Rare earth carbonate material and preparation method thereof

Abstract

The invention provides a rare earth carbonate material and a preparation method thereof, the rare earth carbonate material is needle-shaped, and the relative standard deviation of the long diameter of the rare earth carbonate material is less than or equal to 5%. As the relative standard deviation of the long diameter of the rare earth carbonate material is less than or equal to 5%, the particle size distribution of the rare earth carbonate material is concentrated, that is, the morphology consistency of the rare earth carbonate material is high, and the size distribution is uniform. The size consistency can optimize the fluidity of the 3D printing slurry during extrusion and improve the problem of uneven extrusion, and the rare earth carbonate material uniformly dispersed in the printing matrix can reduce local stress concentration of a printed product and reduce generation of internal defects, so that the fidelity of the printed product is improved.

Description

Technical Field

[0001] This invention belongs to the field of rare earth materials technology, specifically relating to a rare earth carbonate material and its preparation method. Background Technology

[0002] Rare earth carbonate materials have great potential for application in reinforced 3D printing materials due to their excellent mechanical properties, thermal stability, and corrosion resistance. They not only have high strength and hardness, providing excellent structural load-bearing capacity for printed parts, but also maintain structural integrity in high-temperature 3D printing environments while resisting external environmental erosion, making them suitable for complex printing and usage scenarios.

[0003] Chemical precipitation is a common method for preparing rare earth carbonate materials. However, rare earth carbonate materials prepared by chemical precipitation have poor dimensional uniformity. When applied to the field of 3D printing technology, this results in uneven extrusion rate and spreading morphology during the 3D printing process, leading to a decrease in the shape accuracy (fidelity) of the printed object, ultimately limiting the large-scale application of rare earth carbonate materials in the field of 3D printing.

[0004] Therefore, developing a rare earth carbonate material with good dimensional uniformity has become an urgent technical problem to be solved. Summary of the Invention

[0005] This application is made in view of the above-mentioned issues, and its purpose is to provide a rare earth carbonate material and a method for preparing the same. The relative standard deviation of the major diameter of the rare earth carbonate material is less than or equal to 5%. When this rare earth carbonate material is applied to the field of 3D printing, the 3D printed products have improved fidelity.

[0006] To achieve the above objectives, this application provides a rare earth carbonate material in the form of needles, wherein the relative standard deviation of the major diameter of the rare earth carbonate material is less than or equal to 5%.

[0007] In some embodiments, the rare earth carbonate material has an average major diameter of 3 μm to 5 μm.

[0008] In some embodiments, the rare earth carbonate material has an average minor diameter of 0.4 μm to 0.5 μm.

[0009] In some implementations, the rare earth carbonate material has an average aspect ratio of 6 to 12.5.

[0010] In some implementations, the mass ratio of oxygen to carbon in the rare earth carbonate material is greater than or equal to 4.

[0011] In some embodiments, the rare earth carbonate material includes at least one of praseodymium carbonate, neodymium carbonate, promethium carbonate, and samarium carbonate.

[0012] A second aspect of this application provides a method for preparing rare earth carbonate materials, comprising: Step 1: Mix rare earth metal salts, polyethylene glycol and deionized water to obtain a mixture. Polyethylene glycol is used to adsorb rare earth metal cations contained in the rare earth metal salts. Step 2: Add ammonium bicarbonate to the mixture while stirring, so that the rare earth metal cations adsorbed on the surface of polyethylene glycol combine with the carbonate ions in the ammonium bicarbonate solution to form rare earth metal carbonates. Step 3: Remove the polyethylene glycol used to adsorb rare earth metal carbonates to obtain rare earth carbonate material. The rare earth carbonate material is needle-shaped, and the relative standard deviation of the major axis of the rare earth carbonate material is less than or equal to 5%.

[0013] In some implementations, the pH of the mixture is 2 to 3.

[0014] In some embodiments, the mass ratio of polyethylene glycol to rare earth metal salt in the mixture is (8 to 13):100; In some embodiments, the relative molecular mass of polyethylene glycol is between 2,000 and 6,000.

[0015] In some embodiments, the pH of the mixture of the solution and ammonium bicarbonate is 6.4 to 6.7.

[0016] In some embodiments, the molar concentration of rare earth metal salts in the mixture is from 0.03 mol / L to 0.3 mol / L.

[0017] In some embodiments, the molar ratio of rare earth metal salt to ammonium bicarbonate is (0.03 to 0.3):(0.2 to 2).

[0018] In some embodiments, the stirring method includes at least one of ultrasonic stirring and magnetic stirring.

[0019] In some embodiments, rare earth metal carbonates are washed alternately with deionized water and ethanol to obtain rare earth carbonate materials.

[0020] This application can achieve the following effects: In this application, the relative standard deviation of the major diameter of the rare earth carbonate material is less than or equal to 5%, indicating that the rare earth carbonate material has a concentrated particle size distribution, meaning that the rare earth carbonate material has high morphological consistency and uniform size distribution. This particle size uniformity gives the slurry prepared with this rare earth carbonate material good fluidity, enabling it to have stable and uniform extrusion characteristics during the 3D printing process. This effectively reduces the problem of uneven stress distribution inside the printed product, thereby significantly reducing the risk of local performance defects in the 3D printed product and improving the fidelity of the printed product. In addition, the rare earth carbonate material is needle-shaped and has a uniform size, which allows the rare earth carbonate material to be uniformly dispersed in the printing matrix, avoiding performance fluctuations in the printed product caused by local agglomeration or uneven dispersion, thus further improving the fidelity of the 3D printed product. Attached Figure Description

[0021] Figure 1 This is a flowchart of a method for preparing rare earth carbonate materials provided in this application. Detailed Implementation

[0022] The following detailed description, with appropriate reference to the accompanying drawings, discloses an embodiment of a rare earth carbonate material and its preparation method according to this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of essentially identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0023] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0024] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0025] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0026] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0027] Unless otherwise specified, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0028] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in this application.

[0029] Currently, chemical precipitation is a commonly used method for preparing rare earth carbonate materials. However, rare earth carbonate materials prepared by chemical precipitation have poor dimensional uniformity. When this rare earth carbonate material is applied to the field of 3D printing technology, it leads to uneven extrusion rate and spreading morphology during the 3D printing process, resulting in a decrease in the shape accuracy (fidelity) of the printed object, ultimately limiting the large-scale application of rare earth carbonate materials in the field of 3D printing.

[0030] To address the aforementioned technical problems, this application provides a rare earth carbonate material in a needle-like shape. The relative standard deviation of the major axis of the rare earth carbonate material is less than or equal to 5%. When this rare earth carbonate material is applied to 3D printed products, the 3D printed products exhibit improved fidelity. Furthermore, the needle-like morphology of the rare earth carbonate material imparts a higher specific surface area, thereby exposing more active sites. When applied to the catalysis field, this rare earth carbonate material is beneficial for improving reaction contact efficiency.

[0031] The first aspect of this application provides a rare earth carbonate material, which is needle-shaped, and the relative standard deviation of the major and minor diameters of the rare earth carbonate material is less than or equal to 5%.

[0032] In this application, the relative standard deviation of the major diameter of the rare earth carbonate material is less than or equal to 5%, indicating a concentrated particle size distribution and high dimensional uniformity. This dimensional uniformity gives the slurry prepared with this rare earth carbonate material good flowability, enabling stable and uniform extrusion characteristics during 3D printing. This reduces uneven stress distribution within the 3D printed product, significantly lowering the risk of local performance defects and improving the fidelity of the 3D printed product. Furthermore, the needle-like shape and uniform size of the rare earth carbonate material allow for uniform dispersion within the printing matrix, avoiding performance fluctuations in the 3D printed product due to local agglomeration or uneven dispersion, thus further enhancing the fidelity of the 3D printed product. In addition, the needle-like morphology of the rare earth carbonate material provides a higher specific surface area, exposing more active sites. Applying this rare earth carbonate material in the catalysis field can improve catalytic efficiency.

[0033] In some embodiments, the average major diameter of the rare earth carbonate material is 3 μm to 5 μm. If the average major diameter of the rare earth carbonate material is too short, it is difficult to form effective structural support in the 3D printing slurry, resulting in insufficient structural density of the 3D printed product and thus reducing the fidelity of the printed product. At the same time, the number of active sites exposed by the shorter needle-like morphology is relatively limited, which may affect the reaction contact efficiency in the catalytic reaction. If the average major diameter of the rare earth carbonate material is too long, it is easy to increase the flow resistance of the 3D printing slurry, and the excessively long major diameter may also cause local structural defects in the 3D printed product. Therefore, controlling the average major diameter of the rare earth carbonate material within the above-mentioned range can balance the flow stability of the slurry and the fidelity of the printed product during the 3D printing process, as well as the exposure efficiency and performance stability of the active sites of the material during the catalytic process. For example, the average major diameter of the rare earth carbonate material is a value between 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or any combination thereof.

[0034] In some embodiments, the average minor axis of the rare earth carbonate material is 0.4 μm to 0.5 μm. If the average minor axis of the rare earth carbonate material is too short, it is prone to local agglomeration in the 3D printing slurry due to Brownian motion, which affects the slurry's flowability and extrusion uniformity. It may also agglomerate during catalysis due to excessively high surface energy, reducing the exposure efficiency of active sites. If the average minor axis of the rare earth carbonate material is too long, it easily increases the flow resistance of the 3D printing slurry, resulting in local structural defects in the 3D printed product. Therefore, controlling the average minor axis of the rare earth carbonate material within the above-mentioned range can balance the flow stability of the slurry and the fidelity of the printed product during 3D printing, as well as the exposure efficiency and performance stability of the material's active sites during catalysis. For example, the average minor axis of the rare earth carbonate material is a value within the range of 0.4 μm, 0.42 μm, 0.44 μm, 0.46 μm, 0.48 μm, 0.5 μm, or any combination thereof.

[0035] In some embodiments, the average aspect ratio of the rare earth carbonate material is between 6 and 12.5. If the average aspect ratio of the rare earth carbonate material is too small, the needle-like morphology of the material is not significant, the specific surface area of ​​the material is too small, and the exposure of active sites in the catalytic reaction is insufficient. If the average aspect ratio of the rare earth carbonate material is too large, it can easily increase the flow resistance of the 3D printing slurry, and may also cause local structural defects in the 3D printed product due to the excessively long average aspect ratio. Therefore, controlling the average aspect ratio of the rare earth carbonate material within the above-mentioned range can balance the flow stability of the slurry during the 3D printing process and the exposure efficiency of the active sites of the material during the catalytic reaction.

[0036] In some implementations, the mass ratio of oxygen to carbon in rare earth carbonate materials is greater than or equal to 4. Based on this ratio, the presence of water of crystallization can be inferred. During 3D printing, water of crystallization can regulate the rheological properties of the printing paste, reducing frictional resistance between materials within the paste and thus improving extrusion smoothness. In catalysis, water of crystallization can moderately regulate the electronic environment of active sites on the material surface, enhancing the material's adsorption capacity for reaction substrates, thereby maintaining the material's structural stability and reducing the risk of structural collapse due to high temperatures or solvent effects during catalysis.

[0037] In some embodiments, the rare earth carbonate material includes at least one of praseodymium carbonate, neodymium carbonate, promethium carbonate, and samarium carbonate. During the preparation of this rare earth carbonate material, the adsorption capacity of polyethylene glycol (PEG) for rare earth metal cations is utilized to control the uniformity of particle size. The ionic radii of the rare earth metal cations contained in praseodymium carbonate, neodymium carbonate, promethium carbonate, and samarium carbonate match the spatial structure of the PEG adsorption sites. This matching facilitates the uniform fixation of the rare earth metal cations, forming uniformly distributed adsorption sites, thereby promoting the synchronous combination of rare earth metal cations and carbonate ions at the adsorption sites to generate crystal nuclei of uniform size. Furthermore, the steric hindrance of the PEG molecular chains ensures that all crystal nuclei maintain a uniform confinement environment and a stable ion supply state during growth, ensuring consistent growth direction and rate. In this way, factors causing particle size differences are eliminated in the three key steps of ion distribution, crystal nucleus generation, and crystal nucleus growth, ensuring that the material has a high degree of uniformity with a relative standard deviation of no more than 5% in length and diameter.

[0038] A second aspect of this application provides a method for preparing rare earth carbonate materials, comprising: Step 1: Mix rare earth metal salts, polyethylene glycol and deionized water to obtain a mixture. Polyethylene glycol is used to adsorb rare earth metal cations contained in the rare earth metal salts. Step 2: Add ammonium bicarbonate to the mixture while stirring, so that the rare earth metal cations adsorbed on the surface of polyethylene glycol combine with the carbonate ions in the ammonium bicarbonate solution to form rare earth metal carbonates. Step 3: Remove the polyethylene glycol used to adsorb rare earth metal carbonates to obtain rare earth carbonate material. The rare earth carbonate material is needle-shaped, and the relative standard deviation of the major axis of the rare earth carbonate material is less than or equal to 5%.

[0039] In this application, the high uniformity of the length and diameter of needle-shaped rare earth carbonate materials is achieved through the synergistic regulation of the adsorption effect of polyethylene glycol and the steric hindrance effect. Specifically, in step 1, polyethylene glycol adsorbs rare earth metal cations from rare earth metal salts through coordination, anchoring the cations that were originally uniformly dispersed in the solution onto the surface of polyethylene glycol molecules, forming uniformly distributed cation adsorption sites. In step 2, during the stirring and addition of ammonium bicarbonate, carbonate ions in the solution preferentially combine with the rare earth metal cations anchored on the surface of polyethylene glycol, generating rare earth metal carbonate crystal nuclei in situ on the polyethylene glycol surface. Due to the large steric hindrance of the polyethylene glycol molecular chain, the growth direction and growth rate of the crystal nuclei are restricted. On the one hand, steric hindrance inhibits the disordered growth of crystal nuclei in non-dominant directions, guiding the crystal nuclei to grow into needle-like morphologies along specific directions. On the other hand, the uniform adsorption of cations by polyethylene glycol ensures that the microenvironment (such as ion concentration and growth space) of each crystal nucleus in the system is highly consistent, avoiding large fluctuations in size and length of local crystal nuclei due to differences in growth conditions. Finally, after removing polyethylene glycol in step 3, the relative standard deviation of the major diameter of the obtained needle-shaped rare earth carbonate material is ≤5%.

[0040] In this application, step 1 involves mixing rare earth metal salts, polyethylene glycol (PEG), and deionized water to obtain a mixed solution. PEG is used to adsorb the rare earth metal cations contained in the rare earth metal salts. PEG forms a stable electrostatic adsorption with the cations dissociated from the rare earth metal salts through its chain-terminal hydroxyl groups. The flexible molecular chains of PEG can construct a steric hindrance layer, reducing the local aggregation of rare earth metal cations. This facilitates the simultaneous binding of rare earth metal cations and carbonate ions, generating uniformly sized crystal nuclei, which in turn helps to obtain needle-shaped rare earth carbonate materials with good length-to-diameter consistency.

[0041] In this application, step 2 involves adding ammonium bicarbonate to the mixture while it is being stirred. This allows the rare earth metal cations adsorbed on the surface of polyethylene glycol to combine with the carbonate ions in the ammonium bicarbonate solution to form rare earth metal carbonates. Stirring promotes the uniform diffusion of the carbonate metal cations and carbonate ions in the system, ensuring sufficient contact between the rare earth carbonate cations and carbonate ions. Simultaneously, the steric hindrance effect of polyethylene glycol reduces the aggregation of rare earth metal carbonates, further facilitating the formation of rare earth metal materials with good length-to-diameter consistency.

[0042] In this application, step 3 involves removing the polyethylene glycol used to adsorb rare earth metal carbonates to obtain a rare earth carbonate material. The rare earth carbonate material is needle-shaped, and the relative standard deviation of its major axis is less than or equal to 5%. In step 3, after polyethylene glycol completes its core regulatory role of "uniformly anchoring cations, inducing synchronous nucleation, and restricting the orderly growth of crystal nuclei," removing the polyethylene glycol can, on the one hand, completely eliminate its adsorption force on the surface rare earth carbonate material, preventing the residual polyethylene glycol from causing the rare earth carbonate material to agglomerate due to intermolecular adsorption, thereby significantly improving the dispersion stability of the material; on the other hand, this removal step can strip away the regulator in the preparation process to obtain a high-purity rare earth carbonate material, while completely retaining the needle-shaped morphology and dimensional uniformity (good consistency of major axis) characteristics formed in the previous steps with a relative standard deviation of major axis ≤ 5%.

[0043] In some embodiments, the pH of the mixture is between 2 and 3. If the pH of the mixture is too low, a large number of hydrogen ions compete with rare earth metal cations for the adsorption sites of polyethylene glycol (PEG), reducing the binding effect of PEG on rare earth metal cations and making it difficult to form a sufficient amount of stable "PEG-cation" complex. Furthermore, when ammonium bicarbonate is added subsequently, hydrogen ions will preferentially react with carbonate ions, consuming PEG and affecting the stability of the reaction system. If the pH of the mixture is too high, rare earth metal cations are prone to hydrolysis, thereby destroying the already formed "PEG-cation" complex and causing some cations to become free. These free cations are prone to generating amorphous or aggregated products in subsequent reactions, making it difficult to form a regular needle-like morphology and control the uniformity of the major and minor axes. Therefore, controlling the pH of the mixture within the above range can balance the adsorption effect of PEG on rare earth metal cations and the stable existence state of rare earth metal cations. For example, the pH of the mixture is a value between 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, or any combination thereof.

[0044] In some embodiments, the mass ratio of polyethylene glycol (PEG) to rare earth metal salt in the mixture is (8 to 13):100. If the mass ratio of PEG to rare earth metal salt in the mixture is too low, the adsorption efficiency for rare earth metal cations may be reduced due to insufficient PEG; if the mass ratio is too high, the viscosity of the system may increase due to excess PEG, affecting subsequent desorption difficulties or residues. Therefore, controlling the mass ratio of PEG to rare earth metal salt in the mixture within the above range can reduce cation aggregation through appropriate steric hindrance and reduce the problem of desorption difficulties caused by excess PEG. For example, the mass ratio of PEG to rare earth metal salt in the mixture is a value between 8:100, 9:100, 10:100, 11:100, 12:100, 13:100, or any combination thereof.

[0045] In some embodiments, the relative molecular mass of polyethylene glycol (PEG) is between 2000 and 6000. If the relative molecular mass of PEG is too low, its molecular chains are shorter and its steric hindrance effect is weaker, reducing the adsorption effect on rare earth metal cations and resulting in irregular product shapes. If the relative molecular mass of PEG is too high, the longer molecular chains increase the viscosity of the system, thereby reducing the adsorption efficiency for cations and potentially hindering the diffusion of carbonate ions in ammonium bicarbonate, leading to incomplete reactions and hindering the formation of needle-like products with good length-to-diameter consistency. Therefore, controlling the relative molecular mass of PEG within the above-mentioned range allows for stable electrostatic adsorption between the hydroxyl groups at the PEG chain ends and rare earth metal cations, reducing the local aggregation of cations. Subsequently, PEG guides the directional binding of carbonate ions and cations, growing into regular needle-like rare earth metal carbonate structures.

[0046] For example, the relative molecular mass of polyethylene glycol is a value within a range of 2000, 2200, 2400, 2600, 2800, 3000, 3200, 3400, 3600, 3800, 4000, 4200, 4400, 4600, 4800, 5000, 5200, 5400, 5600, 5800, 6000, or any combination thereof.

[0047] In some embodiments, the pH of the mixture of the solution and ammonium bicarbonate is 6.4 to 6.7. If the pH of the mixture of the solution and ammonium bicarbonate is too low, the generated rare earth metal carbonates are prone to dissolution, which is detrimental to obtaining rare earth carbonate materials with uniform size (good length-to-diameter consistency). If the pH of the mixture of the solution and ammonium bicarbonate is too high, the cations on the surface of the rare earth metal carbonate crystal nuclei will further hydrolyze, thereby destroying the needle-like structure of the rare earth metal carbonates. Therefore, controlling the pH of the mixture of the solution and ammonium bicarbonate within the above-mentioned range can ensure the stable growth of the crystal nuclei of the generated rare earth metal carbonates. For example, the pH of the mixture of the solution and ammonium bicarbonate is a value between 6.4, 6.5, 6.6, 6.7, or any combination thereof.

[0048] In some embodiments, the molar concentration of rare earth metal salts in the mixture is between 0.03 mol / L and 0.3 mol / L. If the molar concentration of rare earth metal salts in the mixture is too low, the content of rare earth metal cations in the mixture is insufficient, resulting in a reduced reaction rate between the rare earth metal cations and carbonate ions, making it difficult to generate sufficient rare earth metal carbonates. If the molar concentration of rare earth metal salts in the mixture is too high, it is easy for rare earth metal cations to accumulate excessively in the mixture, causing uneven growth rates of rare earth metal carbonates and affecting the size uniformity of the rare earth carbonate material. Therefore, controlling the molar concentration of rare earth metal salts in the mixture within the above-mentioned range can balance the reaction rate between rare earth metal salts and carbonate ions with the size uniformity of the rare earth carbonate material. For example, the molar concentration of rare earth metal salts in the mixture is a value within a range of 0.03 mol / L, 0.06 mol / L, 0.09 mol / L, 0.12 mol / L, 0.15 mol / L, 0.18 mol / L, 0.21 mol / L, 0.24 mol / L, 0.27 mol / L, 0.3 mol / L, or any combination thereof.

[0049] In some embodiments, the molar ratio of rare earth metal salt to ammonium bicarbonate is (0.03 to 0.3):(0.2 to 2). If the molar ratio of rare earth metal salt to ammonium bicarbonate is too low, i.e., there is an excess of carbonate ions, the excess carbonate ions are prone to causing excessive local reactions, resulting in agglomeration of the rare earth carbonate material, thus affecting the dimensional uniformity of the material. If the molar ratio of rare earth metal salt to ammonium bicarbonate is too high, i.e., there is insufficient carbonate ions, the rare earth metal cations do not react sufficiently, and the rare earth metal cations are prone to excessive agglomeration, resulting in uneven growth rate of rare earth metal carbonates, affecting the dimensional uniformity of the rare earth carbonate material. Therefore, controlling the molar ratio of rare earth metal salt to ammonium bicarbonate within the above-mentioned range can balance sufficient reaction between rare earth metal cations and carbonate ions with the uniformity of the length and diameter of the rare earth carbonate material. For example, the molar ratio of rare earth metal salt to ammonium bicarbonate is a value between 0.03:2, 0.03:0.2, 0.3:2, 0.3:0.2, or any combination thereof.

[0050] In some embodiments, the stirring method includes at least one of ultrasonic stirring and magnetic stirring. Ultrasonic stirring promotes intermolecular collisions and diffusion through high-frequency vibration, which is beneficial to improving the dispersibility of rare earth metal carbonates. Magnetic stirring, through continuous mechanical disturbance, enables rapid mixing of rare earth metal salts and polyethylene glycol, reduces local concentration differences, and is conducive to the formation of a uniform "polyethylene glycol-rare earth metal cation" complex. After the addition of ammonium bicarbonate, polyethylene glycol guides the uniform diffusion of carbonate ions, thereby reducing the uneven growth rate of rare earth metal carbonates caused by insufficient local carbonate ions and excessively high concentrations of rare earth metal cations.

[0051] In some embodiments, step 3 includes: washing the rare earth metal carbonate with ethanol and deionized water alternately to obtain a rare earth carbonate material. Deionized water can dissolve unreacted rare earth metal salts and ammonium bicarbonate; ethanol can reduce the surface tension of the rare earth carbonate material, reduce the adhesion of moisture to the surface of the rare earth carbonate material, and dissolve unbound polyethylene glycol.

[0052] Example The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Unless otherwise stated, all reagents used are commercially available, and all equipment used is conventional equipment.

[0053] Example 1 Preparation of rare earth carbonate materials: Step 1: Mix neodymium chloride, polyethylene glycol, and deionized water to obtain a mixed solution. The polyethylene glycol is used to adsorb neodymium ions contained in the neodymium chloride. The pH of the mixed solution is 2.5, the relative molecular mass of polyethylene glycol is 6000, the mass ratio of polyethylene glycol to neodymium chloride and deionized water is 0.086:1.076:10, and the molar concentration of neodymium chloride in the mixed solution is 0.3 mol / L.

[0054] Step 2: At 45°C, ammonium bicarbonate is added to the mixture under magnetic stirring to allow the neodymium ions adsorbed on the surface of polyethylene glycol to combine with the carbonate ions in the ammonium bicarbonate solution to form neodymium carbonate. The reaction time is 2.5 h. The pH of the mixture of the solution and ammonium bicarbonate is 6.5, and the molar ratio of neodymium chloride to ammonium bicarbonate is 0.3:2.

[0055] Step 3: Separate the precipitate (neodymium carbonate) from Step 2 by centrifugation (centrifugation speed 8000 r / min, time 5 min).

[0056] Neodymium carbonate was obtained by alternately washing with deionized water and ethanol-water, with five washes of deionized water and five washes of ethanol. The volume of ethanol and deionized water added in each wash was 10 ml.

[0057] Example 2 Step 1: Mix neodymium chloride, polyethylene glycol, and deionized water to obtain a mixed solution. The polyethylene glycol is used to adsorb neodymium ions contained in the neodymium chloride. The pH of the mixed solution is 2.5, the relative molecular mass of polyethylene glycol is 4000, the mass ratio of polyethylene glycol to neodymium chloride and deionized water is 0.086:1.076:10, and the molar concentration of neodymium chloride in the mixed solution is 0.3 mol / L.

[0058] Step 2: Add ammonium bicarbonate to the mixture under magnetic stirring so that the neodymium ions adsorbed on the surface of polyethylene glycol combine with the carbonate ions in the ammonium bicarbonate solution to form neodymium carbonate; wherein, the pH of the mixture of the solution and ammonium bicarbonate is 6.6, and the molar ratio of neodymium chloride to ammonium bicarbonate is 0.3:2.

[0059] Step 3: Wash neodymium carbonate alternately with deionized water and ethanol to obtain neodymium carbonate material. Wash with deionized water 5 times and with ethanol 5 times. The volume of ethanol added each time is 10 ml. The volume of deionized water added is 10 ml.

[0060] Example 3 Step 1: Mix neodymium chloride, polyethylene glycol (PEG), and deionized water to obtain a mixed solution. PEG is used to adsorb neodymium ions contained in the neodymium chloride. The pH of the mixed solution is 2.5, the relative molecular mass of PEG is 4000, the mass ratio of PEG to neodymium chloride to deionized water is 0.0086:0.1076:10, and the molar concentration of neodymium chloride in the mixed solution is 0.03 mol / L.

[0061] Step 2: Add ammonium bicarbonate to the mixture under magnetic stirring so that the neodymium ions adsorbed on the surface of polyethylene glycol combine with the carbonate ions in the ammonium bicarbonate solution to form neodymium carbonate; wherein, the pH of the mixture of the mixture and ammonium bicarbonate is 6.5, the molar concentration of neodymium chloride in the mixture is 0.03 mol / L, and the molar ratio of neodymium chloride to ammonium bicarbonate is 0.03:0.2.

[0062] Step 3: Wash neodymium carbonate alternately with deionized water and ethanol to obtain neodymium carbonate material. Wash with deionized water 5 times and with ethanol 5 times. The volume of ethanol added each time is 10 ml. The volume of deionized water added is 10 ml.

[0063] Example 4 Step 1: Mix neodymium chloride, polyethylene glycol, and deionized water to obtain a mixed solution. The polyethylene glycol is used to adsorb neodymium ions contained in the neodymium chloride. The pH of the mixed solution is 2.5, the relative molecular mass of polyethylene glycol is 2000, the mass ratio of polyethylene glycol to neodymium chloride and deionized water is 0.0086:0.1076:10, and the molar concentration of neodymium chloride in the mixed solution is 0.03 mol / L.

[0064] Step 2: Add ammonium bicarbonate to the mixture under magnetic stirring so that the neodymium ions adsorbed on the surface of polyethylene glycol combine with the carbonate ions in the ammonium bicarbonate solution to form neodymium carbonate; wherein, the pH of the mixture of the solution and ammonium bicarbonate is 6.6, and the molar ratio of neodymium chloride to ammonium bicarbonate is 0.03:0.2.

[0065] Step 3: Wash neodymium carbonate alternately with deionized water and ethanol to obtain neodymium carbonate material. Wash with deionized water 5 times and with ethanol 5 times. The volume of ethanol added each time is 10 ml. The volume of deionized water added is 10 ml.

[0066] Example 5 Example 5 was carried out in the same manner as Example 1, except that neodymium chloride was replaced with praseodymium chloride in step 1.

[0067] Comparative Example 1 Step 1: Mix neodymium chloride and deionized water to obtain a mixture with a pH of 2.5 and a molar concentration of neodymium chloride of 0.03 mol / L.

[0068] Step 2: Add ammonium bicarbonate to the mixture under magnetic stirring to allow neodymium ions to combine with carbonate ions in the ammonium bicarbonate solution to form neodymium carbonate; wherein, the pH of the mixture of the solution and ammonium bicarbonate is 6.5, and the molar ratio of neodymium chloride to ammonium bicarbonate is 0.03:0.2.

[0069] Step 3: Wash neodymium carbonate alternately with deionized water and ethanol to obtain neodymium carbonate material. Wash with deionized water 5 times and with ethanol 5 times. The volume of ethanol added each time is 10 ml. The volume of deionized water added is 10 ml.

[0070] Test of fidelity: The rare earth carbonate materials prepared in Examples 1 to 5 and Comparative Example 1 were formulated into slurries and 3D printed to obtain 3D printed products. The fidelity of the 3D printed products was tested, and the testing process is as follows: Linear dimensions were measured using a scanning electron microscope (SEM), and n(3) indices were measured using a coordinate measuring machine (CMM), namely angle, shape, and position dimensions.

[0071] The deviation rate (%) for each dimension is calculated using the following formula.

[0072] Wherein, deviation rate (%) = (measured value) -Design Value ) / Design value ×100%.

[0073] The average absolute deviation rate (MAD) was obtained by averaging the absolute deviation rates for each size, and the test results are recorded in Table 1.

[0074] Where, the mean absolute deviation rate (MAD) (%) = ×100%, where i is the measurement index.

[0075] MAD is used to characterize the fidelity of 3D printed products. A low MAD indicates good fidelity, while a high MAD indicates poor fidelity.

[0076] Table 1

[0077] As can be seen from the data in Table 1, compared with Comparative Example 1, the relative standard deviation of the major diameter in Examples 1 to 5 is less than or equal to 5%, and they have uniform dimensions, thus resulting in improved fidelity of 3D printed products.

[0078] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A rare earth carbonate material, characterized in that, The rare earth carbonate material is needle-shaped, and the relative standard deviation of the major diameter of the rare earth carbonate material is less than or equal to 5%.

2. The rare earth carbonate material according to claim 1, characterized in that, The rare earth carbonate material has an average major diameter of 3 μm to 5 μm.

3. The rare earth carbonate material according to claim 1, characterized in that, The average minor diameter of the rare earth carbonate material is 0.4 μm to 0.5 μm.

4. The rare earth carbonate material according to claim 1, characterized in that, The rare earth carbonate material has an average aspect ratio of 6 to 12.

5.

5. The rare earth carbonate material according to claim 1, characterized in that, In the rare earth carbonate material, the ratio of the mass percentage of oxygen to the mass percentage of carbon is greater than or equal to 4.

6. The rare earth carbonate material according to any one of claims 1 to 5, characterized in that, The rare earth carbonate material includes at least one of praseodymium carbonate, neodymium carbonate, promethium carbonate, and samarium carbonate.

7. A method for preparing a rare earth carbonate material, characterized in that, include: Step 1: Mix rare earth metal salt, polyethylene glycol and deionized water to obtain a mixture, wherein the polyethylene glycol is used to adsorb the rare earth metal cations contained in the rare earth metal salt; Step 2: Add ammonium bicarbonate to the mixture while stirring, so that the rare earth metal cations adsorbed on the surface of the polyethylene glycol combine with the carbonate ions in the ammonium bicarbonate solution to form rare earth metal carbonates. Step 3: Remove the polyethylene glycol used to adsorb the rare earth metal carbonate to obtain a rare earth carbonate material. The rare earth carbonate material is needle-shaped, and the relative standard deviation of the major axis of the rare earth carbonate material is less than or equal to 5%.

8. The preparation method according to claim 7, characterized in that, Step 1 satisfies at least one of the following: (1) The pH of the mixture is 2 to 3; (2) In the mixture, the mass ratio of the polyethylene glycol to the rare earth metal salt is (8 to 13):100; (3) The relative molecular mass of the polyethylene glycol is 2000 to 6000.

9. The preparation method according to claim 7, characterized in that, Step 2 satisfies at least one of the following: (1) The pH of the mixture of the liquid and the ammonium bicarbonate is 6.4 to 6.7; (2) The molar concentration of the rare earth metal salt in the mixture is from 0.03 mol / L to 0.3 mol / L; (3) The molar ratio of the rare earth metal salt to the ammonium bicarbonate is (0.03 to 0.3):(0.2 to 2); (4) The stirring method includes at least one of ultrasonic stirring and magnetic stirring.

10. The preparation method according to any one of claims 7 to 9, characterized in that, Step 3 includes: The rare earth metal carbonates were washed alternately with deionized water and ethanol to obtain rare earth carbonate materials.

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