KR20230130240A - METHOD FOR CONTROL ELECTRICAL AND MECHENICAL PROPERTIES OF SiC FIBER - Google Patents

Abstract

One embodiment of the present invention provides a method for controlling the electrical and mechanical properties of SiC fibers, which method includes performing a curing process on an organosilicon-based polymer precursor fiber to make it infusible; And it may include the step of heat-treating the infusible organosilicon-based polymer precursor fiber to convert it into SiC fiber, wherein the pressure condition is a low pressure of 1.0 × 10 ^-6 bar or more and less than 1.0 bar or more than 2.0 bar and 100.0 bar. It can be controlled to indicate any one of the following high pressures.

Description

Method for controlling electrical and mechanical properties of SiC fiber {METHOD FOR CONTROL ELECTRICAL AND MECHENICAL PROPERTIES OF SiC FIBER}

The present invention relates to a method for controlling the electrical and mechanical properties of SiC (silicon carbide) fibers. More specifically, the present invention relates to a method of controlling the pressure during thermal decomposition of precursor fibers during the manufacturing process of conventional SiC fibers without applying additional processes or additives. It relates to a method of efficiently controlling the electrical and mechanical properties of SiC fibers.

SiC is a representative non-oxide ceramic material and has excellent heat resistance, oxidation resistance, and chemical resistance at high temperatures, and its importance is growing as a material that can be used in extreme environments such as high temperature, high pressure, or acidic atmosphere.

SiC can be used in various forms such as fibers, plates, and porous materials. In particular, in the case of fibrous form, it is expected to be applied to catalysts and catalyst supports, high-temperature insulation materials, and diesel filter materials through differentiation of the structure or shape of the fiber. In particular, it has great potential as a filter material for high temperature, extreme environments, such as filtration and recovery of acidic gas at high temperatures, which can be used in extreme environments where existing organic or inorganic materials are difficult to access. .

In order to form a ceramic material such as SiC into a fibrous form, a method of melting and spinning the ceramic material by heating it to 1500°C or higher is usually used. However, in the case of SiC materials, the melting point is over 1800°C, so it is difficult to melt-spun traditional SiC materials by heating. Therefore, SiC fibers are typically manufactured using ceramic precursors, which are polymers that are converted into ceramics through thermal decomposition. A representative precursor of SiC is polycarbosilane (PCS). To manufacture SiC fibers, PCS is first heated and melted, and then spun to produce PCS fibers having a fiber shape. Next, a curing process is performed to convert the PCS fibers with thermoplastic properties into thermosetting to prevent the PCS fibers from softening and melting during thermal decomposition. SiC fibers can be manufactured by heat-treating the cured PCS fibers at a temperature of 1000°C or higher in an inert atmosphere to induce thermal decomposition. Typically, the pyrolysis process is carried out under an inert atmosphere by flowing an inert gas such as argon gas up to ambient pressure in a heat treatment furnace.

SiC fibers can be widely applied to various industrial fields, and must exhibit individually required properties depending on the field of application. To this end, technologies have been proposed to control the properties of SiC fibers by adding additional process steps or additives to the general SiC fiber manufacturing process as described above. For example, in order to improve the durability, electrical and mechanical properties of SiC fibers and adjust them to suit the application field, by adding additives to improve properties, forming a coating layer on the outside of the fiber, or through composite technology. Methods for forming complexes have been proposed.

Patent Document 1 refers to drying and fiberizing a transparent light brown solution formed by mixing a polycarbosilane solution and a non-polar organic solvent to obtain a polycarbosilane-based fiber, curing it, subjecting it to primary and secondary heat treatment, and then crystallizing it. A method for manufacturing flexible thermoelectric materials is disclosed. According to Patent Document 1, in order to apply silicon carbide fiber as a thermoelectric material for flexible devices, metal elements such as Fe, Pt, and Pd are added to the polycarbosilane solution to improve conductivity. After dissolving the polycarbosilane, the metal is added to the polycarbosilane solution. Elements must be added and dried again, and the heat treatment process must be performed twice at different temperatures.

Patent Document 2 discloses a method of producing polymer-containing carbon nanotube fibers by providing polymers to carbon nanotube fibers and then twisting them together to produce coil structure fibers. According to Patent Document 2, in order to improve the mechanical properties of composite fibers, carbon nanotube fibers must be immersed in a polymer solution and dried to provide a polymer, and then the polymer must be crystallized through processes such as heat treatment or alcohol immersion, so several steps are required. Additional processes are additionally required.

Patent Document 3 discloses that a raw carbon nanotube fiber having an empty space is immersed in a monomer polymerization solution of phenolic resin, polymerization is performed, phenolic resin is added into the empty space, and then carbon nanotubes are formed through stabilization and carbonization steps. A method for manufacturing fiber is disclosed. According to Patent Document 3, in order to improve the mechanical and electrical properties of carbon nanotube fibers, additional processes such as immersion in a polymerization solution, polymerization, stabilization, and carbonization must be performed.

In this way, in order to improve the electrical and mechanical properties of ceramic fibers such as SiC, additional additives must be added or additional processing steps must be performed, so a method to control and improve the properties of SiC fibers through a simpler and more efficient process The demand still exists.

Patent Document 1: Republic of Korea Patent Publication No. 10-2021-0009752 (2021.01.27.) Patent Document 2: Republic of Korea Patent Publication No. 10-2019-0040556 (2019.04.19.) Patent Document 3: Republic of Korea Patent Publication No. 10-2012429 (2019.08.13.)

The problem to be solved by the present invention is to control the pressure of the atmospheric gas in the thermal decomposition step of converting to ceramic during the SiC fiber manufacturing process without introducing additional additives or process steps, thereby making the SiC fiber suitable for the applied industrial field. The goal is to provide an easy and efficient method to effectively control and improve physical properties such as electrical and mechanical properties.

One embodiment of the present invention to solve the above problem provides a method for controlling the electrical and mechanical properties of SiC fibers, which method includes performing a curing process on the organosilicon-based polymer precursor fiber to make it infusible. ; And it may include the step of converting the infusible organosilicon-based polymer precursor fiber into SiC fiber by heat treatment, wherein the heat treatment includes controlling pressure conditions according to the desired characteristics of the SiC fiber, and the pressure condition is 1.0 It can be controlled to indicate either a low pressure of 10 ^-6 bar or more and less than 1.0 bar or a high pressure of more than 2.0 bar but less than 100.0 bar.

Another embodiment of the present invention to solve the above problem relates to a SiC fiber whose electrical and mechanical properties are controlled by the method according to the above-described embodiment.

According to one embodiment of the present invention, without introducing additional additives or process steps to control or improve the physical properties of SiC fiber, by controlling the pressure of the atmospheric gas in the pyrolysis step where it is converted to ceramic during the SiC fiber manufacturing process. , the electrical and mechanical properties of SiC fibers can be efficiently controlled and improved.

In addition, according to an embodiment of the present invention, the properties of SiC fibers can be controlled and improved in various ways to meet the specific technical requirements of industrial fields to which SiC fibers are applied, significantly increasing the usability of SiC fibers in various fields. It can be enlarged.

Figure 1 is a diagram for explaining a method for controlling the electrical and mechanical properties of SiC fibers according to an embodiment of the present invention.
Figure 2 is a SEM (Scanning Electron Microscopy) image showing the microstructure of SiC fibers according to controlled pressure during heat treatment, according to an embodiment of the present invention.
Figure 3 shows the element content of SiC fiber according to the pressure controlled during heat treatment, in one embodiment of the present invention.
Figure 4 shows the distribution of the element content of SiC fiber according to the pressure controlled during heat treatment, in one embodiment of the present invention.
Figure 5 shows the results of XRD (X-ray diffraction) analysis of SiC fiber according to the pressure controlled during heat treatment in one embodiment of the present invention.
Figure 6 shows the electrical conductivity of SiC fiber according to controlled pressure during heat treatment, in one embodiment of the present invention.
Figure 7 shows the tensile strength of SiC fiber according to controlled pressure during heat treatment, in one embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings in order to provide a detailed description so that those skilled in the art can easily implement the technical idea of the present invention. In the following description, many specific details, such as specific components, are shown, which are provided to facilitate a more general understanding of the present invention, but it is known to those skilled in the art that the present invention can be practiced without these specific details. It will be self-evident to those who have it. Additionally, in describing the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

One embodiment of the present invention includes the steps of performing a curing process on an organosilicon-based polymer precursor fiber to make it infusible; and converting the infusible organosilicon-based polymer precursor fiber into SiC fiber by heat treating it. The heat treatment includes controlling pressure conditions according to the desired characteristics of the SiC fiber. The pressure conditions are characterized by being controlled to indicate at least one of low pressure of 1.0Х10 ^-6 bar or more and less than 1.0 bar and high pressure of more than 2.0 bar and less than 100.0 bar.

In the prior art, in order to improve the physical properties such as durability or electrical conductivity of SiC fiber, it was common to add additional additives and processes, such as adding additives such as metal elements, adding a coating process, or complexing. On the other hand, in this embodiment, in order to control and improve the electrical and mechanical properties of SiC fibers as desired, no additional additives or additional processes are applied, and the normal process for manufacturing SiC fibers is used as is, but the precursor SiC fibers can exhibit improved electrical and mechanical properties required depending on the application field by controlling pressure conditions to achieve desired properties in the heat treatment step of pyrolyzing the fibers and converting them into ceramics.

Referring to FIG. 1, a method for controlling the electrical and mechanical properties of SiC fiber according to an embodiment of the present invention will be described. Figure 1 is a diagram for explaining a method of controlling the electrical and mechanical properties of SiC fiber according to an embodiment of the present invention.

Referring to Figure 1, precursor fibers can be formed (S10).

The precursor may represent the raw material for forming SiC, which can be converted to SiC by thermal decomposition. The precursor may include an organosilicon-based polymer having a Si-C bond in the backbone.

In one embodiment, the precursor is polysiloxanes, polyborosiloxanes, polycarbosiloxanes, polyborosilazanes, polycarbosilane, polysilylcarbodiimides. , or a combination thereof.

A precursor fiber can be formed by spinning a precursor using a spinning method for fiber formation.

In one embodiment, the spinning method may include melt spinning, dry spinning, wet spinning, electro-spinning, or a combination thereof.

Melt spinning is a method of forming a fiber shape by melting the precursor at a temperature above the melting point, extruding it from a spinneret, and cooling it.

For example, to form a precursor fiber, a solid precursor is placed in a spinning block in a melt spinning machine, nitrogen gas, etc. is injected into the interior to create an inert atmosphere, and then heated to 200-300°C to melt the precursor, followed by nitrogen gas, etc. This can be achieved by additionally injecting an inert gas to raise the pressure inside the spinning block to allow the melt to flow to the nozzle, and then controlling the supply of a certain amount of melt to the nozzle by a gear pump. Through this process, precursor fibers can be formed.

For example, during melt spinning, the heating temperature may range from 200 to 300°C. If the temperature is less than 200°C, the viscosity of the molten mixture is too high due to the relatively low temperature and it cannot be effectively injected into the nozzle, resulting in fiberization. It is difficult to melt, and if it exceeds 300°C, the viscosity of the molten mixture becomes too low due to the excessively high temperature, causing it to flow like water and fiberization may not occur.

Dry spinning is a method of dissolving a polymer in a solvent to create a solution, extruding this solution through a spinneret into hot air, and evaporating the solvent to solidify it into a fiber form.

Wet spinning is a method in which a polymer is dissolved in a solvent to create a solution, and this solution is extruded through a spinneret in a coagulating liquid, and the fiber polymer is regenerated and coagulated to solidify into a fiber shape.

Electrospinning is a method of spinning a polymer solution into a fiber shape by applying an electric field to it.

Next, the precursor fiber can be made infusible by performing a curing process (S20).

In the case of a precursor, which is a polymer raw material that is converted to SiC by thermal decomposition, when the temperature is raised for heat treatment, the polymer precursor melts again when it reaches the softening temperature and melting temperature, so it loses its molded form, sticks together, and eventually turns into a liquid. . Therefore, in order to ensure that the molded shape is not lost even if the temperature is increased, the thermoplastic polymer precursor must be converted to thermosetting before heat treatment, which is called curing or infusible treatment.

In one embodiment, the curing process may be selected from oxidation curing, iodine curing, electron beam curing, chemical vapor curing, or a combination thereof.

Oxidation curing is generally carried out by exposure to temperatures above 200°C in air, and oxygen atoms can act as a bridge between silicon and silicon.

Iodine curing can be achieved by inducing a cross-linking reaction by iodine by exposing it to iodine gas at a temperature of 150-200°C for 12-24 hours.

Electron beam curing can be achieved by inducing radical bonds between silicon and silicon in the polymer precursor structure by a powerful electron beam.

Chemical vapor curing can be achieved by a chemical vapor process using various gases as crosslinking accelerators.

Next, heat treatment may be performed on the cured precursor fiber (S30).

Heat treatment is a process for converting cured precursor fibers into ceramic SiC fibers by thermally decomposing them.

Heat treatment may be performed at a temperature ranging from 700°C to 1400°C. If the heat treatment temperature is below the above range, the organic elements of the precursor, such as organosilicon polymers, may not be completely decomposed and may exhibit polymeric properties. If the heat treatment temperature exceeds the above range, excessive decomposition may occur due to impurities and the fiber shape may be maintained. There may not be.

In the prior art, the focus was only on adding additional additives or additional processes to improve and control the properties of SiC fibers, and control of pressure conditions during heat treatment during the SiC fiber manufacturing process was not known. In contrast, the present inventors found that during the heat treatment process of converting cured precursor fibers into SiC fibers by pyrolyzing them, the microstructure, element content and distribution, and contained crystalline phase of the produced SiC fibers vary depending on the pressure inside the heat treatment furnace, Accordingly, it was found that the electrical and mechanical properties such as electrical conductivity or tensile strength of the produced SiC fibers also varied. Based on this knowledge, in the present invention, SiC fibers are produced by a simple method of controlling pressure conditions in the heat treatment step during the normal process of producing SiC fibers, without the need to apply additional additives or additional processes as in the prior art. It can be effectively controlled to exhibit the required electrical and mechanical characteristics depending on the field of application.

During heat treatment, pressure conditions can be controlled depending on the desired SiC properties. Specifically, during heat treatment, pressure conditions can be controlled to indicate either low pressure or high pressure conditions depending on the required characteristics of SiC.

In this specification, based on normal pressure, a pressure lower than this may be indicated as low pressure, and a pressure higher than this may be indicated as high pressure. Normal pressure may typically range from about 1.0 bar to about 2.0 bar, and preferably range from about 1.2 bar to about 1.5 bar. Accordingly, low pressure may refer to a pressure of less than about 1.0 bar, for example, a pressure of 1.0Х10 ^-6 bar or more and less than about 1.0 bar. High pressure may refer to a pressure force greater than about 2.0 bar, for example, a pressure greater than about 2.0 bar but less than or equal to 100.0 bar.

In one embodiment, the low pressure ranges from 1.0×10 ^-6 bar to 10×10 ^-2 bar, preferably from 1.0×10 ^-5 bar to 1.0× ^{10 -3} bar, or from 1.0×10 ^-3 bar to 10×10 It can represent a pressure in the ^-2 bar range, or 1.0×10 ^-5 bar to 1.0×10 ^-6 bar.

In one embodiment, the high pressure ranges from 2.0 bar to 100.0 bar, preferably from 5.0 bar to 100.0 bar, or from 2.0 bar to 30.0 bar, or from 10.0 bar to 100.0 bar, or from 30.0 bar to 50.0 bar, or from 50.0 bar. It can represent pressures from bar to 100.0 bar.

Depending on the control of each pressure condition, the microstructure, element content and distribution, contained crystal phase, electrical conductivity, and tensile strength of the SiC fiber produced may vary. This is explained in detail below.

SiC fibers manufactured by heat treatment with pressure conditions controlled to low pressure can exhibit the following characteristics compared to SiC fibers manufactured by heat treatment with pressure conditions controlled to normal pressure.

- The decomposition of the precursor fiber into SiO and CO gas is accelerated, which can lead to the formation of coarse crystal phases and pores inside the fiber. In addition, the oxygen content of the SiC fiber is significantly reduced, and the difference in distribution of silicon and carbon on the surface and inside the SiC fiber can be reduced.

- SiC fibers may have a β-SiC phase and a graphite phase.

- Electrical conductivity may increase. The high electrical conductivity of SiC fibers prepared by heat treatment with controlled pressure conditions at low pressure can be attributed to their low oxygen content.

- Tensile strength may decrease. The low tensile strength of SiC fibers produced by heat treatment with controlled pressure conditions at low pressure may be due to the non-uniform microstructure such as coarsened crystal phases and pores inside the fiber.

SiC fibers manufactured by heat treatment with pressure conditions controlled to high pressure can exhibit the following characteristics compared to SiC fibers manufactured by heat treatment with pressure conditions controlled to normal pressure.

- The decomposition of the precursor fiber into SiO and CO gas is suppressed, resulting in a uniform structure inside the fiber, resulting in a smooth cut surface, and a bright area layer can be formed on the surface.

- SiC fibers may have a β-SiC phase and a graphene oxide phase.

- Electrical conductivity may decrease. The low electrical conductivity of SiC fibers prepared by heat treatment with controlled pressure conditions at high pressure can be attributed to the high oxygen content.

- Tensile strength may increase. The high tensile strength of SiC fibers prepared by heat treatment with controlled pressure conditions at high pressure can be attributed to the uniform microstructure inside the fibers.

Therefore, in the present invention, the electrical and mechanical properties of the SiC fiber can be efficiently controlled and improved by a simple method of setting the pressure conditions during heat treatment to match the desired characteristics of the SiC fiber.

For example, when applied to fields that require high electrical conductivity, the pressure conditions during heat treatment during the SiC fiber manufacturing process are controlled to a low pressure in the range of 1.0×10 ^-6 bar to 10×10 ^-2 bar to achieve high electrical conductivity. SiC fibers having can be manufactured. In addition, for example, when applied to fields that require high tensile strength, SiC fibers with high tensile strength can be manufactured by controlling the pressure conditions during heat treatment during the SiC fiber manufacturing process to a high pressure in the range of 2.0 bar to 100.0 bar. You can.

In one embodiment, control of pressure conditions may be applied by selecting one of low pressure and high pressure conditions so that the SiC fiber exhibits desired electrical conductivity and tensile strength based on the above correlation.

Another embodiment of the present invention relates to SiC fibers manufactured according to the above-described embodiments.

SiC fibers can exhibit improved electrical and mechanical properties to suit the requirements of the application.

In one embodiment, the SiC fiber may have a β-SiC phase.

In one embodiment, the SiC fiber may have a β-SiC phase and a graphite phase.

In one embodiment, the SiC fiber may have a β-SiC phase and a graphene oxide phase.

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are merely illustrative of the present invention, and the scope of the present invention is not limited to the following examples.

[Example]

1. Fabrication of SiC fibers with improved electrical and mechanical properties

Put the solid PCS into the spinning block of the melt spinner, create an inert atmosphere by injecting nitrogen gas, etc., and then heat to 200~300℃ to melt the solid PCS, and then additionally inject inert gas such as nitrogen gas to spin. PCS fibers were formed by raising the pressure inside the block to allow the melt to flow to the nozzle, and then controlling the gear pump to supply a certain amount of melt to the nozzle.

Subsequently, a curing process was performed on the PCS fiber to make the PCS fiber infusible. Curing was performed by chemical vapor curing using a cross-linker gas.

The cured PCS fiber was converted into SiC fiber by heat treatment. The ringed PCS fiber was set in a graphite mold and loaded into a heat treatment furnace. In the heat treatment furnace, a vacuum atmosphere was created to about 1.0 × 10 ^-6 bar using a vacuum pump, and then argon gas, an inert gas, was flowed to an ambient pressure of 1.0 bar to 2.0 bar.

At this time, the pressure inside the heat treatment furnace was controlled to normal pressure, low pressure, and high pressure conditions, respectively, and the pressure conditions applied in each case are examples belonging to the normal pressure, low pressure, and high pressure conditions according to the present invention, in the following three cases. SiC fibers were manufactured by heat treatment under controlled conditions.

1) Normal pressure conditions: SiC fiber was manufactured by flowing argon gas at a pressure of 1.0 bar to 2.0 bar in the heat treatment furnace and heat treating it up to 1400°C.

2) Low pressure conditions: SiC fibers were manufactured by heat treatment to 1400°C while maintaining a vacuum atmosphere of approximately 1.0×10 ^-6 bar in the heat treatment furnace using a vacuum pump.

3) High pressure conditions: SiC fiber was manufactured by flowing argon gas above normal pressure in the heat treatment furnace and heat treating at 40 bar or higher up to 1400°C.

2. Evaluation of SiC fibers

The SiC fiber prepared in 1 above was evaluated, and the results are shown in Figures 2 to 7.

Figure 2 is an SEM image showing the microstructure of SiC fiber according to controlled pressure during heat treatment, in one embodiment of the present invention.

Referring to Figure 2, the SiC fiber manufactured under normal pressure conditions showed a cut surface of a typical SiC fiber (manufactured according to a conventional manufacturing method). On the other hand, the SiC fiber manufactured under low pressure conditions accelerated decomposition into SiO and CO gas, and coarsened crystal phases and pores were observed inside the fiber. The SiC fiber manufactured under high pressure conditions showed the smoothest cut surface with suppressed decomposition, and a bright oxide layer of approximately 500 nm was formed on the surface. This oxide layer is a layer formed by oxygen excessively distributed in SiC fibers manufactured under high pressure conditions.

Figure 3 shows the element content of SiC fiber according to the pressure controlled during heat treatment in an embodiment of the present invention, and Figure 4 shows the element content of SiC fiber according to the pressure controlled during heat treatment in an embodiment of the present invention. It shows the distribution of content.

Referring to Figures 3 and 4, SiC fibers manufactured under normal pressure conditions showed the element content and distribution of typical SiC fibers. On the other hand, the oxygen content of SiC fibers manufactured under low pressure conditions was extremely reduced, and the distribution of silicon and carbon did not show much difference on the surface and inside the fiber. SiC fibers manufactured under high pressure conditions showed the greatest difference in element distribution between the surface and interior of the fiber, and showed that many elements were distributed on the surface. Accordingly, the impurity oxygen content was found to be highest in SiC fibers manufactured under high pressure conditions.

Figure 5 shows the results of XRD (X-ray diffraction) analysis of SiC fiber according to the pressure controlled during heat treatment in one embodiment of the present invention.

Referring to Figure 5, the SiC fiber manufactured under normal pressure conditions was found to have the β-SiC phase (approximately 36°, 60°, and 72°) seen in general SiC fibers. On the other hand, β-SiC phase (approximately 36°, 42°, 60°, 72°, 76°) and graphite peak (approximately 21°) were observed in SiC fibers manufactured under low pressure conditions, and SiC fibers manufactured under high pressure conditions were observed. Graphene oxide peaks (about 12° and about 24°) were observed along with the β-SiC phase (about 36°, 60°, and 72°).

Figure 6 shows the electrical conductivity of SiC fiber according to controlled pressure during heat treatment, in one embodiment of the present invention.

Referring to Figure 6, the SiC fiber manufactured under low pressure conditions showed the highest electrical conductivity (12.27 S/m), and the SiC fiber manufactured under high pressure conditions showed the lowest electrical conductivity (1.99 S/m). Electrical conductivity was related to the oxygen content within the SiC fiber. In other words, it can be seen that SiC fibers manufactured under low pressure conditions have the lowest oxygen content and thus exhibit high conductivity, while SiC fibers manufactured under high pressure conditions have the highest oxygen content and thus exhibit excellent insulation performance.

Figure 7 shows the tensile strength of SiC fiber according to controlled pressure during heat treatment, in one embodiment of the present invention.

Referring to Figure 7, SiC fibers manufactured under low pressure conditions showed the lowest average tensile strength of 0.22 GPa, while SiC fibers manufactured under high pressure conditions showed a high tensile strength that was 1.32 times improved compared to SiC fibers manufactured under normal pressure conditions. indicated.

As shown in Figures 2 to 7, the microstructure, element content and distribution, and contained elements of SiC fibers produced according to the pressure inside the heat treatment furnace during the heat treatment process of converting the cured precursor fibers into SiC fibers by pyrolyzing them. It can be seen that the crystal phase changes, and the electrical and mechanical properties such as electrical conductivity or tensile strength of the SiC fiber produced also change accordingly. Therefore, according to the present invention, there is no need to apply additional additives or additional processes as in the prior art, by simply controlling the pressure conditions in the heat treatment process of thermally decomposing the precursor fiber and converting it into ceramic during the normal process of manufacturing SiC fiber. Depending on the field of application, it can exhibit the required electrical and mechanical properties. Control of pressure conditions can be applied by selecting either low pressure or high pressure conditions to achieve desired electrical conductivity and tensile strength based on the above experimental results.

As a result, according to the present invention, the electrical and mechanical properties of SiC fibers can be appropriately controlled by an efficient and easy method according to the physical property conditions required in the applied industrial field, and the electrical and mechanical properties of SiC fibers are controlled accordingly. Fibers can be widely applied in a wide range of industries.

The present invention is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible without departing from the technical spirit of the present invention. It will be clear to those who have knowledge.

Claims (13)

Performing a curing process on the organosilicon-based polymer precursor fiber to make it infusible; and
It includes converting the infusible organosilicon-based polymer precursor fiber into SiC fiber by heat treating it,
The heat treatment includes controlling pressure conditions according to the desired characteristics of the SiC fiber,
The pressure conditions are controlled to indicate either a low pressure of 1.0 × 10 ^-6 bar or more and less than 1.0 bar or a high pressure of more than 2.0 bar and less than 100.0 bar.
Methods for controlling electrical and mechanical properties of SiC fibers.
According to paragraph 1,
The heat treatment is performed at a temperature ranging from 700°C to 1400°C.
Methods for controlling electrical and mechanical properties of SiC fibers.
According to paragraph 1,
The low pressure represents a pressure in the range of 1.0×10 ^-6 bar to 10×10 ^-2 bar, and the high pressure represents a pressure in the range of 5.0 bar to 100.0 bar.
Methods for controlling electrical and mechanical properties of SiC fibers.
According to paragraph 1,
During the heat treatment, when the pressure condition is controlled to low pressure, the electrical conductivity of the SiC fiber increases and the tensile strength decreases compared to the case where the pressure condition is controlled to normal pressure.
Methods for controlling electrical and mechanical properties of SiC fibers.
According to paragraph 1,
During the heat treatment, when the pressure condition is controlled to low pressure, compared to the case where the pressure condition is controlled to normal pressure, the oxygen content of the SiC fiber is reduced, and the difference in distribution of silicon and carbon on the surface and inside the SiC fiber becomes smaller.
Methods for controlling electrical and mechanical properties of SiC fibers.
According to paragraph 1,
During the heat treatment, when the pressure condition is controlled to low pressure, the SiC fiber exhibits a β-SiC phase and a graphite phase.
Methods for controlling electrical and mechanical properties of SiC fibers.
According to paragraph 1,
During the heat treatment, when the pressure condition is controlled to high pressure, the electrical conductivity of the SiC fiber is lowered and the tensile strength is increased compared to the case where the pressure condition is controlled to normal pressure.
Methods for controlling electrical and mechanical properties of SiC fibers.
According to paragraph 1,
During the heat treatment, when the pressure condition is controlled to high pressure, the oxygen content of the SiC fiber increases compared to the case where the pressure condition is controlled to normal pressure, and more oxygen, silicon, and carbon are distributed on the surface than the inside of the SiC fiber.
Methods for controlling electrical and mechanical properties of SiC fibers.
According to paragraph 1,
During the heat treatment, when the pressure condition is controlled to high pressure, the SiC fiber exhibits a β-SiC phase and a graphene oxide phase.
Methods for controlling electrical and mechanical properties of SiC fibers.
According to paragraph 1,
During the heat treatment, when the pressure condition is controlled to high pressure, the electrical conductivity of the SiC fiber is lowered and the tensile strength is increased compared to the case where the pressure condition is controlled to normal pressure.
Methods for controlling electrical and mechanical properties of SiC fibers.
According to paragraph 1,
The organosilicon polymer precursor includes polysiloxanes, polyborosiloxanes, polycarbosiloxanes, polyborosilazanes, polycarbosilane, and polysilylcarbodiimides. ), or a combination thereof
Methods for controlling electrical and mechanical properties of SiC fibers.
According to paragraph 1,
The curing process is selected from oxidation curing, iodine curing, electron beam curing, chemical vapor curing, or a combination thereof.
Methods for controlling electrical and mechanical properties of SiC fibers.
A SiC fiber whose electrical and mechanical properties are controlled by the method according to any one of claims 1 to 12.

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