Core-shell structure silicon nitride / silicon nitride magnesium powder, preparation method and application thereof
By developing a method for preparing core-shell structured silicon nitride/silicon nitride magnesium powder, the problems of high energy consumption and additive residue in high-temperature sintering of silicon nitride ceramics have been solved. This method enables the preparation of silicon nitride ceramics with high density and high strength at low temperatures, expanding their application in extreme environments.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YONGJIANG LAB
- Filing Date
- 2026-01-22
- Publication Date
- 2026-06-23
AI Technical Summary
Existing silicon nitride ceramic sintering processes suffer from high energy consumption and high cost at high temperatures, and residual sintering aids can affect material properties, limiting their application in extreme environments.
A method for preparing core-shell structured silicon nitride/silicon nitride magnesium powder is adopted. Magnesium vapor and silicon oxide powder are reacted by high-temperature sintering under a nitrogen atmosphere to form a composite powder with silicon nitride as the core and silicon nitride magnesium as the shell. Subsequently, calcination is carried out to remove residual magnesium and achieve low-temperature high densification.
Low-temperature, high-density, and high-strength sintering of silicon nitride ceramics has been achieved, improving the purity and overall performance of the ceramics, making them suitable for aerospace, precision machinery, and biomedical fields.
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Figure CN121553909B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of structural ceramic materials technology, and in particular to a core-shell structured silicon nitride / magnesium silicon nitride powder, its preparation method, and its application. Background Technology
[0002] Silicon nitride ceramics are widely used in high-end fields such as aerospace engine components, precision mechanical bearings, cutting tools, biomedical implants, and electronic packaging thermal management materials due to their high strength, high hardness, excellent wear resistance, good chemical stability, and outstanding thermal shock resistance.
[0003] However, silicon nitride is a strongly covalent compound with high bond strength and a low self-diffusion coefficient, making its densification through sintering extremely difficult. Densification typically requires extremely high temperatures (above 1700°C) and the assistance of sintering aids. This high-temperature sintering process is not only energy-intensive and costly, but also prone to causing abnormal grain growth, reducing the material's mechanical properties. Furthermore, the introduced sintering aids often remain as a glassy phase at the grain boundaries after sintering, significantly reducing the high-temperature strength, creep resistance, and thermal conductivity of silicon nitride ceramics, thus limiting their application in extreme environments. Summary of the Invention
[0004] This application addresses the problems existing in the sintering process of silicon nitride ceramics by providing a method to promote silicon nitride sintering, achieving low-temperature, high-density, and high-strength sintering of silicon nitride ceramics; the sintering raw materials can be directly sintered, improving the purity of silicon nitride ceramics.
[0005] The objective of this application can be achieved through the following technical solutions.
[0006] The first aspect of this application provides a method for preparing core-shell structured silicon nitride / magnesium silicon nitride powder, characterized by comprising the following steps:
[0007] Silicon nitride powder is provided, and after oxidation pretreatment, silicon nitride pretreated powder with an oxide film layer on the surface is obtained;
[0008] Magnesium powder is provided and heated to form magnesium vapor. The silicon nitride pretreated powder is then placed in a mixed atmosphere containing nitrogen and magnesium vapor for high-temperature sintering reaction to obtain composite powder.
[0009] The composite powder is subjected to a process to remove residual magnesium, followed by calcination to obtain core-shell structured silicon nitride / silicon nitride magnesium powder.
[0010] Preferably, the temperature of the high-temperature sintering reaction is 1200℃~1400℃; and the time of the high-temperature sintering reaction is 1h~4h.
[0011] More preferably, the temperature at which magnesium vapor is formed by heating is 1200℃~1400℃; and / or, the magnesium powder is placed at the inlet of the high-temperature sintering reaction device, and the silicon nitride pretreatment powder is placed at the outlet of the high-temperature sintering reaction device.
[0012] The sintering temperature of this application is 1200℃~1400℃, which is significantly higher than the boiling point of magnesium (1090℃), and can generate a sufficiently high magnesium vapor pressure to ensure efficient gas-phase transport reaction.
[0013] The mass ratio of magnesium powder to silicon nitride powder is (3~5):1; and / or the grain size of the silicon nitride powder is 20nm~100nm.
[0014] The high-temperature sintering reactor is in a nitrogen-sealed state during the reaction process, and the gas pressure of the high-temperature sintering reaction is atmospheric pressure.
[0015] This application describes a process where magnesium powder is vaporized and reacted with pretreated silicon nitride powder under high temperature and nitrogen atmosphere to form a composite powder with residual silicon nitride as the core and newly formed silicon nitride magnesium as the shell. The reaction is a gas-phase transport and interfacial reaction process; the magnesium powder placed at the inlet volatilizes at a high temperature of 1200℃~1400℃, forming highly active magnesium vapor. Under a nitrogen atmosphere, the magnesium vapor first undergoes a reduction-nitriding reaction with the silicon dioxide layer on the surface of the silicon nitride powder. The reaction pathway is as follows:
[0016] SiO2(s) + 2Mg (g) + N2(g) → MgSiN2(s) + 2MgO (s)
[0017] Then, MgSiN2 uses the original Si3N4 particles as heterogeneous nucleation sites, epitaxially growing or encapsulating them to form a continuous shell. The unreacted Si3N4 cores are retained, thus successfully constructing a Si3N4 / MgSiN2 core-shell structure. The mass ratio of Mg to Si3N4 (3~5):1 ensures that sufficient magnesium vapor participates in the reaction to complete the full shell encapsulation.
[0018] The method for removing residual magnesium includes one or more of acid washing, selective oxidation, and high-temperature sublimation treatment.
[0019] The calcination treatment atmosphere includes nitrogen and / or argon, and the calcination treatment temperature is 800℃~1100℃, and the time is 1h~3h.
[0020] The calcination process described in this application results in higher crystallinity of the MgSiN2 shell generated at a lower temperature, eliminates internal stress, and stabilizes its crystal structure; it also heals defects such as microcracks that may occur in the shell during pickling and other processes, improving the density and integrity of the shell; and through slight interdiffusion of atoms at the interface, it enhances the chemical bonding force between the Si3N4 core and the MgSiN2 shell, making the core-shell structure more stable.
[0021] Preferably, the thickness of the oxide film is 2nm to 10nm; and / or, the oxidation pretreatment method includes at least one of high-temperature oxidation, surface coating, and high-energy ball milling reaction.
[0022] The silicon nitride powder described in this application is a strong covalent compound with low surface energy and poor reactivity, making it difficult to sinter. Through controllable pretreatment, a thin and uniform amorphous silicon dioxide layer is generated in situ on its surface. The silicon dioxide layer provides a highly active reaction interface, preferentially undergoing gas-solid reaction with magnesium vapor in the subsequent process, significantly reducing the activation energy of the reaction. The silicon nitride pretreatment method of this application controls the thickness of the silicon dioxide layer by precisely controlling the oxidation conditions, thereby controlling the thickness and uniformity of the silicon nitride magnesium shell layer, and realizing the precise construction of the core-shell structure.
[0023] In a second aspect of this application, this application provides a core-shell structured silicon nitride / magnesium silicon nitride powder obtained by the above preparation method, wherein the particle size of the core-shell structured silicon nitride / magnesium silicon nitride powder is 100nm~300nm; wherein the core-shell structured silicon nitride / magnesium silicon nitride powder has silicon nitride as the core and magnesium silicon nitride as the shell, wherein the thickness of the magnesium silicon nitride shell layer is 10nm~50nm.
[0024] In a third aspect, this application provides the application of core-shell structured silicon nitride / magnesium silicon nitride powder in aerospace engine components, precision mechanical shaft pumps, cutting tools, biomedical implants, or electronic packaging thermal management materials.
[0025] The beneficial effects of the method described in this application include:
[0026] (1) Achieving low-temperature, high-density, and high-strength sintering of silicon nitride ceramics;
[0027] (2) High-purity silicon nitride ceramics can be obtained by sintering;
[0028] (3) To achieve precise design and controllable synthesis of powder microstructure. Attached Figure Description
[0029] Figure 1 This is a SEM image of the oxide film prepared by high-temperature treatment of silicon nitride in Example 1;
[0030] Figure 2Here is a SEM image of the core-shell structured silicon nitride / magnesium silicon nitride powder prepared in Example 1;
[0031] Figure 3 Here is a SEM image of the core-shell structured silicon nitride / magnesium silicon nitride powder prepared in Example 2;
[0032] Figure 4 Here is a SEM image of the core-shell structured silicon nitride / magnesium silicon nitride powder prepared in Example 3;
[0033] Figure 5 This is a SEM image of the core-shell structured silicon nitride / magnesium silicon nitride powder prepared in Example 4;
[0034] Figure 6 Here is a SEM image of the core-shell structured silicon nitride / magnesium silicon nitride powder prepared in Example 5;
[0035] Figure 7 This is a graph showing the hardness data of silicon nitride ceramics prepared using Example 1;
[0036] Figure 8 This is a graph showing the hardness data of the silicon nitride ceramics prepared using Example 2;
[0037] Figure 9 This is a graph showing the hardness data of the silicon nitride ceramics prepared using Example 3;
[0038] Figure 10 This is a graph showing the hardness data of the silicon nitride ceramics prepared using Example 4;
[0039] Figure 11 This is a graph showing the hardness data of the silicon nitride ceramics prepared using Example 5. Detailed Implementation
[0040] The following detailed description, with appropriate reference to the accompanying drawings, discloses an embodiment of magnesium silicon nitride powder, its stepwise gas pressure self-propagating preparation method, and its application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.
[0041] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. The range defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range.
[0042] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.
[0043] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.
[0044] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; unless otherwise stated, the values of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).
[0045] Existing silicon nitride ceramics are difficult to sinter due to their strong covalent bonds. Traditional processes require temperatures exceeding 1700°C and the addition of sintering aids to achieve densification. This not only leads to high energy consumption, but the residual additives also cause the formation of a glassy phase at grain boundaries, which severely degrades the material's high-temperature strength, creep resistance, and thermal conductivity, limiting its application under extreme conditions. To address these issues, this application provides a novel material and preparation method that enables low-temperature, high-density sintering of silicon nitride, while significantly improving the purity and overall performance of the final ceramic product.
[0046] The method for preparing core-shell structured silicon nitride / magnesium silicon nitride powder of this application includes the following steps:
[0047] Silicon nitride powder is provided, and after oxidation pretreatment, silicon nitride pretreated powder with an oxide film layer on the surface is obtained;
[0048] Magnesium powder is provided and heated to form magnesium vapor. The silicon nitride pretreated powder is then placed in a mixed atmosphere containing nitrogen and magnesium vapor for high-temperature sintering reaction to obtain composite powder.
[0049] The composite powder is subjected to a process to remove residual magnesium, followed by calcination to obtain core-shell structured silicon nitride / silicon nitride magnesium powder.
[0050] The temperature of the high-temperature sintering reaction is 1200℃~1400℃; the time of the high-temperature sintering reaction is 1h~4h.
[0051] The temperature at which magnesium vapor is formed by heating is 1200℃~1400℃; and / or, the magnesium powder is placed at the inlet of the high-temperature sintering reactor, and the silicon nitride pretreated powder is placed at the outlet of the high-temperature sintering reactor. The high-temperature sintering reactor is preferably a tube furnace.
[0052] The mass ratio of magnesium powder to silicon nitride powder is (3~5):1; and / or the grain size of the silicon nitride powder is 20nm~100nm.
[0053] The high-temperature sintering reactor is in a nitrogen-sealed state during the reaction process, and the gas pressure of the high-temperature sintering reaction is atmospheric pressure.
[0054] The methods for removing residual magnesium include one or more of pickling, selective oxidation, and high-temperature sublimation treatment.
[0055] The calcination treatment atmosphere includes nitrogen and / or argon, and the calcination temperature is 800℃~1100℃, and the time is 1h~3h.
[0056] The thickness of the oxide film is 2nm to 10nm; and / or the oxidation pretreatment method includes at least one of high-temperature oxidation, surface coating, and high-energy ball milling reaction.
[0057] Example 1:
[0058] A method for preparing core-shell structured silicon nitride / magnesium silicon nitride powder includes the following steps:
[0059] S1. Provide silicon nitride powder and magnesium powder as raw materials, with a mass ratio of magnesium powder to silicon nitride powder of 4:1;
[0060] The silicon nitride powder has a grain size of 20nm to 100nm, and the magnesium powder has a purity of 99.5%.
[0061] S2. Pretreatment of silicon nitride powder: Heat-treating it in air at 800°C for 2 hours to form a silicon dioxide layer with a thickness of approximately 5nm~10nm on its surface. Figure 1 (As shown).
[0062] S3. Place magnesium powder at the inlet of the tube furnace and place the pretreated silicon nitride powder at the outlet of the tube furnace.
[0063] S4. Under a nitrogen atmosphere, the tube furnace is heated to 1300℃ and held at this temperature for 2 hours, with the gas pressure inside the tube maintained at atmospheric pressure during the reaction. After the reaction is complete, the furnace is cooled to room temperature to obtain the composite powder.
[0064] S5. Post-treatment of the obtained composite powder: acid washing with 1 mol / L dilute hydrochloric acid to remove residual metallic magnesium; then, calcination at 1000℃ for 2 hours under nitrogen protection atmosphere to obtain the final core-shell structured silicon nitride / silicon nitride magnesium powder.
[0065] The core-shell structured silicon nitride / magnesium silicon nitride powder prepared by the method in this embodiment has an average particle size of approximately 100 nm to 200 nm. It has a microstructure with silicon nitride as the core and magnesium silicon nitride as the shell, and the shell thickness is 20 nm to 30 nm. Figure 2 (As shown).
[0066] Example 2:
[0067] A method for preparing core-shell structured silicon nitride / magnesium silicon nitride powder includes the following steps:
[0068] S1. Provide silicon nitride powder and magnesium powder as raw materials, with a mass ratio of magnesium powder to silicon nitride powder of 3:1;
[0069] The silicon nitride powder has a grain size of 50nm~100nm, and the magnesium powder has a purity of 99.5%.
[0070] S2. Pretreatment of silicon nitride powder: Heat treatment at 800°C in air for 1 hour to form a silicon dioxide layer with a thickness of 5nm~10nm on its surface.
[0071] S3. Place magnesium powder at the inlet of the tube furnace and place the pretreated silicon nitride powder at the outlet of the tube furnace.
[0072] S4. Under a nitrogen atmosphere, the tube furnace is heated to 1200℃ and held at this temperature for 4 hours. After the reaction is complete, the furnace is cooled to room temperature to obtain the composite powder.
[0073] S5. Post-processing of the obtained composite powder: First, remove residual magnesium by acid washing with dilute hydrochloric acid, and then calcine at 1000℃ for 1 hour under nitrogen protection to obtain the target powder.
[0074] The core-shell structured silicon nitride / magnesium silicon nitride powder prepared by the method in this embodiment has an average particle size of approximately 100 nm to 200 nm. It has a microstructure with silicon nitride as the core and magnesium silicon nitride as the shell, and the shell thickness is 20 nm to 50 nm. Figure 3 (As shown).
[0075] Example 3:
[0076] A method for preparing core-shell structured silicon nitride / magnesium silicon nitride powder includes the following steps:
[0077] S1. Provide silicon nitride powder and magnesium powder as raw materials, with a mass ratio of magnesium powder to silicon nitride powder of 5:1;
[0078] The silicon nitride powder has a grain size of 20nm to 100nm, and the magnesium powder has a purity of 99.5%.
[0079] S2. Pretreatment of silicon nitride powder: Heat treatment in air at 850°C for 3 hours to form a silicon dioxide layer with a thickness of 10nm~20nm on its surface.
[0080] S3. Place magnesium powder at the inlet of the tube furnace and place the pretreated silicon nitride powder at the outlet of the tube furnace.
[0081] S4. Under a nitrogen atmosphere, the tube furnace is heated to 1400℃ and held at this temperature for 1 hour. After the reaction is complete, the furnace is cooled to room temperature to obtain the composite powder.
[0082] S5. Post-treatment of the obtained composite powder: The residual magnesium was removed by high-temperature sublimation at 800℃ in a vacuum environment for 2 hours; then calcined at 1100℃ for 3 hours under argon protection.
[0083] The core-shell structured silicon nitride / magnesium silicon nitride powder prepared by the method in this embodiment has an average particle size of approximately 120 nm to 250 nm. It has a microstructure with silicon nitride as the core and magnesium silicon nitride as the shell, and the shell thickness is 20 nm to 50 nm. Figure 4 (As shown).
[0084] Example 4:
[0085] A method for preparing core-shell structured silicon nitride / magnesium silicon nitride powder includes the following steps:
[0086] S1. Provide silicon nitride powder and magnesium powder as raw materials, with a mass ratio of magnesium powder to silicon nitride powder of 4.5:1;
[0087] The silicon nitride powder has a grain size of 30nm~80nm, and the magnesium powder has a purity of 99.9%.
[0088] S2. Pretreatment of silicon nitride powder: High-energy ball milling is used to ball mill the powder for 4 hours in an oxygen atmosphere to form a uniform silicon dioxide layer with a thickness of about 3nm~7nm on its surface.
[0089] S3. Place magnesium powder at the inlet of the tube furnace and pretreated silicon nitride powder at the outlet.
[0090] S4. Under a nitrogen atmosphere, the tube furnace is heated to 1250℃ and held at that temperature for 3 hours, maintaining atmospheric pressure throughout the reaction. After the reaction is complete, the furnace is cooled to room temperature to obtain the composite powder.
[0091] S5. Post-treatment of the composite powder: First, acid washing with 0.5mol / L dilute nitric acid is used to remove residual magnesium, and then calcination is carried out at 900℃ for 2.5 hours under argon protection to obtain the target powder.
[0092] The core-shell structured silicon nitride / magnesium silicon nitride powder prepared by the method in this embodiment has an average particle size of approximately 120 nm to 180 nm. It has a microstructure with silicon nitride as the core and magnesium silicon nitride as the shell, and the shell thickness is 25 nm to 35 nm. Figure 5 (As shown).
[0093] Example 5:
[0094] A method for preparing core-shell structured silicon nitride / magnesium silicon nitride powder includes the following steps:
[0095] S1. Provide silicon nitride powder and magnesium powder as raw materials, with a mass ratio of magnesium powder to silicon nitride powder of 3.5:1;
[0096] The silicon nitride has a grain size of 40nm~90nm and the magnesium powder has a purity of 99.5%.
[0097] S2. Pretreatment of silicon nitride powder: A layer of amorphous silicon dioxide is deposited on its surface using a surface coating method, with the thickness controlled between 10nm and 15nm.
[0098] S3. Place magnesium powder at the inlet of the tube furnace and pretreated silicon nitride at the outlet.
[0099] S4. Under a nitrogen atmosphere, the tube furnace is heated to 1350℃ and held at that temperature for 1.5 hours, maintaining atmospheric pressure throughout the reaction. After the reaction is complete, the furnace is cooled to obtain the composite powder.
[0100] S5. Post-treatment of the composite powder: Selective oxidation is used to treat it in air at 600℃ for 1 hour to remove residual magnesium, followed by calcination at 950℃ for 2 hours under nitrogen protection.
[0101] The core-shell structured silicon nitride / magnesium silicon nitride powder prepared by the method in this embodiment has an average particle size of approximately 150 nm to 260 nm. It has a microstructure with silicon nitride as the core and magnesium silicon nitride as the shell, and the shell thickness is 20 nm to 40 nm. Figure 6 (As shown).
[0102] Comparative Example 1:
[0103] The difference between this comparative example and Example 1 is that the pretreatment step of silicon nitride powder is omitted, and the original silicon nitride powder is used directly for the reaction. The remaining steps are exactly the same as those in Example 1.
[0104] In this comparative example, only a small amount of silicon nitride magnesium phase can be detected in the silicon nitride powder, and most of it is unreacted silicon nitride, which cannot form a continuous and complete shell structure.
[0105] Comparative Example 2:
[0106] The difference between this comparative example and Example 1 is that the mass ratio of magnesium powder to silicon nitride powder is adjusted to 1:1, while the remaining steps are exactly the same as in Example 1.
[0107] The silicon nitride obtained in this comparative example has an incomplete core-shell structure, with an extremely thin shell that is distributed in an island-like pattern and has a low encapsulation rate.
[0108] Comparative Example 3:
[0109] The difference between this comparative example and Example 1 is that the calcination step was omitted after acid washing to remove residual magnesium; the remaining steps are exactly the same as in Example 1.
[0110] The core-shell structured silicon nitride / magnesium silicon nitride powder obtained in this comparative example has microcracks in the shell layer, and its crystallinity is significantly lower than that of the product in Example 1. The powder is prone to shell peeling during subsequent processing.
[0111] Application Examples 1-5:
[0112] The powders prepared in Examples 1-5 are pre-pressed into graphite molds;
[0113] The pre-pressed sample was placed in an SPS and heated to 1550℃ at a heating rate of 200℃ / min under a normal pressure nitrogen atmosphere. The pressure was 30MPa. After holding at this temperature for 5 min, the sample was allowed to cool naturally to obtain high-strength silicon nitride ceramic.
[0114] The specific properties of the silicon nitride ceramics obtained in Examples 1-5 are shown in Table 1.
[0115] Table 1: Properties of silicon nitride ceramics prepared in Application Examples 1-5
[0116]
[0117] The embodiments herein do not exhaustively cover the points not covered by the technical scope claimed in this application, and new technical solutions formed by equivalent substitutions of one or more technical features in the technical solutions of the embodiments are also within the scope of protection claimed in this application. At the same time, in all the listed or unlisted embodiments of the solution in this application, each parameter in the same embodiment merely represents an instance of its technical solution (i.e., a feasible solution), and there is no strict matching or limiting relationship between the parameters. The parameters can be substituted for each other without violating axioms and the claims of this application, unless otherwise stated.
[0118] The technical means disclosed in this application are not limited to those described above, but also include technical solutions composed of any combination of the above technical features. The above descriptions are specific embodiments of this application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this application, and these improvements and modifications are also considered within the scope of protection of this application.
[0119] The specific embodiments described herein are merely illustrative examples of the spirit of this application. Those skilled in the art to which this application pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of this application or exceeding the scope defined by the appended claims.
Claims
1. A method for preparing a core-shell structure silicon nitride / silicon nitride magnesium powder, characterized in that, The method comprises the following steps: providing silicon nitride powder, and obtaining silicon nitride pretreated powder with an oxide film layer on the surface after an oxidation pretreatment; providing magnesium powder, heating to form magnesium vapor, and placing the silicon nitride pretreated powder in a mixed atmosphere containing nitrogen and the magnesium vapor to perform a high-temperature sintering reaction, thereby obtaining a composite powder, wherein the temperature of the high-temperature sintering reaction is 1200-1400 ℃, and the mass ratio of the magnesium powder to the silicon nitride powder is (3-5) : 1; performing a residual magnesium removal treatment on the composite powder, and obtaining the core-shell structure silicon nitride / silicon nitride magnesium powder after a calcination treatment, wherein the temperature of the calcination treatment is 800-1100 ℃, wherein the pretreatment comprises one of the following methods: heat treating the silicon nitride powder in an air atmosphere at 800-850 ℃ for 1-3 hours to form a 5-20 nm-thick silicon dioxide layer on the surface of the silicon nitride powder; ball-milling the silicon nitride powder in an oxygen atmosphere for 4 hours to form a 3-7 nm-thick silicon dioxide layer on the surface of the silicon nitride powder; depositing an amorphous silicon dioxide layer on the surface of the silicon nitride powder by a surface coating method, and the thickness of the amorphous silicon dioxide is 10-15 nm.
2. The method of claim 1, wherein the core-shell structured silicon nitride / silicon nitride magnesium powder is prepared by the steps of: (a) preparing a silicon nitride powder; (b) preparing a silicon nitride magnesium powder; (c) mixing the silicon nitride powder and the silicon nitride magnesium powder; and (d) performing a surface treatment on the mixed powder. The time of the high-temperature sintering reaction is 1-4 hours.
3. The method of producing core-shell structured silicon nitride / silicon nitride magnesium powder according to claim 1, characterized by: The temperature for heating to form magnesium vapor is 1200-1400 ℃; and / or, the magnesium powder is placed at the gas inlet position of the high-temperature sintering reaction device, and the silicon nitride pretreated powder is placed at the gas outlet position of the high-temperature sintering reaction device.
4. The method of claim 1, wherein the method is characterized by: The grain size of the silicon nitride powder is 20-100 nm.
5. The method of producing core-shell structured silicon nitride / silicon nitride magnesium powder according to claim 3, characterized by: The high-temperature sintering reaction device is in a nitrogen-sealed state during the reaction, and the gas pressure of the high-temperature sintering reaction is normal pressure.
6. The method of producing core-shell structured silicon nitride / silicon nitride magnesium powder according to claim 1, characterized by: The method for removing residual magnesium comprises one or more of acid pickling, selective oxidation, and high-temperature sublimation treatment.
7. The method of claim 1, wherein the method further comprises: The atmosphere of the calcination treatment comprises nitrogen and / or argon, and the time is 1-3 hours. 8. The method of claim 1, wherein the method further comprises: The thickness of the oxide film layer is 2-10 nm; and / or, the oxidation pretreatment method comprises at least one of a high-temperature oxidation method, a surface coating method, and a high-energy ball-milling reaction method. 9. A core-shell structured silicon nitride / silicon nitride magnesium powder, characterized by, The core-shell structure silicon nitride / silicon nitride magnesium powder obtained by the preparation method of any one of claims 1-8 has a particle size of 100-300 nm, and the core-shell structure silicon nitride / silicon nitride magnesium powder has silicon nitride as the core and silicon nitride magnesium as the shell, wherein the thickness of the silicon nitride magnesium shell layer is 10-50 nm.
10. Use of a core-shell structure silicon nitride / silicon nitride magnesium powder obtained by the preparation method of any one of claims 1-8 or the core-shell structure silicon nitride / silicon nitride magnesium powder of claim 9 in aerospace engine components, precision mechanical shaft pumps, cutting tools, biomedical implants, or electronic packaging thermal management materials.