Sealing materials and sintered bodies

Abstract

To provide a sealing material that has excellent heat resistance and flowability, and has its thermal expansion coefficient matched to that of metal and / or ceramic.SOLUTION: A sealing material comprises crystalline glass powder comprising, in mass%, SiO2 40-55%, Al2O3 0.5-4.8%, CaO 10-20%, MgO 10-20%, and SrO 14-20% and corundum powder.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a sealing material suitable for sealing, joining, and coating metals and ceramics. [Background technology]

[0002] Sealing materials used to protect exhaust gas sensors and temperature sensors in automobile engines and to secure the elements are required to have heat resistance.

[0003] Glass ceramics in which feldspar containing Ba or Sr is precipitated have been developed as highly heat-resistant materials. The glass ceramics have high heat resistance, with operating temperatures of 1250 to 1450°C (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Table 2010-537928 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the glass ceramic of Patent Document 1 has insufficient fluidity and a low thermal expansion coefficient of 3.0 to 5.5 ppm / °C, and therefore, when used as a sealing material for metal and / or ceramic, there is a problem that cracks are likely to occur due to mismatch in thermal expansion coefficients.

[0006] An object of the present invention is to provide a sealing material that has excellent heat resistance and flowability and matches the thermal expansion coefficient of metal and / or ceramic. [Means for solving the problem]

[0007] As a result of various experiments, the present inventors have found that the above technical problems can be solved by combining a crystallizable glass powder having a specific glass composition with a corundum powder, and have proposed this invention. That is, the sealing material of the present invention is characterized by containing a crystallizable glass powder containing, by mass%, 40-55% SiO2, 0.5-4.8% Al2O3, 10-20% CaO, 10-20% MgO, and 14-20% SrO, and a corundum powder.

[0008] The sealing material of the present invention preferably contains pyroxene, feldspar, and corundum as main crystals after heat treatment. "Heat treatment" refers to heat treatment at 700 to 1000°C for 10 minutes or more. "Pyroxene" refers to (Ca x Mg 2-x )Si2O6 crystal (0≦x≦1), "feldspar" is (Ca y Sr 1-y )(Al2Si2O8) crystal (0≦y≦1).

[0009] The sealing material of the present invention preferably has a difference ΔT between the softening point and the crystallization temperature of 60°C or more. The "softening point" and "crystallization temperature" refer to values ​​measured using a macro-type differential thermal analyzer. ΔT is an index of the fluidity of the sealing material; the larger ΔT, the better the fluidity during sealing.

[0010] The sealing material of the present invention is preferably used for an exhaust gas sensor or a temperature sensor.

[0011] The sintered body of the present invention is a sintered body obtained by sintering the above-mentioned sealing material, and preferably contains, by mass %, 20-50% SiO2, 10-50% Al2O3, 8-20% CaO, 8-20% MgO, and 10-20% SrO.

[0012] The sintered body of the present invention preferably has a heat-resistant temperature of 1250° C. or higher. The "heat-resistant temperature" refers to the temperature at which the height of a sintered body becomes smaller than 7 mm when the sintered body is processed into a cylindrical shape with a diameter of 7 mm and a height of 7 mm and heated in an electric furnace under a pressure of 1 MPa.

[0013] The sintered body of the present invention preferably has a thermal expansion coefficient of 7 to 9 ppm / ° C. The "thermal expansion coefficient" refers to a value measured in a temperature range of 30 to 380° C. using a thermomechanical analyzer. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a sealing material that has excellent heat resistance and flowability and matches the thermal expansion coefficient of metal and / or ceramic. DETAILED DESCRIPTION OF THE INVENTION

[0015] The sealing material of the present invention contains a crystallizable glass powder and a corundum powder. The corundum powder has the effect of promoting the precipitation of feldspar when a portion of it reacts with the crystallizable glass powder during heat treatment. The content of the crystallizable glass powder is preferably 60 to 90 mass %, and the content of the corundum powder is preferably 10 to 40 mass %. If the content of the corundum powder is too low (the content of the crystallizable glass powder is too high), feldspar crystals are less likely to precipitate, and heat resistance is likely to decrease. On the other hand, if the content of the corundum powder is too high (the content of the crystallizable glass powder is too low), the density of the sintered body tends to decrease.

[0016] Next, the crystallizable glass powder will be described.

[0017] The crystallizable glass powder contains, by mass%, 40-55% SiO2, 0.5-4.8% Al2O3, 10-20% CaO, 10-20% MgO, and 14-20% SrO. The reasons for limiting the content range of each component as above are explained below. Note that in the explanation of the content range of each component, % refers to mass %.

[0018] SiO2 is a component for precipitating pyroxene and feldspar, and also serves as a glass network former. The SiO2 content is 40 to 55%, preferably 45 to 50%, and particularly preferably 46 to 49%. If the SiO2 content is too low, vitrification becomes difficult. Furthermore, the content of pyroxene in the sintered body decreases, which tends to lower the thermal expansion coefficient. On the other hand, if the SiO2 content is too high, the viscosity during melting becomes too high. Furthermore, the content of corundum in the sintered body decreases, which tends to lower the mechanical strength.

[0019] Al2O3 is a component for precipitating feldspar and suppressing devitrification of glass during melting. The Al2O3 content is 0.5 to 4.8%, preferably 1 to 4.7, 2 to 4.6, and particularly preferably 4 to 4.5%. If the Al2O3 content is too low, the glass is prone to devitrification. Furthermore, the corundum content in the sintered body decreases, and the mechanical strength and heat resistance tend to decrease. On the other hand, if the Al2O3 content is too high, the melting property tends to deteriorate. Furthermore, the softening point increases, making sintering at 1000°C or less difficult.

[0020] CaO is a component for precipitating pyroxene and lowering the softening point of the crystallizable glass powder. The CaO content is 10 to 20%, preferably 12 to 28%, and particularly preferably 14 to 16%. If the CaO content is too low, the crystallinity decreases and the softening point tends to increase. Furthermore, the content of pyroxene in the sintered body decreases, which tends to lower the thermal expansion coefficient. On the other hand, if the CaO content is too high, vitrification becomes difficult and weather resistance decreases. Furthermore, the content of corundum in the sintered body decreases, which tends to lower the mechanical strength.

[0021] Like CaO, MgO is a component for precipitating pyroxene and also a component for lowering the softening point of the crystallizable glass powder. The MgO content is 10 to 20%, and preferably 15 to 18%. If the MgO content is too low, the crystallinity decreases and the softening point tends to increase. Furthermore, the amount of pyroxene precipitated in the sintered body decreases, resulting in a lower thermal expansion coefficient. On the other hand, if the MgO content is too high, vitrification becomes difficult. Furthermore, the corundum content in the sintered body decreases, which tends to lower the mechanical strength.

[0022] SrO is a component for precipitating feldspar and also a component for lowering the softening point of the crystallizable glass powder. The SrO content is 14 to 20%, preferably 14 to 18%, and particularly preferably 14 to 16%. If the SrO content is too low, the fluidity decreases and the softening point tends to rise. Furthermore, feldspar becomes difficult to precipitate and heat resistance tends to decrease. On the other hand, if the SrO content is too high, vitrification becomes difficult. Furthermore, the corundum content in the sintered body decreases, and mechanical strength tends to decrease.

[0023] Since BaO is a component that reduces the crystallinity and decreases the heat resistance, it is preferable that BaO is substantially not contained. Note that "substantially not containing BaO" means that the BaO content is less than 0.1 mass%.

[0024] The sealing material of the present invention preferably has a difference ΔT between the softening point and the crystallization temperature of 60°C or more, particularly 70°C or more. If ΔT is too low, the fluidity deteriorates. There is no particular upper limit for ΔT, but in reality it is 200°C or less.

[0025] The sealing material of the present invention preferably contains pyroxene, feldspar, and corundum as main crystals after heat treatment. By containing pyroxene with a high thermal expansion coefficient, feldspar with a high heat resistance temperature, and corundum with a high mechanical strength, a sintered body of the sealing material having high heat resistance, high expansion, and high strength can be obtained.

[0026] The sintered body of the present invention is obtained by sintering the above sealing material, and preferably contains, by mass %, 20-50% SiO2, 10-50% Al2O3, 8-20% CaO, 8-20% MgO, and 10-20% SrO.

[0027] The sintered body of the present invention preferably has a heat-resistant temperature of 1250°C or higher, particularly 1300°C. If the heat-resistant temperature of the sintered body is too low, deformation or cracking may occur at high temperatures. There is no particular upper limit to the heat-resistant temperature, but in reality it is 1500°C or lower.

[0028] The sintered body of the present invention preferably has a thermal expansion coefficient of 7 to 9 ppm / °C. If the thermal expansion coefficient of the sintered body is too low, distortion is likely to occur due to the difference in thermal expansion when used as a sealing material between metal and ceramic. On the other hand, if the thermal expansion coefficient is too high, thermal shock resistance is reduced.

[0029] As described above, the sealing material and sintered body of the present invention have excellent heat resistance and fluidity and match the thermal expansion coefficient of metal and / or ceramic, and are therefore suitable for use in exhaust gas sensors or temperature sensors.

[0030] Next, the method for producing the sealing material and sintered body of the present invention will be described below.

[0031] The crystallizable glass powder contained in the sealing material of the present invention is obtained by preparing raw material powders to have a predetermined composition, melting them at a temperature of 1300 to 1650°C, molding them, cooling them, and then pulverizing and classifying them. The sealing material of the present invention can be produced by mixing the above-mentioned crystallizable glass powder and corundum powder to form a mixed powder.

[0032] Next, the mixed powder is prepared, for example, into a slurry. The slurry can be prepared by adding a binder, a plasticizer, a solvent, etc. to the mixed powder. The content of the mixed powder in the slurry is generally about 30 to 90 mass %.

[0033] The binder is a component that increases the mechanical strength of the film after drying and imparts flexibility, and its content is generally about 0.1 to 30 mass %. Examples of binders that can be used include polyvinyl butyral resins and methacrylic acid resins, and these can be used alone or in combination.

[0034] Plasticizers are components that control the drying speed and impart flexibility to the dried film. Specific examples include butyl benzyl phthalate, dioctyl phthalate, diisooctyl phthalate, dicapryl phthalate, and dibutyl phthalate, which can be used alone or in combination. The content of plasticizers in the raw material is generally about 0 to 10% by mass.

[0035] The solvent is used to make the material into a slurry, and its content is generally about 1 to 30 mass %. Examples of solvents that can be used include toluene and methyl ethyl ketone, and these can be used alone or in combination.

[0036] Next, the slurry is applied to the sealing portion of the first member made of metal or ceramic using a dropper or the like and dried. Furthermore, the second member made of metal or ceramic is fixed in contact with the dried film and heat-treated at a temperature between the softening point of the glass and 1000°C. This heat treatment causes the glass powder to soften and flow, sealing the first and second members. Crystal precipitation occurs when the glass powder has flowed to a certain extent.

[0037] The sealing material of the present invention can be used for purposes other than sealing, such as coating and filling. It can also be used in forms other than a slurry, specifically in the form of a powder, paste, green sheet, tablet, or the like. For example, a metal or ceramic cylinder can be filled with glass powder together with lead wires and heat-treated to form an airtight seal. A preform molded from a green sheet or a tablet produced by powder press molding can also be placed on a metal or ceramic member and heat-treated to coat it. [Example]

[0038] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0039] Tables 1 and 2 show examples of the present invention (samples Nos. 1 to 4) and comparative examples (samples Nos. 5 and 6).

[0040] [Table 1]

[0041] [Table 2]

[0042] First, various oxide glass raw materials were prepared and mixed uniformly to obtain the glass compositions shown in Tables 1 and 2, then placed in a platinum crucible and melted at 1400-1500°C for 3-8 hours, and the molten glass was formed into a thin plate using a water-cooled roller. Next, this was roughly crushed, and then wet-pulverized in a ball mill with the addition of alcohol, and classified to obtain a crystallizable glass powder with an average particle size of 1.5-3 μm.

[0043] Next, the crystallizable glass powder was uniformly mixed with the amount of corundum powder (average particle size: 2 μm) shown in the table to obtain a sealing material. The softening point and crystallization temperature of the sealing material were evaluated.

[0044] The softening point and crystallization temperature were measured using a macro-type differential thermal analyzer. Specifically, for each sealing material sample, measurements were made up to 1050°C using the macro-type differential thermal analyzer. In the obtained chart, the value at the fourth inflection point was taken as the softening point, and the value at the strong exothermic peak was taken as the crystallization temperature. The difference between the softening point and the crystallization temperature was calculated as ΔT.

[0045] Next, 15% by weight of polyvinyl butyral as a binder, 4% by weight of butyl benzyl phthalate as a plasticizer, and 30% by weight of toluene as a solvent were added to the sealing material to prepare a slurry. The slurry was then molded into a green sheet using a doctor blade method, dried, and fired to obtain a sintered body. The firing temperature, main crystal structure, heat resistance temperature, and thermal expansion coefficient of each sample were evaluated. The results are shown in Tables 1 and 2.

[0046] The firing temperature is the lowest temperature at which ink is applied to a sintered body that has been fired at various temperatures for 20 minutes, and then wiped off, leaving no ink behind (i.e. densely sintered).

[0047] The primary crystals were identified using a powder X-ray diffractometer (Rigaku Corporation RINT2100).

[0048] The heat resistance temperature was measured by processing a sintered body sintered at the firing temperature in the table into a cylindrical shape with a diameter of 7 mm and a height of 7 mm, and then heating it in an electric furnace while applying a pressure of 1 MPa, and measuring the temperature at which the height became smaller than 7 mm.

[0049] The thermal expansion coefficient was measured in the temperature range of 30 to 380°C using a thermomechanical analyzer.

[0050] As is clear from Tables 1 and 2, in the example samples Nos. 1 to 4, pyroxene and feldspar precipitated at relatively low firing temperatures below 900°C, and the heat-resistant temperatures were high at 1300 to 1320°C. Furthermore, the expansion coefficients were 7.4 to 7.6 ppm / °C, values ​​suitable for sealing metals and ceramics. Furthermore, ΔT was 80°C or higher, indicating the fluidity suitable for sealing materials. On the other hand, sample No. 5, due to the low SrO content in the crystallizable glass powder, did not precipitate feldspar and the heat-resistant temperature was low at 1200°C. In addition, the softening point was high, resulting in a small ΔT of 40°C. Sample No. 6, due to the high Al2O3 content in the crystallizable glass powder, had a low thermal expansion coefficient of 6.0 ppm / °C.

Claims

1. In mass%, SiO ２ 40-55%, Al ２ O ３ A sealing material comprising a crystallizable glass powder and a corundum powder, the crystallizable glass powder containing 0.5 to 4.8% of Cu, 10 to 20% of CaO, 16.5 to 20% of MgO, and 14 to 20% of SrO, and substantially no BaO.

2. 2. The sealing material according to claim 1, which contains pyroxene, feldspar, and corundum as main crystals after heat treatment.

3. 3. The sealing material according to claim 1, wherein the difference ΔT between the softening point and the crystallization temperature is 60° C. or more.

4. 4. The sealing material according to claim 1, which is used for an exhaust gas sensor or a temperature sensor.

5. A sintered body obtained by sintering the sealing material according to any one of claims 1 to 4, comprising, in mass %, SiO ２ 36-50%, Al ２ O ３ A sintered body characterized by containing 10 to 50% of SiO 2 , 11 to 14.4% of CaO , 8 to 20% of MgO , and 10 to 20% of SrO .

6. 6. The sintered body according to claim 5, wherein the heat-resistant temperature is 1250° C. or higher.

7. 7. The sintered body according to claim 5, wherein the thermal expansion coefficient is 7 to 9 ppm / °C.

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