JP2020083662A - Crystalline glass composition - Google Patents

Abstract

To provide a crystalline glass composition that has a fluidity suitable for adhesion as well as a desired thermal expansion coefficient after heat treatment, and has an excellent heat resistance after adhesion.SOLUTION: Provided is a crystalline glass composition characterized by containing, in mole %, SiOby 38 to less than 50%, MgO by 5 to 40%, CaO by 0.1 to 30%, BaO by 2 to 20%, ZnO by 5 to 40%, RO (R is at least one selected from Li, Na, K and Cs.) by 0 to 5%, BOby 0 to less than 2%, AlOby 0 to less than 2%, LaOby 0 to 15%, and in which ZnO/BaO is 1.9 to 10.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a crystalline glass composition, and more specifically to a crystalline glass composition used for the purpose of adhering a metal such as SUS or Fe or a high expansion ceramic such as ferrite or zirconia.

2. Description of the Related Art In recent years, fuel cells have high energy efficiency and have been drawing attention as a promising technology capable of greatly reducing CO ₂ emission. The types of fuel cells are classified according to the electrolyte used. For example, phosphoric acid type (PAFC), molten carbonate type (MCFC), solid oxide type (SOFC), solid polymer type (PEFC) are used for industrial applications. There are four types. Among them, the solid oxide fuel cell (SOFC) has the highest power generation efficiency in the fuel cell because of its low internal resistance, and the production cost can be suppressed because it is not necessary to use a noble metal for the catalyst. Have Therefore, the system is widely applicable from small-scale applications such as household use to large-scale applications such as power plants, and expectations for its future are increasing.

The structure of a general flat plate SOFC is shown in FIG. As shown in FIG. 1, a general flat-plate SOFC includes an electrolyte 1 made of a ceramic material such as yttria-stabilized zirconia (YSZ), an anode 2 made of Ni/YSZ, and (La, Ca)CrO _3. Has a cell in which the cathode 3 is laminated and integrated. Further, the first support substrate 4 in contact with the anode 2 and the second support substrate 5 in contact with the cathode 3 are fixed to the upper and lower sides of the cell, whereby the passage of the fuel gas (fuel channel 4a) and the passage of the air (air The channel 5a) is formed. The first support substrate 4 and the second support substrate 5 are made of metal such as SUS and are fixed to the cell so that the gas passages are orthogonal to each other.

In the flat plate type SOFC having the above structure, various gases such as hydrogen (H ₂ ) and city gas, natural gas, biogas and liquid fuel are caused to flow in the fuel channel 4a, and at the same time air or oxygen (O ₂ ) is flown in the air channel 5a. Shed. At this time, a reaction of 1/2O ₂ +2e ⁻ →O ^{2 −} occurs at the cathode, and a reaction of H ₂ +O ² → →H ₂ O +2e ⁻ occurs at the anode. By this electrochemical reaction, chemical energy is directly converted into electric energy and power can be generated. In addition, in order to obtain a high output, in an actual flat plate type SOFC, many layers of the structure shown in FIG. 1 are laminated.

In manufacturing the above-mentioned structure, it is necessary to hermetically seal the respective constituent members so that the gases flowing to the anode side and the cathode side do not mix with each other. For that purpose, a method has been proposed in which a sheet-shaped gasket made of an inorganic material such as mica, vermiculite, or alumina is sandwiched and hermetically sealed, but in this method, a slight amount of gas leak easily occurs, and a decrease in fuel use efficiency is a problem. Is becoming In order to solve the problem, a method of melting and adhering the constituent members to each other using an adhesive material made of glass has been studied.

Since a high expansion material such as metal or ceramic is used as a constituent member of the structure, the adhesive material used also needs to have a coefficient of thermal expansion compatible with these high expansion materials. Further, the SOFC has a high temperature range (operating temperature range) in which an electrochemical reaction occurs, that is, 600 to 1000° C., and is operated in the temperature range for a long period of time. Therefore, the adhesive material is required to have high heat resistance so that even if it is exposed to a high temperature for a long period of time, the airtightness and the adhesiveness will not be deteriorated due to the melting of the adhesive portion.

As the high expansion bonding material made of glass, crystalline glass composition exhibiting high expansion characteristics and precipitation heat treatment to the CaO-MgO-SiO ₂ based crystal is disclosed in Patent Document 1. Further, Patent Document 2 discloses a SiO ₂ —B ₂ O ₃ —SrO based amorphous glass composition that can obtain stable gas sealing properties.

International Publication No. 2009/017173 JP, 2006-56769, A

Since the crystalline glass composition described in Patent Document 1 has a high temperature viscosity, it is difficult for the crystalline glass composition to soften and flow during heat treatment, and it is difficult to obtain a dense sintered body. As a result, there is a problem that it is difficult to obtain a stable sealing property. Further, the amorphous glass composition disclosed in Patent Document 2 has a glass transition point of around 600° C., and therefore, in a high-temperature operating environment of about 600 to 1000° C., the bonding site melts, resulting in airtightness and There is a problem that the adhesiveness cannot be secured.

In view of the above, the present invention aims to provide a crystalline glass composition having fluidity suitable for bonding, having a desired coefficient of thermal expansion after heat treatment, and having excellent heat resistance after bonding. To do.

As a result of various experiments conducted by the present inventor, it has been found that the above problems can be solved by a glass composition having a specific composition.

The crystalline glass composition of the present invention is, in mol %, SiO ₂ 38 to less than 50%, MgO 5 to 40%, CaO 0.1 to 30%, BaO 2 to 20%, ZnO 5 to 40%, R ₂ O (R is at least one selected from Li, Na, K, and Cs) 0 to 5%, B ₂ O _{3 to} less than 2%, Al ₂ O _{3 to} less than 2%, La ₂ O _{3 to} 15 %, and ZnO/BaO is 1.9-10. Here, “ZnO/BaO” means a value obtained by dividing the content of ZnO by the content of BaO. In the present invention, the "crystalline glass composition" means a glass composition having a property of precipitating crystals when heat-treated. Further, "heat treatment" means heat treatment at a temperature of 800° C. or higher for 10 minutes or longer.

Crystallizable glass composition of the present invention, by the ZnO / BaO and from 1.9 to 10, after the heat treatment, a low expansion crystal such as 2ZnO · SiO _2, and _{BaO · 2MgO · 2SiO 2, 2SiO} 2 · 2ZnO Highly expanded crystals such as BaO are likely to precipitate. A desired coefficient of thermal expansion can be obtained by precipitating both the low-expansion crystal and the high-expansion crystal, and it becomes easy to have a coefficient of thermal expansion compatible with metals, ceramics and the like. Moreover, these crystals have good heat resistance, and can improve the heat resistance of the bonded portion. Therefore, even if it is used at a high temperature for a long period of time, it becomes difficult for the bonded portion to melt, and it is possible to suppress deterioration of the airtightness or the adhesiveness of the bonded portion.

SiO ₂ and CaO are components that improve fluidity, and by defining their contents as described above, fluidity suitable for adhesion (sealing) can be obtained.

The crystalline glass composition of the present invention preferably contains substantially no P ₂ O _{5 or} Bi ₂ O ₃ . P ₂ O ₅ and Bi ₂ O ₃ are likely to be volatilized by heat treatment, which may adversely affect the power generation characteristics such as lowering the electrical insulating property of the SOFC constituent member. Therefore, it is possible to prevent the power generation characteristics from being unduly deteriorated by substantially not containing these components. In addition, "substantially not containing" means not containing intentionally, and does not exclude mixing of unavoidable impurities. Specifically, it means that the content of the corresponding component is less than 0.1 mol %.

Crystallizable glass composition of the present invention, by heat treatment, the crystals of 2ZnO · SiO _2, it is preferred to precipitate the BaO · 2MgO · 2SiO _2, and / or 2SiO ₂ · 2ZnO · BaO crystals. With this configuration, it is possible to optimize the thermal expansion coefficient and improve the heat resistance of the bonded portion, and it is suitable for the purpose of bonding or coating metal or ceramic.

The crystalline glass composition of the present invention preferably has a thermal expansion coefficient of 80×10 ⁻⁷ /° C. to 110×10 ⁻⁷ /° C. in the temperature range of 30 to 700° C.

The crystalline glass composition of the present invention is suitable for adhesion.

The crystalline glass composition of the present invention has fluidity suitable for bonding, has a desired coefficient of thermal expansion after heat treatment, and is also excellent in heat resistance after bonding. Therefore, even if it is used at a high temperature for a long period of time, it becomes difficult for the bonded portion to melt, and it is possible to suppress the deterioration of the airtightness and the adhesiveness of the bonded portion.

It is a typical perspective view which shows the basic structure of SOFC.

The crystalline glass composition of the present invention is, in mol %, SiO ₂ 38 to less than 50%, MgO 5 to 40%, CaO 0.1 to 30%, BaO 2 to 20%, ZnO 5 to 40%, R ₂ O (R is at least one selected from Li, Na, K, and Cs) 0 to 5%, B ₂ O _{3 to} less than 2%, Al ₂ O _{3 to} less than 2%, La ₂ O _{3 to} 15 %, ZnO/BaO is 1.9-10. The reason for limiting the glass composition as described above will be described below. In the following description regarding the content of each component, "%" means "mol %" unless otherwise specified.

SiO ₂ is a constituent component of high-expansion crystals and low-expansion crystals precipitated by heat treatment, and has the effect of improving water resistance and heat resistance in addition to improving fluidity. The content of SiO ₂ is 38 to less than 50%, preferably 40 to 49.5%, more preferably 45 to 49%. If the content of SiO ₂ is too small, it becomes difficult to obtain fluidity suitable for adhesion. On the other hand, when the content of SiO ₂ is too large, the melting temperature becomes high and the melting tends to be difficult.

MgO is a constituent component of high expansion crystals precipitated by heat treatment. The content of MgO is 5 to 40%, preferably 5 to 39%, more preferably 6 to 38%. If the content of MgO is too small, highly expanded crystals are less likely to precipitate during heat treatment, and heat resistance is likely to decrease. On the other hand, if the content of MgO is too large, the vitrification range tends to be narrowed and devitrification is likely to occur. In addition, the fluidity tends to decrease.

CaO is a component for improving fluidity. The content of CaO is 0.1 to 30%, preferably 1 to 25%, more preferably 3 to 20%. If the content of CaO is too small, it becomes difficult to obtain fluidity suitable for adhesion. On the other hand, if the content of CaO is too large, the vitrification range tends to be narrowed and devitrification is likely to occur.

BaO is a constituent component of high expansion crystals precipitated by heat treatment. The content of BaO is 2 to 20%, preferably 3 to 18%, more preferably 3 to 15%. If the content of BaO is too small, it becomes difficult for highly expanded crystals to precipitate during heat treatment, and heat resistance tends to decrease. On the other hand, if the content of BaO is too large, the vitrification range tends to be narrowed and devitrification is likely to occur. In addition, the fluidity tends to decrease.

ZnO is a constituent component of high expansion crystals and low expansion crystals precipitated by heat treatment. The content of ZnO is 5 to 40%, preferably 5 to 39%, more preferably 6 to 38%. If the content of ZnO is too low, high expansion crystals and low expansion crystals are less likely to precipitate during heat treatment, and heat resistance tends to decrease. On the other hand, if the content of ZnO is too large, the vitrification range tends to be narrow, and devitrification is likely to occur.

BaO/ZnO is 1.9-10, preferably 1.95-8, more preferably 2-5. When BaO / ZnO is too small, high expansion crystal such as _{BaO · 2MgO · 2SiO 2, 2SiO} 2 · 2ZnO · BaO is less likely deposited, tend to thermal expansion coefficient becomes too low. On the other hand, when BaO/ZnO is too large, low-expansion crystals such as 2ZnO.SiO ₂ are less likely to precipitate, and the coefficient of thermal expansion tends to be too high.

R ₂ O (R is at least one selected from Li, Na, K, and Cs) is a component that expands the vitrification range to facilitate vitrification. The content of R ₂ O is 0 to 5%, preferably 0 to 3%, more preferably 0 to 1%. When the content of R ₂ O is too large, when used as an adhesive material for a constituent member of a fuel cell, R ₂ O is volatilized at high temperatures and the power generation characteristics are likely to deteriorate. The content of Li ₂ O, Na ₂ O, K ₂ O, and Cs ₂ O is preferably 0 to 5%, more preferably 0 to 3%, and further preferably 0 to 1%.

B ₂ O ₃ is a component for improving fluidity. The content of B ₂ O ₃ is 0 to less than 2%, preferably 0 to 1%, and more preferably 0 to 0.5%. If the content of B ₂ O ₃ is too large, water resistance and heat resistance tend to decrease. In addition, when used as an adhesive material for a constituent member of a fuel cell, B ₂ O ₃ volatilizes under use at a high temperature, and power generation characteristics are likely to deteriorate.

Al ₂ O ₃ is a component for adjusting viscosity. The content of Al ₂ O ₃ is 0 to less than 2%, preferably 0 to 1.5%, more preferably 0 to 1%. If the content of Al ₂ O ₃ is too large, the vitrification range tends to be narrowed and devitrification is likely to occur.

La ₂ O ₃ is a component for improving fluidity. It is also a component that expands the vitrification range to facilitate vitrification. The content of La ₂ O ₃ is 0 to 15%, preferably 0 to 14%, more preferably 0.1 to 13%. When the content of La ₂ O ₃ is too large, devitrification tends to occur during melting or heat treatment, and it becomes difficult to obtain fluidity suitable for adhesion.

In addition to the above components, various components shown below can be contained.

SrO is a component for improving fluidity. The content of SrO is 0 to 10%, preferably 0 to 5%, more preferably 0 to 3%. If the content of SrO is too large, the vitrification range tends to be narrow, and devitrification is likely to occur.

TiO ₂ is a component that improves fluidity. The content of TiO ₂ is 0 to 10%, preferably 0 to 8%, more preferably 0 to 6%. If the content of TiO ₂ is too large, devitrification tends to occur during melting.

ZrO ₂ is a component that improves fluidity. The content of ZrO ₂ is 0 to 10%, preferably 0 to 8%, more preferably 0.1 to 6%. If the content of ZrO ₂ is too large, devitrification tends to occur during melting.

Furthermore, the crystallizable glass composition of the present invention, is contained _Y 2 _O 3 as a component other than the _{above, Gd 2 O 3, Nb 2} O 5, Ta 2 O 5, SnO 2, WO 3 , etc. up to 2%, respectively be able to. However, P ₂ O ₅ and Bi ₂ O ₃ are likely to volatilize by heat treatment and may adversely affect the power generation characteristics such as lowering the electrical insulating property of the SOFC constituent member, so it is preferable that P ₂ O ₅ and Bi ₂ O ₃ are not substantially contained.

The crystalline glass composition having the above composition has a property of depositing a low expansion crystal and a high expansion crystal when heat-treated. As the low-expansion crystallized _{2ZnO · SiO 2, BaO · 2MgO} · 2SiO 2, and / or 2SiO ₂ · 2ZnO · BaO may be mentioned as a high expansion crystals. The thermal expansion coefficient of the crystalline glass composition after the heat treatment in the temperature range of 30 to 700° C. is 80×10 ⁻⁷ /° C. to 110×10 ⁻⁷ /° C., particularly 85×10 ⁻⁷ /° C. to 105×10 5. It is preferably ⁻⁷ /° C. If the coefficient of thermal expansion is too low or too high, the difference in coefficient of thermal expansion with the adherend made of metal or ceramic becomes large, and the glass (bonded portion) may be damaged. The crystalline glass composition of the present invention is likely to have a high crystallinity after heat treatment. In addition, the precipitated crystal has a high melting point and does not easily flow even if heat treatment is performed again, so that heat resistance can be maintained for a long time.

The crystalline glass composition of the present invention contains magnesia (MgO), zinc white (ZnO), zirconia (ZrO ₂ ), titania (TiO ₂ ), alumina (Al ₂ O) for adjusting fluidity and thermal expansion coefficient. Powders such as ₃ ) may be added and used as filler powders. The addition amount of the filler powder is preferably 0 to 10 parts by mass, 0.1 to 9 parts by mass, and particularly 1 to 8 parts by mass with respect to 100 parts by mass of the crystalline glass composition. If the addition amount of the filler powder is too large, the fluidity is likely to decrease. It is preferable to use a filler powder having a particle diameter d50 of about 0.2 to 20 μm.

Next, an example of a method for producing the crystalline glass composition of the present invention and a method of using the crystalline glass composition of the present invention as an adhesive material will be described.

First, the raw material prepared so as to have the above composition is melted at 1400 to 1600° C. for 0.5 to 2 hours until a homogeneous glass is obtained. Then, the molten glass is formed into a film or the like, crushed and classified to prepare a glass powder made of the crystalline glass composition of the present invention. The particle size (d50) of the glass powder is preferably about 2 to 20 μm. If necessary, various filler powders are added to the glass powder.

Next, a glass paste is prepared by adding a vehicle to glass powder (or a mixed powder of glass powder and filler powder) and kneading. The vehicle contains, for example, an organic solvent, a resin, a plasticizer, a dispersant, and the like.

The organic solvent is a material for making glass powder into a paste, and for example, terpineol (Ter), diethylene glycol monobutyl ether (BC), diethylene glycol monobutyl ether acetate (BCA), 2,2,4-trimethyl-1,3-pentadiol. Monoisobutyrate, dihydroterpineol and the like can be used alone or in combination. The content is preferably 10 to 40% by mass.

The resin is a component that enhances the film strength after drying and imparts flexibility, and the content thereof is generally about 0.1 to 20 mass %. The resin may be a thermoplastic resin, specifically, polybutylmethacrylate, polyvinylbutyral, polymethylmethacrylate, polyethylmethacrylate, ethylcellulose or the like, and these may be used alone or in combination.

The plasticizer is a component that controls the drying speed and imparts flexibility to the dried film, and the content thereof is generally about 0 to 10% by mass. As the plasticizer, butylbenzyl phthalate, dioctyl phthalate, diisooctyl phthalate, dicapryl phthalate, dibutyl phthalate and the like can be used, and these are used alone or in combination.

As the dispersant, an ionic or nonionic dispersant can be used. As the ionic system, a carboxylic acid, a polycarboxylic acid system such as a dicarboxylic acid system, an amine system dispersant, or a nonionic polyester condensation type. A polyhydric alcohol ether type dispersant can be used. The amount used is generally 0 to 5% by mass.

Next, the paste is applied to the bonding portion of the first member made of metal or ceramic and dried. Further, the second member made of metal or ceramic is fixed in a state of being in contact with the paste dry film and heat-treated at 800 to 1050°C. By this heat treatment, the glass powder once softens and flows to fix the first and second members, and crystals are precipitated. In this way, it is possible to obtain a joined body in which the first member and the second member are adhered by the sealing portion made of the crystalline glass composition of the present invention.

The crystalline glass composition of the present invention can be used for the purpose of coating, filling, etc. in addition to adhesion. Further, it can be used in a form other than paste, specifically, powder, green sheet, tablet, or the like. For example, there is a form in which a cylinder made of metal or ceramics is filled with glass powder together with a lead wire, heat-treated, and hermetically sealed. It is also possible to place a green sheet-molded preform, a tablet manufactured by powder press molding, or the like on a member made of metal or ceramic, heat-treat and soften and fluidize it to bond, coat, or fill.

Hereinafter, the crystalline glass composition of the present invention will be described based on examples, but the present invention is not limited to these examples.

Table 1 has shown the Example (sample No. 1-6) and comparative example (sample No. 7) of this invention.

Each sample was prepared as follows.

Raw materials prepared so as to have the respective compositions in the table were melted at 1400 to 1600° C. for about 2 hours and then poured out between a pair of rollers to be formed into a film. The obtained film-shaped molded product was crushed by a ball mill and classified to obtain a sample (crystalline glass composition powder) having a particle size (d50) of about 10 μm.

The thermal expansion coefficient, softening point, crystallization temperature, crystal melting point, precipitated crystals, and fluidity of each sample were measured or evaluated. The results are shown in the table.

As is clear from the table, No. Samples 1 to 6 were excellent in fluidity during heat treatment. Moreover, the thermal expansion coefficient was 98 to 105×10 ⁻⁷ /° C. Further, it was found that the melting point of the precipitated crystal was high and the heat resistance was also excellent.

On the other hand, No. Sample ^{No. 7} had a high coefficient of thermal expansion of 112×10 ⁻⁷ /° C.

The measurement and evaluation of each property were performed as follows.

The thermal expansion coefficient was measured by press-molding each glass powder sample, heat-treating at 1000 to 1100° C. for 3 hours, and then polishing the sample into a cylindrical shape having a diameter of 4 mm and a length of 20 mm. The value in the temperature range of 30 to 700° C. was calculated based on R3102.

The softening point, crystallization temperature and crystal melting point were measured using a macro type differential thermal analyzer. Specifically, for each glass powder sample, in the chart obtained by measuring up to 1050° C. using a macro-type differential thermal analyzer, the value of the fourth inflection point is the softening point and the strong exothermic peak is crystallized. The endothermic peak obtained after temperature and crystallization was defined as the crystal melting point. If the crystal melting point is higher or if the crystal melting point is not confirmed, it means that the crystal is stably present even at high temperature, and it can be determined that the heat resistance is high.

The precipitated crystal was identified by performing XRD measurement on a glass powder sample and comparing it with a JCPDS card. "A" 2ZnO · SiO ₂ as a precipitation crystal seeds identified at this time, the BaO · 2MgO · 2SiO _{2 "B",} "C" 2SiO 2 · 2ZnO · BaO, and MgO · CaO · 2SiO ₂ "D" Is shown in the table as

The fluidity was evaluated as follows. A glass powder sample having a specific gravity was placed in a mold having a diameter of 20 mm, press-molded, and then heat-treated on a SUS430 plate at 900 to 1100° C. for 15 minutes. The molded product having a flow diameter of 18 mm or more after heat treatment was evaluated as “⊚”, the product having a flow diameter of 16 mm or more and less than 18 mm was evaluated as “◯”, and the product less than 16 mm was evaluated as “x”.

The crystalline glass composition of the present invention is suitable as an adhesive material for metals such as SUS and Fe, and high expansion ceramics such as ferrite and zirconia. In particular, it is suitable as an adhesive material for hermetically sealing a support substrate, an electrode member, and the like used when manufacturing an SOFC. Further, the crystalline glass composition of the present invention can be used for the purpose of coating, filling, etc. in addition to the purpose of adhesion. Specifically, it can be used for applications such as thermistors and hybrid ICs.

1 Electrolyte 2 Anode 3 Cathode 4 First Support Substrate 4a Fuel Channel 4a
5 Second support substrate 5a Air channel 5a

Claims (5)

In mol %, SiO ₂ 38 to less than 50%, MgO 5 to 40%, CaO 0.1 to 30%, BaO 2 to 20%, ZnO 5 to 40%, R ₂ O (R is Li, Na, K, At least one selected from Cs) 0 to 5%, B ₂ O _{3 to} less than 0 to 2%, Al ₂ O _{3 to} less than 2%, La ₂ O _{3 to} 0 to 15%, and ZnO/BaO is 1. Crystalline glass composition characterized by being 9 to 10. The crystalline glass composition according to claim 1, which is substantially free of P ₂ O ₅ and Bi ₂ O ₃ . By heat treatment, the crystals of _{2ZnO · SiO 2, BaO · 2MgO} · 2SiO 2, and / or 2SiO crystallizable glass composition according to claim 1 or 2, characterized in that to deposit and ₂ · 2ZnO · BaO crystal object. The thermal expansion coefficient in the temperature range of 30 to 700° C. is 80×10 ⁻⁷ /° C. to 110×10 ⁻⁷ /° C., and the crystalline glass according to claim 1. Composition. The crystalline glass composition according to any one of claims 1 to 4, which is for adhesion.