Alpha-alumina powder and preparation method thereof

Abstract

The invention provides alpha-aluminum oxide powder and a preparation method, and belongs to the field of inorganic nonmetals. The method comprises the following steps: mixing an aluminum oxide precursor, a steric hindrance agent and a solvent to obtain mixed slurry; sanding the mixed slurry to obtain superfine slurry; carrying out spray drying on the superfine slurry to obtain superfine powder; mixing the ultrafine powder and a grain inducer to obtain a roasting precursor; and roasting the roasting precursor under set roasting conditions to obtain the alpha-aluminum oxide powder. Firstly, a steric hindrance agent is added into an aluminum oxide precursor, so that steric hindrance is formed in emulsification and dispersion processes, and agglomeration of powder is inhibited; secondly, through sanding, dispersity and uniformity of raw material particles are guaranteed; thirdly, a seed crystal inducer is added into the superfine powder, so that superfine particles can be formed through induction, and the conversion temperature can be reduced. Therefore, the alpha conversion rate of the alpha-aluminum oxide is improved, and the dispersion stability of the alpha-aluminum oxide is improved.

Description

Technical Field

[0001] The present application relates to the field of inorganic non-metallic technology, and in particular to an α-alumina powder and a preparation method thereof. Background Art

[0002] At present, with the rapid development of the semiconductor industry, the size of electronic devices has been reduced, requiring the surface flatness of the wafer to reach the ultra-fine level. Chemical mechanical polishing (CMP) technology is currently almost the only technology that can provide global flatness. In CMP technology, abrasive particles are the basis and main component of the polishing liquid. The type, structure, particle size, morphology, hardness and other physical, chemical, mechanical and other properties of the abrasive particles play a vital role in the CMP performance and the ultra-smoothness of the crystal surface after polishing. Polishing abrasive (powder) is the core material that determines the CMP polishing effect and plays a key role in the CMP polishing process. Ultrafine alumina (A12O3), as an efficient polishing material, plays an important role in the CMP process. Its unique chemical properties enable it to provide excellent surface flatness while maintaining a high removal rate. A12O3 has good polishing performance due to its high hardness (Mohs hardness is 9), dense structure, good stability, high material removal rate, etc. Especially in recent years, with the growing demand for hard materials such as sapphire (Mohs hardness is 9), silicon carbide (Mohs hardness is 9.3), and silicon nitride (Mohs hardness is about 9), it is more important to select Al2O3 polishing powder with a hardness close to that of the substrate in CMP.

[0003] Alumina has different phases such as α, γ, δ, η, θ, κ and χ. Ultrafine alumina in different phases has different properties. Only α-alumina with high conversion rate has high hardness, high heat stability and chemical corrosion resistance, and can have good polishing rate and material removal rate for hard materials. However, due to its complicated preparation process, after high-temperature calcination, the particles are very likely to increase abnormally. The disadvantages are poor dispersion stability, easy agglomeration, wide distribution, and large particles are prone to scratches and dents. Therefore, how to improve the dispersion stability of α-alumina while improving the α conversion rate of α-alumina is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application provides an α-alumina powder and a preparation method to solve the following technical problem: how to improve the dispersion stability of α-alumina while improving the α conversion rate of α-alumina.

[0005] In a first aspect, the present application provides a method for preparing α-alumina powder, the method comprising:

[0006] Mixing an aluminum oxide precursor, a steric hindering agent and a solvent to obtain a mixed slurry;

[0007] Sand-grinding the mixed slurry to obtain an ultrafine slurry;

[0008] The ultrafine slurry is spray-dried to obtain ultrafine powder;

[0009] Mixing the ultrafine powder and the grain inducing agent to obtain a calcined precursor; and

[0010] The calcined precursor is calcined under set calcination conditions to obtain α-alumina powder.

[0011] Optionally, the aluminum oxide precursor includes: at least one of boehmite and aluminum hydroxide; and / or,

[0012] The mass of the aluminum oxide precursor is 20% to 30% of the total mass of the mixed slurry.

[0013] Optionally, the particle size D50 of the aluminum oxide precursor is ≤2.0 μm.

[0014] Optionally, the steric hindering agent includes: a solvent-type steric hindering agent and a solid-type steric hindering agent; and / or,

[0015] The solvent-based steric hindering agent includes: anhydrous ethanol; and / or,

[0016] The solid steric retardant comprises at least one of C powder and white sugar.

[0017] Optionally, the mass of the solvent-based steric inhibitor is 5% to 10% of the total mass of the mixed slurry; and / or,

[0018] The mass of the solid steric inhibitor is 10% to 20% of the total mass of the mixed slurry.

[0019] Optionally, the ball-to-material ratio of the sand mill is (3-5):1; and / or,

[0020] The sanding time is 20 min to 40 min; and / or,

[0021] The particle size D50 of the powder in the ultrafine slurry is ≤0.4 μm.

[0022] Optionally, the feed rate of the spray drying is 0.5 L / hr to 1.5 L / hr; and / or,

[0023] The drying temperature of the spray drying is 140°C to 180°C.

[0024] Optionally, the grain inducing agent includes: gas phase nano-γ-alumina; and / or,

[0025] The particle size of the gas phase nano-γ-alumina is 20nm to 30nm; and / or,

[0026] The mass of the gas phase nano-γ-alumina is 3% to 10% of the total mass of the calcined precursor.

[0027] Optionally, the setting of roasting conditions includes at least one of the following:

[0028] The heating rate of the calcination is 10°C / min to 15°C / min;

[0029] The end point temperature of the calcination is 1100°C to 1200°C;

[0030] The heat preservation time of the calcination is 60 minutes to 120 minutes.

[0031] In a second aspect, the present application provides an α-alumina powder prepared by the method described in any one of the embodiments of the first aspect, wherein the α-alumina powder satisfies at least one of the following properties:

[0032] Particle size D50 is 100nm~300nm;

[0033] Particle size D100≤500nm;

[0034] α conversion rate ≥96%.

[0035] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0036] The present application provides a method for preparing α-alumina powder, comprising: mixing an alumina precursor, a steric hindrant and a solvent to obtain a mixed slurry; sand-milling the mixed slurry to obtain an ultrafine slurry; spray-drying the ultrafine slurry to obtain an ultrafine powder; mixing the ultrafine powder and a grain inducer to obtain a calcined precursor; and calcining the calcined precursor under set calcination conditions to obtain α-alumina powder. First, adding a steric hindrant to the alumina precursor is conducive to the formation of steric hindrance during the emulsification and dispersion process, thereby effectively isolating the distance between the alumina powder particles and inhibiting the agglomeration of the powder; secondly, sand-milling is used to ensure the dispersion and uniformity of the raw material particles; and thirdly, adding a seed inducer to the ultrafine powder can induce the formation of ultrafine particles and reduce the conversion temperature. Thereby, while improving the α conversion rate of α-alumina, the dispersion stability of α-alumina is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0038] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0039] Figure 1 A flow chart of a method for preparing α-alumina powder provided in an embodiment of the present application;

[0040] Figure 2 A schematic diagram of a method for preparing α-alumina powder provided in an embodiment of the present application;

[0041] Figure 3 This is a scanning electron microscope (SEM) image of the microstructure of the α-alumina powder provided in Example 1 of the present application;

[0042] Figure 4 This is the X-ray diffraction (XRD) diagram of the α-alumina powder provided in Example 1 of the present application. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0044] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0045] In addition, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple. "Parts" such as parts by weight and parts by mass indicate the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one-to-one to the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0046] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0047] Figure 1 A flow chart of a method for preparing α-alumina powder provided in an embodiment of the present application; Figure 2 A schematic diagram of a method for preparing α-alumina powder provided in an embodiment of the present application.

[0048] See also Figure 1 and Figure 2 The present application provides a method for preparing α-alumina powder, the method comprising:

[0049] S1, mixing an aluminum oxide precursor, a steric hindering agent and a solvent to obtain a mixed slurry;

[0050] The selection of alumina precursor as the basic material is the key to the formation of α-alumina. The main purpose of adding steric hindrance (such as high molecular polymer or surfactant) is to form steric hindrance during the emulsification and dispersion of the raw materials, effectively isolate the alumina powder particles, and prevent them from contacting each other and agglomerating. This treatment is crucial for the subsequent acquisition of highly dispersed powders. The choice of solvent should be able to dissolve or disperse the alumina precursor and steric hindrance well to form a uniform mixed slurry.

[0051] In some embodiments, the mixing includes an emulsification dispersion process using a high-speed shear emulsifier.

[0052] In some embodiments, the alumina precursor includes at least one of boehmite and aluminum hydroxide, and the mass of the alumina precursor is 20% to 30% of the total mass of the mixed slurry.

[0053] Boehmite (AlOOH) and aluminum hydroxide (AlOH3) are both common alumina precursors, which will dehydrate to form alumina during heating. The mass of the alumina precursor is limited to 20% to 30% of the total mass of the mixed slurry, thereby ensuring the proper concentration of the precursor in the slurry, helping to form a uniform mixed slurry, reducing agglomeration between particles, and improving the stability and fluidity of the slurry. Exemplarily, the mass of the alumina precursor is 20%, 22%, 24%, 26%, 28%, 30%, etc. of the total mass of the mixed slurry.

[0054] In some embodiments, the particle size D50 of the aluminum oxide precursor is ≤ 2.0 μm.

[0055] The particle size D50 is the particle size of the alumina precursor when the cumulative distribution reaches 50%. The particle size D50 of the alumina precursor is limited to ≤2.0 μm, which provides a good foundation for subsequent steps such as sand milling, spray drying and calcination, thereby facilitating the preparation of high-quality, highly dispersible, and uniformly sized α-alumina powder. Exemplarily, the particle size D50 of the alumina precursor can be 0.5 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2.0 μm, etc.

[0056] In some embodiments, the steric hindering agent includes: a solvent-type steric hindering agent and a solid-type steric hindering agent, the solvent-type steric hindering agent includes: anhydrous ethanol, and the solid-type steric hindering agent includes: at least one of C powder and white sugar.

[0057] C powder refers to carbon powder, which is a fine granular carbon material, mainly composed of carbon elements. It has good electrical conductivity, thermal conductivity, lubricity and chemical stability.

[0058] In some embodiments, the mass of the solvent-based steric inhibitor is 5% to 10% of the total mass of the mixed slurry, and the mass of the solid-based steric inhibitor is 10% to 20% of the total mass of the mixed slurry.

[0059] Steric retardants can form effective steric hindrances during the emulsification and dispersion process, isolate the distance between alumina powder particles, thereby inhibiting the agglomeration of powders and helping to obtain finer and more uniform alumina powder particles. Using anhydrous ethanol as a solvent-based steric retardant can form a thin film on the surface of alumina precursor particles through the interaction between its molecules, increase the distance between particles, reduce direct contact and friction between particles, and effectively inhibit agglomeration. C powder or white sugar is used as a solid steric retardant, and their particles can be physically embedded between alumina precursor particles to form a physical barrier to prevent direct contact and agglomeration between particles. In addition, these solid particles may also form a protective film on the surface of alumina precursors through adsorption. When solvent-based steric retardants and solid-based steric retardants are used in combination, the solvent-based steric retardant can penetrate and preliminarily disperse the particles, while the solid-based steric retardant further stabilizes this dispersed state, forming a more stable and lasting steric hindrance effect. At the same time, solvent-based steric retardants can reduce the interaction between particles, making it easier for particles to disperse in the medium. Solid steric inhibitors further prevent the particles from reaggregating during the dispersion process through the physical barrier effect of their particles. The combined use can significantly improve the dispersion efficiency and stability, so that the final product has a finer and more uniform particle distribution. The mass of the solvent-based steric inhibitor is limited to 5% to 10% of the total mass of the mixed slurry, and the mass of the solid-type steric inhibitor is limited to 10% to 20% of the total mass of the mixed slurry. This can ensure sufficient steric hindrance effect without introducing unnecessary impurities or affecting subsequent processing due to excessive amounts. Exemplarily, the mass of the solvent-based steric inhibitor is 5%, 6%, 7%, 8%, 9%, 10%, etc. of the total mass of the mixed slurry, and the mass of the solid-type steric inhibitor is 10%, 12%, 14%, 16%, 18%, 20%, etc. of the total mass of the mixed slurry.

[0060] S2, sand-milling the mixed slurry to obtain an ultrafine slurry;

[0061] The sand grinding process can further refine the particles in the mixed slurry and improve its dispersion and uniformity. During the sand grinding process, the friction and collision between particles help break up the agglomerates and form smaller particles.

[0062] In some embodiments, the ball-to-material ratio of the sand milling is (3-5):1, the sand milling time is 20 min-40 min; and the particle size D50 of the powder in the ultrafine slurry is ≤0.4 μm.

[0063] After sand milling, the dispersion and uniformity of the raw material particles are significantly improved. During the sand milling process, the collision and friction between the grinding balls and the raw material particles gradually refine the particles and disperse them in the solvent. At the same time, the effect of steric hindrances further enhances the dispersion effect between particles and prevents the occurrence of agglomeration. Therefore, the ultrafine slurry obtained after sand milling has a high degree of dispersion and uniformity. The ball-to-material ratio refers to the mass ratio of the grinding medium (such as grinding balls) to the solid particles in the raw material slurry. The limited ball-to-material ratio is (3-5):1, which helps to achieve uniform crushing and dispersion of the raw material particles while ensuring sufficient grinding efficiency. Exemplarily, the ball-to-material ratio of sand milling can be 3:1, 4:1, 5:1, etc., the sand milling time is 20 min, 22 min, 25 min, 28 min, 30 min, 32 min, 35 min, 38 min, 40 min, etc., and the particle size D50 of the powder in the ultrafine slurry can be 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, etc.

[0064] S3, spray drying the ultrafine slurry to obtain ultrafine powder;

[0065] Ultrafine slurry is converted into ultrafine powder through spray drying technology. During the spray drying process, the slurry is atomized into tiny droplets and quickly contacts with hot air, causing the solvent to evaporate quickly to form dry powder particles.

[0066] In some embodiments, the feed rate of the spray drying is 0.5 L / hr to 1.5 L / hr, and the drying temperature of the spray drying is 140° C. to 180° C.

[0067] The feed rate is limited to 0.5L / hr~1.5L / hr, and the drying temperature is 140℃~180℃. After the liquid is atomized, the surface area increases sharply, and it can quickly exchange heat with hot air, thereby quickly evaporating water. This greatly shortens the drying time, and the drying process usually takes only 5s~40s. Exemplarily, the feed rate of spray drying can be 0.5L / hr, 0.6L / hr, 0.7L / hr, 0.8L / hr, 1.0L / hr, 1.2L / hr, 1.4L / hr, 1.5L / hr, etc., and the drying temperature of spray drying can be 140℃, 150℃, 160℃, 170℃, 180℃, etc.

[0068] S4, mixing the ultrafine powder and the grain inducing agent to obtain a calcined precursor; and

[0069] Adding ultrafine seeds as an inducer can guide the growth of alumina in a specific direction during the calcination process, which helps to form α-alumina powder with specific morphology and structure.

[0070] In some embodiments, the mixing is performed by rotational mixing in a three-dimensional mixer, and the mixing time is 5 min to 10 min.

[0071] In some embodiments, the grain inducing agent includes: gas phase nano-γ-alumina, the particle size of the gas phase nano-γ-alumina is 20nm-30nm, and the mass of the gas phase nano-γ-alumina is 3%-10% of the total mass of the calcined precursor.

[0072] Gas phase nano-γ-alumina was selected as a grain inducing agent because of its small particle size (20nm-30nm) and high purity. This nano-alumina has good dispersibility and surface activity, and can effectively guide the grain growth of alumina during the calcination process. During the calcination process, the gas phase nano-γ-alumina, as a seed, can provide a low-energy nucleation site to guide the orderly arrangement and growth of alumina molecules in a specific direction. This helps to form α-alumina powder with a specific morphology (such as spherical, rod-shaped, etc.) and structure. At the same time, the addition of seeds can reduce the energy barrier for the transformation of alumina from γ phase to α phase, thereby achieving phase change at a lower calcination temperature. This can not only save energy, but also reduce the requirements for equipment and possible side effects of high-temperature calcination. In addition, since the seeds have good dispersibility, they can be evenly distributed between alumina particles, forming a physical barrier to inhibit the agglomeration between particles. This helps to improve the dispersibility and specific surface area of ​​the final product. Exemplarily, the particle size of the gas phase nano-γ-alumina can be 20nm, 22nm, 24nm, 26nm, 28nm, 30nm, etc., and the mass of the gas phase nano-γ-alumina is 3%, 5%, 7%, 9%, 10%, etc. of the total mass of the calcined precursor.

[0073] S5, calcining the calcined precursor under set calcination conditions to obtain α-alumina powder.

[0074] The mixed calcined precursor is placed in a fluidized bed calciner for rapid calcination to obtain α-alumina powder. After being mixed evenly, it is placed in a fluidized bed calciner and suitable calcination conditions are set for low-temperature fluidized bed calcination to ensure a high conversion rate. The fluidized bed calciner is a highly efficient calcination equipment that uses fluidization technology to make the calcined precursor form a boiling-like state in the furnace, thereby achieving rapid and uniform calcination. This equipment is suitable for processing granular materials and can achieve a higher calcination effect in a shorter time.

[0075] In some embodiments, the heating rate of the calcination is 10°C / min to 15°C / min, the terminal temperature of the calcination is 1100°C to 1200°C, and the holding time of the calcination is 60min to 120min.

[0076] Adding ultrafine seeds as an inducing agent can induce the formation of ultrafine particles and reduce the conversion temperature. After mixing evenly, put them into a fluidized bed calcining furnace for rapid calcination. The calcination temperature is 1100℃~1200℃, which is about 100℃ lower than the traditional calcination temperature of α-alumina powder. The heating rate is an important parameter in the calcination process, which affects the thermal stress and phase change process of the calcined precursor. The heating rate is limited to 10℃ / min~15℃ / min to ensure that the calcined precursor can be heated evenly, which is conducive to the concentration of thermal stress or complete phase change of the calcined precursor. The terminal temperature of calcination is limited to 1100℃~1200℃, and the alumina precursor can fully undergo phase change from γ phase or transition phase to stable α phase. The holding time refers to the time that the calcined precursor is kept at the terminal temperature. The holding time is limited to 60min~120min, which can ensure the full progress of the phase change process and improve the conversion rate and crystallinity of α-alumina. Exemplarily, the heating rate of roasting can be 10°C / min, 11°C / min, 12°C / min, 13°C / min, 14°C / min, 15°C / min, etc., the terminal temperature of roasting can be 1100°C, 1120°C, 1140°C, 1160°C, 1180°C, 1200°C, etc., and the holding time of roasting can be 60min, 70min, 80min, 90min, 100min, 110min, 120min, etc.

[0077] In summary, the preparation method of α-alumina powder provided in the embodiment of the present application has significant advantages, which are mainly reflected in the following aspects: 1. Improving dispersibility and uniformity: Adding steric hindrances (such as solvent-based steric hindrances and solid steric hindrances) to the alumina precursor can quickly form effective steric hindrances during the emulsification and dispersion process, effectively isolating the distance between the alumina powder particles, thereby significantly inhibiting the agglomeration of the powder. This helps to obtain finer and more uniform alumina powder particles. 2. The sand milling step further ensures the dispersibility and uniformity of the raw material particles. By physical grinding, the agglomeration between the particles can be further broken, making the particle size finer and the distribution more uniform. 3. Improving the α conversion rate: Adding a seed inducer (such as gas phase nano γ-alumina) to the ultrafine powder can induce alumina to grow in a specific direction during the roasting process, and reduce the energy barrier for the transition from the γ phase or other transition phases to the α phase. This not only helps to form α-alumina powder with specific morphology and structure, but also significantly improves the α conversion rate, ensuring that more alumina precursors can be converted into stable α phases. 4. Reduce the calcination temperature: The addition of seed inducers also helps to reduce the calcination temperature. Since the seeds provide low-energy nucleation sites, alumina molecules are more likely to nucleate and grow on these sites during the calcination process, thereby reducing the energy required to reach the same phase change temperature. This not only saves energy, but also reduces the requirements for equipment and possible side effects of high-temperature calcination. 5. Improve product performance: The prepared α-alumina powder has higher dispersion stability, finer particle size and more uniform particle distribution. These characteristics make α-alumina powder have a wider application prospect and better performance in the fields of fillers, catalyst carriers, ceramic raw materials, etc. 6. Strong process controllability: Each step and parameter in the preparation method (such as the type and amount of steric hindrance, sand milling time, spray drying conditions, the type and amount of seed inducers, calcination temperature and time, etc.) can be precisely controlled and adjusted according to specific needs. This makes the process highly controllable and flexible, and can meet the requirements of product performance in different application scenarios. In summary, this method has significant advantages in improving the α conversion rate, dispersion stability and product performance of α-alumina, and provides an effective way to prepare high-performance α-alumina powder.

[0078] Based on a general inventive concept, the present application provides an α-alumina powder prepared by the method described in any one of the above embodiments, wherein the α-alumina powder satisfies at least one of the following properties: particle size D50 is 100nm~300nm, particle size D100≤500nm, and α conversion rate ≥96%.

[0079] The nano-alumina powder prepared in the embodiment of the present application has a particle size D50 of 100nm to 300nm, a particle size D100 ≤ 500nm, an α conversion rate ≥ 96%, a regular particle morphology, a conversion rate ≥ 96%, high hardness, good dispersibility, no large particles, and is not prone to scratches. It can be applied to chemical mechanical polishing of hard materials such as silicon nitride, silicon carbide, and sapphire. Exemplarily, the particle size D50 can be 100nm, 120nm, 150nm, 180nm, 200nm, 300nm, the particle size D100 can be 200nm, 300nm, 350nm, 400nm, 450nm, 500nm, etc., and the α conversion rate can be 96%, 96.5%, 97%, 97.5%, 98%, etc.

[0080] The α-alumina powder is realized based on the preparation method of the α-alumina powder mentioned above. The specific steps of the preparation method of the α-alumina powder can refer to the above embodiment. Since the α-alumina powder adopts part or all of the technical solutions of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment, which will not be repeated here one by one.

[0081] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0082] Example 1

[0083] This embodiment provides a method for preparing α-alumina powder, which may specifically include the following steps:

[0084] (1) Weigh 160 g of boehmite (particle size D50: 1.479 μm) and add it to a mixed solution of 480 g of pure water and 40 g of anhydrous ethanol, and slowly add 80 g of C powder while stirring manually until the addition of the materials is completed. Place it in a high-speed shear emulsifier for emulsification and dispersion at a speed of 4000 rpm for 30 min to obtain a boehmite slurry;

[0085] (2) adding the boehmite slurry dispersed in step (1) into a horizontal sand mill and sand-milling for 20 minutes to obtain a uniformly dispersed ultrafine slurry;

[0086] (3) spray drying the ultrafine slurry in step (2) at a feed rate of 1.5 L / hr and a drying temperature of 150° C. to obtain ultrafine boehmite (particle size D50: 314 nm);

[0087] (4) Weigh 24 g of 50 nm fumed γ-alumina, add it to the ultrafine boehmite in step (2), and mix them in a three-dimensional mixer for 10 min to obtain a calcined precursor;

[0088] (5) The precursor prepared in step (4) is placed in a fluidized bed calcining furnace, and the temperature is raised to 1100° C. at a heating rate of 10° C. / min, and the temperature is kept at this temperature for 60 min. After the temperature is cooled to room temperature, the sample is taken out to obtain α-alumina powder.

[0089] Example 2

[0090] This embodiment provides a method for preparing α-alumina powder, which may specifically include the following steps:

[0091] (1) Weigh 200 g of boehmite (particle size D50: 1.479 μm) and add it to a mixed solution of 400 g of pure water and 80 g of anhydrous ethanol, and slowly add 100 g of white sugar while stirring manually until the addition of the materials is completed. Place it in a high-speed shear emulsifier for emulsification and dispersion at a speed of 4000 rpm for 30 min to obtain a boehmite slurry;

[0092] (2) adding the boehmite slurry dispersed in step (1) into a horizontal sand mill and sand-milling for 20 minutes to obtain a uniformly dispersed ultrafine slurry;

[0093] (3) spray drying the ultrafine slurry of step (2) at a feed rate of 1.0 L / hr and a drying temperature of 160° C. to obtain ultrafine boehmite (particle size D50: 204 nm);

[0094] (4) Weigh 50 g of 50 nm fumed γ-alumina, add it to the ultrafine boehmite in step (2), and mix them in a three-dimensional mixer for 10 min to obtain a calcined precursor;

[0095] (5) The precursor prepared in step (4) is placed in a fluidized bed calcining furnace, and the temperature is raised to 1150° C. at a heating rate of 10° C. / min. The temperature is kept at this temperature for 120 min, and the sample is taken out after cooling to room temperature to obtain α-alumina powder.

[0096] Example 3

[0097] This embodiment provides a method for preparing α-alumina powder, which may specifically include the following steps:

[0098] (1) Weigh 240 g of boehmite (particle size D50: 1.479 μm) and add it to a mixed solution of 320 g of pure water and 70 g of anhydrous ethanol, and slowly add 120 g of C powder while stirring manually until the addition of the materials is completed. Place it in a high-speed shear emulsifier for emulsification and dispersion at a speed of 4000 rpm for 30 min to obtain a boehmite slurry;

[0099] (2) adding the boehmite slurry dispersed in step (1) into a horizontal sand mill and sand-milling for 30 minutes to obtain a uniformly dispersed ultrafine slurry;

[0100] (3) spray drying the ultrafine slurry of step (2) at a feed rate of 0.5 L / hr and a drying temperature of 160° C. to obtain ultrafine boehmite (particle size D50: 332 nm);

[0101] (4) Weigh 60 g of 50 nm fumed γ-alumina, add it to the ultrafine boehmite in step (2), and mix them in a three-dimensional mixer for 15 minutes to obtain a calcined precursor;

[0102] (5) The precursor prepared in step (4) is placed in a fluidized bed calcining furnace, and the temperature is raised to 1200° C. at a heating rate of 15° C. / min, and the temperature is kept at this temperature for 120 min. After the temperature is cooled to room temperature, the sample is taken out to obtain α-alumina powder.

[0103] Example 4

[0104] This embodiment provides a method for preparing α-alumina powder, which may specifically include the following steps:

[0105] (1) Weigh 160 g of aluminum hydroxide (particle size D50: 1.726 μm) and add it to a mixed solution of 480 g of pure water and 60 g of anhydrous ethanol, and slowly add 80 g of white sugar while stirring manually until the addition of the materials is completed, and place it in a high-speed shear emulsifier for emulsification and dispersion at a speed of 4000 rpm for 30 min to obtain aluminum hydroxide slurry;

[0106] (2) adding the aluminum hydroxide slurry dispersed in step (1) into a horizontal sand mill and grinding for 20 minutes to obtain a uniformly dispersed ultrafine slurry;

[0107] (3) spray drying the ultrafine slurry of step (2) at a feed rate of 0.5 L / hr and a drying temperature of 160° C. to obtain ultrafine aluminum hydroxide powder (particle size D50: 355 nm);

[0108] (4) Weigh 50 g of 50 nm fumed γ-alumina, add it to the ultrafine aluminum hydroxide prepared in step (2), and mix them in a three-dimensional mixer for 10 min to obtain a calcined precursor.

[0109] (5) The precursor prepared in step (4) is placed in a fluidized bed calcining furnace, and the temperature is raised to 1150° C. at a heating rate of 15° C. / min. The temperature is kept at this temperature for 120 min, and a sample is taken out to obtain α-alumina powder.

[0110] Example 5

[0111] This embodiment provides a method for preparing α-alumina powder, which may specifically include the following steps:

[0112] (1) Weigh 200 g of aluminum hydroxide (particle size D50: 1.726 μm) and add it to a mixed solution of 400 g of pure water and 80 g of anhydrous ethanol, and slowly add 140 g of C powder while stirring manually until the addition of the materials is completed, and place it in a high-speed shear emulsifier for emulsification and dispersion at a speed of 4000 rpm for 30 min to obtain aluminum hydroxide slurry;

[0113] (2) adding the aluminum hydroxide slurry dispersed in step (1) into a horizontal sand mill and grinding for 20 minutes to obtain a uniformly dispersed ultrafine slurry;

[0114] (3) spray drying the ultrafine slurry of step (2) at a feed rate of 1.0 L / hr and a drying temperature of 160° C. to obtain ultrafine aluminum hydroxide powder (particle size D50: 355 nm);

[0115] (4) Weigh 80 g of 50 nm fumed γ-alumina, add it to the ultrafine aluminum hydroxide prepared in step (2), and mix in a three-dimensional mixer for 10 min to obtain a calcined precursor.

[0116] (5) The precursor prepared in step (4) is placed in a fluidized bed calcining furnace, and the temperature is increased to 1200° C. at a heating rate of 15° C. / min. The temperature is kept at this temperature for 120 min, and a sample is taken out to obtain α-alumina powder.

[0117] Comparative Example 1

[0118] This comparative example provides a method for preparing α-alumina powder, which may specifically include the following steps:

[0119] (1) Weigh 240 g of boehmite (particle size D50: 1.478 μm), add 560 g of pure water, place in a high-speed shear emulsifier for emulsification and dispersion at a speed of 4000 rpm for 30 min to obtain a boehmite slurry;

[0120] (2) adding the boehmite slurry dispersed in step (1) into a horizontal sand mill and sand-milling for 20 minutes to obtain a uniformly dispersed slurry;

[0121] (3) spray drying the slurry in step (2) at a feed rate of 1.0 L / hr and a drying temperature of 160° C. to obtain ultrafine boehmite (particle size D50: 430 nm);

[0122] (4) Weigh 24 g of 50-80 nm fumed γ-alumina, add it to the ultrafine boehmite of step (3), and mix them in a three-dimensional mixer for 10 minutes to obtain a calcined precursor.

[0123] (5) The precursor prepared in step (4) is placed in a fluidized bed calcining furnace, and the temperature is increased to 1200° C. at a heating rate of 10° C. / min. The temperature is kept at this temperature for 120 min, and a sample is taken out to obtain α-alumina powder.

[0124] Comparative Example 2

[0125] This comparative example provides a method for preparing α-alumina powder, which may specifically include the following steps:

[0126] (1) Weigh 200 g of aluminum hydroxide (particle size D50: 1.726 μm) and add it to a mixed solution of 400 g of pure water and 100 g of anhydrous ethanol, and slowly add 100 g of C powder while stirring manually until the addition of the materials is completed. Place it in a high-speed shear emulsifier for emulsification and dispersion at a speed of 4000 rpm for 30 min to obtain aluminum hydroxide slurry;

[0127] (2) adding the aluminum hydroxide slurry dispersed in step (1) into a horizontal sand mill and sand-milling for 20 minutes to obtain a uniformly dispersed slurry;

[0128] (3) spray drying the slurry in step (2) at a feed rate of 1.5 L / hr and a drying temperature of 160° C. to obtain ultrafine aluminum hydroxide precursor powder (particle size D50: 355 nm);

[0129] (4) directly placing the precursor prepared in step (3) into a fluidized bed calcining furnace, heating the temperature to 1200°C at a heating rate of 15°C / min, keeping the temperature at this temperature for 120 min, taking out the sample, and obtaining α-alumina powder.

[0130] The performance of the α-alumina powders obtained in Examples 1 to 5 and Comparative Examples 1 to 2 was characterized, and the results are shown in Table 1.

[0131] Table 1 Properties of α-alumina powders obtained in Examples 1 to 5 and Comparative Examples 1 to 2

[0132] Group Particle size (D50: nm) Particle size (D100: nm) α conversion rate (%) Example 1 212 385 98.4 Example 2 230 443 97.5 Example 3 245 368 96.8 Example 4 189 377 96.3 Example 5 167 426 97.2 Comparative Example 1 453 1230 93.0 Comparative Example 2 302 2491 82.7

[0133] It can be seen from Table 1 that the α-alumina powder prepared by the method provided in the examples of the present application has a higher α conversion rate and no large particles (D100≤500nm) are present.

[0134] Figure 3 This is a microstructure diagram of the α-alumina powder provided in Example 1 of the present application. Figure 3 It can be seen that the prepared α-alumina powder has regular particle morphology and good dispersibility.

[0135] Figure 4This is the XRD diagram of the α-alumina powder provided in Example 1 of the present application. Figure 4 It can be seen that the characteristic peaks of the α phase are displayed, so the prepared α-alumina powder is all α phase.

[0136] In addition, one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0137] In the embodiment of the present application, the raw materials are first pretreated, and a steric hindrance is added to form steric hindrance during the emulsification and dispersion process, thereby effectively isolating the distance between the alumina powder particles and inhibiting the agglomeration of the powder. The dispersion and uniformity of the raw material particles are ensured by sand grinding, and the particle size D50 of the powder particles after pretreatment is ≤400nm; then ultrafine crystal seeds are added as an inducer, and after uniform mixing, the mixture is placed in a boiling roasting furnace for rapid roasting. The roasting temperature is 1100°C to 1200°C, which is about 100°C lower than the traditional calcination temperature of α-alumina powder.

[0138] In the embodiments of the present application, the α-alumina powder has high hardness, small particle size and narrow distribution, is suitable for chemical mechanical polishing of hard materials, has a high material removal rate, and is not prone to scratches and dents on the surface quality problems.

[0139] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing α-alumina powder, characterized in that: The method comprises: Mixing an aluminum oxide precursor, a steric hindering agent and a solvent to obtain a mixed slurry; Sand-grinding the mixed slurry to obtain an ultrafine slurry; The ultrafine slurry is spray-dried to obtain ultrafine powder; Mixing the ultrafine powder and the grain inducing agent to obtain a calcined precursor; and The calcined precursor is calcined under set calcination conditions to obtain α-alumina powder.

2. The method according to claim 1, characterized in that The alumina precursor includes: at least one of boehmite and aluminum hydroxide; and / or, The mass of the aluminum oxide precursor is 20% to 30% of the total mass of the mixed slurry.

3. The method according to claim 2, characterized in that The particle size D50 of the aluminum oxide precursor is ≤2.0 μm.

4. The method according to claim 1, characterized in that: The steric hindering agent includes: a solvent-type steric hindering agent and a solid-type steric hindering agent; and / or, The solvent-based steric hindering agent includes: anhydrous ethanol; and / or, The solid steric retardant comprises at least one of C powder and white sugar.

5. The method according to claim 4, characterized in that The mass of the solvent-based steric inhibitor is 5% to 10% of the total mass of the mixed slurry; and / or, The mass of the solid steric inhibitor is 10% to 20% of the total mass of the mixed slurry.

6. The method according to claim 1, characterized in that The ball-to-material ratio of the sand mill is (3-5):1; and / or, The sanding time is 20 min to 40 min; and / or, The particle size D50 of the powder in the ultrafine slurry is ≤0.4 μm.

7. The method according to claim 1, characterized in that The feed rate of the spray drying is 0.5L / hr to 1.5L / hr; and / or, The drying temperature of the spray drying is 140°C to 180°C.

8. The method according to claim 1, characterized in that: The grain inducing agent comprises: gas phase nano-γ-alumina; and / or, The particle size of the gas phase nano-γ-alumina is 20nm to 30nm; and / or, The mass of the gas phase nano-γ-alumina is 3% to 10% of the total mass of the calcined precursor.

9. The method according to claim 1, characterized in that: The setting of the roasting conditions includes at least one of the following: The heating rate of the calcination is 10°C / min to 15°C / min; The end point temperature of the calcination is 1100°C to 1200°C; The heat preservation time of the calcination is 60 minutes to 120 minutes.

10. An α-alumina powder prepared by the method according to any one of claims 1 to 9, characterized in that: The α-alumina powder satisfies at least one of the following properties: Particle size D50 is 100nm~300nm; Particle size D100≤500nm; α conversion rate ≥96%.

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