High-temperature-resistant silicon carbide ceramic fiber and preparation method thereof

Abstract

The invention belongs to the technical field of fiber preparation, and relates to a high-temperature-resistant silicon carbide ceramic fiber and a preparation method thereof. The silicon carbide ceramic fiber is prepared from a boron-containing compound modified organosilicon polymer as a precursor through the steps of spinning, electron beam irradiation non-melting, sintering and high-temperature sintering, the boron-containing compound modified organosilicon polymer is obtained by grafting a boron-containing compound onto an organosilicon polymer through electron beam irradiation; the boron-containing compound is a boroxane derivative. The preparation method of the silicon carbide fiber is simple and efficient, the non-melting efficiency is remarkably improved, and the prepared silicon carbide ceramic fiber has low oxygen content, good mechanical property and high temperature resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of fiber preparation and relates to a high-temperature resistant silicon carbide ceramic fiber and a preparation method thereof. Background Art

[0002] Silicon carbide fibers have excellent properties such as high temperature resistance, oxidation resistance, radiation resistance and corrosion resistance, and have important application value in the fields of aviation, aerospace, nuclear industry, etc. The precursor conversion method is currently the mainstream method for preparing fine-diameter continuous silicon carbide fibers, which includes precursor synthesis, spinning, infusibility and sintering processes. Polycarbosilane (PCS) is the main precursor for preparing silicon carbide fibers. PCS precursors and their silicon carbide fibers have been mass-produced and commercialized, and are widely used in many fields. However, the high temperature resistance of PCS-based silicon carbide fibers still needs to be improved. This is mainly because SiC will undergo catabolism at high temperatures. x O y The phase decomposition reaction and the growth and coarsening of SiC grains lead to a sharp decrease in the mechanical properties of SiC fibers.

[0003] The introduction of heterogeneous elements such as aluminum, boron, zirconium, and titanium into PCS precursors can significantly improve the high temperature resistance of silicon carbide fibers. These heterogeneous elements help promote high temperature sintering densification, make the internal structure of the fiber more compact, reduce pores and defects, and thus improve the stability of the fiber at high temperatures. At the same time, they can inhibit the abnormal growth of silicon carbide grains, keep the grain size small and uniform, and avoid the degradation of mechanical properties caused by grain growth. Polyaluminocarbosilane (PACS) is an important precursor for the preparation of high temperature resistant silicon carbide fibers. Aluminum, as a sintering aid, can promote SiC x O y After phase decomposition, the fiber structure is densified, and the abnormal growth of silicon carbide grains is inhibited, thereby improving the high-temperature resistance of the fiber. Japan's Ube Industries and my country's National University of Defense Technology have both used PACS to prepare high-temperature resistant silicon carbide fibers, named Tyranno SA fiber and KD-SA fiber, respectively. Boron is an important sintering aid for silicon carbide ceramics. The introduction of trace amounts of boron can achieve high-temperature sintering densification of silicon carbide ceramics. Although boron is an effective sintering aid, most boron sources are toxic, unstable, and volatile, making it difficult to achieve a uniform distribution of boron in silicon carbide fibers, and thus the sintering densification effect of boron cannot be fully utilized.

[0004] Infusibility is a key step in the preparation of silicon carbide fibers by the precursor conversion method, which transforms PCS fibers from a fusible state to an infusible state, so that the fiber morphology can be maintained during subsequent high-temperature sintering. There are two main infusibility methods: air oxidation and radiation cross-linking. The conventional air oxidation method must be carried out at an extremely slow heating rate to avoid the melting of PCS fibers, because the viscosity of PCS fibers decreases at high temperatures, and they are prone to adhesion and melting. Slow heating can slowly oxidize the fiber surface to form a cross-linked structure to prevent melting, but this results in extremely low production efficiency. The radiation cross-linking method must also be carried out at a lower radiation dose rate, otherwise it will cause excessive fiber degradation or uneven cross-linking, which also leads to low efficiency. The low efficiency of these two methods makes the production efficiency of silicon carbide fibers extremely low and the production cost extremely high, which cannot meet the application needs of some cost-sensitive fields.

[0005] Therefore, developing efficient preparation technology and improving the high temperature resistance of silicon carbide fibers are of great significance to promoting the rapid development of silicon carbide fibers. Summary of the invention

[0006] In order to solve the above problems existing in the prior art, the purpose of the present invention is to provide a high temperature resistant silicon carbide ceramic fiber and a preparation method thereof, so as to overcome the shortcomings of the prior art.

[0007] One object of the present invention is to provide a high temperature resistant silicon carbide ceramic fiber, which is prepared by using a boron-containing compound modified organic silicon polymer as a precursor through the steps of spinning, electron beam irradiation infusibility, firing, and high temperature sintering;

[0008] The boron-containing compound-modified organosilicon polymer is obtained by grafting the boron-containing compound onto the organosilicon polymer through electron beam irradiation;

[0009] The boron-containing compound is a boroxine derivative, and its molecular structure is as follows:

[0010]

[0011] In the formula, R1, R2, and R3 are independently selected from one of phenyl and phenyl containing substituents. The substituent type is not particularly limited, and can be listed as an alkyl substituent (such as methyl, ethyl, propyl, isopropyl, etc.), a phenyl substituent, a halogen substituent, a hydroxyl substituent, an amino substituent, a nitro substituent, a carboxyl substituent, an alkoxy substituent, etc. The substitution position of the substituent can be one or more of ortho substitution, para substitution, and meta substitution. The number of substituents can be 1, 2, 3, 4, or 5.

[0012] Preferably, the organosilicon polymer is polycarbosilane doped with metal elements, also called polymetallic carbosilane (PMCS), and the metal element (M) is one or more of aluminum, zirconium, titanium, yttrium and the like.

[0013] Preferably, the organosilicon polymer is one or more of polyaluminum carbosilane, polyzirconium carbosilane, polytitanium carbosilane, polyyttrium carbosilane and the like.

[0014] More preferably, the organosilicon polymer is polyaluminocarbosilane and polyyttriumcarbosilane. More preferably, the mass ratio of polyaluminocarbosilane to polyyttriumcarbosilane is 70:30 to 95:5.

[0015] Preferably, the metal element doping amount in the metal element doped polycarbosilane is 0.1 to 10 wt %, more preferably 0.5 to 5 wt %.

[0016] Preferably, the method for preparing the boron-containing compound modified organosilicon polymer comprises the following steps:

[0017] The boron-containing compound and the organic silicon polymer are dissolved in a solvent, and electron beam irradiation grafting is performed under an inert atmosphere, and then the solvent is removed by drying to obtain the boron-containing compound modified organic silicon polymer.

[0018] Preferably, the content of the boron-containing compound relative to the organosilicon polymer is 0.05 to 20 wt %, more preferably 0.1 to 10 wt %.

[0019] Preferably, the irradiation dose of the electron beam irradiation grafting is 5 to 200 kGy, more preferably 10 to 100 kGy, and the irradiation time is 1 to 120 min.

[0020] The inert atmosphere herein includes one of nitrogen, argon and helium.

[0021] In the preparation method of the boron-containing compound modified organosilicon polymer, the solvent is any solvent that can dissolve the boron-containing compound and the organosilicon polymer, including but not limited to one or more of benzene, toluene, xylene, carbon tetrachloride, etc. The drying method can be vacuum drying, forced air drying, natural drying at room temperature, etc., as long as it is a drying method that can remove the solvent.

[0022] The spinning includes methods such as melt spinning, dry spinning, electrostatic spinning and melt-blowing spinning, and preferably melt spinning and dry spinning are used to prepare continuous silicon carbide fibrils.

[0023] During melt spinning, the boron-containing compound-modified organosilicon polymer is placed in a spinning barrel, heated to 100-350°C in an inert atmosphere, and spun through a spinneret under pressure (0.1-2 MPa), and collected through a spinning drum to obtain raw fibers. During dry spinning, the boron-containing compound-modified organosilicon polymer is dissolved in an organic solvent to form a spinning solution, and then the spinning solution is placed in a spinning device for spinning. The above-mentioned organic solvent is any solvent that can dissolve the boron-containing compound-modified organosilicon polymer, including one or more of benzene, toluene, xylene, carbon tetrachloride, etc.

[0024] The electron beam irradiation infusibility treatment of the present invention is carried out by electron beam irradiation in an oxygen-containing atmosphere, wherein the electron beam energy is 1 to 5 MeV and the beam current is 1 to 50 mA.

[0025] Preferably, the irradiation dose for electron beam irradiation without melting is 1 to 10 MGy, preferably 2 to 5 MGy.

[0026] Preferably, the electron beam irradiation time for not melting is 0.1 to 5 hours, preferably 0.5 to 2 hours.

[0027] Preferably, the oxygen-containing atmosphere is composed of oxygen and inert gas, wherein the content of oxygen is 0.5 to 10 v / v%, preferably 1 to 8 v / v%.

[0028] Preferably, the calcination is carried out in an inert atmosphere, the treatment temperature is 1000-1300° C., and the treatment time is 10-60 min. More preferably, the calcination is carried out in a nitrogen atmosphere.

[0029] Preferably, the high temperature sintering is performed in an inert atmosphere, the processing temperature is 1500-2000° C., and the processing time is 10-60 minutes. More preferably, the high temperature sintering is performed in an argon atmosphere.

[0030] Preferably, the high temperature resistant silicon carbide ceramic fiber has an oxygen content of ≤1wt%, a tensile strength of ≥2.0GPa, a tensile modulus of ≥350GPa, and a tensile strength loss of ≤10% when treated in an inert atmosphere at 1800-2000°C for 0.5-2h.

[0031] Preferably, the diameter of the high temperature resistant silicon carbide ceramic fiber is 3 to 15 μm, more preferably 5 to 9 μm.

[0032] Another object of the present invention is to provide a method for preparing high temperature resistant silicon carbide ceramic fiber, comprising the following steps:

[0033] Spinning a raw material to obtain raw fibers, wherein the raw material includes a boron-containing compound-modified organosilicon polymer;

[0034] The fibrils are subjected to electron beam irradiation in an oxygen-containing atmosphere to infusibility treatment;

[0035] The fibers after the infusible treatment are fired and sintered at high temperature;

[0036] The boron-containing compound-modified organosilicon polymer is obtained by grafting the boron-containing compound onto the organosilicon polymer through electron beam irradiation;

[0037] The boron-containing compound is a boroxine derivative, and its molecular structure is as follows:

[0038]

[0039] In the formula, R1, R2, and R3 are independently selected from one of a phenyl group and a phenyl group containing a substituent.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The present invention uses a boron-containing compound-modified organosilicon polymer as a raw material for preparing SiC fibers, thereby achieving controllable introduction of boron into SiC fibers, with less loss of boron source and uniform distribution in the fibers, which significantly promotes high-temperature sintering densification; and it has been proven that the use of this raw material can be used for infusibility treatment by electron beam irradiation, and a higher irradiation dose rate can be used, and the infusibility treatment time is greatly shortened from the conventional 10 to 20 hours to 0.5 to 2 hours.

[0042] 2. The silicon carbide fiber prepared by the present invention has excellent mechanical properties, with a tensile strength of ≥2.0 GPa and a tensile modulus of ≥350 GPa.

[0043] 3. The silicon carbide fiber prepared by the present invention has a lower oxygen content, which is ≤1wt%.

[0044] 4. The silicon carbide fiber prepared by the present invention has good high temperature resistance. After being treated in an argon atmosphere at 1900°C for 1 hour, the tensile strength loss of the silicon carbide fiber is ≤10%.

[0045] 5. The present invention uses boron-containing compound-modified polyaluminum carbosilane and polyyttrium carbosilane as raw materials to prepare SiC fibers with better mechanical properties and high temperature resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a SEM photograph of the silicon carbide fiber prepared in Example 1 of the present application;

[0047] Figure 2 This is an XRD photograph of the silicon carbide fiber prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0048] The technical scheme of the present invention is further described below by specific examples and accompanying drawings. It should be understood that the specific examples described herein are only used to help understand the present invention and are not intended for specific limitations of the present invention. The accompanying drawings used herein are only for better illustrating the disclosure of the present invention and do not have a limiting effect on the scope of protection. If not otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used raw materials in the art, and the methods used in the embodiments are all conventional methods in the art.

[0049] In the following examples and comparative examples:

[0050] The weight average molecular weight of polyaluminocarbosilane is about 3000 g / mol, and the aluminum content is about 1 wt%;

[0051] The weight average molecular weight of the polyzirconium carbosilane is about 3000 g / mol, and the zirconium content is about 1 wt %;

[0052] The weight average molecular weight of the polytitanium carbosilane is about 3000 g / mol, and the titanium content is about 1 wt %;

[0053] The weight average molecular weight of polyyttrium carbosilane is about 3000 g / mol, and the yttrium content is about 1 wt%;

[0054] The electron beam irradiation oxidation process uses a 2MeV electron accelerator with a beam current of 2 to 20 mA.

[0055] Structural characterization and performance testing:

[0056] The mechanical properties of silicon carbide fibers were tested using a single fiber physical property analyzer (TEXTECHNO, Germany). The microscopic morphology of silicon carbide fibers was characterized using a scanning electron microscope (SEM, FEI, USA). The crystal structure of silicon carbide fibers was characterized using an X-ray diffractometer (XRD, Bruker, Germany).

[0057] Example 1

[0058] The silicon carbide ceramic fiber of Example 1 is prepared by the following method:

[0059] 1 part by mass of triphenyl boroxine (CAS No.: 3262-89-3) and 100 parts by mass of polyaluminocarbosilane were dissolved in 200 parts by mass of benzene, and electron beam irradiation was performed in a nitrogen atmosphere, with an irradiation dose of 100 kGy and an irradiation time of 10 min, and then vacuum drying was performed to remove the solvent to obtain triphenyl boroxine-modified polyaluminocarbosilane. Triphenyl boroxine-modified polyaluminocarbosilane was used as a raw material, and raw fibers were obtained by melt spinning, and then infusible treatment was performed under electron beam irradiation, with an irradiation dose of 4 MGy and an irradiation time of 1.5 h, and the atmosphere was argon and oxygen (95:5, v / v). The fibers after infusible treatment were sintered in a nitrogen atmosphere at 1200°C for 30 min, and then high-temperature sintering treatment was performed in an argon atmosphere at 1900°C for 30 min to obtain SiC fibers.

[0060] The oxygen content of the SiC fiber prepared in Example 1 is 0.32%, the tensile strength is about 2.2 GPa, and the tensile modulus is about 375 GPa. After the SiC fiber is treated in an argon atmosphere at 1900° C. for 1 hour, the tensile strength loses 8%.

[0061] The SEM photo of the SiC fiber prepared in Example 1 is as follows: Figure 1 As shown in Figure 1, it can be seen that the diameter of the SiC fiber is about 5 μm, the surface and cross section are smooth and dense, and there are no obvious defects; the XRD photos of the SiC fiber are shown in Figure 1. Figure 2 As shown, it can be seen that the SiC fiber has a high degree of crystallinity.

[0062] Example 2

[0063] The silicon carbide ceramic fiber of Example 2 is prepared by the following method:

[0064] 2 parts by mass of triphenyl boroxine and 100 parts by mass of polyaluminocarbosilane were dissolved in 200 parts by mass of toluene, and electron beam irradiated in a nitrogen atmosphere, with an irradiation dose of 80 kGy and an irradiation time of 15 min, and then vacuum dried to remove the solvent to obtain triphenyl boroxine-modified polyaluminocarbosilane. Triphenyl boroxine-modified polyaluminocarbosilane was used as a raw material, and raw fibers were obtained by melt spinning, and then infusible treatment was carried out under electron beam irradiation, with an irradiation dose of 2 MGy and an irradiation time of 1 h, and the atmosphere was argon and oxygen (94:6, v / v). The fibers after infusible treatment were sintered in a nitrogen atmosphere at 1100°C for 35 min, and then high-temperature sintered in an argon atmosphere at 1800°C for 40 min to obtain SiC fibers.

[0065] The oxygen content of the SiC fiber prepared in Example 2 was 0.41%, the tensile strength was about 2.0 GPa, and the tensile modulus was about 354 GPa. After the SiC fiber was treated in an argon atmosphere at 1900° C. for 1 hour, the strength loss was 5%.

[0066] Example 3

[0067] The silicon carbide ceramic fiber of Example 3 is prepared by the following method:

[0068] 10 parts by mass of triphenyl boroxine and 100 parts by mass of polyzirconium carbosilane were dissolved in 200 parts by mass of xylene, and electron beam irradiated in a nitrogen atmosphere, with an irradiation dose of 100 kGy and an irradiation time of 5 min, and then vacuum dried to remove the solvent to obtain triphenyl boroxine-modified polyzirconium carbosilane. Triphenyl boroxine-modified polyzirconium carbosilane was used as a raw material, and raw fibers were obtained by melt spinning, and then infusible treatment was carried out under electron beam irradiation, with an irradiation dose of 5 MGy and an irradiation time of 2 h, and the atmosphere was argon and oxygen (98:2, v / v). The fibers after infusible treatment were sintered in a nitrogen atmosphere at 1200°C for 32 min, and then high-temperature sintered in an argon atmosphere at 1850°C for 45 min to obtain SiC fibers.

[0069] The oxygen content of the SiC fiber prepared in Example 3 was 0.46%, the tensile strength was about 2.1 GPa, and the tensile modulus was about 355 GPa. After the SiC fiber was treated in an argon atmosphere at 1900° C. for 1 hour, the strength loss was 6%.

[0070] Example 4

[0071] The silicon carbide ceramic fiber of Example 4 is prepared by the following method:

[0072] 3 parts by mass of triphenyl boroxine and 100 parts by mass of polytitanium carbosilane were dissolved in 200 parts by mass of carbon tetrachloride, and electron beam irradiation was performed in a nitrogen atmosphere, with an irradiation dose of 70 kGy and an irradiation time of 7 min, and then vacuum drying was performed to remove the solvent to obtain triphenyl boroxine-modified polytitanium carbosilane. Triphenyl boroxine-modified polytitanium carbosilane was used as a raw material, and raw fibers were obtained by melt spinning, and then infusible treatment was performed under electron beam irradiation, with an irradiation dose of 3 MGy and an irradiation time of 2 h, and the atmosphere was argon and oxygen (99:1, v / v). The fibers after infusible treatment were sintered in a nitrogen atmosphere at 1300 ° C for 25 min, and then high-temperature sintering treatment was performed in an argon atmosphere at 1950 ° C for 25 min to obtain SiC fibers.

[0073] The oxygen content of the SiC fiber prepared in Example 4 was 0.22%, the tensile strength was about 2.0 GPa, and the tensile modulus was about 370 GPa. After the SiC fiber was treated in an argon atmosphere at 1900° C. for 1 hour, the tensile strength lost by 9%.

[0074] Example 5

[0075] The silicon carbide ceramic fiber of Example 5 is prepared by the following method:

[0076] 1 part by mass of triphenyl boroxine, 90 parts by mass of polyaluminocarbosilane and 10 parts by mass of polyyttrium carbosilane were dissolved in 200 parts by mass of benzene, and electron beam irradiation was performed under nitrogen atmosphere, with an irradiation dose of 100 kGy and an irradiation time of 10 min, and then vacuum dried to remove the solvent, to obtain triphenyl boroxine-modified polyaluminocarbosilane and polyyttrium carbosilane. Using triphenyl boroxine-modified polyaluminocarbosilane and polyyttrium carbosilane as raw materials, the subsequent steps were the same as in Example 1 to obtain SiC fiber.

[0077] The oxygen content of the SiC fiber prepared in Example 5 was 0.12%, the tensile strength was about 2.5 GPa, and the tensile modulus was about 390 GPa. After the SiC fiber was treated in an argon atmosphere at 1900° C. for 1 hour, the tensile strength lost 6%.

[0078] Example 6

[0079] The silicon carbide ceramic fiber of Example 6 is prepared by the following method:

[0080] 1 part by mass of triphenyl boroxine and 100 parts by mass of polyyttrium carbosilane were dissolved in 200 parts by mass of benzene, and electron beam irradiation was performed under a nitrogen atmosphere, with an irradiation dose of 100 kGy and an irradiation time of 10 min, and then vacuum dried to remove the solvent to obtain triphenyl boroxine-modified polyyttrium carbosilane. Using triphenyl boroxine-modified polyyttrium carbosilane as a raw material, the subsequent steps were the same as in Example 1 to obtain SiC fiber.

[0081] The oxygen content of the SiC fiber prepared in Example 6 was 0.2%, the tensile strength was about 2.2 GPa, and the tensile modulus was about 365 GPa. After the SiC fiber was treated in an argon atmosphere at 1900° C. for 1 hour, the tensile strength lost 8%.

[0082] Comparative Example 1

[0083] The difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, unirradiated polyaluminocarbosilane grafted with cycloboroxine is used as raw material to prepare raw fibers by melt spinning, and the subsequent steps are the same as those in Example 1 to prepare SiC fibers.

[0084] The oxygen content of the SiC fiber prepared in Comparative Example 1 was 0.35%, the tensile strength was about 1.6 GPa, and the tensile modulus was about 320 GPa. After the SiC fiber was treated in an argon atmosphere at 1900° C. for 1 hour, the tensile strength lost 20%.

[0085] Comparative Example 2

[0086] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 uses air infusibility treatment instead of electron beam irradiation infusibility treatment in Example 1. The air infusibility treatment is as follows: the original fiber is infusible in an air atmosphere at 200° C., the heating rate is 10° C. / h, and the constant temperature time is 2 hours to obtain infusible fiber. The rest is the same as Example 1.

[0087] The oxygen content of the SiC fiber prepared in Comparative Example 2 was 0.52%, the tensile strength was about 1.4 GPa, and the tensile modulus was about 300 GPa. After the SiC fiber was treated in an argon atmosphere at 1900° C. for 1 hour, the tensile strength lost 15%.

[0088] Comparative Example 3

[0089] The difference between Comparative Example 3 and Example 1 is that Comparative Example 1 uses polyaluminocarbosilane grafted with unirradiated cycloboroxine as raw material to prepare raw fibers by melt spinning, and Comparative Example 1 uses air infusibility treatment instead of electron beam irradiation infusibility treatment in Example 1, and the specific air infusibility treatment is the same as that of Comparative Example 2.

[0090] The oxygen content of the SiC fiber prepared in Comparative Example 3 was 0.53%, the tensile strength was about 1.3 GPa, and the tensile modulus was about 295 GPa. After the SiC fiber was treated in an argon atmosphere at 1900° C. for 1 hour, the tensile strength lost by 23%.

[0091] Comparative Example 4

[0092] The silicon carbide ceramic fiber of Comparative Example 4 was prepared by the following method:

[0093] 1 part by mass of triphenyl boroxine and 100 parts by mass of polyaluminocarbosilane were dissolved in 200 parts by mass of benzene, stirred for 60 minutes, and then vacuum dried to remove the solvent to obtain a blend of triphenyl boroxine and polyaluminocarbosilane. The blend of triphenyl boroxine and polyaluminocarbosilane was used as a raw material to obtain raw fibers by melt spinning, and the subsequent steps were the same as in Example 1.

[0094] The oxygen content of the SiC fiber prepared in Comparative Example 4 was 0.34%, the tensile strength was about 1.7 GPa, and the tensile modulus was about 330 GPa. After the SiC fiber was treated in an argon atmosphere at 1900° C. for 1 hour, the tensile strength lost 16%.

[0095] Comparative Example 5

[0096] The silicon carbide ceramic fiber of Comparative Example 5 was prepared by the following method:

[0097] 1 part by mass of trimethylcyclotriboroxane (CAS No.: 823-96-1) and 100 parts by mass of polyaluminocarbosilane were dissolved in 200 parts by mass of benzene, and electron beam irradiation was performed under a nitrogen atmosphere, with an irradiation dose of 100 kGy and an irradiation time of 10 min, and then vacuum dried to remove the solvent to obtain trimethylcyclotriboroxane-modified polyaluminocarbosilane. Using trimethylcyclotriboroxane-modified polyaluminocarbosilane as a raw material, raw fibers were obtained by melt spinning, and the subsequent steps were the same as in Example 1.

[0098] The oxygen content of the SiC fiber prepared in Comparative Example 5 was 0.36%, the tensile strength was about 1.8 GPa, and the tensile modulus was about 345 GPa. After the SiC fiber was treated in an argon atmosphere at 1900° C. for 1 hour, the tensile strength lost 15%.

[0099] Comparative Example 6

[0100] The silicon carbide ceramic fiber of Comparative Example 6 was prepared by the following method:

[0101] 1 part by mass of borazine (CAS No.: 6569-51-3) and 100 parts by mass of polyaluminocarbosilane were dissolved in 200 parts by mass of benzene, and electron beam irradiation was performed under a nitrogen atmosphere, with an irradiation dose of 100 kGy and an irradiation time of 10 min, and then vacuum dried to remove the solvent to obtain borazine-modified polyaluminocarbosilane. Using borazine-modified polyaluminocarbosilane as a raw material, raw fibers were obtained by melt spinning, and the subsequent steps were the same as in Example 1.

[0102] The oxygen content of the SiC fiber prepared in Comparative Example 6 was 0.37%, the tensile strength was about 1.8 GPa, and the tensile modulus was about 340 GPa. After the SiC fiber was treated in an argon atmosphere at 1900° C. for 1 hour, the tensile strength lost 16%.

[0103] The tensile strength of the SiC fibers prepared in Examples 1-6 is relatively high, and after being treated under high temperature conditions, the tensile strength loss rate is low, showing excellent high temperature resistance. Example 1, Example 6 and Example 5 use triphenyl boroxine-modified polyaluminocarbosilane, triphenyl boroxine-modified polyyttriumcarbosilane, triphenyl boroxine-modified polyaluminocarbosilane and polyyttriumcarbosilane as raw materials, respectively. It is unexpectedly found that the SiC fibers prepared using triphenyl boroxine-modified polyaluminocarbosilane and polyyttriumcarbosilane as raw materials show better performance than Example 1 and Example 6.

[0104] By comparing Comparative Example 1, Comparative Example 2, Comparative Example 3 and Example 1, it can be seen that using the boron-containing compound-modified silicone polymer as the raw material and combining it with the electron beam irradiation infusibility treatment are beneficial to improving the tensile strength, tensile modulus and high temperature resistance of the SiC fiber.

[0105] Comparative Example 4 physically mixes triphenyl boroxine with polyaluminocarbosilane, but does not perform electron beam irradiation grafting modification. The blend of triphenyl boroxine and polyaluminocarbosilane is used as a raw material, and combined with electron beam irradiation infusibility treatment, the boron element cannot be uniformly introduced into the fiber, resulting in reduced performance of the prepared SiC fiber. Comparative Examples 5 and 6 use trimethyl boroxine and borazine to replace triphenyl boroxine for electron irradiation grafting modification of polyaluminocarbosilane, respectively. It can be found that the effects of trimethyl boroxine-modified polyaluminocarbosilane and borazine-modified polyaluminocarbosilane are not as good as triphenyl boroxine-modified polyaluminocarbosilane.

[0106] The various aspects, embodiments, and features of the present invention should be considered to be illustrative in all aspects and not limiting of the present invention, the scope of which is defined solely by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.

[0107] In the preparation method of the present invention, the order of each step is not limited to the order listed. For those skilled in the art, without creative work, the order of each step is also within the protection scope of the present invention. In addition, two or more steps or actions can be performed simultaneously.

[0108] Finally, it should be noted that the specific embodiments described herein are merely examples of the present invention, and are not intended to limit the implementation methods of the present invention. A person skilled in the art of the present invention may make various modifications or supplements to the specific embodiments described, or replace them in a similar manner. It is not necessary and impossible to provide all examples of all implementation methods here. However, these obvious changes or modifications derived from the essential spirit of the present invention still fall within the scope of protection of the present invention, and interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A high temperature resistant silicon carbide ceramic fiber, characterized in that: The method is prepared by using a boron-containing compound-modified organosilicon polymer as a precursor through the steps of spinning, electron beam irradiation, infusibility, sintering, and high-temperature sintering; The boron-containing compound-modified organosilicon polymer is obtained by grafting the boron-containing compound onto the organosilicon polymer through electron beam irradiation; The boron-containing compound is a boroxine derivative, and its molecular structure is as follows: In the formula, R1, R2, and R3 are independently selected from one of a phenyl group and a phenyl group containing a substituent.

2. The high temperature resistant silicon carbide ceramic fiber according to claim 1, characterized in that: The method for preparing a boron-containing compound-modified organosilicon polymer comprises the following steps: The boron-containing compound and the organic silicon polymer are dissolved in a solvent, and electron beam irradiation grafting is performed under an inert atmosphere, and then the solvent is removed by drying to obtain the boron-containing compound modified organic silicon polymer.

3. A high temperature resistant silicon carbide ceramic fiber according to claim 1 or 2, characterized in that: The organosilicon polymer is polycarbosilane doped with a metal element, wherein the metal element is one or more of aluminum, zirconium, titanium and yttrium.

4. A high temperature resistant silicon carbide ceramic fiber according to claim 1 or 2, characterized in that: The organosilicon polymers are polyaluminocarbosilane and polyyttriumcarbosilane; The mass ratio of polyaluminocarbosilane to polyyttriumcarbosilane is 70:30 to 95:

5.

5. A high temperature resistant silicon carbide ceramic fiber according to claim 1 or 2, characterized in that: The irradiation dose of electron beam irradiation grafting is 5 to 200 kGy; And / or, the content of the boron-containing compound relative to the organosilicon polymer is 0.05 to 20 wt %.

6. The high temperature resistant silicon carbide ceramic fiber according to claim 1, characterized in that: Electron beam irradiation infusion is carried out by electron beam irradiation in an oxygen-containing atmosphere; The irradiation dose for electron beam irradiation without melting is 1 to 10 MGy, and the irradiation time is 0.1 to 5 h; The oxygen-containing atmosphere is composed of oxygen and inert gas, wherein the content of oxygen is 0.5-10 v / v%.

7. The high temperature resistant silicon carbide ceramic fiber according to claim 1, characterized in that: The sintering is carried out in an inert atmosphere at a temperature of 1000 to 1300° C. for a time of 10 to 60 minutes; And / or, the high temperature sintering is carried out in an inert atmosphere, the processing temperature is 1500-2000° C., and the processing time is 10-60 min.

8. The high temperature resistant silicon carbide ceramic fiber according to claim 1, characterized in that: The high temperature resistant silicon carbide ceramic fiber has an oxygen content of ≤1wt%, a tensile strength of ≥2.0GPa, a tensile modulus of ≥350GPa, and a tensile strength loss of ≤10% when treated in an inert atmosphere at 1800-2000°C for 0.5-2h.

9. A method for preparing high temperature resistant silicon carbide ceramic fiber, characterized in that: The following steps are involved: Spinning a raw material to obtain raw fibers, wherein the raw material includes a boron-containing compound-modified organosilicon polymer; The fibrils are subjected to electron beam irradiation in an oxygen-containing atmosphere to infusibility treatment; The fibers after the infusible treatment are fired and sintered at high temperature; The boron-containing compound-modified organosilicon polymer is obtained by grafting the boron-containing compound onto the organosilicon polymer through electron beam irradiation; The boron-containing compound is a boroxine derivative, and its molecular structure is as follows: In the formula, R1, R2, and R3 are independently selected from one of a phenyl group and a phenyl group containing a substituent.

10. The preparation method according to claim 9, characterized in that: The organosilicon polymer is polycarbosilane doped with a metal element, wherein the metal element is one or more of aluminum, zirconium, titanium, and yttrium; and / or, the content of the boron-containing compound relative to the organosilicon polymer is 0.05 to 20 wt %; And / or, the electron beam irradiation infusibility is carried out by electron beam irradiation in an oxygen-containing atmosphere, the irradiation dose is 1 to 10 MGy, the irradiation time is 0.1 to 5 hours, the oxygen-containing atmosphere is composed of oxygen and an inert gas, wherein the oxygen content is 0.5 to 10 v / v%; And / or, the sintering is carried out in an inert atmosphere, the treatment temperature is 1000-1300° C., and the treatment time is 10-60 min; And / or, the high temperature sintering is carried out in an inert atmosphere, the processing temperature is 1500-2000° C., and the processing time is 10-60 min.

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