JPS63297267A - Zirconia composite refractory - Google Patents

Abstract

PURPOSE:To obtain a zirconia composite refractory with excellent thermal shock resistance without adverse effects on excellent properties of zirconia, by adding a prescribed amount of zirconia fibers to a zirconia powder. CONSTITUTION:The subject zirconia composite refractory is obtained by admixing 5-200pts.wt. of zirconia fibers, preferably zirconia fibers stabilized with yttrium to 100pts.wt. of a zirconia powder. The refractory can have a number of voids included by evaporation of organic substance added. in the above embodiment, the amount of the organic substance to be added is less than 100pts.wt. per 100pts.wt. of the refractory. The zirconia composite refractory according to the present invention can inhibit growth of cracks, even if it has fine defects, because having high resistance to the defects.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to ceramic refractories, and more particularly to zirconia composite refractories reinforced with zirconia fibers. 1 inch [Prior art] Zirconia Zr 02 has a high melting point of approximately 2715°C, has very low thermal conductivity, has low electrical resistance at high temperatures, high electrical resistance at low temperatures, and is chemically resistant. It has excellent properties not found in other ceramics, such as being highly stable, not wetted by basic and acidic slag, having low volatility, and having a Mohs hardness of 7 or higher.

Taking advantage of these properties, zirconia can be used as polishing and abrasive materials,
In addition to applications such as electronic materials, ceramic pigments, glass additives, and sensor materials, it is also used in fire-resistant molded products.

[Problem that the invention seeks to solve]

However, molded bodies made only of ittria have low thermal conductivity and a large coefficient of expansion, making them susceptible to thermal shock.
Zirconia heat-insulating refractories, which are used as heat insulating materials that take advantage of their low thermal conductivity, are also susceptible to thermal shock.

This invention was made based on the above-mentioned background, and its purpose is to provide a zirconia-based refractory that has resistance to thermal shock without impairing the excellent properties of zirconia.

[Means for Solving the Problems] The present inventors tried to improve the properties of zirconia refractories by adding various reinforcing materials to zirconia raw material powder, and found that the addition of refractory fibers resulted in relatively improved properties. As a result of further detailed research based on this knowledge, it was discovered that adding zirconia fibers among fire-resistant fibers was effective in achieving the purpose of the invention, and in order to complete this invention. It's arrived.

That is, the zirconia composite refractory of the present invention contains 5 to 2 parts of zirconia fiber per 100 parts by weight of zirconia 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 refractory may be fired.

In a preferred embodiment of the present invention, this refractory material 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 zirconia powder and zirconia fiber.

In another embodiment of this invention, the particle size of the zirconia powder can be 0.1 to 1000 μm.

In a preferred embodiment of the present invention, the refractory is coated with zirconia sol or/and zirconium salt solution as a binder for a total of 10 ml of zirconia powder and zirconia fibers.
It can be included in an amount of 2 to 30 parts by weight relative to 0 parts by weight.

The second invention will be explained in more detail below.

Zirconia Powder The zirconia powder used in this invention consists essentially of zirconium oxide represented by the chemical formula ZrO2, and may also include zirconium compounds such as zirconium carbonate and zirconium hydroxide, or Y2O3. , MgO1CaO, etc., and consists of at least one of these. This powder can be obtained, for example, by a method for producing fine powder by spray drying. The particle size of this zirconia powder is
In the present invention, there is no particular restriction, and the zirconia refractory can be selected as appropriate depending on the use, shape, etc. For example, when a zirconia refractory is used for an oxygen sensor, the particle size is set to 0.5 to 5 μm. be able to.

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 manufactured by converting it into fibers (spinning solution) to form a fiber precursor (precursor) and firing the fiber precursor at a high temperature, and can be appropriately selected depending on the purpose, shape, etc. of the zirconia refractory. be able to.

The fiber length and fiber diameter of the zirconia fibers used in this invention are, for example, 0.1 to 50 mm, and 0.1 to 50 mm, respectively.
It is 20 μm.

The amount of zirconia fiber added is 5 to 200 parts by weight, preferably 10 to 100 parts by weight, and more preferably 30 to 70 parts by weight per 100 parts by weight of zirconia powder. This is because if the amount of zirconia fiber added is less than 5 parts by weight, the effect of adding fiber will be small, while if it exceeds 200 parts by weight, there will be too much fiber and cleave deformation will occur due to the load or own weight during actual use, resulting in poor quality. It is from.

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. , sodium alginate, animal and plant mucilages such as agar, and zirconia sol and/or zirconium salt aqueous solution.

The zirconia sol that can be used in the present invention is, for example, a milky white colloidal liquid in which zirconia having a particle size of about 70 mm is suspended in water.

The zirconium salt aqueous solution is a colloidal solution of zirconia using water as a solvent, and in this invention, for example, zirconyl acetate,
Zirconyl nitrate, zirconyl acid chloride, zirconyl sulfate,
Zirconyl ammonium carbonate and the like can be used.

In order to reduce the weight of the zirconia composite refractory of this invention,
Further, in order to use the molded product as a filter medium, a catalyst carrier, etc., a substance that is burnt out and vaporized during the firing process and leaves a large number of pores in the molded body, that is, a porosity-forming agent may 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 the spherical or fibrous organic material added as a porosity agent varies depending on the use, porosity, and pore diameter. For example, for 100 parts by weight of zirconia powder and zirconia fibers, the amount of spherical or fibrous organic matter added is 5 to 100 parts by weight, preferably 10 to 100 parts by weight.
It is 50 parts by weight. This is because if the porosity is less than 5 parts by weight, the porosity is insufficient, and the 100ffi! This is because, if the zirconia composite refractories exceed 100%, the strength of the obtained zirconia composite refractory decreases and sufficient handling strength cannot be obtained.

Manufacturing method The zirconia refractory of this invention can be prepared and molded by various methods. Specifically, as molding methods that can be used here, in addition to methods such as isostatic press method and hot press method, there are other methods such as -axis press, cast molding, and injection molding.

In this invention, after forming, the refractory 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 zirconia refractory, its use, etc. For example, the zirconia composite 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, 1000 to 2000
℃, preferably 1500 to 1900℃. This is because the sintering strength is weak below 1000°C, and when it exceeds 2000°C, oversintering occurs and deformation occurs.

The obtained zirconia composite refractory is cut into the desired shape.
It can be done in parts.

[For production]

The zirconia fiber used in the zirconia composite refractory of this invention has excellent mechanical strength, so it acts as a reinforcing material for zirconia, which is the main component of the refractory. Since it has a high melting point, phenomena such as decomposition and melting that often occur with fire-resistant fibers other than zirconia fibers do not occur. Zirconia fibers are added to this refractory material, which acts as a reinforcing material, allowing for unlimited molding methods and significantly increasing the mechanical strength of the resulting molded product.

In a preferred embodiment of the present invention in which zirconia sol and/or zirconium salt aqueous solution is added as a binder, the bond between zirconia powder or zirconia fibers is strengthened, and moreover, it forms a strong corrugated film itself and has heat resistance equivalent to that of zirconia fibers. What this does is endow the resulting composite with high mechanical strength and excellent chemical stability.

〔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 zirconia refractory, it has high resistance to the scratches and can suppress the progression of cracks.

(b) Since it contains zirconia fibers that have excellent mechanical and thermal properties, it gives zirconia composite refractories good resistance to thermal shock, and can be used in applications where conventional zirconia refractories cannot withstand, e.g. It can be used as a lining material for fast heating furnaces, etc.

(c) Even if normal fine powder zirconia on the order of microns is used, it can be molded into a container in a variety of ways compared to the case where zirconia fibers are not added.

(d) Since the heat-insulating refractory according to the present invention has excellent thermal shock resistance, it can fully utilize the low thermal conductivity of zirconia to fully exhibit its heat-insulating properties.

(e) Since this refractory contains zirconia fibers with excellent mechanical properties, it exhibits flexibility and is difficult to break under mechanical stress.

〔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 Magnesia-stabilized zirconia powder with an average diameter of 1 to 0.3+am (Mg0 5911;, Z r O2 95%) 5
0 parts by weight, 50 parts by weight of magnesia-stabilized zirconia powder (Mg0 5% 1, Zr 0295%) of 0.3++m, magnesia-added zirconia fibers (made of white brick for goods) with an average diameter of 5 μm and an average length of 20-30 mm 100 parts by weight, 1 part by weight of methylcellulose, and 5 parts by weight of an aqueous zirconium acetate solution (ZrO2-15%) were added and blended,
After cross-contact, uniaxial pressure molding was carried out at a pressure of 50 kg/c-, and the product was dried to obtain a zirconia refractory. This molded body was heated to 1800
Table 1 shows the properties of the fired product fired at °C.

Example 2 Ittria stabilized zirconia powder (720
37%, ZrO29396) 100 parts by weight, 50 parts by weight of Ittria stabilized zirconia fiber (manufactured by Shinyo Shirorenga Co., Ltd.) with an average diameter of 5 μm and an average length of 20 to 30 m+*, 5 parts by weight of zirconium chloride powder, average diameter Two parts by weight of 1 mm expanded polystyrene beads and 30 parts by weight of water were added and blended, and after kneading, the mixture was poured into a mold and dried to obtain a zirconia heat insulating refractory. Table 1 shows the properties of the fired product obtained by firing this refractory at 1800'C.

Comparative Example 1 A zirconia refractory 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.

No cracking occurred after drying during the manufacturing process.

Comparative Example 2 A zirconia refractory was obtained in the same manner as in Example 2, except that the zirconia fibers used in Example 2 were not blended.

During the manufacturing process, several cracks occurred after drying, but the parts without cracks were fired. Its characteristics are shown in Table 1.

Table 1 Note 1) Sample shape 40x40x160mm, span distance 1
001111% 3-point bending test method

Claims (1)

[Scope of Claims] 1. A zirconia composite refractory characterized in that 5 to 200 parts by weight of zirconia fibers are added to 100 parts by weight of zirconia powder. 2. The zirconia fiber according to claim 1, wherein the zirconia fiber is at least one fire-resistant fiber selected from pure zirconia fiber, lime-stabilized zirconia fiber, magnesia-added zirconia fiber, and yttria-stabilized zirconia fiber. Composite refractories. 3. The zirconia composite refractory according to claim 1 or 2, wherein the refractory is fired. 4. The zirconia composite refractory according to claim 3, wherein the refractory has a large number of pores formed by burning out the added organic matter. 5. The zirconia composite refractory 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 zirconia powder and zirconia fiber. 6. The zirconia-based composite refractory according to claim 1 or 5, wherein the zirconia powder has a particle size of 0.1 to 1000 μm. 7. Claims 1 to 7, wherein the refractory contains 2 to 30 parts by weight of zirconia sol or/and zirconium salt solution as a binder based on 100 parts by weight of the zirconia powder and zirconia fibers. The zirconia composite refractory according to any one of Item 6.