KR20160063057A - Manufacturing method for metal-doped Cerium Oxide ultra-fine powders by using plasmas - Google Patents

Abstract

The present invention relates to a method of preparing a cerium oxide fine powder doped with a different kind of metal, comprising the steps of: (1) a first step of using oxides of a dopant metal and cerium oxide as starting materials and quantifying these oxides in accordance with the doping amount; 2) a second step of preparing solid phase mixed precursor powder by mixing, pulverizing or calcining the oxide starting material determined in the first step by a conventional method; 3) a third step of heating the precursor powder obtained through the second step so as to allow physical and chemical changes such as simultaneous melting and vaporization using plasma; 4) quenching the physico-chemically modified product by using the plasma to synthesize oxides doped with different metals (cerium fine particles).

Description

Process for the preparation of cerium oxide fine powder doped with dissimilar metals using plasma {Manufacturing method for metal-doped Cerium Oxide ultra-fine powders by using plasmas}

The present invention relates to a process for preparing a cerium oxide micropowder doped with a heterometal having a CeO2 single phase

The present invention relates to a process for preparing a cerium oxide micropowder doped with a hetero-metal having CeO2 single phase. A method for producing cerium oxide has been disclosed in Korean Patent No. 10-515782 entitled " Method for producing cerium oxide ". However, the present invention relates to a method of producing a cerium oxide fine powder doped with a dissimilar metal, wherein raw powder powders mainly composed of an oxide powder of a desired metal to be doped such as Gd, Sm and Y and a cerium oxide powder are quantitatively ; Mixing and pulverizing the quantified raw material powders by a conventional method, or preparing a solid mixed-up precursor powder through a calcination process; Heating the precursors obtained through this step to allow physicochemical changes such as heating, melting and vaporization using plasma; The physico-chemically modified product is quenched to synthesize a heterogeneous metal-doped cerium oxide fine powder having a CeO 2 single phase crystal structure, which is synthesized using RF plasma.

Cerium oxide is a ceramic having high oxygen ion conductivity, and has attracted great interest in applications such as oxygen sensors, solid oxide fuel cell electrolytes, and the like. The cerium oxide has the characteristic of having high oxygen ion conductivity by forming an oxygen vacancy when Gd ³⁺ , Sm ³⁺ , Y ^3+, or the like is added to an element having a smaller valence number than Ce ⁴⁺ . Because of this characteristic, the ion conductivity of the doped cerium oxide is higher than that of the zirconia oxide used conventionally in an SOFC (solid oxide fuel cell) electrolyte, so that it can be used even in a low temperature region of about 500 ° C And is superior in chemical stability to electrolytes such as LSGM (lanthanum strontium gallate magnesite), and is attracting attention as an electrolyte of middle and low temperature SOFC. Accordingly, a lot of techniques for finding a synthesis path of cerium oxide doped with different metals have been studied extensively. For example, the material can be easily manufactured by a repetitive process consisting of conventional solid phase reaction and mechanical milling. However, the ceria powder doped with heterogeneous metals prepared by the conventional solid-phase method and the mechanical milling method is difficult to obtain a fine powder for producing a sintered compact of a dense electrolyte structure due to limitations in milling efficiency and the like. In addition, this method requires a long reaction time, requires a separate grinding process, and has a disadvantage in that impurities can not be avoided during grinding. Conventional synthesis methods such as a coprecipitation method and a sol-gel method have been proposed in order to overcome the disadvantages of the top-down high-temperature sintering method. However, the formation of the second phase, the discharge of environmental harmful substances such as organic solvents, The difficulty of finding a competitive, heterogeneous metal-doped CeO2 material synthesis method due to the inherent problems of these conventional methods, such as the use of the doped CeO2 material. In addition, the glycine nitrate process (GNP), which is a kind of rotation method, has recently been introduced. It is reported that this process can produce nano-sized fine powders in a very short time without intermediate phase during a rapid exothermic oxidation-reduction reaction process, and that the generated powders can realize a single phase of CeO2. However, this method has difficulties in control of exhaust gas harmful to the process speed and environment, and thus commercialization technology is limited.

The present invention is based on the finding that a mixed oxide precursor consisting of an oxide powder of a metal to be doped and a cerium oxide powder can be produced by using a plasma of high temperature and high enthalpy and using a plasma doped with a heterogeneous metal having an average size of 1 탆 or less and a CeO 2 single phase And a method for easily mass-producing CeO2 fine powder.

In order to accomplish the above object, the present invention provides a method of preparing a cerium oxide fine powder doped with a different kind of metal, comprising the steps of 1) preparing an oxide of a dopant metal and cerium oxide as starting materials, ; 2) a second step of preparing solid phase mixed precursor powder by mixing, pulverizing or calcining the oxide starting material determined in the first step by a conventional method; 3) a third step of heating the precursor powder obtained through the second step so as to allow physical and chemical changes such as simultaneous melting and vaporization using plasma; 4) a third step of synthesizing the resultant of physicochemically changing the plasma using the plasma to quench the resultant to form a heterogeneous metal-doped cerium oxide microparticle.

 In the first step, a powder having a size of 1 to 20 mu m is used as a dopant metal oxide and a cerium oxide powder having a size of 10 to 40 mu m or less can be used.

In the first step, the dopant metal oxide may be any one of Gd2O3, Sm2O3, and Y2O3.

The oxide of the dopant metal and the cerium oxide are mixed so that the weight ratio of Ce to the total weight of Ce and dopant metal atoms is 80 to 90 parts by weight It can be mixed.

In the third step, a plasma of a high frequency induction coupling type having a frequency of 0.5 to 13.56 MHz may be used.

 An arc plasma induced by a DC current of 100 A or more may be used in the third step.

In the third step, plasma generated from a plurality of DC torches arranged in a circle, symmetrically may be used.

In the third step, a plasma generated by microwave local heating of 700 MHz or more may be used.

As described above, unlike the conventional precipitation method, sol-gel method, glycine nitrate method and the like, the present invention can provide relatively easy to obtain, without using a separate metal nitrate salt, expensive organic metal, organic solvent, By directly using the dopant metal oxide such as Gd2O3, Sm2O3, Y2O3, etc., it is possible to induce a relatively easy and safe reaction process free from the discharge of environmental harmful substances after the reaction.

Further, by using the high enthalpy plasma flow, the mixed precursor powder consisting of the dopant metal oxide and cerium oxide is rapidly heated to co-melt and vaporize, thereby enabling fast and uniform doping of the dissimilar metals, It is possible to continuously mass-produce hetero-metal-doped CeO 2 nano-powder having a CeO 2 single phase with a size of 1 μm or less.

1 to 7 are diagrams showing an embodiment according to the present invention

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings. In order to achieve the above object, the present invention provides a method for quantitatively determining source powders composed mainly of an oxide powder of a desired metal such as Gd, Sm and Y, for example, Gd2O3 or Sm2O3 or Y2O3 and CeO2 powder, step; Preparing a solid mixed-mixed precursor powder by pulverizing, mixing or calcining the quantified oxide raw material powders by a conventional method; A heating step of simultaneously melting and vaporizing the oxide precursor obtained through this step using a plasma; And a step of synthesizing the heterogeneous metal-doped cerium oxide microparticles having a crystal structure of CeO2 single phase by quenching the mixed melt and the vaporized vapor produced through the above steps.

In the preparation process, the step of preparing the precursor may be carried out by using an oxide powder of a dopant metal such as Gd2O3 or Sm2O3 or Y2O3 usually having a size of 1 to 20 mu m and a metal oxide powder of 10 to 20 mu m for synthesis of a metal doped CeO2 fine powder having a size of 1 mu m or less, A simple mixture made by mixing CeO2 powders of 40 ㎛ or less in size according to the doping amount of dissimilar metals and uniformly mixed with a ball mill or the like, or calcining or sintering these powders at 1,500 ° C. and pulverizing them. Also, for uniform and smooth transfer into the plasma, the solid-phase mixed precursors prepared in the above-described manner can be well dispersed in an appropriate solvent to form a liquid phase in the form of a slurry, or sprayed in the form of an aerosol, .

Generally, in the doping process using the solid phase method, the metal material is activated from a dopant metal oxide such as Gd 2 O 3, Sm 2 O 3, Y 2 O 3, etc. to diffuse and insert into the CeO 2 structure. And then sintered at a high temperature for a long time. Further, after the sintering, there is a need to carry out a separate milling step in order to obtain a fine powder of 1 mu m or less from the bulk sintered body. On the other hand, in the present invention, an oxide powder of a dopant metal such as Gd 2 O 3 or Sm 2 O 3 or Y 2 O 3 having a size of 1 to 20 μm or less is injected into a plasma stream of a high temperature and a high enthalpy of 3,000 K or more together with a CeO 2 powder having a size of 10 to 40 μm, It is characterized in that rapid heating takes place over the entire area of the fine powder. Such a plasma rapid heating process can produce molten and vaporized oxides of the oxides within a few milliseconds, thereby activating doped metal materials such as Gd, Sm, and Y from their oxide lattice structures and moving into the CeO2 lattice structure It is possible to rapidly realize an environment that can be shortened sharply. Also, by rapidly quenching the melt and the vapor formed through this process, the CeO2 fine powder doped with heterogeneous metals with a thickness of 1 mu m or less can be easily and rapidly obtained in large quantities without any separate grinding step or treatment. As the main heat source for realizing this characteristic of the present invention, a high temperature, high enthalpy plasma flow of 3,000 K or more can be used. Particularly, when the high frequency inductively coupled plasma is used, the above object can be efficiently achieved by using the carrier gas and injecting the mixed oxide precursors into the high temperature, high enthalpy plasma flow in the axial direction.

Hereinafter, the effects of the present invention will be described in detail by way of examples.

The following examples are intended to illustrate the specific application of the present invention, and the scope of the present invention is not limited to the examples.

[Example 1] A Gd-doped CeO2 fine powder synthesized by introducing a precursor of Gd: Ce = 20: 80 at% into a high frequency inductively coupled plasma flow

Fig. 1 is a graph showing the results of measurement of a precursor in which Gd2O3 and ~40 mu m grade CeO2 powder having a particle size of ~ 20 mu m are quantitatively determined to be 20:80 in terms of an atomic ratio of Gd and Ce to a high frequency inductively coupled plasma with a frequency of 1 to 5 MHz and a plate power of 140 kVA (FE-SEM) photograph taken on the fine powder obtained by axially injecting into the flow. It can be seen from Fig. 1 that the overall size of the plasma synthesized fine powder is less than 1 mu m. FIG. 2 is a graph comparing the XRD data of the precursor and the fine powder obtained after the plasma treatment, and FIG. 3 is a diagram showing a transmission electron microscope (TEM) and a selected area electron diffraction (SAED) pattern of the synthesized fine powder. From the precursor XRD data in Fig. 2, it can be seen that the Gd2O3 and CeO2 crystal peaks observed in the raw powder precursor disappeared except for the CeO2 peak in the newly synthesized fine powder. The SAED pattern of FIG. 3 together with FIG. 2 also shows that the synthesized nano-sized individual particles have CeO 2 single phase. On the other hand, from the mapping images of Gd and Ce elements according to the transmission electron microscopy and electron energy loss spectroscopy (TEM-EELS) analysis of the synthesized fine powder of FIG. 4, , And Ce elements uniformly. Thus, from the results of FIGS. 2, 3 and 4, it can be seen that the Gd dopant metal was successfully inserted into the CeO 2 structure during the plasma treatment to form Gd-doped CeO 2 microparticles of CeO 2 single phase. Table 1 shows the results of inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis of synthesized Gd-doped CeO2 fine particles. From this table, it can be seen that the cation composition ratio of the synthesized Gd-doped CeO2 fine particles is well within about 3 at% of the designed composition ratio.

Table 1. ICP-OES compositional change analysis between precursor and synthesized fine powder Constituent (cation at.%) Gd Ce Precursors (A) 18.93 81.07 As-synthesized (B) 15.99 84.01 Increment (B-A) -2.94 + 2.94

[Example 2] Gd: Ce = 10: 90 at. % Precursor is injected into a high frequency inductively coupled plasma flow to synthesize the Gd-doped CeO2 fine powder

Fig. 5 is a graph showing the results of electron micrographs of fine grains obtained under the same plasma treatment conditions as those of Example 1, in which the Gd2O3 and ~ 40 mu m class CeO2 powders of ~ 20 mu m grade were quantitatively determined to have a Gd and Ce atomic ratio of 10: Scanning electron microscope (FE-SEM) photograph. From FIG. 5, it can be confirmed that the total size of the fine powder synthesized as in Example 1 is 1 占 퐉 or less.

6 is a graph comparing XRD data of a precursor and a fine powder obtained after a plasma treatment. From Fig. 6, it can be seen that the Gd2O3 and CeO2 crystal peaks observed from the precursor XRD data disappear except for the CeO2 peak in the newly synthesized fine powders, as in Example 1. From the ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometer) analysis results shown in Table 2, it can be seen that the cation composition ratio of the synthesized Gd-doped CeO2 fine particles is well within 1.31 at% of the designed composition ratio. From this, it can be seen that, as in the case of Example 1, it is possible to synthesize a heterogeneous metal-doped CeO2 single phase fine powder through the method disclosed in the present invention.

Table 2. ICP-OES compositional change analysis between precursor and synthesized fine powder Constituent (cation at.%) Gd Ce Precursors (A) 10.16 89.84 As-synthesized (B) 8.85 91.15 Increment (B-A) -1.31 +1.31

As described above, the method of manufacturing a cerium oxide fine powder doped with a hetero-metal using plasma, which has been introduced in the present invention, uses a high-temperature and high-enthalpy plasma source such as a high-frequency inductively coupled plasma to generate Gd2O3 or Sm2O3 Y 2 O 3 and cerium oxide powder are instantaneously heated to activate the doping metal materials such as Gd, Sm, and Y from their oxide lattice structures and move into the CeO 2 lattice structure. ms in a short time. Also, by rapidly quenching the melt and the vapor formed through this process, the CeO2 fine powder doped with a heterogeneous metal of 1 mu m or less can be easily obtained in a large amount without any separate pulverizing step or treatment.

As described above, unlike the conventional precipitation method, sol-gel method, glycine nitrate method and the like, the present invention can provide relatively easy to obtain, without using a separate metal nitrate salt, expensive organic metal, organic solvent, By directly using the dopant metal oxide such as Gd2O3, Sm2O3, Y2O3, etc., it is possible to induce a relatively easy and safe reaction process free from the discharge of environmental harmful substances after the reaction.

Further, by using the high enthalpy plasma flow, the mixed precursor powder consisting of the dopant metal oxide and cerium oxide is rapidly heated to co-melt and vaporize, thereby enabling fast and uniform doping of the dissimilar metals, It is possible to continuously mass-produce hetero-metal-doped CeO 2 nano-powder having a CeO 2 single phase with a size of 1 μm or less.

Claims (8)

A method of producing a cerium oxide fine powder doped with a dissimilar metal,
1) a first step of using an oxide of a dopant metal and cerium oxide as starting materials and quantitatively providing these oxides in accordance with the doping amount;
2) a second step of preparing solid phase mixed precursor powder by mixing, pulverizing or calcining the oxide starting material determined in the first step by a conventional method;
3) a third step of heating the precursor powder obtained through the second step so as to allow physical and chemical changes such as simultaneous melting and vaporization using plasma;
4) a step of synthesizing cerium oxide fine particles doped with a dissimilar metal by quenching the resultant which is physically and chemically changed using the plasma;
A method for producing a heterometallically doped cerium oxide fine powder using plasma The method of claim 1, wherein the first step uses a powder having a size of 1 to 20 mu m as a dopant metal oxide and a cerium oxide powder having a size of 10 to 40 mu m or less. For preparing cerium oxide fine powder The method according to claim 2, wherein in the first step, the dopant metal oxide is any one of Gd 2 O 3, Sm 2 O 3, and Y 2 O 3, and a method for producing a heterometallically doped cerium oxide fine powder using plasma The hetero-metal-doped cerium oxide fine particle according to claim 3, wherein an oxide of the dopant metal and cerium oxide are mixed so that the weight ratio of Ce to the total weight of the dopant metal atoms is in the range of 80 to 90 parts by weight. Method of manufacturing powder The method of claim 4, wherein in the third step, plasma of a high-frequency inductively-coupled type having a frequency of 0.5 to 13.56 MHz is used, and a method of manufacturing a heterometallically doped cerium oxide fine powder using plasma The method for producing heterometallically doped cerium oxide fine powder using plasma according to claim 1, wherein an arc plasma induced by a DC current of 100 A or more is used in the third step The method according to claim 1, wherein the plasma generated from a plurality of circular toroids arranged in a circular shape and symmetrically in the third step is used to manufacture a heterometallically doped cerium oxide fine powder using plasma The method according to claim 1, wherein the plasma generated by microwave local heating at 700 MHz or more is used in the third step, and a method for producing a heterometallically doped cerium oxide fine powder using plasma

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