KR20210095847A - Silicon carbide powder synthetic material - Google Patents

Abstract

A raw material for synthesizing silicon carbide powder according to an embodiment of the present invention includes a carbon source, a silicon source, and particles having a density of 0.2 to 1.5 g/cm^3. The present invention can increase the loading amount of a reaction vessel.

Description

Silicon carbide powder synthetic raw material {SILICON CARBIDE POWDER SYNTHETIC MATERIAL}

The present invention relates to a raw material for synthesizing silicon carbide powder.

Silicon carbide powder has recently been used as a semiconductor material for various electronic devices and purposes. Silicon carbide powder is particularly useful because of its physical strength and high resistance to chemical attack. Silicon carbide powder also has a radiation hardness, a relatively wide bandgap, a high saturated electron drift velocity, a high operating temperature, and a spectrum of blue, violet, and ultraviolet. ) has excellent electronic properties including absorption and emission of high-energy protons in the region.

There are various methods for the production of silicon carbide powder, and for example, the Acheson method, the carbon thermal reduction method, the liquid phase polymer pyrolysis method, or the CVD method is used. In particular, the high-purity silicon carbide powder synthesis method uses a liquid-phase polymer pyrolysis method or a carbon-thermal reduction method.

That is, the silicon carbide powder can be synthesized by mixing the carbon source and the silicon source material, and performing a carbonization process and a synthesizing process for the mixture.

The silicon carbide powder can be synthesized as a final silicon carbide powder by charging the mixture into a reaction vessel and applying heat and pressure to the crucible. At this time, in this synthesis process, depending on the characteristics of the mixture, the amount of charging to be filled in the crucible is different, there is a problem that the properties of the silicon carbide powder are different.

Therefore, there is a need for a mixture capable of producing a silicon carbide powder that can be charged in a larger amount and has improved properties.

An embodiment of the present invention is to provide a raw material for synthesizing silicon carbide powder capable of producing an improved silicon carbide powder and increasing the loading amount of the reaction vessel.

The raw material for synthesizing silicon carbide powder according to an embodiment of the present invention includes a carbon source and a silicon source, and includes particles having a density of 0.2 g/cm 3 to 1.5 g/cm 3 .

The raw material for synthesizing silicon carbide powder according to an embodiment of the present invention may have bulk-shaped particles, a density of about 0.2 g/cm 3 to about 1.5 g/cm 3 , and a pore size of 1,100 μm to 5 cm.

Accordingly, since it has a high density, it is possible to increase the amount of the silicon carbide powder synthesis raw material in the reaction vessel when synthesizing the silicon carbide powder.

In addition, since the reaction gas generated during the reaction can be smoothly discharged due to the wide pore size, the silicon carbide powder can be smoothly synthesized at a high temperature increase rate.

Therefore, it is possible to have an improved process efficiency when manufacturing the silicon carbide powder as a raw material for synthesizing the silicon carbide powder according to the embodiment of the present invention.

1 is a view showing a process flow diagram of a silicon carbide powder manufacturing method according to an embodiment of the present invention.
2 and 3 are views showing a cross-section in which the silicon carbide powder synthesis raw material according to an embodiment of the present invention is filled in the reaction vessel.
4 to 8 are views showing SEM photographs of silicon carbide powder according to Preparation Examples and Comparative Examples of the present invention.

Hereinafter, a method for manufacturing silicon carbide powder according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a process flow diagram illustrating a method for manufacturing a silicon carbide powder according to an embodiment of the present invention.

Referring to FIG. 1 , the method for manufacturing silicon carbide powder according to an embodiment of the present invention may include forming a mixture (ST10) and reacting the mixture (ST20).

Each step is described in more detail as follows.

In the step of forming the mixture (ST10), a silicon source and a carbon source may be prepared, and the mixture may be mixed.

The silicon source may include various materials capable of providing silicon. For example, the silicon source may include silica. In addition to silica, silica powder, silica sol, silica gel, quartz powder, etc. may be used as the silicon source. However, the embodiment is not limited thereto, and an organosilicon compound including silicon may be used as the silicon source.

In addition, the carbon source may include a solid carbon source or an organic carbon compound.

Examples of the solid carbon source include graphite, carbon black, carbon nanotube (CNT), fullerene (C ₆₀ ), and the like.

Examples of the organic carbon compound include phenol, franc, xylene, polyimide, polyurethane, polyvinyl alcohol, polyacrylonitrile, or polyvinyl acetate (poly (vinyl acetate)); and the like. In addition, cellulose, sugar, pitch, tar, etc. may be used.

The process of mixing the carbon source and the silicon source may be classified into a dry mixing process or a wet mixing process depending on whether a solvent is used. In this case, according to the wet mixing process, it is possible to aggregate the carbon source and the silicon source, thereby improving productivity. In addition, according to the dry mixing process, it is possible to prevent problems of cost and contamination due to the use of a solvent, and it is possible to omit the carbonization process and the like, thereby simplifying the process.

For example, the silicon source and the carbon source may be mixed by a method such as a ball mill or an attrition bill to recover a mixture. However, embodiments are not limited thereto, and the silicon source and the carbon source may be mixed by various methods such as a 3D mixer, a paste mill, a spray dryer or a planetary mill to recover the mixture. This mixture can be recovered by sieving.

This mixture can produce silicon carbide powder through a subsequent reaction step. That is, the mixture may be a raw material for synthesizing silicon carbide powder.

The silicon source and the carbon source may be mixed in a predetermined ratio. For example, a mole ratio of carbon contained in the carbon source to silicon contained in the silicon source (hereinafter, “the molar ratio of carbon to silicon”) may be about 1:1.5 to about 1:3.

When the molar ratio of carbon to silicon exceeds about 3, the amount of carbon remaining increases without participating in the reaction due to a large amount of carbon, thereby reducing the recovery rate. In addition, when the molar ratio of carbon to silicon is less than about 1.5, the amount of silicon remaining increases without participating in the reaction because the amount of silicon is large, thereby reducing the recovery rate. That is, the molar ratio of carbon to silicon is determined in consideration of the recovery rate.

In this case, considering that the silicon source is volatilized in a gaseous state at a high temperature in the reaction step, the molar ratio of carbon to silicon may be about 1.8 to about 2.7.

The mixture, that is, the raw material for synthesizing the silicon carbide powder may be particles in the form of bulk. For example, the raw material for synthesizing the silicon carbide powder may include a granule shape or a block shape.

For example, referring to FIGS. 2 and 3 , the raw material for synthesizing the silicon carbide powder may include a spherical or hemispherical circular shape, or a polygonal shape such as a square or a triangle.

In addition, the raw material for synthesizing the silicon carbide powder may have a density of a certain size. For example, the density of the raw material for synthesizing the silicon carbide powder may have a size of about 0.2 g/cm 3 or more. In detail, the density of the raw material for synthesizing the silicon carbide powder may have a size of about 0.2 g/cm 3 to 1.5 g/cm 3 . In more detail, the density of the raw material for synthesizing the silicon carbide powder may have a size of about 0.6 g/cm 3 to about 1.2 g/cm 3 .

The density of the raw material for synthesizing the silicon carbide powder may be related to a loading amount of the raw material for synthesizing the silicon carbide powder charged to the reaction vessel when the raw material for synthesizing the silicon carbide powder is charged to the reaction vessel.

That is, since the raw material for synthesizing silicon carbide powder is composed of particles in bulk form, the density of the raw material is higher than that of raw material in powder form. Silicon carbide powder synthetic raw material can be charged.

When the density of the raw material for synthesizing the silicon carbide powder is less than about 0.2 g / ㎤, the density of the raw material becomes small, and the loading amount of the raw material charged into the reaction vessel may be reduced. there is.

The silicon carbide powder synthetic raw material according to the embodiment may have an improved loading amount as it has a density in the size range as described above.

In addition, the raw material for synthesizing the silicon carbide powder may include voids, that is, pores generated between the particles in the bulk form.

In this case, the pores of the raw material for synthesizing the silicon carbide powder may have a certain size. For example, the size (d) of the pores of the silicon carbide powder synthetic raw material may be about 1,100㎛ to about 5cm. In detail, the size (d) of the pores of the silicon carbide powder synthetic raw material may be about 1,100㎛ to about 1cm.

The pore size of the raw material for synthesizing the silicon carbide powder may be related to a discharge passage of a reaction gas generated during the synthesis process when the silicon carbide powder raw material is charged into a reaction vessel to synthesize the raw material.

In detail, when the silicon carbide powder synthesis raw material is charged into a reaction vessel and reacted by applying heat and pressure, various reaction gases may be generated by this reaction inside. The reaction gas is related to the temperature increase rate, and when the temperature increase rate is lowered to control the discharge amount of the reaction gas, there are problems in that process efficiency is lowered and the synthesis of silicon carbide powder is not performed smoothly.

When the pore size of the silicon carbide powder synthesis raw material is less than about 1,100 μm, the pore size is small and the reaction gas cannot be smoothly discharged, and when it exceeds about 5 cm, the amount of the silicon carbide powder synthesis raw material charged into the reaction vessel this may be lowered.

The raw material for synthesizing silicon carbide powder according to the embodiment may smoothly discharge the reaction gas as it has pores in the size range as described above, and accordingly, improved process efficiency and the synthesis of silicon carbide powder may be facilitated.

The raw material for synthesizing the silicon carbide powder may include bulk particles having a size of about 110 μm or more. For example, the raw material for synthesizing the silicon carbide powder may include bulk particles having a size of about 110 μm to about 200 mm.

When the size of the bulk particles is less than about 110 μm or exceeds about 200 mm, the density and pore size of the raw material for synthesizing the silicon carbide powder may be out of the above range.

Subsequently, in the reaction step (ST20), the silicon carbide powder synthesis raw material, that is, the silicon carbide powder synthesis raw material obtained by mixing the silicon source and the carbon source may be heated to form a silicon carbide powder. The synthesis step ST20 may be divided into a carbonization process and a synthesis process.

In the carbonization process, the organic carbon compound may be carbonized to generate carbon. The carbonization process may be performed at a temperature of about 600 °C to about 1,200 °C. In more detail, the carbonization process may be performed at a temperature of about 800 °C to about 1,100 °C. When the solid carbon source is used as a carbon source, the carbonization process may not proceed.

Thereafter, the synthesis process proceeds. In the synthesis process, the silicon source and the solid carbon source react or the silicon source and the organic carbon compound react to form a silicon carbide powder by the entire reaction formula of Reaction Scheme 3 according to the steps of Reaction Schemes 1 and 2 below. there is.

[Scheme 1]

SiO2(s) + C(s) -> SiO(g) + CO(g)

[Scheme 2]

SiO(g) + 2C(s) -> SiC(s) + CO(g)

[Scheme 3]

SiO2(s) + 3C(s) -> SiC(s) + 2CO(g)

The heating temperature may be about 1,300° C. or higher so that the above-described reaction can occur smoothly. At this time, the silicon carbide powder produced by setting the heating temperature to about 1,300° C. to about 1,900° C. may have a beta phase, which is a low-temperature stable phase. The beta phase may be formed of fine particles to improve the strength of the silicon carbide powder. However, the embodiment is not limited thereto, and the silicon carbide powder may have an alpha phase, which is a high-temperature stable phase, by setting the heating temperature to exceed about 1,900°C. The synthesis process may be performed for about 2 to 4 hours.

Hereinafter, the present invention will be described in more detail through a method for producing silicon carbide powder according to Preparation Examples and Comparative Examples. These manufacturing examples are merely presented as examples in order to explain the present invention in more detail. Therefore, the present invention is not limited to these preparation examples.

Preparation Example 1

10 g of fumed silica and 10 g of phenolic resin were mixed to form a mixture. At this time, the phenolic resin had a carbon residual rate of about 60% after the carbonization process, and a viscosity of 500 cps.

At this time, the density of the mixture was about 1.2 g / ㎤, the pore size of the mixture was about 500㎛,

In addition, the shape of the mixture was spherical.

Then, the raw material was put into the crucible 500φ × 100H, and the charging amount was measured.

The mixing device was mixed by operating at 130 rpm for 3 minutes using a fast mill.

Thereafter, the mixture 1 is subjected to a carbonization process for 1 hour at a temperature of about 800°C at a temperature increase of 3°C/min, and a synthesis process at a temperature of about 1,650°C for about 3 hours at a temperature increase of 10°C/min. Through this, a silicon carbide powder was formed.

The reaction atmosphere starts at an initial vacuum degree of 5 × 10 ^-2 Torr or less and proceeds by operating a low-speed rotary pump.

after. The prepared silicon carbide powder was observed with a scanning electron microscope.

Preparation 2

A silicon carbide powder was prepared in the same manner as in Preparation Example 1, except that the pore size of the mixture was about 1 cm and the shape of the mixture was polygonal.

Preparation 3

A silicon carbide powder was prepared in the same manner as in Preparation Example 1, except that the density of the mixture was about 0.8 g/cm 3 and the pore size of the mixture was about 1 cm.

Comparative Example 1

A silicon carbide powder was prepared in the same manner as in Preparation Example 1, except that the density of the mixture was about 0.2 g/cm 3 and the pore size of the mixture was about nanometers.

Comparative Example 2

A silicon carbide powder was prepared in the same manner as in Preparation Example 1, except that the density of the mixture was about 1.7 g/cm 3 and the pore size of the mixture was about 450 μm.

Loading (kg) Vacuum process time (sec) Preparation Example 1 4 1000 Preparation 2 4 1000 Preparation 3 2.5 1000 Comparative Example 1 One 3600 Comparative Example 2 5 1000

Referring to Table 1 and FIGS. 4 to 8 , in the case of Preparation Examples 1 to 3, it can be seen that more raw materials can be charged into the crucible. In addition, it can be seen that the high density can reduce the problem of scattering, thereby shortening the vacuum process time. In addition, it can be seen that the reaction gases can be smoothly discharged through a sufficient pore size, so that the silicon carbide powder synthesis is smoothly performed at a rapidly elevated temperature.

On the other hand, in the case of Comparative Example 1, it can be seen that the density of the raw material is small, so that the amount charged into the crucible is smaller than that of the Preparation Example. In addition, it can be seen that scattering occurs due to the small density, thereby increasing the vacuum process time.

In addition, in the case of Comparative Example 2, it can be seen that the charging amount is increased and the vacuum process time is shortened, but the reaction gases are not smoothly discharged due to the small pore size, so that the silicon carbide powder synthesis cannot be proceeded at a rapidly elevated temperature.

Features, structures, effects, etc. described in the above-described embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, features, structures, effects, etc. illustrated in each embodiment can be combined or modified for other embodiments by those of ordinary skill in the art to which the embodiments belong. Accordingly, the contents related to such combinations and modifications should be interpreted as being included in the scope of the present invention.

In addition, although the embodiments have been mainly described above, these are merely examples and do not limit the present invention, and those of ordinary skill in the art to which the present invention pertains are exemplified above in a range that does not depart from the essential characteristics of the present embodiment. It can be seen that various modifications and applications that have not been made are possible. For example, each component specifically shown in the embodiments may be implemented by modification. And the differences related to these modifications and applications should be construed as being included in the scope of the present invention defined in the appended claims.

Claims (3)

comprising a carbon source and a silicon source;
It contains particles having a density of 0.2 g/cm 3 to 1.5 g/cm 3 ,
Including pores formed between adjacent particles,
The size of the pores is defined as the maximum distance between the adjacent particles,
The pores are 1,100㎛ to 5㎝ in size,
The particle is a silicon carbide powder synthetic raw material having a size of 110㎛ to 200㎜. The method according to claim 1,
The molar ratio of carbon contained in the carbon source to the silicon contained in the silicon source is 1:1.5 to 1:3 of silicon carbide powder synthetic raw material. The method according to claim 1 or 2,
The silicon source includes at least one of silica powder, silica sol, silica gel, and quartz powder,
The carbon source is a silicon carbide powder synthetic raw material comprising at least one of phenol, franc, xylene, polyimide, polyurethane, polyvinyl alcohol, polyacrylonitrile, and polyvinyl acetate.

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