KR20150022217A - Method for producing oxide dispersion mixed powder using polyvinyl alcohol and oxide dispersion mixed powder thereby - Google Patents

Abstract

The present invention relates to a method for producing oxide dispersed composite alloy powders and oxide dispersed composite alloy powders produced thereby. More specifically, provided are the method for producing oxide dispersed composite alloy powders including: a step (step 1) for dissolving first metallic salts including nickel salt for nickel-based alloy powders and second metallic salts including a raw metal for metal oxide in distilled water; a step (step 2) for forming precursor sol by adding polyvinyl alcohol (PVA) solution in the mixed solution of the step 1; a step (step 3) for forming precursor gel by stirring and drying the precursor sol of the step 2; a step (step 4) for heat-treating the precursor gel of the step 3 under a reduction atmosphere, and the oxide dispersed composite alloy powders produced thereby. According to the present invention, the method for producing oxide dispersed composite alloy powders can easily form a metal alloy and produce alloy powders in a low temperature range by adding polyvinyl alcohol with large molecular weight, as a fixing material of metal element, in the nickel-based alloy and metal oxide precursor solution, and also can synthesize high purity and porous alloy powders with a nano-crystal structure in a simple process for heat-treating the mixed solution under a dry and reduction atmosphere. The nickel-based oxide dispersed composite alloy powders manufactured thereby can be provided at lower costs by being produced in a simpler production process than the conventional method, thereby being supplied as a structural material of a nuclear reactor.

Description

TECHNICAL FIELD The present invention relates to a method for producing an oxide-dispersed composite alloy powder using polyvinyl alcohol (PVA) and an oxide-dispersed composite alloy powder produced thereby,

The present invention relates to a process for producing an oxide-dispersed composite alloy powder and an oxide-dispersed composite alloy powder produced thereby, and more particularly to a process for producing an oxide-dispersed composite alloy powder using polyvinyl alcohol (PVA) Dispersed composite alloy powder.

In order to realize a future high-efficiency energy generation system, an energy generating device capable of high-efficiency and long-time operation under high temperature conditions is required. In order to secure a core material component having a soundness that can be safely operated even under such operating conditions very important.

 For this purpose, basic material properties development research is needed. In particular, the development of materials for future nuclear power commercialization takes considerable time, and practical manufacturing know-how is an important technology with national competitiveness.

Nuclear advanced countries are investing in materials development researches of a considerable scale through international cooperation programs to develop core materials of future nuclear power systems. In some countries, Oxide alloyed oxide (ODS) alloy has been produced. In the case of ORNL, the US National Institute of Advanced Industrial Science and Technology (ORNL) Development has recently been carried out. Some domestic research institutes have conducted researches on manufacturing and characterizing test alloys with a level of several hundred grams through mechanical alloying such as tungsten base (W-base), MoSi ₂ and Al-Ti-Si alloys .

On the other hand, an oxide dispersion strengthened (ODS) method of dispersing oxides in a matrix is known to be a particularly useful method at high temperatures. This is because the oxide is stable even at a relatively high temperature and exhibits a dispersion strengthening effect. These ODS alloys maintain high strength even at high temperatures and thus can be usefully used in various fields.

The oxide dispersion strengthening is generally performed through a mechanical alloying method in which a raw alloy powder and an oxide powder are repeatedly pulverized in a ball mill. By the mechanical alloying, the raw alloy powder and the oxide powder Very uniformly mixed, and the oxide is pulverized to several nanometers. The oxide dispersion strengthened alloy powder is then subjected to a degassing step, a high temperature sintering step, a hot isostatic pressing (HIP) forming step, a hot and cold forming step, a heat treatment step, ODS < / RTI >

As a conventional technique related to the production of the oxide-dispersed reinforced alloy, the Korean Registered Patent No. 10-0694335 discloses an aluminum oxide dispersion strengthened copper alloy powder and a manufacturing method thereof. Concretely, the powders of copper, copper and aluminum are charged into a mixer and stirred. Then, the agitated raw materials are charged into a ball-mill and sealed. Mechanical energy is applied by a ball-mill in an inert atmosphere, Wherein the copper-aluminum alloy powder is formed from a copper-aluminum alloy powder, characterized in that the copper-aluminum alloy powder is a powder of a copper-aluminum alloy powder. A manufacturing method has been disclosed.

However, when the powder is produced by the mechanical alloying method as described above, it is necessary to control the atmosphere at a high level, and it is difficult to control the composition of the powder, and a lot of procedures and time are required in the manufacturing process.

Accordingly, the inventors of the present invention have conducted research on a method for producing an oxide-dispersed composite alloy powder by adding polyvinyl alcohol (PVA) to a solution of a nickel-based metal and a metal oxide precursor and heat- The present inventors have developed a method for manufacturing an oxide-dispersed composite alloy powder having a nanocrystal structure of high purity, porosity and excellent characteristics, and completed the present invention.

SUMMARY OF THE INVENTION

Dispersed composite alloy powder of the present invention.

Another object of the present invention is

Dispersed composite alloy powder produced by the above method.

Another object of the present invention is to provide

And to provide a reactor structure material containing the oxide-dispersed composite alloy powder.

According to an aspect of the present invention,

Dissolving a first metal salt containing a nickel salt for nickel-based alloy powder and a second metal salt containing a starting metal for the metal oxide in distilled water (step 1);

Adding a polyvinyl alcohol (PVA) solution to the mixed solution of step 1 to form a precursor sol (step 2);

Stirring and drying the precursor sol of step 2 to form a precursor gel (step 3); And

And a step (4) of heat treating the precursor gel of the step 3 in a reducing atmosphere. The present invention also provides a method for producing an oxide-dispersed composite alloy powder.

Further, according to the present invention,

There is provided an oxide-dispersed composite alloy powder produced by the above method.

Further,

And the oxide-dispersed composite alloy powder.

The method for producing an oxide-dispersed composite alloy powder according to the present invention is characterized in that a metal alloy is easily formed by adding polyvinyl alcohol having a high molecular weight as a fixing material of a metal element to a nickel-based alloy and a metal oxide precursor solution, Can be manufactured.

Further, there is an effect that an alloy powder having a high purity and porous nanocrystal structure can be synthesized by a simple process of heat-treating the mixed solution under a drying and reducing atmosphere.

Further, the nickel-based oxide-dispersed composite alloy powder produced according to the above-described production method can be provided at a lower cost because it is manufactured by a simpler manufacturing process than that of the conventional nickel-oxide-alloy composite alloy powder.

1 is a schematic view of a method for producing an oxide-dispersed composite alloy powder according to the present invention;
FIG. 2 is a graph showing differential thermal analysis and thermogravimetric analysis according to temperature changes of the precursor sol prepared in Step 2 of Example 1 and Example 2; FIG.
FIG. 3 shows X-ray diffraction analysis results of the oxide-dispersed composite alloy powder prepared in Examples 1 to 4, Comparative Examples 1 and 2;
4 is a photograph of the oxide-dispersed composite alloy powder produced in Example 1 and Example 2 by transmission electron microscope;
FIG. 5 is a photograph of the oxide-dispersed composite alloy powder prepared in Example 3 and Example 4, observed with a transmission electron microscope.

According to the present invention,

Dissolving a first metal salt containing a nickel salt for nickel-based alloy powder and a second metal salt containing a starting metal for the metal oxide in distilled water (step 1);

Adding a polyvinyl alcohol (PVA) solution to the mixed solution of step 1 to form a precursor sol (step 2);

Stirring and drying the precursor sol of step 2 to form a precursor gel (step 3); And

And a step (4) of heat treating the precursor gel of the step 3 in a reducing atmosphere. The present invention also provides a method for producing an oxide-dispersed composite alloy powder.

Here, an example of a method for producing an oxide-dispersed composite alloy powder according to the present invention is schematically shown in FIG. 1,

Hereinafter, the method for producing the oxide-dispersed composite alloy powder according to the present invention will be described in detail for each step.

In the process for producing an oxide-dispersed composite alloy powder according to the present invention, the first metal salt containing a nickel salt for a nickel-based alloy powder and the second metal salt containing a starting metal for a metal oxide are dissolved in distilled water .

 In the step 1, a mixed solution containing a first metal salt including nickel and a second metal salt for a metal oxide is prepared. In the case of preparing the powder with the mixed solution, an ODS powder such as A617-ODS Can be produced.

At this time, according to the prior art, the conventional ODS powder was produced by ball milling a metal alloy powder and a metal oxide by a mechanical method.

However, such a mechanical manufacturing method has a problem in that it is difficult to control the composition of the powder, and the manufacturing process takes a long time.

On the other hand, in the present invention, the ODS powder is produced through a reaction in a liquid phase rather than a conventional mechanical production process. To this end, in the step 1, a first metal salt including a nickel salt for a nickel- The second metal salt containing the starting metal is dissolved in distilled water.

Specifically, in the step 1, the mixed solution is prepared by dissolving a first metal salt containing a nickel salt for a nickel-based alloy powder and a second metal salt containing a fuel metal for a metal oxide in distilled water, The first metal salt and the second metal salt are ionized.

As the metal salts are ionized, the metal salts can be dispersed by the hydroxyl groups contained in the polyvinyl alcohol in the subsequent step 2, whereby a high purity powder can be obtained.

The first metal salt of step 1 may further include at least one selected from the group consisting of a cobalt precursor solution, a chromium precursor solution, a molybdenum precursor solution, an iron precursor solution, and a tungsten precursor solution.

The metal alloy powder produced by further including the metal precursor as described above has an effect of forming an A617 alloy composition composed of Ni-Co-Cr-Mo-Fe-W-carbon having a very high strength even at a high temperature.

On the other hand, the starting metal for the metal oxide of the step 1 may be at least one selected from the group consisting of yttrium, aluminum, zirconium and magnesium.

At this time, the first metal salt and the second metal salt of step 1 may independently include at least one anion selected from the group consisting of nitrate and sulfate.

For example, the first metal salt in step 1 may be nickel nitrate, cobalt nitrate, chromium nitrate, and the second metal salt may be in the form of yttrium nitrate or aluminum nitrate, and may be dissolved in distilled water .

In the method for producing an oxide-dispersed composite alloy powder according to the present invention, the step 2 is a step of forming a precursor sol by adding a polyvinyl alcohol (PVA) solution to the mixed solution of the step 1.

The polyvinyl alcohol has a hydroxyl group (OH group) dissolved in a solvent, which can contribute to increase the degree of dispersion of the solution of step 1 by binding with the ionized metal ion of step 1 above.

At this time, the solvent of the polyvinyl alcohol may be distilled water, and may be ionized as the polyvinyl alcohol powder is dissolved in a solvent to have a hydroxyl group.

However, the solvent of the polyvinyl alcohol is not limited to the distilled water.

The content of polyvinyl alcohol in the polyvinyl alcohol solution may be 0.1 to 6% by weight.

If the content of the polyvinyl alcohol in the polyvinyl alcohol solution is less than 0.1% by weight, there is a problem that the sites of the polyvinyl alcohol to which the metal ions can bind are insufficient and complete dispersion can not be achieved. When the content exceeds 6% by weight, excess carbon is present and the purity of the powder is lowered.

At this time, the molar ratio of the metal cation included in the first metal salt in step 1 to the hydroxyl group contained in the polyvinyl alcohol in step 2 may be 4 to 12: 1.

As the polyvinyl alcohol is contained so as to satisfy the molar ratio of the above range, the metal salts can be dispersed evenly by the hydroxyl groups of the polyvinyl alcohol, and the dispersion of the oxide-dispersed composite alloy powder synthesized by controlling the content of the polyvinyl alcohol The particle size is also adjustable.

If the molar ratio of the metal cation to the hydroxyl group is less than the above range, excess carbon may be present, which may result in poor powder purity and large particle size, and the metal cation and hydroxyl group If the molar ratio of the metal cations exceeds the above range, there may be a problem that the powder is not formed finely due to insufficient sites to which the metal ions can bind and the complete dispersion is not achieved.

In the method for producing an oxide-dispersed composite alloy powder according to the present invention, the step 3 is a step of forming a precursor gel by stirring and drying the precursor sol.

In Step 3, distilled water of the solution prepared in Step 1 and solvent of the polyvinyl alcohol solution of Step 2 are evaporated through stirring and drying, thereby forming a precursor gel from the precursor sol.

At this time, the precursor gel formed due to gas generated during stirring may be porous.

As an example, when a nitrate salt is used as an anion of a metal salt, NOx gas may be generated during stirring, and the precursor gel may exhibit porosity characteristics due to the NOx gas.

At this time, the stirring in the step 3 can be performed at room temperature, but the stirring temperature is not limited thereto.

The drying of step 3 may be performed at a temperature of 100 to 200 degrees for 20 to 30 hours.

If the drying of the step 3 is carried out at a temperature of less than 100 ° C., the precursor sol may not be formed into a gel because the water and the solvent are not properly dried. There is a problem that the process cost is increased at a process temperature higher than necessary for performing drying.

If the drying of step 3 is carried out for less than 20 hours, drying of the adhered water and solvent may not be performed properly, and thus the precursor sol may not be formed into a gel. Is performed for more than 30 hours, there may occur a problem that the process cost rises more than necessary for drying.

In the method for producing an oxide-dispersed composite alloy powder according to the present invention, the step 4 is a step of heat-treating the precursor gel of the step 3 in a reducing atmosphere.

The precursor gel of the step 3 is heat treated in a reducing atmosphere to prevent oxidation of the metal powder and to decompose the polymer salt of the polyvinyl alcohol and the decomposition of the metal salt. From the precursor gel, ODS powder Can be prepared.

At this time, the heat treatment in step 4 may be performed at a temperature of 300 to 500 ° C. for 30 minutes to 2 hours.

If the heat treatment in step 4 is carried out at a temperature of less than 300 deg. C, decomposition of polyvinyl alcohol may not be carried out, so that it may be difficult to have a nanocrystal structure. In the case where the heat treatment in step 4 is performed at a temperature higher than 500 deg. Temperature, the size of the powder particles may be increased due to the growth of the nanocrystalline grains.

If the heat treatment of step 4 is performed for less than 30 minutes, unreacted phases may be generated. If the heat treatment of step 4 is performed for more than 2 hours, the growth of nanocrystals The size of the powder particles may be increased.

Meanwhile, the heat treatment in step 4 may be performed under a reducing atmosphere gas such as an argon-hydrogen mixed gas, hydrogen gas, and ammonia. As the heat treatment in the step 4 is performed under the reducing atmosphere gas as described above, the oxidation of the metal powder is suppressed, and the ODS powder having a high purity nanocrystal structure can be produced.

Further, according to the present invention,

There is provided an oxide-dispersed composite alloy powder produced by the above production method.

Since the oxide-dispersed composite alloy powder according to the present invention is prepared through a sol-gel process using polyvinyl alcohol, it can be provided at a lower price because of the lower processing cost as compared with the conventional manufacturing process.

Further, since the mixed solution is prepared by heat treatment in a drying and reducing atmosphere, it can exhibit a nanocrystal structure having characteristics of higher purity and porosity than powders produced by the conventional mechanical alloying method.

On the other hand, the oxide-dispersed composite alloy powder according to the present invention may have a particle size of 10 to 50 nm, and since it is easy to control the particle size of the powder by controlling the amount of polyvinyl alcohol used in the production process, It is possible to provide a powder having a particle size suitable for the field to which the dispersed composite alloy powder is to be applied.

Further,

And the oxide-dispersed composite alloy powder.

The oxide-dispersed composite alloy powder has characteristics such as high purity and porosity and can be used as a core material of a nuclear power system which requires high efficiency and long-time operation even under a high temperature environment.

≪ Example 1 >

Step 1: As the first metal salt containing a nickel salt, nickel nitrate (Ni (NO ₃ ) ₂ .6H ₂ O), chromium nitrate (Cr (NO ₃ ) ₃ .9H ₂ O), cobalt nitrate Co (NO ₃ ) ₂ .6H ₂ O), molybdenum nitrate, iron nitrate and

Yttrium nitrate was dissolved in distilled water as a second metal salt for the metal oxide.

Step 2: A polyvinyl alcohol solution (Ni: PVA, OH group = 4: 1) mixed with 4 wt% of polyvinyl alcohol was mixed with the mixed solution to form a precursor sol.

Step 3: The precursor sol was stirred at room temperature for several minutes using a heat agitator, and dried at 120 DEG C for 24 hours to form a precursor gel.

Step 4: The precursor gel was heated in an alumina crucible at a rate of 3 DEG C / min to 300 DEG C and then heat-treated in an argon-4% hydrogen atmosphere for 60 minutes to prepare an oxide-dispersed composite alloy powder.

≪ Example 2 >

The oxide-dispersed composite alloy powder was prepared in the same manner as in Example 1 except that the polyvinyl alcohol solution was added so that the OH group of Ni: PVA was 8: 1 in the step 2 of Example 1 above.

≪ Example 3 >

An oxide-dispersed composite alloy powder was prepared in the same manner as in Example 1 except that the heat treatment was performed at 400 ° C. in the step 4 of Example 1.

<Example 4>

The oxide-dispersed composite alloy powder was prepared in the same manner as in Example 2, except that the heat treatment was performed at 400 ° C. in the step 4 of Example 2.

&Lt; Comparative Example 1 &

The oxide-dispersed composite alloy powder was produced in the same manner as in Example 1, except that the step 2 was not carried out in Example 1.

&Lt; Comparative Example 2 &

The oxide-dispersed composite alloy powder was produced in the same manner as in Example 3, except that the step 2 was not carried out in Example 3.

Heat treatment temperature (캜) Molar ratio (cation: hydroxyl group)  Whether PVA is added Example 1 300 4: 1 ○ Example 2 300 8: 1 ○ Example 3 400 4: 1 ○ Example 4 400 8: 1 ○ Comparative Example 1 300 4: 1 × Comparative Example 2 400 4: 1 ×

<Analysis>

1. Differential thermal analysis and thermogravimetric analysis of precursor sol

FIG. 2 shows the result of differential thermal analysis and thermogravimetric analysis according to the temperature change of the precursor sol prepared in Step 2 of Example 1 and Example 2. FIG.

In the case of the precursor sol prepared in Example 1, as shown in the differential thermal analysis graph, in the case of Example 1 in which the hydroxyl group of the polyvinyl alcohol and the cation of the metal salt are in a molar ratio of 1: 4, the hydroxyl group of the polyvinyl alcohol and the metal salt The addition amount of polyvinyl alcohol was larger than that of Example 2 in which the cation was in a molar ratio of 1: 8, and therefore, the effect of polyvinyl alcohol was strong, and a strong exothermic peak appeared at around 170 degrees and 300 degrees.

On the other hand, as shown in the thermogravimetric analysis graph, a weight reduction of two times is shown. In the region of 170 to 200 degrees, the weight decreases due to the evaporation of the adhesion water. In the region of 200 to 300 degrees, .

It can be seen that no further reduction in weight is observed in the temperature range of 300 DEG C or more, and the final pyrolysis zone is 300 DEG C.

In the case of the precursor sol prepared in Example 2, as shown in the differential thermal analysis graph, since the addition amount of polyvinyl alcohol was relatively smaller than that in Example 1, the effect of nitrate was more pronounced and the endothermic peak appeared.

On the other hand, as shown in the thermogravimetric analysis graph, in the case of the precursor sol prepared in Example 2, weight reduction twice occurs due to evaporation of adhered water and decomposition of nitrate, similarly to Example 1, It can be seen that the temperature range is 300 degrees.

<Experimental Example 1>

In order to observe the compositions of the oxide-dispersed composite alloy powders prepared in Examples 1 to 4 and Comparative Examples 1 and 2, X-ray diffraction analysis was performed and the results are shown in FIG.

As shown in Fig. 3, NiO peaks were observed in Comparative Example 1 in which the heat treatment was performed at 300 deg., But in Examples 1 and 2 treated with polyvinyl alcohol, NiO peaks were not found and only Ni peaks were found.

In the case of Comparative Example 2 and Examples 1 and 2 in which the heat treatment was performed at 400 ° C, it was confirmed that no NiO peak was found but only Ni peak was found even when polyvinyl alcohol was not treated.

As described above, it can be seen that when polyvinyl alcohol is used at a low temperature of 300 degrees, the metal is not oxidized and a pure metal powder can be obtained.

<Experimental Example 2>

The oxide-dispersed composite alloy powder prepared in Examples 1 to 4 was observed with a transmission electron microscope and the results are shown in FIGS. 4 and 5. FIG.

As shown in FIG. 4, it can be seen that although Examples 1 and 2 were synthesized at a low temperature of 300 ° C., they had a porous, highly uniform particle form.

Further, as shown in Fig. 5, it can be seen that Example 3 synthesized at a temperature of 400 degrees had particles with an average size of 20 nm and Example 4 had an average size of 40 nm, and had a very uniform size.

As described above, in the case of Examples 1 and 2, many sites of polyvinyl alcohol remain in the form of precursors by bonding with metal Ni, and organic substances and minerals are decomposed in the atmosphere heat treatment step, The decomposable polyvinyl alcohol is decomposed and the metal particles in each region become very uniform and remain in the form of porous metal nanoparticles.

Further, in the case of Examples 3 and 4, since the content of polyvinyl alcohol is larger than that of Example 3, the particle size can be controlled according to the content of polyvinyl alcohol. .

Claims (11)

Dissolving a first metal salt containing a nickel salt for nickel-based alloy powder and a second metal salt containing a starting metal for the metal oxide in distilled water (step 1);
Adding a polyvinyl alcohol (PVA) solution to the mixed solution of step 1 to form a precursor sol (step 2);
Stirring and drying the precursor sol of step 2 to form a precursor gel (step 3); And
(Step 4) of heat treating the precursor gel of step 3 in a reducing atmosphere.
The method according to claim 1,
Wherein the first metal salt and the second metal salt of step 1 each independently include at least one anion selected from the group consisting of nitrate and sulfate.
The method according to claim 1,
Wherein the first metal salt of step 1 further comprises at least one selected from the group consisting of a cobalt precursor solution, a chromium precursor solution, a molybdenum precursor solution, an iron precursor solution and a tungsten precursor solution. Gt;
The method according to claim 1,
Wherein the raw metal for the metal oxide of step 1 is at least one selected from the group consisting of yttrium, aluminum, zirconium and magnesium.
The method according to claim 1,
Wherein the molar ratio of the metal cation included in the first metal salt in step 1 to the hydroxyl group included in the polyvinyl alcohol in step 2 is 4 to 12: 1.
The method according to claim 1,
Wherein the polyvinyl alcohol solution of step 2 is a polyvinyl alcohol aqueous solution containing 0.1 to 6 wt% of polyvinyl alcohol.
The method according to claim 1,
Wherein the stirring of step (3) is carried out at room temperature.
The method according to claim 1,
Wherein the drying of step 3 is performed at a temperature of 100 to 200 degrees for 20 to 30 hours.
The method according to claim 1,
Wherein the heat treatment in step 4 is performed at a temperature of 300 to 500 ° C for 30 minutes to 2 hours.
The method according to claim 1,
Wherein the reducing atmosphere in step (4) is at least one gas atmosphere selected from the group consisting of an argon-hydrogen mixed gas, a hydrogen gas and an ammonia gas.
The oxide-dispersed composite alloy powder according to claim 1, wherein the oxide-dispersed composite alloy powder has a particle size of 10 to 50 nm.

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