Working component and object for magnetic heat exchange, use of a magnetocalorically active phase and method for generating a working component for magnetic cooling

Abstract

Working component for a magnetic heat exchange, comprising: a magnetocaloric active phase having La1-aRa(Fe1-x-yTyMx)13Hz, a hydrogen content, z, with 90% or higher of a saturation value, zsat, and values ​​for a, x and y selected to give a Curie temperature Tc, wherein M is one or more of the elements from the group consisting of Al and Si, and R is one or more of the elements from the group consisting of Ce, Nd, Y and Pr, wherein Tcmax is the Curie temperature of a La1-aRa(Fe1-x-yTyMx)13Hz phase having a hydrogen content of z = zsat and the selected values ​​for a, x and y, where (Tcmax- Tc) ≤ 20 K, where 1.2 ≤ z ≤ 3 or 1.4 ≤ z ≤ 3, where 0.05 ≤ x ≤ 0.3, 0.003 ≤ y ≤ 0.2 and optionally 0.005 ≤ a 0.5, where T is Mn and the Curie temperature Tc of the work component lies within ±10 K of the value of the Curie temperature, Tc(calc), derived from the relationship Tc(calc)(°C) = 80.672 - 26.957 × Mnm,where Mnmder is the metallic mass fraction of manganese, wherein the working component has a peak in a graph of heat flux versus temperature, wherein the peak has a width and a maximum, the maximum corresponding to the Curie temperature, and after exposing the working component to temperatures within ±1°C of the Curie temperature of the working component for 30 days, the width of the peak increases by less than 20%.

Description

[0001] The present invention relates to a working component for magnetic heat exchange and a method for manufacturing an object for magnetic heat exchange.

[0002] A magnetocalorically active material exhibits the magnetocaloric effect. The magnetocaloric effect describes the adiabatic conversion of a magnetically induced entropy change into heat generation or heat absorption. The magnetic entropy of the material changes depending on whether a magnetic field is applied or not, due to the difference in degrees of freedom of the electronic spin system. This entropy change transfers entropy between the electronic spin system and the lattice system. A magnetocalorically active phase therefore has a magnetic phase transition temperature Tg. trans , where this entropy change occurs.

[0003] Magnetic heat exchangers utilize a magnetocalorically active material as the working component or medium to provide cooling and / or heating. Applying a magnetic field to a magnetocalorically active material induces an entropy change, resulting in heat generation or absorption. This effect can be harnessed to provide cooling and / or heating.

[0004] Magnetic heat exchangers are generally more energy-efficient than gas compression / expansion cycle systems. They are also considered environmentally friendly because they do not use chemicals such as chlorofluorocarbons (CFCs), which are believed to contribute to ozone depletion.

[0005] Practical magnetic heat exchangers, as disclosed in US 6,676,772, typically include a pumped circulation system, a heat exchange medium such as a cooling fluid, a chamber filled with particles of a working material, exhibiting the magnetocaloric effect, and a means of applying a magnetic field to the chamber.

[0006] In practice, the magnetic phase transition temperature of the magnetocalorically active material is translated as the working temperature. Therefore, to provide cooling over a wider temperature range, the magnetic heat exchanger requires a magnetocalorically active material exhibiting several different magnetic phase transition temperatures. In addition to multiple magnetic phase transition temperatures, a practical working medium should also exhibit a large entropy change to provide effective cooling and / or heating.

[0007] A variety of magnetocalorically active phases are known that exhibit magnetic phase transition temperatures within a suitable range for providing domestic and commercial air conditioning and cooling. One such magnetocalorically active material, disclosed, for example, in US 7,063,754, has a NaZn 13 -Type crystal structure and can be described by a general formula La(Fe 1-x-y T y M x ) 13 H z The magnetic phase transition temperature of this material can be adjusted by modifying its composition. M can be at least one element from the group consisting of Si and Al, and T can be one or more transition metal elements such as Co, Ni, Mn, and Cr.

[0008] Consequently, magnetic heat exchanger systems have been developed to practically realize the advantages provided by the recent development of magnetocaloric materials. However, further improvements are desirable to enable more widespread application of magnetic heat exchanger technology.

[0009] Therefore, it is desirable to provide a material for use as a working medium in a magnetic heat exchanger that can be manufactured to have a range of different magnetic phase transition temperatures as well as a large entropy change.

[0010] In one embodiment of the present application, a working component for magnetic heat exchange is provided, comprising a magnetocalorically active phase. The magnetocalorically active phase comprises La 1-a R a (Fe 1-x-y T y M x ) 13 H z, a hydrogen content, z, that is 90% more hydrogen saturation value, z sat , and values ​​of a, x and y that are selected to define a Curie temperature T c to be submitted. M is one or more of the elements from the group consisting of Al and Si, T is one or more of the elements from the group consisting of Co, Ni, Mn, Cr, Cu, Ti and V, and R is one or more of the elements from the group consisting of Ce, Nd, Y and Pr. T cmax is the Curie temperature of a la 1-a R a (Fe 1-x-y T y M x ) 13 H z Phase containing a hydrogen content z = z sat includes and has the selected values ​​of a, x, and y. The difference between T cmax and T c The work component is less than 20 K, that is (T cmax – T c ) ≤ 20 K.

[0011] The La 1-a R a (Fe 1-x-y T y M x ) 13 Hz Phase has a NaZn 13 -Type structure in which the hydrogen atoms occupy interstitial lattice sites. The working component therefore comprises a hydrogen content that is at least 90% of the hydrogen saturation content. In a further embodiment, the hydrogen content, z, is at least 95% of the hydrogen saturation content, z sat , and (T cmax – T c ) ≤ 10 K.

[0012] The hydrogen saturation level, z sat , the La 1-a R a (Fe 1-x-y T y M x ) 13 H z The hydrogen saturation level of the -based phase is not constant, but varies depending on R, T, and M, and the values ​​of a, x, and y. Therefore, the hydrogen saturation level depends on... sat , depending on the type of metallic element as well as the quantity of metallic elements that are substitutional elements in LaFe 13 The basic phase is included, starting from.

[0013] For a sample with selected values ​​of a, x, and y, the hydrogen saturation content can be experimentally determined by heating a hydrogenated sample in a hydrogen-containing atmosphere at a temperature between 20°C and 100°C for at least one hour. The hydrogen-containing atmosphere can have a hydrogen partial pressure in the range of 0.5 bar to 2.0 bar. The sample can be preheated in a hydrogen atmosphere to temperatures between 200°C and 500°C before being held at a temperature between 20°C and 100°C for at least one hour.

[0014] The preheating step helps to avoid activation difficulties.

[0015] If the hydrogen content of the sample does not increase measurably, it can be said that the sample is fully hydrogenated and has reached a hydrogen saturation level, e.g. satThe hydrogen content of the sample can be measured using techniques such as the hot gas extraction method. Alternatively or additionally, the change in hydrogen content can be evaluated by measuring the Curie temperature before and after heat treatment.

[0016] In the La 1-a R a (Fe 1-x-y T y M x ) 13 H z Phase is the maximum Curie temperature reached in compositions where the hydrogen content, z, is equal to the hydrogen saturation content, z sat , for a given value of a, x and y.

[0017] The metallic elements R and T can be selected to adjust the Curie temperature for both the hydrogenated and unhydrogenated phases. For example, substituting Nd, Pr, and / or Ce for La and / or Mn, Cr, V, and Ti for Fe leads to a reduction in the Curie temperature. The Curie temperature can also be increased by substituting Fe with Co and Ni.

[0018] The Curie temperature of the La 1-a R a (Fe 1-x-y T y M x ) 13 H z The phase can also be adjusted to a selected value by adjusting the hydrogen content. The Curie temperature can be set to a maximum value T. cmaxThis can be reduced by lowering the hydrogen content and partially dehydrating the sample. However, partial hydrogenation of the samples has been observed during aging, with the Curie temperature becoming unstable when the sample is stored at or near the Curie temperature for a period of, for example, 30 to 45 days. This can also occur for a working component in a practical magnetic heat exchanger. Furthermore, partially hydrogenated La(Fe,Si) 13 H z Samples can also be observed, similar to fully hydrogenated La(Fe, Si) samples. 13 H sat Samples show that they exhibit thermal hysteresis, which is undesirable in practical magnetic heat exchangers.

[0019] By keeping the hydrogen content as high as possible in the La 1-a R a (Fe 1-x-y T y M x ) 13 H zIn hydrogen-based phases, the aging of the working component can be prevented. Therefore, by selecting suitable elements R and T and keeping the hydrogen content as high as possible, a working component with a desired T value can be achieved. c be provided that is stable over a long working time.

[0020] Additionally, the substitution of elements R and / or T, particularly Mn, can lead to a reduction in the thermal hysteresis observed for the working component, compared to samples lacking elements R and T. The combination of essentially complete hydrogenation and substitution with elements R and T can reduce thermal hysteresis and improve the efficiency of the working component in a magnetic heat exchanger.

[0021] A magnetocalorically active material is defined here as a material that undergoes a change in entropy when exposed to a magnetic field. This entropy change can result from a shift from ferromagnetic to paramagnetic behavior, for example. The magnetocalorically active material may only exhibit this behavior within a portion of a temperature range, at an inflection point where the sign of the second derivative of the magnetization with respect to an applied magnetic field changes from positive to negative.

[0022] A magnetocaloric passive material is defined herein as a material that does not show a significant change in entropy when exposed to a magnetic field.

[0023] A magnetic phase transition temperature is defined here as a transition from one magnetic state to another. Some magnetocalorically active phases exhibit a transition from antiferromagnetic to ferromagnetic behavior, which is associated with an entropy change. Magnetocalorically active phases such as La 1-a R a (Fe 1-x-y T y M x ) 13 H z These materials exhibit a transition from ferromagnetic to paramagnetic, which is associated with a change in entropy. For these materials, the magnetic transition temperature can also be referred to as the Curie temperature.

[0024] In further embodiments, the working component comprises a magnetocalorically active phase La 1-a R a (Fe 1-x-y T y M x ) 13 H z, in which 1.2 ≤ z ≤ 3 or 1.4 ≤ z ≤ 3 and / or 0.05 ≤ x ≤ 0.3, 0.003 ≤ y ≤ 0.2 and optionally 0.005 ≤ a ≤ 0.5. In a further embodiment, 1.2 ≤ z ≤ 3 and 0.05 ≤ a ≤ 0.5 and 0.05 ≤ x ≤ 0.2 and 0.003 ≤ y ≤ 0.2.

[0025] As discussed above, the Curie temperature of the working component can be adjusted by modifying the set of substitution elements R and T. In one embodiment, T is Mn and the Curie temperature is T. c The operating temperature of the components lies within ±10 K of the Curie temperature value, T. c(calc) , which is derived from the relationship T c(calc) (°C) = 80.672 – 26.957 × Mn m , where Mn m The metallic fraction by weight of manganese. In another embodiment, T c within ±5 K of T c(calc)

[0026] As used herein, the subscript m denotes the metallic weight fractions. The metallic weight fraction is defined herein as the result of a calculation that separates and removes the rare earth elements, RE, from the content bound in the form of RE oxides and RE nitrides of the total composition according to the following formulas (for RE = La): La2O3 = 6.79*O LaN = 10.9*N f = 100 100 – La₂O₃ – LaN

[0027] Consequently: La m = (La – 5.8* – 9.9*N) * f Si m = Si * f CO m = CO * f Mn m = Mn * f where the subscript m denotes the metallic weight fraction of La, O, N, Si, Co and Mn, and so on, the weight percent of that element is shown.

[0028] As a first approximation, the metallic RE content can also be calculated from the La-rich alloys using: Re m = (RE – 5,8*0 – 9,9*N) × 100 100 – 6,8*0 – 10,9*N

[0029] For Si, Co, Mn, and so on, the metallic contents are close to the total content when the factor f is approximately 1.02. However, for the RE element, there is a larger difference. For example, in the embodiments described here, a content of approximately 18 wt.% La is used to provide a metallic content of 16.7 wt.%, which corresponds to the stoichiometry of the 1:13 phase.

[0030] In further embodiments, the proportion of element M can be adjusted depending on the type and amount of the substituted elements R and T in order to achieve a greater entropy change in the La 1-a R a (Fe 1-x-y T y M x ) 13 H z to reach the phase. In one embodiment, M is Si and the metallic weight fraction of Si, Si act , lies within ±5% of the value of the metallic weight fraction of silicon, Si m, derived from the relationship Si m = 3.85 – 0.0573 x Co m – 0.045 x Mn m 2 + 0.2965 x Mn m ., where Mn m the metallic weight fraction of Mn is and Co m The metallic weight fraction of Co is.

[0031] In one embodiment, M is Si and the metallic weight fraction of Si, Si act , lies within ±5% of the value of the metallic weight fraction of silicon, Si m , derived from the relationship Si m = 3.85 – 0.045 × Mn m 2 + 0.2965 × Mn m + (0.198 – 0.066 × Mn m ) × Ce(MM) m , where Ce(MM) m The metallic weight fraction of cerium mischmetal (mischmetal) is.

[0032] In another embodiment, Si act within ±-2% of Si m .

[0033] The working component can take a number of physical forms. For example, the working component can be a powder, a sintered block, a reactively sintered block, or a compacted powder.

[0034] The term "reactively sintered" describes an object in which the crystalline grains are bonded together to form congruent crystal grains through a reactive sintered composite. A reactively sintered composite is produced by heat-treating a mixture of precursor powders with varying compositions. The particles of these different compositions react chemically with one another during the reactive sintering process to form the desired final phase or product. The composition of the particles therefore changes as a result of the heat treatment. This phase formation process can cause the particles to bond together to form a sintered body that exhibits mechanical integrity.

[0035] Reactive sintering differs from conventional sintering because, in conventional sintering, the particles of the sintered final phase remain as they were before the sintering process. The conventional sintering process causes diffusion of atoms between neighboring particles to bond them together. Therefore, the particle composition remains unchanged as a result of the conventional sintering process.

[0036] The working component according to one of the embodiments described above exhibits good stability when exposed to temperatures such as its Curie temperature. This can be measured, for example, using differential scanning calorimetry. Differential scanning calorimetry generates a graph of heat flux versus temperature. In such a graph, the working component includes a peak with a width and a maximum, where the maximum of the peak corresponds to the Curie temperature.

[0037] In one embodiment, after the working component is stored at a temperature within ±1°C of its Curie temperature for 30 days, the tip width increases by less than 20%. This demonstrates that the working component is stable when stored at its Curie temperature, which would be the case if the working component were operated in a magnetic cooling device.

[0038] In another embodiment, after the working component is stored at a temperature within ±1°C of the Curie temperature of the working component for 40 days, the width of the tip increases by less than 20%.

[0039] In another embodiment, after the working component has been stored at a Curie temperature of the working component for 30 days, the width of the tip will increase by less than 20%.

[0040] The working component can further comprise a magnetocaloric passive phase. This magnetocaloric passive phase can provide a matrix in which the magnetocaloric active phase is embedded. Alternatively, the magnetocaloric passive phase can be a coating on a solid magnetocaloric active block. In both cases, the magnetocaloric phase can provide a corrosion-resistant coating to prevent corrosion of the magnetocaloric active phase.

[0041] As mentioned above, a practical magnetic heat exchanger typically comprises a magnetocalorically active working medium having two or more different Curie temperatures. In one embodiment, a magnetic heat exchange device is provided that has two or more working components according to one of the previously described embodiments. The two or more working components have different Curie temperatures and different values ​​for a and / or c and / or y to provide the different Curie temperatures. In each case, the hydrogen content, z, of two or more working components is 90%, or at least 95%, of the saturation value, z sat , for a La 1-a R a (Fe 1-x-y T y M x ) 13 H z The phase that has these special values ​​of a, x and y is included in the work component.

[0042] In another embodiment, the object comprises at least three working components with different Curie temperatures. The at least three working components are arranged such that the Curie temperature of the working components increases in one direction along the object. The object can contain as many working components with different Curie temperatures as desired. For example, the object can contain 5, 6, or 7 working components with different Curie temperatures, arranged such that the Curie temperature of the working components increases in one direction along the object.

[0043] A method for manufacturing a working component for magnetic cooling comprises selecting a desired Curie temperature and selecting a set of one or more elements T, R, and M, wherein T is one or more of the elements in the group consisting of Mn, Co, Ni, Cu, Ti, V, and Cr, R is one or more of the elements in the group consisting of Ce, Nd, Y, and Pr, and M is one or more of the elements Si and Al, wherein the set of one or more elements T, R, and M is selected to produce the chosen Curie temperature when a La 1-a R a (Fe 1-x-y T y M x ) 13 H z The phase contains a hydrogen content that is at least 90% of the hydrogen saturation value, e.g. sat The set of selected elements T, R, and M is combined with La and Fe or precursors thereof in quantities suitable to produce the La 1-a R a (Fe 1-x-y T y Mx ) 13 H z The phase is mixed to create a precursor powder mixture at the desired Curie temperature. The precursor powder mixture is then heat-treated to produce an intermediate product that has a la 1-a R a (Fe 1-x-y T y M x ) 13 H z The phase contains z = 0. The intermediate is hydrogenated to produce a working component, which the La 1-a R a (Fe 1-x-y T y M x ) 13 H z phase containing, to generate which encompasses the desired Curie temperature and a hydrogen content z of at least 90% or at least 95% of the hydrogen saturation value, z sat , to include.

[0044] The quantity of one or more of the elements R, T, and M can be selected within a range of 0.05 ≤ x ≤ 0.2, 0.003 ≤ y ≤ 0.2, and optionally 0.005 ≤ a ≤ 0.5 to provide the desired Curie temperature when the La 1-a R a (Fe 1-x-y T y M x ) 13 H z Phase has a hydrogen content z of at least 90% of the hydrogen saturation value, z sat , includes. In a further embodiment, the quantity of one or more of the elements R, T and M is selected in a range of 0.005 ≤ a ≤ 0.5 and 0.05 ≤ x ≤ 0.2 and 0.003 ≤ y ≤ 0.2.

[0045] In one embodiment, the element T comprises Mn and the amount of manganese Mn m is used to generate the desired Curie temperature T according to T c (°c) = 80.672 – 26.957 × Mn m selected, where Mn m The metallic weight fraction of manganese is...

[0046] In another embodiment, M is Si and the amount of Si is accordingly Si m = 3.85 – 0.0573 × Co m – 0.045 × Mn m 2 + 0.2965 × Mn m selected, where Mn m the metallic weight fraction of manganese is and Co m The metallic weight fraction of cobalt is...

[0047] In another embodiment, M is Si and the amount of Si is accordingly Si m = 3.85 – 0.045 × Mn m 2 + 0.2965 × Mn m + (0.198 – 0.006 × Mn m ) × Ce(MM) m selected, where Mn m the metallic weight fraction of manganese is and Ce(MM) m is the metallic weight fraction of the cerium mischmetal.

[0048] The precursor powder mixture can be pressed to form one or more green bodies before heat treatment and hydrogenation processes. Isostatic or compression pressing can be employed. This embodiment can be carried out to produce the working component in the form of a reactively sintered block. Alternatively, pressing can be performed to increase the reaction rate and phase formation within the green body. After the formation of the working component with the magnetocalorically active phase, the working component can subsequently be milled to provide a working component powder.

[0049] As discussed above, hydrogenation is carried out to produce a working component with a hydrogen content, z, of at least 90% or at least 95% of the hydrogen saturation value, z sat , to provide. In one embodiment, an intermediate product is hydrogenated to increase the La 1-a Ra (Fe 1-x-y T y M x ) 13 H z to produce a phase with a hydrogen content z of 1.2 ≤ z ≤ 3, preferably 1.4 ≤ z ≤ 3.

[0050] The hydrogenation conditions are chosen to introduce enough hydrogen into the La 1-a R a (Fe 1-x-y T y M x ) 13 H z to introduce a phase to achieve a hydrogen content z of at least 90% of the hydrogen saturation value, z sat, to achieve this. The hydrogenation can be carried out by heat treatment of the intermediate product under a hydrogen partial pressure of 0.5 to 2 bar. The hydrogen partial pressure can be increased during the hydrogenation heat treatment. The hydrogenation can include heat treatment at a temperature in the range of 0°C to 100°C, and preferably in the range of 15°C to 35°C. A final heat treatment at temperatures of less than 100°C in a hydrogen atmosphere, preferably at 1.5 to 2 bar, has shown that reliable working components with a hydrogen content, z, of at least 90% of the hydrogen saturation value, z sat , can be manufactured.

[0051] In further embodiments, the hydrogenation includes a residence time at a temperature T. hyd , where 300°C ≤ T hyd ≤ 700°C and the residence time at a temperature T hyd in the range of 400°C ≤ T hyd≤ 500°C, followed by cooling at a temperature of less than 100°C.

[0052] In further embodiments, the intermediate is exposed only to hydrogen gas above a threshold temperature. In one embodiment, the hydrogenation comprises heating the intermediate from a temperature of less than 50°C to at least 300°C in an inert atmosphere and introducing hydrogen gas only when a temperature of at least 300°C is reached. The intermediate is held in the hydrogen-containing atmosphere at a temperature in the range of 300°C to 700°C for a selected duration and cooled to a temperature of less than 50°C in a hydrogen-containing atmosphere to obtain the working component. For this process, it was found that working components with a hydrogen content, z, of 90% and more of the hydrogen saturation content, z sat, and also result in mechanically stable working components. This hydrogenation process can be used to produce working components in the form of a sintered block or a reactively sintered block.

[0053] In particular, it was found that if hydrogen is introduced at a temperature below 300°C, the mass of the precursor can disintegrate into parts or at least lose its previous mechanical strength. However, this problem can be avoided by introducing hydrogen only when the mass of the precursor is at a temperature of at least 300°C.

[0054] Alternatively or additionally, hydrogen gas can only be introduced once a temperature of 400°C to 600°C has been reached. After hydrogenation, the working component can contain at least 0.18 wt.% hydrogen.

[0055] To form the intermediate product that is a La 1-a Ra (Fe 1-x-y T y M x ) 13 H z If the phase has z = 0, the pre-product powder mixture can be prepared at a temperature T sinter , where 1050°C ≤ T sinter ≤ 1200°C, are heat-treated.

[0056] A multi-step heat treatment process can also be used to heat-treat the powder mixture and to produce the intermediate product. In one embodiment, a multi-step heat treatment includes an initial residence time at T sinter for a time t1 in a vacuum and a time t2 in argon, followed by cooling at a temperature T2, where T2 < T sinterThis is followed by a second residence time at T2 for a time of t3, followed by rapid cooling. Typical parameter ranges for such a multi-step heat treatment can be 1000°C ≤ T2 ≤ 1080°C and / or 0.5 h ≤ t1 ≤ 10 h and / or 0.5 h ≤ t2 ≤ 10 h and / or 1 h ≤ t3 ≤ 20 h and / or rapid cooling at a rate of 5 to 200°C / min.

[0057] In embodiments where the working component has a silicon content, the silicon content, Si act the work component within ±5% or ±2% of the Si m lay.

[0058] The mixing of the pre-product powder can be carried out using steel balls or, optionally, with isopropanol to ensure more thorough mixing of the elements. The grinding time can be limited to a maximum of one hour.

[0059] The working component can be supplied in a number of shapes, depending on the design of the magnetic heat exchanger. Subsequently, the working components can be milled to produce a working component powder. This powder can then be heat-treated at temperatures ranging from 100°C to 200°C for 5 to 60 minutes. This heat treatment can be carried out in argon.

[0060] If the working component is provided in the form of a block, whether a sintered block or a reactively sintered block, it may be desirable to machine the working component by removing at least one part to change its external dimensions. For example, it may be desirable to split the working component into two or more separate parts and / or to adjust the external dimensions and / or to introduce channels or through-holes into the working component through which a heat exchanger fluid can flow.

[0061] The at least one section can be removed from that of the working component by one or more machining steps, mechanical grinding, mechanical polishing, chemomechanical polishing, electric spark cutting, wheel erosion cutting, laser cutting and laser drilling or by waterjet cutting.

[0062] However, it was found that the magnetocalorically active phase is difficult to machine due to its mechanical instability. Therefore, a number of alternative methods are employed to remove one or more sections of the working component in such a way as to reliably achieve the desired external dimensions.

[0063] In one embodiment, at least one section of the working component is removed, while the working component is maintained at a temperature above or below the Curie temperature. This prevented unwanted breakage of the working sample.

[0064] Heating or cooling the object can be carried out by applying a heated or cooled working fluid such as water, an organic solution, or oil, for example.

[0065] Without being bound by theory, if the temperature of the object changes during processing, causing the object to undergo a phase change, this phase change may result in the formation of cracks within the object.

[0066] The magnetocalorically active phase can exhibit a temperature-dependent transition in length and volume. In this case, at least one section can be removed at a temperature above or below the transition temperature to prevent a transition in length or volume during the removal of the section(s). The temperature at which this transition in length or volume occurs can roughly correspond to the Curie temperature.

[0067] This transition can be achieved by (L 10% –L 90% ) × 100 / L (T) > 0.35, where L is the length of the object at temperatures below the transition, L 10%the length of the object at 10% of the maximum length change is and L 90% This range represents 90% of the maximum length change. It characterizes the fastest change in length per unit temperature T.

[0068] Performing the machining of the object by removing one or more sections while maintaining the object at a temperature where no phase change occurs prevents phase changes from occurring during machining and avoids any stress associated with phase changes during the machining process. Therefore, the object can be machined reliably, the production rate increased, and production costs reduced.

[0069] A combination of these processes can also be applied to a single object. For example, the object can be singulated into two or more parts by removing part of the object through wire EDM cutting, and then the surfaces can be subjected to mechanical grinding, removing further sections to provide the desired surface finish or more precisely defined external dimensions.

[0070] Typically, removing sections of the workpiece, for example by grinding or sawing, generates heat within the workpiece due to friction between the tool and the workpiece. Therefore, active cooling at a temperature sufficient to compensate for this heat generation protects the magnetocalorically active phase from undergoing a phase change, allowing the workpiece to be reliably shaped into the desired external dimensions.

[0071] In a further set of embodiments, the working component is heat-treated to decompose the magnetocalorically active phase and to create an intermediate. This intermediate can then be machined, for example, to remove at least a portion of it, and the intermediate or intermediates can be heat-treated again after machining to regenerate the magnetocalorically active phase. By removing sections from the intermediate that do not contain a magnetocalorically active phase, such as a La 1-a R a (Fe 1-x-y T y M x ) 13 H z If the phase contains a substantial amount, the intermediate can be reliably processed without unwanted breakage of the intermediate.

[0072] Especially in this case of the processed objects, which contain the magnetocalorically active phase La 1-a R a (Fe 1-x-y T y Mx ) 13 H z When the objects contain phases and have larger dimensions, for example blocks with dimensions of at least 5 mm up to several tens of millimeters, the inventors have recently observed that undesirable fractures are formed in the objects during processing, which limits the number of smaller objects with desired dimensions that can be produced from one large object.

[0073] The inventors further observed that this undesirable breakage can be largely avoided by heat-treating the object to form an intermediate element containing a permanent magnet. The intermediate element has a coercive field strength greater than 10 Oe, according to the definitions of permanent magnets used here.

[0074] Without being bound to the theory, it is assumed that the observed breakage of objects exhibiting the magnetocalorically active phase during processing could be caused by a temperature-dependent phase change occurring within the magnetocalorically active phase. This phase change could be a change in entropy, a change from ferromagnetic to paramagnetic behavior, a change in volume, or a change in linear extent.

[0075] By performing the machining of the object while it is in a non-magnetocalorically active machining state, the phase change that occurs in the object during machining is avoided, as is any stress associated with this phase change. Therefore, the object can be machined reliably, increasing the production rate and reducing production costs.

[0076] In one embodiment, the working component is heat-treated at a temperature T2 to form an intermediate article having at least one permanent magnetic phase, wherein T2 < T sinter T2 can be in the range of 600°C to 1000°C.

[0077] The work component can be selected under conditions to determine the La 1-a R a (Fe 1-x-y T y M x ) 13 H zPhase which is a NaZn 13 The intermediate must have a -type crystal structure to decompose and form at least one α-Fe-type phase in it. The heat treatment conditions can be selected to produce an intermediate with an α-Fe content greater than 50 vol%. The intermediate can then be processed at room temperature.

[0078] After the intermediate has been machined by removing at least one section of the intermediate, the intermediate can be heat-treated to produce a final component product containing at least one magnetocalorically active La 1-a R a (Fe 1-x-y T y M x ) 13 H z The intermediate can be heat-treated at a temperature T3 to produce the final product, which has at least one magnetocalorically active La. 1-a R a (Fe 1-x-y Ty M x ) 13 H z has a phase where T3 > T2. In one embodiment, T3 < T sinter T3 can be around 1050°C.

[0079] The composition of the working component can be chosen to allow for a reversible decomposition of the phase with the NaZn 13 -Type crystal structure to generate at T2 and to reverse the NaZn 13 -Type crystal structure to be generated at T3.

[0080] In one embodiment, the composition of at least one La 1-a R a (Fe 1-x-y T y M x ) 13 H z The phase was selected to exhibit a reversible decomposition reaction. This allows the La 1-a R a (Fe 1-x-y T y M x ) 13 H zThe phase is formed in a first step, which is decomposed to provide the intermediate product and then regenerated in a further heat treatment when the machining is complete.

[0081] The composition of at least one La 1-a R a (Fe 1-x-y T y M x ) 13 H z The phase can be chosen to exhibit a reversible phase decomposition reaction into at least one α-Fe-based phase and La-rich and Si-rich phases.

[0082] In another embodiment, the composition of the at least one La 1-a R a (Fe 1-x-y T y M x ) 13 H z Phase selected so that at least one La 1-a R a (Fe 1-x-y T y M x ) 13 H zThe phase can be formed through liquid-phase sintering. This makes it possible to produce an object with a high density, and also an object with a high density that can be manufactured in an acceptable time.

[0083] In one embodiment, the intermediate item has an overall composition in which a = 0, T is Co and M is Si and z = 0, and in a first embodiment 0 < y ≤ 0.075 and 0.05 < x ≤ 0.1, when a = 0, T is Co and M is Si and z = 0.

[0084] In further embodiments, the intermediate object comprises the following magnetic properties: B r > 0.35 T and H cJ > 80 Oe and / or B s > 1.0 T.

[0085] The intermediate object can have a coercive field strength greater than 10 oe but less than 600 oe. Objects with such a coercive field strength are sometimes also referred to as semi-hard magnets.

[0086] The intermediate can comprise a compositional structure featuring a non-magnetic matrix and a variety of α-Fe inclusions distributed throughout the non-magnetic matrix. As used herein, non-magnetic refers to the condition of the matrix at room temperature and includes paramagnetic and diamagnetic materials, as well as ferromagnetic materials with very low saturation polarization.

[0087] The embodiments will now be described with reference to the drawings.

[0088] Fig. Figure 1 shows an object for magnetic heat exchange which has five separate working components,

[0089] Fig. Figure 2 shows a graph of the entropy change for a magnetic field change of 16 kOe as a function of temperature for different Mn contents.

[0090] Fig. Figure 3 shows differential scanning calorimetry measurements for a sample with a manganese content of 2.5 wt.% both in the prepared state and after storage for 45 days at 11°C.

[0091] Fig. Figure 4 shows differential scanning calorimetry measurements for a sample with a manganese content of 2.0 wt.% both in the prepared state and after storage for 45 days at 26°C.

[0092] Fig. Figure 5 shows a comparison sample that has a lower hydrogen content.

[0093] Fig. Figure 6 shows a graph of the temperature dependence of the adiabatic temperature change in a magnetic field at 19.6 kOe for three different samples and a Gd comparison.

[0094] Fig. Figure 7 shows a graph of the entropy change upon a magnetic field change of 16 kOe as a function of temperature for essentially fully hydrogenated samples containing different metallic substitutions.

[0095] Fig. Figure 8 shows a graph of the entropy change for samples with different Mn and Si contents.

[0096] Fig. Figure 9 shows the entropy change as a function of temperature for a group of samples according to a second embodiment,

[0097] Fig. Figure 10 shows the entropy change as a function of temperature for a group of samples according to a second embodiment,

[0098] Fig. Figure 11 shows a graph illustrating the decrease in Curie temperature for increasing manganese content, and

[0099] Fig. Figure 12 shows a graph of the manganese content and hydrogen content of the samples of the second embodiment.

[0100] Fig. 1 shows an object 1 for a magnetic heat exchange involving five working components 2 , 3 , 4 , 5 , 6 exhibits each of the work components 2 , 3 , 4 , 5 , 6 includes a magnetocaloric active phase, which La 1-a R a (Fe 1-x-y T y M x ) 13 H z M can contain one or more of the elements in the group consisting of Al and Si. T can contain one or more of the elements in the group consisting of Co, Ni, Mn, Cr, Cu, Ti and V, and R can contain one or more of the elements in the group consisting of Ce, Nd, Y and Pr.

[0101] The hydrogen content, z, of each of the working components is 90% or higher than a hydrogen saturation value, z satThe values ​​for a, x, and y are chosen to define the function of each work component. 2 , 3 , 4 , 5 , 6 to assign a different Curie temperature T. The different Curie temperatures are not achieved by essentially expanding the working components through partial dehydration, but by selecting appropriate amounts of the elements R, T, and M.

[0102] T cmax La is the Curie temperature of the respective working component 1-a R a (Fe 1-x-y T y M x ) 13 H z Phase that has a hydrogen content z = zsat and the selected values ​​of a, x and y for each work component 2 , 3 , 4 , 5 , 6 The work components 2 , 3 , 4 , 5 , 6 are at least 90% fully hydrogenated, so that the Curie temperature T cfor each of the working components within 20 Kelvin of T cmax lies. In other words (T cmax – T c ) ≤ 20 K. In this particular embodiment, for each of the working components 2 , 3 , 4 , 5 , 6 The element M Si and the element T is Mn and the element R is omitted.

[0103] The Curie temperature T c the work components 2 , 3 , 4 , 5 , 6 lies within ±10 K of the value of the Curie temperature, T c(calc) , derived from the relationship T c(calc) (°C) = 80.672 – 26.957 x Mn m , where Mn m The metallic fraction of manganese by weight. By adjusting the amount of manganese in the working component. 2 , 3 , 4 , 5 , 6The Curie temperature of the working component can be selected so that it lies within a range of +80°C to -90°C.

[0104] The values ​​of x and y satisfy the following relationship for each of the working components: the metallic weight fraction for Si, Si act , lies within ±5% of the value of the metallic weight fraction of silicon, Si m , derived from the relationship Si m = 3.85 – 0.0573 × Co m – 0.045 × Mn m 2 + 0.2965 × Mn m By adjusting the silicon content in relation to the amount of substituting metals R and T, the NaZn 13 -Type structure can be stabilized.

[0105] In this embodiment, each of the working components 2 , 3 , 4 , 5 , 6The elements are produced by reactive sintering or by pre-production of them in the form of working components in the form of a reactive sintered block. In other embodiments, the working components comprise powder, a sintered block, or a compact powder.

[0106] The work components 2 , 3 , 4 , 5 , 6 can also be provided as a composition that still has a magnetocalorically passive phase, such as copper, in which the magnetocalorically active phases are embedded.

[0107] The work components 2 , 3 , 4 , 5 , 6 are in the object 1 arranged such that T c the work components sequentially in a longitudinal direction of the object 1 increases. This arrangement produces better overall cooling quality when the object 1is used in a magnetic heat exchanger.

[0108] The work components 2 , 3 , 4 , 5 , 6 can be used using one of the following embodiments.

[0109] In one embodiment, La, Fe, and Si are mixed as precursor alloys with either 1.67 wt.% or 10 wt.% manganese powder and milled in a jet mill under a protective atmosphere to produce two fine powders with a particle size of approximately 6 μm. The two powders are mixed together in appropriate proportions to generate four different powders with varying manganese contents. Each of the samples includes 18 wt.% La, 4.2 wt.% Si, and one of each of 1.67 wt.%, 2.0 wt.%, 2.5 wt.%, and 3.0 wt.% Mn, with the balance being Fe.

[0110] The powders are isostatically pressed to form a green body and sintered at 1100°C for 4 hours, followed by cooling to 1050°C over 72 hours. After a residence time of 6 hours at 1050°C, the samples are cooled at approximately 50°C per minute to a temperature below 300°C. The samples are then heated to 500°C under argon, and the argon is replaced with hydrogen at 1.9 bar at this temperature. The samples are then cooled to room temperature over 6 hours in a hydrogen-containing atmosphere. This heat treatment yields a material with particles approximately 10 mm in size. These particles are mechanically milled and sieved to produce a particle size of less than 250 μm. These powders are then heated to 150°C for 15 minutes.

[0111] Fig. Figure 2 shows a graph of the entropy change (–ΔS m) after applying a magnetic field change of 16 kOe as a function of temperature (in °C) for the four compositions, it shows that an increase in manganese content leads to a systematic reduction in the measured peak temperature. The measured peak temperature corresponds to the Curie temperature.

[0112] The following relationship can be used to provide a suitable Mn content to achieve the desired T c to provide for fully or substantially fully hydrated samples: T c (°c) = 80.672 – 26.957 × Mn m where Mn m The metallic weight fraction of manganese is...

[0113] Fig. Figure 3 shows differential scanning calorimetry measurements for the sample with a manganese content of 2.5 wt.% in the prepared state and after storage for 45 days at the Curie temperature. The position of the peaks and the shape of the curves did not change significantly after storage.

[0114] Fig. Figure 4 shows differential scanning calorimetry measurements for the sample with a manganese content of 2.0 wt.% in the prepared state and after storage for 45 days at the Curie temperature. The position of the tip and the shape of the curve did not change significantly after storage.

[0115] Fig. Figure 5 shows a comparison sample with a lower hydrogen content estimated at 1.145 wt.%. The composition of the sample is La1. . 04 (Fe 0.88 Si 0.12 ) 13The lower hydrogen content was achieved by hydrogenating the sample at 241°C for 4 hours in a mixture of 22% hydrogen and 78% helium. Differential scanning calorimetry curves were obtained from this sample before and after storage at 35°C for 35 days at approximately the Curie temperature of 36°C (±0.5°C). Before storage, the sample is characterized by a single, relatively narrow peak. After 35 days of storage, two peaks can be observed, indicating that the sample is unstable and has decomposed into two phases, each with a different Curie temperature. Unstable material with an unstable Curie temperature is undesirable for use in practical magnetic heat exchangers.

[0116] The temperature dependence of the diabatic temperature change (ΔT) AD ) in a magnetic rock of 19.6 kOe was measured for the following three samples in comparison to Gd and is shown in the graph of the Fig. 6 shown.

[0117] The sample 1012 It has a composition of 2.2 wt.% Mn and a hydrogen content of 0.187 wt.% and is essentially completely hydrogenated.

[0118] The sample 1015 It has a composition of 17.8 wt.% La, 3.81 wt.% Si, balance Fe, and is almost completely saturated with hydrogen.

[0119] The sample 1014 It has a composition of 17.8 wt.% La, 3.81 wt.% Si, balance Fe, and is partially dehydrated.

[0120] The measurements were initially varied by adjusting the magnetic field between 0 and 19.6 kOe while the temperature increased. The temperature change for each sample was measured using a thermocouple. After the maximum temperature was reached, the adiabatic temperature change was measured again while the temperature decreased. For the manganese-free sample... 1015It was found to exhibit a clear hysteresis effect, which is undesirable for use in magnetic heat exchangers. The manganese-containing sample 1012 exhibits significantly lower hysteresis than the manganese-free samples. 1014 and 1015 The temperature change for the fully hydrogenated sample 1015 is larger than that for the partially dehydrated sample 1014 .

[0121] Therefore, the fully hydrated sample 1012 With a Curie temperature determined by a suitable manganese content, it is stable when stored at the Curie temperature for up to 45 days, exhibits low hysteresis, and a large temperature range. This combination of characteristics is desirable for a working component of a practical magnetic heat exchanger.

[0122] In another embodiment, a reduction of the Curie temperature from the value obtained by complete hydrogenation of La(Fe, Si) was achieved. 13 The phase was achieved through the use of substitution of Ce, Nd, and Pr, also in combination with manganese and Mn. The composition of the samples is shown in Table 1. In Table 1, RE denotes the amount of the additional rare earth elements Pr, Ce(MM), and Nd, excluding the La content. The compositions are: 17.8 wt.% La, 3.8 wt.% Si, balance Fe; 5.2 wt.% Pr, 12.7 wt.% La, 3.8 wt.% Si, balance Fe; 7.0 wt.% Ce(MM), 10.6 wt.% La, 3.9 wt.% Si, balance Fe; 6.0 wt.% Nd, 11.9 wt.% La, 4.4 wt.% Si, balance Fe; 2.9 wt.% Pr, 15.4 wt.% La, 2.2 wt.% Mn, 4.2 wt.% Si, balance Fe, and 6.1 wt.% Ce(MM), 11.9 wt.% La, 1.9 wt.% Mn, 4.6 wt.% Si, balance Fe.

[0123] Fig. Figure 7 shows a graph of the entropy change (–ΔS m) for a magnetic field change of 16 kOe as a function of temperature for essentially fully hydrogenated samples containing different metallic substitutions.

[0124] The samples were assembled by mixing suitable starter powders, prepared similarly to the preceding embodiments, in appropriate quantities and by isostatic pressing to form green bodies, which were then sintered at different temperatures in the range of 1090°C to 1160°C. The sintering temperature for each composition is given in Table 1. After sintering, the samples were homogenized at 1050°C for 6 hours and rapidly cooled to room temperature.

[0125] To hydrogenate the samples, they were heated in argon at 500°C, the argon was replaced with hydrogen at 1.9 bar, and the samples were slowly cooled to room temperature. The compositions of the samples are summarized in Table 1.

[0126] The La(Fe, Si) 13 The -phase has a Curie temperature of +85°C. By substituting only Ce, Nd, or Pr, a reduction in the Curie temperature was observed compared to one of the ternary compositions La(Fe, Si) 13 Cerium in the form of a cerium mischmetal (Ce(MM)) containing a composition of 26.2 wt.% La, 16 wt.% Nd, 5.2 wt.% Pr, balance Ce, was used. The combination of Pr and Mn and Ce and Mn leads to a greater reduction in the Curie temperature than the use of Pr, Nd, or Ce alone. The entropy change for the samples containing Pr, Nd, and Ce alone is not significantly lower than that obtained with Mn alone (see [reference]). Fig. 2.

[0127] The combination of Ce and Mn can be used to adjust the peak temperature across the entire temperature range that is technically relevant for domestic cooling.

[0128] Fig. Figure 8 shows a graph with maximum entropy change (–ΔS m,max ) for samples that have different Mn and Si contents. Fig. Figure 8 shows that a reduction in entropy change for a (La, Ce)(Fe, Mn, Si) 13 The composition with 3.8 wt.% Ce(MM) can be at least partially compensated for by a suitable increase in the silicon content. The following relationship was found to be helpful for calculating a suitable silicon content: Si m = 3.85 – 0.045 × Mn m 2 + 0.2965 × Mn m where Si m the metallic weight fraction of silicon is and Mn m The metallic weight fraction of manganese is...

[0129] When cobalt is present in combination with manganese, the following relationship has been found to be helpful: Si m = 3.85 – 0.0573 × Co m – 0.045 × Mn m 2 + 0.2965 × Mnm , where Si m The metallic fraction of silicon by weight is Mn. m the metallic weight fraction of manganese is and Co m The metallic weight fraction of cobalt is...

[0130] If Ce(MM) is present, the silicon content is selected according to the following relationship: Si m = 3.85 – 0.045 × Mn m 2 + 0.2965 × Mn m + (0.198 – 0.006 × Mn m ) × Ce (MM) m where Ce(MM) m is the metallic weight fraction of the cerium mischmetal.

[0131] In the following embodiment, five working components are desired with Curie temperatures of 8.5°C, 11.6°C, 14.9°C, 18.2°C, and 21.3°C. The equations above were used to determine the La, Si, and Mn compositions required to generate Curie temperatures of 3.5°C and 26.3°C in a phase with the corresponding fully hydrogenated metallic components. The compositions are summarized in Table 2 and are 16.7 wt% La, 4.33 wt% Si, 2.86 wt% Mn, balance Fe, and 16.7 wt% La, 4.26 wt% Si, and 2.02 wt% Mn, balance Fe.

[0132] Precursor powders, prepared similarly to the preceding embodiments, were mixed to produce a total batch weight of about 2500 g, which was mixed in steel containers with 1250 g of steel balls having a diameter of 6 mm, 10 mm and 50 mm for 4 hours in a drum mill.

[0133] These two powders were mixed in appropriate amounts, as shown in Table 3, to achieve the desired five Curie temperatures of 8.45°C, 11.55°C, 14.85°C, 18.15°C, and 21.25°C. These powder mixtures were blended with 1.5% isopropanol, isostatically pressed, and sintered by heating to 1095°C for 3 hours under vacuum, followed by 1 hour in argon and cooling to 1050°C for 1 hour. This temperature was maintained for 6 hours before the samples were rapidly cooled to room temperature.

[0134] The five samples were individually wrapped in iron foil and hydrogenated as follows. The samples were heated under vacuum to 500°C, hydrogen was introduced into the furnace at 1.9 bar, and the samples were cooled to a temperature of less than 100°C. Samples 3 and 4 were cooled to room temperature more quickly. However, sample 4 was held overnight in an atmosphere of 1.9 bar hydrogen.

[0135] The magnetocaloric properties of the samples were measured and are shown in Table 4 and Fig. 9 summarized. In the tables and figures, samples 1, 2, 3, 4, and 5 are designated by VZ1003-MCE-1XX, VZ1003-MCE-2XX, and so on. Samples 3 and 4 were cooled more rapidly and had a Curie temperature corresponding to the temperature at which the greatest entropy change (-ΔSm) occurs. Fig. 9 occurs, which is slightly lower than the desired Curie temperature specified in Fig. Samples 1, 2, and 5, marked as the target, each had a similar Curie temperature to the desired value. Samples 3 and 4 were rehydrated and heated to 150°C, with the hydrogen atmosphere changed to 1.9 bar and then slowly cooled overnight. Table 4 and Fig. Figure 10 shows that after heat treatment, the Curie temperature of samples 3 and 4, marked by * in Table 4, and the position of the peak temperature relative to the target temperature shown in Fig. As shown in 10, near the desired T c lies.

[0136] The working components were milled and sieved to produce a powder with a mean particle size in the range of 250 μm to 400 μm. As can be seen from the results given in Table 5 for samples 1 and 3 compared with the results given in Table 4, this additional milling did not appear to significantly alter the magnetocaloric properties.

[0137] A further heat treatment was performed by heating the final samples to approximately 140°C in argon for about 30 minutes and then cooling them to room temperature in flowing argon. The effect of this stabilization heating treatment is represented by the two sets of data in Table 4, indicated by the column "stabilized".

[0138] As summarized in Table 6 and in the Fig. 11 and Fig. Shown in 12, the peak temperature T peak (°C), which corresponds to the temperature at which the greatest entropy change occurs and which corresponds to the Curie temperature, decreases with decreasing manganese content. As in Fig. As shown in Figure 12, the hydrogen content of the five samples with different manganese contents is generally similar. The different Curie temperatures are achieved by the increasing manganese content.

[0139] One possible explanation for the improved aging behavior of the fully hydrogenated samples is as follows. It can be assumed that even at room temperature, the hydrogen atoms interstitially bound via NaZn 13 -Type structure of the La 1-a R a (Fe 1-x-y T y M x ) 13 H z Phases arranged in a specific direction exhibit relatively high mobility. One indication of this is the observation of hydrogen loss from the structure at temperatures above approximately 150°C.

[0140] Furthermore, the magnetic phase transition in these alloys from the ferromagnetic state to the paramagnetic state is associated with a volume increase of approximately 1.5%. If a partially hydrogenated alloy, in which not all of the usual interstitial sets are filled with hydrogen atoms, is stored at a temperature near the Curie temperature, it is possible for the hydrogen atoms to move along the concentration gradient and diffuse from regions of low hydrogen content towards regions of high hydrogen content.

[0141] Hydrogen atoms can diffuse from the paramagnetic region, which has a low hydrogen content but a small volume, into the ferromagnetic region, which has a higher hydrogen content but also a larger lattice constant and a larger volume. This movement will likely occur at temperatures around the Curie temperature, since the volume difference between the two phases can be assumed to be the driving force in this region.

[0142] This provides an explanation for the stability of the fully hydrated la 1-a R a (Fe 1-x-y T y M x ) 13 H zThis phase occurs when the sample is stored at the Curie temperature, with all interstitial sites fully occupied. Therefore, hydrogen atoms cannot diffuse through the sample between occupied and unoccupied interstitial sites, creating low and high concentration regions.

[0143] However, since the fully hydrated La 1-a R a (Fe 1-x-y T y M x ) 13 H z If the phase has a Curie temperature greater than approximately +80°C, desired temperatures of less than +80°C can be suitable for cooling applications and can be produced by substituting suitable metal ions for La and Fe.

[0144] La can be substituted by rare earth elements such as Y, Nd, and Pr, which have small atomic radii. This should result in a reduction of the lattice parameters and a reduction in the Curie temperature. Alternatively or additionally, Fe can be substituted with 3d elements that have a lower coordination number and therefore a lower number of electrodes in the 3d band, which affects the magnetism. Substitutions of Mn, Cr, V, and Ti for Fe can lead to a reduction in the Curie temperature. If temperatures above +80°C are desired, this can be achieved by substituting the Fe with Co and / or Ni.

[0145] If a Curie temperature close to 80°C is desirable, elements such as Mn and Co can both be placed in the La(Fe,Si) 13 )H zPhase substitution occurs. In this case, each of the substituting metallic elements loses its effect on the Curie temperature relative to the other. However, alloys of this composition exhibit a narrower hysteresis compared to La(Fe,Si) alloys. 13 H z Alloys with the same Curie temperature, but without the two differently substituting elements.

[0146] However, for all metallic compositions, the hydrogen content should be kept as high as possible in order to provide a stable Curie temperature. QUOTES INCLUDED IN THE DESCRIPTION

[0147] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0148] US 6676772

[0005] US 7063754

[0007]

Claims

[1] Working component for a magnetic heat exchange, comprising: a magnetocaloric active phase, La 1-a R a (Fe 1-x-y T y M x ) 13 H z exhibits a hydrogen content, e.g., with 90% or higher of a saturation value, e.g. sat , and has values ​​for a, x and y that are selected to define a Curie temperature T c to give, wherein M is one or more of the elements from the group consisting of Al and Si, T is one or more of the elements from the group consisting of Co, Ni, Mn, Cr, Cu, Ti and V, and R comprises one or more of the elements from the group consisting of Ce, Nd, Y and Pr, wherein T cmax the Curie temperature of a la 1-a R a (Fe 1-x-y T y M x ) 13 H z Phase is one that has a hydrogen content of z = z sat and the selected values ​​for a, x and y, where (T cmax – Tc ) ≤ 20 K. [2] Working component according to claim 1, wherein the hydrogen content, z, is 95% or higher of the hydrogen saturation value, z sat , and (T cmax – T c ) ≤ 10 K is. [3] Working component according to claim 1 or claim 2, wherein 1,2 ≤ z ≤ 3 or 1,4 ≤ z ≤ 3. [4] Working component according to any one of claims 1 to 3, wherein 0.05 ≤ x ≤ 0.3, 0.003 ≤ y ≤ 0.2 and optionally 0.005 ≤ a ≤ 0.

5. [5] Working component according to any one of claims 1 to 3, wherein 0.005 ≤ a ≤ 0.5 and 0.05 ≤ x ≤ 0.2 and 0.003 ≤ y < 0.

2. [6] The working component according to any one of claims 1 to 5, wherein T is Mn and the Curie temperature T is c the work component within ±10 K of the value of the Curie temperature, T c(calc) , is derived from the relationship T c(calc) (°C) = 80.672 – 26.957 × Mn m , where Mn m The metallic weight fraction of manganese is... [7] Working component according to claim 6, wherein T c within ±5 K of the T c(calc) lies. [8] Working component according to any one of claims 1 to 7, wherein M is Si and the metallic weight fraction of Si, Si act , within ±5% of the value of the metallic weight fraction of silicon, Si m , lies, where Si m is derived from the relationship Si m = 3.85 – 0.0573 × Co m – 0.045 × Mn m 2 + 0.2965 × Mn m , where Co m the metallic weight fraction of cobalt and Mn m The metallic weight fraction of manganese is... [9] Working component according to any one of claims 1 to 7, wherein M is Si and the metallic weight fraction of Si, Si act , within ±5% of the value of the metallic weight fraction of silicon, Si m , which is derived from the relationship Si m = 3.85 – 0.045 × Mn m 2+ 0.2965 × Mn m + (0.198 – 0.066 × Mn m ) × Ce(MM) m , where Mn m the metallic weight fraction of manganese is and Ce(MM) m The metallic weight fraction of a cerium mischmetal. [10] Working component according to claim 8 or claim 9, wherein Si act within ±-2% of Si m lies. [11] Working component according to any one of claims 1 to 10, wherein the working component comprises powder or a sintered block or a relatively sintered block or a compacted powder. [12] Working component according to any one of claims 1 to 11, wherein the working component has a peak in a graph of heat flux versus temperature, wherein the peak has a width and a maximum, wherein the maximum corresponds to the Curie temperature. [13] Working component according to claim 12, wherein after storing the working component at a temperature within ±1°C of the Curie temperature of the working component for 30 days the size of the tip increases by less than 20%. [14] Working component according to claim 13, wherein after storing the working component at a temperature of ±1°C of the Curie temperature of the working component for 40 days the size of the tip increases by less than 20%. [15] Working component according to one of claims 12 to 14, wherein after storage the working component at a Curie temperature of the working component for 30 days the size of the tip increases by less than 20%. [16] Working component according to any one of claims 1 to 15, wherein the working component further comprises a magnetocaloric passive phase. [17] Working component according to claim 16, wherein the magnetocaloric passive phase provides a matrix in which the magnetocaloric active phase is embedded. [18] An article for magnetic heat exchange comprising two or more working components according to any one of claims 1 to 17, wherein the two or more working components have different values ​​for a and / or x and / or y and different Curie temperatures. [19] The object according to claim 18, wherein the object comprises at least three working components arranged such that the Curie temperature of the at least three working components increases in one direction of the object. [20] Method for manufacturing a working component for magnetic cooling comprising: Selecting a desired Curie temperature, Selecting a set of one or more elements T, R and M, where T is one or more of the elements of the group consisting of Mn, Co, Ni, Cu, Ti, V and Cr, R is one or more components of the elements of a group consisting of Ce, Nd, Y and Pr, M is one or more elements of Si and Al, and the quantity of the one or more elements T, R and M are selected to produce a desired Curie temperature when a La 1-a R a (Fe 1-x-y T y M x ) 13 H z The phase contains a hydrogen content that is at least 90% of a hydrogen saturation value, e.g. sat , exhibits, Mixing the quantity of the selected elements T, R and M with La and Fe or precursors thereof in quantities suitable to increase the La 1-a R a (Fe 1-x-y T y M x ) 13 H z to generate a phase with the desired Curie temperature in order to produce a precursor powder mixture, Heat treatment of the precursor powder mixture to produce an intermediate product that has a La 1-a R a (Fe 1-x-y T y M x ) 13 H z Phase with z = 0, Hydrogenation of the intermediate to produce a working component which the La 1-a R a (Fe 1-x-y T y M x ) 13 H z phase exhibiting the desired Curie temperature and a hydrogen content z of at least 90% of the hydrogen saturation value, z sat , exhibits. [21] Method according to claim 20, wherein the set of one or more elements R, T and M is selected within a range 0.05 ≤ x ≤ 0.2, 0.003 ≤ y ≤ 0.2 and optionally 0.005 ≤ a ≤ 0.

5. [22] Method according to claim 20 or claim 21, wherein the set of one or more elements R, T and M is selected within the ranges 0.005 ≤ a ≤ 0.5 and 0.05 ≤ x ≤ 0.2 and 0.003 ≤ y ≤ 0.

2. [23] Method according to any one of claims 20 to 22, wherein the elements T Mn and the amount of manganese Mn m includes achieving the desired Curie temperature T c to generate which according to T c (°c) = 80.672 – 26.957 x Mn m is selected, where Mn m a metallic weight fraction of manganese. [24] Method according to any one of claims 20 to 23, wherein M is Si and the amount of Si is selected according to the Si m = 3.85 – 0.0573 × Co m – 0.045 × Mn m 2 + 0.2965 × Mn m , where Si m the metallic weight fraction of silicon, Mn m the metallic weight fraction of manganese and co m The metallic weight fraction of cobalt is... [25] Method according to any one of claims 20 to 23, wherein M is Si and the amount of Si is selected to be Si m = 3.85 – 0.045 x Mn m 2+ 0.2965 × Mn m + (0.198 – 0.066 x Mn m ) × Ce(MM) m , where Si m the metallic weight fraction of silicon, Mn m the metallic weight fraction of manganese and Ce(MM) m is the metallic weight fraction of the cerium mischmetal. [26] Method according to any one of claims 20 to 25, wherein the precursor is a powder mixture which is pressed to form one or more green bodies. [27] Method according to any one of claims 20 to 26, wherein the intermediate is hydrogenated to increase the La 1-a R a (Fe 1-x-y T y M x ) 13 H z To generate a phase with a hydrogen content z of 1.2 ≤ z ≤ 3. [28] Method according to any one of claims 20 to 27, wherein the hydrogenation comprises a heat treatment under an H2 partial pressure of 0.5 to 2 bar. [29] Method according to any one of claims 20 to 28, wherein an H2 partial pressure is increased during hydrogenation. [30] Method according to any one of claims 20 to 29, wherein the hydrogenation comprises heat treatment at a temperature in the range of 0°C to 100°C. [31] Method according to claim 30, wherein the hydrogenation comprises a heat treatment at a temperature in the range of 15°C to 35°C. [32] Method according to any one of claims 20 to 31, wherein the hydrogenation involves a residence time at a temperature T hyd includes, where 300°C ≤ T hyd ≤ 700°C. [33] The method of claim 32, wherein the hydrogenation involves a residence time at a temperature T hyd includes, where 300°CT hyd ≤ 700°C, followed by cooling to a temperature of less than 100°C. [34] Method according to any one of claims 30 to 33, wherein the hydrogenation comprises: Heating the intermediate product from a temperature of less than 50°C to at least 300°C in an inert atmosphere, Hydrogen gas should only be introduced when a temperature of at least 300°C has been reached. Maintaining the intermediate product in a hydrogen-containing atmosphere at a temperature in the range of 300°C to 700°C for a selected duration, and Cooling the intermediate product to a temperature of less than 50°C to produce the working component. [35] The method of claim 34, wherein the intermediate product is cooled to a temperature of less than 50°C in a hydrogen-containing atmosphere. [36] Method according to any one of claims 20 to 35, wherein hydrogen gas is only introduced when a temperature of 400°C to 600°C is reached. [37] Method according to any one of claims 20 to 35, wherein after hydrogenation the working component contains at least 0.18 wt.% hydrogen. [38] Method according to any one of claims 20 to 37, wherein the precursor powder mixture is heat-treated at a temperature T sinter , where 1050°C ≤ T sinter ≤ 1200°C. [39] Method according to any one of claims 20 to 38, wherein a multi-step heat treatment process is used to heat treat the pre-product powder mixture. [40] Method according to claim 39, wherein the multi-step heat treatment includes a first residence time at T sinter for a time t1 in vacuum and a time t2 in argon, followed by cooling to a temperature T1, where T1 < T sinter , followed by a second residence time at T1 for a time t3, followed by rapid cooling. [41] Method according to claim 40, wherein 1000°C ≤ T1 ≤ 1080°C and / or 0.5 h ≤ t1 ≤ 10 h and / or 0.5 h ≤ t2 ≤ 10 h and / or 1 h ≤ t3 ≤ 20 h and / or rapid cooling is carried out at a rate of 5 to 200°C / min. [42] Method according to any one of claims 24 to 41, wherein the working component has a silicon content Si, of Si act exhibits, which is within ±5% of Si m lies. [43] Method according to claim 42, wherein Si act within ±2% of Si m lies. [44] Method according to any one of claims 20 to 34, wherein the mixing is carried out using steel balls and optionally under isopropanol. [45] Method according to any one of claims 20 to 44, further comprising grinding the working component to produce a working component powder. [46] Method according to claim 45, further comprising a heat treatment of the working component powder at a temperature in the range of 100°C to 200°C for 5 to 60 minutes. [47] Method according to claim 46, wherein the heat treatment is carried out in argon. [48] ​​A method according to any one of claims 20 to 47, further comprising removing at least one section of the working component while the working component is at a temperature above the Curie temperature T c or below the Curie temperature T c is held. [49] Method according to claim 48, wherein the working component is heated to a temperature sufficient to prevent the magnetocaloric phase from undergoing a phase change during the removal of the section of the working component. [50] Method according to one of claims 48 or 49, wherein after the formation of the magnetocalorically active phase, the working component is heated at a temperature above its magnetic phase transition temperature T c will be held until the processing of the work component is completed. [51] Method according to claim 48, wherein the working component is cooled to a temperature sufficient to prevent the magnetocaloric phase from undergoing a phase change during the removal of the section of the component. [52] Method according to any one of claims 48 to 51, wherein the magnetocalorically active phase exhibits a temperature-dependent transition in length or volume and the at least one section is removed in length or volume at a temperature above or below the transition temperature. [53] Method according to claim 52, wherein the transition is effected by (L 10% -L 90%) × 100 / L(T) > 0.35 is characterized. [54] Method according to any one of claims 40 to 47, further comprising: Heat-treating the working component at a temperature T2 to form an intermediate object having at least one permanent magnetic phase, where T2 < T sinter is. [55] Method according to claim 54, wherein the working component is heat-treated under conditions selected to ensure the La 1-a R a (Fe 1-x-y T y M x ) 13 H z Phase that includes a NaZn 13 -Type crystal structure, to decompose and form at least one α-Fe-type phase in the intermediate. [56] Method according to claim 54 or 55, wherein the working component is heat-treated under conditions selected to produce an α-Fe content greater than 50 vol% in the intermediate. [57] Method according to any one of claims 54 to 56, further comprising: Machining the intermediate by removing at least one section of the intermediate, and then heat-treating the intermediate to produce a second machined component product that has at least one magnetocaloric active La 1-a R a (Fe 1-x-y T y M x ) 13 H z exhibits phase. [58] Method according to claim 57, wherein the intermediate is heat-treated to produce an α-Fe content of less than 5 vol% in the second processed component product. [59] Method according to claim 57 or claim 58, wherein the intermediate is heat-treated at a temperature T3 to produce the second machined component product, wherein T3 > T2. [60] Method according to claim 59, wherein T3 < T sinter is. [61] Method according to any one of claims 54 to 60, wherein the composition of the working component is selected to ensure reversible decomposition of the phase with the NaZn 13 -Type crystal structure to generate at T2 and to reverse the NaZn 13 -Type crystal structure to be produced at T3. [62] Method according to any one of claims 48 to 61, wherein at least one section is removed by one or more machining operations, mechanical lubrication, mechanical polishing, chemomechanical polishing, electric spark cutting, wire erosion cutting, laser cutting and laser drilling or water jet cutting. [63] Method according to any one of claims 48 to 62, wherein the at least one section is removed in such a way as to produce at least two separate parts. [64] Method according to any one of claims 48 to 63, characterized in that the at least one section is removed in such a way that at least one channel is formed in a surface or at least one through-hole is created.

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