KR100752954B1 - Method for preparing nano porous powders by ultrasonic pyrolysis and its nano powders - Google Patents

Abstract

The present invention relates to a method for preparing nanoporous powder using ultrasonic spray pyrolysis and to nanoparticles prepared by the above, and more particularly, by adding a water-soluble polymer to a metal salt precursor to prepare using ultrasonic spray pyrolysis. It is possible to obtain a nanoporous powder with a very large surface area and nano-sized pores, and to use the nitrate solution as a starting point at a small concentration below the decimal point. The present invention relates to a method for preparing nanoporous powder using ultrasonic spray pyrolysis, which is applicable to energy saving / storage / conversion materials, chemical / electrochemically active materials, and information / electronic materials, and nanoparticles prepared by the powder. .

The present invention comprises the steps of preparing a solution by adding and stirring a ceramic or metal raw material in a solvent, preparing a solution by adding and stirring a polymer in the ceramic or metal raw material solution, and spraying the solution with an ultrasonic atomizer And spraying the sprayed droplets into a preheated chamber, thermally decomposing the spray, and collecting the powder generated after the thermal decomposition.

Therefore, the present invention is prepared by the ultrasonic spray pyrolysis method by adding a water-soluble polymer to the metal salt precursor, it is possible to obtain a uniform nanoporous powder with a very large specific surface area and having nano-sized pores, as a starting material aqueous solution of nitrate By using a weak concentration below the decimal point, the main by-product generated during the process is water, which is environmentally friendly. In addition, the powder has an effect that can be applied to energy saving / storage / conversion material, chemical / electrochemically active material, information / electronic materials.

Ultrasonic spray pyrolysis, nano porous powder, metal salt precursor, water soluble polymer, uniformity, environmentally friendly.

Description

Method for preparing nanoporous powder using ultrasonic spray pyrolysis and nanopowder manufactured by the same method METHOD FOR PREPARING NANO POROUS POWDERS BY ULTRASONIC PYROLYSIS AND ITS NANO POWDERS

1 is a view schematically showing an ultrasonic spray pyrolysis apparatus used in the method for producing nanoporous powder according to an embodiment of the present invention.

2 is a flow chart of a method for producing nanoporous powder according to an embodiment of the present invention.

3 is a scanning electron micrograph of nanoporous LSC powder synthesized by adding 50 cc of PAA per liter of solvent according to Example 1 of the present invention.

Figure 4 is a transmission electron micrograph of the nanoporous LSC powder synthesized by adding 50 cc of PAA per liter of the solvent according to Example 1 of the present invention.

5 is a scanning electron micrograph of the LSC powder synthesized without the addition of a water-soluble polymer according to Comparative Example 1 of the present invention.

6 is a scanning electron micrograph of nanoporous LSC powder synthesized by adding 100 cc of PAA per liter of solvent according to Example 2 of the present invention.

7A is a micropore distribution curve of LSC powder synthesized according to Examples 1 and 2 and Comparative Example 1 of the present invention.

Figure 7b is a summary of the fine pore amount of LSC powder synthesized according to Examples 1, 2 and Comparative Example 1 of the present invention.

8 is a scanning electron micrograph of the nanoporous LSC powder synthesized by adding 50 cc of PEG per liter of the solvent according to Example 3 of the present invention.

Figure 9 is a primary particle size and specific surface area arrangement of LSC powder synthesized according to Examples 1, 2 and Comparative Example 1 of the present invention.

<Explanation of symbols for main parts of the drawings>

100: ultrasonic nebulizer 110: solution source

120: carrier gas source 130: ultrasonic oscillator

200: reactor 210: chamber

220: heater 230: temperature sensor

240: temperature controller 300: collector

310: collection filter 320: pump

The present invention relates to a method for preparing nanoporous powder using ultrasonic spray pyrolysis and to nanoparticles prepared by the above, and more particularly, by adding a water-soluble polymer to a metal salt precursor to prepare using ultrasonic spray pyrolysis. It is possible to obtain a nanoporous powder with a very large surface area and nano-sized pores, and to use the nitrate aqueous solution as a starting point at a weak concentration below the decimal point. The present invention relates to a method for preparing nanoporous powder using ultrasonic spray pyrolysis, which is applicable to energy saving / storage / conversion materials, chemical / electrochemically active materials, and information / electronic materials, and nanoparticles prepared by the powder. .

Interest in porous powders and porous bodies has been steadily maintained from an industrial or academic point of view. In particular, porous bodies having pores of a regular sized regular array have been continuously applied to various industrial fields by using adsorption and separation functions of pores. Currently, micrometers or sub-nm porous materials have many industrial applications. However, many researches have been made on nanoporous porous bodies having a size of 0.4 to 100 nm containing medium pores in order to overcome unique functionalities and application limitations. These porous powders and porous bodies are spotlighted as key technologies for the development of energy saving / storage / conversion materials, chemical / electrochemically active materials, and information / electronic materials, and are recognized as very important technologies having high added value.

Materials with mesopores ranging in size from 2 to 50 nm were developed by researchers at Mobil in the United States in 1992 using a cetyltrimethyl-ammonium bromide (CTAB) surfactant to successfully synthesize an array of silica After synthesis, full-scale research began. In addition, methods for synthesizing porous bodies having various thicknesses and pore sizes by using anionic or neutral ion surfactants or inorganic materials of cations or neutral ions have been developed and applied. However, silica-based porous bodies generally have no catalytic activity and are more thermally and chemically unstable than other metal oxides. In addition, silica has little electrical, magnetic, and optical properties, and thus is limited in various industrial applications. Therefore, many studies on the synthesis and application of non-silica-based nano-sized pore porous bodies have been made. However, unlike silica-based materials, non-silica-based nanoporous porous bodies are difficult to control the hydrolysis reaction, condensation reaction, and oxidation / reduction reaction of metal ions.

Aerogels, a field of porous materials, are also highly porous, high specific surface materials having a porosity of greater than 90% and a pore size in the range from 1 to 50 nm. The synthesis of aerogels is synthesized using a sol-gel process. The most important step of the synthesis process is a drying process, which greatly affects the characteristics of the airgel. In general, the drying process involves firstly drying a solvent such as an alcohol with a supercritical fluid, secondly replacing carbon dioxide or another low critical solvent, and thirdly maintaining a low drying rate. Convection drying or drying using a DCCA (drying control chemical additive) is used. When the residual solution is removed from the porous solid by using a supercritical fluid, since the gas-liquid interface does not occur, severe shrinkage and cracking due to capillary forces can be prevented, so that the solid material can be dried and dried. Therefore, the first and second methods have the advantages of maintaining a high porosity and producing a transparent airgel, but have a high risk and have a limited economic feasibility because the process requires a high pressure. In addition, the third and fourth methods have the advantage of drying at normal pressure, but they are less perfect and dense because it is difficult to avoid shrinkage and cracking of the gel during the diffusion and removal of the solvent by dry stress such as surface tension and osmotic pressure. It is prepared in the form of an airgel.

As described above, the conventional methods for producing a porous body show a number of limitations in materials and processes, and in particular, nanoporous powders cannot be produced by conventional techniques that are vulnerable.

Therefore, it is possible to obtain a nanoporous powder with a very large specific surface area and uniform pore size, and is environmentally friendly since the main by-products generated during the process are water, energy saving / storage / conversion materials, and chemical / electrochemical activities. There is an urgent need for development of manufacturing methods that can be applied to materials and information / electronic materials.

The present invention has been conceived to solve the above problems, by adding a water-soluble polymer to the metal salt precursor prepared by the ultrasonic spray pyrolysis method, to produce a uniform nanoporous powder having a very large specific surface area and having nano-sized pores It is an object of the present invention to provide a method for preparing nanoporous powder using ultrasonic spray pyrolysis, which can be obtained, and a nanopowder prepared thereby.

Another object of the present invention is to prepare a nano-porous powder using an environmentally friendly ultrasonic spray pyrolysis method by using a nitrate aqueous solution as a starting material in a slight concentration below the decimal point, since the main by-products generated during the process is water To provide the prepared nano powder.

Another object of the present invention is a method for producing nanoporous powder using ultrasonic spray pyrolysis, which is applicable to energy saving / storage / conversion materials, chemical / electrochemically active materials, information / electronic materials, and the powders. To provide nanoparticles.

According to a preferred embodiment of the present invention, there is provided a method of preparing nanoporous powder using ultrasonic spray pyrolysis, which comprises preparing a solution by adding and stirring a metal raw material of ceramic or metal nitrate to a solvent, and the ceramic Or preparing a solution by adding and stirring a polymer to a metal raw material solution, which is a metal nitrate, spraying the solution with an ultrasonic atomizer, spraying the sprayed droplets into a preheated chamber, Pyrolyzing the object and collecting the powder generated after the pyrolysis.

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In the present invention, the ceramic and metal raw material is characterized in that it includes all raw materials that are dissolved in pure or alcoholic solvents.

In the present invention, characterized in that it further comprises the step of adjusting the size of the final powder by adjusting the concentration of the solution by adjusting the mixing ratio of the ceramic or metal raw material and the solvent.

In the present invention, it characterized in that it further comprises the step of adjusting the size of the final powder and pores by adjusting the mixing ratio of the ceramic or metal solution and the added polymer.

In the present invention, the added polymer is characterized in that it includes PEG, PAA or any polymer that can be dissolved.

In the present invention, it is characterized in that it further comprises the step of adjusting the size of the final powder which is secondary particles by adjusting the frequency of the ultrasonic atomizer.

In the present invention, the spraying the sprayed droplets into the preheated chamber is characterized in that the spraying the droplets into the heating chamber using a carrier gas.

In the present invention, the carrier gas is characterized in that it comprises air, oxygen, nitrogen, inert gas or a mixed gas of the gas.

In the present invention, the temperature of the step of pyrolyzing the spray is characterized in that 100 ℃ to 1200 ℃.

In the present invention, the powder produced after the pyrolysis is characterized in that the size of less than microns.

In addition, the nano-porous powder according to a preferred embodiment of the present invention is characterized in that it is prepared using any one of the above methods.

1 is a schematic configuration diagram of an ultrasonic spray pyrolysis apparatus used to prepare nanoporous powder according to embodiments of the present invention.

As shown in FIG. 1, the ultrasonic spray pyrolysis apparatus may be basically divided into three regions, an ultrasonic spraying region A, a heat treatment region B, and a collecting region C. FIG. The process in each zone is performed in the ultrasonic nebulizer 100, the reactor 200, and the collector 300, respectively. A solution supply source 110 and a carrier gas supply source 120 are connected to the ultrasonic nebulizer 100, and an ultrasonic vibrator 130 is mounted below the ultrasonic nebulizer 100. The solution source 110 supplies a solution in which a metal salt precursor and a water-soluble polymer raw material are dissolved in a solvent into the ultrasonic nebulizer 100. The ultrasonic vibrator 130 at the bottom of the ultrasonic nebulizer 100 sprays the solution supplied from the solution source 110 into droplets of several microns in size. The sprayed droplets are moved into the chamber 210 of the reactor 200 by using a carrier gas supplied from the carrier gas source 120. The reactor 200 is a device for maintaining the temperature in the chamber 210 to a desired value, and includes a heater 220 mounted around the chamber, a temperature sensor 230 and a temperature controller 240 mounted in the chamber. do. The temperature controller 240 controls the heater 220 based on the temperature in the chamber received from the temperature sensor 230 to maintain the temperature in the chamber 210 at the set temperature. Droplets introduced into the chamber 210 of the reactor 200 together with the carrier gas are pyrolyzed at a set temperature. A collector 300 including a collecting filter 310 and a pump 320 is provided at an upper portion of the reactor 200 to collect various powders generated at the same time while emitting various gases generated during the pyrolysis reaction. That is, the generated powder in which the reaction is completed in the chamber 210 of the reactor 200 and the gas generated as a by-product during the pyrolysis reaction pass through the collector 300 by the pump 320. The powder is trapped by the collecting filter 310 and the gas generated in the pyrolysis reaction is discharged to the outside through the collecting filter 310.

2 is a flow chart of a method for producing nanoporous powder according to an embodiment of the present invention.

A description with reference to FIG. 2 is as follows. In the present invention, La _0.6 Sr _0.4 CoO _{3- ??} used in SOFC (solid oxide fuel cell) electrode or oxygen separation permeation membrane (LSC) nanopowders were attempted to be synthesized. Metal nitrates such as La (NO ₃ ) ₂ · 6H ₂ O, Sr (NO ₃ ) ₂ , Co (NO ₃ ) ₂ · 6H ₂ O were used as starting materials for the LSC nanopowders. To prepare, a water-soluble polymer, Poly Acrylic Acid (PAA, C ₃ H ₄ O ₂ ) or PEG (Poly Ethylene Glycol, C ₂ H ₆ O ₂ ) was added. Thus, all raw materials which can be dissolved in not only nitrate hydrate but also other pure water (ultra pure water) or alcohol solvent can be used. Polymeric raw materials can be used for all materials that can be dissolved in a solvent. The raw materials are added to the ultrapure water at an appropriate ratio and sufficiently stirred. The prepared solution is sprayed in an ultrasonic atomizer. The ultrasonic frequency here has the most suitable frequency (1.67 MHz for ultrapure water) at which the solvent is sprayed. The sprayed droplets are sprayed by the carrier gas into the preheated chamber to the set temperature (400-1000 ° C.). These sprays cause pyrolysis in the chamber to produce porous nanopowders with nano-sized pores with NO _x and H ₂ O. The resulting nanoporous powder is collected and NO _X and H ₂ O are released to the outside. This overall reaction is usually under atmospheric pressure.

NO _x is generated using aqueous solution of nitrate as a starting material, but it is eco-friendly because the main by-product generated during the process is water. Nanoporous powders produced by ultrasonic spray pyrolysis have primary particles of about 20 nm in size forming secondary particles of submicron size. The pore size ranges from 20 to 30 nm, and the specific surface area of the powder has increased more than three times by the addition of polymer during the process.

Hereinafter, preferred embodiments of the present invention will be described in detail.

Example 1

As starting materials for the LSC powder, metal nitrates of La (NO ₃ ) ₂ · 6H ₂ O, Sr (NO ₃ ) ₂ , Co (NO ₃ ) ₂ · 6H ₂ O were used. Poly Acrylic Acid (PAA, C ₃ H ₄ O ₂ ) was used. Metal nitrates have a composition of LSC of La _0.6 Sr _0.4 CoO _{3- ??} It was weighed so as to dissolve in ultrapure water at a concentration of 0.1 M. After that, 50 cc of PAA was added per liter of solvent, followed by stirring sufficiently. The prepared solution is sprayed by an ultrasonic atomizer and moved by a carrier gas into a chamber previously heated to a set temperature (1000 ° C.) to cause a pyrolysis reaction. The carrier gas used at this time may include air, oxygen, nitrogen, inert gas or a mixture of two or more of these gases. NO _x and H ₂ O were released by this pyrolysis reaction to form nanoporous powder, and the whole reaction process was performed under atmospheric pressure.

3 is a photograph of the nanoporous powder (LSC, La _0.6 Sr _0.4 CoO _{3- ??} ) prepared by the method of Example 1 in the ultrasonic spray pyrolysis apparatus of FIG. 1 with a scanning electron microscope. As can be seen from the photo, the primary particle size is about 20 nm, it can be seen that it has a similar size pores. Figure 4 is to observe the powder prepared by the method of Example 1 with a transmission electron microscope. It can be seen that the pores having a size of about 20 nm are uniformly distributed.

Comparative Example 1

In Comparative Example 1, the powder was prepared without adding the water-soluble polymer in order to determine the powder characteristics by the addition of the water-soluble polymer. Other conditions were prepared powder under the same conditions as in Example 1.

5 is a photograph observing the LSC powder prepared by the method of Comparative Example 1 with a scanning electron microscope. The size of the primary particles was shown to be the same size as in Example 1, but the pores did not exist. In other words, it was possible to confirm the occurrence of nano-pores in accordance with the participation of the water-soluble polymer.

Example 2

In Example 2, nanoporous powder was prepared under the same conditions as in Example 1 except that the amount of PAA added was changed to 100 cc per liter of solvent. This is an experiment for observing the change of the properties of the powder according to the addition amount of the water-soluble polymer.

Figure 6 is a photograph of the LSC powder prepared by the method of Example 2 observed with a scanning electron microscope. The size of the primary particles has the same size as the powder prepared by the method of Example 1, but it can be seen that the pore size is somewhat larger.

7A is a micropore distribution curve analyzed by BET to confirm the micropore size and distribution of powders prepared by the methods of Examples 1 and 2 and Comparative Example 1, and the same results as the photographs observed with the scanning electron microscope described above. Indicates. In other words, as the water-soluble polymer PAA increases, the micropore size increases. This is interpreted as the pore of the powder synthesized in the droplet increases as the amount of water-soluble polymer is decomposed in one droplet during the thermal decomposition reaction. FIG. 7B summarizes the amount of micropores calculated by integrating the micropore distribution curve of FIG. 7A. It can be seen that as the amount of PAA, which is a water-soluble polymer, increases, the amount of micropores increases rapidly. That is, the addition of the water-soluble polymer may be considered an important factor in the preparation of the nanoporous powder.

Example 3

In Example 3, the water-soluble polymer to be added was PEG, and the amount was 50cc per liter of solvent. Other conditions were prepared nanoporous powder under the same conditions as in Example 1 and Example 2. In Example 3 is an experiment for observing the change in the properties of the powder according to the type of water-soluble polymer to be added.

8 is a photograph observing the LSC powder prepared by the method of Example 3 with a scanning microscope. As in Examples 1 and 2 and Comparative Example 1 described above, the primary particles showed a size of about 20 nm and some pores were present. However, when compared with the results of Example 1, which is an experiment in which the same amount of PAA was added, the amount of pores is considered to be reduced.

FIG. 9 summarizes primary particle size and specific surface area values obtained by analyzing LSC powders prepared by the methods of Examples 1, 2, and 3 and Comparative Example 1 described above. The primary particle size was obtained by calculating the XRD results by Scherrer's equation, and the specific surface area was analyzed by BET. As shown in Figure 9 it can be seen that the size of the primary particles was reduced when the water-soluble polymer is added. This is interpreted as a result of the reduction of the amount of metal salt precursor that can be synthesized as a powder in the droplets as the water-soluble polymer coexists in the droplets. In addition, it can be seen that the specific surface area was rapidly increased due to the addition of the water-soluble polymer. This result suggests that the water-soluble polymer that coexisted in the droplets was decomposed during the pyrolysis reaction to form pores between the particles.

From the above results, it can be seen that when the polymer is dissolved in a solvent when the powder is prepared by ultrasonic spray pyrolysis, nano-sized pores are uniformly generated. This not only preserves the powder properties but also the process advantages over other nanoporous powder preparation methods currently under study.

As described above, the method for producing nanoporous powder using ultrasonic spray pyrolysis according to the present invention and the nanopowder prepared thereby have the following effects.

First, the present invention is prepared by the ultrasonic spray pyrolysis method by adding a water-soluble polymer to the metal salt precursor, it is possible to obtain a uniform nanoporous powder having a very large specific surface area and having nano-sized pores.

Second, the present invention is environmentally friendly because the main by-product generated during the process is water by using a nitrate aqueous solution as a starting material in a weak concentration below the decimal point.

Third, the present invention is applicable to the field of energy saving / storage / conversion material, chemical / electrochemically active material, information / electronic materials.

Claims (13)

delete Preparing a solution by adding and stirring a metal raw material which is ceramic or metal nitrate to a solvent, Preparing a solution by adding and stirring a polymer to the metal raw material solution which is ceramic or metal nitrate; Spraying the solution with an ultrasonic atomizer; Spraying the sprayed droplets into a preheated chamber; Pyrolyzing the spray; Method for producing a nano-porous powder using the ultrasonic spray pyrolysis method comprising the step of collecting the powder produced after the pyrolysis. delete The method of claim 2, The method of producing a nano-porous powder using the ultrasonic spray pyrolysis method, characterized in that the ceramic and metal raw materials include all raw materials dissolved in pure water or alcohol solvents. The method of claim 2, And adjusting the concentration of the solution by controlling the mixing ratio of the ceramic or metal raw material and the solvent to adjust the size of the final powder. The method of claim 2, And adjusting the size of the final powder and the pores by controlling the mixing ratio of the ceramic or metal solution and the added polymer. The method of claim 2, The added polymer is PEG, PAA or a method for producing a nano-porous powder using the ultrasonic spray pyrolysis method, characterized in that it includes any polymer that can be dissolved. The method of claim 2, And adjusting the frequency of the ultrasonic atomizer to adjust the size of the final powder, which is secondary particles. The method of claim 2, And spraying the sprayed droplets into the preheated chamber comprises spraying the droplets into the heating chamber using a carrier gas. The method of claim 9, The carrier gas is air, oxygen, nitrogen, an inert gas or a method of producing a nano-porous powder using the ultrasonic spray pyrolysis method, characterized in that containing a mixture of the gas. The method of claim 2, The temperature of the step of pyrolyzing the spray is a method for producing nanoporous powder using ultrasonic spray pyrolysis, characterized in that 100 ℃ to 1200 ℃. The method of claim 2, The powder produced after the pyrolysis is a nanoporous powder manufacturing method using the ultrasonic spray pyrolysis method, characterized in that the size of less than microns. The method of claim 2, Nanoporous powder, characterized in that prepared using the method.

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