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CN-122025328-A - Composite passivation and insulation coated low-loss FeNi/FeSiAl soft magnetic material and preparation method and application thereof

CN122025328ACN 122025328 ACN122025328 ACN 122025328ACN-122025328-A

Abstract

The invention discloses a composite passivation and insulation coated low-loss FeNi/FeSiAl soft magnetic material, a preparation method and application thereof, comprises a FeNi/FeSiAl inner core, a composite phosphate-chromate conversion coating attached to the surface of the inner core and a composite layer of kaolin and white carbon black. And passivating the mixed alloy powder by using a phosphoric acid-chromic acid composite passivating solution to form a composite phosphate-chromate conversion film. Then mixing the mixed metal powder with composite insulating slurry containing kaolin and white carbon black, further carrying out cladding treatment, and finally drying and heat treating to form a composite insulating structure taking a phosphate-chromate film as a bottom layer and taking the kaolin/white carbon black as an outer layer on the surface of the mixed metal powder. The effective magnetic permeability of the soft magnetic material under MHz is 80-140, the magnetic core loss is lower than 900mW/cm 3 , and the soft magnetic material is particularly suitable for the fields of high-frequency switch power supplies, MHz-level power inductors, radio frequency devices and the like which are extremely sensitive to loss.

Inventors

  • ZHANG XUEFENG
  • ZHANG ERPAN
  • BAI ZIYU

Assignees

  • 杭州电子科技大学

Dates

Publication Date
20260512
Application Date
20260306

Claims (10)

  1. 1. A composite passivation and insulation coated low-loss FeNi/FeSiAl soft magnetic material is characterized by comprising an inner core, a composite phosphate-chromate conversion film and a composite layer, wherein the inner core is formed by mixing FeNi alloy powder and FeSiAl alloy powder, the composite phosphate-chromate conversion film is attached to the surface of the inner core, the composite layer is formed by kaolin and white carbon black, the composite phosphate-chromate conversion film is attached to the surface of the conversion film, the effective magnetic conductivity of the soft magnetic material at 1MHz frequency is 80-140, and the magnetic core loss under 1MHz and 50mT test conditions is lower than 900mW/cm 3 .
  2. 2. A preparation method of a composite passivation and insulation coated low-loss FeNi/FeSiAl soft magnetic material is characterized by comprising the following steps: preparing a phosphoric acid-chromic acid composite passivation solution with the concentration of phosphoric acid of 0.5-5 wt% and the concentration of chromic acid of 0.5-5 wt%; dispersing kaolin and nano white carbon black in a solvent, and adding a silane coupling agent to prepare composite insulating slurry; the mixed FeNi alloy powder and FeSiAl alloy powder are washed and activated, then are immersed into phosphoric acid-chromic acid composite passivation solution, so that oxidation-passivation reaction is carried out on the surface of the powder to form a composite phosphate-chromate conversion film, then the composite phosphate-chromate conversion film is mixed with composite insulating slurry, coating treatment is further carried out, finally drying and heat treatment are carried out, and a composite insulating structure taking the phosphate-chromate film as a bottom layer and kaolin/white carbon black as an outer layer is formed on the surface of the mixed powder.
  3. 3. The method for preparing the composite passivation and insulation coated low-loss FeNi/FeSiAl soft magnetic material is characterized in that FeNi alloy powder is Fe 50 Ni 50 or Fe 45 Ni 55 , the particle size D50 is 5-10 mu m, feSiAl alloy powder is Fe 85 Si 9 Al 5 , the particle size D50 is 5-10 mu m, and the mass ratio of FeNi alloy powder to FeSiAl alloy powder is (30:70) - (90:10).
  4. 4. The method for preparing the composite passivation and insulating coated low-loss FeNi/FeSiAl soft magnetic material is characterized by immersing the mixed powder into phosphoric acid-chromic acid composite passivation solution, stirring and reacting for 10-60 minutes at 50-80 ℃ to enable the surface of the powder to undergo oxidation-passivation reaction, so as to form a composite phosphate-chromate conversion film with the thickness of 30-100 nm.
  5. 5. The method for preparing the composite passivation and insulation coated low-loss FeNi/FeSiAl soft magnetic material according to claim 4, wherein the phosphoric acid-chromic acid composite passivation solution further comprises deionized water and an accelerator, and the accelerator is sodium nitrate or sodium fluoride.
  6. 6. The preparation method of the composite passivation and insulation coated low-loss FeNi/FeSiAl soft magnetic material is characterized in that the mass ratio of kaolin to nano white carbon black in the composite insulation slurry is (1-5): 1.
  7. 7. The method for preparing the composite passivation and insulation coated low-loss FeNi/FeSiAl soft magnetic material according to claim 2, wherein the total mass of the kaolin and the nano white carbon black accounts for 0.5-3.0% of the mass of the mixed powder, and the total mass of the silane coupling agent accounts for 0.5-3% of the mass of the mixed powder.
  8. 8. The method for preparing the composite passivation and insulation coated low-loss FeNi/FeSiAl soft magnetic material according to claim 2, wherein the composite insulation paste coated material is dried at a low temperature of 80-150 ℃, and then is subjected to heat treatment for 0.5-2 hours in an inert atmosphere at 300-450 ℃ to crosslink the silane coupling agent, solidify the composite insulation paste and form stable combination with the composite phosphate-chromate conversion film.
  9. 9. The application of the composite passivation and insulation coated low-loss FeNi/FeSiAl soft magnetic material is characterized in that the FeNi/FeSiAl soft magnetic material prepared by the method of claim 1 or the FeNi/FeSiAl soft magnetic material prepared by the method of any one of claims 2-8 is uniformly mixed with a lubricant, then pressed into a magnetic core green compact, and then annealed in a reducing atmosphere to prepare the soft magnetic core.
  10. 10. A power electronic device having an operating frequency of 1MHz or higher, comprising the soft magnetic core as set forth in claim 9.

Description

Composite passivation and insulation coated low-loss FeNi/FeSiAl soft magnetic material and preparation method and application thereof Technical Field The invention belongs to the technical field of electronic materials, relates to a high-frequency soft magnetic composite material, and particularly relates to a composite passivation and insulation coated low-loss FeNi/FeSiAl soft magnetic material, and a preparation method and application thereof. Background With the development of power electronic equipment to high frequency, high efficiency and miniaturization, extremely stringent requirements are put on the loss performance of the soft magnetic composite material in the MHz frequency band. At present, the MHz frequency band soft magnetic composite material is mostly formed by pressing single alloy powder after insulating coating, but a single soft magnetic alloy system is difficult to achieve high saturation magnetic induction intensity, high magnetic permeability and low high frequency loss. In addition, the traditional insulation methods such as phosphate passivation, chromate passivation and the like can improve the surface resistance of the material, but the formed passivation layer is often insufficient in compactness and general in thermal stability, and particularly has insufficient insulation performance under MHz high frequency. Part of the methods try to add inorganic insulating filler in a mechanical mixing mode, so that the filler is unevenly distributed and is easy to form weak points of magnetic performance, the interface combination of the inorganic insulating filler and metal powder is poor, defects are easy to generate under high-pressure molding and thermal stress, and loss is increased and reliability is reduced. Therefore, developing a soft magnetic composite material which can integrate the advantages of different alloy systems and has high magnetic permeability, high resistivity and ultra-low total loss in the MHz frequency band has become a technical problem to be solved in the art. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a composite passivation and insulation coated low-loss FeNi/FeSiAl soft magnetic material, a preparation method and application thereof, and a multilayer and synergistic insulation system is constructed on the surface of powder and among particles by optimally compounding FeNi and FeSiAl powder and combining a phosphoric acid-chromic acid composite passivation and kaolin/white carbon black composite insulation technology, so that the optimal balance of electric, magnetic, thermal and force performances is realized. The soft magnetic composite material with ultra-low magnetic core loss, high effective magnetic permeability and excellent frequency stability in the MHz frequency band and the preparation method thereof capable of large-scale production are provided. A composite passivation and insulation coated low-loss FeNi/FeSiAl soft magnetic material comprises FeNi alloy powder, an inner core of the FeSiAl alloy powder, a composite phosphate-chromate conversion film attached to the surface of the inner core and a composite layer of kaolin and white carbon black attached to the surface of the conversion film. The effective magnetic permeability of the soft magnetic material at the frequency of 1MHz is 80-140, and the magnetic core loss under the test conditions of 1MHz and 50mT is lower than 900mW/cm 3. A preparation method of a composite passivation and insulation coated low-loss FeNi/FeSiAl soft magnetic material comprises the following specific steps: Step 1, mechanically mixing FeNi alloy powder and FeSiAl alloy powder, and then cleaning and drying the mixed powder to activate the surface. Preferably, the mass ratio of the FeNi alloy powder to the FeSiAl alloy powder is (30:70) - (90:10). Preferably, the FeNi alloy powder is Fe 50Ni50 or Fe 45Ni55, the granularity D50 is 5-10 mu m, the FeSiAl alloy powder is Fe 85Si9Al5, and the granularity D50 is 5-10 mu m. And 2, immersing the pretreated mixed powder into a phosphoric acid-chromic acid composite passivation solution, stirring and reacting for 10-60 minutes at 50-80 ℃ to enable the surface of the powder to undergo oxidation-passivation reaction, and forming a layer of compact and strong-adhesion composite phosphate-chromate conversion film with the thickness of 30-100 nm on the surface. The pH value of the phosphoric acid-chromic acid composite passivation solution is 1.5-3.5, wherein the concentration of phosphoric acid is 0.5-5 wt% and the concentration of chromic acid is 0.5-5 wt%. Preferably, the phosphoric acid-chromic acid composite passivation solution further comprises deionized water and an accelerator, wherein the accelerator is sodium nitrate or sodium fluoride. And step 3, dispersing kaolin and nano white carbon black in a solvent, adding a silane coupling agent, preparing composite insulating slurry, and coating the mixed powder subjected to insulatio