TW201529529A - Method for produce porous ceramics, porous ceramics, setter and sintering jig - Google Patents

Abstract

An embodiment of a method for producing a porous ceramics of the present application comprises: a step of gelatin a dispersion; a step of freezing the gelatinized dispersion to form a freeze product; a step of removing the ice generated in the freeze product to form holes; and a step of sintering the ice-removed freeze body. The dispersion comprises ceramics particle, water-soluble polymer and water. The viscose [eta] (mPa,s) of the dispersion prior gelatin at 20 DEG C and the average particle size d([mu]m) of the ceramics particles has a relationship of [eta] ≥ 950*d<SP>-0.77</SP>.

Description

Method for producing porous ceramic, porous ceramic, bracket and firing aid

The embodiment disclosed in the present invention relates to a method for producing a porous ceramic, a porous ceramic, a bracket, and a baking aid.

Conventionally, porous ceramics in which a large number of pores are formed in ceramics, such as a filter or an adsorbent for removing impurities from a gas or a liquid, or a supporting material for an exhaust gas purifying catalyst for automobiles, are used for various purposes. on.

In the method for producing a porous ceramic, a method in which a gelation freezing method for freezing a suspension (slurry) is used (for example, refer to Patent Document 1) is known. This suspension (slurry) is obtained by dispersing ceramic particles in an aqueous solution of a water-soluble polymer.

(previous technical literature) (Patent Literature)

Patent Document 1: Japanese Patent No. 5176198

However, in the manufacturing method described in Patent Document 1, a porous ceramic having various pore diameters and porosity can be obtained by changing the freezing temperature or the amount of ceramic particles, but on the other hand, heat resistance is produced. There is still room for improvement in the area of porous ceramics with excellent punching properties and bending strength.

In view of the above-described problems, an object of the present invention is to provide a method for producing a porous ceramic having excellent heat-resistant punching properties and bending strength, a porous ceramic, a bracket, and a firing aid.

The method for producing a porous ceramic according to the embodiment includes a step of gelling a suspension, a step of freezing the gelled suspension to form a frozen body, and removing the ice grown on the frozen body to form pores. And firing the step of removing the aforementioned frozen body of the ice. The suspension system contains ceramic particles, a water-soluble polymer, and water. The viscosity η (mPa.s) of the suspension before gelation at 20 ° C and the average particle diameter d (μm) of the ceramic particles have a relationship of η ≧ 950 × d - ^0.77 .

According to one aspect of the embodiment, a porous ceramic, a method for producing a porous ceramic, and a cooling device having a small variation in pore diameter can be provided.

1, 1a‧‧‧ceramic particles

2, 2a‧‧‧Water soluble polymer

3, 3a‧‧‧ water

4, 4a‧‧‧ suspension

5, 5a‧‧‧ ice

6, 6a‧‧‧ frozen body

7, 7a‧‧‧ lower surface

8, 8a‧‧‧ upper surface

9, 9a‧‧‧ ceramic skeleton

10, 10a‧‧‧ stomata

11, 11a‧‧‧ Porous ceramics

12, 12a‧‧‧ Cooling device

13‧‧‧Burning aids

14‧‧‧Abutment

15‧‧‧ Board Department

16‧‧‧Support

17‧‧‧ bracket

17a‧‧‧Upper surface

18‧‧‧Furned goods

Fig. 1 is an explanatory view showing an outline of a method for producing a porous ceramic according to an embodiment.

Fig. 2A is a schematic perspective view showing the outline of the configuration of the firing aid of the embodiment.

Fig. 2B is a schematic plan view of the firing aid of Fig. 2A.

Fig. 3 is a partial cross-sectional view showing a porous ceramic produced by Example 1.

Fig. 4A is a partial cross-sectional view showing a porous ceramic produced by Example 8.

Fig. 4B is a partial cross-sectional view of the porous ceramic produced by the eighth embodiment.

Fig. 5 is a view for explaining a method of measuring variations in average pore diameter and pore diameter.

Fig. 6 is a flow chart showing an example of a method for producing a porous ceramic according to an embodiment.

Fig. 7 is an explanatory view for explaining an outline of a method for producing a porous ceramic.

Fig. 8 is a partial cross-sectional view showing a porous ceramic produced by Comparative Example 1.

Hereinafter, embodiments of the method for producing a porous ceramic disclosed in the present invention, a porous ceramic, a bracket, and a firing aid will be described in detail with reference to the accompanying drawings. Further, the present invention is not limited to the embodiments described below.

The porous ceramic of the embodiment is compatible with a conventional porous ceramic in that it can be produced by a production method including steps of gelation, freezing, drying, degreasing, and firing. On the other hand, in the method for producing a porous ceramic according to the embodiment, since the viscosity η at 20 ° C and the average particle diameter d of the ceramic particles have a specific relationship in the suspension before gelation, it is formed and known. Porous ceramics with different manufacturing methods. Hereinafter, first, a method for producing a porous ceramic or a porous ceramic according to an embodiment will be described.

Fig. 1 is an explanatory view showing an outline of a method for producing a porous ceramic according to an embodiment. Fig. 7 is an explanatory view for explaining an outline of a method for producing a porous ceramic to which a gelation freezing method is applied. In addition, in the first drawing and the seventh drawing, the steps of gelatinization, freezing, and firing from the left in the above-described manufacturing steps are illustrated, and the steps corresponding to the steps of drying and degreasing are omitted. Show.

First, the gelation step will be described. The gelation step is a step of placing the suspension 4 into a mold and gelating the same, the suspension system comprising the ceramic particles 1a, the water-soluble polymer 2, and the water 3a, and uniformly dispersing the ceramic particles 1a in a water-soluble state. In the aqueous solution of molecule 2. By the gelation of the suspension 4, a structure (gelled body) temporarily fixed in a state in which the ceramic particles 1a are dispersed in the aqueous solution of the water-soluble polymer 2 is formed.

Next, the freezing step will be described. The freezing step is a step of cooling the gelled suspension 4 to form a frozen body 6. When the gelled suspension 4 is cooled, the water 3 system separated from the aqueous solution of the water-soluble polymer 2 changes to ice 5, and crystallizes on one side. Structure, grow on one side. As a result, the frozen body 6 is obtained, and the frozen body 6 includes a portion (not shown) in which the aqueous solution of the ceramic particles 1 and the water-soluble polymer 2 is gelled, and a portion of the crystallized ice 5.

In the conventional manufacturing method, for example, the cooling device 12a is disposed on the lower surface 7a side to cool the gelled suspension 4 from one side, and the water 3a in the gelled suspension 4a is from the lower surface. The 7a side is frozen and the state is changed to ice 5a, and the crystal of the ice 5a is intended to grow from the lower surface 7a side toward the upper surface 8a side. In addition, when the crystal of the ice 5a grows, for example, there is a sufficient pressing force for moving the relatively small ceramic particles 1a having an average particle diameter of about 0.01 to 5 μm. Therefore, when the ceramic particles 1a are present in the direction in which the crystals of the ice 5a are to be grown, the ceramic particles 1a temporarily fixed by gelation are moved so as to be excluded from the crystal of the grown ice 5a.

Thus, in the conventional manufacturing method shown in Fig. 7, when the gelled suspension 4a is cooled from one direction, the ice 5a which grows into a column shape from one side to the other side is surrounded. In the manner of crystallization, the ceramic particles 1a are rearranged, whereby the frozen body 6 which is densely distributed in the distribution of the ceramic particles 1a is obtained.

On the other hand, in the method for producing a porous ceramic according to the embodiment, the viscosity is adjusted so that the viscosity of the suspension 4 becomes larger as the average particle diameter of the ceramic particles 1 to be used becomes smaller. 4. Specifically, the viscosity η (mPa.s) of the suspension before gelation at 20 ° C and the average particle diameter d (μm) of the ceramic particles have a relationship of η ≧ 950 × d - 0.77.

When the average particle diameter d and the viscosity η have such a relationship, even if the crystal of the ice 5 grows and approaches or collides with the ceramic particle 1, the ceramic particle 1 can withstand the pressing force generated by the crystal growth accompanying the ice 5 regardless of its size. Therefore, the ceramic particles 1 at this portion hardly move in the freezing step, and stay at the position where they remain as the gelled body.

Further, the ice 5 system changes the growth direction of the crystal every time the ceramic particles 1 are collided, and the crystal grows in a zigzag shape from the side of the lower surface 7 where the cooling device 12 is disposed toward the upper surface 8 side. Further, since the crystals of the ice 5 grow in a zigzag manner, the crystals of the ice 5 close to each other grow and collide with each other depending on the situation. Therefore, in the method for producing a porous ceramic according to the embodiment, as shown in Fig. 1, even if the gelled suspension 4 is cooled from the lower surface 7 side, it is possible to obtain ice 5 which grows in a random direction. The frozen body 6 at the portion between the ceramic particles 1.

As described above, in the method for producing a porous ceramic according to the embodiment, even when the gelled suspension 4 is cooled from the lower surface 7 side, ceramic particles 1 having ice 5 grown in a random direction and uniformly dispersed can be obtained. The frozen body 6 between the parts. Further, when the average particle diameter d and the viscosity η particularly have a relationship of η ≧ 1630 × d - ^0.77 , the frozen body 6 in which the ice is grown 5 times and the whole is grown in the random direction can be obtained.

Next, the drying step will be described. The drying step is a step of removing the ice 5 which has grown into the frozen body 6 to form the pores 10. For example, when the frozen body 6 in which the ice 5 is grown is dried by vacuum drying, the crystal of the ice 5 is sublimated and disappears, and the pores 10 are formed instead. That is, the drying step is a step of replacing the ice 5 with the pores 10.

Next, the degreasing step will be described. The degreasing step is a step of removing the organic component of the water-soluble polymer 2 or the like from the frozen body 6 which forms the pores 10 in the drying step. Specifically, depending on the type of the ceramic particles 1, a treatment for decomposing the organic component of the water-soluble polymer 2 or the like under a predetermined temperature condition and removing it is performed.

Finally, the firing step is explained. In the firing step, the organic component such as ice 5 and water-soluble polymer 2 is removed, and the frozen body 6 in which the pores 10 are formed is fired to produce a porous ceramic 11 . The porous ceramic 11 obtained by firing has the pores 10 formed in the above-described drying step, and the ceramic skeleton 9 which is densified by bonding the ceramic particles 1 to each other so as to surround the pores 10.

The porous ceramic 11 obtained after firing has a different shape depending on the shape of the frozen body 6 formed in the freezing step. In other words, in the conventional manufacturing method, as shown in Fig. 7, a porous ceramic 11a in which a ceramic skeleton 9a is formed is formed around a columnar pore 10a formed from one direction side toward the other direction side. On the other hand, in the method for producing the porous ceramics 11 of the embodiment, the ceramic skeleton 9 is formed into a three-dimensional mesh shape so that the pores 10 are formed in a random direction, thereby generating heat-resistant punching property and bending strength. Good porous ceramic 11 (see Figure 3). Here, the "holes 10 are formed in a random direction" means that the average aspect ratio of the pores 10 is 2.0 or more, and more preferably 3.5 or more. Further, the average aspect ratio of the pores 10 can be measured by the method described in the examples below.

Manufacturing method of porous ceramic 11 in embodiment In the meantime, the ceramic particles 1 are not particularly limited as long as they can be appropriately fired in the firing step. Specifically, for example, zirconia, alumina, ceria, titania, tantalum carbide, boron carbide, tantalum nitride, boron nitride, cordierite, hydroxyphosphorus lime, sialon, zircon, One or more of aluminum titanate and mullite are used as the ceramic particles 1, but the invention is not limited thereto. Further, for example, alumina or cerium oxide is used to produce mullite, or zirconia and alumina are used to produce a composite, and a plurality of ceramic particles 1 are used in combination depending on desired characteristics.

Further, the ceramic particles 1 are preferably those having a practical average particle diameter of 100 μm or less. When the average particle diameter of the ceramic particles 1 exceeds 100 μm, it is difficult to appropriately fire the ceramic particles 1 due to the shape or size of the desired porous ceramics 11. Here, the "average particle diameter" refers to an intermediate value diameter (d50) obtained by a particle size distribution based on a volume equivalent to a sphere equivalent diameter in a laser diffraction type particle size distribution measuring apparatus (wet method). Further, as long as the same result can be obtained, the measurement method is not limited.

The blending amount of the ceramic particles 1 in the suspension is preferably in the range of 1 to 50 vol%, more preferably 1 to 30 vol%. When the amount of the ceramic particles 1 is less than 1 vol%, for example, the shape may not be maintained in the drying step, and it is difficult to produce the porous ceramic 11 having a desired strength. Further, when the compounding amount of the ceramic particles 1 exceeds 50 vol%, the porosity of the obtained porous ceramics 11 may become low, and the desired characteristics of the porous body may not be sufficiently exhibited. Here, "porosity" means the value obtained by the Archimedes method according to the method specified in JISR1634:2008. In this assay, by The closed pores are not considered, so they are also called "appearance porosity". Further, in the present embodiment, since the air vent is hardly formed, the "appearance porosity" can be treated as "porosity".

Further, in order to appropriately fire the ceramic particles 1, one or two or more kinds of firing aids may be blended in the suspension depending on the type of the ceramic particles 1. Specific examples of the baking aid include alumina, calcium carbonate, cerium oxide, boron carbide, cerium oxide, and the like, but are not limited thereto. Further, calcium carbonate (CaCO ₃ ) added as a baking aid is decomposed by firing and becomes calcium oxide (CaO) and remains in the porous ceramic 11 .

Further, in order to appropriately gel the suspension, if necessary, various additives such as a pH adjuster, an initiator, a crosslinking agent, and a tackifier may be added depending on the type of the water-soluble polymer.

In addition, as for the water-soluble polymer 2, the dispersion of the ceramic particles 1 can be stably maintained from the gelation step to the drying step, and the growth of the ice 5 does not hinder the growth of the ice 5 in the freezing step. There are no special restrictions. Specifically, for example, an N-alkyl guanamine-based polymer, an N-isopropyl acrylamide-based polymer, a sulfonic acid methylated acrylamide-based polymer, and an N-dimethylaminopropyl group are used. Methyl acrylamide-based polymer, polyalkyl acrylamide-based polymer, alginic acid, sodium alginate, ammonium alginate, polyethyleneimine, carboxymethylcellulose, hydroxymethylcellulose, methylcellulose , hydroxyethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, sodium polyacrylate, polyethylene glycol, polyethylene oxide, polyvinyl alcohol, polyvinyl pyrrolidone, Carboxyvinyl polymer, starch, gelatin, agar, pectin, glucomannan, sambag, locust bean gum, One or two or more kinds of carrageenan, guar gum, and gellan gum are used as the water-soluble polymer 2, but are not limited thereto. In the case where the water-soluble polymer 2 having the property of gelling the suspension 4 is applied by cooling, it is practically preferable to easily mix the ceramic particles 1 and 3 when the suspension 4 is produced. The gelation temperature of the water-soluble polymer 2 is 50 ° C or lower. Further, specific examples of the water-soluble polymer 2 include gelatin, agar, carrageenan, and gellan gum.

Further, in order to easily and uniformly disperse the ceramic particles 1 in the suspension 4, for example, a dispersant such as a carboxylic acid-based dispersant or a maleic acid-based dispersant may be used. Further, in order to adjust the viscosity η of the suspension 4 to a desired degree corresponding to the average particle diameter d of the ceramic particles 1, a water-soluble tackifier which can be used in combination with the water-soluble polymer 2 may be blended. Specific examples of such a tackifier include, for example, a thickening polysaccharide, a cellulose dielectric, a polyethylene, a polyester, a polyamine, a polyethylene glycol, or a polyvinyl alcohol. The polyepoxyalkyl group, the polyacrylic acid, and the compounds of the combinations are not limited to the above. Further, although the exemplified tackifier is the same as the above-described water-soluble polymer 2, the ungelled component is defined as a "tackifier" in the above gelation step.

Further, in the freezing step, a known cooling device 12 can be utilized. Specifically, a cooling device 12 to which the following various cooling methods are applied is provided: the lower surface 7 side of the gelled body which gels the suspension 4 is brought into contact with a solid such as a cooled metal plate, and impregnated with a mold. In a cooled liquid. In addition, for example, in a manner that does not cause stagnation or waves near the liquid level of ethanol, from one side to the other side In the formula, the ethanol is cooled to a predetermined temperature, whereby an ethanol cooling device that maintains the temperature in the vicinity of the liquid surface to a constant temperature can be applied as the cooling device 12. By applying the ethanol cooling device having the above configuration, the bottom surface of the mold in which the suspension 4 is placed is brought into contact with or immersed in the liquid surface of the cooled ethanol to hold the frozen body 6, thereby producing a variation in the pore diameter. Less porous ceramics 11.

Further, the freezing temperature of the gelled body in the freezing step is not limited as long as the water 3 in the gelled body can be frozen to form ice 5 . Further, depending on the type of the water-soluble polymer 2, there is a case where the gelled body does not freeze at a temperature higher than -10 ° C due to the interaction between the water-soluble polymer 2 and the water 3, and therefore it is preferably Freezing temperature below -10 °C.

Further, in the drying step, it is possible to use a drying method in which the ice 5 is gradually replaced with the pores 10 while suppressing the difference in the drying speed between the inside and the outside of the frozen body 6 to prevent cracking. Specifically, the ice 5 can be replaced with the pores 10 by freeze-drying the frozen body 6 or by immersing the frozen body 6 in a water-soluble organic solvent or a water-soluble organic solvent aqueous solution and air drying.

For example, when the frozen body 6 is immersed in a water-soluble organic solvent or an aqueous solution of a water-soluble organic solvent, the ice 5 in the frozen body 6 is dissolved and mixed with a water-soluble organic solvent. By performing the operation one or more times, first, the portion of the frozen body 6 belonging to the ice 5 is replaced with a water-soluble organic solvent. Then, the frozen body 6 replaced by the water-soluble organic solvent inside the frozen body 6 is dried in the atmosphere or under reduced pressure, in the freezing step. The portion belonging to the ice 5 is replaced with the air hole 10.

In the drying step using a water-soluble organic solvent, the water-soluble organic solvent is suitable for those which do not erode the water-soluble polymer 2 and have a higher volatility than water 3. Specific examples thereof include methanol, ethanol, isopropanol, acetone, ethyl acetate, and the like, but are not limited thereto. The pores 10 are formed in the frozen body 6 by the use of the water-soluble organic solvent alone or in plural times, or in combination with a plurality of types of drying, in the portion of the frozen body 6 which belongs to the ice 5.

Further, in the degreasing step, for example, a degreasing temperature of 300 ° C to 900 ° C is applied. Here, when a non-oxide ceramic such as tantalum carbide or tantalum nitride is degreased. Degreasing is preferably carried out under an inert gas atmosphere such as argon or nitrogen. On the other hand, when an oxide ceramic such as alumina, zirconia or apatite is used as a raw material, it is preferable to carry out degreasing in an atmospheric environment.

Further, in the firing step, the firing temperature, the firing time, and the firing environment are appropriately adjusted depending on the type or blending amount of the ceramic particles 1 to be used, the hardness of the target, and the like, thereby producing heat-resistant punching properties and bending. Porous ceramic 11 with good strength.

The porosity of the porous ceramic 11 obtained as described above is preferably in the range of 50% to 99%, more preferably 70% to 99%. When the porosity of the porous ceramics 11 is less than 50%, the necessity of using the method for producing the porous ceramics 11 of the embodiment is reduced. Further, when the porosity of the porous ceramics 11 exceeds 99%, for example, the shape may not be maintained in the drying step, and it is difficult to produce the porous ceramic 11 having a desired strength.

Further, the porous ceramic 11 is preferably a communication hole having an average pore diameter of 10 μm to 300 μm, more preferably 10 μm. Up to 100 μm. Further, the average pore diameter can be measured by the method described in the examples below.

Further, the average bending strength of the porous ceramics 11 is preferably 10 MPa in practical use. Further, the heat-resistant punchability of the porous ceramics 11 is preferably 450 ° C or more, more preferably 600 ° C or more. Further, the average bending strength and the heat-resistant punching property can be measured by the method described in the examples below.

As the porous ceramic 11 produced as described above, for example, a firing aid used in the step of firing an electronic component included in the process of manufacturing an electronic component such as a laminated ceramic capacitor can be used. In the firing step, the electronic component belonging to the object to be fired is placed in the firing aid and fired in the kiln.

Hereinafter, the firing aid for the porous ceramic 11 to which the embodiment is applicable will be described with reference to FIGS. 2A and 2B. In addition, in FIGS. 2A and 2B, in order to more easily explain, the X-axis direction, the Y-axis direction, and the Z-axis direction orthogonal to each other are defined, and the Z-axis positive direction is defined as a vertical upward direction.

Fig. 2A is a schematic perspective view showing the outline of the configuration of the firing aid of the embodiment. Fig. 2B is a schematic plan view showing the firing aid shown in Fig. 2A viewed from the negative side of the Y-axis.

As shown in FIGS. 2A and 2B, the firing aid 13 is provided with a base 14 and a bracket 17. Further, the fired material 18 is placed on the bracket 17 of the baking aid 13 .

The object to be fired 18 is an electron such as a laminated ceramic capacitor. Components. That is, the above-described firing aid 13 is a firing aid for electronic parts. Further, in the above description, the object 18 to be fired is used as a laminated ceramic capacitor, but it is exemplified, and is not limited thereto. In other words, the object to be fired 18 may be any type as long as it is an electronic component that is fired, such as a wafer sensor or a semiconductor substrate.

The baking aid 13 is placed in a kiln (not shown) in a state where the object 18 to be fired on the upper surface 17a of the bracket 17, and the workpiece 18 is fired.

The base 14 of the baking aid 13 is provided with a plate portion 15 and a support portion 16. The plate portion 15 is formed in a shape in which the bracket 17 can be placed on the upper surface, and specifically, for example, has a substantially flat shape and is substantially rectangular in plan view.

The support portion 16 has a plurality of (for example, four, one of which is not visible in the second AA), and is formed at an appropriate position on the lower surface side of the plate portion 15. Specifically, the support portion 16 is formed to protrude from the square corner portion of the lower surface of the plate portion 15 in the negative direction of the Z-axis to support the plate portion 15.

Further, the base 14 is not limited to the shape shown in FIGS. 2A and 2B. That is, the base 14 may be, for example, a sleeve (a basin) or a carrier plate, and the like, and the shape of the bracket 17 may be mainly placed. Further, the base 14 and the bracket 17 do not have to be different bodies, and may be configured to be integrated.

Further, the shape of the plate portion 15 is not limited to the above-described substantially rectangular shape. That is, the shape of the plate portion 15 may be a polygonal shape such as a square or a triangle, or other shapes such as a circular shape or an elliptical shape.

Further, the bracket 17 of the present embodiment is formed into a substantially rectangular shape in a plan view and has a thin plate shape having a thin thickness in the Z-axis direction. Thus, by making the bracket 17 into a thin plate shape, the bracket 17 and even the baking aid 13 itself can be made lighter.

The porous ceramics 11 of the embodiment can be applied to the firing aid 13 configured as described above. Further, the plate portion 15 and the support portion 16 constituting the base 14 may be integrally molded, and the plate portion 15 and the support portion 16 which are separately formed may be formed by a variety of other joining methods such as adhesion, pressure bonding, and sintering.

Further, when the porous ceramics 11 of the embodiment is used as the firing aid 13, the porous ceramics 11 preferably contains 0.01 to 1.5% by mass of Al ₂ O with respect to the fully stabilized zirconia as the ceramic particles 1 . ₃ and 0.01 to 2.0% by mass of CaO. When the porous ceramic 11 of the embodiment contains an appropriate amount of Al ₂ O ₃ and Ca with respect to the fully stabilized zirconia, the heat-resistant squeezing property and the bending strength are further improved.

In this way, since the porous ceramics 11 of the embodiment are used as the baking aid 13, the hot air in the kiln passes through the abutment disposed on the lower surface side of the object 18 when the workpiece 18 is fired. 14 and the bracket 17 reach the lower side and the side of the kiln. Therefore, the temperature unevenness in the kiln can be reduced, and the fired material 18 can be efficiently fired. Further, when degreasing is performed to remove other organic components such as a binder to be prepared in the object 18 to be fired, the organic component can be efficiently removed from the object 18 to be fired.

Further, in the drawings 2A and 2B, although one firing aid 13 is shown, the present invention is not limited thereto. For example, the firing aid 13 may be stacked in a plurality of stages in the positive direction of the Z-axis, and placed. Burning in the plural Most of the fired articles 18 of the aid 13 are simultaneously fired.

Further, in the above description, the porous ceramic 11 of the embodiment is applied to the base 14 and the bracket 17, but the porous ceramic 11 may be applied to the base 14 and the bracket 17. One. Further, the porous ceramic 11 of the embodiment may be applied to one of the plate portion 15 and the support portion 16 constituting the base 14.

Next, a method of producing the porous ceramic 11 of the embodiment will be described in detail with reference to FIG. Fig. 6 is a flow chart showing the processing procedure of the porous ceramic 11 of the embodiment.

As shown in Fig. 6, first, the ceramic particles 1, the water-soluble polymer 2, and the water 3 are mixed to prepare a suspension 4 (step S101). Various additives such as a baking aid, a pH adjuster, a starter, and a crosslinking agent can be added at this point in time. In addition, the water-soluble polymer 2 may be used by mixing with the water 3 before mixing with the ceramic particles 1 to form an aqueous solution, or may be added to the water during stirring by mixing the water-soluble polymer 2 and the ceramic particles 1 in advance. 3. Further, when a dispersant is used, it is preferred to mix with the ceramic particles 1 in advance.

Next, the suspension 4 prepared in the step S101 is gelated to form a gelled body (step S102). In order to promote gelation of the suspension 4, the suspension 4 may be heated if necessary.

Next, the gelled body 4 is frozen to form a frozen body 6 having a portion where the crystal of the ice 5 grows in a random direction (step S103). Then, the frozen body 6 is dried and the ice 5 grown on the frozen body 6 is removed to form the pores 10 (step S104).

Furthermore, the removal of the water-soluble polymer 2 from the frozen body 6 is performed. Degreasing of the organic component (step S105), followed by firing (S106), wherein the frozen body 6 removes the ice 5 to form the pores 10. By the above steps, the production of a series of porous ceramics 11 of one embodiment is completed.

As described above, the method for producing a porous ceramic according to the embodiment includes the step of gelling the suspension, the step of freezing the gelled suspension to form a frozen body, and the ice grown in the frozen body. The step of removing the pores and the step of firing the frozen body after removing the ice. The suspension system contains ceramic particles, a water-soluble polymer, and water. The viscosity η (mPa.s) of the suspension before gelation at 20 ° C and the average particle diameter d (μm) of the ceramic particles have a relationship of η ≧ 950 × d - ^0.77 .

Therefore, according to the method for producing a porous ceramic according to the embodiment, a porous ceramic having excellent heat resistance and excellent bending strength can be produced.

In addition, in the above-described embodiment, the cooling device 12 that freezes the gelled body in which the suspension 4 is gelated is disposed on one side of the gelled body, but the invention is not limited thereto. . For example, the gelled body may be placed in a freezing chamber set to a predetermined freezing temperature depending on the mold, or may be a method in which the upper and lower surfaces are blocked by a heat insulating material and cooled from the side by radiation heat. In other words, according to the method for producing the porous ceramics 11 of the embodiment, regardless of the configuration of the cooling device 12, the porous ceramics 11 in which the pores 10 are formed in a random direction and which have excellent heat-resistant punchability and bending strength are formed.

Further, in the above-described embodiment, the ethanol cooling device is used as the cooling device 12 as an example, but the solidification temperature is as long as it is A liquid refrigerant having a low degree and reaching a desired temperature for freezing the gelled body may be used other than ethanol. Specific examples thereof include ethanol, methanol, isopropanol, acetone, ethylene glycol, and the like, but are not limited thereto. Further, the refrigerants 17 may be used singly or in combination of plural kinds, and may be used by mixing with water as needed.

Further, in the above-described embodiment, the degreasing step (step S105) is described as an essential step, but the type and the amount of the water-soluble polymer 2 may be omitted. At this time, the water-soluble polymer 2 is decomposed and removed in the firing step (step S106).

Further, the relationship between the viscosity η at 20 ° C and the average particle diameter d of the ceramic particles 1 of the suspension 4 before gelation in the method for producing the porous ceramic 11 of the embodiment is obtained as follows. First, the characteristics required for the porous ceramic 11 of the embodiment are focused on the average aspect ratio, the average bending strength, and the heat-resistant punchability of the pores 10. Next, the average particle diameter d (μm) of the ceramic particles 1 and the viscosity η (mPa.s) of the suspension 4 before gelation at 20 ° C were changed, and the porous ceramic 11 was produced, and the obtained porous material was measured. The above three characteristics of the ceramic 11. Further, when the correlation is evaluated from the values of d and η which satisfy the conditions of the average aspect ratio of the pores 10 to 1.4, the average bending strength of 10 MPa or more, and the heat-resistant punching property of 450 ° C or more, the relationship η can be obtained. ≧1630×d ^-0.77 . Then, by using the suspension 4 adjusted in such a manner as to conform to the relationship, it was confirmed that the porous ceramic 11 having excellent heat resistance and bending strength can be produced.

Further, when the viscosity η and the average particle diameter d have a relationship of 950 × d - ^0.77 ≦ η < 1630 × d - ^0.77, it is also known that the pores 10 are not randomly formed at all, and are partially aligned. The method is formed, but the porous ceramic 11 having excellent heat resistance and bending strength is formed.

[Examples]

(Example 1)

20 vol% of fully stabilized zirconia (YSZ) particles (corresponding to ceramic particles 1) having an average particle diameter of 9 μm, 1.5% by mass of alumina as a sintering aid (relative to stabilized zirconia), and calcium carbonate 3.5 % by mass (2.0% by mass in terms of fully stabilized zirconia, in terms of calcium oxide), and 80.0 vol% in water. In the mixed liquid, a small amount of hydroxypropylcellulose as a tackifier and 3.0% by mass (relative to water 3) of gelatin (corresponding to water-soluble polymer 2) were added to prepare a suspension 4. The prepared suspension 4 was placed in a mold and allowed to stand in a refrigerator at 5 ° C to effect gelation of the suspension 4 .

Next, the mold 23 in which the gelled suspension 4 was placed was placed in a freezer at -15 ° C to form a frozen body 6. Next, the frozen body 6 was taken out from the mold and dried by a freeze-drying apparatus for 24 hours. Further, after degreasing at 600 ° C for 2 hours in an electric furnace in an air atmosphere, and then firing at 1600 ° C for 2 hours, a porous ceramic 11 having a thickness of c = 9 mm in the vertical direction can be obtained, and By performing the processing in which the width in the horizontal direction is uniformly uniform, it is set to a × b × c = 100 mm × 100 mm × 9 mm (refer to Fig. 5). Further, the width a × b in the horizontal direction of the porous ceramics 11 before the processing is about (104 to 106) mm × (104 to 106) mm. The viscosity of the suspension 4 before gelation at 20 ° C, the porosity of the obtained porous ceramic 11, the average pore diameter, the average aspect ratio of the pores 10, the heat-resistant punchability, and the average bending strength are shown in the table. 1. The variation of the pore diameter of the porous ceramic 11 is shown in Table 2. Further, Fig. 3 is a partial cross-sectional view showing the porous ceramic 11 produced by the present embodiment.

Here, the "viscosity η of the suspension 4" is determined by using a B-type viscometer (a digital viscometer manufactured by Brookfield, model (DV1, PRIME)), a shaft No. SC4-34, and a number of revolutions of 20 rpm to measure the viscosity of the suspension 4. Value. In addition, the "average bending strength" is a value measured in accordance with the 3-point bending test prescribed in JISR1601:2008.

Furthermore, the "aspect ratio of the air holes 10" can be calculated from the image analysis of the partial longitudinal cross-sectional view shown in Fig. 3. That is, the cross-sectional portion of the pores 10 is approximated to the ellipsoid, and the value obtained by dividing the short diameter of the measured area, the long diameter, and the short diameter by the long diameter is referred to as "the aspect ratio of the pores 10". Further, the average value of the aspect ratio of the arbitrarily selected 50 pores 10 is defined as "the average aspect ratio of the pores 10".

In addition, "heat-resistant squeezing property" is measured in a row. First, a sample of 100 mm □ x thickness of 3 mm was produced. Then, the sample is sandwiched from the upper and lower sides by the pillars provided in the four corners of the tile bracket of the same size, heated at a high temperature in an electric furnace, and after being held at a desired temperature for one hour or more, the sample is taken out from the electric furnace. The temperature was exposed to room temperature, and the presence or absence of cracking of the sample was visually evaluated. The temperature was raised from 350 ° C to 700 ° C in a unit of 50 ° C, and the upper limit of the temperature at which cracking did not occur was referred to as "heat-resistant squeezing property".

Further, the "average pore diameter" and "variation in pore diameter" of the porous ceramic 11 were calculated by the following methods. First, as shown in Fig. 5, the porous ceramic 11 produced was made into a sample piece having a width a ₁ × b ₁ = 15 mm × 15 mm and a thickness c = 9 mm from the center (α) and the end (β, γ, The total of δ and ε) were cut and taken out respectively. Next, the average pore diameter was calculated for each of the five sample pieces. Here, the "average pore diameter" of each sample piece refers to the measurement of each sample piece by a mercury intrusion method at a contact angle of 140 degrees, and the median diameter (d50) obtained by arranging the pores when the pores 10 are approximated to a cylinder. ).

Furthermore, the difference between the maximum value and the minimum value in each average pore diameter is obtained, and the percentage of the value obtained by dividing the value ((maximum value - (minimum value)) by the average value of each average pore diameter is set as "Variation of pore size" (%). Further, the average value of the average pore diameters obtained from the test pieces was defined as the "average pore diameter" of the porous ceramics 11.

(Example 2)

An alumina 1.5 (corresponding to ceramic particles 1) having an average particle diameter of 0.5 μm was mixed with 10 vol%, water of 80.0 vol%, and a trace amount of a carboxylic acid-based dispersant. To the mixed liquid, a small amount of hydroxypropylcellulose and gelatin (corresponding to water-soluble polymer 2) as a tackifier were added in an amount of 3% by mass (relative to water 3) to prepare a suspension 4. The prepared suspension is placed in a mold to effect gelation of the suspension 4.

Next, the mold 23 in which the gelled suspension 4 was placed was placed in a freezing tank at -15 ° C and cooled to form a frozen body 6. The frozen body 6 is then taken out of the mold and dried with methanol. Further, after firing in an electric furnace in an air atmosphere at 1600 ° C for 2 hours, it was fired at 1600 ° C for 2 hours, whereby the porous ceramic 11 was obtained. The suspension 4 before gelation obtained in the same manner as in Example 1 was The viscosity η at 20 ° C, the porosity of the obtained porous ceramic 11, the average pore diameter, the average aspect ratio of the pores 10, the heat-resistant punchability, and the average bending strength are shown in Table 1.

(Example 3)

The average particle diameter of the completely stabilized zirconia (YSZ) particles (corresponding to ceramic particles 1) was changed to 1.5 μm, and the mixing ratio of ceramic particles 1 and water 3 expressed in units of vol% was set to 15:85. And the gelled suspension 4 was placed in a mold and placed on a copper plate cooled to -15 ° C for 2 hours to form a frozen body 6 by the same method as in Example 1. Porous ceramic 11. The viscosity of the suspension 4 before gelation obtained in the same manner as in Example 1 at 20 ° C, the porosity of the obtained porous ceramic 11, the average pore diameter, the average aspect ratio of the pores 10, and the heat-resistant ramification The properties and average bending strength are shown in Table 1. Further, the variation of the pore diameter of the porous ceramic 11 is shown in Table 2.

(Example 4)

Porous ceramics 11 were produced in the same manner as in Example 1 except that fully stabilized zirconia (YSZ) particles having an average particle diameter of 5.8 μm were used, and a cooling device 12 to be described later was used instead of the cooled copper plate. . In the cooling step, an ethanol cooling device is applied as the cooling device 12, and the bottom surface of the mold in which the gelled suspension 4 is placed is brought into contact with the liquid surface, and held for 20 minutes and cooled, and the ethanol cooling device is cooled. The flow is not generated in the vicinity of the liquid surface of the ethanol, but is circulated from the opposite side to the other side, and the temperature in the vicinity of the liquid surface is maintained at -15 °C. The suspension before gelation obtained in the same manner as in Example 1 The viscosity η of the body 4 at 20 ° C, the porosity of the obtained porous ceramic 11, the average pore diameter, the average aspect ratio of the pores 10, the heat-resistant punchability, and the average bending strength are shown in Table 1.

(Example 5)

10 vol% of niobium carbide (corresponding to ceramic particle 1) having an average particle diameter of 0.7 μm, a trace amount of carbon as a sintering aid, boron carbide, water 90 vol%, and agar (corresponding to water-soluble polymer 2) 1.0 mass % (relative to water 3) to modulate the suspension 4.

Next, the prepared suspension 4 is placed in a mold 23 and placed in a refrigerator, and the suspension 4 placed in the mold is gelated. The mold in which the gelled suspension 4 was placed was immersed in a freezing tank at -15 ° C and allowed to cool to form a frozen body 6. The frozen body 6 is then taken out of the mold and dried with methanol. Further, firing was performed at 1600 ° C for 2 hours in an electric furnace in an atmospheric environment. The viscosity of the suspension 4 before gelation obtained in the same manner as in Example 1 at 20 ° C, the porosity of the obtained porous ceramic 11, the average pore diameter, the average aspect ratio of the pores 10, and the heat-resistant ramification The properties and average bending strength are shown in Table 1.

(Example 6)

Nitridium nitride (corresponding to ceramic particles 1) having an average particle diameter of 2.1 μm was mixed at 10 vol%, a trace amount of alumina and cerium oxide as a sintering aid, and water of 90 vol%. To the mixture, a small amount of hydroxypropylcellulose, polyethyleneimine (corresponding to water-soluble polymer 2), 5% by mass (relative to water 3), and a crosslinking agent (diglycerol propylene oxide) were added as a tackifier. The ether was 2.5% by mass (relative to water 3) and mixed to prepare the suspension 4.

Next, the prepared suspension 4 was placed in a mold and allowed to stand at 20 ° C for 6 hours, and the suspension 4 was gelated. The mold in which the gelled suspension 4 was placed was immersed in a freezing tank at -15 ° C and allowed to cool to form a frozen body 6. Next, the frozen body 6 was taken out from the mold and dried by a freeze-drying apparatus for 24 hours. The receiver was fired at 1700 ° C for 2 hours in an electric furnace under a nitrogen atmosphere. The viscosity of the suspension 4 before gelation obtained in the same manner as in Example 1 at 20 ° C, the porosity of the obtained porous ceramic 11, the average pore diameter, the average aspect ratio of the pores 10, and the heat-resistant ramification The properties and average bending strength are shown in Table 1.

(Example 7)

The porous ceramic 11 was produced in the same manner as in Example 3 except that the baking aid was not used. The viscosity of the suspension 4 before gelation obtained in the same manner as in Example 1 at 20 ° C, the porosity of the obtained porous ceramic 11, the average pore diameter, the average aspect ratio of the pores 10, and the heat-resistant ramification The properties and average bending strength are shown in Table 1.

(Example 8)

The porous ceramic 11 was produced in the same manner as in Example 3 except that the amount of the tackifier added was adjusted to lower the viscosity. The viscosity of the suspension 4 before gelation obtained in the same manner as in Example 1 at 20 ° C, the porosity of the obtained porous ceramic 11, the average pore diameter, the average aspect ratio of the pores 10, and the heat-resistant ramification The properties and average bending strength are shown in Table 1. Further, Figs. 4A and 4B are partial longitudinal sectional views of the porous ceramic 11 produced in the present embodiment.

(Example 9)

The porous ceramic 11 was produced in the same manner as in Example 4 except that the amount of the tackifier added was adjusted and the viscosity was lowered. The viscosity of the suspension 4 before gelation obtained in the same manner as in Example 1 at 20 ° C, the porosity of the obtained porous ceramic 11, the average pore diameter, the average aspect ratio of the pores 10, and the heat-resistant ramification The properties and average bending strength are shown in Table 1.

(Comparative Example 1)

Porous ceramics 11 were produced in the same manner as in Example 4 except that fully stabilized zirconia (YSZ) particles having an average particle diameter of 1.5 μm were used without adding a tackifier. The viscosity of the suspension 4 before gelation obtained in the same manner as in Example 1 at 20 ° C, the porosity of the obtained porous ceramic 11, the average pore diameter, the average aspect ratio of the pores 10, and the heat-resistant ramification The properties and average bending strength are shown in Table 1. The variation of the pore diameter of the porous ceramic 11 is shown in Table 2. Further, Fig. 8 is a partial longitudinal sectional view of the porous ceramic 11 produced by the comparative example.

(Comparative Example 2)

The porous ceramic 11 was produced in the same manner as in Example 4 except that the tackifier was not added. The viscosity of the suspension 4 before gelation obtained in the same manner as in Example 1 at 20 ° C, the porosity of the obtained porous ceramic 11, the average pore diameter, the average aspect ratio of the pores 10, and the heat-resistant ramification The properties and average bending strength are shown in Table 1.

(Comparative Example 3)

The same method as in Example 7 except that fully stabilized zirconia (YSZ) particles having an average particle diameter of 0.5 μm were used without adding a tackifier. The method is to produce a porous ceramic 11. The viscosity of the suspension 4 before gelation obtained in the same manner as in Example 1 at 20 ° C, the porosity of the obtained porous ceramic 11, the average pore diameter, the average aspect ratio of the pores 10, and the heat-resistant ramification The properties and average bending strength are shown in Table 1.

The ceramic particles 1 used in Examples 1 to 3 and the porous ceramic 11 produced were collectively shown in Table 1.

As shown in Table 1, the average aspect ratio of the pores 10 of the porous ceramics 11 (Examples 1 to 7) was 1.4 or less, and the porous ceramic 11 was condensed with respect to the average particle diameter d of the ceramic particles 1. The viscosity η at 20 ° C of the suspension 4 before gelation has a specific relationship, that is, the relationship η ≧ 1630 × d - ^0.77 to modulate the viscosity of the suspension 4 . Further, from the viewpoint of image analysis, it is apparent from the viewpoint of image analysis that the porous ceramics 11 having the pores 10 communicating in the random direction are formed in accordance with Examples 1 to 7 (see Fig. 3).

Further, the average aspect ratio of the pores 10 of the porous ceramics 11 (Examples 8 and 9) is more than 1.4 and 2.0 or less, and the porous ceramic 11 has such a viscosity η and an average particle diameter d. The viscosity of the suspension 4 is obtained by modulating the relationship of 950 × d - ^0.77 ≦ η < 1630 × d - ^0.77 . Further, from the viewpoint of image analysis, it is apparent from the viewpoint of image analysis that, according to Examples 8 and 9, a portion having the formed pores 10 communicating in a random direction (see FIG. 4A) is produced, and anisotropy is obtained. In the manner of the porous ceramics 11 (see Fig. 4B) in which the portions are aligned and connected (see Fig. 4B).

Further, as shown above, the average of the pores 10 of the porous ceramics 11 (Examples 8 and 9) obtained by modulating the viscosity of the suspension 4 in a manner corresponding to the relationship of 950 × d - ^0.77 ≦ η < 1630 × d - ^0.77 The aspect ratio is calculated in the following manner in consideration of the variation in the alignment of the pores 10 at the measurement site. In other words, the obtained porous ceramics 11 were divided into five, and SEM photographs were taken at the respective portions in the same manner as the partial longitudinal cross-sectional views shown in Fig. 3 . Next, image analysis was performed on each of the obtained SEM photographs, and the aspect ratio of ten or a total of 50 pores 10 arbitrarily selected from the respective images was calculated, and the average value was defined as "the average height and width of the pores 10". ratio".

On the other hand, the average aspect ratio of the pores 10 of the porous ceramics 11 produced in Comparative Examples 1 to 3 was more than 2.0, and was carried out by Example 1. As compared with the porous ceramic 11 produced in the ninth aspect, it was found that the pores 10 were formed to have an anisotropy. Moreover, the production of the porous ceramic 11 is also apparent from the viewpoint of image analysis (refer to Fig. 8).

Further, as shown in Table 1, the porous ceramics 11 having the pores 10 formed in the random direction are more resistant to heat than the porous ceramics 11 formed by the pores 10 having anisotropy throughout. And the average bending strength is high. In other words, according to the method for producing the porous ceramic 11 of the embodiment, the porous ceramic 11 having excellent heat resistance and bending strength can be produced.

Next, in Example 1 to Comparative Example 3, the presence or absence of the tackifier used in the preparation of the suspension 4 in Example 1, Example 3, and Comparative Example 1 and the pore diameter of the porous ceramic 11 produced were described. The variation is shown in Table 2 as a representative example.

As shown in Table 2, the porous ceramic 11 produced by using the suspension 4 to which the tackifier is added has pores 10 having a pore diameter variation of 10% or less and a small variation in pore diameter. The reason may be that the growth of the ice 5 is suppressed by the addition of the tackifier, and the growth rate of the ice 5 is homogenized. The reason.

Further effects and modifications can be easily derived by the relevant industry. Therefore, the invention in its broader aspects is not limited to the specific details and Accordingly, various modifications may be made without departing from the spirit and scope of the inventions.

1‧‧‧ceramic particles

2‧‧‧Water soluble polymer

3‧‧‧ water

4‧‧‧suspension

5‧‧‧ ice

6‧‧‧Freezing body

7‧‧‧ lower surface

8‧‧‧ upper surface

9‧‧‧Ceramic skeleton

10‧‧‧ stomata

11‧‧‧Porous ceramics

12‧‧‧Cooling device

Claims (15)

A method for producing a porous ceramic, comprising: a step of gelling a suspension containing ceramic particles, a water-soluble polymer, and water; and a step of freezing the gelled suspension to form a frozen body; a step of forming pores in the ice of the frozen body; and a step of firing the frozen body through the ice; the viscosity η (mPa.s) of the suspension before gelation at 20 ° C, and the ceramic The average particle diameter d (μm) of the particles has a relationship of η ≧ 950 × d - ^0.77 . The method for producing a porous ceramic according to the first aspect of the invention, wherein the viscosity η and the average particle diameter d of the ceramic particles have a relationship of η ≧ 1630 × d - ^0.77 . The method for producing a porous ceramic according to the first aspect of the invention, wherein the water-soluble polymer comprises an N-alkyl amide amine polymer, an N-isopropyl acrylamide polymer, and a sulfonic acid. Methylated acrylamide-based polymer, N-dimethylaminopropylmethacrylamide-based polymer, polyalkyl acrylamide-based polymer, alginic acid, sodium alginate, ammonium alginate, Polyethyleneimine, carboxymethylcellulose, hydroxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, sodium polyacrylate, polyethyl Glycol, polyethylene oxide, polyvinyl alcohol, polyvinylpyrrolidone, carboxyvinyl One or more of a polymer, a starch, a gelatin, agar, a pectin, a polyglucomannan, a tri-sac, a locust bean gum, a carrageenan, a guar gum, and a gellan gum. The method for producing a porous ceramic according to claim 1, wherein the ceramic particles comprise zirconia, alumina, ceria, titania, tantalum carbide, boron carbide, tantalum nitride, boron nitride, One or more of cordierite, hydroxyphosphorus lime, sialon ceramics, zircon, aluminum titanate, and mullite. The method for producing a porous ceramic according to the first aspect of the invention, wherein the porous ceramic has a porosity of 50% to 99%. The method for producing a porous ceramic according to claim 1, wherein the average aspect ratio of the pores is 1 to 2. The method for producing a porous ceramic according to the first aspect of the invention, wherein the porous ceramic has an average bending strength of 10 MPa or more. The method for producing a porous ceramic according to the first aspect of the invention, wherein the porous ceramic has a heat-resistant squeezing property of 450 ° C or higher. A porous ceramic produced by the method for producing a porous ceramic according to any one of claims 1 to 8. A porous ceramic comprising 95% by mass or more of fully stabilized zirconia, a porosity of 50% to 99%, and an average aspect ratio of pores of 1 to 2. The porous ceramic according to claim 10, wherein the average bending strength is 10 MPa or more. The porous ceramic according to claim 10, wherein the resistant ceramic The thermal flushing property is 450 ° C or more. The porous ceramic according to claim 10, wherein the variation of the average pore diameter is 10% or less. A porous ceramic according to any one of claims 10 to 13, wherein the porous ceramic further comprises 0.01 to 1.5% by mass of Al relative to the fully stabilized zirconia. ₂ O ₃ and 0.01 to 2.0% by mass of CaO. A firing aid comprising: a base; and a bracket according to claim 14 placed on the base.