KR101446840B1 - Manufacturing method for iron powder - Google Patents

Abstract

The present invention relates to a method for producing iron powder for a heat-generating heat source, comprising the steps of: preparing a solution containing iron by adding and stirring a solution of an iron metal compound to a fatty acid solvent; heating the solution with stirring to form a uniform iron precursor Preparing iron oxide powder by pyrolyzing the iron precursor in the air, and reducing iron oxide powder in a reducing atmosphere to obtain zero valent iron nano powder. . The zero valent iron powder produced by the above-described method can obtain nano-sized uniform particles, does not contain impurities, is excellent in ignition characteristics, and forms a compact having sufficient space for oxygen to be inserted during molding.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for manufacturing iron powder,

More particularly, the present invention relates to a method for producing iron powder for manufacturing a heat source for activating a thermocouple, which is a kind of military or industrial non-accumulator, .

Since most of the development of thermocouples has been applied to packaging, there are very few reports on the results of research on thermoelectric materials. In addition, studies on the production of metal powders have focused on the microfabrication and sphering of powders due to the characteristics of the domestic or global industry, and therefore there is a report about the powder synthesis technology having some special characteristics such as coral shape There is no domestic technology.

It is difficult to develop and produce iron powder suitable as an exothermic material for thermal cells through the liquid phase and solid phase processes applied to synthesize most metal powders. Conventional powder synthesis techniques have focused on miniaturization and sphering, and because iron used as a thermal conductive material is molded into a pellet, spherical and prismatic particles have a molding characteristic such as filling rate and breaking strength . In order to increase the purity of the iron powder, reduction treatment is indispensable. In this process, grain growth occurs, and the thickness of the grain structure is increased to decrease the surface area.

It is preferable that iron powder used as a heat source of a thermal battery has coral-shaped particles having a large specific surface area. In the synthesis of iron powder used as a heat-source of heat energy, the conventional general metal powder manufacturing processes include shape, size, ignition sensitivity, It is difficult to satisfy complex and various required characteristics such as burning rate, arrival temperature, heat quantity, purity, specific surface area, molding strength, density and microstructure.

According to embodiments of the present invention, there is provided a method of manufacturing iron powder for manufacturing a heat source for activating a thermocouple, which is a kind of military or industrial non-storage battery.

The method of manufacturing the nano-scale zero valent iron powder according to the embodiments of the present invention includes the steps of preparing an iron-containing solution by adding and stirring an iron metal compound to a fatty acid solvent, heating the iron- Forming an iron precursor; thermally decomposing the iron precursor in the air to prepare an iron oxide powder; and reducing the iron oxide powder in a reducing atmosphere to obtain a zero valent iron nano powder.

According to one aspect, the fatty acid may be a mixture of one or more selected from saturated or unsaturated fatty acids.

According to one aspect of the present invention, the iron metal compound may be at least one selected from the group consisting of iron nitrate, iron nitrate, iron chloride, iron hydrate, iron oxide and iron oxalate. Here, the amount of the iron metal compound may be 10 wt% or more to 60 wt% or less with respect to the iron-containing solution. Further, in the step of producing the iron-containing solution, the iron-containing solution may be heated and stirred at 80 ° C for 30 minutes to remove moisture in the solution.

According to one aspect, in the step of forming the iron precursor, the iron-containing solution is heated while stirring at 80 ° C to 300 ° C. The heating time of the iron-containing solution in the iron precursor forming step is 0.1 to 24 hours.

According to one aspect, the step of forming the iron oxide powder may further include washing and drying the iron precursor. Alternatively, in the step of forming the iron oxide powder, the iron precursor may be burned without water so as to produce an iron oxide powder. The pyrolysis step in the step of forming the iron oxide powder is carried out at a temperature of 400 ° C. to 800 ° C. for 1 to 24 hours in an air atmosphere.

According to one aspect, the reducing treatment temperature in the reducing treatment is 500 ° C to 800 ° C. The reducing gas may be a mixed gas obtained by mixing H2 gas with an inert gas selected from N2 and Ar.

As described above, according to the embodiments of the present invention, a high-purity iron powder having no impurity content can be produced, and the iron powder thus produced can play an effective role as a heat source for thermal battery.

FIG. 1 is a photograph showing the surface characteristics of iron powder produced by the method of manufacturing iron powder according to an embodiment of the present invention, and is a photograph of the surface of oxidized powder in an air atmosphere.
FIG. 2 is a photograph showing the surface characteristics of the iron powder produced by the method for producing iron powder according to an embodiment of the present invention, which is a surface photograph after heat treatment in air and heat treatment in a reducing atmosphere.
FIG. 3 is a graph showing crystal characteristics of iron powder produced by the method of manufacturing iron powder according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments will be described in detail with reference to the accompanying drawings, but the present invention is not limited to or limited by the embodiments. In describing the embodiments, a detailed description of well-known functions or constructions may be omitted so as to clarify the gist of the present invention.

Hereinafter, a method for producing a nano-sized zero valent iron powder according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3. FIG.

First, an iron-containing solution is prepared by mixing an iron compound in the form of a metal salt with a fatty acid solvent, which is formed of a mixture of one or more kinds selected from saturated fatty acids and unsaturated fatty acids.

Specifically, a fatty acid is first added to a reactor and heated to 80 ° C. to dissolve the fatty acid. Then, the iron compound in the form of a metal salt is added thereto and stirred for 30 minutes to remove moisture in the solution to prepare a uniform iron-containing solution.

For example, as the iron compound in the form of a metal salt, there may be used iron nitrate, iron nitrate, iron chloride, iron hydrate, iron oxide, iron oxalate, etc. These may be used alone or in combination of two or more.

Saturated fatty acids and unsaturated fatty acids are used as fatty acids. The fatty acid plays a role as a solvent and a reducing agent in the production of iron powder, and generates a gas inside when the iron-containing solution is heated to make the iron powder porous. Here, saturated fatty acids and unsaturated fatty acids are used as the fatty acid, and there is no limitation in the kind. For example, as the saturated fatty acid, any one or a combination of two or more selected from lauric acid, myristic acid, palmitic acid and stearic acid may be used. As the unsaturated fatty acid, any one or a combination of two or more selected from oleic acid, linoleic acid and linoleic acid may be used. The fatty acids may be used alone or in combination.

The fatty acid is an important parameter for the shape of the iron oxide powder in the pyrolysis step described later. Preferably, the iron compound may comprise from 10% to 60% by weight of the total iron fortified solution. If the amount of the iron compound exceeds 60% by weight, the production of the iron oxide powder is difficult, and if the amount of the iron compound is less than 10% by weight, the manufacturing cost may increase.

Next, the iron-containing solution prepared as described above is heated while stirring to form a uniform iron precursor.

The iron-containing solution prepared above is heated by stirring in a stirrer-capable reactor for a certain period of time to produce an iron precursor. The heating temperature is preferably 80 ° C to 300 ° C, and the mixture is heated with stirring for 0.1 to 24 hours. Here, when the temperature is less than 80 ° C or less than 0.1 hour in stirring and heating, complete formation of the precursor may be difficult. If the temperature exceeds 300 ° C or the time exceeds 24 hours, the manufacturing cost may increase .

And, while the iron-containing solution is heated while stirring, the iron oxide particles have a porous property due to the gases generated as the fatty acid contained in the iron-containing solution is decomposed by heating at a high temperature.

Next, the iron precursor which has been stirred and heated is pyrolyzed to produce an iron oxide powder.

Here, in order to form the iron oxide powder, the iron precursor may be washed with water and dried to form an iron oxide powder. Alternatively, the step of washing and drying the iron precursor may be omitted, and the iron precursor itself may be burned to form the iron oxide powder.

Drying and pyrolysis of the iron precursor takes place in an air atmosphere. At this time, the temperature for pyrolysis is preferably 400 ° C. to 800 ° C., and it is preferable to carry out heat treatment for 30 minutes to 24 hours. If the pyrolysis temperature is less than 400 ° C or the pyrolysis time is less than 30 minutes, complete decomposition of the precursor may be difficult. If the temperature exceeds 800 ° C or the time exceeds 24 hours, the production may be reduced.

The iron oxide powder thus obtained is subjected to reduction treatment in a reducing atmosphere to obtain nano-sized zero valence iron powder.

A mixed gas obtained by mixing an inert gas such as Ar or N 2 with H 2 gas at a high temperature can be used for treating the iron oxide powder with a reducing gas atmosphere. The reduction temperature is preferably 500 ° C to 800 ° C, and the reduction time is preferably 30 minutes to 24 hours. The number of times of reduction is preferably two or more times. Here, when the reduction temperature is less than 500 ° C or the reduction treatment time is less than 30 minutes, complete reduction to iron powder may not occur. When the reduction temperature is higher than 800 ° C, excessive aggregation of particles occurs, which is not preferable. When the reduction treatment time is 24 hours or more, it is not economical.

The nano-sized iron powder thus produced is a high-purity iron powder having no impurity content and can play an effective role as a heat source of the heat battery.

Example 1

A method for producing nano-sized iron powder from iron nitrate using oleic acid will be described.

First, in order to prepare an iron-containing solution, 40 g of oleic acid is added to a three-necked reactor and heated at 80 DEG C to dissolve oleic acid. 80 g of iron nitrate tetrahydrate was added thereto and stirred for 30 minutes to remove moisture in the solution to prepare a uniform iron-containing solution.

Next, the temperature of the reactor was raised to 120 ° C, stirred at a constant rate for 2 hours to proceed the reaction, and cooled to prepare an iron precursor. The prepared iron precursor was washed several times with a certain solvent and then dried in a vacuum oven at 80 ° C for 5 hours.

Next, the dried iron precursor is oxidized in a box furnace at 800 DEG C for 2 hours in an air atmosphere to produce iron oxide.

The iron oxide thus produced is subjected to a reduction treatment under a mixed gas of H2 / N2 to obtain nano-sized iron powder. At this time, the reduction treatment temperature was 700 ° C and the reduction treatment time was 4 hours.

FIG. 1 is a photograph showing the surface characteristics of iron powder produced by the method of manufacturing iron powder according to an embodiment of the present invention, wherein the iron powder prepared from oleic acid and nitrate iron is oxidized in an air atmosphere. And FIG. 2 is a photograph showing the surface characteristics of the iron powder produced by the method for producing iron powder according to an embodiment of the present invention, wherein iron powder prepared from oleic acid and nitrate iron is heat treated in a reducing atmosphere after air heat treatment It is a surface photograph. Referring to FIGS. 1 and 2, the iron particles prepared using a fatty acid solvent are nano-sized and have a coral shape. Therefore, it can be seen that a nano-sized and coral-shaped iron powder having a large specific surface area can be obtained as a heat source for heat transfer.

3 is a graph showing crystal characteristics of iron powder produced according to the change of reaction time according to an embodiment of the present invention. It was confirmed that the iron powder showed only iron crystal peaks at a reaction time of 30 minutes or more without a peak of impurities.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. For example, it is to be understood that the techniques described may be performed in a different order than the described methods, and / or that components of the described systems, structures, devices, circuits, Lt; / RTI > or equivalents, even if it is replaced or replaced.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

Claims (12)

Adding an iron metal compound to a fatty acid solvent and stirring to prepare an iron-containing solution;
Heating the iron-containing solution at 80 ° C to 300 ° C with stirring for 0.1 hour to 24 hours to form a uniform iron precursor;
Pyrolyzing the iron precursor in air to produce an iron oxide powder; And
Reducing the iron oxide powder in a reducing atmosphere to obtain a zero valent iron nano powder;
Wherein the ferrous iron powder is heated to a temperature of about < RTI ID = 0.0 > 300 C < / RTI >
The method according to claim 1,
Wherein the fatty acid is a mixture of at least one selected from saturated or unsaturated fatty acids.
The method according to claim 1,
Wherein the metal iron compound is at least one selected from the group consisting of iron nitrate, iron nitrate, iron chloride, iron hydrate, iron oxide and iron oxalate.
The method according to claim 1,
Wherein the amount of the iron metal compound is not less than 10% by weight and not more than 60% by weight based on the iron-containing solution.
The method according to claim 1,
Wherein the step of preparing the iron-containing solution comprises heating and stirring the iron-containing solution at 80 DEG C for 30 minutes to remove moisture in the solution.
delete delete The method according to claim 1,
Wherein the forming of the iron oxide powder further comprises washing and drying the iron precursor.
The method according to claim 1,
Wherein the iron oxide powder is formed by burning the iron precursor without water washing to produce iron oxide powder.
The method according to claim 1,
Wherein the pyrolysis step in the step of forming the iron oxide powder is carried out in an air atmosphere at a temperature of 400 ° C to 800 ° C for 1 to 24 hours in an air atmosphere.
The method according to claim 1,
Wherein the reducing treatment temperature during the reducing treatment is 500 ° C to 800 ° C.
The method according to claim 1,
Wherein the reducing gas used in the reduction treatment is a mixed gas obtained by mixing an H2 gas and an inert gas selected from N2 and Ar.

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