KR102271842B1 - Method for preparing tungsten oxide - Google Patents

Abstract

The present application relates to a method for producing amorphous tungsten oxide in powder form. The manufacturing method of the present application includes a step of mixing a calcium precursor and sodium tungstate dissolved in an acidic solution having a concentration of 1 M to 4 M, and a low-temperature drying step.

Description

Method for preparing tungsten oxide {Method for preparing tungsten oxide}

The present application relates to a method for producing tungsten oxide.

Tungsten (W) has a very high melting point, high strength, and excellent high-temperature corrosion resistance. Therefore, tungsten is widely used in filaments of light bulbs, X-ray tubes, tool steel or cutting bites, nozzles of rockets, or other aerospace materials. Such tungsten is generally used in the form of tungsten oxide (WO _{3 ).}

Tungsten oxide can generally be produced by precipitating sodium tungsten through an ion exchange resin, or by hydrolysis and then heat treatment. However, the wet synthesis method as described above can produce only tungsten oxide having a hexagonal or monoclinic structure.

On the other hand, amorphous tungsten oxide can be manufactured through methods such as sputtering, thermal deposition, and pulsed laser deposition (PLD), but the above-described process is an expensive vacuum process, and amorphous tungsten oxide can be obtained only in the form of a thin film. The disadvantage is that the field that can be used is limited.

Therefore, in order to widely utilize amorphous tungsten oxide in various fields, it is required to develop an effective manufacturing method capable of producing it in powder form.

An object of the present application is to provide a method for preparing amorphous tungsten oxide in powder form.

The above and other objects of the present application can all be achieved by the present application described in detail below.

In an example related to the present application, the present application relates to a method for producing tungsten oxide. In one example, the manufacturing method according to the present invention includes mixing a calcium precursor and sodium tungstate dissolved in an acidic solution having a molar concentration of 1M to 4M, and drying the precipitated particles.

The present inventors have completed the present invention by using sodium tungstate among tungsten precursors and discovering that amorphous tungsten oxide can be prepared in powder form when the sodium tungstate is reacted with a calcium precursor.

That is, in the manufacturing method of the present application, amorphous tungsten oxide can be prepared in powder form by using a calcium precursor and sodium tungstate. In addition, in the manufacturing method of the present application, by controlling the molar concentration of the acidic solution within the above range, the mixing degree between components constituting the mixture can be increased, and the production yield and quality of tungsten oxide can be improved.

In one example, the sodium tungstate may be mixed in an aqueous solution state. More specifically, the step of mixing the calcium precursor and sodium tungstate dissolved in an acidic solution having a concentration of 1M to 4M is prepared by dissolving a solution A prepared by dissolving the calcium precursor in the acidic solution and sodium tungstate in water. It may be a step of mixing solution B.

In one example, the acidic solution having a concentration of 1M to 4M may include hydrochloric acid, nitric acid, sulfuric acid, acetic acid, or a mixture thereof, but is not particularly limited as long as the concentration is satisfied.

In another example, the acidic solution may have a pH of -1 to 3. By using the acidic solution in the above pH range, it is possible to increase the degree of mixing between the components, and to improve the production yield and quality of tungsten oxide.

In one example, the calcium precursor and sodium tungstate may be mixed in a molar ratio of 1:0.5 to 1:2, preferably in a molar ratio of 1:1. The molar ratio means the ratio of the number of moles of the calcium precursor participating in the reaction to the number of moles of sodium tungstate participating in the reaction.

In one example, the calcium precursor may be calcium chloride, calcium nitrate, calcium sulfate, calcium hydroxide, calcium carbonate, or a mixture thereof, but is not limited thereto.

In order to induce a sufficient reaction in the mixing step, the mixing time is not particularly limited, and, for example, may be carried out for 10 minutes or more. Tungsten oxide may be precipitated through the mixing step.

The manufacturing method of the present application may include drying the precipitated tungsten oxide after the mixing step. The drying step corresponds to a low-temperature drying step, and in the present application, the low-temperature drying step refers to a drying step performed at a temperature of 100° C. or less. The lower limit of the low-temperature drying temperature is not particularly limited, but may be made at a temperature of 50°C or higher, 60°C or higher, or 70°C or higher. When drying in the above temperature range, the solvent or moisture may be evaporated, and amorphous tungsten oxide may be obtained.

The time of the low-temperature drying step is not particularly limited and may be appropriately adjusted according to the components and content of the solvent used. For example, the low-temperature drying time may be 1 hour or more.

In one example, the manufacturing method according to the present application may further include removing impurities after the mixing step and before the low temperature drying step. A method of removing the impurities is not particularly limited, and for example, centrifugation and/or washing may be performed using water and an organic solvent. The manufacturing method may increase the purity and uniformity of the tungsten oxide particles through the step of removing impurities.

In one example, the manufacturing method according to the present application may further include a high-temperature drying step made under a nitrogen atmosphere. In the present application, the high-temperature drying step refers to a drying step performed at a temperature of 150° C. or higher. Higher purity tungsten oxide particles can be obtained by performing a high temperature drying step under a nitrogen atmosphere after the low temperature drying step.

The upper limit of the temperature of the high temperature drying step may be 350 °C or less, or 300 °C or less. When drying is performed in the above temperature range, higher purity tungsten oxide can be obtained while maintaining the amorphous structure of the tungsten oxide. In addition, when the temperature is out of the above range, diffusion may occur in the tungsten oxide particles, and accordingly, a structural change may occur from amorphous tungsten oxide to crystalline tungsten oxide having a monoclinic structure.

In addition, when the drying process is performed under a nitrogen atmosphere, it is possible to suppress the oxidation reaction that may occur during the drying process, thereby suppressing the crystal growth of amorphous tungsten oxide.

The time of the high temperature drying step is not particularly limited, and may be performed for 1 hour or more.

According to the manufacturing method of the present application, the amorphous tungsten oxide may be provided in a powder form to be utilized in various fields. In addition, the manufacturing method of the present application can mass-produce amorphous tungsten oxide, and the productivity is excellent.

1 is a graph showing the XRD measurement result of tungsten oxide according to Example 1 of the present application.
2 is a graph showing the XRD measurement result of tungsten oxide according to Example 2 of the present application.
3 is a graph showing the XRD measurement result of tungsten oxide according to Example 3 of the present application.
4 is a graph showing the XRD measurement result of tungsten oxide according to Comparative Example 1 of the present application.
5 is a graph showing the XRD measurement result of tungsten oxide according to Comparative Example 2 of the present application.
6 is a graph showing the XRD measurement result of tungsten oxide according to Comparative Example 3 of the present application.
7 is a graph showing an XRD measurement result of tungsten oxide according to Comparative Example 4 of the present application.

Hereinafter, the present application will be described in detail through examples. However, the protection scope of the present application is not limited by the examples described below.

1. Structural analysis of tungsten oxide ( XRD Measure)

Structural analysis of tungsten oxide was performed through XRD measurement. For XRD analysis, the prepared tungsten oxide was measured using a Bruker D4 Endeavor (40 kV, 40 mA). The measurement results are shown in FIGS. 1 to 7 , where the x-axis represents 2θ (degree) and the y-axis represents intensity (a.u).

Experimental example 1: Preparation of amorphous tungsten oxide

Example 1.

2.94 g of calcium chloride was dissolved in 20 mL of 3M HCl to prepare a solution A. Sodium tungstate 6.60 g was dissolved in 20 mL of water to prepare a solution B. Thereafter, the solution A and the solution B were stirred for 30 minutes or more to obtain precipitated particles. The precipitated particles were centrifuged, washed three or more times with water and ethanol to remove impurities, and then dried at 80°C for 12 hours at low temperature to prepare tungsten oxide powder. The prepared tungsten oxide was measured by XRD, and the results are shown in FIG. 1 .

Example 2.

A tungsten oxide powder was prepared in the same manner as in Example 1, except that 4.72 g of calcium nitrate was used instead of calcium chloride when preparing the solution A. The prepared tungsten oxide was measured by XRD, and the results are shown in FIG. 2 .

Comparative Example 1.

2.37 g of nickel chloride was dissolved in 20 mL of 2M HCl to prepare a solution C. A solution D was prepared by dissolving 3.30 g of sodium tungstate in 20 mL of water. Thereafter, the solution C and the solution D were stirred for 30 minutes or more to obtain precipitated particles. The precipitated particles were centrifuged, washed three or more times with water and ethanol to remove impurities, and then dried at 80° C. for 12 hours at low temperature to prepare tungsten oxide powder. The prepared tungsten oxide was XRD-measured, and the results are shown in FIG. 4 .

Comparative Example 2.

A tungsten oxide powder was prepared in the same manner as in Example 1, except that 20 mL of 9M HCl was used instead of 3M HCl when preparing the solution A. The prepared tungsten oxide was XRD-measured, and the results are shown in FIG. 5 .

As a result of XRD measurement, it can be confirmed that only broad peaks were measured in FIGS. 1 and 2 as a whole. Therefore, it can be confirmed that there is no crystalline region, and amorphous tungsten oxide is produced. On the other hand, in FIGS. 4 and 5, specific peaks were measured, and thus, it can be confirmed that crystalline tungsten oxide is prepared.

Experimental example 2: Obtaining high purity amorphous tungsten oxide

Example 3

The tungsten oxide powder of Example 1 was further subjected to a high-temperature drying step at 300° C. for 2 hours under a nitrogen atmosphere. The prepared tungsten oxide was XRD-measured, and the results are shown in FIG. 3 .

Comparative Example 3

The tungsten oxide powder of Example 1 was further subjected to a high-temperature drying step at 400° C. for 2 hours under a nitrogen atmosphere. The prepared tungsten oxide was XRD-measured, and the result is shown in FIG. 6 .

Comparative Example 4

The tungsten oxide powder of Example 1 was further subjected to a high-temperature drying step at 300° C. for 2 hours in an air atmosphere. The prepared tungsten oxide was measured by XRD, and the results are shown in FIG. 7 .

As a result of XRD measurement, in the case of FIG. 3 , it can be confirmed that the amorphous structure of tungsten oxide is maintained as it is. On the other hand, in FIGS. 6 and 7 , specific peaks were measured, and thus, it can be confirmed that a structural change occurred from amorphous tungsten oxide to crystalline tungsten oxide.

Claims (10)

Precipitating tungsten oxide by mixing a calcium precursor and sodium tungstate dissolved in an acidic solution having a concentration of 1 M to 4 M;
Drying the precipitated tungsten oxide at a low temperature; and
In a nitrogen atmosphere, drying at a high temperature in a temperature range of 150 ° C to 350 ° C to obtain amorphous tungsten oxide;
The calcium precursor is calcium chloride, calcium nitrate, calcium sulfate, calcium hydroxide, calcium carbonate, or a mixture thereof.
The method of claim 1, wherein the sodium tungstate is mixed in an aqueous solution state.
The method of claim 1, wherein the acidic solution comprises hydrochloric acid, nitric acid, sulfuric acid, acetate, or a mixture thereof.
The method of claim 3, wherein the acidic solution has a pH of -1 to 3.
The method of claim 1, wherein the calcium precursor and sodium tungstate are mixed in a molar ratio of 1:0.5 to 1:2.
delete The method of claim 1, wherein the temperature of the low-temperature drying step is 60°C to 100°C.
The method of claim 1, further comprising the step of removing impurities before the low-temperature drying step.
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