JPH08268771A - Glass joined body and its production - Google Patents

Abstract

PURPOSE: To provide a glass joined body having improved reliability of the glass joined parts. CONSTITUTION: When glass 3 is joined to ceramics 1, 2, crystals 4 having the same compsn. as the glass 1 or the ceramics 1, 2 or crystals 4 of an oxide contained in the compsn. of the glass 1 or the ceramics 1, 2 are deposited on the interface between the glass 3 and each of the ceramics 1, 2 and the objective glass joined body is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass joined body exposed to a corrosive substance, and more particularly to a glass joined body having high corrosion resistance to a corrosive substance and a method for producing the same.

[0002]

2. Description of the Related Art Up to now, glass has been used as a sealing material for an extremely large number of places by utilizing its excellent sealing property and insulating property. Further, the glass joined body joined by the glass seal is often required to be used at a place exposed to a corrosive substance. Examples of the glass bonded body exposed to such a corrosive substance include a sodium-sulfur battery and a thermoelectric conversion device.

A sodium-sulfur battery is a high temperature secondary battery which operates at 300 to 350 ° C., and uses molten sodium as a cathode active material, molten sulfur or sodium polysulfide or both as an anode active material, and sodium ion as a solid electrolyte. With the cathode active material and the anode active material arranged inside and outside the conductive beta alumina tube, the beta alumina tube was glass-bonded to an insulator such as alpha alumina and housed in a metal container. I am configuring.

In the above-mentioned conventional sodium-sulfur battery, there is a problem that the bonding glass between the beta-alumina tube and the insulator is corroded by sodium, which causes a decrease in battery life. With respect to this problem, the present applicant has disclosed in
In Japanese Patent No. 26565 and Japanese Patent Laid-Open No. 4-175271, a sealing glass composition having excellent sodium resistance has been disclosed. With these techniques, the corrosion rate of glass due to sodium was remarkably slowed, and the corrosion resistance of the glass bonding portion of the battery could be improved.

[0005]

When the applicant further conducted research on a bonded glass in a sodium-sulfur battery, he found that the above-described glass corrosion has two forms of corrosion. That is, as shown in FIG. 3, when the beta-alumina tube 11 and the alpha-alumina insulating plate 12 are bonded by the bonding glass 13, the surface corrosion 14 that occurs on the surface of the bonding glass 3 and the bonding glass 13
Interface between glass and beta-alumina tube 11 or bonded glass 13
It has been newly found that there is an interfacial corrosion 15 that occurs at the interface between the alpha alumina insulating plate 12 and the alpha alumina insulating plate 12.

Of these, the surface corrosion 14 has a slower growth rate than the interfacial corrosion 15, and only the surface is peeled off, and no serious problems such as destruction of the joint portion occur, but the interface corrosion 15 has a growth rate. It has been found that the cracking occurs from the interface when the interface corrosion 15 progresses and the interface corrosion 15 progresses, which leads to the destruction of the joint and the shortening of the battery life.

The object of the present invention is to solve the above problems,
An object of the present invention is to provide a glass joined body in which the reliability of the glass joined portion of the glass joined body is improved, and a method for producing the same.

[0008]

The glass bonded body of the present invention comprises a crystal composed of the same component as glass or ceramics, or an oxide component contained in each composition at the interface between glass and ceramics. It is characterized in that the constituent crystals are precipitated.

The method for producing a glass joined body of the present invention is
In the above method for manufacturing a glass joined body, the crystal is deposited at an interface between glass and ceramics.

[0010]

In the above-mentioned structure, the crystal deposited at the interface between the glass and the ceramic has a pinning effect against corrosion and acts so as not to cause interface corrosion. Therefore,
Since the only form of corrosion is surface corrosion, which has a slow corrosion rate,
It is possible to obtain a glass joined body having a remarkably long life.

In the present invention, it is defined that the crystal precipitated at the interface is a crystal composed of the oxide component contained in the same composition as that of glass or ceramics or each composition. This is because, in the case of different crystals, the sodium resistance of the precipitated crystals is rather poor, and the pinning effect of corrosion may not be achieved.

The coefficient of thermal expansion of the precipitated crystals is
It is desirable that the value be the same as that of glass or ceramics, or an intermediate value. This is because if the value deviates from this value, the stress generated by the difference in thermal expansion may cause cracks in the joint. Further, the crystal grain size is preferably 50 μm or less, more preferably 20 μm or less. This is because when the grain size of the precipitated crystals increases to 50 μm or more, cracks easily run at the interface with the glass, leading to a decrease in the strength of the joint.

[0013]

EXAMPLE FIG. 1 shows an example of a glass joined body of the present invention.
It is a figure which shows an example of the state of the joint interface of a sodium-sulfur battery. In FIG. 1, 1 is a beta alumina tube, 2 is an alpha alumina insulator, and 3 is a bonding glass for bonding the beta alumina tube 1 and the alpha alumina insulator 2. A feature of the present invention is that crystals 4 are deposited on the interface between the beta alumina tube 1 and the bonding glass 3 and the interface between the alpha alumina insulator 2 and the bonding glass 3.

The composition of the crystal 4 is such that the bonding glass 3 or the beta alumina tube 1 or the alpha alumina insulator 2 is used.
And the oxide component contained in each composition. The coefficient of thermal expansion of the crystal 4 is not particularly limited, but is preferably the same as that of glass or ceramics, or an intermediate value. Further, the grain size of crystal 4, that is, the maximum length is not particularly limited, but is preferably 50 μm or less. Any method can be used as the manufacturing method as long as such a crystal 4 can be deposited at the bonding interface. In the example shown in FIG. 1, since there is the crystal 4, interface corrosion does not occur, and only surface corrosion 5 that does not pose a problem occurs.

An actual example will be described below. SiO ₂ ,
B ₂ O ₃ as the main component, other components are Al ₂ O ₃ , Na ₂ O, Ti
For borosilicate glasses A to H composed of a combination of several kinds of oxides in O ₂ and MgO, the following tests were carried out in order to investigate the corrosion resistance to sodium when used as a simple substance or a joined body.

First, the glass frits A to H of borosilicate glass were heat-treated in a platinum crucible under the same joining schedule as that for the maximum temperature of 1100 ° C. to obtain a single glass. A 3 x 4 x 5 mm sample is cut out from this and N ₂
After immersing in sodium at 400 ° C. in an atmosphere and removing sodium with methanol, the thickness of the surface discoloration layer was measured after 1000 hours. The thickness of the color-change layer was measured using an optical microscope after mirror polishing the cross section of the sample.

Next, as shown in FIG. 2, using the glass frit as the bonding glass 6, the α-alumina ring 7 and the beta-alumina disk 8 were bonded according to the bonding schedule of the maximum temperature of 1100 ° C. Then, the manufactured glass bonded body was immersed in sodium at 400 ° C in an N ₂ atmosphere, and
After taking out every 0 hours and removing sodium with methanol, the presence or absence of cracks was examined by fluorescent flaw detection. The test results are shown in Table 1 below. In Table 1, the grain size of the interfacial crystal was determined from the maximum length of the interfacial crystal.

[0018]

[Table 1]

From the results shown in Table 1, in the test Nos. 1 to 4 of the present invention, no cracks are generated for at least 1000 hours and the corrosion resistance is good, whereas in the test Nos. 5 to 8 of the comparative examples, all of them are shown.
It was found that cracks were generated by 1000 hours and the corrosion resistance was not sufficient. Further, as can be seen by comparing the present invention example and the comparative example, even if the corrosion rate of the glass simple substance does not change (for example, glass B and F), the glass bonded body in which crystals are precipitated at the interface has better corrosion resistance. Was found to show.

Analysis of samples in which cracks were observed at the joints revealed that cracks propagated from the corroded portion of the interface as the starting point. Furthermore, crystals were precipitated in the interface in the present invention example, was identified using an X-ray diffractometer, such _{2Al 2 O 3 · B 2 O} 3, 3MgO · B 2 O 3 or Al ₂ O _3, It was an oxide component contained in each composition of glass or ceramics, or a crystal composed of the same composition. From these test results, it was considered that the crystal at the interface was generated by the reaction between glass and ceramics.

[0021]

As is apparent from the above description, according to the present invention, the crystal deposited at the interface between glass and ceramics has a pinning effect against corrosion and acts so as not to cause interface corrosion. Therefore, the form of corrosion is only surface corrosion with a slow corrosion rate, and it is possible to obtain a glass joined body having a significantly long life.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a state of a bonding interface of a glass bonded body of the present invention.

FIG. 2 is a cross-sectional view of a test body used in an example of the present invention.

FIG. 3 is a diagram showing an example of a state of a bonding interface of a conventional glass bonded body.

[Explanation of symbols]

1 beta-alumina tube, 2 alpha-alumina insulator,
3 bonded glass, 4 crystal

Claims (4)

[Claims] 1. A crystal composed of the same component as glass or ceramics at the interface between glass and ceramics,
Alternatively, the glass bonded body is characterized in that crystals composed of oxide components contained in the respective compositions are precipitated. 2. The glass joined body according to claim 1, wherein the precipitated crystal has a thermal expansion coefficient which is the same as that of glass or ceramics, or in the middle thereof. 3. The glass joined body according to claim 1, wherein the crystal grain size is 50 μm or less. 4. The method for producing a glass joined body according to claim 1, wherein the crystal is precipitated at an interface between glass and ceramics. .