Process for reducing air output rate of ferrite surface

Abstract

The invention relates to the technical field of extremely high vacuum acquisition, in particular to a process for reducing the surface air output rate of ferrite. The process comprises the steps of S1, pretreatment, S2, high-temperature degassing and S3, aftertreatment. Wherein the step S2 of high-temperature degassing comprises the following steps: placing the ferrite in a degassing furnace; vacuumizing the degassing furnace; starting a heating system of the degassing furnace, heating the ferrite to 500-600 DEG C at the heating rate of 1-2 DEG C / min, preserving heat for 0.5-1 hour, heating to 850-900 DEG C at the heating rate of 1-2 DEG C / min, preserving heat for 1-2 hours, cooling to 300-500 DEG C at the cooling rate of 1-2 DEG C / min, closing the heating system, and cooling the ferrite along with the furnace. According to the process, the surface gas outlet rate of the ferrite can be effectively reduced, the ferrite can be used for an extremely high vacuum system of 10 <-10 > Pa, and meanwhile, the situation that the ferrite is cracked and damaged in the degassing process can be avoided.

Description

Technical Field

[0001] The invention relates to the technical field of obtaining extremely high vacuum, and in particular to a process for reducing the outgassing rate of a ferrite surface. Background Art

[0002] In particle accelerators, kicker magnets are special dipole magnets that work in a fast pulse mode and are mainly used in the injection and extraction systems of circular accelerator beams. In the high-current heavy ion accelerator (HIAF), the inductance voltage generated by the fast pulse magnets is extremely high. In order to prevent high-voltage sparking and breakdown, the kicker magnets are installed in an extremely high vacuum environment, and the beam will pass directly through the center of the kicker magnet. In order to reduce eddy current losses, the core is made of ferrite material with extremely high resistivity. Considering that the kicker magnet will be placed in an extremely high vacuum environment, the outgassing rate of the ferrite surface determines the final vacuum degree. Ferrite will dissolve and adsorb a certain amount of gas during the processing process. If the surface treatment process is not in place, a large amount of gas will gradually be released into the system under vacuum, and it will not be possible to reach 10 -10 Pa extremely high vacuum state. Traditional technology generally uses high temperature degassing to reduce the outgassing rate of the material surface, but the degassing temperature, degassing rate, insulation scheme and other processes are mainly for stainless steel materials, which do not match the performance of ferrite materials and cannot meet the demand for reducing the outgassing rate on the surface. In addition, the ferrite will also crack and be damaged during the degassing process. Therefore, it is very necessary to propose a process to reduce the outgassing rate on the surface of ferrite to solve the above problems. Summary of the invention

[0003] The present invention provides a process for reducing the outgassing rate of the surface of ferrite, so as to solve the problems that the process of reducing the outgassing rate of the material surface by high-temperature degassing in the prior art cannot meet the demand of reducing the outgassing rate of the ferrite surface, and the ferrite may be cracked and damaged during the degassing process.

[0004] According to a first aspect of the present invention, the present invention provides a process for reducing the outgassing rate of the ferrite surface, comprising step S1 pre-treatment, step S2 high temperature degassing and step S3 post-treatment; Among them, step S2 high temperature degassing specifically includes the following steps: S2.1: placing the ferrite in a degassing furnace; S2.2: evacuate the degassing furnace; S2.3: Start the heating system of the degassing furnace, heat the ferrite to 500-600°C at a heating rate of 1-2°C / min and keep it at that temperature for 0.5-1h, then heat it to 850-900°C at a heating rate of 1-2°C / min and keep it at that temperature for 1-2h, then cool it to 300-500°C at a cooling rate of 1-2°C / min, turn off the heating system, and allow the ferrite to cool down with the furnace.

[0005] The present invention has experimentally found that the degassing parameters such as temperature, heating rate, cooling rate and holding time during the high-temperature degassing process have a great influence on the final ferrite surface outgassing rate and cracking. The present invention takes into account that the ferrite heating rate and cooling rate are too fast, which will cause cracking due to uneven heat distribution. Therefore, the heating rate and cooling rate need to be controlled within 1-2°C / min. When the baking temperature reaches 500-600°C, keep warm for 0.5~1h depending on the volume of the ferrite to allow the heat to be fully conducted, and then continue to heat up. When the temperature reaches 850-900°C, keep warm for 1~2h, and then enter the cooling stage at a cooling rate of 1-2°C / min. When the temperature drops to 300-500°C, turn off the heating system and the ferrite is cooled with the degassing furnace. Through the above-mentioned strict control of the degassing parameters during the high-temperature degassing process, the ferrite surface outgassing rate can be more effectively reduced, so that the ferrite can be used in 10 -10 Even in an extremely high vacuum environment of 0.3 Pa, the ferrite will not crack or be damaged.

[0006] The process of reducing the outgassing rate of the ferrite surface of the present invention has obvious improvement effects on ferrites with different surface areas and different shapes. For some ferrites with large surface areas and bent shapes, it is difficult to reduce their surface outgassing rate while ensuring that the ferrite surface does not crack. The present invention has found through experiments that the process of reducing the outgassing rate of the ferrite surface of the present invention can also show a good improvement effect on ferrites with large surface areas and bent shapes. For example, the surface area of ​​ferrite is 500-1000cm 2 The external shape is "U"-shaped, triangular, square, etc. In some specific embodiments, the external surface area of ​​the ferrite is 800-900cm 2 , the external shape is "U" type.

[0007] Furthermore, in step S2.1, the ferrites are placed in a degassing furnace at intervals to facilitate the discharge of gas adsorbed on the surface of the ferrites. Preferably, the interval distance is ≥ 20 mm.

[0008] Furthermore, in step S2.2, the degassing furnace is evacuated to a vacuum degree of ≤10 -3 Pa is beneficial to remove gas from the material and improve the surface quality of the material.

[0009] Furthermore, the vacuum degassing furnace determines the vacuum obtaining equipment according to the size of the furnace chamber, and the main principle is to avoid the oil vapor generated by the lubricating oil from affecting the degassing effect of the ferrite. Therefore, when the degassing furnace chamber is small, an oil-free lubricated vortex dry pump combined with a turbomolecular pump can be used; when the degassing furnace chamber is large, a pumping system consisting of a sliding valve pump, a Roots pump, an oil diffusion pump, and a liquid nitrogen cold trap can be used.

[0010] Furthermore, the pre-processing of step S1 specifically includes the following steps: S1.1: Nitrogen purging or vacuum cleaner removal; Specifically, use high-pressure nitrogen to purge the surface of the ferrite to remove visible impurities. For ferrites with larger areas, a vacuum cleaner can also be used to remove impurities.

[0011] S1.2: Use a non-woven cloth dipped in alcohol to wipe the surface of the ferrite for primary cleaning; S1.3: Ultrasonic cleaning; S1.4: Rinse repeatedly with running deionized water until there is no foam; S1.5: Drying.

[0012] The present invention treats the ferrite through nitrogen purging or vacuum cleaner impurity removal, primary cleaning, ultrasonic cleaning, repeated flushing with flowing deionized water and drying, so that the surface of the ferrite can be cleaned, which is more conducive to the subsequent high-temperature degassing and can improve the effect and quality of these treatments. Among them, nitrogen purging and vacuum cleaner impurity removal can effectively remove granular impurities on the surface of the ferrite, such as dust, debris, etc. Primary cleaning can remove chemical residues on the surface of the ferrite, such as oil stains, residual chemical reagents, etc. Ultrasonic cleaning can penetrate into the tiny gaps on the surface of the ferrite and thoroughly remove extremely small particles of dust and dirt with high cleanliness. Repeated flushing with flowing deionized water can completely wash away the dirt generated during the cleaning process and the residual cleaning liquid, further improving the cleanliness of the ferrite surface.

[0013] Furthermore, in step S1.1, the purity of nitrogen during the nitrogen purging process is ≥99.99%.

[0014] Furthermore, in step S1.3, the cleaning solution used in ultrasonic cleaning includes one or more of a weakly acidic water-based solution, a weakly alkaline water-based solution or isopropyl alcohol.

[0015] Weakly acidic water-based solutions generally refer to cleaning solutions with a pH value between 4 and 6, which can be prepared using hydrochloric acid, sulfuric acid, citric acid, etc. Weakly alkaline water-based solutions generally refer to cleaning solutions with a pH value between 8 and 10, which can be prepared using sodium hydroxide, sodium carbonate, etc.

[0016] In some specific embodiments, in step S1.3, the cleaning liquid used in ultrasonic cleaning is a weak acidic water-based solution and a weak alkaline water-based solution. During ultrasonic cleaning, a weak acidic water-based solution is first used to remove oil stains, the temperature is 50-65°C, and the ultrasonic cleaning time is 15-30 minutes, and then a weak alkaline water-based solution is used to neutralize the weak acidic water-based solution, the temperature is 50-65°C, and the ultrasonic cleaning time is 15-30 minutes.

[0017] In some specific embodiments, in step S1.3, the cleaning liquid used in ultrasonic cleaning is isopropyl alcohol. Specifically, the ferrite is placed in an ultrasonic cleaning tank, and clean ceramic blocks are placed at intervals at the contact part between the bottom of the ferrite and the ultrasonic cleaning tank, so that there is enough cleaning liquid at the bottom of the ferrite to improve the cleaning effect, and 3-5 blocks are placed each time, and ultrasonic cleaning is performed for 15-30 minutes.

[0018] Furthermore, in step S1.3, during ultrasonic cleaning, a gap is left between the ferrite and the contact area of ​​the ultrasonic cleaning tank to facilitate complete infiltration of the cleaning liquid and improve the cleaning effect.

[0019] Furthermore, in step S1.5, the drying temperature is 100° C. to 150° C. A vacuum drying oven or a forced air drying oven may be used for drying.

[0020] Furthermore, the post-processing in step S3 specifically includes appearance inspection after degassing, and wrapping with aluminum foil and storing in a vacuum environment or a nitrogen environment. With this storage method, the treated ferrite will not be contaminated by impurities such as oxygen, water vapor, and dust in the environment. If the ferrite is not stored in the above manner after degassing, the surface of the ferrite may re-absorb oxygen, water vapor, and other gases, affecting its surface quality.

[0021] Furthermore, during the entire operation, the operator wears clean clothes and latex gloves.

[0022] The beneficial effect of the technical solution provided by the present invention is that: compared with the prior art, a process for reducing the outgassing rate on the surface of ferrite can effectively reduce the outgassing rate on the surface of ferrite, so that ferrite can be used for 10 -10 The extremely high vacuum system of Pa can also avoid crack damage to the ferrite during the degassing process. This process has the advantages of simple process operation, low equipment requirements and significant degassing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 This is a process flow chart for reducing the outgassing rate on the surface of ferrite provided in Example 1 of the present invention.

[0025] Figure 2 It is a process curve diagram of high temperature degassing in a process for reducing the outgassing rate on the surface of ferrite provided in Example 1 of the present invention.

[0026] Figure 3 It is a comparison diagram of the ferrite surface gas emission rate curves of Example 1 of the present invention and Comparative Examples 1, 3 and 4.

[0027] Figure 4 It is a diagram of the cracking state of the ferrite of comparative example 2 of the present invention.

[0028] Figure 5 This is a diagram showing the partial cracking state of the ferrite of Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example 1 The embodiment uses CMD5005 Ni-Zn ferrite produced by American International Magnetic Materials Company, with an outer surface area of ​​816cm 2 , density is 5.27g / cm 3 , the external shape is "U" type, and 22 pieces are processed in the same batch.

[0031] Specifically, this embodiment provides a process for reducing the outgassing rate of the ferrite surface, such as Figure 1 As shown, the following steps are included: Step S1: pre-treat the ferrite. The pre-treatment uses nitrogen purging combined with ultrasonic cleaning to clean the batch of ferrites. During transportation, the operator wears clean clothes and latex gloves.

[0032] Specifically, S1.1: Use high-pressure nitrogen with a purity of 99.99% to purge the ferrite to remove visible impurities and packaging residues.

[0033] S1.2: Use non-woven fabric dipped in alcohol to perform primary cleaning on the ferrite. Replace the non-woven fabric immediately if it is stained.

[0034] S1.3: In this embodiment, the ultrasonic cleaning liquid is isopropyl alcohol. Put the ferrite into the ultrasonic cleaning tank, and place clean ceramic blocks at intervals between the bottom of the ferrite and the contact part of the ultrasonic cleaning tank, so that there is enough cleaning liquid at the bottom of the ferrite to improve the cleaning effect. Place 4 blocks each time and perform ultrasonic cleaning for 15 minutes.

[0035] S1.4: Rinse the ferrite repeatedly with deionized water.

[0036] S1.5: Dry in a vacuum drying oven at 100°C.

[0037] Step S2: Using a vacuum degassing furnace to perform high-temperature baking and degassing on 22 pieces of ferrite.

[0038] S2.1: Place the ferrite in a vacuum degassing furnace, leaving a certain space (about 20~30mm) between adjacent ferrites and between the ferrite and the rack to better discharge the gas adsorbed by the material.

[0039] S2.2: Remove the air from the furnace until the pressure is ≤10 -3 Pa.

[0040] S2.3: Start the heating system, set the heating rate and cooling rate to 2℃ / min, heat to 600℃ and keep it for 1h, heat to 900℃ and keep it for 2h, then enter the cooling stage, cool to 400℃ and turn off the heating system to let the ferrite cool with the furnace. The specific baking process curve is as follows: Figure 2 shown.

[0041] Step S3: After the temperature of the ferrite drops to room temperature, the ferrite is taken out for inspection and wrapped in aluminum foil to ensure that there is no quality problem, and then packaged and sealed by a vacuum packaging machine. During the entire operation, the operator wears clean clothes and latex gloves.

[0042] Comparative Example 1 This comparative example provides a process for reducing the outgassing rate of the ferrite surface. Compared with Example 1, the comparative example 1 does not perform the high-temperature vacuum degassing process in step S2, and the other steps are the same as those in Example 1.

[0043] Comparative Example 2 This comparative example provides a process for reducing the outgassing rate of the ferrite surface. Compared with Example 1, in the S2.2 stage of Comparative Example 2, the heating rate and the cooling rate are both 5°C / min, and the remaining process steps are the same as those of Example 1.

[0044] Comparative Example 3 This comparative example provides a process for reducing the outgassing rate of the ferrite surface. Compared with Example 1, in step S2.2, the temperature is directly raised to 900°C and kept for 2 hours, and then enters the cooling stage. The remaining process steps are the same as Example 1.

[0045] Comparative Example 4 This comparative example provides a process for reducing the outgassing rate of the ferrite surface. Compared with Example 1, in step S2.2, the temperature is raised to 300°C and kept for 1 hour, then raised to 600°C and kept for 2 hours, and then enters the cooling stage. The remaining process steps are the same as Example 1.

[0046] In summary, the ferrite outgassing rates of Example 1 of the present invention and Comparative Examples 1, 3 and 4 are compared as follows: Figure 3 As shown in the figure, it can be seen that the process method adopted by the present invention significantly reduces the outgassing rate of the ferrite surface. Four ferrites were selected from Example 1 and Comparative Example 1 for ultimate vacuum test. The main pump of the test device adopted a sputtering ion pump and a titanium sublimation pump. After baking at 250°C, as shown in Table 1, the ultimate vacuum of Example 1 was 9.6×10 -10 Pa, the limit vacuum of comparative example 1 is 1.5×10 -8 Pa, it can be seen that the ferrite processed by the process of the present invention can be used for 10 -10 Ultra-high vacuum system. In addition, Figure 4 As shown, the ferrite treated in Comparative Example 2 has obvious cracking phenomenon, such as Figure 5 As shown, there is a small amount of cracking on the surface of the ferrite after treatment in Comparative Example 3, and all ferrites in Example 1 are tested to have no cracking or damage. Therefore, the process method adopted by the present invention is highly safe, will not cause cracking, and has a significant effect of reducing the surface outgassing rate.

[0047] Table 1

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for reducing the outgassing rate of ferrite surface, characterized in that: It includes step S1 pre-treatment, step S2 high temperature degassing and step S3 post-treatment; Among them, step S2 high temperature degassing specifically includes the following steps: S2.1: placing the ferrite in a degassing furnace; S2.2: evacuate the degassing furnace; S2.3: Start the heating system of the degassing furnace, heat the ferrite to 500-600°C at a heating rate of 1-2°C / min and keep it at that temperature for 0.5-1h, then heat it to 850-900°C at a heating rate of 1-2°C / min and keep it at that temperature for 1-2h, then cool it to 300-500°C at a cooling rate of 1-2°C / min, turn off the heating system, and allow the ferrite to cool down with the furnace.

2. A process for reducing the outgassing rate on the surface of ferrite according to claim 1, characterized in that: In step S2.1, the ferrites are placed in a degassing furnace at intervals; preferably, the interval distance is ≥ 20 mm.

3. A process for reducing the outgassing rate on the surface of ferrite according to claim 1 or 2, characterized in that: In step S2.2, the degassing furnace is evacuated to a vacuum degree of ≤10 -3 Pa.

4. A process for reducing the outgassing rate on the surface of ferrite according to claim 1, characterized in that: Step S1 pre-processing specifically includes the following steps: S1.1: Nitrogen purging or vacuum cleaner to remove impurities; S1.2: Use a non-woven cloth dipped in alcohol to wipe the surface of the ferrite for primary cleaning; S1.3: Ultrasonic cleaning; S1.4: Rinse repeatedly with running deionized water until there is no foam; S1.5: Drying.

5. A process for reducing the outgassing rate on the surface of ferrite according to claim 4, characterized in that: In step S1.1, the purity of nitrogen during the nitrogen purge process is ≥99.99%.

6. A process for reducing the outgassing rate on the surface of ferrite according to claim 4, characterized in that: In step S1.3, the cleaning solution used in ultrasonic cleaning includes one or more of a weakly acidic water-based solution, a weakly alkaline water-based solution or isopropyl alcohol.

7. A process for reducing the outgassing rate on the surface of ferrite according to claim 4, characterized in that: In step S1.3, during ultrasonic cleaning, a gap is left between the contact area between the ferrite and the ultrasonic cleaning tank.

8. A process for reducing the outgassing rate on the surface of ferrite according to claim 4, characterized in that: In step S1.5, the drying temperature is 100°C to 150°C.

9. A process for reducing the outgassing rate on the surface of ferrite according to any one of claims 1 to 8, characterized in that: The post-processing in step S3 specifically includes appearance inspection after degassing, and wrapping with aluminum foil and storing in a vacuum environment or a nitrogen environment.

10. A process for reducing the outgassing rate on the surface of ferrite according to any one of claims 1 to 9, characterized in that: During the entire operation, operators wear clean clothes and latex gloves.

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