KR101358911B1 - Nanopowder using a rf plasma combustion and method of manufacturing thereof - Google Patents

Abstract

The present invention relates to a nanopowder using plasma combustion and a method for producing the same. Method of manufacturing a nano powder according to an embodiment of the present invention, the step of preparing a magnesium oxide (MgO) and metal oxide powder having a diameter of 10 ㎛ to 100 ㎛, mechanically mixing the prepared powder to prepare a mixed powder, Injecting the mixed powder with a carrier gas into a RF (Radio Frequency) plasma combustor, supplying a central gas and a sheath gas to the RF plasma combustor And supplying a quenching gas to an RF (Radio Frequency) plasma combustion apparatus. Nanopowder according to an embodiment of the present invention is prepared by the above-described method so that the metal oxide is evenly distributed in the crystal of magnesium oxide.

Plasma combustion, nanopowder, dielectric layer, plasma display, PDP

Description

Nano powder using plasma combustion and its manufacturing method {NANOPOWDER USING A RF PLASMA COMBUSTION AND METHOD OF MANUFACTURING THEREOF}

The present invention relates to a nanopowder production method and a nanopowder manufactured by the method, and more particularly, to a nanopowder using plasma combustion and a method for producing the same.

Magnesium oxide (MgO) is widely used as a material for forming a protective film in a space where discharge occurs, such as a plasma display (PDP). The protective film formed of magnesium oxide in the PDP serves to protect the dielectric layer from sputtering of ions. In addition, the magnesium oxide oxide has a high secondary electron generation coefficient, thus enabling the normal operation of the PDP even when low energy ions collide during discharge. Therefore, it may also serve to lower the driving and holding voltages of the discharge plasma.

As a method of forming such a magnesium oxide protective film, it can be roughly divided into vacuum deposition and non-vacuum deposition. Vacuum deposition may be further divided into a sputtering method, an electron beam method, and an ion plating method, and the non-vacuum deposition method may be a screen printing method. Non-vacuum deposition has the advantage that the protective film can be formed at a lower cost than vacuum deposition, but there is a problem that requires a high temperature sintering step. Therefore, PDP producers are currently forming a protective film using an electron beam method and an ion plating method among vacuum deposition methods.

On the other hand, in the vapor deposition method, a target of the magnesium oxide protective film used for vapor deposition is a polycrystalline target formed by sintering with a single crystal. However, in the case of single crystal targets, all the requirements for fast response, high electrical insulation, sputtering resistance, high secondary electron emission coefficient, long-term stability, high light transmittance and low refractive index are required for achieving high resolution of PDP. Magnesium oxide targets formed by sintering are preferred because of problems that are difficult to meet. Even when it is desired to add an additive for improving specific physical properties, there is a problem that is difficult to apply in the case of a single crystal target, the situation has recently increased interest in the polycrystalline target formed by sintering fine powder.

However, in order to form the target by sintering, a micron-sized high purity powder is required. However, the smaller the powder is, the larger the total area that can be reacted, so that it can easily react with impurities such as water in the air or in a solution. Therefore, such a fine powder is difficult to handle, there was a problem that a complex process to obtain a high purity fine powder.

In order to solve the above problems, a high purity nanopowder using plasma combustion and a method of manufacturing the same are provided.

In the method for preparing nanopowders according to the first embodiment of the present invention, i) preparing magnesium oxide (MgO) and metal oxide powder having a diameter of 10 μm to 100 μm, ii) mechanically mixing the prepared powder and mixing powder (Iii) injecting the mixed powder into the RF (Radio Frequency) plasma combustion apparatus together with the carrier gas, and iii) the central gas in the RF plasma combustion apparatus, blocking Supplying a gas (sheath gas), i) Supplying a quenching gas to a Radio Frequency (RF) plasma combustion apparatus.

The metal oxide may be an alkaline earth metal oxide or an alkaline earth metal oxide to which aluminum oxide is added.

In addition, the mixed powder may be an amount of the alkaline earth metal oxide powder or the amount of the alkaline earth metal oxide powder to which the aluminum oxide (Al ₂ O ₃ ) is added. have.

In addition, the alkaline earth metal oxide may be calcium oxide (CaO).

In addition, the central gas and the quench gas may be an inert gas, the blocking gas may be a mixed gas of an inert gas and oxygen, and the powder injection gas may be oxygen.

In addition, the central gas is supplied at 5 ~ 40slpm, the quenching gas is supplied at 50 ~ 400slpm, the blocking gas is supplied by mixing 10 ~ 80slpm of inert gas and 10 ~ 100splm of oxygen, and the powder injection gas is supplied at 5 ~ 40slpm Can be. (The SLPM unit is the flow rate measured in temperatures of 20 ^o C and atmospheric pressure (14.7 psi) in Liter / Minute.)

In addition, the nano-powder may be manufactured by supplying power of 15 to 150 KW to the RF plasma combustion device.

In addition, the RF plasma combustion apparatus may include a nozzle for injecting the mixed powder and an induction coil for generating RF (Radio Frequency) energy, and the interval between the nozzle and the center of the induction coil may be 0.1 cm to 3 cm.

On the other hand, the method of manufacturing a deposition target (Target) according to an embodiment of the present invention further comprises the step of molding and sintering the nano-powder prepared by the method for manufacturing nano-powder according to the first embodiment of the present invention.

In addition, the nanopowder according to an embodiment of the present invention may be a magnesium oxide (MgO) nanopowder doped with a metal oxide prepared by the method for preparing a nanopowder according to the first embodiment of the present invention. The metal oxide may be calcium oxide (CaO) or calcium oxide (CaO) + aluminum oxide (Al ₂ O ₃ ).

In the method of manufacturing nanopowders according to the second embodiment of the present invention, (iii) preparing magnesium oxide (MgO), calcium oxide (CaO) and aluminum oxide (Al ₂ O ₃ ) powder having a diameter of 10 μm to 100 μm. Ii) each powder was prepared by calcium oxide (CaO) and aluminum oxide (Al ₂ O ₃ ); Mechanically mixing the powder so that the sum of the powders is 0.001 to 1 wt%, iii) injecting the mixed powder into the RF (Radio Frequency) plasma combustion apparatus together with the powder carrier gas. Step, iii) supplying a central gas (sheath gas) to the RF plasma combustion device, iii) supplying a quenching gas to the RF (Radio Frequency) plasma combustion device It includes the step, the powder injection gas to supply oxygen to 5 ~ 40slpm, the inert gas to 5 ~ 40slpm to the central gas, the quench gas to supply the inert gas to 50 ~ 400slpm, the inert gas as the blocking gas 10 ~ 80slpm and oxygen 10 ~ 100splm are mixed and supplied, and 15 ~ 150KW power can be supplied to RF (Radio Frequency) Plasma combustion device.

On the other hand, the method of manufacturing a deposition target according to a second embodiment of the present invention further comprises the step of molding and sintering the nanopowder prepared by using the nanopowder manufacturing method according to the second embodiment of the present invention.

In addition, the nanopowder according to the second embodiment of the present invention is doped with calcium oxide (CaO) and aluminum oxide (Al ₂ O ₃ ) prepared by the nanopowder manufacturing method according to the second embodiment of the present invention. It may be magnesium oxide (MgO) nano powder.

In the method of manufacturing nanopowders according to the embodiment of the present invention, plasma powders may be used to produce nanopowders having a constant particle size.

In addition, the power of the plasma apparatus is set to 15 to 150 kW, and the powder and the gas, the central gas, the quenching gas and the kind and speed of the blocking gas can be optimized to produce a nanopowder having a size of 100 nm or less.

In addition, by adjusting the position of the powder injection nozzle of the plasma apparatus to the lower position of 0.1 ~ 3cm in the center of the induction coil it can supply the appropriate thermal energy to the precursor. On the other hand, in the nanopowder according to the embodiment of the present invention, the doped metal oxide is uniformly positioned between the grains of magnesium oxide due to the plasma combustion method. Therefore, through the sintering it is possible to manufacture a deposition target that is evenly positioned doped metal oxide.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily carry out the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In addition, in order to demonstrate this invention clearly, the part which is not related to description is abbreviate | omitted.

Hereinafter, the operation of the RF (Radio-Frequency) plasma apparatus 10 used in the method of manufacturing nanopowders according to the embodiment of the present invention will be described with reference to FIG. 1.

1 schematically shows a cross section of an RF plasma apparatus 10. The RF plasma apparatus 10 includes a powder that is a precursor and an injection hole into which each gas is injected, and includes an induction coil 101 for generating RF and supplying energy and a nozzle 103 for melt spraying the powder. . The gas supplied to the plasma apparatus 10 is a central gas injected into the outer wall of the nozzle 103 into which the precursor is initially injected, and a blocking gas that prevents the vaporized powder from adsorbing to the outer wall of the induction coil 101. (Sheath gas), the carrier gas for injecting and transporting the powder (Carrier gas) and the quenching gas (Quenching gas) for quenching the vaporized or dissolved powder.

The operation of the device is as follows. The micron unit powder, which is a precursor, is supplied to the nozzle 103 together with the powder injection gas (aa), and the central gas bb and the blocking gas cc are supplied in respective directions. At the same time, the induction coil 101 of the device 10 is supplied with a constant current to generate energy and create a high temperature environment of 5,000 to 10,000K. The precursor transported by the powder injection gas is vaporized or dissolved due to the high temperature formed by the induction coil 101 while passing through the nozzle 103 and sprayed to the outside of the nozzle 103. When the quenching gas is strongly injected (dd) toward the injector, the hot injector becomes a nano-sized powder while condensing or quenching.

Next, a method of manufacturing a nanopowder according to an embodiment of the present invention will be described with reference to FIG. 2. 2 is a flowchart illustrating a method of manufacturing nanopowders according to an embodiment of the present invention.

First, a powder of magnesium oxide (MgO) and a metal oxide is prepared as a nanopowder material (201). The size of the powder is preferably microns, and the metal oxide may be an alkaline earth metal oxide or an alkaline earth metal oxide to which aluminum oxide (Al ₂ O ₃ ) is added. In addition, calcium oxide (CaO) may be used as the alkaline earth metal oxide.

Next, mechanically mixing the prepared powder to prepare a mixed powder that is a precursor (203). It is preferable to mix the mixed powder so that the amount of the metal oxide is 0.001 to 2 wt%, and various methods may be used as the mixing method, but a ball mill using zirconia oxide (ZrO ₂ ) may be used.

Next, as illustrated in FIG. 1, a mixed powder is injected into the plasma apparatus to prepare a nanopowder (205). In this case, the powder injection gas, the central gas and the blocking gas are injected together with the mixed powder (213), and the nano-powder is formed by quenching the vaporized and molten powder using the quench gas (215).

The amount and speed of the injected powder injection gas, the central gas and the quench gas determine the particle size and particle size distribution of the nanopowder, and the temperature distribution of the plasma flame is determined according to the type, quantity and speed of the blocking gas, thus the amount and speed of the gas. Silver is an important factor in the production method of nanopowders.

Variables mainly affecting the particle size of the nanopowder include power supplied to the RF plasma apparatus, the relative height between the nozzle and the induction coil generating the RF, the amount and speed of the precursor supply, and the amount and speed of the quench gas. In addition, whether the nanopowder is correctly formed and whether the second or third phase is formed by impurities is determined by the gas atmosphere inside the plasma apparatus and three kinds of gases (blocking gas, central gas, and powder injection gas) supplied to the apparatus. Is determined.

In the method for preparing nanopowders according to the embodiment of the present invention, the following conditions are set in order to prepare nanoparticles having a size of 1 to 100 nm.

The central gas is supplied to the inert gas at 5 ~ 40slpm, the quenching gas is supplied to the inert gas at 50 ~ 400slpm, the cutoff gas is supplied by mixing 10 ~ 80slpm of inert gas and 10 ~ 100splm of oxygen, the powder injection gas Supply oxygen at 5 ~ 40slpm.

In addition, the power supplied to the RF plasma apparatus is 15 to 150 kW to maintain the proper temperature of the plasma flame, and the ejection portion and the induction coil 101 of the nozzle 103 (the same as shown below in FIG. 1) and the same as shown below in FIG. 1. Adjust the distance from the center of the c) to 0.1 to 3 cm to adjust the vaporization temperature of the powder.

The produced nanopowder is transported through a vacuum pump and a compressor to separate micron-sized particles and relatively large nanoparticles through filtering and cyclone methods (207, 209). In addition, cooling of the powder takes place through the cyclone, and the gas is separated from the powder and discharged to the outside.

Through this process, the mixed powder of metal oxide and magnesium oxide is synthesized into magnesium oxide nano powder doped with metal oxide through pyrolysis and regrowth due to heat generated by RF plasma. Therefore, the nano-powder doped with a metal oxide can be prepared through this method (211).

The nanopowder thus produced is introduced into a molding machine and a pressure is applied to prepare a molded body. The polycrystalline sintered target is manufactured by heat-treating the prepared X-shaped bodies.

The present invention will be described in more detail with reference to the following experimental examples.

(Experimental Example 1)

In Experimental Example 1, calcium oxide (CaO), an alkaline earth metal oxide, was used as the metal oxide. First, magnesium oxide and calcium oxide (CaO) having a size of 10 to 100 μm and a purity of 99.9% were prepared as precursors to prepare nanopowders using the RF plasma apparatus. Magnesium oxide and calcium oxide were mixed and adjusted so that the calcium oxide became 0.001 to 1 wt%.

The mixed powder was placed in a powder feed container and subjected to 30% vibration while rotating at 10 RPM to feed the mixed powder through the nozzle of the RF plasma apparatus. The device was supplied with a voltage of 25-60 kW, and the flow rate, speed, and type of each gas introduced were adjusted as shown in Table 1 below.

Condition Power supply 20-60 kW gas Blocking gas Ar: 10-80O _2: 10-100 slpm Central gas Ar: 5-40 slpm Quench gas Ar: 100-400 slpm Powder injection gas O ₂ : 5-40 slpm

The SLPM unit is the Liter / Minute (liter / minute) of the flow rate measured at 20 ^° C and atmospheric pressure (14.7 psi).

The final collected nanopowders were collected to determine whether the nanopowder was formed and whether the second phase was present through X-ray diffraction.

Figure 3 shows the X-ray diffraction results of the nanopowder according to the first experimental example of the present invention. Referring to FIG. 3, only a peak related to magnesium oxide is observed, and no calcium oxide is observed, and it can be seen that calcium oxide is mixed in the crystal of magnesium oxide without forming a separate crystal. That is, it can be seen that another second phase is not formed.

Hereinafter, the state and particle size of the nanopowder according to the first experimental example of the present invention will be described with reference to FIGS. 4 and 5.

4 is a transmission electron microscope (TEM) photograph of the nanopowder according to the first experimental example of the present invention. Referring to FIG. 4, it can be seen that the particle size is about 100 nm. As a result of component analysis of the sample using TEM, it was confirmed that calcium oxide doped evenly in the main component magnesium oxide was evenly distributed.

5 is a graph showing in more detail the particle size of the nanopowder according to the first experimental example of the present invention. Referring to Figure 5 it can be seen that the average particle size of the particle is about 100nm. Particles over 200nm in size are extremely small, about 1% of the total, and can also be removed through separation processes such as cyclones.

On the other hand, the same sample was subjected to ICP AES component analysis for more accurate component analysis. As a result of the component analysis, it can be seen that there is almost no change in the impurity component, and it was confirmed that high purity magnesium oxide doped with calcium oxide was prepared as nano powder.

In addition, the prepared nanopowders are mixed using alcohol as a dispersant and then molded using a press. Next, the molded powder was sintered at 1000 to 1700 ° C. for 1 to 7 hours to form a target, and the size and the like of the crystal grains of the target were analyzed. As a result, it was confirmed that the calcium oxide is located in the grains of magnesium oxide to uniformize the size of the grains.

As a result of the discharge test using the deposition target manufactured as described above, the discharge voltage is lower than that of the target sintered the magnesium oxide powder of micro unit, and the response speed of the PDP manufactured by using this can be confirmed to be greatly improved. there was.

(Experimental Example 2)

In Experimental Example 2, a mixture of calcium oxide (CaO) and aluminum oxide (Al ₂ O ₃ ), which are alkaline earth metal oxides, was used as a metal oxide (hereinafter referred to as a 'mixed metal oxide'). First, magnesium oxide and mixed metal oxides having a size of 10 to 100 μm and a purity of 99.9% were prepared to prepare nanopowders using the RF plasma apparatus. Magnesium oxide and mixed metal oxides were mixed and adjusted so that calcium oxide and aluminum oxide constituting the mixed metal oxide were 0.001 to 1 wt%, respectively.

The mixed powder thus mixed was put into a powder feed container and subjected to 30% vibration while rotating at 10 RPM to supply the mixed powder through the nozzle of the RF plasma apparatus. The device was supplied with a voltage of 25-60 kW, and the flow rate, speed, and type of each gas introduced were adjusted as shown in Table 2 below.

Condition Power supply 20-60 kW gas Blocking gas Ar: 10-80O _2: 10-100 slpm Central gas Ar: 5-40 slpm Quench gas Ar: 100-400 slpm Powder injection gas O ₂ : 5-40 slpm

The SLPM unit is the Liter / Minute (liter / minute) of the flow rate measured at 20 ^° C and atmospheric pressure (14.7 psi).

The final collected nanopowders were collected to determine whether the nanopowder was formed and whether the second phase was present through X-ray diffraction.

Figure 6 shows the X-ray diffraction results of the nanopowder according to the second experimental example of the present invention. Referring to FIG. 6, as in Experimental Example 1, only a peak related to magnesium oxide was observed, and no peak was observed for the mixed metal oxide, so that the mixed metal oxide did not form a separate crystal but crystals of magnesium oxide. It can be seen that they are mixed in. That is, it can be seen that another second phase is not formed.

Hereinafter, the state and particle size of the nanopowder according to the second experimental example of the present invention will be described with reference to FIGS. 7 and 8.

7 is a transmission electron microscope (TEM) photograph of the nanopowder according to the second experimental example of the present invention. Referring to FIG. 7, it can be seen that the particle size is about 100 nm. As a result of component analysis of the sample using TEM, it was confirmed that the mixed metal oxide doped in magnesium oxide as a main component was evenly distributed.

8 is a graph showing in more detail the particle size of the nanopowder according to the second experimental example of the present invention. Referring to Figure 8 it can be seen that the average particle size of the particle is about 100nm. Particles over 200nm in size are extremely small, about 3% of the total, and can also be removed through separation processes such as cyclones.

On the other hand, the same sample was subjected to ICP AES component analysis for more accurate component analysis. As a result of the component analysis, it can be seen that there is almost no change in the impurity component, and it was confirmed that the high-purity magnesium oxide doped with the mixed metal oxide was prepared as nano powder.

In addition, the prepared nanopowders are mixed using alcohol as a dispersant and then molded using a press. Next, the molded powder was sintered at 1000 to 1700 ° C. for 1 to 7 hours to form a target, and the size and the like of the crystal grains of the target were analyzed. As a result, it was confirmed that the mixed metal oxide is located in the crystal grains of magnesium oxide to uniformize the grain size.

As a result of the discharge test using the deposition target manufactured as described above, the discharge voltage is lower than that of the target sintered the magnesium oxide powder of micro unit, and the response speed of the PDP manufactured by using this can be confirmed to be greatly improved. there was.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Of course.

1 is a schematic cross-sectional view of an RF plasma combustion device.

2 is a flow chart of a nano powder manufacturing method according to an embodiment of the present invention.

3 is an X-ray diffraction graph of the nanopowder according to the first experimental example of the present invention.

4 is a transmission electron micrograph of the nanopowder according to the first experimental example of the present invention.

5 is a particle size analysis graph of the nanopowder according to the first experimental example of the present invention.

6 is an X-ray analysis graph of the nanopowder according to the second experimental example of the present invention.

7 is a transmission electron micrograph of the nanopowder according to the second experimental example of the present invention.

8 is a graph illustrating particle size analysis of nanopowders according to a second experimental example of the present invention.

Claims (14)

Preparing magnesium oxide (MgO) and metal oxide powder having a diameter of 10 μm to 100 μm, Mechanically mixing the prepared powder to prepare a mixed powder, Injecting the mixed powder into a RF (Radio Frequency) plasma combustion device together with a carrier gas; Supplying a central gas and a sheath gas to the RF plasma combustion apparatus; The nano-powder manufacturing method comprising the step of supplying a quenching gas (quenching gas) to the RF (Radio Frequency) plasma combustion apparatus. The method of claim 1, The metal oxide is an alkaline earth metal oxide to which an alkaline earth metal oxide or aluminum oxide is added. 3. The method of claim 2, The mixed powder is an amount of alkaline earth metal oxide powder or an alkaline earth metal oxide powder added with aluminum oxide (Al ₂ O ₃ ) is 0.001 ~ 2 wt%, the remainder is a nano powder consisting of magnesium oxide (MgO) and unavoidable impurities Manufacturing method. 4. The method according to any one of claims 1 to 3, The alkaline earth metal oxide is calcium oxide (CaO) nano powder manufacturing method. The method of claim 1, The central gas and the quench gas is an inert gas, The blocking gas is a mixed gas of an inert gas and oxygen, The powder injection gas is oxygen powder manufacturing method. The method of claim 5, The central gas is supplied at 5 ~ 40slpm, The quench gas is supplied to 50 ~ 400slpm, The blocking gas is supplied by mixing 10 ~ 80slpm of inert gas and 10 ~ 100splm of oxygen, The powder injection gas is a nano powder manufacturing method for supplying 5 ~ 40slpm. The method of claim 1, Nanopowder manufacturing method for supplying power of 15 ~ 150KW to the RF plasma combustion device. The method of claim 1, The plasma combustion device includes a nozzle for injecting the mixed powder and an induction coil for generating RF (Radio Frequency) energy, The nano-powder manufacturing method of the nozzle and the guide coil in the interval of 0.1cm to 3cm. The method of claim 1, Forming and sintering the prepared nano-powder further comprising the method of manufacturing a deposition target (target). Prepared by the method of claim 1, Magnesium oxide (MgO) nanopowder doped with metal oxides. The method of claim 10, The metal oxide is calcium oxide nano powder (CaO) or calcium oxide (CaO) + aluminum oxide (Al ₂ O ₃ ). Preparing magnesium oxide (MgO), Ca 0 and aluminum oxide (Al 2 O 3) powders having a diameter of 10 μm to 100 μm, Each powder prepared above was prepared by calcium oxide (CaO) and aluminum oxide (Al 2 O 3). Preparing a mixed powder by mechanically mixing so that the sum of the powders is 0.001 to 1 wt%, Injecting the mixed powder together with a powder injection gas into an RF plasma combustion device; Supplying a central gas and a blocking gas to the RF plasma combustion device; Supplying a quench gas to the RF plasma combustion device; As the powder injection gas is supplied to oxygen 5 ~ 40slpm, The central gas is supplied to the inert gas 5 ~ 40slpm, As the quenching gas is supplied to the inert gas 50 ~ 400slpm, As the blocking gas, 10 to 80 slp of inert gas and 10 to 100 splm of oxygen are supplied and mixed. Nanopowder manufacturing method for supplying power of 15 ~ 150kW to the RF plasma combustion device. The method of claim 12, Forming and sintering the prepared nano-powder further comprising the method of manufacturing a deposition target (target). Prepared by the method of claim 12, Magnesium oxide (MgO) nanopowder doped with calcium oxide (CaO) and aluminum oxide (Al ₂ O ₃ ).

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