Silicon nitride and aluminum nitride powders and their preparation methods

Abstract

This disclosure provides silicon nitride and aluminum nitride powders and their preparation method, relating to the field of ceramic powder technology. The preparation method includes: 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; spreading the first and second mixtures in a material frame lined with carbon felt, using the carbon felt to separate the first and second mixtures; placing the material frame in a self-propagating reactor, evacuating it, and then introducing nitrogen gas to ignite the first mixture, thereby inducing a combustion synthesis reaction in the second mixture; after the combustion synthesis reaction, cooling to room temperature, releasing the pressure inside the self-propagating reactor, removing the synthesized product, and grinding the synthesized product to obtain silicon nitride powder and aluminum nitride powder. This disclosure can improve the purity of powder materials.

Description

Technical Field

[0001] This disclosure relates to the field of ceramic powder technology, and more specifically, to a silicon nitride and aluminum nitride powder and a method for preparing them. Background Technology

[0002] Silicon nitride (Si3N4) is a typical strong covalent compound. It not only has a high melting point, high hardness, and wear resistance, but also high bending strength and good thermal conductivity. It plays an irreplaceable role in key fields such as engineering and electronic information, and is related to social security and national economic development.

[0003] Aluminum nitride (AlN) has advantages such as high thermal conductivity, insulation, low dielectric constant, and small coefficient of thermal expansion, and has broad application prospects in fields such as thermally conductive ceramic substrates for integrated circuits, packaging fillers for electronic devices, and special structural ceramic materials.

[0004] Currently, the problem with the above-mentioned materials is that the purity of the prepared powder materials is low.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this disclosure is to provide silicon nitride and aluminum nitride powders and their preparation method, thereby overcoming, at least to some extent, the problem of low purity of the prepared powder materials.

[0007] According to a first aspect of this disclosure, a method for preparing silicon nitride and aluminum nitride powders 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; spreading the first mixture and the second mixture in a material frame lined with carbon felt, and using the carbon felt to separate the first mixture and the second mixture; placing the material frame in a self-propagating reactor, evacuating the reactor and then introducing nitrogen gas to ignite the first mixture to induce a combustion synthesis reaction of the second mixture; after the combustion synthesis reaction, cooling to room temperature, releasing the pressure in the self-propagating reactor, removing the synthesis product, and grinding the synthesis product to obtain silicon nitride powder and aluminum nitride powder.

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

[0009] Optionally, the particle size of silicon powder is 1~5μm, and the particle size of silicon nitride raw powder is 2.5~5μm; wherein the mass ratio of silicon powder, silicon nitride raw powder and 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 feed box, the first mixture is positioned below, to the side, or in the middle of the second mixture.

[0013] Optionally, igniting the first mixture includes igniting one side of the first mixture using a heated tungsten filament.

[0014] Optionally, the nitrogen pressure is 4~6 MPa.

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

[0016] According to a second aspect of this disclosure, silicon nitride and aluminum nitride powders are provided, prepared using any of the above-described methods for preparing silicon nitride and aluminum nitride powders.

[0017] In the exemplary embodiments of this disclosure, on the one hand, the heat from the combustion synthesis reaction of aluminum nitride ignites silicon powder, thereby inducing the combustion synthesis reaction of silicon nitride. This avoids the use of ignition agents such as titanium powder and avoids the adverse effects of introducing foreign impurities easily by traditional electrode ignition methods, significantly improving at least the purity of silicon nitride. On the other hand, this disclosure can significantly reduce the combustion synthesis temperature of silicon nitride by controlling the amount of raw materials, especially the amount of ammonium salt, which is beneficial to increasing the α-phase content and reducing the agglomeration of silicon nitride powder. In addition, by controlling the amount of ammonium salt, the oxygen impurity content of silicon nitride can be reduced. Furthermore, by using a material frame padded with carbon felt, the method of this disclosure can be used to prepare silicon nitride powder and aluminum nitride powder in separate sections, improving the economic efficiency of the material. Moreover, the preparation method of this disclosure is simple in process, low in energy consumption, highly controllable, and easy to implement.

[0018] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[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] Furthermore, the accompanying drawings are merely illustrative of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. The flowcharts shown in the drawings are merely exemplary illustrations and do not necessarily include all steps. For example, some steps may be broken down, while others may be combined or partially combined; therefore, the actual order of execution may change depending on the actual situation. Additionally, all terms such as "first," "second," etc., used below are for distinction purposes only and should not be construed as limiting the content of this disclosure.

[0027] Methods for preparing silicon nitride and aluminum nitride powders include direct nitriding, carbothermal reduction, thermal decomposition, combustion synthesis, sol-gel method, and vapor deposition. Among these, direct nitriding and carbothermal reduction are currently the main methods for industrial production of silicon nitride and aluminum nitride, respectively. Combustion synthesis for preparing silicon nitride and aluminum nitride powders offers advantages such as high efficiency, energy saving, and environmental friendliness, making it a highly promising method suitable for industrial production. However, during powder preparation, the reaction rate is too fast, making the reaction process difficult to control, and the obtained products still suffer from problems such as low purity, high oxygen content, difficulty in controlling the crystal phase, and large and uneven grain size.

[0028] To address or at least mitigate these problems, this disclosure provides a novel method for preparing silicon nitride and aluminum nitride powders.

[0029] Figure 1 A flowchart illustrating a method for preparing silicon nitride and aluminum nitride powders according to embodiments of this disclosure is shown schematically. (Reference) Figure 1 The method for preparing silicon nitride and aluminum nitride powders according to the present disclosure may include the following steps:

[0030] S10. Mix aluminum powder and aluminum nitride raw powder to obtain a first mixture.

[0031] In an exemplary embodiment of this disclosure, the aluminum powder has a particle size of 40-50 μm, for example, 44 μm. The aluminum nitride powder has a particle size of 1.5-10 μm. The mass ratio of the aluminum powder to the aluminum nitride powder is (30-45):(55-70).

[0032] It should be noted that the method of mixing aluminum powder and aluminum nitride raw powder as described in this disclosure can be mechanical mixing. For example, the two can be mixed by stirring, ball milling, etc., and this disclosure does not limit this.

[0033] S12. Mix silicon powder, silicon nitride raw powder and ammonium salt to obtain a second mixture.

[0034] In an exemplary embodiment of this disclosure, the silicon powder has a particle size of 1-5 μm, for example, 3 μm. The silicon nitride powder has a particle size of 2.5-5 μm. The ammonium salt can be ammonium chloride or ammonium fluoride. The mass ratio of silicon powder, silicon nitride powder and ammonium salt can be (31.5-38):(54-61.75):(5-10).

[0035] It should be noted that the method of mixing silicon powder, silicon nitride powder and ammonium salt as described in this disclosure can be mechanical mixing. For example, the three can be mixed by stirring, ball milling, etc., and this disclosure does not limit this.

[0036] S14. Spread the first mixture and the second mixture on a material frame lined with carbon felt, and use the carbon felt to separate the first mixture from the second mixture.

[0037] In an exemplary embodiment of this disclosure, in order to fully achieve the induced combustion of step S16, the first mixture may be placed below, to the side or in the middle of the second mixture.

[0038] In the exemplary preparation schemes applied to this disclosure, the mass ratio of the first mixture to the second mixture can be 1:(2~5).

[0039] S16. Place the material frame inside the self-propagating reactor, evacuate the reactor, and then introduce nitrogen gas to ignite the first mixture, thereby inducing the second mixture to undergo a combustion synthesis reaction.

[0040] According to some embodiments of this disclosure, the nitrogen gas pressure is 4~6 MPa.

[0041] Specifically, a heating tungsten filament can be used to ignite one side of the first mixture, which may be, for example, the side away from the second mixture, and this disclosure does not limit this.

[0042] By igniting the first mixture, the heat from the combustion synthesis reaction of aluminum nitride can ignite the silicon powder, inducing the combustion synthesis reaction of silicon nitride. This avoids the use of ignition agents such as titanium powder and significantly reduces the adverse effects of introducing foreign impurities that are easily introduced by traditional electrode ignition methods, thus at least significantly improving the purity of silicon nitride products.

[0043] S18. After the combustion synthesis reaction, cool to room temperature, release the pressure in the self-propagating reactor, take out the synthesis product, and grind the synthesis product to obtain silicon nitride powder and aluminum nitride powder.

[0044] In an exemplary embodiment of this disclosure, the particle size of the silicon nitride powder obtained in step S18 is larger than that of the silicon nitride precursor powder, and the particle size of the aluminum nitride powder is larger than that of the aluminum nitride precursor powder. The particle sizes of the silicon nitride powder and aluminum nitride powder prepared in this disclosure are in the micrometer range.

[0045] It should be noted that the silicon nitride powder and aluminum nitride powder prepared in this disclosure are present in greater quantities than the aforementioned 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.

[0046] On the one hand, the present invention can solve the problem that silicon powder is not easy to ignite when the amount of ammonium salt added is high by controlling the ratio of aluminum powder and aluminum nitride powder in the Al / AlN mixture and the amount of mixture. This increases the amount of NH4Cl and NH4F added, significantly reduces the combustion synthesis temperature of silicon nitride, and is beneficial to increasing the α phase content and reducing the agglomeration degree of silicon nitride powder.

[0047] On the other hand, the presence of oxygen-containing impurities typically promotes the vaporization of Si into SiO, which in turn generates the oxygen-containing impurity Si₂N₂O in the product. However, the presence of NH₄Cl and NH₄F leads to decomposition, producing HCl and HF, which transform SiO into SiCl₄ and SiF₄ under high-temperature conditions, ultimately resulting in silicon nitride powder. Increasing the amount of NH₄Cl and NH₄F added can further reduce the oxygen impurity content of the silicon nitride powder.

[0048] Furthermore, the preparation method disclosed herein avoids the use of ignition agents such as titanium powder, thus reducing resource consumption. Additionally, it allows for the simultaneous preparation of micron-sized silicon nitride and aluminum nitride powders in separate zones, which helps improve economic efficiency and is suitable for industrial production.

[0049] The reaction principle of the preparation process based on the raw powder disclosed below is explained below.

[0050] The preparation method disclosed herein is combustion synthesis. Combustion synthesis is a method of synthesizing materials by utilizing the exothermic reaction between reactants. Once the reactants are ignited, they automatically propagate to unreacted areas until the reaction is complete. The entire process requires almost no external energy supply, and the reaction is rapid with a short synthesis time. Compared with synthesis methods such as direct nitriding and carbothermic synthesis, combustion synthesis has the advantages of simple process, short cycle, low energy consumption, and low cost.

[0051] However, during the preparation of silicon nitride powder, the reaction rate is too fast, the reaction temperature is too high, and the reaction process is difficult to control, leading to incomplete reaction, abnormal growth of silicon nitride grains, and a decrease in the α-phase content. The difficulty in obtaining a high α-phase content stems from the fact that the α-phase transforms into the β-phase relatively easily and is highly sensitive to temperature. Therefore, controlling the heat is crucial for synthesizing high-quality silicon nitride powder using self-propagating combustion technology.

[0052] Since combustion synthesis is a violent, rapid, and self-contained reaction, it is impossible to intervene once the reaction begins. Therefore, the control of the silicon nitride reaction process and product quality in this disclosure starts with optimizing the initial reaction conditions. The method for controlling heat is to add a heat "diluent" to the raw materials. This not only reduces liquid-phase silicon and inhibits the formation of coarse blocks, but also disperses molten silicon, promoting nitrogen penetration and accelerating the reaction. Furthermore, it lowers the combustion synthesis temperature and increases the α-phase content. In this disclosure, Si3N4 powder is used as a diluent, which reduces the reaction temperature by decreasing the heat released per unit volume. Simultaneously, Si3N4 powder also acts as a seed crystal, enhancing the nucleation and growth of the gas-phase reaction. This disclosure employs a method of using Si3N4 diluent in conjunction with ammonium salts to control the reaction heat.

[0053] The purpose of using aluminum nitride powder in this embodiment is similar, also serving as a diluent.

[0054] Furthermore, this disclosure also provides silicon nitride and aluminum nitride powders, which can be prepared using the preparation methods described in steps S10 to S18 above.

[0055] The preparation method of Embodiment 1 of this disclosure will be described below.

[0056] First, 21g of aluminum powder with a particle size of 44μm and 49g of aluminum nitride powder with a particle size of 1.5μm were mixed by mechanical stirring to obtain a first mixture. Then, 66.5g of silicon powder with a particle size of 2.5μm, 123.5g of silicon nitride powder with a particle size of 2.5μm and 10g of NH4Cl were mixed by mechanical stirring to obtain a second mixture.

[0057] Next, the first mixture and the second mixture are spread on a frame lined with carbon felt, and the first mixture and the second mixture are separated by carbon felt, with the first mixture placed to the side of the second mixture.

[0058] Subsequently, the material frame was placed in a self-propagating reactor, and nitrogen gas was introduced into the vacuum to 4 MPa. The first mixture was ignited on one side using a heating tungsten wire, which also induced the second mixture to undergo a combustion synthesis reaction.

[0059] After the reaction was completed, the mixture was cooled to room temperature, the pressure inside the self-propagating reactor was released, the synthesized product was taken out, and the synthesized product was ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0060] The preparation method of Embodiment 2 of this disclosure will be described below.

[0061] First, 18g of aluminum powder with a particle size of 40μm and 22g of aluminum nitride powder with a particle size of 1.5μm were mixed by mechanical stirring to obtain a first mixture. Then, 66.5g of silicon powder with a particle size of 2.5μm, 123.5g of silicon nitride powder with a particle size of 2.5μm and 10g of NH4Cl were mixed by mechanical stirring to obtain a second mixture.

[0062] Next, the first mixture and the second mixture are spread on a frame lined with carbon felt, and the first mixture and the second mixture are separated by carbon felt, with the first mixture placed to the side of the second mixture.

[0063] Subsequently, the material frame was placed in a self-propagating reactor, and nitrogen gas was introduced into the vacuum to 4 MPa. The first mixture was ignited on one side using a heating tungsten wire, which also induced the second mixture to undergo a combustion synthesis reaction.

[0064] After the reaction was completed, the mixture was cooled to room temperature, the pressure inside the self-propagating reactor was released, the synthesized product was taken out, and the synthesized product was ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0065] The preparation method of Example 3 of this disclosure will be described below.

[0066] First, 20g of aluminum powder with a particle size of 50μm and 30g of aluminum nitride powder with a particle size of 10μm were mixed by mechanical stirring to obtain a first mixture. Then, 66.5g of silicon powder with a particle size of 2.5μm, 123.5g of silicon nitride powder with a particle size of 2.5μm and 10g of NH4Cl were mixed by mechanical stirring to obtain a second mixture.

[0067] Next, the first mixture and the second mixture are spread on a frame lined with carbon felt, and the first mixture and the second mixture are separated by carbon felt, with the first mixture placed to the side of the second mixture.

[0068] Subsequently, the material frame was placed in a self-propagating reactor, and nitrogen gas was introduced into the vacuum to 4 MPa. The first mixture was ignited on one side using a heating tungsten wire, which also induced the second mixture to undergo a combustion synthesis reaction.

[0069] After the reaction was completed, the mixture was cooled to room temperature, the pressure inside the self-propagating reactor was released, the synthesized product was taken out, and the synthesized product was ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0070] The preparation method of Embodiment 4 of this disclosure will be described below.

[0071] First, 20g of aluminum powder with a particle size of 44μm and 30g of aluminum nitride powder with a particle size of 1.5μm were mixed by mechanical stirring to obtain a first mixture. Then, 66.5g of silicon powder with a particle size of 2.5μm, 123.5g of silicon nitride powder with a particle size of 5μm and 10g of NH4F were mixed by mechanical stirring to obtain a second mixture.

[0072] Next, the first mixture and the second mixture are spread on a frame lined with carbon felt, and the first mixture and the second mixture are separated by carbon felt, with the first mixture placed to the side of the second mixture.

[0073] Subsequently, the material frame was placed in a self-propagating reactor, and nitrogen gas was introduced into the vacuum to 4 MPa. The first mixture was ignited on one side using a heating tungsten wire, which also induced the second mixture to undergo a combustion synthesis reaction.

[0074] After the reaction was completed, the mixture was cooled to room temperature, the pressure inside the self-propagating reactor was released, the synthesized product was taken out, and the synthesized product was ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0075] The preparation method of Embodiment 5 of this disclosure will be described below.

[0076] First, 20g of aluminum powder with a particle size of 44μm and 30g of aluminum nitride powder with a particle size of 1.5μm were mixed by mechanical stirring to obtain a first mixture. Then, 66.5g of silicon powder with a particle size of 5μm, 123.5g of silicon nitride powder with a particle size of 2.5μm and 10g of NH4Cl were mixed by mechanical stirring to obtain a second mixture.

[0077] Next, the first mixture and the second mixture are spread on a frame lined with carbon felt, and the first mixture and the second mixture are separated by carbon felt, with the first mixture placed to the side of the second mixture.

[0078] Subsequently, the material frame was placed in a self-propagating reactor, and nitrogen gas was introduced into the vacuum to 4 MPa. The first mixture was ignited on one side using a heating tungsten wire, which also induced the second mixture to undergo a combustion synthesis reaction.

[0079] After the reaction was completed, the mixture was cooled to room temperature, the pressure inside the self-propagating reactor was released, the synthesized product was taken out, and the synthesized product was ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0080] The preparation method of Embodiment 6 of this disclosure will be described below.

[0081] First, 20g of aluminum powder with a particle size of 44μm and 30g of aluminum nitride powder with a particle size of 1.5μm were mixed by mechanical stirring to obtain a first mixture. Then, 65.8g of silicon powder with a particle size of 2.5μm, 122.2g of silicon nitride powder with a particle size of 2.5μm and 12g of NH4Cl were mixed by mechanical stirring to obtain a second mixture.

[0082] Next, the first mixture and the second mixture are spread on a frame lined with carbon felt, and the first mixture and the second mixture are separated by carbon felt, with the first mixture placed to the side of the second mixture.

[0083] Subsequently, the material frame was placed in a self-propagating reactor, and nitrogen gas was introduced into the vacuum to 4 MPa. The first mixture was ignited on one side using a heating tungsten wire, which also induced the second mixture to undergo a combustion synthesis reaction.

[0084] After the reaction was completed, the mixture was cooled to room temperature, the pressure inside the self-propagating reactor was released, the synthesized product was taken out, and the synthesized product was ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0085] The preparation method of Embodiment 7 of this disclosure will be described below.

[0086] First, 20g of aluminum powder with a particle size of 44μm and 30g of aluminum nitride powder with a particle size of 1.5μm were mixed by mechanical stirring to obtain a first mixture. Then, 65.1g of silicon powder with a particle size of 1μm, 120.9g of silicon nitride powder with a particle size of 2.5μm and 14g of NH4Cl were mixed by mechanical stirring to obtain a second mixture.

[0087] Next, the first mixture and the second mixture are spread on a frame lined with carbon felt, and the first mixture and the second mixture are separated by carbon felt, with the first mixture placed to the side of the second mixture.

[0088] Subsequently, the material frame was placed in a self-propagating reactor, and nitrogen gas was introduced into the vacuum to 4 MPa. The first mixture was ignited on one side using a heating tungsten wire, which also induced the second mixture to undergo a combustion synthesis reaction.

[0089] After the reaction was completed, the mixture was cooled to room temperature, the pressure inside the self-propagating reactor was released, the synthesized product was taken out, and the synthesized product was ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0090] The preparation method of Embodiment 8 of this disclosure will be described below.

[0091] First, 45g of aluminum powder with a particle size of 44μm and 55g of aluminum nitride powder with a particle size of 1.5μm were mixed by mechanical stirring to obtain a first mixture. Then, 72g of silicon powder with a particle size of 2.5μm, 108g of silicon nitride powder with a particle size of 2.5μm and 20g of NH4Cl were mixed by mechanical stirring to obtain a second mixture.

[0092] Next, the first mixture and the second mixture are spread on a material frame lined with carbon felt, and the first mixture and the second mixture are separated by carbon felt, with the first mixture placed in the middle of the second mixture.

[0093] Subsequently, the material frame was placed in a self-propagating reactor, and nitrogen gas was introduced into the vacuum to 4 MPa. The first mixture was ignited on one side using a heating tungsten wire, which also induced the second mixture to undergo a combustion synthesis reaction.

[0094] After the reaction was completed, the mixture was cooled to room temperature, the pressure inside the self-propagating reactor was released, the synthesized product was taken out, and the synthesized product was ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0095] The preparation method of Example 9 of this disclosure will be described below.

[0096] First, 28g of aluminum powder with a particle size of 44μm and 42g of aluminum nitride powder with a particle size of 1.5μm were mixed by mechanical stirring to obtain a first mixture. Then, 72g of silicon powder with a particle size of 2.5μm, 108g of silicon nitride powder with a particle size of 2.5μm and 20g of NH4Cl were mixed by mechanical stirring to obtain a second mixture.

[0097] Next, the first mixture and the second mixture are spread on a material frame lined with carbon felt, and the first mixture and the second mixture are separated by carbon felt, with the first mixture placed below the second mixture.

[0098] Subsequently, the material frame was placed in a self-propagating reactor, and nitrogen gas was introduced into the vacuum to 6 MPa. The first mixture was ignited on one side using a heating tungsten wire, which also induced the second mixture to undergo a combustion synthesis reaction.

[0099] After the reaction was completed, the mixture was cooled to room temperature, the pressure inside the self-propagating reactor was released, the synthesized product was taken out, and the synthesized product was ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0100] The preparation method of Embodiment 10 of this disclosure will be described below.

[0101] First, 27g of aluminum powder with a particle size of 44μm and 33g of aluminum nitride powder with a particle size of 1.5μm were mixed by mechanical stirring to obtain a first mixture. Then, 72.8g of silicon powder with a particle size of 2.5μm, 109.2g of silicon nitride powder with a particle size of 2.5μm and 18g of NH4Cl were mixed by mechanical stirring to obtain a second mixture.

[0102] Next, the first mixture and the second mixture are spread on a frame lined with carbon felt, and the first mixture and the second mixture are separated by carbon felt, with the first mixture placed to the side of the second mixture.

[0103] Subsequently, the material frame was placed in a self-propagating reactor, and nitrogen gas was introduced into the vacuum to 4 MPa. The first mixture was ignited on one side using a heating tungsten wire, which also induced the second mixture to undergo a combustion synthesis reaction.

[0104] After the reaction was completed, the mixture was cooled to room temperature, the pressure inside the self-propagating reactor was released, the synthesized product was taken out, and the synthesized product was ground to obtain micron-sized silicon nitride powder and aluminum nitride powder.

[0105] Taking Examples 1, 3, and 8 as examples, the composition of the prepared silicon nitride powder and aluminum nitride powder was tested.

[0106] Figure 2 The XRD pattern of the corresponding silicon nitride powder is shown. (Reference) Figure 2 The products prepared in these examples are all composed of α-Si3N4 (PDF #09-0250) and β-Si3N4 (PDF #33-1160), with the α phase content being above 92%.

[0107] Figure 3 The XRD pattern of the corresponding aluminum nitride powder is shown. (Reference) 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.

[0108] in addition, Figure 4 and Figure 5 SEM images of silicon nitride powder and aluminum nitride powder prepared using the method described in Example 1 of this disclosure are shown respectively.

[0109] It should be noted that although the steps of the method in this disclosure are described in a specific order in the accompanying drawings, this does not require or imply that the steps must be performed in that specific order, or that all the steps shown must be performed to achieve the desired result. Additional or alternative steps may be omitted, multiple steps may be combined into one step, and / or a step may be broken down into multiple steps.

[0110] Furthermore, the above figures are merely illustrative of the processes included in the method according to exemplary embodiments of this disclosure and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0111] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the claims.

[0112] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

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. The aluminum powder and aluminum nitride raw powder are mixed to obtain a first mixture; the particle size of the aluminum powder is 40-50 mu m, the particle size of the aluminum nitride raw powder is 1.5-10 mu m, and the mass ratio of the aluminum powder to the aluminum nitride raw powder is (30-45):(55-70); The silicon powder, silicon nitride raw powder and ammonium salt are mixed to obtain a second mixture; the particle size of the silicon powder is 1-5 mu m, 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), the mass ratio of the first mixture to the second mixture is 1:(2-5), the ammonium salt is ammonium chloride or ammonium fluoride; 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; The material frame is placed in a self-propagating reaction kettle, nitrogen is introduced after vacuumizing, one side of the first mixture is ignited by using a heating tungsten wire to induce the second mixture to carry out a combustion synthesis reaction, and the pressure of the nitrogen is 4-6 MPa. After the combustion synthesis reaction, the material frame 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 method of claim 1, wherein the silicon nitride and aluminum nitride powder is prepared by the steps of: In the material frame, the first mixture is arranged below, on the side or in the middle of the second mixture. ​ 3. The method of claim 1, wherein the silicon nitride and aluminum nitride powder is prepared by the steps of: preparing a mixture of silicon and aluminum powders; and nitriding the mixture of silicon and aluminum powders in a nitrogen atmosphere. 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.

4. A silicon nitride and aluminum nitride powder, characterized by, The silicon nitride and aluminum nitride powders are prepared by the preparation method of any one of claims 1-3.

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