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WO2025205635A1 - Poudre de nitrure de silicium - Google Patents

Poudre de nitrure de silicium

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Publication number
WO2025205635A1
WO2025205635A1 PCT/JP2025/011503 JP2025011503W WO2025205635A1 WO 2025205635 A1 WO2025205635 A1 WO 2025205635A1 JP 2025011503 W JP2025011503 W JP 2025011503W WO 2025205635 A1 WO2025205635 A1 WO 2025205635A1
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Prior art keywords
silicon nitride
nitride powder
sintered body
powder
less
Prior art date
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PCT/JP2025/011503
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English (en)
Japanese (ja)
Inventor
脩平 野中
智宏 野見山
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Denka Co Ltd
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Denka Co Ltd
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Publication of WO2025205635A1 publication Critical patent/WO2025205635A1/fr
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Classifications

    • 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 silicon nitride powder.
  • Silicon nitride is a material with excellent strength, hardness, toughness, heat resistance, corrosion resistance, and thermal shock resistance, and is therefore used in various industrial parts such as die-casting machines and melting furnaces, as well as automotive parts. Furthermore, because silicon nitride also has excellent mechanical properties at high temperatures, its use in gas turbine parts, which require high-temperature strength and high-temperature creep properties, is being considered.
  • Patent Document 1 describes a silicon nitride sintered body characterized by a thermal conductivity of 100 to 300 W/(m ⁇ K) at room temperature and a three-point bending strength of 600 to 1500 MPa at room temperature.
  • the purpose of this disclosure is to provide silicon nitride powder that can be used to prepare sintered bodies with excellent bending strength.
  • One aspect of the present disclosure provides the following silicon nitride powder:
  • the BET specific surface area is 10.3 m 2 /g or more;
  • the particle diameter when the cumulative value from small particle diameters reaches 10% of the total is defined as D10
  • the particle diameter when the cumulative value from small particle diameters reaches 50% of the total is defined as D50
  • the particle diameter when the cumulative value from small particle diameters reaches 90% of the total is defined as D90.
  • Silicon nitride powder, wherein (D90-D10)/D50 is 1.70 or less.
  • the silicon nitride powder of [1] above has a BET specific surface area of 10.3 m 2 /g or more, and (D90 - D10)/D50 of 1.70 or less.
  • a large BET specific surface area of the silicon nitride powder corresponds to fine silicon nitride particles constituting the silicon nitride powder.
  • silicon nitride powder contains silicon nitride with a relatively stable ⁇ phase, it will not melt but will act as nuclei for crystal growth. Grain growth will proceed preferentially from these nuclei, resulting in the generation of coarse particles in the sintered body. The presence of coarse particles in the sintered body will concentrate stress on the coarse particles, reducing the bending strength of the sintered body.
  • the silicon nitride powder described in [1] above has a controlled particle size so that the specific surface area is above a predetermined value, and the particle distribution is also narrow.
  • silicon nitride particles with a ⁇ phase are present, their size as crystal nuclei is small, allowing for a more uniform environment within the system during sintering.
  • silicon nitride powder is used as a sintered body raw material, it is possible to reduce the number of coarse particles within the resulting sintered body, and the resulting sintered body will exhibit excellent bending strength.
  • the silicon nitride powder described in [2] above has an alpha conversion rate of 96.0% by mass or less. Using silicon nitride powder with a low alpha conversion rate allows for reduced manufacturing costs.
  • the silicon nitride powder described in [3] above has a D97 of 2.25 ⁇ m or less.
  • Such silicon nitride powder allows for more complete melting of the silicon nitride, and even if the silicon nitride having the ⁇ phase does not melt and begins to grow, it is possible to reduce the difference in particle size between it and the new silicon nitride particles produced by reprecipitation. This therefore further reduces the generation of coarse particles, and further improves the bending strength of the sintered body.
  • the silicon nitride powder [4] above has an oxygen content of 0.65 to 1.60 mass%. Silicon nitride powder with this oxygen content improves reactivity during sintering while suppressing the formation of embrittled phases in the sintered body caused by oxygen, thereby suppressing embrittlement of the sintered body itself. This can therefore further improve the bending strength of the sintered body.
  • This disclosure provides silicon nitride powder that can be used to prepare sintered bodies with excellent bending strength.
  • 1 is a scanning electron microscope photograph showing a cross section of a sintered body produced using the silicon nitride powder of Comparative Example 4. 1 is a scanning electron microscope photograph showing a cross section of a sintered body produced using the silicon nitride powder of Example 4. 1 is a scanning electron microscope photograph showing a cross section of a sintered body produced using the silicon nitride powder of Example 7.
  • Embodiments of the present disclosure are described below. However, the following embodiments are merely examples for explaining the present disclosure and are not intended to limit the present disclosure to the following content.
  • the upper or lower limit of a numerical range specified in this disclosure may be replaced with any value shown in the examples. Furthermore, individually stated upper and lower limit values may be combined in any combination.
  • the symbol "to” used in a numerical range indicates a numerical range that includes the upper and lower limit. For example, "X to Y” indicates a numerical range of "greater than or equal to X and less than or equal to Y.” Unless otherwise specified, the materials or components exemplified in this disclosure can be used alone or in combination of two or more types.
  • the silicon nitride powder (Si 3 N 4 powder) according to one embodiment has a BET specific surface area of 10.3 m 2 /g or more, and in the cumulative distribution of volumetric particle diameters measured with a particle size distribution analyzer using a laser diffraction/scattering method, when the particle diameter when the integrated value from the small particle diameters reaches 10% of the total is defined as D10, the particle diameter when the integrated value from the small particle diameters reaches 50% of the total is defined as D50, and the particle diameter when the integrated value from the small particle diameters reaches 90% of the total is defined as D90, the ratio (D90-D10)/D50 is 1.70 or less.
  • a sintered body having excellent bending strength can be obtained.
  • the BET specific surface area may be, for example, 20.0 m 2 /g or less, 15.0 m 2 /g or less, or 13.0 m 2 /g or less.
  • the oxygen content generally increases as the BET specific surface area increases. Therefore, as the BET specific surface area increases, the oxygen content increases excessively, which generates an embrittlement phase during the production of a sintered body, resulting in a decrease in strength.
  • a silicon nitride powder having an upper limit for the BET specific surface area in this range can maintain the oxygen content within an appropriate range. This can further improve the bending strength of the resulting sintered body.
  • the BET specific surface area of silicon nitride powder may be adjusted, for example, by changing the grinding conditions during production of the silicon nitride powder.
  • the BET specific surface area in this disclosure is a value measured by the single-point BET method using nitrogen gas in accordance with the method described in JIS R 1626:1996, "Method for measuring the specific surface area of fine ceramic powders by the gas adsorption BET method.”
  • D90 may be, for example, 2.00 ⁇ m or less, 1.50 ⁇ m or less, or 1.30 ⁇ m or less. Silicon nitride powder with an upper D90 value in this range is composed of smaller particles, and when used as a sintered body raw material, the formation of coarse particles in the sintered body can be further suppressed, resulting in a sintered body with higher bending strength. Furthermore, D90 may be, for example, 0.60 ⁇ m or more, 0.80 ⁇ m or more, or 1.20 ⁇ m or more. Having a lower D90 value in this range prevents excessive increases in oxygen content due to smaller particle size, further suppresses the formation of embrittlement phases during sintered body production, and further improves the bending strength of the sintered body.
  • the D90 range may be, for example, 0.60 to 2.00 ⁇ m, 0.60 to 1.50 ⁇ m, or 0.60 to 1.30 ⁇ m.
  • D50 may be, for example, 1.00 ⁇ m or less, 0.90 ⁇ m or less, 0.80 ⁇ m or less, or 0.70 ⁇ m or less. Silicon nitride powder with an upper D50 value in this range is composed of smaller particles, and when used as a sintered body raw material, the formation of coarse particles in the sintered body can be further suppressed, resulting in a sintered body with higher bending strength. Furthermore, D50 may be, for example, 0.30 ⁇ m or more, or 0.40 ⁇ m or more. Having a lower D50 value in this range prevents excessive increases in oxygen content due to smaller particle size, further suppresses the formation of embrittlement phases during sintered body production, and further improves the bending strength of the sintered body.
  • the D50 range may be, for example, 0.30 to 1.00 ⁇ m, 0.30 to 0.90 ⁇ m, 0.30 to 0.80 ⁇ m, or 0.30 to 0.70 ⁇ m.
  • D10 may be, for example, 0.60 ⁇ m or less, 0.50 ⁇ m or less, or 0.40 ⁇ m or less. Silicon nitride powder with an upper D10 value in this range is composed of smaller particles, and when used as a sintered body raw material, the formation of coarse particles in the sintered body can be further suppressed, resulting in a sintered body with even higher bending strength. Furthermore, D10 may be, for example, 0.05 ⁇ m or more, or 0.10 ⁇ m or more. Having a lower D10 value in this range prevents excessive increases in oxygen content due to smaller particle size, further suppresses the formation of embrittlement phases during sintered body production, and further improves the bending strength of the sintered body.
  • the D10 range may be, for example, 0.05 to 0.60 ⁇ m, 0.05 to 0.50 ⁇ m, or 0.05 to 0.40 ⁇ m.
  • D97 In the cumulative volumetric particle size distribution of silicon nitride powder measured with a particle size distribution analyzer using laser diffraction/scattering, if the particle size D97 is the particle size at which the cumulative value from the smallest particle size reaches 97% of the total, D97 may be 2.25 ⁇ m or less, 2.00 ⁇ m or less, 1.80 ⁇ m or less, 1.60 ⁇ m or less, or 1.40 ⁇ m or less. Silicon nitride powder with a D97 in this range has a sufficiently small particle size. Silicon nitride powder with a D97 in this range can further suppress the generation of coarse particles during sintering, even when it contains a large amount of ⁇ phase, which easily becomes crystal nuclei during sintering. Therefore, the generation of coarse particles in the sintered body can be further suppressed. Such sintered bodies have even higher bending strength.
  • D97 may be, for example, 0.80 ⁇ m or more, 0.90 ⁇ m or more, or 1.00 ⁇ m or more.
  • the range of D97 may be, for example, 0.80 to 2.25 ⁇ m, 0.80 to 2.00 ⁇ m, 0.80 to 1.80 ⁇ m, 0.80 to 1.60 ⁇ m, or 0.80 to 1.40 ⁇ m.
  • the laser diffraction/scattering method can be used in accordance with the method described in JIS R 1629:1997, "Method for measuring particle size distribution of fine ceramic raw materials using laser diffraction/scattering.” Measurements can be performed using a laser diffraction/scattering particle size distribution analyzer (manufactured by Microtrac-Bell, product name: MT-3300EX) or similar.
  • the silicon nitride powder according to the present disclosure has an adjusted BET specific surface area and (D90-D10)/D50 value, it is possible to prepare a sintered body that exhibits excellent bending strength even if the alpha phase ratio is not very high.
  • the alpha phase ratio of the silicon nitride powder (the mass ratio of ⁇ -Si 3 N 4 to the total amount of Si 3 N 4 ) may be 96.0 mass% or less, 95.0 mass% or less, or 94.0 mass% or less. By keeping the alpha phase ratio within this range, the proportion of the ⁇ phase in the silicon nitride powder is further increased, resulting in excellent productivity.
  • the alpha phase ratio may be, for example, 89.0 mass% or more, or 90.0 mass% or more.
  • the range of the gelatinization rate may be, for example, 89.0 to 96.0 mass%, 89.0 to 95.0 mass%, 89.0 to 94.0 mass%, 90.0 to 96.0 mass%, 90.0 to 95.0 mass%, or 90.0 to 94.0 mass%.
  • the alpha phase ratio of silicon nitride powder can be adjusted by adjusting the conditions for calcining the silicon nitride powder.
  • Silicon nitride powder with a high alpha phase ratio can be obtained by chemical synthesis using imide pyrolysis or by high-temperature vapor phase synthesis, which forms idiomorphic particles through crystal growth at high temperatures. These manufacturing methods are costly because they require chemical synthesis, which generates a large amount of by-products.
  • silicon nitride powder with a low alpha phase ratio can be obtained by a nitridation reaction in which metallic silicon is directly nitrided, allowing for simple production while keeping costs down.
  • the alpha phase ratio of silicon nitride powder can be determined by the diffraction line intensity of X-ray diffraction. Specifically, the alpha phase ratio of silicon nitride powder is determined by the method described in the Examples.
  • the oxygen content of the silicon nitride powder may be, for example, 0.65 to 1.60 mass%.
  • the oxygen content in this disclosure refers to the total oxygen content.
  • Silicon nitride powder with such an oxygen content contains a sufficient amount of oxygen to promote sintering while further suppressing the formation of embrittled phases due to excess oxygen. Furthermore, when the oxygen content is within the above range, a certain amount of oxygen is present on the surface of the silicon nitride particles, further promoting the sintering reaction and producing a sintered body with higher bending strength. Therefore, sintered bodies made using silicon nitride powder with such an oxygen content have even higher bending strength.
  • the oxygen content of the silicon nitride powder By keeping the oxygen content of the silicon nitride powder within the above range, it is possible to achieve a higher level of both the effect of promoting the sintering reaction based on the amount of oxygen contained in the silicon nitride particles and the contact area with the liquid phase of the sintering aid, and the effect of suppressing the formation of embrittled phases based on adjusting the amount of oxygen contained in the silicon nitride particles.
  • the oxygen content can be measured using a commercially available oxygen/nitrogen analyzer.
  • the oxygen content may be, for example, 1.50% by mass or less, or 1.30% by mass or less. Silicon nitride powder with such an oxygen content can further suppress the formation of embrittlement phases due to excess oxygen during sintering, and further improve the bending strength of the sintered body.
  • the oxygen content may be in the range of, for example, 0.70 to 1.60% by mass, 0.80 to 1.60% by mass, 0.65 to 1.50% by mass, 0.70 to 1.50% by mass, 0.80 to 1.50% by mass, 0.65 to 1.30% by mass, 0.70 to 1.30% by mass, or 0.80 to 1.30% by mass.
  • This production method uses silicon nitride powder as a raw material and adjusts the particle size, making it a relatively simple method for producing the desired silicon nitride powder. Therefore, silicon nitride powder can be produced at a lower cost than the production cost of silicon nitride powder with a high degree of alpha conversion as a raw material for sintered compacts that exhibit excellent bending strength.
  • the step of preparing the raw silicon nitride powder may include at least one step selected from the group consisting of a mixing step of mixing silicon-containing raw materials to obtain a mixture, a nitriding step of firing the mixture to obtain a nitride, and a post-treatment step of treating the nitride with hydrofluoric acid.
  • the raw silicon nitride powder may be obtained via the mixing step, nitriding step, and post-treatment step.
  • the nitride is mixed with hydrofluoric acid having a hydrogen fluoride concentration of, for example, 1.0 to 4.0% by mass and treated.
  • the nitride may be dispersed in hydrofluoric acid for treatment.
  • the hydrogen fluoride concentration in the hydrofluoric acid may be, for example, 1.3 to 2.3% by mass.
  • the temperature of the hydrofluoric acid in the post-treatment process is, for example, 40 to 80°C.
  • the nitride is immersed in hydrofluoric acid for, for example, 1 to 10 hours.
  • the alpha phase ratio of the raw silicon nitride powder may be 96.0% by mass or less, 95.0% by mass or less, or 94.0% by mass or less.
  • Silicon nitride powder with an alpha phase ratio within the above-mentioned range has low production costs and excellent productivity, and can be easily obtained or prepared. Even when raw material powder with an alpha phase ratio within the above-mentioned range is used, it is possible to provide silicon nitride powder from which sintered bodies with excellent bending strength can be produced.
  • the alpha phase ratio may be 89.0% by mass or more, or 90.0% by mass or more.
  • the alpha phase ratio range of the raw silicon nitride powder may be, for example, 89.0 to 96.0% by mass, 89.0 to 95.0% by mass, 89.0 to 94.0% by mass, 90.0 to 96.0% by mass, 90.0 to 95.0% by mass, or 90.0 to 94.0% by mass.
  • the time for the grinding process (grinding time) in the grinding step may be, for example, 5 to 15 hours, or 8 to 12 hours. This allows the silicon nitride powder to be sufficiently fine.
  • the ground product obtained in the ball mill grinding process may be further ground in a vibration mill grinding process.
  • the ball filling rate in the container in the vibration mill grinding process may be, for example, 50 to 80 volume %, or 60 to 75 volume %.
  • the grinding time (grinding time) in the vibration mill grinding process may be 8 to 20 hours, or 12 to 17 hours. This allows the raw silicon nitride powder to be sufficiently fine, adjusts the D97, and more easily obtains the silicon nitride powder specified in the present application.
  • the particle size adjustment step can also employ a method of dry classification to obtain silicon nitride powder having a BET specific surface area of 10.3 m 2 /g or more and (D90-D10)/D50 of 1.70 or less.
  • agglomerated particles also called secondary particles
  • this increases the particle size of the silicon nitride powder as a whole. Therefore, the particle size distribution of the silicon nitride powder can be adjusted by eliminating at least some of these agglomerated particles, and the particle size distribution of the silicon nitride powder can also be adjusted by eliminating some of the primary silicon nitride particles with large particle diameters.
  • Dry classification can be performed by sieving or using an air classifier.
  • Classification can be performed using a swirling air classifier that uses primary and secondary air.
  • An example of such an air classifier is the "MP-150" manufactured by Nippon Pneumatic Mfg. Co., Ltd.
  • the operating conditions of the air classifier can be adjusted, for example, by adjusting the classification air volume and the louver opening of the air guide vanes to control the swirling air velocity.
  • the classification air volume refers to the amount of air required to generate a swirling flow within the air classifier.
  • Primary air introduced into the air classifier becomes a swirling flow as it passes through the air guide vanes.
  • a large centrifugal force can be applied to coarse particles, allowing for easy classification.
  • air (secondary air) compressed more than the primary air into the swirling flow the accuracy of classification can be further improved.
  • silicon nitride powder having a BET specific surface area of 10.3 m 2 /g or more and a (D90-D10)/D50 of 1.70 or less.
  • Such silicon nitride powder has high bending strength when sintered.
  • the classification air volume may be 1 to 4 m 3 /min, or may be 1 to 3 m 3 /min.
  • the louver opening of the air guide vane may be 12 mm or more and 2 mm or less, for example, in the range of 2 to 8 mm.
  • the louver opening refers to the distance between the centers of the louvers.
  • the louver opening can also be expressed by the angle of the louvers. In this case, the angle may be 70°, 80°, or 90°.
  • the louver opening indicates the size of the inlet for compressed air (secondary air). If the distance between the centers of the louvers is small or the louver angle is large, the inlet becomes smaller, increasing the pressure and the airflow rotation speed.
  • the secondary air pressure may be 0.2 to 1.0 MPa, or 0.4 to 0.8 MPa.
  • the swirling air velocity can be adjusted to 100 to 300 m/s, and agglomerated particles that are not sufficiently pulverized in the pulverization step can be removed as coarse particles with high precision.
  • the desired silicon nitride powder can be produced more easily than by mixing powders of different particle sizes or adjusting particle size by pulverization.
  • the swirling air velocity can also be measured using, for example, a thermal airflow transducer (trade name: TA10 ZG2d, manufactured by Centronic Co., Ltd.).
  • D10 may be adjusted to, for example, 0.60 ⁇ m or less, 0.50 ⁇ m or less, or 0.40 ⁇ m or less. Silicon nitride powder with an upper D10 value in this range has an even smaller particle size, which further suppresses the generation of coarse particles in the sintered body, resulting in a sintered body with even higher bending strength. Furthermore, D10 may be adjusted to, for example, 0.05 ⁇ m or more, or 0.10 ⁇ m or more. D10 may be adjusted to, for example, the range of 0.05 to 0.60 ⁇ m, 0.05 to 0.50 ⁇ m, or 0.05 to 0.40 ⁇ m.
  • the value of (D90 - D10)/D50 may be adjusted to 1.60 or less, or to 1.50 or less.
  • the variation in bending strength of each sintered body can be reduced. In other words, the Weibull modulus of the sintered body can be increased.
  • the silicon nitride powder of this embodiment can be manufactured through the above steps. However, the above manufacturing method is only an example and is not limiting. Because the silicon nitride powder of this embodiment has reduced coarse particles, it can be suitably used as a raw material for sintered bodies with high bending strength.
  • the sintering raw material containing the above-mentioned silicon nitride powder is molded and sintered.
  • the sintering raw material may also contain an oxide-based sintering aid.
  • oxide-based sintering aids 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 pressure in the secondary firing step, in which the sintered body obtained in the primary firing step is fired may be, for example, 70 MPa or more, preferably 100 MPa or more.
  • the firing temperature may be, for example, 1650 to 1850°C, or 1700 to 1800°C.
  • the firing time at this firing temperature may be, for example, 0.5 to 5 hours, or 1 to 2 hours.
  • the rate of temperature rise to the firing temperature may be, for example, 1.0 to 10.0°C/hour.
  • the resulting sintered body has a reduced amount of coarse particles and a highly uniform, fine structure. It also has a sufficiently dense structure, resulting in excellent bending strength. Furthermore, because variation in particle size is reduced, variation in the properties of the silicon nitride sintered body can be reduced.
  • the fracture toughness value of the sintered body can be 4.5 (MPa/m 2 ) or more, 4.8 (MPa/m 2 ) or more, or 5.2 (MPa/m 2 ) or more.
  • Such silicon nitride sintered bodies have excellent strength and can be suitably used as parts for various industries.
  • the fracture toughness value of the sintered body can be measured in accordance with JIS R 1607:2015.
  • the fracture toughness value of the sintered body may be 6.0 (MPa/m 2 ) or less.
  • the range of the fracture toughness value of the sintered body may be, for example, 4.5 to 6.0 (MPa/m 2 ), 4.8 to 6.0 (MPa/m 2 ), or 5.2 to 6.0 (MPa/m 2 ).
  • the Vickers hardness of the sintered body can be 1.400 HV or more, 1.420 HV or more, or 1.430 HV or more.
  • Such silicon nitride sintered bodies have excellent wear resistance and are suitable for use as parts in various industries.
  • the Vickers hardness of the sintered body can be measured in accordance with JIS R1610:2003.
  • the Vickers hardness of the sintered body may be 1.600 HV or less.
  • the Vickers hardness range of the sintered body may be, for example, 1.400 to 1.600 HV, 1.420 to 1.600 HV, or 1.430 to 1.600 HV.
  • the silicon nitride sintered body has a highly uniform microstructure, which sufficiently suppresses the distribution of the bending strength described above.
  • the silicon nitride sintered body exhibits a relatively large Weibull coefficient in a Weibull statistical analysis of its bending strength.
  • the Weibull coefficient for bending strength of the silicon nitride sintered body is, for example, 10.0 or greater, 12.0 or greater, 13.0 or greater, 15.0 or greater, 17.0 or greater, or 20.0 or greater.
  • the Weibull coefficient can also be 25.0 or less.
  • the range of the Weibull coefficient may be, for example, 10.0 to 25.0, 12.0 to 25.0, 13.0 to 25.0, 15.0 to 25.0, 17.0 to 25.0, or 20.0 to 25.0.
  • Weibull statistics are used to evaluate the distribution of bending strength.
  • a Weibull plot is created for a silicon nitride sintered body, with the fracture probability F( ⁇ ) on the vertical axis and the bending strength ⁇ (strength at fracture, transverse strength) on the horizontal axis, the slope m is the Weibull coefficient.
  • a large Weibull coefficient means that the bending strength distribution is narrow and close to a normal distribution.
  • ⁇ is a fitting parameter.
  • a raw material powder was prepared by blending 1 part by mass of fluorite with 100 parts by mass of silicon powder. That is, the raw material powder contained 1 part by mass of fluoride (fluorite) with 100 parts by mass of silicon powder.
  • An alumina container having a main body with a recess and a lid was prepared. The raw material powder was filled into the recess. The filling shape of the raw material powder was a rectangular parallelepiped, and the filling height was 45 mm. The recess of the main body was covered with a lid, and the raw material powder was placed in the alumina container. The raw material powder placed in the container was fired using the following procedure.
  • the container containing the raw material powder was placed in an electric furnace and fired under the following temperature conditions.
  • the temperature was increased from 20°C to 1150°C at a rate of 5°C/min. After holding at 1150°C for 8 hours, the temperature was increased to 1450°C at a rate of 0.15°C/min. After holding at 1450°C for 4 hours, it was allowed to cool naturally to room temperature.
  • the atmosphere in the electric furnace was nitrogen gas.
  • the time from the start of holding at 1150°C to the end of holding at 1450°C was 45 hours.
  • the resulting ingot was coarsely crushed and then wet-ground in an attritor mill for 8 hours.
  • the ball filling rate of the attritor mill was 70% by volume. It was then dried under a nitrogen atmosphere.
  • the ground material obtained by wet grinding was immersed in hydrofluoric acid (hydrogen fluoride concentration: 1.6% by mass) at 70°C for 4 hours for acid treatment. The ground material was then removed from the hydrofluoric acid, washed with water, and dried under a nitrogen atmosphere. In this way, raw silicon nitride powder (powder a) was obtained.
  • hydrofluoric acid hydrogen fluoride concentration: 1.6% by mass
  • Comparative Example 4 A raw material silicon nitride powder (powder d) of Comparative Example 4 was prepared in the same manner as in Comparative Example 1, except that the hydrogen fluoride concentration of the hydrofluoric acid was changed to 1.7 mass %.
  • Example 1 ⁇ Classification of raw silicon nitride powder>
  • the silicon nitride powder (powder a) of Comparative Example 1 was used as a raw material silicon nitride powder and was classified using an air classifier (manufactured by Nippon Pneumatic Mfg. Co., Ltd., product name: EVX-1) to obtain a silicon nitride powder.
  • the classification conditions were as follows: Classification air volume: 1.1m 3 /min Louver opening in main air guide vane: 2 mm Secondary air pressure: 0.4 MPa Swirling air velocity: 230 m/s
  • Example 3 The silicon nitride powder (powder c) of Comparative Example 3 was used as a raw material silicon nitride powder and was classified using an air classifier (manufactured by Nippon Pneumatic Mfg. Co., Ltd., product name: EVX-1) to obtain a silicon nitride powder.
  • the classification conditions were as follows: Classification air volume: 1.1m 3 /min Louver opening in main air guide vane: 2 mm Secondary air pressure: 0.4 MPa Swirling air velocity: 230 m/s
  • Example 4 The silicon nitride powder (powder d) of Comparative Example 4 was used as a raw material silicon nitride powder and was classified using an air classifier (manufactured by Nippon Pneumatic Mfg. Co., Ltd., product name: EVX-1) to obtain a silicon nitride powder.
  • the classification conditions were as follows: Classification air volume: 1.1m 3 /min Louver opening in main air guide vane: 2 mm Secondary air pressure: 0.4 MPa Swirling air velocity: 230 m/s
  • Example 5 The silicon nitride powder (powder b) of Comparative Example 2 was used as a raw material silicon nitride powder and was classified using an air classifier (manufactured by Nippon Pneumatic Mfg. Co., Ltd., product name: MP-150) to obtain a silicon nitride powder.
  • the classification conditions were as follows: Classification air volume: 2.3m 3 /min Louver opening in main air guide vane: 3 mm Secondary air pressure: 0.6 MPa Swirling air velocity: 160 m/s
  • Example 6 The silicon nitride powder (powder c) of Comparative Example 3 was used as a raw material silicon nitride powder and was classified using an air classifier (manufactured by Nippon Pneumatic Mfg. Co., Ltd., product name: MP-150) to obtain a silicon nitride powder.
  • the classification conditions were as follows: Classification air volume: 2.3m 3 /min Louver opening in main air guide vane: 3 mm Secondary air pressure: 0.6 MPa Swirling air velocity: 160 m/s
  • Example 8 The silicon nitride powder (powder e) of Comparative Example 5 was used as a raw material silicon nitride powder and was classified using an air classifier (manufactured by Nisshin Engineering Inc., product name: AC-20) to obtain a silicon nitride powder.
  • the classification conditions were as follows: Classification air volume: 2.0m 3 /min Louver opening angle of main air guide vane: 90° Secondary air pressure: 0.7 MPa Swirling air velocity: 200 m/s
  • Example 9 The silicon nitride powder (powder e) of Comparative Example 5 was used as a raw material silicon nitride powder and was classified using an air classifier (manufactured by Nisshin Engineering Inc., product name: AC-20) to obtain a silicon nitride powder.
  • the classification conditions were as follows: Classification air volume: 2.4m 3 /min Louver opening angle of main air guide vane: 90° Secondary air pressure: 0.8 MPa Swirling air velocity: 300 m/s
  • the BET specific surface area of the silicon nitride powder was measured by the single-point BET method using nitrogen gas in accordance with JIS R 1626:1996 "Method for measuring the specific surface area of fine ceramic powders by the gas adsorption BET method.” The measurement results for each example and comparative example are shown in Table 1.
  • the oxygen content of the silicon nitride powder was determined as the total amount of oxygen.
  • the oxygen content was measured using an oxygen/nitrogen analyzer (manufactured by Horiba, Ltd., device name: EMGA-920). Specifically, the silicon nitride powder was heated from 20°C to 2000°C at a temperature increase rate of 8°C/s in a helium atmosphere, and the amount of oxygen released was quantified to determine the oxygen content (mass%) of the entire silicon nitride powder.
  • the measurement results for each example and comparative example are shown in Table 1.
  • the fracture toughness (K IC ) is a value measured by the IF method in accordance with JIS R1607:2015 using a commercially available measuring device (manufactured by Matsuzawa Co., Ltd., device name: Via-F). The results are shown in Table 2.

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  • Organic Chemistry (AREA)
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Abstract

La présente invention concerne une poudre de nitrure de silicium ayant une surface spécifique BET supérieure ou égale à 10,3 m2/g, dans une distribution cumulative des diamètres de particule basés sur le volume mesurés par un dispositif de mesure de distribution de taille de particule à l'aide d'un procédé de diffraction/diffusion laser, (D90 - D10) / D50 étant inférieur ou égal à 1,70, D10 étant le diamètre de particule lorsque la valeur intégrée à partir du petit diamètre de particule atteint 10 % du total, D50 étant le diamètre de particule lorsque la valeur intégrée à partir du petit diamètre de particule atteint 50 % du total, et D90 étant le diamètre de particule lorsque la valeur intégrée à partir du petit diamètre de particule atteint 90 % du total.
PCT/JP2025/011503 2024-03-29 2025-03-24 Poudre de nitrure de silicium Pending WO2025205635A1 (fr)

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