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CN-122007408-A - Method for preparing iron-based soft magnetic powder with silicon dioxide coating layer

CN122007408ACN 122007408 ACN122007408 ACN 122007408ACN-122007408-A

Abstract

The invention discloses a preparation method of an iron-based soft magnetic powder with a silicon dioxide coating layer, which comprises the steps of carrying out ultrasonic-assisted silane hydrolysis and modification, dispersing the iron-based soft magnetic powder in a solvent, adding a silane coupling agent, wherein the mass-volume ratio of the iron-based soft magnetic powder to the silane coupling agent is 1kg (0.002-0.5) L, continuously applying an ultrasonic field and mechanical stirring to enable the silane coupling agent to be hydrolyzed and primarily adsorbed on the surface of the iron-based soft magnetic powder, carrying out ultrasonic promotion on silicon dioxide polycondensation and densification coating, namely placing suspension of the iron-based soft magnetic powder, the solvent, the silane coupling agent and hydrolysis products thereof into a container, adding a pH regulator, regulating the pH value to 8-10, adding an organosilicon source, and continuously applying the ultrasonic field and mechanical stirring to the suspension in the container to complete the polycondensation reaction of silicon dioxide and form a dense coating layer on the surface of the iron-based soft magnetic powder. The pretreatment process is simple, particle agglomeration can be effectively inhibited, and the coating uniformity, compactness and bonding firmness can be remarkably improved.

Inventors

  • KONG WEI
  • Jiang Lingjing
  • CAI JIANLIANG
  • ZHANG HENG
  • LIU QIANG
  • ZHANG TIANQI

Assignees

  • 宁波广新纳米材料有限公司
  • 江苏博迁新材料股份有限公司

Dates

Publication Date
20260512
Application Date
20260209

Claims (9)

  1. 1. The preparation method of the iron-based soft magnetic powder with the silicon dioxide coating layer is characterized by comprising the following steps of: 1) Dispersing the iron-based soft magnetic powder prepared by a plasma evaporation condensation method in a solvent to form a solid-liquid mixture, performing ultrasonic cleaning treatment to realize deagglomeration and uniform dispersion of the powder, and performing solid-liquid separation after the ultrasonic treatment is finished to obtain the iron-based soft magnetic powder after the ultrasonic pretreatment and dispersion; 2) The method comprises the steps of (1) carrying out ultrasonic-assisted silane hydrolysis and modification, namely, redispersing the washed and dispersed iron-based soft magnetic powder obtained in the step 1) in a solvent, adding a silane coupling agent, wherein the mass-volume ratio of the iron-based soft magnetic powder to the silane coupling agent is 1kg (0.002-0.1) L, and continuously applying an ultrasonic field and mechanically stirring to obtain the ultrasonic-assisted silane modified iron-based soft magnetic powder; 3) And ultrasonic promotion of silicon dioxide polycondensation and densification coating, namely adding a pH regulator into the solid-liquid mixture of the iron-based soft magnetic powder obtained in the step 2), the solvent, the silane coupling agent and the hydrolysate thereof, regulating the pH value to 8-10, adding an organosilicon source, wherein the mass-volume ratio of the iron-based soft magnetic powder to the organosilicon source is 1 kg (0.005-0.5) L, and finishing the polycondensation reaction of the silicon dioxide and forming a densification coating on the surface of the iron-based soft magnetic powder under the conditions of constant temperature water bath, continuously applying an ultrasonic field and mechanically stirring.
  2. 2. The method of claim 1, wherein the iron-based soft magnetic powder is any one of iron powder, iron-nickel powder, iron-cobalt powder, iron-silicon-chromium powder, iron-silicon-aluminum powder, iron-silicon-nickel powder, iron-nickel-chromium powder, and iron-nickel-cobalt powder.
  3. 3. The method of claim 1, wherein in step 1), step 2) and step 3), the ultrasonic fields are performed by an ultrasonic dispersion machine, the ultrasonic field frequencies are 20-120 kHz, and the power densities are 0.3-3W/cm 2 .
  4. 4. The method for preparing the iron-based soft magnetic powder with the silicon dioxide coating layer according to claim 1, wherein the solvent in the step 1) is one or more than two of absolute ethyl alcohol, isopropanol and acetone, the mass-volume ratio of the iron-based soft magnetic powder to the solvent is 1 kg (1-10) L, and the ultrasonic cleaning treatment time is 30-60 min.
  5. 5. The method of claim 1, wherein in the step 1), the mass-volume ratio of the iron-based soft magnetic powder to the solvent is 1kg (3-6) L.
  6. 6. The preparation method of the iron-based soft magnetic powder with the silicon dioxide coating layer is characterized in that the solvent in the step 2) is one or more of absolute ethyl alcohol, isopropanol and deionized water, the mass-volume ratio of the iron-based soft magnetic powder to the solvent is 1 kg (1-10) L, the silane coupling agent is one or more of KH-550, KH-792, KH-560 and KH-570, the rotating speed of mechanical stirring is 300-800 r/min, and the reaction time is 30-90 min.
  7. 7. The method of claim 6, wherein in step 2), the mass-volume ratio of the iron-based soft magnetic powder to the solvent is 1kg (3-6) L.
  8. 8. The preparation method of the iron-based soft magnetic powder with the silicon dioxide coating layer, which is characterized in that the pH regulator in the step 3) is one or more of ammonia water, sodium hydroxide, potassium hydroxide and organic alkali, the organic silicon source is one or more of tetraethoxysilane, methyl orthosilicate and tetrapropylorthosilicate, the temperature of a constant-temperature water bath is 30-60 ℃, the rotating speed of mechanical stirring is 300-800 r/min, and the reaction time is 1-5 h.
  9. 9. The method for preparing the iron-based soft magnetic powder with the silicon dioxide coating layer according to claim 1, further comprising the step of 4) post-treatment, wherein the solid-liquid mixture after the coating reaction in the step of 3) is separated, the obtained powder is sequentially washed 3 times by deionized water and absolute ethyl alcohol respectively, and then the washed powder is dried in a vacuum oven at 60-90 ℃ for 5-8 hours, and finally the iron-based soft magnetic powder with the continuous compact silicon dioxide coating layer is obtained.

Description

Method for preparing iron-based soft magnetic powder with silicon dioxide coating layer Technical Field The invention relates to the technical field of preparation of magnetic functional materials, in particular to a preparation method of iron-based soft magnetic powder with a silicon dioxide coating layer. Background The iron-based soft magnetic powder is widely applied to the fields of high-frequency inductance, electromagnetic shielding and new energy devices by virtue of high saturation magnetization and low coercivity, but the high-frequency eddy current loss caused by the inherent low resistance of the material severely restricts the practical application. To overcome these shortcomings, the conventional process generally comprises two types of organic coating and inorganic passivation, but each has defects: Although the organic coating such as organic resin coating can improve the insulativity, the organic coating needs pre-activation treatment due to poor interfacial compatibility of powder and organic matters, and the organic layer has insufficient thermal stability and is easy to decompose and lose efficacy in the high-temperature heat treatment process of the magnetic powder core. The failure brings double adverse effects that firstly, the internal stress cannot be eliminated due to the failure of the coating layer, and secondly, the loss of the coating layer causes extremely high eddy current loss and remarkable heating when the magnetic powder core works at high frequency, the heating further aggravates the aging process of the coating layer, and the internal stress residue and the continuously worsened insulation condition act together, so that the overall performance of the magnetic powder core cannot be kept stable finally. While inorganic passivation such as phosphate passivation produces a dense coating layer by chemical reaction, there are two drawbacks, namely, the phosphate passivation layer itself has limited thermal stability, and when the temperature exceeds about 550 ℃, the passivation film may decompose, the crystal form changes or the protective properties such as becoming porous or cracking are lost, so that the soft magnetic powder passivated by the phosphate is not suitable for the subsequent process requiring high temperature treatment. Secondly, the phosphoric acid consumption and the reaction time are required to be precisely balanced, if the concentration of the phosphoric acid in passivation treatment is too low or the reaction time is insufficient, the generated passivation layer is easy to be incomplete, too thin or not compact and cannot provide effective protection, and if the phosphoric acid consumption is too large or the reaction time is too long, the reaction can be excessively carried out, not only the passivation layer is formed, but also excessive magnetic phases on the powder surface layer can be consumed, for example, the phosphoric acid can react with Fe, namely iron on the surface of iron powder to generate FePO 4, namely iron phosphate and the like, so that the overall magnetic property of the iron powder is reduced, namely the magnetic property is obviously reduced. Compared with the former two, the SiO 2 coating, namely the silicon dioxide coating, is an ideal coating material because the coating has both ultrahigh resistivity and excellent thermal stability, and can realize eddy current loss inhibition and high-temperature annealing stress elimination in a synergistic way. However, the silica coating of the prior art still has the following two disadvantages in achieving high performance coatings: 1. The adopted base powder has inherent defects, and the soft magnetic powder prepared by the traditional process such as water atomization, coprecipitation method and decomposition method generally has the problems of high surface roughness, irregular morphology, serious oxidation or pollution and the like, and the poor surface state not only needs to carry out complex and high-cost surface pretreatment which possibly damages the inherent performance of the powder before coating, but also restricts the uniform nucleation and growth of a silicon dioxide coating layer, thereby further causing uneven thickness, incomplete coverage, cracks or holes and the like of the silicon dioxide coating layer of the iron-based soft magnetic powder. 2. The prior art silica coating technology has obvious defects, such as a method of coating a single layer or multiple layers by adopting a sol-gel method, coating nano silica by adopting a physical adsorption method or doping soft magnetic ferrite in a silica coating layer by adopting a St-ber method improved process, and the like. The prior art generally has the problems of poor powder dispersibility, serious agglomeration, uneven thickness, excessive local thickness or excessive thinness, even leakage package or weak binding force and the like of the coated powder, and is difficult to form a uniform, compact and firmly-combined