Gradient functionalized high-performance iron-nickel magnetic powder core and preparation method thereof

Abstract

The application relates to the technical field of magnetic materials, and provides a gradient functionalized high-performance iron-nickel magnetic powder core and a preparation method. The preparation method is as follows: after iron-nickel powder is subjected to particle size grading, the iron-nickel powder is firstly coated with quartz powder, and then is secondarily and cooperatively coated with phosphoric acid and silica sol, and is pressed into shape after being bonded and lubricated, and the gradient functionalized high-performance iron-nickel magnetic powder core is obtained after sintering. The method is based on the gradient functionalization design of the coating layer, the electron migration path is blocked by a high-density quartz layer, and a composite insulating layer is formed by the phosphoric acid-silica sol cooperatively coating, so that a quartz-phosphate-nano silicon dioxide gradient functionalized coating layer with uniform thickness and thinness is finally formed on the surface of the iron-nickel powder; the obtained iron-nickel magnetic powder core is not only low in loss but also good in direct current bias performance; the method is simple, environment-friendly and low in cost.

Description

Technical Field

[0001] This invention belongs to the field of soft magnetic functional materials, specifically relating to a gradient functionalized high-performance iron-nickel magnetic powder core and its preparation method. Background Technology

[0002] With the rapid development of modern power electronics, information communication, and technology, the importance of soft magnetic materials in these fields is increasingly prominent, and the demand is growing daily. Soft magnetic materials, as core passive components, play a crucial role in the conversion and transmission of electromagnetic energy, and are key magnetic materials for the generation, transmission, and conversion of electrical energy. In the context of artificial intelligence, power electronic devices are trending towards higher frequencies, higher efficiency, and energy saving, requiring more efficient and miniaturized electronic components. With the development of power electronic devices, communication equipment, electric vehicles, and smart grids, the demand for the DC bias characteristics and loss performance of iron-nickel materials is increasing. Iron-nickel soft magnetic materials have high permeability and excellent DC bias characteristics, but their complex manufacturing processes, high costs, environmental pollution from older processes, and high eddy current losses limit their widespread application and development in various fields. Therefore, reducing eddy current losses, manufacturing methods, and costs while maintaining the original high DC bias characteristics of iron-nickel soft magnetic materials is currently a research hotspot.

[0003] Currently, the preparation method of iron-nickel magnetic powder cores involves combining iron-nickel magnetic powder cores with insulating materials and performing multiple complex processes to coat the surface of the magnetic powder with an insulating material coating layer. However, the coating of the magnetic powder cores using these complex processes is not complete or uniform, and the processes are complicated, cumbersome, and costly, failing to meet the current requirements for high performance and low cost. Therefore, it is necessary to develop a multi-layer uniform coating and gradient functionalized powder coating process that is simple, low-cost, and uses appropriate annealing processes to improve the magnetic properties of iron-nickel soft magnetic powder cores, thereby expanding their applications in various fields. Summary of the Invention

[0004] This invention provides a gradient functionalized high-performance iron-nickel magnetic powder core and its preparation method, aiming to solve the problem that iron-nickel magnetic powder cores are difficult to have both low loss and excellent DC bias characteristics, while also solving the problem of cumbersome preparation process.

[0005] A method for preparing gradient functionalized high-performance iron-nickel magnetic powder cores is disclosed, which uses quartz powder, phosphoric acid, and silica sol as insulating reagents to perform gradient insulating coating on the surface of iron-nickel magnetic powder particles. Through multi-layer insulating coating, the problem of conductivity or electromagnetic interference caused by direct contact between particles is effectively solved. The preparation method is simple, environmentally friendly, and low in cost. The resulting coating layer has good stability and high temperature resistance, and its thickness can be flexibly adjusted by increasing or decreasing the amount of reagents. A gradient functionalized high-performance iron-nickel magnetic powder core obtained by the above method has significantly reduced eddy current losses while maintaining the original excellent DC bias characteristics.

[0006] A method for preparing gradient functionalized high-performance iron-nickel magnetic powder cores includes the following steps:

[0007] (1) Particle size distribution: The iron-nickel powder is sieved according to the particle size using a tapping vibrating screen to obtain the iron-nickel powder of the required particle size. Then, it is mixed in a certain proportion to obtain iron-nickel powder with good particle size distribution.

[0008] (2) First passivation coating: Add quartz powder to the iron-nickel powder with good particle size distribution obtained in step (1), put it into a ball mill for mixing, and coat the iron-nickel powder with a first passivation layer.

[0009] (3) Secondary passivation coating: Add a mixed ethanol solution of phosphoric acid and silica sol to the iron-nickel powder coated with the first passivation layer obtained in step (2), stir evenly, and then react in a rotating instrument. After the reaction is completed, cool and sieve to coat the iron-nickel powder with the second passivation layer.

[0010] (4) Bonding and lubrication: Add an ethanol solution of organosilicon resin to the iron-nickel powder coated with the second passivation layer obtained in step (3), stir evenly, dry at low temperature, and then sieve; then add lubricant, stir evenly, and sieve to obtain the iron-nickel composite powder to be pressed.

[0011] (5) Pressing and annealing: The iron-nickel composite magnetic powder is pressed into a ring shape, and after pressing, it is annealed at high temperature to obtain a gradient functionalized high-performance iron-nickel magnetic powder core.

[0012] In step (1), the preferred raw materials for the iron-nickel magnetic powder are 200-mesh FeNi50 alloy powder and 400-mesh FeNi50 alloy powder. The number of taps of the tapping vibrating screen is 140-160 times / min, the tapping time is 30-60min, and the screen mesh is 100-400 mesh.

[0013] Furthermore, in step (1), taking the well-graded iron-nickel powder as 100%, the particle size distribution combination is: -200 mesh to +325 mesh: -325 mesh to +400 mesh: -400 mesh = (30%~50%): (20%~30%): (20%~50%);

[0014] As a preferred option, the particle size distribution is: -200 mesh to +325 mesh : -325 mesh to +400 mesh : -400 mesh = 50% : 20% : 30%;

[0015] In step (2), 2 to 5 parts of quartz powder are added to every 500 parts of iron-nickel powder, and the ball milling time is 10 to 30 minutes.

[0016] In step (3), 0.2 to 2 parts of phosphoric acid, 0.5 to 5 parts of silica sol and 5 to 25 parts of ethanol are added to every 500 parts of iron-nickel powder, and the stirring time is 5 to 10 minutes.

[0017] Furthermore, in step (3), the rotation speed of the rotating instrument is 60~80 r / min, the reaction temperature is 120~160℃, the reaction time is 40~80 min, and the sieve is 60~100 mesh;

[0018] In step (4), based on the iron-nickel composite powder, the amount of silicone resin solution added is 0.3~0.9%, and the amount of anhydrous ethanol added is 3~6%; the stirring time is 10~20min, the drying temperature is 60~120℃, the drying time is 30~60min, and the sieve is 100 mesh.

[0019] Furthermore, in step (4), based on the iron-nickel composite powder, the amount of lubricant added is 0.4~0.8wt%, and the lubricant is one or more of zinc stearate, aluminum stearate, magnesium stearate, paraffin wax, etc.

[0020] In step (5), a magnetic ring with an outer diameter of 26.80~27.20mm, an inner diameter of 14.50~14.80mm, and a height of 10.95~11.20mm is pressed, and the pressing pressure is 18~20t / cm. 2 The annealing temperature is 680~770℃, and the annealing time is 5~8h.

[0021] This invention provides a gradient functionalized high-performance iron-nickel magnetic powder core and its preparation method. The principle is as follows:

[0022] Iron-nickel powder is sieved according to particle size and mixed according to a specific particle size ratio to promote the formation of a dense packing structure between the powders, adjust the distribution of air gaps inside the magnetic core, and effectively reduce magnetic core loss.

[0023] Then, quartz powder is physically coated on the surface of iron-nickel powder particles by ball milling. The ball milling generates strong impact, shearing and compression, which causes the quartz powder particles to repeatedly collide, deform, cold weld, break and finally attach / embed onto the relatively soft surface of iron-nickel powder particles, so that a highly dense inorganic layer is formed on the surface, blocking the electron migration path and inhibiting the metal oxidation / corrosion reaction.

[0024] Then, through the synergistic coating of phosphoric acid and silica sol, and the reaction at high temperature (120~160℃), phosphoric acid first passivates the particle surface in situ, forming a dense phosphate main insulating layer. Subsequently, the nano-silica in the silica sol acts as an auxiliary insulating agent, filling the micropores of the main insulating layer. Finally, a gradient functionalized coating layer of quartz-phosphate-nano-silica is formed on the surface of the iron-nickel powder, providing a flexible interface buffer, adapting to thermal expansion differences, and enhancing compatibility with the matrix material. After bonding and lubrication, it is pressed into shape and annealed to obtain a gradient functionalized high-performance iron-nickel magnetic powder core.

[0025] Annealing can promote the transformation of amorphous oxide coatings such as quartz powder into crystalline state, reduce structural defects, and densify the coatings; phosphate coatings dehydrate and polymerize to transform into pyrophosphate crystals, which increases resistivity and reduces eddy current loss.

[0026] Furthermore, the porosity of the coating layer decreases after annealing, eliminating residual stress during cold pressing and reducing the risk of magnetic powder core cracking. In addition, the organic binder can promote cross-linking and curing during annealing, enhancing interlayer bonding.

[0027] This invention provides a gradient functionalized high-performance iron-nickel magnetic powder core and its preparation method, which has the following advantages compared with the prior art:

[0028] 1. This invention employs a multi-insulation coating method, using a "gradient functionalization" design to form a ternary coating layer of quartz-phosphate-nano silica on the surface of iron-nickel powder particles. The quartz layer blocks electron migration paths, while the phosphate-nano silica composite coating layer provides a flexible buffer interface. This results in a dense, uniform, and thin gradient functionalized coating layer, effectively reducing conductivity or electromagnetic interference problems caused by direct contact between particles. The resulting iron-nickel magnetic powder core exhibits excellent DC bias performance (94.6%, 100Oe) and low power loss (95.6 kW / m²). 3 (50kHz*100mT)

[0029] 2. In this invention, regarding the selection of coating agents, silica sol has the characteristics of high temperature resistance, good dispersibility, good penetration and low viscosity, which is conducive to firmly adhering to and uniformly coating the surface of iron-nickel powder particles, and together with phosphoric acid, it coats the surface of iron-nickel particles to form a non-magnetic material coating layer.

[0030] 3. The method for preparing iron-nickel magnetic powder cores of the present invention achieves a "gradient functionalization" design on the surface of iron-nickel powder particles. The preparation method is simple and economical. On the one hand, the use of organosilicon resin as a binder can be combined with solvents such as ethanol and water, reducing costs and process hazards. On the other hand, the silica sol used for passivation coating has certain adhesion, which can reduce the amount of binder used, thereby reducing costs. Detailed Implementation

[0031] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0032] Example 1

[0033] (1) Particle size distribution: 500g of 200-mesh and 200g of 400-mesh iron-nickel powder were placed in a tapping vibrating screen. The tapping vibrating screen time was set to 60min. The screens were 200-mesh, 325-mesh and 400-mesh. The sieved iron-nickel powder was then mixed in a ratio of -200-mesh to +325-mesh: -325-mesh to +400-mesh: -400-mesh = 5:2:3 to obtain iron-nickel powder with good particle size distribution.

[0034] (2) One passivation coating: 2.5g of quartz powder and 500g of iron-nickel powder with good particle size distribution are put into a ball mill and ball milled for 20 minutes to obtain iron-nickel powder with one passivation coating.

[0035] (3) Secondary passivation coating: 1g of phosphoric acid, 2g of silica sol and 15g of anhydrous ethanol are mixed, and then the solution is added to 500g of iron-nickel powder that has been passedivated once. After stirring evenly, the mixture is placed in a rotating apparatus for reaction at a temperature of 150℃ for 60min. After the reaction is completed, the powder is taken out and dried, and then sieved through a 100-mesh sieve to obtain iron-nickel powder with secondary passivation coating.

[0036] (4) Bonding and lubrication: Mix 1.5g of silicone resin solution and 15g of anhydrous ethanol, then add the mixed solution to the iron-nickel powder coated in step (3), stir evenly, place it in a 60℃ oven and dry for 30 minutes, and after cooling, pass it through a 100-mesh sieve; take 2g of zinc stearate powder, add it to 500g of bonded iron-nickel powder, mix and stir evenly, and pass it through a 100-mesh sieve to obtain the iron-nickel composite powder to be pressed;

[0037] (5) Pressing and annealing: The iron-nickel composite powder is pressed into a magnetic ring with an outer diameter of 27.00 mm, an inner diameter of 14.70 mm, and a height of 11.00 mm. The pressure is 18 t / cm. 2 After pressing, the powder is subjected to high-temperature annealing at 680℃ for 8 hours to obtain uniformly coated and fully functionalized high-performance iron-nickel magnetic powder cores.

[0038] Comparative Example 1

[0039] The difference between this comparative example and Example 1 is that the 200-mesh raw iron-nickel powder used was not sized using a tapping vibrating screen.

[0040] Comparative Example 2

[0041] The difference between this comparative example and Example 1 is that in the secondary passivation coating, only phosphoric acid is used as the coating agent, and no silica sol is added for co-coating.

[0042] Comparative Example 3

[0043] The difference between this comparative example and Example 1 is that in the secondary passivation coating, only silica sol is used as the powder coating agent, and phosphoric acid is not added for co-coating.

[0044] Comparative Example 4

[0045] The difference between this comparative example and Example 1 is that it does not use quartz powder for a first passivation coating, but only performs a second coating.

[0046] The core composite powder obtained in Example 1 and Comparative Examples 1-4 was pressed into a magnetic ring with an outer diameter of 27.00 mm, an inner diameter of 14.70 mm, and a height of 11.10 ± 0.10 mm. After high-temperature heat treatment, the magnetic ring was wound with a coil for testing. The magnetic permeability and DC bias performance were calculated by testing the magnetic ring inductance value; at the same time, the magnetic ring loss performance was tested.

[0047] The performance test results of Example 1 and Comparative Examples 1-4 are shown in Table 1:

[0048] Table 1 Performance test results of Example 1 and Comparative Examples 1-4

[0049]

[0050] Based on the test results in Table 1, comparing Example 1 and Comparative Example 1, it can be concluded that the present invention utilizes a sieving and grading method for iron-nickel raw powder using a slapping vibrating screen, which can effectively reduce the loss of iron-nickel magnetic powder cores and improve the superposition performance of iron-nickel magnetic powder cores. This is because after particle size gradation, the magnetic powder is more densely distributed during the pressing process, which increases the density of the magnetic powder core after pressing, thereby reducing losses and improving DC bias performance.

[0051] Comparing Example 1 with Comparative Examples 2-4, it can be concluded that the gradient multi-insulation coating method using a mixed solution of quartz powder, phosphoric acid, and silica sol in this invention exhibits excellent coating effects, resulting in superior DC bias performance and loss performance of the coated iron-nickel magnetic powder core. This is because the quartz powder is ball-milled onto the surface of the metal particles, followed by passivation of the iron-nickel powder particles by phosphoric acid reaction, forming a passivation coating layer. Silica sol, with its adhesive and high-temperature resistance properties, acts as an auxiliary insulating agent, firmly adhering to and filling the micropores of the phosphoric acid insulating layer. This makes the coating layer more uniform and stable, enhancing the stability of the iron-nickel coated powder under high temperature and pressure, thereby improving the stability and loss performance of the iron-nickel magnetic powder core.

[0052] Example 2

[0053] (1) Particle size distribution: 500g of 200-mesh and 200g of 400-mesh iron-nickel powder were placed in a tapping vibrating screen. The tapping vibrating screen time was set to 60min. The screens were 200-mesh, 325-mesh and 400-mesh. The sieved iron-nickel powder was then mixed in a ratio of -200-mesh to +325-mesh: -325-mesh to +400-mesh: -400-mesh = 5:2:3 to obtain iron-nickel powder with good particle size distribution.

[0054] (2) One passivation coating: 4g of quartz powder and 500g of iron-nickel powder with good particle size distribution are put into a ball mill and ball milled for 20 minutes to obtain iron-nickel powder with one passivation coating.

[0055] (3) Secondary passivation coating: Mix 1g of phosphoric acid, 3g of silica sol and 15g of anhydrous ethanol, then add the solution to 500g of iron-nickel powder that has been passedivated once, stir evenly and place it in a rotating apparatus for reaction at 150℃ for 60min; after the reaction is completed, take out the powder and dry it, then sieve it through 100 mesh to obtain iron-nickel powder that has been passedivated twice.

[0056] (4) Bonding and lubrication: Mix 3g of silicone resin solution and 15g of anhydrous ethanol, then add the mixed solution to the iron-nickel powder coated in step (2), stir evenly, place it in a 60℃ oven, dry for 30min, and after cooling, pass it through a 100-mesh sieve; take 2g of zinc stearate powder, add it to 500g of bonded iron-nickel powder, mix and stir evenly, and pass it through a 100-mesh sieve to obtain the iron-nickel composite powder to be pressed;

[0057] (5) Pressing and annealing: The iron-nickel composite powder is pressed into a magnetic ring with an outer diameter of 27.00 mm, an inner diameter of 14.70 mm, and a height of 11.00 mm. The pressure is 20 t / cm. 2 After pressing, the powder is subjected to high-temperature annealing at 770℃ for 5 hours to obtain uniformly coated and fully functionalized high-performance iron-nickel magnetic powder cores.

[0058] Comparative Example 5 is as follows:

[0059] The difference between this comparative example and Example 2 is that the particle size distribution ratio after using the tapping vibrating screen is -200 mesh to +325 mesh : -325 mesh to +400 mesh : -400 mesh = 7 : 2 : 1.

[0060] Comparative Example 6 is as follows:

[0061] The difference between this comparative example and Example 2 is that the amount of phosphoric acid used in the secondary passivation coating is 2g, the amount of silica sol is 8g, and after being stirred evenly with iron-nickel magnetic powder, it is placed in a rotating apparatus for reaction at a reaction temperature of 180°C.

[0062] Comparative Example 7 is as follows:

[0063] The difference between this comparative example and Example 2 is that after the phosphoric acid and silica sol are co-coated, no silicone resin is used for bonding.

[0064] The iron-nickel composite powder obtained in Example 2 and Comparative Examples 5, 6 and 7 was pressed into a magnetic ring with an outer diameter of 27.00 mm, an inner diameter of 14.70 mm and a height of 11.10 ± 0.10 mm. After heat treatment, the magnetic ring was wound with a coil. The magnetic permeability and DC bias performance were calculated by testing the magnetic ring inductance value. At the same time, the magnetic ring loss performance was tested.

[0065] The performance test results of Example 2 and Comparative Examples 5-7 are shown in Table 2:

[0066] Table 2 Performance test results of Example 2 and Comparative Examples 5-7

[0067]

[0068] The test results in Table 2 show that, compared with Example 2 and Comparative Example 5, different particle size distribution formulations have a significant impact on the inductance and stacking performance of the metal magnetic powder particles. The particle size distribution ratio in Example 2 is the optimal one in this invention. Comparing Example 2 and Comparative Example 6, it can be seen that the proportion of coating reagent and the reaction temperature of the powder have a significant impact on the permeability and stacking performance of the iron-nickel magnetic powder. Only a suitable proportion of coating reagent and reaction temperature can maintain good DC bias characteristics while keeping losses low. Comparing Example 2 and Comparative Example 7, it can be seen that the use of binder only affects the permeability performance of the iron-nickel metal powder and does not lead to an increase in magnetic powder loss or a decrease in DC bias characteristics, indicating that quartz powder, phosphoric acid, and silica sol are the main insulating reagents in the process of this invention.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a gradient functionalized high performance iron-nickel magnetic powder core, characterized in that, The method comprises the following steps: (1) particle size grading: the iron-nickel powder is sieved by a tapping sieve, and then particle size grading is performed, so that the particle size grading combination is: -200 mesh to +325 mesh: -325 mesh to +400 mesh: -400 mesh = (30%-50%):(20%-30%):(20%-50%), based on 100% of the particle size graded iron-nickel powder; the iron-nickel powder is FeNi50 alloy powder with a mesh size of 200 mesh and 400 mesh, the tapping frequency is 140-160 times / min, the tapping time is 30-60 min, and the screen mesh is 100 mesh-400 mesh; (2) first passivation coating: quartz powder is added to the particle size graded iron-nickel powder, and ball milling is performed in a ball mill for 10-30 min to coat a first passivation layer on the surface of the iron-nickel powder, wherein the mass ratio of the iron-nickel powder to the quartz powder is 500:(2-5); (3) second passivation coating: a mixed solution of phosphoric acid and silica sol in ethanol is added to the iron-nickel powder coated with the first passivation layer, and reaction is performed in a rotary instrument at a speed of 60-80 r / min at 120-160°C for 40-80 min, and then cooling and sieving are performed with a screen mesh of 60-100 mesh to coat a second passivation layer on the surface of the iron-nickel powder, wherein the mass ratio of the iron-nickel powder to the phosphoric acid, the silica sol and the ethanol is 500:(0.2-2):(0.5-8):(5-25); (4) bonding and lubrication: a bonding agent is added to the iron-nickel powder coated with the second passivation layer, stirring is performed for 10-20 min, drying is performed at 60-120°C for 30-60 min, and then sieving is performed with a 100 mesh screen, and then a lubricant is added to obtain an iron-nickel composite powder; the bonding agent is an organic silicon resin ethanol solution, and the addition amount of the organic silicon resin is 0.3-0.9 wt% and the addition amount of anhydrous ethanol is 3-6%, based on the iron-nickel composite powder; (5) pressing and annealing: the iron-nickel composite powder is pressed and formed, and then annealing is performed to obtain a gradient functionalized high-performance iron-nickel magnetic powder core.

2. The method for preparing gradient functionalized high-performance iron-nickel magnetic powder cores as described in claim 1, characterized in that, In step (1), the particle size grading combination is: -200 mesh to +325 mesh: -325 mesh to +400 mesh: -400 mesh = 50%:20%:30%, based on 100% of the particle size graded iron-nickel powder.

3. The method for preparing gradient functionalized high-performance iron-nickel magnetic powder cores as described in claim 1, characterized in that, In step (4), after the lubricant is added, stirring and sieving are performed, and the lubricant is one or more of zinc stearate, aluminum stearate, magnesium stearate and paraffin, and the addition amount is 0.4-0.8 wt% of the iron-nickel composite powder.

4. The method for preparing gradient functionalized high-performance iron-nickel magnetic powder cores as described in claim 1, characterized in that, In step (5), the iron-nickel composite powder is pressed into a magnetic ring with an outer diameter of 26.80-27.20 mm, an inner diameter of 14.50-14.80 mm, and a height of 10.95-11.20 mm, wherein the pressing pressure is 18-20 t / cm 2 , the annealing temperature is 680-770℃, and the annealing time is 5-8 h.

5. A gradient functionalized high performance iron nickel magnetic powder core, characterized in that, The gradient functionalized high-performance iron-nickel magnetic powder core is prepared by the method of any one of claims 1-4.

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