KR20220037168A - Method for manufacturing porous ceramic by direct foaming method and porous ceramic manufactured thereby - Google Patents

Abstract

The present invention provides a method for manufacturing a porous ceramic, which includes the steps of: mixing fumed silica, a blowing agent, and an aqueous alkali solution to obtain a mixed slurry; forming and drying the mixed slurry to obtain a molded article for the porous ceramic; and sintering the molded body for the porous ceramic. Accordingly, it is possible to manufacture the porous ceramic having excellent thermal and mechanical properties.

Description

Method for manufacturing porous ceramic by direct foaming method and porous ceramic manufactured thereby

The present invention relates to a method for producing a porous ceramic, and more particularly, by adding silicon sludge as a foaming agent to fumed silica, which is the main raw material of the porous ceramic, and adding an aqueous alkali solution for gas generation by direct foaming. It relates to a method for producing a porous ceramic, and to a porous ceramic produced by the method.

The semiconductor process is divided into pre/post processes and inspection processes based on the time at which wafers, which are raw materials, are separated into individual chips, and specialized equipment and materials are used for each process.

Among the semiconductor processes, the annealing process performed using a semiconductor furnace equipment includes ohmic contactalloying, ion-implantation damage annealing, dopant activation, TiN, TiSi ₂ , CoSi ₂ Corresponds to an essential process used to form a thin film, etc., and the ceramic insulator used in the semiconductor furnace equipment is required to have excellent thermal properties such as low thermal conductivity.

On the other hand, thermal conductivity depends on the degree to which atoms constituting the material form a uniform and dense layered structure. For example, when the density of atoms constituting the material is high to form a dense structure, heat transfer between the atoms easily occurs to increase thermal conductivity, whereas when the density of the atoms is low, heat between atoms The transfer efficiency is lower than that of the dense structure, and as a result, the thermal conductivity is lowered. Accordingly, a material having a low density of atoms constituting the material, for example, a material having a porous structure, exhibits excellent performance as a heat insulating material due to low thermal conductivity.

However, when the material of the porous structure is used as an insulator, the mechanical strength is low due to the structural characteristic having a high porosity, and structural changes such as cracks easily occur when subjected to thermal shock due to repeated temperature changes, When the porous heat insulator is used in the above-described semiconductor furnace equipment, when cracks occur, the structure and shape of the insulator are deformed, and in this process, due to a chain reaction in which dust from the heat insulator forming the structure is generated, the semiconductor In the heat treatment process during the process, it has a fatal adverse effect on the ultra-high purity semiconductor wafer.

In the case of a material with a dense structure, it is easy to maintain structural stability because it has relatively superior thermal stability than a porous structure even when subjected to thermal shock because of its excellent mechanical properties. not suitable

Therefore, there is a need for a ceramic insulator for semiconductor furnace equipment that has a porous structure with excellent thermal properties but has excellent mechanical properties such as compressive strength, and research and development are being actively conducted on this.

However, the conventional ceramic insulator for semiconductor furnace equipment has disadvantages in that the manufacturing process is complicated and it is difficult to secure price competitiveness by using expensive main raw materials.

There is a need for a method for manufacturing a porous ceramic using a material that has a simple manufacturing process, is inexpensive and can be easily supplied.

Republic of Korea Patent Registration No. 10-0573406

One object of the present invention is to obtain a mixed slurry by mixing fumed silica, a foaming agent and an aqueous alkali solution; forming and drying the mixed slurry to obtain a molded article for a porous ceramic; and sintering the molded body for the porous ceramic, wherein the foaming agent is silicon sludge.

Another object of the present invention is to provide a porous ceramic manufactured using the method for manufacturing the porous ceramic.

The technical problems to be achieved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by those of ordinary skill in the art to which the present invention belongs from the description below. There will be.

One aspect of the present invention comprises the steps of obtaining a mixed slurry by mixing fumed silica, a foaming agent and an aqueous alkali solution; forming and drying the mixed slurry to obtain a molded article for a porous ceramic; and sintering the molded body for the porous ceramic, wherein the foaming agent is silicon sludge.

In an embodiment of the present invention, the fumed silica and the blowing agent may be mixed in a ratio of 99.99 wt%: 0.01 wt% to 99.50 wt%: 0.50 wt% of the fumed silica and the blowing agent.

In one embodiment of the present invention, the alkali component of the aqueous alkali solution may be sodium hydroxide (NaOH) or potassium hydroxide (KOH).

In one embodiment of the present invention, the normal concentration (N) of the aqueous alkali solution may be 7 N to 10 N.

In an embodiment of the present invention, the water in silica (W/S) of the mixed slurry may be 0.2 to 1.0.

In one embodiment of the present invention, the drying step may be performed at 50 ℃ to 70 ℃.

One aspect of the present invention provides a porous ceramic, characterized in that it is prepared using a direct foaming method by mixing fumed silica, a foaming agent and an aqueous alkali solution, and the foaming agent is silicon sludge.

In one embodiment of the present invention, the porosity of the porous ceramic may be 70 vol% to 80 vol% based on the total volume of the porous ceramic.

In an embodiment of the present invention, the thermal conductivity of the porous ceramic may be 0.2 W/m·K to 0.7 W/m·K.

In an embodiment of the present invention, the density of the porous ceramic may be 0.2 g/cm ³ to 0.5 g/cm ³ .

The method for producing a porous ceramic of the present invention is carried out by using a direct foaming method using silicon sludge in fumed silica as a foaming agent. Compared with the process, the overall process time is shortened, and a porous ceramic having excellent thermal and mechanical properties can be manufactured by a simple method of mixing a ceramic raw material and a foaming agent and then drying and sintering.

In addition, by using fumed silica having a size of several nm to several tens of μm, it is easy to secure excellent thermal and mechanical properties as a thermal insulator of porous ceramics, and dispersion stabilization and weight reduction of the mixed slurry are possible.

In addition, fumed silica is used as the main raw material and silicon sludge, a waste generated in the semiconductor manufacturing process, is used as a foaming agent, and at the same time, it is possible to reduce the consumption of thermal energy in the sintering step. There are advantages.

1 is a flowchart of a method for manufacturing a porous ceramic according to the present invention.
Figure 2 is a Na ₂ O—SiO ₂ two-component phase equilibrium diagram.
3 is an image of fumed silica (a) and silicon sludge (b) used in an embodiment of the present invention.
4 is a crystal phase analysis graph (a), particle size analysis graph (b) and microstructure analysis image (c) of fumed silica used in an embodiment of the present invention.
5 is a graph (a) and particle size analysis result graph (b) of the TG/DTA analysis result of silicon sludge used in an embodiment of the present invention.
6 is an optical image of a porous ceramic according to an embodiment of the present invention.
7 is a crystal acid analysis result according to a change in the amount of silicon sludge added to the porous ceramic according to an embodiment of the present invention.
8 is a specific gravity measurement result (a) and compressive strength measurement result (b) of the porous ceramic according to an embodiment of the present invention.
9 is an SEM image according to a magnification of a porous ceramic according to an embodiment of the present invention.
10 is a pore size distribution graph of a porous ceramic according to an embodiment of the present invention.
11 is a thermal diffusion coefficient graph (a) and thermal conductivity graph (b) of the porous ceramic according to an embodiment of the present invention.

In the following description of the present invention, if it is determined that a detailed description of a related well-known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

Since the embodiment according to the concept of the present invention may have various changes and may have various forms, specific embodiments will be illustrated in the drawings and described in detail in the present specification or application. However, this is not intended to limit the embodiment according to the concept of the present invention to a specific disclosed form, and it should be understood that the present invention includes all changes, equivalents, or substitutes included in the spirit and scope of the present invention.

When an element is referred to as being “connected” or “connected” to another element, it is understood that it may be directly connected or connected to the other element, but other elements may exist in between. it should be On the other hand, when it is said that a certain element is "directly connected" or "directly connected" to another element, it should be understood that the other element does not exist in the middle. Other expressions describing the relationship between elements, such as "between" and "immediately between" or "neighboring to" and "directly adjacent to", etc., should be interpreted similarly.

The terms used herein are used only to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present specification, terms such as “comprise” or “have” are intended to designate that the described feature, number, step, operation, component, part, or a combination thereof exists, and includes one or more other features or numbers. , it is to be understood that it does not preclude the possibility of the existence or addition of steps, operations, components, parts, or combinations thereof.

One aspect of the present invention provides a method of manufacturing a porous ceramic.

1 is a flowchart of a method for manufacturing a porous ceramic according to the present invention.

Referring to FIG. 1 , the method for producing a porous ceramic of the present invention includes the steps of mixing fumed silica, a foaming agent, and an aqueous alkali solution to obtain a mixed slurry (S10); forming and drying the mixed slurry to obtain a molded article for a porous ceramic (S20); and sintering the molded body for the porous ceramic (S30), wherein the foaming agent is silicon sludge.

First, the method for producing a porous ceramic of the present invention includes a step (S10) of obtaining a mixed slurry by mixing fumed silica, a foaming agent, and an aqueous alkali solution.

The porous ceramic produced by the method for producing a porous ceramic of the present invention has fumed silica as a main raw material.

The fumed silica is silica particles prepared under high temperature conditions containing SiO ₂ as a main component, and is prepared by vaporizing silicon tetrachloride under hydrogen and oxygen conditions at high temperature, and is amorphous with a size of several nm to several tens of μm. of silica microparticles associating with each other to form a pore structure, and thus has a high specific surface area.

The SiO ₂ has low thermal conductivity, and in particular, the fumed silica is composed of silica fine particles as described above, and corresponds to a material suitable for manufacturing an ultra-light porous ceramic.

In an embodiment of the present invention, the particle size of the fumed silica may be several nm to several tens of μm, and fumed silica particles having a particle size in the above range may be mixed.

In an embodiment of the present invention, the fumed silica may prepare a porous ceramic having a high porosity structure.

In one embodiment of the present invention, the foaming agent may be silicone sludge.

In the semiconductor and photovoltaic industries, silicon wafers are used to manufacture semiconductor devices and solar cells. The silicon wafer is made from the cutting of a silicon ingot, and silicon sludge is generated in the process.

More specifically, a slicing process for thinly cutting a silicon ingot using a wire saw to obtain a silicon wafer and a surface polishing process for planarizing the surface of the sliced silicon wafer, etc. , silicon (Si), abrasives, cooling oil and a large amount of by-products including wire saw wear components are discharged in the form of sludge, where, in general, silicon carbide (SiC) may be used as an abrasive, and as cooling oil A water-soluble oil such as PEG or DEG may be used, or a fat-soluble oil may be used.

Accordingly, the silicon sludge may contain silicon carbide, silicon particles, cutting oil, and metal, which is a component of wire saw wear.

Most of the silicon sludge has been landfilled by waste treatment companies, but a technology that can separate and recover silicon carbide, cutting oil, metal, etc. and reuse it has been developed and is currently being applied.

In an embodiment of the present invention, the silicon sludge may be silicon sludge containing silicon carbide silicon particles, cutting oil, metal components, etc. produced in the above-described semiconductor process, and a foaming agent in the method for producing a porous ceramic of the present invention The silicon sludge used as the above may not be separated and recovered as described above.

In one embodiment of the present invention, the silicon sludge reacts with an aqueous alkali solution in the porous ceramic manufacturing method of the present invention to form Si capable of forming pores in the porous ceramic by a direct forming method. The fumed silica and the fumed silica and the blowing agent 99.99 wt%: 0.01 wt% to 99.50 wt%: 0.50 wt%, for example, 99.99 wt%: 0.01 wt% to 99.70 wt%: 0.30 It can be mixed in a proportion of wt% to sufficiently act as a foaming agent.

In an embodiment of the present invention, the ratio of the fumed silica and the silicon sludge may be a factor for forming the pore size and uniform pores of the porous ceramic manufactured by the manufacturing method of the present invention. For example, when the ratio of the fumed silica and silicon sludge is less than 99.99 wt%: 0.01 wt%, uniform pores may not be formed, and when the ratio is greater than 99.50 wt%: 0.50 wt%, the porous ceramic If the size of the pores is too large, mechanical properties such as compressive strength may be deteriorated.

The porous ceramic manufacturing method of the present invention is performed using silicon sludge that has not undergone the separation and recovery process as described above. Compared with the conventional porous ceramic manufacturing method, the porous ceramic can be manufactured by a cheap and simple process. It has the advantage of being economical.

In one embodiment of the present invention, the aqueous alkali solution is added to the mixture of the fumed silica and polysilicon sludge to generate a gas, and to perform a direct foaming method, NaOH or KOH, for example, NaOH is water ( It may be dissolved in H ₂ O).

In one embodiment of the present invention, when the aqueous alkali solution, for example, NaOH is added to the mixture of the fumed silica and silicon sludge, hydrogen gas may be generated by the mechanism shown in Formula 1 below, and the hydrogen gas can cause foaming reactions in the mixed slurry:

[Formula 1]

Si+2NaOH+H ₂ O → Na ₂ SiO ₃ +2H ₂

In this case, the normal concentration (N) of the aqueous alkali solution may be 7 N to 10 N, for example, 9 N, and W/S (water in silica) of the mixed slurry produced by adding the aqueous alkali solution is 0.2 to 1.0, for example 0.3.

In an embodiment of the present invention, the normal concentration and W/S may act as a control factor for the porosity of the porous ceramic manufactured by the method for manufacturing the porous ceramic of the present invention.

In an embodiment of the present invention, the aqueous alkali solution may act as a sintering agent. For example, the normal concentration (N) of the aqueous alkali solution determines the sintering temperature of the step (S30) of sintering the porous ceramic molded body to be described later. can be a factor

SiO ₂ has the advantage of low thermal conductivity, but at the same time has the disadvantage of having a high melting point.

Figure 2 is a Na ₂ O—SiO ₂ two-component phase equilibrium diagram.

Referring to Chemical Formulas 1 and 2, according to the mechanism of Chemical Formula 1, when the normal concentration of the aqueous solution increases, the amount of hydrogen gas generated increases, and Na ₂ O—SiO ₂ Two-component phase equilibrium diagram of FIG. 2 As a result, it can be seen that the melting point is lowered.

Next, the method for manufacturing a porous ceramic according to the present invention includes a step (S20) of obtaining a molded article for a porous ceramic by molding and drying the mixed slurry.

In the present specification, the direct forming method refers to a chemical method in which gas is generated in a ceramic slurry state, unlike the foaming method in which air is forcibly injected with a strong stirring force and the bubbles are maintained using a foaming agent, etc. As a method of producing a porous ceramic by forming a porous expanded molded article by using the It may be adjusted according to the process conditions of the step (S20) of obtaining a ceramic molded body.

In one embodiment of the present invention, in the step (S20) of obtaining the molded body for the porous ceramic, first, a process of forming the mixed slurry obtained in the step (S10) of obtaining the mixed slurry is performed.

The forming process may be performed, for example, by using a molding capable of obtaining a shape of the porous ceramic to be manufactured, and a packing process, but is not limited thereto.

In one embodiment of the present invention, the occurrence of a foaming reaction may change depending on the molding conditions for molding, and pores of various sizes may be formed in the porous ceramic manufactured by the change of gas generation, so that the molding conditions can be a factor that can control the size of the pores.

For example, after stirring the mixed slurry, by packing in a situation in which no gas is generated, the coalescence of pores is suppressed by collective gas generation, and the gas is sequentially generated. A process of drying to be described later for each local site. By providing a molded article for porous ceramics having uniform pores can be obtained.

Next, in the step (S20) of obtaining the molded body for the porous ceramic, a process of drying the mixed slurry on which the molding process is performed is performed.

In an embodiment of the present invention, the drying process may be performed at 50° C. to 70° C., for example, 50° C., and the drying time may vary depending on the drying temperature. For example, when the drying process is performed at 50° C., the drying time may be 3 days.

The drying conditions of the drying process, for example, drying temperature and drying time, can prevent cracks in the porous ceramic manufactured by the manufacturing method of the present invention, and the drying conditions control the porosity of the porous ceramic. can be a factor

In the step (S20) of obtaining a molded body for porous ceramic by molding and drying the mixed slurry of the present invention, it is possible to obtain a molded body for a porous ceramic through the molding process and drying process under the above-described preferred conditions.

Next, the method of manufacturing a porous ceramic of the present invention includes the step of sintering the molded body for the porous ceramic (S30).

The sintering means a process of densifying a molded body made using powder as a raw material at a high temperature, and in an embodiment of the present invention, the step of sintering the molded body for porous ceramic (S30) is high in the molded body for porous ceramics. It can be carried out by applying heat of temperature. For example, the sintering step (S30) is a method of normal pressure sintering (Normal Sintering) in a box electric furnace, the maximum temperature at a temperature increase rate of about 5 ℃ / min about 75% of the melting temperature of the molded body for porous ceramics It can be carried out by setting the phosphorus to 900 °C.

In one embodiment of the present invention, fumed silica includes SiO ₂ , and the SiO ₂ has the advantage of low thermal conductivity, but at the same time has the disadvantage of having a high melting point. There was a problem of lowering the economy.

In the manufacturing method of the porous ceramic of the present invention, Na ₂ O acting as a flux may be generated during the manufacturing process, and the Na ₂ O lowers the melting point of SiO- ₂ , so that sintering can be performed at a relatively low temperature. This can reduce the consumption of thermal energy.

One aspect of the present invention provides a porous ceramic, characterized in that it is prepared using a direct foaming method by mixing fumed silica, a foaming agent and an aqueous alkali solution, and the foaming agent is silicon sludge.

In an embodiment of the present invention, the method for manufacturing the porous ceramic using the direct foaming method may be the same as the method for manufacturing the porous ceramic described in the above aspect, and the specific process of fumed silica, silicon sludge, aqueous alkali solution and each step is It is replaced with that described in the above aspect.

In an embodiment of the present invention, the porosity of the porous ceramic may be 70 vol% to 80 vol%, for example, 71 vol% to 75 vol%, based on the total volume of the porous ceramic, and the thermal conductivity is 0.2 W /m·K to 0.7 W/m·K, for example 0.238 W/mK to 0.618 W/mK.

In addition, in one embodiment of the present invention, the density of the porous ceramic is 0.2 g/cm ³ to 0.4 g/cm ³ , for example, 0.26 g/cm ³ to 0.42 g/cm ³ It may be, and the compressive strength is It may be 1 MPa to 4 MPa.

The method for producing a porous ceramic of the present invention is carried out by using a direct foaming method using silicon sludge in fumed silica as a foaming agent. Compared with the process, the overall process time is shortened, and a porous ceramic having excellent thermal and mechanical properties can be manufactured by a simple method of mixing a ceramic raw material and a foaming agent and then drying and sintering.

In addition, by using fumed silica having a size of several nm to several tens of μm, it is easy to secure excellent thermal and mechanical properties as a thermal insulator of porous ceramics, and dispersion stabilization and weight reduction of the mixed slurry are possible.

In addition, fumed silica is used as the main raw material and silicon sludge, a waste generated in the semiconductor manufacturing process, is used as a foaming agent, and at the same time, it is possible to reduce the consumption of thermal energy in the sintering step. There are advantages.

Hereinafter, preferred experimental examples are presented to help the understanding of the present invention. However, the following experimental examples are only for helping understanding of the present invention, and the present invention is not limited by the following experimental examples.

Example

Examples 1 to 5. Preparation of porous ceramics

Fumed silica having a particle size of 6 μm to 425 μm (purity 97%, Elchem, NETHERLANDS) and silicone sludge having a particle size of 106 μm or less are mixed at the mixing ratio shown in Table 1 below, and ball milling for uniform mixing Then, 9 N NaOH was mixed to prepare a mixed slurry having a W/S ratio of 0.3, and the mixed slurry was stirred at a stirring speed of 400 rpm for 5 minutes:

Fumed Silica (wt%) Silicon sludge (wt%) W/S ratio NaOH (N) Comparative Example 1 (S00) 100.00 0.00 0.3 9 Example 1 (S01) 99.99 0.01 Example 2 (S05) 99.95 0.05 Example 3 (S10) 99.90 0.10 Example 4 (S20) 99.80 0.20 Example 5 (S30) 99.70 0.30

The stirred mixed slurry was molded into a cube shape of 2 cm X 2 cm using acrylic molding, and dried at a temperature of 50 to 70 °C for 3 days to obtain a molded body for porous ceramics.

The porous ceramic molded body was heat-treated in a box electric furnace at a temperature increase rate of 5 °C/min and a maximum temperature of 900 °C for 1 hour to prepare a porous ceramic.

Comparative Example 1. Preparation of porous ceramic

A porous ceramic was prepared in the same manner as in Example 1, except that in Example 1, a mixed slurry was prepared without silicon sludge.

Experimental Example 1. Analysis of raw materials

3 is an image of fumed silica (a) and silicon sludge (b) used in the method for producing a porous ceramic of the present invention.

i) Fumed Silica

XRF (X-ray Fluorenscene; ZSX-100e, Rigaku, Japan) analysis was performed to identify the raw material components of fumed silica, and the chemical composition is shown in Table 2 below:

SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ Cao MgO Na ₂ O K ₂ O TiO ₂ L.O.I. gun 98.04 0.23 0.17 0.33 0.14 0.12 0.27 0.01 0.71 100

In order to observe the crystal phase of the fumed silica, XRD (D8 ADVANCE, Bruker Co., U.S.A) analysis, particle size analysis, and microstructure analysis were performed, and the results are shown in FIG. 4 .

4 is a crystal phase analysis graph (a), particle size analysis graph (b), and microstructure analysis image (c) of the fumed silica.

Referring to FIG. 4 , the fumed silica exhibited an amorphous peak, and it was found that the particle size had a size of several nm to several tens of μm. could confirm that

ii) silicone sludge

5 is a graph (a) and particle size analysis result graph (b) of TG/DTA analysis of silicon sludge.

Referring to FIG. 5 , it was confirmed that the weight of the silicon sludge increased as the temperature increased, which could be expected to be due to the formation of SiO ₂ oxide due to the oxidation of silicon. In addition, as a result of particle size analysis, it was confirmed that the particle size distribution was 120 μm or less.

Experimental Example 2. Analysis of physical properties of porous ceramics

i) Optical image and crystal phase analysis

Optical images of the porous ceramics prepared in Examples 1 to 3 and Comparative Example 1 were obtained, and are shown in FIG. 6 .

Referring to FIG. 6 , pore formation was observed even in Comparative Example 1 in which no silicone sludge was added, but it was confirmed that the shape and size of the pores were not uniform. was found to be uniformly formed.

The porous ceramics prepared in Examples 1 to 3 and Comparative Example 1 were analyzed using XRD (D8 ADVANCE, Bruker Co., U.S.A.) to show the crystal phase analysis results according to the change in the amount of silicon sludge added in FIG. 7 .

Referring to FIG. 7 , it was confirmed that various types of silica crystal phases such as α-, β-quartz, tridymite and cristobalite were observed.

ii) Specific gravity and compressive strength analysis

The specific gravity of the porous ceramics prepared in Examples 1 to 5 and Comparative Example 1 was measured, and the results are shown in FIG. 8 (a), and compressive strength using UTM (DTU-900MH series UTM, Ssaul Bestech) The measurement result is shown in FIG. 8(b).

Referring to (a) of FIG. 8 , it was confirmed that the specific gravity decreased as the amount of silicon sludge added increased. In particular, in the case of Examples 2 and 3, the specific gravity was 0.38 and 0.35, respectively, the comparative example It can be seen that the ratio is similar.

Referring to (b) of FIG. 8 , it was confirmed that all porous ceramics exhibited a compressive strength of 5 MPa or less, and in the case of Example 1, it was found that the highest compressive strength was 3.82 MPa. As can be seen from the above specific gravity measurement results, it could be expected that as the amount of silicone sludge added increased, the pores due to the foaming phenomenon increased.

iii) microstructure analysis

The results of microstructure analysis using a scanning electron microscope (SEM, Nova Nano 200) of the porous ceramics prepared in Examples 1 to 3 and Comparative Example 1 are shown in FIG. 9 .

Referring to FIG. 9 , it was confirmed that a microstructure in which pores of various sizes were mixed, and in Comparative Example 1, foaming occurred, but a relatively non-uniform foaming phenomenon was observed, and in Examples 1 to 3, In this case, it was confirmed that the size of the macropores tended to increase as the amount of silicon sludge added increased.

It was confirmed that this trend is consistent with the results of compressive strength and specific gravity described above.

iv) Analysis of pore size and porosity

The results of the average pore size and porosity measured using Mercury Porosimetry of the porous ceramics prepared in Examples 1 and 3 are shown in Table 3 below, and the pore size distribution is shown in FIG. 10 shown in:

Average pore size (μm) Porosity (v%) Example 1 32.33 75.45 Example 3 43.34 71.46

Referring to Table 3 and FIG. 10 , in the case of the porous ceramics of Examples 1 and 3, it was confirmed that the pore size distribution was widely observed in the range of 10 μm to 100 μm.

v) Thermal diffusion coefficient and thermal conductivity analysis

In order to confirm the applicability of the insulating material of the porous ceramics prepared in Examples 1 to 3, the thermal diffusion coefficient (a) and thermal conductivity (b) were measured using LFA (Laser Flash Apparatus, LFA457) equipment, and the results were It is shown in FIG. 11 .

Referring to (a) of FIG. 11 , in the case of the thermal diffusion coefficient, the porous ceramic of Example 1 exhibited a value of 0.628 mm ² /s, and the thermal diffusion coefficient decreased in the range of room temperature to 200 ° C. It could be confirmed that a large increase was shown, and the porous ceramic of Example 3 exhibited a value of the thermal diffusion coefficient in the range of 0.431 mm ² /s to 0.805 mm ² /s.

11 (b), the porous ceramic of Example 2 exhibited a thermal conductivity value of 0.321 W/mK to 0.763 W/mK, and in Example 3, a value of 0.238 W/mK to 0.618 W/mK It could be confirmed that the thermal conductivity decreased as the amount of silicon sludge added increased, and it was confirmed that it was applicable as a heat insulator.

Although the technical idea of the present invention described above has been specifically described in the preferred embodiment, it should be noted that the embodiment is for the description and not the limitation. In addition, those of ordinary skill in the technical field of the present invention will understand that various embodiments are possible within the scope of the technical spirit of the present invention. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

Claims (10)

mixing fumed silica, a foaming agent and an aqueous alkali solution to obtain a mixed slurry;
forming and drying the mixed slurry to obtain a molded article for a porous ceramic; and
sintering the molded body for the porous ceramic;
including,
The method for producing a porous ceramic, characterized in that the foaming agent is silicon sludge (silicon sludge). The method of claim 1,
The fumed silica and the foaming agent 99.99 wt%: 0.01 wt% to 99.50 wt%: A method of producing a porous ceramic, characterized in that mixed in a ratio of 0.50 wt%. The method of claim 1,
The alkali component of the aqueous alkali solution is a method of manufacturing a porous ceramic, characterized in that sodium hydroxide (NaOH) or potassium hydroxide (KOH). The method of claim 1,
The normal concentration (N) of the aqueous alkali solution is a method of manufacturing a porous ceramic, characterized in that 7 N to 10 N. The method of claim 1,
The method for producing a porous ceramic, characterized in that the W/S (water in silica) of the mixed slurry is 0.2 to 1.0. The method of claim 1,
The method for producing a porous ceramic, characterized in that the step of obtaining the ceramic molded body is carried out at 50 °C to 70 °C. A porous ceramic, characterized in that it is prepared using a direct foaming method by mixing fumed silica, a foaming agent, and an aqueous alkali solution, and the foaming agent is silicon sludge. 8. The method of claim 7,
A porous ceramic, characterized in that the porosity is 70 vol% to 80 vol% based on the total volume of the porous ceramic. 8. The method of claim 7,
The porous ceramic, characterized in that the thermal conductivity is 0.2 W/m·K to 0.7 W/m·K. 8. The method of claim 7,
The porous ceramic, characterized in that the density is 0.2 g/cm ³ to 0.5 g/cm ³ .

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