JPH05213681A - Fiber reinforced honeycomb ceramic body and its production - Google Patents

Abstract

PURPOSE:To obtain a fiber reinforced honeycomb ceramic body hardly causing brittle fracture by molding and firing a compsn. contg. ceramic powder, inorg. fibers and an inorg. substance having binding property or further contg. an org. binder having plasticity. CONSTITUTION:Ceramic powder such as alumina, spinel or silicon carbide powder, inorg. fibers such as ceramic, metal or carbon fibers and an inorg. substance having binding property such as colloidal silica, sepiolite or an alumina sol are prepd. and a ceramic-contg. compsn. is obtd. by using these starting materials or further using an org. binder such as PVA or methylcellulose. This compsn. having satisfactory extrusion moldability is extrusion-molded into a honeycomb shape with holes 2 having a square cross section formed by partition walls 3. The resulting molding is dried and fired at a temp. below the m.p. or oxidation point of the inorg. fibers to obtain a fiber reinforced honeycomb ceramic body 1 hardly causing brittle fracture and having a large surface area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a honeycomb-shaped fiber-reinforced ceramic body and a method for manufacturing the same. For more details,
The present invention relates to a honeycomb-shaped fiber-reinforced ceramic body containing ceramic powder and inorganic fibers, which is used for an adsorbent, a catalyst, a catalyst carrier, a filter, a heater, a wall material, a heat insulating material, and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Ceramics have inferior toughness as compared with plastics and metal materials, so that they have a drawback that they break brittlely once cracks start to develop, but heat resistance, It has excellent strength and wear resistance, and is used as a structural material or heat-resistant material in the form of granules or molded bodies. A honeycomb-shaped ceramic body has been attracting attention as a structure body using such a ceramic and having a large surface area. Known methods for producing a molded body using ceramics include hydrostatic molding such as slurry casting, extrusion molding, and rubber pressing, and hot pressure molding such as hot pressing that simultaneously performs heating and molding. As a method for manufacturing a honeycomb-shaped ceramic body, an extrusion molding method and a sheet laminating method are known,
For example, Japanese Patent Laid-Open No. 63-242980 proposes a honeycomb structure of an extruded product obtained by extruding slurry powder of a ceramic raw material into a honeycomb shape and firing. The honeycomb structure formed by this extrusion molding has a flat plate shape or a corrugated plate like the honeycomb structure having a structure in which ceramic sheets are laminated, which are proposed in Japanese Patent Publication No. 59-15028 and Japanese Patent Application Laid-Open No. 64-11808. Compared with the method of secondary molding of a ceramic sheet that has been once shaped into a three-dimensional mesh structure or swirl laminated structure, the manufacturing process can be performed because a honeycomb product can be obtained by directly drying and firing the extruded product. It has the feature of being extremely simple. However, these extrusion-molded and sheet-laminated honeycomb structures have brittleness, which is a general property of the above-mentioned ceramics. Particularly, since the extrusion-molded honeycomb structure is an integrally molded ceramic product, cracks are generated once. If it occurs, there is a drawback that structural destruction over the entire molded body is likely to occur.

It is believed that the cause of brittleness of ceramics is mainly due to its crystal structure, but as a method for improving the brittleness of ceramic materials, a composite of materials using fibers other than the honeycomb structure is used. Technology, ie fiber reinforced ceramics (FRC) combining ceramic powder and fibers
It has been known. This FRC is based on a composite technology of dissimilar materials with fibers, which is used as a method of strengthening materials in plastics and metal materials.
(1) Highly elastic and high-strength fibers are dispersed and mixed in the ceramic matrix (matrix), and the stress applied to the matrix is applied to the fibers to improve the strength of the molded body. (2) Dispersed in the matrix Prevents cracks generated by the formed fiber from developing in the molded body, and improves fracture toughness by using the fiber. (3) Prevents structural damage throughout the molded body by propagating the generated cracks along the fiber. It has the characteristics of being capable of (4) improving the high temperature strength of the molded product by using heat resistant fibers, etc., and is attracting attention as a structural material with high heat resistance and moderate strength and excellent toughness. There is. Although various methods for producing FRC have been proposed, they can be roughly classified into a solid phase method, a vapor phase method, a melt injection method, a thermal spraying method, etc., depending on the state of the ceramic matrix in which the fibers are mixed. The solid-phase method is not different from the usual solid powder sintering technique except that it uses fibers in combination, and it is preliminarily pressed from a molding raw material in which ceramic powder, fibers, and an organic binder are appropriately combined in advance. A molded product is prepared, dried, and then fired to obtain an FRC, and an FRC product can be obtained by a simpler process than the vapor phase method, the melt press-in method, the thermal spraying, and the like.

However, in the FRC in which the ceramic material and the fiber are used in combination, the sinterability of the ceramic material is hindered by the increase in the porosity of the molded body due to the compounded fiber. For this reason, the FRC by the solid phase method requires a higher firing temperature than a molded body made of only ceramic powder, and there is a problem that the fiber is deteriorated due to the severe firing conditions and the merit of the composite is lost. is there. Hot press molding such as hot pressing is effective for relaxing the firing conditions, while pressing at the same time as heating, but the shape of the molded product is limited in hot press molding using a special press molding machine. However, the cost is high. The melt press-fitting method is a method in which a ceramic material that melts at a relatively low temperature such as glass is used, and fibers are pressed into a ceramic matrix in a molten state to obtain an FRC product. However, since this method can be applied only to a ceramic material that melts at a relatively low temperature, there are problems that the raw material is limited and that the melted ceramic deteriorates the fiber. The vapor phase method is an FRC manufacturing technology that uses a ceramic material in a gas state by applying CVD (Chemical Vapor Deposition) and the like, and uses a preformed fiber as a skeleton, and deposits and deposits a ceramic matrix on this to obtain an FRC product. It is a thing. However, this method uses a special gas state as a ceramic material, and thus has a drawback that the raw material is limited as in the melt press-fitting method. Further, in order to maintain the ceramic material in a gas state, usually, a decompression condition is required, and since the deposition rate of the ceramic on the fiber is slow, the FRC by the vapor phase method is not suitable for manufacturing a large structure, and the cost is also high. high. Compared to these methods, extrusion molding, which is a general method for molding ceramics, has a simple process, so it is expected to have great merits as a manufacturing method for FRC. However, in the conventional ceramic industry, a fiber component was added. It is natural that ceramics are inferior in moldability, and it has not been considered to obtain a ceramic molded product to which a fiber component is added by extrusion molding. Furthermore, there has been no consideration at all for extrusion-molding a fiber-containing ceramic to produce a complicated molded body having a shape such as a honeycomb structure.

[0005]

However, the present inventors have found that extrusion molding is the simplest method for producing a honeycomb structure, and in order to improve the brittleness of the honeycomb body, the fibers of the FRC are I thought that the use was useful, and tried to manufacture a fiber-reinforced honeycomb body by extrusion molding,
A composition containing a ceramic powder, an inorganic material having a binding property with an inorganic fiber, and an organic binder having a plasticity as required has unexpectedly good extrudability, and is extruded from this ceramic-containing composition. The present invention has been completed by succeeding in obtaining a honeycomb-shaped fiber-reinforced ceramic body reinforced with inorganic fibers by molding. That is, the present invention relates to a honeycomb-shaped fiber-reinforced ceramic body obtained by forming a composition containing a ceramic powder, an inorganic substance having a binding property with an inorganic fiber, and an organic binder having a plasticity, if necessary, into a honeycomb shape and firing it. , And a composition containing the ceramic powder, an inorganic substance having a bondability with the inorganic fiber, and an organic binder having a plasticity as required, is extruded into a honeycomb shape, and the extruded product is dried, and then the inorganic fiber is added. The present invention provides a method for manufacturing a honeycomb-shaped fiber-reinforced ceramic body, which comprises firing at a temperature equal to or lower than the melting point or oxidation point of

Hereinafter, the honeycomb-shaped fiber-reinforced ceramic body of the present invention and the method for manufacturing the same will be described in detail. In the honeycomb-shaped fiber-reinforced ceramic body of the present invention, the ceramic raw material of the ceramic-containing composition component to be extruded into a honeycomb shape is not particularly limited, and may be arbitrarily selected depending on the properties required for the honeycomb-shaped fiber-reinforced ceramic body product. It can be chosen and either natural or synthetic products can be used. The ceramic raw material may be either oxide-based or non-oxide-based ceramic. Typical examples of such ceramics include oxide-based ceramics such as one-component oxides such as alumina, silica, zirconia, magnesia, and titania, spinel, mullite, barium titanate, cordierite, and β. Examples include multi-component oxides such as -spodumene, β-eucryptite, and talc, and silica gel can also be used. Examples of non-oxide ceramics include silicon carbide, silicon nitride, boron carbide, boron nitride, and the like, and carbon materials such as graphite and activated carbon can also be used. Furthermore, metal alkoxides, chelate compounds, hydroxides, which produce the oxide-based ceramics or non-oxide-based ceramics by thermal decomposition, etc.
Salts such as chlorides, nitrates and carbonates can also be used. The above ceramics may be used alone or in combination of two or more. In the present invention, such a ceramic raw material is used, but a ceramic powder having an average particle size of about 0.1 to 20 μm, particularly 0.3 to 10 μm is preferable.

The ceramic-containing composition used in the present invention contains inorganic fibers for the purpose of imparting appropriate toughness to the molded product and improving its brittleness. Here, ceramic fibers, metal fibers, or the like can be used as the inorganic fibers, and the ceramic fibers can be oxide-based or non-oxide-based. Typical examples of such inorganic fibers include oxide-based ceramic fibers such as glass fibers, alumina fibers, alumina / silica fibers, silica fibers, potassium titanate fibers, zirconia fibers, and alumina-boroa. A silica fiber etc. can be mentioned. Examples of non-oxide ceramic fibers include carbon fibers, silicon carbide fibers, boron carbide fibers, boron nitride fibers and the like. Examples of the metal fiber include stainless steel fiber and steel fiber. These inorganic fibers may be used alone or in combination of two or more.

As the carbon fibers, those generally used as fillers for fiber reinforced plastics (FRP) and fiber reinforced ceramics (FRC) can be used without particular limitation. Specific examples of such carbon fibers include, for example, pitch-based carbon fibers, rayon-based carbon fibers,
Examples thereof include polyacrylonitrile (PAN) -based carbon fibers, mesophase-based carbon fibers, vapor-grown carbon fibers, and the like. For these carbon fibers, graphite having a relatively high crystallinity and carbon having a relatively low crystallinity can be used, and whiskers can also be used. Furthermore, S
It may be coated and reinforced with another ceramic such as iC-coated carbon fiber. The metal fibers include ceramic-coated metal fibers such as boron-coated tungsten fibers and silicon carbide-coated tungsten fibers, in addition to those exemplified above.
In the present invention, the fiber length and fiber diameter of the inorganic fiber differ depending on the type and cannot be generally stated, but a fiber length of about 0.02 to 2 mm and a fiber diameter of about 0.1 to 20 μm are suitable.

Further, the ceramic-containing composition contains an inorganic substance having a binding property, and the ceramic powder and the inorganic fiber are appropriately dispersed and held in the molded body through the inorganic substance. Alternatively, an organic binder having plasticity or the like is added to impart appropriate extrusion moldability to the ceramic-containing composition. Here, examples of the binding inorganic substance include colloidal silica, alumina sol, ethyl silicate, silica sol, zirconia sol, sepiolite (fibrous), and clay minerals (kaolinite, nacrite, etc.). Two or more kinds can be used in combination. Among these, colloidal silica,
Sepiolite is preferably used. Further, as an organic binder used as desired, polyvinyl alcohol (PVA), sulphonic methyl chloride (SM
C), methyl cellulose (MC), carboxymethyl cellulose (CMC), starch and the like can be mentioned. Note that these organic binders are decomposed and removed in the firing step described later. In the present invention, the content ratio of each component varies depending on the type of ceramic powder and the like, and cannot be generally stated.
The solid content is about 30 to 87% by weight of ceramic powder, 0.5 to 10% by weight of inorganic fiber, and 10 to 40% by weight of an inorganic substance having a binding property such as sepiolite or clay mineral.

The method of the present invention for producing the above-mentioned honeycomb-shaped fiber-reinforced ceramic body comprises the steps of preparing a composition containing the above-mentioned components, extruding the composition containing the ceramic, and then drying the molded article. It consists of firing the dried molded product at a temperature below the melting point or oxidation point of the inorganic fibers. The method of the present invention basically comprises simple operations such as extrusion molding and firing, and has a feature that the steps can be carried out extremely easily and at low cost. In the present invention, the method for extrusion-molding the ceramic-containing composition is not particularly limited, and an extrusion-molding machine having an extrusion die (die) having a desired shape is used, and the composition is put therein, preferably 20 to 1000 cm / A molded product can be obtained by extruding at a speed of about a minute. The drying is carried out at room temperature for about 24 hours by natural drying, but it may also be carried out by slightly heating to about 50 to 100 ° C. Firing is performed at a temperature below the melting point or oxidation point of the inorganic fiber. Therefore, although the firing temperature and the firing time vary depending on the material of the inorganic fibers and the like and cannot be generally stated, generally firing conditions of at least about 20 minutes at a temperature of about 400 to 700 ° C are adopted. When the firing is carried out at a temperature exceeding the melting point or the oxidation point of the inorganic fiber, the inorganic fiber is melted or deteriorated, and the compounding of the inorganic fiber imparts appropriate toughness to the molded article and improves its brittleness. I cannot achieve my purpose.

The honeycomb-shaped fiber-reinforced ceramic body of the present invention thus obtained has a reinforced structure of fibers which are appropriately dispersed and held by the ceramic powder and the inorganic fibers through an inorganic material having a binding property, and has heat resistance and A structure having a large surface area that is excellent in strength and is less likely to cause brittle fracture. In the present invention, the shape and size of the honeycomb-shaped fiber-reinforced ceramic body are not particularly limited and can be appropriately selected according to the purpose of use and the like. In the present specification, the term "honeycomb shape" includes not only a so-called honeycomb shape (hexagonal shape) having a hole of a cross section but also a square shape, a triangular shape, another polygonal shape, a circular shape, or the like.

[0012]

The present invention will be described in more detail based on the following examples. Example 1 A honeycomb-shaped fiber-reinforced ceramic body 1 having a structure shown in FIG. 1 was produced as follows. That is, the honeycomb-shaped fiber-reinforced ceramic body 1 shown in FIG. 1 penetrates along the extrusion direction of the cylinder and is formed into a honeycomb structure having a rectangular cross section which is formed by a plurality of holes 2 having a rectangular cross section and separated by partition walls 3. And has a structure in which a fluid (gas, liquid, etc.) freely flows through the hole 2. Therefore, the honeycomb-shaped fiber-reinforced ceramic body 1 is used as a desiccant to be filled and used in a dry air generator or a catalyst carrier for treating exhaust gas in automobiles, factories, etc. It is useful for applications. In this example, the honeycomb-shaped fiber-reinforced ceramic body 1 is used.
When making (diameter 5 cm, height 10 cm), first, 40 parts by weight of silica gel powder (commercially available product, Mizusawa Chemical Co., Ltd., average particle size 1 μm) as a ceramic raw material, and sepiolite (commercially available product, Mizusawa) as a binding inorganic substance. Made by Kagaku, diameter 0.
A ceramic-containing composition prepared by blending 11 parts by weight of 01 μm, fiber length 3 μm), 45 parts by weight of colloidal silica (solid content of about 20%), 1 part by weight of carbon fiber, and 3 parts by weight of methyl cellulose as an organic binder having plasticity. It was adjusted.

Next, this composition (10 kg) was fed to an extruder having an extrusion die configured so that the extruded shape was a columnar structure having a plurality of holes 2 as shown in FIG. It was extruded at an extrusion speed of 200 cm / min. This molded product was heated and dried by microwave. Next, this molded product was allowed to stand in a firing furnace (electric furnace) and then heated at a heating rate of 2 ° C./min for 5 minutes.
The temperature was raised to a temperature of 00 ° C., and the temperature was maintained for 1 hour for firing. After that, the power supply to the firing furnace was stopped and the molded product was left to stand in the furnace and cooled to room temperature to obtain a honeycomb fiber-reinforced ceramic body 1 of the present invention as illustrated in FIG. This ceramic body was uniformly dispersed and held in the inorganic substances sepiolite and colloidal silica having a binding property between silica gel powder and carbon fiber, and it was difficult to cause brittle fracture with sufficient strength as a structure.

Example 2 A ceramic powder was used as alumina powder (commercially available product, average particle size 1 μm).
A honeycomb-shaped fiber-reinforced ceramic body of the present invention was obtained in the same manner as in Example 1 except that m) was used. Similar to the honeycomb-shaped fiber-reinforced ceramic body of Example 1, this ceramic body had sufficient strength as a structural body and was unlikely to cause brittle fracture.

In each of the above embodiments, the honeycomb-shaped fiber-reinforced ceramic body has a columnar shape, but in the present invention, the shape of the honeycomb-shaped fiber-reinforced ceramic body is not particularly limited to the columnar shape illustrated in FIG. For example, as shown in FIG. 2, a honeycomb fiber-reinforced ceramic body 4 having a honeycomb structure having a granular honeycomb structure formed by a plurality of holes 5 penetrating along the extrusion direction of a prism is used. A cylinder, depending on the purpose of use of the body, etc.
Various shapes such as a prism or an elliptic cylinder can be appropriately selected.

[0016]

As described above, the present invention provides a honeycomb-shaped fiber-reinforced ceramic body and a method for producing the same. According to the present invention, heat resistance and strength are excellent by a simple method of extrusion molding, It has become possible to provide a honeycomb-shaped fiber-reinforced ceramic body reinforced with an inorganic fiber and having a large surface area that is unlikely to cause brittle fracture. Such a honeycomb-shaped fiber-reinforced ceramic body of the present invention can be effectively used as an adsorbent, a catalyst, a catalyst carrier, a filter, a heater, a wall material, a heat insulating material and the like.

[Brief description of drawings]

FIG. 1 is a perspective view showing an outline of a honeycomb-shaped fiber-reinforced ceramic body according to an example of the present invention.

FIG. 2 is a perspective view showing an outline of another example of the honeycomb-shaped fiber-reinforced ceramic body of the present invention.

[Explanation of symbols]

 1 Honeycomb Fiber Reinforced Ceramic Body 2 Hole 3 Partition Wall 4 Honeycomb Fiber Reinforced Ceramic Body 5 Hole

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Ganzo Ishikawa, 5-30-30, Akaashiadai, Sanda City, Hyogo Prefecture 2 Akaashiadai Heights No. 2, 3rd Building 206 (72) Inventor, Yoshihiko Suketa 4-13, Asakuraminami, Takarazuka-shi, Hyogo Prefecture No. 43 Fleglance Takarazuka No. 105 (72) Inventor Kyoji Kyōsai 3-11 Ohbuki-cho, Takarazuka-shi, Hyogo Prefecture Marumien No. 203

Claims (2)

[Claims] 1. A honeycomb-shaped fiber-reinforced ceramic body obtained by molding a composition containing a ceramic powder, an inorganic substance having a binding property to an inorganic fiber, and an organic binder having a plasticity, if necessary, and firing the honeycomb-shaped composition. 2. A composition containing a ceramic powder, an inorganic material having a binding property with an inorganic fiber, and an organic binder having a plasticity, if necessary, is extruded into a honeycomb shape, and the extruded material is dried. A method for manufacturing a honeycomb-shaped fiber-reinforced ceramic body, which comprises firing at a temperature equal to or lower than a melting point or an oxidation point of an inorganic fiber.