A sheet-like rare earth-based molybdate ceramic material and a method for producing the same

Abstract

The application discloses a flaky rare earth-based molybdate ceramic material and a preparation method thereof. The chemical formula of the ceramic material is Re2MoO6, wherein the rare earth element Re is selected from one, two or more of La, Ce, Pr, Eu, Ho, Er, Yb and Tm. The ceramic material is prepared by an electrostatic spinning method, and specifically comprises the following steps: (1) mixing a rare earth salt, a metal molybdenum salt, a spinning aid and a spinning solvent to prepare a precursor solution capable of electrostatic spinning, and then converting the precursor solution into a precursor film by the electrostatic spinning method; (2) drying the precursor film, and then placing the precursor film in a muffle furnace for ceramicization heat treatment to obtain a rare earth-based molybdate ceramic material with a flaky structure. The thickness of the flaky rare earth-based molybdate ceramic material can be controlled to obtain a larger specific surface area, so that more active sites are exposed to improve the catalytic performance and optical performance of the material.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials technology, and relates to a sheet-like rare earth-based molybdate ceramic material and its preparation method, specifically to a two-dimensional sheet-like rare earth-based molybdate ceramic material with nanometer thickness and its preparation method. Background Technology

[0002] Rare earth molybdates Re₂MoO₆ (Re selected from La, Ce, Pr, Eu, Ho, Er, Yb, or Tm) possess excellent thermal and chemical stability and a broad excitation band, making them promising candidates for applications in catalysis, luminescence, and energy. Numerous studies have shown that the main factors influencing the performance of Re₂MoO₆ are the selection and combination of rare earth elements and the crystal structure and morphology. Due to the differences in electronic structure among different rare earth elements, their excitation energy transfer and absorption efficiencies also vary. Therefore, optimizing the rare earth element composition can compensate for the performance shortcomings of Re₂MoO₆, thereby improving the overall performance of the material. Furthermore, preparing nanoscale Re₂MoO₆ and adjusting its crystal structure and morphology can yield a larger specific surface area, thereby exposing more active sites and improving the catalytic and optical properties of the material.

[0003] Currently, the commonly used methods for preparing Re2MoO6 are mainly the high-temperature solid-state method and the precipitation method. Among them, the high-temperature solid-state method is a popular choice due to the abundance of raw materials and the relatively simple preparation process. However, the Re2MoO6 powder prepared by this method has a large particle size (usually ranging from several micrometers to tens of micrometers), and the morphology of the powder particles is uncontrollable. The precipitation method can prepare nanostructured Re2MoO6, but the Re2MoO6 powder particles prepared by this method have defects such as easy agglomeration and low dimensional accuracy. Therefore, it usually needs to be combined with other materials to be utilized, thus limiting its application development. However, there are no reports on the preparation of two-dimensional sheet-like rare-earth-based molybdate ceramic materials with nanometer thickness. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a sheet-like rare earth-based molybdate ceramic material and its preparation method. By employing electrospinning combined with ceramic heat treatment and other processes, the ceramic material prepared by this invention exhibits a two-dimensional sheet-like structure with a nanometer thickness, thereby broadening its applications in catalysis, luminescence, and other fields.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0006] A sheet-like rare earth-based molybdate ceramic material is disclosed. This ceramic material has a two-dimensional sheet structure, preferably an irregularly shaped two-dimensional sheet structure, and more preferably a two-dimensional thin sheet structure. Preferably, the thickness of the sheet-like rare earth-based molybdate ceramic material is 5–30 nm, for example, 5–15 nm, 10–20 nm, or 20–30 nm.

[0007] According to the present invention, the chemical formula of the sheet-like rare earth-based molybdate ceramic material is Re2MoO6, wherein: Re is selected from one, two or more of La, Y, Ce, Pr, Eu, Ho, Er, Yb, and Tm, preferably five of the above elements.

[0008] Preferably, the rare earth elements in the sheet-like rare earth-based molybdate ceramic material are uniformly distributed.

[0009] According to the present invention, the sheet-like rare earth-based molybdate ceramic material is prepared by electrospinning a precursor thin film from a precursor solution including a Re source, a Mo source and a spinning aid, and then subjected to ceramic heat treatment.

[0010] The present invention also provides a method for preparing the above-mentioned sheet-like rare earth-based molybdate ceramic material, comprising preparing a precursor film by electrospinning a precursor solution containing a Re source, a Mo source and a spinning aid, and then preparing the sheet-like rare earth-based molybdate ceramic material by ceramic heat treatment.

[0011] According to the present invention, the Re source is selected from salts containing the Re element, preferably nitrates containing the Re element; wherein: Re is selected from one, two or more of La, Y, Ce, Pr, Eu, Ho, Er, Yb, and Tm, preferably five of the above elements.

[0012] According to the present invention, the Mo source is selected from salts containing the element Mo, such as MoCl5 or molybdenum nitrate (Mo(NO3)2).

[0013] According to the present invention, the spinning aid is polyvinylpyrrolidone (PVP).

[0014] According to the present invention, the concentration of the spinning aid in the precursor solution is 1% to 10%, exemplarily 1%, 2%, 5%, 8%, and 10%.

[0015] According to the present invention, the precursor solution uses at least one solvent selected from anhydrous ethanol and N,N-dimethylformamide (DMF). Preferably, when the solvent is a mixture of two solvents, the mass ratio of the two solvents is 1:(0.5-2), with examples being 1:1.2, 1:1.4, and 1:1.5.

[0016] According to the present invention, the voltage of the electrospinning method is 10-20kV, exemplarily 20kV; the feed rate of the electrospinning method is 0.4-1.2mL / h. -1 The example is 0.6 ml / h; the spinning distance of the electrospinning method is 10-15 cm, the example is 12 cm; the relative humidity of the environment of the electrospinning method is (30±3)% and the temperature is (25±3)℃.

[0017] According to the present invention, the temperature of the ceramicizing heat treatment is 600-800℃, preferably 700-800℃, and exemplarily 750℃; the isothermal time of the ceramicizing heat treatment is 1-4h, exemplarily 2h; and the heating rate of the ceramicizing heat treatment is 0.1-5℃ / min, exemplarily 1℃ / min.

[0018] Through extensive experimentation, the applicant unexpectedly discovered that when the ceramicizing heat treatment temperature was 650℃, the resulting Re2MoO6 ceramic material contained other phases, indicating that the precursor was not completely transformed into Re2MoO6. When the ceramicizing heat treatment temperature was increased to 700-800℃, the precursor was completely transformed into Re2MoO6. Furthermore, when the ceramicizing heat treatment temperature exceeded 800℃, the Re2MoO6 grains grew significantly, no longer exhibiting a lamellar structure. Therefore, in this invention, the preferred ceramicizing heat treatment temperature is 700-800℃.

[0019] According to the present invention, the preparation method of the sheet-like rare earth-based molybdate ceramic material includes the following steps:

[0020] (1) Add Re source (such as Re(NO3)3·6H2O) and Mo source (such as MoCl5) (the molar ratio of Re element to Mo element is 2:1) to the solvent according to the stoichiometric ratio, and then add spinning aid (such as PVP) to obtain a precursor solution that can be electrospun.

[0021] (2) The precursor solution obtained in step (1) is spun (into an electrospinning machine), and the precursor film is collected after spinning is completed.

[0022] (3) The precursor film prepared in step (2) is dried and subjected to ceramic heat treatment. After the heat treatment is completed, a sheet-like Re2MoO6 ceramic material is obtained.

[0023] In one embodiment of the present invention, the drying temperature is 40 to 100°C, exemplarily 60°C.

[0024] The present invention also provides the application of the above-mentioned sheet-like rare earth-based molybdate ceramic material in the fields of catalysis, luminescence, and energy.

[0025] The present invention also provides a catalyst containing the above-mentioned plate-like rare earth-based molybdate ceramic material.

[0026] The beneficial effects of this invention:

[0027] This invention utilizes a combined electrospinning and ceramic heat treatment process to successfully prepare sheet-like rare-earth-based molybdate ceramic materials for the first time. The sheet-like rare-earth-based molybdate ceramic materials prepared by this invention possess nanometer-thickness, and the thickness of the sheet-like rare-earth-based molybdate ceramic materials can be controllably adjusted to obtain a larger specific surface area, thereby exposing more active sites and improving the catalytic and optical properties of the material. Compared with existing preparation methods, this invention effectively solves the shortcomings of nano-molybdate ceramic powder particles, such as easy agglomeration and low dimensional accuracy. Attached Figure Description

[0028] Figure 1 The image shows the morphology (scanning electron microscope image) of the sheet-like (LaYErHoTm)2MoO6 ceramic prepared according to Example 1.

[0029] Figure 2 The image shows the morphology (scanning electron microscope image) of the sheet-like (LaYErHoTm)2MoO6 ceramic prepared according to Example 2.

[0030] Figure 3 The image shows the morphology (scanning electron microscope image) of the sheet-like (LaYErHoTm)2MoO6 ceramic prepared according to Example 3.

[0031] Figure 4 The image shows the XRD pattern of the sheet-like (LaYErHoTm)2MoO6 ceramic prepared according to Example 3.

[0032] Figure 5 This is a schematic diagram illustrating the preparation of sheet-like rare earth-based molybdate ceramic materials. Detailed Implementation

[0033] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0034] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0035] Example 1

[0036] A method for preparing a sheet-like rare earth-based molybdate ceramic material includes the following steps:

[0037] (1) Weigh 0.0004 mol of La(NO3)3·6H2O, 0.0004 mol of Y(NO3)3·6H2O, 0.0004 mol of Ho(NO3)3·6H2O, 0.0004 mol of Er(NO3)3·6H2O, 0.0004 mol of Tm(NO3)3·6H2O and 0.001 mol of MoCl5 and add them to a beaker containing 5 g of anhydrous ethanol and 7 g of N,N-dimethylformamide mixed solution. Then, stir magnetically to dissolve the mixture. After the solution becomes clear, add 1 g of polyvinylpyrrolidone (PVP) and stir magnetically. After the mixture is completely dissolved, the desired electrospinning precursor solution is obtained.

[0038] (2) The electrospinning solution prepared in step (1) is loaded into the spinning machine for spinning. The spinning voltage is 20kV, the spinning distance is 12cm, the injection pump speed is 0.6ml / h, the ambient humidity is 30%, and the spinning temperature is 25℃. The precursor film can be collected after spinning is completed.

[0039] (3) The precursor film obtained in step (2) is dried in an oven at 60°C, and then placed in a muffle furnace at 750°C for ceramic heat treatment for 2 hours at a heating rate of 1°C / min. After cooling to room temperature, the sheet-like (LaYErHoTm)2MoO6 ceramic is obtained.

[0040] Figure 1 The image shows a scanning electron microscope (SEM) image of the (LaYErHoTm)2MoO6 ceramic prepared in this embodiment. The image shows that the ceramic material is a large, solid sheet structure with a thickness of 20-30 nm, and a small amount of fiber filaments are interspersed in the middle.

[0041] Example 2

[0042] A method for preparing a sheet-like rare earth-based molybdate ceramic material includes the following steps:

[0043] (1) Weigh 0.0004 mol of La(NO3)3·6H2O, 0.0004 mol of Y(NO3)3·6H2O, 0.0004 mol of Ho(NO3)3·6H2O, 0.0004 mol of Er(NO3)3·6H2O, 0.0004 mol of Tm(NO3)3·6H2O and 0.001 mol of MoCl5 and add them to a beaker containing 5 g of anhydrous ethanol and 6 g of N,N-dimethylformamide mixed solution. Then, stir magnetically to dissolve the solution. After the solution becomes clear, add 0.9 g of polyvinylpyrrolidone (PVP) and stir magnetically. After the mixture is completely dissolved, the desired electrospinning precursor solution is obtained.

[0044] (2) The electrospinning solution prepared in step (1) is loaded into the spinning machine for spinning. The spinning voltage is 20kV, the spinning distance is 12cm, the injection pump speed is 0.6ml / h, the ambient humidity is 30%, and the spinning temperature is 25℃. The precursor film can be collected after spinning is completed.

[0045] (3) The precursor film obtained in step (2) is dried in an oven at 60°C, and then placed in a muffle furnace at 750°C for ceramic heat treatment for 2 hours at a heating rate of 1°C / min. After cooling to room temperature, the sheet-like (LaYErHoTm)2MoO6 ceramic is obtained.

[0046] Figure 2 The image shows a scanning electron microscope (SEM) image of the (LaYErHoTm)2MoO6 ceramic prepared in this embodiment. The image reveals that the ceramic material has an irregularly shaped sheet-like structure with a thickness of 10-20 nm. Compared to Example 1, the ceramic material prepared in this embodiment has a dispersed sheet-like structure with a reduced thickness and no embedded fibers.

[0047] Example 3

[0048] A method for preparing a sheet-like rare earth-based molybdate ceramic material includes the following steps:

[0049] (1) Weigh 0.0004 mol of La(NO3)3·6H2O, 0.0004 mol of Y(NO3)3·6H2O, 0.0004 mol of Ho(NO3)3·6H2O, 0.0004 mol of Er(NO3)3·6H2O, 0.0004 mol of Tm(NO3)3·6H2O and 0.001 mol of MoCl5 and add them to a beaker containing 4 g of anhydrous ethanol and 6 g of N,N-dimethylformamide mixed solution. Then, stir magnetically to dissolve the mixture. After the solution becomes clear, add 0.8 g of polyvinylpyrrolidone (PVP) and stir magnetically. After the mixture is completely dissolved, the desired electrospinning precursor solution is obtained.

[0050] (2) The electrospinning solution prepared in step (1) is loaded into the spinning machine for spinning. The spinning voltage is 20kV, the spinning distance is 12cm, the injection pump speed is 0.6ml / h, the ambient humidity is 30%, and the spinning temperature is 25℃. The precursor film can be collected after spinning is completed.

[0051] (3) The precursor film obtained in step (2) is dried in an oven at 60°C, and then placed in a muffle furnace at 750°C for ceramic heat treatment for 2 hours at a heating rate of 1°C / min. After cooling to room temperature, the sheet-like (LaYErHoTm)2MoO6 ceramic is obtained.

[0052] Figure 3 The image shows a scanning electron microscope (SEM) image of the (LaYErHoTm)2MoO6 ceramic prepared in this embodiment. The image reveals that the ceramic material has an irregularly shaped sheet-like structure with a thickness of 5-15 nm. Compared to Examples 1 and 2, the ceramic material prepared in this embodiment has a dispersed sheet-like structure, a further reduced thickness, and no embedded fibers.

[0053] Figure 4 This is the XRD pattern of the sheet-like (LaYErHoTm)2MoO6 ceramic prepared in Example 3.

[0054] Example 4

[0055] A method for preparing a sheet-like rare earth-based molybdate ceramic material includes the following steps:

[0056] (1) Weigh 0.0004 mol of La(NO3)3·6H2O, 0.0004 mol of Y(NO3)3·6H2O, 0.0004 mol of Ho(NO3)3·6H2O, 0.0004 mol of Er(NO3)3·6H2O, 0.0004 mol of Tm(NO3)3·6H2O and 0.001 mol of MoCl5 and add them to a beaker containing 4 g of anhydrous ethanol and 6 g of N,N-dimethylformamide mixed solution. Then, stir magnetically to dissolve the solution. After the solution becomes clear, add 0.8 g of polyvinylpyrrolidone (PVP) and stir magnetically. After the mixture is completely dissolved, the desired electrospinning precursor solution is obtained.

[0057] (2) The electrospinning solution prepared in step (1) is loaded into the spinning machine for spinning. The spinning voltage is 20kV, the spinning distance is 12cm, the injection pump speed is 0.6ml / h, the ambient humidity is 30%, and the spinning temperature is 25℃. The precursor film can be collected after spinning is completed.

[0058] (3) The precursor film obtained in step (2) is dried in an oven at 60°C, and then placed in a muffle furnace at 650°C for ceramic heat treatment for 2 hours at a heating rate of 1°C / min. After cooling to room temperature, sheet-like (LaYErHoTm)2MoO6 ceramics can be obtained.

[0059] At this temperature, the precursor film did not completely transform into the (LaYErHoTm)2MoO6 ceramic phase during the ceramic heat treatment, and an intermediate phase was still present.

[0060] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a ceramic material, characterized in that, The preparation method includes preparing a precursor film by electrospinning a precursor solution containing Re source, Mo source and spinning aid, and then preparing a sheet-like rare earth-based molybdate ceramic material by ceramic heat treatment. The temperature of the ceramicizing heat treatment is 700-800℃; the voltage of the electrospinning method is 10-20kV; and the feed rate of the electrospinning method is 0.4-1.2mL / h. -1 The spinning distance in the electrospinning method is 10-15 cm. The Re source is selected from nitrates containing the Re element; wherein: Re is selected from five of the following: La, Y, Ce, Pr, Eu, Ho, Er, Yb, and Tm; The Mo source is selected from MoCl5; The spinning aid is polyvinylpyrrolidone (PVP).

2. The preparation method according to claim 1, characterized in that, The concentration of the spinning aid in the precursor solution is 1-10%.

3. The preparation method according to claim 1, characterized in that, The precursor solution uses at least one of anhydrous ethanol and DMF as the solvent.

4. The preparation method according to claim 3, characterized in that, When the solvent is a mixture of two solvents, the mass ratio of the two solvents is 1:(0.5-2).

5. The preparation method according to any one of claims 1-4, characterized in that, The isothermal time for the ceramicization heat treatment is 1-4 hours; the heating rate for the ceramicization heat treatment is 0.1-5℃ / min.

6. The preparation method according to any one of claims 1-5, characterized in that, The preparation method of the plate-like rare earth-based molybdate ceramic material includes the following steps: (1) Add Re source and Mo source to solvent according to stoichiometric ratio, and then add spinning aid to obtain precursor solution that can be electrospinned; (2) The precursor solution obtained in step (1) is spun, and the precursor film is collected after the spinning is completed. (3) The precursor film prepared in step (2) is dried and subjected to ceramic heat treatment. After the heat treatment is completed, a sheet-like Re2MoO6 ceramic material is obtained.

7. The application of the sheet-like rare earth-based molybdate ceramic material prepared by the preparation method according to any one of claims 1-6 in the fields of catalysis, luminescence, and energy.

8. A catalyst, characterized in that, It contains the sheet-like rare earth-based molybdate ceramic material prepared by the preparation method according to any one of claims 1-6.

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