JPH01212289A - Ceramic structure - Google Patents

Abstract

PURPOSE:To obtain a ceramic structure having light weight, high strength, and having no fluid permeability and being preferably used for wall material and decorating material, etc., by coating a surface layer of a porous ceramic body with a vitreous thin layer having no fluid permeability. CONSTITUTION:The title ceramic structure is formed by coating a surface layer of a porous ceramic body with a vitreous thin layer consisting primarily of silicates. Said porous ceramic body is produced from powder of a ceramic material and starch. Its mean pore size is pref. <=200mum, and its porosity is pref. >=70%. The coating of the porous ceramic body with a vitreous thin layer consisting primarily of silicates is executed generally by applying a glaze on a surface layer of the porous ceramic body, and calcining at a necessary temp.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a lightweight, high-strength, and low-permeability ceramic structure suitable for wall materials, decorative materials, and the like.

[Conventional technology]

Generally, as a ceramic porous body, bisque clay, which is obtained by using Honbushi clay, Honbushi clay, feldspar, silica stone, etc. alone or in combination with water, and firing at high temperature is known. This kind of bisque firing is a porous body, but the pores are formed by the voids between the clay particles that are the raw material, and the percentage of voids in the entire structure can be too high, making it lightweight. There is a problem in terms of compatibility. In addition, regarding new ceramics made by molding refined and classified fine powders such as alumina, zirconia, cordierite, and silicate, and firing them at high temperatures,
Although it has been significantly improved in terms of strength, it has gone in the opposite direction in terms of weight reduction, making it denser and heavier.

On the other hand, as a method for making ceramics porous, we have also proposed a method in which organic particles such as thermoplastic resin powder and papermaking sludge are kneaded during preparation of the precursor, and these are burned off during firing and the traces are used as voids. However, the materials obtained by these methods have large pores and are problematic in terms of fineness in appearance, making them unsuitable for use as wall materials or decorative materials.

Furthermore, as a method for obtaining ceramics with fine pores, a method using starch as a pore-forming material has been proposed by the present applicant (Japanese Patent Application Laid-open No. 87472/1983, etc.), and the ceramics obtained by this method have fine pores. It has continuous pores, fine grain, and good appearance. However, since the surface also has a porous structure, there are problems such as liquid permeability and staining, and if left as is, there are some problems in using it as a wall material or decorative material.

(Problems to be Solved by the Invention) In view of the above-mentioned problems, the inventors of the present invention have conducted intensive research and found that by coating the surface layer of a porous ceramic body with a thin layer that is not permeable to liquid, the entire The present invention was completed based on the discovery that a structure with no liquid permeability can be obtained as a result. An object of the present invention is to provide a ceramic porous body that is lightweight, has high strength, and is suitable for use as wall materials and decorative materials that are impermeable to liquid.

(Means for Solving the Problems) The above-mentioned object is achieved by a ceramic structure formed by coating the surface layer of a porous ceramic body with a glassy thin layer mainly composed of silicate.

The ceramic structure according to the present invention can be obtained by the following method.

The above ceramic porous body can be manufactured using ceramic material powder and starch.

As the ceramic material powder, it is preferable to use alumina or solid ceramic material powder. As these ceramic material powders, it is particularly preferable to use powders whose particle sizes are made uniform through classification. Note that the above ceramic material powders may be used alone or in combination.

As the starch used together with the ceramic material powder, commonly used starches can be used as they are. In general, starch isolated and extracted from various plants has a uniform particle size that is unique to the parent plant. Starches made from cereals have relatively fine particles, and starches from potatoes and fruits have a uniform particle size. The matrix is relatively coarse grained. The starch to be used in the present invention may be appropriately selected from these starches depending on the required pore size.

The ceramic porous body according to the present invention can be obtained by a commonly known method. That is, for example, the ceramic material powder and starch are mixed and dispersed in water. Next, this dispersion is kneaded at a temperature that does not cause gelatinization of starch (70° C. or less) to prepare a slurry or paste-like mixture, which is placed in a predetermined mold and molded. In this molded body, ceramic material particles are densely arranged with starch particles sandwiched between them, and the contact state (filling state) between the material particles is extremely good.

Next, the molded body is heat-treated for a predetermined period of time at a temperature (generally 70° C. or higher) to gelatinize the starch while still being placed in the mold. As a result, the starch becomes pregelatinized and becomes a secondary material, loses its initial particle shape, and enters between the particles of the ceramic material, thereby exerting its effect as a binder. At this time, traces of the presence of starch particles become pores, which form the basis of the structure of the porous material. In addition, the porosity is influenced by adjusting the proportion of starch mixed in, and when the amount of starch exceeds a certain level, starch particles become adjacent to each other and form a continuous mesh structure.

If the temperature of the molded product is raised rapidly during heat treatment, drying will proceed at the same time as side formation and water will be rapidly lost. This causes the body (precursor) to become misshapen, cracked, or cracked.

Therefore, in the heat treatment, it is preferable to gradually raise the temperature. The precursor obtained in this way is in a fairly strong bonded state and cleavage at this stage.

Shaping processing such as molding and cutting is possible.

Next, the precursor obtained as described above is placed in a firing furnace and fired while raising the temperature from a low temperature to a high temperature range. During this temperature raising process, the starch that was functioning as a binder is burned out. It is something that

As is well known, starch consists of three elements: carbon, oxygen, and hydrogen, and does not generate any undesirable gases during calcination, and the thermal energy during thermal decomposition is low, so starch does not reach the starch decomposition region during the calcination stage. Increase the required baking time (
Furthermore, damage and deformation of the ceramic body due to generated gas are extremely reduced. The furnace required for the above-mentioned firing is not particularly limited as long as it has an oxidizing atmosphere, and an electric furnace, a gas furnace, etc. may be appropriately selected and used. When the sintering temperature of each particle is reached, the particles sinter together to form a strong porous ceramic body. In order to form a preferable three-dimensional network structure and obtain a lightweight ceramic structure, it is desirable to set the weight of starch to the ceramic material powder at 30 times or more.

Further, the upper limit of the size of the micropores is 200 mμ, and if the size is larger than this, the surface becomes rough and liquid easily penetrates.

In addition, the higher the porosity, the more advantageous it is in terms of light weight.For example, if fine powder of cordierite is used as a raw material and the porosity is set to 75%, the apparent specific gravity of the entire structure will be approximately 1, meaning that it will be water-resistant. It is possible to obtain a lightweight ceramic structure that can float on the ground.

In order to achieve the object of the present invention, which is weight reduction, it is preferable that the porosity is 70% or more.

The porous ceramic body thus obtained is coated with a thin glassy layer mainly composed of silicate.Generally, glaze is applied to the surface layer of the porous ceramic body and fired at the required temperature. can be melted to form a thin layer that is shiny and impermeable to liquids.

In the case of the present invention, for example, a frit glaze, that is, a crushed product obtained by melting and vitrifying silica, feldspar, kaolin, etc. with alkali carbonates, nitrates, borates, etc., is applied to the surface layer,
It may be fired at a temperature of about 800 to 200°C.

(Effects of the Invention) Although the ceramic structure of the present invention has a porous structure, the pores are so minute that they are almost invisible to the naked eye, and the appearance is similar to ordinary fine ceramics or porcelain. It is at the point where it has. Furthermore, the entire surface layer is coated with a glassy thin layer mainly composed of silicate, and specifically, glaze is applied and fired to suppress its liquid permeability.

In other words, it has a lighter specific gravity than general earthenware and porcelain (and has the same external appearance as these, but is also different from general earthenware and porcelain because its framework is so-called new ceramics). Its major feature is that it is excellent in strength.

The ceramic structure of the present invention has a lightness not found in conventional ceramics, and has fine pores that make it look thin, but it also has the disadvantages of ventilation, liquid permeability, and easy staining that are inherent to porous structures. Moreover, it is suitable as wall material and decorative material.

In particular, it is extremely useful as it meets the purpose of building high-rise buildings by reducing the weight of building materials.

In addition, by using colored shafts or painting during glazing, it can become a wall material with an aesthetic appearance, and it can also have a fashionable element.

The present invention will be explained below with reference to Examples.

Example: High-purity cordierite (
My2A/4 S i 5018) Average particle size 1036G
F was added to the mixture to raise the temperature to 60°C, and the mixture was sufficiently kneaded to obtain a uniform paste-like fluid. This was poured into a plate-shaped mold for SOXS OXS parrot, placed in a dryer set at 75°C, and left for 3 hours.

The obtained bent-over body was released from the mold, placed in a dryer at 70° C., and left for 24 hours to dry.

This precursor was put into an electric Matsukuru furnace, and from room temperature to 1.7
The temperature was gradually raised to 00° C. and fired for 100 hours to obtain a ceramic porous body.

This surface was glazed with a thin layer of frit glaze, and after air drying, it was put into the Matsukuru furnace again and fired at 950° C. for 10 hours to obtain a glossy ceramic structure.

The ceramic structure obtained here has a pore diameter of 5 to 10 μm.
It had a good porosity of 79% and an apparent specific gravity of 0.98, and had an appearance comparable to that of earthenware or porcelain.

Claims (3)

[Claims] (1) A ceramic structure formed by coating the surface layer of a ceramic porous body with a glassy thin layer mainly composed of silicate. (2) The ceramic porous body has an average pore diameter of 200 μm or less and a porosity of 70% or more (
The ceramic structure described in item 1). (3) The ceramic structure according to claim (1), wherein the porous ceramic body has a three-dimensional network structure.