Preparation method of single crystal alumina powder with high thermal conductivity
High thermal conductivity single-crystal alumina powder was prepared through steps such as ball milling, precipitation, additive treatment, and vacuum freeze drying. This solved the problem of insufficient thermal conductivity in existing technologies and enabled the preparation of low-cost, high-insulation, and high-thermal-conductivity alumina powder, which is suitable for fields such as electric heating tubes.
Patent Information
- Application Number
- CN202511295839.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-11
- Publication Date
- 2025-12-16
AI Technical Summary
Existing technologies make it difficult to prepare low-cost, high-insulation, and high-thermal-conductivity thermally conductive fillers. The thermal conductivity of α-alumina powder is not ideal, and the poor insulation of metallic aluminum powder cannot meet the requirements.
High thermal conductivity single-crystal alumina powder is prepared through steps such as ball milling, precipitation, additive treatment, rinsing and vacuum freeze-drying. Sodium fluoride and organosilicon oil are used as additives to improve fluidity and compact packing, and vacuum freeze-drying is combined to ensure purity and thermal conductivity.
High thermal conductivity single-crystal alumina powder has been manufactured, which is suitable for fields such as electric heating tubes and has broad application prospects. The thermal conductivity is significantly improved and the cost is low.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of inorganic non-metallic mineral powder preparation technology, and in particular to a method for preparing high thermal conductivity single-crystal alumina powder. Background Technology
[0002] Thermally conductive polymers, due to their excellent heat exchange properties, are widely used in many fields such as aerospace vehicles, electronic packaging, chemical heat exchangers, and LEDs. Improving the thermal conductivity of these materials is crucial. Currently, the simplest and most effective method for producing thermally conductive polymers is to add thermally conductive fillers.
[0003] Alpha-alumina possesses advantages such as thermal conductivity and insulation, making it suitable as a thermally conductive filler for preparing thermally conductive insulating adhesives, potting compounds, and other polymeric materials. Compared to other fillers, alpha-alumina's thermal conductivity is not ideal, but it generally meets the application requirements for fillers in fields such as thermally conductive interface materials, thermally conductive engineering polymers, and aluminum-based copper-clad laminates. Furthermore, due to its low price and wide availability, alumina is an economical and practical filler for high thermal conductivity insulating polymers.
[0004] Large single-crystal α-alumina powder has a thermal conductivity of 20–25 W / (m·K), but its production process is complex and its price is relatively high. Metallic aluminum powder, on the other hand, has a very high thermal conductivity, exceeding 220 W / (m·K), but its insulation properties are poor, failing to meet the requirements for thermally conductive fillers. Therefore, there is an urgent need to obtain low-cost, high-insulation, and high-thermal-conductivity thermally conductive fillers by improving their composition and processing.
[0005] Based on this, this application proposes an alumina powder with high thermal conductivity to solve the above problems. Summary of the Invention
[0006] In view of the above, it is necessary to provide a method for preparing high thermal conductivity single crystal alumina powder. The present invention produces high thermal conductivity single crystal alumina powder through the synergistic effect between the various steps.
[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0008] (1) Ball milling: Mix the α-alumina clinker processed by the tunnel kiln with water, stir evenly and place it in a ball mill for ball milling for 1-2 hours to obtain a slurry for later use;
[0009] (2) Sedimentation: Let the ball-milled slurry stand for sedimentation for 4-5 hours, take the lower layer of slurry obtained after sedimentation, put it into a dryer for drying treatment, and obtain alumina powder for later use;
[0010] (3) Additive treatment: Alumina powder is mixed with additives, and then the resulting mixture is melted in a crystallization furnace, cooled and solidified into a melt for later use;
[0011] (4) Rinsing: Add hydrochloric acid to the cooled melt and soak it at a temperature of 22-28℃ for 1-2 hours, and then rinse with deionized water;
[0012] (5) Crushing: The material obtained in step (4) is crushed and then dried to obtain high thermal conductivity single crystal alumina powder.
[0013] Furthermore, the mass ratio of the clinker α-alumina powder to water in step (1) is 1-2:5.
[0014] Furthermore, the drying in step (2) involves placing the slurry into a dryer and using hot air generated by burning natural gas to dry the slurry. The drying temperature is 180~200℃ and the time is 11-13h.
[0015] Furthermore, the grinding balls used in step (1) of the ball mill have a diameter of 1-3 mm.
[0016] Furthermore, the additive in step (3) is composed of sodium fluoride and organosilicon oil in a mass ratio of 1:1-2.
[0017] Furthermore, in step (3), the mass ratio of alumina powder to additives is 4:1-2.
[0018] Furthermore, the drying in step (5) is carried out under vacuum freeze drying at -20 to -10°C.
[0019] The present invention has at least the following beneficial effects:
[0020] 1. This invention provides a high thermal conductivity single-crystal alumina powder. Through the synergistic effect between various steps, high thermal conductivity single-crystal alumina powder can be manufactured. The resulting alumina powder can be used in fields such as electric heating tubes and has a very broad application prospect.
[0021] 2. This application develops a high thermal conductivity monocrystalline alumina powder. Using clinker processed in a tunnel kiln as the main raw material, it is first wet-milled with water, then precipitated and dried. Through this process, alumina powder with uniform particle size is obtained. Next, additives, including sodium fluoride and organosilicon oil, are added to the alumina powder. After adding the additives, the material is melted. During the melting process, the organosilicon oil improves fluidity and promotes the close arrangement of oxygen and aluminum atoms, thus forming a highly ordered crystal structure that allows for rapid heat transfer. Furthermore, after cooling and solidifying the melt, it is soaked in hydrochloric acid to remove excess additives, ensuring the purity of the alumina powder and guaranteeing its high thermal stability and corrosion resistance. In addition, this application uses vacuum freeze-drying in the subsequent drying process. Experiments have shown that the vacuum freeze-drying method of this application achieves significant improvements compared to conventional drying, resulting in a higher thermal conductivity in the obtained monocrystalline alumina powder. Detailed Implementation
[0022] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.
[0023] Unless otherwise stated, each feature disclosed in this specification (including any appended claims and abstract) is merely one example of a series of equivalent or similar features.
[0024] Example 1:
[0025] This embodiment provides a method for preparing high thermal conductivity single-crystal alumina powder, including the following steps:
[0026] (1) Ball milling: The α-alumina clinker processed by the tunnel kiln is mixed with water, stirred evenly and placed in a ball mill. The grinding balls with a diameter of 1 mm are used for ball milling for 1 hour to obtain a slurry for later use; the mass ratio of α-alumina powder to water in step (1) is 1:5.
[0027] (2) Sedimentation: The slurry after ball milling is allowed to settle for 4 hours. The lower layer of slurry obtained after sedimentation is taken and put into a dryer for drying to obtain alumina powder for later use. The drying in step (2) is to put the slurry into a dryer and use hot air generated by burning natural gas to dry the slurry. The drying temperature is 180℃ and the time is 11 hours.
[0028] (3) Additive treatment: Alumina powder and additive are mixed, and then the resulting mixture is melted in a crystallization furnace, cooled and solidified, and set aside; the additive in step (3) is composed of sodium fluoride and organosilicon oil in a mass ratio of 1:1; the mass ratio of alumina powder and additive in step (3) is 10:1.
[0029] (4) Rinsing: Add hydrochloric acid to the cooled melt and soak it at 22°C for 1 hour, and then rinse with deionized water;
[0030] (5) Crushing: The material obtained in step (4) is crushed and then dried to obtain high thermal conductivity single crystal alumina powder; the drying in step (5) is vacuum freeze drying at -20℃.
[0031] Example 2:
[0032] This embodiment provides a method for preparing high thermal conductivity single-crystal alumina powder, including the following steps:
[0033] (1) Ball milling: The α-alumina clinker processed by the tunnel kiln is mixed with water, stirred evenly and placed in a ball mill. The grinding balls with a diameter of 5 mm are used for ball milling for 1.5 hours to obtain a slurry for later use; the mass ratio of α-alumina powder to water in step (1) is 1:5.
[0034] (2) Sedimentation: The slurry after ball milling is allowed to settle for 4.5 hours. The lower layer of slurry obtained after sedimentation is taken and put into a dryer for drying to obtain alumina powder for later use. The drying in step (2) is to put the slurry into a dryer and use hot air generated by burning natural gas to dry the slurry. The drying temperature is 190℃ and the time is 12 hours.
[0035] (3) Additive treatment: Alumina powder and additive are mixed, and then the resulting mixture is melted in a crystallization furnace, cooled and solidified, and set aside; the additive in step (3) is composed of sodium fluoride and organosilicon oil in a mass ratio of 1:1; the mass ratio of alumina powder and additive in step (3) is 10:1.
[0036] (4) Rinsing: Add hydrochloric acid to the cooled melt and soak it at 25°C for 1.5 hours, and then rinse with deionized water;
[0037] (5) Crushing: The material obtained in step (4) is crushed and then dried to obtain high thermal conductivity single crystal alumina powder; the drying in step (5) is vacuum freeze drying at -15℃.
[0038] Example 3:
[0039] This embodiment provides a method for preparing high thermal conductivity single-crystal alumina powder, including the following steps:
[0040] (1) Ball milling: The α-alumina clinker processed by the tunnel kiln is mixed with water, stirred evenly and placed in a ball mill. The grinding balls with a diameter of 3 mm are used for ball milling for 2 hours to obtain a slurry for later use; the mass ratio of α-alumina powder to water in step (1) is 2:5.
[0041] (2) Sedimentation: The slurry after ball milling is allowed to settle for 5 hours. The lower layer of slurry obtained after sedimentation is taken and placed in a dryer for drying to obtain alumina powder for later use. The drying in step (2) is to put the slurry into a dryer and use hot air generated by burning natural gas to dry the slurry. The drying temperature is 200℃ and the time is 13 hours.
[0042] (3) Additive treatment: Alumina powder and additive are mixed, and then the resulting mixture is melted in a crystallization furnace, cooled and solidified, and set aside; the additive in step (3) is composed of sodium fluoride and organosilicon oil in a mass ratio of 1:2; the mass ratio of alumina powder and additive in step (3) is 5:1.
[0043] (4) Rinsing: Add hydrochloric acid to the cooled melt and soak it at 28°C for 2 hours, and then rinse with deionized water;
[0044] (5) Crushing: The material obtained in step (4) is crushed and then dried to obtain high thermal conductivity single crystal alumina powder; the drying in step (5) is vacuum freeze drying at -10℃.
[0045] Experimental example:
[0046] To illustrate the practical value of this application, the applicant compared the thermal conductivity of different groups of alumina powders, grouped as follows:
[0047] Group 1: Alumina powder prepared by the method described in Example 2;
[0048] Group 2: The ball milling process is dry milling, without adding water, and the other methods are the same as Group 1.
[0049] Group 3: Remove the additives, otherwise the method is the same as Group 1;
[0050] Group 4: Remove the silicone oil from the additives; otherwise, the process is the same as Group 1.
[0051] Group 5: Omit the rinsing step; all other steps are the same as Group 1.
[0052] Group 6: The drying in step (5) is done by using hot air at 100℃, and the other methods are the same as in Group 1.
[0053] The thermal conductivity of the alumina powders prepared by the above methods is compared, and the results are shown in Table 1:
[0054] Table 1 Comparison of thermal conductivity among groups
[0055]
[0056] As shown in Table 1, the alumina powder prepared using the method described in this application has high thermal conductivity. The process is simple and easy to operate, making it worthy of promotion. The second group, which changed from wet grinding to dry grinding, experienced a decrease in thermal conductivity, possibly due to significantly reduced uniformity of the alumina under dry grinding conditions. The third group removed additives, and the fourth group removed silicone oil, potentially resulting in insufficient material flowability during melting. Therefore, the packing density of these groups was lower than that of the first group, ultimately leading to a decrease in thermal conductivity. The sixth group, which only changed the drying method, saw a decrease in thermal conductivity from 32 W / (m·K) to 25 W / (m·K). This indicates that the low-temperature drying method described in this application can ensure the thermal conductivity of the alumina powder, and not all drying methods can achieve the same effect. Based on the comparison of thermal conductivity data, the drying method described in this application possesses unexpected technical advantages.
[0057] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.
Claims
1. A method for preparing high thermal conductivity single-crystal alumina powder, characterized in that, The method includes the following steps: (1) Ball milling: Mix the α-alumina clinker processed by the tunnel kiln with water, stir evenly and place it in a ball mill for ball milling for 1-2 hours to obtain a slurry for later use; (2) Sedimentation: Let the ball-milled slurry stand for sedimentation for 4-5 hours, take the lower layer of slurry obtained after sedimentation, put it into a dryer for drying treatment, and obtain alumina powder for later use; (3) Additive treatment: Alumina powder is mixed with additives, and then the resulting mixture is melted in a crystallization furnace, cooled and solidified into a melt for later use; (4) Rinsing: Add hydrochloric acid to the cooled melt and soak it at a temperature of 22-28℃ for 1-2 hours, and then rinse with deionized water; (5) Crushing: The material obtained in step (4) is crushed and then dried to obtain high thermal conductivity single crystal alumina powder.
2. The method according to claim 1, characterized in that, The mass ratio of α-alumina powder to water in step (1) is 1-2:
5.
3. The method according to claim 1, characterized in that, The drying process in step (2) involves placing the slurry into a dryer and using hot air generated by burning natural gas to dry the slurry. The drying temperature is 180~200℃ and the drying time is 11-13h.
4. The method according to claim 1, characterized in that, The grinding balls used in step (1) have a diameter of 1-3 mm.
5. The method according to claim 1, characterized in that, The additive in step (3) is composed of sodium fluoride and organosilicon oil in a mass ratio of 1:1-2.
6. The method according to claim 1, characterized in that, In step (3), the mass ratio of alumina powder to additives is 10:1-2.
7. The method according to claim 1, characterized in that, The drying in step (5) is carried out under vacuum freeze drying at -20 to -10°C.