Silicon nitride and aluminum nitride powder and preparation method thereof

Abstract

The invention provides silicon nitride and aluminum nitride powder and a preparation method, and relates to the technical field of ceramic powder. The preparation method of the silicon nitride and aluminum nitride powder comprises the following steps: mixing aluminum powder and aluminum nitride raw powder to obtain a first mixture; mixing silicon powder, silicon nitride raw powder and ammonium salt to obtain a second mixture; paving the first mixture and the second mixture in a material frame padded with a carbon felt, and separating the first mixture from the second mixture by using the carbon felt; the material frame is placed in a self-propagating reaction kettle, nitrogen is introduced after vacuumizing, and the first mixture is ignited so as to induce a combustion synthesis reaction of the second mixture; and after the combustion synthesis reaction, cooling to room temperature, releasing the pressure in the self-propagating reaction kettle, taking out a synthetic product, and grinding the synthetic product to obtain silicon nitride powder and aluminum nitride powder. The purity of the powder material can be improved.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of ceramic powder, in particular to a silicon nitride and aluminum nitride powder and a preparation method. BACKGROUND

[0002] Silicon nitride (Si3N4) is a typical strong covalent compound, which has high melting point, high hardness, high wear resistance, high bending strength and good thermal conductivity, and plays an irreplaceable role in engineering, electronic information and other key fields, which is related to social safety and national economic development.

[0003] Aluminum nitride (AlN) has high thermal conductivity, insulation, low dielectric constant, small thermal expansion coefficient and other advantages, and has broad application prospects in integrated circuit heat conducting ceramic substrate, electronic device packaging filler, special structure ceramic material and other fields.

[0004] At present, for the above-mentioned materials, there is a problem that the purity of the prepared powder material is low.

[0005] 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

[0006] The purpose of the present disclosure is to provide a silicon nitride and aluminum nitride powder and a preparation method, and to at least partially overcome the problem of low purity of the prepared powder material.

[0007] According to a first aspect of the present disclosure, a preparation method of a silicon nitride and aluminum nitride powder is provided, comprising: mixing aluminum powder and aluminum nitride raw powder to obtain a first mixture; mixing silicon powder, silicon nitride raw powder and ammonium salt to obtain a second mixture; laying the first mixture and the second mixture in a material frame padded with carbon felt, and separating the first mixture from the second mixture by using the carbon felt; placing the material frame in a self-propagating reaction kettle, introducing nitrogen gas after vacuumizing, igniting the first mixture to induce the second mixture to perform a combustion synthesis reaction; after the combustion synthesis reaction, cooling to room temperature, releasing the pressure in the self-propagating reaction kettle, taking out the synthesis product, and grinding the synthesis product to obtain a silicon nitride powder and an aluminum nitride powder.

[0008] Optionally, the particle size of the aluminum powder is 40-50 μm, and the particle size of the aluminum nitride raw powder is 1.5-10 μm; wherein the mass ratio of the aluminum powder to the aluminum nitride raw powder is (30-45):(55-70).

[0009] Optionally, the particle size of the silicon powder is 1-5 μm, and the particle size of the silicon nitride raw powder is 2.5-5 μm; wherein the mass ratio of the silicon powder, the silicon nitride raw powder and the ammonium salt is (31.5-38):(54-61.75):(5-10).

[0010] Optionally, the ammonium salt is ammonium chloride or ammonium fluoride.

[0011] Optionally, the mass ratio of the first mixture to the second mixture is 1:(2-5).

[0012] Optionally, in the material frame, the first mixture is placed below, beside or in the middle of the second mixture.

[0013] Optionally, the igniting of the first mixture comprises igniting one side of the first mixture by using the heating tungsten wire.

[0014] Optionally, the pressure of the nitrogen gas is 4-6 MPa.

[0015] Optionally, the particle size of the silicon nitride powder is greater than the particle size of the silicon nitride raw powder, and the particle size of the aluminum nitride powder is greater than the particle size of the aluminum nitride raw powder.

[0016] According to a second aspect of the present disclosure, there is provided a silicon nitride and aluminum nitride powder prepared by using any of the above-mentioned preparation methods.

[0017] In the exemplary embodiments of the present disclosure, on the one hand, the silicon powder is ignited by the heat of the combustion synthesis reaction of the aluminum nitride, thereby inducing the combustion synthesis reaction of the silicon nitride, avoiding the use of the ignition agent such as titanium powder, avoiding the adverse effects of the traditional electrode ignition mode which is easy to introduce foreign impurities, and significantly improving the purity of at least the silicon nitride. On the other hand, the present disclosure can significantly reduce the combustion synthesis temperature of the silicon nitride by controlling the amount of raw materials, especially by regulating the amount of ammonium salt, which is beneficial to improve the content of alpha phase and reduce the agglomeration degree of the silicon nitride powder. In addition, by regulating the amount of ammonium salt, the oxygen impurity content of the silicon nitride can be reduced. On the other hand, by using the material frame padded with carbon felt, the application of the scheme of the present disclosure can prepare the silicon nitride powder and the aluminum nitride powder in different zones, thereby improving the economic benefits of the materials. On the other hand, the preparation scheme of the present disclosure has the advantages of simple process, low energy consumption, strong controllability and easy implementation.

[0018] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0020] Figure 1 A flowchart illustrating the preparation method of silicon nitride and aluminum nitride powders according to embodiments of the present disclosure is shown.

[0021] Figure 2 The XRD (X-Ray Diffraction) patterns of silicon nitride powder prepared using the methods of Examples 1, 3, and 8 of this disclosure are shown.

[0022] Figure 3 The XRD patterns of aluminum nitride powder prepared using the methods of Examples 1, 3, and 8 of this disclosure are shown.

[0023] Figure 4 The SEM (Scanning Electron Microscope) images of silicon nitride powder prepared using the method of Example 1 of this disclosure are shown. Wherein, a, b, c, and d are morphology images of silicon nitride powder at different locations magnified at 5,000x, 5,000x, 2,000x, and 2,000x, respectively.

[0024] Figure 5 SEM images of aluminum nitride powder prepared using the method of Example 1 of this disclosure are shown. Wherein, a, b, c, and d are morphology images of aluminum nitride powder at different locations magnified at 5,000x, 5,000x, 2,000x, and 2,000x, respectively. Detailed Implementation

[0025] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided to make this disclosure more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a full understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced with one or more of these specific details omitted, or other methods, processes, steps, etc., can be employed. In other instances, well-known technical solutions are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0026] Further, the accompanying drawings are included to provide a thorough understanding of the present disclosure and are not intended to be exhaustive or to limit the present disclosure to the precise outline described herein. The same or similar reference numerals in different drawings represent the same or similar parts, and thus repetitive description will be omitted. The flowcharts shown in the drawings are merely illustrative and do not necessarily include all the steps. For example, some steps can be further divided, and some steps can be combined or partially combined, so that the actual execution order can be changed according to the actual situation. In addition, all the terms "first", "second", etc. below are only for the purpose of distinction and should not be regarded as a limitation of the present disclosure.

[0027] The preparation method of the silicon nitride and aluminum nitride powder can include direct nitridation, carbothermal reduction, thermal decomposition, combustion synthesis, sol-gel method, and vapor deposition method, etc. Among them, the direct nitridation and the carbothermal reduction are the main methods for the industrial production of silicon nitride and aluminum nitride at present. The combustion synthesis method for preparing the silicon nitride and aluminum nitride powder has the advantages of high efficiency, energy saving, environmental protection, etc., and is a very potential method suitable for industrial production. However, when preparing the powder, due to the too fast reaction speed, the reaction process is difficult to control, and the obtained product still has problems such as low purity, high oxygen content, difficult to control crystal phase, coarse and uneven grain size, etc.

[0028] In order to solve or at least alleviate these problems, the present disclosure provides a new preparation scheme of the silicon nitride and aluminum nitride powder.

[0029] Figure 1 The flowchart of the preparation method of the silicon nitride and aluminum nitride powder of the present disclosure is schematically shown. Referring to Figure 1 The preparation method of the silicon nitride and aluminum nitride powder of the present disclosure can include the following steps: S10. Mixing aluminum powder and aluminum nitride raw powder to obtain a first mixture.

[0030] In the exemplary embodiment of the present disclosure, the particle size of the aluminum powder is 40-50 μm, for example, 44 μm. The particle size of the aluminum nitride raw powder is 1.5-10 μm. The mass ratio of the aluminum powder to the aluminum nitride raw powder is (30-45):(55-70).

[0031] It should be noted that the mixing method of the aluminum powder and the aluminum nitride raw powder in the present disclosure can be mechanical mixing. For example, the two are mixed by stirring, ball milling, etc., which is not limited in the present disclosure.

[0032] S12. Mixing silicon powder, silicon nitride raw powder and ammonium salt to obtain a second mixture.

[0033] In the example embodiment of the present disclosure, the particle size of the silicon powder is 1-5 μm, for example, 3 μm. The particle size of the silicon nitride raw powder is 2.5-5 μm. The ammonium salt can be ammonium chloride or ammonium fluoride. The mass ratio of the silicon powder, the silicon nitride raw powder and the ammonium salt can be (31.5-38):(54-61.75):(5-10).

[0034] It should be noted that the mixing of the silicon powder, the silicon nitride raw powder and the ammonium salt can be mechanical mixing. For example, the three can be mixed by stirring, ball milling or the like, which is not limited in the present disclosure.

[0035] S14. The first mixture and the second mixture are laid in a mold with carbon felt, and the first mixture is separated from the second mixture by the carbon felt.

[0036] In the example embodiment of the present disclosure, in order to fully realize the induced combustion of step S16, the first mixture can be placed below, beside or in the middle of the second mixture.

[0037] In the example preparation scheme of the present disclosure, the mass ratio of the first mixture to the second mixture can be 1:(2-5).

[0038] S16. The mold is placed in a self-propagating reaction kettle, vacuum is drawn and nitrogen is introduced, the first mixture is ignited to induce the combustion synthesis reaction of the second mixture.

[0039] According to some embodiments of the present disclosure, the gas pressure of the nitrogen is 4-6 MPa.

[0040] Specifically, the first mixture can be ignited by a heating tungsten wire, for example, the side away from the second mixture, which is not limited in the present disclosure.

[0041] By igniting the first mixture, the combustion synthesis reaction heat of the aluminum nitride can ignite the silicon powder to induce the combustion synthesis reaction of the silicon nitride. Thus, the use of the ignition agent such as titanium powder is avoided, and the adverse effects of the foreign impurities easily introduced by the traditional electrode ignition method are greatly reduced, and at least the purity of the silicon nitride product is significantly improved.

[0042] S18. After the combustion synthesis reaction, cooling to room temperature, releasing the pressure in the self-propagating reaction kettle, taking out the synthesis product, and grinding the synthesis product to obtain silicon nitride powder and aluminum nitride powder.

[0043] In the example embodiment of the present disclosure, the particle size of the silicon nitride powder obtained in step S18 is larger than the particle size of the above-mentioned silicon nitride raw powder, and the particle size of the aluminum nitride powder is larger than the particle size of the above-mentioned aluminum nitride raw powder. The particle size of the silicon nitride powder and the aluminum nitride powder prepared by the present disclosure is micron level.

[0044] It should be noted that the silicon nitride powder and the aluminum nitride powder prepared by the present disclosure are more than the above-mentioned silicon nitride raw powder and aluminum nitride raw powder. That is, the weight of the prepared silicon nitride powder is greater than the weight of the silicon nitride raw powder, and the weight of the prepared aluminum nitride powder is greater than the weight of the aluminum nitride raw powder.

[0045] In one aspect, the present disclosure can solve the problem that the silicon powder is not easy to ignite when the ammonium salt addition amount is high by controlling the ratio of aluminum powder and aluminum nitride powder in the Al / AlN mixture and the amount of the mixture, thereby increasing the addition amount of NH4Cl and NH4F, significantly reducing the combustion synthesis temperature of silicon nitride, and being beneficial to increasing the α phase content and reducing the agglomeration degree of the silicon nitride powder.

[0046] On the other hand, generally in the presence of oxygen-containing impurities, Si is promoted to vaporize into SiO, and then the oxygen-containing impurities Si2N2O in the product are generated. When NH4Cl and NH4F are present, HCl and HF are generated by decomposition, SiO is converted into SiCl4 and SiF4 under high temperature conditions, and then nitrided into silicon nitride powder. The increase of the addition amount of NH4Cl and NH4F can further reduce the oxygen impurity content of the silicon nitride powder.

[0047] In still another aspect, the preparation scheme of the present disclosure avoids the use of ignition agents such as titanium powder, and reduces the consumption of resources. In addition, micron-sized silicon nitride and aluminum nitride powder can be prepared in different zones at the same time, which is helpful to improve economic benefits and is suitable for industrial production.

[0048] The reaction principle of the preparation process based on the raw powder of the present disclosure is described below.

[0049] The preparation method adopted by the present disclosure is combustion synthesis. Combustion synthesis is a method of synthesizing materials by using the heat released by the reaction between reactants. Once the reactants are ignited, they will automatically spread to the unreacted area until the reaction is complete, and almost no external energy is needed during the whole process. The reaction is rapid and the synthesis time is short. Compared with direct nitriding method, carbonthermal synthesis method and other synthesis methods, combustion synthesis method has the characteristics of simple process, short cycle, low energy consumption and low cost.

[0050] However, when preparing silicon nitride powder, the reaction speed is too fast, the reaction temperature is too high, and the reaction process is difficult to control, resulting in incomplete reaction, abnormal growth of silicon nitride grains and reduction of α phase content. The internal reason for being difficult to obtain high α phase is that α phase is easily converted into β phase and is very sensitive to temperature. Therefore, how to control the heat is the key to synthesizing high-quality silicon nitride powder by self-propagating combustion technology.

[0051] Since the combustion synthesis is a violent, rapid self-sustaining reaction, once the reaction starts, it cannot be intervened, therefore, for the control of the silicon nitride reaction process and product quality, the embodiments of the present disclosure start from optimizing the initial reaction conditions. The method for controlling heat is to add a heat "diluent" in the raw materials, which can not only reduce the liquid silicon and inhibit the formation of coarse bulk, but also disperse the molten silicon and promote the penetration of nitrogen, promote the reaction, in addition, it can also reduce the combustion synthesis temperature and improve the content of the alpha phase. In the embodiments of the present disclosure, the Si3N4 raw powder is used as a diluent, which reduces the reaction temperature by reducing the heat release per unit volume, and the Si3N4 powder also acts as a crystal seed to strengthen the nucleation and growth of the gas phase reaction. The present disclosure uses the method of combining Si3N4 diluent with ammonium salt to control the reaction heat.

[0052] The purpose of using aluminum nitride raw powder in the embodiments of the present disclosure is similar, which also plays a role of diluent.

[0053] Further, the embodiments of the present disclosure also provide a silicon nitride and aluminum nitride powder, which can be prepared by the preparation method of steps S10 to S18 described above.

[0054] The preparation scheme of Example 1 of the present disclosure is described below.

[0055] First, 21 g of aluminum powder with a particle size of 44 μm and 49 g of aluminum nitride raw powder with a particle size of 1.5 μm are dosed and uniformly mixed by mechanical stirring to obtain a first mixture. 66.5 g of silicon powder with a particle size of 2.5 μm, 123.5 g of silicon nitride raw powder with a particle size of 2.5 μm and 10 g of NH4Cl are dosed and uniformly mixed by mechanical stirring to obtain a second mixture.

[0056] Next, the first mixture and the second mixture are laid in a material frame padded with carbon felt, and the first mixture and the second mixture are separated by the carbon felt, and the first mixture is placed on the side of the second mixture.

[0057] Subsequently, the material frame is placed in a self-propagating reaction kettle, vacuumized and nitrogenized to 4 MPa, the first mixture side is ignited by using a heating tungsten wire, and the second mixture is induced to carry out a combustion synthesis reaction.

[0058] After the reaction is completed, it is cooled to room temperature, the pressure in the self-propagating reaction kettle is released, the synthesis product is taken out, and the synthesis product is ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0059] The preparation scheme of Example 2 of the present disclosure is described below.

[0060] First, 18 g of aluminum powder with a particle size of 40 μm and 22 g of aluminum nitride raw powder with a particle size of 1.5 μm are dosed, mixed uniformly by mechanical stirring, and a first mixture is obtained. 66.5 g of silicon powder with a particle size of 2.5 μm, 123.5 g of silicon nitride raw powder with a particle size of 2.5 μm, and 10 g of NH4Cl are dosed, mixed uniformly by mechanical stirring, and a second mixture is obtained.

[0061] Next, the first mixture and the second mixture are laid in a mold frame padded with carbon felt, and the first mixture and the second mixture are separated by the carbon felt, with the first mixture being placed on the side of the second mixture.

[0062] Subsequently, the mold frame is placed in a self-propagating reaction kettle, vacuum is drawn and nitrogen is introduced to 4 MPa, the first mixture side is ignited by a heating tungsten wire, and the second mixture is induced to perform a combustion synthesis reaction.

[0063] After the reaction is completed, the temperature is cooled to room temperature, the pressure in the self-propagating reaction kettle is released, the synthesis product is taken out, and the synthesis product is ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0064] The preparation scheme of Example 3 of the present disclosure is described below.

[0065] First, 20 g of aluminum powder with a particle size of 50 μm and 30 g of aluminum nitride raw powder with a particle size of 10 μm are dosed, mixed uniformly by mechanical stirring, and a first mixture is obtained. 66.5 g of silicon powder with a particle size of 2.5 μm, 123.5 g of silicon nitride raw powder with a particle size of 2.5 μm, and 10 g of NH4Cl are dosed, mixed uniformly by mechanical stirring, and a second mixture is obtained.

[0066] Next, the first mixture and the second mixture are laid in a mold frame padded with carbon felt, and the first mixture and the second mixture are separated by the carbon felt, with the first mixture being placed on the side of the second mixture.

[0067] Subsequently, the mold frame is placed in a self-propagating reaction kettle, vacuum is drawn and nitrogen is introduced to 4 MPa, the first mixture side is ignited by a heating tungsten wire, and the second mixture is induced to perform a combustion synthesis reaction.

[0068] After the reaction is completed, the temperature is cooled to room temperature, the pressure in the self-propagating reaction kettle is released, the synthesis product is taken out, and the synthesis product is ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0069] The preparation scheme of Example 4 of the present disclosure is described below.

[0070] First, 20 g of aluminum powder with a particle size of 44 μm and 30 g of aluminum nitride raw powder with a particle size of 1.5 μm are dosed, mixed uniformly by mechanical stirring, and a first mixture is obtained. 66.5 g of silicon powder with a particle size of 2.5 μm, 123.5 g of silicon nitride raw powder with a particle size of 5 μm, and 10 g of NH4F are dosed, mixed uniformly by mechanical stirring, and a second mixture is obtained.

[0071] Next, the first mixture and the second mixture are laid in a mold frame padded with carbon felt, and the first mixture and the second mixture are separated by the carbon felt, with the first mixture placed on the side of the second mixture.

[0072] Subsequently, the mold frame is placed in a self-propagating reaction kettle, vacuum is drawn and nitrogen is introduced to 4 MPa, the first mixture is ignited on one side by using a heating tungsten wire, and the second mixture is induced to perform a combustion synthesis reaction.

[0073] After the reaction is completed, the temperature is cooled to room temperature, the pressure in the self-propagating reaction kettle is released, the synthesis product is taken out, and the synthesis product is ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0074] The preparation scheme of the embodiment 5 of the present disclosure is described below.

[0075] First, 20 g of aluminum powder with a particle size of 44 μm and 30 g of aluminum nitride raw powder with a particle size of 1.5 μm are dosed, mixed uniformly by mechanical stirring, and a first mixture is obtained. 66.5 g of silicon powder with a particle size of 5 μm, 123.5 g of silicon nitride raw powder with a particle size of 2.5 μm, and 10 g of NH4Cl are dosed, mixed uniformly by mechanical stirring, and a second mixture is obtained.

[0076] Next, the first mixture and the second mixture are laid in a mold frame padded with carbon felt, and the first mixture and the second mixture are separated by the carbon felt, with the first mixture placed on the side of the second mixture.

[0077] Subsequently, the mold frame is placed in a self-propagating reaction kettle, vacuum is drawn and nitrogen is introduced to 4 MPa, the first mixture is ignited on one side by using a heating tungsten wire, and the second mixture is induced to perform a combustion synthesis reaction.

[0078] After the reaction is completed, the temperature is cooled to room temperature, the pressure in the self-propagating reaction kettle is released, the synthesis product is taken out, and the synthesis product is ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0079] The preparation scheme of the embodiment 6 of the present disclosure is described below.

[0080] First, 20 g of aluminum powder with a particle size of 44 μm and 30 g of aluminum nitride raw powder with a particle size of 1.5 μm are dosed, mixed uniformly by mechanical stirring, and a first mixture is obtained. 65.8 g of silicon powder with a particle size of 2.5 μm, 122.2 g of silicon nitride raw powder with a particle size of 2.5 μm, and 12 g of NH4Cl are dosed, mixed uniformly by mechanical stirring, and a second mixture is obtained.

[0081] Next, the first mixture and the second mixture are laid in a mold frame padded with carbon felt, and the first mixture and the second mixture are separated by the carbon felt, with the first mixture being placed on the side of the second mixture.

[0082] Subsequently, the mold frame is placed in a self-propagating reaction kettle, vacuum is drawn and nitrogen is introduced to 4 MPa, the first mixture side is ignited by a heating tungsten wire, and the second mixture is induced to perform a combustion synthesis reaction.

[0083] After the reaction is completed, the temperature is cooled to room temperature, the pressure in the self-propagating reaction kettle is released, the synthesis product is taken out, and the synthesis product is ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0084] The preparation scheme of Example 7 of the present disclosure is described below.

[0085] First, 20 g of aluminum powder with a particle size of 44 μm and 30 g of aluminum nitride raw powder with a particle size of 1.5 μm are dosed, mixed uniformly by mechanical stirring, and a first mixture is obtained. 65.1 g of silicon powder with a particle size of 1 μm, 120.9 g of silicon nitride raw powder with a particle size of 2.5 μm, and 14 g of NH4Cl are dosed, mixed uniformly by mechanical stirring, and a second mixture is obtained.

[0086] Next, the first mixture and the second mixture are laid in a mold frame padded with carbon felt, and the first mixture and the second mixture are separated by the carbon felt, with the first mixture being placed on the side of the second mixture.

[0087] Subsequently, the mold frame is placed in a self-propagating reaction kettle, vacuum is drawn and nitrogen is introduced to 4 MPa, the first mixture side is ignited by a heating tungsten wire, and the second mixture is induced to perform a combustion synthesis reaction.

[0088] After the reaction is completed, the temperature is cooled to room temperature, the pressure in the self-propagating reaction kettle is released, the synthesis product is taken out, and the synthesis product is ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0089] The preparation scheme of Example 8 of the present disclosure is described below.

[0090] First, 45 g of aluminum powder with a particle size of 44 μm and 55 g of aluminum nitride raw powder with a particle size of 1.5 μm are dosed, mixed uniformly by mechanical stirring, and a first mixture is obtained. 72 g of silicon powder with a particle size of 2.5 μm, 108 g of silicon nitride raw powder with a particle size of 2.5 μm, and 20 g of NH4Cl are dosed, mixed uniformly by mechanical stirring, and a second mixture is obtained.

[0091] Next, the first mixture and the second mixture are laid in a mold frame padded with carbon felt, and the first mixture and the second mixture are separated by the carbon felt, with the first mixture being placed in the middle position of the second mixture.

[0092] Subsequently, the mold frame is placed in a self-propagating reaction kettle, vacuum is drawn and nitrogen is introduced to 4 MPa, the first mixture side is ignited by a heating tungsten wire, and the second mixture is induced to perform a combustion synthesis reaction.

[0093] After the reaction is completed, the temperature is cooled to room temperature, the pressure in the self-propagating reaction kettle is released, the synthesis product is taken out, and the synthesis product is ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0094] The preparation scheme of Example 9 of the present disclosure is described below.

[0095] First, 28 g of aluminum powder with a particle size of 44 μm and 42 g of aluminum nitride raw powder with a particle size of 1.5 μm are dosed, mixed uniformly by mechanical stirring, and a first mixture is obtained. 72 g of silicon powder with a particle size of 2.5 μm, 108 g of silicon nitride raw powder with a particle size of 2.5 μm, and 20 g of NH4Cl are dosed, mixed uniformly by mechanical stirring, and a second mixture is obtained.

[0096] Next, the first mixture and the second mixture are laid in a mold frame padded with carbon felt, and the first mixture and the second mixture are separated by the carbon felt, with the first mixture being placed below the second mixture.

[0097] Subsequently, the mold frame is placed in a self-propagating reaction kettle, vacuum is drawn and nitrogen is introduced to 6 MPa, the first mixture side is ignited by a heating tungsten wire, and the second mixture is induced to perform a combustion synthesis reaction.

[0098] After the reaction is completed, the temperature is cooled to room temperature, the pressure in the self-propagating reaction kettle is released, the synthesis product is taken out, and the synthesis product is ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0099] The preparation scheme of Example 10 of the present disclosure is described below.

[0100] First, 27 g of aluminum powder with a particle size of 44 μm and 33 g of aluminum nitride raw powder with a particle size of 1.5 μm are dosed, mixed uniformly by mechanical stirring to obtain a first mixture. 72.8 g of silicon powder with a particle size of 2.5 μm, 109.2 g of silicon nitride raw powder with a particle size of 2.5 μm and 18 g of NH4Cl are dosed, mixed uniformly by mechanical stirring to obtain a second mixture.

[0101] Next, the first mixture and the second mixture are laid in a mold frame padded with carbon felt, and the first mixture and the second mixture are separated by the carbon felt, with the first mixture being placed on the side of the second mixture.

[0102] Subsequently, the mold frame is placed in a self-propagating reaction kettle, vacuumized and nitrogenized to 4 MPa, the first mixture side is ignited by a heating tungsten wire, and the second mixture is induced to perform a combustion synthesis reaction.

[0103] After the reaction is completed, the temperature is cooled to room temperature, the pressure in the self-propagating reaction kettle is released, the synthesis product is taken out, and the synthesis product is ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0104] The compositions of the prepared silicon nitride powder and aluminum nitride powder are tested, taking Example 1, Example 3 and Example 8 as examples.

[0105] Figure 2 The XRD diagram corresponding to the silicon nitride powder is shown. Referring to Figure 2 The products prepared in these examples are all composed of α-Si3N4 (PDF #09-0250) and β-Si3N4 (PDF #33-1160), and the α-phase content is all above 92%.

[0106] Figure 3 The XRD diagram corresponding to the aluminum nitride powder is shown. Referring to Figure 3 The diffraction peaks of the products prepared in these examples all belong to hexagonal aluminum nitride (PDF #25-1133), and do not contain other impurities.

[0107] In addition, Figure 4 and Figure 5 The SEM diagrams of the silicon nitride powder and the aluminum nitride powder prepared in the manner of Example 1 of the present disclosure are shown respectively.

[0108] It should be noted that although the various steps of the method in the present disclosure are described in a specific order in the drawings, this does not require or imply that the 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, a plurality of steps can be combined into one step, and / or one step can be divided into a plurality of steps, etc.

[0109] Further, the above-described diagrams are merely schematic illustrations of the processes included in the method according to the exemplary embodiments of the present disclosure, and are not intended for limiting purposes. It is readily understood that the processes shown in the above-described diagrams do not indicate or limit the time sequence of the processes. In addition, it is readily understood that the processes can be executed, for example, synchronously or asynchronously in a plurality of modules.

[0110] Other embodiments of the present disclosure will be readily apparent to those skilled in the art upon considering the description herein, the drawings, and the appended claims. The application is intended to cover any adaptations or variations of the present disclosure followed in the general principles of the present disclosure and including such modifications as would be readily apparent to those skilled in the art and desired to be protected by the claims that follow. The application is to be limited only by the claims that follow.

[0111] It is to be understood that the present disclosure is not limited to the precise structures described hereinabove and illustrated in the accompanying drawings, and that various modifications and changes can be made without departing from the scope thereof. The scope of the present disclosure is limited only by the claims that follow.

Claims

1. A method for producing a silicon nitride and aluminum nitride powder, characterized by, The application relates to a preparation method of silicon nitride and aluminum nitride powders. aluminum powder and aluminum nitride raw powder are mixed to obtain a first mixture; silicon powder, silicon nitride raw powder and ammonium salt are mixed to obtain a second mixture; the first mixture and the second mixture are laid in a mold frame padded with carbon felt, and the first mixture is separated from the second mixture by the carbon felt; the mold frame is placed in a self-propagating reaction kettle, vacuumized, filled with nitrogen, the first mixture is ignited to induce the second mixture to carry out a combustion synthesis reaction; after the combustion synthesis reaction, the self-propagating reaction kettle is cooled to room temperature, the pressure in the self-propagating reaction kettle is released, the synthesis product is taken out, and the synthesis product is ground to obtain silicon nitride powder and aluminum nitride powder.

2. The production method according to claim 1, characterized by, The particle size of the aluminum powder is 40-50 mu m, and the particle size of the aluminum nitride raw powder is 1.5-10 mu m. The mass ratio of the aluminum powder to the aluminum nitride raw powder is (30-45):(55-70).

3. The preparation method according to claim 1, characterized in that, The particle size of the silicon powder is 1-5 mu m, and the particle size of the silicon nitride raw powder is 2.5-5 mu m. The mass ratio of the silicon powder, the silicon nitride raw powder and the ammonium salt is (31.5-38):(54-61.75):(5-10).

4. The production method according to claim 1 or 3, characterized by, The ammonium salt is ammonium chloride or ammonium fluoride.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the first mixture to the second mixture is 1:(2-5).

6. The production method according to claim 1 or 5, characterized by, In the mold frame, the first mixture is arranged below, on the side or in the middle of the second mixture.

7. The preparation method according to claim 1, characterized in that, The first mixture is ignited by using a heating tungsten wire to ignite one side of the first mixture. The pressure of the nitrogen is 4-6 MPa.

8. The method of claim 1, wherein, The particle size of the silicon nitride powder is larger than that of the silicon nitride raw powder, and the particle size of the aluminum nitride powder is larger than that of the aluminum nitride raw powder.

9. The method of claim 1, wherein, The silicon nitride and aluminum nitride powders are prepared by using the preparation method of any one of claims 1-9.

10. A silicon nitride and aluminum nitride powder, characterized by, ​

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