Α-aluminum oxide powder and preparation method therefor

Abstract

The present application provides an α-aluminum oxide powder and a preparation method therefor. The method comprises: mixing an aluminum oxide precursor, a steric hindrance agent, and a solvent to obtain a mixed slurry; sand-milling the mixed slurry to obtain an ultra-fine slurry; spray-drying the ultra-fine slurry to obtain an ultra-fine powder; mixing the ultra-fine powder with a grain inducer to obtain a roasting precursor; and roasting the roasting precursor under set roasting conditions to obtain the α-aluminum oxide powder.

Description

An α-alumina powder and its preparation method

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese patent application No. 202411598055.7, filed on November 11, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of inorganic non-metallic technology, and in particular to an α-alumina powder and its preparation method. Background Technology

[0004] Currently, with the rapid development of the semiconductor industry and the shrinking size of electronic devices, the requirements for wafer surface flatness have reached ultra-fine levels. Chemical Mechanical Polishing (CMP) technology is almost the only technology that can provide global flatness. In CMP technology, polishing abrasives (usually in powder form as raw materials) are the foundation and main component of the CMP polishing slurry. The physical, chemical, and mechanical properties of the polishing abrasives, such as their type, structure, particle size, morphology, and hardness, play a crucial role in CMP performance and achieving ultra-smooth crystal surfaces after polishing. Therefore, polishing abrasives are the core materials that determine the polishing effect of CMP and play a key role in the CMP polishing process. Ultrafine alumina (Al2O3), as a highly 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. Al2O3 has excellent polishing performance due to its high hardness (Mohs hardness of 9), dense structure, good stability, and high material removal rate. In recent years, in particular, with the increasing demand for hard materials such as sapphire (Mohs hardness of 9), silicon carbide (Mohs hardness of 9.3), and silicon nitride (Mohs hardness of around 9), it has become increasingly important to select Al2O3, whose hardness is close to that of these hard materials, as the polishing abrasive in the CMP process.

[0005] Alumina exists in different phases, including α, γ, δ, η, θ, κ, and χ. Different phases of ultrafine alumina exhibit different properties. Among them, only α-alumina with high conversion rate, due to its high hardness, high thermal stability, and resistance to chemical corrosion, can achieve good polishing rates and material removal rates for hard materials. However, the preparation process of α-alumina is complex and requires high-temperature calcination, leading to problems such as abnormal particle growth, agglomeration, and wide particle size distribution. These drawbacks result in poor dispersion stability of α-alumina, and large particles can easily cause scratches and dents on the polished surface. Therefore, improving the α-conversion rate of α-alumina while simultaneously improving its dispersion stability is a pressing technical problem that needs to be solved. Summary of the Invention

[0006] An α-alumina powder and its preparation method, utilizing one or more embodiments of the present disclosure, solves the problem of how to improve the α-conversion rate of α-alumina while simultaneously improving its dispersion stability.

[0007] In a first aspect, this disclosure provides a method for preparing α-alumina powder, comprising: mixing an alumina precursor, a steric hindrance agent, and a solvent to obtain a mixed slurry; milling the mixed slurry to obtain an ultrafine slurry; spray-drying the ultrafine slurry to obtain an ultrafine powder; mixing the ultrafine powder with a grain inducing agent to obtain a calcination precursor; and calcining the calcination precursor under set calcination conditions to obtain α-alumina powder.

[0008] In a second aspect, this disclosure provides an α-alumina powder prepared by the method described in any one embodiment of the first aspect, wherein the α-alumina powder satisfies at least one of the following properties: particle size D 50 The particle size ranges from 100nm to 300nm; the particle size D 100 ≤500nm; α conversion rate ≥96%. Attached Figure Description

[0009] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0010] To more clearly illustrate the technical solutions in the embodiments or related technologies of this disclosure, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0011] Figure 1 shows a flowchart of a method for preparing α-alumina powder according to some embodiments of the present disclosure.

[0012] Figure 2 shows a schematic diagram of a method for preparing α-alumina powder according to some embodiments of the present disclosure.

[0013] Figure 3 shows a scanning electron microscope (SEM) image of the microstructure of α-alumina powder provided according to Embodiment 1 of this disclosure;

[0014] Figure 4 shows an X-ray diffraction (XRD) pattern of α-alumina powder provided according to Embodiment 1 of this disclosure. Embodiments of the present invention

[0015] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0016] Various embodiments of this disclosure may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this disclosure; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges 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., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0017] Furthermore, in the description of this disclosure, the terms "comprising," "including," etc., mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely 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 document, "and / or" describes the relationship between related objects, indicating that three relationships may exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than" means two or more. "At least one," "at least one of the following," or similar expressions mean 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 both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. "Parts representation" such as parts by weight or parts by mass indicates the proportional relationship between components. In the proportional relationships discussed in this article, parameters that need to be described by proportion should be understood as the first term of the proportion in the order of description, while the proportion figure should be understood as the second term. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substances A, B, and C should correspond one-to-one with the proportion figure in the proportion in the order of description, i.e., the mass of substance A : the mass of substance B : the mass of substance C = 1:2:3.

[0018] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this disclosure are available on the market or can be prepared by existing methods.

[0019] Figure 1 shows a flowchart of a method for preparing α-alumina powder according to some embodiments of the present disclosure; Figure 2 shows a schematic diagram of a method for preparing α-alumina powder according to some embodiments of the present disclosure.

[0020] Please refer to Figures 1 and 2. This disclosure provides a method for preparing α-alumina powder, including:

[0021] S1. The alumina precursor, steric hindrance agent, and solvent are mixed to obtain a mixed slurry. S2. The mixed slurry is milled to obtain an ultrafine slurry.

[0022] S3. Spray dry the ultrafine slurry to obtain ultrafine powder.

[0023] S4. Mix the ultrafine powder and the grain inducer to obtain the calcination precursor.

[0024] S5. The calcination precursor is calcined under the set calcination conditions to obtain α-alumina powder.

[0025] In some embodiments, the selection of alumina precursor as the matrix material is crucial for obtaining α-alumina. The main purpose of adding steric hindrance agents (such as polymers or surfactants) during this process is to create steric hindrance during the mixing (including emulsification and dispersion) of raw materials such as the alumina precursor, effectively isolating the alumina precursor particles and preventing them from agglomerating due to contact. The addition of steric hindrance agents is essential for obtaining highly dispersible α-alumina powder. Furthermore, the selected solvent should be able to effectively dissolve or disperse the alumina precursor and the steric hindrance agent to ensure the formation of a homogeneous slurry.

[0026] In some embodiments, the mixing process of the alumina precursor, steric hindrance agent and solvent includes an emulsification and dispersion process using a high-speed shear emulsifier.

[0027] In some embodiments, the alumina precursor includes at least one of boehmite and aluminum hydroxide.

[0028] In some embodiments, the mass of the alumina precursor is 20% to 32% of the total mass of the mixed slurry.

[0029] In some embodiments, the mass of the alumina precursor is 20% to 30% of the total mass of the mixed slurry.

[0030] Boehmite (AlOOH) and aluminum hydroxide (Al(OH)3) are common alumina precursors, which dehydrate to form alumina during heating.

[0031] In some embodiments, the mass ratio of the alumina precursor to the total mass of the mixed slurry can be controlled between 20% and 32%. Optionally, the mass ratio of the alumina precursor to the total mass of the mixed slurry can be controlled between 20% and 30%. This range ensures an appropriate concentration of the alumina precursor in the slurry, which helps to form a homogeneous mixed slurry and can reduce the agglomeration of alumina precursor particles, thereby improving the stability and flowability of the slurry. Exemplarily, the mass of the alumina precursor is 20%, 22%, 24%, 26%, 28%, 30%, 32%, etc., of the total mass of the mixed slurry.

[0032] In some embodiments, the particle size D of the alumina precursor 50 ≤2.0μm.

[0033] Particle size D 50The particle size of the alumina precursor is defined as the particle size at which the cumulative distribution reaches 50%. The particle size of the alumina precursor is controlled within D... 50 Within the ≤2.0 μm range, a good foundation can be provided 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. For example, the particle size D of the alumina precursor... 50 It can be 0.5μm, 0.8μm, 1.0μm, 1.2μm, 1.4μm, 1.6μm, 1.8μm, 2.0μm, etc.

[0034] In some embodiments, the steric hindrance includes solvent-based steric hindrance and solid-based steric hindrance. Solvent-based steric hindrance includes anhydrous ethanol, and / or, solid-based steric hindrance includes at least one of C powder and white sugar.

[0035] Carbon powder (C-powder) refers to finely granular carbon material, primarily composed of carbon elements. Carbon powder possesses excellent electrical conductivity, thermal conductivity, lubricity, and chemical stability.

[0036] In some embodiments, the mass of the solvent-based steric hindrance is 5% to 11% of the total mass of the mixed slurry, and the mass of the solid steric hindrance is 10% to 20% of the total mass of the mixed slurry.

[0037] Steric hindrance agents can form effective steric hindrance during the mixing (including emulsification and dispersion) of raw materials such as alumina precursors, isolating the distance between alumina precursor particles and thus inhibiting their agglomeration, which helps to obtain finer and more uniform alumina powder particles. Based on their morphology, steric hindrance agents can be divided into solvent-based and solid-based steric hindrance agents. Optionally, anhydrous ethanol can be used as a solvent-based steric hindrance agent. Through intermolecular interactions, anhydrous ethanol can form a thin film on the surface of alumina precursor particles, increasing the distance between them and reducing direct contact and friction, thereby effectively inhibiting agglomeration. Carbon powder or sugar can be used as solid-based steric hindrance agents. Carbon powder or sugar particles can not only physically embed themselves between alumina precursor particles, forming a physical barrier to prevent direct contact and agglomeration, but also form a protective film on the surface of the alumina precursor particles through adsorption. When solvent-based and solid-based steric hindrance agents are used in combination, the solvent-based steric hindrance agent first wets and coats the alumina precursor particles, achieving initial dispersion and reducing the interaction forces between the particles. The solid-based steric hindrance agent then provides physical barrier properties, further preventing the alumina precursor particles from re-aggregating during dispersion, thus stabilizing the dispersion and forming a more stable and durable steric hindrance effect. This combination of solvent-based and solid-based steric hindrance agents significantly improves dispersion efficiency and stability, resulting in a finer and more uniform particle distribution in the final α-alumina powder product.

[0038] By controlling the proportion of solvent-based steric hindrance agents in the total mass of the mixed slurry to be within the range of 5% to 11%, and the proportion of solid steric hindrance agents to be within the range of 10% to 20%, sufficient steric hindrance effect can be ensured without introducing unnecessary impurities due to excessive steric hindrance agents, which could affect subsequent processing. For example, the mass of solvent-based steric hindrance agents can be 5%, 6%, 7%, 8%, 9%, 10%, or 11% of the total mass of the mixed slurry, and the mass of solid steric hindrance agents can be 10%, 12%, 14%, 16%, 18%, or 20% of the total mass of the mixed slurry.

[0039] In some embodiments, during the sand milling process of the mixed slurry, all solid particles in the mixed slurry (e.g., the solid particles in the mixed slurry may include alumina precursor particles and solid steric hindrance particles) can be further refined through the sand milling process, and its dispersibility and uniformity can be improved. During the sand milling process, the collision and friction between the grinding balls and the solid particles help to break up agglomerates and form smaller solid particles, so that the solid particles are gradually refined and dispersed in the solvent. At the same time, the presence of the steric hindrance further enhances the dispersion effect between solid particles and reduces agglomeration. After sand milling, the dispersibility and uniformity of solid particles are significantly improved. Therefore, the ultrafine slurry obtained after sand milling has high dispersibility and uniformity.

[0040] In some embodiments, the ball-to-powder ratio in the sand mill is (3~5):1, the milling time is 20min~40min, and the particle size D of the powder in the ultrafine slurry is... 50 ≤0.4μm.

[0041] The ball-to-particle ratio refers to the mass ratio of grinding media (such as grinding balls) to solid particles in the mixed slurry. Controlling the ball-to-particle ratio within the range of 3~5:1 helps to achieve uniform crushing and dispersion of solid particles in the mixed slurry while ensuring sufficient grinding efficiency. For example, the ball-to-particle ratio in sand milling can be 3:1, 4:1, 5:1, etc., and the sand milling time can be 20 min, 22 min, 25 min, 28 min, 30 min, 32 min, 35 min, 38 min, 40 min, etc., with the particle size D of the powder in the ultrafine slurry being... 50 It can be 0.1μm, 0.15μm, 0.2μm, 0.25μm, 0.3μm, 0.35μm, 0.4μm, etc.

[0042] In some embodiments, during the spray drying process of the ultrafine slurry, spray drying technology can be used to convert the ultrafine slurry into ultrafine powder. During the spray drying process, the ultrafine slurry is atomized into tiny droplets and rapidly comes into contact with hot air, causing the solvent to evaporate quickly and forming dried ultrafine powder.

[0043] In some embodiments, the feed rate for spray drying is 0.5 L / hr to 1.5 L / hr, and the drying temperature for spray drying is 140°C to 180°C.

[0044] The feed rate for spray drying can be controlled within the range of 0.5L / hr to 1.5L / hr, and the drying temperature can be set within the range of 140℃ to 180℃. Under these conditions, the surface area of ​​the ultrafine slurry increases dramatically after atomization, and it can quickly exchange heat with hot air, causing rapid evaporation of moisture and significantly shortening the drying time. The entire drying process can typically be completed in only 5 to 40 seconds. For example, the feed rate for 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 can be 140℃, 150℃, 160℃, 170℃, 180℃, etc.

[0045] In some embodiments, ultrafine powder and grain inducer are mixed to obtain a calcination precursor. By adding grain inducer to the calcination precursor, the alumina precursor can be guided to grow in a specific direction during the calcination process, which helps to form α-alumina powder with a specific morphology and structure.

[0046] In some embodiments, during the mixing of ultrafine powder and grain inducer, the ultrafine powder and grain inducer can be mixed by rotating and mixing in a three-dimensional mixer, wherein the mixing time is 5 min to 10 min.

[0047] In some embodiments, the grain inducer includes fumed nano-gamma alumina with a particle size of 50 nm and a mass of 3% to 10% of the total mass of the calcined precursor.

[0048] Vapor-phase nano-gamma-alumina is used as a grain inducing agent due to its small particle size (50 nm) and high purity. It exhibits good dispersibility and surface activity, effectively guiding grain growth of alumina precursors during calcination. During calcination, vapor-phase nano-gamma-alumina acts as a seed crystal, providing low-energy nucleation sites and guiding the alumina precursors to align and grow in a specific direction, thus contributing to the formation of α-alumina powder with specific morphologies (e.g., spherical, rod-shaped) and structures. Simultaneously, the addition of the seed crystal (vapor-phase nano-gamma-alumina) lowers the energy barrier for the transformation of alumina from the γ-phase to the α-phase, thereby achieving the crystal transformation at a lower calcination temperature. This not only saves energy but also reduces the equipment requirements and potential side effects of high-temperature calcination. Furthermore, due to the excellent dispersibility of the seed crystals (vapor-phase nano-γ-alumina), they can be uniformly distributed among the alumina precursor particles, forming a physical barrier that inhibits agglomeration among the alumina precursor particles, thereby helping to improve the dispersibility and specific surface area of ​​the final product (α-alumina powder). For example, the mass of the vapor-phase nano-γ-alumina is 3%, 5%, 7%, 9%, 10%, etc., of the total mass of the calcined precursor.

[0049] In some embodiments, the homogeneously mixed calcination precursor is placed in a fluidized bed calciner, and suitable calcination conditions are set for low-temperature fluidized bed calcination to obtain high-conversion α-alumina powder. The fluidized bed calciner used in this process is a highly efficient calcination device that utilizes fluidization technology to create a fluidized bed-like state within the furnace, thereby achieving rapid and uniform calcination. Therefore, this equipment is particularly suitable for processing granular materials and can achieve high calcination results in a short time, resulting in a high conversion rate of α-alumina.

[0050] In some embodiments, the heating rate of calcination is 10℃ / min to 15℃ / min, the final temperature of calcination is 1100℃ to 1200℃, and the holding time of calcination is 60min to 120min.

[0051] As mentioned above, grain inducing agents can induce the formation of ultrafine α-alumina powder and lower the conversion temperature. Therefore, when the uniformly mixed calcining precursor is placed in a fluidized bed calciner for rapid calcination, the calcination temperature can be set to 1100℃~1200℃, which is about 100℃ lower than the traditional calcination temperature for α-alumina powder. The heating rate is an important parameter in the calcination process, affecting the thermal stress and phase transformation process of the calcined precursor. Therefore, the heating rate is set to 10℃ / min~15℃ / min to ensure that the calcined precursor is heated uniformly, thereby avoiding thermal stress concentration and ensuring complete phase transformation. The final calcination temperature can be set to 1100℃~1200℃ to ensure that the alumina precursor can undergo sufficient phase transformation, changing from the γ phase or transition phase to the stable α phase. The holding time refers to the time the calcined precursor is held at the final temperature. The holding time can be set to 60 min to 120 min to ensure the phase transformation process proceeds fully and to improve the conversion rate and crystallinity of α-alumina. For example, the heating rate of calcination can be 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min, 15℃ / min, etc., the final temperature of calcination can be 1100℃, 1120℃, 1140℃, 1160℃, 1180℃, 1200℃, etc., and the holding time of calcination can be 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, etc.

[0052] In summary, the method for preparing α-alumina powder provided in this disclosure has significant advantages, mainly in the following aspects.

[0053] 1. Improve the dispersibility and uniformity of alumina powder particles. Adding steric hindrance agents (such as solvent-based and solid-based steric hindrance agents) to the alumina precursor can rapidly form effective steric hindrance during the mixing (including emulsification and dispersion) of raw materials such as the alumina precursor, effectively isolating the distance between alumina precursor particles and thus significantly inhibiting particle agglomeration. This helps to obtain finer and more uniform alumina precursor particles. Furthermore, the subsequent sand milling step further ensures the dispersibility and uniformity of solid particles in the mixed slurry. Through physical grinding, the agglomeration of solid particles in the mixed slurry can be further broken down, resulting in better dispersion and size uniformity of the solid particles in the mixed slurry.

[0054] 2. Improve α-conversion rate. Adding grain-inducing agents (such as fumed nano-γ-alumina) to ultrafine powders can induce the alumina precursor to grow along a specific direction during calcination and lower the energy barrier for the transformation 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 of the alumina precursor, ensuring that more alumina precursor can be transformed into the stable α phase.

[0055] 3. Lowering the calcination temperature. The addition of grain inducers also helps to lower the calcination temperature. Because the seed crystals (vapor-phase nano-γ-alumina) provide low-energy nucleation sites, the alumina precursor is more likely to nucleate and grow at these sites during calcination, thereby reducing the energy required to reach the same phase transition temperature. This not only saves energy but also reduces the equipment requirements and potential side effects of high-temperature calcination.

[0056] 4. Improved product performance. The prepared α-alumina powder exhibits higher dispersion stability, finer particle size, and more uniform particle distribution. These characteristics make α-alumina powder more promising and offer superior performance in applications such as fillers, catalyst supports, ceramic raw materials, and polishing abrasives.

[0057] 5. High process controllability. Each step and parameter in this preparation method (such as the type and amount of steric hindrance agent, milling time, spray drying conditions, the type and amount of grain-inducing agent, calcination temperature and time, etc.) can be precisely controlled and adjusted according to specific needs. This makes the process highly controllable and flexible, capable of meeting the performance requirements of different application scenarios.

[0058] In summary, this method has significant advantages in improving the α-conversion rate, dispersion stability, and product performance of α-alumina, providing an effective approach for preparing high-performance α-alumina powder.

[0059] Based on a general inventive concept, this disclosure provides an α-alumina powder prepared by the method of any of the above embodiments, wherein the α-alumina powder satisfies at least one of the following properties: particle size D 50 The particle size is 100nm~300nm, and the particle size D is... 100 ≤500nm, α conversion rate ≥96%.

[0060] The particle size D of the α-alumina powder in the embodiments of this disclosure is... 50 The particle size is 100nm~300nm, and the particle size D is... 100With a particle size ≤500nm, α-conversion rate ≥96%, regular particle morphology, high hardness, good dispersibility, no large particles, and low susceptibility to scratches, it can be applied to the chemical mechanical polishing of hard materials such as silicon nitride, silicon carbide, and sapphire. For example, the particle size D of α-alumina powder... 50 It can be 100nm, 120nm, 150nm, 180nm, 200nm, 300nm, with a particle size D. 100 The wavelengths can be 200nm, 300nm, 350nm, 400nm, 450nm, 500nm, etc., and the α conversion rate can be 96%, 96.5%, 97%, 97.5%, 98%, etc.

[0061] The α-alumina powder is prepared using the above-described method for preparing α-alumina powder. The specific steps of the preparation method can be found in the above embodiments. Since the α-alumina powder employs all the technical features of some of the above embodiments, it possesses at least all the beneficial effects brought about by some of the above embodiments, which will not be elaborated upon here.

[0062] The present disclosure is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the disclosure. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0063] Example 1

[0064] This embodiment provides a method for preparing α-alumina powder, which may specifically include the following steps:

[0065] (1) Weigh 160g of boehmite (particle size D) 50 Add 1.479μm) to a mixed solution consisting of 480g of pure water and 40g of anhydrous ethanol. While stirring, slowly add 80g of C powder. After all the materials have been added, transfer the resulting mixture to a high-speed shear emulsifier and emulsify and disperse it at 4000rpm for 30min to obtain a mixed slurry.

[0066] (2) Add the mixed slurry obtained in step (1) to a horizontal sand mill and sand mill for 20 minutes to obtain a uniformly dispersed ultrafine slurry;

[0067] (3) The ultrafine slurry obtained in step (2) is spray-dried at a feed rate of 1.5 L / hr and a drying temperature of 150 °C to obtain ultrafine powder (particle size D). 50 (314nm);

[0068] (4) Weigh 24g of γ-alumina produced by gas-phase method (particle size D)50 (50nm), and place it together with the ultrafine powder obtained in step (3) in a three-dimensional mixer, and mix for 10 minutes to obtain the calcination precursor;

[0069] (5) The calcination precursor prepared in step (4) is placed in a fluidized bed calcination furnace and heated to 1100°C at a heating rate of 10°C / min. The temperature is maintained at this temperature for 60 min. After cooling to room temperature in the fluidized bed calcination furnace, the sample is taken out to obtain α-alumina powder.

[0070] Example 2

[0071] This embodiment provides a method for preparing α-alumina powder, which may specifically include the following steps:

[0072] (1) Weigh 200g of boehmite (particle size D) 50 Add 1.479 μm) to a mixed solution consisting of 400 g pure water and 80 g anhydrous ethanol. While stirring, slowly add 100 g of white sugar. After all the materials have been added, transfer the resulting mixture to a high-speed shear emulsifier and emulsify and disperse it at 4000 rpm for 30 min to obtain a mixed slurry.

[0073] (2) Add the mixed slurry dispersed in step (1) to a horizontal sand mill for sand milling for 20 minutes to obtain a uniformly dispersed ultrafine slurry;

[0074] (3) The ultrafine slurry obtained in step (2) is spray-dried with a feed rate of 1.0 L / hr and a drying temperature of 160 °C to obtain ultrafine powder (particle size D). 50 (204nm);

[0075] (4) Weigh 50g of fumed γ-alumina (particle size D) 50 (50nm), and put it together with the ultrafine powder obtained in step (3) into a three-dimensional mixer, and mix for 10 minutes to obtain the calcination precursor;

[0076] (5) The calcination precursor prepared in step (4) is placed in a fluidized bed calcination furnace and heated to 1150°C at a heating rate of 10°C / min. The temperature is maintained at this temperature for 120 min. After cooling to room temperature in the fluidized bed calcination furnace, the sample is taken out to obtain α-alumina powder.

[0077] Example 3

[0078] This embodiment provides a method for preparing α-alumina powder, which may specifically include the following steps:

[0079] (1) Weigh 240g of boehmite (particle size D) 50Add 120g of C powder to a mixed solution consisting of 320g of pure water and 70g of anhydrous ethanol while stirring. After all the materials have been added, transfer the resulting mixture to a high-speed shear emulsifier and emulsify and disperse it at 4000rpm for 30min to obtain a mixed slurry.

[0080] (2) Add the mixed slurry obtained in step (1) to a horizontal sand mill and sand mill for 30 minutes to obtain a uniformly dispersed ultrafine slurry;

[0081] (3) Spray dry the ultrafine slurry obtained in step (2), setting the feed rate to 0.5 L / hr and the drying temperature to 160℃ to obtain ultrafine powder (particle size D). 50 :332nm);

[0082] (4) Weigh 60g of fumed γ-alumina (particle size D) 50 (50nm), and place it together with the ultrafine powder obtained in step (3) in a three-dimensional mixer, and mix for 15 minutes to obtain the calcination precursor;

[0083] (5) The calcination precursor prepared in step (4) is placed in a fluidized bed calcination furnace and heated to 1200°C at a heating rate of 15°C / min. The temperature is maintained at this temperature for 120 min. After cooling to room temperature in the fluidized bed calcination furnace, the sample is taken out to obtain α-alumina powder.

[0084] Example 4

[0085] This embodiment provides a method for preparing α-alumina powder, which may specifically include the following steps:

[0086] (1) Weigh 160g of aluminum hydroxide (particle size D) 50 Add 1.726μm) to a mixed solution consisting of 480g pure water and 60g anhydrous ethanol. While stirring, slowly add 80g of white sugar. After all the materials have been added, transfer the resulting mixture to a high-speed shear emulsifier and emulsify and disperse it at 4000rpm for 30min to obtain a mixed slurry.

[0087] (2) Add the mixed slurry obtained in step (1) to a horizontal sand mill and sand mill for 20 minutes to obtain a uniformly dispersed ultrafine slurry;

[0088] (3) The ultrafine slurry obtained in step (2) is spray-dried with a feed rate of 0.5 L / hr and a drying temperature of 160 °C to obtain (particle size D) 50 355nm) ultrafine powder;

[0089] (4) Weigh 50g of fumed γ-alumina (particle size D)50 (50nm), and place it together with the ultrafine powder obtained in step (3) in a three-dimensional mixer, and mix for 10 minutes to obtain the calcination precursor.

[0090] (5) The calcination precursor prepared in step (4) is placed in a fluidized bed calcination furnace and heated to 1150°C at a heating rate of 15°C / min. The temperature is maintained at this temperature for 120 min. After cooling to room temperature in the fluidized bed calcination furnace, the sample is taken out to obtain α-alumina powder.

[0091] Example 5

[0092] This embodiment provides a method for preparing α-alumina powder, which may specifically include the following steps:

[0093] (1) Weigh 200g of aluminum hydroxide (particle size D) 50 Add 1.726μm) to a mixed solution consisting of 400g pure water and 80g anhydrous ethanol. While stirring, slowly add 140g of C powder. After all the materials have been added, transfer the resulting mixture to a high-speed shear emulsifier and emulsify and disperse it at a speed of 4000rpm for 30min to obtain a mixed slurry.

[0094] (2) Add the mixed slurry obtained in step (1) to a horizontal sand mill and sand mill for 20 minutes to obtain a uniformly dispersed ultrafine slurry;

[0095] (3) The ultrafine slurry obtained in step (2) is spray-dried with a feed rate of 1.0 L / hr and a drying temperature of 160 °C to obtain ultrafine powder (particle size D). 50 (355nm);

[0096] (4) Weigh 80g of γ-alumina produced by gas-phase method (particle size D) 50 (50nm), and place it together with the ultrafine powder obtained in step (3) in a three-dimensional mixer, and mix for 10 minutes to obtain the calcination precursor;

[0097] (5) The calcination precursor prepared in step (4) is placed in a fluidized bed calcination furnace and heated to 1200°C at a heating rate of 15°C / min. The temperature is maintained at this temperature for 120 min. After cooling to room temperature in the fluidized bed calcination furnace, the sample is taken out to obtain α-alumina powder.

[0098] Comparative Example 1

[0099] This comparative example provides a method for preparing α-alumina powder, which may specifically include the following steps:

[0100] (1) Weigh 240g of boehmite (particle size D) 50Add 1.478μm) to 560g of pure water, transfer the resulting mixture to a high-speed shear emulsifier, and emulsify and disperse at 4000rpm for 30min to obtain boehmite slurry;

[0101] (2) Add the boehmite slurry obtained in step (1) to a horizontal sand mill and sand mill for 20 minutes to obtain a uniformly dispersed slurry;

[0102] (3) Spray dry the slurry obtained in step (2), setting the feed rate to 1.0 L / hr and the drying temperature to 160℃ to obtain ultrafine powder (particle size D). 50 (430nm);

[0103] (4) Weigh 24g of γ-alumina produced by gas-phase method (particle size D) 50 (50-80nm), and place it together with the ultrafine powder obtained in step (3) in a three-dimensional mixer, and mix for 10 minutes to obtain the calcination precursor;

[0104] (5) The calcination precursor prepared in step (4) is placed in a fluidized bed calcination furnace and heated to 1200°C at a heating rate of 10°C / min. The temperature is maintained at this temperature for 120 min. After cooling to room temperature in the fluidized bed calcination furnace, the sample is taken out to obtain α-alumina powder.

[0105] Comparative Example 2

[0106] This comparative example provides a method for preparing α-alumina powder, which may specifically include the following steps:

[0107] (1) Weigh 200g of aluminum hydroxide (particle size D) 50 Add 1.726μm) to a mixed solution consisting of 400g pure water and 100g anhydrous ethanol. While stirring, slowly add 100g of C powder. After all the materials have been added, transfer the resulting mixture to a high-speed shear emulsifier and emulsify and disperse it at 4000rpm for 30min to obtain a mixed slurry.

[0108] (2) Add the mixed slurry obtained in step (1) to a horizontal sand mill and sand mill for 20 minutes to obtain a uniformly dispersed slurry;

[0109] (3) Spray dry the slurry obtained in step (2), setting the feed rate to 1.5 L / hr and the drying temperature to 160℃ to obtain ultrafine powder (particle size D). 50 :355nm);

[0110] (4) The ultrafine powder prepared in step (3) is placed directly into a fluidized bed calcining furnace and heated to 1200°C at a heating rate of 15°C / min. The temperature is then maintained at this temperature for 120 min. After cooling to room temperature in the fluidized bed calcining furnace, the sample is taken out to obtain α-alumina powder.

[0111] The performance of the α-alumina powders obtained in Examples 1-5 and Comparative Examples 1-2 was characterized, and the results are shown in Table 1.

[0112] Table 1. Properties of α-alumina powders obtained in Examples 1-5 and Comparative Examples 1-2

[0113]

[0114] As shown in Table 1, the α-alumina powder prepared by the method provided in the embodiments of this disclosure not only has a high α-conversion rate, but also a particle size D 100 500nm or less, with no large particles present.

[0115] Figure 3 shows a microstructure of the α-alumina powder provided according to Example 1 of this disclosure. As can be seen from Figure 3, the prepared α-alumina powder has a regular particle morphology and good dispersibility.

[0116] Figure 4 shows the X-ray diffraction (XRD) pattern of the α-alumina powder prepared according to Example 1 of this disclosure. The pattern in Figure 4 shows that all diffraction peaks correspond to α-alumina, indicating that the prepared α-alumina powder is pure α-phase alumina.

[0117] Compared with related technologies, the technical solutions provided in this disclosure have the following advantages:

[0118] Adding steric hindrance agents to alumina precursors facilitates the formation of steric hindrance during the mixing (including emulsification and dispersion) of raw materials such as alumina precursors, effectively isolating the distance between alumina precursor particles and inhibiting particle agglomeration. Sand milling ensures the dispersibility and uniformity of solid particles during mixing and weight reduction. Adding grain-inducing agents to ultrafine powders can induce the formation of ultrafine α-alumina powder from the alumina precursors and lower the conversion temperature. Therefore, it is possible to improve the α-conversion rate of α-alumina while simultaneously enhancing its dispersion stability.

[0119] Furthermore, one or more technical solutions in the embodiments of this disclosure have at least the following technical effects or advantages:

[0120] In some embodiments of this disclosure, raw materials such as alumina precursors are first mixed. By adding a steric hindrance agent to the alumina precursors, steric hindrance is formed during the mixing (emulsification, dispersion) process, effectively increasing the distance between alumina precursor particles and thus inhibiting particle agglomeration. After milling, the dispersibility and uniformity of the raw material particles are further ensured. After processing including mixing and milling, the powder particles with a particle size D in the ultrafine slurry are obtained. 50 ≤400nm; then, a grain inducing agent is added to the ultrafine powder after spray drying. After the ultrafine powder and the grain inducing agent are mixed evenly, they are placed in a fluidized bed calcination furnace for rapid calcination. The calcination temperature can be set to 1100℃~1200℃, which is about 100℃ lower than the traditional calcination temperature of α-alumina powder.

[0121] The α-alumina powder prepared in the embodiments of this disclosure has the characteristics of high hardness, small particle size and narrow distribution. The high hardness of the α-alumina powder ensures a high material removal rate during polishing, while the uniform and fine particles can effectively avoid quality problems such as scratches and pitted surfaces, making it particularly suitable for chemical mechanical polishing of hard materials.

[0122] The above are merely specific embodiments of this disclosure, enabling those skilled in the art to understand or implement this disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing α-alumina powder, comprising: The alumina precursor, steric hindrance agent and solvent are mixed to obtain a mixed slurry; The mixed slurry is then milled to obtain an ultrafine slurry; The ultrafine slurry was spray-dried to obtain ultrafine powder; The ultrafine powder and the grain inducer are mixed to obtain a calcination precursor; as well as The calcination precursor was calcined under set calcination conditions to obtain α-alumina powder.

2. The method according to claim 1, wherein, The alumina precursor includes at least one of boehmite and aluminum hydroxide; and / or, The mass of the alumina precursor is 20% to 32% of the total mass of the mixed slurry.

3. The method according to claim 2, wherein, The mass of the alumina precursor is 20% to 30% of the total mass of the mixed slurry.

4. The method according to claim 2, wherein, The particle size D of the alumina precursor 50 ≤2.0μm.

5. The method according to claim 1, wherein, The steric hindrance includes solvent-based steric hindrance and solid-type steric hindrance.

6. The method according to claim 5, wherein, The solvent-based steric hindrance includes anhydrous ethanol.

7. The method according to claim 5 or 6, wherein, The solid steric hindrance includes at least one of carbon powder and white sugar.

8. The method according to claim 5, wherein, The mass of the solvent-based steric hindrance is 5% to 11% of the total mass of the mixed slurry; and / or, The mass of the solid steric hindrance is 10% to 20% of the total mass of the mixed slurry.

9. The method according to claim 1, wherein, The ball-to-material ratio of the sand mill is (3~5):1; and / or, The grinding time is 20 min to 40 min; and / or, The particle size D of the powder particles in the ultrafine slurry 50 ≤0.4μm.

10. The method according to claim 1, wherein, The feed rate for the spray dryer is 0.5 L / hr to 1.5 L / hr; and / or, The drying temperature of the spray drying is 140℃~180℃.

11. The method according to claim 1, wherein, The grain-inducing agent includes: vapor-phase nano-γ-alumina; The particle size of the vapor-phase nano-γ-alumina is 50 nm; and / or, The mass of the vapor-phase nano-γ-alumina is 3% to 10% of the total mass of the calcined precursor.

12. The method according to claim 1, wherein, The set roasting conditions include at least one of the following: The heating rate of the calcination is 10℃ / min to 15℃ / min; The final temperature of the roasting is 1100℃~1200℃; The roasting holding time is 60 min to 120 min.

13. An α-alumina powder prepared by the method according to any one of claims 1 to 12, satisfying at least one of the following properties: Particle size D 50 The range is 100nm to 300nm; Particle size D 100 ≤500nm; α conversion rate ≥96%.

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