Method for preparing aluminum nitride nanopowder based on continuous gas phase activation

Abstract

The present disclosure relates to a preparation method of aluminum nitride nanopowder based on continuous gas phase activation, and relates to the technical field of aluminum nitride nanopowder preparation. The preparation method comprises: 1. adding an ethanol solution of aluminum chloride hexahydrate into an ethanol solution of urea in batches, stirring, cooling, drying the solid after filtration, and obtaining an Al[(CON2H4)n]Cl3 precursor, wherein n is 3-6; 2. placing a first crucible containing the Al[(CON2H4)n]Cl3 precursor in a constant temperature section of a tubular heating furnace; placing a second crucible containing melamine in a non-constant temperature section of the tubular heating furnace close to the air inlet; reacting at 1000-1400 DEG C under a nitrogen atmosphere to obtain aluminum nitride coarse powder; and 3. decarburizing the aluminum nitride coarse powder to obtain aluminum nitride nanopowder. n n ]Cl3 precursor; 2. placing a first crucible containing the Al[(CON2H4)n]Cl3 precursor in a constant temperature section of a tubular heating furnace; placing a second crucible containing melamine in a non-constant temperature section of the tubular heating furnace close to the air inlet; reacting at 1000-1400 DEG C under a nitrogen atmosphere to obtain aluminum nitride coarse powder; and 3. decarburizing the aluminum nitride coarse powder to obtain aluminum nitride nanopowder.​

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of aluminum nitride nanopowder preparation, in particular, to a method for preparing aluminum nitride nanopowder based on continuous gas phase activation. BACKGROUND

[0002] Aluminum nitride is an excellent phonon thermal conductor, with a theoretical thermal conductivity of 320 W / (m·K), i.e. heat is transferred by lattice or crystal vibration. Aluminum nitride has high strength and the strength decreases slowly with the increase of temperature, and also has high stability (stable up to 2200℃), high volume resistivity, high insulation withstand voltage, and thermal expansion coefficient matching silicon. High thermal conductivity is the most prominent feature of aluminum nitride, but in practical applications, the thermal conductivity of aluminum nitride material is often lower than the theoretical value, because the presence of a large amount of oxygen and other impurities and crystal defects will have a strong scattering effect on phonons, thereby affecting heat conduction. Therefore, controlling the oxygen and other impurity content in aluminum nitride and improving the sintering performance of the powder are the key to obtaining high thermal conductivity. High sintering activity requires the powder to have a particle size of nanometer size and uniform distribution. Currently, common methods for preparing aluminum nitride powder include: direct nitriding of aluminum powder, carbon thermal reduction of aluminum oxide powder, self-propagating high-temperature synthesis, chemical vapor deposition, sol-gel method, and plasma method. Among them, the carbon thermal reduction method is the most commonly used method for preparing high-performance aluminum nitride powder. However, this method has a high process temperature and a long time, which requires higher temperatures for subsequent sintering into porcelain, resulting in high energy consumption and high cost.

[0003] Improving the reactivity of the precursor and reducing the preparation temperature are important factors for obtaining nanometer aluminum nitride powder. Currently, there are many reported methods. The use of complex Al[(CON2H4) n]Cl3 as a precursor to prepare nano-aluminum nitride powder has been reported many times (references: Appl. Surface Sci. 2013, 280, 42-49; Ceram. Int. 2018, 44, 5774-5779; Mater. Chem. Phys. 2022, 287, 126280), that is, the "urea glass route" method. This method can significantly improve the reactivity of the precursor and reduce the reaction temperature, but the prepared aluminum nitride has a small amount of alpha-alumina phase, and the powder agglomeration is more serious. The Chinese patent with publication number CN103072961A discloses a method for preparing nano-aluminum nitride powder. Aluminum metal is heated and evaporated by a high-temperature metal evaporator, and then enters a high-temperature nitriding reaction chamber filled with nitrogen for nitriding reaction to prepare nano-aluminum nitride powder. However, this method is complex in equipment and operation, high in production cost, and difficult to mass produce. The Chinese patent with publication number CN103539088A discloses a method for preparing nano-aluminum nitride powder. Aluminum nitrate nonahydrate and melamine are used as raw materials to prepare a precursor with uniform molecular-level mixing in an aqueous solution, and then the precursor is subjected to high-temperature carbon thermal reduction reaction in an ammonia atmosphere to prepare nano-aluminum nitride powder. However, the preparation process of the precursor is complex and time-consuming (10-20 hours are required).

[0004] It should be noted that the information disclosed in the above background section is only used to strengthen the understanding of the background of the present disclosure, and therefore can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0005] The purpose of the present disclosure is to overcome the shortcomings of the prior art described above, and to provide a method for preparing aluminum nitride nano-powder based on continuous gas-phase activation, which improves the reactivity of the aluminum source by generating continuous decomposition products of melamine and reduces the temperature of aluminum nitride preparation.

[0006] According to one aspect of the present disclosure, a method for preparing aluminum nitride nano-powder based on continuous gas-phase activation includes the following steps:

[0007] S1, obtaining an ethanol solution of aluminum chloride hexahydrate and an ethanol solution of urea; adding the ethanol solution of aluminum chloride hexahydrate to the ethanol solution of urea in batches, stirring, cooling and filtering, drying the solid after filtering, and obtaining Al[(CON2H4) n ]Cl3 precursor, wherein n is 3-6, that is, the molar ratio of aluminum chloride hexahydrate to urea is 3-6;

[0008] S2, heating the Al[(CON2H4) nThe Al[(CON2H4)nCl3 precursor is placed in a first crucible, and the first crucible is placed in a constant temperature section of a tube furnace; the melamine is placed in a second crucible, and the second crucible is placed in a non-constant temperature section of the tube furnace close to an air inlet; nitrogen is continuously introduced into the tube furnace, and a carbothermic reduction reaction is carried out at 1000-1400°C for 1-6 hours to obtain aluminum nitride coarse powder;

[0009] S3, decarburization of the aluminum nitride coarse powder obtained in step S2 to obtain aluminum nitride nano powder.

[0010] In an exemplary embodiment of the present disclosure, in step S1, the Al[(CON2H4)nCl3 precursor is Al[(CON2H4)4Cl3. n ]Cl3 precursor, n is 4.

[0011] In an exemplary embodiment of the present disclosure, in step S2, the mass ratio of the Al[(CON2H4)nCl3 precursor to the melamine is 1:(1-5). n ]Cl3 precursor to the melamine is 1:2.

[0012] In an exemplary embodiment of the present disclosure, in step S2, the mass ratio of the Al[(CON2H4)nCl3 precursor to the melamine is 1:(1-5). n ]Cl3 precursor to the melamine is 1:2.

[0013] In an exemplary embodiment of the present disclosure, in step S3, the decarburization of the aluminum nitride coarse powder is carried out at 600-800°C in an air environment for 1-4 hours.

[0014] In an exemplary embodiment of the present disclosure, in step S2, the first crucible is a graphite crucible, and the second crucible is any one of a graphite crucible and a corundum crucible.

[0015] In an exemplary embodiment of the present disclosure, in step S2, the furnace tube of the tube furnace is made of corundum.

[0016] In an exemplary embodiment of the present disclosure, in step S1, the ethanol solution of aluminum chloride hexahydrate and the ethanol solution of urea are obtained as follows:

[0017] The aluminum chloride hexahydrate is dissolved in an ethanol solution at 75-85°C to obtain an ethanol solution of aluminum chloride hexahydrate; the urea is dissolved in an ethanol solution at 75-85°C to obtain an ethanol solution of urea;

[0018] The ethanol solution of aluminum chloride hexahydrate is added to the ethanol solution of urea in batches as follows:

[0019] The temperature is maintained at 75-85°C, and the ethanol solution of aluminum chloride hexahydrate is added to the ethanol solution of urea in batches.

[0020] In an exemplary embodiment of the present disclosure, the temperature of the filtered solid is 70-150°C in step S1.

[0021] In an exemplary embodiment of the present disclosure, the particle size of the aluminum nitride nano-powder is less than 100 nm in step S3.

[0022] The present disclosure places melamine as an activator in the non-constant temperature zone of the tube furnace close to the gas inlet side, uses the characteristics of gradually increasing temperature curve of the non-constant temperature zone, so that melamine can be continuously decomposed, and gaseous decomposition products are generated to enter the constant temperature zone with nitrogen gas from the gas inlet, providing nitrogen source and carbon source for carbothermal reduction reaction, improving the activity of reaction with aluminum source, reducing the temperature of carbothermal reduction reaction, and further reducing the temperature of preparing aluminum nitride nano-powder, thereby reducing the preparation cost of aluminum nitride nano-powder, and the prepared aluminum nitride nano-powder has small particle size, and the subsequent sintering activity of the aluminum nitride nano-powder is improved.

[0023] It should be understood that the foregoing general description and the following detailed description are only exemplary and explanatory, and cannot limit the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0024] The drawings herein are incorporated into the specification and form a part of the specification, show embodiments consistent with the present disclosure, and together with the specification serve to explain the principles of the present disclosure. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without creative labor.

[0025] Figure 1 is the XRD characteristic diagram of aluminum nitride.

[0026] Figure 2 is the XRD characteristic diagram of aluminum nitride obtained by a plurality of embodiments and a control embodiment in an embodiment of the present disclosure; wherein (a) is the XRD characteristic diagram of aluminum nitride obtained by the control example 2, (b) is the XRD characteristic diagram of aluminum nitride obtained by the control example 1, (c) is the XRD characteristic diagram of aluminum nitride obtained by the example 7, (d) is the XRD characteristic diagram of aluminum nitride obtained by the example 1, (e) is the XRD characteristic diagram of aluminum nitride obtained by the example 4, and (f) is the XRD characteristic diagram of aluminum nitride obtained by the example 8.

[0027] Figure 3 is the SEM image of aluminum nitride nano-powder prepared by the steps of the example 1 in an embodiment of the present disclosure; wherein (a) and (b) are SEM images at different magnifications.

[0028] Figure 4For one embodiment of the present disclosure, TEM images of the aluminum nitride nanopowder prepared using the procedure of Example 1 are shown; wherein (a) and (b) are TEM images at different magnifications.

[0029] Figure 5 For one embodiment of the present disclosure, SEM images of the aluminum nitride nanopowder prepared using the procedure of Comparative Example 1 are shown; wherein (a) and (b) are SEM images at different magnifications.

[0030] Figure 6 For one embodiment of the present disclosure, TEM images of the aluminum nitride nanopowder prepared using the procedure of Comparative Example 1 are shown; wherein (a) and (b) are TEM images at different magnifications. DETAILED DESCRIPTION

[0031] Example implementations will now be described more fully with reference to the accompanying drawings. Example implementations may, however, be implemented in many different forms and should not be construed as limited to the implementations set forth herein; rather, these implementations are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example implementations to those skilled in the art.

[0032] The terms "a", "an", and "the" are used to mean one or more than one, unless specified otherwise. The term "includes" and "including" means, but is not limited to, "comprising". The terms "first", "second", and the like, do not mean any order, quantity, or importance, but are used to denote the different features. The terms "comprises", "comprising", "including", and "having" has the same meaning in the context and are used to specify the presence of stated features but does not preclude the presence or addition of one or more other features.

[0033] One embodiment of the present disclosure provides a method for preparing aluminum nitride nanopowder based on continuous gas phase activation, comprising the following steps:

[0034] S1, obtaining an ethanol solution of aluminum chloride hexahydrate and an ethanol solution of urea. The ethanol solution of aluminum chloride hexahydrate is added to the ethanol solution of urea in batches, stirred, cooled and filtered, and the filtered solid is dried to obtain Al[(CON2H4) nCl3 precursor, wherein n is 3-6, i.e. the molar ratio of aluminum chloride hexahydrate to urea is 3-6. For example, when preparing the ethanol solution of aluminum chloride hexahydrate and the ethanol solution of urea, the molar ratio of aluminum chloride hexahydrate to urea can be 1:3, that is, n is 3; or the molar ratio of aluminum chloride hexahydrate to urea can be 1:4, that is, n is 4; or the molar ratio of aluminum chloride hexahydrate to urea can be 1:5, that is, n is 5; or the molar ratio of aluminum chloride hexahydrate to urea can be 1:6, that is, n is 6. In this way, the aluminum source and the carbon source are reacted in the liquid phase to prepare the precursor, which can uniformly mix the aluminum source and the carbon source at the molecular level, and is beneficial to the preparation of aluminum nitride powder of nanometer size. It should be noted that urea can be used as a carbon source to form a reaction precursor with aluminum chloride hexahydrate, and urea can improve the activity of the reaction precursor; at the same time, urea can also be used as a nitrogen source to participate in the subsequent carbothermal reduction reaction.

[0035] In an example, the ethanol solution of aluminum chloride hexahydrate can be prepared by dissolving aluminum chloride hexahydrate in an ethanol solution at 75-85°C to obtain a clear ethanol solution of aluminum chloride hexahydrate. The ethanol solution of urea can be prepared by dissolving urea in an ethanol solution at 75-85°C to obtain a clear ethanol solution of urea. During the mixing of the ethanol solution of aluminum chloride hexahydrate and the ethanol solution of urea, the temperature of the two solutions is maintained in the range of 75-85°C. For example, the above-mentioned dissolution temperature and mixing temperature of aluminum chloride hexahydrate and urea can be 75°C, 78°C, 80°C, 83°C or 85°C.

[0036] In an example, the drying temperature of the filtered solid is 70-150°C. For example, the drying temperature can be 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C.

[0037] S2, placing the Al[(CON2H4) n Cl3 precursor in the first crucible, and placing the first crucible in the constant temperature zone of the tube furnace. Further, the Al[(CON2H4) n Cl3 precursor is laid flat in the first crucible, and the Al[(CON2H4) nThe contact area of the Al[(CON2H4)3] precursor with nitrogen and the melamine decomposition product. The melamine is placed in a second crucible, and the second crucible is placed in the non-constant temperature zone on the side of the tubular heating furnace close to the gas inlet. Further, the melamine is laid flat in the second crucible. In this way, the melamine close to the constant temperature zone can first reach the decomposition temperature and decompose, and the melamine far from the constant temperature zone can reach the decomposition temperature later, so that the melamine is released gradually and continuously, and the carbonthermal reduction reaction is continuously activated. Nitrogen is continuously introduced into the tubular heating furnace from the gas inlet, and the carbonthermal reduction reaction is carried out at 1000-1400°C for 1-6 hours to obtain aluminum nitride coarse powder.

[0038] It should be noted that the tubular heating furnace includes a constant temperature zone in the middle section and non-constant temperature zones at both ends. The constant temperature zone is heated constantly, and the temperature is also constant; the non-constant temperature zone includes two parts, namely, the non-constant temperature zone on the side close to the gas inlet and the non-constant temperature zone on the side close to the gas outlet. It can be understood that the temperature of the non-constant temperature zone on the side close to the gas inlet gradually decreases in the direction from the constant temperature zone to the gas inlet.

[0039] The thermal decomposition temperature of melamine is about 350°C. In the embodiment of the present disclosure, the melamine is placed in the non-constant temperature zone on the side close to the gas inlet, so that the melamine close to the constant temperature zone can be preferentially raised to the thermal decomposition temperature and decomposed, and the gasification gas generated by the decomposition can enter the constant temperature zone as a nitrogen source to participate in the high-temperature carbonthermal reduction reaction with the nitrogen gas from the gas inlet. At the same time, the C-N intermediate in the gasification gas generated by the decomposition of the melamine reacts with the aluminum source to generate aluminum nitride, further improving the reactivity of the aluminum source and reducing the preparation temperature of the aluminum nitride powder. Based on the temperature gradient of the non-constant temperature zone, the melamine can gradually decompose and the gas generated by the decomposition can enter the constant temperature zone with the nitrogen gas from the gas inlet as an activator to continuously participate in the high-temperature carbonthermal reduction reaction. In this way, the melamine can play a continuous gas phase activation role in the carbonthermal reduction reaction, improve the reactivity of the aluminum source, and reduce the preparation temperature of the aluminum nitride nano-powder. The reaction temperature of the method for preparing aluminum nitride by the carbonthermal reduction reaction is generally greater than 1600°C at present, and in step S2 of the embodiment of the present disclosure, the temperature of the carbonthermal reduction reaction is 1000-1400°C, which greatly reduces the reaction temperature, shortens the reaction time, reduces the preparation cost of the aluminum nitride, and also reduces the subsequent processing difficulty of the aluminum nitride nano-powder.

[0040] In one embodiment of the present disclosure, the mass ratio of the Al[(CON2H4)3] precursor to melamine is 1:(1-5). Further, the mass ratio of the Al[(CON2H4)3] precursor to melamine is 1:2. For example, the mass ratio of the Al[(CON2H4)3] precursor to melamine is 1:2. n ]Cl3 precursor and melamine is 1:2. For example, the mass ratio of the Al[(CON2H4)3] precursor to melamine is 1:2. n ]Cl3 precursor and melamine is 1:2. For example, the mass ratio of the Al[(CON2H4)3] precursor to melamine is 1:2. nThe mass ratio of the Cl3 precursor to melamine can be 1:1, or 1:1.5, or 1:2.4, or 1:3, or 1:3.5, or 1:4, or 1:5.

[0041] In an example, the first crucible is a graphite crucible, and the second crucible can be any one of a graphite crucible, a corundum crucible. The second crucible can be selected to be the same as the first crucible, or can be selected to be different from the first crucible.

[0042] In an example, the furnace tube of the tube furnace is made of corundum.

[0043] S3, decarburizing the aluminum nitride coarse powder obtained in step S2 to obtain aluminum nitride nano powder. Illustratively, the particle size of the aluminum nitride nano powder is less than 100 nm.

[0044] In an example, the decarburization of the aluminum nitride coarse powder is carried out in air at 600-800°C for 1-4 hours. For example, the decarburization conditions of the mixed powder can be 3 hours at 600°C, or 1 hour at 600°C, or 4 hours at 600°C, or 3 hours at 700°C, or 2 hours at 700°C, or 1 hour at 800°C, or 2 hours at 800°C, or 2 hours at 600°C followed by 1 hour at 700°C, or 1 hour at 700°C followed by 1 hour at 800°C, or 1 hour at 600°C followed by 2 hours at 800°C, etc.

[0045] The process of the method for preparing aluminum nitride nano powder based on continuous gas phase activation and the properties of the prepared aluminum nitride nano powder are further described below in combination with specific examples.

[0046] Example 1

[0047] S1, Al[(CON2H4) n Preparation of the Cl3 precursor: 0.1 mol of aluminum chloride hexahydrate and 0.6 mol of urea were respectively dissolved in an ethanol solution at 80°C, and a water bath was used for heating to obtain a clear ethanol solution of aluminum chloride hexahydrate and an ethanol solution of urea.

[0048] The ethanol solution of aluminum chloride hexahydrate was added dropwise in batches to the ethanol solution of urea at 80°C. After stirring, the obtained solid product was filtered and dried at 120°C to obtain white Al[(CON2H4)6]Cl3 precursor.

[0049] S2, Preparation of aluminum nitride coarse powder: 3 g of Al[(CON2H4)6]Cl3 precursor prepared in step S1 was placed in a graphite crucible, and the graphite crucible containing the Al[(CON2H4)6]Cl3 precursor was placed in the constant temperature section of the corundum tube furnace. Another 6 g of melamine was placed in a corundum crucible, and the corundum crucible containing the melamine was placed in the non-constant temperature section of the corundum tube furnace close to the gas inlet. The melamine was gradually decomposed during the heating process, thereby continuously producing the activation. Nitrogen gas was introduced into the gas inlet, and the carbothermic reduction reaction was carried out at 1200°C for 3 hours in a nitrogen atmosphere to obtain aluminum nitride coarse powder.

[0050] S3, Decarburization treatment of aluminum nitride coarse powder: The aluminum nitride coarse powder prepared in step S2 was decarburized at 700°C for 3 hours in air to obtain off-white aluminum nitride nanometer powder.

[0051] The raw materials such as aluminum chloride hexahydrate, urea and melamine used in the examples are easy to obtain and have low cost, which further reduces the preparation cost of aluminum nitride nanometer powder.

[0052] Referring to Figure 2 , Figure 2 , the XRD characterization graph of the aluminum nitride powder prepared by the carbothermic reduction reaction at 1200°C is shown. The XRD characterization graph of the aluminum nitride nanometer powder obtained in the present embodiment corresponds to the result shown in (d) of Figure 2 . Compared with the standard XRD characterization graph of aluminum nitride in Figure 1 , it can be seen that the powder obtained in the present embodiment is pure aluminum nitride with low impurity content. The SEM and TEM of the aluminum nitride nanometer powder obtained in the present embodiment correspond to Figure 3 and Figure 4 , respectively. It can be seen that the particle size of the prepared aluminum nitride nanometer powder is less than 100 nm, and the particle size is uniformly dispersed.

[0053] Example 2

[0054] The difference between the present embodiment and example 1 is:

[0055] In step S1, 0.3 mol of urea was dissolved in an ethanol solution, and Al[(CON2H4)3]Cl3 precursor was obtained after reaction with aluminum chloride hexahydrate.

[0056] The other steps are the same as those in example 1. It is detected that the aluminum nitride nanometer powder prepared in the present embodiment has the same characteristics as the aluminum nitride nanometer powder prepared in example 1.

[0057] Example 3

[0058] The difference between the present embodiment and example 1 is:

[0059] In step S1, 0.4 mol of urea was dissolved in an ethanol solution, and reacted with aluminum chloride hexahydrate to obtain the Al[(CON2H4)4]Cl3 precursor.

[0060] The other steps were the same as in Example 1. It was detected that the aluminum nitride nano-powder prepared in this example had the same characteristics as the aluminum nitride nano-powder prepared in Example 1.

[0061] Example 4

[0062] The difference between this example and Example 1 is that:

[0063] In step S2, 9 g of melamine was laid in a corundum crucible and placed in the non-constant temperature zone near the gas inlet side of the corundum tube furnace.

[0064] The other steps were the same as in Example 1.

[0065] Referring to Figure 2 , the XRD characterization graph of the aluminum nitride nano-powder obtained in this example corresponds to the result shown in (e) of Figure 2 . Compared with the aluminum nitride standard XRD characterization graph in Figure 1 , it can be seen that the characteristics of the aluminum nitride powder obtained in this example are the same as those in Example 1, and the impurity content is less.

[0066] Example 5

[0067] The difference between this example and Example 1 is that:

[0068] In step S2, the carbothermic reduction reaction was carried out under a nitrogen atmosphere at 1000°C.

[0069] The other steps were the same as in Example 1. It was detected that the aluminum nitride nano-powder prepared in this example had the same characteristics as the aluminum nitride nano-powder prepared in Example 1.

[0070] Example 6

[0071] The difference between this example and Example 1 is that:

[0072] In step S2, the carbothermic reduction reaction was carried out under a nitrogen atmosphere at 1300°C.

[0073] The other steps were the same as in Example 1. It was detected that the aluminum nitride nano-powder prepared in this example had the same characteristics as the aluminum nitride nano-powder prepared in Example 1.

[0074] Example 7

[0075] The difference between this example and Example 1 is that:

[0076] In step S2, the carbothermic reduction reaction was carried out for 5 hours.

[0077] Other steps are the same as those in Example 1.

[0078] Referring to Figure 2 , the XRD characterization chart of the aluminum nitride nano-powder obtained in this example corresponds to the result shown in (c) of Figure 2 . Compared with the standard XRD characterization chart of aluminum nitride in Figure 1 , it can be seen that the characteristics of the aluminum nitride powder obtained in this example are the same as those in Example 1, and the impurity content is less.

[0079] Example 8

[0080] The difference between this example and Example 1 is that:

[0081] In step S2, 3 g of melamine is laid in the corundum crucible and placed in the non-constant temperature zone near the gas inlet side of the corundum tube furnace; the carbon thermal reduction reaction is performed for 5 hours.

[0082] Other steps are the same as those in Example 1.

[0083] Referring to Figure 2 , the XRD characterization chart of the aluminum nitride nano-powder obtained in this example corresponds to the result shown in (f) of Figure 2 . Compared with the standard XRD characterization chart of aluminum nitride in Figure 1 , it can be seen that the characteristics of the aluminum nitride powder obtained in this example are the same as those in Example 1, and the impurity content is less.

[0084] Comparative Example 1

[0085] The difference between this example and Example 1 is that:

[0086] In step S2, no melamine is laid in the corundum crucible; the carbon thermal reduction reaction time is 3 hours according to Example 1.

[0087] Other steps are the same as those in Example 1.

[0088] Referring to Figure 2 , the XRD characterization chart of the aluminum nitride nano-powder obtained in this example corresponds to the result shown in (b) of Figure 2 . Compared with the standard XRD characterization chart of aluminum nitride in Figure 1 , it can be seen that although the product obtained in this example is mostly the same as the characteristics in Example 1, it contains more impurities, such as more unreacted α-alumina. The SEM and TEM of the powder obtained in this comparative example correspond to Figure 5 and Figure 6 , respectively, it can be seen that the particle size of the prepared powder is larger than that in Example 1, the particle size is not uniform, the dispersion is not uniform, and there is a serious agglomeration phenomenon.

[0089] Comparative Example 2

[0090] The difference from Example 1 is:

[0091] In step S2, melamine is not laid in the corundum crucible; the carbonthermal reduction reaction time is 5 hours.

[0092] The other steps are the same as those in Example 1.

[0093] Referring to Figure 2 , the XRD characterization graph of the aluminum nitride nanometer powder obtained in the present example corresponds to the result shown in (a). Compared with the aluminum nitride standard XRD characterization graph in Figure 2 , it can be seen that the characteristics of the product obtained in the present example are the same as those in Comparative Example 1, and also contain impurities, but the content of unreacted α-aluminum oxide is greatly reduced. Figure 1 Result analysis:

[0094] By comparing Comparative Example 1 and Comparative Example 2, it is shown that under the reaction condition of 1200℃, without adding the continuous gas phase activator melamine, although prolonging the reaction time can increase the conversion rate of the raw material to a certain extent, and more aluminum nitride is obtained, the carbonthermal reduction reaction is still incomplete, so that the obtained aluminum nitride powder contains more impurities.

[0095] By comparing the two comparative examples with the above-mentioned Examples 1 to 8, it can be seen that after adding the activator melamine in the carbonthermal reduction process, under the same reaction temperature (1200℃), even if the carbonthermal reduction reaction time is shorter (for example, the reaction time is 3 hours in Examples 1 and 6), the characteristics of the obtained aluminum nitride nanometer powder are the same as those obtained by prolonging the reaction time (for example, the reaction time is 5 hours in Examples 7 and 8). Thus, it is shown that by adding the activator melamine, the reaction temperature can be lowered (for example, 1200℃), and the reaction time can be reduced, while obtaining aluminum nitride nanometer powder with good performance. Compared with the commonly used carbonthermal reduction reaction above 1600℃, the reaction temperature is greatly reduced, thereby reducing the difficulty and cost of preparing aluminum nitride nanometer powder.

[0096] It should be noted that although the steps of the method for preparing aluminum nitride nanometer powder based on continuous gas phase activation in the present disclosure are described in a specific order in the accompanying drawings, this does not require or imply that these steps must be performed in this specific order, or that all the steps shown must be performed to achieve the desired result. In addition or alternatively, certain steps can be omitted, multiple steps can be combined into one step, and / or one step can be divided into multiple steps, etc.

[0097]

[0098] ​Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the features disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

Claims

1. A method for producing aluminum nitride nano-powder based on continuous gas phase activation, characterized by, The method comprises the following steps: S1, obtaining an ethanol solution of aluminum chloride hexahydrate and an ethanol solution of urea; adding the ethanol solution of aluminum chloride hexahydrate into the ethanol solution of urea in batches, stirring, cooling and filtering, drying the filtered solid, to obtain an Al[(CON2H4) n ]Cl3 precursor, wherein n is 3-6; S2, placing Al[(CON2H4) n ]Cl3 precursor in a first crucible and placing the first crucible in a constant temperature zone of a tube furnace; placing melamine in a second crucible and placing the second crucible in a non-constant temperature zone of the tube furnace close to an air inlet; continuously supplying nitrogen into the tube furnace, and carrying out carbothermic reduction reaction at 1000-1400°C for 1-6 hours to obtain aluminum nitride coarse powder; S3, decarburizing the aluminum nitride coarse powder obtained in step S2 to obtain aluminum nitride nano powder; In step S3, the particle size of the aluminum nitride nano powder is less than 100 nm; The step of adding the ethanol solution of aluminum chloride hexahydrate into the ethanol solution of urea in batches comprises: The ethanol solution of aluminum chloride hexahydrate is added into the ethanol solution of urea in batches while keeping the temperature at 75-85°C; The step of placing the melamine in the second crucible comprises: The melamine is laid flat in the second crucible, so that the melamine close to the constant temperature zone reaches the decomposition temperature first to decompose, and the melamine far from the constant temperature zone reaches the decomposition temperature later, so that the melamine is released gradually and slowly, and the carbonthermal reduction reaction is continuously produced to have an activation effect.

2. The method for preparing aluminum nitride nanopowder based on continuous vapor phase activation according to claim 1, characterized in that, In step S1, the Al[(CON2H4) n ]Cl3 precursor, n is 4.

3. The method for preparing aluminum nitride nanopowder based on continuous vapor phase activation according to claim 1, characterized in that, In step S2, the mass ratio of the Al[(CON2H4) n ]Cl3 precursor to the melamine is 1: (1~5).

4. The method for producing aluminum nitride nanopowder based on continuous vapor phase activation according to claim 3, characterized in that, In step S2, the mass ratio of the Al[(CON2H4) n ]Cl3 precursor to the melamine is 1:

2.

5. The method for producing aluminum nitride nanopowder based on continuous gas phase activation according to any one of claims 1 to 4, characterized in that, In step S3, the decarburization of the aluminum nitride coarse powder is carried out at 600-800°C in an air environment for 1-4 hours.

6. The method for producing aluminum nitride nanopowder based on continuous vapor phase activation according to claim 5, characterized in that, In step S2, the first crucible is a graphite crucible, and the second crucible is any one of a graphite crucible and a corundum crucible.

7. The method for producing aluminum nitride nanopowder based on continuous gas phase activation according to claim 6, characterized in that, In step S2, the furnace tube of the tubular heating furnace is made of corundum.

8. The method for producing aluminum nitride nanopowder based on continuous gas phase activation according to claim 7, characterized in that, In step S1, the ethanol solution of aluminum chloride hexahydrate and the ethanol solution of urea are obtained as follows: The aluminum chloride hexahydrate is dissolved in an ethanol solution at 75-85°C to obtain the ethanol solution of aluminum chloride hexahydrate, and the urea is dissolved in an ethanol solution at 75-85°C to obtain the ethanol solution of urea.

9. The method for producing aluminum nitride nanopowder based on continuous gas phase activation according to claim 8, characterized in that, In step S1, the temperature for drying the filtered solid is 70-150°C.

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