WO2021008089A1 - 一种通过金属还原制备氮化硅粉末的方法 - Google Patents

一种通过金属还原制备氮化硅粉末的方法 Download PDF

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WO2021008089A1
WO2021008089A1 PCT/CN2019/129456 CN2019129456W WO2021008089A1 WO 2021008089 A1 WO2021008089 A1 WO 2021008089A1 CN 2019129456 W CN2019129456 W CN 2019129456W WO 2021008089 A1 WO2021008089 A1 WO 2021008089A1
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powder
silicon nitride
nitride powder
combustion synthesis
purity
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PCT/CN2019/129456
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English (en)
French (fr)
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崔巍
张�杰
李飞
成会明
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青岛瓷兴新材料有限公司
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Priority to JP2022502489A priority Critical patent/JP7411279B2/ja
Priority to EP19937629.4A priority patent/EP3974380A4/en
Publication of WO2021008089A1 publication Critical patent/WO2021008089A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B21/00—Nitrogen; Compounds thereof
    • C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
    • C01B21/068—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with silicon
    • C01B21/0682—Preparation by direct nitridation of silicon
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer

Definitions

  • the invention relates to a technology for preparing high-quality silicon nitride ceramic powder, in particular to a process technology for preparing silicon nitride powder with low oxygen content by adding active metal powder as a reducing agent, and belongs to the field of inorganic non-metal powder materials.
  • Silicon nitride ceramics have a variety of excellent properties such as low density, high thermal conductivity, high hardness, good thermal stability and chemical stability, and are the most comprehensive class of materials in the structural ceramic family. It is widely used in ceramic engines, cutting tools, thermal conductive substrates and other fields. As its main raw material, silicon nitride powder has an important position. In the sintering process of silicon nitride ceramics, the oxygen in the silicon nitride raw materials has an adverse effect on the performance of the ceramics, which will greatly reduce the mechanical properties and thermal conductivity of the silicon nitride ceramics. Therefore, preparing a silicon nitride powder with low oxygen content and particularly suitable for ceramic sintering will greatly improve the performance of ceramics. However, there is no effective method to reduce the oxygen content in the powder in the process of preparing commercial silicon nitride powder.
  • the purpose of the present invention is to provide a process for preparing high-quality silicon nitride powder by adding active metal powder as a reducing agent in the raw material, so that the oxygen content of the silicon nitride powder is less than 1wt%, and the final product is High-quality silicon nitride with adjustable phase content, average particle size 1-50 ⁇ m, metal oxide content 0-10wt%, and impurity content less than 1wt%.
  • the embodiment of the present invention provides a method for preparing silicon nitride powder by metal reduction, the method comprising the following steps:
  • step (3) The combustion synthesis raw material obtained in step (3) is subjected to combustion synthesis to obtain silicon nitride powder.
  • the purity of the silicon powder raw material in step (1) is >99wt%.
  • the particle size range of the silicon powder in step (1) is 100-200 mesh.
  • the metal powder added in step (3) accounts for 0.01-10% by weight of all components.
  • the step (4) includes: loosely distributing the mixture obtained in step (3) to the reaction boat, and then placing the boat in the combustion synthesis
  • the reaction device is evacuated and filled with high-purity nitrogen.
  • the pressure in the combustion synthesis reaction device is maintained at 1-8 MPa, and the igniting agent is ignited by the energized tungsten coil to induce the combustion synthesis reaction;
  • the pressure in the synthesis reaction device begins to drop.
  • the gas in the device is released and circulating water is used for cooling; finally a soft, easily broken block product is obtained, and after grinding, the coarse silicon nitride powder is obtained; preferably, the high The purity of pure nitrogen is over 97%, or the purity of the high-purity nitrogen is over 99.9%.
  • the method further includes a step (5) after step (4): pickling the silicon nitride powder obtained in step (4) Purify to obtain silicon nitride powder.
  • the diluent in step (1) is high-purity silicon nitride powder with an average particle size of 0.5-10 ⁇ m, and the high-purity silicon nitride powder The content of alpha phase is >60wt%.
  • the average particle size of the ammonium chloride additive in step (1) is 0.1-50 ⁇ m, and the purity is >99wt%.
  • the mixing mode in step (2) includes sand milling, ball milling, stirring mill, V-type mixer mixing milling and/or drum milling.
  • the metal powder described in step (3) includes magnesium, calcium, iron, nickel, zinc, aluminum, lithium, sodium, potassium, yttrium, ytterbium At least one.
  • the sieving in step (3) includes sieving with a sieve with 40-100 mesh openings; further preferably, the sieving in step (3) includes sieving with a 60-mesh sieve Sifted.
  • the purpose of "mixing the mixed mixture uniformly and/or sieving in a V-type mixer" in step (3) is to improve the stacking state of the reaction raw materials, making the reaction raw materials more fluffy, which is beneficial to the follow-up The combustion synthesis.
  • further sieving after being evenly mixed in a V-type mixer can further improve the accumulation of reaction raw materials.
  • 40-100 mesh is suitable as the sieve for sieving, and better, 60 mesh sieve can be selected. A screen that is too fine may change the composition of the reaction raw materials; a screen that is too thick cannot fully improve the accumulation of the reaction raw materials.
  • the metal powder described in step (3) has a particle size of 20-1000 mesh, an oxygen content of ⁇ 5 wt%, and a purity of >99 wt%.
  • the oxygen content in the purity is Not an impurity.
  • the particle size of the reducing metal powder is 50-200 mesh; preferably, the particle size of the reducing metal powder is 200-1000 mesh.
  • the metal powder is too fine (for example, metal powder above 200 mesh)
  • the oxygen content carried by the metal powder itself will increase due to the influence of oxygen in the air.
  • the particle size of the reducing metal powder can be as fine as possible, for example as small as 1000 mesh.
  • the mixing method in step (3) includes sand milling, ball milling, stirring mill, V-type mixer mixing milling and/or drum milling.
  • the mixing process in the method, for example, for metal powders that are prone to oxidation in the air, the mixing process should be performed in an inert gas atmosphere.
  • the metal powder that is easily oxidized in the air includes calcium, lithium, sodium, potassium, yttrium, and ytterbium.
  • the sieving described in step (3) is performed with a sieve with a mesh size of 20-1000.
  • the step (5) includes: coarsely sieving the silicon nitride powder obtained in the step (4) with a 20-500 mesh screen, and using nitric acid The mixed acid of hydrochloric acid and sulfuric acid is pickled to remove the metal oxide in the silicon nitride powder.
  • the volume content ratios of the nitric acid, the hydrochloric acid, and the sulfuric acid in the mixed acid are 10%-20%, 60%-80%, respectively , 10%-20%, mass fractions of less than 68%, less than 20%, less than 70%, pickling for 1-10 hours, the powder after pickling is washed 1-5 times to remove water-soluble substances, and then used after suction filtration Drying is carried out by press drying, spray drying or vacuum drying.
  • the embodiment of the present invention also provides a silicon nitride powder prepared according to the above method, the silicon nitride powder has an average particle size of 1-50 ⁇ m, a metal oxide content of 0-10 wt%, and an impurity content of less than 1 wt%.
  • the metal oxide content in the silicon nitride powder is less than 1 wt%
  • the sintered body has a thermal conductivity of 90 W/mK or more, and a bending strength of 700 MPa or more.
  • the sintering condition of the sintered body is: mixing the silicon nitride powder with MgO and Y 2 O 3 , grinding, and dry pressing to form a green body, and the green body Air pressure sintering at 1900°C and 1MPa nitrogen pressure for 8 hours.
  • the embodiment of the present invention also provides a sintered body, the sintered body is made by sintering the silicon nitride powder prepared by the above method, the average particle size of the silicon nitride powder is 1-50 ⁇ m, and the metal oxide content is 0-10wt% , The impurity content is less than 1wt%.
  • An embodiment of the present invention also provides a method for manufacturing the above-mentioned sintered body, the method including:
  • Silicon powder 20-70wt%
  • Silicon nitride diluent 70%-20wt%
  • Ammonium chloride additive 0-20wt%
  • step (4) The silicon nitride powder obtained in step (4) is purified by acid washing to obtain silicon nitride powder;
  • the silicon nitride powder is mixed with MgO and Y 2 O 3 , ground, and dry pressed to form a green body, and the green body is air-sintered at 1900° C. and a nitrogen pressure of 1 MPa for 8 hours.
  • the above step (6) includes: respectively weighing 90% by weight of the product silicon nitride powder of Example 2, 5% by weight of MgO, and 5% by weight of Y 2 O 3 , and
  • the three raw materials are mixed with alcohol, using silicon nitride balls as the medium, ball milled on a planetary mill for 2 hours, and then vacuum dried at 80°C; the dried powder is passed through a 60-mesh sieve, and the sieved powder is dried Press molding with a molding pressure of 20MPa, and then perform cold isostatic pressing on the dry pressed blank under 220MPa pressure; the formed blank is sintered at 1900°C under 1MPa nitrogen pressure for 8 hours, and then cooled with the furnace after sintering; The sintered sample was tested for thermal conductivity and three-point bending strength. The thermal conductivity was 100W/mK and the bending strength was 800MPa.
  • the purity of the silicon powder raw material in step (1) is >99wt%.
  • the particle size range of the silicon powder in step (1) is 100-200 mesh.
  • the metal powder added in step (3) accounts for 0.01-10% by weight of all components.
  • the step (4) includes: loosely packing the mixture obtained in step (3) into a reaction boat, and then placing the boat in the combustion synthesis
  • the reaction device is evacuated and filled with high-purity nitrogen.
  • the pressure in the combustion synthesis reaction device is maintained at 1-8 MPa.
  • the igniting agent is ignited by the energized tungsten coil to induce the combustion synthesis reaction; after the reaction, the combustion The pressure in the synthesis reaction device begins to drop.
  • the gas in the device is released and circulating water is used for cooling; finally a soft, easily broken block product is obtained, and after grinding, the coarse silicon nitride powder is obtained; preferably, the high The purity of pure nitrogen is over 97%, or the purity of the high-purity nitrogen is over 99.9%.
  • the method further includes a step (5) after step (4): pickling the silicon nitride powder obtained in step (4) Purify to obtain silicon nitride powder.
  • the diluent in step (1) is high-purity silicon nitride powder with an average particle size of 0.5-10 ⁇ m, and the high-purity silicon nitride powder The content of alpha phase is >60wt%.
  • the average particle size of the ammonium chloride additive in step (1) is 0.1-50 ⁇ m, and the purity is >99wt%.
  • the mixing mode in step (2) includes sand milling, ball milling, stirring mill, V-type mixer mixing milling and/or drum milling.
  • the metal powder described in step (3) includes magnesium, calcium, iron, nickel, zinc, aluminum, lithium, sodium, potassium, yttrium, ytterbium At least one.
  • the reducing metal powder described in step (3) has a particle size of 20-1000 mesh, an oxygen content of ⁇ 5 wt%, and a purity of >99 wt%.
  • the oxygen content is not considered as an impurity.
  • the particle size of the reducing metal powder is 50-200 mesh; preferably, the particle size of the reducing metal powder is 200-1000 mesh.
  • the metal powder is too fine (for example, metal powder above 200 mesh)
  • the oxygen content carried by the metal powder itself will increase due to the influence of oxygen in the air.
  • the particle size of the reducing metal powder can be as fine as possible, for example as small as 1000 mesh.
  • the mixing method in step (3) includes sand milling, ball milling, stirring mill, V-type mixer mixing milling and/or drum milling.
  • the mixing process in the method, for example, for metal powders that are prone to oxidation in the air, the mixing process should be performed in an inert gas atmosphere.
  • the metal powder that is easily oxidized in the air includes calcium, lithium, sodium, potassium, yttrium, and ytterbium.
  • the sieving described in step (3) is performed with a sieve with a mesh size of 20-1000.
  • the step (5) includes: coarsely sieving the silicon nitride powder obtained in the step (4) with a 20-500 mesh screen, and using nitric acid The mixed acid of hydrochloric acid and sulfuric acid is pickled to remove the metal oxide in the silicon nitride powder.
  • the volume content ratios of the nitric acid, the hydrochloric acid, and the sulfuric acid in the mixed acid are 10%-20%, 60%-80%, respectively , 10%-20%, mass fractions of less than 68%, less than 20%, less than 70%, pickling for 1-10 hours, the powder after pickling is washed 1-5 times to remove water-soluble substances, and then used after suction filtration Drying is carried out by press drying, spray drying or vacuum drying.
  • the invention has the characteristics of low energy consumption, simple equipment, energy saving, no pollution, no toxicity, etc.
  • the prepared silicon nitride powder phase content can be controlled, and its outstanding advantages are:
  • oxygen in the system generally exists in the form of silicon oxide, and the active metal powder can reduce the O in the silicon oxide to produce a metal oxide, thus achieving the purpose of eliminating oxygen in the system.
  • the lattice oxygen in the silicon nitride powder obtained by the method is significantly lower than that of the silicon nitride powder prepared by other methods. Since the lattice oxygen in the powder cannot be removed after the silicon nitride is formed, the powder prepared by the method is very suitable for ceramic sintering that requires a high oxygen content (that is, a very low oxygen content) in.
  • the silicon nitride powder obtained by the method has good crystallinity and uniform morphology.
  • Figure 1 is an XRD analysis chart of the combustion synthesis of silicon nitride powder in Example 1;
  • Example 2 is a SEM image of the product of combustion synthesis of silicon nitride powder in Example 1;
  • Figure 3 is an XRD analysis chart of the combustion synthesis of silicon nitride powder in Example 2;
  • Figure 4 is an SEM image of the combustion synthesis of silicon nitride powder in Example 2.
  • Figure 5 is an XRD analysis chart of the combustion synthesis of silicon nitride powder in Example 5;
  • Figure 6 is an XRD analysis chart of the combustion synthesis of silicon nitride powder in Example 8.
  • Fig. 7 is an XRD analysis chart of the combustion synthesis of silicon nitride powder in Example 11.
  • Figure 8 is a SEM image of the combustion synthesis of silicon nitride powder in Comparative Example 2;
  • FIG. 9 is an SEM image of the product of combustion synthesis of silicon nitride powder in Comparative Example 3.
  • FIG. 9 is an SEM image of the product of combustion synthesis of silicon nitride powder in Comparative Example 3.
  • the reducing metal powder refers to an active metal powder with stronger reducing properties than silicon powder and silicon nitride.
  • the combustion synthesis raw material is loosely packed in a reaction boat and placed in the combustion synthesis equipment. After vacuuming, it is filled with 8MPa high-purity nitrogen. Use titanium powder as ignition agent to induce combustion synthesis reaction. After the combustion reaction is over, the gas in the device is released, and when circulating water is cooled to below 40°C, the chamber door is opened and the reaction product is taken out. The product is in a relatively soft lump shape with a white overall appearance and a small amount of unreacted residual silicon powder on the surface. After cleaning, collecting, weighing, and calculating the product, it is known that the product recovery rate is 95%. The product was tested by XRD, and the test results are shown in Figure 1.
  • the analysis showed that the ⁇ phase content was 100%, the oxygen content in silicon nitride was 0.8%, and the total amount of impurities was less than 1 wt%. It can be seen from the XRD pattern shown in FIG. 1 that the product has very good crystallization performance. Compared with the method of the present application, for example, silicon nitride synthesized by the gas phase method has no crystallinity, and there is no characteristic peak on the XRD spectrum. It can be seen from the SEM image of the product ( Figure 2) that the silicon nitride powder of this example has good crystallinity and uniform morphology.
  • the silicon nitride powder particles are short rods with different lengths, and the width and height of a single particle are 1-2 ⁇ m. The length is between 1 ⁇ m and 20 ⁇ m, and the aspect ratio is between 1-10.
  • oxygen content refers to the oxygen content in all states of the silicon nitride powder, including free or combined oxygen on the surface of the powder and in the silicon nitride crystal lattice. Same below.
  • the dried above mixture and magnesium powder are mixed uniformly in a V-type mixer to obtain combustion synthesis raw materials (in the combustion synthesis raw materials, 200 mesh silicon powder is 20wt%, and silicon nitride (average particle size 2 ⁇ m) is 70% by weight, 9% by weight of ammonium chloride, and 1% by weight of magnesium powder), the particle size of the magnesium powder is 60 mesh, the purity is >99% by weight, and the mixing process is protected by inert gas.
  • the combustion synthesis raw material is loosely packed in a reaction boat and placed in the combustion synthesis equipment. After vacuuming, it is filled with 8MPa high-purity nitrogen. Use titanium powder as ignition agent to induce combustion synthesis reaction.
  • the gas in the device is released, and when circulating water is cooled to below 40°C, the chamber door is opened and the reaction product is taken out.
  • the product is in a relatively soft lump shape with a white overall appearance and a small amount of unreacted residual silicon powder on the surface. After cleaning, collecting, weighing, and calculating the product, it is known that the product recovery rate is 95%.
  • the product was tested by XRD, and the test results are shown in Figure 3. The analysis showed that the content of ⁇ phase was 95%, the oxygen content in silicon nitride was 0.5%, and the total amount of impurities was less than 1 wt%.
  • the SEM image of the product shows that the silicon nitride powder of this example has good crystallinity and uniform morphology.
  • the silicon nitride powder particles present irregular polyhedrons. Most of the particles are between 1-2 ⁇ m in size, and a few are relatively large. The size of large particles can reach more than 5 ⁇ m, and the size of a few smaller particles is less than 1 ⁇ m.
  • the dried above mixture and magnesium powder are mixed uniformly in a V-type mixer to obtain combustion synthesis raw materials (in the combustion synthesis raw materials, 200 mesh silicon powder is 20wt%, and silicon nitride (average particle size 2 ⁇ m) is 70wt%, ammonium chloride is 5wt%, and magnesium powder is 5wt%), the magnesium powder has a particle size of 200 mesh and a purity of >99wt%, and the mixing process is protected by inert gas.
  • the combustion synthesis raw material is loosely packed in a reaction boat and placed in the combustion synthesis equipment. After vacuuming, it is filled with 8MPa high-purity nitrogen. Use titanium powder as ignition agent to induce combustion synthesis reaction.
  • the gas in the device is released, and when circulating water is cooled to below 40°C, the chamber door is opened and the reaction product is taken out.
  • the product is in a relatively soft lump shape with a white overall appearance and a small amount of unreacted residual silicon powder on the surface. After cleaning, collecting, weighing, and calculating the product, it is known that the product recovery rate is 95%.
  • the alpha phase content is 95%
  • the oxygen content in silicon nitride is 0.5%
  • the total amount of impurities is less than 1wt%.
  • the combustion synthesis raw material is loosely packed in a reaction boat and placed in the combustion synthesis equipment. After vacuuming, it is filled with 8MPa high-purity nitrogen. Use titanium powder as ignition agent to induce combustion synthesis reaction. After the combustion reaction is over, the gas in the device is released, and when circulating water is cooled to below 40°C, the chamber door is opened and the reaction product is taken out. The product is in a relatively soft lump shape with a white overall appearance and a small amount of unreacted residual silicon powder on the surface. After cleaning, collecting, weighing, and calculating the product, it is known that the product recovery rate is 95%. The alpha phase content is 95%, the oxygen content in silicon nitride is 0.5%, and the total amount of impurities is less than 1wt%.
  • Example 3 Comparing the results of Example 3 and Example 4, it can be known that when the magnesium powder is added in a large amount (for example, greater than 1 wt%), further increasing the amount of reducing metal powder has little effect on the performance of the final product. The reason is that, under normal circumstances, 1wt% of the reducing metal is sufficient to react with the oxygen in the raw material.
  • the purpose of further adding excessive metal powder is to ensure that most of the oxygen reacts with the reducing metal to form the corresponding oxide; and Since the self-propagating reaction temperature can reach 1900°C, which is far above the melting boiling point of the corresponding metal powder, the excess unreacted reducing metal will volatilize.
  • the dried mixture and magnesium powder are mixed uniformly in a V-type mixer to obtain a combustion synthesis raw material (in the combustion synthesis raw material, 100 mesh silicon powder is 35wt%, and silicon nitride (average particle size 2 ⁇ m) is 35wt%, ammonium chloride 20wt%, magnesium powder 10wt%), the magnesium powder has a particle size of 1000 mesh (the crushing process and mixing process of the magnesium powder are carried out under the protection of inert gas), the purity is >99wt%, the mixing process Use inert gas for protection. Subsequently, the combustion synthesis raw material is loosely packed in a reaction boat and placed in the combustion synthesis equipment. After vacuuming, 5MPa high-purity nitrogen is filled.
  • the combustion synthesis raw material is loosely packed in a reaction boat and placed in the combustion synthesis equipment. After vacuuming, 5MPa high-purity nitrogen is filled. Use titanium powder as ignition agent to induce combustion synthesis reaction. After the combustion reaction is over, the gas in the device is released, and when circulating water is cooled to below 40°C, the chamber door is opened and the reaction product is taken out.
  • As 1000 mesh magnesium powder is very easy to oxidize in the air, a large amount of oxygen is brought into the reaction raw materials, resulting in the product being lumpy, the whole is yellow-white, and there are a small amount of unreacted residual silicon powder and magnesium oxide powder on the surface. After cleaning, collecting, weighing, and calculating the product, the product recovery rate is 90%.
  • the alpha phase content is 95%
  • the oxygen content in silicon nitride is 1%
  • the total amount of impurities is 1.5% by weight.
  • Comparative Example 1 and Example 5 The only difference between Comparative Example 1 and Example 5 is that the crushing and mixing process of the magnesium powder in Comparative Example 1 is completed in air, while the crushing process and the mixing process of the magnesium powder in Example 5 are all performed under the protection of inert gas. Otherwise, the experimental conditions of Comparative Example 1 and Example 5 are the same. Comparing the results of Comparative Example 1 and Example 5, it can be seen that since the crushing process and mixing process of magnesium powder did not isolate oxygen, the final product obtained in Comparative Example 1 had a certain degree of oxygen content and total impurities compared to Example 5. Elevated.
  • the dried above mixture and aluminum powder are mixed uniformly in a V-type mixer to obtain a combustion synthesis raw material (in the combustion synthesis raw material, 200 mesh silicon powder is 70wt%, and silicon nitride (average particle size 2 ⁇ m) is 20wt%, ammonium chloride is 9.99wt%, and aluminum powder is 0.01wt%), the aluminum powder has a particle size of 200 mesh and a purity of >99wt%, and the mixing process is protected by inert gas. Subsequently, the combustion synthesis raw material is loosely packed in a reaction boat and placed in the combustion synthesis equipment. After vacuuming, it is filled with 8MPa high-purity nitrogen. Use titanium powder as ignition agent to induce combustion synthesis reaction.
  • the gas in the device is released, and when circulating water is cooled to below 40°C, the chamber door is opened and the reaction product is taken out.
  • the product is in a relatively soft lump shape with a white overall appearance and a small amount of unreacted residual silicon powder on the surface. After cleaning, collecting, weighing, and calculating the product, it is known that the product recovery rate is 95%.
  • the product was tested by XRD, and the analysis showed that the ⁇ phase content was 100%, the oxygen content in silicon nitride was 0.8%, and the total amount of impurities was less than 1 wt%.
  • the dried mixture and aluminum powder are uniformly mixed in a V-type mixer to obtain combustion synthesis raw materials (in the combustion synthesis raw materials, 200 mesh silicon powder is 20wt%, and silicon nitride (average particle size 2 ⁇ m) is 70% by weight, 9% by weight of ammonium chloride, 1% by weight of aluminum powder), the aluminum powder has a particle size of 200 mesh and a purity of >99% by weight, and the mixing process is protected by inert gas.
  • the combustion synthesis raw material is loosely packed in a reaction boat and placed in the combustion synthesis equipment. After vacuuming, it is filled with 8MPa high-purity nitrogen. Use titanium powder as ignition agent to induce combustion synthesis reaction.
  • the gas in the device is released, and when circulating water is cooled to below 40°C, the chamber door is opened and the reaction product is taken out.
  • the product is in a relatively soft lump shape with a white overall appearance and a small amount of unreacted residual silicon powder on the surface. After cleaning, collecting, weighing, and calculating the product, it is known that the product recovery rate is 95%.
  • the product was tested by XRD, and the analysis showed that the alpha phase content was 95%, the oxygen content in silicon nitride was 0.5%, and the total amount of impurities was less than 1wt%.
  • the combustion synthesis raw material is loosely packed in a reaction boat and placed in the combustion synthesis equipment. After vacuuming, 5MPa high-purity nitrogen is filled. Use titanium powder as ignition agent to induce combustion synthesis reaction. After the combustion reaction is over, the gas in the device is released, and when circulating water is cooled to below 40°C, the chamber door is opened and the reaction product is taken out. The product is in a relatively soft lump shape with a white overall appearance and a small amount of unreacted residual silicon powder on the surface. After cleaning, collecting, weighing, and calculating the product, it is known that the product recovery rate is 95%. The product was tested by XRD, and the test results are shown in Figure 6. The analysis showed that the alpha phase content was 95%, the oxygen content in silicon nitride was 0.3%, and the total amount of impurities was less than 1 wt%.
  • the dried mixture and yttrium powder are uniformly mixed in a V-type mixer to obtain a combustion synthesis raw material (in the combustion synthesis raw material, 200 mesh silicon powder is 70wt%, and silicon nitride (average particle size 2 ⁇ m) is 20wt%, ammonium chloride is 9.99wt%, and yttrium powder is 0.01wt%), the yttrium powder has a particle size of 200 mesh and a purity of >99wt%, and the mixing process is protected by inert gas. Subsequently, the combustion synthesis raw material is loosely packed in a reaction boat and placed in the combustion synthesis equipment. After vacuuming, it is filled with 8MPa high purity nitrogen. Use titanium powder as ignition agent to induce combustion synthesis reaction.
  • a combustion synthesis raw material 200 mesh silicon powder is 70wt%, and silicon nitride (average particle size 2 ⁇ m) is 20wt%, ammonium chloride is 9.99wt%, and yttrium powder is 0.01
  • the gas in the device is released, and when circulating water is cooled to below 40°C, the chamber door is opened and the reaction product is taken out.
  • the product is in a relatively soft lump shape with a white overall appearance and a small amount of unreacted residual silicon powder on the surface. After cleaning, collecting, weighing, and calculating the product, it is known that the product recovery rate is 95%.
  • the product was tested by XRD, and the analysis showed that the ⁇ phase content was 100%, the oxygen content in silicon nitride was 0.8%, and the total amount of impurities was less than 1 wt%.
  • the dried mixture and yttrium powder are uniformly mixed in a V-type mixer to obtain a combustion synthesis raw material (in the combustion synthesis raw material, 200 mesh silicon powder is 20wt%, and silicon nitride (average particle size 2 ⁇ m) is 70wt%, ammonium chloride is 9wt%, yttrium powder is 1wt%), the yttrium powder has a particle size of 200 mesh and a purity of >99wt%, and the mixing process is protected by inert gas. Subsequently, the combustion synthesis raw material is loosely packed in a reaction boat and placed in the combustion synthesis equipment. After vacuuming, it is filled with 8MPa high-purity nitrogen. Use titanium powder as ignition agent to induce combustion synthesis reaction.
  • the gas in the device is released, and when circulating water is cooled to below 40°C, the chamber door is opened and the reaction product is taken out.
  • the product is in a relatively soft lump shape with a white overall appearance and a small amount of unreacted residual silicon powder on the surface. After cleaning, collecting, weighing, and calculating the product, it is known that the product recovery rate is 95%.
  • the product was tested by XRD, and the analysis showed that the alpha phase content was 95%, the oxygen content in silicon nitride was 0.5%, and the total amount of impurities was less than 1wt%.
  • the dried mixture and yttrium powder are uniformly mixed in a V-type mixer to obtain a combustion synthesis raw material (in the combustion synthesis raw material, 100 mesh silicon powder is 35wt%, and silicon nitride (average particle size 2 ⁇ m) is 35wt%, ammonium chloride 20wt%, yttrium powder 10wt%), the yttrium powder has a particle size of 200 mesh and a purity of >99wt%, and the mixing process is protected by inert gas. Subsequently, the combustion synthesis raw material is loosely packed in a reaction boat and placed in the combustion synthesis equipment. After vacuuming, 5MPa high-purity nitrogen is filled. Use titanium powder as ignition agent to induce combustion synthesis reaction.
  • the gas in the device is released, and when circulating water is cooled to below 40°C, the chamber door is opened and the reaction product is taken out.
  • the product is in a relatively soft lump shape with a white overall appearance and a small amount of unreacted residual silicon powder on the surface.
  • After cleaning, collecting, weighing, and calculating the product it is known that the product recovery rate is 95%.
  • the product was tested by XRD, and the test results are shown in Fig. 7. The analysis showed that the alpha phase content was 95%, the oxygen content in silicon nitride was 0.3%, and the total amount of impurities was less than 1 wt%.
  • the dried above mixture and 0.01% iron powder are mixed uniformly in a V-type mixer to obtain a combustion synthesis raw material (in the combustion synthesis raw material, 200 mesh silicon powder is 70wt%, silicon nitride (average particle size 2 ⁇ m) ) Is 20wt%, ammonium chloride is 9.99wt%, and iron powder is 0.01wt%), the iron powder has a particle size of 200 mesh and a purity of >99wt%, and the mixing process is protected by inert gas. Subsequently, the combustion synthesis raw material is loosely packed in a reaction boat and placed in the combustion synthesis equipment. After vacuuming, it is filled with 8MPa high-purity nitrogen. Use titanium powder as ignition agent to induce combustion synthesis reaction.
  • the gas in the device is released, and when circulating water is cooled to below 40°C, the chamber door is opened and the reaction product is taken out.
  • the product is in a relatively soft lump shape with a white overall appearance and a small amount of unreacted residual silicon powder on the surface. After cleaning, collecting, weighing, and calculating the product, it is known that the product recovery rate is 95%.
  • the product was tested by XRD, and the analysis showed that the ⁇ phase content was 100%, the oxygen content in silicon nitride was 0.8%, and the total amount of impurities was less than 1 wt%.
  • the dried mixture and ytterbium powder are uniformly mixed in a V-type mixer to obtain combustion synthesis raw materials (in the combustion synthesis raw materials, 200 mesh silicon powder is 70wt%, and silicon nitride (average particle size 2 ⁇ m) is 20wt%, ammonium chloride is 9.99wt%, ytterbium powder is 0.01wt%), the ytterbium powder has a particle size of 200 mesh and a purity of >99wt%, and the mixing process is protected by inert gas. Subsequently, the combustion synthesis raw material is loosely packed in a reaction boat and placed in the combustion synthesis equipment. After vacuuming, it is filled with 8MPa high-purity nitrogen.
  • Example 2 Weigh the following components according to the weight ratio of Example 2, 200 mesh silicon powder, silicon nitride (average particle size 2 ⁇ m), ammonium chloride, after mixing the above three components with alcohol, use silicon nitride balls as the medium , Ball milled on a rolling ball mill for 1 hour, and then vacuum dried at 80 °C, to obtain a mixture (in the mixture, 200 mesh silicon powder is 20 parts by weight, silicon nitride (average particle size 2 ⁇ m) is 70 parts by weight, chlorinated Ammonium is 9 parts by weight). Then the above mixture was loosely packed in a reaction boat and placed in a combustion synthesis equipment. After vacuuming, it is filled with 8MPa high-purity nitrogen. Use titanium powder as ignition agent to induce combustion synthesis reaction. After the combustion reaction is completed, the gas in the device is released, and when circulating water is cooled to below 40°C, the chamber door is opened and the reaction product silicon nitride powder is taken out.
  • 200 mesh silicon powder is 20 parts by weight
  • Example 14 Compare the results of Example 14 with the results of Comparative Example 2.
  • the test conditions of Example 14 and Comparative Example 2 are the same. The only difference is that Example 14 adds 1% magnesium powder during the combustion synthesis of silicon nitride powder. , And Comparative Example 2 did not add any reducing metal powder. From the test results, the thermal conductivity of the final sintered product increased from 85 W/mK in Comparative Example 2 to 100 W/mK in Example 14, and the flexural strength increased from 650 MPa in Comparative Example 2 to 800 MPa in Example 14.
  • adding reducing metal powder in the process of preparing silicon nitride powder by combustion synthesis can greatly improve the sintering performance of silicon nitride powder, and can obtain a sintered product based on the silicon nitride powder with excellent performance.
  • the combustion synthesis raw material is loosely packed in a reaction boat and placed in the combustion synthesis equipment. After vacuuming, it is filled with 8MPa high-purity nitrogen.
  • the product is in a relatively soft lump shape with a white overall appearance and a small amount of unreacted residual silicon powder on the surface. After cleaning, collecting, weighing, and calculating the product, it is known that the product recovery rate is 90%.
  • the alpha phase content is 50%
  • the oxygen content in silicon nitride is 1%
  • the total amount of impurities is 1 wt%.
  • the combustion synthesis raw material is loosely packed in a reaction boat and placed in the combustion synthesis equipment. After vacuuming, it is filled with 8MPa high-purity nitrogen.

Abstract

一种使用硅粉为原料，利用活泼金属作为还原剂，通过燃烧合成方法直接制备高质量氮化硅粉末的方法，所述方法包括以下步骤：将硅粉氮化硅稀释剂等反应原料按照比例混合，再加入定量的金属粉末与反应原料混合，混合均匀后，布料于燃烧合成反应装置中，在特定压力下诱发反应，得到高质量氮化硅粉末。本发明工艺方法中利用具有比反应原料更强的还原性的活泼金属，将反应原料中的氧进行还原，从而生成相应的金属氧化物。本发明工艺方法中所制备的氮化硅粉末氧含量低，结晶性好，纯度高，具有优异的烧结性能。

Description

一种通过金属还原制备氮化硅粉末的方法
本申请要求2019年7月16日向中国国家知识产权局提交的专利申请号为201910642283.2，发明名称为“一种通过金属还原制备氮化硅粉末的方法”的在先申请的优先权。所述在先申请的全文通过引用的方式结合于本申请中。
技术领域
本发明涉及高质量氮化硅陶瓷粉体制备技术，特别涉及一种通过添加活泼金属粉末作为还原剂，制备低氧含量氮化硅粉末的工艺技术，属于无机非金属粉体材料领域。
背景技术
氮化硅陶瓷具有低密度、高导热系数、高硬度、良好的热稳定性和化学稳定性等多种优异性能，是结构陶瓷家族中综合性能最为优良的一类材料。广泛应用于陶瓷发动机、切削刀具、导热基板等领域。氮化硅粉末作为其主要原料，重要地位可见一斑。在氮化硅陶瓷的烧结过程中，氮化硅原料中的氧对陶瓷性能有着不良的影响，会大大降低氮化硅陶瓷的力学性能以及导热性能。因此，制备一种氧含量低，特别适合于陶瓷烧结的氮化硅粉末将大大提高陶瓷的性能。但目前已商业化的氮化硅粉末制备过程中，尚无行之有效的降低粉体中氧含量的方法。
发明内容
本发明的目的是提供一种通过在原料中加入活泼金属粉末作为还原剂制备高质量氮化硅粉末的工艺方法，使得制得的氮化硅粉末氧含量低于1wt％，最终获得的产物为高质量氮化硅，相含量可调控，平均粒度1-50μm，金属氧化物含量0-10wt％，杂质含量低于1wt％。
本发明的实施例提供一种通过金属还原制备氮化硅粉末的方法，所述方法包含以下步骤：
(1)准备以下组分：
硅粉；
氮化硅稀释剂；
氯化铵添加剂；
(2)将上述各组分混合均匀，得到混合物；
(3)向所述混合物中加入还原性金属粉末，然后将所述金属粉末与所述混合物混合均匀，并将混合后的混合物在V型混料机中混合均匀和/或过筛，得到燃烧合成原料；在所述燃烧合成原料中，所述硅粉占20-70wt％，所述氮化硅稀释剂占70-20wt％，所述氯化铵添加剂0-20wt％；
(4)将步骤(3)得到的所述燃烧合成原料进行燃烧合成，得到氮化硅粉末。
根据本发明的一种实施方式，在所述方法中，例如，步骤(1)中所述硅粉原料的纯度>99wt％。
根据本发明的一种实施方式，在所述方法中，例如，步骤(1)中所述硅粉的粒度范围是100-200目。
根据本发明的一种实施方式，在所述方法中，例如，步骤(3)中加入的所述金属粉末占所有组分的重量百分比为0.01-10％。
根据本发明的一种实施方式，在所述方法中，例如，所述步骤(4)包括：将步骤(3)所得混合物松装布料于反应料舟，然后将所述料舟放置在燃烧合成反应装置内，抽真空后，充入高纯氮气，所述燃烧合成反应装置内压力保持在1-8MPa，以通电钨丝圈点燃引燃剂，诱发燃烧合成反应；反应结束后，所述燃烧合成反应装置内压力开始下降，此时释放装置内的气体，同时通循环水进行冷却；最终得到松软、易破碎的块状产物，研磨之后即得到氮化硅粗粉；优选的，所述高纯氮气的纯度在97％以上，或者所述高纯氮气的纯度在99.9％以上。
根据本发明的一种实施方式，在所述方法中，例如，所述方法还包括在步骤(4)之后的步骤(5)：对步骤(4)得到的所述氮化硅粉末进行酸洗提纯，得到氮化硅粉末。
根据本发明的一种实施方式，在所述方法中，例如，步骤(1)中所述稀释剂为高纯氮化硅粉末，平均粒径在0.5-10μm，所述高纯氮化硅粉末的α相含量>60wt％。
根据本发明的一种实施方式，在所述方法中，例如，步骤(1)中所述氯化铵添加剂平均粒径在0.1-50μm，纯度>99wt％。
根据本发明的一种实施方式，在所述方法中，例如，步骤(2)所述的混合方式包括砂磨、球磨、搅拌磨、V型混合机混磨和/或滚筒磨。
根据本发明的一种实施方式，在所述方法中，例如，步骤(3)所述的金属粉末包括镁、钙、铁、镍、锌、铝、锂、钠、钾、钇、镱中的至少一种。
优选的，步骤(3)中所述过筛包括采用具有40-100目筛孔的筛网过筛；进一步优选的，步骤(3)中所述过筛包括采用具有60目筛孔的筛网过筛。其中，步骤(3)中所述“并将混合后的混合物在V型混料机中混合均匀和/或过筛”的目的在于改善反应原料的堆积状态，使得反 应原料更加蓬松，有利于后续的燃烧合成。特别的，在V型混料机中混合均匀之后进一步过筛，可以更进一步地改善反应原料的堆积状态。过筛的筛网选择40-100目为宜，更佳的，可以选择60目筛孔的筛网。过细的筛网可能导致反应原料组成改变；过粗的筛网又不能充分起到改善反应原料的堆积状态的效果。
根据本发明的一种实施方式，在所述方法中，例如，步骤(3)所述的金属粉末粒度为20-1000目，氧含量<5wt％，纯度>99wt％，所述纯度中氧含量不算杂质。优选的，所述还原性金属粉末粒度为50-200目；优选的，所述还原性金属粉末粒度为200-1000目。一般还原性金属粉末粒度控制在50-200目为好，这是针对还原性金属粉末的破碎过程及混合过程在空气中进行的情况而言。因为在这样的情况下，如果金属粉末太细了(例如200目以上金属粉末)，由于空气中氧的影响，金属粉末本身携带的氧含量就升高。但如果还原性金属粉末的破碎过程及混合过程全程都在惰性气体的保护下进行，隔绝空气的情况下，氧气无法进入，则还原性金属粉末的粒度可以尽量的细，例如细到1000目。
根据本发明的一种实施方式，在所述方法中，例如，步骤(3)所述的混合方式包括砂磨、球磨、搅拌磨、V型混合机混磨和/或滚筒磨。
根据本发明的一种实施方式，在所述方法中，例如，对于在空气中易发生氧化的金属粉末，混合过程应在惰性气体的气氛中进行。
根据本发明的一种实施方式，在所述方法中，例如，所述空气中易发生氧化的金属粉末包括钙、锂、钠、钾、钇和镱。
根据本发明的一种实施方式，在所述方法中，例如，步骤(3)所述的过筛，采用目数为20-1000目的筛网进行。
根据本发明的一种实施方式，在所述方法中，例如，所述步骤(5)包括：以20-500目的筛网对步骤(4)得到的氮化硅粉末进行粗筛，并以硝酸、盐酸、硫酸的混合酸进行酸洗，以除去所述氮化硅粉末中的金属氧化物。
根据本发明的一种实施方式，在所述方法中，例如，所述混合酸中所述硝酸、所述盐酸、所述硫酸的体积含量比例分别为10％-20％、60％-80％、10％-20％，质量分数分别小于68％、小于20％、小于70％，酸洗1-10小时，将酸洗后的粉末水洗1-5次，除去水溶性物质，抽滤后采用压滤干燥、喷雾干燥或真空干燥的方法进行干燥。
本发明的实施例还提供根据上述方法制备得到的氮化硅粉末，所述氮化硅粉末平均粒度1-50μm，金属氧化物含量0-10wt％，杂质含量低于1wt％。
根据本发明的一种实施方式，例如，所述氮化硅粉末中金属氧化物含量小于1wt％，烧结 后的烧结体热导率90W/mK以上，抗弯强度700MPa以上。
根据本发明的一种实施方式，例如，所述烧结体的烧结条件为：将所述氮化硅粉末与MgO、Y 2O 3混合、研磨、干压成型素坯，将所述素坯在1900℃，1MPa氮气压力的条件下气压烧结8h。
本发明的实施例还提供一种烧结体，所述烧结体采用上述方法制备得到的氮化硅粉末烧结而成，所述氮化硅粉末平均粒度1-50μm，金属氧化物含量0-10wt％，杂质含量低于1wt％。
本发明的实施例还提供上述烧结体的制造方法，所述方法包括：
(1)以按照以下重量百分比准备原料：
硅粉：20-70wt％；
氮化硅稀释剂：70％-20wt％；
氯化铵添加剂：0-20wt％；
(2)将上述各原料混合均匀；
(3)向所述原料中加入还原性金属粉末，然后将所述还原性金属粉末与所述原料混合均匀，并将混合后的混合物过筛；
(4)将步骤(3)所得混合物进行燃烧合成，得到氮化硅粉末；
(5)对步骤(4)得到的所述氮化硅粉末进行酸洗提纯，得到氮化硅粉末；
(6)将所述氮化硅粉末与MgO、Y 2O 3混合、研磨、干压成型素坯，将所述素坯在1900℃，1MPa氮气压力的条件下气压烧结8h。
根据本发明的一种实施方式，在上述方法中，例如，上述步骤(6)包括：分别称取90wt％实施例2的产物氮化硅粉，5wt％MgO，5wt％Y 2O 3，将三种原料与酒精混合，以氮化硅球为介质，在行星磨上球磨2h，随后在80℃下真空干燥；将干燥后的粉体过60目筛，并将过筛后的粉体干压成型，成型压力20MPa，随后将干压成型的素坯在220MPa压力下进行冷等静压；成型后的素坯在1900℃，1MPa氮气压力的条件下气压烧结8h，烧结后随炉降温；将烧结后的样品进行热导率及三点抗弯强度的测试，热导率为100W/mK，抗弯强度800MPa。
根据本发明的一种实施方式，在所述方法中，例如，步骤(1)中所述硅粉原料的纯度>99wt％。
根据本发明的一种实施方式，在所述方法中，例如，步骤(1)中所述硅粉的粒度范围是100-200目。
根据本发明的一种实施方式，在所述方法中，例如，步骤(3)中加入的所述金属粉末占所有组分的重量百分比为0.01-10％。
根据本发明的一种实施方式，在所述方法中，例如，所述步骤(4)包括：将步骤(3) 所得混合物松装布料于反应料舟，然后将所述料舟放置在燃烧合成反应装置内，抽真空后，充入高纯氮气，所述燃烧合成反应装置内压力保持在1-8MPa，以通电钨丝圈点燃引燃剂，诱发燃烧合成反应；反应结束后，所述燃烧合成反应装置内压力开始下降，此时释放装置内的气体，同时通循环水进行冷却；最终得到松软、易破碎的块状产物，研磨之后即得到氮化硅粗粉；优选的，所述高纯氮气的纯度在97％以上，或者所述高纯氮气的纯度在99.9％以上。
根据本发明的一种实施方式，在所述方法中，例如，所述方法还包括在步骤(4)之后的步骤(5)：对步骤(4)得到的所述氮化硅粉末进行酸洗提纯，得到氮化硅粉末。
根据本发明的一种实施方式，在所述方法中，例如，步骤(1)中所述稀释剂为高纯氮化硅粉末，平均粒径在0.5-10μm，所述高纯氮化硅粉末的α相含量>60wt％。
根据本发明的一种实施方式，在所述方法中，例如，步骤(1)中所述氯化铵添加剂平均粒径在0.1-50μm，纯度>99wt％。
根据本发明的一种实施方式，在所述方法中，例如，步骤(2)所述的混合方式包括砂磨、球磨、搅拌磨、V型混合机混磨和/或滚筒磨。
根据本发明的一种实施方式，在所述方法中，例如，步骤(3)所述的金属粉末包括镁、钙、铁、镍、锌、铝、锂、钠、钾、钇、镱中的至少一种。
根据本发明的一种实施方式，在所述方法中，例如，步骤(3)所述的还原性金属粉末粒度为20-1000目，氧含量<5wt％，纯度>99wt％，所述纯度中氧含量不算杂质。优选的，所述还原性金属粉末粒度为50-200目；优选的，所述还原性金属粉末粒度为200-1000目。一般还原性金属粉末粒度控制在50-200目为好，这是针对还原性金属粉末的破碎过程及混合过程在空气中进行的情况而言。因为在这样的情况下，如果金属粉末太细了(例如200目以上金属粉末)，由于空气中氧的影响，金属粉末本身携带的氧含量就升高。但如果还原性金属粉末的破碎过程及混合过程全程都在惰性气体的保护下进行，隔绝空气的情况下，氧气无法进入，则还原性金属粉末的粒度可以尽量的细，例如细到1000目。
根据本发明的一种实施方式，在所述方法中，例如，步骤(3)所述的混合方式包括砂磨、球磨、搅拌磨、V型混合机混磨和/或滚筒磨。
根据本发明的一种实施方式，在所述方法中，例如，对于在空气中易发生氧化的金属粉末，混合过程应在惰性气体的气氛中进行。
根据本发明的一种实施方式，在所述方法中，例如，所述空气中易发生氧化的金属粉末包括钙、锂、钠、钾、钇和镱。
根据本发明的一种实施方式，在所述方法中，例如，步骤(3)所述的过筛，采用目数为 20-1000目的筛网进行。
根据本发明的一种实施方式，在所述方法中，例如，所述步骤(5)包括：以20-500目的筛网对步骤(4)得到的氮化硅粉末进行粗筛，并以硝酸、盐酸、硫酸的混合酸进行酸洗，以除去所述氮化硅粉末中的金属氧化物。
根据本发明的一种实施方式，在所述方法中，例如，所述混合酸中所述硝酸、所述盐酸、所述硫酸的体积含量比例分别为10％-20％、60％-80％、10％-20％，质量分数分别小于68％、小于20％、小于70％，酸洗1-10小时，将酸洗后的粉末水洗1-5次，除去水溶性物质，抽滤后采用压滤干燥、喷雾干燥或真空干燥的方法进行干燥。
本发明具备能耗低、设备简单、节约能源、无污染、无毒害等特点，制备的氮化硅粉末相含量可控制，其突出优点为：
1.通过加入活泼金属粉末，在反应过程中由于金属具有强于硅粉及氮化硅的还原性，会优先与反应体系内的氧进行反应，生成相应的金属氧化物，从而降低反应生成氮化硅中的氧含量，提高了粉体的烧结性能。上述“体系内的氧”一般是以硅氧化物形式存在的，活泼金属粉末能够将硅氧化物中的O还原出来，生成金属氧化物，这样就达到了消除体系中氧的目的。
2.由于氧在氮化硅生成以前就被还原掉一部分，因此使用所述方法得到的氮化硅粉末中的晶格氧显著低于其他方法制备的氮化硅粉末。由于粉体中的晶格氧在氮化硅生成后便无法去除，因此使用所述方法制得的粉体非常适合用于对氧含量要求较高(即要求极低的氧含量)的陶瓷烧结中。
3.使用所述方法得到的氮化硅粉末结晶性良好，形貌均一。
4.节约能源。除引发反应过程需要少量能源外，整个合成过程全部依靠反应放热来维持和实现，无需外加能源。
5.生产效率高，合成反应迅速。
附图说明
为了更清楚地说明本发明实施例的技术方案，下面将对实施例的附图作简单地介绍，显然，下面描述中的附图仅仅涉及本发明的一些实施例，而非对本发明的限制。
图1是实施例1中燃烧合成氮化硅粉末产物的XRD分析图谱；
图2是实施例1中燃烧合成氮化硅粉末产物的SEM图；
图3是实施例2中燃烧合成氮化硅粉末产物的XRD分析图谱；
图4是实施例2中燃烧合成氮化硅粉末产物的SEM图；
图5是实施例5中燃烧合成氮化硅粉末产物的XRD分析图谱；
图6是实施例8中燃烧合成氮化硅粉末产物的XRD分析图谱；
图7是实施例11中燃烧合成氮化硅粉末产物的XRD分析图谱。
图8是对比例2中燃烧合成氮化硅粉末产物的SEM图；
图9是对比例3中燃烧合成氮化硅粉末产物的SEM图。
具体实施方式
下文将结合具体实施例对本发明的氮化硅、氮化硅陶瓷浆料做更进一步的说明。应当理解，下列实施例仅为示例性地说明和解释本发明，而不应被解释为对本发明保护范围的限制。凡基于本发明上述内容所实现的技术均涵盖在本发明旨在保护的范围内。
在本文中，除非另有说明，所有百分比均为质量百分比。
在本文中，所述还原性金属粉末是指还原性强于硅粉及氮化硅的活泼金属粉末。
为便于理解，下面结合具体燃烧合成制备氮化硅粉末实例，对本发明作进一步解释说明。
实施例1
取以下组分，200目硅粉，氮化硅(平均粒径2μm)，将上述组分与酒精混合后，以氮化硅球为介质，在滚动球磨机上球磨1h，随后在80℃下真空干燥，得到混合物。将干燥后的上述混合物与镁粉在V型混料机中混合均匀，得到燃烧合成原料(在所述燃烧合成原料中，200目硅粉为70wt％，氮化硅(平均粒径2μm)为29.99wt％，氯化铵为0wt％，镁粉为0.01wt％)，所述镁粉粒度200目，纯度>99wt％，混合过程采用惰性气体进行保护。随后将所述燃烧合成原料松装于反应料舟中，放置在燃烧合成设备内。抽真空后充入8MPa高纯氮气。使用钛粉为点火剂，诱发燃烧合成反应。燃烧反应结束后释放装置内气体，同时通循环水冷却至40℃以下时，打开腔门，取出反应产物。产物呈较为松软的块状，整体呈白色，表面有少量未反应的残余硅粉。将产物清理、收集、称量、计算后可知，产品回收率为95％。对产物进行XRD检测，检测结果如图1所示，分析表明其中β相含量为100％，氮化硅中氧含量为0.8％，杂质总量低于1wt％。由图1所示的XRD图可见产物结晶性能很好，与本申请的方法相对比，例如气相法合成的氮化硅就没有结晶性，XRD谱图上没有特征峰。由产物的SEM图(图2)可见，本实施例的氮化硅粉末结晶性良好，形貌均一，氮化硅粉末颗粒呈现长短不一的短棒状，单一颗粒的宽、高在1-2μm之间，而长度则在1μm到20μm不等，长径比在1-10之间。
上述“氧含量”是指氮化硅粉末中全部状态的氧含量，包括粉体表面的以及氮化硅晶格中的游离态或者化合态的氧。下同。
实施例2
取以下组分，200目硅粉，氮化硅(平均粒径2μm)，氯化铵，将上述三种组分与酒精混合后，以氮化硅球为介质，在滚动球磨机上球磨1h，随后在80℃下真空干燥，得到混合物。将干燥后的上述混合物与镁粉在V型混料机中混合均匀，得到燃烧合成原料(在所述燃烧合成原料中，200目硅粉为20wt％，氮化硅(平均粒径2μm)为70wt％，氯化铵为9wt％，镁粉为1wt％)，所述镁粉粒度60目，纯度>99wt％，混合过程采用惰性气体进行保护。随后将所述燃烧合成原料松装于反应料舟中，放置在燃烧合成设备内。抽真空后充入8MPa高纯氮气。使用钛粉为点火剂，诱发燃烧合成反应。燃烧反应结束后释放装置内气体，同时通循环水冷却至40℃以下时，打开腔门，取出反应产物。产物呈较为松软的块状，整体呈白色，表面有少量未反应的残余硅粉。将产物清理、收集、称量、计算后可知，产品回收率为95％。对产物进行XRD检测，检测结果如图3所示，分析表明其中α相含量为95％，氮化硅中氧含量为0.5％，杂质总量低于1wt％。
产物的SEM图(图4)可见，本实施例的氮化硅粉末结晶性良好，形貌均一，氮化硅粉末颗粒呈现不规则的多面体，大部分颗粒尺寸在1-2μm之间，少数较大的颗粒尺寸可达5μm以上，少数较小颗粒尺寸不到1μm。
实施例3
取以下组分，200目硅粉，氮化硅(平均粒径2μm)，氯化铵，将上述三种组分与酒精混合后，以氮化硅球为介质，在滚动球磨机上球磨1h，随后在80℃下真空干燥，得到混合物。将干燥后的上述混合物与镁粉在V型混料机中混合均匀，得到燃烧合成原料(在所述燃烧合成原料中，200目硅粉为20wt％，氮化硅(平均粒径2μm)为70wt％，氯化铵为5wt％，镁粉为5wt％)，所述镁粉粒度200目，纯度>99wt％，混合过程采用惰性气体进行保护。随后将所述燃烧合成原料松装于反应料舟中，放置在燃烧合成设备内。抽真空后充入8MPa高纯氮气。使用钛粉为点火剂，诱发燃烧合成反应。燃烧反应结束后释放装置内气体，同时通循环水冷却至40℃以下时，打开腔门，取出反应产物。产物呈较为松软的块状，整体呈白色，表面有少量未反应的残余硅粉。将产物清理、收集、称量、计算后可知，产品回收率为95％。α相含量为95％，氮化硅中氧含量为0.5％，杂质总量低于1wt％。
实施例4
取以下组分，200目硅粉，氮化硅(平均粒径2μm)为，氯化铵，将上述三种组分与酒精混合后，以氮化硅球为介质，在滚动球磨机上球磨1h，随后在80℃下真空干燥，得到混合物。将干燥后的上述混合物与镁粉在V型混料机中混合均匀，得到燃烧合成原料(在所述燃烧合成原料中，200目硅粉为20wt％，氮化硅(平均粒径2μm)为70wt％，氯化铵为2wt％，镁粉为8wt％)，所述镁粉粒度200目，纯度>99wt％，混合过程采用惰性气体进行保护。随后将所述燃烧合成原料松装于反应料舟中，放置在燃烧合成设备内。抽真空后充入8MPa高纯氮气。使用钛粉为点火剂，诱发燃烧合成反应。燃烧反应结束后释放装置内气体，同时通循环水冷却至40℃以下时，打开腔门，取出反应产物。产物呈较为松软的块状，整体呈白色，表面有少量未反应的残余硅粉。将产物清理、收集、称量、计算后可知，产品回收率为95％。α相含量为95％，氮化硅中氧含量为0.5％，杂质总量低于1wt％。
对比实施例3和实施例4的结果可以知道，在镁粉添加量较多(例如，大于1wt％)的情况下，进一步增加还原性金属粉末的用量对于最终产品性能影响不大。原因在于，一般情况下1wt％的还原性金属添加量就已经足以与原料中的氧反应了，进一步添加过量的金属粉末目的是确保绝大部分氧与还原性金属反应生成相应的氧化物；而由于自蔓延反应温度可达1900℃，远超过相应金属粉末的熔沸点，多余的没有反应的还原性金属会挥发掉。
实施例5
取以下组分，100目硅粉，氮化硅(平均粒径2μm)，氯化铵，将上述三种组分与酒精混合后，以氮化硅球为介质，在砂磨机上磨1h，随后在80℃下真空干燥，得到混合物。将干燥后的上述混合物与镁粉在V型混料机中混合均匀，得到燃烧合成原料(在所述燃烧合成原料中，100目硅粉为35wt％，氮化硅(平均粒径2μm)为35wt％，氯化铵为20wt％，镁粉为10wt％)，所述镁粉粒度1000目(镁粉的破碎过程及混合过程都在惰性气体的保护下进行)，纯度>99wt％，混合过程采用惰性气体进行保护。随后将所述燃烧合成原料松装于反应料舟中，放置在燃烧合成设备内。抽真空后充入5MPa高纯氮气。使用钛粉为点火剂，诱发燃烧合成反应。燃烧反应结束后释放装置内气体，同时通循环水冷却至40℃以下时，打开腔门，取出反应产物。产物呈较为松软的块状，整体呈白色，表面有少量未反应的残余硅粉。将产物清理、收集、称量、计算后可知，产品回收率为95％。对产物进行XRD检测，检测结果如图5所示，分析表明其中α相含量为95％，氮化硅中氧含量为0.3％，杂质总量低于1wt％。
对比例1
取以下组分，100目硅粉，氮化硅(平均粒径2μm)，氯化铵，将上述三种组分与酒精混合后，以氮化硅球为介质，在砂磨机上磨1h，随后在80℃下真空干燥，得到混合物。将干燥后的上述混合物与镁粉在V型混料机中混合均匀，得到燃烧合成原料(在所述燃烧合成原料中，100目硅粉为35wt％，氮化硅(平均粒径2μm)为35wt％，氯化铵为20wt％，镁粉为10wt％)，所述镁粉粒度1000目，纯度>99wt％，所述混合过程在空气中完成。随后将所述燃烧合成原料松装于反应料舟中，放置在燃烧合成设备内。抽真空后充入5MPa高纯氮气。使用钛粉为点火剂，诱发燃烧合成反应。燃烧反应结束后释放装置内气体，同时通循环水冷却至40℃以下时，打开腔门，取出反应产物。由于1000目镁粉在空气中极易氧化，将大量氧带入反应原料，导致产物呈块状，整体呈黄白色，表面有少量未反应的残余硅粉以及氧化镁粉。将产物清理、收集、称量、计算后可知，产品回收率为90％。其中α相含量为95％，氮化硅中氧含量为1％，杂质总量1.5wt％。
对比例1与实施例5的唯一区别在于，对比例1镁粉的粉碎和混合过程在空气中完成，而实施例5中镁粉的破碎过程及混合过程都在惰性气体的保护下进行。除此之外，对比例1与实施例5的实验条件均相同。对比对比例1与实施例5的结果可知，由于镁粉的破碎过程及混合过程没有隔绝氧气，对比例1最终得到的产品中的氧含量及杂质总量相对于实施例5都有一定程度的升高。
实施例6
取以下组分，200目硅粉，氮化硅(平均粒径2μm)，氯化铵为，将上述三种组分与酒精混合后，以氮化硅球为介质，在滚动球磨机上球磨1h，随后在80℃下真空干燥，得到混合物。将干燥后的上述混合物与铝粉在V型混料机中混合均匀，得到燃烧合成原料(在所述燃烧合成原料中，200目硅粉为70wt％，氮化硅(平均粒径2μm)为20wt％，氯化铵为9.99wt％，铝粉为0.01wt％)，所述铝粉粒度200目，纯度>99wt％，混合过程采用惰性气体进行保护。随后将所述燃烧合成原料松装于反应料舟中，放置在燃烧合成设备内。抽真空后充入8MPa高纯氮气。使用钛粉为点火剂，诱发燃烧合成反应。燃烧反应结束后释放装置内气体，同时通循环水冷却至40℃以下时，打开腔门，取出反应产物。产物呈较为松软的块状，整体呈白色，表面有少量未反应的残余硅粉。将产物清理、收集、称量、计算后可知，产品回收率为95％。对产物进行XRD检测，分析表明其中β相含量为100％，氮化硅中氧含量为0.8％，杂质总量低于1wt％。
实施例7
取以下组分，200目硅粉，氮化硅(平均粒径2μm)，氯化铵，将上述三种组分与酒精混合后，以氮化硅球为介质，在滚动球磨机上球磨1h，随后在80℃下真空干燥，得到混合物。将干燥后的上述混合物与铝粉在V型混料机中混合均匀，得到燃烧合成原料(在所述燃烧合成原料中，200目硅粉为20wt％，氮化硅(平均粒径2μm)为70wt％，氯化铵为9wt％，铝粉为1wt％)，所述铝粉粒度200目，纯度>99wt％，混合过程采用惰性气体进行保护。随后将所述燃烧合成原料松装于反应料舟中，放置在燃烧合成设备内。抽真空后充入8MPa高纯氮气。使用钛粉为点火剂，诱发燃烧合成反应。燃烧反应结束后释放装置内气体，同时通循环水冷却至40℃以下时，打开腔门，取出反应产物。产物呈较为松软的块状，整体呈白色，表面有少量未反应的残余硅粉。将产物清理、收集、称量、计算后可知，产品回收率为95％。对产物进行XRD检测，分析表明其中α相含量为95％，氮化硅中氧含量为0.5％，杂质总量低于1wt％。
实施例8
取以下组分，100目硅粉，氮化硅(平均粒径2μm)，氯化铵，将上述三种组分与酒精混合后，以氮化硅球为介质，在砂磨机上磨1h，随后在80℃下真空干燥，得到混合物。将干燥后的上述混合物与铝粉在V型混料机中混合均匀，得到燃烧合成原料(在所述燃烧合成原料中，100目硅粉为35wt％，氮化硅(平均粒径2μm)为35wt％，氯化铵为20wt％，铝粉为1wt％)，所述铝粉粒度200目，纯度>99wt％，混合过程采用惰性气体进行保护。随后将所述燃烧合成原料松装于反应料舟中，放置在燃烧合成设备内。抽真空后充入5MPa高纯氮气。使用钛粉为点火剂，诱发燃烧合成反应。燃烧反应结束后释放装置内气体，同时通循环水冷却至40℃以下时，打开腔门，取出反应产物。产物呈较为松软的块状，整体呈白色，表面有少量未反应的残余硅粉。将产物清理、收集、称量、计算后可知，产品回收率为95％。对产物进行XRD检测，检测结果如图6所示，分析表明其中α相含量为95％，氮化硅中氧含量为0.3％，杂质总量低于1wt％。
实施例9
取以下组分，200目硅粉，氮化硅(平均粒径2μm)，氯化铵，将上述三种组分与酒精混合后，以氮化硅球为介质，在滚动球磨机上球磨1h，随后在80℃下真空干燥，得到混合物。将干燥后的上述混合物与钇粉在V型混料机中混合均匀，得到燃烧合成原料(在所述燃烧合成原料中，200目硅粉为70wt％，氮化硅(平均粒径2μm)为20wt％，氯化铵为9.99wt％，钇粉为0.01wt％)，所述钇粉粒度200目，纯度>99wt％，混合过程采用惰性气体进行保护。随后将所述燃烧合成原料松装于反应料舟中，放置在燃烧合成设备内。抽真空后充入 8MPa高纯氮气。使用钛粉为点火剂，诱发燃烧合成反应。燃烧反应结束后释放装置内气体，同时通循环水冷却至40℃以下时，打开腔门，取出反应产物。产物呈较为松软的块状，整体呈白色，表面有少量未反应的残余硅粉。将产物清理、收集、称量、计算后可知，产品回收率为95％。对产物进行XRD检测，分析表明其中β相含量为100％，氮化硅中氧含量为0.8％，杂质总量低于1wt％。
实施例10
取以下组分，200目硅粉，氮化硅(平均粒径2μm)，氯化铵，将上述三种组分与酒精混合后，以氮化硅球为介质，在滚动球磨机上球磨1h，随后在80℃下真空干燥，得到混合物。将干燥后的上述混合物与钇粉在V型混料机中混合均匀，得到燃烧合成原料(在所述燃烧合成原料中，200目硅粉为20wt％，氮化硅(平均粒径2μm)为70wt％，氯化铵为9wt％，钇粉为1wt％)，所述钇粉粒度200目，纯度>99wt％，混合过程采用惰性气体进行保护。随后将所述燃烧合成原料松装于反应料舟中，放置在燃烧合成设备内。抽真空后充入8MPa高纯氮气。使用钛粉为点火剂，诱发燃烧合成反应。燃烧反应结束后释放装置内气体，同时通循环水冷却至40℃以下时，打开腔门，取出反应产物。产物呈较为松软的块状，整体呈白色，表面有少量未反应的残余硅粉。将产物清理、收集、称量、计算后可知，产品回收率为95％。对产物进行XRD检测，分析表明其中α相含量为95％，氮化硅中氧含量为0.5％，杂质总量低于1wt％。
实施例11
取以下组分，100目硅粉，氮化硅(平均粒径2μm)，氯化铵，将上述三种组分与酒精混合后，以氮化硅球为介质，在砂磨机上磨1h，随后在80℃下真空干燥，得到混合物。将干燥后的上述混合物与钇粉在V型混料机中混合均匀，得到燃烧合成原料(在所述燃烧合成原料中，100目硅粉为35wt％，氮化硅(平均粒径2μm)为35wt％，氯化铵为20wt％，钇粉为10wt％)，所述钇粉粒度200目，纯度>99wt％，混合过程采用惰性气体进行保护。随后将所述燃烧合成原料松装于反应料舟中，放置在燃烧合成设备内。抽真空后充入5MPa高纯氮气。使用钛粉为点火剂，诱发燃烧合成反应。燃烧反应结束后释放装置内气体，同时通循环水冷却至40℃以下时，打开腔门，取出反应产物。产物呈较为松软的块状，整体呈白色，表面有少量未反应的残余硅粉。将产物清理、收集、称量、计算后可知，产品回收率为95％。对产物进行XRD检测，检测结果如图7所示，分析表明其中α相含量为95％，氮化硅中氧含量为0.3％，杂质总量低于1wt％。
实施例12
取以下组分，200目硅粉，氮化硅(平均粒径2μm)为，氯化铵，将上述三种组分与酒精混合后，以氮化硅球为介质，在滚动球磨机上球磨1h，随后在80℃下真空干燥，得到混合物。将干燥后的上述混合物与0.01％铁粉在V型混料机中混合均匀，得到燃烧合成原料(在所述燃烧合成原料中，200目硅粉为70wt％，氮化硅(平均粒径2μm)为20wt％，氯化铵为9.99wt％，铁粉为0.01wt％)，所述铁粉粒度200目，纯度>99wt％，混合过程采用惰性气体进行保护。随后将所述燃烧合成原料松装于反应料舟中，放置在燃烧合成设备内。抽真空后充入8MPa高纯氮气。使用钛粉为点火剂，诱发燃烧合成反应。燃烧反应结束后释放装置内气体，同时通循环水冷却至40℃以下时，打开腔门，取出反应产物。产物呈较为松软的块状，整体呈白色，表面有少量未反应的残余硅粉。将产物清理、收集、称量、计算后可知，产品回收率为95％。对产物进行XRD检测，分析表明其中β相含量为100％，氮化硅中氧含量为0.8％，杂质总量低于1wt％。
实施例13
取以下组分，200目硅粉，氮化硅(平均粒径2μm)，氯化铵，将上述三种组分与酒精混合后，以氮化硅球为介质，在滚动球磨机上球磨1h，随后在80℃下真空干燥，得到混合物。将干燥后的上述混合物与镱粉在V型混料机中混合均匀，得到燃烧合成原料(在所述燃烧合成原料中，200目硅粉为70wt％，氮化硅(平均粒径2μm)为20wt％，氯化铵为9.99wt％，镱粉为0.01wt％)，所述镱粉粒度200目，纯度>99wt％，混合过程采用惰性气体进行保护。随后将所述燃烧合成原料松装于反应料舟中，放置在燃烧合成设备内。抽真空后充入8MPa高纯氮气。使用钛粉为点火剂，诱发燃烧合成反应。燃烧反应结束后释放装置内气体，同时通循环水冷却至40℃以下时，打开腔门，取出反应产物。产物呈较为松软的块状，整体呈白色，表面有少量未反应的残余硅粉。将产物清理、收集、称量、计算后可知，产品回收率为95％。对产物进行XRD检测，分析表明其中β相含量为100％，氮化硅中氧含量为0.8％，杂质总量低于1wt％。
实施例14
分别称取90wt％实施例2的产物氮化硅粉，5wt％MgO，5wt％Y 2O 3，将三种原料与酒精混合，以氮化硅球为介质，在行星磨上球磨2h，随后在80℃下真空干燥。将干燥后的粉体过60目筛，并将过筛后的粉体干压成型，成型压力20MPa，随后将干压成型的素坯在220MPa压力下进行冷等静压。成型后的素坯在1900℃，1MPa氮气压力的条件下气压烧结8h，烧结后随炉降温。将烧结后的样品进行热导率及三点抗弯强度的测试，热导率为100W/mK，抗弯强度800MPa。
对比例2
按照实施例2的重量比称取以下组分，200目硅粉，氮化硅(平均粒径2μm)，氯化铵，将上述三种组分与酒精混合后，以氮化硅球为介质，在滚动球磨机上球磨1h，随后在80℃下真空干燥，得到混合物(在所述混合物中，200目硅粉为20重量份，氮化硅(平均粒径2μm)为70重量份，氯化铵为9重量份)。随后将上述混合物松装于反应料舟中，放置在燃烧合成设备内。抽真空后充入8MPa高纯氮气。使用钛粉为点火剂，诱发燃烧合成反应。燃烧反应结束后释放装置内气体，同时通循环水冷却至40℃以下时，打开腔门，取出反应产物氮化硅粉。
分别称取90wt％上述反应产物氮化硅粉，5wt％MgO，5wt％Y 2O 3，将上述三种原料与酒精混合，以氮化硅球为介质，在行星磨上球磨2h，随后在80℃下真空干燥。将干燥后的粉体过60目筛，并将过筛后的粉体干压成型，成型压力20MPa，随后将干压成型的素坯在220MPa压力下进行冷等静压。成型后的素坯在1900℃，1MPa氮气压力的条件下气压烧结8h，烧结后随炉降温。将烧结后的样品进行热导率及三点抗弯强度的测试，热导率为85W/mK，抗弯强度650MPa。
将实施例14的结果与对比例2的结果进行对比，实施例14与对比例2的试验条件相同，唯一区别是实施例14在燃烧合成氮化硅粉的过程中加入了1％的镁粉，而对比例2没有加入任何还原性的金属粉末。从试验结果来看，最终烧结产品的热导率由对比例2的85W/mK提高到实施例14的100W/mK，抗弯强度由对比例2的650MPa提高到实施例14的800MPa。可见，在燃烧合成制备氮化硅粉末的过程中加入还原性金属粉末，能够大幅度提高氮化硅粉末的烧结性能，能够获得性能优异的基于该氮化硅粉末的烧结产品。
实施例15
取以下组分，200目硅粉，氮化硅(平均粒径2μm)，氯化铵，将上述三种组分与酒精混合后，以氮化硅球为介质，在滚动球磨机上球磨1h，随后在80℃下真空干燥，得到混合物。将干燥后的原料与镁粉在V型混料机中混合均匀，得到燃烧合成原料(在所述燃烧合成原料中，200目硅粉为20wt％，氮化硅(平均粒径2μm)为70wt％，氯化铵为9wt％，镁粉为1wt％)，所述镁粉粒度40目，杂质含量(Fe、Al、Ca等金属杂质)>1wt％，O含量＝8wt％，混合过程采用惰性气体进行保护。随后将所述燃烧合成原料松装于反应料舟中，放置在燃烧合成设备内。抽真空后充入8MPa高纯氮气。使用钛粉为点火剂，诱发燃烧合成反应。燃烧反应结束后释放装置内气体，同时通循环水冷却至40℃以下时，打开腔门，取出反应产物。产物呈较为松软的块状，整体呈白色，表面有少量未反应的残余硅粉。将产物清理、 收集、称量、计算后可知，产品回收率为90％。其中α相含量为50％，氮化硅中氧含量为1％，杂质总量1wt％。
从产物的SEM图(图8)可见，氮化硅粉末产生严重团聚，大部分颗粒尺寸在1-5μm之间，团聚尺寸达到10μm。
分别称取90wt％上述反应产物氮化硅粉，5wt％MgO，5wt％Y 2O 3，将上述三种原料与酒精混合，以氮化硅球为介质，在行星磨上球磨2h，随后在80℃下真空干燥。将干燥后的粉体过60目筛，并将过筛后的粉体干压成型，成型压力20MPa，随后将干压成型的素坯在220MPa压力下进行冷等静压。成型后的素坯在1900℃，1MPa氮气压力的条件下气压烧结8h，烧结后随炉降温。将烧结后的样品进行热导率及三点抗弯强度的测试，热导率为50W/mK，抗弯强度500MPa。
对比实施例2、14、15的结果可知，采用粒度较大、纯度较低(纯度的影响比粒度更明显)的镁粉，氮化硅粉末的性能以及基于该氮化硅粉末的烧结产物的性能都受到了一定程度的影响。
实施例16
取以下组分，200目硅粉，氮化硅(平均粒径2μm)，氯化铵，将上述三种组分与酒精混合后，以氮化硅球为介质，在滚动球磨机上球磨1h，随后在80℃下真空干燥，得到混合物。将干燥后的所述混合物与镁粉在V型混料机中混合均匀，得到燃烧合成原料(在所述燃烧合成原料中，200目硅粉为20wt％，氮化硅(平均粒径2μm)为70wt％，氯化铵为9wt％，镁粉为1wt％)，所述镁粉粒度300目，杂质含量(Fe、Al、Ca等金属杂质)>1wt％，O含量＝20wt％，混合过程采用惰性气体进行保护。随后将所述燃烧合成原料松装于反应料舟中，放置在燃烧合成设备内。抽真空后充入8MPa高纯氮气。使用钛粉为点火剂，诱发燃烧合成反应。燃烧反应结束后释放装置内气体，同时通循环水冷却至40℃以下时，打开腔门，取出反应产物。产物呈较为松软的块状，整体呈白色，表面有少量未反应的残余硅粉。将产物清理、收集、称量、计算后可知，产品回收率为50％。分析表明其中α相含量为0％，氮化硅中氧含量为2％，杂质总量2％。
从产物的SEM图(图9)可见，氮化硅粉末产生严重团聚，大部分颗粒尺寸在5μm以上，团聚尺寸达到10μm。
分别称取90wt％上述反应产物氮化硅粉，5wt％MgO，5wt％Y 2O 3，将上述三种原料与酒精混合，以氮化硅球为介质，在行星磨上球磨2h，随后在80℃下真空干燥。将干燥后的粉体过60目筛，并将过筛后的粉体干压成型，成型压力20MPa，随后将干压成型的素坯在 220MPa压力下进行冷等静压。成型后的素坯在1900℃，1MPa氮气压力的条件下气压烧结8h，烧结后随炉降温。将烧结后的样品进行热导率及三点抗弯强度的测试，热导率为20W/mK，抗弯强度500MPa。
对比实施例2、14、16的结果可知，采用粒度过小、纯度较低(纯度的影响比粒度更明显)的镁粉，氮化硅粉末的性能以及基于该氮化硅粉末的烧结产物的性能都受到了一定程度的影响。

Claims (10)

  1. 一种通过金属还原制备氮化硅粉末的方法，其特征在于，所述方法包含以下步骤：
    (1)准备以下组分：
    硅粉；
    氮化硅稀释剂；
    氯化铵添加剂；
    (2)将上述各组分混合均匀，得到混合物；
    (3)向所述混合物中加入还原性金属粉末，然后将所述金属粉末与所述混合物混合均匀，并将混合后的混合物在V型混料机中混合均匀和/或过筛，得到燃烧合成原料；在所述燃烧合成原料中，所述硅粉占20-70wt％，所述氮化硅稀释剂占70-20wt％，所述氯化铵添加剂0-20wt％；
    (4)将步骤(3)得到的所述燃烧合成原料进行燃烧合成，得到氮化硅粉末。
  2. 根据权利要求1所述的方法，其特征在于，步骤(1)中所述硅粉原料的纯度>99wt％；
    优选的，步骤(1)中所述硅粉的粒度范围是100-200目；
    优选的，步骤(3)中加入的所述金属粉末占所有组分的重量百分比为0.01-10％；
    优选的，所述步骤(4)包括：将步骤(3)所得混合物松装布料于反应料舟，然后将所述料舟放置在燃烧合成反应装置内，抽真空后，充入高纯氮气，所述燃烧合成反应装置内压力保持在1-8MPa，以通电钨丝圈点燃引燃剂，诱发燃烧合成反应；反应结束后，所述燃烧合成反应装置内压力开始下降，此时释放装置内的气体，同时通循环水进行冷却；最终得到松软、易破碎的块状产物，研磨之后即得到氮化硅粗粉；优选的，所述高纯氮气的纯度在97％以上，或者所述高纯氮气的纯度在99.9％以上；
    优选的，所述方法还包括在步骤(4)之后的步骤(5)：对步骤(4)得到的所述氮化硅粉末进行酸洗提纯，得到氮化硅粉末；
    优选的，步骤(1)中所述稀释剂为高纯氮化硅粉末，平均粒径在0.5-10μm，所述高纯氮化硅粉末的α相含量>60wt％；
    优选的，步骤(1)中所述氯化铵添加剂平均粒径在0.1-50μm，纯度>99wt％；
    优选的，步骤(2)所述的混合方式包括砂磨、球磨、搅拌磨、V型混合机混磨和/或滚筒磨；
    优选的，步骤(3)中所述过筛包括采用具有40-100目筛孔的筛网过筛；进一步优选的，步骤(3)中所述过筛包括采用具有60目筛孔的筛网过筛。
  3. 根据权利要求1所述的方法，其特征在于，步骤(3)所述的金属粉末包括镁、钙、铁、镍、锌、铝、锂、钠、钾、钇、镱中的至少一种。
  4. 根据权利要求1所述的方法，其特征在于，步骤(3)所述的金属粉末粒度为20-1000目，氧含量<5wt％，纯度>99wt％，所述纯度中氧含量不算杂质。
  5. 根据权利要求1所述的方法，其特征在于，步骤(3)所述的混合方式包括砂磨、球磨、搅拌磨、V型混合机混磨和/或滚筒磨；
    优选的，对于在空气中易发生氧化的金属粉末，混合过程应在惰性气体的气氛中进行；
    优选的，所述空气中易发生氧化的金属粉末包括钙、锂、钠、钾、钇和镱。
  6. 根据权利要求1所述的方法，其特征在于，步骤(3)所述的过筛，采用目数为20-1000目的筛网进行。
  7. 根据权利要求2所述的方法，其特征在于，所述步骤(5)包括：以20-500目的筛网对步骤(4)得到的氮化硅粉末进行粗筛，并以硝酸、盐酸、硫酸的混合酸进行酸洗，以除去所述氮化硅粉末中的金属氧化物；
    优选的，所述混合酸中所述硝酸、所述盐酸、所述硫酸的体积含量比例分别为10％-20％、60％-80％、10％-20％，质量分数分别小于68％、小于20％、小于70％，酸洗1-10小时，将酸洗后的粉末水洗1-5次，除去水溶性物质，抽滤后采用压滤干燥、喷雾干燥或真空干燥的方法进行干燥。
  8. 根据权利要求1-7任一项所述的方法制备得到的氮化硅粉末，其特征在于，所述氮化硅粉末平均粒度1-50μm，金属氧化物含量0-10wt％，杂质含量低于1wt％；
    优选的，所述氮化硅粉末中金属氧化物含量小于1wt％，烧结后的烧结体热导率90W/mK以上，抗弯强度700MPa以上；
    优选的，所述烧结体的烧结条件为：将所述氮化硅粉末与MgO、Y 2O 3混合、研磨、干压成型素坯，将所述素坯在1900℃，1MPa氮气压力的条件下气压烧结8h。
  9. 一种烧结体，其特征在于，所述烧结体采用权利要求1-7任一项所述的方法制备得到的氮化硅粉末烧结而成，所述氮化硅粉末平均粒度1-50μm，金属氧化物含量0-10wt％，杂质含量低于1wt％。
  10. 如权利要求9所述烧结体的制造方法，其特征在于，所述方法包括：
    (1)以按照以下重量百分比准备原料：
    硅粉：20-70wt％；
    氮化硅稀释剂：70％-20wt％；
    氯化铵添加剂：0-20wt％；
    (2)将上述各原料混合均匀；
    (3)向所述原料中加入还原性金属粉末，然后将所述金属粉末与所述原料混合均匀，并将混合后的混合物过筛；
    (4)将步骤(3)所得混合物进行燃烧合成，得到氮化硅粉末；
    (5)对步骤(4)得到的所述氮化硅粉末进行酸洗提纯，得到氮化硅粉末；
    (6)将所述氮化硅粉末与MgO、Y 2O 3混合、研磨、干压成型素坯，将所述素坯在1900℃，1MPa氮气压力的条件下气压烧结8h；
    优选的，上述步骤(6)包括：分别称取90wt％实施例2的产物氮化硅粉，5wt％MgO，5wt％Y 2O 3，将三种原料与酒精混合，以氮化硅球为介质，在行星磨上球磨2h，随后在80℃下真空干燥；将干燥后的粉体过60目筛，并将过筛后的粉体干压成型，成型压力20MPa，随后将干压成型的素坯在220MPa压力下进行冷等静压；成型后的素坯在1900℃，1MPa氮气压力的条件下气压烧结8h，烧结后随炉降温；将烧结后的样品进行热导率及三点抗弯强度的测试，热导率为100W/mK，抗弯强度800MPa。
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