KR101342923B1 - Syntheses of LaCrO₃nanopowder by hydrothermal method for Solid fuel cell interlayer - Google Patents

Abstract

The present invention relates to the synthesis of LaCrO ₃ perovskite-type conductive nanopowder for solid oxide fuel cell interconnector using hydrothermal synthesis and a method of manufacturing the same. By using Nitrate precursor, Acetate precursor, Precipitant as NaOH, KOH, NH ₄ OH, NH ₂ CONH ₂ as starting materials, hydrothermally synthesized powder at reaction temperature of 100 ~ 250 ℃ for 8 ~ 24 hours at 100 ~ 350 ℃ Single-phase perovskite doped LaCrO ₃ nanopowders can be prepared. The particles are spherical and elliptical in shape and have a particle size of 30 to 400 nm.

Description

Syntheses of LaCrO₃nanopowder by hydrothermal method for Solid fuel cell interlayer}

The present invention relates to a method for producing a perovskite-type nanopowder for a solid oxide fuel cell connector by a hydrothermal synthesis method, and more specifically, high purity and conductivity without secondary phase in the form of plate, ellipse, sphere, etc. by hydrothermal synthesis method. The present invention relates to a method for synthesizing a perovskite type LaCrO ₃ nanopowder having. Selecting the optimal precursor based on metal salts using the wet method based hydrothermal synthesis, which enables particle nanonization and manufacturing of high-purity materials, to derive optimal hydrothermal conditions for particle nanoparticles, and to optimize starting materials and synthesis conditions for particle shape control The nanoparticle synthesis process, which is essential for the nanoparticles, aims to develop a nanoparticle synthesis process for secondary oxide-free solid oxide fuel cell (SOFC) connectors.

As a method of synthesizing nanopowders having excellent conductivity characteristics, homogeneous precipitation, Sol-Gel, gas phase oxidation, spray pyrolysis, hydrothermal synthesis, and the like have been attempted. Among them, hydrothermal synthesis is easy to control the particle size and shape, and has a great advantage in synthesizing at low temperature. It is a process of synthesize | combining particle | grains using the characteristic which depends on.

These methods attempt to obtain the desired nanopowder by designing chemical reactions at the nanoscale, atomic or molecular scale. Each process has advantages and disadvantages and it is necessary to select a process suitable for the synthesis of the desired nanopowder. Solid oxide fuel cells (SOFCs) operating at high temperatures in the range of 700 ° C to 1000 ° C must have chemical stability, high electrical conductivity, high thermal conductivity, thermal expansion coefficient similar to that of electrolyte, and high mechanical strength in gas-tight, oxidizing and reducing atmospheres. , Should have excellent manufacturability. Until now, the most popular material for connecting the solid oxide fuel cell is LaCrO ₃ system. Using a ceramic material as a connector material has an advantage of suppressing cathode poisoning caused by chromium volatilization and increase in contact resistance due to the formation of an oxide film of the existing metal separator plate. Therefore, it is necessary to develop new ceramic materials, powder synthesis, and coating slurry technology. When the nano-composite material is nanocomposite, the sintering temperature can be reduced, the electronic conductivity can be improved, and the microstructure can be easily controlled to form a highly durable dense film, and the present invention provides a connector material by the hydrothermal synthesis method. The purpose of this study is to develop a composition and synthesis technology of doped LaCrO ₃ nanopowder with high purity and conductivity to control particle size and shape according to the type of starting material and synthesis conditions.

An object of the present invention is to synthesize a nano powder for a solid oxide fuel cell (SOFC) connector without secondary phase at low temperature by using hydrothermal synthesis. That is, the present invention is to synthesize various types of conductive nano powders according to the type of starting material and precipitant at low temperature, and solid oxide fuel cell connector conductivity using hydrothermal synthesis method that can effectively produce perovskite-type nanopowders. It is to provide a method for producing a nanopowder.

In order to achieve the above object, a method for preparing a conductive nanopowder for a connector using the hydrothermal synthesis method according to an embodiment of the present invention is to precipitate by adding a precipitant to a solution obtained by quantitatively mixing Nitrate precursor and Acetate precursor as respective starting materials. After the solution is made, the solution is hydrothermally reacted to provide a method for producing perovskite-type nanopowders through washing and drying. In the method of preparing nanopowders using hydrothermal synthesis of the present invention, the La / Cr ratio of the starting materials La (NO ₃ ) ₂ · 6H ₂ O and Cr (NO ₃ ) ₂ · 9H ₂ O when prepared using nitrate precursor It is quantified to 0.8 ~ 1.3 and then mixed with the quantified solution of Precipitant to form a precipitation solution, the hydrothermal treatment of the mixed aqueous solution, the slurry obtained after the hydrothermal treatment by washing and drying the powder It is characterized in that to produce a LaCrO ₃ conductive nano-powder free of impurities through a step of obtaining.

According to another embodiment of the present invention for solving the above technical problem, Lanthanium (III) acetate hydrate (La (CH ₃ CO ₂ ) ₃ · 1.5H ₂ O) and Chromium (III) as a starting material acetate hydroxide ((CH ₃ CO ₂ ) ₇ Cr ₃ (OH) ₂ ) La / Cr molar ratio of 0.7 ~ 1.7 quantitatively mixed solution was stirred for about 30mim, the precipitant was slowly mixed and stirred at 130 ℃ for 4 hours Reacting while, the step of hydrothermally treating the mixed aqueous solution at 200 ~ 230 ℃ 24 hours, washing the slurry obtained after the hydrothermal treatment to obtain a powder by washing and drying process to produce a LaCrO ₃ conductive nano-powder free of impurities It is characterized by.

By the method of producing nanopowders by hydrothermal synthesis according to the present invention, single phase perovskite-type nanopowders without secondary phases can be economically prepared, and the particle size and shape can be easily controlled, and they can be synthesized at low temperatures. There is an advantage. In addition, nano powders having conductivity may be synthesized by doping (Ca, Co) doping.

1 (a) to 7 (a) show X-ray diffraction patterns showing crystal phases of hydrothermally synthesized samples under respective reaction conditions according to Examples 1 to 7 of the present invention.
1 (b) to 7 (b) show scanning electron microscopy (SEM) photographs (50,000 magnifications) showing powder form changes and particle sizes according to Examples 1-7.
8 shows electrical conductivity measurements of sintered specimens of each composition at 750 ° C. and air conditions using a four-terminal method.

Hereinafter, the embodiment of the present invention will be described in more detail. However, the following examples are illustrative of the present invention, and the content of the present invention is not limited by the examples.

[Example 1]

La (NO ₃ ) ₃ · 6H ₂ O (Sigma-Aldrich Co., USA) and Cr (NO ₃ ) ₃ · 9H ₂ O (Sigma-Aldrich Co., USA) samples used as starting materials were matched to the molar ratio. The composition ratio of La / Cr is 0.8-1.3 and dissolved in ultrapure water to prepare a mixture of 0.05 M concentration. The mixture and a 0.5 M sodium hydroxide (GR, Kanto Chemical Co., Tokyo, Japan) aqueous solution are slowly mixed and stirred. After sonicating the solution for 30 minutes, the solution was placed in a hydrothermal synthesis vessel with a teflon liner and sealed, and reacted for 8 to 32 hours at 200 to 250 ° C. The prepared slurry was washed 9 times with deionized water using Centrifuge (FLETA5, Hanil) and then dried at 350 ° C. for 8 hours to LaCrO ₃ Nano powder is prepared. As shown in Figure 1 (a) and Figure 1 (b), the spherical and elliptical nanoparticles exhibit a particle size of 100 ~ 300nm.

[Example 2]

La (NO ₃ ) ₃ · 6H ₂ O (Sigma-Aldrich Co., USA) and Cr (NO ₃ ) ₃ · 9H ₂ O (Sigma-Aldrich Co., USA) samples used as starting materials were matched to the molar ratio. The composition ratio of La / Cr is 0.8-1.3 and dissolved in ultrapure water to prepare a mixture of 0.05 M concentration. This mixture and 0.35 ~ 0.4M potassium hydroxide (GR, Dae Jung Chemical, Korea) aqueous solution is slowly mixed and stirred. After sonicating the solution for 30 minutes, the solution was placed in a hydrothermal synthesis vessel with a teflon liner and sealed, and reacted at 100 to 230 ° C. for 8 to 30 hours. The prepared slurry was washed 7 times with deionized water using Centrifuge (FLETA5, Hanil), and then dried at 250 ° C to 300 ° C for 12 hours to prepare LaCrO ₃ nanopowder. As shown in Fig. 2 (a) and 2 (b), the elliptical nanoparticles have a particle size of 50 ~ 200nm.

[Example 3]

La (NO ₃ ) ₃ · 6H ₂ O (Sigma-Aldrich Co., USA) and Cr (NO ₃ ) ₃ · 9H ₂ O (Sigma-Aldrich Co., USA) samples used as starting materials were matched to the molar ratio. The composition ratio of La / Cr ranges from 0.8 to 1.3, and then dissolved in ultrapure water to prepare a mixture of 1M concentration. Precipitant is slowly mixed with Urea (NH ₂ CONH ₂ , Junsei, Chemical Co., Tokyo, Japan) 4M-6M aqueous solution to this mixture. The mixed solution is stirred at 70 ° C. for 3 to 5 hours and then hydrothermally reacted at 200 to 250 ° C. for 8 to 24 hours. The prepared slurry was washed four times with deionized water using Centrifuge (FLETA5, Hanil), and then dried at 250 ° C to 300 ° C for 12 hours to prepare LaCrO ₃ nanopowder. As shown in Figure 3 (a) and Figure 3 (b), the needle-shaped nanoparticles exhibit a particle size of 50 ~ 400nm.

[Example 4]

Lanthanium (III) acetate hydrate (La (CH ₃ CO ₂ ) ₃ · 1.5H ₂ O, 99.9%, Sigma-Aldrich Co., USA)), Chromium (III) acetate hydroxide ((CH ₃ CO ₂ ) ₇ Cr ₃ (OH) ₂ , Sigma-Aldrich Co., USA))) The sample was quantified so that the La / Cr composition ratio ranged from 0.7 to 1.7, and the two reagents were dissolved in deionized water to prepare a mixture of 0.05 M concentration. Manufacture. After stirring the mixed solution for about 30mim, slowly mix KOH aqueous solution of 0.35M ~ 0.4M concentration with precipitant. The solution was stirred at 130 ° C. for 4 hours and then hydrothermally treated at 200˜250 ° C. for 24 hours. The slurry thus prepared was washed 7 times with deionized water using Centrifuge (FLETA5, Hanil), and 250 ° C. LaCrO ₃ nanopowder is prepared by drying at 300 ° C. for 12 to 24 hours. As shown in Figure 4 (a) and 4 (b), the spherical and elliptical nanoparticles exhibit a particle size of 40 ~ 150nm.

[Example 5]

Lanthanium (III) acetate hydrate (La (CH ₃ CO ₂ ) ₃ · 1.5H ₂ O, 99.9%, Sigma-Aldrich Co., USA)), Chromium (III) acetate hydroxide ((CH ₃ CO ₂ ) ₇ Cr ₃ (OH) ₂ , Sigma-Aldrich Co., USA))) The sample was quantified so that the composition ratio of La / Cr was 0.7-1.7, and the two reagents were dissolved in deionized water to prepare a mixture of 0.05 M concentration. do. The mixture was slowly mixed with a 6M Ammonia aqueous solution as a precipitant, and then stirred at 130 ° C for 4 hours and hydrothermally treated at 200 to 250 ° C for 24 hours using ultra centrifuge (FLETA5, Hanil) to prepare a slurry. water) and Ethanol was cross-washed five times, and dried at 300 ~ 350 ℃ 12 ~ 24 hours to prepare a nano LaCrO ₃ powder. As shown in Figure 5 (a) and Figure 5 (b), the spherical and elliptical nanoparticles exhibit a particle size of 80 ~ 250nm.

Example 6

La (NO ₃ ) ₃ · 6H ₂ O (Sigma-Aldrich Co., USA) and Cr (NO ₃ ) ₃ · 9H ₂ O (Sigma-Aldrich Co., USA) samples used as starting materials were used as dopants. _{NO 3) 2 · 4H 2 O} (98 +%, Sigma-Aldrich Co., USA) using the _{La 1 -. x Ca x /} Cr ( here, x is greater than 0 and smaller than 1) molar ratio is 0.8. It is quantified to ˜1.3, and then dissolved in ultrapure water to prepare a mixture of 0.05 M concentration. 0.35 ~ 0.4M potassium hydroxide (GR, Dae Jung Chemical, Korea) aqueous solution is slowly mixed and stirred to this mixed solution. After sonicating the solution for 30 minutes, the solution was placed in a hydrothermal synthesis vessel with a teflon liner and sealed, and reacted at 100 to 230 ° C. for 8 to 30 hours. The prepared slurry was washed 7 times with deionized water using Centrifuge (FLETA5, Hanil), and then dried at 250 ° C. to 300 ° C. for 12 hours to form a three-component perovskite type La _{1 - x} Ca _x CrO ₃ (here X is greater than 0 and less than or equal to 0.4.) Nanopowders were prepared. As shown in Figure 6 (a) and 6 (b), the spherical and elliptical nanoparticles have a particle size of 30 ~ 120nm. As shown in FIG. 8, the electrical conductivity when Ca is used as a dopant is 5-17 Scm <^-1> .

Example 7

La (NO ₃ ) ₃ · 6H ₂ O (Sigma-Aldrich Co., USA) and Cr (NO ₃ ) ₃ · 9H ₂ O (Sigma-Aldrich Co., USA) samples used as starting materials were used as dopants. _{NO 3) 2 · 4H 2 O} (98 +%, Sigma-Aldrich Co., USA) and _{Co (NO 3) 2 · 6H} 2 O (, 98 +%, La 1 using the Sigma-Aldrich Co.) _{- x} Ca _x / Co _y Cr _1-y O ₃ (where x and y are each greater than 0 and less than 0.4), quantitated to a molar composition ratio of 0.8 to 1.3, and dissolved in ultrapure water to 0.05 M concentration. Prepare a mixture of 0.35 ~ 0.4M potassium hydroxide (GR, Dae Jung Chemical, Korea) aqueous solution is slowly mixed with this mixed solution. After sonicating the solution for 30 minutes, the solution was placed in a hydrothermal synthesis vessel with a teflon liner and sealed, and reacted at 100 to 230 ° C. for 8 to 30 hours. The prepared slurry was washed 7 times with deionized water using Centrifuge (FLETA5, Hanil), and then dried at 250 ° C. to 300 ° C. for 12 hours to form a 4-component perovskite type La _{1 - x} Ca _x Co _y Cr _{1 - y} O ₃ (Where x and y are each greater than 0 and less than or equal to 0.4). Nanopowders were prepared. As shown in Figure 7 (a) and 7 (b), the spherical and elliptical nanoparticles have a particle size of 30 ~ 120nm. As shown in FIG. 8, the electrical conductivity when Ca and Co are used as co-dopants is 5 to 25 Scm ⁻¹ .

Claims (2)

La (NO ₃ ) ₂ · 6H ₂ O, Cr (NO ₃ ) ₂ · 9H ₂ O, Ca (NO ₃ ) ₂ · 4H ₂ O were used as starting materials, and La _1-x Ca _x / Cr (here, x is greater than 0 and less than 1). The molar ratio is 0.8 to 1.3 and 30 to 120 nm, which shows conductivity by doping Ca with hydrothermal synthesis at 100 to 230 ° C. for 8 to 30 hours using KOH as a precipitant. La _1-x Ca _x CrO ₃ having an elliptic form of (where x is greater than 0 and less than 0.4). Starting material La (NO ₃ ) ₂ · 6H ₂ O, Cr (NO ₃ ) ₂ · 9H ₂ O, Ca (NO ₃ ) ₂ · 4H _{2 in} the method for producing perovskite-type nanopowder using hydrothermal synthesis O, Co (NO ₃ ) ₂ · 6H ₂ O and KOH as a precipitant, 30 ~ 120nm oval characterized in that the conductivity is shown by doping Ca and Co by hydrothermal synthesis at 100 ~ 230 ℃ 8 ~ 30 hours La _{1 - x} Ca _x Co _y Cr _{1 - y} O ₃ having the form (where x and y are each greater than 0 and less than 0.4).

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