Alpha-type aluminum oxide, preparation method thereof and polishing powder
Through the chemical reaction of sodium bicarbonate and Bayer sodium aluminate solution in the preparation process of alumina, combined with calcination and washing steps, high-performance α-type alumina polishing powder was successfully prepared, solving the problem of high preparation cost in the prior art and achieving efficient and uniform polishing effect.
Patent Information
- Application Number
- CN202411784639.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-06
- Publication Date
- 2025-03-14
AI Technical Summary
The prior art is difficult to efficiently prepare high-performance alpha-type alumina polishing powder, resulting in high production costs and limiting its large-scale production and application.
The sodium bicarbonate solution was chemically reacted with the Bayer process sodium aluminate solution to obtain a seed slurry and mixed with the Bayer process sodium aluminate solution for decomposition reaction to obtain aluminum hydroxide with a set particle size. The first calcination, washing and the second calcination are then performed to obtain an alpha-type alumina of high alpha phase.
It has achieved the preparation of high α-phase, small and uniform α-type alumina, which is suitable for the precision polishing industry, and improves the quality and market competitiveness of the polishing surface.
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Figure CN119612562A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of aluminum oxide, and in particular to an alpha aluminum oxide and a preparation method and polishing powder thereof. Background Art
[0002] In the field of polishing, alumina polishing powder is widely used in vibration polishing (machine polishing, rolling polishing), manual polishing (grinding polishing) of artificial gemstones, zircon, glass, natural gemstones, jade, jadeite, agate, etc., as well as grinding and polishing of aluminum, copper, stainless steel, stone, glass, wall and floor tiles, metal surface polishing, polishing strips, polishing slurry, paint surface, acrylic, stainless steel mirror, non-ferrous metal, jade, marble, granite, crystal, optical glass, etc. due to its high hardness, small and uniform distribution of particles, strong grinding force, fast polishing, bright light, good mirror effect and other advantages. Its fine polishing alumina powder has a wide range of applications in precision polishing, ceramics, metal processing, refractory materials and other fields due to its unique physical and chemical properties, and is an indispensable polishing material in modern industry.
[0003] At present, the preparation technology of industrially produced α-phase ultrafine spherical alumina and flaky alumina is difficult and the production cost is high, which limits the large-scale production and application of high-performance fine polishing alumina powder. If the production process is further improved, the quality and output of fine polishing alumina powder can be improved and the production cost can be reduced, which will help improve its market competitiveness and promote market growth. Summary of the invention
[0004] The present application provides an α-type aluminum oxide and a preparation method thereof, and polishing powder to solve the following technical problems: providing a new preparation method of α-type aluminum oxide.
[0005] In a first aspect, the present application provides a method for preparing α-type alumina, the method comprising:
[0006] The sodium bicarbonate solution is chemically reacted with the Bayer sodium aluminate solution to obtain a seed slurry;
[0007] The seed slurry is mixed with the Bayer sodium aluminate solution to perform a decomposition reaction to obtain aluminum hydroxide having a set particle size;
[0008] The aluminum hydroxide with a set particle size is first calcined to obtain an aluminum oxide intermediate;
[0009] washing the alumina intermediate;
[0010] The washed alumina intermediate is subjected to a second calcination at a set temperature to obtain α-type alumina.
[0011] Optionally, the set temperature is 1200°C to 1400°C.
[0012] Optionally, the set particle size is D50 < 2 μm.
[0013] Optionally, the process parameters of the decomposition reaction include: a seed ratio of ≤1.5% and a decomposition temperature of 60°C to 70°C.
[0014] Optionally, the alumina content of the Bayer process sodium aluminate solution is 160 g / L to 180 g / L.
[0015] Optionally, the process parameters of the first calcination include: a calcination temperature of 500° C. to 600° C., and a calcination time of 0.5 h to 1 h.
[0016] Optionally, the washing includes: acid washing and water washing; wherein,
[0017] The end point pH of the pickling is 6 to 7; and / or,
[0018] The water washing temperature is 60°C to 80°C.
[0019] Optionally, the α-type alumina meets the following indicators: D50 is <2 μm, (D90-D10) / D50 is <2, and α phase is >95%.
[0020] In a second aspect, the present application provides an α-type alumina, which is prepared by any method described in the first aspect.
[0021] In a third aspect, the present application provides a polishing powder, wherein the raw material of the polishing powder includes the α-type alumina as described in any one of the second aspects.
[0022] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:
[0023] The preparation method of the α-type alumina provided in an embodiment of the present application comprises: chemically reacting a sodium bicarbonate solution with a Bayer sodium aluminate solution to obtain a seed slurry; mixing the seed slurry with the Bayer sodium aluminate solution to carry out a decomposition reaction to obtain aluminum hydroxide with a set particle size; performing a first calcination on the aluminum hydroxide with the set particle size to obtain an alumina intermediate; washing the alumina intermediate; and performing a second calcination on the washed alumina intermediate at a set temperature to obtain α-type alumina. A seed slurry is prepared by using a sodium bicarbonate solution and a Bayer sodium aluminate solution. The seed slurry has a wide source of raw materials and low cost, and can be grafted with the Bayer process for producing alumina. The seed slurry, as a crystal seed, can promote the decomposition reaction of the Bayer sodium aluminate solution, thereby obtaining aluminum hydroxide with a set particle size, fine particle size, concentrated distribution, and good polishing effect. The aluminum hydroxide with the set particle size is subjected to a first calcination, and the specific surface area of the product of the first calcination can be adjusted, thereby facilitating subsequent washing and impurity removal. The alumina intermediate is washed to remove impurities carried by the alumina intermediate, thereby improving the purity of the alumina intermediate, and then the alumina intermediate with high purity is subjected to a second calcination at a set temperature, which can be fully converted into high-α-phase α-type alumina, and the particle size of the α-type alumina is fine and uniform, so that the α-type alumina can be used as polishing powder in the precision polishing industry to achieve uniform polishing and improve the quality of the polished surface. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] 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.
[0025] 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.
[0026] Figure 1 A schematic diagram of a process for preparing α-alumina provided in an embodiment of the present application;
[0027] Figure 2 This is a scanning electron microscope image of an α-type aluminum oxide provided in an embodiment of the present application. DETAILED DESCRIPTION
[0028] 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.
[0029] 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.
[0030] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present specification, the terms "including", "comprising", etc. refer to "including but not limited to". In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of the associated objects, indicating that there may be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A, B can be singular or plural. In this article, "at least one" refers to one or more, and "plural" refers to 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 singular or plural items. For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc or abc, where a, b, c can be single or plural, respectively.
[0031] 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.
[0032] In a first aspect, the present application provides a method for preparing α-alumina. Figure 1 A schematic diagram of a process for preparing α-alumina provided in the embodiment of the present application; see Figure 1 , the method comprising:
[0033] S1, chemically reacting a sodium bicarbonate solution with a Bayer process sodium aluminate solution to obtain a seed slurry;
[0034] In some embodiments, the Bayer process sodium aluminate solution has an alumina content of 160 g / L to 180 g / L.
[0035] In the embodiment of the present application, the seed slurry is prepared by sodium bicarbonate solution and Bayer sodium aluminate solution. The raw material source of the slurry is wide and the cost is low. It can be grafted with the Bayer process for producing alumina. The alumina (AO) content of the Bayer sodium aluminate solution can be 160g / L to 180g / L, and it can be directly grafted with the sodium aluminate solution in the Bayer process for producing alumina. The Al(OH) generated by the above chemical reaction 3 Aluminum hydroxide precipitate is the so-called "seed", and a large amount of aluminum hydroxide precipitate is suspended in the solution to form a seed slurry. Exemplarily, the alumina content of the Bayer process sodium aluminate solution can be 160g / L, 163g / L, 165g / L, 168g / L, 170g / L, 173g / L, 175g / L, 178g / L, 180g / L, etc.
[0036] S2, mixing the seed slurry with the Bayer process sodium aluminate solution to perform a decomposition reaction to obtain aluminum hydroxide with a set particle size;
[0037] In some embodiments, the process parameters of the decomposition reaction include: a seed ratio of ≤1.5% and a decomposition temperature of 60°C to 70°C.
[0038] In some embodiments, the set particle size is D50 < 2 μm.
[0039] In the embodiment of the present application, the aluminum hydroxide seeds in the seed slurry can induce the Bayer sodium aluminate solution to undergo a decomposition reaction. Since the aluminum hydroxide seeds provide crystallization cores, the aluminate ions in the sodium aluminate solution will be precipitated and transformed into aluminum hydroxide, thereby obtaining aluminum hydroxide with a set particle size with fine particle size and concentrated distribution and good polishing effect. The weight of aluminum hydroxide in the seed slurry / the weight of aluminum hydroxide that the Bayer sodium aluminate solution is completely decomposed into in theory is equal to the seed ratio. The seed ratio can be ≤1.5%, and the particle size of the product of the decomposition reaction can be regulated. If the seed ratio is higher than 1.5%, the product of the decomposition reaction may be fine and agglomerated. The decomposition temperature can be 60°C to 70°C, which can achieve a high decomposition rate of the Bayer sodium aluminate solution, and the aluminum hydroxide with a set particle size has a good morphology. Exemplarily, the seed ratio can be 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, 1.0%, etc., and the decomposition temperature can be 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, etc. Generally speaking, the slurry containing aluminum hydroxide with a set particle size obtained by the above decomposition reaction needs to be separated from the solid and liquid, washed, dried and dispersed, and then subjected to a first calcination; wherein the washing temperature can be 60°C to 80°C.
[0040] S3, calcining the aluminum hydroxide with a set particle size to obtain an aluminum oxide intermediate;
[0041] In some embodiments, the process parameters of the first calcination include: a calcination temperature of 500° C. to 600° C., and a calcination time of 0.5 h to 1 h.
[0042] In the embodiment of the present application, aluminum hydroxide with a set particle size is subjected to the first calcination, and the specific surface area of the product of the first calcination can be regulated, so as to facilitate subsequent washing and impurity removal. The temperature of the first calcination can be 500°C to 600°C, and an aluminum oxide intermediate with a specific surface area can be obtained, which can effectively remove surface impurities in subsequent washing. The time for synergistic action with the temperature of the first calcination can be 0.5h to 1h. Exemplarily, the temperature of the first calcination can be 500°C, 520°C, 540°C, 560°C, 580°C, 600°C, etc., and the time of the first calcination can be 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h, etc.
[0043] S4, washing the alumina intermediate;
[0044] In some embodiments, the washing comprises: acid washing and water washing; wherein,
[0045] The end point pH of the pickling is 6 to 7; and / or,
[0046] The water washing temperature is 60°C to 80°C.
[0047] In the embodiment of the present application, the alumina intermediate is washed to remove impurities carried by the alumina intermediate, thereby improving the purity of the alumina intermediate and avoiding the influence of impurities on the subsequent second calcination of the alumina intermediate. The end point pH of the pickling can be 6 to 7, and the pickling can be fully utilized to effectively remove the alkaline substances in the slurry, reduce the impurity content of the alumina intermediate, and ensure that other impurities are not introduced; the pickling can be washed with an acid solution or by passing an acidic gas. One of the pickling methods includes: slurrying the alumina intermediate with hot water to obtain a slurry to be washed with a solid content of 200 to 500 g / L; passing CO into the slurry to be washed 2 Stir and wash. Water washing further removes surface impurities of the alumina intermediate after acid washing. The water washing temperature can be 60°C to 80°C, which can achieve a good washing effect. Exemplarily, the end point pH of the acid washing can be 6, 6.2, 6.4, 6.6, 6.8, 7, etc.; the water washing temperature can be 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, etc. Generally speaking, the above washing is followed by drying and breaking up, and then a subsequent second calcination is carried out.
[0048] S5. At a set temperature, the washed alumina intermediate is subjected to a second calcination to obtain α-type alumina.
[0049] In some embodiments, the set temperature is 1200°C to 1400°C.
[0050] In the embodiment of the present application, the above-mentioned washed alumina intermediate has high purity, and then the alumina intermediate with high purity is subjected to a second calcination at a set temperature, which can be fully converted into high α-phase α-type alumina, and the particle size of the α-type alumina is fine and uniform, so that it can be used as polishing powder in the precision polishing industry to achieve uniform polishing and improve the quality of the polished surface. The set temperature can be 1200℃~1400℃, which can achieve the conversion of high α-phase α-type alumina, and the particle size of the α-type alumina is fine and uniform. Exemplarily, the set temperature can be 1200℃, 1230℃, 1250℃, 1280℃, 1300℃, 1330℃, 1350℃, 1380℃, 1400℃, etc.; the time of synergistic effect with the temperature of the second calcination can be 1h~8h.
[0051] In some embodiments, the α-type alumina meets the following indicators: D50 is <2 μm, (D90-D10) / D50 is <2, and the α phase is >95%.
[0052] In the embodiments of the present application, the α-alumina prepared by the above method meets the indicators: D50 is <2μm, (D90-D10) / D50 is <2, α phase is >95%, the particles are small and evenly distributed, high α phase, and high morphology uniformity. It can be used in the precision polishing industry to achieve uniform polishing and improve the quality of the polished surface.
[0053] In summary, the preparation method of α-alumina provided in this application has the following advantages:
[0054] 1. Preparation of seed slurry
[0055] The seed slurry is obtained by chemically reacting sodium bicarbonate solution with Bayer sodium aluminate solution. The advantage of this method is that the raw material source is wide and the cost is low. Since the Bayer process is a common method in alumina production, using Bayer sodium aluminate solution as one of the raw materials can be well combined with the existing alumina production process.
[0056] 2. Decomposition reaction to obtain aluminum hydroxide
[0057] The seed slurry is mixed with the Bayer sodium aluminate solution to undergo a decomposition reaction to generate aluminum hydroxide with a set particle size. The aluminum hydroxide in the seed slurry acts as a seed crystal, which can induce the aluminate ions in the sodium aluminate solution to decompose and generate aluminum hydroxide. The aluminum hydroxide obtained by this method has a fine particle size and a concentrated distribution. Because the presence of the seed crystal provides a core for the crystallization of aluminum hydroxide, aluminum hydroxide can grow in an orderly manner on the surface of the seed crystal, thereby obtaining aluminum hydroxide with a good particle size and distribution, which is crucial for the subsequent preparation of high-quality polishing powder, because aluminum hydroxide with a fine particle size and a concentrated distribution is easier to obtain α-type alumina with excellent performance after calcination.
[0058] 3. The first calcination obtains an alumina intermediate
[0059] The specific surface area of the product can be adjusted by the first calcination. The control of the specific surface area is critical for the subsequent washing and impurity removal steps. The appropriate specific surface area can make it easier to remove impurities.
[0060] 4. Washing of alumina intermediates
[0061] Washing the alumina intermediate can remove the impurities it carries. During the previous reaction and calcination process, some impurity ions, such as etc., may be attached to the alumina intermediate. Washing can improve the purity of the alumina intermediate, laying the foundation for the subsequent high-purity α-alumina.
[0062] 5. Second calcination to obtain α-type alumina
[0063] The washed alumina intermediate is subjected to a second calcination at a set temperature to obtain α-alumina. The second calcination at a specific temperature can fully convert the alumina intermediate into high-α-phase α-alumina. High-α-phase alumina has the advantages of high hardness and good chemical stability, and is the basis of excellent polishing powder. Moreover, the α-alumina obtained by this method has a fine and uniform particle size, which is very suitable for the precision polishing industry as polishing powder. The fine and uniform particle size can achieve uniform polishing during the polishing process, avoiding polishing surface defects caused by uneven polishing powder particle size, thereby improving the quality of the polishing surface.
[0064] In a second aspect, the present application provides an α-type alumina, which is prepared by any method described in the first aspect.
[0065] The α-type alumina is realized based on the preparation method of the α-type alumina mentioned above. The specific steps of the preparation method of the α-type alumina can refer to the above-mentioned embodiment. Since the α-type alumina adopts part or all of the technical solutions of the above-mentioned embodiment, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be described one by one here.
[0066] In a third aspect, the present application provides a polishing powder, wherein the raw material of the polishing powder includes the α-type alumina as described in any one of the second aspects.
[0067] In the embodiment of the present application, α-alumina is an important polishing material, the main component of which is α-Al calcined at high temperature. 2 O 3 Powder. Performance characteristics: high hardness, good chemical stability and strong thermal stability. The narrower the particle size distribution of α-alumina, the higher the polishing efficiency. Therefore, α-alumina with D50 <2μm, (D90-D10) / D50 <2, and α phase >95% has a stable crystal phase, small particles and uniform distribution, which helps to achieve uniform polishing and improve the quality of the polished surface.
[0068] 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 the unrecorded specific conditions in the following examples are usually measured according to national standards. If there is no corresponding national standard, then carry out according to general international standards, normal conditions or according to the conditions recommended by the manufacturer.
[0069] Example 1
[0070] A method for preparing alpha-type alumina, comprising:
[0071] chemically reacting a supersaturated sodium bicarbonate solution with a Bayer sodium aluminate solution to obtain a seed slurry;
[0072] The seed slurry is mixed with a Bayer sodium aluminate solution to perform a decomposition reaction to obtain aluminum hydroxide with a set particle size; wherein the AO of the Bayer sodium aluminate solution is 165 g / L, and the process parameters of the decomposition reaction include: a seed ratio of 1.0%, a decomposition temperature of 65° C., and a decomposition time of 40 hours; and the set particle size is D50=1.3 μm;
[0073] The aluminum hydroxide of the set particle size is first calcined to obtain an aluminum oxide intermediate; wherein the first calcination temperature is 500° C. and the first calcination time is 1 hour;
[0074] The alumina intermediate is washed; the washing includes: acid washing and water washing in sequence; wherein the end point pH of the acid washing is 6.5, the acid washing time is 30 minutes; the water washing temperature is 70°C;
[0075] At a set temperature, the washed alumina intermediate is subjected to a second calcination to obtain α-type alumina; wherein the set temperature is 1300° C. and the second calcination time is 4 hours.
[0076] Example 2
[0077] A method for preparing alpha-type alumina, comprising:
[0078] chemically reacting a supersaturated sodium bicarbonate solution with a Bayer sodium aluminate solution to obtain a seed slurry;
[0079] The seed slurry is mixed with a Bayer sodium aluminate solution to perform a decomposition reaction to obtain aluminum hydroxide with a set particle size; wherein the AO of the Bayer sodium aluminate solution is 165 g / L, and the process parameters of the decomposition reaction include: a seed ratio of 0.8%, a decomposition temperature of 65° C., and a decomposition time of 40 hours; and the set particle size is D50=1.5 μm;
[0080] The aluminum hydroxide of the set particle size is first calcined to obtain an aluminum oxide intermediate; wherein the temperature of the first calcination is 550° C. and the time of the first calcination is 1 hour;
[0081] The alumina intermediate is washed; the washing includes: acid washing and water washing in sequence; wherein the end point pH of the acid washing is 6.5, the acid washing time is 30 minutes; the water washing temperature is 70°C;
[0082] At a set temperature, the washed alumina intermediate is subjected to a second calcination to obtain α-type alumina; wherein the set temperature is 1200° C. and the second calcination time is 8 hours.
[0083] Example 3
[0084] A method for preparing alpha-type alumina, comprising:
[0085] chemically reacting a supersaturated sodium bicarbonate solution with a Bayer sodium aluminate solution to obtain a seed slurry;
[0086] The seed slurry is mixed with a Bayer sodium aluminate solution to perform a decomposition reaction to obtain aluminum hydroxide with a set particle size; wherein the AO of the Bayer sodium aluminate solution is 170 g / L, and the process parameters of the decomposition reaction include: a seed ratio of 1.0%, a decomposition temperature of 67° C., and a decomposition time of 40 hours; and the set particle size is D50=1.6 μm;
[0087] The aluminum hydroxide of the set particle size is first calcined to obtain an aluminum oxide intermediate; wherein the temperature of the first calcination is 600° C., and the time of the first calcination is 0.5 h;
[0088] The alumina intermediate is washed; the washing includes: acid washing and water washing in sequence; wherein the end point pH of the acid washing is 6, the acid washing time is 30 minutes; the water washing temperature is 70°C;
[0089] At a set temperature, the washed alumina intermediate is subjected to a second calcination to obtain α-type alumina; wherein the set temperature is 1400° C. and the time of the second calcination is 1 hour.
[0090] Example 4
[0091] A method for preparing alpha-type alumina, comprising:
[0092] chemically reacting a supersaturated sodium bicarbonate solution with a Bayer sodium aluminate solution to obtain a seed slurry;
[0093] The seed slurry is mixed with a Bayer sodium aluminate solution to perform a decomposition reaction to obtain aluminum hydroxide with a set particle size; wherein the AO of the Bayer sodium aluminate solution is 170 g / L, and the process parameters of the decomposition reaction include: a seed ratio of 1.5%, a decomposition temperature of 60° C., and a decomposition time of 40 hours; and the set particle size is D50=1.1 μm;
[0094] The aluminum hydroxide of the set particle size is first calcined to obtain an aluminum oxide intermediate; wherein the first calcination temperature is 500° C. and the first calcination time is 1 hour;
[0095] The alumina intermediate is washed; the washing includes: acid washing and water washing in sequence; wherein the end point pH of the acid washing is 7, the acid washing time is 30 minutes; the water washing temperature is 70°C;
[0096] At a set temperature, the washed alumina intermediate is subjected to a second calcination to obtain α-type alumina; wherein the set temperature is 1350° C. and the second calcination time is 2 hours.
[0097] Example 5
[0098] A method for preparing alpha-type alumina, comprising:
[0099] chemically reacting a supersaturated sodium bicarbonate solution with a Bayer sodium aluminate solution to obtain a seed slurry;
[0100] The seed slurry is mixed with a Bayer sodium aluminate solution to perform a decomposition reaction to obtain aluminum hydroxide with a set particle size; wherein the AO of the Bayer sodium aluminate solution is 170 g / L, and the process parameters of the decomposition reaction include: a seed ratio of 0.5%, a decomposition temperature of 70° C., and a decomposition time of 40 hours; and the set particle size is D50=1.3 μm;
[0101] The aluminum hydroxide of the set particle size is first calcined to obtain an aluminum oxide intermediate; wherein the first calcination temperature is 500° C. and the first calcination time is 1 hour;
[0102] The alumina intermediate is washed; the washing includes: acid washing and water washing in sequence; wherein the end point pH of the acid washing is 6, the acid washing time is 30 minutes; the water washing temperature is 70°C;
[0103] At a set temperature, the washed alumina intermediate is subjected to a second calcination to obtain α-type alumina; wherein the set temperature is 1250° C. and the second calcination time is 6 hours.
[0104] Comparative Example 1
[0105] A method for preparing alpha-type alumina, comprising:
[0106] chemically reacting a supersaturated sodium bicarbonate solution with a Bayer sodium aluminate solution to obtain a seed slurry;
[0107] The seed slurry is mixed with a Bayer sodium aluminate solution to perform a decomposition reaction to obtain aluminum hydroxide with a set particle size; wherein the AO of the Bayer sodium aluminate solution is 165 g / L, and the process parameters of the decomposition reaction include: a seed ratio of 1.0%, a decomposition temperature of 65° C., and a decomposition time of 40 hours; and the set particle size is D50=1.3 μm;
[0108] The aluminum hydroxide of the set particle size is first calcined to obtain an aluminum oxide intermediate; wherein the first calcination temperature is 500° C. and the first calcination time is 1 hour;
[0109] The alumina intermediate is washed; the washing includes: acid washing and water washing in sequence; wherein the end point pH of the acid washing is 6.5, the acid washing time is 30 minutes; the water washing temperature is 70°C;
[0110] At a set temperature, the washed alumina intermediate is subjected to a second calcination to obtain α-type alumina; wherein the set temperature is 1500° C. and the time of the second calcination is 2 hours.
[0111] Comparative Example 2
[0112] A method for preparing alpha-type alumina, comprising:
[0113] chemically reacting a supersaturated sodium bicarbonate solution with a Bayer sodium aluminate solution to obtain a seed slurry;
[0114] The seed slurry is mixed with a Bayer sodium aluminate solution to perform a decomposition reaction to obtain aluminum hydroxide with a set particle size; wherein the AO of the Bayer sodium aluminate solution is 170 g / L, and the process parameters of the decomposition reaction include: a seed ratio of 1.0%, a decomposition temperature of 70° C., and a decomposition time of 40 hours; and the set particle size is D50=1.3 μm;
[0115] The aluminum hydroxide of the set particle size is first calcined to obtain an aluminum oxide intermediate; wherein the first calcination temperature is 500° C. and the first calcination time is 1 hour;
[0116] The alumina intermediate is washed; the washing includes: acid washing and water washing in sequence; wherein the end point pH of the acid washing is 6, the acid washing time is 30 minutes; the water washing temperature is 70°C;
[0117] At a set temperature, the washed alumina intermediate is subjected to a second calcination to obtain α-type alumina; wherein the set temperature is 1150° C. and the second calcination time is 8 hours.
[0118] The α-alumina prepared in Examples 1 to 5 and Comparative Examples 1 to 2 were subjected to index tests, and the test results are shown in Table 1.
[0119] Table 1 Index of α-type alumina
[0120]
[0121] As shown in Table 1, the α-alumina prepared by the preparation method of the α-alumina provided in the embodiment of the present application meets the following indicators: D50 is <2 μm, (D90-D10) / D50 is <2, α phase is >95%, the particles are small and evenly distributed, the α phase and the morphology are highly uniform, and the Na content of the α-alumina is 0.1%. 2 O content is less than 0.03wt%, indicating that the Na 2 O impurity content is low. Therefore, the α-alumina can be used as polishing powder in the precision polishing industry to achieve uniform polishing and improve the quality of the polished surface. Figure 2 For a scanning electron microscope image of an α-type aluminum oxide provided in the embodiment of this application, please see Figure 2, indicating that the particles of α-alumina are small and evenly distributed. However, in Comparative Example 1, the set temperature is too high, and the particle size of α-alumina is high and the distribution is wide; in Comparative Example 2, the set temperature is too low, and the α-Al 2 O 3 The conversion rate is low.
[0122] One or more technical solutions in the embodiments of the present application also have at least the following technical effects or advantages:
[0123] (1) In the present embodiment, ultrafine aluminum hydroxide precursor powder is obtained by the Bayer process sodium aluminate solution seed separation method, and then calcined at low temperature, washed to remove impurities, and finally calcined at high temperature to obtain ultrafine calcined α-alumina with uniform morphology;
[0124] (2) The α-alumina prepared in the embodiment of the present application has a D50 of <2 μm, a (D90-D10) / D50 of <2, an α phase of >95%, small and evenly distributed particles, a high α phase, and high morphology uniformity. It can be used in the precision polishing industry to achieve uniform polishing and improve the quality of the polished surface.
[0125] 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 scope consistent with the principles and novel features applied for herein.
Claims
1. A method for preparing α-alumina, the method comprising: The sodium bicarbonate solution is chemically reacted with the Bayer sodium aluminate solution to obtain a seed slurry; The seed slurry is mixed with the Bayer sodium aluminate solution to perform a decomposition reaction to obtain aluminum hydroxide having a set particle size; The aluminum hydroxide with a set particle size is first calcined to obtain an aluminum oxide intermediate; washing the alumina intermediate; The washed alumina intermediate is subjected to a second calcination at a set temperature to obtain α-type alumina.
2. The method according to claim 1, characterized in that The set temperature is 1200°C to 1400°C.
3. The method according to claim 1, characterized in that The set particle size is D50 < 2 μm.
4. The method according to claim 1 or 3, characterized in that: The process parameters of the decomposition reaction include: a seed ratio of ≤1.5% and a decomposition temperature of 60°C to 70°C.
5. The method according to claim 1, characterized in that: The alumina content of the Bayer process sodium aluminate solution is 160 g / L to 180 g / L.
6. The method according to claim 1, characterized in that The process parameters of the first calcination include: a calcination temperature of 500° C. to 600° C., and a calcination time of 0.5 h to 1 h.
7. The method according to claim 1, characterized in that The washing includes: acid washing and water washing; wherein, The end point pH of the pickling is 6 to 7; and / or, The water washing temperature is 60°C to 80°C.
8. The method according to claim 1, characterized in that: The α-type alumina meets the following indicators: D50 is <2 μm, (D90-D10) / D50 is <2, and α phase is >95%.
9. An α-alumina prepared by the method according to any one of claims 1 to 8. 10 . A polishing powder, wherein the raw material of the polishing powder comprises the α-alumina according to claim 9 .