KR101588292B1 - A TaC Powder and A Manufacturing method of the same - Google Patents

Abstract

The present invention relates to a manufacturing method of TaC powder comprising the steps of: making a slurry mixture comprising tantalum oxide (Ta_2O_5) and a carbon source; making a powder mixture by drying the slurry mixture; and heating the powder mixture wherein the heating rate is 50 to 500°C per a minute. Nano-sized TaC powder having consistent and fine sizes is manufactured by using tantalum oxide and a carbon source as starting materials, dissolving the two materials in an organic solvent, and drying the solution when used to prevent local concentration of the chemical composition.

Description

TaC powder and a manufacturing method thereof [0002]

The present invention relates to a TaC powder and a method of manufacturing the same, and more particularly, to a nano TaC powder having a fine particle size and a manufacturing method thereof.

TaC has a very high melting point of about 3800 ° C, has excellent mechanical properties such as excellent strength and hardness characteristics, has a wide range of applications in industry, and many studies have been carried out especially for military and aerospace applications .

Especially, ZrB ₂ is superior to ZrB ₂ which has undergone much research in the past.

However, in the case of TaC, ovarian integrity, which is a characteristic of high melting point materials, has many limitations in industrial application processes.

As one of the methods for overcoming this ovoid formation, a method of increasing the driving force for sintering by reducing the size of the TaC as the raw material powder and increasing the surface area can be considered.

However, TaC powder, which is currently commercially available, is mostly in the range of 1 - 3 μm in size. When such a starting material is used as raw material powder, pressure sintering should be performed at an ultra-high temperature of 2200 ° C. or higher. Can be achieved.

TaC powder was synthesized by solid-phase reduction, precursor method, mechanical alloying, hydrothermal method and self-propagating high-temperature synthesis (SHS) method. However, in these studies, it was difficult to synthesize very fine nano powders of about 80 to 200 nm due to grain growth occurring during high temperature treatment for synthesis.

In addition, Japanese Patent Application Laid-Open No. 2005-068002 discloses a method of forming a TaC coating layer, which is disclosed in U.S. Patent No. 4,866,012, U.S. Patent No. 4,784,839, U.S. Patent No. 4,948,573 and U.S. Patent No. 5,567,662 disclose a carbide-based ceramic powder synthesis method using a carbothermal reduction method. However, these patents disclose a method of molding a raw powder into spherical granules (U.S. Patent No. 4,784,839) (U.S. Patent No. 4,866,012), or a method of simultaneously performing the above two (U.S. Patent No. 4,948,573) and a method of obtaining a fine powder by adjusting the reducing atmosphere (US Pat. No. 5,567,662) And is not directly related to the present invention.

Therefore, to improve the sinterability of the TaC powder, commercially available TaC powder was pulverized by a wet grinding method using an advanced grinding apparatus such as attrition mill and planetary mill and a liquid dispersion medium.

However, since TaC has a high modulus of elasticity, hardness and fracture toughness, it is not easy to grind and it is difficult to prevent a large amount of contaminants from entering the grinding bowl and the grinding container at the time of grinding.

Japanese Patent Laid-Open No. 2005-068002 US registered patent 4,866,012 United States Patent 4,784,839 United States Patent 4,948,573 United States Patent No. 5,567,662

Disclosure of Invention Technical Problem [8] The present invention provides a nano TaC powder having a fine particle size and a method of manufacturing the same.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

In order to solve the above-mentioned problems, the present invention provides a method for producing a mixed slurry comprising: preparing a mixed slurry containing tantalum oxide (Ta ₂ O ₅ ) and a carbon source; Drying the mixed slurry to prepare a mixed powder; And heating the mixed powder, wherein the rate of heating is 50 to 500 ° C per minute.

Further, the present invention provides a method for manufacturing a TaC powder, wherein the step of heating the mixed powder is performed by using a Spark plasma sintering (SPS) method.

Also, the present invention provides a method for producing TaC powder, wherein the heating temperature is 1400 to 1600 ° C.

The present invention is a tantalum oxide (Ta ₂ O ₅₎ and a mixed slurry containing the carbon source, the tantalum oxide (Ta ₂ O ₅₎ and the carbon source, Ta2O5 and C by the thermal decomposition in the step of heating the mixture powder Wherein the mass ratio of Ta ₂ O ₅ : C is 1: 7.0 to 9.0, based on the mass converted to TaCrO ₂ .

Further, the present invention provides the TaC powder produced by the above production method.

In the present invention as described above, tantalum oxide (Ta ₂ O ₅ ) and a carbon source are used as a starting material for preparing TaC powder, and these are dissolved in an organic solvent and dried again , Local concentration of chemical composition is prevented, and nanot TaC powder having a uniform and fine size can be produced.

In addition, in the present invention, by using a spark plasma sintering (SPS) method capable of rapid temperature raising and cooling instead of a conventional heating furnace, coarsening of particles due to side reactions occurring during temperature rise can be prevented, The effect of minimizing the neck formation between the particles due to the formation can be achieved.

1 is a flow chart for explaining a method for producing TaC powder according to the present invention.
2 is XRD data of TaC powder synthesized under various conditions.
3 is a SEM photograph of powder synthesized under various conditions.
Fig. 4 shows the particle size distribution of TaC powder synthesized by varying the heating rate and the synthesis temperature using powder of the optimum composition.
FIG. 5 shows XRD data and shape distribution and particle size distribution of TC8 composition powder synthesized in large quantities.
6 is TEM analysis data of the synthesized TaC powder, which is a shape, a lattice constant, a SAED pattern, and EDS data.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. &Quot; and / or "include each and every combination of one or more of the mentioned items. ≪ RTI ID = 0.0 >

Although the first, second, etc. are used to describe various components, it goes without saying that these components are not limited by these terms. These terms are used only to distinguish one component from another. Therefore, it goes without saying that the first component mentioned below may be the second component within the technical scope of the present invention.

The terminology used herein is for the purpose of illustrating embodiments and is not intended to be limiting of the present invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. The terms " comprises "and / or" comprising "used in the specification do not exclude the presence or addition of one or more other elements in addition to the stated element.

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless explicitly defined otherwise.

The terms spatially relative, "below", "beneath", "lower", "above", "upper" And can be used to easily describe a correlation between an element and other elements. Spatially relative terms should be understood in terms of the directions shown in the drawings, including the different directions of components at the time of use or operation. For example, when inverting an element shown in the figures, an element described as "below" or "beneath" of another element may be placed "above" another element . Thus, the exemplary term "below" can include both downward and upward directions. The components can also be oriented in different directions, so that spatially relative terms can be interpreted according to orientation.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flow chart for explaining a method for producing TaC powder according to the present invention.

Referring to FIG. 1, a method of manufacturing a TaC powder according to the present invention includes the step of preparing a mixed slurry containing tantalum oxide (Ta ₂ O ₅ ) and a carbon source (S 100).

More specifically, the step of preparing a mixed slurry containing tantalum oxide (Ta ₂ O ₅ ) and a carbon source comprises mixing a tantalum oxide (Ta ₂ O ₅ ) and a carbon source in a liquid phase dispersion medium to prepare a slurry.

At this time, the carbon source may be at least one carbon species selected from graphite, carbon black, activated carbon, phenol resin, pitch, sucrose and poly acrylonitrile (PAN) Although not limited, it is preferable to use a carbon stream that can be dissolved in a dispersion medium such as water or alcohol, such as sucrose.

In addition, a magnetic stirrer may be used to produce the slurry, but the mixing method is not limited in the present invention.

The dispersion medium may be an alcohol such as water or ethanol. However, the present invention does not limit the kind of the dispersion medium.

Through such a method, a mixed slurry containing tantalum oxide (Ta ₂ O ₅ ) and a carbon source can be prepared.

Meanwhile, in the mixed slurry containing the tantalum oxide (Ta ₂ O ₅ ) and the carbon source, in the present invention, the mixture of the tantalum oxide (Ta ₂ O ₅ ) and the carbon source is pyrolyzed in the heating step (S 130) The mass ratio of Ta ₂ O ₅ : C, based on the mass converted to Ta ₂ O _{5 and} C, is preferably 1: 7.0 to 9.0.

1, a method of manufacturing a TaC powder according to the present invention includes a step of drying the mixed slurry to prepare a mixed powder (S110).

More specifically, the mixed slurry may be dried at 70 to 100 ° C to produce a mixed powder having a uniform composition.

That is, in the present invention, as a starting material for preparing TaC powder, tantalum oxide (Ta 2 O 5) and a carbon source are used as a starting material, the carbon source is dissolved in the dispersion medium, The nano TaC powder having a uniform and fine size can be produced.

Meanwhile, although not shown in the drawing, a method of manufacturing TaC powder according to the present invention includes: preparing a mixed powder by drying the mixed slurry, pulverizing the mixed powder using induction or the like, and sieving As shown in FIG.

The method may further include heating the mixed powder to a temperature of 600 to 800 ° C. in a vacuum, nitrogen or argon atmosphere after the step of drying the mixed slurry to prepare a mixed powder.

In addition, in the present invention, the mixed powder may be molded into a pellet form and used.

1, a method of manufacturing a TaC powder according to the present invention includes heating the mixed powder (S120).

In the present invention, the heating step may be performed by using a spark plasma sintering (SPS) method. That is, for the synthesis of TaC powder, a preformed mixed powder, that is, a preform powder is sintered by spark plasma sintering plasma sintering (SPS) method, it is possible to synthesize nano TaC powder having a fine size.

At this time, the heating may be performed under vacuum (preferably 20 Pa or less), and the heating temperature is preferably 1400 to 1600 ° C, and more preferably, the heating temperature may be 1400 to 1500 ° C.

 If the heating temperature is lower than 1400 ° C, a large amount of unreacted oxides may be present in the powder. If the heating temperature exceeds 1600 ° C, nanopowders having a size of 200 nm or less can be obtained by rapid grain growth Therefore, in the present invention, the heating temperature of 1400 to 1600 占 폚 has a critical meaning.

The heating and holding time is preferably 0.5 to 3 hours. When the heating and holding time is less than 0.5 hour, the remaining unreacted oxide can not be completely suppressed. When the heating and holding time exceeds 3 hours, The nano powder can not be obtained by excessive grain growth. Therefore, in the present invention, the heating and holding time is preferably 0.5 to 3 hours.

If the heating rate is less than 50 ° C per minute, the effect of inhibiting grain growth and reducing side reaction can not be attained. If the heating rate is 500 ° C per minute It is difficult to secure a uniform temperature increase on the equipment limit, and therefore, the heating heating rate is preferably 50 to 500 DEG C per minute.

In the present invention, by using a spark plasma sintering (SPS) method, the temperature rise rate is less than 50 ° C per minute, which is attainable even by using a conventional furnace. Reduction effect can be achieved.

That is, in the present invention, by using a spark plasma sintering (SPS) method capable of rapid temperature raising and cooling instead of a conventional heating furnace, coarsening of particles due to side reactions occurring during the temperature rise can be prevented, An effect of minimizing neck formation between particles due to image formation can be achieved.

As a result, it is possible to synthesize a nanot TaC powder having a fine size, and the TaC powder can be pulverized using induction, and the pulverized TaC powder can be produced to a size of 150 nm or less.

Hereinafter, preferred experimental examples according to the present invention will be described. However, the following experimental examples are only examples of the present invention, but the present invention is not limited to the following experimental examples.

[Experimental Example]

Commercial tantalum oxide (Ta ₂ O ₅ ) was added to ethanol and the phenolic resin (carbon source) was mixed with stirring using a magnetic stirrer.

For the synthesis of TaC powder, the preformed precursor powder was heated by using a specially designed discharge plasma sintering furnace (SPS) using graphite mold for powder synthesis. The heating conditions for the synthesis proceeded in the range of 1400 to 1500 ° C under vacuum (20 Pa or less). The heating holding time was 1 to 2 hours, and the heating heating rate was 50 to 100 ° C per minute. The compositions TC2 and TC3 had a molar ratio of C / Ta of 7 and 7.7, respectively.

The synthesized powder was gently pulverized using a mortar.

The analysis was performed using XRD, SEM and TEM. Residual oxygen content in the synthesized powder was measured using nitrogen / oxygen content analyzer and impurity content was measured using GDMS (Glow-discharge mass-spectrometry).

The ideal Ta ₂ O ₅ : C ratio by reaction formula (1) is 1: 7, and when mixed in this ratio, many oxides are observed after synthesis, and the ratio of C to Ta ₂ O ₅ is gradually increased from 1: 8 Respectively.

Ta ₂ O ₅ + 7C = 2TaC + 5CO Reaction formula (1)

As can be seen from the above reaction formula (1), the carbon content during the synthesis is reduced at high temperature because it is vaporized in CO form. Therefore, considering the reduction of carbon content in the raw material, the ratio of Ta ₂ O ₅ : TC1 to TC3 in that order.

Figure 2 is XRD data of TaCs fabricated under different composition and synthesis conditions. In this case, a in FIG. 2 represents XRD data of the TC1 composition powder before synthesis.

First, it was found that the residual oxides were present on the XRD even after the heat treatment under the optimal conditions of synthesis when the molar ratios of C: Ta ₂ O ₅ were 7 and 7.7 (TC1, TC2) according to the compositional change.

Also, as can be seen from the XRD pattern after synthesizing the powder having a molar ratio of C: Ta ₂ O ₅ of 8.4, which is the optimum composition determined in this experiment, at different temperatures of 1400 to 1500 ° C, , But the synthesis of single phase TaC was found at 1450 ℃. From the results of the conventional furnace, the synthesis temperature of 1600 ~ 2000 ℃ was required to obtain single - phase TaC. In contrast, single - phase TaC was obtained at lower temperature by SPS.

2 and Table 3 show the effect of the composition holding time and the heating rate on the phase formation and the residual oxygen content. In the case of synthesis at 1400 ° C, 1.5 hours or 1450 ° C for 1 hour, a trace amount of oxide is present and the residual oxygen content is comparatively Respectively. When the heating rate was lowered to 50 ° C per minute, formation of a trace amount of Ta ₂ C phase was confirmed. From this, it was found that undesired side reactions occurred during heating when the heating rate was low. When the ratio of Ta ₂ O ₅ : C was maintained at 1: 8.4 at a rate of 100 ° C per minute and maintained at 1450 ° C for 1.5 hours, single phase TaC was obtained and the residual oxygen content was as low as 0.5% or less. However, as the synthesis temperature increases, the time required for synthesis decreases sharply.

From these results, it can be seen that the minimum temperature for synthesizing TaC is 1400 ° C., and when the synthesis temperature exceeds 1600 ° C., the grain growth is large and the desired nano powder can not be obtained. Therefore, the heating temperature for synthesis of TaC is 1400 Deg.] C to 1600 [deg.] C.

3 is a photograph showing the shape of TaC powder synthesized under various conditions with Ta ₂ O ₅ as a raw material powder.

Referring to FIG. 3, it can be seen that the average particle size of Ta ₂ O ₅ as starting material is larger than that of TaC powder having an average particle size of about 80 nm synthesized at 200 nm, so that the raw material powders are simultaneously refined during carbothermal reduction. When the synthesis temperature increased from 1400 ℃ to 1450 ℃ or when the synthesis time of 1450 ℃ increased from 1 hour to 1.5 hours, no significant growth was observed at 1500 ℃. It is possible to synthesize TaC powder having a desired size of about 80 to 200 nm by increasing the synthesis temperature or increasing the synthesis time.

When the powder is synthesized by using the existing furnace, the reaction by the reaction formulas (2) and (3) occurs actively during the heating.

_{Ta 2 O 5 (s) +} (2 + xy) C (s) → TaC x O y (s) + (2-y) CO (g) (0 <x, y <1) Equation (2)

TaC _x O _{y (s)} + (1 + yx) C _(s) TaC _(s) + yCO _(g )

The reaction occurring at the lowest temperature among the three reactions of the above reaction formulas (1) to (3) is in the case of the reaction formula (2), and the result for the TaC _x O _y formed in this case is not reported, It is known that HfC _x O _y phase, when formed during powder synthesis, induces grain growth and strong agglomeration.

However, in the present invention, the reaction of the reaction formula (2) was suppressed to the utmost.

That is, in the present invention, the reaction of the reaction formula (2) can quickly pass through the low-temperature region where the reaction can be most thermodynamically due to the high-temperature elevation rate (the heating rate of 50 ° C or higher per minute)

Powder synthesis using SPS not only inhibits grain growth due to rapid synthesis but also reduces residual oxygen content of the formed non - oxide powder.

The residual oxygen content of nano TaC powders synthesized through this experiment is 0.5 wt%, which is lower than that reported in the literature.

Also, considering that the size of the powder obtained in this experiment is 80 nm, but the powder obtained from the existing literature does not show the particle size or the particle size is larger than 1 mm, the powder synthesized in this experiment has a very low residual oxygen content And this is one of the important characteristics of the present invention.

In principle, pulsed alternating current flows through a specimen, which is known to form a plasma and remove oxide impurities on the specimen surface. Therefore, it is considered that some of the residual oxide is removed by the surface cleaning effect during the SPS.

4 is the particle size distribution of the TaC powder synthesized by changing the heating rate and the synthesis temperature using the powder of the optimum composition. TEM data of the synthesized TaC powder.

Referring to FIG. 4, when the heating rate was increased from 50 ° C./min to 100 ° C./min, the particle size decreased from 49 nm to 44 nm.

Accordingly, it can be seen that the present invention can suppress the grain growth at the time of synthesizing the nano powder at a rapid heating rate using SPS.

Also, when the synthesis temperature was increased from 1450 ° C to 1500 ° C, a noticeable increase in particle size was observed.

Fig. 5 shows XRD data, SEM and particle size distribution of TC8 composition powder synthesized in large quantities.

Referring to FIG. 5, XRD analysis showed that no residue such as Ta ₂ O ₅ was present in the case of mass synthesis.

SEM and particle size analysis showed that the particle size was larger than that of the small amount of powder synthesis because the synthesis time was increased from 1 hour to 1 hour and 30 minutes for the complete reaction in mass synthesis.

Fig. 6 shows the result of TEM analysis of powder having a composition of TC8. (A) is a powder shape, (b) is a high resolution image and a lattice constant, (c) is a selected-area electron-diffraction image, and (d) is energy dispersive X-ray spectroscopy (EDS) data.

Referring to FIG. 6, most of the particles were found to have a size of 50100 nm by TEM analysis as shown in FIG. 6A. As a result of observation with high resolution in FIG. 6B, it was found that the lattice phase was a well developed high quality powder, and the lattice constant obtained was in good agreement with the lattice constant of HfC. As a result of the SAED pattern analysis in FIG. 6C, TaC powder having high crystallinity was synthesized. In addition, the EDS analysis of FIG. 6D reveals that TaC powder having a high purity is formed in which no elements other than Ta and C are detected except oxygen formed during preparation of specimen and Cu peak originating from TEM grid.

Table 3 shows that the TaC powder synthesized by GDMS is a high purity TaC powder of 99.94% when the oxygen content is excluded.

As described above, TaC was produced by using Ta ₂ O ₅ and C, but since Ta ₂ O ₅ was used as a starting material and a conventional heating furnace was used, So that only relatively comparatively assembled TaC powder of 1 mm or more was synthesized.

For example, Japanese Patent Application Laid-Open No. 2005-068002 discloses a process for producing a tantalum or tantalum alloy by introducing a carbon source into a vacuum heat treatment furnace and heating the tantalum or tantalum alloy at a temperature of 1860 DEG C to 2500 DEG C, A method for producing a carbide &quot; is described. However, the synthesis temperature of Japanese Patent Laid-Open No. 2005-068002 is much higher than the temperature range proposed in the present invention, and TaC synthesized by the production method of Japanese Patent Application Laid-Open No. 2005-068002 forms a coarse microstructure I will do it.

On the contrary, the synthesis of TaC powder according to the present invention suppresses the formation of TaC _x O _y phase which induces grain growth during synthesis through the rapid increase of temperature by the discharge plasma sintering method to a minimum, and lowers the synthesis temperature to 1400 to 1600 ° C, A nano TaC powder of about 40 to 100 nm or so can be synthesized.

Thus, compared with the prior art, the present invention can achieve better effects in ease of operation, purity and powder size.

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 will be understood. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (7)

mixing tantalum oxide (Ta ₂ O ₅ ) and a carbon source in a liquid dispersion medium to dissolve the carbon source in the dispersion medium to prepare a mixed slurry;
Drying the mixed slurry to prepare a mixed powder; And
And heating the mixed powder,
Wherein the heating rate is 50 to 500 ° C per minute. The method according to claim 1,
Wherein the heating of the mixed powder is performed by spark plasma sintering (SPS). 3. The method of claim 2,
Wherein the heating temperature is 1400 to 1600 ° C. The method according to claim 1,
The step of drying the mixed slurry to prepare a mixed powder comprises:
And the mixed slurry is dried at 70 to 100 占 폚. The method according to claim 1,
After the step of drying the mixed slurry to prepare a mixed powder,
And heating the mixed powder to a temperature of 600 to 800 DEG C in a vacuum, argon or nitrogen atmosphere. The method according to claim 1,
The mixed slurry containing the tantalum oxide (Ta2O5) and the carbon source,
Wherein the tantalum oxide (Ta 2 O 5) and the carbon source have a mass ratio of Ta ₂ O ₅ : C of from 1: 7.0 to 9.0 based on the mass converted into Ta ₂ O ₅ and C by pyrolysis in the step of heating the mixed powder &Lt; / RTI &gt; delete

Images