JP2020200230A - Ceramic body and method of producing ceramic body - Google Patents

Abstract

To provide a ceramic body and a method of producing the same, which makes it possible to reduce the variation in pore diameter of open pores and suppress the reduction in the strength of ceramic bodies caused by the presence of open pores having a relatively large pore diameter.SOLUTION: A ceramic body comprises a plurality of open pores that open to the outside, wherein the ratio of the volume of fine open pores to the volume of all open pores in the ceramic body is 70% or more, the fine open pores being open pores having a pore diameter of 100 nm or less.SELECTED DRAWING: Figure 2

Description

The techniques disclosed herein relate to ceramic bodies.

Conventionally, for example, as a bone filling member or the like, a ceramic body having a plurality of open pores that open to the outside is known (see Patent Document 1 below).

Japanese Unexamined Patent Publication No. 2013-79172

In the conventional ceramic body having such a plurality of open pores, there is a problem that the performance of the product in which the ceramic body is used is deteriorated because the pore diameters of the plurality of open pores vary. Further, in the conventional ceramic body, there is a problem that the strength of the ceramic body may decrease because there are open pores having a relatively large pore diameter.

It should be noted that such a problem is not limited to the ceramic body used for the above-mentioned bone filling member, but is a problem common to ceramic bodies used for other purposes and having a plurality of open pores.

This specification discloses a technique capable of solving the above-mentioned problems.

The technique disclosed in the present specification can be realized, for example, in the following forms.

(1) The ceramic body disclosed in the present specification is a ceramic body having a plurality of open pores that open to the outside, and is an open pore having a pore diameter of 100 nm or less within the volume of the total open pores in the ceramic body. The volume ratio of a certain fine open pore is 70% or more. In the present ceramic body, the ratio of the volume of the fine open pores having a pore diameter of 100 nm or less to the volume of the total open pores is 70% or more. Therefore, according to the present ceramic body, the variation in the pore diameter of the open pores is reduced and the open pores having a relatively large pore diameter are reduced as compared with the configuration in which the volume ratio of the fine open pores is less than 70%. It is possible to suppress a decrease in the strength of the ceramic body due to the presence of.

(2) In the ceramic body, the volume ratio of the open pores to the volume of the pores in the ceramic body may be 20% or more. According to the present ceramic body, the volume of the open pores opened to the outside is larger than that of the structure in which the volume ratio of the open pores is less than 20% of the volume of the pores in the ceramic body. The surface area used for the ceramic can be increased.

(3) The method for producing a ceramic body disclosed in the present specification is a method for producing a ceramic body having a plurality of open pores that open to the outside, wherein the powder of a forming material containing the main component of the ceramic body and the formation thereof. A step of preparing a mixture containing a liquid that dissolves a part of the powder of the material and the amount of the powder dissolved per liter is less than 0.1 g, and the step of preparing the mixture from the boiling point of the liquid. The present invention comprises a step of forming the ceramic body by pressurizing while heating at a high temperature. According to the method for producing the present ceramic body, it is possible to manufacture the ceramic body in which the variation in the pore diameter of the open pores and the decrease in the strength of the ceramic body due to the presence of the open pores having a relatively large pore diameter are suppressed. it can.

It is a flowchart which shows an example of the manufacturing method of the ceramic body 100 in this embodiment. It is explanatory drawing which shows a part of the manufacturing process of the ceramic body 100 in this embodiment schematically. It is explanatory drawing which shows the performance evaluation result.

A. Embodiment:
A-1. Composition of ceramic body 100:
The ceramic body 100 (see FIG. 2C described later) is a porous body formed of a material containing ceramic as a main component (referred to as “ceramic material”) and having a plurality of pores formed therein. The plurality of pores include open pores that form an open space on the outside (outer surface) of the ceramic body 100 and open pores that form a closed space inside the ceramic body 100. The main component referred to here means that the volume content of the ceramic is the largest among the volume content (vol%) of each component with respect to the volume of the portion of the porous body excluding the pores. For example, the volume content of the ceramic with respect to the volume of the portion of the porous body excluding the pores is preferably 50 vol% or more. The ceramic material is preferably, for example, magnesium fluoride (MgF ₂ ), an oxide or a phosphoric acid compound. Oxides, such as alumina _{(Al 2 O} 3), silica _(SiO 2), zirconia _(ZrO 2), mullite _{(3Al 2 O 3 · 2SiO 2} ), cordierite _{(2MgO · 2Al 2 O 3 ·} 5SiO 2) , Titania (TiO ₂ ), Magnesia (MgO), etc. Examples of the phosphoric acid compound include hydroxyapatite (Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ ), LAGP (Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ ) and the like. Further, in order to utilize the characteristics of the ceramic body 100, the porosity of the ceramic body 100 is preferably 20% or more. Further, in order to secure the strength of the ceramic body 100, the porosity of the ceramic body 100 is preferably 80% or less.

The ceramic body 100 satisfies the following first requirement with respect to pores.
First requirement: In the ceramic body 100, the ratio of the volume of the fine open pores to the volume of the total open pores (hereinafter, simply referred to as "the ratio of the fine open pores") is 70% or more. The fine open pores are open pores having a pore diameter of 100 nm or less.
The ratio of fine open pores is preferably 80% or more, and more preferably 90% or more. The pore diameter of the finely opened pores is preferably 1 nm or more.

Further, the ceramic body 100 satisfies the following second requirement with respect to pores.
Second requirement: The volume ratio of open pores (hereinafter referred to as "open porosity") in the volume of pores in the ceramic body 100 is 20% or more.
The open porosity is preferably 30% or more.

A-2. Manufacturing method of ceramic body 100:
Next, an example of the method for manufacturing the ceramic body 100 in the present embodiment will be described. FIG. 1 is a flowchart showing an example of a method for manufacturing the ceramic body 100 in the present embodiment, and FIG. 2 is an explanatory diagram schematically showing a part of the manufacturing process of the ceramic body 100 in the present embodiment. FIG. 2 shows Z-axes that are orthogonal to each other to specify the direction. In the present specification, for convenience, the Z-axis positive direction is referred to as an upward direction, and the Z-axis negative direction is referred to as a downward direction, but the ceramic body 100 or the like is actually in a direction different from such a direction. It may be installed.

First, for example, a ceramic powder containing MgF ₂ as a main component is humidified by adding a predetermined amount of a liquid (for example, pure water, oil, alcohol, etc.) that dissolves a part of the ceramic powder under a predetermined temperature and pressure. Mixing is performed to prepare a ceramic humidified powder 110 (see S110 in FIG. 1 and FIG. 2 (A)). The liquid (humidifying liquid) melts the surface of the ceramic particles to form a slight liquid phase portion, and heat pressing is performed to promote the solidification of the liquid, and as a result, the ceramic becomes dense.

Here, the amount of the ceramic powder dissolved in 1 L of the liquid is less than 0.1 g. If the amount of the ceramic powder dissolved in 1 L of the liquid is 0.1 g or more, the solidification of the liquid proceeds excessively, and the press sintered body 120 (see FIG. 2B) described later has pores. This is because it is not sufficiently formed. Moreover, it is preferable that the liquid does not contain impurities. As a result, when the press-sintered body 120 is produced, it is possible to prevent the porosity of the press-sintered body 120 (ceramic body 100) from becoming extremely low due to the impurities blocking the pores. For example, when the ceramic powder is MgF ₂ , the liquid is preferably pure water (specific resistance is 1 MΩ · cm or more). The amount of MgF ₂ dissolved in 1 L of pure water is about 0.0073 g. The ceramic humidifying powder 110 corresponds to a mixture within the claims.

Next, the ceramic humidifying powder 110 is provided in, for example, a hot press machine (not shown), and is filled in a uniaxial press die 10 having an upper punch 12, a lower punch 14, and a side mold 16 for a predetermined time (for example,). For 1 hour or more), pressurize in a predetermined direction (vertical direction) at a predetermined pressure while heating at the first temperature. As a result, a press-sintered body 120, which is a dense porous body in which a plurality of fine pores are formed, is produced (see S120 in FIG. 1 and FIG. 2B in FIG. 2). That is, the press-sintered body 120 is produced by simultaneously molding and firing the ceramic humidified powder 110.

The pressure at the time of pressing is preferably a pressure in which the surface of the ceramic powder dissolves in the liquid and the distance between the ceramic particles becomes short and the frequency of point contact increases, for example, it is larger than 125 MPa and 500 MPa or less. preferable. Further, the first temperature during the heating press is preferably equal to or higher than the boiling point of the added liquid. As a result, it is possible to suppress the residual of a large amount of liquid in the press sintered body 120. Further, the first temperature is preferably not more than the upper limit temperature obtained by adding 300 ° C. to the boiling point of the liquid. This makes it possible to prevent the liquid from evaporating (volatilizing) before the surface of the ceramic powder reacts with the liquid during the heating press. Further, in the present embodiment, during the heating press, the ceramic humidifying powder 110 and the upper punch 12 in the uniaxial pressing die 10 and the ceramic humidifying powder 110 and the lower punch 14 are respectively. A polyimide sheet 18 was arranged. As a result, it is possible to prevent the obtained press-sintered body 120 from sticking to the uniaxial press die 10. That is, the polyimide sheet 18 has heat resistance to a firing temperature of about 300 ° C., and can be easily peeled off from the pressed sintered body 120 after firing.

The obtained press sintered body 120 is taken out from the uniaxial press die 10 and subjected to a predetermined heat treatment (for example, a drying treatment at a second temperature lower than the first temperature) (S130 in FIG. 1). As a result, the residual water content is substantially removed from the press-sintered body 120, and the above-mentioned ceramic body 100 is produced (see FIG. 2C).

A-3. Effect of this embodiment:
As described above, in the ceramic body 100 of the present embodiment, the ratio of the volume of the fine open pores (the ratio of the fine open pores) of the open pores having a pore diameter of 100 nm or less to the volume of the total open pores is 70. % Or more (first requirement above). Therefore, according to the ceramic body 100 of the present embodiment, the variation in the pore diameter of the open pores is reduced and the pore diameter is relatively large as compared with the configuration in which the ratio of the fine open pores is less than 70%. It is possible to suppress a decrease in strength of the ceramic body due to the presence of open pores. Specifically, according to the present embodiment, for example, when the ceramic body 100 is used as a catalyst carrier for purifying automobile exhaust gas, the following effects are obtained. That is, according to the present embodiment, it is possible to suppress the deterioration of performance due to the formation of a non-uniform reaction field by reducing the variation in the pore diameter of the open pores. In addition, it is possible to suppress a decrease in the amount of catalyst supported due to the increase in the number of open pores having a pore diameter larger than 100 nm.

Further, in the ceramic body 100 of the present embodiment, the volume ratio of the open pores (open porosity) to the volume of the pores in the ceramic body 100 is 20% or more (the second requirement above). As a result, according to the present embodiment, since the volume of the open pores is large as compared with the configuration in which the open pore ratio of the ceramic body 100 is less than 20%, the surface area used for various functions such as a filter is increased. be able to.

Further, in the method for producing the ceramic body 100 of the present embodiment, the powder of the forming material containing the main component of the ceramic body 100 (ceramic powder) and the liquid that dissolves a part of the powder of the forming material are per 1 L. A mixture (ceramic humidified powder 110) containing a liquid in which the dissolved amount of the powder is less than 0.1 g is prepared (see S110 in FIG. 1 and FIG. 2 (A) in FIG. 2). Next, the mixture is pressurized while being heated at a first temperature higher than the boiling point of the liquid (see S120 in FIG. 1 and FIG. 2B) to form the ceramic body 100 (FIG. 2 (FIG. 2). See C)). As a result, according to the manufacturing method of the present embodiment, the variation in the pore diameter of the open pores and the decrease in the strength of the ceramic body 100 due to the presence of the open pores having a relatively large pore diameter are suppressed. Can be manufactured. That is, the liquid added to the ceramic powder slightly dissolves the surface of the ceramic particles, and the supersaturated solute reprecipitates in the portion where the ceramic particles are in contact with each other due to heating and pressurization, and the solidified body. The skeleton of (press sintered body 120) is formed. Since the amount of solute reprecipitated is very small, the ceramic particles come into partial contact rather than whole contact. As a result, gaps between the ceramic particles remain, and many pores are formed. Further, since the liquid volatilization path exists continuously from the inside to the outside of the press sintered body 120, the pores become open pores. Moreover, the open pores are not due to the pore-forming material, but are formed due to the solidification of the contact portion of the ceramic particles and the raw material powder structure. Therefore, the ceramic body 100 in which many fine open pores are formed is produced.

Further, in the present embodiment, the press-sintered body 120 is produced by simultaneously molding and firing the ceramic humidified powder 110. Therefore, according to the present embodiment, it is not necessary to separately perform the step of molding the ceramic powder to form the molded body and the step of firing the molded body, so that the number of steps in the manufacturing process of the ceramic body 100 is not required. Can be reduced.

Further, according to the present embodiment, the above-mentioned ceramic body 100 can be manufactured without using a pore-forming material. The effects in this case are as follows.
(1) Purity of Ceramic in Ceramic Body In the conventional manufacturing method using a pore-forming material, the purity of ceramic in the ceramic body may decrease due to the remaining pore-forming material inside the ceramic body. On the other hand, in the manufacturing method of the present embodiment, since the pore-forming material is not used, the purity of the ceramic in the ceramic body does not decrease due to the residue of the pore-forming material, so that the purity of the ceramic in the ceramic body is improved. be able to.
(2) Types of materials for forming ceramic bodies In the conventional manufacturing method using a pore-forming material, heating at an extremely high temperature is required to burn the pore-forming material remaining inside the ceramic body. As a result, the material for forming the ceramic body may be limited to the material having high heat resistance. On the other hand, in the manufacturing method of the present embodiment, since the pore-forming material is not used, it is not necessary to adjust the temperature for burning the pore-forming material, and as a result, the types of materials for forming the ceramic body are limited. Can be suppressed.
(3) Energy required for manufacturing the ceramic body In the conventional manufacturing method using a pore-forming material, a high-temperature and long-time heat treatment is required to burn the pore-forming material remaining inside the ceramic body. The energy required to fabricate the ceramic body is relatively large. On the other hand, in the manufacturing method of the present embodiment, since the pore-forming material is not used, the energy required for producing the ceramic body is relatively small because the energy for burning the pore-forming material is not required. As a result, there are high environmental merits such as reduction of CO ₂ emissions.

A-4. Performance evaluation:
A plurality of ceramic body samples were prepared, and the performance was evaluated using the prepared samples. FIG. 3 is an explanatory diagram showing the performance evaluation result.

A-4-1. For each sample:
As shown in FIG. 3, seven ceramic body samples (S1 to S7) were used for the performance evaluation. Of the seven samples, samples S1 and S2 were produced according to the production method described in the above-described embodiment, and samples S3 to S7 were produced according to a production method different from that of the embodiment. More specific methods for producing samples S1 to S7 are as follows.

In sample S1, in the above manufacturing method, performs humidification mixed in a mortar adding 50 wt% of purified water to the MgF ₂ powder, to prepare a humidified powder MgF _2. Next, the humidified powder of MgF ₂ was placed in a uniaxial press die having an inner diameter of 12 mm, pressed at a pressure of 350 MPa while heating at 300 ° C. (firing temperature, first temperature), and held for 1 hour. The obtained solidified product was dried at 120 ° C. for 4 hours to completely remove residual water. As a result, the ceramic body of sample S1 was produced. Sample S2 differs from the method for producing sample S1 in that the heating temperature is 400 ° C.

Sample S3 differs from the method for producing sample S1 in that the heating temperature is 80 ° C. Sample S4 differs from the method for producing sample S1 in that pure water is not added to the powder of MgF ₂ . Sample S5 differs from the method for producing sample S1 in that the pressure is 50 MPa. Sample S6, with respect to the manufacturing method of the sample S1, the of MgF ₂ powder, instead of pure water, the difference is that adding 50 wt% of NaCl aqueous solution of 1M. In sample S7, 50 wt% pure water was added to the powder of trilithium phosphate (Li ₃ PO ₄ ) instead of MgF ₂ and humidified and mixed in a mortar with respect to the production method of sample S1, and Li ₃ PO was performed. _{The difference is that} the humidified powder of No. ₄ is prepared and the humidified powder of Li ₃ PO ₄ is heated at 140 ° C.

A-4-2. Evaluation method:
For the ceramic bodies of each sample S1 to S7, the volume and pore diameter (cross-sectional diameter) of each open pore were measured at 25 ° C. using a known measurement method using a mercury porosimeter. The average pore diameter (nm) of the open pores was calculated from the measurement results of the volume and the pore diameter of each open pore. Further, from the measurement result, the ratio (%) of the fine open pores is calculated, and when the ratio of the fine open pores is 90% or more, it is judged as the best "◎", and when the ratio of the fine open pores is 70% or more. In some cases, it was judged as "○", and when the ratio of the finely opened pores was less than 70%, it was judged as "×".

Further, for the ceramic bodies of each sample S1 to S7, the open porosity was specified in the volume of pores in the ceramic body. First, the volumes of all pores in the ceramic body were calculated. That is, the density of each sample was measured by a known Archimedes method. Next, from the density measured in each sample, the porosity of the ceramic body of each sample was calculated using the following equation 1, and the total porosity in the ceramic body was calculated from the porosity and the measured volume of the ceramic body. The volume of was calculated.
<Equation 1>
Porosity of ceramic body = [1- (measurement density / theoretical density)] x 100
Measurement density: Density of the sample measured by the Archimedes method described above Theoretical density: Theoretical density of the ceramic material Next, from the measurement result by the mercury porosimeter described above and the calculated volume of all pores in the ceramic body, the open porosity Was identified.

A-4-3. Evaluation results:
As shown in FIG. 3, in sample S1, the ratio of fine open pores was 94.6% (satisfying the first requirement above), and it was determined to be the best “⊚”. Further, in sample S1, the average pore diameter of the open pores was 27.5 nm, and the open porosity was 30.8%. In sample S2, the ratio of fine open pores was 93.3% (satisfying the first requirement), and it was judged to be the best "⊚". Further, in sample S2, the average pore diameter of the open pores was 29.4 nm, and the open porosity was 31.5%. From these results, the first requirement was satisfied by heating at 300 ° C. or higher and 400 ° C. or lower and pressurizing at 350 MPa, and further, the ratio of fine open pores was 90% or more, and the average pore diameter of the open pores was 30%. Below, it can be seen that a porous ceramic body having a porosity of 30% or more can be produced. In each of the ceramic bodies of Samples S1 and S2, the apparent density (density of the portion of the porous ceramic body excluding the open pores) was 95% or more. When the apparent density is 95% or more, most of the pores in the ceramic body are open pores, and the density of the portion excluding the open pores is high, so that the strength is relatively high.

In sample S3, no solidified product was obtained, and the result was determined to be "x". It is considered that the reason why the solidified body was not obtained is that the heating temperature was lower than the boiling point of pure water, so that the solute dissolved by pure water did not sufficiently reprecipitate and did not sufficiently solidify. In addition, sample S4 also failed to obtain a solidified body and was judged to be "x". It is considered that the reason why the solidified product was not obtained is that the liquid was not added to the MgF ₂ powder in the first place.

In sample S5, the ratio of fine open pores was 72.7% (satisfying the first requirement above), and the result was judged to be “◯”. Further, in sample S5, the average pore diameter of the open pores was 81.9 nm, and the open porosity was 37.2%. From this result, it can be seen that a ceramic porous body satisfying the first requirement can be produced by heating at 300 ° C. and pressurizing at 50 MPa.

In sample S6, the porosity was extremely low and the first requirement was not satisfied, so the result was determined to be "x". The reason for this is that since the dissolved amount of the powder per 1 L of the NaCl aqueous solution is 0.1 g or more, the dissolved amount of the MgF ₂ powder becomes excessively large, and as a result, sufficient pores are formed in the solidified body. It is possible that it was not. In sample S7, the proportion of fine open pores was less than 1%, which did not satisfy the first requirement, and therefore, it was determined to be rejected “x”. The reason for this is that the humidified powder of Li ₃ PO ₄ has a dissolved amount of 0.39 g per 1 L of pure water, and the dissolved amount of the powder of Li ₃ PO ₄ becomes excessively large, resulting in pores in the solidified body. It is probable that it was not sufficiently formed.

B. Modification example:
The technique disclosed in the present specification is not limited to the above-described embodiment, and can be transformed into various forms without departing from the gist thereof. For example, the following modifications are also possible.

The configuration of the ceramic body 100 in the above embodiment is merely an example and can be variously deformed. For example, as the shape of the ceramic body 100, various shapes such as a rectangular parallelepiped shape, a flat plate shape, a columnar shape, and a tubular shape can be adopted. Further, the ceramic body 100 does not have to satisfy the above-mentioned second requirement.

Further, the material for forming each member constituting the ceramic body 100 in the above embodiment is merely an example and can be variously deformed. For example, in the above embodiment, the material for forming the ceramic body 100 is MgF ₂ , but other types of ceramic materials may be used.

Further, the method for manufacturing the ceramic body 100 in the above embodiment is merely an example and can be variously deformed. For example, in the method for manufacturing the ceramic body 100 in the above embodiment, the sheet 18 does not have to be arranged in the uniaxial pressing die 10. Further, in the above embodiment, pure water is exemplified as the liquid, but the present invention is not limited to this, and a part of the powder of the material for forming the ceramic body is dissolved, and the dissolved amount of the powder per 1 L is 0.1 g. Any liquid that is less than or equal to is sufficient. Further, in the above embodiment, as the powder of the forming material containing the main component of the ceramic body, the ceramic powder containing MgF ₂ as the main component is exemplified, but the ceramic powder containing the ceramic material other than MgF ₂ as the main component is used. There may be. As is clear from the above-mentioned mechanism and evaluation results, the method for producing the ceramic body 100 of the present invention includes a powder of a forming material containing the main component of the ceramic body and a liquid that dissolves a part of the powder of the forming material. If the relationship between the two is established, the above-mentioned ceramic body can be manufactured by carrying out the steps S110 to S130 shown in FIG. In the method for manufacturing the ceramic body 100 in the above embodiment (FIG. 1), the ceramic body 100 was manufactured without using the pore-forming material, but the method for manufacturing the ceramic body of the present invention does not use the pore-forming material. Not limited to the case, even when a pore-forming material is used, a ceramic body having fine pores (including the fine pores and the pores formed by the pore-forming material) can be produced.

Further, the ceramic body 100 in the above embodiment is not limited to the ceramic body used for the catalyst carrier, and is used for other purposes (for example, a filter (filtration membrane), a heat insulating material, a sound absorbing or muffling member, a humidity control material, and a substance selectively. It may be a ceramic body used for a separating member, an optical material).

10: Single-screw press die 12: Upper punch 14: Lower punch 16: Side mold 18: Sheet 100: Ceramic body 110: Humidifying powder 120: Press sintered body

Claims (3)

In a ceramic body having a plurality of open pores that open to the outside,
In the ceramic body, the ratio of the volume of the fine open pores having a pore diameter of 100 nm or less to the volume of the total open pores is 70% or more.
A ceramic body characterized by this. In the ceramic body according to claim 1,
The volume ratio of the open pores to the volume of the pores in the ceramic body is 20% or more.
A ceramic body characterized by this. In a method for manufacturing a ceramic body having a plurality of open pores that open to the outside,
It contains a powder of a forming material containing the main component of the ceramic body and a liquid that dissolves a part of the powder of the forming material and the dissolved amount of the powder per liter is less than 0.1 g. The process of making the mixture and
A step of producing the ceramic body by pressurizing the mixture while heating it at a temperature higher than the boiling point of the liquid.
To prepare
A method for manufacturing a ceramic body.

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