JP2012151259A - Magnetic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the characteristics of a magnetic material without using a rare earth element which is a rare resource.SOLUTION: On the surface of particles of a magnetic powder, a film of a fluorine compound containing hydrogen, nitrogen, fluorine, and a metal element, where hydrogen is contained more than nitrogen and fluorine is contained more than the metal element, is formed. A magnetic material in which the magnetic characteristics of the magnetic powder are improved without using a rare earth element can be obtained by making an element contained in the film intrude between the lattices of a crystal composing the particles of the magnetic powder.

Description

  The present invention relates to a magnetic material whose magnetic properties are improved by a film not using a rare earth element, and a method for producing the same.

Patent Documents 1 to 3 disclose conventional rare earth magnets containing a fluorine compound or an oxyfluorine compound. Moreover, the Brazil patent of patent document 4 describes an example in which Sm ₂ Fe ₁₇ is fluorinated.

JP 2010-027852 A JP 2008-147634 A JP 2007-116088 A Brazilian patent 9701631-4A

In the above conventional invention, an Nd—Fe—B magnetic material or Sm—Fe magnetic material is reacted with a fluorine-containing compound, thereby improving or preventing the magnetic properties from being lowered. . However, among the disclosed fluorine compounds, those that have improved magnetic properties use rare earth elements including Sc and Y, and the principle of manifesting the effect is that these elements enter the magnetic material. Yes. Therefore, fluorine does not enter the magnetic material, but is only used as a simple element of rare earth elements. On the other hand, rare earth elements are valuable resources with a low abundance ratio in the crust, and their supply is unstable due to local uneven distribution. Therefore, reduction of their use is required. On the other hand, as disclosed in Patent Document 4, it is also disclosed to improve the characteristics of the Sm ₂ Fe ₁₇ based magnetic material using fluorine gas without using rare earth elements, but its Curie temperature is as low as 155 ° C. It has not been confirmed whether fluorine has entered the main phase. Further, since the reactivity of fluorine gas is extremely high, it is necessary to proceed the reaction while keeping its concentration extremely low, and therefore the reaction time described ranges from several days to several tens of days. However, even with the progress of the reaction, partial decomposition of the Sm ₂ Fe ₁₇ structure is inevitable, and a practical magnetic material cannot be obtained even if fluorine penetrates into the main phase.

  In order to improve the properties of magnetic materials by using fluorine instead of rare earth elements, it is necessary to allow fluorine atoms to enter between the lattices without destroying the crystal structure of the magnetic material. However, a fluorinating agent such as fluorine gas is not practical because it is too reactive.

  Therefore, an object of the present invention is to allow fluorine atoms to enter between lattices without destroying the crystal structure of the magnetic material, and to improve the magnetic properties of the magnetic material without using rare earth elements.

  The magnetic material of the present invention that solves the above problems is a magnetic material that has both a function of protecting from direct contact with a fluorinating agent that has high reactivity and causes decomposition of the magnetic material and a function of allowing permeation of fluorine atoms. It is formed on the particle surface, and fluorine atoms enter between crystal lattices without causing destruction of the crystal structure, thereby improving the magnetic properties.

  A film having such properties contains hydrogen, nitrogen, fluorine, and metal elements as constituent elements, and the film contains more hydrogen than nitrogen and more fluorine than metal elements. It is. By satisfying this condition, the membrane becomes dense enough to block the fluorinating agent, and at the same time, the crystal has sufficient fluorine permeability. A magnetic material with improved magnetic properties can be obtained without using rare earth elements by applying a fluorinating agent to the magnetic material on which such a film is formed.

  According to the present invention, it is possible to obtain a magnetic material in which the Curie temperature, which is one of the magnetic characteristics, is increased by 50 ° C. or more from the time before the penetration by allowing fluorine atoms to enter between crystal lattices without using rare earth elements. In addition, the magnetic material is less decomposed than the conventional method, and the magnetic characteristics can be improved in a shorter time.

The figure which shows the typical structure | tissue of the ferromagnetic particle which has the fluorine compound film | membrane which concerns on this invention. The figure which shows the XRD pattern of the ferromagnetic particle which has the fluorine compound film | membrane which concerns on this invention. The figure which shows the Curie temperature measurement result of the ferromagnetic particle which has the fluorine compound film | membrane which concerns on this invention.

  The iron-based ferromagnetic particles according to the present invention have a fluorine compound coating formed on the surface thereof, and the fluorine compound has at least hydrogen, nitrogen, fluorine, and metal elements constituting the iron-based ferromagnetic particles as constituent elements. The compound which contains one or more kinds and forms a fluorine compound has a feature that the number of atoms contained in the compound is more hydrogen than nitrogen and more fluorine than the metal element. A fluorine compound film with such characteristics prevents the iron-based ferromagnetic material from decomposing and changing to another crystal structure to lose its magnetic properties, and at the same time exhibits the property of allowing fluorine atoms to move through the film. . As a result, one or more of the elements constituting the fluorine compound enter between the lattices of the crystals constituting the iron-based ferromagnetic particles, and the lattice volume of the crystals is increased. As a result of adjusting the interatomic distance, it is possible to increase the magnetic characteristics, that is, the Curie temperature.

  The fluorine compound film can be formed by allowing a suitable fluorinating agent to act on the iron-based ferromagnetic material in a solution. For example, ammonium fluoride can be used as the fluorinating agent. On the other hand, fluorinating agents that are too reactive, such as fluorine gas, are not applicable as they are because they destroy the crystal structure of the iron-based ferromagnetic particles and lose their magnetic properties. After formation, the fluorine derived from the fluorinating agent can be reduced while preventing the reaction due to direct contact between the iron-based ferromagnetic material that causes the loss of magnetic properties and the fluorinating agent that is too reactive. By diffusing into the iron-based ferromagnetic material through the compound film, it can be used to improve its magnetic properties.

  Examples will be described below.

  In the present embodiment, the magnetic powder is fluorinated using a nonpolar solvent having a dielectric constant of 10 or less, and the surface contains hydrogen, nitrogen, fluorine, and a metal element, and is included in the compound forming the fluorine compound. A procedure for obtaining a magnetic material having a film characterized in that the number of atoms is more hydrogen than nitrogen and more fluorine than metal elements will be described.

First, 100 g of Sm ₂ Fe ₁₇ magnetic powder having a particle size of 0.1 to 50 μm and a fluorinating agent are added to 500 ml of squalane (main component 2,6,10,15,19,23-hexamethyltetracosane) which is a high-boiling saturated hydrocarbon. 25 g of ammonium fluoride powder was added, and the mixture was heated to 100 to 300 ° C. with an oil bath and stirred for 1 to 10 hours while stirring in a container at 20 rpm, and fluorination treatment was performed. After completion of the reaction, the flask was allowed to cool and the supernatant was poured out. The remaining powder was recovered, washed with an organic solvent, and then vacuum dried to obtain a magnetic material powder.

When this powder was observed with a scanning electron microscope, as shown in FIG. 1A, a 0.1-5 μm dense film and a porous film of 1 μm or more on the outer surface were observed on the particle surface of the magnetic powder. When these were subjected to composition analysis by secondary ion mass spectrometry, from the dense film on the particle surface, the metal elements Fe and Sm, which are magnetic powder components, and ammonium fluoride, which is a fluorinating agent, are constituent components. H, N, and F were detected, and each concentration had more H than N and more fluorine than metal elements. Further, the elements H, N, and F detected in the dense film were also detected inside the magnetic powder particles although the concentration was low. The powder X-ray diffraction as shown in the reaction after the A in FIG. 2, the position of the X-ray diffraction peak due to Sm ₂ Fe ₁₇ is shifted to a lower angle side than before the reaction by the fluorination treatment, Sm ₂ Fe ₁₇ magnetic powder In some of the crystals, the lattice volume is 0.794 to 0.904 nm ³ after the reaction with respect to 793 nm ³ before the reaction, and is increased by 0.1 to 13%. It can be seen that any or all of the elements penetrate the interstices of the crystals composing the Sm ₂ Fe ₁₇ magnetic powder to increase the distance between Sm and Fe. Then, due to the expansion of the lattice, Fe atoms that are too close to each other before the expansion are separated from each other, so that the magnetic properties of the magnetic powder, that is, the Curie temperature and the magnetization increase. The lattice volume expansion coefficient and the Curie temperature obtained under each reaction condition are as shown in Table 1. Further, the improvement of the magnetic property due to the penetration of the F element is possible even when F ₂ gas is used, but the crystal structure of Sm ₂ Fe ₁₇ is prevented from being destroyed by the high reactivity of F ₂ gas. Therefore, it is necessary to control the gas concentration to be low, and a long time is required for the reaction. On the other hand, the film obtained in this example contains a compound containing Fe or Sm and fluorine, for example, NH ₄ FeF ₃ , (NH ₄ ) ₃ FeF ₆ , NH ₄ Fe ₂ F ₆ , NH ₄ SmF _{4 and the} like as the crystal phase, These have large gaps in the crystal and easily diffuse fluorine, but are less reactive than F ₂ gas because they are a compound of metal and fluorine. Therefore, even when a high concentration fluorinating agent is used, Sm ₂ Fe ₁₇ It is possible to proceed the fluorination reaction.

On the other hand, in the porous film on the outer side of the dense film on the surface of the magnetic powder, more oxygen was detected than in other parts by secondary ion mass spectrometry, and Fe, F, etc. were detected in addition. This porous film is thought to be generated by oxygen present in the reaction environment. Most of the fluorinating agents are usually hygroscopic, and the contained water becomes an oxygen supply source and oxidizes Sm ₂ Fe ₁₇ from the surface. On the other hand, it is particularly difficult to remove water from the fluorinating agent, and even if it can be done, it cannot be handled in the atmosphere containing moisture and has poor operability, so that oxygen can be removed during the progress of the fluorination reaction. desirable. The formation of an oxide film has the effect of reducing the amount of oxygen in the reaction environment, and since the movement path of the fluorinating agent is secured by making the film porous, the fluorination reaction can be performed even after the oxidation reaction. It is possible to proceed. Furthermore, when magnetic powder is hardened with a binder to form a bonded magnet, the binder is inserted between the holes so that the magnetic powder is firmly bonded by the anchor effect and can be used to obtain a magnet with high mechanical strength. .

  In this example, the magnetic powder using a polar solvent is fluorinated, and the surface contains hydrogen, nitrogen, fluorine, and a metal element, and the number of atoms contained in the compound forming the fluorine compound is more hydrogen than nitrogen. A procedure for obtaining a magnetic material having a film characterized in that it has a large amount of fluorine and more metal elements than fluorine is described.

First, 450 ml of squalane (main component 2,6,10,15,19,23-hexamethyltetracosane), which is a high-boiling saturated hydrocarbon, and 50 ml of 2- (2-butoxyethoxy) ethanol, which is a polar solvent, are mixed. A homogeneous solution was obtained. To this was added 100 g of Sm ₂ Fe ₁₇ magnetic powder having a particle size of 0.1 to 50 μm and 25 g of ammonium fluoride powder as a fluorinating agent, and the mixture was stirred at 20 rpm in a flask in an oil bath for 0.5 to 2 hours. The temperature was raised to 100 to 230 ° C. and held for 1 to 10 hours to perform fluorination treatment. The polar solvent has an action of dissolving ammonium fluoride, which is a fluorinating agent, in the solvent, and the dissolved fluorinating agent reaches the magnetic powder more efficiently than the solid state, so that the reaction easily proceeds. In addition, a tube for cooling the solvent vapor is attached to the flask, and 2- (2-butoxyethoxy) ethanol having a boiling point of about 230 ° C. is condensed and becomes a liquid even if part of it evaporates. It does not need to be replenished because it falls and returns to the mixed solution.

  After the heating of the flask, the oil bath was lowered, allowed to cool to room temperature, and the supernatant of the solution was poured out, and then the remaining powder was recovered, washed with an organic solvent and vacuum dried.

  The scanning electron microscope image of the obtained powder is FIG. 1B, and the thickness of the dense film increased while the thickness of the porous film decreased compared to Example 1 in which no polar solvent was used.

When composition analysis was performed by secondary ion mass spectrometry, the dense film had a higher concentration of F than the metal element and a smaller amount of hydrogen than nitrogen. Further, F, H, and N elements were also detected inside the magnetic powder particles. The powder X-ray diffraction is B after the reaction in FIG. 2, and the proportion of the Sm ₂ Fe ₁₇ phase that has undergone lattice expansion is increased as compared with Example 1 (after reaction A), that is, the element has entered the lattice. Indicates that the proportion of the portion is increasing. These are considered to be derived from the improved reactivity of the fluorinating agent by the addition of a polar solvent.

On the other hand, when the Curie temperature was measured with a vibrating sample magnetometer, it was about 240 ° C. (T _c2 ) as shown in FIG. 3, which was significantly higher than about 120 ° C. (T _c1 ) before the reaction. It was confirmed. Here, the lattice volume after the reaction of the Sm ₂ Fe ₁₇ phase is increased by 4% or more than before the reaction.

  In addition to cellosolve solvents such as 2-n-butoxyethanol, polar solvents applicable to this method include alcohol solvents, amine solvents, glycol solvents, ketone solvents, aldehyde solvents, carboxylic solvents. An acid solvent or the like can be used.

Sm ₂ Fe ₁₇ N powder is held in N ₂ and NH ₃ gas atmosphere at 400 to 500 ° C. for 5 to 24 hours, and nitrogen is intruded between the lattices of Sm ₂ Fe ₁₇ to produce Sm ₂ Fe ₁₇ N _{0.1 to 3.5} powder. Got. 100 g of this powder and 50 g of ammonium fluoride as a fluorinating agent are placed in 500 ml of 2- (2-butoxyethoxy) ethanol as a polar solvent, and the temperature is about 230 ° C. while stirring at 20 rpm with a stirring blade in the flask. For 1 to 24 hours. The flask is equipped with a cooling tube, which causes the evaporated solvent to reflux, so that the internal temperature is automatically kept near the boiling point of the solvent. This temperature is about 230 ° C. for 2- (2-butoxyethoxy) ethanol.

Sm ₂ Fe ₁₇ after reacting with nitrogen has improved its chemical durability due to element intrusion into the interstitial space, and is less oxidized than unreacted Sm ₂ Fe _17. The reactivity with the agent is reduced. On the other hand, unlike Example 2, by not using squalane as a solvent and using only a polar solvent, dissolution of the fluorinating agent can be promoted and the reactivity can be improved. However, since the performance of the solvent to protect the magnetic powder from oxidation is reduced by not using squalane, which is difficult to dissolve oxygen and water, it is not possible to use Sm ₂ Fe _{17 in} which no element penetrates between the lattices. It is not desirable because much oxidation occurs.

After completion of the reaction, the supernatant liquid was poured out, and the residue was washed with an organic solvent and vacuum dried to obtain a magnetic material powder. When the cross section of this powder was observed with a scanning electron microscope, a dense film was observed on the surface of the magnetic powder particles of 0.1 to 2 μm, and the composition was analyzed by wavelength dispersion X-ray analysis. The concentration of the metal element was 4 to 20 atomic%, and the concentration of F was 20 to 60 atomic%. In addition, the F concentration in the particles was 0.1 to 16 atomic%, and the concentration became lower as the particle central part was approached. As a result, a film containing F and Fe is formed on the surface of Sm ₂ Fe ₁₇ N _{0.1 to 3.5} by heat treatment in the solution, and F moves inside the film to replace F inside the particle. It is shown that it was done. Further, in powder X-ray diffraction, a crystal phase such as a compound containing Fe or Sm and fluorine, for example, NH ₄ FeF ₃ , (NH ₄ ) ₃ FeF ₆ , NH ₄ Fe ₂ F ₆ , NH ₄ SmF ₄ was detected. Among these NH ₄ -containing compounds, NH ₄ has a structure filled between Fe or Sm and F crystal lattices, and is relatively easy to move. Since N is relatively easily taken into the film, the substituted N becomes N ₂ gas and does not peel off at the particle interface with these films. As a result, the film does not remove particles such as oxygen or high-concentration F. It enables mass transfer necessary for substitution of elements between lattices while protecting against decomposition factors. As a result, the lattice volume increased by 0.5 to 12% due to the penetration of N and F between the crystal lattices of Sm ₂ Fe ₁₇ . Along with this, the magnetic properties of the magnetic powder were improved, and the Curie temperature showed a value of about 280 to 550 ° C. Here, the Curie temperature has increased by 160 ° C. or more from before the reaction. In addition to cellosolve solvents such as 2- (2-butoxyethoxy) ethanol, polar solvents applicable to this method include alcohol solvents, amine solvents, glycol solvents, ketone solvents, aldehyde solvents. Although a solvent, a carboxylic acid solvent, etc. can be used, it is advantageous to use a high temperature for the progress of the reaction, and the reaction temperature is limited by the boiling point of the solvent. .

100 g of Sm ₂ Fe ₁₇ magnetic powder was placed in squalane together with 10 g of ammonium fluoride as a fluorinating agent, and the mixture was heated at 170 ° C. for 1 hour with stirring while rotating the stirring blade at 20 rpm. Next, 50 g of tin fluoride was added to the reaction solution, and the mixture was kept at 270 ° C. for 1 to 5 hours with stirring in the same manner. Tin fluoride became a liquid by heating, the liquid inside the flask was divided into two layers, the upper layer was squalane, the lower layer was a tin fluoride liquid, and Sm ₂ Fe ₁₇ was present in the tin fluoride liquid because of its high specific gravity. . By the first heating with ammonium fluoride, a film similar to that of Example 1 is formed on the surface of Sm ₂ Fe ₁₇ and stable fluorination is possible, but the amount of ammonium fluoride used is suppressed. Therefore, the fluorination inside the particles does not progress so much. Therefore, by adding tin fluoride, which is another fluorinating agent, fluorination inside the particles can be advanced. Tin fluoride has a melting point of 230 ° C. to 260 ° C. and can liquefy itself below the boiling point of the solution, and a fluorine compound liquid having a high fluorine concentration and high reactivity can be obtained. However, when it is directly applied to Sm ₂ Fe ₁₇ , the reactivity is too high, causing partial decomposition of Sm ₂ Fe ₁₇ and changing to a non-magnetic fluorine compound such as FeF ₂ or FeF ₃ , resulting in a decrease in magnetic properties. Will be invited. On the other hand, by forming a protective film that can move F with ammonium fluoride before acting on tin fluoride, the reaction can proceed while avoiding direct reaction between tin fluoride and Sm ₂ Fe ₁₇ Can do. As a result, the Sm ₂ Fe ₁₇ particles are surrounded by a tin fluoride liquid having a higher F concentration than a solution in which ammonium fluoride is dissolved through a film formed of ammonium fluoride, and this large F concentration difference The presence of a large chemical potential causes the diffusion of F into the Sm ₂ Fe ₁₇ particles using this as a driving force, and at the same time, since the film contains Fe and F, the decomposition of the Sm ₂ Fe ₁₇ structure is suppressed. The reaction in which F enters between the lattices occurs preferentially.

After completion of the reaction, the magnetic powder was moved to the squalane phase by adsorbing with a magnet from the outside of the flask at 270 ° C. when the tin fluoride was liquid, and allowed to cool to room temperature as it was. Oxygen and moisture are less likely to enter the squalane phase, and the magnetic powder after the reaction can be protected from the atmosphere. Since it is liquid even at room temperature, subsequent recovery is easy. If the magnetic powder is placed in the tin fluoride and cooled, the tin fluoride solidifies and becomes difficult to recover, but can be recovered by grinding and washing with hydrofluoric acid or the like. When the magnetic particles cooled and recovered in squalane are observed with a scanning electron microscope, a dense film is formed on the surface of the Sm ₂ Fe ₁₇ particles by the same reaction with ammonium fluoride as in Example 1, and on the outside thereof. There was a film composed of a residual component of tin fluoride, and the fluorine concentration thereof was 10 atomic% lower than that of tin fluoride before the reaction. Since this tin fluoride residual component changes into a high melting point fluorine compound by mixing and heating metal Ca powder, etc., it can be used as a raw material for a binder agent when forming a bonded magnet, and it is well applied to the surface of the magnetic powder. High mechanical properties can be expected from the close contact. Lattice volume of Sm ₂ Fe ₁₇ phase by addition F from entering into between the Sm ₂ Fe ₁₇ grid increased 9-14%, where the magnetic properties of the magnetic powder is improved, to measure the Curie temperature in a vibrating sample magnetometer A value of 330 ° C. to 470 ° C. was exhibited. Here, the Curie temperature has increased by 210 ° C. or more from before the reaction.

50 g of Sm ₂ Fe ₁₇ magnetic powder was put into squalane together with 10 g of ammonium fluoride as a fluorinating agent, and the mixture was heated at 170 ° C. for 1 hour with stirring while rotating the stirring blade at 20 rpm in a fluororesin flask. Next, after cooling to 100 ° C., 30 g of xenon fluoride powder as another fluorinating agent was added to the reaction solution, and held at 90 to 110 ° C. for 3 to 12 hours. The liquid was divided into two layers in the flask, the upper part was squalane, the lower part was liquefied xenon fluoride, and the magnetic powder was present in the lower xenon fluoride. Squalane is hygroscopic and has the effect of protecting xenon fluoride which decomposes by reaction with water and suppressing volatilization of xenon fluoride itself. During the reaction, xenon gas was released as bubbles along with the decomposition of xenon fluoride. Therefore, a flask equipped with a xenon recovery tube was used. A dense film similar to that of Example 1 was formed on the surface of the magnetic powder by the first reaction with ammonium fluoride, and the thickness thereof was 0.1 to 1 μm. As in Example 4, this dense film prevents Sm ₂ Fe ₁₇ from coming into direct contact with xenon fluoride, which is a highly reactive fluorinating agent, and suppresses the decomposition of crystals while allowing F to permeate. There is work to advance. However, the boiling point of xenon fluoride is about 114 ° C, and it is disadvantageous that the reaction temperature cannot be raised any more. However, when these are used because the fluorine concentration is higher than tin fluoride and the reactivity is high. Fluorine intrusion into the crystal lattice of Sm ₂ Fe ₁₇ proceeds without any difference. The xenon fluoride used in this example is a rare gas compound of Xe and F, is a solid at room temperature, is easy to handle, and is a strong fluorinating agent, and it is extremely reactive to remain after fluorinating the target. Therefore, it is easy to remove the residue of the fluorinating agent after the reaction. Another example of the fluorinating agent that does not leave a residue after the reaction is fluorine gas F ₂ , which has a boiling point of −188 ° C. and must be handled in a gaseous state, and at the same time has strong toxicity. Therefore, when using it, strict safety measures are required. Further, xenon fluoride includes XeF ₂ , XeF ₄ , XeF _{6 and the} like depending on the ratio of fluorine and xenon, but other than XeF ₂ is explosive and difficult to handle and is not recommended for use. Furthermore, since Kr, which is a rare gas other than xenon, also forms krypton fluoride, a compound such as KrF ₂ can be used as well, but it is less stable than xenon fluoride and the synthesis of krypton fluoride is also possible. Use is not desirable because it is difficult and uneasy to supply.

The magnetic powder after the reaction was recovered and washed, and observed with a scanning electron microscope. As a result, a dense film remained. On the other hand, no xenon fluoride remained in the surrounding area, and those that did not react and did not scatter as xenon gas could be removed by washing with an organic solvent. In the obtained magnetic powder, the lattice volume of the Sm ₂ Fe ₁₇ phase was increased by 10 to 14%. Further, when the Curie temperature was measured with a vibrating sample magnetometer, it was 300 to 420 ° C. The magnetization in a 2T magnetic field was 150 to 170 emu / g, which was 10% or more higher than that in Example 4. This increase in magnetization is due to the absence of non-magnetic residual fluorinating agent. Here, the Curie temperature has increased by 180 ° C. or more from before the reaction.

  In addition, since the sensitivity of xenon fluoride to water is high in this example, addition of a polar solvent to the reaction system causes not only the invasion of water and the reaction does not proceed, but also depending on the type, the reaction with the polar solvent itself may occur. Not recommended because of danger.

200 ml of a 1 mol% aqueous cesium hydroxide solution is gradually added dropwise to 1000 ml of 0.2 mol% hydrofluoric acid while stirring, and the mixture is spray-heated and dried to obtain a particle size of 0.5 to 2 μm. About 30 g of cesium fluoride powder was obtained. This powder was put into squalane together with 200 g of Sm ₂ Fe ₁₇ magnetic powder and 10 g of ammonium fluoride, and kept at 250 ° C. for 0.1 to 0.5 hours while stirring at 250 rpm with a stirring blade in a flask. In the initial stage of the reaction, white turbidity was observed due to the white powder of cesium fluoride flying in the liquid, but it was hardly seen after completion, and the liquid became almost transparent supernatant, leaving a gray powdery precipitate at the bottom of the container It was. The supernatant was poured out, and the residue was filtered and washed with an organic solvent and then vacuum dried. When the powder thus obtained was observed with a scanning electron microscope, a dense film of 0.1 to 2 μm was formed on the surface of the Sm ₁ Fe ₁₇ particles, and the surface of the film was covered with cesium fluoride particles. It was. That is, particles having a coating of cesium fluoride serving as a fluorinating agent on the surface of the coating having a protective property of Sm ₂ Fe ₁₇ were obtained. This was filled in a mold, pressure-molded at 10 MPa to form a temporary molded body, and then heated in an electric furnace at 350 ° C. for 3 to 8 hours in an Ar atmosphere. By this treatment, fluorine in cesium fluoride contained in the temporary molded body diffuses into Sm ₂ Fe ₁₇ through a dense film and enters between crystal lattices without damaging the crystal structure of Sm ₂ Fe ₁₇ . In addition, since there is no solution such as squalane during this heat treatment, the heating temperature can be set without being limited to the boiling point of the solution. Cesium fluoride is less hygroscopic than other fluorinating agents, and even if it has absorbed moisture, it can be easily dried by vacuum drying at 100 ° C. Is easy. The molded body after heating contracted by 5% in volume compared to before heating, and was bound by the cesium fluoride reaction product. When the cross section of this molded body was observed with an optical microscope, a film having a white to brown color tone was densely formed on the surface of Sm ₂ Fe ₁₇ particles having a metallic luster of 1 to 20 μm, in which a reaction was observed. White particles similar to the previous cesium fluoride are not seen, and it can be said that no unreacted fluorinating agent remains. On the other hand, the lattice volume of the Sm ₂ Fe ₁₇ phase was increased by 11 to 15%. Moreover, when the Curie temperature of this heated molded body was measured using a vibrating sample magnetometer, it was 330 ° C. to 440 ° C. Here, the Curie temperature has increased by 210 ° C. or more from before the reaction.

  In this embodiment, in addition to cesium fluoride, lithium fluoride, sodium fluoride, potassium fluoride, and rubidium fluoride can be used. However, these are less reactive than cesium fluoride and absorb moisture. Note that it is disadvantageous in terms of efficiency and handling because it is sometimes difficult to dry. On the other hand, since sodium fluoride and potassium fluoride are less expensive than cesium fluoride, it is effective to use them when facilities are sufficient.

50 g of Nd ₂ Fe ₁₇ magnetic powder was mixed with 10 g of ammonium fluoride and 200 ml of trimethylamine · hydrogen trifluoride, placed in a fluororesin container, and held at 70 ° C. for 3 to 12 hours with stirring at 20 rpm. Since gases such as ammonia and hydrogen are generated during the reaction, a pipe that can be used for expectations is connected to the container, and a scrubber for processing these gases is installed at the end. The amines such as trimethylamine used in this example have the property of dissolving hydrogen fluoride, and trimethylamine and hydrogen trifluoride contain about 35% of F atoms by weight, and these all exist as liquids. Therefore, as compared with the case where a solid fluorinating agent is used, F easily moves, and sufficient fluorine diffusion is possible even in a reaction at 100 ° C. or lower. After the reaction, the supernatant liquid in the contents was poured out, and the residue was washed with an organic solvent and vacuum dried to obtain a magnetic material powder. When this powder was subjected to cross-sectional observation with a scanning electron microscope, a thin dense film having a thickness of 0.1 to 0.3 μm was observed on the surface of the Nd ₂ Fe ₁₇ particles. Further, in secondary ion mass spectrometry, the composition of this film was Co 4 to 12 atoms, Nd 10 atom% or less, F 20 to 60 atom%, N 1 to 14 atom%, and hydrogen 15 to 40 atom%. As a result of analysis by powder X-ray diffraction, the lattice volume of the crystal of Nd ₂ Fe ₁₇ having a Th ₂ Zn ₁₇ structure increased by 1 to 14% from that before the reaction. The measured value of the temperature was 250 to 290 ° C. (the Curie temperature of the Nd ₂ Fe ₁₇ magnetic powder before the reaction was about 60 ° C.). Here, the Curie temperature has increased by 190 ° C. or more from before the reaction.

  Amines other than triethylamine used in this example can also be used as a solvent for hydrogen fluoride. For example, trimethylamine, triethanolamine, NN, -diisopropylethylamine, piperidine, 4-dimethylaminopyridine and the like can be used. . In addition, the amine solution after the reaction can be used again as a reaction solution by replenishing the consumed hydrogen fluoride. In this case, moisture mixed during handling can be removed from silica gel, molecular sieves, etc. It is desirable to separate by an adsorbent or an operation such as distillation.

100 g of Y ₂ Fe ₁₇ magnetic powder having a Th ₂ Ni ₁₇ structure and 40 g of fluorinating ammonium fluoride powder are placed in 500 ml of perfluoropolyether oil having a molecular weight of 1000 to 10000, and stirred at 20 rpm with a stirring blade in a flask at 280. Hold at 4 ° C. for 4-20 hours. Perful polyether has a molecular structure in which the terminal is substituted with F, and has high chemical stability and nonflammability, so it is highly safe. The cost of the liquid itself is higher than that of squalane, but it can be reused. Is possible. Furthermore, since a large number of fluorine is contained in the structure, it is possible to dissolve a fluorinating agent such as ammonium fluoride. After completion of the reaction, the supernatant was poured out, and the residue was washed with hydrochlorocarbon and vacuum dried. The cleaning liquid is an alternative chlorofluorocarbon and has a large global warming potential, so all of it was collected, separated into the original perfluoropolyether and hydrochlorocarbon by distillation, and reused. The obtained powder has a dense film of 0.2 to 5 μm, and its composition is Fe 4 to 18 atoms, Y 10 atom% or less, F 20 to 60 atom%, N 1 to 12 atom%, hydrogen 13 to 40 atom%. there were. On the other hand, the lattice volume of the Y ₂ Fe ₁₇ phase of the magnetic powder increased by 10 to 12%. Furthermore, in the Curie temperature measurement in a vibration sample type magnetometer, it showed 220-250 degreeC, and rose significantly compared with 42-56 degreeC before a process. In the present method, it is also possible to use fluorinated oils other than perfluoropolyether, for example, fluoroalkanes and perfluoroalkanes in which part or all of the hydrogen in the alkane is substituted with fluorine. These molecules are mainly composed of carbon and fluorine, and the stability is higher than that of perfluoropolyether, but the cost is also higher, so the use of perfluoropolyether is recommended for industrial production scale. .

300 g of Sm ₂ Fe ₁₇ magnetic powder was put into 1000 ml of squalane together with 100 g of ammonium ammonium fluoride, and kept at 180 ° C. for 1 hour while stirring at 20 rpm with a stirring blade in a container. Thereafter, the mixture was allowed to cool to room temperature, the supernatant liquid was poured out, and the residue was washed with an organic solvent and dried in vacuo. The powder thus obtained was placed in a vacuum container capable of supplying gas and heating inside, and after evacuating to 10 ⁻³ Pa, HF gas was introduced as a fluorinating agent to set the internal pressure to 10 kPa. Thereafter, the internal temperature was maintained at 200 ° C., and the internal pressure was maintained for 10 hours while appropriately adjusting and adjusting the internal pressure to 10 ± 5 kPa. Thereafter, the supply of HF gas is stopped, the inside of the container is cooled to room temperature, and then the operation of introducing Ar gas to 10 kPa and exhausting to 10 ⁻³ Pa is repeated three times to remove the HF gas remaining in the container, Was opened to obtain a powder after the reaction. When HF gas is brought into contact with Sm ₂ Fe ₁₇ powder as it is at such a pressure or partial pressure, it causes destruction of the crystal lattice constituting Sm ₂ Fe _17. Since a protective film having fluorine permeability is formed, fluorine can be introduced between the crystal lattices without being decomposed. Further, since a high concentration fluorinating agent gas can be used, the reaction can be completed in a shorter time compared with the case where the reaction is performed with a low concentration gas.

In the powder after the reaction, the lattice volume of the Sm ₂ Fe ₁₇ phase was increased by 13 to 15%. When the Curie temperature was measured with a vibrating sample magnetometer, it showed 320 ° C to 350 ° C, and as a result of analysis by powder X-ray diffraction, the intensity of the peak showing the α-Fe phase generated with the decomposition of the Sm ₂ Fe ₁₇ phase was There was no significant difference between before and after the reaction. Here, the Curie temperature has increased by 200 ° C. or more from before the reaction.

A gas other than HF can be used as a fluorinating agent in the same manner as in the present embodiment. For example, F ₂ gas, boron trifluoride, nitrogen trifluoride, chlorine trifluoride, carbonyl fluoride, tetrafluoride, etc. There are silicon oxide and the like.

50 g of a fluoro complex (NH ₄ ) ₂ [CoF ₆ ] as a fluorinating agent is added to 100 g of Sm ₂ Fe ₁₇ magnetic powder and placed in 300 ml of 1-octyl-3-allylimidazolium hexafluorophosphate which is an ionic liquid, The mixture was held at 200 ° C. for 2 to 7 hours while stirring at 300 rpm with a stirring blade. Thereafter, the mixture was allowed to cool to room temperature, and the supernatant liquid was poured out. The contents were washed with an organic solvent and then vacuum dried to obtain a magnetic material powder. When the obtained powder was analyzed with a scanning electron microscope, a dense film was formed on the surface of the Sm ₂ Fe ₁₇ particles. In composition analysis using secondary ion mass spectrometry, the composition of this film is such that the total of Fe and Co is 4 to 12 atomic%, Sm is 10 atomic% or less, F is 20 to 60 atomic%, N is 1 to 14 atomic%, hydrogen is 15 to It was 40 atomic%. The elements found in these films are also detected in the Sm ₂ Fe ₁₇ particles. F is 1 atomic% or more and H is 0.1 atomic% or more near the center of the particle. It became higher as it approached. Further, with the penetration of these elements into the magnetic powder, the lattice volume of the Sm ₂ Fe ₁₇ phase increased by 13 to 15%, and the Curie temperature increased to 320 ° C. to 350 ° C. Here, the Curie temperature has increased by 200 ° C. or more from before the reaction.

A fluorinating agent other than the fluoro complex having the [CoF ₆ ] ²⁻ structure used in this example can be used, and Fe ²⁺ , Co ²⁺ , Cu ²⁺ , Pb ²⁺ , Ti can be used as central metal ions. ³⁺ , ^{V3 +} , Cr3 ⁺ , Mn3 ⁺ , Fe3 ⁺ , Co3 ⁺ , Ni3 ⁺ , Cu3 ⁺ , Ir3 ⁺ , Al3 ⁺ , Ti4 ⁺ , ^{V4 +} , Cr4 ⁺ , Mn ⁴⁺ , Ni ⁴⁺ , Ru ⁴⁺ , Rh ⁴⁺ , Ir ⁴⁺ , Pd ⁴⁺ , Pt ⁴⁺ , Os ⁴⁺ , Zr ⁴⁺ , U ⁴⁺ , Mo ⁵⁺ , W ⁵⁺ , Ru ⁵⁺ , Ir5 ⁺ , ^{Re5 +} , Os5 ⁺ , Ta5 ⁺ , Nb5 ⁺ , Cr5 ⁺ , Mo5 ⁺ , ^{W5 +} , Rh5 ⁺ , Os5 ⁺ , Ir5 ⁺ , Pt5 ⁺ , U ⁵⁺ , Np ⁵⁺ , Pu ^{5+ and the} like, and one or more F ⁻ as a ligand can be used. As the ionic liquid, pyrrolidinium salt, pyridinium salt, ammonium salt, phosphonium salt, sulfonium salt and the like can be used in addition to the imidazolium salt. However, some of them have a melting point close to room temperature and high viscosity, and some of them are relatively difficult to separate from the powder after completion of the reaction. Therefore, it is desirable to use those having a low melting point and low viscosity.

Claims (8)

In a magnetic material composed of iron-based ferromagnetic particles and a fluorine compound film present on the surface of the iron-based ferromagnetic particles,
The fluorine compound contains hydrogen, nitrogen, fluorine, a metal element,
A magnetic material characterized in that the fluorine compound contains more hydrogen than nitrogen and more fluorine than metal elements. The magnetic material according to claim 1,
A magnetic material characterized in that at least one of fluorine, hydrogen or nitrogen, which is an atomic species contained in the fluorine compound, penetrates between crystal lattices of an alloy constituting the iron-based ferromagnetic particles . The magnetic material according to claim 1 or 2,
A magnetic material in which the atomic species contained in the fluorine compound penetrates at a concentration of 0.1 to 15 atomic%. The magnetic material according to claim 3,
A magnetic material characterized in that the volume of the crystal lattice of the alloy constituting the iron-based ferromagnetic particles is expanded by 0.1 to 15% from before the penetration. The magnetic material according to claim 3,
A magnetic material characterized in that the Curie temperature of the iron-based ferromagnetic particles is increased by 50 ° C. or more than before the penetration. The magnetic material according to any one of claims 1 to 5,
The fluorine compound present on the surface of the iron-based ferromagnetic particles includes any one of the crystal phases of NH ₄ FeF ₃ , (NH ₄ ) ₃ FeF ₆ , NH ₄ Fe ₂ F ₆ , and NH ₄ SmF _4. Magnetic material. The magnetic material according to any one of claims 1 to 6,
The magnetic material, wherein the iron-based ferromagnetic particles are Sm ₂ Fe ₁₇ magnetic powder, Nd ₂ Fe ₁₇ magnetic powder, or Y ₂ Fe ₁₇ magnetic powder. The magnetic material according to any one of claims 1 to 7,
The said fluorine compound is formed by making ammonium fluoride act on an iron-type ferromagnetic material in a solution, The magnetic material characterized by the above-mentioned.

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