A method for preparing high-dispersibility aluminum nitride spherical particles

Abstract

The application discloses a preparation method of high-dispersity aluminum nitride spherical particles. Nitrogen-containing chemical reagents and aluminum-containing compounds are dissolved in an aqueous solution in a certain mass ratio, and are stirred and reacted at a certain temperature to obtain solution material I. The solution material I is pumped into a spray drying granulation equipment, and the solution material I is dispersed into aerosol under the action of an atomizer. Under the action of high-temperature air flow generated by the equipment, water is instantaneously volatilized to obtain powder material II with a spherical morphology. The powder material II is placed into a high-temperature environment with a protective atmosphere or a reaction atmosphere for heat treatment to obtain spherical aluminum nitride powder III. The product has high crystallinity, good spherical morphology, wide spherical particle size size distribution, high nitriding rate, high purity, good dispersity and a green and pollution-free production process.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of high-end functional ceramic spherical particles, in particular to a preparation method of high-dispersity aluminum nitride spherical particles. BACKGROUND

[0002] Aluminum nitride (AlN) is a covalent compound with a hexagonal wurtzite structure, and the lattice parameters are a=3.114 and c=4.986. The aluminum nitride has high thermal conductivity, small dielectric constant, good insulation, high material strength at high temperature, and low thermal expansion coefficient. The aluminum nitride is a wide-bandgap semiconductor and is widely used in the electronic field.

[0003] The aluminum nitride powder material has flexible fluidity and is easy to disperse, and can reasonably improve the performance of a series of materials such as aluminum nitride ceramics and composite ceramics, and has great development prospects. The synthesis of aluminum nitride powder is mainly through the direct nitriding method of aluminum powder, and the method has the defects of low conversion rate of aluminum powder and impurities. Commercially, the preparation of aluminum nitride powder is mainly through the carbothermal reduction method, but the nitriding temperature of the method is as high as 1650 DEG C, the process flow is complex, the cost is high, and the particle size distribution range is narrow. The self-propagating high-temperature method has fast reaction speed, low cost and no environmental pollution, but also has the defects of incomplete nitriding and difficult crushing of the agglomerates. At present, only a few enterprises can realize the industrial production of AlN, and the technology is mature and the commercialization degree is very high. However, optimizing the preparation process, improving the quality of the powder to a higher level, improving and perfecting the production equipment, greatly improving the productivity and reducing the cost of powder preparation are still the topics of concern. SUMMARY

[0004] The application aims to provide a preparation method of high-dispersity aluminum nitride spherical particles, and the method has the advantages that the spray drying granulation forming process is simple, high crystallinity, good dispersity and good spherical morphology of the aluminum nitride can be obtained without ultrahigh temperature treatment, the steps are simple, the energy consumption is low, and the method is easy to operate.

[0005] The application does not need to add various aids, and high-crystallinity aluminum nitride products can be obtained without ultrahigh temperature treatment, the products have high nitriding rate, good crystallinity, high purity, are not easy to agglomerate, have good spherical morphology, and have wide spherical particle size distribution, and the production process is green and pollution-free.

[0006] The technical scheme for realizing the object of the application is as follows:

[0007] A preparation method of high-dispersity aluminum nitride spherical particles, the preparation method comprises the following steps:

[0008] a) heating or directly stirring the mixture of nitrogen-containing chemical reagent and aluminum-containing compound in an aqueous solution, wherein an acid-base solution is added to the aqueous solution, and the acid-base solution accounts for 1-10 vol. % of the aqueous solution;

[0009] The aluminum-containing compound is an aluminum-containing substance containing Al 3+ and / or AlO2 - ;

[0010] b) feeding the solution material I into a spray drying granulation forming device through a peristaltic pump to perform a spray granulation process, and collecting dry powder material II in a material collecting device, wherein the powder material II has a spherical morphology and is a precursor powder of an aluminum nitride spherical particle product; wherein the air blowing temperature of the spray granulation is 60-350℃, and the feeding speed of the peristaltic pump is 5-1000 mL / min;

[0011] c) heat treating the collected powder material II in a high-temperature environment with a protective atmosphere or a reaction atmosphere to obtain powder III, which is a high-dispersion aluminum nitride product with a spherical morphology; and the target temperature range of the heat treatment is 800-1200℃.

[0012] When the aluminum-containing compound is a metaborate, the heat treatment process in step c) is performed in a protective atmosphere.

[0013] In step (a), the stirring reaction temperature is 25-80℃, the stirring reaction time is 0.5-72 hours, and the heating mode includes but is not limited to oil bath and water bath. Other modes with the same effect can also obtain solution material I, wherein the molar ratio of the nitrogen-containing chemical reagent to the aluminum-containing compound is 0.1-10, preferably the aqueous solution is deionized water or pure water, and ordinary tap water can also obtain solution material I.

[0014] The acid-base solution is a dilute acid solution and a basic solution:

[0015] The dilute acid solution is at least one of dilute hydrochloric acid, dilute nitric acid or dilute sulfuric acid; the mass content of the hydrochloric acid is 20-40 wt. %, preferably 37 wt. %; and the mass content of the dilute sulfuric acid is 10-25 wt. %, preferably 20 wt. %.

[0016] The basic solution is at least one of ammonia water and sodium hydroxide solution; the concentration of the sodium hydroxide solution is 0.5-2 M, preferably 1 M; and the mass content of the ammonia water is 10-25 wt. %, preferably 20 wt. %.

[0017] If the direct dissolution reaction in aqueous solution in step (a) is not used, but a high-purity nitrogen-containing aluminum-containing precursor crystal is first obtained by several common crystal growth methods, and then a certain amount of nitrogen-containing aluminum-containing precursor crystal is dissolved in water containing a certain amount of acid or alkali solution within a certain temperature range, solution substance I can also be obtained. Although this method increases the process flow, it can effectively improve the yield due to the extremely low impurity content.

[0018] The ratio of the mass of the mixture in step (a) to the mass of the aqueous solution is 1%-80% by weight; preferably 2%-10%, 20%-50%, 30%-60%, 40%-70%, etc.

[0019] When the weight ratio of the mixture to the aqueous solution in step (a) is small, the dry powder substance II obtained after step (b) cannot maintain a good spherical morphology at room temperature for a long time. The reason is that the dry powder substance II still contains a certain amount of crystal water, and the crystal phase in the spherical precursor will grow under appropriate conditions, causing the spherical morphology to change. Therefore, in the case of long-term storage of dry powder substance II, it is necessary to remove the crystal water in the dry powder substance II by certain means, such as drying at a certain temperature range for a period of time. The drying temperature is 60-105°C, and the drying time depends on the weight ratio of the mixture to the aqueous solution.

[0020] When the solution substance I is sent to the spray drying granulation equipment for spray granulation in step (b), the temperature of the solution substance I is 15-50°C, the air blowing temperature of the spray drying granulation equipment is 100-350°C, the air outlet temperature of the spray drying granulation equipment is 100-350°C, and the upper limit of the feeding speed depends on the scale and production capacity level of the spray drying granulation equipment.

[0021] The temperature of the heat treatment in step (c) is 800-1200°C, preferably 1000-1100°C, including but not limited to 850°C, 900°C, 1000°C, 1050°C, 1100°C, 1200°C, etc.

[0022] The protective atmosphere is an inert atmosphere, including nitrogen, argon, or nitrogen+argon; the reaction atmosphere is an atmosphere containing ammonia, including nitrogen+ammonia, argon+ammonia, and ammonia, wherein the volume content of ammonia in nitrogen+ammonia or argon+ammonia is not higher than 10%;

[0023] The heating rate of the heat treatment is 1-50°C / min, and the holding time of the target temperature of the heat treatment is 1-10 hours.

[0024] The flow rate of the protective atmosphere or the reaction atmosphere is in the range of 1-1500 mL / min.

[0025] When the protective atmosphere or the reaction atmosphere is pure ammonia atmosphere: the dry powder substance II is directly treated at high temperature of 800-1100 ℃ to obtain the powder III with spherical morphology, at this time the powder III has better spherical morphology.

[0026] The nitrogen-containing chemical reagent is at least one of guanidine-containing, triazole-containing or triazine-containing nitrogen-containing chemical reagents: preferably the nitrogen-containing chemical reagent mainly contains guanidine-containing nitrogen-containing compounds.

[0027] The guanidine-containing nitrogen-containing chemical reagent is one or more of guanidine acetate, guanazole, guanidine, guanidine hydrochloride, cyanoguanidine, guanidine carbonate and guanidine sulfate;

[0028] The triazole-containing nitrogen-containing chemical reagent is aminotriazole or 4-amino-1,2,4-triazole;

[0029] The triazine-containing nitrogen-containing chemical reagent is at least one of melamine, trichloromelamine, cyanuric chloride or cyanuric acid.

[0030] The aluminum-containing compound is at least one of aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum hydroxide, met aluminic acid and met aluminic acid salt; the met aluminic acid salt is at least one of sodium met aluminic acid, potassium met aluminic acid and ammonium met aluminic acid.

[0031] The mechanism of the solution substance I in step (a) forming the powder III with spherical morphology under the spray drying granulation technology is as follows: the solution substance I containing Al component and N component is prepared by using the nitrogen-containing compound, the two component substances in the solution are uniformly distributed in the solution after sufficient reaction, the solution substance I is pumped into the spray drying granulation equipment under the action of the peristaltic pump, the high-speed airflow generated by the air compressor of the equipment passes through the atomizer, the solution substance I rapidly forms aerosol, the airflow with certain heat blown by the fan in the equipment and the aerosol simultaneously undergo heat and mass transfer process in a short time, the water is instantly evaporated, the crystal phase uniformly distributed in the aerosol is bound into spherical state under the surface tension of the aerosol droplets, and due to the principle of minimum energy, the crystal phase components are uniformly distributed and tightly combined into spherical particles, so the powder III with spherical morphology is formed. If the above-mentioned several types of nitrogen-containing compounds are used, the same effect can be obtained, and the powder III with the same spherical morphology is finally formed; therefore, the nitrogen-containing compounds and the aluminum-containing compounds in the present application are not limited to the above-mentioned several types of compounds, other nitrogen-containing compounds and aluminum-containing compounds meeting the spray drying granulation forming principle proposed in the present application can also be selected.

[0032] The dry powder substance II in step (b) is subjected to high-temperature treatment in a protective gas containing ammonia components, at which other non-N, Al elements in the precursor crystal become gas such as CO2, H2O, etc. under the action of high temperature, thereby being removed; ammonia gas reacts with the precursor crystal at high temperature, N in the ammonia gas can be effectively supplemented into the precursor crystal, and at the same time, N-Al bond is continuously formed, and finally the spherical powder III is obtained.

[0033] The spray drying granulation equipment used in step (b) is a conventional spray drying granulation equipment that can be purchased in the market, and the method does not have special requirements for the spray drying granulation equipment, but the solution substance I obtained by reaction in step (a) is the most typical feature of the present application, that is, the solution substance I containing uniformly dispersed phase obtained by reaction is the most critical link for obtaining the spherical aluminum nitride product in the present application.

[0034] The present application can realize the regulation and optimization of the particle size range span of the precursor spherical particles by adjusting the parameters of the spray drying granulation equipment and the change of the raw material ratio, and the diameter of the spherical particles can be controlled and optimized from quasi-nanometer to micrometer, so that the diameter of the aluminum nitride spherical particles obtained after high-temperature treatment in step (c) can be as small as quasi-nanometer and as large as micrometer.

[0035] Compared with the prior art, the present application has the following beneficial effects:

[0036] Compared with the current synthesis technology, the present application does not need to add various aids, and can obtain aluminum nitride spherical particles with high crystallinity without ultra-high temperature treatment, the product has high nitriding rate, high purity, is not easy to agglomerate, has good spherical morphology, and has wide spherical particle size distribution. The product conversion rate is high in the production process, and there is no excessive consumption of raw materials, and the production process is green and pollution-free.

[0037] The nitrogen-containing chemical reagent and the aluminum-containing compound in the present application can be well dispersed in an aqueous solution with acid-base liquid to obtain a uniform and stable solution, i.e. solution substance I, instead of slurry, the product obtained by the preparation method of the present application has regular spherical morphology, high crystallinity and purity, good dispersibility, and the particles are not easy to agglomerate, can be uniformly dispersed in a resin-based material, and is beneficial to the use in the later stage engineering, such as improving the thermal conductivity and insulation of ceramic materials. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly introduce the technical solutions and product types of the present application, the following will briefly describe and explain the drawings needed to be used in the embodiment description. It is emphasized that these drawing examples are only a part of the embodiments of the present application, and for the ordinary skilled in the art, without any creative labor, these have the possibility to extend and proliferate other similar and related drawing examples, and in the case of similar and similar figures as new creative embodiments, it is considered as infringement of the present application.

[0039] Figure 1 XRD diffraction pattern of the powder substance II obtained by using the guanidine-containing nitrogen-containing compound in Example 1;

[0040] Figure 2 XRD diffraction pattern of the high-dispersion aluminum nitride product with spherical morphology obtained by high-temperature treatment of the powder substance II of Example 1 in an ammonia gas atmosphere;

[0041] Figure 3 Fourier infrared spectrum of the powder substance II obtained by using the guanidine-containing nitrogen-containing compound in Example 1;

[0042] Figure 4 Fourier infrared spectrum of the high-dispersion aluminum nitride product with spherical morphology obtained by high-temperature treatment of the powder substance II of Example 1 in an ammonia gas atmosphere;

[0043] Figure 5 Scanning electron microscope image of the powder substance II obtained by using the guanidine-containing nitrogen-containing compound in Example 1 under 1000 times;

[0044] Figure 6 Scanning electron microscope image of the powder substance II obtained by using the guanidine-containing nitrogen-containing compound in Example 1 under 2000 times;

[0045] Figure 7 Scanning electron microscope image of the high-dispersion aluminum nitride product with spherical morphology obtained by high-temperature treatment of the powder substance II of Example 1 in an ammonia gas atmosphere under 1000 times;

[0046] Figure 8 Scanning electron microscope image of the high-dispersion aluminum nitride product with spherical morphology obtained by high-temperature treatment of the powder substance II of Example 1 in an ammonia gas atmosphere under 2000 times;

[0047] Figure 9 Scanning electron microscope image of the powder substance II obtained by using guanazole in Example 2;

[0048] Figure 10 Scanning electron microscope image of the high-dispersion aluminum nitride product with spherical morphology obtained by high-temperature treatment of the powder substance II of Example 2 in an ammonia+nitrogen mixed gas atmosphere under 5000 times;

[0049] Figure 11 Scanning electron microscope picture of the high-dispersed aluminum nitride product with spherical morphology obtained after high-temperature treatment of the product of Example 2 under the mixed gas atmosphere of ammonia + nitrogen, at 30000 times;

[0050] Figure 12 Scanning electron microscope picture of the powder substance II obtained by using guanazole in Example 3;

[0051] Figure 13 Scanning electron microscope picture of the high-dispersed aluminum nitride product with spherical morphology obtained after high-temperature treatment of the product of Example 3 under the mixed gas atmosphere of ammonia + nitrogen, at 30000 times;

[0052] Figure 14 Scanning electron microscope picture of the powder substance II obtained by using guanazole in Example 3;

[0053] Figure 15 Scanning electron microscope picture of the high-dispersed aluminum nitride product with spherical morphology obtained after high-temperature treatment of the product of Example 4 under the mixed gas atmosphere of ammonia + nitrogen, at 30000 times;

[0054] Figure 16 Scanning electron microscope picture of the powder substance II obtained by using guanazole in Example 3;

[0055] Figure 17 Scanning electron microscope picture of the high-dispersed aluminum nitride product with spherical morphology obtained after high-temperature treatment of the product of Example 5 under the mixed gas atmosphere of ammonia + nitrogen, at 30000 times. DETAILED DESCRIPTION

[0056] In order to facilitate the understanding of the skilled in the art, the following examples are further described in the present application, it is necessary to point out that the following examples are only used to further illustrate the present application, can not be understood as limiting the scope of the present application, the skilled in the art according to the content of the present application to the present application makes some improvements and adjustment still belong to the scope of the present application.

[0057] Unless otherwise defined, the professional terms used in the present application are consistent with the meanings commonly understood by those skilled in the art, the raw materials, reagents, instruments, equipment and some loss materials used in the present application can be purchased through the market, or can be prepared by the prior art and method.

[0058] The present application is a kind of preparation method of aluminum nitride spherical particles, comprising the following steps:

[0059] (a) weighing a certain weight ratio of guanidine nitrogen-containing chemical reagent and aluminum-containing compound, adding a certain amount of water and a certain volume of acid-base solution, heating and stirring in a certain temperature range, so that a certain proportion of the mixture of nitrogen-containing chemical reagent and aluminum-containing compound is fully dissolved in the solution, after a period of reaction, solution material I is obtained;

[0060] The molar ratio of the mixture of nitrogen-containing chemical reagent and aluminum-containing compound is in the range of 0.1-10, the temperature range of the dissolution reaction is 15-50℃, the total time required for the dissolution reaction is in the range of 0.5-72 hours, and the ratio of the mass (g) of the mixture to the weight (g) of the solvent is in the range of 2.4%-50%; if there is a precipitate after the dissolution reaction, the clear solution or the solution that can maintain the characteristics of clear and transparent uniform liquid phase at a certain temperature is also considered to have the characteristics of a transparent and uniform liquid phase system, and is regarded as solution material I. Alternatively, a mixture of nitrogen-containing chemical reagent and aluminum-containing compound is used as raw material to obtain a precursor crystal with high purity through several common crystal growth methods, and then a certain amount of precursor crystal is dissolved in water in a certain temperature range, and solution material I can also be obtained. Therefore, the important feature of the solution material I obtained in step (a) is that it contains a guanidine nitrogen source, a triazine nitrogen source or a triazole nitrogen source, and an Al component aluminum source in a uniform liquid phase system in water at a certain temperature range, which is the key to forming spherical precursor.

[0061] (b) Solution material I is pumped into a spray drying granulation forming device using a peristaltic pump, and solution material I is pumped into the spray drying granulation device under the action of the peristaltic pump, and is subjected to high-speed airflow generated by the air compressor of the spray drying device through the atomizer. Solution material I rapidly forms an aerosol, and the heat-containing air flow and the aerosol simultaneously undergo heat and mass transfer processes in a very short time. The water is instantly evaporated, and the uniformly distributed crystal phase in the aerosol is tightly combined into spherical particles, and the obtained powder particle product is powder material II with spherical morphology;

[0062] The temperature of solution material I when it is pumped into the spray drying granulation device is in the range of 15-50℃, the temperature of the air flow of the spray drying granulation device is in the range of 60-350℃, preferably 100-220℃, the temperature of the air outlet of the spray drying granulation device is in the range of 60-220℃, and the upper limit of the feeding speed depends on the scale and production capacity level of the spray drying granulation device.

[0063] Through XRD analysis, it can be known that the spherical precursor powder in step (b) has obvious crystal state characteristics, sharp characteristic peaks, and high crystallinity (as shown in Figure 1 The crystal state characteristics of the formed spherical precursor particles are obviously good in spherical morphology (as shown in Figure 5The crystalline components formed in the spherical particles are uniformly distributed; using the other nitrogen-containing compounds, similar clear liquid characteristics and good spherical morphology of the product obtained after high-temperature treatment can be obtained as with the guanidine nitrogen source;

[0064] (c) The collected large amount of precursor powder II product is loaded into a high-temperature device with a protective atmosphere for high-temperature treatment to obtain a spherical powder product, which is the final spherical aluminum nitride product III.

[0065] The temperature range of the high-temperature treatment is 800-1100°C, the flow rate range of the protective atmosphere or reaction atmosphere is 1-1500 mL / min, the heating rate range is 0.1-30°C / min, and the reaction time range is 1-72 hours.

[0066] The reason is that during the high-temperature treatment stage, the non-N, Al components are continuously converted into a gas phase and removed, and at the same time, nitrogen in the ammonia gas is supplemented into the precursor powder II to form N-Al bonds, and the position where other elements are removed is supplemented with nitrogen in the ammonia gas, so that the spherical morphology of the powder III is maintained. If the aluminum source is selected as a metaborate salt, such as sodium metaborate, even if the protective gas does not contain ammonia gas components, only completely inert gas components, such as nitrogen, argon or a mixture of the two, the final powder substance II can obtain the powder III with spherical morphology after high-temperature treatment, the reason is that the crystalline material formed by the guanidine nitrogen source and the metaborate salt can be directly pyrolyzed into aluminum nitride in the inert gas, and this process does not require nitrogen supplementation. Replacing the guanidine nitrogen source with the other nitrogen sources described above also has the same effect.

[0067] Example 1:

[0068] The present embodiment is a method for preparing highly dispersed spherical aluminum nitride particles, comprising the following steps:

[0069] (a) 18.017 g of guanidine carbonate and 144.86 g of aluminum chloride hexahydrate (molar ratio about 1:6) are stirred and dissolved in 300 mL of water at 45°C in an oil bath, 10 mL of hydrochloric acid solution (37 wt.%) is added, and the dissolution reaction is carried out for 4 h to obtain solution substance I;

[0070] (b) The obtained solution material I is kept in an oil bath, and at this time, the oil bath temperature is 45°C. The solution material I is driven into the spray drying granulation equipment through a peristaltic feeding tube for spray drying granulation. The temperature of the hot air blown into the heating drum is set to 220°C. The spray drying inlet temperature is 220°C, the outlet temperature is 200°C, and the feeding speed is 50 mL / min. After the solution material I is completely driven into the spray drying granulation equipment, the heating of the spray drying granulation equipment is stopped, and the temperature is allowed to drop to room temperature. A large amount of powder product is obtained in the collection device of the spray drying granulation equipment. The obtained powder product is the precursor powder of the aluminum nitride spherical particle product, which is recorded as powder material II;

[0071] (c) The powder material II is loaded into a tube furnace for heat treatment, and ammonia gas is introduced. The high-temperature heat treatment stage temperature is 1000°C. The tube furnace has a temperature rising rate of 5°C / min. The flow rate of the introduced ammonia gas is 50 mL / min. The reaction time at 1000°C is 2 hours. Then, the tube furnace program is ended, and the temperature is allowed to drop naturally. After the temperature drops, the powder is taken out of the tube furnace. The obtained powder product is the final high-dispersion aluminum nitride product with a spherical morphology.

[0072] The powder material II obtained in this example has a good spherical morphology (as shown in the SEM photos of Figure 5 、 Figure 6 ), and the diameter distribution of the spherical particles of the powder material II product ranges from several hundred nanometers to tens of microns, with an average value of about ten microns. The crystal phases of the two component materials are uniformly distributed in the aqueous solution. The solution material I is pumped into the spray drying granulation equipment under the action of the peristaltic pump. The solution material I rapidly forms an aerosol under the high-speed airflow generated by the air compressor of the spray drying equipment through the atomizer. The airflow with a certain amount of heat blown by the fan in the equipment and the aerosol simultaneously undergo heat and mass transfer processes in a short time. The water is instantly evaporated. The crystal phases uniformly distributed in the aerosol are bound into a spherical state under the surface tension of the aerosol droplets. Due to the principle of minimum energy, the crystal phases are uniformly distributed and tightly combined into spherical particles. In this way, the powder material II with a spherical morphology is formed. In the further high-temperature ammonia gas treatment process, the pre-formed Al-N bond component plays an important role in maintaining the spherical structure of the precursor. The nitrogen in the ammonia gas is supplemented to the positions left by the removal of other elements, and continuously forms bonds with N. Therefore, the spherical morphology is well maintained (as shown in Figure 7 、 Figure 8 ), and the diameter of the spherical particles is slightly contracted. The diameter of the obtained aluminum nitride spherical particles ranges from about several hundred microns to tens of microns, with an average value of about ten microns.

[0073] Example 2:

[0074] (a) 9.91 g of guanazole and 55.52 g of aluminum nitrate nonahydrate (molar ratio of about 1:5) were stirred and dissolved in 200 mL of water at 45°C in an oil bath, 8 mL of sodium hydroxide solution (1 M) was added, and the solution was reacted for 2 h to obtain solution material I;

[0075] (b) The obtained solution material I was kept in an oil bath at 45°C, and the solution material I was driven into a spray drying granulation device through a peristaltic feeding tube for spray drying granulation. The temperature of the hot air blown into the heating drum was set to 200°C, the inlet temperature of the spray drying was set to 200°C, the outlet temperature was set to 180°C, and the feeding speed was set to 50 mL / min. After the solution material I was completely driven into the spray drying granulation device, the heating of the spray drying granulation device was stopped, and the temperature was allowed to drop to room temperature. A large amount of powder product was obtained in the collection device of the spray drying granulation device, and the obtained powder product was spherical aluminum nitride precursor powder material II;

[0076] (c) The powder material II was loaded into a tube furnace for heat treatment, and a mixed gas of ammonia and nitrogen was introduced, with the volume content of ammonia in the mixed gas being 10%. The temperature of the high-temperature heat treatment stage was 900°C, the temperature rising rate of the tube furnace was 5°C / min, the flow rate of the introduced ammonia and nitrogen was 50 mL / min, and the reaction time at 900°C was 4 hours. Then the tube furnace program was ended, and the temperature was allowed to drop naturally. After the temperature dropped, the powder product was taken out from the tube furnace, and the obtained powder product was the final high-dispersion aluminum nitride product with spherical morphology.

[0077] Example 3:

[0078] (a) 9.91 g of guanazole and 33.19 g of sodium metaaluminate (molar ratio of about 1:4) were stirred and dissolved in 300 mL of water at 45°C in an oil bath, 5 mL of hydrochloric acid solution (37 wt.%) was added, and the solution was reacted for 2 h to obtain solution material I;

[0079] (b) The obtained solution material I was kept in an oil bath at 45°C, and the solution material I was driven into a spray drying granulation device through a peristaltic feeding tube for spray drying granulation. The temperature of the hot air blown into the heating drum was set to 200°C, the inlet temperature of the spray drying was set to 200°C, the outlet temperature was set to 180°C, and the feeding speed was set to 50 mL / min. After the solution material I was completely driven into the spray drying granulation device, the heating of the spray drying granulation device was stopped, and the temperature was allowed to drop to room temperature. A large amount of powder product was obtained in the collection device of the spray drying granulation device, and the obtained powder product was powder material II;

[0080] (c) The powder substance II is loaded into a tube furnace for heat treatment, and nitrogen gas is introduced, the high-temperature heat treatment stage temperature is 1100°C, the tube furnace temperature rising rate is 5°C / min, the nitrogen gas flow rate is 50 mL / min, the reaction time at 1100°C is 4 hours, then the tube furnace program ends, and it is waited to be naturally cooled, after the cooling is completed, the powder product is taken out from the tube furnace, and the obtained powder product is the final high-dispersion aluminum nitride product with spherical morphology.

[0081] Example 4:

[0082] (a) 8.41 g of aminotriazole and 45.41 g of aluminum chloride hexahydrate (molar ratio is about 1:3) are stirred and dissolved in 200 mL of water at 45°C in an oil bath, 3 mL of hydrochloric acid solution (37 wt.%) is added, and the dissolution reaction is carried out for 2 hours to obtain solution substance I;

[0083] (b) The obtained solution substance I is kept in an oil bath, and at this time the oil bath temperature is 45°C. The solution substance I is driven into a spray drying granulation device through a peristaltic feeding pipe for spray drying granulation. The temperature of the hot air introduced by the heating drum is set to 200°C, the spray drying inlet temperature is 200°C, the outlet temperature is 180°C, and the feeding speed is 50 mL / min. After the solution substance I is completely driven into the spray drying granulation device, the heating of the spray drying granulation device is stopped, and it is waited to be cooled to room temperature. A large amount of powder product is obtained in the collection device of the spray drying granulation device, and the obtained powder product is powder substance II;

[0084] (c) The powder substance II is loaded into a tube furnace for heat treatment, and nitrogen gas is introduced, the high-temperature heat treatment stage temperature is 1100°C, the tube furnace temperature rising rate is 5°C / min, the nitrogen gas flow rate is 50 mL / min, the reaction time at 1100°C is 4 hours, then the tube furnace program ends, and it is waited to be naturally cooled, after the cooling is completed, the powder product is taken out from the tube furnace, and the obtained powder product is the final high-dispersion aluminum nitride product with spherical morphology.

[0085] Example 5:

[0086] (a) 12.61 g of melamine and 68.43 g of aluminum chloride hexahydrate (molar ratio is about 1:2) are stirred and dissolved in 350 mL of water at 45°C in an oil bath, 7 mL of sodium hydroxide solution (1M) is added, and the dissolution reaction is carried out for 3 hours to obtain solution substance I;

[0087] (b) the obtained solution material I is kept in an oil bath, and at this time, the oil bath temperature is 45℃, the solution material I is driven into the spray drying granulation equipment through a peristaltic feeding tube for spray drying granulation, the temperature of the heated air blown into the drum is set to 200℃, the spray drying air inlet temperature is 220℃, the air outlet temperature is 200℃, the feeding speed is 55mL / min, after the solution material I is completely driven into the spray drying granulation equipment, the heating of the spray drying granulation equipment is stopped, and the temperature is lowered to room temperature, and a large amount of powder product is obtained in the collection device of the spray drying granulation equipment, and the obtained powder product is powder material II;

[0088] (c) the powder material II is loaded into a tube furnace for heat treatment, and a mixed gas of ammonia and nitrogen is blown in, the volume content of ammonia in the mixed gas is 10%, the high-temperature heat treatment stage temperature is 1100℃, the tube furnace heating rate is 5℃ / min, the flow rate of the mixed gas blown in is 50mL / min, the reaction time at 1100℃ is 3 hours, then the tube furnace program is ended, and the temperature is naturally lowered, after the temperature is lowered, the powder product is taken out from the tube furnace, and the obtained powder product is the final high-dispersion aluminum nitride product with spherical morphology.

[0089] Figure 16 and Figure 17 The electron microscope image of the powder material II and the high-dispersion aluminum nitride product obtained in Example 5 is shown in the figure, and it can be seen from the figure that the product has spherical morphology and has large hollow spherical particles, the hollow spherical particles obtained in Example 5 have poor strength, and the fragments in the electron microscope image are in a state after the spherical particles are broken.

[0090] The nitrogen sources of Examples 1-5 are guanidine acetate, thiocyanic acid, trichlorotriazine, cyanuric chloride or a mixture of guanazole and thiocyanic acid, and the other operations are the same as those in Example 1, and the spherical morphology high-dispersion aluminum nitride product is obtained.

[0091] The present application is applicable to the prior art.

Claims

1. A method for producing high dispersibility aluminum nitride spherical particles, characterized by, The preparation method comprises the following steps: a) heating or directly stirring at room temperature a mixture of a nitrogen-containing chemical reagent and an aluminum-containing compound in an aqueous solution, wherein a sodium hydroxide solution or a hydrochloric acid solution is added to the aqueous solution, and the volume content of the sodium hydroxide solution or the hydrochloric acid solution in the aqueous solution ranges from 1 vol.% to 10 vol.%; b) feeding the solution material I obtained in step a) into a spray drying granulation forming device through a peristaltic pump to perform a spray granulation process, and collecting dry powder material II in a material collecting device, wherein the powder material II has a spherical morphology and is a precursor powder of an aluminum nitride spherical particle product; the air blowing temperature of the spray granulation is 60-350 DEG C, and the feeding speed of the peristaltic pump is 5-1000 mL / min; c) heat treating the collected powder material II in a high-temperature environment with a protective atmosphere or a reaction atmosphere to obtain powder III, which is a high-dispersion aluminum nitride product with a spherical morphology; the target temperature range of the heat treatment is 800-1200 DEG C; when the aluminum-containing compound is a meta-aluminate, the heat treatment process in step c) is performed in an inert protective atmosphere. The aluminum-containing compound is an aluminum-containing species containing Al 3+ or AlO2 - . The nitrogen-containing chemical reagent is at least one of a guanidine-containing, a triazole-containing or a triazine-containing nitrogen-containing chemical reagent. The guanidine-containing nitrogen-containing chemical reagent is one or more of guanidine acetate, guanazole, guanidine, guanidine hydrochloride, cyanoguanidine, guanidine carbonate and guanidine sulfate. The triazole-containing nitrogen-containing chemical reagent is amino triazole or 4-amino-1, 2, 4-triazole.

2. The production method according to claim 1, characterized by, The triazine-containing nitrogen-containing chemical reagent is at least one of melamine, trichloromelamine, cyanuric chloride or cyanuric acid. The aluminum-containing compound is at least one of aluminum chloride, aluminum nitrate, aluminum sulfate and meta-aluminate. The meta-aluminate is at least one of sodium meta-aluminate, potassium meta-aluminate or ammonium meta-aluminate. The solution material I is a clear and transparent solution; the molar ratio of the nitrogen-containing chemical reagent to the aluminum-containing compound ranges from 0.1 to 10; the weight ratio of the mixture of the nitrogen-containing chemical reagent and the aluminum-containing compound to the aqueous solution ranges from 1% to 80%; the stirring reaction temperature ranges from 25 DEG C to 80 DEG C, and the stirring reaction time ranges from 0.5 hours to 72 hours. The protective atmosphere is an inert atmosphere, which is nitrogen, argon or nitrogen+argon; the reaction atmosphere is an atmosphere containing ammonia, which is one of nitrogen+ammonia, argon+ammonia and ammonia, wherein the volume content of ammonia in the nitrogen+ammonia or the argon+ammonia is not higher than 10%; 3. The preparation method according to claim 1, characterized in that, The heating rate of the heat treatment is 1 DEG C / min-50 DEG C / min, and the holding time of the target temperature of the heat treatment is 1-10 hours.

4. The method of claim 1, wherein, The diameter distribution of the spherical aluminum nitride particles in the powder III ranges from several hundred nanometers to tens of microns.

5. The preparation method according to claim 1, characterized in that, The preparation method is obtained by any one of claims 1-6. ​ 6. The method of claim 1, wherein, ​ 7. A spherical particle of aluminum nitride, characterized by, ​

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