KR20020083651A - Preparation of ZnO Powder by Pyrophoric Synthesis Method - Google Patents

Abstract

PURPOSE: Provided is a method for preparing high purity and nano-size zinc oxide(ZnO) powder reproducibly by ignition reaction which supplements conventional dry and wet methods, and removes impurities easily. CONSTITUTION: The preparation method of ZnO powder, being less than 1micrometer in size, comprises the steps of: dissolving Zn or Zn-compound, such as Zn, Zn(NO3)2, ZnCO3, zinc citrate, etc., into 0.1-5M HNO3; adding an organic acid such as malic acid, maleic acid, citric acid, oxalic acid, etc. to form precursor; adding NH4OH to adjust pH of the solution between 3-9; ignition reacting at 200-500deg.C to form ZnO precursor powder; and calcining at 400-900deg.C.

Description

Preparation method of zinc oxide (ZnO) powder by ignition synthesis method {Preparation of ZnO Powder by Pyrophoric Synthesis Method}

The present invention relates to a method for producing a ZnO oxide powder, which is suitable for the production of nanopowders having a particle size of 1 μm or less, and is manufactured by a wet method using chemical properties, so that ZnO ultrafine powder having high quality is superior to conventional dry and wet methods. It is related with the technology which can manufacture powder efficiently.

The ignition synthesis method according to the present invention specifically dissolves Zn and Zn compounds (Zn (NO ₃ ) ₂ , ZnCO ₃ , Znic Citrate, Zinc Oxalate, etc.) in a nitric acid solution in a chemical manner as shown in FIG. ), A step of making a precursor by adding an organic acid to the solution prepared in the first step (second step), adjusting the pH to a pH 3-9 range by adding NH ₄ OH to the second step solution (third step) ), Preparing a precursor powder by firing the solution of the third step at a temperature of 200 ~ 500 ℃ (fourth step), calcining the precursor powder prepared in the fourth step to prepare the ultra fine powder (the fifth step) Step) is a manufacturing method consisting of.

Zinc oxide is used in glass, glaze, enamel, magnetic ferrite, etc. In particular, ZnO is widely used as a material because of its various functions such as semiconductivity, piezoelectricity, fluorescence, and photoconductivity.

There are generally dry and wet methods for the preparation of ZnO, and dry methods are divided into direct and indirect methods. The indirect method is called the French method. In 1845, Leclair, France, externally heated to about 1100 to 1400 ° C. to burn Zn vapor to produce crystals having a particle diameter of 0.3 to 0.8 μm. The direct method is also called the US method. It is obtained by adding reducing agent such as coke and coal to zinc ore and heating and reducing it in a reflection furnace, retort furnace, or electric furnace to vaporize it, and to obtain ZnO by oxidation in air. The disadvantage is that it contains impurities such as Pb and Cd. The wet method is also called the German method, and precipitates a basic zinc carbonate (xZnCO ₃ · yZn (OH) ₂ · zH ₂ O) by reacting a ZnSO ₄ or ZnCl ₂ solution with a Na ₂ CO ₃ solution, which is then filtered and washed with water. Pyrolysis at about 400 ° C. produces ZnO. The diameter of the ZnO particles produced by the wet method is smaller than that of the dry method ZnO, and the specific surface area is large. The purity of ZnO is controlled depending on the application, but many fine particles having a specific surface area of 90 to 93% are produced. The shape of the particles is determined by the secondary agglomeration of the fine particles of 0.1 ㎛ or less because the particles are agglomerated during precipitation or pyrolysis.

However, the ignition synthesis method can improve the shortcomings of the conventional methods, and since the raw materials are chemically liquid-liquid mixed, impurities in the raw materials can be easily removed to produce reproducibly high-quality nano-sized ZnO powders of high quality. After confirming that it is an excellent manufacturing method, it is possible to apply the batch and continuous process to find out that an efficient mass production process can be configured to complete the present invention.

As described above, the present invention not only can compensate for the disadvantages of the dry method (direct method, indirect method) and wet method, which are the traditional methods of preparing ZnO powder, but also easily remove impurities of Zn or Zn compound as starting materials. It is an object of the present invention to provide a method for obtaining a high purity ZnO oxide ultrafine powder having a size of 1 μm or less.

1 is a process chart showing the manufacturing process of ZnO oxide powder by the ignition synthesis method used in the present invention.

FIG. 2 is X-ray diffraction analysis data of ZnO powders prepared by firing synthesis method and calcined at 500 ° C., 600 ° C. and 700 ° C. for 2 hours.

3 is an electron microscope (TEM) photograph of a ZnO precursor powder prepared by a ignition synthesis method, calcined at 500 ° C. for 2 hours.

Figure 4 is a particle size analysis data of the ZnO powder calcined ZnO precursor powder prepared by the ignition synthesis method at 700 ℃ for 2 hours.

In order to achieve the above object, the configuration and operation of the present invention are specifically described in detail, and a method of preparing high purity ZnO powder is provided through a preferred embodiment for preparing ZnO powder by a ignition synthesis method.

The ignition synthesis method according to the present invention specifically dissolves Zn and Zn compounds (Zn (NO ₃ ) ₂ , ZnCO ₃ , Znic Citrate, Zinc Oxalate, etc.) in a nitric acid solution in a specific manner as shown in FIG. Step 1), adding an organic acid to the solution prepared in step 1 to form a precursor (step 2), and adding pH ₄ OH to the step 2 solution to adjust the pH to a pH range of 3-9 Step 3), the step of preparing the precursor powder by firing the solution of the third step at a temperature of 200 ~ 500 ℃ (fourth step), the step of calcining the precursor powder prepared in the fourth step to prepare the ultra fine powder ( The fifth step) is a manufacturing method characterized by the configuration.

The following examples are intended to illustrate the invention and should not be understood as limiting the scope of the invention.

Example 1

Representative methods for the production of ZnO powders by the inventors' ignition synthesis method have been described as an example.

First, completely dissolving 189.38 g of Zn (NO ₃ ) ₂ xH ₂ O as a starting material in a ₁ M HNO ₃ solution (first step), and first weighing 134.09 g of malic acid in the dissolved solution Adding and stirring to form a precursor (second step), adding NH ₄ OH to the second step solution to adjust the pH in the range of pH 3-9 (step 3), and adding the solution of the third step to 200 Preparation step (fourth step) of the precursor powder through the ignition reaction at a temperature of ~ 500 ℃, and the step of producing a powder by calcining the ZnO precursor powder prepared in the fourth step at 500 ℃ for 2 hours (the fifth step) It is characterized by consisting of). Figure 2 (a) confirmed that the ZnO precursor powder prepared by the ignition synthesis method was formed by the X-ray diffraction analysis of the calcined treatment at 500 ℃ for 2 hours to form a complete ZnO phase. From the electron microscope (TEM) photograph of FIG. 3 and the particle size distribution analysis results of FIG. 4, it was confirmed that the powder prepared under the above conditions was prepared with a ZnO powder having an average particle diameter of about 50 nm.

Example 2

In Example 1, the first to fourth steps were the same, and the powder was prepared by calcining the calcining temperature of the fifth step from 500 ° C. to 700 ° C. for 2 hours. X-ray diffraction analysis of the prepared powder is shown in Fig. 2 (c), it was confirmed that the complete ZnO phase was formed from this result.

Example 3

In Example 1, 65.38 g of Zn was completely dissolved in 1M HNO ₃ solution instead of Zn (NO ₃ ) ₂ · xH ₂ O as the starting material of the first step, and the remaining 2 to 4 steps were prepared in the same manner. The ZnO precursor powder prepared in the fourth step was calcined at 600 ° C. for 2 hours to prepare a powder. X-ray diffraction analysis of the powder prepared by this process is shown in Fig. 2 (b), it was confirmed that the complete ZnO phase was formed from this result.

Although the present invention has been described in detail only with respect to specific examples, various modifications and variations are possible within the technical scope of the present invention, and it is obvious that such modifications and modifications are included in the claims.

As described above, the production method of the zinc oxide powder by the ignition synthesis method of the present invention is a method that can be easily applied to the current industry. In addition, since high purity or low level Zn or Zn compound combined with Zn is dissolved in nitric acid solution to produce a complete liquid phase and then ignited to obtain precursor powder, impurities can be removed in solution state and ignition process. By calcining the removed precursor powder, it provides the effect of the invention that a high purity ultrafine powder of 1 μm or less can be obtained.

Claims (6)

In producing a high purity ZnO oxide powder of 1 μm or less by the ignition synthesis method of the present invention (1) preparing a homogeneous solution by weighing Zn or a Zn compound, and then dissolving in 0.1-5 M HNO ₃ solution by chemical method (first step) (2) adding an organic acid to the solution prepared in the first step at a constant calculated molar ratio and then adding to form a precursor (second step) (3) adjusting the pH to pH 3-9 by adding NH ₄ OH to the second solution (third step) (4) preparing a ZnO precursor powder by ignition reaction of the solution of the third step in the temperature range of 200 ~ 500 ℃ (fourth step) (5) preparing a fine powder by calcining the precursor of the fourth step at a temperature of 400 ~ 900 ℃ (the fifth step) The raw material of zinc oxide (ZnO) according to claim 1, consisting of Zn or Zn such as Zn, Zn (NO ₃ ) ₂ , ZnCO ₃ and Znic Citrate as a starting material (raw material) of the first step as a raw material of zinc oxide (ZnO). Each compound is prepared using an oxide compound, a nitrate compound, a carbonate compound, a hydroxide compound, and other Zn compounds, and prepared by dissolving the starting material in a HNO ₃ solution within a concentration range of 0.1 to 5 M. Manufacturing method. The organic acid other than Malic acid, Maleic acid, Citric acid, Oxalic acid, Stearic acid, etc. is used to make a precursor by weighing and adding the organic acid to the dissolved solution according to claim 1 in a constant calculated molar ratio. ZnO manufacturing method characterized in that. The method of claim 3, wherein the precursor is prepared by adding the organic acid in a stoichiometric ratio corresponding to the valence of Zn based on the COO ⁻ group of the organic acid when determining the content of the organic acid. The method for producing ZnO according to claim 1, wherein the pH of the ignition reaction solution is adjusted to pH 3-9 by adding NH ₄ OH. The method for producing ZnO according to claim 1, wherein the ignition reaction solution is prepared at a temperature of 200 to 500 ° C. in a batch reactor or a continuous reactor to produce a precursor powder by ignition reaction.