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Composite permagnetferrite with functions of two-phase exchange coupling and keeping high coercive force

A permanent magnet ferrite and exchange coupling technology, applied in the field of composite permanent magnet ferrite, can solve the problems of sample coercivity drop, coercivity drop, etc., and achieve the effect of high coercivity and cost saving

Active Publication Date: 2015-04-22
扬州华翀电力电子科技有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the methods described in the above two patents will lead to a great drop in the coercive force of the sample
[0004] Our published and pending patent (publication number CN 104211387A) uses CoFe with relatively small coercivity 2 o 4 As the matrix, it is found that adding SrM ferrite with only 2%-10% mass ratio and high coercive force can greatly improve the CoFe 2 o 4 The coercive force can even achieve a technical effect of more than 90% improvement. The technical principle is firstly closely related to the pinning effect of SrM ferrite. Secondly, we propose SrM-CoFe 2 o 4 Although the exchange coupling effect between them may greatly reduce the coercive force of the "hard magnetic phase" SrM, it will also greatly increase the "soft magnetic phase" CoFe 2 o 4 coercive force
The patent applied for this time is based on this background. The "hard magnetic phase" SrM is used as the matrix, and the "soft magnetic phase" CoFe is mixed in a mass ratio of 3 to 2:1. 2 o 4 , greatly reducing the costly CoFe 2 o 4 However, it can ensure the realization of exchange coupling in SrM while maintaining a high coercive force, so as to improve the exchange coupling effect will lead to the contradiction that the coercive force of the "hard magnetic phase" will drop greatly

Method used

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  • Composite permagnetferrite with functions of two-phase exchange coupling and keeping high coercive force
  • Composite permagnetferrite with functions of two-phase exchange coupling and keeping high coercive force
  • Composite permagnetferrite with functions of two-phase exchange coupling and keeping high coercive force

Examples

Experimental program
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Effect test

Embodiment 1

[0029] Preparation of SrFe 12 O 19 Powder: as analytically pure nitrate Sr (NO 3 ) 2 , Fe(NO 3 ) 3 Preparation of 2 mmol of SrFe as starting material 12 O 19 Powder, the molar ratio of Fe and Sr in the raw material is 4:1, and Sr (NO 3 ) 2 2mmol, Fe(NO 3 ) 3 8mmol; according to the molar ratio of OH - / NO - 3 =3 ratio of required NaOH, that is, 84mmol NaOH is required. The nitrate raw material was dissolved in 45 ml of deionized water and the NaOH was dissolved in 30 ml of deionized water. Then, add NaOH solution dropwise to the mixed nitrate solution while stirring to make the metal ions precipitate, move the precipitation solution and the precipitate into a 100ml hydrothermal reactor for hydrothermal reaction, and control the reactor filling degree to be 80% simultaneously, and the reaction conditions are 220 ℃×5h. The powder obtained after the reaction was washed 3 times and 2 times with deionized water and absolute ethanol, respectively. To ensure the purit...

Embodiment 2

[0034] The preparation method of composite ferrite is the same as that in Example 1, and the parameters that change are: the SrFe prepared 12 O 19 and CoFe 2 O 4 The nano-powders were pressed into discs according to the mass ratio of 2:1. Figure 5 The hysteresis loop plot of the VSM test is given in (a). It can be seen from the figure that the composite ferrite powder sample does not have a stepped or necked two-phase characteristic curve, but a good single-phase permanent magnet characteristic curve, which indicates that there is a good exchange coupling effect in the sample. The coercivity of the sample is 152.5kA / m (about 1915Oe), which still maintains a high value; its saturation magnetization is 65.1emu / g, which is significantly higher than that of Example 1. The sloping recovery curve (b) also further confirms the existence of exchange coupling in the sample.

Embodiment 3

[0036] The preparation method of the composite ferrite is the same as that in Example 1, and the changed parameters are: the sintering temperature is 900°C. from Image 6 The hysteresis loop in (a) shows that the composite ferrite exhibits a single-phase permanent magnet characteristic curve, which indicates that there is a good exchange coupling effect in the sample. The coercivity of the sample is 200.7kA / m (about 2521Oe), which still maintains a high value; its saturation magnetization is 68.0emu / g, which is significantly higher than that of Example 2. The sloping recovery curve (b) also further confirms the existence of exchange coupling in the sample.

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Abstract

The invention discloses a composite permagnetferrite with functions of two-phase exchange coupling and keeping high coercive force and belongs to the technical field of preparation of magnetic ferrites. The composite ferrite is prepared by pressing SrFe12O19 ferrite nano-powder and CoFe2O4 ferrite nano-powder which are prepared by adopting a hydrothermal method alone and subjected to acid washing according to a certain mass ratio to form circular sheets, and finally calcining at the temperature of 700-900 DEG C for 2h respectively. The ferrite containing two phases displays single-phase magnetic behavior to the outside, namely the exchange coupling effect exists. As the composite ferrite adopts a CoFe2O4 ferrite with high saturation magnetization and coercive force as a 'soft magnetic phase', the composite ferrite is conductive to improving the saturation magnetization and can ensure that the composite ferrite can still keep the high coercive force which is 152.5kA / m (about 1915Oe) at least after be calcined.

Description

technical field [0001] The invention belongs to the technical field of preparation of magnetic ferrite, and in particular relates to a composite permanent magnet ferrite with dual-phase exchange coupling effect but still maintaining high coercivity. Background technique [0002] M-type SrFe in hexagonal system 12 O 19 (SrM) ferrite, due to its high cost performance, cheap raw materials and excellent chemical stability, is still widely used in electronics, home appliances, automobiles and other industries, and is one of the magnetic materials with the largest output. However, unfortunately, although China is a big country in the production of SrM permanent magnet ferrite, it is not a strong country in production. At present, the products are mainly medium and low-grade, and the production technology level is still far behind that of Europe, America and Japan. For this reason, it is urgent to seek a new preparation method of SrM permanent ferrite to improve its production le...

Claims

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Application Information

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IPC IPC(8): C04B35/26C04B35/622
Inventor 夏爱林任素贞晋传贵李婷婷李阳吴胜华刘先国
Owner 扬州华翀电力电子科技有限公司
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