Silicon magnesium nitride powder, method for preparing the same, ceramic matrix composite and application thereof

Abstract

The application relates to a silicon magnesium nitride powder, a preparation method and application thereof. The application belongs to the technical field of structural ceramic materials, and the method comprises the following steps: mixing silicon powder and a conductive agent to perform first-stage ultrafast heat treatment, synthesizing silicon nitride powder; then mixing the silicon nitride powder and magnesium powder to perform second-stage ultrafast heat treatment, synthesizing a silicon magnesium nitride coarse product; and finally performing pulse annealing treatment on the coarse product to obtain the silicon magnesium nitride powder. The obtained silicon magnesium nitride powder has the characteristics of superfine particle size (50nm-150nm), low oxygen content (<=0.15wt%) and high specific surface area (50 m 2 / g-100 m 2 / g), and is suitable for preparing high-toughness ceramic matrix composites.

Description

Technical Field

[0001] This application relates to the field of structural ceramic materials technology, and in particular to a silicon magnesium nitride powder, its preparation method, ceramic matrix composite materials and their applications. Background Technology

[0002] Silicon nitride ceramics are considered key high-temperature structural materials in aerospace, high-end equipment manufacturing, and other fields due to their excellent high-temperature mechanical properties, good thermal stability, and chemical stability. However, the strong covalent bonding of silicon nitride makes its densification through sintering extremely difficult, typically requiring the addition of large amounts of sintering aids to promote the densification process via a liquid-phase sintering mechanism. While this method can achieve dense sintering, the residual grain boundary glass phase significantly degrades the material's high-temperature strength, creep resistance, and thermal conductivity, limiting its application in extreme environments.

[0003] Magnesium silicon nitride, as a sintering aid or reactive sintering medium, can decompose at high temperatures to produce active Mg, which reacts with silicon dioxide on the surface of silicon nitride particles to generate a Mg-Si-ON liquid phase, thereby significantly reducing the sintering temperature. At the same time, this process can effectively purify silicon nitride grain boundaries and reduce low-melting-point grain boundary phases, which is beneficial for preparing high-performance silicon nitride ceramics.

[0004] Existing methods for preparing silicon magnesium nitride powder tend to cause grain coarsening during high-temperature, long-term reactions, making it difficult to obtain ultrafine powders with small particle sizes and uniform distribution. Excessively large particle sizes or wide distributions directly affect the dispersibility and reactivity of the powder as a sintering aid. Low-temperature rapid synthesis, on the other hand, is an effective method to suppress grain coarsening and obtain ultrafine silicon magnesium nitride powders with low oxygen content and high chemical homogeneity. Summary of the Invention

[0005] To address the problem of effectively refining the particle size of existing silicon nitride magnesium powder, this application develops a three-step Joule thermal shock method to prepare ultrafine silicon nitride magnesium powder with extremely low oxygen content.

[0006] The objective of this application can be achieved through the following technical solutions.

[0007] In a first aspect, this application provides a method for preparing magnesium silicon nitride powder, comprising the following steps:

[0008] Silicon powder and conductive agent powder are mixed evenly and then subjected to a first-stage heat treatment, followed by sintering to obtain silicon nitride powder. The silicon nitride powder is then mixed with magnesium powder and subjected to a second-stage heat treatment, followed by sintering to obtain crude silicon-magnesium nitride. The crude silicon-magnesium nitride is then subjected to pulse annealing to obtain silicon-magnesium nitride powder. The silicon-magnesium nitride powder has a particle size of 50 nm to 150 nm, an oxygen content of less than 0.15 wt%, and a specific surface area of ​​50 m². 2 / g~100 m 2 / g.

[0009] Preferably, the temperature of the first-stage heat treatment is 1300℃~1450℃, the heating rate is 100℃ / s~500℃ / s, and the holding time is 10s~20s.

[0010] The primary heat treatment process of this application utilizes the instantaneous high temperature and ultra-short process window of ultra-fast sintering to enable silicon powder to complete the nitriding reaction and generate silicon nitride in a very short time, while effectively suppressing the excessive growth and coarsening of silicon nitride grains.

[0011] More preferably, the temperature of the secondary heat treatment is 1500℃~1600℃, the heating rate is 100℃ / s~500℃ / s, and the holding time is 5~10s.

[0012] The secondary heat treatment process of this application utilizes the extremely high heating rate and brief high temperature of ultra-fast sintering to drive a violent solid-state reaction between magnesium and silicon nitride, directly synthesizing magnesium silicon nitride. By taking advantage of its instantaneous nature, the volatilization loss of magnesium and the formation of by-products are minimized, ensuring the efficient completion of the main reaction.

[0013] Preferably, the discharge voltage of the pulse annealing is 40V~60V, the maximum current is 200A~320A, the single discharge time is 2500ms~3500ms, the cycle time is 2000ms~3000ms, and the cumulative discharge is 3~5 times.

[0014] This application employs a pulse annealing process, which utilizes the Joule heating effect generated by high-energy electrical pulses in the powder and electromagnetic stirring to achieve instantaneous high-temperature refining and structural relaxation of the crude product. This effectively eliminates lattice defects, refines grains, and improves the crystallinity and phase purity of the product, resulting in high-performance silicon magnesium nitride powder.

[0015] Furthermore, the conductive agent includes carbon powder and / or magnesium powder, and the conductive agent accounts for 2% to 5% of the total mass.

[0016] By introducing a conductive agent with a mass ratio of 2% to 5%, the aim is to utilize its high conductivity to form a conductive network during the first-stage ultra-fast thermal treatment process, thereby significantly enhancing the absorption efficiency of the reaction precursor to the pulse current, providing the necessary instantaneous high-temperature field for the instantaneous nitridation of silicon powder, and ensuring that the reaction proceeds rapidly and fully.

[0017] Preferably, the silicon powder and the conductive agent powder are mixed by ball milling, the ball milling speed is 300 rpm to 500 rpm, and the ball milling time is 4 h to 10 h.

[0018] The molar ratio of magnesium powder to silicon nitride powder is (0.95~1.05):1; and / or, the silicon nitride powder and magnesium powder are mixed by ball milling, the ball milling speed is 100 rpm~200 rpm, and the ball milling time is 2h~5h.

[0019] This application controls the molar ratio of magnesium powder to silicon nitride powder within the range of (0.95~1.05):1, and mixes them by ball milling at a low speed of 100 rpm to 200 rpm to achieve uniform mixing of reactants at the molecular level and maintain a precise stoichiometric ratio, thereby synthesizing high-purity magnesium silicon nitride.

[0020] The primary heat treatment, the secondary heat treatment, and the pulse annealing are all performed under a nitrogen atmosphere.

[0021] This application involves conducting the high-temperature reaction under a nitrogen atmosphere to prevent the oxidation of active metal elements such as silicon and magnesium, as well as the final product, at high temperatures, thereby ensuring the purity of the synthesis reaction and the quality of the product.

[0022] The silicon powder has a particle size of 20nm to 100nm; the magnesium powder has a particle size of 10μm to 100μm.

[0023] In a second aspect, this application provides a silicon-magnesium nitride powder obtained by the above preparation method, wherein the particle size of the silicon-magnesium nitride powder is 50 nm to 150 nm; the oxygen content in the silicon-magnesium nitride powder is less than 0.15 wt%, and the specific surface area is 50 m². 2 / g~100 m 2 / g.

[0024] In a third aspect of this application, this application provides a ceramic matrix composite material, comprising ceramic matrix powder and high-toughness reinforcing phase powder, wherein the high-toughness reinforcing phase powder comprises the aforementioned silicon magnesium nitride powder.

[0025] In a fourth aspect of this application, this application provides the application of the above-mentioned ceramic matrix composite material in lightweight high-strength metal matrix composite materials, lithium-ion battery anode materials, and thermally conductive substrates.

[0026] The beneficial effects of the preparation method described in this application include:

[0027] (1) Achieve efficient and low-energy instantaneous synthesis;

[0028] (2) Significantly refines grain size and optimizes microstructure;

[0029] (3) Improve reaction uniformity and product consistency. Attached Figure Description

[0030] Figure 1 This is the XRD pattern of the magnesium silicon nitride powder prepared in Example 1;

[0031] Figure 2 Here is a SEM image of the magnesium silicon nitride powder prepared in Example 1;

[0032] Figure 3 This is the XRD pattern of the magnesium silicon nitride powder prepared in Example 2;

[0033] Figure 4 Here is a SEM image of the magnesium silicon nitride powder prepared in Example 2;

[0034] Figure 5 This is the XRD pattern of the magnesium silicon nitride powder prepared in Example 3;

[0035] Figure 6 Here is a SEM image of the magnesium silicon nitride powder prepared in Example 3;

[0036] Figure 7 This is the XRD pattern of the magnesium silicon nitride powder prepared in Example 4;

[0037] Figure 8 Here is a SEM image of the magnesium silicon nitride powder prepared in Example 4;

[0038] Figure 9 This is the XRD pattern of the magnesium silicon nitride powder prepared in Comparative Example 1. Detailed Implementation

[0039] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of a silicon magnesium nitride powder, its preparation method, ceramic matrix composites, and their applications. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of essentially 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.

[0040] 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.

[0041] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0042] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0043] 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).

[0044] Existing technologies for preparing silicon-magnesium nitride powder generally suffer from problems such as slow heating rates, long high-temperature residence times, and reliance on specialized equipment, resulting in high energy consumption, easy grain coarsening, poor product uniformity, and high production costs. This application adopts a composite process route of conductive agent-assisted ultra-fast sintering + pulse annealing. By using instantaneous ultra-high temperature and second-level holding time, it achieves efficient and low-energy synthesis of reactants. Furthermore, it utilizes the electronic activation effect of pulsed current to refine grains and optimize the microstructure. Finally, it successfully prepares high-performance silicon-magnesium nitride powder based on conventional equipment, effectively overcoming the inherent defects of existing technologies.

[0045] This application technology prepares an ultrafine silicon-magnesium nitride powder via a three-step Joule heating method, achieving efficient and low-energy instantaneous synthesis of silicon-magnesium nitride, significantly refining grain size and optimizing microstructure, reaction uniformity, and product consistency. The preparation method of this silicon-magnesium nitride powder includes the following steps:

[0046] Silicon powder and conductive agent powder are mixed evenly and then subjected to a first-stage heat treatment, followed by sintering to obtain silicon nitride powder. The silicon nitride powder is then mixed with magnesium powder and subjected to a second-stage heat treatment, followed by sintering to obtain crude silicon-magnesium nitride. The crude silicon-magnesium nitride is then subjected to pulse annealing to obtain silicon-magnesium nitride powder. The silicon-magnesium nitride powder has a particle size of 50 nm to 150 nm, an oxygen content of less than 0.15 wt% (mass content), and a specific surface area of ​​50 m². 2 / g~100 m 2 / g.

[0047] The heat treatment includes an ultra-fast sintering method;

[0048] The temperature of the first-stage heat treatment is 1300℃~1450℃, the heating rate is 100℃ / s~500℃ / s, and the holding time is 10s~20s;

[0049] The secondary heat treatment temperature is 1500℃~1600℃, the heating rate is 100℃ / s~500℃ / s, and the holding time is 5s~10s.

[0050] The pulse annealing discharge voltage is 40V~60V, the maximum current is 200A~320A, the single discharge time is 2500ms~3500ms, the cycle time is 2000ms~3000ms, and the cumulative discharge is 3~5 times.

[0051] The conductive agent includes carbon powder and / or magnesium powder, and the mass percentage of the conductive agent is 2% to 5%, that is, the mass of the conductive agent is 2% to 5% of the total mass of the conductive agent and silicon powder.

[0052] The silicon powder and conductive agent powder are mixed by ball milling, with a ball milling speed of 300 rpm to 500 rpm and a ball milling time of 4 h to 10 h.

[0053] The molar ratio of magnesium powder to silicon nitride powder is (0.95~1.05):1; and / or, the silicon nitride powder and magnesium powder are mixed by ball milling, the ball milling speed is 100 rpm~200 rpm, and the ball milling time is 2h~5h.

[0054] The primary heat treatment, the secondary heat treatment, and the pulse annealing are all performed under a nitrogen atmosphere.

[0055] The silicon powder has a particle size of 20nm to 100nm; the magnesium powder has a particle size of 10μm to 100μm.

[0056] Example 1:

[0057] A method for preparing magnesium silicon nitride powder includes the following steps:

[0058] S1. Take silicon powder and carbon powder as raw materials, and ball mill them in a planetary ball mill at a speed of 400 rpm for 6 hours in a mass ratio of 97:3 to obtain primary reaction precursor powder.

[0059] The particle size of the silicon powder is 30nm~50nm.

[0060] S2. The primary reaction precursor powder is added into the reaction chamber of the Joule heating equipment, and after evacuation, high-purity nitrogen gas is introduced to atmospheric pressure; the sample is heated to 1400°C at a heating rate of 400°C / s and held at this temperature for 15 seconds, and then naturally cooled to obtain silicon nitride powder.

[0061] S3. Mix the obtained silicon nitride powder with magnesium powder at a molar ratio of 1:1. Place the mixed powder in a planetary ball mill and ball mill at a speed of 150 rpm for 3 hours to obtain the secondary reaction precursor powder;

[0062] The particle size of the magnesium powder is 10μm~80μm.

[0063] S4. The secondary reaction precursor powder is added into the reaction chamber of the Joule heating equipment, and after evacuation, high-purity nitrogen gas is introduced to atmospheric pressure; the sample is heated to 1550°C at a heating rate of 300°C / s and held at this temperature for 8 seconds, and then naturally cooled to obtain crude silicon magnesium nitride product.

[0064] S5. The crude silicon magnesium nitride product is added into the reaction chamber of the Joule heating equipment and subjected to pulse annealing under the protection of flowing nitrogen. The discharge voltage is set to 50V, the maximum current is 260A, the single discharge time is 3000ms, the interval time is 2500ms, and the discharge is repeated 4 times to finally obtain silicon magnesium nitride powder.

[0065] The silicon magnesium nitride powder prepared in this embodiment was analyzed by XRD, and the main phase was silicon magnesium nitride (…). Figure 1 SEM showed that its particle size distribution was uniform, with an average particle size of 85 nm. Figure 2 The oxygen content was determined to be 0.12 wt% by an oxygen and nitrogen analyzer (Table 1); the specific surface area was determined to be 78 m² by the BET method. 2 / g (Table 1).

[0066] Example 2

[0067] A method for preparing magnesium silicon nitride powder includes the following steps:

[0068] S1. Take silicon powder and magnesium powder as raw materials, and ball mill them in a planetary ball mill at a speed of 300 rpm for 8 hours at a mass ratio of 98:2 to obtain primary reaction precursor powder.

[0069] The silicon powder has a particle size of 20nm to 40nm.

[0070] S2. The primary reaction precursor powder is added into the reaction chamber of the Joule heating equipment, and after evacuation, high-purity nitrogen gas is introduced to atmospheric pressure; the sample is heated to 1300°C at a heating rate of 100°C / s and held at this temperature for 20 seconds, and then naturally cooled to obtain silicon nitride powder.

[0071] S3. Mix the obtained silicon nitride powder with magnesium powder at a molar ratio of 0.95:1. Place the mixed powder in a planetary ball mill and ball mill at a speed of 100 rpm for 5 hours to obtain the secondary reaction precursor powder;

[0072] The magnesium powder has a particle size of 20μm to 80μm.

[0073] S4. The secondary reaction precursor powder is added into the reaction chamber of the Joule heating equipment, and after evacuation, high-purity nitrogen gas is introduced to atmospheric pressure; the sample is heated to 1500°C at a heating rate of 100°C / s and held at this temperature for 10s, and then cooled naturally to obtain crude silicon magnesium nitride product.

[0074] S5. The crude silicon magnesium nitride product is added into the reaction chamber of the Joule heating equipment and subjected to pulse annealing under the protection of flowing nitrogen. The discharge voltage is set to 40V, the maximum current is 200A, the single discharge time is 3500ms, the interval time is 3000ms, and the discharge is repeated 3 times to finally obtain silicon magnesium nitride powder.

[0075] The silicon magnesium nitride powder prepared in this embodiment was analyzed by XRD, and the main phase was silicon magnesium nitride (…). Figure 3 SEM showed that its particle size distribution was uniform, with an average particle size of 52 nm. Figure 4 The oxygen content was determined to be 0.08 wt% by an oxygen and nitrogen analyzer (Table 1); the specific surface area was determined to be 95 m² by the BET method. 2 / g (Table 1).

[0076] Example 3

[0077] A method for preparing magnesium silicon nitride powder includes the following steps:

[0078] S1. Take silicon powder, magnesium powder and carbon powder as raw materials, and ball mill them in a planetary ball mill at a speed of 500 rpm for 4 hours in a mass ratio of 95:1.5:3.5 to obtain primary reaction precursor powder.

[0079] The silicon powder has a particle size of 50nm to 100nm.

[0080] S2. The primary reaction precursor powder is added into the reaction chamber of the Joule heating equipment, and after evacuation, high-purity nitrogen is introduced to atmospheric pressure; the sample is heated to 1450°C at a heating rate of 500°C / s and held at this temperature for 10s, and then naturally cooled to obtain silicon nitride powder.

[0081] S3. Mix the obtained silicon nitride powder with magnesium powder at a molar ratio of 1.05:1. Place the mixed powder in a planetary ball mill and ball mill at a speed of 200 rpm for 2 hours to obtain the secondary reaction precursor powder;

[0082] The magnesium powder has a particle size of 50μm to 100μm.

[0083] S4. The secondary reaction precursor powder is added into the reaction chamber of the Joule heating equipment, and after evacuation, high-purity nitrogen is introduced to atmospheric pressure; the sample is heated to 1600°C at a heating rate of 500°C / s and held at this temperature for 5s, and then cooled naturally to obtain crude silicon magnesium nitride product.

[0084] S5. The crude silicon magnesium nitride product is added into the reaction chamber of the Joule heating equipment and subjected to pulse annealing under the protection of flowing nitrogen. The discharge voltage is set to 60V, the maximum current is 320A, the single discharge time is 2500ms, the interval time is 2000ms, and the discharge is repeated 5 times to finally obtain silicon magnesium nitride powder.

[0085] The silicon magnesium nitride powder prepared in this embodiment was analyzed by XRD, and the main phase was silicon magnesium nitride (…). Figure 5 SEM showed that its particle size distribution was uniform, with an average particle size of 142 nm. Figure 6 The oxygen content was determined to be 0.14 wt% by an oxygen and nitrogen analyzer (Table 1); the specific surface area was determined to be 55 m² by the BET method. 2 / g (Table 1).

[0086] Example 4

[0087] A method for preparing magnesium silicon nitride powder includes the following steps:

[0088] S1. Take silicon powder and carbon powder as raw materials, and ball mill them in a planetary ball mill at a speed of 450 rpm for 7 hours in a mass ratio of 95:5 to obtain primary reaction precursor powder.

[0089] The particle size of the silicon powder is 30nm~70nm.

[0090] S2. The primary reaction precursor powder is added into the reaction chamber of the Joule heating equipment, and after evacuation, high-purity nitrogen gas is introduced to atmospheric pressure; the sample is heated to 1420°C at a heating rate of 350°C / s and held at this temperature for 12 seconds, and then naturally cooled to obtain silicon nitride powder.

[0091] S3. Mix the obtained silicon nitride powder with magnesium powder at a molar ratio of 1.02:1. Place the mixed powder in a planetary ball mill and ball mill at a speed of 200 rpm for 2 hours to obtain the secondary reaction precursor powder;

[0092] The magnesium powder has a particle size of 50μm to 70μm.

[0093] S4. The secondary reaction precursor powder is added into the reaction chamber of the Joule heating equipment, and after evacuation, high-purity nitrogen is introduced to atmospheric pressure; the sample is heated to 1570°C at a heating rate of 450°C / s and held at this temperature for 6s, and then cooled naturally to obtain crude silicon magnesium nitride product.

[0094] S5. The crude silicon magnesium nitride product is added into the reaction chamber of the Joule heating equipment and subjected to pulse annealing under the protection of flowing nitrogen. The discharge voltage is set to 55V, the maximum current is 300A, the single discharge time is 2800ms, the interval time is 2200ms, and a total of 4 discharges are performed to finally obtain silicon magnesium nitride powder.

[0095] The silicon magnesium nitride powder prepared in this embodiment was analyzed by XRD, and the main phase was silicon magnesium nitride (…). Figure 7 SEM showed that its particle size distribution was uniform, with an average particle size of 110 nm. Figure 8 The oxygen content was determined to be 0.10 wt% by an oxygen and nitrogen analyzer (Table 1); the specific surface area was determined to be 65 m² by the BET method. 2 / g (Table 1).

[0096] Comparative Example 1

[0097] The difference between this comparative example and Example 1 is that the pulse annealing step was omitted. Specifically, after obtaining the crude silicon magnesium nitride product through a two-stage ultra-fast heat treatment, the sample was collected directly without pulse annealing.

[0098] The silicon-magnesium nitride powder prepared in this comparative example was analyzed by XRD, and the main phase was silicon-magnesium nitride (MgN). Figure 9 However, the oxygen content was determined to be 1.5 wt% by an oxygen and nitrogen analyzer (Table 1); its specific surface area was determined to be 15 m² by the BET method. 2 / g (Table 1). This indicates that the lack of a pulse annealing step cannot effectively eliminate defects, refine grains, and reduce oxygen content, resulting in a significant decrease in product quality.

[0099] Comparative Example 2

[0100] The difference between this comparative example and Example 1 is that the two-stage ultra-fast heat treatment is replaced with conventional tube furnace sintering. Specifically:

[0101] The first-stage heat treatment was carried out in a nitrogen atmosphere, with a heating rate of 10℃ / min to 1400℃ and held at that temperature for 2 hours.

[0102] The secondary heat treatment involves heating to 1550°C at a heating rate of 10°C / min under a nitrogen atmosphere and holding at that temperature for 1 hour.

[0103] The subsequent pulse annealing process is the same as in Example 1.

[0104] The magnesium silicon nitride powder prepared in this comparative example, as analyzed by XRD, contained a large amount of unreacted Si and MgO impurities, with a weak peak intensity in the MgSiN2 main phase. The grain size was very large, reaching the micrometer scale. Oxygen content was determined to be 2.5 wt% using an oxygen-nitrogen analyzer (Table 1). Its specific surface area, determined by the BET method, was 5 m² / s.2 / g (Table 1). This indicates that conventional sintering, due to its excessively long reaction time, results in severe grain coarsening, significant magnesium volatilization and oxidation, and incomplete reaction, thus failing to obtain ultrafine powder.

[0105] Comparative Example 3

[0106] The difference between this comparative example and Example 1 is that no conductive agent is added to the primary reaction precursor. Specifically, silicon powder with an average particle size of 50 nm is directly used for primary ultrafast thermal treatment, while the other steps are exactly the same as in Example 1.

[0107] In this comparative example, after the first-stage heat treatment, the product was a mixture of incompletely nitrided silicon powder and a small amount of silicon nitride, with an extremely low reaction conversion rate. This resulted in the ineffectiveness of subsequent steps, and the final product had a complex composition, mainly consisting of unreacted Si, Mg, and MgO, with almost no detectable MgSiN2 phase. This comparative example demonstrates that without a conductive agent to construct a conductive network, the ultrafast thermal effect cannot be effectively achieved, and the nitriding reaction of silicon powder cannot be completed within seconds.

[0108] Comparative Example 4

[0109] The difference between this comparative example and Example 1 is that the amount of magnesium powder used in the secondary heat treatment deviates significantly from the stoichiometric ratio. Specifically, in the secondary precursor, the molar ratio of magnesium powder to silicon nitride powder is 0.5:1. All other steps are exactly the same as in Example 1.

[0110] XRD analysis of the magnesium silicon nitride powder prepared in this comparative example showed that the main phase was unreacted Si3N4, with a large amount of MgO and a small amount of MgSiN2. This was because the amount of magnesium powder was insufficient to react with all the silicon nitride, leaving excess silicon nitride residue. Furthermore, magnesium reacts more readily with trace amounts of oxygen in the system at high temperatures to form magnesium oxide. The final product was not the target product, magnesium silicon nitride, and the reaction failed. This comparative example highlights the crucial role of precisely controlling the molar ratio of reactants in obtaining high-purity magnesium silicon nitride.

[0111] Table 1. Basic characterization data of each embodiment and comparative example.

[0112]

[0113] Note: In Table 1, “\” indicates that the relevant data could not be obtained because the product did not meet the test requirements.

[0114] 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.

[0115] 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.

[0116] 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 magnesium silicon nitride powder, characterized in that, Includes the following steps: Silicon powder and conductive agent powder are mixed evenly and then subjected to a first-stage heat treatment, followed by sintering to obtain silicon nitride powder. The silicon nitride powder is then mixed with magnesium powder and subjected to a second-stage heat treatment, followed by sintering to obtain crude silicon-magnesium nitride. The crude silicon-magnesium nitride is then subjected to pulse annealing to obtain silicon-magnesium nitride powder. The silicon-magnesium nitride powder has a particle size of 50 nm to 150 nm, an oxygen content of less than 0.15 wt%, and a specific surface area of ​​50 m². 2 / g~100 m 2 / g; The temperature of the first-stage heat treatment is 1300℃~1450℃, the heating rate is 100℃ / s~500℃ / s, and the holding time is 10~20s; The secondary heat treatment temperature is 1500℃~1600℃, the heating rate is 100℃ / s~500℃ / s, and the holding time is 5~10s; The primary heat treatment, the secondary heat treatment, and the pulse annealing all occur in a nitrogen atmosphere and a Joule heating device.

2. The method for preparing silicon magnesium nitride powder according to claim 1, characterized in that, The temperature of the first-stage heat treatment is 1400℃; Alternatively, the temperature of the first-stage heat treatment is 1300℃; Alternatively, the temperature of the first-stage heat treatment is 1450°C; Alternatively, the temperature of the first-stage heat treatment is 1420°C.

3. The method for preparing silicon magnesium nitride powder according to claim 1, characterized in that, The temperature of the secondary heat treatment is 1550℃; Alternatively, the temperature of the secondary heat treatment is 1500℃; Alternatively, the temperature of the secondary heat treatment is 1600℃; Alternatively, the temperature of the secondary heat treatment is 1570°C.

4. The method for preparing silicon magnesium nitride powder according to claim 1, characterized in that, The pulse annealing discharge voltage is 40V~60V, the maximum current is 200A~320A, the single discharge time is 2500ms~3500ms, the cycle time is 2000ms~3000ms, and the cumulative discharge is 3~5 times.

5. The method for preparing silicon magnesium nitride powder according to claim 1, characterized in that, The conductive agent includes carbon powder and / or magnesium powder, and the mass percentage of the conductive agent is 2% to 5%.

6. The method for preparing silicon magnesium nitride powder according to claim 1, characterized in that, The silicon powder and conductive agent powder are mixed by ball milling, the ball milling speed is 300 rpm to 500 rpm, and the ball milling time is 4 h to 10 h.

7. The method for preparing silicon magnesium nitride powder according to claim 1, characterized in that, The molar ratio of magnesium powder to silicon nitride powder is (0.95~1.05):1; and / or, the silicon nitride powder and magnesium powder are mixed by ball milling, the ball milling speed is 100 rpm~200 rpm, and the ball milling time is 2h~5h.

8. The method for preparing silicon magnesium nitride powder according to claim 1, characterized in that, The silicon powder has a particle size of 20nm to 100nm; the magnesium powder has a particle size of 10μm to 100μm.

9. The method for preparing magnesium silicon nitride powder according to claim 8, characterized in that, The particle size of the silicon powder is 30nm~50nm; Alternatively, the particle size of the silicon powder is 20nm~40nm; Alternatively, the particle size of the silicon powder is 50nm~100nm; Alternatively, the particle size of the silicon powder is 30nm~70nm.

10. The method for preparing silicon magnesium nitride powder according to claim 8, characterized in that, The particle size of the magnesium powder is 10μm~80μm; Alternatively, the particle size of the magnesium powder is 20μm~80μm; Alternatively, the particle size of the magnesium powder is 50μm~100μm; Alternatively, the particle size of the magnesium powder is 50μm~70μm.

Images