Preparation method of ultra-thin beryllium sheet, ultra-thin beryllium sheet and beryllium window welding method

Abstract

The invention discloses a preparation method of an ultra-thin beryllium sheet, the ultra-thin beryllium sheet and a beryllium window welding method, and belongs to the fields of energy, aerospace, material analysis and high-energy physics, the preparation method of the beryllium sheet precisely and controllably thinns an original beryllium sheet of 190-200 microns to 70-80 microns through a specific chemical corrosion process, and a clean and activated surface is obtained. According to the beryllium window welding method, the ultra-thin beryllium sheet prepared through the method and a metal supporting ring (such as a nickel ring and a copper-nickel alloy ring) are assembled and welded through an optimized vacuum brazing process, and a high-strength and high-airtightness sealing structure is formed. The technical problem that an ultra-thin beryllium window is difficult to machine and reliably weld is solved, the prepared beryllium window can remarkably improve the transmittance of X rays, and the beryllium window is particularly suitable for the field of analysis with the high requirement for low-energy X-ray sensitivity.

Description

Technical Field

[0001] This invention relates to the fields of energy, aerospace, materials analysis and high-energy physics, and particularly to a method for preparing an ultrathin beryllium sheet, and a method for welding the ultrathin beryllium sheet and beryllium window. Background Technology

[0002] In cutting-edge fields such as energy, aerospace, materials analysis, and high-energy physics, X-ray detection technology places extremely high demands on the performance of a key component—the X-ray output window. Beryllium has the highest X-ray transmittance in nature, making it a common choice for X-ray tube output windows. Currently, commercially available X-ray tubes typically use beryllium windows with a thickness of approximately 800 μm, which perform stably in routine applications. However, as the detection targets expand to lower-energy X-rays (such as soft X-rays), the significant attenuation caused by thick windows has become a core bottleneck in improving detection sensitivity and signal-to-noise ratio. Existing 800 μm beryllium windows cannot meet the requirements for higher transmittance. Therefore, reducing the beryllium window thickness to below 100 μm is crucial to unlocking the potential of next-generation high-precision X-ray technology.

[0003] However, beryllium is a brittle, hard, and chemically reactive metal. Fabricating it into ultrathin sheets (typically referring to sheets less than 100 micrometers thick (high-purity beryllium sheets), and even less than 10 micrometers thick (beryllium-copper alloys)) faces three major challenges: 1. Brittle and difficult to process: Beryllium has extremely poor ductility and high hardness at room temperature. Traditional thinning processes such as mechanical rolling and grinding are prone to introducing microcracks, stress concentration or overall brittle fracture when the thickness is close to 100μm, resulting in a very low yield.

[0004] 2. Toxicity control: Beryllium and its compound dust are highly toxic, and the entire processing must be carried out in a closed environment to ensure that there is no beryllium dust leakage. The safety protection requirements for the production equipment are extremely stringent, which greatly increases the complexity and cost of manufacturing ultrathin beryllium sheets.

[0005] 3. Internal Quality: To ensure good X-ray transmittance and mechanical stability, ultrathin beryllium sheets must possess high purity, few internal defects, and a uniform microstructure. This requires top-level process control throughout the entire process, from powder metallurgy to precision hot working and extreme rolling.

[0006] The fabrication of ultrathin beryllium sheets is a cutting-edge manufacturing process that integrates powder metallurgy, precision hot working, extreme rolling technology, and stringent safety precautions, representing a country's technological level in the field of rare metal deep processing. Current processing technology cannot directly produce ultrathin beryllium windows smaller than 100μm. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems existing in the prior art and provide a method for preparing ultrathin beryllium sheets, an ultrathin beryllium sheet and a beryllium window welding method. By introducing chemical treatment, a 100μm beryllium window can be made into a 70-80μm beryllium window without affecting its physical structure, without cracking, and while ensuring airtightness, thus meeting the research and development requirements.

[0008] The objective of this invention is achieved through the following technical solution: In a first aspect, a method for preparing an ultrathin beryllium sheet is provided, comprising the following steps: S1. The original beryllium sheet with a thickness of 190-200μm is thinned by chemical etching to obtain a target beryllium sheet with a thickness of 70-80μm; S2. Rinse the thinned beryllium sheet with deionized water; S3. Rinse the rinsed beryllium plates in running deionized water; S4. The rinsed beryllium sheet is dehydrated with anhydrous ethanol to obtain the final ultrathin beryllium sheet.

[0009] In some embodiments, the chemical etching thinning includes: The original beryllium sheet was immersed in a mixed solution of sulfuric acid and hydrogen peroxide at a volume ratio of 10:1 for 30-60 seconds in a water bath at 30-50°C. In some embodiments, the rinsing time with deionized water is 5-10 seconds.

[0010] In some embodiments, the rinsing time with flowing deionized water is 5-10 seconds.

[0011] In some embodiments, the dehydration time with anhydrous ethanol is 30-60 seconds.

[0012] In a second aspect, an ultrathin beryllium sheet is provided, which is prepared by the method described in the first aspect, and has a thickness of 70-80 μm.

[0013] Thirdly, a welding method for an ultra-thin beryllium window is provided, comprising the following steps: Assembly steps: The ultrathin beryllium sheet with a thickness of 70-80 μm prepared by the method described in the first aspect is clamped between the first nickel ring and the second nickel ring, and together they are placed on a copper-nickel alloy ring; Vacuum brazing step: Place the assembled components in a vacuum brazing furnace, and braze at a vacuum level below 5×10⁻⁻⁻⁶. 4 Under the condition of Pa, a multi-stage temperature-controlled welding process is performed; Leak detection steps: Use a helium mass spectrometer to test the airtightness of the welded components.

[0014] In some embodiments, pure silver solder sheets are respectively disposed between the contact surfaces of the ultrathin beryllium sheet and the first nickel ring and the second nickel ring, and between the contact surface of the second nickel ring and the copper-nickel alloy ring.

[0015] In some embodiments, the multi-stage temperature-controlled welding process includes: First stage: Increase the temperature to 160℃-180℃ within 50min-60min and hold for 60min-90min; Second stage: Increase the temperature to 480℃-500℃ within 70min-90min and hold for 60min-90min; The third stage: raise the temperature to 945℃-955℃ within 150min-180min and hold it for 40min-60min; Fourth stage: Increase the temperature to 965℃-970℃ in 15-20 minutes and hold for 30-90 seconds.

[0016] In some embodiments, the airtightness test requires a leak rate of less than 1×10⁻¹¹ Pa·m³ / s.

[0017] It should be further noted that the technical features corresponding to the above-mentioned options and embodiments can be combined or substituted with each other to form new technical solutions without conflict.

[0018] Compared with the prior art, the method for preparing ultrathin beryllium sheets of the present invention has the following beneficial effects: 1. Precise and Controllable Thinning: Chemical etching is used to thin raw beryllium sheets with a thickness of 190-200μm. By introducing a chemical treatment method and using a specific acid solution ratio and precisely controlled temperature and time parameters, the beryllium sheets can be efficiently and controllably thinned from 190-200μm to a target thickness of 70-80μm, with good thickness uniformity and high yield. Furthermore, it does not affect its physical structure, does not crack, and ensures airtightness.

[0019] 2. Excellent surface quality: This chemical etching method can not only reduce the thickness, but also remove the surface oxide layer and contaminants at the same time, resulting in a clean and activated surface, which lays a solid foundation for subsequent high-quality welding.

[0020] 3. Avoid mechanical damage: Compared with mechanical thinning, chemical corrosion avoids the introduction of stress and microcracks, maintaining the inherent mechanical integrity and X-ray transmittance of the beryllium sheet.

[0021] The welding method for the ultra-thin beryllium window of the present invention has the following beneficial effects: 1. Extremely high welding reliability: The optimized multi-stage vacuum brazing process effectively eliminates thermal stress in the assembly by slow heating and segmented heat preservation, avoiding deformation and cracking of the ultra-thin beryllium sheet during the welding process.

[0022] 2. Excellent sealing performance: The welded components were verified by helium mass spectrometry leak detection, and the leakage rate was less than 10⁻¹¹ Pa·m³ / s, which fully meets the long-term stability requirements of high vacuum and even ultra-high vacuum application environments.

[0023] 3. Improved final product performance: The successful application of ultra-thin beryllium windows of 70-80μm to X-ray tubes significantly reduced the attenuation of low-energy X-rays, improved the output intensity and detection sensitivity of X-ray tubes, and broadened their application in cutting-edge fields such as surface analysis and light element detection. Attached Figure Description

[0024] Figure 1 This is a flowchart of a method for preparing an ultrathin beryllium sheet according to the present invention; Figure 2 This is a flowchart of a welding method for an ultra-thin beryllium window according to the present invention; Figure 3 This is a schematic diagram of the beryllium window assembly of the present invention.

[0025] In the diagram: 1-First nickel ring; 2-Second nickel ring; 3-Very thin beryllium sheet; 4-Copper-nickel alloy ring. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] It should be noted that the defects in the solutions in the prior art are all the results of the inventors' practice and careful research. Therefore, the discovery process of the above problems and the solutions proposed by the embodiments of this application in the following text should be the inventors' contributions to this application in the process of invention and creation, and should not be understood as technical content known to those skilled in the art.

[0028] In view of the technical problems pointed out in the background art, the present invention provides the following embodiments: In one exemplary embodiment, such as Figure 1 As shown, a method for preparing an ultrathin beryllium sheet is provided, comprising the following steps: S1. The original beryllium sheet with a thickness of 190-200μm is thinned by chemical etching to obtain a target beryllium sheet with a thickness of 70-80μm; S2. Rinse the thinned beryllium sheet with deionized water; S3. Rinse the rinsed beryllium plates in running deionized water; S4. The rinsed beryllium sheet is dehydrated with anhydrous ethanol to obtain the final ultrathin beryllium sheet.

[0029] Specifically, the original beryllium sheet with a thickness of 190-200μm is thinned by chemical etching. By introducing chemical treatment, using a specific ratio of acid and precisely controlled temperature and time parameters, the beryllium sheet can be efficiently and controllably thinned from 190-200μm to a target thickness of 70-80μm without affecting its physical structure, without cracking, and while ensuring airtightness.

[0030] For example, the chemical etching thinning includes: The original beryllium sheet was immersed in a mixed solution of sulfuric acid and hydrogen peroxide at a volume ratio of 10:1 for 30-60 seconds in a water bath at 30-50°C.

[0031] Concentrated sulfuric acid, as a strong oxidizing acid, effectively dissolves beryllium oxide (BeO) and metallic beryllium itself on the beryllium surface. The addition of hydrogen peroxide further enhances the oxidizing power of the mixed solution, rapidly decomposing more stable oxides on the beryllium surface and generating microbubbles that act as physical stripping agents, making the corrosion process more uniform and efficient. This ratio balances the control of corrosion rate and surface roughness, achieving rapid and uniform corrosion while obtaining a relatively smooth and clean beryllium surface, providing an ideal interface for welding.

[0032] Temperature is a key factor in controlling the rate of chemical reactions. Below 30°C, the reaction is too slow, resulting in low production efficiency and potentially incomplete cleaning; above 50°C, the reaction is too vigorous, making it difficult to control the corrosion depth and easily leading to localized over-corrosion (porosity) or a rough surface on the beryllium sheet. Within this temperature range of 30-50°C, the corrosion reaction is stable and controllable, which is beneficial for achieving precise thinning from 190-200μm to 70-80μm while maintaining good thickness consistency.

[0033] The immersion time directly determines the amount of material removed. This time window, determined experimentally under the aforementioned acid ratio and temperature conditions, represents the optimal time range required to thin beryllium sheets within the target thickness range by approximately 110-130 μm. Too short a time results in insufficient thinning, while too long a time may lead to beryllium sheet penetration.

[0034] Further, after pickling, the beryllium wafer is rinsed in deionized water for 5-10 seconds, followed by rinsing in flowing deionized water for another 5-10 seconds. The surface of the pickled beryllium wafer is coated with a high concentration of acidic waste liquid and dissolved products. Rinsing with deionized water first quickly removes most of the residual liquid. Then, rinsing with flowing deionized water utilizes the shear force and continuous dilution effect of the flowing water to thoroughly remove ionic contaminants adhering to the microscopic pits of the beryllium wafer, preventing them from forming contamination points after drying and affecting welding. This ensures that the beryllium wafer surface reaches an "electrochemically clean" level, free of any ionic residues that could potentially affect welding quality.

[0035] Finally, dehydration is performed with anhydrous ethanol for 30-60 seconds. Water has a high surface tension, which can cause the extremely thin beryllium sheets to curl or stick together during drying. Ethanol has a much lower surface tension than water, and it is miscible with water and easily evaporates. Replacing water with ethanol allows for rapid drying at low temperatures, avoiding the deformation problems of the beryllium sheets caused by the surface tension and slow evaporation of water, while also preventing surface oxidation during drying. This step yields dry, flat, and oxidation-free fresh beryllium sheets, which can be directly used for subsequent assembly and welding.

[0036] In another exemplary embodiment, such as Figure 2 As shown, a welding method for an ultra-thin beryllium window is provided, comprising the following steps: Assembly steps: The ultrathin beryllium sheet 3 with a thickness of 70-80 μm, prepared by the method described in the first aspect, is clamped between the first nickel ring 1 and the second nickel ring 2, and together they are mounted on a copper-nickel alloy ring 4, as shown. Figure 3 As shown.

[0037] Vacuum brazing step: Place the assembled components in a vacuum brazing furnace, and braze at a vacuum level below 5×10⁻⁻⁻⁶. 4 Under the condition of Pa, a multi-stage temperature-controlled welding process is performed; Leak detection steps: Use a helium mass spectrometer to test the airtightness of the welded components.

[0038] In some examples, such as Figure 3 As shown, pure silver solder sheets are respectively provided between the contact surfaces of the ultrathin beryllium sheet 3 and the first nickel ring 1, the second nickel ring 2 and the ultrathin beryllium sheet 3, and between the contact surfaces of the second nickel ring 2 and the copper-nickel alloy ring 4.

[0039] For example, the multi-stage temperature-controlled welding process includes: The first stage involves heating to 160℃-180℃ within 50-60 minutes and holding at this temperature for 60-90 minutes. This slow heating and prolonged holding at a lower temperature allows for the initial release of residual mechanical stress within the assembly. It also promotes the desorption of volatile contaminants such as moisture adsorbed deep within the parts and on the surface of the fixture, which are then removed by the vacuum system. This stage prevents the sudden release of these contaminants in subsequent high-temperature stages, which could compromise the vacuum level or contaminate metal surfaces. It provides a more stable and clean vacuum environment and dimensionally stable components for subsequent high-temperature stages.

[0040] The second stage involves heating to 480℃-500℃ within 70-90 minutes and holding at this temperature for 60-90 minutes. At this temperature, the differences in thermal expansion between the different materials (beryllium, nickel, and silver) become significant. Slow heating and prolonged holding ensure extremely uniform temperature throughout the entire module, minimizing internal thermal stress. Although the melting point of silver is not reached, atomic activity is significantly enhanced, allowing for weak interfacial diffusion in the solid state, which helps improve the bonding quality during the final liquid brazing. This stage further homogenizes the module's temperature field, effectively preventing instantaneous massive thermal stress caused by rapid heating and protecting the extremely thin beryllium window.

[0041] The third stage: Heating to 945℃-955℃ within 150-180 minutes and holding at this temperature for 40-60 minutes; this stage is the main brazing process. The temperature is very close to the melting point of pure silver. The extremely slow heating rate is crucial. This is the stage with the highest thermal stress in the entire cycle. The slow heating (approximately 2-3℃ / min) gives the components sufficient time to adapt to and equalize the stress caused by the different expansion rates of the materials. Holding at this temperature for an extended period allows the silver solder to fully melt (above the solidus line) and fill the entire brazing gap through capillary action. The holding process allows for sufficient dissolution and diffusion of the liquid silver at the interface with beryllium and nickel, forming a strong metallurgical bonding layer. This achieves complete melting and spreading of the solder, forming the main brazed joint and ensuring the basic strength and sealing of the connection.

[0042] The fourth stage involves heating to 965℃-970℃ over 15-20 minutes and holding at that temperature for 30-90 seconds. This stage focuses on precision welding and interface optimization. The temperature is ultimately raised to approximately 5-10℃ above the melting point of silver to completely liquefy any remaining unmelted or slightly unevenly composed areas within the brazed joint, improving its density. The extremely short holding time is designed to minimize the formation of brittle intermetallic compounds due to excessive reaction between silver and the base material (especially brittle beryllium) while achieving the aforementioned goals. Excessive holding time would result in an overly thick intermetallic compound layer, which would reduce the joint's strength and toughness. This stage optimizes the microstructure of the brazed joint, making it more uniform and dense, while avoiding joint embrittlement caused by excessive reaction, ultimately achieving a balance between high strength and high airtightness.

[0043] For example, the airtightness test requires a leak rate of less than 1 × 10⁻¹¹ Pa·m³ / s. This leak detection step is the final verification of weld quality. Only components that meet this standard can ensure their long-term reliability and lifespan as vacuum sealing windows in practical use.

[0044] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.

Claims

1. A method of producing an extremely thin beryllium sheet, characterized by, The method comprises the following steps: S1. chemically etching a raw beryllium sheet with a thickness of 190-200 μm to obtain a target beryllium sheet with a thickness of 70-80 μm; S2. rinsing the thinned beryllium sheet with deionized water; S3. rinsing the rinsed beryllium sheet in flowing deionized water; S4. dehydrating the rinsed beryllium sheet with anhydrous ethanol to obtain a final ultra-thin beryllium sheet.

2. The method of claim 1, wherein the beryllium sheet has a thickness of 0.1 mm or less. The chemical etching thinning comprises: immersing the raw beryllium sheet in a mixed solution prepared from sulfuric acid and hydrogen peroxide at a volume ratio of 10:1, and soaking for 30-60 s in a water bath at 30-50 °C.

3. The method of claim 1, wherein the beryllium sheet has a thickness of 0.1 mm or less. The rinsing with deionized water lasts for 5-10 s.

4. The method of claim 1, wherein the beryllium sheet has a thickness of 0.1 mm or less. The rinsing in flowing deionized water lasts for 5-10 s.

5. The method of claim 1, wherein the beryllium sheet has a thickness of 0.1 mm or less. The dehydrating with anhydrous ethanol lasts for 30-60 s.

6. An extremely thin beryllium sheet, characterized by, The final ultra-thin beryllium sheet with a thickness of 70-80 μm is prepared by the method of any one of claims 1-5.

7. A method of welding an extremely thin beryllium window, comprising: The method comprises the following steps: an assembly step: clamping the ultra-thin beryllium sheet with a thickness of 70-80 μm prepared by the method of any one of claims 1-5 between a first nickel ring and a second nickel ring, and placing them together on a copper-nickel alloy ring; Vacuum brazing step: The assembled components are placed in a vacuum brazing furnace, and a multi-stage temperature-controlled welding process is performed under a vacuum of less than 5 x 10⁻ 4 Pa. a leak detection step: using a helium mass spectrometry leak detector to detect the air tightness of the welded assembly.

8. The method of claim 7 wherein, A pure silver solder sheet is arranged between the contact surfaces of the ultra-thin beryllium sheet and the first nickel ring and the second nickel ring, and between the contact surfaces of the second nickel ring and the copper-nickel alloy ring.

9. The method of claim 7 wherein, The multi-stage temperature control welding process comprises: a first stage: heating to 160-180 °C within 50-60 min, and maintaining the temperature for 60-90 min; a second stage: heating to 480-500 °C within 70-90 min, and maintaining the temperature for 60-90 min; a third stage: heating to 945-955 °C within 150-180 min, and maintaining the temperature for 40-60 min; a fourth stage: heating to 965-970 °C within 15-20 min, and maintaining the temperature for 30-90 s.

10. The method of claim 7 wherein, The air tightness test requires a leak rate of less than .

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