A method of glass brazing a sapphire-beryllia hetero-output window

Abstract

The application discloses a method for preparing a sapphire-beryllium oxide heterogeneous output window by glass brazing, and belongs to the technical field of vacuum electron devices. The method is based on the similar intrinsic properties of glass, sapphire and beryllium oxide ceramic, uses glass solder for connecting the sapphire and the beryllium oxide ceramic, and provides a specific glass solder preparation mode. The main crystal precipitated from the glass solder prepared according to the application is CaSiO3, the glass solder has a thermal expansion coefficient between the two parent materials, can effectively reduce the thermal stress caused by the anisotropy of the thermal expansion coefficient of the parent material, and makes the welding seam have good mechanical properties and long-term service stability. In addition, the process for connecting the two ceramic materials by using the glass solder is simple, the cost is low, and the excellent performances of high reliability, low reflection and wide frequency band of the heterogeneous material output window can be realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of vacuum electron devices, and particularly relates to a connection preparation method of a heterogeneous ceramic output window of a high-power gyrotron. BACKGROUND

[0002] The gyrotron can convert the kinetic energy of moving electrons into microwave energy and is widely applied to fields such as radars, electronic countermeasures, satellite communications and accelerators. Research shows that the bandwidth of the gyrotron is often limited by the working bandwidth of the output window, and the gyrotron also needs a high-vacuum internal environment to reliably operate. Therefore, the output window is one of the key components of the gyrotron, and the performance of the output window directly determines the overall performance of the gyrotron. The output windows applied internationally are mainly divided into single-layer, double-layer and multi-layer window sheets. The multi-layer dielectric window sheet can obtain a larger bandwidth and suppress sideband oscillation. However, the limited types of materials make it difficult to match the dielectric constant with the design result, so that perfect matching cannot be achieved, resulting in a relatively narrow working frequency band of the output window. The metasurface structure can form an arbitrary dielectric constant by changing the structure design of one or two materials through the equivalent dielectric theory, and then realize a wide bandwidth, thereby overcoming the problem of difficulty in achieving dielectric matching due to material limitations. Therefore, the metasurface output window has important value and urgent needs in the application of high-power millimeter wave amplifiers.

[0003] The sapphire-beryllium oxide heterogeneous output window comprehensively utilizes the excellent heat conduction performance of beryllium oxide and the excellent mechanical strength advantage of sapphire, and finally obtains an output window with dielectric matching, good heat dissipation and a wide frequency band. However, the sapphire-beryllium oxide heterogeneous output window has actual processing problems. The sapphire and beryllium oxide cannot be effectively connected, which may cause displacement due to vibration in the working and transportation environments, resulting in performance loss. Therefore, the scheme currently remains in the simulation stage and cannot be practically applied. SUMMARY

[0004] In view of the deficiencies in the prior art, the application provides a method for glass brazing to prepare a sapphire-beryllium oxide heterogeneous output window, which effectively solves the problem that the multi-layer output window cannot be tightly connected due to the limitation of the types of materials.

[0005] The technical scheme adopted by the application is as follows:

[0006] A method for glass brazing to prepare a sapphire-beryllium oxide heterogeneous output window, characterized in that the method comprises the following steps:

[0007] S1. According to the structure size of the sapphire-beryllium oxide heterogeneous output window, the sapphire parent material is processed into a first welding piece, the beryllium oxide parent material is processed into a second welding piece, and the welding surfaces of the welding pieces are polished flat and polished.

[0008] S2. The glass solder is uniformly mixed with terpineol at a volume ratio of 1:1-1.5, and then coated on the welding surface by screen printing; and placed in a drying oven, with a drying temperature of 150°C and a drying time of 30 min.

[0009] S3. The welding surface coated with the glass solder is aligned and placed in a mold to obtain a welding test piece.

[0010] S4. The welding test piece is placed in a muffle furnace, and heated to 1200-1350°C under air reaction conditions, and held for 1-2 hours to fully crystallize the glass solder; finally, the furnace is cooled to room temperature, and the preparation of the sapphire-beryllia heterogeneous output window is completed.

[0011] Further, in step S1, the sapphire-beryllia heterogeneous output window comprises a middle layer of sapphire window sheet and beryllia matching layers arranged on both sides of the sapphire window sheet, and the beryllia matching layers on both sides are mirror-symmetric about the sapphire window sheet; the beryllia matching layer on one side comprises five cuboid-shaped beryllia lattices; the beryllia lattices are parallel to each other and have the same spacing, and the loading positions are left-right symmetric about the diameter as the axis; the beryllia lattice at the center position has the longest length, and the beryllia lattices on both sides have gradually decreasing lengths.

[0012] Further, the thickness of the middle layer of sapphire window sheet is t=1 mm, and the radius is r=4.66 mm; the height of the beryllia lattice is h=1.35 mm, the width is d=0.45 mm, and the distance between adjacent lattices is p=1.03 mm.

[0013] Further, the thickness of the welding seam is between 30-80 um.

[0014] Further, in step S2, the preparation method of the glass solder comprises the following steps:

[0015] A1. Analytically pure raw materials are mixed according to the mass percentage, i.e., 38.6wt.% SiO2 powder, 16.4wt.% Al2O3 powder, 40wt.% CaO powder, and 5wt.% B2O3, wherein the B2O3 is provided by boric acid.

[0016] A2. The mixed raw materials are placed in an air muffle furnace, and heated from room temperature to a smelting temperature of 1300-1500°C at a heating rate of 10-20°C / min, and held for 30-60 min. At this time, the raw materials are in a completely molten state.

[0017] A3. The mixed material in a molten state obtained in step A2 is poured into water at room temperature to cool and obtain glass particles.

[0018] A4. The glass particles are ground into glass powder by an alcohol wet grinding method, and finally the glass powder is filtered through a 400-mesh sieve to obtain the glass solder.

[0019] Further, the specific operation of the gradient heating in step S4 is: heating from room temperature to 1200-1350℃ at a heating rate of 10-20℃ / min.

[0020] Further, the specific operation process of polishing the surface to be welded in step S1 is: polishing the surface to be welded with sandpaper of #240, #600, #800, #1000 in turn, and then polishing with diamond polishing agent of 0.5-1.0 μm for 20-30 min at a speed of 500-600 r / min.

[0021] The advantages of the present application are: the present application is based on the similar intrinsic properties of glass, sapphire and beryllia ceramics, which all have excellent insulation, corrosion resistance, and similar chemical bonds and good chemical compatibility. Therefore, using glass solder to connect sapphire and beryllia ceramics can better wet the surface of sapphire and beryllia ceramics; and the main crystal precipitated from the glass solder prepared according to the present application is CaSiO3, which has a thermal expansion coefficient between the two parent materials, which can effectively reduce the thermal stress caused by the anisotropy of the thermal expansion coefficient of the parent material, so that the weld has good mechanical properties and long-term service stability. In addition, the process of connecting two ceramic materials with glass solder is simple, low in cost, and can realize the excellent performance of high reliability, low reflection and wide frequency band of the output window of heterogeneous materials. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a schematic diagram of the three-dimensional structure of the output window of the present application

[0023] Figure 2 is a front view of the output window of the present application

[0024] Figure 3 is a side view of the output window of the present application

[0025] Figure 4 is a S11 parameter diagram of the output window of the present application

[0026] BRIEF DESCRIPTION OF DRAWINGS DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0028] The present embodiment provides a preparation method of a Ka-band sapphire-beryllia heterogeneous output window. The structure of the output window is as followsFigures 1-3 As shown, it comprises a middle sapphire window sheet and beryllium oxide matching layers arranged on both sides of the sapphire window sheet, and the beryllium oxide matching layers on both sides are mirror symmetric about the sapphire window sheet; wherein the beryllium oxide matching layer on one side comprises five cuboid-shaped beryllium oxide lattices; the thickness t of the middle sapphire window sheet is 1 mm, and the radius r is 4.66 mm.

[0029] Figure 2 A schematic diagram of the arrangement of the middle beryllium oxide medium on a circular window sheet, the medium size is wxdh, the pitch is p=1.03 mm, the lengths are w1=9.3 mm, w2=8.8 mm, and w3=7.1 mm, the width d is 0.45 mm, the height h is 1.35 mm, and the thickness of the weld h0 is 0.05 mm.

[0030] The sapphire-beryllium oxide hetero output window with the above structure is prepared by glass brazing, and the steps are as follows:

[0031] S1. According to the structure size of the sapphire-beryllium oxide hetero output window, the sapphire parent material is processed into a first welding part, the beryllium oxide parent material is processed into a second welding part, and the welding surface of the welding part is polished and polished.

[0032] The operation process of polishing and polishing is as follows: the welding surface is polished with #240, #600, #800, and #1000 sandpaper in turn, and then polished with 1.0 μm diamond polishing agent for 20 min at a speed of 500.

[0033] S2. The glass solder and terpineol are uniformly mixed in a volume ratio of 1:1.2, and then coated on the welding surface by screen printing method; placed in a drying oven, the drying temperature is 150℃, and the time is 30min.

[0034] S3. The welding surface coated with glass solder is contacted and aligned and placed in a mold to obtain a welding test piece.

[0035] S4. The welding test piece is placed in a muffle furnace, heated to 1300 at a heating rate of 10℃ / min under air reaction conditions, then cooled to crystallization temperature 1000℃ and kept for 1 hour to make the glass solder fully crystallize; then cooled to 650℃ and kept for 60 min; finally, the furnace is cooled to room temperature to complete the preparation of the sapphire-beryllium oxide hetero output window. In this embodiment, the weld width h0 of the output window prepared is 0.05 mm.

[0036] In this embodiment, the preparation method of the glass solder is as follows:

[0037] A1. Analytical pure raw materials were mixed according to the mass percentage, 38.6wt.% SiO2 powder, 16.4wt.% Al2O3 powder, 40wt.% CaO powder, 5wt.% B2O3, wherein B2O3 was provided by boric acid.

[0038] A2. The mixed raw materials were placed in an air muffle furnace, and the temperature was raised from room temperature to a melting temperature of 1350°C at a rate of 15°C / min, and maintained for 50 min. At this time, the raw materials were in a completely molten state.

[0039] A3. The mixed material in a molten state obtained in step A2 was poured into 20° water to cool down and obtain glass particles.

[0040] A4. The glass particles were ground into glass powder by alcohol wet grinding method, the ball milling speed was 600r / min, and the ball milling time was 10h; then the glass powder was dried at 60°C; finally, the glass powder was filtered through a 400 mesh screen to obtain the glass solder.

[0041] Figure 4 is the TE11 mode reflection coefficient S11 result diagram of the output window prepared in this embodiment, the connection weld width is 50μm, and the glass dielectric constant is 20. The frequency band with a reflection coefficient S11 less than -20dB is 27GHz to 35GHz, and the bandwidth reaches 8GHz.

Claims

1. A method of glass brazing to produce a sapphire-beryllia hetero-output window, characterized in that, The method comprises the following steps: S1. According to the structural size of the sapphire-beryllia hetero output window, a sapphire parent material is processed into a first welding piece, a beryllia parent material is processed into a second welding piece, and the welding surfaces of the welding pieces are polished and polished; S2. The glass solder is uniformly mixed with terpineol at a volume ratio of 1:1-1.5, and then coated on the welding surface by screen printing method; then placed in a drying oven, the drying temperature is 150 DEG C, and the time is 30 min; The preparation method of the glass solder comprises the following steps: A1. The analytical pure raw materials are mixed according to the mass percentage, and the mass fraction is 38.6wt.%SiO2 powder, 16.4wt.%Al2O3 powder, 40wt.%CaO powder, and 5wt.%B2O3, wherein B2O3 is provided by boric acid; A2. The mixed raw materials are placed in an air muffle furnace, and the temperature is raised from room temperature to a smelting temperature of 1300-1500 DEG C at a rate of 10 DEG C / min-20 DEG C / min, and kept for 30 min-60 min; A3. The molten mixed material obtained in step A2 is poured into normal temperature water to cool down and obtain glass particles; A4. The glass particles are ground into glass powder by alcohol wet grinding method, and finally the glass powder is filtered through a 400 mesh screen to obtain the glass solder; S3. The welding surfaces coated with the glass solder are contacted and aligned and placed in a mold to obtain a welding test piece; S4. The welding test piece is placed in a muffle furnace, and is heated to 1200-1350 DEG C under air reaction conditions, and is kept for 1-2 hours to fully crystallize the glass solder; finally, the furnace is cooled to room temperature to complete the preparation of the sapphire-beryllia hetero output window.

2. A method of glass brazing to produce a sapphire-beryllia hetero-output window as claimed in claim 1, wherein, In step S1, the sapphire-beryllia hetero output window comprises a middle layer sapphire window sheet and beryllia matching layers arranged on both sides of the sapphire window sheet, and the beryllia matching layers on both sides are mirror symmetric about the sapphire window sheet; wherein the beryllia matching layer on one side comprises five beryllia lattices in the shape of cuboid; the beryllia lattices are parallel to each other and have the same spacing, and the loading positions are left-right symmetric with the diameter as the axis; the beryllia lattice at the center position has the longest length, and the beryllia lattices on both sides gradually decrease in length.

3. A method of glass brazing a sapphire-beryllia hetero-output window as claimed in claim 2, wherein, The thickness of the middle layer sapphire window sheet is t=1 mm, and the radius is r=4.66 mm; the height of the beryllia lattice is h=1.35 mm, the width is d=0.45 mm, and the distance between adjacent lattices is p=1.03 mm.

4. A method of glass brazing a sapphire-beryllia hetero-output window as claimed in claim 3, wherein, The thickness of the weld is between 30-80 um.

5. A method of glass brazing a sapphire-beryllia hetero-output window according to any one of claims 1-3, wherein, In step S4, the specific operation of gradient heating is: heating at a rate of 10-20 DEG C / min from room temperature.

6. A method of glass brazing a sapphire-beryllia hetero-output window as claimed in claim 5, wherein, In step S1, the specific operation process of polishing and polishing the welding surface is: the welding surface is polished with #240, #600, #800, #1000 sandpaper in turn, and then polished with 0.5-1.0 um diamond polishing agent for 20-30 min, at a speed of 500-600 r / min.

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