New composition and method

Abstract

The present disclosure relates to an iron-based soft magnetic powder composition for passive soft magnetic components comprising: (i) soft magnetic iron-based core particles, wherein at least 80% by weight of the soft magnetic iron-based core particles have particle sizes of 63 µm or below as measured according to ISO 4497:2020; and (ii) a first coating, at least partly covering and being in contact with the soft magnetic iron-based core particles, wherein the first coating comprises - a silicate of the general formula (K2O)α(SiO2)β, wherein α is moles of K2O, β is moles of SiO2, and the β / α molar ratio is in the interval from 0.5 to 4.1, wherein the silicate is present in an amount of 0.02 to 1.0 wt% calculated based on the total weight of the iron-based soft magnetic powder composition, - 0 flux agent particles of a compound comprising bismuth and oxygen having a D50 measured according to ISO 13320:2020 in the interval of 0.1 to 10 μm, and - nanoparticles comprising one or more compounds selected from TiO2, Y2O3 and ZrO2.

Description

[0001] NEW COMPOSITION AND METHOD

[0002] Technical field

[0003] The present invention relates to an iron-based soft magnetic powder composition for passive soft magnetic components. The present invention further relates to an iron-based soft magnetic powder mixture; to a method of producing an iron-based soft magnetic powder composition; and to a method of manufacturing an object from the iron-based soft magnetic powder composition. Yet further, the present invention relates to an object comprising a compacted iron-based soft magnetic powder composition.

[0004]

[0005] Soft magnetic materials are used for various applications, such as core materials in inductors, stators and rotors for electrical machines, actuators, sensors and transformer cores. Soft magnetic composites (SMC) may be based on soft magnetic powders, usually iron-based, with an electrically insulating coating on each particle. Such powders may be used to obtain soft magnetic components or parts, such as by compacting the powders into the desired shape. These components or parts may be used as an alternative to laminated steel components in electric motors, generators, or electromagnets in a wide range of applications, whereby a higher degree of freedom in the design is provided.

[0006] An inductor or reactor is a passive electrical component that can store energy in form of a magnetic field created by electric current passing through coil surrounding the component. An inductor's ability to store energy, inductance (L), is measured in Henrys (H). The magnetic permeability (p) of a soft magnetic powder is an indication of its ability to carry a magnetic flux or its ability to become magnetised. Permeability is defined as the ratio of the induced magnetic flux (B) to the magnetising force (H), or field intensity.

[0007] Magnetic permeability does not only depend on the material carrying the magnetic flux but also on the applied electric field and the frequency thereof. Maximum permeability is commonly referred to for technical systems which is the maximum permeability (pmax) during one cycle of the varying electrical field and defined as the highest value of B / H.

[0008] In order to function efficiently an inductor core for such application shall have a low maximum relative permeability. When a magnetic material is exposed to a varying field, energy losses occur due to both hysteresis losses (DC-loss) and eddy current losses (AC- loss). At high frequencies it is especially desired to reduce the eddy current loss and still maintaining a low level of hysteresis losses. Therefore, it may be desired to increase the resistivity (R) of the magnetic core, and accordingly, the resistivity of the coating of the soft magnetic particles that becomes an important parameter for defining the characteristics and useability of the soft magnetic core particles.W02012084801 Al discloses a composite iron-based powder being especially suited to be used for production of inductor cores for power electronics. The iron-based powder comprises core particles coated with a first phosphorous containing layer and a second layer containing kaolin and sodium silicate. Drawbacks of the composite iron-based powder include high hysteresis loss and low transverse rupture strength (TRS).

[0009] WO2012136758 Al discloses an iron based composite powder composition being especially suited to be used for production of inductor cores for power electronics. The powder was primarily intended for use at higher frequencies, i.e. frequencies above 2 kHz and particularly between 5 and 100 kHz, where higher resistivity and lower core losses are essential. In one embodiment, the iron-based powder comprises atomized iron particles mixed with Sendust, the mixture being phosphorous coated with a second layer metalorganic coating. In another embodiment, the composition was coated with phosphorous and a second coating layer with 2%kaolin and O.4%sodium silicate. The composites display decent hysteresis loss, but drawbacks include low TRS and poor thermodurability.

[0010] WO2024041930 Al discloses ferromagnetic powder compositions comprising soft magnetic iron-based core particles comprising a first coating containing potassium silicate, Bi(OH)s, Y2O3 and a second coating of a silane, suitable as alternatives to laminated steel components in electric motors, generators, electromagnets. Drawbacks of the compositions include a high permeability and low DC-bias.

[0011] Patent application JP2002170707A describes an alloyed iron particle coated with a phosphorous containing layer. In a second step the coated powder is mixed with a water solution of sodium silicate followed by drying. It would be desirable to improve a poor pressability and low TRS.

[0012] In order to obtain high performance with soft magnetic composite components produced by compression moulding, the electrically insulated powder must withstand high shear forces and high pressures, as it is often desired to obtain parts having high density to improve the magnetic properties. High densities may keep hysteresis losses at a low level and provide high saturation flux density. Additionally, the electrical insulation must withstand the compaction pressures needed without being damaged when the compacted part is ejected from the die. Stress releasing heat treatment of the compacted part may be desired to reduce hysteris losses.

[0013] Passive soft magnetic components are primarily intended for use at higher frequencies above 2 kHz, for example, between 5 and 100 kHz. There is, thus, a need for higher resistivity and lower core losses. Further, there is a need for improved flux density and decreased hysteresis loss.Summary of the invention

[0014] It is an object to, at least partly, mitigate, alleviate, or eliminate one or more of the aboveidentified deficiencies in the art and disadvantages singly or in any combination and solve at least the above-mentioned problem.

[0015] It is a further object to provide an iron-based soft magnetic powder composition and mixtures comprising soft magnetic core particles having improved electrical, magnetic and / or structural properties.

[0016] It is a yet further object to provide an iron-based soft magnetic powder composition and mixtures comprising soft magnetic core particles for passive soft magnetic components.

[0017] According to a first aspect there is provided an iron-based soft magnetic powder composition for passive soft magnetic components comprising: (i) soft magnetic iron-based core particles, wherein at least 80% by weight of the soft magnetic iron-based core particles have particle sizes of 63 pm or below as measured according to 1504497:2020; and (ii) a first coating, at least partly covering and being in contact with the the soft magnetic iron-based core particles, wherein the first coating comprises a silicate of the general formula (KzOjctjSiOzjP, wherein a is moles of K2O, |3 is moles of SiO2, and the |3 / a molar ratio is in the interval from 0.5 to 4.1, wherein the silicate is present in an amount of 0.02 to 1.0 wt% calculated based on the total weight of the iron-based soft magnetic powder composition, flux agent particles of a compound comprising bismuth and oxygen having a D50 measured according to ISO 13320:2020 in the interval of 0.1 to 10 pm, and nanoparticles comprising one or more compounds selected from TiO2, Y2O3 and ZrO2.

[0018] The first coating comprising silicate comprising K2O allows for improved density of the iron-based soft magnetic powder composition, and objects compacted therefrom, as compared to, for example, sodium based silicates. Further, less amount of silicate, by weight of the core particles, can be used with maintained or improved resistivity, as compared to, for example, sodium based silicates.

[0019] In particular, a presence of the silicate comprising K2O and the nanoparticles, in the first coating, allows for less amount of silicate required and / or provides improved density, as compared to sodium or lithium based silicate.

[0020] A content of nanoparticles further provides improved ageing properties.

[0021] The flux agent particles of a compound comprising bismuth and oxygen allows for full relaxation and lower hysteresis losses, which may be particularly beneficial for high frequency applications, such as for passive components.

[0022] The flux agent particles of a compound comprising bismuth and oxygen comprised in the first coating, further allows improved properties of the first coating during heattreatment. The flux agent particles of a compound comprising bismuth and oxygen may be dispersed in the first coating, e.g. dispersed in the silicate. The flux agent particles of a compound comprising bismuth and oxygen may react with the silicate during heat treatment and be included in a formed glassy coating.

[0023] At least 80% by weight of the soft magnetic iron-based core particles having particle sizes of 63 pm or below as measured according to ISO 4497:2020 allows for a powder composition having a large fraction of fine particles to be used, which provides the powder composition with properties suitable for passive soft magnetic components.

[0024] ISO 13320:2020 is the current (published 2020-01) international standard for particle size analysis using laser diffraction methods.

[0025] ISO 13320:2020 corresponds to the Swedish standard ISO 13320-1, i.e. SS-ISO 13320-1. ISO 4497:2020 is the current (published 2020-04) international standard for deteremination of particle size of metallic powders by dry sieving.

[0026] At least 80% by weight of the soft magnetic iron-based core particles have particle sizes of 63 pm or below as measured according to ISO 4497:2020. Expressed differently, at least 80% by weight of the soft magnetic iron-based core particles have diameters, i.e. maximum diameters, of 63 pm or below. Accordingly, a particle size as measured according to ISO 4497:2020 corresponds to a maximum diameter of the particle measured.

[0027] At least 80% by weight of the soft magnetic iron-based core particles may have particle sizes in the range of 63 pm to 3 pm as measured according to 1504497:2020.

[0028] Thereby, a fine powder with improved properties for passive soft magnetic components is allowed.

[0029] It has been discovered that such a fine powder, and in particular in combination with the nanoparticles, suitably can be combined with larger amount of potassium based silicate, based on the total weight of the iron-based soft magnetic powder composition, thereby increasing resistivity.

[0030] The silicate may be present in an amount of 0.2-0.8 wt%, preferably 0.35-0.45 wt%, calculated based on the total weight of the iron-based soft magnetic powder composition.

[0031] With such a minimum level of silicate, desirable resistivity is achievable, and further, fine particle sizes can be used.

[0032] Preferably the silicate may be present in an amount of 0.35-0.45 wt%. This provides good properties for when at least 80% by weight of the soft magnetic iron-based core particles have particle sizes of 63 pm or below as measured according to ISO 4497:2020.

[0033] Alternatively the silicate may be present in an amount of 0.55-0.95 wt%, preferably 0.55-0.8 wt%, calculated based on the total weight of the iron-based soft magnetic powdercomposition. These ranges are preferred when at least 80% by weight of the soft magnetic iron-based core particles have particle sizes of 53 pm or below, more preferably 45 pm or below, most preferably 37 pm or below, as measured according to ISO 4497:2020.

[0034] The first coating may further comprise clay minerals, optionally selected from one or more of bentonite, kaolin, muscovite, and talc.

[0035] Thereby, properties of compacted and heat treated soft magnetic components can be controlled and optimized.

[0036] At least 90% by weight of the soft magnetic iron-based core particles may have particle sizes in the range of 53 pm to 3 pm, such as 37 pm or below, preferably 37 pm to 3 pm, as measured according to 1504497:2020.

[0037] Thereby, a fine powder with improved properties for passive soft magnetic components is allowed.

[0038] It has been discovered that such a fine powder suitably can be combined with larger amount of silicate.

[0039] The nanoparticles may be characterised by having a Dso of 10-200 nm as determined according to ISO 13320:2020, or characterised by having a specific surface area of 6-120 m2 / g as determined according to ISO 9277:2022.

[0040] The iron-based soft magnetic powder composition may further comprise:

[0041] (iii) a second coating at least partially covering the surface of the core particles and / or the first coating, the second coating comprising:

[0042] (a) at least one metal-organic compound having the general formula R1[(R1)x(R2)y(M)]nOn-lR1(I)

[0043] or

[0044] R2[M(OH)2(n+l)](n+l)O(n)R2(II)

[0045] wherein M is selected from the group consisting of Si, Ti, Al, and Zr; O is oxygen; R1is a hydrolysable group; R2is an organic moiety and wherein at least one R2contains at least one nitrogen containing group, preferably an amino group; wherein n is the number of repeating units being an integer between 1 and 20; wherein x is 0 or 1; and wherein y is 1 or 2, and x+y is 2, wherein the content of the at least one metal-organic compound is 0.2-1.4 wt% , based on the total weight of the iron-based soft magnetic powder composition.

[0046] The second coating further improves the electrical, structural and magnetic properties of components or parts manufactured from the iron-based soft magnetic powder composition. It appears that the second coating may provide lubrication and additional silicon which helps formation of a glassy coating during heat treatment.According to a second aspect, there is provided an iron-based soft magnetic powder mixture comprising: the iron-based soft magnetic powder composition according to the first aspect or variants thereof; and an alloyed iron-based soft magnetic powder composition comprising iron alloy particles having a higher electrical resistivity than the soft magnetic iron-based core particles of the iron-based soft magnetic powder composition. The iron alloy particles may be harder than the the soft magnetic iron-based core particles.

[0047] An alloyed iron-based soft magnetic powder composition allows the magnetic and electrical properties of components or parts manufactured from the soft magnetic powder composition to be further adjusted. If the soft magnetic iron-based core particles of the alloyed iron-based soft magnetic powder composition comprise or consist of an iron alloy having a higher electrical resistivity than the soft magnetic iron-based core particles of ironbased soft magnetic powder composition, the iron-based soft magnetic powder mixture may have an even lower core loss at higher frequencies.

[0048] The soft magnetic iron-based core particles of the alloyed iron-based soft magnetic powder composition may comprise or consist of an iron alloy selected from the group consisting of FeSi, FeAl, FeP, FeSiAl, FeNi, FeCo, and FeNiCo, or combinations or mixtures of such alloys.

[0049] The iron alloy may be selected from the group consisting of FeSi, preferably with 3-6.8 wt% Si, and FeSiAl, preferably with 8.5-10.5 wt% Si and 4.5-6.5 wt% Al or 2.5-6.0 wt% Si and 2.5-4.0wt% Al.

[0050] The content of the alloyed iron-based soft magnetic powder composition may be up to 90 wt%, such as 30-90 wt%, based on the weight of the iron-based soft magnetic powder mixture.

[0051] The above-mentioned features of the first aspect, when applicable, apply to this second aspect as well. In order to avoid undue repetition, reference is made to the above.

[0052] According to a third aspect, there is provided a method of producing an iron-based soft magnetic powder composition comprising the steps of:

[0053] (i) providing iron-based soft magnetic core particles;

[0054] (ii) contacting the iron-based soft magnetic core particles with a first aqueous solution comprising: (a) a silicate of the general formula (KzOjafSiChJP, wherein a is moles of K2O, |3 is moles of SiCh, and the |3 / a molar ratio is in the interval from 0.5 to 4.1, and wherein the silicate is present in an amount of 0.02 to 1.0 wt% calculated based on the total weight of the iron-based soft magnetic powder composition; (b) flux agent particles of a compoundcomprising bismuth and oxygen having a Dso measured according to ISO 13320:2020 in the interval of 0.1 to 2 pm; and (c) nanoparticles comprising a compound selected from TiOz, Y2O3 and ZrO2.

[0055] The method of the third aspect may further comprise one or more of the steps of:

[0056] (iii) drying the iron-based soft magnetic core particles, and / or

[0057] (iv) contacting the iron-based soft magnetic core particles with at least one metalorganic compound having the general formula

[0058] R1[(R1)x(R2)y(M)]nOn-lR1(I)

[0059] or

[0060] R2[M(OH)2(n+l)](n+l)O(n)R2(II)

[0061] wherein M is selected from the group consisting of Si, Ti, Al, and Zr; O is oxygen; R1is a hydrolysable group; R2is an organic moiety and wherein at least one R2contains at least one nitrogen containing group, preferably an amino group; wherein n is the number of repeating units being an integer between 1 and 20; wherein x is 0 or 1; and wherein y is 1 or 2, and x+y is 2,

[0062] wherein the content of the at least one metal-organic compound is 0.2 to 1.40 wt%, for example 0.40 to 1.4 wt%, based on the total weight of the iron-based soft magnetic powder composition, and / or

[0063] (v) mixing the soft magnetic iron-based core particles with a lubricant, preferably a particulate lubricant.

[0064] The above-mentioned features of the first and / or second aspects, when applicable, apply to this third aspect as well. In order to avoid undue repetition, reference is made to the above.

[0065] According to a fourth aspect, there is provided a method of manufacturing an object from the iron-based soft magnetic powder composition according to the first aspect or variants thereof or the iron-based soft magnetic powder mixture according to the second aspect or variants thereof, comprising the steps of:

[0066] (i) compacting the iron-based soft magnetic powder composition according to the first aspect or variants thereof or the iron-based soft magnetic powder mixture according to the second aspect or variants thereof in a die at a compaction pressure in the range of 500-2000 MPa, preferably 600-1800 MPa, to obtain a compacted part, and

[0067] (ii) heat treating the compacted part in a nonreducing atmosphere, preferably comprising 0-22% by volume, more preferably 0.5 to 2% by volume, oxygen (O2) ata temperature in the range of 300-800 °C, preferably 400-750 °C, more preferably 600-700 °C, to obtain the object.

[0068] The step (ii) of heat treating may comprise heat treating the compacted part at a temperature within an interval of 650-730°C. For example, the temperature may be 650-700°C; or 680-730°C, such as 680-710°C.

[0069] According to a fifth aspect, there is provided an object comprising a compacted iron-based soft magnetic powder composition according the first aspect or variants thereof or a compacted iron-based soft magnetic powder mixture according to the second aspect or variants thereof.

[0070] A further scope of applicability of the present disclosure will become apparent from the detailed description given below. However, it should be understood that the detailed description and specific examples, while indicating preferred variants of the present inventive concept, are given by way of illustration only, since various changes and modifications within the scope of the inventive concept will become apparent to those skilled in the art from this detailed description. Hence, it is to be understood that this inventive concept is not limited to the particular steps of the methods described or component parts of the systems described as such method and system may vary. It is also to be understood that the terminology used herein is for purpose of describing particular embodiments only and is not intended to be limiting. It must be noted that, as used in the specification and the appended claim, the articles "a", "an", "the", and "said" are intended to mean that there are one or more of the elements unless the context clearly dictates otherwise. Thus, for example, reference to "a unit" or "the unit" may include several devices, and the like. Furthermore, the words "comprising", "including", "containing" and similar wordings do not exclude other elements or steps.

[0071] Brief description of the drawings

[0072] The above and other aspects of the present inventive concept will now be described in more detail, with reference to appended drawings showing variants of the inventive concept. The figures should not be considered limiting the inventive concept to the specific variant; instead, they are used for explaining and understanding the inventive concept. As illustrated in the figures, the sizes of layers and regions are exaggerated for illustrative purposes and, thus, are provided to illustrate the general structures of variants of the present inventive concept. Like reference numerals refer to like elements throughout.Figure 1 illustrates a schematical cross-sectional view of a particle of a soft magnetic powder composition.

[0073] Figure 2 illustrates a method according to a variant of the third aspect concerning a method of producing an iron-based soft magnetic powder composition.

[0074] Detailed description

[0075] The present inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred variants of the inventive concept are shown. This inventive concept may, however, be implemented in many different forms and should not be construed as limited to the variants set forth herein; rather, these variants are provided for thoroughness and completeness, and fully convey the scope of the present inventive concept to the skilled person.

[0076] The present invention is, at least in part, based on a realisation by the present inventors that the magnetic and electrical properties of a soft magnetic powder composition, and parts made from the soft magnetic powder composition, can be further improved for purposes including passive soft magnetic components, by using a fine core particles combined with the first coating as defined in aspects and variants of aspects disclosed herein. Further, by increasing the amount of silicate unexpectedly improvements, for example concerning eddy current losses and resistivity, may be obtained.

[0077] An iron-based soft magnetic powder composition for passive soft magnetic components will now be discussed, with reference to schematical figure 1, illustrating a schematical cross-sectional view of a particle 1 of a soft magnetic powder composition according to a variant of the first aspect. The iron-based soft magnetic powder composition comprises: soft magnetic iron-based core particles 2, wherein at least 80% by weight of the soft magnetic iron-based core particles have particle sizes of 63 pm or below as measured according to 1504497:2020; and a first coating 4, at least partly covering and being in contact with the the soft magnetic iron-based core particles 2, wherein the first coating 4 comprises (i) a silicate 6 of the general formula (K2O)a(SiO2)|3, wherein a is moles of K2O, |3 is moles of SiO2, and the |3 / a molar ratio is in the interval from 0.5 to 4.1, wherein the silicate is present in an amount of 0.02 to 1.0 wt% calculated based on the total weight of the iron-based soft magnetic powder composition, (ii) flux agent particles 8 of a compound comprising bismuth and oxygen having a D50 measured according to ISO 13320:2020 in the interval of 0.1 to 10 pm, and (iii) nanoparticles 10 comprising one or more compounds selected from TiO2, Y2O3 and ZrO2.At least 80% by weight of the soft magnetic iron-based core particles may have particle sizes in the range of 63 pm to 3 pm as measured according to 1504497:2020.

[0078] 80% by weight of the soft magnetic iron-based core particles having particle sizes in the range of 63 pm to 3 pm as measured according to 1504497:2020 may correspond to 230 mesh US standard.

[0079] Preferably at least 90% by weight of the soft magnetic iron-based core particles have particle sizes in the range of 63 pm to 3 pm as measured according to 1504497:2020. At least 80% by weight of the soft magnetic iron-based core particles may have particle sizes in the range of 53 pm, or below, such as in the range of 53 pm to 3 pm as measured according to 1504497:2020.

[0080] Preferably at least 90% by weight of the soft magnetic iron-based core particles have particle sizes in the range of 53 pm to 3 pm as measured according to 1504497:2020.

[0081] Thereby, benefits with fine powders for passive components may be provided. It shall be relised and appreciated that even finer powders may be used with variants of aspects herein. For example, powder compositions with soft magnetic iron-based core particles having particle sizes of 45 pm and below as measured according to 1504497:2020, or even 25 pm or below as measured according to 1504497:2020, have been succesfully used for production of compacted objects with core loss desirable for high frequency applications and / or passive components.

[0082] Less than 10% by weight of the soft magnetic iron-based core particles may have a size below 3 pm as measured according to 1504497:2020.

[0083] The compound comprising bismuth and oxygen, of the flux agent particles 8, may comprise oxides and hydroxides of bismuth, in particular the compound may comprise or consist of Bi(OH )3- The flux agent particles allows lowering the melting temperature of the silicate.

[0084] When the soft magnetic powder composition, such as in form of a compacted part produced from the soft magnetic powder is heat treated, the first coating, and any second coating applied in contact with the first coating, for example, on top of the first coating, may react to form a glassy coating formed from the silicate and the flux agent particles of the compound comprising bismuth and oxygen, when present, dispersed therein.

[0085] The flux agent particles of a compound comprising bismuth and oxygen comprised by or in the first coating, such as, for example, by being dispersed in the first coating, further improve the properties of a glassy coating formed from the silicate and the flux agent particles during heat treatment of the powder composition. During and after heat treatment, the flux agent particles may react with the silicate and be included in the formed glassy coating.The flux agent particles of a compound comprising bismuth and oxygen allows for improved relaxation and lowering hysteresis losses.

[0086] The flux agent particles of a compound comprising bismuth and oxygen may have Dso measured according to ISO 13320:2020 in the interval of 0.5 to 2 pm.

[0087] The content of the flux agent particles of the compound comprising bismuth and oxygen in the first coating may be 0.015-0.75 wt%, for example, 0.15-0.5 wt%, such as 0.15-0.4 wt%, based on the total weight of the soft magnetic powder composition.

[0088] Experiments indicate that such ranges of content of the flux agent particles of the compound comprising bismuth and oxygen provides good results.

[0089] The silicate of the general formula (KzOjafSiChJp is a potassium silicate or alternatively may be referred to as K-silicate, K-waterglass, potassium waterglass or simply, as used herein, silicate.

[0090] The p / a molar ratio (i.e., the molar ratio of SiCh to K2O) is in the interval from 0.5 to 4.1. For example, the molar ratio P / ct may be in the interval of 2.0 to 3.75, such as in the interval of 2.5 to 3.5. Further, the molar ratio P / a may be in the interval of 2.0 to 4.1.

[0091] The iron-based soft magnetic powder composition comprises soft magnetic iron-based core particles, that is the powder composition comprises a plurality of soft magnetic iron-based core particles. The soft magnetic iron-based core particles may comprise or consist of iron or an alloy of iron. The soft magnetic iron-based core particles may comprise at least 90% iron, such as at least 99% iron, or at least 99.5% iron. When present, the alloy of iron may be alloyed iron Fe-Si having up to 7% by weight, such as up to 3% by weight of silicon, or another alloy of iron selected from the groups Fe-AI, Fe-P, Fe-Si-AI, Fe-Ni, Fe-Co, Fe-Ni-Co, or combinations or mixtures of such alloys. The soft magnetic iron-based core particles may comprise mixtures of particles such as mixtures of iron particles and iron alloy particles or a mixture of particles made from two or more iron alloys. In particular, the soft magnetic iron-based core particles may be made of essentially pure iron, i.e., iron with inevitable impurities.

[0092] At least 80% by weight of the soft magnetic iron-based core particles may have particle sizes of 53 pm or below as measured according to 1504497:2020. Further, according to a variant of aspects herein, at least 80% by weight of the soft magnetic ironbased core particles may have particle sizes in the range of 53 pm to 3 pm, as measured according to ISO 4497:2020. It shall be understood and appreciated that coarser particles than the 53 pm and finer particles than the 3 pm may be present amongst the soft magnetic iron-based core particles of the powder composition, hower not more than allowed by the provision that 80% by weight, or 90% by weight, of the soft magnetic ironbased core particles may have particle sizes in the range of 53 pm to 3 pm as measured according to 1504497:2020. The size distribution of the soft magnetic iron-based coreparticles of the powder composition may depend on the method of manufacturing of the soft magnetic iron-based core particles, and / or any fractionation method applied to the manufactured soft magnetic iron-based core particles.

[0093] According an example of a variant of aspects herein, the soft magnetic iron-based core particles, wherein at least 80% by weight of the soft magnetic iron-based core particles have particle sizes in the range of 53 pm to 3 pm as measured according to 1504497:2020, may be obtained by sieving through a 270 mesh, US standard.

[0094] According another example of a variant of aspects herein, the soft magnetic ironbased core particles, wherein at least 80% by weight of the soft magnetic iron-based core particles have particle sizes in the range of 63 pm to 3 pm as measured according to 1504497:2020, may be obtained by sieving through a 230 mesh, US standard.

[0095] At least 80% by weight of the soft magnetic iron-based core particles may have particle sizes of 63 pm or below. Further, according to a variant of aspects herein, at least 80% by weight of the soft magnetic iron-based core particles may have particle sizes in the range of 63 pm to 3 pm, as measured according to ISO 4497:2020.

[0096] Further, at least 90%, such as at least 95%, or 99%, or even up to and including 100% by weight of the soft magnetic iron-based core particles may have particle sizes of 53 pm or below, or of 53 pm to 3 pm as measured according to 1504497:2020.

[0097] At such levels of particle sizes of the soft magnetic iron-based core particles, i.e. including wherein at least 80% by weight of the soft magnetic iron-based core particles have particle sizes of 63 pm or below, or of 63 pm to 3 pm, as measured according to ISO 4497:2020, components manufactured from the powder composition are particularly suitable for high frequency applications and / or for passive soft magnetic components, such as, for example, sensors, inductors, and converters. Such powder compositions provide improved properties for passive soft magnetic components, and such a fine powder can suitably be combined with larger amount of silicate.

[0098] At least 80% by weight of the soft magnetic iron-based core particles may have particle sizes of 45 pm or below, such as in the range of 45 pm to 3 pm; or may have particle sizes of 37 pm or below, such as in the range of 37 pm to 3 pm; or may have particle sizes of 25 pm or below, such as in the range of 25 pm to 3 pm, as measured according to 1504497:2020.

[0099] In particular, at least 80% by weight of the soft magnetic iron-based core particles may have particle sizes of 37 pm or below, such as in the range of 37 pm to 3 pm.

[0100] At least 90% by weight of the soft magnetic iron-based core particles may have particle sizes of 45 pm or below, such as in the range of 45 pm to 3 pm; or may have particle sizes of 37 pm or below, such as in the range of 37 pm to 3 pm; or may have particle sizes of 25 pm or below, such as in the range of 25 pm to 3 pm, as measured according to 1504497:2020.In particular, at least 90% by weight of the soft magnetic iron-based core particles may have particle sizes of 37 pm or below, such as in the range of 37 pm to 3 pm.At least 95% by weight of the soft magnetic iron-based core particles may have particle sizes of 45 pm or below, such as in the range of 45 pm to 3 pm; or may have particle sizes of 37 pm or below, such as in the range of 37 pm to 3 pm; or may have particle sizes of 25 pm or below, such as in the range of 25 pm to 3 pm, as measured according to 1504497:2020.

[0101] In particular, at least 95% by weight of the soft magnetic iron-based core particles may have particle sizes of 37 pm or below, such as in the range of 37 pm to 3 pm.

[0102] Further, at least 99% by weight of the soft magnetic iron-based core particles may have particle sizes of 45 pm or below, such as in the range of 45 pm to 3 pm; or may have particle sizes of 37 pm or below, such as in the range of 37 pm to 3 pm; or may have particle sizes of 25 pm or below, such as in the range of 25 pm to 3 pm, as measured according to 1504497:2020.

[0103] In particular, at least 99% by weight of the soft magnetic iron-based core particles may have particle sizes of 37 pm or below, such as in the range of 37 pm to 3 pm.

[0104] The soft magnetic iron-based core particles may be spherical or irregular shaped, irregular shaped particles being preferred. The AD (apparent density) may be between 2.8 and 4.0 g / cm3, preferably between 3.1 and 3.7 g / cm3.

[0105] The soft magnetic iron-based core particles may be water atomized, gas atomized or a sponge iron powder. Generally, water atomized soft magnetic iron-based core particles are irregular shaped.

[0106] The soft magnetic iron-based core particles may be water atomized annealed ironbased particles.

[0107] The soft magnetic iron-based core particles may have irregular shapes or regular shapes, or combinations thereof. For example, the soft magnetic iron-based core particles may be essentially spherical. For such essentially spherical particles, the particle size of the soft magnetic iron-based core particles may correspond to a diameter of the particles.

[0108] Presence of the nanoparticles in the powder composition improves resistivity of the glassy coating formed from the first coating and any second coating applied on top thereof during heating. Presence of the nanoparticles further work well together with the dopant. The nanoparticles, may be dispersed in the first coating, e.g., dispersed in the silicate.

[0109] During and after heat treatment, the nanoparticles become embedded in a formed glassy coating.

[0110] The nanoparticles may comprise a mixture of nanoparticles, such as a mixture of two or more of TiOz, Y2O3 and ZrC>2. Alternatively and suitably, the nanoparticles may comprise only one of TiC>2, Y2O3 and ZrC>2. The nanoparticles may comprise or consist of Y2O3.The nanoparticles provide improved magnetic and electric properties for objects manufactured from the iron-based soft magnetic powder composition.

[0111] The content of nanoparticles in the first coating may be 1-30 mol%, such as 1-20 mol% based on the molar content of K (potassium) in the first coating. These general molar contents of nanoparticles provide good results.

[0112] The first coating is at least partially covering and is in direct contact with the soft magnetic iron-based core particles, or the surface of the iron-based core particles. The first coating may, desirably, cover all of the surface of at least 50 wt%, such as at least 75 wt% of the core particles in the soft magnetic powder composition. Further desirably, the first coating may cover all of the surface of at least 90 wt%, such as at least 95 wt%, such as at least 99 wt% of the core particles in the iron-based soft magnetic powder composition.

[0113] Expressed differently, the first coating may cover at least 50%, such as at least 75%, for example at least 90%, such as at least 95%, such as at least 99% of the total surface area of the core particles.

[0114] The typical total thickness of the first and the second coatings combined may be about 20-800 nm, such as 20-400 nm. Typically, the permeability of component is about 25-150. The typical total thickness of the first and the second coatings combined may be about 20-400 nm with a permeability of about 25-150.

[0115] The silicate may be present in an amount of 0.2-0.8 wt%, such as 0.3-0.8 wt% or 0.2-0.6 wt%, such as 0.3-0.6 wt%, calculated based on the total weight of the iron-based soft magnetic powder composition.

[0116] With such a level of silicate, desirable resistivity is achievable, and further, is suitable with the fine particle sizes of the powder composition of variants of the first aspect. Such amount of the silicate is suitable for providing a thickness of the first coating, and the second coating when present, in the range of 20-200 nm or a typical total thickness of the first and the second coatings combined of about 20-400 nm, for example 80-250 nm.

[0117] Preferably the silicate may be present in an amount of 0.35-45 wt%. This provides good properties for when at least 80% by weight of the soft magnetic iron-based core particles have particle sizes of 63 pm or below as measured according to ISO 4497:2020.

[0118] Alternatively the silicate may be present in an amount of 0.55- 0.95 wt%, preferably 0.55-0.8 wt%, calculated based on the total weight of the iron-based soft magnetic powder composition. These ranges are preferred when at least 80% by weight of the soft magnetic iron-based core particles have particle sizes of 53 pm or below, more preferably 45 pm or below, most preferably 37 pm or below, as measured according to ISO 4497:2020.

[0119] The first coating may be applied using an aqueous solution 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 of the other components, such as the particles of a compound comprising bismuth and oxygen, and nanoparticles, end up in the first coating, and / or in any present second coating. Accordingly, contents and ratios between components in the aqueous solution and the soft magnetic iron-based core particles carry over to the contents and ratios between components in the first coating and the soft magnetic iron-based core particles.

[0120] The first coating may further comprise clay minerals, optionally selected from one or more of bentonite, kaolin, muscovite, and talc.

[0121] Thereby, properties of compacted and heat treated soft magnetic components can be controlled and optimized. For example, precense of clay minerals, in particular in combination with iron alloy particles, provides lower and / or more stable permeability, even at relatively low levels of silicate. Thereby, a higher B-flux density resulting in lower core loss is achievable. Further, a passive component with a stable response to signals, even at higher fields, i.e. good DC-bias, can be produced.

[0122] The amount of clay minerals may be between 0.2-5%, such as between 0.5-4%, such as between 0.5-3% by weight, of the soft magnetic iron-based core particles.

[0123] At least 90% by weight of the soft magnetic iron-based core particles may have particle sizes in the range of 53 pm to 3 pm as measured according to 1504497:2020.

[0124] Thereby, a fine powder with improved properties for passive soft magnetic components is allowed.

[0125] Such a fine powder can suitably be combined with larger amount of silicate.

[0126] At least 90% by weight of the soft magnetic iron-based core particles have particle sizes in the range of 53 pm to 3 pmmay correspond to 270 mesh US standard.

[0127] Preferably at least 90 % by weight of the soft magnetic iron-based core particles have particle sizes of 37 pm or below, preferably 37 pm to 3 pm, as measured according to 1504497:2020.

[0128] The nanoparticles may be characterised by having a Dso of 10-200 nm as determined according to ISO 13320:2020, or characterised by having a specific surface area of 6-120 m2 / g as determined according to ISO 9277:2022.

[0129] The Dso measured according to ISO 13320:2020 is defined in ISO 13320:2020 as the median particle diameter used on a volumetric basis, i.e., 50% by volume of the particles is smaller than this diameter and 50% is larger. Generally, references herein to ISO-standards are equivalent to references to SS-ISO standards where SS merely indicates that the concerned ISO standard has been adopted as a Swedish standard.The Dso measured according to ISO 13320:2020 can be determined using e.g., a Mastersizer 3000 from Malvern instruments.

[0130] An alternative parameter for determining the size of the nanoparticles is the specific surface area (SSA) [m2 / g], i.e., the surface area of the particles per g of particles.

[0131] Accordingly, a D50 measured according to ISO 13320:2020 of 10-200 nm may be equivalently replaced by a specific surface area (SSA) in the range of 6-120 m2 / g.

[0132] The SSA for the nanoparticles is preferably determined using the BET-method, which is a method for determination of the specific surface area of solids by gas adsorption.

[0133] More preferably, the SSA for the nanoparticles is preferably determined according to ISO 9277:2022.

[0134] Accordingly, a D50 measured according to ISO 13320:2020 of 10-200 nm may be equivalently replaced by a specific surface area (SSA) of 6-120 m2 / g as determined according to ISO 9277:2022.

[0135] Preferably, the specific surface area (SSA) of the nanoparticles is 10-50, more preferably 10-30, most preferably 15-30 m2 / g. One example is 18 m2 / g. As above, these ranges are preferably determined according to ISO 9277:2022.

[0136] The specific surface area may be measured using a Micromeritics TriStar 3000 gas adsorption instrument which calculates the BET surface area.

[0137] For comparison, an average diameter for the nanoparticles may be calculated from the specific surface area if the particles are assumed to be spherical. The equation for calculating the average particle diameter in nanometres is 6000 / (BET surface area in m2 / g) x (density in g / cm3). For Y2O3 (density 5.01 g / cm3), the specific surface areas of 120, 6, 50, 10, and 18 m2 / g respectively yield the average diameters of 10, 200, 24, 120, and 67 nm respectively.

[0138] Preferably, the nanoparticles have a D50 measured according to ISO 13320:2020 of 10 -100 nm. Most preferably the nanoparticles have a D50 measured according to ISO 13320:2020 of 20-100 nm.

[0139] The former interval corresponds to a SSA of 12-120 m2 / g, whereas the latter interval corresponds to a SSA of 12-60 m2 / g.

[0140] The D so measured according to ISO 13320:2020 is preferably between 10 and 100 nm, where 90 wt% of the particles shall have maximum diameters between 1 and 500 nm.

[0141] In examples herein the nanoparticles may generally have a D50 of 10 nm, and this size of nanoparticles have been shown to provide desirable results.

[0142] Alternatively, the nanoparticles may have diameters of 1-200 nm, preferably 1-50 nm, more preferably 5-50 nm, such as 30-50 nm or such as 5-20 nm such as 10 nm.

[0143] The iron-based soft magnetic powder composition may further comprise:(iii) a second coating at least partially covering the surface of the core particles and / or the first coating, the second coating comprising:

[0144] (a) at least one metal-organic compound having the general formula R1[(R1)x(R2)y(M)]nOn-lR1(I)

[0145] or

[0146] R2[M(OH)2(n+l)](n+l)O(n)R2(II)

[0147] wherein M is selected from the group consisting of Si, Ti, Al, and Zr; O is oxygen; R1is a hydrolysable group; R2is an organic moiety and wherein at least one R2contains at least one nitrogen containing group, preferably an amino group; wherein n is the number of repeating units being an integer between 1 and 20; wherein x is 0 or 1; and wherein y is 1 or 2, and x+y is 2, wherein the content of the at least one metal-organic compound is 0.2-1.4 wt%, , based on the total weight of the iron-based soft magnetic powder composition.

[0148] The second coating further improves the electrical, structural and magnetic properties of components or parts manufactured from the iron-based soft magnetic powder composition. It appears that the second coating may provide lubrication and additional silicon which helps formation of a glassy coating during heat treatment.

[0149] R1may be an alkoxy-group having less than 4, such as less than 3 carbon atoms. R2is an organic moiety, in the meaning that the R2-group contains an organic part or portion. R2preferably includes 1-6, such as 1-3, carbon atoms. R2may further include one or more hetero atoms selected from the group consisting of N, O, S and P. The R2group may be linear, branched, cyclic, or aromatic. R2may include one or more of the following functional groups: amine, diamine, amide, imide, epoxy, hydroxyl, ethylene oxide, ureido, urethane, isocyanato, acrylate, glyceryl acrylate, benzyl-amino, vinyl-benzyl-amino. The R2group may alter between any of the mentioned functional R2-groups and a hydrophobic alkyl group with repeatable units.

[0150] When n=l the metal-organic compound is a monomer (formula I) or a dimer (Formula II). If the metal-organic compound is a monomer it may be selected from the group of trialkoxy and dialkoxy silanes, titanates, aluminates, or zirconates. The monomer of the metal-organic compound may thus be selected from 3-aminopropyl-trimethoxysilane, 3-aminopropyl-triethoxysilane, 3-aminopropyl-methyl-diethoxysilane, N-aminoethyl-3-aminopropyl / ethyl / methyl-alkoxy-silane such as N-aminoethyl-3-aminopropyl-trimethoxysilane and N-aminoethyl-3-aminopropyl-methyl-dimethoxysilane, l,7-bis(triethoxysilyl)-4-azaheptan, triamino-functional propyl-trimethoxysilane, 3-ureidopropyl-triethoxysilane, 3-isocyanatopropyl-triethoxysilane, tris(3-trimethoxysilylpropyl)-isocyanurate, 0-(propargyloxy)-N-(triethoxysilylpropyl)-urethane, 1-aminomethyl-triethoxysilane, 1-aminoethyl-methyl-dimethoxysilane, or mixtures thereof.When n=2-20 the metal-organic compound is an oligomer. An oligomer of the metal-organic compound may be selected from alkoxy-terminated alkyl-alkoxy-oligomers of silanes, titanates, aluminates, or zirconates. The oligomer of the metal-organic compound may thus be selected from methoxy, ethoxy or acetoxy-terminated amino-silsesquioxanes, amino-siloxanes, oligomeric 3-aminopropyl-methoxy-silane, 3-aminopropyl / propyl-alkoxy-silanes, N-aminoethyl-3-aminopropyl-alkoxy-silanes, or N-aminoethyl-3-aminopropyl / methyl-alkoxy-silanes or mixtures thereof.

[0151] Examples of suitable metal-organic compounds in particular include Dynasylan® 1146 and Dynasylan® SIVO 203 from Evonik Industries AG, or XIAMETER™ OFS-6020 Silane from Dow Chemical Company.

[0152] Water-borne amino- or multifunctional silane systems are also comprised by the metal-organic compound, such as the corresponding Dynasylan® HYDROSIL products supplied by Evonik industries AG. In these products the hydrolysable alkoxy-groups have almost fully been replaced with hydroxyl groups, i.e., as per Formula (II), while the functionality is similar, e.g., hydrophobic alkyl-groups in combination with amino- or diamino-alkyl-groups. Examples include the Dynasylan® HYDROSIL 2627, T1 , and 1151 silane systems. Examples of such compounds can be l,3-Bis(3-aminopropyl)disiloxane-1,1,3,3-tetrol or (3-aminopropyl)({[(propyl)dihydroxysilyl]oxy})silanediol.

[0153] The content of the at least one metal-organic compound suitably may be approximately double the content of silicate. The content of the at least one metal-organic compound suitably may be 2 x (content of silicate, in wt%) + / - 20%, or, put differently, in the range of 2.4 x (content of silicate) to 1.6 x (content of silicate), in wt%, based on the total weight of the iron-based soft magnetic powder composition.

[0154] The iron-based soft magnetic powder composition may further comprise:

[0155] (iv) a lubricant, preferably a particulate lubricant.

[0156] Including a lubricant in the iron-based soft magnetic powder composition improves compaction and leads to an increased density and strength of an object manufactured from the iron-based soft magnetic powder composition. The lubricant may be selected from the group consisting of primary and secondary fatty acid amides, trans-amides (bisamides) or fatty acid amides or alcohols. The lubricating moiety of the lubricant may be a saturated or unsaturated chain containing between 12-22 carbon atoms. The lubricant may preferably be selected from stearamide, behenyl alcohol, erucamide, stearylerucamide, erucyl-stearamide, behenyl alcohol, erucyl alcohol, ethylene-bisstearamide (i.e., EBS or amide wax). Preferably the lubricant is an amide wax. Preferably is also a mixture of stearamide or behenyl alcohol and an amide wax. One example is 0.1 wt% stearamide combined with 0.3 wt% amide wax.The lubricant may be present in an amount of 0.05-0.80 wt%, preferably 0.20-0.40 wt%, or preferably 0.40-0.60 wt%, of the iron-based soft magnetic powder composition. Generally, the finer particle size of the soft magnetic core particle the relatively more lubricant is desired. If a very low amount of lubricant is added in the composition (0.05 to 0.20 wt%), the compaction and ejection can be facilitated by using die wall lubrication (DWL). The low amount of internal lubricant will increase compact density, permeability and mechanical strength.

[0157] According to a second aspect, there is provided an iron-based soft magnetic powder mixture comprising: the iron-based soft magnetic powder composition according to the first aspect or variants thereof; and an alloyed iron-based soft magnetic powder composition comprising iron alloy particles having a higher electrical resistivity than the soft magnetic iron-based core particles of the iron-based soft magnetic powder composition.

[0158] An alloyed iron-based soft magnetic powder composition allows the magnetic and electrical properties of components or parts manufactured from the soft magnetic powder composition to be further adjusted. If, as preferred, the soft magnetic iron-based core particles of the alloyed iron-based soft magnetic powder composition comprise or consist of an iron alloy having a higher electrical resistivity than the soft magnetic iron-based core particles of iron-based soft magnetic powder composition, then the iron-based soft magnetic powder mixture will have an even lower core loss at higher frequencies.

[0159] As further discussed above in relation to clay minerals, a combination of iron alloy particles and clay minerals allows provision of lower and / or more stable permeability, even at relatively low levels of silicate. Thereby, a higher B-flux density resulting in lower core loss is achievable. In combination with the amounts of silicate provided according to variants of present aspects, in combination with the fine particles, even lower core losses can be achieved.

[0160] The iron alloy particles powder may be coated similarly to the soft magnetic iron-based core particles or, for example, be coated with a phosphorous-containing insulating layer.

[0161] Thus, the alloyed iron-based soft magnetic powder composition may comprise the first coating as described according to the first aspect and variants thereof, at least partly covering and being in contact with the iron alloy particles.

[0162] The alloyed iron-based soft magnetic powder composition may comprise a phosphate-coating, at least partly covering and being in contact with the iron alloy particles.The alloyed iron-based soft magnetic powder composition may comprise an oxide coating obtained by annealing, at least partly covering and being in contact with the iron alloy particles.

[0163] In the powder mixture, the soft magnetic iron-based core particles of the iron-based soft magnetic powder composition preferably comprises or consists of essentially pure iron, i.e., iron with inevitable impurities.

[0164] The alloyed iron-based soft magnetic powder composition may further comprise a coating or surface treatment on the soft magnetic iron-based core particles therein. The coating or surface treatment preferably comprises the first, and optionally also the second, coating as described above. Typically, however, when comprising an iron alloy, the soft magnetic ironbased core particles of the alloyed iron-based soft magnetic powder composition may be coated or treated with another coating, such as by being treated with phosphoric acid diluted in acetone.

[0165] The soft magnetic iron-based core particles or the alloyed iron-based soft magnetic powder composition may have the same particle sizes as the soft magnetic iron-based core particles of the iron-based soft magnetic powder composition according to the first aspect of the technology proposed herein as described further above.

[0166] The soft magnetic iron-based core particles of the alloyed iron-based soft magnetic powder composition may comprise or consist of an iron alloy selected from the group consisting of FeSi, FeAl, FeP, FeSiAl, FeNi, FeCo, and FeNiCo, or combinations or mixtures of such alloys.

[0167] For example, the alloyed iron-based soft magnetic powder composition may comprise or consist of gas-atomized Sendust powder (Fe9.5SiAI5.5), and / or gas-atomized Fe6.8Si-powder. The average particle size may be around Dso, 13pm, and around Dso, 22pm, respectively.

[0168] The iron alloy may be selected from the group consisting of FeSi, preferably with 3-6.8 wt% Si, and FeSiAl, preferably with 8.5-10.5 wt% Si and 4.5-6.5 wt% Al or 2.5-6.0 wt% Si and 2.5-4.0wt% Al.

[0169] The content of the alloyed iron-based soft magnetic powder composition may be up to 90 wt%, such as 30-90 wt%, based on the weight of the iron-based soft magnetic powder mixture.

[0170] For example, the content of the alloyed iron-based soft magnetic powder composition may be 30-90 wt% or 40-90 wt%, such as 40-80 wt% or 45-75%, for example 50-70 wt%, based on the weight of the iron-based soft magnetic powder mixture.Such levels of further iron-based soft magnetic powder composition are unexpectedly particularly suitable and beneficial for high frequency application.

[0171] With reference to figure 2, the third aspect will now be discussed. According to the third aspect, there is provided a method 100 of producing an iron-based soft magnetic powder composition comprising the steps of:

[0172] (i) providing 102 iron-based soft magnetic core particles;

[0173] (ii) contacting 104 the iron-based soft magnetic core particles with a first aqueous solution comprising: (a) a silicate of the general formula (K2O)a(SiO2)|3, wherein a is moles of K2O, p is moles of SiCh, and the P / a molar ratio is in the interval from 0.5 to 4.1, and, wherein the silicate is present in an amount of 0.02 to 1.0 wt% calculated based on the total weight of the iron-based soft magnetic powder composition; (b) flux agent particles of a compound comprising bismuth and oxygen having a D50 measured according to ISO 13320:2020 in the interval of 0.1 to 2 pm; and (c) nanoparticles comprising a compound selected from TiOz, Y2O3 and ZrO2.

[0174] The (ii) contacting of the iron-based soft magnetic core particles with the first aqueous solution may be performed by mixing, e.g., in a mixer. The result of contacting the soft magnetic iron-based core particles with the first aqueous solution is that the first coating is formed on the magnetic iron-based core particles so as to at least partially cover the magnetic iron-based core particles. In other words, the method according to the third aspect of the technology proposed herein produces soft magnetic iron-based core particles coated with the first coating, i.e., the iron-based soft magnetic powder composition according to the first aspect of the technology proposed herein. The soft magnetic ironbased core particles coated with the first coating and optionally also coated with the second coating as described below may alternatively be referred to as coated core particles or coated soft magnetic iron-based core particles.

[0175] When performing the method according to variants of the third aspect, it may occur that the nanoparticles as provided or obtained are agglomerated into agglomerates having a diameter above 200 nm and / or such that the agglomerated nanoparticles have a D50 above 200 nm. These agglomerates may suitably be fully or partially disintegrated so as to obtain, or increase the number of, nanoparticles having the desired D50 or diameter of 1-200 nm or smaller as preferred above because well distributed nanoparticles within the first coating is preferred. Where the nanoparticles used in the method comprises significant amounts of agglomerates, and when no further disintegration is performed on the nanoparticles, then the mol% of nanoparticles in the first coating may be increased compared to when nanoparticles comprising no or only a minor number of agglomerates and having a lower D50 or diameter are used.The disintegration may take place before or during the preparation of the first aqueous solution, or during the contacting of the soft magnetic iron-based core particles with the first aqueous solution. As an example, sonication may be used for disintegration.

[0176] The method of the third aspect may further comprise one or more of the steps of:

[0177] (iii) drying the iron-based soft magnetic core particles, and / or

[0178] (iv) contacting the iron-based soft magnetic core particles with at least one metalorganic compound having the general formula

[0179] R1[(R1)x(R2)y(M)]nOn-lR1(I)

[0180] or

[0181] R2[M(OH)2(n+l)](n+l)O(n)R2(II)

[0182] wherein M is selected from the group consisting of Si, Ti, Al, and Zr; O is oxygen; R1is a hydrolysable group; R2is an organic moiety and wherein at least one R2contains at least one nitrogen containing group, preferably an amino group; wherein n is the number of repeating units being an integer between 1 and 20; wherein x is 0 or 1; and wherein y is 1 or 2, and x+y is 2,

[0183] wherein the content of the at least one metal-organic compound is 0.2 to 1.40 wt%, based on the total weight of the iron-based soft magnetic powder composition, and / or

[0184] (v) mixing the soft magnetic iron-based core particles with a lubricant, preferably a particulate lubricant.

[0185] Step (iii) of drying may be performed after step (ii) of contacting.

[0186] Step (iii) of drying may be performed by heating the soft magnetic iron-based core particles while stirring. The drying may, for example, be conducted during stirring at 60°C for 1 h, which may be followed by further drying without stirring at 120°C.

[0187] According to a fourth aspect, there is provided a method of manufacturing an object from the iron-based soft magnetic powder composition according to the first aspect or variants thereof or the iron-based soft magnetic powder mixture according to the second aspect or variants thereof, comprising the steps of:

[0188] (i) compacting the iron-based soft magnetic powder composition according to the first aspect or variants thereof or the iron-based soft magnetic powder mixture according to the second aspect or variants thereof in a die at a compactionpressure in the range of 500-2000 MPa, preferably 600-1800 MPa, to obtain a compacted part, and

[0189] (ii) heat treating the compacted part in a nonreducing atmosphere, preferably comprising 0-22 % by volume, more preferably 0.5 to 2 % by volume, oxygen (O2) at a temperature in the range of 300-800 °C, preferably 400-750 °C, more preferably 600-700 °C, to obtain the object.

[0190] The (i) compacting may be cold die compaction, warm die compaction, or high-velocity compaction, preferably a controlled die temperature compaction (50-120°C) with an unheated powder is used. During the compaction, the coated soft magnetic iron-based core particles are pressed together and may be deformed so as to adhere to each other and form the compacted part. During the heat treatment the flux agent particles of the compound comprising bismuth and oxygen together with the nanoparticles and the silicate in the first coating and the amino- and / or alkyl-groups of the metal-organic compound of the second coating form an evenly distributed bismuth-silicate glass on the surface of the soft magnetic iron-based core particles which provides the desired electrical resistivity between the individual particles of the compacted and heat treated iron-based soft magnetic powder composition in the finished object. Additionally, the heat treatment relieves the stress formed during the compaction.

[0191] When using iron-based soft magnetic powder composition comprising iron alloy particles, typically, a relatively higher compaction pressure may be desirable, such as 1200-1800 MPa. In absence of iron alloy particles, typically, a relatively lower compaction pressure may be desirable, such as 600-1200 MPa. For example, the compaction pressure may be in the range of 500-2000 MPa, such as 600-1800 MPa.

[0192] The heat treating may be in vacuum, non-reducing, inert or in weakly oxidizing atmospheres, e.g., 0.01 to 3 % by volume of oxygen in nitrogen. In one embodiment, an essentially pure nitrogen atmosphere is used as a non-reducing atmosphere. In one embodiment with addition of 0-22 wt% oxygen, preferably 0.5-2 wt% oxygen. Higher temperature, above 680-700 °C, may require lower oxygen levels such as 500-3000 ppm (0.05-0.3 wt%). Generally, the oxygen levels may be higher during the initial heating, e.g., during melting and / or delubrication of the lubricant. Optionally, the heat treatment may be performed in an inert atmosphere and thereafter exposed quickly in an oxidizing atmosphere, such as 0.5-22 wt% oxygen / nitrogen mixtures or in steam / nitrogen mixtures, to improve the resitivity and build a superficial crust of higher strength and / or corrosion resistance. The temperature may in one embodiment be up to 800°C. Heat treating the compacted part at a temperature in the range 300-800 °C means that the temperature compacted part is exposed to a temperature in the range 300-800 °C. This may typically beconducted for a time period sufficient to cause the compacted part to be heated to a temperature in the range 300-800 °C, such as for example 20-120 minutes.

[0193] Typically the heat treating may be performed in three phases: a delubrication stage at about 300-400°C during which the compacted part is heated up towards the curing stage, a curing stage at about 350-450°C (first temperature and time) in which the first coating is cured so as to cause the formation of the electrically insulating glassy coating (the silicate and any present silane is being polymerised to form the silicate glass) from the first, and second coating, when present, and a relaxation stage at 600-700°C (second temperature and time) in which the glassy coating flows out to cover the core particles and the stresses from the compaction was released. The temperature in the range of 300-800 °C given for step (ii) above corresponds to this last (second) temperature. The first and second time period may typically be 0-60 minutes each, such as 1-60 minutes.

[0194] The compacted part may further be heat treated at a temperature below the glass crystallisation temperature of formed glassy coating comprising bismuth and silicate.

[0195] Causing crystallisation of the formed glassy coating may decrease the resistivity and mechanical strength of the final component. Further, crystallisation of the glassy coating may cause cracks in the glassy coating formed by the first coating and the second coating during the heat treatment.

[0196] The heat treatment may comprise a delubrication stage, wherein the temperature may be between 300 and 400°C, such as 320-380°C, such as 330-370°C. The atmosphere in the delubrication stage may be an inert atmosphere, such as an IXMg.) atmosphere.

[0197] Step (ii) may comprise heat treating the compacted part at a (second) temperature of at least 650°C, such as, for example, at least 670°C to substantially or fully eliminate the stress in the compacted part. The temperature where maximum elimination of stress in the compacted part occurs is called the maximum relaxation temperature.

[0198] Step (ii) accordingly may comprise heat treating the compacted part at a second temperature of 670-700 °C, preferably 680-700 °C.

[0199] For heat treating at higher second temperatures, e.g., between 700°C and 750°C or 750°C and up to 800°C, it may be preferred that a thicker first coating, i.e., a higher wt% of the silicate, such as 0.25 wt%, is used as such thicker coating provide acceptable remaining resistivity while having the potential to provide even better ageing properties. This also applies to iron-based soft magnetic powder mixture comprising harder or alloyed particles which benefit from being treated at these higher second temperatures as that allows a higher degree of relaxation of the comparative less degree of plastic deformation duringthe compaction. In particular very fine powders, e.g., 400-600 mesh, may advantageously be coated with an extra thick coating as the resulting higher resistivity and lower permeability may be more beneficial for the type of passive components in which these extra fine powders suitably may be used.

[0200] The inclusion of the dopant allows these high heat treatment step temperatures with corresponding low coercivity while maintaining acceptable resistivity and thus acceptable core loss.

[0201] The step (ii) of heat treating may comprise heat treating the compacted part at a temperature within an interval of 650-730°C. For example, the temperature may be 650-700°C; or 680-730°C, such as 680-710°C..

[0202] The heat treatment may further comprise an initial preoxidation step in ambient air at between 200 and 250°C for 1-30 h, such as 2-18 h. This improves electrical resistivity.

[0203] In particular, the heat treating step may comprise the preoxidation step followed by delubrication at 400-500°C in inert atmosphere (e.g. nitrogen), followed by curing and stress relaxation treatment at between 600 and 700°C in between 5000 and 15000 ppm oxygen. This improves mechanical strength (TRS) without sacrificing the magnetic properties such as resistivity, coercivity and core loss significantly.

[0204] According to a fifth aspect, there is provided a an object comprising a compacted ironbased soft magnetic powder composition according to the first aspect or variants thereof or a compacted iron-based soft magnetic powder mixture according to the second aspect or variants thereof.

[0205] Preferably, the object has a resistivity, as measured using 4-point probe method with 10 mm distance between measuring points, of at least 750000 pQm, more preferably at least 950000 pQm.

[0206] In the following examples, various iron-based soft magnetic powder compositions comprising soft magnetic iron-based core particles according to variants of the first aspect of the technology proposed herein will be discussed. Further, coating soft magnetic ironbased core particles with various first and second coatings in accordance with variants of the third aspect of the technology proposed herein will be discussed and exemplified. The iron-based soft magnetic powder compositions have been used to produce test parts or test objects which were compacted and heat treated according to variants of the method according to the fourth aspect of the technology proposed herein. Finished test parts were finally investigated for relevant properties such as resistivity (Res) and initial permeability (Ri).

[0207] More specifically, the test parts used in the examples were produced in the following steps:Step 1: Soft magnetic iron-based core particles were mixed (10 min) with an aqueous solution of a silicate of the general formula (K2O)a(SiO2)|3 (potassium silicate K12, Sibelco Nordic AB, |3 / a molar ratio of about 3.36, solids content 34,7 wt%) at a concentration (based on dry matter content) of between 0.2 and 0.7 wt% to form the first coating on the core particles. Particles of a compound containing bismuth and oxygen, specifically Bi(OH)3 at an amount of 75 wt% of the solid content of the silicate, unless specified otherwise, were also included in the aqueous solution. It has been found advantageously that the silicate coating is coated twice, i.e. a portion of, such as half, the amount of the ingredients is added as a first layer followed by a semi-drying step.

[0208] Thereafter, the second part of the silicate coating is added, distributed and then dried while stirring. Nanoparticles were included in the first silicate coating, the nanoparticles being Y2O3 particles (nominally 10 nm) at 20 mol% based on the content of K, unless otherwise specified.

[0209] After the initial mixing, distributing the ingredients, the, thus coated, core particles where dried while being stirred at 60°C for 1 h, followed by further drying without stirring at 120°C.

[0210] Step 2: The mixture from step 1 was further mixed with a liquid silane (oligomeric diaminofunctional silane Dynasylan® 1146 from Evonik Industries AG) for 5 min to form the second coating, and the resulting mixture was dried at 50°C for 2 h to produce a finished iron-based soft magnetic powder composition comprising coated soft magnetic iron-based core particles. The added amount of silane was 200% of the dry matter silicate, unless otherwise specified.

[0211] Step 3. A lubricant (0.5 wt% amide wax, unless otherwise specified) was added to the iron-based soft magnetic powder composition in order to facilitate producing the test part, and the iron-based soft magnetic powder composition was then shaped and compacted (die temperature of 60°C, unless otherwise specified) into test parts which were heat treated to release stress from the compaction to form the finished test parts.

[0212] The soft magnetic iron-based core particles were a water atomized annealed iron powder having dimensions according to 100 mesh (D50 ~105pm). Thereafter, the powders were sieved to 300 mesh (<45pm), 400 mesh (<35pm) or 500 mesh (<25pm), respectively. Wherein less than 10% by weight of the soft-magnetic iron-based core particles have a size above the sieved mesh. For comparison, electrolytic iron was used having an average particle size (D50) of 20pm. The alloyed iron-based powder was gas-atomized Sendust powder (Fe9.5Si AI5.5) (average particle size Dso~13pm) and gas-atomized Fe6.8Si-powder (average particle size Dso~22pm), unless otherwise specified.

[0213] The heat treatment was performed in three stages in a pre-heated furnace. The three stages comprised a delubrication stage at about 300-400°C during which the compacted part was heated up towards the curing stage, a curing stage at about 350-450°C(first time and temperature given for each sample) in which the first and second coatings were cured so as to cause the formation of an electrically insulating silicate glass from the first and second coatings, and a relaxation stage at between 600-750°C in which the stress from the compaction was released. The standard maximum temperature was 690°C for 35 min in an oxygen partial pressure of 1500 ppm (0.15 wt% oxygen in nitrogen), unless otherwise specified.

[0214] The finished test parts (OD40 / ID30 / H5 mm magnetic square toroids) were subjected to test to determine inter alia:

[0215] Electrical resistivity (Res) was measured using 4-point probe method with 10 mm distance between measuring points [pQm],

[0216] Coercivity* (Hc) was measured at a maximum field of 10 kA / m [A / m],

[0217] Initial permeability* (pi) - the ratio between the magnetization that a material obtains in response to a low applied magnetic field, relative the permeability of air [unitless].

[0218] Total core loss* for a test part obtained for a given induction and frequency [W / kg], The core losses are measured at O.lT / lOkHz, 0.1T / 30kHz and 0.05T / 100kHz, unless otherwise specified.

[0219] B10 - the magnetic flux density of the material at the magnetic field of 10 kA / m [T], DC-bias* - the p as a function of applied magnetic field. The value is the field [A / m] where the p has decreased to 80% of the initial value (pi).

[0220] *For the measurement of magnetic properties, the square toroids were wound with 70 drive and 70 sense turns of resin coated copper wire (diameter 0.63 mm) and measured using a Brockhaus MPG 200D. The high frequency core losses were measured with an AMH-200K-S from Laboratorio Elettrofisico. References: IEC 60404-4 (DC measurements) and IEC 60404-6 (AC-measurements) the square toroids were wound similarly but with 25 drive and 10 sense turns. The initial permeability was measured using an LCR meter (HP 4284A) on the 25-turn coil. For DC-bias measurements the copper wire (diameter 1.0 mm) was wound 30 turns.

[0221] Square toroid density (d) - density of the square toroid test part [g / cm3].

[0222] TRS -Transverse rupture strength according to SS-EN ISO 3325:2000, on bars with dimensions of 30x12x6 mm [MPa],

[0223] GS - Green strength, measured as TRS but on test parts prior to heat treatment [MPa],

[0224] Example 1: Particle size and coating load

[0225] To restrict the eddy current losses at high frequency it has been found important to decrease the particle size of the base powder. The present example shows the effect on magnetic properties for different particle size distributions of essentially pure iron powder.To maintain sufficient electrical resistivity, it is evident from the results that the coating load benefits from being increased for finer powders, i.e. from 0.2 wt% to 0.5 wt% solid content of silicate, other ingredients according to the procedure described above. Sample 6 is based on annealed electrolytic iron of a similar particle size distribution as sample 5. Sample 1 is a comparing example with coarser iron-based core particles.

[0226] Table 1. Iron powder of different coating thickness. Dens, denotes density.

[0227] <

[0228] <

[0229] <

[0230] <

[0231] <

[0232]

[0233] * Electrolytic iron powder product produced by North American Hbganas Inc.

[0234] From the results above it is clear that a smaller particle size distribution requires a higher coating load to achieve sufficient electrical resistivity to suppress eddy current losses. However, smaller particles show higher coercivity resulting in higher hysteresis loss. At high frequencies it is evident that the total core loss decreases with smaller base powder particle size, as a result of the reduced AC loss. For example, using particle sizes finer than 200 mesh, for example 300 mesh or <63 pm or below, the total loss is reduced. Hence, to minimize the total core loss for a specific application there is an optimal particle size distribution. Suitably for a composition wherein at least 80% by weight of the soft magnetic iron-based core particles have particle sizes of 63 pm or below, the amount of silicate is 0.3 to 0.5 wt%, as calculated based on the total weight of the iron-based soft magnetic powder composition. More preferably, for a composition wherein at least 80% by weight of the soft magnetic iron-based core particles have particle sizes of 63 pm or below, the amount of silicate is 0.35 to 0.45 wt% as calculated based on the total weight of the ironbased soft magnetic powder composition.It was unexpexted that the increased silicate amount provided a better composition since increased silicate content decreases the iron content, i.e. the density, of the composition.

[0235] Example 2: Mixtures of essentially pure iron powder and alloyed powder

[0236] Example 2 shows the effect on magnetic properties and mechanical strength for different load of Sendust powder, compacted at 1100 MPa.

[0237] Table 2A. Iron powder (<45pm) mixed with different load of Sendust powder. The iron powders are coated with 0.3 wt% silicate coating, while the Sendust powder has either been coated with 0.4wt% silicate or coated with phosphoric acid (phosphate coating).

[0238]

[0239]

[0240] By increasing the load of Sendust the coercivity can be decreased. However, with increasing load of Sendust the density, induction, permeability, and mechanical strength are reduced which shows the need of optimization to meet the requirements for the application.

[0241] Phosphate-coated alloyed powder, such as Sendust, will markedly increase the permeability but is beneficial for the core loss.

[0242] Table 2B. Iron powder (<25pm) mixed with different load of Sendust powder.

[0243]

[0244] Using even finer iron powder (<25pm) the benefit in total core loss at high frequencies is evident.

[0245] Table 2C. Mechanical properties of the samples in table 2A.

[0246] <

[0247]

[0248]

[0249] The results show the possibility to decrease the total core loss by optimizing the load of alloyed powders, while maintaining an acceptable TRS and GS. In addition, the load of alloyed powder will also have an impact on electrical resistivity, permeability and mechanical strength. If the alloyed powder is instead coated with phosphate, and thereafter mixed with the coated iron powder, this will have a positive effect on the core loss but influences the permeability and mechanical strength (TRS), as shown in table 2C.

[0250] Example 3: The effect of particle shape of the Sendust powder

[0251] The present example shows the impact on magnetic properties when using milled versus gas atomized Sendust powder. The particle shape of gas atomized powders is significantly more resembling spherical particles as compared to milled powders. The composition is 50% iron powder (<45pm; coated with 0.3% silicate) and 50% phosphate-coated Sendust powder, compacted at 1100 MPa.

[0252] Table 3. The effect of using milled Sendust versus gas atomized Sendust, the latter having particle shapes more resemb ing spherical particles.

[0253]

[0254] The results show that it is beneficial using gas atomized (GA) Sendust powder as the magnetic properties are improved, such as lower permeability and better DC-bias.

[0255] Example 4: Compaction using die wall lubrication (DWL)

[0256] The present example shows the possibility to compact the composition using die wall lubrication in order to reach higher density and magnetic induction. The iron powders arecoated with 0.3 wt% silicate coating, while the Sendust powder (50% load) has been coated with 0.4wt% silicate.

[0257] Table 4. The effect using DWL to reach higher magnetic induction and lower core loss.

[0258]

[0259] The present example shows the possibility to compact the powder composition using DWL to reach higher magnetic induction and lower core loss. Note that DWL facilitates the use of 0.1 wt% internal lubricant only, thus, also allowing for higher compaction pressures.

[0260] Example 5: The effect of adding mineral clay into the composition

[0261] The addition of mineral clay into the composition has a similar effect as adding more silicate in that it increases resistivity and lower permeability of the component. This illustrates a possibility to tailor the magnetic properties of the component. The used mineral clay in this example is kaolinite, or kaolin, provided by KaMin LLC (Polygloss 90).

[0262] Table 5. Effect of adding kaolin into the composition (50% Sendust), compacted at HOOMPa.

[0263] <

[0264] <

[0265]

[0266] <

[0267]

[0268] <

[0269] In the present example the impact of adding mineral clay into the composition is shown. The clay contributes, similar to silicate, to higher resistivity and lower permeability showing the possibility to tailor magnetic properties to find the best option for every application.

[0270] Example 6: The effect of using other alloyed powders

[0271] The present example illustrates the effect of replacing Sendust alloy with FeSi-a Hoy.

[0272] Table 6. Comparison between Sendust of FeSi- alloys (llOOMPa). The resistivity is high for all samples, beyond reliable measurements.

[0273] <

[0274] <

[0275] <

[0276] <

[0277]

[0278] The improved density and induction of the FeSi-alloy, allows the amount of silicate and / or clay to be increased in order to lower the permeability without sacrificing the total core losses. The present example further illustrates the benefit of combining different ironbased alloys, which may give a low total core loss in combination with good DC-bias properties for a specific application.

[0279] Example 7: The effect of using different clays

[0280] The present example illustrates that the effect is not limited to kaolin, or kaolinite (Polygloss 90; <lpm), as mineral clay. Similar effect on performance can also be obtainedby other types of clay minerals, such as muscovite (such as Micafort SX800; <20pm), montmorillonite (such as Bentonite MB350S; <53pm), talc (such as French chalk; ~10 pm).

[0281] Table 7. Comparison between different mineral clays. The composition is iron powder (<45pm) mixed with 50% Sendust, coated with 0.5 wt% silicate, compacted at llOOMPa

[0282]

[0283] The present example illustrates the possibility to use different mineral clays but may require further optimization of the particle size and processing to obtain an even distribution.

[0284] Example 8: Effect of compaction pressure

[0285] The present example illustrates the effect of compaction pressure, i.e. density, on magnetic properties. Increased pressure results in improved density and induction. However, other parameters such as resistivity, and DC-bias are worse. The permeability is increased.

[0286] Table 8. The effect of compaction pressure on the composition <45pm iron powder and 50% Sendust powder, coated with 0,5wt% silicate.

[0287]

[0288] The total core loss is normally decreased for higher component density. The application, however, might require a low but a specified level of permeability. In general, to reach lower permeability it is more favourable to introduce clay mineral instead of lowering the compaction pressure.Example 9: Effect of heat treatment temperature

[0289] The present example illustrates the effect of relaxation temperature, for two different compaction pressures (800MPa and llOOMPa, respectively).

[0290] Table 9. The effect of compaction pressure on composition <45pm iron powder and 50% Sendust powder, coated with 0,5wt% silicate. The resistivity is very high for all sa m p I e s .

[0291]

[0292] The increased temperature results in lower coercivity and hence lower total core loss given that the electrical resistivity is kept sufficiently high. Lower density (lower compaction pressure) can provide lower coercivity but result in relatively lower induction level.

[0293] Example 10: Comparison with WO 2012 / 136758 A2

[0294] A study was conducted comparing a composition of coated iron powder (<75pm; 200mesh) mixed with 30% coated Sendust (according to Sample LI, example 11 in WO 2012 / 136758 A2), and a powder composition according to a variant of present aspects, represented by iron powder (<45pm; 300mesh) mixed with 50% Sendust.

[0295] Table 10. Mechanical strength, density and magnetic induction. The ageing of the comparative sample was done at 200°C for 5 days, while the present invention was instead aged at 240°C for 20 days. The total core loss change (0.1T / 30kHz) caused by the ageing

[0296] <

[0297]

[0298] <

[0299]

[0300] The comparative example shows superior properties of variants of present aspects compared to the mixture according to Sample LI of example 11 in WO 2012 / 136758 A2. The improved mechanical strength allows for an increased load of alloyed powder (>30%). The example also shows significantly improved ageing properties, i.e. higher stability of magnetic performance after subjecting the component to elevated temperatures over time.

[0301] It can be concluded that a fine iron-based soft magnetic powder, wherein at least 80% by weight of the soft magnetic iron-based core particles have particle sizes of 63 pm or below, or more precisely 45 pm or below, mixed with further iron-based soft magnetic powder composition comprising iron alloy particles have improved properties for as compared to a prior art powder having no clay mineral, different coating and having coarser iron core particles.

[0302] Example 11: Comparison with WO 2012 / 136758 A2

[0303] A study was conducted with a comparing composition of coated iron powder (<75pm; 200mesh) mixed with 30% coated Sendust (Sample 1) and a powder composition according to a variant of present aspects, represented by an iron powder (<45pm; 300mesh) mixed with 50% Sendust, with two different levels of permeability (Samples 2 and 3). Sample 1 is a coated iron powder (<75pm; 200mesh) mixed with 30% coated Sendust, with a first layer of phosphorous coating and a second layer coating consisting of 2% kaolin clay and 0.4% sodium silicate (Sample R in Example 3 in WO 2012 / 136758 A2).

[0304] Table 11. The density, magnetic induction, initial permeability, total core loss and DC- bias.

[0305] <

[0306] <

[0307] <

[0308]

[0309] The comparative example shows the superior coating concept (Sample 2 and 3) showing improved mechanical strength and DC-bias compared to the sample R in example 3 in WO2012 / 136758 A2. For a similar level of total core loss, the invention can achieve significantly improved DC-bias properties (and lower permeability) (Sample 2). Furthermore, for a similar level of permeability the invention results in lower total core losses (Sample 3).

Claims

CLAIMS1. An iron-based soft magnetic powder composition for passive soft magnetic components comprising:(i) soft magnetic iron-based core particles, wherein at least 80% by weight of the soft magnetic iron-based core particles have particle sizes of 63 pm or below as measured according to ISO 4497:2020; and(ii) a first coating, at least partly covering and being in contact with the soft magnetic iron-based core particles, wherein the first coating comprises- a silicate of the general formula (K2O)a(SiO2)|3, wherein a is moles of K2O, |3 is moles of SiO2, and the |3 / a molar ratio is in the interval from 0.5 to 4.1, wherein the silicate is present in an amount of 0.02 to 1.0 wt% calculated based on the total weight of the iron-based soft magnetic powder composition,- flux agent particles of a compound comprising bismuth and oxygen having a D50 measured according to ISO 13320:2020 in the interval of 0.1 to 10 pm, and - nanoparticles comprising one or more compounds selected from TiO2, Y2O3 and ZrO2.

2. The iron-based soft magnetic powder composition according to claim 1, wherein at least 80% by weight of the soft magnetic iron-based core particles have particle sizes in the range of 63 pm to 3 pm as measured according to ISO 4497:2020.

3. The iron-based soft magnetic powder composition according to claim 1 or 2, wherein the silicate is present in an amount of 0.3-0.8 wt%, such as 0.3-0.6 wt%, calculated based on the total weight of the iron-based soft magnetic powder composition.

4. The iron-based soft magnetic powder composition according to any one of claims 1 to 3, wherein the first coating further comprises clay minerals, optionally selected from one or more of bentonite, kaolin, muscovite, and talc.

5. The iron-based soft magnetic powder composition according to any one of claims 1 to 4, wherein at least 80% by weight of the soft magnetic iron-based core particles have particle sizes of 53 pm or below, such as 45 pm or below, such as 37 pm or below, as measured according to ISO 4497:2020.

6. The iron-based soft magnetic powder composition according to any one of claims 1 to 5, wherein the nanoparticles are characterised by having a Dso of 10-200 nm as determinedaccording to ISO 13320:2020, or characterised by having a specific surface area of 6-120 m2 / g as determined according to ISO 9277:2022.

7. The iron-based soft magnetic powder composition according to any one of claims 1 to 6, further comprising:(iii) a second coating at least partially covering the surface of the core particles and / or the first coating, the second coating comprising:(a) at least one metal-organic compound having the general formula R1[(R1)x(R2)y(M)]nOn-lR1(I)orR2[M(OH)2(n+l)](n+l)O(n)R2(II)wherein M is selected from the group consisting of Si, Ti, Al, and Zr; O is oxygen; R1is a hydrolysable group; R2is an organic moiety and wherein at least one R2contains at least one nitrogen containing group, preferably an amino group; wherein n is the number of repeating units being an integer between 1 and 20; wherein x is 0 or 1; and wherein y is 1 or 2, and x+y is 2, wherein the content of the at least one metal-organic compound is 0.2-1.4 wt%, preferably 0.4 to 1.0 wt%, based on the total weight of the iron-based soft magnetic powder composition.

8. An iron-based soft magnetic powder mixture comprising:- the iron-based soft magnetic powder composition according to any one of claims 1 to 7, and- an alloyed iron-based soft magnetic powder composition comprising iron alloy particles having a higher electrical resistivity than the soft magnetic iron-based core particles of the iron-based soft magnetic powder composition.

9. The iron based soft magnetic powder mixture according to claim 8, wherein the soft-magnetic iron based core particles of the alloyed iron-based soft magnetic powder composition comprise or consist of an iron alloy selected from the group consisting of FeSi, FeAl, FeP, FeSiAl, FeNi, FeCo, and FeNiCo, or combinations or mixtures of such alloys.

10. The iron based soft magnetic powder mixture according to claim 9, wherein the iron alloy is selected from the group consisting of FeSi, preferably with 3-6.8 wt% Si, and FeSiAl, preferably with 8.5-10.5 wt% Si and 4.5-6.5 wt% Al or 2.5-6.0 wt% Si and 2.5-4.0 wt% Al.

11. The iron based soft magnetic powder mixture according to any one of claims 8 to 10, wherein the content of the alloyed iron-based soft magnetic powder composition is up to90 wt%, such as 30-90 wt%, based on the weight of the iron-based soft magnetic powder mixture.

12. A method of producing an iron-based soft magnetic powder composition comprising the steps of:(i) providing iron-based soft magnetic core particles,(ii) contacting the iron-based soft magnetic core particles with a first aqueous solution comprising:(a) a silicate of the general formula (K2O)a(SiO2)|3, wherein a is moles of K2O, P is moles of SiCh, and the P / a molar ratio is in the interval from 0.5 to 4.1, and wherein the silicate is present in an amount of 0.02 to 1.0 wt% calculated based on the total weight of the iron-based soft magnetic powder composition,(b) flux agent particles of a compound comprising bismuth and oxygen having a D50 measured according to ISO 13320:2020 in the interval of 0.1 to 2 pm, and(c) nanoparticles comprising a compound selected from TiOz, Y2O3 and ZrO2.

13. The method according to claim 12, further comprising one or more of the steps of:(iii) drying the iron-based soft magnetic core particles, and / or(iv) contacting the iron-based soft magnetic core particles with at least one metalorganic compound having the general formulaR1[(R1)x(R2)y(M)]nOn-lR1(I)orR2[M(OH)2(n+l)](n+l)O(n)R2(II)wherein M is selected from the group consisting of Si, Ti, Al, and Zr; O is oxygen; R1is a hydrolysable group; R2is an organic moiety and wherein at least one R2contains at least one nitrogen containing group, preferably an amino group; wherein n is the number of repeating units being an integer between 1 and 20; wherein x is 0 or 1; and wherein y is 1 or 2, and x+y is 2,wherein the content of the at least one metal-organic compound is 0.2 to 1.40 wt%, based on the total weight of the iron-based soft magnetic powder composition, and / or(v) mixing the soft magnetic iron-based core particles with a lubricant, preferably a particulate lubricant.

14. A method of manufacturing an object from the iron-based soft magnetic powder composition according to any of the claims 1-7 or the iron-based soft magnetic powder mixture according to any of the claims 8-11, comprising the steps of:(i) compacting the iron-based soft magnetic powder composition according to any of the claims 1-7 or the iron-based soft magnetic powder mixture according to any of the claims 8-11 in a die at a compaction pressure in the range of 500-2000 MPa, preferably 600-1800 MPa, to obtain a compacted part, and(ii) heat treating the compacted part in a nonreducing atmosphere, preferably comprising 0-22% by volume, more preferably 0.5 to 2% by volume, oxygen (O2) at a temperature in the range of 300-800 °C, preferably 400-750 °C, more preferably 600-700 °C, to obtain the object.

15. An object comprising a compacted iron-based soft magnetic powder composition according to any of the claims 1-7 or a compacted iron-based soft magnetic powder mixture according to any of the claims 8-11.

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