A low cost silicon carbide fiber and method of making same

Abstract

The application belongs to the technical field of silicon carbide fiber preparation, and particularly relates to a low-cost silicon carbide fiber and a preparation method thereof. The silicon carbide fiber is prepared from polycarbosilane including one or both of vinyl siloxane and vinyl polysiloxane as a precursor, and is prepared through steps including spinning, ultraviolet radiation cross-linking and high-temperature sintering. The application provides a novel preparation method of the silicon carbide fiber, successfully realizes the preparation of the silicon carbide fiber by using polycarbosilane including one or both of vinyl siloxane and vinyl polysiloxane as a precursor and combining the ultraviolet radiation cross-linking process, and the preparation method is simple, and the comprehensive preparation cost is greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of silicon carbide fiber preparation technology, specifically relating to a low-cost silicon carbide fiber and its preparation method. Background Technology

[0002] SiC fibers possess advantages such as high temperature resistance, oxidation resistance, corrosion resistance, and low density, making them a rapidly developing toughening and reinforcing fiber for high-temperature ceramic matrix composites in recent years. They are widely used in aerospace structural components, nuclear reactors, high-speed brake pads, turbines, and other fields. Currently, the main method for preparing SiC fibers is the precursor conversion method pioneered by Professor Yajima of Japan. Its typical preparation process involves four steps: precursor synthesis, spinning, air-insoluble treatment, and high-temperature pyrolysis. For example, typical Nicalon fibers are prepared using polycarbosilane (PCS) as a precursor through melt spinning, air-insoluble treatment, and high-temperature pyrolysis. However, air-insoluble treatment introduces a large amount of oxygen into the fiber, which, after high-temperature firing, forms a large amount of high-temperature unstable SiCxOy phase. Studies have shown that when the temperature exceeds 1200℃, the SiCxOy phase decomposes to produce CO and SiO, resulting in severe fiber quality loss, numerous defects and pores within the fiber, rapid grain coarsening, and a sharp decline in mechanical properties, severely impacting fiber performance.

[0003] To avoid the introduction of oxygen (O), later researchers employed different curing processes instead of air-based infusibility. For example, Okamura et al. (J. Am. Ceram. Soc., 1995, 78: 1013-1017.) used electron beam irradiation in helium to achieve infusibility of the fibers, ultimately obtaining SiC fibers with an oxygen content of less than 0.5 wt%. Further research on the fiber properties showed that after holding at 1600℃ for 10 hours in an inert atmosphere, the tensile strength of the fiber remained at 2.0 GPa, and the fiber modulus at 270 GPa; however, due to the high cost of the irradiation process, only small-batch production of SiC fibers was possible. Mao Xianhe et al. (Journal of Materials Research, 2007, 21: 177-182) used an active atmosphere to perform infusibility treatment on polycarbosilane precursor fibers, but the oxygen content in the resulting SiC fibers still reached 5-6 wt%. In patent CN101280474A, Luo Xuetao et al. mixed polycarbosilane with oxygen-containing organometallic compounds (zirconium isopropoxide, aluminum isopropoxide, or titanium isopropoxide, etc.) and carried out dry spinning. Then, thermal crosslinking was completed through the reaction between the organometallic compounds and polycarbosilane. However, after the reaction, a Si-OMO-Si structure was formed, and the oxygen content in the prepared fiber was 0.5-0.9 wt%. While introducing oxygen, metal elements were also introduced. The introduction of heterogeneous elements can effectively inhibit grain coarsening and act as a sintering aid, making SiC fibers re-densified. Hesagawa et al. (Compos.Sci.Technol.,1994,51(2):161-166.) passed unsaturated hydrocarbons such as cyclohexene and 1-hexyne into the PCS precursor at a certain temperature for non-melting treatment. The final SiC fiber prepared had a lower oxygen content and better mechanical properties, but this method had poor reproducibility and was only suitable for experimental research.

[0004] Among the aforementioned methods for preparing silicon carbide fibers, the non-melting process is relatively complex, requires a long time, has stringent equipment requirements, high preparation costs, and may even cause environmental pollution. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a low-cost silicon carbide fiber and its preparation method, which uses ultraviolet radiation crosslinking to reduce crosslinking time, improve curing efficiency, and reduce production costs.

[0006] One objective of this invention is achieved through the following technical solution:

[0007] A low-cost silicon carbide fiber is prepared by using polycarbosilane, including one or two of vinylsiloxane and vinylpolysiloxane, as precursors, through steps including spinning, ultraviolet radiation crosslinking, and high-temperature firing.

[0008] In the aforementioned low-cost silicon carbide fibers, polycarbosilanes that include one or both of vinyl siloxane and vinyl polysiloxane refer to polycarbosilanes that include vinyl siloxane, polycarbosilanes that include vinyl polysiloxane, or polycarbosilanes that include both vinyl siloxane and vinyl polysiloxane.

[0009] The aforementioned low-cost silicon carbide fibers, including polycarbosilane comprising one or both of vinylsiloxane and vinylpolysiloxane, are prepared by mixing one or both of vinylsiloxane and vinylpolysiloxane with polycarbosilane. The method of mixing one or both of vinylsiloxane and vinylpolysiloxane with polycarbosilane is not limited; any step capable of mixing one or both of vinylsiloxane and vinylpolysiloxane with polycarbosilane is within the scope of protection of this invention. For example, a method of mixing one or both of vinylsiloxane and vinylpolysiloxane with polycarbosilane includes the following steps: dissolving one or both of vinylsiloxane and vinylpolysiloxane with polycarbosilane in an organic solvent, and then removing the organic solvent by distillation to obtain polycarbosilane comprising one or both of vinylsiloxane and vinylpolysiloxane. The organic solvent refers to any organic solvent capable of dissolving polycarbosilane, and one or both of vinylsiloxane and vinylpolysiloxane, such as tetrahydrofuran.

[0010] Preferably, in the precursor, one or both of vinylsiloxane and vinylpolysiloxane are in a mass ratio of 1:100 to 1:1 with polycarbosilane.

[0011] In the aforementioned low-cost silicon carbide fibers, vinylsiloxane is a siloxane containing C=C and Si-O chemical bonds in its molecular structure, and vinylpolysiloxane is a polysiloxane containing C=C and Si-O chemical bonds in its molecular structure. Preferably, the vinylsiloxane includes, but is not limited to, one or more of tetramethyltetravinylcyclotetrasiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, divinyltetramethyldisiloxane, vinyltriisopropoxysiloxane, and vinyltriethoxysiloxane; the vinylpolysiloxane includes, but is not limited to, one or more of terminal vinylpolymethylvinylsiloxane, terminal vinylpolydimethylsiloxane, and polydimethylmethylvinylsiloxane.

[0012] In the aforementioned low-cost silicon carbide fiber, the polycarbosilane is an organosilicon polymer with Si-C bonds forming the main chain. Its molecular main chain contains CH3SiHCH2 structural units and is solid at room temperature. Preferably, the polycarbosilane has a softening point greater than 100°C and a number-average molecular weight of 100 to 5000.

[0013] Preferably, the polycarbosilane contains a heterogeneous element; more preferably, the heterogeneous element includes one or more of aluminum, yttrium, nickel, hafnium, lithium, iron, cobalt, lanthanum, zirconium, titanium, beryllium, magnesium, calcium, vanadium, and boron. When the polycarbosilane contains a heterogeneous element, using it as a raw material to prepare silicon carbide fibers can more effectively reduce the oxygen content in the silicon carbide fibers and endow the silicon carbide fibers with certain functional properties, such as wave absorption and electromagnetic shielding. The content of the heterogeneous element in the polycarbosilane is not limited.

[0014] Preferably, the spinning is melt spinning, dry spinning, or electrospinning. The precursor of the present invention can be produced by any one of melt spinning, dry spinning, or electrospinning to obtain the fibrils.

[0015] When the spinning is melt spinning, the melt spinning process conditions include, for example, grinding one or two of vinylsiloxane and vinylpolysiloxane into powder and placing them in a spinning barrel, heating to 100-250°C under an inert atmosphere, and spinning through a spinneret through a spinneret under pressure (for example, 0.01-2 MPa), collecting the fibers through a spinning roller to obtain fibrils with a diameter of 5-20 μm;

[0016] When the spinning is electrospinning, the electrospinning process conditions include, by way of example, the inner diameter of the spinneret is 0.5-3 mm, the spinning voltage is 10-20 kV, the distance between the spinneret and the take-up device is 5-40 cm, and the spinning speed is 10-50 μL / min.

[0017] When the spinning is dry spinning, the process conditions for dry spinning include, by way of example, raising the spinning solution to 50-150°C in the spinning device under an inert atmosphere, holding it at that temperature for 0.5-5 hours, and then extruding it through the spinneret under pressure to form fibrils.

[0018] In electrospinning and dry spinning, a polycarbosilane, including one or both of vinylsiloxane and vinylpolysiloxane, is dissolved in an organic solvent to prepare a spinning solution, which is then placed in a spinning apparatus for spinning. The aforementioned organic solvent can be any solvent capable of dissolving polycarbosilanes including one or both of vinylsiloxane and vinylpolysiloxane, including one or more of toluene, xylene, tetrahydrofuran, acetone, n-hexane, and chloroform.

[0019] Preferably, the ultraviolet radiation crosslinking step includes: subjecting the fibrils obtained by spinning to ultraviolet radiation crosslinking, wherein the light intensity of the ultraviolet lamp is 10-1000 mW / cm². 2 The wavelength of ultraviolet light is 185–400 nm, and the irradiation time is 1–180 min.

[0020] Preferably, the high-temperature firing step includes: heating the cross-linked fiber under ultraviolet light to 1000-1800°C at a rate of 1-20°C / min in an inert atmosphere, and holding at that temperature for 0.5-5 hours.

[0021] The inert atmosphere mentioned in this article includes, but is not limited to, argon atmosphere and nitrogen atmosphere.

[0022] Another objective of this invention is achieved through the following technical solution:

[0023] A method for preparing low-cost silicon carbide fibers includes the following steps:

[0024] The fibrils are obtained by spinning using one or both of polycarbosilanes, including vinylsiloxanes and vinylpolysiloxanes, as precursors.

[0025] The fibrils are cross-linked by ultraviolet radiation;

[0026] The fibers cross-linked by ultraviolet radiation are then fired at high temperatures.

[0027] Preferably, the conditions for ultraviolet radiation crosslinking include: the light intensity of the ultraviolet lamp is 10-1000 mW / cm². 2 The wavelength of ultraviolet light is 185–400 nm, and the irradiation time is 1–180 min.

[0028] Preferably, the conditions for high-temperature firing include: heating to 1000-1800°C at a rate of 1-20°C / min under an inert atmosphere, and holding at that temperature for 0.5-5 hours.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention provides a new method for preparing silicon carbide fiber: using one or two of vinyl siloxane and vinyl polysiloxane as precursors, precursor fibers are prepared by spinning, and then crosslinked by ultraviolet radiation at room temperature to make the precursor fibers non-melting. Then, the non-melting fibers are subjected to high-temperature heat treatment in an inert atmosphere to obtain silicon carbide fiber.

[0031] (2) The present invention uses one or two of the following polycarbosilanes as precursors, including vinyl siloxane and vinyl polysiloxane, and combines them with ultraviolet radiation crosslinking process to successfully prepare silicon carbide fibers with smooth and dense surface and cross-section.

[0032] (3) The present invention uses one or two of the following polycarbosilanes as precursor raw materials: vinylsiloxane and vinylpolysiloxane. The polycarbosilanes are subjected to non-melting treatment under ultraviolet radiation crosslinking to replace air non-melting. The preparation process is simpler and the non-melting time is greatly shortened, thereby reducing the overall preparation cost.

[0033] (4) When polycarbosilanes including one or two of vinylsiloxanes and vinylpolysiloxanes contain heterogeneous elements, using them as raw materials to prepare silicon carbide fibers can more effectively reduce the oxygen content in silicon carbide fibers and endow silicon carbide fibers with certain functional properties, such as wave absorption and electromagnetic shielding. Attached Figure Description

[0034] Figure 1 This refers to PACS, D4Vi, and PVACS1-30min in Embodiment 1 of the present invention. 1 H NMR spectrum;

[0035] Figure 2 This is a scanning electron microscope image of the silicon carbide fiber obtained in Example 1 of the present invention. Detailed Implementation

[0036] The technical solution of the present invention will be further described and illustrated below with reference to specific embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of helping to understand the present invention and are not intended to limit the specific scope of the present invention. Furthermore, the accompanying drawings used herein are merely for better illustrating the content disclosed in the present invention and do not limit the scope of protection. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used in the art, and the methods used in the embodiments are all conventional methods in the art.

[0037] Example 1

[0038] The method for preparing silicon carbide fibers in this embodiment includes the following steps:

[0039] (1) 19.5 g of polyaluminosilane (PACS) and 10.5 g of tetramethyltetravinylcyclotetrasiloxane (D4Vi) were mixed and dissolved in tetrahydrofuran solvent. After complete dissolution and dispersion, the solvent was removed by vacuum distillation to finally obtain a pale yellow brittle resin - polyaluminosilane (PVACS1) including vinylsiloxane. The polyaluminosilane has a softening point of 205.5 °C, a number average molecular weight of 883, a weight average molecular weight of 3191, and an Al content of 0.5 wt%.

[0040] (2) Melt spinning: 20g of PVACS1 precursor is placed in the spinning drum of the melt spinning device, heated to 160℃ under N2 protection and kept at that temperature for 2h, and then the precursor is extruded from the spinneret under a pressure of 0.15MPa and collected by the roller to obtain PVACS1 fibrils with a diameter of 13-18μm.

[0041] (3) Ultraviolet radiation crosslinking: The spun PVACS1 fibrils were placed in an ultraviolet lamp box and irradiated for 30 minutes, with an irradiation wavelength of 365 nm and a light intensity of 300 mW / cm². 2At a distance of 15cm from the light source, PVACS1 non-melting fibers were obtained.

[0042] (4) High temperature firing: The obtained PVACS1 non-melting fiber is placed in a high temperature furnace, heated to 1800℃ at 3℃ / min under nitrogen gas protection, held for 1h, and then cooled to obtain silicon carbide fiber.

[0043] The tested silicon carbide fibers have an oxygen content of 0.29 wt%, a C / Si ratio of 1.03, a fiber diameter of 11-13 μm, a tensile strength of 2.1 GPa, and a tensile modulus of 340 GPa.

[0044] Figure 1 This refers to PACS, D4Vi, and PVACS1-30min (PVACS1 fibrils irradiated with ultraviolet light for 30 minutes) in Example 1 of this invention. 1 The 1H NMR spectrum shows a peak at 7.26 ppm, attributed to the solvent CDCl3. Two sharp resonance peaks at 5.99 ppm and 5.54 ppm are attributed to the -CH=CH2 group in D4Vi. The broad peaks from 3.7 to 5.5 ppm are the Si-H resonance peaks in the PACS precursor. The peak at 0.17 ppm is attributed to the Si-CH3 group. After UV irradiation, the intensities of the -CH=CH2 and Si-H peaks significantly decreased, and a new peak of approximately 1.66 ppm, representing Si-CH2-CH2-Si, appeared in PVACS-30 min, confirming that the PACS reacted with D4Vi during UV curing, thus curing the fiber.

[0045] Figure 2 This is a scanning electron microscope image of the silicon carbide fiber prepared in Example 1 of the present invention. After sintering at 1800℃, the PVACS fiber has a smooth and dense surface and cross-section with no obvious defects, and the grains are tightly connected. The fiber cross-section exhibits a transgranular fracture morphology.

[0046] Example 2

[0047] The method for preparing silicon carbide fibers in this embodiment includes the following steps:

[0048] (1) Take 15g of polycarbosilane (PCS) and 15g of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane and dissolve them in tetrahydrofuran solvent. After sufficient dissolution and dispersion, remove the solvent by vacuum distillation to finally obtain a pale yellow brittle resin - polycarbosilane (PVCS1) including vinylsiloxane. The softening point of the polycarbosilane is 210.6℃, the number average molecular weight is 920, and the weight average molecular weight is 3215.

[0049] (2) Melt spinning: 20g of PVCS1 precursor is placed in the spinning drum of the melt spinning device, heated to 160℃ under N2 protection and kept at that temperature for 2h, and then the precursor is extruded from the spinneret under a pressure of 0.25MPa and collected by the roller to obtain PVCS1 fibrils with a diameter of 15-19μm.

[0050] (3) Ultraviolet radiation crosslinking: The spun PVCS1 fibrils were placed in an ultraviolet lamp box and irradiated for 30 minutes, with an irradiation wavelength of 365 nm and a light intensity of 400 mW / cm². 2 At a distance of 15cm from the light source, PVCS1 non-melting fibers were obtained.

[0051] (4) High temperature firing: The obtained PVCS1 non-melting fiber is placed in a high temperature furnace and heated to 1200℃ at 5℃ / min under nitrogen gas protection. The temperature is held for 1 hour and then cooled to obtain silicon carbide fiber.

[0052] The tested silicon carbide fibers have an oxygen content of 8.9 wt%, a C / Si ratio of 1.28, a fiber diameter of 13 μm, a tensile strength of 1.8 GPa, and a tensile modulus of 230 GPa.

[0053] Example 3

[0054] The method for preparing silicon carbide fibers in this embodiment includes the following steps:

[0055] (1) 2g of polyaluminum carbosilane (PACS) and 1.6g of tetramethyltetravinylcyclotetrasiloxane (D4Vi) were mixed and dissolved in tetrahydrofuran solvent. After complete dissolution and dispersion, the solvent was removed by vacuum distillation to finally obtain a pale yellow brittle resin - polyaluminum carbosilane (PVACS2) including vinylsiloxane. The polyaluminum carbosilane has a softening point of 205.5℃, a number average molecular weight of 883, a weight average molecular weight of 3191, and an Al content of 0.6wt%.

[0056] (2) Electrospinning: 2.5g of PVACS2 precursor, 0.5g of acetone and 1.5g of xylene were mixed evenly to prepare a spinning solution. The prepared spinning solution was then loaded into a syringe, air bubbles were removed, and electrospinning was performed to obtain PVACS2 fibrils. The spinning conditions were as follows: spinning voltage 8KV, spinning speed 22μL / min, spinning distance 10cm, roller speed 200r / min, and spinneret inner diameter 3.0mm.

[0057] (3) Ultraviolet radiation crosslinking: The spun PVACS2 fibrils were placed in an ultraviolet lamp box and irradiated for 20 minutes, with an irradiation wavelength of 254 nm and a light intensity of 600 mW / cm². 2 At a distance of 15cm from the light source, PVACS2 non-melting fibers were obtained.

[0058] (4) High temperature firing: The obtained PVACS2 non-melting fiber is placed in a high temperature furnace, heated to 1800℃ at 2℃ / min under nitrogen gas protection, held for 1h, and then cooled to obtain silicon carbide fiber.

[0059] The tested silicon carbide fibers had an oxygen content of 0.21 wt% and a fiber diameter of 1.8 μm.

[0060] Example 4

[0061] The method for preparing silicon carbide fibers in this embodiment includes the following steps:

[0062] (1) 2.1 g of polycarbosilane (PCS) and 0.9 g of vinyl-terminated polymethylvinylsiloxane (vinyl content 0.8 wt%) were mixed and dissolved in tetrahydrofuran solvent. After sufficient dissolution and dispersion, the solvent was removed by vacuum distillation to finally obtain a pale yellow brittle resin - polycarbosilane (PVCS2) including vinyl polysiloxane. The polycarbosilane has a softening point of 210.6 °C, a number-average molecular weight of 920, and a weight-average molecular weight of 3215.

[0063] (2) Electrospinning: Take 2.5g of PVCS2 precursor, 0.5g of tetrahydrofuran and 2.5g of xylene and mix them evenly to prepare a spinning solution. Then, put the prepared spinning solution into a syringe, remove air bubbles, and perform electrospinning to obtain PVCS2 fibrils. The spinning conditions are: spinning voltage 15KV, spinning speed 40μL / min, spinning distance 15cm, roller speed 250r / min, and spinneret inner diameter 3.0mm.

[0064] (3) Ultraviolet radiation crosslinking: The spun PVCS2 fibrils were placed in an ultraviolet lamp box and irradiated for 15 minutes, with an irradiation wavelength of 365 nm and a light intensity of 800 mW / cm². 2 At a distance of 15cm from the light source, PVCS2 non-melting fibers were obtained.

[0065] (4) High temperature firing: The obtained PVCS2 non-melting fiber is placed in a high temperature furnace and heated to 1200℃ at 5℃ / min under nitrogen gas protection. The temperature is held for 1 hour and then cooled to obtain silicon carbide fiber.

[0066] The tested silicon carbide fibers had an oxygen content of 8.5 wt% and a fiber diameter of 2.1 μm.

[0067] Example 5

[0068] The method for preparing silicon carbide fibers in this embodiment includes the following steps:

[0069] (1) Take 2.1g of zirconium-containing polycarbosilane (PZCS) and 0.9g of divinyltetramethyldisiloxane and dissolve them in tetrahydrofuran solvent. After they are fully dissolved and dispersed, remove the solvent by vacuum distillation to finally obtain a pale yellow brittle resin - polyzirconium carbosilane (PVZCS) including vinylsiloxane; wherein the softening point of the polyzirconium carbosilane is 220.7℃, the number average molecular weight is 1020, the weight average molecular weight is 3400, and the zirconium content is 1.2wt%.

[0070] (2) Electrospinning: 2.5g of PVZCS precursor, 0.5g of acetone and 2.5g of xylene are mixed evenly to prepare a spinning solution. The prepared spinning solution is then loaded into a syringe, air bubbles are removed, and electrospinning is performed to obtain PVZCS fibrils. The spinning conditions are as follows: spinning voltage 15KV, spinning speed 40μL / min, spinning distance 15cm, roller speed 250r / min, and spinneret inner diameter 1.0mm.

[0071] (3) Ultraviolet radiation crosslinking: The spun PVZCS fibrils were placed in an ultraviolet lamp box and irradiated for 35 minutes, with an irradiation wavelength of 254 nm and a light intensity of 300 mW / cm. 2 At a distance of 15cm from the light source, PVZCS non-melting fibers were obtained.

[0072] (4) High temperature firing: The obtained PVZCS non-melting fiber is placed in a high temperature furnace, heated to 1400℃ at 4℃ / min under nitrogen gas protection, held for 1h, and then cooled to obtain silicon carbide fiber.

[0073] The tested silicon carbide fibers had an oxygen content of 7.9 wt% and a fiber diameter of 1.5 μm.

[0074] Example 6

[0075] The method for preparing silicon carbide fibers in this embodiment includes the following steps:

[0076] (1) Take 20g of polycarbosilane (PCS) and 10g of vinyltriisopropoxysiloxane and dissolve them in tetrahydrofuran solvent. After sufficient dissolution and dispersion, remove the solvent by vacuum distillation to finally obtain a pale yellow brittle resin - polycarbosilane (PVCS3) including vinylsiloxane. The polycarbosilane has a softening point of 210.6℃, a number average molecular weight of 920, and a weight average molecular weight of 3215.

[0077] (2) Dry spinning: Take 20g of PVCS3 precursor and 15g of xylene and mix them evenly to prepare a spinning solution. Place the spinning solution in the spinning tube and heat it to 130℃ under N2 protection and keep it at that temperature for 2 hours. Then, under a pressure of 0.3MPa, the precursor is extruded from the spinneret and collected by the roller to obtain PVCS3 fibrils with a diameter of 10-15μm.

[0078] (3) Ultraviolet radiation crosslinking: The spun PVCS3 fibrils were placed in an ultraviolet lamp box and irradiated for 20 minutes, with an irradiation wavelength of 365 nm and a light intensity of 800 mW / cm². 2 At a distance of 15cm from the light source, PVCS3 non-melting fibers were obtained.

[0079] (4) High temperature firing: The obtained PVCS3 non-melting fiber is placed in a high temperature furnace and heated to 1300℃ at 4.5℃ / min under nitrogen gas protection. The temperature is held for 1 hour and then cooled to obtain silicon carbide fiber.

[0080] The tested silicon carbide fibers had an oxygen content of 8.7 wt%, a fiber diameter of 11–14 μm, a tensile strength of 2.1 GPa, and a tensile modulus of 220 GPa.

[0081] All aspects, embodiments, and features of this invention should be considered illustrative in all respects and not limiting of the invention; the scope of the invention is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0082] In the preparation method of this invention, the order of the steps is not limited to the listed order. For those skilled in the art, variations in the order of the steps without creative effort are also within the scope of protection of this invention. Furthermore, two or more steps or actions can be performed simultaneously.

[0083] Finally, it should be noted that the specific embodiments described herein are merely illustrative examples of the invention and are not intended to limit the implementation of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them; it is neither necessary nor possible to exemplify all embodiments here. However, these obvious variations or modifications derived from the essential spirit of the invention still fall within the scope of protection of the invention, and interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A low cost silicon carbide fiber, characterized by, The silicon carbide fiber is prepared by using polycarbosilane, including one or two of vinylsiloxane and vinylpolysiloxane, as a precursor, through spinning, ultraviolet radiation crosslinking, and high-temperature firing. Polycarbosilanes comprising one or both of vinylsiloxanes and vinyl polysiloxanes are prepared by mixing one or both of vinylsiloxanes and vinyl polysiloxanes with polycarbosilane. The mixing method includes the following steps: dissolving one or both of vinylsiloxanes and vinyl polysiloxanes with polycarbosilane in an organic solvent, and then removing the organic solvent by distillation to obtain polycarbosilanes comprising one or both of vinylsiloxanes and vinyl polysiloxanes.

2. The low-cost silicon carbide fiber according to claim 1, characterized in that, In the precursor, one or both of vinylsiloxane and vinylpolysiloxane are in a mass ratio of 1:100 to 1:1 with polycarbosilane.

3. The low-cost silicon carbide fiber according to claim 1, characterized in that, The vinylsiloxane is a siloxane containing C=C and Si-O chemical bonds in its molecular structure, and the vinyl polysiloxane is a polysiloxane containing C=C and Si-O chemical bonds in its molecular structure.

4. A low-cost silicon carbide fiber according to any one of claims 1 to 3, characterized in that, The vinyl siloxane includes one or more of tetramethyltetravinylcyclotetrasiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, divinyltetramethyldisiloxane, vinyltriisopropoxysiloxane, and vinyltriethoxysiloxane; the vinyl polysiloxane includes one or more of terminal vinyl polymethylvinylsiloxane, terminal vinyl polydimethylsiloxane, and polydimethylmethylvinylsiloxane.

5. A low-cost silicon carbide fiber according to any one of claims 1 to 3, characterized in that, The polycarbosilane has a softening point greater than 100 °C and a number-average molecular weight of 100~5000.

6. The low-cost silicon carbide fiber according to claim 1, characterized in that, The polycarbosilane contains heterogeneous elements; The heterogeneous elements include one or more of the following: aluminum, yttrium, nickel, hafnium, lithium, iron, cobalt, lanthanum, zirconium, titanium, beryllium, magnesium, calcium, vanadium, and boron.

7. The low-cost silicon carbide fiber according to claim 1, characterized in that, The spinning process is melt spinning, dry spinning, or electrospinning.

8. The low-cost silicon carbide fiber according to claim 1, characterized in that, The step of cross-linking by ultraviolet radiation includes: cross-linking the original fiber obtained by spinning by ultraviolet radiation, the light intensity of the ultraviolet lamp is 10-1000 mW / cm 2 , the wavelength of the ultraviolet light is 185-400 nm, and the radiation time is 1-180 min.

9. The low-cost silicon carbide fiber according to claim 1, characterized in that, The high-temperature firing step includes: heating the cross-linked fiber under ultraviolet light to 1000-1800 ℃ at a rate of 1-20 ℃ / min in an inert atmosphere, and holding it at that temperature for 0.5-5 h.

10. A method for preparing low-cost silicon carbide fibers, characterized in that, Includes the following steps: The fibrils are obtained by spinning using one or both of polycarbosilanes, including vinylsiloxanes and vinylpolysiloxanes, as precursors. The fibrils are cross-linked by ultraviolet radiation; The fiber cross-linked by ultraviolet radiation is then fired at high temperature. Polycarbosilanes comprising one or both of vinylsiloxanes and vinyl polysiloxanes are prepared by mixing one or both of vinylsiloxanes and vinyl polysiloxanes with polycarbosilane. The mixing method includes the following steps: dissolving one or both of vinylsiloxanes and vinyl polysiloxanes with polycarbosilane in an organic solvent, and then removing the organic solvent by distillation to obtain polycarbosilanes comprising one or both of vinylsiloxanes and vinyl polysiloxanes.

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