JP7029227B2 - Method for manufacturing porous zirconia sintered body - Google Patents

Description

The present specification relates to a method for producing a porous zirconia sintered body.

Stabilized element-added zirconia sintered bodies are used as typical solid electrolytes as elements of structures such as fuel cells and oxygen sensors. Such structures are generally manufactured as porous bodies to ensure a reaction area. The ceramic porous body is generally made into a porous body by mixing raw ceramic particles and a pore-forming agent and burning off the pore-forming agent at the time of firing (Patent Document 1).

Japanese Unexamined Patent Publication No. 2014-227324

However, when a porous body is produced using a pore-forming agent, the pore size distribution of the obtained porous body depends on the particle size distribution of the pore-forming agent, but it is difficult to control the pore size with high accuracy. The reason is that in a porous ceramic sintered body, it is usually intended to be sintered together with porosity, but since it is necessary to give priority to sintering, it is difficult to optimize the raw material composition and firing conditions for pore size control, etc. Because it is. In addition, it is difficult to uniformly distribute the pore-forming agent to the ceramic material, and a non-porous portion, that is, a portion that is invalidated as the reaction surface is generated.

It is an object of the present specification to provide a more practical method for producing a porous zirconia sintered body.

Based on the speculation that it will be difficult to control the pore size because the present inventors intend two contradictory events of densification of zirconia particles and porosification due to burning of the pore-forming agent in the process of sintering. By imparting porosity to the zirconia-based particles used in the production of the sintered body, a porous zirconia sintered body whose porosity and sinterability are well controlled without using a pore-forming agent can be obtained. I got the finding that it can be obtained.

In addition, the present inventors have investigated the preparation of a raw material solution using a vanishing agent (burning agent) and a carboxylic acid as a dispersant in the spray pyrolysis method. It was found that a sintering material containing porous zirconia particles, which can be suitably used for producing a porous zirconia sintered body, can be produced by a spray pyrolysis method. The present specification provides the following means based on such findings.

(1) A method for producing a porous zirconia sintered body.
A molding process for obtaining a molded product containing a zirconia material containing spherical porous zirconia particles, and
The step of firing the molded product to sinter the zirconia to obtain a porous zirconia sintered body, and
How to prepare.
(2) The porous zirconia sintered body has an average pore diameter of 0.1 μm or more and 0.5 μm or less, and includes 80% or more of all pores in the range of 0.1 μm including the average pore diameter. The method according to (1), which is a sintered body.
(3) The method according to (1) or (2), wherein the relative density of the sintered body is 50% or more.
(4) The method according to any one of (1) to (3), wherein the specific surface area of the sintered body is 0.8 m ² / g or more.
(5) Further, the following steps for obtaining the zirconia material;
A raw material solution preparation step of adding a carboxylic acid to a first raw material solution containing zirconium hydride as an insoluble matter to prepare a second raw material solution which is a zirconium-containing colloid.
A particle formation step of heating droplets of the second raw material liquid to thermally decompose at least a part of the zirconia hydroxide into particles.
The method according to any one of (1) to (4).
(6) The method according to (5), wherein the zirconium hydride is a gel-like zirconium hydride.
(7) The method according to (5) or (6), wherein the carboxylic acid is one or more selected from the group consisting of acetic acid, citric acid, oxalic acid and malic acid.
(8) The method according to (7), wherein the carboxylic acid is citric acid.
(9) The method according to any one of (5) to (7), wherein the second raw material liquid is substantially transparent.
(10) The method according to any one of (5) to (9), further comprising a firing step of heating the particles obtained in the particle formation step to adjust the characteristics of the particles.
(11) A method for producing a material for obtaining a porous zirconia sintered body.
A raw material solution preparation step of adding a carboxylic acid to a first raw material solution containing zirconium hydride as an insoluble matter to prepare a second raw material solution which is a zirconium-containing colloid.
A particle formation step of heating droplets of the second raw material liquid to thermally decompose at least a part of the zirconia hydroxide into particles.
A firing step of heating the particles obtained in the particle formation step to adjust the characteristics of the particles, and a firing step of adjusting the characteristics of the particles.
How to prepare.
(12) A material for obtaining a porous zirconia sintered body.
Spherical porous zirconia particles and
Heat shrinkage preparation, which is an organic material,
Including materials.
(13) The material according to (12), wherein the organic material is derived from a synthetic raw material of the porous zirconia particles.
(14) The material according to (13), wherein the synthetic source is a carboxylic acid.
(15) A porous zirconia sintered body.
A sintered body having an average pore diameter of 0.1 μm or more and 0.5 μm or less, and containing 80% or more of all pores in the range of 0.1 μm including the average pore diameter.
(16) The sintered body according to (15), which has a relative density of 50% or more.
(17) The sintered body according to (15) or (16), which has a specific surface area of 0.8 m ² / g or more.
(18) A method for producing a laminate of a porous zirconia layer and a dense zirconia layer.
A step of firing and integrating a laminate of a porous zirconia material layer containing spherical porous zirconia particles and a dense zirconia material layer.
Equipped with
The porous zirconia particles are subjected to the following steps;
A raw material solution preparation step of adding a carboxylic acid to a first raw material solution containing zirconium hydride as an insoluble matter to prepare a second raw material solution which is a zirconium-containing colloid.
A particle formation step of heating droplets of the second raw material liquid to thermally decompose at least a part of the zirconia hydroxide into particles.
A firing step of heating the particles obtained in the particle formation step to adjust the characteristics of the particles so as to improve the integrity with the dense zirconia layer.
How to prepare.

It is a figure which shows an example of the manufacturing process of the porous zirconia sintered body in this specification. It is a figure which shows the relative density of the porous zirconia sintered body synthesized in Example 3. FIG. It is a figure which shows the evaluation result of the pore distribution and porosity about a part of the porous zirconia sintered body synthesized in Example 3. FIG. It is a figure which shows the evaluation result about the relative density etc. about a part of the porous zirconia sintered body synthesized in Example 3. FIG. It is a figure which shows the evaluation result about the manufacturing of the laminated body of a porous zirconia sintered body and 8YSZ dense body.

The present specification relates to a porous zirconia sintered body, and more particularly to a porous zirconia sintered body and a method for producing the same, a method for producing a laminate of a porous zirconia layer and a dense zirconia layer, and the like.

According to the method for producing a porous zirconia sintered body disclosed in the present specification, a zirconia material containing spherical porous zirconia particles is used as the sintered body material. As a result, it is possible to obtain a sintered body having excellent porosity and excellent sinterability. In addition, such a sintered body material can intentionally control the residual amount of the disappearing material due to its crystallinity and porosity. Due to the controlled particle characteristics, in addition to the porosity and sinterability of the sintered body, the heat shrinkage rate can be easily controlled to obtain a sintered body having desired characteristics. That is, for example, a porous zirconia sintered body having a high porosity and a large specific surface area can be obtained. Further, for example, in the case of integrally sintering with another ceramic material, the heat shrinkage rate generated in the porous zirconia sintered body can be adjusted according to the heat shrinkage of the other ceramic material.

Further, the porous zirconia particle material disclosed in the present specification can be suitably used as raw material particles for a porous zirconia sintered body, which is required to have high porosity and a specific surface area.

As used herein, zirconia includes stabilized zirconia and partially stabilized zirconia, as well as pure zirconia. Stabilized zirconia and partially stabilized zirconia are generally stabilized with one or more oxides selected from the group consisting of yttrium, magnesium, calcium, hafnium and the like.

Hereinafter, a method for producing a porous zirconia sintered body, a method for producing a porous zirconia sintered body, a method for producing a laminate, a method for producing a laminate, a method for producing a porous zirconia particle material, a porous zirconia particle material, etc. Various embodiments of the disclosure will be described with reference to the drawings as appropriate. FIG. 1 is a diagram showing an outline of a method for producing a porous zirconia sintered body.

(Manufacturing method of porous zirconia sintered body)
The method for producing a porous zirconia sintered body disclosed in the present specification is a molding for obtaining a molded body containing a porous zirconia particle material containing spherical porous zirconia particles (hereinafter, also simply referred to as the present particle material). A step and a step of calcining the molded body to sintered zirconia to obtain a porous zirconia sintered body can be provided. According to this production method, by using a porous zirconia particle material as a raw material for a sintered body, a sintered body having excellent porosity and sinterability can be obtained. In addition, the heat shrinkage during sintering can be easily adjusted.

(Molding process)
As the present sintered body, a molded body can be obtained by a usual method except that the present particle material is used. As the binder used in the molding step, a known resin binder or the like can be used. For molding, a known molding method can be used to obtain a ceramic molded body, but for example, in order to obtain a self-standing molded body having a certain strength or higher, pressure molding is preferable. For pressure molding, known molding methods such as press molding, extrusion molding, injection molding, cold isotropic pressurization (CIP) and the like can be used alone or in combination. In addition, methods such as tape casting and doctor blade can also be mentioned.

Hereinafter, according to FIG. 1, a method for producing a porous zirconia particle material (hereinafter, also simply referred to as the present particle material) used in the molding step of the present production method and the obtained zirconia particle material will be described first.

(Manufacturing method of this particle material)
As illustrated in FIG. 1, this particle material is a raw material for preparing a second raw material liquid which is a zirconium-containing colloid by adding a carboxylic acid to a first raw material liquid containing zirconium hydroxide as an insoluble matter. It can be produced by a liquid preparation step and a particle formation step of heating droplets of the second raw material liquid to thermally decompose at least a part of the zirconia hydroxide into particles. Further, as illustrated in FIG. 1, the particle material can further include a firing step of heating the particles.

(Raw material liquid preparation process)
The raw material liquid preparation step is a step of preparing a second raw material liquid from the first raw material liquid. The second raw material liquid can be subjected to a spray pyrolysis method.

(First raw material liquid)
The first raw material liquid can be a liquid containing a zirconium compound as an insoluble matter. The first raw material liquid can be prepared by various methods. The zirconium compound is not particularly limited, but may be, for example, zirconium hydride.

The first raw material liquid can be a dispersion liquid in which zirconium hydride in the form of powder or the like is put into water and dispersed. In general, zirconium hydride (Zr (OH) ₄ ) is insoluble in water.

Further, the first raw material liquid may be prepared by adjusting the pH of the liquid in which the zirconium salt is dissolved to precipitate zirconium hydride. In the first raw material liquid of this embodiment, zirconium hydride is contained as a gel-like precipitate. Furthermore, the first raw material liquid may be prepared by adding a separately prepared zirconium hydride gel to water or the like, or a zirconium hydride gel powder prepared in advance so as to gel when added to water or the like. (Commercially available) may be prepared by putting it in water.

The first raw material liquid preferably contains gel-like zirconium hydride produced from a zirconium salt in consideration of operability and subsequent preparation of the second raw material liquid. By containing such zirconium hydride, it is possible to form a zirconium-containing colloid suitable for forming porous particles by the spray pyrolysis method by adding carboxylic acid, and the content of carboxylic acid as a vanishing agent is made porous. It is possible to disperse in various forms suitable for the above. Further, since relatively large colloidal particles can be formed, it becomes easy to control the porosity and / or the specific surface area.

In the first raw material liquid, the liquid that retains or disperses zirconium hydride is, for example, water or a mixed liquid with an organic solvent that is compatible with water. Examples of the organic solvent include lower alcohols having about 1 to 4 carbon atoms such as methanol and ethanol, acetonitrile, DMSO and the like. The mixed solution preferably contains water as a main component, that is, contains more than 50% by volume of water, for example, 60% by volume or more, for example, 70% by volume or more, and for example, 80% by volume or more. Further, for example, it can be 90% by volume or more, and further, for example, 95% by volume or more.

The concentration of zirconium hydride (Zr (OH) ₄ ) contained in the first raw material liquid is not particularly limited, but can be 0.05 M or more and 5 M or less, and for example, 0.05 M or more and 2 M or less. Can be done. Further, for example, it can be 0.1 M or more and 1.5 M or less.

When the first raw material liquid is prepared from a zirconium salt, the zirconium salt is not particularly limited, and a water-soluble zirconium salt can be used. For example, zirconium chloride, zirconium chloride, zirconium nitrate, zirconium nitrate, zirconium sulfate, zirconium lactate, zirconium acetate, zirconium oxalate, zirconium phosphate, etc. Be done. Such a water-soluble zirconium salt may be a hydrate. The concentration of the zirconium salt can be a concentration at which the molar concentration of zirconium hydride described above can be obtained.

When the first raw material solution is prepared from a zirconium salt, the pH can be adjusted to about 4 or more and 11 or less by using an alkali such as ammonia. By doing so, a gel-like precipitate of zirconium hydride can be precipitated. The amount of alkali added such as ammonia is not particularly limited. For example, when ammonia is added to a zirconium salt (zirconium), the amount of ammonia can be about 2 mol or more and 8 mol or less with respect to 1 mol of zirconium. Further, for example, it may be about 3 mol or more and 6 mol or less.

At the time of preparation of the first raw material liquid, a carboxylic acid described later may be contained in advance. Since the first raw material liquid contains a carboxylic acid, the first raw material liquid contains a gel-like precipitate of zirconium hydride that easily produces a zirconium hydride colloid in the second raw material liquid prepared in the subsequent stage. be able to. From this point of view, the carboxylic acid needs to be contained in the first raw material liquid prior to the formation of the zirconium hydride gel. The carboxylic acid content in the first raw material liquid is not particularly limited, but can be, for example, 0.08 to 0.8 mol% with respect to 0.4 mol / l of zirconium hydride. This is because the dispersibility of the particles is good in this range.

(Second raw material liquid)
The second raw material solution can be prepared as a colloidal solution in which carboxylic acid is added to the first raw material solution and zirconium hydride, which is an insoluble matter, is dispersed as colloidal particles. In the second raw material liquid, the carboxylic acid is adsorbed on the zirconium hydride generated as a gel-like precipitate, and as a result, a repulsive force is generated between the particles so that the particles can be dispersed as colloidal particles. In addition, various dispersoids (colloidal particles) including zirconium-containing compounds in which the carboxylic acid partially replaces the hydroxide ion will be contained.

In addition, the carboxylic acid can be eliminated by heating to form pores in the particles. Therefore, preparing a zirconium-containing colloid using a carboxylic acid for the zirconium hydride particles produced as an insoluble matter can generate relatively large zirconium hydride colloid particles and disappears with zirconium ions. Since it can be dispersed in various forms with the agent, it is possible to prepare a raw material solution suitable for spray thermal decomposition for producing a porous zirconia particle material.

A large number of such zirconium hydride-containing colloidal particles are formed in the second raw material liquid. Therefore, the droplets formed from the second raw material liquid can contain the carboxylic acid in a high concentration and in various forms, which can contribute to the porosity and the increase in the specific surface area of the obtained zirconia particles. ..

Examples of the carboxylic acid include monocarboxylic acids such as formic acid, acetic acid, propionic acid and lactic acid, dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid and malic acid, and citric acid. Examples thereof include tricarboxylic acids such as aconitic acid, α-hydroxycarboxylic acids such as lactic acid, malic acid and citric acid. Alternatively, it may be EDTA or a salt thereof. Preferably, α-hydroxycarboxylic acid can be used. More preferably, a divalent α-hydroxydicarboxylic acid or a trivalent α-hydroxytricarboxylic acid such as citric acid can be mentioned. Further, it may be one or more selected from the group consisting of acetic acid, citric acid, oxalic acid and malic acid.

The formation of the zirconium hydride colloid can be confirmed by adding a carboxylic acid to the first raw material liquid so that the gel-like precipitate disappears and the liquid gradually becomes transparent. Although not particularly limited, it is preferable to add the carboxylic acid until the gel-like precipitate is almost eliminated and the liquid becomes almost transparent.

The amount of carboxylic acid also affects the porosity and specific surface area. According to this production method, since zirconium hydride is made into a colloid by carboxylic acid, zirconium hydride can be dispersed in the second raw material liquid together with a large amount of carboxylic acid. Therefore, the degree of freedom in designing the porosity and the specific surface area is improved.

The amount of the carboxylic acid added is not particularly limited, and depends on the type of the carboxylic acid used, the intended porosity and / or the specific surface area, but generally, with respect to the zirconium (zirconium salt) in the first raw material liquid. The molar ratio can be about 1 or more and 4 or less. Further, for example, the number may be 1 or more and 3 or less. The concentration of the carboxylic acid can be, for example, 0.1 M or more and 1 M or less, and for example, 0.1 M or more and 0.8 M or less.

As described above, the second raw material liquid thus prepared is a zirconium-containing colloid containing colloidal particles of various embodiments. Therefore, in the second raw material liquid, both zirconium and carboxylic acid are well dispersed and contained in the second raw material liquid.

The zirconium-containing colloid is considered to have colloidal particles (dispersible) having a relatively large particle size. Further, in this colloid, in addition to colloidal particles in which a carboxylic acid is adsorbed on zirconium hydroxide (Zr (OH) ₄ ), for example, Zr (OH) ₂ (R (COOH) ₄ ) _2/4 , Zr ( OH) (R (COOH) ₄ ) _3/4 , Zr (R (COOH) _4/4 ) ₄ , etc. Zr (OH) ₃ (RCOOH) ₁ to Zr (OH) ₂ (RCOOH) ₂ to Zr (RCOOH) It is considered that the dispersoid as a zirconium-containing compound in various embodiments is contained depending on the type of carboxylic acid such as ₄ .

By evaporating and thermally decomposing the second raw material liquid, which is a zirconium-containing colloid of such an embodiment, as droplets, the progress of sintering on the surface and inside of the droplet is suppressed, and voids are also formed on the surface of the droplet and inside the droplet. It is thought that it becomes easier to form.

In the production of this particle material, a powder synthesis method called a so-called spray pyrolysis method is used. That is, a solution or dispersion containing the raw material of the powder to be obtained is made into droplets by an appropriate means, and by heating the droplets, the liquid is evaporated and the raw material is at least partially thermally decomposed. It is a method of atomizing.

(Particle process)
In the particle formation step, the droplets of the second raw material liquid can be heated to form particles. In the particle formation step, the second raw material liquid is made into droplets by an appropriate droplet forming means, the droplets are heated to evaporate the liquid, and the raw materials in the second raw material are thermally decomposed to contain zirconia. Can produce particles. The particle formation step can be carried out according to the so-called spray pyrolysis method.

The droplet obtained from the second raw material liquid is a zirconium-containing colloid that is relatively large and contains colloidal particles of various embodiments. That is, the zirconium-containing colloid of the second raw material liquid has larger particles than the zirconium-carboxylic acid chelate obtained by supplying a carboxylic acid to a water-soluble zirconium salt. Therefore, it is possible to control the desired specific surface area and relative density depending on various conditions such as temperature, gas flow rate, and atomization in the particle formation step, and temperature conditions in the subsequent firing step.

The droplet forming means used in the particle forming step is not particularly limited, and a means applied to a known spray pyrolysis method can be used. Therefore, without particular limitation, a spray nozzle, ultrasonic atomizing means, electrostatic atomizing means and the like can be appropriately selected and used.

Further, in the particle formation step, a heating furnace using various heat sources can be used. The heating furnace is not particularly limited, and various heating furnaces such as an infrared heating furnace, a microwave heating furnace, and a resistance heating furnace, which are applied to a known spray pyrolysis method, can be appropriately used.

In addition to the raw material concentration in the second raw material liquid in the particle formation step, the temperature, gas type, gas flow rate, etc. can be appropriately set from the viewpoints of particle size control, composition control, particle structure control, and productivity. .. For example, the temperature may be a constant temperature, but a form in which the temperature is gradually raised from the introduction portion to the discharge portion of the heating furnace can be adopted. Typically, the temperature can be set as intended for thermal decomposition from the drying of the droplets. For drying the droplets, a temperature of about 200 ° C. to 600 ° C. can be set. Further, for example, for thermal decomposition, a temperature of about 600 ° C. to 1600 ° C. can be set.

As an example, the entire heating furnace is heated in the range of 200 ° C. to 1000 ° C., for example, 200 ° C. to 800 ° C., and these temperature ranges are set to 2 or more, more preferably 3 or more. More preferably, it is preferable to arrange and heat a heat source controlled to four or more different temperatures (for example, 200 ° C., 400 ° C., 600 ° C. and 800 ° C.).

As the gas, an oxidizing gas containing oxygen, typically air, can be used from the viewpoint of producing zirconia. The flow rate can be set according to a known spray pyrolysis method, and can be appropriately set, for example, in the range of 2 L / min to 10 L / min, or, for example, 3 L / min to 7 L / min. ..

The characteristics of the obtained particles can be appropriately controlled by the temperature conditions and gas flow conditions in the particle formation step. That is, the degree of thermal decomposition of the zirconium salt in the particles (in other words, the degree of zirconia formation), the degree of zirconia crystallinity (monoclinic, tetragonal, cubic), the degree of zirconia sintering and heat shrinkage, and the degree of carboxylic acid. The degree of disappearance (in other words, the degree of porosity of the particles) can be controlled. These particle identifications can contribute to the characteristics of the sintered body when the zirconia particle material is used as the sintered body material.

For example, the particles obtained by the particle formation step can contain at least a part of zirconia particles. In addition, at least a part of the particles are porous or hollow due to the disappearance of the carboxylic acid. Further, zirconia may be amorphous or crystalline. The particles may also contain a zirconium salt that has not been thermally decomposed, and may contain uncrystallized zirconia or a carboxylic acid that has not disappeared.

The particles obtained in the particle formation step are appropriately captured by known capture means. As such a trapping means, a trapping means generally used in the spray pyrolysis method can be appropriately adopted.

(Baking process)
For the particles obtained in the particle formation step, an additional firing step is performed to adjust the particle characteristics such as the crystallinity and crystal type of zirconia, the porosity and the specific surface area, and the shrinkage rate of the particles themselves. be able to. Such adjustment of particle characteristics can contribute to the identification of the sintered body.

The firing step may be carried out, for example, as a crystallization step in which the particles obtained in the particle formation step are heated to promote the crystallization of zirconia, or the carboxylic acid is completely eliminated to improve the porosity. And / or may be carried out as a step of increasing the specific surface area. Further, it is possible to make adjustments such as retaining a certain amount of carboxylic acid, suppressing the crystallinity of zirconia and the degree of sintering, and ensuring the shrinkage rate at the time of obtaining the sintered body.

For example, when the crystallization step is carried out, the firing temperature can be set according to the crystal form of the zirconia to be obtained. For example, when tetragonal zirconia is used as the main crystal form, the temperature can be about 400 ° C. or higher and lower than 1000 ° C. When cubic zirconia is the main crystalline form, the temperature can be 400 ° C. or higher and 1000 ° C. or lower, more preferably 600 ° C. or higher and 900 ° C. or lower. Further, the firing time can be appropriately set, but for example, it can be set to about 1 hour to 3 or 4 hours or less, typically within 2 or 3 hours.

In order to improve the porosity and increase the specific surface area, for example, it may be carried out at about 400 ° C. or higher and 800 ° C. or lower for a required time.

According to such a method for producing the particle material, a second raw material liquid which is a zirconium-containing colloid containing zirconium can be prepared in various embodiments. Particles having excellent porosity and / or specific surface area can be obtained from the droplets obtained from the second raw material liquid. Therefore, to produce a porous zirconia particle material having a porous and / or specific surface area, that is, a desired porous and / or specific surface area, such as the porous zirconia particle material disclosed in the present specification described later. Can be done.

In this production method, a particle crushing step for releasing the aggregated state of the obtained particles may be carried out at any stage after the particle formation step. Such a crushing step may be ultrasonic crushing in a liquid phase in addition to normal crushing.

(Porous zirconia particle material)
The present particle material can have a specific surface area of 20 m ² / g or more and 90 m ² / g or less and have porosity, for example. This is because according to the method for producing a zirconia particle material, the porosity and specific surface area can be adjusted by controlling the zirconium hydride concentration and the carboxylic acid concentration. Such particle materials are suitable for conventional zirconia applications. In particular, it is useful for materials that require specific surface area and porosity, such as solid electrolytes and oxygen sensors.

Further, since the present particle material is obtained by the spray pyrolysis method, it is spherical. This particle material has zirconia. Zirconia can be confirmed by the X-ray diffraction spectrum.

Further, the particle material preferably has a tap bulk density of 0.8 g / cm ³ or more and 2.5 g / cm ³ or less. More preferably, it is 0.8 g / cm ³ or more and 2.2 g / cm ³ or less, more preferably 0.9 g / cm ³ or more and 2.2 g / cm ³ or less, and still more preferably 0.9 g / cm ³ . More than 2.0 g / cm ³ or less. In the present specification, the tap bulk density can be measured by the bulk density measuring method of JIS R1628 fine ceramic powder.

The specific surface area of the particle material may be 40 m ² / g or more, 50 m ² / g or more, for example, 60 m ² / g or more, and for example, 80 m ² or more. It can be / g or more. When the non-surface area is 40 m ² / g or more, 50 m ² / g or more, 60 m ² / g or more, or 80 m ² / g or more, the surface area is sufficient for use in a catalyst carrier, a solid oxide fuel cell, or the like. It can be said that it has. The specific surface area is measured by using nitrogen as the gas and an adsorption isotherm measuring device (Bellthorpe Mini, manufactured by Nippon Bell) as the device, and measuring the measurement conditions at 5 points in the range of 0.1 to 0.5 kPa. be able to. That is, the value of the specific surface area can be obtained from the slope by linear extrapolation to these points. Other measurement conditions can be measured with the default settings of the device used.

Further, when obtaining the present sintered body, the average particle size of the present particle material itself does not significantly affect the characteristics of the sintered body and is not particularly limited, but the average particle size is 0.1 μm or more. It can be 10 μm or less. Further, the average pore diameter may be 0.5 μm or more and 2 μm or less. The average particle size can be measured by the light dispersion method. Moreover, the average pore diameter can be measured by the adsorption isotherm.

As described above, according to the present specification, there is provided a method for producing a porous zirconia particle material and a porous zirconia particle material suitable for obtaining a zirconia sintered body.

(Baking process)
The firing step can be carried out by firing the molded product obtained in the molding step at a temperature at which zirconia is sintered. For example, it can be 1300 ° C. or higher, for example, 1350 ° C. or higher, and further, for example, 1400 ° C. or higher. Generally, the temperature can be 1300 ° C. or higher and 1400 ° C. or lower.

The heating time at the above temperature is not particularly limited, but can be, for example, about 1 hour or more and 6 hours or less.

By carrying out the firing step, the finally intended porous zirconia sintered body can be obtained. That is, in the firing step, since the present particle material is porous, it is easy to control the pore size distribution in the sintered body. That is, for use by the present particle material, the sintered body can have a pore distribution having a central pore diameter in the vicinity of the pores provided in the present particle material. Further, the sintered body can obtain a porous sintered body having pores provided in the particles of the present particle material itself and pores based on the interparticle gap formed when the particles are sintered with each other. A sintered body having such a pore size distribution can have a high specific surface area and a high porosity in the entire sintered body, and a large specific surface area for reaction is required, and gas permeability and the like are also required at the same time. It is possible to obtain a sintered body suitable for the electrode or catalyst to be used.

Further, in the present particle material, the degree of thermal decomposition of zirconia, the degree of crystallinity, the degree of thermal shrinkage of particles, and the degree of residual carboxylic acid are adjusted. Therefore, sintering and heat shrinkage caused by firing of the molded product can be easily controlled. That is, since it can be made porous without the disappearance of the vanishing agent in the molded product as in the conventional case, the firing step can be carried out under the firing conditions for controlling sintering and heat shrinkage.

(Porous zirconia sintered body)
The porous zirconia sintered body disclosed in the present specification (hereinafter, also simply referred to as the present sintered body) is a porous sintered body containing zirconia as a main component. The present sintered body contains 50% by mass or more of zirconia, preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, still more preferably 90% by mass or more, and further. It preferably contains 95% by mass or more, more preferably 97% by mass or more, further preferably 98% by mass or more, and even more preferably 99% by mass or more.

In addition to zirconia, the present sintered body may contain, for example, an appropriate sintering aid, or may contain an unavoidable component.

The present sintered body can be ensured regardless of its porosity and burning of the pore-forming agent. Further, it can be controlled by the particle size distribution, the pore size distribution, etc. of the present particle material using the porosity. Therefore, the relative density (porosity) and specific surface area of the present sintered body are easily adjusted by adjusting the sintering in the manufacturing process.

(Pore diameter distribution)
The present sintered body has a peak pore diameter at 0.1 μm or more and 0.5 μm or less with respect to the pore diameter distribution, and is 0.1 μm including the peak pore diameter (hereinafter referred to as the first peak pore diameter) as a center. It is possible to have the first feature that the pore size distribution includes 70% or more of all the pores in the range of. The porous zirconia sintered body having such a pore size distribution can have a good specific surface area and porosity. Such a first feature is generally a feature in the pore diameter range of 0.05 μm or more and less than 10 μm in the entire pore diameter distribution.

The first peak pore diameter in the present sintered body may be, for example, 0.15 μm or more, for example, 0.2 μm or more, and may be, for example, 0.3 μm or more. The first peak pore diameter is, for example, 0.9 μm or less, for example, 0.8 μm or less, further, for example, 0.7 μm or less, for example, 0.6 μm or less, further, for example, 0.5 μm or less, and further. Further, for example, it is 0.4 μm or less. The first peak pore diameter is 0.1 μm or more and 0.5 μm or less.

In the pore size distribution of the present sintered body, 70 of all pores are within 0.1 μm (that is, in the range of the first peak pore size ± 0.05 μm) including the first peak pore size as the center. % Or more is preferably contained. By having such a distribution, the present sintered body can have uniform reactivity as a whole. For example, the pore diameter range may include 80% or more of all pores, for example, 85% or more, or further, for example, 90% or more. However, it may be, for example, 95% or more. On the other hand, as will be described later, it is preferable that less than 99% of the total pores are contained in the range. This is because if 99% or more of the pores are included in the range, the air permeability of the entire sintered body may be limited. For example, the upper limit may be 95% or less, for example, 90% or less, further, for example, 85% or less, and further, for example, 80% or less. It may be 75% or less, for example.

The present sintered body can have a second feature of having another pore group in a range of 10 μm or more and 1000 μm or less with respect to the pore size distribution. By providing such a pore group, a better porosity can be provided. For example, the present sintered body can have a peak of another pore diameter, that is, a second peak pore diameter, in addition to the first peak pore diameter, at 10 μm or more and 1000 μm or less. For example, the present sintered body can be provided with such a second peak pore diameter generally in the range of 50 μm or more and 1000 μm or less, for example, 50 μm or more and 800 μm or less.

The present sintered body can have pores of 10 μm or more and 1000 μm or less, which are 1% or more and less than 30% of the total pores. If it is less than 1%, the effect obtained even if the second peak pore diameter is provided is small, and if it is 30% or more, the effect due to the distribution including the first peak pore diameter tends to be reduced. be. For example, the lower limit may be 5% or more, for example, 10% or more, and further, for example, 15% or more. For example, the upper limit may be 25% or less, for example, 20% or less, and further, for example, 15% or less.

The first feature of the pore size distribution of the sintered body can be obtained by using the zirconia particles as raw material particles. Since the zirconia particles themselves are fine porous particles, they can contribute to the porosity of the sintered body.

Further, the second feature of the pore size distribution of the sintered body can also be obtained by using the zirconia particles as raw material particles. Since the zirconia particles are substantially spherical and have a highly controlled particle size distribution, when the zirconia particles are sintered, the gaps between the zirconia particles can form pores having a constant distribution. Is.

The pore size distribution of the sintered body can be measured by, for example, a mercury porosimeter. Based on the obtained pore size distribution, it is possible to obtain the first peak pore size, the pore content within the range of 0.1 μm centered on the first peak pore size, and the second peak pore size. can. In the measurement with a mercury porosimeter, for example, a mercury porosimeter manufactured by Micromeritics can be used to apply a pressure of about 0.03 atm to 4000 atm (0.5 to 60,000 psi) for measurement.

(Relative density)
The relative density of the sintered body is preferably, for example, 50% or more. Further, for example, it may be 55% or more, further, for example, 60% or more, further, for example, 65% or more, and for example, 70% or more. Further, the upper limit may be, for example, 80% or less, for example, 75% or less, and further, for example, 70% or less. By using the zirconia particle material and appropriately adjusting the sintering temperature, the sintered body having the intended relative density can be obtained. The relative density can be measured by the Archimedes method.

(Specific surface area)
The specific surface area of the sintered body may be, for example, 0.8 m ² / g or more. Further, for example, 0.9 m ² / g or more, further, for example, 1.0 m ² / g or more, further, for example, 1.1 m ² / g or more, and for example, 1.2 m ² / g or more, further, for example, 1. It is 3 m ² / g or more. The upper limit is not particularly limited, but is, for example, 2.0 m ² / g or less. The larger the specific surface area, the more reactive the material can be used. The specific surface area can be measured by the nitrogen gas adsorption method.

(Open porosity)
The ratio of open pores (open pore ratio (%)) to the total volume of the sintered body can be, for example, 15% or more. Further, for example, it is 20% or more, further, for example, 25% or more, and further, for example, 30% or more. The open porosity can be measured, for example, by the Archimedes method.

(Sintered laminate of dense zirconia layer and porous zirconia layer)
As the laminated body disclosed in the present specification, a laminated sintered body of a first layer made of the present sintered body and a second layer which is a dense zirconia layer is provided. Here, the dense zirconia means that the relative density is 90% or more. The present laminated body may be a sintered body obtained by batch firing a first material layer for obtaining a first layer and a second material layer for obtaining a second layer.

The first layer can contain the present particle material, and the present particle material controls the particle size distribution, the pore size distribution, the specific surface area, etc. by controlling the particle size distribution and the firing process as described above. be able to. These properties are also related to heat shrinkage during sintering. By using the particle material as the raw material particles for the first layer of the laminate, it can be adapted to the thermal shrinkage that can occur in the sintering of the dense zirconia layer, resulting in good integrity and the intended shape. It is possible to obtain a sintered body by batch firing.

As a method for producing the present laminate, for example, a laminate precursor of a first material layer containing the present particle material and a second material layer is obtained by a known method, and then the precursor is integrated by firing. And can be obtained by sintering. As for the temperature for sintering and the like, the temperature for sintering zirconia already described can be appropriately adopted. In addition, the present laminate can be carried out following the method for producing the present particle material. That is, among the steps constituting the method for producing the present particle material, at least the raw material liquid preparation step and the particle formation step may be carried out to obtain the laminate precursor, and then sintered.

The following examples embody and explain the disclosure of the present specification, but do not limit the disclosure of the present specification.

(Synthesis of porous yttria-stabilized zirconia particle material by spray pyrolysis method)
Porous zirconia particle material was synthesized according to the scheme shown in FIG.

(1) Preparation of raw material solution (Example sample)
As raw materials, the concentrations shown in Table 1 below are combined so that zirconia (8YSZ) containing 8 mol% of itria is used for zirconium nitrate hexahydrate (ZrO (NO ₃ ) 2.9H ₂ O) and _ittrium nitrate. Then, a part of the citric acid in the amount shown in Table 1 was added, aqueous ammonia was added, and the rest of the citric acid was added to form a transparent colloid. A zirconium hydroxide solution was used (Table 1).

(2) Spray pyrolysis For the 11 types of prepared example samples, the entire length is provided with heat sources of 200 ° C, 400 ° C, 600 ° C and 800 ° C in order from the inlet using a spray pyrolysis device equipped with an ultrasonic atomizer. Air was supplied as a carrier gas at 5 L / min to a 120 cm heating furnace, and particle synthesis was performed by spray pyrolysis.

After collecting each material (zirconia precursor) in the collecting part of the spray pyrolysis apparatus, it was further calcined in air at 800 ° C. for 2 hours to obtain a white powder.

In this example, the tap bulk density of the porous zirconia particle material synthesized in Example 1 was measured and calculated by JIS R1628. The results are shown in the table below.

(Manufacturing of a porous yttria-stabilized zirconia sintered body using 11 kinds of porous yttria-stabilized zirconia particle materials produced in Example 1)
Using the porous yttria-stabilized zirconia particle material prepared in Example 1, PVA was mixed as a binder so as to be 2% by mass, and molded into a disk (diameter 10 mm × thickness 1 mm) by a uniaxial press (49 MPa). .. Further, it was molded by CIP (245 MPa). This disc was fired at 1300 ° C., 1350 ° C. and 1400 ° C. for 2 hours to obtain a sintered body.

The relative densities of these are measured by the dimensions and the Archimedes method, and the results are shown in FIG.

As shown in FIG. 2, it was found that the relative density can be adjusted from 55% to 83% depending on the type of the porous yttria-stabilized zirconia particle material used and the firing temperature of the sintered body.

The pore size distribution of the four types of porous yttria-stabilized zirconia sintered bodies (firing temperature: 1350 ° C.) produced in Example 3 was evaluated by a mercury porosimeter. The results are shown in FIG. As shown in FIG. 3, the peaks of the pore diameters exist in the range of 0.1 μm to 0.5 μm, and in each pore diameter distribution, 80 of all pores are within the range of 0.1 μm of the peak. % Was present. It was also found that another peak existed in the vicinity of 100 μm.

The relative density (and porosity) of one type of porous yttria-stabilized zirconia sintered body (firing temperature: 1350 ° C.) produced in Example 3 was evaluated by the Archimedes method, and the specific surface area was determined by the nitrogen gas adsorption method. evaluated. These results are shown in FIG. As shown in FIG. 4, the relative density was 66%, showing good porosity, and the specific surface area was 1.3 m ² / g, which was extremely large for a sintered body.

One type of porous yttria-stabilized zirconia particle material (YSZ15) produced in Example 1, which was subjected to each firing step of 800 ° C. for 2 hours and 500 ° C. for 6 hours after the particle formation step. The chemical zirconia particle materials (YSZ15, YSZ19) are supplied in layers on a molded body of commercially available zirconia powder (8YSZ, for dense zirconia) by the same operation as in Example 3, formed into a disk, and fired. (However, the firing temperature was 1350 ° C.). I compared this disc. The results are shown in FIG.

As shown in FIG. 5, when the porous zirconia particle material (YSZ15) subjected to the firing step at 800 ° C. is used, the shrinkage on the dense zirconia layer side is large, so that the laminated disk warps (the dense side shrinks). , A form in which the porous side is elongated) has occurred. On the other hand, when the porous zirconia particle material (YSZ19) subjected to the firing step at 500 ° C. is used, the porous zirconia layer can also follow the shrinkage on the dense zirconia layer side, and there is no warp. I was able to get a flat disc. It is considered that this is because the shrinkage rate could be controlled by lowering the firing temperature. As described above, it was found that according to the present particle material, the porosity and shrinkage rate of the sintered body can be easily controlled.

Claims (12)

A method for producing a porous zirconia sintered body.
One or more carboxylic acids selected from the group consisting of acetic acid, citric acid, oxalic acid and malic acid are added to the first raw material solution containing gel-like zirconium hydride, and the zirconium-containing colloid is added. The raw material liquid preparation process for preparing the second raw material liquid, which is
A particle formation step of heating droplets of the second raw material liquid to thermally decompose at least a part of the zirconium hydride to obtain porous zirconia particles.
A molding step of obtaining a molded product containing a zirconia material using the porous zirconia particles, and
A sintering step of firing the molded body to sinter the porous zirconia particles to obtain a porous zirconia sintered body.
How to prepare. The porous zirconia sintered body has a peak pore diameter of 0.1 μm or more and 0.5 μm or less in the volume-based pore diameter distribution , and is completely fine in the range of 0.1 μm including the peak pore diameter as the center . The method of claim 1, wherein the sintered body comprises 80% or more of the pores. The method according to claim 1 or 2, wherein the relative density of the sintered body is 50% or more. The method according to any one of claims 1 to 3, wherein the specific surface area of the sintered body is 0.8 m ² / g or more. The method according to any one of claims 1 to 4, wherein the carboxylic acid is citric acid. The method according to any one of claims 1 to 5, wherein the second raw material liquid is transparent. Prior to the molding step, the porous zirconia particles obtained in the particle formation step are heated and selected from the group consisting of the degree of disappearance of the carboxylic acid with respect to the particles, the specific surface area, the shrinkage rate and the crystallinity of zirconia. The method according to any one of claims 1 to 6, comprising a firing step for adjusting the characteristics of one or more of the particles. A method for manufacturing a material for obtaining a porous zirconia sintered body.
One or more carboxylic acids selected from the group consisting of acetic acid, citric acid, oxalic acid and malic acid are added to the first raw material solution containing gel-like zirconium hydride, and the zirconium-containing colloid is added. The raw material liquid preparation process for preparing the second raw material liquid, which is
A particle formation step of heating droplets of the second raw material liquid to thermally decompose at least a part of the zirconium hydride to obtain porous zirconia particles.
The porous zirconia particles obtained in the particle formation step are further heated and selected from the group consisting of the degree of disappearance of the carboxylic acid with respect to the porous zirconia particles, the specific surface area, the shrinkage rate and the crystallinity of zirconia 1. A firing step that adjusts the properties of a seed or two or more species,
How to prepare. Porous zirconia sintered body
The peak pore diameter in the volume-based pore size distribution is 0.1 μm or more and 0.5 μm or less, and 80% or more of the total pores are included in the range of 0.1 μm including the peak pore diameter as the center . A sintered body having an open porosity of 15% or more. The sintered body according to claim 9 , wherein the relative density is 50% or more. The sintered body according to claim 9 or 10 , wherein the specific surface area is 0.8 m ² / g or more. A method for producing a laminate of a porous zirconia layer and a dense zirconia layer.
A process of firing and integrating a laminate of a porous zirconia material layer containing porous zirconia particles and a dense zirconia material layer.
Equipped with
The porous zirconia particles are subjected to the following steps;
One or more carboxylic acids selected from the group consisting of acetic acid, citric acid, oxalic acid and malic acid are added to the first raw material solution containing gel-like zirconium hydride, and the zirconium-containing colloid is added. The raw material liquid preparation process for preparing the second raw material liquid, which is
A particle formation step of heating droplets of the second raw material liquid to thermally decompose at least a part of the zirconium hydride to obtain the porous zirconia particles.
The porous zirconia particles obtained in the particle formation step are heated and selected from the group consisting of the degree of disappearance of the carboxylic acid with respect to the porous zirconia particles, the specific surface area, the shrinkage rate and the crystallinity of zirconia 1. A firing step that adjusts the properties of a seed or two or more species,
How to prepare.

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