KR20100096389A - Preparation method of nio-ysz thin film - Google Patents

Abstract

PURPOSE: A method for preparation of a NiO-YSZ thin film is provided to change an oxide thin film of a porous structure into a dense structure and an amorphous crystal structure into a perovskite structure according to process conditions. CONSTITUTION: A method for preparation of a NiO-YSZ thin film comprises steps of: dissolving a nickel precursor, a yttrium precursor and a zirconium precursor in a solvent to prepare a precursor solution; carrying the precursor solution to an electric field atomizer and injecting it into a nozzle; spraying the precursor solution through the nozzle in an electric field so as to form droplets; and uniformly adsorbing the droplets onto a preheated substrate and drying it.

Description

Manufacturing method of NiO-WSS thin film {Preparation method of NiO-YSZ thin film}

According to the present invention, the NiO-YSZ thin film can be controlled by controlling the process conditions so that the oxide thin film can be controlled from porous to dense structure and the crystal structure from amorphous to perovskite structure can be applied as a cathode of a solid oxide fuel cell. It relates to a manufacturing method.

Due to the depletion of fossil fuel, the main energy source, and global warming due to environmental pollution, research on environmentally friendly and efficient energy sources is underway.

Fuel cells are attracting attention as next-generation energy sources as environmentally friendly power generation devices that generate electricity from hydrogen. Such fuel cells include alkaline fuel cells (AFC), phosphoric acid fuel cells (PAFC), solid oxide fuel cells (SOFC), polymer electrolyte fuel cells (SPEFC), molten carbonate fuel cells (MCFC), and the like.

Among them, the solid oxide fuel cell (SOFC) is composed of all solid components, which is simpler in structure than other fuel cells, has high efficiency, and has low pollution, so it is a new clean energy of the future. It is attracting attention as one of the circles.

OFC operates at 700 to 1000 ° C, the highest temperature of a fuel cell because the electrolyte and the electrode exhibit sufficient electrical conductivity only at high temperatures. However, this high temperature operation requires that the interconnector or cell housing of the SOFC also be able to withstand high temperatures, thus limiting the choice of materials to ceramic materials. Therefore, the manufacturing process of the SOFC is difficult and requires a high level of technology, such as a well-controlled powder manufacturing technology and precise molding technology is accompanied by a problem that the manufacturing cost increases.

Therefore, when implementing a low-temperature SOFC by lowering the operating temperature of the SOFC below 700 ℃, the manufacturing process is easier and relatively inexpensive metal material can be used to obtain a significant economic effect.

In order to realize the low-temperature SOFC, a method of reducing the resistance of the electrolyte may be considered by using an alternative electrolyte having a higher ion conductivity than the existing stabilized zirconia and thinning. However, in the case of such a low-temperature SOFC, as the electrode / electrolyte interfacial polarization resistance rises sharply and another problem occurs that lowers the efficiency of the fuel cell, it is necessary to control the microstructure at the interface between the electrode / electrolyte.

Control of the microstructure may be achieved through various methods such as a method of changing a material, a method of modifying a material, and a method of adjusting a film manufacturing process. Therefore, in the present invention, it is possible to control the microstructure through the control of the membrane manufacturing process.

As is known, a wet coating method of forming a thick film and a dry coating method of forming a thin film are employed to produce a film.

Wet coating methods include dry pressing, slurry coating, printing, tape casting, dip coating, and spin coating.

Dry coating methods also include sputtering, pulse-laser deposition, electrochemical vapor deposition, metal-organic chemical vapor deposition, thermal spraying, and droplet flame deposition. The dry coating method is suitable for the production of dense thin film, has a low deposition rate, there is a limit in the selection of the composition of the starting material, and because the process is required in a vacuum state, there is a disadvantage that the manufacturing cost increases because of the complexity and cost of the equipment.

Therefore, there is still a need for technology development regarding ceramic thin film manufacturing method as well as thin film manufacturing method of solid oxide fuel cell component having high deposition rate and wide selection of starting materials. Remains.

On the other hand, in order to realize low cost as an electrode of SOFC, NiO, which is lower in price than conventional cathode materials Co, Pt, Pd, and Ru, is used as a general anode material of a solid oxide fuel cell.

In order to maintain the thermal expansion coefficient of the cathode similar to Yttria Stabilized Zirconia (YSZ), which is an electrolyte material, and to increase the bonding strength between the electrolyte and the cathode, YSZ, which is generally an electrolyte material, is added to the cathode layer.

The YSZ not only serves to maintain the porous structure of NiO at high temperatures, but also serves to improve the electrochemical performance of the cathode by forming YSZ / NiO / Gas three-phase interface, which is an electrochemically active point, three-dimensionally throughout the cathode layer.

NOMURA Hiroshi et al . Have mentioned the use of polyethylene glycol (PEG) as a NiO-YSZ binder to produce a porous thin film by electrostatic spray deposition (ESD) [NOMURA Hiroshi et al . solid oxide fuel cell using electrostatic spray deposition: II-Cell performance, Journal of Applied Electrochemistry, 35, 1121-1126, 2005]

NEAGU Roberto et al . Have proposed the manufacture of thin and dense films using electrostatic spray deposition (ESD) [Roberto Neagu, et al ., "Influence of the process parameters on the ESD synthesis of thin film YSZ electrolytes", Solid State Ionics , 177, 1981-1984, 2006].

Accordingly, the present inventors studied a method of forming a thin film by using an electrospray method, which is simpler to manufacture and lower in manufacturing cost than a vacuum deposition method, in order to manufacture a NiO-YSZ thin film as an electrode of SOFC. As a result, the microstructure of the thin film can be controlled from the porous to the dense structure, and the process conditions for the wide selection of starting materials can be established.

An object of the present invention is to provide a method for producing a NiO-YSZ thin film that can easily control the microstructure.

In order to achieve the above object,

Dissolving the nickel precursor, the yttrium precursor, and the zirconium precursor in a solvent to prepare a precursor solution;

Transferring the precursor solution into an electric field spraying device and injecting it into a nozzle;

Spraying a precursor solution using the nozzle to form droplets; And

Uniformly adsorbing the droplets onto a preheated substrate and drying the droplets

It provides a method for producing a NiO-YSZ thin film comprising a.

The manufacturing method according to the present invention can easily control the microstructure of the thin film by changing the process conditions. In addition, the deposition rate and thickness of the thin film can be easily adjusted, and the selection range of raw materials is wide, and the equipment is simple because the process is performed at atmospheric pressure, and thus the cost is competitive in terms of manufacturing cost.

Such a method can be widely applied to the production of electrolyte, cathode and anode thin films of fuel cells, micro sensors and porous ceramic thin films, and the like, and in particular, NiO-YSZ thin films can be applied as a cathode of a solid oxide fuel cell.

Preparation of the NiO-YSZ thin film according to the present invention is carried out by using an electric field spray method, the present invention will be described in more detail below.

1 is a series of devices implemented for applying the manufacturing method according to the present invention. Such a device may be inserted into each component by another person having ordinary skill in the art.

Referring to FIG. 1, the electric field spray device includes an electric field spray chamber 10, a precursor solution reservoir 11, a nozzle 12, a syringe pump 13, a potential difference generator 14, a substrate 15, and a substrate support ( 16), temperature controller 17, and step motor 18.

A method of manufacturing a NiO-YSZ thin film using such a device is as follows (see FIG. 2).

First, the nickel precursor, the yttrium precursor, and the zirconium precursor are dissolved in a solvent to prepare a precursor solution and inject into the precursor solution reservoir 11.

The nickel precursor, the yttrium precursor, and the zirconium precursor are one selected from the group consisting of alkoxides, chlorides, hydroxides, oxyhydroxides, nitrates, carbonates, acetates, oxalates, and mixtures thereof containing nickel, yttrium, and zirconium, respectively. It is possible and it does not specifically limit in this invention.

Preferably, nickel nitrate hexahydrate is used as the nickel precursor, yttrium acetate hydrate is used as the yttrium precursor, and zirconium nitrate hexahydrate is used as the zirconium precursor.

At this time, the molar ratio of each of the nickel precursor, the yttrium precursor, and the zirconium precursor is selected in consideration of the molar ratio to be finally obtained.

The solvent is used by mixing with lower alcohol alone or with water, and mixing the respective compositions in a volume ratio of 1:10 to 10: 1. The lower alcohols include methanol, ethanol, propanol, isopropanol, and butanol. These solvents have a high vapor pressure and high viscosity to facilitate vaporization in the droplets, thereby making it possible to produce denser particles.

The precursor and the solvent are mixed with each other to prepare a precursor solution, and the concentration thereof is adjusted to a concentration of 0.01 to 0.1 M in consideration of ease of nozzle injection, droplet size, and the like.

Next, the precursor solution from the precursor solution reservoir 11 is transferred to the nozzle 12 side by pressurization using the syringe pump 13.

At this time, the nozzle 12 preferably has a cylindrical shape to form droplets and has a long thin capillary shape along the inside. At this time, the nozzle 12 uses a diameter of 0.5 to 1.0 mm, preferably 0.31 mm to form micron-level droplets. The diameter of the nozzle 12 can be modified in consideration of the voltage applied, the concentration of the mixed solution, and the like as appropriate. In addition, the nozzle uses an inner diameter of 0.02 to 0.04 mm and an outer diameter of 0.50 to 0.70 mm.

The nozzle 12 is connected to a potential difference generator 14 for generating an electric field. This potential difference generator 14 allows the precursor solution to be charged with a positive charge when ground flows with a negative charge.

Next, the precursor solution is sprayed using the nozzle 12 to form droplets.

Specifically, the precursor solution is sprayed through the nozzle 12 of the electric field spraying device to form droplets, in which droplets of finer and more uniform size are formed by the electric field.

At this time, it is possible to control the size of the droplet formed by adjusting the electric field formed in the chamber, that is, the voltage. For example, the larger the voltage, the smaller the droplet, and the voltage is applied at 0.1 to 50 kV, preferably 5 to 18 kV, more preferably 12 to 18 kV to form a micron level droplet. In addition, as a result of the following experimental example, it was confirmed that the change in porosity structure as the applied voltage increases.

Next, the droplets are uniformly adsorbed onto the preheated substrate 15 and dried.

That is, a charged precursor solution is sprayed through the nozzle 12 to form droplets, which are adsorbed onto the preheated substrate 15.

The droplet size is proportional to the flow rate of the precursor solution (AM Ganan-Calvo, J. Aerosol. Sci. 28, 249, 1997). Pores are formed in the thin film.

In this case, the substrate 15 is disposed to be spaced apart from the nozzle 12 by a predetermined distance, that is, a difference occurs in the morphology of the NiO-YSZ thin film formed according to the distance between the nozzles and the substrates 12 and 15. Preferably, the distance from the nozzle-substrate 12, 15 is adjusted to be 4-6 cm. According to Experimental Example 3 of the present invention, the oxide thin film formed when the distance from the nozzle-substrate 12 and 15 is 4 cm exhibits a porous structure, and when the distance is increased to 5.5 cm to form a thin film, Converted to thin film. Therefore, the distance between the nozzles and the substrates 12 and 15 is adjusted to obtain physical properties suitable for the purpose of use of the thin film.

In addition, the substrate support 16 is connected to the step motor 18 so that the droplets transferred through the spray can be evenly distributed on the substrate 15. The step motor 18 is a device that enables reciprocation, vibration, and rotational movement about one axis. The step motor 18 adsorbs droplets on the substrate 15 with a uniform thickness.

Deposition time through the spray affects the physical properties of the final NiO-YSZ thin film obtained, it is carried out for 1 to 16 minutes. According to Experimental Example 3 of the present invention, the thin film having a dense structure is converted into a thin film having a porous structure as the deposition time increases.

Next, the droplet adsorbed on the substrate 15 is dried to remove the solvent and by-products contained in the droplet to form NiO-YSZ.

The drying is preferably carried out at 350 to 500 ℃, the density of the NiO-YSZ thin film increases as the drying temperature increases. This drying process can be carried out through a separate drying device, in the present invention is performed by heating the substrate 15 to the temperature.

The droplets adsorbed on the substrate 15 are oxidized to oxides by evaporation of the solvent contained in the droplets by the temperature of the substrate 15. The temperature is controlled via a temperature controller 17 which is separately connected to the substrate support 16 supporting the substrate 15, preferably to be heated to 350 to 500 ℃. According to Experimental Example 2 of the present invention, it can be seen that the thin film showing the porous structure is converted into a thin film having a more dense structure as the temperature of the substrate increases.

Through sufficient deposition, a NiO-YSZ thin film is formed on the substrate 15 having a predetermined thickness.

The NiO-YSZ thin film exhibits porosity, and the morphology of the thin film may be controlled by adjusting an applied voltage, a distance from a nozzle-substrate, a substrate temperature, a spraying time, and a heat treatment temperature.

In addition, the NiO-YSZ thin film is capable of switching the crystal state of the oxide from amorphous to crystalline form through a high temperature heat treatment.

This heat treatment may be performed by controlling the temperature of the temperature controller 16 in the electric field spray chamber 10 or by transferring to a separate heat treatment apparatus such as a microwave furnace.

Preferably, the heat treatment is performed at 1200 to 1350 ° C. for 1 minute to 5 hours, more preferably for 5 minutes. According to Experimental Example 5 of the present invention, the thin film showing the porous structure may increase the heat treatment temperature. As a result, it can be seen that the film is converted into a thinner film having a more dense perovskite structure.

In particular, the manufacturing method according to the present invention can control the structure of the thin film from the porous to a dense structure by changing the process conditions, as well as the above-described process is performed at normal pressure without the need to apply a separate pressure, There is an advantage in terms of cost compared to expensive equipment for deposition.

This method can be widely applied to all fields for the production of porous thin films of 10 mm or less, for example, the electrolyte, cathode and anode thin films of fuel cells, micro sensors and porous ceramic thin films, etc. This is possible.

In particular, the NiO-YSZ thin film can be applied as a negative electrode of a solid oxide fuel cell, and when the thin film is used as a negative electrode, the interface resistance between the electrolyte and the electrode is low, so that the NiO-YSZ thin film operates at not only a solid oxide fuel cell which is operated above 700 ° C. There is an advantage that can be used even in low-temperature battery. In addition, by lowering the operating temperature, not only can the manufacturing cost of the SOFC be lowered, but there is an advantage of improving the reliability, portability, and operating time of the fuel cell.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are merely provided to more easily understand the present invention, and the contents of the present invention are not limited by the examples.

Experimental Example 1

0.6 ml of Ni (NO ₃ ) ₂ .6H ₂ O, 0.032 mol of C ₆ H ₉ O ₆ Y.H ₂ O and 0.368 mol of ZrO ₂ (NO ₃ ) ₂ .H ₂ O 1: 1 V / V) to dissolve by ultrasonic vibration to prepare a precursor solution.

A syringe pump was used to transfer the precursor solution to a stainless nozzle with an inner diameter of 0.03 mm and an outer diameter of 0.64 mm. Then, a 17 kV high voltage was applied from a DC power source connected to the nozzle to form an electric field, and the temperature of the substrate was performed at 400 ° C. At this time, the distance between the substrate and the nozzle was changed to 4 cm, 4.5 cm, 5 cm and 5.5 cm, and the flow rate of the precursor solution was 4.0 ml / h, followed by deposition for 3 minutes to obtain a NiO-YSZ thin film.

Scanning electron microscope

The surface of the thin film obtained above was measured by the scanning electron microscope, and the obtained result is shown in FIG.

3A to 3D show scanning electron micrographs of the NiO-YSZ thin film according to the distance between the nozzle and the substrate.

Referring to (a) to (d) of FIG. 3, it can be seen that as the distance between the substrate and the nozzle is increased, the porous structure is converted into a thin film having a dense structure.

That is, as the distance from the nozzle-substrate is closer, new droplets are deposited on the substrate surface after the droplets sprayed from the nozzles are deposited on the substrate surface, and thus, solvents and impurities through drying cannot be sufficiently removed, indicating a porous structure. Therefore, as the distance from the nozzle-substrate increases, the time is sufficient to be converted into a thinner film having a more dense structure.

Experimental Example 2

A precursor solution was prepared in the same manner as in Experimental Example 1 and transferred to a stainless steel nozzle.

Subsequently, an electric field was formed by applying a high voltage of 17 kV from a DC power source connected to the nozzle, and the temperature of the substrate was changed to 350 ° C., 400 ° C., 450 ° C. and 500 ° C., respectively. At this time, the distance between the substrate and the nozzle was 4 cm, and the flow rate of the precursor solution was 4.0 ml / h for 3 minutes to obtain a NiO-YSZ thin film.

Scanning electron microscope

The surface of the thin film obtained above was measured by the scanning electron microscope, and the obtained result is shown in FIG.

4 (a) to (d) show scanning electron micrographs of the NiO-YSZ thin film according to the substrate temperature.

Referring to FIG. 4, it can be seen that the thin film of the porous structure in (a) is converted into a thin film of dense structure as shown in (d) as the temperature of the substrate increases.

In other words, the lower the temperature of the substrate (350 ° C., a), the more unstable the volatilization of the solvent in the droplets results in the formation of a wet deposit on the substrate. This wet deposit affects the volatilization of solvents and by-products such as NOx and COx that cause pore formation by previous deposition. Conversely, as the temperature of the substrate increases (500 ° C., d), the precursor is adsorbed and oxidized on the substrate while the solvent and by-products in the droplet are removed, thereby forming a thinner film having a more dense structure.

Experimental Example 3

A precursor solution was prepared in the same manner as in Experimental Example 1 and transferred to a stainless steel nozzle.

Subsequently, an electric field was formed by applying a high voltage of 17 kV from a DC power source connected to the nozzle, and the deposition was performed by changing the deposition time of the substrate at 400 ° C. for 90 seconds, 120 seconds, 150 seconds, and 180 seconds. At this time, the substrate-nozzle distance was 4 cm, and the flow rate of the precursor solution was deposited at 4.0 mL / h to obtain a porous NiO-YSZ thin film.

Scanning electron microscope

The surface of the porous thin film obtained above was measured with a scanning electron microscope, and the obtained result is shown in FIG.

5 (a) to (d) show a scanning electron micrograph of the porous NiO-YSZ thin film according to the deposition time.

Referring to FIG. 5, it can be seen that the thin film having a dense structure in (a) is converted into a porous thin film as shown in (d) as the deposition time increases.

That is, the faster the deposition time, the denser the thin film is formed, and a crack-free thin film is formed by the complete volatilization of the solvent and impurities in the droplets. However, as the deposition time increases, the thickness of the thin film becomes thicker, and the volatilization of the solvent and impurities in the droplet is incomplete, thereby forming pores in the thin film.

Experimental Example 4

A precursor solution was prepared in the same manner as in Experimental Example 1 and transferred to a stainless steel nozzle.

Subsequently, 12 kV, 14 kV, 16 kV, and 18 kV were applied to the DC power source connected to the nozzle to form an electric field, and the temperature of the substrate was adjusted to 400 ° C. At this time, the distance between the substrate and the nozzle was maintained at 4 cm, and deposition was performed for 3 minutes at a flow rate of the precursor solution at 4.0 ml / h to obtain a porous NiO-YSZ thin film.

Scanning electron microscope

The surface of the porous thin film obtained above was measured with a scanning electron microscope, and the obtained result is shown in FIG.

6 (a) to (d) show a scanning electron micrograph of the porous NiO-YSZ thin film according to the voltage.

Referring to FIG. 6, it can be seen that the thin film having a dense structure in (a) is converted into a porous thin film as shown in (d) as the applied voltage increases.

Experimental Example 5

A precursor solution was prepared in the same manner as in Experimental Example 1 and transferred to a stainless steel nozzle.

Subsequently, a 17 kV high voltage was applied from a DC power source connected to the nozzle to form an electric field, and the substrate was deposited at 400 ° C. for 3 minutes to obtain a NiO-YSZ thin film. In this case, the distance between the substrate and the nozzle was 4 cm, and the flow rate of the precursor solution was performed at 4.0 ml / h.

In addition, the porous thin film was mounted in an ultrasonic furnace and heat-treated at 1200 to 1350 ° C. for 5 minutes to obtain a NiO-YSZ thin film having a perovskite structure.

X-ray diffraction pattern

The oxide of the perovskite structure obtained through the heat treatment was measured by an X-ray diffractometer, and the results obtained are shown in FIG. 7.

7 is an X-ray diffraction pattern of NiO-YSZ obtained after heat treatment of a NiO-YSZ thin film at a) 1200 ° C, b) 1250 ° C, c) 1300 ° C, and d) 1350 ° C.

Referring to FIG. 7, it can be seen that the NiO-YSZ thin film is converted from amorphous to crystalline through heat treatment using an ultrasonic furnace. In particular, when the heat treatment is performed at 1300 ° C. for 5 minutes, the NiO-YSZ thin film having a perovskite structure is formed. It was confirmed that it can be obtained.

NiO-YSZ thin film prepared according to the present invention can be applied as a cathode of a solid oxide fuel cell.

1 is a series of devices implemented for applying the manufacturing method according to the present invention.

FIG. 2 is a flowchart illustrating a method of manufacturing a NiO-YSZ thin film using the apparatus of FIG. 1.

3A to 3D show scanning electron micrographs of the NiO-YSZ thin film according to the distance between the nozzle and the substrate.

4 (a) to (d) show scanning electron micrographs of the NiO-YSZ thin film according to the substrate temperature.

5A to 5D show scanning electron micrographs of NiO-YSZ thin films according to voltages.

6 (a) to (d) show a scanning electron micrograph of the NiO-YSZ thin film according to the deposition time.

7 is an X-ray diffraction pattern of NiO-YSZ obtained after heat treatment of NiO-YSZ at a) 1200 ° C, b) 1250 ° C, c) 1300 ° C, and d) 1350 ° C.

Claims (10)

Dissolving the nickel precursor, the yttrium precursor, and the zirconium precursor in a solvent to prepare a precursor solution; Transferring the precursor solution into an electric field spraying device and injecting it into a nozzle; Spraying a precursor solution using the nozzle under an electric field atmosphere to form droplets; And Uniformly adsorbing the droplets onto a preheated substrate and drying the droplets NiO-YSZ thin film manufacturing method comprising a. The method of claim 1, The nickel precursor, yttrium precursor, and zirconium precursor is one selected from the group consisting of alkoxides, chlorides, hydroxides, oxyhydroxides, nitrates, carbonates, acetates, oxalates and mixtures thereof containing nickel, yttrium or zirconium, respectively Method of manufacturing NiO-YSZ thin film. The method of claim 1, Nickel nitrate hexahydrate is used as the nickel precursor, yttrium acetate hydrate is used as the yttrium precursor, and zirconium precursor is used as zirconium nitrate hexahydrate. The method of claim 1, The solvent is a method for producing a NiO-YSZ thin film comprising one selected from water, methanol, ethanol, propanol, isopropanol, or butanol. The method of claim 1, The electric field atmosphere is performed by applying a voltage of 0.1 ~ 50kV NiO-YSZ thin film manufacturing method. The method of claim 1, The nozzle is a method for producing a NiO-YSZ thin film using an inner diameter of 0.02 to 0.04 mm, an outer diameter of 0.50 to 0.70 mm. The method of claim 1, When spraying the substrate is a method for producing a NiO-YSZ thin film is carried out by preheating to 300 to 500 ℃. The method of claim 1, The method of manufacturing a NiO-YSZ thin film is performed by adjusting the distance between the nozzle and the substrate when the spraying is 4 ~ 6cm. The method of claim 1, The entire step is performed for 1 to 16 minutes NiO-YSZ manufacturing method of the thin film. The method of claim 1, Further drying and heat treatment at 1200 ~ 1350 ℃ to produce a NiO-YSZ thin film having a perovskite (perovskite) structure.

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