A method for preparing spherical aluminum oxide-zinc oxide composite powder

Abstract

The present invention provides a method for preparing a spherical aluminum oxide-zinc oxide composite powder. The method comprises heating a zinc source, an aluminum source, an alkali source, and distilled water in a reactor to obtain an aluminum oxide-zinc oxide precursor slurry. The aluminum oxide-zinc oxide precursor slurry is then uniformly mixed with an yttrium salt and a peptizing agent, followed by spray granulation to obtain a spherical aluminum oxide-zinc oxide precursor. The precursor is then melt-calcined in a methane fluoride furnace under air or oxygen conditions to obtain a spherical aluminum oxide-zinc oxide powder. The spherical aluminum oxide-zinc oxide prepared by the present invention has high sphericity, uniform size, a smooth surface, and is not easily broken, significantly improving the powder's packing and compatibility in polymer materials.

Description

Technical Field

[0001] The invention belongs to the field of inorganic non-metallic powder preparation, and particularly relates to a method for preparing spherical aluminum oxide-zinc oxide composite powder. Background Art

[0002] Zinc oxide is an important inorganic material with various crystal structures, including hexagonal wurtzite, cubic zinc blende, and sodium chloride octahedron. With a hardness of approximately 4.5, it is a relatively soft material with high breakdown voltage, excellent piezoelectric properties, good thermal stability, and thermal conductivity. Its room temperature thermal conductivity is approximately 30 W / (m·K), making it widely used as a thermally conductive filler in polymers.

[0003] Alumina is a highly hard inorganic compound with excellent electrical insulation and high thermal conductivity, with a thermal conductivity of approximately 36 W / (m·K). Alumina is not only a commonly used electrically insulating and thermally conductive particle, but also relatively affordable, making it widely used in thermally conductive materials. Alumina also has a high melting point and excellent high-temperature resistance, making it stable under high-temperature conditions. This has led to its widespread use as a thermally conductive filler in polymers.

[0004] In recent years, much research has been devoted to preparing inorganic composite materials with good dispersibility and excellent compatibility. Invention patent CN118027709A discloses a method for preparing an alumina filler and its use in a two-component organosilicon potting compound. This method involves mixing alumina and zinc oxide into an alcohol solution of a silane coupling agent, followed by ball milling to produce a zinc oxide-coated alumina powder. This is intended to enhance its compatibility in organosilicon polymer materials. However, the ball milling process does not allow the zinc oxide to be completely coated on the alumina surface, resulting in limited dispersibility and compatibility enhancement. Invention patent CN112876849A discloses a method for preparing a composite thermal conductive interface material, thermal conductive silicone grease. This method directly compounds aluminum oxide, zinc oxide and other powders to make the thermal conductive silicone grease have good electrical insulation and high-temperature stability. However, since the powders are simply compounded, there are gaps between the particles, and fine-particle aluminum oxide and fine-particle zinc oxide are easy to agglomerate and difficult to disperse in the polymer matrix material, resulting in poor compatibility between the polymer and the polymer. Summary of the Invention

[0005] Based on the problems described in the background technology, the purpose of the present invention is to provide a method for preparing spherical alumina-zinc oxide composite powder, thereby realizing the preparation of alumina-zinc oxide composite powder; the prepared spherical alumina-zinc oxide powder has high sphericity, a smooth surface, and no voids, and has good dispersibility and excellent compatibility in an organic matrix.

[0006] The present invention provides a method for preparing spherical aluminum oxide-zinc oxide composite powder, the specific formation process and principle of which are as follows:

[0007] (1) First, in a reactor, a zinc source and an alkali source react under high-temperature hydrothermal conditions to generate a zinc oxide precursor. Simultaneously, an aluminum source and an alkali source also react hydrothermally under the same conditions to generate an aluminum oxide precursor. Under the action of a peptizing agent, the aluminum oxide precursor is converted into aluminum sol, which is uniformly adsorbed on the surface of the zinc oxide precursor.

[0008] (2) Subsequently, the aluminum oxide-zinc oxide precursor slurry is spray granulated into spherical aluminum oxide-zinc oxide precursor particles. The spherical precursor is then subjected to a high-temperature sintering treatment in a muffle furnace under air or oxygen atmosphere to obtain the final spherical aluminum oxide-zinc oxide powder.

[0009] (3) During the high-temperature sintering process, the yttrium salt melts under high-temperature conditions to form a liquid substance with a strong adhesive effect, effectively preventing the breakage of the spherical aluminum oxide-zinc oxide particles, thereby maintaining good sphericity and ensuring the quality of the final product. Experimental results show that the present invention successfully prepares spherical aluminum oxide-zinc oxide composite powders with good sphericity and stability, verifying the feasibility and effectiveness of this method.

[0010] The present invention provides a method for preparing spherical aluminum oxide-zinc oxide, comprising the following steps:

[0011] (1) Preparation of spherical aluminum oxide-zinc oxide precursor: zinc source, aluminum source, alkali source and distilled water are transferred into a stainless steel reactor lined with polytetrafluoroethylene, heated at 300-500°C for reaction for 24-72 hours, and naturally cooled to room temperature to obtain aluminum oxide-zinc oxide precursor slurry, and the aluminum oxide-zinc oxide precursor slurry, yttrium salt and peptizing agent are placed in a spray dryer for granulation to obtain spherical aluminum oxide-zinc oxide precursor; the air inlet temperature of the spray dryer is 200-350°C, the fan frequency is 20-40 Hz, the needle-passing time is 1-5 seconds, and the peristaltic pump speed is 10-30 r / min;

[0012] (2) Preparation of spherical alumina-zinc oxide powder: The spherical alumina-zinc oxide precursor prepared in the above (1) is added to a crucible, and the crucible is placed in an atmosphere furnace and calcined in air or oxygen at a calcination temperature of 800-1300°C and a holding time of 1-12 hours. After the sintered body is naturally cooled to room temperature, it is placed in a planetary ball mill at a rotation speed of 100-300 r / min and ball milled for 5-90 minutes to obtain spherical alumina-zinc oxide powder.

[0013] In the step (1), the mass ratio of the zinc source, the aluminum source, the alkali source, the distilled water, the peptizing agent and the yttrium salt is 3-10:1-3:3-10:10-200:1-10:0.1-5.

[0014] In the step (1), the zinc source is one or more of zinc chloride, zinc sulfate, zinc nitrate, and zinc carbonate.

[0015] The aluminum source in step (1) is one or more of aluminum chloride, aluminum nitrate, aluminum sulfate, sodium aluminate, and potassium aluminate.

[0016] In the step (1), the alkali source is one or more of ammonia water, cyanuric chloride, melamine, urea, and imidourea.

[0017] The yttrium salt in step (1) is one or more of yttrium chloride, yttrium nitrate, and yttrium acetate.

[0018] In the step (1), the peptizing agent is one or more of acetic acid and citric acid.

[0019] In the step (2), the calcination is carried out in air or oxygen, and the calcination temperature is 800-1300°C.

[0020] The present invention has the following technical advantages:

[0021] (1) The present invention successfully prepares aluminum oxide-zinc oxide composite powders and realizes the sphericity of aluminum oxide-zinc oxide. The spherical aluminum oxide-zinc oxide is firmly bonded, has high sphericity and is not easily broken.

[0022] (2) The surface of the spherical aluminum oxide-zinc oxide powder prepared by the present invention is smooth and void-free, so that it has good dispersibility and compatibility, and significantly improves the filling performance and thermal conductivity of the spherical aluminum oxide-zinc oxide powder in the composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the SEM image of the spherical aluminum oxide-zinc oxide composite powder prepared in Example 1.

[0024] Figure 2 This is the SEM image of the product prepared in Comparative Example 1.

[0025] Figure 3 This is the SEM image of the product prepared in Comparative Example 2.

[0026] Figure 4 This is the SEM image of the product prepared in Comparative Example 3. DETAILED DESCRIPTION

[0027] The embodiments described below provide a detailed description of the above contents of the present invention, and in particular illustrate that, based on the principles of the present invention, several adjustments and improvements may be made, and these adjustments and improvements are also considered to be within the scope of protection of the embodiments of the present invention.

[0028] Example 1

[0029] (1) Preparation of spherical aluminum oxide-zinc oxide precursor: 30 g zinc chloride, 10 g aluminum chloride, 30 g ammonia water, and 100 g distilled water were transferred into a polytetrafluoroethylene-lined stainless steel reactor, heated at 300° C. for 24 h, and naturally cooled to room temperature to obtain an aluminum oxide-zinc oxide precursor slurry. The aluminum oxide-zinc oxide precursor slurry, 10 g acetic acid, and 1 g yttrium chloride were placed in a spray dryer for granulation to obtain a spherical aluminum oxide-zinc oxide precursor; the air inlet temperature of the spray dryer was 200° C., the fan frequency was 20 Hz, the needle passage time was 1 s, and the peristaltic pump speed was 10 r / min (the mass ratio of zinc chloride, aluminum chloride, ammonia water, distilled water, acetic acid, and yttrium chloride was 30:10:30:100:10:1);

[0030] (2) Preparation of spherical alumina-zinc oxide powder: 500 g of spherical alumina-zinc oxide precursor was added to a crucible, and the crucible was placed in an atmosphere furnace and calcined under air or oxygen at a calcination temperature of 800°C for 1 h. After the sintered body was naturally cooled to room temperature, it was placed in a planetary ball mill at a speed of 100 r / min and ball milled for 5 min to obtain spherical alumina-zinc oxide powder;

[0031] Example 2

[0032] (1) Preparation of spherical aluminum oxide-zinc oxide precursor: 60 g of zinc sulfate, 20 g of aluminum nitrate, 60 g of ammonia water, and 300 g of distilled water were transferred into a polytetrafluoroethylene-lined stainless steel reactor, heated at 400° C. for 48 h, and naturally cooled to room temperature to obtain an aluminum oxide-zinc oxide precursor slurry. The aluminum oxide-zinc oxide precursor slurry, 30 g of acetic acid, and 3 g of yttrium nitrate were placed in a spray dryer for granulation to obtain a spherical aluminum oxide-zinc oxide precursor; the air inlet temperature of the spray dryer was 280° C., the fan frequency was 30 Hz, the needle-passing time was 3 s, and the peristaltic pump speed was 20 r / min (the mass ratio of zinc sulfate, aluminum nitrate, ammonia water, distilled water, acetic acid, and yttrium nitrate was 60:20:60:300:30:3);

[0033] (2) Preparation of spherical alumina-zinc oxide powder: 800 g of spherical alumina-zinc oxide precursor was added to a crucible, and the crucible was placed in an atmosphere furnace and calcined in air or oxygen at a calcination temperature of 1000°C for 6 h. After the sintered body was naturally cooled to room temperature, it was placed in a planetary ball mill at a speed of 200 r / min and ball milled for 30 min to obtain spherical alumina-zinc oxide powder;

[0034] Example 3

[0035] (1) Preparation of spherical aluminum oxide-zinc oxide precursor: 100 g of zinc carbonate, 30 g of aluminum sulfate, 100 g of urea, and 2000 g of distilled water were transferred into a polytetrafluoroethylene-lined stainless steel reactor, heated at 500° C. for 72 h, and naturally cooled to room temperature to obtain an aluminum oxide-zinc oxide precursor slurry. The aluminum oxide-zinc oxide precursor slurry, 100 g of citric acid, and 50 g of yttrium acetate were placed in a spray dryer for granulation to obtain a spherical aluminum oxide-zinc oxide precursor; the air inlet temperature of the spray dryer was 350° C., the fan frequency was 40 Hz, the needle-passing time was 5 s, and the peristaltic pump speed was 30 r / min (the mass ratio of zinc carbonate, aluminum sulfate, urea, distilled water, citric acid, and yttrium acetate was 100:30:100:2000:100:50);

[0036] (2) Preparation of spherical alumina-zinc oxide powder: 1500 g of spherical alumina-zinc oxide precursor was added to a crucible, and the crucible was placed in an atmosphere furnace and calcined under air or oxygen at a calcination temperature of 1300° C. for 12 h. After the sintered body was naturally cooled to room temperature, it was placed in a planetary ball mill at a speed of 300 r / min and ball milled for 90 min to obtain spherical alumina-zinc oxide powder;

[0037] Comparative Example 1

[0038] The aluminum oxide-zinc oxide precursor slurry in step (1) of Example 1 was replaced with a slurry mixed with 5 μm irregular aluminum oxide, 5 μm irregular zinc oxide, acetic acid, yttrium chloride, and distilled water. The mass of each component in the slurry was the same as in Example 1, and the subsequent steps were the same as in Example 1.

[0039] Comparative Example 2

[0040] The method and steps of Example 1 were basically repeated, except that acetic acid was not added in step (1).

[0041] Comparative Example 3

[0042] The method and steps of Example 1 are basically repeated, except that yttrium chloride is not added in step (1).

[0043] The performance test methods and standards are as follows:

[0044] Maximum filling ratio test: 60g of 500cP vinyl silicone oil, 1.52g of hydrogenated silicone oil, 0.2g of ethynylcyclohexanol, and 0.3g of 3000ppm chloroplatinic acid were mixed uniformly, and a certain amount of powder fillers according to the examples of the present invention and the comparative example were added. After preliminary dispersion, the mixture was placed in a vacuum stirring degassing machine at a speed of 800r / min and stirred for 4 minutes. The mixture was then pressed into a 2mm thick cured sheet using a molding machine. The cured sheet was placed in a 120°C oven and dried for 1 hour. The cured sheet was taken out and naturally cooled to room temperature. The maximum filling ratio was achieved if the cured sheet did not shed powder and the surface did not crack.

[0045] Table 1: Maximum filling amount of spherical aluminum oxide-zinc oxide composite powder prepared in each case

[0046] serial number Maximum number of fillings Example 1 1200 copies Example 2 1100 copies Example 3 1000 copies Comparative Example 1 400 copies Comparative Example 2 400 copies Comparative Example 3 400 copies

[0047] From the attached figure and the data in Table 1, we can see that:

[0048] (1) Scanning electron microscopy ( Figure 1-4 ) analysis, comparative example 1 ( Figure 2 ) in which irregular aluminum oxide and irregular zinc oxide were used to carry out spherical granulation experiments, and the particle morphology was irregular agglomerates; Comparative Example 2 ( Figure 3 ) was not added with a peptizing agent to carry out a spherical granulation experiment, and the particle morphology was an agglomerate of irregular shape; Comparative Example 3 ( Figure 4 ) was not added with yttrium salt to conduct spherical granulation experiments, and the particle morphology was irregular agglomerates; while the spherical aluminum oxide-zinc oxide composite powder ( Figure 1 ), its morphology is spherical with smooth surface and no pores.

[0049] (2) Analysis of the maximum filling ratio of the spherical alumina-zinc oxide composite powder prepared in each example (Table 1) shows that compared with comparative examples 1 to 3, the spherical alumina-zinc oxide composite powder examples 1 to 3 of the present invention are more excellent in dispersion performance, and the filling ratio in 500 cP vinyl silicone oil can be increased by 150 to 200%, indicating that the spherical alumina-zinc oxide composite powder greatly improves the dispersion performance of alumina / zinc oxide and its compatibility with silicone, and greatly improves the thermal conductivity of the spherical alumina-zinc oxide composite material.

[0050] As can be seen from the above examples, the present invention successfully prepares spherical aluminum oxide-zinc oxide powders, resolving the drawback of poor aluminum oxide / zinc oxide dispersion in the prior art. Furthermore, the method is simple, rapid, environmentally friendly, and amenable to large-scale production, facilitating process promotion.

[0051] The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, any equivalent changes or modifications made according to the structures, features and principles described in the scope of the patent application of the present invention are included in the scope of protection of the present invention.

Claims

1. A method for preparing spherical aluminum oxide-zinc oxide composite powder, characterized in that: The following steps are involved: (1) Preparation of spherical aluminum oxide-zinc oxide precursor: zinc source, aluminum source, alkali source and distilled water are transferred into a stainless steel reactor lined with polytetrafluoroethylene, heated at 300-500°C for reaction for 24-72 hours, and naturally cooled to room temperature to obtain aluminum oxide-zinc oxide precursor slurry, and the aluminum oxide-zinc oxide precursor slurry, yttrium salt and peptizing agent are placed in a spray dryer for granulation to obtain spherical aluminum oxide-zinc oxide precursor; the air inlet temperature of the spray dryer is 200-350°C, the fan frequency is 20-40 Hz, the needle-passing time is 1-5 seconds, and the peristaltic pump speed is 10-30 r / min; (2) Preparation of spherical alumina-zinc oxide composite powder: The spherical alumina-zinc oxide precursor prepared in the above step (1) is added to a crucible, and the crucible is placed in a muffle furnace and calcined in air or oxygen at a calcination temperature of 800-1300°C for 1-12 hours. After the sintered body is naturally cooled to room temperature, it is placed in a planetary ball mill at a rotation speed of 100-300 r / min and ball milled for 5-90 minutes to obtain spherical alumina-zinc oxide powder.

2. The method for preparing a spherical aluminum oxide-zinc oxide composite powder according to claim 1, characterized in that: In the step (1), the mass ratio of the zinc source, the aluminum source, the alkali source, the distilled water, the peptizing agent and the yttrium salt is 3-10:1-3:3-10:10-200:1-10:0.1-5.

3. The method for preparing a spherical aluminum oxide-zinc oxide composite powder according to claim 1, characterized in that: In the step (1), the zinc source is one or more of zinc chloride, zinc sulfate, zinc nitrate, and zinc carbonate.

4. The method for preparing a spherical aluminum oxide-zinc oxide composite powder according to claim 1, wherein: The aluminum source in step (1) is one or more of aluminum chloride, aluminum nitrate, aluminum sulfate, sodium aluminate, and potassium aluminate.

5. The method for preparing a spherical aluminum oxide-zinc oxide composite powder according to claim 1, characterized in that: In the step (1), the alkali source is one or more of ammonia water, cyanuric chloride, melamine, urea, and imidourea.

6. The method for preparing a spherical aluminum oxide-zinc oxide composite powder according to claim 1, characterized in that: The yttrium salt in step (1) is one or more of yttrium chloride, yttrium nitrate, and yttrium acetate.

7. The method for preparing a spherical aluminum oxide-zinc oxide composite powder according to claim 1, characterized in that: In the step (1), the peptizing agent is one or more of acetic acid and citric acid.

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