KR20180082760A - Manufacturing method using two-step reduction for iron metal powders and iron metal powders by the same - Google Patents

Abstract

The present invention relates to a metal powder manufacturing method. More particularly, the present invention relates to a method for producing high-purity porous metal powder having a coral shape by applying primary and secondary reduction processes, and metal powder produced by the same. The coral-shaped high-purity porous metal powder manufacturing method according to the present invention includes: a first step of introducing an alumina crucible containing iron oxide powder into a furnace; a second step of preparing mixed powder by primarily reducing the iron oxide powder by using a mixed gas in which 5 to 10 vol% of hydrogen is mixed with argon; and a third step of preparing metal powder by secondarily reducing the mixed powder by using a mixed gas of argon and 10-20 vol% of hydrogen.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing iron powder by a first and second reduction process,

More particularly, the present invention relates to a method for producing a high purity porous iron powder having a coral shape by applying primary and secondary reduction processes, and an iron powder produced thereby.

A thermal cell is a cell that does not operate normally while the electrolyte is in a solid salt state and does not operate, and when necessary, it is heated by using an igniter to melt the electrolyte and operate at a high temperature.

The heat source of the thermal battery is composed of fuel and oxidizer. Among them, a metal is mainly used as a fuel, and a metal which is a fuel at the time of combustion reacts with a mixed oxidant to release a large amount of energy as a metal oxide, and the energy necessary for melting the solid electrolyte of the thermal battery to provide.

The above-mentioned heat source is composed of a mixture containing iron (Fe) powder and potassium perchlorate (KClO ₄ ) powder, and the mixture is molded into a pellet shape.

Generally, iron has a spherical shape, but iron powder used as a heat source of a thermal battery has a coral shape due to agglomeration of particles, so that contact with oxygen required for ignition is smooth and excellent ignition characteristics are exhibited.

Generally, iron powders are prepared by using iron oxide powder as a precursor and reducing it with a hydrogen (H ₂ ) gas having a purity of about 100%. This method has a high risk of process due to high purity hydrogen gas However, there is a great difficulty in controlling iron powder to have a coral shape.

The matters described in the background art are intended to aid understanding of the background of the invention and may include matters which are not known to the person of ordinary skill in the art.

Korean Patent Publication No. 10-2016-0141200

In order to solve the problems as described above, the present invention provides a method for manufacturing a high purity porous iron powder having a coral shape by applying a primary gas and a secondary reduction process by increasing the process safety by using a mixed gas, Iron powder. ≪ / RTI >

According to an aspect of the present invention, there is provided a method of manufacturing a porous iron powder having a coral shape, the method including: a first step of introducing an alumina crucible containing iron oxide powder into an electric furnace; A second step of preparing a mixed powder by first reducing the iron oxide powder by using a mixed gas in which 5 to 10 vol% of hydrogen is mixed with argon; And a third step of preparing iron powder by secondary reduction of the mixed powder by using a mixed gas of argon and 10-20 vol% of hydrogen.

In addition, in the first step, the iron oxide powder is characterized in that at least one of iron oxide (FeO), ferric trioxide (Fe ₂ O ₃ ), iron ( _III ) oxide (Fe ₃ O ₄ ), and FeOOH is mixed.

Further, in the first step, the iron oxide powder is contained in the alumina crucible at a height of 0.5 mm or less.

In the second step and the third step, the reduction temperature during the first reduction and the second reduction is 600 to 800 ° C, and the reduction time is 1 to 2 hours.

The mixed powder is characterized in that at least one of iron monoxide (FeO), ferric trioxide (Fe ₂ O ₃ ), iron ( _III ) oxide (Fe ₃ O ₄ ), and FeOOH is mixed with iron (Fe).

In addition, after the third step, a fourth step of stabilizing the iron powder by using an inert gas; And a fifth step of sieving the stabilized iron powder in a vibrating manner to adjust the particle size.

On the other hand, the iron powder produced by the above-mentioned production method is mixed with potassium perchlorate (KClO ₄ ) powder and is applied to the thermal battery.

The present invention has an effect that the produced high-purity porous iron powder can be controlled to have a coral shape by applying the primary and secondary reduction processes using mixed gases having different contents of hydrogen. The iron powder thus produced has excellent ignition characteristics by being in contact with oxygen smoothly, and as a result, it can be effectively applied to a thermal battery as a heat source.

Further, by using a mixed gas of argon and hydrogen, there is an effect in terms of process safety and economy from the conventional process using high purity hydrogen gas.

1 is a flowchart of a method for manufacturing iron powder according to an embodiment of the present invention.
2 is a schematic diagram showing a reduction process of a comparative example.
3 is a schematic diagram showing the reduction process of the embodiment.
4- (a) is a graph of XRD results of the iron oxide powder before the first reduction.
4- (b) is a graph of XRD results of mixed powders prepared after the first reduction of the examples.
4- (c) is a graph of XRD results of the iron powder produced after the second reduction of the example.
4- (d) is a graph showing the XRD results of the iron powder produced after the first reduction of the comparative example.
5- (a) is a SEM photograph of the iron oxide powder before the first reduction.
5 (b) is a SEM photograph of the mixed powder produced after the first reduction of the example.
5- (c) is an SEM photograph of the iron powder produced after the second reduction of the example.
5 (d) is a SEM photograph of the iron powder produced after the reduction process of the comparative example.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings in order to fully understand the present invention. The embodiments of the present invention can be modified in various forms, and the scope of the present invention should not be construed as being limited to the embodiments described in detail below. The present embodiments are provided to enable those skilled in the art to more fully understand the present invention. Therefore, the shapes and the like of the elements in the drawings can be exaggeratedly expressed to emphasize a clearer description. It should be noted that the same components are denoted by the same reference numerals in the drawings. Detailed descriptions of well-known functions and constructions which may be unnecessarily obscured by the gist of the present invention are omitted.

Also, as used herein, the terms " consisting of, " " consisting of, " or " comprising ", are not necessarily to be construed as necessarily including the various elements or steps described in the specification, Some of the elements or some of the steps may not be included, or may be interpreted to include additional elements or steps.

FIG. 1 is a flow chart of a method of manufacturing iron powder according to an embodiment of the present invention. As shown in FIG. 1, the method of manufacturing iron powder according to the present invention includes a first step (S110) of charging an alumina crucible containing iron oxide powder into an electric furnace A second step (S120) of producing a mixed powder by first reducing the powder by using a mixed gas in which 5 to 10 vol% of hydrogen is mixed with argon, and mixing the prepared mixed powder with 10 to 20 vol% of hydrogen And a third step (S130) of producing an iron powder by performing a secondary reduction using a mixed gas obtained by using the mixed gas.

Hereinafter, each step of the method for producing iron powder of the present invention will be described in more detail.

Wherein the iron oxide powder to be used in step 1 (S110) shall mean that the powder-form having at least one oxygen atom bonded oxide composition on iron (Fe), relatively the amount of oxygen low work iron oxide (FeO), iron sesquioxide (Fe ₂ O ₃ ), iron ( _III ) oxide (Fe ₃ O ₄ ) and FeOOH, but it is not limited to these and may further include those having the formula of Fe _x O _y . (Wherein x may be any one of 1 to 3 and y may be any one of 1 to 4, but is not limited thereto).

The shape of the iron oxide powder is preferably acicular, but is not limited thereto. The iron oxide powder having a shape including a spherical shape, a cubic shape, a rod shape, a flake shape, Available.

The larger the particle size of the iron oxide powder is, the more advantageous it is, and the more preferable it is 5 to 10 탆. However, the iron oxide powder having a more various particle size can be used.

Meanwhile, the iron oxide powder is put into a furnace such as an electric furnace or a tube furnace capable of controlling the atmosphere by being contained in an alumina crucible (S110). At this time, the iron oxide powder is added to the inside surface of the alumina crucible The uniformity of the iron oxide powder located on the upper side and the iron oxide powder located on the lower side after the reduction process are lowered. Therefore, it is preferable that the iron oxide powder be as thin and wide as possible at a height of 0.5 mm or less from the inner bottom surface of the alumina crucible.

After the first step (S110) in which the iron oxide powder is placed in the alumina crucible, the mixture is continuously flowed using a mixed gas of argon (Ar) and hydrogen (H ₂ ) And the temperature is increased at a rate of about 5 ° C / min. When the set temperature is reached at 600 ° C to 800 ° C, the iron oxide powder is firstly reduced by keeping it for 1 to 2 hours. Then, the temperature is lowered to room temperature again at a rate of about 5 deg. C / min (S120).

At this time, the conditions such as the content of hydrogen, the reduction temperature and the reduction time of the mixed gas used for the first reduction in the second step (S120) are such that the partial reduction of the iron oxide powder is not performed at the first reduction Through this, a mixed powder in which iron (Fe) powder formed by reducing iron oxide powder after the first reduction and mixed with unreduced iron oxide powder is produced.

Thus, the powder mixture is first subject to the iron oxide powder used in step 1 (S110). However, preferably the first one of iron oxide (FeO) is not reduced to the reduction, iron sesquioxide (Fe ₂ O _3), sasanhwasam iron (Fe ₃ O ₄ ) and FeOOH and at least one powder of iron (Fe) powder are mixed.

It is preferable that the mixed powder has an iron powder content of about 80 vol% or more with respect to the total volume of the mixed powder, but is not limited thereto.

The reason for manufacturing the mixed powder in which the iron powder and the iron oxide powder are mixed by making the partial reduction without causing any reduction of the iron oxide powder in the second step (S120) In order to form a network among the particles.

More specifically, it is preferable that the mixed gas used for the first reduction is a mixed gas of 5 to 10 vol% of hydrogen mixed with argon. If the hydrogen content is less than 5 vol%, the content of hydrogen is too low, If the content of hydrogen is more than 10 vol%, the content of hydrogen is too high, and most of the iron oxide powder may be reduced. This is because it is difficult to produce the mixed powder as described above.

Similarly, when the reduction temperature is less than 600 ° C. and the reduction time is less than 1 hour in the first reduction, the temperature and time necessary for the partial reduction are not supplied, so that the iron oxide powder may not be substantially reduced. When the reduction temperature is higher than 800 ° C. and the reduction time is more than 2 hours, the iron oxide powder is most likely to be reduced, which is not preferable for producing the mixed powder. Therefore, the reduction temperature is 600 ° C. to 800 ° C., Most preferably, the time is 1 to 2 hours.

Step 2 (S120) since the production of mixed powders to have to re-use the mixed gas mixture of argon (Ar) and hydrogen (H ₂₎ while still flowing them and create an atmosphere to which the mixed powder position, about 5 ℃ / min to reach a set temperature of 600 to 800 DEG C, and the mixed powder is subjected to second reduction by maintaining the temperature for 1 to 2 hours. Thereafter, low-temperature cooling is performed again at a rate of about 5 [deg.] C / min (S130).

The conditions such as the content of hydrogen, the reduction temperature and the reduction time of the mixed gas used for the second reduction in the third step (S130) are such that the mixed powder is completely reduced by the iron (Fe) powder during the secondary reduction, (Fe) powder having a coral shape after the secondary reduction is produced by controlling the corundum shape by preventing abrupt shape deformation and agglomeration.

More specifically, it is preferable that the mixed gas used for the secondary reduction is a mixed gas in which 10-20 vol% of hydrogen is mixed with argon. If the hydrogen content is less than 10 vol%, the iron oxide powder contained in the mixed powder is completely If the content of hydrogen is more than 20 vol%, the risk of the process becomes high. In addition, even if the content of hydrogen is less than 20 vol%, the powder of iron is completely reduced and the iron powder having high purity can be produced.

Similarly, when the reduction temperature is less than 600 ° C. and the reduction time is less than 1 hour in the second reduction, the iron oxide powder contained in the mixed powder is not supplied with the temperature and time necessary for complete reduction of the iron oxide powder, . When the reduction temperature is more than 800 ° C and the reduction time is more than 2 hours, rapid deformation and agglomeration may occur. In addition, even when the reduction temperature is less than 800 ° C and the reduction time is less than 2 hours, The reduction temperature is preferably 600 to 800 ° C. and the reduction time is most preferably 1 to 2 hours because the efficiency of the process deteriorates in view of cost and time.

A third step of manufacturing an iron powder (S130) After that, from a temperature below about 50 ℃ argon (Ar), nitrogen (N ₂₎ by using an inert gas while still flowing it at room temperature the above-prepared iron powder slowly, such as (S140) for stabilizing the iron powder for a predetermined period of time by cooling it, and recovering the iron powder that has been cooled and stabilized. The iron powder is rapidly transferred to a glove box and then sieved by a device ) May be adjusted to be relatively uniform or may be further divided into particle sizes (S150).

Hereinafter, the present invention will be described in more detail with reference to Comparative Examples and Examples. However, the following Comparative Examples and Examples are for illustrative purposes only, and the scope of the present invention is not limited thereto.

Comparative Example

1 g of iron oxide powder having a pellet shape and having a purity of 99.9% or more and FeOOH was placed in a rectangular parallelepiped alumina crucible with a thickness of 0.3 to 0.4 mm, and this was put into a tube furnace having a quartz tube. Then, as shown in FIG. 2, the mixture was heated at a rate of 5 ° C / min while flowing a mixed gas containing 20% by volume of hydrogen in argon, and then subjected to a primary reduction at 700 ° C for 2 hours. Thereafter, the temperature was lowered at a rate of 5 [deg.] C / min. Then, when the temperature was lowered to 50 ° C, argon gas was lowered to room temperature, cooled and stabilized. After that, the powder was transferred to a glove box and sieved by a vibrating method to adjust the particle size to finally produce iron powder.

Example

1 g of an iron oxide powder having a pellet-shaped purity of 99.9% or more and FeOOH was placed in a rectangular parallelepiped alumina crucible in a thickness of 0.3 to 0.4 mm, and this was put into a tube furnace having a quartz tube (S110). Thereafter, as shown in FIG. 3, the mixture was heated at a rate of 5 ° C / min while flowing a mixed gas containing 5 vol% of hydrogen in argon, and then subjected to a primary reduction at 700 ° C for 1 hour. Thereafter, the temperature was lowered to room temperature at a rate of 5 DEG C / min and then cooled (S120). Thereafter, the mixture was heated at a rate of 5 ° C / min while flowing a mixed gas containing 20vol% of hydrogen in argon, and then subjected to a secondary reduction at 700 ° C for 2 hours. Thereafter, the temperature was lowered at a rate of 5 deg. C / min and then cooled (S130). Then, when the temperature was lowered to 50 ° C., argon gas was lowered to room temperature, cooled and stabilized (S140), and then transferred to a glove box and sieved by a vibration method to adjust the particle size to finally produce iron powder.

4- (a) is a graph of the XRD results of the iron oxide powder before the first reduction of the comparative example and the example, Fig. 4- (b) is a graph of the XRD result of the mixed powder produced after the first reduction of the embodiment, (c) is a graph of XRD results of the iron powder produced after the second reduction of the embodiment, and Fig. 4- (d) is a graph of XRD results of the iron powder produced after the first reduction of the comparative example.

4, it can be seen that the iron oxide powder was completely reduced after the first reduction to produce pure iron powder. On the other hand, in the example, after the first reduction, a mixed powder containing iron powder and iron oxide powder was partially produced, and the iron oxide powder remaining after the second reduction was reduced to produce pure iron powder.

The comparative examples and the examples are the same in that iron powder is produced through the reduction process as a result, but the difference can be confirmed from the following results.

5- (a) is an SEM photograph of the iron oxide powder before the first reduction of the comparative example and the example, Fig. 5- (b) is an SEM photograph of the mixed powder produced after the first reduction of the embodiment, ) Is an SEM photograph of the iron powder prepared after the second reduction of the embodiment, and FIG. 5- (d) is an SEM photograph of the iron powder produced after the first reduction of the comparative example.

It can be seen from the results of FIG. 5 that the shape of the iron powder prepared in the examples is closer to the coral shape than the comparative example. In other words, it can be seen that the iron powder prepared in the Examples is closer to the coral shape than the iron powder produced in the comparative example, having a large aspect ratio, which means a ratio of the lengthwise length to the lengthwise length have.

As compared with the comparative example, the iron powder prepared in the examples had a coral shape, and the iron powder was reduced in the first order and the second order twice without being reduced at the first time. More specifically, it is possible to form a network of particles by preparing a mixed powder in which iron powder and iron oxide powder are mixed using a mixed gas having a low hydrogen content in the first reduction, Gas is used for complete reduction and particle necking is smoothly performed. Thus, a porous iron powder having a high aspect ratio and a high specific surface area, which is closer to the corrugated shape, is manufactured Could.

water division Physicochemical properties One Fe Purity (%) > 98 2 Fe element (%) 95.45 3 Fe powder shape Porous coral shape 4 Specific surface area (m ² / g) 0.64 5 Particle size <50 μm, 80% min
> 100 μm, 1% max 6 Apparent density (g / cm ³ ) 0.93

Table 1 shows the physical and chemical properties of the iron powders prepared in the examples, and it was confirmed that the iron powders of the present invention had similar performances as those of the foreign-used products having excellent performance.

The high-purity porous iron powder having a coral shape produced by the iron powder production method of the present invention as described above is mixed with potassium perchlorate (KClO ₄ ) powder as a heat source of heat battery with smooth contact with oxygen and excellent ignition property , The performance of the thermal battery can be enhanced.

Further, by using a mixed gas of argon and hydrogen, there is an effect in terms of process safety and economy from the conventional process using high purity hydrogen gas.

The iron powder manufacturing method using the first and second reduction processes of the present invention and the iron powder manufactured by the method of the present invention can be easily carried out by a person having ordinary skill in the art to which the present invention belongs The present invention is not limited to the above-described embodiments and the accompanying drawings, and thus the scope of the present invention is not limited thereto. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims. It will be apparent to those skilled in the art that various substitutions, modifications and variations are possible within the scope of the present invention, and it is obvious that the parts easily changeable by those skilled in the art are included in the scope of the present invention .

Claims (7)

A first step of introducing an alumina crucible containing iron oxide powder into a furnace;
A second step of preparing a mixed powder by first reducing the iron oxide powder by using a mixed gas in which 5 to 10 vol% of hydrogen is mixed with argon;
And a third step of preparing iron powder by secondary reduction of the mixed powder by using a mixed gas of argon and 10 to 20 vol% of hydrogen. [3] The method of claim 1, Powder. The method according to claim 1,
In the first step,
Wherein the iron oxide powder is a mixture of one or more of iron monoxide (FeO), ferric trioxide (Fe ₂ O ₃ ), iron ( _III ) tetraoxide (Fe ₃ O ₄ ) and FeOOH, Method of manufacturing iron powder. The method according to claim 1,
In the first step,
Wherein the iron oxide powder is contained in the alumina crucible at a height of 0.5 mm or less. The method according to claim 1,
In the second step and the third step,
Wherein the reduction temperature during the first reduction and the second reduction is 600 to 800 ° C. and the reduction time is 1 to 2 hours. The method according to claim 1,
In the second step,
The mixed powder is one of iron oxide (FeO), iron sesquioxide (Fe ₂ O _3), sasanhwasam iron (Fe ₃ O ₄₎ and at least one of FeOOH as iron (Fe) of high purity having a coral-like, characterized in that the mixed &Lt; / RTI &gt; The method according to claim 1,
After the third step,
A fourth step of stabilizing the iron powder by using an inert gas; And
And a fifth step of sieving the stabilized iron powder in an oscillating manner to adjust the particle size of the iron powder. The iron powder according to any one of claims 1 to 6, wherein the iron powder is mixed with potassium perchlorate (KClO ₄ ) powder and applied to a thermal battery.

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