KR102327874B1 - Method for producing porous ceramic material, porous ceramic material, setter, and firing jig - Google Patents

Abstract

A method for manufacturing a porous ceramics according to an embodiment includes a step of gelling a suspension, a step of freezing the gelled suspension to form a frozen body, a step of removing ice grown on the frozen body to create pores, and ice and a step of calcining the removed frozen body. The suspension contains ceramic particles, a water-soluble polymer, and water. And the viscosity η (m㎩ · s) at 20 ℃ body before gelation of the suspension, the average particle diameter d (㎛) of ceramic particles, and has a relation d × η≥950 ^-0.77.

Description

The manufacturing method of porous ceramics, porous ceramics, a setter, and a firing jig TECHNICAL FIELD

Embodiment of indication relates to the manufacturing method of porous ceramics, porous ceramics, a setter, and a baking jig.

Conventionally, porous ceramics in which many pores are formed in ceramics, such as filters for removing impurities from gases or liquids, adsorbents, and materials for supporting catalysts for exhaust gas purification of automobiles, have been used for various purposes.

As a method for producing such porous ceramics, there is known a method in which a suspension (slurry) in which ceramic particles are dispersed in an aqueous solution of a water-soluble polymer is gelled, followed by applying a gelation freezing method in which it is frozen (see, for example, Patent Document 1).

Japanese Patent No. 5176198

However, in the manufacturing method described in Patent Document 1, porous ceramics having various pore diameters and porosity are obtained by changing the freezing temperature or the mixing amount of ceramic particles, while improving the porous ceramics having excellent thermal shock resistance and bending strength. There is room.

One aspect of embodiment is made in view of the above, and aims at providing the manufacturing method of porous ceramics excellent in thermal shock resistance and bending strength, porous ceramics, a setter, and a baking jig.

A method for manufacturing a porous ceramics according to an embodiment includes a step of gelling a suspension, a step of freezing the gelled suspension to form a frozen body, a step of removing ice grown on the frozen body to create pores; , and calcining the frozen body from which the ice has been removed. The suspension contains ceramic particles, a water-soluble polymer, and water. Viscosity η (m㎩ · s) at 20 ℃ of the suspension body before gelation, and the average particle diameter d (㎛) of the ceramic particles, and has a relation d × η≥950 ^-0.77.

ADVANTAGE OF THE INVENTION According to one aspect of embodiment, the manufacturing method of porous ceramics excellent in thermal shock resistance and bending strength, porous ceramics, a setter, and a baking jig can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing explaining the outline|summary of the manufacturing method of the porous ceramics which concerns on embodiment.
It is a schematic perspective view which shows the outline|summary of the structure of the baking jig which concerns on embodiment.
Fig. 2B is a schematic front view of the firing jig shown in Fig. 2A.
Fig. 3 is a partial cross-sectional view of the porous ceramics produced in Example 1.
Fig. 4A is a partial cross-sectional view of porous ceramics produced in Example 8;
Fig. 4B is a partial cross-sectional view of the porous ceramics produced in Example 8;
Fig. 5 is a diagram for explaining an average pore diameter and a method for measuring the deviation of the pore diameter;
6 is a flowchart showing an example of a method for manufacturing porous ceramics according to an embodiment.
It is explanatory drawing explaining the outline|summary of the manufacturing method of the conventional porous ceramics.
Fig. 8 is a partial cross-sectional view of the porous ceramics produced in Comparative Example 1.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of the manufacturing method of the porous ceramics disclosed by this application, a porous ceramics, a setter, and a baking jig is described in detail with reference to an accompanying drawing. In addition, this invention is not limited by embodiment shown below.

The porous ceramics which concern on embodiment are common with the conventional porous ceramics at the point which can be produced by the manufacturing method including each process of gelation, freezing, drying, degreasing, and baking. On the other hand, in the method for producing porous ceramics according to the embodiment, the viscosity η at 20° C. of the suspension before gelation and the average particle diameter d of the ceramic particles have a specific relationship, so that they have different features from the conventional production method. A porous ceramics is formed. Hereinafter, the porous ceramics which concern on embodiment, and the manufacturing method of porous ceramics are demonstrated, comparing with the prior art.

1 : is explanatory drawing explaining the outline|summary of the manufacturing method of the porous ceramics which concerns on embodiment, FIG. 7 : is explanatory drawing explaining the outline|summary of the conventional manufacturing method of the porous ceramics to which the gelatinization freezing method is applied. In addition, in FIGS. 1 and 7, each process of gelatinization, freezing, and baking is shown sequentially from the left among the manufacturing processes mentioned above, and illustration corresponding to each process of drying and degreasing is abbreviate|omitted.

First, the gelation process is demonstrated. The gelation process includes a ceramic particle (1), a water-soluble polymer (2), and water (3), and a suspension (4) in which the ceramic particles (1) are uniformly dispersed in an aqueous solution of the water-soluble polymer (2). It is a process of gelling by putting it in a mold. By gelation of the suspension 4, a structure (gelling body) in which the ceramic particles 1 are dispersed in an aqueous solution of the water-soluble polymer 2 is temporarily fixed (gelled body) is formed.

Next, the freezing process is demonstrated. The freezing step is a step of cooling the gelled suspension 4 to produce the frozen body 6 . When the gelled suspension 4 is cooled, the water 3 separated from the aqueous solution of the water-soluble polymer 2 changes state to ice 5 and grows while forming a crystal structure. As a result, a frozen body 6 containing the ceramic particles 1, a gelled portion (not shown) of an aqueous solution of the water-soluble polymer 2, and a crystallized portion of the ice 5 is obtained.

In the conventional manufacturing method, for example, when the suspension 4a containing the water-soluble polymer 2a gelled by arranging the cooling device 12a on the lower surface 7a side is cooled from one side, the gelled suspension Water 3a in (4a) freezes from the lower surface 7a side and changes state to ice 5a, and the crystals of this ice 5a try to grow from the lower surface 7a side toward the upper surface 8a side. . Then, when the crystals of the ice 5a grow, a pressing force sufficient to move the relatively small ceramic particles 1a having an average particle diameter of, for example, about 0.01 to 5 mu m is applied. For this reason, if the ceramic particles 1a exist in the direction in which the crystals of the ice 5a are going to grow, the ceramic particles 1a temporarily fixed by gelation will move around the growing crystals of the ice 5a. move to be excluded.

In this way, in the conventional manufacturing method shown in Fig. 7, when the gelled suspension 4a is cooled from one direction, the ceramic particles ( 1a) is rearranged, thereby obtaining a frozen body 6a in which the distribution of the ceramic particles 1a is dense.

On the other hand, in the manufacturing method of the porous ceramics which concerns on embodiment, the viscosity η of the suspension 4 becomes large as the average particle diameter d of the ceramic particle 1 used becomes small, the suspension 4 whose viscosity is adjusted. apply Specifically, the average particle diameter d (㎛) of gelling before suspension body (4) 20 ℃ viscosity η (m㎩ · s), and ceramic particles (1) in a, a relation d × η≥950 ^-0.77 have

If the average particle diameter d and the viscosity η have such a relationship, even if the crystals of the ice 5 grow and approach or collide with the ceramic particles 1, the ceramic particles 1 are the same as the crystals of the ice 5 regardless of their size. It becomes possible to resist the pressing force accompanying growth. For this reason, it is thought that the ceramic particle 1 in such a location hardly moves also in a freezing process, and remains in the position hold|maintained as a gelled body.

Then, the ice 5 changes the crystal growth direction each time it collides with the ceramic particles 1, while forming the crystals in a zigzag manner from the lower surface 7 side where the cooling device 12 is disposed toward the upper surface 8 side. Grow. Further, since the crystals of the ice 5 grow in a zigzag manner, it is considered that, in some cases, adjacent crystals of the ice 5 grow while repeating collisions or contact. For this reason, in the manufacturing method of the porous ceramics which concerns on embodiment, as shown in FIG. 1, even if it cools the gelled suspension 4 from the lower surface 7 side, as a result, between the ceramic particles 1, ice 5 ), a frozen body 6 having a location where it grows in a random direction is obtained.

In this way, in the method for manufacturing porous ceramics according to the embodiment, even when the gelled suspension 4 is cooled from one direction, ice 5 grows in a random direction between the uniformly dispersed ceramic particles 1 . A frozen body 6 having a location is obtained. And, Having a relationship between the average particle diameter d, and the viscosity is particularly η≥1630 × d ^-0.77 η described above, the freeze throughout the grown ice (5) The random orientation support 6 is obtained.

Next, a drying process is demonstrated. The drying process is a process of removing the ice 5 grown on the frozen body 6 to generate the pores 10 . When the frozen body 6 on which the ice 5 has grown is dried by, for example, freeze-drying, crystals of the ice 5 sublimate and disappear, and 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 process is demonstrated. A degreasing process is a process of removing organic components, such as the water-soluble polymer 2, from the frozen body 6 which produced|generated the pore 10 in the drying process. Specifically, a process for decomposing and removing organic components such as the water-soluble polymer 2 under a predetermined temperature condition is performed according to the type of the ceramic particles 1 .

Finally, the firing step will be described. The firing step is a step of producing the porous ceramics 11 by firing the frozen body 6 from which the ice 5 and organic components such as the water-soluble polymer 2 are removed and the pores 10 are formed. The porous ceramics 11 obtained by firing have the pores 10 formed in the drying step described above, and the ceramic skeleton 9 in which the ceramic particles 1 are bonded to each other so as to surround the pores 10 and are densified.

The porous ceramics 11 obtained after baking have different shapes based on the difference in the shape of the frozen body 6 produced|generated in the freezing process. That is, in the conventional manufacturing method, as shown in FIG. 7, the porous ceramics 11a in which the ceramic skeleton 9a was formed around the columnar pore 10a formed from one direction side to the other direction side is produced|generated. In contrast, in the method for manufacturing the porous ceramics 11 according to the embodiment, the ceramic skeleton 9 is formed in a three-dimensional network shape so that the pores 10 are formed in a random direction, whereby thermal shock resistance And the porous ceramics 11 excellent in bending strength are produced (refer FIG. 3). Here, the phrase "the pores 10 are formed in a random direction" means that the average aspect ratio of the pores 10 is 1 to 2, preferably 1 to 1.4. Incidentally, the average aspect ratio of the pores 10 can be measured by the method described in Examples to be described later.

In the manufacturing method of the porous ceramics 11 which concerns on embodiment, there will be no restriction|limiting in particular as long as the ceramic particle 1 can be appropriately baked in a baking process. Specifically, for example, at least one of zirconia, alumina, silica, titania, silicon carbide, boron carbide, silicon nitride, boron nitride, cordierite, hydroxyapatite, sialon, zircon, aluminum titanate, and mullite is used as ceramics. Although applicable as particle 1, it is not limited to these. Among them, when zirconia is applied as the ceramic particles (1), 95% by mass or more of fully stabilized zirconia stabilized by dissolving calcium oxide, magnesium oxide or yttrium oxide in a solid solution is blended to improve stability against temperature change. It is preferable to do In addition, for example, a plurality of ceramic particles 1 can be used in combination according to desired characteristics, such as preparing a mullite by applying alumina and silica, or preparing a composite by applying zirconia and alumina.

Moreover, it is preferable that the average particle diameter of the ceramic particle 1 is 100 micrometers or less practically. When the average particle diameter of the ceramic particles 1 exceeds 100 µm, appropriate firing of the ceramic particles 1 may be difficult depending on the desired shape and size of the porous ceramics 11 . Here, the "average particle diameter" refers to the median diameter (d50) obtained based on the volume-based particle size distribution converted to the spherical diameter in the laser diffraction type particle size distribution measuring apparatus (wet method). Moreover, as long as the same result is obtained, there is no restriction|limiting in a measuring method.

As for the compounding quantity of the ceramic particle 1 in the suspension 4, the range of 1-50 vol% is preferable, More preferably, it is 1-30 vol%. When the blending 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 becomes difficult to produce the porous ceramics 11 having a desired strength. Moreover, when the compounding quantity of the ceramic particle 1 exceeds 50 vol%, the porosity of the porous ceramics 11 obtained becomes low, and it may not fully exhibit the characteristic desired as a porous body. Here, "porosity" means the value obtained by the Archimedes method based on the method prescribed|regulated to JISR1634:2008. In this measurement, since the closed pores are not considered, it is also called "apparent porosity". Moreover, in this embodiment, since closed pores are hardly formed, this "apparent porosity" can be handled as a "porosity".

In addition, in order to properly bake the ceramic particle 1, you may mix|blend 1 or 2 or more types of baking adjuvant according to the kind of the ceramic particle 1 to the suspension body 4. Specific examples of the calcination aid include, but are not limited to, alumina, calcium carbonate, yttria, boron carbide, and ceria. In addition, calcium carbonate was added as a sintering aid (CaCO ₃₎ is, it is decomposed by the baking, it remains in the as calcium oxide (CaO) oxide porous ceramics (11).

In addition, in order to gel the suspension 4 properly, you may add various additives, such as a pH adjuster, an initiator, and a crosslinking agent, according to the kind of water-soluble polymer 2, if necessary.

In addition, as the water-soluble polymer 2, if the dispersion of the ceramic particles 1 can be stably maintained from the gelation process to the drying process, and does not inhibit the growth of the ice 5 in the freezing process, the type and blending amount There are no restrictions on Specifically, for example, N-alkylamide-based polymer, N-isopropylacrylamide-based polymer, sulfomethylated acrylamide-based polymer, N-dimethylaminopropylmethacrylamide-based polymer, polyalkylacrylamide-based polymer, alginic acid , sodium alginate, ammonium alginate, polyethyleneimine, carboxymethylcellulose, hydroxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, sodium polyacrylate, polyethylene glycol, polyethylene oxide, poly At least one of vinyl alcohol, polyvinylpyrrolidone, carboxyvinyl polymer, starch, gelatin, agar, pectin, glucomannan, xanthan gum, locust bean gum, carrageenan gum, guar gum and gellan gum is applied as a water-soluble polymer (2) can, but are not limited to. Among these, in the case of applying the water-soluble polymer (2) having a property of gelling the suspension (4) by cooling, mixing of the ceramic particles (1) and water (3) at the time of preparation of the suspension (4) For ease of use, it is practically preferable that the gelation temperature of the water-soluble polymer 2 is 50° C. or less. Moreover, as a specific example of such a water-soluble polymer (2), gelatin, agar, carrageenan gum, and gellan gum are mentioned.

Moreover, in order to facilitate uniform dispersion of the ceramic particles 1 in the suspension 4, a dispersing agent such as a polycarboxylic acid dispersant or a maleic acid dispersant may be applied. In addition, in order to adjust the viscosity η of the suspension 4 to a desired degree according to the average particle diameter d of the ceramic particles 1, a water-soluble thickener that can be used in combination with the water-soluble polymer 2 may be blended. As a specific example of such a thickener, for example, thickening polysaccharide, cellulose-derived system, polyvinyl-based, polyester-based, polyamide-based, polyglycol-based, polyvinyl alcohol-based, polyalkylene oxide-based, polyacrylic-based, and combinations thereof compounds and the like, but are not limited thereto. Moreover, although the illustrated thickener may overlap with the water-soluble polymer (2) mentioned above, here, the component which does not gelatinize in the above-mentioned gelatinization process is prescribed|regulated as a "thickener".

Further, in the freezing step, it is possible to use a known cooling device 12 . Specifically, various cooling methods are applied, such as contacting the lower surface 7 side of the gelled body in which the suspension 4 is gelled, with a solid such as a cooled metal plate, and immersing the entire mold in a cooled liquid. The cooling device 12 is mentioned. Further, for example, ethanol cooled to a predetermined temperature is circulated from one side facing to the other so that it flows without stagnation or ripple near the liquid level of the ethanol, thereby maintaining a constant temperature near the liquid level. A cooling device may be applied as the cooling device 12 . An ethanol cooling device having such a configuration is applied, and the bottom surface of the mold containing the suspension 4 is contacted or immersed in the liquid level of the cooled ethanol to hold it, and the frozen body 6 is produced, thereby creating a porous material with little variation in pore diameter. Ceramics 11 can be produced.

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 freeze to form ice 5 . Also, depending on the type of the water-soluble polymer 2, the gelled body may not freeze at a temperature higher than -10°C due to the interaction between the water-soluble polymer 2 and water 3, so -10°C or less A freezing temperature of

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

For example, when the frozen body 6 is immersed in a water-soluble organic solvent or a water-soluble organic solvent aqueous solution, the ice 5 in the frozen body 6 is melted and mixed with the water-soluble organic solvent. By performing this operation once or a plurality of times, first, a portion of the frozen body 6 that used to be the ice 5 is replaced with a water-soluble organic solvent. Thereafter, when the frozen body 6 , which has been replaced with a water-soluble organic solvent, is dried in the air or under reduced pressure conditions, the portion that used to be the ice 5 in the freezing step is replaced with the pores 10 .

In the drying step using the water-soluble organic solvent, the water-soluble organic solvent does not corrode the water-soluble polymer (2) and is more volatile than the water (3). Specific examples thereof include, but are not limited to, methanol, ethanol, isopropyl alcohol, acetone, and ethyl acetate. By drying these water-soluble organic solvents individually or in combination of a plurality of types once or plural times, pores 10 are formed in the portion that used to be ice 5 in the frozen body 6 .

In the degreasing step, for example, a degreasing temperature of 300°C to 900°C is applied. At this time, for example, when degreasing non-oxide ceramics such as silicon carbide and silicon nitride, it is preferable to degrease in an inert gas atmosphere such as argon or nitrogen. On the other hand, for example, when using oxide ceramics, such as alumina, zirconia, apatite, as a raw material, it is preferable to degrease in an atmospheric condition.

In the firing step, the firing temperature, firing time, and firing atmosphere are appropriately adjusted according to the type and blending amount of the ceramic particles 1 to be used, the target hardness, etc., so that the porous material having excellent thermal shock resistance and bending strength Ceramics 11 are manufactured.

As for the porosity of the porous ceramics 11 obtained in this way, the range of 50 % - 99 % is preferable, More preferably, it is 70 % - 99 %. The necessity of using the manufacturing method of the porous ceramics 11 which concerns on embodiment that the porosity of the ceramic particle 1 is less than 50 % reduces. Further, when the porosity of the ceramic particles 1 exceeds 99%, for example, the shape may not be maintained in the drying step, and it becomes difficult to produce the porous ceramics 11 having a desired strength.

In addition, it is preferable practically that the porous ceramics 11 have communicating holes with an average pore diameter of 10 micrometers - 300 micrometers, More preferably, they are 10 micrometers - 100 micrometers. In addition, the average pore diameter can be measured by the method described in the Example mentioned later.

Moreover, it is preferable practically that the average bending strength of the porous ceramics 11 is 10 Mpa or more. Moreover, as for the porous ceramics 11, it is practically preferable that thermal shock resistance is 450 degreeC or more, More preferably, it is 600 degreeC or more. In addition, average bending strength and thermal shock resistance can be measured by the method described in the Example mentioned later.

The porous ceramics 11 produced in this way can be used as a baking jig used in the process of baking an electronic component included in the process of manufacturing electronic components, such as a multilayer ceramic capacitor, for example. In such a baking process, the electronic component which is a to-be-baked object is mounted on a baking jig, and it is trying to bake in a furnace.

Below, the baking jig which can apply the porous ceramics 11 which concerns on embodiment is demonstrated using FIG. 2A, FIG. 2B. In addition, in FIG. 2A and FIG. 2B, in order to make the explanation easy to understand, the X-axis direction, the Y-axis direction, and the Z-axis direction orthogonal to each other are prescribed|regulated, and let the Z-axis direction be a perpendicularly upward direction.

Fig. 2A is a schematic perspective view showing the outline of the configuration of the firing jig according to the embodiment, and Fig. 2B is a schematic front view of the firing jig shown in Fig. 2A when viewed from the minus side of the Y-axis.

2A and 2B , the firing jig 13 includes a base 14 and a setter 17 . And on the setter 17 of the firing jig 13, the to-be-baked object 18 is mounted.

The to-be-fired object 18 is an electronic component, such as a multilayer ceramic capacitor, for example. That is, the above-described firing jig 13 is a firing jig for electronic components. In addition, although the to-be-baked object 18 was made into the multilayer ceramic capacitor in the above, this is an illustration and is not limited. That is, the to-be-fired object 18 may be of any kind as long as it is an electronic component to which baking is performed, such as a chip inductor and a semiconductor substrate, for example.

The baking jig 13 is arrange|positioned in the furnace (not shown) in the state in which the to-be-baked object 18 was mounted on the upper surface 17a of the setter 17, and the process of baking the to-be-baked object 18 is performed.

The base 14 of the firing jig 13 includes a plate portion 15 and a support portion 16 . The plate part 15 is a shape in which the setter 17 can be mounted on the upper surface, specifically, for example, it is substantially flat-plate shape, and becomes a substantially rectangular shape in planar view.

There are a plurality of support portions 16 (for example, four, one is not shown in FIG. 2A ), and is formed at an enemy position on the lower surface side of the plate portion 15 . Specifically, the support part 16 is formed so as to protrude from the four corners of the lower surface of the plate part 15 toward the minus direction of the Z-axis, and supports the plate part 15 .

In addition, the base 14 is not limited to the shape shown to FIG. 2A, 2B. That is, the base 14 may be, for example, a saya or a rack, and may be any shape in which the setter 17 can be placed on the yaw. In addition, the base 14 and the setter 17 do not need to be separate and may be comprised so that it may be integrated.

In addition, the shape of the plate part 15 is not limited to said substantially rectangular shape. That is, the shape of the plate part 15 may be, for example, other shapes, such as polygons, such as a square or a triangle, or a circle|round|yen, an ellipse.

In addition, while the setter 17 in this embodiment is formed in the substantially rectangular shape in planar view, the thickness in the Z-axis direction becomes comparatively thin and thin plate shape. In this way, when the setter 17 is made into a thin plate shape, the setter 17 and, by extension, the firing jig 13 itself can be reduced in weight.

As the firing jig 13 configured as described above, the porous ceramics 11 according to the embodiment can be applied. In addition, the plate part 15 and the support part 16 which comprise the base 14 may be integrally molded, and are attached to the plate part 15 and the support part 16 produced individually, for example, bonding, crimping|bonding, sintering, etc. You may produce the base 14 by applying other various joining methods.

Further, when the porous ceramics 11 according to the embodiment is applied as the firing jig 13 , the porous ceramics 11 contains 0.01 to 1.5% by mass of Al _{2 with respect to the fully stabilized zirconia blended as the ceramic particles 1 .} O _3, and preferably contains 0.01 to 2.0% by weight of CaO. When the porous ceramic 11 according to the embodiment contains a proper amount of Al ₂ O ₃ and CaO for a fully stabilized zirconia, the thermal shock resistance and the bending strength further improved.

In this way, when the porous ceramics 11 according to the embodiment is applied as the firing jig 13 , when the to-be-fired object 18 is fired, the hot air in the urinary tract is disposed on the lower surface side of the to-be-fired object 18 and the base 14 and It passes through the setter (17) to reach the lower and lateral sides of the urinary tract. For this reason, the temperature nonuniformity in a urinary path|route can be reduced and the to-be-baked object 18 can be baked efficiently. In addition, at the time of degreasing to remove the binder and other organic components blended in the to-be-fired object 18 , the organic component can be efficiently removed from the to-be-fired object 18 .

In addition, in FIGS. 2A and 2B, although one firing jig 13 was shown, it is not limited to this, For example, the firing jig 13 is piled up in multiple stages in the Z-axis positive direction, and a multiple stage firing jig ( You may make it bake the many to-be-fired objects 18 mounted in 13) at once.

In addition, in the above-mentioned, although the porous ceramics 11 which concern on embodiment demonstrated as what is applied to the base 14 and the setter 17, only one of the base 14 and the setter 17 porous ceramics 11 may be applied. In addition, you may apply the porous ceramics 11 which concern on embodiment only to one of the plate part 15 and the support part 16 which comprise the base 14. As shown in FIG.

Next, the method of manufacturing the porous ceramics 11 which concerns on embodiment is demonstrated in detail using FIG. 6 : is a flowchart which shows the process procedure which manufactures the porous ceramics 11 which concern on embodiment.

As shown in Fig. 6, first, ceramic particles 1, water-soluble polymer 2, and water 3 are mixed to prepare a suspension 4 (step S101). What is necessary is just to add various additives, such as a baking aid, a thickener, a pH adjuster, an initiator, and a crosslinking agent, at this timing. The water-soluble polymer 2 may be mixed with water 3 before mixing with the ceramic particles 1 to obtain an aqueous solution, and the water-soluble polymer 2 and the ceramic particles 1 are mixed in advance. You may add one thing to the water 3 in stirring. In addition, when using a dispersing agent, it is preferable to mix with the ceramic particle 1 beforehand.

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

Next, the gelled body is frozen to produce the frozen body 6 having locations where the crystals of the ice 5 grow in random directions (step S103). Subsequently, the crystals of the ice 5 grown by drying the frozen body 6 are removed to form pores 10 (step S104).

Further, degreasing is performed to remove organic components, such as water-soluble polymer 2, from the frozen body 6 in which the ice 5 is removed and the pores 10 are generated (step S105), followed by firing (S106). ). According to each of the above steps, production of a series of porous ceramics 11 according to the embodiment is completed.

As described above, the method for manufacturing porous ceramics 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 a step of calcining the frozen body from which the ice has been removed. The suspension contains ceramic particles, a water-soluble polymer, and water. Viscosity η (m㎩ · s) at 20 ℃ of the suspension body before gelation, and the average particle diameter d (㎛) of the ceramic particles, and has a relation d × η≥950 ^-0.77.

Therefore, according to the manufacturing method of the porous ceramics which concerns on embodiment, the porous ceramics excellent in thermal shock resistance and bending strength can be manufactured.

Moreover, although the above-mentioned embodiment gave and demonstrated the example in which the cooling device 12 for freezing the gelatinized body which gelled the suspension 4 was arrange|positioned on the one direction side of the gelatinized body, it is not limited to this. For example, the method may be a method in which the gelling body is placed in a freezing chamber set at a predetermined freezing temperature from the first mold, or a method in which the upper and lower surfaces are blocked with an insulating material and cooled by radiant heat from the side surface. That is, according to the manufacturing method of the porous ceramics 11 according to the embodiment, the pores 10 are formed in random directions regardless of the configuration of the cooling device 12, and the porous ceramics 11 having excellent thermal shock resistance and bending strength. ) is created.

Further, in the above-described embodiment, an ethanol cooling device is used as the cooling device 12 as an example. However, if the solidification temperature is low and the coolant is liquid to a desired temperature in order to freeze the gelled body, a coolant other than ethanol may be applied. Specific examples thereof include, but are not limited to, methanol, isopropyl alcohol, acetone, and ethylene glycol. Moreover, these refrigerants can be used alone or in combination with a plurality of types, and mixed with water as needed.

In addition, in the above-mentioned embodiment, although the degreasing process (step S105) was demonstrated as an essential process, you may abbreviate|omit depending on the kind and compounding quantity of the water-soluble polymer (2). At this time, the water-soluble polymer 2 is decomposed and removed in the firing step (step S106).

Moreover, in the manufacturing method of the porous ceramics 11 which concerns on embodiment, the relational expression between the viscosity η at 20°C of the suspension 4 before gelation and the average particle diameter d of the ceramic particles 1 is as follows obtained together. First, attention was paid to the average aspect ratio of the pores 10, average bending strength, and thermal shock resistance as characteristics required for the porous ceramics 11 according to the embodiment. Next, while changing the values of the average particle diameter d (μm) of the ceramic particles 1 and the viscosity η (mPa·s) at 20° C. of the suspension 4 before gelation, the porous ceramics 11 are produced, The above-mentioned three characteristics of the obtained porous ceramics 11 were measured. In addition, the correlation was evaluated from the values of d and η that satisfy all the conditions of the pores 10 with an average aspect ratio of 1 to 1.4, an average bending strength of 10 MPa or more, and a thermal shock resistance of 450° C. or more, the relational expression η≥ 1630×d ^−0.77 was obtained. And it was confirmed that the porous ceramics 11 excellent in thermal shock resistance and bending strength could be produced by using the suspension body 4 adjusted so that this relational expression might be satisfied.

Further, forming the above-described viscosity η and the average particle diameter d, 950 × d ^-0.77 ≤η Having a relationship of <1630 × d ^-0.77, pores 10 are formed are not completely at random, in part, to have the orientation However, it was also found that the porous ceramics 11 excellent in thermal shock resistance and bending strength were produced.

[Example]

(Example 1)

20 vol% of fully stabilized zirconia (YSZ) particles having an average particle diameter of 9 μm (corresponding to ceramic particles (1)), 1.5% by mass of alumina as a firing aid (relative to stabilized zirconia), and 3.5% by mass of calcium carbonate (to fully stabilized zirconia) About 2.0 mass % in conversion of calcium oxide) and 80.0 vol% of water were mixed. As a thickener, a trace amount of hydroxypropylmethylcellulose and 3.0% by mass of gelatin (corresponding to water-soluble polymer (2)) (with respect to water (3)) were added to this to prepare a suspension (4). The prepared suspension 4 was put into a mold, and it left still in a refrigerator at 5 degreeC, and the suspension 4 was gelatinized.

Next, the mold containing the gelled suspension 4 was put in a -15 degreeC freezer and cooled, and the frozen body 6 was produced|generated. Subsequently, the frozen body 6 was taken out from the mold and dried for 24 hours with a freeze drying apparatus. Furthermore, after degreasing at 600°C for 2 hours in an electric furnace under an atmospheric atmosphere, by baking at 1600°C for 2 hours, the porous ceramics 11 having a thickness c = 9 mm in the vertical direction is obtained, and further, the width in the horizontal direction By performing processing to align the , a × b × c = 100 mm × 100 mm × 9 mm (refer to Fig. 5). Moreover, the width a x b in the horizontal direction of the porous ceramics 11 before processing is set to about (104-106) mm x (104-106) mm. The viscosity η at 20° C. of the suspension 4 before gelation, the porosity of the obtained porous ceramics 11, the average pore diameter, the average aspect ratio of the pores 10, thermal shock resistance, and average bending strength are shown in Table 1, Table 2 shows variations in the pore diameter of the porous ceramics 11, respectively. Fig. 3 is a partial longitudinal sectional view of the porous ceramics 11 produced in the present Example.

Here, "viscosity η of the suspension 4" is a B-type viscometer (digital viscometer manufactured by Brookfield, model (DV1, PRIME)), spindle No. SC4-34, rotation speed of the suspension 4 at 20 rpm. Viscosity is the measured value. In addition, "average bending strength" is a value measured based on the 3-point bending test prescribed|regulated to JISR1601:2008.

In addition, "the aspect-ratio of the pore 10" is computable based on the image analysis of the partial longitudinal sectional view shown in FIG. That is, the value obtained by dividing the minor axis from the major axis when the cross-section of the pores 10 is approximated to an ellipsoid and measuring the area, major axis, and minor axis is called “aspect ratio of pores 10” do. Then, an average value of the aspect ratios of 50 arbitrarily selected pores 10 is defined as “average aspect ratio of pores 10”.

In addition, "thermal shock resistance" was measured as follows. First, a sample of 100 mm square x thickness 3 mm was produced. Next, this sample is sandwiched from the vertical direction through the posts arranged at the four corners of the soft cortex setter of the same size, heated in an electric furnace at a high temperature and maintained at the desired temperature for at least 1 hour, and then taken out from the electric furnace Then, it exposed to room temperature and visually evaluated the presence or absence of the crack of a sample. The set temperature was changed from 350°C to 700°C by 50°C, and the upper limit of the temperature at which cracks did not occur was defined as “thermal shock resistance”.

In addition, "average pore diameter" and "variation in pore diameter" of the porous ceramics 11 were computed as follows. First, as shown in FIG. 5, the produced porous ceramics 11 was made into _{a sample piece of width a 1} x b ₁ =15 mm x 15 mm, and thickness c = 9 mm, and the center (alpha) and the edge part were made into it. (β, γ, δ, ε) were cut out from a total of 5 locations, respectively. Next, the average pore diameter was calculated for each of these five sample pieces. Here, the "average pore diameter" of each sample piece is measured for each sample piece using a mercury intrusion method at a contact angle of 140 degrees, and the median diameter ( d50).

Then, among the average pore diameters, the difference between the maximum value and the minimum value is calculated, and the percentage of the value obtained by dividing this value ((maximum value)-(minimum value)) by the average value of each average pore diameter is "variation of pore diameter" (%) did with In addition, the average value of the average pore diameter obtained for each sample piece is prescribed|regulated as "average pore diameter" of the porous ceramics 11. As shown in FIG.

(Example 2)

10 vol% of alumina particles (corresponding to ceramic particles (1)) having an average particle diameter of 0.5 µm, 90 vol% of water, and a trace amount of a polycarboxylic acid-based dispersant were mixed. As a thickener, a trace amount of hydroxyethylmethylcellulose and 3% by mass of gelatin (corresponding to water-soluble polymer (2)) (with respect to water (3)) were added to this to prepare a suspension (4). The prepared suspension 4 was placed in a mold, left still, and the suspension 4 was gelled.

Next, the mold containing the gelled suspension (4) was immersed in a freezing bath at -15°C and cooled to produce a frozen body (6). Subsequently, the frozen body 6 was taken out from the mold and dried using methanol. Then, the porous ceramics 11 were obtained by baking at 1600 degreeC for 2 hours in the electric furnace in atmospheric condition. Viscosity η at 20°C of the suspension 4 before gelation obtained in the same manner as in Example 1, porosity of the obtained porous ceramics 11, average pore diameter, average aspect ratio of pores 10, thermal shock resistance, and The average bending strength is shown in Table 1.

(Example 3)

The average particle diameter of the fully stabilized zirconia (YSZ) particles (corresponding to the ceramic particles (1)) was changed to 1.5 μm, and the mixing ratio of the ceramic particles (1) and water (3) expressed in vol% was 15:85 In the same manner as in Example 1, the porous ceramics ( 11) was produced. Viscosity η at 20°C of the suspension 4 before gelation obtained in the same manner as in Example 1, porosity of the obtained porous ceramics 11, average pore diameter, average aspect ratio of pores 10, thermal shock resistance, and The average bending strength is shown in Table 1. Table 2 shows variations in the pore diameter of the porous ceramics 11 .

(Example 4)

The porous ceramics 11 were prepared in the same manner as in Example 3, except that fully stabilized zirconia (YSZ) particles having an average particle diameter of 5.8 μm were used and a cooling device 12 described later was applied instead of the cooled copper plate. made In the cooling process, an ethanol cooling device in which the temperature near the liquid level is maintained at -15°C by circulating so that ethanol flows without stagnation or ripple near the liquid level near the liquid level is used as the cooling apparatus 12 from one facing to the other side. It was applied, and the bottom of the mold containing the gelled suspension 4 was brought into contact with the liquid level, held for 20 minutes, and cooled. Viscosity η at 20°C of the suspension 4 before gelation obtained in the same manner as in Example 1, porosity of the obtained porous ceramics 11, average pore diameter, average aspect ratio of pores 10, thermal shock resistance, and The average bending strength is shown in Table 1.

(Example 5)

10 vol% of silicon carbide (corresponding to ceramic particles (1)) having an average particle diameter of 0.7 µm, trace amounts of carbon and boron carbide as a calcination aid, and 90 vol% of water are mixed, and further, agar (corresponding to water-soluble polymer (2)) ) 1.0 mass % (with respect to water (3)) was added, and the suspension (4) was prepared.

Next, the prepared suspension 4 was placed in a mold, left to stand in a refrigerator, and the suspension 4 placed in the mold was gelled. The mold containing the gelled suspension (4) was immersed in a freezing bath at -15°C and cooled to produce a frozen body (6). Subsequently, the frozen body 6 was taken out from the mold and dried using methanol. Then, it baked at 2100 degreeC in the electric furnace under argon atmosphere for 2 hours. Viscosity η at 20°C of the suspension 4 before gelation obtained in the same manner as in Example 1, porosity of the obtained porous ceramics 11, average pore diameter, average aspect ratio of pores 10, thermal shock resistance, and The average bending strength is shown in Table 1.

(Example 6)

10 vol% of silicon nitride (corresponding to the ceramic particles 1) having an average particle diameter of 2.1 µm, trace amounts of alumina and yttria as a firing aid, and 90 vol% of water were mixed. To this, a trace amount of hydroxypropylmethylcellulose as a thickener, 5% by mass of polyethyleneimine (corresponding to water-soluble polymer (2)) (relative to water (3)), and 2.5% by mass of a crosslinking agent (diglycerol glycidyl ether) ( Water (3) was added and further mixed to prepare a suspension (4).

Next, the prepared suspension (4) was placed in a mold, left still at 20°C for 6 hours, and the suspension (4) was gelled. The mold containing the gelled suspension (4) was immersed in a freezing bath at -15°C and cooled to produce a frozen body (6). Subsequently, the frozen body 6 was taken out from the mold and dried for 24 hours with a freeze drying apparatus. Then, it baked at 1700 degreeC in the electric furnace under nitrogen atmosphere for 2 hours. Viscosity η at 20°C of the suspension 4 before gelation obtained in the same manner as in Example 1, porosity of the obtained porous ceramics 11, average pore diameter, average aspect ratio of pores 10, thermal shock resistance, and The average bending strength is shown in Table 1.

(Example 7)

The porous ceramics 11 were produced by the method similar to Example 3 except not using a baking aid. Viscosity η at 20°C of the suspension 4 before gelation obtained in the same manner as in Example 1, porosity of the obtained porous ceramics 11, average pore diameter, average aspect ratio of pores 10, thermal shock resistance, and The average bending strength is shown in Table 1.

(Example 8)

A porous ceramics 11 was produced in the same manner as in Example 3, except that the viscosity was reduced by adjusting the amount of the thickener added. Viscosity η at 20°C of the suspension 4 before gelation obtained in the same manner as in Example 1, porosity of the obtained porous ceramics 11, average pore diameter, average aspect ratio of pores 10, thermal shock resistance, and The average bending strength is shown in Table 1. In addition, the partial longitudinal sectional views of the porous ceramics 11 produced in this Example are shown to FIG. 4A, FIG. 4B.

(Example 9)

A porous ceramics 11 was produced in the same manner as in Example 4, except that the viscosity was reduced by adjusting the amount of the thickener added. Viscosity η at 20°C of the suspension 4 before gelation obtained in the same manner as in Example 1, porosity of the obtained porous ceramics 11, average pore diameter, average aspect ratio of pores 10, thermal shock resistance, and The average bending strength is shown in Table 1.

(Comparative Example 1)

The porous ceramics 11 were produced by the method similar to Example 4 except not adding a thickener while using fully stabilized zirconia (YSZ) particle|grains with an average particle diameter of 1.5 micrometers. Viscosity η at 20°C of the suspension 4 before gelation obtained in the same manner as in Example 1, porosity of the obtained porous ceramics 11, average pore diameter, average aspect ratio of pores 10, thermal shock resistance, and The average bending strength is shown in Table 1, and the variation in the pore diameter of the porous ceramics 11 is shown in Table 2, respectively. In addition, the partial longitudinal sectional view of the porous ceramics 11 produced by this comparative example is shown in FIG.

(Comparative Example 2)

The porous ceramics 11 were produced by the method similar to Example 4 except not adding a thickener. Viscosity η at 20°C of the suspension 4 before gelation obtained in the same manner as in Example 1, porosity of the obtained porous ceramics 11, average pore diameter, average aspect ratio of pores 10, thermal shock resistance, and The average bending strength is shown in Table 1.

(Comparative Example 3)

The porous ceramics 11 were produced by the method similar to Example 7 except not adding a thickener while using fully stabilized zirconia (YSZ) particle|grains with an average particle diameter of 0.5 micrometer. Viscosity η at 20°C of the suspension 4 before gelation obtained in the same manner as in Example 1, porosity of the obtained porous ceramics 11, average pore diameter, average aspect ratio of pores 10, thermal shock resistance, and The average bending strength is shown in Table 1.

About the ceramic particle 1 used in Examples 1-3 and the comparative example 3, and the produced porous ceramics 11, Table 1 puts together and shows.

[Table 1]

As shown in Table 1, with respect to the average particle diameter d of the ceramic particles (1), the viscosity at 20 ℃ of the suspension unit 4 before gelation η is the specific relationship, i.e., the relation d × η≥1630 ^{of-suspending} so as to have a ^0.77 All of the porous ceramics 11 (Examples 1 to 7) obtained by adjusting the viscosity of the sieve 4 had an average aspect ratio of the pores 10 of 1.4 or less. And according to Examples 1-7, it is visually clear from image analysis that the porous ceramics 11 in which the pores 10 communicating in random directions were formed are produced (refer FIG. 3).

Further, the above-described viscosity η and the average particle diameter ^{d, 950 × d -0.77 ≤η <} 1630 × d -0.77 porous ceramics (11) thus obtained to prepare a viscosity of the suspension member 4 so as to have a relation of (Example 8, In all of 9), the average aspect ratio of the pores 10 is greater than 1.4 and less than or equal to 2.0. And, according to Examples 8 and 9, porous ceramics 11 having a portion in which the formed pores 10 communicate in a random direction (see FIG. 4A ) and a portion in communication with an anisotropic orientation (see FIG. 4B ) (see FIG. 4B ). It is visually clear from the image analysis that is produced.

The relational expression ^{950 × d -0.77 ≤η <1630 ×} d as described above ^- in the porous ceramic 11 is obtained by preparing the viscosity of the suspension so as to satisfy body 4 to ^0.77 (Examples 8 and 9) The average aspect-ratio of the pores 10 was calculated as follows in consideration of the variation in the orientation of the pores 10 at each measurement location. That is, the obtained porous ceramics 11 was divided into 5, and the SEM photograph was image|photographed similarly to the partial longitudinal sectional view shown in FIG. 3 at each location. Next, image analysis is performed on each obtained SEM photograph, the aspect ratio of 10 arbitrarily selected from each image, a total of 50 pores 10 is calculated, and the average value is defined as "average aspect ratio of pores 10". ' did.

On the other hand, in the porous ceramics 11 produced as in Comparative Examples 1 to 3, the average aspect ratio of the pores 10 exceeded 2.0, and compared with the porous ceramics 11 produced in Examples 1 to 9, pores It can be seen that (10) is formed to have anisotropy. Moreover, this is also clear from image analysis (refer FIG. 8).

And, as shown in Table 1, in the porous ceramics 11 having a portion in which the pores 10 are formed in a random direction, the pores 10 are formed to have anisotropy over the whole compared to the porous ceramics 11, Both thermal shock resistance and average bending strength are high. That is, according to the manufacturing method of the porous ceramics 11 which concerns on embodiment, the porous ceramics 11 excellent in thermal shock resistance and bending strength can be produced.

Next, among Examples 1 to 3, in Example 1, Example 3, and Comparative Example 1, the presence or absence of a thickener used in the preparation of the suspension 4, and variation in the pore diameter of the produced porous ceramics 11 About this, it is put together in Table 2 as a representative example, and is shown.

[Table 2]

As shown in Table 2, in all of the porous ceramics 11 produced by applying the suspension 4 to which the thickener was added, the pore size variation is 10% or less, and pores 10 with small variation in pore diameter are formed. . The reason for this is considered to be that the growth of the ice 5 is suppressed by the addition of the thickener, and the growth rate of the ice 5 is homogenized.

Additional effects and modifications can be easily derived by those skilled in the art. For this reason, the broader aspect of this invention is not limited to the specific detail and typical embodiment shown and described as mentioned above. Accordingly, various modifications are possible without departing from the spirit or scope of the overall inventive concept defined by the appended claims and their equivalents.

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: pores
11, 11a: porous ceramics 12, 12a: cooling device
13: firing jig 14: expectation
15: plate part 16: support part
17: setter 17a: upper surface
18: burned object

Claims (17)

A step of gelling a suspension containing ceramic particles, a water-soluble polymer, and water;
Freezing the gelled suspension to produce a frozen body;
removing the ice grown on the frozen body to create pores;
The process of calcining the frozen body from which the ice has been removed
including
The viscosity η (mPa·s) at 20° C. of the suspension before gelation, and the average particle diameter d (μm) of the ceramic particles,
η≥950 ^-0.77 × d
A method for producing porous ceramics, characterized in that it has a relationship of According to claim 1,
The viscosity η and the average particle size d are,
η≥1630 ^-0.77 × d
A method for producing porous ceramics, characterized in that it has a relationship of According to claim 1,
The water-soluble polymer is an N-alkylamide-based polymer, N-isopropylacrylamide-based polymer, sulfomethylated acrylamide-based polymer, N-dimethylaminopropylmethacrylamide-based polymer, polyalkylacrylamide-based polymer, alginic acid, sodium alginate , ammonium alginate, polyethyleneimine, carboxymethylcellulose, hydroxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, sodium polyacrylate, polyethylene glycol, polyethylene oxide, polyvinyl alcohol, Preparation of porous ceramics comprising at least one of polyvinylpyrrolidone, carboxyvinyl polymer, starch, gelatin, agar, pectin, glucomannan, xanthan gum, locust bean gum, carrageenan gum, guar gum and gellan gum Way. According to claim 1,
The ceramic particles, characterized in that it comprises at least one of zirconia, alumina, silica, titania, silicon carbide, boron carbide, silicon nitride, boron nitride, cordierite, hydroxyapatite, sialon, zircon, aluminum titanate and mullite A method for producing porous ceramics. According to claim 1,
A method for producing porous ceramics, wherein the porosity of the porous ceramics is 50% to 99%. According to claim 1,
A method for producing porous ceramics, characterized in that the average aspect ratio of the pores is 1 to 2. According to claim 1,
The average bending strength of porous ceramics is 10 MPa or more, The manufacturing method of porous ceramics characterized by the above-mentioned. According to claim 1,
A method for producing porous ceramics, wherein the porous ceramics have a thermal shock resistance of 450°C or higher. a base; and a setter mounted on the base;
The setter has porous ceramics,
The porous ceramics,
95 mass % or more of fully stabilized zirconia is included.
The porosity is 50% to 99%, the average aspect ratio of the pores is 1 to 2, the average pore diameter is 10㎛ to 100㎛,
An average bending strength of 10 MPa or more and 26.8 MPa or less
A firing jig, characterized in that. delete 10. The method of claim 9,
The porous ceramics are a firing jig, characterized in that the thermal shock resistance is 450 ℃ or more. 10. The method of claim 9,
The porous ceramic is a firing jig, characterized in that the deviation of the average pore diameter is 10% or less. 13. The method of claim 9, 11 or 12,
_{The said porous ceramics further contain 0.01-1.5 mass % of Al 2} O ₃ and 0.01-2.0 mass % of CaO with respect to the said fully stabilized zirconia.
A firing jig, characterized in that. delete It was produced by the manufacturing method of the porous ceramics in any one of Claims 1-8, The porous ceramics characterized by the above-mentioned. Having the porous ceramics according to claim 15,
_{The said porous ceramics further contain 0.01-1.5 mass % of Al 2} O ₃ and 0.01-2.0 mass % of CaO with respect to the said fully stabilized zirconia.
Setter, characterized in that. expectations and
The setter according to claim 16 placed on top of said base.
to have
A firing jig, characterized in that.

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