KR101461080B1 - Composition for semiconducting castable ceramic composite and the manufacturing method of composite - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for a semicrystalline castable ceramic composite and a method for producing the same, and more particularly, to a method for producing a semiconductive ceramic powder, A method of preparing a semiconducting castable ceramic composite having an appropriate resistance value by adding a certain amount of alumina cement as a binder and casting it in a casting mold by mixing with water and then densely sintering, do.
To this end, the present invention provides a composition by adding an appropriate amount of alumina cement as a binder to a semiconductive ceramic powder prepared by dissolving an insulating material having the same crystal structure in calcium manganate (CaMnO3) having a low resistivity and having an appropriate resistance value, It is possible to maintain proper molding strength and react without volatilization in the sintering process to form a composite body, and as a result, the densification degree of the composite body can be improved.

Description

TECHNICAL FIELD The present invention relates to a composition for a semicrystalline castable ceramic composite and a method for producing the same,

The present invention relates to a composition for a semiconductive castable ceramic composite and a method for producing the same, and more particularly, to a method for producing a semiconductive castable ceramic composite having a complicated shape and a large size, A composition capable of producing a semiconducting castable ceramic composite having an appropriate resistance value by adding a certain amount of alumina cement as a binder to a powder, casting it in water by casting the mixture with water, and then densely sintering, .

To this end, the present invention provides a composition by adding an appropriate amount of alumina cement as a binder to a semiconductive ceramic powder prepared by dissolving an insulating material having the same crystal structure in calcium manganate (CaMnO3) having a low resistivity and having an appropriate resistance value, It is possible to maintain proper molding strength and react without volatilization in the sintering process to form a composite body, and as a result, the densification degree of the composite body can be improved.

The electrostatic removing material is an electrostatically conductive, usually electrically insulating material. Since the electrostatic removing material has an appropriate resistance value, the electrostatic discharge is appropriately and quickly removed without a spark discharge even when static electricity is generated, thereby preventing an electric shock or a short circuit It is a very useful semiconductor material which prevents the adherence of foreign matter by electrostatic attraction.

Such a static eliminator material should have an appropriate resistance value among other things, for example, a surface resistivity of 10 ³ to 10 ¹¹ ohm.cm, preferably 10 ⁵ to 10 ⁹ ohm.cm, which is suitable for removing static electricity , Yet high density and strength are required for durability, and it should be cheap and easy to manufacture.

Currently, there are electroconductive materials / resin composites and semiconductive ceramic materials used as static eliminators, and in Korean patent application No. 2011-0110348 (Oct. 27, 2011), calcium manganate (CaMnO3) with low resistivity The present invention proposes a semiconductive ceramic composition which stably realizes a change in specific resistance in a wide area by employing an insulating material having the same crystal structure.

However, the above-mentioned technology has a problem that the cost of the product is very high when manufacturing a large-sized member due to the expensive equipment and the complicated process, which limits the application.

On the other hand, castable means that there is fluidity to flow, and it is widely used in the manufacturing process of unshaped refractories whose shape is not constant, and the binder such as alumina cement is used for refractory aggregate whose particle size is controlled, 30 parts by weight, and a small amount of an additive is added to adjust workability and curing time. In addition to alumina cement, aluminum, sodium silicate and polymer resins are used as binders.

In this connection, Korean Patent Application No. 2011-0128950 (Dec. 05, 2011), which is devised by the present inventor, is an eco-friendly and environmentally friendly material by maintaining the molding strength by adding alumina cement in an appropriate amount as a binder, An eco-friendly castable ceramic composition in which densification is promoted by adding an appropriate amount of an alkali glass powder as a sintering aid.

However, in the case of the above-mentioned technique, the surface resistivity is 10 ¹⁰ ohm.cm or more by using alumina, zirconia, or magnesia as a ceramic powder as a base material, and thus it is difficult to remove static electricity.

Currently, semiconductive ceramics for static elimination is a core member applied to various industries, and it is necessary to build a system that meets the trend of large size and complicated shaping. The construction of such a system requires a lot of expensive equipment, Therefore, there is a desperate need for a new method of manufacturing dense ceramics simply and efficiently without expensive equipment.

On the other hand, general methods for forming a general ceramics include pressing, casting, plastic forming, and tape forming.

Among them, casting is performed by dispersing a ceramic powder in a solvent to prepare a fluid suspension, injecting the suspension into a mold such as a gypsum, and allowing the solvent portion to be absorbed by the mold, thereby producing a ceramic molded body . However, it is necessary to disperse the suspension preferably such that the density gradient of the molded body and the sintered body does not occur, but it is difficult to control such dispersion conditions, so that the powder dispersed in the suspension after being injected into the mold is precipitated by gravity, Due to the non-uniform dispersion, there is a difference in absorption rate depending on the upper and lower positions of the suspension in the gypsum frame.

Although the molded body produced by the incomplete process is planned and molded to have a certain thickness, the thickness varies depending on the point of the molded body, and a local density gradient occurs, which causes cracking and deformation in the sintering process.

Most of all, ceramic powders other than clay are difficult to handle due to their weak strength even after molding. Therefore, a binder is used in order to maintain a constant molding strength. Such a binder is mainly composed of a polymer such as polyvinyl alcohol (PVA) Such a polymer is decomposed and volatilized in the course of calcination or sintering. However, if the calcination or sintering conditions are not well controlled, the polymer decomposes and volatilizes due to rapid decomposition and volatilization, Air pollution by combining with oxygen in the atmosphere and generating carbon dioxide is a problem.

Particularly, in the production of large-thickness ceramics having a large thickness and a large size, it is much more difficult to set such dispersion conditions, to uniformize the water absorption rate, to uniformly disperse the density of the compact, Cracks are likely to occur, resulting in difficulties in manufacturing and handling.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a semiconductive ceramic powder which is prepared by dissolving an insulating material having the same crystal structure in calcium manganate (CaMnO3) , Alumina cement as an additive in an appropriate amount to maintain the molding strength, and reacting without volatilization during the sintering process to form a composite body, thereby producing dense semiconductive ceramics.

Another object of the present invention is to provide alumina cement as a binder instead of a conventional polymer to produce a large-sized article by curing, and to provide a molded body having a large molding strength.

In order to achieve the above object, the present invention provides a method for preparing a composition by adding a weight part of alumina cement to a (100-a) weight part of calcium manganate (CaMnO3) semiconductive ceramic powder, wherein a is in the range of 6 to 24 Wherein the composition for a semicrystalline castable ceramic composite is provided.

It is preferable that the semiconductive ceramic powder is obtained by solidifying an insulating material having the same perovskite crystal structure in calcium manganate (CaMnO3).

The present invention also relates to a method for producing a mixture comprising mixing 76 to 94 parts by weight of semiconductive ceramic powder, 6 to 24 parts by weight of alumina cement as a binder, and water to prepare a mixture; Casting the mixture into a mold and curing the mixture; And sintering and densifying the cured mixture. The present invention also provides a method of manufacturing a semiconductive castable ceramic composite.

In order to improve the moldability of the composition, 0.5 to 3 parts by weight of an additive including a water reducing agent, a dispersing agent and a defoaming agent is preferably added.

 According to the present invention, by applying the semiconductive ceramic material to the production of a composite, it is possible to more effectively remove the static electricity generated in the manufacturing process of devices and systems of the electronic and optical industries, thereby preventing spark discharge, The effect is expected.

Further, according to the present invention, it is expected that an action and effect of producing a semicrystalline castable ceramic composite inexpensively and easily.

Further, according to the present invention, it is expected that the function and the effect contributing to the enhancement of the reliability and application of the parts and devices to which the present invention is applied are expected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process flow diagram of a process for producing a semiconductive castable ceramic composite according to an embodiment of the present invention,
2 is a graph showing a change in specific resistance of a semiconductive castable ceramic composite according to an alumina cement content according to an embodiment of the present invention,
3 is an X-ray diffraction analysis graph of a semiconductive castable ceramic composite according to an embodiment of the present invention,
FIG. 4 is a graph showing changes in viscosity of a composition for the production of a semiconductive castable ceramic composite according to an embodiment of the present invention,
FIG. 5 is a graph showing a change in the linear shrinkage ratio according to the moisture addition amount of the composition for producing a semiconductive castable ceramic composite according to an embodiment of the present invention.

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

<Production Example>

The semi-conductor castable ceramic composite composition according to the present invention is specifically prepared by adjusting the composition ratio of (a) to (a-6) to (a-a) calcium manganate (CaMnO3) semiconductive ceramic powder + a alumina cement , And an appropriate amount of alumina cement (alumina content: 80 parts by weight), which is a hydraulic binder, is added to the semi-conductive ceramic powder having no viscosity for molding strength.

In this case, alumina cement (union cement, UAC80N) was used as the hydraulic binder, but other cements such as Portland cement and gypsum are also available, but physical properties such as semiconductor characteristics and strength may be deteriorated due to impurities or unwanted components contained therein Some of them can be used depending on purposes, but in the present invention, high purity alumina cement is used in consideration of purity.

By using the composition of the present invention as described above, it is possible to easily produce a semiconductive castable ceramic composite by a simple general method as shown in FIG.

First, manganese oxide (MnO2), titanium oxide (TiO2), zirconium oxide (ZrO2), calcium carbonate (CaCO3), strontium carbonate (SrCO3), and barium carbonate (BaCO3) were weighed to the composition shown in Table 1, Were mixed well with distilled water and ground.

At this time, manganese oxide can be used in place of MnO 2 because Mn 2 O 3, MnO, and MnCO 3 can also play the same roles through decomposition and valence change in the synthesis process. The process may also be carried out by other methods that can be substituted at the level of those skilled in the art.

On the other hand, if the composition according to the present invention can be included, the starting material may be used in various forms such as a single compound, a salt, and a compound.

The mixed raw materials were calcined at 1000 to 1150 ° C for 2 hours to synthesize them, and the synthesized raw materials were sintered again by ball milling with distilled water.

When the amount is less than the lower limit, synthesis is not performed well, and when the slurry is mixed with water, more than 10% of water content is added to allow smooth synthesis, resulting in a decrease in sintering density and an increase in porosity. If the upper limit is exceeded, the grain growth and sintering of the ceramic powder proceed, the grinding is not smooth, and the sintering density is lowered. Therefore, the calcination temperature is critical in the above range.

On the other hand, the calcination time can be adjusted within a usual range, and is not limited to the above two hours.

 The ceramic powder thus synthesized and the alumina cement as a binder were weighed at a certain ratio, and were mixed dry for 12 hours using an alumina ball mill and pulverized to prepare a composition for a semicontinuous castable ceramic composite. However, the mixing time is not to be construed as being limited by the above time.

 The combined compositions were mixed with water to prepare a fluid slurry, and the mixture was poured into a plastic mold of a certain shape to cure for a day, followed by demolding to produce a shaped body having a predetermined shape.

  At this time, it is necessary to add a small amount of a dispersant or a water reducing agent in order to reduce the amount of water to produce a dense shaped body, and it is preferable to add a small amount of defoaming agent in order to remove bubbles generated at the time of mixing.

  0.5 to 1 part by weight of the composition was added to the dispersing agent (Nopco 5468 CF from KNO) and 0.5 to 1 part by weight of the composition was added to the antifoaming agent (Nopko SN 485, Korea).

The molded body was dried in an oven at 120 ° C for 12 hours to evaporate the residual moisture and then sintered at a temperature of 1350 to 1450 ° C for 2 hours using an electric furnace to prepare a composite body. The resistivity was evaluated. The sintering temperature of the sintered body is in the range of the upper limit and the lower limit according to the conventional sintering theory.

Hereinafter, the present invention will be described in more detail by way of the following examples, but the scope of the present invention is not limited to these examples.

&Lt; Evaluation example &

In order to evaluate the sinterability of the prepared composition, a circular metal mold having a diameter of 15 mm was molded into a disc shape at a pressure of 100 MPa and sintered at 1350 to 1450 ° C for 2 hours using an electric furnace. The sintered density and the porosity were measured using Archimedes The resistivity was measured by forming electrodes on both sides.

The measurement results are shown in Table 1 below.

Characteristics of Calcium Manganate (CaMnO3) Semiconductive Ceramic Powder - Alumina Cement Semiconducting Castable Ceramic Composition number Semi-conductive ceramic powder Alumina
cement
(wt%) Sintering temperature
(° C) Relative density
(%) Resistivity
(ohm.cm) Furtherance wt% Example 1 CaMn0.3Ti0.7O3 94 6 1350 99.72 5.2x10 ⁷ Example 2 CaMn0.3Ti0.7O3 91 9 1350 99.66 7.3 x 10 ⁷ Example 3 CaMn0.3Ti0.7O3 88 12 1350 99.56 8.4x10 ⁷ Example 4 CaMn0.3Ti0.7O3 85 15 1375 98.24 1.4x10 ⁸ Example 5 CaMn0.3Ti0.7O3 82 18 1375 98.31 9.8 x 10 ⁷ Example 6 CaMn0.3Ti0.7O3 79 21 1400 98.12 3.2 x ^{10 8} Example 7 CaMn0.3Ti0.7O3 76 24 1400 97.89 6.5 x ^{10 8} Example 8 CaMn0.4Ti0.6O3 88 12 1350 99.13 8.1x10 ⁵ Example 9 CaMn0.4Ti0.6O3 85 15 1350 98.20 7.5x10 ⁵ Example 10 CaMn0.4Ti0.6O3 82 18 1350 96.77 1.3x10 ⁶ Example 11 CaMn0.5Ti0.5O3 88 12 1350 99.39 6.2x10 ⁴ Example 12 CaMn0.5Ti0.5O3 85 15 1350 97.79 6.3x10 ⁴ Example 13 CaMn0.5Ti0.5O3 82 18 1350 96.87 8.7x10 ⁴ Example 14 CaMn0.15Ti0.35Zr0.5O3 85 15 1425 98.12 1.2x10 ⁷ Example 15 CaMn0.175Ti0.325Zr0.5O3 85 15 1425 98.22 8.4x10 ⁶ Example 16 CaMn0.2Ti0.3Zr0.5O3 85 15 1425 98.35 4.2 x 10 ⁶ Example 17 CaMn0.225Ti0.275Zr0.5O3 85 15 1425 98.54 2.3x10 ⁵ Example 18 CaMn0.25Ti0.25Zr0.5O3 85 15 1425 98.88 2.1 x 10 ⁴ Example 19 CaMn0.2Zr0.8O3 85 15 1450 98.21 6.5 x 10 ⁶ Example 20 CaMn0.15Zr0.85O3 85 15 1450 98.04 8.1x10 ⁷ Example 21 Ca0.4Sr0.6Mn0.4Ti0.6O3 85 15 1400 98.12 2.4 x 10 ⁶ Example 22 Ca0.4Ba0.6Mn0.4Ti0.6O3 85 15 1400 97.99 4.6 x 10 ⁶ Example 23 Ca0.7Sr0.3Mn0.4Ti0.6O3 85 15 1375 98.35 8.5x10 ⁷ Example 24 Ca0.7Ba0.3Mn0.4Ti0.6O3 85 15 1375 98.11 9.2x10 ⁷

As shown in Table 1, the composition of the alumina cement-added semiconducting castable ceramic composite exhibited excellent sinterability and specific resistance even when alumina cement was added as a binder, and the content of alumina cement and zirconium Zr) as the substitution amount increases, the sintering density is slightly decreased and the sintering temperature is increased.

Further, the resistivity of the semiconductive castable ceramic composite according to the alumina cement content shown in FIG. 2 is not significantly affected by the increase of the alumina cement content, and depending on the basic composition of the semiconductive ceramic powder, And the value is highly dependent.

However, the alumina cement as a binder is a functional material for maintaining the molding strength only and does not significantly lower the resistivity value and the sintering property but forms a second phase such as calcium aluminate (CaAl12O19) by acting as an impurity in the base material, It is preferable to limit the content to about 15 parts by weight or less. In the present invention, 6 to 24 parts by weight is added, and this range is regarded as a critical range without deteriorating the properties of the composite.

When the alumina cement is added in an amount exceeding 24 parts by weight, it is impossible to obtain a desired characteristic value due to an increase in specific resistance, and the viscosity of the composition is shortened due to an increase in viscosity. Further, when the alumina cement is added in an amount of less than 6 parts by weight, the molding strength is lowered in the demoulding process after the preparation of the mixed slurry and the hydration hardening process. Therefore, the content of the alumina cement is critical in the above range.

Meanwhile, as can be seen from the X-ray diffraction analysis in FIG. 3, it can be seen that alumina cement as a binder exists in the form of alumina (Al2O3) or calcium aluminate (CaAl12O19) during sintering, (CaMnO3) phase but it is considered that it does not affect the overall resistivity value because the content is small.

The viscosity change of the slurry according to the addition amount of water in the semicrystalline castable ceramic composite composition shown in FIG. 4 shows that the viscosity is drastically lowered by adding water for the slurry preparation, and when the alumina cement content is high, The viscosity is high.

 In this case, it is preferable to use a dispersant and a defoaming agent in order to reduce the amount of water and improve the fluidity. In the present invention, 0.5 to 1 part by weight of the dispersant and defoaming agent are added, respectively.

  5, when the moisture content of the semi-conductive castable ceramic composite composition shown in FIG. 5 shows a change in the linear shrinkage ratio after sintering, the fluidity is good at the higher water content, but the residual moisture increases and the porosity increases due to the hydration reaction. It was found that cracks were formed in the sintering process.

Accordingly, the composition is well mixed and homogenized according to the process shown in FIG. 1, the amount of water is minimized by adding an appropriate amount of the additive, and after the hydration is cured, the residual moisture is removed through the drying process and baking is carried out to a temperature of 10 ⁵ to 10 ⁹ ohm.cm It is possible to produce a large-sized, dense and excellent semiconducting castable ceramic composite having an appropriate specific resistance of about 1 to 20% by weight.

The present invention relates to a method for producing semiconductive ceramics having a complicated and large size by mixing a semiconductive ceramic powder with alumina cement as a binder in a certain amount, mixing the resulting mixture with water, casting the mixture in a mold, densely sintering the mixture, To provide a composition capable of producing a semiconductive castable ceramic having a resistance value and a method for producing the same.

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. That is, the scope of protection of the present invention is to be interpreted by the interpretation of the following claims, and the above embodiments should be construed as supplementary if unavoidable.

Claims (4)

 (A) is in the range of 6 to 24, and a part by weight of alumina cement is added to the (100-a) part by weight of calcium manganate (CaMnO3) semiconductive ceramic powder. / RTI &gt; The method according to claim 1,
Wherein the semiconductive ceramic powder comprises calcium manganate (CaMnO3) dissolved in an insulating material having the same perovskite crystal structure. Mixing 76 to 94 parts by weight of semiconductive ceramic powder, 6 to 24 parts by weight of alumina cement as a binder, and water to prepare a mixture;
Casting the mixture into a mold and curing the mixture;
Sintering and densifying the cured mixture;
The method of manufacturing a semicrystalline castable ceramic composite according to claim 1, The method of claim 3,
Wherein 0.5 to 3 parts by weight of an additive including a water reducing agent, a dispersant, and an antifoaming agent is added to the mixture to improve the formability of the mixture.

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