Lightweight periclase-carbon refractory with multi-scale core-shell structure and preparation method thereof

Abstract

The present application relates to a kind of lightweight periclase-carbon refractory with multi-scale core-shell structure and preparation method.The technical scheme is:16-24wt% of microporous periclase refractory aggregate I,22-32wt% of microporous periclase refractory aggregate II and 16-24wt% of microporous periclase refractory aggregate III are total aggregate,24-38wt% of magnesia powder,0.1-1.5wt% of elemental silicon powder and 0.5-3wt% of flake graphite powder are total matrix.First, total aggregate is placed in the mixer,2-6wt% of modified liquid thermosetting phenolic resin is added to total aggregate and total matrix, and mixed evenly;Then, total matrix is added, stirred;Machine is pressed into shape, 200-320 ℃ is kept for 12-36h, and the lightweight periclase-carbon refractory with multi-scale core-shell structure is prepared.The product has the characteristics of multi-scale core-shell structure, low thermal conductivity, high strength, good thermal shock stability and strong erosion resistance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of periclase-carbon refractories. In particular, it relates to a lightweight periclase-carbon refractory with a multi-scale core-shell structure and a preparation method. BACKGROUND

[0002] Periclase-carbon refractories have excellent thermal shock resistance and high-temperature slag corrosion resistance due to the presence of carbon components such as flake graphite, and are widely used as slag line bricks for steelmaking ladles.

[0003] There are many methods for preparing periclase-carbon refractories at present:

[0004] For example, the patent technology "Preparation method of magnesia-carbon brick" (CN202110472563.0) uses magnesia, tar, phenolic resin, silicon carbide whiskers, carbon fiber powder, and nano rare earth oxides as raw materials to prepare a periclase-carbon refractory. However, dense magnesia is used as the aggregate, and the bond at the aggregate / matrix interface is poor, resulting in poor strength of the refractory.

[0005] For example, the patent technology "Magnesia-carbon brick and preparation method thereof" (CN201611236533.5) uses fused magnesia particles, fused magnesia fine powder, carbon, antioxidant, and silica sol as raw materials to prepare a periclase-carbon refractory. However, dense fused magnesia is used as the aggregate, resulting in high thermal conductivity and energy waste.

[0006] For example, the patent technology "High-performance magnesia-carbon brick and preparation method thereof" (CN201810919187.3) uses fused magnesia, aluminum powder, spinel-calcium aluminate composite material, flake graphite, and binder as raw materials to prepare a periclase-carbon refractory. However, the introduction of low-melting-point substances in the magnesia-carbon brick results in poor erosion and penetration resistance of the material.

[0007] For example, the patent technology "Magnesia-carbon brick and preparation method thereof" (CN202010565496.2) uses fused magnesia, carbon fiber powder, graphite, carbon black, titanium carbonitride, aluminum powder, glycerol, and phenolic resin as raw materials to prepare a periclase-carbon refractory. However, the material has high thermal conductivity and high heat loss. SUMMARY

[0008] The present application aims to overcome the shortcomings of existing technologies and provide a lightweight periclase-carbon refractory with a multi-scale core-shell structure, low thermal conductivity, high strength, and good erosion and penetration resistance, as well as a preparation method.

[0009] To achieve the above-mentioned purposes, the technical solution adopted by the present application is as follows:

[0010] Step 1, preparation of a multi-microporous periclase ceramic with a micro-nucleus-shell structure

[0011] Step 1.1, any one of magnesium oxide nanopowder, magnesium oxide micropowder and magnesium hydroxide micropowder is used as a magnesium source, or a mixture of any two of the magnesium oxide nanopowder, magnesium oxide micropowder and magnesium hydroxide micropowder is used as a magnesium source, or a mixture of the three of the magnesium oxide nanopowder, magnesium oxide micropowder and magnesium hydroxide micropowder is used as a magnesium source.

[0012] Step 1.2, the magnesium hydroxide fine powder is 40-94wt% and the magnesium source is 6-60wt% to be dosed, the magnesium hydroxide fine powder and the magnesium source are mixed to obtain a mixture.

[0013] Step 1.3, the mixture is machine-pressed into a shape under the condition of 100-200MPa, then the green body is placed in a high-temperature furnace, heated to 400-500℃ at a rate of 1-3℃ / min, kept for 1-2h, then heated to 1600-1800℃ at a rate of 3-5℃ / min, kept for 3-8h, cooled with the furnace, broken and sieved; respectively obtain a multi-microporous periclase refractory aggregate I with a particle size less than 5mm and greater than or equal to 3mm, a multi-microporous periclase refractory aggregate II with a particle size less than 3mm and greater than or equal to 1mm, and a multi-microporous periclase refractory aggregate III with a particle size less than 1mm and greater than or equal to 0.1mm. The multi-microporous periclase refractory aggregate I, the multi-microporous periclase refractory aggregate II and the multi-microporous periclase refractory aggregate III are collectively referred to as a multi-microporous periclase refractory aggregate.

[0014] The multi-microporous periclase refractory aggregate has a micro-nucleus-shell structure with a multi-microporous magnesium oxide microparticle containing nanopores as a nucleus and a dense magnesium oxide layer as a shell; the particle size of the multi-microporous magnesium oxide microparticle is 30-50μm, and the thickness of the dense magnesium oxide layer is 2-5μm; the multi-microporous periclase refractory aggregate has an apparent porosity of 22.6-40%, a bulk density of 2.10-2.77g / cm 3 , an average pore size of 500-900nm and a compressive strength of 30-100MPa.

[0015] Step 2, preparation of a lightweight periclase-carbon refractory material with a multi-scale nucleus-shell structure

[0016] The multi-microporous periclase refractory aggregate I is 16-24wt%, the multi-microporous periclase refractory aggregate II is 22-32wt%, and the multi-microporous periclase refractory aggregate III is 16-24wt% as total aggregate, and the magnesia fine powder is 24-38wt%, the elemental silicon powder is 0.1-1.5wt%, and the flake graphite powder is 0.5-3wt% as total matrix.

[0017] First, place the total aggregate in a mixer, add 2-6 wt% of the modified liquid thermosetting phenolic resin (the sum of the total aggregate and the total matrix), and mix. Then, add the total matrix and stir until homogeneous. Press the mixture under 150-200 MPa and hold it at 200-320℃ for 12-36 hours to obtain a lightweight periclase-carbon refractory material with a multi-scale core-shell structure.

[0018] The lightweight periclase-carbon refractory material has a micro-core-shell structure with microporous periclase refractory aggregate as the core and a dense magnesia layer as the shell, and a multi-scale core-shell structure with a continuous magnesia layer as the shell; wherein the thickness of the continuous magnesia layer is 0.1 to 0.3 mm.

[0019] The modified phenolic resin is prepared by mixing the liquid thermosetting phenolic resin and the magnesium source evenly according to the mass ratio of liquid thermosetting phenolic resin to magnesium source of 100:(30-150) to obtain the modified phenolic resin.

[0020] The magnesium source mentioned in step 2 is the same as the magnesium source mentioned in step 1.

[0021] The magnesium oxide nanopowder has a particle size of <50nm and an MgO content of >99wt%.

[0022] The particle size of the magnesium oxide micro powder is <3μm; the MgO content of the magnesium oxide micro powder is >99wt%.

[0023] The particle size of the magnesium hydroxide micro powder is <5μm; the MgO content of the magnesium hydroxide micro powder is 66-67wt%.

[0024] The particle size of the magnesium hydroxide fine powder is <100μm; the MgO content of the magnesium hydroxide fine powder is 66-67wt%.

[0025] The particle size of the fine magnesia powder is <88μm; the MgO content of the fine magnesia powder is 95-97wt%.

[0026] The elemental silicon powder has a particle size of <50μm and a Si content of 98-99.5wt%.

[0027] The particle size of the flake graphite powder is <18μm; the C content of the flake graphite powder is 97-98.5wt%.

[0028] The residual carbon content of the liquid thermosetting phenolic resin is ≥35%.

[0029] By adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0030] This invention designs the entire process from raw materials and refractory aggregates to refractory materials. For the aggregate, it utilizes the in-situ decomposition of magnesium hydroxide to form nanoporous magnesium oxide microparticles as the core, and introduces magnesium oxide or magnesium hydroxide of a specific particle size to form a continuous and dense magnesium oxide layer as the shell, thus obtaining a micro-core-shell structured microporous periclase refractory aggregate. Specifically, the particle size of the microporous magnesium oxide microparticles is 30–50 μm, and the thickness of the continuous and dense magnesium oxide layer is 2–5 μm. Compared to existing technologies, the magnesium oxide of a specific particle size promotes grain aggregation and growth, forming a dense magnesium oxide layer. The resulting aggregate has high purity, high-temperature structural stability, low thermal conductivity, and excellent high-temperature service performance. For refractory materials, after obtaining lightweight periclase-carbon refractory materials with multi-scale core-shell structures, they are fired under carbon-burying conditions. At high temperatures, magnesium oxide micro-nano powder promotes grain merging and growth, constructing a continuous magnesium oxide layer of 0.1-0.3 mm on the surface of the aggregate with micro-core-shell structure. On the one hand, a flake graphite-dense magnesium oxide interlocking structure is formed at the shell-matrix interface, and on the other hand, a sawtooth interlocking interface structure is formed at the shell-aggregate interface. Together with the microporous periclase refractory aggregate with micro-core-shell structure, it constitutes a multi-scale core-shell structure, giving full play to the advantages of nanoscale pores, magnesium oxide and flake graphite.

[0031] This invention utilizes high-purity, nano-porous periclase refractory aggregate with a micro-core-shell structure. The dense magnesia shell layer with a cross-linked network structure within the aggregate bridges the microporous magnesia particles, enhancing the aggregate's strength. Furthermore, the aggregate exhibits high purity, low impurity content, low liquid phase content at high temperatures, structural stability at high temperatures, and excellent high-temperature service performance. In terms of refractory materials, this invention prepares a core-shell structure where a continuous, dense magnesia shell encapsulates the microporous periclase refractory aggregate. A serrated interlocking interface structure is formed at the shell-aggregate interface, ensuring a tight bond between the shell and aggregate. At the shell-matrix interface, a flake graphite-dense magnesia mosaic structure is formed, further strengthening the shell-matrix bond. Both elements contribute to improved product strength. This overcomes the problem of weak aggregate / matrix interface bonding and poor strength in existing dense magnesia-carbon refractories.

[0032] This invention utilizes microporous periclase refractory aggregate with nanoscale pores, which prevents slag and gas phases from easily penetrating. Simultaneously, the high purity of the aggregate results in less liquid phase at high temperatures, leading to less dissolution into the slag and improving the erosion and oxidation resistance of the refractory material. Regarding the refractory material itself, the serrated interlocking interface structure formed at the shell-aggregate interface creates a tighter bond, preventing slag and gas phases from penetrating along the shell-aggregate interface and effectively improving the oxidation and erosion resistance of the refractory material. Furthermore, the flake graphite in the flake graphite-dense magnesia mosaic structure formed at the shell-matrix interface exhibits poor wettability to slag, while the dense magnesia in the mosaic structure hinders the oxidation of carbon at the interface by oxygen, effectively improving the erosion and oxidation resistance of the finished product. It overcomes the problem that existing dense magnesia refractories have many microcracks between aggregates / matrix, and that slag and oxygen can easily penetrate along the microcracks. It also solves the problem that there are many low-melting phases and Ca2SiO4 at the grain boundaries of dense aggregates, which dissolve into the slag quickly and are prone to spalling and damage.

[0033] This invention designs the raw material ratio, particle size, and molding pressure to prepare a structure with magnesium hydroxide microparticles as the skeleton and magnesium source with large particle size differences filling the spaces between the magnesium hydroxide microparticles. The pore size and particle size of the microparticles within the multi-microporous magnesium oxide microparticles formed after magnesium hydroxide decomposition are controlled by adjusting the firing process. Simultaneously, at high temperature, magnesium oxide micro-nano powder promotes grain merging and growth to form a continuous, dense magnesium oxide shell. By adjusting the proportion of micro-nano powder, the thickness of this continuous, dense magnesium oxide shell is controlled, allowing the formed cross-linked network structure to bridge the multi-microporous magnesium oxide microparticles together through neck connections. This results in a multi-microporous periclase refractory aggregate with a continuous, dense magnesium oxide shell tightly encapsulating a multi-microporous magnesium oxide core micro-shell structure. Furthermore, the ratio of micro-nano powder to liquid thermosetting phenolic resin is designed to uniformly disperse the micro-nano powder in the liquid thermosetting phenolic resin, ensuring that the micro-nano powder is uniformly coated on the surface of the multi-microporous periclase refractory aggregate. During the reaction sintering process, the sintering driving force is increased, causing the micro-nano powder grains to merge and grow, forming a dense magnesium oxide shell. This shell forms a tightly bonded interface between the aggregate and the shell and the matrix, which together with the core-shell structure inside the aggregate constitutes a multi-scale core-shell structure. This improves the strength and erosion resistance of the lightweight periclase-carbon refractory material with a multi-scale core-shell structure.

[0034] The lightweight periclase-carbon refractory material with a multi-scale core-shell structure prepared by this invention was tested and found to have an apparent porosity of 22-30% and a bulk density of 2.31-2.57 g / cm³. 3 The compressive strength is 70-150 MPa.

[0035] Therefore, the lightweight periclase-carbon refractory material with a multi-scale core-shell structure prepared by this invention has the characteristics of low thermal conductivity, high strength, good thermal shock stability and strong resistance to erosion and penetration. Detailed Implementation

[0036] The present invention will be further described below with reference to specific embodiments, but this is not intended to limit the scope of protection thereof.

[0037] A lightweight periclase-carbon refractory material with a multi-scale core-shell structure and its preparation method are disclosed. The specific steps of the preparation method described in this embodiment are as follows:

[0038] Step 1.1: Use any one of magnesium oxide nanopowder, magnesium oxide micropowder, and magnesium hydroxide micropowder as the magnesium source, or use a mixture of any two of magnesium oxide nanopowder, magnesium oxide micropowder, and magnesium hydroxide micropowder as the magnesium source, or use a mixture of the three types of magnesium oxide nanopowder, magnesium oxide micropowder, and magnesium hydroxide micropowder as the magnesium source.

[0039] Step 1.2: Mix the magnesium hydroxide fine powder (40-94 wt%) and the magnesium source (6-60 wt%) to obtain a mixture.

[0040] Step 1.3: Press the mixture into shape under 100-200 MPa, then place the green body in a high-temperature furnace and heat it to 400-500℃ at a rate of 1-3℃ / min, hold it for 1-2 hours, then heat it to 1600-1800℃ at a rate of 3-5℃ / min, hold it for 3-8 hours, cool it in the furnace, crush it, and sieve it to obtain microporous periclase refractory aggregate I with a particle size of less than 5 mm and greater than or equal to 3 mm, microporous periclase refractory aggregate II with a particle size of less than 3 mm and greater than or equal to 1 mm, and microporous periclase refractory aggregate III with a particle size of less than 1 mm and greater than or equal to 0.1 mm.

[0041] The microporous periclase refractory aggregate has an apparent porosity of 22.6–40% and a bulk density of 2.10–2.77 g / cm³. 3 The average pore size is 500–900 nm; the compressive strength is 30–100 MPa.

[0042] Step 2: Preparation of lightweight periclase-carbon refractory materials with multi-scale core-shell structure

[0043] The total aggregate consists of 16–24 wt% of the aforementioned microporous periclase refractory aggregate I, 22–32 wt% of the aforementioned microporous periclase refractory aggregate II, and 16–24 wt% of the aforementioned microporous periclase refractory aggregate III, with 24–38 wt% of magnesia fine powder, 0.1–1.5 wt% of elemental silica powder, and 0.5–3 wt% of flake graphite powder as the total matrix.

[0044] First, place the total aggregate in a mixer, add 2-6 wt% of the modified liquid thermosetting phenolic resin (the sum of the total aggregate and the total matrix), and mix. Then, add the total matrix and stir evenly. Press the mixture under 150-200 MPa and hold it at 200-320°C for 12-36 hours to obtain a lightweight periclase-carbon refractory material with a multi-scale core-shell structure.

[0045] The modified phenolic resin is prepared by mixing the liquid thermosetting phenolic resin and the magnesium source evenly according to the mass ratio of liquid thermosetting phenolic resin to magnesium source of 100:(30-150) to obtain the modified phenolic resin.

[0046] The magnesium source mentioned in step 2 is the same as the magnesium source mentioned in step 1.

[0047] The magnesium oxide nanopowder has an MgO content > 99 wt%.

[0048] The MgO content of the magnesium oxide micro powder is >99wt%.

[0049] The magnesium hydroxide micro powder has an MgO content of 66-67 wt%.

[0050] The MgO content of the fine magnesium hydroxide powder is 66-67 wt%.

[0051] The MgO content of the fine magnesia powder is 95-97 wt%.

[0052] The elemental silicon powder has a Si content of 98–99.5 wt%.

[0053] The carbon content of the flake graphite powder is 97-98.5 wt%.

[0054] The residual carbon content of the liquid thermosetting phenolic resin is ≥35%.

[0055] In this specific implementation:

[0056] The particle size of the magnesium oxide nanopowder is <50nm;

[0057] The particle size of the magnesium oxide micro powder is <3μm;

[0058] The particle size of the magnesium hydroxide micro powder is <5μm;

[0059] The particle size of the magnesium hydroxide fine powder is <100μm;

[0060] The particle size of the fine magnesia powder is <88μm;

[0061] The particle size of the elemental silicon powder is <50μm;

[0062] The particle size of the flake graphite powder is <18μm;

[0063] The microporous periclase refractory aggregate I, microporous periclase refractory aggregate II and microporous periclase refractory aggregate III are collectively referred to as microporous periclase refractory aggregate.

[0064] The microporous periclase refractory aggregate described in this specific embodiment has a micro-core-shell structure with nanoporous microporous magnesium oxide microparticles as the core and a dense magnesium oxide layer as the shell.

[0065] The lightweight periclase-carbon refractory material with a multi-scale core-shell structure described in this specific embodiment is a multi-scale core-shell structure with a micro-core-shell structure, consisting of microporous magnesia microparticles containing nanopores as the core and a dense magnesia layer as the shell, and a multi-scale core-shell structure with a continuous magnesia layer as the shell.

[0066] The details will not be repeated in the examples.

[0067] The lightweight periclase-carbon refractory material with a multi-scale core-shell structure was tested and found to have a continuous magnesium oxide layer thickness of 0.1–0.3 mm. The microporous periclase refractory aggregate and the lightweight periclase-carbon refractory material with a multi-scale core-shell structure were tested and found to have a microporous magnesium oxide microparticle size of 30–50 μm and a dense magnesium oxide layer thickness of 2–5 μm.

[0068] Example 1

[0069] A lightweight periclase-carbon refractory material with a multi-scale core-shell structure and its preparation method are disclosed. The specific steps of the preparation method described in this embodiment are as follows:

[0070] Step 1: Preparation of microporous periclase ceramics with microcore-shell structure

[0071] Step 1.1: Use magnesium oxide nanoparticles as the magnesium source.

[0072] Step 1.2: Mix the magnesium hydroxide fine powder (94 wt%) and the magnesium source (6 wt%) to obtain a mixture.

[0073] Step 1.3: The mixture is machine-pressed at 100MPa, and then the blank is placed in a high-temperature furnace and heated to 400℃ at a rate of 1℃ / min, held for 2.2h, and then heated to 1600℃ at a rate of 3℃ / min, held for 6h, cooled in the furnace, crushed, and sieved; respectively, microporous periclase refractory aggregate I with a particle size of less than 5mm and greater than or equal to 3mm, microporous periclase refractory aggregate II with a particle size of less than 3mm and greater than or equal to 1mm, and microporous periclase refractory aggregate III with a particle size of less than 1mm and greater than or equal to 0.1mm are obtained.

[0074] The microporous periclase refractory aggregate has an apparent porosity of 40% and a bulk density of 2.10 g / cm³. 3 The average pore size is 900 nm; the pressure resistance is 30 MPa.

[0075] Step 2: Preparation of lightweight periclase-carbon refractory materials with multi-scale core-shell structure

[0076] The total aggregate consists of 16 wt% of the aforementioned microporous periclase refractory aggregate I, 22 wt% of the aforementioned microporous periclase refractory aggregate II, and 24 wt% of the aforementioned microporous periclase refractory aggregate III, with 37 wt% of magnesia fine powder, 0.1 wt% of elemental silica powder, and 0.9 wt% of flake graphite powder as the total matrix.

[0077] First, the total aggregate is placed in a mixer, and 6 wt% of the modified liquid thermosetting phenolic resin, which is the sum of the total aggregate and the total matrix, is added and mixed. Then, the total matrix is ​​added and stirred evenly. The mixture is machine-pressed at 150 MPa and kept at 200°C for 12 hours to obtain a lightweight periclase-carbon refractory material with a multi-scale core-shell structure.

[0078] The modified phenolic resin is prepared by mixing the liquid thermosetting phenolic resin and the magnesium source evenly according to the mass ratio of liquid thermosetting phenolic resin to magnesium source of 100:150 to obtain the modified phenolic resin.

[0079] The magnesium source mentioned in step 2 is the same as the magnesium source mentioned in step 1.

[0080] The magnesium oxide nanopowder has an MgO content of 99.9 wt%.

[0081] The MgO content of the fine magnesium hydroxide powder is 66.2 wt%.

[0082] The MgO content of the fine magnesia powder is 95.8 wt%.

[0083] The elemental silicon powder has a Si content of 98 wt%.

[0084] The carbon content of the flake graphite powder is 97.7 wt%.

[0085] The residual carbon content of the liquid thermosetting phenolic resin is 35.5%.

[0086] The lightweight periclase-carbon refractory material with a multi-scale core-shell structure prepared by this invention was tested and found to have: an apparent porosity of 28.0% and a bulk density of 2.38 g / cm³. 3 The compressive strength is 109 MPa.

[0087] Example 2

[0088] A lightweight periclase-carbon refractory material with a multi-scale core-shell structure and its preparation method are disclosed. The specific steps of the preparation method described in this embodiment are as follows:

[0089] Step 1: Preparation of microporous periclase ceramics with microcore-shell structure

[0090] Step 1.1: Use magnesium oxide micro powder as the magnesium source.

[0091] Step 1.2: Mix the magnesium hydroxide fine powder (91 wt%) and the magnesium source (9 wt%) to obtain a mixture.

[0092] Step 1.3: The mixture is machine-pressed at 120 MPa, and then the blank is placed in a high-temperature furnace and heated to 380°C at a rate of 1.5°C / min, held for 4 hours, and then heated to 1650°C at a rate of 3.5°C / min, held for 8 hours, cooled in the furnace, crushed, and sieved; respectively, microporous periclase refractory aggregate I with a particle size of less than 5 mm and greater than or equal to 3 mm, microporous periclase refractory aggregate II with a particle size of less than 3 mm and greater than or equal to 1 mm, and microporous periclase refractory aggregate III with a particle size of less than 1 mm and greater than or equal to 0.1 mm are obtained.

[0093] The microporous periclase refractory aggregate has an apparent porosity of 33.2% and a bulk density of 2.37 g / cm³. 3 The average pore size is 832 nm; the compressive strength is 65 MPa.

[0094] Step 2: Preparation of lightweight periclase-carbon refractory materials with multi-scale core-shell structure

[0095] The total aggregate consists of 18 wt% of the aforementioned microporous periclase refractory aggregate I, 28 wt% of the aforementioned microporous periclase refractory aggregate II, and 22 wt% of the aforementioned microporous periclase refractory aggregate III, with 28 wt% of magnesia fine powder, 1 wt% of elemental silica powder, and 3 wt% of flake graphite powder as the total matrix.

[0096] First, the total aggregate is placed in a mixer, and 4.2 wt% of the modified liquid thermosetting phenolic resin (the sum of the total aggregate and the total matrix) is added and mixed. Then, the total matrix is ​​added and stirred evenly. The mixture is then machine-pressed at 170 MPa and kept at 320°C for 22 hours to obtain a lightweight periclase-carbon refractory material with a multi-scale core-shell structure.

[0097] The modified phenolic resin is prepared by mixing the liquid thermosetting phenolic resin and the magnesium source evenly according to the mass ratio of liquid thermosetting phenolic resin to magnesium source of 100:30 to obtain the modified phenolic resin.

[0098] The magnesium source mentioned in step 2 is the same as the magnesium source mentioned in step 1.

[0099] The magnesium oxide micro powder has an MgO content of 99.8 wt%.

[0100] The MgO content of the fine magnesium hydroxide powder is 67 wt%.

[0101] The MgO content of the fine magnesia powder is 95 wt%.

[0102] The elemental silicon powder has a Si content of 98.2 wt%.

[0103] The carbon content of the flake graphite powder is 97.9 wt%.

[0104] The residual carbon content of the liquid thermosetting phenolic resin is 35%.

[0105] The lightweight periclase-carbon refractory material with a multi-scale core-shell structure prepared by this invention was tested and found to have an apparent porosity of 23.0% and a bulk density of 2.54 g / cm³. 3 The compressive strength is 135 MPa.

[0106] Example 3

[0107] A lightweight periclase-carbon refractory material with a multi-scale core-shell structure and its preparation method are disclosed. The specific steps of the preparation method described in this embodiment are as follows:

[0108] Step 1: Preparation of microporous periclase ceramics with microcore-shell structure

[0109] Step 1.1: Use magnesium hydroxide micro powder as the magnesium source.

[0110] Step 1.2: Mix the magnesium hydroxide fine powder (88 wt%) and the magnesium source (12 wt%) to obtain a mixture.

[0111] Step 1.3: The mixture is machine-pressed at 150 MPa, and then the blank is placed in a high-temperature furnace and heated to 350°C at a rate of 2.5°C / min, held for 3.5 h, and then heated to 1600°C at a rate of 4.5°C / min, held for 3 h, cooled in the furnace, crushed, and sieved; respectively, microporous periclase refractory aggregate I with a particle size of less than 5 mm and greater than or equal to 3 mm, microporous periclase refractory aggregate II with a particle size of less than 3 mm and greater than or equal to 1 mm, and microporous periclase refractory aggregate III with a particle size of less than 1 mm and greater than or equal to 0.1 mm are obtained.

[0112] The microporous periclase refractory aggregate has an apparent porosity of 36% and a bulk density of 2.29 g / cm³. 3 The average pore size is 859 nm; the compressive strength is 45 MPa.

[0113] Step 2: Preparation of lightweight periclase-carbon refractory materials with multi-scale core-shell structure

[0114] The total aggregate consists of 20 wt% of the aforementioned microporous periclase refractory aggregate I, 23 wt% of the aforementioned microporous periclase refractory aggregate II, and 20 wt% of the aforementioned microporous periclase refractory aggregate III, with 35 wt% of magnesia fine powder, 0.7 wt% of elemental silica powder, and 1.3 wt% of flake graphite powder as the total matrix.

[0115] First, the total aggregate is placed in a mixer, and 5.3 wt% of the modified liquid thermosetting phenolic resin (the sum of the total aggregate and the total matrix) is added and mixed. Then, the total matrix is ​​added and stirred evenly. The mixture is machine-pressed at 160 MPa and kept at 220°C for 18 hours to obtain a lightweight periclase-carbon refractory material with a multi-scale core-shell structure.

[0116] The modified phenolic resin is prepared by mixing the liquid thermosetting phenolic resin and the magnesium source evenly according to the mass ratio of liquid thermosetting phenolic resin to magnesium source of 100:60 to obtain the modified phenolic resin.

[0117] The magnesium source mentioned in step 2 is the same as the magnesium source mentioned in step 1.

[0118] The magnesium hydroxide micro powder has an MgO content of 66 wt%.

[0119] The MgO content of the fine magnesium hydroxide powder is 66 wt%.

[0120] The MgO content of the fine magnesia powder is 97 wt%.

[0121] The elemental silicon powder has a Si content of 98.6 wt%.

[0122] The carbon content of the flake graphite powder is 97.2 wt%.

[0123] The residual carbon content of the liquid thermosetting phenolic resin is 35.2%.

[0124] The lightweight periclase-carbon refractory material with a multi-scale core-shell structure prepared by this invention was tested and found to have an apparent porosity of 27.0% and a bulk density of 2.41 g / cm³. 3 The compressive strength is 88 MPa.

[0125] Example 4

[0126] A lightweight periclase-carbon refractory material with a multi-scale core-shell structure and its preparation method are disclosed. The specific steps of the preparation method described in this embodiment are as follows:

[0127] Step 1: Preparation of microporous periclase ceramics with microcore-shell structure

[0128] Step 1.1: Use a mixture of magnesium oxide nanopowder and magnesium oxide micropowder as the magnesium source.

[0129] Step 1.2: Mix the magnesium hydroxide fine powder (40 wt%) and the magnesium source (60 wt%) to obtain a mixture.

[0130] Step 1.3: The mixture is machine-pressed under 200MPa, and then the blank is placed in a high-temperature furnace and heated to 360℃ at a rate of 3℃ / min, held for 1.5h, and then heated to 1750℃ at a rate of 4.8℃ / min, held for 4h, cooled in the furnace, crushed, and sieved; respectively obtained microporous periclase refractory aggregate I with a particle size of less than 5mm and greater than or equal to 3mm, microporous periclase refractory aggregate II with a particle size of less than 3mm and greater than or equal to 1mm, and microporous periclase refractory aggregate III with a particle size of less than 1mm and greater than or equal to 0.1mm.

[0131] The microporous periclase refractory aggregate has an apparent porosity of 22.6% and a bulk density of 2.77 g / cm³. 3 The average pore size is 500 nm; the pressure resistance is 100 MPa.

[0132] Step 2: Preparation of lightweight periclase-carbon refractory materials with multi-scale core-shell structure

[0133] The total aggregate consists of 24 wt% of the aforementioned microporous periclase refractory aggregate I, 30 wt% of the aforementioned microporous periclase refractory aggregate II, and 18 wt% of the aforementioned microporous periclase refractory aggregate III, with 24 wt% of magnesia fine powder, 1.5 wt% of elemental silica powder, and 2.5 wt% of flake graphite powder as the total matrix.

[0134] First, the total aggregate is placed in a mixer, and 2.8 wt% of the modified liquid thermosetting phenolic resin (the sum of the total aggregate and the total matrix) is added and mixed. Then, the total matrix is ​​added and stirred evenly. The mixture is machine-pressed at 180 MPa and kept at 260°C for 36 hours to obtain a lightweight periclase-carbon refractory material with a multi-scale core-shell structure.

[0135] The modified phenolic resin is prepared by mixing the liquid thermosetting phenolic resin and the magnesium source evenly according to the mass ratio of liquid thermosetting phenolic resin to magnesium source of 100:80 to obtain the modified phenolic resin.

[0136] The magnesium source mentioned in step 2 is the same as the magnesium source mentioned in step 1.

[0137] The magnesium oxide nanopowder has an MgO content of 99.6 wt%.

[0138] The magnesium oxide micro powder has an MgO content of 99.6 wt%.

[0139] The MgO content of the fine magnesium hydroxide powder is 66.5 wt%.

[0140] The MgO content of the fine magnesia powder is 96.2 wt%.

[0141] The elemental silicon powder has a Si content of 99.1 wt%.

[0142] The carbon content of the flake graphite powder is 97 wt%.

[0143] The residual carbon content of the liquid thermosetting phenolic resin is 36.2%.

[0144] The lightweight periclase-carbon refractory material with a multi-scale core-shell structure prepared by this invention was tested and found to have an apparent porosity of 22.0% and a bulk density of 2.57 g / cm³. 3 The compressive strength is 150 MPa.

[0145] Example 5

[0146] A lightweight periclase-carbon refractory material with a multi-scale core-shell structure and its preparation method are disclosed. The specific steps of the preparation method described in this embodiment are as follows:

[0147] Step 1: Preparation of microporous periclase ceramics with microcore-shell structure

[0148] Step 1.1: Use a mixture of magnesium oxide nanopowder and magnesium hydroxide micropowder as the magnesium source.

[0149] Step 1.2: Mix the magnesium hydroxide fine powder (60 wt%) and the magnesium source (40 wt%) to obtain a mixture.

[0150] Step 1.3: The mixture is machine-pressed at 180 MPa, and then the blank is placed in a high-temperature furnace and heated to 300℃ at a rate of 1.8℃ / min, held for 3.8h, and then heated to 1720℃ at a rate of 5℃ / min, held for 6h, cooled in the furnace, crushed, and sieved; respectively obtained microporous periclase refractory aggregate I with a particle size of less than 5mm and greater than or equal to 3mm, microporous periclase refractory aggregate II with a particle size of less than 3mm and greater than or equal to 1mm, and microporous periclase refractory aggregate III with a particle size of less than 1mm and greater than or equal to 0.1mm.

[0151] The microporous periclase refractory aggregate has an apparent porosity of 25.1% and a bulk density of 2.68 g / cm³. 3 The average pore size is 586 nm; the compressive strength is 91 MPa.

[0152] Step 2: Preparation of lightweight periclase-carbon refractory materials with multi-scale core-shell structure

[0153] The total aggregate consists of 22 wt% of the aforementioned microporous periclase refractory aggregate I, 29 wt% of the aforementioned microporous periclase refractory aggregate II, and 21 wt% of the aforementioned microporous periclase refractory aggregate III, with 25 wt% of magnesia fine powder, 0.9 wt% of elemental silica powder, and 2.1 wt% of flake graphite powder as the total matrix.

[0154] First, the total aggregate is placed in a mixer, and 3.4 wt% of the modified liquid thermosetting phenolic resin (the sum of the total aggregate and the total matrix) is added and mixed. Then, the total matrix is ​​added and stirred evenly. The mixture is then machine-pressed at 200 MPa and kept at 280°C for 29 hours to obtain a lightweight periclase-carbon refractory material with a multi-scale core-shell structure.

[0155] The modified phenolic resin is prepared by mixing the liquid thermosetting phenolic resin and the magnesium source evenly according to the mass ratio of liquid thermosetting phenolic resin to magnesium source of 100:130 to obtain the modified phenolic resin.

[0156] The magnesium source mentioned in step 2 is the same as the magnesium source mentioned in step 1.

[0157] The magnesium oxide nanopowder has an MgO content of 99.5 wt%.

[0158] The magnesium hydroxide micro powder has an MgO content of 67 wt%.

[0159] The MgO content of the fine magnesium hydroxide powder is 67 wt%.

[0160] The MgO content of the fine magnesia powder is 96.8 wt%.

[0161] The elemental silicon powder has a Si content of 99.5 wt%.

[0162] The carbon content of the flake graphite powder is 98.2 wt%.

[0163] The residual carbon content of the liquid thermosetting phenolic resin is 35.8%.

[0164] The lightweight periclase-carbon refractory material with a multi-scale core-shell structure prepared by this invention was tested and found to have an apparent porosity of 24.0% and a bulk density of 2.51 g / cm³. 3 The compressive strength is 141 MPa.

[0165] Example 6

[0166] A lightweight periclase-carbon refractory material with a multi-scale core-shell structure and its preparation method are disclosed. The specific steps of the preparation method described in this embodiment are as follows:

[0167] Step 1: Preparation of microporous periclase ceramics with microcore-shell structure

[0168] Step 1.1: Use a mixture of magnesium oxide powder and magnesium hydroxide powder as the magnesium source.

[0169] Step 1.2: Mix the magnesium hydroxide fine powder and the magnesium source at a concentration of 50 wt% to obtain a mixture.

[0170] Step 1.3: The mixture is machine-pressed at 140 MPa, and then the blank is placed in a high-temperature furnace and heated to 330°C at a rate of 2.8°C / min, held for 1.8 hours, and then heated to 1700°C at a rate of 4.2°C / min, held for 5 hours, cooled in the furnace, crushed, and sieved; microporous periclase refractory aggregate I with a particle size of less than 5 mm and greater than or equal to 3 mm, microporous periclase refractory aggregate II with a particle size of less than 3 mm and greater than or equal to 1 mm, and microporous periclase refractory aggregate III with a particle size of less than 1 mm and greater than or equal to 0.1 mm are obtained respectively.

[0171] The microporous periclase refractory aggregate has an apparent porosity of 27.8% and a bulk density of 2.58 g / cm³. 3 The average pore size is 685 nm; the compressive strength is 81 MPa.

[0172] Step 2: Preparation of lightweight periclase-carbon refractory materials with multi-scale core-shell structure

[0173] The total aggregate consists of 17 wt% of the aforementioned microporous periclase refractory aggregate I, 32 wt% of the aforementioned microporous periclase refractory aggregate II, and 16 wt% of the aforementioned microporous periclase refractory aggregate III, with 32 wt% of magnesia fine powder, 1.2 wt% of elemental silica powder, and 1.8 wt% of flake graphite powder as the total matrix.

[0174] First, the total aggregate is placed in a mixer, and 4.6 wt% of the modified liquid thermosetting phenolic resin (the sum of the total aggregate and the total matrix) is added and mixed. Then, the total matrix is ​​added and stirred evenly. The mixture is machine-pressed at 190 MPa and kept at 300°C for 25 h to obtain a lightweight periclase-carbon refractory material with a multi-scale core-shell structure.

[0175] The modified phenolic resin is prepared by mixing the liquid thermosetting phenolic resin and the magnesium source evenly according to the mass ratio of liquid thermosetting phenolic resin to magnesium source of 100:90 to obtain the modified phenolic resin.

[0176] The magnesium source mentioned in step 2 is the same as the magnesium source mentioned in step 1.

[0177] The magnesium oxide micro powder has an MgO content of 99.3 wt%.

[0178] The magnesium hydroxide micro powder has an MgO content of 66.4 wt%.

[0179] The MgO content of the fine magnesium hydroxide powder is 66.4 wt%.

[0180] The MgO content of the fine magnesia powder is 95.2 wt%.

[0181] The elemental silicon powder has a Si content of 98.8 wt%.

[0182] The carbon content of the flake graphite powder is 97.3 wt%.

[0183] The residual carbon content of the liquid thermosetting phenolic resin is 36%.

[0184] The lightweight periclase-carbon refractory material with a multi-scale core-shell structure prepared by this invention was tested and found to have an apparent porosity of 26.0% and a bulk density of 2.44 g / cm³. 3 The compressive strength is 126 MPa.

[0185] Example 7

[0186] A lightweight periclase-carbon refractory material with a multi-scale core-shell structure and its preparation method are disclosed. The specific steps of the preparation method described in this embodiment are as follows:

[0187] Step 1: Preparation of microporous periclase ceramics with microcore-shell structure

[0188] Step 1.1: Use a mixture of magnesium oxide nanopowder, magnesium oxide micropowder, and magnesium hydroxide micropowder as the magnesium source.

[0189] Step 1.2: Mix the magnesium hydroxide fine powder (70 wt%) and the magnesium source (30 wt%) to obtain a mixture.

[0190] Step 1.3: The mixture is machine-pressed at 160 MPa, and then the blank is placed in a high-temperature furnace and heated to 380°C at a rate of 2°C / min, held for 2.8 h, and then heated to 1800°C at a rate of 3.8°C / min, held for 7 h, cooled in the furnace, crushed, and sieved; respectively, microporous periclase refractory aggregate I with a particle size of less than 5 mm and greater than or equal to 3 mm, microporous periclase refractory aggregate II with a particle size of less than 3 mm and greater than or equal to 1 mm, and microporous periclase refractory aggregate III with a particle size of less than 1 mm and greater than or equal to 0.1 mm are obtained.

[0191] The microporous periclase refractory aggregate has an apparent porosity of 26% and a bulk density of 2.64 g / cm³. 3 The average pore size is 645 nm; the compressive strength is 86 MPa.

[0192] Step 2: Preparation of lightweight periclase-carbon refractory materials with multi-scale core-shell structure

[0193] The total aggregate consists of 19 wt% of the aforementioned microporous periclase refractory aggregate I, 25 wt% of the aforementioned microporous periclase refractory aggregate II, and 17 wt% of the aforementioned microporous periclase refractory aggregate III, with 38 wt% of magnesia fine powder, 0.5 wt% of elemental silica powder, and 0.5 wt% of flake graphite powder as the total matrix.

[0194] First, the total aggregate is placed in a mixer, and 2 wt% of the modified liquid thermosetting phenolic resin, which is the sum of the total aggregate and the total matrix, is added and mixed. Then, the total matrix is ​​added and stirred evenly. The mixture is machine-pressed at 150 MPa and kept at 240°C for 31 h to obtain a lightweight periclase-carbon refractory material with a multi-scale core-shell structure.

[0195] The modified phenolic resin is prepared by mixing the liquid thermosetting phenolic resin and the magnesium source evenly according to the mass ratio of liquid thermosetting phenolic resin to magnesium source of 100:110 to obtain the modified phenolic resin.

[0196] The magnesium source mentioned in step 2 is the same as the magnesium source mentioned in step 1.

[0197] The magnesium oxide nanopowder has an MgO content of 99.5 wt%.

[0198] The magnesium oxide micro powder has an MgO content of 99.5 wt%.

[0199] The magnesium hydroxide micro powder has an MgO content of 66.8 wt%.

[0200] The MgO content of the fine magnesium hydroxide powder is 66.8 wt%.

[0201] The MgO content of the fine magnesia powder is 96.4 wt%.

[0202] The elemental silicon powder has a Si content of 99.2 wt%.

[0203] The carbon content of the flake graphite powder is 98.5 wt%.

[0204] The residual carbon content of the liquid thermosetting phenolic resin is 35.6%.

[0205] The lightweight periclase-carbon refractory material with a multi-scale core-shell structure prepared by this invention was tested and found to have an apparent porosity of 30.0% and a bulk density of 2.31 g / cm³. 3 The compressive strength is 70 MPa.

[0206] Therefore, the lightweight periclase-carbon refractory material with a multi-scale core-shell structure prepared in this specific embodiment has the characteristics of nanoscale pores, multi-scale core-shell structure, low thermal conductivity, high strength and strong resistance to erosion and penetration.

[0207] This specific implementation method has the following advantages compared with the prior art:

[0208] This specific embodiment designs the entire process from raw materials and refractory aggregates to refractory materials. Regarding the aggregate, it utilizes in-situ decomposition of magnesium hydroxide to form nanoporous magnesium oxide microparticles as the core, and introduces magnesium oxide or magnesium hydroxide of a specific particle size to form a continuous, dense magnesium oxide layer as the shell, thus obtaining a micro-core-shell structured microporous periclase refractory aggregate. The microporous magnesium oxide microparticles have a particle size of 30–50 μm, and the continuous, dense magnesium oxide layer has a thickness of 2–5 μm. Compared to existing technologies, the magnesium oxide of a specific particle size promotes grain aggregation and growth, forming a dense magnesium oxide layer. The resulting aggregate has high purity, high-temperature structural stability, low thermal conductivity, and excellent high-temperature service performance. In terms of refractory materials, after obtaining a lightweight periclase-carbon refractory material with a multi-scale core-shell structure, it is fired under carbon-burying conditions. At high temperature, magnesium oxide micro-nano powder promotes grain merging and growth, and a continuous magnesium oxide layer of 0.1-0.3 mm is constructed on the surface of the aggregate with a micro-core-shell structure. On the one hand, a flake graphite-dense magnesium oxide interlocking structure is formed at the shell-matrix interface, and on the other hand, a sawtooth interlocking interface structure is formed at the shell-aggregate interface. Together with the microporous periclase refractory aggregate with a micro-core-shell structure, it constitutes a multi-scale core-shell structure, giving full play to the advantages of nanoscale pores, magnesium oxide and flake graphite.

[0209] This specific embodiment uses high-purity, multi-microporous periclase refractory aggregate with nanoscale pores and a micro-core-shell structure. The dense magnesia shell layer with a cross-linked network structure within the aggregate bridges the multi-microporous magnesia microparticles, improving the aggregate's strength. Furthermore, the aggregate has high purity, low impurity content, low liquid phase content at high temperatures, stable structure at high temperatures, and excellent high-temperature service performance. Regarding the refractory material, this specific embodiment prepares a continuous, dense magnesia shell encapsulating the multi-microporous periclase refractory aggregate core-shell structure. A serrated interlocking interface structure is formed at the shell-aggregate interface, ensuring a tight bond between the shell and aggregate. At the shell-matrix interface, a flake graphite-dense magnesia mosaic structure is formed, further strengthening the shell-matrix bond. Both aspects jointly improve the strength of the product. This overcomes the problem of weak aggregate / matrix interface bonding and poor strength in existing dense magnesia-carbon refractories.

[0210] This specific embodiment uses microporous periclase refractory aggregate with nanoscale pores, which makes it difficult for molten slag and gas phases to penetrate. Simultaneously, the high purity of the aggregate results in less liquid phase in the aggregate at high temperatures, leading to less dissolution into the molten slag and improving the erosion and oxidation resistance of the refractory material. Regarding the refractory material itself, the serrated interlocking interface structure formed at the shell-aggregate interface makes the interface bonding tighter, preventing molten slag and gas phases from penetrating along the shell-aggregate interface, effectively improving the oxidation and erosion resistance of the refractory material. Furthermore, the flake graphite in the flake graphite-dense magnesia mosaic structure formed at the shell-matrix interface has poor wettability to molten slag, while the dense magnesia in the mosaic structure hinders the oxidation of carbon at the interface by oxygen, effectively improving the erosion and oxidation resistance of the product. It overcomes the problem that existing dense magnesia refractories have many microcracks between aggregates / matrix, and that slag and oxygen can easily penetrate along the microcracks. It also solves the problem that there are many low-melting phases and Ca2SiO4 at the grain boundaries of dense aggregates, which dissolve into the slag quickly and are prone to spalling and damage.

[0211] This specific embodiment designs the raw material ratio, particle size, and molding pressure to prepare a structure with magnesium hydroxide microparticles as the skeleton and magnesium source with large particle size differences filling the spaces between the magnesium hydroxide microparticles. The pore size and particle size of the microparticles within the multi-microporous magnesium oxide microparticles formed after magnesium hydroxide decomposition are controlled by adjusting the firing process. Simultaneously, at high temperature, magnesium oxide micro-nano powder promotes grain merging and growth to form a continuous, dense magnesium oxide shell. The thickness of this continuous, dense magnesium oxide shell is controlled by adjusting the proportion of micro-nano powder, allowing the formed cross-linked network structure to bridge the multi-microporous magnesium oxide microparticles together through neck connections. This results in a multi-microporous periclase refractory aggregate with a continuous, dense magnesium oxide shell tightly encapsulating a multi-microporous magnesium oxide core-shell structure. Furthermore, the ratio of micro-nano powder to liquid thermosetting phenolic resin is designed to uniformly disperse the micro-nano powder in the liquid thermosetting phenolic resin, ensuring that the micro-nano powder is uniformly coated on the surface of the multi-microporous periclase refractory aggregate. During the reaction sintering process, the sintering driving force is increased, causing the micro-nano powder grains to merge and grow, forming a dense magnesium oxide shell. This shell forms a tightly bonded interface between the aggregate and the shell and the matrix, which together with the core-shell structure inside the aggregate constitutes a multi-scale core-shell structure. This improves the strength and erosion resistance of the lightweight periclase-carbon refractory material with a multi-scale core-shell structure.

[0212] The lightweight periclase-carbon refractory material with a multi-scale core-shell structure prepared according to this specific embodiment was tested and found to have an apparent porosity of 22-30% and a bulk density of 2.31-2.57 g / cm³. 3 The compressive strength is 70-150 MPa.

[0213] Therefore, the lightweight periclase-carbon refractory material with a multi-scale core-shell structure prepared in this specific embodiment has the characteristics of low thermal conductivity, high strength, good thermal shock stability and strong resistance to erosion and penetration.

Claims

1. A method for the production of lightweight periclase-carbon refractory materials with a multiscale core-shell structure, characterized in that The steps of the preparation method are: Step 1, preparation of the microporous periclase refractory aggregate Step 1.1, taking any one of the magnesium oxide nanometer powder, the magnesium oxide micro powder and the magnesium hydroxide micro powder as the magnesium source, or taking the mixed powder of any two of the magnesium oxide nanometer powder, the magnesium oxide micro powder and the magnesium hydroxide micro powder as the magnesium source, or taking the mixed powder of the three of the magnesium oxide nanometer powder, the magnesium oxide micro powder and the magnesium hydroxide micro powder as the magnesium source; Step 1.2, according to the proportioning of 40-94wt% of the magnesium hydroxide fine powder and 6-60wt% of the magnesium source, mixing the magnesium hydroxide fine powder and the magnesium source uniformly to obtain a mixture; Step 1.3, machine pressing the mixture under the condition of 100-200MPa to form a green body, then placing the green body in a high-temperature furnace, heating at a rate of 1-3℃ / min to 300-400℃, keeping the temperature for 1-4h, then heating at a rate of 3-5℃ / min to 1600-1800℃, keeping the temperature for 3-8h, cooling with the furnace, crushing and sieving; respectively obtaining the microporous periclase refractory aggregate I with a particle size less than 5mm and greater than or equal to 3mm, the microporous periclase refractory aggregate II with a particle size less than 3mm and greater than or equal to 1mm, and the microporous periclase refractory aggregate III with a particle size less than 1mm and greater than or equal to 0.1mm; The microporous periclase refractory aggregate has a micro-core-shell structure with a microporous magnesium oxide micro-particle containing nano-pores as a core and a dense magnesium oxide layer as a shell; the particle size of the microporous magnesium oxide micro-particle is 30-50μm, and the thickness of the dense magnesium oxide layer is 2-5μm; the microporous periclase refractory aggregate has a porosity of 22.6-40%, a bulk density of 2.10-2.77g / cm3, an average pore size of 500-900nm and a compressive strength of 30-100MPa; Step 2, preparation of the lightweight periclase-carbon refractory material with a multi-scale core-shell structure taking 16-24wt% of the microporous periclase refractory aggregate I, 22-32wt% of the microporous periclase refractory aggregate II and 16-24wt% of the microporous periclase refractory aggregate III as total aggregate, and taking 24-38wt% of the magnesia fine powder, 0.1-1.5wt% of the elemental silicon powder and 0.5-3wt% of the flake graphite powder as total matrix; firstly, placing the total aggregate in a stirrer, adding 2-6wt% of the modified phenolic resin based on the sum of the total aggregate and the total matrix, and mixing; then adding the total matrix and stirring uniformly; machine pressing under the condition of 150-200MPa, and keeping the temperature at 200-320℃ for 12-36h to obtain the lightweight periclase-carbon refractory material with a multi-scale core-shell structure; The preparation method of the modified phenolic resin is: taking the mass ratio of the liquid thermosetting phenolic resin to the magnesium source as 100:(30-150), mixing the liquid thermosetting phenolic resin and the magnesium source uniformly to obtain the modified phenolic resin; The magnesium source in step 2 is the same as the magnesium source in step 1; The particle size of the magnesium oxide nanometer powder is <50nm; The particle size of the magnesium oxide micro powder is <3μm; The particle size of the magnesium hydroxide micro powder is <5μm; The particle size of the magnesium hydroxide fine powder is <100 μm.

2. The method for producing a lightweight periclase-carbon refractory material having a multi-scale core-shell structure according to claim 1, characterized in that The MgO content of the magnesium oxide nano-powder is >99 wt%.

3. The method of producing lightweight periclase-carbon refractory material having a multi-scale core-shell structure according to claim 1, characterized in that The MgO content of the magnesium oxide micro-powder is >99 wt%.

4. The method of producing lightweight periclase-carbon refractory material having a multi-scale core-shell structure according to claim 1, characterized in that The MgO content of the magnesium hydroxide micro-powder is 66-67 wt%.

5. The method of producing lightweight periclase-carbon refractory material having a multi-scale core-shell structure according to claim 1, characterized in that The MgO content of the magnesium hydroxide fine powder is 66-67 wt%.

6. The method of producing lightweight periclase-carbon refractory material having a multi-scale core-shell structure according to claim 1, characterized in that The particle size of the magnesia fine powder is <88 μm; and the MgO content of the magnesia fine powder is 95-97 wt%.

7. The method of producing lightweight periclase-carbon refractory material having a multi-scale core-shell structure according to claim 1, characterized in that The particle size of the elemental silicon powder is <50 μm; and the Si content of the elemental silicon powder is 98-99.5 wt%.

8. The method of producing lightweight periclase-carbon refractory material with a multiscale core-shell structure according to claim 1, characterized in that The particle size of the flake graphite powder is <18 μm; and the C content of the flake graphite powder is 97-98.5 wt%.

9. The method of producing lightweight periclase-carbon refractory material with a multiscale core-shell structure according to claim 1, characterized in that The carbon residue rate of the liquid thermosetting phenolic resin is ≥35%.

10. Lightweight periclase-carbon refractory having a multiscale core-shell structure, characterized in that The lightweight periclase-carbon refractory material with a multi-scale core-shell structure is prepared according to the preparation method of the lightweight periclase-carbon refractory material with a multi-scale core-shell structure according to any one of claims 1-9. The lightweight periclase-carbon refractory material has a multi-scale core-shell structure with a multi-microporous periclase refractory aggregate with a micro-core-shell structure taking multi-microporous magnesium oxide micro-particles with nanopores as a core and a dense magnesium oxide layer as a shell as a core and a continuous magnesium oxide layer as a shell; and the thickness of the continuous magnesium oxide layer is 0.1-0.3 mm.