KR100684648B1 - Manufacturing method of semi-crystallized silicon carbide fiber made from polycarbosilane - Google Patents

Abstract

A method for manufacturing a semi-crystallized silicon carbide fiber from poly-carbosilane is provided to control an amount of molecules of poly-carbosilane, thereby securing the spinning property of the poly-carbosilane fiber. A poly-de-methylsilane and the zeolite catalyst are reacted at the first temperature so that the poly-de-methylsilane is converted into a poly-carbosilane. The poly-carbosilane is polymerized by the ascended second temperature. The polymerized poly-carbosilane is melted and spun so that the poly-carbosilane fiber is manufactured. The poly-carbosilane fiber is stabilized at 100-300 degrees in centigrade in the air. The poly-carbosilane fiber is heated at 1000-1400 degrees in centigrade so that the partially crystallized SiC fiber is manufactured.

Description

MANUFACTURING METHOD OF SEMI-CRYSTALLIZED SILICON CARBIDE FIBER MADE FROM POLYCARBOSILANE

1 is a diagram illustrating an exemplary temperature rising schedule for schematically illustrating a two-step reaction for molecular weight control of polycarbosilanes in accordance with a preferred embodiment of the present invention.

2 is a graph showing the FT-IR spectrum of each sample obtained in the process of conversion from polydimethylsilane to polycarbosilane according to a preferred embodiment of the present invention.

Figure 3 is a graph showing the measurement of the change in molecular weight distribution appearing through the polymerization process by GPC.

Figure 4 is a graph showing the results of GPC analysis by collecting the sample according to the distance away from the center of the tube after distilling for 1 hour in a quartz tube maintained at 250 ℃ vacuum after polymerization for 10 hours at 400 ℃.

5 is a GPC graph of a sample obtained by repolymerizing PCS at 400 ° C. for 5-15 hours.

6 is a thermal analysis curve for a sample obtained by repolymerization at 400 ° C. for 5 to 15 hours.

FIG. 7 is a diagram showing electron micrographs of fracture surfaces of silicon carbide fibers prepared according to an embodiment of the present invention, and the results of EDS line mapping of the fracture surfaces. FIG.

8 is an XRD chart of silicon carbide fibers prepared according to an embodiment of the present invention.

9 is a graph showing the results of TG analysis of silicon carbide fibers prepared according to an embodiment of the present invention.

10A and 10B are SEM photographs of the surface of silicon carbide fibers before and after the oxidation experiment, respectively.

11A and 11B are cross-sectional SEM photographs of silicon carbide fibers before and after the oxidation experiment, respectively.

The present invention relates to a method for producing silicon carbide (SiC) fibers, and more specifically to producing a polycarbosilane using a zeolite as a catalyst and then spinning it to produce a polycarbosilane fiber, the poly The present invention relates to a method of preparing SiC fibers by stabilizing and then decomposing the carbosilane fibers.

Polycarbosilane (PCS) is widely used as a precursor for preparing SiC fibers, or as a precursor for SiC coating, SiC powder, and SiC composite materials to enhance oxidation resistance and heat resistance.

The polycarbosilane has been mainly used in the Yajima method (disclosed in US Pat. No. 4,052,430) by high temperature pressurization at 400 ° C. or higher using polydimethylsilane (PDMS) as a starting material. However, this method is pressurized using a pressurized vessel, which generates pyrolysis by-products such as Me2SiH2, Me3SiH, etc. during the reaction, and the internal pressure of the pressurized vessel rises above 100 atm during the reaction. When these gases leak during the reaction, there is a problem in stability such as the risk of ignition.

To overcome this problem, Yajima has synthesized polycarbosilane at atmospheric pressure using a polyborodiphenylsiloxane catalyst (Nature Vol. 273 No. 15, 525-527). In addition, Kurosaki Refractories Co. Ltd. synthesized polycarbosilane at a normal pressure of 320 ° C. to 370 ° C. using solid acids such as AlCl 3, ZrCl 2, VCl 3, and SbCl 3 as catalysts. US 4,590,253, Japanese Patent JP 87-79228).

However, since these solid acid catalysts exhibit strong acidity, it is difficult to control the acidity of the catalyst, resulting in low yield of the final product and difficulty in controlling the molecular weight of the product.

The radioactivity of polycarbosilanes is highly dependent on the molecular weight distribution and melting point. For example, low molecular weight polycarbosilanes allow for low temperature spinning but adversely affect the formation and physical properties of ceramic fibers in stabilization and heat treatment processes, thereby purifying them. Should be removed from the process.

In order to solve the above problems of the prior art, the present invention, by controlling the molecular weight of the polycarbosilane in the process of producing a polycarbosilane using a zeolite as a catalyst to secure the radioactivity of the polycarbosilane fibers, high yield semicrystalline SiC It is an object of the present invention to provide a method for producing SiC fibers which enables the production of fibers.

It is also an object of the present invention to provide a method for producing SiC fibers having high mechanical strength through control of the polycarbosilane molecular weight.

The present invention to achieve the above technical problem,

Converting the polydimethylsilane into a polycarbosilane by reacting a polydimethylsilane and a zeolite catalyst at a first temperature, and heating the polycarbosilane to a second temperature higher than the first temperature to polymerize Preparing polycarbosilane fibers by melt spinning polycarbosilane, stabilizing the polycarbosilane fibers in an atmosphere of 100 to 300 ° C., and heat-treating the polycarbosilane fibers at 1000 to 1400 ° C. to partially crystallize SiC fibers. It provides a method for producing a SiC fiber comprising the step of preparing a.

In the present invention, the first temperature (conversion reaction temperature) is 300 ~ 400 ℃, the second temperature (polymerization reaction temperature) is preferably 350 ~ 450 ℃.

The present invention may further comprise a step of distilling at 200 ~ 300 ℃ after the polymerization step. In addition, the present invention may further include a step of repolymerization for 5 to 20 hours in a nitrogen atmosphere 350 ~ 450 ℃ after the distillation step.

The zeolite used in the conversion of the polydimethylsilane in the present invention has a three-dimensional structure in which oxygen atoms are bonded to a vertex of a tetrahedron around a silicon atom or an aluminum atom, for example, the general formula Nam (AlO 2) m (SiO 2). ) n x H2O. This is not an acid. However, when Na + is exchanged with ammonium ions or the like for calcination, it is a bronsted acid catalyst. Since the zeolite catalyst can control the acidity of the catalyst by adjusting the Si / Al ratio or Si / B ratio, it is easy to control the molecular weight of the final product compared to the conventional solid acid catalyst and the product yield can be expected to be improved. It is preferable that the said zeolite catalyst has a Si / Al ratio or Si / B ratio in the range of 1-200.

In the production method of the present invention, in order to prevent oxidation of the polydimethylsilane, the conversion reaction and the polymerization reaction must be performed in an inert gas atmosphere. Examples of the inert gas include nitrogen, argon, helium, carbon monoxide, carbon dioxide, and the like.

In addition, in the present invention, the conversion reaction and the polymerization reaction may be performed at a low pressure of about 1 to 20 atm, and preferably at about 10 atm or less. When carried out under vacuum, the yield of the product decreases because the low molecular weight component is distilled off from the reaction system, and when it is carried out at high pressure, a large amount of by-products are generated and the pressure rises, which causes a problem in stability.

In addition, in the process of the present invention, the conversion reaction and the temperature of the polymerization reaction are usually carried out in the range of 250 ° C to 450 ° C. If the reaction temperature is less than 250 ° C sufficient conversion to the polycarbosilane does not occur, and if it exceeds 450 ° C high pressure may be caused by the rapid pyrolysis of the polydimethylsilane.

Also in the process of the invention, the reaction time is usually 3 to 72 hours, preferably 5 to 20 hours. If the reaction time is less than 3 hours, sufficient conversion to polycarbosilane does not occur, and if it exceeds 72 hours, no further yield improvement can be expected.

In the method of the present invention, the zeolite is used in an amount of 0.1 to 10% by weight based on the weight of the polydimethylsilane. If the amount is less than 0.1% by weight, the yield of polycarbosilane that is not converted is high, and the yield is lowered. Even when it is used more than 10% by weight, no further improvement of yield can be expected.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The process for producing SiC of the present invention is prepared through the process of conversion from polydimethylsilane to polycarbosilane, spinning of polycarbosilane and pyrolysis of polycarbosilane.

In the method of the present invention, the conversion from the polydimethylsilane to the polycarbosilane is characterized by a two-step reaction.

Figure 1 shows an exemplary heating schedule for schematically illustrating the two step reaction of the present invention.

Referring to FIG. 1, the reaction of step 1 represents a conversion reaction from PDMS to PCS, and the reaction of step 2 represents a polymerization reaction for increasing the molecular weight of the obtained PCS. As shown, distillation may be interposed in the middle of the polymerization reaction. In the present invention, the reaction temperature of step 2 is higher than the reaction temperature of step 1. For example, when the reaction temperature of the step 1 is 300 ~ 400 ℃, the reaction temperature of the step 2 is preferably 350 ~ 450 ℃.

Example

Synthesis Example of Polydimethylsilane

First, a 10 L six-necked flask and a large mantle capable of heating it were prepared. In order to effectively condense dimethyldichlorosilane and toluene evaporated during the reaction, a large condenser tower with a double coil inside at a height of 40 cm was attached to both ends of the flask. In a glove bag which is blown with nitrogen and cut off the air, a large block of Na block is cut into 8 cm3 or more and placed in a reaction flask containing 3 L toluene, which is then mounted on the reaction mantle and the stirring speed is controlled. After the installation of two condenser towers with a stirrer, a dropping funnel containing 1300cc was attached by vacuum suction method, and nitrogen was flowed to create an air-free atmosphere. At this time, it was confirmed that the bubble comes out from the bubbler installed in the final line to maintain a positive pressure of nitrogen inside the reactor without leakage. When the reactor temperature is raised to 120 ° C. while stirring at 100 rpm, Na melts at 100 ° C. or higher and begins to disperse in toluene. At this time, Na was dispersed in small droplets of several mm or less by high-speed stirring at 400 rpm or more, and then 1300 cc of dimethylchlorosilane was added dropwise at 110 ° C. over 8 hours. During the dropping of dimethylchlorosilane into the reactor, more gas than the nitrogen flow rate was released through the bubbler and the temperature of the reactor varied by about 3 degrees. When the dropwise addition of dimethyldichlorosilane was completed, the reaction was further performed at the same temperature for 8 hours. At the end of the reaction, a progressive purple reactant was formed and the unreacted Na and reaction by-products were present with NaCl together with polydimethylsilane. Anhydrous methanol was used to remove unreacted Na, and toluene and anhydrous methanol were separated from the progressive purple reactant by vacuum filtration. The separated reaction was washed again with distilled water 4 times, methanol 3 times and toluene once. After each cleaning, the filtrate was separated by vacuum filtration, and a fine white powdery phase was separated from the washing solution. This was recovered and vacuum dried again for at least one day to obtain a polydimethylsilane powder.

Zeolite Catalyst Synthesis Example

A. Al-ZSM-5 Catalyst

Si / Al ratio of 30 or ZSM-5 zeolite is prepared Tetrapropylammonium bromide in a reaction vessel with Teflon sodium hydroxide (97 wt%) of 1.37g and 5.43 g (98% by weight) and 0.619g of Na ₂ O ^of. Al ₂ O ₃ ^. Add H ₂ O, add 126 g of water, and stir for 1 hour to dissolve. 12 g of fumed silica or TEOS was added thereto, followed by stirring for 12 hours, and the Teflon reactor was placed in a container made of stainless steel and heated at 100 ° C.-150 ° C. for 5 days. The ZSM-5 zeolite solid product obtained above was washed several times with distilled water and then dried in an oven at 100 ° C. The calcined ZSM-5 zeolite was calcined in air at 550 ° C. for 12 hours to remove amines contained in the ZSM-5 zeolite. After refluxing, the mixture was washed several times with distilled water, dried and calcined in air at 500 ° C. for 4 hours.

B. B-ZSM-5 Catalyst

1.37 g of sodium hydroxide (97%), 5.43 g of Tetrapropylammonium bromide (98% by weight) and 0.420 g of H ₃ BO ₄ were added to a Teflon reaction vessel, and 126 g of water was added thereto, followed by stirring for 1 hour. Thereafter, 12 g of fumed silica was added thereto, followed by stirring for 12 hours. Then, the Teflon container was placed in a stainless steel container and heated at 150 ° C. for 5 days to carry out a ZSM-5 zeolite catalyst having a Si / B ratio of 30 with impurities. Got. The zeolite catalyst containing boron was washed several times with distilled water, dried in an oven at 100 ° C., and then refluxed for 12 hours using 100 g of 0.1 M aqueous ammonium nitrate solution per 1 g of catalyst to remove Na ions. Thereafter, the catalyst was washed several times with distilled water, dried in an oven, and further calcined in air at 500 ° C. for 4 hours to obtain a pure Si / B ratio 30 ZSM-5 zeolite catalyst.

C. Zeolite Y Catalyst

   4.07 g of sodium hydroxide (97%) and 2.09 g of sodium aluminate were completely dissolved in 19.95 g of distilled water, and 22.72 g of sodium silicate solution was added thereto, and aged at room temperature for one day to obtain a seed gel. Separately, 0.14 g of sodium hydroxide (97%) and 13.09 g of sodium aluminate were completely dissolved in 130.97 g of distilled water, and then 142.43 g of sodium silicate solution was added thereto and aged at room temperature for one day to obtain a feed stock gel. Seed gel 16.50 was added to the feed stock gel, mixed well, and heated at 100 ° C. for 4 days to obtain zeolite Y having a Si / Al ratio of 2.37.

   The catalyst obtained by the above method was washed several times with distilled water, dried in an oven at 100 ° C., and then refluxed for 12 hours using 100 g of 0.1 M aqueous ammonium nitrate solution per 1 g of catalyst to remove Na ions contained in the catalyst. Thereafter, the catalyst was washed several times with distilled water, dried in an oven, and further calcined in air at 500 ° C. for 4 hours to obtain zeolite Y having a pure Si / Al ratio of 2.37.

D. Zeolite A Catalyst

   Zeolite A having a Si / Al ratio of 1.020 was prepared as follows. 0.723 g sodium hydroxide (97% by weight) is dissolved in 80 ml of distilled water and then divided into two Teflon reaction vessels. Dissolve 8.258 g of Sodium Aluminate in one sodium hydroxide solution, completely dissolve 15.48 g of Sodium Metasilicate in the other, and quickly pour the silicate solution into the aluminate solution to form a gel. Stir until the gel is released completely and then prepared by heating at 100 ℃ for 4 days.

   The zeolite A solid product obtained above was washed several times with distilled water and then dried in an oven at 100 ° C. In order to remove Na ions contained in zeolite, the mixture was refluxed in 100 g of 1.0 M aqueous ammonium nitrate solution per 1 g of zeolite A for 12 hours, washed several times with distilled water, dried and calcined in air at 500 ° C. for 4 hours. It was.

 Synthesis Example of Polycarbosilane

The polydimethylsilane and 1% zeolite catalyst were stirred in a high temperature and high pressure reactor including a reflux device and a polycarbosilane was synthesized through a two step process. In the first step, the reactor was maintained at 350 ° C. for 10 to 20 hours for the purpose of conversion to polycarbosilane through a catalytic process, and in the second step, the reaction temperature was raised to 400 ° C. and polymerized for 10 hours. All of the above processes were carried out in a nitrogen atmosphere. The obtained sample was purified and repolymerized for 5-15 hours in a nitrogen atmosphere at 400 ° C.

Through such conversion, polymerization, purification and repolymerization, polycarbosilanes having various molecular weights such as samples having a molecular weight of 100 or less, 1000 to 3000, and 10000 or more were obtained.

Table 1 below shows the average molecular weight and yield of the polycarbosilane samples obtained according to the reaction conditions.

Sample Reaction condition Molecular Weight yield(%) PCS1 350 ℃, 20h 427 85 PCS2 350 ° C, 20h + 400 ° C, 10h 973 60 PCS3 Distillation Residue of PCS2 1489 Solid fraction in residue: 70 Liquid fraction in residue: 30 PCS4 400 ° C, 5h (additional repolymerization) 4605 - PCS5 400 ° C, 10h (additional repolymerization) 24935 (high molecular weight) 3207 (low molecular weight) - PCS6 400 ° C, 15h (additional repolymerization) 29090 (high molecular weight) 4460 (low molecular weight) -

FIG. 2 is a graph showing the FT-IR spectrum of each sample obtained in the process of conversion from polydimethylsilane to polycarbosilane.

First, Figure 2 (a) is the spectrum of the polydimethylsilane used as the starting material. And the peak due to Si-CH3 bend at 736cm ^-1 and 828cm ^-1, the peak can be observed due to the Si-CH3 stretch at 1242cm ^-1.

2 (b) and 2 (c) show a new binding due to the conversion of polycarbosilane to the IR spectrum after 1 hour conversion process, that is, 2 hours and 15 hours of reaction at 350 ° C., respectively, 2100 cm ⁻¹ (Si-H) And 1020, 1355 cm ^-1 (Si-CH2-Si).

Figure 2 (d) is an IR spectrum after the polycarbosilane was prepared through a conversion reaction at 350 ℃ for 20 hours and then repolymerized at 400 ℃ for 10 hours. It can be seen that the intensity of the 1355 cm ⁻¹ peak was further increased.

Table 2 shows the conversion ratio of polydimethylsilane to polycarbosilane calculated from the intensity ratios of the 1355 cm ⁻¹ and 1405 cm ⁻¹ peaks.

Sample Reaction conditions Rate (1355cm-1 / 1405cm-1) yield(%) Polydimethylsilane - - Polysilacabosilane 350 ℃, 2h 0.32 25.8 Polycarbosilane oligomer 350 ℃, 15h 0.43 34.9 Polycarbosilane 350 ° C, 20h + 400 ° C, 10h 0.98 79.1

Figure 3 is a graph showing the measurement of the change in molecular weight distribution appearing through the polymerization process by GPC. In FIG. 3, (a) shows a polysilane carbosilane, (b) shows a polycarbosilane oligomer, and (c) shows the GPC graph of polycarbosilane.

Referring to FIG. 3, the initially formed liquid silane has a narrow molecular weight distribution, while (a) appears to have a wide molecular weight distribution, with a broad peak of retention time of 26 minutes and sharp peaks of 27 and 27.5 minutes. Appearing. The peak at 27.5 minutes appears to be a peak including unconverted liquid silane and cyclic silane, and as the reaction proceeds at 350 ° C., the size decreases and the peak generally shifts to the left. On the other hand, the two peaks on the left showed an increase in molecular weight due to the increase in size, but the average molecular weight value did not increase significantly. In (c), the peak at 27.5 minutes was almost disappeared while the peak at 26 minutes was greatly increased, and the average molecular weight was also greatly increased.

Ishikawa et al. Synthesized polycarbosilane at 350 ° C. using a polyborodiphenylsiloxane catalyst, and the average molecular weight increased significantly with the reaction time. The yield was about 65%. However, in the method of the present invention, the average molecular weight is small, and even if the reaction time is long, the change in the value does not increase significantly, but it can be seen that the reaction yield is high as 80% or more. This result is believed to be due to the zeolite effectively acting on the conversion process to carbosilane at 350 ° C. Polycarbosilane polymerization depends on the reaction temperature and reaction time and is also affected by the low molecular weight fraction. Therefore, the effective removal of low molecular weight fraction in polycarbosilane seems to accelerate the rate of polymerization.

Figure 4 is a graph showing the results of GPC analysis by collecting the sample according to the distance away from the center of the tube after distilling for 1 hour in a quartz tube maintained at 250 ℃ vacuum after polymerization for 10 hours at 400 ℃. There was a yellow solid polycarbosilane at the center of the tube with an average molecular weight of 1450 and a PDI (polydispersity) of 2.6, which was smaller than before purification. The removed polycarbosilanes were transparent liquid or viscous and had a molecular weight of less than 300. These polycarbosilanes were low molecular weight polycarbosilanes and cyclic silanes which had already been converted to carbosilanes from the characteristic spectra of the polycarbosilanes shown in the IR spectral analysis. I could see that.

FIG. 5 is a GPC graph of a sample obtained by repolymerizing purified polycarbosilane at 400 ° C. for 5 to 15 hours. In the graph, (a) is a sample distilled at 250 ° C. for 1 hour after reaction at 350 ° C., 20 hours, and 400 ° C. for 10 hours, and (b), (c) and (d) are respectively 5 hours at 400 ° C., Curves of samples after 10 and 15 hours additional repolymerization.

It can be seen that as the reaction time increases, the molecular weight peak below the middle decreases and a new peak appears in the high molecular weight portion above 10000. This is because the polymerization is accelerated within a short reaction time when the low molecular weight polycarbosilane is removed and then repolymerized.

6 is a thermal analysis curve for a sample obtained by repolymerization at 400 ℃ for 5 to 15 hours. In Figure 6 (a) is a sample obtained by reacting 350 ℃ 20 hours and 400 ℃ 10 hours, (b) is a sample obtained by distilling this sample under vacuum at 250 ℃ 1 hour, (c), (d) and (e) Shows the curves of the samples which were further repolymerized at 400 ° C. for 5 hours, 10 hours and 15 hours, respectively. From this graph, it can be seen that as the polymerization proceeds, the yield also greatly increases to 75% or more.

Semicrystalline SiC Fiber Preparation Example

Polycarbosilane having an average molecular weight of 1000 to 3000 was charged to a syringe-type melt spinning machine having one nozzle, and melt-spun after maintaining a vacuum. The spun fibers were wound into a 0.5 m diameter drum, cut to 15 cm, and recovered, and the recovered fibers were stabilized for 4 hours in an atmosphere of 200 ° C. The fibers before stabilization were brittle and brittle, but after stabilization they became pliable and increased in strength.

The stabilized fibers were heated at 1200 ° C. for 12 hours in an alumina tubular furnace in which argon was maintained, and maintained for 1 hour to make SiC fibers and then recovered at room temperature. In addition, after oxidizing a part of the prepared SiC fibers in an atmosphere of 1200 ℃, the microstructure was observed, and using a universal testing machine (Instron model 4024) tensioning 30 mm span fibers at a crosshead speed of 0.5 mm / min The test was carried out to measure the room temperature strength of the fiber.

It is a figure which shows the electron micrograph of the fracture surface of a SiC fiber, and the result of EDS line mapping of the fracture surface.

The fiber exhibited a typical ceramic failure behavior at break. It can be seen from the photograph that the surface of the fiber is smooth, and the diameter of the fiber cross section was about 20 µm, and the difference in composition was found from the surface of the fiber to the center of the fiber. Si concentration, on the other hand, was relatively low.

8 is an XRD chart of SiC fibers. 8 shows a broad form at the characteristic peak of β-SiC and it is determined that the nano-size SiC particles are finely dispersed. Room temperature tensile strength for SiC fibers was about 1.5-1.8 GPa.

9 is a graph showing the results of TG analysis when SiC fiber was heated to 1200 ° C. at 10 ° C./min and oxidized for 12 hours while flowing 80% N 2-20% O 2 mixed gas.

9, it can be seen that after 4 hours of temperature increase, the weight increase becomes almost constant at 1.5%. This is because the rate of oxidation is fast until the continuous oxide film is formed on the surface of SiC fiber at the beginning, and after about 1 hour of oxidation, the SiO2 oxide film is formed and the oxidation proceeds by diffusion through the film. The dense SiO2 film diffuses oxygen. This is because the speed is lowered.

10A and 10B are SEM photographs of the surfaces of SiC fibers before and after oxidation experiments, respectively. From this photograph, it can be seen that the surface is very smooth before oxidation. After oxidation, a thin SiO 2 layer is formed on the surface, and in part, SiO 2 forms α-crystoballite.

11A and 11B are cross-sectional SEM photographs of SiC fibers before and after oxidation experiments, respectively. It can be seen from this photograph that an oxide layer having a thickness of about 350 nm is uniformly formed on the surface after the oxidation treatment. In addition, it can be seen that the oxide layer is well bonded to the fiber surface without peeling off from the surface.

12 is a graph showing the tensile strength measurement results of SiC fibers before and after oxidation treatment. The tensile strength of the SiC fiber after oxidation was about 1.5 GPa, indicating that the decrease in strength hardly occurs compared to before oxidation.

Although the above has been illustrated and described with reference to the preferred embodiments of the present invention, the present invention is not limited to the above-described specific embodiments, and the present invention belongs to the present invention without departing from the gist of the present invention as claimed in the claims. Various modifications can be made by those skilled in the art, and such changes are within the scope of the appended claims.

According to the present invention, a specific zeolite of polycarbosilane is used as a catalyst to prepare polydimethylsilane as polycarbosilane at low pressure, and then polymerize it to increase the yield of SiC fibers obtained by excellent spinning in melt spinning. . In the process of the present invention, polycarbosilane fibers are easy to control the molecular weight by polymerization and repolymerization, and it is possible to obtain a high yield of SiC fibers despite the polymerization.

In addition, according to the method of the present invention, it is possible to provide a SiC fiber having a higher mechanical strength than that of a conventional SiC fiber because hardly any decrease in the mechanical strength of the SiC fiber after the oxidation treatment occurs compared to before the oxidation treatment.

Claims (4)

Converting the polydimethylsilane to polycarbosilane by reacting the polydimethylsilane and the zeolite catalyst at a first temperature; Heating the polycarbosilane to a second temperature higher than the first temperature to polymerize the polycarbosilane; Melt spinning the polycarbosilane that is expanded to produce polycarbosilane fibers; Stabilizing the polycarbosilane fibers in an atmosphere of 100 to 300 ° C .; And Heat treating the polycarbosilane fibers at 1000 to 1400 ° C. to produce SiC fibers partially crystallized. The method of claim 1, Said 1st temperature is 300-400 degreeC, and said 2nd temperature is 350-450 degreeC manufacturing method of SiC fiber. The method of claim 1, Method for producing a SiC fiber characterized in that it further comprises the step of distilling at 200 ~ 300 ℃ after the polymerization step. The method of claim 3, After the distillation step further comprises the step of repolymerizing for 5 to 20 hours in a 350 ~ 450 ℃ nitrogen atmosphere.

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