KR20040088808A - Method for fabricating porous SiC ceramics using plant - Google Patents

Abstract

PURPOSE: A method for preparing porous silicon carbide ceramics by using plants is provided, to lower cost and to reduce the generation of pollutant materials by using the fibrous material of a natural plant. CONSTITUTION: The method comprises the steps of (S110) extracting a basic source material from a plant; (S120) maturing the basic source material; (S130) processing the matured source material; (S140, S150) carbonizing the processed source material to prepare a carbon precursor; and (S160, S170) melting and sintering a metal silicon and the carbon precursor in vacuum at a sintering temperature of the carbon precursor to prepare the porous silicon carbide ceramics. Preferably the plant is dishcloth gourd plant, and the basic source material is the fibrous stalk cell of the plant. Preferably the maturing process comprises cutting the separated source material into a plated shape, drying it, coating a resin or an organic binder to it and maturing it. Preferably the resin is a phenol-based resin diluted with an alcohol in the ratio of 1:0.5-1:3.

Description

Method for fabricating porous SiC ceramics using plant

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing porous silicon carbide ceramics used in industrial fields such as steelmaking, steelmaking, chemical industry, incinerators, heat-using equipment, etc. The present invention relates to a method for producing porous silicon carbide ceramics by producing a carbon precursor and then reacting and sintering the carbon precursor and metal silicon to improve thermal efficiency and combustion efficiency, and to remove environmental inhibitors.

Ceramics have high mechanical properties such as high strength, high hardness, and abrasion resistance, as well as excellent oxidation resistance, corrosion resistance, low thermal conductivity, and thermal properties such as high thermal shock and high temperature strength due to thermal expansion coefficient. And a lot of investment in commercialization.

Among the ceramics, silicon carbide (SiC) has a strong covalent bonding due to the characteristics of the material and thus has low sinterability. Sintering refers to a phenomenon in which a bond formed between a powder is hardened when a non-metal or metal powder is formed by heat treatment at a temperature below the melting point. It is an important technique for producing urine pressure products or ceramics, powder metallurgy, cermet, and the like. The driving force of the sintering is the extra surface energy of the powder, ie the sum of the surface energies in the state where the powder is simply aggregated is thermodynamically non-equilibrium, not the minimum. When the powder is heat-treated, mass transfer occurs in a direction to reduce the surface energy, that is, in a direction in which the surface area is reduced, thereby causing bonding of the particles. The microstructure change in the sintering process can be divided into three stages: initial stage, intermediate stage, and final stage.

In the early stages, adhesions between particles occur, which in turn increases the area of the area, which is called cervical growth. At this stage, the relative density is about 0.5 to 0.6, and shrinkage is about 4% to 5%. In the middle stage, the channel-shaped gap is narrowed gradually, so that the relative density is 0.6 to 0.95 and the shrinkage ratio is about 5% to 20%. The relative density is 0.95 or more in the boil stage, and the amount of pores (or also called voids) remains in the part or particle of the polyhedralized particle angle. The pores that communicate with the outside air are called open pores, and the pores that do not pass through are called closed pores. In this boil stage, densification takes place as the pores disappear. Therefore, porous ceramics with many pores and dense ceramics with many pores are different depending on the pores and accordingly, their functions are also different.

The conventional method of manufacturing porous silicon carbide ceramics is a method using urethane foam as a basic raw material. This technique coated the silicon carbide suspension on the surface of the urethane foam using a coating method such as wash coating or dip coating, followed by dehydration and drying to remove the residual suspension on the surface of the urethane foam. . The fine powder of silicon carbide was applied and the dried urethane foam was heat-treated at a temperature of about 800 ° C. or more to completely burn the organic urethane. Next, porous silicon carbide ceramics were prepared by atmospheric sintering at a temperature of about 1800 ° C. or higher and a nitrogen atmosphere. The conventional method of manufacturing porous silicon carbide ceramics includes a ceramic suspension coating process, a heat treatment, and a sintering process at a high temperature, so that the overall process is complicated and the energy cost for manufacturing is increased due to the high sintering temperature, resulting in a cost of the final finished product. There was a disadvantage of increasing. In addition, the emission of pollutants due to the combustion of the organic polymer material when heat-treating the urethane foam has been pointed out as a problem. In order to solve this problem, various studies have been conducted on the basic raw materials of porous silicon carbide ceramics.

One of the studies to solve this problem is Korean Patent No. 267797. The patent discloses a method for producing dense high toughness ceramics using charcoal. However, the patent is not a technology for producing porous ceramics but a method for manufacturing dense ceramics, and the final product is made of carbon fiber-silicon carbide composite by reaction sintering. Therefore, there has been a continuing need for a method for producing porous silicon carbide ceramics that solves the above problems.

The present invention has been conceived to solve the above problems, in order to improve the thermal efficiency and combustion efficiency, and to remove the elements that interfere with the environment to extract the basic raw material from the plant to produce a carbonized precursor through a certain process and then use it The purpose is to provide a method for producing a porous silicon carbide sintered body by reaction sintering.

1 is a flow chart showing a method of manufacturing porous silicon carbide ceramics according to the present invention;

FIG. 2A is a flow diagram illustrating a specific embodiment of the manufacturing method shown in FIG. 1, and

FIG. 2B shows a flowchart illustrating another specific embodiment of the manufacturing method shown in FIG. 1.

Method for producing a porous silicon carbide ceramic according to the present invention for achieving the above object, (a) extracting the basic raw material from the plant, (b) aging the basic raw material, (c) the aged raw material (D) carbonizing the processed raw material to produce a carbon precursor, and (e) melting and reacting and sintering the metal silicon and the carbon precursor to a sintering temperature of the carbon precursor in a vacuum atmosphere. Include.

In step (a), the plant is a plant belonging to the loofah family and the basic raw material is preferably the fibrous stem cells of the plant.

In this case, step (b) is a step of cutting the separated basic raw material into a plate shape, drying, and then applying the resin or an organic binder to mature for a predetermined time.

It is preferable that the resin apply | coated here is a phenol type resin in which the ratio of resin and alcohol is mixed in the range of 1: 0.5-1: 3, and diluted.

It is more preferable that the carbon powder is further added to the phenolic resin diluted with alcohol in the range of 1 to 50% by weight.

(c) step (c-1) putting the aged base material into a mold having a predetermined shape, and laminating (c-2) hot pressing the laminated base material within a range of 150 ° C to 500 ° C. It is preferable that the step and (c-2) comprises the step of processing the low-temperature hot-pressed basic raw material into a predetermined shape.

Meanwhile, in step (a), the basic raw material is preferably a stem or root of a plant.

In this case, step (b) is a step of ripening the separated basic raw material in water.

Step (c) is a step of weaving the mature raw material in two or three dimensions in a frame of a predetermined shape.

Hereinafter, a method of manufacturing porous silicon carbide ceramics according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

Referring to Figure 1, the method for producing a porous silicon carbide ceramics according to the present invention first extracting the basic raw material (S110), the step of ripening the basic raw material (S120), processing the basic raw material (S130), basic Carbonizing the raw material (S140), preparing a carbon precursor (S150), the step of reacting and sintering silicon and the carbon precursor (S160), and preparing a porous silicon carbide ceramics (S170).

Depending on the basic raw materials, there are differences in the manufacturing method from the aging of the basic raw materials to the production of porous silicon carbide ceramics, and the resulting porous silicon carbide ceramics also differs. A method of producing a preferred porous silicon carbide ceramics according to the basic raw material is shown in FIGS. 2A and 2B.

Referring to FIG. 2A, a preferred method of manufacturing porous silicon carbide ceramics using fibrous stem cells of a plant belonging to a loofah family as a basic raw material is shown. When the basic raw material is a fibrous stem cell of a plant belonging to a loofah, first the basic raw material is extracted (S210), the basic raw material is cut and dried (S221), and the basic raw material is applied with a resin or a binder (S222) Mature the raw material (S223). The basic raw material is placed in a mold having a predetermined shape and stacked (S231), and then hot-pressed at low temperature (S232), and processed into a predetermined shape (S233). Carbonized processed base material (S240) to produce a carbon precursor (S250). Next, porous silicon carbide ceramics are manufactured by reacting and sintering silicon and this carbon precursor (S260). When following this manufacturing method, the produced porous silicon carbide sintered compact becomes a microporous porous silicon carbide sintered compact whose pore is fine.

Referring to FIG. 2B, there is shown a method for producing a porous porous silicon carbide ceramic in the case of using the stem or root of a plant as a basic raw material. If the basic raw material is the stem or root of the plant, first extract the basic raw material (S310), and aged it in water (S320), and weaving the matured basic raw material in a frame of a predetermined shape in two or three dimensions (S331) Process (S332). Then carbonizing the basic raw material (S340) to produce a carbon precursor (S350). Next, porous silicon carbide ceramics are manufactured by reacting and sintering silicon and the carbon precursor (S360). When following this manufacturing method, the manufactured porous silicon carbide sintered compact becomes a large pore and irregular coarse pore porous silicon carbide sintered compact.

The production of porous silicon carbide ceramics having fine pores is as follows.

As a basic raw material, fibrous stem cells are isolated from plants belonging to the loofah family, cut into plates and dried. A resin or an organic binder is applied to the basic raw material.

It is preferable to use a phenol resin as resin. When using a phenol resin, the phenol resin (resin) which mixed and diluted phenol resin and alcohol in the ratio of 1: 0.5-1: 3 is used.

The base material coated with resin or organic binder is aged for a certain time. When using a phenol resin, the carbon yield of a carbon precursor can be improved by adding and apply | coating 1-50 weight% of carbon powder to the phenol resin diluted with alcohol before apply | coating a phenol resin to a fiber.

The aged basic raw material is placed in a mold having a predetermined shape and laminated, and then molded by a low temperature hot press within a range of about 150 ° C to 500 ° C. The basic raw material formed by low temperature hot press is first processed into a desired shape, and carbonized in a vacuum atmosphere or an inert gas atmosphere at a temperature in the range of 800 ° C to 1300 ° C to produce a carbon precursor.

At this time, in order to control the size and distribution of the pores of the carbon precursor, the amount of the resin or organic binder applied to the base material, the lamination method when laminating the aged base material to the mold, or the pressure during hot pressing are appropriately adjusted. It is important. In addition, it is also important to control the carbon yield of the carbon precursor in accordance with the vacuum or inert gas atmosphere or heat treatment time in the carbonization step.

The preparation of porous silicon carbide ceramics having coarse pores is as follows.

After aging in water using the stem or root of the plant as a basic raw material, and then weaving in a two-dimensional or three-dimensional in a certain shape of the frame to prepare a molded body of the basic raw material with controlled pores. Thereafter, the molded base material is first processed into a desired shape, and carbonized in a vacuum atmosphere or an inert gas atmosphere at a temperature in the range of 800 ° C. to 1300 ° C. as in the case of fine pores, thereby producing a carbon precursor. .

The porous silicon carbide ceramics are prepared by reaction sintering with metal silicon using the carbon precursor prepared as described above.

There are a variety of sintering methods for producing silicon carbide by reacting metal silicon with a carbon precursor. For example, there are sintering methods such as Pressureless Sintering, Hot Pressing, Hot Isostatic Pressing, and Reaction Sintering.

Among them, sintering methods such as atmospheric sintering, hot pressing sintering, and hot isostatic sintering have to use expensive fine powder as a main raw material and sintering aids, so that the stem, root or fiber of the plant of the present invention is used as a basic raw material. It is not suitable for the production of silicon carbide sintered compact.

The liquid phase reaction sintering method is capable of sintering at a relatively low temperature (within the range of about 1,500 ° C to 1,700 ° C) compared with other sintering methods without adding fine powder and expensive sintering aid, and the sintering reaction is performed with carbon and molten silicon. It proceeds very rapidly by exothermic reaction and has the advantage of sintering with little dimensional change such as shrinkage or expansion during sintering, so that it is easy to sinter precision products or complicated shapes or large products. Therefore, it is a process which can reduce energy cost with productivity improvement, and is a sintering method suitable for this invention. Such a liquid phase reaction sintering method is disclosed in Korean Patent No. 10-0299099, and the liquid phase reaction sintering method disclosed in the same patent may be used.

Hereinafter, a method of manufacturing a porous silicon carbide sintered body according to the present invention will be described in detail with reference to an embodiment of manufacturing porous silicon carbide ceramics having micropores.

{Example}

Isolate fibrous stem cells from plants belonging to the loofah family. The isolated fibrous stem cells are cut into plates and dried. Then, the diluted phenolic resin (resin) is applied to the fiber by mixing the phenolic resin and alcohol in a ratio of 1: 0.5 to 1: 3 and aged for 24 hours. At this time, the carbon yield of the carbon precursor can be increased by adding 1 to 50% by weight of carbon powder to the phenol resin diluted with alcohol before applying the phenol resin to the fiber. The aged fibers are placed in a 100 mm x 100 mm square mold and laminated. Then, it is pressurized at a low pressure of about 1 kg / cm 3 at a temperature of 200 ° C. to perform a low temperature hot press. The low temperature hot pressed molded product is first processed into a desired shape and then carbonized under a nitrogen gas atmosphere at 1300 ° C. to prepare a porous carbon precursor.

Metal silicon (Si) having a particle size of 2 mm to 3 mm was placed under the prepared carbon precursor and melted in a vacuum resistance heating furnace adjusted to a sintering temperature of 1650 ° C. and a vacuum atmosphere of 10 ⁻¹ torr. Next, the porous silicon carbide sintered body by liquid phase sintering is produced by reacting the silicon penetrated with the carbon precursor and the carbon component of the carbon precursor.

The porous silicon carbide sintered body manufactured by the above method is a porous sintered body having each of the fibrous bundles having mesh micropores formed of silicon carbide by reaction of silicon and carbon.

According to the method for manufacturing the porous silicon carbide ceramic according to the present invention as described above, by using the fiber of the natural plant as a starting material to reduce the cost and also to reduce the cost by producing a silicon carbide ceramic sintered body having excellent mechanical and thermal properties By using the porous silicon carbide ceramic products according to the method for heat-use equipment, etc., it is possible to save fuel and reduce emissions of pollutants, thereby providing energy saving and environmental protection.

While the above has been shown and described with respect to preferred embodiments of the present invention, the invention is not limited to the specific embodiments described above, it is usually in the art to which the invention belongs without departing from the spirit of the invention claimed in the claims. Anyone of ordinary skill in the art can make various modifications, as well as such modifications are within the scope of the claims.

Claims (9)

(a) extracting the basic raw material from the plant; (b) aging the basic raw material; (c) processing the aged raw material; (d) carbonizing the processed raw material to produce a carbon precursor; And (e) melting and reacting and sintering the metal silicon and the carbon precursor at the sintering temperature of the carbon precursor in a vacuum atmosphere. The method of claim 1, In the step (a), the plant is a plant belonging to the loofah family and the basic raw material is a method for producing porous silicon carbide ceramics, characterized in that the plant's fibrous stem cells. The method of claim 2, The step of aging of (b) is a method for producing porous silicon carbide ceramics, characterized in that the step of cutting the separated basic raw material into a plate shape, dried and then applied with a resin or an organic binder for a certain time. The method of claim 3, wherein The resin of (b) is a method for producing porous silicon carbide ceramics, characterized in that the ratio of the resin and alcohol is mixed in the range of 1: 0.5 to 1: 3 diluted phenolic resin. The method of claim 4, wherein Method for producing a porous silicon carbide ceramics, characterized in that the carbon powder is further added in the range of 1 to 50% by weight to the phenol-based resin diluted with alcohol. The method of claim 2, The processing step of (c), (c-1) stacking the aged basic raw materials into a mold having a predetermined shape; (c-2) hot pressing the stacked basic raw materials within a range of 150 ° C to 500 ° C; And (c-2) processing the low temperature hot pressed basic raw material into a predetermined shape; a method of manufacturing porous silicon carbide ceramics, characterized in that consisting of. The method of claim 1, In the step (a), the basic raw material is a method for producing porous silicon carbide ceramics, characterized in that the stem or root of the plant. The method of claim 7, wherein The aging step of (b) is a method for producing porous silicon carbide ceramics, characterized in that the step of aging the separated raw material in water. The method of claim 7, wherein Wherein the step of (c) is a method of manufacturing porous silicon carbide ceramics, characterized in that the step of weaving the mature raw material in a predetermined shape in a two-dimensional or three-dimensional process.