Metal ink and method for producing porous ceramic composite material using the same

Abstract

To provide a metal ink excellent in impregnation property into a porous ceramic having a small pore diameter.SOLUTION: A metal ink comprises metal particles, a binder, a dispersant, and a liquid medium. By measuring a dynamic contact angle X of a droplet formed by dropping the metal ink onto a glass plate using a contact angle meter, data composed of a plurality of pairs of a time t (ms) after dropping the metal ink and a dynamic contact angle X (deg) are obtained. When fitting the data to the formula X=αt-β to determine fitting parameters α and β, α is 50 or more and β is 0.10 or more. A dynamic contact angle E of the droplet when the droplet is left to stand until the dynamic contact angle X no longer changes is 18 deg or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a metal ink and a method for producing a porous ceramic composite material using the same. [Background technology]

[0002] The widespread use of clean energy throughout society is recognized as a key challenge for building a sustainable world, and fuel cells offer a concrete solution. Solid oxide fuel cells (SOFCs), made of ceramic materials, can operate at high temperatures and have the highest power generation efficiency of any fuel cell. The solid electrolyte, a key component of SOFCs, is made of a material that selectively allows ions to pass through, and oxide-ion conductors have traditionally been used. In recent years, it has been reported that the use of proton conductors instead of oxide-ion conductors can theoretically dramatically improve the power generation efficiency of SOFCs. This has raised expectations for the realization of proton-conducting ceramic fuel cells (PCFCs), which use proton-conducting ceramics in the electrolyte layer.

[0003] As anode materials for PCFCs, the use of cermets, for example, consisting of proton-conducting ceramic materials and metal catalysts, has been proposed. NiO is often used as the metal catalyst. However, the manufacturing process for such cermets requires firing the ceramic material and metal catalyst at high temperatures of approximately 1400°C, which can produce by-products that can increase electrical resistance. Ni nanoparticles can also be used as the metal catalyst, but this method has problems such as aggregation of the Ni nanoparticles during firing and difficulty in sintering due to differences in the thermal expansion coefficient between the Ni nanoparticles and the ceramic material. Regardless of the metal catalyst used, firing the metal catalyst at high temperatures can reduce the three-phase interface in the resulting anode, resulting in a decrease in the reaction activity of the anode. Therefore, it has been studied to solve the above-mentioned problems by first firing the porous ceramic material and then supporting the metal catalyst, thereby avoiding heating the metal catalyst to a temperature above the operating temperature of the fuel cell. In this regard, for example, Patent Documents 1 and 2 propose supporting a metal catalyst by bringing a slurry containing the metal catalyst into contact with a pre-fired porous ceramic, and using the resulting material as an anode for an SOFC. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-230874 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-053146 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the slurries containing metal catalysts used in Patent Documents 1 and 2 do not have sufficient impregnation properties for porous ceramics with small pore sizes, making it difficult to successfully support the metal catalysts in some cases.

[0006] Therefore, an object of the present invention is to provide a metal ink that has excellent impregnation properties into porous ceramics having small pore diameters. [Means for solving the problem]

[0007] A metallic ink comprising metal particles, a binder, a dispersant, and an organic solvent, measuring the dynamic contact angle X of a droplet formed by dropping the metal ink onto a glass plate using a contact angle meter to obtain data consisting of multiple pairs of time t (ms) after dropping the metal ink and dynamic contact angle X (deg); Formula X=αt -βis fitted to the data to determine the fitting parameters α and β. α is 50 or more, β is 0.10 or more, The present invention provides a metal ink in which, when the droplet is allowed to stand until the dynamic contact angle X of the droplet no longer changes, the dynamic contact angle E is 18 degrees or less.

[0008] The present invention also provides a method for manufacturing a ceramic ceramic material by disposing metal particles in pores of the porous ceramic material, A method for producing a porous ceramic composite material, comprising firing the ceramic material in which the metal particles are disposed to produce a sintered body of the metal particles in the pores of the ceramic material, The present invention provides a method for producing a porous ceramic composite material, in which the metal particles are disposed in the pores by impregnating the pores of the porous ceramic material with the metal ink. [Effects of the Invention]

[0009] According to the present invention, a metal ink is provided that has excellent impregnation ability into porous ceramics having small pore diameters. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a method for obtaining a porous ceramic composite material by impregnating the pores of a porous ceramic material with the metallic ink of the present invention. [Figure 2] FIG. 2 is an optical microscope image of a cross section obtained by cutting the porous ceramic composite material of Example 1 along the thickness direction. [Figure 3] FIG. 3 is an optical microscope image of a cross section obtained by cutting the porous ceramic composite material of Comparative Example 2 along the thickness direction. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described below based on preferred embodiments. The metallic ink of the present invention is a metallic ink in which metal particles are dispersed in an organic solvent. The metallic ink of the present invention is used, for example, by impregnating a porous ceramic material with the ink and then firing the material to obtain a porous ceramic composite material in which a sintered body of metal particles is disposed in the pores of the ceramic material. However, the use of the metallic ink of the present invention is not limited to this.

[0012] The metallic ink of the present invention can be characterized by the dynamic contact angle X of a droplet formed by dropping the metallic ink onto a glass plate. That is, when the droplet formed by dropping the metallic ink is allowed to stand until the dynamic contact angle X of the droplet with the glass plate stops changing, the dynamic contact angle E is 18 degrees or less. An E of 18 degrees or less indicates that the viscosity of the metal ink is sufficiently low and that the metal ink has high impregnation ability into porous ceramics with small pore diameters. From this perspective, E is preferably 15 degrees or less, and more preferably 10 degrees or less.

[0013] In this specification, the dynamic contact angle X of the metal ink is measured using a contact angle meter DropMaseter 500 and a dispenser Auto Dispenser AD-31 manufactured by Kyowa Interface Science Co., Ltd. Details of the measurement conditions will be explained in the Examples below. As the glass plate onto which the metal ink is dropped, a slide glass S7213 manufactured by Matsunami Glass Industrial Co., Ltd. can be used.

[0014] In this specification, the phrase "until the dynamic contact angle X stops changing" is defined as follows for convenience: t is the time from when the metal ink is dropped (i.e., the time from when the metal ink droplet comes into contact with the glass plate), X1 is the dynamic contact angle X at t=t1 (t1 is 300 ms or more), X2 is the dynamic contact angle X at t=t1-Δt (Δt represents the measurement interval and satisfies Δt>0), and X3 is the dynamic contact angle X at t=t1+Δt, where f(t1)={(X3-X1)-(X1-X2)} / (Δt). 2In this case, f(t1) is 1.0×10 -7 deg / (ms) 2 Below (0.1deg / s 2 If (below) the dynamic contact angle X is considered to have stopped changing at the time t=t1. The measurement interval Δt in measuring the dynamic contact angle X is not particularly limited, but can be set to, for example, 300 ms. Here, f(t1) is a value corresponding to the second derivative at t=t1 of the curve obtained by plotting the dynamic contact angle X against time t.

[0015] In order to prevent the viscosity of the metal ink from becoming excessively low, the dynamic contact angle E is preferably 0.5 degrees or more, more preferably 1 degree or more, and even more preferably 2 degrees or more.

[0016] Furthermore, when an approximation curve of the measurement data of the dynamic contact angle of the metallic ink of the present invention is obtained by nonlinear regression analysis, the fitting parameters of the approximation curve fall within a predetermined range. Specifically, the dynamic contact angle X is measured using a contact angle meter to obtain data consisting of multiple pairs of the time t (ms) after dropping the metallic ink and the dynamic contact angle X (deg), and the equation X = αt -β is fitted to the data to determine fitting parameters α and β. In this case, α is preferably 50 or more, more preferably 150 or more, and even more preferably 200 or more. Furthermore, β is preferably 0.10 or more, more preferably 0.20 or more, and even more preferably 0.30 or more. By setting α and β within the above-mentioned ranges, the impregnation of the porous ceramic material with the metal ink can be improved.

[0017] From the same viewpoint, α is preferably equal to or less than 500, more preferably equal to or less than 400, and even more preferably equal to or less than 300. In addition, β is preferably equal to or less than 1.0, more preferably equal to or less than 0.80, and even more preferably equal to or less than 0.70.

[0018] The fitting can be performed based on the nonlinear least squares method using, for example, the multi-function integrated analysis software FAMAS manufactured by Kyowa Interface Science Co., Ltd. Specifically, the dynamic contact angle X of the metal ink is measured 10 times (n=10), and the arithmetic mean of the 10 measured values ​​of the dynamic contact angle X at each time t is calculated to obtain the average value of the change in the dynamic contact angle X over time. Then, the formula X=αt -β is fitted to the average value of the time-dependent change in the dynamic contact angle X using the nonlinear least squares method and the Levenberg-Marquardt method. Measured values ​​that are greater than 1.65 standard deviations from the fitted value (outside the 90% confidence interval) are excluded as outliers, and the fitting process is repeated. Once the exclusion of outliers is complete, the fitting is deemed to have converged, and the values ​​of α and β obtained at convergence are calculated.

[0019] As mentioned above, it is preferable that the metallic ink of the present invention has a predetermined viscosity in order to enhance impregnation into porous ceramic materials. Specifically, the viscosity of the metallic ink is preferably 35 mPa s or less, more preferably 25 mPa s or less, and even more preferably 10 mPa s or less. The viscosity of the metal ink is preferably 3 mPa·s or more, more preferably 6 mPa·s or more, and even more preferably 8 mPa·s or more. In this specification, the viscosity of the metal ink is the viscosity measured at 40°C using a Brookfield viscometer.

[0020] In order to adjust the viscosity of the metallic ink within the above-mentioned range, the metallic ink preferably contains a binder. This binder is preferably easily removable by heating. By using a binder with such properties, the binder can be removed by impregnating the metallic ink of the present invention into a porous ceramic material and then firing the material. Therefore, it is possible to suppress an increase in resistance and a decrease in catalytic activity due to the binder remaining in the pores of the porous ceramic material. From this viewpoint, it is preferable that the binder completes its thermal decomposition in air at a temperature of 700°C or less (hereinafter, the temperature at which thermal decomposition completes is also referred to as the "thermal decomposition completion temperature") and disappears after decomposition (leaving no residue such as charcoal), more preferably the thermal decomposition completion temperature in air is 400°C or less, and even more preferably the thermal decomposition completion temperature in air is 300°C or less. The thermal decomposition yield temperature of the binder in air can be the temperature at which 95% of the weight loss occurs during the weight loss process when analyzed using a thermogravimetric analyzer at a temperature increase rate of 10°C / min.

[0021] Examples of binders include (meth)acrylic resins, ethyl cellulose, polyvinyl butyral, etc. Among them, it is preferable to use (meth)acrylic resins, and it is more preferable to use methacrylic resins, because they have an appropriate viscosity. More specifically, Techpolymer IBM-2 (manufactured by Sekisui Plastics Co., Ltd.) and Oricox KC-1300 (manufactured by Kyoeisha Chemical Co., Ltd.) can be suitably used as the binder.

[0022] The metallic ink of the present invention preferably contains 0.1% by mass or more of the binder, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, and preferably 25% by mass or less of the binder, more preferably 10% by mass or less, and even more preferably 3% by mass or less. By setting the binder content in the metallic ink within the above range, it is possible to easily control the viscosity of the metallic ink to an appropriate value. Furthermore, it is possible to effectively suppress the increase in resistance and the decrease in catalytic activity caused by excessive binder remaining in the pores of the porous ceramic material. Furthermore, it is possible to suppress adverse effects on electrochemical performance.

[0023] From a similar perspective, when the content of metal particles in the metallic ink is taken as 100 parts by mass, the content of binder in the metallic ink is preferably 0.010 parts by mass or more, more preferably 0.10 parts by mass or more, even more preferably 1.0 part by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 10 parts by mass or less.

[0024] The metal particles contained in the metal ink include one or more types selected from various metal simple substances, alloys, and metal compounds, and can be appropriately selected from these depending on the application of the metal ink. For example, when a metal ink is used for the purpose of manufacturing a PCFC anode by impregnating the pores of a porous ceramic material, the metal particles preferably contain one or more elements selected from the group consisting of Ni (nickel), Pt (platinum), Ir, Fe, and Co, and more preferably contain Ni, in order to impart catalytic activity to the porous ceramic material.

[0025] There are no particular limitations on the shape of the metal particles, and examples thereof include spherical, polyhedral, flat, irregular, and combinations thereof. Volume cumulative particle size D at 50% cumulative volume by laser diffraction scattering particle size distribution measurement of metal particles 50 (Hereinafter, simply referred to as "particle size D 50 " is also referred to as ". The particle diameter D of the metal particles is preferably 1 nm or more, more preferably 3 nm or more, and even more preferably 5 nm or more. 50 is preferably 1000 nm or less, more preferably 500 nm or less, and even more preferably 300 nm or less. Metal particle diameter D 50 By setting the thickness to 1 nm or more, it is possible to obtain the effect of suppressing aggregation of metal particles. In addition, the particle size D of the metal particles 50 By setting the particle size to 1000 nm or less, the effect of making it easier for the metal particles to fill the pores of the porous ceramic material can be obtained.

[0026] Metal particles can be prepared by conventional methods. For example, a solid or liquid compound consisting of a metal oxide, metal hydroxide, or metal salt can be suspended in a polyol and heated to a temperature of at least 85°C to reduce the compound to the corresponding metal particles. The polyol can be a liquid aliphatic glycol or a polyether of such a glycol. A method for preparing such metal particles is described, for example, in Japanese Patent Publication No. 4-24402. The metal particles obtained in this manner have a relatively smooth particle surface, which has the advantage of allowing them to be easily impregnated into porous ceramic materials.

[0027] The metallic ink preferably contains 5% by mass or more of metal particles, more preferably 10% by mass or more, and even more preferably 15% by mass or more, and preferably 40% by mass or less of metal particles, more preferably 30% by mass or less, and even more preferably 25% by mass or less. When the metal ink contains metal particles in an amount of 15 mass % or more, the catalytic activity of the porous ceramic material can be sufficiently increased. Furthermore, by including 25 mass % or less of metal particles in the metal ink, the impregnation of the porous ceramic material with the metal ink can be further improved.

[0028] Various organic solvents can be used as the organic solvent contained in the metal ink. From the viewpoint of improving the impregnation into the porous ceramic material, it is preferable that the metal ink does not contain water.

[0029] The metal ink preferably contains a first organic solvent and a second organic solvent as the organic solvent. The first organic solvent is a high-boiling organic solvent used to improve the storage stability of the metal paste described below. From this perspective, the boiling point of the first organic solvent is preferably 50°C or higher, more preferably 100°C or higher, and even more preferably 150°C or higher. The boiling point of the first organic solvent is preferably 700°C or lower, more preferably 500°C or lower, and even more preferably 400°C or lower. As the first organic solvent, terpineol, butyl carbitol, or the like can be used.

[0030] The second organic solvent is used to adjust the viscosity of the metal ink, and by including the second organic solvent in the metal ink, the impregnation of the metal particles can be improved. The second organic solvent may be ethanol, isopropyl alcohol, hexane, octane, or the like.

[0031] From the viewpoint of dispersibility of metal particles and impregnation into porous ceramic materials, the mass ratio of the second organic solvent to the first organic solvent in the metal ink (second organic solvent / first organic solvent) is preferably 0.01 or more and 50 or less, more preferably 0.1 or more and 10 or less, and even more preferably 0.3 or more and 5 or less.

[0032] In order to make the advantages of the first organic solvent more pronounced, the metal ink preferably contains 0.1% by mass or more of the first organic solvent, more preferably 0.2% by mass or more, and even more preferably 0.5% by mass or more. From the viewpoint of storage stability, the metal ink preferably contains 50% by mass or less of the first organic solvent, more preferably 40% by mass or less, and even more preferably 25% by mass or less.

[0033] In order to make the advantages of the second organic solvent more pronounced, the metal ink preferably contains 20% by mass or more of the second organic solvent, more preferably 30% by mass or more, and even more preferably 40% by mass or more. The metal ink preferably contains 90% by mass or less of the second organic solvent, more preferably 85% by mass or less, and even more preferably 80% by mass or less.

[0034] The metallic ink of the present invention preferably contains a dispersant, which makes it easier to obtain a metallic ink in which the metal particles are more uniformly dispersed in the organic solvent, improving handling properties and impregnation properties into porous ceramic materials.

[0035] The dispersant may be, for example, a compound having a solvent-affinity unit and a powder-affinity unit bonded to the solvent-affinity unit. By using such a compound, the powder-affinity unit bonds to the metal particles, while the solvent-affinity unit enhances the dispersibility of the metal particles, thereby more effectively enhancing the dispersibility of the metal particles. The solvent-affinity unit has a structure that enhances the affinity with the solvent. In order to enhance the affinity with the solvent, the solvent-affinity unit is preferably hydrophobic. Examples of the solvent-affinity unit include polyalkylene glycol structures such as polyethylene glycol structures, polypropylene glycol structures, and polybutylene glycol structures, as well as polyurethane structures, polyester structures, unsaturated polyamide structures, phosphate ester structures, polycarboxylic acid ester structures, hydroxyl group-containing polycarboxylic acid ester structures, polysiloxane structures, and alkyl groups. The powder affinity unit has a structure that enhances affinity with metal particles. To enhance affinity with metal particles, the powder affinity unit preferably has a polar group. The polar group preferably has one or more selected from the group consisting of a carboxy group, an amino group, a sulfo group, a carbonyl group, and a hydroxyl group. The polar group may be ionized. For example, the polar group may be a carboxylate formed by ionizing a carboxy group.

[0036] Furthermore, a polymer compound having a comb structure or a block polymer structure can also be used as the dispersant. A comb structure refers to a structure including a main chain and molecular chains arranged in a comb shape relative to the main chain. An example of a comb structure is a structure including a main chain including powder-affinity units and solvent-affinity units arranged in a comb shape relative to the main chain. An example of a dispersant having a block polymer structure is a structure in which a structure containing a powder-affinity unit and a structure containing a solvent-affinity unit are arranged in separate blocks.

[0037] To improve the handling properties of the metal ink and its ability to impregnate porous ceramic materials, the metal ink preferably contains 0.1% by mass or more of dispersant, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more. The metal ink also preferably contains 5% by mass or less of dispersant, more preferably 4% by mass or less, even more preferably 3% by mass or less, and particularly preferably 2% by mass or less.

[0038] From a similar perspective, when the content of metal particles in the metallic ink is taken as 100 parts by mass, the content of dispersant in the metallic ink is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less.

[0039] The metallic ink of the present invention contains the above-mentioned dispersant, which results in high dispersion stability of the metal particles contained in the metallic ink. Specifically, the sedimentation velocity of the metal particles in the metallic ink is preferably 5 mm / min or less, more preferably 1 mm / min or less, and even more preferably 0.1 mm / min or less. The lower the sedimentation velocity, the better. The sedimentation rate is a value measured at 25°C. More specifically, the sedimentation rate of metal particles can be evaluated by adding metal ink to a test tube, shaking the test tube, and then leaving the test tube to stand.

[0040] The metallic ink of the present invention may contain other components in addition to the metal particles, solvent, binder, and dispersant described above, as long as the effects of the present invention are not impaired. The content of other components can be, for example, 5% by mass or less, and may be 10% by mass or less.

[0041] The metallic ink of the present invention can be preferably prepared by the following method. First, metal particles and a dispersant are mixed to obtain a metal particle dispersion. Separately, a binder and a first organic solvent are mixed to obtain a binder solution. Finally, the metal particle dispersion and the binder solution are mixed to obtain a metal paste. The metal paste obtained in this manner corresponds to the metallic ink of the present invention from which the second organic solvent has been removed, and can be stored in this state for long periods of time. The metal ink is prepared by adding a second organic solvent to the metal slurry and thoroughly mixing. Because the volatility of the second organic solvent may make the metal ink unsuitable for long-term storage, it is preferable to prepare the metal ink immediately before use.

[0042] The metallic ink prepared in this manner can be used to impregnate the pores of porous ceramic materials, and can also be used to form circuits by printing, for example.

[0043] Next, a method for obtaining a porous ceramic composite material by impregnating a porous ceramic material with a metal ink will be described with reference to Fig. 1. The porous ceramic material 1 shown in Fig. 1 comprises a porous layer 2 having a large number of pores 4 and a dense layer 3 without such pores 4. When the porous ceramic material 1 has the dense layer 3, the resistance can be reduced if the porous ceramic material 1 is proton conductive. There are no particular limitations on the impregnation method, but for example, the metal ink can be impregnated into the pores 4 by bringing the metal ink into contact with the upper surface (the surface on the porous layer 2 side) of the porous ceramic material 1. In this way, metal particles can be arranged in the pores 4. In order to bring the upper surface of the porous ceramic material 1 into contact with the metal ink, for example, the metal ink may be dropped or applied to the upper surface. After the metal ink is dropped or applied to the upper surface of the porous ceramic material 1, it may be dried under vacuum and / or by heating, as necessary. Alternatively, the dropping or application of the metal ink and the vacuum drying and / or the heat drying may be alternately repeated to more reliably impregnate the porous ceramic material 1 with the metal ink.

[0044] Next, the porous ceramic material 1 having the metal particles disposed therein is fired to form a sintered body 5 of the metal particles in the pores 4, thereby obtaining a porous ceramic composite material 10. By sintering the metal particles, the electrical conductivity of the porous ceramic composite material 10 can be increased. From the viewpoint of sufficiently sintering the metal particles, the firing temperature is preferably 400°C or higher, more preferably 500°C or higher, and even more preferably 600°C or higher. Furthermore, the firing temperature is preferably 1000°C or lower, more preferably 900°C or lower, and even more preferably 800°C or lower. From the same viewpoint, the baking time is preferably 15 minutes or more and 120 minutes or less, more preferably 30 minutes or more and 90 minutes or less, and even more preferably 45 minutes or more and 75 minutes or less. Although there are no particular limitations on the firing atmosphere, firing is preferably carried out in an inert atmosphere or a reducing atmosphere. Specific examples include a nitrogen atmosphere, an argon atmosphere, a hydrogen-nitrogen atmosphere, etc. Firing may also be carried out in an air atmosphere.

[0045] In the porous ceramic composite material 10, it is preferable from the viewpoint of enhancing catalytic activity that sintered bodies 5 of metal particles are present in the pores 4 located near the dense layer 3. Because the metallic ink of the present invention has high impregnation properties, even when the metallic ink is impregnated by contacting the surface on the porous layer 2 side with the metallic ink, the metallic ink easily reaches the pores 4 located near the dense layer 3.

[0046] The porous ceramic material to be impregnated with the metal ink can be selected depending on the application. For example, when the porous ceramic material is used as the anode of a PCFC, it is preferable that the porous ceramic material has proton conductivity. Examples of such porous ceramic materials include yttrium-doped barium zirconate (hereinafter also referred to as "BZY") and yttrium-doped barium cerate (hereinafter also referred to as "BCY").

[0047] The average pore diameter d of the porous ceramic material (when the porous ceramic material has a porous layer and a dense layer, such as the porous ceramic material 1 shown in FIG. 1, the average pore diameter of the porous layer) is preferably within a predetermined numerical range. Specifically, the average pore diameter d is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. When the average pore diameter d is equal to or greater than the lower limit, the impregnation of the metal ink is further improved. The average pore diameter d of the porous ceramic material is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less. When the average pore diameter d is equal to or less than the upper limit, the performance of a fuel cell produced using the porous ceramic material is further improved. The average pore diameter d of the porous ceramic material can be measured by mercury intrusion porosimetry.

[0048] The porous ceramic material 1 having a porous layer 2 and a dense layer 3 shown in FIG. 1 can be suitably produced, for example, by the following method. First, the raw powder of the porous ceramic material 1 (e.g., BZY) is mixed with a pore-forming agent and an organic solvent. If necessary, additional components may be added. Examples of such components include a binder such as polyvinyl butyral. The organic solvent is then removed to obtain a powder, which is then molded in a CIP molding machine to obtain pellets. These pellets correspond to the porous layer 2. Separately from the pellets, the raw material powder is mixed with an organic solvent and a surfactant to prepare a slurry for the dense layer. Examples of surfactants that can be used include polyoxyethylene lauryl ether sodium acetate. Other components, such as a binder such as polyvinyl butyral, may also be added. Once the dense layer slurry is prepared, it is applied to one side of the pellet. The application of the dense layer slurry can be carried out, for example, using an applicator. The pellet to which the dense layer slurry has been applied is heated at 1500°C to obtain a porous ceramic material 1 having a porous layer 2 and a dense layer 3.

[0049] The porous ceramic composite material 10 manufactured by the above-described method is used as an electrode and an electrolyte layer in a battery (e.g., PCFC and SOFC) that has a cathode, an anode, and an electrolyte layer disposed therebetween. Specifically, the porous layer 2 of the porous ceramic composite material 10 is suitably used as an electrode, particularly an anode, and the dense layer 3 is used as the electrolyte layer.

[0050] Although the present invention has been described above based on the preferred embodiments, the present invention is not limited to these embodiments. For example, in FIG. 1, the outer walls of the pores 4 are entirely covered with the sintered body 5 of metal particles, but only a portion of the outer walls of the pores 4 may be covered with the sintered body 5 of metal particles. In addition, although the porous ceramic material 1 has a dense layer 3 in FIG. 1, a porous ceramic material without a dense layer 3 may be used instead.

[0051] The above-described embodiments of the present invention encompass the following technical ideas. [1] A metal ink containing metal particles, a binder, a dispersant, and an organic solvent, measuring the dynamic contact angle X of a droplet formed by dropping the metal ink onto a glass plate using a contact angle meter to obtain data consisting of multiple pairs of time t (ms) after dropping the metal ink and dynamic contact angle X (deg); death, Formula X=αt -β is fitted to the data to determine the fitting parameters α and β. α is 50 or more, β is 0.10 or more, A metallic ink, wherein when the droplet is left to stand until the dynamic contact angle X of the droplet stops changing, the dynamic contact angle E is 18 degrees or less. [2] The metal particles are contained in an amount of 5% by mass or more and 40% by mass or less, The binder is contained in an amount of 0.1% by mass or more and 25% by mass or less, The metallic ink according to [1], containing 0.1% by mass or more and 5% by mass or less of the dispersant. [3] The metallic ink according to [1] or [2], wherein the binder completes its thermal decomposition in air at a temperature of 700°C or less. [4] The metallic ink according to [3], wherein the binder is a (meth)acrylic resin. [5] The metal ink according to any one of [1] to [4], wherein the dispersant is a polymer compound having a comb structure or a block polymer structure, or a compound having a solvent affinity unit and a powder surface affinity unit bonded to the solvent affinity unit.

[0052] [6] The metallic ink according to any one of [1] to [5], which is used for impregnating the pores of a porous ceramic material. [7] Metal particles are placed in the pores of porous ceramic materials. A method for producing a porous ceramic composite material, comprising firing the ceramic material in which the metal particles are disposed to produce a sintered body of the metal particles in the pores of the ceramic material, A method for producing a porous ceramic composite material, comprising impregnating the pores of the porous ceramic material with the metal ink described in any one of [1] to [6], thereby arranging the metal particles in the pores. [8] The manufacturing method according to [7], wherein the average pore diameter d of the pores in the porous ceramic material measured by mercury intrusion porosimetry is 1 μm or more and 200 μm or less. [9] The porous ceramic material has proton conductivity, The method according to any one of [7] and [8], wherein the metal particles contain nickel. [Example]

[0053] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, "%" means "% by mass."

[0054] [Examples 1 to 12 and Comparative Examples 1 to 3] In the present examples and comparative examples, the following metal particles, dispersants, and binders were used. Metal particles: Ni powder with a roughly spherical shape and a particle size D50 of 0.080 μm Dispersant: NOF Corporation Esleam C-2093I ·Binder: Sekisui Plastics Co., Ltd. IBM-2

[0055] 1. Metallic Ink Preparation Metal particles were dispersed in ethanol or isopropyl alcohol, and 3% of a dispersant was added to the metal particles. The dispersion was then wet-dispersed using a Nanomizer. The resulting dispersion was centrifuged and decanted to remove the organic solvent. The Ni powder thus obtained was dried at 100°C to obtain Ni dry powder. After crushing the Ni dry powder in a mortar, 3% of a dispersant was added to the dry powder, and the mixture was mixed and degassed using a planetary centrifugal mixer manufactured by Thinky Corp. In this way, a Ni dispersion was obtained. Separately, a binder was dissolved in α-terpineol (first organic solvent), and the mixture was mixed and degassed using a planetary centrifugal mixer to obtain a binder solution. The Ni dispersion and binder solution were mixed and degassed using a rotation-revolution mixer, then kneaded using a three-roll mill (gap = 5 μm), and then mixed and degassed again using a rotation-revolution mixer to obtain a metal paste. Ethanol (second organic solvent) was added to this metal paste, and then the mixture was mixed by ultrasonic treatment and bubbling treatment using a dropper to obtain a metal ink. Table 1 shows the contents of various components in the metallic ink.

[0056] 2. Fabrication of porous ceramic composite materials A cathode paste containing 18% by mass of lanthanum strontium cobalt ferrite (LSCF), 54.4% by mass of 2-propanol, 27.4% by mass of toluene, and 0.2% by mass of marilynium (dispersant) was applied to the dense layer 3 side of the porous ceramic material 1 (shown in Figure 1, with an average pore diameter of the porous layer 2: 20 μm) to a thickness of 100 μm. This was then fired at 1000°C for 2 hours to form a cathode. The cathode part of the fired product thus obtained was protected with a film to prevent metal ink from adhering to the cathode. The protected fired product was then vacuum-dried for 1 hour and left to stand with the cathode part facing downwards. The above-mentioned metal ink was then dripped onto the porous layer 2 side using a dropper. The dripping was repeated until the metal ink no longer soaked into the surface. The porous ceramic material 1 was then vacuum dried until the top surface was no longer wet, and then heated and dried at 180°C in a N2 atmosphere at normal pressure. The above-mentioned metallic ink dropping, vacuum drying, and heated drying were repeated until the metallic ink was no longer easily absorbed. After peeling off the protective film on the cathode, the material was fired at 700°C in an air atmosphere at normal pressure to obtain a porous ceramic composite material.

[0057] 〔evaluation〕 The dynamic contact angle of the metal ink and the cross-section of the porous ceramic composite material were observed as follows.

[0058] [Measurement of dynamic contact angle] The dynamic contact angle X of a droplet formed by dropping metal ink onto a glass plate was measured using a contact angle meter DropMaster 500 and a dispenser Auto Dispenser AD-31 manufactured by Kyowa Interface Science Co., Ltd. The measurement conditions were as follows: Measurement start time: 200 ms after the droplet contacts the glass plate ·Measurement interval (Δt): 300ms Measurement time: 14000ms Based on the measurement results, the dynamic contact angle E at which the dynamic contact angle X no longer changed was determined using the method described above. Also, X=αt -β The fitting parameters α and β were determined by fitting the above measurement results. The fitting was performed using the multifunctional integrated analysis software FAMAS manufactured by Kyowa Interface Science Co., Ltd., in the manner described above. These results are shown in Table 1.

[0059] [Cross-section observation of porous ceramic composite material] The porous ceramics of each example and comparative example were cut along their thickness direction, and the cross sections were observed with an optical microscope. The observation results for Example 1 are shown in Figure 2, and the observation results for Comparative Example 2 are shown in Figure 3. Based on the observation results, the impregnation of the metallic ink in each example and comparative example was evaluated. The evaluation criteria are shown below, and the evaluation results are shown in Table 1.

[0060] <Evaluation criteria for impregnation> A: The metallic ink reaches the dense layer, and the degree of coloring by the metallic ink is particularly large. B: The metallic ink reaches the dense layer and is sufficiently colored by the metallic ink. C: The metal ink does not reach the dense layer.

[0061] [Table 1]

[0062] 2 and 3, the porous ceramic composite material of Example 1 was impregnated with the metal ink up to the lower part of the porous ceramic material (near the dense layer) compared to the porous ceramic composite material of Comparative Example 2. Furthermore, as shown in Table 1, similar results were obtained in the other Examples and Comparative Examples. Therefore, it can be seen that the metal ink produced in each Example has excellent impregnation ability into porous ceramic materials. [Explanation of symbols]

[0063] 1. Porous ceramic materials 2 Porous layer 3 Layer compacta 4 pores 5. Sintered metal particles 10 Porous ceramic composite materials

Claims

1. A metallic ink comprising metal particles, a binder, a dispersant, and an organic solvent, a contact angle meter is used to measure the dynamic contact angle X of a droplet formed by dropping the metal ink onto a glass plate, thereby obtaining data consisting of a plurality of pairs of time t (ms) after dropping the metal ink and the dynamic contact angle X (deg); Formula X=αt －β is fitted to the data to determine the fitting parameters α and β. α is 50 or more, β is 0.10 or more, A metallic ink, wherein when the droplet is left to stand until the dynamic contact angle X of the droplet no longer changes, the dynamic contact angle E is 18 degrees or less.

2. The metal particles are contained in an amount of 5% by mass or more and 40% by mass or less, The binder is contained in an amount of 0.1% by mass or more and 25% by mass or less, The metallic ink according to claim 1 , comprising 0.1% by mass or more and 5% by mass or less of the dispersant.

3. 3. The metallic ink according to claim 1, wherein the binder is one whose thermal decomposition is completed in air at a temperature of 700°C or less.

4. The metallic ink according to claim 3 , wherein the binder is a (meth)acrylic resin.

5. 3. The metal ink according to claim 1, wherein the dispersant is a polymer compound having a comb structure or a block polymer structure, or a compound having a solvent-affinity unit and a powder surface-affinity unit bonded to the solvent-affinity unit.

6. The metallic ink according to claim 1 or 2, which is used for impregnating the pores of a porous ceramic material.

7. Metal particles are placed in the pores of a porous ceramic material; A method for producing a porous ceramic composite material, comprising firing the ceramic material having the metal particles disposed therein to produce a sintered body of the metal particles in the pores of the ceramic material, A method for producing a porous ceramic composite material, comprising: impregnating the pores of the porous ceramic material with the metal ink according to claim 1, thereby disposing the metal particles in the pores.

8. The method according to claim 7, wherein the pores of the porous ceramic material have an average pore diameter d of 1 μm or more and 200 μm or less as measured by mercury intrusion porosimetry.

9. the porous ceramic material has proton conductivity, The method according to claim 7 or 8, wherein the metal particles comprise nickel.

Images