Low-temperature high-coercivity permanent magnet ferrite and production process thereof

Abstract

The application relates to the technical field of permanent ferrite, in particular to a low-temperature high-coercivity permanent ferrite and a production process, wherein SrCO3, CaCO3, Al2O3, Fe2O3, Cr2O3 and La2O3 are used as raw materials, and the raw materials are proportioned according to Sr 1‑x‑y Ca x La y Al z Cr w Fe 12‑z‑w O 19 (x=0.1-0.4; y=0-0.3; z=1.5-3, w=0-2, z+w<4) are proportioned, high-energy ball milling is first used, then low-energy ball milling is adopted, after the ball milling, the first ball milling material is sequentially dried, sieved and pre-sintered; subsequently, the pre-sintered material is coarsely broken, additives are added, high-energy ball milling is adopted for wet milling, then low-energy ball milling is adopted for secondary ball milling of the pre-sintered material, the secondary ball milling slurry is pressed into a green body sample under an external magnetic field, and a dense block high-coercivity ferrite magnet is prepared by high-temperature sintering, and the low-temperature high-coercivity ferrite magnet has high coercivity.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet ferrite technology, and in particular to a low-temperature high coercivity permanent magnet ferrite and its manufacturing process. Background Technology

[0002] Permanent magnet ferrites belong to the principal-axis hexagonal crystal system, mainly including barium ferrite, strontium ferrite, and lead ferrite. The general molecular formula of these compounds is AB12O19. Here, A represents a cation with a radius similar to that of oxygen ions, such as Ba2+, Sr2+, and Pb2+, while B represents a trivalent cation, such as Fe, Al, and Mn. Currently, strontium ferrite is the most widely used type of permanent magnet. It has good magnetic properties, its raw materials are inexpensive, and its production process is relatively simpler than other materials, making it very cost-effective and widely used in various industrial fields.

[0003] To meet the demands of upgraded applications and continuously enhance competitiveness, researchers are focusing on improving the performance parameters, reducing costs, and increasing efficiency of strontium ferrites. For example, cation substitution is used to improve the magnetic properties of strontium ferrites. Studies have investigated the substitution of Sr²⁺ with metal ions such as Ca²⁺, Pb²⁺, Nd³⁺, Sm³⁺, and Gd³⁺, and the substitution of Fe³⁺ with transition metal ions such as Zn²⁺, Co²⁺, Mn²⁺, Cu²⁺, Cr³⁺, and In³⁺. Furthermore, combined substitution with metal ions such as Co-Al, Nd-Zn, La-Co, Ca-La-Co, and Ce-Cu is used to prepare strontium ferrites. Despite this, currently commercially available strontium ferrites exhibit low coercivity, especially at low temperatures, leading to a significant reduction in magnetic performance below zero degrees Celsius. This patent utilizes elemental doping and optimized ball milling technology to achieve the preparation of strontium ferrites with excellent low-temperature magnetic properties. Summary of the Invention

[0004] The purpose of this invention is to provide a low-temperature high-coercivity permanent magnet ferrite and its manufacturing process, which solves the problem that general ferrites have very low coercivity and poor magnetic properties at low temperatures in the prior art.

[0005] To achieve the above objectives, the present invention provides a low-temperature high-coercivity permanent magnet ferrite, the raw materials for which are prepared by weight include:

[0006] The composition of SrCO3, CaCO3, Al2O3, Fe2O3, Cr2O3, and La2O3 is as follows: Sr 1-x-y Ca x La y Al z Cr w Fe 12-z-w O 19(x = 0.1-0.4; y = 0-0.3; z = 1.5-3, w = 0-2, z+w < 4); additives (SiO2, H3BO3 and CaCO3), with a total mass ratio of 1-3%.

[0007] This invention also provides a low-temperature high-coercivity permanent magnet ferrite production process, which uses the aforementioned low-temperature high-coercivity permanent magnet ferrite and includes the following steps:

[0008] Using SrCO3, CaCO3, Al2O3, Fe2O3, Cr2O3 and La2O3 as raw materials, the materials were first ball-milled using a high-energy ball mill, and then ball-milled using a low-energy ball mill. Hard steel balls were selected as the ball milling media, and the ball-to-material-to-water ratio was 10-12:1:2.

[0009] After drying the ball milling material, it is sieved and then placed in a programmable furnace. The temperature is raised to 1150-1280℃ and sintered. The temperature is held for 2 hours and then cooled with the furnace.

[0010] The pre-burned material is coarsely crushed, and additives SiO2, H3BO3 and CaCO3 (total mass ratio of 1-3%) are added. It is then wet-milled using a high-energy ball mill, and then ball-milled using a low-energy ball mill.

[0011] After ball milling and drying to a certain extent, the secondary ball milling slurry is pressed into a 29mm cylindrical green sample under an external magnetic field;

[0012] Cylindrical green samples are placed in a programmed furnace for sintering, heated to 1150-1250℃, held for 1-2 hours, and then cooled with the furnace.

[0013] In the process of using SrCO3, CaCO3, Al2O3, Fe2O3, Cr2O3, and La2O3 as raw materials, first ball milling is performed using a high-energy ball mill, followed by ball milling using a low-energy ball mill, with hard steel balls selected as the grinding media and a ball-to-material-to-water ratio of 10-12:1:2:

[0014] High-energy ball milling for 0.5-2 hours, low-energy ball milling for 2-8 hours, raw material purity: SrCO3 99%, CaCO3 98.5%, Al2O3 99.9%, Fe2O3 99%, Cr2O3 99%, La2O3 99.9%.

[0015] In the process of drying the ball milled material, sieving it, placing it in a programmable furnace, heating it to 1150-1280℃, sintering it, holding it at that temperature for 2 hours, and then cooling it in the furnace:

[0016] The temperature is increased at a gradient rate of 3 to 4 °C.

[0017] In the steps of coarsely crushing the pre-calcined material, adding additives SiO2, H3BO3 and CaCO3 (total mass ratio of 1-3%), wet milling with a high-energy ball mill, and then ball milling with a low-energy ball mill:

[0018] High-energy ball mill wet milling for 0.5-2 hours, low-energy ball milling for 2-8 hours, additive purity is 99% for SiO2, 99.5% for H3BO3 and 98.5% for CaCO3.

[0019] In the step of sintering cylindrical green samples in a programmed furnace, heating to 1150-1250℃, holding at that temperature for 1-2 hours, and then cooling with the furnace:

[0020] The temperature is increased at a gradient rate of 3 to 4 °C.

[0021] This invention discloses a low-temperature, high-coercivity permanent magnet ferrite and its production process. Using SrCO3, CaCO3, Al2O3, Fe2O3, La2O3, and Cr2O3 as raw materials, the process involves first ball milling with a high-energy ball mill, followed by ball milling with a low-energy ball mill. Hard steel balls are selected as the milling medium, and the ball-to-material-to-water ratio is 10:1:2. After the first-stage ball-milled material is dried and sieved, it is placed in a programmed furnace, heated to 1200℃, sintered, held at that temperature for 2 hours, and then cooled with the furnace. The pre-sintered material is then coarsely crushed, additives are added, and high-energy... The material is wet-milled in a ball mill, and then ball-milled again using a low-energy ball mill. After ball milling, it is dried to a certain degree, and the secondary ball-milled slurry is pressed into 29mm cylindrical green samples under an external magnetic field. The cylindrical green samples are then placed in a programmable furnace for sintering, heated to 1160℃, held for 1.5 hours, and then cooled with the furnace. This yields ferrite with high and low temperature magnetic properties. Generally, ferrite has very low coercivity at low temperatures. High coercivity is achieved by adding Cr and Al, and high saturation magnetization is achieved by adding La, thus maintaining a relatively good magnetic performance. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0023] Figure 1 The Sr of this invention 0.67 Ca 0.33 Fe9Al3O 19 M(H) curve of sample (x=0.0).

[0024] Figure 2 The Sr of this invention 0.67 Ca 0.33 Fe9Al 2.5 Cr 0.5 O 19 M(H) curve of sample (x=0.5).

[0025] Figure 3 The Sr of this invention 0.67 Ca 0.33 Fe9Al2CrO 19 M(H) curve of sample (x=1.0).

[0026] Figure 4 These are the XRD patterns of three samples from this invention.

[0027] Figure 5 This is a flowchart of the steps of the first embodiment of the present invention.

[0028] Figure 6 This is a flowchart of the steps of the second embodiment of the present invention.

[0029] Figure 7 This is a flowchart of the steps of the third embodiment of the present invention. Detailed Implementation

[0030] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

[0031] First embodiment:

[0032] Please see Figures 1 to 5 This invention provides a low-temperature, high-coercivity permanent magnet ferrite production process, comprising the following steps:

[0033] S1: Using SrCO3 (99% purity), CaCO3 (98.5% purity), Al2O3 (99.9% purity), Fe2O3 (99% purity), Cr2O3 (99% purity) and La2O3 (99.9% purity) as raw materials, hard steel balls were selected as the ball milling media, and the ball-to-material-to-water ratio was 10:1:2. First, the materials were ball-milled for 2 hours using a high-energy ball mill, and then ball-milled for 2 hours using a low-energy ball mill.

[0034] S2: After drying the primary ball milling material at 100℃, it is sieved and then placed in a program furnace. The temperature is raised to 1200℃ at a gradient heating rate of 3-4℃ and sintered. The temperature is held for 2 hours and then cooled with the furnace.

[0035] S3: The pre-burned material is coarsely crushed, and 2% of additives (SiO2 (purity 99%), H3BO3 (purity 99.5%), CaCO3 (purity 98.5%) and La2O3 (purity 99.9%)) are added. The material is then wet-milled in a high-energy ball mill for 0.5 hours, and then ball-milled in a low-energy ball mill for 8 hours.

[0036] S4: After ball milling and drying to a certain extent, the secondary ball milling slurry is pressed into a 29mm cylindrical green sample under an external magnetic field.

[0037] S5: Place the cylindrical green sample in a programmable furnace for sintering, heat to 1160℃ for sintering, hold for 1.5h and then cool with the furnace.

[0038] Among them, SrCO3 (99% purity), CaCO3 (98.5% purity), Al2O3 (99.9% purity), Fe2O3 (99% purity), Cr2O3 (99% purity), and La2O3 (99.9% purity) were used as raw materials to synthesize SrCO3 with an atomic ratio of 99.9% using a solid-state method. 1-x- y Ca x La y Al z Cr w Fe 12-z-w O 19 Prepare 75 grams of Sr from a bulk material with (x = 0.1 - 0.4; y = 0 - 0.3; z = 1.5 - 3, w = 0 - 2, z + w < 4). 0.67 Ca 0.33 Fe9Al3O 19 Weigh 7.393 g SrCO3, 2.469 g CaCO3, 11.431 g Al2O3 and 53.708 g Fe2O3. Select hard steel balls as the ball milling medium. The ball-to-material-to-water ratio is 10:1:2. First, use a high-energy ball mill for 2 hours, and then use a low-energy ball mill for 2 hours. After drying the first ball milling material at 100℃, sieve it and then place it in a programmable furnace. Heat it to 1200℃ at a gradient heating rate of 3-4℃ and sinter it. Hold it at that temperature for 2 hours and then cool it with the furnace. The pre-calcined material was coarsely crushed, and 2wt% additives (SiO2 (99% purity), H3BO3 (99.5% purity), and CaCO3 (98.5% purity)) were added. The mixture was then wet-milled in a high-energy ball mill for 0.5 hours, followed by ball milling in a low-energy ball mill for 8 hours. After ball milling, the mixture was dried to a certain degree. The secondary ball-milled slurry was pressed into 29mm cylindrical green samples under an external magnetic field. The cylindrical green samples were then sintered in a programmed furnace at a gradient heating rate of 3-4℃ to 1160℃. After holding at that temperature for 1.5 hours, the samples were cooled with the furnace. This process yielded ferrite with high and low temperature magnetic properties. Generally, ferrite has very low coercivity at low temperatures. High coercivity was achieved by adding Cr and Al, while high saturation magnetization was achieved by adding La, thus maintaining relatively good magnetic properties. In addition, the combination of high-energy and low-energy ball milling greatly reduced the powder preparation and grinding time.

[0039] List of magnetic properties of other components:

[0040] Element Saturation magnetization (em / g) Innate coercivity (kOe) <![CDATA[Sr 0.6 Ca 0.4 Al3Fe9O 19 ]]> 22 13 <![CDATA[Sr 0.6 Ca 0.4 A l1.5 Cr2Fe 8.5 O 19 ]]> 32 9.6 <![CDATA[Sr 0.9 That 0.1 Al2Fe 10 A 19 ]]> 30 11.3 <![CDATA[Sr 0.37 That 0.33 to 0.3 Al2Cr 0.5 Fe 9.5 A 19 ]]> 48 10.7

[0041] Second embodiment:

[0042] Please see Figure 6 This invention provides a low-temperature, high-coercivity permanent magnet ferrite production process, comprising the following steps:

[0043] S1: Using SrCO3 (99% purity), CaCO3 (98.5% purity), Al2O3 (99.9% purity), Fe2O3 (99% purity) and Cr2O3 (99% purity) as raw materials, hard steel balls were selected as the ball milling media, and the ball-to-material-to-water ratio was 11:1:2. First, the material was ball-milled for 1 hour using a high-energy ball mill, and then ball-milled for 4 hours using a low-energy ball mill.

[0044] S2: After drying the primary ball milling material at 100℃, it is sieved and then placed in a program furnace. The temperature is raised to 1280℃ at a gradient heating rate of 3-4℃ and sintered. The temperature is held for 2 hours and then cooled with the furnace.

[0045] S3: The pre-burned material is coarsely crushed, and 1wt% of additives (SiO2 (purity 99%), H3BO3 (purity 99.5%) and CaCO3 (purity 98.5%)) are added. The material is then wet-milled in a high-energy ball mill for 1 hour, and then ball-milled in a low-energy ball mill for 4 hours.

[0046] S4: After ball milling and drying to a certain extent, the secondary ball milling slurry is pressed into a 29mm cylindrical green sample under an external magnetic field.

[0047] S5: Place the cylindrical green sample in a programmable furnace for sintering, heat to 1200℃ for sintering, hold for 2 hours and then cool with the furnace.

[0048] Among them, SrCO3 (99% purity), CaCO3 (98.5% purity), Al2O3 (99.9% purity), Fe2O3 (99% purity), and Cr2O3 (99% purity) were used as raw materials to synthesize SrCO3 with an atomic ratio of 99.9% using a solid-state method. 1-x-y Ca x La y Al z Cr w Fe 12-z-w O 19 Prepare 75 grams of Sr from a bulk material with (x = 0.1 - 0.4; y = 0 - 0.3; z = 1.5 - 3, w = 0 - 2, z + w < 4). 0.67 Ca 0.33 Fe9Al 2.5 Cr 0.5 O 19Weigh 7.302 g SrCO3, 2.438 g CaCO3, 9.408 g Al2O3, 53.047 g Fe2O3 and 2.805 g Cr2O3. Select hard steel balls as the ball milling medium. The ball-to-material-to-water ratio is 11:1:2. First, use a high-energy ball mill for 1 hour, then use a low-energy ball mill for 4 hours. After drying the first ball milling material at 100℃, sieve it and then place it in a programmable furnace. Heat it to 1280℃ at a gradient heating rate of 3-4℃ and sinter it. Hold it at that temperature for 2 hours and then cool it with the furnace. The pre-calcined material was coarsely crushed, and 1 wt% additives (SiO2 (99% purity), H3BO3 (99.5% purity) and CaCO3 (98.5% purity)) were added. The mixture was wet-milled for 1 hour using a high-energy ball mill, and then ball-milled for 4 hours using a low-energy ball mill. After ball milling, the mixture was dried to a certain degree. The secondary ball-milled slurry was pressed into 29 mm cylindrical green samples under an external magnetic field. The cylindrical green samples were placed in a programmable furnace for sintering, and the temperature was raised to 1200℃ at a gradient heating rate of 3-4℃. After holding at this temperature for 2 hours, the mixture was cooled with the furnace, thereby obtaining high-temperature magnetic ferrite.

[0049] Third embodiment:

[0050] Please see Figure 7 This invention provides a low-temperature, high-coercivity permanent magnet ferrite production process, comprising the following steps:

[0051] S1: Using SrCO3 (99% purity), CaCO3 (98.5% purity), Al2O3 (99.9% purity), Fe2O3 (99% purity) and Cr2O3 (99% purity) as raw materials, hard steel balls were selected as the ball milling media, and the ball-to-material-to-water ratio was 12:1:2. First, the ball mill was used for 0.5 hours in a high-energy ball mill, and then for 8 hours in a low-energy ball mill.

[0052] S2: After drying the primary ball milling material at 100℃, it is sieved and then placed in a program furnace. The temperature is raised to 1150℃ at a gradient heating rate of 3-4℃ and sintered. The temperature is held for 2 hours and then cooled with the furnace.

[0053] S3: The pre-burned material is coarsely crushed, and additives (SiO2 (purity 99%), H3BO3 (purity 99.5%) and CaCO3 (purity 98.5%) are added at a mass ratio of 3%. The mixture is then wet-milled in a high-energy ball mill for 1.5 hours, and then ball-milled in a low-energy ball mill for 3 hours.

[0054] S4: After ball milling and drying to a certain extent, the secondary ball milling slurry is pressed into a 29mm cylindrical green sample under an external magnetic field.

[0055] S5: Place the cylindrical green sample in a programmable furnace for sintering, heat to 1250℃ for sintering, hold for 1 hour and then cool with the furnace.

[0056] Among them, SrCO3 (99% purity), CaCO3 (98.5% purity), Al2O3 (99.9% purity), Fe2O3 (99% purity), and Cr2O3 (99% purity) were used as raw materials to synthesize SrCO3 with an atomic ratio of 99.9% using a solid-state method. 1-x-y Ca x La y Al z Cr w Fe 12-z-w O 19 Prepare 75 grams of Sr from a bulk material with (x = 0.1 - 0.4; y = 0 - 0.3; z = 1.5 - 3, w = 0 - 2, z + w < 4). 0.67 Ca 0.33 Fe9Al2CrO 19 Weigh 7.213 g SrCO3, 2.409 g CaCO3, 7.435 g Al2O3, 52.402 g Fe2O3 and 5.542 g Cr2O3. Select hard steel balls as the ball milling medium and the ball-to-material-to-water ratio is 10:1:2. First, use a high-energy ball mill for 0.5 h, then use a low-energy ball mill for 8 h. After drying the first ball milling material at 100℃, sieve it and then place it in a programmable furnace. Heat it to 1150℃ at a gradient heating rate of 3-4℃ and sinter it. Hold it at that temperature for 2 h and then cool it with the furnace. The pre-calcined material was coarsely crushed, and an additive with a mass ratio of 3% was added. It was then wet-milled for 1.5 hours using a high-energy ball mill, followed by ball milling for 3 hours using a low-energy ball mill. After ball milling, the material was dried to a certain degree. The slurry from the second ball milling was pressed into 29mm cylindrical green samples under an external magnetic field. The cylindrical green samples were then placed in a programmable furnace for sintering. The temperature was increased to 1250℃ at a gradient heating rate of 3-4℃. After holding at that temperature for 1 hour, the material was cooled with the furnace, thus obtaining ferrite with high and low temperature magnetic properties.

[0057] The above-disclosed embodiments are merely one or more preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art can understand that all or part of the processes for implementing the above embodiments and equivalent changes made in accordance with the claims of this application still fall within the scope of this application.

Claims

1. A low-temperature high-coercivity permanent magnet ferrite production process, wherein the raw materials for preparation include: The composition of SrCO3, CaCO3, Al2O3, Fe2O3, Cr2O3, and La2O3 is as follows: Sr 1-x- y Ca x La y Al z Cr w Fe 12-z-w O 19 Where: x = 0.1-0.4; y = 0-0.3; z = 1.5-3; w = 0-2; z+w < 4; the additives are: SiO2, H3BO3 and CaCO3, the total mass of the additives SiO2, H3BO3 and CaCO3 accounts for 1-3% of the raw materials, characterized by including the following steps: Using SrCO3, CaCO3, Al2O3, Fe2O3, Cr2O3 and La2O3 as raw materials, the materials were first ball-milled using a high-energy ball mill, and then ball-milled using a low-energy ball mill. Hard steel balls were selected as the grinding media, and the ball-to-material-to-water ratio was 10-12:1:

2. After drying the ball milling material, it is sieved and then placed in a programmable furnace. The temperature is raised to 1150-1280℃ and sintered. The temperature is held for 2 hours and then cooled with the furnace. The pre-burned material is coarsely crushed, and additives SiO2, H3BO3 and CaCO3 are added. The total mass of additives SiO2, H3BO3 and CaCO3 accounts for 1-3% of the raw material. The material is then wet-milled using a high-energy ball mill, and then ball-milled using a low-energy ball mill. After ball milling and drying to a certain extent, the secondary ball milling slurry is pressed into a 29mm cylindrical green sample under an external magnetic field; Cylindrical green samples are placed in a programmed furnace for sintering, heated to 1150-1250℃, held for 1-2 hours, and then cooled with the furnace.

2. The low-temperature high-coercivity permanent magnet ferrite production process as described in claim 1, characterized in that, In the process of using SrCO3, CaCO3, Al2O3, Fe2O3, Cr2O3, and La2O3 as raw materials, first ball milling is performed using a high-energy ball mill, and then ball milling is performed using a low-energy ball mill. Hard steel balls are selected as the grinding media, and the ball-to-material-to-water ratio is 10-12:1:2: High-energy ball milling for 0.5-2 hours, low-energy ball milling for 2-8 hours, raw material purity is 99% for SrCO3, 98.5% for CaCO3, 99.9% for Al2O3, 99% for Fe2O3, 99% for Cr2O3, and 99.9% for La2O3.

3. The low-temperature high-coercivity permanent magnet ferrite production process as described in claim 2, characterized in that, After drying the primary ball milling material, it is sieved, then placed in a programmed furnace, heated to 1150-1280℃, sintered, held at that temperature for 2 hours, and then cooled with the furnace. The temperature is increased at a gradient rate of 3~4℃.

4. The low-temperature high-coercivity permanent magnet ferrite production process as described in claim 3, characterized in that, In the process of coarsely crushing the pre-calcined material, with the total mass of additives SiO2, H3BO3, and CaCO3 accounting for 1-3% of the raw material, wet milling using a high-energy ball mill, and then ball milling using a low-energy ball mill: High-energy ball mill wet milling for 0.5-2 hours, low-energy ball milling for 2-8 hours, additive purity is 99% for SiO2, 99.5% for H3BO3 and 98.5% for CaCO3.

5. The low-temperature high-coercivity permanent magnet ferrite production process as described in claim 4, characterized in that, In the step of placing the cylindrical green sample in a programmed furnace for sintering, heating to 1150-1250℃ for sintering, holding at that temperature for 1-2 hours, and then cooling it with the furnace: The temperature is increased at a gradient rate of 3~4℃.

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