby improving the high-temperature resistance of the calcium carbonate-carbon nanotube co-coated magnesia-calcium refractories under service conditions. Carbon can also fill micro-cracks and pores in the material, reducing its permeability and improving its slag corrosion resistance. In addition, the in-situ generation of carbon nanotubes on the surface of the magnesia-calcium sand solves the problem of uniform dispersion of carbon nanotubes in magnesia-calcium refractories. This reduces the amount of graphite carbon added, thus reducing the carburization of molten steel by the calcium carbonate-carbon nanotube co-coated magnesia-calcium refractories.

[0028] 2. The carbon source used in this invention is waste oil, which has the advantages of wide availability and low production cost. The pyrolysis and reuse of waste oil can effectively reduce the problems of oil waste accumulation and disposal, and lower environmental pollution. By reusing waste oil to produce high-value-added products such as calcium carbonate and carbon nanotubes, comprehensive resource utilization can be achieved, resource utilization efficiency can be improved, and production costs are low. At the same time, harmful substances in waste oil can also be treated through the pyrolysis process, reducing negative environmental impacts, lowering the consumption of natural resources, and making it environmentally friendly.

[0029] 3. This invention transforms the free calcium oxide on the surface of magnesia-calcium refractory materials into a dense calcium carbonate film. The calcium carbonate film has a strong bond with the magnesia-calcium refractory material matrix, exhibiting excellent bonding strength and peel resistance, effectively protecting the magnesia-calcium refractory material from external moisture erosion and wear. Furthermore, the hierarchical micro / nano structure constructed from carbon nanotubes provides stable superhydrophobic properties, significantly reducing the water absorption of the calcium carbonate-carbon nanotube co-coated magnesia-calcium refractory material. The combined effect of calcium carbonate and carbon nanotubes not only effectively improves the hydration resistance of the calcium carbonate-carbon nanotube co-coated magnesia-calcium refractory material but also enhances its physical strength and chemical stability, thereby improving its service life and stability.

[0030] 4. The calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material prepared by this invention has been tested and found to have minimal impact on its performance; a static water contact angle of 140–160°; a hydration weight gain rate of 0.29–4%; and features superhydrophobicity and good hydration resistance.

[0031] Therefore, the present invention utilizes the pyrolysis products of waste oil, which has extremely low production costs, low energy consumption, simple process and environmental friendliness; the prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has superhydrophobicity, excellent hydration resistance, high coating layer bonding strength and good high temperature resistance under service conditions. Attached Figure Description

[0032] Figure 1 This is a photograph of the water contact angle of the magnesium-calcium refractory material used in this invention.

[0033] Figure 2 SEM image of a calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material prepared according to the present invention;

[0034] Figure 3 The XRD pattern of another calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material prepared according to the present invention;

[0035] Figure 4 for Figure 2 The image shows a static water contact angle test photograph of a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes. Detailed Implementation

[0036] 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.

[0037] To avoid repetition, the relevant technical parameters of this specific embodiment are described in a unified manner as follows, and will not be repeated in the embodiments:

[0038] The magnesium-calcium refractory material is a refractory material containing magnesium oxide and calcium oxide;

[0039] Magnesium-calcium refractory products refer to refractory products with a certain shape and size that are made through molding, sintering or other processing techniques;

[0040] The purity of the inert gas is 99%.

[0041] Example 1

[0042] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0043] Step 1: Add the compound precursor to the magnesium-calcium refractory material and stir evenly to obtain a magnesium-calcium refractory material with surface loading of any one of Fe, Co and Ni.

[0044] The precursor of the compound is a nitrate.

[0045] The nitrate is one of ferric nitrate, cobalt nitrate, and nickel nitrate.

[0046] The amount of the compound precursor added is 6 to 10 wt% of the mass of the compound precursor containing any one of Fe, Co and Ni in the magnesium-calcium refractory material.

[0047] Step 2: According to the mass ratio of waste oil to the magnesium-calcium refractory material with one of Fe, Co and Ni on the surface, the waste oil and the magnesium-calcium refractory material with one of Fe, Co and Ni on the surface are 1:1 to 3, and the mixture is placed in an atmosphere furnace; under inert atmosphere conditions, the temperature is raised to 500 to 700°C at a rate of 2 to 5°C / min, and the reaction is carried out for 0.5 to 2.5 hours. The mixture is then cooled with the furnace to obtain a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes.

[0048] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 145-155° and a hydration weight gain rate of 0.3-2.1% after being placed at 70°C and 85% relative humidity for 24 hours.

[0049] The method of addition is adsorption.

[0050] Magnesium-calcium refractory materials are magnesium-calcium refractory powders: the calcium oxide content of the magnesium-calcium refractory powder is 40-80 wt%; the particle size of the magnesium-calcium refractory powder is less than 3 mm.

[0051] The waste oil is vegetable oil.

[0052] The inert gas is argon.

[0053] Example 2

[0054] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0055] Step 1: Add the compound precursor to the magnesium-calcium refractory material and stir evenly to obtain a magnesium-calcium refractory material with any two of Fe, Co and Ni loaded on the surface.

[0056] The precursor of the compound is a nitrate.

[0057] The nitrate is a mixture of any two of ferric nitrate, cobalt nitrate, and nickel nitrate.

[0058] The amount of the compound precursor added is 3 to 6 wt% of the mass of any two of Fe, Co and Ni in the compound precursor and the amount of the magnesia-calcium refractory material.

[0059] Step 2: According to the mass ratio of waste oil to any two of the magnesium-calcium refractory materials with surface loading of Fe, Co, and Ni, which is 1:3-4, the waste oil and the magnesium-calcium refractory materials with surface loading of Fe, Co, and Ni are mixed and placed in an atmosphere furnace; under inert atmosphere conditions, the temperature is raised to 600-850℃ at a rate of 5-7℃ / min, and the reaction is carried out for 2.5-3.5h. The mixture is then cooled with the furnace to obtain a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes.

[0060] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 140–152° and a hydration weight gain rate of 0.29–1.9% after being placed at 70°C and 85% relative humidity for 24 hours.

[0061] The method of addition is dissolution.

[0062] Magnesia-calcium refractory material is magnesium-calcium refractory powder: the calcium oxide content of magnesium-calcium refractory powder is 30-40 wt%; the particle size of magnesium-calcium refractory powder is less than 5 mm and greater than or equal to 3 mm.

[0063] The waste oil is animal fat.

[0064] The inert gas is nitrogen.

[0065] Example 3

[0066] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0067] Step 1: Add the compound precursor to the magnesium-calcium refractory material and stir evenly to obtain a magnesium-calcium refractory material with Fe, Co and Ni loaded on the surface.

[0068] The precursor of the compound is a nitrate.

[0069] The nitrate is a mixture of ferric nitrate, cobalt nitrate, and nickel nitrate.

[0070] The amount of the compound precursor added is 0.5 to 3 wt% of the mass of Fe, Co and Ni contained in the compound precursor and the magnesium-calcium refractory material.

[0071] Step 2: According to the mass ratio of waste oil to the magnesium-calcium refractory material with Fe, Co and Ni surface loading, the waste oil and the magnesium-calcium refractory material with Fe, Co and Ni surface loading are 1:4-5, and the mixture is placed in an atmosphere furnace; under inert atmosphere conditions, the temperature is raised to 800-1000℃ at a rate of 7-10℃ / min, and the reaction is carried out for 3.5-5 hours. The mixture is then cooled with the furnace to obtain a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes.

[0072] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 140-155° and a hydration weight gain rate of 2-3.7% after being placed at 70°C and 85% relative humidity for 24 hours.

[0073] The method of addition is mixing.

[0074] Magnesia-calcium refractory material is magnesium-calcium refractory powder: the calcium oxide content of magnesium-calcium refractory powder is 20-30 wt%; the particle size of magnesium-calcium refractory powder is less than 50 mm and greater than or equal to 5 mm.

[0075] The waste oil is fossil biomass oil.

[0076] The inert gas is helium.

[0077] Example 4

[0078] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0079] Step 1: Add the compound precursor to the magnesium-calcium refractory material and stir evenly to obtain a magnesium-calcium refractory material with surface loading of any one of Fe, Co and Ni.

[0080] The precursor of the compound is a chloride salt.

[0081] The chloride salt is any one of ferric chloride, cobalt chloride, and nickel chloride.

[0082] The amount of the compound precursor added is 6.5 to 10 wt% of the mass of any one of Fe, Co and Ni in the magnesia-calcium refractory material.

[0083] Step 2: According to the mass ratio of waste oil to the magnesium-calcium refractory material with one of Fe, Co and Ni on the surface, the waste oil and the magnesium-calcium refractory material with one of Fe, Co and Ni on the surface are 1:1 to 2, and the mixture is placed in an atmosphere furnace; under inert atmosphere conditions, the temperature is raised to 500 to 700°C at a rate of 2 to 5°C / min, and the reaction is carried out for 0.5 to 2 hours. The mixture is then cooled with the furnace to obtain a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes.

[0084] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 145-152° and a hydration weight gain rate of 0.5-2.6% after being placed at 70℃ and 85% relative humidity for 24 hours.

[0085] The method of addition is co-precipitation.

[0086] Magnesium-calcium refractory materials are magnesium-calcium refractory powders: the calcium oxide content of the magnesium-calcium refractory powder is 60-80 wt%; the particle size of the magnesium-calcium refractory powder is less than 3 mm.

[0087] The waste oil is vegetable oil.

[0088] The inert gas is argon.

[0089] Example 5

[0090] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0091] Step 1: Add the compound precursor to the magnesium-calcium refractory material and stir evenly to obtain a magnesium-calcium refractory material with any two of Fe, Co and Ni loaded on the surface.

[0092] The precursor of the compound is a chloride salt.

[0093] The chloride salt is a mixture of any two of ferric chloride, cobalt chloride, and nickel chloride.

[0094] The amount of the compound precursor added is 2.5 to 6.5 wt% of the mass of any two of Fe, Co and Ni in the compound precursor.

[0095] Step 2: According to the mass ratio of waste oil to any two of the magnesium-calcium refractory materials with surface loading of Fe, Co, and Ni, which is 1:2-3, the waste oil and the magnesium-calcium refractory materials with surface loading of Fe, Co, and Ni are mixed and placed in an atmosphere furnace; under inert atmosphere conditions, the temperature is raised to 600-850℃ at a rate of 5-7℃ / min, and the reaction is carried out for 2-3 hours. The mixture is then cooled with the furnace to obtain a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes.

[0096] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 147–153° and a hydration weight gain rate of 0.7–2.2% after being placed at 70°C and 85% relative humidity for 24 hours.

[0097] The method of addition is coating.

[0098] Magnesia-calcium refractory material is magnesium-calcium refractory powder: the calcium oxide content of magnesium-calcium refractory powder is 40-60 wt%; the particle size of magnesium-calcium refractory powder is less than 5 mm and greater than or equal to 3 mm.

[0099] The waste oil is animal fat.

[0100] The inert gas is nitrogen.

[0101] Example 6

[0102] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0103] Step 1: Add the compound precursor to the magnesium-calcium refractory material and stir evenly to obtain a magnesium-calcium refractory material with Fe, Co and Ni loaded on the surface.

[0104] The precursor of the compound is a chloride salt.

[0105] The chloride salt is a mixture of ferric chloride, cobalt chloride, and nickel chloride.

[0106] The amount of the compound precursor added is 0.5 to 2.5 wt% of the mass of Fe, Co and Ni contained in the compound precursor and the magnesium-calcium refractory material.

[0107] Step 2: According to the mass ratio of waste oil to the magnesium-calcium refractory material with Fe, Co and Ni surface loading, the waste oil and the magnesium-calcium refractory material with Fe, Co and Ni surface loading are 1:3 to 5. The mixture is placed in an atmosphere furnace. Under inert atmosphere conditions, the temperature is raised to 800 to 1000°C at a rate of 7 to 10°C / min, and the reaction is carried out for 3 to 5 hours. The mixture is then cooled with the furnace to obtain a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes.

[0108] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 143–157° and a hydration weight gain rate of 1.6–3.3% after being placed at 70°C and 85% relative humidity for 24 hours.

[0109] The method of addition is adsorption.

[0110] Magnesia-calcium refractory material is magnesium-calcium refractory powder: the calcium oxide content of magnesium-calcium refractory powder is 20-40 wt%; the particle size of magnesium-calcium refractory powder is less than 50 mm and greater than or equal to 5 mm.

[0111] The waste oil is fossil biomass oil.

[0112] The inert gas is helium.

[0113] Example 7

[0114] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0115] Step 1: Add the compound precursor to the magnesium-calcium refractory material and stir evenly to obtain a magnesium-calcium refractory material with surface loading of any one of Fe, Co and Ni.

[0116] The precursor of the compound is an oxide.

[0117] The oxide is any one of iron oxide, cobalt oxide, and nickel oxide.

[0118] The amount of the compound precursor added is 7-10 wt% of the mass of Fe, Co and Ni contained in the compound precursor and the magnesia-calcium refractory material.

[0119] Step 2: According to the mass ratio of waste oil to the magnesium-calcium refractory material with one of Fe, Co and Ni on the surface, the waste oil and the magnesium-calcium refractory material with one of Fe, Co and Ni on the surface are 1:1 to 2.5, and the mixture is placed in an atmosphere furnace; under inert atmosphere conditions, the temperature is raised to 500 to 700°C at a rate of 2 to 5°C / min, and the reaction is carried out for 0.5 to 3 hours. The mixture is then cooled with the furnace to obtain a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes.

[0120] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 141–153° and a hydration weight gain rate of 0.31–2.2% after being placed at 70°C and 85% relative humidity for 24 hours.

[0121] The method of addition is dissolution.

[0122] Magnesium-calcium refractory materials are magnesium-calcium refractory powders: the calcium oxide content of the magnesium-calcium refractory powder is 50-80 wt%; the particle size of the magnesium-calcium refractory powder is less than 3 mm.

[0123] The waste oil is vegetable oil.

[0124] The inert gas is argon.

[0125] Example 8

[0126] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0127] Step 1: Add the compound precursor to the magnesium-calcium refractory material and stir evenly to obtain a magnesium-calcium refractory material with any two of Fe, Co and Ni loaded on the surface.

[0128] The precursor of the compound is an oxide.

[0129] The oxide is a mixture of any two of iron oxide, cobalt oxide, and nickel oxide.

[0130] The amount of the compound precursor added is 4 to 7 wt% of the mass of any two of Fe, Co and Ni in the compound precursor and the amount of the precursor in the magnesium-calcium refractory material.

[0131] Step 2: According to the mass ratio of waste oil to any two of the magnesium-calcium refractory materials with surface loading of Fe, Co, and Ni, which is 1:2.5-3.5, the waste oil and the magnesium-calcium refractory materials with surface loading of Fe, Co, and Ni are mixed and placed in an atmosphere furnace; under inert atmosphere conditions, the temperature is raised to 600-850℃ at a rate of 5-7℃ / min, and the reaction is carried out for 3-4 hours. The mixture is then cooled with the furnace to obtain a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes.

[0132] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 146–155° and a hydration weight gain rate of 0.5–2.9% after being placed at 70°C and 85% relative humidity for 24 hours.

[0133] The method of addition is mixing.

[0134] Magnesium-calcium refractory material is magnesium-calcium refractory powder: the calcium oxide content of magnesium-calcium refractory powder is 30-50 wt%; the particle size of magnesium-calcium refractory powder is less than 5 mm and greater than or equal to 3 mm.

[0135] The waste oil is animal fat.

[0136] The inert gas is nitrogen.

[0137] Example 9

[0138] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0139] Step 1: Add the compound precursor to the magnesium-calcium refractory material and stir evenly to obtain a magnesium-calcium refractory material with Fe, Co and Ni loaded on the surface.

[0140] The precursor of the compound is an oxide.

[0141] The oxide is a mixture of iron oxide, cobalt oxide and nickel oxide.

[0142] The amount of the compound precursor added is 0.5 to 4 wt% of the mass of Fe, Co and Ni contained in the compound precursor and the magnesium-calcium refractory material.

[0143] Step 2: According to the mass ratio of waste oil to the magnesium-calcium refractory material with Fe, Co and Ni surface loading, the waste oil and the magnesium-calcium refractory material with Fe, Co and Ni surface loading are 1:3.5-5. The mixture is placed in an atmosphere furnace. Under inert atmosphere conditions, the temperature is raised to 800-1000℃ at a rate of 7-10℃ / min and reacted for 4-5 hours. The mixture is then cooled with the furnace to obtain a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes.

[0144] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 148-154° and a hydration weight gain of 2.4-4% after being placed at 70°C and 85% relative humidity for 24 hours.

[0145] The method of addition is coating.

[0146] Magnesia-calcium refractory material is magnesium-calcium refractory powder: the calcium oxide content of magnesium-calcium refractory powder is 20-30 wt%; the particle size of magnesium-calcium refractory powder is less than 50 mm and greater than or equal to 5 mm.

[0147] The waste oil is fossil biomass oil.

[0148] The inert gas is helium.

[0149] Example 10

[0150] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0151] Step 1: Add the elemental catalyst to the magnesium-calcium refractory material and stir until homogeneous to obtain a magnesium-calcium refractory material with any one of Fe, Co and Ni loaded on its surface.

[0152] The elemental catalyst is any one of iron powder, cobalt powder, and nickel powder.

[0153] The amount of the elemental catalyst added is 6.5 to 10 wt% of the magnesium-calcium refractory material.

[0154] Step 2: According to the mass ratio of waste oil to the magnesium-calcium refractory material with one of Fe, Co and Ni on the surface, the waste oil and the magnesium-calcium refractory material with one of Fe, Co and Ni on the surface are 1:1 to 1.5, and the mixture is placed in an atmosphere furnace; under inert atmosphere conditions, the temperature is raised to 500 to 700°C at a rate of 2 to 4°C / min, and the reaction is carried out for 0.5 to 2 hours. The mixture is then cooled with the furnace to obtain a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes.

[0155] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 142–151° and a hydration weight gain rate of 0.5–1.9% after being placed at 70°C and 85% relative humidity for 24 hours.

[0156] The method of addition is co-precipitation.

[0157] Magnesium-calcium refractory materials are magnesium-calcium refractory powders: the calcium oxide content of the magnesium-calcium refractory powder is 60-80 wt%; the particle size of the magnesium-calcium refractory powder is less than 3 mm.

[0158] The waste oil is vegetable oil.

[0159] The inert gas is argon.

[0160] Example 11

[0161] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0162] Step 1: Add the elemental catalyst to the magnesium-calcium refractory material and stir evenly to obtain a magnesium-calcium refractory material with any two of Fe, Co and Ni loaded on its surface.

[0163] The elemental catalyst is any two of iron powder, cobalt powder, and nickel powder.

[0164] The amount of the elemental catalyst added is 3.5 to 6.5 wt% of the magnesium-calcium refractory material.

[0165] Step 2: According to the mass ratio of waste oil to any two of the magnesium-calcium refractory materials with surface loading of Fe, Co, and Ni, which is 1:1.5-3, the waste oil and the magnesium-calcium refractory materials with surface loading of any two of Fe, Co, and Ni are mixed and placed in an atmosphere furnace; under inert atmosphere conditions, the temperature is raised to 600-850℃ at a rate of 4-7℃ / min, and the reaction is carried out for 2-3 hours. The mixture is then cooled with the furnace to obtain a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes.

[0166] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 148–160° and a hydration weight gain rate of 1.8–3.1% after being placed at 70°C and 85% relative humidity for 24 hours.

[0167] The method of addition is dissolution.

[0168] Magnesia-calcium refractory material is magnesium-calcium refractory powder: the calcium oxide content of magnesium-calcium refractory powder is 50-60 wt%; the particle size of magnesium-calcium refractory powder is less than 5 mm and greater than or equal to 3 mm.

[0169] The waste oil is animal fat.

[0170] The inert gas is nitrogen.

[0171] Example 12

[0172] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0173] Step 1: Add the elemental catalyst to the magnesium-calcium refractory material and stir until homogeneous to obtain a magnesium-calcium refractory material with Fe, Co and Ni loaded on its surface.

[0174] The elemental catalyst is a mixture of iron powder, cobalt powder, and nickel powder.

[0175] The amount of the elemental catalyst added is 0.5 to 3.5 wt% of the magnesium-calcium refractory material.

[0176] Step 2: According to the mass ratio of waste oil to the magnesium-calcium refractory material with Fe, Co and Ni surface loading, the waste oil and the magnesium-calcium refractory material with Fe, Co and Ni surface loading are 1:3 to 5. The mixture is placed in an atmosphere furnace. Under inert atmosphere conditions, the temperature is raised to 800 to 1000°C at a rate of 7 to 10°C / min, and the reaction is carried out for 3 to 5 hours. The mixture is then cooled with the furnace to obtain a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes.

[0177] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 143-155° and a hydration weight gain rate of 2.3-4% after being placed at 70°C and 85% relative humidity for 24 hours.

[0178] The method of addition is co-precipitation.

[0179] Magnesia-calcium refractory material is magnesium-calcium refractory powder: the calcium oxide content of magnesium-calcium refractory powder is 20-50 wt%; the particle size of magnesium-calcium refractory powder is less than 50 mm and greater than or equal to 5 mm.

[0180] The waste oil is fossil biomass oil.

[0181] The inert gas is nitrogen.

[0182] Example 13

[0183] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. This embodiment is identical to Embodiment 1 except as described below.

[0184] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 140-150° and a hydration weight gain rate of 0.5-1.85% after being placed at 70°C and 85% relative humidity for 24 hours.

[0185] The magnesia-calcium refractory material is a magnesia-calcium refractory material product: the porosity of the magnesia-calcium refractory material product is 55-70%, the calcium oxide content of the magnesia-calcium refractory material product is 60-80 wt%, and the size of the magnesia-calcium refractory material product is less than 100 mm and greater than or equal to 50 mm.

[0186] Example 14

[0187] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. This embodiment is identical to Embodiment 2 except as described below.

[0188] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 147–152° and a hydration weight gain rate of 1.4–3.2% after being placed at 70°C and 85% relative humidity for 24 hours.

[0189] The magnesia-calcium refractory material is a magnesia-calcium refractory material product: the porosity of the magnesia-calcium refractory material product is 30-60%, the calcium oxide content of the magnesia-calcium refractory material product is 30-60 wt%, and the size of the magnesia-calcium refractory material product is less than 170 mm and greater than or equal to 100 mm.

[0190] Example 15

[0191] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. This embodiment is identical to Example 3 except as described below.

[0192] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 141-151° and a hydration weight gain rate of 2.7-4% after being placed at 70°C and 85% relative humidity for 24 hours.

[0193] The magnesia-calcium refractory material is a magnesia-calcium refractory material product: the porosity of the magnesia-calcium refractory material product is 2-40%, the calcium oxide content of the magnesia-calcium refractory material product is 20-30 wt%, and the size of the magnesia-calcium refractory material product is less than 240 mm and greater than or equal to 170 mm.

[0194] Example 16

[0195] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. This embodiment is identical to Example 4 except as described below.

[0196] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 149–160° and a hydration weight gain rate of 1–2.2% after being placed at 70°C and 85% relative humidity for 24 hours.

[0197] The magnesia-calcium refractory material is a magnesia-calcium refractory material product: the porosity of the magnesia-calcium refractory material product is 50-70%, the calcium oxide content of the magnesia-calcium refractory material product is 55-80 wt%, and the size of the magnesia-calcium refractory material product is less than 100 mm and greater than or equal to 50 mm.

[0198] Example 17

[0199] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. This embodiment is identical to Example 5 except as described below.

[0200] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 142–156° and a hydration weight gain rate of 1.3–3.17% after being placed at 70°C and 85% relative humidity for 24 hours.

[0201] The magnesia-calcium refractory material is a magnesia-calcium refractory material product: the porosity of the magnesia-calcium refractory material product is 25-55%, the calcium oxide content of the magnesia-calcium refractory material product is 35-55 wt%, and the size of the magnesia-calcium refractory material product is less than 170 mm and greater than or equal to 100 mm.

[0202] Example 18

[0203] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. This embodiment is identical to Example 6 except as described below.

[0204] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 144–154° and a hydration weight gain rate of 2.4–3.9% after being placed at 70°C and 85% relative humidity for 24 hours.

[0205] The magnesia-calcium refractory material is a magnesia-calcium refractory material product: the porosity of the magnesia-calcium refractory material product is 2-35%, the calcium oxide content of the magnesia-calcium refractory material product is 20-35 wt%, and the size of the magnesia-calcium refractory material product is less than 240 mm and greater than or equal to 170 mm.

[0206] Example 19

[0207] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. This embodiment is identical to Example 7 except as described below.

[0208] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 143–155° and a hydration weight gain rate of 0.7–2.2% after being placed at 70°C and 85% relative humidity for 24 hours.

[0209] The magnesia-calcium refractory material is a magnesia-calcium refractory material product: the porosity of the magnesia-calcium refractory material product is 45-70%, the calcium oxide content of the magnesia-calcium refractory material product is 55-80 wt%, and the size of the magnesia-calcium refractory material product is less than 100 mm and greater than or equal to 50 mm.

[0210] Example 20

[0211] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. This embodiment is identical to Example 8 except as described below.

[0212] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 146–158° and a hydration weight gain rate of 1.8–3.2% after being placed at 70°C and 85% relative humidity for 24 hours.

[0213] The magnesia-calcium refractory material is a magnesia-calcium refractory material product: the porosity of the magnesia-calcium refractory material product is 30-55%, the calcium oxide content of the magnesia-calcium refractory material product is 45-55 wt%, and the size of the magnesia-calcium refractory material product is less than 170 mm and greater than or equal to 100 mm.

[0214] Example 21

[0215] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. This embodiment is identical to Example 9 except as described below.

[0216] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 143-152° and a hydration weight gain rate of 2.1-4% after being placed at 70°C and 85% relative humidity for 24 hours.

[0217] The magnesia-calcium refractory material is a magnesia-calcium refractory product: the porosity of the magnesia-calcium refractory product is 2-40%, the calcium oxide content of the magnesia-calcium refractory product is 20-45 wt%, and the size of the magnesia-calcium refractory product is less than 240 mm and greater than or equal to 170 mm.

[0218] Example 22

[0219] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. This embodiment is identical to Example 10 except as described below.

[0220] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 144–152° and a hydration weight gain rate of 0.9–2.6% after being placed at 70°C and 85% relative humidity for 24 hours.

[0221] The magnesia-calcium refractory material is a magnesia-calcium refractory material product: the porosity of the magnesia-calcium refractory material product is 45-70%, the calcium oxide content of the magnesia-calcium refractory material product is 65-80 wt%, and the size of the magnesia-calcium refractory material product is less than 100 mm and greater than or equal to 50 mm.

[0222] Example 23

[0223] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. This embodiment is identical to Example 11 except as described below.

[0224] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 148–160° and a hydration weight gain rate of 1.2–2.8% after being placed at 70°C and 85% relative humidity for 24 hours.

[0225] The magnesia-calcium refractory material is a magnesia-calcium refractory material product: the porosity of the magnesia-calcium refractory material product is 25-50%, the calcium oxide content of the magnesia-calcium refractory material product is 35-65 wt%, and the size of the magnesia-calcium refractory material product is less than 170 mm and greater than or equal to 100 mm.

[0226] Example 24

[0227] A calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material and its preparation method. This embodiment is identical to Example 12 except as described below.

[0228] The prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 149–160° and a hydration weight gain rate of 2.5–4% after being placed at 70°C and 85% relative humidity for 24 hours.

[0229] The magnesia-calcium refractory material is a magnesia-calcium refractory material product: the porosity of the magnesia-calcium refractory material product is 2-38%, the calcium oxide content of the magnesia-calcium refractory material product is 20-35 wt%, and the size of the magnesia-calcium refractory material product is less than 240 mm and greater than or equal to 170 mm.

[0230] This specific implementation method has the following advantages compared with the prior art:

[0231] 1. In this specific embodiment, a single-element catalyst or compound precursor is added to a magnesium-calcium refractory material, and then placed in an atmosphere furnace with waste oil. The mixture is heated to 500-1000°C in an inert atmosphere and reacted for 0.5-5 hours. The mixture is then cooled with the furnace to obtain a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes. Therefore, this specific embodiment has advantages such as simple process flow, controllable operation, low required pyrolysis temperature, and high safety.

[0232] This specific embodiment uses magnesia-calcium sand with in-situ generated carbon nanotubes as raw material. The resulting calcium carbonate-carbon nanotube co-coated magnesia-calcium refractories provide excellent thermal shock resistance and slag corrosion resistance. This is because carbon is a highly chemically stable element with good resistance to most acidic and alkaline substances. Furthermore, the addition of carbon can form carbon-containing compounds, which have high thermal stability and corrosion resistance, thereby improving the high-temperature resistance of the calcium carbonate-carbon nanotube co-coated magnesia-calcium refractories under service conditions. Carbon can also fill micro-cracks and pores in the material, reducing its permeability and improving its slag corrosion resistance. In addition, the in-situ generation of carbon nanotubes on the surface of the magnesia-calcium sand solves the problem of uniform dispersion of carbon nanotubes in magnesia-calcium refractories. This reduces the amount of graphite carbon added, thus reducing the carburization of molten steel by the calcium carbonate-carbon nanotube co-coated magnesia-calcium refractories.

[0233] 2. The carbon source used in this specific embodiment is waste oil, which has the advantages of wide availability and low production cost. The pyrolysis and reuse of waste oil can effectively reduce the accumulation and disposal of oily waste, thus reducing environmental pollution. By reusing waste oil to produce high-value-added products such as calcium carbonate and carbon nanotubes, comprehensive resource utilization is achieved, resource utilization efficiency is improved, and production costs are low. At the same time, harmful substances in waste oil can also be treated through the pyrolysis process, reducing negative environmental impacts, lowering the consumption of natural resources, and making it environmentally friendly.

[0234] 3. In this specific embodiment, the free calcium oxide on the surface of the magnesia-calcium refractory material is converted into a dense calcium carbonate film. The calcium carbonate film has a strong bond with the magnesia-calcium refractory material matrix, exhibiting excellent bonding strength and peel resistance, effectively protecting the magnesia-calcium refractory material from external moisture erosion and wear. Furthermore, the calcium carbonate-carbon nanotube co-coated magnesia-calcium refractory material prepared in this specific embodiment is shown in the attached figure. Figure 1 This is a photograph of the water contact angle of the magnesium-calcium refractory material used in this specific embodiment. Figure 2 SEM image of a calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material prepared in Example 1; Figure 3 The XRD pattern of a calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material prepared in Example 13; Figure 4 for Figure 2 The image shown is a static water contact angle test photograph of a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes. From... Figure 1 It can be seen that magnesium-calcium refractory materials are hydrophilic; from Figure 2 It can be seen that the prepared superhydrophobic magnesium-calcium refractory material has a large number of carbon nanotubes woven into a network structure on its surface, and these nanotubes are uniformly distributed in the pores or on the surface of the magnesium-calcium refractory material; from Figure 3 It can be seen that the calcium oxide on the sample surface is basically converted into calcium carbonate, and it is this conversion that improves the hydration resistance of the magnesium-calcium refractory material; from Figure 4 It can be seen that the prepared calcium carbonate-carbon nanotube co-coated superhydrophobic magnesium-calcium refractory material exhibits hydrophobicity with a hydrophobic angle of 157°. Water droplets can remain on the sample surface for more than 3 minutes, indicating that the prepared carbon nanotube-coated superhydrophobic magnesium-calcium refractory material has superhydrophobicity.

[0235] The product manufactured in this specific embodiment provides stable superhydrophobic properties due to the hierarchical micro-nano structure constructed from carbon nanotubes. This significantly reduces the water absorption of calcium carbonate-carbon nanotube co-coated magnesia-calcium refractory materials. The combined effect of calcium carbonate and carbon nanotubes not only effectively improves the hydration resistance of calcium carbonate-carbon nanotube co-coated magnesia-calcium refractory materials, but also enhances their physical strength and chemical stability, thereby improving their service life and stability.

[0236] 4. The calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material prepared in this specific embodiment has been tested and found to have minimal impact on its performance; a static water contact angle of 140–160°; a hydration weight gain rate of 0.29–4%; and features superhydrophobicity and good hydration resistance.

[0237] Therefore, this specific embodiment utilizes the pyrolysis products of waste oil, which has extremely low production costs, low energy consumption, simple process and environmental friendliness; the prepared calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has superhydrophobicity, excellent hydration resistance, high coating layer bonding strength and good high temperature resistance under service conditions.

Claims

1. A method for preparing a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes, characterized in that... The preparation method comprises the following steps: Step 1: Add the elemental catalyst or compound precursor to the magnesium-calcium refractory material and stir evenly to obtain a magnesium-calcium refractory material with one or more of Fe, Co and Ni on the surface. The elemental catalyst is one or more of iron powder, cobalt powder, and nickel powder; The precursor of the compound is one of nitrate, chloride, and oxide; The nitrate is one or more of ferric nitrate, cobalt nitrate, and nickel nitrate; The chloride salt is one or more of ferric chloride, cobalt chloride, and nickel chloride; The oxide is one or more of iron oxide, cobalt oxide and nickel oxide; The amount of the elemental catalyst added is 0.5-10 wt% of the magnesium-calcium refractory material, and the amount of the compound precursor added is 0.5-10 wt% of the magnesium-calcium refractory material. Step 2: According to the mass ratio of waste oil to one or more of the magnesium-calcium refractory materials of Fe, Co and Ni on the surface, the waste oil and the magnesium-calcium refractory materials on the surface are mixed at 1:1 to 5 and placed in an atmosphere furnace; under inert atmosphere conditions, the temperature is raised to 500 to 1000°C at a rate of 2 to 10°C / min, and the reaction is carried out for 0.5 to 5 hours. The mixture is then cooled with the furnace to obtain a magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes.

2. The method for preparing the calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material according to claim 1, characterized in that: The method of addition is one of adsorption, dissolution, mixing, coating, and coprecipitation.

3. The method for preparing the calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material according to claim 1, characterized in that: The magnesia-calcium refractory material is a refractory material containing magnesium oxide and calcium oxide, and is either magnesia-calcium refractory powder or magnesia-calcium refractory product; wherein: The calcium oxide content of the magnesium-calcium refractory powder is 20~80wt%; the particle size of the magnesium-calcium refractory powder is one of the following: less than 3mm, less than 5mm and greater than or equal to 3mm, and less than 50mm and greater than or equal to 5mm. Magnesia-calcium refractory products refer to refractory products with a certain shape and size that are formed and sintered. The porosity of magnesium-calcium refractory products is 2~70%, and the calcium oxide content is 20~80wt%. The size of magnesium-calcium refractory products is one of the following: less than 100mm and greater than or equal to 50mm, less than 170mm and greater than or equal to 100mm, and less than 240mm and greater than or equal to 170mm.

4. The method for preparing the calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material according to claim 1, characterized in that: The waste oil is one of the following: vegetable oil, fossil biomass oil, or animal fat.

5. The method for preparing the calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material according to claim 1, characterized in that: The inert gas is either argon or helium; the purity of the inert gas is 99%.

6. A magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes, characterized in that... The calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material is prepared by the method described in any one of claims 1 to 5.

7. The magnesium-calcium refractory material co-coated with calcium carbonate and carbon nanotubes according to claim 6, characterized in that... The calcium carbonate-carbon nanotube co-coated magnesium-calcium refractory material has a water contact angle of 140~160° and a hydration weight gain rate of 0.29~4% after being placed at 70℃ and 85% relative humidity for 24 hours.

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