A low-temperature brazing connection method for strontium titanate ceramics

Abstract

The present application discloses a low-temperature brazing connection method for strontium titanate ceramics, specifically relating to the field of ceramic brazing. A method for preparing the above-mentioned glass powder comprises: mixing V2O5 powder, B2O3 powder, Al2O3 powder and CaO powder according to mass fraction to obtain a mixed powder; heating the mixed powder to obtain a glass liquid, and preparing it into glass powder. The above-mentioned glass powder is mixed with a binder to obtain a glass solder paste; the glass solder paste is applied to the surface to be welded of the strontium titanate ceramic to obtain a strontium titanate ceramic to be welded; two strontium titanate ceramics to be welded are stacked to obtain a strontium titanate ceramic-glass solder paste-strontium titanate ceramic "sandwich structure" as a workpiece to be welded; the workpiece to be welded is heated to obtain the strontium titanate ceramic after brazing. Vanadate glass powder is used as a brazing material. The thermal expansion coefficient of the vanadate glass powder matches the thermal expansion coefficient of the strontium titanate ceramic, and the brazing temperature is low, thereby effectively reducing the residual stress of the joint and improving the joint strength.

Description

Technical Field

[0001] The present application relates to the field of ceramic brazing, and in particular to a low-temperature brazing connection method for strontium titanate ceramics. Background Art

[0002] Strontium titanate (SrTiO3) ceramics have excellent dielectric properties and thermal stability and are widely used in industries such as chemical engineering, aerospace, and electronics. Currently, the main methods for joining ceramic materials include transient liquid phase diffusion welding, microwave bonding, and brazing. Brazing, among others, offers advantages such as ease of operation and excellent joint performance. Therefore, this method is used in the present invention to join strontium titanate ceramics.

[0003] Brazing fillers for ceramic brazing are primarily based on traditional active metals such as Ag, Cu, and Ti. However, the significant difference in thermal expansion coefficients between the active metal and the ceramic, coupled with high brazing temperatures, can lead to significant residual stress within the joint. Therefore, the present invention incorporates a vanadate glass filler as a brazing filler. Because this filler has a similar thermal expansion coefficient to the ceramic and the brazing temperature is low, it minimizes residual stress in the joint during cooling. Summary of the Invention

[0004] The main purpose of this application is to provide a low-temperature brazing connection method for strontium titanate ceramics, aiming to solve the problem of residual stress in the joint caused by the large difference in thermal expansion coefficient between the existing brazing material and the ceramic and the high brazing temperature.

[0005] To achieve the above-mentioned purpose, the present application provides a glass powder, the raw materials of which include the following components in mass fraction: 40-50% V2O5, 15-20% B2O3, 20-35% Al2O3 and 3-5% CaO, and the sum of the mass fractions of the above components is 100%.

[0006] To achieve the above-mentioned purpose, the present application also provides a method for preparing the above-mentioned glass powder, comprising: mixing 40-50% V2O5 powder, 15-20% B2O3 powder, 20-35% Al2O3 powder and 3-5% CaO powder according to mass fraction to obtain a mixed powder, wherein the sum of the mass fractions of the above-mentioned components is 100%; heating the mixed powder to obtain a glass liquid; wherein the heating temperature is 900-1100°C and the heating time is 1.2-1.6h; quenching the glass liquid to obtain glass particles, and crushing the glass particles to obtain glass powder.

[0007] Optionally, when the mixed powder is heated, the heating rate is 5 to 10° C. / min.

[0008] To achieve the above objectives, the present application also provides an application of the above glass powder in low-temperature brazing connection of strontium titanate ceramics.

[0009] To achieve the above-mentioned purpose, the present application also provides a low-temperature brazing connection method for strontium titanate ceramics, comprising: mixing the above-mentioned glass powder with a binder to obtain a glass solder paste; applying the glass solder paste to the surface to be welded of the strontium titanate ceramic to obtain a strontium titanate ceramic to be welded; stacking two strontium titanate ceramics to be welded to obtain a strontium titanate ceramic-glass solder paste-strontium titanate ceramic, which is used as a workpiece to be welded; heating the workpiece to be welded to obtain a brazed strontium titanate ceramic; wherein the heating temperature is 540-650°C and the holding time is 1-15 minutes.

[0010] Optionally, the heating rate during the heating process is 10° C. / min.

[0011] Optionally, the mass ratio of the glass powder to the binder is 7 to 10:1.

[0012] Optionally, the binder is terpineol.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] The glass powder of the present invention contains vanadium ions in the form of VO6 octahedra within the glass structure, effectively lowering the melting point of the solder, thereby enabling low-temperature brazing. Vanadate has a wider transmittance range in the visible and near-infrared regions, ensuring the optical transparency of the strontium titanate ceramic after brazing. Furthermore, B2O3 exhibits excellent glass-forming properties even when slowly cooled from a molten state. The present invention's low-temperature brazing method for strontium titanate ceramics uses vanadate glass powder as the solder. Compared to active solders, the thermal expansion coefficient of the vanadate glass powder is more closely matched to that of the strontium titanate ceramic, resulting in a lower brazing temperature, effectively reducing residual stress in the joint and improving joint strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a diagram showing the wetting results of the glass powder on the strontium titanate ceramic obtained in Example 1 of a low-temperature brazing connection method for strontium titanate ceramics of this application;

[0016] Figure 2 This is a scanning electron microscope morphology image of the brazed strontium titanate ceramic joint obtained in Example 1 of a low-temperature brazing connection method for strontium titanate ceramics of this application;

[0017] Figure 3 This is a diagram showing the wetting results of the glass powder on the strontium titanate ceramic obtained in Example 2 of a low-temperature brazing connection method for strontium titanate ceramics of this application;

[0018] Figure 4 This is a diagram showing the wetting results of the glass powder on the strontium titanate ceramic obtained in Comparative Example 1 of a low-temperature brazing connection method for strontium titanate ceramics of this application;

[0019] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0021] A first embodiment of the present invention provides a glass powder, wherein the raw materials of the glass powder include the following components in percentage by mass:

[0022] 40-50% V2O5, 15-20% B2O3, 20-35% Al2O3 and 3-5% CaO, the sum of the above components is 100%.

[0023] In this embodiment, the vanadium ions in the vanadate glass powder exist in the form of VO6 octahedra within the glass structure, effectively lowering the melting point of the brazing material, thereby enabling low-temperature brazing. Vanadate has a wider transmittance range in the visible and near-infrared regions, ensuring the optical transparency of the brazed strontium titanate ceramic. Furthermore, B2O3 exhibits excellent glass-forming properties, resisting crystallization even when slowly cooled from a molten state. Compared to active brazing materials, the thermal expansion coefficient of vanadate glass more closely matches that of the strontium titanate ceramic, allowing for lower brazing temperatures. This can significantly reduce residual stress in the joint and improve joint strength.

[0024] A second embodiment of the present invention provides a method for preparing glass powder, which specifically includes the following steps:

[0025] Step S1, mixing 40-50% of V2O5 powder, 15-20% of B2O3 powder, 20-35% of Al2O3 powder, and 3-5% of CaO powder according to mass fraction to obtain a mixed powder, and heating the mixed powder at 900-1100°C for 1.2-1.6 hours to obtain a molten glass liquid;

[0026] Specifically, the mixed powder is placed in a platinum crucible, and the crucible is placed in a muffle furnace, and the temperature is increased to 900-1100° C. at a rate of 5-10° C. / min, and kept at this temperature for 1.2-1.6 hours.

[0027] Step S2: quenching the glass liquid to obtain glass particles, and crushing the glass particles to obtain glass powder.

[0028] A third embodiment of the present invention provides a low-temperature brazing connection method for strontium titanate ceramics, comprising the following steps:

[0029] Step S3, mixing the glass powder and the binder at a mass ratio of 7 to 10:1 to obtain a glass solder paste; wherein the binder is terpineol;

[0030] Step S4, applying glass solder paste to the surface of the strontium titanate ceramic to be welded to obtain the strontium titanate ceramic to be welded;

[0031] Before applying the glass solder paste, the strontium titanate ceramic needs to be pretreated. The specific method is to cut the strontium titanate ceramic into shape using a diamond cutter, polish it using 400#, 800#, 1500#, and 2000# diamond abrasive discs, and finally ultrasonically clean it with anhydrous ethanol for 15 minutes before drying. The coating thickness is 50 to 300 μm.

[0032] Step S5, placing two strontium titanate ceramics to be welded in a stack to obtain a strontium titanate ceramic-glass solder paste-strontium titanate ceramic "sandwich structure" as the welded part;

[0033] Step S6, heating the workpiece to be welded to obtain a brazed strontium titanate ceramic; wherein the heating rate is 10°C / min, the heating temperature is 540-650°C, and the holding time is 1-15 minutes;

[0034] Specifically, the workpiece to be welded is placed in a muffle furnace and heated to 300°C at a heating rate of 10°C / min, then kept warm for 10 minutes. After the insulation is completed, the temperature is further increased to 540-650°C at a rate of 10°C / min, and finally cooled in the furnace to obtain the brazed strontium titanate ceramic.

[0035] Example 1

[0036] Step S1, mixing 45% of V2O5 powder, 15% of B2O3 powder, 35% of Al2O3 powder, and 5% of CaO powder according to mass fraction to obtain a mixed powder, placing the mixed powder in a platinum crucible, then placing the crucible in a muffle furnace, heating to 1100°C at a heating rate of 5°C / min, and keeping the temperature for 1.5 hours to obtain a molten glass liquid;

[0037] Step S2, quenching the glass liquid to obtain glass particles, and crushing the glass particles to obtain vanadate glass powder;

[0038] Step S3, mixing vanadate glass powder and terpineol in a mass ratio of 10:1 to obtain a glass solder paste;

[0039] Step S4, cutting the strontium titanate ceramic into shape using a diamond cutting machine, polishing it using 400#, 800#, 1500# and 2000# diamond sandpaper in sequence, and finally ultrasonically cleaning it with anhydrous ethanol for 15 minutes and then drying it to obtain the pretreated strontium titanate ceramic;

[0040] Step S5, applying glass solder paste to the surface to be welded of the pretreated strontium titanate ceramic, wherein the coating thickness is 60 μm, to obtain the strontium titanate ceramic to be welded;

[0041] Step S6, placing two strontium titanate ceramics to be welded in a stack to obtain a strontium titanate ceramic-glass solder paste-strontium titanate ceramic "sandwich structure" as the welded part;

[0042] Step S7: Place the workpiece to be welded in a muffle furnace, heat it to 300°C at a heating rate of 10°C / min, and then keep it warm for 10 minutes. After the insulation is completed, continue to heat it to 610°C at a rate of 10°C / min and keep it warm for 10 minutes. Finally, cool it with the furnace to obtain the brazed strontium titanate ceramic.

[0043] The remaining melt in step S2 of this embodiment was quickly placed in a stainless steel mold at a temperature above 200°C to form a 5mm×5mm×1mm vanadate glass sheet. The vanadate glass sheet was placed on the pretreated strontium titanate ceramic, and then placed in a muffle furnace and heated to 610°C at a heating rate of 10°C / min. After holding for 10 minutes, the furnace was cooled. The wetting angle at this temperature and holding time was measured to be 45°. Figure 1 , it can be seen that the vanadate glass obtained in this example has excellent wettability on strontium titanate ceramics.

[0044] The strontium titanate ceramic brazed joint obtained in this example was characterized using a scanning electron microscope, and the morphology is shown in FIG. Figure 2 The figure shows that using the glass powder obtained in this example as a brazing filler material to join strontium titanate ceramics produces a high-quality weld free of holes and cracks. Testing has shown that the shear strength of the strontium titanate ceramic / vanadate glass / strontium titanate ceramic joint obtained in this example reaches 42 MPa.

[0045] Example 2

[0046] Step S1, 50% V2O5 powder, 20% B2O3 powder, 25% Al2O3 powder and 5% CaO powder are mixed according to mass fraction to obtain a mixed powder, the mixed powder is placed in a platinum crucible, and the crucible is placed in a muffle furnace, and heated to 1100°C at a heating rate of 5°C / min, and kept at this temperature for 1.5 hours to obtain a molten glass liquid;

[0047] Step S2, quenching the glass liquid to obtain glass particles, and crushing the glass particles to obtain vanadate glass powder;

[0048] Step S3, mixing vanadate glass powder and terpineol in a mass ratio of 8:1 to obtain a glass solder paste;

[0049] Step S4, cutting the strontium titanate ceramic into shape using a diamond cutting machine, polishing it using 400#, 800#, 1500# and 2000# diamond sandpaper in sequence, and finally ultrasonically cleaning it with anhydrous ethanol for 15 minutes and then drying it to obtain the pretreated strontium titanate ceramic;

[0050] Step S5, applying glass solder paste to the surface to be welded of the pretreated strontium titanate ceramic, wherein the coating thickness is 50 μm, to obtain the strontium titanate ceramic to be welded;

[0051] Step S6, placing two strontium titanate ceramics to be welded in a stack to obtain a strontium titanate ceramic-glass solder paste-strontium titanate ceramic "sandwich structure" as the welded part;

[0052] Step S7: Place the workpiece to be welded in a muffle furnace, heat it to 300°C at a heating rate of 10°C / min, and then keep it warm for 10 minutes. After the insulation is completed, continue to heat it to 610°C at a rate of 10°C / min and keep it warm for 10 minutes. Finally, cool it with the furnace to obtain the brazed strontium titanate ceramic.

[0053] The remaining melt in step S2 of this embodiment was quickly placed in a stainless steel mold at a temperature above 200°C to form a 5mm×5mm×1mm vanadate glass sheet. The vanadate glass sheet was placed on the pretreated strontium titanate ceramic, which was then placed in a muffle furnace and heated to 540°C at a heating rate of 10°C / min. After holding for 10 minutes, the furnace was cooled. The wetting angle at this temperature and holding time was measured to be 43°. Figure 3 , it can be seen that the vanadate glass powder obtained in this embodiment has excellent wettability on strontium titanate ceramics.

[0054] After testing, the shear strength of the joint of strontium titanate ceramic / vanadate glass / strontium titanate ceramic obtained in this embodiment reached 34 MPa.

[0055] Comparative Example 1

[0056] Step S1, mixing 50% B2O3 powder, 35% Al2O3 powder, and 15% CaO powder according to mass fraction to obtain a mixed powder, placing the mixed powder in a platinum crucible, then placing the crucible in a muffle furnace, heating to 1100°C at a heating rate of 5°C / min, and keeping the temperature for 1.5 hours to obtain a molten glass liquid;

[0057] Step S2, quenching the glass liquid to obtain glass particles, and crushing the glass particles to obtain vanadate glass powder;

[0058] Step S3, mixing borate glass powder and terpineol in a mass ratio of 10:1 to obtain a glass solder paste;

[0059] Step S4, cutting the strontium titanate ceramic into shape using a diamond cutting machine, polishing it using 400#, 800#, 1500# and 2000# diamond sandpaper in sequence, and finally ultrasonically cleaning it with anhydrous ethanol for 15 minutes and then drying it to obtain the pretreated strontium titanate ceramic;

[0060] Step S5, applying glass solder paste to the surface to be welded of the pretreated strontium titanate ceramic, wherein the coating thickness is 60 μm, to obtain the strontium titanate ceramic to be welded;

[0061] Step S6, placing two strontium titanate ceramics to be welded in a stack to obtain a strontium titanate ceramic-glass solder paste-strontium titanate ceramic "sandwich structure" as the welded part;

[0062] Step S7: Place the workpiece to be welded in a muffle furnace, heat it to 300°C at a heating rate of 10°C / min, and then keep it warm for 10 minutes. After the insulation is completed, continue to heat it to 780°C at a rate of 10°C / min and keep it warm for 10 minutes. Finally, cool it with the furnace to obtain the brazed strontium titanate ceramic.

[0063] The remaining melt in step S2 of this embodiment was quickly placed in a stainless steel mold at a temperature above 200°C to form a 5mm×5mm×1mm vanadate glass sheet. The borate glass sheet was placed on the pretreated strontium titanate ceramic, which was then placed in a muffle furnace and heated to 780°C at a heating rate of 10°C / min. After holding for 10 minutes, the furnace was cooled. The wetting angle at this temperature and holding time was measured to be 73°. Figure 4 ,It can be seen that the wetting effect of glass powder without V2O5 added on ceramics is not ideal.

[0064] The above are only preferred embodiments of the present application and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A glass powder, characterized in that: The raw materials of the glass powder include the following components in terms of mass fraction: 40-50% V2O5, 15-20% B2O3, 20-35% Al2O3 and 3-5% CaO, the sum of the mass fractions of the above components is 100%.

2. A method for preparing glass powder according to claim 1, characterized in that: include: Mixing 40-50% of V2O5 powder, 15-20% of B2O3 powder, 20-35% of Al2O3 powder, and 3-5% of CaO powder according to mass fraction to obtain a mixed powder, wherein the sum of the mass fractions of the above components is 100%; Heating the mixed powder to obtain glass liquid; wherein the heating temperature is 900-1100° C. and the heating time is 1.2-1.6 hours; The glass liquid is quenched to obtain glass particles, and the glass particles are crushed to obtain glass powder.

3. The method for preparing glass powder according to claim 2, wherein: When the mixed powder is heated, the heating rate is 5-10° C. / min.

4. Use of the glass powder according to claim 1 in low-temperature brazing connection of strontium titanate ceramics.

5. A low-temperature brazing connection method for strontium titanate ceramics, characterized in that: include: Mixing the glass powder according to claim 1 with a binder to obtain a glass solder paste; Applying the glass solder paste to the surface of the strontium titanate ceramic to be welded to obtain the strontium titanate ceramic to be welded; Laying two strontium titanate ceramics to be welded in layers to obtain a strontium titanate ceramic-glass solder paste-strontium titanate ceramic, which is used as a workpiece to be welded; The parts to be welded are heated to obtain brazed strontium titanate ceramics; wherein the heating temperature is 540-650° C. and the holding time is 1-15 minutes.

6. The low-temperature brazing connection method of strontium titanate ceramics according to claim 5, characterized in that: The heating rate during the heating process was 10°C / min.

7. The low-temperature brazing connection method of strontium titanate ceramics according to claim 5, characterized in that: The mass ratio of the glass powder to the binder is 7 to 10:

1.

8. The low-temperature brazing connection method of strontium titanate ceramics according to claim 5, characterized in that: The binder is terpineol.

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