Ferromagnetic powder composition and method of manufacturing same

Abstract

A ferromagnetic powder composition comprising (i) soft magnetic iron-based core particles and (ii) a first coating at least partially covering the surface of said core particles and in direct contact with the surface of said core particles, said first coating comprising: a) a silicate of general formula (K2O)α(SiO2)β, where α is the moles of K2O and β is the moles of SiO2, the β / α molar ratio being between 0.5 and 4.1, said silicate being present in an amount of 0.02 to 1.0 wt. %, calculated on the total weight of the ferromagnetic powder composition; and b) a D between 0.1 and 10 μm. 50 and c) particles of a compound containing bismuth and oxygen having a D of 10 to 200 nm. 50 and nanoparticles having the formula: Also provided are methods for producing the ferromagnetic powder composition and for producing objects from the ferromagnetic powder composition, as well as objects obtained by the methods or comprising the compacted ferromagnetic powder composition.

Description

[Technical Field]

[0001] The technology proposed herein relates generally to the field of ferromagnetic powder compositions comprising soft magnetic iron-based core particles and methods of making ferromagnetic powder compositions. [Background technology]

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

[0003] Two important properties of soft magnetic core particles and corresponding components made from such particles are the magnetic permeability μ and the core loss characteristic P c The magnetic permeability μ of a material is a measure of its ability to be magnetized or to carry magnetic flux. The maximum magnetic permeability (μ max ) is defined as the maximum value of B / H, i.e., the ratio of magnetizing force B or magnetic field strength to induced magnetic flux H. When a magnetic material is exposed to a varying magnetic field, energy losses occur due to both hysteresis and eddy current losses. Hysteresis losses (DC losses), which make up the majority of the total core losses in most motor applications, result from the expenditure of energy required to overcome the coercive forces in components made from soft magnetic core particles, resulting in remanence, i.e., residual magnetism B R , and coercive force H C is affected by.

[0004] The magnetic retention within a component can be minimized by improving the quality and purity of the soft magnetic core particles, particularly by heat treating the component to relieve stresses caused by compressive shear forces within the component. Energy loss is further caused by eddy current (AC) losses, which are caused by the induction of current within the component by changing magnetic flux caused by alternating current (AC) conditions. Eddy current losses are minimized by an electrically insulating coating on each particle, thereby insulating the soft magnetic core particles from each other. Therefore, the resistivity (R) of the coating is an important parameter for defining the properties and usability of soft magnetic core particles. The level of electrical resistivity (R) required to minimize AC losses in components made from soft magnetic core particles depends on the size distribution of the soft magnetic core particles, the size of the component, and the frequency of the AC magnetic field in which the component will be used.

[0005] EP 2252419 generally discloses a ferromagnetic powder composition comprising soft magnetic iron-based core particles, the surface of which is provided with a first inorganic insulating layer and at least one metal-organic layer located outside the first layer.

[0006] U.S. Pat. No. 10,741,316 generally discloses ferromagnetic powder compositions comprising soft magnetic iron-based core particles, the surfaces of which are coated with at least one phosphorus-based inorganic insulating layer and then at least partially covered with metal-organic compound(s).

[0007] EP 3411169 generally discloses a powder mixture comprising phosphorus-coated iron alloy particles and phosphorus-coated iron particles.

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

[0009] Despite the advantages offered by the techniques described in the prior art documents cited above, there remains a need to provide ferromagnetic powder compositions comprising soft magnetic core particles with improved electrical, magnetic, and structural properties. Summary of the Invention [Problem to be solved by the invention]

[0010] the purpose The primary objective of the technology proposed herein is to provide ferromagnetic powder compositions and mixtures containing soft magnetic core particles with improved electrical, magnetic and / or structural properties.

[0011] It is a further object of the technology proposed herein to provide ferromagnetic powder compositions and mixtures comprising soft magnetic core particles that offer an improved balance between two or more of electrical, magnetic, and structural properties.

[0012] A further object of the technology proposed herein is to provide a method for producing a powder composition comprising soft magnetic core particles.

[0013] A further object of the technology proposed herein is to provide a method for producing an object from a ferromagnetic powder composition or mixture.

[0014] Further objects of the technology proposed herein include objects made from and including compacted ferromagnetic powder compositions or mixtures. [Means for solving the problem]

[0015] overview At least one of the above objects or at least one further object that will become apparent from the following description is to provide a method for manufacturing a computer-readable recording medium comprising: (i) soft magnetic iron-based core particles; (ii) a first coating at least partially covering and in direct contact with the surface of the core particle, a. Silicates of the general formula (K2O)α(SiO2)β, where α is the moles of K2O, β is the moles of SiO2, and the β / α molar ratio is between 0.5 and 4.1, i. said silicate present in an amount of 0.02 to 1.0 weight percent calculated based on the total weight of the ferromagnetic powder composition; b. Contains bismuth and oxygen and D between 0.1 and 10 μm measured according to SS-ISO 13320-1 50 Particles of a compound having the formula: c. D from 10 to 200 nm measured according to SS-ISO 13320-1 50 a first coating comprising nanoparticles having a ferromagnetic powder composition comprising: and, 1. A method for producing a ferromagnetic powder composition, comprising: (i) providing soft magnetic iron-based core particles; (ii) said soft magnetic iron-based core particles being: a. Silicates of the general formula (K2O)α(SiO2)β, where α is the moles of K2O, β is the moles of SiO2, and the β / α molar ratio is between 0.5 and 4.1, i. said silicate present in an amount of 0.02 to 1.0 weight percent calculated based on the total weight of the ferromagnetic powder composition; b. Contains bismuth and oxygen and D between 0.1 and 10 μm measured according to SS-ISO 13320-1 50 Particles of a compound having the formula: c. D from 10 to 200 nm measured according to SS-ISO 13320-1 50 and a nanoparticle having with a first aqueous solution comprising: a method comprising: This is achieved by the corresponding first and second aspects of the technology proposed herein.

[0016] At least one of the above objects or at least one further object that will become apparent from the following description is achieved according to a third aspect of the technology proposed herein by a method for producing an object from a ferromagnetic powder composition or a ferromagnetic powder mixture, (i) compressing the ferromagnetic powder composition or ferromagnetic powder mixture in a die at a compression pressure in the range of 300 to 2000 MPa, preferably 400 to 1200 MPa, to obtain a compacted part; (ii) heat treating the pressed part in a non-reducing atmosphere containing preferably 0-22 wt. % oxygen (O), more preferably 0.5-2 wt. % oxygen (O), at a temperature in the range of 300-800°C, preferably 400-750°C, more preferably 600-700°C to obtain an object; Includes:

[0017] At least one of the above objects, or at least one further object that will become apparent from the following description, is achieved by the object obtained by the method according to the third aspect of the presently proposed technology and by an object comprising a compacted ferromagnetic powder composition or a compacted ferromagnetic powder mixture according to the corresponding fourth and fifth aspects of the presently proposed technology. [Brief explanation of the drawings]

[0018] [Figure 1A] 1 shows SEM and EDS mapping images of soft magnetic iron-based core particles coated with a silicate first coating. [Figure 1B] 1 shows SEM and EDS mapping images of soft magnetic iron-based core particles coated with a silicate first coating. [Figure 1C] 1 shows SEM and EDS mapping images of soft magnetic iron-based core particles coated with a silicate first coating. [Figure 2A] 1 shows SEM and EDS mapping images of soft magnetic iron-based core particles coated with a silicate first coating further comprising 20 mol % Y2O3 nanoparticles. [Figure 2B]1 shows SEM and EDS mapping images of soft magnetic iron-based core particles coated with a silicate first coating further comprising 20 mol % Y2O3 nanoparticles. [Figure 2C] 1 shows SEM and EDS mapping images of soft magnetic iron-based core particles coated with a silicate first coating further comprising 20 mol % Y2O3 nanoparticles. [Figure 3] FIG. 1 shows a schematic cross-sectional view of a single particle of a ferromagnetic powder composition according to an embodiment of the first aspect of the presently proposed technology, showing a soft magnetic iron-based core particle having a first coating comprising silicate, nanoparticles, and particles of a compound comprising bismuth and oxygen, and a second coating comprising at least one metal-organic compound. DETAILED DESCRIPTION OF THE INVENTION

[0019] The corresponding first and second aspects of the technology proposed herein are as follows: (i) soft magnetic iron-based core particles; (ii) a first coating at least partially covering and in direct contact with the surface of the core particle, a. Silicates of the general formula (K2O)α(SiO2)β, where α is the moles of K2O, β is the moles of SiO2, and the β / α molar ratio is between 0.5 and 4.1, i. said silicate present in an amount of 0.02 to 1.0 weight percent calculated based on the total weight of the ferromagnetic powder composition; b. Contains bismuth and oxygen and D between 0.1 and 10 μm measured according to SS-ISO 13320-1 50 and particles of a compound having the formula: c. D from 10 to 200 nm measured according to SS-ISO 13320-1 50 a first coating comprising nanoparticles having a ferromagnetic powder composition comprising: and, 1. A method for producing a ferromagnetic powder composition, comprising: (i) providing soft magnetic iron-based core particles; (ii) said soft magnetic iron-based core particles being: a. Silicates of the general formula (K2O)α(SiO2)β, where α is the moles of K2O, β is the moles of SiO2, and the β / α molar ratio is between 0.5 and 4.1, i. said silicate present in an amount of 0.02 to 1.0 weight percent calculated based on the total weight of the ferromagnetic powder composition; b. Contains bismuth and oxygen and D between 0.1 and 10 μm measured according to SS-ISO 13320-1 50 Particles of a compound having the formula: c. D from 10 to 200 nm measured according to SS-ISO 13320-1 50 and a nanoparticle having with a first aqueous solution comprising: a method comprising: Regarding.

[0020] Thus, the technology proposed herein is based on the inventors' recognition that the magnetic and electrical properties of ferromagnetic powder compositions and parts made from them can be improved by including nanoparticles in a first coating on soft magnetic iron-based core particles. As observed from the examples and figures, including nanoparticles in the first coating appears to result in a more uniform distribution of the coating on the surface of the core particles. This improves electrical insulation between core particles and increases the resistivity of parts made from the ferromagnetic powder composition. Furthermore, a more distributed coating allows for more efficient compaction of the ferromagnetic powder composition, thus maintaining or improving the density and magnetic properties of parts and objects made from the ferromagnetic powder composition.

[0021] A further advantage of the technique proposed herein is that the first coating can be applied in a single step using an aqueous solution of silicate, particles of a compound containing bismuth and oxygen, and nanoparticles.

[0022] In the ferromagnetic powder composition, the silicate, particles of the bismuth- and oxygen-containing compound, and nanoparticles are all provided in the same first coating. In other words, the particles and nanoparticles of the bismuth- and oxygen-containing compound are dispersed in the silicate in the first coating or reacted with the nanoparticles dispersed therein so that the first coating is essentially a glass formed from the silicate and particles of the bismuth- and oxygen-containing compound. The particles and nanoparticles of the bismuth- and oxygen-containing compound may be substantially uniformly dispersed in the first coating.

[0023] The first coating of the ferromagnetic powder composition can be distinguished from a ferromagnetic powder composition having two distinct coatings on a soft magnetic iron-based core particle, for example, the first coating can be distinguished as an oxide layer of the nanoparticle and a glassy layer covering the oxide layer.

[0024] Surprisingly, it has been discovered that it is not necessary to have a first oxide layer to create a humid condition to anchor the vitreous layer.

[0025] An advantage of the technology proposed herein is that the nanoparticles are provided in the same first coating as the silicate and particles of the compound containing bismuth and oxygen. As shown by Example 8, the nanoparticles provide a more uniform distribution in the first coating embodiment. Furthermore, the silicate is in the coating (first coating) that directly contacts the surface of the core particle, i.e., the silicate contacts the surface of the core particle. Embodiments of the ferromagnetic powder composition have a substantially unfirm distribution of the components of the first coating on the surface of the core particle, thereby improving the electrical insulation and more efficient compression of the ferromagnetic powder composition.

[0026] The ferromagnetic powder composition includes a plurality of soft magnetic iron-based core particles.

[0027] The soft magnetic iron-based core particles comprise or consist of iron or an iron alloy containing at least 90% iron, preferably at least 99% iron, and more preferably at least 99.5% iron. The iron alloy may be an ferroalloy Fe-Si having up to 7% (by weight), preferably up to 3% (by weight), silicon, an ferroalloy selected from the group Fe-Al, Fe-Si-Al, Fe-Ni, Fe-Co, or Fe-Ni-Co, or a combination or mixture of such alloys. The soft magnetic iron-based core particles may also comprise a mixture of particles, such as a mixture of iron particles and iron alloy particles, or a mixture of particles made from two or more iron alloys. Preferably, the soft magnetic iron-based core particles are made from essentially pure iron, i.e., iron with unavoidable impurities. Preferably, at least 80% by weight, more preferably at least 90% by weight, of all core particles have a diameter within the range of 20 to 1000 μm, as measured according to ISO 4497.

[0028] Within this range, more specific ranges may be more appropriate depending on the intended use of the part, component, or object made from the ferromagnetic powder composition. Thus, for high frequency applications such as sensors, inductors, and converters, preferably at least 80 wt. %, more preferably at least 90 wt. %, e.g., at least 99 wt. %, of the core particles, based on the total weight of the core particles, have a diameter of 20 to 75 μm (approximately 45 μm D), as measured according to ISO 4497. 50 For low to medium frequency applications such as electric motors, generators, and converters, preferably at least 80 wt. %, more preferably at least 90 wt. %, for example at least 99 wt. %, based on the total weight of the core particles, have a particle size of 45 to 150 μm (approximately 95 to 100 μm D) as measured according to ISO 4497. 50 For low frequency applications such as electric motors, preferably at least 80 wt. %, more preferably at least 90 wt. %, for example at least 99 wt. %, based on the total weight of the core particles, have a diameter of 75 to 380 μm (approximately 180 to 210 μm D) as measured according to ISO 4497. 50(40 mesh corresponding to the

[0029] The soft magnetic iron-based core particles may be spherical or irregularly shaped, with irregularly shaped particles being preferred. The AD (apparent density) is 2.8 to 4.0 g / cm. 3 between 3.1 and 3.7 g / cm 3 It can be between.

[0030] The soft magnetic iron-based core particles may be water atomized iron powder, gas atomized iron powder, or sponge iron powder.

[0031] The first coating at least partially covers and is in direct contact with the surface of the core particles. Preferably, the first coating covers at least 50% by weight of the surface of the core particles in the ferromagnetic powder composition, for example, at least 75% by weight of the surface. More preferably, the first coating covers at least 90% by weight of the surface of the core particles in the ferromagnetic powder composition, for example, at least 95% by weight of the surface.

[0032] By partially covering, it is meant that the first coating may cover at least 50% of the surface area of ​​the core particle by weight, such as at least 75% of the surface area by weight or at least 90% of the surface area by weight.

[0033] Typically, the first coating has an average thickness in the range of 20 to 100 nm. The thickness of the coating can be estimated from the magnetic permeability: for a 40 mesh core particle, a maximum relative permeability of approximately 3000 corresponds to a thickness of zero, and a maximum relative permeability of approximately 700 corresponds to a thickness of approximately 20 nm.

[0034] Silicates of the general formula (K2O)α(SiO2)β are potassium silicates, or alternatively referred to as K-silicates, K-waterglass, potassium waterglass, or simply silicates herein.

[0035] The β / α molar ratio (i.e., the molar ratio of SiO2 to K2O) is between 0.5 and 4.1. Preferably, the molar ratio β / α is between 2.00 and 3.75. More preferably, the molar ratio β / α is between 2.5 and 3.5.

[0036] The silicate is present in an amount of 0.02 to 1.0 wt %, more preferably 0.05 to 0.5 wt %, calculated based on the total weight of the ferromagnetic powder composition. Preferably, the silicate is present in an amount of 0.05 to 0.2 wt %, calculated based on the total weight of the ferromagnetic powder composition, when at least 80 wt % of the core particles are 75 μm or larger, based on the total weight of the core particles. The silicate is present in an amount of 0.1 to 0.5 wt %, calculated based on the total weight of the ferromagnetic powder composition, when at least 80 wt % of the core particles are less than 75 μm, based on the total weight of the core particles. The first coating may be applied as shown using an aqueous solution. It has been found that when soft magnetic iron-based core particles are contacted with such a solution, substantially all of the silicate and other components, such as particles or nanoparticles of compounds containing bismuth and oxygen, ultimately become coated with the first coating. Therefore, the contents and ratios of the components and the soft magnetic iron-based core particles in the aqueous solution are carried over to the contents and ratios of the components and the soft magnetic iron-based core particles in the first coating.

[0037] The particles of the compound containing bismuth and oxygen preferably contain oxide and hydroxide of bismuth. Preferably, the D measured in accordance with SS-ISO 13320-1 50 is between 0.5 and 2 μm.

[0038] The soft magnetic iron-based core particles can be contacted with the first aqueous solution by, for example, mixing in a mixer. As a result of contacting the soft magnetic iron-based core particles with the first aqueous solution, a 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 second aspect of the technology proposed herein produces soft magnetic iron-based core particles coated with a first coating, i.e., a ferromagnetic powder composition according to the first aspect of the technology proposed herein. The soft magnetic iron-based core particles coated with the first coating and, optionally, with the second coating described below, can alternatively be referred to as coated core particles or coated soft magnetic iron-based core particles.

[0039] SS-D measured according to ISO 13320-1 50 is defined in SS-ISO 13320-1 as the median particle diameter used on a volume basis (i.e., 50% of the particles (by volume) are smaller than this diameter and 50% are larger than this diameter).

[0040] SS-D measured according to ISO 13320-1 50 can be determined, for example, using a Mastersizer 3000 from Malvern instruments.

[0041] An alternative parameter for determining the size of nanoparticles is the specific surface area (SSA) [m 2 / g], i.e., the surface area of ​​the particle per g of particle.

[0042] Therefore, D of 10 to 200 nm measured according to SS-ISO 13320-1 50 6~120m 2 can be equivalently replaced by a specific surface area (SSA) in the range of / g.

[0043] The SSA of the nanoparticles is preferably determined using the BET method, which is a method for determining the specific surface area of ​​a solid by gas adsorption.

[0044] More preferably, the SSA of the nanoparticles is preferably determined according to ISO 9277:2010, or preferably according to ISO 9277:2022.

[0045] Therefore, D of 10 to 200 nm measured according to SS-ISO 13320-1 50 is 6 to 120 m determined according to ISO 9277:2010 or preferably ISO 9277:2022 2 It can be equivalently replaced by the specific surface area (SSA) in g / g.

[0046] Preferably, the specific surface area (SSA) of the nanoparticles is 10 to 50, more preferably 10 to 30, for example 15 to 25, preferably 15 to 20, most preferably 18 m 2 / g. As stated above, these ranges are preferably determined according to ISO 9277:2010 or preferably ISO 9277:2022.

[0047] The specific surface area can be measured using a Micromeritics TriStar 3000 gas adsorption apparatus which calculates the BET surface area.

[0048] For comparison, if the particles are assumed to be spherical, the average diameter of the nanoparticles can be calculated from the specific surface area. The formula for calculating the average particle diameter (nanometers) is 6000 / (BET surface area (m)) 2 / g))×(density(g / cm 3 )) Y2O3 (density 5.01 g / cm 3 ) for 120, 6, 50, 10, and 18m 2 The specific surface areas of 10, 200, 24, 120, and 67 nm / g result in mean diameters of 10, 200, 24, 120, and 67 nm, respectively.

[0049] The nanoparticles are preferably selected from the group consisting of Y2O3 nanoparticles, ZrO2 nanoparticles, ZnO nanoparticles, MgOH2 nanoparticles, MgO nanoparticles, CaCO3 nanoparticles, Al2O3 nanoparticles, SiO2 nanoparticles, and TiO2 nanoparticles, and the nanoparticles preferably comprise or consist of Y2O3 nanoparticles.

[0050] As can be seen in Example 3a, many different nanoparticles are effective in obtaining improved magnetic and electrical properties of objects made from ferromagnetic powder compositions. Furthermore, Example 3a shows that YO nanoparticles, also known as yttria nanoparticles and yttrium oxide nanoparticles, provide the best magnetic and electrical properties currently contemplated. The nanoparticles may include a mixture of nanoparticles, for example, a mixture of two or more of the listed nanoparticles. However, it is currently preferred that only one type of nanoparticle, such as preferably YO nanoparticles, be present in the first coating.

[0051] The content of nanoparticles in the first coating is preferably 1 to 30 mol %, preferably 1 to 20 mol %, based on the molar content of K (potassium) in the first coating. As seen in Examples 1a and 3a, these typical molar contents of nanoparticles provide good results. For reference, 20 mol % of YO particles when contained in a first coating containing 0.1 wt % potassium silicate with a β / α ratio of 3.4 for 5 kg of soft magnetic iron-based core particles corresponds to 0.94 g of YO particles, or 0.0188 wt % based on the weight of the ferromagnetic powder composition.

[0052] Preferably, the nanoparticles have a D measured according to SS-ISO 13320-1 of 1 to 100 nm or 50 to 200 nm, preferably 1 to 50 nm, more preferably 5 to 50 nm, for example 30 to 50 nm or for example 5 to 20 nm, for example 10 nm. 50 It has.

[0053] More preferably, the nanoparticles have a D of 10 to 100 nm as measured according to SS-ISO 13320-1. 50 Most preferably, the nanoparticles have a D of 20 to 100 nm as measured according to SS-ISO 13320-1. 50 It has.

[0054] The former is 12 to 120 meters 2 / g SSA, and the latter ranges from 12 to 60 m 2 / g of SSA.

[0055] SS-D measured according to ISO 13320-1 50 is preferably 10 to 100 nm, and 90% by weight of the particles have a maximum diameter of 1 to 500 nm.

[0056] Alternatively, the nanoparticles have a diameter of 1 to 100 nm or 50 to 200 nm, preferably 1 to 50 nm, more preferably 5 to 50 nm, such as 30 to 50 nm or such as 5 to 20 nm, for example 10 nm. In embodiments, the nanoparticles generally have a diameter of 10 nm. 50 and nanoparticles of this size have been shown to provide the best results.

[0057] When carrying out the method according to the second aspect of the technology presented herein, the provided or obtained nanoparticles are aggregated into agglomerates having a diameter of more than 200 nm, and / or the aggregated nanoparticles have a diameter of more than 200 nm. 50 These aggregates are preferably well-distributed nanoparticles within the first coating, and therefore have the desired D of 1 to 200 nm or less, as described above. 50 The nanoparticles used in the present method should be fully or partially crushed to obtain or increase the content of nanoparticles having a diameter of 0.01 mm or 0.1 mm or 0.2 mm or 0.3 mm. If the nanoparticles used in the present method contain a significant amount of agglomerates and no further crushing is performed on the nanoparticles, the mole percent of nanoparticles in the first coating will be zero or only a small amount of agglomerates and have a lower D 50 or diameter may be preferably increased compared to when nanoparticles having a diameter are used.

[0058] The disintegration preferably occurs before or during the preparation of the first aqueous solution, or during contact of the soft magnetic iron-based core particles with the first aqueous solution. As an example, ultrasonic treatment can be used for disintegration.

[0059] The first coating is - 10 to 25 mol %, more preferably 15 to 22 mol %, for example 20 mol %, of Y2O3 nanoparticles, based on the content of K in the first coating, or - 1 to 20 mol %, preferably 1 to 15 mol %, more preferably 1 to 10 mol %, for example 5 mol % of ZrO2 nanoparticles, based on the content of K in the first coating, or - 1 to 20 mol %, preferably 5 to 20 mol %, more preferably 10 to 20 mol % of MgOH2 nanoparticles, based on the content of K in the first coating, or - 1 to 20 mol %, preferably 5 to 20 mol %, more preferably 10 to 20 mol % of CaCO3 nanoparticles, based on the content of K in the first coating, or - 1 to 20 mol %, preferably 5 to 20 mol %, more preferably 10 to 20 mol % of ZnO nanoparticles, based on the content of K in the first coating, or - 1 to 30 mol %, preferably 10 to 30 mol %, more preferably 15 to 25 mol %, for example 20 mol %, of MgO nanoparticles, based on the content of K in the first coating, or - 1 to 30 mol %, preferably 10 to 30 mol %, more preferably 15 to 25 mol %, for example 20 mol %, of TiO2 nanoparticles, based on the content of K in the first coating, or - 1 to 20 mol %, preferably 5 to 15 mol %, more preferably 10 mol % of Al2O3 nanoparticles, based on the content of K in the first coating, or - 1 to 20 mol %, preferably 1 to 10 mol %, more preferably 5 mol % of ZnO nanoparticles, based on the content of K in the first coating, Includes:

[0060] Examples 1a and 3a show that these contents of various nanoparticles give good results. As mentioned above, different nanoparticles according to these ranges may be combined in the first coating.

[0061] Preferably, the content of the particles of the compound containing bismuth and oxygen in the first coating is 0.025 to 0.3 wt %, preferably 0.05 to 0.25 wt %, more preferably 0.07 to 0.22 wt %, for example 0.08 to 0.22 wt %, for example 0.08 to 0.11 wt %, calculated based on the total weight of the ferromagnetic powder composition.

[0062] Example 3a shows that these ranges of content of particles of bismuth and oxygen containing compounds give good results.

[0063] A content of 0.08-0.11 wt% is currently the best range for soft magnetic iron-based core particles with a size of 100 mesh.

[0064] When the soft magnetic iron-based core particles are larger, for example of 40 mesh size, the content of particles of the bismuth-containing compound is preferably at least 0.05% by weight, for example 0.05-0.10% by weight.

[0065] When the soft magnetic iron-based core particles are smaller, for example of 200 mesh size, the content of particles of the bismuth-containing compound is preferably at least 0.15% by weight, for example 0.15-0.30% by weight.

[0066] The bismuth and oxygen-containing compound may be selected from the group consisting of bismuth(III) oxide (BiO) and bismuth(III) hydroxide (Bi(OH)), and the bismuth and oxygen-containing compound is preferably Bi(OH). As shown in Examples 1a and 1b and Example 2, the presence of BiO or Bi(OH) particles increases the resistivity. Also, as shown in Example 1b, the resistivity of Bi(OH) particles is increased more than that of BiO particles.

[0067] As used herein, soft magnetic iron-based core particles are defined as follows: Silicates of the general formula (KO)α(SiO)β, where α is the moles of KO and β is the moles of SiO, with a β / α molar ratio between 0.5 and 4.1, said silicate being present in an amount of 0.02 to 1.0% by weight calculated based on the total weight of the ferromagnetic powder composition; Particles of a compound containing bismuth and oxygen and having a D50 measured in accordance with SS-ISO 13320-1 between 0.1 and 10 μm; SS-nanoparticles having a D50 of 10 to 200 nm as measured in accordance with ISO 13320-1; Disclosed is the above-mentioned ferromagnetic powder composition, wherein a first coating is applied by contacting the composition with a first aqueous solution comprising:

[0068] The ferromagnetic powder composition preferably comprises: (iii) a second coating at least partially covering the surface of the core particle and / or the first coating, a. The general formula: R1[(R1) x (R2) y (M)] n O n-1 R1(I) or R2[M(OH) 2(n+1) ] (n+1) O (n) R2(II) wherein M is selected from the group consisting of Si, Ti, Al, and Zr; O is oxygen; R1 is a hydrolyzable group; R2 is an organic moiety, and at least one R2 contains at least one amino group; wherein n is the number of repeating units, which is an integer from 1 to 20; wherein x is 0 or 1; wherein y is 1 or 2, and x+y is 2. and a second coating comprising at least one metal-organic compound having The content of the at least one metal-organic compound is 0.05 to 0.40% by weight, preferably 0.1 to 0.30% by weight, based on the total weight of the ferromagnetic powder composition.

[0069] The second coating further improves the electrical, structural and magnetic properties of the component or part made from the ferromagnetic powder composition.

[0070] R1 can be an alkoxy group having fewer than 4, preferably fewer than 3, carbon atoms. R2 is an organic moiety, meaning that the R2 group contains an organic part or moiety. R2 preferably contains 1 to 6, more preferably 1 to 3, carbon atoms. R2 may further contain one or more heteroatoms selected from the group consisting of N, O, S, and P. The R2 group may be linear, branched, cyclic, or aromatic. R2 may contain one or more of the following functional groups: amine, diamine, amide, imide, epoxy, hydroxyl, ethylene oxide, ureido, urethane, isocyanato, acrylate, glyceryl acrylate, benzylamino, and vinyl-benzylamino. The R2 group can vary between any of the functional R2 groups described above and a hydrophobic alkyl group having repeating units.

[0071] When n=1, the metal-organic compound is a monomer (Formula I) or a dimer (Formula II). When the metal-organic compound is a monomer, it may be selected from the group of trialkoxy and dialkoxy silanes, titanates, aluminates, or zirconates. Thus, the monomer of the metal-organic compound may be selected from 3-aminopropyl-trimethoxysilane, 3-aminopropyl-triethoxysilane, 3-aminopropyl-methyl-diethoxysilane, N-aminoethyl-3-aminopropyl / ethyl / methyl-alkoxysilanes such as N-aminoethyl-3-aminopropyl-trimethoxysilane and N-aminoethyl-3-aminopropyl-methyl-dimethoxysilane, 1,7-bis(triethoxysilyl)-4-azaheptane, triaminofunctional propyl-trimethoxysilane, 3-ureidopropyl-triethoxysilane, 3-isocyanatopropyl-triethoxysilane, tris(3-trimethoxysilylpropyl)-isocyanurate, O-(propargyloxy)-N-(triethoxysilylpropyl)-urethane, 1-aminomethyl-triethoxysilane, 1-aminoethyl-methyl-dimethoxysilane, or mixtures thereof.

[0072] When n=2 to 20, the metal-organic compound is an oligomer. The metal-organic compound oligomer can be selected from alkoxy-terminated alkyl-alkoxy-oligomers of silanes, titanates, aluminates, or zirconates. Thus, the metal-organic compound oligomer can be selected from methoxy-, ethoxy-, or acetoxy-terminated amino-silsesquioxanes, amino-siloxanes, oligomeric 3-aminopropyl-methoxy-silanes, 3-aminopropyl / propyl-alkoxy-silanes, N-aminoethyl-3-aminopropyl-alkoxy-silanes, or N-aminoethyl-3-aminopropyl / methyl-alkoxy-silanes, or mixtures thereof.

[0073] Examples of suitable metal-organic compounds include, inter alia, Dynasylan® 1146 and Dynasylan® SIVO 203, both from Evonik Industries AG.

[0074] Aqueous amino or polyfunctional silane systems are also comprised of metal-organic compounds, such as the corresponding Dynasylan® HYDROSIL products supplied by Evonik Industries AG. In these products, the hydrolyzable alkoxy groups are almost completely replaced with hydroxyl groups, i.e., as in formula (II), but the functionality is similar, e.g., a hydrophobic alkyl group combined with an amino or diamino-alkyl group. Examples include the HYDROSIL 2627, 2776, and 1151 silane systems. Examples of such compounds are 1,3-bis(3-aminopropyl)disiloxane-1,1,3,3-tetrol or (3-aminopropyl)({[(propyl)dihydroxysilyl]oxy})silanediol.

[0075] Example 5 shows that a wide variety of metal organic compounds in the second coating can be successfully used in the ferromagnetic powder composition.

[0076] Preferably, at least one metal-organic compound has the general formula (I): Alternatively, at least one metal-organic compound has the general formula (II):

[0077] The ferromagnetic powder composition preferably further comprises a lubricant, preferably a particulate lubricant.

[0078] The inclusion of a lubricant in a ferromagnetic powder composition improves compaction and increases the density and strength of objects made from the ferromagnetic 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 portion of the lubricant may be a saturated or unsaturated chain containing 12 to 22 carbon atoms. The lubricant may preferably be selected from stearamide, erucamide, stearyl erucamide, erucyl-stearamide, behenyl alcohol, erucyl alcohol, and ethylene-bisstearamide (i.e., EBS wax or amide wax). Preferably, the lubricant is an amide wax. Mixtures of stearamide or behenyl alcohol with amide wax are also preferred. One example is 0.1 wt. % stearamide combined with 0.3 wt. % amide wax.

[0079] The lubricant may be present in an amount of 0.05 to 0.80% by weight of the ferromagnetic powder composition, preferably 0.20 to 0.40% by weight. Example 6 shows that several different lubricants can be used.

[0080] The ferromagnetic powder composition according to the first aspect of the technology proposed herein is preferably used in a ferromagnetic powder mixture.

[0081] The ferromagnetic powder mixture is - a ferromagnetic powder composition according to the first aspect of the technology proposed herein; a further ferromagnetic powder composition; and The further ferromagnetic powder composition comprises soft magnetic iron-based core particles that are different from the soft magnetic iron-based core particles of the ferromagnetic powder composition; Preferably, the soft magnetic iron-based core particles of the further ferromagnetic powder composition comprise or consist of an iron alloy having a higher electrical resistivity than the soft magnetic iron-based core particles of the ferromagnetic powder composition according to said first aspect.

[0082] This is advantageous in that it allows further tuning of the magnetic and electrical properties of components or parts made from the ferromagnetic powder composition. When, as preferred, the soft magnetic iron-based core particles of the additional ferromagnetic powder composition comprise or consist of an iron alloy having a higher electrical resistivity than the soft magnetic iron-based core particles of the ferromagnetic powder composition, the ferromagnetic powder mixture has lower core loss at higher frequencies. Furthermore, as surprisingly shown in Example 7a, the ferromagnetic powder mixture also exceeded acceptable mechanical strength (TRS) at the tested weight percent (30 wt%) of the added additional ferromagnetic powder composition. This allows the content of the additional ferromagnetic powder composition, including its iron alloy-based core particles, to be increased beyond 30 wt%, thus providing for the production of usable components with even lower overall core loss at higher frequencies due to acceptable mechanical strength.

[0083] The soft magnetic iron-based core particles of the further ferromagnetic powder compositions preferably comprise or consist of an iron alloy selected from the group consisting of FeSi, FeAl, FeSiAl, FeNi, FeCo, and FeNiCo, or a combination or mixture of such alloys, with FeSi (typically 3-6.8 wt. % Si) and FeSiAl (also known as Sendust; typically 9 wt. % Si and 6 wt. % Al) being particularly preferred.

[0084] The content of the additional ferromagnetic powder composition may be up to 60% by weight, for example 30 to 60% by weight, based on the weight of the ferromagnetic powder mixture with the ferromagnetic powder composition according to the first aspect of the technology proposed herein constituting the remainder, but is typically 10 to 50% by weight, for example 20 to 40% by weight, for example 20 to 30% by weight.

[0085] In the powder mixture, the soft magnetic iron-based core particles of the ferromagnetic powder composition preferably comprise or consist of essentially pure iron, i.e. iron with unavoidable impurities.

[0086] Preferably, the further ferromagnetic powder composition further comprises a coating or surface treatment on the soft magnetic iron-based core particles therein. The coating or surface treatment preferably comprises the first coating and optionally the second coating described above. Typically, however, when comprising an iron alloy, the soft magnetic iron-based core particles of the further ferromagnetic powder composition may be coated or treated with a less insulating coating or treatment, for example, by treatment with phosphoric acid in acetone, due to the higher resistivity of the iron alloy compared to essentially pure iron, and for such coating to be able to withstand heat treatment at higher temperatures, such as 700°C.

[0087] The soft magnetic iron-based core particles of the further ferromagnetic powder composition preferably have the same particle size as the soft magnetic iron-based core particles of the ferromagnetic powder composition according to the first aspect of the technology proposed herein, as further described above.

[0088] A method according to a second aspect of the technology proposed herein comprises the steps of: (iii) drying the coated soft magnetic iron-based core particles; and / or (iv) contacting the coated soft magnetic iron-based core particles with at least one metal-organic compound as described above, and / or (v) mixing the coated soft magnetic iron-based core particles with a lubricant as described above; The method may further include one or more of the following steps.

[0089] Step (iii) is preferably carried out after step (ii).Step (iii) may be carried out by heating the soft magnetic iron-based core particles while stirring.

[0090] Preferably, step (iv) is carried out after step (ii) or (iii) and before step (v).

[0091] Step (v) is preferably carried out after steps (iii) and (iv).

[0092] A third aspect of the technology proposed herein is a method for producing an object from a ferromagnetic powder composition or ferromagnetic powder mixture, comprising the steps of: (i) compressing the ferromagnetic powder composition or ferromagnetic powder mixture in a die at a compression pressure in the range of 300 to 2000 MPa, preferably 400 to 1200 MPa, to obtain a compacted part; (ii) heat treating the compacted part in a non-reducing atmosphere containing preferably 0-22 wt. % O, more preferably 0.5-2 wt. % O, at a temperature in the range of 300-800°C, preferably 400-750°C, more preferably 600-700°C to obtain an object; The present invention relates to a method comprising:

[0093] Compaction can be cold die compaction, warm die compaction, or high-speed compaction; preferably, controlled die temperature compaction (50-120°C) is used with unheated powder. During compaction, the coated soft magnetic iron-based core particles are pressed together, deforming and adhering to each other to form a compacted part. During heat treatment, the particles of the bismuth- and oxygen-containing compound, together with the nanoparticles and silicates in the first coating and the amino and / or alkyl groups of the metal-organic compound in the second coating, form a uniformly 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 ferromagnetic powder composition in the finished object. Furthermore, heat treatment reduces the stresses formed during compaction.

[0094] The heat treatment process may be carried out in a vacuum, a non-reducing, inert, or weakly oxidizing atmosphere, such as nitrogen with 0.01-3 wt.% oxygen. In one embodiment, an essentially pure nitrogen atmosphere is used as the non-reducing atmosphere. In one embodiment, 0-22 wt.% oxygen, preferably 0.5-2 wt.% oxygen, is added. Optionally, the heat treatment is carried out in an inert atmosphere, followed by a quick exposure to an oxidizing atmosphere, such as a 0.5-22 wt.% oxygen / nitrogen mixture, or a steam / nitrogen mixture, to build a surface crust for greater strength and / or corrosion resistance. In one embodiment, the temperature may be up to 800°C.

[0095] Corresponding fourth and fifth aspects of the presently proposed technology relate to objects obtainable by the method according to the third aspect of the presently proposed technology, and to objects comprising a compacted ferromagnetic powder composition or a compacted ferromagnetic powder mixture.

[0096] The object may alternatively be referred to as a part or a component and may be selected from the group consisting of sensors, inductors, converters, transformers, electric motors, and soft magnetic components of generators. [Example]

[0097] In the following examples, various ferromagnetic powder compositions comprising soft magnetic iron-based core particles according to the first aspect of the present technology were produced by coating the soft magnetic iron-based core particles with various first and second coatings, as according to various embodiments of the method according to the second aspect of the present technology. The ferromagnetic powder compositions were then used to produce test parts or objects that were compressed and heat-treated according to various embodiments of the method according to the third aspect of the present technology. Finally, the completed test parts were investigated for relevant properties such as resistivity (Res) and permeability (μ-max). More specifically, the test parts used in the examples were manufactured by the following steps.

[0098] Step 1: Soft magnetic iron-based core particles were mixed (10 min) with an aqueous solution of silicate of the general formula (KO)α(SiO)β (potassium silicate, Sibelco Nordic AB, β / α molar ratio 3.37, solids content 14 wt%) at a concentration of 0.1 wt% (based on dry matter content) to form a first coating on the core particles. The aqueous solution further contained one or more additional compounds of interest or additives as specified for each sample. After initial mixing, the core particles were dried at 60°C with stirring for 1 hour, followed by further drying at 120°C without stirring.

[0099] Step 2: The mixture from Step 1 was mixed with silane (unless otherwise stated, oligomeric diamino-functional silane Dynasylan® 1146 from Evonik Industries AG, 1.5 g in 1 g HO) for 5 minutes to form a second coating, and the resulting mixture was dried at 50° C. for 2 hours to produce the finished ferromagnetic powder composition comprising coated soft magnetic iron-based core particles.

[0100] Step 3: To facilitate the manufacture of test parts, a lubricant (0.4 wt % amide wax unless otherwise stated) was added to the ferromagnetic powder composition, which was then molded and compressed (800 MPa at a die temperature of 100°C) into test parts, which were heat treated to relieve stress from the compression and form the finished test parts.

[0101] Soft magnetic iron-based core particles are measured in accordance with 100 mesh and 3.32 g / cm unless otherwise stated. 3 The water atomized annealed iron powder had an apparent density of 10 ...

[0102] The heat treatment was performed in a preheating furnace in three stages. The three stages included a release stage at approximately 300-400 °C, in which the compressed parts were heated to a curing stage; a cure stage at approximately 350-450 °C (first time and temperature for each sample), in which the coatings were cured to form an electrically insulating bismuth-silicate glass from the first and second coatings; and a relaxation stage at 600-700 °C (second time and temperature for each sample), in which the stress from compression was released. The oxygen partial pressure during the heat treatment was 15,000 ppm (1.5 wt.% oxygen in nitrogen) unless otherwise noted. The completed test part (a magnetic square toroid with an OD55 / ID45 / H5mm) was subjected to testing to determine, among other things:

[0103] Electrical resistivity (Res) - how a material resists electric current [μΩm]. Measured using the four-point probe method with a distance of 20 mm between the measurement points. Coercive force at 10kA / m*(H c )[A / m] maximum permeability * (μ-max) - The maximum value [unitless] of the ratio between the magnetizations that a material acquires in response to an applied magnetic field. Square toroid density (d) - density of the square toroid test part [g / cm 3 ]. magnetic flux density * - Induction obtained for a given applied magnetic field [T]. B4 * - magnetic flux density at 4 kA / m [T], B10 * - Magnetic flux density at 10kA / m [T] Total Core Loss * (1T / 1kHz) - Total core loss [W / kg] of the test component obtained for a given induction and frequency. * For the measurement of the magnetic properties, the square toroid was wound with 100 drive and 100 sense turns of resin-coated copper wire (0.63 mm diameter) and measured using a Brockhaus MPG 200D, reference: IEC 60404-4 (DC measurements) and IEC 60404-6 (AC measurements). TRS - Transverse breaking strength [MPa] according to SS-EN ISO 3325:2000 for bars with dimensions 30 x 12 x 6 mm. AD - apparent density [g / cm ] according to ISO standard 3923-1:2018, measured as the ratio of the dry mass of a powder sample to the apparent volume. 3 ]. Flow - SS-Hole flow [sec] according to EN ISO 4490:2018. GS – green strength [MPa] measured as TRS on test parts before heat treatment.

[0104] Example 1a: Yttria (Y) in the first coating 2 O 3 ) nanoparticles improve the resistivity R and permeability μ-max for a given coercivity Hc at 10 kA / m in the heat treated formed component. Example 1a tested the effect of including YO nanoparticles (nominal 10 nm) in aqueous silicate solutions in Step 1 at concentrations of 10, 20, and 30 mole % (based on the molar weight of K), and bismuth oxide (BiO) at 0.1 wt %, when producing coated soft magnetic iron-based core particles in Step 2. The test resulted in four different test parts made according to Step 3, which were tested to determine their properties relative to Reference 1 and Reference 2, as listed in Table 1a below.

[0105] Reference 2 was included to provide further reference data for nanoparticle samples. Reference 2 was produced using an alternative process that uses phosphoric acid. Specifically, alternative process step 1 was divided into substeps 1a-1c: - sub-step 1a consists in mixing soft magnetic iron-based core particles with an aqueous solution of a silicate of general formula (K2O)α(SiO2)β and drying the mixture to obtain dry particles; - sub-step b consists in treating the dry particles with dilute phosphoric acid (25-75 g / l water); - Sub-step c consisted of mixing the particles with bismuth oxide (Bi2O3). [Table 1a]

[0106] As can be seen from the results, the inclusion of 20 mol% Y2O3 nanoparticles (Sample 1-2) resulted in a resistivity of 3368 μΩm and a coercivity of 134.8 A / m after heat treatment at 450 / 650°C. In comparison, the Reference 1 sample provided a significantly lower resistivity of 1435 μΩm. Sample 1-2 also provided a higher μ-max and lower total core loss. Thus, Sample 1-2 provided overall better properties than the Reference 1 sample for forming soft magnetic components or parts.

[0107] Furthermore, it can be seen that the Reference 2 sample required heat treatment at a higher temperature of 450 / 670°C to achieve a low coercivity of 135.2, similar to Reference 1 and Sample 1-2, however this resulted in an even lower resistivity of 1053 μΩm.

[0108] Table 1a further shows that the inclusion of 20 mol% Y2O3 nanoparticles (Sample 1-2) provided better overall properties than the 10 mol% (Sample 1-1) and 30 mol% (Sample 1-3) samples, which had lower resistivity. However, Sample 1-1 exhibited moderate resistivity, the lowest coercivity, and the highest permeability at 450 / 650°C heat treatment.

[0109] Furthermore, Table 1a also shows that bismuth hydroxide (Bi(OH)) significantly increases the resistivity (Sample 4) compared to bismuth oxide (BiO) (Samples 1-2) in both heat treatments, but the permeability is slightly lower. Without wishing to be bound by theory, this is believed to be due to the hydroxide being less susceptible to reduction by carbon in the metal-organic second layer.

[0110] Therefore, from Example 1a, it can be concluded that the amount of YO nanoparticles in the first coating can be suitably 10-30 mol%, preferably 15-25 mol%, more preferably 18-22 mol%, for example 20 mol%, based on the amount of K in the silicate. It can further be concluded that the inclusion of YO nanoparticles provided better properties than treatment of the core particles with phosphoric acid by the alternative process. It can further be concluded that the first coating can contain bismuth oxide (BiO) or bismuth hydroxide (Bi(OH)), preferably bismuth hydroxide (Bi(OH)).

[0111] Unless otherwise stated, in the further examples below, bismuth hydroxide (Bi(OH)) was used at a concentration of 0.08 wt %. Furthermore, unless otherwise stated, the nanoparticles were of a nominal diameter of 10 nm. 50 The nanoparticle content was 20 mol % based on the amount of K in the silicate first coating.

[0112] Example 1b: 20 mol % Y 2 O 3 Further experiments using nanoparticles - effect of silicate and silane concentration Further experiments were carried out using the same conditions as in Example 1a, but with different contents of the first and second coatings, i.e. different silicate and silane concentrations (heat treatment at 450 / 650°C (30 / 30 min)). The experimental parameters and results are shown in Table 1b below: [Table 1b]

[0113] As can be seen from the table, bismuth hydroxide (Bi(OH)3) significantly increases resistivity (Samples 1-6) compared to bismuth oxide (Bi2O3) (Samples 1-5). Halving the silane content in the second coating still produces acceptable resistivity (Sample 1-7). Halving the addition of the first coating (silicate, Bi(OH)3, YO3) results in lower resistivity (Samples 1-8, 1-9).

[0114] From Example 1b, it can be concluded that the silane content in the second coating can be reduced compared to Example 1a while maintaining acceptable resistivity values.

[0115] Example 2: Further experiments using different core particle sizes Further experiments were conducted to determine that the addition of nanoparticles to an aqueous solution of silicate, i.e., the first coating, provides benefits over a wide range of core particle sizes (mesh) and apparent densities (AD). The experimental parameters and results are shown in Table 2 below (heat treatment at 450 / 650°C (30 / 30 min)). [Table 2-1] [Table 2-2]

[0116] Therefore, the results show that soft magnetic iron-based core particles with different sizes can be efficiently coated with the first and second coatings.

[0117] Furthermore, the results show that the first and second coatings provide good electrical resistivity for soft magnetic iron-based core particles with different apparent densities, which have a clear effect on the mechanical strength and coercive force, and therefore on the total core loss.

[0118] Furthermore, the results show that good results can be obtained with different silicate concentrations in the first coating as well as different silane concentrations in the second coating, the amounts of which can be further adjusted to optimize both electrical resistivity and magnetic permeability.

[0119] Example 3a: Further experiments using different types of nanoparticles Further experiments were carried out to determine whether the Y2O3 nanoparticles could be replaced with other nanoparticles while providing the same or similar improvement in the properties of the test parts. The experimental parameters and results are shown in Table 3a below (heat treatment at 450 / 650°C (30 / 30 min)). Three series of tests were carried out, corresponding to three reference samples (ref1, ref2, ref3). Due to unavoidable variations between test series, the properties determined for each sample can only be fully compared with the properties of other samples with the same reference, i.e., belonging to the same test series. Comparisons between samples from different test series are still possible. The AD of the soft magnetic iron-based core particles used was 3.35 g / cm unless otherwise noted. 3 It was. [Table 3a-1] [Table 3a-2] [Table 3a-3] [Table 3a-4]

[0120] As can be seen from the table, nanoparticles of ZrO2, Mg(OH)2, CaCO3, ZnO, MgO, TiO2, and Al2O3 can also be used in the first coating to improve resistivity, but of these materials, Y2O3 nanoparticles provided the best overall performance for the test parts.

[0121] ZrO2 and ZnO nanoparticles showed increased electrical resistivity at lower molar concentrations (up to 2.5 mol% and 5 mol%, respectively).

[0122] Example 3b: Further experiments using different nanoparticle diameters Further experiments were carried out to investigate the effect of varying the diameter of the Y2O3 nanoparticles. The β / α molar ratio was 3.2. The experimental parameters and results are shown in Table 3b below (heat treatment at 450 / 650 °C (30 / 30 min)). [Table 3b]

[0123] As can be seen from the table, nanoparticles of various sizes perform well in the first coating, providing good electrical and magnetic properties. Furthermore, the yttria product, nominally designated 0.5-1.0 μm, was found by SEM to have an average particle size D of 200 nm. 50 It has been experimentally determined that the nanoparticles comprise aggregates having the following structure:

[0124] Example 4 - Further experiments using different β / α molar ratios and silicate concentrations Further experiments were conducted to investigate the effect of varying the β / α molar ratio (SiO2 / KO) and different concentrations of silicate in the first coating. The experimental parameters and results are shown in Table 4 below (heat treatment at 450 / 650 °C (30 / 30 min)). 0.08 wt% Bi(OH)3 was used for each sample. [Table 4]

[0125] As can be seen from the table, a β / α ratio of 2.5 gives slightly better resistivity results. The table further shows that increasing the weight percent of silicate (e.g., doubling it to 0.2 wt%) allows the mole percent of YO nanoparticles to be decreased (e.g., halving it to 10 mole%). Note that the total weight loading of nanoparticles was the same for the two selected β / α ratios, i.e., the molar content of nanoparticles relative to silicon was kept constant.

[0126] Example 5: Further experiments using different metal-organic compounds in the second coating Further experiments were performed to determine the effect of using various metal-organic compounds in place of the standard Dynasylan® 1146 silane in the second coating. The experimental parameters and results are shown in Table 5 below (heat treatment at 450 / 650°C (30 / 30 min)). [Table 5]

[0127] As can be seen from Table 5, all metal-organic compounds containing at least one amino group, ie, all samples except 7-154, provided good electrical resistivity and TRS values.

[0128] Example 6 - Further experiments using different lubricants Further experiments were conducted to determine the effect of various lubricants on the properties of the test parts, and the experimental parameters and results are shown in Table 6 below. [Table 6]

[0129] As can be seen from the table, the choice of lubricant has only a limited effect on the electrical and magnetic properties, so different lubricants can be used.

[0130] Example 7a: Further experiments using mixtures of ferromagnetic powder compositions with other or additional ferromagnetic powder compositions Further experiments were conducted to determine whether the ferromagnetic powder composition could be blended with other ferromagnetic powder compositions containing soft magnetic core particles, particularly alloyed core particles. Such alloyed core particles have greater internal resistivity, which can provide manufactured parts with lower core losses in high frequency applications. Therefore, these experiments investigated the feasibility of such blends and their effect on manufactured part properties. The experimental parameters and results are shown in Table 7a below. [Table 7a]

[0131] As can be seen from the table, the incorporation of alloyed core particles resulted in an increase in resistivity and a decrease in total core loss. At the same time, the mechanical strength (TRS) decreased, but the TRS remained above acceptable levels, which is believed to be caused by the increase in TRS of the ferromagnetic powder composition compared to prior art ferromagnetic powder compositions with other types of coatings. This means that the content of the additional ferromagnetic powder composition, i.e., the content of alloyed core particles, can be increased beyond the tested 30 wt. % to, for example, up to 50 wt. % or even up to 60 wt. %, thus providing for the production of usable components with even lower total core losses at higher frequencies due to acceptable mechanical strength.

[0132] These advantages are particularly useful for passive components (transformers, inductors) made from 200-300 mesh core particles.

[0133] Example 7b: Effect of Thermal Aging Further experiments were performed to determine the effect of thermal aging on the properties of the test parts. The experimental parameters and results are shown in Table 7b below: [Table 7b]

[0134] As shown in the table, the change in core loss, i.e., the increase in core loss, is smaller for the test part compared to the reference part. Therefore, the ferromagnetic powder composition according to the first aspect of the presently proposed technology produces components with improved thermal stability due to the good distribution and high surface coverage of the first coating on the core particles. This is advantageous in applications exposed to high temperatures, i.e., above 200°C, e.g., 200-260°C.

[0135] Example 8: Surface inspection using SEM / EDS In this example, soft magnetic iron-based core particles were mixed with an aqueous solution of silicate of the general formula (K2O)α(SiO2)β at a β / α ratio of 3.1-3.4 and a concentration of 0.1 wt%, with or without 20 mol% YO nanoparticles (10 nm) as in step 1 above.

[0136] The core particles were examined using a field-emission gun scanning electron microscope (FEG-SEM) (Hitachi SU6600) equipped with an energy-dispersive spectrometer (Oxford Instruments Ultima Max 65 mm). Measurements were performed at a distance of 10 mm (working distance) using an accelerating voltage of 20 kV. The results are shown in Figures 1A-1C and 2A-2C and further summarized in Table 8 below. Here, Figure 1A shows an SEM image of a core particle coated with silicate but without nanoparticles. In contrast, Figure 2A shows an SEM image of a core particle coated with silicate and nanoparticles. Comparing the images, it can be seen that the core particle in Figure 2A has a more detailed, i.e., refined, surface structure compared to the core particle in Figure 1A. This indicates that the first coating is thinner on the core particle in Figure 2A. Figures 1B and 2B show EDS mapping images of the corresponding core particles, showing the K content on the surface as light gray to white. It can be further observed that the first silicate coating varies in thickness across the surface, forming thicker areas, referred to as patches with high K content (see Figures 1B and 2B), and thinner areas between the patches. As can be seen in Figure 2B, there are numerous spatially separated K deposits on the silicate- and nanoparticle-coated core particle compared to only a few larger deposits in Figure 1B. Figures 1C and 2C show EDS mapping images of the corresponding core particle, showing the Si content on the surface in light gray to white. Figure 2C shows that the Si content is more uniformly distributed with numerous small deposits on the surface of the silicate- and nanoparticle-coated core particle compared to the few larger deposits in Figure 1C. [Table 8]

[0137] As shown in the table, the addition of nanoparticles increases the detected level of Fe in the patches. Because SEM / EDS measurements determine some material content within the surface of the particle, not just on it (the minimum detection area at 20 kV is approximately 1.5 μm deep, and the diameter for EDS point analysis is approximately 1 μm), the increased Fe content detected in the patches of the coating containing nanoparticles (79.8 wt %, bold) indicates that the patches are thinner and the silicate coating is more uniformly distributed across the surface of the core particle. This is supported by the increased silicon content (1.10 wt %, bold) measured between patches of the coating containing nanoparticles compared to the sample without nanoparticles (0.48 wt % Si). There is also a slight decrease in Fe content between patches (93.0 vs. 95.5 wt %), further indicating a thicker silicate coating. Therefore, by including nanoparticles in the first coating, silicate becomes more uniformly distributed across the surface of the core particle, which correlates with the increased resistivity observed in the previous example. Increasing the number of smaller patches on the core particle coated with the silicate coating containing nanoparticles further improves particle behavior during pressing and heat treatment of the particles to form parts or components, because the dispersed patches with a relatively high potassium content have lubricating properties that can protect the first coating during pressing.

[0138] Example 9: Schematic cross-section of a particle of a ferromagnetic powder composition Building on the above examples, Figure 3 shows a highly schematic cross-sectional view of a single particle 10 of a ferromagnetic powder composition according to an embodiment of the first aspect of the presently proposed technology. Particle 10 comprises a soft magnetic iron-based core particle 11 covered by a first coating 12 comprising a silicate. A second coating 13 is also shown, comprising a metal-organic compound. Particles (one of which is designated by reference numeral 14) of a compound comprising bismuth and oxygen and having an approximate diameter of about 1 μm are shown dispersed within first coating 12. Additionally, nanoparticles (one of which is designated by reference numeral 15) having an approximate diameter of about 200 nm or less are also shown dispersed within first coating 12.

[0139] 3 shows the particles before heat treatment, i.e., before the ferromagnetic powder is compressed and heat treated to produce an object according to a method in accordance with the third aspect of the presently proposed technology. During heat treatment, the particles 14 of the bismuth and oxygen-containing compound, together with the nanoparticles 15 and silicate in the first coating 12 and the amino and / or alkyl groups of the metal-organic compound in the second coating 13, are believed to form a uniformly distributed bismuth-silicate glass, which provides electrical resistivity between the individual particles of the compressed and heat-treated ferromagnetic powder composition.

[0140] While FIG. 3 shows that particles 14 of the bismuth and oxygen-containing compound are present in the first coating 12, it is contemplated that particles 14 of the bismuth and oxygen-containing compound may be further dispersed within the second coating 13.

[0141] Furthermore, although FIG. 3 shows that the first coating 12 and the second coating 13 completely coat the soft magnetic iron-based core particle 11, one or both of these coatings may alternatively only partially cover the soft magnetic iron-based core particle 11.

[0142] Possible modifications of the technology proposed herein The technology proposed herein is not limited to the embodiments described above and shown in the drawings, which are primarily for illustrative and exemplary purposes. This patent application is intended to cover all modifications and variations of the preferred embodiments described herein. Accordingly, the present invention is defined by the language of the appended claims and their equivalents. Thus, the device can be modified in all manners within the scope of the appended claims.

[0143] Throughout this specification and the appended claims, unless the context requires otherwise, the word "comprise" and variations such as "comprises" or "comprising" are understood to mean the inclusion of a stated integer or step or group of integers or steps, but not the exclusion of any other integer or step or group of integers or steps.

Claims

1. (i) soft magnetic iron-based core particles; (ii) a first coating at least partially covering and in direct contact with the surface of the core particle; 1. A ferromagnetic powder composition comprising: the first coating comprising: a. General formula (K ２ O)α(SiO ２ ) β (wherein α is K ２ is the moles of O, and β is SiO ２ and the β / α molar ratio is between 0.5 and 4.1, i. said silicate present in an amount of 0.02 to 1.0 weight percent calculated based on the total weight of said ferromagnetic powder composition; b. Containing bismuth and oxygen, D between 0.1 and 10 μm as measured in accordance with SS-ISO 13320-1 ５０ Particles of a compound having the formula: c. D from 10 to 200 nm measured according to SS-ISO 13320-1 ５０ and a nanoparticle having Including, Ferromagnetic powder composition.

2. The nanoparticles are Y ２ O ３ Nanoparticles, ZrO ２ Nanoparticles, ZnO nanoparticles, MgOH ２ nanoparticles, MgO nanoparticles, CaCO ３ Nanoparticles, Al ２ O ３ Nanoparticles, SiO ２ Nanoparticles and TiO ２ nanoparticles, said nanoparticles preferably being selected from the group consisting of Y ２ O ３ 10. The ferromagnetic powder composition of claim 1, comprising or consisting of nanoparticles.

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

4. The nanoparticles have a D of 10 to 100 nm as measured in accordance with SS-ISO 13320-1 ５０ The ferromagnetic powder composition according to any one of claims 1 to 3, wherein

5. the first coating comprising: Based on the content of K in the first coating, 10 to 25 mol %, more preferably 15 to 22 mol %, for example 20 mol % of Y ２ O ３ nanoparticles, or Based on the content of K in the first coating, 1 to 20 mol %, preferably 1 to 15 mol %, more preferably 1 to 10 mol %, for example 5 mol % of ZrO ２ nanoparticles, or 1 to 20 mol %, preferably 5 to 20 mol %, more preferably 10 to 20 mol % of MgOH based on the content of K in the first coating. ２ nanoparticles, or 1 to 20 mol %, preferably 5 to 20 mol %, more preferably 10 to 20 mol % of CaCO based on the content of K in the first coating ３ nanoparticles, or 1 to 20 mol %, preferably 5 to 20 mol %, more preferably 10 to 20 mol % of ZnO nanoparticles based on the content of K in the first coating, or 1 to 30 mol %, preferably 10 to 30 mol %, more preferably 15 to 25 mol %, for example 20 mol % MgO nanoparticles based on the content of K in the first coating, or Based on the content of K in the first coating, 1 to 30 mol %, preferably 10 to 30 mol %, more preferably 15 to 25 mol %, for example 20 mol % of TiO ２ nanoparticles, or 1 to 20 mol %, preferably 5 to 15 mol %, more preferably 10 mol % Al based on the content of K in the first coating. ２ O ３ nanoparticles, or 1 to 20 mol %, preferably 1 to 10 mol %, more preferably 5 mol % of ZnO nanoparticles based on the content of K in the first coating, The ferromagnetic powder composition according to any one of claims 1 to 4, comprising:

6. 6. A ferromagnetic powder composition according to any one of claims 1 to 5, wherein the content of the particles of the compound containing bismuth and oxygen in the first coating is 0.025 to 0.3 wt%, preferably 0.05 to 0.25 wt%, more preferably 0.07 to 0.22 wt%, for example 0.08 to 0.22 wt%, for example 0.08 to 0.11 wt%, based on the total weight of the ferromagnetic powder composition.

7. The compound containing bismuth and oxygen is bismuth(III) oxide (Bi ２ O ３ ) and bismuth(III) hydroxide (Bi(OH) ３ ), and the compound containing bismuth and oxygen is preferably Bi(OH) ３ The ferromagnetic powder composition according to any one of claims 1 to 6, wherein

8. (iii) a second coating at least partially covering the surface of the core particle and / or the first coating, a. a molecule of the following general formula: R １ [(R １ ) ｘ (R ２ ) ｙ (M)] ｎ O ｎ－１ R １ (I) or ( ２ [*()) ２（ｎ＋１） ] （ｎ＋１） . （ｎ） ( ２ (=) wherein M is selected from the group consisting of Si, Ti, Al, and Zr; O is oxygen; R １ is a hydrolyzable group; R ２ is an organic moiety, and at least one R ２ contains at least one amino group; wherein n is the number of repeating units, which is an integer from 1 to 20; wherein x is 0 or 1; wherein y is 1 or 2, and x+y is 2. and a second coating comprising at least one metal-organic compound having the content of said at least one metal-organic compound is 0.05 to 0.40 wt %, preferably 0.10 to 0.30 wt %, based on the total weight of said ferromagnetic powder composition; The ferromagnetic powder composition according to any one of claims 1 to 7.

9. A ferromagnetic powder composition according to any one of claims 1 to 8, further comprising a lubricant, preferably a particulate lubricant.

10. The ferromagnetic powder composition according to any one of claims 1 to 9, a further ferromagnetic powder composition; A ferromagnetic powder mixture comprising: the further ferromagnetic powder composition comprises soft magnetic iron-based core particles different from the soft magnetic iron-based core particles of the ferromagnetic powder composition according to any one of claims 1 to 9, Preferably, the soft magnetic iron-based core particles of the further ferromagnetic powder composition comprise or consist of an iron alloy having a higher electrical resistivity than the soft magnetic iron-based core particles of the ferromagnetic powder composition according to any one of claims 1 to 9. Ferromagnetic powder mixture.

11. 1. A method for producing a ferromagnetic powder composition, comprising: (i) providing soft magnetic iron-based core particles; (ii) the soft magnetic iron-based core particles are a. General formula (K ２ O)α(SiO ２ ) β (wherein α is K ２ is the moles of O, and β is SiO ２ and the β / α molar ratio is between 0.5 and 4.1, i. said silicate present in an amount of 0.02 to 1.0 weight percent calculated based on the total weight of said ferromagnetic powder composition; b. Containing bismuth and oxygen, D between 0.1 and 10 μm as measured in accordance with SS-ISO 13320-1 ５０ Particles of a compound having the formula: c. D from 10 to 200 nm measured according to SS-ISO 13320-1 ５０ and a nanoparticle having with a first aqueous solution comprising: A method comprising:

12. (iii) drying the soft magnetic iron-based core particles; and / or (iv) forming the soft magnetic iron-based core particles into a magnetic material having the following general formula: R １ [(R １ ) ｘ (R ２ ) ｙ (M)] ｎ O ｎ－１ R １ (I) or ( ２ [*()) ２（ｎ＋１） ] （ｎ＋１） . （ｎ） ( ２ (=) wherein M is selected from the group consisting of Si, Ti, Al, and Zr; O is oxygen; R １ is a hydrolyzable group; R ２ is an organic moiety, and at least one R ２ contains at least one amino group; wherein n is the number of repeating units, which is an integer from 1 to 20; wherein x is 0 or 1; wherein y is 1 or 2, and x+y is 2. with at least one metal-organic compound having the content of said at least one metal-organic compound is 0.05-0.40 wt. %, preferably 0.10-0.30 wt. %, based on the total weight of said ferromagnetic powder composition; and / or (v) mixing the soft magnetic iron-based core particles with a lubricant; The method of claim 11 , further comprising one or more of the steps:

13. A method for producing an object from a ferromagnetic powder composition according to any one of claims 1 to 9 or a ferromagnetic powder mixture according to claim 10, comprising the steps of: (i) compressing the ferromagnetic powder composition according to any one of claims 1 to 9 or the ferromagnetic powder mixture according to claim 10 in a die at a compression pressure in the range of 300 to 2000 MPa, preferably 400 to 1200 MPa, to obtain a compacted part; (ii) oxygen (O ２ heat treating the pressed part in a non-reducing atmosphere containing SiO 2 at a temperature in the range of 300 to 800°C, preferably 400 to 750°C, more preferably 600 to 700°C to obtain the body; A method comprising:

14. An object obtainable by the method of claim 13.

15. An object comprising a compacted ferromagnetic powder composition according to any one of claims 1 to 9 or a ferromagnetic powder mixture according to claim 10.

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