A method for preparing nanometer gadolinium oxide powder

Abstract

This invention discloses a method for preparing nano-gadolinium oxide powder, comprising the following steps: S1, dissolving 4.5–18 g of gadolinium salt in 95–105 mL of water to obtain a precursor solution; dissolving 48–52 mg of initiator in 30–50 mL of anhydrous ethanol to obtain a solution; adding 10–12 g of polymer monomer, 1–3 g of crosslinking agent, and the solution to the precursor solution, and heating and stirring to obtain a gel; S2, freezing the gel and then vacuum drying to obtain a dry gel; S3, ball milling and sieving the dry gel to obtain a precursor powder, and calcining the precursor powder for the first time to obtain a pre-calcined powder; S4, calcining the pre-calcined powder for the second time and grinding to obtain nano-gadolinium oxide powder. The preparation method of this invention is simple and easy to operate, with a short preparation cycle, and the obtained nano-gadolinium oxide powder has the characteristics of high purity, small particle size, and uniform size distribution.

Description

Technical Field

[0001] This invention relates to the field of inorganic nanomaterial preparation technology, and in particular to a method for preparing nano-gadolinium oxide powder. Background Technology

[0002] With the rapid development of science and technology, human beings have increasingly higher requirements for the performance of materials, posing new demands on materials. Among these, nanomaterials are one of the most promising materials in the field of new materials research today. In the 1990s, the preparation of nanopowders entered the stage of industrial development. To date, the preparation of nanomaterials occupies an important position in current materials science research. Nanomaterials possess numerous interfaces and a large proportion of grain boundary atoms. The scale of their nanostructure units is comparable to many characteristic lengths in matter. This special structure gives them quantum size effects, volume effects, surface effects, macroscopic quantum tunneling effects, and small size effects. These unique effects enable nanomaterials to be widely used in optoelectronics, microelectronic devices, human protective equipment, sensing, new energy, and other fields, driving the development of basic research. The preparation methods of nanomaterials are mainly divided into chemical methods and physical methods. Chemical methods mainly include hydrothermal synthesis, sol-gel methods, and microemulsion methods. Physical methods mainly include vapor deposition, sputtering deposition, and mechanical pulverization methods.

[0003] In recent years, rare earth elements have been widely used in functional ceramics, glass, optical materials, and catalysts due to their high electron valence, large radius, strong reducing properties, good chemical stability, and thermal stability. Among various rare earth materials, gadolinium, with its unique valence electron structure and the characteristics of 4f orbital electrons, can largely compensate for the "weak absorption region" of the outer K-layer electron shell, and has been widely used in optical, electronic, and magnetic materials. Gadolinium mainly exists in nature as gadolinium oxide. Currently, the main methods for preparing nano-gadolinium oxide powder are co-precipitation, hydrothermal, and sol-gel methods. However, these methods have drawbacks such as long processing cycles, complex conditions, and large particle size, low purity, and uneven morphology of the prepared gadolinium oxide powder. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing nano-gadolinium oxide powder.

[0005] The technical solution adopted by this invention to solve its technical problem is: a method for preparing nano-gadolinium oxide powder, comprising the following steps:

[0006] S1. Dissolve 4.5-18g of gadolinium salt in 95-105mL of water to obtain a precursor solution; dissolve 48-52mg of initiator in 30-50mL of anhydrous ethanol to obtain a solution; add 10-12g of polymer monomer, 1-3g of crosslinking agent and solution to the precursor solution, and heat and stir to obtain a gel;

[0007] S2. The gel is frozen and then vacuum dried to obtain a dry gel;

[0008] S3. The dry gel is ball-milled and sieved to obtain precursor powder. The precursor powder is then calcined for the first time to obtain pre-calcined powder.

[0009] S4. The pre-calcined powder is calcined a second time and ground to obtain nano-gadolinium oxide powder.

[0010] Preferably, in step S1, the gadolinium salt is Gd(NO3)3•6H2O or GdCl3•6H2O, and the concentration of the gadolinium salt is 0.1~0.4 mol / L.

[0011] Preferably, in step S1, the initiator is an azo radical initiator, specifically 2,2'-azobisisobutyronitrile or azobisisoheptanenitrile.

[0012] Preferably, in step S1, the polymer monomer is acrylamide, and / or the crosslinking agent is N,N'-methylenebisacrylamide.

[0013] Preferably, in step S1, the heating and stirring process is as follows: stirring at a speed of 200~500 r / min for 20~40 min, while heating to 80~90℃.

[0014] Preferably, in step S2, the freezing treatment is performed by freezing at -60 to -50°C for 2 to 4 hours.

[0015] Preferably, in step S3, the sieving process involves passing the material through an 80-120 mesh sieve.

[0016] Preferably, in step S3, the first calcination is performed by heating the temperature to 380-420°C at a heating rate of 5-10°C / min, holding the temperature for 90-120 minutes, and then cooling to room temperature.

[0017] Preferably, in step S4, the second calcination is performed by heating the temperature to 900-1100°C at a heating rate of 3-8°C / min, holding the temperature for 90-120 minutes, and then cooling it to room temperature.

[0018] Preferably, in step S4, the particle size of the nano-gadolinium oxide powder is 100~300nm.

[0019] The beneficial effects of this invention are:

[0020] This invention prepares gadolinium oxide nanoparticles via a sol-gel method. The reactants can be uniformly mixed at the molecular level in the liquid phase, and the raw materials are free of other elements. The low reaction temperature results in a powder with high purity and a narrow particle size distribution. Adding anhydrous ethanol during gel preparation not only rapidly dissolves the initiator but also increases the viscosity of the system, thereby shortening the gelation time and improving the stability of the colloid. Freeze-drying the gel ensures the integrity of its internal structure and improves the dispersibility of the gadolinium oxide nanoparticles. The double calcination process results in a more perfect calcination system, eliminating hydroxyl and carbon residues in the gadolinium oxide powder, leading to higher purity. Furthermore, the double calcination further optimizes the crystal structure and physical properties of the material, thus improving the overall performance of the gadolinium oxide nanoparticles. The preparation process of this invention is simple, easy to operate, has a short preparation cycle, produces stable and safe finished products, and is environmentally friendly, enabling industrial-scale production and meeting the needs of kilogram-level preparation. The gadolinium oxide nanoparticles obtained by this invention are characterized by high purity, small particle size, and uniform size distribution. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0022] Figure 1 Thermogravimetric analysis (TGA) of the precursor powder in step S3 of Example 1 of this invention;

[0023] Figure 2 The X-ray diffraction pattern of the nano-gadolinium oxide powder prepared in Example 1 of this invention;

[0024] Figures 3-4 This is a scanning electron microscope image of the nano-gadolinium oxide powder prepared in Example 1 of the present invention. Detailed Implementation

[0025] To provide a clearer understanding of the technical features, objectives, and effects of this invention, the invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the invention and do not constitute a limitation on the scope of protection of this invention.

[0026] This invention proposes a method for preparing nano-gadolinium oxide powder, comprising the following steps:

[0027] S1. Dissolve 4.5-18g of gadolinium salt in 95-105mL of water (preferably deionized water) to obtain a precursor solution. The amount of gadolinium salt can be 4.5g, 6g, 9g, 12g, 15g, 18g, etc., and the amount of water can be 95mL, 98mL, 100mL, 102mL, 105mL, etc. Dissolve 48-52mg of initiator in 30-50mL of anhydrous ethanol to obtain a solution. The amount of initiator can be 48mg, 49mg, 50mg, 51mg, 52mg, etc., and the amount of anhydrous ethanol can be 30mL, 35mL, 40mL, 45mL, 50mL, etc. Take 10-12g of polymer monomer, 1-3g of crosslinking agent and solution and add them to the precursor solution, and heat and stir to obtain a gel. The amount of polymer monomer can be 10g, 10.5g, 11g, 11.5g, 12g, etc., and the amount of crosslinking agent can be 1g, 1.5g, 2g, 2.5g, 3g, etc.

[0028] The gadolinium salt can undergo hydrolysis. The gadolinium salt is either Gd(NO3)3•6H2O or GdCl3•6H2O, preferably Gd(NO3)3•6H2O. The concentration of the gadolinium salt needs to be sufficient for complete hydrolysis. The concentration is 0.1~0.4 mol / L, and can be selected from 0.1 mol / L, 0.14 mol / L, 0.2 mol / L, 0.3 mol / L, 0.38 mol / L, 0.4 mol / L, etc., without specific limitation in this invention. The concentration of the gadolinium salt is related to the amount of water used; generally, the higher the concentration of the gadolinium salt, the less water is needed. The morphology and size of nano-gadolinium oxide powder can be controlled by adjusting the concentration and type of gadolinium salt. Specifically, the concentration of gadolinium salt affects the size and distribution of colloidal particles in the gel, resulting in gadolinium oxide powder of different sizes and morphologies during calcination. Lower gadolinium salt concentrations promote the formation of smaller colloidal particles, leading to smaller gadolinium oxide powder after calcination. The gadolinium metal ions generated from the hydrolysis of different gadolinium salts have varying effects on the morphology and size of nano-gadolinium oxide powder.

[0029] The initiator is an azo radical initiator, specifically 2,2'-azobisisobutyronitrile or azobisisoheptanenitrile, preferably 2,2'-azobisisobutyronitrile. The addition of anhydrous ethanol not only rapidly dissolves the initiator but also increases the viscosity of the system, thereby shortening the gelation time and improving the stability of the colloid. The polymer monomer is acrylamide, and the crosslinking agent is N,N'-methylenebisacrylamide, which together form a polyacrylamide network structure. The thermal decomposition products of the polymer monomer, crosslinking agent, and initiator used to prepare the gel are all non-toxic, exhibiting environmental friendliness.

[0030] The above-mentioned gadolinium nitrate hexahydrate (Gd(NO3)3•6H2O, 99.99%), acrylamide (C3H5NO, 99% electrophoretic grade), and N,N'-methylenebisacrylamide (C7H 10 N2O2, 99% electrophoretic grade), 2,2'-azobisisobutyronitrile (C8H) 12 N4 (98%), all of which are commercially available products and can be purchased from Maclean Biotechnology Co., Ltd.

[0031] In step S1, polymer monomers and crosslinking agents undergo free radical polymerization under the initiator, suitable solvent, and temperature to generate a high-molecular-weight polymer that forms a sol-gel framework. Subsequently, the high-molecular-weight polymer undergoes a complexation reaction with gadolinium metal ions provided by gadolinium salts to form a gel.

[0032] Further, the heating and stirring process involves stirring at a speed of 200-500 r / min for 20-40 min while simultaneously heating to 80-90℃ and maintaining this temperature until a transparent gel is obtained. The speed can be 200 r / min, 300 r / min, 350 r / min, 400 r / min, 500 r / min, etc., the stirring time can be 20 min, 23 min, 25 min, 30 min, 40 min, etc., and the heating temperature can be 80℃, 82℃, 85℃, 88℃, 90℃, etc. Magnetic stirring can be used. The heating temperature, stirring speed, and stirring time are interrelated; for example, the higher the heating temperature, the shorter the stirring time.

[0033] S2. The gel is freeze-dried, followed by vacuum drying to obtain a dry gel. Specifically, the gel is placed in a freeze dryer and frozen at -60 to -50°C for 2 to 4 hours, followed by vacuum drying. The freezing temperature can be -60°C, -57°C, -55°C, -53°C, -50°C, etc., and the freezing time can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, etc. During the freeze-drying process, the gel can be pulverized using a tool (such as a glass rod) to increase the freeze-drying rate. Freeze-drying ensures that the water in the gel is completely frozen at low temperatures. Then, under vacuum conditions, the ice directly sublimates into water vapor and is removed to obtain a completely dry gel. Compared with existing high-temperature drying methods, freeze-drying of the gel can ensure the integrity of the internal structure of the gel and improve the dispersibility of the nano-gadolinium oxide powder.

[0034] S3. The dry gel is ball-milled and sieved to obtain precursor powder. The precursor powder is then calcined for the first time to obtain pre-calcined powder. Specifically, the ball mill can use a corundum ball mill jar, and the sieving process is to pass through an 80-120 mesh sieve, where the mesh size of the sieve can be 80, 90, 100, 110, 120, etc. The precursor powder is placed in a heating device (such as a muffle furnace), and the first calcination is as follows: the initial temperature is about 25℃, the temperature is raised to 380-420℃ at a heating rate of 5-10℃ / min, and then held at that temperature for 90-120min, and then cooled to room temperature. The heating rate can be 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, etc., the temperature can be 380℃, 390℃, 400℃, 410℃, 420℃, etc., and the holding time can be 90min, 100min, 105min, 110min, 120min, etc.

[0035] S4. The pre-calcined powder is calcined a second time and ground to obtain nano-gadolinium oxide powder. Specifically, the pre-calcined powder needs to be ground before the second calcination, and choosing a longer or finer grinding time helps to ensure more complete calcination in the later calcination, thereby obtaining smaller nano-powder. The pre-calcined powder after grinding is placed in a heating device, and the second calcination is carried out as follows: the initial temperature is about 25℃, the temperature is raised to 900~1100℃ at a heating rate of 3~8℃ / min, and then held for 90~120min. Then it is cooled to room temperature. The heating rate can be 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, etc., the temperature can be 900℃, 950℃, 1000℃, 1050℃, 1100℃, etc., and the holding time can be 90min, 100min, 105min, 110min, 120min, etc. The powder is then ground in a mortar to obtain nano-gadolinium oxide powder with a particle size of 100~300nm. The particle size of the nano-gadolinium oxide powder can be 100nm, 150nm, 200nm, 250nm, 300nm, etc. The process parameters for the above-mentioned grinding operation can be selected according to actual needs, and the present invention does not impose specific limitations.

[0036] The gadolinium salts used in the preparation process, as well as the moisture contained in the precursor powder, may release -OH (hydroxyl groups) during calcination. In the sol-gel method, a carbon (C) sol-gel framework is formed, which can be oxidized or volatilized through high-temperature calcination. Using a two-calcination method to prepare nano-gadolinium oxide powder results in a more perfect calcination system, and eliminates the residue of -OH and C in the gadolinium oxide powder, leading to higher powder purity. Furthermore, the two-calcination process further optimizes the crystal structure and physical properties of the material, thereby improving the overall performance of the nano-gadolinium oxide powder.

[0037] This invention prepares gadolinium oxide nanoparticles via a sol-gel method. The reactants are uniformly mixed at the molecular level in the liquid phase, and the raw materials are free of other elements. The reaction temperature is low, resulting in powders with high purity and a narrow particle size distribution. The preparation process is simple, easy to operate, and has a short cycle time. The finished product has stable quality and is safe and environmentally friendly. Therefore, only larger-scale reaction equipment is needed to achieve kilogram-scale preparation of gadolinium oxide nanoparticles. The gadolinium oxide nanoparticles obtained by this invention are characterized by high purity, small particle size, and uniform size distribution. They have wide applications in photoluminescence, rare earth permanent magnets, high-temperature ceramics, rare earth extraction, and absorption materials, demonstrating good practical application value and providing a research foundation for the research and application of rare earth materials.

[0038] The following is an illustration through specific examples:

[0039] Nano-gadolinium oxide powders of Examples 1 to 7 were prepared using the above preparation method. The composition and amount of the raw materials are shown in Table 1. The process parameters of heating and stirring in step S1, freezing in step S2, sieving and first calcination in step S3, and second calcination in step S4 are shown in Table 2.

[0040] Table 1. Raw material composition and dosage for Examples 1 to 7

[0041]

[0042] Table 2. Process parameters of the preparation methods in Examples 1 to 7

[0043]

[0044] Thermogravimetric analysis (TG) was performed on the precursor powder in step S3 of Example 1. The purpose was to obtain preliminary mass loss data to infer the approximate calcination temperature range, so as to quickly determine the subsequent calcination temperature. The obtained TG spectrum is shown below. Figure 1 As shown.

[0045] Depend on Figure 1 It can be seen that the thermal decomposition process of the precursor powder mainly consists of three stages: The first stage, around 200℃, involves a 5.03% weight loss due to moisture evaporation, possibly caused by incomplete removal of crystal water during freeze-drying or adsorption of moisture from the air during subsequent operations. The second stage, from 200 to 420℃, primarily involves the transformation of organic groups into a carbon skeleton, with a weight loss of 39.28%. The third stage, from 420 to 780℃, involves a 34.15% weight loss, mainly due to the combustion of C and N into gases and the crystallization and agglomeration of gadolinium oxide. After 800℃, the TG curve tends to flatten, indicating the complete transformation of gadolinium oxide, with a total weight loss exceeding 75%.

[0046] Performance testing:

[0047] X-ray diffraction (XRD) analysis, scanning electron microscopy observation, and dynamic light scattering (DLS) testing were performed on the gadolinium oxide nanoparticles prepared in Example 1. The X-ray diffraction patterns are shown below. Figure 2 As shown, the scanning electron microscope image is as follows: Figures 3-4 The results of the DLS test are shown in Table 3. The DLS test involved cyclically dispersing the nano-gadolinium oxide powder prepared in Example 1 in an aqueous solution three times.

[0048] Table 3 DLS Test Results

[0049]

[0050] according to Figure 2 It can be seen that the gadolinium oxide nanopowder of Example 1 has a good match with the diffraction peaks of the standard gadolinium oxide diffraction file (PDF), and the diffraction peaks have high intensity and sharp shape, with no other impurity phases appearing, indicating that the gadolinium oxide nanopowder prepared by this invention has the characteristics of good crystallinity and high purity. Figures 3-4 As can be seen, the gadolinium oxide nanoparticles of Example 1 are granular. According to Table 3, the average particle size of the gadolinium oxide nanoparticles of Example 1 is 151.17 ± 2.44 nm. Therefore, this invention produces gadolinium oxide nanoparticles with high purity, small particle size, and uniform size distribution.

[0051] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method for preparing nano-gadolinium oxide powder, characterized in that, Includes the following steps: S1. Dissolve 4.5-18g of gadolinium salt in 95-105mL of water to obtain a precursor solution; dissolve 48-52mg of initiator in 30-50mL of anhydrous ethanol to obtain a solution; add 10-12g of polymer monomer, 1-3g of crosslinking agent and the solution to the precursor solution, and heat and stir to obtain a gel; In step S1, the initiator is an azo radical initiator, specifically 2,2'-azobisisobutyronitrile or azobisisoheptanenitrile. In step S1, the polymer monomer is acrylamide and the crosslinking agent is N,N'-methylenebisacrylamide; S2. The gel is frozen and then vacuum dried to obtain a dry gel; S3. The dry gel is ball-milled and sieved to obtain precursor powder. The precursor powder is then calcined for the first time to obtain pre-calcined powder. S4. The pre-calcined powder is calcined a second time and ground to obtain nano-gadolinium oxide powder.

2. The method for preparing nano-gadolinium oxide powder according to claim 1, characterized in that, In step S1, the gadolinium salt is Gd(NO3)3•6H2O or GdCl3•6H2O, and the concentration of the gadolinium salt is 0.1~0.4 mol / L.

3. The method for preparing nano-gadolinium oxide powder according to claim 1, characterized in that, In step S1, the heating and stirring process is as follows: stirring at a speed of 200~500 r / min for 20~40 min, while heating to 80~90℃.

4. The method for preparing nano-gadolinium oxide powder according to claim 1, characterized in that, In step S2, the freezing process involves freezing at -60 to -50°C for 2 to 4 hours.

5. The method for preparing nano-gadolinium oxide powder according to claim 1, characterized in that, In step S3, the sieving process involves passing the material through an 80-120 mesh sieve.

6. The method for preparing nano-gadolinium oxide powder according to claim 1, characterized in that, In step S3, the first calcination is performed by heating the temperature to 380-420°C at a rate of 5-10°C / min, holding the temperature for 90-120 minutes, and then cooling it to room temperature.

7. The method for preparing nano-gadolinium oxide powder according to claim 1, characterized in that, In step S4, the second calcination is performed by heating the temperature to 900-1100°C at a rate of 3-8°C / min, holding the temperature for 90-120 minutes, and then cooling it to room temperature.

8. The method for preparing nano-gadolinium oxide powder according to claim 1, characterized in that, In step S4, the particle size of the nano-gadolinium oxide powder is 100~300nm.

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