Preparation method of corundum-mullite system alkali corrosion resistant composite refractory

Abstract

The application discloses a kind of high stability alkali erosion resistant low-grade bauxite-coal gangue based corundum-mullite system of preparation application technology of complex refractory material.Electrofusion magnesia is innovatively introduced into low-grade bauxite-based corundum-mullite system in the application, effectively improving the overall structural stability of the composite material, and a high-performance erosion-resistant composite material with a compressive strength of 89.88 MPa and a bulk density of 3.16 g / cm³ is obtained. And through the modification of zirconium silicate and yttrium oxide, the alkali erosion resistance of the composite material can be greatly improved, so that the material can adapt to the strong alkali working environment of sodium ion battery positive electrode material synthesis, and has excellent comprehensive performance. The application realizes the efficient utilization of low-grade bauxite and coal gangue resources, and the prepared composite material has structural stability and alkali erosion resistance, and can be widely used in high-performance kiln car, furnace lining, crucible and furnace lining, etc. Refractory scene, has good practical value and industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of high-performance refractory materials technology, specifically relating to a multiphase refractory material of low-grade bauxite-coal gangue-based corundum-mullite system reinforced by fused magnesia, zirconium silicate and yttrium oxide, and its preparation method. Background Technology

[0002] Against the backdrop of increasingly prominent global energy supply and demand contradictions, energy conservation, emission reduction, and resource utilization of solid waste have become key research areas in materials science and engineering. Low-grade bauxite and coal gangue, as bulk industrial solid wastes, possess natural potential for preparing aluminosilicate refractory materials due to their rich content of valuable components such as aluminum and silicon. Currently, there are numerous reports on the process route for preparing corundum-mullite composite materials through high-temperature sintering using low-grade bauxite and coal gangue as the main raw materials, supplemented with additives such as smokeless calcined coal and carboxymethyl cellulose. The incorporation of a small amount of smokeless calcined coal not only creates a weak reducing atmosphere during high-temperature sintering, effectively promoting the in-situ generation of the silicon carbide hard phase within the system, but also refines the matrix grains, optimizes the internal pore structure of the material, reduces the apparent porosity, and improves the high-temperature toughness and thermal shock resistance of the composite material, thus compensating for the shortcomings of traditional aluminosilicate refractory materials, such as insufficient toughness and susceptibility to thermal shock cracking. However, such corundum-mullite composite materials prepared from solid waste generally suffer from defects such as low compressive strength, high porosity, and unstable microstructure, which seriously restrict their practical application in the field of high-performance refractory materials.

[0003] Zirconium dioxide (ZrO2), as a high-quality functional modifier, is not used to promote the formation of magnesium aluminum spinel. Its core role is to optimize the overall service performance of composite materials and regulate the phase composition of the system. During high-temperature sintering, ZrO2 can work synergistically with other system components to refine grains, inhibit abnormal grain growth, improve material toughness through a phase transformation toughening mechanism, and enhance the high-temperature structural stability and mechanical properties of the material. Simultaneously, the doping of ZrO2 can stably generate a monoclinic zirconium phase in the sample. This phase can further optimize the material's interface structure, buffer high-temperature thermal stress, and reduce the risk of high-temperature cracking.

[0004] The erosion of refractory materials is mainly classified into three categories: chemical erosion, physical erosion, and penetrating erosion. The mechanisms of each type differ significantly. Chemical erosion primarily occurs under high-temperature conditions, where media such as melts, strong alkalis, and molten salts react chemically with the material matrix and phases, generating low-melting-point, easily leached compounds, leading to matrix loss and structural damage. Physical erosion involves the continuous impact of high-speed flowing high-temperature melts, fumes, and solid particles on the material surface, causing surface wear, peeling, and delamination. Penetrating erosion is the most insidious and damaging form of erosion. At high temperatures, the corrosive medium continuously penetrates and diffuses into the material along pores, grain boundaries, and microcracks, forming a modified layer within the material. This leads to matrix component decomposition, phase degradation, and internal stress concentration, ultimately causing overall material cracking, delamination, and detachment, significantly shortening its service life. Yttrium oxide can effectively seal internal pores, stabilize the phase structure, and hinder the penetration and diffusion of corrosive media, fundamentally inhibiting penetrating erosion and its coupled destructive effects, significantly improving the material's service stability under harsh environments such as strong alkalis and high-temperature molten salts.

[0005] Against this backdrop, this invention aims to systematically investigate the influence of synergistic doping of zirconium silicate and yttrium oxide on the phase composition, microstructure, and macroscopic properties of materials by determining the optimal doping ratio of fused magnesia powder and subjecting it to heat treatment at 1300-1700℃, thereby further optimizing the material's structure-performance relationship. Simultaneously, this invention pays particular attention to the alkali corrosion resistance of the prepared samples, an indicator crucial for evaluating the long-term stability and service life of materials in strongly alkaline operating environments such as the synthesis of sodium-ion battery cathode materials. By constructing a simulated alkali corrosion experimental environment, the performance evolution of materials under harsh operating conditions can be effectively revealed, thus providing reliable theoretical support and experimental basis for the engineering application of this type of multiphase material. Summary of the Invention

[0006] Purpose of the Invention: The purpose of this invention is to overcome the shortcomings of existing low-grade bauxite-based corundum-mullite composite materials, such as low compressive strength, high porosity, and unstable performance, and to provide a method for preparing a multiphase refractory material based on a low-grade bauxite-coal gangue system reinforced with fused magnesia, zirconium silicate, and yttrium oxide. Specific objectives include:

[0007] (1) By introducing fused magnesia, magnesium aluminum spinel phase is generated in situ during high-temperature sintering, which significantly improves the density, compressive strength and microstructure stability of the composite material.

[0008] (2) By utilizing the synergistic doping effect of zirconium silicate and yttrium oxide, the phase composition and sintering densification behavior of the material are further optimized, thereby improving the high-temperature stability and comprehensive mechanical properties of the material;

[0009] (3) It endows the multiphase material with excellent resistance to alkali corrosion, enabling it to meet the long-term service requirements of strong alkaline environments such as the synthesis of sodium-ion battery cathode materials.

[0010] (4) To realize the high-value utilization of low-grade bauxite and coal gangue, and to provide a technical solution that is both economical and reliable for high-performance saggers and high-temperature furnace lining materials.

[0011] Technical Solution: A mixture of bauxite, coal gangue, smokeless calcined coal, fused magnesia, and carboxymethyl cellulose binder is stirred to ensure uniform mixing. An appropriate amount of deionized water is then added and stirred until homogeneous. After mixing, the mixture is allowed to rest at room temperature, followed by sample pressing. After demolding, the samples are transferred to an electrically heated drying oven for heat preservation and curing. After drying, the samples are placed in a crucible and completely covered with fine coke powder and coke particles. The crucible is then sintered in a box-type resistance furnace. The static crucible method is subsequently used to evaluate the samples' resistance to alkali corrosion.

[0012] Beneficial effects: The synthesis principle of this invention is as follows:

[0013] Magnesium aluminum spinel possesses high hardness, good thermal shock resistance, and excellent chemical corrosion resistance. Its formation effectively fills internal pores in materials, strengthens grain boundary bonding, and significantly improves the density, compressive strength, and microstructural stability of multiphase materials. The introduction of appropriate amounts of zirconium silicate decomposes at high temperatures to produce ZrO2. The presence of ZrO2 is beneficial for the full formation of the magnesium aluminum spinel phase. Furthermore, ZrO2 itself has a high melting point and good chemical inertness, which further improves the high-temperature stability and corrosion resistance of multiphase materials. Yttrium oxide (Y2O3), as a rare earth oxide sintering aid, can reduce grain boundary migration rate, inhibit abnormal grain growth, and promote liquid-phase sintering and mass diffusion processes during sintering. This accelerates the densification process, reduces residual porosity, and makes the microstructure more uniform and dense, comprehensively improving the mechanical properties and service reliability of the material. Both the magnesium aluminum spinel phase and the ZrO2 component have excellent resistance to alkaline chemical corrosion. In addition, the porosity of the material is significantly reduced after the Y2O3 promotes densification, which can effectively block the penetration and diffusion of alkaline media into the material. The synergistic effect of the three gives the multiphase material excellent long-term chemical stability in a strongly alkaline environment.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] (1) This invention introduces fused magnesia into a low-grade bauxite-based corundum-mullite system. By utilizing the high chemical purity, dense crystal structure and excellent high-temperature stability of fused magnesia, a magnesium aluminum spinel reinforcing phase is generated in situ during the high-temperature sintering process at 1500℃. This enables the compressive strength of the multiphase material to reach 89.88 MPa and the bulk density to reach 3.16 g / cm³, effectively overcoming the defects of low strength and high porosity of traditional corundum-mullite materials.

[0016] (2) The present invention utilizes the synergistic doping of zirconium silicate and yttrium oxide to promote the full generation of magnesium aluminum spinel phase by ZrO2 component, thereby further improving the high temperature stability of the material; on the other hand, it utilizes the sintering aid effect of Y2O3 to promote the densification of the material, making the microstructure more uniform and dense, and comprehensively improving the mechanical properties and service reliability of the material.

[0017] (3) The multiphase material prepared by the present invention has excellent resistance to alkali corrosion and exhibits excellent chemical stability in strong alkaline working conditions such as the synthesis of sodium-ion battery cathode materials. It can effectively extend the service life of crucible and high-temperature furnace lining materials and reduce maintenance costs in industrial production.

[0018] (4) This invention uses low-grade bauxite as the main raw material, realizing the high-value utilization of bulk industrial solid waste. The raw materials are widely available and inexpensive, and the preparation process is simple and controllable. It has both significant economic and environmental benefits and is suitable for industrial promotion and application. Attached Figure Description

[0019] Figure 1 XRD patterns of samples from Embodiments 1, 2, and 3.

[0020] Figure 2 SEM images of samples after sintering in Embodiments 1, 2, and 3, along with corresponding images showing sodium ion erosion concentrations. Detailed Implementation

[0021] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0022] Example 1

[0023] Weigh the following raw materials by mass percentage: 86.5 wt% low-grade bauxite, 10 wt% coal gangue, 3.5 wt% smokeless calcined coal, 15 wt% fused magnesia, and 4 wt% carboxymethyl cellulose binder. First, stir and mix the raw materials to ensure the binder and raw materials are evenly mixed. Then, add an appropriate amount of deionized water and stir until homogeneous. After mixing, allow the mixture to rest at room temperature for 12 hours before packaging. Place an appropriate amount of the mixed raw material in a mold and press it using a powder tablet press at a gauge pressure of 10 MPa for 60 seconds to obtain a sample. After demolding, transfer the sample to an electric heating drying oven at 80℃ for 24 hours to cure. After drying, place the sample in a crucible, completely cover it with coke powder and coke particles, and then place it in a box-type resistance furnace at a sintering temperature of 1500℃. The static crucible method is used to evaluate the alkali erosion resistance of the sample; the crucible is filled with Na2CO3 and then carbonized. The sample was heated to 1000℃ and then held at that temperature for 3 hours. After the sample cooled to room temperature, it was removed from the crucible and cut along the axial center of the sample. Representative samples were selected for surface polishing and gold plating, followed by microscopic morphology characterization and mechanism analysis using scanning electron microscopy.

[0024] Example 2

[0025] Weigh the following raw materials by mass percentage: 86.5 wt% low-grade bauxite, 10 wt% coal gangue, 3.5 wt% smokeless calcined coal, 15 wt% fused magnesia, 4 wt% carboxymethyl cellulose binder, and 20 wt% zirconium silicate. First, stir and mix them to ensure the binder and raw materials are evenly mixed. Then, add an appropriate amount of deionized water and stir until homogeneous. After mixing, allow the mixture to rest at room temperature for 12 hours, then bag it for later use. Place an appropriate amount of the mixed raw material in a mold and press it using a powder tablet press at a gauge pressure of 10 MPa for 60 seconds to obtain a sample. After demolding, transfer the sample to an electric heating drying oven at 80℃ for 24 hours to cure. After drying, place the sample in a crucible, completely cover it with coke powder and coke particles, and then place it in a box-type resistance furnace at a sintering temperature of 1500℃. The static crucible method was used to evaluate the alkali corrosion resistance of the samples. The crucible was filled with Na2CO3 and then carbonized. The temperature was heated to 1000℃ and then held at that temperature for 3 hours. After the samples cooled to room temperature, they were removed from the crucible and cut along the axial center of the crucible. Representative samples were selected for surface polishing and gold plating, followed by microscopic morphology characterization and mechanism analysis using scanning electron microscopy.

[0026] Example 3

[0027] Weigh the following raw materials by mass percentage: 86.5 wt% low-grade bauxite, 10 wt% coal gangue, 3.5 wt% smokeless calcined coal, 15 wt% fused magnesia, 4 wt% carboxymethyl cellulose binder, 20 wt% zirconium silicate, and 4 wt% yttrium oxide. First, stir and mix the materials to ensure the binder and raw materials are evenly mixed. Then, add an appropriate amount of deionized water and stir until homogeneous. After mixing, allow the mixture to rest at room temperature for 12 hours before packaging. Place an appropriate amount of the mixed raw material in a mold and press it using a powder tablet press at a gauge pressure of 10 MPa for 60 seconds to obtain a sample. After demolding, transfer the sample to an electric heating drying oven at 80℃ for 24 hours to cure. After drying, place the sample in a crucible, completely cover it with coke powder and coke particles, and then place it in a box-type resistance furnace at a sintering temperature of 1500℃. The static crucible method was used to evaluate the alkali corrosion resistance of the samples. The crucible was filled with Na2CO3 and then carbonized. The temperature was heated to 1000℃ and then held at that temperature for 3 hours. After the samples cooled to room temperature, they were removed from the crucible and cut along the axial center of the crucible. Representative samples were selected for surface polishing and gold plating, followed by microscopic morphology characterization and mechanism analysis using scanning electron microscopy.

[0028] In summary, a comparison of the various implementation schemes shows that the prepared multiphase refractory material exhibits excellent performance as a crucible and furnace lining material during the synthesis of cathode materials for lithium-ion and sodium-ion batteries. In particular, the synergistic effect of magnesium aluminum spinel zirconium silicate and yttrium oxide can further improve the material's resistance to alkali corrosion, making its widespread application in future battery material preparation possible.

[0029] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing an alkali-erosion resistant multiphase refractory material based on a corundum-mullite system, characterized in that: The raw material composition and weight percentage are as follows: low-grade bauxite 70-90 wt%, coal gangue 5-15 wt%, smokeless calcined coal 0-10 wt%, fused magnesia 1-40 wt%, and carboxymethyl cellulose binder 2-8%. First, bauxite, coal gangue, smokeless calcined coal, fused magnesia, and carboxymethyl cellulose binder are mixed to ensure uniform mixing. Then, an appropriate amount of deionized water is added and stirred until homogeneous. After mixing, the mixture is allowed to rest at room temperature and then bagged for later use. An appropriate amount of the mixed material is placed in a mold and pressed to obtain a sample. After demolding, the sample is transferred to an electric heating drying oven for heat preservation and curing. After drying, the sample is placed in a crucible and completely covered with coke powder and coke particles. Then, it is placed in a box-type resistance furnace and sintered at a temperature of 1300-1700℃. The static crucible method is used to evaluate the alkali erosion resistance of the sample. The crucible is filled with Na2CO3 and then carbonized and heated to 1000℃ to obtain the eroded sample. After the sample cools to room temperature, it is removed from the crucible and the morphology of the eroded section is observed. Subsequently, the microstructure and mechanism are characterized by scanning electron microscopy.

2. The preparation method of the corundum-mullite system alkali-erosion resistant multiphase refractory material as described in claim 1, characterized in that: Continue to add 5-25 wt% zirconium silicate.

3. The preparation method of the corundum-mullite system alkali-erosion resistant multiphase refractory material as described in claim 1, characterized in that: Continue to add 1-5 wt% yttrium oxide.

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