Ferrite powder, ferrite resin composite, and electromagnetic wave shielding material, electronic material or electronic component

Abstract

Provided is a ferrite powder, a ferrite resin composite, and an electromagnetic wave shielding material, electronic material, or electronic component, which suppresses magnetic loss at a frequency of less than 100 MHz and, when applied to a composite, a composite body, can suppress particle drop-off without impairing formability and fillability. The ferrite powder is a Mn-Zn-based ferrite powder containing at least ferrite particles in a spherical or polyhedral shape having a spinel phase as a main phase. Also, the ferrite particles have a stepped structure having a convex polygonal profile on the surface. Furthermore, the BET specific surface area of the ferrite powder is 0.35 m 2 / g or more and 10.00 m 2 / g or less, and the content of a zinc oxide (ZnO) phase is 0 mass% or more and 0.8 mass% or less.

Description

Technical Field

[0001] This invention relates to ferrite powder, ferrite resin composite materials, electromagnetic wave shielding materials, electronic materials, or electronic components. Background Technology

[0002] Composite materials composed of ferrite powder and resin, exemplified by electromagnetic wave shielding materials, are widely used in various applications. These composite materials are manufactured by mixing ferrite powder and resin. The composite material is then shaped into sheets or other forms to become a composite (molded body). In this case, if the shape of the ferrite powder particles is close to spherical, the flowability during molding increases, and the ferrite powder filling rate in the composite becomes higher. Therefore, the formability becomes better, and properties such as electromagnetic wave shielding performance are also improved. From this perspective, ferrite powders (particles) composed of spherical or polyhedral particles have been proposed.

[0003] For example, Patent Document 1 (International Publication No. 2017 / 212997) discloses a ferrite particle characterized by being a single crystal with an average particle size of 1 to 2000 nm and having a spherical particle shape. The ferrite particle does not substantially contain Zn, but contains 3 to 25 wt% Mn and 43 to 65 wt% Fe. The real part μ' of the complex permeability measured by the molded body composed of the ferrite particle and the binder resin has a maximum value in the frequency band of 100 MHz to 1 GHz. It is described that if the ferrite particle is used as an electromagnetic wave shielding material for electronic devices, it can stably shield broadband electromagnetic waves regardless of frequency (claims 1 and

[0078] of Patent Document 1).

[0004] Patent Document 2 (Japanese Patent Application Publication No. 2016-60682) discloses a spherical ferrite powder, characterized in that it contains 15 to 30% by weight of ferrite particles with a particle size of less than 11 μm and a volume average particle size of 10 to 50 μm. It describes that since it has good filling and forming properties when used as a filler, it has excellent workability and high electrical resistance. Therefore, the spherical ferrite powder is used to form a resin composition with a resin and then formed into a molded body, which can be used for various applications, such as IC sealants for absorbing electromagnetic waves (claims 1 and

[0093] of Patent Document 2).

[0005] Patent Document 3 (International Publication No. 2018 / 061327) discloses a Ni-Zn-Cu ferrite particle, characterized in that it is a single crystal with an average particle size of 1 to 2000 nm and has a polyhedral particle shape, containing 5 to 10% by weight of Ni, 15 to 30% by weight of Zn, 1 to 5% by weight of Cu, and 25 to 50% by weight of Fe. It states that the ferrite particle is suitable as a magnetic filler and a raw material for forming bodies because it simultaneously possesses high saturation magnetization and high resistivity (claims 1 and

[0089] of Patent Document 3).

[0006] Patent Document 4 (Japanese Patent Application Publication No. 2006-160560) discloses a spherical sintered ferrite particle with (a) a soluble ion content of 5 ppm or less, (b) an average particle size in the range of 10 to 50 μm, and (c) a spinel structure as obtained by X-ray diffraction. It describes a semiconductor sealing resin composition containing a filler material composed of the spherical sintered ferrite particle and silicon dioxide particles. The resin composition has low viscosity and good flow characteristics, and has electromagnetic wave shielding function. By using the resin composition as a sealing material, the obtained semiconductor device is a semiconductor device with excellent EMC (claims 1 and

[0023] of Patent Document 4).

[0007] Patent Document 5 (Japanese Patent Application Publication No. 04-304700) discloses a powder for an electromagnetic wave absorber material composed of Mn-Zn ferrite particle powder, characterized in that the powder consists of spherical particles with an average particle size of 50 to 150 μm. It describes that by forming spherical particles with an average particle size of 150 μm or less, the blockage of the gate during injection molding, which has been a previous obstacle to the large particle size of the material, can be improved by increasing the fluidity (claims 1 and

[0008] of Patent Document 5).

[0008] In addition, although it is used for a different purpose than composite materials such as electromagnetic wave shielding materials, Patent Document 6 (Japanese Patent No. 5921801) discloses a method for manufacturing a carrier core material for an electrophotographic developer. The method is characterized by granulating a mixture of Fe2O3 as a raw material, carbonate as a by-product at a rate of 10 to 50 g per 10 kg of Fe2O3 powder, and a reducing agent, and then firing it at a temperature of 1000°C or below to manufacture a carrier core material with a stepped, uneven surface on the surface of the particles, which is a collection of concentrically expanding raised portions. The method also describes that the sphericity of the carrier core material is 0.8 or more (claims 1 and

[0024] of Patent Document 6).

[0009] [Prior Technology Documents]

[0010] [Patent Literature]

[0011] Patent Document 1: International Publication No. 2017 / 212997

[0012] Patent Document 2: Japanese Patent Application Publication No. 2016-60682

[0013] Patent Document 3: International Publication No. 2018 / 061327

[0014] Patent Document 4: Japanese Patent Application Publication No. 2006-160560

[0015] Patent Document 5: Japanese Patent Application Publication No. 04-304700

[0016] Patent Document 6: Japanese Patent No. 5921801 Summary of the Invention

[0017] [The problem the invention aims to solve]

[0018] Thus, it has been proposed to improve the formability and filling properties of composite materials or complexes by using spherical or polyhedral ferrite powders. However, the inventors have found that when such ferrite powders and resins are used to make composites, there is a problem that ferrite particles easily detach from the composite. In particular, a large amount of ferrite particle detachment (particle separation) has been observed during composite processing. Since such ferrite particle detachment leads to a deterioration in the smoothness of the composite surface, this is undesirable.

[0019] In investigating the cause of particle detachment, the inventors believed that the surfaces of spherical and polyhedral ferrite particles were too smooth, resulting in poor adhesion to resin. Further research led to the following insights, and this invention was completed: even with spherical and polyhedral ferrite particles, the adhesion to resin can be improved by setting polygonal stepped structures on their surfaces; and ferrite powder with such particles, when applied to composite materials and complexes, can suppress particle detachment without compromising formability and filling properties.

[0020] Therefore, the objective of this invention is to provide a ferrite powder, a ferrite resin composite material, an electromagnetic wave shielding material, an electronic material, or an electronic component that suppresses magnetic loss at frequencies below 100MHz, has a higher permeability μ' than Mn-based ferrites containing the same amount of Mn, and suppresses particle shedding when applied to composite materials or complexes without compromising formability and filling properties.

[0021] [Technical solutions used to address technical problems]

[0022] This invention includes the following solutions (1) to (10). Furthermore, in this specification, the expression “~” includes the numerical values ​​at both ends. That is, “X~Y” has the same meaning as “X or more, Y or less”.

[0023] (1) A ferrite powder, which is a Mn-Zn based ferrite powder containing at least spherical or polyhedral ferrite particles with spinel phase as the main phase.

[0024] The ferrite particles have a stepped structure with a convex polygonal profile on their surface.

[0025] The ferrite powder has a BET specific surface area of ​​0.35 m². 2 / g or more 10.00m 2 / g or less

[0026] The content of zinc oxide (ZnO) phase is more than 0% by mass and less than 0.8% by mass.

[0027] (2) The ferrite powder of (1) above, wherein the ferrite powder has a manganese (Mn) content of 3.5% to 20.0% by mass, a zinc (Zn) content of 1.0% to 18.0% by mass, and an iron (Fe) content of 43.0% to 65.0% by mass, which is a manganese (Mn)-zinc (Zn) ferrite composition.

[0028] (3) The ferrite powder of (1) or (2) above, wherein the stepped structure has two or more steps.

[0029] (4) The ferrite powders of (1) to (3) above, wherein the shape factor SF-1 of the ferrite powder is 100 or more and 110 or less.

[0030] (5) The ferrite powder of any one of (1) to (4) above, wherein the content of spherical step particles (Ps) in the ferrite powder is 50% or more.

[0031] (6) The ferrite powder of any one of (1) to (5) above, wherein the microcrystal diameter of the spinel phase is more than 1 nm and less than 100 nm.

[0032] (7) The ferrite powder of any one of (1) to (6) above, wherein the lattice constant of the spinel phase is above the following.

[0033] (8) The ferrite powder of any one of (1) to (7) above, wherein the 50% diameter (D50) of the volume particle size distribution of the ferrite powder is 0.10 μm or more and 20.00 μm or less.

[0034] (9) A ferrite resin composite material comprising ferrite powder and resin of any one of (1) to (8) above.

[0035] (10) An electromagnetic wave shielding material, electronic material or electronic component comprising the ferrite resin composite material of (9) above.

[0036] [Invention Effects]

[0037] According to the present invention, a ferrite powder, a ferrite resin composite material, an electromagnetic wave shielding material, an electronic material or an electronic component are provided, which suppress magnetic loss at high frequencies and, when applied to composite materials or composites, suppress particle shedding without impairing formability and filling properties. Attached Figure Description

[0038] Figure 1 The image shows a surface SEM image of the sample from Example 3.

[0039] Figure 2 A cross-sectional schematic diagram showing the stepped structure.

[0040] Figure 3 This shows the surface SEM image of the comparative sample (Example 15). Detailed Implementation

[0041] Specific embodiments of the present invention (hereinafter referred to as "this embodiment") will be described. Furthermore, the present invention is not limited to the following embodiments, and various modifications can be made without altering the spirit of the invention.

[0042] <<1. Ferrite Powder>>

[0043] The ferrite powder of this embodiment is a Mn-Zn based ferrite powder containing at least spherical or polyhedral ferrite particles with a spinel phase as the main phase. These ferrite particles have a stepped structure with a convex polygonal profile on their surface. Furthermore, the BET specific surface area of ​​the ferrite powder is 0.35 m². 2 / g or more 10.00m 2 The content of zinc oxide (ZnO) phase is between 0% and 0.8% by mass, and the content is below 0% by mass.

[0044] The ferrite powder of this embodiment is composed of multiple ferrite particles. That is, the ferrite powder is an aggregate of multiple ferrite particles. The ferrite particles are predominantly spinel phase. The spinel phase is a compound with a stoichiometric composition of MO·Fe2O3 (M is a transition metal element) and a cubic spinel-type crystal structure. However, the ferrite powder of this embodiment is not limited to containing a spinel phase with a stoichiometric composition. Deviations in composition are allowed as long as the spinel-type crystal structure is maintained.

[0045] The ferrite powder of this embodiment contains at least spherical or polyhedral ferrite particles (spherical stepped particles). That is, the ferrite particles constituting the ferrite powder may be partly spherical stepped particles, or all of them may be spherical stepped particles.

[0046] By shaping the particles in ferrite powder into spherical or polyhedral forms, the powder's formability and filling properties can be significantly improved. This is because spherical or polyhedral particles can easily avoid contact with other particles during forming. Therefore, this results in good flowability and tight filling during forming. In contrast, particles with anisotropic or irregular shapes, such as plate-like or needle-like forms, have poor formability and filling properties.

[0047] When ferrite powder does not contain components with high saturated vapor pressure, such as those containing manganese (Mn) ferrite, the particles tend to form spherical shapes. Conversely, when ferrite powder contains components with high saturated vapor pressure, such as zinc (Zn) or strontium (Sr), the particles tend to form polyhedral shapes. This is believed to be because during the high-temperature heating (spraying) process in ferrite powder manufacturing, components with high saturated vapor pressure move from the interior to the exterior of the particles and function as flux, thus allowing the particles to grow into polyhedral shapes that reflect the crystal structure. However, even when ferrite powder contains components with high saturated vapor pressure, spherical particles can be obtained by adjusting the amount of binder resin added during manufacturing.

[0048] Polyhedral particles are essentially shaped by a combination of multiple polygons. The polygons constituting a polyhedron are typically composed of triangles, quadrilaterals, hexagons, octagons, decagons, or combinations thereof. For example, a rhombic truncated cubic octahedron composed of quadrilaterals, hexagons, and octagons can be cited as an example. Furthermore, the more faces a polyhedron has, the closer it is to a sphere. Therefore, polyhedral particles preferably have 10 or more decanters, more preferably 12 or more dodecahedrons, and even more preferably 14 or more dodecahedrons. Additionally, polyhedral particles typically have 100 or fewer dodecahedrons, more typically 72 or fewer dodecahedrons, and even more typically 24 or fewer dodecahedrons.

[0049] Furthermore, as long as the particle can be identified as polyhedral when observed as a whole, particles that are cut off at one or more points by the straight lines forming the polygon, and particles whose part of the straight lines is curved, are also included in polyhedral particles. Additionally, particles with finely serrated edges added to the straight lines forming the polygon are also included in polyhedral particles. Moreover, spherical-like stepped particles have a stepped structure on their surface, and strictly speaking, are sometimes not perfectly spherical or polyhedral. However, this stepped structure is exceptionally small compared to the particle's size. Therefore, even with such a microscopic stepped structure, particles that appear spherical or polyhedral when observed macroscopically are also spherical or polyhedral particles.

[0050] The ferrite powder of this embodiment contains ferrite particles (spherical stepped particles) with a stepped structure. Figure 1 To illustrate this stepped structure. Figure 1 This is a surface SEM image of spherical stepped particles from one embodiment of this invention. The observation shows that the particle surface is not smooth, forming a stepped structure. By including particles with such a stepped structure, when ferrite powder is applied to composite materials or complexes, the adhesion to the resin is improved, and particle detachment is suppressed. The detailed mechanism is unclear, but it is speculated that the presence of a stepped structure on the particle surface increases the particle surface area, i.e., the contact area with the resin, resulting in a higher chemical bonding force between the particles and the resin. Furthermore, it is speculated that the step difference in the stepped structure causes the particles to intercalate with the resin, the resin's anchoring effect plays a role, and the physical bonding force between the particles and the resin is increased.

[0051] The stepped structure has a convex polygonal outline on the surface of the ferrite particles. That is, when the particle surface is observed, the shape (outline) of the stepped structure is a convex polygon. In other words, the stepped structure can also be set by combining straight lines to enclose a region of the particle surface. By setting such a stepped structure, it is possible to more effectively prevent particles from falling off. Here, a convex polygon refers to any polygon with an interior angle of 180° or less. Alternatively, it can refer to a polygon in which the line segment connecting any two points located inside or on the boundary does not protrude outward. That is, it is not a concave polygon (non-convex polygon) such as a star. There is no limitation on the outline of the stepped structure as long as it is polygonal. However, reflecting the crystal structure of ferrite, the outline is typically triangular, quadrilateral, hexagonal, octagonal, or decagonal. In addition, ferrite particles can also have multiple stepped structures on their surface. This can effectively prevent particles from falling off. It is preferable that each ferrite particle has 4 or more but less than 50 stepped structures, more preferably 4 or more but less than 30.

[0052] The steps constituting the stepped structure can be one segment or multiple segments. However, the more segments there are, the more effectively particles can be prevented from falling off. Therefore, the number of segments is preferably two or more, more preferably four or more. On the other hand, if the number of segments is too large, the flowability of the ferrite powder may deteriorate. Therefore, the number of segments is preferably 100 or less, more preferably 80 or less. Furthermore, when the stepped structure is composed of multiple segments, the area enclosed by the upper segment of the step is smaller than the area enclosed by the lower segment. That is, the stepped structure can also be composed of a stack of convex polygonal plates with smaller areas at the top.

[0053] When the stepped structure consists of multiple steps, the average spacing (Hs) of the steps is preferably between 0.001 μm and 0.2 μm (1 nm to 200 nm). Here, the average spacing (Hs) is the average distance between adjacent steps of the stepped structure. Figure 2 This needs to be explained. Figure 2 A cross-sectional schematic diagram showing a multi-segment stepped structure. (Example) Figure 2 As shown, the multi-segment stepped structure contains multiple steps, with adjacent steps separated by a certain distance. The average distance between these adjacent steps is taken as the average interval (Hs) of the steps. The average interval (Hs) can be determined by observing the surface of the ferrite particles using a scanning electron microscope (SEM) or similar means. Hs is more preferably 3 nm or more, and even more preferably 10 nm or more. Furthermore, Hs is more preferably 100 nm or less, even more preferably 50 nm or less, particularly preferably 25 nm or less, and most preferably 20 nm or less.

[0054] When the volume average particle size (D50) is 2.0 μm or more, the content ratio (Ps) of spherical stepped particles in the ferrite powder, based on the number of particles, is preferably 3% or more, more preferably 20% or more, and even more preferably 50% or more. The higher the Ps, the better the adhesion to the resin, and the more suppressed the particle shedding. Therefore, the higher the Ps, the more preferred. However, it is typically 90% or less, more typically 80% or less, and even more typically 70% or less. In addition, Ps can be determined by observing the ferrite powder using a scanning electron microscope (SEM) or the like. Furthermore, Ps can be adjusted by controlling the conditions during the manufacture of the ferrite powder.

[0055] On the other hand, when the volume average particle size (D50) is 0.1 μm or more and less than 2.0 μm, the proportion (Ps) of spherical stepped particles in the ferrite powder, based on the number of particles, is preferably 0.5% or more, more preferably 1% or more, and even more preferably 2% or more. The higher the Ps, the stronger the adhesion to the resin, and the more suppressed the particle detachment. However, particles larger than 0.3 μm are problematic due to detachment from the resin. If the volume average particle size is in the range of 0.1 μm or more and less than 2.0 μm, the particle size is small and the BET specific surface area is large. Therefore, it is sufficient for Ps to be in the range of 0.5% or more. Ps is typically 95% or less. Furthermore, Ps can be determined by observing the ferrite powder using a scanning electron microscope (SEM) or the like. In addition, Ps can be adjusted by controlling the conditions during the manufacture of the ferrite powder.

[0056] Regardless of the volume average particle size (D50), the proportion (Ps) of spherical step-like particles in the ferrite powder can be 50% or more, 60% or more, 70% or more, or 80% or more.

[0057] The BET specific surface area of ​​the ferrite powder in this embodiment is 0.35 m². 2 / g or more 10.00m 2 / g or less. By setting the BET specific surface area to 10.00m². 2 Below a certain value (e.g., g / g), it can suppress the agglomeration of ferrite powder, resulting in superior formability and filling properties. Additionally, if the BET specific surface area exceeds 10.00 m² / g... 2 If the specific surface area is less than 10.00 m² / g, the diameter of the particles constituting the ferrite powder is too small, making it difficult to observe the surface stepped structure. Therefore, in this embodiment, the BET specific surface area is limited to 10.00 m² / g. 2 / g or less. On the other hand, by setting the BET specific surface area to 0.35m². 2 Below a certain value (e.g.), the formation of interparticle voids can be suppressed, resulting in superior filling properties. Furthermore, by setting the BET specific surface area within the aforementioned range, the adhesion between the ferrite powder and the resin is improved when applied to composite materials and complexes. A more preferable BET specific surface area is 0.50 m² / g. 2 / g or more. Furthermore, a BET specific surface area of ​​7.50 m² is more preferable. 2 / g or less, more preferably 5.00m 2 / g or less, preferably 2.50m 2 / g or less.

[0058] The preferred lattice constant of the spinel phase of the ferrite particles contained in the ferrite powder is... above The magnetic properties of ferrite powder, particularly saturation magnetization (σs), can be improved by limiting the lattice constant within this range. For example, small particles react quickly due to their large specific surface area. Therefore, elements with large ionic radii (e.g., Zn) are easily introduced during particle growth in ferrite powder synthesis, resulting in a tendency for the lattice constant to increase. On the other hand, large particles tend to have a smaller lattice constant. Conventionally, it has been difficult to appropriately control the particle growth rate and reaction rate, especially to increase the lattice constant of large particles. The ferrite powder of this embodiment achieves excellent magnetic properties by controlling the lattice constant within an appropriate range.

[0059] The shape factor (SF-1) of the ferrite powder is preferably 100 or higher and 110 or lower. SF-1, as an indicator of the sphericity of the particles constituting the powder, is 100 when the particles are perfectly spherical, and increases as they move further away from a sphere. By setting SF-1 to 110 or lower, the flowability of the powder is improved, and its formability and filling properties are superior, regardless of whether the particles are spherical or polyhedral. SF-1 is more preferably 105 or lower, and even more preferably 103 or lower.

[0060] The shape factor (SF-2) of the ferrite powder is preferably 100 or higher and 110 or lower. SF-2 is an indicator of the roughness of the particle surface constituting the powder. SF-2 is 100 if there is no surface roughness, and larger if the roughness is deeper. The ferrite powder of this embodiment has a microscopic stepped structure on the particle surface, thereby improving the adhesion to the resin and suppressing particle shedding when making composite materials or complexes. Therefore, a moderately high SF-2 is preferred. SF-2 is more preferably 101 or higher, and even more preferably 102 or higher. On the other hand, if SF-2 is too high, the flowability of the powder deteriorates, and the formability and filling properties may be deteriorated. SF-2 is more preferably 105 or lower.

[0061] The 50% diameter (volume average particle size; D50) of the ferrite powder's volumetric particle size distribution is preferably 0.10 μm or more and 20.00 μm or less. Setting D50 to 0.10 μm or more suppresses agglomeration of the ferrite powder, resulting in better formability and filling properties. Conversely, setting D50 to 20.00 μm or less suppresses the formation of interparticle voids, resulting in better filling properties. D50 is more preferably 0.50 μm or more, further preferably 0.60 μm or more, particularly preferably 0.80 μm or more, and most preferably 1.00 μm or more. Furthermore, D50 is more preferably 10.00 μm or less, further preferably 8.00 μm or less, particularly preferably 6.00 μm or less, and most preferably 4.00 μm or less.

[0062] In the particle size distribution determination of ferrite powder described later, the proportion of particles with a diameter of 0.3 μm or larger (P0.05) is considered. 0.3≦ The content is preferably 0.1% or more, more preferably 5.0% or more, further preferably 10.0% or more, and most preferably 20.0% or more. Furthermore, the content (P) 0.3≦ It can be obtained by converting the volumetric particle size distribution measurement results into number distribution data.

[0063] The preferred true specific gravity of the ferrite powder is 5.00 g / cm³. 3 The above, and more preferably 5.05 g / cm³ 3 The above, and more preferably, is 5.10 g / cm³. 3 The above points illustrate how increasing the true specific gravity can improve the magnetic properties of ferrite powder, particularly its saturation magnetization (σs) and permeability (μ).

[0064] The tap density of the ferrite powder is preferably 0.50 g / cm³. 3 Above 3.50g / cm 3 The following, or more preferably, is 1.00 g / cm³. 3 Above 3.00g / cm 3 The following is an explanation of how mixing small-diameter and large-diameter particles can improve tap density, resulting in superior overall filling properties of the ferrite powder.

[0065] The ferrite powder of this embodiment is a Mn-Zn based ferrite powder. That is, it has a composition of manganese (Mn)-zinc (Zn) based ferrite. Manganese (Mn)-zinc (Zn) based ferrite is a ferrite mainly containing manganese (Mn), zinc (Zn), iron (Fe), and oxygen (O), and may also contain other components such as magnesium (Mg) and / or strontium (Sr). Ferrite may also have the following composition: containing no other components, containing manganese (Mn), zinc (Zn), iron (Fe), and oxygen (O), with the remainder consisting of unavoidable impurities. Preferably, the ferrite powder has a manganese (Mn) content of 3.5% to 20.0% by mass, a zinc (Zn) content of 1.0% to 18.0% by mass, and an iron (Fe) content of 43.0% to 65.0% by mass. By setting such a composition, the magnetic properties of the ferrite powder and the composite materials and composites made therefrom can be made good. The manganese (Mn) content is more preferably 5.0% by mass or more and 20.0% by mass or less, and even more preferably 7.0% by mass or more and 20.0% by mass or less. The zinc (Zn) content is more preferably 1.0% by mass or more and 16.0% by mass or less, and even more preferably 2.0% by mass or more and 16.0% by mass or less. The iron (Fe) content is more preferably 43.0% by mass or more and 62.5% by mass or less, and even more preferably 45.0% by mass or more and 62.5% by mass or less.

[0066] By setting the composition of the ferrite powder to Mn-Zn based ferrite, magnetic properties can be improved at frequencies below 100 MHz compared to setting it to Mn based ferrite. For example, by including Zn while maintaining the Mn content at the same level, magnetic loss can be kept at a low level and magnetic permeability (μ') can be increased.

[0067] The saturation magnetization (σs) of the ferrite powder is preferably 70.0 Am. 2 / kg or more, preferably 75.0Am 2 / kg or more, preferably 80.0Am 2 / kg or more. Furthermore, the coercivity (Hc) of the ferrite powder is preferably 100 Oe or less, more preferably 75 Oe or less, and even more preferably 50 Oe or less. By increasing the saturation magnetization (σs), the permeability (μ) of the ferrite powder can be increased. Therefore, composite materials containing ferrite powder can be endowed with excellent magnetic properties, such as electromagnetic wave shielding performance.

[0068] The content of the spinel phase in the ferrite powder is preferably 80.0% by mass or more, more preferably 85.0% by mass or more, further preferably 90.0% by mass or more, particularly preferably 95.0% by mass or more, and most preferably 99.0% by mass or more. By increasing the content of the spinel phase, the saturation magnetization (σs) and permeability (μ) of the ferrite powder can be improved.

[0069] The particles constituting the ferrite powder can be composed of either single crystals or polycrystalline materials. However, polycrystalline materials are preferred. Furthermore, the average crystallite diameter of the particles constituting the ferrite powder is preferably 1 nm to 100 nm, more preferably 3 nm to 50 nm, and even more preferably 5 nm to 20 nm. Moreover, the ratio of the average crystallite diameter to the volume average particle size (D50) is preferably 0.0010 to 0.2000, more preferably 0.0020 to 0.1000, and even more preferably 0.0025 to 0.0700.

[0070] The zinc oxide (ZnO) phase content of the ferrite powder in this embodiment is 0.0% by mass or more and 0.8% by mass or less. When zinc (Zn) is used as a constituent element in ferrite powder, it sometimes contains a free zinc oxide (ZnO) phase. This free ZnO phase is different from the Zn constituting the ferrite and is a heterogeneous phase existing independently of the ferrite. Ferrite powder containing an excessive amount of free ZnO phase can increase its viscosity when applied to resin compositions. Therefore, less free ZnO phase is preferred. The zinc oxide (ZnO) phase content in the ferrite powder is further preferably 0.0% by mass or more and 0.5% by mass or less.

[0071] Thus, the ferrite powder of this embodiment is characterized by containing ferrite particles having a specific shape and a specific stepped structure on their surface. This ferrite powder is suitable for use in electromagnetic wave shielding materials, electronic materials, and / or electronic components. Furthermore, the ferrite powder, ferrite resin composite material, electromagnetic wave shielding material, electronic material, or electronic component of this embodiment can suppress ferrite particle shedding without compromising formability and fillability. In contrast, Patent Documents 1-5 do not describe anything related to the surface structure of ferrite particles and do not address particle shedding. Additionally, the carrier core material disclosed in Patent Document 6 has a concentric circle stepped surface irregularity, which differs from the stepped structure shape of the object of this embodiment. Furthermore, its objective is to improve the charge-imparting capability of the carrier core material (Patent Document 6

[0026] ), and is unrelated to particle shedding.

[0072] <<2. Manufacturing Method of Ferrite Powder>>

[0073] The manufacturing method of the ferrite powder in this embodiment is not limited as long as the above-mentioned requirements are met. However, as shown below, it can be manufactured by spraying a mixture of ferrite raw materials under specified conditions and then subjecting it to quenching.

[0074] <Ingredient Mixing>

[0075] First, the ferrite raw materials are mixed to form a raw material mixture. Known ferrite raw materials such as oxides, carbonates, hydroxides, and / or chlorides can be used. Furthermore, the raw materials are mixed using a known mixer such as a Henschel mixer, either dry or wet, or both.

[0076] <Pre-firing and grinding>

[0077] Next, the obtained raw material mixture is pre-fired to produce a pre-fired product. Pre-firing can be performed using known methods. For example, it can be carried out using a rotary kiln, continuous furnace, or intermittent furnace. The pre-firing conditions can also be known conditions. For example, conditions such as holding the product in an atmosphere or at a temperature of 700°C to 1300°C for a period of 2 to 12 hours can be given.

[0078] <Granulation>

[0079] The pre-fired material is then pulverized and granulated to produce granules. The pulverization method is not particularly limited. For example, known pulverizers such as vibratory mills, ball mills, or bead mills can be used, either dry or wet, or both. The granulation method can also be a known method. For example, water is added to the pulverized pre-fired material, and as needed, binders such as polyvinyl alcohol (PVA), dispersants, and / or defoamers are added to adjust the viscosity, followed by granulation using a spray dryer or similar granulator.

[0080] In the conventional manufacture of ferrite particles, the binder components are typically removed before formal firing. However, in the manufacturing method of this embodiment, a binder removal process is preferably not performed. By performing spraying while the binder components are still present, a staggered shape can be stably generated.

[0081] Furthermore, as mentioned above, even when the ferrite powder contains components with high saturated vapor pressure, spherical particles can be obtained by adjusting the amount of binder resin added during manufacturing. That is, even for elements with high saturated vapor pressure, if the temperature is controlled during the high-temperature heating process (spraying), thereby making the precipitation rate of Fe, the main component of ferrite, consistent with the precipitation rate of elements with high saturated vapor pressure, a perfectly spherical particle shape can be maintained and a fine, multi-faceted stepped structure can be generated on the particle surface.

[0082] <Spray coating>

[0083] The resulting granules are then spray-coated to produce a coated product. In the spray-coating process, the gas-conveyed granules are melted and ferrite-coated by a spray-coating flame. Afterward, the ferrite-coated particles are quenched and solidified by a cooling gas, and then recovered via a cyclone separator or filter. The cooling gas can be ambient air at room temperature, or, to prevent quenching and oxidation, air at a temperature lower than room temperature or an inert gas (nitrogen, helium, argon, etc.) can be used. The recovered ferrite particles can also be graded as needed. In the grading process, existing methods such as airflow grading, screen filtration, sieve grading, and sedimentation are used to adjust the particle size to the desired range. Larger particles can also be separated and recovered in a single process using airflow grading methods such as cyclone separators.

[0084] To obtain ferrite particles with a stepped structure (spherical stepped particles), it is important to spray-coat the granules under specified conditions. During spray-coating, the granules are melted and then rapidly cooled. The detailed mechanism is unclear, but it is speculated that by forming a polygonal stepped structure on the particle surface that reflects the crystal structure of ferrite when it melts at high temperatures, and then rapidly cooling, the structure is cooled while remaining intact. In contrast, it is believed that when ferrite particles are made by firing the granules at temperatures below the melting temperature, it is difficult to form a polygonal stepped structure, and even if it does form, the stepped structure will disappear with slow cooling. For example, in Patent Document 6, a carrier core material with stepped unevenness on the particle surface is manufactured by granulating a raw material mixture and firing it at a temperature below 1000°C (claim 1 of Patent Document 6). However, the stepped unevenness is concentric, which is different from the shape of the stepped structure that is the object of this embodiment.

[0085] In spray coating, a mixture of combustion gas and oxygen can be used as the combustion flame source for the combustible gas. The volume ratio of combustion gas to oxygen is preferably 1:3.5 to 1:6.0, more preferably 1:4.9 to 1:6.0, and even more preferably 1:4.9 to 1:5.3. This allows for the condensation of the volatile raw materials, enabling the formation of appropriately small-diameter particles. For example, a flow rate of 7 Nm³ relative to the fuel gas flow rate can be used. 3 / hour, oxygen flow rate is 35 Nm 3 The conditions are: / hour (the volume ratio of combustion gas to oxygen is 1:5).

[0086] If there is excessive combustion gas or oxygen during combustion, the unused combustion gas may steal heat from the combustion process, causing the flame temperature to drop. The amount of unused combustion gas is preferably less than 20% of the supplied combustion gas. Similarly, the amount of unused oxygen is preferably less than 20% of the supplied oxygen.

[0087] The amount of combustion gas relative to the amount of raw material supplied is also important. Specifically, the preferred net combustion gas ratio is 1.1 Nm³. 3 / kg or more 2.00Nm 3 / kg or less. Here, the net gas quantity ratio is the ratio of the net combustion gas quantity to the raw material supply quantity, which is calculated according to the following formula (1). In addition, the net combustion gas quantity is the amount of combustion gas used for net combustion, which is calculated according to the following formula (2) or formula (3).

[0088] [Formula 1]

[0089]

[0090] [Equation 2]

[0091]

[0092] (When the amount of fuel gas supplied is 5 - the amount of oxygen supplied is ≥0)

[0093] [Formula 3]

[0094] Net combustion gas quantity = Quantity of combustion gas supplied...(3)

[0095] (When the amount of fuel gas supplied × 5 - the amount of oxygen supplied < 0)

[0096] Examples of combustible gases used for spraying include propane, propylene, and acetylene, with propane being the most preferred. To convey the granules into the combustible gas, nitrogen, oxygen, or air can be used as the conveying gas. The flow rate of the conveyed granules is preferably 20 m / s to 60 m / s. The spraying temperature is preferably 1000°C to 3500°C, more preferably 2000°C to 3500°C.

[0097] The amount of raw material supplied during spraying is also important. Specifically, the mechanism of the stepped structure changes depending on the time it takes for the raw material particles to cool from their temperature (the heat imparted to them) during the spraying flame to room temperature. In particular, the stepped structure is achieved when raw material particles passing through a high-temperature flame are quenched sequentially. Even with flames at the same temperature, a stepped structure is difficult to achieve if the number of raw material particles passing through per unit time (the throughput per time) increases. From the viewpoint of achieving a stepped structure, a low supply of spraying raw material is preferable. For example, a supply of 20 kg / hour or less is preferred, more preferably 10 kg / hour or less, and most preferably 7 kg / hour or less.

[0098] The feed flow rate during spraying also affects the shape of the resulting ferrite powder. For example, the growth of sprayed particles is influenced by elements with high vapor pressure, such as zinc (Zn). That is, if the cooling rate of the ferrite particles passing through the spraying flame is too high, particles with high vapor pressure elements such as zinc (Zn) as nuclei are easily generated. Therefore, there is a tendency to generate ferrite powder with a large BET specific surface area. On the other hand, if the cooling rate is too low, the particles come into contact with each other in the spraying flame and easily become aggregated particles. In addition, due to the long residence time in the spraying flame, the stepped structure is prone to disappear. From this point of view, the feed flow rate is preferably 20 m / s or more and 35 m / s or less.

[0099] The proportion (Ps) of spherical stepped particles in ferrite powder can also be adjusted by controlling the spraying conditions. Specifically, by reducing the flow rate of the combustion gas (propane gas) and the total oxygen flow rate during spraying, the temperature of the spraying flame decreases, thereby controlling Ps. Due to the decrease in the temperature of the spraying flame, the ferrite particles undergo a shorter period of rapid cooling after passing through the spraying flame. It is speculated that because they are cooled before the stepped structure is fully formed, it is difficult to generate spherical stepped particles. In addition, it is believed that by partially heating the raw material particles (granules), aggregated particles consisting of multiple interconnected non-spherical particles can also be generated. Such aggregated particles do not have a stepped structure and are easily broken. Therefore, if such aggregated particles exist in the resin molded body, they sometimes agglomerate and disintegrate during the processing of the resin molded body.

[0100] As described above, the ferrite powder of this embodiment effectively exhibits a stepped structure by containing elements with high vapor pressure, such as zinc (Zn). However, not only the element content but also the conditions during spraying are important. That is, the sprayed material is cooled from a high temperature at a moderate rate by the spraying flame, thereby easily exhibiting a stepped structure. In sintering, which is different from spraying, the cooling rate is slower. Therefore, as the grain boundaries of the particles grow, the outer periphery of the stepped structure is not straight.

[0101] The cooling rate also has a significant impact on magnetic properties, especially the frequency characteristics of permeability. Specifically, particles rapidly cooled during spraying have smaller grain sizes. Therefore, the loss coefficient (tanδ) decreases at frequencies above 10 MHz. On the other hand, particles cooled slowly during firing have larger grain sizes and crystallite diameters, resulting in a larger loss coefficient at high frequencies.

[0102] In this way, the properties of ferrite powder can be adjusted by controlling the spraying conditions. By performing spraying under optimized conditions, the volatile raw materials condense, enabling the formation of particles with smaller particle sizes. Furthermore, the shape of the resulting ferrite particles can be appropriately adjusted.

[0103] <<3. Ferrite Resin Composite Materials>>

[0104] The ferrite resin composite material of this embodiment comprises the aforementioned ferrite powder and resin. According to this composite material, ferrite particle shedding is suppressed without compromising formability and filling properties.

[0105] Examples of resins constituting composite materials include epoxy resins, polyurethane resins, acrylic resins, silicone resins, polyamide resins, polyimide resins, polyamide-imide resins, fluoropolymers, or combinations thereof. Here, the silicone resin may also be a modified silicone resin modified with acrylic, polyurethane, epoxy, and / or fluorine.

[0106] Composite materials may also contain components other than ferrite powder and resin. Examples of such components include solvents, fillers (organic fillers, inorganic fillers), plasticizers, antioxidants, dispersants, colorants such as pigments, and / or thermally conductive particles.

[0107] The proportion of ferrite powder to the total solids content in the composite material is preferably 50% to 95% by mass, more preferably 80% to 95% by mass. Furthermore, the proportion of resin to the total solids content in the composite material is preferably 5% to 50% by mass, more preferably 5% to 20% by mass. By setting the proportions of ferrite powder and resin within the above ranges, the dispersion stability of the ferrite powder in the composite material, as well as the storage stability and formability of the composite material, are excellent. Furthermore, the mechanical strength, electromagnetic wave shielding performance, and other properties of the composite obtained by molding the composite material are also superior.

[0108] <<4. Electromagnetic wave shielding materials, electronic materials, and electronic components>>

[0109] The electromagnetic wave shielding material, electronic material, or electronic component of this embodiment comprises the aforementioned ferrite resin composite material. The electromagnetic wave shielding material, electronic material, or electronic component can be manufactured by molding the composite material using known methods. The molding method is not particularly limited; examples include compression molding, extrusion molding, injection molding, blow molding, or calendering. Alternatively, a coating film of the composite material can be formed on a substrate.

[0110] [Example]

[0111] This embodiment is further described in detail using the following examples and comparative examples. However, the present invention is not limited to the following examples.

[0112] (1) Preparation of ferrite powder

[0113] [Example 1]

[0114] <Ingredient Mixing>

[0115] Iron oxide (Fe2O3), manganese tetroxide (Mn3O4), and zinc oxide (ZnO) were weighed in a molar ratio of Fe2O3:MnO:ZnO = 53.1:36.7:10.2 and mixed using a Henschel mixer.

[0116] <Pre-firing and grinding>

[0117] The resulting mixture was pre-fired using a rotary kiln. Pre-firing was performed by holding the mixture at 900°C for 4 hours in atmospheric pressure. The pre-fired material was coarsely ground using a dry bead mill (3 / 16-inch steel balls), followed by the addition of water and fine grinding using a wet bead mill (0.65 mm zirconia balls). The particle size of the pulverized powder was 2.53 μm.

[0118] <Granulation>

[0119] Polyvinyl alcohol (PVA, 10% aqueous solution) was added as a binder to the resulting slurry. The amount of PVA added was 0.024% by mass relative to the pulverized powder in terms of solids content. The slurry with binder was then granulated using a spray dryer.

[0120] <Spray coating>

[0121] The resulting granules were sprayed and quenched in a combustible gas combustion flame. Spraying was carried out under the following conditions: propane gas flow rate 7.3 m³ / h. 3 / hour, total oxygen flow rate 38m 3 / hour (raw material oxygen supply 4m) 3 / hour, oxygen production 34m³ 3 / hour), raw material supply rate 5.5kg / hour, air volume 1100m³ / .... 3 The flow rate is 22.2 m / s, and the raw material flow rate is 22.2 m / s. Additionally, atmospheric cooling is introduced into the combustion gases after spraying to rapidly cool the product. The product is then recovered using a downstream cyclone separator to obtain the sprayed material. Coarse powder is removed from the obtained sprayed material using a sieve, and fine powder is removed using a classification device to obtain ferrite powder composed of multiple manganese (Mn)-zinc (Zn) ferrite particles.

[0122] [Example 2]

[0123] The raw material supply speed during spraying was changed to 6.0 kg / hour, and the air volume was changed to 900 m³ / h. 3 / hour. Additionally, a bag filter located downstream of the airflow is used to recover the product (sprayed material) after quenching. Coarse powder is removed from the resulting sprayed material by airflow classification, but fine powder removal is not performed. Ferrite powder is prepared otherwise in the same manner as in Example 1.

[0124] [Example 3]

[0125] When mixing the raw materials, they were weighed in a molar ratio of Fe2O3:MnO:ZnO = 66.4:26.7:6.9. The ferrite powder was prepared in the same manner as in Example 1. In Example 3, the particle size of the pulverized powder was 2.42 μm.

[0126] [Example 4]

[0127] The raw material supply speed during spraying was changed to 6.0 kg / hour, and the air volume was changed to 900 m³ / h. 3 / hour. Additionally, a bag filter located downstream of the airflow is used to recover the product (sprayed material) after quenching. Coarse powder is removed from the resulting sprayed material by airflow classification, but fine powder removal is not performed. Ferrite powder is prepared otherwise in the same manner as in Example 3.

[0128] [Example 5]

[0129] When mixing the raw materials, they were weighed in a molar ratio of Fe2O3:MnO:ZnO = 73.9:20.7:5.4. The ferrite powder was prepared in the same manner as in Example 1. In Example 5, the particle size of the pulverized powder was 2.65 μm.

[0130] [Example 6]

[0131] The raw material supply speed during spraying was changed to 6.0 kg / hour, and the air volume was changed to 900 m³ / h. 3 / hour. Additionally, a bag filter located downstream of the airflow is used to recover the product (sprayed material) after quenching. Coarse powder is removed from the resulting sprayed material by airflow classification, but fine powder removal is not performed. Ferrite powder is prepared otherwise in the same manner as in Example 5.

[0132] [Example 7]

[0133] When mixing the raw materials, they were weighed in a molar ratio of Fe2O3:MnO:ZnO = 51.7:28.0:20.3. Otherwise, the ferrite powder was prepared in the same manner as in Example 1. In Example 7, the particle size of the pulverized powder was 2.61 μm.

[0134] [Example 8]

[0135] The raw material supply speed during spraying was changed to 6.0 kg / hour, and the air volume was changed to 900 m³ / h. 3 / hour. Additionally, a bag filter located downstream of the airflow is used to recover the product (sprayed material). Coarse powder is removed from the resulting sprayed material by airflow classification, but fine powder removal is not performed. Otherwise, ferrite powder is prepared in the same manner as in Example 7.

[0136] [Example 9]

[0137] When mixing the raw materials, they were weighed in a molar ratio of Fe2O3:MnO:ZnO = 51.9:24.1:24.0. Otherwise, the ferrite powder was prepared in the same manner as in Example 1. In Example 9, the particle size of the pulverized powder was 2.33 μm.

[0138] [Example 10]

[0139] The raw material supply speed during spraying was changed to 6.0 kg / hour, and the air volume was changed to 900 m³ / h. 3 / hour. Additionally, a bag filter located downstream of the airflow is used to recover the product (sprayed material). Coarse powder is removed from the resulting sprayed material by airflow classification, but fine powder removal is not performed. Ferrite powder is prepared otherwise in the same manner as in Example 9.

[0140] [Example 11 (Comparison)]

[0141] Spray coating was performed under the following conditions: propane gas flow rate 5.5 m³ / h. 3 / hour, total oxygen flow rate 30.5m 3 / hour (raw material oxygen supply 3m) 3 / hour, oxygen production 27.5m³ 3 / hour), raw material supply rate 5.5kg / hour, air volume 900m³ / ... 3 The flow rate was 17.7 m / s, and the raw material flow rate was 17.7 m / s. Otherwise, the ferrite powder was prepared in the same manner as in Example 3.

[0142] [Example 12 (Comparison)]

[0143] <Raw material mixing, granulation, and calcination>

[0144] During raw material mixing, the raw materials were weighed and mixed in a molar ratio of Fe2O3:MnO:ZnO = 59.0:30.0:11.0. Water was added to the resulting raw material mixture, and the mixture was pulverized to prepare a slurry with a solid content of 50% by mass. The prepared slurry was granulated using a spray dryer and then calcined once. The granules were then classified using an air classifier to produce granules with an average particle size of 25 μm. Next, the obtained granules were kept at 1100°C in the atmosphere for 4 hours and then pulverized using a hammer mill to obtain calcined powder with an average particle size of 20 μm.

[0145] <Spray coating>

[0146] The calcined powder obtained is sprayed and rapidly cooled in a combustible gas combustion flame. Spraying is carried out under the following conditions: propane gas flow rate 10 m³ / h. 3 / hour, total oxygen flow rate 38m 3 / hour (raw material oxygen supply 3m) 3 / hour, oxygen production 35m³ 3 / hour), raw material supply rate 6.0kg / hour, air volume 900m³ / h 3 The flow rate is 40.0 m / s, and the raw material flow rate is 40.0 m / s. The spraying temperature (heating temperature) is 2000℃.

[0147] Next, the product is conveyed in an air-supply airflow and quenched in the atmosphere. Because the granules are continuously flowed while being sprayed and quenched, the resulting particles are independent and do not adhere to each other. The cooled product is then collected using a bag filter located downstream of the airflow. At this point, large particles fall during the airflow and are not collected by the bag filter. The collected (recovered) product (granules) is graded to remove coarse powder with a particle size exceeding 2000 nm, producing ferrite powder. The resulting ferrite powder contains particles with a particle size of less than 2000 nm.

[0148] [Example 13 (Comparison)]

[0149] <Ingredient Mixing>

[0150] Iron oxide (Fe2O3) and manganese tetroxide (Mn3O4) were used as raw materials. The raw materials were weighed in a molar ratio of Fe2O3:MnO = 79.6:20.4 (Fe:Mn = 7.8:1) and mixed using a Henschel mixer.

[0151] <Pre-firing and grinding>

[0152] The resulting mixture was pre-fired using a rotary kiln. Pre-firing was performed by holding the mixture at 900°C for 4 hours in atmospheric pressure. The pre-fired material was coarsely ground using a dry bead mill (3 / 16-inch steel balls), followed by the addition of water and fine grinding using a wet bead mill (0.65 mm zirconia balls). The particle size of the pulverized powder was 2.26 μm.

[0153] <Granulation>

[0154] Polyvinyl alcohol (PVA, 10% aqueous solution) was added as a binder to the resulting slurry. The amount of PVA added was 0.017% by mass relative to the pulverized powder in terms of solids content. The slurry with binder was then granulated using a spray dryer.

[0155] <Spray coating>

[0156] The resulting granules were spray-coated and rapidly cooled in a combustible gas combustion flame. Spray coating was carried out under the following conditions: propane gas flow rate 7 m³ / h. 3 / hour, total oxygen flow rate 38m 3 / hour (raw material oxygen supply 3.5m) 3 / hour, oxygen production 34.5m³ 3 / hour), raw material supply rate 6.5kg / hour, air volume 850m³ / .... 3The flow rate is 22.5 m / s and the raw material flow rate is 22.5 m / s. Next, a cyclone separator located downstream of the airflow is used to recover the cooled product (particles) to obtain the sprayed material. Coarse powder is removed from the obtained sprayed material using a sieve, and fine powder is removed by airflow classification to obtain ferrite powder composed of multiple manganese (Mn) ferrite particles.

[0157] [Example 14 (Comparison)]

[0158] During the spray coating process, the oxygen supply to the raw materials was changed to 3.0m. 3 / hour, change the oxygen consumption to 35.0m 3 In addition, a bag filter located downstream of the airflow is used to recover the cooled product (particles) to produce a sprayed product. Coarse powder is removed from the obtained sprayed product by airflow classification, but fine powder is not removed. Ferrite powder is produced in the same manner as in Example 13.

[0159] [Example 15 (Comparison)]

[0160] Instead of spraying, the granules are debound and formally fired. The resulting fired product is then crushed, and coarse and fine powders are removed from the crushed product by air classification. The debinding and formal firing are performed by holding the granules at 650°C for 4 hours in atmosphere, followed by holding them at 1250°C for 4 hours in an atmosphere with 0% oxygen by volume. Crushing is carried out using a hammer crusher. Furthermore, coarse and fine powders are removed from the resulting fired product by air classification. Ferrite powder is then produced in the same manner as in Example 13.

[0161] For Examples 1 to 15, the manufacturing conditions for ferrite powder are shown in Table 1.

[0162] [Table 1]

[0163]

[0164] (2) Fabrication of composite materials

[0165] Ferrite resin composites were prepared using the ferrite powders obtained in Examples 1 to 15. The composites were prepared as follows: The obtained ferrite powder and commercially available epoxy resin were weighed to a volume ratio of 60% (volume of ferrite powder) and gelatinized using a rotary mixer. The viscosity of the paste was measured using a viscometer. The resulting paste was poured into a silicone resin mold and thermocured to prepare a sample (composite material) for particle removal evaluation.

[0166] (3) Evaluation

[0167] The ferrite powders and composite materials obtained from Examples 1 to 15 are evaluated for various properties as follows.

[0168] <Elemental analysis - Metal component content>

[0169] The metal component content of the ferrite powder was measured as follows. First, 0.2 g of the test sample (ferrite powder) was weighed, and after adding 60 ml of pure water, 20 ml of 1N hydrochloric acid, and 20 ml of 1N nitric acid thereto, it was heated to prepare an aqueous solution in which the test sample was completely dissolved. The obtained aqueous solution was set in an ICP analyzer (Shimadzu Corporation, ICPS - 10001V) to measure the metal component content.

[0170] <XRD (Ferrite powder)>

[0171] Analysis based on the X - ray diffraction (XRD) method was performed on the ferrite powder. The analysis conditions are as follows.

[0172] - X - ray diffractometer: X'pert MPD manufactured by PANalytical (including high - speed detector)

[0173] - Line source: Co - Kα

[0174] - Tube voltage: 45 kV

[0175] - Tube current: 40 mA

[0176] - Scanning speed: 0.002° / second (continuous scanning)

[0177] - Scanning range (2θ): 15 - 90°

[0178] In the obtained X - ray diffraction curve, the integrated intensity (I 311 ) of the diffraction peak of the (311) plane of the spinel phase was obtained. In addition, based on the X - ray diffraction curve, the content ratios of the spinel phase and the non - spinel phase were obtained respectively.

[0179] Furthermore, Rietveld analysis was performed on the X - ray diffraction curve to estimate the lattice constant of the spinel phase, and then the crystallite diameter of the spinel phase was obtained according to the Scherrer formula.

[0180] <Surface structure of particles - Ps>

[0181] The surface structure of the particles in the ferrite powder was evaluated as follows. First, the ferrite powder was observed using a scanning electron microscope (SEM: Hitachi High - Technologies Corporation, SU - 8020). During the observation, the magnification of the particles with an average particle diameter of 2 μm or more was set to 50,000 times, and the particles with an average particle diameter less than 2 μm were set to 200,000 times. Then, in any case, photographs were taken in a state where 1 - 30, preferably 1 - 10, particles with a horizontal Feret diameter of 0.3 μm or more entered the field of view.

[0182] Regarding the imaging, 10 random field-of-view measurements were taken to confirm the presence or absence of polygonal staircases for particles with a horizontal Ferrette diameter greater than 0.3 μm. Then, the proportion (Ps) of spherical staircase particles was calculated according to the following formula (4). In addition, particles with a horizontal Ferrette diameter less than 0.3 μm may have their electron beam pass through them during imaging, making it impossible to determine whether they have staircases. Therefore, they were excluded from the evaluation.

[0183] [Formula 4]

[0184]

[0185] Here, N i Let n be the number of particles with a horizontal Ferrette diameter greater than 0.3 μm captured in the i-th field of view. i Let be the number of particles with spherical step-like structures captured in the i-th field of view. Additionally, particles appearing partially outside the field of view are also counted as one particle.

[0186] <Particle Surface Structure - Hs>

[0187] When observing with a scanning electron microscope (SEM), the magnification is set to 200,000, and images are taken with 1 to 30, preferably 1 to 10, spherical step particles entering the center of the field of view. Then, the average interval (Hs) of the steps is calculated according to the following formula (5) based on the scale of the SEM image.

[0188] [Formula 5]

[0189]

[0190] <Shape factor - for cases with an average particle size of 2μm or larger>

[0191] For particles with an average diameter greater than 2 μm, the shape factor (SF-1 and SF-2) of the ferrite powder was determined using a particle image analysis device (Malvern Panalytical, Morphologi G3). First, the ferrite powder was analyzed using the particle image analysis device. During analysis, images were analyzed for each of the 30,000 particles in the powder, and the circularity, circumference, and equivalent circle diameter (CE Diameter) were automatically determined. At this time, a 10x objective lens was used with a sample volume of 3 mm. 3 Under a dispersion pressure of 5 bar, the particles are dispersed on a glass slide using the dispersion fixture provided with this device.

[0192] The average of the data of particles with a volume average particle size within ±5% of the obtained data is used as the average roundness, average perimeter, and average equivalent circle diameter (CE Diameter). SF-1 and SF-2 are calculated according to the following formulas (6) and (7).

[0193] [Formula 6]

[0194] SF-1 = (Average Circularity) -1 ×100···(6)

[0195] [Formula 7]

[0196]

[0197] <Shape factor - for cases where the average particle size is less than 2 μm>

[0198] For particles with an average particle size less than 2 μm, the shape factor of the ferrite powder (SF-1 and SF-2) was determined using FE-SEM (Field Emission Scanning Electron Microscopy). First, ferrite powder images were taken in multiple fields of view using FE-SEM. Images were taken at 100,000x magnification. Then, image analysis software (Image-Pro Plus) was used for image analysis. For analysis, 100 particles with an equivalent circle diameter of ±5% of the volume average particle size were selected, and analysis was performed on each particle. The maximum length (horizontal Feret diameter) R (in μm), projected perimeter L (in μm), and projected area S (in μm) were then measured. 2 ), equivalent circle diameter r (unit: μm).

[0199] Next, SF-1 and SF-2 are calculated according to the following formulas (8) and (9), and their average values ​​are taken as SF-1 and SF-2 of the ferrite powder.

[0200] [Formula 8]

[0201]

[0202] [Formula 9]

[0203]

[0204] <Alien Particle Ratio>

[0205] The proportion of irregularly shaped particles in the ferrite powder is determined as follows. During analysis using a particle image analysis device, the number N of particles with a roundness of 0.965 to 1.000 and the number n of particles with a roundness of 0.950 to 0.965 are counted, and the proportion of irregularly shaped particles is calculated according to the following formula (10). Furthermore, since particles with a roundness less than 0.950 are agglomerated particles, they are excluded from the evaluation.

[0206] [Formula 10]

[0207]

[0208] <Proportion of condensed particles>

[0209] The proportion of aggregated particles in ferrite powder is determined as follows. When analyzing the particle image, the number N of particles with a volume average particle size of ±10% and a roundness of 0.900 to 1.000 and the number n of particles with a volume average particle size of ±10% and a roundness of 0.900 to 0.950 are counted, and the proportion of aggregated particles is calculated according to the following formula (11).

[0210] [Equation 11]

[0211]

[0212] <Tap density>

[0213] The tap density of the ferrite powder was measured using a USP tap density measuring apparatus (Hosokawa Micron Co., Ltd., Powder Tester PT-X) in accordance with JIS Z 2512-2012.

[0214] True specific gravity

[0215] The true specific gravity of the ferrite powder was determined using the gas displacement method according to JIS Z8807:2012. Specifically, it was determined using a fully automated true density measuring device (Mountech, Macpycno Co., Ltd.).

[0216] <Particle Size Distribution>

[0217] The particle size distribution of the ferrite powder is measured as follows. First, 10 g of the sample (ferrite powder) and 80 ml of water are placed in a 100-ml beaker, and 2 drops of sodium hexametaphosphate are added as a dispersant. Next, dispersion is carried out using an ultrasonic homogenizer (SMT Co., Ltd., model UH-150). At this time, the output level of the ultrasonic homogenizer is set to 4, and dispersion is carried out for 20 seconds. After that, the bubbles formed on the surface of the beaker are removed, and the obtained dispersion is introduced into a laser diffraction particle size distribution measuring device (Shimadzu Corporation, SALD-7500nano) and measured. The measurement conditions are set as a pump speed of 7, an internal ultrasonic irradiation condition of 30, and a refractive index of 1.70 - 050i. Through this measurement, the 10% diameter (D10), 50% diameter (volume average particle size, D50), and 90% diameter (D90) in the volume particle size distribution are obtained.

[0218] In addition, the obtained volume particle size distribution is converted into a number particle size distribution, and the content ratio (P 0.3≦ ) of particles with a particle size of 0.3 μm or more is obtained in this number particle size distribution.

[0219] <BET specific surface area>

[0220] The BET specific surface area of the ferrite powder is measured using a specific surface area measuring device (Mountech Co., Ltd., Macsorb HM model-1208). First, approximately 10 g of the ferrite powder is placed on a filter paper packet and degassed using a vacuum dryer. After confirming that the vacuum degree is below -0.1 MPa, it is heated at 200 °C for 2 hours to remove the moisture adhering to the particle surface. Then, the ferrite powder (approximately 0.5 - 4 g) with the moisture removed is placed in a standard sample cell dedicated to the measuring device and accurately weighed using a precision balance. Next, the weighed ferrite particles are set at the measuring port of the measuring device for measurement. The measurement is carried out by the single-point method. The measurement atmosphere is set as a temperature of 10 - 30 °C and a relative humidity of 20 - 80% (no condensation).

[0221] <Magnetic properties - saturation magnetization, remanent magnetization, and coercive force>

[0222] The magnetic properties (saturation magnetization, remanent magnetization, and coercive force) of the ferrite powder are measured as follows. First, the sample (ferrite powder) is loaded into a cell with an inner diameter of 5 mm and a height of 2 mm and set in a vibrating sample type magnetic measuring device (Toei Industry Co., Ltd., VSM-C7-10A). The applied magnetic field is scanned up to 5 kOe, and then the applied magnetic field is reduced to draw a hysteresis curve. Based on the data of this curve, the saturation magnetization σs, remanent magnetization σr, and coercive force Hc of the sample are obtained.

[0223] <Magnetic permeability>

[0224] The magnetic permeability of the ferrite powder was measured using an RF impedance / material analyzer (Agilent Technologies, E4991A) and a magnetic material measuring electrode (16454A). First, 9 g of the sample (ferrite powder) and 1 g of the binder resin (Kynar301F: polyvinylidene fluoride) were placed in a polyethylene container (100 ml capacity) and mixed using a bead mill at 100 rpm. Next, approximately 0.6 g of the resulting mixture was filled into a die (4.5 mm inner diameter, 13 mm outer diameter) and pressed at 40 MPa for 1 minute to form a molded body. The molded body was then cured at 140°C for 2 hours using a hot air dryer to produce the test sample. The test sample was then placed in the RF impedance / material analyzer, and the previously measured outer diameter, inner diameter, and height of the test sample were entered. During the measurement, the amplitude was set to 100mV, and the measurement frequency range of 1MHz to 3GHz was scanned using a logarithmic scale. The real part (μ') and imaginary part (μ”) of the complex permeability at frequencies of 10MHz, 50MHz and 100MHz were obtained, and the loss coefficient (tanδ) was calculated according to the following formula (12).

[0225] [Equation 12]

[0226]

[0227] <Paste viscosity>

[0228] For pastes containing ferrite powder and epoxy resin used in the fabrication of composite materials, the viscosity of the paste after preparation is measured using a type B viscometer.

[0229] <Proportion of particles detached>

[0230] The proportion of detached particles in the composite material (composite) is determined as follows. First, the composite material is ground using a grinder to expose the particle cross-section. The grinder cross-section is observed in multiple fields of view using a field emission scanning electron microscope (FE-SEM), and the number of ferrite particles exposed on the outermost surface and the number of detached particles are counted. Here, since the detached particles become recesses in the ground cross-section, the number of recesses is taken as the number of detached particles. Then, the proportion of detached particles is calculated according to the following formula (13).

[0231] [Equation 13]

[0232]

[0233] (4) Results

[0234] For Examples 1 to 15, the evaluation results are shown in Tables 2 to 4. Additionally, for Examples 3 and 15, the surface SEM images of the ferrite particles are shown in Tables 2 to 4. Figure 1 and Figure 3 .

[0235] As shown in Table 3, the ferrite powders produced by spraying in Examples 1 to 14 contain particles that are either spherical or polyhedral. Examples 1, 3, 5, 7, 9, 11, and 13, where coarse and fine powders were removed by sieving and air classifying respectively, have a larger volume average particle size D50 (3.24–4.22 μm) and exhibit a spherical particle shape. In contrast, Examples 2, 4, 6, 8, 10, 12, and 14, where coarse powder was removed by air classifying but fine powder was not, have a smaller D50 (0.19–0.83 μm) and are polyhedral. Furthermore, it can be seen that the shape factors (SF-1 and SF-2) of any one of Examples 1–11 and Examples 13–14 are small, indicating excellent sphericity. In contrast, Examples 12 and 15 have large shape factors (106–110) and poor sphericity.

[0236] Examples 1-10 and 12-14 have polygonal stepped structures on the particle surface. Therefore, the proportion of detached particles when forming the composite material is small, less than 6%. In contrast, Example 11, which had modified spraying conditions and lacked a stepped structure, had a detached particle proportion of 12%, and Example 15, which underwent electric furnace firing, had a detached particle proportion of 15%, both significantly higher. Furthermore, Example 12, with its large specific surface area, had a low proportion of detached particles, but its paste viscosity was high (300,000 mPa·s), making it difficult to produce the composite material.

[0237] Regarding magnetic properties, Example 13, as a Mn-based ferrite, and Example 5, which contains Zn, have the same amount of Mn and the same BET specific surface area, but their μ' values ​​differ at 10 MHz, 50 MHz, and 100 MHz. Similarly, Examples 14 and 6 have the same Mn content, but their μ' values ​​differ at 10 MHz, 50 MHz, and 100 MHz. Furthermore, Examples 5 and 14 have different BET specific surface areas, but their μ' values ​​are the same at 100 MHz. On the other hand, Example 14 shows a difference in μ' at 10 MHz and 50 MHz. This is presumably because the μ' value increases near 100 MHz due to the resonance of the magnetic wall. Furthermore, Examples 1 through 14 have small crystallite diameters and reduced magnetic loss tanδ at 100 MHz. In contrast, Example 15, sintered in an electric furnace, has a larger crystallite diameter and a larger tanδ.

[0238] [Table 2]

[0239]

[0240] [Table 3]

[0241]

[0242] [Table 4]

[0243]

Claims

1. A ferrite powder, which is a Mn-Zn based ferrite powder containing at least spherical or polyhedral ferrite particles with spinel phase as the main phase. The ferrite particles have a stepped structure on their surface with a convex polygonal outline that reflects the crystal structure of the ferrite. The ferrite powder has a BET specific surface area of ​​0.35 m². 2 / g or more, 10.00m 2 / g or less; The content of zinc oxide phase is above 0% by mass and below 0.8% by mass.

2. The ferrite powder as described in claim 1, The ferrite powder comprises a manganese-zinc ferrite with a manganese content of 3.5% to 20.0% by mass, a zinc content of 1.0% to 18.0% by mass, and an iron content of 43.0% to 65.0% by mass.

3. The ferrite powder as described in claim 1 or 2, The stepped structure has two or more steps.

4. The ferrite powder as described in claim 1 or 2, The shape factor SF-1 of the ferrite powder, which is an indicator of the sphericity of the particles constituting the powder, is 100 or more and 110 or less.

5. The ferrite powder as described in claim 1 or 2, The ferrite powder contains more than 50% spherical stepped particles, based on the number of particles.

6. The ferrite powder as described in claim 1 or 2, The spinel phase has a crystallite diameter of 1 nm or more and 100 nm or less.

7. The ferrite powder as described in claim 1 or 2, The spinel phase has a lattice constant of ≥8.350 Å and ≤8.475 Å.

8. The ferrite powder as described in claim 1 or 2, The D50 of the ferrite powder in the volumetric particle size distribution is above 0.10 μm and below 20.00 μm.

9. A ferrite resin composite material, It comprises ferrite powder as described in any one of claims 1 to 8 and resin.

10. An electromagnetic wave shielding material, It comprises the ferrite resin composite material as described in claim 9.

11. An electronic material, It comprises the ferrite resin composite material as described in claim 9.

12. An electronic component, It comprises the ferrite resin composite material as described in claim 9.

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