WO2018023720A1 - Hydrothermal synthesis of monoclinic vanadium dioxide nanowires with high aspect ratio - Google Patents
Hydrothermal synthesis of monoclinic vanadium dioxide nanowires with high aspect ratio Download PDFInfo
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- 239000002070 nanowire Substances 0.000 title claims abstract description 26
- 238000001027 hydrothermal synthesis Methods 0.000 title claims abstract description 17
- 229910021542 Vanadium(IV) oxide Inorganic materials 0.000 title description 4
- GRUMUEUJTSXQOI-UHFFFAOYSA-N vanadium dioxide Chemical compound O=[V]=O GRUMUEUJTSXQOI-UHFFFAOYSA-N 0.000 title description 4
- 230000007704 transition Effects 0.000 claims abstract description 16
- 238000010438 heat treatment Methods 0.000 claims description 23
- 238000000034 method Methods 0.000 claims description 21
- 239000002243 precursor Substances 0.000 claims description 21
- 238000001816 cooling Methods 0.000 claims description 19
- 238000006243 chemical reaction Methods 0.000 claims description 10
- 239000002019 doping agent Substances 0.000 claims description 9
- 238000011049 filling Methods 0.000 claims description 9
- GNTDGMZSJNCJKK-UHFFFAOYSA-N divanadium pentaoxide Chemical compound O=[V](=O)O[V](=O)=O GNTDGMZSJNCJKK-UHFFFAOYSA-N 0.000 abstract description 8
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 abstract description 7
- 230000007423 decrease Effects 0.000 abstract description 2
- 239000012535 impurity Substances 0.000 abstract description 2
- 238000010587 phase diagram Methods 0.000 abstract description 2
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 abstract 3
- 235000006408 oxalic acid Nutrition 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 29
- 239000002244 precipitate Substances 0.000 description 9
- 239000013078 crystal Substances 0.000 description 8
- 229920000265 Polyparaphenylene Polymers 0.000 description 5
- 238000002441 X-ray diffraction Methods 0.000 description 5
- -1 poly (para-phenylene) Polymers 0.000 description 5
- 239000000047 product Substances 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 239000008367 deionised water Substances 0.000 description 4
- 229910021641 deionized water Inorganic materials 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000000725 suspension Substances 0.000 description 4
- 239000004809 Teflon Substances 0.000 description 3
- 229920006362 Teflon® Polymers 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- GEVPUGOOGXGPIO-UHFFFAOYSA-N oxalic acid;dihydrate Chemical compound O.O.OC(=O)C(O)=O GEVPUGOOGXGPIO-UHFFFAOYSA-N 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 102100021202 Desmocollin-1 Human genes 0.000 description 2
- 101000968043 Homo sapiens Desmocollin-1 Proteins 0.000 description 2
- 101000880960 Homo sapiens Desmocollin-3 Proteins 0.000 description 2
- 238000001069 Raman spectroscopy Methods 0.000 description 2
- 238000001237 Raman spectrum Methods 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
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- 238000000113 differential scanning calorimetry Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000008030 elimination Effects 0.000 description 2
- 238000003379 elimination reaction Methods 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 229910002483 Cu Ka Inorganic materials 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
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- 238000012512 characterization method Methods 0.000 description 1
- 230000002860 competitive effect Effects 0.000 description 1
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
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- 229910052750 molybdenum Inorganic materials 0.000 description 1
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- 238000001878 scanning electron micrograph Methods 0.000 description 1
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- GWEVSGVZZGPLCZ-UHFFFAOYSA-N titanium dioxide Inorganic materials O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G31/00—Compounds of vanadium
- C01G31/02—Oxides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/50—Solid solutions
- C01P2002/52—Solid solutions containing elements as dopants
- C01P2002/54—Solid solutions containing elements as dopants one element only
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
- C01P2002/82—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by IR- or Raman-data
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/10—Particle morphology extending in one dimension, e.g. needle-like
- C01P2004/16—Nanowires or nanorods, i.e. solid nanofibres with two nearly equal dimensions between 1-100 nanometer
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/54—Particles characterised by their aspect ratio, i.e. the ratio of sizes in the longest to the shortest dimension
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/32—Thermal properties
- C01P2006/33—Phase transition temperatures
Definitions
- the present application provides a method for the hydrothermal synthesis of VO 2
- pH of precursor solution concentration of the ions, doping amount, reaction time, filling ratio and reaction temperature contribute to the formation of VO 2 (M) NWs with different sizes and Tcs.
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- Inorganic Compounds Of Heavy Metals (AREA)
Abstract
Scalable hydrothermal synthesis of VO2(M) nanowires with high aspect ratio is achieved via the reduction of V2O5 by oxalic acid in a diluted H2SO4 solution, and the maximum length of as-synthesized nanowires can reach 90μm. Doping of Sb changes the structural phase diagram of VO2 lattice, accompanied with a large decline of its phase temperature to even subzero temperature, at the same time impurity VO2(A) is effectively eliminated. Interestingly, the phase transition temperature of the un-doped sample is also obviously lower than the theoretical value.
Description
Description
Title of Invention: Hydrothermal synthesis of monoclinic vanadium dioxide nanowires with high aspect ratio Technical Field
[0001] The present application relates to the field of nanotechnology, in particular, it relates to a direct hydrothermal method for the scalable fabrication of monoclinic vanadium dioxide nanowires.
Background Art
[0002] Monoclinic vanadium dioxide, VO 2 (M), is a popular functional material with a reversible MIT (metal-insulator transition) at a temperature slightly above room temperature, Tc=341K (68°C). This transition from a low temperature, insulating, monoclinic phase (M) to a high temperature, metallic, tetragonal phase (R) is followed by some amazing changes in various properties including electrical properties, optical properties and lattice parameters. Based on these changes, VO 2 (M) has a great potential to be utilized in a wide-range of energy related devices, such as ther- mosensitive switches, thermochromic windows and electro-opto-thermal actuators.
[0003] It has been reported that Cr/VO 2 (M) nanowire (NW)-based bimorph can take
advantage of the large transformation strain (~1% ) along the rutile c-axis (cR) of VO 2 (M/R) responding to the change of temperature, and perform pretty well with large amplitudes, high working frequencies and good compatibility in different conditions, such as in air and in water. Theoretically speaking, the high volumetric work density of VO 2 (M) single crystals, 7J/cm 3, which can be comparable to that of shape memory alloys (~6J/cm 3) and is much higher than that of natural muscle (~0.0008J/cm 3), makes VO 2 (M)-based bimorph actuators more competitive.
[0004] However, the mass application of such high-efficiency VO 2 (M)-based actuators is still limited.
[0005] Although the well-developed vapor transport method can be used to synthesize ultra- long VO 2 (M) NWs, its further development is limited by the low yield and high reaction temperature. By contrast, hydrothermal method is a more promising and convenient way to fabricate VO 2 (M) crystals in large amounts, but existing publications show that the length of VO 2 (M) NWs prepared by direct hydrothermal synthesis is generally limited within 30μιη, which cannot meet the requirements of actuator structures. There still exists a need for an improved synthesis method for the preparation of VO 2 (M) NWs with greater length and high quality.
Technical Problem
[0006] The present application aims to solve the technical problems above.
Solution to Problem
Technical Solution
[0007] The present application provides a method for the hydrothermal synthesis of VO 2
(M) NWs with a high aspect ratio of around 60. Furthermore, with the assistance of Sb 20 3, VO 2 (A) can be eliminated and the Tc can be reduced to near room temperature.
[0008] This method comprises the following steps: preparing a precursor solution with V 20 5 and H 2C 20 4 by a mole ratio of 0.2-1 in diluted H 2SO 4 solution; heating the precursor solution at 80-120°C for 6-24h and filtrating at room temperature; keeping the solution under a temperature of more than 240°C for more than 16h; wherein a hydrothermal reaction is carried out and the VO 2 (M) nanowires are synthesized.
[0009] The precursor solution is prepared via the redox reaction between V 20 5 and H 2C 20 4, after stirring at room temperature for more than 2h, a bright orange suspension is formed; after heating at 80-120°C for 6-24h and filtrating at room temperature, dark blue precursor solution and dark green precipitates are obtained respectively.
[0010] Further, a dopant is added into the precursor solution before the hydrothermal
reaction is carried out.
[0011 ] Further, the dopant is Sb 20 3.
[0012] Further, the mole ratio of V 20 5 to H 2C 20 4 is 0.45-0.7.
[0013] Further, the solution is kept under a temperature of 260°C for 24h.
[0014] Further, the VO 2 (M) nanowires are dried. After reaction, the precipitates in the container are collected and washed with deionized water and alcohol for several times before it is dried.
[0015] The precipitates are dried at 60°C for lOh.
[0016] Further, the hydrothermal reaction is carried in an autoclave, and the filling ratio (reactant volume/container volume) to the autoclave is 0.5-0.7.
[0017] Further, the VO 2 (M) nanowires have a length of 10-90μιη.
[0018] Further, the VO 2 (M) nanowires have a diameter of 0.5-1.5μιη.
[0019] Further, the VO 2 (M) nanowires have a general aspect ratio of 60.
[0020] Further, the un-doped VO 2 (M) nanowires have a phase transition temperature of 40-46°C for heating cycles and 20-27°C for cooling cycles.
[0021] Further, the VO 2 (M) nanowires doped have a minimum heating phase transition temperature of 25°C and a minimum cooling phase transition temperature of -12.3°C.
[0022] The doping of Sb changes the structural phase diagram of VO 2 lattice, accompanied with a large decline of its phase temperature to even subzero temperature, at the same time impurity VO 2 (A) is effectively eliminated. In addition, increasing filling ratio is another effective way for the phase purification of final products.
Advantageous Effects of Invention
Advantageous Effects
[0023] The method for hydrothermal synthesis of VO 2 (M) NWs provides a more promising and convenient way to synthesize VO 2 (M) crystals in large amounts with a length greater than 30μιη, which meets the requirements of actuator structures. In addition, its low actuation temperatures can effectively reduce the energy consumption caused by the activation of the device. Furthermore, heavily Sb-doped VO 2 (M) NWs have a great potential in the smart devices which would be required to work in the extremely cold conditions, such as poles.
Brief Description of Drawings
Description of Drawings
[0024] Figure 1 shows a XRD pattern of as-prepared un-doped VO 2 (M) NWs and Sb- doped VO 2 (M) NWs in this application.
[0025] Figure 2 shows SEM images of as-prepared VO 2 (M) NWs with different sizes.
Insets of (A) and (C) show magnified views of the nanowires/nanorods.
[0026] Figure 3A shows DSC traces measured for as-prepared VO 2 (M) NWs during
cooling cycles.
[0027] Figure 3B shows DSC traces measured for as-prepared VO 2 (M) NWs during the heating cycles.
[0028] Figure 4 shows Raman spectrum of a single VO 2 (M) NW prepared via the method in this application on a SiO 2 substrate.
[0029] Figure 5 shows a XRD pattern of un-doped VO 2 (M) NWs prepared with different filling ratios in this application.
Mode for the Invention
Mode for Invention
[0030] In order to make the purposes, technical solutions and advantages of the present application more clear, the present application will be further described in detail hereafter with reference to the following specific embodiments.
[0031] The present application provides a method for the hydrothermal synthesis of VO 2 (M) NWs, which comprises the following steps:
[0032] (1) Preparation of a precursor solution: vanadium pentoxide (V 20 5) and oxalic acid dihydrate (H 2C 20 4·2Η 20) are uniformly mixed with a mole ratio of 0.45-0.7 in 85mL 0.04-0.065mol/L sulfuric acid (H 2SO 4) aqueous solution. After being stirred at room temperature for more than 3h to form a bright orange suspension, the final mixture is transferred into a lOOmL Teflon container and then sealed in a stainless autoclave. After heating at 80-120°C in an oven for 6-24h and a filtration at room temperature, dark blue precursor solution and dark green precipitates are obtained, respectively.
[0033] (2) Addition of a dopant: precursor solution is mixed with 0-5μg Sb 20 3 powder in a high-density poly (para-phenylene) container with a filling ratio of 0.5-0.7 and then sealed into a stainless autoclave (stannum, tungsten and molybdenum can also work as effective dopants).
[0034] (3) Fabrication of VO 2 (M) NWs: The autoclave is kept under a system temperature of higher than 240°C for more than 16h. After cooling to room temperature, the precipitates in the container are collected and washed with deionized water and alcohol for several times, and then dried at 60°C for lOh.
[0035] VO 2 NWs are synthesized when the reaction is complete, washing and drying help to purify the product roughly.
[0036] The morphology of as- synthesized VO 2 (M) NWs is examined by a TESCAN
scanning electron microscope (SEM, VEGA 3LMH). According to the present method, the as-prepared VO 2 (M) NWs have a length of 10-90μιη and a diameter of 0.5-1.5μιη, as shown in the Figure 2(A), (B) & (C). From a sampling survey, the general aspect ratio, which is the ratio of the length to the diameter of the NWs can reach 60.
[0037] The phase purity of the samples is examined by X-ray diffraction (XRD) on a D8 ADVANCE ECO (Bruker) X-ray diffractometer. The wavelength of generated X-ray is 1.5418 A (Cu Ka, isolated with a Ni foil filter). The working voltage and current are 40kV and 25mA, respectively.
[0038] By comparing the XRD pattern of the sample before and after doping in Figure 1, the roles played by Sb 20 3 in the hydrothermal process become much clearer:
[0039] (1) Elimination of VO 2 (A).
[0040] (2) Modification of the crystal structure. There is an obvious shift of the strongest diffraction peak after doping, which means that the crystal structure of as-prepared VO 2 (M) NWs is changed.
[0041] The chemical components and symmetry of as-prepared NWs are determined by Raman spectrum using a HORIBA Raman spectroscopy (LabRAM HR Evolution). The wavelength of working laser is 532nm.
[0042] The result as shown in Figure 4 gives strong evidence to the identity of a single as- prepared VO 2 (M) NW in chemical component and lattice structure.
[0043] Thus, Figure 1 and Figure 4 strongly support the fact that the sample prepared in this embodiment has the crystal structure and chemical components of VO 2 (M).
[0044] It has been reported that due to super-cooling and super-heating, there is a gap
between the Tcs during the heating and cooling cycles. And the reported Tcs during heating and cooling are 68°C and 61°C, respectively.
[0045] The phase transition processes of the products are studied by a METTLER differential scanning calorimetry (DSC, TOLEDO DSC1), and the measurement temperature range is from -40°C to 70°C under multiple heating/cooling cycles.
[0046] To our surprise, the result as shown in Figure 3 demonstrates that the un-doped VO 2 (M) NWs obtained by the method in one of the embodiment have lower Tcs (46°C for heating cycles and 27°C for cooling cycles) than the reported values. Figure 3 shows the DSC traces of a Sb-doped sample with a heating Tc of 32°C and a cooling Tc of 5.7°C. As discussed above, Sb-doping can change the crystal structure of VO 2 (M) NWs, which can also explain why the Tcs of Sb-doped NWs are reduced.
[0047] It is further discovered that with increasing the doping amount of Sb 20 3, the Tcs will continue to fall off. Figure 3 shows that the experimental minimum heating Tc can be 25°C and minimum cooling Tc can be as low as -12.3°C. This discovery indicates that the Tcs of VO 2 (M) crystals are controllable.
[0048] According to a preferred embodiment of the present application, filling ratio is also an important factor influencing the phase purity of final products. In order to investigate the influence of filling ratio to the phase purity of final products, the precursor solution is prepared from the reaction of 1.2g V 20 5 and 1.2g H 2C 20 4·2Η 2 O in 85mL 0.04M H 2SO 4 solution. Then, 15mL, 18mL and 20mL precursor solution is transferred to 30mL containers and heated at 260°C for 24h, respectively.
[0049] The result as shown in Figure 5 demonstrates that an increasing filling ratio can help the elimination of VO 2 (A) as well.
[0050] According to other embodiments of the present application, pH of precursor solution, concentration of the ions, doping amount, reaction time, filling ratio and reaction temperature contribute to the formation of VO 2 (M) NWs with different sizes and Tcs.
[0051] Sample Characterizations: All the samples above are examined by a Bruker X-ray powder diffraction (XRD, D8 ADVANCE ECO), a TESCAN scanning electron microscope (SEM, VEGA 3LMH), a METTLER differential scanning calorimetry (DSC, TOLEDO DSC1) and a HORIBA Raman spectroscopy (LabRAM HR Evolution).
[0052] Example 1
[0053] This embodiment provides a method for the hydrothermal synthesis of VO 2 (M) NWs, which comprises the following steps:
[0054] (1) 1.2g vanadium pentoxide (V 20 5) and 1.2g oxalic acid dihydrate (H 2C 20 4·2Η 2 O) are added into 85mL 0.05mol/L sulfuric acid (H 2SO 4). After stirring at room temperature for 3h to form a bright orange suspension, the final mixture is transferred into a lOOmL Teflon container and then sealed in a stainless autoclave. After heating at 100°C in an oven for lOh and a filtration at room temperature, dark blue precursor solution and dark green precipitates are obtained, respectively.
[0055] (2) 18.5mL precursor solution is transferred to a 30mL high-density poly
(para-phenylene) container and then sealed into a stainless autoclave.
[0056] (3) Fabrication of VO 2 (M) NWs: The autoclave is kept in an oven with a system temperature of 260°C for 24h. After cooling to room temperature, the precipitates in
the container are collected and washed with deionized water and alcohol for several times, and then dried at 60°C for lOh.
[0057] The pure VO 2 (M) NWs prepared in this example have an average length of around 30μιη, and the maximum can reach 90μιη, accompanied with a phase transition temperature of 46°C for heating cycles and 27°C for cooling cycles.
[0058] Example 2
[0059] (1) 1.2g vanadium pentoxide (V 20 5) and 1.2g oxalic acid dihydrate (H 2C 20 4·2Η 2 O) are added into 85mL 0.04mol/L sulfuric acid (H 2SO 4). After stirring at room temperature for 3h to form a bright orange suspension, the final mixture is transferred into a lOOmL Teflon container and then sealed in a stainless autoclave. After heating at 100°C in an oven for lOh and a filtration at room temperature, dark blue precursor solution and dark green precipitates are obtained, respectively.
[0060] (2) 18mL precursor solution is mixed with 0^g Sb 20 3 powder in a 30mL high- density poly (para-phenylene) container and then sealed into a stainless autoclave.
[0061] (3) Fabrication of VO 2 (M) NWs: The autoclave is kept in an oven with a system temperature of 260°C for 24h. After cooling to room temperature, the precipitates in the container are collected and washed with deionized water and alcohol for several times, and then dried at 60°C for lOh.
[0062] The doped VO 2 (M) NWs prepared in this example have an average length of around 25μιη, accompanied with a heating phase transition temperature of 25°C and a cooling phase transition temperature of -12.3°C.
[0063] Example 3
[0064] After a reaction of 0.9g V 20 5 and 1.3g H 2C 20 4·2Η 20 in 85mL 0.05M H 2SO 4 solution at 100°C for lOh, 24mL precursor solution without dopant is kept in a 37mL high-density poly (para-phenylene) container at 260°C for 24h.
[0065] The pure VO 2 (M) NWs prepared in this example have an average length of around
15μιη, accompanied with a phase transition temperature of 42°C for heating cycles and
20°C for cooling cycles.
[0066] Example 4
[0067] After a reaction of 0.9g V 20 5 and 1.4g H 2C 20 4·2Η 20 in 85mL 0.065M H 2SO 4 solution at 120°C for 6h, 22mL precursor solution without dopant is kept in a 37mL high-density poly (para-phenylene) container at 265°C for 16h.
[0068] The pure VO 2 (M) NWs prepared in this example have an average length of around
15μιη, accompanied with a phase transition temperature of 46°C for heating cycles and
23°C for cooling cycles.
[0069] Example 5
[0070] After a reaction of 1.2g V 20 5 and 1.2g H 2C 20 4·2Η 20 in 85mL 0.05M H 2SO 4 solution at 80°C for 24h, 18mL precursor solution without dopant is kept in a 30mL
high-density poly (para-phenylene) container at 250°C for 36h.
[0071] The VO 2( ) NWs prepared in this example have an average length of around 30μιη, accompanied with a phase transition temperature of 45°C for heating cycles and 26°C for cooling cycles. However, VO 2 (A) appears as a by-product in this example.
[0072] The above examples are merely preferred embodiments of the present application.
Any common changes and replacements made within the scope of the technical solution of the present application by one of ordinary skill in the art should be included in the protection scope of the present application.
Claims
[Claim 1] A method for hydrothermal synthesis of VO 2 (M) nanowires,
comprising the step of:
preparing a precursor solution with V 20 5 and H 2C 20 4 by a mole ratio of 0.2-1 in diluted H 2SO 4 solution;
heating the precursor solution at 80-120°C for 6-24h and filtrating at room temperature;
keeping the solution under a temperature of more than 240°Cfor more than 16h;
wherein a hydrothermal reaction is carried out and the VO 2 (M) nanowires are synthesized.
[Claim 2] A method according to claim 1, wherein a dopant is added into the precursor solution before hydrothermal reaction.
[Claim 3] The method according to claim 2, wherein the dopant is Sb 20 3.
[Claim 4] The method according to claim 1 or 2, wherein the mole ratio of V 20 5 to H 2C 20 4 is 0.45-0.7.
[Claim 5] The method according to claim 1 or 2, wherein the solution is kept under a temperature of 260°C for 24h.
[Claim 6] The method according to claim 1, wherein the VO 2 (M) nanowires are dried after reaction.
[Claim 7] The method according to claim 1, wherein the hydrothermal reaction is carried in an autoclave, and the filling ratio to the autoclave is 0.5-0.7.
[Claim 8] The method according to claim 1, wherein the VO 2 (M) nanowires have a length of 10-90μιη.
[Claim 9] The method according to claim 1, wherein the VO 2 (M) nanowires have a diameter of 0.5-1.5μιη.
[Claim 10] The method according to claim 1, wherein the VO 2 (M) nanowires have a general aspect ratio of 60.
[Claim 11] The method according to claim 1, wherein the un-doped VO 2 (M) nanowires have a phase transition temperature of 40-46°C for heating cycles and 20-27°C for cooling cycles.
[Claim 12] The VO 2 (M) nanowires according to claim 2, wherein the VO 2 (M) nanowires doped have a minimum heating phase transition temperature of 25°C and a minimum cooling phase transition temperature of - 12.3°C.
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CN112209439A (en) * | 2020-10-16 | 2021-01-12 | 成都先进金属材料产业技术研究院有限公司 | Undoped low-temperature thermotropic VO2Method for preparing powder material |
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