阅读说明：本技术 一种具有介孔结构包覆层的铁基软磁复合材料及其制备方法 (Iron-based soft magnetic composite material with mesoporous structure coating layer and preparation method thereof ) 是由 孙海身 杜皎 解传娣 张雷 陶景聪 吕荣青 于 2020-12-31 设计创作，主要内容包括：本发明公开了一种具有介孔结构包覆层的铁基软磁复合材料及其制备方法,属于金属粉末冶金及磁性材料制备技术领域。该方法通过采用限域界面胶束组装法并结合聚乙二醇作为粘结润滑剂的温压压制工艺,在铁基合金粉末表面形成一层坚硬的薄壁介孔结构TiO-2绝缘包覆层。介孔结构的形成来自于胶束的自组装,依赖于甘油在组装过程中的限域效应和溶剂选择,故通过调节甘油的添加量实现包覆层厚度及介孔尺寸的有效调控,TiO-2水凝胶包覆层的厚度在11-50nm范围内可调,介孔尺寸在4.5-20nm范围内可调。本发明能够减小磁导率的损失,提高产品密度和强度。同时,通过介孔结构涂层的生成,能够显著提高SMC软磁复合材料的饱和磁感应强度,降低磁损耗,具有重要的意义。(The invention discloses an iron-based soft magnetic composite material with a mesoporous structure coating layer and a preparation method thereof, belonging to the technical field of metal powder metallurgy and magnetic material preparation. The method forms a layer of hard thin-wall mesoporous TiO structure on the surface of iron-based alloy powder by adopting a limited-area interface micelle assembly method and combining a warm-pressing process of using polyethylene glycol as a bonding lubricant 2 And an insulating coating layer. The mesoporous structure is formed by self-assembly of micelle, depends on the domain-limiting effect of glycerol in the assembly process and solvent selection, so that the thickness of a coating layer and the size of a mesoporous are effectively regulated and controlled by regulating the addition amount of the glycerol, and TiO 2 The thickness of the hydrogel coating layer is adjustable within the range of 11-50nm, and the mesoporous size is adjustable within the range of 4.5-20 nm. The invention can reduce the loss of magnetic conductivity and improve the density and strength of the product. Meanwhile, the generation of the mesoporous structure coating can obviously improve SMC soft magnetismThe saturation magnetic induction intensity of the composite material reduces the magnetic loss, and has important significance.)

1. A preparation method of an iron-based soft magnetic composite material with a mesoporous structure coating layer is characterized by comprising the following steps:

(1) mixing a proper amount of spherical iron-based alloy powder with acetone, adding a silane coupling agent to activate the surface of the powder, and drying for later use after full reaction;

(2) mixing a proper amount of F127, acetic acid and 30-40 wt% of concentrated hydrochloric acid with tetrahydrofuran, strongly stirring for 15-20min, dropwise adding tetrabutyl titanate, adding deionized water, and magnetically stirring for 10-15 min; drying the obtained mixed solution at 50-60 deg.C for 20-24h to form TiO₂A surfactant composite hydrogel;

(3) weighing a proper amount of the gel, mixing with absolute ethyl alcohol, strongly stirring for 10-15min to form a transparent solution, and dropwise adding glycerol while continuously stirring; mixing the obtained solution with the dried alloy powder in the step (1), transferring the mixture into a reaction kettle, and reacting at the temperature of 100 ℃ and 130 ℃ for 10-12 h; cooling to room temperature after the reaction is finished, filtering to obtain alloy powder, cleaning with absolute ethyl alcohol, and drying to obtain raw alloy powder;

(4) placing the raw alloy powder into a burning boat, placing the burning boat into a tubular furnace, calcining the raw alloy powder for 4 to 6 hours at the temperature of 380 ℃ in a protective atmosphere, cooling the raw alloy powder to room temperature along with the furnace, and sieving the raw alloy powder through a 200-mesh sieve for later use after crushing;

(5) fully stirring and mixing the sieved alloy powder and polyethylene glycol, drying, and pressing into a magnetic ring green body by warm pressing; heating the magnetic ring green compact to 400 ℃ at the speed of 4-6 ℃/min, preserving heat for 0.5-1h, removing polyethylene glycol, and then sintering at the temperature of 750 ℃ and 1120 ℃ for 0.5-1.5h to finally obtain the TiO with the mesoporous structure and the low coercive force and high magnetic conductivity₂An iron-based soft magnetic composite material of a coating layer.

2. The method for preparing an iron-based soft magnetic composite material with a mesoporous structure coating layer according to claim 1, wherein the spherical iron-based alloy powder in the step (1) comprises one or more of spherical pure iron powder, spherical iron-silicon-aluminum alloy powder and spherical iron-silicon-chromium alloy powder; the grain size of the alloy powder is 1-20 μm.

3. The method for preparing an iron-based soft magnetic composite material with a mesoporous structure coating layer according to claim 1, wherein the ratio of the volume of the acetone added in the step (1) to the mass of the spherical iron-based alloy powder is 0.25-0.5 mL/g; the ratio of the volume of the added silane coupling agent to the mass of the spherical iron-based alloy powder is 0.05-0.1 mL/g; the drying temperature is 50-70 ℃.

4. The method for preparing an iron-based soft magnetic composite material with a mesoporous structure coating layer according to claim 1, wherein the mass ratio of F127, acetic acid and concentrated hydrochloric acid in the step (2) is 3:5: 7; the ratio of the volume of the added tetrahydrofuran to the mass of the F127 is 20-30 mL/g; the mass ratio of the tetrabutyl titanate to the F127 is 2-3; the ratio of the volume of the added deionized water to the mass of the F127 is 0.1-0.5 mL/g.

5. The method for preparing an iron-based soft magnetic composite material with a mesoporous structure coating layer according to claim 1, wherein the ratio of the volume of the absolute ethyl alcohol added in the step (3) to the mass of the gel is 15-30 mL/g; the ratio of the volume of the added glycerol to the mass of the gel is 15-20 mL/g; the mixing ratio of the obtained gel mixed solution and the dried alloy powder in the step (1) is 0.01-0.1 mL/g.

6. The method for preparing an iron-based soft magnetic composite material with a mesoporous structure coating layer according to claim 1, wherein the reaction kettle is shaken every 1h for 5-10min during the reaction of the gel and the alloy powder in the step (3); the drying temperature is 60-80 ℃.

7. The method for preparing an iron-based soft magnetic composite material with a mesoporous structure coating layer as claimed in claim 1, wherein the sieving particle size in step (4) is 200-220 mesh.

8. The preparation method of the iron-based soft magnetic composite material with the mesoporous structure coating layer according to claim 1, wherein the mass ratio of the polyethylene glycol to the addition amount of the alloy powder in the step (5) is 0.5-1%; the drying temperature is 60-80 ℃; the size of the magnetic ring green body is 25mm multiplied by 15mm multiplied by 4.5 mm; the temperature of the warm-pressing mold is 130 ℃ to 160 ℃, and the pressure of the warm-pressing mold is 350 MPa to 1500 MPa.

9. The method for preparing an iron-based soft magnetic composite material with a mesoporous structure coating layer according to claim 1, wherein the TiO in the step (5)₂The thickness of the coating layer is 11-50nm, and the mesoporous size is 4.5-20 nm.

10. An iron-based soft magnetic composite having a mesostructured cladding layer prepared by the method of any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of metal powder metallurgy and magnetic material preparation, and particularly relates to an iron-based soft magnetic composite material and a preparation method thereof.

Background

Currently, mesoporous core-shell nanostructures have gained a great deal of attention in many research areas. This structure, by combining the core and shell functions, can improve the stability and dispersion of the core particle, even with respect to the original photonic and electronic properties. Most of the shells formed around the core usually consist of a dense solid part, changing the dense shell into a mesoporous shell can significantly improve the performance of the material, since such mesopores on the shell are able to accommodate molecules and allow diffusion into and out of the core, which is related to their textural properties, high porosity and high surface area. For example, mesoporous TiO₂The shell can greatly increase the affinity of the material to reactants and the number of catalytic active sites, and can even well improve the conductivity and structural stability of the medium carbon coating material. The construction of the core-shell nanostructure depends on the controllable composition, distribution and thickness of the core and shell layers. At present, a representative construction method is a surfactant-template method, namely, under an alkaline condition, soft core particles, a structure directing agent and a silicon dioxide source are adopted for preparation. The method has been widely used for SiO with mesopores₂Preparing the nano coating material of the shell.

Soft Magnetic Composite (SMC) is a new iron-based powder Soft Magnetic material that has been gradually developed in recent years. It usually selects the base material of high-purity iron powder, and makes the mixed powder into isotropic material by means of powder metallurgical technology and insulating coating treatment with organic material and inorganic material. The inorganic compound coating layer may chemically react with the magnetic powder, resulting in an increase in intrinsic coercivity of the new magnetic compound, while affecting magnetic loss. The annealing temperature of the organic material coating is lower than that of the inorganic material coating, which is not favorable for eliminating residual stress generated during pressing, and this is generally verified from the total magnetic loss. Therefore, although the surface of the existing SMC material has an insulator coating, the thickness, chemical composition, type selection, preparation process and other aspects of the existing SMC material are not completely optimized, the thickness of the existing coating process used by the soft magnetic composite material is large, the used coating material has no magnetism, so that the loss of the magnetic conductivity of the material is large, the thickness of the coating layer is uncontrollable, and the stability of the product is not good. The melting point of a plurality of organic matter coating layers is low, so that the heat treatment temperature of the product is not high, the residual stress generated by the press forming of the product is not completely eliminated, and the magnetic performance of the product is poor. This continues to be an important factor limiting the widespread use of SMC materials.

Disclosure of Invention

Aiming at the technical problems of low heat treatment temperature, thick coating layer and difficult regulation in the existing SMC material insulating coating technology, the invention provides an iron-based soft magnetic composite material with a mesoporous structure coating layer and a preparation method thereof. Forming a layer of hard thin-wall mesoporous TiO structure on the surface of the iron-based alloy powder by adopting a limited-area interface micelle assembly method and combining a warm-pressing process of using polyethylene glycol as a bonding lubricant₂The process can effectively regulate and control the thickness of the coating, reduce the loss of magnetic conductivity and improve the density and strength of the product. Meanwhile, through the generation of the mesoporous structure coating, the saturation magnetic induction intensity of the SMC soft magnetic composite material can be obviously improved, and the magnetic loss is reduced, so that the method has important significance.

In order to achieve the purpose, the invention adopts the following technical scheme:

one aspect of the present invention provides a method for preparing an iron-based soft magnetic composite material having a mesoporous structure coating layer, comprising the steps of:

(1) mixing a proper amount of spherical iron-based alloy powder with acetone, adding a silane coupling agent to activate the surface of the powder, and drying for later use after full reaction;

(2) mixing a proper amount of F127, acetic acid and 30-40 wt% of concentrated hydrochloric acid with tetrahydrofuran, strongly stirring for 15-20min, dropwise adding tetrabutyl titanate, adding deionized water, and magnetically stirring for 10-15 min; drying the obtained mixed solution at 50-60 deg.C for 20-24h to form TiO₂A surfactant composite hydrogel;

(3) weighing a proper amount of the gel, mixing with absolute ethyl alcohol, strongly stirring for 10-15min to form a transparent solution, and dropwise adding glycerol while continuously stirring; mixing the obtained solution with the dried alloy powder in the step (1), transferring the mixture into a reaction kettle, and reacting at the temperature of 100 ℃ and 130 ℃ for 10-12 h; cooling to room temperature after the reaction is finished, filtering to obtain alloy powder, cleaning with absolute ethyl alcohol, and drying to obtain raw alloy powder;

(4) placing the raw alloy powder into a burning boat, placing the burning boat into a tubular furnace, calcining the raw alloy powder for 4 to 6 hours at the temperature of 380 ℃ in a protective atmosphere, cooling the raw alloy powder to room temperature along with the furnace, and sieving the raw alloy powder through a 200-mesh sieve for later use after crushing;

(5) fully stirring and mixing the sieved alloy powder and polyethylene glycol, drying, and pressing into a magnetic ring green body by warm pressing; heating the magnetic ring green compact to 400 ℃ at the speed of 4-6 ℃/min, preserving heat for 0.5-1h, removing polyethylene glycol, and then sintering at the temperature of 750 ℃ and 1120 ℃ for 0.5-1.5h to finally obtain the TiO with the mesoporous structure and the low coercive force and high magnetic conductivity₂An iron-based soft magnetic composite material of a coating layer.

Further, the spherical iron-based alloy powder in the step (1) comprises one or more of spherical pure iron powder, spherical iron-silicon-aluminum alloy powder and spherical iron-silicon-chromium alloy powder; the grain size of the alloy powder is 1-20 μm.

Further, the ratio of the volume of the acetone added in the step (1) to the mass of the spherical iron-based alloy powder is 0.25-0.5 mL/g; the ratio of the volume of the added silane coupling agent to the mass of the spherical iron-based alloy powder is 0.05-0.1 mL/g.

Further, the drying temperature in the step (1) is 50-70 ℃.

Further, in the step (2), the F127 is a triblock polymer PEO₁₀₆PPO₇₀PEO₁₀₆The molecular formula PEO-PPO-PEO is polyoxyethylene-polyoxypropylene-polyoxyethylene; the mass ratio of the F127 to the acetic acid to the concentrated hydrochloric acid is 3:5: 7; the ratio of the volume of the added tetrahydrofuran to the mass of the F127 is 20-30 mL/g; the mass ratio of the tetrabutyl titanate to the F127 is 2-3; the volume of the deionized water added and the mass of the F127The ratio is 0.1-0.5 mL/g.

Further, the ratio of the volume of the absolute ethyl alcohol added in the step (3) to the mass of the gel is 15-30 mL/g; the ratio of the volume of the added glycerol to the mass of the gel is 15-20 mL/g; the mixing ratio of the obtained gel mixed solution and the dried alloy powder in the step (1) is 0.01-0.1 mL/g.

Further, the reaction kettle is shaken every 1h for 5-10min during the reaction of the gel and the alloy powder in the step (3) so as to ensure that the reaction is fully carried out.

Further, the drying temperature in the step (3) is 60-80 ℃.

Further, the sieving particle size in the step (4) is 200-220 meshes.

Further, in the step (5), the mass ratio of the addition amount of the polyethylene glycol to the alloy powder is 0.5-1%; the polyethylene glycol functions as a binding lubricant during warm compaction.

Further, the drying temperature in the step (5) is 60-80 ℃.

Further, the size of the magnetic ring green body in the step (5) is 25mm multiplied by 15mm multiplied by 4.5 mm; the temperature of the warm-pressing mold is 130 ℃ to 160 ℃, and the pressure of the warm-pressing mold is 350 MPa to 1500 MPa.

Further, the high-temperature sintering in the step (5) is sintering in a protective atmosphere or sintering in an air state.

Further, the TiO in the step (5)₂The thickness of the coating layer is 11-50nm, and the mesoporous size is 4.5-20 nm.

Another aspect of the present invention is to provide an iron-based soft magnetic composite material having a mesoporous structure coating layer prepared by the above method.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects and technical advantages:

the invention can realize the TiO-based bonding by adopting a domain-limited interface micelle assembly method₂The thickness of the coating and the aperture of the mesoporous are accurately regulated and controlled. The mesoporous structure is formed by self-assembly of micelles, depends on the domain limiting effect of glycerol in the assembly process and solvent selection, and is adjusted by adding glycerolThe amount of the TiO-based mesoporous material can effectively regulate and control the thickness and the mesoporous size of the coating layer₂The thickness of the hydrogel coating layer is adjustable within the range of 11-50nm, and the mesoporous size is adjustable within the range of 4.5-20 nm. Meanwhile, the existence of the mesoporous structure can obviously reduce the loss of the magnetic conductivity of the product and ensure the resistivity of the product. Then polyethylene glycol is used as a bonding lubricant to carry out warm pressing on the raw alloy powder, and finally, the raw alloy powder is sintered at high temperature to form a layer of hard thin-wall mesoporous TiO on the surface of the alloy powder₂The insulating coating layer eliminates residual stress, reduces coercive force and reduces magnetic loss at high frequency.

Drawings

FIG. 1 shows TiO with mesoporous structure prepared in an embodiment of the present invention₂SEM image of iron-based soft magnetic composite of cladding layer.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in further detail below.

The invention discloses an iron-based soft magnetic composite material with a mesoporous structure coating layer and a preparation method thereof. The process can form evenly coated mesoporous structure TiO on the surface of the spherical iron-based magnetically soft alloy powder₂The insulating coating layer has the advantages of flexible adjustment of the thickness of the coating layer and the size of the mesopores, and a product with high magnetic permeability and low magnetic loss can be obtained. The microstructure of the composite material is shown in figure 1, and it can be seen from the figure that mesopores are uniformly distributed on the coating layer on the surface of the spherical iron-based alloy particle.

Example 1

Step one, placing superfine spherical pure iron powder with the particle size of 1 mu m into an acetone solvent, adding a silane coupling agent to activate the surface of the powder, and then placing the powder into a blast drying oven to dry at 50 ℃ for later use;

step two, TiO₂Preparing hydrogel: measuring F1273.0 g, acetic acid 5.0g and concentrated hydrochloric acid 7.0g with the mass fraction of 36 wt%, putting the concentrated hydrochloric acid into a beaker containing 60mL of tetrahydrofuran solvent, strongly stirring for 15min, dropwise adding 7.0g of tetrabutyl titanate, then putting 0.3mL of deionized water, and magnetically stirringStirring for 10min to obtain yellowish white solution, transferring the solution into air drying oven, and drying at 50 deg.C for 24 hr to obtain TiO₂Surfactant compounded light yellow hydrogel;

weighing 2g of the light yellow gel, placing the light yellow gel into a beaker containing 30mL of absolute ethyl alcohol, strongly and mechanically stirring for 10min to form a transparent solution, dropwise adding 30mL of glycerol and continuously stirring for 15min, mixing the obtained solution with 50g of alloy powder, transferring the mixture into a 50mL reaction kettle, placing the reaction kettle into a forced air drying oven, reacting for 12h at 100 ℃, shaking the reaction kettle for 5min every 1h, cooling to room temperature after the reaction is finished, filtering the obtained mixture solution, washing the obtained new alloy powder with absolute ethyl alcohol, filtering, and placing the filtered mixture into the forced air drying oven for drying at 60 ℃ to obtain alloy powder raw powder;

step four, placing the alloy powder raw powder into a burning boat, placing the burning boat into a tube furnace, calcining for 5 hours at the temperature of 360 ℃ in the argon protective atmosphere, cooling to room temperature along with the furnace, and taking out TiO₂Coating alloy powder, crushing and sieving by a 200-mesh sieve for later use;

step five, mixing the TiO₂Fully stirring and mixing the coated alloy powder and a polyethylene glycol alcohol solution, drying the mixture in a blast drying oven at the temperature of 80 ℃ to obtain cohesive gold powder, pressing the powder into a magnetic ring green body with the thickness of 25mm multiplied by 15mm multiplied by 4.5mm at the temperature of 6 ℃/min, heating the magnetic ring green body to 300 ℃, preserving the temperature for 1h to remove polyethylene glycol, sintering the magnetic ring green body at the high temperature of 750 ℃ for 1.5h to finally obtain the TiO with the mesoporous structure and the low coercive force and high permeability₂And coating the iron-based soft magnetic composite material.

Example 2

Step one, placing superfine spherical pure iron powder and spherical iron-silicon-aluminum alloy powder with the particle size of 10 mu m into an acetone solvent, adding a silane coupling agent to activate the surface of the powder, and then placing the powder into a blast drying oven to dry at 60 ℃ for later use;

step two, TiO₂Preparing hydrogel: measuring F1273.0 g, acetic acid 5.0g and concentrated hydrochloric acid 7.0g with the mass fraction of 36 wt%, putting the concentrated hydrochloric acid into a beaker containing 60mL of tetrahydrofuran solvent, strongly stirring the mixture for 15min, dropwise adding 9.0g of tetrabutyl titanate, and then putting the mixture into 0.5mLMagnetically stirring deionized water for 12min to obtain yellowish white solution, drying at 55 deg.C for 22 hr to obtain TiO₂Surfactant compounded light yellow hydrogel;

weighing 4g of the light yellow gel, placing the light yellow gel into a beaker filled with 120mL of absolute ethyl alcohol, intensively and mechanically stirring for 10min to form a transparent solution, dropwise adding 80mL of glycerol and continuously stirring for 15min, mixing the obtained solution with 50g of alloy powder, transferring the mixture into a reaction kettle, placing the reaction kettle into a forced air drying oven, reacting for 12h at 110 ℃, shaking the reaction kettle for 5min every 1h, cooling to room temperature after the reaction is finished, filtering the obtained mixture solution, washing the obtained new alloy powder with absolute ethyl alcohol, filtering, and placing the filtered mixture into the forced air drying oven for drying at 70 ℃ to obtain alloy powder raw powder;

step four, placing the alloy powder raw powder into a burning boat, placing the burning boat into a tube furnace, calcining for 5 hours at the temperature of 360 ℃ in the argon protective atmosphere, cooling to room temperature along with the furnace, and taking out TiO₂Coating alloy powder, crushing and sieving by a 210-mesh sieve for later use;

step five, mixing the TiO₂Fully stirring and mixing the coated alloy powder and a polyethylene glycol alcohol solution, drying the mixture in a blast drying oven at 80 ℃ to obtain cohesive gold powder, pressing the powder into a magnetic ring green body with the thickness of 25mm multiplied by 15mm multiplied by 4.5mm at a warm pressure, heating the magnetic ring green body to 350 ℃ at the speed of 5 ℃/min, preserving the temperature for 0.6h to remove polyethylene glycol, sintering the magnetic ring green body at the high temperature of 1000 ℃ for 1h to finally obtain the TiO with the mesoporous structure and the low coercive force and high permeability₂And coating the iron-based soft magnetic composite material.

Example 3

Step one, placing superfine spherical iron-silicon-chromium alloy powder with the particle size of 20 mu m into an acetone solvent, adding a silane coupling agent to activate the surface of the powder, and then placing the powder into a forced air drying oven to dry at 70 ℃ for later use;

step two, TiO₂Preparing hydrogel: measuring F1273.0 g, acetic acid 5.0g and concentrated hydrochloric acid 7.0g with the mass fraction of 36 wt%, putting the concentrated hydrochloric acid into a beaker containing 60mL of tetrahydrofuran solvent, strongly stirring the mixture for 15min, dropwise adding 7.0g of tetrabutyl titanate, and then adding the tetrabutyl titanate dropwiseAdding 0.3mL deionized water, magnetically stirring for 10min to obtain yellowish white solution, transferring the solution into a forced air drying oven, and drying at 60 deg.C for 20 hr to obtain TiO₂Surfactant compounded light yellow hydrogel;

weighing 2g of the light yellow gel, placing the light yellow gel into a beaker containing 30mL of absolute ethyl alcohol, strongly and mechanically stirring for 10min to form a transparent solution, dropwise adding 30mL of glycerol and continuously stirring for 15min, mixing the obtained solution with 50g of alloy powder, transferring the mixture into a 50mL reaction kettle, placing the reaction kettle into a forced air drying oven, reacting for 10h at 130 ℃, shaking the reaction kettle for 5min every 1h, cooling to room temperature after the reaction is finished, filtering the obtained mixture solution, washing the obtained new alloy powder with absolute ethyl alcohol, filtering, and placing the filtered mixture into the forced air drying oven for drying at 80 ℃ to obtain raw alloy powder;

step four, placing the alloy powder raw powder into a burning boat, placing the burning boat into a tube furnace, calcining for 4 hours at the temperature of 380 ℃ in the argon protective atmosphere, cooling to room temperature along with the furnace, and taking out TiO₂Coating alloy powder, crushing, and sieving with a 220-mesh sieve for later use;

step five, mixing the TiO₂Fully stirring and mixing the coated alloy powder and a polyethylene glycol alcohol solution, drying in a blast drying oven at 60 ℃ to obtain cohesive gold powder, pressing the powder at a high temperature to obtain a magnetic ring green body with the thickness of 25mm multiplied by 15mm multiplied by 4.5mm, heating the magnetic ring green body to 400 ℃ at the speed of 4 ℃/min, preserving the temperature for 0.5h to remove polyethylene glycol, sintering at the high temperature of 1120 ℃ for 0.5h to finally obtain the TiO with the mesoporous structure and the low coercive force and high permeability₂And coating the iron-based soft magnetic composite material.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.