An impregnating solution for visually detecting the impregnation depth of soft magnetic powder cores

Abstract

The present invention discloses an impregnating solution for visually detecting the impregnation depth of soft magnetic powder cores, belonging to the technical field of soft magnetic materials. The impregnating solution of the present invention adds functionalized fluorescent carbon quantum dots as an indicator, and can visually judge the impregnation depth according to the change of fluorescence intensity during the impregnation process. The present invention performs surface modification on the carbon quantum dots to make their surfaces carry specific functional groups, so that they can be better compatible with other organic components in the impregnating solution. This surface modification can not only improve the dispersibility of carbon quantum dots in the impregnating solution, reduce the aggregation phenomenon, but also avoid chemical reactions with magnetic particles in the soft magnetic powder core, thereby reducing the impact on the electrical and mechanical properties of the soft magnetic powder core.

Description

Technical Field

[0001] The present invention belongs to the technical field of soft magnetic materials, and particularly relates to an impregnating solution for visually detecting the impregnation depth of soft magnetic powder cores. Background Art

[0002] Soft magnetic powder cores are widely used in electronic, electrical and communication equipment, and their performance is closely related to the uniformity and impregnation depth of the impregnating solution. However, in traditional impregnation processes, the detection of impregnation depth often relies on empirical judgment or destructive testing, which is not only inefficient but also may affect product quality. Therefore, it is of great significance to develop an impregnating solution that can visually detect the impregnation depth. Summary of the Invention

[0003] The purpose of the present invention is to provide an impregnating solution for visually detecting the impregnation depth of soft magnetic powder cores. By adding functionalized fluorescent carbon quantum dots as indicators, this impregnating solution can intuitively judge the impregnation depth according to the change of fluorescence intensity during the impregnation process, without affecting the electrical and mechanical properties of the soft magnetic powder cores. Fluorescent carbon quantum dots have small sizes and good dispersibility, which enables them to migrate rapidly in solutions or media. Their nanoscale sizes help reduce the resistance during the migration process, thereby increasing the migration rate. Secondly, fluorescent carbon quantum dots have strong fluorescence characteristics. This characteristic not only makes them easy to detect and track but also provides real-time visual information during the migration process. This characteristic is of great significance for studying the migration behavior of carbon quantum dots in complex systems. Fluorescent carbon quantum dots have good solution processing characteristics, which means they can be easily dissolved in various solvents and maintain stable fluorescence properties in these solvents. This characteristic contributes to the rapid migration and dispersion of carbon quantum dots in solutions.

[0004] The impregnating solution of the present invention consists of a basic impregnating solution and a certain amount of functionalized fluorescent carbon quantum dots. The basic impregnating solution is composed of bisphenol A epoxy resin (E44 or E51), a curing agent (dicyandiamide, methyltetrahydrophthalic anhydride or methylhexahydroaniline), and a diluent (dimethyl mixed adipate). The fluorescent carbon quantum dots are subjected to special functionalization treatment to ensure their stable dispersion in the impregnating solution and their ability to penetrate deep into the soft magnetic powder cores along with the impregnating solution. Under ultraviolet light or light of a specific wavelength excitation, the fluorescent carbon quantum dots emit fluorescence, and the intensity is proportional to the impregnation depth, thereby realizing the visual detection of the impregnation depth. The present invention performs surface modification on the carbon quantum dots so that their surfaces carry specific functional groups, enabling them to be better compatible with other organic components in the impregnating solution. This surface modification can not only improve the dispersibility of carbon quantum dots in the impregnating solution and reduce the agglomeration phenomenon but also prevent them from reacting chemically with the magnetic particles in the soft magnetic powder cores, thereby reducing the impact on the electrical and mechanical properties of the soft magnetic powder cores.

[0005] The mass concentration of the functionalized fluorescent carbon quantum dots in the impregnating solution system is 0.5 wt% to 1.0 wt%. The present invention determines the optimal addition ratio of carbon quantum dots in the impregnating solution through a large number of experiments. In the experiment, different gradients of addition amounts are set, ranging from 0.1% to 5%. Electrical property tests (such as magnetic permeability, iron loss, etc.) and mechanical property tests (such as hardness, compressive strength, etc.) are carried out on these samples. The results show that when the addition amount is between 0.5% - 1%, it can not only ensure visually judging the impregnation depth according to the change of fluorescence intensity during the impregnation process, but also have the least influence on the electrical and mechanical properties of the soft magnetic powder core.

[0006] The impregnating solution also includes a stabilizer to improve the long-term stability of the fluorescent carbon quantum dots. The stabilizer is polyethyleneimine.

[0007] The preparation method of the functionalized fluorescent carbon quantum dots includes the following steps:

[0008] Step 1: Pretreatment

[0009] Citric acid is selected as the carbon source because of its good carbonization and fluorescence properties. Dissolve citric acid in deionized water to form a citric acid aqueous solution with a concentration of 0.1 M. Place the citric acid aqueous solution in an ultrasonic processor and ultrasonically disperse it for 30 minutes to ensure that citric acid molecules are fully dissolved and evenly dispersed.

[0010] Step 2: Carbonization treatment

[0011] Place the pretreated citric acid aqueous solution in a microwave oven and heat it at 200 °C for 5 minutes for preliminary carbonization treatment. Transfer the preliminarily carbonized product to a tube furnace and heat it to 800 °C at a heating rate of 5 °C / minute under the protection of an inert gas (such as argon), and keep it at this temperature for 2 hours for deep carbonization treatment. After the carbonization treatment is completed, cool the product to room temperature to obtain crude carbon quantum dots.

[0012] Step 3: Surface passivation treatment

[0013] Disperse the crude carbon quantum dots obtained in Step 2 in ethanol to form a dispersion with a concentration of 1 mg / mL. Add polyvinyl alcohol (PVA) to the dispersion, and the mass ratio of PVA to carbon quantum dots is 1:5. Stir and react at 80 °C for 4 hours to make PVA fully coat the surface of the carbon quantum dots for surface passivation treatment. After the reaction is completed, remove the unreacted PVA and impurities through centrifugation and washing steps to obtain passivated carbon quantum dots.

[0014] Step 4: Functionalization modification

[0015] The passivated carbon quantum dots are dispersed in deionized water to form a dispersion with a concentration of 0.5 mg / mL. A compound containing amino or carboxyl groups (such as ethylenediamine or acrylic acid) is added to the dispersion, and the molar ratio of the compound to the carbon quantum dots is 1:10. The reaction is stirred at room temperature for 24 hours to allow the compound to bind to the functional groups on the surface of the carbon quantum dots through chemical bonds for functional modification. After the reaction, the unreacted compound and impurities are removed by dialysis or centrifugation steps to obtain functionalized fluorescent carbon quantum dots.

[0016] The fluorescent carbon quantum dots can visually reflect the impregnation depth according to the change of fluorescence intensity during the impregnation process, and do not affect the electrical and mechanical properties of the soft magnetic powder core.

[0017] The beneficial effects of the present invention are reflected in:

[0018] 1. Intuitive judgment of impregnation depth: By adding functionalized fluorescent carbon quantum dots as indicators, the present invention realizes the intuitive judgment of the impregnation depth of the soft magnetic powder core during the impregnation process. The strong fluorescence characteristics of the fluorescent carbon quantum dots enable the real-time and accurate monitoring of the impregnation depth according to the change of fluorescence intensity during the impregnation process, thus greatly improving the detection efficiency and accuracy and avoiding the errors and uncertainties that may exist in traditional detection methods.

[0019] 2. Do not affect the performance of the soft magnetic powder core: The addition of functionalized fluorescent carbon quantum dots not only realizes the visual detection of the impregnation depth, but also does not have a negative impact on the electrical and mechanical properties of the soft magnetic powder core. This ensures the stability and reliability of the soft magnetic powder core in applications and meets the application requirements of high-performance soft magnetic materials.

[0020] 3. Improve the migration rate and dispersibility: The fluorescent carbon quantum dots have a small size and good dispersibility, which enables them to migrate rapidly in the impregnating solution, reducing the resistance during the migration process, thereby improving the migration rate. At the same time, the good dispersibility also ensures the uniform distribution of the fluorescent carbon quantum dots in the impregnating solution, improving the accuracy and reliability of the detection. Description of the Drawings

[0021] Figure 1 Fluorescent position map of the impregnated soft magnetic powder core in Example 1 under ultraviolet light irradiation.

[0022] Figure 2 Fluorescence intensity vs. impregnation depth graph.

[0023] Figure 3 Fluorescence intensity vs. storage time graph.

[0024] Figure 4 Fluorescent position map of the impregnated soft magnetic powder core in Example 2 under ultraviolet light irradiation.

[0025] Figure 5 Fluorescence position map of the impregnated soft magnetic powder core in Example 3 under ultraviolet lamp irradiation.

[0026] Figure 6 Fluorescence position map of the impregnated soft magnetic powder core in Example 4 under ultraviolet lamp irradiation. Detailed implementation mode

[0027] The technical solution of the present invention will be further analyzed and described through specific examples below.

[0028] Preparation example:

[0029] The preparation method of the functionalized fluorescent carbon quantum dots of the present invention includes the following steps:

[0030] Step 1: Pretreatment

[0031] Select citric acid as the carbon source because it has good carbonization and fluorescence properties. Dissolve citric acid in deionized water to form a citric acid aqueous solution with a concentration of 0.1 M. Place the citric acid aqueous solution in an ultrasonic processor and ultrasonically disperse it for 30 minutes to ensure that citric acid molecules are fully dissolved and evenly dispersed.

[0032] Step 2: Carbonization treatment

[0033] Place the pretreated citric acid aqueous solution in a microwave oven and heat it at 200 °C for 5 minutes for preliminary carbonization treatment. Transfer the preliminarily carbonized product to a tubular furnace and heat it to 800 °C at a heating rate of 5 °C / minute under the protection of an inert gas (argon) and keep it for 2 hours for deep carbonization treatment. After the carbonization treatment is completed, cool the product to room temperature to obtain crude carbon quantum dots.

[0034] Step 3: Surface passivation treatment

[0035] Disperse the crude carbon quantum dots obtained in Step 2 in ethanol to form a dispersion with a concentration of 1 mg / mL. Add polyvinyl alcohol (PVA) to the dispersion, and the mass ratio of PVA to carbon quantum dots is 1:5. Stir and react at 80 °C for 4 hours to make PVA fully coat the surface of the carbon quantum dots for surface passivation treatment. After the reaction is completed, remove the unreacted PVA and impurities through centrifugation and washing steps to obtain passivated carbon quantum dots.

[0036] Step 4: Functionalization modification

[0037] The passivated carbon quantum dots are dispersed in deionized water to form a dispersion with a concentration of 0.5 mg / mL. A compound containing an amino group or a carboxyl group (such as ethylenediamine or acrylic acid) is added to the dispersion, and the molar ratio of the compound to the carbon quantum dots is 1:10. The mixture is stirred at room temperature for 24 hours to allow the compound to bind to the functional groups on the surface of the carbon quantum dots through chemical bonds for functional modification. After the reaction, the unreacted compound and impurities are removed by dialysis or centrifugation to obtain functionalized fluorescent carbon quantum dots.

[0038] Application Example 1:

[0039] Base resin system: Epoxy resin E44 is selected as the base resin system.

[0040] Curing agent: The amine curing agent liquid dicyandiamide is selected.

[0041] Indicator: The functionalized fluorescent carbon quantum dots prepared according to the above synthesis method, with amino functional groups modified on their surfaces.

[0042] Preparation process: Epoxy resin, curing agent, and diluent are mixed evenly in a mass ratio of 28:22:50, and then the fluorescent carbon quantum dot indicator is added thereto, with the concentration of the fluorescent carbon quantum dots being 0.5%, to obtain the impregnating solution A. The soft magnetic powder core is immersed in the impregnating solution for 30 minutes. Observe the change in the position of the fluorescence. When the fluorescence position reaches the predetermined position, it indicates that the predetermined impregnation depth has been achieved.

[0043] Performance test:

[0044] Change in fluorescence intensity: The impregnated soft magnetic powder core is irradiated with an ultraviolet lamp, and the fluorescence position map is as Figure 1 shown. At the same time, it is observed that the fluorescence intensity decreases linearly with the increase in the impregnation depth, as Figure 2 shown.

[0045] Color stability: When placed at room temperature for 72 hours, there is no obvious change in the fluorescence color, and the stability is good, as Figure 3 shown.

[0046] Magnetic permeability: The magnetic permeability of the impregnated soft magnetic powder core is tested. Compared with the sample without using the fluorescent indicator, the change rate is less than 2%, as shown in Table 1.

[0047] Mechanical properties: A tensile strength test is carried out, and the results are shown in Table 1, indicating that the tensile strength of the impregnated sample is increased compared with that before impregnation, and the change rate of the breaking tensile force is only 2% compared with Comparative Example 1 without adding the indicator.

[0048] Application Example 2:

[0049] Base resin system: Epoxy resin E44 is selected as the base resin system.

[0050] Curing agent: Select the amine curing agent liquid dicyandiamide.

[0051] Indicator: The functionalized fluorescent carbon quantum dots prepared according to the above synthesis method, and its surface is modified with amino functional groups.

[0052] Preparation process: Mix the epoxy resin, curing agent, and diluent evenly at a ratio of 28:22:50, then add the fluorescent carbon quantum dot indicator thereto, and adjust the concentration of the fluorescent carbon quantum dots to 1.0% to obtain the impregnating liquid B. Immerse the soft magnetic powder core in the impregnating liquid for 30 minutes. Observe the change in the position of the fluorescence. When the fluorescence position reaches the predetermined position, it means that the predetermined impregnation depth is reached.

[0053] Performance test: The results are similar to those of Example 1, but the change in fluorescence intensity is more significant, as Figure 4 shown, and at the same time, the influence on the mechanical properties of the magnetic permeability remains within an acceptable range, and the results are shown in Table 1.

[0054] Application Example 3:

[0055] Base resin system: Select epoxy resin E44 as the base resin system.

[0056] Curing agent: Select the amine curing agent liquid dicyandiamide.

[0057] Indicator: The functionalized fluorescent carbon quantum dots prepared according to the above synthesis method, the difference is that a carboxyl functional group is introduced, specifically, acrylic acid is used instead of ethylenediamine for the reaction in the functionalization modification step.

[0058] Preparation process: Mix the epoxy resin, curing agent, and diluent evenly at a ratio of 28:22:50, then add the fluorescent carbon quantum dot indicator thereto, and the concentration of the fluorescent carbon quantum dots is 1.0% to obtain the impregnating liquid C. Immerse the soft magnetic powder core in the impregnating liquid for 30 minutes. Observe the change in the position of the fluorescence. When the fluorescence position reaches the predetermined position, it means that the predetermined impregnation depth is reached.

[0059] Performance test shows that the impregnating liquid C can reach uniform penetration faster, as Figure 5 shown, the change in fluorescence intensity is more uniform, and the influence on the electrical and mechanical properties of the soft magnetic powder core is further reduced, and the results are shown in Table 1.

[0060] Application Example 4:

[0061] Base resin system: Select epoxy resin E44 as the base resin system.

[0062] Curing agent: The anhydride curing agent methyltetrahydrophthalic anhydride.

[0063] Indicator: The modified functionalized fluorescent carbon quantum dots the same as those in Example 3.

[0064] Preparation process: Epoxy resin, curing agent, and diluent were mixed evenly at a ratio of 28:22:50. Then, a fluorescent carbon quantum dot indicator was added thereto. The concentration of the fluorescent carbon quantum dot was 1.0%, and 0.5% of the stabilizer polyethyleneimine was added to improve the long-term stability of the fluorescent carbon quantum dot, obtaining the impregnating solution D. The soft magnetic powder core was immersed in the impregnating solution for 30 minutes. Observe the change in the position of the fluorescence. When the fluorescence position reaches the predetermined position, it indicates that the predetermined impregnation depth is achieved.

[0065] Performance tests show that even after long-term storage, the fluorescence intensity remains stable and the color does not fade significantly, as Figure 6 shown, and the impact on the performance of the soft magnetic powder core is equivalent to that of the freshly prepared impregnating solution. The results are shown in Table 1.

[0066] Comparative Example 1:

[0067] Base resin system: Epoxy resin E44 was selected as the base resin system.

[0068] Curing agent: The amine curing agent liquid dicyandiamide was selected.

[0069] Preparation process: Epoxy resin, curing agent, and diluent were mixed evenly at a ratio of 28:22:50 to obtain the impregnating solution A. The soft magnetic powder core was immersed in the impregnating solution for impregnation treatment for 30 minutes.

[0070] Comparative Example 2:

[0071] Base resin system: Epoxy resin E44 was selected as the base resin system.

[0072] Curing agent: The anhydride curing agent methyltetrahydrophthalic anhydride.

[0073] Indicator: The modified functionalized fluorescent carbon quantum dots identical to those in Example 3.

[0074] Preparation process: Epoxy resin, curing agent, and diluent were mixed evenly at a ratio of 28:22:50. Then, a fluorescent carbon quantum dot indicator was added thereto. The concentration of the fluorescent carbon quantum dot was 2.0%, and 0.5% of the stabilizer polyethyleneimine was added to improve the long-term stability of the fluorescent carbon quantum dot, obtaining the impregnating solution D. The soft magnetic powder core was immersed in the impregnating solution for 30 minutes. Observe the change in the position of the fluorescence. When the fluorescence position reaches the predetermined position, it indicates that the predetermined impregnation depth is achieved.

[0075] Performance tests show that the fluorescence intensity is stable, the color does not fade significantly, and the impact on the performance of the soft magnetic powder core is slightly greater. The results are shown in Table 1.

[0076]

[0077] Through the above embodiments, the impregnating solution provided by the present invention has successfully achieved the visual detection of the impregnation depth of soft magnetic powder cores, and under different concentrations, basic liquid formulations, and stabilizer addition conditions, it has shown good fluorescence intensity changes, color stability, and minimal impact on the magnetic permeability and mechanical properties of soft magnetic powder cores. Specifically, the magnetic permeability change rate in all embodiments does not exceed 2%, and the mechanical property change rate does not exceed 3%, demonstrating the effectiveness and practicality of the present invention.

Claims

1. An impregnating solution for visually detecting the impregnation depth of soft magnetic powder cores, characterized in that: The impregnating solution includes a basic impregnating solution and a certain amount of functionalized fluorescent carbon quantum dots; The basic impregnating solution includes bisphenol A epoxy resin, a curing agent, and a diluent; the mass concentration of the functionalized fluorescent carbon quantum dots in the impregnating solution system is 0.5wt% to 1.0wt%; The functionalized fluorescent carbon quantum dots are prepared by a method including the following steps: Step 1: Pretreatment Select citric acid as the carbon source, dissolve citric acid in deionized water, and ultrasonically disperse it evenly to form an aqueous citric acid solution; Step 2: Carbonization treatment Place the aqueous citric acid solution obtained in Step 1 in a microwave oven for preliminary carbonization treatment; transfer the preliminarily carbonized product to a tubular furnace and carry out deep carbonization treatment under the protection of an inert gas; after the carbonization treatment is completed, cool the product to room temperature to obtain a crude carbon quantum dot; Step 3: Surface passivation treatment Disperse the crude carbon quantum dots obtained in Step 2 in ethanol to form a dispersion with a concentration of 1mg / mL; add polyvinyl alcohol to the dispersion and stir and react at 80°C for 4 hours to fully coat the carbon quantum dots with polyvinyl alcohol for surface passivation treatment; After the reaction is completed, remove the unreacted polyvinyl alcohol and impurities through centrifugation and washing steps to obtain passivated carbon quantum dots; Step 4: Functionalization modification Disperse the passivated carbon quantum dots in deionized water to form a dispersion with a concentration of 0.5mg / mL; add a compound containing amino or carboxyl to the dispersion and stir and react at room temperature for 24 hours to make the compound bind to the functional groups on the surface of the carbon quantum dots through chemical bonds for functionalization modification; after the reaction is completed, remove the unreacted compound and impurities through dialysis or centrifugation steps to obtain functionalized fluorescent carbon quantum dots; In Step 2, the preliminary carbonization treatment is heating at 200°C for 5 minutes, and the deep carbonization treatment is holding at 800°C for 2 hours; In Step 3, the mass ratio of polyvinyl alcohol to carbon quantum dots is 1:5; In Step 4, the compound containing amino or carboxyl is ethylenediamine or acrylic acid, and the molar ratio of the compound containing amino or carboxyl to carbon quantum dots is 1:

10.

2. The impregnating solution according to claim 1, characterized in that: The impregnating solution further includes a stabilizer to improve the long-term stability of the fluorescent carbon quantum dots, and the stabilizer is polyethyleneimine.

3. The impregnating solution according to claim 1, characterized in that: In Step 2, when carrying out the deep carbonization treatment, the heating rate is 5°C / minute.

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