Nano-alumina-based high-wear-resistance grinding medium and sintering method thereof

Abstract

The application discloses a kind of nano-alumina-based high-wear-resistant grinding medium and its sintering method, belong to the technical field of grinding medium processing, for solving the technical problems that the sphericity, crushing strength and wear resistance of nano-alumina-based high-wear-resistant grinding medium in the prior art need to be further improved, specifically comprising the following steps: mixing nano-alumina, nano-zirconia, magnesium oxide, rare earth oxides, sodium dodecyl sulfate and deionized water to obtain a slurry to be ground.The application is to enhance nano-alumina with nano-zirconia, magnesium oxide and rare earth oxides, and then to prepare a spherical powder by constructing a shell coating layer on the surface of the particles after coating with shell material.Increase the sphericity, hardness, crushing strength and wear resistance of the grinding medium by two-stage die forming, combined with multi-stage program slow heating, pre-burning and two-stage high-temperature holding sintering.

Description

Technical Field

[0001] This invention relates to the field of abrasive media processing technology, specifically to a nano-alumina-based high wear-resistant abrasive media and its sintering method. Background Technology

[0002] In recent years, as industries such as ceramics, electronics, lithium batteries, pigments, and pharmaceuticals have developed towards higher purity and finer processes, wet ultrafine grinding and ultrafine dispersion processes have placed higher demands on grinding media. Grinding media not only need to have high hardness, strength, and wear resistance to ensure a long service life and stable grinding efficiency, but also must have good sphericity and dimensional consistency to reduce energy consumption and equipment wear, and reduce impurity contamination of the ground materials.

[0003] Currently, commonly used grinding media mainly include natural pebbles, steel balls, cast iron balls, alumina ceramic balls, zirconia ceramic balls, and zirconium-aluminum composite grinding media. Alumina ceramic balls have a relatively low cost, but they are prone to breakage and spalling under high load, high impact, and long-cycle working conditions, and have a high self-wear rate, making it difficult to meet the requirements of high-end fields for wear resistance and reliability.

[0004] To improve the overall performance of alumina-based grinding media, it is proposed to introduce metal oxides such as ZrO2 as a second phase or additive into the Al2O3 matrix. The toughness and strength of the material can be improved by toughening the second phase and inhibiting grain growth. Alternatively, rare earth oxides can be used to modify the grain boundaries and improve the high-temperature sintering behavior. However, nano-alumina and nanocomposite powders generally suffer from the problem of small primary particle size but severe secondary agglomeration. After sintering, large pores, weak bonding interfaces and hidden cracks are easily formed inside the material, resulting in insufficient crushing strength and long-term reliability, and high self-wear rate. Furthermore, under conventional sintering conditions, high-temperature and long-term sintering can easily lead to abnormal growth of α-Al2O3 grains, loss of fine grain strengthening effect, and decrease in material hardness and strength. If the sintering temperature is artificially reduced or the holding time is shortened, insufficient densification and more residual pores will occur, affecting the compressive strength and wear resistance of the grinding media.

[0005] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a nano-alumina-based high wear-resistant grinding media and its sintering method, which solves the technical problem that the sphericity, crush resistance and wear resistance of nano-alumina-based high wear-resistant grinding media in the prior art need to be further improved.

[0007] The objective of this invention can be achieved through the following technical solution: a sintering method for a nano-alumina-based high-wear-resistant grinding media, comprising the following steps:

[0008] S1. Nano alumina, nano zirconium oxide, magnesium oxide, rare earth oxides, sodium dodecyl sulfate and deionized water are mixed to obtain a slurry to be ground. The slurry to be ground is placed in a ball mill containing abrasives and ball milled for 5-6 hours. The abrasives are then removed to obtain alumina slurry.

[0009] S2. Add the shell coating material to the alumina slurry and stir and disperse for 60-80 minutes to obtain a mixed slurry. Dry the mixed slurry by spray drying to prepare shell-coated alumina powder. Then, ball mill and disperse the shell-coated alumina powder to obtain alumina-based powder.

[0010] S3. Mix and stir alumina-based powder, zinc stearate and polyvinyl alcohol for 8-12 minutes, spray the dispersion into the reaction system, and vacuum knead for 20-30 minutes to obtain spherical powder with a water content of 8-10 wt%.

[0011] S4. Place the spherical powder into a spherical mold cavity with a diameter of 3mm, close the mold, set the molding pressure to 30-40MPa, hold the pressure for 3-5s, increase the pressure to 120-150MPa, hold the pressure for 4-6s, and discharge the material to obtain alumina spherical material.

[0012] S5. Dry and degrease the alumina balls to obtain a grinding media blank, and then densify and sinter the grinding media blank to obtain the grinding media.

[0013] Furthermore, the ratio of the nano-alumina, nano-zirconia, magnesium oxide, rare earth oxides, sodium dodecyl sulfate, and deionized water is 100g:5-7g:0.3-0.5g:0.5-0.8g:5g:300mL. The rare earth oxides are composed of yttrium oxide, cerium oxide, and lanthanum oxide in a weight ratio of 5:2.1-2.7:1.1-1.7. The ball mill is a planetary ball mill. The ratio of the slurry to the abrasive is 7mL:13-17g. The abrasive is composed of 3mm alumina grinding balls and 5mm alumina grinding balls in a weight ratio of 7:3. The ball milling speed is 400-500r / min.

[0014] Furthermore, the solid-liquid ratio of the shell coating material and the alumina slurry is 4-5:100, and the shell coating material is composed of tetraethyl orthosilicate, sodium silicate and aluminum acetate in a weight ratio of 10:1-2:2-3.

[0015] Furthermore, the preparation method of alumina-based powder is as follows: place shell-coated alumina powder in a ball mill containing abrasive, dry ball mill for 3-4 hours, and then perform post-treatment to obtain alumina-based powder.

[0016] Furthermore, the weight ratio of the shell-coated alumina powder to the abrasive is 2:3-5, the abrasive is composed of 3mm alumina grinding balls and 5mm alumina grinding balls in a weight ratio of 5:3, the ball milling speed is 400-500 r / min, and the post-processing includes: after ball milling, sieving to remove fine powder with a particle size <10nm to obtain alumina-based powder.

[0017] Furthermore, the weight ratio of the alumina-based powder, zinc stearate, and polyvinyl alcohol is 100:0.2-0.5:0.6-0.8, and the dispersion is composed of polyethylene glycol-400 and deionized water at a ratio of 0.5-0.8g:100mL.

[0018] Furthermore, the drying and degreasing operation includes: placing the alumina balls in a tube furnace, heating the tube furnace to 80-90°C at a rate of 2-3°C / min, holding and drying for 4-5 hours, then heating the tube furnace to 200-220°C at a rate of 1°C / min, holding and drying for 60-80 minutes, then heating the tube furnace to 350-370°C at a rate of 0.3-0.5°C / min, holding and drying for 2-3 hours, then heating the tube furnace to 600-650°C at a rate of 0.5-0.8°C / min, holding and drying for 1.5-2 hours, and finally heating the tube furnace to 800-850°C at a rate of 1°C / min, holding and drying for 1 hour to obtain the grinding media blank.

[0019] Furthermore, the densification sintering operation is as follows: the grinding media blank is placed in a muffle furnace, the air inside the muffle furnace is vented, the muffle furnace is heated to 1200℃ at a rate of 2-3℃ / min, held at that temperature for 20-30min, the muffle furnace is then heated to 1600-1620℃ at a rate of 0.8-1℃ / min, held at that temperature for 4-5h, the muffle furnace is allowed to cool naturally to room temperature, and the material is discharged to obtain the grinding media.

[0020] The present invention also proposes a nano-alumina-based high wear-resistant grinding media, which is prepared by the sintering method of the above-mentioned nano-alumina-based high wear-resistant grinding media.

[0021] The present invention has the following beneficial effects:

[0022] 1. This invention uses nano-alumina as the main component, and introduces nano-zirconia, magnesium oxide, and rare earth oxides formulated in a specific ratio. These components are then subjected to prolonged wet ball milling in the presence of sodium dodecyl sulfate, resulting in highly uniform dispersion of the components at the nanoscale. On one hand, after sintering, the nano-zirconia is uniformly distributed as a fine, dispersed phase, which passivates crack tips through stress-induced phase transformation, significantly improving the material's fracture toughness and crushing capacity. On the other hand, magnesium oxide and rare earth oxides participate in grain boundary pinning and second-phase formation at high temperatures, inhibiting abnormal growth of α-Al₂O₃ grains and resulting in a highly dense, fine-grained, and uniformly structured microstructure. Simultaneously, the wet ball milling process effectively disperses powder agglomerates, reducing potential large pores and weak interfaces, thereby suppressing the generation of internal defects in the grinding media. This improves the hardness and crushing strength of the grinding media, laying the microstructural foundation for subsequent high wear resistance and high strength properties.

[0023] 2. This invention also utilizes a combination of tetraethyl orthosilicate, sodium silicate, and aluminum acetate in an aqueous phase through hydrolysis, condensation, and deposition processes. This process preferentially enriches Si and Al-containing precursors on the particle surface, forming a Si-Al-rich shell precursor network containing a small amount of Na. Subsequently, spray drying yields secondary particles with a distinct core-shell structure. Dry ball milling further breaks down larger agglomerates, refines the shell distribution scale, and improves the uniformity of the shell between particles and on the particle surface. During sintering, the local Al₂O₃-SiO₂-Na₂O system in this shell transforms into a small amount of aluminosilicate or mullite-like phase at high temperatures, coexisting with a limited amount of silicate glass phase in the grain boundaries and shell regions. Compared to pure silicate glass, the mullite-like phase exhibits higher hardness and better thermal stability. It can act as a "bridge" and pinning agent for grain boundaries, significantly improving grain boundary shear strength and inhibiting the propagation of cracks along grain boundaries. On the other hand, constrained by the ratio of tetraethyl orthosilicate, sodium silicate, and aluminum acetate, as well as the homogenization effect of dry ball milling, the Na2O content and glass phase volume fraction are kept within a reasonable range. The glass phase plays a role in filling micropores and assisting in densification, forming a composite interface structure of a highly dense main body, aluminosilicate / mullite-like reinforced grain boundaries, and limited glass filling pores. While maintaining high hardness, it significantly reduces grain boundary spalling and particle shedding during the wear process, keeping the self-wear rate at a low level and improving long-term service stability.

[0024] 3. This invention also introduces polyethylene glycol-400, zinc stearate, and polyvinyl alcohol into the powder base, and prepares spherical powder through vacuum kneading. This gives the powder good flowability, lubricity, and adhesion. A high-precision spherical mold, combined with two-stage pressure loading, achieves uniform filling and high-density compaction of the powder in the mold cavity, resulting in a spherical preform with stable geometry and uniform internal density distribution. Subsequently, a multi-stage slow heating and segmented heat preservation debinding-pre-firing process is adopted in a tube furnace to gradually and uniformly remove organic components and establish an initial neck. The connection avoids internal cracks and closed pores caused by concentrated decomposition of organic matter and rapid gas release; finally, combined with two-stage high-temperature sintering, the nano-alumina matrix is ​​highly densified, and works synergistically with the aforementioned nanocomposite toughening and grain boundary strengthening. While ensuring that the sphericity of the sintered grinding media can reach a stable high level, it reduces geometric deviations caused by deformation and density inhomogeneity, and also improves the crushing strength and self-wearing performance of the grinding media, thereby achieving a comprehensive beneficial effect of high sphericity, high hardness and high reliability. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 The image shows the XRD pattern of the grinding media prepared in Example 3 of this invention. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] In this application, the purity of the nano-alumina is 99.9%, and the particle size is 50-100 nm;

[0029] In this application, the purity of the nano-zirconia is 99.9% and the particle size is 20-60 nm;

[0030] In this application, the purity of magnesium oxide is 99.5% and the particle size is 80-120 nm;

[0031] In this application, the purity of yttrium oxide is 99.9% and the particle size is 30-50 nm;

[0032] In this application, the purity of cerium oxide is 99.9% and the particle size is 30-50 nm;

[0033] In this application, the lanthanum oxide has a purity of 99.9% and a particle size of 30-50 nm.

[0034] Example 1

[0035] This embodiment provides a sintering method for nano-alumina-based high wear-resistant grinding media, specifically including the following steps:

[0036] Step 1: Preparation of alumina slurry

[0037] Yttrium oxide, cerium oxide, and lanthanum oxide were mixed in a weight ratio of 5:2.1:1.1 to obtain rare earth oxides.

[0038] Weigh out 500g of nano-alumina, 25g of nano-zirconia, 1.5g of magnesium oxide, 2.5g of rare earth oxides, 25g of sodium dodecyl sulfate, and 1500mL of deionized water to obtain the slurry to be ground.

[0039] Abrasive is obtained by mixing 3mm alumina grinding balls and 5mm alumina grinding balls at a weight ratio of 7:3.

[0040] Add the slurry to be ground and the abrasive to a ball mill at a ratio of 7 mL: 13 g. Set the ball mill speed to 4000 r / min and ball mill for 5 h. Remove the abrasive to obtain the alumina slurry.

[0041] Step 2, alumina-based powder

[0042] Tetraethyl orthosilicate, sodium silicate, and aluminum acetate were mixed in a weight ratio of 10:1:2 to obtain the shell coating material.

[0043] The shell coating material and alumina slurry were mixed and dispersed at a solid-liquid ratio of 4:100 for 60 minutes to obtain a mixed slurry. The mixed slurry was placed in a spray dryer, and the atomization pressure was set to 5MPa, the inlet air temperature was set to 150℃, and the outlet air temperature was set to 90℃. The mixture was then spray dried to obtain shell-coated alumina powder.

[0044] Abrasive is obtained by mixing 3mm alumina grinding balls and 5mm alumina grinding balls at a weight ratio of 5:3.

[0045] Alumina powder coated with shell and abrasive were added to a ball mill at a weight ratio of 2:3. The ball milling speed was 400 r / min, and the dry ball milling was carried out for 3 hours. The ball-milled material was then sieved to remove fine powder with a particle size <10 nm to obtain alumina-based powder.

[0046] Step 3: Prepare spherical powder

[0047] Polyethylene glycol-400 and deionized water were mixed at a ratio of 0.5 g: 100 mL to obtain a dispersion.

[0048] Alumina-based powder, zinc stearate, and polyvinyl alcohol were mixed and stirred for 8 minutes at a weight ratio of 100:0.2:0.6. The dispersion was then sprayed into the reaction system and vacuum kneaded for 20 minutes to obtain a pelletized powder with a water content of 8 wt%.

[0049] Step 4: Prepare grinding media blanks

[0050] The spherical powder is placed in a spherical mold cavity with a diameter of 3mm, the mold is closed, the molding pressure is set to 30MPa, the pressure is held for 3s, the pressure is increased to 120MPa, the pressure is held for 4s, and the material is discharged to obtain alumina spherical material.

[0051] The alumina pellets were placed in a tube furnace, which heated the material to 80°C at a rate of 2°C / min and held for 4 hours. The temperature was then increased to 200°C at a rate of 1°C / min and held for 60 minutes. The temperature was then increased to 350°C at a rate of 0.3°C / min and held for 2 hours. The temperature was then increased to 600°C at a rate of 0.5°C / min and held for 1.5 hours. Finally, the temperature was increased to 800°C at a rate of 1°C / min and held for 1 hour to obtain the grinding media blank.

[0052] Step 5: Prepare grinding media

[0053] The grinding media blank is placed in a muffle furnace. After the air inside the muffle furnace is purged, the muffle furnace is heated to 1200℃ at a rate of 2℃ / min and held for 20min. Then, the muffle furnace is heated to 1600℃ at a rate of 0.8℃ / min and held for 4h. The muffle furnace is then allowed to cool naturally to room temperature, and the material is discharged to obtain the grinding media.

[0054] Example 2

[0055] This embodiment provides a sintering method for nano-alumina-based high wear-resistant grinding media, specifically including the following steps:

[0056] Step 1: Preparation of alumina slurry

[0057] Yttrium oxide, cerium oxide, and lanthanum oxide were mixed in a weight ratio of 5:2.4:1.4 to obtain rare earth oxides.

[0058] Weigh out 500g of nano-alumina, 30g of nano-zirconia, 2.0g of magnesium oxide, 3.25g of rare earth oxides, 25g of sodium dodecyl sulfate, and 1500mL of deionized water to obtain the slurry to be ground.

[0059] Abrasive is obtained by mixing 3mm alumina grinding balls and 5mm alumina grinding balls at a weight ratio of 7:3.

[0060] Add the slurry to be ground and the abrasive to a ball mill at a ratio of 7 mL: 15 g. Set the ball mill speed to 450 r / min and ball mill for 5.5 h. Remove the abrasive to obtain the alumina slurry.

[0061] Step 2, alumina-based powder

[0062] Tetraethyl orthosilicate, sodium silicate, and aluminum acetate were mixed in a weight ratio of 10:1.5:2.5 to obtain the shell coating material;

[0063] The shell coating material and alumina slurry were mixed and dispersed at a solid-liquid ratio of 4.5:100 for 70 minutes to obtain a mixed slurry. The mixed slurry was placed in a spray dryer with the atomization pressure set to 6.5 MPa, the inlet air temperature set to 175℃, and the outlet air temperature set to 95℃. The mixture was then spray dried to obtain shell-coated alumina powder.

[0064] Abrasive is obtained by mixing 3mm alumina grinding balls and 5mm alumina grinding balls at a weight ratio of 5:3.

[0065] Alumina powder coated with shell and abrasive were added to a ball mill at a weight ratio of 2:4. The ball milling speed was 450 r / min, and the dry ball milling was carried out for 3.5 h. The ball-milled material was then sieved to remove fine powder with a particle size <10 nm to obtain alumina-based powder.

[0066] Step 3: Prepare spherical powder

[0067] Polyethylene glycol-400 and deionized water were mixed at a ratio of 0.65 g: 100 mL to obtain a dispersion.

[0068] Alumina-based powder, zinc stearate, and polyvinyl alcohol were mixed and stirred for 10 min by weight ratio of 100:0.35:0.7. The dispersion was then sprayed into the reaction system and vacuum kneaded for 25 min to obtain a pelletized powder with a water content of 9 wt%.

[0069] Step 4: Prepare grinding media blanks

[0070] The spherical powder is placed in a spherical mold cavity with a diameter of 3mm, the mold is closed, the molding pressure is set to 35MPa, the pressure is held for 4s, the pressure is increased to 135MPa, the pressure is held for 5s, and the material is discharged to obtain alumina spherical material.

[0071] Alumina pellets were placed in a tube furnace, which heated the material to 85°C at a rate of 2.5°C / min and held for 4.5 hours. The temperature was then increased to 210°C at a rate of 1°C / min and held for 70 minutes. The temperature was then increased to 360°C at a rate of 0.4°C / min and held for 2.5 hours. The temperature was then increased to 625°C at a rate of 0.65°C / min and held for 1.7 hours. Finally, the temperature was increased to 825°C at a rate of 1°C / min and held for 1 hour to obtain the grinding media blank.

[0072] Step 5: Prepare grinding media

[0073] The grinding media blank is placed in a muffle furnace. After the air inside the muffle furnace is purged, the muffle furnace is heated to 1200℃ at a rate of 2.5℃ / min and held for 25min. Then, the muffle furnace is heated to 1610℃ at a rate of 0.9℃ / min and held for 4.5h. The muffle furnace is then allowed to cool naturally to room temperature, and the material is discharged to obtain the grinding media.

[0074] Example 3

[0075] This embodiment provides a sintering method for nano-alumina-based high wear-resistant grinding media, specifically including the following steps:

[0076] Step 1: Preparation of alumina slurry

[0077] Yttrium oxide, cerium oxide, and lanthanum oxide were mixed in a weight ratio of 5:2.7:1.7 to obtain rare earth oxides.

[0078] Weigh out 500g of nano-alumina, 35g of nano-zirconia, 2.5g of magnesium oxide, 4g of rare earth oxides, 25g of sodium dodecyl sulfate, and 1500mL of deionized water to obtain the slurry to be ground.

[0079] Abrasive is obtained by mixing 3mm alumina grinding balls and 5mm alumina grinding balls at a weight ratio of 7:3.

[0080] Add the slurry to be ground and the abrasive to a ball mill at a ratio of 7 mL: 17 g. Set the ball mill speed to 500 r / min and ball mill for 6 hours. Remove the abrasive to obtain the alumina slurry.

[0081] Step 2, alumina-based powder

[0082] Tetraethyl orthosilicate, sodium silicate, and aluminum acetate were mixed in a weight ratio of 10:2:3 to obtain the shell coating material.

[0083] The shell coating material and alumina slurry were mixed and dispersed at a solid-liquid ratio of 5:100 for 80 minutes to obtain a mixed slurry. The mixed slurry was placed in a spray dryer, and the atomization pressure was set to 8MPa, the inlet air temperature was set to 200℃, and the outlet air temperature was set to 100℃. The mixture was then spray dried to obtain shell-coated alumina powder.

[0084] Abrasive is obtained by mixing 3mm alumina grinding balls and 5mm alumina grinding balls at a weight ratio of 5:3.

[0085] Alumina powder coated with shell and abrasive were added to a ball mill at a weight ratio of 2:5. The ball milling speed was 500 r / min, and the dry ball milling was carried out for 4 hours. The ball-milled material was then sieved to remove fine powder with a particle size <10 nm to obtain alumina-based powder.

[0086] Step 3: Prepare spherical powder

[0087] Polyethylene glycol-400 and deionized water were mixed at a ratio of 0.8 g: 100 mL to obtain a dispersion.

[0088] Alumina-based powder, zinc stearate, and polyvinyl alcohol were mixed and stirred for 12 minutes at a weight ratio of 100:0.5:0.8. The dispersion was then sprayed into the reaction system and vacuum kneaded for 30 minutes to obtain a pelletized powder with a water content of 10 wt%.

[0089] Step 4: Prepare grinding media blanks

[0090] The spherical powder is placed in a spherical mold cavity with a diameter of 3mm, the mold is closed, the molding pressure is set to 40MPa, the pressure is held for 5s, the pressure is increased to 150MPa, the pressure is held for 6s, and the material is discharged to obtain alumina spherical material.

[0091] The alumina pellets were placed in a tube furnace, which heated the material to 90°C at a rate of 3°C / min and held it at that temperature for 5 hours. The temperature was then increased to 220°C at a rate of 1°C / min and held for 80 minutes. The temperature was then increased to 370°C at a rate of 0.5°C / min and held for 3 hours. The temperature was then increased to 650°C at a rate of 0.8°C / min and held for 2 hours. Finally, the temperature was increased to 850°C at a rate of 1°C / min and held for 1 hour to obtain the grinding media blank.

[0092] Step 5: Prepare grinding media

[0093] The grinding media blank is placed in a muffle furnace. After the air inside the muffle furnace is purged, the muffle furnace is heated to 1200℃ at a rate of 3℃ / min and held for 30min. Then, the muffle furnace is heated to 1620℃ at a rate of 1℃ / min and held for 5h. The muffle furnace is then allowed to cool naturally to room temperature, and the material is discharged to obtain the grinding media.

[0094] Comparative Example 1

[0095] The difference between this comparative example and Example 3 is that rare earth oxides were not added in step 1.

[0096] Comparative Example 2

[0097] The difference between this comparative example and Example 3 is that no shell coating material was added in the preparation process of the shell-coated alumina powder in step 2.

[0098] Comparative Example 3

[0099] The difference between this comparative example and Example 3 is that, in step 4, when preparing the grinding media blank, the programmed temperature rise was eliminated, and the tube furnace was directly heated to 850°C at a rate of 3°C / min, and then held at that temperature for 1 hour.

[0100] Comparative Example 4

[0101] The difference between this comparative example and Example 3 is that in step 5, the muffle furnace is heated to 1620°C at a rate of 3°C / min and then held at that temperature for 5 hours.

[0102] Performance testing:

[0103] The Vickers hardness, self-wear rate, sphericity, and normalized crushing strength of the grinding media samples prepared in Examples 1-3 and Comparative Examples 1-4 were determined according to the standard JC / T 2522-2019 "Zirconium-aluminum composite grinding media balls". The specific test data are shown in Table 1 below.

[0104] Table 1 - Performance Test Data of Samples

[0105]

[0106] Data Analysis:

[0107] Comparative analysis of the data in Table 1 shows that the nano-alumina-based high-wear-resistant grinding media prepared by this invention achieves a sphericity of 99.2-99.5%, a Vickers hardness (HV) of 14.5-14.9 GPa, a self-wear rate of 0.11-0.12 g·(kg·h)⁻¹, and a normalized crushing strength of 286-291 MPa. All performance test data are superior to the comparative example. This indicates that this invention, by using nano-alumina as a base material and introducing nano-zirconia, magnesium oxide, and a specific proportion of rare earth oxides, achieves multi-component nanoscale uniform dispersion through wet ball milling, and then uses tetraethyl orthosilicate, sodium silicate, and aluminum acetate to construct a surface shell coating for the particles. Alumina-based powder with a potential grain boundary strengthening structure of aluminosilicate / mullite was obtained by spray drying and dry ball milling. Then, it was combined with polyethylene glycol-400, zinc stearate and polyvinyl alcohol to prepare spherical powder with good flowability and adhesion by vacuum kneading. The powder was then formed by two-stage molding in a spherical mold, combined with multi-stage slow temperature rise debinding, pre-firing and two-stage high temperature holding sintering, so that the material formed a composite microstructure with a high-density fine-grained α-Al2O3 matrix, dispersed ZrO2 toughening phase and grain boundary strengthening aluminosilicate / limited glass phase working together. This prepared nano-alumina-based grinding media with high sphericity, high hardness, low self-wear and high crushing strength.

[0108] The XRD pattern of the grinding media prepared in Example 3 was analyzed. The XRD pattern showed clear and sharp diffraction peaks in the range of 2θ = 10-80°. The main peaks were concentrated around 25.6°, 35.1°, 37.8°, 43.4°, 52.6°, 57.5°, 66.5° and 68.2°. Each peak had high intensity and narrow half-width. No broad diffuse peaks or obvious amorphous background enhancement phenomenon were observed. The characteristic peaks of this series are consistent with the standard diffraction peaks of α-Al2O3 (corundum phase), indicating that the sample has been completely transformed into a stable α-Al2O3 crystalline phase after long-term sintering at 1620℃. No residual γ-Al2O3 or other transition phases were detected, indicating that the matrix crystalline phase of the grinding medium prepared in Example 3 is highly crystalline α-Al2O3, the sintering reaction is sufficient, the crystalline phase transformation is complete, and no abnormal phase transformation or decomposition has occurred. Secondary diffraction peaks with significantly lower intensity than the main peak of α-Al2O3 but clearly distinguishable can be detected near 30.2°, 34.9°, 50.2° and 60.2°. The peak positions of this group match the characteristic peaks of tetragonal ZrO2, and no obvious enhancement of the characteristic peaks of monoclinic ZrO2 is observed, indicating that nano-zirconia still exists as an independent crystalline phase after sintering, without complete solid solution or vitrification, and ZrO2 maintains an independent crystalline structure. Weak diffraction peaks were detected near 16.4°, 26.0°, and 40.8°, with peak intensities much lower than the main peak of α-Al2O3, but reproducible and higher than the background noise. The peak positions of this group coincide with the characteristic diffraction peaks of aluminosilicate or mullite-like structures, indicating that a large amount of continuous amorphous glass phase was not formed at the grain boundaries, and the Si and Al related components mainly exist in the form of crystalline aluminosilicate or mullite-like structures. All main peaks have sharp morphologies and small half-peak widths, without severe peak broadening, indicating high crystallinity, no large proportion of nano-disordered regions, and no obvious amorphous coating layer.

[0109] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A sintering method for a nano-alumina-based high-wear-resistant grinding media, characterized in that, Includes the following steps: S1. Nano alumina, nano zirconium oxide, magnesium oxide, rare earth oxides, sodium dodecyl sulfate and deionized water are mixed to obtain a slurry to be ground. The slurry to be ground is placed in a ball mill containing abrasives and ball milled for 5-6 hours. The abrasives are then removed to obtain alumina slurry. S2. Add the shell coating material to the alumina slurry and stir and disperse for 60-80 minutes to obtain a mixed slurry. Dry the mixed slurry by spray drying to prepare shell-coated alumina powder. Then, ball mill and disperse the shell-coated alumina powder to obtain alumina-based powder. S3. Mix and stir alumina-based powder, zinc stearate and polyvinyl alcohol for 8-12 minutes, spray the dispersion into the reaction system, and vacuum knead for 20-30 minutes to obtain spherical powder with a water content of 8-10 wt%. S4. Place the spherical powder into a spherical mold cavity with a diameter of 3mm, close the mold, set the molding pressure to 30-40MPa, hold the pressure for 3-5s, increase the pressure to 120-150MPa, hold the pressure for 4-6s, and discharge the material to obtain alumina spherical material. S5. Dry and degrease the alumina balls to obtain a grinding media blank, and then densify and sinter the grinding media blank to obtain the grinding media.

2. The sintering method for a nano-alumina-based high-wear-resistant grinding media according to claim 1, characterized in that, The ratio of nano-alumina, nano-zirconia, magnesium oxide, rare earth oxides, sodium dodecyl sulfate, and deionized water is 100g:5-7g:0.3-0.5g:0.5-0.8g:5g:300mL. The rare earth oxides are composed of yttrium oxide, cerium oxide, and lanthanum oxide in a weight ratio of 5:2.1-2.7:1.1-1.

7. The ball mill is a planetary ball mill. The ratio of the slurry to the abrasive is 7mL:13-17g. The abrasive is composed of 3mm alumina grinding balls and 5mm alumina grinding balls in a weight ratio of 7:

3. The ball milling speed is 400-500r / min.

3. The sintering method for a nano-alumina-based high-wear-resistant grinding media according to claim 1, characterized in that, The solid-liquid ratio of the shell coating material and the alumina slurry is 4-5:

100. The shell coating material is composed of tetraethyl orthosilicate, sodium silicate and aluminum acetate in a weight ratio of 10:1-2:2-3.

4. The sintering method for a nano-alumina-based high-wear-resistant grinding media according to claim 1, characterized in that, The preparation method of alumina-based powder is as follows: place shell-coated alumina powder in a ball mill containing abrasive, dry ball mill for 3-4 hours, and then perform post-treatment to obtain alumina-based powder.

5. The sintering method for a nano-alumina-based high-wear-resistant grinding media according to claim 4, characterized in that, The weight ratio of the shell-coated alumina powder to the abrasive is 2:3-5. The abrasive is composed of 3mm alumina grinding balls and 5mm alumina grinding balls in a weight ratio of 5:

3. The ball milling speed is 400-500 r / min. The post-processing includes: after ball milling, sieving to remove fine powder with a particle size <10nm to obtain alumina-based powder.

6. The sintering method for a nano-alumina-based high-wear-resistant grinding media according to claim 1, characterized in that, The weight ratio of the alumina-based powder, zinc stearate, and polyvinyl alcohol is 100:0.2-0.5:0.6-0.8, and the dispersion is composed of polyethylene glycol-400 and deionized water at a ratio of 0.5-0.8g:100mL.

7. The sintering method for a nano-alumina-based high-wear-resistant grinding media according to claim 1, characterized in that, The drying and degreasing operation includes: placing alumina balls in a tube furnace, heating the tube furnace to 80-90℃ at a rate of 2-3℃ / min, holding and drying for 4-5 hours, then heating the tube furnace to 200-220℃ at a rate of 1℃ / min, holding and drying for 60-80 minutes, then heating the tube furnace to 350-370℃ at a rate of 0.3-0.5℃ / min, holding and drying for 2-3 hours, then heating the tube furnace to 600-650℃ at a rate of 0.5-0.8℃ / min, holding and drying for 1.5-2 hours, and finally heating the tube furnace to 800-850℃ at a rate of 1℃ / min, holding and drying for 1 hour to obtain a grinding media blank.

8. The sintering method for a nano-alumina-based high-wear-resistant grinding media according to claim 1, characterized in that, The densification sintering operation is as follows: the grinding media blank is placed in a muffle furnace, the air inside the muffle furnace is vented, the muffle furnace is heated to 1200℃ at a rate of 2-3℃ / min, held at that temperature for 20-30min, the muffle furnace is then heated to 1600-1620℃ at a rate of 0.8-1℃ / min, held at that temperature for 4-5h, the muffle furnace is allowed to cool naturally to room temperature, and the material is discharged to obtain the grinding media.

9. A nano-alumina-based high-wear-resistant abrasive media, characterized in that, The nano-alumina-based high wear-resistant abrasive media is prepared by the sintering method described in any one of claims 1-8.

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