CA2789797A1 - Magnetocaloric materials - Google Patents
Magnetocaloric materials Download PDFInfo
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- CA2789797A1 CA2789797A1 CA2789797A CA2789797A CA2789797A1 CA 2789797 A1 CA2789797 A1 CA 2789797A1 CA 2789797 A CA2789797 A CA 2789797A CA 2789797 A CA2789797 A CA 2789797A CA 2789797 A1 CA2789797 A1 CA 2789797A1
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- magnetocaloric
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/012—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials adapted for magnetic entropy change by magnetocaloric effect, e.g. used as magnetic refrigerating material
- H01F1/015—Metals or alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/02—Making ferrous alloys by powder metallurgy
- C22C33/0207—Using a mixture of prealloyed powders or a master alloy
- C22C33/0214—Using a mixture of prealloyed powders or a master alloy comprising P or a phosphorus compound
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/02—Making ferrous alloys by powder metallurgy
- C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
- C22C33/0278—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C9/00—Alloys based on copper
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24V—COLLECTION, PRODUCTION OR USE OF HEAT NOT OTHERWISE PROVIDED FOR
- F24V99/00—Subject matter not provided for in other main groups of this subclass
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/06—Metallic powder characterised by the shape of the particles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
- B22F2009/043—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling by ball milling
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
- B22F2998/10—Processes characterised by the sequence of their steps
Abstract
What are described are magnetocaloric materials of the general formula (MnxFe1-x)2+zP1ySiy where 0.20=x =0.40 0.4=y =0.8 -0.1 =z =0.1.
Description
Magnetocaloric materials Description The invention relates to polycrystalline magnetocaloric materials, to processes for their production and to their use in coolers, heat exchangers or generators, in particular in refrigerators.
Thermomagnetic materials, also referred to as magnetocaloric materials, can be used for cooling, for example in refrigerators or air conditioning units, in heat pumps or for direct generation of power from heat without intermediate connection of a conversion to mechanical energy.
Such materials are known in principle and are described, for example, in 2. Magnetic cooling techniques are based on the magnetocaloric effect (MCE) and may constitute an alternative to the known vapor circulation cooling methods. In a material which exhibits a magnetocaloric effect, the alignment of randomly aligned magnetic moments by an external magnetic field leads to heating of the material. This heat can be removed from the MCE material to the surrounding atmosphere by a heat transfer. When the magnetic field is then switched off or removed, the magnetic moments revert back to a random arrangement, which leads to cooling of the material below ambient temperature. This effect can be exploited for cooling purposes, but also for heating. Typically, a heat transfer medium such as water is used for heat removal from the magnetocaloric material.
The materials used in thermomagnetic generators are likewise based on the magnetocaloric effect. In a material which exhibits a magnetocaloric effect, a small change in temperature can lead to a big change in magnetization. Magnetized by an external magnetic field, when the material is heated, a big change in the induction flow through a coil and thus an electromotive force are generated. Cooling the material below the critical temperature leads again to the occurrence of an electromotive force.
This effect can be exploited for conversion of heat to electrical energy.
The magnetocaloric generation of electrical energy is associated with magnetic heating and cooling. At the time of first conception, the process for energy generation was described as pyromagnetic energy generation. Compared to devices of the Peltier or Seebeck type, these magnetocaloric devices can have a significantly higher energy efficiency.
The research into this physical phenomenon began in the late 19th century, when two scientists, Tesla and Edison, filed a patent on pyromagnetic generators. In 1984, Kirol described numerous possible applications and conducted thermodynamic analyses thereof. At that time, gadolinium was considered to be a potential material for applications close to room temperature.
A pyromagnetoelectric generator is described, for example, by N. Tesla in US
428,057.
It is stated that the magnetic properties of iron or other magnetic substances can be destroyed partially or entirely or can disappear as a result of heating to a particular temperature. In the course of cooling, the magnetic properties are re-established and return to the starting state. This effect can be exploited to generate electrical power.
When an electrical conductor is exposed to a varying magnetic field, the changes in the magnetic field lead to the induction of an electrical current in the conductor. When, for example, the magnetic material is surrounded by a coil and is then heated in a permanent magnetic field and then cooled, an electrical current is induced in the coil in the course of heating and cooling in each case. This allows thermal energy to be converted to electrical energy, without an intermediate conversion to mechanical work.
In the process described by Tesla, iron, as the magnetic substance, is heated by means of an oven or a closed fireplace and then cooled again.
For the thermomagnetic or magnetocaloric applications, the material should permit efficient heat exchange in order to be able to achieve high efficiencies. Both in the course of cooling and in the course of power generation, the thermomagnetic material is used in a heat exchanger.
US 2006/0117758 and WO 2009/133049 disclose magnetocaloric materials of the general formula MnFe(PWGeXSi,). Preferred materials are MnFeP0.45-0.7oGeo.55-0.30 or MnFeP0.5-0.70(Si/Ge)0.5-0.30= In each case, the example compositions comprise proportions of Ge. These substances still do not have a sufficiently great magnetocaloric effect for all applications.
EP patent application 10 150 411.6 entitled "Magnetocaloric materials", which was filed on January 11, 2010 and was yet to be published at the priority date of the present application, describes magnetocaloric materials of the general formula (MnXFe1-x)2+ P1-,5i,, where 0.555x<1 0.4 5 y 5 0.8 -0.1 5 z 5 0.1.
It is an object of the present invention to provide magnetocaloric materials having a large magnetocaloric effect, low thermal hysteresis and a working temperature in the range from 0 to 150 C.
The object is achieved in accordance with the invention by magnetocaloric materials of the general formula (Mn.Fe1_X)2+Z P1_ySiy where 0.20 0.4 5 y 5 0.8 - 0.1 5 z 5 0.1.
Preferably, 0.25 5 x 5 0.35. x preferably has a minimum value of 0.28, more preferably of 0.3. The maximum value of x is preferably 0.34, in particular 0.33. More preferably 0.285x50.34, in particular 0.305x50.33.
y preferably has a minimum value of 0.4. The maximum value of y is preferably 0.6, more preferably 0.44. More preferably 0.4 5 y 5 0.6, in particular 0.4 5 y 5 0.44.
z may differ from 0 by small values. Preferably -0.05 5 z 5 0.05, in particular -0.02 5 z 5 0.02, especially z = 0.
The inventive magnetocaloric materials preferably have a hexagonal structure of the Fe2P type.
It has been found in accordance with the invention that especially an Mn/Fe element ratio of less than 0.54, especially in the range from 0.5/1.5 to 0.7/1.3, leads to magnetocaloric materials with stabilized phase formation and low thermal hysteresis.
The inventive materials allow a working temperature in application in the range from 0 C to + 150 C.
The magnetocaloric effect of the inventive materials is comparable to the magnetocaloric effect of what are known as giant magnetocaloric materials such as MnFePXAs1_X,Gd5(Si, Ge)4 or La(Fe, Si)13.
The thermal hysteresis, determined in a magnetic field of 1 T with a sweep rate of 1 C/min, is preferably < 5 C, more preferably < 2 C, due to the balanced Mn/Fe and P
Si ratios.
Thermomagnetic materials, also referred to as magnetocaloric materials, can be used for cooling, for example in refrigerators or air conditioning units, in heat pumps or for direct generation of power from heat without intermediate connection of a conversion to mechanical energy.
Such materials are known in principle and are described, for example, in 2. Magnetic cooling techniques are based on the magnetocaloric effect (MCE) and may constitute an alternative to the known vapor circulation cooling methods. In a material which exhibits a magnetocaloric effect, the alignment of randomly aligned magnetic moments by an external magnetic field leads to heating of the material. This heat can be removed from the MCE material to the surrounding atmosphere by a heat transfer. When the magnetic field is then switched off or removed, the magnetic moments revert back to a random arrangement, which leads to cooling of the material below ambient temperature. This effect can be exploited for cooling purposes, but also for heating. Typically, a heat transfer medium such as water is used for heat removal from the magnetocaloric material.
The materials used in thermomagnetic generators are likewise based on the magnetocaloric effect. In a material which exhibits a magnetocaloric effect, a small change in temperature can lead to a big change in magnetization. Magnetized by an external magnetic field, when the material is heated, a big change in the induction flow through a coil and thus an electromotive force are generated. Cooling the material below the critical temperature leads again to the occurrence of an electromotive force.
This effect can be exploited for conversion of heat to electrical energy.
The magnetocaloric generation of electrical energy is associated with magnetic heating and cooling. At the time of first conception, the process for energy generation was described as pyromagnetic energy generation. Compared to devices of the Peltier or Seebeck type, these magnetocaloric devices can have a significantly higher energy efficiency.
The research into this physical phenomenon began in the late 19th century, when two scientists, Tesla and Edison, filed a patent on pyromagnetic generators. In 1984, Kirol described numerous possible applications and conducted thermodynamic analyses thereof. At that time, gadolinium was considered to be a potential material for applications close to room temperature.
A pyromagnetoelectric generator is described, for example, by N. Tesla in US
428,057.
It is stated that the magnetic properties of iron or other magnetic substances can be destroyed partially or entirely or can disappear as a result of heating to a particular temperature. In the course of cooling, the magnetic properties are re-established and return to the starting state. This effect can be exploited to generate electrical power.
When an electrical conductor is exposed to a varying magnetic field, the changes in the magnetic field lead to the induction of an electrical current in the conductor. When, for example, the magnetic material is surrounded by a coil and is then heated in a permanent magnetic field and then cooled, an electrical current is induced in the coil in the course of heating and cooling in each case. This allows thermal energy to be converted to electrical energy, without an intermediate conversion to mechanical work.
In the process described by Tesla, iron, as the magnetic substance, is heated by means of an oven or a closed fireplace and then cooled again.
For the thermomagnetic or magnetocaloric applications, the material should permit efficient heat exchange in order to be able to achieve high efficiencies. Both in the course of cooling and in the course of power generation, the thermomagnetic material is used in a heat exchanger.
US 2006/0117758 and WO 2009/133049 disclose magnetocaloric materials of the general formula MnFe(PWGeXSi,). Preferred materials are MnFeP0.45-0.7oGeo.55-0.30 or MnFeP0.5-0.70(Si/Ge)0.5-0.30= In each case, the example compositions comprise proportions of Ge. These substances still do not have a sufficiently great magnetocaloric effect for all applications.
EP patent application 10 150 411.6 entitled "Magnetocaloric materials", which was filed on January 11, 2010 and was yet to be published at the priority date of the present application, describes magnetocaloric materials of the general formula (MnXFe1-x)2+ P1-,5i,, where 0.555x<1 0.4 5 y 5 0.8 -0.1 5 z 5 0.1.
It is an object of the present invention to provide magnetocaloric materials having a large magnetocaloric effect, low thermal hysteresis and a working temperature in the range from 0 to 150 C.
The object is achieved in accordance with the invention by magnetocaloric materials of the general formula (Mn.Fe1_X)2+Z P1_ySiy where 0.20 0.4 5 y 5 0.8 - 0.1 5 z 5 0.1.
Preferably, 0.25 5 x 5 0.35. x preferably has a minimum value of 0.28, more preferably of 0.3. The maximum value of x is preferably 0.34, in particular 0.33. More preferably 0.285x50.34, in particular 0.305x50.33.
y preferably has a minimum value of 0.4. The maximum value of y is preferably 0.6, more preferably 0.44. More preferably 0.4 5 y 5 0.6, in particular 0.4 5 y 5 0.44.
z may differ from 0 by small values. Preferably -0.05 5 z 5 0.05, in particular -0.02 5 z 5 0.02, especially z = 0.
The inventive magnetocaloric materials preferably have a hexagonal structure of the Fe2P type.
It has been found in accordance with the invention that especially an Mn/Fe element ratio of less than 0.54, especially in the range from 0.5/1.5 to 0.7/1.3, leads to magnetocaloric materials with stabilized phase formation and low thermal hysteresis.
The inventive materials allow a working temperature in application in the range from 0 C to + 150 C.
The magnetocaloric effect of the inventive materials is comparable to the magnetocaloric effect of what are known as giant magnetocaloric materials such as MnFePXAs1_X,Gd5(Si, Ge)4 or La(Fe, Si)13.
The thermal hysteresis, determined in a magnetic field of 1 T with a sweep rate of 1 C/min, is preferably < 5 C, more preferably < 2 C, due to the balanced Mn/Fe and P
Si ratios.
The inventive materials additionally have the advantage that they are formed from elements which are available in large amounts and are generally classified as nontoxic.
The thermomagnetic materials used in accordance with the invention can be produced in any suitable manner.
The inventive magnetocaloric materials can be produced by solid phase conversion or liquid phase conversion of the starting elements or starting alloys for the material, subsequently cooling, then pressing, sintering and heat treating under inert gas atmosphere and subsequently cooling to room temperature, or by melt spinning of a melt of the starting elements or starting alloys.
The thermomagnetic materials are produced, for example, by solid phase reaction of the starting elements or starting alloys for the material in a ball mill, subsequent pressing, sintering and heat treatment under inert gas atmosphere and subsequent cooling, for example slow cooling, to room temperature. Such a process is described, for example, in J. Appl. Phys. 99, 2006, 08Q107.
For example, suitable amounts of Mn, Fe, P and Si in element form or in the form of preliminary alloys such as Mn2P or Fe2P can be ground in a ball mill. The powders are pressed and sintered at temperatures in the range from 900 to 1300 C, preferably of about 1100 C, for a suitable time, preferably 1 to 5 hours, especially about 2 hours, and then heat treated at temperatures in the range from 700 to 1000 C, preferably about 850 C, for suitable periods, for example 1 to 100 hours, more preferably 10 to hours, especially about 20 hours, under a protective gas atmosphere.
Alternatively, the element powders or preliminary alloy powders can be melted together in an induction oven. It is then possible in turn to perform a heat treatment as specified 30 above.
Processing via melt spinning is also possible. This makes possible a more homogeneous element distribution which leads to an improved magnetocaloric effect;
cf. Rare Metals, Vol. 25, October 2006, pages 544 to 549. In the process described there, the starting elements are first induction-melted in an argon gas atmosphere and then sprayed in the molten state through a nozzle onto a rotating copper roller. There follows sintering at 1000 C and slow cooling to room temperature. In addition, reference may be made to WO 2004/068512 and WO 2009/133049 for the production.
Preference is given to a process for producing the thermomagnetic materials, comprising the following steps:
a) converting chemical elements and/or alloys in a stoichiometry which corresponds to the magnetocaloric material in the solid and/or liquid phase, b) optionally converting the reaction product from stage a) to a solid, c) sintering and/or heat treating the solid from stage a) or b), d) quenching the sintered and/or heat treated solid from stage c) at a cooling rate of at least 100 K/s.
The thermal hysteresis can be reduced significantly and a large magnetocaloric effect can be achieved when the magnetocaloric materials are not cooled slowing to ambient temperature after the sintering and/or heat treatment, but rather are quenched at a high cooling rate. This cooling rate is at least 100 K/s. The cooling rate is preferably from 100 to 10 000 K/s, more preferably from 200 to 1300 K/s. Especially preferred cooling rates are from 300 to 1000 K/s.
The quenching can be achieved by any suitable cooling processes, for example by quenching the solid with water or aqueous liquids, for example cooled water or ice/water mixtures. The solids can, for example, be allowed to fall into ice-cooled water.
It is also possible to quench the solids with subcooled gases such as liquid nitrogen.
Further processes for quenching are known to those skilled in the art. What is advantageous here is controlled and rapid cooling.
The rest of the production of the magnetocaloric/thermomagnetic materials is less critical, provided that the last step comprises the quenching of the sintered and/or heat treated solid at the inventive cooling rate. The process may be applied to the production of any suitable thermomagnetic materials, as described above.
In step (a) of the process, the elements and/or alloys which are present in the later thermomagnetic material are converted in a stoichiometry which corresponds to the thermomagnetic material in the solid or liquid phase.
Preference is given to performing the reaction in stage a) by combined heating of the elements and/or alloys in a closed vessel or in an extruder, or by solid phase reaction in a ball mill. Particular preference is given to performing a solid phase reaction, which is effected especially in a ball mill. Such a reaction is known in principle;
cf. the documents cited above. Typically, powders of the individual elements or powders of alloys of two or more of the individual elements which are present in the later thermomagnetic material are mixed in pulverulent form in suitable proportions by weight. If necessary, the mixture can additionally be ground in order to obtain a microcrystalline powder mixture. This powder mixture is preferably heated in a ball mill, which leads to further comminution and also good mixing, and to a solid phase reaction in the powder mixture. Alternatively, the individual elements are mixed as a powder in the selected stoichiometry and then melted.
The combined heating in a closed vessel allows the fixing of volatile elements and control of the stoichiometry. Specifically in the case of use of phosphorus, this would evaporate easily in an open system.
The reaction is followed by sintering and/or heat treatment of the solid, for which one or more intermediate steps can be provided. For example, the solid obtained in stage a) can be subjected to shaping before it is sintered and/or heat treated.
Alternatively, it is possible to send the solid obtained from the ball mill to a melt-spinning process. Melt-spinning processes are known per se and are described, for example, in Rare Metals, Vol. 25, October 2006, pages 544 to 549, and also in WO 2004/068512 and WO 2009/133049.
In these processes, the composition obtained in stage a) is melted and sprayed onto a rotating cold metal roller. This spraying can be achieved by means of elevated pressure upstream of the spray nozzle or reduced pressure downstream of the spray nozzle. Typically, a rotating copper drum or roller is used, which can additionally optionally be cooled. The copper drum preferably rotates at a surface speed of from 10 to 40 m/s, especially from 20 to 30 m/s. On the copper drum, the liquid composition is cooled at a rate of preferably from 102 to 107 K/s, more preferably at a rate of at least 104 K/s, especially with a rate of from 0.5 to 2 x 106 K/s.
The melt-spinning, like the reaction in stage a) too, can be performed under reduced pressure or under an inert gas atmosphere.
The melt-spinning achieves a high processing rate, since the subsequent sintering and heat treatment can be shortened. Specifically on the industrial scale, the production of the thermomagnetic materials thus becomes significantly more economically viable.
Spray-drying also leads to a high processing rate. Particular preference is given to performing melt spinning.
Alternatively, in stage b), spray cooling can be carried out, in which a melt of the composition from stage a) is sprayed into a spray tower. The spray tower may, for example, additionally be cooled. In spray towers, cooling rates in the range from 103 to 105 K/s, especially about 104 K/s, are frequently achieved.
The thermomagnetic materials used in accordance with the invention can be produced in any suitable manner.
The inventive magnetocaloric materials can be produced by solid phase conversion or liquid phase conversion of the starting elements or starting alloys for the material, subsequently cooling, then pressing, sintering and heat treating under inert gas atmosphere and subsequently cooling to room temperature, or by melt spinning of a melt of the starting elements or starting alloys.
The thermomagnetic materials are produced, for example, by solid phase reaction of the starting elements or starting alloys for the material in a ball mill, subsequent pressing, sintering and heat treatment under inert gas atmosphere and subsequent cooling, for example slow cooling, to room temperature. Such a process is described, for example, in J. Appl. Phys. 99, 2006, 08Q107.
For example, suitable amounts of Mn, Fe, P and Si in element form or in the form of preliminary alloys such as Mn2P or Fe2P can be ground in a ball mill. The powders are pressed and sintered at temperatures in the range from 900 to 1300 C, preferably of about 1100 C, for a suitable time, preferably 1 to 5 hours, especially about 2 hours, and then heat treated at temperatures in the range from 700 to 1000 C, preferably about 850 C, for suitable periods, for example 1 to 100 hours, more preferably 10 to hours, especially about 20 hours, under a protective gas atmosphere.
Alternatively, the element powders or preliminary alloy powders can be melted together in an induction oven. It is then possible in turn to perform a heat treatment as specified 30 above.
Processing via melt spinning is also possible. This makes possible a more homogeneous element distribution which leads to an improved magnetocaloric effect;
cf. Rare Metals, Vol. 25, October 2006, pages 544 to 549. In the process described there, the starting elements are first induction-melted in an argon gas atmosphere and then sprayed in the molten state through a nozzle onto a rotating copper roller. There follows sintering at 1000 C and slow cooling to room temperature. In addition, reference may be made to WO 2004/068512 and WO 2009/133049 for the production.
Preference is given to a process for producing the thermomagnetic materials, comprising the following steps:
a) converting chemical elements and/or alloys in a stoichiometry which corresponds to the magnetocaloric material in the solid and/or liquid phase, b) optionally converting the reaction product from stage a) to a solid, c) sintering and/or heat treating the solid from stage a) or b), d) quenching the sintered and/or heat treated solid from stage c) at a cooling rate of at least 100 K/s.
The thermal hysteresis can be reduced significantly and a large magnetocaloric effect can be achieved when the magnetocaloric materials are not cooled slowing to ambient temperature after the sintering and/or heat treatment, but rather are quenched at a high cooling rate. This cooling rate is at least 100 K/s. The cooling rate is preferably from 100 to 10 000 K/s, more preferably from 200 to 1300 K/s. Especially preferred cooling rates are from 300 to 1000 K/s.
The quenching can be achieved by any suitable cooling processes, for example by quenching the solid with water or aqueous liquids, for example cooled water or ice/water mixtures. The solids can, for example, be allowed to fall into ice-cooled water.
It is also possible to quench the solids with subcooled gases such as liquid nitrogen.
Further processes for quenching are known to those skilled in the art. What is advantageous here is controlled and rapid cooling.
The rest of the production of the magnetocaloric/thermomagnetic materials is less critical, provided that the last step comprises the quenching of the sintered and/or heat treated solid at the inventive cooling rate. The process may be applied to the production of any suitable thermomagnetic materials, as described above.
In step (a) of the process, the elements and/or alloys which are present in the later thermomagnetic material are converted in a stoichiometry which corresponds to the thermomagnetic material in the solid or liquid phase.
Preference is given to performing the reaction in stage a) by combined heating of the elements and/or alloys in a closed vessel or in an extruder, or by solid phase reaction in a ball mill. Particular preference is given to performing a solid phase reaction, which is effected especially in a ball mill. Such a reaction is known in principle;
cf. the documents cited above. Typically, powders of the individual elements or powders of alloys of two or more of the individual elements which are present in the later thermomagnetic material are mixed in pulverulent form in suitable proportions by weight. If necessary, the mixture can additionally be ground in order to obtain a microcrystalline powder mixture. This powder mixture is preferably heated in a ball mill, which leads to further comminution and also good mixing, and to a solid phase reaction in the powder mixture. Alternatively, the individual elements are mixed as a powder in the selected stoichiometry and then melted.
The combined heating in a closed vessel allows the fixing of volatile elements and control of the stoichiometry. Specifically in the case of use of phosphorus, this would evaporate easily in an open system.
The reaction is followed by sintering and/or heat treatment of the solid, for which one or more intermediate steps can be provided. For example, the solid obtained in stage a) can be subjected to shaping before it is sintered and/or heat treated.
Alternatively, it is possible to send the solid obtained from the ball mill to a melt-spinning process. Melt-spinning processes are known per se and are described, for example, in Rare Metals, Vol. 25, October 2006, pages 544 to 549, and also in WO 2004/068512 and WO 2009/133049.
In these processes, the composition obtained in stage a) is melted and sprayed onto a rotating cold metal roller. This spraying can be achieved by means of elevated pressure upstream of the spray nozzle or reduced pressure downstream of the spray nozzle. Typically, a rotating copper drum or roller is used, which can additionally optionally be cooled. The copper drum preferably rotates at a surface speed of from 10 to 40 m/s, especially from 20 to 30 m/s. On the copper drum, the liquid composition is cooled at a rate of preferably from 102 to 107 K/s, more preferably at a rate of at least 104 K/s, especially with a rate of from 0.5 to 2 x 106 K/s.
The melt-spinning, like the reaction in stage a) too, can be performed under reduced pressure or under an inert gas atmosphere.
The melt-spinning achieves a high processing rate, since the subsequent sintering and heat treatment can be shortened. Specifically on the industrial scale, the production of the thermomagnetic materials thus becomes significantly more economically viable.
Spray-drying also leads to a high processing rate. Particular preference is given to performing melt spinning.
Alternatively, in stage b), spray cooling can be carried out, in which a melt of the composition from stage a) is sprayed into a spray tower. The spray tower may, for example, additionally be cooled. In spray towers, cooling rates in the range from 103 to 105 K/s, especially about 104 K/s, are frequently achieved.
The sintering and/or heat treatment of the solid is effected in stage c) as described above.
In the case of use of the melt-spinning process, the period for sintering or heat treatment can be shortened significantly, for example to periods of from 5 minutes to 5 hours, preferably from 10 minutes to 1 hour. Compared to the otherwise customary values of 10 hours for sintering and 50 hours for heat treatment, this results in a major time advantage.
The sintering/heat treatment results in partial melting of the particle boundaries, such that the material is compacted further.
The melting and rapid cooling in stage b) thus allows the duration of stage c) to be reduced considerably. This also allows continuous production of the thermomagnetic materials.
The inventive magnetocaloric materials can be used in any suitable applications. For example, they are used in coolers, heat exchangers or generators. Particular preference is given to use in refrigerators.
The invention is illustrated in detail by examples.
Examples Preparation of the magnetocaloric materials 15 g of a mixture of Mn flakes, Si flakes and Fe2P powder with a nominal stoichiometry of Mn0.6Fel.4P0.6Si0.4 were ground in a planetary ball mill with a BPR (ball to powder weight ratio) of 4 for 10 hours. The powder obtained in the grinding was then pressed into cylinder form and sealed in an ampoule under 200 mbar of argon gas. This was followed by a sintering step at 1100 C for 2 hours and a heat treatment at 850 C for 20 hours. The sample was removed after the furnace had been cooled down.
Samples with the nominal composition Mn0.66Fe1.34P0.53Si0.42, Mn0.62Fe1.33P0.53Si0.42 and Mn0.66Fe1.34P0.56Si0.44 were prepared in the same way.
Magnetic properties The magnetic properties of the samples thus prepared were determined in a Quantum Design MPMSXL SQUID magnetometer.
Figure 1 shows the temperature dependence of the magnetization M(Am2kg-'), determined with a sweep rate of 1 K/min in a magnetic field of 1 T. The temperature dependence between the heating and cooling curves at the transition shows the thermal hysteresis of the first-order magnetic transition for these samples.
The value depends on the particular sample, but is always less than 2 K in the samples studied.
The significant change in magnetization in the region of about 70 Am2kg_1 as a result of the sharp magnetic transition shows a large magnetocaloric effect.
Figure 2 shows the change in magnetic entropy -OSn(J/kg K) as a function of temperature for these samples. The change in magnetic entropy was derived from the magnetic isotherms, measured at different temperatures close to the transition, using the Maxwell equation. The values obtained for the change in magnetic entropy are comparable to corresponding values for the so-called GMCEs (giant magnetocaloric effect materials).
The unfilled symbols relate to a field change of 0-1 T. The filled symbols represent a field change for 0-2 T.
In the case of use of the melt-spinning process, the period for sintering or heat treatment can be shortened significantly, for example to periods of from 5 minutes to 5 hours, preferably from 10 minutes to 1 hour. Compared to the otherwise customary values of 10 hours for sintering and 50 hours for heat treatment, this results in a major time advantage.
The sintering/heat treatment results in partial melting of the particle boundaries, such that the material is compacted further.
The melting and rapid cooling in stage b) thus allows the duration of stage c) to be reduced considerably. This also allows continuous production of the thermomagnetic materials.
The inventive magnetocaloric materials can be used in any suitable applications. For example, they are used in coolers, heat exchangers or generators. Particular preference is given to use in refrigerators.
The invention is illustrated in detail by examples.
Examples Preparation of the magnetocaloric materials 15 g of a mixture of Mn flakes, Si flakes and Fe2P powder with a nominal stoichiometry of Mn0.6Fel.4P0.6Si0.4 were ground in a planetary ball mill with a BPR (ball to powder weight ratio) of 4 for 10 hours. The powder obtained in the grinding was then pressed into cylinder form and sealed in an ampoule under 200 mbar of argon gas. This was followed by a sintering step at 1100 C for 2 hours and a heat treatment at 850 C for 20 hours. The sample was removed after the furnace had been cooled down.
Samples with the nominal composition Mn0.66Fe1.34P0.53Si0.42, Mn0.62Fe1.33P0.53Si0.42 and Mn0.66Fe1.34P0.56Si0.44 were prepared in the same way.
Magnetic properties The magnetic properties of the samples thus prepared were determined in a Quantum Design MPMSXL SQUID magnetometer.
Figure 1 shows the temperature dependence of the magnetization M(Am2kg-'), determined with a sweep rate of 1 K/min in a magnetic field of 1 T. The temperature dependence between the heating and cooling curves at the transition shows the thermal hysteresis of the first-order magnetic transition for these samples.
The value depends on the particular sample, but is always less than 2 K in the samples studied.
The significant change in magnetization in the region of about 70 Am2kg_1 as a result of the sharp magnetic transition shows a large magnetocaloric effect.
Figure 2 shows the change in magnetic entropy -OSn(J/kg K) as a function of temperature for these samples. The change in magnetic entropy was derived from the magnetic isotherms, measured at different temperatures close to the transition, using the Maxwell equation. The values obtained for the change in magnetic entropy are comparable to corresponding values for the so-called GMCEs (giant magnetocaloric effect materials).
The unfilled symbols relate to a field change of 0-1 T. The filled symbols represent a field change for 0-2 T.
Claims (9)
1. A magnetocaloric material of the general formula (Mn x Fe1-x)2+z P1-y Si y where 0.20<= x <=0.40 0.4 <= y <= 0.8 -0.1 <= z <= 0.1.
2. The magnetocaloric material according to claim 1, wherein 0.27 <= x <= 0.35.
3. The magnetocaloric material according to claim 1 or 2, wherein 0.4 <=
y <= 0.6.
y <= 0.6.
4. The magnetocaloric material according to any of claims 1 to 3, wherein -0.05 <= z <=0.05.
5. The magnetocaloric material according to any of claims 1 to 4, which has a hexagonal structure of the Fe2P type.
6. A process for producing the magnetocaloric materials according to any of claims 1 to 5 by solid phase conversion or liquid phase conversion of the starting elements or starting alloys for the material, optionally cooling, then pressing, sintering and heat treating under inert gas atmosphere and subsequently cooling to room temperature, or by melt spinning of a melt of the starting elements or starting alloys.
7. The process according to claim 6, comprising the following steps:
a) converting chemical elements and/or alloys in a stoichiometry which corresponds to the magnetocaloric material in the solid and/or liquid phase, b) optionally converting the reaction product from stage a) to a solid, c) sintering and/or heat treating the solid from stage a) or b), d) quenching the sintered and/or heat treated solid from stage c) at a cooling rate of at least 100 K/s.
a) converting chemical elements and/or alloys in a stoichiometry which corresponds to the magnetocaloric material in the solid and/or liquid phase, b) optionally converting the reaction product from stage a) to a solid, c) sintering and/or heat treating the solid from stage a) or b), d) quenching the sintered and/or heat treated solid from stage c) at a cooling rate of at least 100 K/s.
8. The use of the magnetocaloric materials according to any of claims 1 to 5 in coolers, heat exchangers or generators.
9. The use according to claim 8 in refrigerators.
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EP10156184.3 | 2010-03-11 | ||
EP10156184 | 2010-03-11 | ||
PCT/IB2011/050982 WO2011111004A1 (en) | 2010-03-11 | 2011-03-09 | Magnetocaloric materials |
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JP (1) | JP5809646B2 (en) |
KR (1) | KR101848520B1 (en) |
CN (1) | CN102792393B (en) |
AU (1) | AU2011225713A1 (en) |
BR (1) | BR112012021783A2 (en) |
CA (1) | CA2789797A1 (en) |
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RU (1) | RU2012143308A (en) |
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CN102513536A (en) * | 2011-12-28 | 2012-06-27 | 北京工业大学 | Process for preparing magnetic cooling material |
US9245673B2 (en) | 2013-01-24 | 2016-01-26 | Basf Se | Performance improvement of magnetocaloric cascades through optimized material arrangement |
CN105190200A (en) | 2013-05-08 | 2015-12-23 | 巴斯夫欧洲公司 | Use of a rotating magnetic shielding system for a magnetic cooling device |
US9887027B2 (en) | 2013-09-27 | 2018-02-06 | Basf Se | Corrosion inhibitors for Fe2P structure magnetocaloric materials in water |
KR101575861B1 (en) | 2014-02-13 | 2015-12-10 | 충북대학교 산학협력단 | Magnetocaloric metal compound and method for preparing thereof |
JP6606790B2 (en) * | 2014-12-26 | 2019-11-20 | 大電株式会社 | Method for manufacturing magnetic refrigeration material |
KR102563429B1 (en) * | 2015-10-30 | 2023-08-04 | 테크니쉐 유니버시테이트 델프트 | Magnetocaloric materials containing manganese, iron, silicon, phosphorus, and nitrogen |
CN109313971B (en) * | 2016-06-10 | 2021-02-19 | 巴斯夫欧洲公司 | Magnetocaloric materials comprising manganese, iron, silicon, phosphorus and carbon |
US11056265B2 (en) | 2017-10-04 | 2021-07-06 | Calagen, Inc. | Magnetic field generation with thermovoltaic cooling |
AU2018345384B2 (en) * | 2017-10-04 | 2023-08-03 | Calagen, Inc. | Thermo-electric element driven by electric pulses |
KR102069770B1 (en) | 2018-06-07 | 2020-01-23 | 한국생산기술연구원 | Magneto-caloric alloy and preparing method thereof |
JP2022545008A (en) | 2019-08-20 | 2022-10-24 | カラジェン インコーポレイテッド | A circuit for generating electrical energy |
US11942879B2 (en) | 2019-08-20 | 2024-03-26 | Calagen, Inc. | Cooling module using electrical pulses |
KR102651747B1 (en) | 2021-11-30 | 2024-03-28 | 한국재료연구원 | Magneto-caloric alloy and preparing method thereof |
CN114540657B (en) * | 2022-03-24 | 2022-11-25 | 中南大学 | Rare earth copper alloy material with broadband electromagnetic shielding function and preparation method thereof |
KR102589531B1 (en) * | 2022-04-20 | 2023-10-16 | 한국재료연구원 | Magneto-caloric alloy and preparing method thereof |
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US428057A (en) | 1890-05-13 | Nikola Tesla | Pyromagneto-Electric Generator | |
NL1018668C2 (en) * | 2001-07-31 | 2003-02-03 | Stichting Tech Wetenschapp | Material suitable for magnetic cooling, method of preparing it and application of the material. |
CA2514773C (en) * | 2003-01-29 | 2012-10-09 | Stichting Voor De Technische Wetenschappen | A magnetic material with cooling capacity, a method for the manufacturing thereof and use of such material |
GB2424901B (en) * | 2005-04-01 | 2011-11-09 | Neomax Co Ltd | Method of making a sintered body of a magnetic alloyl |
DE102006046041A1 (en) * | 2006-09-28 | 2008-04-03 | Siemens Ag | Heat transfer system used as a cooling/heating system comprises a magnetizable body having an open-pore foam made from a material with a magneto-calorific effect |
US8293030B2 (en) * | 2007-04-05 | 2012-10-23 | Universite De Lorraine | Intermetallic compounds, their use and a process for preparing the same |
EP2107575B1 (en) * | 2008-03-31 | 2011-07-13 | Université Henri Poincaré - Nancy 1 | New intermetallic compounds, their use and a process for preparing the same |
TW201003024A (en) * | 2008-04-28 | 2010-01-16 | Basf Se | Open-cell porous shaped bodies for heat exchangers |
JP5855457B2 (en) | 2008-04-28 | 2016-02-09 | テクノロジー、ファウンデーション、エステーヴェー | Method for producing metal-based material for magnetic cooling or heat pump |
TW201145319A (en) * | 2010-01-11 | 2011-12-16 | Basf Se | Magnetocaloric materials |
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WO2011111004A1 (en) | 2011-09-15 |
BR112012021783A2 (en) | 2016-05-17 |
JP2013527308A (en) | 2013-06-27 |
CN102792393A (en) | 2012-11-21 |
TW201140625A (en) | 2011-11-16 |
KR20130051440A (en) | 2013-05-20 |
JP5809646B2 (en) | 2015-11-11 |
KR101848520B1 (en) | 2018-04-12 |
EP2545563A4 (en) | 2016-02-17 |
NZ601798A (en) | 2014-01-31 |
EP2545563B1 (en) | 2017-05-31 |
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