JP2004083371A - Process for producing ceramic porous body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a uniform ceramic porous body in which mutually independent pores having a uniform diameter are three-dimensionally regularly arranged. <P>SOLUTION: The surface of each spherical polymer particle (1) is uniformly modified with ceramic fine particles (2) by heteroaggregation in a slurry having a prescribed pH, and thereafter, the slurry is formed, and fired. When the slurry is fired, the polymer particles are burnt and removed, and the ceramic fine particles are joined with one another. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The invention of this application relates to a method for producing a porous ceramic body. More specifically, the invention of this application relates to a method for manufacturing a ceramic porous body capable of manufacturing a uniform ceramic porous body in which mutually independent pores having a uniform diameter are regularly arranged three-dimensionally.
[0002]
[Prior art]
Ceramic porous bodies are widely used in exhaust gas filters, catalyst carriers, bioreactors, gas-insulating materials, and the like. In particular, a ceramic porous body having pores of uniform size and regularly arranged three-dimensionally is expected to be used for a photonic crystal.
[0003]
As a method for producing such a ceramic porous body, a ceramic raw material in which ceramic powder, a curable resin, and one or more types of starch powder are blended into voids of a resin particle molded body formed by binding spherical resin particles. And then heating the blended starch powder to a temperature above the minimum gelatinization temperature to produce a green body, followed by drying and baking (Japanese Patent Application Laid-Open No. 5-97537, No. 2-4). page).
[0004]
In addition, a molecular assembly of a surfactant, an aggregate in which a surfactant molecule and a predetermined organic molecule coexist, and an aggregate selected from a molecular assembly of a different surfactant are used as a template, and the molecular The aggregate is mixed with a ceramic material or a precursor thereof to produce a precursor of a ceramic porous body having an inorganic-organic structure, and then a surfactant in the precursor of the ceramic porous body is removed by photo-oxidation, and the nano-structure is removed. There is also known a method of producing a ceramic porous body having pores of a metric scale at a low temperature (JP-A-2001-80976, page 2-3, FIG. 1).
[0005]
[Problems to be solved by the invention]
However, in the former method, the spherical resin particles are bound not only by filling and compressing or bonding, for example, so that continuous pores are formed, but also by functioning as a binder by gelatinizing starch powder mixed with the ceramic raw material. In addition, while solidifying the green body, the starch powder also functions as a pore-forming agent so that fine continuous pores are formed. Therefore, the ceramic porous body obtained by the former method has two or more continuous air holes having different diameters, and is not a uniform one in which mutually independent pores having a uniform diameter are regularly arranged three-dimensionally.
[0006]
The latter patent document neither discloses nor suggests any technical means for producing a uniform ceramic porous body in which mutually independent pores having a uniform diameter are regularly arranged three-dimensionally. In order to obtain such a porous ceramic body, it is not enough to make the particle diameter of the raw material powder of the ceramic material or its precursor uniform. It is necessary to disperse the fine particles without aggregating them, and to uniformly adhere the fine particles of the ceramic or its precursor to the surface of the molecular assembly.
[0007]
The invention of this application has been made in view of such circumstances, and a ceramic porous material capable of producing a uniform ceramic porous body in which mutually independent pores having uniform diameters are regularly arranged three-dimensionally. An object of the present invention is to provide a method for producing a body.
[0008]
[Means for Solving the Problems]
The invention of this application solves the above problems by uniformly modifying ceramic fine particles on the surface of spherical polymer particles in a slurry having a predetermined pH by hetero-aggregation, then forming the slurry, firing and firing. A ceramic porous body characterized in that the polymer particles are sometimes burned off and the ceramic fine particles are combined with each other to produce a uniform ceramic porous body in which mutually independent pores having a uniform diameter are regularly arranged three-dimensionally. A method for producing a body (claim 1) is provided.
[0009]
The invention of this application also separately prepares a slurry in which spherical polymer particles are dispersed and a slurry in which ceramic fine particles are dispersed, at the same pH where one particle surface is positive and the other particle surface is negatively charged, Thereafter, the two slurries are mixed to hetero-aggregate the ceramic fine particles on the surface of the spherical polymer particles (claim 2).
[0010]
Hereinafter, the method for producing a ceramic porous body of the present invention will be described in more detail with reference to examples.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
In the method for producing a ceramic porous body of the invention of this application, as shown in FIG. 1, ceramic particles (2) are uniformly modified by hetero-aggregation on the surface of spherical polymer particles (1) in a slurry having a predetermined pH. Then, the slurry is formed (FIG. 1 <c>), fired (FIG. 1 <d>), the spherical polymer particles (1) are burned off during firing, and the ceramic fine particles (FIG. 2) Join each other. In other words, according to the method for producing a porous ceramic body of the invention of the present application, the surfaces of the spherical polymer particles (1) serving as a nucleus and the ceramic fine particles (2) whose surface is to be modified have different polarities in a slurry. The particles of the same kind are uniformly dispersed by utilizing the electrostatic force acting on both, and the heterogeneous spherical polymer particles (1) and the ceramic fine particles (2) are spherically dispersed by hetero-aggregation. The surface of the polymer particles (1) is uniformly modified with the ceramic fine particles (2), and their uniform dispersion and uniform modification are simultaneously realized. As a result, when the slurry is formed and baked, the spherical polymer particles (1) are burned off and the ceramic fine particles (2) are bonded to each other, and mutually independent pores having a uniform diameter are formed in a three-dimensional manner. Thus, a uniform ceramic porous body (4) regularly arranged is obtained (FIG. 1 <d>).
[0012]
Specifically, as shown in FIG. 1 <a>, a slurry in which spherical polymer particles (1) are dispersed and a slurry in which ceramic fine particles (2) are dispersed are prepared such that one particle surface is positive and the other particle is positive. Prepare separately at the same pH where the surface is negatively charged. Generally, the surface of the spherical polymer particles (1) is negatively charged, and the surface of the ceramic fine particles (2) is positively charged. However, depending on the type of the polymer and the ceramic used, the opposite may be used. When the slurries are separately prepared in this manner, the particles are more uniformly dispersed in the slurry due to the electrostatic repulsion between the particles. It is preferable to set the pH of the slurry so that the absolute value of the surface potential of the particles used, that is, the zeta potential, is as large as possible in order to increase the magnitude of the electrostatic force. To this end, adding a so-called dispersant such as a polymer electrolyte to the slurry may be considered as a proposal. However, the slurry in which the spherical polymer particles (1) are dispersed and the slurry in which the ceramic fine particles (2) are dispersed are mixed as described above so that the absolute value of the zeta potential does not change due to subsequent mixing. Are kept the same. If the pH is different, hetero-aggregation does not occur uniformly during slurry mixing, and as a result, a uniform ceramic porous body cannot be finally obtained.
[0013]
In this way, the slurry prepared separately and having the particles more uniformly dispersed is mixed. In the mixed slurry, electrostatic attraction acts between different kinds of particles, and the surface of the spherical polymer particles (1) is uniformly modified with the ceramic fine particles (2).
[0014]
In the method for producing a porous ceramic body of the present invention, there is no particular limitation on the molding method, and various methods such as a casting method, a pressure casting method, a reduced pressure casting method, a centrifugal sedimentation method, and an electrophoresis method are used. The method can be appropriately adopted. The same applies to the firing method, and the firing conditions can be appropriately set according to the type of the ceramic fine particles (2) and the like.
[0015]
【Example】
(Example 1)
An aqueous slurry of PMMA (polymethyl methacrylate) particles having a particle diameter of 350 nm and γ-alumina particles having a particle diameter of 34 nm, in which water is a dispersion medium, is charged negatively on the PMMA particle surface and positively on the γ-alumina particle surface. , PH 8 at which the absolute value of the zeta potential was maximized. FIG. 2 is a graph showing the relationship between the zeta potential and pH of PMMA particles having a particle size of 350 nm and γ-alumina particles having a particle size of 34 nm.
[0016]
Both slurries were stirred for 10 minutes after ultrasonic irradiation for 1 hour to disperse each particle. Thereafter, the alumina slurry was slowly added to and mixed with the PMMA slurry. Heterocoagulation occurred quickly, and the surface of the PMMA particles was modified with alumina particles. The mixed slurry is solidified and formed by vacuum casting, dried at room temperature, and calcined at 500 ° C. for 4 hours and calcined at 850 ° C. for 2 hours to produce an alumina porous body by two-stage firing. Was. FIG. 3 is an SEM photograph instead of a drawing showing a fracture surface of the obtained alumina porous body. As can be seen from FIG. 3, in the obtained alumina porous body, mutually independent pores having a uniform diameter are regularly arranged three-dimensionally. The porosity is 74.0%.
(Example 2)
An aqueous slurry was prepared at pH 8 using water of PMMA particles having a particle diameter of 800 nm and α-alumina particles having a particle diameter of 150 nm as a dispersion medium. FIG. 4 is a graph showing the relationship between zeta potential and pH of PMMA particles having a particle size of 800 nm and α-alumina particles having a particle size of 150 nm. As can be seen from FIG. 4, the surface of the α-alumina particles is negatively charged similarly to the surface of the PMMA particles. PEI (polyethyleneimine) was added to the slurry. As a result, as shown in FIG. 4, the surface of the α-alumina particles was positively charged.
[0017]
After that, it was solidified and formed through the same process as in Example 1, dried at room temperature, and calcined at 500 ° C for 4 hours, fired at 1100 ° C for 2 hours, and fired for 2 hours to produce an alumina porous body. Was. FIG. 5 is a SEM photograph instead of a drawing showing a fracture surface of the obtained porous alumina body. As can be seen from FIG. 5, in the obtained alumina porous body, mutually independent pores having a uniform diameter are regularly arranged three-dimensionally. The porosity is 75.4%.
[0018]
Of course, the invention of this application is not limited by the above embodiments. It goes without saying that various aspects are possible for details such as the type and particle size of the polymer particles and ceramic fine particles, the molding method, and the sintering method.
[0019]
【The invention's effect】
As described in detail above, according to the invention of this application, a uniform ceramic porous body in which mutually independent pores having a uniform diameter are regularly arranged three-dimensionally is manufactured.
[Brief description of the drawings]
FIGS. 1A, 1B, 1C, and 1D are process diagrams showing one process of a method for manufacturing a porous ceramic body according to the present invention.
FIG. 2 is a graph showing the relationship between zeta potential and pH of PMMA particles having a particle size of 350 nm and γ-alumina particles having a particle size of 34 nm.
FIG. 3 is a SEM photograph instead of a drawing showing a fracture surface of the alumina porous body obtained in Example 1.
FIG. 4 is a graph showing the relationship between zeta potential and pH of PMMA particles having a particle size of 800 nm and α-alumina particles having a particle size of 150 nm.
FIG. 5 is a SEM photograph instead of a drawing showing a fracture surface of the porous alumina obtained in Example 2.
[Explanation of symbols]
1 Spherical polymer particles 2 Ceramic fine particles 3 Pores 4 Ceramic porous body

Claims (2)

Ceramic particles are uniformly modified on the surface of the spherical polymer particles by hetero-aggregation in a slurry having a predetermined pH, and then the slurry is formed and fired, and the polymer particles are burnt and removed at the time of firing, and the ceramic particles are joined together. A method for producing a uniform ceramic porous body in which independent pores having a uniform diameter are regularly arranged in a three-dimensional manner. A slurry in which spherical polymer particles are dispersed and a slurry in which ceramic fine particles are dispersed are separately prepared at the same pH where one particle surface is positive and the other particle surface is negatively charged, and then both slurries are mixed. 2. The method for producing a ceramic porous body according to claim 1, wherein the ceramic fine particles are hetero-aggregated on the surface of the spherical polymer particles.

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