Method for efficiently preparing high-alpha-phase silicon nitride powder and application of high-alpha-phase silicon nitride powder

Abstract

The invention relates to a method for efficiently preparing high-alpha-phase silicon nitride powder and application of the high-alpha-phase silicon nitride powder, and the method specifically comprises the following steps: dissolving polysilazane in an organic solvent to prepare a 10wt%-40wt% polysilazane solution; adding 75wt%-95wt% of silicon powder and 5wt%-25wt% of a diluent into the polysilazane solution, and mixing for a period of time to obtain mixed slurry; and adding the obtained mixed slurry into a sintering mold, and roasting the mixed slurry under a certain pressure in a protective atmosphere to finally obtain the high-alpha-phase silicon nitride powder. The method has the advantages of high efficiency, high alpha-phase content and narrow particle size distribution.

Description

Technical Field

[0001] The present invention relates to the field of silicon nitride material preparation, and in particular to a method for efficiently preparing high-alpha phase silicon nitride powder and application thereof. Background Art

[0002] The existing silicon powder nitriding method for preparing nitriding powder has the following problems: first, because the silicon powder will partially dissolve at a certain temperature, it will cause adhesion between the silicon powders, reducing the contact area with the reaction atmosphere and affecting the reaction rate. At the same time, the resulting silicon nitride powder particle size is difficult to crush, increasing production costs. Second, the silicon oxide layer on the surface of the silicon powder further affects the nitriding rate of the silicon powder. Finally, the nitriding of the silicon powder releases a large amount of heat, which leads to heat accumulation and an increase in the β-phase content.

[0003] Therefore, it is necessary to provide a method for efficiently preparing high-α-phase silicon nitride powder. Summary of the Invention

[0004] In order to solve the above problems, it is necessary to provide a method for efficiently preparing high-α-phase silicon nitride powder and its application.

[0005] A method for efficiently preparing high-α-phase silicon nitride powder comprises the following steps:

[0006] Step (S1) dissolving polysilazane in an organic solvent to prepare a 10 wt% to 40 wt% polysilazane solution.

[0007] Polysilazane is used as an auxiliary silicon source in the entire process. Its application purpose is to:

[0008] (1) If silicon powder and diluent are mixed in solid phase, the mixing will be uneven. Polysilazane solution can provide a solvent to achieve liquid phase mixing and achieve uniform coating;

[0009] (2) Polysilazane will undergo inorganic transformation before 800°C. This process will decompose gases such as hydrogen and methane. The reducing atmosphere produced by the decomposition will not only reduce part of the silicon oxide layer on the surface of the silicon powder, but also increase the contact area between the silicon powder and nitrogen, making the reaction more complete.

[0010] (3) Before 1000°C, the furnace is in a negative pressure state, and the organic gas generated by the polysilazane solution will be immediately discharged out of the furnace;

[0011] (4) Polysilazane will form pure α-phase silicon nitride at the last holding point of silicon powder.

[0012] Specifically, polysilazane can decompose into a reducing atmosphere during the heating process, removing the silicon oxide layer on the surface of the silicon nitride powder, causing the silicon powder to react with nitrogen at an early stage, thereby avoiding the problem of increased β phase due to temperature increase. Secondly, polysilazane acts as a pore-forming agent, and the pores generated at different reaction stages increase the contact area between the silicon powder and the atmosphere, saving time. At the same time, the generated holes can release the heat accumulation caused by the nitridation of the silicon powder, reducing the generation of β phase. Finally, the final calcination product of polysilazane is a single-phase α-phase silicon nitride powder, which improves the quality of the silicon nitride powder.

[0013] The polysilazane used in this solution does not contain oxygen impurities; during the mixing process, the polysilazane is always dissolved in the organic solvent and does not directly come into contact with the air, thus avoiding contact with oxygen; during the entire sintering process, the furnace is maintained in a negative pressure state and an atmosphere containing nitrogen and its mixed gas, and is not exposed to the air, so oxidation does not occur.

[0014] Step (S2) adds 75wt%-95wt% silicon powder and 5wt%-25wt% diluent to the polysilazane solution and mixes for a period of time to obtain a mixed slurry; the present application adopts conventional mixing methods, including but not limited to ball milling, high-speed stirring, ultrasonic magnetic stirring, and the mixing time is within the range of 1-5 hours.

[0015] In the present application, the addition of a certain amount of diluent not only provides a nucleation inducer for the silicon powder nitriding process, but also absorbs a large amount of heat released by the silicon powder nitriding during the process. The liquid phase mixing allows the diluent to be evenly attached to the silicon powder, and the dissolved polysilazane is also evenly coated on the surface of the raw material. After high-temperature calcination, the polysilazane not only decomposes into an atmosphere with a certain reducing property, removing the silicon oxide layer on the surface of the silicon powder; but also generates a uniform gas path in the raw material, increasing the reaction area between the silicon powder and the atmosphere, saving a lot of time and cost. Moreover, the final product after calcining the polysilazane is a single-phase α-phase silicon nitride powder, and ultimately a silicon nitride powder with a high α-phase content is obtained.

[0016] Step (S3) adds the obtained mixed slurry into a sintering mold, and bakes the mixed solution under a certain pressure and protective atmosphere to finally obtain high α-phase silicon nitride powder (α-Si3N4).

[0017] The protective atmosphere can be selected from one or more of an ammonia-containing atmosphere and a rare gas; in this embodiment, the rare gas can include argon, helium, neon, etc. In an exemplary embodiment, the protective atmosphere can be any one of ammonia, nitrogen, argon, helium, and neon. The protective atmosphere can be a combination of ammonia and nitrogen, a combination of ammonia and argon, etc. This embodiment does not limit the ratio of the two gases.

[0018] In this embodiment, the ammonia-containing atmosphere can be ammonia, a combination of ammonia and nitrogen, or a combination of ammonia and hydrogen. When the ammonia-containing atmosphere is a combination of ammonia and nitrogen, the nitrogen concentration can be in the range of 10 vol% to 50 vol%. When the ammonia-containing atmosphere is a combination of ammonia and hydrogen, the hydrogen concentration can be in the range of 10 vol% to 20 vol%. In this embodiment, the oxygen content in the ammonia-containing atmosphere can be less than 100 ppm, preferably less than 50 ppm. More preferably, the ammonia-containing atmosphere is completely free of oxygen.

[0019] Furthermore, the organic solvent in step (S1) is one or both of toluene and xylene. Polysilazane has good solubility in both toluene and xylene. For example, if toluene and xylene are mixed in a mass ratio of 1:0.5-1:5, preferably, toluene and xylene are mixed in a mass ratio of 1:1-1:3, the solubility range of polysilazane in the mixed organic solvent can be further expanded, making the polysilazane more evenly dispersed in the solution.

[0020] Furthermore, the silicon powder in step (S2) has a particle size of 500 nm to 50 μm, preferably 1 to 20 μm, and has a metal impurity content of ≤5 wt%, and an oxygen impurity content of ≤5 wt%. Preferably, the metal impurity content of the silicon powder is less than or equal to 1 wt%, and the oxygen impurity content is less than or equal to 2 wt%.

[0021] Silicon powder with small particle size has a large specific surface area, a large contact area with nitrogen, high reaction activity, can accelerate the nitridation reaction rate, and shorten the reaction time. Silicon powder with small particle size is more conducive to the diffusion of nitrogen into the interior of the silicon powder, making the nitridation reaction more complete, and the resulting silicon nitride powder has high purity and good nitridation degree. However, there may be incompletely nitrided silicon nuclei inside the silicon powder with large particle size. The particle size of silicon powder will affect the particle size distribution of silicon nitride powder. The particle size of the silicon powder of the present application is 500nm-50μm, preferably 1-20μm. The smaller the particle size of the silicon powder and the more evenly distributed it is, the finer the particle size of the generated silicon nitride powder and the more evenly distributed it is.

[0022] An appropriate amount of oxygen impurities can promote sintering to a certain extent, improving the density and mechanical properties of silicon nitride ceramics. However, excessive oxygen content can lead to a thickening of the oxide layer on the surface of the silicon nitride powder particles, weakening the bonding force between the particles, and affecting the sintering performance of the powder and the quality of the final product. In this application, the oxygen impurity content of the silicon powder is controlled to ≤5wt%, preferably ≤2wt%, which is beneficial for promoting sintering and ensuring the bonding force of the silicon nitride powder particles, thereby ensuring the sintering performance of the powder and the quality of the final product.

[0023] Furthermore, the diluent in step (S2) is silicon nitride powder.

[0024] Furthermore, the α-phase content of the silicon nitride powder as the diluent in step (S2) is ≥70wt%, and the oxygen content is ≤5wt%. Preferably, the α-phase content of the diluent is greater than or equal to 85wt%, and the oxygen content is less than or equal to 3wt%.

[0025] Furthermore, the calcination in step (S3) is specifically performed as follows: the pressure range of the atmosphere furnace is 10-1000 kPa when the calcination temperature is below 200°C; when the calcination temperature is greater than 1000°C, the pressure range of the atmosphere furnace is 10-700 kPa. Preferably, the pressure range of the atmosphere furnace is 50-500 kPa before 200°C, and 50-300 kPa when the calcination temperature is greater than 1000°C.

[0026] Furthermore, the calcination is specifically carried out as follows: when the temperature is in the range of 1100-1200°C, the heating rate is maintained at 0.01-5°C / min; when the temperature is greater than 1330°C, the heating rate is maintained at 10-20°C / min. Preferably, when the temperature is in the range of 1100-1200°C, the heating rate is maintained at 0.1-1°C / min; when the temperature is greater than 1330°C, the heating rate is maintained at 15-18°C / min; and the heating rate in the remaining stages is 5°C / min.

[0027] Furthermore, during the heating stage from 1150 to 1200° C., the holding time is 0.5 to 20 hours per 10° C. interval. More preferably, during the heating stage from 1150 to 1200° C., the holding time is 10 to 15 hours per 10° C. interval.

[0028] Furthermore, the α-phase content of the silicon nitride powder prepared in step (S3) is greater than 95 wt %. Preferably, the α-phase content of the silicon nitride powder is greater than 97 wt %.

[0029] The method for efficiently preparing high-alpha phase silicon nitride powder and the application of the prepared alpha phase silicon nitride powder in the preparation of silicon nitride bearing balls, ceramic cutting tools or integrated circuit packaging substrates.

[0030] The mechanism of action of the present application is as follows: silicon powder does not undergo nitridation reaction before 1000°C, while polysilazane gradually decomposes to produce reducing gases such as hydrogen before 1000°C. This gas not only forms pores between the raw materials, increasing the contact area between nitrogen and silicon powder, but also reduces the silicon oxide layer on the surface of the silicon powder, promoting the reaction rate of the subsequent silicon powder nitridation. Before 1000°C, the temperature is in a negative pressure state, which extracts excess organic gas from the decomposition. The pores remaining in the early stage of the reaction serve as channels for nitrogen to enter, and the reduced silicon powder accelerates the reaction of the silicon powder at low temperatures, reducing the possibility of forming β-phase silicon nitride. Finally, at the final reaction temperature of the silicon powder, polysilazane will produce almost pure α-phase silicon nitride, increasing the overall silicon nitride powder phase content.

[0031] The present application adopts the method of mixing silicon powder and diluent in a polysilazane solvent to achieve liquid phase mixing, so that the two are mixed more evenly, and the polysilazane can also achieve uniform coating; secondly, the solid phase mixture will generate heat during the mixing process, causing some silicon powder to oxidize, while liquid phase mixing can avoid direct contact with gas, reducing the possibility of contact with gas.

[0032] The present application uses polysilazane as an auxiliary silicon source, which has the following advantages: the role of polysilazane is that the pyrolysis product can not only reduce a portion of the silicon oxide layer on the surface of the silicon powder, but also the gas generated by the pyrolysis product will leave pores in the powder material, increasing the reaction channel between the silicon powder and nitrogen, making the reaction more complete, and preventing a large amount of unreacted silicon powder from reacting in the later stage, thereby increasing the possibility of generating β-silicon nitride; finally, a small amount of polysilazane will form pure α-phase powder after the final holding temperature.

[0033] The present invention has the advantages of high efficiency, high α-phase content, and narrow particle size distribution. When the 10% volume-based particle size measured by laser scattering is set as D10, the 50% volume-based particle size is set as D50, and the 90% volume-based particle size is set as D90, the particle size distribution width W is defined as W = D10 / D50-D90-D50. The particle size distribution width W of the silicon nitride powder is within the range of 0.3-3. The powder with a narrow particle size distribution of the present invention is more densely packed during the molding process, has a low shrinkage rate during sintering, and has a high density, thereby reducing internal defects in the ceramic and improving the mechanical and thermal conductivity of the ceramic.

[0034] The high-α-phase silicon nitride powder produced in this application has the following advantages in the preparation of silicon nitride bearing balls, ceramic cutting tools, or integrated circuit packaging substrates: The silicon nitride powder produced in this application is high-α-phase (α phase >95%) silicon nitride powder with high sintering activity, easily converting to β-phase, forming a long columnar grain structure, and significantly improving the material's flexural strength and fracture toughness through grain bridging and crack deflection mechanisms. At the same time, the narrow particle size distribution results in denser powder packing, lower porosity, reduced microstructural defects, and a longer service life. The silicon nitride powder produced in this application significantly improves the mechanical properties and functional characteristics of ceramics. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings are used to provide an understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0036] Figure 1 This is the XRD pattern of the silicon nitride powder prepared in Example 1 of the present application;

[0037] Figure 2 This is an SEM image of silicon nitride powder prepared in Example 1 of the present application;

[0038] Figure 3 This is a volume distribution diagram of silicon nitride powder prepared in Example 1 of the present application;

[0039] Figure 4 This is the XRD pattern of the silicon nitride powder prepared in Example 2 of the present application;

[0040] Figure 5 This is the XRD pattern of the silicon nitride powder prepared in Example 3 of the present application;

[0041] Figure 6 XRD pattern of silicon nitride powder prepared in Comparative Example 1 of the present application;

[0042] Figure 7 This is an SEM image of the silicon nitride powder prepared in Comparative Example 1 of the present application;

[0043] Figure 8 This is the XRD pattern of the silicon nitride powder prepared in Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0044] For ease of understanding of the present application, the present application will be described more fully below. The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0045] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the description of this application, the meaning of "several" is at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0047] In this application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0048] In this application, when referring to numerical ranges, unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges subsumed therein.

[0049] Unless otherwise specified, the percentages and mass fractions involved in this application refer to mass percentages for solid-liquid mixing and solid-solid mixing, and refer to volume percentages for liquid-liquid mixing.

[0050] The percentage concentrations mentioned in this application, unless otherwise specified, refer to the final concentration, which refers to the percentage of the added component in the system after the addition of the component.

[0051] The temperature parameters in this application, unless otherwise specified, allow for both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows for temperature fluctuations within the precision range of instrument control.

[0052] The "particles" mentioned in this application, or materials with a defined particle size distribution, are not necessarily spherical in shape but may be irregular, primary or secondary. The particle size of irregular particles is the average of their maximum and minimum diameters.

[0053] Unless otherwise specified, the silicon powder used in the following examples and comparative examples is commercially available silicon powder, the content of metal impurities and oxygen impurities of which are less than 2 wt %, and the particle size is in the range of 500 nm-10 μm.

[0054] The organic solvents used in the following examples are all commercially available. The polysilazane used in the following examples and comparative examples are all commercially available. Other materials used in the following examples and comparative examples, unless otherwise specified, are all commercially available.

[0055] Example 1: This example provides a method for efficiently preparing high-α-phase silicon nitride powder. 30 g of polysilazane is added to a mixed organic solvent of 35 g of toluene and 35 g of xylene to form a polysilazane solution with a mass fraction of 30 wt%. The mixture is mixed by ultrasonic magnetic stirring for 30 minutes to form a uniformly mixed polysilazane solution. 80 g of silicon powder with a particle size of 3 μm and 20 g of a silicon nitride powder diluent with an α-phase content of 90 wt% are added to the mixed solution. The ultrasonic magnetic stirring is continued for 30 minutes to obtain a mixed slurry. The mixed slurry is poured into a graphite mold and placed in a high-temperature roasting furnace. The organic solvent is fully volatilized at 500°C under a pressure of 70 Pa. The temperature is then increased at a rate of 5°C / min under normal pressure and kept at 1500°C for 10 minutes to obtain high-α-phase silicon nitride powder.

[0056] Example 2: This example provides a method for efficiently preparing high-α-phase silicon nitride powder. 10 g of polysilazane is added to 90 g of toluene solvent to form a polysilazane solution with a mass fraction of 10 wt%. The mixture is mixed by ultrasonic magnetic stirring for 30 minutes to form a uniformly mixed polysilazane solution. 75 g of silicon powder with a particle size of 1 μm and 25 g of a silicon nitride powder diluent with an α-phase content of 92 wt% are added to the mixed solution. The ultrasonic magnetic stirring is continued for 30 minutes to obtain a mixed slurry. The mixed slurry is poured into a graphite mold and placed in a high-temperature roasting furnace. The organic solvent is fully volatilized at 200°C under a pressure of 50 Pa. The temperature is then increased at a rate of 0.1°C / min in a mixed atmosphere of ammonia and nitrogen and at normal pressure. The mixture is kept at 1350°C for 7 hours to obtain high-α-phase silicon nitride powder.

[0057] Example 3: This example provides a method for efficiently preparing high-α-phase silicon nitride powder. 40 g of polysilazane is added to a mixed organic solvent of 20 g of toluene and 35 g of xylene to form a polysilazane solution with a mass fraction of 40 wt%. The mixture is mixed by ultrasonic magnetic stirring for 30 minutes to form a uniformly mixed polysilazane solution. 95 g of silicon powder with a particle size of 10 μm and 5 g of a silicon nitride powder diluent with an α-phase content of 93 wt% are added to the mixed solution. The ultrasonic magnetic stirring is continued for 30 minutes to obtain a mixed slurry. The mixed slurry is poured into a graphite mold and placed in a high-temperature roasting furnace. The organic solvent is fully volatilized at 200°C under a pressure of 500 Pa. The temperature is then increased at a rate of 10°C / min in a mixed atmosphere of ammonia and nitrogen and at normal pressure. The mixture is kept at 1400°C for 5 hours to obtain high-α-phase silicon nitride powder.

[0058] Example 4: This example provides a method for efficiently preparing high-α-phase silicon nitride powder. 30 g of polysilazane is added to 70 g of xylene solvent to form a polysilazane solution with a mass fraction of 30 wt%. The mixture is mixed by ultrasonic magnetic stirring for 30 minutes to form a uniformly mixed polysilazane solution. 85 g of silicon powder with a particle size of 100 μm and 15 g of silicon nitride powder diluent with an α-phase content of 92 wt% are added to the mixed solution. The ultrasonic magnetic stirring is continued for 30 minutes to obtain a mixed slurry. The mixed slurry is poured into a graphite mold and placed in a high-temperature roasting furnace. The organic solvent is fully volatilized at 500°C under a pressure of 100 Pa. The temperature is then increased at a rate of 1°C / min in a mixed atmosphere of ammonia and nitrogen and at normal pressure. The mixture is kept at 1450°C for 8 hours to obtain high-α-phase silicon nitride powder.

[0059] Comparative Example 1: Add 70 g of silicon powder with a particle size of 5 μm and 30 g of a silicon nitride powder diluent with an α-phase content of 93 wt%, and continue ball milling the mixture for 30 minutes to obtain a mixed powder. The mixed powder is poured into a graphite mold, placed in a high-temperature calcination furnace, and heated at a rate of 10°C / min under a nitrogen atmosphere and normal pressure. It is kept at 1450°C for 25 hours to obtain α-phase silicon nitride powder.

[0060] Comparative Example 2: 10 g of polysilazane, 75 g of silicon powder with a particle size of 1 μm, and 25 g of a silicon nitride powder diluent with an α-phase content of 92 wt% were added to a ball mill, and the mixture was ball-milled for 30 minutes to obtain a mixed powder. The mixed powder was poured into a graphite mold and placed in a high-temperature calcination furnace. The organic solvent was fully evaporated at 200°C under a pressure of 50 Pa. The temperature was then increased at a rate of 0.1°C / min in a mixed atmosphere of ammonia and nitrogen at normal pressure, and kept at 1350°C for 7 hours to obtain α-phase silicon nitride powder.

[0061] Performance testing:

[0062] The silicon nitride powder prepared in Example 1 was subjected to X-ray diffraction detection, and the results were as follows: Figure 1 shown. Figure 1 The prepared silicon nitride powder showed an α-phase content of 98.5% by weight, with the morphology of individual silicon nitride particles and good dispersion. The polysilazane evenly coated the surface of the silicon powder and diluent powder, releasing heat from the nitridation of the silicon powder while also releasing gas to form pathways to prevent agglomeration.

[0063] The silicon nitride powder obtained in Example 1 was examined by scanning electron microscopy. Figure 2 shown. Figure 2The morphology of the prepared silicon nitride powder is similar to that of equiaxed silicon nitride powder, with a particle size of approximately 1 μm, an aspect ratio of approximately 1:1, and relatively dispersed particles. This is because the gases produced by the decomposition of polysilazane at a certain temperature form pathways within the silicon powder, preventing the particles from sticking to each other after the silicon powder reaches its melting point during nitridation, which would increase the cost of subsequent crushing.

[0064] The silicon nitride powder prepared in Example 1 was tested by laser scattering method, and the results were as follows: Figure 3 shown. Figure 3 The results of the particle size test determined by the laser scattering method show that the particle size distribution width W is in the range of 0.3-3, which is a silicon nitride powder with a narrow particle size distribution.

[0065] The silicon nitride powder prepared in Example 2 was subjected to X-ray diffraction detection, and the results were as follows: Figure 4 shown. Figure 4 It shows that the α-phase content of the prepared silicon nitride powder is 97.4 wt%.

[0066] The silicon nitride powder obtained in Example 3 was subjected to X-ray diffraction analysis. Figure 5 shown. Figure 5 It shows that the α-phase content of the prepared silicon nitride powder is 97.1 wt%.

[0067] The silicon nitride powder prepared in Comparative Example 1 was subjected to X-ray diffraction test, and the results were as follows: Figure 6 shown. Figure 6 It shows that the α-phase content of the prepared silicon nitride powder is 89.4 wt%.

[0068] The silicon nitride powder obtained in Comparative Example 1 was examined by scanning electron microscopy. Figure 7 shown. Figure 7 It shows that there is a certain agglomeration phenomenon between the prepared silicon nitride powder particles, and the particle size of the product increases.

[0069] The silicon nitride powder prepared in Comparative Example 2 was subjected to X-ray diffraction test, and the results were as follows: Figure 8 shown. Figure 8 It shows that the α-phase content of the prepared silicon nitride powder is 91.1 wt%.

[0070] Table 1 Test results of α-phase content, morphology and particle size of samples of Examples 1-7 and Comparative Examples 1-2.

[0071]

[0072] According to the data in Table 1, the α-phase content of the silicon nitride powder obtained in Examples 1-4 is greater than 97wt%, and the obtained silicon nitride powder particles are uniform, are separate equiaxed particles, have an aspect ratio of about 1:1-1.5, and a particle size of about 1-1.5μm. However, since Comparative Example 1 was not added to the polysilazane solution for mixing, there was sintering and agglomeration between the powders, and the β-phase content was high. However, since Comparative Example 2 did not use an organic solvent for mixing, the mixing between the powders was uneven. Therefore, there was a certain degree of agglomeration in the product, and the β-phase was improved compared with Example 2.

[0073] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0074] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for efficiently preparing high α-phase silicon nitride powder, characterized in that: The method comprises the following steps: step (S1) dissolving polysilazane in an organic solvent to prepare a 10wt%-40wt% polysilazane solution; step (S2) adding 75wt%-95wt% silicon powder and 5wt%-25wt% diluent to the polysilazane solution and mixing for a period of time to obtain a mixed slurry; Step (S3) adds the obtained mixed slurry into a sintering mold, and bakes the mixed solution under a certain pressure and in a protective atmosphere to finally obtain high α-phase silicon nitride powder.

2. The method for efficiently preparing high α-phase silicon nitride powder according to claim 1, characterized in that: The organic solvent in step (S1) is one or two of polysilazanes such as toluene and xylene.

3. The method for efficiently preparing high α-phase silicon nitride powder according to claim 1, characterized in that: The particle size of the silicon powder in step (S2) is 500 nm-50 μm, the metal impurity content of the silicon powder is ≤5 wt%, and the oxygen impurity content is ≤5 wt%.

4. The method for efficiently preparing high α-phase silicon nitride powder according to claim 1, characterized in that: The diluent in step (S2) is silicon nitride powder.

5. The method for efficiently preparing high α-phase silicon nitride powder according to claim 4, characterized in that: The silicon nitride powder as the diluent in step (S2) has an α-phase content of ≥70 wt% and an oxygen content of ≤5 wt%.

6. The method for efficiently preparing high α-phase silicon nitride powder according to claim 1, characterized in that: The roasting in step (S3) is specifically as follows: when the roasting temperature is below 200°C, the pressure range of the atmosphere furnace is 10-1000 kPa; when the roasting temperature is greater than 1000°C, the pressure of the atmosphere furnace is 10-700 kPa.

7. The method for efficiently preparing high α-phase silicon nitride powder according to claim 6, characterized in that: The calcination is specifically as follows: when the temperature is within the range of 1100-1200° C., the heating rate is maintained at 0.01-5° C. / min; when the temperature is greater than 1330° C., the heating rate is maintained at 10-20° C. / min.

8. The method for efficiently preparing high α-phase silicon nitride powder according to claim 1, characterized in that: The α-phase content of the silicon nitride powder prepared in the step (S3) is greater than 95 wt%.

9. The method for efficiently preparing high-α-phase silicon nitride powder according to any one of claims 1 to 8, and use of the prepared α-phase silicon nitride powder in the preparation of silicon nitride bearing balls, ceramic cutting tools, or integrated circuit packaging substrates.

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