WO2024019143A1 - 窒化ケイ素焼結体及び窒化ケイ素焼結体の製造方法 - Google Patents

窒化ケイ素焼結体及び窒化ケイ素焼結体の製造方法 Download PDF

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WO2024019143A1
WO2024019143A1 PCT/JP2023/026759 JP2023026759W WO2024019143A1 WO 2024019143 A1 WO2024019143 A1 WO 2024019143A1 JP 2023026759 W JP2023026759 W JP 2023026759W WO 2024019143 A1 WO2024019143 A1 WO 2024019143A1
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silicon nitride
sintered body
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nitride sintered
content
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French (fr)
Japanese (ja)
Inventor
雄斗 大越
弘法 佐藤
直通 宮川
佳孝 西條
晴彦 吉野
慧之 築山
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AGC Inc
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Asahi Glass Co Ltd
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    • 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
    • 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
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/64—Burning or sintering processes
    • C04B35/645—Pressure sintering

Definitions

  • the present invention relates to a silicon nitride sintered body and a method for manufacturing a silicon nitride sintered body.
  • a silicon nitride sintered body containing silicon nitride particles and a grain boundary phase is known.
  • it contains 7 to 18% by mass of rare earth elements in terms of oxide, and at least one element M selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W.
  • a silicon nitride sintered body is described that contains 0.1 to 3% by mass in terms of oxide and has a content of impurity cation elements of 0.3% by mass or less.
  • Such silicon nitride sintered bodies are required to have good mechanical properties and high strength as products.
  • An object of the present invention is to provide a silicon nitride sintered body with good mechanical properties and a method for manufacturing the silicon nitride sintered body.
  • a silicon nitride sintered body is a silicon nitride sintered body including silicon nitride particles and a grain boundary phase located around the silicon nitride particles, wherein the content of the silicon nitride particles is The grain boundary phase contains Al, Mg, and Si, and the content of Al in terms of oxide is 95 wt% or more based on the entire silicon nitride sintered body, and the grain boundary phase contains Al, Mg, and Si.
  • the Mg content is 6 mol% or more and 50 mol% or less
  • the Mg content when converted to oxide is 20 mol% or more and 60 mol% or less
  • the content of Si is 33 mol% or more and 60 mol% or less with respect to the entire grain boundary phase.
  • a method for manufacturing a silicon nitride sintered body includes the steps of: heat-treating a silicon nitride molded body, which is a molded body containing silicon nitride particles, under a first condition; and treating the ceramic molded body heat-treated under the first conditions. , heat treating under a second condition having a higher pressure than the first condition, and heating the silicon nitride molded body heat-treated under the second condition from the heating temperature under the second condition to 800° C. at 800° C./h or more. manufacturing a silicon nitride sintered body, which is a sintered body containing the silicon nitride, by cooling at a temperature decreasing rate of .
  • a silicon nitride sintered body with good mechanical properties can be provided.
  • FIG. 1 is a schematic diagram of a silicon nitride sintered body according to this embodiment.
  • FIG. 2 is a schematic diagram of a STEM image of a cross section of a silicon nitride sintered body.
  • FIG. 3 is a flowchart illustrating a method for manufacturing a silicon nitride sintered body according to this embodiment.
  • any cross section is a cross section passing through the center of the sintered body and a cross section located 0.3 mm or more inside from the surface of the sintered body. If the sintered body is a sphere, the cross section should be a cross section passing through the center of the sphere and at least 0.3 mm inside from the surface of the sintered body. Furthermore, in the measurement using an "arbitrary cross section", the average of three observation points separated by 1 mm or more is used.
  • FIG. 1 is a schematic diagram of a silicon nitride sintered body according to this embodiment.
  • the silicon nitride sintered body 1 according to this embodiment is a sintered body of silicon nitride particles.
  • the silicon nitride sintered body 1 may be used for any purpose, and may be used, for example, as a ball of a ball bearing (such as a bearing ball), or as a raw ball for a bearing ball.
  • the raw ball here means an intermediate product when the final product is a bearing ball. For example, by polishing the surface of the silicon nitride sintered body 1, the final product, the bearing ball, is formed.
  • the shape of the silicon nitride sintered body 1 may be arbitrary, in this embodiment, it is spherical.
  • the spherical shape here is not limited to a perfect sphere.
  • the silicon nitride sintered body 1 may have a sphericity of preferably within 3%, more preferably within 2.5%, and still more preferably within 2% of the diameter.
  • the sphericity is preferably 1.5 mm or less, more preferably 1.25 mm or less, and even more preferably 1.0 mm or less.
  • the sphericity is preferably 0.3 mm or less, more preferably 0.25 mm or less, and even more preferably 0.2 mm or less.
  • the diameter here may refer to an average diameter (arithmetic mean value of the maximum value and minimum value of the diameter).
  • the diameter of the silicon nitride sintered body 1 is preferably 0.5 mm or more and 80 mm or less, more preferably 30 mm or more and 55 mm or less, even more preferably 45 mm or more and 55 mm or less, and 49 mm or more and 51 mm or less. It is even more preferable. If the diameter is within this range, it can be suitably used, for example, as a bearing ball.
  • FIG. 2 is a schematic diagram of a STEM image of a cross section of a silicon nitride sintered body.
  • silicon nitride sintered body 1 includes silicon nitride particles 2 and a grain boundary phase 3 located around silicon nitride particles 2.
  • the periphery here is not limited to the entire section of the outer periphery of the silicon nitride particles 2, but may refer to a part of the entire section of the outer periphery of the silicon nitride particles 2. That is, it can be said that the grain boundary phase 3 is not precipitated inside the silicon nitride particles 2, but is provided outside the silicon nitride particles 2 (adjacent to the silicon nitride particles 2). Note that FIG.
  • FIG. 2 schematically shows an example of an image (STEM image) obtained when a cross section of the silicon nitride sintered body 1 is photographed using a STEM (scanning transmission electron microscope).
  • STEM image an image obtained when a cross section of the silicon nitride sintered body 1 is photographed using a STEM (scanning transmission electron microscope).
  • STEM-EDX energy dispersive X-ray spectrometer
  • an arbitrary cross section of the silicon nitride sintered body 1 is processed into a thin piece with a thickness of 100 nm or less using FIB (focused ion beam: Helios 1200 manufactured by FEI), and STEM-EDX (TEM: JEM-2010F manufactured by JEOL Ltd.) is processed.
  • FIB focused ion beam: Helios 1200 manufactured by FEI
  • STEM-EDX TEM: JEM-2010F manufactured by JEOL Ltd.
  • the range where the nitrogen concentration is 15 at% or more is determined to be silicon nitride particle 2
  • the range where the oxygen concentration is 30 at% or more may be determined to be grain boundary phase 3.
  • the high-density range can be determined visually when a mapping image is created using black for the low-density areas and any color other than black for the high-density areas.
  • the silicon nitride particles 2 refer to particles of silicon nitride (Si 3 N 4 ).
  • the length of the silicon nitride particles 2 is preferably 1 ⁇ m or more and 20 ⁇ m or less, more preferably 2 ⁇ m or more and 15 ⁇ m or less, and even more preferably 3 ⁇ m or more and 12 ⁇ m or less. When the size of the silicon nitride particles 2 falls within this range, good mechanical properties can be achieved.
  • the length of the silicon nitride particles 2 is the length of the longest part of the target silicon nitride particles 2 in a unit area of 20 ⁇ m x 20 ⁇ m when an arbitrary cross section of the silicon nitride sintered body 1 is photographed (long diameter ) is the average value of Only silicon nitride particles completely contained within a unit area are used to calculate the average value. That is, silicon nitride particles that exist only partially within a unit area are excluded from the calculation of the average value. Note that STEM may be used to photograph the cross section of the silicon nitride sintered body 1 here.
  • the content of silicon nitride particles 2 is 95 wt% or more, preferably 95 wt% or more and 99.5 wt% or less, and 95.5 wt% or more and 99 wt% or less, based on the entire silicon nitride sintered body 1. It is more preferable that there be. By setting the content of silicon nitride particles 2 within this range, an appropriate amount of silicon nitride particles 2 can be included and mechanical properties can be appropriately improved. The content of silicon nitride particles 2 can be measured from the impurity concentration of silicon nitride sintered body 1.
  • the impurity concentration is determined by processing the silicon nitride sintered body 1 into a prismatic size of 10 mm x 10 mm x 20 mm, powdering it, and then using ICP emission spectroscopy (manufactured by Hitachi High-Tech Science Co., Ltd.: SPS-3520UVDD).
  • the impurity concentration (wt%) can be measured to determine the silicon nitride content of the residue.
  • the sample is not limited to the above, and any shape may be used as long as the sample has a volume that weighs approximately 5 mg.
  • the grain boundary phase 3 is a phase formed around the silicon nitride particles 2, and can also be said to be a phase located between the silicon nitride particles 2.
  • the area ratio which is the ratio of the area of the grain boundary phase 3 to the area of the entire cross section, is preferably 10% or less, and 1% or more and 7% or less. More preferably, it is 1.5% or more and 3% or less. When the area ratio falls within this range, an appropriate amount of silicon nitride particles 2 can be included and good mechanical properties can be achieved.
  • the area ratio of the grain boundary phase 3 is the ratio of the grain boundary phase 3 included in the unit area to the unit area of 10 ⁇ m x 10 ⁇ m when an arbitrary cross section of the silicon nitride sintered body 1 is photographed. It can be calculated as a ratio of area.
  • STEM may be used to photograph the cross section of the silicon nitride sintered body 1 here.
  • the oxygen distribution in the STEM-EDX oxygen mapping image may be binarized using a predetermined brightness value as a threshold, and the range of high oxygen concentration may be taken as the area of the grain boundary phase 3 per unit area.
  • the area ratio can be determined from an image binarized by the brightness corresponding to a place where the oxygen concentration is 30 at % or more and the brightness other than that.
  • the components contained in the grain boundary phase 3 will be explained.
  • the components contained in the grain boundary phase 3 and the content of the components can be measured by STEM-EDX.
  • an arbitrary cross section of the silicon nitride sintered body 1 is processed into a thin piece with a thickness of 100 nm or less using FIB (focused ion beam), the sample surface is coated with Pt (10 nm), and quantitative analysis is performed using STEM-EDX. You can go. Further, the analysis may be performed using a carbon coat (approximately 6 nm) instead of the Pt coat.
  • the acceleration voltage during observation and measurement was 200 kV.
  • Grain boundary phase 3 contains Al, Mg, and Si.
  • the content of Al in the grain boundary phase 3 in terms of oxide is preferably 6 mol% or more and 50 mol% or less, and preferably 7 mol% or more and 40 mol% or less, based on the entire grain boundary phase 3. More preferably, it is 8 mol% or more and 35 mol% or less.
  • the content of Al in terms of oxides refers to the content of Al in terms of the content of each component contained in the grain boundary phase 3, assuming that all components other than oxygen and nitrogen contained in the grain boundary phase 3 are oxides. It refers to the ratio of the content of Al oxide (Al 2 O 3 ) contained in the grain boundary phase 3 to the total oxide of the components.
  • the mechanical properties of the silicon nitride sintered body 1 can be appropriately improved. More specifically, when the Al content is 6 mol % or more, it is possible to suppress the generation of MgSiO 3 and suppress the decrease in fracture toughness value. Moreover, since the content of Al is 50 mol % or less, it is possible to suppress the melting point of the liquid phase from becoming high and to suppress a decrease in sinterability.
  • the grain boundary phase 3 preferably has an Mg content of 20 mol% or more and 60 mol% or less, and preferably 23 mol% or more and 57 mol% or less, based on the entire grain boundary phase 3, when converted to oxide. More preferably, it is 25 mol% or more and 55 mol% or less.
  • the content of Mg in terms of oxide refers to the total amount of oxide of each component contained in the grain boundary phase 3, assuming that each component contained in the grain boundary phase 3 is an oxide. It refers to the ratio of the content of Mg oxide (MgO) contained in the grain boundary phase 3 to With the Mg content within this range, the mechanical properties of the silicon nitride sintered body 1 can be appropriately improved.
  • the Mg content is 20 mol % or more, it is possible to suppress a decrease in wettability of the liquid phase, thereby suppressing a decrease in sinterability. Further, by setting the Mg content to 60 mol % or less, it is possible to suppress thermal expansion of the grain boundary phase from becoming a problem and to suppress the formation of defects.
  • the grain boundary phase 3 preferably has a Si content of 33 mol% or more and 60 mol% or less, and preferably 35 mol% or more and 53 mol% or less, based on the entire grain boundary phase 3 in terms of oxide. More preferably, it is 37 mol% or more and 47 mol% or less.
  • the Si content in terms of oxides refers to the total amount of oxides of each component contained in the grain boundary phase 3, assuming that each component contained in the grain boundary phase 3 is an oxide. It refers to the ratio of the content of Si oxide (SiO 2 ) contained in the grain boundary phase 3 to With the Si content within this range, the mechanical properties of the silicon nitride sintered body 1 can be appropriately improved.
  • the Si content is 33 mol% or more, it is possible to suppress the melting point of the liquid phase from becoming high, thereby suppressing a decrease in sinterability. Moreover, since the content of Si is 60 mol% or less, it is possible to suppress the generation of cristobalite and suppress a decrease in fracture toughness value.
  • the grain boundary phase 3 has an amorphous structure containing Al, Mg, and Si.
  • the grain boundary phase 3 is not limited to only an amorphous structure, but may also include a crystalline structure containing at least one component of Al, Mg, and Si. Whether the grain boundary phase 3 contains a crystal structure can be confirmed by a STEM electron diffraction image of the grain boundary phase 3.
  • the silicon nitride sintered body 1 may contain Ti.
  • the silicon nitride sintered body 1 does not contain Ca and Fe, it may contain them as impurities.
  • the impurity concentration can be measured by processing the silicon nitride sintered body 1 into a prismatic size of 10 mm x 10 mm x 20 mm, powdering it, and then using ICP emission spectroscopy (manufactured by Hitachi High-Tech Science Co., Ltd.: SPS-3520UVDD).
  • the content of Ca in the silicon nitride sintered body 1 is preferably 0.3 wt% or less, and preferably 0.2 wt% or less, based on the entire silicon nitride sintered body 1.
  • the content is preferably 0.1 wt% or less, and more preferably 0.1 wt% or less.
  • the content of Fe in the silicon nitride sintered body 1 is 0.1 wt% or less, and 0.07 wt% with respect to the entire silicon nitride sintered body 1 when converted into an oxide. It is preferably at most 0.05 wt%, more preferably at most 0.05 wt%. With such a small content of Ca and Fe, it is possible to suppress the deterioration of the mechanical properties of the silicon nitride sintered body 1. If the content of Ca and Fe is high, metal silicon and iron silicon oxides will precipitate due to the reduction of silicon, and there is a concern that mechanical properties will deteriorate.
  • the silicon nitride sintered body 1 does not contain Y, it may contain it as an impurity.
  • the content of Y in the silicon nitride sintered body 1 is preferably 1.0 wt% or less, and preferably 0.7 wt% or less, based on the entire silicon nitride sintered body 1.
  • the content is preferably 0.5 wt% or less, and more preferably 0.5 wt% or less. This low content of Y makes it possible to produce a sintered body with a sintering aid that does not contain Y, thereby reducing costs.
  • a silicon nitride sintered body 1 with high sinterability can be manufactured without including Y.
  • the content of Y in terms of oxide is defined similarly to the content of Ca and Fe, and in this embodiment, Y is a component that may be unavoidably mixed, for example, in the manufacturing process.
  • the silicon nitride sintered body 1 does not contain Zr, it may contain it as an impurity.
  • the content of Zr in the silicon nitride sintered body 1 in terms of oxide is preferably 1.0 wt% or less, and preferably 0.7 wt% or less, based on the entire silicon nitride sintered body 1. It is more preferable that the amount is 0.5 wt% or less. This low content of Zr makes it possible to produce a sintered body with a sintering aid that does not contain Zr, thereby reducing costs.
  • a silicon nitride sintered body 1 with high sinterability can be manufactured without including Zr.
  • the content of Zr in terms of oxide is defined similarly to the content of Ca and Fe, and in this embodiment, Zr is a component that may be unavoidably mixed, for example, in the manufacturing process.
  • the fracture toughness value Kc of the silicon nitride sintered body 1 is preferably 6.0 MPa ⁇ m 1/2 or more, more preferably 6.2 MPa ⁇ m 1/2 or more, and 6.5 MPa ⁇ m 1 It is more preferable that it is /2 or more. When the fracture toughness value Kc falls within this range, it can be confirmed that the mechanical properties were appropriately improved. The higher the fracture toughness value Kc of the silicon nitride sintered body 1 is, the more preferable it is, but the upper limit may be, for example, 7.8 MPa ⁇ m 1/2 . Note that the fracture toughness value Kc can be measured according to the method specified in JIS R 1669.
  • the bending strength of the silicon nitride sintered body 1 is preferably 900 MPa or more, more preferably 910 MPa or more, and even more preferably 915 MPa or more.
  • the bending strength is a three-point bending strength at a span of 30 mm measured according to the method specified in JIS R 1669.
  • the number of pores with a diameter of 1 ⁇ m or less is preferably 50 or less, more preferably 30 or less, and even more preferably 10 or less.
  • the number of pores with a diameter of 1 ⁇ m or less falls within this range, mechanical properties can be appropriately improved.
  • the number of pores with a diameter of 1 ⁇ m or less can be measured as follows. Specifically, in SEM (scanning electron microscope: Regulus 8230 manufactured by Hitachi High-Tech) observation of an arbitrary cross section, the number of pores with a diameter of 1 ⁇ m or less included in a field of view of 30 ⁇ m ⁇ 40 ⁇ m was determined in the silicon nitride sintered body 1. The number of pores included has a diameter of 1 ⁇ m or less. The number of pores of other sizes can be measured in the same manner.
  • the number of pores with a diameter of 1 ⁇ m or less is preferably 50 or less, more preferably 30 or less, and even more preferably 10 or less.
  • the number of pores with a diameter of 1 ⁇ m or less falls within this range, mechanical properties can be appropriately improved.
  • pores with a diameter of 1 ⁇ m or less refer to pores with a sphere (circle with the same area as the pore) having the same volume as the pore and a diameter of 1 ⁇ m or less.
  • the number of pores with a diameter of more than 1 ⁇ m and less than 5 ⁇ m is preferably 20 or less, more preferably 10 or less, and even more preferably 5 or less.
  • the lower limit may be 0.
  • the number of pores with a diameter of more than 1 ⁇ m and less than 5 ⁇ m falls within this range, mechanical properties can be appropriately improved.
  • the pores having a diameter larger than 1 ⁇ m and 5 ⁇ m or less refer to pores in which a sphere having the same volume as the pore (a circle having the same area as the pore) has a diameter larger than 1 ⁇ m and 5 ⁇ m or less.
  • the number of pores with a diameter larger than 5 ⁇ m is preferably 10 or less, more preferably 5 or less, and even more preferably 2 or less.
  • the number of pores with a diameter larger than 5 ⁇ m falls within this range, mechanical properties can be appropriately improved.
  • pores having a diameter larger than 5 ⁇ m refer to pores in which a sphere having the same volume as the pore (a circle having the same area as the pore) has a diameter larger than 5 ⁇ m.
  • FIG. 3 is a flowchart illustrating a method for manufacturing a silicon nitride sintered body according to this embodiment.
  • a silicon nitride molded body is a molded body obtained by molding a raw material containing silicon nitride particles into a desired shape.
  • silicon nitride particles and a sintering aid are mixed to obtain a raw material.
  • Components other than the silicon nitride particles and the sintering aid may also be mixed into the raw material.
  • the surface of the silicon nitride particles used as a raw material may be coated with silicon oxide in addition to the silicon nitride component.
  • Silicon oxide is a compound containing silicon and oxygen, and may have any composition containing silicon and oxygen, for example, silicon oxide (SiO 2 ).
  • a sintering aid containing Al and Mg As the sintering agent used as a raw material, it is preferable to use a sintering aid containing Al and Mg.
  • spinel magnesia alumina spinel; MgO.Al 2 O 3
  • the sintering aid is not limited to this, and any one containing Al and Mg may be used.
  • a sintering aid containing Al e.g. Al 2 O 3
  • a sintering aid containing Mg e.g. MgO
  • Sintering aids other than spinel may be used.
  • a sintering aid containing Si in addition to Al and Mg may be used.
  • a sintering aid containing Al, a sintering aid containing Mg, and a sintering aid containing Si may be used in combination, or among Al, Mg, and Si, a sintering aid containing Al, Mg, and Si may be used.
  • a sintering aid containing two of these may be mixed with a sintering aid containing the remaining one, or a sintering aid containing all of Al, Mg, and Si may be used. .
  • the blending ratio of silicon nitride particles and sintering aid in the raw materials may be arbitrary.
  • the content of silicon nitride particles 2 in the silicon nitride sintered body 1 and the content of each of Al, Mg, and Si contained in the grain boundary phase 3 of the silicon nitride sintered body 1 are set as above. It is preferable to set the blending ratio within a range.
  • the amount of the sintering aid added to the total amount of silicon nitride particles and sintering aid in the raw material is preferably 2 mol% or more and 5 mol% or less, and 2 It is more preferably .5 mol% or more and 5 mol% or less, and even more preferably 3 mol% or more and 4 mol% or less.
  • the mechanical properties of the sintered body can be appropriately improved.
  • a mold is filled with a raw material containing silicon nitride particles and a sintering aid, and then demolded to obtain a silicon nitride molded body.
  • the method for producing the molded body may be arbitrary.
  • the silicon nitride molded body may be molded by a gel casting method. The molding method using the gel casting method will be explained below.
  • silicon nitride particles, a sintering aid, and a solvent are mixed to produce a raw material slurry as a raw material.
  • the raw material slurry is a slurry in which silicon nitride particles and a sintering aid are dispersed in a solvent.
  • the method for producing the raw material slurry is not particularly limited, and at least one of a dispersant, a resin, and a resin curing agent may be appropriately added to the slurry containing silicon nitride particles, a sintering aid, and a solvent depending on the type of solvent. Bye.
  • the solvent is a liquid for uniformly mixing and molding the silicon nitride particles, sintering aid, resin, and resin curing agent.
  • the solvent is, for example, water, an organic solvent, or an alcohol, and it is preferable to use a solvent that does not remain in the silicon nitride sintered body 1 after sintering.
  • the alcohol for example, methyl alcohol and ethyl alcohol can be used.
  • the organic solvent for example, benzene, toluene, and xylene can be used. These solvents may be used alone or may be mixed as appropriate.
  • a dispersant is an additive that assists in dispersing silicon nitride particles into a solvent.
  • Dispersants include, for example, pH adjusters such as tetramethylammonium hydroxide, polymeric dispersants such as polycarboxylic acid polymers, inorganic dispersants such as phosphates such as sodium hexametaphosphate, anionic dispersants, and cationic dispersants.
  • Organic surfactant type dispersants such as surfactants and nonionic types may be used.
  • silicon nitride particles, a solvent, a dispersant, and a sintering aid are first mixed to form a slurry.
  • the amount of silicon nitride particles added to the solvent is preferably 35% by volume or more and 65% by volume or less, more preferably 40% by volume or more and 60% by volume or less, and 45% by volume. More preferably, the content is 55% by volume or less. With such a blending ratio, a silicon nitride molded body can be appropriately produced.
  • the amount of dispersant added to the silicon nitride particles is preferably 0.3% by weight or more and 3% by weight or less, and preferably 0.4% by weight or more and 2% by weight or less. is more preferable, and even more preferably 0.5% by weight or more and 1% by weight or less. With such a blending ratio, a silicon nitride molded body can be appropriately produced.
  • a resin and a resin curing agent are added to the mixed slurry to produce a raw material slurry for casting. More specifically, a resin and a resin curing agent (polymerization initiator) are added to the slurry.
  • the resin is a resin that polymerizes and hardens when a resin curing agent is added, and in this embodiment, it is preferably a resin that dissolves in the solvent of the slurry (here, a water-soluble resin).
  • the resin here is, for example, a water-soluble epoxy resin, but is not limited to an epoxy resin, and may be any resin that polymerizes and hardens when a resin curing agent is added.
  • a resin curing agent is an additive that is added to a resin to polymerize and harden the resin.
  • the resin curing agent here is, for example, a mixture of triethylenetetramine and dimethylaminomethyl, but is not limited thereto, and may be any additive that polymerizes and hardens the resin when added to the resin. .
  • a resin-added raw material slurry (hereinafter also referred to as a first raw material slurry) in which a resin is added to a slurry, and a curing agent-added raw material slurry in which a resin curing agent is added to a slurry (hereinafter also referred to as a second raw material slurry) and prepare. Then, the first raw material slurry and the second raw material slurry are mixed to obtain a mixed raw material slurry.
  • the amount of resin added to the silicon nitride particles in the raw material slurry is preferably 1% by weight or more and 10% by weight or less, more preferably 1.5% by weight or more and 8% by weight or less.
  • the content is preferably 2% by weight or more and 5% by weight or less.
  • the amount of the resin curing agent added to the resin is preferably a stoichiometrically appropriate amount of the added resin. With such a blending ratio, a silicon nitride molded body can be appropriately produced.
  • the raw material slurry is injected into the mold.
  • the resin and the resin curing agent are separately added to the slurry and then mixed, that is, the first raw material slurry and the second raw material slurry are separately generated and mixed, but the invention is not limited thereto.
  • both a resin and a resin curing agent may be added to the slurry, and the raw material slurry to which both have been added may be poured into a mold.
  • the raw material slurry is supplied to the mold and held at a predetermined holding temperature for a predetermined holding time.
  • the holding temperature here is preferably 25°C or more and 100°C or less, more preferably 30°C or more and 80°C or less, and even more preferably 40°C or more and 60°C or less.
  • the holding time here is preferably 1 hour or more and 48 hours or less, more preferably 2 hours or more and 24 hours or less, and even more preferably 3 hours or more and 12 hours or less.
  • pressing processing is not performed on the mold to which the raw material slurry is supplied. That is, a pressure higher than atmospheric pressure is not applied to the mold to which the raw material slurry is supplied.
  • a pressure higher than atmospheric pressure may be applied to the raw material slurry.
  • the cured body obtained by hardening the raw material slurry is demolded (taken out) from the mold, and the cured body is appropriately dried and degreased to obtain a silicon nitride molded body.
  • the demolded cured body is dried to form a dry molded body, and the dried molded body is degreased to form a silicon nitride molded body.
  • the drying conditions are arbitrary, for example, a humidification drying process and a hot air drying process are performed. In the humidification and drying process, the cured product is maintained for 24 hours or more and 120 hours or less in an environment where the humidity is 30% or more and 98% or less and the temperature is 25°C or more and 50°C or less.
  • the cured product is held in a hot air drying process for 3 to 48 hours while blowing air at a temperature of 40°C to 100°C to obtain a dry molded product.
  • the degreasing method is also arbitrary, but for example, the dried molded body is held in an environment with a temperature of 550° C. or more and 750° C. or less for 2 hours or more and 12 hours or less to degrease and obtain a silicon nitride molded body.
  • drying is a process of removing the solvent in the cured body
  • degreasing is a process of removing the resin in the cured body (dried molded body).
  • the silicon nitride molded body formed by this manufacturing method preferably has a relative density of 40% or more, more preferably 45% or more, and even more preferably 50% or more. Although a higher relative density is preferable, it may be 65% or less, 60% or less, or 55% or less.
  • the relative density here refers to the value obtained by dividing the molded body density by the material density.
  • the compact density is a value obtained by dividing the volume obtained from the dimensions of the silicon nitride compact by the weight of the silicon nitride compact.
  • the material density is calculated from the composition ratio of silicon nitride particles and sintering aid and the theoretical density of each material. For example , the material density is X mol% and Y When mixed at a composition ratio of mol %, it can be calculated from the following formula (1).
  • a silicon nitride molded body is prepared using the gel casting method as described above.
  • the method for producing the silicon nitride molded body is not limited to the gel casting method, and may be any method.
  • a powder press method may be used in which silicon nitride particles and a sintering aid filled in a mold are pressurized to form a silicon nitride molded body.
  • the produced silicon nitride molded body is heat treated (fired) under the first conditions (step S12).
  • the temperature at which the silicon nitride molded body is heated is the first heating temperature
  • the pressure applied to the silicon nitride molded body is the first pressure
  • the time for maintaining the silicon nitride molded body at the first heating temperature is the first heating temperature. This is the first heating time.
  • the first conditions, that is, the first heating temperature, the first pressure, and the first heating time may be set as appropriate, and may be in the following ranges, for example.
  • the first heating temperature is preferably 1600°C or more and 1800°C or less, more preferably 1620°C or more and 1780°C or less, and even more preferably 1650°C or more and 1750°C or less.
  • the first pressure is preferably 0.01 MPa or more and 5 MPa or less, more preferably 0.05 MPa or more and 3 MPa or less, and even more preferably 0.1 MPa or more and 1 MPa or less.
  • the heat treatment under the first condition is most preferably performed at normal pressure (atmospheric pressure), that is, 0.1 MPa, from the viewpoint of mass productivity and ease of operation.
  • the first heating time is preferably 1 hour or more and 24 hours or less, more preferably 2 hours or more and 20 hours or less, and even more preferably 5 hours or more and 15 hours or less.
  • each parameter under the first condition falls within this range, the relative density of the molded body can be appropriately increased and the sinterability can be improved.
  • the heat treatment under the first condition is preferably performed under a nitrogen atmosphere.
  • the silicon nitride particles can be appropriately sintered.
  • the heat treatment under the second and third conditions described below is preferably performed under a nitrogen atmosphere, but can also be performed under a mixed atmosphere of nitrogen and an inert gas such as argon.
  • the silicon nitride molded body is thus subjected to the heat treatment under the first conditions, thereby performing the first sintering, that is, the primary sintering.
  • the first sintering that is, the primary sintering.
  • the primary sintered body (silicon nitride molded body heat-treated under the first conditions) is heat-treated (fired) under the second conditions (step S14).
  • silicon nitride sintered body 1 is obtained.
  • the heat treatment under the second conditions is heat treatment in a higher pressure environment than the heat treatment under the first conditions, and HIP (Hot Isostatic Pressing) treatment may be applied.
  • the temperature at which the primary sintered body (silicon nitride molded body heat-treated under the first condition) is heated is the second heating temperature
  • the pressure applied to the primary sintered body is the second pressure
  • the time to maintain the temperature at the second heating temperature (heating time) is the second heating time
  • the rate at which the temperature is raised to the second heating temperature is the second heating rate
  • the temperature decreasing rate from the second heating temperature after heating is the second cooling rate.
  • the second conditions that is, the second heating temperature, the second pressure, the second heating time, the second temperature increase rate, and the second temperature decrease rate may be set as appropriate, and may be set, for example, in the following ranges.
  • the second heating temperature is preferably 1,600°C or more and 1,900°C or less, more preferably 1,680°C or more and 1,850°C or less, and even more preferably 1,700°C or more and 1,800°C or less.
  • the second pressure is higher than the first pressure, preferably 50 MPa or more and 200 MPa or less, more preferably 80 MPa or more and 195 MPa or less, and even more preferably 100 MPa or more and 190 MPa or less.
  • the difference between the first pressure and the second pressure is preferably 50 MPa or more, more preferably 80 MPa or more, and most preferably 100 MPa or more.
  • the second heating time is preferably 0.1 hours or more and 10 hours or less, more preferably 1 hour or more and 7 hours or less, and even more preferably 3 hours or more and 5 hours or less.
  • the first heating time and the second heating time are preferably the first heating time ⁇ the second heating time.
  • the second temperature increase rate is preferably 200°C/h or more and 1000°C/h or less, more preferably 300°C/h or more and 800°C/h or less, and 400°C/h or more and 600°C/h or less. It is more preferable that The temperature increase rate is an average temperature increase rate from a predetermined temperature to a predetermined temperature.
  • the second temperature increase rate is an average temperature increase rate from room temperature to the second heating temperature.
  • the second temperature decreasing rate is preferably 800°C/h or more, more preferably 800°C/h or more and 10,000°C/h or less, and 1,500°C/h or more and 5,000°C/h or less. It is more preferable that The second temperature drop rate refers to the temperature drop rate from the second heating temperature to 800 °C, and the temperature drop rate from 800 °C to room temperature may be, for example, 300 °C / h or more and 1,500 °C / h or less. .
  • the temperature decreasing rate is an average temperature decreasing rate from a predetermined temperature to a predetermined temperature. For example, the second temperature decreasing rate is an average temperature decreasing rate from the second heating temperature to 800°C.
  • the temperature decreasing rate from 800°C to room temperature is the average temperature decreasing rate from 800°C to room temperature.
  • the primary sintered body can be appropriately sintered and the mechanical properties of the sintered body can be appropriately improved.
  • the second cooling rate is set to 800° C./h or more, compressive stress can be applied to the surface of the primary sintered body, thereby suppressing cracking during cooling.
  • the temperature decreasing rate is as high as 800° C./h or more, the manufacturing process can be shortened.
  • the second temperature drop rate 800°C or higher, the contents of Al, Mg, and Si in the silicon nitride sintered body 1 can be maintained within the ranges described in this embodiment, and the silicon nitride sintered body Decrease in mechanical properties of the body 1 can be suppressed. Furthermore, by setting the second temperature drop rate to 10,000° C./h or less, it is possible to suppress tensile stress from acting on the surface of the sintered body, thereby suppressing damage. Conventionally, it was thought that it was necessary to gradually lower the temperature from the heating temperature in order to relieve thermal stress.
  • the silicon nitride molded body is subjected to two stages of heat treatment, that is, heat treatment under the first condition and heat treatment under the second condition.
  • Heat treatment under the third condition may be performed between the heat treatment under the second condition and the heat treatment under the second condition. That is, in this case, the silicon nitride molded body heat-treated under the first condition is heat-treated under the third condition, and the silicon nitride molded body heat-treated under the third condition is heat-treated under the second condition to obtain silicon nitride sintered body 1.
  • heat treatment may also be performed under other conditions.
  • the heat treatment under the third condition is heat treatment under a higher pressure environment than the heat treatment under the first condition, and is heat treatment under a lower pressure environment than the heat treatment under the second condition.
  • the temperature at which the primary sintered body (the silicon nitride molded body heat-treated under the first condition) is heated is the third heating temperature
  • the pressure applied to the primary sintered body is the third pressure
  • the third conditions, that is, the third heating temperature, the third pressure, and the third heating time may be set as appropriate, and may be in the following ranges, for example.
  • the third heating temperature is preferably 1650°C or more and 1900°C or less, more preferably 1680°C or more and 1850°C or less, and even more preferably 1700°C or more and 1800°C or less.
  • the third pressure is higher than the first pressure and lower than the second pressure.
  • the third pressure is preferably 0.5 MPa or more and 20 MPa or less, more preferably 0.6 MPa or more and 15 MPa or less, and even more preferably 0.7 MPa or more and 10 MPa or less.
  • the third heating time is preferably 0.1 hours or more and 10 hours or less, more preferably 1 hour or more and 7 hours or less, and even more preferably 3 hours or more and 5 hours or less.
  • the first condition in the case where the heat treatment is not performed in three stages is as follows.
  • the first heating temperature is more preferably 1700°C or more and 1750°C or less
  • the first pressure is preferably 0.1 MPa or more and 1 MPa or less
  • the first heating time is 10 The duration is preferably at least 20 hours.
  • the first condition in the case of performing heat treatment in three stages is as follows.
  • the first heating temperature is more preferably 1650°C or more and 1750°C or less
  • the first pressure is preferably 0.1 MPa or more and 1 MPa or less
  • the first heating time is 5 The duration is preferably at least 10 hours.
  • the silicon nitride sintered body 1 containing Al, Mg, and Si in the grain boundary phase 3 is manufactured by the above manufacturing method, but in this manufacturing method, the grain boundary phase 3
  • the present invention is not limited to the silicon nitride sintered body 1 containing Al, Mg, and Si, but can be applied to a silicon nitride sintered body containing any composition in the grain boundary phase 3.
  • the silicon nitride sintered body 1 containing Al, Mg, and Si in the grain boundary phase 3 in order to manufacture the silicon nitride sintered body 1 containing Al, Mg, and Si in the grain boundary phase 3, the above-mentioned sintering aid was used.
  • the step of heat-treating a silicon nitride molded body, which is a molded body containing silicon nitride particles, under the first condition, and the ceramic molded body heat-treated under the first condition are performed under the first condition.
  • the sintered body containing silicon nitride is heat-treated under a second condition of high pressure, and the ceramic sintered body heat-treated under the second condition is cooled at a cooling rate of 800°C/h or more.
  • the manufacturing method including the step of manufacturing a certain silicon nitride sintered body can be applied to materials other than the silicon nitride sintered body 1 containing Al, Mg, and Si.
  • a sintering aid is used that matches the composition of the silicon nitride sintered body to be obtained.
  • rare earth oxides such as yttrium oxide (Y 2 O 3 ) and ytterbium oxide (Yb 2 O 3 ) can be used as the sintering aid.
  • the silicon nitride sintered body 1 includes silicon nitride particles 2 and the grain boundary phase 3 located around the silicon nitride particles 2.
  • the content of silicon nitride particles 2 is 95 wt% or more based on the entire silicon nitride sintered body 1
  • the grain boundary phase 3 contains Al, Mg, and Si.
  • the content of Al in terms of oxide is 6 mol% or more and not more than 50 mol% with respect to the entire grain boundary phase 3
  • the content of Mg in terms of oxide is The amount of Si is 20 mol% or more and 60 mol% or less with respect to the entire grain boundary phase 3, and the Si content when converted to oxide is 33 mol% or more and 60 mol% with respect to the entire grain boundary phase 3. It is as follows.
  • the silicon nitride sintered body 1 of the present disclosure appropriately improves mechanical properties because the content of silicon nitride particles 2 and the content of Al, Mg, and Si contained in the grain boundary phase 3 are within the above ranges. can.
  • a silicon nitride sintered body 1 according to a second aspect of the present disclosure is a silicon nitride sintered body according to the first aspect, in which, in an arbitrary cross section of the silicon nitride sintered body 1, a grain boundary phase 3 with respect to the entire cross section It is preferable that the area ratio of is 10% or less. When the area ratio of the grain boundary phase 3 falls within this range, an appropriate amount of silicon nitride particles 2 can be included, and the mechanical properties can be improved more appropriately.
  • the silicon nitride sintered body 1 according to the third aspect of the present disclosure is the silicon nitride sintered body according to the first aspect or the second aspect, in which the grain boundary phase 3 contains Ca in terms of oxides.
  • the amount of Fe is 0.3 wt% or less with respect to the entire grain boundary phase 3, and the Fe content when converted to oxide is 0.3 wt% or less with respect to the entire grain boundary phase 3. It is preferable that there be. With such a low content of Ca and Fe, mechanical properties can be improved more appropriately.
  • a silicon nitride sintered body 1 according to a fourth aspect of the present disclosure is a silicon nitride sintered body according to any one of the first to third aspects, wherein the grain boundary phase 3 is The content of Y is 1.0 wt% or less with respect to the entire grain boundary phase 3, and the content of Zr when converted to oxide is 1.0 wt% with respect to the entire grain boundary phase 3. % or less. With such a low content of Y and Zr, manufacturing costs can be reduced. Further, by setting the contents of Al, Mg, and Si within the above ranges, it is possible to manufacture a silicon nitride sintered body 1 with high sinterability.
  • a silicon nitride sintered body 1 according to a sixth aspect of the present disclosure is a silicon nitride sintered body according to any one of the first to fifth aspects, and has a fracture toughness value Kc of 6.0 or more, and has a fracture toughness value Kc of 6.0 or more. It is preferable that the strength is 900 or more. When the fracture toughness value and bending strength are within this range, mechanical properties can be improved more appropriately.
  • the silicon nitride sintered body 1 according to the seventh aspect of the present disclosure is the silicon nitride sintered body according to any one of the first to sixth aspects, and is preferably used as a bearing ball.
  • the silicon nitride sintered body 1 of the present disclosure can be appropriately applied to bearing balls.
  • a method for producing a silicon nitride sintered body includes the steps of heat-treating a silicon nitride molded body, which is a molded body containing silicon nitride particles, under a first condition; a step of heat treating the molded body under a second condition having a higher pressure than the first condition; and heating the silicon nitride molded body heat-treated under the second condition from the heating temperature of the second condition to 800°C at 800°C/h or more; manufacturing a silicon nitride sintered body that is a sintered body containing silicon nitride by cooling at a temperature decreasing rate (second temperature decreasing rate).
  • second temperature decreasing rate a temperature decreasing rate
  • Table 1 is a table showing the sintered bodies of each example.
  • Example 1 silicon nitride particles (manufactured by Denka: SN-9FWS), spinel powder as a sintering aid, ion-exchanged water as a solvent, and tetramethylammonium hydroxide as a dispersant were put into a bead mill. and mixed and milled for 1.5 hours to produce a slurry.
  • the amount of Sp that is, the ratio of the amount of added Sp of the spinel powder to the silicon nitride particles was 3.6 mol%.
  • a water-soluble epoxy resin manufactured by Nagase ChemteX: EX614B, EX512
  • a resin is added and mixed to a part of the slurry to produce a first raw material slurry, and another part of the slurry is mixed with a water-soluble epoxy resin as a resin.
  • the first silicon nitride slurry and the second silicon nitride slurry are depressurized and degassed in separate tanks, and while being stirred in the tanks, they are simultaneously sent to a mixing mixer and mixed to form a raw material slurry. and supplied to a mold connected to the mixer outlet. Then, the mold filled with the raw material slurry (a mixture of the first raw material slurry and the second raw material slurry) was held at 50° C. for 5 hours to cure the raw material slurry and obtain a cured body. Then, the cured product was removed from the mold, humidified and dried at 30°C for 4 days, and then dried with hot air at 50°C to obtain a dry molded product.
  • the raw material slurry a mixture of the first raw material slurry and the second raw material slurry
  • the dried molded body was then heated at 600° C. for 3 hours to degrease it to obtain a silicon nitride molded body.
  • the obtained silicon nitride molded body was heat treated under the first conditions and then heat treated under the second conditions to obtain a silicon nitride sintered body.
  • the heating temperature (first heating temperature) was 1650° C.
  • the holding time (first holding time) was 15 h
  • the pressure (first pressure) was 0.1 MPa.
  • the heating temperature (second heating temperature) was 1750°C
  • the holding time (second holding time) was 5 hours
  • the pressure (second pressure) was 190 MPa
  • the cooling rate (second cooling rate) was 600°C/ It was set as h. Note that in Example 1, heat treatment under the third condition was not performed.
  • the obtained silicon nitride sintered body is subjected to the method described in this embodiment to determine the content (wt%) of silicon nitride (Si 3 N 4 ) particles relative to the entire silicon nitride sintered body and the content of oxides.
  • Table 1 shows the density and relative density of the silicon nitride sintered body (primary sintered body) after the heat treatment under the first condition or the first and third conditions.
  • Example 2-Example 6 silicon nitride sintered bodies were prepared in the same manner as in Example 1, except that the amount of Sp and the heat treatment under the first, second, and third conditions were as shown in Table 1. Obtained.
  • Table 1 shows the measurement results of the contents of silicon nitride, Al, Mg, and Si in the obtained silicon nitride sintered body. Table 1 also shows the results of the density and relative density of the primary sintered body.
  • Example 7-Example 10 silicon nitride sintered bodies were prepared in the same manner as in Example 1, except that the amount of Sp and the heat treatment under the first, second, and third conditions were as shown in Table 1. Obtained.
  • Table 1 shows various measurement results on the obtained silicon nitride sintered body. Table 1 also shows the results of the density and relative density of the primary sintered body.
  • Example 11 In Example 11, yttrium oxide and aluminum oxide were used instead of spinel powder as sintering aids, and the heat treatments under the first, second, and third conditions were as shown in Table 1.
  • a silicon nitride sintered body was obtained in the same manner as in Example 1. The amount of yttrium oxide added to the silicon nitride particles was 3.1 mol%, and the amount of aluminum oxide added to the silicon nitride particles was 6.9 mol%.
  • Table 1 shows various measurement results on the obtained silicon nitride sintered body. Table 1 also shows the results of the density and relative density of the primary sintered body.
  • Evaluation 1 was conducted for Examples 1-7.
  • the fracture toughness value Kc (MPa ⁇ m 1/2 ), the bending strength (MPa), and the number of pores with a diameter of 1 ⁇ m or less were measured.
  • the method described in this embodiment was used for each measurement method.
  • the results of each measurement are shown in Table 1. Those with a fracture toughness value Kc of 6.0 or more and a bending strength of 900 or more are passed (rating A). Items that did not satisfy at least one of the above conditions were rated as failure (rating B).
  • the content of Al does not satisfy at least one of the following: 6 mol% or more and 50 mol% or less, Mg content 20 mol% or more and 60 mol% or less, and Si content 33 mol% or more and 60 mol% or less.
  • the silicon nitride sintered body of Example 1 which is a comparative example, failed in fracture toughness value Kc and bending strength, and could not sufficiently improve mechanical properties.
  • the silicon nitride sintered bodies of Examples 2 to 7, which are Examples that meet the above conditions pass the fracture toughness value Kc and bending strength, indicating that the mechanical properties can be sufficiently improved.
  • the number of pores with a diameter greater than 1 ⁇ m and 5 ⁇ m or less, the number of pores with a diameter greater than 1 ⁇ m and 5 ⁇ m or less, and the number of pores with a diameter greater than 5 ⁇ m. was measured.
  • the method described in this embodiment was used for each measurement method. The results of each measurement are shown in Table 1.
  • Evaluation 2 was conducted for Examples 1-4 and 7-11.
  • evaluation was performed using the results of fracture toughness value Kc (MPa ⁇ m 1/2 ).
  • those whose fracture toughness value Kc was 6.0 or more were evaluated as C (pass), and those whose fracture toughness value Kc was less than 6.0 were evaluated as D (fail).
  • Examples 2-4, 7, 8, 10, and 11 in which the temperature decreasing rate (second temperature decreasing rate) in the heat treatment under the second condition was 800° C./h or more were evaluated as C.
  • Examples 1 and 9 according to comparative examples in which the second temperature decreasing rate was less than 800° C./h were evaluated as D.
  • Examples 5 and 6 were evaluated as C.
  • Examples 1 and 2 differ in the temperature decreasing rate (second temperature decreasing rate) in the heat treatment under the second condition in the manufacturing method other than the composition of the grain boundary phase.
  • the relative density after the first condition in Examples 1 and 2 is low at 97%, by setting the second cooling rate to 800°C/h or more as in Example 2, the fracture toughness value Kc becomes acceptable and the mechanical It can be seen that the characteristics can be improved. It can be seen that in Examples 3, 4, 7, and 10, the second cooling rate was 800° C./h or more, the fracture toughness value Kc passed, and the mechanical properties were good. Examples 8 and 9 have different second temperature reduction rates.
  • Example 11 is an example in which yttrium oxide and aluminum oxide were used as sintering aids. It can be seen that the second temperature reduction rate of Example 11 was 800° C./h or more, the fracture toughness value Kc passed, and the mechanical properties were good. It was confirmed that the effect of rapid cooling at the second temperature reduction rate was exhibited even when a sintering aid for spinel powder was not used (for example, when a rare earth sintering aid was used).
  • the embodiment of the present invention has been described above, the embodiment is not limited by the content of this embodiment. Furthermore, the above-mentioned components include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those that are in a so-called equivalent range. Furthermore, the aforementioned components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the constituent elements can be made without departing from the gist of the embodiments described above.

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JP2007039331A (ja) * 2006-09-25 2007-02-15 Toshiba Corp 窒化けい素焼結体の製造方法、それを用いた耐薬品性部材の製造方法および軸受部材の製造方法
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