Mullite refractory material with high mechanical property and preparation method thereof

Abstract

The invention belongs to the technical field of refractory materials, and particularly relates to a mullite refractory material with high mechanical property and a preparation method thereof. The mullite refractory material is prepared by taking coal gangue, bauxite and fly ash as raw materials, and the three industrial solid wastes are converted into the refractory material with high additional value, so that the concept of circular economy is met. According to the invention, coal gangue, bauxite and fly ash are used as raw materials, CaF2, V2O5 and lanthanide rare earth oxide are used as sintering aids, the problems of insufficient mechanical properties and overhigh sintering temperature of the mullite refractory material prepared by purely using coal gangue, bauxite and fly ash as raw materials are solved, and the performance of the mullite refractory material can be greatly improved. CaF2 and V2O5 promote substance transport and grain growth, and rare earth oxide inhibits excessive growth of grains. The balance of'promotion 'and'inhibition' is favorable for forming a compact, fine, uniform and interlaced mullite crystal network, and meanwhile, the mullite crystal network has high strength and good toughness.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, and particularly relates to a high mechanical property mullite refractory material and its preparation method. Background Technology

[0002] Mullite plays a vital role in both traditional and advanced ceramics due to its high melting point, low coefficient of thermal expansion, good chemical stability, thermal shock resistance, and excellent mechanical properties. It is also widely used in refractory materials for industries such as metallurgy, glass, and gas. Furthermore, mullite's excellent infrared transmittance, good dielectric properties, and high-temperature strength at high temperatures make it a promising candidate for applications in optics and electronics, including infrared transparent windows, catalyst supports, and computer chips. Classic applications of mullite include its use in the metallurgical industry as a refractory material for electric furnace roofs, molten iron mixing furnaces, and low-frequency induction furnaces. In the glass industry, these refractory materials are used in the upper structure of glass melting tanks and in the construction of drawing chambers. Mullite is commonly used in kiln plates and columns in high-temperature reactors for firing ceramic products. However, mullite is scarce in nature and is mainly synthesized artificially; therefore, finding a low-cost method to prepare high-performance mullite remains a challenge that researchers are continuously exploring and overcoming.

[0003] Mullite belongs to the orthorhombic crystal system and is a sillimanite structure with oxygen vacancy defects. A mullite unit cell consists of four sillimanite unit cells. Without external resistance, it readily undergoes significant anisotropic growth, thus typically exhibiting a rod-like morphology. The properties of mullite are greatly influenced by its crystal structure, as oxygen atoms are easily lost. This characteristic is often utilized by adding metal oxides to mullite to activate the crystal lattice and promote ceramic sintering. Mullite is scarce in nature, and its industrial applications primarily rely on artificial methods for preparation. Currently, the main methods for mullite preparation include solid-state methods, mechanical ball milling, sol-gel methods, and molten salt methods.

[0004] The structure of mullite determines its diverse properties, with the cross-linking of its main bonds directly influencing its mechanical and thermal properties. Because the octahedral chains and tetrahedral double chains parallel to the c-axis of the crystallography hinder deformation, mullite exhibits small plastic deformation and excellent high-temperature creep resistance. Furthermore, the dense overlap of orbitals parallel to the c-axis lattice direction in the mullite structure forms strong bonds, contributing to its high mechanical strength. In addition, the presence of oxygen vacancies weakens the stability of the crystal structure, resulting in a lower average elastic hardness in mullite compared to sillimanite without oxygen vacancies. Therefore, the superior properties of mullite ceramics make them highly promising for applications in high-temperature thermal structural materials and thermal protection. However, the relatively poor strength of existing mullite ceramics limits their applications to some extent. Summary of the Invention

[0005] This invention addresses the drawbacks of high cost and poor mechanical properties in mullite refractories by using natural raw materials to prepare mullite refractories. The prepared mullite refractories have high strength, can replace traditional mullite refractories, and can meet the energy-saving needs of high-temperature industrial applications.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A high-mechanical-performance mullite refractory material, comprising the following components in parts by weight: 60-80 parts coal gangue, 40-50 parts bauxite, 5-20 parts fly ash, 10-50 parts alumina powder, 1-2 parts CaF2, 1-2 parts V2O5, and 0.1-1 parts lanthanide rare earth oxides.

[0007] Coal gangue is composed of various minerals and belongs to the sedimentary rock category. Its mineral composition is mainly clay minerals and quartz. Common mineral components in coal gangue include kaolinite, montmorillonite, feldspar, illite, calcite, pyrite, and gibbsite. Due to the large-scale mining of coal and the low comprehensive utilization rate of coal gangue, it has become the largest industrial solid waste in my country. From an environmental resource perspective, coal gangue possesses the dual attributes of waste and resource. If rationally utilized, it can become a low-cost, abundant mineral resource. Currently, the comprehensive utilization of coal gangue in my country mainly includes resource recycling, geotechnical applications (highways, railways, construction, etc.), chemical production, and other aspects, while its application in mullite refractory materials is relatively limited.

[0008] Compared to coal gangue, bauxite has a higher aluminum content and can be used as a supplementary raw material for coal gangue. Fly ash, on the other hand, is a solid waste emitted by thermal power plants. It is produced by the combustion of coal powder of a certain particle size in a combustion furnace, and is collected by a dust collector. It is a powdery substance composed of highly dispersed fine particle aggregates and is a pozzolanic material.

[0009] This invention uses coal gangue, bauxite, and fly ash as natural raw materials to prepare mullite refractory materials. Coal gangue, whose main components are SiO2 and Al2O3, is the primary raw material for preparing silicon-aluminum mullite refractory materials. Bauxite, rich in Al2O3, is a key raw material for increasing the Al2O3 content in the material and ensuring sufficient mullite phase formation. Fly ash, also mainly composed of SiO2 and Al2O3, allows for precise control of the aluminum-silicon ratio in the final product by adjusting the ratio of these three components.

[0010] Preferably, the SiO2 content in the coal gangue is 45-55 wt%, and the Al2O3 content is 30-40 wt%.

[0011] Preferably, the bauxite contains 10-20 wt% SiO2 and 60-70 wt% Al2O3.

[0012] Preferably, the fly ash contains 40-50 wt% SiO2 and 35-45 wt% Al2O3.

[0013] Preferably, the chemical composition of the coal gangue, by weight percentage, mainly comprises the following components: SiO2 45-55%, Al2O3 30-40%, Fe2O3 0.2-0.6%, TiO2 0.25-0.45%, K2O 0.01-0.1%, Na2O 0.01-0.05%, CaO 0.1-0.4%, MgO 0.2-0.4%, with a loss on ignition of 10-20%. Specifically, the coal gangue selected in this invention, by weight percentage, mainly comprises the following components: SiO2 48.12%, Al2O3 35.01%, Fe2O3 0.45%, TiO2 0.35%, K2O 0.07%, Na2O 0.02%, CaO 0.21%, MgO 0.32%, with a loss on ignition of 14.38%.

[0014] Preferably, the chemical composition of bauxite, by weight percentage, mainly comprises the following components: SiO2 10-20%, Al2O3 60-70%, Fe2O3 0.5-0.8%, MgO 0.2-0.4%, CaO 0.2-0.4%, Na2O 0.02-0.07%, K2O 0.3-0.7%, TiO2 2-3%, P2O5 0.3-0.5%, with a loss on ignition of 10-17%. Specifically, the bauxite selected in this invention, by weight percentage, mainly comprises the following components: SiO2 14.73%, Al2O3 65.82%, Fe2O3 0.62%, MgO 0.35%, CaO 0.32%, Na2O 0.05%, K2O 0.51%, TiO2 2.51%, P2O5 0.42%, with a loss on ignition of 14.15%.

[0015] Preferably, the chemical composition of fly ash, by weight percentage, mainly comprises the following components: SiO2 40-50%, Al2O3 35-45%, CaO 5-7%, Fe2O3 1-3%, TiO2 2-3%, SO3 0.4-0.7%, K2O 0.2-0.5%, P2O5 0.2-0.5%, and loss on ignition 1-3%. Specifically, the fly ash selected in this invention, by weight percentage, mainly comprises the following components: SiO2 44.62%, Al2O3 41.41%, CaO 6.06%, Fe2O3 1.82%, TiO2 2.61%, SO3 0.58%, K2O 0.37%, P2O5 0.34%, and loss on ignition 1.33%.

[0016] Preferably, the alumina powder is one or more of α-Al2O3 powder or γ-Al2O3 powder.

[0017] Preferably, the lanthanide rare earth oxide is one or more of CeO2 and La2O3. CaF2, V2O5, and lanthanide rare earth oxides, as sintering aids, can significantly improve the performance of mullite refractory materials. Specifically, CeO2 and La2O3 can be selected. Lanthanum and cerium rare earth elements have different atomic radii; the simultaneous addition of both CeO2 and La2O3 can better suppress abnormal growth of mullite grains at high temperatures, contributing to the formation of a fine and uniform structure. Specifically, it can be a mixture of rare earth oxides with a CeO2:La2O3 mass ratio of (0.1-10):1. Further, it can be a mixture of rare earth oxides with a CeO2:La2O3 mass ratio of (0.2-5):1. Even further, it can be a mixture of rare earth oxides with a CeO2:La2O3 mass ratio of (2-4):1.

[0018] CaF2 is one of the most commonly used sintering aids in mullite materials. At high temperatures, CaF2 can promote the generation of a liquid phase, introduce a liquid-phase sintering mechanism, accelerate mass transport, and fill pores, thereby greatly promoting the densification of the green body. Furthermore, fluoride ions can generate lattice defects, activate the lattice, and accelerate solid-phase reactions, thus significantly reducing the sintering temperature, increasing the bulk density, and reducing apparent porosity. However, excessive CaF2 can easily lead to a loose material structure and may cause abnormal grain growth. Therefore, this invention adds a certain amount of V2O5 and lanthanide rare earth oxides as sintering aids. V2O5 itself has a low melting point and is a very effective liquid-phase forming agent. It can form a melt at relatively low temperatures, promoting the anisotropic growth of mullite needle-like crystals and forming long columnar or needle-like interwoven structures, which is crucial for improving the toughness and strength of the material. V2O5 is relatively expensive, and excessive use may also lead to high-temperature deformation of the material (the load softening temperature may be affected) and a decrease in strength. Lanthanide rare earth oxides (La₂O₃, CeO₂) typically do not directly form a large liquid phase; their role is more focused on improving the "quality." They inhibit abnormal grain growth and prevent excessive grain growth. This helps to form a fine and uniform microstructure, improving the mechanical properties and density of mullite. Overall, CaF₂ and V₂O₅ promote mass transport and grain growth, while rare earth oxides inhibit excessive grain growth. This balance between "promotion" and "inhibition" is conducive to forming an ideal structure of mullite that is both dense and possesses a fine, uniform, and interwoven crystal network. This structure simultaneously exhibits high strength and good toughness.

[0019] On the other hand, the present invention also provides a method for preparing a high-mechanical-performance mullite refractory material, comprising the following steps: S1 grinds and mixes the raw materials to form a compound; S2 compression molding; S3 is sintered at high temperature and then cooled to obtain a mullite refractory material with high mechanical properties.

[0020] Preferably, the pressing pressure in step S2 is 5-30 MPa.

[0021] Preferably, the high-temperature sintering in step S3 is a gradient heating process, specifically, heating from room temperature to 900-1000℃ at a heating rate of 1-10℃ / min, holding at that temperature for 0.5-1.5h; then heating to 1400-1550℃ at a heating rate of 1-10℃ / min, holding at that temperature for 1-3h. Gradient heating allows for a smooth phase transformation, ensuring a stable and slow release of components, protecting the integrity of the green body, and preventing microcracks caused by internal stress due to sudden volume changes. The holding period provides sufficient time for long-range atomic / ionic diffusion, the elimination of pores, and the uniform distribution of the liquid phase, thereby achieving higher bulk density and lower apparent porosity.

[0022] Preferably, the cooling in step S3 is natural cooling.

[0023] Beneficial effects: The preparation of mullite refractories from coal gangue, bauxite, and fly ash is a typical high-value-added resource utilization technology that "treats waste with waste and turns waste into treasure." Transforming these three types of industrial solid waste into high-value-added refractory materials aligns with the concept of a circular economy. This not only solves environmental pollution and land occupation problems but also creates economic benefits, achieving a win-win situation for both environmental and economic benefits. CaF2, V2O5, and lanthanide rare earth oxides, as sintering aids, address the issues of insufficient mechanical properties and excessively high sintering temperatures in mullite refractories prepared solely from coal gangue, bauxite, and fly ash, significantly improving the performance of mullite refractories. CaF2 and V2O5 promote mass transport and grain growth, while rare earth oxides inhibit excessive grain growth. This balance between "promotion" and "inhibition" facilitates the formation of an ideal structure that is both dense and possesses a fine, uniform, and interwoven mullite crystal network. This structure simultaneously exhibits high strength and good toughness. Detailed Implementation

[0024] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0025] Unless otherwise specified, the raw material types for the following examples and comparative examples are consistent. The chemical composition of coal gangue, by weight percentage, mainly includes the following components: SiO2 48.12%, Al2O3 35.01%, Fe2O3 0.45%, TiO2 0.35%, K2O 0.07%, Na2O 0.02%, CaO 0.21%, MgO 0.32%, with a loss on ignition of 14.38%. The chemical composition of bauxite, by weight percentage, mainly includes the following components: SiO2 14.73%, Al2O3 65.82%, Fe2O3 0.62%, MgO 0.35%, CaO 0.32%, Na2O 0.05%, K2O 0.51%, TiO2 2.51%, P2O5 0.42%, with a loss on ignition of 14.15%. The chemical composition of fly ash, by weight percentage, mainly includes the following components: SiO2 44.62%, Al2O3 41.41%, CaO 6.06%, Fe2O3 1.82%, TiO2 2.61%, SO3 0.58%, K2O 0.37%, P2O5 0.34%, and loss on ignition 1.33%. The bulk density (GB / T2997-2015) and compressive strength (GB / T5072-2023) of the following examples were tested respectively.

[0026] Example 1 A high-mechanical-performance mullite refractory material, comprising the following components in parts by weight: The composition consists of 60 parts coal gangue, 40 parts bauxite, 8 parts fly ash, 30 parts α-Al2O3 powder, 1 part CaF2, 2 parts V2O5, and 0.1 parts lanthanide rare earth oxides, with the lanthanide rare earth oxide being La2O3.

[0027] The preparation method includes the following steps: S1 grinds and mixes the raw materials to form a compound; S2 compression molding; the compression molding pressure is 10MPa; S3 was heated from room temperature to 900℃ at a heating rate of 3℃ / min and held at that temperature for 0.5h; then heated to 1490℃ at a heating rate of 3℃ / min and held at that temperature for 3h, followed by natural cooling, to obtain a mullite refractory material with high mechanical properties. The mullite refractory material prepared in this embodiment was tested and found to have a bulk density of 2.08 g / cm³. 3 The compressive strength is 121 MPa.

[0028] Example 2 A high-mechanical-performance mullite refractory material, comprising the following components in parts by weight: The composition consists of 70 parts coal gangue, 50 parts bauxite, 14 parts fly ash, 50 parts α-Al2O3 powder, 2 parts CaF2, 1 part V2O5, and 0.5 parts lanthanide rare earth oxides, with CeO2 being the lanthanide rare earth oxide.

[0029] The preparation method includes the following steps: S1 grinds and mixes the raw materials to form a compound; S2 compression molding; the compression molding pressure is 15MPa; S3 was heated from room temperature to 1000℃ at a heating rate of 7℃ / min and held at that temperature for 1.5 hours; then heated to 1530℃ at a heating rate of 7℃ / min and held at that temperature for 1.7 hours, followed by natural cooling, to obtain a mullite refractory material with high mechanical properties. The mullite refractory material prepared in this embodiment was tested and found to have a bulk density of 1.99 g / cm³. 3 The compressive strength is 115 MPa.

[0030] Example 3 A high-mechanical-performance mullite refractory material, comprising the following components in parts by weight: The mixture contains 60 parts coal gangue, 50 parts bauxite, 10 parts fly ash, 40 parts α-Al2O3 powder, 1.2 parts CaF2, 1.2 parts V2O5, and 0.4 parts lanthanide rare earth oxides, which are a mixture of La2O3.

[0031] The preparation method includes the following steps: S1 grinds and mixes the raw materials to form a compound; S2 compression molding; the compression molding pressure is 12MPa; S3 was heated from room temperature to 950℃ at a heating rate of 5℃ / min and held at that temperature for 1 hour; then heated to 1500℃ at a heating rate of 5℃ / min and held at that temperature for 2.5 hours, followed by natural cooling, to obtain a mullite refractory material with high mechanical properties. The mullite refractory material prepared in this embodiment was tested and found to have a bulk density of 2.07 g / cm³. 3 The compressive strength is 124 MPa.

[0032] Example 4 A high-mechanical-performance mullite refractory material, comprising the following components in parts by weight: The mixture contains 60 parts coal gangue, 50 parts bauxite, 8 parts fly ash, 30 parts α-Al2O3 powder, 1.1 parts CaF2, 1.8 parts V2O5, and 0.3 parts lanthanide rare earth oxides, which are a mixture of CeO2 and La2O3 in a mass ratio of 2:1.

[0033] The preparation method includes the following steps: S1 grinds and mixes the raw materials to form a compound; S2 compression molding; the compression molding pressure is 11MPa; S3 was heated from room temperature to 910℃ at a heating rate of 4℃ / min and held at that temperature for 1.4 hours; then heated to 1510℃ at a heating rate of 4℃ / min and held at that temperature for 2 hours, followed by natural cooling, to obtain a mullite refractory material with high mechanical properties. The mullite refractory material prepared in this embodiment was tested and found to have a bulk density of 2.25 g / cm³. 3 The compressive strength is 130 MPa.

[0034] Example 5 A high-mechanical-performance mullite refractory material, comprising the following components in parts by weight: The composition consists of 60 parts coal gangue, 50 parts bauxite, 10 parts fly ash, 40 parts α-Al2O3 powder, 1.2 parts CaF2, 1.2 parts V2O5, and 0.4 parts lanthanide rare earth oxides, with CeO2 being the lanthanide rare earth oxide.

[0035] The preparation method includes the following steps: S1 grinds and mixes the raw materials to form a compound; S2 compression molding; the compression molding pressure is 12MPa; S3 was heated from room temperature to 950℃ at a heating rate of 5℃ / min and held at that temperature for 1 hour; then heated to 1500℃ at a heating rate of 5℃ / min and held at that temperature for 2.5 hours, followed by natural cooling, to obtain a mullite refractory material with high mechanical properties. The mullite refractory material prepared in this embodiment was tested and found to have a bulk density of 2.02 g / cm³. 3 The compressive strength is 118 MPa.

[0036] Example 6 A high-mechanical-performance mullite refractory material, comprising the following components in parts by weight: The mixture contains 63 parts coal gangue, 42 parts bauxite, 11 parts fly ash, 28 parts α-Al2O3 powder, 1.3 parts CaF2, 1.4 parts V2O5, and 0.4 parts lanthanide rare earth oxides, which are a mixture of CeO2 and La2O3 in a mass ratio of 0.5:1.

[0037] The preparation method includes the following steps: S1 grinds and mixes the raw materials to form a compound; S2 compression molding; the compression molding pressure is 11MPa; S3 was heated from room temperature to 930℃ at a heating rate of 8℃ / min and held at that temperature for 0.8h; then heated to 1530℃ at a heating rate of 8℃ / min and held at that temperature for 2.8h, followed by natural cooling, thus obtaining a mullite refractory material with high mechanical properties. The mullite refractory material prepared in this embodiment was tested and found to have a bulk density of 2.06 g / cm³. 3The compressive strength is 126 MPa.

[0038] Example 7 A high-mechanical-performance mullite refractory material, comprising the following components in parts by weight: The mixture contains 60 parts coal gangue, 50 parts bauxite, 10 parts fly ash, 40 parts α-Al2O3 powder, 1.2 parts CaF2, 1.2 parts V2O5, and 0.4 parts lanthanide rare earth oxides, which are a mixture of CeO2 and La2O3 in a mass ratio of 1:3.

[0039] The preparation method includes the following steps: S1 grinds and mixes the raw materials to form a compound; S2 compression molding; the compression molding pressure is 12MPa; S3 was heated from room temperature to 950℃ at a heating rate of 5℃ / min and held at that temperature for 1 hour; then heated to 1500℃ at a heating rate of 5℃ / min and held at that temperature for 2.5 hours, followed by natural cooling, to obtain a mullite refractory material with high mechanical properties. The mullite refractory material prepared in this embodiment was tested and found to have a bulk density of 2.18 g / cm³. 3 The compressive strength is 129 MPa.

[0040] Example 8 A high-mechanical-performance mullite refractory material, comprising the following components in parts by weight: The mixture contains 68 parts coal gangue, 48 parts bauxite, 12 parts fly ash, 37 parts α-Al2O3 powder, 1.8 parts CaF2, 1.3 parts V2O5, and 0.6 parts lanthanide rare earth oxides, which are a mixture of CeO2 and La2O3 in a mass ratio of 1:1.

[0041] The preparation method includes the following steps: S1 grinds and mixes the raw materials to form a compound; S2 compression molding; the compression molding pressure is 14MPa; S3 was heated from room temperature to 980℃ at a heating rate of 6℃ / min and held at that temperature for 1.2 hours; then heated to 1500℃ at a heating rate of 6℃ / min and held at that temperature for 2.8 hours, followed by natural cooling, to obtain a mullite refractory material with high mechanical properties. The mullite refractory material prepared in this embodiment was tested and found to have a bulk density of 2.16 g / cm³. 3 The compressive strength is 138 MPa.

[0042] Example 9 A high-mechanical-performance mullite refractory material, comprising the following components in parts by weight: The composition includes 63 parts coal gangue, 50 parts bauxite, 8 parts fly ash, 25 parts α-Al2O3 powder, 1.1 parts CaF2, 1.1 parts V2O5, and 1 part lanthanide rare earth oxide, with CeO2 as the lanthanide rare earth oxide.

[0043] The preparation method includes the following steps: S1 grinds and mixes the raw materials to form a compound; S2 compression molding; the compression molding pressure is 10MPa; S3 was heated from room temperature to 960℃ at a heating rate of 7℃ / min and held at that temperature for 1.2 hours; then heated to 1550℃ at a heating rate of 7℃ / min and held at that temperature for 2.6 hours, followed by natural cooling, to obtain a mullite refractory material with high mechanical properties. The mullite refractory material prepared in this embodiment was tested and found to have a bulk density of 2.10 g / cm³. 3 The compressive strength is 125 MPa.

[0044] Example 10 A high-mechanical-performance mullite refractory material, comprising the following components in parts by weight: The mixture contains 60 parts coal gangue, 50 parts bauxite, 10 parts fly ash, 40 parts α-Al2O3 powder, 1.2 parts CaF2, 1.2 parts V2O5, and 0.4 parts lanthanide rare earth oxides, which are a mixture of CeO2 and La2O3 in a mass ratio of 3:1.

[0045] The preparation method includes the following steps: S1 grinds and mixes the raw materials to form a compound; S2 compression molding; the compression molding pressure is 12MPa; S3 was heated from room temperature to 950℃ at a heating rate of 5℃ / min and held at that temperature for 1 hour; then heated to 1500℃ at a heating rate of 5℃ / min and held at that temperature for 2.5 hours, followed by natural cooling, to obtain a mullite refractory material with high mechanical properties. The mullite refractory material prepared in this embodiment was tested and found to have a bulk density of 2.24 g / cm³. 3 The compressive strength is 136 MPa.

[0046] Comparative Example 1 A high-mechanical-performance mullite refractory material, comprising the following components in parts by weight: The mixture contains 60 parts coal gangue, 50 parts bauxite, 10 parts fly ash, 40 parts α-Al2O3 powder, 0 parts CaF2, 2.1 parts V2O5, and 0.7 parts lanthanide rare earth oxides, which are a mixture of CeO2 and La2O3 in a mass ratio of 3:1.

[0047] The preparation method includes the following steps: S1 grinds and mixes the raw materials to form a compound; S2 compression molding; the compression molding pressure is 12MPa; S3 was heated from room temperature to 950℃ at a heating rate of 5℃ / min and held at that temperature for 1 hour; then heated to 1500℃ at a heating rate of 5℃ / min and held at that temperature for 2.5 hours, followed by natural cooling, to obtain a mullite refractory material with high mechanical properties. The mullite refractory material prepared in this embodiment was tested and found to have a bulk density of 1.76 g / cm³. 3 The compressive strength is 85 MPa.

[0048] Comparative Example 2 A high-mechanical-performance mullite refractory material, comprising the following components in parts by weight: The mixture contains 60 parts coal gangue, 50 parts bauxite, 10 parts fly ash, 40 parts α-Al2O3 powder, 2.1 parts CaF2, 0 parts V2O5, and 0.7 parts lanthanide rare earth oxides, which are a mixture of CeO2 and La2O3 in a mass ratio of 3:1.

[0049] The preparation method includes the following steps: S1 grinds and mixes the raw materials to form a compound; S2 compression molding; the compression molding pressure is 12MPa; S3 was heated from room temperature to 950℃ at a heating rate of 5℃ / min and held at that temperature for 1 hour; then heated to 1500℃ at a heating rate of 5℃ / min and held at that temperature for 2.5 hours, followed by natural cooling, to obtain a mullite refractory material with high mechanical properties. The mullite refractory material prepared in this embodiment was tested and found to have a bulk density of 1.82 g / cm³. 3 The compressive strength is 91 MPa.

[0050] Comparative Example 3 A high-mechanical-performance mullite refractory material, comprising the following components in parts by weight: 60 parts coal gangue, 50 parts bauxite, 10 parts fly ash, 40 parts α-Al2O3 powder, 1.4 parts CaF2, and 1.4 parts V2O5.

[0051] The preparation method includes the following steps: S1 grinds and mixes the raw materials to form a compound; S2 compression molding; the compression molding pressure is 12MPa; S3 was heated from room temperature to 950℃ at a heating rate of 5℃ / min and held at that temperature for 1 hour; then heated to 1500℃ at a heating rate of 5℃ / min and held at that temperature for 2.5 hours, followed by natural cooling, to obtain a mullite refractory material with high mechanical properties. The mullite refractory material prepared in this embodiment was tested and found to have a bulk density of 1.78 g / cm³. 3 The compressive strength is 82 MPa.

[0052] Comparative Example 4 A high-mechanical-performance mullite refractory material, comprising the following components in parts by weight: The mixture contains 60 parts coal gangue, 50 parts bauxite, 10 parts fly ash, 40 parts α-Al2O3 powder, 1.2 parts CaF2, 1.2 parts V2O5, and 2 parts lanthanide rare earth oxides, which are a mixture of CeO2 and La2O3 in a mass ratio of 3:1.

[0053] The preparation method includes the following steps: S1 grinds and mixes the raw materials to form a compound; S2 compression molding; the compression molding pressure is 12MPa; S3 was heated from room temperature to 950℃ at a heating rate of 5℃ / min and held at that temperature for 1 hour; then heated to 1500℃ at a heating rate of 5℃ / min and held at that temperature for 2.5 hours, followed by natural cooling, to obtain a mullite refractory material with high mechanical properties. The mullite refractory material prepared in this embodiment was tested and found to have a bulk density of 1.88 g / cm³. 3 The compressive strength is 106 MPa.

[0054] As can be seen from the above examples and comparative examples, high-mechanical-performance mullite refractories were prepared using coal gangue, bauxite, and fly ash as raw materials. CaF2, V2O5, and lanthanide rare earth oxides, as sintering aids, solved the problems of insufficient mechanical properties and excessively high sintering temperatures in mullite refractories prepared solely from coal gangue, bauxite, and fly ash, significantly improving the performance of mullite refractories. CaF2 and V2O5 promote mass transport and grain growth, while rare earth oxides inhibit excessive grain growth. This balance between "promotion" and "inhibition" is beneficial for forming an ideal structure that is both dense and possesses a fine, uniform, and interwoven mullite crystal network. This structure simultaneously exhibits high strength and good toughness. Specifically, compared to Example 10, Comparative Examples 1-3 lacked CaF2, V2O5, and lanthanide rare earth oxides, respectively, resulting in reduced density and compressive strength of the mullite refractories. This indicates that CaF2 can promote the generation of the liquid phase, lower the sintering temperature, increase the bulk density, and reduce apparent porosity. V₂O₅ itself has a low melting point, allowing it to melt at relatively low temperatures. This promotes the anisotropic growth of mullite needle-like crystals, forming a long columnar or needle-like interwoven structure, which is crucial for improving the material's toughness and strength. Lanthanide rare earth oxides (La₂O₃, CeO₂) can generally inhibit abnormal grain growth and prevent excessive grain growth. This helps to form a fine and uniform microstructure, improving the mechanical properties and density of mullite. In particular, as shown in Comparative Example 4, although the amount of rare earth oxides used is small, their impact on product performance is significant. When the rare earth content is too high, the mullite performance actually decreases. Moreover, from a cost perspective, excessive rare earth addition will increase the material cost. Therefore, the amount of lanthanide rare earth oxides used should not be excessive.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.

Claims

1. A mullite refractory material with high mechanical properties, characterized in that, The components include the following parts by weight: 60-80 parts coal gangue, 40-50 parts bauxite, 5-20 parts fly ash, 10-50 parts alumina powder, 1-2 parts CaF2, 1-2 parts V2O5, and 0.1-1 parts lanthanide rare earth oxides.

2. The high-mechanical-performance mullite refractory material as described in claim 1, characterized in that, The coal gangue contains 45-55 wt% SiO2 and 30-40 wt% Al2O3.

3. The high-mechanical-performance mullite refractory material as described in claim 1, characterized in that, The bauxite contains 10-20 wt% SiO2 and 60-70 wt% Al2O3.

4. The high mechanical properties mullite refractory material as described in claim 1, characterized in that, The fly ash contains 40-50 wt% SiO2 and 35-45 wt% Al2O3.

5. The high mechanical properties mullite refractory material as described in claim 1, characterized in that, The alumina powder is one or more of α-Al2O3 powder or γ-Al2O3 powder.

6. The high-mechanical-performance mullite refractory material as described in claim 1, characterized in that, The lanthanide rare earth oxides are one or more of La2O3 and CeO2.

7. A method for preparing a high-mechanical-performance mullite refractory material as described in any one of claims 1-6, characterized in that, Includes the following steps: S1 grinds and mixes the raw materials to form a compound; S2 compression molding; S3 is sintered at high temperature and then cooled to obtain a mullite refractory material with high mechanical properties.

8. The method for preparing a high-mechanical-performance mullite refractory material as described in claim 7, characterized in that, The pressure for pressing in step S2 is 5-30 MPa.

9. The method for preparing a high-mechanical-performance mullite refractory material as described in claim 7, characterized in that, In step S3, the high-temperature sintering is a gradient heating process, specifically, heating from room temperature to 900-1000℃ at a heating rate of 1-10℃ / min and holding for 0.5-1.5h; then heating to 1400-1550℃ at a heating rate of 1-10℃ / min and holding for 1-3h.

10. The method for preparing a high-mechanical-performance mullite refractory material as described in claim 7, characterized in that, In step S3, the cooling is natural cooling.