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WO2015025951A1 - Porous ceramic and method for producing same - Google Patents

Porous ceramic and method for producing same Download PDF

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Publication number
WO2015025951A1
WO2015025951A1 PCT/JP2014/071986 JP2014071986W WO2015025951A1 WO 2015025951 A1 WO2015025951 A1 WO 2015025951A1 JP 2014071986 W JP2014071986 W JP 2014071986W WO 2015025951 A1 WO2015025951 A1 WO 2015025951A1
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ceramic
particles
porous
carbonaceous
pore diameter
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PCT/JP2014/071986
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French (fr)
Japanese (ja)
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宮本 欽生
衛武 陳
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東洋炭素株式会社
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Priority to JP2015532913A priority Critical patent/JPWO2015025951A1/en
Publication of WO2015025951A1 publication Critical patent/WO2015025951A1/en

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    • C04B35/00Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/515Shaped 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
    • C04B35/56Shaped 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 carbides or oxycarbides
    • C04B35/565Shaped 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 carbides or oxycarbides based on silicon carbide
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    • C04B35/58Shaped 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
    • C04B35/581Shaped 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 aluminium nitride
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    • C04B35/515Shaped 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
    • C04B35/58Shaped 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
    • C04B35/584Shaped 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
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    • C04B35/00Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • C04B35/628Coating the powders or the macroscopic reinforcing agents
    • C04B35/62802Powder coating materials
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    • C04B38/00Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
    • C04B38/06Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by burning-out added substances by burning natural expanding materials or by sublimating or melting out added substances
    • C04B38/063Preparing or treating the raw materials individually or as batches
    • C04B38/0635Compounding ingredients
    • C04B38/0645Burnable, meltable, sublimable materials
    • C04B38/068Carbonaceous materials, e.g. coal, carbon, graphite, hydrocarbons
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    • C04B2235/02Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/30Constituents and secondary phases not being of a fibrous nature
    • C04B2235/32Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/3217Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
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    • C04B2235/32Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/3224Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
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    • C04B2235/42Non metallic elements added as constituents or additives, e.g. sulfur, phosphor, selenium or tellurium
    • C04B2235/422Carbon
    • C04B2235/425Graphite
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    • C04B2235/66Specific sintering techniques, e.g. centrifugal sintering
    • C04B2235/666Applying a current during sintering, e.g. plasma sintering [SPS], electrical resistance heating or pulse electric current sintering [PECS]

Definitions

  • the present invention relates to a novel porous ceramic and a method for producing the same.
  • porous ceramics As a method for producing porous ceramics, a method in which ceramic particles are sintered and pores are formed as particle gaps is the most common and widely used. However, in this manufacturing method, since pores are formed by the gaps between the ceramic particles, it is difficult to independently control the pore diameter and the porosity. Moreover, since a hole is formed with sintering, the deformation
  • Patent Document 1 a method of forming a molded body by molding powder containing alumina hollow particles into a predetermined shape, and sintering the obtained molded body
  • Patent Document 2 true spherical resin beads as a pore forming agent
  • Patent Document 2 since the manufacturing method of Patent Document 2 uses resin beads as a pore-forming agent and sinters after degreasing, the ceramic granulated powder penetrates into the pores during sintering, resulting in deformation, complicated shape and high Precision machining was difficult.
  • the present invention provides a porous ceramic that can be processed in a complicated shape and with high accuracy, and that can control the pore diameter, the pore shape, and the porosity independently, and has high strength, and a method for producing the same. It is an object.
  • the present invention provides ceramic particles containing at least one selected from the group consisting of aluminum nitride, silicon carbide, and silicon nitride, and carbonaceous particles on the surface of the carbonaceous particles. After mixing the two so that the ceramic particles adhere uniformly, while pressing the mixture or pressing the mixture, sintering is performed to obtain a sintered body, and then the carbon contained in the sintered body It is characterized by being a porous ceramic produced by oxidizing and burning the porous particles.
  • a porous ceramic having a high strength and capable of independently controlling the pore diameter, the pore shape and the porosity, and capable of processing a complicated shape and high precision, and a method for producing the same. There are excellent effects.
  • FIG. 1 is a structural diagram of a porous ceramic of the present invention.
  • FIG. 6 is a structural diagram of another embodiment of the porous ceramic of the present invention, where (a) is a porous ceramic in which carbonaceous particles are present in some independent pores, and (b) is a carbon for a ceramic material. Porous ceramics in which the weight ratio of the porous material is reduced in the thickness direction. SEM (scanning electron microscope) photograph of material A1 ((a) is 1000 times magnification, (b) is an enlarged view of part B of FIG. 1 (a), and is 5000 times magnification). The graph which shows the relationship between the diameter of the space
  • ceramic particles containing at least one selected from the group consisting of aluminum nitride, silicon carbide, and silicon nitride, and carbonaceous particles are adhered uniformly to the surface of the carbonaceous particles. After mixing the two in this manner, while pressing the mixture or pressing the mixture, the sintered body is obtained by sintering, and then the carbonaceous particles contained in the sintered body are oxidized and burned off. It is manufactured by.
  • the porous ceramic produced in this manner is obtained by mixing and sintering the carbonaceous particles as the pore-forming agent and the ceramic particles as the raw material of the porous ceramic, that is, after forming the ceramic wall, Since it is oxidized and burned off, it can be processed with a complicated shape and high accuracy with almost no deformation during the formation of porous ceramics.
  • that the ceramic particles are uniformly attached to the carbonaceous particles means that the ceramic particles are attached to 90% or more of the entire surface of the carbonaceous particles.
  • the porous ceramic of the present invention can be used in various fields (for example, high-strength heat insulating materials, artificial bones, oil filters, crucibles, vacuum chucks, catalysts). Carrier, spray nozzle, lubricating liquid impregnated bearing, etc.).
  • the particle diameter, shape and amount of carbonaceous particles which are pore forming agents can be independently controlled to desired values.
  • the porous ceramic of the present invention comprises ceramic particles containing at least one selected from the group consisting of aluminum nitride, silicon carbide, and silicon nitride, and carbonaceous particles.
  • the ceramic particles are on the surface of the carbonaceous particles.
  • the carbonaceous particles are preferably spherical or plate-like natural graphite and artificial graphite, or carbon fiber.
  • the carbonaceous particles may include only one type or a plurality of types.
  • the particle size of the carbonaceous particles is preferably 1 ⁇ m or more and 500 ⁇ m or less, more preferably 5 ⁇ m or more and 50 ⁇ m or less, and further preferably 10 ⁇ m or more and 30 ⁇ m or less. If the particle size of the carbonaceous particles becomes too small, there is a possibility of aggregation.
  • the carbonaceous particles are agglomerated too much, the ceramic particles cannot uniformly adhere to the surface of the carbonaceous particles when the carbonaceous particles and the ceramic particles are mixed (that is, where the carbonaceous particles and the carbonaceous particles are in close contact). Since ceramic particles are difficult to adhere to), the thickness of the ceramic wall may not be uniform, and the strength of the structure of the porous ceramic may be reduced. On the other hand, if the particle size of the carbonaceous particles becomes too large, the porosity and the pore size of the independent pores become too large, and the strength of the structure of the porous ceramics may be lowered. Furthermore, the particle diameter of the carbonaceous particles is preferably constant.
  • the particle size distribution of the carbonaceous particles is preferably 80% or more in the range of ⁇ 10% from the average particle size, and 90% or more in the range of ⁇ 10% from the average particle size. More preferred.
  • the particle diameter of the carbonaceous particles is constant, the pore diameter of the independent pores existing in the produced porous ceramic is constant, so that a homogeneous porous structure is obtained and the strength is improved.
  • the ceramic particles may include all of aluminum nitride, silicon carbide, and silicon nitride, may include any two of them, or may include only one of them. However, the ceramic particles are preferably only one of aluminum nitride, silicon carbide, and silicon nitride.
  • the particle diameter of the ceramic particles is preferably 100 nm or more and 50 ⁇ m or less, more preferably 200 nm or more and 5 ⁇ m or less, and further preferably 300 nm or more and 1 ⁇ m or less. If the particle size of the ceramic particles becomes too small, they may aggregate.
  • the ceramic particles are too agglomerated, the ceramic particles cannot uniformly adhere to the surface of the carbonaceous particles when the carbonaceous particles and the ceramic particles are mixed (that is, the location where the agglomerated ceramic particles are attached is the amount of the ceramic particles.
  • the thickness of the ceramic wall is not uniform, and the strength of the porous ceramic structure may be reduced.
  • the particle size of the ceramic particles is too large, the carbon particles cannot be covered uniformly, and the strength of the structure of the porous ceramics may be reduced.
  • the particle diameter of the ceramic particles is preferably constant.
  • the particle size distribution of the ceramic particles is preferably 80% or more in the range of ⁇ 10% from the average particle size, and more preferably 90% or more in the range of ⁇ 10% from the average particle size. preferable.
  • the particle diameter of the ceramic particles is constant, the thickness of the ceramic wall existing in the produced porous ceramic becomes more uniform, and the pore diameter of the voids becomes constant, so that the strength is improved.
  • the particle diameter of the ceramic particles is preferably 1/5 or less, more preferably 1/10 or less of the particle diameter of the carbonaceous particles.
  • the mixing ratio of the carbonaceous particles and the ceramic particles is preferably such that the weight of the carbonaceous particles: the weight of the ceramic particles is 95: 5 to 20:80, and 80:20 to 40: 60 is more preferable.
  • the weight ratio of the ceramic particles is less than 20 wt% (particularly less than 5 wt%), the amount of ceramic is reduced, so that it is difficult to form the thickness of the ceramic wall uniformly, and the strength may be too low.
  • the weight ratio of the ceramic particles exceeds 60 wt% (particularly, exceeds 80 wt%), the amount of the ceramic increases, so that it becomes hard and processing may be difficult.
  • a sintering aid may be added when mixing the carbonaceous particles and the ceramic particles.
  • the sintering aid include yttrium oxide such as Y 2 O 3 , aluminum oxide such as Al 2 O 3, calcium oxide such as CaO, silicon oxide such as SiO 2 , and other rare earth oxides.
  • the method for mixing the carbonaceous particles and the ceramic particles is not particularly limited.
  • a gas phase method, a liquid phase method, a solvent mixing method, a mechanical mixing method, a slurry method, or a combination of these methods can be given.
  • Specific examples of the vapor phase method include a chemical vapor deposition method (CVD method) and a conversion method (CVR method).
  • Specific examples of the liquid phase method include a chemical precipitation method.
  • Specific examples of the slurry method include a gel casting method, slip casting, tape casting, and the like.
  • the method for obtaining the sintered body is not particularly limited. Examples thereof include a discharge plasma sintering method and a hot press method.
  • the firing temperature, firing time, kind of firing atmosphere, firing pressure, and the like can be appropriately set according to the kind, shape, size, and the like of the material to be used.
  • the firing temperature may be 1700 ° C. or higher, for example.
  • the firing temperature is preferably 1700 ° C. or higher and 2100 ° C. or lower, and more preferably 1800 ° C. or higher and 2000 ° C. or lower.
  • the firing time can be, for example, 5 minutes or more and 2 hours or less.
  • the kind of baking atmosphere can be made into inert gas atmosphere, such as a vacuum, nitrogen, argon, for example.
  • the pressure of baking can be 0.01 MPa or more and 50 MPa or less, for example.
  • the ceramic particles uniformly adhered to the surface of the carbonaceous particles are sintered to form a ceramic layer that three-dimensionally covers the carbonaceous particles.
  • the ceramic layer preferably has a continuous structure, and more preferably has a three-dimensional network structure. That is, the plurality of carbonaceous particles are preferably integrated by a ceramic wall having a three-dimensional network structure.
  • silicon carbide is formed on the surface of the carbonaceous particles by a reaction during sintering. This silicon carbide is formed between a plurality of carbonaceous particles. That is, the plurality of carbonaceous particles are covered with silicon carbide and bonded by silicon carbide by sintering. Note that silicon nitride may remain in the porous ceramic.
  • a method for obtaining a porous ceramic is not particularly limited. For example, the method etc. which heat with an atmospheric furnace are mentioned.
  • the temperature and time for oxidizing and burning, the type of atmosphere, the pressure of the atmosphere, and the like can be appropriately set according to the type, shape, size, etc. of the material used.
  • the oxidation burning temperature may be, for example, 500 ° C. or higher, and is preferably 500 ° C. or higher and 1000 ° C. or lower.
  • the oxidation burning time can be, for example, 5 minutes or more and 48 hours or less.
  • the type of the oxidation burnout atmosphere can be, for example, an oxygen pressure controlled atmosphere in which an inert gas such as air, vacuum or nitrogen is mixed.
  • the pressure of the oxidation burnout atmosphere can be set to, for example, 0.01 MPa or more and 10 MPa or less.
  • the sintered body may be formed into a desired shape by machining, or may be near-net molded by mold molding.
  • the method for obtaining a porous ceramic as shown in FIGS. 2A and 2B by oxidizing and burning only a part of the carbonaceous particles is not particularly limited (FIG. 2A).
  • 1 is independent pores
  • 2 is a ceramic wall
  • 3 is a void communicating between the independent pores
  • 4 is a remaining carbonaceous material).
  • rapid heating in an atmospheric furnace, surface oxidation method using a burner flame, and the like can be mentioned.
  • the porous ceramic shown in FIG. 2B is obtained using a burner flame, the burner flame is sprayed from the direction of the arrow A.
  • the sintered body may be formed into a desired shape by machining, or near-net formed by mold forming.
  • the porous ceramic of the present invention is a porous ceramic comprising ceramic particles containing at least one selected from the group consisting of aluminum nitride, silicon carbide, and silicon nitride, and a part of the ceramic particles is A ceramic wall formed by bonding and a plurality of independent pores formed by being surrounded by the ceramic wall, the plurality of independent pores being communicated with each other by a gap having a pore diameter smaller than the independent pore diameter, The pore diameter of the void is from 10 nm to 5 ⁇ m. Since the porous ceramic has independent pores and there are voids communicating between the independent pores, for example, when used as an artificial bone, the connectivity between the pores becomes high. Therefore, the new bone can invade to the deep part of the pores at an early stage, and the function as a bone can be recovered early.
  • the cumulative pore volume is calculated using the mercury intrusion method, it is desirable that 60% or more of the total cumulative pore volume exists in the range of ⁇ 50% from the average pore diameter of the voids, and particularly 75% or more. It is desirable to exist. If it is such a structure, when a liquid and gas permeate
  • the porosity of the porous ceramic is desirably 50% or more and 80% or less.
  • the porosity is 50% or more and 80% or less, the number of pores is increased, and the advantage of having the structure of the porous ceramic of the present invention having independent pores and voids is further increased. For this reason, when it uses, for example as a high intensity
  • the pore diameter of the void is 20% or less of the pore diameter of the independent pore, and the pore diameter of the independent pore is 5 ⁇ m or more and 50 ⁇ m or less.
  • the independence of the independent pores is maintained when the pore diameter is 20% or less of the pore diameter of the independent pores.
  • the pore diameter of the independent pores is less than 5 ⁇ m, the pore diameter of the independent pores becomes too small.
  • the pore diameter of the independent pores exceeds 50 ⁇ m, the pore diameter becomes too large, and the strength of the porous ceramics may be lowered.
  • the pore diameter of the independent pores is constant. When the pore diameter of the independent pores is constant, a homogeneous porous structure is obtained and the strength is improved.
  • the thickness of the ceramic wall is preferably 0.1 ⁇ m or more and 7 ⁇ m or less.
  • the thickness of the ceramic wall is less than 0.1 ⁇ m, the strength of the porous ceramic may become too low.
  • the thickness of the ceramic wall exceeds 7 ⁇ m, the strength becomes too high, and processing may be difficult. Since the ceramic wall has a thickness of 0.1 ⁇ m or more and 7 ⁇ m or less, it can be easily processed and has a high strength, and thus is particularly suitable for applications such as a high-strength heat insulating material.
  • the inner walls of the independent pores have a fine uneven shape.
  • the three-point bending strength is 1 MPa or more and 200 MPa or less.
  • the three-point bending strength is 1 MPa or more and 200 MPa or less, it can be used for various applications.
  • a carbonaceous material may remain in some of the independent pores. Further, when the carbonaceous material remains in some of the independent pores, the weight of the carbonaceous material with respect to the ceramic wall from the front surface to the back surface of the porous ceramic as shown in FIG. The ratio may be decreased in an inclined manner.
  • Porous ceramics laminated without a joint surface are required to have heat resistance and non-carbonization on the outermost surface of the material, and as a whole material, metal surface heat treatment is desired that has a larger surface area and higher strength. It is particularly suitable for applications such as mounts and high-efficiency radiant heat dissipation materials.
  • Example 1 As carbonaceous particles, spherical graphite particles (average particle size 20 ⁇ m, manufactured by Toyo Tanso Co., Ltd.) were used. As ceramic particles, silicon nitride fine particles (average particle diameter 500 nm, manufactured by Ube Industries) were used. Further, as a sintering aid was used Y 2 O 3 and Al 2 O 3.
  • Silicon nitride fine particles, Y 2 O 3 , and Al 2 O 3 were mixed at a weight ratio of 91: 3: 6. Further, these and spherical graphite particles were prepared at a weight ratio of 35:65, and mixed by a solvent mixing method using 1-propanol as a solvent to obtain a mixture. The weight ratio of carbonaceous particles to ceramic particles in this mixture was 63:37. Further, silicon nitride fine particles were uniformly attached to the surface of the spherical graphite particles of the mixture. Next, the obtained mixture was put in a mold and dried to obtain a molded body. Furthermore, the obtained molded body was sintered in a vacuum atmosphere at 1900 ° C.
  • porous silicon carbide was obtained. Carbon disappeared and there was no dimensional change.
  • the porous ceramic produced in this manner is hereinafter referred to as material A1.
  • material A1 when the thickness of the ceramic wall of the material A1 was measured at two places, they were 1.3 ⁇ m and 6.1 ⁇ m.
  • Example 2 As the carbonaceous particles, spherical graphite particles (particle diameter 20 ⁇ m, manufactured by Toyo Tanso Co., Ltd.) were used. Silicon carbide fine particles (average particle diameter 600 nm, manufactured by Shinano Denki Smelting Co., Ltd.) were used as ceramic particles. Further, as a sintering aid was used Y 2 O 3 and Al 2 O 3.
  • Silicon carbide fine particles, Y 2 O 3 , and Al 2 O 3 were mixed at a weight ratio of 91: 3: 6. Further, these and spherical graphite particles were prepared in a weight ratio of 50:50, and mixed by a solvent mixing method using 1-propanol as a solvent to obtain a mixture. The weight ratio of carbonaceous particles to ceramic particles in the mixture was 55:45. Further, silicon carbide fine particles were uniformly attached to the surface of the spherical graphite particles of the mixture. Next, the obtained mixture was put in a mold and dried to obtain a molded body. Further, the obtained molded body was sintered by a hot press method at 2000 ° C. for 1 hour in a nitrogen atmosphere to obtain a sintered body. As a result of oxidizing this sintered body at 1000 ° C. for 10 hours in an atmospheric furnace, porous silicon carbide was obtained. Carbon disappeared and there was no dimensional change.
  • the porous ceramic produced in this manner is hereinafter referred to as material A2.
  • Example 3 As the carbonaceous particles, spherical graphite particles (particle diameter 20 ⁇ m, manufactured by Toyo Tanso Co., Ltd.) were used. As ceramic particles, aluminum nitride fine particles (average particle size 500 nm, manufactured by Tokuyama Corporation) were used. Y 2 O 3 was used as a sintering aid.
  • Aluminum nitride fine particles and Y 2 O 3 were mixed at a weight ratio of 95: 5. Further, these and spherical graphite particles were prepared at a weight ratio of 20:80, and mixed by a solvent mixing method using 1-propanol as a solvent to obtain a mixture. The weight ratio of carbonaceous particles to ceramic particles in the mixture was 74:26. Further, aluminum nitride fine particles were uniformly attached to the surface of the spherical graphite particles of the mixture. Next, the obtained mixture was put in a mold and dried to obtain a molded body. Furthermore, the obtained molded body was sintered in a vacuum atmosphere at 1900 ° C. for 5 minutes by a discharge plasma sintering method to obtain a sintered body.
  • porous aluminum nitride was obtained. Carbon disappeared and there was no dimensional change.
  • the porous ceramic produced in this manner is hereinafter referred to as material A3.
  • Comparative Example 1 As carbonaceous particles, spherical graphite particles (average particle size 20 ⁇ m, manufactured by Toyo Tanso Co., Ltd.) were used. As ceramic particles, silicon nitride fine particles (average particle diameter 500 nm, manufactured by Ube Industries) were used. Further, as a sintering aid was used Y 2 O 3 and Al 2 O 3.
  • Silicon nitride fine particles, Y 2 O 3 , and Al 2 O 3 were mixed at a weight ratio of 91: 3: 6. Further, these and spherical graphite particles were prepared at a weight ratio of 35:65, and mixed for 24 hours by a dry mixing method using a ball mill to obtain a mixture. The weight ratio of carbonaceous particles to ceramic particles in the mixture was 63:37. Further, the silicon nitride fine particles were not uniformly adhered to the surface of the spherical graphite particles of the mixture, and were partially agglomerated. Next, the obtained mixture was put in a mold and dried to obtain a molded body. Furthermore, the obtained molded body was sintered in a vacuum atmosphere at 1900 ° C.
  • the porous ceramic thus produced is hereinafter referred to as material Z1.
  • material Z1 when the thickness of the ceramic wall of the material Z1 was measured in two places, they were 1.8 ⁇ m and 11.1 ⁇ m.
  • the pore diameter of the independent pores was obtained from the microstructural observation photograph of the porous ceramics by SEM, and the average value was calculated.
  • the bending strength was measured by a three-point bending strength test. Specifically, it was measured based on JIS A1509-4.
  • the material A1 As is clear from FIG. 3A, in the material A1, it is understood that spherical independent pores having a diameter of about 20 ⁇ m are formed by ceramic walls that are three-dimensionally connected. It can also be seen that the thickness of the ceramic wall is 1.3 to 6.1 ⁇ m. Furthermore, it can be seen from FIG. 3B that the inner walls of the independent pores have a fine uneven shape. On the other hand, as is apparent from FIGS. 6A and 6B, the material Z1 does not have a structure formed by ceramic walls in which spherical independent pores are three-dimensionally connected, and has an uneven pore structure. It can be seen that
  • the average pore diameter of the voids is 2.1 ⁇ m from the Incremental Intrusion curve (differential pore volume distribution curve), and all the fine pores are within the range of ⁇ 50% from the average pore diameter. It can be seen that 62% of the pore volume is present.
  • the distribution of Incremental Intrusion having a pore diameter of about 100 to 400 ⁇ m is due to mercury pressed into the concave portion of the sample surface.
  • gap has a magnitude
  • the total porosity was analyzed as 70% from the CumulativetiIntrusion curve (integrated pore volume distribution curve).
  • the material A1 of the present invention has a peak at the position shown in Table 2, and therefore it can be seen that the material A1 of the present invention is composed only of silicon carbide.
  • Example 2 In the materials A3 and Z1, the relationship between the void radius and the accumulated pore volume and the relationship between the void radius and the differential pore volume were examined, and the results are shown in FIGS. In addition, the experiment method was performed by the method similar to the method shown in the above [Experiment 1 average pore diameter]. Further, when the integrated pore volume is calculated using the mercury intrusion method, the ratio (%) of the integrated pore volume to the total integrated pore volume in the range of ⁇ 50% from the average pore diameter of the voids is shown in FIGS. It calculated using.
  • the average pore diameter (radius) of the void is 2.16 ⁇ m
  • ⁇ 50% of the average pore diameter of the void is 1.08 ⁇ m
  • + 50% of the average pore diameter of the void is 3.24 ⁇ m. It is.
  • the cumulative pore volume when the average pore diameter of the voids is 1.08 ⁇ m is 1.02 mL / g
  • the cumulative pore volume when the average pore diameter of the voids is 3.24 ⁇ m is 0.07 mL / g
  • the total cumulative pore volume is 1.19 mL / g.
  • the average pore diameter is 2.18 ⁇ m
  • ⁇ 50% of the average pore diameter is 1.09 ⁇ m
  • + 50% of the average pore diameter is 3.27 ⁇ m.
  • the cumulative pore volume when the average pore diameter of the voids is 1.09 ⁇ m is 0.58 mL / g
  • the cumulative pore volume when the average pore diameter of the voids is 3.27 ⁇ m is 0.18 mL / g
  • the total cumulative pore volume is 0.73 mL / g.
  • the porous ceramics of the present invention include a high-strength heat insulating material, an artificial bone, an oil filter, a crucible, a vacuum chuck, a catalyst carrier, a spray nozzle, a lubricant-impregnated bearing, a metal heat treatment stand, a high-efficiency radiation heat dissipation material, and a reactor wall It can be used as a material, a containment vessel, etc.
  • independent pores 2 ceramic wall 3: voids communicating between independent pores 4: carbonaceous material remaining in independent pores

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Abstract

 The purpose is to provide a high-strength porous ceramic that permits complex shapes and precision processing and makes it possible to control pore diameter and porosity simultaneously, and a method for producing the same. A porous ceramic provided with ceramic particles containing at least one selected from the group consisting of aluminum nitride, silicon carbide, and silicon nitride, the porous ceramic characterized by having ceramic walls (2) created by bonding of some of the ceramic particles and a plurality of independent pores (1) formed by being surrounded by these ceramic walls, the plurality of independent pores (1) being connected by gaps (3) having a smaller pore size than the pore size of the independent pores (1), and the pore size of the gaps (3) being from 10 nm to 5 μm.

Description

多孔質セラミックス及びその製造方法Porous ceramics and method for producing the same
 本発明は新規な多孔質セラミックス及びその製造方法に関するものである。 The present invention relates to a novel porous ceramic and a method for producing the same.
 多孔質セラミックスの製造方法としては、セラミックス粒子を焼結し、粒子間隙として空孔を形成させる方法が最も一般的であり、広く用いられている。しかし、この製造方法はセラミックス粒子の間隙によって孔が形成されるため、気孔径と気孔率をそれぞれ独立に制御することは困難であった。また、焼結とともに孔が形成されるため、焼結時の変形が大きく、複雑な形状及び高精度の加工が困難であった。 As a method for producing porous ceramics, a method in which ceramic particles are sintered and pores are formed as particle gaps is the most common and widely used. However, in this manufacturing method, since pores are formed by the gaps between the ceramic particles, it is difficult to independently control the pore diameter and the porosity. Moreover, since a hole is formed with sintering, the deformation | transformation at the time of sintering was large, and the complicated shape and the highly accurate process were difficult.
 また、最近では、アルミナ中空粒子を含む粉末を所定形状に成形して成形体を形成し、得られた成形体を焼結する方法(特許文献1)、造孔剤である真球状の樹脂ビーズとセラミックス造粒粉とを混合し、加圧・成形した後に脱脂し、焼結させる方法(特許文献2)が提案されている。 Also, recently, a method of forming a molded body by molding powder containing alumina hollow particles into a predetermined shape, and sintering the obtained molded body (Patent Document 1), true spherical resin beads as a pore forming agent (Patent Document 2) has been proposed in which ceramic granulated powder is mixed, pressed and molded, degreased and sintered.
特開2001-002479号公報JP 2001-002479 A 特開2006-036624号公報JP 2006-036624 A
 ところが、特許文献1の製造方法では、焼結時にアルミナ中空粒子がアルミナ中実粒子へと結晶相転移(形状変移)することによって気孔が形成されるため、焼結時の変形が大きく、複雑な形状及び高精度の加工が困難であった。また、セラミックス壁の厚みが不均一であるため、同様のかさ密度を有し、且つセラミックス壁の厚みが均一である多孔質セラミックスと比較すると強度が低くなるという課題を有していた。 However, in the manufacturing method of Patent Document 1, pores are formed by the crystal phase transition (shape transition) of the alumina hollow particles to the alumina solid particles during the sintering, so that the deformation during the sintering is large and complicated. Shape and high-precision processing were difficult. Further, since the thickness of the ceramic wall is not uniform, there is a problem that the strength is low as compared with a porous ceramic having the same bulk density and a uniform thickness of the ceramic wall.
 また、特許文献2の製造方法は、樹脂ビーズを造孔剤に用い、脱脂後に焼結させるため、焼結時にセラミックス造粒粉が気孔部分へ浸透することで変形が生じ、複雑な形状及び高精度の加工が困難であった。 In addition, since the manufacturing method of Patent Document 2 uses resin beads as a pore-forming agent and sinters after degreasing, the ceramic granulated powder penetrates into the pores during sintering, resulting in deformation, complicated shape and high Precision machining was difficult.
 そこで本発明は、複雑な形状及び高精度の加工が可能であり、且つ、気孔径、気孔形状及び気孔率をそれぞれ独立に制御できるとともに高強度である多孔質セラミックス及びその製造方法を提供することを目的としている。 Therefore, the present invention provides a porous ceramic that can be processed in a complicated shape and with high accuracy, and that can control the pore diameter, the pore shape, and the porosity independently, and has high strength, and a method for producing the same. It is an object.
 上記目的を達成するために本発明は、窒化アルミニウム、炭化ケイ素、及び窒化ケイ素からなる群から選択される少なくとも1種を含むセラミックス粒子と、炭素質粒子とを、この炭素質粒子の表面に前記セラミックス粒子が均一に付着するように両者を混合した後、混合物を押圧しつつ、又は混合物を押圧した後に、焼結して焼結体を得、しかる後、前記焼結体に含まれる前記炭素質粒子を酸化焼失させることにより製造される多孔質セラミックスであることを特徴としている。 In order to achieve the above object, the present invention provides ceramic particles containing at least one selected from the group consisting of aluminum nitride, silicon carbide, and silicon nitride, and carbonaceous particles on the surface of the carbonaceous particles. After mixing the two so that the ceramic particles adhere uniformly, while pressing the mixture or pressing the mixture, sintering is performed to obtain a sintered body, and then the carbon contained in the sintered body It is characterized by being a porous ceramic produced by oxidizing and burning the porous particles.
 本発明によれば、複雑な形状及び高精度の加工が可能であり、且つ、気孔径、気孔形状及び気孔率をそれぞれ独立に制御できるとともに高強度である多孔質セラミックス及びその製造方法を提供できるといった優れた効果を奏する。 According to the present invention, it is possible to provide a porous ceramic having a high strength and capable of independently controlling the pore diameter, the pore shape and the porosity, and capable of processing a complicated shape and high precision, and a method for producing the same. There are excellent effects.
本発明の多孔質セラミックスの構造図。1 is a structural diagram of a porous ceramic of the present invention. 本発明の多孔質セラミックスにおける他の実施形態の構造図であって、(a)は一部の独立気孔に炭素質粒子が存在している多孔質セラミックスであり、(b)はセラミックス材料に対する炭素質材料の重量割合が厚み方向に傾斜的に低下した多孔質セラミックス。FIG. 6 is a structural diagram of another embodiment of the porous ceramic of the present invention, where (a) is a porous ceramic in which carbonaceous particles are present in some independent pores, and (b) is a carbon for a ceramic material. Porous ceramics in which the weight ratio of the porous material is reduced in the thickness direction. 材料A1のSEM(走査型電子顕微鏡)写真((a)は倍率1000倍、(b)は同図(a)のB部拡大図であり、倍率5000倍)。SEM (scanning electron microscope) photograph of material A1 ((a) is 1000 times magnification, (b) is an enlarged view of part B of FIG. 1 (a), and is 5000 times magnification). 材料A1における空隙の直径と差分細孔容積及び積算細孔容積との関係を示すグラフ。The graph which shows the relationship between the diameter of the space | gap in material A1, a difference pore volume, and an accumulation pore volume. 材料A1のX線回折図。X-ray diffraction pattern of material A1. 材料Z1のSEM(走査型電子顕微鏡)写真((a)は倍率100倍、(b)は同図(a)のC部拡大図であり、倍率1000倍)。SEM (scanning electron microscope) photograph of material Z1 ((a) is 100 times magnification, (b) is an enlarged view of part C of FIG. 1 (a), and magnification is 1000 times). 材料A3における空隙の半径と差分細孔容積との関係を示すグラフ。The graph which shows the relationship between the radius of the space | gap in material A3, and differential pore volume. 材料A3における空隙の半径と積算細孔容積との関係を示すグラフ。The graph which shows the relationship between the radius of the space | gap in material A3, and an accumulation pore volume. 材料Z1における空隙の半径と差分細孔容積との関係を示すグラフ。The graph which shows the relationship between the radius of the space | gap in material Z1, and a difference pore volume. 材料Z1における空隙の半径と積算細孔容積との関係を示すグラフ。The graph which shows the relationship between the radius of the space | gap in material Z1, and an integrated pore volume.
 本発明は、窒化アルミニウム、炭化ケイ素、及び窒化ケイ素からなる群から選択される少なくとも1種を含むセラミックス粒子と、炭素質粒子とを、この炭素質粒子の表面に前記セラミックス粒子が均一に付着するように両者を混合した後、混合物を押圧しつつ、又は混合物を押圧した後に、焼結して焼結体を得、しかる後、前記焼結体に含まれる前記炭素質粒子を酸化焼失させることにより製造されることを特徴としている。
 このようにして作製された多孔質セラミックスは、造孔剤である炭素質粒子と多孔質セラミックスの原料であるセラミックス粒子とを混合、焼結した後に、すなわちセラミックス壁を形成した後に炭素質粒子を酸化焼失させるため、多孔質セラミックスの形成時に変形がほとんど生じることなく、複雑な形状や高精度に加工することが可能である。
 なお、本発明において、セラミックス粒子が炭素質粒子に均一に付着しているとは、炭素質粒子の全表面の90%以上にセラミックス粒子が付着していることをいう。
In the present invention, ceramic particles containing at least one selected from the group consisting of aluminum nitride, silicon carbide, and silicon nitride, and carbonaceous particles are adhered uniformly to the surface of the carbonaceous particles. After mixing the two in this manner, while pressing the mixture or pressing the mixture, the sintered body is obtained by sintering, and then the carbonaceous particles contained in the sintered body are oxidized and burned off. It is manufactured by.
The porous ceramic produced in this manner is obtained by mixing and sintering the carbonaceous particles as the pore-forming agent and the ceramic particles as the raw material of the porous ceramic, that is, after forming the ceramic wall, Since it is oxidized and burned off, it can be processed with a complicated shape and high accuracy with almost no deformation during the formation of porous ceramics.
In the present invention, that the ceramic particles are uniformly attached to the carbonaceous particles means that the ceramic particles are attached to 90% or more of the entire surface of the carbonaceous particles.
 また、造孔剤である炭素質粒子とセラミックス粒子とを混合した時に、炭素質粒子の周りに付着するセラミックス粒子によるセラミックス厚みが均一となるため、焼結した後もセラミックス壁の厚みが均一となる。したがって、同じかさ密度であるがセラミックス壁の厚みが不均一な多孔質セラミックスと比較して、高強度になる。このように、同じかさ密度であるにも関わらず強度が非常に高いため、本発明の多孔質セラミックスは多様な分野(例えば、高強度断熱材、人工骨、オイルフィルター、ルツボ、真空チャック、触媒担体、噴霧ノズル、潤滑液含浸軸受け等)で用いることができる。 In addition, when carbonaceous particles and ceramic particles, which are pore formers, are mixed, the ceramic thickness due to the ceramic particles adhering around the carbonaceous particles becomes uniform, so that the thickness of the ceramic wall is uniform even after sintering. Become. Therefore, the strength is higher than that of porous ceramics having the same bulk density but non-uniform ceramic wall thickness. As described above, since the strength is very high despite the same bulk density, the porous ceramic of the present invention can be used in various fields (for example, high-strength heat insulating materials, artificial bones, oil filters, crucibles, vacuum chucks, catalysts). Carrier, spray nozzle, lubricating liquid impregnated bearing, etc.).
 さらに、造孔剤である炭素質粒子の粒子径、形状及び添加量を選択することで、気孔径、気孔形状及び気孔率をそれぞれ独立に所望の値に制御することが可能である。 Furthermore, by selecting the particle diameter, shape and amount of carbonaceous particles which are pore forming agents, the pore diameter, the pore shape and the porosity can be independently controlled to desired values.
 本発明の多孔質セラミックスは、窒化アルミニウム、炭化ケイ素、及び窒化ケイ素からなる群から選択される少なくとも1種を含むセラミックス粒子と、炭素質粒子とを、この炭素質粒子の表面に前記セラミックス粒子が均一に付着するように混合し、混合体を得る第1の工程と、前記混合体を加圧しつつ焼結し、又は前記混合体を加圧した後に焼結して、焼結体を得る第2の工程と、前記焼結体に含まれる、前記炭素質粒子を酸化焼失させる第3の工程とを経て製造することができる。 The porous ceramic of the present invention comprises ceramic particles containing at least one selected from the group consisting of aluminum nitride, silicon carbide, and silicon nitride, and carbonaceous particles. The ceramic particles are on the surface of the carbonaceous particles. A first step of obtaining a mixture by mixing so as to adhere uniformly, and sintering while pressing the mixture, or after pressing the mixture and sintering to obtain a sintered body It can be manufactured through step 2 and a third step of oxidizing and burning out the carbonaceous particles contained in the sintered body.
 上記炭素質粒子は、球状あるいは板状の天然黒鉛及び人造黒鉛、または炭素繊維が好ましい。炭素質粒子は1種類のみを含んでいてもよいし、複数種類が含まれていてもよい。また、炭素質粒子の粒子径は、1μm以上500μm以下であることが好ましく、5μm以上50μm以下であることがより好ましく、10μm以上30μm以下であることがさらに好ましい。炭素質粒子の粒子径が小さくなりすぎると、凝集する可能性がある。炭素質粒子が凝集しすぎると、炭素質粒子とセラミックス粒子を混合する際に、セラミックス粒子が炭素質粒子表面に均一に付着できないため(すなわち、炭素質粒子と炭素質粒子が密着している箇所にはセラミックス粒子が付着し難いため)、セラミックス壁の厚みが均一でなくなり、多孔質セラミックスの構造の強度が低下する場合がある。一方、炭素質粒子の粒子径が大きくなりすぎると、気孔率及び独立気孔の孔径が大きくなりすぎるため、多孔質セラミックスの構造の強度が低下する場合がある。さらに、炭素質粒子の粒子径は一定であることが好ましい。具体的には、炭素質粒子の粒子径分布が、平均粒子径から±10%の範囲に80%以上存在することが好ましく、平均粒子径から±10%の範囲に90%以上存在することがより好ましい。炭素質粒子の粒子径が一定であると、作製された多孔質セラミックスに存在する独立気孔の孔径が一定となるため、均質な多孔質構造となり、強度が向上する。 The carbonaceous particles are preferably spherical or plate-like natural graphite and artificial graphite, or carbon fiber. The carbonaceous particles may include only one type or a plurality of types. The particle size of the carbonaceous particles is preferably 1 μm or more and 500 μm or less, more preferably 5 μm or more and 50 μm or less, and further preferably 10 μm or more and 30 μm or less. If the particle size of the carbonaceous particles becomes too small, there is a possibility of aggregation. If the carbonaceous particles are agglomerated too much, the ceramic particles cannot uniformly adhere to the surface of the carbonaceous particles when the carbonaceous particles and the ceramic particles are mixed (that is, where the carbonaceous particles and the carbonaceous particles are in close contact). Since ceramic particles are difficult to adhere to), the thickness of the ceramic wall may not be uniform, and the strength of the structure of the porous ceramic may be reduced. On the other hand, if the particle size of the carbonaceous particles becomes too large, the porosity and the pore size of the independent pores become too large, and the strength of the structure of the porous ceramics may be lowered. Furthermore, the particle diameter of the carbonaceous particles is preferably constant. Specifically, the particle size distribution of the carbonaceous particles is preferably 80% or more in the range of ± 10% from the average particle size, and 90% or more in the range of ± 10% from the average particle size. More preferred. When the particle diameter of the carbonaceous particles is constant, the pore diameter of the independent pores existing in the produced porous ceramic is constant, so that a homogeneous porous structure is obtained and the strength is improved.
 上記セラミックス粒子は、窒化アルミニウム、炭化ケイ素、窒化ケイ素の全てを含んでいてもよいし、いずれか2種を含んでいてもよいし、いずれか1種類のみを含んでいてもよい。但し、セラミックス粒子は、窒化アルミニウムあるいは炭化ケイ素あるいは窒化ケイ素のいずれか1種類のみであることが好ましい。また、セラミックス粒子の粒子径は、100nm以上50μm以下であることが好ましく、200nm以上5μm以下であることがより好ましく、300nm以上1μm以下であることがさらに好ましい。セラミックス粒子の粒子径が小さくなりすぎると、凝集する可能性ある。セラミックス粒子が凝集しすぎると、炭素質粒子とセラミックス粒子を混合する際に、セラミックス粒子が炭素質粒子表面に均一に付着できないため(すなわち、凝集したセラミックス粒子が付着した箇所は、セラミックス粒子の量が多くなるが、その他の箇所はセラミックス粒子の量が少なくなるため)、セラミックス壁の厚みが均一でなくなり、多孔質セラミックスの構造の強度が低下する場合がある。一方、セラミックス粒子の粒子径が大きくなりすぎると、炭素粒子を均一に覆えなくなるため、多孔質セラミックスの構造の強度が低下する場合がある。さらに、セラミックス粒子の粒子径は一定であることが好ましい。具体的には、セラミックス粒子の粒子径分布が、平均粒子径から±10%の範囲に80%以上存在することが好ましく、平均粒子径から±10%の範囲に90%以上存在することがより好ましい。セラミックス粒子の粒子径が一定であると、作製された多孔質セラミックスに存在するセラミックス壁の厚みがより均一となり、また空隙の孔径が一定となるため、強度が向上する。 The ceramic particles may include all of aluminum nitride, silicon carbide, and silicon nitride, may include any two of them, or may include only one of them. However, the ceramic particles are preferably only one of aluminum nitride, silicon carbide, and silicon nitride. The particle diameter of the ceramic particles is preferably 100 nm or more and 50 μm or less, more preferably 200 nm or more and 5 μm or less, and further preferably 300 nm or more and 1 μm or less. If the particle size of the ceramic particles becomes too small, they may aggregate. If the ceramic particles are too agglomerated, the ceramic particles cannot uniformly adhere to the surface of the carbonaceous particles when the carbonaceous particles and the ceramic particles are mixed (that is, the location where the agglomerated ceramic particles are attached is the amount of the ceramic particles. However, the thickness of the ceramic wall is not uniform, and the strength of the porous ceramic structure may be reduced. On the other hand, if the particle size of the ceramic particles is too large, the carbon particles cannot be covered uniformly, and the strength of the structure of the porous ceramics may be reduced. Further, the particle diameter of the ceramic particles is preferably constant. Specifically, the particle size distribution of the ceramic particles is preferably 80% or more in the range of ± 10% from the average particle size, and more preferably 90% or more in the range of ± 10% from the average particle size. preferable. When the particle diameter of the ceramic particles is constant, the thickness of the ceramic wall existing in the produced porous ceramic becomes more uniform, and the pore diameter of the voids becomes constant, so that the strength is improved.
 セラミックス粒子の粒子径は、炭素質粒子の粒子径の1/5以下であることが好ましく、1/10以下であることがより好ましい。セラミックス粒子の粒子径を、炭素質粒子の粒子径よりも十分に小さくすることによって、セラミックス粒子と炭素質粒子を混合した際に、セラミックス粒子が炭素質粒子の表面に均一に付着することができる。したがって、作製された多孔質セラミックスのセラミックス壁の厚みが均一となるため、強度が向上する。 The particle diameter of the ceramic particles is preferably 1/5 or less, more preferably 1/10 or less of the particle diameter of the carbonaceous particles. By making the particle size of the ceramic particles sufficiently smaller than the particle size of the carbonaceous particles, the ceramic particles can adhere uniformly to the surface of the carbonaceous particles when the ceramic particles and the carbonaceous particles are mixed. . Therefore, since the thickness of the ceramic wall of the produced porous ceramic becomes uniform, the strength is improved.
 前記第1の工程において、炭素質粒子とセラミックス粒子との混合比は、炭素質粒子の重量:セラミックス粒子の重量が、95:5~20:80であることが好ましく、80:20~40:60であることがより好ましい。セラミックス粒子の重量割合が20wt%未満(特に、5wt%未満)であると、セラミックスの量が少なくなるため、セラミックス壁の厚みを均一に形成しにくくなり、強度が低くなりすぎる場合がある。一方、セラミックス粒子の重量割合が60wt%を超える(特に、80wt%を超える)と、セラミックスの量が多くなるため、硬くなり、加工が困難になる場合がある。炭素質粒子とセラミックス粒子との重量比を95:5~20:80(特に、80:20~40:60)にすることによって、より高強度で、かつ、より加工のしやすい多孔質セラミックスとなる。 In the first step, the mixing ratio of the carbonaceous particles and the ceramic particles is preferably such that the weight of the carbonaceous particles: the weight of the ceramic particles is 95: 5 to 20:80, and 80:20 to 40: 60 is more preferable. When the weight ratio of the ceramic particles is less than 20 wt% (particularly less than 5 wt%), the amount of ceramic is reduced, so that it is difficult to form the thickness of the ceramic wall uniformly, and the strength may be too low. On the other hand, when the weight ratio of the ceramic particles exceeds 60 wt% (particularly, exceeds 80 wt%), the amount of the ceramic increases, so that it becomes hard and processing may be difficult. By setting the weight ratio of carbonaceous particles to ceramic particles to 95: 5 to 20:80 (particularly 80:20 to 40:60), a porous ceramic with higher strength and easier to process can be obtained. Become.
 また、炭素質粒子とセラミックス粒子とを混合する際に、焼結助剤を添加してもよい。焼結助剤としては、Yなどの酸化イットリウム、Al等の酸化アルミニウム、CaOなどの酸化カルシウム、SiOなどの酸化ケイ素、その他の希土類酸化物などが挙げられる。 Further, a sintering aid may be added when mixing the carbonaceous particles and the ceramic particles. Examples of the sintering aid include yttrium oxide such as Y 2 O 3 , aluminum oxide such as Al 2 O 3, calcium oxide such as CaO, silicon oxide such as SiO 2 , and other rare earth oxides.
 炭素質粒子とセラミックス粒子とを混合する方法は、特に限定されない。例えば、気相法、液相法、溶媒混合法、機械的混合法、スラリー法またはこれらを組み合わせた方法が挙げられる。気相法の具体例としては、化学気相蒸着法(CVD法)、転化法(CVR法)などが挙げられる。液相法の具体例としては、例えば、化学沈殿法等が挙げられる。スラリー法の具体例としては、例えばゲルキャスト法、スリップキャスティング、テープキャスティングなどが挙げられる。 The method for mixing the carbonaceous particles and the ceramic particles is not particularly limited. For example, a gas phase method, a liquid phase method, a solvent mixing method, a mechanical mixing method, a slurry method, or a combination of these methods can be given. Specific examples of the vapor phase method include a chemical vapor deposition method (CVD method) and a conversion method (CVR method). Specific examples of the liquid phase method include a chemical precipitation method. Specific examples of the slurry method include a gel casting method, slip casting, tape casting, and the like.
 前記第2の工程において、焼結体を得る方法は、特に限定されない。例えば、放電プラズマ焼結法やホットプレス法等が挙げられる。焼成温度や焼成時間、焼成雰囲気の種類、焼成の圧力等は、使用する材料の種類、形状、大きさ等に応じて適宜設定することができる。焼成温度は、例えば1700℃以上とすればよい。焼成温度は、1700℃以上2100℃以下であることが好ましく、1800℃以上2000℃以下であることがより好ましい。焼成時間は、例えば、5分以上2時間以下とすることができる。焼成雰囲気の種類は、例えば、真空、窒素、アルゴンなどの不活性ガス雰囲気とすることができる。焼成の圧力は、例えば、0.01MPa以上50MPa以下とすることができる。 In the second step, the method for obtaining the sintered body is not particularly limited. Examples thereof include a discharge plasma sintering method and a hot press method. The firing temperature, firing time, kind of firing atmosphere, firing pressure, and the like can be appropriately set according to the kind, shape, size, and the like of the material to be used. The firing temperature may be 1700 ° C. or higher, for example. The firing temperature is preferably 1700 ° C. or higher and 2100 ° C. or lower, and more preferably 1800 ° C. or higher and 2000 ° C. or lower. The firing time can be, for example, 5 minutes or more and 2 hours or less. The kind of baking atmosphere can be made into inert gas atmosphere, such as a vacuum, nitrogen, argon, for example. The pressure of baking can be 0.01 MPa or more and 50 MPa or less, for example.
 前記焼結時に、炭素質粒子の表面に均一に付着したセラミックス粒子が焼結し、炭素質粒子を3次元的に被覆するセラミックス層が形成される。セラミックス層は、連続した構造を有していることが好ましく、3次元網目構造を有していることがより好ましい。すなわち、複数の炭素質粒子は、3次元網目構造を有するセラミックス壁によって一体化されていることが好ましい。 During the sintering, the ceramic particles uniformly adhered to the surface of the carbonaceous particles are sintered to form a ceramic layer that three-dimensionally covers the carbonaceous particles. The ceramic layer preferably has a continuous structure, and more preferably has a three-dimensional network structure. That is, the plurality of carbonaceous particles are preferably integrated by a ceramic wall having a three-dimensional network structure.
 また、セラミックス粒子に窒化ケイ素が含まれている場合、焼結時の反応によって炭素質粒子の表面に炭化ケイ素が形成される。この炭化ケイ素は、複数の炭素質粒子の間に形成される。すなわち、焼結によって、複数の炭素質粒子は、炭化ケイ素に覆われ、かつ炭化ケイ素により接着される。なお、多孔質セラミックスには、窒化ケイ素が残っていてもよい。 Also, when silicon nitride is contained in the ceramic particles, silicon carbide is formed on the surface of the carbonaceous particles by a reaction during sintering. This silicon carbide is formed between a plurality of carbonaceous particles. That is, the plurality of carbonaceous particles are covered with silicon carbide and bonded by silicon carbide by sintering. Note that silicon nitride may remain in the porous ceramic.
 前記第3の工程において、前記炭素質粒子の全部を酸化焼失させて、図1(図1において、1は独立気孔、2はセラミックス壁、3は独立気孔間を連通する空隙である)のような多孔質セラミックスを得る方法は、特に限定されない。例えば、大気炉で加熱する方法等が挙げられる。酸化焼失させる温度や時間、雰囲気の種類、雰囲気の圧力等は、使用する材料の種類、形状、大きさ等に応じて適宜設定することができる。酸化焼失温度は、例えば500℃以上とすればよく、500℃以上1000℃以下であることが好ましい。酸化焼失時間は、例えば、5分間以上48時間以下とすることができる。酸化焼失雰囲気の種類は、例えば、大気、真空内や窒素等の不活性ガスを混合した酸素圧制御雰囲気とすることができる。酸化焼失雰囲気の圧力は、例えば、0.01MPa以上10MPa以下とすることができる。また、第3の工程を行う前に、前記焼結体を機械加工により所望の形状にしたり、型成形によって、ニアネット成形してもよい。 In the third step, all the carbonaceous particles are oxidized and burned, and as shown in FIG. 1 (in FIG. 1, 1 is an independent pore, 2 is a ceramic wall, and 3 is a void communicating between the independent pores). A method for obtaining a porous ceramic is not particularly limited. For example, the method etc. which heat with an atmospheric furnace are mentioned. The temperature and time for oxidizing and burning, the type of atmosphere, the pressure of the atmosphere, and the like can be appropriately set according to the type, shape, size, etc. of the material used. The oxidation burning temperature may be, for example, 500 ° C. or higher, and is preferably 500 ° C. or higher and 1000 ° C. or lower. The oxidation burning time can be, for example, 5 minutes or more and 48 hours or less. The type of the oxidation burnout atmosphere can be, for example, an oxygen pressure controlled atmosphere in which an inert gas such as air, vacuum or nitrogen is mixed. The pressure of the oxidation burnout atmosphere can be set to, for example, 0.01 MPa or more and 10 MPa or less. Further, before performing the third step, the sintered body may be formed into a desired shape by machining, or may be near-net molded by mold molding.
 前記第3の工程において、前記炭素質粒子の一部のみを酸化焼失させて、図2(a)(b)のような多孔質セラミックスを得る方法は、特に限定されない(図2(a)(b)において、1は独立気孔、2はセラミックス壁、3は独立気孔間を連通する空隙、4は残存した炭素質材料である)。例えば、大気炉での急速加熱や、バーナー火炎による表面酸化法等が挙げられる。尚、バーナー火炎を用いて図2(b)に示す多孔質セラミックスを得る場合には、矢符A方向からバーナー火炎を吹き付ける。また、第4の工程を行う前に、前記焼結体を機械加工により所望の形状にしたり、型成形によって、ニアネット成形してもよい。 In the third step, the method for obtaining a porous ceramic as shown in FIGS. 2A and 2B by oxidizing and burning only a part of the carbonaceous particles is not particularly limited (FIG. 2A). In b), 1 is independent pores, 2 is a ceramic wall, 3 is a void communicating between the independent pores, and 4 is a remaining carbonaceous material). For example, rapid heating in an atmospheric furnace, surface oxidation method using a burner flame, and the like can be mentioned. When the porous ceramic shown in FIG. 2B is obtained using a burner flame, the burner flame is sprayed from the direction of the arrow A. Further, before performing the fourth step, the sintered body may be formed into a desired shape by machining, or near-net formed by mold forming.
 また、本発明の多孔質セラミックスは、窒化アルミニウム、炭化ケイ素、及び窒化ケイ素からなる群から選択される少なくとも1種を含むセラミックス粒子を備えた多孔質セラミックスであって、前記セラミックス粒子の一部が結合してなるセラミックス壁と、前記セラミックス壁に囲まれることにより形成された複数の独立気孔とを有し、前記複数の独立気孔間が、前記独立気孔径より小さい孔径の空隙により連通され、前記空隙の孔径が10nm以上5μm以下であることを特徴とする。
 上記多孔質セラミックスは、独立気孔を有するとともに、独立気孔間を連通する空隙が存在するため、例えば人工骨として用いた場合、気孔間の連通性が高くなる。したがって、新生骨が気孔の深部まで早期に侵入し、骨としての機能を早期に回復することができる。
The porous ceramic of the present invention is a porous ceramic comprising ceramic particles containing at least one selected from the group consisting of aluminum nitride, silicon carbide, and silicon nitride, and a part of the ceramic particles is A ceramic wall formed by bonding and a plurality of independent pores formed by being surrounded by the ceramic wall, the plurality of independent pores being communicated with each other by a gap having a pore diameter smaller than the independent pore diameter, The pore diameter of the void is from 10 nm to 5 μm.
Since the porous ceramic has independent pores and there are voids communicating between the independent pores, for example, when used as an artificial bone, the connectivity between the pores becomes high. Therefore, the new bone can invade to the deep part of the pores at an early stage, and the function as a bone can be recovered early.
 水銀圧入法を用いて積算細孔容積を算出した場合、前記空隙の平均孔径から±50%の範囲に、全積算細孔容積の60%以上が存在することが望ましく、特に、75%以上が存在することが望ましい。
 このような構成であれば、多孔質セラミックス内に液体や気体が透過、浸入する際、円滑に透過、浸入することができる。
When the cumulative pore volume is calculated using the mercury intrusion method, it is desirable that 60% or more of the total cumulative pore volume exists in the range of ± 50% from the average pore diameter of the voids, and particularly 75% or more. It is desirable to exist.
If it is such a structure, when a liquid and gas permeate | transmit and penetrate | invade in porous ceramics, it can permeate | transmit and penetrate smoothly.
 多孔質セラミックスの気孔率は50%以上80%以下であることが望ましい。気孔率が50%以上80%以下であることによって、気孔部分が多くなり、独立気孔と空隙を有する本発明の多孔質セラミックスの構造を有する利点がより高くなる。このため、例えば高強度断熱材として用いた場合に、その断熱効果がより高くなる。なお、本発明において、気孔率とは、下記式(1)で示す値である。
気孔率=[(独立気孔の体積+空隙の体積)/多孔質セラミックスの体積]×100・・・(1)
The porosity of the porous ceramic is desirably 50% or more and 80% or less. When the porosity is 50% or more and 80% or less, the number of pores is increased, and the advantage of having the structure of the porous ceramic of the present invention having independent pores and voids is further increased. For this reason, when it uses, for example as a high intensity | strength heat insulating material, the heat insulation effect becomes higher. In the present invention, the porosity is a value represented by the following formula (1).
Porosity = [(volume of independent pores + volume of voids) / volume of porous ceramics] × 100 (1)
 前記空隙の孔径は、前記独立気孔の気孔径の20%以下であり、前記独立気孔の気孔径が5μm以上50μm以下であることが望ましい。前記空隙の孔径が、前記独立気孔の気孔径の20%以下であることによって、独立気孔の独立性が保持される。また、独立気孔の気孔径が5μm未満の場合は、独立気孔の気孔径が小さくなりすぎて、例えば、高強度断熱材として用いた場合に、独立気孔内に空気を十分に保持することができない場合がある。一方、独立気孔の気孔径が50μmを超えると気孔径が大きくなりすぎるため、多孔質セラミックスの強度が低くなる場合がある。さらに、前記独立気孔の気孔径は一定であることが望ましい。独立気孔の気孔径が一定であると、均質な多孔質構造となり、強度が向上する。 It is desirable that the pore diameter of the void is 20% or less of the pore diameter of the independent pore, and the pore diameter of the independent pore is 5 μm or more and 50 μm or less. The independence of the independent pores is maintained when the pore diameter is 20% or less of the pore diameter of the independent pores. Moreover, when the pore diameter of the independent pores is less than 5 μm, the pore diameter of the independent pores becomes too small. For example, when used as a high-strength heat insulating material, air cannot be sufficiently retained in the independent pores. There is a case. On the other hand, if the pore diameter of the independent pores exceeds 50 μm, the pore diameter becomes too large, and the strength of the porous ceramics may be lowered. Furthermore, it is desirable that the pore diameter of the independent pores is constant. When the pore diameter of the independent pores is constant, a homogeneous porous structure is obtained and the strength is improved.
 前記セラミックス壁の厚みは0.1μm以上7μm以下であることが望ましい。セラミックス壁の厚みが0.1μm未満の場合は、多孔質セラミックスの強度が低くなりすぎる場合がある。一方、セラミックス壁の厚みが7μmを超えると、強度が高くなりすぎるため、加工が困難になる場合がある。セラミックス壁の厚みが0.1μm以上7μm以下であることによって、加工が容易で、かつ、強度の高い材料となるため、例えば高強度断熱材等のような用途に特に適している。 The thickness of the ceramic wall is preferably 0.1 μm or more and 7 μm or less. When the thickness of the ceramic wall is less than 0.1 μm, the strength of the porous ceramic may become too low. On the other hand, if the thickness of the ceramic wall exceeds 7 μm, the strength becomes too high, and processing may be difficult. Since the ceramic wall has a thickness of 0.1 μm or more and 7 μm or less, it can be easily processed and has a high strength, and thus is particularly suitable for applications such as a high-strength heat insulating material.
 前記独立気孔の内壁が微細な凹凸形状であることが望ましい。前記独立気孔の内壁が微細な凹凸形状であることによって、触媒等を担持させやすくなる。 It is desirable that the inner walls of the independent pores have a fine uneven shape. When the inner walls of the independent pores have a fine uneven shape, it becomes easy to carry a catalyst or the like.
 3点曲げ強度が1MPa以上200MPa以下であることが望ましい。3点曲げ強度が1MPa以上200MPa以下であることによって、さまざまな用途に対応できる。 It is desirable that the three-point bending strength is 1 MPa or more and 200 MPa or less. When the three-point bending strength is 1 MPa or more and 200 MPa or less, it can be used for various applications.
 本発明の多孔質セラミックスは、一部の前記独立気孔内に炭素質材料が残存していてもよい。また、一部の前記独立気孔内に炭素質材料が残存している場合、図2(b)のように、多孔質セラミックスの表面から裏面に向かって、前記セラミックス壁に対する前記炭素質材料の重量割合が傾斜的に低下していても良い。このように、セラミックスのみからなり、高耐熱性の性質を有する部分と、多孔質セラミックスの独立気孔の中に造孔剤である炭素質粒子が残存し、高強度の性質を有する部分とが、接合面を有さずに積層された多孔質セラミックスは、材料の最表面に耐熱性と非炭化性が望まれ、材料全体としては、より表面積が大きく、高強度な性質が望まれる、金属熱処理架台や高効率輻射放熱材のような用途に特に適している。 In the porous ceramic of the present invention, a carbonaceous material may remain in some of the independent pores. Further, when the carbonaceous material remains in some of the independent pores, the weight of the carbonaceous material with respect to the ceramic wall from the front surface to the back surface of the porous ceramic as shown in FIG. The ratio may be decreased in an inclined manner. In this way, a part consisting of ceramics only and having a high heat resistance property, and a part having carbonaceous particles as a pore-forming agent remaining in the independent pores of the porous ceramic material and having a high strength property, Porous ceramics laminated without a joint surface are required to have heat resistance and non-carbonization on the outermost surface of the material, and as a whole material, metal surface heat treatment is desired that has a larger surface area and higher strength. It is particularly suitable for applications such as mounts and high-efficiency radiant heat dissipation materials.
(実施例1)
 炭素質粒子として、球状黒鉛粒子(平均粒子径20μm、東洋炭素株式会社製)を、使用した。セラミックス粒子として、窒化ケイ素微粒子(平均粒子径500nm、宇部興産社製)を使用した。また、焼結助剤として、Y及びAlを使用した。
Example 1
As carbonaceous particles, spherical graphite particles (average particle size 20 μm, manufactured by Toyo Tanso Co., Ltd.) were used. As ceramic particles, silicon nitride fine particles (average particle diameter 500 nm, manufactured by Ube Industries) were used. Further, as a sintering aid was used Y 2 O 3 and Al 2 O 3.
 窒化ケイ素微粒子、Y、Alを、91:3:6の重量比で混合した。さらに、これらと球状黒鉛粒子とを、35:65の重量比で調製し、溶媒として1-プロパノールを用いて溶媒混合法により混合して混合体を得た。この混合体中の炭素質粒子とセラミックス粒子との重量比は63:37であった。また、混合体の球状黒鉛粒子の表面には、窒化ケイ素微粒子が均一に付着していた。次に、得られた混合体を鋳型に入れて乾燥し、成形体を得た。さらに、得られた成形体を放電プラズマ焼結法にて、1900℃で5分間、真空雰囲気下で焼結し、焼結体を得た。この焼結体を、大気炉で1000℃、5時間酸化処理した結果、多孔質炭化ケイ素を得た。炭素は消失しており、寸法変化はなかった。
 このようにして作製した多孔質セラミックスを、以下、材料A1と称する。
 尚、材料A1のセラミックス壁の厚みを2カ所で測定したところ、1.3μmと6.1μmであった。
Silicon nitride fine particles, Y 2 O 3 , and Al 2 O 3 were mixed at a weight ratio of 91: 3: 6. Further, these and spherical graphite particles were prepared at a weight ratio of 35:65, and mixed by a solvent mixing method using 1-propanol as a solvent to obtain a mixture. The weight ratio of carbonaceous particles to ceramic particles in this mixture was 63:37. Further, silicon nitride fine particles were uniformly attached to the surface of the spherical graphite particles of the mixture. Next, the obtained mixture was put in a mold and dried to obtain a molded body. Furthermore, the obtained molded body was sintered in a vacuum atmosphere at 1900 ° C. for 5 minutes by a discharge plasma sintering method to obtain a sintered body. As a result of oxidizing this sintered body in an atmospheric furnace at 1000 ° C. for 5 hours, porous silicon carbide was obtained. Carbon disappeared and there was no dimensional change.
The porous ceramic produced in this manner is hereinafter referred to as material A1.
In addition, when the thickness of the ceramic wall of the material A1 was measured at two places, they were 1.3 μm and 6.1 μm.
(実施例2)
 炭素質粒子として、球状黒鉛粒子(粒子径20μm、東洋炭素株式会社製)を、使用した。セラミックス粒子として、炭化ケイ素微粒子(平均粒子径600nm、信濃電気製錬株式会社製)を使用した。また、焼結助剤として、Y及びAlを使用した。
(Example 2)
As the carbonaceous particles, spherical graphite particles (particle diameter 20 μm, manufactured by Toyo Tanso Co., Ltd.) were used. Silicon carbide fine particles (average particle diameter 600 nm, manufactured by Shinano Denki Smelting Co., Ltd.) were used as ceramic particles. Further, as a sintering aid was used Y 2 O 3 and Al 2 O 3.
 炭化ケイ素微粒子、Y、Alを、91:3:6の重量比で混合した。さらに、これらと球状黒鉛粒子とを、50:50の重量比で調製し、溶媒として1-プロパノールを用いて溶媒混合法により混合し、混合体を得た。混合体中の炭素質粒子とセラミックス粒子との重量比は55:45であった。また、混合体の球状黒鉛粒子の表面には、炭化ケイ素微粒子が均一に付着していた。次に、得られた混合体を鋳型に入れて乾燥し、成形体を得た。さらに、得られた成形体をホットプレス法にて、2000℃で1時間、窒素雰囲気下で焼結し、焼結体を得た。この焼結体を、大気炉で1000℃、10時間酸化処理した結果、多孔質炭化ケイ素を得た。炭素は消失しており、寸法変化はなかった。
 このようにして作製した多孔質セラミックスを、以下、材料A2と称する。
Silicon carbide fine particles, Y 2 O 3 , and Al 2 O 3 were mixed at a weight ratio of 91: 3: 6. Further, these and spherical graphite particles were prepared in a weight ratio of 50:50, and mixed by a solvent mixing method using 1-propanol as a solvent to obtain a mixture. The weight ratio of carbonaceous particles to ceramic particles in the mixture was 55:45. Further, silicon carbide fine particles were uniformly attached to the surface of the spherical graphite particles of the mixture. Next, the obtained mixture was put in a mold and dried to obtain a molded body. Further, the obtained molded body was sintered by a hot press method at 2000 ° C. for 1 hour in a nitrogen atmosphere to obtain a sintered body. As a result of oxidizing this sintered body at 1000 ° C. for 10 hours in an atmospheric furnace, porous silicon carbide was obtained. Carbon disappeared and there was no dimensional change.
The porous ceramic produced in this manner is hereinafter referred to as material A2.
(実施例3)
 炭素質粒子として、球状黒鉛粒子(粒子径20μm、東洋炭素株式会社製)を、使用した。セラミックス粒子として、窒化アルミニウム微粒子(平均粒子径500nm、株式会社トクヤマ製)を使用した。また、焼結助剤として、Yを使用した。
Example 3
As the carbonaceous particles, spherical graphite particles (particle diameter 20 μm, manufactured by Toyo Tanso Co., Ltd.) were used. As ceramic particles, aluminum nitride fine particles (average particle size 500 nm, manufactured by Tokuyama Corporation) were used. Y 2 O 3 was used as a sintering aid.
 窒化アルミニウム微粒子と、Yとを、95:5の重量比で混合した。さらに、これらと球状黒鉛粒子とを、20:80の重量比で調製し、溶媒として1-プロパノールを用いて溶媒混合法により混合し、混合体を得た。混合体中の炭素質粒子とセラミックス粒子との重量比は74:26であった。また、混合体の球状黒鉛粒子の表面には、窒化アルミニウムの微粒子が均一に付着していた。次に、得られた混合体を鋳型に入れて乾燥し、成形体を得た。さらに、得られた成形体を放電プラズマ焼結法にて、1900℃で5分間、真空雰囲気下で焼結し、焼結体を得た。この焼結体を、大気炉で600℃、24時間酸化処理した結果、多孔質窒化アルミニウムを得た。炭素は消失しており、寸法変化はなかった。
 このようにして作製した多孔質セラミックスを、以下、材料A3と称する。
Aluminum nitride fine particles and Y 2 O 3 were mixed at a weight ratio of 95: 5. Further, these and spherical graphite particles were prepared at a weight ratio of 20:80, and mixed by a solvent mixing method using 1-propanol as a solvent to obtain a mixture. The weight ratio of carbonaceous particles to ceramic particles in the mixture was 74:26. Further, aluminum nitride fine particles were uniformly attached to the surface of the spherical graphite particles of the mixture. Next, the obtained mixture was put in a mold and dried to obtain a molded body. Furthermore, the obtained molded body was sintered in a vacuum atmosphere at 1900 ° C. for 5 minutes by a discharge plasma sintering method to obtain a sintered body. As a result of oxidizing this sintered body in an atmospheric furnace at 600 ° C. for 24 hours, porous aluminum nitride was obtained. Carbon disappeared and there was no dimensional change.
The porous ceramic produced in this manner is hereinafter referred to as material A3.
(比較例1)
 炭素質粒子として、球状黒鉛粒子(平均粒子径20μm、東洋炭素株式会社製)を、使用した。セラミックス粒子として、窒化ケイ素微粒子(平均粒子径500nm、宇部興産社製)を使用した。また、焼結助剤として、Y及びAlを使用した。
(Comparative Example 1)
As carbonaceous particles, spherical graphite particles (average particle size 20 μm, manufactured by Toyo Tanso Co., Ltd.) were used. As ceramic particles, silicon nitride fine particles (average particle diameter 500 nm, manufactured by Ube Industries) were used. Further, as a sintering aid was used Y 2 O 3 and Al 2 O 3.
 窒化ケイ素微粒子、Y、Alを、91:3:6の重量比で混合した。さらに、これらと球状黒鉛粒子とを、35:65の重量比で調製し、ボールミルによる乾式混合法にて、24時間混合し、混合体を得た。混合体中の炭素質粒子とセラミックス粒子との重量比は63:37であった。また、混合体の球状黒鉛粒子の表面には、窒化ケイ素微粒子が均一に付着しておらず、一部凝集していた。次に、得られた混合体を鋳型に入れて乾燥し、成形体を得た。さらに、得られた成形体を放電プラズマ焼結法にて、1900℃で5分間、真空雰囲気下で焼結し、焼結体を得た。この焼結体を、大気炉で1000℃、5時間酸化処理した結果、多孔質炭化ケイ素を得た。炭素は消失しており、寸法変化はなかった。
 このようにして作製した多孔質セラミックスを、以下、材料Z1と称する。
 尚、材料Z1のセラミックス壁の厚みを2カ所で測定したところ、1.8μmと11.1μmであった。
Silicon nitride fine particles, Y 2 O 3 , and Al 2 O 3 were mixed at a weight ratio of 91: 3: 6. Further, these and spherical graphite particles were prepared at a weight ratio of 35:65, and mixed for 24 hours by a dry mixing method using a ball mill to obtain a mixture. The weight ratio of carbonaceous particles to ceramic particles in the mixture was 63:37. Further, the silicon nitride fine particles were not uniformly adhered to the surface of the spherical graphite particles of the mixture, and were partially agglomerated. Next, the obtained mixture was put in a mold and dried to obtain a molded body. Furthermore, the obtained molded body was sintered in a vacuum atmosphere at 1900 ° C. for 5 minutes by a discharge plasma sintering method to obtain a sintered body. As a result of oxidizing this sintered body in an atmospheric furnace at 1000 ° C. for 5 hours, porous silicon carbide was obtained. Carbon disappeared and there was no dimensional change.
The porous ceramic thus produced is hereinafter referred to as material Z1.
In addition, when the thickness of the ceramic wall of the material Z1 was measured in two places, they were 1.8 μm and 11.1 μm.
(実験1)
 上記材料A1~A3、Z1における空隙の平均孔径、気孔率、独立気孔の平均気孔径、かさ密度、セラミックス壁の厚み、3点曲げ強度を調べたので、その結果を表1に示す。なお、上記各物性は下記の要領で測定した。
(Experiment 1)
The average pore diameter, porosity, average pore diameter of independent pores, bulk density, ceramic wall thickness, and three-point bending strength in the materials A1 to A3 and Z1 were examined. The results are shown in Table 1. In addition, each said physical property was measured in the following way.
 〔空隙の平均孔径〕
 水銀圧入法により、JIS R 1655:2003に準拠し、空隙の平均孔径を測定した。測定圧力は0.003~379MPaで行った。尚、材料A1については、空隙の気孔径分布を図4に示す。
[Average pore diameter]
The average pore diameter of the voids was measured by a mercury intrusion method according to JIS R 1655: 2003. The measurement pressure was 0.003 to 379 MPa. For material A1, the pore size distribution of the voids is shown in FIG.
 〔気孔率〕
 水銀圧入法により、JIS R 1655:2003に準拠し、気孔率を測定した。測定圧力は0.003~379MPaで行った。
[Porosity]
The porosity was measured according to JIS R 1655: 2003 by the mercury intrusion method. The measurement pressure was 0.003 to 379 MPa.
 〔独立気孔の平均気孔径〕
 SEMによる多孔質セラミックスの微細組織観察写真により、独立気孔の気孔径を求め、平均値を算出した。
[Average pore diameter of independent pores]
The pore diameter of the independent pores was obtained from the microstructural observation photograph of the porous ceramics by SEM, and the average value was calculated.
 〔かさ密度〕
 アルキメデス法により、かさ密度を測定した。具体的には、JIS A1509-3に基づき測定した。
[Bulk density]
The bulk density was measured by the Archimedes method. Specifically, it was measured based on JIS A1509-3.
 〔セラミックス壁の厚み〕
 SEM(走査型電子顕微鏡)写真よりセラミックス壁の厚みを2カ所測定した。尚、材料A1のSEM(走査型電子顕微鏡)写真を図3(a)(b)[(a)倍率1000倍(b)倍率5000倍)]に、材料Z1のSEM(走査型電子顕微鏡)写真を図6(a)(b)[(a)倍率100倍(b)倍率押し1000倍]に示す。
[Ceramic wall thickness]
Two ceramic wall thicknesses were measured from SEM (scanning electron microscope) photographs. In addition, the SEM (scanning electron microscope) photograph of the material A1 is shown in FIGS. 3A and 3B [(a) magnification 1000 times (b) magnification 5000 times)], and the SEM (scanning electron microscope) photograph of the material Z1. Is shown in FIGS. 6 (a) and 6 (b) [(a) magnification 100 times (b) magnification push 1000 times].
 〔3点曲げ強度〕
 3点曲げ強度試験により、曲げ強度を測定した。具体的には、JIS A1509-4に基づき測定した。
[3-point bending strength]
The bending strength was measured by a three-point bending strength test. Specifically, it was measured based on JIS A1509-4.
 また材料A1のX線回折を行ったので、その結果を図5に示す。 Further, since the X-ray diffraction of the material A1 was performed, the result is shown in FIG.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
 表1において、材料A1と材料Z1を比較すると、気孔率及びかさ密度は同じであるにも関わらず、3点曲げ強度は材料A1が材料Z1の約1.4倍になっており、高強度な多孔質セラミックスとなっていることが分かる。また、材料A2と材料Z1を比較すると、材料A2は材料Z1と比べて、気孔率は20%減少し、かさ密度は約1.7倍となっているに過ぎないが、曲げ強度は10倍以上となっており、非常に高強度な多孔質セラミックスとなっていることが分かる。また、材料A3は、曲げ強度は2MPaと低いものの、従来技術では、気孔率が80%の多孔質セラミックスを得ることは困難であったことから、本発明の多孔質セラミックスの製造方法では、気孔率が80%以上の多孔質セラミックスを製造できることが分かった。 In Table 1, when comparing the material A1 and the material Z1, the three-point bending strength is about 1.4 times that of the material Z1 even though the porosity and bulk density are the same. It can be seen that this is a porous ceramic. Further, when comparing the material A2 and the material Z1, the material A2 has a porosity reduced by 20% and the bulk density is only about 1.7 times that of the material Z1, but the bending strength is 10 times. As described above, it can be seen that the porous ceramics has a very high strength. In addition, although the material A3 has a bending strength as low as 2 MPa, it was difficult to obtain porous ceramics having a porosity of 80% with the prior art. Therefore, in the method for producing porous ceramics according to the present invention, It was found that porous ceramics having a rate of 80% or more can be produced.
 図3(a)から明らかなように、材料A1では、約20μm径の球状の独立気孔が、3次元的に連結したセラミックス壁によって形成されていることがわかる。また、セラミックス壁の厚みが1.3~6.1μmであることがわかる。さらに図3(b)より、独立気孔の内壁が微細な凹凸形状であることがわかる。
 一方、図6(a)(b)から明らかなように、材料Z1では、球状の独立気孔が3次元的に連結したセラミックス壁によって形成された構造を有しておらず、不均一な気孔組織を有していることがわかる。
As is clear from FIG. 3A, in the material A1, it is understood that spherical independent pores having a diameter of about 20 μm are formed by ceramic walls that are three-dimensionally connected. It can also be seen that the thickness of the ceramic wall is 1.3 to 6.1 μm. Furthermore, it can be seen from FIG. 3B that the inner walls of the independent pores have a fine uneven shape.
On the other hand, as is apparent from FIGS. 6A and 6B, the material Z1 does not have a structure formed by ceramic walls in which spherical independent pores are three-dimensionally connected, and has an uneven pore structure. It can be seen that
 図4から明らかなように、材料A1では、Incremental Intrusionカーブ(差分細孔容積分布曲線)から、空隙の平均孔径は2.1μmであり、且つ、平均孔径から±50%の範囲に、全細孔容積の62%が存在していることが分かる。なお、細孔径100~400μm程度のIncremental Intrusionの分布はサンプル表面の凹部に圧入された水銀によるものである。また、上記の独立気孔径と比較すると、空隙の孔径は、独立気孔の10.5%の大きさを有していることが分かった。全気孔率はCumulative Intrusionカーブ(積算細孔容積分布曲線)から70%と解析された。 As is clear from FIG. 4, in the material A1, the average pore diameter of the voids is 2.1 μm from the Incremental Intrusion curve (differential pore volume distribution curve), and all the fine pores are within the range of ± 50% from the average pore diameter. It can be seen that 62% of the pore volume is present. The distribution of Incremental Intrusion having a pore diameter of about 100 to 400 μm is due to mercury pressed into the concave portion of the sample surface. Moreover, it turned out that the hole diameter of a space | gap has a magnitude | size of 10.5% of an independent pore compared with said independent pore diameter. The total porosity was analyzed as 70% from the CumulativetiIntrusion curve (integrated pore volume distribution curve).
 図5から明らかなように、本発明材料A1は表2の位置にピークが存在するので、本発明材料A1は炭化ケイ素のみから構成されることがわかる。 As is clear from FIG. 5, the material A1 of the present invention has a peak at the position shown in Table 2, and therefore it can be seen that the material A1 of the present invention is composed only of silicon carbide.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
(実験2)
 上記材料A3、Z1において、空隙の半径と積算細孔容積との関係、及び、空隙の半径と差分細孔容積との関係を調べたので、その結果を図7~図10に示す。なお、実験方法は上記実験1の〔空隙の平均孔径〕に示した方法と同様の方法で行った。また、水銀圧入法を用いて積算細孔容積を算出した場合、空隙の平均孔径から±50%の範囲における積算細孔容積の全積算細孔容積に対する割合(%)を、図8及び図10を用いて算出した。
(Experiment 2)
In the materials A3 and Z1, the relationship between the void radius and the accumulated pore volume and the relationship between the void radius and the differential pore volume were examined, and the results are shown in FIGS. In addition, the experiment method was performed by the method similar to the method shown in the above [Experiment 1 average pore diameter]. Further, when the integrated pore volume is calculated using the mercury intrusion method, the ratio (%) of the integrated pore volume to the total integrated pore volume in the range of ± 50% from the average pore diameter of the voids is shown in FIGS. It calculated using.
 図8に示すように、材料A3の場合、空隙の平均孔径(半径)は2.16μmであり、空隙の平均孔径の-50%は1.08μm、空隙の平均孔径の+50%は3.24μmである。また、空隙の平均孔径が1.08μmのときの積算細孔容積は1.02mL/gであり、空隙の平均孔径が3.24μmのときの積算細孔容積は0.07mL/gであり、更に、全積算細孔容積は1.19mL/gである。したがって、全積算細孔容積に対する空隙の平均孔径から±50%の範囲における積算細孔容積の割合(%)は、下記(2)式に示す通りである。
〔(1.02-0.07)/1.19〕×100=79.8(%)・・・(2)
As shown in FIG. 8, in the case of the material A3, the average pore diameter (radius) of the void is 2.16 μm, −50% of the average pore diameter of the void is 1.08 μm, and + 50% of the average pore diameter of the void is 3.24 μm. It is. The cumulative pore volume when the average pore diameter of the voids is 1.08 μm is 1.02 mL / g, and the cumulative pore volume when the average pore diameter of the voids is 3.24 μm is 0.07 mL / g, Furthermore, the total cumulative pore volume is 1.19 mL / g. Therefore, the ratio (%) of the cumulative pore volume in the range of ± 50% from the average pore diameter of the voids with respect to the total cumulative pore volume is as shown in the following formula (2).
[(1.02-0.07) /1.19] × 100 = 79.8 (%) (2)
 また、図10に示すように、材料Z1の場合、空隙の平均孔径は2.18μmであり、空隙の平均孔径の-50%は1.09μm、空隙の平均孔径の+50%は3.27μmである。また、空隙の平均孔径が1.09μmのときの積算細孔容積は0.58mL/gであり、空隙の平均孔径が3.27μmのときの積算細孔容積は0.18mL/gであり、更に、全積算細孔容積は0.73mL/gである。したがって、全積算細孔容積に対する空隙の平均孔径から±50%の範囲における積算細孔容積の割合(%)は、下記(3)式に示す通りである。
〔(0.58-0.18)/0.73〕×100=54.8(%)・・・(3)
 このような結果となることは、図7及び図9のグラフからも明らかである。
Further, as shown in FIG. 10, in the case of the material Z1, the average pore diameter is 2.18 μm, −50% of the average pore diameter is 1.09 μm, and + 50% of the average pore diameter is 3.27 μm. is there. Further, the cumulative pore volume when the average pore diameter of the voids is 1.09 μm is 0.58 mL / g, and the cumulative pore volume when the average pore diameter of the voids is 3.27 μm is 0.18 mL / g, Furthermore, the total cumulative pore volume is 0.73 mL / g. Therefore, the ratio (%) of the cumulative pore volume in the range of ± 50% from the average pore diameter of the voids with respect to the total cumulative pore volume is as shown in the following formula (3).
[(0.58-0.18) /0.73] × 100 = 54.8 (%) (3)
It is obvious from the graphs of FIGS. 7 and 9 that such a result is obtained.
 本発明の多孔質セラミックスは、高強度断熱材、人工骨、オイルフィルター、ルツボ、真空チャック、触媒担体、噴霧ノズル、潤滑剤含浸軸受け、金属熱処理架台、高効率輻射放熱材、原子炉用炉壁材、原子炉格納容器等として用いることができる。 The porous ceramics of the present invention include a high-strength heat insulating material, an artificial bone, an oil filter, a crucible, a vacuum chuck, a catalyst carrier, a spray nozzle, a lubricant-impregnated bearing, a metal heat treatment stand, a high-efficiency radiation heat dissipation material, and a reactor wall It can be used as a material, a containment vessel, etc.
 1:独立気孔
 2:セラミックス壁
 3:独立気孔間を連通する空隙
 4:独立気孔に残存した炭素質材料
1: independent pores 2: ceramic wall 3: voids communicating between independent pores 4: carbonaceous material remaining in independent pores

Claims (14)

  1.  窒化アルミニウム、炭化ケイ素、及び窒化ケイ素からなる群から選択される少なくとも1種を含むセラミックス粒子と、炭素質粒子とを、この炭素質粒子の表面に前記セラミックス粒子が均一に付着するように両者を混合した後、混合物を押圧しつつ、又は混合物を押圧した後に、焼結して焼結体を得、しかる後、前記焼結体に含まれる前記炭素質粒子を酸化焼失させることにより製造されることを特徴とする多孔質セラミックス。 Ceramic particles containing at least one selected from the group consisting of aluminum nitride, silicon carbide, and silicon nitride, and carbonaceous particles are bonded together so that the ceramic particles are uniformly attached to the surface of the carbonaceous particles. After mixing, while pressing the mixture or after pressing the mixture, it is sintered to obtain a sintered body, and then manufactured by oxidizing and burning out the carbonaceous particles contained in the sintered body. Porous ceramics characterized by that.
  2.  前記炭素質粒子の一部が残存している、請求項1に記載の多孔質セラミックス。 The porous ceramic according to claim 1, wherein a part of the carbonaceous particles remains.
  3.  窒化アルミニウム、炭化ケイ素、及び窒化ケイ素からなる群から選択される少なくとも1種を含むセラミックス粒子を備えた多孔質セラミックスであって、
     前記セラミックス粒子の一部が結合してなるセラミックス壁と、
     前記セラミックス壁に囲まれることにより形成された複数の独立気孔と、
     を有し、
     前記複数の独立気孔間が、前記独立気孔径より小さい孔径の空隙により連通され、
     前記空隙の孔径が10nm以上5μm以下であることを特徴とする多孔質セラミックス。
    Porous ceramics comprising ceramic particles containing at least one selected from the group consisting of aluminum nitride, silicon carbide, and silicon nitride,
    A ceramic wall formed by bonding a part of the ceramic particles;
    A plurality of independent pores formed by being surrounded by the ceramic wall;
    Have
    The plurality of independent pores are communicated with each other by a gap having a pore size smaller than the independent pore size,
    A porous ceramics characterized in that the pore diameter of the voids is 10 nm or more and 5 μm or less.
  4.  水銀圧入法を用いて積算細孔容積を算出した場合、前記空隙の平均孔径から±50%の範囲に、全積算細孔容積の60%以上が存在する、請求項3に記載の多孔質セラミックス。 The porous ceramics according to claim 3, wherein when the cumulative pore volume is calculated using a mercury intrusion method, 60% or more of the total cumulative pore volume exists in a range of ± 50% from the average pore diameter of the voids. .
  5.  水銀圧入法を用いて積算細孔容積を算出した場合、前記空隙の平均孔径から±50%の範囲に、全積算細孔容積の75%以上が存在する、請求項4に記載の多孔質セラミックス。 The porous ceramics according to claim 4, wherein when the cumulative pore volume is calculated using a mercury intrusion method, 75% or more of the total cumulative pore volume exists in a range of ± 50% from the average pore diameter of the voids. .
  6.  気孔率が50%以上80%以下である、請求項3~5のいずれか1項に記載の多孔質セラミックス。 The porous ceramic according to any one of claims 3 to 5, having a porosity of 50% or more and 80% or less.
  7.  前記空隙の孔径は、前記独立気孔の気孔径の20%以下であり、前記独立気孔の気孔径が5μm以上50μm以下である、請求項3~6のいずれか1項に記載の多孔質セラミックス。 The porous ceramics according to any one of claims 3 to 6, wherein the pore diameter of the voids is 20% or less of the pore diameter of the independent pores, and the pore diameter of the independent pores is 5 µm or more and 50 µm or less.
  8.  前記セラミックス壁の厚みが0.1μm以上7μm以下である、請求項3~7のいずれか1項に記載の多孔質セラミックス。 The porous ceramic according to any one of claims 3 to 7, wherein a thickness of the ceramic wall is 0.1 µm or more and 7 µm or less.
  9.  前記独立気孔の内壁が微細な凹凸形状である、請求項3~8のいずれか1項に記載の多孔質セラミックス。 The porous ceramic according to any one of claims 3 to 8, wherein an inner wall of the independent pore has a fine uneven shape.
  10.  3点曲げ強度が1MPa以上200MPa以下である、請求項3~9のいずれか1項に記載の多孔質セラミックス。 The porous ceramic according to any one of claims 3 to 9, wherein the three-point bending strength is 1 MPa or more and 200 MPa or less.
  11.  前記独立気孔のうち、一部の独立気孔内には炭素質材料が存在している、請求項3~10のいずれか1項に記載の多孔質セラミックス。 The porous ceramic according to any one of claims 3 to 10, wherein a carbonaceous material is present in some of the independent pores.
  12.  前記セラミックス壁に対する前記炭素質材料の重量割合が厚み方向に傾斜的に低下する、請求項11に記載の多孔質セラミックス。 The porous ceramic according to claim 11, wherein a weight ratio of the carbonaceous material to the ceramic wall is gradually decreased in a thickness direction.
  13.  窒化アルミニウム、炭化ケイ素、及び窒化ケイ素からなる群から選択される少なくとも1種を含むセラミックス粒子と、炭素質粒子とを、この炭素質粒子の表面に前記セラミックス粒子が均一に付着するように混合し、混合体を得る第1の工程と、
     前記混合体を加圧しつつ焼結し、又は前記混合体を加圧した後に焼結して、焼結体を得る第2の工程と、
     前記焼結体に含まれる、前記炭素質粒子を酸化焼失させる第3の工程と、
     を備えることを特徴とする多孔質セラミックスの製造方法。
    Ceramic particles containing at least one selected from the group consisting of aluminum nitride, silicon carbide, and silicon nitride, and carbonaceous particles are mixed so that the ceramic particles uniformly adhere to the surface of the carbonaceous particles. A first step of obtaining a mixture;
    Sintering while pressing the mixture, or sintering after pressing the mixture to obtain a sintered body;
    A third step of oxidizing and burning out the carbonaceous particles contained in the sintered body;
    A method for producing porous ceramics, comprising:
  14.  前記第3の工程において、前記炭素質粒子の一部を残存させるように酸化焼失させる、請求項13に記載の多孔質セラミックスの製造方法。 The method for producing porous ceramics according to claim 13, wherein in the third step, the carbonaceous particles are oxidized and burned out so as to leave a part of the carbonaceous particles.
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