An alpha-Al2Mo3O 12 Nanosheets, methods of making and using the same
By epitaxially growing α-Al2Mo3O12 nanosheets on c-plane sapphire substrates, the problems of complex preparation and low quality in existing technologies have been solved, and nanosheets with high orientation and low thermal conductivity have been realized, expanding their application in the fields of thermal insulation coatings and thermoelectric conversion.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CENT SOUTH UNIV
- Filing Date
- 2024-12-31
- Publication Date
- 2026-07-03
AI Technical Summary
In the existing technology, the synthesis method of α-Al2Mo3O12 is complicated, and the product exists in powder form with low quality, which hinders its application in many fields.
α-Al2Mo3O12 nanosheets were epitaxially grown on c-plane sapphire substrates using chemical vapor deposition (CVD). By controlling the heating temperature and time, α-Al2Mo3O12 nanosheets with high orientation and extremely low thermal conductivity were obtained.
The preparation process was simplified, the crystal quality was improved, the production cost was reduced, and α-Al2Mo3O12 nanosheets were made suitable for thermal insulation coatings and thermoelectric conversion.
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Figure CN119776988B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of crystal preparation technology, specifically relating to an α-Al₂Mo₃O₃ crystal. 12 Nanosheets, their preparation methods, and applications. Background Technology
[0002] Metal molybdates have attracted widespread attention due to their advantages such as chemical flexibility, negative thermal expansion, and good thermal stability, and have broad applications in fuel cell electrolytes, gas sensors, laser materials, electronics, and supercapacitors. Among them, α-Al₂Mo₃O₃... 12 It possesses a wide bandgap and excellent microwave dielectric properties, ε r =4.99, Q×f=49579GHz (f=14.8GHz), τ f =26ppm / ℃.
[0003] Currently, α-Al2Mo3O 12 It is mainly synthesized through a classic solid-state reaction method, and the product mainly exists in powder form. However, this method is complex, produces low-quality products, and has a long processing time, which hinders the synthesis of α-Al2Mo3O. 12 Applications. Summary of the Invention
[0004] The purpose of this invention is to provide an α-Al2Mo3O 12 Nanosheets, their preparation methods, and applications: The preparation method provided by this invention is simple and yields α-Al₂Mo₃O₃ in a non-powder state. 12 Nanosheets possess excellent performance due to their high orientation and extremely low thermal conductivity.
[0005] To achieve the above objectives, the present invention provides the following technical solution:
[0006] This invention provides an α-Al2Mo3O 12 The method for preparing nanosheets includes the following steps:
[0007] The c-plane sapphire and the Mo source were subjected to a first heating and a second heating in a protective atmosphere. The final temperature of the second heating was 750–800°C, and the holding time was 20–30 minutes, to obtain the α-Al₂Mo₃O₃. 12 Nanosheets.
[0008] Preferably, the Mo source is MoO3 powder; the purity of the MoO3 powder is 99.99% or higher.
[0009] Preferably, the distance between the c-facet sapphire and the Mo source is 3 to 9 cm; the c-facet sapphire is placed downstream of the Mo source.
[0010] Preferably, the single dose of the Mo source is 30 mg.
[0011] Preferably, the final temperature of the first heating is 700–720°C, and the holding time is 5–10 min; the flow rate of the protective atmosphere is 10–30 cm⁻¹. 3 / min.
[0012] Preferably, the heating rate of the first heating is 13.75 to 20.5 °C / min.
[0013] Preferably, preheating is performed before the first heating; the final temperature of the preheating is 280–320°C, the holding time is 10–30 min, and the heating rate is not less than 13.75°C / min; the flow rate of the protective atmosphere is 250–350 cm⁻¹. 3 / min.
[0014] Preferably, the heating rate of the second heating is not less than 1.3°C / min.
[0015] The present invention also provides α-Al2Mo3O prepared by the method described above. 12 Nanosheets.
[0016] The present invention also provides the α-Al2Mo3O described in the above-mentioned scheme. 12 Applications of nanosheets in thermal insulation coatings or thermoelectric conversion.
[0017] This invention provides an α-Al2Mo3O 12 Preparation method of nanosheets. This invention employs chemical vapor deposition (CVD) to epitaxially grow highly oriented α-Al₂Mo₃O₃ nanosheets on a c-plane sapphire substrate. 12 Single-crystal nanosheets improve crystal quality, reduce production costs, and can be mass-produced.
[0018] The present invention also provides α-Al2Mo3O prepared by the method described above. 12 Nanosheets. The α-Al₂Mo₃O₃ provided by this invention... 12 Nanosheets are two-dimensional crystals composed of multiple atomic layers, exhibiting extremely low thermal conductivity and excellent chemical, optical, and electronic properties. Systematic variable-temperature Raman spectroscopy revealed that the characteristic phonons possess an ultrashort lifetime (~0.12 ps), indicating that α-Al₂Mo₃O₃... 12 Nanosheets have extremely low thermal conductivity coefficients.
[0019] The present invention also provides the α-Al2Mo3O described in the above-mentioned scheme. 12 Applications of nanosheets in thermal insulation coatings or thermoelectric conversion. The α-Al₂Mo₃O₃ provided by this invention... 12Nanosheets, with their extremely low thermal conductivity, are suitable for use in thermal insulation coatings or thermoelectric conversion applications. Attached Figure Description
[0020] Figure 1 α-Al2Mo3O provided by the present invention 12 Crystal structure diagram of nanosheets;
[0021] Figure 2 α-Al2Mo3O on c-plane sapphire 12 XPS full spectrum of nanosheets (a) and fine XPS spectra of Mo 3d, Al2p and O1s nuclear energy levels corresponding to the full spectrum (b-d);
[0022] Figure 3 Sapphire substrate and α-Al2Mo3O 12 EDS spectra (a and c) of nanosheets and α-Al2Mo3O 12 SEM image of the nanosheets and corresponding EDS elemental maps of Al, O and Mo (b);
[0023] Figure 4 α-Al2Mo3O 12 XRD pattern of nanosheets;
[0024] Figure 5 α-Al2Mo3O transferred to copper mesh 12 Optical images of nanosheets (a) and α-Al2Mo3O 12 Low-magnification TEM image of the nanosheet (b) and HRTEM image of the region indicated by the white box in the low-magnification TEM image (c); insets show Fourier-filtered images and corresponding SAED images of the region indicated by the red box.
[0025] Figure 6 α-Al2Mo3O 12 Schematic diagram of CVD growth on c-plane sapphire;
[0026] Figure 7 α-Al2Mo3O as described in Example 1 12 Optical image of nanosheet (a), inset: α-Al2Mo3O 12 AFM image of the nanosheet; and the corresponding Raman spectrum (b);
[0027] Figure 8 α-Al2Mo3O (Example 2) 12 Optical image of the nanosheet (a) and the corresponding Raman spectrum (b);
[0028] Figure 9Optical image (a) of the ultrathin α-MoO3 nanosheets in Comparative Example 1, with an inset showing the AFM pattern of the α-MoO3 nanosheets and the corresponding Raman spectrum (b);
[0029] Figure 10 Photograph (a) and corresponding Raman spectrum (b) of centimeter-sized α-MoO3 nanosheets in Comparative Example 2. Detailed Implementation
[0030] This invention provides an α-Al2Mo3O 12 The method for preparing nanosheets includes the following steps:
[0031] The c-plane sapphire and the Mo source were subjected to a first heating and a second heating in a protective atmosphere to obtain the α-Al2Mo3O. 12 Nanosheets.
[0032] In this invention, the c-facet sapphire is preferably cleaned and then dried before use; the cleaning reagent is preferably acetone, isopropanol and hydrogen peroxide; the cleaning method is preferably ultrasonic cleaning; the drying is preferably blow-drying; and the blow-drying equipment is preferably a nitrogen gun.
[0033] In this invention, the Mo source is preferably MoO3 powder; the purity of the MoO3 powder is preferably 99.99% or higher; and the MoO3 powder is preferably purchased from Aladdin. This invention uses MoO3 powder as the Mo source, and a c-plane sapphire substrate as both the Al source and the substrate, epitaxially growing α-Al2Mo3O on its surface. 12 Nanosheets.
[0034] In this invention, the distance between the c-facet sapphire and the Mo source is preferably 3-9 cm, more preferably 6-8 cm; the c-facet sapphire is preferably placed downstream of the Mo source (e.g., Figure 6 (As shown). This invention regulates the α-Al2Mo3O3 content by controlling the distance between MoO3 powder and the substrate. 12 Growth of nanosheets.
[0035] In this invention, the preferred dosage of the Mo source is 30 mg per application.
[0036] In this invention, the protective atmosphere is preferably nitrogen. Nitrogen is introduced into the gas as both the carrier gas and the protective gas.
[0037] In this invention, the first heating device is preferably a tube furnace and a quartz boat; the quartz boat is preferably placed at the center of the quartz tube in the tube furnace; the inner diameter of the quartz tube is preferably 2 cm, and the length is preferably 40 cm; the final temperature of the first heating is preferably 700-720℃, more preferably 710℃, and the holding time is preferably 5-10 min, more preferably 7-8 min; the flow rate of the protective atmosphere is preferably 10-30 cm⁻¹. 3 / min, more preferably 15-25cm 3 / min, further preferably 20cm 3 / min. This invention uses a quartz boat to hold the raw materials. This invention can regulate the temperature and crystal growth time in a tube furnace to control α-Al2Mo3O. 12 Growth of nanosheets.
[0038] In this invention, the heating rate of the first heating is preferably 13.75 to 20.5 °C / min, more preferably 16 to 18 °C / min.
[0039] In this invention, preheating is preferably performed before the first heating; the final temperature of the preheating is preferably 280–320°C, more preferably 300–310°C, the holding time is preferably 10–30 min, more preferably 15–25 min, the heating rate is preferably not less than 13.75°C / min, more preferably 13.75–60°C / min, and even more preferably 20–40°C / min; the flow rate of the protective atmosphere is preferably 250–350 cm⁻¹. 3 / min, more preferably 280-320cm 3 / min. This invention removes air from the quartz tube through preheating.
[0040] In this invention, the second heating device is preferably a tube furnace and a quartz boat; the quartz boat is preferably placed at the center of the quartz tube in the tube furnace; the inner diameter of the quartz tube is preferably 2 cm, and the length is preferably 40 cm; the final temperature of the second heating is preferably 750–800°C, more preferably 770–790°C, and the holding time is preferably 20–30 min, more preferably 24–27 min; the flow rate of the protective atmosphere is preferably 10–30 cm⁻¹. 3 / min, more preferably 15-22cm 3 / min. This invention uses a quartz boat to hold the raw materials. This invention can regulate the temperature and crystal growth time in a tube furnace to control α-Al2Mo3O. 12 Growth of nanosheets.
[0041] In this invention, the heating rate of the second heating is preferably not less than 1.3°C / min, more preferably 2 to 18°C / min, and even more preferably 5 to 10°C / min.
[0042] In this invention, the second heating process preferably includes post-treatment; the post-treatment includes system cooling, exhaust gas treatment and / or ventilation.
[0043] In this invention, the cooling is preferably natural cooling; the final temperature of the natural cooling is preferably room temperature.
[0044] In this invention, the reagent used for exhaust gas treatment is preferably an alkaline solution. This invention ensures stable gas pressure and prevents alkaline solution backflow through exhaust ventilation.
[0045] The present invention also provides α-Al2Mo3O prepared by the method described above. 12 Nanosheets.
[0046] The α-Al2Mo3O provided by this invention 12 Nanosheets, monoclinic Al2Mo3O 12 (α-Al2Mo3O 12 It belongs to space group P21 / a (No.14) and has lattice parameters a = 1.549 nm, b = 0.911 nm, c = 1.800 nm, α = γ = 90°, β = 125.30°.
[0047] The α-Al2Mo3O provided by this invention 12 The crystal structure of nanosheets is as follows Figure 1 As shown, Al atoms and Mo atoms are surrounded by 6 oxygen atoms and 4 oxygen atoms, respectively, forming AlO6 octahedrons and MoO4 tetrahedrons. The AlO6 and MoO4 polyhedra are connected by O atoms sharing corners to form a framework structure.
[0048] The present invention also provides the α-Al2Mo3O described in the above-mentioned scheme. 12 Applications of nanosheets in thermal insulation coatings or thermoelectric conversion.
[0049] The α-Al2Mo3O provided by this invention 12 Nanosheets, with their extremely low thermal conductivity, are suitable for use in thermal insulation coatings or thermoelectric conversion applications.
[0050] To further illustrate the present invention, the following detailed description of the embodiments is provided in conjunction with the present invention, but these descriptions should not be construed as limiting the scope of protection of the present invention.
[0051] Example 1
[0052] In this embodiment, α-Al₂Mo₃O₃ is epitaxially grown on a c-plane sapphire substrate.12 Nanosheets, the devices used are as follows Figure 6 As shown, the specific steps are as follows:
[0053] (1) First, use a glass cutter to cut the c-face sapphire substrate along its [11-20] crystal direction. First, make cuts around the substrate, then use tweezers to pry it open. The substrate will break along the crystal direction and be cut into a long strip. During the cutting process, a large amount of fine debris will fall onto the substrate. Clean the substrate with deionized water, acetone, isopropanol and hydrogen peroxide in an ultrasonic oscillator. Each cleaning process takes 15 minutes. Dry the substrate with a nitrogen gun for later use.
[0054] (2) Place the weighed 30mg MoO3 powder into a quartz boat. Place the quartz boat containing the MoO3 powder and the c-face sapphire substrate in the center of a quartz tube (2cm inner diameter, 40cm long). Then place the quartz tube containing the MoO3 powder in the inner heating zone. Place the pre-cleaned c-face sapphire substrate 5cm downstream of the MoO3 powder. Then seal the tube furnace and pass N2 as the carrier gas and protective gas.
[0055] (3) At 300cm 3 At an N2 flow rate of 20 cm³ / min, the heating zone was heated from room temperature to 300°C in 20 min and held at that temperature for 20 min. Subsequently, the N2 flow rate was adjusted to 20 cm³ / min. 3 The heating zone was heated to 710℃ for 20 min and held for 5 min, then heated to 750℃ for 30 min and held for 20 min to obtain α-Al2Mo3O. 12 Nanosheets. The tube furnace is naturally cooled to room temperature; the exhaust gas is introduced from the tube furnace through a silicone tube connected to a graduated pipette, inserted into a glass gas washing bottle, sealed with a rubber stopper, and filled with alkaline solution to absorb the exhaust gas. The outlet of the gas washing bottle is connected to an exhaust fan system through a silicone tube.
[0056] Example 2
[0057] The preparation method in this embodiment is the same as in Example 1, except that the growth time and temperature of the second heating are 30 min and 800 °C, respectively; the product characterization results are as follows. Figure 8 As shown. According to Figure 8 It can be seen that α-Al2Mo3O3 with a single orientation is epitaxially grown on the surface of the c-plane sapphire substrate. 12 Nanosheets suggest that increasing nucleation density by appropriately raising growth time and temperature may facilitate breaking energy degeneracy, thereby promoting α-Al2Mo3O4. 12 Highly directional growth of nanosheets.
[0058] Comparative Example 1
[0059] The preparation method of this comparative example is the same as that of Example 1, except that the c-plane sapphire substrate is placed 10 cm downstream of the MoO3 powder; the product characterization results are as follows. Figure 9 As shown. According to Figure 9 It can be seen that, apart from a small amount of square α-Al2Mo3O 12 Beyond the nanosheets, most of the c-plane sapphire substrate surface is covered by irregular α-MoO3 nanosheets with a thickness of ~5.6 nm. This indicates that the large distance between the c-plane sapphire substrate and the MoO3 powder, i.e., the low MoO3 concentration, may limit the bonding reaction and allow the α-Al2Mo3O3 nanosheets to bond. 12 Nanosheets are difficult to form, but MoO3 precursor molecules adsorb onto the c-plane sapphire substrate to form α-MoO3 nanosheets.
[0060] Comparative Example 2
[0061] The preparation method of this comparative example is the same as that of Example 1, except that the c-plane sapphire substrate is placed 20 cm downstream of the MoO3 powder; the product characterization results are as follows. Figure 10 As shown. According to Figure 10 It can be seen that due to the significant temperature difference with the external environment, the temperature at the quartz tube nozzle drops sharply, creating a large degree of supercooling. This supercooling acts as a driving force for MoO3 condensation, resulting in the deposition of a large number of centimeter-sized α-MoO3 flakes at the quartz tube nozzle. Meanwhile, no α-Al2Mo3O3 is deposited on the c-plane sapphire substrate. 12 And α-MoO3 nanosheets.
[0062] Test Example 1
[0063] The α-Al₂Mo₃O₃ prepared in Example 1 was characterized using optical microscopy (OM), Raman spectroscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and transmission electron microscopy. 12 The nanosheets were characterized.
[0064] α-Al2Mo3O prepared in Example 1 12 The nanosheets were subjected to XPS and EDS tests, and the results were as follows: Figure 2 As shown. Figure 2 In the middle (a), α-Al2Mo3O is present. 12 The XPS full spectrum of the nanosheets revealed four main elements: O, C, Mo, and Al. The C1s peak at 284.80 eV represents the signal of amorphous carbon, and this peak is typically used to calibrate the XPS spectrum position through charge compensation. Its origin generally stems from amorphous C contamination during sample transfer. O, Mo, and Al originate from the nanosheets and the substrate. Figure 2Images b through d show the fine XPS spectra of the Mo 3d, Al 2p, and O1s core levels corresponding to the full spectrum. The peaks at 74.28 and 531.46 eV correspond to the Al 2p and O1s levels, respectively. A pair of peaks at 233.15 and 236.30 eV corresponds to the Mo 3d core levels in MoO3. 6+ 3D 5 / 2 and 3D 3 / 2 The consistent energy levels indicate that Mo exists in the product in the +6 valence form; XPS spectra confirm that the chemical composition of the nanosheets consists of three elements: O, Mo, and Al.
[0065] To determine the amounts of O, Mo, and Al components, α-Al₂Mo₃O₃ on a c-sapphire substrate was analyzed. 12 EDS measurements were performed on the nanosheets, and the results are as follows: Figure 3 As shown. Figure 3 (a) shows the EDS spectrum of the sapphire substrate, revealing an atomic ratio of Al:O = 41.3:58.7 ≈ 2:3. Since the EDS measurement depth far exceeds the sample thickness, and the Al and O signals primarily originate from the sapphire substrate; Figure 3 The EDS spectrum in (b) shows that the atomic contents of O, Al, and Mo are 60.1%, 37.4%, and 2.5%, respectively. By subtracting the contributions of Al and O in a 2:3 ratio, the proportions of O, Mo, and Al in the nanosheet are approximately 1.6:2.5:9.9:2:3:12, thus confirming that the nanosheet is α-Al₂Mo₃O. 12 ; Figure 3 The EDS elemental diagram in (c) reveals α-Al2Mo3O 12 Uniform distribution of Mo, O and Al in nanosheets.
[0066] For α-Al2Mo3O in Example 1 12 XRD pattern analysis of nanosheets yielded the following results: Figure 4 As shown. Figure 4 α-Al2Mo3O on c-plane sapphire substrate 12 The XRD pattern of the nanosheets showed four diffraction peaks at 2θ = 14.18°, 28.51°, 43.33°, and 58.93°, corresponding to α-Al₂Mo₃O₃, respectively. 12 The (200), (400), (600), and (800) crystal planes; based on the diffraction angles and combined with Bragg's diffraction theorem, the interplanar spacing of the (100) nanosheet can be determined to be 1.25 nm, which is similar to that of α-Al2Mo3O. 12 (ICDD-JCPDS-PDFNo.01084-1652) The uniform lattice spacing in the (100) crystal plane indicates that the nanosheets epitaxially grown on the c-plane sapphire substrate are α-Al2Mo3O. 12 .
[0067] To further verify α-Al2Mo3O 12 The atomic structure of the nanosheets, including α-Al₂Mo₃O 12 Nanosheets transferred to copper mesh (e.g.) Figure 5 As shown in Figure a), HRTEM and SAED measurements were performed, and the results are as follows. Figure 5 As shown in b and c. Figure 5 Image b shows the corresponding low-magnification TEM image, in which the nanosheets are truncated rectangular in shape; the missing parts are all isosceles right triangles. Figure 5 c in the middle shows Figure 5 HRTEM image of the white square region in b, with atomic resolution; Figure 5 Inserting the corresponding SAED pattern in the upper right corner of b shows rectangular symmetry and confirms that the directions of
[010] and
[001] are respectively aligned with α-Al2Mo3O 12 The right-angled sides of the nanosheets form a 45° angle; the Fourier-filtered image of the red square highlighted area inserted in the lower right corner shows that the lattice spacing is ~0.45 nm and 0.91 nm, corresponding to α-Al₂Mo₃O₃, respectively. 12 (020) and α-Al2Mo3O 12 (002) Interplanar spacing, therefore, α-Al2Mo3O epitaxially grown on the c-plane sapphire substrate 12 The crystal structure of the nanosheets was further confirmed.
[0068] α-Al2Mo3O prepared in Example 1 12 AFM and Raman spectroscopy analyses were performed on the nanosheets, and the results are as follows: Figure 7 As shown. According to Figure 7 It can be seen that α-Al2Mo3O was epitaxially grown on the c-plane sapphire substrate. 12 Nanosheets.
[0069] As can be seen from the above embodiments, the preparation method provided by the present invention allows for the epitaxial growth of highly oriented α-Al₂Mo₃O₃ on a c-plane sapphire substrate. 12 Single-crystal nanosheets improve crystal quality, reduce production costs, and can be mass-produced.
[0070] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.
Claims
1. An a-Al2Mo3O 12 The method for producing a nanosheet is characterized by, Includes the following steps: The c-plane sapphire and the Mo source were sequentially preheated, first heated, and second heated in a protective atmosphere. The final temperature of the second heating was 750~800℃, and the holding time was 20~30 min, to obtain the α-Al2Mo3O. 12 Nanosheets; The Mo source is MoO3 powder; the purity of the MoO3 powder is above 99.99%; The distance between the c-face sapphire and the Mo source is 3~9cm; the c-face sapphire is placed downstream of the Mo source; The final temperature of the first heating is 700~720℃, and the holding time is 5~10min; The final temperature of the preheating is 280~320℃, and the holding time is 10~30min.
2. The production method according to claim 1, characterized by, The single dose of the Mo source is 30 mg.
3. The method of claim 1, wherein, The flow rate of the protective atmosphere is 10 to 30 cm 3 / min.
4. The production method according to claim 1 or 3, characterized by, The heating rate of the first heating is 13.75~20.5℃ / min.
5. The preparation method according to claim 1, characterized in that, The preheating temperature increasing rate is not less than 13.75℃ / min before the first heating; and the flow rate of the protective atmosphere is 250~350cm 3 / min.
6. The production method according to claim 1 or 5, characterized by, The heating rate of the second heating is not less than 1.3℃ / min.
7. The α-Al2Mo3O12 obtained by the production process according to any one of claims 1 to 6. 12 nanosheets.
8. The α-Al2Mo3O 12 Use of nanosheets in thermal barrier coatings or thermoelectric conversion.