A spherical silicon nitride powder, a preparation method thereof and application thereof

Abstract

The application discloses spherical silicon nitride powder and a preparation method and application thereof, and belongs to the field of nitride ceramic materials. The spherical silicon nitride powder has a beta phase silicon nitride content of greater than or equal to 95%, an average sphericity of greater than or equal to 0.80, a tap density in a range of 1.9-2.2 g / cm 3 , and a particle size in a range of 10-170 mu m. The preparation method comprises the following steps: in an organic solvent, taking beta-Si3N4 as an aggregate, taking silicon nitride precursors as an activator, taking a beta-diketone rare earth complex as a sintering aid, taking a mixture of polysilazane and PVB as a binder, and after pretreatment, high-temperature calcination is carried out under a nitrogen atmosphere to obtain the spherical silicon nitride powder. The prepared spherical silicon nitride powder can be used as a raw material for preparing an insulating heat-conducting material. The application can realize the preparation of high-density and high-thermal-conductivity spherical silicon nitride powder, and the prepared insulating heat-conducting material has high thermal conductivity.

Description

Technical Field

[0001] This invention belongs to the field of nitride ceramic materials, specifically relating to a spherical silicon nitride powder, its preparation method, and its application. Background Technology

[0002] With the miniaturization and high integration of integrated circuits, the assembly density of electronic components continues to increase. While providing powerful functionalities, this also leads to a sharp increase in power consumption and heat generation. High temperatures can have detrimental effects on the stability, reliability, and lifespan of electronic components. For example, excessively high temperatures can endanger semiconductor junctions, damage circuit interfaces, increase conductor resistance, and cause mechanical stress damage. Thermal interface materials, as commonly used packaging materials in the thermal management of microelectronic devices, have been extensively studied. Among them, thermally conductive fillers play a crucial role in thermal interface materials, and their thermal conductivity and microstructure are the determining factors affecting the overall performance of thermal interface materials.

[0003] Compared to traditional insulating and thermally conductive fillers such as silicon oxide and aluminum oxide, silicon nitride possesses an intrinsic thermal conductivity as high as 320 W / m·K. Furthermore, silicon nitride exhibits excellent chemical stability and thermal shock resistance, making it an ideal insulating and thermally conductive filler. Ideally, silicon nitride thermally conductive fillers are spherical to improve their flowability and filling rate. Therefore, the preparation of spherical silicon nitride thermally conductive filler powder is of great significance.

[0004] A search revealed that Chinese patent application number 202310013590.0, published on April 25, 2023, discloses a rapid preparation method for spherical silicon nitride powder. This patent uses β-Si3N4 powder, MgSiN2, and rare earth oxide sintering aids as raw materials, and obtains spherical silicon nitride powder through spray granulation based on the principle of ultrafast high-temperature sintering. Chinese patent application number 202010855055.6, published on December 4, 2020, discloses a preparation method for high-reliability, long-life silicon nitride ceramic balls for aerospace bearings. This patent uses metal acetate as a precursor for sintering aids and aluminum isopropoxide as a binder, and prepares silicon nitride ceramic balls through hydrolysis, spray drying, and calcination processes.

[0005] Therefore, currently, in the process of preparing spherical silicon nitride powder by spray granulation:

[0006] (1) Using one of α-Si3N4 / β-Si3N4 as raw material, rare earth oxides and alkaline earth metal oxides are added as sintering aids. The sintering aids and silicon nitride raw powder are subjected to aqueous phase ball milling, which results in high oxygen content and low thermal conductivity of the sintered powder. During solid phase ball milling, the sintering aids are prone to agglomeration and cannot be uniformly dispersed on the surface of silicon nitride raw material, resulting in poor sphericity and low reliability of the sintered powder. Using metal acetate as a precursor for sintering aids, although hydrolysis can coat the sintering aids onto the surface of silicon nitride, the metal acetates themselves contain a lot of water of crystallization, which increases the oxygen content of the granulated powder after sintering, resulting in low thermal conductivity of the powder.

[0007] (2) The granulation process based on α-Si3N4 powder involves a phase transformation process during sintering, which causes abnormal growth of β-silicon nitride, resulting in poor sphericity of the powder. The granulation process based on β-silicon nitride powder has the defects of difficult sintering and low powder density.

[0008] (3) Using PVA series and PVB series as binders, after debinding and sintering, more pores are generated inside the powder, resulting in low density of the powder; the generated pores will hinder the formation of the internal thermal conductivity network of the granulated powder, affecting the further improvement of the intrinsic thermal conductivity of the granulated powder.

[0009] In summary, there is currently a lack of a method in this field for preparing silicon nitride spherical powder with high density and high thermal conductivity. Summary of the Invention

[0010] 1. The problem to be solved

[0011] To address the problems of poor sphericity, low thermal conductivity, and low density in existing spherical silicon nitride powders, this invention provides a method for preparing spherical silicon nitride powder. Through optimization of the raw material formulation, a high-density and high-thermal-conductivity spherical silicon nitride powder is prepared. Furthermore, a high-density and high-thermal-conductivity spherical silicon nitride powder is obtained, and its application in insulating and thermally conductive materials is proposed.

[0012] 2. Technical Solution

[0013] To address the aforementioned technical challenges, this invention utilizes β-Si3N4 as aggregate, silicon nitride precursor as activator, β-diketone rare earth complex as sintering aid, and a mixture of polysilazane and a small amount of PVB as binder to achieve the preparation of high-density and high-thermal-conductivity spherical silicon nitride powder. Details are as follows:

[0014] A method for preparing spherical silicon nitride powder involves mixing crystalline β-Si3N4 as aggregate, silicon nitride precursor as activator, β-diketone rare earth complex as sintering aid, and a mixture of polysilazane and PVB as binder in an organic solvent in a mixer to obtain a stable slurry. After pretreatment, the slurry is calcined at high temperature under a nitrogen atmosphere to obtain spherical silicon nitride powder.

[0015] Furthermore, the rare earth content in the β-diketone rare earth complex accounts for 1.5% to 5.5% of the total mass of the preparation reaction system.

[0016] Furthermore, the β-diketone rare earth complex is one or more of tri(acetylacetone) rare earth, tri(2,2,6,6-tetramethyl-3,5-heptanedione) rare earth, and tri(1,3-diphenyl-1,3-propanedione) rare earth in any proportion, and the rare earth is selected from the group consisting of yttrium, ytterbium, europium, and lanthanum.

[0017] Furthermore, the silicon nitride precursor is one or more combinations of amino silicon, imino silicon, and amorphous silicon nitride powder.

[0018] Furthermore, the median particle size D50 of β-Si3N4 is ≤3 micrometers, and the median particle size D50 of the silicon nitride precursor is ≤1 micrometer.

[0019] Furthermore, in the mixture of polysilazane and PVB, the mass ratio of polysilazane to PVB is 1:(0.16 to 0.20).

[0020] Furthermore, the polysilazane is one or more of phenyl polysilazane, ethynyl polysilazane, propylene polysilazane, and perhydropolysilazane, combined in any proportion.

[0021] Further, the pretreatment sequentially includes spray granulation (spheroidization), hot shaping (further spheroidization), and cold isostatic pressing (to improve its density and strength); wherein, the hot shaping is carried out under rotary heating, the temperature of the hot shaping is 150-400℃, the holding time is 5-20 min, and the rotation speed is 2-20 rpm; the pressure of the cold isostatic pressing is 100-200 MPa, and the holding time is 3-15 min; the high-temperature calcination process is as follows: under a nitrogen atmosphere, the temperature is raised to 700-1400℃ at a rate of 3-10℃ / min, held for 1-3 h, then raised to 1600-1800℃ at a rate of 3-10℃ / min, held for 1-3 h, and then cooled to room temperature at a rate of 3-10℃ / min.

[0022] Furthermore, the mass percentages of each material are as follows:

[0023] Organic solvents 35%–55%;

[0024] β-Si3N4 25%–50%;

[0025] Silicon nitride precursor 5%–15%;

[0026] Sintering aids: 5%–15%;

[0027] Adhesive 5%–15%;

[0028] The organic solvent is one or more of acetone, ethyl acetate, and butyl acetate. The mixing ratio of the organic solvents is arbitrary, and the total mass percentage of each material is 100%.

[0029] A spherical silicon nitride powder, prepared by the above-described method, wherein the β-phase silicon nitride content is ≥95%, the average sphericity is ≥0.80, and the tap density ranges from 1.9 to 2.2 g / cm³. 3 The particle size ranges from 10 to 170 μm.

[0030] One application of the above-mentioned spherical silicon nitride powder is as a raw material for preparing insulating and thermally conductive materials.

[0031] The above technical solution has the following significant advantages:

[0032] (1) Using β-Si3N4 powder with a small amount of silicon nitride precursor as raw material, the abnormal growth of β-Si3N4 powder will not occur during the sintering process. At the same time, the silicon nitride precursor has high sintering activity, which can activate the crystal plane of β-Si3N4 and promote the densification sintering of β-Si3N4 powder.

[0033] (2) Using β-diketone rare earth complex as a sintering aid, which does not contain water of crystallization, and can remove the hydroxyl groups on the surface of silicon nitride powder through the displacement reaction that occurs at the interface, thereby reducing the oxygen content of silicon nitride powder; dissolving the β-diketone rare earth complex sintering aid in an organic solvent and mixing it thoroughly in a mixer, so that the sintering aid is uniformly coated on the surface of silicon nitride powder, thereby achieving uniform dispersion of the sintering aid in silicon nitride, thus avoiding the problem of poor sphericity and low density of granulated powder caused by uneven mixing of sintering aid and silicon nitride powder.

[0034] (3) A mixture of polysilazane and a small amount of PVB is used as a binder. During the sintering process, polysilazane is converted into silicon nitride, which plays a filling role between β silicon nitride grains, reducing the formation of pores in the granulated powder, resulting in small powder volume shrinkage and improved density of the granulated powder. The silicon nitride ceramic generated in situ is integrated with the main raw material to form a new thermal conductivity path, which improves the intrinsic thermal conductivity of the granulated powder.

[0035] 3. Beneficial effects

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] The present invention has the following advantages after adopting the above method: Because an organic solvent is used as the dispersion medium, silicon nitride powder in a certain mass ratio is mixed with a certain amount of organic solvent and binder in a certain order to form a slurry. After homogenization in a mixer, spherical granulated silicon nitride powder is obtained after spray granulation, hot shaping, cold isostatic pressing, and sintering. The resulting spherical silicon nitride powder has high density, high sphericity, good flowability, narrow particle size distribution, and adjustable particle size, making it suitable as an insulating and thermally conductive filler. Using the spherical silicon nitride powder of the present invention as a thermally conductive filler to prepare polybenzoxazine resin-based composite materials, compared with rod-shaped or random β-Si3N4 powder, the filling rate of the spherical silicon nitride powder is significantly improved. Under the same filling rate, the thermal conductivity of the composite material prepared by the spherical silicon nitride powder is significantly higher than that of the rod-shaped or random β-Si3N4 powder. Attached Figure Description

[0038] Figure 1 The XRD pattern of the spherical silicon nitride powder in Example 1 is shown below.

[0039] Figure 2 Here is a SEM image of the spherical silicon nitride powder from Example 2;

[0040] Figure 3 Here is a SEM image of the spherical silicon nitride powder from Example 3;

[0041] Figure 4 This is a SEM image of the spherical silicon nitride powder from Comparative Example 1. Detailed Implementation

[0042] The present invention will be further described below with reference to specific embodiments.

[0043] Example 1

[0044] (1) 35 parts by weight of acetone, 5 parts by weight of binder, 40 parts by weight of β-Si3N4 aggregate, 5 parts by weight of aminosilane, and 15 parts by weight of ytterbium acetylacetonate (III) (CAS: 14284-98-1, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) were added to a mixer and mixed evenly to obtain a stable slurry. The binder was a mixture of PVB and acetylenic polysilazane, with a mass ratio of PVB to acetylenic polysilazane of 0.18; wherein the median particle size D50 of β-Si3N4 was ≤3 micrometers, the median particle size D50 of aminosilane was ≤1 micrometer, and the mass percentage of rare earth element ytterbium in ytterbium acetylacetonate (III) was 5.5%.

[0045] (2) Spray granulation is performed on the silicon nitride mixed slurry obtained in step (1) to obtain spherical silicon nitride green powder.

[0046] (3) The spherical silicon nitride green powder obtained in step (2) is subjected to heat shaping in a rotary tube furnace (Nanjing Boyuntong Instrument Technology Co., Ltd. RTL1200). The heat shaping temperature is 150℃, the holding time is 20min, and the rotation speed is 2rpm.

[0047] (4) The silicon nitride green powder obtained in step (3) is subjected to cold isostatic pressing at 100 MPa for 15 min.

[0048] (5) The cold isostatically pressed silicon nitride green powder obtained in step (4) is placed in the furnace and heated to 700°C at a rate of 3°C / min under a high-purity nitrogen atmosphere. It is held for 1 hour, then heated to 1600°C at a rate of 6°C / min and held for 3 hours. Finally, it is cooled to room temperature at a rate of 6°C / min to obtain spherical silicon nitride powder after calcination.

[0049] The spherical silicon nitride powder prepared by the above process has a tap density of 1.9 g / cm³. 3 The particle size ranged from 10 to 170 μm, and XRD tests were performed on them. The results are as follows: Figure 1 As shown, its β-phase silicon nitride content is 95%. SEM observation revealed that the prepared silicon nitride powder has a spherical morphology with an average sphericity of 0.83.

[0050] Polybenzoxazine resin-based composites were prepared by using spherical silicon nitride powder at a volume fraction of 40%, and the thermal conductivity of the composites was measured to be 2.2 W / (m·K).

[0051] Example 2

[0052] (1) 35 parts by weight of organic solvent, 15 parts by weight of binder, 35 parts by weight of β-Si3N4 powder, 7 parts by weight of iminosilicone, and 8 parts by weight of tris(2,2,6,6-tetramethyl-3,5-pimerconic acid) europium (CAS: 15522-71-1, purchased from Shanghai Mairui Biochemical Technology Co., Ltd.) were added to a mixer and mixed evenly to obtain a stable slurry. The organic solvent was ethyl acetate, and the binder was a mixture of PVB and perhydropolysilazane (mass ratio of 0.2). The median particle size D50 of β-Si3N4 was ≤3 micrometers, the median particle size D50 of iminosilicone was ≤1 micrometer, and the mass percentage of europium in tris(2,2,6,6-tetramethyl-3,5-pimerconic acid) europium was 1.7%.

[0053] (2) Spray granulation is performed on the silicon nitride mixed slurry obtained in step (1) to obtain spherical silicon nitride green powder.

[0054] (3) The spherical silicon nitride green powder obtained in step (2) is subjected to hot shaping treatment in a rotating tube furnace. The hot shaping temperature is 250℃, the holding time is 15min, and the rotation speed is 6rpm.

[0055] (4) The silicon nitride green powder obtained in step (3) is subjected to cold isostatic pressing at 150 MPa for 12 min.

[0056] (5) The cold isostatically pressed silicon nitride green powder obtained in step (4) is placed in the furnace and heated to 800°C at a rate of 3°C / min under a high-purity nitrogen atmosphere. It is held for 1.5 hours, then heated to 1700°C at a rate of 6°C / min and held for 2 hours. Finally, it is cooled to room temperature at a rate of 5°C / min to obtain spherical silicon nitride powder after calcination.

[0057] The spherical silicon nitride powder prepared by the above process has a tap density of 2.1 g / cm³. 3 The particle size ranged from 10 to 170 μm, and XRD analysis showed that the β-phase silicon nitride content was 95%. SEM observation revealed that the prepared silicon nitride powder had a spherical morphology with an average sphericity of 0.87. Figure 2 As shown.

[0058] Polybenzoxazine resin-based composites were prepared by using spherical silicon nitride powder at a volume fraction of 45%, and the thermal conductivity of the composites was measured to be 2.7 W / (m·K).

[0059] Example 3

[0060] (1) 55 parts by weight of acetone, 10 parts by weight of binder, 25 parts by weight of β-Si3N4 aggregate, 5 parts by weight of amorphous silicon nitride, and 5 parts by weight of lanthanum acetylacetonate (III) (CAS: 14284-88-9, purchased from Shanghai Mairui Biochemical Technology Co., Ltd.) were added to a mixer and mixed evenly to obtain a stable slurry. The binder was a mixture of PVB and phenyl polysilazane, with a mass ratio of PVB to phenyl polysilazane of 0.16; wherein the median particle size D50 of β-Si3N4 was ≤3 micrometers, the median particle size D50 of amorphous silicon nitride was ≤1 micrometer, and the mass percentage of rare earth element lanthanum in lanthanum acetylacetonate (III) was 1.6%.

[0061] (2) Spray granulation is performed on the silicon nitride mixed slurry obtained in step (1) to obtain spherical silicon nitride green powder.

[0062] (3) The spherical silicon nitride green powder obtained in step (2) is subjected to heat shaping in a rotating tube furnace. The heat shaping temperature is 320℃, the holding time is 10min, and the rotation speed is 10rpm.

[0063] (4) The silicon nitride green powder obtained in step (3) is subjected to cold isostatic pressing at 180 MPa for 7 min.

[0064] (5) The cold isostatically pressed silicon nitride green powder obtained in step (4) is placed in the furnace and heated to 1400°C at a rate of 8°C / min under a high-purity nitrogen atmosphere. It is held for 1 hour, then heated to 1750°C at a rate of 5°C / min and held for 2 hours. Finally, it is cooled to room temperature at a rate of 10°C / min to obtain spherical silicon nitride powder after calcination.

[0065] The spherical silicon nitride powder prepared by the above process has a tap density of 2.2 g / cm³. 3 The particle size ranged from 10 to 170 μm, and XRD analysis showed that the β-phase silicon nitride content was 95%. SEM observation revealed that the prepared silicon nitride powder had a spherical morphology with an average sphericity of 0.90. Figure 3 As shown.

[0066] Polybenzoxazine resin-based composites were prepared by using spherical silicon nitride powder at a volume fraction of 50%, and the thermal conductivity of the composites was measured to be 3.3 W / (m·K).

[0067] Example 4

[0068] (1) 35 parts by weight of a mixed solution of acetone and ethyl acetate (mass ratio of acetone to ethyl acetate is 1:1), 5 parts by weight of binder, 50 parts by weight of β-Si3N4 aggregate, 5 parts by weight of amorphous silicon nitride, and 5 parts by weight of europium acetylacetone (III) (CAS: 18702-22-2, purchased from Shanghai Mairui Biochemical Technology Co., Ltd.) were added to a mixer and mixed evenly to obtain a stable mixed slurry. The binder is a mixture of PVB and propylene-based polysilazane, with a mass ratio of PVB to propylene-based polysilazane of 0.17; wherein the median particle size D50 of β-Si3N4 is ≤3 micrometers, the median particle size D50 of amorphous silicon nitride is ≤1 micrometer, and the mass percentage of europium rare earth element in europium acetylacetone (III) is 1.6%.

[0069] (2) Spray granulation is performed on the silicon nitride mixed slurry obtained in step (1) to obtain spherical silicon nitride green powder.

[0070] (3) The spherical silicon nitride green powder obtained in step (2) is subjected to hot shaping treatment in a rotating tube furnace. The hot shaping temperature is 400℃, the holding time is 5min, and the rotation speed is 20rpm.

[0071] (4) The silicon nitride green powder obtained in step (3) is subjected to cold isostatic pressing at 200 MPa for 3 min.

[0072] (5) The cold isostatically pressed silicon nitride green powder obtained in step (4) is placed in the furnace and heated to 1200°C at a rate of 6°C / min under a high-purity nitrogen atmosphere, held for 2 hours, then heated to 1800°C at a rate of 10°C / min, held for 2 hours, and then cooled to room temperature at a rate of 10°C / min to obtain spherical silicon nitride powder after calcination.

[0073] The spherical silicon nitride powder prepared by the above process has a tap density of 2.0 g / cm³. 3 The particle size ranged from 10 to 170 μm, and XRD tests showed that the β-phase silicon nitride content was 95%. SEM observation showed that the prepared silicon nitride powder had a spherical morphology with an average sphericity of 0.90.

[0074] Polybenzoxazine resin-based composites were prepared by using spherical silicon nitride powder at a volume fraction of 60%, and the thermal conductivity of the composites was measured to be 4.5 W / (m·K).

[0075] Example 5

[0076] (1) 35 parts by weight of ethyl acetate, 15 parts by weight of binder, 25 parts by weight of β-Si3N4 aggregate, 15 parts by weight of amorphous silicon nitride, 10 parts by weight of yttrium acetylacetonate (III) (CAS: 15554-47-9, purchased from Shanghai Mairui Biochemical Technology Co., Ltd.) and tris(1,3-diphenyl-1,3-propanedione)(1,10-phenanthroline) europium (CAS: 17904-83-5, purchased from Shanghai Yingxin Laboratory Equipment Co., Ltd.) were added to a mixer and mixed evenly to obtain a stable mixed slurry. The binder is a mixture of PVB and propylene-based polysilazane, with a mass ratio of PVB to propylene-based polysilazane of 0.17; wherein the median particle size D50 of β-Si3N4 is ≤3 micrometers, the median particle size D50 of amorphous silicon nitride is ≤1 micrometer, and the mass percentage of rare earth elements yttrium and europium in yttrium(III) acetylacetone and tris(1,3-diphenyl-1,3-propanedione)(1,10-phenanthroline)euphrates is 2.0%.

[0077] (2) Spray granulation is performed on the silicon nitride mixed slurry obtained in step (1) to obtain spherical silicon nitride green powder.

[0078] (3) The spherical silicon nitride green powder obtained in step (2) is subjected to hot shaping treatment in a rotating tube furnace. The hot shaping temperature is 400℃, the holding time is 5min, and the rotation speed is 20rpm.

[0079] (4) The silicon nitride green powder obtained in step (3) is subjected to cold isostatic pressing at 200 MPa for 3 min.

[0080] (5) The cold isostatically pressed silicon nitride green powder obtained in step (4) is placed in the furnace and heated to 1200°C at a rate of 6°C / min under a high-purity nitrogen atmosphere, held for 2 hours, then heated to 1800°C at a rate of 10°C / min, held for 2 hours, and then cooled to room temperature at a rate of 10°C / min to obtain spherical silicon nitride powder after calcination.

[0081] The spherical silicon nitride powder prepared by the above process has a tap density of 1.9 g / cm³. 3 The particle size ranges from 10 to 170 μm, and XRD tests show that the β-phase silicon nitride content is 95%. SEM observation shows that the prepared silicon nitride powder has a spherical morphology with an average sphericity of 0.85.

[0082] Polybenzoxazine resin-based composites were prepared by using spherical silicon nitride powder at a volume fraction of 65%, and the thermal conductivity of the composites was measured to be 5.1 W / (m·K).

[0083] Comparative Example 1

[0084] (1) 35 parts by weight of acetone, 5 parts by weight of binder, 40 parts by weight of β-Si3N4 aggregate, 5 parts by weight of aminosilicon, and 15 parts by weight of ytterbium oxide are added to a mixer and mixed evenly to obtain a stable slurry. The binder is a mixture of PVB and acetylene-based polysilazane, with a mass ratio of PVB to acetylene-based polysilazane of 0.18; wherein the median particle size D50 of β-Si3N4 is ≤3 micrometers, the median particle size D50 of aminosilicon is ≤1 micrometer, and the mass percentage of rare earth element ytterbium in ytterbium oxide is 13%.

[0085] (2) Spray granulation is performed on the silicon nitride mixed slurry obtained in step (1) to obtain spherical silicon nitride green powder.

[0086] (3) The spherical silicon nitride green powder obtained in step (2) is subjected to heat shaping in a rotating tube furnace. The heat shaping temperature is 150℃, the holding time is 20min, and the rotation speed is 2rpm.

[0087] (4) The silicon nitride green powder obtained in step (3) is subjected to cold isostatic pressing at 100 MPa for 15 min.

[0088] (5) The cold isostatically pressed silicon nitride green powder obtained in step (4) is placed in the furnace and heated to 700°C at a rate of 3°C / min under a high-purity nitrogen atmosphere. It is held for 1 hour, then heated to 1600°C at a rate of 6°C / min and held for 3 hours. Finally, it is cooled to room temperature at a rate of 6°C / min to obtain spherical silicon nitride powder after calcination.

[0089] The spherical silicon nitride powder prepared by the above process has a β-phase silicon nitride content of 95%, an average sphericity of 0.5, and a tap density of 1.2 g / cm³. 3 The particle size ranges from 1 to 100 μm. SEM observation shows that the prepared silicon nitride powder has a spherical morphology with an average sphericity of 0.5. Figure 4 As shown.

[0090] Polybenzoxazine resin-based composites were prepared by using spherical silicon nitride powder at a volume fraction of 40%, and the thermal conductivity of the composites was measured to be 0.6 W / (m·K).

[0091] Comparative Example 2

[0092] (1) 35 parts by weight of acetone, 5 parts by weight of binder, 45 parts by weight of β-Si3N4 aggregate, and 15 parts by weight of ytterbium acetylacetonate (III) (CAS: 14284-98-1, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) were added to a mixer and mixed evenly to obtain a stable slurry. The binder was a mixture of PVB and acetylenic polysilazane, with a mass ratio of PVB to acetylenic polysilazane of 0.18; wherein the median particle size D50 of β-Si3N4 was ≤3 micrometers, and the mass percentage of rare earth element ytterbium in ytterbium acetylacetonate (III) was 5.5%.

[0093] (2) Spray granulation is performed on the silicon nitride mixed slurry obtained in step (1) to obtain spherical silicon nitride green powder.

[0094] (3) The spherical silicon nitride green powder obtained in step (2) is subjected to heat shaping in a rotating tube furnace. The heat shaping temperature is 150℃, the holding time is 20min, and the rotation speed is 2rpm.

[0095] (4) The silicon nitride green powder obtained in step (3) is subjected to cold isostatic pressing at 100 MPa for 15 min.

[0096] (5) The cold isostatically pressed silicon nitride green powder obtained in step (4) is placed in the furnace and heated to 700°C at a rate of 3°C / min under a high-purity nitrogen atmosphere. It is held for 1 hour, then heated to 1600°C at a rate of 6°C / min and held for 3 hours. Finally, it is cooled to room temperature at a rate of 6°C / min to obtain spherical silicon nitride powder after calcination.

[0097] The spherical silicon nitride powder prepared by the above process has a β-phase silicon nitride content of 95%, an average sphericity of 0.4, and a tap density of 1.1 g / cm³. 3 The particle size ranges from 1 to 120 μm.

[0098] Polybenzoxazine resin-based composites were prepared by using spherical silicon nitride powder at a volume fraction of 40%, and the thermal conductivity of the composites was measured to be 0.65 W / (m·K).

[0099] Comparative Example 3

[0100] (1) 35 parts by weight of acetone, 5 parts by weight of binder, 40 parts by weight of β-Si3N4 aggregate, 5 parts by weight of aminosilicone, and 15 parts by weight of ytterbium acetylacetonate (III) (CAS: 14284-98-1, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) were added to a mixer and mixed evenly to obtain a stable slurry. The binder was PVB; wherein the median particle size D50 of β-Si3N4 was ≤3 micrometers, the median particle size D50 of aminosilicone was ≤1 micrometer, and the mass percentage of rare earth element ytterbium in ytterbium acetylacetonate (III) was 5.5%.

[0101] (2) Spray granulation is performed on the silicon nitride mixed slurry obtained in step (1) to obtain spherical silicon nitride green powder.

[0102] (3) The spherical silicon nitride green powder obtained in step (2) is subjected to heat shaping in a rotating tube furnace. The heat shaping temperature is 150℃, the holding time is 20min, and the rotation speed is 2rpm.

[0103] (4) The silicon nitride green powder obtained in step (3) is subjected to cold isostatic pressing at 100 MPa for 15 min.

[0104] (5) The cold isostatically pressed silicon nitride green powder obtained in step (4) is placed in the furnace and heated to 700°C at a rate of 3°C / min under a high-purity nitrogen atmosphere. It is held for 1 hour, then heated to 1600°C at a rate of 6°C / min and held for 3 hours. Finally, it is cooled to room temperature at a rate of 6°C / min to obtain spherical silicon nitride powder after calcination.

[0105] The spherical silicon nitride powder prepared by the above process has a β-phase silicon nitride content of 95%, an average sphericity of 0.6, and a tap density of 1.3 g / cm³. 3 The particle size ranges from 10 to 120 μm.

[0106] Polybenzoxazine resin-based composites were prepared by using spherical silicon nitride powder at a volume fraction of 40%, and the thermal conductivity of the composites was measured to be 0.9 W / (m·K).

[0107] The above embodiments have described in detail the purpose and effects of the present invention. It should be understood that the above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the concept and scope of the present invention. All modifications, equivalent substitutions, improvements, etc., made by those skilled in the art or by adopting the technical concept and technical solution of the present invention within the spirit and principles of the present invention and without departing from the design concept of the present invention are within the protection scope of the present invention.

Claims

1. A method for preparing spherical silicon nitride powder, characterized in that: In an organic solvent, β-Si3N4 is used as aggregate, silicon nitride precursor is used as activator, β-diketone rare earth complex is used as sintering aid, and a mixture of polysilazane and PVB is used as binder. After pretreatment, spherical silicon nitride powder is obtained by high-temperature calcination under a nitrogen atmosphere. The silicon nitride precursor is one or more of aminosilicon, iminosilicon, and amorphous silicon nitride powder.

2. The method for preparing spherical silicon nitride powder according to claim 1, characterized in that: The rare earth content in the β-diketone rare earth complex accounts for 1.5% to 5.5% of the total mass of the preparation reaction system.

3. The method for preparing spherical silicon nitride powder according to claim 1, characterized in that: β-Diketone rare earth complexes are one or more of tri(acetylacetone) rare earth, tri(2,2,6,6-tetramethyl-3,5-heptanedione) rare earth, and tri(1,3-diphenyl-1,3-propanedione) rare earth, and the rare earths include yttrium, ytterbium, europium or lanthanum.

4. The method for preparing spherical silicon nitride powder according to claim 1, characterized in that: The median particle size D50 of β-Si3N4 is ≤3 μm, and the median particle size D50 of silicon nitride precursors is ≤1 μm.

5. A method for preparing spherical silicon nitride powder according to claim 1, characterized in that: In the mixture of polysilazane and PVB, the mass ratio of polysilazane to PVB is 1: (0.16~0.20).

6. The method for preparing spherical silicon nitride powder according to claim 5, characterized in that: Polysilazane is one or a mixture of phenyl polysilazane, ethynyl polysilazane, propylene polysilazane, and perhydropolysilazane.

7. A method for preparing spherical silicon nitride powder according to claim 1, characterized in that: The pretreatment process includes granulation, hot shaping, and cold isostatic pressing. The hot shaping is performed under rotary heating at a temperature of 150-400°C for 5-20 minutes and a rotation speed of 2-20 rpm. The cold isostatic pressing is performed at a pressure of 100-200 MPa for 3-15 minutes. The high-temperature calcination process is as follows: under a nitrogen atmosphere, the temperature is increased to 700-1400°C at a rate of 3-10°C / min and held for 1-3 hours, then increased to 1600-1800°C at a rate of 3-10°C / min and held for 1-3 hours, and then cooled to room temperature at a rate of 3-10°C / min.

8. A method for preparing spherical silicon nitride powder according to any one of claims 1 to 7, characterized in that: The mass percentages of each material are as follows: Organic solvents 35%~55%; β-Si3N4 25%~50%; Silicon nitride precursor 5%~15%; Sintering aids 5%~15%; Adhesive 5%~15%; The organic solvent is one or more of acetone, ethyl acetate, and butyl acetate, and the total mass percentage of each material is 100%.

9. A spherical silicon nitride powder, characterized in that: The spherical silicon nitride powder prepared by any one of claims 1 to 8 has a β-phase silicon nitride content ≥95%, an average sphericity ≥0.80, and a tap density ranging from 1.9 to 2.2 g / cm³. 3 The particle size ranges from 10 to 170 μm.

10. An application of the spherical silicon nitride powder according to claim 9, characterized in that: As a raw material for preparing insulating and thermally conductive materials.

Images