Ferromagnetic powder composition and its production method

Abstract

A ferromagnetic powder composition comprising (i) soft magnetic iron-based core particles and (ii) a first coating layer that at least partially covers and is in direct contact with the surface of the core particles, the first coating layer comprising a) a general formula (K₂O). α (SiO2) β a) silicates, wherein α is the molar number of K2O, β is the molar number of SiO2, and the β / α molar ratio is in the range of 0.5 to 4.1, wherein the silicates are present in an amount of 0.02 wt% to 1.0 wt% based on the total weight of the ferromagnetic powder composition; b) optionally, particles comprising a compound of bismuth and oxygen having a Di in the range of 0.1 μm to 10 μm as measured according to ISO 13320-1. 50 c) as a dopant dissolved in silicate (a) by oxoanions or hydroxyanions. A second coating layer may be provided. Methods for producing the composition and manufacturing an object, and an object comprising the composition.

Description

Technical Field

[0001] The techniques presented in this article generally relate to the field of ferromagnetic powder compositions containing soft magnetic iron-based core particles and methods for producing ferromagnetic powder compositions.

[0002] background Ferromagnetic powders include soft magnetic composite (SMC) powders, which contain soft magnetic core particles, typically iron-based, with an electrically insulating coating on each particle. Such powders can be used to obtain soft magnetic components or parts, such as by compacting the powder into a desired shape. These components or parts, also known as soft magnetic composites, can be used in a wide range of applications as a replacement for laminated steel components in electric motors, generators, and electromagnets.

[0003] Two key characteristics of soft magnetic core particles and corresponding components made from such particles are permeability μ and core loss characteristics P. c The permeability μ of a material is an indicator of its ability to be magnetized or its ability to carry magnetic flux. Maximum permeability (µ) max The ratio B / H is defined as the maximum value of the magnetizing force B, or field strength, to the induced magnetic flux H. When a magnetic material is exposed to a changing field, energy loss occurs due to both hysteresis loss and eddy current loss. In most motor applications, the majority of the total core loss, hysteresis loss (DC loss), is caused by the energy required to overcome the retained magnetism within components made of soft magnetic core particles, and is affected by remanence or retentivity B. R and coercivity H C The impact.

[0004] By improving the quality and purity of the soft magnetic core particles, and particularly by heat-treating the assembly to release stress caused by compaction shear forces within the assembly, the retained magnetic force within the assembly can be minimized. Energy loss is also caused by eddy current losses (AC losses), which are induced currents in the component due to flux changes caused by alternating current (AC) conditions. Eddy current losses are minimized by an electrically insulating coating on each particle, which thus isolates the soft magnetic core particles from each other. Therefore, the resistivity R of the coating becomes an important parameter limiting the characteristics and usability of the soft magnetic core particles. The level of resistivity R required to minimize AC losses in components made from soft magnetic core particles depends on the size distribution of the soft magnetic core particles, the size of the component or the cross-sectional area of ​​the magnetic flux, and the frequency of the alternating magnetic field in which the component is used.

[0005] EP 2 252 419 B1 generally discloses a ferromagnetic powder composition comprising soft magnetic iron-based core particles, wherein the surface of the core particles is provided with a first inorganic insulating layer and at least one metal-organic layer located outside the first layer.

[0006] US 10,741,316 generally discloses a ferromagnetic powder composition comprising soft magnetic iron-based core particles, wherein the surface of the core particles is coated with at least one phosphorus-based inorganic insulating layer and then at least partially coated with an organometallic compound.

[0007] EP 3 411 169 B1 generally discloses a powder mixture comprising phosphorus-coated ferroalloy particles and phosphorus-coated iron particles.

[0008] WO 2020 / 252551 generally relates to a particulate material comprising ferromagnetic particles covered by at least one oxide layer composed of nanoparticles and at least one glassy layer covering the oxide layer.

[0009] BE 44 486 generally relates to a method for constructing a magnetic core by mixing particles of magnetic material covered by an insulator with a particle-separated material.

[0010] Despite the advantages of the techniques described in the cited literature, there is still a need to provide additional ferromagnetic powder compositions containing soft magnetic core particles with improved electrical, magnetic, and / or structural properties.

[0011] More specifically, there remains a need to allow for heat treatment at higher temperatures while maintaining an acceptable resistivity of the electrically insulating coating on each particle. Meeting this requirement for a given level of coercivity and coating density / thickness will provide improved aging properties and higher resistivity, especially due to the improved coverage of the coating. It will also provide improved properties for harder particles, which undergo less plastic deformation during compaction and therefore require higher relaxation temperatures during heat treatment.

[0012] Target The first and second objectives of the technology proposed herein relate to providing ferromagnetic powder compositions and mixtures containing soft magnetic core particles with improved electrical, magnetic, and / or structural properties.

[0013] Another objective of the technology presented herein relates to providing ferromagnetic powder compositions and mixtures comprising soft magnetic core particles that provide an improved balance among two or more of electrical, magnetic, and / or structural properties.

[0014] Another objective of the technology presented herein involves providing ferromagnetic powder compositions and mixtures that exhibit improved aging properties and higher resistivity for a given level of coercivity and coating density / thickness.

[0015] Another objective of the technology presented herein relates to providing ferromagnetic powder compositions and mixtures that can be used to produce objects with improved thermal aging properties.

[0016] The third objective of the technology presented herein relates to providing a method for producing ferromagnetic powder compositions and mixtures.

[0017] The fourth objective of the technology presented herein relates to providing a method for manufacturing an object from a ferromagnetic powder composition or mixture.

[0018] The fifth and sixth objectives of the technology presented herein relate to an object comprising a compacted ferromagnetic powder composition or mixture, and an object manufactured from a ferromagnetic powder composition or mixture.

[0019] Overview At least one of the above objectives, or at least one of the other objectives, which will become apparent from the following description, is achieved by the corresponding first and third aspects of the technology proposed herein, through the following: Ferromagnetic powder composition comprising: (i) Soft magnetic iron-based core particles, and (ii) a first coating layer that at least partially covers and is in direct contact with the surface of the core particle, the first coating layer comprising: a. General formula (K₂O) α (SiO2) β The silicate, where α is the molar amount of K₂O, β is the molar amount of SiO₂, and the β / α molar ratio is in the range of 0.5 to 4.1. i. wherein the silicate is present in an amount of 0.02 wt% to 1.0 wt% based on the total weight of the ferromagnetic powder composition. b. Optionally, particles comprising a compound of bismuth and oxygen, having a D0 in the range of 0.1 μm to 10 μm as measured according to ISO 13320-1. 50 ,as well as c. As a dopant for the dissolution of oxoanions or hydroxyl anions in silicate (a), as well as A method for producing a ferromagnetic powder composition, the method comprising the following steps: (i) Provide soft magnetic iron-based core particles. (ii) Contacting the soft magnetic iron-based core particles with a first aqueous solution, the first aqueous solution comprising: a. General formula (K₂O) α (SiO2) β The silicate, where α is the molar amount of K₂O, β is the molar amount of SiO₂, and the β / α molar ratio is in the range of 0.5 to 4.1. i. wherein the silicate is present in an amount of 0.02 wt% to 1.0 wt% based on the total weight of the ferromagnetic powder composition. b. Optionally, particles comprising a compound of bismuth and oxygen, having a D0 in the range of 0.1 μm to 10 μm as measured according to ISO 13320-1. 50 , c. As a dopant for the dissolution of oxoanions or hydroxyl anions in silicate (a), and d. Optionally, nanoparticles having a D0 of 10 nm–200 nm as measured according to ISO 13320-1. 50 Alternatively, it may have 6 m as defined in ISO 9277:2022. 2 / g-120 m 2 Specific surface area (SSA) per g.

[0020] At least one or more of the above objectives, as will become apparent from the following description, are achieved according to the second aspect of the technology proposed herein by means of a ferromagnetic powder composition comprising: According to the first aspect of the technology presented herein, a ferromagnetic powder composition, and Other ferromagnetic powder compositions, The additional ferromagnetic powder composition contains soft magnetic iron-based core particles that are different from the soft magnetic iron-based core particles of the ferromagnetic powder composition, and Preferably, the soft magnetic iron-based core particles of the additional ferromagnetic powder composition comprise or are composed of an iron alloy having a higher resistivity and / or hardness than the soft magnetic iron-based core particles of the ferromagnetic powder composition.

[0021] At least one of the above objectives, or at least one of the other objectives, as will become apparent from the following description, is achieved according to the fourth aspect of the art proposed herein by a method for manufacturing an object from a ferromagnetic powder composition according to the first aspect of the art proposed herein or a ferromagnetic powder mixture according to the second aspect of the art proposed herein, the method comprising the following steps: (i) A ferromagnetic powder composition according to the first aspect of the technology presented herein or a ferromagnetic powder mixture according to the second aspect of the technology presented herein is compacted in a mold at a compaction pressure in the range of 300 MPa-2000 MPa, preferably 400 MPa-1200 MPa, to obtain a compacted component, and (ii) The compacted component is heat-treated in a non-reducing atmosphere at a temperature in the range of 300°C-800°C, preferably 400°C-750°C, more preferably 600°C-700°C, to obtain the object, wherein the non-reducing atmosphere preferably contains 0 wt%-22 wt%, more preferably 0.5 wt% to 2 wt% oxygen (O2).

[0022] At least one of the above objectives, or at least one of the other objectives, as will become apparent from the following description, is achieved by an object comprising a compacted ferromagnetic powder composition according to the first aspect of the present invention or a compacted ferromagnetic powder mixture according to the second aspect of the present invention, and by an object obtained by a method according to the fourth aspect of the present invention. Brief description of the attached diagram Figure 1 A schematic cross-sectional view of a single particle of a ferromagnetic powder composition according to an embodiment of a first aspect of the technology presented herein is shown, illustrating a soft magnetic iron-based core particle and a first coating layer and a second coating layer, the first coating layer comprising silicates, nanoparticles, particles comprising a compound containing bismuth and oxygen, and a dopant, the second coating layer comprising at least one organometallic compound.

[0024] Detailed description The corresponding first and third aspects of the technology presented herein relate to: a ferromagnetic powder composition comprising: (i) Soft magnetic iron-based core particles, and (ii) a first coating layer that at least partially covers and is in direct contact with the surface of the core particle, the first coating layer comprising: a. General formula (K₂O) α (SiO2) β The silicate, where α is the molar amount of K₂O, β is the molar amount of SiO₂, and the β / α molar ratio is in the range of 0.5 to 4.1. i. wherein the silicate is present in an amount of 0.02 wt% to 1.0 wt% based on the total weight of the ferromagnetic powder composition. b. Optionally, particles comprising a compound of bismuth and oxygen, having a D0 in the range of 0.1 μm to 10 μm as measured according to ISO 13320-1. 50 ,as well as c. As a dopant for the dissolution of oxoanions or hydroxy anions in silicates (a); And a method for producing a ferromagnetic powder composition, the method comprising the following steps: (i) Provide soft magnetic iron-based core particles. (ii) Contacting the soft magnetic iron-based core particles with a first aqueous solution, the first aqueous solution comprising: a. General formula (K₂O) α (SiO2) β The silicate, where α is the molar amount of K₂O, β is the molar amount of SiO₂, and the β / α molar ratio is in the range of 0.5 to 4.1. ii. Wherein the silicate is present in an amount of 0.02 wt% to 1.0 wt% based on the total weight of the ferromagnetic powder composition, b. Optionally, particles comprising a compound of bismuth and oxygen, having a D0 in the range of 0.1 μm to 10 μm as measured according to ISO 13320-1. 50 , c. As a dopant for the dissolution of oxoanions or hydroxyl anions in silicate (a), and d. Optionally, nanoparticles having a D0 of 10 nm–200 nm as measured according to ISO 13320-1. 50 Alternatively, it may have 6 m as defined in ISO 9277:2022. 2 / g-120 m 2 Specific surface area (SSA) per g.

[0025] Therefore, the technology presented herein is based on the inventors' understanding that the magnetic and electrical properties of ferromagnetic powder compositions and parts made from ferromagnetic powder compositions can be further improved by doping in the first coating layer on soft magnetic iron-based core particles. As observed from the embodiments and figures, including doping in the first coating layer provides improved aging properties and higher resistivity for a given coercivity level and coating layer density / thickness level for parts made from ferromagnetic powder compositions. Specifically, these parts can be heat-treated at higher temperatures while maintaining acceptable resistivity properties. In other words, including doping in the first coating layer provides better thermal stability and / or specific resistivity for a given coercivity level and coating layer density / thickness level for a glassy coating layer formed by the first coating layer and any second coating layer applied on top of the first coating layer when the ferromagnetic powder composition is compacted into a part and heat-treated. This allows for heat treatment at higher temperatures. When parts are manufactured from ferromagnetic powder compositions, heat treatment at higher temperatures provides a more complete or full release of stress induced in the part, and thus results in lower coercivity in the part.

[0026] Alternatively, improved thermal stability can be viewed as obtaining or maintaining improved coverage of the glassy cladding formed by the first cladding layer and any second cladding layer on top of the first cladding layer, and thus obtaining or maintaining higher resistivity and therefore lower coercivity of the soft magnetic iron-based core particles.

[0027] Another advantage observed in components made from ferromagnetic powder compositions is improved aging properties. Therefore, components made from ferromagnetic powder compositions suffer less property degradation, particularly in resistivity and core loss, when subjected to aging caused by the component's environment (such as elevated temperatures, e.g., 30°C–250°C, or corrosive gases or fluids).

[0028] In the ferromagnetic powder composition, silicate, particles containing a bismuth and oxygen compound (when present), and dopant are all provided in the same first coating layer. In other words, when present, particles containing a bismuth and oxygen compound are dispersed in silicate. The dopant is dissolved in silicate.

[0029] Therefore, the dopant is distributed in silicate (a) as an oxo anion or a hydroxy anion. In other words, the oxo anion or hydroxy anion of the dopant is provided, for example, distributed in silicate (a). In other words, the first coating layer contains the dopant distributed in silicate as an oxo anion or a hydroxy anion. Regardless of the state of the coating layer, the dopant is dissolved in silicate because the oxo anion or hydroxy anion interacts with silicate in both the first aqueous solution and the first coating layer.

[0030] When a component produced from a ferromagnetic powder composition is heat-treated, a first coating layer and any second coating layer applied on top of the first coating layer react to form a glassy coating layer made of silicates and dopants, wherein particles containing compounds comprising bismuth and oxygen (if present) are dispersed.

[0031] The ferromagnetic powder composition comprises more than one soft magnetic iron-based core particle. The soft magnetic iron-based core particle comprises iron or an iron alloy, or is composed of iron or an iron alloy, wherein the iron alloy comprises at least 90% iron, preferably at least 99% iron, more preferably at least 99.5% iron. The iron alloy may be an alloyed iron Fe-Si having at most 7% by weight, preferably at most 3% by weight, silicon, or another iron alloy selected from the group consisting of Fe-Al, Fe-Si-Al, Fe-Ni, Fe-Co, Fe-Ni-Co, or combinations or mixtures of such alloys. The soft magnetic iron-based core particle may comprise a mixture of particles, such as a mixture of iron particles and iron alloy particles, or a mixture of particles made of two or more iron alloys. Preferably, the soft magnetic iron-based core particle is made of substantially pure iron (i.e., iron with unavoidable impurities). Preferably, at least 80 wt%, more preferably at least 90 wt%, of all core particles have a diameter in the range of 20 μm to 1000 μm as measured according to ISO 4497.

[0032] Within this range, a more specific range may be more suitable depending on the intended use of the part, component, or object produced from the ferromagnetic powder composition. Therefore, for high-frequency applications such as sensors, inductors, and converters, a preferred content of at least 80 wt%, more preferably at least 90 wt%, based on the total weight of the core particles, such as at least 99 wt% of the core particles being in the range of 20 μm-75 μm (200 mesh, corresponding to approximately 50 μm-55 μm D0.05), is preferred. 50 As measured according to ISO 4497. For low- to medium-frequency applications, such as motors, generators, and converters, the core particles preferably comprise at least 80 wt%, more preferably at least 90 wt%, based on the total weight of the core particles, such as at least 99 wt% of the core particles being in the range of 45 μm to 150 μm (100 mesh, corresponding to approximately 95 μm to 100 μm D). 50 ), as measured according to ISO 4497. For low-frequency applications, such as electric motors, the core particles preferably comprise at least 80 wt%, more preferably at least 90 wt%, based on the total weight of the core particles, such as at least 99 wt% of the core particles being in the range of 75 μm-380 μm (40 mesh, corresponding to approximately 180 μm-210 μm D). 50 (e.g., measured according to ISO 4497).

[0033] The soft magnetic iron-based core particles can be spherical or irregularly shaped, with irregularly shaped particles being preferred. The apparent density (AD) can be 2.8 g / cm³. 3 and 4.0 g / cm 3 Between, preferably between 3.1 g / cm³ 3 and 3.7 g / cm 3 between.

[0034] Soft magnetic iron-based core particles can be water-atomized iron powder, gas-atomized iron powder, or sponge-like iron powder. Typically, water-atomized soft magnetic iron-based core particles are irregularly shaped.

[0035] The first coating layer at least partially covers and is in direct contact with the surface of the core particles. Preferably, the first coating layer covers at least 50 wt%, such as at least 75 wt%, of the entire surface of the core particles in the ferromagnetic powder composition. More preferably, the first coating layer covers at least 90 wt%, such as at least 95 wt%, of the entire surface of the core particles in the ferromagnetic powder composition.

[0036] In other words, the first coating layer preferably covers at least 50% of the total surface area of ​​the core particles, such as at least 75%, more preferably at least 90%, such as at least 95%, such as at least 99%.

[0037] Typically, the first and second coating layers (when present) have an average thickness in the range of 20 nm to 100 nm. The typical total thickness of the combined first and second coating layers is approximately 20 nm to 200 nm, with a permeability of approximately 400 to 600. The coating thickness can be estimated based on the permeability, where for a 40-mesh core particle, a maximum relative permeability of approximately 3000 corresponds to zero thickness, and a maximum relative permeability of approximately 700 corresponds to a thickness of approximately 30 nm.

[0038] General formula (K₂O) α (SiO2) β The silicate is potassium silicate or alternatively referred to as K-silicate, K-water glass, potassium water glass, or simply silicate in this document.

[0039] The β / α molar ratio (i.e., the molar ratio of SiO2 to K2O) is in the range of 0.5 to 4.1. Preferably, the molar ratio β / α is in the range of 2.0 to 3.75, and more preferably, the molar ratio β / α is in the range of 2.5 to 3.5.

[0040] Therefore, the molar ratio β / α can be optionally in the range of 2.0 to 4.1.

[0041] The silicate is present in an amount of 0.02 wt% to 1.0 wt%, more preferably 0.05 wt% to 0.5 wt%, based on the total weight of the ferromagnetic powder composition. Preferably, when at least 80 wt% of the core particles based on the total weight of the core particles are 75 μm or larger, the silicate is present in an amount of 0.05 wt% to 0.2 wt%, based on the total weight of the ferromagnetic powder composition, and when at least 80 wt% of the core particles based on the total weight of the core particles are less than 75 μm, the silicate is present in an amount of 0.1 wt% to 0.5 wt%, based on the total weight of the ferromagnetic powder composition. The first coating layer can be applied using an aqueous solution as shown, and it has been found that when the soft magnetic iron-based core particles are contacted with such a solution, substantially all of the silicate and all other components, such as particles (when present) and nanoparticles (when present) containing compounds of bismuth and oxygen, are ultimately incorporated into the first coating layer. Therefore, the content and ratio of the components in the aqueous solution to the soft magnetic iron-based core particles continue to the content and ratio of the components in the first coating layer to the soft magnetic iron-based core particles.

[0042] Particles containing bismuth and oxygen compounds are optional, but preferably included (i.e., contained) in the first coating layer, as they further improve the properties of the glassy coating layer formed by the silicate and dopant during heat treatment. When present, the particles containing bismuth and oxygen compounds are dispersed in the first coating layer, for example, dispersed in silicate. During and after heat treatment, the particles containing bismuth and oxygen compounds react with silicate and are contained within the formed glassy coating layer.

[0043] Particles containing compounds of bismuth and oxygen preferably contain bismuth oxides and hydroxides. Preferably, D, measured according to ISO 13320-1, is... 50 Within the range of 0.5 μm to 2 μm.

[0044] Preferably, the first coating layer contains particles of bismuth and oxygen compounds in an amount of 0.025 wt%-0.3 wt% based on the total weight of the ferromagnetic powder composition, preferably 0.05 wt%-0.25 wt%, more preferably 0.07 wt%-0.22 wt%, such as 0.08 wt%-0.22 wt%, such as 0.08 wt%-0.11 wt%.

[0045] Example 8 shows that these content ranges of particles containing compounds containing bismuth and oxygen yielded good results.

[0046] Currently, a content of 0.08 wt%–0.11 wt% is the optimal range for soft magnetic iron-based core particles with a size of 100 mesh.

[0047] When the soft magnetic iron-based core particles are large, for example, 40 mesh size, the content of bismuth-containing compound particles is preferably at least 0.05 wt%, such as 0.05 wt%-0.10 wt%.

[0048] When the soft magnetic iron-based core particles are small, such as 200 mesh size, the content of bismuth-containing compound particles is preferably at least 0.15 wt%, such as 0.15 wt%-0.30 wt%.

[0049] The compound containing bismuth and oxygen can be selected from the group consisting of bismuth(III) oxide (Bi₂O₃) and bismuth(III) hydroxide (Bi(OH)₃), with Bi(OH)₃ being the preferred compound containing bismuth and oxygen. As shown in Example 9, the presence of Bi₂O₃ or Bi(OH)₃ particles increases the resistivity. Furthermore, as shown in Example 9, the increase in resistivity is greater for Bi(OH)₃ particles than for Bi₂O₃ particles.

[0050] D measured according to ISO 13320-1 50 The median particle size is defined in ISO 13320-1 as a volume-based particle size, i.e., 50% of the particles by volume are smaller than this diameter and 50% of the particles by volume are larger than this diameter.

[0051] Generally, references to ISO standards in this article are equivalent to references to SS-ISO standards, where SS simply indicates that the relevant ISO standard has been adopted as a Swedish standard.

[0052] D measured according to ISO 13320-1 50 This can be determined using, for example, the Mastersizer 3000 from Malvern Instruments.

[0053] The dopant is dissolved in silicate (a) as an oxoanion or a hydroxy anion. The oxoanion or hydroxy anion can be a monoanion or a polyanion, preferably a monoanion to maximize its distribution in the silicate. In addition to the improved distribution, using a monoanion can reduce the risk of increased melting temperature of the glassy coating formed by the first coating layer and any second coating layer applied on top of the first coating layer during heat treatment. Specifically, an increase in melting temperature is expected to be caused by the presence of longer polyanions in the glassy coating layer that compete with polysilicate ions. Such an increase in melting temperature can make it more difficult to obtain a good distribution of the glassy coating layer.

[0054] Dopants that dissolve oxoanions or hydroxyl anions encompass oxoanion dopants or hydroxyl anion dopants. The term dopant covers both: compounds that form oxoanions or hydroxyl anions when dissolved in an aqueous solution of silicates or silicates, and oxoanions or hydroxyl anions themselves. Since the first aqueous solution containing silicates is typically alkaline, a dopant can be a compound that forms oxoanions or hydroxyl anions when dissolved in an alkaline aqueous solution.

[0055] Typically, the dopant content can be 0.5 mol%-30 mol% based on the molar content of K (potassium) in the first coating layer, preferably 1 mol%-30 mol%, more preferably 1 mol%-25 mol%.

[0056] Contact between the soft magnetic iron-based core particles and the first aqueous solution can be achieved, for example, by mixing in a mixer. Contacting the soft magnetic iron-based core particles with the first aqueous solution results in the formation of a first coating layer on the magnetic iron-based core particles, thereby at least partially covering them. In other words, the method according to the third aspect of the present invention produces soft magnetic iron-based core particles coated with the first coating layer, i.e., the ferromagnetic powder composition according to the first aspect of the present invention. The soft magnetic iron-based core particles coated with the first coating layer and optionally also coated with a second coating layer, as described below, may optionally be referred to as coated core particles or coated soft magnetic iron-based core particles.

[0057] Preferably, the first coating layer further comprises nanoparticles having a density of 10 nm to 200 nm as measured according to ISO 13320-1. 50 Alternatively, it may have 6 m as defined in ISO 9277:2022. 2 / g-120 m 2 Specific surface area (SSA) per g.

[0058] As seen in the embodiments (especially Embodiment 1), the inclusion of nanoparticles further enhances the resistivity of the glassy coating formed by the first coating layer and any second coating layer applied on top of the first coating layer. The inclusion of nanoparticles also works well in conjunction with the dopant.

[0059] Nanoparticles (if present) are dispersed in a first coating layer, for example, dispersed in silicate. During and after heat treatment, the nanoparticles are embedded in the formed glassy coating layer.

[0060] The nanoparticles have a density of 10 nm–200 nm as measured according to ISO 13320-1. 50 .

[0061] D measured according to ISO 13320-1 50 The median particle size is defined in ISO 13320-1 as a volume-based particle size, i.e., 50% of the particles by volume are smaller than this diameter and 50% of the particles by volume are larger than this diameter.

[0062] Generally, references to ISO standards in this article are equivalent to references to SS-ISO standards, where SS simply indicates that the relevant ISO standard has been adopted as a Swedish standard.

[0063] D measured according to ISO 13320-1 50 This can be determined using, for example, the Mastersizer 3000 from Malvern Instruments.

[0064] One selectable parameter for determining the size of nanoparticles is specific surface area (SSA) [m²]. 2 / g], which is the surface area of ​​particles per gram of particles.

[0065] Therefore, D10–200 nm as measured according to ISO 13320-1 50 It can be equivalent to 6 m 2 / g-120 m 2 Replace with specific surface area (SSA) within the range of / g.

[0066] The specific surface area (SSA) of nanoparticles is preferably determined using the BET method, which is a method for determining the specific surface area of ​​a solid through gas adsorption.

[0067] More preferably, the SSA of the nanoparticles is preferably determined according to ISO 9277:2022.

[0068] Therefore, D10–200 nm as measured according to ISO 13320-1 50 It can be equivalently represented by 6 m as defined in ISO 9277:2022. 2 / g-120 m 2 Replace it with / g specific surface area (SSA).

[0069] Preferably, the specific surface area (SSA) of the nanoparticles is 10 m². 2 / g-50 m 2 / g, more preferably 10 m 2 / g-30 m 2 / g, most preferably 15 m 2 / g-30 m 2 / g. One example is 18 m 2 / g. As mentioned above, these ranges are preferably determined according to ISO 9277:2022.

[0070] Specific surface area can be measured using the Micromeritics TriStar 3000 gas adsorption instrument, which calculates BET surface area.

[0071] For comparison, if we assume the particles are spherical, the average diameter of the nanoparticles can be calculated from the specific surface area. The equation for calculating the average particle size in nanometers is 6000 / (BET surface area, in m). 2 (g) × (density, in g / cm³) 3 (Calculated). For Y2O3 (density is 5.01 g / cm³), 3 ), respectively 120 m 2 / g、6 m 2 / g、50 m 2 / g、10 m 2 / g and 18 m 2 The specific surface area of ​​ / g produces average diameters of 10 nm, 200 nm, 24 nm, 120 nm and 67 nm, respectively.

[0072] Preferably, the nanoparticles have a density of 10 nm to 100 nm as measured according to ISO 13320-1. 50 Most preferably, the nanoparticles have a density of 20 nm to 100 nm as measured according to ISO 13320-1. 50 .

[0073] The preceding interval corresponds to 12 m 2 / g-120 m 2 / g of SSA, while the subsequent interval corresponds to 12 m 2 / g-60 m 2 / g of SSA.

[0074] D measured according to ISO 13320-1 50 Preferably, the diameter is between 10 nm and 100 nm, wherein 90 wt% of the particles should have a maximum diameter between 1 nm and 500 nm.

[0075] In the example, the nanoparticles typically have a D0 of 10 nm. 50 Furthermore, it has been shown that nanoparticles of this size provide optimal results.

[0076] Alternatively, the nanoparticles may have a diameter of 1 nm to 200 nm, preferably 1 nm to 50 nm, more preferably 5 nm to 50 nm, such as 30 nm to 50 nm or such as 5 nm to 20 nm, such as 10 nm.

[0077] When the method according to the third aspect of the technology proposed herein is executed, it is possible that the provided or obtained nanoparticles agglomerate into aggregates having a diameter greater than 200 nm and / or that the agglomerated nanoparticles have a D-value greater than 200 nm. 50 These aggregates should preferably disintegrate completely or partially in order to obtain the desired Do having 1 nm-200 nm or smaller, as preferred above. 50 The nanoparticles may have a diameter of [specific value], or the number of said nanoparticles may be increased, as well-distributed nanoparticles within the first coating layer are preferred. In cases where the nanoparticles used in this method comprise a large number of aggregates, and when no further disintegration of the nanoparticles is performed, it is preferable to use nanoparticles that contain little or no aggregates and have a lower D [specific value]. 50 Compared to nanoparticles with a diameter of 1 or 2, the mol% of nanoparticles in the first coating layer can preferably be increased.

[0078] Disintegration preferably occurs before or during the preparation of the first aqueous solution, or during contact between the soft magnetic iron-based core particles and the first aqueous solution. As an example, ultrasonic treatment can be used for disintegration.

[0079] The nanoparticles are preferably selected from the group consisting of Y2O3 nanoparticles, ZrO2 nanoparticles, ZnO nanoparticles, Mg(OH)2 nanoparticles, MgO nanoparticles, CaCO3 nanoparticles, Al2O3 nanoparticles, SiO2 nanoparticles and TiO2 nanoparticles, and more preferably, the nanoparticles include or are composed of Y2O3 nanoparticles.

[0080] Nanoparticles may include mixtures of nanoparticles, such as mixtures of two or more of the listed nanoparticles. However, it is currently preferred that only one type of nanoparticle is present, for example, Y2O3 nanoparticles are preferably present in the first coating layer.

[0081] Dopant is effective for many different nanoparticles.

[0082] As seen in Example 8, many different nanoparticles are effective in obtaining improved magnetic and electrical properties of objects made from ferromagnetic powder compositions. Furthermore, Example 8 shows that Y₂O₃ nanoparticles, also known as yttrium oxide nanoparticles and yttrium oxide nanoparticles, provide what is currently considered to be the best magnetic and electrical properties.

[0083] The content of nanoparticles in the first coating layer is preferably 1 mol%-30 mol%, more preferably 1 mol%-20 mol%, based on the molar content of K (potassium) in the first coating layer. These typical molar contents of nanoparticles provide good results, see, for example, Example 8.

[0084] Preferably, the first covering layer comprises: Based on the K content in the first coating layer, ranging from 1 mol% to 25 mol%, more preferably 8 mol% to 22 mol%, and most preferably 10 mol% to 20 mol%, such as 20 mol% Y₂O₃ nanoparticles, or Based on the K content in the first coating layer of 1 mol%-20 mol%, preferably 1 mol%-15 mol%, more preferably 1 mol%-10 mol%, such as 5 mol% ZrO2 nanoparticles, or Based on 1 mol%-20 mol% K content in the first coating layer, preferably 5 mol%-20 mol%, more preferably 10 mol%-20 mol% Mg(OH)2 nanoparticles, or Based on the K content of 1 mol%-20 mol% in the first coating layer, preferably 5 mol%-20 mol%, more preferably 10 mol%-20 mol% of CaCO3 nanoparticles, or Based on ZnO nanoparticles with a K content of 1 mol%-20 mol%, preferably 5 mol%-20 mol%, more preferably 10 mol%-20 mol%, in the first coating layer, or Based on the K content in the first coating layer of 1 mol%-30 mol%, preferably 10 mol%-30 mol%, more preferably 15 mol%-25 mol%, such as 20 mol% MgO nanoparticles, or Based on the K content in the first coating layer of 1 mol%-30 mol%, preferably 10 mol%-30 mol%, more preferably 15 mol%-25 mol%, such as 20 mol% TiO2 nanoparticles, or Based on Al2O3 nanoparticles with a K content of 1 mol%-20 mol%, preferably 5 mol%-15 mol%, and more preferably 10 mol%, in the first coating layer, or ZnO nanoparticles with a K content of 1 mol%-20 mol%, preferably 1 mol%-10 mol%, and more preferably 5 mol% in the first coating layer.

[0085] Example 8 shows that these contents of various nanoparticles yield good results. As mentioned above, different nanoparticles in these ranges can be combined in the first coating layer.

[0086] Preferably, the nanoparticles comprise or are composed of Y2O3 nanoparticles, and the content of nanoparticles in the first coating layer is 10 mol%-20 mol% based on the molar content of K (potassium) in the first coating layer.

[0087] As seen in Example 8, the Y2O3 nanoparticles provide what is currently considered to be the best magnetic and electrical properties.

[0088] For reference, 20 mol% of Y2O3 particles, when included in a first coating layer containing 0.1 wt% of potassium silicate with a β / α molar ratio of 3.4 on 5 kg of soft magnetic iron-based core particles, corresponds to 0.94 g of Y2O3 particles, or 0.0188 wt% based on the weight of the ferromagnetic powder composition.

[0089] Preferably, the dopant contains at least one element from Group 5, such as V (vanadium) or Nb (niobium), or at least one element from Group 6, such as Cr (chromium), W (tungsten) or Mo (molybdenum), or Al (aluminum) or P (phosphorus).

[0090] Preferred Group 5 elements include V (vanadium), Nb (niobium), and Ta (tantalum).

[0091] Preferred Group 6 elements include Cr (chromium), Mo (molybdenum), and W (tungsten).

[0092] Exemplary dopants include V (vanadium), Nb (niobium), Ta (tantalum), Cr (chromium), Mo (molybdenum), W (tungsten), and P (phosphorus). Examples include V (vanadium), Nb (niobium), Ta (tantalum), Cr (chromium), Mo (molybdenum), and W (tungsten). Examples include V (vanadium), Nb (niobium), Cr (chromium), Mo (molybdenum), and W (tungsten).

[0093] It is known that Group 5 and Group 6 elements form oxoanions or hydroxyl anions in alkaline aqueous solutions. Furthermore, Al (aluminum) can dissolve as a hydroxyl anion in strongly alkaline solutions and is therefore used as a dopant. Phosphorus in phosphate form, such as KHPO4, H3PO4, and (NH4)3PO4, can also be used. Nb and tantalum can also form oxoanions and / or hydroxyl anions similar to W, Mo, and W.

[0094] Preferred dopants are those that are readily soluble and stable in silicate solutions. Toxic dopants, such as ions including Cr(VI), are less preferred.

[0095] The dopant is preferably provided to the first coating layer by dissolving a suitable compound containing the dopant (such as, for example, an oxide) in a first aqueous solution in contact with the soft magnetic iron-based core particles. This typically results in the provision of dopant ions in the first aqueous solution.

[0096] Preferred elements for use as dopants include Al, Nb, V, Mo, and Cr. More preferred elements include Al and Nb.

[0097] Vanadium (V) is preferably provided to the first coating layer by dissolving vanadium oxide (V)₂O₅ in a first aqueous solution in contact with the soft magnetic iron-based core particles. In strongly alkaline aqueous solutions such as potassium silicate solutions, vanadium will primarily form (VO₄). 3- Ions (pH>12). This will lead to VO4+. 3- The ions are provided in the first aqueous solution. In a less strongly alkaline environment, vanadium tends to form polyvanadate ions with more than four oxo or hydroxyl groups, such as (VO3). n - It is similar to a polyphosphate chain. Therefore, the size of the vanadate ion can vary depending on the potassium concentration and the pH of the silicate solution.

[0098] It is believed that, in order to maximize the atomic distribution of dopants in the final glassy cladding, dopant ions should preferably not exist as polyanions in the silicate before heat treatment, which theoretically can increase the resistivity of bismuth silicate glass.

[0099] Mo, preferably, is provided to the first coating layer by dissolving molybdenum oxide (VI) MoO3 in a first aqueous solution in contact with the soft magnetic iron-based core particles. This results in molybdate ions (MoO4) similar to tungstate ions. 2- It is provided to the first aqueous solution.

[0100] W, tungsten, is preferably provided to the first coating layer by dissolving tungsten oxide (VI) WO3 in a first aqueous solution in contact with the soft magnetic iron-based core particles. This results in tungstate ions (WO4) similar to vanadate ions. 2- It is provided in the first aqueous solution.

[0101] Al, aluminum, is preferably provided to the first coating layer by dissolving aluminum hydroxide (III) Al(OH)3 in a first aqueous solution in contact with the soft magnetic iron-based core particles. This results in Al(OH)4 - The ions are provided in the first aqueous solution.

[0102] Preferably: The dopant contains V, and the dopant content in the first coating layer is 1 mol%-30 mol%, preferably 5 mol%-20 mol%, more preferably 5 mol%-15 mol%, based on the molar content of K (potassium) in the first coating layer. The dopant contains Nb, and the dopant content in the first coating layer is 1 mol%-30 mol%, preferably 5 mol%-20 mol%, more preferably 5 mol%-15 mol%, based on the molar content of K in the first coating layer. The dopant contains Cr, and the dopant content in the first coating layer is 1 mol%-30 mol%, preferably 5 mol%-20 mol%, more preferably 5 mol%-15 mol%, based on the molar content of K in the first coating layer. The dopant contains Mo, and the dopant content in the first coating layer is 1 mol%-30 mol%, preferably 5 mol%-20 mol%, more preferably 5 mol%-15 mol%, based on the molar content of K in the first coating layer. The dopant contains W, and the dopant content in the first coating layer is 1 mol%-30 mol%, preferably 5 mol%-20 mol%, more preferably 5 mol%-15 mol%, based on the molar content of K in the first coating layer. The dopant comprises Al, and the dopant content in the first coating layer is 0.5 mol%-5 mol% based on the molar content of K in the first coating layer, preferably 1 mol%-3 mol%, more preferably 1.71 mol%-2.58 mol%, and / or, The dopant contains P, and the dopant content in the first coating layer is 1 mol%-30 mol%, preferably 5 mol%-20 mol%, more preferably 5 mol%-15 mol%, based on the molar content of K in the first coating layer.

[0103] More preferably, the dopant contains V, and the content of the dopant in the first coating layer is 1 mol%-30 mol%, preferably 5 mol%-20 mol%, and more preferably 10 mol%-15 mol%, based on the molar content of K in the first coating layer.

[0104] As shown in Examples 1 and 3, for a given coercivity level and coating density / thickness level, 10 mol%–15 mol% V dopant produces a higher resistivity. This is believed to be due to a better distribution of the glassy coating formed during heat treatment by the first coating layer and any second coating layer on top of the first coating layer.

[0105] Optionally, the dopant comprises Al, and the dopant content in the first coating layer is 0.5 mol%-5 mol% based on the molar content of potassium K in the first coating layer, preferably 1 mol%-3 mol%, more preferably 1.5 mol%-2.7 mol%, such as 1.71 mol%-2.58 mol%.

[0106] As seen in Example 7, providing Al dopant to the first coating layer at concentrations within this range allows for higher heat treatment temperatures, resulting in lower coercivity while maintaining good resistivity. The effect is less than that of V, but Al has a smaller environmental impact and presents less health risk.

[0107] Preferably, the ferromagnetic powder composition further comprises: (iii) a second coating layer that at least partially covers the surface of the core particle and / or the first coating layer, the second coating layer comprising: a. At least one organometallic compound having the following general formula R1[(R1) x (R2) y (M)] n O n-1 R1 (I) or R2[M(OH) 2(n+1) ] (n+1) O (n) R2 (II) Where M is selected from the group consisting of Si, Ti, Al, and Zr; O is oxygen; R1 is a hydrolyzable group; R2 is an organic moiety, and at least one R2 contains at least one nitrogen-containing group, preferably an amino group; where n is the number of repeating units, which is an integer between 1 and 20; where x is 0 or 1; and where y is 1 or 2, and x+y is 2. The content of the at least one organometallic compound is from 0.05 wt% to 0.40 wt% based on the total weight of the ferromagnetic powder composition, preferably from 0.10 wt% to 0.30 wt%.

[0108] The second coating further improves the electrical, structural, and magnetic properties of components or parts made from the ferromagnetic powder composition. Without being bound by theory, it appears that the second coating can provide lubrication and additional silicon and carbon, which facilitates the formation of a glassy coating during heat treatment.

[0109] R1 can be an alkoxy group having fewer than 4, preferably fewer than 3, carbon atoms. R2 is an organic part, meaning that the R2- group contains an organic part or portion. R2 preferably includes 1-6, more preferably 1-3 carbon atoms. R2 may also include one or more heteroatoms selected from the group consisting of N, O, S, and P. The R2 group can be straight-chain, branched, cyclic, or aromatic. R2 can include one or more of the following functional groups: amine, diamine, amide, imide, epoxy, hydroxyl, ethylene oxide, urea, urethane, isocyanate, acrylate, glyceryl acrylate, benzyl-amino, vinyl-benzyl-amino. The R2 group can be varied between any of the mentioned functional groups and hydrophobic alkyl groups having repeating units.

[0110] When n=1, the organometallic compound is a monomer (Formula I) or a dimer (Formula II). If the organometallic compound is a monomer, it may be selected from the group consisting of trialkoxysilanes and dialkoxysilanes, titanates, aluminates, or zirconates. Therefore, the monomers of organometallic compounds can be selected from 3-aminopropyl-trimethoxysilane, 3-aminopropyl-triethoxysilane, 3-aminopropyl-methyl-diethoxysilane, N-aminoethyl-3-aminopropyl / ethyl / methyl-alkoxysilane such as N-aminoethyl-3-aminopropyl-trimethoxysilane and N-aminoethyl-3-aminopropyl-methyl-diethoxysilane, 1,7-bis(triethoxysilyl)-4-azaheptane, triaminofunctional propyl-trimethoxysilane, 3-ureopropyl-triethoxysilane, 3-isocyanopropyl-triethoxysilane, tris(3-trimethoxysilylpropyl)-isocyanurate, O-(propoxy)-N-(triethoxysilylpropyl)-carbamate, 1-aminomethyl-triethoxysilane, 1-aminoethyl-methyl-diethoxysilane, or mixtures thereof.

[0111] When n=2-20, the organometallic compound is an oligomer. The oligomer of the organometallic compound can be selected from alkoxy-terminated alkyl-alkoxy oligomers of silanes, titanates, aluminates, or zirconates. Therefore, the oligomer of the organometallic compound can be selected from methoxy, ethoxy, or acetoxy-terminated amino-silsesquioxanes, amino-siloxanes, oligomeric 3-aminopropyl-methoxy-silanes, 3-aminopropyl / propyl-alkoxy-silanes, N-aminoethyl-3-aminopropyl-alkoxy-silanes, or N-aminoethyl-3-aminopropyl / methyl-alkoxy-silanes, or mixtures thereof.

[0112] Examples of suitable organometallic compounds include, in particular, Dynasylan from Evonik Industries AG. ® 1146 and Dynasylan ® SIVO 203, or XIAMETER™ OFS-6020 silane from Dow Chemical Company.

[0113] Organometallic compounds also include aqueous amino or multifunctional silane systems, such as the corresponding Dynasylan supplied by Evonikindustries AG. ® HYDROSIL products. In these products, the hydrolyzable alkoxy groups are almost entirely replaced by hydroxyl groups, i.e., according to formula (II), while the functional groups are similar, such as combinations of hydrophobic alkyl groups with aminoalkyl groups or diaminoalkyl groups. Examples include Dynasylan. ® HYDROSIL 2627, 2776 and 1151 silane systems. Examples of such compounds can be 1,3-bis(3-aminopropyl)disiloxane-1,1,3,3-tetraol or (3-aminopropyl)({[(propyl)dihydroxysilyl]oxy})silanediol.

[0114] It is also anticipated that the product contains bismuth and oxygen and has a Do in the range of 0.1 μm to 10 μm as measured according to ISO 13320-1. 50 Some or all of the particles of the compound are optionally contained in a first coating layer, or alternatively provided in a second coating layer.

[0115] Example 8 shows that various organometallic compounds in the second coating layer can be successfully used in ferromagnetic powder compositions.

[0116] Preferably, at least one organometallic compound has general formula (I). Alternatively, at least one organometallic compound has general formula (II).

[0117] The ferromagnetic powder composition preferably further comprises: (iv) Lubricant, preferably a particulate lubricant.

[0118] Incorporating a lubricant into the ferromagnetic powder composition improves compaction and results in increased density and strength of objects manufactured from the ferromagnetic powder composition. The lubricant can be selected from the group consisting of primary and secondary fatty acid amides, trans-amides (bisamides), or fatty acid amides or alcohols. The lubricating portion of the lubricant can be a saturated or unsaturated chain containing between 12 and 22 carbon atoms. The lubricant can preferably be selected from stearamide, betaine alcohol, erucamide, stearyl erucamide, erucic acid-stearamide, betaine alcohol, erucic acid alcohol, ethylene-bisstearamide (i.e., EBS or amide wax). Preferably, the lubricant is an amide wax. A mixture of stearamide or betaine alcohol and amide wax is also preferred. One example is 0.1 wt% stearamide combined with 0.3 wt% amide wax.

[0119] The lubricant can be present in an amount of 0.05 wt% to 0.80 wt%, preferably 0.20 wt% to 0.40 wt%, of the ferromagnetic powder composition. Adding a very small amount of lubricant (0.05 wt% to 0.20 wt%) to the composition can promote compaction and demolding by using die wall lubrication (DWL). A small amount of internal lubricant will improve compaction density, permeability, and mechanical strength.

[0120] The second aspect of the technology presented herein relates to a ferromagnetic powder composition comprising: According to the first aspect of the technology presented herein, a ferromagnetic powder composition, and Other ferromagnetic powder compositions, The additional ferromagnetic powder composition contains soft magnetic iron-based core particles that are different from the soft magnetic iron-based core particles of the ferromagnetic powder composition, and Preferably, the soft magnetic iron-based core particles of the additional ferromagnetic powder composition comprise or are composed of an iron alloy having a higher resistivity and / or hardness than the soft magnetic iron-based core particles of the ferromagnetic powder composition.

[0121] This is advantageous because it allows for further tuning of the magnetic and electrical properties of components or parts made from the ferromagnetic powder composition. Preferably, if the soft magnetic iron-based core particles of the additional ferromagnetic powder composition comprise or are composed of an iron alloy having a higher resistivity than the soft magnetic iron-based core particles of the ferromagnetic powder composition, the ferromagnetic powder mixture exhibits even lower core losses at higher frequencies. The soft magnetic iron-based core particles of the additional ferromagnetic powder composition are also generally harder and thus provide further improvements in properties.

[0122] The soft magnetic iron-based core particles of the additional ferromagnetic powder composition preferably comprise or consist of an iron alloy, said iron alloy being selected from the group consisting of FeSi, FeAl, FeSiAl, FeNi, FeCo, and FeNiCo, or combinations or mixtures of such alloys. Particularly preferred are FeSi (typically 3 wt%-6.8 wt% Si) and FeSiAl (also known as Sendust, typically 9 wt% Si and 6 wt% Al, or alternatively 3.5 wt% Si and 3 wt% Al).

[0123] Based on the weight of the ferromagnetic powder mixture, the content of the additional ferromagnetic powder composition can be up to 60 wt%, such as 30 wt%-60 wt%, but typically 10 wt%-50 wt%, such as 20 wt%-40 wt%, such as 20 wt%-30 wt%, wherein the ferromagnetic powder composition according to the first aspect of the technology presented herein constitutes the remainder. Furthermore, for mid-frequency or low-frequency applications, the content of the additional ferromagnetic powder composition is preferably low or absent so as not to reduce density, magnetic induction, and permeability. Conversely, for high-frequency applications, the content of the additional ferromagnetic powder composition can be increased to up to 90 wt%.

[0124] In the powder mixture, the soft magnetic iron-based core particles of the ferromagnetic powder composition preferably contain substantially pure iron (i.e., iron with unavoidable impurities) or consist of said substantially pure iron.

[0125] Preferably, the additional ferromagnetic powder composition also includes a coating or surface treatment on the soft magnetic iron-based core particles therein. The coating or surface treatment preferably includes a first coating as described above, and optionally also includes a second coating as described above. However, typically, when an iron alloy is included, the soft magnetic iron-based core particles of the additional ferromagnetic powder composition can be coated or treated with another coating, such as by treatment with phosphoric acid diluted in acetone.

[0126] The soft magnetic iron-based core particles of the additional ferromagnetic powder composition preferably have the same particle size as the soft magnetic iron-based core particles of the ferromagnetic powder composition according to the first aspect of the art presented herein, as further described above.

[0127] The method according to the third aspect of the technology proposed in this paper may also include one or more of the following steps: (iii) Dry-coated soft magnetic iron-based core particles, and / or (iv) Contacting the coated soft magnetic iron-based core particles with at least one organometallic compound as described above, and / or (v) Mix the coated soft magnetic iron-based core particles with the lubricant described above.

[0128] Step (iii) is preferably performed after step (ii). Step (iii) can be performed by heating the soft magnetic iron-based core particles while stirring.

[0129] Step (iv) is preferably performed after step (ii) or step (iii) and before step (v).

[0130] Step (v) is preferably performed after steps (iii) and (iv).

[0131] A fourth aspect of the technology presented herein relates to a method for manufacturing an object from a ferromagnetic powder composition according to a first aspect of the technology presented herein or a ferromagnetic powder mixture according to a second aspect of the technology presented herein, the method comprising the following steps: (i) A ferromagnetic powder composition according to the first aspect of the technology presented herein or a ferromagnetic powder mixture according to the second aspect of the technology presented herein is compacted in a mold at a compaction pressure in the range of 300 MPa-2000 MPa, preferably 400 MPa-1200 MPa, to obtain a compacted component, and (ii) The compacted component is heat-treated in a non-reducing atmosphere at a temperature in the range of 300°C-800°C, preferably 400°C-750°C, more preferably 600°C-700°C, to obtain the object, wherein the non-reducing atmosphere preferably contains 0 wt%-22 wt%, more preferably 0.5 wt% to 2 wt% oxygen (O2).

[0132] Compaction can be cold mold compaction, warm mold compaction, or high-speed compaction, preferably using controlled mold temperature compaction (50°C-120°C) of unheated powder. During compaction, the coated soft magnetic iron-based core particles are pressed together and deformed, thereby adhering to each other and forming a compacted part. During heat treatment, particles containing bismuth and oxygen compounds, together with the nanoparticles and silicates in the first coating layer and the amino and / or alkyl groups of the organometallic compounds in the second coating layer, form a uniformly distributed bismuth silicate glass on the surface of the soft magnetic iron-based core particles. This provides the desired resistivity between the individual particles of the compacted and heat-treated ferromagnetic powder composition in the finished object. In addition, heat treatment relieves the stress formed during compaction.

[0133] The heat treatment process can be carried out in a vacuum atmosphere, a non-reducing atmosphere, an inert atmosphere, or a weakly oxidizing atmosphere, such as in nitrogen with 0.01 wt% to 3 wt% oxygen. In one embodiment, a substantially pure nitrogen atmosphere is used as the non-reducing atmosphere. In one embodiment, 0 wt% to 22 wt% oxygen is added, preferably 0.5 wt% to 2 wt% oxygen. Higher temperatures above 680°C to 700°C may require lower oxygen levels, such as 500 ppm to 3000 ppm (0.05 wt% to 0.3 wt%). Typically, oxygen levels may be higher during initial heating (e.g., delubrication). Optionally, the heat treatment is carried out in an inert atmosphere and then rapidly exposed to an oxidizing atmosphere, such as 0.5 wt% to 22 wt% oxygen / nitrogen mixtures or vapor / nitrogen mixtures, to build a surface shell with higher strength and / or corrosion resistance. In one embodiment, the temperature can be up to 800°C. Heat-treating compacted parts in the temperature range of 300°C to 800°C means exposing the temperature-compacted parts to temperatures in the range of 300°C to 800°C. This is typically done for a duration sufficient to heat the compacted parts to the temperature range of 300°C to 800°C, such as, for example, 20 to 120 minutes.

[0134] Typically, the heat treatment is carried out in three stages: a delubrication stage at approximately 300°C–400°C, during which the compacted part is heated to a curing stage; a curing stage at approximately 350°C–450°C (first temperature and first time), in which the first coating layer cures, resulting in the formation of an electrically insulating glassy coating layer (silicate and any present silane polymerized to form silicate glass) from the first and second coating layers (if present); and a relaxation stage at 600°C–700°C (second temperature and second time), in which the glassy coating layer flows out to cover the core particles and releases the stress from compaction. The temperature range of 300°C–800°C given for step (ii) above corresponds to this final (second) temperature. The first and second time periods can each typically be 0–60 minutes, such as 1 minute–60 minutes.

[0135] The compacted component is further preferably heat-treated at a temperature below the glass crystallization temperature of the first cladding layer. This is because the crystallization of silicates in the cladding layer may reduce the resistivity and mechanical strength of both the silicates and the first cladding layer. Furthermore, the crystallization of silicates in the first cladding layer may lead to cracks in the glassy cladding layer formed by the first and second cladding layers during heat treatment.

[0136] The heat treatment may include a delubrication stage, wherein the temperature during the delubrication stage may be between 400°C and 500°C, such as 420°C-480°C, or 430°C-470°C. The atmosphere in the delubrication stage may be an inert atmosphere, such as N2(g) atmosphere.

[0137] Preferably, step (ii) includes heat-treating the compacted component at a (second) temperature of at least 650°C, more preferably at least 670°C, to substantially or completely eliminate stress in the compacted component. The temperature at which the maximum stress relief occurs in the compacted component is referred to as the maximum relaxation temperature.

[0138] Therefore, preferably, step (ii) includes heat treatment of the compacted component at a (second) temperature of 670°C-700°C, preferably 680°C-700°C.

[0139] For heat treatment at a higher second temperature, such as between 700°C and 750°C, or between 750°C and at most 800°C, it is preferable to use a thicker first coating layer, i.e., a higher wt% such as 0.25 wt% silicate, because such a thicker coating layer provides acceptable residual resistivity while having the potential to provide even better aging properties. This also applies to ferromagnetic powder mixtures containing harder or alloyed particles that benefit from treatment at these higher second temperatures, as this allows for a higher degree of relaxation of relatively small plastic deformation during compaction. In particular, finer powders, such as 200-300 mesh, can advantageously be coated with a thicker first coating layer because the resulting lower permeability is generally acceptable for the type of passive components that typically use these finer powders.

[0140] As seen in Example 1, the inclusion of dopants allows for these high thermal processing step temperatures and correspondingly low coercivity, while maintaining acceptable resistivity and therefore acceptable core loss.

[0141] Heat treatment can also include an initial pre-oxidation step, such as 2 h to 18 h, lasting between 200 °C and 250 °C in ambient air for 1 h to 30 h. This improves resistivity.

[0142] Specifically, heat treatment step (ii) may include a pre-oxidation step, followed by delubrication in an inert atmosphere (e.g., nitrogen) at 400-500°C, and then curing and stress relaxation treatment in oxygen at 5000 ppm to 15000 ppm between 600-700°C. This improves mechanical strength (TRS) without significantly sacrificing magnetic properties such as resistivity, coercivity, and core loss.

[0143] The corresponding fifth and sixth aspects of the technology proposed herein relate to objects comprising a compacted ferromagnetic powder composition according to the first aspect of the technology proposed herein or a compacted ferromagnetic powder mixture according to the second aspect of the technology proposed herein, and objects obtained by a method according to the fourth aspect of the technology proposed herein.

[0144] The object can be optionally referred to as a component or assembly. The object can be selected as a group of soft magnetic components, such as sensors, inductors, converters, transformers, motors, and generators.

[0145] Example In the following embodiments, according to various implementations of the method of the third aspect of the art proposed herein, various ferromagnetic powder compositions comprising soft magnetic iron-based core particles are produced by coating soft magnetic iron-based core particles with various first and second coating layers, according to the first aspect of the art proposed herein. The ferromagnetic powder compositions are then used to produce test components or test objects, which are then compacted and heat-treated according to various implementations of the method of the fourth aspect of the art proposed herein. Finally, relevant properties of the finished test components, such as resistivity Res and permeability μ-max, are investigated.

[0146] More specifically, the test components used in the embodiments are manufactured in the following steps: Step 1: Mix the soft magnetic iron-based core particles with approximately 0.11 wt% (also tested at 0.165 wt% and 0.275 wt%) of the general formula (K₂O) at a concentration (based on dry matter content). α (SiO2) β An aqueous solution of silicate (potassium silicate K12, Sibelco Nordic Ab, β / α molar ratio of approximately 3.35, solids content 35 wt%) was mixed (10 min) to form a first coating layer on the core particles. Unless otherwise specified, 0.08 wt% (0.11 wt% and 0.205 wt%) of particles containing bismuth and oxygen, particularly Bi(OH)3, were also included in the aqueous solution.

[0147] Unless otherwise specified, when nanoparticles are included in the first coating layer, these nanoparticles are Y2O3 particles (nominally 10 nm) at a K content of 20 mol%.

[0148] The aqueous solution also contains one or more other compounds or additives of interest, as specified for each sample. After initial mixing, the core particles were dried while being stirred at 60°C for 1 h, followed by further drying at 120°C without stirring.

[0149] Step 2: Unless otherwise specified, the mixture from Step 1 is mixed with silane (2.0 g of oligomeric diaminofunctional silane Dynasylan® 1146 from Evonik Industries AG) and 1 g of H2O (corresponding to 2 g silane / kg of core particles coated with the first coating layer) for 5 min to form a second coating layer, and the resulting mixture is dried at 50°C for 2 h to produce a finished ferromagnetic powder composition containing coated soft magnetic iron-based core particles.

[0150] Step 3. Add a lubricant (0.4 wt% amide wax, unless otherwise specified) to the ferromagnetic powder composition to facilitate the production of the test part, and then mold and compact the ferromagnetic powder composition (800 MPa and mold temperature of 100°C) into the test part, and heat treat the test part as detailed for each sample to release the stress from compaction to form the finished test part.

[0151] Unless otherwise stated, the soft magnetic iron-based core particles have a size of 100 mesh and a density of 3.32 g / cm³. 3 The apparent density of water-atomized annealed iron powder.

[0152] The heat treatment was performed in a preheating furnace in three stages. These three stages included: a delubrication stage at approximately 300°C–400°C, during which the compacted part was heated toward a curing stage; a curing stage at approximately 350°C–450°C (for each sample, a first time and a first temperature were given), in which the first and second coating layers were cured to induce the formation of an electrically insulating silicate glass from the first and second coating layers; and a relaxation stage at 600°C–700°C (for each sample, a second time and a second temperature were given), in which the stress from compaction was released and an improved coverage of the glassy coating layer was obtained. Unless otherwise specified, the oxygen partial pressure during the heat treatment was 15,000 ppm (1.5 wt% oxygen in nitrogen).

[0153] The finished test component (OD55 / ID45 / H5 mm magnetic square toroidal coil) was subjected to testing to specifically determine: Resistivity (Res) – How a material resists electric current [μ] [m] Measurements were taken using a 4-point probe method, with a distance of 20 mm between the measurement points.

[0154] Coercivity at 10 kA / m* (H c [A / m] Maximum permeability* (µ-max) – The maximum value of the ratio between the magnetizations a material acquires in response to an applied magnetic field [unitless].

[0155] Total core loss* (at 1T / 1kHz) – Total core loss of the test component [W / kg] obtained for a given inductance and frequency.

[0156] *To measure magnetic properties, a square toroidal coil was wound with resin-coated copper wire (0.63 mm in diameter) consisting of 100 drive turns and 100 induction turns, and measurements were taken using a Brockhaus MPG 200D. References: IEC 60404-4 (DC measurement) and IEC 60404-6 (AC measurement).

[0157] Further measurements include: Square toroidal coil density (d) – Density of the square toroidal coil test component [g / cm³] 3 ].

[0158] TRS – Transverse breaking strength [MPa] on a bar having dimensions of 30 mm × 12 mm × 6 mm, according to SS-EN ISO 3325:2000.

[0159] AD – Apparent density according to ISO standard 3923-1:2018, is measured as the ratio between the dry mass and apparent volume of a powder sample [g / cm³]. 3 ].

[0160] FLOW – Hall flow rate [seconds] according to SS-EN ISO 4490:2018.

[0161] GS – Green strength, which is measured as TRS but on the test piece before heat treatment [MPa].

[0162] Example 1: Initial experiments with and without nanoparticles and dopants Example 1 tested the effect of adding dopants to a first coating layer containing silicate particles and bismuth and oxygen-containing compounds. To further explore this, nanoparticles were also added to the first coating layer.

[0163] Table 1A: Dopant-free or Nanoparticle-free The results in Table 1 illustrate the problems encountered when heat-treated at higher temperatures. However, when heat-treated at temperatures up to 650°C, the sample part exhibited 2158 μm. The resistivity of μm, after heat treatment at a higher temperature of 670℃, is reduced to approximately 1 / 86, resulting in a resistivity of 25 μm. Such a low resistivity is unacceptable for almost all applications.

[0164] Table 1B: Doped The results in Table 1B indicate that the resistivity of the V dopant will increase to 5649 μm in the sample heat-treated at 650 °C. m, which is approximately 2.6 times the resistivity of sample 1-1. More importantly, the resistivity after the higher temperature heat treatment at 670°C is now 309 μm. m is greater than 12 times the resistivity of sample 1-1 and only about 1 / 18 times the resistivity of sample 1-2 at the lower temperature of 650 °C. Therefore, the addition of V dopant affects the thermal stability of the coating layer on the core particle.

[0165] Table 1C: Products with nanoparticles The results in Table 1C indicate that adding nanoparticles to the first coating layer increased the resistivity (14841 μm in samples 1-3 at 650 °C). m is 2158 μ in sample 1-1 at 650℃. (Approximately 6.9 times that of m). When heat-treated at a higher temperature of 670 °C, the resistivity is 1758 μm. m is approximately 1 / 8.4 times the resistivity at lower temperatures. Comparing Tables 1A-1C, it is evident that dopants can have a greater impact on thermal stability, while nanoparticles can have a greater impact on general resistivity levels.

[0166] Table 1D: Dopants and Nanoparticles The results in Table 1D indicate that the nanoparticles and dopant together provide high resistivity at both lower and higher heat treatment temperatures. Furthermore, the results indicate that the dopant provides a higher proportion of resistivity when higher temperatures are used. As an example, the resistivity after heat treatment at 670 °C with 10 mol% V dopant is 9345 μm. m is approximately 5.3 times the resistivity of samples 1-3 at the same temperature.

[0167] Table 1E: Higher Silicate Concentrations and Other Temperatures Table 1E shows the results obtained for higher concentrations of silicate (i.e., thicker first coating layers). Similar to Table 1D, the results show that the addition of dopant also provides a higher proportion of low-temperature processing resistivity when using temperatures of 680°C or even higher.

[0168] In summary, these results demonstrate that, for a given level of coercivity and coating density / thickness, adding a single dopant or preferably adding a dopant together with nanoparticles provides better thermal stability and higher resistivity.

[0169] Based on these results, it was decided to use a ferromagnetic powder composition in which the first coating layer contains 20 mol% Y2O3 nanoparticles and the silicate concentration is 0.11 wt%, as a general reference for further evaluating the role of the dopant in the following examples.

[0170] Example 2: Adding V dopant to the first coating layer ensures that it retains its properties even after elevated temperature heat treatment. Acceptable resistivity.

[0171] Example 2 further tested the effect of adding a V dopant (in the form of V₂O₅) to the silicate aqueous solution in step 1 when producing the coated soft magnetic iron-based core particles in step 2. All samples also contained 20 mol% (molar weight based on K) of Y₂O₃ nanoparticles (nominal 10 nm) and 0.12 wt% of bismuth hydroxide (Bi(OH₃)) in the first coating layer.

[0172] Table 2: Addition of V dopant As can be seen from the results, the gradually increasing maximum temperature during the heat treatment steps provided the samples with a gradually decreasing coercivity. This also applies to samples in which V dopant has been added. However, and compared to the reference 1B sample, these subsequent samples maintained an acceptable resistivity even at the highest maximum temperature of 700 °C. Furthermore, the results show that the resistivity increases with increasing dopant content for each heat treatment. Therefore, adding preferably at least 5 mol%, more preferably 10 mol%, or even more preferably 15 mol% V dopant to the solution used to obtain the first coating layer provides that parts manufactured from the ferromagnetic powder composition can be heat-treated at higher maximum temperatures, such as 680 °C and 700 °C, to obtain coercivity values ​​in the range of 132 to 134, while maintaining resistivity values ​​in the range of 1889 to 6214.

[0173] The consistently lower coercivity values ​​obtained with higher amounts of V point to smaller stresses introduced into the coated soft magnetic iron-based core particles. Not wanting to be bound by theory, one possible mechanism is the addition of a V₂O₅ compound to the solution used to obtain the first coating layer, and the subsequent speculation that VO₄ is present in the first coating layer. 3-Ions provide a more thermally stable first coating layer that is less prone to cracking during heat treatment. Improved thermal stability can have various causes. Without being bound by theory, dopants can i) enhance the resistivity of bismuth silicate glasses. Higher resistivity allows for higher relaxation temperatures, which reduces the viscosity of the formed glass, thus promoting improved coverage of the particle surface. Dopants can also ii) lower the glass-forming temperature; and / or iii) lower the viscosity of the glass, which in turn promotes glass distribution and particle coverage; and / or iv) induce smaller volume changes during heat treatment or cooling processes, resulting in less crack formation. Cracks expose the soft magnetic iron-based core particles to oxidation, which causes a relative increase in coercivity during heat treatment and also leads to aging during use in applications involving elevated temperatures.

[0174] The distribution of the first coating layer was further promoted by the nanoparticles, which are believed to play a role in preventing cracks from forming during the drying process of the first coating layer.

[0175] Regardless of the mechanism, the results demonstrate the advantages of including V dopant in the first coating layer.

[0176] Example 3: Further experiments using different dopants Further experiments were conducted to determine whether the dopant used in Example 2 could be replaced by other dopants, while providing the same or similar improvements to the properties of the test components. The experimental parameters and results are presented in Table 3.

[0177] Table 3: Other Dopants As can be seen from the table, both Mo (MoO3) and Al (Al(OH)3) dopants offer higher resistivity than the reference at heat treatments of 450 °C / 700 °C. Therefore, similar to V, these dopants allow for heat treatment at higher temperatures to achieve lower coercivity values ​​while maintaining acceptable resistivity values. Compared to the reference at 450 °C / 680 °C, W offers similar but lower resistivity, but retains more of its initial resistivity (6% compared to 5% of the reference). It should also be noted that at both highest temperatures, all samples with dopants exhibit a higher percentage of residual resistivity than the reference.

[0178] Example 4: Different amounts of nanoparticles Further experiments were conducted to investigate the results obtained using dopants with varying amounts of Y₂O₃ nanoparticles. The experimental parameters and results are presented in Table 4.

[0179] Table 4: Nanoparticles with different amounts As can be seen from the table, the dopant is effective for different amounts of nanoparticles.

[0180] Example 5: The effect of thermal aging Further experiments were conducted to determine the effect of thermal aging on the properties of the test parts. As detailed in Table 5A below, test parts manufactured from powders produced by heat treatment at 420°C / 640°C, 450°C / 680°C, and 450°C / 700°C were further maintained at 260°C for 5 days.

[0181] Table 5A: Effects of Thermal Aging As shown in the table, the samples containing V dopants exhibit better aging properties and higher resistivity values.

[0182] Further XRD experiments were performed to examine the ratio of Fe-oxides to Fe on the surface of the powder particles, as shown in Table 5B below. Quantitative analysis of the crystalline phase was performed using Rietveld analysis with Highscore Plus software from Malvern Panalytical. The samples analyzed were flat surfaces of compacted test bars after different heat treatments.

[0183] Table 5B: XRD results of thermal aging As shown in the table, the sample without dopant has a higher FeO content than the sample with dopant. x FeO with a higher Fe ratio x / Fe ratio. Therefore, due to the improved coverage of the glassy coating, a low ratio contributes to the improved aging resistance of heat-treated parts. This applies to all dopants tested.

[0184] Example 6: Further experiments with an increased amount of silicate in the first coating layer Further experiments were conducted to evaluate the effects of the dopant in the first coating layer and the further increase in silicate content. The experimental parameters and results are presented in Table 6 below.

[0185] Table 6: The role of silicate content in the first coating layer As shown in the table, the sample without dopant has a higher FeO content than the sample with dopant. x FeO with a higher Fe ratio x / Fe ratio. Therefore, due to the improved coverage of the glassy coating, a low ratio contributes to the improved aging resistance of heat-treated parts. This applies to all dopants tested.

[0186] Example 6: Further experiments with an increased amount of silicate in the first coating layer Further experiments were conducted to evaluate the effects of the dopant in the first coating layer and the further increase in silicate content. The experimental parameters and results are presented in Table 6 below.

[0187] Table 6: The role of silicate content in the first coating layer As can be seen from the table, higher concentrations of silicates provide generally increased resistivity at the cost of lower μ-max.

[0188] Example 7: Further experiments using Al(OH)3 as a dopant Aluminum, such as aluminum derived from Al(OH)3, is an interesting dopant because it has a smaller environmental impact and presents less health risk than V2O5. Therefore, further experiments were conducted to evaluate the effects of the dopant in the first coating layer and the increased amount of silicate. For these experiments, a silicate solution with a higher β / α ratio (3.82) was used to compensate for the decrease in the β / α ratio when Al(OH)3 was dissolved with the aid of additional KOH. The experimental parameters and results are presented in Table 7 below.

[0189] Table 7: Further experiments using Al(OH)3 As can be seen from the table, Al dopant provides better resistivity than the reference resistivity at higher temperatures and higher silicate concentrations. At lower silicate concentrations, Al dopant provides lower but comparable resistivity to the reference resistivity.

[0190] Example 8: Changes in the composition of the undoped agent Further experiments were conducted to evaluate changes in other components of the first coating layer in the absence of dopant. Heat treatments were performed at 450°C / 650°C (30 min / 30 min). The results are shown in Table 8 below: Table 8: Changes in undoped composition As can be seen from the results above, the undoped composition of ferromagnetic powder compositions can vary widely.

[0191] Example 9: Schematic cross-sectional view of the particles of the ferromagnetic powder composition Based on the embodiments described above, a highly schematic cross-sectional view of a single particle 10 of a ferromagnetic powder composition according to an embodiment of the first aspect of the technology presented herein is shown. Particle 10 comprises a soft magnetic iron-based core particle 11 covered by a first coating layer 12 containing silicate. A second coating layer 13 is also shown, and the second coating layer 13 comprises a metal-organic compound. Particles (one of which is designated as reference numeral 14) of a compound containing bismuth and oxygen and having an approximate diameter of about 1 μm are shown dispersed within the first coating layer 12. Additionally, nanoparticles (one of which is designated as reference numeral 15) having an approximate diameter of about 10 nm to 200 nm are also shown dispersed within the first coating layer 12. Finally, as specified by reference numeral 16, a dopant is schematically shown dissolved in the silicate of the first coating layer 11.

[0192] Figure 1 The particles are shown prior to heat treatment, i.e., before the ferromagnetic powder is compacted and heat-treated to manufacture an object according to the method of the fourth aspect of the art presented herein. During heat treatment, the particles 14 containing bismuth and oxygen compounds in the first coating layer 12, together with nanoparticles 15 and silicates and their dissolved dopants 16, and the amino and / or alkyl groups of the organometallic compounds in the second coating layer 13, are considered to form a uniformly distributed glassy coating (bismuth silicate glass) that provides resistivity and improved mechanical strength between the individual particles of the compacted and heat-treated ferromagnetic powder composition.

[0193] although Figure 1 Particles 14 containing a bismuth and oxygen compound are shown to be present in the first coating layer 12, but it is contemplated that the particles 14 containing the bismuth and oxygen compound may be additionally dispersed within the second coating layer 13 or distributed between the first and second coating layers.

[0194] Furthermore, despite Figure 1 A first coating layer 12 and a second coating layer 13 are shown that completely cover the soft magnetic iron-based core particles 11, but one or both of these coating layers may optionally only partially cover the soft magnetic iron-based core particles 11.

[0195] Example 10: Adding alloyed soft magnetic powder to a ferromagnetic powder composition Further experiments were conducted to evaluate the effect of adding additional ferromagnetic powder compositions, particularly iron-silicon powder (6.8 wt% Si), to ferromagnetic powder compositions containing core particles composed of substantially pure iron. Core particles composed of substantially pure iron (0.1375 wt% silicate and 15 mol% V) were coated according to the procedure described in Example 1. Alloyed iron-silicon soft magnetic core particles (“FeSi”) of additional ferromagnetic powder compositions were coated with 0.11 wt% silicate (sample 9-3) or treated with phosphoric acid diluted in acetone (sample 9-4).

[0196] Compaction with the reference mixture (containing 0.3% amide wax) was performed at 1100 MPa (mold temperature 100°C), and heat treatment was carried out at a maximum of 700°C. The mixture containing alloying powder (samples 9-2 to 9-4, containing 0.1% amide wax) was replaced with compaction at 1600 MPa using die wall lubrication (DWL; mold temperature 60°C) and heat treatment at a maximum of 740°C. The results are shown in Table 9 below: Table 9: Addition of alloyed soft magnetic powder Reference sample (9-1) exhibits excellent density and mechanical strength; however, it shows higher coercivity and DC loss compared to the alloyed mixture. Sample 9-2, mixed with 30% FeSi powder, shows a slight reduction in coercivity. However, due to the reduced density (and permeability μmax), the DC loss remains similar to the reference. By introducing 50% coated FeSi powder, a significant reduction in DC loss is shown, see sample 9-3. Sample 9-4, containing 50% phosphate-coated FeSi powder and a relatively thick silicate coating on essentially pure iron powder (0.165 wt%), shows improved total core loss and DC loss compared to the reference sample.

[0197] Example 11: Increased mechanical strength Further experiments were conducted to evaluate the factors affecting the mechanical strength of objects and parts produced from the ferromagnetic powder composition. Achieving higher mechanical strength (e.g., as measured by transverse breaking strength (TRS)) without sacrificing magnetic properties allows parts to be used in more demanding environments, such as for high-speed motors or heavy-duty robots. In short, in this embodiment, it was found that by varying heat treatment parameters, mechanical and magnetic properties can be tuned to better meet the requirements of different applications.

[0198] Table 10 below lists examples of different heat treatment schemes. The ferromagnetic powder composition typically has 0.11 wt% silicate, as described above. The lubricant is amide wax (EBS).

[0199] Standard treatment (reference) is performed in a controlled atmosphere, where the internal lubricant (approximately 400 mg / L) is carefully removed. C, 20 min), followed by direct curing and stress relaxation treatment (615). C, 20 min). The stationary atmosphere is typically 0.5%–1.5% oxygen (5000 ppm–15000 ppm) in nitrogen. Delubrication is alternatively performed in an inert atmosphere (e.g., nitrogen), followed by [further details needed - likely a temperature range]. In sample C, a single relaxation step in 0.5% oxygen (5000 ppm) for 20 min resulted in an increase in TRS (A). However, by introducing a pre-oxidation step in ambient air at 200–250 °C (i.e., below the lubricant's evaporation temperature), resistivity was further improved (C, EI). A slight increase in oxygen concentration during the final relaxation step further increased TRS without increasing coercivity (D vs. E). Samples F and H provided the highest TRS.

[0200] Pre-oxidation facilitates the beneficial burning and / or evaporation of the lubricant. Table 10 also shows that it is beneficial to avoid oxygen in the furnace atmosphere during delubrication, otherwise the coercivity increases due to the oxidation of the ferromagnetic powder composition (D). Delubrication during relaxation treatment followed by oxidation in 1.5% oxygen (15000 ppm) should also be avoided (J).

[0201] Table 10: Heat Treatment Feasible modifications to the technology proposed in this paper The techniques presented herein are not limited to the embodiments described above and shown in the accompanying drawings, which are primarily illustrative and exemplary. This patent application is intended to cover all modifications and variations of the preferred embodiments described herein, and therefore the invention is defined by the wording of the appended claims and their equivalents.

[0202] Throughout this specification and the appended claims, unless the context otherwise requires, the word “comprise” and variations such as “comprises” or “comprising” shall be understood to mean including the stated integer or step or group of integers or steps but excluding any other integer or step or group of integers or steps.

Claims

1. A ferromagnetic powder composition comprising: (i) Soft magnetic iron-based core particles, and (ii) a first coating layer that at least partially covers and is in direct contact with the surface of the core particle, the first coating layer comprising: a. General formula (K₂O) α (SiO2) β The silicate, where α is the molar amount of K₂O, β is the molar amount of SiO₂, and the β / α molar ratio is in the range of 0.5 to 4.

1. i. The silicate is present in an amount of 0.02 wt% to 1.0 wt% based on the total weight of the ferromagnetic powder composition. b. Optionally, particles comprising a compound of bismuth and oxygen, having a D0 in the range of 0.1 μm to 10 μm as measured according to ISO 13320-1. 50 ,as well as c. As a dopant for dissolving oxoanions or hydroxy anions in the silicate (a).

2. The ferromagnetic powder composition according to claim 1, wherein the first coating layer further comprises nanoparticles having a density of 10 nm to 200 nm as measured according to ISO 13320-1. 50 Alternatively, it may have 6 m as defined in ISO 9277:2022. 2 / g-120 m 2 Specific surface area (SSA) per g.

3. The ferromagnetic powder composition according to claim 2, wherein the nanoparticles are selected from the group consisting of Y2O3 nanoparticles, ZrO2 nanoparticles, ZnO nanoparticles, Mg(OH)2 nanoparticles, MgO nanoparticles, CaCO3 nanoparticles, Al2O3 nanoparticles, SiO2 nanoparticles and TiO2 nanoparticles, and wherein the nanoparticles preferably include or are composed of Y2O3 nanoparticles.

4. The ferromagnetic powder composition according to any one of claims 2-3, wherein the content of nanoparticles in the first coating layer is 1 mol%-30 mol% based on the molar content of K (potassium) in the first coating layer, preferably 1 mol%-20 mol%.

5. The ferromagnetic powder composition according to any one of claims 2-4, wherein the nanoparticles comprise or are composed of Y2O3 nanoparticles, and wherein the content of nanoparticles in the first coating layer is 10 mol%-20 mol% based on the molar content of K (potassium) in the first coating layer.

6. The ferromagnetic powder composition according to any of the preceding claims, wherein the dopant comprises at least one element from Group 5, such as V (vanadium) or Nb (niobium); or comprises at least one element from Group 6, such as Cr (chromium), W (tungsten) or Mo (molybdenum); or comprises Al (aluminum) or P (phosphorus).

7. The ferromagnetic powder composition according to any of the preceding claims, wherein: The dopant comprises V, and the dopant content in the first coating layer is 1 mol%-30 mol%, preferably 5 mol%-20 mol%, more preferably 5 mol%-15 mol%, based on the molar content of K (potassium) in the first coating layer. The dopant comprises Nb, and the dopant content in the first coating layer is 1 mol%-30 mol%, preferably 5 mol%-20 mol%, more preferably 5 mol%-15 mol%, based on the molar content of K in the first coating layer. The dopant contains Cr, and the dopant content in the first coating layer is 1 mol%-30 mol%, preferably 5 mol%-20 mol%, and more preferably 5 mol%-15 mol%, based on the molar content of K in the first coating layer. The dopant comprises Mo, and the dopant content in the first coating layer is 1 mol%-30 mol%, preferably 5 mol%-20 mol%, more preferably 5 mol%-15 mol%, based on the molar content of K in the first coating layer. The dopant comprises W, and the dopant content in the first coating layer is 1 mol%-30 mol%, preferably 5 mol%-20 mol%, more preferably 5 mol%-15 mol%, based on the molar content of K in the first coating layer. The dopant comprises Al, and the dopant content in the first coating layer is 0.5 mol%-5 mol% based on the molar content of K in the first coating layer, preferably 1 mol%-3 mol%, more preferably 1.71 mol%-2.58 mol%, and / or, The dopant contains P, and the dopant content in the first coating layer is 1 mol%-30 mol% based on the molar content of K in the first coating layer, preferably 5 mol%-20 mol%, more preferably 5 mol%-15 mol%.

8. The ferromagnetic powder composition according to any of the preceding claims, wherein the dopant comprises V, and the content of the dopant in the first coating layer is 1 mol%-30 mol%, preferably 5 mol%-20 mol%, more preferably 10 mol%-15 mol% based on the molar content of K in the first coating layer.

9. The ferromagnetic powder composition according to any of the preceding claims, wherein the β / α molar ratio is in the range of 2.0 to 4.

1.

10. The ferromagnetic powder composition according to any preceding claim, wherein the first coating layer comprises particles of a compound containing bismuth and oxygen, the particles of the compound containing bismuth and oxygen having a density (D) in the range of 0.1 μm to 10 μm as measured according to ISO 13320-1. 50 .

11. The ferromagnetic powder composition according to any of the preceding claims, wherein the oxoanion or hydroxyanion of the dopant is a monoanion.

12. The ferromagnetic powder composition according to any of the preceding claims, further comprising: (iii) a second coating layer that at least partially covers the surface of the core particle and / or the first coating layer, the second coating layer comprising: a. At least one organometallic compound having the following general formula R1[(R1) x (R2) y (M)] n O n-1 R1 (I) or R2[M(OH) 2(n+1) ] (n+1) O (n) R2 (II) Where M is selected from the group consisting of Si, Ti, Al, and Zr; O is oxygen; R1 is a hydrolyzable group; R2 is an organic moiety, and at least one R2 contains at least one nitrogen-containing group, preferably an amino group; where n is the number of repeating units, which is an integer between 1 and 20; where x is 0 or 1; and where y is 1 or 2, and x+y is 2. The content of the at least one organometallic compound is from 0.05 wt% to 0.40 wt% based on the total weight of the ferromagnetic powder composition, preferably from 0.10 wt% to 0.30 wt%.

13. A ferromagnetic powder mixture, comprising: The ferromagnetic powder composition according to any of the preceding claims, and Other ferromagnetic powder compositions, The additional ferromagnetic powder composition comprises soft magnetic iron-based core particles that are different from the soft magnetic iron-based core particles of the ferromagnetic powder composition, and Preferably, the soft magnetic iron-based core particles of the additional ferromagnetic powder composition comprise or are composed of an iron alloy having a resistivity and / or hardness higher than that of the soft magnetic iron-based core particles of the ferromagnetic powder composition.

14. The ferromagnetic powder mixture of claim 13, wherein the soft magnetic iron-based core particles of the additional ferromagnetic powder composition comprise or are composed of an iron alloy selected from the group consisting of FeSi, FeAl, FeSiAl, FeNi, FeCo and FeNiCo or combinations or mixtures of such alloys.

15. The ferromagnetic powder mixture according to claim 14, wherein the ferroalloy is selected from the group consisting of: FeSi, preferably having 3 wt%-6.8 wt% Si; and FeSiAl, preferably having 9 wt% Si and 6 wt% Al or 3.5 wt% Si and 3 wt% Al.

16. The ferromagnetic powder mixture according to any one of claims 13-15, wherein the content of the additional ferromagnetic powder composition is at most 90 wt% based on the weight of the ferromagnetic powder mixture, such as 30 wt%-60 wt% or 10 wt%-50 wt%, preferably 20 wt%-40 wt%, such as 20 wt%-30 wt%, or alternatively 40 wt%-60 wt%, such as 45 wt%-55 wt%.

17. A method for producing a ferromagnetic powder composition, comprising the following steps: (i) Provide soft magnetic iron-based core particles. (ii) Contacting the soft magnetic iron-based core particles with a first aqueous solution, the first aqueous solution comprising: a. General formula (K₂O) α (SiO2) β The silicate, where α is the molar amount of K₂O, β is the molar amount of SiO₂, and the β / α molar ratio is in the range of 0.5 to 4.

1. i. The silicate is present in an amount of 0.02 wt% to 1.0 wt% based on the total weight of the ferromagnetic powder composition. b. Optionally, particles comprising a compound of bismuth and oxygen, having a D0 in the range of 0.1 μm to 10 μm as measured according to ISO 13320-1. 50 , c. As a dopant for dissolving oxoanions or hydroxy anions in the silicate (a); as well as d. Optionally, nanoparticles having a D0 of 10 nm–200 nm as measured according to ISO 13320-1. 50 Alternatively, it may have 6 m as defined in ISO 9277:2022. 2 / g-120 m 2 Specific surface area (SSA) per g.

18. The method of claim 17, further comprising one or more of the following steps: (iii) Drying the soft magnetic iron-based core particles, and / or (iv) Contact the soft magnetic iron-based core particles with at least one organometallic compound having the following general formula: R1[(R1) x (R2) y (M)] n O n-1 R1 (I) or R2[M(OH) 2(n+1) ] (n+1) O (n) R2 (II) Where M is selected from the group consisting of Si, Ti, Al, and Zr; O is oxygen; R1 is a hydrolyzable group; R2 is an organic moiety, and at least one R2 contains at least one nitrogen-containing group, preferably an amino group; where n is the number of repeating units, which is an integer between 1 and 20; where x is 0 or 1; and where y is 1 or 2, and x+y is 2. The content of said at least one organometallic compound is from 0.05 wt% to 0.40 wt% based on the total weight of the ferromagnetic powder composition, preferably from 0.10 wt% to 0.30 wt%, and / or (v) The soft magnetic iron-based core particles are mixed with a lubricant, preferably a particulate lubricant.

19. A method for manufacturing an article from a ferromagnetic powder composition according to any one of claims 1-12 or a ferromagnetic powder mixture according to any one of claims 13-16, comprising the following steps: (i) The ferromagnetic powder composition according to any one of claims 1-12 or the ferromagnetic powder mixture according to any one of claims 13-16 is compacted in a mold at a compaction pressure in the range of 300 MPa-2000 MPa, preferably 400 MPa-1200 MPa, to obtain a compacted component, and (ii) The compacted component is heat-treated in a non-reducing atmosphere at a temperature in the range of 300°C-800°C, preferably 400°C-750°C, more preferably 600°C-700°C, to obtain the object, wherein the non-reducing atmosphere preferably contains 0 wt%-22 wt%, more preferably 0.5 wt% to 2 wt% oxygen (O2).

20. The method of claim 19, wherein step (ii) comprises heat-treating the compacted component at a temperature of 670°C-700°C, preferably 680°C-700°C.

21. An object comprising a compacted ferromagnetic powder composition according to any one of claims 1-12 or a compacted ferromagnetic powder mixture according to any one of claims 13-16.

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