JP5656044B2 - High expansion crystalline glass composition - Google Patents

Description

  The present invention relates to a high expansion crystalline glass composition, and more specifically to a high expansion crystalline glass composition used for the purpose of bonding metals such as SUS and Fe, and high expansion ceramics such as ferrite and zirconia. is there.

In recent years, a fuel cell has been attracting attention as an effective technology that has high energy efficiency and can greatly reduce CO ₂ emissions. The type of fuel cell differs depending on what is used for the electrolyte, but those used in industrial applications include phosphoric acid type (PAFC), molten carbonate type (MCFC), solid oxide type (SOFC), and solid polymer type. There are four types (PEFC). Among them, the solid oxide fuel cell (SOFC) has the characteristics that it has the highest power generation efficiency among the fuel cells because of its low internal resistance, and it is not necessary to use a precious metal for the catalyst. This system is applicable to a wide range of applications from small-scale applications such as power plants to large-scale applications such as power plants, and its future is highly expected.

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

The flat plate-type SOFC having the above structure allows various gases such as hydrogen (H ₂ ), city gas, natural gas, biogas, and liquid fuel to flow through the fuel channel 4a of the first support substrate 4 at the same time. Air or oxygen (O ₂ ) is allowed to flow through the air channel 5 a of the support substrate 5. At this time, 1 / 2O ₂ + 2e ⁻ → O ^{2− at the} cathode.
The reaction of H ₂ + O ₂ − → H ₂ O + 2e ⁻ occurs at the anode.
Reaction occurs. By this electrochemical, chemical energy can be directly converted into electric energy to generate electricity. In order to obtain a high output, an actual flat-plate SOFC has a number of layers of the structure shown in FIG.

JP-A-6-87630 JP 7-69676 A

  In producing the structure, an airtight seal between the support substrates, an adhesion between the solid electrolyte and the support substrate, or an airtight seal between the solid electrolytes is required. In the case of SOFC, it is necessary to hermetically seal each constituent member so that the gas flowing to the anode side and the cathode side does not mix.

  For that purpose, a method of hermetically sealing by sandwiching an inorganic sheet-shaped gasket such as mica, palm curite, alumina, etc. has been proposed, but there is concern about sealing performance because it is sandwiched but not bonded. Adhesion with a glass material is desired.

  On the other hand, in the case of an adhesive material made of a glass material, high expansion materials such as metals and ceramics are bonded to each other. Moreover, the temperature range (operation temperature range) at which the electrochemical reaction occurs is as high as 650 to 1000 ° C., and the SOFC is operated at this temperature for a long period of time. Therefore, the glass material is required to have high heat resistance so that the bonded portion does not loosen even when exposed to a high temperature for a long time. Moreover, since it is adhesion | attachment of high expansion materials, such as a metal and a ceramic, the fluidity | liquidity and sealing property of glass with the moderate temperature increase rate of 5 degrees C / min or less at the time of baking are calculated | required.

As high-expansion glass materials, MgO—B ₂ O ₃ —SiO ₂ based crystalline glass compositions as disclosed in Patent Documents 1 and ₂ are disclosed. When these materials are heat-treated, BaO.2MgO.2SiO ₂ crystals and 2MgO.B ₂ O ₃ crystals are precipitated, and show a high expansion of 110 × 10 ⁻⁷ / ° C. or more.

  However, since the crystalline glass compositions disclosed in Patent Documents 1 and 2 are designed to cover the substrate, the crystallinity is not sufficiently controlled and the fluidity is insufficient. In addition, when exposed to a high temperature for a long period of time, a problem such as a crystal melting and a decrease in heat resistance is expected, and it is not necessarily a material suitable for a sealing material for a fuel cell.

The object of the present invention is to exhibit a high thermal expansion coefficient after heat treatment, specifically about 100 to 130 × 10 ⁻⁷ / ° C., fluidity suitable for sealing in the heat treatment process, and a long period of time. And providing a material having stable heat resistance.

As a result of various studies, the present inventors have found that the flowability of glass is improved by containing a large amount of P ₂ O ₅ . Further, it has been found that if the content of P ₂ O ₅ is increased, phosphoric acid crystals are easily precipitated. This phosphoric acid type crystal has the property that the precipitation temperature and the melting point are higher than those of BaO.2MgO.2SiO ₂ crystal and 2MgO.B ₂ O ₃ crystal.

High-expansion crystallizable glass composition of the present invention, in _{mol%, 50~70% MgO, BaO 1~15} %, B 2 O 3 8~25%, SiO 2 8~23%, P 2 O 5 3. It characterized in that it has 5-15% free. In the present invention, “crystallinity” means the property of precipitating crystals from the glass matrix upon heat treatment.

In the present invention, it is preferable to deposit phosphoric acid crystals upon heat treatment. In particular, it is preferable to deposit MgO—P ₂ O ₅ based crystals such as 3MgO · P ₂ O ₅ and (MgO · BaO) —P ₂ O ₅ . In the present invention, the “phosphate crystal” means a crystal containing P ₂ O ₅ as a crystal constituent component. “MgO—P ₂ O ₅ -based crystal” means a crystal containing MgO and P ₂ O ₅ as essential components as crystal constituent components. Note that “when heat-treated” means a case where heat treatment is performed at a temperature of 800 ° C. or more for 10 minutes or more.

  According to the said structure, since the phosphoric acid type | system | group crystal | crystallization with high precipitation temperature and melting temperature precipitates, during the operation | movement of SOFC over a long period of time, the unexpected situation that a crystal | crystallization melt | dissolves and an adhesion location loosens can be avoided.

  In the present invention, it is preferably for bonding.

  According to the said structure, the effect of this invention can be enjoyed exactly.

The high expansion crystalline glass composition of the present invention exhibits a thermal expansion coefficient of about 100 to 130 × 10 ⁻⁷ / ° C. after heat treatment. Also since the high content of P ₂ O _5, it shows fluidity suitable for sealing during the heat treatment. Moreover, when exposed to high temperatures for a long period of time or when the temperature rises abnormally, precipitation of phosphoric acid crystals is promoted and heat resistance is maintained. As a result, stable heat resistance can be ensured over a long period of time.

  Therefore, the material of the present invention is suitable as an adhesive material used for adhesion and coating of a high expansion material, particularly for production of SOFC.

It is explanatory drawing which shows the basic structure of SOFC.

  The reason for limiting the glass composition as described above in the high expansion crystalline glass composition of the present invention will be described below.

  The content of MgO is 50 to 70%, preferably 51 to 69%. When the content of MgO is less than 50%, the crystallization of the glass composition does not proceed sufficiently, resulting in poor heat resistance. On the other hand, when the content of MgO exceeds 70%, the solubility becomes poor and it becomes difficult to obtain a homogeneous glass.

  The content of BaO is 1 to 15%, preferably 3 to 12%, more preferably 4 to 10%. When the content of BaO is less than 1%, the glass becomes unstable, devitrification becomes remarkable, and molding becomes difficult. On the other hand, if the content of BaO exceeds 15%, the crystallinity becomes weak, sufficient crystal precipitation cannot be obtained, and the heat resistance decreases.

The content of B ₂ O ₃ is 8 to 25%, preferably 8.5 to 24%. When the content of B ₂ O ₃ is less than 8%, the solubility is deteriorated. On the other hand, if the content of B ₂ O ₃ exceeds 25%, the thermal expansion coefficient is not sufficiently high, and the water resistance and heat resistance deteriorate.

The content of SiO ₂ is 8 to 23%, preferably 8 to 22%, more preferably 9 to 21%. When the content of SiO ₂ is less than 8%, the water resistance and heat resistance are poor. On the other hand, when the content of SiO ₂ exceeds 23%, dissolution becomes difficult. Also, crystal precipitation becomes difficult during heat treatment.

The content of P ₂ O ₅ is 3.5 to 15%, preferably 3.5 to 10%. When the content of P ₂ O ₅ is 3.5 % or less, the fluidity during heat treatment is poor. Further, MgO · P ₂ O ₅ and (MgO · BaO) -P ₂ O ₅ based crystals are difficult to precipitate, and long-term stability is difficult to obtain at high temperatures. On the other hand, when the content of P ₂ O ₅ exceeds 15%, BaO · 2MgO · 2SiO ₂ crystals and 2MgO · B ₂ O ₃ crystals are difficult to precipitate, resulting in a decrease in crystallinity, resulting in a decrease in heat resistance. .

Moreover, the high expansion crystalline glass composition of the present invention contains SnO ₂ , ZrO ₂ , TiO ₂ , ZnO, CaO, SrO, Al ₂ O ₃ , La ₂ O ₃ , Y ₂ O _3, etc. as components other than those described above. It may be added up to mol%. However, the addition of an alkali metal oxide that degrades electrical insulation is not preferred.

Crystalline glass composition having a composition such as described above, BaO _· 2MgO _· 2SiO 2 When the heat _{treatment, 2MgO · B 2 O 3,} 3MgO · P 2 O 5, (MgO · BaO) -P 2 O 5 crystal such And exhibit a thermal expansion coefficient of 100 × 10 ⁻⁷ / ° C. or higher. Further, after the heat treatment, high crystallinity is obtained, so that the heat resistance is high, and even when the heat treatment is performed again, it does not flow. Moreover, phosphate crystals such as 3MgO · P ₂ O ₅ and (MgO · BaO) -P ₂ O ₅ have high precipitation and melting temperatures. Precipitation and growth progress. Thereby, heat resistance can be maintained over a long period of time.

Incidentally glass powder material formed of the above glass compositions, for the adjustment of the fluidity, which is part of magnesium phosphate precipitated crystals (3MgO _· P 2 _{O 5)} and magnesia (MgO), zinc oxide (ZnO), Powders such as zirconia (ZrO ₂ ), titania (TiO ₂ ), and alumina (Al ₂ O ₃ ) may be added as filler powders up to 10 parts by weight, preferably up to 8 parts by weight with respect to 100 parts by weight of the glass powder. . The reason why the addition amount is limited to the above range is that when the amount is more than 10 parts by weight, the decrease in fluidity becomes too large. In addition, it is preferable to use a filler powder having a d50 particle size of about 0.2 to 20 μm.

  Next, a method for using the high expansion crystalline glass composition of the present invention as an adhesive material will be described. In addition, the usage method of the glass composition of this invention is not restrict | limited to the following description.

  First, the glass raw material prepared so as to have the above composition is melted at 1400-1500 ° C. for 0.5-2 hours. Next, after the molten glass is formed into a film or the like, it is pulverized and classified to produce glass powder. In addition, it is preferable that the particle size (d50) of glass powder is about 2-20 micrometers.

  Further, various filler powders are added to the glass powder as necessary.

  Next, glass powder or a mixed powder of glass powder and filler powder is prepared into, for example, a glass paste. When used in a glass paste, it can contain a plasticizer, a dispersant and the like in addition to an organic solvent, a resin, and glass powder.

  The organic solvent is a material for pasting glass powder, such as terpineol (Ter), diethylene glycol monobutyl ether (BC), diethylene glycol monobutyl ether acetate (BCA), 2,2,4-trimethyl-1,3-pentadiol. Monoisobutyrate, dihydroterpineol, etc. can be used alone or in admixture. The content is preferably 10 to 40% by mass.

  The resin is a component that increases the film strength after drying and imparts flexibility, and the content is generally about 0.1 to 20% by mass. As the resin, a thermoplastic resin, specifically, polybutyl methacrylate, polyvinyl butyral, polymethyl methacrylate, polyethyl methacrylate, ethyl cellulose and the like can be used, and these are used alone or in combination.

  The plasticizer is a component that controls the drying speed and imparts flexibility to the dry 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 type, a carboxylic acid, a polycarboxylic acid type such as a dicarboxylic acid type, an amine type, etc., as a nonionic type, a polyester condensation type or A polyhydric alcohol ether type can be used. The amount used is 0 to 5% by mass.

  The paste can be produced by kneading the above materials at a predetermined ratio.

Next, the paste is applied to the bonding location 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 where it is in contact with the dry paste film, and heat-treated at 800 to 900 ° C. By this heat treatment, the glass powder is once softened and fluidized to fix the first and second members. BaO.2MgO.2SiO ₂ and 2MgO.B ₂ O ₃ are first precipitated at a stage where the glass powder has flowed to some extent, and at higher temperatures, phosphorus such as 3MgO.P ₂ O ₅ and (MgO.BaO) -P ₂ O ₅ Acidic crystals are precipitated.

  Since these crystals have a high melting point and a large amount of precipitation, it is possible to obtain an adhesive bonded body having high thermal stability of the material and excellent heat resistance.

  The high expansion crystalline glass composition of the present invention can be used for purposes such as coating and filling in addition to adhesion. Moreover, it can be used in forms other than paste, specifically in a powdered state, a green sheet, a tablet, or the like. For example, the form which fills glass powder with a lead wire in the cylinder made from a metal or ceramics, heat-processes, and performs airtight sealing is mentioned. Moreover, a preform formed by green sheet molding, a tablet produced by powder press molding, or the like can be placed on a metal or ceramic member and coated by heat treatment.

  Hereinafter, the high expansion crystalline glass composition of the present invention will be described based on examples.

  Table 1 shows examples of the present invention made of glass (sample Nos. 1 to 7), and Table 2 shows comparative examples (samples No. 8 and 9).

  Each sample was prepared as follows.

  The glass raw material prepared so as to have the composition in the table was melted at the temperature shown in the table for about 1 hour, and then formed into a film through a pair of rollers. Next, the obtained film-like molded product was pulverized with a ball mill and classified to obtain a sample having a particle size (d50) of about 10 μm.

  Next, for each sample, the presence or absence of devitrified material during molding, thermal expansion coefficient, transition point, yield point, softening point, fluidity, precipitated crystal, crystallinity, crystallization temperature, and crystal melting point are shown in the table. .

As is apparent from Table 1, sample No. which is an example of the present invention. In Nos. 1 to 7, devitrified materials were not recognized during molding, and molding was easy. The coefficient of thermal expansion was as high as 105 to 118 × 10 ⁻⁷ / ° C.

On the other hand, sample No. which is a comparative example. Since No. 8 had a low content of P ₂ O ₅ , the thermal expansion coefficient was as high as 117 × 10 ⁻⁷ / ° C., but the fluidity was poor. In addition, no precipitation of phosphoric acid crystals was observed, and the crystal melting point was low. Sample No. Although the fluidity of No. 9 was good, the SiO ₂ content was as high as 25% and the MgO content was as low as 48%, so the crystallinity was low and the heat resistance was poor.

  In addition, the presence or absence of the devitrified substance at the time of shaping | molding observed the said film-form molded object with the microscope (50 times), and it was set as what had the thing recognized without the thing with which the devitrified substance was not recognized. If there is no devitrified material, it can be determined that the stability of the glass is high.

  Regarding the thermal expansion coefficient of the glass, each glass powder sample was powder press-molded, heat-treated at 850 ° C. for 15 minutes, polished into a cylindrical shape having a diameter of 4 mm and a length of 20 mm, and measured according to JIS R3102. A value in a temperature range of 30 to 700 ° C. was obtained. At this time, when the transition point and yield point were obtained, the values were shown. When the glass component remains after crystallization, a transition point is observed, but when the crystallinity is low, not only the transition point but also the yield point is confirmed.

  The softening point, crystallization temperature, and crystal melting point of the glass were measured using a macro type differential thermal analyzer. That is, the sample was measured up to 1100 ° C. with the same analyzer, the value of the fourth inflection point was the softening point, the strong exothermic peak was the crystallization temperature, and the endothermic peak obtained after crystallization was the crystal melting point. Note that the higher the melting point of the crystal, or the more the melting point is not confirmed, it means that the crystal exists stably even at a high temperature, and therefore it can be determined that the heat resistance is high.

  The fluidity was evaluated as follows. A glass powder with a specific gravity is placed in a 20 mm diameter mold and pressed, and then heat-treated by holding it at 850 ° C. for 15 minutes on a SUS430 plate, and the corners of the sintered body become round and a flow diameter of 17 mm or more is obtained. What has it is indicated by ◯, and what has less is indicated by ×.

Precipitated crystals were measured by XRD and identified by comparison with JCPDS card. In the table, BaO · 2MgO · 2SiO ₂ is identified as “A”, 2MgO · B ₂ O ₃ is denoted as “B”, and (MgO · BaO) —P ₂ O ₅ is denoted as “C”. It was.

  The degree of crystallinity was measured by a halo method using halos before and after crystallization by XRD measurement.

  The high expansion 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. Moreover, it is suitable as an adhesive material for hermetically sealing a support substrate, an electrolyte, an electrode, and the like used when manufacturing an SOFC.

DESCRIPTION OF SYMBOLS 1 Electrolyte 2 Anode 3 Cathode 4 First support substrate 4a Fuel channel 4a
5 Second support substrate 5a Air channel 5a

Claims (4)

In _{mole%, 50~70% MgO, BaO 1~15} %, B 2 O 3 8~25%, SiO 2 8~23%, high, characterized in that it comprises containing _P 2 O 5 3.5 _~15% Expanded crystalline glass composition. The high-expansion crystalline glass composition according to claim 1, wherein phosphoric acid-based crystals are precipitated upon heat treatment. The high expansion crystalline glass composition according to claim 2, wherein MgO—P ₂ O ₅ -based crystals are precipitated by heat treatment. The high expansion crystalline glass composition according to any one of claims 1 to 3, wherein the composition is used for bonding.

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