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WO2024195299A1 - Méthode de production de poudre de nitrure de silicium, et méthode de production de corps fritté de nitrure de silicium - Google Patents

Méthode de production de poudre de nitrure de silicium, et méthode de production de corps fritté de nitrure de silicium Download PDF

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WO2024195299A1
WO2024195299A1 PCT/JP2024/002693 JP2024002693W WO2024195299A1 WO 2024195299 A1 WO2024195299 A1 WO 2024195299A1 JP 2024002693 W JP2024002693 W JP 2024002693W WO 2024195299 A1 WO2024195299 A1 WO 2024195299A1
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silicon nitride
powder
nitride powder
producing
raw material
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Japanese (ja)
Inventor
厚樹 五十嵐
一輝 鎌田
賢史 平田
竜之介 長與
聖治 小橋
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Denka Co Ltd
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Denka Co Ltd
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Priority to CN202480017878.8A priority Critical patent/CN120835865A/zh
Priority to JP2025508175A priority patent/JPWO2024195299A1/ja
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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
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
    • C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
    • C04B35/584—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicon nitride
    • C04B35/587—Fine ceramics

Definitions

  • This disclosure relates to a method for producing silicon nitride powder and a method for producing sintered silicon nitride.
  • Silicon nitride sintered compacts are a material with excellent strength, hardness, toughness, heat resistance, corrosion resistance, and thermal shock resistance, and are therefore used in various industrial parts such as die-casting machines and melting furnaces, as well as insulating substrates for automotive parts. Silicon nitride powder, the raw material for silicon nitride sintered compacts, has a high alpha conversion rate in order to obtain high-quality sintered compacts.
  • Patent Document 1 attempts to manufacture silicon nitride powder with a high alpha conversion rate using a continuous fluidized bed reactor in order to improve productivity.
  • Patent Document 1 proposes using, as the raw material, metal silicon powder with a metal impurity content within a specified range that has been granulated and molded to 100 ⁇ m to 10 mm.
  • the present disclosure provides a method for producing silicon nitride powder that is capable of efficiently producing silicon nitride powder with excellent sinterability and sufficiently reduced variation in quality. It also provides a method for efficiently producing silicon nitride sintered bodies with sufficiently reduced variation in quality.
  • One aspect of the present disclosure provides the following silicon nitride powder:
  • a method for producing silicon nitride powder comprising the step of sintering a raw material powder containing metal silicon powder in a continuous furnace in an atmosphere containing nitrogen gas to obtain a sintered product containing silicon nitride components, wherein the metal silicon powder has a particle diameter D10 of 4 to 10 ⁇ m when the cumulative value from small particle diameters reaches 10% of the total in the cumulative distribution of volumetric particle diameters measured by a laser diffraction/scattering method.
  • the method for producing silicon nitride powder described above in [1] uses a raw material powder containing metal silicon powder with a particle diameter D10 of 4 to 10 ⁇ m.
  • This metal silicon powder has a sufficiently small ratio of small metal silicon powder with a particle diameter of less than 4 ⁇ m, so excessive heat generation during the nitriding reaction can be suppressed. Therefore, even if the heating rate is increased, excessive heat generation can be suppressed and the nitriding reaction can proceed with high uniformity.
  • This can suppress the metal silicon powder from melting and becoming lumpy, and the silicon nitride component contained in the sintered product from becoming ⁇ -converted. Therefore, silicon nitride powder with a sufficiently high ⁇ -conversion rate and a uniformity can be produced.
  • the raw material powder is sintered using a continuous furnace. These factors make it possible to efficiently produce silicon nitride powder with excellent sinterability and sufficiently reduced quality variation. If such silicon nitride powder is used as a sintering raw material, for example, it is possible to efficiently produce silicon nitride sintered bodies with sufficiently reduced quality variation.
  • the use of the silicon nitride powder obtained by the above production method is not limited to the production of silicon nitride sintered bodies.
  • the manufacturing method of the above [1] may be any of the following [2] to [8].
  • the atmosphere contains hydrogen gas
  • the method for producing a silicon nitride powder according to [1] wherein in the atmosphere, the ratio of the nitrogen gas is 95.1 vol% or more and the ratio of the hydrogen gas is 2.0 vol% or more.
  • [5] The method for producing a silicon nitride powder according to any one of [1] to [4], wherein the ratio of the particle diameter D90 to the particle diameter D10 is 10 or less.
  • [6] The method for producing a silicon nitride powder according to any one of [1] to [5], wherein in the cumulative distribution, a particle diameter D50 when an integrated value from small particle diameters reaches 50% of the total is 15 to 30 ⁇ m.
  • [7] The method for producing a silicon nitride powder according to any one of [1] to [6], wherein the ratio of the particle diameter D10 to the particle diameter D50 is 0.20 or more.
  • the manufacturing method [2] above can promote the nitriding reaction and produce silicon nitride powder more efficiently.
  • the silicon nitride powder obtained by the manufacturing method [3] above has better sinterability because the silicon nitride component has a sufficiently high alpha conversion rate.
  • the manufacturing methods [4], [5], or [6] above can produce silicon nitride powder with a sharper particle size distribution of metal silicon powder and higher uniformity.
  • the manufacturing method [7] above uses metal silicon powder with a sufficiently reduced amount of fine particles, so it can further suppress excessive heat generation during the nitriding reaction. Therefore, it can sufficiently suppress the silicon nitride component from becoming beta.
  • the manufacturing method [8] above uses metal silicon powder with an appropriate primary particle size, so it can suppress excessive heat generation and promote the nitriding reaction more efficiently.
  • the manufacturing method [9] or [10] above can produce silicon nitride powder more efficiently.
  • One aspect of the present disclosure provides the following method for producing a silicon nitride sintered body.
  • a method for producing a silicon nitride sintered body comprising the step of sintering a sintering raw material containing silicon nitride powder obtained by any one of the methods described in [1] to [10] above to obtain a silicon nitride sintered body.
  • the manufacturing method [11] above uses a sintering raw material containing silicon nitride powder obtained by any one of the manufacturing methods described in [1] to [10] above.
  • This silicon nitride powder has a sufficiently high and uniform alpha conversion rate.
  • the manufacturing method of the above [11] may be the following [12].
  • [12] The method for producing a silicon nitride sintered body according to [11], wherein the silicon nitride sintered body has a Weibull coefficient of 9 or more.
  • the silicon nitride sintered body obtained by the manufacturing method [12] above has less variation in bending strength, and the variation in quality can be sufficiently reduced.
  • the present disclosure can provide a method for producing silicon nitride powder that can efficiently produce silicon nitride powder with excellent sinterability and sufficiently reduced variation in quality. It can also provide a method for producing silicon nitride sintered bodies that can efficiently produce silicon nitride sintered bodies with sufficiently reduced variation in quality.
  • FIG. 2 is a perspective view showing an example of a container having a container portion for containing raw material powder.
  • FIG. 2 is a vertical cross-sectional view showing the container of FIG. 1 and the raw material powder filled therein.
  • the numerical range exemplified in the format of "a-b" is a numerical range inclusive of a and b, with a lower limit of a and an upper limit of b.
  • Each embodiment also includes those in which the upper or lower limit of each numerical range is replaced with the numerical value of any of the examples.
  • Each embodiment includes both cases in which there is one material (element) exemplified in parallel, and cases in which multiple materials (elements) are combined.
  • the method for producing silicon nitride powder includes a heating step in which a raw material powder containing metal silicon powder is sintered in a continuous furnace in an atmosphere containing nitrogen gas to obtain a sintered product containing silicon nitride components.
  • Metal silicon powder may be obtained by pulverizing metal silicon particles or metal silicon lumps. Examples of pulverizing devices for pulverizing metal silicon particles or metal silicon lumps include a hammer mill, a pin mill, a ball mill, a vibration mill, a bead mill, and a jet mill.
  • the metal silicon powder has a particle diameter D10 of 4 to 10 ⁇ m when the cumulative value from the small particle diameter reaches 10% of the total in the cumulative distribution of volumetric particle diameters measured by a laser diffraction/scattering method.
  • the particle diameter D10 may be 5 ⁇ m or more, or 6 ⁇ m or more. This can sufficiently suppress excessive exothermic reactions during the heating process. As a result, it is possible to further suppress the metal silicon powder from melting and becoming lumpy, and the silicon nitride component from becoming beta.
  • the particle diameter D10 may be 9 ⁇ m or less, or 8 ⁇ m or less. This can sufficiently promote the nitriding reaction. As a result, it is possible to obtain silicon nitride powder with an even higher rate of alpha conversion.
  • the particle diameter D90 when the cumulative value from the small particle diameter reaches 90% of the total may be 35 to 75 ⁇ m.
  • the particle diameter D90 may be 70 ⁇ m or less, 60 ⁇ m or less, or 55 ⁇ m or less. This sufficiently promotes the overall nitriding reaction, and the average nitriding rate can be sufficiently increased. As a result, a silicon nitride powder with a higher alpha conversion rate can be obtained.
  • the particle diameter D90 may be 35 ⁇ m or more, or 40 ⁇ m or more. Such silicon powder is easy to prepare, and can improve the production efficiency of silicon nitride.
  • the particle diameter D50 (median diameter) when the cumulative value from the small particle diameter reaches 50% of the total may be 15 to 30 ⁇ m.
  • the particle diameter D50 may be 28 ⁇ m or less, or 25 ⁇ m or less. This allows the average nitriding rate to be sufficiently fast.
  • the particle diameter D50 may be 18 ⁇ m or more, or 20 ⁇ m or more.
  • Such silicon powder is easy to prepare, and can improve the production efficiency of silicon nitride.
  • the particle size distribution in this specification is determined based on the method described in JIS Z 8825:2013 "Particle size analysis - Laser diffraction and scattering method.”
  • the particle size distribution (cumulative distribution) is shown based on the above method, with the horizontal axis representing particle size [ ⁇ m] in logarithmic scale and the vertical axis representing frequency [volume %].
  • the measuring device described in the examples can be used.
  • the ratio of particle diameter D90 to particle diameter D10 may be 10 or less, 9.0 or less, 8.0 or less, or 7.0 or less.
  • Such metal silicon powder has a sharp particle size distribution, so that the variability of the nitridation reaction can be sufficiently reduced. Therefore, it is possible to obtain silicon nitride powder with sufficiently high uniformity in terms of the alpha conversion rate and purity of silicon nitride.
  • the ratio of particle diameter D10 to particle diameter D50 may be 0.20 or more, or 0.25 or more. Since such metal silicon powder has a sufficiently reduced amount of fine particles, it is possible to sufficiently suppress excessive heat generation during nitridation. Therefore, it is possible to sufficiently suppress the silicon nitride component from becoming beta-phase.
  • the ratio of particle diameter D90 to particle diameter D50 may be 4.0 or less, 3.5 or less, 3.0 or less, or 2.5 or less.
  • Such metal silicon powder has a sharp particle size distribution, so that the variability of the nitridation reaction can be sufficiently reduced. Therefore, it is possible to obtain silicon nitride powder with sufficiently high uniformity in terms of the alpha conversion rate and purity of silicon nitride.
  • the particle sizes D10, D50, D90 and their ratios of the metal silicon powder can be adjusted by changing the operating conditions of the grinding device and the grinding time.
  • the particle sizes D10, D50, D90 and their ratios can also be adjusted by sieving the metal silicon powder after grinding.
  • the BET specific surface area of the metal silicon powder may be 0.40 m 2 /g or more, 0.45 m 2 /g or more, or 0.50 m 2 /g or more. This promotes the nitriding reaction and allows the average nitriding rate to be sufficiently high.
  • the BET specific surface area of the metal silicon powder may be less than 1.00 m 2 /g, less than 0.90 m 2 /g, less than 0.80 m 2 /g, or less than 0.70 m 2 /g. This suppresses excessive exothermic reaction and allows the silicon nitride component to be sufficiently suppressed from being converted into ⁇ -form.
  • the BET specific surface area of the metal silicon powder can be adjusted by changing the pulverization time and pulverization conditions by the pulverization device. The BET specific surface area may be adjusted by sieving the pulverized metal silicon powder.
  • the BET specific surface area of metal silicon powder is a value measured by the BET single point method using nitrogen gas in accordance with the method described in JIS Z 8830:2013 "Method for measuring the specific surface area of powders (solids) by gas adsorption.”
  • the purity of the metal silicon powder may be 98% by mass or more, or 99% by mass or more.
  • the metal silicon powder may also contain impurities that are mixed in during pulverization using a pulverizer.
  • the metal silicon powder may be used as it is as the raw material powder, or the raw material powder may be prepared by blending the metal silicon powder, fluorite, and other metal powders or metal compound powders.
  • the content of the metal silicon powder relative to 100 parts by mass of the raw material powder may be 92 parts by mass or more, 95 parts by mass or more, or 97 parts by mass or more.
  • the content of the fluorite relative to 100 parts by mass of the metal silicon powder may be 0.2 to 3.0 parts by mass. From the viewpoint of sufficiently promoting the nitridation of the metal silicon, the content of the fluorite relative to 100 parts by mass of the metal silicon powder may be 0.5 parts by mass or more, or 0.8 parts by mass or more. From the viewpoint of reducing the Ca and F contents in the obtained silicon nitride powder, the content of the fluorite relative to 100 parts by mass of the metal silicon powder may be 2.0 parts by mass or less, or 1.5 parts by mass or less.
  • the raw powder may contain, as the metal compound powder, a metal compound powder (metal oxide powder) having at least one constituent element selected from the group consisting of chromium and nickel.
  • the total amount of the metal compound powder (metal oxide powder) in the raw powder may be 0.005 to 0.2 parts by mass, 0.01 to 0.1 parts by mass, or 0.02 to 0.07 parts by mass per 100 parts by mass of metallic silicon.
  • the raw material powder is sintered using a continuous furnace to obtain a sintered product containing silicon nitride components.
  • continuous furnaces include container-transporting furnaces, such as tunnel-type pusher furnaces and roller hearth kilns.
  • Such continuous furnaces may have a temperature gradient within the furnace. That is, they may have a heating zone in which the temperature gradually increases from the furnace entrance to the furnace exit.
  • the raw material powder (container) introduced into the heating zone of such a continuous furnace is gradually heated as it moves within the continuous furnace.
  • the container containing the raw material powder can be continuously heated within the furnace. Since the raw material powder can be sintered without being molded, the nitriding reaction proceeds efficiently.
  • the silicon nitride component contained in the sintered product has a high alpha conversion rate and the variation in the alpha conversion rate is sufficiently suppressed.
  • the container to be filled with the raw material powder can be made of a material that does not change in quality even at temperatures up to about 1500°C in an inert gas atmosphere.
  • the container can be made of, for example, carbon, alumina, or boron nitride.
  • There are no particular restrictions on the structure of the container and it can be one that has a storage section for storing the raw material powder.
  • the container can be one that has a container body with a recess in which the raw material powder is filled, and a lid that covers the recess in the main body.
  • multiple containers can be stacked, with the upper container used as the lid for the lower container.
  • FIG. 1 shows three containers 10 each having a storage section 20 for storing raw material powder stacked on top of each other.
  • Raw material powder is not shown in the storage section 20 in FIG. 1.
  • the storage section 20 of each container 10 is filled with raw material powder 22 as shown in FIG. 2.
  • the containers 10 are then stacked as shown in FIGS. 1 and 2 and introduced into the continuous furnace.
  • silicon nitride calcined bodies can be produced with high production efficiency.
  • the lower and middle containers 10 are provided with vents 12. This allows sufficient contact between the metallic silicon contained in the raw material powder 22 and the nitrogen gas contained in the atmosphere.
  • the filling height H of the raw material powder 22 in each of the containers 10 may be 40 mm or less, 35 mm or less, or 30 mm or less. By lowering the filling height H in this way, the nitriding reaction proceeds smoothly. Therefore, it is possible to obtain a sintered product containing a silicon nitride component that has a high alpha conversion rate and in which the variation in the alpha conversion rate is sufficiently reduced. From the viewpoint of improving production efficiency, the filling height H may be 5 mm or more, 10 mm or more, or 15 mm or more. If the surface of the raw material powder 22 filled in the container 10 is uneven, the maximum value of the filling height of the raw material powder 22 is taken as the filling height H.
  • the shape of the container and the filling form of the raw material powder are not limited to those shown in Figures 1 and 2.
  • the maximum temperature when firing the raw material powder contained in the container is 1300 to 1500°C.
  • the temperature is increased to this temperature at a rate of 10 to 150°C/hour.
  • the temperature may be increased from 30°C to 1100°C at a rate of 50 to 150°C/hour, and then increased from 1100°C to the maximum temperature at a rate of 10 to 40°C/hour. This allows the exothermic reaction caused by the nitriding of the raw material powder to be appropriately controlled.
  • the atmosphere (sintering atmosphere) in the continuous furnace may contain nitrogen gas and hydrogen gas.
  • the ratio of nitrogen gas in the sintering atmosphere is 95.1 vol% or more, and may be 96.0 vol% or more.
  • the ratio of hydrogen gas in the sintering atmosphere may be 2.0 vol% or more, 3.0 vol% or more, or 4.0 vol% or more.
  • An example of the ratio of nitrogen gas in the sintering atmosphere is 95.1 to 98.0 vol%.
  • An example of the ratio of hydrogen gas in the sintering atmosphere is 2.0 to 4.9 vol%.
  • the sintering atmosphere may contain gases other than nitrogen gas and hydrogen gas. Examples of such gases include argon gas.
  • the ratio (vol%) of each gas in this specification is a value in standard state (0 ° C, 1 atm).
  • the time T during which the raw powder is heated to 1100°C or higher in the continuous furnace may be 24 hours or less, 22 hours or less, 20 hours or less, or 18 hours or less. Even if the heating time at high temperature is shortened in this way, nitridation can proceed smoothly and silicon nitride powder with sufficiently high purity can be obtained.
  • the time T may be 10 hours or more, or 12 hours or more.
  • the average nitriding rate in the heating step may be 3 mass%/hour or more, 4 mass%/hour or more, or 5 mass%/hour or more. This allows silicon nitride powder to be produced with sufficiently high productivity. There is no particular upper limit to the average nitriding rate in the heating step, and it may be, for example, 10 mass%/hour or less, or 8 mass%/hour or less.
  • the average nitriding rate can be obtained by dividing the mass fraction of silicon nitride in the fired product by the time T.
  • the fired product obtained by the above firing contains silicon nitride (silicon nitride component) as the main component.
  • silicon nitride powder By pulverizing this fired product, silicon nitride powder can be obtained.
  • the pulverization can be performed, for example, using a coarse grinding device, a wet attritor, a ball mill, a vibrating mill, etc. Since the silicon nitride component contained as the main component in the fired product has a high alpha conversion rate, the fired product can be pulverized smoothly. In addition, since the alpha conversion rate of the silicon nitride component contained as the main component in the fired product varies little, silicon nitride powder with sufficiently high particle size uniformity can be obtained.
  • a treatment step may be carried out as necessary.
  • the pulverized sintered material may be mixed with hydrofluoric acid having a hydrogen fluoride concentration of 10 to 40% by mass to reduce impurities.
  • the pulverized sintered material may be dispersed in hydrofluoric acid for treatment.
  • the hydrogen fluoride concentration in the hydrofluoric acid may be 15 to 30% by mass.
  • the temperature of the hydrofluoric acid in the treatment step is, for example, 40 to 80°C.
  • the time for immersing the silicon nitride powder in hydrofluoric acid is, for example, 1 to 10 hours. The treatment step does not have to be carried out.
  • the silicon nitride powder (Si 3 N 4 powder) thus obtained contains silicon nitride as a main component.
  • the content of the silicon nitride component in the silicon nitride powder may be 90% by mass or more, 95% by mass or more, 98% by mass or more, 99% by mass or more, or 99.5% by mass or more.
  • the content of the silicon nitride component in the silicon nitride powder can be measured using a commercially available X-ray diffraction device.
  • the alpha-phase ratio of the silicon nitride component (phase ratio of alpha-Si 3 N 4 to the whole Si 3 N 4 ) is 90.0% or more. Since such silicon nitride powder has excellent sinterability, when used as a sintering raw material, a silicon nitride sintered body having excellent mechanical properties and sufficiently reduced quality variation can be obtained. From the viewpoint of sufficiently increasing the Weibull coefficient of the silicon nitride sintered body, the alpha-phase ratio of the silicon nitride component may be 90.0% or more, 92.0% or more, 93.0% or more, or 94.0% or more.
  • the alpha-phase ratio of the silicon nitride component may be 98.0% or less, 97.0% or less, or 96.5% or less.
  • An example of the alpha-phase ratio of the silicon nitride component is 90.0 to 98.0%.
  • the alpha-phase ratio of the silicon nitride component can be determined by the method described in the examples.
  • the silicon nitride powder obtained by the above manufacturing method contains silicon nitride components with a high alpha conversion rate and small variation in the alpha conversion rate. If such silicon nitride powder is used as a sintering raw material, sintering proceeds with high uniformity, and a silicon nitride sintered body with sufficiently reduced quality variation can be obtained.
  • the use of silicon nitride powder is not limited to the production of silicon nitride sintered bodies, and it may be mixed with other types of powders (e.g., ceramic powders such as boron nitride) and used to manufacture composites.
  • Silicon nitride powder may contain components other than silicon nitride. For example, it may contain calcium compounds, halogen compounds, iron compounds, or other metal compounds. Iron compounds may be derived from metal silicon particles, the manufacturing process, etc. Such silicon nitride powder and silicon nitride sintered body can be produced using relatively low-cost raw materials and manufacturing processes, thereby reducing manufacturing costs.
  • the average particle size of the silicon nitride powder may be 0.5 to 2.0 ⁇ m. Such silicon nitride powder has sufficiently excellent sinterability and can sufficiently suppress abnormal grain growth during sintering.
  • the upper limit of the average particle size of the silicon nitride powder may be 1.8 ⁇ m or 1.6 ⁇ m. This can further suppress abnormal grain growth during sintering.
  • the lower limit of the average particle size of the silicon nitride powder may be 1.0 ⁇ m or 1.2 ⁇ m. This can shorten the pulverization time and improve the productivity of the silicon nitride powder.
  • the average particle size (D50) of the silicon nitride powder can be measured by the same procedure as the D50 of the metal silicon powder.
  • the average particle size of the silicon nitride powder can be adjusted by changing the particle size of the raw material powder, the sintering temperature and sintering time when producing the silicon nitride powder, and the conditions when pulverizing the sintered product
  • the BET specific surface area of the silicon nitride powder may be 5 to 15 m 2 /g. Such silicon nitride powder has sufficiently excellent sinterability and can sufficiently suppress abnormal grain growth.
  • the upper limit of the BET specific surface area of the silicon nitride powder may be 8 m 2 /g or 7 m 2 /g. This can further increase the sinterability.
  • the lower limit of the BET specific surface area of the silicon nitride powder may be 5 m 2 /g or 6 m 2 /g. This can further suppress abnormal grain growth during sintering.
  • the BET specific surface area of the silicon nitride powder can be measured by the same procedure as the BET specific surface area of the metal silicon powder.
  • the BET specific surface area of the silicon nitride powder can be adjusted by changing the particle size of the raw material powder, the sintering temperature and the sintering time when producing the silicon nitride powder.
  • the raw material powder is sintered using a continuous furnace. Therefore, silicon nitride powder with excellent sinterability and sufficiently reduced quality variation can be efficiently manufactured. If such silicon nitride powder is used as a sintering raw material, for example, a silicon nitride sintered body with sufficiently reduced quality variation can be efficiently manufactured.
  • the method for producing a silicon nitride sintered body includes a sintering step of molding and firing a sintering raw material containing the above-mentioned silicon nitride powder as a main component.
  • the sintering raw material may contain an oxide-based sintering aid in addition to the silicon nitride powder.
  • the oxide-based sintering aid include Y 2 O 3 , MgO, and Al 2 O 3.
  • the content of the oxide-based sintering aid in the sintering raw material may be, for example, 3 to 10 mass %.
  • the sintering raw material obtained by blending silicon nitride powder and an oxide-based sintering aid is pressed at a molding pressure of, for example, 3.0 to 200 MPa to obtain a molded body.
  • the molded body may be produced by uniaxial pressing or by CIP. It may also be fired while being molded by hot pressing.
  • the molded body may be fired in an inert gas atmosphere such as nitrogen gas or argon gas.
  • the pressure during firing may be 0.7 to 1 MPa.
  • the firing temperature may be 1700 to 2100°C or 1800 to 2000°C.
  • the firing time at the firing temperature may be 2 to 20 hours or 4 to 16 hours.
  • the heating rate to the firing temperature may be, for example, 1.0 to 10.0°C/hour. In this manner, a silicon nitride sintered body can be obtained.
  • the above-mentioned manufacturing method uses a sintering raw material containing silicon nitride powder with reduced quality variation, which makes it possible to increase the uniformity of the particles that make up the silicon nitride sintered body. In other words, the composition distribution can be made sufficiently narrow.
  • Such silicon nitride sintered bodies have sufficiently reduced quality variation and are highly reliable.
  • the Weibull coefficient (m) of the silicon nitride sintered body may be 9 or more, 10 or more, or 11 or more. This allows the variation in quality to be sufficiently reduced.
  • the Weibull coefficient (m) in this specification is a shape parameter in JIS R 1625:2010, and can be obtained by statistically processing the bending strength ( ⁇ ).
  • the single-mode, two-parameter Weibull distribution function (F( ⁇ )) is expressed by the following formula (1).
  • ⁇ is the bending strength measured in accordance with JIS R 1601:2008
  • ⁇ is the scale parameter.
  • the Weibull coefficient m can be obtained as the slope of a straight line in a Weibull plot obtained by a graph with the vertical axis being ln(ln(1/(1-F( ⁇ )))) and the horizontal axis being ln ⁇ .
  • F( ⁇ ) 1-exp[-( ⁇ / ⁇ ) m ]...(1)
  • the bending strength of the silicon nitride sintered body measured in accordance with JIS R 1601:2008 may be 920 MPa or more, 1000 MPa or more, or 1050 MPa or more.
  • the relative density of the silicon nitride sintered body may be 97% or more, or 98% or more, from the viewpoint of improving bending strength.
  • the bulk density of the silicon nitride sintered body may be 3.1 g/ cm3 or more, from the viewpoint of improving bending strength.
  • the relative density and bulk density of the silicon nitride sintered body in this specification are measured by the Archimedes method.
  • the silicon nitride sintered body contains a silicon nitride component as a main component.
  • the content of the silicon nitride component in the silicon nitride sintered body may be 90 mass% or more, 93 mass% or more, 95 mass% or more, or 97 mass% or more.
  • the content of the silicon nitride component in the silicon nitride sintered body can be measured using a commercially available X-ray diffraction device.
  • the silicon nitride sintered body may contain a subcomponent other than the silicon nitride component.
  • the subcomponent may include a component derived from a sintering aid and an iron-containing component.
  • the sintering aid may be an oxide-based one such as Y 2 O 3 , MgO, and Al 2 O 3.
  • the content of the component derived from the sintering aid in the silicon nitride sintered body may be, for example, 3 to 10 mass%.
  • Example 1 Preparation and Evaluation of Metallic Silicon Powder> A metal silicon chunk having a particle size of 10 to 50 mm was prepared. The metal silicon chunk was coarsely crushed using a crushing device (device name: jaw crusher, manufactured by Makino Corporation) and a crushing device (device name: roll crusher, manufactured by Makino Corporation), and then finely crushed using a crushing device (device name: vibration mill, manufactured by Chuo Kakoki Co., Ltd.) to obtain a metal silicon powder. The crushing time using the vibration mill was 310 minutes. The particle size distribution and BET specific surface area of the metal silicon powder were measured. The particle size distribution was measured by a laser diffraction/scattering method. Specifically, the following procedure was performed in accordance with the method described in JIS Z 8825:2013 "Particle size analysis-laser diffraction/scattering method".
  • the BET specific surface area was measured by the single-point BET method using nitrogen gas in accordance with JIS Z 8830:2013 "Method for measuring the specific surface area of powders (solids) by gas adsorption.”
  • the measurement results for D10, D50 (median diameter), D90, and BET specific surface area (SSA) of the metal silicon powder are shown in Table 1.
  • Table 1 also shows the ratio of D90 to D10 (D90/D10), the ratio of D90 to D50 (D90/D50), and the ratio of D10 to D50 (D10/D50).
  • ⁇ Preparation of raw material powder> The above-mentioned metallurgical silicon powder was mixed with fluorite, chromium oxide powder ( Cr2O3 ) and nickel oxide powder ( NiO) to prepare a raw material powder. 1 part by mass of fluorite, 0.02 part by mass of chromium oxide powder and 0.01 part by mass of nickel oxide powder were mixed with 100 parts by mass of metallurgical silicon powder.
  • the temperature was raised from room temperature to 1100°C in an atmosphere containing nitrogen gas and hydrogen gas over 11 hours, and then raised from 1100°C to the maximum temperature (1400°C) over 18 hours.
  • the ratio of nitrogen gas in the atmosphere was 96% by volume, and the ratio of hydrogen gas was 4.0% by volume.
  • After raising the temperature to the maximum temperature it was cooled to 200°C in the above atmosphere to obtain a sintered product containing silicon nitride as the main component.
  • the time T (excluding the time after cooling began) during which the raw material powder was heated to 1100°C or higher was 18 hours.
  • the sintered product was then allowed to cool to room temperature in the air to obtain the sintered product.
  • the fired material was coarsely crushed using a coarse crushing device (device name: jaw crusher, manufactured by Makino Corporation) and then dry-ground in a vibration mill to obtain silicon nitride powder.
  • a coarse crushing device device name: jaw crusher, manufactured by Makino Corporation
  • the alpha-phase ratio of the silicon nitride component contained in the silicon nitride powder was measured by the following procedure. X-ray diffraction of the silicon nitride powder was performed with CuK ⁇ radiation using an X-ray diffraction device (manufactured by Rigaku Corporation, device name: Ultima IV). The alpha phase was represented by the diffraction line intensity I a102 of the (102) plane and the diffraction line intensity I a210 of the (210) plane. The beta phase was represented by the diffraction line intensity I b101 of the (101) plane and the diffraction line intensity I b210 of the (210) plane.
  • the silicon nitride content in the sintered product in the above formula was calculated based on the results of X-ray diffraction when measuring the alpha conversion rate.
  • the silicon nitride content in the sintered product was as shown in Table 1.
  • 0.02 mass% of metallic silicon was detected as a component other than silicon nitride.
  • the average nitridation rate calculated using the above formula was as shown in Table 1.
  • the silicon nitride content in the sintered product was considered to be 100 mass%, and the average nitridation rate was calculated using the above formula.
  • the average particle size (D50, median size) and BET specific surface area of the silicon nitride powder are shown in Table 1.
  • the average particle size and BET specific surface area of the silicon nitride powder were measured in the same manner as for the metal silicon powder. The results are shown in Table 1.
  • the obtained molded body was set in a carbon crucible together with a packing powder consisting of a mixed powder of silicon nitride powder and BN powder, and sintered at a temperature of 1800 ° C for 4 hours in a nitrogen pressure atmosphere of 1 MPa to prepare a silicon nitride sintered body.
  • Example 2 A metal silicon powder was prepared in the same manner as in Example 1, except that the time for grinding with a vibration mill to obtain the metal silicon powder was changed to 360 minutes. Using this metal silicon powder, a raw material powder, a silicon nitride powder, and a silicon nitride sintered body were each prepared under the same conditions as in Example 1. The metal silicon powder, the silicon nitride powder, and the silicon nitride sintered body were evaluated in the same manner as in Example 1. The evaluation results were as shown in Table 1.
  • Example 3 A metal silicon powder was prepared in the same manner as in Example 1, except that the time for grinding with a vibration mill to obtain the metal silicon powder was changed to 250 minutes. Using this metal silicon powder, a raw material powder, a silicon nitride powder, and a silicon nitride sintered body were each prepared under the same conditions as in Example 1. The metal silicon powder, the silicon nitride powder, and the silicon nitride sintered body were evaluated in the same manner as in Example 1. The evaluation results were as shown in Table 1.
  • Example 4 A metal silicon powder was prepared in the same manner as in Example 1, except that the time for grinding with a vibration mill to obtain the metal silicon powder was changed to 330 minutes. Using this metal silicon powder, a raw material powder, a silicon nitride powder, and a silicon nitride sintered body were each prepared under the same conditions as in Example 1. The metal silicon powder, the silicon nitride powder, and the silicon nitride sintered body were evaluated in the same manner as in Example 1. The evaluation results were as shown in Table 1.
  • Example 5 A metal silicon powder was prepared in the same manner as in Example 1, except that the time for grinding with a vibration mill to obtain the metal silicon powder was changed to 270 minutes. Using this metal silicon powder, a raw material powder, a silicon nitride powder, and a silicon nitride sintered body were each prepared under the same conditions as in Example 1. The metal silicon powder, the silicon nitride powder, and the silicon nitride sintered body were evaluated in the same manner as in Example 1. The evaluation results were as shown in Table 1.
  • Example 6 A metal silicon powder was prepared in the same manner as in Example 1, except that the time for grinding with a vibration mill to obtain metal silicon powder was changed to 320 minutes.
  • a raw material powder, a silicon nitride powder, and a silicon nitride sintered body were each prepared under the same conditions as in Example 1, except that this metal silicon powder was used and that the maximum temperature reached when preparing the silicon nitride powder was set to the temperature shown in Table 2.
  • the metal silicon powder, the silicon nitride powder, and the silicon nitride sintered body were evaluated in the same manner as in Example 1. The evaluation results were as shown in Table 2.
  • Example 7 The raw material powder, silicon nitride powder, and silicon nitride sintered body were prepared under the same conditions as in Example 6, except that the maximum temperature reached when preparing the silicon nitride powder was set to the temperature shown in Table 2.
  • Example 8 The raw material powder, silicon nitride powder, and silicon nitride sintered body were prepared under the same conditions as in Example 6, except that the maximum temperature reached during preparation of the silicon nitride powder and the ratio of hydrogen gas in the atmosphere were set to the temperatures and ratios shown in Table 2.
  • Example 9 The raw material powder, silicon nitride powder, and silicon nitride sintered body were prepared under the same conditions as in Example 8, except that the ratio of hydrogen gas in the atmosphere during preparation of the silicon nitride powder was set to the ratio shown in Table 2.
  • Example 1 A metal silicon powder was prepared in the same manner as in Example 1, except that the time for grinding with a vibration mill to obtain the metal silicon powder was changed to 480 minutes. Using this metal silicon powder, a raw material powder, a silicon nitride powder, and a silicon nitride sintered body were each prepared under the same conditions as in Example 1. The metal silicon powder, the silicon nitride powder, and the silicon nitride sintered body were evaluated in the same manner as in Example 1. The evaluation results were as shown in Table 2.
  • Example 2 A metal silicon powder was prepared in the same manner as in Example 1, except that the time for grinding with a vibration mill to obtain the metal silicon powder was changed to 210 minutes. Using this metal silicon powder, a raw material powder, a silicon nitride powder, and a silicon nitride sintered body were each prepared under the same conditions as in Example 1. The metal silicon powder, the silicon nitride powder, and the silicon nitride sintered body were evaluated in the same manner as in Example 1. The evaluation results were as shown in Table 2.
  • the silicon nitride powders of Examples 1 to 9 were prepared at a sufficiently fast average nitriding rate, but ⁇ -conversion was suppressed and they had a high ⁇ -conversion rate.
  • ⁇ -conversion was not sufficiently suppressed and the silicon nitride content in the nitride was also low. The reason why ⁇ -conversion could not be suppressed is thought to be the occurrence of an excessive exothermic reaction.
  • the Weibull coefficients of the silicon nitride sintered bodies prepared using the silicon nitride powders of Examples 1 to 9 were 9 or more, which was greater than the Weibull coefficients of Comparative Examples 1 and 2. This confirmed that the silicon nitride sintered bodies of Examples 1 to 9 had less variation in bending strength than the silicon nitride sintered bodies of Comparative Examples 1 and 2, and that the variation in quality had been sufficiently reduced.

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Abstract

Cette méthode de production d'une poudre de nitrure de silicium comprend une étape de cuisson d'une poudre brute contenant une poudre de silicium métallique à l'aide d'un four continu dans une atmosphère contenant de l'azote gazeux pour obtenir un produit cuit contenant un composant de nitrure de silicium. Dans une distribution cumulative de la taille de particule basée sur le volume telle que mesurée par une méthode de diffraction/diffusion laser, la taille de particule D10 de la poudre de silicium métallique, lorsque la valeur intégrée à partir de la plus petite taille de particule atteint 10% du total, est de 4 à 10 µm.
PCT/JP2024/002693 2023-03-22 2024-01-29 Méthode de production de poudre de nitrure de silicium, et méthode de production de corps fritté de nitrure de silicium Pending WO2024195299A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10182115A (ja) * 1996-12-26 1998-07-07 Denki Kagaku Kogyo Kk 窒化珪素質粉末及びその製造方法
JP2000178013A (ja) * 1998-12-14 2000-06-27 Denki Kagaku Kogyo Kk 窒化ケイ素粉末及びその製造方法
JP2002284585A (ja) * 2001-03-26 2002-10-03 Ngk Insulators Ltd 窒化珪素多孔体及びその製造方法
JP2004115334A (ja) * 2002-09-27 2004-04-15 Denki Kagaku Kogyo Kk 高α型窒化ケイ素微粉末の製造方法
JP2013071864A (ja) * 2011-09-28 2013-04-22 Denki Kagaku Kogyo Kk 離型剤用窒化ケイ素粉末およびその製造方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10182115A (ja) * 1996-12-26 1998-07-07 Denki Kagaku Kogyo Kk 窒化珪素質粉末及びその製造方法
JP2000178013A (ja) * 1998-12-14 2000-06-27 Denki Kagaku Kogyo Kk 窒化ケイ素粉末及びその製造方法
JP2002284585A (ja) * 2001-03-26 2002-10-03 Ngk Insulators Ltd 窒化珪素多孔体及びその製造方法
JP2004115334A (ja) * 2002-09-27 2004-04-15 Denki Kagaku Kogyo Kk 高α型窒化ケイ素微粉末の製造方法
JP2013071864A (ja) * 2011-09-28 2013-04-22 Denki Kagaku Kogyo Kk 離型剤用窒化ケイ素粉末およびその製造方法

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