Impregnation liquid for visually detecting impregnation depth of soft magnetic powder core

Abstract

The invention discloses an impregnation liquid for visually detecting the impregnation depth of a soft magnetic powder core, and belongs to the technical field of soft magnetic materials. According to the impregnation liquid disclosed by the invention, the functionalized fluorescent carbon quantum dots are added as an indicator, so that the impregnation depth can be intuitively judged according to the change of the fluorescence intensity in the impregnation process. The carbon quantum dots are subjected to surface modification, so that the surfaces of the carbon quantum dots have specific functional groups, and the carbon quantum dots can be better compatible with other organic components in the impregnation liquid. The surface modification not only can improve the dispersibility of the carbon quantum dots in the impregnation liquid and reduce the agglomeration phenomenon, but also can avoid the chemical reaction of the carbon quantum dots and magnetic particles in the soft magnetic powder core, thereby reducing the influence on the electrical and mechanical properties of the soft magnetic powder core.

Description

Technical Field

[0001] The invention belongs to the technical field of soft magnetic materials, and in particular relates to an impregnation liquid for visually detecting the impregnation depth of a soft magnetic powder core. Background Art

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

[0003] The object of the present invention is to provide an impregnation solution for visually detecting the impregnation depth of a soft magnetic powder core. The impregnation solution can intuitively judge the impregnation depth according to the change in fluorescence intensity during the impregnation process by adding functionalized fluorescent carbon quantum dots as indicators, while not affecting the electrical and mechanical properties of the soft magnetic powder core. Fluorescent carbon quantum dots have a small size and good dispersibility, which enables them to migrate rapidly in a solution or medium. Its nanoscale size helps to reduce resistance during migration, thereby increasing the migration rate. Secondly, fluorescent carbon quantum dots have strong fluorescence properties, which not only makes them easy to detect and track, but also provides real-time visual information during migration. This property is of great significance for studying the migration behavior of carbon quantum dots in complex systems. Fluorescent carbon quantum dots have good solution processing properties, which means that they can be easily dissolved in a variety of solvents and maintain stable fluorescence properties in these solvents. This property contributes to the rapid migration and dispersion of carbon quantum dots in solution.

[0004] The impregnation liquid of the present invention comprises a basic impregnation liquid and a certain amount of functionalized fluorescent carbon quantum dots. The basic impregnation liquid is composed of bisphenol A type epoxy resin (E44 or E51), a curing agent (dicyandiamide, methyltetrahydrophthalic anhydride or methylhexahydroaniline), and a diluent (dimethyl ester of mixed diacids). The fluorescent carbon quantum dots are specially functionalized to ensure that they are stably dispersed in the impregnation liquid and can penetrate into the soft magnetic powder core with the impregnation liquid. Under the excitation of ultraviolet light or light of a specific wavelength, the fluorescent carbon quantum dots emit fluorescence, and its 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 the surface thereof has specific functional groups, so that it can be better compatible with other organic components in the impregnation liquid. This surface modification can not only improve the dispersibility of the carbon quantum dots in the impregnation liquid and reduce the agglomeration phenomenon, but also avoid chemical reactions between the carbon quantum dots and the magnetic particles in the soft magnetic powder core, thereby reducing the impact on the electrical and mechanical properties of the soft magnetic powder core.

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

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

[0007] The method for preparing the functionalized fluorescent carbon quantum dots comprises the following steps: Step 1: Preprocessing Citric acid was selected as the carbon source because of its good carbonization and fluorescence properties. Citric acid was dissolved in deionized water to form a 0.1 M citric acid aqueous solution. The citric acid aqueous solution was placed in an ultrasonic processor and ultrasonically dispersed for 30 minutes to ensure that the citric acid molecules were fully dissolved and evenly dispersed.

[0008] Step 2: Carbonization The pretreated citric acid aqueous solution was placed in a microwave oven and heated at 200°C for 5 minutes for preliminary carbonization. The product after preliminary carbonization was transferred to a tube furnace and heated to 800°C at a heating rate of 5°C / min under the protection of an inert gas (such as argon) and kept warm for 2 hours for deep carbonization. After the carbonization treatment, the product was cooled to room temperature to obtain a crude carbon quantum dot product.

[0009] Step 3: Surface passivation The crude carbon quantum dots obtained in step 2 were dispersed in ethanol to form a dispersion with a concentration of 1 mg / mL. Polyvinyl alcohol (PVA) was added to the dispersion, and the mass ratio of PVA to carbon quantum dots was 1:5. The reaction was stirred at 80°C for 4 hours to allow PVA to fully coat the surface of the carbon quantum dots for surface passivation. After the reaction was completed, the unreacted PVA and impurities were removed by centrifugation and washing steps to obtain passivated carbon quantum dots.

[0010] Step 4: Functionalization 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 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 is completed, the unreacted compounds and impurities are removed by dialysis or centrifugation steps to obtain functionalized fluorescent carbon quantum dots.

[0011] The fluorescent carbon quantum dots can intuitively 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.

[0012] The beneficial effects of the present invention are embodied in: 1. Intuitive judgment of impregnation depth: The present invention adds functionalized fluorescent carbon quantum dots as indicators to achieve intuitive judgment of the impregnation depth of the soft magnetic powder core during the impregnation process. The strong fluorescence characteristics of fluorescent carbon quantum dots enable real-time and accurate monitoring of the impregnation depth according to the changes in fluorescence intensity during the impregnation process, thereby greatly improving the detection efficiency and accuracy and avoiding the errors and uncertainties that may exist in traditional detection methods.

[0013] 2. No impact on the performance of soft magnetic powder core: The addition of functionalized fluorescent carbon quantum dots not only enables visual detection of the impregnation depth, but also does not negatively affect the electrical and mechanical properties of the soft magnetic powder core. This ensures the stability and reliability of the soft magnetic powder core in the application and meets the application requirements of high-performance soft magnetic materials.

[0014] 3. Improve migration rate and dispersibility: Fluorescent carbon quantum dots have a small size and good dispersibility, which enables them to migrate quickly in the impregnation liquid, reducing the resistance during the migration process, thereby increasing the migration rate. At the same time, good dispersibility also ensures the uniform distribution of fluorescent carbon quantum dots in the impregnation liquid, improving the accuracy and reliability of detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Fluorescence position diagram of the soft magnetic powder core after impregnation in Example 1 under ultraviolet light.

[0016] Figure 2 Fluorescence intensity versus impregnation depth.

[0017] Figure 3 Fluorescence intensity versus storage time.

[0018] Figure 4 Fluorescence position diagram of the soft magnetic powder core after impregnation in Example 2 under ultraviolet light.

[0019] Figure 5Fluorescence position diagram of the soft magnetic powder core after impregnation in Example 3 under ultraviolet light.

[0020] Figure 6 Fluorescence position diagram of the soft magnetic powder core after impregnation in Example 4 under ultraviolet light. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further analyzed and explained below through specific embodiments.

[0022] Preparation Example: The method for preparing functionalized fluorescent carbon quantum dots of the present invention comprises the following steps: Step 1: Preprocessing Citric acid was selected as the carbon source because of its good carbonization and fluorescence properties. Citric acid was dissolved in deionized water to form a 0.1 M citric acid aqueous solution. The citric acid aqueous solution was placed in an ultrasonic processor and ultrasonically dispersed for 30 minutes to ensure that the citric acid molecules were fully dissolved and evenly dispersed.

[0023] Step 2: Carbonization The pretreated citric acid aqueous solution was placed in a microwave oven and heated at 200°C for 5 minutes for preliminary carbonization. The product after preliminary carbonization was transferred to a tube furnace and heated to 800°C at a heating rate of 5°C / min under the protection of an inert gas (argon) and kept warm for 2 hours for deep carbonization. After the carbonization treatment, the product was cooled to room temperature to obtain a crude carbon quantum dot product.

[0024] Step 3: Surface passivation The crude carbon quantum dots obtained in step 2 were dispersed in ethanol to form a dispersion with a concentration of 1 mg / mL. Polyvinyl alcohol (PVA) was added to the dispersion, and the mass ratio of PVA to carbon quantum dots was 1:5. The reaction was stirred at 80°C for 4 hours to allow PVA to fully coat the surface of the carbon quantum dots for surface passivation. After the reaction was completed, the unreacted PVA and impurities were removed by centrifugation and washing steps to obtain passivated carbon quantum dots.

[0025] Step 4: Functionalization 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 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 is completed, the unreacted compounds and impurities are removed by dialysis or centrifugation steps to obtain functionalized fluorescent carbon quantum dots.

[0026] Application Example 1: Base resin system: Epoxy resin E44 is selected as the base resin system.

[0027] Curing agent: Use amine curing agent liquid dicyandiamide.

[0028] Indicator: The functionalized fluorescent carbon quantum dots prepared according to the above synthesis method have amino functional groups modified on their surface.

[0029] Preparation process: Epoxy resin, curing agent and diluent are mixed evenly at a mass ratio of 28:22:50, and then fluorescent carbon quantum dot indicator is added thereto, wherein the concentration of fluorescent carbon quantum dots is 0.5%, to obtain impregnation solution A. The soft magnetic powder core is immersed in the impregnation solution for 30 minutes. Observe the change in the position of fluorescence. When the fluorescence position reaches the predetermined position, it means that the predetermined impregnation depth has been reached.

[0030] Performance Testing: Fluorescence intensity change: Use ultraviolet light to irradiate the impregnated soft magnetic powder core, and the fluorescence position diagram is as follows: Figure 1 As shown in Figure 2, it was also observed that the fluorescence intensity linearly decreased with increasing immersion depth, as shown in Figure 2. Figure 2 shown.

[0031] Color stability: After being placed at room temperature for 72 hours, the fluorescent color has no obvious change, and the stability is good. Figure 3 shown.

[0032] Magnetic permeability: The magnetic permeability of the soft magnetic powder core after impregnation was tested. Compared with the sample without using fluorescent indicator, the change rate was less than 2%, as shown in Table 1.

[0033] Mechanical properties: The tensile strength test was carried out, and the results are shown in Table 1, which shows that the tensile strength of the sample after impregnation is higher than that before impregnation, and the breaking tensile force change rate is only 2% compared with the comparative example 1 without adding the indicator.

[0034] Application Example 2: Base resin system: Epoxy resin E44 is selected as the base resin system.

[0035] Curing agent: Use amine curing agent liquid dicyandiamide.

[0036] Indicator: The functionalized fluorescent carbon quantum dots prepared according to the above synthesis method have amino functional groups modified on their surface.

[0037] Preparation process: Epoxy resin, curing agent, and diluent are mixed evenly at a ratio of 28:22:50, and then fluorescent carbon quantum dot indicator is added thereto, and the concentration of fluorescent carbon quantum dots is adjusted to 1.0% to obtain impregnation solution B. The soft magnetic powder core is immersed in the impregnation solution 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 has been reached.

[0038] Performance test: The results are similar to those in Example 1, but the fluorescence intensity changes are more significant, such as Figure 4 As shown, the influence of magnetic permeability on mechanical properties is kept within an acceptable range. The results are shown in Table 1.

[0039] Application Example 3: Base resin system: Epoxy resin E44 is selected as the base resin system.

[0040] Curing agent: Use amine curing agent liquid dicyandiamide.

[0041] Indicator: The functionalized fluorescent carbon quantum dots prepared according to the above synthesis method are different in that a carboxyl functional group is introduced, specifically, in the functionalization modification step, acrylic acid is used instead of ethylenediamine for the reaction.

[0042] Preparation process: Epoxy resin, curing agent and diluent are mixed evenly at a ratio of 28:22:50, and then fluorescent carbon quantum dot indicator is added thereto, and the concentration of fluorescent carbon quantum dots is 1.0%, to obtain impregnation liquid C. The soft magnetic powder core is immersed in the impregnation liquid for 30 minutes. Observe the change of the fluorescence position. When the fluorescence position reaches the predetermined position, it means that the predetermined impregnation depth has been reached.

[0043] Performance tests show that impregnation liquid C can achieve uniform penetration faster. Figure 5 As shown, the fluorescence intensity changes more uniformly, and the influence on the electrical and mechanical properties of the soft magnetic powder core is further reduced. The results are shown in Table 1.

[0044] Application Example 4: Base resin system: Epoxy resin E44 is selected as the base resin system.

[0045] Curing agent: anhydride curing agent methyltetrahydrophthalic anhydride.

[0046] Indicator: the same modified functionalized fluorescent carbon quantum dots as in Example 3.

[0047] Preparation process: Epoxy resin, curing agent and diluent are mixed evenly at a ratio of 28:22:50, and then fluorescent carbon quantum dot indicator is added thereto, the concentration of fluorescent carbon quantum dots is 1.0%, and 0.5% of stabilizer polyethyleneimine is added to improve the long-term stability of fluorescent carbon quantum dots to obtain impregnation liquid D. The soft magnetic powder core is immersed in the impregnation liquid for 30 minutes. Observe the change in the position of fluorescence. When the fluorescence position reaches the predetermined position, it means that the predetermined impregnation depth has been reached.

[0048] Performance tests show that even after long-term storage, the fluorescence intensity remains stable and the color does not decay significantly. Figure 6As shown, the effect on the properties of the soft magnetic powder core is equivalent to that of the freshly prepared impregnation solution. The results are shown in Table 1.

[0049] Comparative Example 1: Base resin system: Epoxy resin E44 is selected as the base resin system.

[0050] Curing agent: Use amine curing agent liquid dicyandiamide.

[0051] Preparation process: Epoxy resin, curing agent and diluent are mixed evenly at a ratio of 28:22:50 to obtain impregnation solution A. The soft magnetic powder core is immersed in the impregnation solution for 30 minutes.

[0052] Comparative Example 2: Base resin system: Epoxy resin E44 is selected as the base resin system.

[0053] Curing agent: anhydride curing agent methyltetrahydrophthalic anhydride.

[0054] Indicator: the same modified functionalized fluorescent carbon quantum dots as in Example 3.

[0055] Preparation process: Epoxy resin, curing agent, and diluent are mixed evenly at a ratio of 28:22:50, and then fluorescent carbon quantum dot indicator is added thereto, the concentration of fluorescent carbon quantum dots is 2.0%, and 0.5% of stabilizer polyethyleneimine is added to improve the long-term stability of fluorescent carbon quantum dots to obtain impregnation liquid D. The soft magnetic powder core is immersed in the impregnation liquid for 30 minutes. Observe the change in the position of fluorescence. When the fluorescence position reaches the predetermined position, it means that the predetermined impregnation depth has been reached.

[0056] The performance test shows that the fluorescence intensity is stable, the color has no obvious decay, and the impact on the performance of the soft magnetic powder core is slightly greater. The results are shown in Table 1.

[0057]

[0058] Through the above examples, the impregnation liquid provided by the present invention successfully realizes the visual detection of the impregnation depth of the soft magnetic powder core, and under different concentrations, basic liquid formulas and stabilizer addition conditions, it shows good fluorescence intensity changes, color stability and minimal impact on the magnetic permeability and mechanical properties of the soft magnetic powder core. Specifically, the change rate of magnetic permeability in all examples does not exceed 2%, and the change rate of mechanical properties does not exceed 3%, which proves the effectiveness and practicality of the present invention.

Claims

1. An impregnation liquid for visually detecting the impregnation depth of a soft magnetic powder core, characterized in that: The impregnation liquid includes a basic impregnation liquid and functionalized fluorescent carbon quantum dots; The functionalized fluorescent carbon quantum dots are prepared by a method comprising the following steps: Step 1: Preprocessing Citric acid is selected as a carbon source, and the citric acid is dissolved in deionized water and uniformly dispersed by ultrasonication to form a citric acid aqueous solution; Step 2: Carbonization The citric acid aqueous solution obtained in step 1 is placed in a microwave oven for preliminary carbonization treatment; the product after preliminary carbonization is transferred to a tube furnace for deep carbonization treatment under the protection of inert gas; after the carbonization treatment is completed, the product is cooled to room temperature to obtain a crude carbon quantum dot product; Step 3: Surface passivation The crude carbon quantum dots obtained in step 2 are dispersed in ethanol to form a dispersion with a concentration of 1 mg / mL; polyvinyl alcohol is added to the dispersion, and the mixture is stirred at 80° C. for 4 hours to allow the polyvinyl alcohol to fully coat the surface of the carbon quantum dots for surface passivation treatment; After the reaction is completed, unreacted polyvinyl alcohol and impurities are removed by centrifugation and washing steps to obtain passivated carbon quantum dots; Step 4: Functionalization 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 is added to the dispersion, and the reaction is stirred at room temperature for 24 hours to allow the compound to combine with the functional groups on the surface of the carbon quantum dots through chemical bonds to perform functional modification; after the reaction is completed, unreacted compounds and impurities are removed by dialysis or centrifugation steps to obtain functionalized fluorescent carbon quantum dots.

2. The impregnation liquid according to claim 1, characterized in that: The basic impregnation solution comprises bisphenol A type epoxy resin, a curing agent and a diluent.

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

4. The impregnation liquid according to claim 1, characterized in that: The mass concentration of the functionalized fluorescent carbon quantum dots in the impregnation liquid system is 0.5wt% to 1.0wt%.

5. The impregnation liquid according to claim 1, characterized in that: In step 2, the preliminary carbonization treatment is performed by heating at 200° C. for 5 minutes.

6. The impregnation liquid according to claim 1, characterized in that: In step 2, the deep carbonization treatment is carried out at 800° C. for 2 hours.

7. The impregnation liquid according to claim 6, characterized in that: During the deep carbonization treatment, the heating rate is 5°C / min.

8. The impregnation liquid according to claim 1, characterized in that: In step 3, the mass ratio of polyvinyl alcohol to carbon quantum dots is 1:

5.

9. The impregnation liquid according to claim 1, characterized in that: In step 4, the compound containing an amino group or a carboxyl group is ethylenediamine or acrylic acid.

10. The impregnation liquid according to claim 9, characterized in that: The molar ratio of the compound containing amino or carboxyl groups to the carbon quantum dots is 1:10.

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