An ultra coarse plate-like tungsten oxide and a method for preparing the same

Abstract

The application belongs to the technical field of functional materials, and particularly relates to super coarse plate-shaped tungsten oxide and a preparation method thereof. The preparation method of the super coarse plate-shaped tungsten oxide comprises the following steps: S1, ammonium tungstate is added into deionized water, and is stirred and dissolved at a temperature of 70-90 DEG C to obtain a clear ammonium tungstate solution; S2, the clear ammonium tungstate solution is cooled to normal temperature at a cooling rate of 0.5-2 DEG C / h, and then plate-shaped ammonium tungstate crystals are obtained by suction filtration; S3, the plate-shaped ammonium tungstate crystals are calcined to obtain super coarse plate-shaped tungsten oxide; the application uses ammonium tungstate as raw material, has high controllability, and obtains tungsten oxide with uniform particle size and complete plate shape through optimized crystallization and calcination, and the purity is greater than or equal to 99%, so that the problems of traditional tungsten oxide agglomeration and chaotic morphology are solved, the functional adaptability is strong, the plate-shaped structure can be oriented, the dielectric, breakdown and other performances are improved, and the application is suitable for multiple high-end scenes; the parameters are easy to control, the operation is simple, and the application is green and safe.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of functional materials, and particularly relates to super coarse plate-shaped tungsten oxide and a preparation method thereof. BACKGROUND

[0002] In the current field of functional materials, tungsten oxide is widely used in functional ceramics, energy storage, photocatalysis, sensing and protection and other important fields due to its unique physical and chemical properties, and becomes one of the key materials for promoting the development of related industries.

[0003] The current tungsten oxide has obvious limitations: nano-tungsten oxide is prone to agglomeration, has high cost and safety risks, resulting in fluctuations in the dielectric properties of functional ceramics, short battery cycle life, and decreased sensitivity of sensors; block or ordinary particle tungsten oxide has many grain boundary defects, small specific surface area and poor processing compatibility, resulting in low ceramic breakdown field strength, insufficient catalytic activity, weak coating protection, and overall imbalance between form and performance, poor long-term reliability, and difficulty in meeting the needs of high-end applications.

[0004] The development of super coarse plate-shaped tungsten oxide can solve the above problems, and through unique structural design, it can realize the synergistic optimization of performance and practicability, promote the technological upgrading of strategic industries such as functional ceramics and energy storage, enrich the theoretical system of functional materials, meet the needs of performance and reliability in multiple fields, reduce production costs, and has broad application prospects and significant economic and social benefits. SUMMARY

[0005] To solve the above technical problems, the application provides a preparation method of super coarse plate-shaped tungsten oxide, comprising the following steps:

[0006] S1, ammonium tungstate is added to deionized water, stirred and dissolved at a temperature of 70-90 DEG C to obtain a clear ammonium tungstate solution;

[0007] S2, the clear ammonium tungstate solution is cooled to room temperature at a cooling rate of 0.5-2 DEG C / h, and then filtered to obtain plate-shaped ammonium tungstate crystals;

[0008] S3, the plate-shaped ammonium tungstate crystals are calcined to obtain super coarse plate-shaped tungsten oxide.

[0009] Further, ammonium tungstate is added to deionized water, and the temperature for stirring and dissolving is any one or a range between two of 70 DEG C, 80 DEG C and 90 DEG C;

[0010] Further, the cooling rate of the clear ammonium tungstate solution to room temperature is any one or a range between two of 0.5 DEG C / h, 1.0 DEG C / h, 1.5 DEG C / h and 2.0 DEG C / h.

[0011] The concentration of the clarified ammonium tungstate solution in step S1 is 300-450 g / L in terms of WO3.

[0012] The temperature of the calcination in step S3 is 500-700 DEG C, and the time is 1-3 hours.

[0013] The step S3 is specifically that the plate-shaped ammonium tungstate crystal is placed in a ceramic boat, and then is placed in a muffle furnace to perform aerobic calcination to obtain the super coarse plate-shaped tungsten oxide.

[0014] The ceramic boat is an alumina ceramic boat, and the purity of the alumina ceramic boat is greater than or equal to 99%.

[0015] To solve the above technical problems, the application further provides a super coarse plate-shaped tungsten oxide, which is prepared by the preparation method of the super coarse plate-shaped tungsten oxide.

[0016] The purity of the super coarse plate-shaped tungsten oxide is greater than or equal to 99%.

[0017] The crystallinity of the super coarse plate-shaped tungsten oxide is greater than or equal to 90% in terms of WO3.

[0018] The aspect ratio of the super coarse plate-shaped tungsten oxide is greater than or equal to 5:1.

[0019] The average width of the super coarse plate-shaped tungsten oxide is greater than or equal to 180 microns.

[0020] The application uses ammonium tungstate as a raw material, has high controllability, and obtains tungsten oxide with uniform particle size and complete plate shape through optimized crystallization and calcination, has a purity of greater than or equal to 99%, solves the problems of traditional tungsten oxide agglomeration and chaotic morphology, has strong functional adaptability, the plate-shaped structure can be oriented, improves the dielectric, breakdown and other performances, is suitable for many high-end scenes, and is easy to control and simple to operate. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only show some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from the structures shown in the drawings without creative labor.

[0022] Figure 1 The SEM graph of the super coarse plate-shaped tungsten oxide prepared in Example 1 is shown in FIG. 1.

[0023] Figure 2 The XRD graph of the super coarse plate-shaped tungsten oxide prepared in Example 1 is shown in FIG. 2.

[0024] Figure 3 SEM image of the ultra coarse plate-like tungsten oxide prepared in Example 2;

[0025] Figure 4 SEM image of the ultra coarse plate-like tungsten oxide prepared in Example 3;

[0026] Figure 5 SEM image of the ultra coarse plate-like tungsten oxide prepared in Comparative Example 1;

[0027] Figure 6 SEM image of the ultra fine tungsten oxide prepared in Comparative Example 2;

[0028] Figure 7 SEM image of the polygonal tungsten oxide prepared in Comparative Example 4.

[0029] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0031] The present application provides a preparation method of ultra coarse plate-like tungsten oxide, comprising the following steps:

[0032] S1, adding ammonium tungstate into deionized water, stirring and dissolving at a temperature of 70-90℃ to obtain a clear ammonium tungstate solution;

[0033] In the present application, the concentration of the clear ammonium tungstate solution is 300-450g / L in terms of WO3. Too low concentration is easy to result in low crystallization efficiency and fine crystal particles; too high concentration is easy to cause local supersaturation and caking due to large solution viscosity.

[0034] In the present application, the temperature for dissolving ammonium tungstate is 70-90℃. Too high temperature will increase energy consumption, and too low temperature may result in insufficient dissolution and residual undissolved solids.

[0035] S2, cooling the clear ammonium tungstate solution to room temperature at a cooling rate of 0.5-2℃ / h, and then performing suction filtration to obtain plate-like ammonium tungstate crystals;

[0036] In the present application, the rate of cooling the clear ammonium tungstate solution is 0.5-2℃ / h, slow cooling can promote the ordered growth of crystals, forming crystalline with uniform particles and high purity; the cooling rate is too fast, a large number of small crystal nuclei are easily produced, the crystals are easily agglomerated, and the cooling rate is too slow, which leads to too long cooling time.

[0037] S3, calcining the plate-shaped ammonium tungstate crystal to obtain the ultra-coarse plate-shaped tungsten oxide.

[0038] In the present application, the calcining temperature is 500-700℃, the temperature is too low, the ammonium tungstate is not completely decomposed, and the crystal cannot be fully converted into WO3, it is difficult to form an integrated plate-shaped structure, and irregular particles with loose and porous structure are easily produced; the temperature is too high, the WO3 crystal grains are easily overgrown and sintered and agglomerated, the plate-shaped structure is destroyed, and blocky or molten tungsten oxide is formed, losing the morphological characteristics of "ultra-coarse plate-shaped".

[0039] In the present application, the calcining time is 1-3h, the ammonium tungstate is not completely decomposed if the calcining time is too short, the tungsten oxide is mixed with undecomposed products, and the plate-shaped structure is not fully developed; although complete decomposition can be ensured if the time is too long, the energy consumption is increased, and the edges of the WO3 plate-shaped crystal grains may be over-sintered, making the plate-shaped structure thicker and more brittle, and affecting the processing performance in subsequent applications.

[0040] In the present application, high-purity alumina ceramic boats (purity greater than or equal to 99%) are used for calcining, which avoids the reaction between the boat material and WO3 at high temperature, and ensures the purity and morphological stability of the ultra-coarse plate-shaped tungsten oxide.

[0041] Example 1

[0042] Ammonium tungstate is taken and added to deionized water to prepare a clear ammonium tungstate solution with a concentration of 300g / L (calculated as WO3), which is dissolved by stirring at 70℃; the ammonium tungstate solution is cooled at a rate of 0.5℃ / h to room temperature after being placed in a crystallization container; the cooled ammonium tungstate solution is filtered to obtain plate-shaped ammonium tungstate crystals; the plate-shaped ammonium tungstate crystals are placed in a ceramic boat, and then placed in a muffle furnace for calcination, the calcination temperature is 500℃, and the calcination time is 1h, to obtain ultra-coarse plate-shaped tungsten oxide.

[0043] Please refer to Figure 1 , Figure 1 The SEM image of the ultra-coarse plate-shaped tungsten oxide prepared in Example 1 is shown in Figure 1 , from which it can be seen that the crystal has a complete ultra-coarse plate-shaped morphology, the particles are uniformly dispersed, there is no obvious agglomeration, the plate-shaped edges are regular, the surface is smooth, and the size uniformity is good; please further refer to Figure 2 , Figure 2 The XRD image of the ultra-coarse plate-shaped tungsten oxide prepared in Example 1 is shown in Figure 2As can be seen in the figure, the WO3 characteristic diffraction peaks in the atlas are sharp and high in intensity, and there is no any impurity peak, indicating that the crystal internal structure is regular, the lattice arrangement is ordered, and there is no impurity phase interference.

[0044] The ultra-coarse plate-shaped tungsten oxide was detected, and the purity was 99.99%, the crystallization rate was 91.43% (calculated as WO3), the aspect ratio was greater than 5:1, and the average width was 220 μm.

[0045] Example 2

[0046] Ammonium tungstate was taken and added to deionized water to prepare a clear ammonium tungstate solution with a concentration of 450 g / L (calculated as WO3), which was dissolved by stirring at a temperature of 90°C; the ammonium tungstate solution was placed in a crystallization container and cooled at a rate of 2°C / h to room temperature; the cooled ammonium tungstate solution was subjected to suction filtration to obtain plate-shaped ammonium tungstate crystals; the plate-shaped ammonium tungstate crystals were placed in a ceramic boat, which was then placed in a muffle furnace for calcination, the calcination temperature was 700°C, and the calcination time was 3 h, to obtain ultra-coarse plate-shaped tungsten oxide;

[0047] Please refer to Figure 3 , Figure 3 The SEM image of the ultra-coarse plate-shaped tungsten oxide prepared in Example 2 is shown in Figure 3 As can be seen in the figure, the plate-shaped tungsten oxide crystal size is significantly increased, the plate-shaped is thick and the edge is complete, the dispersibility is excellent, and there is no sintering agglomeration trace.

[0048] The ultra-coarse plate-shaped tungsten oxide was detected, and the purity was 99.99%, the crystallization rate was 95.64% (calculated as WO3), the aspect ratio was greater than 5:1, and the average width was 241 μm.

[0049] Example 3

[0050] Ammonium tungstate was taken and added to deionized water to prepare a clear ammonium tungstate solution with a concentration of 400 g / L (calculated as WO3), which was dissolved by stirring at a temperature of 80°C; the ammonium tungstate solution was placed in a crystallization container and cooled at a rate of 1°C / h to room temperature; the cooled ammonium tungstate solution was subjected to suction filtration to obtain plate-shaped ammonium tungstate crystals; the plate-shaped ammonium tungstate crystals were placed in a ceramic boat, which was then placed in a muffle furnace for calcination, the calcination temperature was 600°C, and the calcination time was 2 h, to obtain ultra-coarse plate-shaped tungsten oxide;

[0051] Please refer to Figure 4 , Figure 4 The SEM image of the ultra-coarse plate-shaped tungsten oxide prepared in Example 3 is shown in Figure 4 As can be seen in the figure, the plate-shaped surface is flat, the particle uniformity is high, and the size and morphology are between those of Example 1 and Example 2.

[0052] The ultra coarse plate-like tungsten oxide was detected, and the purity was 99.99%, the crystallization rate was 93.25% (calculated by WO3), the length-width ratio was greater than 5:1, and the average width was 190 μm.

[0053] Comparative Example 1

[0054] Different from Example 1, the stirring was carried out at 60℃, and there were undissolved ammonium tungstate crystals in the ammonium tungstate solution;

[0055] Referring to Figure 5 , Figure 5 The SEM image of the ultra coarse plate-like tungsten oxide prepared in Comparative Example 1 can be seen from Figure 5 It can be seen that the crystal still retains part of the plate-like characteristics, but there are a small amount of fine particle agglomerates, part of the plate-like crystal size is small, and the edge is slightly rough. The low dissolution temperature leads to incomplete dissolution of ammonium tungstate, and the residual raw material affects the uniformity of crystal growth.

[0056] The ultra coarse plate-like tungsten oxide was detected, and the purity was 99.99%, the crystallization rate was 92.71% (calculated by WO3), the length-width ratio was greater than 5:1, and the average width was 131 μm.

[0057] Comparative Example 2

[0058] Different from Example 1, the ammonium tungstate solution was placed in the crystallization container and cooled to room temperature at a rate of 5℃ / h;

[0059] Ultrafine tungsten oxide was obtained;

[0060] Referring to Figure 6 , Figure 6 The SEM image of the ultrafine tungsten oxide prepared in Comparative Example 2 can be seen from Figure 6 It can be seen that there is no plate-like structure, and only a large number of nanoscale fine particle aggregation states are presented, and the particle size is small. The rapid cooling rate produces too many crystal nuclei, and the crystal cannot grow in order.

[0061] The ultrafine tungsten oxide was detected, and the purity was 99.99%, and the crystallization rate was 90.89% (calculated by WO3).

[0062] Comparative Example 3

[0063] Different from Example 1, a clear ammonium tungstate solution was prepared, and the concentration was 100 g / L (calculated by WO3);

[0064] The ultra coarse plate-like tungsten oxide was detected, and the purity was 99.99%, the crystallization rate was 66.87% (calculated by WO3), the length-width ratio was greater than 5:1, and the average width was 201 μm.

[0065] Comparative Example 4

[0066] Different from example 1, the plate-shaped ammonium tungstate crystal is placed in a ceramic boat, and then placed in a muffle furnace for calcination, the calcination temperature is 800 DEG C, and the calcination time is 1 h, to obtain the tungsten oxide with irregular polygons;

[0067] Please refer to Figure 7 , Figure 7 The SEM image of the tungsten oxide with irregular polygons prepared in comparative example 4 can be seen from Figure 7 It can be seen from that the plate-shaped structure is destroyed, and the crystal presents irregular polygonal block, and the WO3 grains grow excessively and agglomerate due to the excessively high calcination temperature.

[0068] The purity of the tungsten oxide with irregular polygons is 99.99%, and the crystallinity is 91.76% (calculated by WO3).

[0069] The tungsten oxide with irregular polygons prepared by the method has the advantages of high controllability, uniform particle size, complete plate-shaped structure, purity ≥ 99%, and solves the problems of agglomeration and disordered morphology of traditional tungsten oxide.

[0070] The function is strong, the plate-shaped structure can be oriented, the dielectric and breakdown performances are improved, and it is suitable for many high-end scenes; the parameters are easy to control, the operation is simple, and it is green and safe.

[0071] The above only describes the preferred embodiments of the present application, and does not limit the patent range of the present application, and any equivalent structural transformation made according to the content of the present application, or direct / indirect application in other related technical fields is included in the patent protection range of the present application.

Claims

1. A method for preparing ultra-coarse plate-shaped tungsten oxide, characterized in that, Includes the following steps: S1. Add ammonium tungstate to deionized water and stir to dissolve at a temperature of 70~90℃ to obtain a clear ammonium tungstate solution; S2. Cool the clarified ammonium tungstate solution to room temperature at a cooling rate of 0.5~2℃ / h, and then filter it to obtain plate-shaped ammonium tungstate crystals; S3. Calcining the plate-shaped ammonium tungstate crystals yields ultra-coarse plate-shaped tungsten oxide; In step S1, the concentration of the clarified ammonium tungstate solution, calculated as WO3, is 300~450 g / L; In step S3, the calcination temperature is 500~700℃ and the time is 1~3h; The aspect ratio of the ultra-coarse plate-shaped tungsten oxide is greater than or equal to 5:1; The average width of the ultra-coarse plate-shaped tungsten oxide is greater than or equal to 180 μm.

2. The method for preparing ultra-coarse plate-shaped tungsten oxide according to claim 1, characterized in that, Specifically, step S3 involves placing the plate-shaped ammonium tungstate crystals in a ceramic boat and then calcining them in a muffle furnace under aerobic conditions to obtain ultra-coarse plate-shaped tungsten oxide.

3. The method for preparing ultra-coarse plate-shaped tungsten oxide according to claim 2, characterized in that, The ceramic boat is an alumina ceramic boat, and the purity of the alumina ceramic boat is greater than or equal to 99%.

4. A type of ultra-coarse plate-shaped tungsten oxide, characterized in that, The ultra-coarse plate-shaped tungsten oxide is prepared by the preparation method of ultra-coarse plate-shaped tungsten oxide according to any one of claims 1 to 3.

5. The ultra-coarse plate-shaped tungsten oxide according to claim 4, characterized in that, The purity of the ultra-coarse plate-shaped tungsten oxide is greater than or equal to 99%.

6. The ultra-coarse plate-shaped tungsten oxide according to claim 4, characterized in that, The crystallinity of the ultra-coarse plate-shaped tungsten oxide is greater than or equal to 90% when calculated as WO3.

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