CN110858508A - High-performance anisotropic nanocrystalline dual-phase magnetic powder and preparation method thereof - Google Patents
High-performance anisotropic nanocrystalline dual-phase magnetic powder and preparation method thereof Download PDFInfo
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Abstract
The invention discloses high-performance anisotropic nanocrystalline dual-phase magnetic powder and a preparation method thereof. The preparation method comprises the following steps: carrying out mild wet ball milling treatment on the coarse grain anisotropic hard magnetic powder to obtain nano fine grain anisotropic ball milling hard magnetic powder with high coercivity and high remanence, carrying out surface activation treatment on the nano fine grain anisotropic ball milling hard magnetic powder by using an acidic substance, and assembling the nano-scale soft magnetic powder on the activated ball milling hard magnetic powder by adopting a chemical deposition method to obtain the high-performance anisotropic nanocrystalline two-phase magnetic powder. The invention regulates and controls the grain size of the hard magnetic powder by a mild wet ball milling process, avoids the problems of low hard magnetic coercive force and reduced remanence caused by factors such as coarse grains, non-crystallization and the like of anisotropic common commercial hard magnetic powder, smelted and crushed hard magnetic powder and high-energy ball-milled hard magnetic powder, and is matched with hard magnetic activation to carry out nano soft magnetic assembly, thereby being convenient for obtaining the anisotropic nanocrystalline double-phase magnetic powder with high coercive force, high remanence and high magnetic energy product.
Description
Technical Field
The invention relates to a preparation method of a magnetic material, in particular to anisotropic nanocrystalline dual-phase magnetic powder with high coercivity and high magnetic energy product and a preparation method thereof, and belongs to the technical field of dual-phase composite material preparation.
Background
The nano composite permanent magnetic material has ultrahigh theoretical magnetic energy product depending on the unique magnetic coupling effect of the nano hard magnetic material and the nano soft magnetic material, and is an important way for developing a new generation of permanent magnetic material and meeting the requirements of world energy conservation and emission reduction permanent magnetic application. At present, the great difference exists between the experimental value and the theoretical value of the magnetic energy product of the nano composite magnet and the powder, and the main reason is that the orientation texturing of the hard magnetic phase of the nano crystal and the size (d is less than 20nm) and distribution control of the soft magnetic phase are difficult to realize simultaneously. The bottom-up method for depositing the nano soft magnetic phase on the surface of the anisotropic hard magnetic phase is an important preparation method in the biphase permanent magnetic material because the highly oriented texturing of the hard magnetic phase is easy to realize. Wang and Lv et al uniformly distribute soft Magnetic Particles having a size of 7-20nm on a hard Magnetic material having an oriented texture by an acid pretreatment (see F.Q.Wang, X.J.Hu, G.W.Huang, F.C.Hou, X.Y.Zhang.F.factor synthesis of Anisotropic nano structure Sm-Pr-Co/Co Magnetic composites with dense coating of fine cobalt nanoparticles journal of alloy and composites, 2015,626: 212. quadrature 216.; L.Lv, F.Q.Wang, Q.Zheng, J.Du, X.L.Dong, P.Cui, J.Ping Liu, Preparation and Magnetic Properties of additive 5/25, Co.201143. hard Magnetic Particles prepared by an acid pretreatment), while achieving a high-phase Magnetic particle size distribution of soft Magnetic Particles due to the simultaneous control of the hard Magnetic Particles and hard Magnetic Particles of single phase Magnetic Particles (see F.Q.Q.Wang., X.J.Q.J.J.J.J.J.J.J.J.J.C.Act, P.143. Magnetic powders, and single phase Magnetic Particles of hard Magnetic powders, and Magnetic Particles of hard Particles, wherein the Magnetic Particles are prepared by an acid pretreatment, its coarse grains result in a lower coercivity of the hard magnet, thus limiting further improvement of coercivity and magnetic energy product in the dual phase composite. The wet high-energy ball milling can prepare high-coercivity nanocrystalline anisotropic hard magnetic powder, but the high-energy ball milling causes the hard magnetism to be non-crystallized, so that the remanence of the anisotropic hard magnetic powder is low, and high-coercivity, high-remanence and high-magnetic-energy-product two-phase magnetic powder is difficult to obtain.
Disclosure of Invention
The invention mainly aims to provide high-performance anisotropic nanocrystalline two-phase magnetic powder and a preparation method thereof, so as to overcome the defects in the prior art.
In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:
the embodiment of the invention provides a preparation method of high-performance anisotropic nanocrystalline dual-phase magnetic powder, which comprises the following steps:
carrying out mild wet ball milling treatment on the coarse grain anisotropic hard magnetic powder to obtain nano fine grain anisotropic ball milled hard magnetic powder with high coercivity and high remanence;
and performing surface activation treatment on the nano fine-grain anisotropic ball-milled hard magnetic powder by using an acidic substance, and assembling the nano-scale soft magnetic powder on the activated ball-milled hard magnetic powder by adopting a chemical deposition method to obtain the high-performance anisotropic nano-crystalline dual-phase magnetic powder.
As one of preferable embodiments, the preparation method comprises: in a protective atmosphere, uniformly mixing coarse grain anisotropic hard magnetic powder, a ball milling medium and a ball milling solvent, and carrying out wet ball milling treatment for 5-120 min to obtain high coercivity and high remanence nano fine grain anisotropic ball milling hard magnetic powder, wherein the mass ratio of the ball milling medium to the coarse grain anisotropic hard magnetic powder is 1: 1-8: 1.
further, the mass ratio of the ball-milling solvent to the coarse-grain anisotropic hard magnetic powder is 40-150: 100
The embodiment of the invention also provides the high-performance anisotropic nanocrystalline dual-phase magnetic powder prepared by the method.
Further, the high-performance anisotropic nanocrystalline dual-phase magnetic powder comprises a hard magnetic phase and a soft magnetic phase, wherein the soft magnetic phase is tightly distributed on the surface of the hard magnetic phase to form a compact soft magnetic phase coating layer, and the grain size of the soft magnetic phase is 7-50 nm.
Further, the intrinsic coercive force of the high-performance anisotropic nanocrystalline dual-phase magnetic powder is higher than 11kOe, preferably 16-20 kOe, the remanence is higher than 9kG, preferably 9.5-10.5 kG, and the magnetic energy product is larger than 20MGOe, preferably 22-29.6 MGOe.
Compared with the prior art, the invention has the advantages that:
1) the method regulates and controls the grain size of the hard magnetic powder by a mild wet ball milling process, avoids the problems of low hard magnetic coercive force and reduced remanence caused by factors such as large grains, serious amorphousness and the like of common anisotropic commercial hard magnetic powder, smelted and crushed hard magnetic powder and high-energy ball-milled hard magnetic powder, and is matched with hard magnetic activation to carry out nano soft magnetic assembly, so that anisotropic nanocrystalline dual-phase magnetic powder with high coercive force, high remanence and high magnetic energy product can be conveniently obtained;
2) microstructure analysis shows that soft magnetic phases in the high-performance anisotropic nanocrystalline double-phase magnetic powder are closely distributed on the surface of a hard magnetic phase, the particle size of the soft magnetic phase is preferably less than 20nm, and when the coating content of the soft magnetic phase is less than 15 wt%, a hysteresis curve does not collapse to the waist, so that the residual magnetism and the magnetic energy product of the double-phase magnetic powder can be further improved by utilizing the coupling effect of the nano hard magnetic phase and the soft magnetic phase;
3) macroscopic magnetism measurement shows that the intrinsic coercive force of the high-performance anisotropic nanocrystalline dual-phase magnetic powder prepared by the invention is higher than 11kOe and can reach 20kOe, the remanence is higher than 9kG and can reach 10.5kG, the magnetic energy product is higher than 20MGOe and can reach 29.6 MGOe;
4) the preparation method of the high-performance anisotropic nanocrystalline dual-phase magnetic powder provided by the invention is simple, low in cost and easy to implement.
Drawings
FIG. 1 shows SmCo prepared in examples 1, 5 and 8 of the present invention5Demagnetization curve diagram of the oriented/Fe-Co nanocrystalline dual-phase magnetic powder and the corresponding ball-milling hard magnetic powder.
FIGS. 2a and 2b are SmCo prepared according to example 6 of the present invention5SEM images of the/Fe-Co nanocrystalline dual-phase magnetic powder under low power and high power.
Detailed Description
Aiming at the defects of the prior art, the inventor provides the technical scheme of the invention through long-term research and massive practice. The technical solution, its implementation and principles, etc. will be further explained as follows. It is to be understood, however, that within the scope of the present invention, each of the above-described features of the present invention and each of the features described in detail below (examples) may be combined with each other to form new or preferred embodiments. Not to be reiterated herein, but to the extent of space.
One aspect of the embodiments of the present invention provides a method for preparing a high-performance anisotropic nanocrystalline dual-phase magnetic powder, which includes:
carrying out mild wet ball milling treatment on the coarse grain anisotropic hard magnetic powder to obtain nano fine grain anisotropic ball milled hard magnetic powder with high coercivity and high remanence;
and performing surface activation treatment on the nano fine-grain anisotropic ball-milled hard magnetic powder by using an acidic substance, and assembling the nano-scale soft magnetic powder on the activated ball-milled hard magnetic powder by adopting a chemical deposition method to obtain the high-performance anisotropic nano-crystalline dual-phase magnetic powder.
Preferably, the coarse grain anisotropic hard magnetic powder comprises SmCo5、PrCo5And CeCo5Etc., preferably SmCo5Hard magnetic powder, but not limited thereto.
Further, the coarse grain anisotropic hard magnetic powder is a coarse grain anisotropic hard magnetic powder obtained by commercial or melt crushing, but is not limited thereto.
Further, the grain size of the nanometer fine-grain anisotropic ball-milling hard magnetic powder is 10-40 nm.
Further, the intrinsic coercive force of the nano fine-grain anisotropic ball-milling hard magnetic powder is higher than 12kOe, particularly preferably higher than 18kOe, the remanence is higher than 9kG, particularly preferably higher than 9.5kG, and the magnetic energy product is higher than 18 MGOe.
As one of preferable embodiments, the preparation method may include: in a protective atmosphere, uniformly mixing coarse grain anisotropic hard magnetic powder, a ball milling medium and a ball milling solvent, and carrying out wet ball milling treatment for 5-120 min to obtain high coercivity and high remanence nano fine grain anisotropic ball milling hard magnetic powder, wherein the mass ratio (namely the ball-to-material ratio) of the ball milling medium to the coarse grain anisotropic hard magnetic powder is 1: 1-8: 1, preferably 1: 1-3: 1.
further, the time of the wet ball milling treatment is 15-50 min.
Further, the mass ratio of the ball-milling solvent to the coarse-grain anisotropic hard magnetic powder is 40-150: 100.
further, the preparation method may specifically include: under the protection of inert gas, commercial coarse grain anisotropic hard magnetic powder, a grinding medium and a ball-milling solvent are mixed according to a ball-material ratio of 1: 1-8: 1. the mass ratio of the ball-milling solvent to the coarse-grain anisotropic hard magnetic powder is 40-150: 100, sealing in a ball milling tank, and performing ball milling for 15-50 min to prepare the high-coercivity and high-remanence nanometer fine-grain anisotropic ball-milled hard magnetic powder.
Further, the ball milling solvent includes any one or a combination of two or more of ethanol, a mixed solvent of ethanol and polyvinylpyrrolidone, a mixed solvent of ethanol and oleic acid, a mixed solvent of ethanol and oleylamine, a mixed solvent of n-alkane and oleic acid, a mixed solvent of n-alkane and oleylamine, and the like, but is not limited thereto.
As one of preferable embodiments, the preparation method may include: and uniformly dispersing the nano fine-grained anisotropic ball-milled hard magnetic powder in a solvent to form a dispersion system in a protective atmosphere, and adding the acidic substance at 20-70 ℃ to perform surface activation treatment to obtain activated ball-milled hard magnetic powder.
Further, the preparation method comprises the following steps: and uniformly dispersing the nano fine-grain anisotropic ball-milled hard magnetic powder in a solvent by adopting an ultrasonic and mechanical stirring mode.
Preferably, the surface activation treatment and the soft magnetic phase deposition are protected by high-purity inert gas, and the hard magnetic powder is dispersed by using ultrasonic and electric stirring modes.
Further, the temperature of the surface activation treatment is 20-70 ℃, and the time is 8-15 min.
Further, the acidic substance includes any one or a combination of two or more of hydrochloric acid, sulfuric acid, acetic acid, nitric acid, and the like, and is preferably hydrochloric acid, but not limited thereto.
Further, the solvent in the dispersion system includes any one or a combination of two or more of ethanol, deionized water, a mixed solvent of ethanol and polyvinylpyrrolidone, a mixed solvent of deionized water and polyvinylpyrrolidone, a mixed solvent of ethanol and oleylamine, and the like, but is not limited thereto.
As one of preferable embodiments, the preparation method may include: and uniformly dispersing the activated ball-milling hard magnetic powder in a solvent in a protective atmosphere at the temperature of 20-80 ℃, slowly adding a soft magnetic particle precursor, an alkaline agent and a reducing agent, and assembling the nano-scale soft magnetic powder on the activated ball-milling hard magnetic powder to obtain the high-performance anisotropic nanocrystalline dual-phase magnetic powder.
Further, the preparation method may specifically include: uniformly dispersing the nano fine-grain anisotropic ball-milled hard magnetic powder into a solvent, adding acid liquor to activate the ball-milled hard magnetic powder at the water bath temperature of 20-70 ℃, separating the ball-milled hard magnetic powder from the acid liquor after activation, re-dispersing the ball-milled hard magnetic powder into the solvent at the water bath temperature of 20-80 ℃, slowly adding a soft magnetic particle precursor, an alkaline agent and a reducing agent, and further assembling the nano-scale soft magnetic powder on the activated ball-milled hard magnetic powder; and finally, carrying out solid-liquid separation, solid powder cleaning and drying to obtain the anisotropic nanocrystalline dual-phase magnetic powder with high performance.
Further, the soft magnetic particle precursor includes any one or a combination of two or more of cobalt chloride hexahydrate, cobalt sulfate, ferric chloride hexahydrate, ferrous chloride tetrahydrate, ferric sulfate hexahydrate, ferrous sulfate tetrahydrate, and the like, but is not limited thereto.
Further, the alkaline agent includes any one or a combination of two or more of sodium hydroxide, sodium bicarbonate and ammonia water, but is not limited thereto.
Further, the reducing agent includes sodium borohydride, hydrazine hydrate, and the like, but is not limited thereto.
Further, the purity of the hydrazine hydrate is more than 80%.
Further, the preparation method comprises the following steps: slowly adding a soft magnetic particle precursor, an alkaline agent and a reducing agent in a protective atmosphere, and uniformly dropwise adding hydrazine hydrate serving as the reducing agent at a speed of 0.1-0.3 ml/min by preferably adopting a peristaltic pump.
Preferably, the protective atmosphere includes an inert gas such as Ar, but is not limited thereto.
Further, the mass ratio of the activated ball-milling hard magnetic powder to the soft magnetic particle precursor is 1: 1-3: 1.
further, the mass ratio of the soft magnetic particle precursor to the alkaline agent to the reducing agent is 1: (2-20): (17-200).
Further, the assembly temperature is 20-80 ℃, and preferably 50-70 ℃.
In some embodiments, the method of making further comprises: and after the assembly is finished, separating solid matters from the reaction mixture, and cleaning and drying to obtain the high-performance anisotropic nanocrystalline two-phase magnetic powder.
The method regulates and controls the grain size of the hard magnetic powder by a mild wet ball milling process, avoids the problems of low hard magnetic coercive force and reduced remanence caused by factors such as large grains, serious amorphousness and the like of common anisotropic commercial hard magnetic powder, smelted and crushed hard magnetic powder and high-energy ball-milled hard magnetic powder, and is matched with hard magnetic activation to carry out nano soft magnetic assembly, so that anisotropic nanocrystalline dual-phase magnetic powder with high coercive force, high remanence and high magnetic energy product can be conveniently obtained; meanwhile, the preparation method is simple, low in cost and easy to implement.
Another aspect of the embodiments of the present invention also provides a high-performance anisotropic nanocrystalline dual-phase magnetic powder prepared by the foregoing method.
Further, the high-performance anisotropic nanocrystalline dual-phase magnetic powder comprises a hard magnetic phase and a soft magnetic phase, wherein the soft magnetic phase is tightly distributed on the surface of the hard magnetic phase to form a compact soft magnetic phase coating, and the particle size of the soft magnetic phase is 7-50 nm, preferably 7-20 nm.
Preferably, the size of the deposited soft magnetic phase is 7-20nm and is uniformly distributed on the surface of the high-performance nanocrystalline anisotropic hard magnetic powder to form a compact soft magnetic coating layer.
Further, the soft magnetic phase includes any one or a combination of two or more of Fe, Co and Fe-Co, etc., preferably Fe-Co phase, but is not limited thereto.
Further, the intrinsic coercive force of the high-performance anisotropic nanocrystalline dual-phase magnetic powder is higher than 11kOe, preferably 16-20 kOe, the remanence is higher than 9kG and can be as high as 10.5kG, preferably 9.5-10.5 kG, the magnetic energy product is higher than 20MGOe and can be as high as 29.6MGOe, preferably 22-29.6 MGOe.
Microstructure analysis shows that the soft magnetic phase in the high-performance anisotropic nanocrystalline double-phase magnetic powder is tightly distributed on the surface of the hard magnetic phase, the particle size of the soft magnetic phase is preferably less than 20nm, and when the coating content of the soft magnetic phase is less than 15 wt%, the hysteresis curve does not collapse down, so that the residual magnetism and the magnetic energy product of the double-phase magnetic powder can be further improved by utilizing the coupling effect of the nano hard magnetic phase and the soft magnetic phase.
The present invention is described in further detail below with reference to the attached drawings and examples, which are intended to facilitate the understanding of the present invention and are not intended to limit the present invention in any way.
Example 1
(1) In a glove box of high purity Ar inert gas, 4g of commercial coarse grain SmCo5Hard magnetic powder, 2.2g of n-heptane solvent, 0.4g of oleic acid and 12g of hard alloy balls are sealed in a ball milling tank, and the ball-material ratio is 3: 1, placing the mixture on a high-energy ball mill for ball milling for 15min to obtain nanocrystalline anisotropic SmCo with the grain size of about 22nm5Hard magnetic powder.
(2) Under the protection of high-purity Ar gas, 0.12g of nanocrystalline anisotropic SmCo5Putting the magnetic powder and 60ml of absolute ethyl alcohol into a four-neck flask, and performing ultrasonic and mechanical stirring in a water bath at 60 DEG CAnd (3) uniformly dispersing the hard magnetic powder, adding 0.2-0.4mmol of dilute hydrochloric acid to activate the hard magnetic powder, and removing the acid solution after activating for 10min to obtain the activated nanocrystalline anisotropic hard magnetic powder. Then, the activated SmCo is mixed by ultrasonic and mechanical stirring5Dispersing hard magnetic powder in 60ml absolute ethyl alcohol solvent, dissolving 0.4g NaOH in 20ml absolute ethyl alcohol and dripping into SmCo with syringe5To the dispersion, 3ml of hydrazine hydrate at a concentration of 85% was added dropwise at a rate of 0.15ml/min to SmCo using a peristaltic pump5In the dispersion, 0.0286g of FeCl was simultaneously added2·4H2O in 20ml of absolute ethanol and 0.0184g of CoCl2·6H2O is dissolved in 20ml of absolute ethyl alcohol and is respectively added into SmCo dropwise by a syringe5Reacting in a dispersion liquid in a water bath at 60 ℃ for 30min, cleaning a sample for 3-4 times by using absolute ethyl alcohol and acetone after the reaction is finished, and pumping to dry in a small chamber of a glove box to obtain SmCo with the coating amount of 10 wt%5the/FeCo nanocrystalline two-phase magnetic powder.
Example 2
In this example, the raw materials are exactly the same as those in example 1, specifically as follows:
(1) substantially the same as in step (1) of example 1, the ball milling solvent was 4g of ethanol and 2g of polyvinylpyrrolidone, the ball to feed ratio was 8: 1, ball milling time is 50 min.
(2) Substantially the same as in step (2) of example 1, except that the hard magnetic activation temperature was 50 ℃ and the activation time was 12 min; when the soft magnet is assembled, the water bath temperature is 20 ℃, and the solvent is a mixed solvent of ethanol and 1g of polyvinylpyrrolidone.
Example 3
In this embodiment, basically the same as embodiment 2, specifically, the following are provided:
(1) substantially the same as in step (1) of example 2, except that the starting material for the ball mill was (Sm, Pr)1Co5Magnetic powder, ball material ratio 1:1, ball milling for 30 min;
(2) substantially the same as in step (2) of example 2, except that the hard magnetic activation temperature was 70 ℃ and the activation time was 8 min; the water bath temperature is 80 ℃ during the assembly of the soft magnet, and FeCl is adopted2·4H2O and CoCl2·6H2Addition amount of OThe solvent is a mixed solvent of ethanol and 2ml of oleic acid, and the amount of the solvent is increased to 1.5 times.
Example 4
In this example, the raw materials are exactly the same as those in example 1, specifically as follows:
(1) substantially the same as in step (1) of example 1, except that the ball-to-feed ratio was 6: 1, ball milling for 5 min;
(2) basically the same as the step (2) of the example 1, except that the hard magnetic activation solvent is deionized water, the temperature is 20 ℃, and the activation time is 15 min; the water bath temperature is 40 ℃ at the soft magnetic assembly temperature, and the assembled soft magnetic phase is Co, CoCl2·6H2The O feedstock was increased in equal amounts without the addition of FeCl2·4H2And O soft magnetic raw material.
Example 5
In this example, the raw materials are exactly the same as those in example 1, specifically as follows:
(1) exactly the same as in step (1) of example 1, except that the ball milling solvent was 1g of ethanol, 3g of polyvinylpyrrolidone and 0.6g of oleic acid, the ball to feed ratio was 1:1, ball milling time is 120 min;
(2) substantially the same as in step (2) of example 1, except that the hard magnetic activation temperature was 70 ℃ and the activation time was 8 min; when the soft magnet is assembled, the temperature is 50 ℃, and the mass ratio of the activated ball-milling hard magnetic powder to the soft magnet particle precursor is 1:1, the mass ratio of the soft magnetic particle precursor to the alkaline agent sodium bicarbonate to the reducing agent sodium borohydride in soft magnetic assembly is 1: 2: 17, the solvent is a mixed solvent of ethanol and 1g of polyvinylpyrrolidone.
Example 6
In this example, the raw materials are exactly the same as those in example 1, specifically as follows:
(1) exactly the same as in step (1) of example 1;
(2) substantially the same as in step (2) of example 1, except that the temperature at the time of soft magnetic assembly was 70 ℃, the mass ratio of the activated ball-milled hard magnetic powder to the soft magnetic particle precursor was 3: 1, the solvent is a mixed solvent of ethanol and 4ml of oleylamine.
Example 7
In this example, the raw materials are exactly the same as those in example 1, specifically as follows:
(1) exactly the same as in step (1) of example 1;
(2) substantially the same as in step (2) of example 1, except that the solvent for soft magnetic assembling was a mixed solvent of ethanol and 2ml of oleic acid.
Example 8
In this example, the raw materials are exactly the same as those in example 1, specifically as follows:
(1) exactly the same as in step (1) of example 1;
(2) substantially the same as in step (2) of example 1, except that in the soft magnetic assembly, FeCl2·4H2O and CoCl2·6H2The amount of O added was increased to 1.5 times, and the solvent was a mixed solvent of ethanol and 4ml of oleic acid.
Example 9
This embodiment is substantially the same as embodiment 5 except that: when the soft magnet is assembled, the mass ratio of the soft magnet particle precursor to the alkaline agent sodium bicarbonate to the reducing agent sodium borohydride is 1: 20: 200.
comparative example 1
In this example, the raw materials are completely the same as those in example 1, specifically as follows:
(1) the ball milling process of the step (1) of the embodiment 1 is not carried out, namely, commercial hard magnetic powder is used as a hard magnetic phase;
(2) exactly the same as in step (2) of example 1.
Comparative example 2
In this example, the raw materials are completely the same as those in example 1, specifically as follows:
(1) substantially the same as in step (1) of example 1, except that the ball milling was high energy ball milling, i.e., the ball to material ratio was 12: 1, ball milling time is 240 min;
(2) exactly the same as in step (2) of example 1.
Comparative example 3
In this example, the starting material was commercially available (Sm, Pr)1Co5The powder is specifically as follows:
(1) the ball milling process of the step (1) of the embodiment 1 is not carried out, namely, the smelted and crushed anisotropic coarse-grain magnetic powder is used as a hard magnetic phase;
(2) substantially the same as the step (2) of example 2, except that in the case of soft magnetic assembly, the soft magnetic phase of the assembly is Co, CoCl2·6H2The O feedstock was increased in equal amounts without the addition of FeCl2·4H2And O soft magnetic raw material.
The obtained nanocrystalline two-phase composite magnetic powder is mixed with epoxy resin and solidified in a magnetic field of 2.7T to prepare oriented nanocrystalline two-phase composite magnetic powder, and magnetic measurement is carried out on the oriented crystalline two-phase magnetic powder of the examples 1-9 and the comparative example by using a vibrating sample magnetometer, so that the intrinsic coercive force of the obtained two-phase magnetic powder of the examples 1-9 is higher than 11kOe, the residual magnetism is higher than 9kG, and the magnetic energy product is higher than 20MGOe, which are obviously improved compared with the coercive force, the residual magnetism and the magnetic energy product of the comparative example 1-3. The demagnetization curves of the corresponding ball-milled hard magnetic powder in examples 1, 5 and 8 and the corresponding examples after orientation are shown in fig. 1.
The microstructure of the two-phase magnetic powder of example 6 was observed by a field emission scanning electron microscope, and the observation results at low power and high power are shown in fig. 2a and 2b, which shows that the assembled soft magnetic particles are densely and uniformly distributed on the surface of the hard magnetic phase, and the size is more between 10 nm and 25 nm.
The residual magnetism, intrinsic coercive force and maximum magnetic energy product of the anisotropic nanocrystalline dual-phase magnetic powder and the ball-milled hard magnetic powder obtained in the above examples 1 to 9 after orientation are shown in table 1.
Table 1: magnetic properties of the anisotropic nanocrystalline two-phase magnetic powders obtained in examples 1 to 9 and comparative examples 1 to 3
Through the embodiments 1 to 9, it can be found that the invention regulates and controls the grain size of the hard magnetic powder through the mild wet ball milling process, avoids the problems of low hard magnetic coercive force and reduced remanence caused by the factors of coarse grains, amorphization and the like of the anisotropic common commercial hard magnetic powder, the smelted and crushed hard magnetic powder and the high-energy ball-milled hard magnetic powder, and is convenient to obtain the anisotropic nanocrystalline biphase magnetic powder with high coercive force, high remanence and high magnetic energy product by matching with the hard magnetic activation to carry out the nano soft magnetic assembly.
In addition, the inventors have also conducted experiments with other raw materials and conditions and the like listed in the present specification by referring to the manner of examples 1 to 9, and also obtained anisotropic nanocrystalline two-phase magnetic powder of high coercive force, high remanence and high magnetic energy product.
It should be understood that the above-mentioned embodiments are merely illustrative of the technical concepts and features of the present invention, and are intended to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (10)
1. A preparation method of high-performance anisotropic nanocrystalline dual-phase magnetic powder is characterized by comprising the following steps:
carrying out mild wet ball milling treatment on the coarse grain anisotropic hard magnetic powder to obtain nano fine grain anisotropic ball milled hard magnetic powder with high coercivity and high remanence;
and performing surface activation treatment on the nano fine-grain anisotropic ball-milled hard magnetic powder by using an acidic substance, and assembling the nano-scale soft magnetic powder on the activated ball-milled hard magnetic powder by adopting a chemical deposition method to obtain the high-performance anisotropic nano-crystalline dual-phase magnetic powder.
2. The method of claim 1, wherein: the coarse grain anisotropic hard magnetic powder comprises SmCo5、PrCo5And CeCo5Any one or a combination of two or more of them, preferably SmCo5Hard magnetic powder; and/or the coarse grain anisotropic hard magnetic powder is obtained by commercial or smelting and crushing; and/or the grain size of the nanometer fine-grain anisotropic ball-milling hard magnetic powder is 10-40 nm; preferably, the intrinsic coercive force of the nano fine-grain anisotropic ball-milling hard magnetic powder is higher than 12kOe, particularly preferably higher than 18kOe, and the remanenceAbove 9kG, particularly preferably above 9.5kG, and a magnetic energy product above 18 MGOe.
3. The production method according to claim 1, characterized by comprising: in a protective atmosphere, uniformly mixing coarse grain anisotropic hard magnetic powder, a ball milling medium and a ball milling solvent, and carrying out wet ball milling treatment for 5-120 min to obtain high coercivity and high remanence nano fine grain anisotropic ball milling hard magnetic powder, wherein the mass ratio of the ball milling medium to the coarse grain anisotropic hard magnetic powder is 1: 1-8: 1, preferably 1: 1-3: 1; preferably, the time of the wet ball milling treatment is 15-50 min.
4. The production method according to claim 3, characterized in that: the mass ratio of the ball-milling solvent to the coarse-grain anisotropic hard magnetic powder is 40-150: 100, respectively; and/or the ball milling solvent comprises any one or the combination of more than two of ethanol, a mixed solvent of ethanol and polyvinylpyrrolidone, a mixed solvent of ethanol and oleic acid, a mixed solvent of ethanol and oleylamine, a mixed solvent of n-alkane and oleic acid and a mixed solvent of n-alkane and oleylamine.
5. The production method according to claim 1, characterized by comprising: and uniformly dispersing the nano fine-grained anisotropic ball-milled hard magnetic powder in a solvent to form a dispersion system in a protective atmosphere, and adding the acidic substance at 20-70 ℃ to perform surface activation treatment to obtain activated ball-milled hard magnetic powder.
6. The production method according to claim 5, characterized by comprising: uniformly dispersing the nanometer fine-grain anisotropic ball-milled hard magnetic powder in a solvent by adopting an ultrasonic and mechanical stirring mode; and/or the temperature of the surface activation treatment is 20-70 ℃, and the time is 8-15 min; and/or the acidic substance comprises any one or the combination of more than two of hydrochloric acid, sulfuric acid, acetic acid and nitric acid, preferably hydrochloric acid; and/or the solvent comprises any one or the combination of more than two of ethanol, deionized water, a mixed solvent of ethanol and polyvinylpyrrolidone, a mixed solvent of deionized water and polyvinylpyrrolidone and a mixed solvent of ethanol and oleylamine.
7. The production method according to claim 5, characterized by comprising: and uniformly dispersing the activated ball-milling hard magnetic powder in a solvent in a protective atmosphere at the temperature of 20-80 ℃, slowly adding a soft magnetic particle precursor, an alkaline agent and a reducing agent, and assembling the nano-scale soft magnetic powder on the activated ball-milling hard magnetic powder to obtain the high-performance anisotropic nanocrystalline dual-phase magnetic powder.
8. The method of claim 7, wherein: the soft magnetic particle precursor comprises any one or the combination of more than two of cobalt chloride hexahydrate, cobalt sulfate, ferric chloride hexahydrate, ferrous chloride tetrahydrate, ferric sulfate hexahydrate and ferrous sulfate tetrahydrate; and/or the alkaline agent comprises any one or the combination of more than two of sodium hydroxide, sodium bicarbonate and ammonia water; and/or, the reducing agent comprises sodium borohydride and/or hydrazine hydrate; preferably, the purity of the hydrazine hydrate is more than 80%; preferably, the preparation method comprises the following steps: and uniformly dropwise adding hydrazine hydrate serving as a reducing agent at the speed of 0.1-0.3 ml/min.
9. The production method according to any one of claims 3 to 8, characterized in that: the protective atmosphere comprises an inert gas atmosphere; preferably, the inert gas comprises Ar;
and/or the mass ratio of the activated ball-milling hard magnetic powder to the soft magnetic particle precursor is 1: 1-3: 1; and/or the mass ratio of the soft magnetic particle precursor to the alkaline agent to the reducing agent is 1: (2-20): (17-200);
and/or the assembly temperature is 20-80 ℃, preferably 50-70 ℃;
and/or, the preparation method further comprises the following steps: and after the assembly is finished, separating solid matters from the reaction mixture, and cleaning and drying to obtain the high-performance anisotropic nanocrystalline two-phase magnetic powder.
10. A high performance anisotropic nanocrystalline two-phase magnetic powder produced by the method of any one of claims 1-9;
preferably, the high-performance anisotropic nanocrystalline dual-phase magnetic powder comprises a hard magnetic phase and a soft magnetic phase, wherein the soft magnetic phase is tightly distributed on the surface of the hard magnetic phase to form a compact soft magnetic phase coating, and the particle size of the soft magnetic phase is 7-50 nm, preferably 7-20 nm; particularly preferably, the soft magnetic phase comprises any one or a combination of two or more of Fe, Co and Fe-Co phases, preferably Fe-Co phases;
preferably, the intrinsic coercive force of the high-performance anisotropic nanocrystalline dual-phase magnetic powder is higher than 11kOe, particularly preferably 16-20 kOe, the remanence is higher than 9kG, particularly preferably 9.5-10.5 kG, and the magnetic energy product is larger than 20MGOe, particularly preferably 22-29.6 MGOe.
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