Preparation method of spherical aluminum nitride granulation powder

Abstract

The invention relates to the technical field of aluminum nitride powder, provides a preparation method of spherical aluminum nitride granulated powder, and solves the problems that the existing spherical aluminum nitride granulated powder is easy to sink and damage and is easy to hydrolyze. Comprising the following steps: 1) stirring and mixing slurry A and slurry B for 2-6 hours to form slurry C; and 2) carrying out spray granulation on the slurry C to obtain the spherical aluminum nitride granulation powder, wherein the preparation process of the slurry A comprises the following steps: weighing modified AlN powder, a sintering aid, a dispersing agent and an organic solvent, sequentially adding into a ball milling tank, and carrying out wet ball milling for 4-8 hours to obtain the slurry A; a preparation process of the slurry B comprises the following steps: adding a binder, a plasticizer and granulation powder spheroidization molding resin into an organic solvent, and stirring and mixing for 8-16 hours to obtain the slurry B. The preparation method comprises the following steps: adding the binder, the plasticizer and the granulation powder spheroidization molding resin into the organic solvent;

Description

Technical Field

[0001] The invention relates to the technical field of aluminum nitride powder, and in particular to a method for preparing spherical aluminum nitride granulated powder. Background Art

[0002] Aluminum nitride ceramics have excellent properties such as high thermal conductivity, low dielectric constant, high insulation and matching the thermal expansion coefficient of silicon. They can be used as ideal ceramic heat dissipation substrates and packaging materials, and are widely used in high-end fields such as integrated circuits, automobiles, new energy and military industry.

[0003] The main forming methods of aluminum nitride ceramics include dry pressing, isostatic pressing, injection molding and tape casting. Among them, dry pressing and isostatic pressing have been widely used in the preparation of some aluminum nitride ceramic structural parts with simple geometric shapes due to their simple forming methods and low costs. The aluminum nitride powder used for dry pressing and isostatic pressing needs to be granulated to form large-particle powder with certain fluidity and filling properties. Therefore, the shape of the granulated powder has an important influence on the consistency and uniformity of ceramic molding and the quality of aluminum nitride ceramics after sintering. Among them, spherical granulated powder has the best fluidity and filling properties, and is particularly suitable for application in dry pressing and isostatic pressing processes. Therefore, for aluminum nitride ceramics using dry pressing and isostatic pressing processes, preparing spherical aluminum nitride granulated powder is the key to obtaining high-quality aluminum nitride ceramics.

[0004] At present, in the process of preparing aluminum nitride granulated powder, in order to have better molding characteristics when the granulated powder is pressed, it is usually necessary to add a certain amount of plasticizer to plasticize the binder polyvinyl butyral. However, due to the unreasonable ratio of powder slurry, poor matching of binder and plasticizer, and insufficient slurry consistency caused by poor dispersion effect, the droplets of slurry will be non-spherical when sprayed, and the granulated powder will be irregular non-spherical granulated powder such as strip, ellipse and concave apple after drying. In addition, the atomization drying conditions are not set reasonably, such as the atomizer speed is too fast, resulting in too much fine powder in the granulated powder; the drying temperature is too high, and the drying speed is too fast, resulting in the granulated powder to have concave and damaged morphology, so that it is impossible to obtain highly spherical aluminum nitride granulated powder.

[0005] Chinese patent application No. 202211017792.4 discloses an aluminum nitride powder and a preparation method thereof, wherein the aluminum nitride powder has a hexagonal, lamellar structure, an average particle size of 5-30 μm, and a thickness of 0.5-3 μm. The aluminum nitride powder has a unique hexagonal lamellar structure, a large original crystal grain size, and a regular shape. It can be used as a filler, toughening agent, etc. for polishing materials and high thermal conductivity materials. It is significantly different from the application scenarios of existing aluminum nitride products and can enrich the product structure and application range of aluminum nitride. However, the aluminum nitride powder is prone to morphologies such as depressions and breakages, making it impossible to obtain highly spherical aluminum nitride granulated powder.

[0006] Chinese patent application No. 201811120192.4 discloses a method for preparing high-purity, spherical nano-aluminum nitride particles, comprising the following steps: (1) weighing Al 2 O 3 (1) preparing a nano-aluminum nitride particle containing a trace amount of carbon by heating the nano-aluminum nitride particles to a temperature of 1000-1000 °C at a rate of 0.1-5 °C / min and then heating the nano-aluminum nitride particles to a temperature of 1000-1000 °C at a rate of 1-20 °C / min and then heating the nano-aluminum nitride particles to a temperature of 1000-1000 °C ... 2 The carbon is removed in the atmosphere to obtain high-purity, spherical nano-aluminum nitride particles. The raw materials of the application are widely available, the equipment and process are simple, the cost is low, and it is particularly suitable for industrial production. The prepared AlN powder has the advantages of high purity, narrow particle size distribution range, and high specific surface area. However, the aluminum nitride particles are easily hydrolyzed, which brings great difficulties to the transportation and storage of aluminum nitride particles.

[0007] In view of the above problems, the present invention provides a method for preparing spherical aluminum nitride granulated powder from the perspective of improving the sphericity of aluminum nitride granulated powder, which can effectively improve the preparation quality of spherical aluminum nitride granulated powder. Summary of the invention

[0008] Therefore, in view of the above problems, the present invention provides a method for preparing spherical aluminum nitride granulated powder to solve the problems that the existing spherical aluminum nitride granulated powder is prone to depression and breakage, and is easily hydrolyzed.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] A method for preparing spherical aluminum nitride granulated powder comprises the following steps:

[0011] S1. Weigh 50-80 wt% of slurry A and 20-50 wt% of slurry B, and stir and mix the slurry A and slurry B for 2-6 hours to form slurry C;

[0012] S2, spray granulating the slurry C to obtain the spherical aluminum nitride granulated powder;

[0013] Wherein, the preparation process of the slurry A is:

[0014] Weigh 40-50wt% of modified AlN powder, 2-5wt% of sintering aid, 0.1-0.5wt% of dispersant, and 30-50wt% of organic solvent, add them into a ball mill in sequence, and use a drum ball mill for wet milling for 4-8h, using alumina balls as the ball milling medium, to obtain the slurry A;

[0015] The preparation process of the slurry B is as follows:

[0016] Weigh 5-15wt% of a binder, 0.5-5wt% of a plasticizer, 5-15wt% of a granulation powder spheroidizing resin, and 60-80wt% of an organic solvent, add the binder, plasticizer, and granulation powder spheroidizing resin into the organic solvent, and stir and mix for 8-16h to obtain the slurry B;

[0017] The process of the modification treatment is:

[0018] I. Weigh 90-95 parts by weight of aluminum nitride powder, 2-5 parts by weight of palmitic acid, and 100-150 parts by weight of anhydrous ethanol, mix them evenly, perform ultrasonic treatment for 2-4 hours, and let stand to obtain a first mixture;

[0019] II. Add 0.5-2 parts by weight of Tween 80 to the first mixture obtained in step I, raise the temperature to 50-60° C., stir for 2-4 hours, filter and take out the filter powder, wash the filter powder with anhydrous ethanol for 3-5 times, and vacuum dry to complete the modification treatment.

[0020] Furthermore, the granulation powder spheroidization molding resin is: one or a mixture of several of acrylic acid polyacetal, polyethylene glycol, and polyvinyl alcohol in any proportion.

[0021] Furthermore, the spray granulation is as follows: the slurry C is transported to an atomizer at a speed of 1 to 20 kg / h by a peristaltic pump for atomization, a nitrogen atmosphere is maintained in the atomization chamber, the atomizer speed is 2000 to 5000 rpm, the dry air inlet temperature of the granulation tower is 140 to 250°C, and the air outlet temperature is 90 to 110°C.

[0022] Further, the sintering aid is Y2 O 3 Powder.

[0023] Furthermore, the dispersant is castor oil.

[0024] Furthermore, the organic solvent is anhydrous ethanol.

[0025] Furthermore, the binder is polyvinyl butyral.

[0026] Furthermore, the plasticizer is dibutyl phthalate.

[0027] Furthermore, the vacuum drying is carried out in a vacuum atmosphere furnace at a temperature of 50-60°C.

[0028] By adopting the above technical solution, the beneficial effects of the present invention are:

[0029] 1. Palmitic acid and Tween 80 were used to modify aluminum nitride powder. The chain structure of palmitic acid enables it to be tightly coated on the surface of AlN particles, forming a dense barrier and improving the hydrolysis resistance of AlN powder. As a non-ionic surfactant, Tween 80 mainly plays a role of physical adsorption and dispersion stability in the modification process. Since the molecular structure of Tween 80 contains hydrocarbon chains (hydrophobic groups) and polyethylene glycol long chains (hydrophilic groups), during the modification process, the hydrocarbon chain ends of Tween 80 will extend into the interior of AlN particles, while the polyethylene glycol long chain ends will extend into the water phase, forming a hydration layer. This hydration layer can isolate a latex particle (here it can be understood as AlN particles) from other latex particles, thereby inhibiting the demulsification of the emulsion. At the same time, Tween 80 can also improve the wettability, dispersibility and suspension of AlN powder in water, making the modified AlN powder more stable in water and less prone to hydrolysis.

[0030] 2. The present invention can reduce the deformation effect of the plasticizer on the binder by adding a spherical molding resin, and effectively improve the sphericity of the granulated powder.

[0031] 3. The aluminum nitride granulated powder prepared by the present invention has an average particle size ranging from tens of microns to more than one hundred microns, has a high degree of sphericity, and the particle size distribution range of the granulated powder is narrow.

[0032] 4. The granulated powder prepared by the present invention has good sphericity, so that the powder has good fluidity and filling properties, and is more suitable for dry pressing and isostatic pressing processes to prepare aluminum nitride ceramics with high density and high dimensional accuracy.

[0033] 5. The aluminum nitride granulated powder prepared by the present invention has a controllable average particle size (D50) in the range of 20 to 200 μm and a narrow particle size distribution range, and has high sphericity. This granulated powder can be directly degreased and sintered to prepare aluminum nitride filler powder with the required particle size and high sphericity, which has a high filling rate and high thermal conductivity.

[0034] 6. The present invention controls the particle size of the droplets after atomization by adjusting the atomizer rotation speed, thereby obtaining granulated powders with different particle sizes; and controls the drying speed of the droplets by adjusting the drying temperature, thereby obtaining dry granulated powder with a high spherical shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a detection diagram of spherical aluminum nitride granulated powder in Example 1 of the present invention;

[0036] Figure 2 is a detection diagram of spherical aluminum nitride granulated powder in Example 2 of the present invention;

[0037] Figure 3 This is a detection diagram of the spherical aluminum nitride granulated powder in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0038] Example 1

[0039] A method for preparing spherical aluminum nitride granulated powder comprises the following steps:

[0040] (1) Modification of AlN powder

[0041] I. Weigh 90 parts by weight of aluminum nitride powder, 2 parts by weight of palmitic acid, and 100 parts by weight of anhydrous ethanol, mix them evenly, perform ultrasonic treatment for 2 hours, and let them stand to obtain a first mixture;

[0042] II. Add 1 part by weight of Tween 80 to the first mixture obtained in step I, raise the temperature to 60° C., stir for 2 hours, filter and take the filter powder, wash the filter powder with anhydrous ethanol for 3 times, and vacuum dry it in a vacuum atmosphere furnace at a temperature of 60° C. to complete the modification treatment;

[0043] (2) Preparation of slurry A

[0044] Weigh 50wt% of the modified AlN powder and 2.5wt% of Y 2 O 3 The powder, 0.5wt% of castor oil and 47wt% of anhydrous ethanol are sequentially added into a ball mill, and wet-milled for 8h using a drum ball mill with alumina balls as the milling medium to obtain the slurry A;

[0045] (3) Preparation of slurry B

[0046] Weigh 10 wt % of polyvinyl butyral, 2 wt % of dibutyl phthalate, 8 wt % of acrylic acid polyacetal, and 80 wt % of anhydrous ethanol, add the polyvinyl butyral, dibutyl phthalate, and acrylic acid polyacetal into the anhydrous ethanol, and stir and mix for 8 hours to obtain the slurry B;

[0047] (4) Weighing 80 wt% of slurry A and 20 wt% of slurry B, stirring and mixing the slurry A and slurry B for 4 h to form slurry C;

[0048] (5) The slurry C is subjected to spray granulation, and the spray granulation is as follows: the slurry C is transported to an atomizer by a peristaltic pump at a speed of 10 kg / h for atomization, a nitrogen atmosphere is maintained in the atomization chamber, the atomizer speed is 3000 rpm, the dry air inlet temperature of the granulation tower is 200° C., and the air outlet temperature is 100° C., to obtain the spherical aluminum nitride granulated powder.

[0049] refer to Figure 1 The spherical aluminum nitride granulated powder prepared in this embodiment was tested. The sphericity of the granulated powder was good, the sphericity was 0.9, and the bulk density was 1.0 g / cm 3 .

[0050] Example 2

[0051] A method for preparing spherical aluminum nitride granulated powder comprises the following steps:

[0052] (1) Modification of AlN powder

[0053] I. Weigh 95 parts by weight of aluminum nitride powder, 5 parts by weight of palmitic acid, and 150 parts by weight of anhydrous ethanol, mix them evenly, perform ultrasonic treatment for 4 hours, and let them stand to obtain a first mixture;

[0054] II. Add 2 parts by weight of Tween 80 to the first mixture obtained in step I, raise the temperature to 60° C., stir for 4 hours, filter and take the filter powder, wash the filter powder with anhydrous ethanol for 3 times, and vacuum dry it in a vacuum atmosphere furnace at a temperature of 60° C. to complete the modification treatment;

[0055] S2. Preparation of slurry A

[0056] Weigh 50wt% of the modified AlN powder and 3wt% of Y 2 O 3 The powder, 1wt% of castor oil and 46wt% of anhydrous ethanol are sequentially added into a ball mill, and wet-milled for 8h using a drum ball mill with alumina balls as the milling medium to obtain the slurry A;

[0057] S3. Preparation of slurry B

[0058] Weigh 5 wt % of polyvinyl butyral, 5 wt % of dibutyl phthalate, 10 wt % of polyethylene glycol, and 80 wt % of anhydrous ethanol, add the polyvinyl butyral, dibutyl phthalate, and polyethylene glycol into the anhydrous ethanol, and stir and mix for 8 hours to obtain the slurry B;

[0059] S4, weighing 80 wt% of slurry A and 20 wt% of slurry B, stirring and mixing the slurry A and slurry B for 4 hours to form slurry C;

[0060] S5. The slurry C is subjected to spray granulation. The spray granulation is as follows: the slurry C is transported to an atomizer at a speed of 10 kg / h by a peristaltic pump for atomization. A nitrogen atmosphere is maintained in the atomization chamber. The atomizer speed is 3000 rpm. The dry air inlet temperature of the granulation tower is 200° C., and the air outlet temperature is 100° C., to obtain the spherical aluminum nitride granulated powder.

[0061] refer to Figure 2 The spherical aluminum nitride granulated powder prepared in this embodiment was tested, and the sphericity of the granulated powder was good, the sphericity was 0.85, and the bulk density was 0.95 g / cm 3 .

[0062] Comparative Example 1

[0063] The difference from Example 1 is that in step (3), no granulation powder is added to spheroidize the molding resin, namely, acrylic polyacetal. Other technical solutions are the same as those in Example 1.

[0064] refer to Figure 3 The spherical aluminum nitride granulated powder prepared in this embodiment was tested and found to be severely concave and damaged in shape, and the granulation morphology effect was poor.

[0065] Although the present invention has been specifically shown and described in conjunction with the preferred embodiments, it should be understood by those skilled in the art that various changes may be made to the present invention in form and details without departing from the spirit and scope of the present invention as defined by the appended claims, all of which are within the scope of protection of the present invention.

Claims

1. A method for preparing spherical aluminum nitride granulated powder, characterized in that: The following steps are involved: S1. Weigh 50-80 wt% of slurry A and 20-50 wt% of slurry B, and stir and mix the slurry A and slurry B for 2-6 hours to form slurry C; S2, spray granulating the slurry C to obtain the spherical aluminum nitride granulated powder; Wherein, the preparation process of the slurry A is: Weigh 40-50wt% of modified AlN powder, 2-5wt% of sintering aid, 0.1-0.5wt% of dispersant, and 30-50wt% of organic solvent, add them into a ball mill in sequence, and use a drum ball mill for wet milling for 4-8h, using alumina balls as the ball milling medium, to obtain the slurry A; The preparation process of the slurry B is as follows: Weigh 5-15wt% of a binder, 0.5-5wt% of a plasticizer, 5-15wt% of a granulation powder spheroidizing resin, and 60-80wt% of an organic solvent, add the binder, plasticizer, and granulation powder spheroidizing resin into the organic solvent, and stir and mix for 8-16h to obtain the slurry B; The process of the modification treatment is: I. Weigh 90-95 parts by weight of aluminum nitride powder, 2-5 parts by weight of palmitic acid, and 100-150 parts by weight of anhydrous ethanol, mix them evenly, perform ultrasonic treatment for 2-4 hours, and let stand to obtain a first mixture; II. Add 0.5-2 parts by weight of Tween 80 to the first mixture obtained in step I, raise the temperature to 50-60° C., stir for 2-4 hours, filter and take out the filter powder, wash the filter powder with anhydrous ethanol for 3-5 times, and vacuum dry to complete the modification treatment.

2. The method for preparing spherical aluminum nitride granulated powder according to claim 1, characterized in that: The granulation powder spheroidization molding resin is one or a mixture of several of acrylic acid polyacetal, polyethylene glycol and polyvinyl alcohol in any proportion.

3. The method for preparing spherical aluminum nitride granulated powder according to claim 1, characterized in that: The spray granulation is as follows: the slurry C is transported to an atomizer at a speed of 1 to 20 kg / h by a peristaltic pump for atomization, a nitrogen atmosphere is maintained in the atomization chamber, the atomizer speed is 2000 to 5000 rpm, the dry air inlet temperature of the granulation tower is 140 to 250° C., and the air outlet temperature is 90 to 110° C.

4. The method for preparing spherical aluminum nitride granulated powder according to claim 1, characterized in that: The sintering aid is Y2O3 powder.

5. The method for preparing spherical aluminum nitride granulated powder according to claim 1, characterized in that: The dispersant is castor oil.

6. The method for preparing spherical aluminum nitride granulated powder according to claim 1, characterized in that: The organic solvent is anhydrous ethanol.

7. The method for preparing spherical aluminum nitride granulated powder according to claim 1, characterized in that: The binder is polyvinyl butyral.

8. The method for preparing spherical aluminum nitride granulated powder according to claim 1, characterized in that: The plasticizer is dibutyl phthalate.

9. The method for preparing spherical aluminum nitride granulated powder according to claim 1, characterized in that: The vacuum drying is carried out in a vacuum atmosphere furnace at a temperature of 50-60°C.

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