JPS63291874A - Refractory molded article of yttria material - Google Patents

Abstract

PURPOSE:To obtain a readily moldable refractory molded article of yttria material, having excellent mechanical impact resistance and thermal shock resistance suppressing development of cracks even if fine flaws exist, by blending yttria powder with a specific weight ratio of zirconia fibers and molding. CONSTITUTION:100pts.wt. yttria powder is blended with 5-100pts.wt. zirconia fibers and molded to give the refractory molded article of yttria material. Refractory fibers selected from pure zirconia fibers, lime stabilized zirconia fibers, magnesia added zirconia fibers and yttria stabilized zirconia fibers are used as the zirconia fibers. The yttria powder is blended with the zirconia fibers and an organic material (e.g. polyethylene beads), molded, the molded article is burnt to eliminate the organic material and to form a great number of pores so that the molded article is made lightweight and is suitable for a catalytic carrier.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a ceramic refractory molded body, and more particularly to an ittrian refractory molded body.

[Conventional technology]

Ittria Y2O3 has a melting point of about 2410°C, which is higher than alumina, a coefficient of thermal expansion smaller than alumina, magnesia, and zirconia, and has no phase transformation. That is, it has no crystal transition and exhibits good corrosion resistance against slag, so it is attracting attention as a stable refractory material in high-temperature oxidizing atmospheres. Therefore, compacts made from yttria powder are expected to find applications in a wide range of fields, from lining materials for high-temperature reactors to oxygen sensors, condensers, and reactor materials for nuclear reactors.

[Problem that the invention seeks to solve]

However, molded bodies made only of ittria have the problem of being brittle to minute scratches and susceptible to thermal and mechanical shocks.Moreover, molding using commonly supplied ittria powder on the micron order, Cracks are extremely likely to occur, and molding methods such as isostatic press molding (rubber press) and hot press have been limited.

This invention was made based on the above-mentioned background, and its purpose is to provide a material that is strong against minute scratches, resistant to thermal and mechanical shock, and that can replace isostatic presses. It is an object of the present invention to provide an ittria refractory molded article that can be obtained by a simple molding method.

[Means for solving problems]

The present inventors tried to improve the characteristics of the Ittria molded product by adding various reinforcing materials to the Ittria raw material powder, and found that the addition of refractory fibers would relatively improve the properties. Based on this, various fire-resistant fibers such as graphite fibers, carbon fibers, SiC fibers, Si3N4 fibers, alumina fibers, etc. were investigated, but all of them burn out, decompose, oxidize, melt, etc. during firing treatment or actual use, and are not sufficient. It was not possible to obtain a significant effect of adding fiber. However, as a result of further detailed research, the inventor discovered that
Among the refractory fibers that were thought to be unable to obtain sufficient fiber addition effects, it was surprisingly discovered that zirconia fibers do not react with ittria and do not form a low-melting substance, leading to the completion of this invention.

That is, the ittria refractory molded article of the present invention contains 5 to 1 zirconia fiber per 100 parts by weight of ittria powder.
00 parts by weight is added.

In a preferred embodiment of the present invention, the zirconia fiber used in the present invention is at least one refractory fiber selected from pure zirconia fiber, lime-stabilized zirconia fiber, magnesia-added zirconia fiber, and ittria-stabilized zirconia fiber, preferably ittria. It can be a stabilized zirconia fiber.

In one embodiment of the present invention, the molded body can be fired.

In a preferred embodiment of the present invention, the molded body can be provided with a large number of pores formed by burning off the added organic matter.

In the above embodiment, the amount of the organic substance added can be less than 100 parts by weight based on 100 parts by weight of the total amount of ittria powder and zirconia fiber.

In another aspect of the invention, the particle size of the ittria powder can be between 0.1 and 100 μm.

This invention will be explained in more detail below.

Ittria Powder The ittria powder used in this invention consists essentially of oxide ceramics represented by the chemical formula Y2O3, and includes zirconium compounds such as zirconyl carbonate and zirconyl hydroxide, as well as zirconium compounds such as Y2O3 and MgO1C.
It is a powder to which a stabilizer such as aO is added. These can be obtained, for example, by a method for producing fine powders by spray drying. The particle size of the ittria powder is not particularly limited in the present invention, and can be appropriately selected depending on the use, shape, etc. of the ittria molded product.
When the Ittria molded body is used for an oxygen sensor, its particle size can be set to 1 to 3 μm.

Zirconia fibers Examples of the zirconia fibers that can be used in the present invention include pure zirconia fibers, lime-stabilized zirconia fibers, magnesia-added zirconia fibers,
Examples include itria-doped zirconia fibers and mixtures thereof, and preferably itria-doped zirconia fibers.

This zirconia fiber can be produced by various methods. For example, an aqueous solution of zirconium salt is used as a starting material (
It can be produced by converting it into fibers as a spinning solution to form a fiber precursor and firing the fiber precursor at high temperature, and it can be selected as appropriate depending on the use, shape, etc. of the Ittria molded product. be able to.

The amount of zirconia fiber added is 5 to 100 parts by weight, preferably 10 to 80 parts by weight, and more preferably 30 to 70 parts by weight, based on 100 parts by weight of ittria powder. this is,
This is because if the amount of zirconia fiber added is less than this lower limit, the effect of adding the fiber will be small, whereas if it exceeds the upper limit, there will be too much fiber and creep deformation due to the load or own weight during actual use will easily occur.

Additives In the present invention, the raw material for the molded body may contain various additives in addition to the above-mentioned components depending on the purpose. Examples of such additives include binders, porosity-forming agents, surfactants, dispersants, and flocculants.

Examples of binders that can be used include synthetic polymers such as polyethylene oxide, polyvinyl alcohol, and polyacrylic acid, cellulose derivatives such as methylcellulose, carboxyethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, and cellulose phosphate, starch and starch derivatives, and pectin. , animal and plant mucilages such as sodium alginate and agar, and water-soluble yttrium compounds such as yttrium acetate, yttrium chloride, yttrium nitrate, and yttrium sulfate.

In order to reduce the weight of the Ittria molded body of this invention, and to use it for applications such as filter media and catalyst carriers, we have developed a material that is burnt off and φ vaporized during the firing process, leaving a large number of pores in the molded body. Agents may also be added. Examples of such pore-forming agents include organic fibers such as organic fibers such as expanded styrene beads, expanded urethane foam beads, and polyethylene beads, as well as synthetic fibers and natural fibers such as linen thread and cotton. The amount of spherical or fibrous organic material added as a porosity agent varies depending on the application, porosity, and pore size, but for example, when using ittria molded bodies for filter media, the amount of addition of ittria powder and zirconia fibers is 1
The amount of the spherical or fibrous organic substance added is less than 100 parts by weight, preferably 10 to 50 parts by weight. This is because if the upper limit amount is exceeded, the strength of the obtained Ittria molded product will decrease and sufficient handling strength will not be obtained.

Manufacturing method The ittria molded article of the present invention can be prepared and molded by various methods, including isostatic pressing, hot pressing, and other methods such as -axis pressing, casting molding, and injection molding.

In this invention, after molding, the molded body may be dried and may or may not be subjected to a firing treatment,
It can be selected as appropriate depending on the type of components of the Ittria molded product, its use, etc. For example, the ittria molded body may be dried after being molded and used as is as a so-called unfired refractory.

In addition, firing treatment is performed when gas components generated from the added binder or firing shrinkage become a problem.

When firing, the firing temperature is, for example, 1300 to 2000.
℃, preferably 1500 to 1900℃. This is because if the temperature is below the lower limit, the sintering strength will be weak, and if it exceeds the upper limit, oversintering will occur and deformation will occur.

The obtained ittria molded product can be cut and divided into desired shapes.

[For production]

The zirconia fibers used in the ittria molded body of this invention do not react with ittria, which is the main component of the molded body, and therefore do not form a low-melting substance.
Since it has a high melting point of ℃ or higher, phenomena such as decomposition and melting that often occur with refractory fibers other than zirconia fibers do not occur. Zirconia fibers with excellent mechanical strength are added to this molded body, which acts as a reinforcing material for the molded body, enabling unlimited molding methods and improving the Significantly increases the mechanical strength of the body.

〔Effect of the invention〕

This invention having the above configuration and operation has the following effects.

(a) Even if there are minute scratches on the Ittria molded product, it has high resistance to the scratches and can suppress the progression of cracks.

(b) Since it contains zirconia fibers having excellent mechanical and thermal properties, it imparts good resistance to mechanical and thermal shock to the Ittria molded article.

(c) Even if ordinary fine powder powder of micron order is used, it can be molded more easily by various methods than when no zirconia fiber is added.

〔Example〕

This invention will be explained in more detail below using Examples and Comparative Examples, but this invention is not limited to the following Examples unless it exceeds the gist thereof.

Example 1 100 parts by weight of Ittria powder with an average diameter of 1 μm, 20 parts by weight of Ittria stabilized zirconia fibers (manufactured by Shinagawa Shirorenga Co., Ltd.) with an average diameter of 5 μm and an average length of 20 to 30 mm;
1 part by weight of methylcellulose, 1 part by weight of yttrium chloride powder, and 40 parts by weight of water were added and blended, mixed, poured into a mold, and dried to obtain an yttrium molded body. This molded body is 1
Table 1 shows the properties of the fired product fired at 600°C.

Example 2 100 parts by weight of Ittria powder with an average diameter of 50 to 100 μm, 70 parts by weight of lime-stabilized zirconia fiber (manufactured by Shinagawa Shirorenga Co., Ltd.) with an average diameter of 5 μm and a layer of 20 to 30 m in average length, 1 part by weight of carboxycellulose, average Diameter 1m+s
2 parts by weight of expanded polystyrene beads and 20 parts by weight of water were added and blended, uniaxially pressure molded at a pressure of 50 kg/cd, and dried to obtain an ittria molded product. This molded body was heated to 1700°C.
Table 1 shows the properties of the fired product.

Comparative Example 1 An Ittria molded body was obtained and fired in the same manner as in Example 1, except that the zirconia fiber used in Example 1 was not blended. Its characteristics are shown in Table 1.

During the manufacturing process, numerous cracks appeared after drying.

Comparative Example 2 An Ittria molded body was obtained and fired in the same manner as in Example 2, except that the zirconia fibers used in Example 2 were not blended. Its characteristics are shown in Table 1.

During the manufacturing process, cracks appeared when the frame was removed after press molding, and numerous cracks also appeared after drying.

Table 1

Claims (1)

[Scope of Claims] 1. An yttria refractory molded article characterized in that 5 to 100 parts by weight of zirconia fibers are added to 100 parts by weight of yttria powder. 2. The yttria fiber according to claim 1, wherein the zirconia fiber is at least one refractory fiber selected from pure zirconia fiber, lime-stabilized zirconia fiber, magnesia-added zirconia fiber, and yttria-stabilized zirconia fiber. Fireproof molded body. 3. The yttria refractory molded body according to claim 1 or 2, wherein the molded body has been subjected to a firing treatment. 4. The yttria refractory molded product according to claim 3, wherein the molded product has a large number of pores formed by burning out the added organic matter. 5. The yttria refractory molded article according to claim 4, wherein the amount of the organic substance added is less than 100 parts by weight based on 100 parts by weight of the total amount of yttria powder and zirconia fiber. 6. The yttria refractory molded article according to claim 1 or 5, wherein the yttria powder has a particle size of 0.1 to 100 μm.