Joined glass, glass joined body, method for producing glass joined body, and method for inspecting glass joined body

Abstract

Provided is a joined glass for joining a beta-alumina solid electrolyte and an alpha-alumina insulator, the joined glass containing 29.0-38.0 mass% of SiO2, 14.0-22.0 mass% of Al2O3, 29.0-42.5 mass% of B2O3, 5.0-8.5 mass% of MgO, 2.5-6.5 mass% of Na2O, less than 0.20 mass% of Fe2O3, less than 0.25 mass% of CaO, less than 0.20 mass% of K2O, and less than 0.50 mass% of As2O3.

Description

Bonded glass, glass bonded body, manufacturing method of glass bonded body, and inspection method of glass bonded body

[0001] The present invention relates to a bonded glass, a glass bonded body, a method for manufacturing a glass bonded body, and a method for inspecting a glass bonded body.

[0002] A sodium-sulfur battery, for example, has a bottomed cylindrical part made of a solid electrolyte such as β-alumina placed inside a metal container on the positive electrode side, which serves as a storage case, with sodium as the negative electrode active material housed inside the bottomed cylindrical part and sulfur as the positive electrode active material housed outside. During discharge, sodium-sulfur batteries generate electricity as ionized sodium permeates the solid electrolyte and reacts with sulfur to produce sodium polysulfide, while charging is achieved by the reverse reaction, which produces sodium and sulfur.

[0003] In the manufacturing process of such sodium-sulfur batteries, the solid electrolyte, such as β-alumina, and the insulator, such as α-alumina, are bonded together using borosilicate glass or the like. The borosilicate glass used has been selected to have a linear expansion coefficient intermediate between that of the solid electrolyte and the insulator, taking into consideration mechanical strength, airtightness, corrosion resistance, and other properties, so as to prevent cracks from forming in the glass. However, even when such bonding glass is used, there is a problem in that the bonding strength between the solid electrolyte and the insulator is not sufficient.

[0004] Patent Document 1 describes the use of a bonding glass for forming a sodium-sulfur battery having a composition of 53.6 to 66.4 wt % of SiO, 7.0 to 15.5 wt % of AlO, 12.5 to 23.5 wt % of BO, and 8.0 to 14.1 wt % of NaO, in which the total amount of NaO and BO is 25 wt % or more.

[0005] Patent Document 2 describes that alumina borosilicate glass having four basic components, namely, SiO: 0-80%, AlO: 0-30%, BO: 0-80%, and NaO: 0-30% by weight, and glass solder having a linear expansion coefficient equal to or slightly smaller than those of a solid electrolyte tube and an insulating ring, is used as the joining glass of a glass joined body.

[0006] Patent No. 2619061 Patent No. 2693264

[0007] Glass used to bond a solid electrolyte and an insulator is required to have durability against expansion and contraction caused by temperature changes during charging and discharging, in addition to bonding strength, corrosion resistance, etc. The techniques described in Patent Documents 1 and 2 have achieved certain effects in terms of improving bonding strength, etc., but there is still room for improvement in order to obtain bonded glass that combines corrosion resistance and durability against expansion and contraction caused by temperature changes during charging and discharging.

[0008] In view of the above problems, the present invention provides a bonded glass, a glass bonded body, a method for manufacturing a glass bonded body, and a method for inspecting a glass bonded body, which have both corrosion resistance and durability against expansion and contraction caused by temperature changes during charging and discharging.

[0009] The present inventors have conducted extensive research to solve the above problems and have created the present invention, which is exemplified below.

[0010] [Aspect 1] In one embodiment, the present invention provides a bonding glass for bonding a β-alumina solid electrolyte and an α-alumina insulator, the bonding glass containing 29.0 to 38.0 mass% SiO2, 14.0 to 22.0 mass% Al2O3, 29.0 to 42.5 mass% BO3, 5.0 to 8.5 mass% MgO, 2.5 to 6.5 mass% Na2O, less than 0.20 mass% Fe2O3, less than 0.25 mass% CaO, less than 0.20 mass% KO, and less than 0.50 mass% As2O3. [Aspect 2] In another embodiment, the present invention provides the bonding glass according to Aspect 1, containing 0.10 mass% or more As2O3. [Aspect 3] In another embodiment, the present invention provides a bonding glass having a linear expansion coefficient at 0 to 300°C as defined in JIS R3102 (2005) of 3.0 to 7.0 x 10 -6 / °C. [Aspect 4] In yet another embodiment, the present invention is the bonded glass according to any one of Aspects 1 to 3, having a glass transition temperature of 480 to 640°C. [Aspect 5] In yet another embodiment, the present invention is the bonded glass according to any one of Aspects 1 to 4, having a glass softening temperature of 610 to 790°C. [Aspect 6] In yet another embodiment, the present invention provides a glass joined body, comprising an α-alumina insulating ring joined to an open end of a bottomed cylindrical β-alumina tube via a joining glass containing 29.0 to 38.0 mass% of SiO, 14.0 to 22.0 mass% of AlO, 29.0 to 42.5 mass% of BO, 5.0 to 8.5 mass% of MgO, 2.5 to 6.5 mass% of NaO, less than 0.20 mass% of FeO, less than 0.25 mass% of CaO, less than 0.20 mass% of KO, and less than 0.50 mass% of AsO. [Aspect 7] In yet another embodiment, the present invention is the glass joined body according to Aspect 6, wherein the insulating ring includes a base portion having a first inner diameter, a main joining portion coaxially connected to the base, the main joining portion having a second inner diameter larger than the first inner diameter, and an outer peripheral surface of the open end of the β-alumina tube joined to the inner peripheral surface thereof via a joining glass, a filling portion coaxially connected to the main joining portion, the filling portion having a third inner diameter larger than the second inner diameter, and an outer peripheral surface of the open end of the β-alumina tube joined to the inner peripheral surface thereof via the joining glass, and a β-tube standing surface between the main joining portion and the base, and the open end of the β-alumina tube is joined to the inner peripheral surface thereof via the joining glass. [Aspect 8] In yet another embodiment, the present invention is the glass joined body according to Aspect 7, wherein the inner peripheral surface of the main joining portion has a polygonal shape when observed from a direction parallel to the axial direction, and the β-tube standing surface has a plurality of protrusions arranged along a circumferential direction.[Aspect 9] In yet another embodiment, the present invention is a method for manufacturing a glass joined body, comprising joining a bottomed cylindrical β-alumina tube and an α-alumina insulating ring via a joining glass, the method comprising: heating the joining glass, containing 29.0 to 38.0 mass% of SiO, 14.0 to 22.0 mass% of AlO, 29.0 to 42.5 mass% of BO, 5.0 to 8.5 mass% of MgO, 2.5 to 6.5 mass% of NaO, less than 0.20 mass% of FeO, less than 0.25 mass% of CaO, less than 0.20 mass% of KO, and less than 0.50 mass% of AsO, between the β-alumina tube and the insulating ring, to a glass softening point of the joining glass or higher, and then cooling the joining glass. Aspect 10 In yet another embodiment, the present invention provides the method for producing a glass bonded body according to Aspect 9, wherein the bonding step includes a heating step of heating the bonded glass from room temperature to a maximum temperature range of 1100 to 1160°C; a holding step of holding the heated bonded glass in the maximum temperature range for 10 minutes or more; a first cooling step of cooling the held bonded glass to 500 to 600°C; an annealing step of annealing the cooled bonded glass at 500 to 600°C for 25 minutes or more; and a second cooling step of cooling the annealed bonded glass to room temperature. [Aspect 11] In yet another embodiment, the present invention is the method for producing a glass bonded body according to Aspect 9 or 10, wherein the insulating ring includes a base portion having a first inner diameter, a main bonding portion coaxially connected to the base and having a second inner diameter larger than the first inner diameter, a filling portion coaxially connected to the main bonding portion and having a third inner diameter larger than the second inner diameter, and a β-tube standing surface between the main bonding portion and the base, wherein the bonding step is performed after accommodating the β-alumina tube in the insulating ring such that the open end of the β-alumina tube abuts on the β-tube standing surface facing downward and accommodating the bonding glass in the filling portion. [Aspect 12] In yet another embodiment, the present invention is the method for producing a glass bonded body according to Aspect 11, wherein the inner peripheral surface of the main bonding portion has a polygonal shape when observed from a direction parallel to the axial direction, and the β-tube standing surface has a plurality of protrusions arranged along a circumferential direction.[Aspect 13] In yet another embodiment, the present invention provides a method for inspecting a glass bonded body manufactured by the method for manufacturing a glass bonded body according to Aspect 11 or 12, the method including: measuring a first amount of exudation of bonding glass exuding from an end face of an open end of the β-alumina tube onto an inner peripheral surface of a base portion of the insulating ring in an axial direction of the insulating ring; measuring a second amount of exudation of bonding glass exuding from an end of a filling portion of the insulating ring onto an outer peripheral surface of the open end of the β-alumina tube in the axial direction of the insulating ring; and determining whether a bonding state between the β-alumina tube and the insulating ring is good or bad based on the measurement results of the first and second exudation amounts. [Aspect 14] In yet another embodiment, the present invention provides a method for inspecting a glass bonded body produced by the method for producing a glass bonded body according to any one of Aspects 9 to 12, the method including: capturing an image of an exterior surface of the β-alumina tube with an imaging device, and measuring by image processing whether or not there is a defect in appearance of the β-alumina tube, including chips, cracks, scratches, dirt, or attachments; capturing an image of an exterior surface of the insulating ring with the imaging device, and measuring by image processing whether or not there is a defect in appearance of the insulating ring, including chips, cracks, scratches, dirt, or attachments; capturing an image of an exterior surface of the bonded glass with the imaging device, and measuring by image processing whether or not there is a defect in appearance of the bonded glass, including voids, cracks, scratches, dirt, or attachments; and determining whether or not the glass bonded body is passable based on the measurement results of the defects in appearance of the β-alumina tube, the insulating ring, and the bonded glass. [Aspect 15] In yet another embodiment, the present invention provides a method for inspecting a glass bonded body, including, before producing the glass bonded body according to Aspect 6, a quality inspection step of inspecting whether or not a sintered density, a maximum particle size, a strength, an outer diameter, a roundness, and a straightness of a β-alumina tube satisfy control values.

[0011] According to the present invention, it is possible to provide a bonded glass, a glass bonded body, a method for manufacturing a glass bonded body, and a method for inspecting a glass bonded body, which have both corrosion resistance and durability against expansion and contraction caused by temperature changes during charging and discharging.

[0012] FIG. 1( a) is a schematic cross-sectional view illustrating a glass bonded body according to one embodiment of the present invention, FIG. 1( b) is a schematic cross-sectional view illustrating an insulating ring, and FIG. 1( c) is a schematic perspective view further illustrating the structure of a base portion and a main bonding portion of the insulating ring. FIG. 2( a) is a schematic view illustrating a continuous annealing furnace, and FIG. 2( b) is a graph showing an example of a heat curve in the continuous annealing furnace. FIG. 3( a) is a schematic view illustrating the assembly of a glass bonded body to be introduced into a continuous annealing furnace, and FIG. 3( b) is a cross-sectional view thereof. FIG. 4 is a schematic view illustrating an inspection device for a glass bonded body according to one embodiment of the present invention. FIG. 5( a) is a schematic cross-sectional view illustrating a method for measuring a first oozing amount and a second oozing amount of bonded glass. FIG. 5( b) is a photograph showing a measurement example of a first oozing amount E1, and FIG. 5( c) is a photograph showing a measurement example of a second oozing amount E2. FIG. 6 is a schematic view illustrating an inspection device for a glass bonded body according to another embodiment of the present invention. FIG. 7 is a photograph showing an example of voids (air bubbles) formed in the bonded glass.

[0013] (Bonding Glass) A bonding glass according to an embodiment of the present invention is suitable for bonding a β-alumina solid electrolyte to an α-alumina insulator in a sodium-sulfur battery. This bonding glass contains 29.0 to 38.0 mass% of SiO, 14.0 to 22.0 mass% of AlO, 29.0 to 42.5 mass% of BO, 5.0 to 8.5 mass% of MgO, 2.5 to 6.5 mass% of NaO, less than 0.20 mass% of FeO, less than 0.25 mass% of CaO, less than 0.20 mass% of KO, and less than 0.50 mass% of AsO.

[0014] If the SiO2 content is less than 29.0% by mass, the linear expansion coefficient of the bonded glass will be small and the bonding residual stress will be large, which may result in cracking. On the other hand, if the SiO2 content exceeds 38.0% by mass, corrosion by Na will occur, deteriorating corrosion resistance, reducing bonding strength and making it difficult to achieve the desired durability. The SiO2 content is preferably 29.5 to 37.0% by mass, more preferably 30.0 to 36.5% by mass, even more preferably 32.0 to 35.0% by mass, and even more preferably 33.0 to 35.0% by mass.

[0015] If the Al2O3 content exceeds 22.0% by mass, crystallization occurs, making the glass more susceptible to cracking. Furthermore, the glass softening temperature increases, making it difficult to achieve high workability. On the other hand, if the Al2O3 content is less than 14.0% by mass, the softening temperature decreases, resulting in poor corrosion resistance. The Al2O3 content is preferably 14.0 to 21.5% by mass, more preferably 14.5 to 21.0% by mass, even more preferably 16.5 to 20.5% by mass, and even more preferably 18.0 to 20.0% by mass.

[0016] BO is a substance added to adjust the glass softening temperature without changing the linear expansion coefficient or durability. If the BO content exceeds 42.5% by mass, the glass softening temperature decreases, which can lead to poor corrosion resistance. On the other hand, if the BO content is less than 29.0% by mass, the glass softening temperature increases, which can prevent high workability. The BO content is preferably 30.0 to 41.5% by mass, more preferably 31.5 to 40.5% by mass, even more preferably 34.0 to 37.5% by mass, and even more preferably 35.0 to 36.5% by mass.

[0017] If the MgO content exceeds 8.5% by mass, the linear expansion coefficient of the bonding glass will not fall within an appropriate range, and crystallization may occur during bonding, making cracks more likely to occur. On the other hand, if the MgO content is less than 5.0% by mass, durability may decrease. The MgO content is preferably 5.2 to 8.4% by mass, more preferably 5.5 to 8.3% by mass, and even more preferably 5.8 to 7.0% by mass.

[0018] If the Na2O content exceeds 6.5 mass%, the linear expansion coefficient of the bonding glass will not fall within an appropriate range, and crystallization may occur during bonding, making cracks more likely to occur. On the other hand, if the Na2O content is less than 2.5 mass%, the glass softening temperature may decrease, resulting in reduced durability. The Na2O content is preferably 2.7 to 6.4 mass%, more preferably 3.0 to 6.3 mass%, even more preferably 3.5 to 5.0 mass%, and even more preferably 3.7 to 4.8 mass%.

[0019] The bonding glass according to the embodiment of the present invention contains FeO, CaO, KO, and AsO as impurities, and the content of these impurities is small. In particular, since residual bubbles in the bonding glass reduce the bonding strength, the bonding glass according to the present embodiment preferably contains AsO, which contains a trace amount of arsenic, as a defoaming element.

[0020] The As2O3 content is less than 0.50 mass%, preferably less than 0.45 mass%, more preferably less than 0.40 mass%, and even more preferably less than 0.35 mass%.The As2O3 content is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, even more preferably 0.10 mass% or more, and still more preferably 0.20 mass% or more.

[0021] Fe2O3 is less than 0.20% by weight, preferably less than 0.15% by weight, and more preferably less than 0.10% by weight. CaO is less than 0.25% by weight, preferably less than 0.20% by weight, and more preferably less than 0.15% by weight. KO is less than 0.20% by weight, preferably less than 0.15% by weight, and more preferably less than 0.10% by weight.

[0022] The bonding glass according to the embodiment of the present invention is a ternary system, and the specific concentrations of the components constituting the bonding glass can be changed appropriately within the above-mentioned ranges depending on the linear expansion coefficient, glass transition temperature, and glass softening temperature required for the bonding glass. In addition, in this specification, the concentrations of the components constituting the bonding glass are measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES).

[0023] The bonding glass according to the embodiment of the present invention having the above-described composition has a linear expansion coefficient of 3.0 to 7.0 × 10 at 0 to 300°C as specified in JIS R3102 (1995). -6 / °C. The linear expansion coefficient is 3.5 to 6.5 × 10 -6 / °C, and 4.0 to 6.0 × 10 -6 / °C is more preferable.

[0024] The bonding glass according to an embodiment of the present invention has a glass transition temperature of 480 to 640 °C. The glass transition temperature is preferably 490 to 630 °C, more preferably 500 to 620 °C, and still more preferably 520 to 600 °C. Further, the bonding glass according to an embodiment of the present invention has a glass softening temperature of 610 to 790 °C. The glass softening temperature is preferably 620 to 780 °C, more preferably 630 to 770 °C, and still more preferably 650 to 750 °C. In this specification, the glass transition temperature refers to the glass transition temperature and the glass softening temperature measured based on JIS R3103-3 (2001), and the glass softening temperature refers to the glass transition temperature and the glass softening temperature measured based on JIS R3103-1 (2001).

[0025] According to an embodiment of the present invention, SiO2, which is easily affected by the corrosion of Na, is made relatively small at about 29.0 to 38.0% by mass, Al2O3 is 14.0 to 22.0% by mass, and Na2O is 2.5 to 6.5% by mass and MgO is 5.0 to 8.5% by mass as components necessary to satisfy the above linear expansion coefficient, and B2O3 is contained at 29.0 to 42.5% by mass, and by adjusting the content of impurities to less than a predetermined value, a bonding glass having excellent bonding strength, corrosion resistance and durability for bonding a β-alumina solid electrolyte and an α-alumina insulator can be provided.

[0026] (Glass bonded body) By using the above bonding glass, a glass bonded body 10 as shown in Fig. 1(a) in which a β-alumina tube 1 disposed in a sodium-sulfur battery and an α-alumina insulating ring 2 are bonded to each other can be manufactured. That is, according to an embodiment of the present invention, on the open end of a bottomed cylindrical β-alumina tube 1, a bonding glass 3 containing 29.0 to 38.0% by mass of SiO2, 14.0 to 22.0% by mass of Al2O3, 29.0 to 42.5% by mass of B2O3, 5.0 to 8.5% by mass of MgO, 2.5 to 6.5% by mass of Na2O, less than 0.20% by mass of Fe2O3, less than 0.25% by mass of CaO, less than 0.20% by mass of K2O, and less than 0.50% by mass of As2O3 is used to bond an α-alumina insulating ring 2, and a glass bonded body 10 is obtained.

[0027] As the material for the β-alumina tube 1, one or both of β-alumina and β″-alumina are preferably used. As shown in FIGS. 1( a) and 1(b), the insulating ring 2 includes: a base portion 21 having a first inner diameter D1; a main joining portion 22 coaxially connected to the base portion 21, the main joining portion 22 having a second inner diameter D2 larger than the first inner diameter D1, and the open end outer peripheral surface 11 of the β-alumina tube 1 being joined to an inner peripheral surface 222 thereof via a joining glass 3; a filling portion 23 coaxially connected to the main joining portion 22, the filling portion 23 having a third inner diameter D3 larger than the second inner diameter D2, and the open end outer peripheral surface 11 of the β-alumina tube 1 being joined to an inner peripheral surface 232 thereof via the joining glass 3; and a β-tube standing surface 211 between the main joining portion 22 and the base portion 21, to which the open end surface 12 of the β-alumina tube 1 is joined via the joining glass 3.

[0028] As shown in FIG. 1( c), the inner peripheral surface 222 of the main joint portion 22 preferably has a polygonal shape when viewed from a direction parallel to the axial direction of the insulating ring 2 (plan view). Forming such an inner peripheral surface 222 in the main joint portion 22 forms a certain gap between the open end outer peripheral surface 11 of the β-alumina tube 1 and the inner peripheral surface 222 of the main joint portion 22. Therefore, when joining the β-alumina tube 1 and the insulating ring 2, the joining glass 3 is heated and melted, and enters these gaps, thereby improving the connection strength between the β-alumina tube 1 and the insulating ring 2. The number of flat or curved surfaces formed on the inner peripheral surface 222 may be appropriately determined depending on the expected joining strength, etc. Although not shown, the inner peripheral surface 232 of the filling portion 23 may also have a plurality of flat or curved surfaces that are continuous with each other, similar to the inner peripheral surface 222 of the main joint portion 22.

[0029] The β-tube standing surface 211 has a plurality of protrusions 213 arranged along its circumferential direction. Because the plurality of protrusions 213 are formed on the β-tube standing surface 211 of the main joint portion 22 in this manner, when the β-alumina tube 1 and the insulating ring 2 are joined, the joining glass 3 is heated and melted, and enters these gaps. This allows the joining glass 3 to be more reliably disposed over the entire circumferential direction between the open end face 12 of the β-alumina tube 1 and the β-tube standing surface 211, thereby further improving the connection strength. The number of the plurality of protrusions 213 formed on the β-tube standing surface 211 may be determined appropriately depending on the expected joining strength, etc.

[0030] The joining glass 3 used to join the β-alumina tube 1 and the insulating ring 2 may be in powder form or may be formed into a predetermined shape in advance. In one embodiment, a molded body of the joining glass 3 formed into a ring shape in advance is used to join the β-alumina tube 1 and the insulating ring 2. This eliminates the need for weighing, unlike the case where a powdered joining glass 3 is used, thereby improving processing efficiency. Furthermore, the use of the molded body of the joining glass 3 improves the handleability of the joining glass 3, thereby improving workability during joining.

[0031] (Method for Manufacturing Glass Joined Body) A method for manufacturing a glass joined body 10 in which a β-alumina tube 1 and an insulating ring 2 are joined together via a joining glass 3 includes a joining step of heating the joining glass 3 having the above-described composition between the β-alumina tube 1 and the insulating ring 2 to a temperature equal to or higher than the glass softening point of the joining glass 3, and then cooling the joining glass 3.

[0032] This bonding process can include a heating process of heating the bonding glass 3 from room temperature to a maximum temperature range of 1100 to 1160°C, a holding process of holding the heated bonding glass 3 at the maximum temperature range for 10 minutes or more, a first cooling process of cooling the held bonding glass 3 to 500 to 600°C, an annealing process of annealing the cooled bonding glass 3 at 500 to 600°C for 25 minutes or more, and a second cooling process of cooling the annealed bonding glass 3 to room temperature.

[0033] The joining step can be performed using, for example, a continuous annealing furnace 4 as shown in Fig. 2(a) . The continuous annealing furnace 4 includes a high-temperature section 41 provided with a heater for raising the temperature of the workpiece W, a first cooling section 42 for cooling the workpiece W heated in the high-temperature section 41, an annealing section 43 provided with a heater for annealing the workpiece W cooled in the first cooling section 42 at a predetermined temperature, and a second cooling section 44 for cooling the workpiece W after annealing.

[0034] In joining the β-alumina tube 1 and the insulating ring 2 using such a continuous annealing furnace 4, the workpiece W, which is assembled in a predetermined order from the β-alumina tube 1, the insulating ring 2, and the bonding glass 3, is continuously heated in the high-temperature section 41 until it reaches a maximum temperature range of 1100 to 1160°C, preferably 1120 to 1160°C, and more preferably 1125 to 1150°C, as shown in the heat curve of FIG. 2(b). In the high-temperature section 41, the heating rate of the workpiece W is set to 500°C / hr or more, more preferably 600°C / hr or more, and even more preferably 700°C / hr or more, thereby shortening the bonding process time. In the latter stage of the high-temperature section 41, the workpiece W after heating is held in the maximum temperature range for 10 minutes or more, more preferably 20 minutes or more. Holding the workpiece W in the maximum temperature range for 10 minutes or more ensures sufficient melting of the bonding glass 3, thereby improving the corrosion resistance of the bonded β-alumina tube 1 and the insulating ring 2. In the first cooling section 42, the workpiece W is cooled from its maximum temperature to 500 to 600°C. In the annealing section 43, the workpiece W transferred from the first cooling section 42 is annealed at 500 to 600°C, preferably 550 to 600°C, more preferably 570 to 590°C, for 25 minutes or more, more preferably 30 minutes or more, and even more preferably 40 minutes or more. By sufficiently annealing the workpiece W in this manner, distortion in the bonded glass 3 is sufficiently removed and a predetermined crystalline structure is formed. Thereafter, the workpiece W is cooled to room temperature in the second cooling section 44, thereby obtaining a glass bonded body 10 having excellent bonding strength, corrosion resistance, and durability.

[0035] In order to obtain a glass bonded body 10 having sufficient bonding strength, corrosion resistance, and durability, it is important to control the temperature in the bonding process and the temperature of the atmosphere in the furnace. For example, a thermometer may be attached to a conveying means (not shown) that introduces and conveys the workpieces W into the continuous annealing furnace 4. Then, when the workpieces W move through the continuous annealing furnace 4, the temperature of the atmosphere in the furnace can be measured by the thermometer attached to the conveying means. The continuous annealing furnace 4 may be equipped with a management device 45 that manages whether the workpieces W are always treated at an appropriate temperature based on the measurement result of the temperature of the atmosphere in the furnace. A memory-type thermometer is preferably used as the thermometer attached to the conveying means that conveys the workpieces W into the continuous annealing furnace 4. As the memory-type thermometer, for example, a thermometer that measures the temperature based on the voltage generated by a thermocouple and a data logger that can store the temperature measured by the thermometer in association with time is used.

[0036] (Assembly of Glass Joint) FIG. 3( a) is a schematic diagram illustrating the assembly of a glass joined body 10, which is used as a workpiece W to be introduced into a continuous annealing furnace 4 and includes a β-alumina tube 1, an insulating ring 2, and a joining glass 3. FIG. 3( b) is a cross-sectional view thereof. The glass joined body 10 is assembled by placing the β-alumina tube 1 in the insulating ring 2 so that the open end surface 12 of the β-alumina tube 1 faces downward and abuts against the β-tube standing surface 211 of the insulating ring 2, and placing the joining glass 3 in the filling portion 23 of the insulating ring 2. A protective cover 6 is disposed on the open end outer peripheral surface 11 of the β-alumina tube 1 and on the filling portion 23 of the insulating ring 2 to prevent evaporation of components such as Na from the joining glass 3. Taking into account deformation of the insulating ring 2 due to differences in linear expansion coefficients, the protective cover 6 is preferably formed of the same material as the insulating ring 2, such as α-alumina. The assembly of the workpiece W can be performed by automated assembly.

[0037] 4 is an inspection device 7 for determining whether the bonding state of the bonded glass 3 of the glass bonded body 10 manufactured by the above-described method for manufacturing the glass bonded body 10 is good or bad. The inspection device 7 may include a first imaging device 8 a, a second imaging device 8 b, a calculation unit 70, a storage device 76, an input unit 77 a, and an output unit 77 b.

[0038] The first imaging device 8a is a device for imaging the state of the bonding glass 3 seeping from the open end surface 12 of the β-alumina tube 1 to the inner circumferential surface 212 of the base portion 21 of the insulating ring 2 along the circumferential direction of the β-alumina tube 1. The second imaging device 8b is a device for imaging the state of the bonding glass 3 seeping from the filling portion 23 of the insulating ring 2 to the open end outer circumferential surface 11 of the β-alumina tube 1 along the circumferential direction of the β-alumina tube 1. The first imaging device 8a and the second imaging device 8b can be composed of a camera, a video camera, lighting, a light source, etc. The glass bonded body 10 is supported by a rotation drive mechanism (not shown) that can rotate the glass bonded body 10 about its axis. Furthermore, it is preferable that the first imaging device 8a and the second imaging device 8b image the amount of seepage of the bonding glass 3 along the circumferential direction of the β-alumina tube 1. The images acquired by the first imaging device 8a and the second imaging device 8b may be still images or videos. The first imaging device 8 a and the second imaging device 8 b are output to the calculation unit 70 .

[0039] The calculation unit 70 can be configured with a central processing unit (CPU) or microprocessor (MPU) of a computer that can perform various calculations in response to predetermined inputs and output the calculation results. The storage device 76 is configured with a memory or the like for storing the calculation results by the calculation unit 70, analysis information necessary for the calculation processing of the calculation unit 70, and setting values ​​such as inspection standards for pass / fail judgment of the inspection device 7 according to the embodiment of the present invention. The input unit 77a includes a mouse, keyboard, etc. for accepting input of various information, setting values, etc. by an operator. The output unit 77b includes a display unit or the like for outputting the calculation results by the calculation unit 70 to the operator.

[0040] The calculation unit 70 includes a first seepage amount measuring unit 71 that measures a first seepage amount E1 (see FIGS. 5( a) and 5(b)) of the bonding glass 3 that seeps from the open end face 12 of the β-alumina tube 1 to the inner peripheral surface 212 of the base 21 of the insulating ring 2 in the axial direction of the insulating ring 2, a second seepage amount measuring unit 72 that measures a second seepage amount E2 (see FIGS. 5(a) and 5(c)) of the bonding glass 3 that seeps from the end 23 a of the filling portion 23 of the insulating ring 2 to the open end outer peripheral surface of the β-alumina tube 1 in the axial direction of the insulating ring 2, a determination unit 78 that determines whether the first seepage amount E1 and the second seepage amount E2 satisfy the inspection standard, and a warning unit 79 that can warn an operator of the occurrence of a defective product based on the determination result of the determination unit 78.

[0041] The first seepage amount measuring unit 71 acquires the image output by the first imaging device 8a and performs predetermined image processing to measure a first seepage amount E1 of the bonding glass 3 seeping out from the open end surface 12 of the β-alumina tube 1 in the axial direction of the insulating ring 2. The second seepage amount measuring unit 72 acquires the image output by the second imaging device 8b and performs predetermined image processing to measure a second seepage amount E2 of the bonding glass 3 seeping out from the end 23a of the filling portion 23 of the insulating ring 2 onto the open end outer peripheral surface 11 of the β-alumina tube 1 in the axial direction of the insulating ring 2.

[0042] 5(b) and 5(b), the portion where the bonding glass 3 has exuded is glossier than the surrounding area. The first exudation amount measuring unit 71 measures the shortest distance between a boundary p1 of this glossy portion and the open end surface 12 of the β-alumina tube 1 as a first exudation amount E1. The second exudation amount measuring unit 72 measures the shortest distance between a boundary p2 of this glossy portion and the end 23a of the filling portion 23 of the insulating ring 2 as a second exudation amount E2.

[0043] The determination unit 78 determines whether the first and second exudation amounts E1 and E2 measured by the first and second exudation amount measuring units 71 and 72 satisfy an inspection standard. The inspection standard can be appropriately selected depending on the shape and dimensions of the glass bonded body 10. In one embodiment, the inspection standard for the first exudation amount E1 is 0.1 to 10.0 mm, preferably 0.2 to 9.0 mm, and more preferably 0.5 to 8.0 mm. In one embodiment, the inspection standard for the second exudation amount E2 is 0.05 to 5.0 mm, preferably 0.1 to 4.0 mm, and more preferably 0.1 to 3.0 mm. The determination unit 78 determines whether the connection state of the glass bonded body 10 is good or bad based on whether the first and second exudation amounts E1 and E2 satisfy the inspection standard, thereby more appropriately confirming whether the bonded glass 3 is properly bonded to the β-alumina tube 1 and the insulating ring 2.

[0044] The determination unit 78 determines a glass bonded body 10 whose first exudation amount E1 and second exudation amount E2 do not satisfy the inspection standard as a defective product. The warning unit 79 can warn an operator of the occurrence of a defective product when the determination unit 78 determines that a specific glass bonded body 10 does not satisfy the inspection standard and is a defective product. The warning method is arbitrary. For example, the warning unit 79 may display various information such as the lot number and serial number of the glass bonded body 10 determined to be a defective product on the output unit 77b. Alternatively, the warning unit 79 may generate a sound, light, or the like via the output unit 77b to notify the operator of the occurrence of a defective product.

[0045] An inspection method for a glass bonded body 10 according to an embodiment of the present invention can be carried out using an inspection device 7 according to an embodiment of the present invention. The inspection method according to the embodiment includes measuring a first amount E1 of the bonding glass 3 that has leaked from the open end face 12 of the β-alumina tube 1 onto the inner peripheral surface 212 of the base portion 21 of the insulating ring 2 in the axial direction of the insulating ring 2, measuring a second amount E1 of the bonding glass 3 that has leaked from the end 23 a of the filling portion 23 of the insulating ring 2 onto the open end outer peripheral surface 11 of the β-alumina tube 1 in the axial direction of the insulating ring 2, and determining whether the bonding state between the β-alumina tube 1 and the insulating ring 2 is good or bad based on the measurement results of the first and second amounts of leakage.

[0046] The inspection of the glass bonded body 10 preferably includes various other inspections in addition to inspecting the first and second seepage amounts E1 and E2 of the bonded glass 3 between the β-alumina tube 1 and the insulating ring 2 as shown in Fig. 4. The inspection device 7 shown in Fig. 6 may include a plurality of first to seventh imaging devices 8a to 8g for inspecting the appearance of the glass bonded body 10. The calculation unit 70 may further include a β-alumina tube quality measurement unit 73, an insulating ring quality measurement unit 74, and a bonded glass quality measurement unit 75.

[0047] The third imaging device 8c is an imaging device for imaging the exterior surface near the open end of the β-alumina tube 1. Images acquired by the third imaging device 8c can be used to analyze the presence or absence of chips, cracks, scratches, dirt, and attachments on the open end of the β-alumina tube 1. The fourth imaging device 8d is an imaging device for imaging the exterior surface of the insulating ring 2. Images acquired by the fourth imaging device 8d can be used to analyze the presence or absence of chips, cracks, scratches, dirt, and attachments on the insulating ring 2. The fifth imaging device 8e is an imaging device for imaging the exterior surface of the central outer peripheral surface of the β-alumina tube 1. Images acquired by the fifth imaging device 8e can be used to analyze the presence or absence of chips, cracks, scratches, dirt, and attachments on the open end outer peripheral surface 11 of the β-alumina tube 1. The sixth imaging device 8f is an imaging device for imaging the exterior surface of the bonding glass 3 between the β-alumina tube 1 and the insulating ring 2. The images acquired by the sixth imaging device 8f can be used to analyze the presence or absence of voids, cracks, scratches, dirt, and attachments in the bonded glass 3. The seventh imaging device 8g is an imaging device for imaging the exterior surface of the tube bottom 13 of the β-alumina tube 1. The images acquired by the seventh imaging device 8g can be used to analyze the presence or absence of chips, cracks, scratches, dirt, and attachments in the tube bottom 13 of the β-alumina tube 1. The first imaging device 8a and the second imaging device 8b have the same configuration as the inspection device 7 shown in FIG. 4. The third to seventh imaging devices 8c to 8g can be configured with a camera, a video camera, lighting, a light source, etc. Furthermore, each of the first to seventh imaging devices 8a to 8g may include multiple imaging devices.

[0048] The β-alumina tube quality measurement unit 73 acquires images output by the third imaging device 8c, the fifth imaging device 8e, and the seventh imaging device 8g, and measures the presence or absence of chips, cracks, scratches, dirt, and attachments in the β-alumina tube 1 through image processing. The insulating ring quality measurement unit 74 acquires images output by the fourth imaging device 8d, and measures the presence or absence of chips, cracks, scratches, dirt, and attachments in the insulating ring 2 through image processing. The bonded glass quality measurement unit 75 acquires images output by the sixth imaging device 8f, and measures the presence or absence of voids, cracks, scratches, dirt, and attachments in the bonded glass 3 through image processing.

[0049] FIG. 7 is a photograph showing an example of voids (air bubbles) formed in the bonded glass 3. The voids in the bonded glass 3 may be caused by foreign matter attached to the insulating ring 2 or the β-alumina tube 1. Large voids with a dimension φ may cause deterioration in the corrosion resistance of the bonded glass 3 and its durability against expansion and contraction due to temperature changes during charging and discharging. For example, in a glass bonded body in which voids with a length φ of 0.5 mm or more exist in the bonded glass 3, breakage of the bonded portion of the bonded glass 3 is likely to occur from the voids when the temperature difference between the positive and negative electrodes exceeds 150°C. The bonded glass quality measuring unit 75 preferably detects voids with a dimension φ of more than 0.5 mm or φ of more than 1.0 mm by image analysis from images captured by the sixth imaging device 8f along the circumferential direction of the bonded glass 3.

[0050] The determining unit 78 determines whether the glass bonded body 10 is good or bad based on the results of the measurement of appearance defects of the β-alumina tube 1, the insulating ring 2, and the bonded glass 3. For example, the determining unit 78 determines the bonded glass 3 as defective when a void having a dimension φ of 0.5 mm or more is detected in the bonded glass 3. The dimension φ of the void refers to the maximum diameter of a void formed in the bonded glass 3. The warning unit 79 warns the operator, as necessary, via the output unit 77b of the occurrence of a defective glass bonded body comprising the β-alumina tube 1, the insulating ring 2, and the bonded glass 3.

[0051] To facilitate quality assessment during visual inspection of the β-alumina tube 1, it is preferable to apply a colored (red) penetrant to the β-alumina tube 1. A red penetrant liquid or the like is used as the penetrant. It is preferable to include a quality inspection step in which the sintered density, maximum grain size, strength, outer diameter, roundness, and straightness of the β-alumina tube 1 are inspected to determine whether they satisfy the respective control values ​​before fabricating the glass bonded body 10 inspected by the inspection device 7 shown in FIG. 6 . The sintered density of the β-alumina tube 1 is measured by the Archimedes method using an electronic balance. The maximum grain size of the β-alumina tube 1 is measured using an optical microscope and an electron microscope. The strength of the β-alumina tube 1 is measured using an internal hydrostatic pressure testing device. The outer diameter of the β-alumina tube 1 is measured using a vernier caliper, a micrometer, and a laser measuring instrument. The roundness of the β-alumina tube 1 is measured by calculating the outer diameter measurement results. The straightness of the β-alumina tube 1 is measured by calculating the outer diameter measurement result and a measurement value measured by a gauge provided in the rotation mechanism of the inspection device.

[0052] According to the inspection method of the embodiment of the present invention, various inspections are performed on the glass bonded body 10 bonded with the bonding glass 3 having the above-mentioned bonding strength, corrosion resistance, and durability, thereby making it possible to provide a glass bonded body 10 with higher bonding reliability.

[0053] A glass joined body was produced by joining an α-alumina insulating ring to the open end of a bottomed cylindrical β-alumina tube via a joining glass (Examples 1 to 3) containing SiO, AlO, BO, MgO, NaO, FeO, CaO, KO, and AsO adjusted to the composition (mass %) shown in Table 1. As shown in Figures 1(a) to 1(c), the insulating ring had a polygonal (36-sided) inner circumferential surface when observed from a direction parallel to the axial direction, and was formed to have a convex portion on the upright surface of the β-alumina tube. This insulating ring was placed at the open end of the β-alumina tube, and the joining glass interposed between the insulating ring and the β-alumina tube was melted in a continuous annealing furnace to join the β-alumina tube and the insulating ring, thereby producing a glass joined body using the joining glass of Examples 1 to 3. In addition, in all of the produced glass bonded bodies using the bonding glasses of Examples 1 to 3, the first amount of the bonding glass that exuded onto the inner peripheral surface of the base of the insulating ring in the axial direction of the insulating ring was within a suitable range of 0.1 to 10.0 mm, and the second amount of the bonding glass that exuded onto the outer peripheral surface of the β-alumina tube in the axial direction of the insulating ring was within a suitable range of 0.05 to 5.0 mm.

[0054]

[0055] Sodium-sulfur batteries (cells) were fabricated using the glass joined bodies of Examples 1 to 3, and 10 sodium-sulfur battery modules containing 192 cells were fabricated. These sodium-sulfur battery modules were subjected to room-temperature inspections, including an appearance inspection, a wiring electrical continuity inspection, and confirmation of insulation and vacuum conditions. After the room-temperature inspection, the battery was heated to 300 to 340°C, the operating temperature of the battery. After the temperature increase, a module temperature increase / decrease test was conducted, in which the battery was cooled to room temperature after repeated charge / discharge. The sodium-sulfur battery module module temperature increase / decrease test was conducted 10 times, and the number of glass joined bodies containing cracks was evaluated by observing the joined glass portions of the sodium-sulfur battery modules after the 10 temperature increase / decrease treatments using a CCD camera.

[0056] In Example 1, cracks occurred in 0 pieces (0 pieces out of 1920 pieces) after 10 module temperature rise and fall tests, while in Example 2 (1 piece out of 1920 pieces) and in Example 3 (2 pieces out of 1920 pieces) respectively. That is, it is clear that Examples 1 to 3 provide bonding glass that has both corrosion resistance and durability against expansion and contraction due to temperature changes during charge and discharge.

[0057] <Effect of As2O3 Addition on the Generation of Residual Bubbles in Bonded Glass> Glass bonded bodies similar to those of Example 1 were fabricated using the bonded glasses of Examples 4 to 6, in which the As2O3 concentration (mass %) of the bonded glass of Example 1 was adjusted to the composition shown in Table 2. A light source was shone on the bonded glass portion between the insulating ring and the β-alumina tube of the fabricated glass bonded body, and images of the bonded glass were captured around the circumference using a CCD camera. The captured images were analyzed to confirm the presence or absence of bubbles in the bonded glass. If bubbles were detected in the bonded glass, the bubble size φ was measured. The size φ was defined as the maximum diameter of the bubble. Twenty thousand glass bonded bodies were measured, and the percentage of glass bonded bodies with bubbles exceeding φ1.0 mm and bubbles exceeding φ0.5 mm was evaluated. Note that "bubble concentration" in Table 2 refers to the percentage of glass bonded bodies with bubbles with bubble connections exceeding 0.5 mm among the 20,000 glass bonded bodies.

[0058]

[0059] The rate of bubble generation was very low in all of the glass bonded bodies of Examples 4 to 6. As shown in Table 2, the bonded glass containing 0.10 mass% or more of As2O3 generated even fewer bubbles than the glass containing no As2O3. It can also be seen that the bonded glass containing 0.20 mass% of As2O3 suppressed bubble generation more significantly than the bonded glass containing 0.10 mass% of As2O3.

[0060] REFERENCE SIGNS LIST 1: β-alumina tube 2: Insulating ring 3: Bonded glass 4: Continuous annealing furnace 6: Protective cover 7: Inspection device 8a: First imaging device 8b: Second imaging device 8c: Third imaging device 8d: Fourth imaging device 8e: Fifth imaging device 8f: Sixth imaging device 8g: Seventh imaging device 10: Glass bonded body 11: Opening end outer peripheral surface 12: Opening end end surface 13: Tube bottom 21: Base 22: Main bonding portion 23: Filling portion 41: High temperature portion 42: First cooling portion 43: Annealing portion 44: Second cooling portion 45: Management device 70: Calculation portion 71: First seepage amount measurement portion 72: Second seepage amount measurement portion 73: β-alumina tube quality measurement portion 74: Insulating ring quality measurement portion 75: Bonded glass quality measurement portion 76: Storage device 77a: Input section 77b: Output section 78: Determination section 79: Warning section 211: β pipe standing surface 212, 222, 232: Inner peripheral surface 213: Convex portion

Claims

1. A bonding glass for bonding a β-alumina solid electrolyte to an α-alumina insulator, containing 29.0 to 38.0 mass% of SiO2, 14.0 to 22.0 mass% of Al2O3, 29.0 to 42.5 mass% of B2O3, 5.0 to 8.5 mass% of MgO, 2.5 to 6.5 mass% of Na2O, less than 0.20 mass% of Fe2O3, less than 0.25 mass% of CaO, less than 0.20 mass% of K2O, and less than 0.50 mass% of As2O3.

2. The bonding glass according to claim 1, containing 0.10 mass % or more of As2O3.

3. The linear expansion coefficient at 0 to 300°C as specified in JIS R3102 (1995) is 3.0 to 7.0 x 10 -6 The bonding glass according to claim 1, wherein the temperature is 100°C.

4. The bonding glass according to claim 1, which has a glass transition temperature of 480 to 640°C.

5. The bonding glass according to claim 1, wherein the glass softening temperature is 610 to 790°C.

6. A glass joined body in which an insulating ring made of α-alumina is joined to the open end of a bottomed cylindrical β-alumina tube via a joining glass containing 29.0 to 38.0 mass% SiO2, 14.0 to 22.0 mass% Al2O3, 29.0 to 42.5 mass% B2O3, 5.0 to 8.5 mass% MgO, 2.5 to 6.5 mass% Na2O, less than 0.20 mass% Fe2O3, less than 0.25 mass% CaO, less than 0.20 mass% K2O, and less than 0.50 mass% As2O3.

7. The glass joined body according to claim 6, wherein the insulating ring comprises: a base portion having a first inner diameter; a main joining portion connected coaxially to the base portion, the main joining portion having a second inner diameter larger than the first inner diameter, the outer peripheral surface of the open end of the β-alumina tube joined to the inner peripheral surface via the joining glass; a filling portion connected coaxially to the main joining portion, the main joining portion having a third inner diameter larger than the second inner diameter, the outer peripheral surface of the open end of the β-alumina tube joined to the inner peripheral surface via the joining glass; and a β-tube standing surface between the main joining portion and the base portion, the open end surface of the β-alumina tube joined to the joining glass via the joining glass.

8. A glass bonded body according to claim 7, wherein the inner peripheral surface of the main bonded portion is polygonal when observed from a direction parallel to the axial direction, and the β-tube standing surface has a plurality of convex portions arranged along the circumferential direction.

9. A method for manufacturing a glass joined body, comprising joining a cylindrical beta-alumina tube with a bottom and an insulating ring made of alpha-alumina via a joining glass, wherein the joining glass contains 29.0 to 38.0 mass% SiO2, 14.0 to 22.0 mass% Al2O3, 29.0 to 42.5 mass% B2O3, 5.0 to 8.5 mass% MgO, 2.5 to 6.5 mass% Na2O, less than 0.20 mass% Fe2O3, less than 0.25 mass% CaO, less than 0.20 mass% K2O, and less than 0.50 mass% As2O3, and the joining step comprises heating the joining glass to a temperature equal to or higher than the glass softening point of the joining glass, and then cooling the joining glass.

10. The method for manufacturing a glass bonded body according to claim 9, wherein the bonding step includes: a heating step of heating the bonded glass from room temperature to a maximum temperature range of 1100 to 1160°C; a holding step of holding the heated bonded glass at the maximum temperature range for 10 minutes or more; a first cooling step of cooling the held bonded glass to 500 to 600°C; an annealing step of annealing the cooled bonded glass at 500 to 600°C for 25 minutes or more; and a second cooling step of cooling the annealed bonded glass to room temperature.

11. A method for producing a glass joined body according to claim 9, wherein the insulating ring comprises: a base having a first inner diameter; a main joining portion connected coaxially to the base, the main joining portion having a second inner diameter larger than the first inner diameter; a filling portion connected coaxially to the main joining portion, the filling portion having a third inner diameter larger than the second inner diameter; and a β-tube erection surface between the main joining portion and the base; and the joining step is carried out after accommodating the β-alumina tube in the insulating ring so that the open end face of the β-alumina tube abuts on the β-tube erection surface facing downward and after accommodating the joined glass in the filling portion.

12. A method for manufacturing a glass bonded body according to claim 11, wherein the inner peripheral surface of the main bonded portion is polygonal when observed from a direction parallel to the axial direction, and the β-tube standing surface has a plurality of convex portions arranged along the circumferential direction.

13. A method for inspecting a glass joined body manufactured by the method for manufacturing a glass joined body according to claim 11 or 12, comprising: measuring a first amount of the joining glass that has seeped out from the open end face of the β-alumina tube onto the inner peripheral surface of the base of the insulating ring in the axial direction of the insulating ring; measuring a second amount of the joining glass that has seeped out from the end of the filling portion of the insulating ring onto the outer peripheral surface of the open end of the β-alumina tube in the axial direction of the insulating ring; and judging whether the joining state between the β-alumina tube and the insulating ring is good or bad based on the measurement results of the first and second amounts of seepage.

14. A method for inspecting a glass bonded body manufactured by the method for manufacturing a glass bonded body according to claim 9, comprising: taking an image of the external surface of the β-alumina tube with an imaging device, and measuring by image processing whether or not the β-alumina tube has any visual defects, including chips, cracks, scratches, dirt, or attachments; taking an image of the external surface of the insulating ring with an imaging device, and measuring by image processing whether or not the insulating ring has any visual defects, including chips, cracks, scratches, dirt, or attachments; taking an image of the external surface of the bonded glass with an imaging device, and measuring by image processing whether or not the bonded glass has any visual defects, including voids, cracks, scratches, dirt, or attachments; and judging whether or not the glass bonded body is good based on the results of the measurement of visual defects of the β-alumina tube, the insulating ring, and the bonded glass.

15. A method for inspecting a glass bonded body, comprising a quality inspection step of inspecting whether the sintered density, maximum particle size, strength, outer diameter, roundness, and straightness of the β-alumina tube satisfy control values ​​before producing the glass bonded body described in claim 6.

Images