阅读说明：本技术 一种自催化高纯氮化铝的制备方法 (Preparation method of autocatalytic high-purity aluminum nitride ) 是由 田玉伟 许永宾 许士铭 于 2020-07-31 设计创作，主要内容包括：本发明公开了一种自催化高纯氮化铝的制备方法,属于氮化铝合成技术领域,其包括如下步骤：(1)混料：以氢氧化铝粉、碳粉、氮化铝粉为原料并按照一定的重量比混合均匀,得到混合物料；(2)高温合成：将混合物料置于1350-1420℃的一定压力的氮气和丙烷混合气体流中,反应1.5-3小时,得反应产物；(3)脱碳：脱除反应产物中的碳,得到氮化铝粉。本发明公开的自催化高纯氮化铝的制备方法,选取氮化铝作为晶种,反应在一定压力的氮气和丙烷的混合气体流中进行,反应分子热运动增强,扩散渗透速率增大,起到自催化效果,缩短了反应合成时间,反应合成的温度降低了200-400℃；并避免了添加其它助剂而带入的杂质元素污染,保证了制得的氮化铝的纯度。(The invention discloses a preparation method of autocatalytic high-purity aluminum nitride, belonging to the technical field of aluminum nitride synthesis and comprising the following steps: (1) mixing materials: taking aluminum hydroxide powder, carbon powder and aluminum nitride powder as raw materials, and uniformly mixing the raw materials according to a certain weight ratio to obtain a mixed material; (2) high-temperature synthesis: placing the mixed material in a mixed gas flow of nitrogen and propane with a certain pressure of 1350-1420 ℃ for reacting for 1.5-3 hours to obtain a reaction product; (3) decarbonization: and removing carbon in the reaction product to obtain the aluminum nitride powder. The preparation method of the autocatalysis high-purity aluminum nitride disclosed by the invention has the advantages that the aluminum nitride is selected as the seed crystal, the reaction is carried out in the mixed gas flow of nitrogen and propane at a certain pressure, the thermal motion of reaction molecules is enhanced, the diffusion permeation rate is increased, the autocatalysis effect is achieved, the reaction synthesis time is shortened, and the reaction synthesis temperature is reduced by 200-; and impurity element pollution brought by adding other additives is avoided, and the purity of the prepared aluminum nitride is ensured.)

1. A preparation method of autocatalytic high-purity aluminum nitride is characterized by comprising the following steps:

(1) mixing materials:

taking aluminum hydroxide powder, carbon powder and aluminum nitride powder as raw materials, and uniformly mixing the raw materials according to a certain weight ratio to obtain a mixed material;

(2) high-temperature synthesis:

placing the mixed material in a mixed gas flow of nitrogen and propane with a certain pressure of 1350-1420 ℃ for reacting for 1.5-3 hours to obtain a reaction product;

(3) decarbonization:

and removing carbon in the reaction product to obtain the aluminum nitride powder.

2. The method for preparing autocatalytic high purity aluminum nitride according to claim 1, wherein the weight ratio of aluminum hydroxide, carbon powder and aluminum nitride is (60-72): (30-39): (1.6-2.2).

3. The method for preparing autocatalytic high purity aluminum nitride according to claim 1,

the purity of the aluminum hydroxide is 5N, and the granularity is 1-2 mu m;

the purity of the aluminum nitride is 5N, and the granularity is 0.05-0.075 μm;

the purity of the carbon powder is 4N, and the granularity is 2-4 mu m; the raw material of the carbon powder is graphite, carbon black or active carbon, and the active carbon is preferred.

4. The method for preparing autocatalytic high purity aluminum nitride according to claim 1, wherein the pressure of the mixed gas of nitrogen and propane is 0.2-0.6 MPa.

5. The method for preparing autocatalytic high purity aluminum nitride according to claim 1, wherein the volume ratio of nitrogen to propane is 1 (1.0-2.0)%.

6. The preparation method of autocatalytic high purity aluminum nitride according to claim 1, wherein the specific method of high temperature synthesis in step (2) is:

(2.1) introducing nitrogen into the push plate type tunnel furnace to completely exhaust air in the furnace, heating the tunnel furnace to ensure that the temperature of a high-temperature region in the furnace reaches 1350-;

(2.2) putting the mixed material into a carbonaceous crucible, moving the crucible in the reaction furnace at a certain speed, and enabling the time of the mixed material passing through a high-temperature zone in the furnace to reach 1.5-3 hours.

7. The preparation method of autocatalytic high purity aluminum nitride according to claim 6, wherein there are 7 temperature control zones in the tunnel furnace, the heating temperatures of the 7 temperature control zones are respectively: 300 + -5 ℃, 600 + -5 ℃, 900 + -5 ℃, 1200 + -5 ℃, 1350 + -1420 +/-5 ℃ and 1350 + -1420 ℃.

8. The preparation method of autocatalytic high purity aluminum nitride according to claim 1, wherein the specific method of decarburization in step (3) is:

and (3) after the reaction product is taken out of the furnace, sending the reaction product into an oxidation furnace with the temperature of 600-700 ℃ for decarburization for 1-3 hours, and then cooling the reaction product to room temperature to obtain the aluminum nitride powder.

9. The preparation method of the autocatalytic high purity aluminum nitride according to claim 1, characterized in that the concrete method of mixing the materials in the step (1) is as follows:

adding aluminum hydroxide, carbon powder and aluminum nitride into a mixer, and mixing for 12-18 hours at the rotating speed of 12-20 revolutions per minute.

10. The preparation method of autocatalytic high purity aluminum nitride according to claim 1, further comprising step (4) purification:

stirring and mixing the obtained aluminum nitride powder and pure water with the conductivity less than 0.06S/m for 25-35 minutes to obtain slurry, and dehydrating the slurry to obtain powder blocks; uniformly mixing the obtained powder block with pure water again to obtain slurry, dehydrating the slurry again to obtain powder block, and repeating the steps for multiple times to obtain pure aluminum nitride powder block; wherein the weight ratio of the pure water to the aluminum nitride is (3-4) to (0.1-1.2);

drying the obtained powder block at the temperature of 100-110 ℃, and then sieving the powder block by a 100-mesh sieve to obtain the purified aluminum nitride powder.

Technical Field

The invention relates to a preparation method of autocatalytic high-purity aluminum nitride, belonging to the technical field of aluminum nitride synthesis.

Background

The aluminum nitride has the excellent characteristics of high thermal conductivity, low dielectric constant, good insulating property, high mechanical strength, matching expansion coefficient with a silicon chip and the like, is one of raw materials of an excellent circuit substrate and white light LED red fluorescent powder (CaAlSiN3: Eu), has large market demand and has wide application prospect.

For the aluminum nitride ceramic material, the properties of aluminum nitride, such as morphology, purity, particle size, oxygen content and other impurity content, directly affect the properties of the aluminum nitride ceramic material, such as thermal conductivity, and subsequent sintering and forming processes. For example, when the content of impurities in the aluminum nitride powder is relatively high, the sintering performance of the aluminum nitride powder is poor, and it is difficult to obtain a dense aluminum nitride ceramic, so that the thermal conductivity of the ceramic is far lower than a theoretical value; and the aluminum nitride belongs to covalent compounds, the self-diffusion coefficient is low, and sintering densification is difficult if the particle size and the appearance are not uniform. Therefore, to prepare an aluminum nitride product with excellent properties, it is necessary to prepare an aluminum nitride powder with high purity, fine particle size, narrow particle size distribution, and stable properties.

Among various methods for manufacturing aluminum nitride, the direct aluminum powder nitriding method, the carbothermic reduction method, the chemical vapor deposition method, the self-propagating combustion synthesis method and the microwave synthesis method all have the disadvantages of high cost, mass production incapability, defective crystal form of the synthesized aluminum nitride, low purity and the like, and the prepared aluminum nitride powder has complex appearance, so that the prepared aluminum nitride powder has poor flowability, and is difficult to achieve higher filling density, thereby affecting the thermal conductivity of the material. The traditional carbothermic method can realize large-scale production, but has high synthesis temperature, long reaction time and low purity of the obtained aluminum nitride. Therefore, the current aluminum nitride preparation method is yet to be further improved.

The above description is included in the scope of the technical recognition of the inventors, and does not necessarily constitute the conventional art.

Disclosure of Invention

The invention aims to solve the problems in the prior art, and provides a preparation method of autocatalytic high-purity aluminum nitride, which can achieve an autocatalytic effect, shorten the reaction synthesis time, reduce the reaction synthesis temperature and improve the product purity.

The invention adopts the following technical scheme to realize the purpose:

a preparation method of autocatalytic high-purity aluminum nitride comprises the following steps:

(1) mixing materials:

taking aluminum hydroxide powder, carbon powder and aluminum nitride powder as raw materials, and uniformly mixing the raw materials according to a certain weight ratio to obtain a mixed material;

(2) high-temperature synthesis:

placing the mixed material in a mixed gas flow of nitrogen and propane with a certain pressure of 1350-1420 ℃ for reacting for 1.5-3 hours to obtain a reaction product;

(3) decarbonization:

and removing carbon in the reaction product to obtain the aluminum nitride powder.

Optionally, the weight ratio of the aluminum hydroxide, the carbon powder and the aluminum nitride is (60-72): (30-39): 1.6-2.2.

Optionally, the aluminum hydroxide has a purity of 5N and a particle size of 1-2 μm, preferably 1-1.5 μm.

Optionally, the aluminum nitride has a purity of 5N and a particle size of 0.05-0.075 μm, preferably 0.05-0.06 μm.

Optionally, the carbon powder has a purity of 4N and a particle size of 2-4 μm, preferably 2-3 μm.

Optionally, the raw material of the carbon powder is graphite, carbon black or activated carbon, preferably activated carbon, and the activated carbon powder has high specific surface area and good porosity and can enhance carbonization speed.

Optionally, the pressure of the mixed gas of nitrogen and propane is 0.2-0.6MPa, preferably 0.4-0.5 MPa.

Optionally, the volume ratio of nitrogen to propane is 1 (1.0-2.0)%, preferably 1 (1.1-1.3)%.

Optionally, the specific method for high-temperature synthesis in step (2) is as follows:

(2.1) introducing nitrogen into the push plate type tunnel furnace to completely exhaust air in the furnace, heating the tunnel furnace to enable the temperature of a high-temperature region in the furnace to reach 1350-;

(2.2) putting the mixed material into a carbonaceous crucible, moving the crucible in the reaction furnace at a certain speed, and enabling the time of the mixed material passing through a high-temperature zone in the furnace to reach 1.5-3 hours.

Further, the tunnel furnace has 7 temperature control areas, and the heating temperatures of the 7 temperature control areas are respectively as follows: 300 + -5 ℃, 600 + -5 ℃, 900 + -5 ℃, 1200 + -5 ℃, 1350 + -1420 +/-5 ℃ and 1350 + -1420 ℃.

Optionally, the carbonaceous crucible is a graphite crucible.

Optionally, the push plate type tunnel furnace is a graphite push plate.

Optionally, the specific method for decarbonization in step (3) is as follows:

and (3) after the reaction product is taken out of the furnace, sending the reaction product into an oxidation furnace with the temperature of 600-700 ℃ for decarburization for 1-3 hours, and then cooling the reaction product to room temperature to obtain the aluminum nitride powder.

Further, the temperature for decarburization is preferably 640-660 ℃ and the time for decarburization is preferably 2.2 hours.

Optionally, the concrete method for mixing materials in the step (1) comprises the following steps:

adding aluminum hydroxide, carbon powder and aluminum nitride into a mixer, and mixing for 12-18 hours at the rotating speed of 12-20 revolutions per minute.

Further, the rotating speed of the mixed material is preferably 14-16 rpm, and the time is preferably 12-14 hours.

Optionally, the preparation method of high-purity aluminum nitride further comprises the following step (4) of purification:

stirring and mixing the obtained aluminum nitride powder and pure water with the conductivity less than 0.06S/m for 25-35 minutes to obtain slurry, and dehydrating the slurry to obtain powder blocks; uniformly mixing the obtained powder block with pure water again to obtain slurry, dehydrating the slurry again to obtain powder block, and repeating the steps for multiple times to obtain pure aluminum nitride powder block; wherein the weight ratio of the pure water to the aluminum nitride is (3-4) to (0.1-1.2);

drying the obtained powder block at the temperature of 100-110 ℃, and then sieving the powder block by a 100-mesh sieve to obtain the purified aluminum nitride powder.

Further, the weight ratio of pure water to aluminum nitride in purification is preferably (3-4): 1.

Benefits of the present application include, but are not limited to:

the preparation method of the autocatalysis high-purity aluminum nitride provided by the invention comprises the following steps that (1) aluminum nitride with fine crystal grains and large specific surface area is selected as seed crystals, and aluminum ions and nitrogen ions after the aluminum nitride seed crystals induce carbonization are enriched to the seed crystals in the reaction process, so that the thermal motion of reaction molecules is enhanced, the diffusion and permeation rate is increased, the autocatalysis effect is achieved, and the reaction synthesis time is shortened; secondly, the addition of the aluminum nitride seed crystal enhances the binding capacity of aluminum ions and nitrogen ions and promotes the formation of covalent bond compounds. And thirdly, the aluminum nitride is used as the seed crystal to induce the reaction, so that the impurity element pollution brought by adding other auxiliary agents is avoided, and the purity of the prepared aluminum nitride is ensured. (2) The synthesis reaction is carried out in a mixed gas flow of nitrogen and propane with certain pressure, so that the concentration of CO generated by the reaction is reduced, and the reaction is promoted to be carried out in the forward direction; and secondly, the propane promotes the generation of intermediate phase aluminum carbide, further promotes the combination of aluminum and nitrogen ions to form a covalent bond compound aluminum nitride, and improves the reaction efficiency. In addition, the preparation method of the autocatalytic high-purity aluminum nitride provided by the invention has the advantages that the high-temperature synthesis reaction is preferably carried out in a push plate type tunnel furnace, the continuous production is facilitated, the consistency of the temperature and the time of the synthesis reaction is favorably ensured, the stability and the consistency of the properties of the aluminum nitride product are ensured, and the purity is high.

Detailed Description

The present invention will be described in further detail in the following. It should be noted, however, that the following detailed description merely gives specific operation examples of the present invention by way of example, and the scope of the present invention is not limited thereto. The scope of the invention is limited only by the claims. It will be obvious to those skilled in the art that various other modifications and substitutions can be made to the described embodiments of the invention within the scope of the invention as defined by the claims and still achieve the same technical result as the final technical object of the invention.

The present invention will be described in detail with reference to examples.

Unless otherwise specified, each raw material is commercially available in this specification. In order to avoid repetition, the technical parameters involved in the embodiments are described uniformly as follows:

aluminum hydroxide powder: the purity is 5N, and the granularity is 1-2 μm; purchased from Shandong Hengjing New Material Co., Ltd;

activated carbon powder: the purity is 4N, and the granularity is 2-4 mu m; procurement from Li Yang activated carbon GmbH of Chenfeng;

aluminum nitride powder: the purity is 5N, the granularity is 0.05-0.075 mu m, and the product is purchased from limited company of Shandong constant crystal new materials;

push plate type tunnel furnace: the effective size of the hearth is 12000mm multiplied by 270mm multiplied by 220mm (length multiplied by width multiplied by height), a tungsten wire heating pipe and a graphite push plate (the size is 250 multiplied by 40 mm) are adopted, and the inside of the furnace is divided into the following steps in sequence: a furnace body feeding transition zone with the length of 500 mm, a feeding zone with the length of 1000 mm, and a temperature control zone with the length of 5600 mm (7 temperature zones are provided, and the length of each temperature zone is 800mm), and the length of each temperature zone is 4900 mm.

The temperature of the furnace inlet is 50-70 ℃, and the temperature of the furnace outlet is 80-100 ℃.