Spherical-like nano tungsten oxide and preparation method thereof
The preparation of near-spherical tungsten oxide nanoparticles by liquid nitrogen quenching solves the problems of high cost and instability in the preparation of tungsten oxide nanoparticles in the existing technology, and realizes the preparation of tungsten oxide nanoparticles with high specific surface area and good dispersibility, which is suitable for large-scale industrial production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHONGYI ZHANGYUAN TUNGSTEN
- Filing Date
- 2026-03-23
- Publication Date
- 2026-07-03
Smart Images
Figure CN121894707B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of nanomaterial preparation technology, specifically a spherical nano-tungsten oxide and its preparation method. Background Technology
[0002] In the field of materials science, nano-tungsten oxide has attracted attention due to its unique physical and chemical properties. Compared with macroscopic tungsten oxide, nano-tungsten oxide has a significantly smaller particle size, thus endowing it with a higher specific surface area. This characteristic provides abundant active sites for processes such as catalytic reactions and gas adsorption, enhancing the functionality of the material. Simultaneously, the quantum confinement effect of nano-tungsten oxide significantly influences its electronic structure and light absorption characteristics, which is particularly important in optoelectronic devices and energy conversion technologies. Besides particle size and specific surface area, the microstructure of nano-tungsten oxide also plays a decisive role in its overall performance, including key properties such as mechanical strength and thermal stability.
[0003] Current methods for preparing nano-tungsten oxide all have some shortcomings. Chemical vapor deposition (CVD) has limited its industrialization process due to high cost, complex equipment requirements, and strict control of reaction conditions. The sol-gel method has organic residues that affect product performance, and the particle size will increase during heat treatment. The hydrothermal synthesis method has difficult-to-control reaction conditions, resulting in large fluctuations in product performance.
[0004] Therefore, developing a simple, controllable particle size and morphology preparation process for nano-tungsten oxide with high specific surface area is of great significance for promoting the development of nano-tungsten oxide. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention provides a method for preparing spherical nano-tungsten oxide, comprising the following steps:
[0006] S1. Obtain ammonium tungstate solution;
[0007] S2. Liquid nitrogen is added dropwise to the ammonium tungstate solution to obtain spherical nanocrystals;
[0008] S3. Calcining the quasi-spherical nanocrystals yields quasi-spherical nano-tungsten oxide.
[0009] In step S1, the concentration of the ammonium tungstate solution, calculated as WO3, is 300~450 g / L;
[0010] Specifically, step S2 involves adding liquid nitrogen dropwise to the ammonium tungstate solution while stirring, and then filtering to obtain near-spherical nanocrystals. The volume ratio of the liquid nitrogen to the ammonium tungstate solution is (1.5~2.5):1.
[0011] The drop rate of the liquid nitrogen is 50-80 mL / min.
[0012] Furthermore, in step S1, the concentration of the ammonium tungstate solution (WO3) is any one of 300 g / L, 350 g / L, 400 g / L, 450 g / L, or a range between two of them.
[0013] Furthermore, in step S2, the volume ratio of the liquid nitrogen to the ammonium tungstate solution is any one of (1.5:1), (1.7:1), (1.9:1), (2.0:1), (2.2:1), (2.4:1), (2.5:1), or a range between two of them;
[0014] Furthermore, in step S2, the drop rate of the liquid nitrogen is any one of 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, or a range between two of them.
[0015] In step S2, the stirring rate is 300~500 r / min.
[0016] Furthermore, in step S2, the stirring rate is any one of 300 r / min, 350 r / min, 400 r / min, 450 r / min, 500 r / min, or a range between two of them.
[0017] In step S3, the calcination temperature is 500~700℃ and the time is 1~3h.
[0018] Furthermore, the calcination temperature is any one of 500℃, 550℃, 600℃, 650℃, 700℃, or a range between two of them.
[0019] Specifically, step S2 involves placing the ammonium tungstate solution in a crystallization container and then adding liquid nitrogen. The crystallization container has a double-layer jacket structure, with the inner layer being polytetrafluoroethylene and the outer layer being stainless steel.
[0020] The precipitation rate of the spherical nano-tungsten oxide is greater than or equal to 90%.
[0021] To address the aforementioned technical problems, the present invention also provides a near-spherical nano-tungsten oxide, which is prepared by the above-described method for preparing near-spherical nano-tungsten oxide.
[0022] The specific surface area of the spherical nano-tungsten oxide is 50-80 m². 2 / g.
[0023] Compared with existing technologies such as chemical vapor deposition or hydrothermal synthesis, the present invention has a simple process, eliminates the need for long waiting times and cumbersome high-temperature pretreatment, greatly shortens the production cycle, and is highly controllable with easy parameter adjustment. The raw materials are simple and suitable for large-scale industrial production. The introduction of liquid nitrogen quenching process utilizes the ultra-low temperature environment to instantly achieve a high degree of supersaturation of the solution and generate a large number of fine crystal nuclei. At the same time, the tiny nitrogen bubbles formed by the vaporization of liquid nitrogen effectively inhibit the collision and aggregation between the newly formed crystal nuclei, thereby ensuring good product dispersibility. Attached Figure Description
[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.
[0025] Figure 1 SEM image of the near-spherical tungsten oxide nanoparticles prepared in Example 3;
[0026] Figure 2 SEM image of the near-spherical tungsten oxide nanoparticles prepared in Example 4;
[0027] Figure 3 SEM image of the near-spherical tungsten oxide nanoparticles prepared in Example 5;
[0028] Figure 4 SEM image of the near-spherical tungsten oxide nanoparticles prepared in Example 6;
[0029] Figure 5 The image shows a SEM image of the tungsten oxide prepared in Comparative Example 1.
[0030] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation
[0031] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0032] This invention provides a method for preparing near-spherical nano-tungsten oxide, comprising the following steps:
[0033] S1. Obtain ammonium tungstate solution;
[0034] S2. Liquid nitrogen is added dropwise to the ammonium tungstate solution to obtain spherical nanocrystals;
[0035] S3. Calcining the quasi-spherical nanocrystals yields quasi-spherical nano-tungsten oxide.
[0036] The inventors of this invention discovered through research that adding liquid nitrogen to an ammonium tungstate solution of a certain concentration can achieve the preparation of near-spherical nanocrystals. Furthermore, by calcining these near-spherical nanocrystals, near-spherical nano-tungsten oxide can be prepared. The process is simple, requires no long waiting time or cumbersome high-temperature pretreatment, greatly shortens the production cycle, and is highly controllable, with parameters that are easy to adjust. The raw materials are simple, making it suitable for large-scale industrial production.
[0037] Furthermore, the inventors of this invention have discovered through research that by controlling the concentration of ammonium tungstate solution, the volume ratio of liquid nitrogen to ammonium tungstate solution, and the dropping acceleration rate of liquid nitrogen, it is possible to prepare spherical nano-tungsten oxide with high specific surface area and high tungsten oxide precipitation rate.
[0038] S1. Obtain an ammonium tungstate solution, wherein the concentration of the ammonium tungstate solution, calculated as WO3, is 300~450 g / L;
[0039] The concentration of ammonium tungstate solution is crucial for controlling the quality of subsequent crystallization. If the concentration (WO3) is below 300 g / L, the crystallization efficiency will be low. If the concentration is above 450 g / L, the solution viscosity will be too high, and local supersaturation will easily occur during rapid cooling, leading to agglomeration. In addition, the dissolution temperature is controlled at 70~90℃ to ensure that the raw materials are fully dissolved while ensuring reasonable energy consumption, and to avoid the residual undissolved solids becoming heterogeneous nuclei for later crystallization, thereby interfering with the regularity of product particle size and morphology.
[0040] The ammonium tungstate solution in this invention can be obtained by dissolving ammonium tungstate in deionized water at a temperature of 70~90°C.
[0041] S2. Liquid nitrogen is added dropwise to the ammonium tungstate solution while stirring. After filtration, spherical nanocrystals are obtained. The volume ratio of liquid nitrogen to ammonium tungstate solution is (1.5~2.5):1, and the dropping rate is 50~80mL / min.
[0042] In this step, by controlling the synergistic effect of the dropping acceleration rate and the stirring rate, the aim is to avoid sudden drops in local temperature gradients within the solution, ensuring uniform nucleation of ammonium tungstate throughout the entire solution. Utilizing the ultra-low temperature characteristics of liquid nitrogen, the ammonium tungstate solution can be instantly brought to a highly supersaturated state, thereby inducing the formation of a large number of fine and uniform crystal nuclei. During this process, the liquid nitrogen rapidly absorbs heat and vaporizes upon contact with the solution, and the resulting tiny N2 bubbles are evenly distributed with stirring, acting as a "nucleus isolation medium," effectively reducing collisions and secondary agglomeration between newly formed crystal nuclei. This is the core physical mechanism for obtaining high specific surface area and regular spherical nanomorphic morphology. If the dropping acceleration rate is too fast (e.g., exceeding 80 mL / min), ice crystals are easily generated in the solution, making subsequent filtration separation impossible. If the stirring rate is too fast (e.g., exceeding 500 r / min), it will cause uneven crystal nucleation rate, leading to uncontrolled product particle size.
[0043] S3. Calcining the quasi-spherical nanocrystals yields quasi-spherical nano-tungsten oxide.
[0044] In this step, the calcination process realizes the phase transformation of ammonium tungstate to tungsten oxide. The calcination temperature needs to be controlled between 500 and 700℃. If the temperature is too low, the decomposition will be incomplete; if the temperature is too high (such as reaching 900℃), the WO3 grains will undergo violent overgrowth and sintering agglomeration, resulting in the collapse of the spherical morphology and a sharp decrease in specific surface area.
[0045] In the embodiments of the present invention, the crystallization containers used are all double-layered jacketed structures, with the inner layer being polytetrafluoroethylene (PTFE) and the outer layer being stainless steel. The inner PTFE layer can prevent corrosion and prevent new crystals from adhering to the container wall, while the outer stainless steel layer provides sufficient mechanical strength. The double-layered jacketed structure plays a crucial role in cold insulation / heat preservation during the liquid nitrogen quenching process.
[0046] Example 1
[0047] A method for preparing spherical nano-tungsten oxide includes the following steps:
[0048] S1. Obtain an ammonium tungstate solution with a concentration of 300 g / L;
[0049] S2. Liquid nitrogen is added dropwise to the ammonium tungstate solution to obtain near-spherical nanocrystals. The volume ratio of liquid nitrogen to the ammonium tungstate solution is 1:1, and the dropping rate is 50 mL / min.
[0050] S3. Calcining the quasi-spherical nanocrystals yields quasi-spherical nano-tungsten oxide at a temperature of 500°C for 1 hour.
[0051] The obtained spherical nano-tungsten oxide had a specific surface area of 42 m². 2 / g;
[0052] Calculations show that the precipitation rate of spherical nano-tungsten oxide is 81.3%.
[0053] Example 2
[0054] Unlike Example 1, in step S1, the concentration of the ammonium tungstate solution is 200 g / L.
[0055] The obtained spherical nano-tungsten oxide had a specific surface area of 89 m². 2 / g;
[0056] Calculations show that the precipitation rate of spherical nano-tungsten oxide is 86.5%.
[0057] Example 3
[0058] Unlike Example 1, in step S2, the stirring rate is 700 r / min.
[0059] The specific surface area of the obtained tungsten oxide was measured to be 40.53 m². 2 / g;
[0060] The tungsten oxide precipitation rate was calculated to be 88.2% (in this embodiment, only a portion of the tungsten oxide prepared is spherical nano-tungsten oxide, and the specific proportion of spherical nano-tungsten oxide cannot be determined, so only the tungsten oxide precipitation rate is given).
[0061] Please see Figure 1 , Figure 1 The image shows a SEM image of the near-spherical nano-tungsten oxide prepared in Example 3. The SEM image shows that some particles are near-spherical, while others are irregular in shape, indicating a mixture of particles of different sizes.
[0062] Example 4
[0063] Unlike Example 1, in step S2, liquid nitrogen is added dropwise to the ammonium tungstate solution while stirring. After filtration, spherical nanocrystals are obtained. The volume ratio of liquid nitrogen to ammonium tungstate solution is 1.5:1, the dropping rate is 50 mL / min, and the stirring rate is 300 r / min.
[0064] Testing revealed that the specific surface area of the near-spherical nano-tungsten oxide was 76 m². 2 / g;
[0065] Calculations show that the precipitation rate of spherical nano-tungsten oxide is 92.0%.
[0066] Please see Figure 2 , Figure 2 The image shows a SEM image of the near-spherical nano-tungsten oxide prepared in Example 4. The SEM image shows that the crystals exhibit a regular near-spherical nano-morphology with uniform particle size and good dispersion.
[0067] Example 5
[0068] Unlike Example 1, in step S1, the concentration of the ammonium tungstate solution, expressed as WO3, is 450 g / L.
[0069] In step S2, liquid nitrogen is added dropwise to the ammonium tungstate solution while stirring. After filtration, spherical nanocrystals are obtained. The volume ratio of liquid nitrogen to ammonium tungstate solution is 2.5:1, the dropping rate is 80 mL / min, and the stirring rate is 500 r / min.
[0070] In step S3, the near-spherical nanocrystals are calcined to obtain near-spherical nano-tungsten oxide. The calcination temperature is 700℃ and the time is 3h.
[0071] Testing revealed that the specific surface area of the near-spherical nano-tungsten oxide was 53 m². 2 / g;
[0072] Calculations show that the precipitation rate of spherical nano-tungsten oxide is 93.8%.
[0073] Please see Figure 3 , Figure 3 The image shows a SEM image of the near-spherical nano-tungsten oxide prepared in Example 5. The SEM image shows that its morphology still maintains a near-spherical shape, but compared with Example 1, the grain size is slightly larger due to the increase in calcination temperature.
[0074] Example 6
[0075] Unlike Example 1, in step S1, the concentration of the ammonium tungstate solution, expressed as WO3, is 350 g / L.
[0076] In step S2, liquid nitrogen is added dropwise to the ammonium tungstate solution while stirring. After filtration, spherical nanocrystals are obtained. The volume ratio of liquid nitrogen to ammonium tungstate solution is 2:1, the dropping rate is 70 mL / min, and the stirring rate is 400 r / min.
[0077] In step S3, the near-spherical nanocrystals are calcined to obtain near-spherical nano-tungsten oxide. The calcination temperature is 600℃ and the time is 2h.
[0078] Testing revealed that the specific surface area of the near-spherical nano-tungsten oxide was 61 m². 2 / g;
[0079] Calculations show that the precipitation rate of spherical nano-tungsten oxide is 94.5%.
[0080] Please see Figure 4 , Figure 4The image shows a SEM image of the near-spherical nano-tungsten oxide prepared in Example 6. The SEM image shows that the crystals have a regular near-spherical nano-morphology, the particle size uniformity is between that of Example 3 and Example 4, the dispersion is good, and there is no obvious agglomeration.
[0081] Comparative Example 1
[0082] Unlike Example 1, in step S2, liquid nitrogen is not used; instead, natural cooling is employed.
[0083] The specific surface area of the obtained tungsten oxide was measured to be 3.75 m². 2 / g;
[0084] The calculated precipitation rate of tungsten oxide is 75.0%.
[0085] Please see Figure 5 , Figure 5 The image shows the SEM image of the tungsten oxide prepared in Comparative Example 1. The SEM image shows that the product has an irregular spherical morphology, the particles are irregular blocks, the particle size is large and the agglomeration phenomenon is serious. There are no nanoscale crystal nuclei generation characteristics, indicating that nanoscale nucleation cannot be achieved without the liquid nitrogen quenching process.
[0086] Compared with existing technologies such as chemical vapor deposition or hydrothermal synthesis, the present invention has a simple process, eliminates the need for long waiting times and cumbersome high-temperature pretreatment, greatly shortens the production cycle, and is highly controllable with easy parameter adjustment. The raw materials are simple and suitable for large-scale industrial production. The introduction of liquid nitrogen quenching process utilizes the ultra-low temperature environment to instantly achieve a high degree of supersaturation of the solution and generate a large number of micro crystal nuclei. At the same time, the tiny nitrogen bubbles formed by the vaporization of liquid nitrogen effectively inhibit the collision and aggregation between the newly formed crystal nuclei, thereby ensuring good product dispersibility.
[0087] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.
Claims
1. A method for preparing near-spherical nano-tungsten oxide, characterized in that, Includes the following steps: S1. Obtain ammonium tungstate solution; S2. Liquid nitrogen is added dropwise to the ammonium tungstate solution to obtain spherical nanocrystals; S3. Calcining the quasi-spherical nanocrystals yields quasi-spherical nano-tungsten oxide; In step S1, the concentration of the ammonium tungstate solution, calculated as WO3, is 300~450 g / L; Specifically, step S2 involves adding liquid nitrogen dropwise to the ammonium tungstate solution while stirring, and then filtering to obtain near-spherical nanocrystals. The volume ratio of liquid nitrogen to the ammonium tungstate solution is (1.5~2.5):1; the dropping rate of the liquid nitrogen is 50~80 mL / min, and the stirring rate is 300~500 r / min. In step S3, the calcination temperature is 500~700℃; The precipitation rate of the spherical nano-tungsten oxide is greater than or equal to 90%, and the specific surface area of the spherical nano-tungsten oxide is 50~80 m². 2 / g.
2. The method for preparing quasi-spherical nano-tungsten oxide according to claim 1, characterized in that, In step S3, the calcination time is 1-3 hours.
3. The method for preparing quasi-spherical nano-tungsten oxide according to claim 1, characterized in that, Specifically, step S2 involves placing the ammonium tungstate solution in a crystallization container and then adding liquid nitrogen. The crystallization container has a double-layer jacket structure, with the inner layer being polytetrafluoroethylene and the outer layer being stainless steel.
4. A quasi-spherical nano-tungsten oxide, characterized in that, The spherical nano-tungsten oxide is prepared by the method described in any one of claims 1 to 3.