A method of glass brazing a sapphire super surface output window

Abstract

The application discloses a method for preparing a sapphire super surface output window by glass brazing, and belongs to the technical field of vacuum electron devices. The method uses glass brazing filler metal to connect sapphire to prepare a super surface output window, and provides a preparation method of the glass brazing filler metal. The method uses oxide brazing filler metal to form a glass system after melting, penetrates into sapphire and wets the surface of sapphire to realize reliable connection. The method can effectively reduce thermal stress caused by the anisotropy of the thermal expansion coefficient of a base material, so that the welding seam has good mechanical properties and long-term service stability. In addition, the process of connecting sapphire by using the glass brazing filler metal is simple, the cost is low, and the method provides a feasible method for preparing various structure super surface output windows.

Description

TECHNICAL FIELD

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

[0002] The gyrotron can convert 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, so the output window is one of the key components of the gyrotron, and the performance of the output window will directly determine the overall performance of the gyrotron.

[0003] The output window has several different types, such as a single-layer window, a multi-layer window, a box-type window and a metasurface window, and each type has its own application in different scenarios. For the multi-layer output window structure, the dielectric constant mismatch between the intermediate dielectric layer and the matching layer causes the working frequency band of the output window to be relatively narrow. In recent years, the metasurface window is proposed, which adjusts the size of the dielectric lattice loaded on both sides of the circular disc to achieve matching of the equivalent dielectric constant, so that the working bandwidth of the output window is obviously widened.

[0004] Sapphire is a commonly used material for output window sheets, and has low dielectric loss and high mechanical strength. However, due to the high strength of the sapphire material, it is difficult to directly use traditional mechanical processing methods to realize the lattice structure on both sides. Therefore, the current sapphire lattice structure metasurface window only has a theoretical design, and the existing processing technology cannot realize the processing. Therefore, the present scheme prepares the metasurface structure output window from the perspective of sapphire connection, and in view of the processing and application requirements of the gyrotron, the glass solder used for connection requires a softening temperature higher than 830 DEG C, and has good dielectric properties in the working frequency band of the gyrotron.

[0005] The existing sapphire solder cannot meet both requirements. Therefore, it is an urgent problem to provide a solder with high temperature and dielectric properties. SUMMARY

[0006] In view of the defects in the prior art, the application provides a method for glass soldering and preparing a sapphire metasurface output window.

[0007] The technical scheme adopted by the application is as follows:

[0008] A method for glass soldering and preparing a sapphire metasurface output window, characterized in that it comprises the following steps:

[0009] S1. According to the size of the super surface output window structure, the sapphire base material is processed into a welding part (middle layer window piece and matching layer lattice), and the welding surface of the welding part is polished and polished.

[0010] S2. The glass solder is uniformly mixed with terpineol at a volume ratio of 1:0.5-1, 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.

[0011] S3. The welding surface coated with glass solder is contacted and aligned and placed in a mold to obtain a welding test piece.

[0012] S4. The welding test piece is placed in a resistance furnace, and under air reaction conditions, the temperature is increased to 1200-1350℃ at a gradient, and the temperature is kept for 1-2 hours to make the glass solder fully crystallize; finally, the furnace is cooled to room temperature, and the preparation of the sapphire super surface output window is completed.

[0013] Further, in step S1, the specific operation process of polishing and polishing the welding surface is: the welding surface is polished with ink sandpaper of #240, #600, #800, #1000 in turn; then 0.5-1.0μm diamond polishing agent is used, and the sapphire welding surface is polished at a speed of 500-600r / min for 20-30min.

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

[0015] A1. Take CaO, MgO, Al2O3, SiO2 as raw materials, and mix them uniformly according to the proportions of 30-35wt% CaO, 5-15wt% MgO, 20-40wt% Al2O3, and 15-30wt% SiO2.

[0016] A2. Put the mixed raw materials into an air muffle furnace, and heat from room temperature to a smelting temperature of 1300-1500℃ at a heating rate of 10-20℃ / min, and keep for 30-60min. At this time, the raw materials are in a completely molten state.

[0017] A3. Pour the molten mixed material obtained in step A2 into cold water to cool down and obtain glass particles.

[0018] 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.

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

[0020] Advantages of the present application:

[0021] The present application uses glass solder to connect sapphire to prepare a metasurface output window, solves the problem that the existing process cannot cut out a fine structure of sapphire, and causes the metasurface output window to be unable to be processed. The principle is that the oxide solder melts to form a glass system, penetrates into the sapphire and wets the surface of the sapphire to realize reliable connection; and can effectively reduce the thermal stress caused by the anisotropy of the thermal expansion coefficient of the base material, so that the weld has good mechanical properties and long-term service stability; at the same time, the connection weld is narrow, the glass solder may precipitate crystals such as anorthite, wollastonite and diopside, has good electromagnetic properties similar to the base material, the dielectric constant is effectively matched with sapphire, and the service temperature is above 830 DEG C. Compared with metal solder, glass is mainly composed of covalent bond and ionic bond, has the properties of sapphire, has excellent chemical compatibility with sapphire material, and can effectively realize the connection of sapphire material; in addition, the process of connecting sapphire by using glass solder is simple, and the cost is low. The present application provides a feasible method for preparing various structure metasurface output windows. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a front view of a Ku band output window;

[0023] Figure 2 is a side view of a Ku band output window;

[0024] Figure 3 is a schematic diagram of the lattice size of a Ku band output window;

[0025] Figure 4 is a simulation result diagram of the reflection coefficient S11 of the Ku band output window plus the connection weld.

[0026] BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 2 1 is a sapphire dielectric window piece, 2 is a sapphire dielectric lattice, and 3 is a connection weld of the window piece and the lattice.

[0028] Figure 3 w is the side length of the sapphire matching lattice, h is the thickness of the sapphire matching lattice, t is the thickness of the sapphire window piece, and g is the spacing of the sapphire matching lattice. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application is 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 are not used to limit the present application.

[0030] The application firstly designs an output window of a metasurface structure, the output window is used for a Ku band, a TE01 operating mode, Figure 1 and Figure 2 The output window is a front view and a side view, including a middle sapphire window sheet, sapphire matching lattices arranged on both sides of the middle sapphire window sheet. By adjusting the size of the matching layer lattice, the equivalent dielectric constant is matched, and the operating bandwidth of the output window is obviously widened.

[0031] As shown in Figure 3 , the sapphire matching layer lattice is a cuboid structure, the height is h=2.95 mm, the length and the width are w=3 mm, the distance between adjacent lattices is g=1.6 mm, the thickness of the middle sapphire window sheet is t=1.6 mm, the radius r=16 mm, and the welding seam h0 is 0.05 mm.

[0032] The Ku band gyrotron output window provided by the application obviously widens the bandwidth, and the reflection is below-20 dB. This metasurface output window solves the problem that the bandwidth is narrowed because the ideal equivalent dielectric constant material of the matching layer cannot be found in nature.

[0033] The preparation method of the metasurface structure output window in the embodiment includes the following steps:

[0034] S1. According to the size of the metasurface output window structure, the sapphire mother material is processed into a to-be-welded part (a middle window sheet and a matching layer lattice), and the to-be-welded surface of the to-be-welded part is polished and polished until the surface roughness is 0.2-0.3 microns. The specific operation process of polishing and polishing the to-be-welded surface is: the to-be-welded surface is polished with #240, #600, #800, and #1000 water-based ink sandpaper in sequence; then 1.0 microns of diamond polishing agent is used to polish the sapphire to-be-welded surface at a speed of 500 r / min for 25 minutes.

[0035] S2. The glass solder and the terpineol are uniformly mixed at a volume ratio of 1:1, and then are coated on the to-be-welded surface by using a screen printing method; and are placed in a drying oven, the drying temperature is 150 DEG C, and the time is 30 minutes.

[0036] S3. The to-be-welded surface coated with the glass solder is contacted and aligned and is placed in a mold to obtain a to-be-welded test piece.

[0037] S4. The to-be-welded test piece is placed in a resistance furnace, heated to 1250 DEG C at a temperature rising rate of 10 DEG C / min from room temperature under air reaction conditions, and kept for 1.5 hours to make the glass solder fully crystallize; finally, the furnace is cooled to room temperature, and the preparation of the sapphire metasurface output window is completed.

[0038] The preparation method of the glass solder in the step S2 includes the following steps:

[0039] A1. Take CaO, MgO, Al203, SiO2as raw materials, and mix them uniformly according to the proportions of 30wt% CaO, 10wt% MgO, 35wt% Al203, and 25wt% SiO2.

[0040] A2. Put the mixed raw materials into an air muffle furnace, and raise the temperature from room temperature to a smelting temperature of 1400°C at a rate of 10°C / min, and maintain for 40 min. At this time, the raw materials are in a completely molten state.

[0041] A3. Pour the molten mixed material obtained in step A2 into cold water to cool it down and obtain glass particles.

[0042] A4. Grind the glass particles into glass powder using an alcohol wet grinding method, and finally filter the glass powder through a 400-mesh screen to obtain a glass solder.

[0043] Figure 4 is a simulation result diagram of the reflection coefficient S11 of the output window of this embodiment, with a connection weld width of 50μm and a glass dielectric constant of 15; the frequency band with a reflection coefficient S11 less than -20dB is 14GHz to 18GHz, with a bandwidth of 4GHz, and in the frequency band range of 14.5GHz to 17.5GHz, the value of the reflection coefficient is less than -25dB.

Claims

1. A method for fabricating a sapphire metasurface output window using glass brazing, characterized in that, Includes the following steps: S1. Based on the dimensions of the metasurface output window structure, process the sapphire base material into a workpiece to be soldered, and grind and polish the surface of the workpiece to be soldered until the surface roughness is 0.2–0.3 μm; S2. Mix glass solder and terpineol at a volume ratio of 1:0.5-1 evenly, and then apply the mixture to the surface to be soldered using screen printing; place it in a drying oven and dry at 150℃ for 30 minutes. The preparation method of glass solder includes the following steps: A1. Using CaO, MgO, Al2O3, and SiO2 as raw materials, weigh and mix them evenly according to the ratio of 30wt% CaO, 10wt% MgO, 35wt% Al2O3, and 25wt% SiO2. A2. Place the mixed raw materials in an air muffle furnace and raise the temperature from room temperature to the melting temperature of 1400℃ at a heating rate of 10℃ / min, and hold for 40min until the raw materials are in a molten state; A3. Pour the molten mixture obtained in step A2 into cold water to cool it down and obtain glass particles; A4. The glass particles are ground into glass powder using an alcohol wet grinding method, and the glass powder is then filtered through a 400-mesh sieve to obtain glass brazing filler metal. S3. Align the surfaces to be welded, coated with glass brazing filler metal, and place them in the mold to obtain the test piece to be welded; S4. Place the specimen to be soldered in a resistance furnace and heat it to 1200~1350℃ from room temperature at a heating rate of 10℃ / min under air reaction conditions. Hold the temperature for 1.5 hours to allow the glass solder to fully crystallize. Finally, cool the specimen in the furnace to room temperature to complete the preparation of the sapphire metasurface output window.

2. The method for fabricating a sapphire metasurface output window by glass brazing as described in claim 1, characterized in that, In step S1, the specific operation process of grinding and polishing the surface to be soldered is as follows: the surface to be soldered is ground in sequence using #240, #600, #800, and #1000 wet sandpaper; then, using 0.5μm to 1.0μm diamond polishing agent, the sapphire surface to be soldered is polished for 20 to 30 minutes at a rotation speed of 500 to 600 r / min.

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