JP5855457B2 - Method for producing metal-based material for magnetic cooling or heat pump - Google Patents

Description

  The present invention relates to a method for producing a metallic material for magnetic cooling or heat pump, this kind of material, and its use. The material produced in the present invention is used in magnetic cooling, heat pumps and air conditioning systems.

  Such materials are basically known and are described, for example, in WO 2004/068512. The magnetic cooling technique is based on magnetocaloric effect (MCE) and replaces the known steam circulation cooling system. In a material exhibiting a magnetocaloric effect, the material is heated as a result of the randomly arranged magnetic moments being arranged by an external magnetic field. This heat is removed from the MCE material to the surrounding atmosphere by heat transfer. When the magnetic field is extinguished or lost, this magnetic moment returns to a random arrangement, resulting in the material being cooled to below ambient temperature. This effect can be used for cooling; Nature, vol. 415, January 10, 2002, pages 150 to 152. Usually, a heat transfer medium such as water is used to remove heat from the magnetocaloric material.

  A conventional material is produced by subjecting a starting element or starting alloy of the material to a solid phase reaction in a ball mill, followed by pressing, sintering, heat treatment in an inert gas atmosphere, and gradually cooling to room temperature. Has been. Such a process is described, for example, in J. Org. Appl. Phys. 99, 2006, 08Q107.

  Processing by melt spinning is also possible. This allows for a more uniform distribution of the elements, resulting in improved magnetocaloric effect; Rare Metals, vol. 25, October 2006, pages 544-549. In the method described here, the starting elements are first melted by induction overheating in an argon gas atmosphere and sprayed onto a copper roller rotating from a nozzle in the molten state. Then, it sinters at 1000 degreeC and cools to room temperature gradually.

Materials obtained with this known method often exhibit large thermal hysteresis. For example, in a Fe ₂ P-type compound substituted with germanium or silicon, a large range of thermal hysteresis of 10K or more is observed. Therefore, it cannot be said that these materials are very suitable for magnetocaloric cooling.

  An object of the present invention is to provide a method for producing a magnetic material for magnetic cooling with small thermal hysteresis. At the same time a large magnetocaloric effect (MCE) must be achieved.

According to the present invention, this object is
A method for producing a metallic material for magnetic cooling or heat pump,
a) Solid phase reaction in a ball mill of stoichiometric amounts of chemical elements and / or alloys corresponding to metal-based materials ,
b) obtaining a solid by melt spinning of the material obtained in step a) ;
c) heating the solid of step b) at a temperature in the range of 430 to 1200 ° C. for 10 seconds to 5 hours ;
d) rapid cooling of the heat-treated molded product from step c) at a cooling rate of 200 to 1300 K / s ,
Including
The metallic material is ribbon-shaped ,
The metal material is
(1) Compound of general formula (I) (A _y B _1-y ) _{2 + δ} C _w D _x E _z (I)
Where
A is Mn or Co;
B is Fe, Cr, or Ni;
C, D, and E are selected from P, B, Se, Ge, Ga, Si, Sn, N, As, and Sb, and at least two of C, D, and E are different and the concentration is not zero. At least one of C, D and E is Ge or Si;
δ is a number in the range of −0.1 to 0.1,
w, x, y, and z are numbers in the range of 0 to 1 (where w + x + z = 1);
(2) La and Fe compounds of general formula (II) or (III) or (IV)
_{La (Fe x Al 1-x} ) 13 H y or _{La (Fe x Si 1-x} ) 13 H y (II)
Where
x is a number from 0.7 to 0.95;
y is a number from 0 to 3;
_{La (Fe x Al y Co z} ) 13 or _{La (Fe x Si y Co z} ) 13 (III)
Where x is a number from 0.7 to 0.95;
y is a number from 0.05 to 1-x;
z is a number from 0.005 to 0.5;
LaMn _x Fe _2-x Ge (IV)
Where x is a number from 1.7 to 1.95; and (3) MnTP type Heusler alloy (wherein T is a transition metal and P has an electron number e / a of 7 to 8. A p-doped metal in the range of 5)
It is achieved by a method characterized in that it is selected from

  According to the present invention, it has been clarified that the thermal hysteresis can be reduced by quenching the metal-based material after sintering and / or heat treatment at a high cooling rate instead of gradually cooling to ambient temperature. This cooling rate is at least 100 K / s. This cooling rate is preferably 100 to 10000 K / s, and more preferably 200 to 1300 K / s. A particularly preferable cooling rate is 300 to 1000 K / s.

  This quenching can be achieved by any suitable cooling method, for example by cooling the solid with water or an aqueous liquid, for example with cooling water or an ice / water mixture. For example, this solid may be dropped into ice water. It is also possible to quench the solid with a supercooling gas such as liquid nitrogen. Other quenching methods are known to those skilled in the art. Most important is well controlled quenching.

  Without being bound by theory, the decrease in hysteresis may be due to a decrease in composition particle size after quenching.

  In the conventional method, since it is gradually cooled after sintering or heat treatment, the particle size is increased and the thermal hysteresis is increased.

  If the solid after sintering and / or heat treatment in the final step is quenched at the cooling rate of the present invention, the other parts of the production of the metal-based material are not so important. This method is applicable to the production of any suitable magnetic material for magnetic cooling. A typical example of a magnetic cooling material is a multimetallic mixture containing at least three metallic elements and, if appropriate, non-metallic elements. The expression “metallic material” means that the main part of these materials is made of a metal or a metal element. Usually, the proportion in the total material is at least 50% by weight, preferably at least 75% by weight, in particular at least 80% by weight. Suitable metal-based materials are described in detail below.

  In step (a) of the method of the present invention, finally, elements and / or alloys present in the metal-based material are treated in a solid phase or a liquid phase in an amount corresponding to the metal-based material.

  It is preferable to carry out the reaction of step a) by heating these elements and / or alloys in a closed container or an extruder, or by solid phase reaction in a ball mill. It is particularly preferable to perform a solid phase reaction, particularly a solid phase reaction in a ball mill. Such reactions are known in principle (see the document mentioned in the introduction). Usually, powders of individual elements or alloys of two or more elements existing in a desired metal-based material are mixed in a powder state at an appropriate mass ratio. If necessary, this mixture may be further ground to obtain a microcrystalline mixed powder. This mixed powder is preferably heated in a ball mill, whereby pulverization and mixing proceed to cause a solid phase reaction in the mixed powder.

  Alternatively, required amounts of individual elements are mixed and melted.

  When heating in an airtight container is used in combination, it is possible to fix volatile elements and control the amount. For example, when phosphorus is used, phosphorus is easily vaporized in an open system.

  This reaction is followed by sintering and / or heat treatment of the solid, which may be preceded by one or more intermediate steps. For example, the solid obtained in step a) may be pressed before sintering and / or heat treatment. As a result, the density of the material increases and a high density magnetocaloric material is present in a later step. This is particularly advantageous because the volume in which the magnetic field is present can be reduced, which can lead to significant cost savings. The press is publicly known and may or may not be performed using an auxiliary tool for pressing. Any suitable mold can be used for this press. A molded product having a desired three-dimensional structure can be obtained by pressing. This pressing may be followed by sintering and / or heat treatment in step c) followed by quenching in step d).

  Alternatively, the solid obtained in the ball mill can be sent to the melt spinning process. Melt spinning processes are known and are described, for example, in Rare Metals, Vol. 25, October 2006, pages 544 to 549, and WO 2004/068512.

In these processes, the composition obtained in step a) is melted and sprayed onto a rotating cold metal roller. This spraying is performed by pressurizing the upstream of the injection nozzle or reducing the pressure downstream of the injection nozzle. Usually a rotating copper drum or roller is used, which is further cooled if appropriate. The surface speed of this copper drum is preferably 40 m / s, in particular 20-30 m / s. On this copper drum, the liquid composition is preferably at a rate of 10 ² to 10 ⁷ K / s, more preferably at least 10 ⁴ K / s, in particular 0.5 to 2 × 10 ⁶ K / s. Cooled by.

  Similar to the reaction of step a), melt spinning can also be carried out under reduced pressure or in an inert gas atmosphere.

  In melt spinning, the subsequent sintering and heat treatment can be shortened, so that the processing speed can be increased. Specifically, the production of metal-based materials can be carried out more economically on an industrial scale. Even with spraying, a high processing speed is possible. Particularly preferred is melt spinning.

Alternatively, spray cooling can be performed in step b) and the melt of the composition from step a) can be sprayed into the spray tower. For example, the spray tower may be further cooled. In spray towers, cooling rates in the range of 10 ³ to 10 ⁵ K / s, in particular about 10 ⁴ K / s, are often achieved.

  Solid sintering and / or heat treatment is performed in step c), preferably first sintering at a temperature in the range of 800-1400 ° C. and then heat treating at a temperature in the range of 500-750 ° C. These values are especially for moldings, and lower sintering and heat treatment temperatures may be used for the powder. For example, the sintering may be performed at a temperature in the range of 500 to 800 ° C. For moldings / solids, the sintering is more preferably carried out at temperatures in the range of 1000-1300 ° C., in particular at temperatures in the range of 1100-1300 ° C. You may perform heat processing, for example at 600-700 degreeC.

  Sintering is preferably carried out for 1 to 50 hours, more preferably 2 to 20 hours, especially 5 to 15 hours. The heat treatment is preferably performed in the range of 10 to 100 hours, more preferably in the range of 10 to 60 hours, and particularly in the range of 30 to 50 hours. The actual processing time can be determined according to the practical requirements of the material.

When using the melt spinning method, sintering can often be omitted and the heat treatment can be greatly shortened, for example from 5 minutes to 5 hours, preferably from 10 minutes to 1 hour. This is a significant time advantage compared to conventional 10 hour sintering and 50 hour heat treatment.
As a result of the sintering / heat treatment, partial melting of the grain boundary occurs and the material becomes denser.

  Accordingly, the melting time and rapid cooling in step b) significantly reduce the time required for step c). Therefore, continuous production of these metallic materials is possible.

According to the invention, the following processing sequence is preferred.
a) Solid phase reaction of a chemical element and / or alloy in an amount corresponding to a metal-based material in a ball mill,
b) melt spinning of the material obtained in step a),
c) heating of the solid of step b) at a temperature in the range of 430 to 1200 ° C., preferably in the range of 800 to 1000 ° C. for 10 seconds or 1 minute to 5 hours, preferably 30 minutes to 2 hours,
d) Rapid cooling of the heat-treated molded product from step c) at a cooling rate of 200 to 1300 K / s.

  The method of the present invention can be used with any suitable metallic material.

This metal material is preferably selected from the following compounds.
(1) Compound of general formula (I) (A _y B _1-y ) _{2 + δ} C _w D _x E _z (I)
Where
A is Mn or Co;
B is Fe, Cr, or Ni;
C, D and E are different from each other in at least two of C, D and E, and the concentration is not zero, and is selected from P, B, Se, Ge, Ga, Si, Sn, N, As, and Sb. And at least one of C, D and E is Ge or Si;
δ is a number in the range of −0.1 to 0.1,
w, x, y, and z are numbers in the range of 0 to 1 (where w + x + z = 1);
(2) In formula (II) or (III) or (IV) of La and Fe-based compound _{La (Fe x Al 1-x} ) 13 H y or _{La (Fe x Si 1-x} ) 13 H y (II)
Where
x is a number from 0.7 to 0.95;
y is a number from 0 to 3, preferably 0 to 2;
_{La (Fe x Al y Co z} ) 13 or _{La (Fe x Si y Co z} ) 13 (III)
Where x is a number from 0.7 to 0.95;
y is a number from 0.05 to 1-x;
z is a number from 0.005 to 0.5;
LaMn _x Fe _2-x Ge (IV)
Where x is a number from 1.7 to 1.95; and (3) MnTP type Heusler alloy (wherein T is a transition metal and P has an electron number e / a of 7 to 8. A p-doped metal in the range of 5).

  Materials particularly suitable for the present invention are described, for example, in WO 2004/068512, Rare Metals, Vol. 25, 2006, pages 544 to 549, J.A. Appl. Phys. 99.08Q107 (2006), Nature, Vol. 415, January 10, 2002, pages 150 to 152, and Physica B 327 (2003), pages 431 to 437.

  In the compound of the above general formula (I), C, D and E are preferably the same, but may be different and are selected from at least one of P, Ge, Si, Sn and Ga.

  The metal-based material of the general formula (I) is preferably at least Mn, Fe and P and, if appropriate, Sb, Ge, Si, As, Ge and Si, Ge and As, Si and As, or Ge and It is selected from quaternary compounds containing Si and As.

  Preferably, at least 90% by weight of component A, more preferably at least 95% by weight is Mn. Preferably at least 90% by weight of B, more preferably at least 95% by weight is Fe. Preferably, at least 90% by mass of C, more preferably at least 95% by mass is P. Preferably at least 90% by weight of D is Ge, more preferably at least 95% by weight Ge. Preferably, at least 90% by weight of E is more preferably at least 95% by weight Si.

The material preferably has a general formula _{MnFe (P w Ge x Si z} ).

  x is preferably a number in the range of 0.3 to 0.7, w is 1-x or less, and z is 1-x-w.

This material preferably has a crystalline hexagonal Fe ₂ P structure. Examples of suitable structures include MnFeP _0.45-0.7 Ge _0.55-0.30 and MnFeP _0.5-0.70 (Si / Ge) _0.5-0.30 .

Another suitable compound is Mn _{1 + x} Fe _1-x P _1-y Ge _y , x is in the range of −0.3 to 0.5, and in is in the range of 0.1 to 0.6. It is. Likewise suitable are compounds of the general formula Mn _{1 + x} Fe _1-x P _1-y Ge _yz Sb _z , x is in the range of −0.3 to 0.5 and y is 0.1 to In the range of 0.6, z is smaller than y and smaller than 0.2. Compounds of formula _{Mn i + x Fe 1-x} P 1-y Ge yz Si z also suitable. x is in the range of 0.3 to 0.5, y is in the range of 0.1 to 0.66, and z is smaller than y and smaller than 0.6.

Preferred La and Fe compounds of the general formula (II) and / or (III) and / or (IV) are La (Fe _0.90 Si _0.10 ) ₁₃ , La (Fe _0.89 Si _0.11 ) ₁₃ , La (Fe _0.880 Si _{0.120 13} , La (Fe _0.877 Si _0.123 ) ₁₃ , LaFe _11.8 Si _1.2 , La (Fe _0.88 Si _0.12 ) ₁₃ H _0.5 , La (Fe _0.88 Si _0.12 ) ₁₃ H _1.0 , LaFe _11.7 Si _1.3 H _1.1 , LaFe _11.57 Si _1.43 H _1.3 , La (Fe _0.88 Si _0.12 ) H _1.5 , LaFe _11.2 Co _0.7 Si _1.1 , LaFe _11.5 Al _1.5 Co _0.1 , LaFe _11.5 Al _1.5 C _0.2 , LaFe _11.5 Al _1.5 C _0.4 , LaFe _11.5 Al _1.5 Co _0.5 , La ( Fe _0.94 Co _0.06 ) _11.83 Al _1.17 and La (Fe _0.92 Co _0.08 ) _11.83 Al _1.17 .

Suitable manganese-containing compounds are MnFeGe, MnFe _0.9 Co _0.1 Ge, MnFe _0.8 Co _0.2 Ge, MnFe _0.7 Co _0.3 Ge, MnFe _0.6 Co _0.4 Ge, MnFe _0.5 Co _0.5 Ge, MnFe _0.4 Co _0.6 Ge, MnFe _0.3 Co _0.7 Ge , MnFe _0.2 Co _0.8 Ge, MnFe _0.15 Co _0.85 Ge, MnFe _0.1 Co _0.9 Ge, MnCoGe, Mn ₅ Ge _2.5 Si _0.5 , Mn ₅ Ge ₂ Si, Mn ₅ Ge _1.5 Si _1.5 , Mn ₅ GeSi ₂ , Mn ₅ Ge ₃ , Mn ₅ Ge _2.9 Sb _0.1 , Mn ₅ Ge _2.8 Sb _0.2 , Mn ₅ Ge _2.7 Sb _0.3 , LaMn _1.9 Fe _0.1 Ge, LaMn _1.85 Fe _0.15 Ge, LaMn _1.8 Fe _0.2 Ge, (Fe _0.9 Mn _0.1 ) ₃ C, ( Fe _0.8 Mn _0.2 ) ₃ C, (Fe _0.7 Mn _0.3 ) ₃ C, Mn ₃ GaC, MnAs, (Mn, Fe) As, Mn _{1+ δ} As _0.8 Sb _0.2 , MnAs _0.75 Sb _0.25 , Mn _1.1 As _0.75 Sb _0.25 , Mn _1.5 As _0.75 Sb _0.25 .

Examples of Heusler alloys suitable for the present invention include Fe ₂ MnSi _0.5 Ge _0.5 , Ni _52.9 Mn _22.4 Ga _24.7 , Ni _50.9 Mn _24.7 Ga _24.4 , Ni _55.2 Mn _18.6 Ga _26.2 , Ni _51.6 Mn _24.7 Ga _23.8 , Ni _52.7 Mn _23.9 Ga _23.4 , CoMnSb, CoNb _0.2 Mn _0.8 Sb, CoNb _0.4 Mn _0.6 Sb, CoNb _0.6 Mn _0.4 Sb, Ni ₅₀ Mn ₃₅ Sn ₁₅ , Ni ₅₀ Mn ₃₇ Sn ₁₃ , MnFeP _0.45 As _0.55 , MnFeP _0.47 As _0.33 , Mn _1.1 Fe _0.9 P _0.47 As _0.53 , MnFeP _0.89-x Si _x Ge _0.11 , x = 0.22, x = 0.26, x = 0.30, x = 0.33.

  The present invention also relates to a magnetic material for magnetic cooling obtained by the above method.

  The present invention also relates to the above-described metal material for magnetic cooling having an average crystal size in the range of 10 to 400 nm, more preferably 20 to 200 nm, and particularly 30 to 80 nm. . This average crystal size can be determined by X-ray diffraction. If the crystal size becomes too small, the maximum magnetocaloric effect is reduced. On the other hand, if the crystal size is too large, the hysteresis of the system increases.

  As described above, the metal-based material of the present invention is preferably used for magnetic cooling. As mentioned above, the corresponding refrigerator has a metallic material in addition to a magnet, preferably a permanent magnet. Computer chips and solar generators can also be cooled. Other fields of use are heat pumps and air conditioning systems.

  The metal-based material produced by the method of the present invention may be in any solid state. It may be in the form of flakes, ribbons, wires, powders, or may be in the form of a molded product. Molded articles such as monoliths and honeycombs are manufactured by, for example, an extrusion molding method. For example, the cell density may be 400 to 1600 CPI or more. According to the invention, a thin sheet produced by a roll is preferred. Preferred non-porous moldings are those made of thin materials such as tubes, plates, meshes, grids or bars. According to the present invention, molding by metal injection molding (MIM) method is also possible.

  The present invention will be described in detail based on the following examples.

Example 1
A vacuum quartz ampoule containing the pressed MnFePGe sample was maintained at 1100 ° C. for 10 hours to sinter this powder. This sintered product was homogenized by heat treatment at 650 ° C. for 60 hours. Rather than slowly cooling to room temperature in the furnace, the samples were immediately quenched in room temperature water. The sample surface was oxidized to some extent by this rapid cooling in water. The outer oxide film was washed away with dilute acid. XRD patterns showed that all samples were crystallized with a Fe ₂ P type structure.

  The following composition was obtained:

Mn _1.1 Fe _0.9 P _0.81 Ge _0.19 , Mn _1.1 Fe _0.9 P _0.78 Ge _0.22 , Mn _1.1 Fe _0.9 P _0.75 Ge _0.25 , and Mn _1.2 Fe _0.8 P _0.81 Ge _0.19 . The observed values of thermal hysteresis of these samples are 7K, 5K, 2K, 3K in order. The annealed sample has a thermal hysteresis of more than 10K, and the thermal hysteresis is greatly reduced compared to this sample.

  Thermal hysteresis was measured with a magnetic field of 0.5 Tesla.

FIG. 1 shows the result of isothermal magnetization of Mn _1.1 Fe _0.9 B _0.78 Ge _0.22 near the Curie temperature while enhancing the magnetic field. There is a field-induced transition that increases the MCE up to a magnetic field of up to 5 Tesla.

  As with the thermal hysteresis value, the Curie temperature can be adjusted by changing the Mn / Fe ratio and the Ge concentration.

  The change in magnetic entropy calculated from DC magnetization using the Maxwell equation for the maximum magnetic field change of 0-2 Tesla is 14 J / kgK, 20 J / kgK, 12.7 J / kgK for the first three samples, respectively. It is.

  As the Mn / Fe ratio increases, the Curie temperature and thermal hysteresis decrease. As a result, this MnFePGe compound exhibits a relatively large MCE value in a low magnetic field. The thermal hysteresis of these materials is very small.

Example 2
Melt spinning of MnFeP (GeSb) WO 2004/068512 and J.M. Appl. Phys. 99, 08 Q107 (2006), high energy was injected in a ball mill and a polycrystalline MnFeP (Ge, Sb) alloy was first produced by a solid phase reaction method. This material was placed in a quartz tube with a nozzle. The test tank was evacuated to 10 ^-2 mbar and filled with high purity argon gas. The sample was melted at high frequency and sprayed from the nozzle by the differential pressure to the test tank containing the rotating copper drum. The surface speed of the copper wheel was adjustable and a cooling rate of about 10 ⁵ K / s was achieved. Next, the wound ribbon was heat-treated at 900 ° C. for 1 hour.

X-ray diffraction results show that all samples are crystallized with a hexagonal Fe ₂ P structure pattern. Unlike samples produced by methods other than melt spinning, no contaminated phase of MnO was observed.

  Melt spinning was performed at various peripheral speeds, and Curie temperature, hysteresis, and entropy values were measured. The results are summarized in Table 1 and Table 2 below. In both cases, a low hysteresis temperature was measured.

Claims (2)

A method for producing a metallic material for magnetic cooling or heat pump,
a) Solid phase reaction in a ball mill of stoichiometric amounts of chemical elements and / or alloys corresponding to metal-based materials,
b) obtaining a solid by melt spinning of the material obtained in step a);
c) heating the solid of step b) at a temperature in the range of 430 to 1200 ° C. for 10 seconds to 5 hours;
d) rapid cooling of the heat-treated molded product from step c) at a cooling rate of 200 to 1300 K / s,
Including
The metallic material is ribbon-shaped,
The metal material is
(1) Compound of general formula (I) (A _y B _1-y ) _{2 + δ} C _w D _x E _z (I)
Where
A is Mn or Co;
B is Fe, Cr, or Ni;
C, D, and E are selected from P, B, Se, Ge, Ga, Si, Sn, N, As, and Sb, and at least two of C, D, and E are different and the concentration is not zero. At least one of C, D and E is Ge or Si;
δ is a number in the range of −0.1 to 0.1,
w, x, y, and z are numbers in the range of 0 to 1 (where w + x + z = 1);
(2) In formula (II) or (III) or (IV) of La and Fe-based compound _{La (Fe x Al 1-x} ) 13 H y or _{La (Fe x Si 1-x} ) 13 H y (II)
Where
x is a number from 0.7 to 0.95;
y is a number from 0 to 3;
_{La (Fe x Al y Co z} ) 13 or _{La (Fe x Si y Co z} ) 13 (III)
Where x is a number from 0.7 to 0.95;
y is a number from 0.05 to 1-x;
z is a number from 0.005 to 0.5;
LaMn _x Fe _2-x Ge (IV)
Where x is a number from 1.7 to 1.95; and (3) a MnTP type Heusler alloy (wherein T is a transition metal and P has an electron number e / a of 7 to 8. A p-doped metal in the range of 5)
A method characterized in that it is selected from:   In the general formula (I), the metal-based material contains at least Ge, Si, As, Ge and As, Si and As, or Ge, Si, and As in addition to Mn, Fe, and P, and Sb as appropriate. 2. A process according to claim 1 selected from the original compounds.