An injection-molded ferrite magnetic powder and its preparation method, injection-molded ferrite materials and their applications

Abstract

This invention provides an injection-molded ferrite magnetic powder and its preparation method, as well as injection-molded ferrite materials and their applications. The chemical formula of the injection-molded ferrite magnetic powder is Sr. 1‑x‑y La x Ca y Fe 12‑z Co z O 19 The D50 size ranges from 1.5 to 2.5 μm, with an average length-to-diameter ratio (L / D) of 1.2 to 3.0; among which, 0

Description

Technical Field

[0001] This invention belongs to the technical field and relates to an injection ferrite magnetic powder, and more particularly to an injection ferrite magnetic powder and its preparation method, injection ferrite materials and their applications. Background Technology

[0002] Ferrite permanent magnets, due to their advantages such as abundant raw materials, simple manufacturing process, high temperature resistance, corrosion resistance, and low material cost, are widely used in motors, magnetic storage, magnetic adsorption, and magnetic sensing, making them the most widely used type of permanent magnet material. Ferrite permanent magnets can be divided into two categories according to their manufacturing process: sintered ferrites and bonded ferrites. Injection-molded ferrites are a type of bonded ferrite material formed by filling ferrite magnetic powder into an engineering plastic matrix. This material can be injection molded into various complex shapes of magnetic devices, and can also be integrally injection molded with other inserts. Compared with sintered ferrites, injection-molded ferrites have advantages such as high dimensional accuracy in one-time molding, superior mechanical properties, and greater morphological freedom, thus finding widespread application in many micro-motors and precision magnetic sensor devices. The disadvantage of injection-molded ferrite magnets is their relatively low magnetic performance, with a magnetic energy product generally below 2.3 MGOe. In recent years, as magnetic devices have become increasingly miniaturized and lightweight, the market has placed higher demands on the magnetic performance of magnetic materials. Therefore, how to prepare high-performance injection ferrite materials is a hot research topic in the field of magnetic materials.

[0003] Since injection-molded ferrite materials are composite materials made of ferrite magnetic powder and engineering plastic binders, the core of improving injection-molded ferrite materials lies in preparing high-performance ferrite magnetic powder. Generally speaking, magnetic powder suitable for preparing high-performance injection-molded ferrite permanent magnet materials should meet the following conditions: (1) It should have superior magnetic properties, namely high remanence, high coercivity and high energy product; (2) While possessing excellent magnetic properties, the magnetic powder should have a good particle size distribution and particle morphology, so that the composite material can still have good flowability and mechanical strength under the condition of high ferrite magnetic powder filling ratio.

[0004] When the average particle size of the magnetic powder is large (small specific surface area), it is beneficial to improve the flowability and mechanical strength of the injection-molded ferrite composite material. However, excessively coarse particle size will lead to a significant decrease in the coercivity of the magnetic powder. Therefore, seeking a ferrite magnetic powder that simultaneously possesses a relatively large particle size, good particle morphology (ensuring better flowability), and superior magnetic properties is a viable research direction.

[0005] La-Co ion doping can improve the performance of ferrite powder, and even with a relatively coarse particle size, the powder can still maintain high coercivity. However, since La-Co ion doping requires a sufficiently high temperature (above 1200℃), the high temperature can cause the ferrite grains to flatten, resulting in flattened powder particles. This flattened powder is not conducive to achieving high flowability when used in injection-molded ferrite composites.

[0006] CN113889309A discloses a binder ferrite magnetic powder for injection molding, its preparation method, and its application. This binder ferrite magnetic powder is obtained by ball milling fine-grained ferrite magnetic powder with an average particle size of 0.5–1.2 micrometers and coarse-grained ferrite magnetic powder with an average particle size of 3.0–6.0 micrometers in a weight ratio of 10–35 wt% in a ball mill, resulting in a mixed coarse and fine magnetic powder. This binder ferrite magnetic powder can be mixed with rubber-based binders, plasticizers, and stabilizers to prepare injection-molded flexible binder magnets.

[0007] CN118335508A discloses a process for preparing injection-molded ferrite and an injection-molded ferrite magnet. The process for preparing injection-molded ferrite includes the following steps: iron scale powder: 20-40 parts; strontium carbonate powder: 10-60 parts; water: 23-53 parts; iron oxide red: 10-40 parts; barium carbonate: 3-11 parts; silane coupling agent: 1-7 parts; dispersant: 1-6 parts; nylon-6: 10-20 parts; toughening and reinforcing agent: 1-7 parts; defoamer: 1-7 parts; lubricant: 1-9 parts; S1, preparing ferrite magnetic powder: a: mixing iron scale powder and strontium carbonate powder evenly to obtain an additive mixture; b: forming the mixture in a with water into pellets, the ratio of water to mixture is 1.6:1, and then pre-firing to obtain a pre-fired clinker.

[0008] Existing injection-molded ferrite materials all have certain drawbacks, including the inability to simultaneously possess coarse particle size, good particle morphology, and superior magnetic properties, thus failing to ensure that the injection-molded ferrite material simultaneously exhibits excellent flowability and magnetic properties. Therefore, developing a novel injection-molded ferrite magnetic powder and its preparation method is crucial for the development and application of injection-molded ferrite materials. Summary of the Invention

[0009] Aiming at the deficiencies existing in the prior art, the purpose of the present invention is to provide an injection ferrite magnetic powder and its preparation method, an injection ferrite material and its application. The injection ferrite magnetic powder provided in the present invention not only has a relatively coarse particle size, but also has a good particle morphology because the average aspect ratio L / D is 1.2 to 3.0. Therefore, the injection ferrite magnetic powder has better fluidity. In addition, due to the doping of La and Co, the injection ferrite magnetic powder also has excellent magnetic properties.

[0010] To achieve this purpose, the present invention adopts the following technical solutions:

[0011] In the first aspect, the present invention provides an injection ferrite magnetic powder, and the chemical formula of the injection ferrite magnetic powder is Sr ,

[0017] ,

[0016] ,

[0015] , ,

[0014] , , La x Ca y Fe 12-z Co z O 19 , the D50 size is 1.5 to 2.5 μm, and the average aspect ratio L / D is 1.2 to 3.0;

[0012] Among them, 0 < x ≤ 0.4, 0 < y ≤ 0.4, 0 < z ≤ 0.25, 1.3 ≤ x / z ≤ 1.6.

[0013] In the present invention, the D50 size of the injection ferrite magnetic powder is 1.5 to 2.5 μm. For example, it can be 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm or 2.5 μm, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0014] In the present invention, the average aspect ratio L / D of the injection ferrite magnetic powder is 1.2 to 3.0. For example, it can be 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8 or 3.0, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0015] In the present invention, 0 < x ≤ 0.4, and the value of x can be, for example, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35 or 0.4, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0016] In the present invention, 0 < y ≤ 0.4, and the value of y can be, for example, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35 or 0.4, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0017] In the present invention, 0 < z ≤ 0.25. The value of z can be, for example, 0.01, 0.02, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22 or 0.25, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0018] In the present invention, 1.3 ≤ x / z ≤ 1.6. The value of x / z can be, for example, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55 or 1.6, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0019] The injection ferrite magnetic powder provided in the present invention not only has a relatively coarse particle size, but also has a good particle morphology due to the aspect ratio L / D ranging from 1.2 to 3.0. Therefore, the injection ferrite magnetic powder has relatively excellent fluidity. In addition, due to the doping of La and Co, the injection ferrite magnetic powder also has excellent magnetic properties.

[0020] Preferably, the D50 size of the injection ferrite magnetic powder is 1.5 - 2.0 μm, the proportion of particles with sizes between 1 μm and 5 μm is greater than 90%, the proportion of magnetic powder particles with sizes less than 1 μm is less than 5%, and the proportion of magnetic powder particles with sizes greater than 5 μm is less than 5%.

[0021] In the present invention, the D50 size of the injection ferrite magnetic powder is 1.5 - 2.0 μm. It can be, for example, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm or 2.0 μm, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0022] In the present invention, the proportion of the injection ferrite magnetic powder with sizes between 1 μm and 5 μm is greater than 90%. It can be, for example, 90.1%, 90.5%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0023] In the present invention, the proportion of magnetic powder particles of the injection ferrite magnetic powder with sizes less than 1 μm is less than 5%. It can be, for example, 4.9%, 4.8%, 4.5%, 4.3%, 4.0%, 3.5%, 3%, 2.5%, 2.0%, 1.5%, 1.0%, 0.5% or 0.1%, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0024] In this invention, the proportion of magnetic powder particles with a size greater than 5 μm in the injected ferrite magnetic powder is less than 5%, for example, it can be 4.9%, 4.8%, 4.5%, 4.3%, 4.0%, 3.5%, 3%, 2.5%, 2.0%, 1.5%, 1.0%, 0.5%, or 0.1%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] In a second aspect, the present invention provides a method for preparing the injection-embedded ferrite magnetic powder described in the first aspect, the method comprising:

[0026] A mixed powder is obtained by mixing Sr source, La source, Ca source, Fe source, Co source, H3BO3 and SrCl2. The mixed powder is then calcined and pulverized in sequence to obtain the injection ferrite magnetic powder.

[0027] Based on the mass of the mixed powder, the mass fraction of H3BO3 in the mixed powder is 1-1.5 wt%, the mass fraction of SrCl2 is 1-2 wt%, and the mass ratio of H3BO3 to SrCl2 is 0.75-1.

[0028] In this invention, the mass of the mixed powder is taken as 100%. The mass fraction of H3BO3 in the mixed powder is 1 to 1.5 wt%, for example, it can be 1 wt%, 1.05 wt%, 1.1 wt%, 1.15 wt%, 1.2 wt%, 1.25 wt%, 1.3 wt%, 1.35 wt%, 1.4 wt%, 1.45 wt%, or 1.5 wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] In this invention, the mass of the mixed powder is taken as 100%. The mass fraction of SrCl2 in the mixed powder is 1 to 2 wt%, for example, it can be 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, or 2 wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] In this invention, the mass ratio of H3BO3 to SrCl2 is 0.75 to 1, for example, it can be 0.75, 0.78, 0.80, 0.82, 0.85, 0.88, 0.90, 0.92, 0.95, 0.98 or 1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] Preferably, the mixing method includes a first ball milling, the first ball milling time being 1 to 5 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, but not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0032] Preferably, water is added during the first ball milling process, and the mixture is dried after the first ball milling to obtain a mixed powder.

[0033] Preferably, the drying temperature after the first ball milling is 90 to 130°C, for example, it can be 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, the Sr source includes SrCO3.

[0035] Preferably, the La source includes La2O3.

[0036] Preferably, the Ca source includes CaCO3.

[0037] Preferably, the Fe source includes Fe2O3.

[0038] Preferably, the Co source includes Co2O3.

[0039] Preferably, the calcination temperature is 1200–1300°C and the time is 1–3 hours.

[0040] The calcination temperature described in this invention is 1200-1300℃, for example, it can be 1200℃, 1210℃, 1220℃, 1230℃, 1240℃, 1250℃, 1260℃, 1270℃, 1280℃, 1290℃ or 1300℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] The calcination time described in this invention is 1 to 3 hours, for example, it can be 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours or 3 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] Preferably, the pulverization includes Raymond milling, a second ball milling, and vibratory milling performed sequentially.

[0043] Preferably, the D50 particle size of the Raymond milled powder is less than 10 μm, for example, it can be 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm or 1 μm, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0044] Preferably, the second ball milling time is 10 to 15 hours, for example, it can be 10 hours, 10.5 hours, 11 hours, 11.5 hours, 12 hours, 12.5 hours, 13 hours, 13.5 hours, 14 hours, 14.5 hours or 15 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] Preferably, water is added during the second ball milling process, and the ball milling is followed by drying to obtain the powder after the second ball milling.

[0046] Preferably, the drying temperature after the second ball milling is 90 to 130°C, for example, it can be 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] Preferably, the D50 particle size of the powder obtained after the second ball milling is 2.0 to 2.5 μm, for example, it can be 2.0 μm, 2.05 μm, 2.1 μm, 2.15 μm, 2.2 μm, 2.25 μm, 2.3 μm, 2.35 μm, 2.4 μm, 2.45 μm or 2.5 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] Preferably, the D50 particle size of the powder obtained after vibration milling is 1.5 to 2.0 μm, for example, it can be 1.5 μm, 1.55 μm, 1.6 μm, 1.65 μm, 1.7 μm, 1.75 μm, 1.8 μm, 1.85 μm, 1.9 μm, 1.95 μm or 2.0 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] Preferably, the pulverization process further includes sequential heat treatment and deagglomeration.

[0050] Preferably, the process of pulverizing and heat treatment further includes mixing Bi2O3 with the pulverized powder.

[0051] Preferably, the mass ratio of Bi2O3 to the pulverized powder is (0.1 to 1):100, for example, it can be 0.1:100, 0.2:100, 0.3:100, 0.4:100, 0.5:100, 0.6:100, 0.7:100, 0.8:100, 0.9:100 or 1:100, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] Preferably, the heat treatment temperature is 700–1100°C and the time is 0.1–3.0 h.

[0053] The heat treatment temperature described in this invention is 700 to 1100°C, for example, it can be 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C or 1100°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0054] The heat treatment time described in this invention is 0.1 to 3.0 h, for example, it can be 0.1 h, 0.3 h, 0.5 h, 0.7 h, 1 h, 1.2 h, 1.5 h, 1.7 h, 2.0 h, 2.2 h, 2.5 h, 2.7 h or 3.0 h, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0055] Preferably, the deagglomeration includes ball milling the heat-treated powder using a sand mill with lightweight balls.

[0056] Preferably, the density of the lightweight spheres is 1.5–2.0 g / cm³. 3 For example, it could be 1.5g / cm³ 3 1.6g / cm 3 1.7g / cm 3 1.8g / cm 3 1.9g / cm 3 2.0g / cm 3 However, this does not apply to all values ​​listed; other unlisted values ​​within the same range also apply.

[0057] Preferably, the diameter of the lightweight ball is 1 to 3 mm, for example, it can be 1 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm, 2 mm, 2.2 mm, 2.4 mm, 2.6 mm, 2.8 mm or 3 mm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0058] The lightweight ball described in this invention can be, for example, an iron-core nylon ball (8 mm in diameter and 2 mm thick nylon surface).

[0059] As a preferred embodiment of the preparation method of the present invention, the preparation method includes:

[0060] (1) Sr source, La source, Ca source, Fe source, Co source, H3BO3 and SrCl2 are mixed by ball milling for 1 to 5 hours. Water is added during the first ball milling process. After the first ball milling, the mixture is dried at 90 to 130°C to obtain a mixed powder.

[0061] Based on the mass of the mixed powder, the mass fraction of H3BO3 in the mixed powder is 1-1.5 wt%, the mass fraction of SrCl2 is 1-2 wt%, and the mass ratio of H3BO3 to SrCl2 is 0.75-1.

[0062] (2) The mixed powder obtained in step (1) is calcined at 1200-1300℃ for 1-3 hours, and then the D50 particle size of the powder is reduced to less than 10 μm by Raymond milling; then a second ball milling is performed for 10-15 hours, water is added during the second ball milling, and the powder is dried at 90-130℃ after the second ball milling to obtain powder with a D50 particle size of 2.0-2.5 μm; then the powder with a D50 particle size of 1.5-2.0 μm is obtained by vibration milling.

[0063] (3) After mixing Bi2O3 with a mass ratio of (0.1~1):100 with the powder with D50 particle size of 1.5~2.0μm obtained in step (2), heat treatment is carried out at 700~1100℃ for 0.1~3.0h, and then the heat-treated powder is ball-milled and deagglomerated using a sand mill with light balls to obtain the injection ferrite magnetic powder.

[0064] Thirdly, the present invention provides an injectable ferrite material, wherein the injectable ferrite material comprises the injectable ferrite magnetic powder described in the first aspect.

[0065] Fourthly, the present invention provides an application of the injection ferrite material described in the third aspect, wherein the injection ferrite material is used in the fields of motors, magnetic storage, magnetic adsorption and magnetic sensing.

[0066] Compared with the prior art, the present invention has the following beneficial effects:

[0067] (1) The injection ferrite magnetic powder provided in this invention not only has a relatively coarse particle size, but also has a good particle morphology due to the average aspect ratio L / D of 1.2 to 3.0. Therefore, the injection ferrite magnetic powder has excellent flowability. In addition, due to the doping of La and Co, the injection ferrite magnetic powder also has excellent magnetic properties.

[0068] (2) In the preparation method of injection ferrite magnetic powder provided by the present invention, the addition of H3BO3 and SrCl2 serves as a fluxing agent. Utilizing the low melting points of H3BO3 and SrCl2, the interdiffusion of La and Co ions with Sr, Fe, and Ca ions is promoted, allowing Sr to be formed at a relatively low temperature. 1-x-y La x Ca y Fe 12-z Co z O 19 On the other hand, since H3BO3 can promote the axial growth of ferrite grains and SrCl2 can promote the radial growth of ferrite particles, the particle size and aspect ratio L / D of ferrite particles can be controlled by controlling the ratio of H3BO3 to SrCl2, thereby obtaining injection-molded ferrite powder with coarser particle size, good particle morphology and excellent magnetic properties. Detailed Implementation

[0069] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0070] Example 1

[0071] This embodiment provides an injectable ferrite magnetic powder, the chemical formula of which is Sr. 1-x- y La x Ca y Fe 12-z Co z O 19 The average length-to-diameter ratio (L / D) is 2.35.

[0072] Where x = 0.4, y = 0.4, z = 0.25, and x / z = 1.6.

[0073] The injected ferrite magnetic powder has a D50 size of 1.90 μm, with more than 90% of the particles having a size between 1 μm and 5 μm, less than 5% of the magnetic powder particles having a size smaller than 1 μm, and less than 5% of the magnetic powder particles having a size larger than 5 μm.

[0074] The preparation method of the injected ferrite magnetic powder is as follows:

[0075] (1) SrCO3, La2O3, CaCO3, Fe2O3, Co2O3, H3BO3 and SrCl2 were mixed by ball milling for 3 hours. Water was added during the first ball milling process. After the first ball milling, the mixture was dried at 110°C to obtain a mixed powder.

[0076] Based on the mass of the mixed powder, the mass fraction of H3BO3 in the mixed powder is 1.5 wt%, the mass fraction of SrCl2 is 2 wt%, and the mass ratio of H3BO3 to SrCl2 is 0.75.

[0077] (2) The mixed powder obtained in step (1) is calcined at 1200℃ for 2 hours, and then the D50 particle size of the powder is reduced to less than 10 μm by Raymond milling; then it is ball-milled for 15 hours, water is added during the second ball milling process, and the powder is dried at 110℃ after the second ball milling to obtain powder with a D50 particle size of 2.45 μm; then it is vibrated milled to obtain powder with a D50 particle size of 1.85 μm.

[0078] (3) After mixing Bi2O3 with a mass ratio of 0.5:100 with the powder with a D50 particle size of 1.85μm obtained in step (2), the mixture is heat-treated at 900℃ for 2.0h, and then the heat-treated powder is ball-milled and deagglomerated using a sand mill with light balls to obtain the injected ferrite magnetic powder.

[0079] Example 2

[0080] This embodiment provides an injectable ferrite magnetic powder, the chemical formula of which is Sr. 1-x- y La x Ca y Fe 12-z Co z O 19 The average length-to-diameter ratio (L / D) is 1.2.

[0081] Where x = 0.1, y = 0.4, z = 0.077, and x / z = 1.3.

[0082] The injected ferrite magnetic powder has a D50 size of 1.5 μm, with more than 90% of the particles having a size between 1 μm and 5 μm, less than 5% of the magnetic powder particles having a size smaller than 1 μm, and less than 5% of the magnetic powder particles having a size larger than 5 μm.

[0083] The preparation method of the injected ferrite magnetic powder is as follows:

[0084] (1) SrCO3, La2O3, CaCO3, Fe2O3, Co2O3, H3BO3 and SrCl2 were mixed by ball milling for 5 hours. Water was added during the first ball milling process. After the first ball milling, the mixture was dried at 90°C to obtain a mixed powder.

[0085] Based on the mass of the mixed powder, the mass fraction of H3BO3 in the mixed powder is 1.5 wt%, the mass fraction of SrCl2 is 1.5 wt%, and the mass ratio of H3BO3 to SrCl2 is 1.

[0086] (2) The mixed powder obtained in step (1) is calcined at 1300℃ for 1h, and then the D50 particle size of the powder is reduced to less than 10μm by Raymond milling; then it is ball-milled for 15h, water is added during the second ball milling process, and the powder is dried at 90℃ after the second ball milling to obtain powder with a D50 particle size of 2.0μm; then it is vibrated to obtain powder with a D50 particle size of 1.5μm.

[0087] (3) After mixing Bi2O3 with a mass ratio of 0.1:100 with the powder with a D50 particle size of 1.5μm obtained in step (2), heat treatment is carried out at 1100℃ for 0.1h. Then, the heat-treated powder is ball-milled and deagglomerated using a sand mill with light balls to obtain the injected ferrite magnetic powder.

[0088] Example 3

[0089] This embodiment provides an injectable ferrite magnetic powder, the chemical formula of which is Sr. 1-x- y La x Ca y Fe 12-z Co z O 19 The average length-to-diameter ratio (L / D) is 3.0;

[0090] Where x = 0.4, y = 0.1, z = 0.25, and x / z ≤ 1.6.

[0091] The injected ferrite magnetic powder has a D50 size of 2.0 μm, with more than 90% of the particles having a size between 1 μm and 5 μm, less than 5% of the magnetic powder particles having a size smaller than 1 μm, and less than 5% of the magnetic powder particles having a size larger than 5 μm.

[0092] The preparation method of the injected ferrite magnetic powder is as follows:

[0093] (1) SrCO3, La2O3, CaCO3, Fe2O3, Co2O3, H3BO3 and SrCl2 were mixed by ball milling for 1 hour. Water was added during the first ball milling process. After the first ball milling, the mixture was dried at 130°C to obtain a mixed powder.

[0094] Based on the mass of the mixed powder, the mass fraction of H3BO3 in the mixed powder is 1 wt%, the mass fraction of SrCl2 is 1.25 wt%, and the mass ratio of H3BO3 to SrCl2 is 0.8.

[0095] (2) The mixed powder obtained in step (1) is calcined at 1200℃ for 3 hours, and then the D50 particle size of the powder is reduced to less than 10 μm by Raymond milling; then it is ball-milled for 10 hours, water is added during the second ball milling process, and the powder is dried at 130℃ after the second ball milling to obtain powder with a D50 particle size of 2.5 μm; then it is vibrated to obtain powder with a D50 particle size of 2.0 μm.

[0096] (3) After mixing Bi2O3 with a mass ratio of 1:100 with the powder with a D50 particle size of 2.0 μm obtained in step (2), the mixture is heat-treated at 700℃ for 3.0 h, and then ball milled with light balls in a sand mill to deagglomerate the heat-treated powder to obtain the injection ferrite magnetic powder.

[0097] Example 4

[0098] This embodiment provides an injection ferrite magnetic powder. Except that the D50 size of the injection ferrite magnetic powder is 2.13 μm and the average length-to-diameter ratio L / D is 2.55, that is, the powder with a D50 particle size of 1.95 μm is obtained by vibration grinding in step (2) of the preparation method of injection ferrite magnetic powder, the rest is the same as in Example 1.

[0099] Example 5

[0100] This embodiment provides an injection ferrite magnetic powder. Except that the D50 size of the injection ferrite magnetic powder is 1.5 μm and the average length-to-diameter ratio L / D is 1.8, i.e. the vibration grinding in step (2) of the preparation method of the injection ferrite magnetic powder is omitted, the rest is the same as in embodiment 1.

[0101] Example 6

[0102] This embodiment provides an injection ferrite magnetic powder. Except that the D50 size of the injection ferrite magnetic powder is 2.5 μm and the average aspect ratio L / D is 3.0, that is, the mass ratio of Bi2O3 to the powder obtained in step (2) of the preparation method of the injection ferrite magnetic powder is 0.01:100, the rest is the same as in Example 1.

[0103] Example 7

[0104] This embodiment provides an injection ferrite magnetic powder. Except that the D50 size of the injection ferrite magnetic powder is 1.8 μm and the average aspect ratio L / D is 1.3, that is, the mass ratio of Bi2O3 to the powder obtained in step (2) is 2:100 during mixing in step (3) of the preparation method of the injection ferrite magnetic powder, all other aspects are the same as in Example 1.

[0105] Example 8

[0106] This embodiment provides an injection ferrite magnetic powder. Except that the D50 size of the injection ferrite magnetic powder is 1.6 μm and the average length-to-diameter ratio L / D is 2.3, that is, the calcination temperature in step (2) of the preparation method of the injection ferrite magnetic powder is 1350℃, the rest are the same as in Example 1.

[0107] Comparative Example 1

[0108] This comparative example provides an injection ferrite magnetic powder. Except that z=0, the D50 size of the injection ferrite magnetic powder is 2.3 μm, and the average length-to-diameter ratio L / D is 3.1, all other aspects are the same as in Example 1.

[0109] Comparative Example 2

[0110] This comparative example provides an injection-embedded ferrite magnetic powder. Except for z = 0.3, the D50 size of the injection-embedded ferrite magnetic powder is 1.92 μm, and the average length-to-diameter ratio L / D is 2.33, all other aspects are the same as in Example 1.

[0111] Comparative Example 3

[0112] This comparative example provides an injection-embedded ferrite magnetic powder. Except for x = 0.3, y = 0.3, z = 0.3, the D50 size of the injection-embedded ferrite magnetic powder is 3.0 μm, and the average aspect ratio L / D is 1.0. That is, in step (1) of the preparation method of the injection-embedded ferrite magnetic powder, the mass fraction of the mixed powder is 0.5 wt%, the mass fraction of SrCl2 is 0.5 wt%, and the mass ratio of H3BO3 to SrCl2 is 1:1, all other aspects are the same as in Example 1.

[0113] Comparative Example 4

[0114] This comparative example provides an injection-embedded ferrite magnetic powder. Except for x = 0.1, y = 0.1, z = 0.05, the D50 size of the injection-embedded ferrite magnetic powder is 3.5 μm, and the average aspect ratio L / D is 3.3. That is, in step (1) of the preparation method of the injection-embedded ferrite magnetic powder, the mass fraction of the mixed powder is 0.5 wt%, the mass fraction of SrCl2 is 3.0 wt%, and the mass ratio of H3BO3 to SrCl2 is 1:6, all other aspects are the same as in Example 1.

[0115] The particle size of the injected ferrite magnetic powder provided in the above embodiments and comparative examples was tested using a laser particle size analyzer, and the D50 particle size of the injected ferrite magnetic powder in the above embodiments and comparative examples was obtained as shown in the above embodiments and comparative examples.

[0116] The magnetic properties of the injected ferrite magnetic powder provided in the above embodiments and comparative examples were tested using a vibrating sample magnetometer (VSM). The saturation magnetization (Ms), remanent magnetization (Mr), and intrinsic coercivity (Hcj) of the injected ferrite magnetic powder are shown in Table 1.

[0117] Table 1

[0118]

[0119]

[0120] From Table 1, we can obtain:

[0121] (1) The injectable ferrite magnetic powder provided in Examples 1 to 4 has high saturation magnetization, high remanent magnetization and high intrinsic coercivity, and exhibits good fluidity.

[0122] (2) By comparing Example 1 and Example 5, it can be seen that the vibration milling in the preparation method of the injection ferrite magnetic powder is beneficial to improving the performance of the injection ferrite magnetic powder. This is because when the magnetic powder obtained by ball milling breaks, sharp edges and protrusions will be generated. This kind of structure is not conducive to obtaining high fluidity of the magnetic powder. Moreover, after the magnetic powder of this form is mixed and granulated with engineering plastics, the strength and magnetic properties of the material are both low. Therefore, in this invention, a vibration milling step is added. By vibration milling with relatively low energy, these sharp edges and protrusions are reduced or eliminated, thereby improving the fluidity of the magnetic powder.

[0123] (3) By comparing Example 1 with Examples 6 and 7, it can be seen that mixing a suitable mass fraction of Bi2O3 in step (3) of the preparation method of injection ferrite magnetic powder is beneficial to improving the performance of injection ferrite magnetic powder. This is because after adding Bi2O3, the fluxing effect of Bi2O3 makes it easier for the powder to eliminate the deformation stress generated during ball milling and vibratory milling during the annealing process, repair the powder lattice defects, and thus improve the magnetic properties of injection ferrite magnetic powder.

[0124] (4) By comparing Example 1 and Example 8, it can be seen that the calcination temperature in step (2) of the preparation method of injection ferrite magnetic powder in the present invention will affect the performance of injection ferrite magnetic powder. When the calcination temperature is 1200-1300℃, it is beneficial to obtain injection ferrite magnetic powder with better performance. This is because Co ions diffuse more fully in the magnetic powder calcined in this temperature range, and the grains are not too coarse. Moreover, the aspect ratio of the magnetic powder particles is kept in a relatively suitable range.

[0125] (5) By comparing Example 1 with Comparative Examples 1 and 2, it can be seen that the addition of an appropriate amount of Co in this invention is beneficial to improving the performance of the injected ferrite magnetic powder. This is because the addition of Co ions increases the saturation magnetization and anisotropic field of the magnetic powder, thereby improving the intrinsic magnetic properties of the magnetic powder.

[0126] (6) As can be seen from the comparison between Example 1 and Comparative Examples 3 and 4, the injected ferrite magnetic powder provided in this invention not only has a relatively coarse particle size, but also has good particle morphology due to the aspect ratio L / D ranging from 1.2 to 3.0. Therefore, the injected ferrite magnetic powder has excellent flowability. In addition, due to the doping of La and Co, the injected ferrite magnetic powder also has excellent magnetic properties. In the preparation method of the injected ferrite magnetic powder provided in this invention, the addition of H3BO3 and SrCl2 plays a role in fluxing. By utilizing the low melting point of H3BO3 and SrCl2, the interdiffusion of La and Co ions with Sr, Fe, and Ca ions is promoted, and Sr can be formed at a relatively low temperature. 1-x-y La x Ca y Fe 12-z Co z O 19 On the other hand, since H3BO3 can promote the axial growth of ferrite grains and SrCl2 can promote the radial growth of ferrite particles, the particle size and aspect ratio L / D of ferrite particles can be controlled by controlling the ratio of H3BO3 to SrCl2, thereby obtaining injection-molded ferrite powder with coarser particle size, good particle morphology and excellent magnetic properties.

[0127] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for producing an injection-molded ferrite magnet powder, characterized by, The chemical formula of the injected ferrite magnetic powder is Sr 1-x-y La x Ca y Fe 12-z Co z O 19 , the D50 size is 1.5-2.5 μm, and the average length-diameter ratio L / D is 1.2-3.0; Among them, 0 <x≤0.4,0<y≤0.4,0<z≤0.25,1.3≤x / z≤1.6; The preparation method includes: SrCO3, La source, Ca source, Fe source, Co source, H3BO3 and SrCl2 are mixed to obtain a mixed powder, which is then calcined and pulverized in sequence to obtain the injection ferrite magnetic powder. Based on the mass of the mixed powder, the mass fraction of H3BO3 in the mixed powder is 1~1.5wt%, the mass fraction of SrCl2 is 1~2wt%, and the mass ratio of H3BO3 to SrCl2 is 0.75~1.

2. The production method according to claim 1, characterized by, The D50 size of the injected ferrite magnetic powder is 1.5~2.0μm, with the proportion of particles with a size between 1μm and 5μm being greater than 90%, the proportion of magnetic powder particles with a size smaller than 1μm being less than 5%, and the proportion of magnetic powder particles with a size greater than 5μm being less than 5%.

3. The production method according to claim 1, characterized by, The mixing method includes a first ball milling, the first ball milling time being 1 to 5 hours.

4. The method of claim 1, wherein, The La source includes La2O3.

5. The preparation method according to claim 1, characterized in that, The Ca source includes CaCO3.

6. The method of claim 1, wherein, The Fe source includes Fe2O3.

7. The preparation method according to claim 1, characterized in that, The Co source includes Co2O3.

8. The method of claim 1, wherein, The calcination temperature is 1200~1300℃, and the time is 1~3h.

9. The method of claim 1, wherein, The pulverization process includes Raymond milling, a second ball milling, and vibratory milling performed sequentially.

10. The method of claim 9, wherein, The D50 particle size of the Raymond milled powder is less than 10 μm.

11. The preparation method according to claim 9, characterized in that, The D50 particle size of the powder obtained after the second ball milling is 2.0~2.5μm.

12. The method of claim 9, wherein, The D50 particle size of the powder obtained after vibration milling is 1.5~2.0μm.

13. The method of claim 1, wherein, The pulverization process is followed by sequential heat treatment and deagglomeration.

14. The method of claim 13, wherein, The process of pulverizing and heat treatment also includes mixing Bi2O3 with the pulverized powder.

15. The method of claim 14, wherein, The mass ratio of Bi2O3 to the pulverized powder is (0.1~1):

100.

16. The method of claim 13, wherein, The heat treatment temperature is 700~1100℃, and the time is 0.1~3.0h.

17. The method of claim 13, wherein, The deagglomeration process includes ball milling the heat-treated powder using a sand mill with lightweight balls.

18. The method of claim 1, wherein, The preparation method includes: (1) SrCO3, La source, Ca source, Fe source, Co source, H3BO3 and SrCl2 are mixed by ball milling for 1~5h. Water is added during the first ball milling process. After the first ball milling, the mixture is dried at 90~130℃ to obtain a mixed powder. Based on the mass of the mixed powder, the mass fraction of H3BO3 in the mixed powder is 1~1.5wt%, the mass fraction of SrCl2 is 1~2wt%, and the mass ratio of H3BO3 to SrCl2 is 0.75~1; (2) The mixed powder obtained in step (1) is calcined at 1200~1300℃ for 1~3h, and then the D50 particle size of the powder is reduced to less than 10μm by Raymond milling; then a second ball milling is performed for 10~15h, water is added during the second ball milling, and the powder is dried at 90~130℃ after the second ball milling to obtain powder with a D50 particle size of 2.0~2.5μm; then the powder with a D50 particle size of 1.5~2.0μm is obtained by vibration milling. (3) mixing Bi2O3 with a mass ratio of (0.1-1): 100 with the powder obtained in step (2) having a D50 particle size of 1.5-2.0 μm, then performing heat treatment at 700-1100 °C for 0.1-3.0 h, and then performing a ball milling deagglomeration treatment on the heat-treated powder using a sand mill with light balls to obtain the injection ferrite magnetic powder.

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