JP2023032104A - Sealing material and sintered body - Google Patents

Abstract

A sealing material having excellent heat resistance and fluidity and matching the thermal expansion coefficient of metals and/or ceramics is provided. A crystallizable glass powder containing 40-55% SiO, 0.5-4.8% Al2O, 10-20% CaO, 10-20% MgO, and 14-20% SrO in mass % and corundum powder. A sealing material characterized by: [Selection figure] None

Description

TECHNICAL FIELD The present invention relates to a sealing material suitable for sealing, bonding, coating, etc. of metals and ceramics.

Heat resistance is required for sealing materials for protecting exhaust gas sensors and temperature sensors of automobile engines and for fixing elements.

As a material with high heat resistance, a glass-ceramic in which feldspar containing Ba or Sr is precipitated has been developed. The above glass-ceramic has a high heat resistance of 1250 to 1450° C. in use (see Patent Document 1).

Special table 2010-537928

However, the glass ceramic of Patent Document 1 has insufficient fluidity and a low coefficient of thermal expansion of 3.0 to 5.5 ppm/°C. There is a problem that cracks are likely to occur due to the mismatch of thermal expansion coefficients.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sealing material which is excellent in heat resistance and fluidity and which matches the coefficient of thermal expansion of metals and/or ceramics.

As a result of various experiments, the present inventor found that the above technical problems can be solved by combining a crystalline glass powder and a corundum powder having a specific glass composition, and proposes it as the present invention. It is. That is, the sealing material of the present invention contains 40 to 55% by mass SiO ₂ , 0.5 to 4.8% Al ₂ O _{3 ,} 10 to 20% CaO, 10 to 20% MgO, and 14 to 20% SrO. It is characterized by comprising a crystallizable glass powder containing and a corundum powder.

The sealing material of the present invention preferably contains pyroxene, feldspar, and corundum as main crystals after heat treatment. “Heat treatment” means heat treatment at 700 to 1000° C. for 10 minutes or longer. "Pyroxene" means (Ca _x Mg _2-x )Si ₂ O ₆ crystal (0≦x≦1), and "feldspar" means (Ca _y Sr _1-y )(Al ₂ Si ₂ O ₈ ) crystal. (0≦y≦1).

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 terms "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, and the larger the ΔT, the more excellent the fluidity at the time of sealing.

The sealing material of the present invention is preferably used for exhaust gas sensors or temperature sensors.

The sintered body of the present invention is a sintered body obtained by sintering the above-described sealing material, and contains 20 to 50% by mass of SiO ₂ , 10 to 50% by mass of Al ₂ O ₃ , 8 to 20% by mass of CaO, It preferably contains 8-20% MgO and 10-20% SrO.

The sintered body of the present invention preferably has a heat resistance temperature of 1250° C. or higher. The "heat resistance temperature" is measured by processing the sintered body into a cylindrical shape with a diameter of 7 mm and a height of 7 mm, heating it in an electric furnace while applying a pressure of 1 MPa, and measuring the temperature at which the height becomes less than 7 mm. value.

The sintered body of the present invention preferably has a coefficient of thermal expansion of 7 to 9 ppm/°C. "Thermal expansion coefficient" refers to a value measured with a thermomechanical analyzer within a temperature range of 30 to 380°C.

According to the present invention, it is possible to provide a sealing material that is excellent in heat resistance and fluidity and that matches the thermal expansion coefficient of metal and/or ceramic.

The sealing material of the present invention contains crystallizable glass powder and corundum powder. A part of the corundum powder reacts with the crystallizable glass powder during heat treatment to promote the precipitation of feldspar. It is preferable that the content of the crystalline glass powder is 60 to 90% by mass and the content of the corundum powder is 10 to 40% by mass. If the content of the corundum powder is too low (the content of the crystallizable glass powder is too high), feldspar crystals are difficult to precipitate, and heat resistance tends to decrease. On the other hand, if the content of corundum powder is too high (the content of crystallizable glass powder is too low), the compactness of the sintered body tends to decrease.

Next, the crystallizable glass powder will be explained.

The crystallizable glass powder contains 40-55% SiO ₂ , 0.5-4.8% Al ₂ O ₃ , 10-20% CaO, 10-20% MgO, and 14-20% SrO in mass %. The reason why the content range of each component is limited as described above will be described below. In addition, in description of the content range of each component, % notation refers to the mass %.

SiO ₂ is a component for precipitating pyroxene and feldspar, and is a component that becomes a network former of glass. The content of SiO ₂ is 40-55%, preferably 45-50%, in particular 46-49%. If the _SiO2 content is too low, vitrification becomes difficult. In addition, the content of pyroxene in the sintered body decreases, and the coefficient of thermal expansion tends to decrease. On the other hand, if the _SiO2 content is too high, the viscosity during melting will be too high. In addition, the content of corundum in the sintered body decreases, and the mechanical strength tends to decrease.

Al ₂ O ₃ is a component for precipitating feldspar and a component for suppressing devitrification of the glass during melting. The content of Al ₂ O ₃ is 0.5-4.8%, preferably 1-4.7, 2-4.6, especially 4-4.5%. If the Al ₂ O ₃ content is too low, the glass tends to devitrify. In addition, the content of corundum in the sintered body decreases, and the mechanical strength and heat resistance tend to decrease. On the other hand, if the Al ₂ O ₃ content is too high, the meltability tends to deteriorate. In addition, the softening point rises and sintering at 1000° C. or less becomes difficult.

CaO is a component for precipitating pyroxene and a component for lowering the softening point of the crystallizable glass powder. The content of CaO is 10-20%, preferably 12-28%, particularly 14-16%. If the CaO content is too low, the crystallinity is lowered and the softening point tends to rise. Furthermore, the content of pyroxene in the sintered body decreases, and the coefficient of thermal expansion tends to decrease. On the other hand, when the content of CaO is too high, vitrification becomes difficult and the weather resistance deteriorates. In addition, the content of corundum in the sintered body decreases, and the mechanical strength tends to decrease.

MgO, like CaO, is a component for precipitating pyroxene and a component for lowering the softening point of the crystallizable glass powder. The content of MgO is 10-20%, preferably 15-18%. If the content of MgO is too small, the crystallinity is lowered and the softening point tends to rise. In addition, the amount of precipitation of pyroxene in the sintered body decreases, and the coefficient of thermal expansion decreases. On the other hand, when the content of MgO is too high, vitrification becomes difficult. In addition, the content of corundum in the sintered body decreases, and the mechanical strength tends to decrease.

SrO is a component for precipitating feldspar and a component for lowering the softening point of the crystallizable glass powder. The content of SrO is 14-20%, preferably 14-18%, particularly 14-16%. If the content of SrO is too small, the fluidity is lowered and the softening point tends to rise. In addition, it becomes difficult for feldspar to precipitate, and the heat resistance tends to decrease. On the other hand, when the SrO content is too high, vitrification becomes difficult. In addition, the content of corundum in the sintered body decreases, and the mechanical strength tends to decrease.

Since BaO is a component that lowers the degree of crystallinity and lowers the heat resistance, it is preferred that substantially no BaO is contained. The expression "substantially free of BaO" means that the content of BaO is less than 0.1% by mass.

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, fluidity will deteriorate. Although the upper limit of ΔT is not particularly limited, it is practically 200°C or less.

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

The sintered body of the present invention is obtained by sintering the above sealing material, and contains 20 to 50% by mass of SiO ₂ , 10 to 50% by mass of Al ₂ O ₃ , 8 to 20% by mass of CaO, and 8 to 20% of MgO. 20%, SrO 10-20%.

The sintered body of the present invention preferably has a heat resistant temperature of 1250°C or higher, particularly 1300°C. If the heat resistance temperature of the sintered body is too low, deformation or cracking may occur at high temperatures. Although the upper limit of the heat resistance temperature is not particularly limited, it is practically 1500° C. or less.

The sintered body of the present invention preferably has a coefficient of thermal expansion of 7 to 9 ppm/°C. If the coefficient of thermal expansion 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 for metals and ceramics. On the other hand, if the coefficient of thermal expansion is too high, the thermal shock resistance is lowered.

The sealing material and sintered body of the present invention are excellent in heat resistance and fluidity as described above, and match the thermal expansion coefficient of metals and/or ceramics, so they are suitable for exhaust gas sensors or temperature sensors. .

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

The crystallizable glass powder contained in the sealing material of the present invention is prepared by preparing a raw material powder so as to have a predetermined composition, melting it at a temperature of 1300 to 1650° C., molding it, cooling it, pulverizing it, and classifying it. can get. The sealing material of the present invention can be produced by mixing the crystallizable glass powder and the corundum powder to form a mixed powder.

Next, the mixed powder is prepared, for example, in the form of slurry. A slurry can be prepared by adding a binder, a plasticizer, a solvent, and the like to the mixed powder. The content of the mixed powder in the slurry is generally about 30 to 90% by mass.

The binder is a component that increases the mechanical strength of the dried film and imparts flexibility, and its content is generally about 0.1 to 30% by mass. As the binder, for example, polyvinyl butyral resin, methacrylic acid resin, etc. can be used, and these can be used alone or in combination.

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

The solvent is a material for slurrying the material, and its content is generally about 1 to 30% by mass. Examples of solvents that can be used include toluene and methyl ethyl ketone, and these can be used alone or in combination.

Next, the above 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, a second member made of metal or ceramic is fixed in contact with the dry film and heat-treated at a softening point of glass to 1000°C. By this heat treatment, the glass powder is once softened and flowed to seal the first and second members. Precipitation of crystals occurs when the glass powder has flowed to some extent.

In addition, the sealing material of the present invention can be used for purposes other than sealing, such as coating and filling. Moreover, it can be used in a form other than a slurry, specifically in a powder form, a paste, a green sheet, a tablet, or the like. For example, there is a form in which a metal or ceramic cylinder is filled with glass powder together with a lead wire, heat-treated, and hermetically sealed. Alternatively, a preform formed by green sheet molding, a tablet formed by powder press molding, or the like can be placed on a metal or ceramic member and heat-treated to coat the material.

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

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

First, glass raw materials of various oxides were prepared so as to have the glass compositions shown in Tables 1 and 2, mixed uniformly, then placed in a platinum crucible and melted at 1400 to 1500 ° C. for 3 to 8 hours, followed by a water-cooled roller. The molten glass was formed into thin plates. Next, after coarsely pulverizing, alcohol was added, wet pulverization was carried out with a ball mill, and the particles were classified so as to have an average particle size of 1.5 to 3 μm to obtain a crystallizable glass powder.

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

The softening point and crystallization temperature were measured using a macro-type differential thermal analyzer. Specifically, for each sealing material 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 the crystallization point. quenching temperature. Also, the difference between the softening point and the crystallization temperature was calculated as ΔT.

Subsequently, 15% by mass of polyvinyl butyral as a binder, 4% by mass of butylbenzyl phthalate as a plasticizer, and 30% by mass of toluene as a solvent were added to the above sealing material to prepare a slurry. Next, the above slurry was formed into a green sheet by a doctor blade method, dried and fired to obtain a sintered body. Each sample thus obtained was evaluated for firing temperature, main crystals, heat resistance temperature and coefficient of thermal expansion. The results are shown in Tables 1 and 2.

The firing temperature is the lowest temperature at which ink does not remain (=densely sintered) when ink is applied to a sintered body fired at various temperatures for 20 minutes and then wiped off.

The main crystal was identified by a powder X-ray diffractometer (Rigaku RINT2100).

The heat resistance temperature is determined by processing the 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 heating it in an electric furnace while applying a pressure of 1 MPa to make the height smaller than 7 mm. Temperature was measured.

The coefficient of thermal expansion is measured with a thermomechanical analyzer in the temperature range of 30 to 380°C.

As is clear from Tables 1 and 2, sample no. In samples 1 to 4, pyroxene and feldspar precipitated at a relatively low firing temperature of 900°C or less, and the heat resistance temperature was as high as 1300 to 1320°C. Also, the coefficient of expansion was 7.4 to 7.6 ppm/°C, which was a value suitable for sealing metals and ceramics. Furthermore, ΔT was 80° C. or more, and it was found to have fluidity suitable for a sealing material. On the other hand, sample no. In No. 5, since the content of SrO in the crystallizable glass powder was small, no feldspar precipitated and the heat resistance temperature was as low as 1200°C. In addition, the softening point was high and ΔT was as small as 40°C. Sample no. In No. 6, the thermal expansion coefficient was as low as 6.0 ppm/°C due to the large content of Al ₂ O ₃ in the crystallizable glass powder.

Claims (7)

Crystallizable glass powder containing 40-55% SiO _{2 ,} 0.5-4.8% Al ₂ O ₃ , 10-20% CaO, 10-20% MgO, 14-20% SrO, in mass %, and corundum A sealing material comprising powder. 2. The sealing material according to claim 1, which contains pyroxene, feldspar, and corundum as main crystals after heat treatment. 3. The sealing material according to claim 1, wherein the difference .DELTA.T between the softening point and the crystallization temperature is 60.degree. 4. The sealing material according to any one of claims 1 to 3, which is used for an exhaust gas sensor or a temperature sensor. A sintered body obtained by sintering the sealing material according to any one of claims 1 to 4, comprising 20 to 50% by mass of SiO ₂ , 10 to 50% by mass of Al ₂ O _{3 and} 8 to 20% by mass of CaO. , MgO 8-20%, and SrO 10-20%. 6. The sintered body according to claim 5, which has a heat resistance temperature of 1250° C. or higher. 7. The sintered body according to claim 5, wherein the coefficient of thermal expansion is 7-9 ppm/°C.