JPH0694389B2 - Beta-alumina tube manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a beta-alumina tube capable of producing a beta-alumina tube used as a solid electrolyte tube for a sodium-sulfur battery with high accuracy and yield.

[0002]

2. Description of the Related Art For example, in a sodium-sulfur battery, a beta-alumina tube is used as a solid electrolyte tube for separating an anode active material and a cathode active material. Then, in the method for producing the beta-alumina tube, it is known to perform a degreasing treatment for removing the organic binder of the beta-alumina molded body as a pre-treatment step for firing the beta-alumina molded body.

However, in the conventional degreasing process, a bottomed cylindrical beta-alumina molded body having an opening formed at one end is formed into an inverted state in which the opening is closed by a non-breathable baking table. The decomposition gas of the organic binder was released to the outer surface through the thickness of the beta-alumina molded body. As a result, the organic binder in the vicinity of the inner surface of the beta-alumina molded body tends to be insufficiently degreased and cannot be sufficiently degreased, and the residual carbon of the organic binder causes insufficient shrinkage during the firing process which is a post-process, and after firing. The resulting beta-alumina tube is larger than a predetermined size, and many defective products are out of the quality standard value.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, so that the release of the organic binder is not completely performed and insufficient degreasing does not occur, and the beta of a predetermined size is obtained after firing. The present invention has been completed for the purpose of providing a method for producing a beta-alumina tube capable of accurately producing an alumina tube with a high yield.

[0005]

The method for producing a beta-alumina tube of the present invention, which has been made to solve the above problems, comprises:
It is characterized in that a bottomed cylindrical beta-alumina molded body having one end as an opening is degreased and fired in a state where at least a part of the opening is open.

In the present invention, first, a bottomed cylindrical beta-alumina molded body having an opening at one end is molded into a predetermined shape by a conventional method using a pressure molding device or the like, and then this beta-alumina molded body is molded. It is almost the same as the conventional method that the degreasing treatment is performed in a degreasing treatment furnace according to a predetermined temperature condition, but the feature of the present invention is that the opening of the beta alumina molded body is closed. The point is that the degreasing process is performed in a state where at least a part of the organic binder is not opened, and most of the decomposition gas of the organic binder is decomposed by performing the degreasing process in a state where the opening is not closed as described above. Not only is it released to the outer surface through the thickness of the beta-alumina molded body, but also the organic binder near the inner surface of the beta-alumina molded body is sufficiently degreased through the opening, Never cause residual carbon in alumina green body.

Next, the essential points of the degreasing treatment in the method of the present invention will be described in more detail with reference to the drawings. Figure 1 is a baking stand 3
1 shows a case where a through-hole type ventilation passage 4 is used as a bottomed cylindrical beta-alumina molded body 1 whose opening 2 passes through the ventilation passage 4 and a degreasing treatment furnace such as an electric furnace for degreasing treatment. Degreasing treatment is performed by holding it on the baking stand 3 in an inverted state so as to be opened inside. In addition, like this, the baking stand 3
As an alternative to using a through-hole-shaped ventilation passage 4, the beta alumina molded body 1 may be placed horizontally and the opening 2 may be opened by erecting. However, since some of the volatile components in the organic binder are heavier than air, it is preferable to hold them in an inverted state as shown in FIG. 1 and spontaneously release from below.

The opening ratio of the opening 2 of the beta alumina molded body 1 is preferably 10% or more with respect to the total area of the opening 2. Therefore, for example, as shown in FIG. In the case of performing the above, the opening area of the through-hole-shaped ventilation passage 4 is set to a hole having a size satisfying the above condition. Even if the aperture ratio is less than 10%, a certain effect can be obtained as compared with the conventional method, but the aperture ratio is 10%.
If it is less than%, the degreasing of the organic binder in the vicinity of the inner surface of the beta-alumina molded body 1 is insufficient and carbon remains, and it is expected that this residual carbon causes insufficient shrinkage in the firing process in the subsequent step.

Next, FIG. 2 shows a case in which a lattice groove-shaped air passage 5 is formed on the upper surface of the baking table 3, and a large number of beta-alumina moldings are formed on such a baking table 3. If the body 1 is inverted so that the opening 2 of the body 1 is opened to the inside of the furnace through the ventilation passage 4 and the degreasing process is performed, it is possible to efficiently degrease a large number of beta-alumina molded bodies 1 at a time. Suitable for processing.

After the degreasing treatment is completed as described above, it is no different from the conventional method that the obtained beta-alumina molded body is put into a firing furnace and subjected to firing treatment under normal firing conditions. Since the beta-alumina molded body 1 which has been subjected to the degreasing treatment as described above is sufficiently degreased so that there is no residual carbon, it means that the firing is performed without causing insufficient shrinkage, and the beta conforming to the quality standard value is obtained. Alumina tubes will be manufactured.

[0011]

[Example] To a dry powder of a beta-alumina raw material, 5% by weight of polyethylene glycol as an organic binder was added together with water to form a slurry, which was then granulated with a spray dryer, and then dried by a hydrostatic pressure molding apparatus. 45 mm outer diameter, 40 inner diameter at a molding pressure of 2.2 ton / cm ^2.
A bottomed cylindrical beta-alumina compact having a length of 450 mm and a length of 450 mm was produced. Each of the obtained beta-alumina compacts was
As shown in Fig. 1, the opening ratio is changed by 0 and the temperature is raised to 800 ° C at a rate of 270 ° C / hour, held for 1 hour, and then lowered to room temperature at a rate of 270 ° C / hour to degrease. Processed. Then, according to normal conditions, 20 at 1620 ° C
It was held for a minute to perform a firing treatment to obtain a sintered body of beta-alumina tube. The defective rate of the obtained beta-alumina tube exceeding the dimensional standard value is as shown in Table 1, and the excellent effect of the present invention was confirmed.

[Table 1]

[0012]

As is apparent from the above description, in the present invention, the release of the organic binder is not completely performed and the degreasing deficiency does not occur, and the beta-alumina tube having a predetermined dimension can be accurately formed after firing. In addition, it can be produced with a high yield, and it can be used as it is without any modification to the conventional degreasing furnace or firing furnace, and has an advantage of having excellent economical efficiency. Therefore, the present invention greatly contributes to the industrial development as a method for producing a beta-alumina tube that eliminates the conventional problems.

[0013]

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an example of a degreasing process of the present invention.

FIG. 2 is a perspective view showing a baking tray in another embodiment.

[Explanation of symbols]

 1 Beta-alumina molded body 2 Opening part 3 Baking stand 4 Ventilation path

Claims (4)

[Claims] 1. A beta-alumina tube characterized in that a bottomed cylindrical beta-alumina molded body having an opening at one end is degreased and fired in a state where at least a part of the opening is open. Production method. 2. The beta-alumina according to claim 1, wherein the opening portion of the bottomed cylindrical beta-alumina molded body is subjected to degreasing treatment in an inverted state in which at least a part of the opening portion is opened through a ventilation passage of a baking base disposed therebelow. Pipe manufacturing method. 3. The method for producing a beta-alumina tube according to claim 1, wherein the opening of the bottomed cylindrical beta-alumina molded body is degreased in a state where 10% or more of the total area of the opening is open. . 4. A lattice groove-shaped ventilation channel is formed on the upper surface of the baking table, and a large number of beta-alumina molded bodies are inverted on the baking table so that their openings are opened through the ventilation channel to perform degreasing treatment. The method for producing a beta-alumina tube according to claim 2 or 3.