Preparation method of ultrafine holmium oxide nanomaterial

Abstract

The present application relates to the technical field of rare earth material preparation, in particular to a preparation method of superfine holmium oxide nanomaterial. The present application adopts electrochemical deposition technology, deposits holmium precursor film on the electrode surface in holmium ion-containing electrolyte by regulating electrochemical parameters, and then converts the holmium precursor film into superfine holmium oxide nanoparticles through calcination treatment. The preparation method provided by the present application can avoid the complex reaction steps in traditional chemical synthesis, realize the preparation of nanoparticle holmium oxide with controllable particle size and uniform morphology, and the process is green and environmentally friendly, the equipment is simple and easy to operate, and is suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of rare earth material preparation technology, specifically to a method for preparing ultrafine holmium oxide nanomaterials. Background Technology

[0002] Holmium oxide (Ho₂O₃), as an important rare earth oxide, has wide applications in many high-tech fields due to its unique optical, magnetic, and material properties. Holmium-doped yttrium aluminum garnet (Ho:YAG) lasers can emit laser light with a wavelength of 2 μm. This wavelength has extremely high absorption in human tissue, almost three thousand times that of traditional Hd:YAG lasers. Therefore, in medical surgery, it not only improves the efficiency and precision of the procedure but also significantly reduces the area of ​​thermal damage, improving patient safety and postoperative recovery. Furthermore, adding a small amount of holmium to the magnetostrictive alloy Terfenol-D can reduce the external magnetic field strength required for the alloy to reach saturation magnetization, thus improving material properties. Holmium-doped optical fiber materials play an important role in optical communication devices such as fiber lasers, fiber amplifiers, and fiber sensors. With the rapid development of optical communication technology, its application prospects are increasingly broad.

[0003] Currently, nanoscale holmium oxide is widely used in the pressureless sintering process to prepare advanced functional materials such as high-performance silicon nitride (Si3N4) ceramics, transparent ceramics for white LEDs, high-performance CPP films, and permanent magnet materials. Holmium oxide preparation techniques primarily employ chemical precipitation methods, typically using oxalate or ammonia-containing precipitants to form a precursor, followed by high-temperature calcination to obtain holmium oxide. However, existing methods suffer from problems such as uneven particle size, poor dispersibility, and insufficient environmental performance, limiting the stability of holmium oxide applications in high-performance materials and the green and environmentally friendly nature of the preparation process.

[0004] Therefore, developing efficient, environmentally friendly, and controllable holmium oxide nanoparticle preparation technology has become an important direction for promoting technological progress in its application fields. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the present invention aims to provide a method for preparing ultrafine holmium oxide nanomaterials. This invention employs electrochemical deposition technology, depositing a holmium precursor film on the electrode surface in a holmium-ion-containing electrolyte by controlling electrochemical parameters, followed by calcination to transform it into ultrafine holmium oxide nanoparticles. The preparation method provided by this invention avoids the complex reaction steps of traditional chemical synthesis, achieving the preparation of nano-holmium oxide with controllable particle size and uniform morphology. Furthermore, this process is environmentally friendly, requires simple and easy-to-use equipment, and is suitable for large-scale production.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing ultrafine holmium oxide nanomaterials includes the following steps:

[0008] S1. Clean the working electrode sequentially with acetone, ethanol and deionized water using ultrasonic cleaning for 5-10 minutes each step, and then dry it for later use.

[0009] S2. Install the working electrode, reference electrode, and counter electrode in the electrochemical cell in sequence, inject the prepared electrolyte, and connect the working electrode, reference electrode, and counter electrode to the electrochemical workstation.

[0010] S3. Set the constant potential to -0.9 to -0.7 V and stir the electrolyte for 30 to 40 minutes to uniformly deposit a holmium precursor film on the surface of the working electrode;

[0011] S4. Remove the working electrode, scrape off the holmium precursor film with a scraper, place it in a tube furnace, program the temperature to 450-550℃, hold for 2-3 hours, and cool to room temperature to obtain the ultrafine holmium oxide nanomaterial.

[0012] Preferably, in step S1, the working electrode is selected from either a platinum electrode or a graphite electrode.

[0013] Preferably, in step S2, the reference electrode is selected from either a saturated calomel electrode or an Ag / AgCl electrode.

[0014] Preferably, in step S2, the counter electrode is selected from platinum wire or graphite rod.

[0015] Preferably, in step S2, the electrolyte is a 0.05-0.1 mol / L Ho(NO3)3 solution, and 0.1-0.2 mol / L sodium acetate is added to adjust the pH of the electrolyte to 4.5-5.0.

[0016] Preferably, the electrolyte comprises the following components per liter: 0.05-0.1 mol / L Ho(NO3)3 solution, 0.01-0.05 g / L polyethyleneimine, 0.01-0.03 mol / L 1-butyl-3-methylimidazolium tetrafluoroborate, 0.005-0.01 mol / L ethylene glycol, 0.14-0.16 mol / L citric acid, 0.1-0.2 mol / L hexamethylenetetramine, and 0.8-1 g / L polyvinylpyrrolidone.

[0017] Preferably, in step S3, the stirring speed is 200-300 rpm.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1. This invention employs electrochemical deposition technology to deposit a holmium precursor film on the electrode surface in an electrolyte containing holmium ions by adjusting electrochemical parameters. Subsequently, it is converted into ultrafine holmium oxide nanoparticles through calcination. This avoids the complex reaction steps in traditional chemical synthesis, achieving the preparation of nano-holmium oxide with controllable particle size and uniform morphology. Moreover, this process is green and environmentally friendly, and the equipment is simple and easy to use, making it suitable for large-scale production.

[0020] 2. The electrolyte provided by this invention uses Ho(NO3)3 as the main source of holmium ions, ensuring a sufficient supply of metal ions to support a uniform and efficient electrodeposition process. Low-concentration polyethyleneimine, with its abundant amine functional groups, can form stable complexes with holmium ions, regulating the release rate of metal ions, promoting uniform nucleus formation, and effectively inhibiting particle aggregation, thus contributing to a fine and uniform deposition layer. 1-Butyl-3-methylimidazolium tetrafluoroborate, as an ionic liquid component, improves the conductivity and electrochemical stability of the electrolyte while providing a wide electrochemical window, optimizing the reaction environment at the electrode interface, effectively mitigating side reactions such as hydrogen evolution, and promoting the orderly growth of nanostructures. Ethylene glycol mainly improves the wettability and ion diffusion properties of the solution, enhancing the overall mass transfer efficiency of the electrolyte, which is beneficial for forming a dense and uniform deposition layer. The buffer pair formed by citric acid and hexamethylenetetramine controls pH stability and can further stabilize the coordination state of holmium ions in the solution, regulate ion activity, and inhibit undesirable deposition phenomena, thereby improving the controllability of the deposition process and the quality of the deposition layer. Polyvinylpyrrolidone (PVP) acts as a surfactant and film-forming aid, controlling the size and morphology of nanoparticles, improving the density and mechanical bonding of the deposited layer, and enhancing the overall performance and stability of the material.

[0021] The components work synergistically to construct a stable, efficient, and multifunctional electrolyte system, providing a solid foundation for the preparation of high-quality ultrafine holmium oxide nanomaterials. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the preparation process of the ultrafine holmium oxide nanomaterials described in this invention.

[0023] Figure 2 SEM images of ultrafine holmium oxide nanomaterials at different sizes obtained in Example 1 of this invention, wherein: (a) 5 μm size; (b) 2 μm size; (c) 1 μm size; (d) 500 nm size; (e) 300 nm size; (f) 200 nm size;

[0024] Figure 3 This is a SEM image of the ultrafine holmium oxide nanomaterials prepared in Comparative Example 1 of this invention;

[0025] Figure 4This is a BET specific surface area curve of the ultrafine holmium oxide nanomaterial described in Example 1 of the present invention;

[0026] Figure 5 This is a BET specific surface area curve of the ultrafine holmium oxide nanomaterial described in Example 2 of the present invention;

[0027] Figure 6 This is a BET specific surface area curve of the ultrafine holmium oxide nanomaterial described in Example 3 of the present invention;

[0028] Figure 7 This is a particle size distribution diagram of the ultrafine holmium oxide nanomaterial described in Example 1 of the present invention;

[0029] Figure 8 This is a particle size distribution diagram of the ultrafine holmium oxide nanomaterial described in Example 2 of the present invention;

[0030] Figure 9 This is a particle size distribution diagram of the ultrafine holmium oxide nanomaterial described in Example 3 of the present invention;

[0031] Figure 10 This is a particle size distribution diagram of the ultrafine holmium oxide nanomaterial described in Comparative Example 1 of the present invention. Detailed Implementation

[0032] The present invention will now be clearly and completely described in conjunction with embodiments thereof. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] Please see Figure 1-10 The present invention provides a technical solution:

[0034] Example 1: This example provides a method for preparing ultrafine holmium oxide nanomaterials, including the following steps:

[0035] S1. Clean the working electrode sequentially with acetone, ethanol and deionized water using ultrasonic cleaning for 5 minutes each, and then dry it for later use.

[0036] S2. Install the working electrode, reference electrode, and counter electrode in the electrochemical cell in sequence, inject the prepared electrolyte, and connect the working electrode, reference electrode, and counter electrode to the electrochemical workstation.

[0037] S3. Set the constant potential to -0.9 V and stir the electrolyte at 200 rpm for 30 min to uniformly deposit a holmium precursor film on the surface of the working electrode;

[0038] S4. Remove the working electrode, scrape off the holmium precursor film with a scraper, place it in a tube furnace, program the temperature to 450°C, hold for 3 hours, and cool to room temperature to obtain the ultrafine holmium oxide nanomaterial.

[0039] In the above process, the working electrode is a platinum electrode; the reference electrode is a saturated calomel electrode; the counter electrode is a platinum wire; the electrolyte per liter comprises the following components: 0.05 mol / L Ho(NO3)3 solution, 0.01 g / L polyethyleneimine, 0.01 mol / L 1-butyl-3-methylimidazolium tetrafluoroborate, 0.005 mol / L ethylene glycol, 0.14 mol / L citric acid, 0.1 mol / L hexamethylenetetramine, 0.8 g / L polyvinylpyrrolidone, and adjusted to pH 4.5 with 0.1 mol / L sodium acetate.

[0040] Example 2: This example provides a method for preparing ultrafine holmium oxide nanomaterials, including the following steps:

[0041] S1. Clean the working electrode sequentially with acetone, ethanol and deionized water using ultrasonic cleaning for 10 minutes each step, and then dry it for later use.

[0042] S2. Install the working electrode, reference electrode, and counter electrode in the electrochemical cell in sequence, inject the prepared electrolyte, and connect the working electrode, reference electrode, and counter electrode to the electrochemical workstation.

[0043] S3. Set the constant potential to -0.8 V and stir the electrolyte at 250 rpm for 30 min to uniformly deposit a holmium precursor film on the surface of the working electrode;

[0044] S4. Remove the working electrode, scrape off the holmium precursor film with a scraper, place it in a tube furnace, program the temperature to 500°C, hold for 2.5 hours, and cool to room temperature to obtain the ultrafine holmium oxide nanomaterial.

[0045] In the above process, the working electrode is a graphite electrode; the reference electrode is a saturated calomel electrode; the counter electrode is a platinum wire; and the electrolyte comprises the following components per liter: 0.07 mol / L Ho(NO3)3 solution, 0.03 g / L polyethyleneimine, 0.02 mol / L 1-butyl-3-methylimidazolium tetrafluoroborate, 0.007 mol / L ethylene glycol, 0.15 mol / L citric acid, 0.1 mol / L hexamethylenetetramine, and 0.8 g / L polyvinylpyrrolidone, and is adjusted to pH 5 with 0.1 mol / L sodium acetate.

[0046] Example 3: This example provides a method for preparing ultrafine holmium oxide nanomaterials, including the following steps:

[0047] S1. Clean the working electrode sequentially with acetone, ethanol and deionized water using ultrasonic cleaning for 8 minutes each step, and then dry it for later use.

[0048] S2. Install the working electrode, reference electrode, and counter electrode in the electrochemical cell in sequence, inject the prepared electrolyte, and connect the working electrode, reference electrode, and counter electrode to the electrochemical workstation.

[0049] S3. Set the constant potential to -0.7 V and stir the electrolyte at 300 rpm for 30 min to uniformly deposit a holmium precursor film on the surface of the working electrode;

[0050] S4. Remove the working electrode, scrape off the holmium precursor film with a scraper, place it in a tube furnace, program the temperature to 550°C, hold for 2 hours, and cool to room temperature to obtain the ultrafine holmium oxide nanomaterial.

[0051] In the above process, the working electrode is a graphite electrode; the reference electrode is an Ag / AgCl electrode; the counter electrode is a graphite rod; and the electrolyte comprises the following components per liter: 0.1 mol / L Ho(NO3)3 solution, 0.05 g / L polyethyleneimine, 0.03 mol / L 1-butyl-3-methylimidazolium tetrafluoroborate, 0.01 mol / L ethylene glycol, 0.16 mol / L citric acid, 0.2 mol / L hexamethylenetetramine, 1 g / L polyvinylpyrrolidone, and adjusted to pH 4.65 with 0.1 mol / L sodium acetate.

[0052] Comparative Example

[0053] Comparative Example 1: The only difference between Comparative Example 1 and Example 1 is that the use of polyethyleneimine, 1-butyl-3-methylimidazolium tetrafluoroborate, ethylene glycol, and polyvinylpyrrolidone in the electrolyte components originally present in Example 1 is omitted in Comparative Example 1. The remaining steps are exactly the same in Comparative Example 1 and Example 1.

[0054] Performance testing: The ICP test data of the ultrafine holmium oxide nanomaterials prepared in Examples 1-3 and Comparative Example 1 of this invention are shown below:

[0055]

[0056] As can be seen from the ICP test data of Examples 1-3 and Comparative Example 1, the ultrafine holmium oxide nanomaterials prepared by the present invention contain almost no additional rare earth elements and have extremely high purity.

[0057] SEM images of different sizes of the ultrafine holmium oxide nanomaterials prepared in Example 1 are shown below. Figure 2 As shown:

[0058] in, Figure 2a and 2b are low-magnification images. The particle distribution is relatively uniform, and the particle clusters are dispersed on the substrate surface. The size of the aggregates ranges from hundreds of nanometers to several micrometers. There are certain gaps between the particles, showing good dispersibility, but some particles have already shown initial agglomeration.

[0059] Figure 2 c and 2d are medium magnification images. The particle morphology is clearer in the images. Most of the particles are irregular polyhedral in shape. Some particles have smooth surfaces and the degree of aggregation is increased. At the same time, the interfaces between particles are clear, indicating that the deposition process has controlled the uniformity of particles to a certain extent.

[0060] Figure 2 e and 2f are high-magnification images. As shown in the figures, the particle morphology tends to be nearly spherical and the surface has a certain degree of roughness, indicating that the nanoparticles have good crystallinity and good particle size uniformity. However, there is some particle agglomeration, which may affect their dispersibility and subsequent application performance.

[0061] SEM images of different sizes of the ultrafine holmium oxide nanomaterials prepared in Comparative Example 1 are shown below. Figure 3 As shown, the nanoparticles exhibit a certain degree of aggregation, with blurred particle boundaries. The morphology and size of individual particles are difficult to distinguish clearly, and the dispersibility is lower than that of Example 1. The overall particle morphology is relatively irregular, with insufficient surface detail and generally poor crystallinity, indicating limited control over particle uniformity and dispersibility during the preparation process. Compared to the more uniform and clearly morphologically clear particles in Example 1, the material in Comparative Example 1 still has room for improvement in terms of particle distribution and morphological uniformity.

[0062] Figure 4-6 The figure shows the BET specific surface area curves of the ultrafine holmium oxide nanomaterials described in Examples 1-3 of this invention. The specific surface areas of Examples 1-3 are shown below:

[0063]

[0064] The difference in specific surface area between Examples 1 and 3 is mainly due to the fact that in Example 1, the use of platinum electrodes, a lower constant potential (-0.9 V), a lower calcination temperature (450℃), and a longer calcination time (3h) resulted in smaller nano-holmium oxide particles with better dispersion. The particles exhibited a transformation from irregular polyhedrons to near-spherical shapes, good crystallinity, and less agglomeration, resulting in a uniform distribution of the overall particles and thus a larger specific surface area. In contrast, in Example 2, the use of graphite electrodes, a constant potential of -0.8 V, a calcination temperature of 500℃, and a calcination time of 2.5h resulted in larger particle sizes and increased agglomeration compared to Example 1, leading to a decrease in specific surface area to 14.29 m² / g. The increased stirring speed and electrolyte concentration compared to Example 1 may have led to faster particle growth and increased aggregation. In Example 3, a graphite electrode and an Ag / AgCl reference electrode were used, with a constant potential of -0.7 V, the highest calcination temperature (550℃), and the shortest calcination time (2h). This resulted in a further increase in particle size, significant agglomeration, and a further decrease in specific surface area to 13.35 m² / g. The higher calcination temperature promoted particle growth and sintering, thus affecting the specific surface area.

[0065] Figure 7-10 The particle size distribution diagrams of the ultrafine holmium oxide nanomaterials prepared in Examples 1-3 and Comparative Example 1 of this invention are shown in the figure. The D10, D25, D50, D75, D90, and D99 values ​​of Examples 1-3 and Comparative Example 1 are as follows:

[0066]

[0067] The D50 of Example 1 was 0.149 μm, that of Example 2 was 0.155 μm, and that of Example 3 was significantly increased to 0.194 μm, indicating that the particle size of Example 3 was generally larger and the particle size distribution was wider. The D75 and D90 values ​​of Examples 1 and 2 were similar, ranging from 0.227 to 0.262 μm and 1.5 to 1.85 μm respectively, indicating that the particle size distribution of both was relatively concentrated and the particles were relatively uniform. The D90 particle size of Example 3 increased to 2.191 μm, and the D99 reached 5.833 μm, showing the presence of obvious coarse particles or agglomerates, a wider particle size distribution, and relatively poor uniformity. Meanwhile, the D10 values ​​of all examples were in the range of 0.075 to 0.082 μm, indicating that all three preparation conditions could generate a certain proportion of ultrafine particles. However, the particle size distribution data of Comparative Example 1 showed that its particle size was significantly larger and the distribution range was extremely wide, exhibiting significant particle agglomeration and aggregation. Specifically, its D50 value was 0.241 μm, significantly larger than that of Example 1 (0.149 μm) and Example 2 (0.155 μm), reflecting a substantial increase in the average particle size, indicating that particle growth was not effectively controlled during the preparation process. Furthermore, its D90 value was as high as 14.488 μm, and its D99 reached 38.378 μm, indicating the presence of a large number of coarse particles or agglomerates with sizes far exceeding the nanometer scale. The presence of such large particles significantly reduces the specific surface area and activity of the material, affecting its uniformity and subsequent application performance. Compared to the examples where the particle size was relatively concentrated, uniformly distributed, and less agglomerated, the particle size distribution of Comparative Example 1 deviated significantly from the ideal state, showing a lack of effective dispersants and stabilizers in the preparation process. This resulted in excessive agglomeration and sintering of the particles during deposition and calcination, which is not conducive to the formation of uniform and fine nanoparticles.

[0068] The above strongly demonstrates that the preparation method provided by the present invention can avoid the complex reaction steps in traditional chemical synthesis, realize the preparation of nano-holmium oxide with controllable particle size and uniform morphology, and the process is green and environmentally friendly, with simple and easy-to-use equipment, making it suitable for large-scale production.

[0069] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing ultrafine holmium oxide nanomaterials, characterized in that, Includes the following steps: S1. Clean the working electrode sequentially with acetone, ethanol and deionized water using ultrasonic cleaning for 5-10 minutes each step, and then dry it for later use. S2. Install the working electrode, reference electrode, and counter electrode in the electrochemical cell in sequence, inject the prepared electrolyte, and connect the working electrode, reference electrode, and counter electrode to the electrochemical workstation. S3. Set the constant potential to -0.9 to -0.7 V and stir the electrolyte for 30 to 40 min to uniformly deposit a holmium precursor film on the surface of the working electrode; S4. Remove the working electrode, scrape off the holmium precursor film with a scraper, place it in a tube furnace, program the temperature to 450-550℃, hold for 2-3 hours, cool to room temperature, and obtain the ultrafine holmium oxide nanomaterial. The electrolyte comprises the following components per liter: 0.05-0.1 mol / L Ho(NO3)3 solution, 0.01-0.05 g / L polyethyleneimine, 0.01-0.03 mol / L 1-butyl-3-methylimidazolium tetrafluoroborate, 0.005-0.01 mol / L ethylene glycol, 0.14-0.16 mol / L citric acid, 0.1-0.2 mol / L hexamethylenetetramine, and 0.8-1 g / L polyvinylpyrrolidone.

2. The method for preparing ultrafine holmium oxide nanomaterials according to claim 1, characterized in that, In step S1, the working electrode is selected from either a platinum electrode or a graphite electrode.

3. The method for preparing ultrafine holmium oxide nanomaterials according to claim 1, characterized in that, In step S2, the reference electrode is selected from either a saturated calomel electrode or an Ag / AgCl electrode.

4. The method for preparing ultrafine holmium oxide nanomaterials according to claim 1, characterized in that, In step S2, the counter electrode is selected from platinum wire or graphite rod.

5. The method for preparing ultrafine holmium oxide nanomaterials according to claim 1, characterized in that, In step S2, the electrolyte is a 0.05-0.1 mol / L Ho(NO3)3 solution, and 0.1-0.2 mol / L sodium acetate is added to adjust the pH of the electrolyte to 4.5-5.

0.

6. The method for preparing ultrafine holmium oxide nanomaterials according to claim 1, characterized in that, In step S3, the stirring speed is 200-300 rpm.

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