Transparent porous rare earth material, porous rare earth material precursor, and preparation method

Abstract

The present invention discloses a transparent porous rare earth material, a porous rare earth material precursor, and a preparation method. The raw material composition of the transparent porous rare earth material precursor includes the following components: an R-containing compound: 50.16-77.63wt%, wherein the rare earth element R in the R-containing compound is an oxidized rare earth element R; M: 17.94-37.30wt%, wherein M includes one or more of Ca, Li, Na, and Mg. The present invention prepares high-purity rare earth metals and alloys by thermal reduction of rare earth compounds containing Ca, Li, Na, and Mg, and combines this with a foaming process to directly prepare the transparent porous working medium material.

Description

Technical Field

[0001] The invention relates to a transparent porous rare earth material, a porous rare earth material precursor and a preparation method. Background Art

[0002] Rare earth metals and alloys can be used as magnetic refrigeration working fluid materials, and the available forms of the materials usually include porous, plate (sheet), spherical or granular. Spherical working fluids have good heat transfer effects, but large pressure drop losses; flat working fluids have low pressure drop, but the heat transfer effect is not as good as spherical working fluids. Porous working fluids can achieve an optimal balance between heat transfer effect and pressure drop loss, with a lower pressure drop than spherical working fluids and higher heat transfer than flat working fluids. However, porous rare earth metals and alloys have not yet been prepared. In addition, for spherical / granular working fluid materials, since rare earth metals and alloys have good toughness and ductility, it is very difficult to prepare granular and spherical working fluids using conventional preparation methods.

[0003] Taking granular working fluids as an example, pure rare earth metal ingots or rare earth metal alloy ingots are usually used, which are then crushed by hydrogen absorption and then dehydrogenated to obtain metal or alloy powder. Spherical working fluids, on the other hand, require the rare earth metal or alloy to be atomized (such as by gas atomization or rotating electrode atomization). These methods have disadvantages such as difficult crushing, multiple process steps, high raw material consumption, low powder output rate, low material yield, difficulty in large-scale production, high cost, and easy oxidation. Summary of the Invention

[0004] To address the above-mentioned issues, the present invention provides a transparent porous rare earth material, a porous rare earth material precursor, and a preparation method. The rare earth material may include La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, and Y as single elements; the rare earth material may also include an alloy composed of two or more of the rare earth elements La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, and Y.

[0005] The present invention selects Ca, Li, Na, and Mg metals (one of which can be selected alone or used in combination) to reduce rare earth metals to prepare porous rare earth materials (which can be rare earth metals or rare earth alloys). In addition to compensating for losses during the preparation process, excess Ca, Li, Na, and Mg also serve to increase melt viscosity, foaming, and bubble stability.

[0006] Preferably, relatively cheap rare earth fluoride raw materials are used for the initial preparation, and during thermal reduction, fluorides of Ca, Li, Na, and Mg metals (optionally, chlorides of Ca, Li, Na, and Mg metals) can be used to form slag, which has a certain purification effect on impurities in the metal, and the alloy has less slag inclusions. After separation and purification, a transparent and porous rare earth material (which can be a porous rare earth metal or a porous rare earth alloy, and when preparing a porous rare earth alloy, different rare earth fluorides need to be mixed in the required ratio at the beginning), and the transparent and porous rare earth material (which can be a rare earth metal or a rare earth alloy) can be directly used as a magnetic refrigeration medium.

[0007] The present invention also provides a raw material composition for preparing a transparent porous rare earth material precursor, which comprises the following components by weight percentage:

[0008] R-containing compound: 50.16-77.63 wt%, wherein the rare earth element R in the R-containing compound is an oxidized rare earth element R;

[0009] M: 17.94-37.30 wt%, wherein M comprises one or more of Ca, Li, Na and Mg.

[0010] In the present invention, the elemental M can act as a reducing agent, thereby separating the rare earth elements, and can also increase viscosity and foaming. During the preparation of the transparent, porous rare earth material RM, the rare earth element and the elemental M are preferably miscible but not combined, without chemically reacting to form a new compound. When a new compound is formed between the rare earth element and the elemental M, pores can be formed after the RM is formed, but removing the M requires breaking the chemical bonds.

[0011] In the present invention, the rare earth element R in the oxidized rare earth element R can be a rare earth metal element conventional in the art, such as one or more of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc and Y, and another example is Gd.

[0012] In the present invention, the R-containing compound may be one or more of rare earth metal fluoride (RF3), rare earth metal chloride (RCl3), rare earth alloy fluoride and rare earth alloy chloride, such as rare earth metal fluoride (RF3).

[0013] The rare earth metal fluoride may be a conventional rare earth metal fluoride in the art, such as GdF3.

[0014] Wherein, the purity of the rare earth metal fluoride may be no less than 99.9%.

[0015] In the present invention, the R content in the RM alloy after the R-containing compound is reduced by M is 70.00-99.00 wt%. The R content range can be determined according to the required pore size and porosity. The larger the pore and the higher the porosity, the higher the M ratio.

[0016] In the present invention, the content of the R-containing compound may be 50.16-76.03wt%, for example, 50.16wt%, 56.43wt%, 59.23wt%, 60.48wt%, 61.45wt%, 62.06wt%, 66.63wt%, 68.04wt%, 69.82wt%, 72.55wt%, 74.09wt% or 76.03wt%; the percentage refers to the weight percentage in the raw material composition.

[0017] In the present invention, the M may include one or more of Ca, Li and Na, for example, Ca and / or Na, and for example, Ca.

[0018] In the present invention, M may be one or more of Ca, Li, Na and Mg, preferably one or more of Ca, Li and Na, such as Ca and / or Na, and further such as Ca.

[0019] In the present invention, the purity of Ca in the M can be >99%.

[0020] In the present invention, the purity of the Li element and the Na element in the M can be >99.9%.

[0021] In the present invention, in the M, Mg may be a primary reduced magnesium ingot, and the purity may be >99.9%.

[0022] In the present invention, the content of M may be 17.94-36.55wt%, for example, 17.94wt%, 19.52wt%, 20.18wt%, 20.77wt%, 21.96wt%, 21.97wt%, 23.37wt%, 23.91wt%, 25.45wt%, 29.84wt%, 33.57wt% or 36.55wt%; the percentage refers to the weight percentage in the raw material composition.

[0023] In the present invention, the viscosity of the melt, the number and size of bubbles generated, and the stability of the bubbles can be regulated by controlling the addition amount of Ca, Li, Na, and Mg and stirring, thereby preparing transparent porous rare earth metals and alloys with different void sizes, and also making it easier to prepare rare earth metal and alloy granular magnetic refrigeration fluids with different particle sizes.

[0024] In the present invention, the rare earth element in the R-containing compound (such as R fluoride) and the Ca, Li, Na and Mg elements in M ​​form an RM alloy, where R is a rare earth element.

[0025] The amount of Ca, Li, Na and Mg in M ​​can be 1.03-2.12 times of their reaction equivalents.

[0026] Taking the thermal reduction of rare earth Gd by Ca as an example, the reaction equation is as follows.

[0027] 2GdF3+3Ca=2Gd+3CaF2

[0028] At this point, the molar ratio of rare earth fluoride to Ca is 2:3, resulting in a mass ratio of 78.09 wt% GdF3 to 21.91 wt% Ca. Ca is typically added in excess, such as a 3% increase. This 3% refers to the amount of Ca added relative to the reaction equivalent (the amount required to satisfy the chemical equation). Overall, the molar ratio of GdF3 to Ca changes from 2:3 to 2:3.09, resulting in a mass ratio of 77.63 wt% GdF3 to 22.37 wt% Ca. If Ca is added in excess by 20%, the molar ratio becomes 2:3.6, resulting in a mass ratio of 74.81 wt% GdF3 to 25.19 wt% Ca. Similarly, if Ca is added in excess by 112%, the molar ratio becomes 2:6.36, resulting in a mass ratio of 62.70 wt% GdF3 to 37.30 wt% Ca.

[0029] In the present invention, the added amount of Ca, Li, Na and Mg in M ​​is generally greater than the actual required amount for the reaction.

[0030] In the present invention, the excess addition amount of M may be 3-112 wt%, for example, 3-25 wt%, for example, 15-25 wt%, and for example, 20 wt%. The percentage refers to: (actual addition amount of M - addition amount of M that conforms to the chemical reaction equation) / addition amount of M that conforms to the chemical reaction equation * 100%.

[0031] The calculation method of the excess addition amount is as follows:

[0032] “The actual addition amount of Ca, Li, Na and Mg in the M” - “the addition amount of Ca, Li, Na and Mg that conforms to the chemical reaction equation” / “the addition amount of Ca, Li, Na and Mg that conforms to the chemical reaction equation” * 100%.

[0033] In the present invention, the raw material composition may further include one or more of Ca fluoride, Ca chloride, Li fluoride, Li chloride, Na fluoride, Na chloride, Mg fluoride, and Mg chloride, for example, one or more of Ca chloride, Li chloride, Na chloride, and Mg chloride. These substances may be analytically pure. These substances can act as slagging agents and solubilizers, purifying impurities in the metal to a certain extent and reducing slag inclusions in the alloy.

[0034] In the present invention, the raw material composition may further comprise Al2O3 particles and / or SiO2 particles (SiO2 particles may also be referred to as quartz particles).

[0035] Wherein, in the raw material composition, the content of the Al2O3 particles may be 0.01-10.00wt%, for example, 1.00wt%, 5.00wt% or 10.00wt%; the percentage refers to the weight percentage in the raw material composition.

[0036] In the raw material composition, the particle size of the Al2O3 particles may be 20-250 mesh, such as 20-140 mesh, and also such as 35 mesh.

[0037] Wherein, in the raw material composition, the particle size of the SiO2 particles can be 20-250 meshes.

[0038] In the present invention, the Al2O3 particles and / or the SiO2 particles can regulate the melt viscosity of the raw material composition.

[0039] In the present invention, the raw material composition may further comprise TiH2 particles and / or ZrH2 particles.

[0040] Wherein, in the raw material composition, the content of the TiH2 particles may be 0.01-10.00 wt%, for example, 1.00 wt%, 5.00 wt% or 10.00 wt%; the percentage refers to the weight percentage in the raw material composition.

[0041] In the raw material composition, the particle size of the TiH2 particles may be 100-300 mesh, for example, 250 mesh.

[0042] Wherein, in the raw material composition, the particle size of the ZrH2 particles can be 100-300 meshes.

[0043] In the present invention, the TiH2 particles and / or the ZrH2 particles can regulate the foaming process of the melt formed by the raw material composition.

[0044] TiH2 and ZrH2 hydride decomposition at about 510 ° C and about 680 ° C produces a lot of foaming. The pore size formed by ZrH2 addition is usually smaller than that produced by TiH2 addition.

[0045] In the present invention, the raw material composition may further comprise other raw materials that can adjust the viscosity of the melt formed by the raw material composition. These raw materials should generally meet the following conditions:

[0046] (1) It does not react chemically with rare earth metals; (2) It has a high melting point and does not melt; (3) It has a density lower than that of the melt formed by the raw material composition and cannot sink to the bottom, but must have a certain suspension effect.

[0047] In a preferred embodiment of the present invention, the raw material composition includes the following components:

[0048] GdF3, optionally, further comprising TbF3, DyF3, HoF3, ErF3;

[0049] Ca, the excess addition amount of Ca is 3-112%, preferably 15-25%;

[0050] Al2O3 particles and / or SiO2 particles, preferably Al2O3, wherein the particle size of the Al2O3 particles and the SiO2 particles is 20-140 mesh;

[0051] Optionally, TiH2 and ZrH2 are also included.

[0052] The present invention also provides a method for preparing a transparent porous rare earth material precursor, which adopts the following method 1, method 2 or method 3:

[0053] (1) Method 1:

[0054] When the raw material composition is the compound containing R and M, the method for preparing a transparent porous rare earth material precursor comprises the following steps:

[0055] The R-containing compound and the M are mixed, smelted to obtain a melt, and solidified to obtain the porous rare earth material precursor;

[0056] During the smelting process, the R-containing compound and the M undergo a reduction reaction;

[0057] (2) Method 2:

[0058] When the raw material composition includes the R-containing compound, the M, the Al2O3 particles and / or the SiO2 particles, and the TiH2 particles and / or the ZrH2 particles, the method for preparing a transparent porous rare earth material precursor includes the following steps:

[0059] S1: The R-containing compound and the M are mixed and smelted to obtain a melt A1; during the smelting process, the R-containing compound and the M undergo a reduction reaction;

[0060] S2: mixing the Al2O3 particles and / or the SiO2 particles, the TiH2 particles and / or the ZrH2 particles and the melt A1 to obtain melt A2, which is then foamed and solidified;

[0061] (3) Method 3:

[0062] When the raw material composition includes the R-containing compound, the M, the Al2O3 particles and / or the SiO2 particles, and the TiH2 particles and / or the ZrH2 particles, the method for preparing a transparent porous rare earth material precursor includes the following steps:

[0063] S1: mixing, smelting, and solidifying the R-containing compound and the M to obtain an alloy A; during the smelting process, a reduction reaction occurs between the R-containing compound and the M;

[0064] S2: The alloy A is melted to obtain a melt B1; the Al2O3 particles and / or the SiO2 particles, the TiH2 particles and / or the ZrH2 particles and the melt B1 are mixed to obtain a melt B2, which is foamed and then solidified.

[0065] In the present invention, in the method 1, method 2 or method 3, the smelting may include a first smelting process and a second smelting process in sequence;

[0066] During the first smelting process, the R does not melt, but the M melts;

[0067] In the second smelting process, the R is melted and the M is melted.

[0068] The smelting temperature in the first smelting process can be adjusted according to the type of the R-containing compound and the M, and is generally 50-100°C higher than the melting points of elemental Ca, elemental Li, elemental Na, and elemental Mg in M, and at least 50°C lower than the melting point of R. For example, when the R-containing compound is GdF3 and M is Ca, the smelting temperature in the first smelting process is 200-1000°C, for example, 839-1000°C.

[0069] The smelting time in the first smelting process may be 1-5 minutes, for example, 2 minutes.

[0070] The smelting temperature in the second smelting process can be adjusted according to the types of R and M, and can generally be 50-100°C higher than the melting point of R, and at least 50°C higher than the melting points of Ca, Li, Na, and Mg in M, for example, 849-1763°C. For example, when the R-containing compound is GdF3 and M is Ca, the smelting temperature in the second smelting process is 1000-1763°C, for example, 1500°C.

[0071] The smelting time in the second smelting process may be 2-10 minutes, for example, 5 minutes.

[0072] In the present invention, in the method 1, method 2 or method 3, the smelting can be carried out under vacuum conditions, for example, the vacuum degree is higher than 2×10 -3 Pa level conditions.

[0073] In the present invention, in the method 1, method 2 or method 3, the smelting can be carried out under an inert atmosphere, for example, 4×10 4 Pa argon atmosphere.

[0074] In the present invention, in the method 1, method 2 or method 3, the smelting can be carried out in a Ta crucible. Before the smelting, the Ta crucible can be heated and degassed, and the temperature of the heating and degassing is not higher than 600°C.

[0075] In the present invention, in Method 1, Method 2, or Method 3, slag may be removed from the melt after smelting and before solidification. For example, when the R-containing compound is GdF3 and M is Ca, CaF2 slag may be removed from the melt after smelting and before solidification. CaF2 slag floats on the surface of the molten metal and can be directly removed from the molten metal.

[0076] In the present invention, in the second or third method, in S2, the mixing can be performed under stirring. The stirring speed can be 500-2000 rpm, for example, 1000 rpm. The stirring time can be 0.5-5 min, for example, 1 min.

[0077] In the present invention, in the second or third method, in S2, before the mixing, the "Al2O3 particles and / or the SiO2 particles" and "the TiH2 particles and / or the ZrH2 particles" may be preheated. The preheating temperature may not exceed 400°C.

[0078] When the raw material composition includes GdF3, Ca, Al2O3 particles, and TiH2 particles, after being processed by the second or third method, the porous rare earth material precursor can be a Gd-Ca-Al2O3-Ti alloy ingot.

[0079] The present invention also provides a transparent porous rare earth material precursor prepared by the above method for preparing a transparent porous rare earth material precursor.

[0080] The present invention also provides a transparent porous rare earth material precursor, which has a closed-cell porous structure with a pore wall thickness of 0.05-0.8 mm, a porosity of 30-70%, and a relatively uniform pore distribution; wherein:

[0081] Rare earth material (such as rare earth element or rare earth alloy) is the main material of the closed-cell porous structure;

[0082] The composition of the adjacent portion of the rare earth material and the pore structure (ie, the pore wall) is a substance other than the rare earth material (eg, Ca, Al2O3, Ti).

[0083] In the present invention, the "closed-cell porous structure" means that no continuous, unclosed pores can be formed between any two cross sections of the pores.

[0084] The present invention also provides a method for preparing a transparent porous rare earth material, which comprises the following steps:

[0085] The transparent porous rare earth material precursor is subjected to heat treatment to remove substances other than the rare earth element R (such as Ca element, Li element, Na element, Mg element, Al2O3, Ti element) in the transparent porous rare earth material precursor to form a porous structure.

[0086] In the present invention, before the heat treatment, in order to completely remove the impurities, the porous rare earth material precursor may be cut.

[0087] In the present invention, the heat treatment method can be a conventional method in the art for separating rare earth elements from substances other than the rare earth element R (e.g., elemental Ca, elemental Li, elemental Na, and elemental Mg). For example, the separation is performed under conditions where the elements Ca, Li, Na, and Mg are melted and the rare earth elements are not melted. The heat treatment temperature is generally 50-100°C higher than the combined melting and boiling points of the elements Ca, Li, Na, and Mg in M, and at least 50°C lower than the melting point of the rare earth elements.

[0088] When the porous rare earth material precursor is a Gd-Ca-Al2O3-Ti alloy ingot, the heat treatment temperature may be 150-1200°C, for example, 1190°C.

[0089] In the present invention, after the heat treatment, a post-impurity removal treatment may be performed to remove substances other than the rare earth elements. The post-impurity removal treatment may be performed by vacuum distillation, high-pressure argon gas blowing, or rotary centrifugation (e.g., centrifugation at 30,000 rpm) to remove substances other than the rare earth elements (e.g., Ca, Al2O3, Ti, H).

[0090] After the impurity removal process, the porous rare earth material may be punched for individual non-through holes, and the punching method may be mechanical punching, discharge punching, or laser punching.

[0091] After the impurity removal treatment, an acid treatment may be performed to further adjust the size and shape of the pores of the porous rare earth material and activate the surface of the pores, thereby enhancing the heat exchange effect.

[0092] The acid may be hydrochloric acid and / or nitric acid.

[0093] The concentration of the acid may be 0.5-50 vol%, for example 3 vol% (vol% means volume percentage).

[0094] The present invention also provides a transparent porous rare earth material prepared by the above-mentioned method for preparing the transparent porous rare earth material.

[0095] The invention provides a transparent porous rare earth material with a pore wall thickness of 0.05-0.8 mm, a porosity of 30-70%, and uniform pore distribution.

[0096] In the present invention, the transparent porous rare earth material is generally composed of rare earth materials (such as rare earth elements or rare earth alloys).

[0097] In the present invention, the “transparent porous shape” refers to the ability to form continuous, unclosed channels between any two cross sections of the channel.

[0098] In the present invention, the "hole wall thickness" refers to the shortest distance between the hole edges of any two adjacent holes.

[0099] In the present invention, the hole wall thickness may be 0.1-0.8 mm, such as 0.1 mm, 0.4 mm, 0.5 mm or 0.8 mm, preferably 0.5 mm.

[0100] In the present invention, the porosity may be 30-50%, such as 30%, 36%, 40%, 50%, and preferably 36%.

[0101] In the present invention, vacuum degree=absolute pressure.

[0102] On the basis of conforming to the common sense in this field, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0103] The reagents and raw materials used in the present invention are commercially available.

[0104] The positive progress effect of the present invention is:

[0105] The present invention provides a method for producing high-purity rare earth metal and alloy magnetic refrigeration fluids in large quantities and at low cost, and is capable of producing transparent porous fluids with different porosities. Specifically:

[0106] Rare earth fluorides (one or more) can be prepared into high-purity rare earth metals and alloys through thermal reduction of Ca, Li, Na, Mg (one or more). This method can be combined with a foaming process to directly prepare a transparent porous working fluid material. BRIEF DESCRIPTION OF THE DRAWINGS

[0107] Figure 1 Schematic diagram of the porous RM alloy block obtained by solidification in Example 1.

[0108] Figure 2 Schematic diagram of slicing the porous rare earth metal / alloy block after removing M and ceramic particles in Example 1.

[0109] Figure 3 Flow chart of the preparation of porous rare earth metal / alloy in the embodiment, wherein Path 1 corresponds to Method 1 in Example 1, and Path 2 corresponds to Method 2 in Example 1. DETAILED DESCRIPTION

[0110] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0111] Example 1

[0112] Taking the thermal reduction of Ca to prepare a transparent porous rare earth metal, Gd, as an example, the raw materials, by weight percentage, are GdF3 (76.03 wt%), Ca (21.97 wt%), Al2O3 (1 wt%, particle size 20-250 mesh), and TiH2 (1 wt%, particle size 100-250 mesh). The prepared GdF3 and Ca particles are mixed and molded into an ingot, which is then prepared in a vacuum medium-frequency induction furnace. The thermal reduction reaction equation is as follows, with Ca added in excess of 3%.

[0113] 2GdF3+3Ca=2Gd+3CaF2

[0114] Method 1

[0115] Place the molded ingot of GdF3 and Ca particles into a Ta crucible, and Al2O3 and TiH2 into the feeding device. Evacuate to 2Pa, heat the Ta crucible and the feeding device for degassing. The heating and degassing temperature is not higher than 600℃, and the preheating temperature of the feeding device containing Al2O3 and TiH2 does not exceed 400℃. When the vacuum degree in the induction furnace is higher than 2×10 -3 Pa level, after turning off the vacuum pump, argon gas was injected to 4×10 4 Pa (absolute pressure), further heat the Ta crucible to raise the temperature of the raw material ingot to the temperature at which the reduction reaction begins (839-1000°C) and keep it at this temperature for 2 minutes (adjusted according to the amount of charge, at this time Ca melts but Gd does not melt), then quickly raise the temperature to the melting temperature of 1500°C and keep it for 5 minutes (adjusted according to the amount of charge, at this time Ca melts but Gd also melts), so that the molten metal and the CaF2 slag are well separated.

[0116] At this time, you can follow Figure 3 In route 1 of the process flow chart, the CaF2 slag floating on the surface is directly removed from the molten metal. The remaining molten metal is allowed to stand for 1 minute. Preheated Al2O3 and TiH2 are added through the feeding device. After stirring at 1000 rpm for 1 minute, the stirring rod is removed. After foaming is completed, the molten metal is cast into a metal mold to obtain a porous Gd-Ca-Al2O3-Ti alloy ingot.

[0117] The alloy ingot is sliced ​​and placed in a vacuum furnace, heated to 1190°C (at which point the Ca is melted but the Gd is not). Vacuum distillation, high-pressure argon gas blowing, and centrifugation (at 30,000 rpm) are then used to remove Ca, Al2O3, Ti, and H, resulting in a porous rare earth metal Gd. For any unresolved holes, mechanical, electrical discharge, or laser drilling is performed to create a transparent, porous magnetic refrigerant.

[0118] The porous magnetic refrigerant (ie, the porous metal block) can be placed in a 3 vol% hydrochloric acid solution to further control the size and shape of the pores and activate the surface, thereby enhancing the heat transfer effect.

[0119] Method 2

[0120] Place the molded ingot of GdF3 and Ca particles into a Ta crucible, evacuate to 2 Pa, heat the Ta crucible, and heat the degassing temperature to no higher than 600 ° C. When the vacuum degree in the induction furnace is higher than 2×10 -3 Pa level, after turning off the vacuum pump, argon gas was injected to 4×10 4Pa (absolute pressure), further heat the Ta crucible to raise the temperature of the raw material ingot to the temperature at which the reduction reaction begins (839-1000°C) and keep it at this temperature for 2 minutes (adjusted according to the amount of charge, at this time Ca melts but Gd does not melt), then quickly raise the temperature to the melting temperature of 1500°C and keep it for 5 minutes (adjusted according to the amount of charge, at this time Ca melts but Gd also melts), so that the molten metal and the CaF2 slag are well separated.

[0121] At this time, you can follow Figure 3 In the process flow chart, in route 2, the alloy liquid is cast and cooled to solidify, and the CaF2 slag is removed. The alloy ingot is placed back into the Ta crucible of the induction furnace, and Al2O3 and TiH2 are placed in the feeding device. The vacuum is evacuated to ~2Pa, and the Ta crucible and feeding device are heated for degassing. The heating and degassing temperature of the Ta crucible is not higher than 600℃, and the preheating temperature of the feeding device containing Al2O3 and TiH2 does not exceed 400℃. When the vacuum degree in the induction furnace is higher than 2×10 -3 Pa level, after turning off the vacuum pump, argon gas was injected to 4×10 4 Pa (absolute pressure), further heat the Ta crucible to a melting temperature of 1500°C and hold for 5 minutes (adjusted depending on the charge; Ca and Gd melt at this point). The alloy solution is allowed to stand for 1 minute, and preheated Al2O3 and TiH2 are added via a feeding device. Stir at 1000 rpm for 1 minute, then remove the stirring rod. Once foaming is complete, the molten metal is cast into a metal mold to produce a porous Gd-Ca-Al2O3-Ti alloy ingot.

[0122] The alloy ingot is sliced ​​and placed in a vacuum furnace, heated to 1190°C (at which point the Ca is melted but the Gd is not). Vacuum distillation, high-pressure argon gas blowing, and centrifugation (at 30,000 rpm) are then used to remove Ca, Al2O3, Ti, and H, resulting in a porous rare earth metal Gd. For any unresolved holes, mechanical, electrical discharge, or laser drilling is performed to create a transparent, porous magnetic refrigerant.

[0123] The porous magnetic refrigerant (ie, the porous metal block) can be placed in a 3 vol% hydrochloric acid solution to further control the size and shape of the pores and activate the surface, thereby enhancing the heat transfer effect.

[0124] Examples 1-12

[0125] Table 1

[0126]

[0127]

[0128] M a : The actual percentage of M element added; M b: The percentage of excess dosage of M element;

[0129] The particle size of Al2O3 is 35 mesh; the particle size of TiH2 is 250 mesh.

[0130] The formulation ratios of Examples 2-12 are as shown in Table 1, and other process conditions are the same as those of Example 1.

[0131] Explanation of the principles of raw material batching: First, it is necessary to ensure that the rare earth fluoride is thoroughly thermally reduced, which follows the following chemical equation, taking the thermal reduction of rare earth Gd with Ca as an example:

[0132] 2GdF3+3Ca=2Gd+3CaF2

[0133] At this point, the molar ratio of rare earth fluoride to Ca is 2:3, resulting in a mass ratio of 78.09 wt% GdF3 to 21.91 wt% Ca. In practice, some excess Ca is added to compensate for losses during preparation, such as a 3% increase. This 3% represents an increase relative to the original amount of Ca added (to satisfy the chemical equation) (i.e., the amount added to satisfy the chemical equation is compared to the actual amount added). In total, the molar ratio of GdF3 to Ca changes from 2:3 to 2:3.03, resulting in a mass ratio of 77.63 wt% GdF3 to 22.37 wt% Ca. If Ca is added in excess by 20%, the molar ratio becomes 2:3.6, resulting in a mass ratio of 74.81 wt% GdF3 to 25.19 wt% Ca. In short, determining the compensatory Ca addition level determines the weight ratio of GdF3 to Ca.

[0134] The ultimate goal of the preparation process of the present invention is not only to obtain pure rare earth metals / alloys, but also to obtain a porous structure. Therefore, the amount of Ca compensation is higher than that of conventional thermal reduction processes, and Ca itself also serves as a means of pore formation. Mg and Ca have the same valence and the same equation; Li and Na have the same valence and the same equation, as follows:

[0135] GdF3+3Na=Gd+3NaF.

[0136] The transparent porous rare earth material prepared in Examples 1-12 has a pore wall thickness of 0.05-0.8 mm, a porosity of 30-70%, and uniform pore distribution.

Claims

1. A method for preparing a transparent porous rare earth material precursor, characterized in that: It adopts the following method 1, method 2 or method 3: (1) Method 1: When preparing a raw material composition for a transparent porous rare earth material precursor, the raw material composition includes the following components by weight percentage: a compound containing R: 50.16-77.63 wt %, wherein the rare earth element R in the compound containing R is an oxidized rare earth element R; M: 17.94-37.30wt%, wherein M comprises one or more of Ca, Li, Na, and Mg; The amount of M is 1.03-2.12 times its reaction equivalent; The method for preparing a transparent porous rare earth material precursor comprises the following steps: The R-containing compound and the M are mixed, smelted to obtain a melt, and solidified to obtain the porous rare earth material precursor; During the smelting process, the R-containing compound and the M undergo a reduction reaction; The smelting process includes a first smelting process and a second smelting process in sequence; in the first smelting process, the R does not melt, but the M melts; in the second smelting process, the R melts, and the M melts; (2) Method 2: When preparing a raw material composition for a transparent porous rare earth material precursor, the raw material composition includes the following components by weight percentage: a compound containing R: 50.16-77.63 wt %, wherein the rare earth element R in the compound containing R is an oxidized rare earth element R; M: 17.94-37.30wt%, wherein M comprises one or more of Ca, Li, Na, and Mg; the amount of M is 1.03-2.12 times its reaction equivalent; Al2O3 particles and / or SiO2 particles; TiH2 particles and / or ZrH2 particles; The method for preparing a transparent porous rare earth material precursor comprises the following steps: S1: The R-containing compound and the M are mixed and smelted to obtain a melt A1; during the smelting process, the R-containing compound and the M undergo a reduction reaction; The smelting process includes a first smelting process and a second smelting process in sequence; in the first smelting process, the R does not melt, but the M melts; in the second smelting process, the R melts, and the M melts; S2: mixing the Al2O3 particles and / or the SiO2 particles, the TiH2 particles and / or the ZrH2 particles with the melt A1 to obtain a melt A2, foaming the melt and solidifying the melt A2; (3) Method 3: When preparing a raw material composition for a transparent porous rare earth material precursor, the raw material composition includes the following components by weight percentage: a compound containing R: 50.16-77.63 wt %, wherein the rare earth element R in the compound containing R is an oxidized rare earth element R; M: 17.94-37.30wt%, wherein M comprises one or more of Ca, Li, Na, and Mg; the amount of M is 1.03-2.12 times its reaction equivalent; Al2O3 particles and / or SiO2 particles; TiH2 particles and / or ZrH2 particles; The method for preparing a transparent porous rare earth material precursor comprises the following steps: S1: mixing, smelting, and solidifying the R-containing compound and the M to obtain an alloy A; during the smelting process, a reduction reaction occurs between the R-containing compound and the M; The smelting process includes a first smelting process and a second smelting process in sequence; in the first smelting process, the R does not melt, but the M melts; in the second smelting process, the R melts, and the M melts; S2: melting the alloy A to obtain a melt B1; mixing the Al2O3 particles and / or the SiO2 particles, the TiH2 particles and / or the ZrH2 particles with the melt B1 to obtain a melt B2, foaming and then solidifying; The prepared transparent porous rare earth material precursor has a closed-pore porous structure with a pore wall thickness of 0.05-0.8 mm, a porosity of 30-70%, and a relatively uniform pore distribution.

2. The method for preparing a transparent porous rare earth material precursor according to claim 1, wherein: In the method 1, method 2 or method 3, the smelting time in the first smelting process is 1-5 minutes; And / or, when the R-containing compound is GdF3 and M is Ca, the smelting temperature in the second smelting process is 1000-1763°C; And / or, the smelting time in the second smelting process is 2-10 min; and / or, in the method 1, method 2 or method 3, after the smelting and before the solidification, removing slag from the molten liquid; And / or, in the method 2 or the method 3, in S2, the mixing is carried out under stirring conditions; the stirring speed is 500-2000 rpm, and the stirring time is 0.5-5 min.

3. The method for preparing a transparent porous rare earth material precursor according to claim 2, wherein: When the R-containing compound is GdF 3 and M is Ca, the smelting temperature in the second smelting process is 1500° C.

4. The method for preparing a transparent porous rare earth material precursor according to claim 1, wherein: The rare earth element R in the oxidized rare earth element R is one or more of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc and Y; and / or, the compound containing R is one or more of rare earth metal fluorides, rare earth metal chlorides, rare earth alloy fluorides, and rare earth alloy chlorides; and / or, the content of the compound containing R is 50.16-76.03 wt %, where the percentage refers to the weight percentage in the raw material composition; And / or, the M includes one or more of Ca, Li and Na; And / or, the content of M is 17.94-36.55 wt %, where percentage refers to the weight percentage in the raw material composition.

5. The method for preparing a transparent porous rare earth material precursor according to claim 4, wherein: The rare earth element R in the oxidized rare earth element R is Gd; and / or, the compound containing R is a fluoride of a rare earth metal; And / or, the M includes Ca element and / or Na element.

6. The method for preparing a transparent porous rare earth material precursor according to claim 5, wherein: The M includes Ca element.

7. The method for preparing a transparent porous rare earth material precursor according to claim 1, wherein: The raw material composition further comprises one or more of Ca fluoride, Ca chloride, Li fluoride, Li chloride, Na fluoride, Na chloride, Mg fluoride, and Mg chloride; and / or, the content of the Al2O3 particles is 0.01-10.00 wt%, where the percentage refers to the weight percentage in the raw material composition; and / or, the particle size of the Al2O3 particles is 20-250 mesh; and / or, the particle size of the SiO2 particles is 20-250 mesh; and / or, the content of the TiH2 particles is 0.01-10.00 wt%, where the percentage refers to the weight percentage in the raw material composition; and / or, the particle size of the TiH2 particles is 100-300 mesh; And / or, the particle size of the ZrH2 particles is 100-300 mesh.

8. The method for preparing a transparent porous rare earth material precursor according to claim 7, wherein: The particle size of the Al2O3 particles is 20-140 mesh; And / or, the particle size of the TiH2 particles is 250 mesh.

9. The method for preparing a transparent porous rare earth material precursor according to claim 8, wherein: The particle size of the Al2O3 particles is 35 mesh.

10. A transparent porous rare earth material precursor, which is prepared by the method for preparing a transparent porous rare earth material precursor according to any one of claims 1 to 9.

11. The transparent porous rare earth material precursor according to claim 10, characterized in that: Rare earth material is the main material of the closed-cell porous structure; The composition of the adjacent portion of the rare earth material and the pore structure is a substance other than the rare earth material.

12. A method for preparing a transparent porous rare earth material, characterized in that: It includes the following steps: The transparent porous rare earth material precursor as claimed in claim 10 or 11 is subjected to heat treatment to remove substances other than the rare earth element R in the porous rare earth material precursor to form a porous structure.

13. A transparent porous rare earth material, which is prepared by the method for preparing a transparent porous rare earth material according to claim 12.

14. The transparent porous rare earth material according to claim 13, wherein: The pore wall thickness is 0.05-0.8mm, the porosity is 30-70%, and the pores are evenly distributed.

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