JP5759869B2 - Iron-based magnetic material and method for producing the same - Google Patents

Description

  The present invention relates to a fluorine-containing magnetic material having improved heat resistance.

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 2011-014600 A JP 2010-034335 A JP 2007-116088 A PI9701631-4A

  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. . The fluoride used here contains a rare earth element, and the principle of manifesting its effect is to infiltrate the rare earth element into the surface of the particles constituting the magnetic material. However, rare earth elements are rare resources, and there is a need to reduce their usage.

  On the other hand, Patent Document 4 discloses that fluorine gas is allowed to act on the Sm—Fe based magnetic material to improve its magnetic properties, but its Curie temperature is as low as 155 ° C. It has not been confirmed. In addition, since the fluorine gas used has a very high reactivity, it is necessary to proceed while keeping its concentration very low during the reaction, and therefore the reaction time ranges from several days to several tens of days. However, even when treated in this way, the structure of the Sm—Fe-based material is partially destroyed, and a practical magnetic material cannot be obtained.

  Therefore, in the present invention, fluorine atoms are allowed to enter between the crystal lattices of the Sm—Fe-based material, magnetic properties are improved without using rare earth elements, and thermal stability is further improved by controlling the crystal structure. An object is to provide a magnetic material.

Magnetic material of the present invention for solving the above problems, in the process of introducing fluorine into Sm-Fe based material, and controlling the crystal structure, the volume of the crystal lattice is 800 Å ³ or more and, a and c axes of the crystal lattice The ratio (R) of c / a = R ≦ 1.455
Thus, it is characterized in that both improvement in magnetic properties and maintenance of thermal stability are achieved. In order to obtain such a magnetic material, it is necessary to reduce impurities present in the environment as much as possible in the fluorination reaction process of the Sm—Fe-based material. In particular, moisture is easily contained in the fluorinating agent, and the magnetic properties are lowered by oxidizing the Sm—Fe-based material, and the thermal stability is lowered by causing the penetration of hydrogen into the crystal lattice. . Thus, the magnetic material having the desired properties can be obtained by once removing the impurities by once heating the fluorinating agent in a solvent that can be heated to 100 ° C. or higher and then reacting with the Sm—Fe-based material.

  According to the present invention, without using a rare earth element, the saturation magnetization, which is one of the magnetic properties, is increased by 10 emu / g or more from the time before the penetration due to the penetration of fluorine atoms between crystal lattices, and the fluorine released during decomposition at a high temperature. A magnetic material having a thermal stability with a maximum temperature of 200 ° C. or higher can be obtained.

It is a figure which shows the crystal lattice volume of the fluoride magnetic material based on this invention, and the c-axis / a-axis ratio (R) of a crystal | crystallization. It is a figure which shows the thermal stability of the fluoride magnetic material which concerns on this invention.

Fluoride magnetic material according to the present invention and is 800 Å ³ or more, the ratio of a-axis and c-axis of the crystal lattice (R) is c / a = R ≦ 1.455
Is controlled. In order to obtain such a structure by the fluorination reaction of the Sm—Fe-based material, it is necessary to suppress impurities in the environment, and as a method therefor, there is a method using a solution. By performing the reaction in the solution, it is possible to isolate it from oxygen and moisture in the atmosphere and to prevent its influence. However, the fluorinating agent used for fluorination is generally very hygroscopic and if used as it is, impurities are introduced into the reaction system. Even when vacuum drying or the like is performed, it is difficult to store the product with high purity in order to start absorbing moisture at the moment of exposure to the atmosphere. Therefore, it is necessary to purify the fluorinating agent immediately before reacting with the Sm—Fe-based material. Also about this, it can carry out by putting a fluorination agent in a high boiling point solvent, and heating to 100 degreeC or more. Therefore, by introducing the Sm—Fe-based powder into the solvent after the fluorinating agent is generated, the reaction can be advanced using a fluorinating agent with high purity.
Examples will be described below.

In the present embodiment, a method of obtaining Sm ₂ Fe ₁₇ magnetic powder having fluorine intrusion and high heat resistance by treating Sm ₂ Fe ₁₇ magnetic powder with a solution containing a fluorinating agent will be described.

First, 25 g of ammonium fluoride is added to 500 ml of squalane (main component 2,6,10,15,19,23-hexamethyltetracosane), which is a high boiling point solvent, and stirred at 20 rpm in a container at 100 to 170 ° C. At 1 to 30 minutes. Thereafter, 100 g of Sm ₂ Fe ₁₇ magnetic powder having a particle size of 0.1 to 50 μm was added and held at 140 to 270 ° C. for 1 to 10 hours to carry out a fluorination reaction of the magnetic powder. After completion of the reaction, the supernatant of the liquid was poured out, and the magnetic powder was washed with an organic solvent and vacuum dried to obtain a magnetic material powder. By preheating ammonium fluoride, which is a fluorinating agent, before adding Sm ₂ Fe ₁₇ , impurities such as moisture contained in the fluorinating agent can be removed, whereby fluorine entering the Sm ₂ Fe ₁₇ can be removed. The amount of can be increased.

When this powder was analyzed by powder X-ray diffraction, it had a Th ₂ Zn ₁₇ structure in the same manner as Sm ₂ Fe ₁₇ before the reaction. However, the crystal lattice volume in the Sm ₂ Fe ₁₇ before the reaction was 793 ³ , whereas after the reaction, it increased to 800 ³ or more due to the entry of fluorine or the like. At this time, the expansion of the crystal lattice was larger in the a-axis than in the c-axis. When the ratio of the c-axis and a-axis is represented by R as
R = c / a ≦ 1.455
The relationship was established. On the other hand, when the reaction was carried out without preheating the fluorinating agent, R was 1.455 or more. The relationship between the crystal lattice volume and R of the obtained sample is as shown in FIG. The increase in crystal lattice volume improved the magnetic properties, and the saturation magnetization increased from 124 emu / g before the reaction to 156 emu / g or more. Further, the heat resistance of the powder after the reaction was examined by temperature programmed desorption gas analysis. When the temperature was raised at 10 ° C./min in vacuum, the temperature at which the amount of fluorine (F) released by decomposition was maximized as shown in FIG. 2 was 200 ° C. or higher. On the other hand, as a comparison, in the powder that was reacted without preheating the fluorinating agent, the temperature at which the release of fluorine (F) was maximum was 200 ° C. or less.

In the present embodiment, a method of obtaining Sm ₂ Fe ₁₇ magnetic powder into which fluorine has penetrated by treating Sm ₂ Fe ₁₇ magnetic powder with a solution composed of a polar solvent and a fluorinating agent will be described.

25 g of ammonium fluoride is added to 500 ml of dienelene glycol monohexyl ether, which is a high boiling polar solvent, and the mixture is kept at 100 to 170 ° C. for 1 to 30 minutes while stirring at 20 rpm while blowing argon gas at 10 to 20 ml / min. did. Thereafter, 100 g of Sm ₂ Fe ₁₇ magnetic powder having a particle size of 0.1 to 50 μm was added and held at 140 to 230 ° C. for 1 to 10 hours to carry out a fluorination reaction of the magnetic powder. After completion of the reaction, the supernatant was poured out, washed with an organic solvent and vacuum dried to obtain a magnetic material powder. Compared to a non-polar solvent such as squalane, a polar solvent can easily dissolve a fluorinating agent and promote a fluorination reaction in the solution. In this case, moisture in the atmosphere is easily taken up, which causes oxidation of the magnetic powder. Therefore, this is prevented by blowing an inert gas. As the inert gas, helium, neon, krypton, etc. can be used in addition to argon, but nitrogen is unsuitable because it reacts with magnetic powder.

When the powder after the reaction was analyzed by X-ray diffraction, the crystal lattice increased while maintaining the Th ₂ Zn ₁₇ structure, and the crystal lattice volume became 830 ³ or more after the reaction with respect to 793 ³ before the reaction. It was. The ratio R between the c-axis and the a-axis of the crystal lattice was 1.450 or less. Further, when the release behavior of fluorine accompanying decomposition was examined by temperature-programmed desorption gas analysis, the temperature at which the maximum release amount was 220 ° C. or higher.

In the present embodiment, a method for obtaining Sm ₂ Fe ₁₇ magnetic powder into which fluorine has penetrated by treating Sm ₂ Fe ₁₇ magnetic powder with a solution obtained by adding a fluorinating agent to a mixed solution of a nonpolar solvent and a polar solvent will be described. .

To 250 ml of squalane (main component 2,6,10,15,19,23-hexamethyltetracosane) as a nonpolar solvent, 250 ml of dienelene glycol monohexyl ether as a polar solvent was added and mixed. 25 g of ammonium fluoride as a fluorinating agent was added to this mixed solution, and the mixture was held at 100 to 170 ° C. for 1 to 30 minutes while stirring at 20 rpm. Thereafter, 100 g of Sm ₂ Fe ₁₇ magnetic powder having a particle size of 0.1 to 50 μm was added and held at 140 to 230 ° C. for 1 to 10 hours to carry out a fluorination reaction of the magnetic powder. After completion of the reaction, the supernatant was poured out, washed with an organic solvent, and vacuum dried to obtain a magnetic material powder. By mixing a non-polar solvent that hardly dissolves moisture in the atmosphere and a polar solvent with high solubility of the fluorinating agent, fluorination is performed using a highly reactive solution without blowing an inert gas. The reaction can proceed.

When the powder after the reaction was analyzed by X-ray diffraction, the presence of oxide or the like was not confirmed. In addition, the crystal lattice was expanded while maintaining the Th ₂ Zn ₁₇ structure, and was 820 ³ or more after the reaction with respect to 793 ³ before the reaction. The ratio R between the c-axis and a-axis of the crystal lattice was 1.452 or less. In the temperature programmed desorption gas analysis, the temperature at which the maximum amount of released fluorine was 210 ° C. or higher.

In this example, a method of obtaining Sm ₂ Fe ₁₇ magnetic powder into which fluorine has entered by performing a fluorination reaction while pulverizing Sm ₂ Fe ₁₇ magnetic powder in a solution will be described.

25 g of ammonium fluoride as a fluorinating agent was added to 500 ml of squalane (main component 2,6,10,15,19,23-hexamethyltetracosane) and heated at 100 to 140 ° C. for 1 to 30 minutes. This solution was added to a nickel cylindrical container containing 100 g of Sm ₂ Fe ₁₇ magnetic powder and nickel spheres, the inside was replaced with argon gas, the container was sealed, and ball milling was performed by rotating the pot. After rotating for 1 to 24 hours, the mixed solution was filtered, washed with an organic solvent, and then vacuum dried to obtain a magnetic material powder.

When the obtained powder was subjected to X-ray diffraction, as well as before the reaction Sm ₂ Fe ₁₇ is Th ₂ Zn ₁₇ structure is maintained, after the reaction with respect to the crystal lattice before reaction 793Å ³ 835Å It was ³ . The ratio R between the c-axis and the a-axis of the crystal lattice was 1.451 or less. Furthermore, the temperature at which the amount of released fluorine was maximum in the temperature programmed desorption gas analysis was 205 ° C. or higher.

The fluorination reaction using the solution proceeds from the surface of the particles of Sm ₂ Fe ₁₇ , and the efficiency can be increased by performing pulverization simultaneously with the reaction. In addition, by using a preheated solution, the reaction can proceed in an environment with few impurities such as moisture, and in particular in such a sealed system, it is effective to prevent oxidation due to impurities.

In this example, a method for obtaining a magnetic material powder with a small amount of released fluorine at the time of decomposition at a high temperature by treating Sm ₂ Fe ₁₇ magnetic powder with added elements with a solution containing a fluorinating agent will be described. To do.

260 g of metal samarium, 766 g of metal iron, and 4 g of metal calcium were mixed and made into an alloy lump by arc melting. Thereafter, it was kept at 1000 to 1100 ° C. for 10 to 50 hours to obtain Sm ₂ Fe ₁₇ to which calcium was added. This was crushed with a jaw crusher and further pulverized with a ball mill and a jet mill to obtain a powder having a particle size of 5 to 100 μm. This powder was added to a solution in which squalane (main component 2,6,10,15,19,23-hexamethyltetracosane) and a fluorinating agent were mixed and heated at 100 to 140 ° C. for 1 to 30 minutes, and further 160 to The reaction was conducted by heating at 250 ° C. for 1 to 10 hours. After the reaction, the supernatant was removed, washed with an organic solvent, and vacuum dried to obtain a magnetic material powder.

The powder after the reaction had a Th ₂ Zn ₁₇ structure, and its crystal lattice expanded to 830 ^{3 with} respect to 810 ³ before the reaction. The ratio R between the c-axis and the a-axis of the crystal lattice was 1.450 or less. In the temperature-programmed desorption gas analysis, when the temperature was raised at 10 ° C./min in vacuum, the temperature at which the maximum amount of fluorine (F) was released was 250 ° C. or higher.

By adding Ca to the alloy of the raw material, stable CaF ₂ is formed at the time of decomposition at a high temperature, and it becomes a film, and further release of fluorine can be suppressed. As the additive element, magnesium, strontium, barium and the like can be used in addition to calcium, but it is desirable to use calcium from the viewpoints of price and fluoride stability.

In this example, a method for obtaining a fluoride magnetic material by forming Sm ₂ Fe ₁₇ by electrolysis in a solution and treating it with a fluorinating agent in the solution will be described.

  10 g of samarium chloride and 40 g of ferric chloride are dissolved in 500 ml of 1-hexyl-3-methylimidazolium chloride, and a platinum electrode and an iron electrode are put into this, and a direct current is applied at 4 V for 4 to 5 hours using the platinum electrode as a cathode. Washed away. Next, 25 g of ammonium fluoride is heated to 100 ° C. in 100 ml of 1-hexyl-3-methylimidazolium chloride in another container and held for 0.5 to 1 hour, and the resulting solution is a solution containing an electrode. In addition, it was made to react by heating at 140-230 degreeC for 1 to 8 hours. Thereafter, the solid adhered to the surface of the platinum electrode was scraped off, washed with an organic solvent, and vacuum-dried to obtain magnetic material particles.

When the obtained powder was subjected to X-ray diffraction, the volume of the crystal lattice of the particles after the reaction was 840 ³ , and the ratio R of c-axis to a-axis was 1.440 or less. Furthermore, in the temperature-programmed desorption gas analysis, the temperature at which the maximum amount of released fluorine was 230 ° C. or higher.

In an Ar gas atmosphere, Sm ₂ Fe ₁₇ powder having an average powder diameter of 15 μm is inserted into a Ni reaction vessel, and XeF ₂ powder is mixed at a ratio of 1% by weight to Sm ₂ Fe ₁₇ powder and heated. The heating rate was 1 ° C./mim (less than 5 ° C./mim). The heating holding temperature and holding time are 140 ° C. and 5 hours, respectively. This powder is aged in a temperature range higher than the heating and holding temperature and not higher than 500 ° C., which is the decomposition temperature, to promote fluoride growth and fluorine ordering. As a result, Sm ₂ Fe ₁₇ Fx (X = 1-3) was grown, and the average lattice constant was 1.259 nm for the c-axis and 0.876 nm for the a-axis. The Curie temperature was 420 ° C.

An SmFeF-based compound having a Curie temperature of around 200 ° C. is observed before the aging heat treatment, but the volume fraction of Sm ₂ Fe ₁₇ Fx (X = 1-3) is increased by the aging heat treatment. That is, the volume of the SmFeF-based compound having a high Curie temperature is increased by the heat treatment, and the volume ratio of the compound having a low Curie temperature is decreased. Sm ₂ Fe ₁₇ Fx (X = 1-3) begins to decompose at 600 ° C., and SmOF and Fe grow along with the decomposition, and the coercive force decreases. The fluorine concentration is about 10 atomic%. When the fluorine concentration decreases, the lattice constant decreases or the volume fraction of the Sm ₂ Fe ₁₇ F _X phase decreases.

The fluorine concentration depends on the mixing amount of the fluorinating agent (xenon fluoride), the heating rate, and the heating temperature. The reaction is accelerated when the heating temperature is 5 ° C / min or more, and the heat generation makes it easier for iron to grow, resulting in magnet characteristics. Decreases. Therefore, the heating rate is desirably less than 5 ° C./min. A coercive force of 15 kOe can be obtained by pulverizing the reacted SmFeF powder to an average diameter of 2 μm. In order to achieve a coercive force value of 5 kOe or higher that can be applied as a magnet, the fluorine concentration needs to be in the range of 0.1 to 15 atomic%. If it is less than 0.1 atomic%, the Curie temperature is low, and the magnetic anisotropy with the c-axis as the easy magnetization direction is small, so the coercive force is small. The stable acid fluoride in 15 atom% or more _{(SmOF, Sm a F b,} a, b is a positive number) of Fe in the grown bcc coercivity tends to grow decreases.

Claims (11)

In the Sm—Fe based magnetic material in which fluorine is present at the intrusion position of the crystal lattice having the Th ₂ Zn ₁₇ type structure,
The Sm—Fe based magnetic material, wherein a ratio R (= c / a) of the c-axis to the a-axis of the crystal lattice has a relationship of R ≦ 1.455. In the Sm-Fe system magnetic material according to claim 1,
The Sm—Fe based magnetic material, wherein the volume V of the crystal lattice has a relationship of V ≧ 800 (Å ³ ). In the Sm-Fe system magnetic material according to claim 1 or 2,
The Sm—Fe- based magnetic material, wherein the fluorine concentration is in the range of 0.1 to 15 atomic%. In the Sm-Fe based magnetic material according to any one of claims 1 to 3,
Sm-Fe based magnetic material, wherein the amount of released fluorine caused by the decomposition temperature of maximum is 200 ° C. or higher. In the iron-based magnetic material according to any one of claims 1 to 4,
An Sm-Fe- based magnetic material produced by subjecting Sm ₂ Fe ₁₇ magnetic powder to a fluorination reaction with a solution containing a fluorinating agent. Heating the solution containing the fluorinating agent to 100 ° C. or higher ;
A step of fluorination reaction the solution containing the heated said fluorinating agent is mixed with Sm ₂ Fe ₁₇ magnetic powder,
And a step of washing the Sm ₂ Fe ₁₇ magnetic powder with an organic solvent and vacuum drying. A method for producing an Sm—Fe- based magnetic material, comprising: In the manufacturing method of the Sm-Fe type | system | group magnetic material of Claim 6,
The solution containing a fluorinating agent contains a polar solvent, and the method for producing an Sm—Fe based magnetic material. In the manufacturing method of the Sm-Fe type | system | group magnetic material of Claim 7,
The solution containing a fluorinating agent contains a nonpolar solvent, and the method for producing an Sm—Fe based magnetic material. In the manufacturing method of the Sm-Fe type | system | group magnetic material in any one of Claims 6 thru | or 8,
In the step of the fluorination reaction, a manufacturing method of the Sm-Fe based magnetic material, characterized in that for grinding the Sm ₂ Fe ₁₇ magnetic powder during the fluorination reaction. In the manufacturing method of the Sm-Fe type | system | group magnetic material in any one of Claim 6 thru | or 9,
The method for producing an Sm—Fe based magnetic material, wherein the solution containing the fluorinating agent contains Ca. In the manufacturing method of the Sm-Fe type | system | group magnetic material in any one of Claims 6 thru | or 10,
The Sm ₂ Fe ₁₇ magnetic powder, a manufacturing method of the Sm-Fe based magnetic material characterized in that it is formed by electrolysis of solution containing samarium chloride and iron.