WO2016208793A1 - Method for enhancing antioxidant properties of graphite contained in magnesia-carbon refractories by means of surface modifying and magnesia-carbon refractories prepared by means of same - Google Patents

Abstract

The present invention relates to a method for enhancing the antioxidant properties of graphite contained in magnesia-carbon refractories by means of surface modifying and magnesia-carbon refractories prepared by means of same and, more particularly, to a method, for enhancing the antioxidant properties of graphite, in which the surface of graphite particles is surface modified by means of acid treating before having the surface of graphite coated with an aluminum precursor, thereby enhancing the efficiency of a metal precursor coating on the surface of the graphite and thus enhancing the antioxidant properties of the graphite.

Description

Method for enhancing the antioxidant properties of graphite contained in magnesia-carbon refractory through surface modification and magnesia-carbon refractory prepared thereby

The present invention relates to a method capable of enhancing the antioxidant properties of graphite, and in particular, the acid treatment of the graphite particle surface before coating the graphite surface with an aluminum precursor improves the efficiency of coating the metal precursor on the graphite surface, thereby improving the antioxidant activity of the graphite. The present invention relates to a method for enhancing the antioxidant properties of graphite contained in magnesia-carbon refractory through surface modification capable of enhancing its properties, and to magnesia-carbon refractories prepared thereby.

In general, magnesia carbon (MgO-C) refractories are widely used in basic furnaces, electric arc furnaces and metal ladles, which have low elasticity due to the corrosion resistance due to low wettability to molten metal and the presence of graphite used as carbon source. Because of its characteristics.

However, the mechanical and thermal properties of magnesia carbon (MgO-C) refractories continue to deteriorate with use, due to the spalling phenomenon and pore formation by oxidation of graphite.

Therefore, to prevent oxidation of the graphite, an antioxidant having significant reactivity with oxygen is added to the graphite during the manufacturing process, and theoretically almost all graphite should not react with oxygen until the oxidation of the antioxidant proceeds to a considerable extent. .

However, in reality, due to a phenomenon in which pores are generated in the magnesia carbon (MgO-C) refractory, an antioxidant cannot effectively inhibit the oxidation of graphite.

In order to solve this problem, conventionally, graphite was coated with a coating agent of a metal precursor (particularly an aluminum precursor) to prevent oxygen from accessing the graphite.

However, such a prior art has a problem that it is difficult to improve the antioxidant properties of graphite because the efficiency of coating the metal precursor on the graphite surface is low.

On the other hand, as described above, the technique for preventing oxidation of graphite is widely used, and since it is described in the following prior art document, detailed description and illustration thereof will be omitted.

[Preceding technical literature]

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Accordingly, an object of the present invention is to solve the above-mentioned problems and improves the efficiency of coating the metal precursor on the graphite surface by surface modification by acid treatment of the graphite particle surface before coating the graphite surface with the aluminum precursor, thereby improving the graphite. It is to provide a method for enhancing the antioxidant properties of graphite contained in the magnesia-carbon refractory through surface modification that can enhance the antioxidant properties of the magnesia-carbon refractory.

The present invention for achieving the above object comprises a reforming step (S100) for acid treatment of the graphite particles surface contained in the magnesia-carbon refractory, and a coating step (S200) for coating the modified graphite particle surface with an aluminum precursor One method is to enhance the antioxidant properties of graphite contained in magnesia-carbon refractory through surface modification.

In this case, the reforming step (S100) may include an eleventh step (S110) for introducing the graphite particles into a mixture 3: 1 (volume ratio) of sulfuric acid and nitric acid.

In addition, after performing the eleventh step (S110), the twelfth step (S120) of sonicating the mixture to which the graphite particles are added for 3 hours and stirring for 24 hours, and the thirteenth step of washing the stirred graphite particles with distilled water It is also possible to include (S130), and the fourteenth step (S140) for drying the washed graphite particles.

In addition, the 13th step (S130) is washed with distilled water until the pH of the graphite particles to 7, the 14th step (S140) is filtered and dried for 48 hours at 80 ℃ after filtering the washed graphite particles It is also possible.

In addition, the coating step (S200) may include a twenty-first step (S210) of mixing and stirring the graphite particles that have undergone the modification step (S100) in an Al (NO ₃ ) ₃ solution.

In addition, after performing the twenty-first step (S210), filtering the mixed graphite particles and then the twenty-second step (S220) and the 23rd step (S230) for preheating the dried smoking particles to a specific temperature It is also possible.

In addition, the 21 st step (S210) is stirred the graphite particles mixed in the Al (NO 3) 3 solution for 1 hour at room temperature, the 22nd step (S220) is dried at 80 ℃ for 1 hour, the second 23 may be preheated to 300 ° C. for 1 hour in a hydrogen atmosphere.

In addition, the present invention is another feature of the magnesia-carbon refractory produced by the above-described method.

The features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings.

Prior to this, the terms or words used in this specification and claims are not to be interpreted in a conventional and dictionary sense, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that there is.

According to the present invention, the surface of the graphite particles is subjected to surface modification by acid treatment, thereby improving the efficiency of coating the metal precursor on the graphite surface, thereby improving the antioxidant properties of the graphite.

1 is a flowchart according to an embodiment of the present invention.

2 is a photograph showing the dispersibility of graphite particles by the method according to an embodiment of the present invention.

3 is an SEM image of EDS analysis results of surface modified graphite according to an embodiment of the present invention. FIGS. 3A and 3B do not have a coating layer, and FIG. 3A is before heat treatment at 1000 ° C. and FIG. 3B is heat treatment at 1000 ° C. FIG. It shows after. 3C and 3D show the case where the coating layer is present, and FIG. 3C shows the heat treatment at 1000 ° C. and FIG. 3D shows the heat treatment at 1000 ° C. FIG.

4 is a combustion test result for modified graphite particles with and without a coating layer according to an embodiment of the present invention, the numbers 1 to 4 are modified graphite particles, 1 is a photograph after the combustion test at 500 ℃ 2 is a photograph after the combustion test at 700 ° C, 3 at 900 ° C, and 4 at 1000 ° C. In addition, a1 to a4 is a case where there is no coating layer and b1 to b4 is a case where there is a coating layer.

FIG. 5 shows modified graphite XRD results with and without a coating layer according to one embodiment of the invention, where 5 (a) shows modified graphite without coating layer as before heat treatment and 5 (b) at 1000 ° C. FIG. 5 (c) represents modified graphite with a coating layer after heat treatment for 1 period and without coating layer, 5 (c) shows modified graphite with coating layer after heat treatment at 500 ° C, 700 ° C and 900 ° C. And modified graphite with coating as after heat treatment at 1200 ° C.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In this process, the thickness of the lines or the size of the components shown in the drawings may be exaggerated for clarity and convenience of description.

In addition, terms to be described below are terms defined in consideration of functions in the present invention, which may vary according to the intention or convention of a user or an operator. Therefore, definitions of these terms should be made based on the contents throughout the specification.

In addition, the following examples are not intended to limit the scope of the present invention but merely illustrative of the components set forth in the claims of the present invention, which are included in the technical spirit throughout the specification of the present invention and constitute the claims Embodiments that include a substitutable component as an equivalent in the element may be included in the scope of the present invention.

Example

According to an embodiment of the present invention, the method for enhancing antioxidant activity of graphite (S10) includes a modified step (S100) of acid-treating the surface of graphite particles contained in magnesia-carbon refractory, as shown in FIG. 1, and the modified graphite. The coating step (S200) for coating the particle surface with an aluminum precursor.

That is, acid treatment of the surface of the graphite particles before coating the surface of the graphite particles with a metal, that is, an aluminum precursor, may improve the coating efficiency of the aluminum precursor, thereby improving the antioxidant properties of the graphite.

At this time, the reforming step (S100) is acid treatment of the surface of the graphite particles as described above, and for this purpose to include an eleventh step (S110) of injecting the graphite particles into a mixture 3: 1 (volume ratio) of sulfuric acid and nitric acid. Can be.

After the acid treatment of the surface by the eleventh step (S110), the mixture containing the graphite particles is sonicated for 3 hours and the twelfth step (S120) of stirring for 24 hours is performed. Thereafter, a thirteenth step (S130) of washing the stirred graphite particles with distilled water is performed, and the thirteenth step (S130) is preferably washed with distilled water until the pH of the graphite particles reaches 7.

Meanwhile, after washing the graphite particles by the thirteenth step (S130), a fourteenth step (S140) of drying the washed graphite particles is performed, wherein the washed graphite particles are replaced for the fourteenth step (S140). After filtering it is also possible to dry for 48 hours at 80 ℃.

After the acid treatment of the surface by the modification step (S100) of the present invention as described above, the coating step (S200) is performed.

In this case, the coating step (S200) includes a twenty-first step (S210) of mixing and stirring the graphite particles acid-treated by the modifying step (S100) in an Al (NO ₃ ) ₃ (aluminum nitrate) solution.

An aluminum coating is performed on the surface of the graphite particles by the twenty-first step (S210). At this time, it is preferable to stir the graphite particles mixed in the Al (NO ₃ ) ₃ solution at room temperature for 1 hour.

After performing the twenty-first step (S210), performing the twenty-second step (S220) of filtering and drying the mixed graphite particles, the twenty-second step (S220) is preferably dried at 80 ℃ for 1 hour. .

Meanwhile, after performing the twenty-second step S220, a twenty-third step S230 of preheating the dried smoking particles to a specific temperature is performed. In this case, the twenty-third step S230 is performed in the twenty-third step S230. ) Is preferably preheated to 300 ° C. for 1 hour in a hydrogen atmosphere.

With respect to the effects of the present invention described above, the coating efficiency of the aluminum precursor on the graphite surface in the state with and without surface modification is examined through the degree of dispersion of the precursor. And the oxidation behavior of aluminum-coated graphite is examined by the microstructure and state analysis of the said graphite after a combustion test.

First, scanning microscopy (SEM; Model JSM-5610; JEOL, Tokyo, Japan) and energy dispersive x-ray spectrometer (EDS; energy resolution 133eV, Oxford Inst., Oxford, UK) for micro breakfast analysis and elemental analysis of graphite particles Are used respectively.

In addition, a combustion test for the modified graphite particles after or before coating with an aluminum precursor, as described below, is performed at a temperature range of 500 ° C. to 1000 ° C. for 1 hour, and the phase analysis after the combustion test is performed by an X-ray diffraction apparatus. (Model 3040 PW Philips X'pert MPD Eindhoven, The Netherlands) was performed.

As described above, in order to effectively inhibit the oxidation of graphite in the magnesia-carbon refractory, the aluminum precursor should be uniformly and homogeneously coated on the graphite surface and the coating efficiency of the aluminum precursor should be enhanced.

To this end, an anionic hydroxyl group must be provided on the graphite surface, and the surface of the graphite is modified by an acid to provide the hydroxyl group.

In order to confirm the effect of the surface modification, the graphite particles with and without modification are dispersed in an aqueous solution containing aluminum coated graphite particles, which will be described below with reference to FIG. 2.

2 is a photograph showing the dispersibility of graphite particles, numeral 1 represents graphite without a coating layer, numeral 2 represents graphite in three minutes after the coating layer is present, and numeral 3 represents the case of the coating layer 3. Graphite in the elapsed state is shown. In addition, a1, a2, a3 represents original graphite without surface modification, and b1, b2, b3 represents graphite with surface modification.

After the acid treatment, as shown, the surface modified graphite was well dispersed without aggregation (bl in FIG. 2), indicating that the acid produced a hydroxyl group with a negative charge on the graphite surface, resulting in a good aluminum coating.

On the other hand, as shown in FIG. 2 (a1), it can be seen that graphite which is not surface modified is precipitated within a few minutes, and thus surface modification by acid treatment is necessary to improve the efficiency of aluminum coating. .

In particular, comparing the case of coating with an aluminum precursor, it can be seen that the surface-modified graphite (a2 of FIG. 2) is precipitated faster than the surface-modified graphite (b2 of FIG. 2). It can be seen again in favor of the coating.

In other words, it can be seen that the aluminum precursor is better coated on the graphite surface modified by the present invention.

Hereinafter, with reference to FIG. 3, the microstructure and elemental analysis results of the surface-modified graphite particles with and without the coating layer are examined through a heat treatment function.

In this case, Figure 3 is a SEM image of the surface-modified graphite EDS analysis of Figure 3a and 3b without the coating layer, Figure 3a before the heat treatment at 1000 ℃ and Figure 3b shows after the heat treatment at 1000 ℃. 3C and 3D show the case where the coating layer is present, and FIG. 3C shows the heat treatment at 1000 ° C. and FIG. 3D shows the heat treatment at 1000 ° C. FIG.

In FIG. 3A, only O and C are detected in graphite as there is no coating layer. In addition, in FIG. 3C, an element of aluminum is additionally detected in the graphite as there is no coating layer, because the structure after the aluminum layer is preheated at 300 ° C. is amorphous.

Meanwhile, the polygonal Al ₂ O ₃ particles converted in the amorphous aluminum layer after 1000 ° C. heat treatment under the premise that the aluminum precursor was uniformly coated on the graphite surface are completely covered on the graphite surface as shown in FIG. 3d. Review in detail.

Graphite particles with and without coating layers after heat treatment at 1000 ° C. show different behavior. That is, as shown in FIG. 3B, various impurities are detected in the graphite in the absence of the coating layer, which indicates that graphite in the absence of the coating layer is easily decomposed.

However, only Al, O, and C elements are detected in the graphite with the coating layer, and Al and O tend to increase and C decrease after heat treatment (FIG. 3D).

Therefore, it can be assumed that graphite oxidation is suppressed by the aluminum layer (which serves as an oxygen barrier layer) formed on the surface.

4, the combustion test results for the modified graphite particles with and without the coating layer are reviewed.

In FIG. 4, numerals 1 to 4 are modified graphite particles, 1 is a photograph after a combustion test at 500 ° C., 2 is 700 ° C., 3 is a 900 ° C., and 4 is a photograph after a combustion test at 1000 ° C. FIG. In addition, a1 to a4 is a case where there is no coating layer and b1 to b4 is a case where there is a coating layer.

As the temperature increased in the combustion test, the graphite in the absence of the coating layer was decomposed and oxidized (see a in FIG. 4) to give a gray color at 700 ° C. and a brown color at 900 ° C., respectively.

In practice, graphite without coating layer starts the reaction at 700 ° C. and reacts completely at 900 ° C.

However, as shown in b of FIG. 4, graphite coated with an aluminum precursor exhibits desirable conditions in a 700 ° C. combustion test and begins to react with oxygen at 900 ° C. FIG.

Finally, the aluminum coated graphite (the coating layer starts a complete reaction with oxygen at 1000 ° C.) shows a white color.

This means that the coating layer (aluminum precursor) has a significant effect as an antioxidant which delays the oxidation of the graphite by a continuous and homogeneous coating on the graphite surface.

In addition, the mass loss of aluminum coated graphite is less than 10% (mass fraction) after the combustion test. Therefore, the coating process can be seen that the oxidation inhibition of the graphite is enhanced even if the mass gain by the oxidation of the coating layer is considered.

Hereinafter, the modified graphite XRD results with and without the coating layer will be examined with reference to FIG. 5.

5 (a) of FIG. 5 shows modified graphite without a coating layer as before the heat treatment, and 5 (b) shows modified graphite without a coating layer after being heated at 1000 ° C. for 1 hour, and 5 (c) is 500. After the heat treatment at ℃, 700 ℃ and 900 ℃ represents a modified graphite with a coating layer, 5 (d) represents a modified graphite with a coating layer after the heat treatment at 1000 ℃ and 1200 ℃.

In the absence of a coating layer, graphite peaks are detected before heat treatment (FIG. 5 (a)), but disappear after heat treatment at 1000 DEG C. (FIG. 5 (b)).

However, if there is a coating layer, the graphite peak is detected up to 900 ° C. heat treatment (FIG. 5 (c)).

The peaks of alumina (Al ₂ O ₃ ) and graphite coexist after heat treatment having an amorphous peak characteristic after 1000 ° C. heat treatment, indicating that the graphite is decomposed and the coating layer is not completely crystallized (FIG. 5 (d)).

Finally the aluminum coated graphite is converted to alumina at 1200 ° C. The results are in good agreement with the results of the combustion test. As a result of the phase analysis, the oxidation resistance of the graphite is enhanced by the coating of the aluminum precursor.

As described above, in the case of the present invention, graphite was acid treated to improve the coating efficiency of the aluminum precursor. The surface modified graphite exhibits improved dispersibility than the original graphite.

The modified graphite particles coated with the aluminum precursor precipitate over time because the charge due to the reaction between the cation and the graphite anion of the aluminum precursor disappears.

It has been demonstrated that aluminum precursors are well coated on graphite surfaces. Evidence for the coating of aluminum precursors can be observed by microstructure and elemental analysis. The surface modification of the graphite improves the coating efficiency of the aluminum precursor on the graphite surface, the mass gain is 1.5% without surface modification and 1.9% with surface modification.

On the other hand, graphite with no surface modification began to react with oxygen in a combustion test at 700 ° C. and completely reacted at 900 ° C.

However, the aluminum coated graphite exhibited healthy conditions at 700 ° C. in the combustion test and started to react at 900 ° C. The aluminum coated graphite was maintained up to 1000 ° C. even if the color turned white.

This result means that the coating layer coats the graphite surface uniformly and continuously to delay the oxidation of the graphite.

Additionally, aluminum coated graphite is detected up to 900 ° C. and alumina and graphite have peaks at 1000 ° C.

Finally, the aluminum coated graphite was completely converted to alumina at 1200 ° C. As a result, the high antioxidant properties of aluminum coated graphite are achieved by surface modified graphite and in this study aluminum coated graphite can enhance the antioxidant properties of MgO-C refractory.

Claims (8)

1. A reforming step (S100) of acid-treating the surface of the graphite particles contained in the magnesia-carbon refractory material;

   Method for enhancing the antioxidant properties of graphite contained in magnesia-carbon refractory through surface modification comprising the step of coating the modified graphite particle surface with an aluminum precursor (S200).
2. The method of claim 1,

   The reforming step (S100) is to enhance the antioxidant properties of the graphite contained in the magnesia-carbon refractory through the surface modification, including the eleventh step (S110) for introducing the graphite particles into a mixture 3: 1 (volume ratio) of sulfuric acid and nitric acid Way.
3. The method of claim 2,

   After performing the eleventh step (S110), the twelfth step (S120) of sonicating the mixture into which the graphite particles are added for 3 hours and stirring for 24 hours,

   A thirteenth step (S130) of washing the stirred graphite particles with distilled water;

   Method for enhancing the antioxidant properties of graphite contained in magnesia-carbon refractory through surface modification comprising the step 14 of drying the washed graphite particles (S140).
4. The method of claim 3,

   The thirteenth step (S130) is washed with distilled water until the pH of the graphite particles is 7,

   The 14th step (S140) is a method of increasing the antioxidant properties of graphite contained in magnesia-carbon refractory through surface modification after filtering the washed graphite particles and dried for 48 hours at 80 ℃.
5. The method of claim 1,

   The coating step (S200) is contained in the magnesia-carbon refractory through the surface modification comprising a twenty-first step (S210) of mixing and stirring the graphite particles subjected to the modification step (S100) to Al (NO ₃ ) ₃ solution Method of enhancing the antioxidant properties of graphite.
6. The method of claim 5,

   After performing the 21 st step (S210),

   A twenty-second step (S220) of filtering and drying the mixed graphite particles;

   Method for enhancing the antioxidant activity of the graphite contained in the magnesia-carbon refractory through surface modification comprising the twenty-third step (S230) of preheating the dried smoking particles to a specific temperature.
7. The method of claim 6,

   In the twenty-first step (S210), the graphite particles mixed in the Al (NO ₃ ) ₃ solution are stirred for 1 hour at room temperature,

   The twenty-second step (S220) is dried at 80 ℃ for 1 hour,

   The twenty-third step (S230) is a method of increasing the antioxidant properties of graphite contained in the magnesia-carbon refractory through surface modification to preheat to 300 ℃ for 1 hour in a hydrogen atmosphere.
8. Magnesia-carbon refractory produced by the method according to any one of claims 1 to 7.

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