Rare earth doped alpha-alumina powder and preparation method thereof
The preparation of rare earth doped α-alumina powder by hydrothermal method has solved the problem of single crystal growth control of α-alumina powder in the prior art, and achieved powder preparation with high thermal conductivity and good sphericality, which is suitable for ceramics Special uses such as support films and thermal fillers.
Patent Information
- Application Number
- CN202411551059.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-01
- Publication Date
- 2025-02-07
AI Technical Summary
The prior art is difficult to effectively control the single crystal growth of α-alumina powder, resulting in a low thermal conductivity and the introduced mineralizers destroy the crystal structure.
The hydrothermal method is used to mix aluminum hydroxide, water and rare earth nitrates, adjust the pH value and carry out hydrothermal reaction, and then clean and spray-dry to prepare rare earth doped α-alumina powder.
A single crystal α-alumina powder with an average particle size of more than 40 μm was successfully obtained, with good spherical shape and high thermal conductivity, and the preparation method is simple, environmentally friendly and low cost.
Smart Images
Figure CN119390100A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of powder materials, and in particular relates to rare earth doped alpha-alumina powder and a preparation method thereof. Background Art
[0002] α-Alumina powder has the characteristics of good physical and chemical stability, high filling ratio after coupling modification, low price and wide source. It is an economical and applicable filler for high thermal conductivity insulating polymers. As a thermal conductive filler, it can be widely used in organic matrices such as rubber, plastic, and silicone grease. In order to increase the filling rate of α-Alumina powder in organic matrices, people achieve this by regulating the morphology and physical properties of α-Alumina powder. Among them, filling with large single crystal α-Alumina powder is one of the solutions.
[0003] Since α-alumina is a hexagonal crystal system, single crystal growth is difficult to control, and abnormal growth of all-directional grains is common. In order to control the morphology of the powder, people use composite mineralizers combined with high-temperature calcination to control the growth direction of the crystals and achieve the preparation of larger single crystal α-alumina powders (~20μm). However, this method introduces a large amount of mineralizers, which destroys the crystal structure of α-alumina, resulting in low thermal conductivity.
[0004] The hydrothermal method is a method of preparing materials by physical and chemical reactions under high temperature and high pressure. During the synthesis process, the mixture is placed in a closed reactor and an appropriate amount of solvent is added. Then, by controlling the reaction temperature and time, the phases in the mixture react and gradually form single crystals. However, how to control crystal growth to obtain larger α-alumina single crystal powders remains a problem. Summary of the invention
[0005] In view of this, the object of the present invention is to provide a rare earth doped α-alumina powder and a preparation method thereof. The rare earth doped α-alumina powder prepared by the preparation method is a single crystal powder with an average particle size of more than 40 μm.
[0006] In order to achieve the above object, the present invention provides the following technical solutions:
[0007] The present invention also provides a method for preparing rare earth-doped α-alumina powder, comprising the following steps:
[0008] Mixing aluminum hydroxide, water and rare earth nitrate, and adjusting the pH value of the obtained mixed solution to 10-12 to obtain a slurry;
[0009] The slurry is subjected to a hydrothermal reaction, and the obtained rare earth doped α-alumina slurry is washed to a pH value of 7 to 7.5, and then spray-dried to obtain rare earth doped α-alumina powder.
[0010] Preferably, the average particle size of the aluminum hydroxide is 65 to 80 μm, and the sodium content is 0.25 to 0.35 wt%.
[0011] Preferably, the mass of the water is 20 to 100% of the mass of the aluminum hydroxide.
[0012] Preferably, the rare earth nitrate is one or more of lanthanide rare earth nitrates; the mass of the rare earth nitrate is 0.01 to 0.5% of the mass of the aluminum hydroxide.
[0013] Preferably, the mixing time is 2 to 5 hours.
[0014] Preferably, the pH regulator used to adjust the pH value of the obtained mixed solution is sodium hydroxide solution or potassium hydroxide solution.
[0015] Preferably, the temperature of the hydrothermal reaction is 400-500° C.; the pressure of the hydrothermal reaction is 20-35 MPa.
[0016] Preferably, the holding time of the hydrothermal reaction is 18 to 72 hours.
[0017] Preferably, the inlet temperature of the spray drying is 300-350°C, and the outlet temperature is 100-150°C.
[0018] The present invention also provides rare earth doped α-alumina powder prepared by the preparation method described in the above technical solution, which is a single crystal powder with an average particle size of 40 to 150 μm and a sodium content of 0.01 to 0.02 wt%.
[0019] The invention provides a method for preparing rare earth doped alpha-alumina powder, comprising the following steps: mixing aluminum hydroxide, water and rare earth nitrate, adjusting the pH value of the obtained mixed solution to 10-12, and obtaining slurry; subjecting the slurry to a hydrothermal reaction, washing the obtained rare earth doped alpha-alumina slurry to a pH value of 7-7.5, and spray drying to obtain rare earth doped alpha-alumina powder.
[0020] The present invention uses aluminum hydroxide as a raw material and rare earth nitrate as an additive, and adopts a hydrothermal method to prepare rare earth-doped α-alumina powder. In the hydrothermal reaction, aluminum hydroxide is converted into boehmite and then into α-alumina; the doping of rare earth ions promotes the growth of α-alumina grains, thereby obtaining a powder with larger crystals and good sphericity. The rare earth-doped α-alumina powder prepared by the present invention is a single crystal powder with an average particle size of 40 to 150 μm and a sodium content of 0.01 to 0.02 wt%. The preparation method provided by the present invention is simple, environmentally friendly, low-cost, and convenient for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 This is a SEM image of the α-alumina single crystal powder prepared in Example 1;
[0022] Figure 2 This is a SEM image of the α-alumina single crystal powder prepared in Example 3;
[0023] Figure 3 This is the SEM image of the α-alumina single crystal powder prepared in Comparative Example 1. DETAILED DESCRIPTION
[0024] The present invention provides a method for preparing rare earth doped α-alumina powder, comprising the following steps:
[0025] Mixing aluminum hydroxide, water and rare earth nitrate, and adjusting the pH value of the obtained mixed solution to 10-12 to obtain a slurry;
[0026] The slurry is subjected to a hydrothermal reaction, and the obtained rare earth doped α-alumina slurry is washed to a pH value of 7 to 7.5, and then spray-dried to obtain rare earth doped α-alumina powder.
[0027] Unless otherwise specified, the present invention has no special requirements on the sources of the raw materials used, and commercially available products known to those skilled in the art may be used.
[0028] The invention mixes aluminum hydroxide, water and rare earth nitrate, and adjusts the pH value of the obtained mixed solution to 10-12 to obtain slurry.
[0029] As an embodiment, the sodium content of the aluminum hydroxide is 0.25-0.35 wt %, and in a specific embodiment, it is 0.3 wt %, and the average particle size is 65-80 μm, and in a specific embodiment, it is 75 μm.
[0030] As an embodiment, the mass of the water is 20-100% of the mass of the aluminum hydroxide, and in specific embodiments, it is 20%, 30%, 40%, 80% or 100%. In order to prepare the slurry, the mass of the water should not be less than 20%, otherwise it is difficult to form the slurry.
[0031] As an embodiment, the rare earth nitrate is one or more of the lanthanide rare earth nitrates, and in specific embodiments, it is lanthanum nitrate, or lanthanum nitrate and samarium nitrate, or dysprosium nitrate and cerium nitrate, or samarium nitrate, or lutetium nitrate and ytterbium nitrate; the mass of the rare earth nitrate is 0.01-0.5% of the mass of the aluminum hydroxide, and in specific embodiments, it is 0.01%, 0.1%, 0.15%, 0.3% or 0.5%. The addition of rare earth nitrates helps the growth of crystals, and the larger the amount added, the larger the crystals, but excessive addition will affect the purity of the α-alumina powder.
[0032] As an embodiment, the mixing time is 2 to 5 hours, and in a specific embodiment, it is 2 hours or 5 hours.
[0033] As an embodiment, the pH adjuster used to adjust the pH value of the obtained mixed solution is a sodium hydroxide solution or a potassium hydroxide solution; the mass concentration of the sodium hydroxide solution or the potassium hydroxide solution is independently 10%.
[0034] As an embodiment, the pH value of the obtained mixed solution is adjusted to 10, 11, 11.5 or 12.
[0035] After obtaining the slurry, the present invention performs a hydrothermal reaction on the slurry, washes the obtained rare earth doped α-alumina slurry to a pH value of 7 to 7.5, and then spray-dries it to obtain rare earth doped α-alumina powder.
[0036] As an embodiment, the temperature of the hydrothermal reaction is 400-500°C, and in specific embodiments, it is 400°C, 430°C, 450°C or 500°C; the pressure of the hydrothermal reaction is 20-35MPa, and in specific embodiments, it is 20MPa, 23MPa, 30MPa or 35MPa; the insulation time of the hydrothermal reaction is 18-72h, and in specific embodiments, it is 18h, 24h, 36h, 48h or 72h.
[0037] As an implementation manner, the cleaning agent used for cleaning is pure water.
[0038] As an embodiment, the obtained rare earth-doped α-alumina slurry is washed to a pH value of 7 to 7.5, and in specific embodiments, the pH value is 7, 7.2, 7.3 or 7.5.
[0039] As an embodiment, the inlet temperature of the spray drying is 300-350°C, and in a specific embodiment, it is 300°C or 350°C, and the outlet temperature is 100-150°C, and in a specific embodiment, it is 100°C or 150°C.
[0040] The present invention also provides rare earth doped α-alumina powder prepared by the preparation method described in the above technical solution, which is a single crystal powder with an average particle size of 40 to 150 μm and a sodium content of 0.01 to 0.02 wt%.
[0041] As an embodiment, the average particle size of the rare earth doped α-alumina powder is 42 μm, 58 μm, 75 μm, 106 μm or 150 μm, and the sodium content is 0.01 wt% or 0.02 wt%.
[0042] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, but they should not be construed as limiting the protection scope of the present invention.
[0043] Example 1
[0044] 1000 g of aluminum hydroxide (average particle size of 75 μm, sodium content of 0.30 wt%), 200 g of water and 0.1 g of lanthanum nitrate were mixed for 2 h, and a 10 wt% potassium hydroxide solution was added to adjust the pH value of the resulting mixture to 10 to obtain a slurry;
[0045] The slurry is placed in a hydrothermal reactor for hydrothermal reaction at a temperature of 400° C., a pressure of 20 MPa, and a heat preservation time of 18 h to obtain rare earth-doped α-alumina slurry;
[0046] The rare earth doped α-alumina slurry was washed with pure water until its pH value reached 7, and then spray dried at an inlet temperature of 300° C. and an outlet temperature of 100° C. to obtain rare earth doped α-alumina powder.
[0047] Figure 1 This is a SEM image of the α-alumina single crystal powder prepared in Example 1. Figure 1 It can be seen that the rare earth-doped α-alumina powder prepared in Example 1 has an average particle size of 42 μm.
[0048] The sodium content of the α-alumina single crystal powder prepared in Example 1 is 0.02 wt %.
[0049] Example 2
[0050] 1000 g of aluminum hydroxide (average particle size of 75 μm, sodium content of 0.30 wt%), 1000 g of water, 3 g of lanthanum nitrate and 2 g of samarium nitrate were mixed for 5 h, and a 10 wt% sodium hydroxide solution was added to adjust the pH value of the resulting mixture to 12 to obtain a slurry;
[0051] The slurry is placed in a hydrothermal reactor for hydrothermal treatment at a temperature of 500° C., a pressure of 35 MPa, and a holding time of 72 h to obtain a rare earth-doped α-alumina slurry;
[0052] The rare earth doped α-alumina slurry was washed with pure water until the pH value thereof reached 7.5, and then spray dried at an inlet temperature of 350° C. and an outlet temperature of 150° C. to obtain rare earth doped α-alumina powder.
[0053] The rare earth-doped α-alumina powder prepared in Example 2 has an average particle size of 150 μm.
[0054] The sodium content of the α-alumina single crystal powder prepared in Example 2 is 0.01 wt %.
[0055] Example 3
[0056] 1000 g of aluminum hydroxide (average particle size of 75 μm, sodium content of 0.30 wt%), 400 g of water, 1 g of dysprosium nitrate and 2 g of cerium nitrate were mixed for 5 h, and a 10 wt% sodium hydroxide solution was added to adjust the pH value of the resulting mixture to 11 to obtain a slurry;
[0057] The slurry is placed in a hydrothermal reactor for hydrothermal treatment at a temperature of 450° C., a pressure of 30 MPa, and a heat preservation time of 48 h to obtain a rare earth-doped α-alumina slurry;
[0058] The rare earth doped α-alumina slurry was washed with pure water until its pH value reached 7.2, and then spray dried at an inlet temperature of 350° C. and an outlet temperature of 150° C. to obtain rare earth doped α-alumina powder.
[0059] Figure 2 This is a SEM image of the α-alumina single crystal powder prepared in Example 3. Figure 2 It can be seen that the rare earth-doped α-alumina powder prepared in Example 3 has an average particle size of 106 μm.
[0060] The sodium content of the α-alumina single crystal powder prepared in Example 3 is 0.01 wt %.
[0061] Example 4
[0062] 1000 g of aluminum hydroxide (average particle size of 75 μm, sodium content of 0.30 wt%), 800 g of water and 1.5 g of samarium nitrate were mixed for 5 h, and a 10 wt% potassium hydroxide solution was added to adjust the pH value of the resulting mixture to 11.5 to obtain a slurry;
[0063] The slurry is placed in a hydrothermal reactor for hydrothermal treatment at a temperature of 430° C., a pressure of 23 MPa, and a heat preservation time of 24 h to obtain a rare earth-doped α-alumina slurry;
[0064] The rare earth doped α-alumina slurry was washed with pure water until its pH value reached 7, and then spray dried with an inlet temperature of 350° C. and an outlet temperature of 150° C. to obtain rare earth doped α-alumina powder.
[0065] The rare earth-doped α-alumina powder prepared in Example 4 has an average particle size of 75 μm.
[0066] The sodium content of the α-alumina single crystal powder prepared in Example 4 is 0.01 wt %.
[0067] Example 5
[0068] 1000 g of aluminum hydroxide (average particle size of 75 μm, sodium content of 0.30 wt%), 300 g of water, 0.5 g of lutetium nitrate and 0.5 g of ytterbium nitrate were mixed for 5 h, and a 10 wt% sodium hydroxide solution was added to adjust the pH value of the resulting mixture to 11 to obtain a slurry;
[0069] The slurry is placed in a hydrothermal reactor for hydrothermal treatment at a temperature of 400° C., a pressure of 20 MPa, and a holding time of 36 h to obtain a rare earth-doped α-alumina slurry;
[0070] The rare earth doped α-alumina slurry was washed with pure water until its pH value reached 7.3, and then spray dried with an inlet temperature of 300° C. and an outlet temperature of 100° C. to obtain rare earth doped α-alumina powder.
[0071] The rare earth-doped α-alumina powder prepared in Example 5 had an average particle size of 58 μm.
[0072] The sodium content of the α-alumina single crystal powder prepared in Example 5 is 0.02 wt %.
[0073] Comparative Example 1
[0074] 1000 g of aluminum hydroxide (average particle size of 75 μm, sodium content of 0.30 wt%) and 200 g of water were mixed for 2 h, and sodium hydroxide solution was added to adjust the pH value of the resulting mixture to 12 to obtain a slurry;
[0075] The slurry is placed in a hydrothermal reactor for hydrothermal treatment at a temperature of 400° C., a pressure of 20 MPa, and a holding time of 18 h to obtain α-alumina slurry;
[0076] The α-alumina slurry was washed with pure water until its pH value reached 7, and then spray-dried at an inlet temperature of 300° C. and an outlet temperature of 100° C. to obtain α-alumina powder.
[0077] Figure 3 This is a SEM image of the α-alumina single crystal powder prepared in Comparative Example 1. Figure 3 It can be seen that the α-alumina powder prepared in Comparative Example 1 has an average particle size of 18 μm.
[0078] The sodium content of the α-alumina single crystal powder prepared in Comparative Example 1 is 0.02 wt %.
[0079] Comparative Example 2
[0080] 1000 g of aluminum hydroxide (average particle size of 75 μm, sodium content of 0.30 wt%) and 1000 g of water were mixed for 5 h, and potassium hydroxide solution was added to adjust the pH value of the resulting mixture to 10 to obtain a slurry;
[0081] The slurry is placed in a hydrothermal reactor for hydrothermal treatment at a temperature of 500° C., a pressure of 35 MPa, and a holding time of 72 h to obtain α-alumina slurry;
[0082] The rare earth doped α-alumina slurry was washed with pure water until its pH value reached 7.5, and then spray dried with an inlet temperature of 350° C. and an outlet temperature of 150° C. to obtain α-alumina powder.
[0083] The α-alumina powder prepared in Comparative Example 2 had an average particle size of 25 μm.
[0084] The sodium content of the α-alumina single crystal powder prepared in Comparative Example 2 is 0.02 wt %.
[0085] It can be seen from the above embodiments that the preparation method provided by the present invention is simple, has low synthesis temperature and low cost, and the prepared rare earth-doped α-alumina powder can meet special uses such as ceramic support films, thermal conductive fillers, and high-end abrasives.
[0086] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention rather than all the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.
Claims
1. A method for preparing rare earth-doped α-alumina powder, characterized in that: The following steps are involved: Mixing aluminum hydroxide, water and rare earth nitrate, and adjusting the pH value of the obtained mixed solution to 10-12 to obtain a slurry; The slurry is subjected to a hydrothermal reaction, and the obtained rare earth doped α-alumina slurry is washed to a pH value of 7 to 7.5, and then spray-dried to obtain rare earth doped α-alumina powder.
2. The preparation method according to claim 1, characterized in that: The average particle size of the aluminum hydroxide is 65-80 μm, and the sodium content is 0.25-0.35 wt %.
3. The preparation method according to claim 1, characterized in that: The mass of the water is 20-100% of the mass of the aluminum hydroxide.
4. The preparation method according to claim 1, characterized in that: The rare earth nitrate is one or more of lanthanide rare earth nitrates; the mass of the rare earth nitrate is 0.01-0.5% of the mass of the aluminum hydroxide.
5. The preparation method according to claim 1, characterized in that: The mixing time is 2 to 5 hours.
6. The preparation method according to claim 1, characterized in that: The pH value regulator used to adjust the pH value of the obtained mixed solution is sodium hydroxide solution or potassium hydroxide solution.
7. The preparation method according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 400-500° C.; the pressure of the hydrothermal reaction is 20-35 MPa.
8. The preparation method according to claim 1 or 7, characterized in that: The heat preservation time of the hydrothermal reaction is 18 to 72 hours.
9. The preparation method according to claim 1, characterized in that: The inlet temperature of the spray drying is 300-350°C, and the outlet temperature is 100-150°C.
10. The rare earth doped α-alumina powder prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The invention is a single crystal powder with an average particle size of 40 to 150 μm and a sodium content of 0.01 to 0.02 wt %.