KR100643143B1 - Manufacturing method of silicon carbide from rice hull and rice straw - Google Patents

Abstract

The present invention provides a method for producing silicon carbide,

The ash obtained by burning the washed and dried rice husk at 300 ~ 600 ℃ in an oxidizing atmosphere is pulverized to obtain a powder having a powder size of 1 mm or less, and the ash obtained by carbonizing washed and dried rice straw at 200 ~ 550 ℃ in a reducing atmosphere. After pulverizing to obtain a powder having a powder size of 1 mm or less, the mixture of 50 to 80% by weight of rice hulls and 20 to 50% by weight of rice straw was sintered at 750 to 1200 ° C. for 3 to 13 hours and then at 300 to 600 ° C. It relates to a method for producing silicon carbide as a raw material of rice husk and rice straw obtained by grinding, screening and silicon carbide after leaving for 1 to 3 hours.

The method of the present invention has the effect of producing a high-purity silicon carbide using only chaff and rice hulls easily obtained as a byproduct in the process of producing rice.

Silicon Carbide, Chaff, Rice Straw, Silica, Carbon

Description

Manufacturing method of silicon carbide from rice hull and rice husk {Manufacturing method of silicon carbide from rice hull and rice straw}

1 is a graph showing the crystal structure of the reaction temperature of the silicon carbide produced by the present invention.

Figure 2 is a graph showing the XRD analysis results of silicon carbide prepared using rice husk and rice straw according to the present invention.

The present invention relates to a method for producing silicon carbide (silicon carbide) from the rice husk and rice straw.

Silicon carbide is composed of silica (Si) and carbon (C) in a molar ratio of 1: 1. It is excellent in heat resistance, chemical resistance, and abrasion resistance, so it is widely used in various fields such as semiconductor manufacturing equipment parts, electronic information parts, and abrasives. It is a gray crystal widely used.

Silicon carbide (SiC) has been used for a long time and many manufacturing methods are known.

The most representative of them is a method of manufacturing a high-purity silica (SiO ₂ ) and coke (C) by heating the reaction at 1800 ~ 1900 ℃ (SiO ₂ + 3C → SiC + 2CO).

However, this method uses expensive raw materials and requires a long time reaction at a high temperature, thus causing a problem of high manufacturing cost.

In another method, in the semiconductor industry, silica powder and carbon black powder which are by-products when cutting silicon single crystal wafers are mixed to form rods, which are heated at 950 ° C. for 1 hour in an oxidizing atmosphere or 1000 ° C. in a nitrogen atmosphere. A method for producing silicon carbide by heating for 4 hours is known. (Korean Patent Laid-Open Publication No. 2002-0086790) In addition, a silicon carbide polymer is molded by molding a silicon-containing polymer compound such as vinylsilane and vinyldisilane. The manufacturing method has been proposed (Korean Patent Publication No. 1991-0008295). The above methods have a problem in that manufacturing costs are high because they require expensive raw materials or need to be reacted at a high temperature for a long time.

Therefore, there is a need in the art for the development of a method for producing silicon carbide at a relatively low manufacturing cost.

An object of the present invention is to provide a method for producing silicon carbide using as raw material rice husk and rice straw by-produced as a farm by-product in the process of producing rice.
The inventors of the present invention generally silicon carbide is produced by firing a carbon component such as siliceous component (SiO ₂ ) and cokes (cokes) such as silica, the chaff contains a large amount of silicon component (SiO ₂ ), rice straw mainly Focusing on the carbon component, it was confirmed that high purity silicon carbide can be produced using only rice husk and rice straw obtained as a by-product when rice is harvested in a farm.

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The present invention relates to a method for producing silicon carbide based on rice husk and rice straw.

Rice hulls peeled from rice during rice production at rice mills are called rice hulls, and stems from which rice is removed are called rice traw.

Chaff varies depending on the region, but the general composition excluding moisture is as follows.

Lipid: About 3wt%

Cellulose: about 33wt%

Silicate (SiO ₂ ): about 23wt%

Pentosan: About 24wt%

Others: about 17wt%

Rice straw has very low siliceous content and high cellulose content compared to rice husk.

Generally, rice husk and rice straw are produced together after threshing rice ears, and a large amount is generated each year, but the utilization is very low, and the utilization is very limited and used for compost, mushroom cultivation medium, feed, and barn. It is being abandoned.

However, chaff contains carbon components such as cellulose and lignin and SiO ₂ , which is a silicon component, in a natural phase, and thus silica (SiO ₂ ), which can be a raw material of silicon carbide, can be obtained.
Rice straw is mainly composed of cellulose together with a small amount of silica, thereby obtaining a carbon component and a small amount of silica that can be a raw material of silicon carbide.

In the case of preparing silicon carbide using chaff and rice straw, especially in the case of rice husk, the reaction of the silicon carbide chemicals, silica and carbon, is already performed in the natural state, and the reaction was easy.The two materials (chaff and rice straw) Compared with the raw material of the conventional silicon carbide, there is almost no impurity and can be obtained together, so it is very economical in terms of manufacturing cost.Since the silica and carbon powder obtained therefrom are very fine, silicon carbide can be obtained at a relatively low temperature. The silicon carbide was excellent in reactivity even when used directly for production without a separate raw material press molding process such as waste silicon utilization process.

In the present invention, using the characteristics of the chaff and rice straw, it was possible to manufacture high-purity silicon carbide in an economical and simple process.

The present invention will be described in detail with reference to the following Examples.

Example

<Step of obtaining silica raw material using chaff>

The rice husks are collected, dried well after washing with water, heated to a high temperature in an oxidizing atmosphere (in air) and burned to obtain rice husk ash. This material contains a small amount of carbon and a large amount of silica. This cooled material is ground to 1 mm or less.
The reason for burning rice hulls in an oxidizing atmosphere is to burn ingredients other than silica such as cellulose in rice hulls.

The ash composition obtained from the rice husk and rice straw by the same process as described in Table 1 and Table 2 below. Table 1 shows the composition of the ash obtained by bullet at 500 ° C. for 5 hours in a reducing atmosphere. At this time, the carbonization temperature is 300 ~ 600 ℃ is suitable, the oxidation time takes 2 ~ 6 hours depending on the temperature.

<Step of obtaining carbon raw material using rice straw>

The straw is collected, washed with water, dried, cut to about 30 cm in length, and calcined by heating at a high temperature in a reducing atmosphere to obtain ash containing a large amount of carbon and a small amount of silica. This material is ground to 1 mm or less.
The reason why rice straw is heated and fired in a reducing atmosphere is that rice straw is burned in an oxidizing atmosphere, so only a small amount of carbon is obtained, but it is carbonized when fired in the reducing atmosphere.
The firing of the rice straw in the oxidizing atmosphere and the burning of the rice hull in the reducing atmosphere are described in Tables 1 and 2 by reference.

The composition of the ash obtained from the straw in the same manner as described above is as described in Table 1 and Table 2. Table 2 shows the ash composition obtained by carbonization at 500 ° C. for 5 hours in an oxidizing atmosphere. The carbonization temperature is suitable 200 ~ 550 ℃ and the carbonization time is 3 ~ 6 hours depending on the temperature.

[Table 1] Composition of ash obtained by carbonization in reducing atmosphere (Unit: wt%)

SiO ₂ Al ₂ O ₃ MgO P ₂ O ₅ K ₂ O Etc C Rice hull 84.13 3.09 1.25 1.02 1.23 0.68 8.60 Straw straw 1.45 - - - - 3.22 95.33

[Table 2] Composition of ash obtained by carbonization in an oxidizing atmosphere (Unit: wt%)

SiO ₂ Al ₂ O ₃ MgO P ₂ O ₅ K ₂ O Etc C Rice hull 91.37 2.73 1.57 1.32 1.23 0.71 1.04 Straw straw 32.67 - - - - 65.66 1.67

<Production of Silicon Carbide>

60 g of rice hulls listed in [Table 1] and 20 g of rice straw materials shown in [Table 1] were mixed and sintered at 950 ° C. for 6 hours, and left at 450 ° C. for 90 minutes to obtain 30 g of gray mass crystals. The small mass crystals obtained here were pulverized to obtain a powder. Analysis of this powder confirmed that it was silicon carbide with a purity of 97%.

As shown in [Table 1] and [Table 2], the rice hull obtained in the oxidizing atmosphere contains a large amount of silicon components, and the straw straw obtained in the reducing atmosphere mainly consists of carbon components. In addition, the ash content obtained in the oxidizing atmosphere has a relatively low carbon content. Therefore, it is necessary to use them as a raw material of silicon carbide by combining them so that the silicon component and the carbon component constitute an equivalent ratio of 1: 1. In order to make the equivalent ratio of the silicon component and the carbon component 1: 1, the ratio of 60 parts by weight of the silicon component (SiO ₂ ) and 12 parts by weight of the carbon component (C) should be maintained.

The raw material may be used by mixing 50 to 80 parts by weight of rice hulls and 20 to 25 parts by weight of rice straw according to the composition of the ash. The sintering process takes 3 ~ 13 hours at 750 ~ 1200 ℃ and the cooling treatment takes 1 ~ 3 hours at 300 ~ 600 ℃.

Figure 1 is a mixture of rice husk and rice straw in a reduced atmosphere at 500 ℃ for 5 hours after incubation at 60:40 weight ratio of the raw material was mixed and sintered at 950 ℃ for 6 hours and then treated at 450 ℃ for 90 minutes (A) and 1100 After sintering at 7 ° C. for 7 hours and then treating at 450 ° C. for 90 minutes, the XRD analysis results of silicon carbide (B) were compared.

As a result, it can be seen that the optimum sintering condition is 7 hours or more at 1100 ° C.

Figure 2 is based on the results obtained in the Example chaff and rice straw after mixing for 5 hours at 500 ℃ 60:40 weight ratio of the raw material obtained by mixing, sintered at 1100 ℃ for 9 hours and then treated at 450 ℃ 90 minutes of silicon carbide It is a graph which shows the result of XRD analysis.

The method of the present invention has the effect of producing a high-purity silicon carbide using only chaff and rice hulls easily obtained as a byproduct in the process of producing rice.

Claims (2)

In the method of manufacturing silicon carbide, The ash obtained by burning the washed and dried rice husk at 300 ~ 600 ℃ in an oxidizing atmosphere is pulverized to obtain a powder having a powder size of 1 mm or less, and the ash obtained by carbonizing washed and dried rice straw at 200 ~ 550 ℃ in a reducing atmosphere. After pulverizing to obtain a powder having a powder size of 1 mm or less, the mixture of 50 to 80% by weight of rice hulls and 20 to 50% by weight of rice straw was sintered at 750 to 1200 ° C. for 3 to 13 hours and then at 300 to 600 ° C. Method of producing silicon carbide as a raw material of rice husk and rice straw obtained by grinding and screening after leaving for 1 to 3 hours to obtain silicon carbide. delete

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