Method for preparing high-frequency manganese zinc ferrite material

Abstract

The present application relates to the technical field of ferrite materials, and specifically relates to a method for preparing a high-frequency manganese zinc ferrite material, which method comprises the following steps: compounding the iron oxide, manganese oxide and zinc oxide required for a manganese zinc ferrite material, and mixing same until uniform; and transferring the resulting mixture into a pelletizer, spraying a mixed aqueous solution of titanyl sulfate and tin sulfate onto the surface of the resulting powder to realize doping, and rolling same into balls by means of the pelletizer after the mixed aqueous solution is sprayed onto the surface of the powder, followed by pre-sintering, dry crushing, wet ball milling, second-step doping, and granulation, so as to obtain the high-frequency manganese zinc ferrite material. In the present application, by means of an improved two-step doping process, doping elements are uniformly and accurately doped into the crystal grains or at the crystal boundary, thereby effectively improving the frequency characteristic of the material. The obtained product still has relatively good electromagnetic properties under conditions where the working frequency is 300 kHz or more.

Description

A method for preparing high-frequency manganese-zinc ferrite material

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on August 2, 2023, with application number CN202310963462.2 and invention name “A Process for Preparing High-Frequency Ferrite Materials”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of ferrite materials, and in particular to a method for preparing a high-frequency manganese-zinc ferrite material. Background Art

[0003] With the rise of third-generation semiconductors, the operating frequency required for electromagnetic conversion equipment such as switching power supplies has gradually increased. Third-generation semiconductor integrated circuits generally require the operating frequency of soft magnetic ferrite materials to be above 300KHz, while the current generally applicable power of manganese-zinc ferrite materials is within 200KHz.

[0004] The losses of ferrite in the process of transmitting electromagnetic energy mainly include hysteresis loss, eddy current loss and residual loss. As the frequency increases, the eddy current loss will increase significantly, which also limits the application of ferrite, especially manganese zinc ferrite materials, at high frequencies. To reduce eddy current loss, the main method is to increase the resistivity of the material. At present, the more common way to improve the frequency characteristics of materials in the industry is to add submicron silicon dioxide, micron calcium carbonate and other additives during the wet ball milling process. Since the melting point of calcium oxide is around 2700℃ and Ca 2+ The radius of Si is larger than the tetrahedral interstitial A position and the octahedral interstitial B position in the spinel phase with a face-centered cubic structure, so it can only be enriched at the grain boundary to form CaO with high resistivity or combined with silicon dioxide to form CaSiO3, while part of Si combines with calcium to form a grain boundary resistance layer, and the other part will melt into the grain to form a heterogeneous phase, but this part is likely to cause abnormal growth of the grain. In addition, it is also possible to dope titanium dioxide, tin dioxide, etc. into the interior of the grain to limit the Fe inside the grain by occupying the position. 2+ with Fe 3+ Regardless of the doping element, these doping methods generally involve pre-sintering the material and then doping it with micron-sized oxide powder during the ball milling process. Because the aggregation and diffusion of the doping ions occur through solid-phase reactions during the sintering process, the doping is uneven, and the frequency characteristics after doping are not very good.

[0005] At present, the main application scenarios of similar products are below 200KHz. For example, PC40 materials, which are widely used in the market, have a power loss of 400kw / m at 100℃, 200KHz, and 200mT. 3When the operating frequency is increased to 300KHz, the power loss at 100℃ is as high as 500kw / m 3 For example, when a conventional high-permeability 10K material is pressed into a T25*15*10 standard ring, the initial permeability at 300KHz decreases by more than 40% compared to the initial permeability at 1KHz.

[0006] Summary of the Invention

[0007] To address the aforementioned technical issues, this application proposes a method for preparing high-frequency manganese-zinc ferrite materials. Through an improved two-step doping process, the doping element is uniformly and precisely doped into the interior of the grains or at the grain boundaries, effectively improving the material's frequency characteristics. The resulting product exhibits excellent electromagnetic properties even at operating frequencies above 300 kHz.

[0008] The specific technical solutions are as follows:

[0009] A method for preparing a high-frequency manganese-zinc ferrite material comprises the following steps:

[0010] Step (1) mixing: uniformly mixing the iron oxide, manganese oxide, and zinc oxide required for the manganese-zinc ferrite material to obtain a mixture;

[0011] Step (2) pelletizing and performing the first step of doping: transferring the mixture in step (1) into a pelletizing machine, spraying a mixed aqueous solution of titanyl sulfate and tin sulfate onto the surface of the mixture for doping, spraying the mixed aqueous solution onto the surface of the mixture, and rolling it into balls in a pelletizing machine to obtain a ball material;

[0012] Step (3) pre-firing: placing the ball material in step (2) in a kiln for pre-firing to obtain pre-firing microspheres;

[0013] Step (4) dry crushing: dry crushing the pre-calcined microspheres to obtain powder;

[0014] Step (5) wet ball milling and second step doping: placing the powder in step (4) in a ball mill, adding an oxide additive, and then adding water for ball milling to obtain a slurry;

[0015] Step (6) granulation: drying or spray granulating the slurry in step (5) to prepare granules, pressing and forming, and then keeping warm in a nitrogen environment or an air environment to obtain a high-frequency manganese-zinc ferrite material.

[0016] Furthermore, in the step (1), the weight ratios of iron oxide, manganese oxide and zinc oxide are 65-75%, 15-25% and 5-16% respectively.

[0017] Furthermore, in the step (2), in the mixed aqueous solution of titanyl sulfate and tin sulfate, the concentration of titanyl sulfate is 0.1-3%, and the concentration of tin sulfate is 0.1-3%.

[0018] Furthermore, in the step (3), the pre-firing temperature is 850-950° C., and the pre-firing time is 1 hour.

[0019] Furthermore, in the step (5), the oxide additive is at least one of bismuth oxide, vanadium oxide, cobalt oxide, niobium pentoxide and molybdenum trioxide, and the concentration of the oxide additive in the powder is 100 to 3000 ppm.

[0020] Furthermore, the ball milling process of step (5) is specifically as follows: at the beginning of the ball milling, an emulsified silicone oil containing a non-ionic surfactant is added using a metering pump, and finally a soluble calcium compound solution is added dropwise, wherein the amount of the soluble calcium compound solution added is 0.02-0.1% of the total weight of the solids, and then an alkaline solution of 0.2-1% of the total weight of the solid powder is slowly added to hydrolyze the calcium ions.

[0021] Furthermore, the concentration of the soluble calcium compound solution is controlled at 0.1-5%, and the weight of the added emulsified silicone oil is 0.05-0.5% of the weight of the solid powder in the ball mill.

[0022] Furthermore, the calcium compound in the soluble calcium compound solution is one or more of calcium hydroxide, calcium nitrate, calcium bicarbonate and calcium chloride; the alkali solution is one or more of ammonia water, sodium hydroxide solution, potassium hydroxide solution and calcium hydroxide solution with a concentration greater than or equal to 1%.

[0023] Furthermore, in the step (5), the ball milling time is 0.5-3h.

[0024] Furthermore, in the step (6), the nitrogen environment is a nitrogen environment with an oxygen content of 4-6%; the insulation temperature is 1280-1430° C.; and the insulation time is 4-6 hours.

[0025] The beneficial effects of the present application are as follows: 1. The present application provides a novel doping process through a two-step doping method: the first step of doping is in the ball-making process, by adding part of titanyl sulfate and tin sulfate solution during ball-making or tableting, and doping it into the material. After the pre-firing process, titanyl sulfate will quickly hydrolyze at about 100°C to form nano-titanium dioxide, and gradually embed into the grains as the pre-firing temperature increases, and tin sulfate will form nano-scale tin dioxide at about 400°C. This type of additive can react more evenly into the soft ferrite grains, thereby reducing the ion diffusion path in the secondary sintering process, making the impurity ion occupying structure inside the grains more stable and uniform, greatly reducing the eddy current loss inside the material, and improving the frequency characteristics.

[0026] 2. The reason why sulfate solution is used in the first step of doping process is that it has better solubility and lower decomposition temperature, and is safer than chloride solution.

[0027] 3. The second step of doping is to slowly add emulsified silicone oil containing non-ionic surfactants and soluble calcium compound solutions such as calcium bicarbonate, calcium nitrate or calcium chloride during the wet ball milling process. The doping process of adding the solution can make the silicon-calcium composition on the surface of the primary particles of the material more uniform, effectively improve the grain boundary resistance of the material and then improve the frequency characteristics of the material. The doping of other elements adopts the conventional oxide doping method. The performance differences of the products obtained by different doping processes are very obvious. In this application, the silicone oil is added first and then the calcium compound is added, because the calcium compound will cause the viscosity to be too high, affecting the sanding effect.

[0028] 4. The emulsified silicone oil containing a nonionic surfactant used in the second doping step not only evenly dopes silicon onto the material surface, but also improves the material's plasticizing properties and enhances the product's molding and processing characteristics. After secondary sintering, due to the low concentration of the organosilicon solution in the slurry, nano-scale silica is formed during the secondary sintering process. This evenly distributed silica will not penetrate deep into the grains, causing abnormal grain growth. Furthermore, the microscopic pores formed by the decomposition of organic matter will also limit grain growth, ensuring stable grain nucleation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG1 is a flowchart of a method for preparing a high-frequency manganese-zinc ferrite material provided by the present application;

[0030] FIG2 is a comparison of an electron microscope image of the high-frequency, low-power consumption manganese-zinc ferrite material prepared in Example 1 and an electron microscope image of a ferrite material prepared by a conventional process;

[0031] FIG3 is a graph showing the change in initial magnetic permeability versus frequency of the high-frequency, high-permeability manganese-zinc ferrite material prepared in Example 2 and the high-frequency, high-permeability manganese-zinc ferrite material prepared using a conventional process;

[0032] FIG4 is a graph showing the impedance variation with frequency of the high-frequency and high-permeability manganese-zinc ferrite material prepared in Example 3 and the high-frequency and high-permeability manganese-zinc ferrite material prepared by the traditional process. DETAILED DESCRIPTION

[0033] In order to facilitate the understanding of the technical solution of the application, the technical solution is further explained through embodiments.

[0034] The silicone emulsions used in the following examples are all Dow Corning silicone emulsions.

[0035] Example 1

[0036] 1. Ingredients: Prepare 400 kg of materials according to the weight ratio of iron oxide, manganese oxide and zinc oxide of 70%, 23% and 7% respectively, mix well to obtain a mixture;

[0037] 2. Balling and performing the first step of doping: The mixture from step 1 is transferred to a balling machine and stirred and mixed. A 1% aqueous solution of titanyl sulfate and tin sulfate is sprayed onto the surface of the mixture for doping. The tin sulfate and titanyl sulfate contents are 300ppm and 400ppm, respectively. After the aqueous solution is sprayed onto the surface of the mixture, it is rolled and quickly formed into balls to obtain balls.

[0038] 3. Pre-calcination: The ball material in step 2 is placed in a kiln and pre-calcined at 880°C for 1 hour to obtain pre-calcined microspheres;

[0039] 4. Dry crushing: The pre-calcined microspheres are dry crushed using a Raymond mill to an average particle size of less than 2.0 μm to obtain a powder;

[0040] 5. Wet ball milling and second step doping: The powder in step 4 is placed in a ball mill, 150 ppm of bismuth oxide and vanadium oxide are added respectively, and then 180 kg of water is added for ball milling. At the beginning of the ball milling process, 400 g of emulsified silicone oil containing a non-ionic surfactant is slowly added dropwise using a metering pump, and then 10 kg of 0.5% calcium hydroxide solution is slowly added, followed by slowly adding 2 kg of 10% ammonia water to hydrolyze the calcium ions. Finally, the mixture is fully ground for 1.5 hours to obtain a slurry.

[0041] 6. Granulation: Add 40 kg of 10% polyvinyl alcohol to the slurry and then dry or spray granulate it into granules, press it into T25*15*10 magnetic rings, and then heat it at 1300°C for 4.5 hours in a nitrogen environment with an oxygen content of 4.5% to obtain a high-frequency, low-power manganese-zinc ferrite material.

[0042] 7. The high-frequency, low-power magnetic ring prepared by the above method has a power consumption of 380kw / m after being wound with 10 turns of copper wire and tested under the conditions of 100℃, 100mT, and 300KHz. 3 , while the power consumption of products obtained by traditional oxide doping is as high as 500kw / m 3 The scanning electron microscope is shown in Figure 2. From the electron microscope image, it can be seen that the particles of the manganese zinc ferrite material prepared in this embodiment are finer and more uniform, while the particles of the manganese zinc ferrite material prepared in the comparative example are large and uneven.

[0043] Example 2

[0044] 1. Ingredients: Prepare 100 kg of materials according to the weight ratio of iron oxide, manganese oxide and zinc oxide of 69%, 16.5% and 15% respectively, mix well to obtain a mixture;

[0045] 2. Balling and performing the first step of doping: The mixture in step 1 is transferred to a ball-making machine and stirred and mixed. A mixed aqueous solution of 1% titanyl sulfate and 0.1% tin sulfate is sprayed onto the surface of the mixture for doping. The tin sulfate and titanyl sulfate contents are 20 ppm and 50 ppm, respectively. After the mixed aqueous solution is sprayed onto the surface of the mixture, it is rolled and quickly formed into balls to obtain balls.

[0046] 3. Pre-calcination: Place the ball material in step 2 in a kiln at 900°C for 1 hour to obtain pre-calcined microspheres;

[0047] 4. Dry crushing: The pre-calcined microspheres are dry crushed using a Raymond mill to an average particle size of less than 2.0 μm to obtain a powder;

[0048] 5. Wet ball milling and second step doping: Place the powder in step 4 in a ball mill, add 30 g of bismuth oxide, and then add 100 kg of water for ball milling. At the beginning of the ball milling process, 80 g of emulsified silicone oil containing a non-ionic surfactant is slowly added dropwise using a metering pump, and then 30 kg of 1% calcium hydroxide solution is slowly added, followed by slowly adding 0.5 kg of 5% ammonia water to hydrolyze the calcium ions. Finally, fully grind for 3 hours to obtain a slurry.

[0049] 6. Granulation: The slurry is added with 10 kg of 7% polyvinyl alcohol and then dried or spray-granulated to form granules. The granules are then pressed into T25*15*10 magnetic rings and kept at 1390°C in air for 6 hours. During the cooling process, nitrogen is injected to provide a protective atmosphere, ultimately producing a high-frequency, high-permeability manganese-zinc ferrite material. The specific steps are shown in Figure 1.

[0050] 7. The high-frequency and high-permeability magnetic ring prepared by the above method has significantly improved the change of magnetic permeability at different frequencies compared with the traditional process, as shown in Figure 3.

[0051] Example 3

[0052] 1. Ingredients: Prepare 100 kg of material in a weight ratio of 69.2% for iron oxide, 17.9% for manganese oxide, and 13% for zinc oxide, and mix well to obtain a mixture;

[0053] 2. Balling and performing the first step of doping: The mixture from step 1 is transferred to a balling machine and stirred and mixed. A mixed aqueous solution of 0.2% titanyl sulfate and 0.1% tin sulfate is sprayed onto the surface of the mixture for doping. The tin sulfate and titanyl sulfate contents are 40 ppm and 20 ppm, respectively. The mixed aqueous solution is sprayed onto the surface of the mixture and the mixture is rolled to form balls to obtain balls.

[0054] 3. Pre-calcination: The ball material in step 2 is placed in a kiln and pre-calcined at 860°C for 1 hour to obtain pre-calcined microspheres;

[0055] 4. Dry crushing: The pre-calcined microspheres are dry crushed using a Raymond mill to an average particle size of less than 2.0 μm to obtain a powder;

[0056] 5. Wet ball milling and second step doping: Place the powder in step 4 in a ball mill, add 15g of bismuth oxide and 15g of neodymium oxide, then slowly dropwise add 80g of emulsified silicone oil containing a non-ionic surfactant, add 100kg of water and ball mill. At the beginning of the ball milling process, use a metering pump to slowly add 40kg of 1% calcium bicarbonate solution, then slowly add 2kg of 5% ammonia water to hydrolyze the calcium ions, and finally fully grind for 1.5h to obtain a slurry.

[0057] 6. Granulation: Add 9 kg of 9% polyvinyl alcohol to the slurry and then dry or spray granulate it into granules, press it into T31*19*15 magnetic rings, and then keep it at 1360°C in an air environment for 6 hours. During the cooling process, nitrogen is injected for protection to finally obtain a high-frequency and high-impedance manganese-zinc ferrite material.

[0058] 7. The high-frequency, high-impedance magnetic ring prepared by the above method was measured at a high frequency of 500KHz or above after winding 10 turns of copper wire. The impedance of the product prepared by this application was significantly improved compared with the traditional process, as shown in Figure 4.

[0059] Example 4

[0060] 1. Ingredients: Prepare 100 kg of materials according to the weight ratio of iron oxide, manganese oxide and zinc oxide of 71%, 23% and 6% respectively, mix well to obtain a mixture;

[0061] 2. Balling and performing the first step of doping: The mixture in step 1 is transferred to a ball-making machine and stirred and mixed. A mixed aqueous solution of 2% titanyl sulfate and 0.1% tin sulfate is sprayed onto the surface of the mixture for doping. The tin sulfate and titanyl sulfate contents are 200 ppm and 1000 ppm, respectively. After the mixed aqueous solution is sprayed onto the surface of the mixture, it is rolled and quickly formed into balls to obtain balls.

[0062] 3. Pre-calcination: Place the ball material in step 2 in a kiln at 900°C for 1 hour to obtain pre-calcined microspheres;

[0063] 4. Dry crushing: The pre-calcined microspheres are dry crushed using a Raymond mill to an average particle size of less than 2.0 μm to obtain a powder;

[0064] 5. Wet ball milling and second doping: The powder from step 4 was placed in a ball mill, and 2500 ppm of cobalt oxide and 200 ppm of niobium pentoxide were added, respectively. 180 kg of water was then added for ball milling. At the beginning of the ball milling process, 300 g of emulsified silicone oil containing a nonionic surfactant was slowly added dropwise using a metering pump. Then, 10 kg of 0.5% calcium hydroxide solution was slowly added, followed by the slow addition of 2 kg of 10% ammonia water to hydrolyze the calcium ions. Finally, the mixture was fully milled for 1.5 h to obtain a slurry.

[0065] 6. Granulation: Add 40 kg of 10% polyvinyl alcohol to the slurry and then dry or spray granulate it into granules, press it into T25*15*10 magnetic rings, and then heat it at 1300°C for 4.5 hours in a nitrogen environment with an oxygen content of 4.5% to obtain a high-frequency, low-power manganese-zinc ferrite material.

[0066] 7. The high-frequency, wide-temperature, low-power magnetic ring prepared by the above method has a power consumption of 380kw / m after winding 10 turns of copper wire under the test conditions of 25℃, 100mT, and 300KHz. 3 , while the power consumption of products obtained by traditional oxide doping is as high as 400kw / m 3 Above, under the conditions of 100℃, 100mT, 300KHz, the power consumption is 350kw / m 3 , while the power consumption of the product obtained by traditional oxide doping is 380kw / m 3 above.

[0067] Comparative Example

[0068] Ferrite materials are prepared using traditional technology. The specific preparation process is as follows:

[0069] 1. Ingredients: Prepare 400 kg of materials according to the weight ratio of iron oxide, manganese oxide and zinc oxide of 70%, 23% and 7% respectively, mix well to obtain a mixture;

[0070] 2. Balling: Transfer the mixture in step 1 into a ball making machine, stir and mix, and spray pure water on the surface of the mixture. After rolling, the mixture will quickly form balls to obtain ball materials;

[0071] 3. Pre-calcination: The ball material in step 2 is placed in a kiln and pre-calcined at 880°C for 1 hour to obtain pre-calcined microspheres;

[0072] 4. Dry crushing: The pre-calcined microspheres are dry crushed using a Raymond mill to an average particle size of less than 2.0 μm to obtain a powder;

[0073] 5. Wet ball milling and second doping: Place the powder in step 4 in a ball mill, add 150 ppm of bismuth oxide, vanadium oxide, and calcium carbonate, 200 ppm of tin oxide, titanium oxide, and silicon oxide, respectively, then add 180 kg of water for ball milling, and finally grind thoroughly for 1.5 hours to obtain a slurry.

[0074] 6. Granulation: The slurry is added with 40 kg of 10% polyvinyl alcohol and then dried or spray granulated to prepare granules, which are pressed into T25*15*10 magnetic rings and then kept at 1300° C. for 4.5 hours in a nitrogen environment with an oxygen content of 4.5% to obtain a low-power manganese-zinc ferrite material using a traditional process.

[0075] 7. The high-frequency low-power magnetic ring prepared by the above process has a power consumption of 520kw / m after being wound with 10 turns of copper wire and tested under the conditions of 100℃, 100mT and 300KHz. 3 above.

[0076] Although the above embodiment provides a detailed description of the present application, it is only a part of the embodiments of the present application rather than all the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present application.

Claims

1. A method for preparing a high-frequency manganese-zinc ferrite material, characterized in that: The steps include: Step (1) mixing: uniformly mixing the iron oxide, manganese oxide and zinc oxide required for the manganese-zinc ferrite material to obtain a mixture; Step (2) balling and first step doping: the mixture in step (1) is transferred to a balling machine, and a mixed aqueous solution of titanyl sulfate and tin sulfate is sprayed on the surface of the mixture for doping, and the mixed aqueous solution is sprayed on the surface of the mixture and rolled into balls by the balling machine to obtain ball material; Step (3) pre-firing: placing the ball material in step (2) in a kiln for pre-firing to obtain pre-firing microspheres; Step (4) dry crushing: dry crushing the pre-calcined microspheres to obtain powder; Step (5) wet ball milling and second step doping: placing the powder in step (4) in a ball mill, adding an oxide additive, and then adding water for ball milling to obtain a slurry; Step (6) granulation: the slurry in step (5) is dried or spray-granulated to prepare granules, which are pressed and molded, and then kept warm in a nitrogen environment or an air environment to obtain a high-frequency manganese-zinc ferrite material.

2. The preparation method according to claim 1, characterized in that: In the step (1), the weight ratios of iron oxide, manganese oxide and zinc oxide are 65-75%, 15-25% and 5-16% respectively.

3. The preparation method according to claim 1, characterized in that: In the step (2), in the mixed aqueous solution of titanyl sulfate and tin sulfate, the concentration of titanyl sulfate is 0.1-3%, and the concentration of tin sulfate is 0.1-3%.

4. The preparation method according to claim 1, characterized in that: In the step (3), the pre-firing temperature is 850-950° C. and the pre-firing time is 1 hour.

5. The preparation method according to claim 1, characterized in that: In the step (5), the oxide additive is at least one of bismuth oxide, vanadium oxide, cobalt oxide, niobium pentoxide and molybdenum trioxide, and the concentration of the oxide additive in the powder is 100 to 3000 ppm.

6. The preparation method according to claim 1, characterized in that: The ball milling of step (5) is specifically as follows: at the beginning of the ball milling, emulsified silicone oil is added by a metering pump, and then a soluble calcium compound solution is added dropwise, wherein the amount of the soluble calcium compound solution added is 0.02-0.1% of the total weight of the solid, and then 0.2-1% of the total weight of the solid powder is slowly added with alkaline solution to hydrolyze the calcium ions.

7. The preparation method according to claim 6, characterized in that: The concentration of the soluble calcium compound solution is controlled at 0.1-5%, and the added weight of the emulsified silicone oil is 0.05-0.5% of the weight of the solid powder in the ball mill.

8. The preparation method according to claim 6, characterized in that: The calcium compound in the soluble calcium compound solution is one or more of calcium hydroxide, calcium nitrate, calcium bicarbonate and calcium chloride; the alkali solution is one or more of ammonia water, sodium hydroxide solution, potassium hydroxide solution and calcium hydroxide solution with a concentration greater than or equal to 1%.

9. The preparation method according to any one of claims 1 or 5 to 8, characterized in that: In the step (5), the ball milling time is 0.5-3h.

10. The preparation method according to claim 1, characterized in that: In the step (6), the nitrogen environment is a nitrogen environment with an oxygen content of 4-6%; the insulation temperature is 1280-1430° C.; and the insulation time is 4-6 hours.

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