KR101478556B1 - Nickel nano powder with core-shell structure using high temperature plasma and method of manufacturing the same - Google Patents

Abstract

Disclosed are Ni nanopowder having a core-shell structure using high temperature plasma, and a method to manufacture the same. According to the present invention, the method to manufacture Ni nanopowder comprises: step (a) of forming Ni vapor by vaporizing a Ni powder basic material due to high temperature plasma by injecting the Ni powder basic material into a high temperature plasma area at 8000-12000°C; step (b) of forming Ni powder by enabling the Ni vapor to react to a cooling gas; and step (c) of obtaining Ni nanopowder whose average particle diameter is 40-120 nm by classifying the Ni powder. The Ni powder basic material contains dopant selected among silicon, titanium, and aluminum, and the cooling gas contains an inert gas with an oxygen-containing gas. An oxide shell consisting of nickel oxide and oxide of the dopant is formed in the surface while a Ni core is formed in (b) step.

Description

TECHNICAL FIELD The present invention relates to a Ni-Nano powder having a core-shell structure using a high-temperature plasma and a method of manufacturing the Ni-

More particularly, the present invention relates to a nickel nano powder which is excellent in crystallinity, has a high shrinkage starting temperature, and has a small size change even at high temperature firing, and a nickel nano- And a manufacturing method thereof.

Nickel powder is widely used in areas requiring electrical conductivity such as electrode materials and wiring materials.

The mechanical pulverization method, solution synthesis method, and gas phase synthesis method are widely used as a method of producing nickel powder. However, each method has the following problems.

In the case of the mechanical pulverization method, there is a problem in that the purity of the final product is not high because it is mixed with the nickel powder mainly produced impurities such as ceramics.

In the case of the vapor phase synthesis method, impurities such as refractory are mixed in the melting and vaporization of the raw material, and the purity of the final product is also not high.

In the solution synthesis method, various organic substances are adsorbed on the surface of the nickel powder to be produced, which is also poor in terms of purity.

The background art relating to the present invention is a refractory for producing nickel powder disclosed in Korean Patent Laid-Open Publication No. 10-2013-0117293 (published on October 25, 2013) and a method for producing nickel powder using the same.

An object of the present invention is to provide a nickel nano powder having excellent crystallinity, high shrinkage starting temperature, and small size change even at high temperature baking, and a method for producing the same.

According to an aspect of the present invention, there is provided an Ni nanopowder having an average particle diameter of 40 to 120 nm and comprising a Ni core and an oxide shell surrounding the Ni core, , A titanium oxide and a nickel oxide, and the oxide shell acts as a heat-shrinkable barrier, and the shrinkage starting temperature of the powder is 600 ° C or higher and the shrinkage rate at 25 ° C to 1300 ° C is 10% or lower .

At this time, the Ni core may have an average particle diameter of 30 to 100 nm and the oxide shell may have a thickness of 10 to 20 nm.

In addition, the oxide shell may contain 10 to 70% by weight of the oxide of the dopant and 30 to 90% by weight of the nickel oxide.

In addition, both the Ni core and the oxide shell may be crystalline.

According to another aspect of the present invention, there is provided a method of manufacturing a Ni nanopowder, comprising: (a) introducing a Ni powder base material into a high-temperature plasma region at 8000 to 12000 ° C to vaporize the Ni powder base material by high- ; (b) contacting the Ni vapor with a cooling gas to form a Ni powder; And (c) classifying the Ni powder to obtain an Ni nanopowder having an average particle size of 40 to 120 nm, wherein the Ni powder base material contains a dopant selected from silicon, titanium and aluminum, An oxygen-containing gas is included together with an inert gas, and an oxide shell made of an oxide of a dopant and a nickel oxide is formed on the surface while the Ni core is formed in the step (b).

At this time, in the step (b), the Ni core may be formed with an average particle diameter of 30 to 100 nm, and the oxide shell may be formed with a thickness of 10 to 20 nm.

Also, in the step (b), both the Ni core and the oxide shell may be formed of a crystalline material.

In the step (b), the oxide of the dopant may be 10 to 70 wt%, and the nickel oxide may be 30 to 90 wt%.

The cooling gas may exhibit an inert gas and an oxygen-containing gas at a flow rate ratio of 1: 0.05 to 1: 0.2.

Also, the Ni powder base material may be prepared from a suspension in which nickel and a dopant are dispersed in a solvent, and doped with a part of nickel.

Also, the Ni powder base material may be composed of 70 to 95% by weight of nickel and 5 to 30% by weight of dopant.

According to the present invention, Ni nanopowder having excellent crystallinity can be obtained through a series of processes including vaporization of a Ni powder base material by using a high-temperature plasma, powder formation by cooling gas, and classification.

Particularly, according to the present invention, a Ni powder base material contains a dopant such as silicon, titanium and aluminum, and an inert gas and an oxygen-containing gas are contained in the cooling gas to form a crystalline oxide shell having a thickness of 10 to 20 nm can do. This oxide shell acts as a heat-shrinkable barrier to increase the shrinkage temperature of the powder to 600 ° C or more, and the shrinkage rate to 1300 ° C can be 10% or less. As a result, it is possible to solve problems such as generation of cracks at the time of high-temperature firing in the formation of electrodes and wiring using nickel powder.

FIG. 1 is a schematic view illustrating a method of manufacturing a Ni-nano powder having a core-shell structure using a high-temperature plasma according to an embodiment of the present invention.
FIG. 2 illustrates a process of manufacturing a Ni powder base material including a dopant.
Fig. 3 shows the results of XRD analysis of Ni nano powder prepared under the condition that oxygen gas is contained in the cooling gas and Ni nano powder prepared in the condition not containing oxygen gas.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, And the scope of the invention is defined only by the scope of the claims set forth in the following claims.

Hereinafter, Ni nanopowder having a core-shell structure using a high-temperature plasma according to the present invention and a method of manufacturing the same will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic view illustrating a method of manufacturing a Ni-nano powder having a core-shell structure using a high-temperature plasma according to an embodiment of the present invention.

Referring to FIG. 1, the illustrated method for producing Ni nanopowder includes a Ni vapor forming step (S110), a Ni powder forming step (S120), and a classification step (S130).

Referring to FIG. 1, the illustrated method for producing Ni nanopowder includes a Ni vapor forming step (S110), a Ni powder forming step (S120), and a classification step (S130).

In the Ni vapor formation step (S110), the Ni powder base material is put into a high temperature plasma region of about 10,000 DEG C, and the Ni powder base material is vaporized to form Ni vapor.

The temperature of the high-temperature plasma region is the temperature at which the Ni powder base material can be vaporized, preferably 8000 to 12000 ° C. Here, the temperature of the plasma region means the plasma center temperature. If the temperature of the high temperature plasma region is less than 8000 deg. C, the nickel vaporization efficiency may become a problem. Further, even if the temperature of the high-temperature plasma region exceeds 12,000 DEG C, the nickel vaporization efficiency is no longer increased.

The high-temperature plasma generating apparatus preferably uses an RF plasma torch having an output power of 50 to 70 kW, and more preferably an RF plasma torch of 60 kW. When the output power is less than 50 kW, it is difficult to obtain a sufficient high-temperature plasma. Conversely, when the output power exceeds 70 kW, the life of the equipment may be degraded and the stability may be a problem.

The Ni vapor can be transferred to the cooling region through the carrier gas.

As the Ni powder base material, nano-grade or micro-grade powdery nickel may be used, but it is more preferable to be powdery nickel having an average particle diameter (D50) of 200 nm to 20 탆. In the case of powdery nickel having an average particle size of less than 200 nm, the flowability of the powder is low, and control of the introduction into the plasma region may become difficult. On the contrary, in the case of powdery nickel having an average particle diameter exceeding 20 占 퐉, the high-temperature plasma region must be sufficiently large in order to completely vaporize, resulting in a decrease in economy.

At this time, in the present invention, in addition to the Ni powder base material, a dopant selected from silicon, titanium and aluminum is included. By these dopants, the nickel nanopowder to be produced can have a core-shell structure.

The Ni powder base material may be a simple mixture of nickel and a dopant. More preferably, it is possible to suggest that a part of nickel is coated with a dopant in the same manner as the example shown in FIG.

FIG. 2 illustrates a process of manufacturing a Ni powder base material including a dopant.

Referring to FIG. 2, a Ni powder base material 240, which is manufactured from a suspension 230 in which nickel 210 and a dopant 220 are dispersed in a solvent, may be prepared by doping a portion of nickel with a dopant.

Also, the Ni powder base material may be composed of 70 to 95% by weight of nickel and 5 to 30% by weight of dopant. When the dopant content is less than 5% by weight, the effects such as the increase in the shrinkage starting temperature due to the addition of the dopant may be insufficient. On the other hand, when the amount of the dopant is more than 30% by weight, excessive amounts of silicon oxide, aluminum oxide, etc., which are stabilized oxides in the oxide shell, may not be enough to remove oxygen from the oxide shell at high temperature baking.

Next, in the Ni powder forming step (S120), the Ni vapor is brought into contact with the cooling gas and quenched to form Ni powder. As the cooling gas, an inert gas such as argon gas (Ar), nitrogen gas (N ₂ ), or the like may be used.

As the Ni vapor contacts the cooling gas, spherical crystalline Ni powder is formed.

At this time, in the present invention, the Ni powder base material contains a dopant, and an inert gas and an oxygen-containing gas are included in the cooling gas. In the Ni powder formation process, a Ni core is formed, and an oxide of a dopant and an oxide A shell is formed. The surface oxide shell acts as a heat shrinkage barrier to increase the shrinkage temperature of the Ni powder to 600 ° C or higher and decrease the heat shrinkage rate so that the shrinkage rate can be 10% or less at room temperature to 1300 ° C.

At this time, the Ni core may be formed with an average particle diameter of 30 to 100 nm, and the oxide shell may be formed with a thickness of 10 to 20 nm. When the thickness of the oxide shell is less than 10 nm, the heat shrinkage barrier function is not sufficient. On the contrary, when the thickness of the oxide shell is more than 20 nm, oxygen remaining in the oxide shell on the surface during high-temperature baking for forming electrodes and wiring can not be removed, resulting in deterioration of electrical conductivity.

At this time, not only the Ni core but also the outer oxide shell may be formed of crystalline. Usually, the natural oxide film has a thickness of about 2 to 5 nm and an amorphous phase. In the case of the oxide shell formed by the method according to the present invention, the thickness is 10 to 20 nm, and the crystalline oxide is a stable layer. Therefore, it seems that the oxide shell having such characteristics acts as a heat shrinkable barrier to raise the heat shrinkage starting temperature to 600 DEG C or more and lower the heat shrinkage ratio.

In the oxide shell, the oxide of the dopant may be 10 to 70 wt%, and the oxide of nickel may be 30 to 90 wt%. When the oxide of the dopant in the oxide shell is less than 10% by weight, the effect of increasing the heat shrinkage starting temperature may be insufficient. When the oxide of the dopant is more than 70% by weight, stabilized oxides such as silicon oxide and aluminum oxide are formed excessively And oxygen removal of the oxide shell may not be sufficient at high temperature baking.

The oxygen-containing gas may be oxygen (O ₂ ) gas or ozone (O ₃ ) gas.

On the other hand, in order to form a powder having a Ni core and an oxide shell, the flow ratio of the inert gas to the oxygen-containing gas is preferably 1: 0.05 to 1: 0.2. When the flow rate of the oxygen-containing gas with respect to the flow rate of the inert gas is less than 0.05, it is difficult to form an oxide shell of 10 nm or more. On the other hand, when the flow rate of the oxygen-containing gas with respect to the flow rate of the inert gas is more than 0.2, the thickness of the oxide shell becomes excessively large and oxygen on the surface is not removed during the high-temperature baking for forming electrodes and wiring, .

Next, in the classifying step (S130), Ni powder is classified to obtain Ni nanopowder having an average particle diameter of 40 to 120 nm.

The Ni powder formed through the Ni powder formation step (S120) has a large particle size distribution and a large average particle diameter (D50). Ni powder in this state can be classified into a final Ni nano powder having a smallest difference in maximum particle diameter and minimum particle diameter and a mean particle diameter of 40 to 120 nm.

Classification can use a cyclone classifier.

The Ni nanopowder according to the present invention manufactured through the above steps S110 to S130 has an average particle diameter of 40 to 120 nm and is composed of a Ni core and an oxide shell surrounding the Ni core, Is composed of an oxide of a dopant and a nickel oxide selected from silicon, titanium and aluminum. In this case, the Ni core may have an average particle diameter of 30 to 100 nm and the oxide shell may have a thickness of 10 to 20 nm. The oxide shell may contain 10 to 70% by weight of the oxide of the dopant and 30 to 90% by weight of the nickel oxide. Both the Ni core and the oxide shell can exhibit crystalline quality.

The Ni nanopowder according to the present invention having such characteristics can exhibit the shrinkage starting temperature of the powder at 600 ° C or higher and the shrinkage rate at 25 ° C to 1300 ° C of 10% or less because the oxide shell functions as a heat shrinkage barrier. Through this, it is possible to solve problems such as cracking due to excessive shrinkage of Ni powder during high-temperature baking for forming electrodes or wiring, and it is possible to exhibit excellent electrical conductivity and durability.

Example

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

The contents not described here are sufficiently technically inferior to those skilled in the art, and a description thereof will be omitted.

1. Experimental conditions

As the Ni powder base material, Ni powder having a particle diameter of 5.0 to 15.0 mu m and an average particle diameter of 10.2 mu m was used. The raw material feed rate was 15 g / min and argon gas of 50 slpm was used as the carrier gas.

As the Ni powder base material used in the examples, the Ni powder and the powder obtained by removing water from a suspension prepared by dispersing an aluminum powder or an aluminum powder having an average particle diameter of 300 nm in water were used.

As a plasma generation source, a 60 kW RF plasma torch (SYSTEM 71-60 kW, TEKNA) was used. Argon gas of 150 slpm and hydrogen gas of 10 slpm as a reducing gas were used as the ignition gas.

As the cooling gas, argon gas and oxygen gas, argon gas and ozone gas were used.

The classification was carried out using a Cyclone Collector (Dion).

2. Ni nanopowder manufacturing

(1) Example 1

A Ni powder base material containing silicon dopant in an amount of 10% by weight was charged into a high temperature plasma region having a plasma center temperature of approximately 10,000 DEG C to vaporize the Ni powder base material to form Ni vapor and transferred to the cooling region.

Thereafter, 1000 slpm argon gas and 100 slpm oxygen gas were injected into the cooling region to form a primary Ni powder.

Thereafter, final Ni nanopowder was formed through classification.

(2) Example 2

A Ni powder base material containing 15 wt% of aluminum dopant was charged into a high temperature plasma region having a plasma center temperature of approximately 10,000 DEG C to vaporize the Ni powder base material to form Ni vapor and transferred to the cooling region.

Thereafter, 1000 slpm argon gas and 100 slpm oxygen gas were injected into the cooling region to form a primary Ni powder.

Thereafter, final Ni nanopowder was formed through classification.

(3) Comparative Example 1

Ni powder was prepared under the same conditions as in Example 1, except that oxygen was not contained in the cooling gas.

(4) Comparative Example 2

Ni nanopowder was prepared under the same conditions as in Example 1, except that a silicon dopant was not included in the Ni powder base material.

(5) Comparative Example 3

Ni nanopowder was prepared under the same conditions as in Example 1, except that 40 wt% of silicon dopant was contained in the Ni powder base material.

(6) Comparative Example 4

In Example 1, the oxygen gas flow rate was 210 ppm under the same conditions.

3. Ni nanopowder analysis

(1) Evaluation of shape, particle diameter, shrinkage temperature and shrinkage rate

The shape, average particle diameter, shrinkage temperature and the like of the Ni nanopowder thus produced were evaluated.

The aspect ratio of the powder was measured to determine that the sphericity of 85% or more was spherical, and the other was non-spherical.

The average particle size and the oxide shell thickness were analyzed by SEM photographs.

The content of the oxide shell was analyzed by an inductively coupled plasma mass spectrometer (ICP-MS).

The shrinkage temperature and shrinkage were analyzed by TMA.

Table 1 shows the results of Ni nano powder analysis according to Examples 1 to 2 and Comparative Examples 1 to 4.

[Table 1]

 Referring to Table 1, Ni nanopowders prepared according to Examples 1 and 2 satisfying the conditions of the present invention had an average particle diameter of 40 to 120 nm, an oxide shell thickness of 10 to 20 nm, The shrinkage rate at a temperature of 600 ° C or higher and 25 ° C to 1300 ° C was 10% or less.

On the other hand, in the case of the Ni nano powder prepared according to Comparative Example 1 in which the oxygen-containing gas is not contained in the cooling gas, the thickness of the oxide shell was 2 nm, which is considered to be formed by natural oxidation. In the case of the Ni nanopowder according to Comparative Example 1, the heat shrinkage starting temperature was less than 500 ° C and the shrinkage rate exceeded 10%.

In the case of the Ni nanopowder according to Comparative Example 2 in which the dopant was not included in the Ni powder base material, the heat shrinkage starting temperature was higher than that of Comparative Example 1, but could not reach the target temperature of 600 ° C.

In addition, the Ni nanopowder according to Comparative Example 3 in which the dopant was excessively added showed a heat shrinkage starting temperature of 600 ° C or higher and a heat shrinkage of 10% or less, but the content of the dopant oxide in the oxide shell exceeded 70%.

In the case of the Ni nanopowder according to Comparative Example 4 in which oxygen gas was excessively contained in the cooling gas, the heat shrinkage starting temperature was 600 ° C or more and the heat shrinkage rate was 10% or less, but the thickness of the oxide shell exceeded 20 nm.

(2) XRD analysis

XRD analysis was carried out in order to evaluate whether or not an oxide shell was formed as a crystalline material. For the sake of convenience, Ni powder was prepared in the same manner as in Example 1 and Comparative Example 1 except that a dopant was not included. 3.

Referring to FIG. 3, in both Example 1 and Comparative Example 1, Ni peak was strongly observed, and it was found that crystalline Ni nanopowder was produced.

However, in the case of Example 1, a NiO peak was found, whereas in Comparative Example 1, no NiO peak was found. This means that in the case of the Ni nanopowder according to Example 1, the NiO layer on the surface is formed as crystalline.

(3) Evaluation of electrical conductivity after high-temperature firing

Each Ni nanopowder was dispersed in terpineol and ethyl cellulose was added to prepare a paste. The paste thus prepared was applied on a BaTiO ₃ substrate and then fired in a reducing atmosphere at 1200 ° C to prepare an electrode. Then, the electric conductivity of each electrode was measured.

The electrical conductivity measurement results are shown in Table 2.

[Table 2]

Referring to Table 2, it can be seen that the electrode using the nickel nano-powder according to Examples 1 and 2 has a theoretical conductivity close to that of the theoretical nickel (14.30 MSm ^-1 ).

However, in the case of the electrode using the nickel nano powder according to Comparative Example 1, the electric conductivity was relatively low as compared with Examples 1 to 4. In the case of Comparative Example 3 in which the content of the dopant oxide in the oxide cell was more than 70% by weight, and Comparative Example 4 in which the oxide cell thickness was more than 20 nm, the electric conductivity was the lowest, It can be said that the result is not completely removed.

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, It is to be understood that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

S110: Ni vapor formation step
S120: Ni powder formation step
S130: Classification step
210: Nickel
220: dopant
230: Suspension
240: Ni powder base material

Claims (11)

delete An average particle diameter of 40 to 120 nm and comprising an Ni core and an oxide shell surrounding the Ni core,
Wherein the oxide shell is made of an oxide of a dopant selected from silicon, titanium and aluminum and nickel oxide, wherein the Ni core has an average particle diameter of 30 to 100 nm, the oxide shell has a thickness of 10 to 20 nm, Wherein the oxide shell is all crystalline and the oxide shell functions as a heat shrinkage barrier so that the shrinkage starting temperature of the powder is at least 600 ° C and the shrinkage rate at 25 ° C to 1300 ° C is at most 10%.
3. The method of claim 2,
The oxide shell
Wherein the oxide of the dopant is 10 to 70% by weight, and the nickel oxide is 30 to 90% by weight.
delete delete delete (a) introducing a Ni powder base material into a high-temperature plasma region of 8000 to 12000 占 폚, and vaporizing the Ni powder base material by high-temperature plasma to form Ni vapor;
(b) contacting the Ni vapor with a cooling gas to form a Ni powder; And
(c) Classifying Ni powder to obtain Ni nanopowder having an average particle diameter of 40 to 120 nm,
Wherein the Ni powder base material contains a dopant selected from the group consisting of silicon, titanium and aluminum, and an inert gas and an oxygen-containing gas are contained in the cooling gas, wherein an inert gas and an oxygen- The Ni core is formed to have an average particle size of 30 to 100 nm in the step (b), an oxide shell made of an oxide of a dopant and a nickel oxide is formed on the surface to a thickness of 10 to 20 nm, Wherein the shells are all crystalline. ≪ RTI ID = 0.0 > 11. < / RTI >
8. The method of claim 7,
In the step (b), the oxide of the dopant is 10 to 70% by weight and the nickel oxide is 30 to 90% by weight.
delete 8. The method of claim 7,
The Ni powder base material
A method for producing Ni nanopowder, which comprises preparing a suspension of nickel and a dopant dispersed in a solvent, and doping a part of the nickel with a dopant.
8. The method of claim 7,
The Ni powder base material
70 to 95% by weight of nickel and 5 to 30% by weight of a dopant.

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